WO2025211370A1 - Molded body and method for manufacturing same - Google Patents

Abstract

The present invention provides a molded body which has a texture similar to that of paper. The present invention relates to a molded body which contains a resin composition that comprises a thermoplastic resin (A) and a natural fiber (B). If ∆ friction coefficient is the value obtained by subtracting the dynamic friction coefficient from the static friction coefficient, the molded body has a texture region in which (maximum height Sz)/(∆ friction coefficient) is 150 μm to 600 μm on a surface that contains the resin composition.

Description

Molded body and method for producing the same

The present invention relates to a molded body and a method for producing the same.

General-purpose plastics such as polyethylene (PE), polypropylene (PP), and polystyrene (PS) are not only very inexpensive, but also easy to mold and weigh a fraction of the weight of metals or ceramics. For this reason, general-purpose plastics are commonly used as materials for a variety of everyday items such as bags, various types of packaging, various containers, and sheets, as well as for industrial parts such as automobile parts and electrical components, and as materials for daily necessities and miscellaneous goods.

A technique is known for improving the mechanical strength of general-purpose plastics by dispersing fibrous fillers such as natural fibers, glass fibers, and carbon fibers in the plastic's natural resin. Among these, natural fibers such as cellulose are attracting attention as reinforcing fibers due to their low cost and environmental friendliness when disposed of (Patent Document 1).

International Publication No. 2023/013514

However, as a result of research by the inventors, it was found that molded articles made from resin compositions containing natural fibers have a predominantly resinous feel, and do not have the characteristic fiber feel, despite the presence of natural fibers. On the other hand, if it were possible to create a molded article using natural fibers that exhibits a fiber-like (for example, paper-like) feel, it is expected that such molded articles could be used in a variety of applications where such a feel is desired.

The present invention was made in consideration of the above circumstances, and aims to provide a molded product that has a texture similar to that of paper, and a method for manufacturing the same.

One aspect of the present invention relates to the following molded articles [1] to [13].
[1] A molded article comprising a resin composition containing a thermoplastic resin (A) and a natural fiber (B),
When the value obtained by subtracting the dynamic friction coefficient from the static friction coefficient is defined as the Δ friction coefficient,
The molded body has a tactile region on a surface containing the resin composition, the tactile region having a maximum height Sz/Δ friction coefficient of 150 μm or more and 600 μm or less.
Molded body.
[2] The maximum surface height Sz of the tactile area is 42 μm or more and 200 μm or less.
[1] The molded article according to [1].
[3] The tactile area has a surface Δ friction coefficient of 0.250 or more and 0.400 or less.
The molded article according to [1] or [2].
[4] The surface irregularities of the tactile area are regular irregularities.
[1] - [3] The molded article according to any one of [1] to [3].
[5] The resin composition contains 5% by mass or more and 50% by mass or less of the natural fiber (B) relative to the total mass of the resin composition,
[1] - [4] The molded article according to any one of [1] to [4].
[6] The resin composition contains 10% by mass or more and 40% by mass or less of the natural fiber (B) relative to the total mass of the resin composition,
[1] - [5] The molded article according to any one of [1] to [5].
[7] The natural fiber (B) includes a cellulose fiber.
[1] - [6] The molded article according to any one of [1] to [6].
[8] The thermoplastic resin (A) contains a polyolefin,
[1] - [7] The molded article according to any one of [1] to [7].
[9] The polyolefin is a propylene-based polymer.
[8] The molded article according to [8].
[10] The resin composition is composed solely of the resin composition.
[1] - [9] The molded article according to any one of [1] to [9].
[11] The resin composition contains a compatibilizer (C),
[1] The molded article according to any one of [1] to [10].
[12] The compatibilizer (C) is an acid-modified polyolefin resin composition,
[11] The molded article according to [11].
[13] An automobile interior component,
[1] The molded article according to any one of [1] to [12].

Another aspect of the present invention relates to the following methods for producing a resin composition [14] and [15].
[14] A step of molding a resin composition containing a thermoplastic resin and natural fibers;
and treating the surface of the molded resin composition to form a tactile region having a maximum height Sz/Δ friction coefficient of 150 μm or more and 600 μm or less.
A method for manufacturing a molded body.
[15] In the molding step, the resin composition is molded so that regular irregularities are formed on the surface of the molded resin composition.
[14] A method for producing the molded article according to [14].

The present invention provides a molded article that contains a resin composition that includes natural fibers and a thermoplastic resin and has a texture similar to that of paper, as well as a method for producing the resin composition.

FIG. 1 is a SEM image of the surface of the molded body obtained in Example 2. FIG. 2 is an SEM image of the surface of the molded body obtained in Comparative Example 2. FIG. 3 is a SEM image of the surface of the molded body obtained in Comparative Example 3.

In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages.

1. Molded Article The first embodiment of the present invention relates to a molded article comprising a resin composition containing a thermoplastic resin (A) and natural fibers (B).

The molded article has a region on its surface containing the resin composition where the maximum height Sz/Δ friction coefficient is 150 μm or more and 600 μm or less (hereinafter simply referred to as the "tactile region").

The maximum height Sz is the maximum height Sz specified by ISO 25178, and specifically is the sum of the maximum peak height Sp and the maximum valley depth Sv. The maximum height Sz defines the macroscopic roughness of the tactile area, for example, the irregularities that occur during molding. Therefore, the magnitude of the maximum height Sz is thought to represent the tactile feel that results from the structure of the tactile area.

The Δ coefficient of friction is the absolute value of the difference between the static coefficient of friction and the kinetic coefficient of friction, and is usually obtained by subtracting the kinetic coefficient of friction from the static coefficient of friction. When the kinetic coefficient of friction is greater than the static coefficient of friction, the value is obtained by subtracting the static coefficient of friction from the kinetic coefficient of friction. The Δ coefficient of friction determines the state of exposure (fuzzing, etc.) of the natural fiber (B) on the surface of the tactile area. Therefore, the magnitude of the Δ coefficient of friction is thought to represent the tactile feel derived from the natural fiber (B) in the tactile area.

In this embodiment, by optimizing these relationships, the above region is given a paper-like texture and fibrous state. It is believed that this gives the tactile region a paper-like texture. Specifically, when the maximum height Sz/Δ friction coefficient is 150 μm or greater, the tactile region has moderate texture and therefore less of a resin-like smoothness. Furthermore, when the maximum height Sz/Δ friction coefficient is 600 μm or less, the natural fiber (B) is moderately exposed on the surface of the tactile region. Furthermore, the surface texture is not significantly large. It is believed that by adjusting the balance between these, a paper-like texture can be achieved through the natural fiber (B) exposed on the surface and the moderate texture.

From this perspective, the maximum height Sz/Δ friction coefficient is 150 μm or more and 600 μm or less, preferably 150 μm or more and 500 μm or less, more preferably 150 μm or more and 400 μm or less, and even more preferably 180 μm or more and 300 μm or less.

Furthermore, from the perspective of making the feel closer to that of paper, the maximum surface height Sz of the tactile area is preferably 42 μm or more and 200 μm or less, more preferably 50 μm or more and 150 μm or less, and even more preferably 50 μm or more and 120 μm or less.

Furthermore, from the perspective of making the feel closer to that of paper, the maximum peak height Sp of the surface of the tactile area is preferably 30 μm or more and 100 μm or less, more preferably 30 μm or more and 80 μm or less, and even more preferably 35 μm or more and 75 μm or less.

Furthermore, from the perspective of making the tactile feel closer to that of paper, the maximum valley depth Sv of the surface of the tactile area is preferably 10 μm or more and 100 μm or less, more preferably 12 μm or more and 80 μm or less, and even more preferably 14 μm or more and 50 μm or less.

Furthermore, from the perspective of achieving a texture closer to that of paper, the tactile area preferably has an arithmetic mean surface height Sa of 3 μm or more and 20 μm or less, more preferably 3 μm or more and 15 μm or less, and even more preferably 3 μm or more and 10 μm or less.

The maximum height Sz, maximum peak height Sp, maximum valley depth Sv, and arithmetic mean height Sa are values specified by ISO 25178. These values are calculated by taking two measurements of the same tactile area and using the average of the measured values obtained.

Furthermore, from the viewpoint of making the feel closer to that of paper, the tactile region preferably has a Δ coefficient of friction of 0.200 or more and 0.500 or less, and more preferably 0.250 or more and 0.400 or less.

Furthermore, from the viewpoint of making the feel closer to that of paper, the static friction coefficient of the tactile region is preferably 0.800 or more and 1.000 or less, and more preferably 0.820 or more and 0.980 or less.

Furthermore, from the viewpoint of making the feel closer to that of paper, the tactile region preferably has a dynamic friction coefficient of 0.500 or more and 0.700 or less, and more preferably 0.530 or more and 0.650 or less.

Furthermore, from the viewpoint of making the feel closer to that of paper, the static friction force of the tactile area is preferably 40.0 gf or more and 60.0 gf or less, and more preferably 40.0 gf or more and 50.0 gf or less.

Furthermore, from the perspective of making the feel closer to that of paper, the kinetic friction force of the tactile area is preferably 20.0 gf or more and 40.0 gf or less, and more preferably 20.0 gf or more and 30.0 gf or less.

The static friction coefficient, dynamic friction coefficient, static friction force, and dynamic friction force are values obtained by measurement using a reciprocating abrasion tester. The friction element used is made of SUS and measures 20 mm long x 20 mm wide x 30 mm high, with a tip radius of 45 and the surface covered with sapplause. The friction test is performed over a distance of 30 mm, with a load of 50 gf, a speed of 300 mm/min, an ambient temperature of 23±2°C, and an ambient humidity of 50±5%. These values are calculated by taking two measurements on the same tactile area and using the average of the measured values obtained.

The tactile region can be produced by polishing part or all of the surface of a molded object obtained by molding a resin composition containing a thermoplastic resin (A) and natural fibers (B) to adjust the surface irregularities while exposing the natural fibers (B) appropriately. The surface irregularities are not particularly limited as long as the maximum height Sz/Δ friction coefficient is 150 μm or more and 600 μm or less, and may be regular or irregular. From the perspective of easily controlling the surface's tactile feel, regular surface irregularities are preferred, with regular linear irregularities being more preferred. Regular irregularities refer to irregularities that are periodic in at least one direction along the surface. The polishing method and degree can be varied depending on the type and amount of thermoplastic resin (A) contained in the resin composition, the type and amount of natural fibers (B) contained in the resin composition, the molding method, and the surface irregularities of the molded object obtained thereby. Examples of polishing methods include polishing with sandpaper or other emery paper, and blasting.

The molded article is not particularly limited as long as it contains a resin composition containing a thermoplastic resin (A) and natural fibers (B) and has the above-mentioned tactile region on a surface containing the resin composition, but it is preferable that the molded article consist solely of the resin composition. Note that "consisting solely of the resin composition" means that the molded article is composed solely of the resin composition. By having the molded article consist solely of the resin composition, the proportion of the tactile region relative to the entire surface of the molded article can be increased. Furthermore, in the surface treatment (second step) described below, there is no need to perform measures to prevent the resin composition from peeling off from other materials that make up the molded article that are bonded to the resin composition, or masking treatments to prevent the other materials that make up the molded article from being surface treated, making it easier to manufacture the molded article.

