JP3133050B2 - Crosslinked foam - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a crosslinked foam. More specifically, with a lightweight, high hardness compounded with nitrile rubber in ionomer resin to improve the workability of the kneading process in the cross-linking foam molding process,
The present invention relates to a crosslinked foam having high mechanical strength and excellent abrasion resistance and resilience.

[Prior art] A crosslinked product of an ethylene-based ionomer resin, particularly a crosslinked foam, has high hardness, high mechanical strength, excellent resilience,
In addition, energy absorption efficiency is high, so building materials, footwear,
In the fields of flotation materials, automobile parts, miscellaneous goods, etc., their applications are expected to be developed.

However, in order to industrially produce a crosslinked foam of an ionomer resin, there is a major problem that must be solved in terms of its production. In general, a crosslinked foam of a thermoplastic resin or a synthetic rubber includes a first step of uniformly kneading the thermoplastic resin or the synthetic rubber, a crosslinker and a foaming agent under a temperature condition equal to or lower than the decomposition temperature of the crosslinker and the foaming agent, and It is manufactured by a second step in which a molded article such as a pellet or a sheet kneaded in the above is heated and crosslinked and foamed. Conventionally, a kneading machine such as a mixing roll, a calender roll, a Banbury mixer, or a kneader has been used to uniformly knead a crosslinking agent and a foaming agent with a thermoplastic resin, a synthetic rubber, and the like. However, since the ionomer resin has good adhesiveness to metal, the use of the above-mentioned general-purpose kneading machine causes a problem that the ionomer resin sticks to a roll and cannot be kneaded or unfoamed.

In order to avoid such a problem, there is a method of using an extruder provided with a T-die as disclosed in JP-A-63-182359, but it is manufactured using a crosslinked foam of a thermoplastic resin or a synthetic rubber. However, the conventional molding equipment used in the conventional method cannot be used, and a special investment is required.

[Problems to be Solved by the Invention] Accordingly, the present inventors have reduced the adhesiveness of an ionomer resin to a metal, made it possible to use conventional molding equipment, and at the same time, essentially possessed the excellent characteristics inherent in the ionomer resin foam. A raw material blending recipe capable of producing a crosslinked foam held as described above was studied. First, polyethylene which is considered to have good compatibility with the ionomer resin, a polyolefin resin such as ethylene-vinyl acetate copolymer and an ethylene-propylene terpolymer, and a method of compounding a hydrocarbon rubber such as isoprene rubber were examined. There was almost no improvement in workability.

However, when a specific nitrile rubber, which is considered to have low compatibility with the ionomer resin, is added to the ionomer resin, the roll processability of the ionomer resin is surprisingly improved, and the conventional thermoplastic resin or synthetic rubber is sufficiently improved. It can be applied to the manufacturing process of cross-linked foam of
Moreover, it has been found that the obtained cross-linked foam still has the characteristics of the ionomer cross-linked foam which is lightweight, and has excellent resistance to compression deformation and abrasion. By using a composition containing such a nitrile rubber, using a conventional kneading machine such as a mixing roll, a calender roll, a Banbury mixer or a kneader used in a molding process of a crosslinked foam of a thermoplastic resin or a synthetic rubber, It is possible to mold an ionomer crosslinked foam having features such as high hardness, high mechanical strength, excellent friction wear resistance and resilience, and high energy absorption efficiency. Thus, the crosslinked foam of the present invention has been completed.

[Means for Solving the Problems] That is, the present invention provides: A. An unsaturated carboxylic acid content of 0.5 to 15 mol% and a neutralization degree of 10
%, An ethylene-unsaturated carboxylic acid copolymer partial metal salt having a melt flow rate (MFR) of 0.1 to 100 dg / min at 190 ° C. under a load of 2160 g ... 100 parts by weight B. Acrylonitrile content is 20 to 50% by weight , Mooney viscosity
Nitrile rubber with ML _{1 + 4} (100 ° C) of 30 to 100 ... 30 to 300
Parts by weight C. Chemical crosslinking agent 0.1 per 100 parts by weight based on the total amount of AB components
To 5 parts by weight D. Chemical blowing agent 0.1 per 100 parts by weight based on the total amount of AB components
To 20 parts by weight of the crosslinked foaming resin composition, the density obtained by heating is 0.05 to 0.5 g / cm ³ , the expansion ratio is 2 to 20 times, and the surface hardness (Asker C) is 30 to 95. It is a crosslinked foam having a compression set of 0 to 20% and an acron wear loss (1000 revolutions) of 3 ml or less.

Here, the surface hardness (Asker C) is a hardness measured by the Japan Rubber Association Standard SRIS0101, and the Akron abrasion loss (1000 revolutions) is based on the Akron abrasion test of JIS K6264 (Vulcanized rubber abrasion test method). Things.

