JP3795635B2 - Polycarbonate resin foam sheet for thermoforming - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、熱成形用ポリカーボネート系樹脂発泡シートに関するものであり、更に詳しくは、熱成形可能な加熱成形温度範囲が広い熱成形用ポリカーボネート系樹脂発泡シートに関する。
【０００２】
【従来の技術】
ポリカーボネート系樹脂発泡シートはマイナス７０℃からプラス１４０℃まで寸法安定性、機械的物性に優れ、食品包装材料、機械部品包装材料、建築材料、自動車部品等、多種多様の用途展開が期待され、特開平８−６６９５３号公報のように、特定の気泡径及び気泡形状を有する加熱成形加工時の寸法安定性良好なポリカーボネート樹脂押出発泡シートが提案されている。しかし、加熱成形加工時の寸法安定性において優れた効果が得られてはいるものの、ポリカーボネート系樹脂発泡シートは、従来より主に使用されているポリスチレン系樹脂発泡シートと比較して、加熱成形時に良好な発泡シート成形体が得られる加熱成形温度範囲（以下、単に熱成形温度範囲という）が狭く、加熱成形時の温度制御が難しく成形が困難な為、ポリカーボネート系樹脂発泡シートの高機能性にもかかわらず、未だ加熱成形性良好なポリスチレン系樹脂発泡シートが主流を占めているのが現状である。尚、熱成形温度範囲とは、発泡シートを熱成形可能な温度に加熱し金型成形する際の、亀裂や部分的な薄肉化が発生していない発泡シート成形体が得られる加熱温度条件範囲である。
【０００３】
【発明が解決しようとする課題】
本発明は、上記課題を解決する為になされたもので、熱成形温度範囲が広く、熱成形時の温度制御が容易で、しかも加熱成形時間を短かくすることが可能な熱成形用ポリカーボネート系樹脂発泡シートを提供することを目的とする。
【０００４】
【課題を解決するための手段】
本発明者らは、芳香族ポリカーボネート系樹脂に特定の樹脂を混合したものを基材とするポリカーボネート系樹脂発泡シートを使用して熱成形することにより、ポリカーボネート系樹脂発泡シートの持つ高機能性を阻害することなく熱成形温度範囲を広くし得ることを見い出し、本発明を完成するに至った。
【０００５】
すなわち、本発明によれば、芳香族ポリカーボネート系樹脂１００重量部と粘度平均分子量が２０万〜１３０万のアクリル系樹脂０．３〜１０重量部との混合樹脂を基材とする、独立気泡率が７０％以上、密度０．０８〜０．５ｇ／ｃｍ３、厚み０．３〜５ｍｍの熱成形用ポリカーボネート系樹脂発泡シートが提供される。また、本発明によれば、特に前記アクリル系樹脂の粘度平均分子量が、４０万超１００万以下であることを特徴とする請求項１記載の熱成形用ポリカーボネート系樹脂発泡シートが提供される。
【０００６】
【発明の実施の形態】
以下、本発明について詳しく説明する。本発明の熱成形用ポリカーボネート系樹脂発泡シートに使用される芳香族ポリカーボネート系樹脂は、炭酸成分と、ビスフェノール系化合物等の芳香族ジオール成分またはこれを主とするジオール成分から形成されるポリ炭酸エステル、或いはそれらの混合物である。この内、分子鎖にジフェニルアルカンを有する芳香族ポリカーボネート系樹脂は、結晶性が高く高融点の上に、耐熱性、耐侯性及び耐酸性に優れているから好適である。このようなポリカーボネート系樹脂としては、２，２−ビス（４−オキシフェニル）プロパン（別名ビスフェノールＡ）、２，２−ビス（４−オキシフェニル）ブタン、１，１−ビス（４−オキシフェニル）シクロヘキサン、１，１−ビス（４−オキシフェニル）イソブタン、１，１−ビス（４−オキシフェニル）エタン等のビスフェノール系化合物から形成されるポリカーボネート系樹脂が例示される。
【０００７】
一方、芳香族ポリカーボネート系樹脂と混合されるアクリル系樹脂としては、メタクリル酸、アクリル酸、メタクリル酸メチル、アクリル酸メチル、メタクリル酸エチル、アクリル酸エチル、メタクリル酸ブチル、アクリル酸ブチル等のアクリル系モノマー、或いはこれらを主成分とするモノマーを重合させて得られる粘度平均分子量２０万〜１３０万の高分子量のポリマーが挙げられる。
