KR20020054688A - Styrenic Thermoplastic Resin Compositions with Good Vacuum-forming Ability - Google Patents

Abstract

PURPOSE: Provided is a styrene-based thermoplastic resin composition excellent in vacuum-formability, which has improved stretch property by using styrene-acrylonitrile with ultrahigh molecular weight. CONSTITUTION: The styrene-based thermoplastic resin composition comprises: 20-50wt% of a graft copolymer having a weight average molecular weight of 50,000-100,000 and a graft rate of 50-100%, which is produced by graft-polymerizing 30-70wt% of a butadiene rubber and 70-30wt% of a mixture of an aromatic vinyl monomer and a vinyl cyanide monomer; 40-60wt% of a styrene-acrylonitrile copolymer having a weight average molecular weight of 100,000-500,000, which is produced by copolymerizing 50-90wt% of the aromatic vinyl monomer and 50-10wt% of the vinyl cyanide monomer; 0.1-30wt% of the styrene-acrylonitrile copolymer having an ultrahigh molecular weight, which has a weight average molecular weight of 1,000,000-5,000,000 and is produced by copolymerizing 50-90wt% of the aromatic vinyl monomer and 10-50wt% of the vinyl cyanide monomer.

Description

Styrenic Thermoplastic Resin Compositions with Good Vacuum-forming Ability

Field of invention

The present invention relates to a styrene-based thermoplastic resin composition excellent in vacuum formability. More specifically, the present invention relates to a styrene-based thermoplastic resin composition having excellent stretchability due to the use of ultra-high molecular weight styrene-acrylonitrile (SAN) to improve stretching properties.

Background of the Invention

Vacuum molding is a plastic sheet that obtains a product of a desired shape by first extruding a sheet of resin to prepare a sheet sheet, and then softening the sheet in a vacuum molding machine and simultaneously performing vacuum or pressure and vacuum to adhere the softened sheet to a mold. It is a kind of molding method. Vacuum molding is a molding method utilizing the stretching characteristics of the resin. The stretching property of the resin is the degree of resistance when the resin is stretched or expanded by an external force at a temperature high enough to flow. Resin having good stretching property has strong resistance, so that even if the thickness becomes too thin or angled, it can maintain a uniform thickness distribution without tearing. In general, the stretching property of the resin is closely related to the chemical structure of the resin. For olefin resins such as polyolefins, when the resin structure is branched, the stretching property is better than that of the linear structure. It is known that a molded article having a strong and uniform thickness distribution can be obtained.

Vacuum forming is widely used to make inner sheets of refrigerators and generally uses acrylonitrile-butadiene-styrene copolymer (ABS resin). This is because ABS resin not only has good mechanical properties and processability but also has excellent appearance and gloss. The ABS resin herein refers to an acrylonitrile content in a resin composition (G-ABS) obtained by graft copolymerization of a monomer mixture of 10 to 50% by weight of acrylonitrile and 50 to 90% by weight of styrene in the presence of polybutadiene rubber. The resin composition which mixed this 10-50 weight% acrylonitrile- styrene copolymer (SAN) is said. However, in the case of the conventional general ABS resin, when the large molding is manufactured by vacuum molding, the thickness deviation is large, so that a very thin portion is locally generated, thereby causing a lot of appearance defects. In order to solve this problem, SAN copolymers with large molecular weights and molecular weight distributions can reduce thickness variations, but the disadvantages of reduced productivity and color change due to increased extruder load during compounding and sheet production due to fluidity reduction. have.

