JP2014129446A - Method for producing thermoplastic resin foam - Google Patents
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- JP2014129446A JP2014129446A JP2012287050A JP2012287050A JP2014129446A JP 2014129446 A JP2014129446 A JP 2014129446A JP 2012287050 A JP2012287050 A JP 2012287050A JP 2012287050 A JP2012287050 A JP 2012287050A JP 2014129446 A JP2014129446 A JP 2014129446A
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本発明は、微細で且つ略均一な気泡径を有する気泡を含む熱可塑性樹脂発泡体の製造方法に関する。 The present invention relates to a method for producing a thermoplastic resin foam containing bubbles having fine and substantially uniform cell diameters.
近年、不活性ガスである二酸化炭素を用いた熱可塑性樹脂発泡体が様々な分野において利用されつつある。特許文献１には、樹脂に液状のＣＯ2を含浸させた後、該樹脂を発泡させる微細発泡体の製造方法が開示されているが、得られた微細発泡体の気泡径（セルサイズ）が１．８〜５μｍと大きい。発泡体は、発泡倍率が同じである場合、気泡径が微細になればなるほど引張弾性率などの機械的強度が高くなることから、更に微細な気泡を有する発泡体が所望されている。 In recent years, thermoplastic resin foams using carbon dioxide, which is an inert gas, are being used in various fields. Patent Document 1 discloses a method for producing a fine foam in which a resin is impregnated with liquid CO 2 and then foamed, and the cell diameter of the obtained fine foam is small. It is as large as 1.8-5 μm. When the foam has the same expansion ratio, the finer the bubble diameter, the higher the mechanical strength such as the tensile elastic modulus. Therefore, a foam having finer bubbles is desired.
特許文献２には、２種類以上のモノマーの共重合体よりなるミクロ相分離構造を有する樹脂材料に、高圧ガスを接触させた後、発泡させる共重合樹脂発泡体の製造方法が開示されており、従来の製造方法で製造される発泡体の気泡径よりも小さな気泡径を有する発泡体が製造されているが、気泡径が５００ｎｍ程度の発泡体しか得られていない。 Patent Document 2 discloses a method for producing a copolymer resin foam in which a high-pressure gas is brought into contact with a resin material having a microphase separation structure composed of a copolymer of two or more types of monomers and then foamed. A foam having a cell diameter smaller than that of a foam manufactured by a conventional manufacturing method is manufactured, but only a foam having a cell diameter of about 500 nm is obtained.
又、特許文献３には、（ａ）二酸化炭素雰囲気下の圧力容器内で、（共）重合体成形物中に、５〜５０ＭＰａの圧力、且つ１０℃〜４００℃の温度で二酸化炭素を溶解させる工程、（ｂ）上記の工程（ａ）の圧力から、０．０２〜３０ＭＰａ／ｓｅｃの減圧速度で２ＭＰａ以上減圧して、多孔質（共）重合体成形物を得る工程、（ｃ）上記の工程（ｂ）で得られた多孔質（共）重合体成形物を、スライス加工して多孔質（共）重合体フィルムを得る工程からなる多孔質（共）重合体フィルムの製造方法が開示されており、平均気泡径が１００ｎｍの多孔質（共）重合体が製造されているものの、気泡径のバラツキが大きく、多孔質（共）重合体の引張弾性率などの機械的強度が低いという問題点を有している。 Patent Document 3 discloses that (a) carbon dioxide is dissolved in a (co) polymer molded product at a pressure of 5 to 50 MPa and a temperature of 10 ° C. to 400 ° C. in a pressure vessel under a carbon dioxide atmosphere. (B) a step of reducing the pressure by 0.02 to 30 MPa / sec from the pressure in the step (a) by 2 MPa or more to obtain a porous (co) polymer molded product, (c) the step Disclosed is a method for producing a porous (co) polymer film comprising a step of slicing the porous (co) polymer molded product obtained in step (b) to obtain a porous (co) polymer film. Although a porous (co) polymer having an average cell diameter of 100 nm is manufactured, the variation in the cell diameter is large, and the mechanical strength such as the tensile elastic modulus of the porous (co) polymer is low. Has a problem.
本発明は、気泡径が小さくて均一性に優れており、引張弾性率などの機械的強度にも優れた熱可塑性樹脂発泡シートの製造方法を提供する。 The present invention provides a method for producing a thermoplastic resin foam sheet having a small cell diameter, excellent uniformity, and excellent mechanical strength such as tensile elastic modulus.
本発明の熱可塑性樹脂発泡体の製造方法は、互いに非相溶性である熱可塑性樹脂（Ａ）１００重量部及び熱可塑性樹脂（Ｂ）５〜７０重量部を混合して、熱可塑性樹脂（Ａ）を海部、熱可塑性樹脂（Ｂ）を島部とし且つ島部の大きさが１０〜８００ｎｍである海島構造を有する樹脂組成物を製造する混合工程と、上記樹脂組成物に発泡剤を含浸させて発泡性樹脂組成物を製造する含浸工程と、上記発泡性樹脂組成物における上記熱可塑性樹脂（Ａ）のガラス転移温度未満の温度にて上記発泡性樹脂組成物を５〜３００秒間保持する養生工程と、上記発泡性樹脂組成物における上記熱可塑性樹脂（Ａ）のガラス転移温度よりも３０℃高い温度以上にて上記発泡性樹脂組成物を１〜３００秒間に亘って保持して上記発泡性樹脂組成物を発泡させて発泡樹脂組成物を製造する発泡工程と、上記発泡樹脂組成物における上記熱可塑性樹脂（Ａ）のガラス転移温度未満に上記発泡樹脂組成物を冷却する冷却工程とを有する。 The method for producing a thermoplastic resin foam of the present invention comprises mixing thermoplastic resin (A) 100 parts by weight and thermoplastic resin (B) 5 to 70 parts by weight, which are incompatible with each other, to produce a thermoplastic resin (A ) As the sea part, the thermoplastic resin (B) as the island part, and a mixing step for producing a resin composition having a sea-island structure with an island part size of 10 to 800 nm, and impregnating the resin composition with a foaming agent. An impregnation step for producing a foamable resin composition and curing for holding the foamable resin composition for 5 to 300 seconds at a temperature lower than the glass transition temperature of the thermoplastic resin (A) in the foamable resin composition. Holding the foamable resin composition for 1 to 300 seconds at a temperature of 30 ° C. or higher than the glass transition temperature of the thermoplastic resin (A) in the foamable resin composition and the foamable resin composition. Foam the resin composition It has a foaming process to produce a foam resin composition, and a cooling step of cooling the foamed resin composition to below the glass transition temperature of the thermoplastic resin (A) in the foaming resin composition.
先ず、互いに非相溶性である熱可塑性樹脂（Ａ）１００重量部及び熱可塑性樹脂（Ｂ）５〜７０重量部を混合して、熱可塑性樹脂（Ａ）を海部、熱可塑性樹脂（Ｂ）を島部とし且つ島部の大きさが１０〜８００ｎｍである海島構造を有する樹脂組成物を製造する（混合工程）。 First, 100 parts by weight of the incompatible thermoplastic resin (A) and 5 to 70 parts by weight of the thermoplastic resin (B) are mixed, and the thermoplastic resin (A) is the sea part and the thermoplastic resin (B) is mixed. A resin composition having a sea-island structure in which the island portion is 10 to 800 nm in size is manufactured (mixing step).
