JP3681238B2 - Polycarbonate laminated sheet - Google Patents

Description

【００１３】
（式中、Ａｒは二価の芳香族残基であり、例えばフェニレン、ナフチレン、ビフィニレン、ピリジレンや、下記一般式で表されるものが挙げられる。）
【００１４】
【化２】

【００１５】
（式中Ａｒ¹ 及びＡｒ² はそれぞれアリレーン基である。例えばフェニレン、ナフチレン、ビフェニレン、ピリジレン等の基を表し、Ｙは下記一般式で表されるアルキレン基または置換アルキレン基または、−Ｏ−、−ＣＯ−、−Ｓ−、−ＳＯ₂ −、−ＣＯ₂ −、−ＣＯＮ（Ｒ¹ ）−、（Ｒ¹ は前記と同様）等の二価の基である。）
【００１６】
【化３】

【００１７】
（式中Ｒ¹ 、Ｒ² 、Ｒ³ 及びＲ⁴ はそれぞれ水素原子、低級アルキル基、シクロアルキル基、アリール基、アラルキル基であって、場合によりハロゲン原子、アルコシ基で置換されていてもよく、ｋは３〜１１の整数であり、化４の水素原子は、低級アルキル基、アリール基、ハロゲン等で置換されてもよい。）
これら二価の芳香族残基としては、下記一般式のもの等が挙げられる。
【００１８】
【化４】

【００１９】
【化５】

【００２０】
（式中Ｒ⁵ 及びＲ⁶ はそれぞれ水素、ハロゲン、Ｃ₁ 〜Ｃ₁₀アルキル基、Ｃ₁ 〜Ｃ₁₀アルコキシ基、Ｃ₁ 〜Ｃ₁₀シクロアルキル基またはフェニル基である。ｍ及びｎは１〜４の整数で、ｍが２〜４の場合には各Ｒ⁵ はそれぞれ同一でも異ってもよいし、ｎが２〜４の場合は各Ｒ⁶ はそれぞれ同一でも異ってもよい。）
中でも、下記一般式で表されるものが好ましい。特に、このものをＡｒとする繰り返しユニットを８５モル％以上含むものが好ましい。
【００２１】
【化６】

【００２２】
また、本発明におけるポリカーボネートは、三価以上の芳香族残基を共重合成分として含有していてもよいし、脂肪族または芳香族のエステル成分を共重合成分として含有してもよい。
本発明におけるポリカーボネートのー末端の分子構造としては、ヒドロキシ基、アリールカーボネート基、アルキルカーボネート基から選ばれた１種以上の末端基を結合することができる。アリールカーボネート末端基、アルキルカーボネート末端基としては、下記一般式のものが挙げられる。
【００２３】
【化７】

【００２４】
（式中Ａｒ³ は一価の芳香族残基であり、芳香環は置換されていてもよい。または、炭素数１〜２０の直鎖もしくは分岐アルキル基である。）
具体例としては、下記一般式のものが挙げられる。
【００２５】
【化８】