上記アクリル系樹脂において粘度平均分子量が２０万未満の場合はポリカーボネート系樹脂発泡体の熱成形温度範囲を広げる効果が不十分であり、良好な熱成形が困難となる。一方、粘度平均分子量が１３０万を越える場合は、ポリカーボネート系樹脂に混合した際に混合樹脂の加熱流動性低下が見られ、熱成形に適する良好な発泡シート自体が得られなくなるおそれがある。特に、熱成形温度範囲を広げる効果をさらに向上させるには、上記アクリル系樹脂の粘度平均分子量は４０万超１００万以下が好ましい。
【０００８】
尚、本発明においてアクリル系樹脂の粘度平均分子量（Ｍｖ）は、アクリル系樹脂のクロロホルム溶液の粘度をηとし、クロロホルム溶媒の粘度をη0とした場合、下記（１）式で与えられる極限粘度〔η〕（１００ｍｌ／ｇ）をもとに下記（２）式により求められる値である。
〔η〕＝ＫＭｖα ・・・（２）
（但し、Ｋ＝０．３４×１０4、α＝０．８３）
【０００９】
本発明において、上記芳香族ポリカーボネート系樹脂とアクリル系樹脂との混合割合は芳香族ポリカーボネート系樹脂１００重量部に対し、アクリル系樹脂０．３〜１０重量部であり、更に０．５〜７重量部であることが好ましい。混合するアクリル系樹脂が少ない場合には、本発明の目的とする効果が不十分なものとなり、混合するアクリル系樹脂が多すぎる場合は、流動性が大きく変化してしまい発泡シートの熱成形性が悪くなり、得られる成形性の外観悪化、厚み厚薄の発生等を引き起こす可能性がある。
また、上記芳香族ポリカーボネート系樹脂とアクリル系樹脂からなる基材樹脂に、本発明の効果を阻害しない範囲でその他の樹脂又はゴム成分を加えることができる。
【００１０】
本発明に使用される発泡剤は、無機発泡剤、揮発性発泡剤、分解型発泡剤のいずれも使用可能であるが、押し出し発泡法の場合は分解型発泡剤を使うと発泡倍率の高い発泡体を得ることが難しいため、無機発泡剤や揮発性発泡剤を使用するのが好ましい。なお、無機発泡剤としては、二酸化炭素、空気、窒素等が好ましく用いられる。揮発性発泡剤としては、プロパン、ｎ−ブタン、ｉ−ブタン、ｎ−ペンタン、ｉ−ペンタン、ヘキサン等の低級脂肪族炭化水素；シクロブタン、シクロペンタン等の低級脂環式炭化水素；ベンゼン、トルエン、キシレン等の芳香族炭化水素；メタノール、エタノール等の脂肪族低級一価アルコール；アセトン、メチルエチルケトン等の低級脂肪族ケトン；１−クロロ−１，１−ジフロオロエタン、ペンタフルオロエタン、１，１，１，２−テトラフルオロエタン、１，１−ジフルオロエタン等の低沸点ハロゲン化炭化水素；等が例示される。
【００１１】
以上に詳記した発泡剤は、単独又は２種以上混合して使用可能であり、例えば無機発泡剤と揮発性発泡剤のように異なった型の発泡剤の併用も可能である。発泡剤使用量は発泡剤の種類や所望する発泡倍率によっても異なり、発泡倍率によって該発泡シートの密度が定まるから、主に所望する発泡シートの密度で発泡剤の使用量が定まると云える。そして、発泡シートは密度０．０８〜０．５ｇ／ｃｍ３ であるから、この範囲となるように発泡剤を使えばよい。なお、本発明の発泡シート密度が０．０８ｇ／ｃｍ３未満では発泡シートの独立気泡率のコントロールが難しく、熱成形体の独立気泡率は増々低くなってしまう。また、発泡シートの密度の上限は、断熱性の低下や重量増加等の実用性の面から０．５ｇ／ｃｍ ３ である。
【００１２】
本発明において使用する基材樹脂を円滑に発泡させるために、樹脂と発泡剤との溶融混練物中に必要に応じて気泡調整剤を添加することができる。この場合の気泡調整剤としては、タルクやシリカ等の無機粉末、多価カルボン酸の酸性塩、多価カルボン酸と炭酸ナトリウム又は重炭酸ナトリウムとの混合物等が好ましい。その添加量は、樹脂１００重量部当り０．０１〜１．０重量部、好ましくは０．０５〜０．５重量部とするのが良い。また、本発明では、難燃剤、熱安定剤、耐侯性向上剤、着色剤のように、通常の発泡シートに添加される公知の添加剤を添加することができる。
