KR20190108658A - Styrene-based resin composition for optical applications, molded product, and light guide plate - Google Patents

Abstract

An object of the present invention is to provide an optical styrene resin composition, a molded article, and a light guide plate which are excellent in long term thermal stability, have small changes in color and transmittance, and are excellent in colorless transparency. According to the present invention, a styrene resin comprising (a) a styrene resin having a weight average molecular weight of 150,000 to 700,000, a (b) phosphorus antioxidant of a specific structure, and (c) a hindered phenolic antioxidant of a specific structure As a composition, content of (b) is 0.03-0.40 mass% and (c) is 0.02-0.30 mass% in 100 mass% of styrene resin compositions, The optical styrene resin composition is provided.

Description

Styrene-based resin compositions, molded articles and light guide plates for optics {STYRENE-BASED RESIN COMPOSITION FOR OPTICAL APPLICATIONS, MOLDED PRODUCT, AND LIGHT GUIDE PLATE}

The present invention relates to a styrene resin composition, a molded article and a light guide plate excellent in color and transparency and excellent in long-term thermal stability.

The backlight of the liquid crystal display includes a direct backlight having a light source disposed in front of the display device and an edge-lit backlight disposed at a side surface thereof. The light guide plate is installed in the edge light type backlight, serves to guide the light from the side to the liquid crystal panel, and is used for a wide range of applications such as a television, a desktop PC monitor, a notebook PC, a mobile phone, and a car navigation. In addition, a backlight using a light guide plate is also used for illumination. The acrylic resin represented by PMMA (polymethyl methacrylate) is used for the light guide plate. However, since the absorbency is high, the warpage may occur in the molded article or change in dimensions.

Therefore, it is proposed to use MS resin which is a copolymer of styrene and methyl (meth) acrylate which improved these characteristics. Patent document 1 is proposed as an improvement technique, such as water absorption of MS resin, and reduction of discoloration at the time of shaping | molding.

Patent Document 1 discloses a light guide plate having a weight average molecular weight (Mw) of styrene- (meth) acrylic acid ester-based resin resin of 6 to 170,000, a residual monomer amount of 3000 ppm or less, and an oligomer amount of 2% or less. There is a tendency for the dimensional stability to be higher than that of the styrene resin which uses a styrene monomer as a raw material.

On the other hand, styrene-based resins made of styrene-based monomers have low water absorption, but may cause discoloration due to heat in long-term use, yellowing of molded articles, and lower transmittance. As a result, the brightness of the backlight may be lowered and the chromaticity may be changed.

Patent Document 1: Japanese Unexamined Patent Publication No. 2003-075648

An object of the present invention is to provide a styrene resin composition, a molded article, and a light guide plate which are excellent in color and transparency and have small changes in color and transmittance even in long-term use.

According to the present invention, (a) a styrenic resin having a weight average molecular weight of 150,000 to 700,000, (b) at least one phosphorus antioxidant selected from (B-1) to (B-4), and (c ) A styrene resin composition comprising at least one hindered phenolic antioxidant selected from (C-1) to (C-4), wherein the content of (b) in 100% by mass of the styrene resin composition is 0.03 to 0.40. The content of the mass% and (c) is 0.02-0.30 mass%, The optical styrene resin composition is provided.

(B-1) tris (2,4-di-tert-butyl phenyl) phosphite

(B-2) 2,2'-methylenebis (4,6-di-tert-butyl-1-phenyloxy) (2-ethylhexyl oxy) phosphorus

(B-3) bis (2,4-dicumylphenyl) pentaerythritol diphosphite

(B-4) 3,9-bis (2,6-di-tert-butyl-4-methyl phenoxy) -2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] Cannes

(C-1) Octadecyl-3- (3,5-di-t-butyl-4-hydroxy phenyl) propionate

(C-2) 3,9-bis [2- (3- (3-tert-butyl-4-hydroxy-5-methyl phenyl) propionyloxy) -1,1-dimethyl ethyl] -2,4, 8,10-tetraoxaspiro [5.5] Undecan

(C-3) ethylene bis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate]

(C-4) pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]

MEANS TO SOLVE THE PROBLEM The present inventors earnestly examined in order to suppress the discoloration which arises at the time of long-term use, and found that combining phosphorus antioxidant and hindered phenolic antioxidant together is effective for suppressing discoloration. However, further studies have been made, but it has been found that there may be cases where the use of these two types of antioxidants alone does not work well.

Therefore, further studies have been conducted: (1) the phosphorus antioxidant has a specific constitution, (2) the content thereof is an amount in a specific range, (3) the hindered phenolic antioxidant has a specific constitution, and (4) It was found that the discoloration inhibiting effect of the styrene resin composition was very high when the content was in the specific range of amount. Although the effect which can acquire such an effect is not necessarily revealed, it is thought that it is due to the synergistic effect by these 4 conditions from being exhibited effectively only when the said 4 conditions match.

Hereinafter, various embodiment of this invention is illustrated. Various embodiments shown below can be combined with each other.

Preferably, the combination of (b) phosphorus antioxidant and (c) hindered phenolic antioxidant is (B-1), (C-1), (B-1) and (C-2), (B -1) and (C-3), (B-1) and (C-4), (B-2) and (C-1), (B-2) and (C-4), (B-3 ), (C-1), (B-3) and (C-2), (B-3) and (C-3), (B-3) and (C-4), (B-4) and At least one set selected from the combination of (C-1), (B-4) and (C-2), (B-4) and (C-3), (B-4) and (C-4), Furthermore, preferably, (B-1) and (C-1), (B-1) and (C-2), (B-1) and (C-3), (B-1) and (C- 4), (B-2) and (C-1), and (B-2) and at least 1 group chosen from the combination of (C-4).

Moreover, as a styrene- (meth) acrylic acid copolymer resin obtained by copolymerizing a styrene-type monomer and a (meth) acrylic acid, a styrene-based resin has a content of 90.0-99.9 mass% and a (meth) acrylic acid unit of the styrene-based monomer unit. Content of 0.1-10.0 mass%. However, the sum total of content of a styrene-type monomeric unit and a (meth) acrylic-acid unit of styrene resin shall be 100 mass%.

In addition, the styrene resin is a styrene- (meth) acrylic acid ester copolymer resin obtained by copolymerizing a styrene monomer and a (meth) acrylic acid ester, wherein the content of the styrene monomer unit of the styrene resin is 40.0 to 99.9 mass%, (meth). Content of an acrylic ester unit is 1.0-60.0 mass%. However, the sum total of content of the styrene-based monomeric unit and (meth) acrylic acid ester unit of styrene-type resin shall be 100 mass%.