本発明において用いられる熱可塑性樹脂（Ａ）及び（Ｂ）は、互いに非相溶性であって熱可塑性樹脂（Ａ）を海部とし、熱可塑性樹脂（Ｂ）を島部とした海島構造を形成できればよい。熱可塑性樹脂（Ａ）及び（Ｂ）が互いに非相溶性であるとは、熱可塑性樹脂（Ａ）及び（Ｂ）を混合したときに単一相を形成しないことをいう。 The thermoplastic resins (A) and (B) used in the present invention are incompatible with each other, and can form a sea-island structure in which the thermoplastic resin (A) is a sea part and the thermoplastic resin (B) is an island part. Good. That the thermoplastic resins (A) and (B) are incompatible with each other means that no single phase is formed when the thermoplastic resins (A) and (B) are mixed.
熱可塑性樹脂（Ａ）及び（Ｂ）としては、例えば、ポリカーボネート、ポリメタクリル酸メチル、低密度ポリエチレン、高密度ポリエチレン、直鎖状低密度ポリエチレン、エチレン−プロピレン共重合体、エチレン−ブテン共重合体、プロピレン−ブテン共重合体、エチレン−メタクリル酸共重合体、エチレン−アクリル酸共重合体、エチレン−酢酸ビニル共重合体、エチレン−アクリル酸エチル共重合体、アイオノマー樹脂（例えばエチレン−メタクリル酸共重合体アイオノマー樹脂など）、ポリプロピレン、ポリブテン、ポリ（４−メチルペンテン−１）、環状ポリオレフィン系樹脂、エチレン−スチレン共重合体、超高分子量ポリオレフィン系樹脂（例えば、超高分子量ポリエチレン、超高分子量ポリプロピレンなど）、ポリスチレン系樹脂（ポリスチレン、ブタジエン−スチレン共重合体（ＨＩＰＳ）、アクリロニトリル−スチレン共重合体（ＡＳ樹脂）、アクリロニトリル−ブタジエン−スチレン共重合体（ＡＢＳ樹脂）など）、ポリアクリロニトリル、アクリロニトリル−アクリル酸メチル共重合体、ポリ塩化ビニル、ポリ塩化ビニリデン、ポリアセタール、ポリフェニレンオキシド、ポリ酢酸ビニル、ポリビニルアルコール、酢酸セルロース、ポリエステル系樹脂（例えば、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリトリメチレンテレフタレートなど）、ポリアミド樹脂、ポリイミド樹脂、ポリサルフォン、ポリエーテルサルフォン、ポリアリレート、ポリエーテルエーテルケトン、液晶ポリマー、熱可塑性エラストマー、生分解性ポリマー（例えば、ポリ乳酸、ポリグリコール酸などのようなヒドロキシカルボン酸縮合物、ポリブチレンサクシネートのようなジオールとカルボン酸の縮合物など）、ポリウレタン系樹脂（熱可塑性ポリウレタンも含む）、エポキシ樹脂、フッ素樹脂（例えば、ポリテトラフルオロエチレンなど）、フェノール樹脂、ユリア樹脂、メラミン樹脂、ジアリルフタレート樹脂などが挙げられ、互いに非相溶性を有し且つ海島構造を形成する熱可塑性樹脂を組み合わせて用いればよい。 Examples of the thermoplastic resins (A) and (B) include polycarbonate, polymethyl methacrylate, low density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-propylene copolymer, and ethylene-butene copolymer. , Propylene-butene copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ionomer resin (for example, ethylene-methacrylic acid copolymer). Polymer ionomer resin, etc.), polypropylene, polybutene, poly (4-methylpentene-1), cyclic polyolefin resin, ethylene-styrene copolymer, ultra high molecular weight polyolefin resin (eg, ultra high molecular weight polyethylene, ultra high molecular weight) Polypropylene), polystyrene Resin (polystyrene, butadiene-styrene copolymer (HIPS), acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), etc.), polyacrylonitrile, acrylonitrile-methyl acrylate copolymer Polymer, polyvinyl chloride, polyvinylidene chloride, polyacetal, polyphenylene oxide, polyvinyl acetate, polyvinyl alcohol, cellulose acetate, polyester resins (for example, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, etc.), polyamide resin, polyimide resin , Polysulfone, polyethersulfone, polyarylate, polyetheretherketone, liquid crystal polymer, thermoplastic elastomer, biodegradable polymer For example, hydroxycarboxylic acid condensates such as polylactic acid and polyglycolic acid, diol and carboxylic acid condensates such as polybutylene succinate), polyurethane resins (including thermoplastic polyurethanes), epoxy resins, fluorine Examples thereof include resins (for example, polytetrafluoroethylene), phenol resins, urea resins, melamine resins, diallyl phthalate resins, etc., and may be used in combination with thermoplastic resins that are incompatible with each other and form a sea-island structure. .
熱可塑性樹脂（Ａ）及び（Ｂ）の組合せとしては、ポリカーボネートとポリメタクリル酸メチルの組合せが好ましく、熱可塑性樹脂（Ａ）及び（Ｂ）が海島構造を形成し、海部を構成している熱可塑性樹脂（Ａ）がポリカーボネートであり且つ島部を構成している熱可塑性樹脂（Ｂ）がポリメタクリル酸メチルであることが好ましい。島部を構成する熱可塑性樹脂（Ｂ）の量は、少ないと、気泡の分布が偏在化し、多いと、海島構造が逆転するので、熱可塑性樹脂（Ａ）１００重量部に対して熱可塑性樹脂（Ｂ）５〜７０重量部に限定され、１０〜５０重量部が好ましく、２０〜３０重量部がより好ましい。 As a combination of the thermoplastic resins (A) and (B), a combination of polycarbonate and polymethyl methacrylate is preferable, and the thermoplastic resins (A) and (B) form a sea-island structure and constitute the sea part. It is preferable that the thermoplastic resin (A) is polycarbonate and the thermoplastic resin (B) constituting the island portion is polymethyl methacrylate. If the amount of the thermoplastic resin (B) constituting the island portion is small, the distribution of bubbles is unevenly distributed. If the amount is large, the sea-island structure is reversed. Therefore, the thermoplastic resin is used with respect to 100 parts by weight of the thermoplastic resin (A). (B) It is limited to 5 to 70 parts by weight, preferably 10 to 50 parts by weight, and more preferably 20 to 30 parts by weight.
熱可塑性樹脂（Ａ）及び熱可塑性樹脂（Ｂ）を混合して所定の大きさの島部を有する海島構造を有する樹脂組成物を製造する方法としては、例えば、熱可塑性樹脂（Ａ）及び熱可塑性樹脂（Ｂ）を押出機に供給して溶融混練する方法が挙げられる。熱可塑性樹脂（Ａ）及び（Ｂ）を押出機にて溶融混練する条件としては、発泡剤を含浸させる前の熱可塑性樹脂（Ａ）のガラス転移温度よりも１００℃以上高いシリンダー温度で剪断速度１０００ｓｅｃ-1以上で混練することが好ましい。 Examples of a method for producing a resin composition having a sea-island structure having island portions of a predetermined size by mixing the thermoplastic resin (A) and the thermoplastic resin (B) include, for example, the thermoplastic resin (A) and the heat Examples thereof include a method in which the plastic resin (B) is supplied to an extruder and melt kneaded. The conditions for melt-kneading the thermoplastic resins (A) and (B) with an extruder are the shear rate at a cylinder temperature that is 100 ° C. higher than the glass transition temperature of the thermoplastic resin (A) before impregnating the foaming agent. It is preferable to knead at 1000 sec −1 or more.