【００１３】
本発明の熱成形用ポリカーボネート系樹脂発泡シートは、前記芳香族ポリカーボネート系樹脂とアクリル系樹脂との混合樹脂を押出機を使用して高温高圧下で前記発泡剤と溶融混練し発泡性溶融体とし、該溶融体を押出機先端のサーキュラーダイス部又はＴ型ダイスより低圧域に押出して発泡させることにより製造することができる。
【００１４】
また、前記発泡シートの厚みは、０．３〜５ｍｍのものが熱成形の面から好ましく、特に１〜３ｍｍのものが好ましい。発泡シートの厚みが大きすぎる場合は、熱成形時の加熱の際に発泡体内部まで均一に加熱できず、熱成形が困難となり、厚みが小さすぎる場合は深絞り成形性が不十分となる問題がある。
【００１５】
また、発泡シートの独立気泡率は７０％以上のものが好ましく、７０％未満のものは良好な表層が形成されていない為、熱成形による独立気泡率の低下が大きく、成形体の外観、物性、耐油浸透性等の面で不十分なものとなるおそれがある。尚、上記独立気泡率は、ＡＳＴＭ Ｄ２８５６に準拠し、エアーピクノメーター法により下記（３）式により求められる値である。
独立気泡率（％）＝〔Ｖｘ−Ｖａ（ρｆ／ρｓ）〕／〔Ｖａ−Ｖａ（ρｆ／ρｓ）〕×１００ ・・・（３）
〔但し、Ｖｘ：発泡シートサンプルの実容積（ｃｍ3）、Ｖａ：発泡シートサンプルのみかけの容積（ｃｍ3）、ρｆ：発泡シートサンプルのみかけ密度（ｇ／ｃｍ3）、ρｓ：樹脂の密度（ｇ／ｃｍ3）である。〕
【００１６】
本発明の発泡シートの熱成形方法は、上記発泡シートを熱成形可能な温度に加熱することによって軟化せしめ、金型により成形するものである。発泡シートの加熱方法としては、通常、加熱炉を使用し、非接触状態で赤外線ヒーター等による輻射加熱及び／又は伝熱加熱により、加熱不足や加熱オーバーすることなく発泡シートを加熱軟化させる。
【００１７】
本発明の発泡シートの熱成形方法において、熱成形可能な温度に加熱され軟化状態にある発泡シートの表面温度は、１７０〜２３０℃であることが好ましく、該表面温度が１７０℃未満の場合は発泡シートの伸びが所々において不均一となるおそれがあり、一方該表面温度が２３０℃を超える場合は発泡シートの発泡層のセル構造が破壊されて、良好な成形体が得られなくなるおそれがある。特に、３０秒以上の加熱時間で発泡シートを加熱軟化させて、該発泡シートの表面温度を１７５〜２００℃にすることは、発泡シートの内部までより均一に軟化させることができ、成形性がより良好となるため好ましい。尚、本発明でいう軟化した発泡シートの表面温度は、軟化した発泡シートが加熱炉から出てきた直後の発泡シート表面及び裏面の各々の表面温度を赤外線放射温度計にて測定し、それらの平均値により求められる。
【００１８】
本発明の熱成形用発泡シートの熱成形方法において、発泡シートは雄型及び／又は雌型からなる金型を使用して、真空成形、圧空成形や、これらの応用としてフリードローイング成形、プラグ・アンド・リッジ成形、リッジ成形、マッチド・モールド成形、ストレート成形、ドレープ成形、リバースドロー成形、エアスリップ成形、プラグアシスト成形、プラダアシストリバースドロー成形等や、これらを組み合わせた成形方法等を用いて、所望の成形体形状に成形することができる。
【００１９】
本発明の発泡シートの熱成形方法にて得られるポリカーボネート系樹脂発泡シート成形体は、寸法安定性、機械的物性等のポリカーボネート系樹脂発泡シートに期待されている機能を低下させることなく、外観、シート厚み厚薄の面において優れたものである。
【００２０】
【実施例】
以下、本発明を実施例に基づいて具体的に説明する。
【００２１】
実施例１〜３
ポリカーボネート系樹脂として三菱ガス化学社製ユーピロンＭＳ−２０００粘度平均分子量２９０００を使用し、アクリル系樹脂として三菱レイヨン社製メタブレンＰ５０１Ａ（メタクリル酸メチル・アクリル酸アルキル共重合体）を使用し、表１に示す割合で両者をドライブレンドしたものを押出機に投入して加熱、溶融、混練し、ｎ−ペンタンを混合樹脂１ｋｇに対して０．２モルの割合となるように押出機中に圧入した後更に混練し、樹脂温度２１０〜２２０℃で押出機先端のサーキュラーダイスより発泡剤を含有する溶融樹脂を円筒状に押出発泡させ、冷却後、押出方向に切り開いて発泡シートを得た。得られた発泡シートの厚み、密度、独立気泡率を表１に併せて示す。