Moreover, 0.4-2.0 mass% of hydrophilic additives which have a polyether chain are contained.

Moreover, it is a molded article which consists of said optical styrene resin composition.

Moreover, it is a light guide plate which consists of said molded article.

Styrene-based resin compositions and molded articles of the present invention have lower absorption and lower cost than PMMA and MS resins, have little change in color and transmittance in long-term use, and are excellent in colorless transparency, which is suitable for optical applications such as light guide plates. Can be used. Moreover, the coloring prevention effect with respect to the high temperature heat history, such as a molding process, is also high.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail.

 << styrene resin >>

The styrene resin of this invention can be obtained by superposing | polymerizing a styrene monomer. Styrene-based monomers are styrene, α-methyl styrene, o-methyl styrene, p-methyl styrene, m-methyl styrene, ethyl styrene, and pt-butyl styrene, which are aromatic vinyl monomers, or a mixture of two or more thereof. It is styrene. Moreover, you may copolymerize with a styrene-type monomer in the range which does not impair the characteristic of this invention, Acrylic acid monomers, such as acrylic acid and methacrylic acid, Vinyl cyanide monomers, such as acrylonitrile and methacrylonitrile, butyl acrylate, ethyl acrylate And imide monomers such as?-And? -Ethylenically unsaturated carboxylic acids such as acrylic monomers such as methyl acrylate and methyl methacrylate and maleic anhydride and fumaric acid, phenyl maleimide and cyclohexyl maleimide.

It is preferable that a styrene resin composition is comprised with styrene resin and various additives, The ratio of the styrene resin in 100 mass% of styrene resin compositions is 90-99.95 mass%, and 95-99.95 mass% desirable. The ratio of styrene resin is specifically 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.95 mass%, for example, the range between any two of the numerical values illustrated here. You may pay.

When the styrene resin is a styrene- (meth) acrylic acid copolymer resin obtained by copolymerizing a styrene monomer and a (meth) acrylic acid, the content of the styrene monomer unit of the styrene resin is 90.0 to 99.9 mass%, of the (meth) acrylic acid unit. It was experimentally confirmed that even if content is 0.1-10.0 mass%, the objective of this application can be achieved. However, the sum total of content of a styrene monomer unit and a (meth) acrylic acid unit shall be 100 mass%. (Meth) acrylic acid is acrylic acid, methacrylic acid, etc., and methacrylic acid is preferable.

The measurement of the (meth) acrylic acid unit content in styrene resin is performed at room temperature. 0.5 g of styrene resin was weighed and dissolved in a mixed solution of toluene / ethanol = 8/2 (volume ratio), followed by neutralization titration with 0.1 mol / L ethanol solution of potassium hydroxide, the end point being detected, and potassium hydroxide ethanol solution. From the usage-amount, content of the mass reference of a (meth) acrylic acid unit is computed. On the other hand, a potentiometer automatic titrator can be used and can be measured by AT-510 by Kyoto Electronics. Although the content of the (meth) acrylic acid unit in the styrene resin can be adjusted by the composition ratio of the styrene monomer and the (meth) acrylic acid monomer of the raw material at the time of polymerization of the styrene resin, the (meth) acrylic acid is in a compatible range. The styrene resin containing a unit and the styrene resin which does not contain a (meth) acrylic acid unit can also be mix | blended and adjusted.

When the styrene resin is a styrene- (meth) acrylic acid ester copolymer resin obtained by copolymerizing a styrene monomer and a (meth) acrylic acid ester, the content of the styrene monomer unit of the styrene resin is 40.0 to 99.9% by mass, (meth) acrylic acid It was confirmed experimentally that the objective of this application can be achieved even if content of an ester unit is 1.0-60.0 mass%. However, the sum total of content of a styrene monomer unit and a (meth) acrylic acid ester unit shall be 100 mass%. (Meth) acrylic acid ester is methacrylic acid ester, such as methyl methacrylate and ethyl methacrylate, acrylic ester, such as methyl acrylate and ethyl acrylate.

Content of the (meth) acrylic acid ester unit in styrene resin can be measured on condition of the following using pyrolysis gas chromatography.

Pyrolysis Furnace: PYR-2A (manufactured by Shimadzu Corporation)

Temperature setting by pyrolysis: 525 ℃

Gas chromatograph: GC-14A (manufactured by Shimadzu Corporation)

Column: Glass 3mm Diameter × 3m

Filler: FFAP Chromsorb WAW 10%

Injection, detector temperature: 250 ℃

Column temperature: 120 ° C

Carrier Gas: Nitrogen

As polymerization method of styrene resin, well-known styrene polymerization methods, such as a block polymerization method, a solution polymerization method, suspension polymerization method, an emulsion polymerization method, are mentioned. In terms of quality and productivity, the bulk polymerization method and the solution polymerization method are preferable, and continuous polymerization is preferable. As the solvent, for example, alkyl benzenes such as benzene, toluene, ethyl benzene and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane can be used.

At the time of superposition | polymerization of styrene resin, a polymerization initiator and a chain transfer agent can be used as needed. As a polymerization initiator, a radical polymerization initiator is preferable, For example, well-known conventional examples are 1,1-di (t-butylperoxy) cyclohexane, 2,2-di (t-butylperoxy) butane, 2,2 Peroxy ketals, such as di (4,4-di-t-butylperoxycyclohexyl) propane and 1,1-di (t-amyl peroxy) cyclohexane, cumene hydroperoxide, t-butylhydroper Hydroperoxides such as oxides, t-butylperoxy acetate, alkyl peroxides such as t-amylperoxy isononanoate, t-butyl cumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, Dialkyl peroxides such as di-t-hexyl peroxide, t-butyl peroxy acetate, t-butyl peroxy benzoate, peroxy esters such as t-butyl peroxy isopropyl monocarbonate, t-butyl peroxide Peroxy carbonates, such as oxy isopropyl carbonate and polyether tetrakis (t-butylperoxy carbonate), N, N'- azo Bis (cyclohexane-1-carbonitrile), N, N'-azobis (2-methylbutyronitrile), N, N'-azobis (2,4-dimethylvaleronitrile), N, N'- Azobis [2- (hydroxymethyl) propionitrile] etc. can be mentioned, These can be used 1 type or in combination or 2 or more types. Examples of the chain transfer agent include aliphatic melcaptans, aromatic melcaptans, pentaphenylethane, α-methyl styrene dimer, terpinolene, and the like.

