JP3832775B2 - Styrenic resin molded product and method for producing the same - Google Patents

Description

【０００６】
【化７】

【０００７】
【化８】

【０００８】
【化９】

【０００９】
【化１０】

【００１１】
また、本発明は、スチレン系樹脂１００重量部に対して、０．０５〜１．０重量部の請求項１に記載の式（Ｉ）〜（Ｖ）で示される酸化防止剤を含有させてなることを特徴とする請求項１記載のスチレン系樹脂成形品を提供するものである。
【００１２】
さらに第二発明では、上記樹脂シートを熱成形して得られる成形品表面に、ベタイン系帯電防止剤を塗布することを特徴とする、スチレン系樹脂成形品の製造方法を提供するものである。
【００１３】
【発明の実施の形態】
本発明におけるスチレン系樹脂は、上記ゴム質重合体含有量が５〜３０重量％、芳香族ビニル単量体含有量が３０〜９５重量％、シアン化ビニル単量体含有量が０〜５０重量％、及びこれら単量体と共重合可能な他のビニル単量体含量が０〜２５重量％の範囲のもので構成される樹脂を言う。シアン化ビニル単量体含有量は、２０〜４５重量％の範囲が、好ましい。
【００１４】
本発明におけるスチレン系樹脂のゴム質重合体としては、そのガラス転移温度が常温より低いものが対象となり、構成する単量体としては、ブタジエン、イソプレン、ジメチルブタジエン、クロロプレン、シクロペンジエンなどの共役ジエン単量体、２，５−ノルボルナジエン、１，４−シクロヘキサジエン、４−エチリデンノルボルネンなどの非共役ジエン単量体、スチレン、α−メチルスチレン、ビニルトルエン等の芳香族ビニル単量体、アクリロニトリルメタアクリロニトリルなどのシアン化ビニル単量体、メチルメタアクリレート、エチルアクリレート、ブチルアクリレートなどの（メタ）アクリル酸エステル単量体、エチレン、プロピレン、１−ブテン等のオレフィン単量体などが挙げられる。ゴム質重合体は、これら単量体を単独又は２種以上を反応させることによって、容易に製造することが出来る。２種以上の単量体よりなる共重合体は、ランダム共重合体、ブロック共重合体いずれであってもよい。また、ゴム質重合体を製造する場合には架橋用単量体として、少量の多官能性ビニル単量体を存在させて、共重合反応を行うことも可能である。この場合に用いる多官能性ビニル単量体としては、ジビニルベンゼン、エチレングリコールジメタクリレート、シアヌル酸トリアリル、アリルアクリレート、アリルメタクリレート、グリシジルアクリレートなどがある。
これらゴム質重合体を得るための単量体の重合方法は特に制限はなく、乳化重合、溶液重合などの公知の技術を用いうる。
また、スチレン系樹脂を製造する場合のゴム質重合体は、必ずしも一種類である必要はなく、別々に調整された二種類以上の混合物であってもよい。
【００１５】
本発明におけるスチレン系樹脂の製造に用いられる単量体としては、芳香族ビニル単量体シアン化ビニル単量体、及び／又はこれらと共重合可能な他のビニル単量体とよりなる。
【００１６】
芳香族ビニル単量体としては、スチレン、及び側鎖又は（及び）核置換スチレン（置換基は、低級アルキル基、低級アルコキシ基、トリフルオロメチル基、ハロゲン原子、その他）、例えばα−メチルスチレン、ｐ−メチルスチレン、ｏ−メチルスチレン、ｍ−メチルスチレン、核ハロゲン化スチレン、α−、またはβ−ビニルナフタレン、その他、がある。これらは群内または群間で併用してもよい。
【００１７】
シアン化ビニル単量体としては、アクリロニトリル、メタアクリロニトリル、α−クロロアクリロニトリル等がある。これらは一種又は二種以上の混合物であってもよい。
【００１８】
また、上記単量体と共重合可能な他の単量体を少量併用してもよい。このような単量体としては、アクリル酸、メタアクリル酸と炭素数が１〜１０の範囲の一価アルコールとのエステル、特にメチルメタアクリレート、その他がある。
【００２０】
本発明におけるスチレン系樹脂の構成割合が上記の範囲を外れると、樹脂シートの熱成形が困難となり、また、得られるスチレン系樹脂成形品の機械的性質が劣ることとなる。
【００２１】
本発明は、上記スチレン系樹脂１００重量部に対して、０．０１重量部以上１．１重量部未満の下記式（Ｉ）、（II）、（III)、（IV）、（Ｖ）で示される酸化防止剤を含有させてなるスチレン系樹脂成形品及びその製造方法である。
【００２２】
【化１１】

