JP2020139032A - Rubber-modified styrene resin composition, sheet, lighting cover and molded product - Google Patents

Abstract

To provide a rubber-modified styrene resin composition having an excellent balance of total light transmittance, diffused light transmittance, and whitening resistance, by optimizing reinforcing rubber particles dispersed in the rubber-modified styrene resin composition.SOLUTION: The rubber-modified styrene resin composition of the present invention contains a styrene polymer forming a matrix and rubber-like polymer particles dispersed as islands in the matrix. The rubber-like polymer particles include styrene-based polymer particles and have a sea-island structure, containing 99.0 to 94.0% by mass of the styrene-based polymer and 1.0 to 6.0% by mass of the rubber-like polymer. The rubber-like polymer particles are a polybutadiene rubber and/or a styrene-butadiene copolymer. The particle size of the rubber-like polymer particles is 2.0 to 5.5 μm, and a content of methyl ethyl ketone insoluble gel in the rubber-modified styrene resin composition is 2.0 to 15.0% by mass.SELECTED DRAWING: None

Description

The present invention relates to a rubber-modified styrene resin composition having excellent light diffusivity, light transmission, and whitening resistance, a sheet containing the resin composition, and a molded product such as a lighting cover obtained from the sheet.

In recent years, as a light source for lighting, LEDs having stronger directivity have been used instead of fluorescent lamps that have been conventionally used. As a result, as a required characteristic of the lighting cover, stronger light diffusivity is required in order to prevent the light source from being seen through while ensuring sufficient light transmission.

Special Publication No. 60-21662 Japanese Unexamined Patent Publication No. 60-139758 Japanese Patent No. 251544 Japanese Unexamined Patent Publication No. 11-60966 Japanese Unexamined Patent Publication No. 2004-50607 Japanese Unexamined Patent Publication No. 08-198976 Japanese Unexamined Patent Publication No. 2000-296581 Japanese Unexamined Patent Publication No. 2004-90626

By the way, as such a lighting cover, conventionally, by adding a large amount of a light diffusing agent to a transparent resin such as an acrylic resin or a styrene resin, both light diffusivity and light transmission have been achieved.

As a specific method for imparting light diffusivity to a transparent resin, a method of blending fine particles having different refractive indexes with the transparent resin has been disclosed for a long time. For example, a technique for blending 1 to 10 μm fine particles (Patent Document 1), a technique for blending 10 to 50 μm fine particles (Patent Document 2), and a technique for using 1 to 6 μm silicone resin fine particles and 1 to 7 μm inorganic powder in combination. (Patent Document 3) Examples thereof include a technique of using crosslinked resin fine particles of less than 5 μm and a crosslinked resin fine particle of 5 to 10 μm in combination (Patent Document 4), and a technique of blending a light diffusing agent of 1 to 20 μm (Patent Document 5). .. However, these fine particles, whether organic or inorganic, have a problem that they have a low affinity for the resin and the impact resistance is lowered when a large amount is added.

Further, although a technique for adding an acrylic multilayer structure polymer is disclosed for the purpose of improving impact resistance (Patent Documents 6 to 8), the particle size of the multilayer structure polymer usually produced by emulsion polymerization is large. Since it is smaller than 0.5 μm and light on the short wavelength side is easily absorbed, the yellowness of the transmitted color becomes high, which is not preferable.

Further, as a styrene resin having impact resistance, there is a rubber-modified styrene resin (impact resistant polystyrene), but the conventional rubber-modified styrene resin has a high yellowness of a transparent color and further has a light diffusivity. And there was a problem of poor light transmission. Patent Document 9 discloses that by setting the diameter of the particles dispersed in the rubber-modified styrene resin and the cumulative volume ratio of the particles within a specific range, the light transmission is excellent and the light diffusing property is obtained. ing. However, although the diffused light transmittance has been improved by this technology, there is a problem that whitening scratches occur when the product is lightly pressed with a nail, and when the light is turned on, it becomes a shadow and becomes a black spot. It was.

