JPH0692519B2 - Sheet composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a composition for a sheet which is excellent in transparency, impact resistance and rigidity.

[Conventional technology]

A block copolymer composed of a conjugated diene and a vinyl aromatic hydrocarbon has excellent transparency when the content of the vinyl aromatic hydrocarbon is relatively high, and a thermoplastic resin having a better impact resistance than polystyrene can be obtained. In recent years, its usage has been increasing mainly in fields such as food packaging containers, daily sundries, toy boxes, and light electric parts.

Various production methods of such block copolymers are known, and JP-B-36-19286, JP-B-43-17979, JP-B-48-2423 and JP-B-57-49567,
For example, Japanese Patent Publication No. 58-11446.

[Problems to be solved by the invention]

However, the block copolymers disclosed in these methods do not have sufficient impact resistance, and improvement thereof is desired. In particular, extrusion molded products and injection molded products are inferior in the dart impact property, and cracks occur during molding, during transportation of the molded products, during use, and the like, which causes a serious problem in practical use.

As a method for improving the impact resistance of a block copolymer, for example, Japanese Patent Publication No. 55-5544 discloses that the styrene content is different.
Although methods of blending different block copolymers are known, they are still insufficient in terms of balance between transparency and impact resistance.

[Means and Actions for Solving Problems]

The present invention combines a block copolymer having a relatively large molecular weight and a block copolymer having a relatively small molecular weight, and at the same time, increases the vinyl aromatic hydrocarbon content of the former block copolymer by a specific amount as compared with the latter. By doing so, it was found that a composition for a sheet excellent in transparency, impact resistance and rigidity can be obtained, and it is intended to solve the above problems.

That is, the present invention comprises (i) a polymer segment mainly composed of at least two vinyl aromatic hydrocarbons and a polymer segment mainly composed of at least one conjugated diene, and having a vinyl aromatic hydrocarbon content of Block copolymer (A) having a molecular weight of 65 to 95% by weight and a molecular weight of 100,000 to 400,000, 55 to 97 parts by weight, (ii) at least one polymer segment mainly composed of vinyl aromatic hydrocarbon Block copolymer (B) 3 consisting of a polymer segment mainly composed of individual conjugated dienes, having a vinyl aromatic hydrocarbon content of 15% by weight or more and less than 50% by weight and a molecular weight of 60,000 to 150,000. 45 parts by weight, the vinyl aromatic hydrocarbon content of the block copolymer (A) is 15 to 50% by weight higher than the vinyl aromatic hydrocarbon content of the block copolymer (B), and the composition as a whole The vinyl fragrance Sheet composition hydrocarbon content is 60 to 90 wt% about.

Hereinafter, the present invention will be described in detail.

The block copolymer (A) used in the present invention is composed of at least two vinyl aromatic hydrocarbon-based polymer segments and at least one, preferably at least two, conjugated diene-based polymer segments. Have. The block copolymer (B) has at least one polymer segment mainly containing vinyl aromatic hydrocarbons and at least one polymer segment mainly containing conjugated dienes.
In these block copolymers, a polymer segment mainly composed of vinyl aromatic hydrocarbon means a copolymer block of vinyl aromatic hydrocarbon containing 50% by weight or more of vinyl aromatic hydrocarbon and a conjugated diene, or a vinyl aromatic compound. Shows a polymer segment consisting of a group hydrocarbon polymer block or a combination thereof, and a polymer segment mainly composed of a conjugated diene is a conjugated diene and a vinyl aromatic hydrocarbon containing a conjugated diene in an amount exceeding 50% by weight. The polymer segment comprises a copolymer block or a conjugated diene polymer block or a combination thereof. The vinyl aromatic hydrocarbon in the copolymer block may be distributed uniformly or in a taper shape.

In the present invention, the vinyl aromatic hydrocarbon is styrene, O-methylstyrene, p-methylstyrene, p-te.
There are rt-butyl styrene, 1,3-dimethyl styrene, α-methyl styrene, vinyl naphthalene, vinyl anthracene and the like, and styrene is particularly common. These may be used alone or in combination of two or more. The conjugated diene is diolefin having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene),
2,3-Dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and the like, and particularly common ones are 1,3-butadiene and isoprene. These may be used alone or in combination of two or more.