（式中、ｔＢｕはターシャリーブチル基を示す。）
【００２３】
【化１２】

（式中、ｔＢｕはターシャリーブチル基を示す。）
【００２４】
【化１３】

（式中、ｔＢｕはターシャリーブチル基を示す。）
【００２５】
【化１４】

【００２６】
【化１５】

（式中、ｔＢｕはターシャリーブチル基を示す。）
【００２７】
本発明における酸化防止剤は、上記構造式（Ｉ）〜（Ｖ）であり、一種又は二種以上添加してよく、これらの添加量はスチレン系樹脂組成物に対して０．０１重量部〜１．１重量部未満で好ましくは０．０５〜１．０重量部である。
添加量が０．０１重量部未満では目的とする安定剤としての効果が得られず、１．１重量部以上と多くしても着色防止効果はそれほど顕著でない。
【００２８】
スチレン系樹脂に酸化防止剤構造式（Ｉ）〜（Ｖ）を添加するには通常の混合機、例えばリボンブレンダー・ヘンシェルミキサー・タンブラー等で混合後、押出機等で溶融混合する方法、或いは押出機等で溶融混合された樹脂に所定量の酸化防止剤構造式（Ｉ）〜（Ｖ）を添加する方法等がある。
【００２９】
更に、各種の添加剤として、滑剤、可塑剤、安定剤等、例えば、ワックス、高級脂肪酸金属石鹸、光安定剤、紫外線吸収剤等を必要に応じて含有させることが出来る。
【００３０】
上記酸化防止剤とスチレン系樹脂を溶融混合したペレットをシート化するには通常のシート製造装置で行うことが出来る。例えばＴダイ法で押出温度は樹脂の粘度により１６０〜２７０℃の押出温度でシート板厚の０．５〜６．０ｍｍのシートを任意に得る方法等がある。
シート熱成形法は真空成形・圧空成形・真空圧空成形等で、たとえば真空成形法の場合はシート表面で１２０〜１８０℃で、真空圧力は−６００〜−７６０ｍｍＨｇ行う方法がある。
本発明で得られるスチレン系樹脂成形品としてのシート熱成形品には、冷蔵庫内箱、洗面化粧台等の家庭用部品・工業用部品がある。
【００３１】
本発明のシート熱成形品で使用される帯電防止剤はベタイン系帯電防止剤で、例えば、ラウリル酢酸ベタイン等のカルボキシベタイン型のもの、アミノカルボン酸塩ベタイン型のもの等が挙げられる。塗布方法としては、スプレー塗布等が一般的でありベタイン系帯電防止剤を３０〜２５０倍水溶液として、スプレーで１〜３回塗布する方法がある。
【００３２】
【実施例】
下記の実施例及び比較例は、本発明をさらに具体的に説明するためのものである。本発明は、その要旨を超えない限り、以下の例に限定されるものではない。
【００３３】
製造例１
グラフト重合体の製造
ポリブタジエンゴム乳化ラテックス、アクリロニトリル、スチレンを公知乳化重合により重合する際に、アクリロニトリル、スチレン量比を変えて、アクリロニトリル含有量の異なる、表１のグラフト重合体（Ａ）及び（Ｂ）を得た。
【００３４】
【表１】

【００３５】
製造例２
ポリアクリル酸ブチルラバー乳化重合ラテックス、アクリロニトリル、スチレンを公知の乳化重合法で、表２のグラフト共重合体（Ｃ）を得た。
【００３６】
【表２】