樹脂組成物を所望形状に形成する方法としては、例えば、上述のように押出機を用いて製造された樹脂組成物を熱プレス機などの汎用の装置を用いて所望形状に成形する方法、熱可塑性樹脂（Ａ）及び熱可塑性樹脂（Ｂ）を押出機に供給して溶融混練し、押出機の先端に取り付けたダイから押出して所望形状を有する樹脂組成物を製造する方法などが挙げられる。 Examples of a method for forming a resin composition into a desired shape include, for example, a method in which a resin composition produced using an extruder as described above is molded into a desired shape using a general-purpose device such as a heat press machine, Examples include a method of producing a resin composition having a desired shape by supplying the plastic resin (A) and the thermoplastic resin (B) to an extruder, melt-kneading, and extruding from a die attached to the tip of the extruder.
本発明の熱可塑性樹脂発泡体の製造方法によれば、後述するように、熱可塑性樹脂（Ａ）と熱可塑性樹脂（Ｂ）とを混合して熱可塑性樹脂（Ａ）及び（Ｂ）が海島構造を形成した樹脂組成物に発泡剤を含浸させて発泡性樹脂組成物を製造した後、発泡性樹脂組成物を養生した上で所定温度に加熱して発泡させることによって、極めて微細で且つ略均一な気泡を有する熱可塑性樹脂発泡体を製造することができる。 According to the method for producing a thermoplastic resin foam of the present invention, as described later, the thermoplastic resin (A) and the thermoplastic resin (B) are mixed and the thermoplastic resins (A) and (B) are sea islands. A resin composition having a structure is impregnated with a foaming agent to produce a foamable resin composition, and then the foamable resin composition is cured and heated to a predetermined temperature to be foamed. A thermoplastic resin foam having uniform bubbles can be produced.
従って、樹脂組成物の海島構造を構成している島部の大きさは、１０ｎｍより小さく分散させることは現状、技術的に困難であり、大きいと、気泡が粗大になるので、１０〜８００ｎｍに限定され、１０〜９０ｎｍがより好ましい。 Accordingly, it is technically difficult to disperse the island part constituting the sea-island structure of the resin composition to be smaller than 10 nm at present, and if it is large, the bubble becomes coarse. It is limited and 10 to 90 nm is more preferable.
樹脂組成物の海島構造を構成している島部の大きさは、樹脂組成物を染色し、輪郭を明確にした上で透過型電子顕微鏡によって測定し、島部を包囲し得る最小の真円の直径をいう。 The size of the island part constituting the sea-island structure of the resin composition is measured by a transmission electron microscope after staining the resin composition and defining the outline, and is the smallest perfect circle that can surround the island part. The diameter of
発泡剤を含浸させる前の熱可塑性樹脂（Ｂ）のガラス転移温度よりも、発泡剤を含浸させる前の熱可塑性樹脂（Ａ）のガラス転移温度の方が高いことが好ましい。明確には解明されていないが、発泡剤を含浸させる前の熱可塑性樹脂（Ｂ）のガラス転移温度が、発泡剤を含浸させる前の熱可塑性樹脂（Ａ）のガラス転移温度以上の温度であると、発泡性樹脂組成物の発泡工程において、海部の熱可塑性樹脂（Ａ）が島部の熱可塑性樹脂（Ｂ）と同等又は更に軟らかい状態となり、気泡の成長が海部で優先的に成長することになり、その結果、発泡樹脂組成物に均一性に優れ且つ微細な気泡を形成することができない。発泡剤を含浸させる前の熱可塑性樹脂（Ａ）のガラス転移温度は、発泡剤を含浸させる前の熱可塑性樹脂（Ｂ）のガラス転移温度との差が小さいと、気泡の成長が海部でも生じる可能性があり、発泡樹脂組成物に均一性に優れ且つ微細な気泡を形成することができないので、発泡剤を含浸させる前の熱可塑性樹脂（Ｂ）のガラス転移温度よりも２０℃以上高いことが好ましく、発泡剤を含浸させる前の熱可塑性樹脂（Ｂ）のガラス転移温度よりも２５℃以上高いことがより好ましく、発泡剤を含浸させる前の熱可塑性樹脂（Ｂ）のガラス転移温度よりも２５〜５０℃高いことが特に好ましい。なお、本発明において、発泡剤を含浸させる前の熱可塑性樹脂のガラス転移温度は、プラスチックの転移温度測定法（ＪＩＳ Ｋ７１２１）に準拠して測定された温度をいう。 It is preferable that the glass transition temperature of the thermoplastic resin (A) before impregnating the foaming agent is higher than the glass transition temperature of the thermoplastic resin (B) before impregnating the foaming agent. Although not clearly clarified, the glass transition temperature of the thermoplastic resin (B) before impregnating the foaming agent is equal to or higher than the glass transition temperature of the thermoplastic resin (A) before impregnating the foaming agent. And in the foaming process of the foamable resin composition, the thermoplastic resin (A) in the sea part is equal to or softer than the thermoplastic resin (B) in the island part, and the growth of bubbles preferentially grows in the sea part. As a result, it is not possible to form fine bubbles with excellent uniformity in the foamed resin composition. When the difference between the glass transition temperature of the thermoplastic resin (A) before impregnating the foaming agent and the glass transition temperature of the thermoplastic resin (B) before impregnating the foaming agent is small, bubble growth occurs even in the sea. There is a possibility that the foamed resin composition is excellent in uniformity and fine bubbles cannot be formed, so that it is 20 ° C. or higher than the glass transition temperature of the thermoplastic resin (B) before impregnating the foaming agent. Is more preferably 25 ° C. or higher than the glass transition temperature of the thermoplastic resin (B) before impregnating the foaming agent, and is higher than the glass transition temperature of the thermoplastic resin (B) before impregnating the foaming agent. A temperature of 25 to 50 ° C. is particularly preferable. In addition, in this invention, the glass transition temperature of the thermoplastic resin before impregnating a foaming agent means the temperature measured based on the plastics transition temperature measuring method (JISK7121).
次に、得られた樹脂組成物に発泡剤を含浸させて発泡性樹脂組成物を製造する（含浸工程）。発泡剤としては、樹脂組成物を発泡させることができればよく、例えば、二酸化炭素、窒素、アルゴン、水素、酸素、ブタン、プロパン、空気などが挙げられ、二酸化炭素が好ましい。なお、発泡剤は、単独で用いられても二種以上が併用されてもよい。 Next, the obtained resin composition is impregnated with a foaming agent to produce a foamable resin composition (impregnation step). The foaming agent only needs to be able to foam the resin composition. Examples thereof include carbon dioxide, nitrogen, argon, hydrogen, oxygen, butane, propane, and air, and carbon dioxide is preferable. In addition, a foaming agent may be used independently or 2 or more types may be used together.
樹脂組成物に発泡剤を含浸させるときの圧力は、低いと、樹脂組成物に発泡剤を十分な量含浸させることができず、高いと、樹脂組成物の海島構造が崩れてしまい、発泡樹脂組成物に形成される気泡が粗大化し、気泡の均一性も低下する虞れがあるので、３〜２０ＭＰａが好ましく、５〜１５ＭＰａがより好ましい。 If the pressure when the resin composition is impregnated with the foaming agent is low, the resin composition cannot be impregnated with a sufficient amount of the foaming agent. If the pressure is high, the sea-island structure of the resin composition is destroyed, and the foamed resin. Since bubbles formed in the composition may be coarsened and the uniformity of the bubbles may be lowered, 3 to 20 MPa is preferable, and 5 to 15 MPa is more preferable.