In the present invention, the block copolymer (A) has a molecular weight of 100,000 to 400,000, preferably 130,000 to 350,000. If the molecular weight of the block copolymer (A) is less than 100,000, the impact resistance is poor,
If it exceeds 400,000, the moldability becomes poor, and the molecular weight of the block copolymer (B) is 60,000 to 150,000, preferably 70 to 120,000. When the molecular weight of the block copolymer (B) is less than 60,000, impact resistance and rigidity are lowered, and when it exceeds 150,000, transparency is lowered, which is not preferable. Here, the molecular weight means a value obtained by measuring with gel permeation chromatography (GPC) and using a calibration curve prepared using standard polystyrene commercially available for GPC. In the present invention, it is preferable in view of transparency that the molecular weight of the block copolymer (B) is smaller than that of the block copolymer (A) by 20,000 or more, preferably 40,000 or more.

In the present invention, the blending weight ratio of the block copolymer (A) and the block copolymer (B) is 55 to 97:45 to 3, preferably 65 to 95:35 to 5. If the blending ratio of the block copolymer (B) exceeds 45% by weight, the rigidity decreases, and if it is less than 5% by weight, the impact resistance decreases. In the present invention, the vinyl aromatic hydrocarbon content of the block copolymer (A) is higher than the vinyl aromatic hydrocarbon content of the block copolymer (B), and the difference is 15 to 55% by weight. When the difference in vinyl aromatic hydrocarbon content is less than 15% by weight, impact resistance is poor, and when it exceeds 55% by weight, transparency is lowered, which is not preferable. In the present invention, the block copolymer (A) generally has a vinyl aromatic hydrocarbon content of 65 to 95% by weight, preferably 70 to 99% by weight, and the block copolymer (B) is The vinyl aromatic hydrocarbon content is generally 10% by weight or more and less than 65% by weight, preferably 15% by weight or more and less than 15% by weight. Further, in the present invention, the vinyl aromatic hydrocarbon content as a whole of the sheet composition comprising the block copolymers (A) and (B) is 60 to 90.
%, Preferably 65-85% by weight. If the vinyl aromatic hydrocarbon content is less than 60% by weight, the rigidity is poor and 90
If it exceeds 5% by weight, the impact resistance is inferior, which is not preferable.

The block copolymer used in the present invention is a hydrocarbon solvent,
It is obtained by polymerizing an organolithium compound as an initiator.

The polymer structures of the block copolymers (A) and (B) used in the present invention are represented by the general formula: (A) (A-B) n ₊₁ (C) BA-B) n ₊₁ (B) AB-A ) N (In the above formula, A is a polymer segment mainly containing vinyl aromatic hydrocarbons, and B is a polymer segment mainly containing a conjugated diene. The boundary between the A segment and the B segment is not always clear. No need to be distinguished n
Is an integer of 1 or more in the case of the block copolymer (A), 0 or an integer of 1 or more in the cases of (a) and (c) in the case of the block copolymer (B), and 1 or more in the case of (b). Is an integer. Generally, n is 5 or less. ), A linear block copolymer represented by the general formula, or (d) [(B-A _{n m + 2} X (e)] ((A-B _{n m + 2} X (f) [(B-A _n B _{m + 2} X (G) [(A-B _n A _{m + 2} X (In the above formula, A and B are the same as above, and X is, for example, silicon tetrachloride, tin tetrachloride, epoxidized soybean oil, Represents a residue of a coupling agent such as an ester of a carboxylic acid or a residue of an initiator such as a polyfunctional organic lithium compound, m and n are integers of 1 or more, and are generally integers of 1 to 5). It is a radial block copolymer represented.

In the present invention, the polymer structure of the block copolymer (B) is not particularly limited, but it has a property as a conventional thermoplastic elastomer, for example, it is stretched at least twice its original length at room temperature to release the tension. According to the present invention, even a block copolymer having the following polymer structure, which does not exhibit the property of returning to its original length in a short time after being struck, is excellent in impact resistance and transparency according to the present invention. What I could get was quite unexpected. These block copolymers can also be effectively used as the component (B).

(1 ′) B−A (2 ′) B−A−B (3 ′) [B−A _{m + 2} X In the present invention, two or more kinds are selected within the range satisfying each requirement defined in the present invention. The block copolymer (A) or two or more kinds of block copolymers (B) can be used to obtain the sheet composition of the present invention.

The composition for a sheet of the present invention includes a polymer of the vinyl aromatic hydrocarbon monomer, the vinyl aromatic hydrocarbon monomer and another vinyl monomer such as ethylene, propylene, butylene, vinyl chloride or vinylidene chloride. , Vinyl acetate, acrylates such as methyl acrylate; methacrylic acid esters such as methyl methacrylate; copolymers with acrylonitrile etc., thermoplastic resins such as rubber modified impact resistant styrene resin (HIPS) etc. The rigidity and impact resistance can be improved. Particularly suitable thermoplastic resins include polystyrene, polyparamethylstyrene, styrene-α-methylstyrene copolymer, styrene-methylmethacrylate copolymer, and HIPS.

