KR100386816B1 - Impact resistant thermoplastic resin composition - Google Patents

Abstract

PURPOSE: An impact resistant thermoplastic resin composition is provided, to improve impact resistance and the compatibility between a styrene-based resin and a polyolefin resin. CONSTITUTION: The thermoplastic resin composition comprises 5-90 parts by weight of a polyolefin resin, 10-95 parts by weight of a styrene-based resin and a polyolefin-polystyrene graft copolymer, wherein the content of grafted polystyrene exceeds 0.4 wt% based on the total resin; the polyolefin-polystyrene graft copolymer comprises 50-90 parts by weight of a polyolefin resin and 10-50 parts by weight of a base oil radical polymerizable vinyl monomer; and the melt flow index of the polyolefin of the polyolefin-polystyrene graft copolymer is greater than that of the polyolefin resin. Preferably the polyolefin resin is selected from the group consisting of linear low density polyethylene, low density polyethylene, high density polyethylene, polypropylene and ethylene-vinyl acetate; and the styrene-based resin is one or two selected from the group consisting of a styrene homopolymer and high impact polystyrene containing a butadiene elastomer.

Description

Impact resistant thermoplastic resin composition

Field of invention

The present invention relates to a thermoplastic resin composition excellent in impact resistance. More specifically, the present invention relates to a thermoplastic resin composition excellent in impact resistance composed of a polyolefin resin, a styrene resin and a polyolefin / polystyrene graft copolymer prepared by a reaction extrusion process.

Background of the Invention

Styrene-based resins and polyolefin resins are general purpose polymers, and their blends have advantages such as ease of processing, excellent rigidity, impact resistance and low cost, superior impact resistance, and excellent chemical properties, which are advantages of styrene resin. It is expected to be a new material that saves the disadvantages of both resins, but due to the inherent incompatibility between the styrene resin and the polyolefin resin, these simple blends have poor compatibility and result in weak mechanical properties. Therefore, in order for the blend to express the advantages of the two resins, the compatibility must be improved by using an appropriate compatibilizer.

As a method for improving compatibility between two resins, many documents have been reported. A method for improving compatibility using block copolymers as compatibilizers is disclosed in EP 4,685. The polystyrene (PS) / polyethylene (PE) blend according to this method is commercialized as a new material exhibiting the advantages of the styrene resin and the polyolefin resin, and is used as a disposable container requiring oil resistance and moisture permeability. It is used as a thick plate material for a refrigerator internal wound which is required.

However, as a compatibilizer, this block copolymer has a disadvantage in that the manufacturing process is complicated as a product produced by anionic polymerization. Therefore, the need for a more economical commercialization method has emerged, a method for reaction commercialization has recently been proposed.

U.S. Patent No. 4,590,241 uses a linear low density polyethylene (LLDPE) / PS blend using neofunctionalized PE and oxazoline functionalized PS. The American Journal of Polymer Engineering Science, Vol. 27, 1987, pp. 27, 1634, changes the carboxylic acid functionalized PE (9 mol% acid) to 10-90 wt% in styrene / isopropenyloxazoli (1 mol%) copolymer at 225 ° C. A method of reacting in a mixer is proposed. The blend showed a very fine morphological structure, and the elongation increased significantly in the composition of PE continuous phase, but the increase in elongation was not seen in the composition of PS continuous phase despite the good adhesion between the interfaces. . In addition, U.S. Academic Polymer Polymer 1991, pp. 32, 19, reports how to obtain graft copolymers by free radical reaction. This method produces a styrene copolymer having a branched OO bond and when the melt is mixed with PE in an extruder, the peroxide is decomposed to cause a crosslinking reaction between the PE and the styrene copolymer to obtain a PE-g-styrene copolymer. do. In order to increase the contact between peroxide and PE, impregnation polymerization method is used, that is, styrene monomer and peroxide monomer are impregnated into PE pellets at 90 ° C., and benzoyl peroxide is added at 80 ° C. between styrene and peroxide monomers. Copolymerization causes the styrene copolymer with branched peroxide groups to be present in the PE pellets. The PE / styrene copolymer mixture thus obtained was melt mixed in an extruder to obtain a graft copolymer structure. It is reported that the graft efficiency of PS is 41% and the gel content is 33%, and this copolymer has a problem in that a commercially available gel is used.