樹脂組成物に発泡剤を含浸させるときの温度は、低いほど好ましく、高いと、樹脂組成物の海島構造が崩れてしまい、発泡樹脂組成物に形成される気泡が粗大化し、気泡の均一性も低下する虞れがあるので、（発泡剤を含浸させる前の熱可塑性樹脂（Ａ）のガラス転移温度−１５０℃）〜（発泡剤を含浸させる前の熱可塑性樹脂（Ａ）のガラス転移温度−１００℃）が好ましく、（発泡剤を含浸させる前の熱可塑性樹脂（Ａ）のガラス転移温度−１３０℃）〜（発泡剤を含浸させる前の熱可塑性樹脂（Ａ）のガラス転移温度−１００℃）がより好ましい。 The temperature when the resin composition is impregnated with the foaming agent is preferably as low as possible. If the temperature is high, the sea-island structure of the resin composition is destroyed, the bubbles formed in the foamed resin composition are coarsened, and the uniformity of the bubbles is also improved. Since there is a possibility of lowering, (the glass transition temperature of the thermoplastic resin (A) before impregnating the foaming agent -150 ° C.) to (the glass transition temperature of the thermoplastic resin (A) before impregnating the foaming agent) 100 ° C.) is preferable, and (the glass transition temperature of the thermoplastic resin (A) before impregnating the foaming agent—130 ° C.) to (the glass transition temperature of the thermoplastic resin (A) before impregnating the foaming agent—100 ° C. ) Is more preferable.
樹脂組成物に発泡剤を含浸させるときの時間は、短いと、樹脂組成物に発泡剤を含浸させることができないため、１２時間以上が好ましく、２４時間以上がより好ましい。 If the time when the resin composition is impregnated with the foaming agent is short, the resin composition cannot be impregnated with the foaming agent. Therefore, the time is preferably 12 hours or more, and more preferably 24 hours or more.
発泡剤の樹脂組成物への含浸は、樹脂組成物への発泡剤の含浸が不十分であると、樹脂組成物の中央部に未発泡領域が形成される虞れがあるので、熱可塑性樹脂（Ａ）及び熱可塑性樹脂（Ｂ）のそれぞれに発泡剤が飽和溶解度に達するまで行うことが好ましい。なお、熱可塑性樹脂（Ａ）又は熱可塑性樹脂（Ｂ）に発泡剤が飽和溶解度まで含浸しているか否かは下記の方法によって確認することができる。即ち、同じ厚みの樹脂組成物に対して発泡剤を含浸させる時間を１時間毎に増加させ、単位面積当たりの発泡剤の含浸量に増加がない場合を熱可塑性樹脂に発泡剤が飽和溶解度まで含浸しているとみなす。 When the resin composition is impregnated with the foaming agent, if the resin composition is insufficiently impregnated with the foaming agent, an unfoamed region may be formed at the center of the resin composition. It is preferable to carry out until the foaming agent reaches saturation solubility in each of (A) and the thermoplastic resin (B). Whether the thermoplastic resin (A) or the thermoplastic resin (B) is impregnated with the blowing agent up to the saturation solubility can be confirmed by the following method. That is, the time for impregnating the foaming agent into the resin composition having the same thickness is increased every hour, and when the amount of impregnation of the foaming agent per unit area does not increase, the foaming agent is saturated in the thermoplastic resin until the saturation solubility. Considered impregnated.
次に、発泡性樹脂組成物の加圧状態を解除する。発泡性樹脂組成物を大気圧下で、発泡剤が含浸された熱可塑性樹脂（Ａ）のガラス転移温度未満の温度にて発泡性樹脂組成物を所定時間だけ養生する（養生工程）。 Next, the pressurized state of the foamable resin composition is released. The foamable resin composition is cured for a predetermined time at a temperature lower than the glass transition temperature of the thermoplastic resin (A) impregnated with the foaming agent under atmospheric pressure (curing step).
明確に解明されていないが、熱可塑性樹脂（Ａ）及び（Ｂ）に発泡剤を含浸させると、発泡性樹脂組成物中においてスピノーダル分解が生じていると考えられる。熱可塑性樹脂（Ａ）及び（Ｂ）に発泡剤を含浸させている含浸工程において、熱可塑性樹脂（Ａ）及び（Ｂ）に含浸された発泡剤は、熱可塑性樹脂（Ａ）及び（Ｂ）の全体に均一に存在するものではなく、発泡剤の量が少ないpoor相と、発泡剤の量が多いrich相とが存在している。 Although not clearly understood, it is considered that spinodal decomposition occurs in the foamable resin composition when the thermoplastic resins (A) and (B) are impregnated with a foaming agent. In the impregnation step in which the thermoplastic resins (A) and (B) are impregnated with the foaming agent, the foaming agents impregnated in the thermoplastic resins (A) and (B) are thermoplastic resins (A) and (B). In other words, there is a poor phase with a small amount of foaming agent and a rich phase with a large amount of foaming agent.
従って、発泡性樹脂組成物を該発泡性樹脂組成物中にpoor相とrich相とが存在している状態で発泡させると、rich相においては気泡が大きく成長し過ぎて気泡が粗大化する一方、poor相においては気泡が僅かしか成長しないか又は気泡そのものが発生しない状態となり、その結果、得られる発泡樹脂組成物の気泡は、一部が粗大化していると共に、形成される気泡径も不均一になると考えられる。 Therefore, when the foamable resin composition is foamed in a state where the poor phase and the rich phase are present in the foamable resin composition, the bubbles grow excessively in the rich phase, and the bubbles become coarse. In the poor phase, only a small amount of bubbles grow or no bubble itself is generated. As a result, the bubbles of the obtained foamed resin composition are partially coarsened and the bubble diameter formed is not good. It will be uniform.
そこで、本発明の熱可塑性樹脂発泡体の製造方法では、発泡性樹脂組成物を発泡剤が含浸された熱可塑性樹脂（Ａ）のガラス転移温度未満の温度にて５〜３００秒間に亘って保持して養生する。発泡性樹脂組成物を上記条件にて養生すると、明確に解明されていないが、発泡性樹脂組成物を発泡させることなく、発泡性樹脂組成物の表面から発泡剤が徐々に散逸し、この発泡剤の散逸に伴って、発泡性樹脂組成物中のrich相の発泡剤がpoor相に拡散し、発泡性樹脂組成物のrich相とpoor相との間における発泡剤量の差が小さくなると考えられる。しかる後、発泡性樹脂組成物を後述する条件で加熱、発泡させることによって微細で且つ大きさの略均一な気泡が形成される。 Therefore, in the method for producing a thermoplastic resin foam of the present invention, the foamable resin composition is held for 5 to 300 seconds at a temperature lower than the glass transition temperature of the thermoplastic resin (A) impregnated with the foaming agent. And then heal. When the foamable resin composition is cured under the above conditions, it has not been clearly clarified, but without foaming the foamable resin composition, the foaming agent gradually dissipates from the surface of the foamable resin composition. As the agent dissipates, the rich phase foaming agent in the foamable resin composition diffuses into the poor phase, and the difference in the amount of foaming agent between the rich phase and the poor phase of the foamable resin composition is considered to be small. It is done. Thereafter, the foamable resin composition is heated and foamed under the conditions described later to form fine and substantially uniform bubbles.