2. Resin Composition The tactile region is present on the surface of a molded article formed from a resin composition containing a thermoplastic resin (A) and natural fibers (B). The resin composition may further contain a compatibilizer (C), a processing aid (D), and other optional components. In this specification, the amount of each component contained in the resin composition refers to the total amount of the multiple substances present in the resin composition when multiple substances corresponding to each component are present in the resin composition, unless otherwise specified.

2-1. Thermoplastic resin (A)
The type of thermoplastic resin (A) is not particularly limited. For example, thermoplastic resins described in "Practical Plastic Dictionary" (edited by the Practical Plastic Dictionary Editorial Committee, Industrial Research Institute Co., Ltd.) and the like can be widely used. Only one type of thermoplastic resin (A) may be contained, or two or more types may be contained. The thermoplastic resin (A) may be produced using a raw material derived from biomass.

Examples of thermoplastic resin (A) include polyolefins, polyamides, polyesters, polyacetals, styrene-based (co)polymers, acrylic resins, polycarbonates, polyphenylene oxides, chlorinated resins such as polyvinyl chloride and polyvinylidene chloride, vinyl acetate resins, ethylene-(meth)acrylic acid ester copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers or ionomers thereof, vinyl alcohol resins, thermoplastic urethane elastomers, and rubber components. Of these, polyolefins are preferred from the perspective of lightweight properties. Furthermore, polyolefins have a low melting point, and when polyolefins are included in a resin composition, the power consumption required for molding and processing the resin composition can be reduced. Therefore, from the perspective of low LCA (Life Cycle Assessment), it is preferable that thermoplastic resin (A) contain polyolefins.

Examples of polyolefins include olefin homopolymers such as polyethylene, polypropylene, poly-1-butene, and polymethylbutene, as well as olefin copolymers such as ethylene-α-olefin random copolymers, propylene-ethylene random copolymers, and ethylene-α-olefin-non-conjugated polyene copolymers. Of these, polyethylene and polypropylene are preferred, and polypropylene is more preferred from the viewpoint of improving the heat resistance and rigidity of molded articles. The types and proportions of each structural unit constituting various polyolefins can be identified by ^13C -NMR.

The polyolefin may be, for example, an ethylene-based polymer. The ethylene-based polymer is preferably an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms. Specific examples of ethylene homopolymers include ultra-high molecular weight polyethylene, high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, etc.

On the other hand, when the ethylene-based polymer is a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms, the proportion of structural units derived from ethylene is preferably 91.0 mol% to 99.9 mol%. On the other hand, the proportion of structural units derived from an α-olefin having 3 or more carbon atoms is preferably 0.1 mol% to 9.0 mol% (the total amount of structural units derived from ethylene and structural units derived from an α-olefin having 3 or more carbon atoms is taken as 100 mol%).

Examples of the α-olefins having 3 to 12 carbon atoms include linear or branched α-olefins such as propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, and 1-dodecene. By forming a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms, the moldability, appearance, and mechanical strength of the molded article are improved. The structural units derived from these α-olefins may contain only one type, or two or more types.

The polyolefin may also be a propylene homopolymer (polypropylene) or a propylene-based polymer of propylene with ethylene or an α-olefin having 4 to 12 carbon atoms.

When the propylene-based polymer is a copolymer of propylene and ethylene, the proportion of structural units derived from propylene can be 60 mol % or more and 99.5 mol % or less (the total amount of structural units derived from propylene and structural units derived from ethylene is taken as 100 mol %). Using a propylene-based polymer with a high proportion of structural units derived from propylene results in good moldability, appearance, and heat resistance of the molded article.

When the propylene-based polymer is a copolymer of propylene and an α-olefin having from 4 to 12 carbon atoms, examples of the α-olefin having from 4 to 12 carbon atoms include linear or branched α-olefins such as 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, and 1-dodecene. Of these, 1-butene is preferred. Furthermore, the propylene-α-olefin copolymer may contain an olefin other than an α-olefin having from 4 to 12 carbon atoms, such as a small amount, for example, 10 mol% or less, of structural units derived from ethylene. On the other hand, from the viewpoint of improving the balance between the heat resistance and mechanical strength of the molded article, it is also preferable that the copolymer does not contain structural units derived from ethylene. The structural units derived from these α-olefins may be of one type or two or more types.

When the propylene-based polymer is a copolymer of propylene and an α-olefin having 4 to 12 carbon atoms, the proportion of structural units derived from propylene is preferably 60 mol% to 90 mol%. On the other hand, the proportion of structural units derived from an α-olefin having 4 to 12 carbon atoms is preferably 10 mol% to 40 mol% (the total amount of structural units derived from propylene and structural units derived from an α-olefin having 4 to 12 carbon atoms is taken as 100 mol%).

When the composition of the propylene-α-olefin copolymer is within the above range, the appearance, mechanical strength, and heat resistance of the molded article are good. In particular, the crystallization rate is probably slow, which extends the time that the resin composition can flow in the mold, resulting in a good appearance of the molded article.

The melting point (Tm) of the above-mentioned propylene-α-olefin copolymer as determined by DSC is typically 60°C or higher and 120°C or lower, and preferably 65°C or higher and 100°C or lower.

The polyolefin may be an ethylene-α-olefin-non-conjugated polyene copolymer. The copolymer is preferably a copolymer of ethylene, an α-olefin having from 3 to 12 carbon atoms, and a non-conjugated polyene, and more preferably a copolymer in which these are randomly copolymerized. Examples of the α-olefin include α-olefins having from 3 to 12 carbon atoms, such as linear or branched α-olefins having from 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 1-octene, 1-decene, and 1-dodecene. Examples of the non-conjugated polyene include cyclic or linear non-conjugated polyenes. Examples of cyclic non-conjugated polyenes include cyclopentene, cycloheptene, norbornene, 5-ethylidene-2-norbornene, dicyclopentadiene, 5-vinyl-2-norbornene, norbornadiene, methyltetrahydroindene, and tetracyclododecene. Examples of linear non-conjugated polyenes include 1,4-hexadiene, 7-methyl-1,6-octadiene, 4-ethylidene-8-methyl-1,7-nonadiene, and 4-ethylidene-1,7-undecadiene. Of these, 5-ethylidene-2-norbornene, dicyclopentadiene, and 5-vinyl-2-norbornene are preferred. The structural units derived from these non-conjugated polyenes may be of one type or two or more types.

2-2. Natural fibers (B)
Examples of natural fibers (B) include wood flour (processed by peeling wood and grinding it), wood fiber, bamboo flour, bamboo fiber, isolated cellulose fiber, wool, agricultural fiber, wood pulp (pulp made from wood, obtained by removing the bark from the trunk of a tree, chipping the material, and then subjecting it to mechanical, chemical, or combined treatment), other natural pulps, rayon, cotton, etc. Examples of agricultural fibers include wheat straw, rice straw, hemp, flax, kenaf, kapok, jute, ramie, sisal, henequen, corn fiber, coir, nut shells, and rice husks. Examples of wood pulp include bleached softwood kraft pulp (NBKP) and bleached hardwood kraft pulp (LBKP). Examples of other natural pulps include Manila hemp, paper mulberry, mitsumata, and gampi. Of these, wood flour, wood fiber, bamboo, bamboo fiber, cotton, and isolated cellulose fiber are preferred, and isolated cellulose fiber is more preferred from the viewpoint of suppressing variation in the mechanical strength of the molded body and improving the predictability of the strength of the obtained molded body.

The origin of the cellulose fibers is not particularly limited, and they may be cellulose fibers obtained from any material, such as wood, grass, pulp, and paper. Cellulose fibers obtained from trees may be cellulose fibers obtained from any woody raw material, including conifers and broad-leaved trees. Cellulose fibers obtained from grasses may be cellulose fibers obtained from non-woody raw materials, such as grasses, mallows, legumes, and palms. Cellulose fibers obtained from pulp may be cellulose fibers obtained from any pulp, such as cotton linter pulp obtained from the fibers around cotton seeds. Cellulose fibers obtained from paper may be cellulose fibers obtained from any paper, such as newspaper, cardboard, magazines, and fine paper. Of these, cellulose fibers obtained from trees or grasses are preferred because they are easily available and inexpensive, and cellulose fibers obtained from trees are more preferred.

In order to enhance the mechanical strength and impact resistance of the molded body, the cellulose fibers preferably have an average degree of polymerization of 50 or more and 2000 or less, and more preferably 100 or more and 1500 or less. The average degree of polymerization of cellulose fibers can be measured according to the reduced specific viscosity method using a copper ethylenediamine solution described in Verification Test (3) of the "Commentary on the Japanese Pharmacopoeia, 15th Edition (published by Hirokawa Shoten)."

The cellulose fibers used may be unmodified or unamorphized, or may be modified or amorphized. The modified cellulose fibers may be those obtained by reacting hydroxyl groups of cellulose with ether compounds, alkyl chlorides, alkyl acid anhydrides, alkyl acid chlorides, etc. The amorphized cellulose fibers may be those obtained by reducing the crystallinity of cellulose using known methods.

The above-mentioned cellulose fibers have hydroxyl groups, as well as polar functional groups such as hydroxyl groups, carboxyl groups, amino groups, and quaternary ammonium groups that have been introduced through modification.

Commercially available examples of the above cellulose fibers include the KC Flock GK series, a powdered cellulose manufactured by Nippon Paper Industries Co., Ltd. ("KC Flock" is a registered trademark of the company).

2-3. Compatibilizer (C)
The compatibilizer (C) enhances the compatibility between the thermoplastic resin (A) and the natural fibers (B). By enhancing the compatibility, the compatibilizer facilitates fine dispersion of the natural fibers (B), thereby improving the processability, heat resistance, mechanical strength, and appearance of the molded article.

When the amount of natural fiber (B) is high or when the surface area of the natural fiber (B) is large (when the natural fiber (B) is thin), the thermoplastic resin (A) and the natural fiber (B) may not be compatible with each other. In particular, in such cases, the effect of using the compatibilizer (C) to improve compatibility and increase the fine dispersion of the natural fiber (B) is remarkable.

The compatibilizer (C) includes a modified polyolefin (C1) or a petroleum resin (C2). According to the inventors' new findings, compatibilizers (C) that have polar functional groups such as oxygen atoms in their molecular chains, or cyclic structures such as styrene, are thought to have a high affinity for natural fibers (B) that have a cellulose skeleton, a cyclic structure containing oxygen atoms, and tend to localize on the surface of the natural fibers (B). Therefore, the use of these compatibilizers (C), which have good compatibility with the thermoplastic resin (A) and high affinity for the natural fibers (B), is thought to significantly enhance the fine dispersion of the natural fibers (B).

(1) Modified polyolefin (C1)
The modified polyolefin (C1) may be an unsaturated carboxylic acid-modified polyolefin, a styrene-modified polyolefin, or an air-oxidized polyolefin. These modified polyolefins (C1) can be obtained by modifying an unmodified polyolefin by a known method. The modified polyolefin (C1) may also be produced using a biomass-derived raw material.