次に得られた発泡シートを加熱炉雰囲気温度２４５℃の遠赤外線ヒーター加熱炉にて加熱時間２５、３０、３５、４０、４５、５０秒の６種類の加熱条件にて発泡シートを軟化させ、軟化した発泡シートを真空成形金型を使用しプラグアシスト成形により開口面積１３３ｃｍ2、深さ５ｃｍのドンブリ形状の容器を成形し、各成形条件にて得られた発泡シート成形体について下記の基準により成形性の評価を行ない、結果を表２に示した。
【００２２】
成形性の評価
○：金型再現性も良く、成形品に亀裂や部分的な薄肉部もない良好な状態
△：金型再現性は若干悪くなるが、成形は可能な状態
×：破れが生じて成形不可能な状態、もしくは加熱オーバーにより成形品のセル破壊が起きた状態。
尚、表２のおける発泡シートの表面温度は、加熱炉から出てきた直後の発泡シート表面及び裏面の温度を、赤外線放射温度計にて測定し、表面と裏面の温度の平均値として求めた値である。
【００２３】
比較例１
表１に示すように、アクリル系樹脂を住友化学社製スミペックス（メタクリル酸メチル重合体）に代えた以外は実施例１と同様にして発泡シートを製造し、該発泡シートの物性等を表１に、また成形性の評価についても実施例１と同様に行ない、結果を表２に、それぞれ示した。
【００２４】
比較例２
表１に示すように、アクリル系樹脂を三菱レイヨン社製メタブレンＰ５５１Ａ（メタクリル酸メチル・アクリル酸アルキル共重合体）に代えた以外は実施例１と同様に行ない、発泡シートの物性等を表１に、また発泡シートの成形性の評価結果を表２にそれぞれ示した。
【００２５】
比較例３
表１に示すように、アクリル系樹脂を三菱レイヨン社製メタブレンＰ５３０Ａ（メタクリル酸メチル・アクリル酸アルキル共重合体）に代えた以外は実施例１と同様に行ない、発泡シートの物性等を表１に、また発泡シートの成形性の評価結果を表２にそれぞれ示した。
【００２６】
比較例４
アクリル系樹脂を使用しなかった以外は実施例１と同様に行ない、発泡シートの物性等を表１に、また発泡シートの成形性の評価結果を表２に示した。
【００２７】
【表１】
【表２】
表１及び表２に示す実施例及び比較例の結果より、芳香族ポリカーボネート系樹脂に特定のアクリル系樹脂を混合したものを基材とする発泡シートを熱成形する場合、良好な成形体が得られる成形時間の範囲が１５秒以上あり、アクリル系樹脂を混合しないものを基材とする発泡シートを熱成形する場合と比較して熱成形温度範囲が広いことが判る。又、本発明で特定する粘度平均分子量から外れるアクリル系樹脂を混合すると逆に良好な成形体が得られる成形時間の範囲が狭くなり、熱成形温度範囲が逆に狭くなってしまうことが判る。
【００３０】
【発明の効果】
本発明は、芳香族ポリカーボネート系樹脂に特定のアクリル系樹脂を特定量混合した混合樹脂を基材とする発泡シートを軟化させ金型により成形するポリカーボネート系樹脂発泡シートに係るものであり、本発明の発泡シートは熱成形において、熱成形温度範囲が広く、そのことによって外観が良好で、シート厚み厚薄のなく、寸法安定性、機械的物性等の高機能性も低下させることはなく、良好なポリカーボネート系樹脂発泡シート熱成形体を、短い成形サイクルにて得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polycarbonate-based resin foam sheet for thermoforming , and more particularly to a polycarbonate-based resin foam sheet for thermoforming having a wide thermoforming temperature range in which thermoforming is possible.