Therefore, in the present invention, by optimizing the reinforcing rubber particles dispersed in the rubber-modified styrene resin composition, the rubber-modified styrene has an excellent balance of total light transmittance, diffused light transmittance, and whitening resistance. An object of the present invention is to provide a based resin composition, a sheet containing the resin composition, and a molded product such as a lighting cover obtained from the sheet.

In view of the current situation, the present inventors have examined in detail the structure of the reinforcing rubber particles contained in the rubber-modified styrene resin composition and its content, and as a result, the amount of the specific rubber-like polymer and the rubber particle structure are determined. We have found that a rubber-modified styrene resin composition having an excellent balance between diffused light transmission and whitening resistance, which is preferably used for a lighting cover, can be obtained, and have reached the present invention.

That is, the present invention
[1] A styrene-based polymer forming a matrix and rubber-like polymer particles dispersed in the matrix in an island shape are contained, and the rubber-like polymer particles contain the styrene-based polymer particles and have a sea-island structure. It is a rubber-modified styrene resin composition having
The rubber-like weight was 99.0 to 94.0% by mass of the styrene-based polymer with respect to 100% by mass of the total of the styrene-based polymer and the rubber-like polymer forming the rubber-like polymer particles. Containing 1.0 to 6.0% by mass of coalescence,
The rubber-like polymer is a polybutadiene rubber and / or a styrene-butadiene copolymer.
The rubber-like polymer particles have a particle size of 2.0 to 5.5 μm.
A rubber-modified styrene-based resin composition, wherein the content of the methyl ethyl ketone-insoluble gel content of the rubber-modified styrene-based resin composition is 2.0 to 15.0% by mass.
[2] The rubber-modified styrene-based resin composition according to the above [1], wherein the swelling index of the toluene-insoluble component of the rubber-modified styrene-based resin composition with respect to toluene is in the range of 10 to 14.
[3] A sheet obtained by extrusion-molding the rubber-modified styrene resin composition according to the above [1] or [2].
[4] A molded product obtained by thermoforming the sheet according to the above [3].
[5] A lighting cover formed by thermoforming the sheet according to the above [3].

According to the present invention, a rubber-modified styrene resin composition having an excellent balance of total light transmittance, diffused light transmittance, and whitening resistance, a sheet containing the resin composition, and a lighting cover obtained from the sheet. Etc. can be provided.

Hereinafter, embodiments of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail, but the present invention is not limited to the present embodiment.

The rubber-modified styrene-based resin composition of the present embodiment contains a styrene-based polymer forming a matrix and rubber-like polymer particles dispersed in an island shape in the matrix, and the rubber-like polymer particles are said to be the same. It contains styrene-based polymer particles and has a sea-island structure.
Here, examples of the styrene-based monomer forming the styrene-based polymer in the rubber-modified styrene-based resin composition in the present embodiment include styrene, α-methylstyrene, p-methylstyrene, and pt-butylstyrene. Etc., and these may be used alone or in combination of two or more. Of these, styrene is preferable.
If necessary, other monomers copolymerizable with the styrene-based monomer may be used as long as the object of the present invention is not impaired. Other copolymerizable monomers that can be used here include, for example, cyanide vinyl monomers such as acrylonitrile and maleimide, methyl (meth) acrylate, ethyl (meth) acrylate, and (meth). ) (Meta) acrylic acid ester monomer such as butyl acrylate, anhydride group-containing monomer such as maleic anhydride and itaconic anhydride, maleimide, N-methylmaleimide, N-phenylmaleimide, N-cyclohexylmaleimide and the like. Examples thereof include dicarboxylic acidimide-containing monomers, acrylic acid, methacrylic acid, maleic anhydride, itaconic acid and other carboxyl group-containing monomers.
The amount of the other monomer copolymerizable with the styrene monomer is preferably 25% by mass or less, more preferably 10% by mass or less as the monomer constituting the matrix.

The rubber-modified styrene-based resin composition in the present embodiment has a sea-island structure, in which the styrene-based polymer forms a matrix, and the rubber-like polymer particles are dispersed in the matrix in an island shape. Further, the rubber-like polymer particles in the rubber-modified styrene resin composition contain a styrene-based polymer (particles) in the rubber-like polymer particles. In the rubber-modified styrene-based resin composition of the present embodiment, the styrene-based polymer particles encapsulated in the rubber-like polymer particles preferably have an extremely small particle size and are uniform.

