JPS6026429B2 - transparent thermoplastic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transparent thermoplastic resin composition, and in particular, it has a high rigidity (flexural modulus) without covering the transparency, which is the excellent physical property of a styrene-butadiene block copolymer. The present invention relates to a transparent thermoplastic resin composition with improved practical properties such as heat resistance and heat resistance.

In general, various types of styrene-butadiene block copolymers are known, such as those with linear block structures and those with radially branched block structures. It has excellent transparency, and generally changes from rubber-like to resin-like as the styrene content increases.

However, such styrene-butadiene flock copolymers have the disadvantage of being inferior in practical physical properties such as rigidity and heat resistance, and in the past, polystyrene has been blended to overcome these disadvantages. is being carried out. By the way, blending polystyrene into a styrene-butadiene block copolymer improves rigidity, heat resistance, etc., but it impairs transparency, which is an excellent property of the styrene-butadiene block copolymer. However, the degree of cloudiness of the styrene-ptadiene block copolymer and polystyrene varies greatly depending on the blending ratio, and there are problems such as a large rate of decrease in strength and elongation.

Based on this viewpoint, the present invention provides a modification that can improve practical physical properties such as rigidity and heat resistance without impairing transparency, which is the excellent physical property of styrene-ptadiene floc copolymer. As a result of various studies regarding materials, the present invention was completed. That is, the present invention provides general formula (A-B)xY
(However, A represents the pinyl aromatic hydrocarbon polymer block, B represents the conjugated gene polymer block, Y represents the residue of the polyfunctional coupling agent used to form the radial polymer, and ×
represents the number of functional groups of the polyfunctional coupling agent, and is an integer of at least 3 or more. It is a transparent thermoplastic resin composition consisting of 90-5% of a radially branched block copolymer represented by ) and 10-5% of a styrene-methacrylic acid ester copolymer. The present invention will be explained in detail below.

In the radially branched block copolymer represented by the general formula (A-B) The conjugated diene polymer block B, which is a polymer block formed of any of group hydrocarbon compounds, is, for example, a polymer block formed of any of conjugated diene compounds such as putadiene and isoprene.

The atom(s) Y may also be used for polyfunctional processing agents used in the formation of radial polymers, such as polyepoxides, polyisocyanates, polyaldehydes, polyketones, polyamines, tetraallyltin, fluorinated The central atom of a branched block copolymer derived from a trifunctional or more functional coupling agent such as a tin compound such as stannic oxide, or
It is a central atomic group and the statement is an integer of at least 3 or more.

Furthermore, the ratio of the vinyl aromatic hydrocarbon polymer block A to the conjugated gene polymer block B is as follows:
A so-called resin-like branched block copolymer with a low rubber content is preferred, having a content of 40 to 1% and a vinyl aromatic hydrocarbon polymer content of 60 to 9%. It takes,
The branched block copolymer has excellent physical properties such as strength and processability, as well as particularly excellent transparency. Specific methods for producing the branched block copolymer are described in Japanese Patent Publication No. 48-4106 and Japanese Patent Publication No. 49-49. An example thereof is described in detail in Japanese Patent No.-86957.

Furthermore, the styrene-methacrylic acid ester copolymer referred to in the present invention has an optical refractive index close to that of the radially branched block copolymer described above, and from this point of view, the styrene content is low. It is preferable that the composition contains at least 6 t% or more (4 t% or less of methacrylic acid ester).

Specifically, they are copolymers such as styrene-methyl methacrylate IJ rate copolymer resin (PMS) and Q-methylstyrene-methyl methacrylate copolymer resin. In the present invention, the radially branched block copolymer has a breakage content of preferably 85 to 4%, rather than 90% to 5%, while the styrene-methacrylic acid ester copolymer has a breakage content of 10 to 5%.
More preferably, the blending ratio is 15 to 5%. The reason for this limitation is that the Izod impact strength of the above-mentioned compounding ratio is 10% of the radially branched block copolymer
% and 10% styrene-methacrylic acid ester copolymer. It will also be improved.

In particular, the reason for the abnormal increase in Izod impact value is not clear, but it is not observed in ordinary linear block copolymers.
It is thought that the radially branched block copolymer and the styrene-methacrylic acid ester copolymer have appropriate compatibility and form a unique mixed layer that absorbs impact energy.

Furthermore, in the present invention, in order not to impair the transparency of the radially branched block copolymer, the optical refractive index of the styrene-methacrylic acid ester copolymer blended therein is made as close as possible. As a result of various studies, it was found that the difference in the optical refractive index between the two must be close to within ±0.003.

It has been found that as long as these conditions are satisfied, the transparency remains unchanged even if the two are mixed in any proportion. below,
The present invention will be explained in more detail based on examples. Example 1 A radially branched block copolymer (product name: K-Resin, manufactured by Philips Co., Ltd.) having a light refractive index of 1.572 and a styrene content of approximately 75 wt% was selected.