[0002]
[Prior art]
Polycarbonate-based resin foam sheet is dimensionally stable from minus 70 ° C. until plus 140 ° C., excellent mechanical properties, food packaging materials, machine parts packaging materials, building materials, automobile parts, etc., a wide variety of applications development is expected, As disclosed in JP-A-8-66953, a polycarbonate resin extruded foam sheet having a specific cell diameter and cell shape and good dimensional stability during thermoforming has been proposed. However, although an excellent effect is obtained in dimensional stability at the time of thermoforming, the polycarbonate resin foam sheet is more suitable for heat molding than the polystyrene resin foam sheet mainly used conventionally. The heat molding temperature range (hereinafter simply referred to as the thermoforming temperature range) that provides a good foamed sheet molding is narrow, making it difficult to control the temperature during heat molding, making it difficult to mold. Nevertheless, the current situation is that polystyrene resin foam sheets with good heat moldability still dominate. The thermoforming temperature range refers to a heating temperature condition range in which a foamed sheet molded body in which cracks and partial thinning are not generated when the foamed sheet is heated to a temperature at which thermoforming can be performed and die molding is performed. It is.
[0003]
[Problems to be solved by the invention]
The present invention has been made to solve the above-mentioned problems, and is a polycarbonate for thermoforming that has a wide thermoforming temperature range, can be easily controlled at the time of thermoforming, and can shorten the heat forming time. It aims at providing a resin foam sheet.
[0004]
[Means for Solving the Problems]
The present inventors have found that by thermoforming using a polycarbonate-based resin foam sheet as a base for the even mixing a specific resin to the aromatic polycarbonate resin, highly functional with a polycarbonate-based resin foam sheet It has been found that the thermoforming temperature range can be widened without hindering the above, and the present invention has been completed.
[0005]
That is, according to the present invention, the closed cell ratio is based on a mixed resin of 100 parts by weight of an aromatic polycarbonate resin and 0.3 to 10 parts by weight of an acrylic resin having a viscosity average molecular weight of 200,000 to 1.3 million. Is a polycarbonate resin foam sheet for thermoforming having a density of 0.08 to 0.5 g / cm 3 and a thickness of 0.3 to 5 mm. According to the present invention, there is provided a polycarbonate resin foam sheet for thermoforming according to claim 1, wherein the acrylic resin has a viscosity average molecular weight of more than 400,000 and less than 1,000,000.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below. The aromatic polycarbonate resin used in the polycarbonate resin foam sheet for thermoforming according to the present invention is a polycarbonate formed from a carbonic acid component and an aromatic diol component such as a bisphenol compound or a diol component mainly composed thereof. Or a mixture thereof. Of these, aromatic polycarbonate resins having diphenylalkane in the molecular chain are preferred because of their high crystallinity and high melting point, as well as excellent heat resistance, weather resistance and acid resistance. Such polycarbonate resins include 2,2-bis (4-oxyphenyl) propane (also known as bisphenol A), 2,2-bis (4-oxyphenyl) butane, and 1,1-bis (4-oxyphenyl). ) Polycarbonate resins formed from bisphenol compounds such as cyclohexane, 1,1-bis (4-oxyphenyl) isobutane and 1,1-bis (4-oxyphenyl) ethane.
[0007]
On the other hand, acrylic resins mixed with aromatic polycarbonate resins include acrylic resins such as methacrylic acid, acrylic acid, methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, butyl methacrylate, and butyl acrylate. Examples thereof include a high molecular weight polymer having a viscosity average molecular weight of 200,000 to 1,300,000 obtained by polymerizing a monomer or a monomer containing these as a main component.
When the viscosity average molecular weight of the acrylic resin is less than 200,000, the effect of expanding the thermoforming temperature range of the polycarbonate resin foam is insufficient, and good thermoforming becomes difficult. On the other hand, when the viscosity average molecular weight exceeds 1,300,000, when mixed with a polycarbonate-based resin, the heat fluidity of the mixed resin is reduced, and a good foamed sheet suitable for thermoforming may not be obtained. In particular, in order to further improve the effect of expanding the thermoforming temperature range, the acrylic resin preferably has a viscosity average molecular weight of more than 400,000 and less than 1,000,000.