In the case of continuous polymerization, the polymerization reaction is first controlled by adjusting the polymerization temperature or the like so as to achieve a target molecular weight, molecular weight distribution, reaction conversion ratio, and the like by using a complete mixing tank stirring tank, a tower reactor or the like known in the polymerization step. The polymerization solution containing the polymer that has undergone the polymerization process is transferred to a devolatilization process, and unreacted monomers and polymerization solvents are removed. The devolatilization process is composed of a vacuum devolatilization tank having a heater, a devolatilization extruder with a vent, and the like. The polymer of the molten state which passed through the devolatilization process is transferred to a granulation process. In the granulation step, the molten resin is extruded from the porous die into a strand shape and processed into a pellet shape by a cold cut method, an air hot cut method, or an underwater hot cut method.

The weight average molecular weight of the styrene resin is 150,000 to 700,000, preferably 160,000 to 700,000, and more preferably 160,000 to 400,000 or 180,000 to 500,000. If it is less than 150,000, the strength of the molded article is insufficient, and if it exceeds 700,000, moldability is remarkably lowered. The weight average molecular weight of the styrene resin can be controlled by the reaction temperature of the polymerization step, the residence time, the type and amount of the polymerization initiator, the type and amount of the chain transfer agent, the type and amount of the solvent used during the polymerization, and the like.

The weight average molecular weight (Mw), Z average molecular weight (Mz), and number average molecular weight (Mn) were measured on the following conditions using gel permeation chromatography (GPC).

GPC type: Shodex GPC-101 made by Showa Denko

Column: PLLab 10 μm MIXED-B manufactured by Polymer Laboratories

Mobile phase: tetrahydrofuran

Sample concentration: 0.2 mass%

Temperature: oven 40 ° C, inlet 35 ° C, detector 35 ° C

Detector: Differential Refractometer

The molecular weight calculates the molecular weight in each elution time from the elution curve of monodisperse polystyrene, and computes it as polystyrene conversion molecular weight.

<< phosphorus antioxidant, hindered phenolic antioxidant >>

The styrene resin composition contains (b) phosphorus antioxidant and / or (c) hindered phenolic antioxidant, and the content of (b) in 100% by mass of the styrene resin composition is 0.03 to 0.40% by mass, (c) The content of is 0.02 to 0.30 mass%. Preferably, content of (b) is 0.05-0.30 mass% and content of (c) is 0.02-0.20 mass%. Furthermore, Preferably, content of (b) is 0.10 to 0.25 mass%, and content of (c) is 0.05 to 0.15 mass%. If the content of (b) and (c) is outside the above range, the long term thermal stability is not good. Long-term heat stability indicates a change in color and transmittance due to heat in long-term use, and a change in color and transmittance is small in the case of excellent heat stability. Long-term thermal stability is an accelerated test, in which molded articles are stored at high temperature conditions (60 to 90 ° C.) at which the resin does not deform, and can be evaluated by time-dependent changes in color and transmittance. Content of phosphorus antioxidant in 100 mass% of styrene resin compositions is specifically, for example, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40 mass% It may be in the range between any two of the numerical values exemplified herein. Content of the hindered phenolic antioxidant in 100 mass% of styrene resin compositions is specifically, for example, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.15, 0.20, 0.25, 0.30 mass %, It may be in the range between any two of the numerical values illustrated here.

Phosphorus antioxidant is phosphorous acid ester which is a trivalent phosphorus compound, and a hindered phenolic antioxidant is antioxidant which has a phenolic hydroxyl group in a basic skeleton. Although there are very many compounds that can be used as the phosphorus- or hindered phenol-based antioxidant, the present inventors have at least one phosphorus-based antioxidant selected from (B-1) to (B-4) shown below; It was experimentally found that the combination of at least one hindered phenolic antioxidant selected from C-1) to (C-4) is very effective in preventing discoloration of styrene resin composition.

(B-1) tris (2,4-di-tert-butyl phenyl) phosphite

(B-2) 2,2'-methylenebis (4,6-di-tert-butyl-1-phenyloxy) (2-ethylhexyl oxy) phosphorus

(B-3) bis (2,4-dicumylphenyl) pentaerythritol diphosphite

(B-4) 3,9-bis (2,6-di-tert-butyl-4-methyl phenoxy) -2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] Cannes

(C-1) Octadecyl-3- (3,5-di-t-butyl-4-hydroxy phenyl) propionate

(C-2) 3,9-bis [2-3- (3-tert-butyl-4-hydroxy-5-methyl phenyl) propionyloxy] -1,1-dimethyl ethyl] -2,4,8 , 10-tetraoxaspiro [5.5] Undecan

(C-3) ethylene bis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate]

(C-4) pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]

As a method of adding a phosphorus antioxidant and a hindered phenolic antioxidant, a method of adding and mixing in a polymerization step, a devolatilization step, a granulation step of a styrene resin, a method of adding and mixing by an extruder, an injection molding machine, etc. during molding processing, and a hydrophilic additive The method of diluting and mixing the resin composition which adjusted the density | concentration to high concentration with desired content with the addition of the styrene resin is not specifically limited.

<< Other additives >>

The styrene resin composition may contain mineral oil within a range that does not impair the colorless transparency of the present invention. In addition, additives such as internal lubricants such as stearic acid and ethylene bis stearylamide, sulfur-based antioxidants, lactone-based antioxidants, ultraviolet absorbers, hindered amine-based stabilizers, antistatic agents and external lubricants may be included. As the external lubricant, ethylene bis stearylamide is suitable, and the content is preferably 30 to 200 ppm in the resin composition.

The ultraviolet absorber has a function of suppressing deterioration and coloring caused by ultraviolet rays, and examples thereof include benzophenone series, benzotriazole series, triazine series, benzoate series, salicylate series, cyano acrylate series, And ultraviolet absorbers such as oxalic anilide, malonic ester and formamidine. These can be used individually or in combination of 2 or more types, You may use together light stabilizers, such as a hindered amine.

Styrene-based resins capable of polymerizing styrene-based monomers may have a turbidity due to environmental changes such as temperature, humidity, and hot water immersion.However, styrene-based resins may be obtained by copolymerizing styrene-based monomers with (meth) acrylic acid. Cloudiness can be prevented by setting it as-(meth) acrylic acid copolymer resin or the styrene- (meth) acrylic acid ester copolymer resin obtained by copolymerizing a styrene-type monomer and (meth) acrylic acid ester. In addition, cloudiness can be prevented even if the styrene resin composition contains a hydrophilic additive having a polyether chain. In addition, the method of changing the kind of styrene resin, and the method of adding a hydrophilic additive can also be used together.