発泡性樹脂組成物を養生するときの温度は、高いと、発泡性樹脂組成物からの発泡剤の散逸が多くなりすぎて発泡性樹脂組成物の発泡性が低下すると共に、発泡性樹脂組成物が発泡を開始してしまい、得られる熱可塑性樹脂発泡体の気泡の均一性が低下するので、発泡性樹脂組成物を構成している、発泡剤が含浸された熱可塑性樹脂（Ａ）のガラス転移温度未満に限定され、発泡剤が含浸された熱可塑性樹脂（Ａ）のガラス転移温度Ｔ1よりも１０℃低い温度以下が好ましい。一方、発泡性樹脂組成物を養生するときの温度は、低すぎると、発泡性樹脂組成物からの発泡剤の散逸が不十分となり、発泡性樹脂組成物中におけるrich相からpoor相への発泡剤の拡散が不十分となり、発泡性樹脂組成物において発泡剤量が部分的に多い又は少ない状態の改善がみられず、その結果、得られる発泡樹脂組成物に形成される気泡径の均一性が低下することがあるので、（発泡剤が含浸された熱可塑性樹脂（Ａ）のガラス転移温度Ｔ1−３０℃）以上が好ましく、（発泡剤が含浸された熱可塑性樹脂（Ａ）のガラス転移温度Ｔ1−２０℃）以上がより好ましい。 If the temperature when curing the foamable resin composition is high, the foaming agent composition is excessively dissipated from the foamable resin composition, and the foamability of the foamable resin composition is lowered. Starts foaming, and the uniformity of the bubbles of the resulting thermoplastic resin foam is reduced. Therefore, the glass of the thermoplastic resin (A) impregnated with the foaming agent constituting the foamable resin composition The temperature is lower than the transition temperature, and is preferably 10 ° C. or lower than the glass transition temperature T 1 of the thermoplastic resin (A) impregnated with the foaming agent. On the other hand, if the temperature when curing the foamable resin composition is too low, dissipation of the foaming agent from the foamable resin composition becomes insufficient, and foaming from the rich phase to the poor phase in the foamable resin composition Diffusion of the agent becomes insufficient, and there is no improvement in the foaming resin composition in which the amount of the foaming agent is partially large or small, and as a result, the uniformity of the bubble diameter formed in the resulting foamed resin composition Or higher, (the glass transition temperature T 1 -30 ° C. of the thermoplastic resin (A) impregnated with the foaming agent) or higher, and (the glass of the thermoplastic resin (A) impregnated with the foaming agent) (Transition temperature T 1 -20 ° C.) or higher is more preferable.
発泡剤が含浸された熱可塑性樹脂のガラス転移温度は、発泡剤が含浸されていない時に比して低くなる。例えば、二酸化炭素の含浸前後において、ポリカーボネートのガラス転移温度はそれぞれ１５０℃、３５℃であり、ポリメタクリル酸メチルのガラス転移温度はそれぞれ１１０℃、１２．５℃である。本発明において、発泡剤が含浸された熱可塑性樹脂のガラス転移温度は、高圧示差走査熱量測定（高圧ＤＳＣ）によって測定された温度をいう。 The glass transition temperature of the thermoplastic resin impregnated with the foaming agent is lower than when the thermoplastic resin is not impregnated. For example, before and after impregnation with carbon dioxide, the glass transition temperatures of polycarbonate are 150 ° C. and 35 ° C., respectively, and the glass transition temperatures of polymethyl methacrylate are 110 ° C. and 12.5 ° C., respectively. In the present invention, the glass transition temperature of a thermoplastic resin impregnated with a foaming agent refers to a temperature measured by high pressure differential scanning calorimetry (high pressure DSC).
発泡剤が含浸された熱可塑性樹脂（Ｂ）のガラス転移温度よりも、発泡剤が含浸された熱可塑性樹脂（Ａ）のガラス転移温度の方が高いことが好ましい。発泡剤が含浸された熱可塑性樹脂（Ａ）のガラス転移温度は、発泡剤が含浸された熱可塑性樹脂（Ｂ）のガラス転移温度との差が小さいと、熱可塑性樹脂（Ｂ）の中だけで発泡させることできず、生成される気泡が粗大化し又は気泡径が不均一となることがあるので、発泡剤が含浸された熱可塑性樹脂（Ｂ）のガラス転移温度よりも１５℃以上高いことが好ましく、発泡剤が含浸された熱可塑性樹脂（Ｂ）のガラス転移温度よりも２０〜４０℃高いことがより好ましい。 The glass transition temperature of the thermoplastic resin (A) impregnated with the foaming agent is preferably higher than the glass transition temperature of the thermoplastic resin (B) impregnated with the foaming agent. If the difference between the glass transition temperature of the thermoplastic resin (A) impregnated with the foaming agent and the glass transition temperature of the thermoplastic resin (B) impregnated with the foaming agent is small, it is only in the thermoplastic resin (B). The foam may not be foamed, and the generated bubbles may become coarse or the bubble diameter may be non-uniform, so that the glass transition temperature of the thermoplastic resin (B) impregnated with the foaming agent is 15 ° C. or higher. The glass transition temperature of the thermoplastic resin (B) impregnated with the foaming agent is more preferably 20 to 40 ° C.
発泡性樹脂組成物を養生するときの時間は、短いと、発泡性樹脂組成物からの発泡剤の散逸が不十分となり、発泡性樹脂組成物中におけるrich相からpoor相への発泡剤の拡散が不十分となり、発泡性樹脂組成物において発泡剤量が部分的に多く又は少ない状態の改善がみられず、その結果、得られる発泡樹脂組成物に形成される気泡径の均一性が低下し、長いと、発泡性樹脂組成物中からの発泡剤の散逸が大きくなりすぎて、発泡性樹脂組成物の発泡性が低下し又は発泡しなくなるので、５〜３００秒に限定され、３０〜６０秒が好ましい。 If the time for curing the foamable resin composition is short, the dissipation of the foaming agent from the foamable resin composition is insufficient, and the foaming agent diffuses from the rich phase to the poor phase in the foamable resin composition. The foaming resin composition does not show improvement in the state where the amount of the foaming agent is partially increased or decreased, and as a result, the uniformity of the bubble diameter formed in the resulting foamed resin composition is reduced. If the length is long, dissipation of the foaming agent from the foamable resin composition becomes too large, and the foamability of the foamable resin composition decreases or does not foam. Therefore, it is limited to 5 to 300 seconds, and 30 to 60 Seconds are preferred.
上述の条件にて発泡性樹脂組成物を養生した後、発泡性樹脂組成物を該発泡性樹脂組成物を構成している熱可塑性樹脂（Ａ）のガラス転移温度よりも３０℃高い温度以上に加熱し、発泡性樹脂組成物を発泡させて発泡樹脂組成物を製造する（発泡工程）。 After curing the foamable resin composition under the above-mentioned conditions, the foamable resin composition is heated to a temperature 30 ° C. higher than the glass transition temperature of the thermoplastic resin (A) constituting the foamable resin composition. The foamed resin composition is produced by heating and foaming the foamable resin composition (foaming step).
発泡性樹脂組成物の加熱方法としては、例えば、遠赤外線加熱炉、熱風循環式加熱炉、ウォーターバス、オイルバスを用いた加熱方法などが挙げられ、発泡性樹脂組成物の加熱温度の急激な上昇及び低下を容易に制御することができることから、ウォーターバスを用いた加熱方法が好ましい。 Examples of the method for heating the foamable resin composition include a far infrared heating furnace, a hot air circulation heating furnace, a water bath, a heating method using an oil bath, and the like, and the heating temperature of the foamable resin composition is abrupt. A heating method using a water bath is preferable because the rise and fall can be easily controlled.