The rubber-like polymer forming the rubber-like polymer particles in the present embodiment is a polybutadiene rubber (locis polybutadiene, high cis polybutadiene) and / or a styrene-butadiene copolymer (random and blocked styrene-butadiene copolymer). (SBR)), polybutadiene rubber is preferable, and high cis polybutadiene is particularly preferable. When a styrene-butadiene copolymer is used as the rubber-like polymer, the content of the styrene polymer in the copolymer is preferably 25% by mass or less, more preferably 10% by mass or less. When the content of the styrene polymer in the styrene-butadiene copolymer increases, the difference in refractive index from the matrix becomes close, and the diffusibility tends to decrease.

The rubber-modified styrene-based resin composition of the present embodiment contains 1.0 to 6.0% by mass of the rubber-like polymer and 1.0 to 6.0% by mass of the rubber-like polymer with respect to 100% by mass of the total of the styrene-based polymer and the rubber-like polymer. Is included in the range of 99.0 to 94.0 mass%. Further, the rubber polymer is preferably contained in the range of 1.5 to 5.0% by mass, the styrene polymer is contained in the range of 98.5 to 95.0% by mass, and the rubber polymer is more preferably 2.0 to 4% by mass. It contains 5.5% by mass and a styrene-based polymer in the range of 98.0 to 95.5% by mass. If the rubber-like polymer is less than 1.0% by mass, the light diffusivity and impact resistance are lowered, and if it exceeds 6.0% by mass, the light transmission and rigidity are lowered, and whitening scratches are likely to occur.

The particle size of the dispersed particles of the rubber-like polymer of the rubber-modified styrene resin composition is 2.0 to 5.5 μm, preferably 2.5 to 5.0 μm, and more preferably 3.0 to 4. It is 5 μm. If the particle size is less than 2.0 μm, the diffusivity is lowered, the light source is easily seen through when used for light diffusing applications such as lighting covers, the yellowness of the transmitted color is increased, and the impact resistance is further increased. Inferior to. On the other hand, if the particle size exceeds 5.5 μm, it is necessary to add a large amount of rubber-like polymer particles in order to satisfy high light diffusivity, and if too much rubber-like polymer particles are added, the rigidity decreases. , Whitening scratches are likely to occur, which is not preferable.

The methyl ethyl ketone insoluble gel content of the rubber-modified styrene resin composition is in the range of 2.0 to 15.0% by mass, preferably 4.0 to 13.0% by mass, and more preferably 5.0 to 12.0% by mass. %. As the amount of the methyl ethyl ketone insoluble gel decreases, the impact strength tends to decrease and the light diffusivity tends to decrease, and as the amount increases, whitening scratches tend to occur and the light transmission tends to decrease.

The content of the methyl ethyl ketone insoluble gel in the rubber-modified styrene resin composition is measured by dissolving the resin in a solvent, centrifuging and then decanting to separate the soluble and dispersed phases of the insoluble gel, and then insoluble. Is determined by the operation of drying. Generally, toluene is used as the solvent. However, in a rubber-modified styrene resin composition in which the diameter of the dispersed particles is small or the degree of cross-linking of the rubber-like polymer is low, when toluene is used, the affinity between toluene and the gel is good. During decantation, the gel content may flow out and the content of the dispersed phase may become lower than the true value. Therefore, in the present invention, methyl ethyl ketone is used as the solvent. By using methyl ethyl ketone, the content of the dispersed phase can be measured without the outflow of gel during decantation.

The swelling index of the toluene-insoluble component of the rubber-modified styrene resin composition with respect to toluene is 10 to 14, preferably 10 to 13, and more preferably 11 to 13. The swelling index represents the crosslink density of the rubber-like polymer. The smaller the value, the higher the crosslink density, and the larger the value, the lower the crosslink density. As the swelling index becomes smaller, the strength of the rubber-modified styrene resin composition tends to decrease. On the other hand, as the swelling index increases, the dispersed particles tend to be deformed due to the orientation during the molding process, the strength in the direction orthogonal to the orientation direction decreases, and the diffusivity tends to decrease.