Styrene-based resins have a problem of whitening of molded products due to environmental changes such as temperature, humidity, and hot water immersion (Textile Journal, 34, 6, pages 245 ~ 253, 1978). Transparency, which is an advantage, could be compromised. Specifically, when a molded article is exposed to an environmental change from a high temperature, high humidity environment to a room temperature environment, or from a room temperature environment to a low temperature environment, moisture uniformly present in the styrene resin is unstable and phase-separated. Defects are generated, and as a result, the inside of the molded article is cloudy. In addition, after immersing a molded article of styrene resin in hot water for a predetermined time or more, the molded article may be whitened, but this is also a phenomenon caused by the same mechanism.

As a method of preventing the turbidity of a molded article due to environmental changes, when the styrene resin is a styrene- (meth) acrylic acid copolymer resin obtained by copolymerizing a styrene monomer and a (meth) acrylic acid, the styrene monomer unit of the styrene resin It is preferable that content is 90.0-99.9 mass%, and content of a (meth) acrylic acid unit is 0.8-10.0 mass%, 0.8-4.5 mass% is more preferable, and, as for content of a (meth) acrylic acid unit, 1.8-3.0 mass% More preferred. However, the sum total of content of a styrene monomer unit and a (meth) acrylic acid unit shall be 100 mass%. (Meth) acrylic acid is acrylic acid, methacrylic acid, etc., and methacrylic acid is preferable. When content of a (meth) acrylic acid unit is less than 0.8 mass%, the whitening inhibitory effect tends to become inadequate. Moreover, when it exceeds 10.0 mass%, initial stage color and transmittance will deteriorate easily.

Styrene-based monomers of styrene-based resins as a method of preventing cloudiness of molded articles due to environmental changes, when styrene-based resins are styrene- (meth) acrylic acid ester copolymerized resins obtained by copolymerizing styrene-based monomers with (meth) acrylic acid esters. It is preferable that content of a unit is 40-96 mass%, and content of the (meth) acrylic acid ester unit is 4-60 mass%, As for content of the (meth) acrylic acid ester unit, 4-15 mass% is more preferable, 6- It is more preferable that it is 12 mass%, and it is more preferable that it is 7-9 mass%. However, the sum total of content of a styrene monomer unit and a (meth) acrylic acid ester unit shall be 100 mass%. (Meth) acrylic acid ester is methacrylic acid ester, such as methyl methacrylate and ethyl methacrylate, acrylic ester, such as methyl acrylate and ethyl acrylate. When content of a (meth) acrylic acid ester unit is less than 4 mass%, a whitening inhibitory effect tends to become inadequate. Moreover, when it exceeds 60.0 mass%, water absorption will deteriorate easily. In addition, when the content of the (meth) acrylic acid ester unit increases, fluidity tends to decrease, and moldability tends to decrease in applications where high fluidity similar to that of injection molding is required.

A hydrophilic additive is a compound having a hydrophilic group that can interact with (hydrogen bond) with water. The hydrophilic group is preferably a polyether chain. The polyether chain is a skeleton structure in which ether bonds are connected, and for example, polyoxyethylene chain, polyoxypropylene chain, polyoxybutyl chain synthesized by addition reaction of alkylene oxide such as ethylene oxide, propylene oxide, butylene oxide, and the like. Although the polyglycerol chain synthesize | combined by a len chain, dehydration condensation of glycerin, etc. is mentioned, It is preferable that it is a polyoxyethylene chain. The polyether chain may have not only 1 group but 1 or more sets in 1 molecule.

As a hydrophilic additive having a polyoxyethylene chain, polyoxyethylene type interfaces such as polyoxyethylene type nonionic surfactants, polyoxyethylene type anionic surfactants, polyoxyethylene type cationic surfactants, and polyoxyethylene type amphoteric surfactants. Activators, polyethylene glycols, and the like. In polyoxyethylene type | mold surfactant, polyoxyethylene type | mold nonionic surfactant is preferable.

The polyoxyethylene type nonionic surfactants include polyoxyethylene alkyl ethers represented by the following general formula (1), polyoxyethylene fatty acid esters represented by the following general formula (2), polyoxyethylene hydrogenated castor oil, and polyoxyethylene sorbitan fatty acid. Although ester, polyoxyethylene sorbitol fatty acid ester is mentioned, It is preferable that it is at least 1 type chosen from the group of polyoxyethylene alkyl ether and / or polyoxyethylene fatty acid ester. The object of the present invention can also be used by using a polyvalent polyoxyethylene alkyl ether having a plurality of polyoxyethylene alkyl ether skeletons in one molecule or a polyvalent polyoxyethylene fatty acid ester having a plurality of polyoxyethylene fatty acid ester skeletons in one molecule. Can be achieved. The valence of a polyoxyethylene alkyl ether and a polyoxyethylene fatty acid ester means the polyoxyethylene alkyl ether frame | skeleton and polyoxyethylene fatty acid ester frame | skeleton number which exist in 1 molecule.

 In the formula, R represents an alkyl group having 8 to 20 carbon atoms. Moreover, up to 6-valent polyvalent polyoxyethylene alkyl ether having a plurality of polyoxyethylene alkyl ether skeletons and up to 6-valent polyvalent poly having a polyoxyethylene fatty acid ester skeleton Oxyethylene fatty acid ester may be sufficient, n is an integer and represents the number-of-moles added of an ethylene oxide unit.)

Polyoxyethylene alkyl ether is made by adding ethylene oxide to alcohol, polyoxyethylene fatty acid ester is made by adding ethylene oxide to fatty acid or directly esterifying fatty acid and polyethylene glycol, and the average added mole number of ethylene oxide is 7 ~ It is preferable that it is 100, and it is more preferable that it is 10-50.

As for the average molecular weight of polyethyleneglycol, 200-10000 are preferable. It is more preferable that it is 200-4000, and it is more preferable that it is 300-1000. When the average molecular weight of polyethyleneglycol is less than 200, since gas is produced at the time of shaping | molding process, and a mold and a roll are dirty, it is unpreferable. Moreover, when it exceeds 10000, there exists a tendency for the effect of preventing whitening phenomenon to fall, compatibility with a styrene resin falls, and a styrene resin composition and its molded article may become cloudy. The average molecular weight is calculated from the concentration of hydroxyl groups (based on JIS K1557) measured by pyridine phthalic anhydride method.