発泡工程において、発泡性樹脂組成物の加熱温度は、低いと、気泡が成長しないので、発泡性樹脂組成物を構成している、発泡剤が含浸された熱可塑性樹脂（Ａ）のガラス転移温度よりも３０℃高い温度以上に限定され、発泡性樹脂組成物を構成している、発泡剤が含浸された熱可塑性樹脂（Ａ）のガラス転移温度よりも３５℃高い温度以上が好ましい。一方、発泡性樹脂組成物の加熱温度が高すぎると、発泡性樹脂組成物の発泡が急激に進み、発泡樹脂組成物に形成される気泡径が不均一となることがあるので、発泡性樹脂組成物を構成している、発泡剤が含浸された熱可塑性樹脂（Ａ）のガラス転移温度よりも６０℃高い温度以下が好ましい。なお、発泡性樹脂組成物の加熱温度は、上述の温度範囲であれば、変動してもよいが、気泡の成長が不安定となるので一定温度に保持することが好ましい。 In the foaming step, if the heating temperature of the foamable resin composition is low, bubbles do not grow. Therefore, the glass transition temperature of the thermoplastic resin (A) impregnated with the foaming agent constituting the foamable resin composition. The temperature is higher than the temperature 30 ° C. or higher, and preferably 35 ° C. or higher than the glass transition temperature of the thermoplastic resin (A) impregnated with the foaming agent constituting the foamable resin composition. On the other hand, if the heating temperature of the foamable resin composition is too high, foaming of the foamable resin composition proceeds rapidly, and the bubble diameter formed in the foamed resin composition may become uneven. The temperature is preferably 60 ° C. or lower than the glass transition temperature of the thermoplastic resin (A) impregnated with the foaming agent constituting the composition. The heating temperature of the foamable resin composition may vary as long as it is within the above-mentioned temperature range, but it is preferable to keep the temperature constant because the growth of bubbles becomes unstable.
このように、発泡性樹脂組成物に養生工程を施した上で所定温度にて発泡させているので、発泡性樹脂組成物は全体的に略均一に発泡し、得られる発泡樹脂組成物中の気泡はその気泡径が略均一にして微細なものとなる。 Thus, since the foaming resin composition is subjected to a curing process and then foamed at a predetermined temperature, the foamable resin composition foams substantially uniformly as a whole, and the foamed resin composition in the resulting foamed resin composition The bubbles are fine with a substantially uniform bubble diameter.
発泡工程において、発泡性樹脂組成物を加熱、発泡させる時間は、短いと、島部の気泡の成長が不十分となり、得られる熱可塑性樹脂発泡体の発泡倍率が低くなる虞れがあり、長いと、気泡の成長が過度に進行し又は気泡同士の合体によって、気泡の粗大化又は気泡径の不均一化が生じる虞れがあるので、１〜３００秒に限定され、１〜１２０秒が好ましく、１〜９０秒がより好ましい。 In the foaming process, if the time for heating and foaming the foamable resin composition is short, the growth of bubbles in the island portion is insufficient, and the foaming ratio of the resulting thermoplastic resin foam may be low, and is long. And, since the growth of the bubbles proceeds excessively or the bubbles are coalesced, there is a possibility that the bubbles are coarsened or the bubble diameter is not uniform. Therefore, it is limited to 1 to 300 seconds, preferably 1 to 120 seconds. 1 to 90 seconds are more preferable.
次に、発泡工程において得られた発泡樹脂組成物を大気圧下にて所定温度に冷却して発泡を停止させて熱可塑性樹脂発泡体を製造する（冷却工程）。発泡樹脂組成物の冷却温度は、高いと、発泡樹脂組成物の発泡を停止させることができず、気泡の粗大化又は気泡径の不均一化を生じるので、発泡樹脂組成物を構成している熱可塑性樹脂（Ａ）のガラス転移温度未満に限定され、低すぎると、常温、大気圧に戻った時に熱可塑性樹脂発泡体が変形することがあるので、発泡樹脂組成物を構成している熱可塑性樹脂（Ａ）のガラス転移温度よりも５０℃低い温度以上で且つガラス転移温度未満が好ましい。 Next, the foamed resin composition obtained in the foaming step is cooled to a predetermined temperature under atmospheric pressure to stop foaming and produce a thermoplastic resin foam (cooling step). If the cooling temperature of the foamed resin composition is high, foaming of the foamed resin composition cannot be stopped, resulting in coarsening of the bubbles or non-uniformity of the bubble diameter. It is limited to less than the glass transition temperature of the thermoplastic resin (A), and if it is too low, the thermoplastic resin foam may be deformed when it returns to room temperature and atmospheric pressure, so the heat constituting the foamed resin composition It is preferably at least 50 ° C. lower than the glass transition temperature of the plastic resin (A) and lower than the glass transition temperature.
冷却工程において、発泡樹脂組成物を冷却する時間は、短いと、発泡樹脂組成物の発泡を停止させることができず、気泡の粗大化又は気泡径の不均一化を生じるので、３００秒以上が好ましく、３００〜９００秒がより好ましく、５００〜７００秒が特に好ましい。 In the cooling step, if the time for cooling the foamed resin composition is short, foaming of the foamed resin composition cannot be stopped, resulting in coarsening of the bubbles or nonuniformity of the bubble diameter. Preferably, 300 to 900 seconds are more preferable, and 500 to 700 seconds are particularly preferable.
得られた熱可塑性樹脂発泡体の気泡は非常に微細で且つ均一性に優れているので、発泡倍率が同じ従来の熱可塑性樹脂発泡体に比して引張弾性率などの機械的強度に優れており、照明用の光反射板、看板、ディスプレイ、建築材料などに好適に用いることができる。 Since the bubbles of the obtained thermoplastic resin foam are very fine and excellent in uniformity, the mechanical strength such as tensile elastic modulus is excellent as compared with the conventional thermoplastic resin foam having the same expansion ratio. And can be suitably used for lighting light reflectors, signboards, displays, building materials, and the like.
熱可塑性樹脂発泡体の平均気泡径は、大きいと、熱可塑性樹脂発泡体の引張弾性率などの機械的強度が低下するので、２００ｎｍ以下が好ましく、１８０ｎｍ以下がより好ましい。 If the average cell diameter of the thermoplastic resin foam is large, the mechanical strength such as the tensile elastic modulus of the thermoplastic resin foam is lowered, so that it is preferably 200 nm or less, and more preferably 180 nm or less.
なお、熱可塑性樹脂発泡体の平均気泡径は、ＡＳＴＭ Ｄ３５７６−７７に準拠して測定された値をいう。具体的には、熱可塑性樹脂発泡体を任意の箇所にて切断し、この切断面のＳＥＭ写真を倍率１５００００倍にて撮影し、ＳＥＭ写真上に互いに直交し且つ実寸法の長さ６００ｎｍに相当する長さを有する二本の直線を描き、各直線上に位置する気泡の長さｔを測定し、全ての気泡の長さｔの相加平均値ｔ0を算出する。ＳＥＭ写真の倍率をＭ（倍）として、下記式に基づいて、熱可塑性樹脂発泡体の平均気泡径を算出する。 In addition, the average cell diameter of a thermoplastic resin foam means the value measured based on ASTMD3576-77. Specifically, the thermoplastic resin foam is cut at an arbitrary location, an SEM photograph of this cut surface is taken at a magnification of 150,000 times, and the length of the actual dimension is equivalent to 600 nm orthogonal to each other on the SEM photograph. Two straight lines having the lengths to be drawn are drawn, the length t of the bubbles located on each straight line is measured, and the arithmetic average value t 0 of the lengths t of all the bubbles is calculated. The average cell diameter of the thermoplastic resin foam is calculated based on the following formula, where the magnification of the SEM photograph is M (times).