【００３７】
製造例３
共重合体の製造
アクリロニトリル、スチレン等の単量体の組み合わせで、量比を変えて公知の懸濁重合により、表３のビーズ状共重合体（ａ）及び（ｂ）を得た。
【００３８】
【表３】

【００３９】
酸化防止剤
実施例及び比較例において使用した酸化防止剤を表４に示す。
【００４０】
【表４】

【００４１】
【表５】

【００４２】
実施例１〜２７
上記で製造したグラフト共重合体（Ａ）、（Ｂ）及び（Ｃ）、ビーズ状共重合体（ａ）及び（ｂ）を用い、表４の量比で配合し、これに酸化防止剤前記（Ｉ）〜（Ｖ）を一種又は二種以上加え、更に、顔料（酸化チタン）とマグネシウムステアレートを加えて後、通常のドラムブレンダーで２０分攪拌後、スクリュー回転数１５０ｒｐｍ、押出温度２２０℃の条件下で二軸押出機で混練し、スチレン系樹脂ペレットを得た。
このペレットを、日立造船産業（株）製ＳＨＴ９０シート製造装置を用いて、押出温度２３０℃、スクリュー回転数６０ｒｐｍの条件下で巾４００ｍｍ×長さ７００ｍｍ×厚さ２．４ｍｍの白色シートを成形した。
【００４３】
次に、この成形した白色シートを（株）浅野研究所製ＦＣ−４ＡＰＡ−Ｗ型全自動汎用真空成型機でヒーター電圧２００Ｖ、加熱時間６０秒の条件下で２００ｍｍ角×深さ５０ｍｍの箱を製造した。
この箱体内面に、１％ラウリル酢酸ベタイン水溶液を、ハケで２回塗布し常温で３時間乾燥した。
ベタイン系帯電防止剤を塗布した内箱スチレン系樹脂成形品をアルミホイルで包み、５０℃及び７０℃の暗所恒温槽で、１０日間保持し、スガ試験機製ＳＭカラーコンピューターで試験前後の色調を測色しΔＥを求め着色度とした。
この結果を実施例１〜２７として、表５に示す。
【００４４】
【表６】

【００４５】
実施例２８〜４９
上記で製造したグラフト共重合体（Ａ）、（Ｂ）及び（Ｃ）、ビーズ状共重合体（ａ）、（ｂ）を用い、表３の量比で配合し、これに酸化防止剤前記（Ｉ）〜（Ｖ）を一種又は二種以上加え、更に、顔料（酸化チタン）とマグネシウムステアレートを加えて後、通常のドラムブレンダーで２０分攪拌後、スクリュー回転数１５０ｒｐｍ、押出温度２２０℃の条件下で二軸押出機で混練し、スチレン系樹脂ペレットを得た。
このペレットを、日立造船産業（株）製ＳＨＴ９０シート製造装置を用いて、押出温度２３０℃、スクリュー回転数６０ｒｐｍの条件下で巾４００ｍｍ×長さ７００ｍｍ×厚さ２．４ｍｍの白色シートを成形した。
【００４６】
次に、この成形した白色シートを（株）浅野研究所製ＦＣ−４ＡＰＡ−Ｗ型全自動汎用真空成型機でヒーター電圧２００Ｖ、加熱時間６０秒の条件下で２００ｍｍ角×深さ５０ｍｍの箱を製造した。
この箱体内面に、１％ラウリル酢酸ベタイン水溶液を、ハケで２回塗布し常温で３時間乾燥した。
１％ラウリル酢酸ベタイン水溶液を塗布したスチレン系樹脂成形品である箱体を塗料用退色試験機（スガ試験機製）で２４時間照射した。
ベタイン系帯電防止剤を塗布し塗料用退色試験機で照射した、内箱スチレン系樹脂成形品をアルミホイルで包み、７０℃の暗所恒温槽で、７日間保持し、スガ試験機製ＳＭカラーコンピューターで試験前後の色調を測色しΔＥを求め着色度とした。
この結果を実施例２８〜４９として表６に示す。
【００４７】
【表７】