As a hydrophilic additive which has a polyether chain, for example, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene octyldoethyl ether, polyoxyethylene myristyl ether, poly Polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene alkyl ethers such as oxyethylene 2-ethylhexyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan tristearate, and polyoxyethylene sorbitan tetraoleate Polyoxyethylene fatty acid esters such as polyoxyethylene sorbitol fatty acid ester, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene cured castor oil, polyethylene Recall, polyoxyethylene monomethyl ether, polyoxyethylene dimethyl ether, polyoxyethylene glyceryl ether, polyoxyethylene tetraoleic acid, polyoxyethylene triisostephosphite, polyoxyethylene coconut fatty acid glyceryl, diglycerin, polyglycerol , Polyoxyethylene polyglyceryl ether, polyglycerol fatty acid ester and the like.

It is preferable that it is 8 or more, and, as for the HLB value of the hydrophilic additive which has a polyether chain, it is more preferable that it is 10-20. HLB (Hydrophilic-lipophilic balance) is a value which shows the hydrophilicity of an additive, and when HLB value is 8-10, it is disperse | distributed stably in water, and when it exceeds 10, it becomes a state which is completely melt | dissolved transparently from the dispersion state with transparency. In nonionic surfactants having a polyether chain, HLB = (molecular weight of the hydrophilic moiety) / (molecular weight of the additive) x 20, such as paraffin containing no hydrophilic group is HLB = 0, and in polyethylene glycol only hydrophilic group HLB = 20, and in a nonionic surfactant, HLB will be 0-20.

It is preferable that the temperature loss of the hydrophilic additive which has a polyether chain in 200 degreeC, and nitrogen atmosphere is 10 mass% or less. Loss of heating in a temperature of 200 ° C. and nitrogen atmosphere can be obtained by thermogravimetric analysis (TGA), heated at a temperature increase rate of 10 ° C./min from room temperature in a nitrogen atmosphere, and can be obtained by weight loss at a temperature of 200 ° C. The additive having a heating loss of more than 10% by mass under a temperature of 200 ° C. and a nitrogen atmosphere has high volatility, and gas may be generated during molding processing of the styrene resin, resulting in dirty mold or roll.

As for the hydrophilic additive which has a polyether chain, content in 100 mass% of styrene resin compositions is 0.4-2.0 mass%, and it is preferable that it is 0.7-1.6 mass%. When content of the hydrophilic additive which has a polyether chain is less than 0.4 mass%, prevention of the whitening phenomenon by environmental change is difficult, and when it exceeds 2.0 mass%, the heat resistance of a styrene resin composition will fall.

As a method of adding a hydrophilic additive having a polyether chain, a method of adding and mixing a styrene resin in a polymerization step, a devolatilization step, a granulation step, a method of adding and mixing in an extruder, etc. during molding processing, and a resin composition obtained by adjusting a hydrophilic additive at a high concentration The method of diluting and mixing to a desired content with no addition styrene resin etc. is mentioned, It does not specifically limit.

For example, a styrene resin composition containing 0.5 to 50.0% by mass of a hydrophilic additive and a non-added styrene resin are mixed using an extruder or an injection molding machine to obtain a styrene resin composition, a molded article or a light guide plate having a desired concentration. Can be mentioned.

It is preferable that it is 95-104 degreeC, and, as for the bicat softening temperature of the styrene resin composition of this invention, it is more preferable that it is 97-104 degreeC. When the vicat softening temperature is less than 95 ° C, heat resistance is insufficient, and the molded article may be deformed depending on the use environment.

The cloudiness of the styrene resin composition of the present invention is a 4 mm thick molded article, preferably 5% or less, and more preferably 1% or less.

The styrene resin composition of the present invention can be molded by a molding method according to the purpose, such as injection molding, extrusion molding, compression molding, blow molding, and the like, but the shape thereof is not limited. For example, if it is a plate-shaped molded product, it can process with a light guide plate. The obtained molded article can be employed as an optical member that functions by transmitting light inside a molded article such as a light guide plate. As optical members, such as a light guide plate, since the light transmission distance (light path length) is long, it is preferable that it is a material with high transmittance and excellent color. The initial transmittance at the optical path length of 115 mm is preferably 84% or more and the YI value is 7.0 or less. Moreover, it is preferable that it is 3.0 or less, and, as for the initial YI difference after storing for 1000 hours at 80 degreeC, it is more preferable that it is 1.5 or less.

The transmittance and YI value of the optical path length of 115 mm were measured by the following means. Using a pellet of a styrene resin composition, injection molding was carried out at a cylinder temperature of 230 ° C. and a mold temperature of 50 ° C. to form a plate-shaped molded article having a thickness of 127 × 127 × 3 mm. Samples evaluating long term thermal stability were stored in an oven at 80 ° C. for 1000 hours. Next, the test piece of 115x85x3mm thickness was cut out with the plate-shaped molded object, the cross section was polished by buff polishing, and the plate-shaped molded product which has a mirror surface at the cross section was created. About the plate-shaped molded object after grinding | polishing, using the ultraviolet-visible-spectrophotometer V-670 by Nihon Bunco Co., Ltd., the incident light of size 20x1.6mm and spreading angle of 0 degrees, 350-800 nm of wavelengths in optical path length 115mm are used. The spectral transmittance was measured and the YI value in the field of view 2 degrees was computed according to JIS K7105 in C light source. In addition, a transmittance | permeability is an average transmittance of wavelength 380nm-780nm.

The light guide plate has a function of injecting light from the end face (side surface) of the plate-shaped molded article, inducing light to the front surface (light emitting surface) of the molded article, and emitting the surface by a reflection pattern formed on the rear surface (non-light emitting surface) of the molded article. It is a member with. The reflective pattern can be formed by a screen printing method, an injection molding method, a laser method or an ink jet method. When processing into a light guide plate from a plate-shaped molded article, it is preferable to polish the incident surface or the entire cross-section of the light to be a mirror surface. Moreover, in order to improve the uniformity of output light, a prism pattern etc. can be provided in the front surface (light emitting surface) of a plate-shaped molded article. The pattern of the front surface or the rear surface of the plate-shaped molded article can be formed at the time of molding of the plate-shaped molded article. For example, the pattern can be formed by die shape in injection molding, roll transfer in extrusion molding, or the like.

Example

Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these Examples.