平均気泡径＝ｔ0／（０．６１６×Ｍ） Average bubble diameter = t 0 /(0.616×M)
熱可塑性樹脂発泡体の厚みは、薄いと、熱可塑性樹脂発泡体のハンドリング性が低下することがあるので、３００μｍ以上が好ましく、５００μｍ〜２．５ｍｍがより好ましい。熱可塑性樹脂発泡体の厚みは、ダイヤルゲージによって測定された値をいう。 When the thickness of the thermoplastic resin foam is thin, the handling property of the thermoplastic resin foam may be lowered. Therefore, the thickness is preferably 300 μm or more, and more preferably 500 μm to 2.5 mm. The thickness of the thermoplastic resin foam refers to a value measured by a dial gauge.
熱可塑性樹脂発泡体の発泡倍率は、用途によって好適範囲は異なるが、低いと、熱可塑性樹脂発泡体の用途が限定されることがあり、高いと、熱可塑性樹脂発泡体の引張弾性率などの機械的強度が低下することがあるので、２〜５倍が好ましい。 The preferred range of the expansion ratio of the thermoplastic resin foam varies depending on the application, but if it is low, the application of the thermoplastic resin foam may be limited. If it is high, the tensile modulus of elasticity of the thermoplastic resin foam, etc. Since mechanical strength may fall, 2 to 5 times is preferable.
なお、熱可塑性樹脂発泡体の発泡倍率は下記の要領で測定された値をいう。先ず、熱可塑性樹脂発泡体の比重ρｆをＪＩＳ Ｋ７１１２に準拠して水中置換法によって測定する。熱可塑性樹脂発泡体を構成している熱可塑性樹脂の比重ρｓを算出する。熱可塑性樹脂発泡体を構成している熱可塑性樹脂の比重ρｓは、熱可塑性樹脂発泡体を構成している熱可塑性樹脂をＲ1〜Ｒｎとし、熱可塑性樹脂Ｒ1〜Ｒｎの比重をそれぞれρ1〜ρｎ、含有量をそれぞれＷ1〜Ｗ2（重量％）としたとき、下記式によって算出された値をいう。熱可塑性樹脂発泡体の発泡倍率は、ρｓをρｆで除した値をいう。 The expansion ratio of the thermoplastic resin foam is a value measured in the following manner. First, the specific gravity ρf of the thermoplastic resin foam is measured by an underwater substitution method in accordance with JIS K7112. The specific gravity ρs of the thermoplastic resin constituting the thermoplastic resin foam is calculated. The specific gravity ρs of the thermoplastic resin constituting the thermoplastic resin foam is R 1 to Rn as the thermoplastic resin constituting the thermoplastic resin foam, and the specific gravity of the thermoplastic resins R 1 to Rn is ρ, respectively. When 1 to ρn and the content are respectively W 1 to W 2 (% by weight), they are values calculated by the following formula. The expansion ratio of the thermoplastic resin foam is a value obtained by dividing ρs by ρf.
熱可塑性樹脂発泡体の引張弾性率は、１００〜１０００ＭＰａが好ましく、５００〜１０００ＭＰａがより好ましい。なお、熱可塑性樹脂発泡体の引張弾性率は、ＪＩＳ Ｋ７１６１によって測定された値をいう。 The tensile elastic modulus of the thermoplastic resin foam is preferably 100 to 1000 MPa, and more preferably 500 to 1000 MPa. In addition, the tensile elasticity modulus of a thermoplastic resin foam says the value measured by JISK7161.
本発明の熱可塑性樹脂発泡体の製造方法は、上述の如き構成を有しており、二種類の熱可塑性樹脂（Ａ）及び（Ｂ）を島部となる熱可塑性樹脂（Ｂ）の大きさが所定大きさとなるように混合して海島構造を有する樹脂組成物に発泡剤を含浸させて発泡性樹脂組成物を製造し、この発泡性樹脂組成物を所定条件下にて養生した後に所定条件下で発泡させていることから、微細で且つ略均一な気泡径を有する気泡を含む熱可塑性樹脂発泡体を容易に製造することができる。 The method for producing a thermoplastic resin foam of the present invention has the above-described configuration, and the two types of thermoplastic resins (A) and (B) are the size of the thermoplastic resin (B) that becomes an island portion. The resin composition having a sea-island structure is mixed so as to have a predetermined size and impregnated with a foaming agent to produce a foamable resin composition. After curing the foamable resin composition under predetermined conditions, the predetermined conditions are satisfied. Since foaming is performed underneath, a thermoplastic resin foam containing bubbles having fine and substantially uniform cell diameters can be easily produced.
得られた熱可塑性樹脂発泡体は微細で且つ略均一な気泡径を有する気泡を含んでいるので、発泡倍率が同じ従来の熱可塑性樹脂発泡体に比して引張弾性率などの機械的強度に優れており、照明用の光反射板、看板、ディスプレイ、建築材料などに好適に用いることができる。特に、熱可塑性樹脂発泡体は、微細で且つ略均一な気泡を多数有しているので光反射性に優れており、光反射板に好適に用いることができる。 Since the obtained thermoplastic resin foam contains fine and substantially uniform bubbles, the mechanical strength such as tensile elastic modulus is higher than that of a conventional thermoplastic resin foam having the same expansion ratio. It is excellent and can be suitably used for light reflectors for lighting, signboards, displays, building materials, and the like. In particular, the thermoplastic resin foam has a large number of fine and substantially uniform bubbles, and thus has excellent light reflectivity, and can be suitably used for a light reflecting plate.
次に本発明の実施例を説明するが、本発明は下記実施例に限定されるものではない。 Next, examples of the present invention will be described, but the present invention is not limited to the following examples.
（実施例１〜５、比較例１〜４）
熱可塑性樹脂（Ａ）としてポリカーボネート（ＰＣ、帝人化成社製 商品名「パンライト（グレード：１２５０Ｙ）」、ガラス転移温度Ｔｇ：１５０℃、比重：１．１９）と、熱可塑性樹脂（Ｂ）としてポリメタクリル酸メチル（ＰＭＭＡ、三菱レイヨン社製 商品名「アクリペット（グレード：ＶＨ００１）」、ガラス転移温度Ｔｇ：１１０℃、比重：１．１９）とをそれぞれ表１に示した所定量ずつ押出機（スクリュー径：φ２０ｍｍ、スクリュー長／スクリュー径＝２５）に供給してシリンダー温度２８０℃にて剪断速度１０００ｓｅｃ-1の条件下にて溶融混練して押出機から押出して樹脂組成物を製造した。樹脂組成物は、ポリカーボネートを海部とし且つポリメタクリル酸メチルを島部とした海島構造を有しており、島部の大きさは表１に示した通りであった（混合工程）。得られた樹脂組成物を汎用の熱プレス機を用いて２８０℃にてプレスすることによって厚みが５００μｍの樹脂シートに成形した。
(Examples 1-5, Comparative Examples 1-4)
As thermoplastic resin (A), polycarbonate (PC, manufactured by Teijin Chemicals Ltd., trade name “Panlite (grade: 1250Y)”, glass transition temperature Tg: 150 ° C., specific gravity: 1.19), and thermoplastic resin (B) Polymethylmethacrylate (PMMA, manufactured by Mitsubishi Rayon Co., Ltd., trade name “ACRYPET (grade: VH001)”, glass transition temperature Tg: 110 ° C., specific gravity: 1.19) each in a predetermined amount shown in Table 1 (Screw diameter: φ20 mm, screw length / screw diameter = 25), melt kneaded at a cylinder temperature of 280 ° C. under a shear rate of 1000 sec −1 , and extruded from an extruder to produce a resin composition. The resin composition had a sea-island structure with polycarbonate as the sea part and polymethyl methacrylate as the island part, and the size of the island part was as shown in Table 1 (mixing step). The obtained resin composition was pressed at 280 ° C. using a general-purpose hot press machine to form a resin sheet having a thickness of 500 μm.