【００２６】
【化９】

【００２７】
これらの中で、フェニルカーボネート基、ｐ−ｔ−ブチルフェニルカーボネート基、ｐ−クミルフェニルカーボネート基等が好ましい。またヒドロキシ基末端と他の末端との比率は１／１００以上が好ましく、更には１／４０以上が好ましい。
本発明におけるポリカーボネートに含有される加水分解可能な塩素は１ｐｐｍ以下、更には０．５ｐｐｍ以下が好ましい。１ｐｐｍを超える量と、成形加工時等長時間高温下にさらされ、着色し、ポリカーボネートの特徴である透明感が失われてしまう。
【００２８】
本発明におけるポリカーボネートの製造としては、芳香族ジヒドロキシ化合物とカーボネート前駆体とを反応せしめる方法、例えば芳香族ジヒドロキシ化合物とホスゲンを水酸化ナトリウム水溶液及び塩化メチレン溶媒の存在下に反応させる界面重合法（ホスゲン法）、芳香族ジヒドロキシ化合物とジフェニルカーボネートを反応させるエステル交換法（溶融法）、結晶化カーボネートプレポリマーを固相重合する方法（特開平１−１５８０３３、特開平１−２７１４２６、特開平３−６８６２７）等が挙げられる。
【００２９】
基板に用いるポリカーボネートの粘度は、２８０℃で１００ｃｍ^-1のせん断速度における溶融粘度で５００〜３０００Ｐａ・ｓであり、好ましくは７００〜２８００Ｐａ・ｓ、更に好ましいは１０００〜２５００Ｐａ・ｓである。
該溶融粘度が５００Ｐａ・ｓ以下ではシート形状での引き取りが困難になり、逆に３０００Ｐａ・ｓを超える粘度では成形機に過度な負荷がかかるため押出成形困難に陥る。
【００３０】
被覆層に用いるポリカーボネートの粘度は、基板ポリカーボネートの粘度と同じであることが層間流動不安定現象を防止し、外観のよい積層シートを得るのに重要であると先行技術では示されている。しかし実際の共押出積層成形においては、同一のポリカーボネートどうしを共押出積層成形しても層間流動不安定現象は発生する。これは成形金型壁面近傍では樹脂が流れにくく、あたかも粘度が上がったような流動性を示し、この見かけの粘度差が同じ粘度の樹脂を共押出積層成形しても層間流動不安定現象が現れる原因であることを本発明者らは見いだした。更に検討の結果、前述の見かけの粘度差が２８０℃で１００ｃｍ^-1のせん断速度における溶融粘度で１０〜５０Ｐａ・ｓであることを見いだし、あらかじめ被覆層ポリカーボネートの粘度をこの粘度差分だけ下げておくことで層間流動不安定現象を防止することができることを見いだした。つまり、被覆層に用いるポリカーボネートの粘度は、基材層ポリカーボネートの粘度に対して、２８０℃で１００ｃｍ^-1のせん断速度における溶融粘度で１０〜５０Ｐａ・ｓ、好ましくは２０〜４０Ｐａ・ｓの範囲で低いことが層間流動不安定を防止し積層界面を平滑にし、外観のよい積層シートを得るのに重要である。
【００３１】
その差が１０Ｐａ・ｓ未満の場合、前述の理由から、層間流動不安定現象が生じ、積層界面が乱れるため外観不良になり商品価値がなくなる。
また逆に粘度差が５０Ｐａ・ｓを超えると被覆層が２００μｍを越えるような積層厚みになる場合は、特開平８−２２４８４８号公報などに示されているように外観の優れたポリカーボネートシートが得ることができるが、積層厚みが２００μｍ以下の場合、やはり基材層、被覆層樹脂間の粘度差から先行技術にあるような積層界面の層間流動不安定現象が生じ、積層界面が平滑で外観の優れたシートを得ることは困難である。
【００３２】
本発明におけるポリカーボネートには必要に応じて各種添加剤を配合してよく、例えば耐熱安定剤、酸化防止剤、耐候剤、紫外線吸収剤、離型剤、滑剤、帯電防止剤、可塑剤、他樹脂やゴム等の重合体、顔料、染料、充填剤、強化剤、難燃剤等を挙げることができる。