On the other hand, blow molding is a molding technology for making hollow products such as plastic bottles, and its use range is gradually expanded from molding of small containers to manufacturing of large structural materials. This method is cheaper than injection molding, and the structure can be curved, so that various designs are possible, and in particular, the use of the structure has been gradually expanded due to the advantage of having low residual stress. In the case of manufacturing large molded articles, polyolefins such as low density polyethylene have excellent moldability, but when coating is required, there is a problem in application to structural materials due to low adhesion strength of the coating film, and in the case of modified polyphenylene ether, coating film adhesion, heat resistance, etc. It is excellent, but the chemical resistance is not good, so stress cracks are caused by thinners, etc. ABS resin, an acrylonitrile-butadiene-styrene copolymer, has been widely used in injection molding and vacuum molding because of its mechanical properties, ease of molding, and beautiful appearance, but it has a heavy drawdown and a thick molding of the molded article. Often difficult to use.

Japanese Patent Publication JP95015039 discloses a technique for applying ABS resin having excellent paintability to blow molding of large parts. Although the above problem is somewhat solved by a resin composition having a specific molecular weight and a molecular weight distribution, a unique technique cannot be found except that it has a slightly larger molecular weight and molecular weight distribution than a general ABS resin used for injection molding. In fact, simply increasing the molecular weight and molecular weight distribution does not significantly improve the blowability of ABS.

Japanese Patent Publication JP95005820 discloses a technique using a copolymer copolymerized with an organosilane compound to improve blow formation, but this method is manufactured by solution polymerization, which makes it difficult to mass-produce and increase manufacturing costs. .

In order to solve the above problems, the present inventors have developed ultra-high molecular weight products by adjusting the molecular weight of vinyl cyanide compound-aromatic vinyl compound copolymers, and greatly improved the existing stretching properties, so that vacuum forming, blow molding or stretching properties are important. It has led to the development of a resin composition that can solve all the problems that occur in the case of molding processing that works.

An object of the present invention is to provide a styrene-based thermoplastic resin composition excellent in vacuum forming.

It is another object of the present invention to provide a styrene-based thermoplastic resin composition having excellent stretchability by using an ultra high molecular weight styrene-acrylonitrile (SAN) to improve drawing properties.

It is still another object of the present invention to provide a general problem in vacuum molding, blow molding, or other molding processes caused by a lack of stretching characteristics of a conventional vinyl cyanide compound-aromatic vinyl compound copolymer and a thermoplastic resin used in blending therewith, That is, in order to solve the fall of fluidity, the occurrence of drawdown, or the thickness variation, it is to provide a styrene-based thermoplastic resin composition having excellent vacuum formability by improving the stretching property by using a SAN having ultra high molecular weight.

The above and other objects of the present invention can be achieved by the present invention described below. Hereinafter, the content of the present invention will be described in detail.

The ABS resin composition of this invention consists of (A) graft copolymer, (B) SAN copolymer, and (C) ultra high molecular weight SAN copolymer. These components will be described in detail below.

(A) Graft Copolymer

Graft copolymer according to the present invention is one aromatic vinyl monomer and unsaturated nitrile in the presence of 30 to 70% by weight of butadiene-based rubber having a particle size of 500 to 3500 Pa of 90% or more in the rubber, 50% or more of the gel content 70-30 weight% of 1 monomers are thrown in, and it is obtained by graft copolymerization. As the unsaturated nitrile monomer, a vinyl cyanide monomer is preferable. The graft copolymer has a graft ratio of 50 to 100% and a weight average molecular weight of the grafted resin is 50,000 to 100,000. The copolymer is preferably used in an amount of about 20 to 50% by weight based on the final resin composition.

(B) SAN copolymer

The SAN copolymer according to the present invention is prepared by copolymerizing 50 to 90% by weight of an aromatic vinyl monomer and 10 to 50% by weight of an unsaturated nitrile monomer. As the unsaturated nitrile monomer, a vinyl cyanide monomer is preferable. The copolymer is a commonly used SAN copolymer having a PS reduction weight average molecular weight of 100,000 to 500,000, preferably 40 to 60% by weight based on the final resin composition.