【００４８】
比較例１〜２６
本発明で特定する以外の表４の酸化防止剤を使用し、実施例１〜２７と同様にして評価を行い、結果を表７に示した。
なお、表５〜７中、実施例及び比較例の、パーセント、部は重量基準による。変色度ΔＥ値は、２未満が実使用上問題がない範囲で、２以上になると最終製品として実質的に許容できない値である。
【００４９】
【表８】

【００５０】
【発明の効果】
本発明は、以上説明したとおりであり、次のように特別に顕著な効果を奏し、その産業上の利用価値は極めて大である。即ち、本発明方法によれば、ベタイン系帯電防止剤を塗布したスチレン系樹脂成形品において特定の酸化防止剤を含有させることにより、酸化劣化を招くことがなく、成形品を高温暗所、高湿高温暗所に保持した場合、シート成形品表面が部分的に黄色に着色したり変色したりすることが実質的になく、変色度（ΔＥ）が格別に小さくなるという効果を奏する。[0001]
BACKGROUND OF THE INVENTION
In the present invention, when a betaine antistatic agent is applied to the surface of a styrene-based resin molded product, a specific antioxidant is used, so that the resin sheet is thermoformed without impairing various physical properties of the styrene-based resin molded product. The present invention relates to a styrenic resin molded article which is molded by the above-described method without yellowing and coloring and a method for producing the same.
[0002]
[Prior art]
In order to prevent oxidative deterioration, styrene-based resin molded products are made into sheets by adding an antioxidant, and the molded products are molded by thermoforming methods such as vacuum and pressure molding, and are used in households such as refrigerators and vanities. Used for goods and industrial goods.
Since this molded product easily adheres to dust, an antistatic agent is applied to the surface of the molded product.
Although many of these antioxidants and antistatic agents are known, betaine antistatic agents have been widely used from the viewpoint of antistatic effect and cost.
However, if this betaine antistatic agent is applied later, depending on the type of antioxidant, it may cause a chemical reaction with the betaine antistatic agent. There was a drawback that it was partially colored yellow.
[0003]
[Problems to be solved by the invention]
As a result of studying a method for obtaining a sheet molded article without yellowing and coloring even when using a betaine antistatic agent in the above situation, the present inventor has selected this by selecting a specific antioxidant. I found that there was no coloration.
[0004]
[Means for Solving the Problems]
That is, in the first invention of the present invention , in order to solve the above problems, the rubbery polymer content is 5 to 30% by weight, the aromatic vinyl monomer content is 30 to 95% by weight , vinyl cyanide. Thermoforming a resin sheet formed from a styrene resin having a monomer content of 0 to 50% by weight and a content of other vinyl monomers copolymerizable with these monomers of 0 to 25% by weight In a styrene resin molded product obtained by applying a betaine antistatic agent to the surface of the molded product after being processed into a molded product, the resin is added to the styrene resin forming the resin sheet by 100 wt. One or more antioxidants represented by the following formulas (I) to (V) in an amount of 0.01 parts by weight or more and less than 1.1 parts by weight based on 1 part by weight are styrene-based A resin molded product is provided.
[0005]
[Chemical 6]

[0006]
[Chemical 7]

[0007]
[Chemical 8]

[0008]
[Chemical 9]

[0009]
[Chemical Formula 10]