The partial metal salt of the ethylene-α, β-unsaturated carboxylic acid copolymer used as the component A of the present invention is described in, for example,
39 to 6810, produced by a method described in JP-A-39-6810, wherein the unsaturated carboxylic acid content is 0.5 to 15 mol%,
It is preferably 1 to 6 mol%, the degree of neutralization is 10% or more, preferably 15 to 80%, and the melt flow rate is 0.1 to 100 dg / min, preferably 1 to 100 dg / min. That is, a copolymer of ethylene and an unsaturated carboxylic acid having 3 to 8 carbon atoms such as acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, fumaric acid, or further, methyl acrylate, ethyl acrylate, isobutyl acrylate Α having about 4 to 8 carbon atoms, such as normal butyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, and dimethyl fumarate;
β-unsaturated carboxylic acid esters, vinyl acetate, etc.
Examples thereof include those in which a part of a carboxylic acid group in a terpolymer contained as a component is crosslinked with a metal ion.

Examples of metal ions used for metal ion crosslinking include monovalent metal ions such as lithium, sodium, potassium, and cesium; divalent metal ions such as magnesium, calcium, strontium, barium, copper, and zinc; and trivalent metal ions such as aluminum and iron. Valent metal ions.

If the MFR of the component A is smaller than the above range, the moldability will be poor, and if it is larger than the above range, the strength of the molded product will be insufficient.

As the component A, one of them can be selected and used. However, the unsaturated carboxylic acid (ester) content, the type of metal, the degree of neutralization, the MFR, etc. are adjusted to obtain a crosslinked material having desired physical properties. In order to obtain a product, a partial metal salt of two or more copolymers or a blend of a copolymer with a partial metal salt can also be used.

In the present invention, acrylonitrile-butadiene having an acrylonitrile content of 20 to 50% by weight, preferably 20 to 40% by weight, and a Mooney viscosity ML _{1 + 4} (100 ° C.) of 30 to 100, preferably 40 to 90, is used as the B component. Polymerized rubber (nitrile rubber) is used. Such nitrile rubber also has
An unsaturated carboxylic acid such as acrylic acid or methacrylic acid may be copolymerized. At the time of compounding these nitrile rubbers, due to the problem of kneading workability, they are not veiled,
It is desirable to use it in powder, pellet or sheet form. In addition, as these nitrile rubbers, those in which other resins or rubbers, for example, polyvinyl chloride, ethylene-propylene terpolymer, or the like are blended in an amount of about equal weight or less can be used.

The mixing ratio of the nitrile rubber is 3 parts per 100 parts by weight of the partial metal salt of the ethylene-α, β-unsaturated carboxylic acid copolymer.
0 to 300 parts by weight, preferably 50 to 200 parts by weight.
If the compounding ratio of the nitrile rubber is less than 30 parts by weight, poor kneading properties due to adhesion to a metal surface with a mixing roll or a Banbury mixer, which is a drawback of the ionomer resin, cannot be solved, and if it is more than 300 parts by weight, There are many unsaturated bonds in the finally obtained crosslinked foaming composition, and the crosslinking reactivity by the chemical crosslinking agent of the component C is too high. This makes it difficult to adjust the cross-linking and foaming step, which is controlled by the amounts of the chemical cross-linking agent of the component C and the chemical foaming agent of the component D, and the surface of the obtained cross-linked foam becomes rough and the center is cracked. There were problems such as doing.

The chemical crosslinking agent used as the component C of the present invention includes:
An ordinary organic peroxide crosslinking agent which generates a radical by heating and causes a crosslinking reaction in the polymer can be used. Preferred crosslinking agents include, for example, dicumyl peroxide, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, 2,5-dimethyl-2,5-di-tert-butylperoxyhexyne-3 Dialkyl peroxide crosslinking agents represented by the general formula ROOR (where R is an alkyl group and can be substituted with an aryl group or other substituent) such as 1,3-bis (tert-butylperoxyisopropyl) benzene Are generally included, and the total amount of the A and B components is about 100 parts by weight based on 100 parts by weight.
It is used in a ratio of about 0.1 to 5 parts by weight.

It is also possible to appropriately select and use two or more kinds of the crosslinking agents having different decomposition temperatures.

The resin composition for obtaining the crosslinked foam of the present invention is as described above.
The composition contains a chemical foaming agent D as an essential component in addition to the A, B, and C components.

As the foaming agent used as the D component of the present invention, any decomposable type that generates a gas necessary for foaming the resin by heating, that is, any chemical foaming agent can be used. Azodicarbonamide, dinitrosopentamethylenetetramine or the like is used alone or as a mixture at a ratio of about 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the total amount of the A and B components.