(C) Ultra High Molecular Weight SAN Copolymer

The ultrahigh molecular weight SAN copolymer according to the present invention is prepared by copolymerizing 50 to 90% by weight of an aromatic vinyl monomer and 10 to 50% by weight of an unsaturated nitrile monomer. As the unsaturated nitrile monomer, a vinyl cyanide monomer is preferable. The copolymer is an ultra high molecular weight SAN having a PS reduction weight average molecular weight of 1,000,000 to 5,000,000, and preferably 0.1 to 30% by weight based on the final resin composition.

The styrene-containing graft copolymer (A), styrene-containing copolymer (B), and (C) are known by those skilled in the art, that is, emulsion polymerization method, bulk It may be prepared by the law, suspension polymerization, solution polymerization and the like.

The thermoplastic resin composition of the present invention may be added an antidrip agent, an impact modifier, an inorganic additive, a heat stabilizer, an antioxidant, a light stabilizer, a pigment, and / or a dye according to each use. Additional inorganic additives include asbestos, glass fibers, talc and the like.

The present invention may be further embodied by the following examples, which are for illustrative purposes of the present invention and are not intended to limit the scope of protection defined by the appended claims.

Example

Preparation and specifications of (A) graft copolymer, (B) SAN copolymer, and (C) ultra high molecular weight SAN copolymer used in the following Examples and Comparative Examples are as follows.

(A) Graft Copolymer

Butadiene rubber latex having a rubber particle diameter of 0.3 μm was added so that the content of the butadiene rubber was 50 wt% based on the entire monomer, 150 parts by weight of deionized water, 0.9 parts by weight of rosin soap, 0.3 parts by weight of cumene hydroperoxide, 0.2 parts by weight of mercaptan-based chain transfer agent and 0.3 parts by weight of glucose were added and the internal temperature was maintained at 70 ° C. To this, 35 parts by weight of styrene and 15 parts by weight of acrylonitrile were added dropwise for 3 hours, followed by polymerization by a redox initiator to prepare styrene-acrylonitrile-butadiene graft copolymer latex. It was solidified in 1.5% magnesium sulfate aqueous solution and dried to prepare a powdered styrene-acrylonitrile-butadiene graft copolymer resin.

(B) SAN copolymer

Cheil Industries, Ltd. SAN HR-5330 was used.

(C) Ultra High Molecular Weight SAN Copolymer

Styrene monomer 71% by weight, acrylonitrile monomer 29% by weight, ion-exchanged water 150 parts by weight, tricalcium phosphate 0.4 parts by weight, carboxylic acid-based anionic surfactant 0.03 parts by weight, polyoxyethylene alkyl ether phosphate ester, And 0.001 to 1 parts by weight of 2,2'-azobisisobutylonitrile, which is an initiator, were mixed and added, and the reactor was completely sealed. Then, the mixture was sufficiently stirred to disperse, and then the internal temperature of the reactor was raised to 75 ° C. to proceed with polymerization for 3 hours. The reactor was then warmed to 120 ° C. and further polymerized for 3 hours. After the polymerization was completed, the reactor was cooled to room temperature to terminate the reaction, and the obtained polymer was washed, dehydrated and dried to obtain a bead-like copolymer. The weight average molecular weight of the copolymer obtained here was 4,000,000.

Examples 1-3 and Comparative Examples 1-3

The composition of each component used in Example 1-3 and Comparative Example 1-3 is shown in Table 1. Example 1-3 is an example of the resin composition prepared according to the present invention, Comparative Example 1-3 is a case where no ultra high molecular weight SAN is used. In Examples 1-3 and Comparative Examples 1-3, each of the components used was uniformly mixed with a Henshell mixer and then extruded into a twin screw extruder to prepare pellets. The specimen obtained above was extruded to prepare pellets.