<< Exam 1 >>

(Manufacture of styrene resin PS-1-PS-3)

The polymerization process was comprised by connecting the 1st reactor which is a complete mixing type | mold tank, the 3rd reactor which is a plug flow type reactor which has a 2nd reactor, and a static mixer in series, and manufactured the styrene resin by the conditions shown in Table 1. . The capacity of each reactor was 39 liters for the first reactor, 39 liters for the second reactor, and 16 liters for the third reactor. The raw material solution was prepared by the raw material composition of Table 1, and the raw material solution was continuously supplied to the 1st reactor by the flow volume of Table 1. The polymerization initiator was added to the raw material solution at the inlet of the first reactor to the addition concentration shown in Table 1 (concentration based on the total amount of the raw material styrene and methacrylic acid) and mixed uniformly. The polymerization initiator of Table 1 is as follows.

Polymerization Initiator-1: 2,2-di (4,4-t-butylperoxycyclohexyl) propane (patite A manufactured by Nichi Oil Co., Ltd. was used.)

Polymerization Initiator-2: 1,1-di (t-butylperoxy) cyclohexane (Perhex C manufactured by Nichi Oil Co., Ltd. was used.)

On the other hand, in the third reactor, a temperature gradient was given according to the direction of the flow, and the temperature was adjusted to be the temperature of Table 1 at the middle part and the outlet part.

Subsequently, the solution containing the polymer continuously taken out of the third reactor was led to a vacuum devolatilization tank having a preheater composed of two stages in series, and the temperature of the preheater was adjusted so that the resin temperature shown in Table 1 was achieved. By adjusting to the pressure described, unreacted styrene and ethyl benzene were separated, extruded into a strand shape with a porous die, and the strand was cooled and cut in a cold cut manner to pelletize.

(Examples 1-1 to 1-30, Comparative Examples 1-1 to 1-10)

From the contents shown in Table 2, melt-kneading at the cylinder temperature of 230 ° C. and the screw rotation speed of 100 rpm using a single screw extruder having a screw diameter of 40 mm for B and C as the styrene resin PS-1, PS-2, and PS-3 and the additives To obtain a pellet. Additives B and C used in Table 2 are shown below. In addition, additive B represents (b) phosphorus antioxidant, and additive C represents (c) hindered phenolic antioxidant.

B-1: tris (2,4-di-tert- butyl phenyl) phosphite (Irgafos 168 made from BASF Japan)

B-2: 2,2'-methylenebis (4,6-di-tert-butyl-1-phenyloxy) (2-ethylhexyl oxy) phosphorus (adekastop HP-10 by ADEKA Corporation)

B-3: bis (2, 4- dicumylphenyl) pentaerythritol diphosphite (Doverphos S-9228 by Dover Chemical Corporation)

B-4: 3,9-bis (2,6-di-tert-butyl-4-methyl phenoxy) -2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] undecane (Adeka stop PEP-36 made in ADEKA)

B-5: tetrakis (2,4-di-tert-butyl phenyl) [1,1biphenyl] -4,4-diyl bisphosphonite (Hostanox P-EPQ from Clariant Co. Ltd.)

B-6: Bis (2, 4-di-tert- butyl- 6- methyl phenyl) ethyl phosphite ester (Irgafos 38 by BASF Japan Co., Ltd.)

B-7: diphenyl-2-ethylhexyl phosphite (adeka stop C made by ADEKA)

B-8: phosphite triisodecyl (adeka stop 3010 made by ADEKA)

B-9: cyclic neopentane tetraylbis (2,4-di-t-butylphenyl phosphite) (adekastop PEP-8 made from ADEKA)

C-1: Octadecyl-3- (3,5-di-t-butyl-4-hydroxy phenyl) propionate (Irganox 1076 by BASF Japan Co., Ltd.)

C-2: 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methyl phenyl) propionyloxy] -1,1-dimethyl ethyl] -2,4,8 , 10-tetraoxaspiro [5.5] Undecan (ADEKA STOP AO-80, made by ADEKA)

C-3: ethylene bis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate] (Irganox 245 by BASF Japan Co., Ltd.)

C-4: pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (Irganox 1010, manufactured by BASF Japan)

C-5: 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butyl phenyl) butane (ADEKA STOP AO-30 made by ADEKA)

C-6: 4,4'- butylidenebis (3-methyl-6-t-butyl phenol) (ADEKA STOP AO-40 made from ADEKA, KK)

C-7: 2-methyl-4,6-bis (dodecylthiomethyl) phenol (Irganox 1726 made from BASF Japan)

Further, using the obtained pellets, injection molding was performed at a cylinder temperature of 230 ° C. and a mold temperature of 50 ° C. to form a plate-shaped molded article having a thickness of 127 × 127 × 3 mm. In order to evaluate the long term thermal stability, the obtained molded article was stored for 1000 hours in an oven at 80 ℃. In order to evaluate the optical characteristics of the molded article before storage and the molded article after storage, a test piece of 115 × 85 × 3 mm thickness was cut from the plate-shaped molded product, the end face was polished by buff polishing, and the plate-shaped molded product having a mirror surface at the end face. Was written. The plate-shaped molded article after polishing was an incident light having a size of 20 × 1.6 mm and a spread angle of 0 ° using an ultraviolet visible spectrophotometer V-670 manufactured by Nihon Bunko Co., Ltd., with an optical path length of 115 mm and a wavelength of Spectral transmittances of 350 nm to 800 nm were measured, and the YI value in the field of view 2 ° was calculated according to JIS K7105 as the C light source. The transmittance | permeability shown in Table 2 shows the average transmittance in 380 nm-780 nm of wavelengths.

Next, the YI value after (triangle | delta) heating was computed based on the following formula. In the following formula, "no additive" means the case where neither the additive B nor the additive C is added, and the "no additive" means the case when at least one of the additive B and the additive C is added. In addition, an Example, a comparative example, and a reference example are named generically "test example."

△ YI value after heating = ("YI value after 80 degreeC * 1000 hours of a test example in which an additive exists")-("YI value after 80 degreeC * 1000 hour of the test example without additional additive")

In Example 1-1 in which the additive is present, in Example 1-1, the YI value after 80 ° C × 1000 hours is 7.0, and in Reference Example 1-1 in which the type of the styrene resin is the same, the YI value after 80 ° C × 1000 hours is 11.6. "YI value after (triangle | delta) heating" of Example 1-1 is -4.6. This value represents the degree of discoloration prevention effect by the addition of the additives B and C, and the smaller the value, the greater the effect.

Furthermore, based on the YI value after (triangle | delta) heating, the Example and the comparative example were ranked according to the following criteria.

S: YI value after (triangle | delta) <-4.0

A: YI value after −4.0 ≦ Δ heating <-3.5

B: YI value after −3.5 ≦ Δ heating <-2.5

C: YI value after -2.5≤ △ heating

Table 2 shows the characteristics and evaluation results of each resin composition.