Further, the cross-linked foamable resin composition includes a rubber-like elastic polymer such as an ethylene-α-olefin copolymer, a styrene-butadiene rubber, a polybutadiene rubber, and the like, A, B
It can be blended at a ratio of about 50 parts by weight or less per 100 parts by weight of the total amount of the components.

Further, various other additives used in this technical field can be added to the crosslinked foamable resin composition as needed. Examples of such other additives include a crosslinking accelerator, a foaming aid, an antioxidant, a light stabilizer, an ultraviolet absorber, an antistatic agent, a lubricant, an antiblocking agent, an organic or inorganic pigment, a dye, and the like. Can be mentioned.

In order to uniformly mix the above essential components and optional components of A, B, C, D, simultaneously or sequentially, crosslinking of thermoplastic resin such as mixing roll, calender roll, Banbury mixer, kneader or synthetic rubber. What is necessary is just to melt-mix using the conventionally used kneader in the foaming process.

The crosslinked foamable composition is formed into a sheet using a roll or the like, and then crosslinked and foamed by heating using a hot press, a foaming furnace, a foaming bath, or the like.

The temperature conditions for cross-linking and foaming vary depending on the type of chemical cross-linking agent, chemical foaming agent, foaming aid, etc.
Set to ~ 250 ° C.

By adjusting the composition and foaming conditions of the crosslinked foamable composition, the density is 0.05 to 0.5 g / cm ³ , and the expansion ratio is 2 to 20.
A crosslinked foam having a surface hardness (Asker C) of 30 to 95, a permanent compression set of 0 to 20%, and an acron wear loss (1000 revolutions) of 3 ml or less can be obtained.

The crosslinked foam of the present invention can be widely used for various purposes such as heat insulating materials, sound absorbing materials, wall materials, packing shoe soles, fishing floats, miscellaneous goods, and the like, but particularly has high hardness, light weight, abrasion resistance, Because of its excellent resilience, it is excellent as a sole material.

 Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 Ionomer A (Mitsui-Dupont Polychemical Co., Ltd.)
100 parts by weight, Himilan 1601 MFR 1.2 dg / min, Na type), nitrile rubber A (Nippon Synthetic Rubber Co., Ltd., JSR NBR)
N237H Acrylonitrile content 34%, Mooney viscosity 7
8) 100 parts by weight of a chemical crosslinking agent (1,3-bis (tert-butylperoxyisopropyl) -benzene), a foaming agent (azodicarbonamide), a foaming aid (zinc stearate) and titanium oxide, A compound obtained by adding 0.8 parts by weight, 2.5 parts by weight, 2.0 parts by weight, and 2 parts by weight to 100 parts by weight of the total amount of the ionomer A and the nitrile rubber A,
The mixture was kneaded using a pressure kneader (Moriyama Seisakusho, internal volume 3 liters). For kneading, press kneader (wall surface approx. 115 ° C)
, And kneaded at a rotation speed of 30 rpm for 3 minutes without pressurizing. Then, the pressurizing lid was lowered and pressure was applied for further kneading for 2 minutes. The resin temperature at this time was 150 ° C. Thereafter, the mixture was further kneaded for 10 minutes while passing water through the jacket. After completion of the kneading, the contents could be easily discharged from the kneader by reversing the kneader. The obtained kneaded material was formed into a sheet (thickness: 2 mm) using a 10-inch roll (roll surface temperature: 80 ° C.) and used for molding a press-crosslinked foam.

Several obtained sheets (about 460 g) are stacked and placed in a press-crosslinking foaming mold (200 × 200 × 11.5 mm).
After heating under pressure for 20 minutes, the mold was opened to obtain a crosslinked foam.

The cells of the resulting crosslinked foam were white, very dense and uniform. The foam density is 0.21 g / cm ³ , the surface hardness (Asker C) is 50, the permanent compression set (JIS K6767 compliant 40% compression 5000 times) 3.6%, Akron abrasion loss (BS-9)
03 The number of rotations was 1,000 times, the load was 6 pounds, and the inclination was 15 °) 0.38 ml.

 The test results are shown in Table 1.

Comparative Example 1 In Example 1, a compound for crosslinking and foaming using only an ionomer as a resin component without adding nitrile rubber A was kneaded with a pressure kneader. After completion of the kneading, an attempt was made to discharge the contents from the kneader, but the contents adhered to the kneader and could not be discharged at all.

Therefore, in order to evaluate the quality of the crosslinked foam obtained from the crosslinkable foaming composition of Comparative Example 1, a T-tube was prepared according to the method described in Example 9 of JP-A-63-182359 instead of the pressure kneader. After preparing a dispensing sheet with a small extruder equipped with a die, a crosslinked foam was prepared according to Example 1 and the quality was evaluated. The results are shown in Table 1.