これら添加剤等は、重合終了後のポリカーボネートが溶融状態の間に添加してもよく、ポリカーボネートを一旦ペレタイズした後、添加剤を添加再溶融混練してもよいし、シート成形時にポリカーボネートと同時にもしくは成形の途中で添加してもよい。
【００３３】
被覆層ポリカーボネートには特に耐候性を改良するため紫外線吸収剤が２〜２０重量％、好ましくは３〜１０重量％、より好ましくは３〜５重量％である。２重量％未満では、耐候性改良効果がなく、積層シートが紫外線等さらされると黄変してしまう。２０重量％を越えると耐候性には効果が大きいが紫外線吸収剤による着色が目立ち商品価値がなくなる。
【００３４】
被覆層ポリカーボネートに配合される紫外線吸収剤としては、ベンゾトリアゾール系化合物、ベンゾフェノン系化合物、ヒドロキシフェニルトリアジン系化合物、サリチル酸フェニルエステル系化合物などが挙げられる。
ベンゾトリアゾール系化合物としては２−（５−メチル−２−ヒドロキシフェニル）−２Ｈ−ベンゾトリアゾール、２−［２−ヒドロキシ−３，５−ビス（α，αジメチルベンジル）フェニル］−２Ｈ−ベンゾトリアゾール、２−（２’−ヒドロキシ−５’−ｔ−オクチルフェニル）ベンゾトリアゾール、２，２−メチレンビス［４−（１，１，３，３−テトラメチレンブチル）−６−（２Ｈ−ベンゾトリアゾール−２−イル）フェノール］、などが挙げられ、ベンゾフェノン系化合物としては２−ヒドロキシ−４−オクトキシベンゾフェノン、２，４−ジヒドロキシベンゾフェノン、２−ヒドロキシ−４−メトキシ−４’−クロルベンゾフェノン、２，２−ジヒドロキシ−４−メトキシベンゾフェノン、２，２−ジヒドロキシ−４，４’−ジメトキシベンゾフェノン等が挙げられる。
【００３５】
またヒドロキシフェニルトリアジン系化合物からなる紫外線吸収剤としては、例えば２，４−ジフェニル−６−（２−ヒドロキシ−４−メトキシフェニル）−１，３，５−トリアジン、２，４−ジフェニル−６−（２−ヒドロキシ−４−エトキシフェニル）−１，３，５−トリアジン、２，４−ジフェニル−６−（２−ヒドロキシ−４−プロポキシフェニル）−１，３，５−トリアジン、２，４−ジフェニル−６−（２−ヒドロキシ−４−ブトキシフェニル）−１，３，５−トリアジン、２，４−ジフェニル−６−（２−ヒドロキシ−４−ヘキシルオキシフェニル）−１，３，５−トリアジン、２，４−ジフェニル−６−（２−ヒドロキシ−４−オクチルオキシフェニル）−１，３，５−トリアジン、２，４−ジフェニル−６−（２−ヒドロキシ−４−ドデシルオキシフェニル）−１，３，５−トリアジン、２，４−ジフェニル−６−（２−ヒドロキシ−４−ベンジルオキシフェニル）−１，３，５−トリアジン、２，４−ジフェニル−６−（２−ヒドロキシ−４−（２−ブトキシエトキシ）フェニル）−１，３，５−トリアジン、２，４−ジ−ｐ−トルイル−６−（２−ヒドロキシ−４−メトキシフェニル）−１，３，５−トリアジン、２，４−ジ−ｐ−トルイル−６−（２−ヒドロキシ−４−エトキシフェニル）−１，３，５−トリアジン、２，４−ジ−ｐ−トルイル−６−（２−ヒドロキシ−４−プロポキシフェニル）−１，３，５−トリアジン、２，４−ジ−ｐ−トルイル−６−（２−ヒドロキシ−４−ブトキシフェニル）−１，３，５−トリアジン、２，４−ジ−ｐ−トルイル−６−（２−ヒドロキシ−４−ヘキシルオキシフェニル）−１，３，５−トリアジン、２，４−ジ−ｐ−トルイル−６−（２−ヒドロキシ−４−オクチルオキシフェニル）−１，３