[0008]
In the present invention, the viscosity average molecular weight (Mv) of the acrylic resin is the intrinsic viscosity given by the following formula (1) when the viscosity of the chloroform solution of the acrylic resin is η and the viscosity of the chloroform solvent is η 0. [Η] is a value obtained from the following equation (2) based on (100 ml / g).
[Η] = KMv α (2)
(However, K = 0.34 × 10 4 , α = 0.83)
[0009]
In the present invention, the mixing ratio of the aromatic polycarbonate resin and the acrylic resin is 0.3 to 10 parts by weight of the acrylic resin with respect to 100 parts by weight of the aromatic polycarbonate resin, and further 0.5 to 7 weights. Part. When the amount of acrylic resin to be mixed is small, the intended effect of the present invention is insufficient. When the amount of acrylic resin to be mixed is too large, the fluidity is greatly changed and the thermoformability of the foam sheet. May worsen the appearance of the resulting moldability and cause the thickness to be thin.
In addition, other resins or rubber components can be added to the base resin composed of the aromatic polycarbonate resin and the acrylic resin as long as the effects of the present invention are not impaired.
[0010]
As the foaming agent used in the present invention, any of an inorganic foaming agent, a volatile foaming agent, and a decomposable foaming agent can be used. Since it is difficult to obtain a body, it is preferable to use an inorganic foaming agent or a volatile foaming agent. As the inorganic foaming agent, carbon dioxide, air, nitrogen or the like is preferably used. Examples of volatile blowing agents include lower aliphatic hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane and hexane; lower alicyclic hydrocarbons such as cyclobutane and cyclopentane; benzene, toluene Aromatic hydrocarbons such as xylene; aliphatic lower monohydric alcohols such as methanol and ethanol; lower aliphatic ketones such as acetone and methyl ethyl ketone; 1-chloro-1,1-difluoroethane, pentafluoroethane, 1,1,1 , 2-tetrafluoroethane, low-boiling halogenated hydrocarbons such as 1,1-difluoroethane;
[0011]
The foaming agents described in detail above can be used alone or in combination of two or more. For example, different types of foaming agents such as inorganic foaming agents and volatile foaming agents can be used in combination. The amount of foaming agent used depends on the type of foaming agent and the desired foaming ratio, and the density of the foamed sheet is determined by the foaming ratio. Therefore, it can be said that the amount of foaming agent used is mainly determined by the density of the desired foamed sheet. Since the foam sheet has a density of 0.08 to 0.5 g / cm 3 , a foaming agent may be used so as to be in this range. In addition, if the density of the foamed sheet of the present invention is less than 0.08 g / cm 3, it is difficult to control the closed cell ratio of the foamed sheet, and the closed cell ratio of the thermoformed body becomes lower. The upper limit of the density of the foam sheet is 0.5 g / cm 3 from the viewpoint of practicality, such as reduction or increase in the weight of the thermal insulation.
[0012]
In order to smoothly foam the base resin used in the present invention, a cell regulator may be added to the melt-kneaded product of the resin and the foaming agent as necessary. In this case, as the air conditioner, inorganic powders such as talc and silica, acidic salts of polyvalent carboxylic acids, mixtures of polyvalent carboxylic acids and sodium carbonate or sodium bicarbonate are preferable. The added amount is 0.01 to 1.0 part by weight, preferably 0.05 to 0.5 part by weight per 100 parts by weight of the resin. Moreover, in this invention, the well-known additive added to a normal foamed sheet can be added like a flame retardant, a heat stabilizer, a weather resistance improver, and a coloring agent.
[0013]
The polycarbonate resin foam sheet for thermoforming of the present invention is obtained by melting and kneading a mixed resin of the aromatic polycarbonate resin and the acrylic resin with the foaming agent at a high temperature and high pressure using an extruder. The melt can be produced by extruding into a low pressure region from the circular die part or T-type die at the tip of the extruder and foaming.
[0014]
The thickness of the foam sheet is preferably from 0.3 to 5 mm from the viewpoint of thermoforming, and particularly preferably from 1 to 3 mm. When the thickness of the foam sheet is too large, the inside of the foam cannot be heated uniformly during heating during thermoforming, making thermoforming difficult, and if the thickness is too small, the deep drawability becomes insufficient There is.
