JPS5925821B2 - Polymer composition with impact resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the impact resistance of block copolymers comprising vinyl aromatic compounds and conjugated dienes.

Various structures have been studied for the above block copolymer ι, but in general terms, the general structural formula is (A-B)n or (A-B)n-A (A is a block of a polymer of a vinyl aromatic compound, B represents a block of a polymer of a conjugated diene, n represents a positive integer), or a linear block polymer represented by USP-3639517
As seen in the general structural formula A-B-A or A-B-A
It is a star-shaped block copolymer represented by, and the block structure is a complete block structure or JP-A-8-4.
As shown in No. 8546, a so-called tapered block structure containing an AB random copolymer portion in the transition region between block A and block B has been proposed.

Block A substances include vinyl aromatic compounds such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene, and tert-butylstyrene; block B substances include conjugated dienes such as butadiene and isoprene. .

Furthermore, it is well known that these block copolymers function as thermoplastic resins when the conjugated diene component is small, and as thermoplastic rubbers when the conjugated diene component is large. . The branching point of the component ratio that governs the resin region and the rubber region differs slightly depending on the type of component or the structure of the block, and is difficult to express with exact numerical values, but it is approximately when the content of the conjugated diene component is 40%. It is close to % by weight.

Therefore, the present invention relates to the modification of so-called thermoplastic resins having a conjugated diene content of 40% by weight or less.
Thermoplastic resins have interesting physical properties as shown in Japanese Patent Application Laid-Open No. 48-48546, but their impact resistance is not necessarily sufficient and they are subject to limitations in terms of use.

The present inventors have discovered that by mixing an impact-resistant styrene polymer with the above-mentioned block copolymer, the impact strength can be significantly improved.

The impact-resistant styrene polymer is obtained by bulk or suspension polymerization of styrene or a mixture of styrene and a monomer copolymerizable with an elastomer, ie, a styrene-butadiene block polymer.

In this case, the monomer copolymerizable with styrene is α
-Methylstyrene, vinyltoluene, methyl methacrylate, acrylonitrile and the like.

Further, an example of the styrene-butadiene block polymer in this case is the general structural formula (C-D)n or (C-D)n-
A block copolymer represented by C or (D-C)n-D (in the formula, C represents a styrene polymer block, D represents a butadiene polymer block, and n represents a positive integer). be.

The amount of high impact styrenic polymer making up the target composition varies widely depending on the impact strength desired for the final product, but is from 3 to 95% by weight of the target composition.

If the amount is less than 3% by weight or more than 95% by weight, the physical properties of the block copolymer and impact-resistant styrene polymer alone cannot be dramatically improved.

As shown in the examples, it is surprising that the impact strength is dramatically improved by adding only 3% by weight of the impact resistant styrene polymer to the target composition.

What should be further noted is that the mixing of the above two components produces a significant synergistic effect.

Although this additive effect differs depending on the types of constituent components, the impact strength has a maximum value at a certain composition4.

Furthermore, a particularly noteworthy effect is that systems using styrene-butadiene block polymers used in impact-resistant styrene polymers not only exhibit the above-mentioned mutual effect, but also significantly reduce the transparency of the target composition. It has the advantage of not causing any damage.

Note that the impact-resistant styrene polymer-containing component in the composition of the present invention naturally contains a styrene homopolymer or copolymer that has not been graft-polymerized. It may be added before, during and/or after the composition is manufactured. EXAMPLES The present invention will be specifically explained below using Examples and Comparative Examples, but the present invention is not limited to these Examples.

Comparative Example 1 Benzene 801 purified in a 1001 volume autoclave
and add 147% of secondary butyllithium to it.
mmol was added and kept at 40°C.