[0011]
Moreover, this invention contains 0.05-1.0 weight part of antioxidant shown by Formula (I)-(V) of Claim 1 with respect to 100 weight part of styrene resin. The styrenic resin molded product according to claim 1 is provided.
[0012]
Furthermore, the second invention provides a method for producing a styrene resin molded product , characterized in that a betaine antistatic agent is applied to the surface of a molded product obtained by thermoforming the resin sheet.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Styrene resin definitive to the present invention, the rubber polymer content of 5 to 30 wt%, the aromatic vinyl monomer content of 30 to 95 wt%, the vinyl cyanide monomer content 0-50 It refers to a resin composed of a resin having a content in the range of 0 to 25% by weight and other vinyl monomers copolymerizable with these monomers . The content of vinyl cyanide monomer is preferably in the range of 20 to 45% by weight .
[0014]
The rubbery polymer of the styrenic resin in the present invention is one whose glass transition temperature is lower than room temperature, and the constituent monomers are conjugates such as butadiene, isoprene, dimethylbutadiene, chloroprene, cyclopentene, etc. Non-conjugated diene monomers such as diene monomers, 2,5-norbornadiene, 1,4-cyclohexadiene, 4-ethylidene norbornene, aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, acrylonitrile Examples thereof include vinyl cyanide monomers such as methacrylonitrile, (meth) acrylic acid ester monomers such as methyl methacrylate, ethyl acrylate and butyl acrylate, and olefin monomers such as ethylene, propylene and 1-butene. The rubbery polymer can be easily produced by reacting these monomers alone or in combination of two or more. The copolymer composed of two or more monomers may be either a random copolymer or a block copolymer. In the case of producing a rubbery polymer, it is also possible to carry out a copolymerization reaction in the presence of a small amount of a polyfunctional vinyl monomer as a crosslinking monomer. Examples of the polyfunctional vinyl monomer used in this case include divinylbenzene, ethylene glycol dimethacrylate, triallyl cyanurate, allyl acrylate, allyl methacrylate, and glycidyl acrylate.
There are no particular restrictions on the method of polymerizing the monomers to obtain these rubbery polymers, and known techniques such as emulsion polymerization and solution polymerization can be used.
Moreover, the rubber polymer in the case of manufacturing a styrene resin does not necessarily need to be one type, and may be a mixture of two or more types adjusted separately.
[0015]
The monomer used for the production of the styrenic resin in the present invention comprises an aromatic vinyl monomer, a vinyl cyanide monomer, and / or another vinyl monomer copolymerizable therewith.
[0016]
Examples of the aromatic vinyl monomer include styrene, and side chain or (and) nucleus-substituted styrene (substituents include a lower alkyl group, a lower alkoxy group, a trifluoromethyl group, a halogen atom, and the like) such as α-methylstyrene. , P-methylstyrene, o-methylstyrene, m-methylstyrene, nuclear halogenated styrene, α- or β-vinylnaphthalene, and the like. These may be used in combination or within groups.
[0017]
Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile and the like. These may be one kind or a mixture of two or more kinds.
[0018]
Moreover, you may use a small amount of the other monomer copolymerizable with the said monomer. Such monomers include esters of acrylic acid, methacrylic acid and monohydric alcohols having 1 to 10 carbon atoms, especially methyl methacrylate, and others.
[0020]
When the constituent ratio of the styrene resin in the present invention is out of the above range, it becomes difficult to thermoform the resin sheet, and the mechanical properties of the resulting styrene resin molded product are inferior.
[0021]
The present invention relates to the following formulas (I), (II), (III), (IV), and (V) that are 0.01 parts by weight or more and less than 1.1 parts by weight with respect to 100 parts by weight of the styrenic resin. It is a styrene-based resin molded article containing the indicated antioxidant and a method for producing the same.
[0022]
Embedded image