(Polyolefin raw material)
The type of polyolefin (unmodified polyolefin) used as a raw material for the modified polyolefin is not particularly limited. Examples of unmodified polyolefins include ethylene, propylene, 1-butene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, trimethyl-1-butene, ethyl-1-pentene, 1-octene, methyl-1-pentene, and dimethyl-1-hexene. The unmodified α-olefin may be a homopolymer or copolymer of an α-olefin such as 1-decene, trimethyl-1-pentene, ethyl-1-hexene, methyl-1-ethylpentene, diethyl-1-butene, propyl-1-pentene, 1-decene, methyl-1-nonene, dimethyl-1-octene, trimethyl-1-heptene, ethyl-1-octene, methylethyl-1-heptene, diethyl-1-hexene, 1-dodecene, or 1-hexadodecene. These α-olefins may be selected depending on their compatibility with the thermoplastic resin (A). For example, when the thermoplastic resin (A) is a polyolefin (A-1), it is preferable that the unmodified α-olefin is the same type of resin as the polyolefin (A-1) (when the polyolefin (A-1) is polyethylene, the unmodified polyolefin is also polyethylene, and when the polyolefin (A-1) is polypropylene, the unmodified polyolefin is also polypropylene, etc.). For example, the unmodified polyolefin is preferably a polypropylene, particularly a propylene homopolymer, a propylene-ethylene random copolymer, or a propylene-1-butene random copolymer.

(Unsaturated Carboxylic Acid Modified Unmodified Polyolefin)
The unsaturated carboxylic acid used to modify the unmodified polyolefin may be an unsaturated compound having one or more carboxylic acid groups (unsaturated carboxylic acid in the narrow sense), or a derivative of an unsaturated carboxylic acid, such as an ester of an unsaturated carboxylic acid with an alkyl alcohol or an unsaturated compound having a carboxylic anhydride such as an anhydride of an unsaturated carboxylic acid. The unsaturated group in these unsaturated carboxylic acids may be a vinyl group, a vinylene group, an unsaturated cyclic hydrocarbon group, or the like. Examples of unsaturated carboxylic acids in the narrow sense include acrylic acid, methacrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, nadic acid, and endo-cis-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acid. Examples of derivatives of unsaturated carboxylic acids include acid anhydrides such as maleic anhydride and citraconic anhydride, as well as acid halides, amidates, imides, and esters of (narrowly defined) unsaturated carboxylic acids such as malenyl chloride, malenylimide, monomethyl maleate, and dimethyl maleate. The unsaturated carboxylic acid is preferably maleic acid, nadic acid, or an acid anhydride thereof, and more preferably maleic anhydride. These unsaturated carboxylic acids may be used alone or in combination of two or more.

When unmodified polyolefins are modified with these unsaturated carboxylic acids, organic peroxides are used as radical initiators. Examples of the organic peroxides include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-amyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, t-amyl peroxypivalate, t-hexyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-amyl peroxy-2-ethylhexanoate, t-butyl peroxyisobutyrate, 1,1-di(t-butyl) ... t-butylperoxy)-2-methylcyclohexane, 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-amylperoxy)cyclohexane, 2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane, t-amylperoxyisononanoate, t-hexylperoxyisopropyl monocarbonate, t-amylperoxynormaloctoate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-amylperoxyisopropyl hexanoate, t-butyl ... mylperoxyisopropyl monocarbonate, t-butylperoxyisopropyl monocarbonate, t-amylperoxy-2-ethylhexyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, t-butyl peroxyacetate, t-amyl peroxyacetate, 2,2-di-(t-butylperoxy)butane, t-butylperoxyisononanoate, t-amyl peroxybenzoate, t-butyl peroxybenzoate, n-butyl-4,4-di-(t-butylperoxy)valerate, methyl ethyl ketone peroxide, di(2-t-butylperoxyisopropyl)benzene, Examples of peroxyl groups include ethyl-3,3-di(t-butylperoxy)butyrate, di-t-hexyl peroxide, 1,3-di(2-t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-amyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3, t-amyl hydroperoxide, t-butyl hydroperoxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane. Of these, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, di-t-butyl peroxide, t-butylperoxyisopropyl monocarbonate, and t-butyl peroxybenzoate are preferred. These organic peroxide acids may be used alone or in combination of two or more.

The amount of organic peroxide used during modification can be 0.01 to 30 parts by mass, preferably 1 to 20 parts by mass, and more preferably 2 to 15 parts by mass, per 100 parts by mass of unmodified polyolefin.

(Acid-modified polyolefin resin composition)
In the resin composition, the unsaturated carboxylic acid-modified product is preferably a composition containing the unsaturated carboxylic acid-modified polyolefin and the unsaturated carboxylic acid (hereinafter also simply referred to as "acid-modified polyolefin resin composition"). In other words, the resin composition preferably contains the unsaturated carboxylic acid-modified polyolefin and the unsaturated carboxylic acid. The unsaturated carboxylic acid contained in the acid-modified polyolefin resin composition may be the same as the unsaturated carboxylic acid used to modify the unmodified polyolefin, or it may be a different unsaturated carboxylic acid.

In order to further improve the bending and tensile properties of the resulting molded article, the unsaturated carboxylic acid contained in the acid-modified polyolefin resin composition preferably has a non-polar group, and more preferably the non-polar group has a hydrocarbon group having from 1 to 30 carbon atoms.

Examples of the hydrocarbon group having 1 to 30 carbon atoms include linear or branched alkyl groups having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, including methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, neopentyl, and n-hexyl groups; linear or branched alkenyl groups having 2 to 30 carbon atoms, preferably 2 to 20 carbon atoms, including vinyl, allyl, and isopropenyl groups; linear or branched alkynyl groups having 2 to 30 carbon atoms, preferably 2 to 20 carbon atoms, including ethynyl and propargyl groups; cyclopropyl, cyclobutyl, and cyclopentyl groups. saturated cyclic hydrocarbon groups having from 3 to 30 carbon atoms, preferably from 3 to 20 carbon atoms, such as a cyclohexyl group, adamantyl group, etc.; unsaturated cyclic hydrocarbon groups having from 5 to 30 carbon atoms, such as a cyclopentadienyl group, an indenyl group, and a fluorenyl group; aryl groups having from 6 to 30 carbon atoms, preferably from 6 to 20 carbon atoms, such as a phenyl group, a benzyl group, a naphthyl group, a biphenyl group, a terphenyl group, a phenanthryl group, and anthracenyl group; and alkyl-substituted aryl groups having from 7 to 20 carbon atoms, such as a tolyl group, an isopropylphenyl group, a tert-butylphenyl group, a dimethylphenyl group, and a di-tert-butylphenyl group. Of these, preferred are groups having an aromatic ring, such as aryl groups having 6 to 30 carbon atoms, preferably 6 to 20 carbon atoms, including phenyl groups, benzyl groups, naphthyl groups, biphenyl groups, terphenyl groups, phenanthryl groups, and anthracenyl groups, as well as alkyl-substituted aryl groups including tolyl groups, isopropylphenyl groups, tert-butylphenyl groups, dimethylphenyl groups, and di-tert-butylphenyl groups.

The unsaturated carboxylic acid contained in the acid-modified polyolefin resin composition preferably has a molecular weight of 1,000 or less, more preferably 500 or less, and particularly preferably 300 or less. As such low-molecular-weight unsaturated carboxylic acids having a hydrocarbon group containing 1 to 30 carbon atoms, benzyl succinic acid and benzyl succinic anhydride are preferred. Benzyl succinic acid derivatives may be synthesized by known methods, such as the method described in Journal of Organic Chemistry, Vol. 21, p. 1473, 1956, or commercially available products may be purchased and used.

The amount of unsaturated carboxylic acid contained in the acid-modified polyolefin resin composition is preferably 0.005% by mass or more and 10% by mass or less, more preferably 0.01% by mass or more and 5% by mass or less, and even more preferably 0.02% by mass or more and 3% by mass or less, relative to the total mass of the acid-modified polyolefin resin composition.

The acid-modified polyolefin resin composition may be prepared by a method in which a portion of the unsaturated carboxylic acid is left unreacted when synthesizing an unsaturated carboxylic acid-modified product of an unmodified polyolefin (hereinafter, this preparation method is also referred to as the "single-step method"), or by adding an unsaturated carboxylic acid after synthesizing the unsaturated carboxylic acid-modified product (hereinafter, this preparation method is also referred to as the "two-step method"). The one-step method is preferred because it allows the acid-modified polyolefin composition to be obtained in a single step and is inexpensive. Furthermore, the one-step method can also produce benzyl succinic acid or benzyl succinic anhydride as a by-product when modifying an unmodified polyolefin with maleic anhydride, thereby obtaining an acid-modified polyolefin resin composition containing these by-products. On the other hand, the two-step method is preferred when the unsaturated carboxylic acid used in synthesizing the unsaturated carboxylic acid-modified product of an unmodified polyolefin is different from the unsaturated carboxylic acid contained in the acid-modified polyolefin resin composition, or when the control for regulating the homopolymerization of the unsaturated carboxylic acid becomes complicated.

When preparing an acid-modified polyolefin resin composition by the two-stage method, the unsaturated carboxylic acid-modified unmodified polyolefin and the unsaturated carboxylic acid are mixed using a Henschel mixer, Banbury mixer, V-blender, tumbler blender, ribbon blender, or the like, and then melt-kneaded at 160°C to 300°C, preferably 180°C to 250°C, using a single-screw extruder, multi-screw extruder, roll, kneader, or the like. During this mixing or melt-kneading, other additives may be added as needed. Note that when synthesizing the unsaturated carboxylic acid-modified unmodified polyolefin, the unsaturated carboxylic acid may be melt-kneaded in situ.

(Modified polyolefin wax)
The modified polyolefin (C1) may be a modified polyolefin wax. The modified polyolefin wax may be an unsaturated carboxylic acid-modified product, a styrene-modified product, a sulfonic acid-modified product, an air-oxidized product, or the like, of a polyolefin wax which is a homopolymer or copolymer of ethylene or an α-olefin having from 3 to 12 carbon atoms. These modified polyolefin waxes can be obtained by modifying an unmodified polyolefin wax by a known method.

The type of polyolefin wax (unmodified polyolefin wax) used as the raw material for modified polyolefin wax is not particularly limited, but preferred are ethylene homopolymers, propylene homopolymers, 4-methyl-1-pentene homopolymers, copolymers of ethylene and an α-olefin having from 3 to 12 carbon atoms, copolymers of propylene and ethylene or an α-olefin having from 4 to 12 carbon atoms, and copolymers of 4-methyl-1-pentene and another α-olefin. In the above copolymers, the monomer copolymerized with ethylene or propylene may be propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc., with propylene, 1-butene, 1-hexene, and 4-methyl-1-pentene being preferred.

(Raw material: polyethylene wax)
The unmodified polyolefin wax may be a polyethylene wax which is a homopolymer of ethylene or a copolymer of ethylene and an α-olefin having from 3 to 12 carbon atoms.

Examples of polyethylene wax, which is a homopolymer of ethylene, include high-density polyethylene wax, medium-density polyethylene wax, low-density polyethylene wax, and linear low-density polyethylene wax.