As described above, the method of commercializing the PS / PE blend by the reaction commercialization method has many problems.

In order to solve the above problems, the present inventors prepare a polyolefin / styrene resin copolymer by grafting on a polyolefin by a styrene monomer reaction extrusion process, which acts as a compatibilizer for the styrene resin / polyolefin resin bulland, thereby making it compatible with both resins. The present invention has been found to improve the present invention.

Purpose of the Invention

An object of the present invention is to provide a thermoplastic resin composition excellent in impact resistance.

Another object of the present invention is to provide a thermoplastic resin composition having improved compatibility between styrene resin and polyolefin resin.

The above and other objects of the present invention can be achieved by the present invention described below.

Summary of the Invention

The thermoplastic resin composition of the present invention is composed of 5 to 90 parts by weight of polyolefin resin, 10 to 95 parts by weight of styrene resin, and polyolefin / polystyrene graphene copolymer, and the grafted polystyrene content is more than 0.4% by weight of the total resin. It is a thermoplastic resin composition excellent in impact resistance characterized by the above-mentioned.

The polyolefin resin used in the present invention is linear low density polyethylene, low density polyethylene, high density polyethylene, polypropylene, ethylene vinyl acetate, and the like, and the styrene resin is a high impact polystyrene containing a homopolymer of styrene monomer, butadiene elastomer, or a mixture thereof. Can be used.

The polyolefin / polystyrene graft copolymer prepared by the reaction extrusion process is composed of 50 to 90 parts by weight of polyolefin resin and 10 to 50 parts by weight of vinyl monomer capable of free radical polymerization, wherein the vinyl monomer is styrene, vinyl xylene, vinyl toluene, Ethyl vinyl benzene, isopropyl styrene, para-t-butyl styrene, dichlorostyrene, bromostyrene, fluorostyrene and the like can be used.

The melt flow index of the polyolefin of the graft copolymer is larger than the melt flow index of the polyolefin resin.

Detailed Description of the Invention

The present invention relates to polyolefin resins comprising (1) 5 to 90 parts by weight of polyolefin resin, (2) 10 to 95 parts by weight of styrene resin, and (3) 0.4% by weight of grafted styrene resin components prepared by the reaction extrusion process It relates to an impact resistant thermoplastic resin composition as a styrene resin copolymer. Polyolefin resins used in the present invention include linear low density polyethylene, low density polyethylene and the like.

As the styrene resin component, a high impact polystyrene containing a homopolymer of a styrene monomer and a butadiene elastomer, or a mixture thereof can be used.

The graft copolymer of component (3) is characterized in that it is produced by a reaction extrusion process. A method for preparing the graft copolymer by a reaction extrusion process is shown in US Pat. No. 3,177,270. The polyolefin resin of the graft copolymer includes linear low density polyethylene, low density polyethylene, high density polyethylene, polypropylene, ethylene vinyl acetate, and the like. Preferably, the same resin as the above (1) component is used. As the vinyl monomer polymerized by melt mixing in polyolefin resin, styrene, vinyl xylene, vinyl toluene, ethyl vinyl benzene, isopropyl styrene, para-t-butyl styrene, dichloro styrene, bromostyrene, fluorostyrene, etc. may be used. Among them, styrene is particularly preferable. Radical initiators for initiating graft polymerization include benzoyl peroxide, di-t-butyl peroxide, dicumyl peroxide, 2,3-diphenyl-2,3-methylbutane, 3,4-diphenyl-3 , 4-methylhexane and the like can be used. In the graft copolymerization, the addition amount of the polyolefin resin is less than 50 parts by weight and the melt mixing becomes unstable, so that the extrusion stability is lowered. On the contrary, when the graft copolymer exceeds 90 parts by weight, the yield of the graft copolymer is too low.

The graft copolymer prepared in the present invention is dissolved in toluene, xylene, ethylbenzene and the like at 80 ° C. or higher, and then cooled to room temperature to give an excessive amount of non-solvent methanol to obtain a graft copolymer and homopolystyrene. Homopolystyrene can be removed by extraction with methylene chloride.