Comparative Example 2 In Example 1, a compound for crosslinking and foaming containing only nitrile rubber A as a resin component without adding ionomer A was kneaded with a pressure kneader. A crosslinked foam was formed using the dispensing sheet obtained in the same manner as in Example 1. The obtained crosslinked foam had very rough cells colored brown. The results are shown in Table 1.

Examples 2 to 3 In Example 1, a crosslinked foam was prepared according to Example 1 by using a compound in which the compounding amounts of the ionomer A and the nitrile rubber A were changed as shown in Table 1, and the quality was evaluated. The results are shown in Table 1.

Example 4 Instead of ionomer A in Example 1, 80 parts by weight of ionomer B (Himilan 1707, MFR 0.9 dg / min Na type, manufactured by Du Pont-Mitsui Polychemicals Co., Ltd.) and ionomer C (Mitsui-Dupont Polychemical (Mitsui-Dupont Polychemical)) Co., Ltd.
Himilan 1856, MFR 1.0dg / min Terpolymer type N
a type) Nitrile rubber B (manufactured by Nippon Synthetic Rubber Co., Ltd., JSR NV73, Mooney viscosity 65, medium to high nitrile base vinyl chloride resin content instead of nitrile rubber A)
(30%) 100 parts by weight of the compound was kneaded for 10 minutes on a 10-inch roll (130 ° C. surface temperature). The above composition was easily released from the roll to obtain a sheet (thickness: about 2 mm). A crosslinked foam was molded according to Example 1 using the obtained sheet.

The resulting crosslinked foam had a uniform and dense cell, though slightly colored yellow. The foam density is 0.
23g / cm ³ , Surface hardness (Asker C) 64, Compression set 3.7%, Akron abrasion loss (1000 rotations) 0.37ml
Met.

Comparative Example 3 In Example 1, an ethylene-vinyl acetate copolymer (Evaflex P1905, manufactured by DuPont-Mitsui Polychemicals, Inc., having a vinyl acetate content of 19) was used in place of the nitrile rubber A.
%, MFR 2.5 dg / min), and kneaded with a pressure kneader using a compound for crosslinking and foaming using 100 parts by weight. After completion of the kneading, an attempt was made to discharge the contents from the kneader, but the contents adhered to the kneader and could not be discharged.

Comparative Example 4 A crosslinked foam was obtained in the same manner as in Example 1 except that 100 parts by weight of isoprene rubber (Kuraray Co., Ltd., Kuraprene IR-10, Mooney viscosity: 83) was used in place of nitrile rubber A. And evaluated the quality.

After completion of the kneading, the above-mentioned compound could be easily discharged from the pressure kneader. Further, the obtained crosslinked foam had white and uniform cells. Foam density is 0.21 g / cm ³ , surface hardness (Asker C) is 40, and repeated compression set is 2.5%
However, the acron wear loss amount was as large as 15.6 ml.

[Effects of the Invention] According to the present invention, by blending a specific nitrile rubber with an ionomer resin, the metal tackiness of the ionomer resin is eliminated, and the roll processability is greatly improved.
The crosslinkable foaming composition can be easily manufactured using a usual kneading machine such as a mixing roll, a calender roll, a Banbury mixer or a kneader, and is lightweight, high in hardness, large in mechanical strength, and resistant to compression deformation. Thus, a crosslinked foam excellent in abrasion resistance and resilience can be provided.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08J 9/06 C08L 9/02 C08L 23/08

Claims (1)

(57) [Claims] A. Ethylene-unsaturated carboxylic acid having an unsaturated carboxylic acid content of 0.5 to 15 mol%, a degree of neutralization of 10% or more and a melt flow rate at 190 ° C. under a load of 2160 g of 0.1 to 100 dg / min. Copolymer partial metal salt: 100 parts by weight B. Acrylonitrile content: 20-50% by weight, Mooney viscosity
Nitrile rubber with ML _{1 + 4} (100 ° C) of 30 to 100 ... 30 to 300
Parts by weight C. Chemical crosslinking agent 0.1 per 100 parts by weight based on the total amount of AB components
To 5 parts by weight D. Chemical blowing agent 0.1 per 100 parts by weight based on the total amount of AB components
To 20 parts by weight of the crosslinked foaming resin composition, the density obtained by heating is 0.05 to 0.5 g / cm ³ , the expansion ratio is 2 to 20 times, and the surface hardness (Asker C) is 30 to 95. A crosslinked foam having a compression set of 0 to 20% and an acron wear loss (1000 revolutions) of 3 ml or less.