In polyethylene wax, which is a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms, the proportion of structural units derived from ethylene is preferably 91.0 mol% to 99.9 mol%, more preferably 93.0 mol% to 99.9 mol%, even more preferably 95.0 mol% to 99.9 mol%, and particularly preferably 95.0 mol% to 99.0 mol%. Meanwhile, the proportion of structural units derived from α-olefins having 3 or more carbon atoms is preferably 0.1 mol% to 9.0 mol%, more preferably 0.1 mol% to 7.0 mol%, even more preferably 0.1 mol% to 5.0 mol%, and particularly preferably 1.0 mol% to 5.0 mol% (the total amount of structural units derived from ethylene and structural units derived from α-olefins having 3 or more carbon atoms is taken as 100 mol%).

Examples of the α-olefins having 3 to 12 carbon atoms include linear or branched α-olefins such as propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, and 1-dodecene. Of these, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene are preferred, with α-olefins having 3 to 8 carbon atoms being more preferred, propylene and 1-butene being even more preferred, and 1-butene being particularly preferred. When ethylene is copolymerized with propylene or 1-butene, the addition of even a small amount of propylene or 1-butene likely effectively lowers the melting point and increases the crystallinity of the polyolefin wax, making the compatibilizer (C) harder and less sticky. Therefore, when such a compatibilizer (C) is used, the surface of the molded article is less likely to become sticky. The structural units derived from these α-olefins may be of one type, or two or more types.

In particular, when the thermoplastic resin (A) is polyethylene, using a modified polyethylene wax as the compatibilizer (C) improves the compatibility between the thermoplastic resin (A) and the compatibilizer (C), thereby improving the processability, heat resistance, mechanical strength, and appearance of the molded article.

(Polypropylene wax as raw material)
The unmodified polyolefin wax may be a polypropylene wax which is a homopolymer of propylene or a copolymer of propylene and ethylene or an α-olefin having from 4 to 12 carbon atoms.

These polypropylene waxes may be polypropylene waxes obtained by homopolymerizing propylene or copolymerizing it with other α-olefins in the presence of a stereospecific catalyst, or polypropylene waxes obtained by pyrolysis of high molecular weight polypropylene. Alternatively, polypropylene waxes may be obtained by solvent fractionation of polypropylene based on differences in solubility in solvents, or by molecular distillation to separate the waxes based on differences in boiling points.

When the polypropylene wax is a copolymer of propylene and ethylene, the proportion of structural units derived from propylene can be 60 mol% or more and 99.5 mol% or less, preferably 80 mol% or more and 99 mol% or less, more preferably 90 mol% or more and 98.5 mol% or less, and particularly preferably 95 mol% or more and 98 mol% or less (the total amount of structural units derived from propylene and structural units derived from ethylene is taken as 100 mol%). Using a propylene-based polymer with a high proportion of structural units derived from propylene results in good moldability, appearance, and heat resistance of the molded article.

When the polypropylene wax is a copolymer of propylene and an α-olefin having 4 to 12 carbon atoms, examples of the α-olefin having 4 to 12 carbon atoms include linear or branched α-olefins such as 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, and 1-dodecene. Of these, 1-butene is preferred. The structural units derived from these α-olefins may contain only one type, or two or more types.

When the propylene-based polymer is a copolymer of propylene and an α-olefin having from 4 to 12 carbon atoms, the proportion of structural units derived from propylene is preferably from 60 mol% to 90 mol%, more preferably from 65 mol% to 88 mol%, even more preferably from 70 mol% to 85 mol%, and particularly preferably from 75 mol% to 82 mol%. On the other hand, the proportion of structural units derived from an α-olefin having from 4 to 12 carbon atoms is preferably from 10 mol% to 40 mol%, more preferably from 12 mol% to 35 mol%, even more preferably from 15 mol% to 30 mol%, and particularly preferably from 18 mol% to 25 mol% (the total amount of structural units derived from propylene and structural units derived from an α-olefin having from 4 to 12 carbon atoms is taken as 100 mol%).

When the composition of the propylene-α-olefin copolymer is within the above range, the appearance, mechanical strength, and heat resistance of the molded article are good. In particular, the appearance of the molded article is good, probably because the crystallization rate is slow, which allows the resin composition to flow through the mold for a longer period of time. Furthermore, when the composition of the propylene-α-olefin copolymer is within the above range, the heat resistance and mechanical strength of the injected article are also improved.

In particular, when the thermoplastic resin (A) is polypropylene, using a modified polypropylene wax as the compatibilizer (C) improves the compatibility between the thermoplastic resin (A) and the compatibilizer (C), thereby improving the processability, heat resistance, mechanical strength, and appearance of the molded article.

(Poly 4-methyl-1-pentene wax as raw material)
The unmodified polyolefin wax may be a poly(4-methyl-1-pentene) wax which is a homopolymer of 4-methyl-1-pentene or a copolymer of 4-methyl-1-pentene and another α-olefin.

Poly 4-methyl-1-pentene wax can be obtained by pyrolyzing the 4-methyl-1-pentene polymer described in WO 2011/055803, or the 4-methyl-1-pentene polymer (B-1) and 4-methyl-1-pentene polymer (B-2) described in JP 2005-028187 A.

(Method for producing raw material polyolefin wax)
These unmodified polyolefin waxes may be synthesized by polymerization of raw materials, or may be produced by thermal decomposition of a high molecular weight (co)polymer. Thermal decomposition can be carried out at 300°C to 450°C for 5 minutes to 10 hours. The unmodified polyolefin wax produced by thermal decomposition under these conditions contains unsaturated terminals. Furthermore, a vinylidene group count of 0.5 to 5 per 1,000 carbon atoms as measured by ^1H -NMR is preferred because it facilitates compatibility of the compatibilizer (C) with the natural fibers (B). Alternatively, these unmodified polyolefin waxes may be obtained by solvent fractionation of a high molecular weight (co)polymer based on differences in solubility in the solvent, or by molecular distillation to separate the waxes based on differences in boiling points.

Unmodified polyolefin wax can be synthesized by polymerizing raw materials using known methods, such as polymerization using a Ziegler-Natta catalyst or a metallocene catalyst.

For example, methods that can be used include suspension polymerization, in which the raw material monomers or their polymers are suspended as particles in an inert hydrocarbon medium such as hexane and polymerized; gas-phase polymerization, in which polymerization is carried out without using a solvent; and solution polymerization, in which the raw material is polymerized in a molten state in an inert hydrocarbon medium. Of these, solution polymerization is preferred because it is inexpensive and has good quality. Polymerization can be carried out using either a batch method or a continuous method. Polymerization can also be carried out in two or more stages with different reaction conditions.

Examples of inert hydrocarbon media used in suspension polymerization and solution polymerization include aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, octane, decane, dodecane, and kerosene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; aromatic hydrocarbons such as benzene, toluene, and xylene; and halogenated hydrocarbons such as ethylene chloride, chlorobenzene, and dichloromethane. These inert hydrocarbon media may be used alone or in combination of two or more. It is also possible to use a so-called bulk polymerization method in which the α-olefin itself is used as the solvent.

The catalyst is preferably a metallocene catalyst. Examples of the metallocene catalyst include:
(a) a metallocene compound of a transition metal selected from Group 4 of the periodic table;
(b) (b-1) an organoaluminum oxy compound, (b-2) a compound that reacts with the metallocene compound (a) to form an ion pair (hereinafter also referred to simply as "ionizing ionic compound"), or (b-3) an organoaluminum compound;
(See JP-A-08-239414 and WO 2007/114102).

(a) Examples of metallocene compounds (a) of transition metals selected from Group 4 of the periodic table include the metallocene compounds described in JP-A-08-239414 and WO 2007/114102. Of these, bis(n-butylcyclopentadienyl)zirconium dichloride and bis(n-butylcyclopentadienyl)zirconium dimethyl are preferred.

(b-1) As the organoaluminum oxy compound, known aluminoxanes, such as the organoaluminum oxy compounds described in JP-A-08-239414 and WO 2007/114102, can be used. Of these, methylaluminoxane and modified methylaluminoxane (MMAO) prepared using trimethylaluminum and triisobutylaluminum are preferred because they are commercially available and therefore easily available.

(b-2) Examples of ionizing ionic compounds include those described in JP-A-08-239414 and WO 2007/114102. Of these, triphenylcarbenium tetrakis(pentafluorophenyl)borate and N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate are preferred because they are commercially available and therefore easily available, and because they facilitate increased polymerization activity.

(b-3) Examples of organoaluminum compounds include those described in WO 2007/114102. Of these, trimethylaluminum, triethylaluminum, and triisobutylaluminum are preferred because they are commercially available and therefore easily available, and triisobutylaluminum is more preferred because it is easy to handle.

When combining compounds (b-1) to (b-3), the combination of triisobutylaluminum and triphenylcarbenium tetrakis(pentafluorophenyl)borate and the combination of triisobutylaluminum and N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate are preferred because they can significantly improve polymerization activity.

When polymerizing monomers using the above metallocene catalyst, the content of each component can be set as follows:

(1) (a) The metallocene compound is used in an amount of ^10-9 mol or more and ^10-1 mol or less, preferably ^10-8 mol or more and ^10-2 mol or less per liter of reaction volume. (2) (b-1) The organoaluminum oxy compound is used in an amount such that the molar ratio [Al/M] of the aluminum atom (Al) in the compound (b-1) to the total transition metal atoms (M) in the metallocene compound (a) is 0.01 or more and 5000 or less, preferably 0.05 or more and 2000 or less. (3) (b-2) The ionic compound is used in an amount such that the molar ratio [(b-2)/M] of the compound (b-2) to the total transition metal atoms (M) in the metallocene compound (a) is 1 or more and 10 or less, preferably 1 or more and 5 or less. (4) (b-3) The organoaluminum compound is used in an amount such that the molar ratio of the compound (b-3) to the total transition metal atoms (M) in the metallocene compound (a) [(b-3)/M] is 0.01 or more and 50,000 or less, preferably 0.05 or more and 10,000 or less.

The polymerization temperature at this time should be between 10°C and 200°C, preferably between 60°C and 180°C, and more preferably between 75°C and 170°C. The polymerization pressure can be between atmospheric pressure and 7.8 MPa-G (G is gauge pressure), and preferably between atmospheric pressure and 4.9 MPa-G.

During polymerization, the raw material monomers (ethylene or α-olefin) are supplied to the polymerization system in amounts and proportions that will produce an unmodified polyolefin wax with the composition described above. A molecular weight regulator such as hydrogen may also be added during polymerization.

The polymerization liquid obtained by polymerizing the raw materials in this way can be treated using conventional methods to obtain unmodified polyolefin wax.

The polymer obtained by the above method may also be further purified. Purification can be carried out by degassing under vacuum at a temperature above the melting point, dissolving the polymer in a solvent such as toluene, xylene, hexane, or heptane, then adding a polar solvent such as methanol or acetone and filtering to remove low molecular weight fractions, or dissolving the entire amount in a solvent and then precipitating it at a specific temperature to remove high or low molecular weight fractions.

The number average molecular weight (Mn) and intrinsic viscosity [η] of unmodified polyolefin wax tend to decrease when the polymerization temperature or hydrogen concentration is increased during polymerization, and can be controlled within the above ranges. Alternatively, they can be adjusted by the amount of organoaluminum oxy-compound or ionizing ionic compound used as a co-catalyst. Furthermore, they can also be adjusted by purification after polymerization.

The content of structural units derived from ethylene and each α-olefin can be controlled by adjusting the amount blended during polymerization, as well as by the type of catalyst and polymerization temperature.