An example of the method for producing the rubber-modified styrene resin composition of the present embodiment is shown.
In a typical embodiment, the rubber-modified styrene resin composition is made by polymerizing a styrene-based monomer in the presence of a rubber-like polymer, and the rubber-like polymer is dispersed in the styrene-based polymer. It can be manufactured by methods involving the formation of structures. There are no particular restrictions on the polymerization method of the styrene-based monomer, and ordinary bulk polymerization, solution polymerization, suspension polymerization and the like can be carried out using a solution in which rubber is dissolved in the styrene-based monomer. Further, it is preferable to appropriately select and use a solvent and a chain transfer agent for adjusting the melt flow rate. As the solvent, toluene, ethylbenzene, xylene and the like can be used. The amount of the solvent used is not particularly limited, but is preferably in the range of 0 to 50% by mass with respect to 100% by mass of the total amount of the polymerization raw material liquid. As the chain transfer agent, n-dodecyl mercaptan, t-dodecyl mercaptan, α-methylstyrene dimer and the like are used, and α-methylstyrene dimer is preferable. The amount of the chain transfer agent used is preferably 0.01 to 2% by mass, more preferably 0.03 to 1% by mass, still more preferably 0.05 to 0.2, based on 100% by mass of the total amount of the polymerization raw material liquid. It is in the range of mass%. The polymerization reaction temperature is preferably in the range of 80 to 200 ° C, more preferably 90 to 180 ° C. When the reaction temperature is 80 ° C. or higher, the productivity is good and industrially suitable, while when the reaction temperature is 200 ° C. or lower, it is possible to avoid the formation of a large amount of low molecular weight polymer, which is preferable. If the target molecular weight of the styrene-based polymer cannot be adjusted only by the polymerization temperature, it may be controlled by the amount of the initiator, the amount of the solvent, the amount of the chain transfer agent, or the like. The reaction time is generally 0.5 to 20 hours, preferably 2 to 10 hours. If the reaction time is 0.5 hours or more, the reaction proceeds satisfactorily, while if the reaction time is 20 hours or less, the productivity is good and industrially suitable.

In the above production method, the particle size of the dispersed particles of the rubber-like polymer in the rubber-modified styrene resin composition can be controlled by the rotation speed of the stirrer in the reactor, and the amount of the methyl ethyl ketone insoluble gel. Can be controlled by the amount of initiator, and the swelling index of toluene insoluble in toluene can be controlled by the temperature of the extruder of the recovery system.

The amount of the rubber-like polymer in the rubber-modified styrene resin can be controlled by adjusting the content and the polymerization rate of the rubber-like polymer in the raw material so as to reach the target content. The rubber-modified styrene resin of the present invention can be produced by the above-mentioned production method. Alternatively, the rubber-modified styrene resin composition obtained by the above production method can be produced by mixing and diluting a styrene resin such as a polystyrene resin that does not contain a rubber-like polymer. When the rubber-modified styrene-based resin composition is produced by the above-mentioned production method, the amount of the rubber-like polymer in the rubber-modified styrene-based resin composition is preferably 1 to 6% by mass, more preferably 1.5 to 5%. It is by mass%, more preferably 2 to 4.5% by mass.

Examples of the organic peroxide used as a polymerization initiator include peroxyketals, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, peroxyesters, ketone peroxides, hydroperoxides and the like. Can be mentioned.

As the polymerization solvent, ethylbenzene, toluene, xylene and the like can be used.

In the present embodiment, at any stage before and after the recovery step when producing the rubber-modified styrene resin composition, or at the stage of extrusion processing and molding processing of the rubber-modified styrene resin composition, if necessary, an object of the present invention. Various additives such as UV absorbers, light stabilizers, hindered phenol-based, phosphorus-based, sulfur-based antioxidants, lubricants, plasticizers such as liquid paraffin, antistatic agents, flame retardants, as long as they do not impair , Various dyes and pigments, fluorescent whitening agents, light diffusers, and selective wavelength absorbers may be added.