Each pellet prepared above was used to prepare a compression specimen of 400 mm × 400 mm × 2 mm using a press. After marking the lattice of 50 mm horizontally and vertically on the prepared compression specimen, a vacuum molded product of 300 mm (L) x 30 mm (W) x 200 mm (H) was manufactured through a vacuum molding machine. In the vacuum molded article, the thickness of the lattice intersection point was measured by a thickness meter with an accuracy of 1/100 mm. Large minimum thickness and small standard deviation can be said to be excellent in vacuum forming and stretching characteristics, and the measured thicknesses and deviations are shown in Table 2.

In addition, each of the pellets prepared in the injection specimens were made by the ASTM D236 method and the tensile strength was measured at room temperature and 150 ℃ high temperature. The high temperature tensile strength and the high elongation are excellent in vacuum forming and stretching characteristics, and the results are shown in Table 2.

(A) (B) (C) Example One 30 67 3 2 40 57 3 3 50 47 3 Comparative Example One 30 70 0 2 40 60 0 3 50 50 0

* The content of (A), (B), and (C) is weight percent.

Item Vacuum forming test result Tensile Strength Test Results ⁽¹⁾ Thickness (mm) Standard deviation (mm) Tensile Strength at 23 ℃ (㎏ _f / ㎠) / Elongation (%) Tensile Strength (kg _f / ㎠) / Elongation (%) Example One 0.55 0.10 460/30 7.7 / 1400 2 0.52 0.12 400/40 7.4 / 1400 3 0.50 0.13 360/60 7.3 / 1400 Comparative Example One 0.3 0.23 460/30 4.7 / 800 2 0.28 0.27 400/40 4.1 / 950 3 0.22 0.25 360/60 3.7 / 1000

As shown in Table 2, the vacuum forming test results of Examples 1-3 were larger than those of the comparative example, and the specimen had a large minimum thickness and a small standard deviation. Tensile strength and elongation at room temperature were similar in Examples and Comparative Examples, but the high temperature tensile strength and elongation was much larger in Examples, so it was confirmed that the vacuum forming and stretching characteristics were excellent. Could.

The present invention improves the stretching properties of a resin composition by using a SAN having an ultra high molecular weight, so that various problems during vacuum molding, blow molding, or other molding processing caused by the lack of stretching properties of conventional thermoplastic resins, namely, fluidity deterioration, It has the effect of providing the styrene-based thermoplastic resin composition excellent in vacuum forming by solving occurrence of drawdown or thickness variation.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (4)

(A) 20 to 50 wt% of a graft copolymer having a weight average molecular weight of 50,000 to 100,000 prepared by graft polymerization of 70 to 30 wt% of an aromatic vinyl monomer and a vinyl cyanide monomer mixture on 30 to 70 wt% of butadiene rubber ; (B) 40 to 60% by weight of a styrene-acrylonitrile copolymer having a weight average molecular weight of 100,000 to 500,000 prepared by copolymerizing 50 to 90% by weight of an aromatic vinyl monomer and 50 to 10% by weight of a vinyl cyanide monomer; And (C) 0.1 to 30% by weight of an ultra high molecular weight copolymer having a weight average molecular weight of 1,000,000 to 5,000,000 prepared by copolymerizing 50 to 90% by weight of an aromatic vinyl monomer and 10 to 50% by weight of a vinyl cyanide monomer; Styrene-based thermoplastic resin composition excellent in vacuum forming, characterized in that consisting of. The styrene-based thermoplastic resin composition having excellent vacuum formability according to claim 1, wherein the graft copolymer (A) has a graft ratio of 50 to 100%. The styrene-based thermoplastic resin composition having excellent vacuum formability according to claim 1, wherein at least 90% of the butadiene-based rubber has a particle size of 500 to 3500 Pa and a gel content of 50% or more. The vacuum forming method according to any one of claims 1 to 3, further comprising an antidrip agent, a plasticizer, a heat stabilizer, an antioxidant, a light stabilizer, a compatibilizer, a pigment and / or a dye, and an inorganic additive. This excellent styrene thermoplastic resin composition.