The Mw/Mn of unmodified polyolefin wax can be controlled by the type of catalyst and polymerization temperature. Ziegler-Natta catalysts and metallocene catalysts are generally used for polymerization, but to achieve an Mw/Mn within the desired range, it is preferable to use a metallocene catalyst. It can also be achieved within the desired range by solvent fractionation, which separates waxes based on differences in solubility in solvents, or by refining them using methods such as distillation.

The softening point of unmodified polyolefin wax can be adjusted by the composition of ethylene and α-olefin. For example, in the case of a copolymer of ethylene and α-olefin, increasing the α-olefin content tends to lower the softening point. It can also be controlled by the type of catalyst and polymerization temperature. It can also be adjusted by purification after polymerization.

The density of unmodified polyolefin wax can be adjusted by the composition of ethylene and α-olefin, as well as the polymerization temperature or hydrogen concentration during polymerization.

(Modified polyolefin wax, which is a graft modified product of unmodified polyolefin wax)
Graft-modified unmodified polyolefin waxes can be obtained by graft-modifying unmodified polyolefin waxes with unsaturated carboxylic acids, styrenes, sulfonates, or mixtures thereof. These graft modifications can be carried out by known methods. For example, unmodified polyolefin waxes can be obtained by melt-kneading unmodified polyolefin waxes with unsaturated carboxylic acids, styrenes, or sulfonates in the presence of a polymerization initiator such as an organic peroxide, or by kneading a solution of raw material unmodified polyolefin waxes and unsaturated carboxylic acids, styrenes, or sulfonates in an organic solvent in the presence of a polymerization initiator such as an organic peroxide.

Melt mixing can be carried out using an autoclave, Henschel mixer, V-blender, tumbler blender, ribbon blender, single-screw extruder, multi-screw extruder, kneader, Banbury mixer, etc. Of these, from the perspective of dispersing each component more uniformly and allowing for efficient reaction, it is preferable to use a device such as an autoclave that is capable of batch-type melt mixing, which allows for easy adjustment of residence time and allows for a long residence time.

Examples of unsaturated carboxylic acids used for graft modification include acrylic esters including methyl acrylate, ethyl acrylate, butyl acrylate, sec-butyl acrylate, isobutyl acrylate, propyl acrylate, isopropyl acrylate, 2-octyl acrylate, dodecyl acrylate, stearyl acrylate, hexyl acrylate, isohexyl acrylate, phenyl acrylate, 2-chlorophenyl acrylate, diethylaminoethyl acrylate, 3-methoxybutyl acrylate, diethylene glycol ethoxylate acrylate, and 2,2,2-trifluoroethyl acrylate; methyl methacrylate, ethyl methacrylate, butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, propyl methacrylate, isopropyl methacrylate, 2-octyl methacrylate, dodecyl methacrylate, stearyl methacrylate; methacrylic acid esters such as stearyl methacrylate, hexyl methacrylate, decyl methacrylate, phenyl methacrylate, 2-chlorohexyl methacrylate, diethylaminoethyl methacrylate, 2-hexylethyl methacrylate, and 2,2,2-trifluoroethyl methacrylate; maleic acid esters such as ethyl maleate, propyl maleate, butyl maleate, diethyl maleate, dipropyl maleate, and dibutyl maleate; fumaric acid esters such as ethyl fumarate, butyl fumarate, and dibutyl fumarate; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, crotonic acid, nadic acid, and methylhexahydrophthalic acid; and anhydrides of unsaturated carboxylic acids such as maleic anhydride, itaconic anhydride, citraconic anhydride, allylsuccinic anhydride, glutaconic anhydride, and nadic anhydride. Of these, maleic anhydride is preferred because it has a relatively high reactivity with unmodified polyolefin wax, is less susceptible to major structural changes due to polymerization, and tends to have a stable basic structure. Furthermore, due to the above properties of maleic anhydride, the maleic anhydride-modified polyolefin wax remains stable even in the high-temperature environment during molding and is less likely to lose its effect on the surface of the natural fiber (B). As a result, it is believed that molded articles with excellent appearance, heat resistance, processability, and mechanical strength can be obtained.

The acid value (JIS K 2501 (2003)) of the modified polyolefin wax grafted with an unsaturated carboxylic acid is preferably 1 mgKOH/g or more and 100 mgKOH/g or less, more preferably 20 mgKOH/g or more and 90 mgKOH/g or less, and even more preferably 30 mgKOH/g or more and 87 mgKOH/g or less.

When the acid value of the modified polyolefin wax grafted with an unsaturated carboxylic acid is within the above-mentioned range, the appearance, processability, heat resistance, and mechanical strength of the molded article are improved. This is thought to be because the affinity of the compatibilizer (C) to the natural fiber (B) is sufficiently increased, while the compatibility of the compatibilizer (C) with the thermoplastic resin (A) is sufficiently maintained, thereby sufficiently increasing the compatibility between the thermoplastic resin (A) and the natural fiber (B), improving the uniformity of the entire system and improving the dispersibility of the natural fiber (B). In particular, the above effects are fully achieved even if the modified polyolefin wax grafted with an unsaturated carboxylic acid has a low molecular weight.

In particular, when emphasis is placed on the processability and appearance of the molded product, the acid value of the modified polyolefin wax grafted with an unsaturated carboxylic acid is preferably 1 mgKOH/g or more and 55 mgKOH/g or less. The acid value is more preferably 20 mgKOH/g or more, even more preferably 30 mgKOH/g or more, and particularly preferably 42 mgKOH/g or more. The acid value is more preferably 50 mgKOH/g or less, even more preferably 48 mgKOH/g or less, and particularly preferably 46 mgKOH/g or less.

On the other hand, when emphasis is placed on the heat resistance and mechanical strength of the molded product, the acid value of the modified polyolefin wax grafted with an unsaturated carboxylic acid is preferably 40 mgKOH/g or more and 100 mgKOH/g or less, more preferably 50 mgKOH/g or more and 100 mgKOH/g or less, even more preferably 60 mgKOH/g or more and 100 mgKOH/g or less, even more preferably 60 mgKOH/g or more and 95 mgKOH/g or less, even more preferably 60 mgKOH/g or more and 90 mgKOH/g or less, and particularly preferably 80 mgKOH/g or more and 90 mgKOH/g or less.

Examples of styrenes used for graft modification include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, p-chlorostyrene, m-chlorostyrene, and p-chloromethylstyrene.

The content of styrenes in the modified polyolefin wax graft-modified with styrenes is preferably 1 part by mass or more and 500 parts by mass or less, more preferably 5 parts by mass or more and 200 parts by mass or less, even more preferably 20 parts by mass or more and 160 parts by mass or less, and particularly preferably 22 parts by mass or more and 30 parts by mass or less, per 100 parts by mass of the modified polyolefin wax. When the content of styrenes is within the above range, the compatibility between the modified polyolefin wax and the natural fibers (B) is improved, and excessive interactions that cause viscosity increases and the like are suppressed, thereby improving the processability, appearance, heat resistance, and mechanical strength of the molded body.

When the graft-modified unmodified polyolefin wax is graft-modified with both an unsaturated carboxylic acid and a styrene, the graft ratio of the unsaturated carboxylic acid to the styrene, "(unsaturated carboxylic acid)/(styrene)," is preferably 0.01 or more and 1 or less, more preferably 0.03 or more and 0.8 or less, and even more preferably 0.05 or more and 0.6 or less. By setting these graft ratios to 0.01 or more, the unsaturated carboxylic acid can be allowed to sufficiently interact with the surface of the natural fiber (B), thereby sufficiently enhancing the impact resistance of the molded article. By setting these graft ratios to 1 or less, the melt viscosity of the graft-modified unmodified polyolefin wax can be appropriately suppressed, making production easier.

The content of styrenes in the modified polyolefin wax graft-modified with sulfonate styrenes is preferably 0.1 mmol to 100 mmol, and more preferably 5 mmol to 50 mmol, per 1 g of modified polyolefin wax. When the amount of modification with sulfonate is within the above range, the dispersibility of the natural fibers (B) is improved, and the mechanical strength of the molded body is likely to be improved.

The graft-modified modified polyolefin wax may be a commercially available product. Examples of commercially available products include Diakarna PA30 (Diakarna is a registered trademark of Mitsubishi Chemical Corporation), Hiwax acid-treated type 2203A (Mitsui Chemicals, Inc.), and oxidized paraffin (Nippon Seiro Co., Ltd.).

(Modified polyolefin wax, an air oxidation product of unmodified polyolefin wax)
The air oxidation of unmodified polyolefin wax can be obtained by contacting the raw material unmodified polyolefin wax with oxygen or an oxygen-containing gas while stirring the raw material unmodified polyolefin wax in a molten state at a temperature of 130°C or higher and 200°C or lower, preferably 140°C or higher and 170°C or lower.

The oxygen or oxygen-containing gas may be pure oxygen (oxygen obtained by ordinary liquid air fractional distillation or water electrolysis, and may contain other components at impurity levels), or it may be a mixture of pure oxygen and other gases (such as air or ozone).

The unmodified polyolefin wax is preferably contacted with oxygen or an oxygen-containing gas by continuously supplying the oxygen-containing gas from the bottom of a reactor containing molten unmodified polyolefin wax to bring the unmodified polyolefin wax into contact with the gas. In this case, the oxygen-containing gas is preferably supplied so that 1.0 NL or more and 8.0 NL or less of oxygen is supplied per minute per 1 kg of unmodified polyolefin wax.

The air oxidation acid value (JIS K 5902 (2006)) of the polyolefin wax obtained in this manner is preferably 1 mgKOH/g or more and 100 mgKOH/g or less, more preferably 20 mgKOH/g or more and 90 mgKOH/g or less, and even more preferably 30 mgKOH/g or more and 87 mgKOH/g or less.

When the acid value of the air-oxidized polyolefin wax is within the above-mentioned range, the appearance, processability, heat resistance, and mechanical strength of the molded article are improved. This is thought to be because the affinity of the compatibilizer (C) to the natural fibers (B) is sufficiently increased, while the compatibility of the compatibilizer (C) with the thermoplastic resin (A) is sufficiently maintained, thereby sufficiently increasing the compatibility between the thermoplastic resin (A) and the natural fibers (B), improving the uniformity of the entire system and improving the dispersibility of the natural fibers (B). In particular, the above effects are fully achieved even if the air-oxidized polyolefin wax has a low molecular weight.

In particular, when emphasis is placed on the processability and appearance of the molded product, the acid value of the air oxidation of the polyolefin wax is preferably 1 mgKOH/g or more and 55 mgKOH/g or less. The acid value is more preferably 20 mgKOH/g or more, even more preferably 30 mgKOH/g or more, and particularly preferably 42 mgKOH/g or more. The acid value is more preferably 50 mgKOH/g or less, even more preferably 48 mgKOH/g or less, and particularly preferably 46 mgKOH/g or less.

On the other hand, when emphasis is placed on the heat resistance and mechanical strength of the molded product, the air oxide acid value of the polyolefin wax is preferably 40 mgKOH/g or more and 100 mgKOH/g or less, more preferably 50 mgKOH/g or more and 100 mgKOH/g or less, even more preferably 60 mgKOH/g or more and 100 mgKOH/g or less, even more preferably 60 mgKOH/g or more and 95 mgKOH/g or less, even more preferably 60 mgKOH/g or more and 90 mgKOH/g or less, and particularly preferably 80 mgKOH/g or more and 90 mgKOH/g or less.