Here, an ultraviolet absorber and a light stabilizer can be added to the rubber-modified styrene resin composition of the present embodiment for the purpose of preventing coloring due to ultraviolet rays generated from the light source lamp. Examples of the ultraviolet absorber include 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5 bis (α, α'dimethylbenzyl) phenyl] benzotriazole, 2-( 3,5-Di-t-amyl-2-hydroxyphenyl) benzotriazole-based ultraviolet absorbers such as benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy Benzophenone-based UV absorbers such as -4-n-octoxybenzophenone, phenylsalicylate, salicylic acid-based UV absorbers such as 4-t-butylphenylsalicylate, 2- (1-arylalkydene) malonic acid ester-based UV absorbers , Oxalanilide-based ultraviolet absorbers can be mentioned. Further, examples of the light stabilizer include a hindered amine-based light stabilizer. Examples of the hindered amine-based light stabilizer include bis (2,2,6,6-tetramethyl-4-piperidyl) sepate and N, N'-bis (3-aminopropyl) ethylenediamine / 2,4-bis. [N-Butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino] -6-chloro-1,3,5-triazine condensate can be mentioned. The ultraviolet absorber and the light stabilizer can be used alone or in combination of two or more, and the total amount of the ultraviolet absorber and the light stabilizer added is 0, based on 100 parts by mass of the rubber-modified styrene resin composition. 02 to 2.0 parts by mass is preferable. More preferably, it is 0.1 to 1.5 parts by mass.

Further, a masking agent such as a fluorescent whitening agent or a brewing agent can be arbitrarily used in the rubber-modified styrene resin composition of the present embodiment, if necessary.
A known method can be selected as the method for adding the additive to the rubber-modified styrene resin of the present embodiment. For example, a rubber-modified styrene resin composition, additives, etc. and, if necessary, a styrene resin containing no rubber-like polymer are mixed with a Henschel mixer, a tumbler, etc., and then a single-screw or twin-screw extruder, various kneaders, etc. By melt-kneading with the above, a composition formed into pellets, plates, or the like can be obtained.

In the present embodiment, a sheet can be produced from a rubber-modified styrene resin composition by an extrusion molding method, and a rubber-modified styrene resin composition or the above can be produced by a method such as extrusion molding, injection molding, or compression molding. Various molded products can also be manufactured from the sheet. These sheets and molded products can be suitably used for lighting equipment, electric signboards, liquid crystal displays, liquid crystal televisions, and the like. Among them, the rubber-modified styrene resin composition of the present embodiment is suitably used as a cover for lighting obtained by thermoforming the sheet.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

<Method for producing resin 1>
78.2 parts by mass of styrene as a styrene-based monomer, 9.8 parts by mass of polybutadiene rubber (BR15HB manufactured by Ube Kosan Co., Ltd.) as a rubber-like polymer, 12 parts by mass of ethylbenzene as a solvent, and 1,1-bis (1,1-bis) as a polymerization initiator. Polymerization by mixing and dissolving 0.003 parts by mass of t-butylperoxy) cyclohexane, 0.10 parts by mass of α-methylstyrene dimer as a chain transfer agent, and 0.15 parts by mass of antioxidant Irganox 1076 (manufactured by BASF Japan). The liquid is continuously charged at 3.2 liters / Hr into a 6.2 liter styrene-type reactor-1 equipped with a stirrer and whose temperature can be controlled in 3 zones, and the temperature is set to 117 ° C./123 ° C./129 ° C. Adjusted to. The rotation speed of the stirrer was 120 rpm.

Subsequently, a 6.2-liter laminar-flow reactor-2 equipped with a stirrer and temperature-controllable in three zones, connected in series with the laminar-flow reactor-1, was added to the laminar-flow reactor-1. The reaction solution was sent. The rotation speed of the stirrer was 15 rpm, and the temperature was set to 136 ° C./138 ° C./140 ° C. Subsequently, the reaction solution in the laminar flow reactor-2 was sent to a 6.2 liter laminar flow reactor-3 equipped with a stirrer and whose temperature could be controlled in three zones. The rotation speed of the stirrer was 10 rpm, and the temperature was set to 147 ° C./156 ° C./159 ° C.