Various additives, such as antioxidants, ultraviolet absorbers, antistatic agents, weather stabilizers, lubricants, impact modifiers and pigments, may be appropriately selected and used in the composition of the present invention as needed. Each of the above components can be kneaded simultaneously after dry blending. Kneading may be carried out at a temperature in the range of 180 ° C.-260 ° C., preferably 190 ° C.-230 ° C., using a single screw extruder or a twin screw extruder.

The invention will be further elucidated by the following examples which are set forth only for the purpose of illustrating the invention and are not intended to limit the scope of the invention.

Example

Preparation of Graft Copolymer 1

Hanwha General Chemical Co., Ltd.'s low density polyethylene 724 with melt flow index (hereinafter referred to as "MI") is maintained at 170 ° C, 7.5kg in a twin screw extruder with a screw diameter (D) of 45 mm and a length of 36D. Styrene monomers fed at a rate of / h and containing 0.07 mol / l of t-butylperoxide as an initiator in the middle of the extruder were fed at a rate of 5 kg / h for melt mixing. The molten mixture was mixed and reacted in the remainder of the extruder to form a strand through the die and cooled in water to produce a graft copolymer in pellet form. The copolymer was dried at 80 ° C. to remove unreacted styrene, and analyzed by an analysis method. The results are shown in Table 1 below.

Preparation of Graft Copolymer 2

The polyethylene used above was carried out in the same manner as above except that the melt flow index (MI) was 2.8. The analysis results are shown in Table 1.

In the present invention, the grafting percentage was calculated by the following equation.

Example 1

6.5 wt% polyethylene with a meltflow index of 2.8, 88.5 wt% high impact polystyrene and 5 wt% of the graft copolymer 1 were dry blended. Since the graft copolymer contains homopolystyrene and homopolyethylene regardless of the commercially available action, it is necessary to form a content based on the graft copolymer content. In this case, the polyethylene component in the whole blend is 10% including the PE component of the graft copolymer, the PS component is 90% including the homopolystyrene and the graft polystyrene of the graft copolymer, and the double graft polystyrene The content of was 0.7%.

The mixture was pressed by a twin screw extruder with a barrel temperature of 200 ° C. to prepare pellets. The resulting pellets were prepared using various injection molding machines according to ASTM at 200 ° C., and the physical properties thereof were measured. The measurement results are shown in Table 2.

Example 2

Example 1 was carried out in the same manner as in Example 1, except that the content of the graft polystyrene in the total blend component is 1.0%. The physical properties were measured and the results are shown in Table 2.

Example 3

In Example 1, it carried out similarly to Example 1 except the composition of polyethylene in all the blends is 50%, the composition of graft polystyrene is 3.5%, and MI of polyethylene is 0.3. The physical properties were measured and the results are shown in Table 2.

Example 4

In Example 1, it carried out similarly to Example 1 except the composition of polyethylene in all the blends is 30%, and the composition of graft polystyrene is 2.1%. The physical properties were measured and the results are shown in Table 2.

Comparative Example 1

Example 1 was the same as in Example 1 except that the graft polystyrene content of the entire blend is 0.4%. The physical properties were measured and the results are shown in Table 2.

Comparative Example 2

Example 1 was carried out in the same manner as in Example 1 except that the graft copolymer 2 was used. The physical properties were measured and the results are shown in Table 2.

Simple modifications and variations of the present invention can be easily made 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 (3)

5 to 90 parts by weight of polyolefin resin, 10 to 95 parts by weight of styrenic resin, and polyolefin / polystyrene graft copolymer, wherein the grafted polystyrene content exceeds 0.4% by weight with respect to the total resin, The / polystyrene graft copolymer is composed of 50 to 90 parts by weight of polyolefin resin and 10 to 50 parts by weight of base oil radical polymerizable vinyl monomer, and the melt flow index of the polyolefin of the graft copolymer is higher than the belt flow index of the polyolefin resin. Thermoplastic resin composition characterized in that large The thermoplastic resin composition of claim 1, wherein the polyolefin resin is selected from the group consisting of linear low density polyethylene, low density polyethylene, high density polyethylene, polypropylene, and ethylene vinyl acetate. The thermoplastic resin composition according to claim 1, wherein the styrene resin is one or a mixture of two selected from the group consisting of homopolymers of styrene monomers and high-impact polystyrenes containing butadiene elastomer.