(Physical properties of modified polyolefin wax)
The modified polyolefin wax preferably satisfies one or more of the following requirements (i) to (iv), and more preferably satisfies all of them:

(i) The polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is 300 to 20,000. The number average molecular weight (Mn) is preferably 500 to 18,000, more preferably 1,000 to 12,000, even more preferably 1,500 to 12,000, still more preferably 3,700 to 12,000, still more preferably 6,000 to 12,000, and particularly preferably 8,000 to 10,000. When the number average molecular weight (Mn) is within the above range, the dispersibility of the natural fiber (B) in the resin composition can be improved, and the appearance, heat resistance, and mechanical strength of the molded body can be further improved. Furthermore, the processability and kneadability of the resin composition are also improved.

(ii) The softening point, measured in accordance with JIS K 2207 (2006), is 70°C or higher and 170°C or lower. The softening point is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 145°C or lower. The softening point is preferably 80°C or higher, more preferably 90°C or higher, even more preferably 95°C or higher, and particularly preferably 105°C or higher. When the softening point is within the above range, the appearance, processability, heat resistance, and mechanical strength of the molded product are further improved.

(iii) The density measured by the density gradient tube method is 830 kg/m ³ or more and 1200 kg/m ³ or less. The density is preferably 860 kg/m ³ or more and 1100 kg/m ³ or less, more preferably 890 kg/m ³ or more and 1000 kg/m ³ or less, even more preferably 895 kg/m ³ or more and 960 kg/m ³ or less, and particularly preferably 895 kg/m ³ or more and 935 kg/m ³ or less. When the density is within the above range, the dispersibility of the natural fiber (B) in the resin composition can be improved, and the appearance, heat resistance, and mechanical strength of the molded body can be further improved. In addition, the processability and kneadability of the resin composition are also improved. Although the reason for this is not clear, the density of the natural fiber (B) is generally 1000 kg/m ³ or more. In contrast, it is thought that by using a compatibilizer (C) with a lower density, when the compatibilizer (C) is localized on the surface of the natural fibers (B), the surface tension of the surface of the natural fibers (B) is reduced, thereby reducing the cohesive force of the natural fibers (B).

The difference between the density of the thermoplastic resin (A) and the density of the compatibilizer (C) is preferably less than 50 kg/ ^m3 , more preferably less than 30 kg/ ^m3 , and even more preferably less than 15 kg/ ^m3 . When the density difference is within the above range, the appearance, processability, heat resistance, and mechanical strength of the molded body are further improved. The reason for this is unclear, but it is thought that substances with similar densities tend to be easily mixed with each other. That is, it is thought that increasing the compatibility between the thermoplastic resin (A) and the compatibilizer (C) can improve the dispersibility of the natural fibers (B) coated with the compatibilizer (C) in the thermoplastic resin (A). Furthermore, when the density difference is within the above range, bleeding out of the compatibilizer (C) from the thermoplastic resin (A) is suppressed, which is thought to further improve the appearance, heat resistance, and mechanical strength of the molded body.

(iv) The ratio of weight average molecular weight to number average molecular weight (Mw/Mn), as measured by gel permeation chromatography (GPC), is 7.0 or less. Mw/Mn is preferably 5.0 or less, and more preferably 3.0 or less. When Mw/Mn is within the above range, there is less low molecular weight component that causes a decrease in physical properties, further improving the appearance, heat resistance, and mechanical strength of the molded product.

When two or more modified polyolefin waxes are used in combination as the compatibilizer (C), if the melting points and softening points of the modified polyolefin waxes used in combination are different, the processability of the resin composition and the mechanical strength of the molded product are likely to be improved.

When two or more types of modified polyolefin waxes are used in combination, the difference in softening point between the modified polyolefin wax (CWH) with the highest softening point and the modified polyolefin wax (CWL) with the lowest softening point is preferably 5°C or more, more preferably 10°C or more, even more preferably 20°C or more, even more preferably 30°C or more, and particularly preferably 40°C or more.

When the difference between the softening points of the modified polyolefin wax (CWH) and the modified polyolefin wax (CWL) is within the above range, the molded product has improved processability and mechanical strength. It also enables reduced torque and suppression of shear heat generation when using an extruder. While the reason for this is unclear, it is believed that the earlier melting of the modified polyethylene wax (CWL), which has a lower softening point, in the system improves the dispersion of the natural fiber (B) in the thermoplastic resin (A) and effectively reduces the torque of the extruder. Furthermore, it is believed that the molten modified polyethylene wax (CWL) suppresses shear heat generation in the system, preventing scorching of the natural fiber (B). Meanwhile, the melting of the modified polyolefin wax (CWH), which has a higher softening point, after the dispersion of the natural fiber (B) is improved, increases the contact efficiency between the modified polyolefin wax (CWH) and the natural fiber (B), enhancing the modification effect of the modified polyolefin wax (CWH) on the natural fiber (B). These effects are thought to improve the processability of the resin composition while also effectively improving its mechanical properties.

The softening point of the modified polyolefin wax (CWH) with the highest softening point is preferably 100°C or higher and 180°C or lower, and more preferably 110°C or higher and 175°C or lower. The softening point of the modified polyolefin wax (CWL) with the lowest softening point is preferably 80°C or higher and 150°C or lower, and more preferably 90°C or higher and 145°C or lower.

Furthermore, the melting point of the modified polyolefin wax (CWH) with the highest softening point is preferably 90°C or higher and 170°C or lower, and more preferably 100°C or higher and 165°C or lower. Furthermore, the melting point of the modified polyolefin wax (CWL) with the lowest softening point is preferably 70°C or higher and 140°C or lower, and more preferably 80°C or higher and 135°C or lower.

In this case, the greater the amount of modified polyolefin wax (CWL) with the lowest softening point added, the more likely it is that the dispersibility of the natural fibers (B) will increase. Specifically, the mass ratio (CWH)/(CWL) of the modified polyolefin wax (CWH) to the modified polyolefin wax (CWL) is preferably 1/200 or more and 1/1 or less, more preferably 1/50 or more and 1/1.1 or less, even more preferably 1/20 or more and 1/1.3 or less, and particularly preferably 1/10 or more and 1/1.5 or less.

The modified polyolefin wax (CWH) with the highest softening point is preferably a modified polyolefin wax graft-modified with an unsaturated carboxylic acid.

Furthermore, the acid value of the modified polyolefin wax (CWH) with the highest softening point is preferably 40 mgKOH/g or more and 100 mgKOH/g or less, more preferably 50 mgKOH/g or more and 100 mgKOH/g or less, even more preferably 60 mgKOH/g or more and 100 mgKOH/g or less, even more preferably 60 mgKOH/g or more and 95 mgKOH/g or less, even more preferably 60 mgKOH/g or more and 90 mgKOH/g or less, and particularly preferably 80 mgKOH/g or more and 90 mgKOH/g or less. When the acid value of the modified polyolefin wax (CWH) with the highest softening point is within the above range, the heat resistance and mechanical strength of the molded body are further improved.

The acid value of the modified polyolefin wax (CWL) with the lowest softening point is preferably 90 mgKOH/g or less, and more preferably 65 mgKOH/g or less. There is no particular lower limit for the acid value of the modified polyolefin wax (CWL) with the lowest softening point, but it is preferably 15 mgKOH/g or more. When the acid value of the modified polyolefin wax (CWL) with the lowest softening point is within the above range, the heat resistance of the molded body can be improved (specifically, the deflection temperature under load and softening point can be increased) without reducing the processability of the resin composition. The reason for this is not clear, but it is thought that this is because the modified polyolefin wax (CWL) is unlikely to detach from the surface of the natural fibers (B) even when the molded body is heated to a temperature above its softening point, and therefore the molecular mobility of the natural fibers (B) is unlikely to increase even when heated.

(2) Petroleum resin (C2)
The petroleum resin (C2) can be an aliphatic petroleum resin made primarily from the C5 fraction of tar naphtha, an aromatic petroleum resin made primarily from the C9 fraction, or a copolymer petroleum resin thereof. Examples of the petroleum resin (C2) include C5 petroleum resins (resins obtained by polymerizing the C5 fraction of naphtha cracked oil), C9 petroleum resins (resins obtained by polymerizing the C9 fraction of naphtha cracked oil), and C5C9 copolymer petroleum resins (resins obtained by copolymerizing the C5 fraction and C9 fraction of naphtha cracked oil). When the compatibilizer (C) is a petroleum resin (C2), the compatibilizer (C) can be easily mixed with other components.

Furthermore, petroleum resin (C2) may be a coumarone-indene resin containing styrenes, indenes, coumarone, and other dicyclopentadiene from tar naphtha fractions; an alkylphenol resin typified by the condensation product of p-tert-butylphenol and acetylene; or a xylene resin obtained by reacting o-xylene, p-xylene, or m-xylene with formalin. Furthermore, petroleum resin (C2) may also be produced using raw materials derived from biomass.

(3) Other compatibilizers (C3)
Furthermore, as the compatibilizer (C), a rosin-based resin and a terpene-based resin may be used.

Examples of the rosin-based resin include natural rosin, polymerized rosin, and rosin derivatives such as phenol-modified rosin, its esterified products, and hydrogenated products. Note that other compatibilizers (C3) may also be produced using biomass-derived raw materials.

2-4. Processing aids (D)
The processing aid (D) increases the crystallinity of the thermoplastic resin (A) and improves the processability of the resin composition.

The processing aid (D) can be a polyolefin wax, which is a material used to synthesize the compatibilizer (C). For example, when the thermoplastic resin (A) is a polyolefin (A-1), it is preferable that the processing aid (D) be a resin of a different type from the polyolefin (A-1) (when the polyolefin (A-1) is polyethylene, the processing aid (D) is polypropylene wax, etc., and when the polyolefin (A-1) is polypropylene, the processing aid (D) is polyethylene wax, etc.). For example, polyethylene wax is preferred as the processing aid (D). The processing aid (D) may also be produced using raw materials derived from biomass.

2-5. Other Components The resin composition may contain, as necessary, various additives known in the art, such as antioxidants, weather stabilizers, ultraviolet absorbers, antistatic agents, antislip agents, antiblocking agents, antifogging agents, crystal nucleating agents, lubricants, pigments, dyes, antioxidants, hydrochloric acid absorbers, inorganic or organic fillers, organic or inorganic foaming agents, crosslinking agents, crosslinking aids, adhesives, softeners, and flame retardants. The content of the various additives described above is preferably 5% by mass or less, and more preferably 3% by mass or less, relative to the total mass of the resin composition.

2-6. Amount of Each Component The amount of natural fiber (B) relative to the total mass of the resin composition is preferably 5% by mass to 50% by mass, more preferably 8% by mass to 45% by mass, even more preferably 10% by mass to 40% by mass, and most preferably 25% by mass to 35% by mass. By appropriately adjusting the amount of natural fiber (B), the amount of natural fiber (B) exposed from the surface of the tactile region can be adjusted to adjust the dynamic and static friction coefficients, making the tactile feel closer to that of paper.