The molded article of the Example was excellent in initial transmittance | permeability and YI value, the amount of YI change in storage of 80 degreeC x 1000 hours was small, and long-term thermal stability was also favorable. Moreover, (1) phosphorus antioxidant has a specific structure, (2) the content is the quantity of a specific range, (3) a hindered phenolic antioxidant has a specific structure, and (4) the content is a specific range In the case of the amount of, it was found that the effect of inhibiting discoloration of the styrene resin composition is very high. Moreover, in Example 1-13 and 1-14, it turned out that the same effect can be acquired even if the kind of styrene resin is styrene- (meth) acrylic acid copolymer resin or styrene- (meth) acrylic acid ester copolymer resin.

<< Exam 2 >>

(Examples 2-1 to 2-26)

The polymerization process was comprised by connecting the 1st reactor which is a complete mixing type | mold tank, the 3rd reactor which is a plug flow type reactor with a 2nd reactor, and a static mixer in series, and the styrene resin was manufactured by the condition 1 of Table 1. . The capacity of each reactor was 39 liters for the first reactor, 39 liters for the second reactor, and 16 liters for the third reactor. The raw material solution was created by the raw material composition of condition 1 of 1, and the raw material solution was continuously supplied to the 1st reactor by the flow volume of Table 1.

In addition, a hydrophilic additive D having a polyether chain was added to the inlet of the third reactor so as to be the kind and content shown in Table 3. The types of additives and polyethylene glycols used are as follows.

D-1: polyethyleneglycol having an average molecular weight of 400 (PEG # 400, manufactured by Nichiyu Corp.)

D-2: polyethyleneglycol having an average molecular weight of 1000 (PEG # 1000, manufactured by Nichiyu Corp.)

D-3: polyethyleneglycol having an average molecular weight of 2000 (manufactured by Nichi Oil Co., Ltd. PEG # 2000)

D-4: polyoxyethylene ethylene lauryl ether ethylene oxide average addition mole number = 25 (Emulgen 123P by the Kao Corporation)

D-5: polyoxyethylene ethylene lauryl ether ethylene oxide average addition mole number = 12 (Emulgen 320P by the Kao Corporation)

D-6: polyoxyethylene ethylene lauryl ether ethylene oxide average addition mole number = 9 (Emulgen 109P by Kao Corporation)

D-7: polyoxyethylene ethylene lauryl ether ethylene oxide average addition mole number = 30 (Emulgen 130K by Kao Corporation)

D-8: polyethylene glycol monolaurate ethylene oxide average addition mole number = 12 (Emanon 1112 made by Kao Corporation)

Subsequently, the solution containing the polymer continuously taken out of the third reactor was introduced into a vacuum devolatilization tank having a preheater composed of two stages in series, and the unreacted styrene and ethyl benzene were separated, and then extruded into a strand shape and cooled. After making it cut, it was made into pellets. On the other hand, the resin temperature in the devolatilization tank of the 1st stage was set to 160 degreeC, the pressure of the vacuum devolatilization tank was 65 kPa, the resin temperature in the devolatilization layer of the 2nd stage was set to 235 degreeC, and the pressure of the vacuum devolatilization tank was 0.8 kPa.

The weight average molecular weight (Mw) of the obtained styrene resin was 370,000 in all.

Next, the pellets of the styrene resin and the additives B and C obtained above were melt-kneaded at a cylinder temperature of 230 ° C. and a screw rotation speed of 100 rpm to obtain the contents shown in Table 3, using a single screw extruder having a screw diameter of 40 mm. Got it. The symbols of the additives B and C used in Table 3 are the same as the symbols shown in Test 1.

In addition, melt flow rate (MFR) was based on JISK-7210, and it was measured by 200 degreeC and 49N load conditions, and the non-cart softening temperature based on JISK7206 at the temperature increase rate of 50 degree-C / hr, and the test load of 50N. . The transmittance | permeability and YI value were measured by the method similar to the test 1.

Furthermore, in order to confirm the whitening phenomenon due to environmental change, the plate-shaped molded article having a mirror surface on the cross section was exposed for 150 hours at 60 ° C. and 90% relative humidity, and the test piece was taken out at 23 ° C. and 50% relative humidity. The whitening phenomenon which generate | occur | produced inside the molded article was observed, and it determined as follows as a whitening inhibitory effect.

(Double-circle): Whitening does not generate | occur | produce completely.

(Circle): Although it whitened a little after 1 hour of taking out, it disappears after 24 hours.

(Triangle | delta): Although it whitens after 1 hour of taking out, it mostly disappears after 24 hours.

X: After 1 hour taken out, it whitens remarkably and it does not disappear even if it passes for 24 hours.

Table 3 shows the characteristics and evaluation results of each resin composition.

The molded articles of Examples 2-1 to 2-23 are excellent in the whitening inhibitory effect, are excellent in initial transmittance and YI value, are small in YI variation in storage at 80 ° C x 1000 hours, and have good long-term thermal stability. On the other hand, in Examples 2-24 to 2-25, the hydrophilic additive D was not added or the addition amount was too small, so that whitening phenomenon occurred. Moreover, since Example 2-26 added too much the amount of hydrophilic additive D, heat resistance fell.

<< Exam 3 >>

(Manufacture example of styrene resin A-1-7)

A styrene resin was manufactured under the conditions shown in Table 4 by connecting a first reactor, a second reactor, and a third reactor, a plug flow type reactor having a static mixer, in series to form a polymerization mixture in series. . The capacity of each reactor was 39 liters for the first reactor, 39 liters for the second reactor, and 16 liters for the third reactor. The raw material solution was prepared by the raw material composition of Table 4, and the raw material solution was continuously supplied to the 1st reactor by the flow volume of Table 4. The polymerization initiator was added to the raw material solution at the inlet of the first reactor so as to have the addition concentration shown in Table 4 (concentration based on the total amount of the raw material styrene and methyl methacrylate) and mixed uniformly. The polymerization initiator of Table 4 is as follows.

Polymerization Initiator-1: 1,1-di (t-butylperoxy) cyclohexane (Perhexa C manufactured by Nichi Oil Co., Ltd. was used.)

On the other hand, in the third reactor, a temperature gradient was given according to the direction of flow, and the temperature was adjusted to be the temperature of Table 4 in the middle part and the outlet part.