On the other hand, styrene-methyl methacrylate copolymer (PMS) obtained by copolymerizing five types of styrene-methyl methacrylate monomers with varying styrene content in the range of 85 to 7 t% by bulk polymerization method. ), select
The results of measuring the optical refractive index of each are shown in Table 1. Each of these styrene-methyl methacrylate copolymers (PM
S) were mixed in a ratio of 5:5, formed into pellets using an extruder, and charged into an injection molding machine (3 oz. A plate-shaped molded article was obtained, and the total transmittance and degree of haze were measured for these plate-shaped molded articles. The results are shown in Table 1,
From this result, the larger the difference between the optical refractive index nk of the styrene-butadiene block copolymer and the optical refractive index np of the styrene-acrylic acid ester copolymer, the higher the total transmittance decreases. It can be seen that transparency deteriorates. The appearance of the plate-shaped molded product is almost transparent if the degree of haze is within 5, or the refractive index of both is within the range that does not impede the transparency of the radially branched block copolymer alone (the degree of haze is 3.1). The difference between Ink-npISO. 00
It can be seen that if it is 3, an almost satisfactory blended product can be obtained. Incidentally, the degree of cloudiness was determined by the following formula. Cloudiness (
%) = ore total dispersion transmittance rate X,.

〇Also, when examining the relationship between styrene content and optical refractive index for styrene-methacrylic acid ester copolymers based on the results in Table 1, it was found that as the styrene content (ZM%) increases, the optical refractive index increases. y also increases, and a relational expression such as approximately y=0.00092 chord 11.499 holds between the two. Therefore, if the optical refractive index of the radially branched block copolymer is known, the styrene content of the styrene-methacrylic acid ester copolymer, which does not inhibit its transparency, can be easily selected from the above schematic relational formula. It is. Table 1 Example 2 Radial branched styrene-butadiene block copolymer (b-SBR, manufactured by Philips Co., Ltd., product name K-Resin K
R03) and a styrene-methyl methacrylate copolymer resin (PM680) with a styrene content of 1.572 and a styrene content of t% are mixed in the proportions shown in Table 1, and the mixture is put into an extruder. The mixture was made into pellets and put into an injection molding machine (3-ounce screw-in-line type) to obtain various test pieces.

For each of these test pieces, tensile strength (k9/unlike), elongation (%), bending strength (k9/pine), and bending modulus (kg/
Table 2 shows the results of measuring the following physical properties: Izod impact strength (k9/skin/enemy), heat distortion temperature (°C), light transmittance (%), and degree of haze (%). .

Comparative Example 1 GP polystyrene (G
I5) was blended, and various test pieces were molded in the same manner as in the above example, and the physical properties were measured. The results are shown in Table 3.

Table 2 Physical Properties of Example Blend Product Table 3 Physical Properties of Comparative Example Blend Product As is clear from Tables 2 and 3 above, the Example blend product (a blend product of K-resin and PMS80) has a flexural modulus of elasticity of In addition to being improved in (stiffness) and heat distortion temperature (heat resistance), unlike the comparative blend product (a blend product of K-resin and GP polystyrene), the degree of cloudiness is lower than that of radially branched styrene soap resin. Copolymer (K-resin) 10 skin t% decreases, and the transparency, which is the excellent physical property of styrene-butadiene flock copolymer, is not only not impaired but also improved, and the rate of decrease in elongation is also reduced. It is smaller than that of the comparative blend product, and furthermore, the izot impact strength of the comparative blend product is lower than that of the styrene-butadiene block copolymer (K-resin).
The value is almost the same as the case of 100 wt%, but in the example blend product, 100 wt% of styrene-butadiene block copolymer (K-resin) and 10 skin t% of styrene-acrylic acid ester polymer (PMS80). This shows an abnormally high value compared to the case of .

Comparative Example 2 A linear styrene-butadiene block copolymer with a light refractive index of 1.549 and a styrene content of 4 t% (trade name: Tuffrene, manufactured by Asahi Kasei Kogyo Corporation) and a light refractive index of 1.549 were used. Styrene-methyl methacrylate copolymer (PMS40) with a styrene content of 4 t% was mixed in a ball 7 at the ratio shown in Table 4, and a test piece was molded in the same manner as in Example 2 to measure each physical property. The results are shown in Table 4.

As is clear from the results in Table 4 and Table 3, there is no abnormal increase in the Wizot impact value due to blending.
Furthermore, it can be seen that the degree of cloudiness (%) changes greatly depending on the change in the blending ratio, probably due to the large difference in the optical refractive index between the two.

Claims (1)

[Claims] 1 General formula (A-B)_xY (where A is a vinyl aromatic hydrocarbon polymer block, B is a conjugated diene polymer block, and Y is a polyfunctionality used to form a radial polymer) (represents a residue of a coupling agent, x indicates the number of functional groups in the multifunctional coupling agent, and is an integer of at least 3) 90-5 radially branched block copolymer represented by
0 wt% and 10 to 50 wt% of a styrene-methacrylic acid ester copolymer in which the difference in optical refractive index between this radially branched block copolymer is within ±0.003,
The radially branched block copolymer has a vinyl aromatic hydrocarbon polymer content of 60 to 90 wt%, and the styrene-methacrylic acid ester copolymer has a styrene content of 60 wt% or more. Transparent thermoplastic resin composition.