The polymer solution continuously discharged from the polymerization reactor (laminar flow reactor-3) was guided to an extruder with a vacuum vent, and pelletized after devolatile under a reduced pressure of 10 torr. The temperature of the extruder was set to 230 ° C.
Table 1 shows the properties of the obtained resin 1.

<Method for producing resin 2>
The production was carried out in the same manner as in Resin 1 except that the amount of the polymerization initiator was changed as shown in Table 1. Table 1 shows the properties of the obtained resin 2.

<Method of manufacturing resins 3 and 4>
The production was carried out in the same manner as in Resin 1 except that the temperature of the extruder of the recovery system was changed as shown in Table 1. Table 1 shows the properties of the obtained resins 3 and 4.

<Method for producing resins 5 to 7>
The production was carried out in the same manner as the resin 1 except that the rotation speed of the stirrer of the laminar reactor-1 was changed as shown in Table 1. Table 1 shows the properties of the obtained resins 5 to 7.

<Method for producing resin 8>
The production was carried out in the same manner as the resin 1 except that the raw material composition and the rotation speed of the stirrer of the laminar flow reactor-1 were changed as shown in Table 1. CP-68N manufactured by Idemitsu Kosan Co., Ltd. was used as the raw material liquid paraffin. Table 1 shows the properties of the obtained resin 8.

<Method for producing resin 9>
The production was carried out in the same manner as in Resin 1 except that the raw material composition, the rotation speed of the stirrer of the laminar reactor-1 and the extruder temperature of the recovery system were changed as shown in Table 1. Table 1 shows the properties of the obtained resin 9.

The analysis method and evaluation method are described below.
(1) Rubber-like polymer content 0.4 g of a rubber-modified styrene resin composition was placed in a 100 ml volumetric flask and weighed precisely (W). After 75 ml of chloroform was added and dispersed well, 20 ml of a solution of 18 g of iodine monochloride in 1000 ml of carbon tetrachloride was added and stored in a cool and dark place, and after 8 hours, the mixture was aligned with the marked line with chloroform. 25 ml of this was collected, 60 ml of a solution of 10 g of potassium iodide dissolved in 800 ml of water and 200 ml of ethanol was added, and 10 g of sodium thiosulfate was titrated with a solution (molar concentration x) dissolved in 1000 ml of water. The main test A ml and the blank test B ml were used, and the rubbery polymer content (mass%) was calculated by the following formula.
Rubber polymer content (mass%) = 10.8 × xx (BA) / W

(2) Using COOLTER MULTISIZER III (trade name) manufactured by Beckman Coulter Co., Ltd. equipped with an aperture tube having a particle size of 30 μm of rubber-like polymer particles, 2 to 5 pellets of a rubber-modified styrene resin composition were dimethylformamide. It was placed in 5 ml and left for about 2 to 5 minutes. Next, the dissolved dimethylformamide was measured as an appropriate particle concentration, and the median diameter based on the volume was determined.

(3) Insoluble methyl ethyl ketone (gel)
Weigh 1 g of a rubber-modified styrene resin composition (W1), add 20 ml of a mixed solvent of methyl ethyl ketone / methanol (mixed mass ratio 90/10), shake at 23 ° C. for 2 hours, and then centrifuge (Hitachi, Ltd.). Centrifugation was carried out at 10 ° C. or lower and 20000 rpm for 60 minutes using Hitachi (trade name) CR-20 (rotor: R20A2). The supernatant was decanted and removed to give an insoluble matter. Continue to 160 ° C. After vacuum drying for 60 minutes under the condition of 20 mmHg or less and cooling to room temperature in a desiccator, the mass of the insoluble matter was precisely weighed (W2). The insoluble content (gel content) of methyl ethyl ketone was determined by the following formula.
Methyl ethyl ketone insoluble content (% by mass) = (W2 / W1) x 100