Furthermore, the amount of thermoplastic resin (A) relative to the total mass of the resin composition is preferably 20% by mass or more and 90% by mass or less, more preferably 30% by mass or more and 85% by mass or less, even more preferably 40% by mass or more and 80% by mass or less, and most preferably 55% by mass or more and 75% by mass or less. The greater the amount of thermoplastic resin (A), the higher the mechanical strength and heat resistance of the molded body can be. The smaller the amount of thermoplastic resin (A), the easier it is to expose the natural fibers (B) from the surface of the tactile region, making it easier to achieve a tactile feel closer to that of paper.

Furthermore, the amount of compatibilizer (C) relative to the total mass of the resin composition is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 8% by mass or less, and even more preferably 1% by mass or more and 5% by mass or less. The greater the amount of compatibilizer (C), the better the processability of the resin composition, the appearance of the molded product, the heat resistance, impact resistance, and abrasion resistance. On the other hand, by keeping the amount of compatibilizer (C) within an appropriate range, it is possible to adjust the kneadability and heat resistance stability within appropriate ranges, reduce the generation of smoke and odors during molding processing, and further suppress the occurrence of die buildup (burnt resin, low-molecular-weight components, and additives that accumulate near the exit of the molding machine) and scorching.

Furthermore, the amount of processing aid (D) relative to the total mass of the resin composition is preferably 0.1% by mass or more and 15% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and even more preferably 1% by mass or more and 8% by mass or less.

2-7. Method for Producing Resin Composition The method for producing the thermoplastic resin is not particularly limited. The resin composition can be produced by a known method using equipment known in the art. Specifically, the above-mentioned materials may be kneaded while being heated. Kneading can be carried out using known devices such as a single-screw extruder, a single-screw reciprocating kneading extruder, a twin-screw kneading extruder, a multi-screw kneading extruder, or an MF type mixer/melter.

3. Method for Producing Molded Article The molded article having the above-described tactile region can be produced by the steps of molding the above-described resin composition and treating the surface of the molded resin composition.

3-1. Molding of resin composition (first step)
In this step, the resin composition is molded into the shape of a molded body. The molding method is not particularly limited, and the resin composition may be molded using an additive manufacturing device (3D printer), or the resin composition may be molded into a film and then molded into a film. Alternatively, the resin composition may be directly molded using a known thermoforming method such as injection molding, extrusion molding, blow molding, extrusion blow molding, injection blow molding, press molding, and vacuum molding. Of these, it is preferable to mold the resin composition using an additive manufacturing device, as this allows for easy molding of complex shapes. Furthermore, from the viewpoint of easily controlling the surface feel, it is preferable to mold the resin composition in the molding of the resin composition (first step) so that unevenness is provided on the surface of the molded resin composition. In molding the resin composition (first step), the method of molding the resin composition so that irregularities are provided on the surface of the molded resin composition is not particularly limited, and when molding the resin composition using a manufacturing device for molding, irregularities may be provided by layering the resin composition, or the irregularities may be provided by injection molding or blow molding using a molding die with a geometric grain or leather grain on the cavity surface. From the viewpoint of further facilitating control of the surface feel, the surface irregularities provided in the molding step of the resin composition (first step) are preferably regular irregularities, and more preferably regular linear irregularities.

The additive modeling method is not particularly limited, and known methods can be used, such as a method in which filament-like resin composition melted by heating from an electric heater is ejected from a nozzle and arranged in the shape of each layer, followed by lamination (material extrusion method). The configuration of the additive modeling manufacturing device is not particularly limited, and can be a device having a table as a modeling platform, a cylinder for storing the resin composition, a heating means such as an electric heater for melting the resin composition in the cylinder, a nozzle for ejecting the molten resin composition, and a control unit (computer) for controlling these. Then, using slicer software, the shape to be modeled can be divided into multiple two-dimensional data representing the shapes of each layer, and the nozzle can be scanned in two dimensions to eject the molten resin composition from the nozzle at positions corresponding to the two-dimensional data.

During molding, the resin composition is melted and deformed. There are no particular limitations on the melting temperature, but it is preferable to set the temperature at a temperature 10°C or higher but 150°C higher than the melting point (Tm) or glass transition temperature (Tg) of the resin with the highest melting point (Tm) or glass transition temperature (Tg) among the resins contained in the resin composition. There are no particular limitations on the heating method.

At this time, the molten resin composition may be kneaded. Kneading reduces unevenness in the resin composition and prevents deformation of the molded product caused by unevenness (due to variations in the elastic modulus from part to part). Kneading is particularly effective in reducing unevenness when the resin composition contains a filler (such as glass fiber). Kneading can be performed by stirring, for example, with a screw.

3-2. Surface treatment (second step)
Next, the surface of the molded resin composition is treated to form a tactile region having a maximum height Sz/Δ friction coefficient of 150 μm or more and 600 μm or less.

The surface treatment method is not particularly limited, and may be, for example, a method of polishing the surface. Examples of polishing methods include polishing with sandpaper or other emery paper, and blasting. When the resin composition is molded in the molding process (first step) so that the surface of the molded resin composition has irregularities, it is preferable to polish the surface along the longitudinal direction of the convex surfaces of the irregularities. By polishing the surface along the longitudinal direction of the convex surfaces of the irregularities, the shape of the irregularities molded in the molding process (first step) of the resin composition is more easily maintained, making it easier to control the tactile feel of the surface. A molded product whose surface has been polished along the longitudinal direction of the convex surfaces of the irregularities will have polishing marks along the longitudinal direction of the convex surfaces of the irregularities.

4. Uses The above molded article can be used as exterior components such as outdoor fences for buildings, wood decks, parbolas (grape trellises), and lattices; interior components such as interior wall materials, flooring materials, ceiling materials, and furniture; and other play equipment.

The molded article can also be used as a shock-absorbing material. Examples of shock-absorbing materials include health products, nursing care products (e.g., fall prevention films, mats, sheets), shock-absorbing pads, protectors and protective equipment (e.g., helmets, guards), sporting goods (e.g., sports grips), sports protective gear, rackets, balls, transportation equipment (e.g., shock-absorbing grips for transportation, shock-absorbing sheets), industrial materials (e.g., vibration-damping pallets, shock-absorbing dampers, shock-absorbing materials for footwear, shock-absorbing foam, shock-absorbing film), and automobile shock-absorbing materials (e.g., bumper shock-absorbing materials, cushioning materials).

Furthermore, the above molded articles can be used for automotive interior components such as instrument panels, console boxes, meter covers, door lock bezels, steering wheels, power window switch bases, center clusters, dashboards, roof linings, cowl side trim, door trim substrates, deck trim, inner panels, pillar garnishes, rear packages, package trays, switch bases, quarter panels, seat structural materials, seat backboards, armrest core materials, ceiling substrates, wall materials, floor materials, shock absorbing materials, and sound absorbing materials; weather strips, bumpers, bumper guards, side mudguards, body panels, cowlings, fenders, spoilers, front grilles, strut mounts, wheel caps, center pillars, doors, etc. the surface decorative materials for furniture; architectural interior materials such as walls, ceilings, and floors; architectural exterior materials such as exterior walls such as siding, fences, roofs, gates, and gable boards; surface decorative materials for furniture such as window frames, doors, handrails, thresholds, and lintels; optical components such as various displays, lenses, mirrors, goggles, and window glass; interior and exterior components for various vehicles other than automobiles, such as trains, airplanes, and ships; and various other applications, such as various packaging containers, packaging materials, prizes, and miscellaneous goods such as small items, etc. In particular, because the tactile areas of the molded article are frequently touched, the molded article is preferably used in automobile interior components, and more preferably in instrument panels, console boxes, meter covers, door lock bezels, steering wheels, power window switch bases, center clusters, dashboards, roof linings, cowl side trim, door trim substrates, deck trim, inner panels, package trays, switch bases, and seat structural materials.

The above-mentioned molded articles are also suitable for use in many fields, including electrical insulating materials, industrial parts and materials, building materials, leisure components, agricultural equipment components, marine and fishing equipment components, etc. In particular, they are suitable for use in housing components and building materials, such as baseboards, surface decorative panels, door materials, exterior wall materials, vanity units, countertops, foundation support boards, window frames, wall materials, trim boards, handrails, handles, structural materials, civil engineering timbers, pillars, floor pillars, decorative pillars, earthquake-resistant materials, wallpaper, fixtures and ceiling materials, underlayment materials, tatami mats, floors, concrete panels, scaffolding materials, insulation boards, soundproofing boards, furniture box ceilings, doors, front and back panels, shelves, sleeve boards, fascia boards, deck boards, back panels, seat boards, kitchen components, waterproofing materials, mildew-proofing materials, antiseptic materials, shutter boards, sleeve boards, wainscoting, side panels, bathroom units, floor pans, bathroom ceilings, bathroom walls, It can also be used in baths, buckets, sanitary equipment, toilet seats, toilet covers, home appliances, radio/television receivers, cabinets, stereo cabinets, amplifier cabinets, speakers, speaker boxes, piano organ main panels, main roofs, rolled roofs, upper and lower rolled panels, life jacket buoyancy (foam), surfboards, cold weather glove materials, fishing equipment (floats, decorative balls, fish attractants, artificial baits), camping equipment, agricultural film, gardening poles, greenhouse poles or pole fixing fasteners, marine fenders, flotation devices, etc.

The above-mentioned molded articles can also be used in small vehicles such as bicycles and electrically assisted bicycles, escalators, elevators, etc., aviation materials including manned aircraft, unmanned aircraft, ultra-high-speed passenger aircraft, rockets, and artificial satellites, vehicles such as fuel cell vehicles, hydrogen fuel cell vehicles, and linear motor cars, various play equipment, various robot components, various infrastructure including traffic lights, electric wires, water pipes, gas pipes, and optical fibers, liquid crystal panels, solar cells, antennas, transistors, office equipment interiors, office equipment housings, toilet lighting fixtures, umbrellas, raincoats, heat insulation materials, flooring, paints, barrier agents, hydrophilic/hydrophobic control agents, papermaking materials, tires, dampers, hoses, various rubber materials such as vibration-isolating rubber, food and beverage containers, materials for 3D printers, agricultural films, liquid filters, air filters, semiconductor filters, various nonwoven fabric materials, musical instruments, acoustic materials, wigs, watches, gravestones, eyeglasses, sunglasses, and wearable devices.

1. Preparation of Materials 1-1-1. Preparation of Thermoplastic Resin (A-1) Prime Polypro J137G (polypropylene) manufactured by Prime Polymer Co., Ltd. was used as the thermoplastic resin (A-1).

1-1-2. Preparation of Thermoplastic Resin (A-2) Prime Polypro E222 (polypropylene) manufactured by Prime Polymer Co., Ltd. was used as the thermoplastic resin (A-2).

1-2. Preparation of natural fiber (B) Powdered cellulose (KC Flock (trade name) Grade W-100GK) (apparent specific gravity 0.30 g/ml to 0.40 g/ml, average particle diameter approximately 37 μm) manufactured by Nippon Paper Industries Co., Ltd. was used as natural fiber (B).