得られた樹脂シートを耐圧容器内に供給し、耐圧容器内の空気を二酸化炭素によって置換した上で、耐圧容器内に２３℃にて二酸化炭素を１０ＭＰａの圧力となるように圧入して２４時間に亘って放置し、樹脂シートに二酸化炭素を飽和溶解度に達するまで含浸させて発泡性樹脂シートを製造した（含浸工程）。 The obtained resin sheet is supplied into a pressure vessel, and the air in the pressure vessel is replaced with carbon dioxide. Then, carbon dioxide is injected into the pressure vessel at 23 ° C. to a pressure of 10 MPa for 24 hours. The resin sheet was impregnated with carbon dioxide until the saturation solubility was reached to produce a foamable resin sheet (impregnation step).
耐圧容器内の加圧状態を解除して発泡性樹脂シートを耐圧容器内から取り出した。発泡性樹脂シートを構成しているポリカーボネートのガラス転移温度は３５℃、ポリメタクリル酸メチルのガラス転移温度は１２．５℃であった。 The pressurized state in the pressure vessel was released and the foamable resin sheet was taken out from the pressure vessel. The glass transition temperature of the polycarbonate constituting the foamable resin sheet was 35 ° C., and the glass transition temperature of polymethyl methacrylate was 12.5 ° C.
次に、発泡性樹脂シートを表１に示した温度に表１に示した時間だけ大気圧下にて保持して養生させた（養生工程）。しかる後、養生後の発泡性樹脂シートを表１に示した温度に表１に示した時間だけ大気圧下にて加熱して発泡させて発泡樹脂シートを得た（発泡工程）。発泡樹脂シートを５℃に設定したウォーターバスに供給して３００秒間に亘って冷却して熱可塑性樹脂発泡シートを得た（冷却工程）。 Next, the foamable resin sheet was cured at the temperature shown in Table 1 by maintaining the foamed resin sheet at atmospheric pressure for the time shown in Table 1 (curing process). Thereafter, the foamed resin sheet after curing was heated and foamed at the temperature shown in Table 1 at the atmospheric pressure for the time shown in Table 1 to obtain a foamed resin sheet (foaming step). The foamed resin sheet was supplied to a water bath set at 5 ° C. and cooled for 300 seconds to obtain a thermoplastic resin foam sheet (cooling step).
得られた熱可塑性樹脂発泡シートについて、平均気泡径、厚み、比重、発泡倍率及び引張弾性率を上述の要領で、又、気泡径の標準偏差を下記の要領で測定し、その結果を表２に示した。実施例２で得られた熱可塑性樹脂発泡シートの断面写真（倍率１００００倍）を図１に、比較例１で得られた熱可塑性樹脂発泡シートの断面写真（倍率１００００倍）を図２に示した。図１、２に示した断面写真の右下の一目盛りは５００ｎｍを示している。 With respect to the obtained thermoplastic resin foam sheet, the average cell diameter, thickness, specific gravity, expansion ratio and tensile modulus were measured as described above, and the standard deviation of the cell diameter was measured as described below, and the results are shown in Table 2. It was shown to. FIG. 1 shows a cross-sectional photograph (magnification 10,000 times) of the thermoplastic resin foam sheet obtained in Example 2, and FIG. 2 shows a cross-sectional photograph (magnification 10,000 times) of the thermoplastic resin foam sheet obtained in Comparative Example 1. It was. The scale on the lower right of the cross-sectional photographs shown in FIGS. 1 and 2 indicates 500 nm.
（気泡径の標準偏差）
熱可塑性樹脂発泡シートを任意の部分において厚み方向に切断し、切断面をＳＥＭ（日立ハイテク社製 走査型電子顕微鏡（Ｓ−３７００Ｎ））を用いて、一辺の測定画像範囲が１５μｍとなる範囲（倍率：１００００倍）に拡大して断面写真を得た。
(Standard deviation of bubble diameter)
The thermoplastic resin foam sheet is cut in the thickness direction at an arbitrary portion, and the cut surface is measured with an SEM (scanning electron microscope (S-3700N) manufactured by Hitachi High-Tech Co., Ltd.). (Magnification: 10,000 times) and a cross-sectional photograph was obtained.
得られた断面写真上に透明シートを載置し、透明シートにおける気泡部分に対応する部分を黒インキで塗りつぶした。透明シートに描いた黒色の塗り潰し部分を画像処理ソフト（ナノシステム社製 商品名「Ｎａｎｏ Ｈｕｎｔｅｒ ＮＳ２Ｋ−Ｌｔ」）を用いて取り込み、黒インキで塗り潰された部分であるか否かの識別をして２値化処理を行い、画像計測処理によって全ての気泡の直径を計測し、各気泡の直径の相加平均値を平均気泡径とした。各気泡の直径の計測データに基づいて気泡径の標準偏差を算出した。 A transparent sheet was placed on the obtained cross-sectional photograph, and a portion corresponding to the bubble portion in the transparent sheet was painted with black ink. The black painted part drawn on the transparent sheet is taken in using image processing software (trade name “Nano Hunter NS2K-Lt” manufactured by Nanosystem Co., Ltd.), and it is identified whether or not the part is painted with black ink. Binarization processing was performed, the diameter of all bubbles was measured by image measurement processing, and the arithmetic average value of the diameters of each bubble was defined as the average bubble diameter. The standard deviation of the bubble diameter was calculated based on the measurement data of the diameter of each bubble.
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| JPH05310986A (en) * | 1992-05-13 | 1993-11-22 | Sekisui Plastics Co Ltd | Production of synthetic resin expansion molded body good in dimensional stability |
| JPH10251436A (en) * | 1997-03-10 | 1998-09-22 | Jsp Corp | Molded item produced from expanded inorganic-containing polypropylene resin particle |
| JPH10310658A (en) * | 1997-05-14 | 1998-11-24 | Jsp Corp | Polycarbonate-based resin foam |
| JP2003089727A (en) * | 2001-09-18 | 2003-03-28 | Mitsubishi Chemicals Corp | Method for producing thermoplastic resin foam and thermoplastic resin foam |
| JP2004051961A (en) * | 2002-05-28 | 2004-02-19 | Kanazawa Inst Of Technology | Fluid holder, method for molding the fluid holder, and apparatus for the same |
| JP2012140630A (en) * | 2012-03-08 | 2012-07-26 | Mitsubishi Plastics Inc | Method for manufacturing foam, and foam |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2018532857A (en) * | 2015-10-21 | 2018-11-08 | オウェンス コーニング インテレクチュアル キャピタル リミテッド ライアビリティ カンパニー | Method for producing a foam comprising nanobubble domains |
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| JP5960590B2 (en) | 2016-08-02 |
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