(4) Swelling index with respect to toluene 1 g of a rubber-modified styrene resin composition is precisely weighed (W3), 20 ml of toluene is added, and the mixture is shaken at 23 ° C. for 2 hours, and then a centrifuge (trade name) manufactured by Hitachi, Ltd. ) CR-20 (rotor: R20A2)) at 10 ° C. or lower and 20000 rpm for 60 minutes. The supernatant was decanted and removed, and the mass of the insoluble material containing toluene was precisely weighed (W4). Subsequently, the mixture was vacuum dried at 160 ° C. and 20 mmHg or less for 60 minutes, cooled to room temperature in a desiccator, and then the mass of the insoluble matter was precisely weighed (W5). The swelling index for toluene was calculated by the following formula.
Swelling index for toluene = W4 / W5

(5) Whitening test A rubber-modified styrene resin composition was injection-molded at a temperature of 220 ° C. to prepare a flat plate having a thickness of 1 mm. A flat plate was placed on a DuPont impact tester equipped with a 30.5 mm cradle, a 12.7 mmΦ striking core was placed on it, and the weight of the weight was gently increased every 100 g to measure the load at which whitening scratches occurred.

(6) Total light transmittance, diffused light transmittance, haze, yellowness (yellow index)
The rubber-modified styrene resin composition is injection-molded at a temperature of 220 ° C. to prepare a flat plate with a thickness of 1 mm, and a C light source / 2 degrees using a chromaticity turbidity measuring device COH300A (trade name) manufactured by Nippon Denshoku Co., Ltd. Total light transmittance, diffused light transmittance, haze, and yellow index were measured by transmitted light in a field area of 12 mmΦ.

(7) Charpy Impact Test Using a test piece produced by injection molding under the conditions of a resin temperature of 220 ° C. and a mold temperature of 45 ° C., a notched Charpy impact strength was measured in accordance with ISO 179.

(8) Melt mass flow rate Measurement at 200 ° C. and 49N was carried out in accordance with ISO 1133.

(9) Amount of liquid paraffin Weigh 2 g of a rubber-modified styrene resin composition, add 40 ml of methyl ethyl ketone, shake at 23 ° C. for 40 minutes, add dropwise to 200 ml of methanol, heat at 60 ° C. for 10 minutes, and then 23. It was cooled to ° C. and filtered through a methanol filter having a hole diameter of 0.45 μm. The filtrate separated by filtration was concentrated by distillation under reduced pressure, dried at 80 ° C. for 30 minutes, cooled to 23 ° C., and dissolved in normal hexane to obtain a 10 ml sample. The liquid paraffin content (mass%) of the obtained sample was quantified by liquid chromatography under the following conditions.

Equipment: High Performance Liquid Chromatograph, manufactured by Shimadzu Corporation (trade name) LC-10A
Column: Fully porous silica gel with an average particle diameter of 5 μm, inner diameter 4.6 mm, length 250 mm
Solvent: Normal hexane Temperature: 23 ° C
Solvent flow rate: 2 g / min
Injection volume: 200 μm

[Examples 1 to 9]
In Examples 1 to 8, any one of the resin 1, the resin 2 or the resin 5 and the resin 9 were mixed at the ratios shown in Table 2 and melt-kneaded to prepare a rubber-modified styrene resin composition. Further, in Example 9, resin 8 was used. The obtained rubber-modified styrene resin composition was evaluated as described above, and the results are shown in Table 2.
The rubber-modified styrene-based resin compositions of Examples 1 to 9 all have a high load that causes whitening scratches, and have a good balance between total light transmittance and haze, so that they have high diffused light transmittance and high light diffusivity.

[Comparative Example 1]
In Comparative Example 1, resin 1 and resin 9 were mixed at the ratios shown in Table 2. The obtained rubber-modified styrene resin composition was evaluated as described above, and the results are shown in Table 2.
The rubber-modified styrene resin composition of Comparative Example 1 has a small amount of rubber and a small amount of gel, so that the total light transmittance is high, but the haze is low, so that the diffused light transmittance is low and the impact strength is also low.