(In the formula, tBu represents a tertiary butyl group.)
[0023]
Embedded image

(In the formula, tBu represents a tertiary butyl group.)
[0024]
Embedded image

(In the formula, tBu represents a tertiary butyl group.)
[0025]
Embedded image

[0026]
Embedded image

(In the formula, tBu represents a tertiary butyl group.)
[0027]
The antioxidant in the present invention is the above structural formulas (I) to (V), and may be added singly or in combination of two or more, and these addition amounts are 0.01 parts by weight to the styrene resin composition. Less than 1.1 parts by weight, preferably 0.05 to 1.0 part by weight.
If the addition amount is less than 0.01 parts by weight, the effect as the intended stabilizer cannot be obtained, and even if it is increased to 1.1 parts by weight or more, the anti-coloring effect is not so remarkable.
[0028]
In order to add antioxidant structural formulas (I) to (V) to a styrenic resin, after mixing with an ordinary mixer such as a ribbon blender, a Henschel mixer, a tumbler, etc., melt mixing with an extruder or the like, or extrusion There is a method of adding a predetermined amount of antioxidant structural formulas (I) to (V) to a resin melt-mixed by a machine or the like.
[0029]
Furthermore, as various additives, a lubricant, a plasticizer, a stabilizer, and the like, for example, wax, higher fatty acid metal soap, light stabilizer, ultraviolet absorber, and the like can be contained as necessary.
[0030]
In order to form a pellet obtained by melting and mixing the antioxidant and the styrene resin, it can be carried out with a normal sheet manufacturing apparatus. For example, in the T-die method, there is a method of arbitrarily obtaining a sheet having a sheet thickness of 0.5 to 6.0 mm at an extrusion temperature of 160 to 270 ° C. depending on the viscosity of the resin.
The sheet thermoforming method is vacuum forming, pressure forming, vacuum pressure forming or the like. For example, in the case of the vacuum forming method, there is a method in which the sheet surface is 120 to 180 ° C. and the vacuum pressure is −600 to −760 mmHg.
The sheet thermoformed product as the styrenic resin molded product obtained in the present invention includes household parts and industrial parts such as a refrigerator inner box and a vanity.
[0031]
The antistatic agent used in the sheet thermoformed product of the present invention is a betaine antistatic agent, and examples thereof include carboxybetaine type such as lauryl acetate betaine, aminocarboxylate betaine type and the like. As a coating method, spray coating or the like is generally used, and there is a method in which a betaine antistatic agent is applied 30 to 250 times in an aqueous solution and applied by spraying 1 to 3 times.
[0032]
【Example】
The following examples and comparative examples are provided to further illustrate the present invention. The present invention is not limited to the following examples as long as the gist thereof is not exceeded.
[0033]
Production Example 1
Production of Graft Polymer When polymerizing polybutadiene rubber emulsion latex, acrylonitrile, and styrene by known emulsion polymerization, the ratio of acrylonitrile and styrene is changed to change the acrylonitrile content, and the graft polymers (A) and (B) in Table 1 )
[0034]
[Table 1]

[0035]
Production Example 2
A graft copolymer (C) shown in Table 2 was obtained from polybutyl acrylate rubber emulsion polymerization latex, acrylonitrile and styrene by a known emulsion polymerization method.
[0036]
[Table 2]

[0037]
Production Example 3
Production of Copolymers Bead-like copolymers (a) and (b) shown in Table 3 were obtained by a known suspension polymerization with a combination of monomers such as acrylonitrile and styrene and varying the quantity ratio.
[0038]
[Table 3]

[0039]
Antioxidants used in the antioxidant examples and comparative examples are shown in Table 4.
[0040]
[Table 4]

[0041]
[Table 5]

[0042]
Examples 1-27
Using the graft copolymers (A), (B) and (C) produced above, and the bead-shaped copolymers (a) and (b), they are blended in the quantitative ratios shown in Table 4, and the antioxidants Add one or two or more of (I) to (V), add a pigment (titanium oxide) and magnesium stearate, and then stir for 20 minutes with a normal drum blender. Then, screw rotation speed 150 rpm, extrusion temperature 220 ° C. The mixture was kneaded with a twin-screw extruder under the above conditions to obtain styrene resin pellets.
Using this pellet, a white sheet having a width of 400 mm × a length of 700 mm × a thickness of 2.4 mm was molded under the conditions of an extrusion temperature of 230 ° C. and a screw rotation speed of 60 rpm using an SHT90 sheet manufacturing apparatus manufactured by Hitachi Zosen Sangyo Co., Ltd. .
[0043]
Next, the white sheet thus formed was converted into a 200 mm square x 50 mm deep box with a heater voltage of 200 V and a heating time of 60 seconds using an FC-4APA-W type fully-automatic general-purpose vacuum forming machine manufactured by Asano Laboratory. Manufactured.
A 1% lauryl acetate betaine aqueous solution was applied twice by brush to the inner surface of the box and dried at room temperature for 3 hours.
Inner box styrene resin molded product coated with betaine antistatic agent is wrapped in aluminum foil, held in a constant temperature bath at 50 ° C and 70 ° C for 10 days, and the color tone before and after the test with SM color computer made by Suga Test Instruments The color was measured to obtain ΔE, which was used as the coloring degree.
The results are shown in Table 5 as Examples 1-27.
[0044]
[Table 6]