8 kg of styrene was introduced into this and polymerized while stirring. Next, 4 kg of butadiene was added to complete the polymerization, and then 8k9 of styrene was further added and polymerized. A small amount of alcohol was added to the polymerization solution to stop the polymerization activity, and a thermoplastic resin polymerization solution was obtained. The polymer was precipitated by a steam stripping method and separated and recovered.
After drying, the obtained polymer was mixed with 0.5 parts by weight of 2,6-ditertiarybutyl-4-methylphenol by a conventional method.
Adding 100 parts by weight of polymer, 0.5 parts by weight of trisnonylphenyl phosphite/100 parts by weight of polymer, and 0.2 parts by weight of stearic acid/100 parts by weight of polymer,
Extrusion was carried out at an extrusion temperature of 200°C to obtain pellets. This polymer is a styrene-butadiene-styrene block copolymer, and each styrene block has a molecular weight of 600.
00, and the molecular weight of the butadiene flock is 30,000.
It is.

Izo impact values and H-e of compositions obtained at various mixing ratios of this polymer and high-impact polystyrene obtained by bulk polymerizing a styrene solution in which 5.5% by weight of polybutadiene was dissolved. are shown in Table 1 as experiment numbers 1 to 9. Comparative Example 2 The physical properties of the block copolymer and high-impact polystyrene used in Comparative Example 1 are shown in Table 1 as Experiment Nos. 10 to 11.

Comparative Example 3 Completely the same procedure as in Comparative Example 1 except that the styrene used in the first stage polymerization and the third stage polymerization was changed to 7k9, and the butadiene used in the second stage polymerization was changed to 6 kg. By doing this, the molecular weight of each styrene block was 52,500, and the molecular weight of the butadiene block was 4.
A block copolymer having a molecular weight of 5000 was obtained.

The physical properties of the system using this polymer were determined in Experiment Nos. 12 to 15.
It is shown in Table 1. Comparative Example 4 In Comparative Example 1, the physical properties of the system using styrene-butadiene rubber (butadiene content 75% by weight) as the elastomer for impact-resistant polystyrene are shown in Table 1 as Experiment Nos. 16 to 19.

Comparative Example 5 The physical properties of the impact-resistant polystyrene used in Comparative Example 4 are shown in Table 1 as Experiment No. 20.

*(1) Izot impact value (with notch) is measured according to JIS-K-6871. (2) Haz
e is an ASTM-
Measured by D-1003.

Example 1 In Comparative Example 1, a styrene-butadiene-styrene block copolymer (the molecular weight of each styrene block was 20,000,
The physical properties of the system using butadiene block (molecular weight 60,000) are shown in Table 1 as experiment numbers 21 to 24.

Comparative Example 6 The physical properties of the impact-resistant polystyrene used in Example 1 are shown in Table 1 as Experiment No. 25.

Example 2 and Comparative Example 7 As an elastomer for impact-resistant polystyrene, a styrene-butadiene-styrene-butadiene flock copolymer (the molecular weight of each styrene flock was 20,000,
The physical properties of the system using the terminal butadiene block having a molecular weight of 200,000 and the intermediate butadiene block having a molecular weight of 40,000 are shown in Table 2 as experiment numbers 26 to 30.

Example 3 and Comparative Example 8 A butadiene-styrene-butadiene block copolymer (the molecular weight of the styrene block is 30,000 and the molecular weight of each butadiene block is 35,000) was used as an elastomer for impact-resistant polystyrene. The physical property values of the systems tested are shown in Table 2 as Experiment Nos. 31 to 35.

Comparative Example 9 In Comparative Example 1, a dilithium compound of butadiene oligomer was used instead of secondary butyllithium.
16 kg as a monomer addition method.
A polymer having a tapered block structure of styrene-butadiene was obtained by the same procedure except that a mixture of styrene and 4k9 butadiene was added all at once.

The physical properties of the system of the composition of this polymer and the high-impact polystyrene used in Comparative Example 1 were determined in Experiment Nos. 36 to 36.
39 in Table 3. Comparative Example 10 The same procedure as in Comparative Example 9 was repeated except that the amounts of monomers added were changed to 14 kg as styrene and 6k9 as butadiene.

Claims (1)

[Claims] 1 an effective amount of a high-impact styrenic polymer comprising styrene or a mixture of styrene and a monomer copolymerizable with styrene, mixed with and polymerized with a styrene-butadiene block polymer; and a block copolymer, the block copolymer comprising: A polymer composition having good impact resistance and transparency, characterized in that the copolymer is composed of a vinyl aromatic compound and a conjugated diene, and the content of the conjugated diene is 40% by weight or less.