[0015]
In addition, the closed cell ratio of the foamed sheet is preferably 70% or more. If the foamed sheet is less than 70%, a good surface layer is not formed. There is a risk that the oil penetration resistance may be insufficient. In addition, the said closed cell rate is a value calculated | required by the following (3) Formula by the air pycnometer method based on ASTMD2856.
Closed cell ratio (%) = [Vx−Va (ρf / ρs)] / [Va−Va (ρf / ρs)] × 100 (3)
[However, Vx: actual volume (cm 3 ) of foam sheet sample, Va: apparent volume (cm 3 ) of foam sheet sample, ρf: apparent density (g / cm 3 ) of foam sheet sample, ρs: density of resin (G / cm 3 ). ]
[0016]
The foamed sheet thermoforming method of the present invention is to soften the foamed sheet by heating it to a temperature at which thermoforming is possible and to mold it with a mold. As a method for heating the foamed sheet, a heating furnace is usually used, and the foamed sheet is heated and softened without being insufficiently heated or overheated by radiation heating and / or heat transfer heating with an infrared heater or the like in a non-contact state.
[0017]
In the foamed sheet thermoforming method of the present invention , the surface temperature of the foamed sheet heated to a thermoformable temperature and in a softened state is preferably 170 to 230 ° C., and when the surface temperature is less than 170 ° C. There is a possibility that the expansion of the foamed sheet may be uneven in some places. On the other hand, if the surface temperature exceeds 230 ° C., the cell structure of the foamed layer of the foamed sheet may be destroyed, and a good molded product may not be obtained. . In particular, when the foam sheet is heated and softened for a heating time of 30 seconds or more and the surface temperature of the foam sheet is set to 175 to 200 ° C., the inside of the foam sheet can be softened more uniformly, and the moldability is improved. It is preferable because it becomes better. The surface temperature of the softened foam sheet as used in the present invention is determined by measuring the surface temperature of the foam sheet surface and the back surface immediately after the softened foam sheet comes out of the heating furnace with an infrared radiation thermometer. It is obtained from the average value.
[0018]
In the thermoforming method of the foam sheet for thermoforming according to the present invention, the foam sheet uses a mold comprising a male mold and / or a female mold, vacuum forming, pressure forming, free drawing molding, plug And ridge molding, ridge molding, matched mold molding, straight molding, drape molding, reverse draw molding, air slip molding, plug assist molding, prada assist reverse draw molding, etc. It can be formed into a desired shape.
[0019]
The polycarbonate resin foam sheet molded body obtained by the thermoforming method of the foam sheet of the present invention has an appearance, without reducing the functions expected of the polycarbonate resin foam sheet such as dimensional stability and mechanical properties, It is excellent in terms of sheet thickness.
[0020]
【Example】
Hereinafter, the present invention will be specifically described based on examples.
[0021]
Examples 1-3
Mitsubishi Gas Chemical Co., Ltd. Iupilon MS-2000 viscosity average molecular weight 29000 is used as polycarbonate resin, and Mitsubishi Rayon Co., Ltd. methabrene P501A (methyl methacrylate / alkyl acrylate copolymer) is used as an acrylic resin. A mixture obtained by dry blending both at the indicated ratio is put into an extruder, heated, melted and kneaded, and n-pentane is injected into the extruder at a ratio of 0.2 mol with respect to 1 kg of the mixed resin. Further, kneading was performed, and a molten resin containing a foaming agent was extruded and foamed into a cylindrical shape from a circular die at the tip of the extruder at a resin temperature of 210 to 220 ° C. After cooling, the foamed sheet was obtained by cutting in the extrusion direction. Table 1 also shows the thickness, density, and closed cell ratio of the obtained foam sheet.
Next, the foamed sheet was softened in six types of heating conditions of heating time 25, 30, 35, 40, 45, 50 seconds in a far-infrared heater heating furnace having a heating furnace atmosphere temperature of 245 ° C., Using a vacuum forming mold, the softened foam sheet is molded by plug-assist molding into a container having an opening area of 133 cm 2 and a depth of 5 cm. The foam sheet molded body obtained under each molding condition is in accordance with the following criteria. The moldability was evaluated and the results are shown in Table 2.
[0022]
Evaluation of moldability ○: Good mold reproducibility, good condition with no cracks or partial thin wall in the molded product △: Mold reproducibility is slightly worse, but molding is possible x: Breakage occurs In a state where molding is impossible, or when cell destruction of the molded product occurs due to overheating.