[Comparative Example 2]
In Comparative Example 2, resin 1 and resin 9 were mixed at the ratios shown in Table 2. The obtained rubber-modified styrene resin composition was evaluated as described above, and the results are shown in Table 2.
Since the rubber-modified styrene resin composition of Comparative Example 2 has a large amount of rubber and a large amount of gel, the load at which whitening scratches occur is low. Diffused light transmittance is low because the total light transmittance is low. The degree of yellowness also increases.

[Comparative Example 3]
In Comparative Example 3, resin 2 and resin 9 were mixed at the ratios shown in Table 2. The obtained rubber-modified styrene resin composition was evaluated as described above, and the results are shown in Table 2.
Since the rubber-modified styrene resin composition of Comparative Example 3 has a large amount of gel, the load at which whitening scratches occur is low, and the total light transmittance is low, so that the diffused light transmittance is low. The degree of yellowness also increases.

[Comparative Example 4]
In Comparative Example 4, resin 6 and resin 9 were mixed at the ratios shown in Table 2. The obtained rubber-modified styrene resin composition was evaluated as described above, and the results are shown in Table 2.
Since the rubber-modified styrene resin composition of Comparative Example 4 has a small rubber particle diameter, the yellowness of transmitted light increases.

[Comparative Example 5]
In Comparative Example 5, resin 7 and resin 9 were mixed at the ratios shown in Table 2. The obtained rubber-modified styrene resin composition was evaluated as described above, and the results are shown in Table 2.
The rubber-modified styrene resin composition of Comparative Example 5 has a large rubber particle diameter, and therefore has low light diffusivity (haze).

[Comparative Example 6]
In Comparative Example 6, the resin 3 and the resin 9 were mixed at the ratios shown in Table 2. The obtained rubber-modified styrene resin composition was evaluated as described above, and the results are shown in Table 2.
The rubber-modified styrene resin composition of Comparative Example 6 has a low swelling index and therefore has a low impact strength.

[Comparative Example 7]
In Comparative Example 7, the resin 4 and the resin 9 were mixed at the ratios shown in Table 2. The obtained rubber-modified styrene resin composition was evaluated as described above, and the results are shown in Table 2.
Since the rubber-modified styrene resin composition of Comparative Example 7 has a high swelling index, the light diffusivity is lowered and the diffused light transmittance is lowered.

According to the present invention, a rubber-modified styrene resin composition having an excellent balance between diffused light transmission and whitening resistance by optimizing the reinforcing rubber particles dispersed in the rubber-modified styrene resin composition. It is possible to provide a sheet containing the resin composition and a molded product such as a lighting cover obtained from the sheet.
Further, the rubber-modified styrene resin composition of the present invention is suitably used for applications that require light transmission and light diffusivity, such as a cover for lighting.

Claims (5)

A rubber containing a styrene-based polymer forming a matrix and rubber-like polymer particles dispersed in an island shape in the matrix, and the rubber-like polymer particles contain the styrene-based polymer particles and have a sea-island structure. A modified styrene resin composition
The rubber-like weight was 99.0 to 94.0% by mass of the styrene-based polymer with respect to 100% by mass of the total of the styrene-based polymer and the rubber-like polymer forming the rubber-like polymer particles. Containing 1.0 to 6.0% by mass of coalescence,
The rubber-like polymer is a polybutadiene rubber and / or a styrene-butadiene copolymer.
The rubber-like polymer particles have a particle size of 2.0 to 5.5 μm.
A rubber-modified styrene-based resin composition, wherein the content of the methyl ethyl ketone-insoluble gel content of the rubber-modified styrene-based resin composition is 2.0 to 15.0% by mass. The rubber-modified styrene-based resin composition according to claim 1, wherein the swelling index of the toluene-insoluble component of the rubber-modified styrene-based resin composition with respect to toluene is in the range of 10 to 14. A sheet obtained by extrusion-molding the rubber-modified styrene resin composition according to claim 1 or 2. A molded product obtained by thermoforming the sheet according to claim 3. A lighting cover obtained by thermoforming the sheet according to claim 3.