Subsequently, the solution containing the polymer continuously taken out from the third reactor was introduced into a vacuum devolatilization tank having a preheater composed of two stages in series, and the temperature of the preheater was adjusted to reach the resin temperature shown in Table 4, and Table 4 By adjusting to the pressure described in the above, unreacted styrene and ethyl benzene were separated, extruded into a strand shape with a porous die, and the strand was cooled and cut in a cold cut manner to pelletize.

Content (PMMA amount) of the methyl methacrylate unit in styrene resin was measured on the following conditions by the pyrolysis gas chromatography.

Pyrolysis Furnace: PYR-2A (manufactured by Shimadzu Corporation)

Temperature setting by pyrolysis: 525 ℃

Gas chromatograph: GC-14A (manufactured by Shimadzu Corporation)

Column: Glass 3mm Diameter × 3m

Filler: FFAP Chromsorb WAW 10%

Injection, detector temperature: 250 ℃

Column temperature: 120 ° C

Carrier Gas: Nitrogen

Melt flow rate (MFR) was based on JIS K 7210, and the temperature of 200 degreeC and 49 N load conditions, and the non-cart softening temperature based on JIS K 7206 were measured with the temperature increase rate of 50 degree-C / hr, and test load 50N.

The water supply amount was measured using a plate-shaped molded article described above, and after measuring the mass W1 after drying at a temperature of 80 ° C. for 24 hours, the plate-shaped molded product was stored at an environment of 80% relative humidity at a temperature of 40 ° C., and extracted every fixed time. The weight immediately after was measured and calculated | required as water supply amount = (W2-W1) / W2 * 1000000 (ppm) from the mass W2 when the weight change disappeared (saturated state). Table 4 shows the characteristics of each styrene resin.

(Examples 3-1 to 3-18)

Next, the content shown in Table 5 was melt-kneaded with styrene resin A and B and C as an additive at a cylinder temperature of 230 ° C. and a screw rotation speed of 100 rpm using a single screw extruder having a screw diameter of 40 mm to obtain pellets. The symbols of the additives B and C used in Table 5 are the same as the symbols shown in Test 1.

The transmittance | permeability, YI value, and whitening inhibitory effect were measured or evaluated by the same method as the test 2.

Table 5 shows the characteristics and evaluation results of each resin composition.

The molded articles of Examples 3-1 to 3-16 having a relatively high content of the (meth) acrylic acid ester unit are excellent in the whitening inhibitory effect, have excellent initial transmittance and YI value, and the YI variation in storage at 80 ° C for 1000 hours. This small, long-term thermal stability was also good. On the other hand, in Examples 3-17 to 3-18 in which the (meth) acrylic acid ester unit was not contained or the content thereof was relatively small, the whitening inhibitory effect was not sufficient.

The optical styrenic resin composition and the molded article of the present invention are excellent in color and transparency, and excellent in long-term thermal stability. In addition, since whitening due to environmental changes is prevented, and transparency and color are excellent, transparency, which is an advantage of styrene resins, can be maintained and used suitably even in applications where whitening has occurred in the past due to environmental changes. have. For example, light guide plates, such as a television, a desktop PC, a notebook PC, a mobile phone, and a car navigation system, etc. are mentioned.

Claims (8)

(a) a styrene resin having a weight average molecular weight of 150,000 to 700,000, at least one phosphorus antioxidant selected from (b) (B-1) to (B-4), and (c) (C-1 Styrene-based resin composition composed of at least one hindered phenol-based antioxidant selected from C) to C-4, wherein the content of (b) in 100% by mass of the styrene-based resin composition is 0.03-0.40% by mass, (c Optical styrene resin composition having a content of 0.02-0.30% by mass)
(B-1) tris (2,4-di-tert-butyl phenyl) phosphite
(B-2) 2,2'-methylenebis (4,6-di-tert-butyl-1-phenyloxy) (2-ethylhexyl oxy) phosphorus
(B-3) bis (2,4-dicumylphenyl) pentaerythritol diphosphite
(B-4) 3,9-bis (2,6-di-tert-butyl-4-methyl phenoxy) -2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] Cannes
(C-1) Octadecyl-3- (3,5-di-t-butyl-4-hydroxy phenyl) propionate
(C-2) 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methyl phenyl) propionyloxy] -1,1-dimethyl ethyl] -2,4, 8,10-tetraoxaspiro [5.5] Undecan
(C-3) ethylene bis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate]
(C-4) pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate].
The method of claim 1,
The combination of the said (b) phosphorus antioxidant and said (c) hindered phenolic antioxidant is (B-1), (C-1), (B-1), (C-2), (B-1) ), (C-3), (B-1) and (C-4), (B-2) and (C-1), (B-2) and (C-4), (B-3) and (C-1), (B-3) and (C-2), (B-3) and (C-3), (B-3) and (C-4), (B-4) and (C At least one group of optical styrene selected from a combination of -1), (B-4) and (C-2), (B-4) and (C-3), (B-4) and (C-4) System resin composition.
The method according to claim 1 or 2,
The combination of the said (b) phosphorus antioxidant and said (c) hindered phenolic antioxidant is (B-1), (C-1), (B-1), (C-2), (B-1) ) And at least one selected from the combination of (C-3), (B-1) and (C-4), (B-2) and (C-1), (B-2) and (C-4) Joining optical styrene resin composition.
The method according to any one of claims 1 to 3,
A styrene- (meth) acrylic acid copolymer resin obtained by copolymerizing a styrene-based monomer with (meth) acrylic acid, wherein the styrene-based resin has a content of a styrene-based monomer unit of 90.0-99.9 mass% and a (meth) acrylic acid unit. The content of is 0.1-10.0 mass%, but the styrene resin composition for optics which makes a total of content of the styrene-type monomeric unit of a styrene resin and a (meth) acrylic acid unit 100 mass%.
The method according to any one of claims 1 to 3,
A styrene- (meth) acrylic acid ester copolymer resin obtained by copolymerizing a styrene-based monomer with a (meth) acrylic acid ester, wherein the styrene-based resin has a content of 40.0-99.9 mass% (meth) of the styrene-based monomer unit of the styrene-based resin. The content of an acrylic ester unit is 1.0-60.0 mass%, but the styrene resin composition for optics which makes the sum total of content of the styrene-type monomeric unit of a styrene resin and the (meth) acrylic acid ester unit 100 mass%.
The method according to any one of claims 1 to 5,
0.4-2.0 mass% of hydrophilic additives which have a polyether chain are contained, The optical styrene resin composition characterized by the above-mentioned.
The molded article which consists of an optical styrene resin composition in any one of Claims 1-6.
The light guide plate which consists of a molded article of Claim 7.