1-3. Synthesis of Compatibilizer (C) 100 parts by weight of Prime Polypro (trade name) Grade J106G manufactured by Prime Polymer Co., Ltd., 15 parts by weight of maleic anhydride, and 2.5 parts by weight of dicumyl peroxide (trade name Percumyl D manufactured by NOF Corporation) were mixed and reacted in a toluene solution for 5 hours to obtain compatibilizer (C), an acid-modified polypropylene resin composition containing maleic acid-modified polypropylene and unreacted maleic anhydride. The resulting compatibilizer (C) was dissolved in xylene and purified by reprecipitation in acetone. The graft amount of maleic anhydride was measured by infrared spectroscopy (IR) and found to be 2.8% by weight. The number average molecular weight (Mn) was measured by GPC and found to be Mn 18,000.

1-4. Preparation of Processing Aid (D) Olefin resin C-4 manufactured by Mitsui Chemicals, Inc. and described in the examples of JP-A-2010-150436 was used as processing aid (D).

2. Preparation of resin composition 2-1. Resin composition 1
Thermoplastic resin (A-1) was used as resin composition 1.

2-2. Resin composition 2
Thermoplastic resin (A-1), natural fiber (B), compatibilizer (C), and processing aid (D) were prepared in a mass ratio of 39:55:4:2 (total mass 4 kg).

4 kg of water was added to the natural fibers (B) prepared above and mixed until thoroughly blended. This mixture and thermoplastic resin (A-1) were placed in a batch-type closed-type kneading device equipped with a casing and a rotor with stirring blades (manufactured by HODEN SEIMITSU KAGAKU KENKYUSHO Co., Ltd., MF-type mixing and melting device, model: MF5000R/L), and the materials were kneaded by high-speed stirring with the peripheral speed of the stirring blade tip set to 40 m/s.

When kneading began, the rotor rotational torque rose and reached a maximum value, then decreased as the rate of torque change became smaller. When the rate of torque change fell to 5% or less per second, the rotational torque was deemed to have reached its minimum. Kneading was continued for 7 seconds from this point, yielding Resin Composition 2'.

Resin composition 2' and thermoplastic resin (A-2) were dry blended in a mass ratio of 18:82 to obtain resin composition 2.

2-3. Resin composition 3
Resin composition 2′ and thermoplastic resin (A-2) were dry blended in a mass ratio of 36:64 to obtain resin composition 3.

2-4. Resin composition 4
Resin composition 2′ and thermoplastic resin (A-2) were dry blended in a mass ratio of 55:45 to obtain resin composition 4.

3. Preparation of Test Pieces for Measurement 3-1. 3D Printer Molded Body From each resin composition, a Φ1.7 mm filament was produced at a processing temperature of 190 ° C using an extruder with a screw diameter of 16 mm (Apex Japan Co., Ltd., tabletop extruder AS-1). Using the produced filament, a Φ75 mm x 5 mm thick disk-shaped plate was molded using a Φ0.5 mm nozzle with a Φ0.5 mm nozzle at a molding speed of 20 mm/s, a base temperature of 85 ° C, and a molding temperature of 230 ° C. The surface of the obtained 3D printer molded body was provided with spiral-shaped convex portions, with the center of the disk-shaped plate as the center of the vortex and adjacent convex portions spaced at a regular interval. The convex portions formed regular linear irregularities with periodicity in the radial direction of the disk-shaped plate on the surface of the 3D printer molded body.

Using an injection molding machine (manufactured by The Japan Steel Works, Ltd., J100ADS-180U), each resin composition was injected into a flat plate-shaped mold measuring 90 mm x 90 mm x 2 mm thick at a nozzle temperature of 170°C, a mold temperature of 60°C, an injection pressure of 100 MPa, a holding pressure of 25 MPa, and a cooling time of 20 seconds, followed by pressure molding. The surfaces of the obtained injection-molded articles were smooth.

3-3. Surface Polishing The surfaces of some of the measurement specimens were polished using sandpaper #320 and pressed with the index finger to polish the entire surface. For the 3D printer molded body, the entire surface was polished in a circular motion from the center along the convex surface of the unevenness. For the injection molded body, the entire surface was polished by moving back and forth from one side to the opposite side. For the 3D printer molded body, polished and unpolished test specimens were prepared.

4. Evaluation 4-1. Surface Shape The polished area of each test piece (for unpolished test pieces, an arbitrarily determined area from the surface) was observed using a digital microscope (DSX510, manufactured by Olympus Corporation). A 40x objective lens was used, and the surface shape of the measurement area obtained by observation at a field of view of 4 mm x 0.46 mm and a magnification of 555x was analyzed using the software attached to the device. Specifically, the irregularities on the surface of the molded article were three-dimensionally imaged, and the surface height profile in the measurement range was obtained, and the "maximum peak height Sp,""maximum valley depth Sv,""maximum height Sz," and "arithmetic mean height Sa" were obtained. Note that two measurements were performed at the same position, and the average values were used as the Sp, Sv, Sz, and Sa of each test piece. In addition, the presence or absence of regular irregularities was evaluated from the three-dimensional image of the irregularities on the surface of the molded article.

4-2. Coefficient of Friction The static friction coefficient, dynamic friction coefficient, static friction force, and dynamic friction force of the polished area of each test specimen (or an arbitrarily selected area from the surface for unpolished test specimens) were measured using a reciprocating abrasion tester (manufactured by Shinto Scientific Co., Ltd.). The friction element used was a SUS friction element measuring 20 mm length x 20 mm width x 30 mm height with a tip radius of 45 mm and covered with a sapplause. The friction test was performed over a distance of 30 mm under a load of 50 gf, a speed of 300 mm/min, an ambient temperature of 23±2°C, and an ambient humidity of 50±5%. Two measurements were taken at the same position, and the average values were used to determine the static friction coefficient, dynamic friction coefficient, static friction force, and dynamic friction force of each test specimen. The Δ coefficient of friction was calculated by subtracting the dynamic friction coefficient from the static friction coefficient.

4-3. Tactile Feeling Five researchers working with natural fiber-containing resins were recruited as sensory testers. Test pieces were placed on a smooth table. The sensory testers lightly pressed the polished area of each test piece (or an arbitrarily selected area from the surface for unpolished test pieces) with their index finger and stroked it back and forth over a distance of 40 mm to check the tactile feel. The temperature during the evaluation was 23.0°C to 23.5°C, and the relative humidity was 48% to 53%. The tactile feel was evaluated based on the following evaluation criteria. The scores and average values of the five sensory testers are shown in Table 1. The molded product of Example 1, which had a paper-like feel similar to that of commercially available tissue paper (Itoman ECO Tissue 200WSP, manufactured by Itoman Co., Ltd.), was used as the evaluation standard. Specifically, the tactile feel of the molded body of Example 1 was given a score of 2, and a molded body that was felt to have a similar paper-like feel to the molded body of Example 1 (standard) was given a rating of "had a similar paper-like feel to the molded body of Example 1 (standard)," and the tactile feel of the molded body was given a score of 2. A molded body that was felt to have a paper-like feel similar to that of commercially available high-priced tissue paper (Nepia Nose Celeb Tissue 400 sheets (200 packs) manufactured by Oji Nepia Co., Ltd.) was given a rating of "had a superior paper-like feel to the molded body of Example 1 (standard)," and the tactile feel of the molded body was given a score of 3. A molded body that did not have a paper-like feel to the molded body of Example 1 (standard) was given a rating of "had an inferior paper-like feel to the molded body of Example 1 (standard)," and the tactile feel of the molded body was given a score of 1.
3 points: Compared with the molded article of Example 1 (standard), the paper-like feel was excellent.
2 points: Compared to the molded article of Example 1 (standard), the paper-like feel was about the same.
1 point: Compared with the molded article of Example 1 (standard), the paper-like feel was inferior.

Table 1 shows the manufacturing method for molded bodies (test specimens) from each resin composition, the amount of natural fiber (B) in the resin composition, and the evaluation results.

As is clear from Table 1, molded bodies having regions where the SZ/Δ friction coefficient is 150 μm or more and 600 μm or less had a texture similar to that of paper in these regions.

4-4. SEM Observation of Surface A polished region of each test piece (for unpolished test pieces, an arbitrarily determined region from the surface) was imaged using a scanning electron microscope (manufactured by JEOL Ltd., JSM-IT7000HR/LV) at an acceleration voltage of 10 kV, a tilt of 60°, a working distance of 30 to 35 mm, and a magnification of 100x, to obtain a secondary electron image.

The secondary electron image obtained by SEM observation of Example 3 is shown in Figure 1, the secondary electron image obtained by SEM observation of Comparative Example 2 is shown in Figure 2, and the secondary electron image obtained by SEM observation of Comparative Example 3 is shown in Figure 3.

As shown in Figure 1, the surface of the test piece of Example 2 was fuzzed over the entire surface, with some unevenness (lamination marks) remaining. As shown in Figure 2, the surface of the test piece of Comparative Example 2 was fuzzed over the entire surface, with some clear unevenness (lamination marks). As shown in Figure 3, the surface of the test piece of Comparative Example 3 was not very fuzzed and had no unevenness.

This application claims priority from Japanese Patent Application No. 2024-059677, filed April 2, 2024. The matters set forth in the specification, claims, and drawings of that application as originally filed are hereby incorporated by reference into this application.

The molded article of the present invention has a paper-like feel despite being a molded article of a resin composition. Therefore, the present invention is expected to broaden the applicability of resin compositions to various uses and contribute to the further popularization of such resin compositions.

Claims (15)

A molded article comprising a resin composition containing a thermoplastic resin (A) and natural fibers (B),
When the value obtained by subtracting the dynamic friction coefficient from the static friction coefficient is defined as the Δ friction coefficient,
The molded body has a tactile region on a surface containing the resin composition, the tactile region having a maximum height Sz/Δ friction coefficient of 150 μm or more and 600 μm or less.
Molded body. The tactile area has a maximum surface height Sz of 42 μm or more and 200 μm or less.
The molded article according to claim 1. The tactile area has a surface Δ coefficient of friction of 0.250 or more and 0.400 or less.
The molded article according to claim 1 or claim 2. The surface irregularities of the tactile area are regular irregularities.
The molded article according to claim 1 or claim 2. The resin composition contains 5% by mass or more and 50% by mass or less of the natural fiber (B) relative to the total mass of the resin composition,
The molded article according to claim 1 or claim 2. The resin composition contains 10% by mass or more and 40% by mass or less of the natural fiber (B) relative to the total mass of the resin composition,
The molded article according to claim 1 or claim 2. The natural fibers (B) include cellulose fibers.
The molded article according to claim 1 or claim 2. The thermoplastic resin (A) includes a polyolefin.
The molded article according to claim 1 or claim 2. The polyolefin is a propylene-based polymer.
The molded article according to claim 8. The resin composition is composed solely of the resin composition.
The molded article according to claim 1 or claim 2. The resin composition contains a compatibilizer (C),
The molded article according to claim 1 or claim 2. The compatibilizer (C) is an acid-modified polyolefin resin composition.
The molded article according to claim 11. Automotive interior components,
The molded article according to claim 1 or claim 2. A step of molding a resin composition containing a thermoplastic resin and natural fibers;
and treating the surface of the molded resin composition to form a tactile region having a maximum height Sz/Δ friction coefficient of 150 μm or more and 600 μm or less.
A method for manufacturing a molded body. In the molding step, the resin composition is molded so that regular irregularities are formed on the surface of the molded resin composition.
A method for producing the molded article according to claim 14.