[0045]
Examples 28-49
Using the graft copolymers (A), (B) and (C) produced above, and the bead-shaped copolymers (a), (b), they are blended in the quantitative ratios shown in Table 3, and the antioxidants Add one or two or more of (I) to (V), add a pigment (titanium oxide) and magnesium stearate, and then stir for 20 minutes with a normal drum blender. Then, screw rotation speed 150 rpm, extrusion temperature 220 ° C. The mixture was kneaded with a twin-screw extruder under the above conditions to obtain styrene resin pellets.
Using this pellet, a white sheet having a width of 400 mm × a length of 700 mm × a thickness of 2.4 mm was molded under the conditions of an extrusion temperature of 230 ° C. and a screw rotation speed of 60 rpm using an SHT90 sheet manufacturing apparatus manufactured by Hitachi Zosen Sangyo Co., Ltd. .
[0046]
Next, the white sheet thus formed was converted into a 200 mm square x 50 mm deep box with a heater voltage of 200 V and a heating time of 60 seconds using an FC-4APA-W type fully-automatic general-purpose vacuum forming machine manufactured by Asano Laboratory. Manufactured.
A 1% lauryl acetate betaine aqueous solution was applied twice by brush to the inner surface of the box and dried at room temperature for 3 hours.
A box, which is a styrene resin molded product coated with a 1% lauryl acetate betaine aqueous solution, was irradiated with a fading tester for paint (manufactured by Suga Test Instruments) for 24 hours.
Inner box styrenic resin molded product, coated with betaine antistatic agent and irradiated with paint fading tester, wrapped in aluminum foil, kept in 70 ° C dark constant temperature bath for 7 days, SM color computer made by Suga Test Instruments Then, the color tone before and after the test was measured, and ΔE was obtained as the coloring degree.
The results are shown in Table 6 as Examples 28 to 49.
[0047]
[Table 7]

[0048]
Comparative Examples 1-26
Evaluations were made in the same manner as in Examples 1 to 27 using the antioxidants in Table 4 other than those specified in the present invention, and the results are shown in Table 7.
In Tables 5 to 7, percentages and parts of Examples and Comparative Examples are based on weight. The discoloration degree ΔE value is a value which is substantially unacceptable as a final product when it is 2 or more within a range where there is no problem in practical use when it is less than 2.
[0049]
[Table 8]

[0050]
【The invention's effect】
The present invention is as described above, and has a particularly remarkable effect as follows, and its industrial utility value is extremely large. That is, according to the method of the present invention, by including a specific antioxidant in a styrene resin molded article coated with a betaine antistatic agent, the molded article can be placed in a high-temperature dark place with a high temperature without causing oxidative deterioration. When kept in a humid high temperature dark place, the surface of the sheet molded product is substantially not yellowed or discolored partially, and there is an effect that the discoloration degree (ΔE) is remarkably reduced.

Claims (3)

The rubbery polymer content is 5-30% by weight, the aromatic vinyl monomer content is 30-95% by weight, the vinyl cyanide monomer content is 0-50% by weight, A resin sheet molded from a styrene-based resin having a content of other polymerizable vinyl monomers of 0 to 25% by weight is subjected to a thermoforming process to form a molded product, and then betaine is formed on the surface of the molded product. In the styrenic resin molded product formed by applying an antistatic agent, the styrenic resin forming the resin sheet has a formula of 0.01 parts by weight or more and less than 1.1 parts by weight with respect to 100 parts by weight of the resin. A styrene-based resin molded article comprising one or more of the antioxidants represented by (I) to (V).

  The antioxidant represented by the formulas (I) to (V) according to claim 1 is contained in an amount of 0.05 to 1.0 part by weight based on 100 parts by weight of the styrene resin. The styrene resin molded article according to claim 1.   A method for producing a styrene-based resin molded product, comprising applying a betaine antistatic agent to a surface of a molded product obtained by thermoforming the resin sheet according to claim 1.