The blending amount of these thermoplastic resins is 0.1 to 500 parts by weight, preferably 0.5 to 500 parts by weight with respect to 100 parts by weight of the sheet composition.
300 parts by weight is common. Particularly in applications where the transparency and impact resistance of the sheet composition are emphasized, it is recommended that the blending amount of the thermoplastic resin be less than 100 parts by weight, preferably 50 parts by weight or less.

Various additives can be added to the sheet composition of the present invention depending on the purpose. Suitable additives include 30 parts by weight or less of a coumarone-indene resin, a terpene resin, a softening agent such as oil, and a plasticizer. Further, various stabilizers, pigments, antiblocking agents, antistatic agents, lubricants and the like can be added. Examples of anti-blocking agents, lubricants, and antistatic agents include fatty acid amides, ethylene bis stearamide, sorbitan monostearate, saturated fatty acid esters of aliphatic alcohols, pentaerythritol fatty acid esters, and the like, and ultraviolet absorbers. , Pt-butylphenyl salicylate, 2- (2'-hydroxy-
5'-methylphenyl) benzotriazole, 2-
(2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,5-bis- [5'-t-butylbenzoxazolyl- (2)] thiophene, etc., The compounds described in "Plastics and Rubber Additives Handbook" (Chemical Industry Co., Ltd.) can be used. These are generally 0.01-5% by weight, preferably 0.1-
Used in the range of 2% by weight.

The sheet composition of the present invention can be obtained by any conventionally known compounding method. For example, an open roll, an intensive mixer, an internal mixer, a co-kneader, a continuous kneader with a twin-screw rotor, a melt-kneading method using a general kneader such as an extruder, each component is dissolved in or dispersed in a solvent And the like are used. Alternatively, during the production of the block copolymer,
It is also possible to obtain a sheet composition of the present invention by newly adding a catalyst during the polymerization reaction or by deactivating a part of the active sites of the polymer by adding a deactivator.

〔The invention's effect〕

The sheet composition of the present invention is transparent and has excellent impact resistance, and can be used as a molding material for various molded articles. That is, the composition for a sheet of the present invention is a sheet, an extrusion-molded product such as a film, and a method such as vacuum-molding, pressure-molding or the like by using the same processing means as a usual thermoplastic resin as it is or colored. Thus, it can be used in a wide range of container and packaging material fields such as a thermoformed molded product, specifically, food container packaging, blister packaging material, fruit and fruit packaging film, and the like.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.

Examples 1 to 8 and Comparative Examples 1 to 10 Block copolymers having the polymer structure, styrene content and molecular weight shown in Tables 1 and 2 were prepared in cyclohexane using n-butyllithium as a catalyst. The resulting block copolymer was compounded according to the compounding weight ratio shown in the table, and a sheet having a thickness of 0.7 mm was prepared with a sheet extruder. The physical properties of each sheet are shown in Tables 1 and 2.

Next, in Example 1, methanol was added as a deactivating agent after the polymerization of the B-A-B polymer during the production of the block copolymer (A) to deactivate a part of the B-A-B polymer,
A sheet composition having the same polymer structure, styrene content, molecular weight and blending composition as in Example 1 except that the block copolymer (B) was produced in the same polymerization system was obtained. The composition for a sheet thus obtained exhibited the same performance as that of Example 1.

Examples 9 and 10 Polystyrene and HIPS were further added to the sheet composition of Example 6 to prepare a sheet having a thickness of 0.7 mm with a sheet extruder. The physical properties of the obtained sheet are shown in Table 3.

Claims (1)

[Claims] 1. A composition comprising (i) a polymer segment mainly containing at least two vinyl aromatic hydrocarbons and a polymer segment mainly containing at least one conjugated diene, and having a vinyl aromatic hydrocarbon content of 65. ~ 95% by weight, molecular weight 10
55 to 97 parts by weight of a block copolymer (A) of 10,000 to 400,000, (ii) a polymer segment mainly composed of at least one vinyl aromatic hydrocarbon and a heavy polymer mainly composed of at least one conjugated diene. 3 to 45 parts by weight of a block copolymer (B) having a vinyl aromatic hydrocarbon content of 15% by weight or more and less than 50% by weight and a molecular weight of 60,000 to 150,000. The vinyl aromatic hydrocarbon content of the polymer (A) is 15 to 50% by weight higher than the vinyl aromatic hydrocarbon content of the block copolymer (B), and the vinyl aromatic hydrocarbon content of the composition as a whole is high. A sheet composition comprising 60 to 90% by weight.