In addition, the surface temperature of the foam sheet in Table 2 was obtained by measuring the temperature of the foam sheet surface and the back surface immediately after coming out of the heating furnace with an infrared radiation thermometer, and obtaining the average value of the front and back surface temperatures. Value.
[0023]
Comparative Example 1
As shown in Table 1, a foamed sheet was produced in the same manner as in Example 1 except that the acrylic resin was replaced with Sumipex (methyl methacrylate polymer) manufactured by Sumitomo Chemical Co., Ltd. The moldability was evaluated in the same manner as in Example 1, and the results are shown in Table 2.
[0024]
Comparative Example 2
As shown in Table 1, the same procedure as in Example 1 was conducted except that the acrylic resin was replaced with METABRENE P551A (methyl methacrylate / alkyl acrylate copolymer) manufactured by Mitsubishi Rayon Co., Ltd. Table 2 shows the evaluation results of the moldability of the foam sheet.
[0025]
Comparative Example 3
As shown in Table 1, the same procedure as in Example 1 was conducted except that the acrylic resin was changed to METABRENE P530A (methyl methacrylate / alkyl acrylate copolymer) manufactured by Mitsubishi Rayon Co., Ltd. Table 2 shows the evaluation results of the moldability of the foam sheet.
[0026]
Comparative Example 4
The procedure was the same as in Example 1 except that no acrylic resin was used. Table 1 shows the physical properties and the like of the foamed sheet, and Table 2 shows the evaluation results of the moldability of the foamed sheet.
[0027]
[Table 1]
[Table 2]
From the results of Examples and Comparative Examples shown in Table 1 and Table 2, when a foamed sheet based on a mixture of an aromatic polycarbonate resin and a specific acrylic resin is thermoformed, a good molded body is obtained. It can be seen that the molding time range is 15 seconds or more, and the thermoforming temperature range is wider than that in the case of thermoforming a foam sheet based on a material not mixed with an acrylic resin. It can also be seen that when an acrylic resin deviating from the viscosity average molecular weight specified in the present invention is mixed, the molding time range in which a good molded product is obtained is narrowed, and the thermoforming temperature range is conversely narrowed.
[0030]
【The invention's effect】
The present invention according to the polycarbonate-based resin foam sheet is molded by an aromatic polycarbonate resin specific volume mixed mixed resin to soften the foam sheet as a base mold specific acrylic resin, the The foamed sheet of the invention has a wide thermoforming temperature range in thermoforming , and thereby the appearance is good, the sheet thickness is not thin, and the high functionality such as dimensional stability and mechanical properties is not deteriorated and is good. A heat-molded polycarbonate resin foam sheet can be obtained in a short molding cycle.
Claims (2)
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15916897A JP3795635B2 (en) | 1997-06-02 | 1997-06-02 | Polycarbonate resin foam sheet for thermoforming |
| KR1019980016761A KR100263211B1 (en) | 1997-05-14 | 1998-05-11 | Process for manufacturing foamed body of polycarbonate resin |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15916897A JP3795635B2 (en) | 1997-06-02 | 1997-06-02 | Polycarbonate resin foam sheet for thermoforming |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10329206A JPH10329206A (en) | 1998-12-15 |
| JP3795635B2 true JP3795635B2 (en) | 2006-07-12 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15916897A Expired - Fee Related JP3795635B2 (en) | 1997-05-14 | 1997-06-02 | Polycarbonate resin foam sheet for thermoforming |
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| Country | Link |
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| JP (1) | JP3795635B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001189990A (en) * | 1999-12-28 | 2001-07-10 | Jsp Corp | Speaker diaphragm and material for speaker diaphragm |
| JP2001353773A (en) * | 2000-06-15 | 2001-12-25 | Jsp Corp | Method for producing foamed polycarbonate resin container and foamed polycarbonate resin container |
| JP4596465B2 (en) * | 2005-03-22 | 2010-12-08 | 株式会社ジェイエスピー | Heat treatment method for vehicle carrier covering core material and aromatic polycarbonate resin extruded foam |
| JP4956660B2 (en) * | 2010-10-15 | 2012-06-20 | 株式会社ジェイエスピー | Method for producing polycarbonate resin foam container |
| JP5978181B2 (en) * | 2012-09-28 | 2016-08-24 | 積水化成品工業株式会社 | Polycarbonate resin foam sheet for thermoforming, and method for producing resin molded product |
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1997
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| JPH10329206A (en) | 1998-12-15 |
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