，５−トリアジン、２，４−ジ−ｐ−トルイル−６−（２−ヒドロキシ−４−ドデシルオキシフェニル）−１，３，５−トリアジン、２，４−ジ−ｐ−トルイル−６−（２−ヒドロキシ−４−ベンジルオキシフェニル）−１，３，５−トリアジン、２，４−ジ−ｐ−トルイル−６−（２−ヒドロキシ−４−（２−ヘキシルオキシエトキシ）フェニル）−１，３，５−トリアジン等が挙げられ、またサリチル酸フェニルエステル系紫外線吸収剤としてはパラ−ｔ−ブチルフェニルサリチル酸エステル、パラ−オクチルフェニルサリチル酸エステル等が挙げられる。
【００３６】
このうちより揮発しにくいベンゾトリアゾール系化合物、ヒドロキシフェニルトリアジン系化合物からなる紫外線吸収剤がより好ましい。
被覆層ポリカーボネート層の厚みは１０〜２００μｍ、好ましくは２０〜１００μｍ、更に好ましくは３０〜５０μｍが好ましい。
積層厚みが１０μｍ未満では、均一な厚みで被覆することが困難になり、耐候性改良効果が小さり、耐候性を改良するためには多量の紫外線吸収剤を配合する必要があるため、紫外線吸収剤による着色が目立ち商品価値がなくなる。積層厚みが２００μｍを越えると、紫外線吸収剤の影響で着色が目立つようになり商品価値がなくなる。
【００３７】
本発明のポリカーボネート積層シートの製造方法は共押出法が好ましい。
またポリカーボネート積層シート全体の厚みについては特に制限はなく、押出成形機の能力によって０．５〜２０ｍｍの厚みで自由に設計できる。
【００３８】
【発明の実施の形態】
各項目の評価は以下の方法で測定した。
（１）外観は、作製したポリカーボネート積層シートの目視で検査した。
（２）初期着色は、積層シート成形直後の黄色度をＪＩＳ Ｋ ７１０５に準拠して測定した。黄色度が４を超えると着色が目視で明らかにわかる。
【００３９】
黄色度が４未満の場合を初期着色◎、つまり初期着色が小さいとし、逆に黄色度が４以上の場合を初期着色×、つまり初期着色が大きいとして評価した。
（３）耐候性は、スガ試験機製のサンシャインウエザーメーターでサンシャインスーパーロングライフカーボンを使用し、温度６３℃一定下、降雨無し２時間と降雨１８分のサイクルを繰り返す条件で試験片を３０００時間暴露した。
【００４０】
暴露前後の黄色度及びヘイズ（曇価）の変化をＪＩＳＫ ７１０３に準拠して測定した。
黄変度（ΔＹＩ）＝（暴露前の黄色度）−（暴露前の黄色度）
黄変度の値が大きいと初期値に比べて、黄色味が濃くなった（着色した）ことを意味し、この黄変度が４を超えると着色したことが目視で明らかにわかる。
【００４１】
ヘイズ差（ΔＨ％）＝（暴露後のヘイズ）−（暴露前のヘイズ）
ヘイズ差の値が大きいと初期値に比べて、曇りが大きくなったことを意味し、このヘイズ差が２を超えると透明感の喪失が目視で明らかにわかる。
黄変度が４未満でかつヘイズ差が２未満、つまり黄変も曇りもしない場合を耐候性◎とし、黄変度が４以上もしくはヘイズ差（ΔＨ％）が２以上の場合、つまり黄変するまたは曇る場合を耐候性×として評価した。
【００４２】
【実施例１】
基板用ポリカーボネートとして２８０℃で１００ｃｍ^-1のせん断速度における溶融粘度が１６５０Ｐａ・ｓを有するポリカーボネートを用い、また被覆層用ポリカーボネートとして２８０℃で１００ｃｍ^-1のせん断速度における溶融粘度が１５９０Ｐａ・ｓのポリカーボネートを用い、共押出シート試作機にて板厚８ｍｍの２種３層のポリカーボネート積層シートを作成した。
【００４３】
該被覆層用ポリカーボネートにはあらかじめ２，４−ジフェニル−６−（２−ヒドロキシ−４−ヘキシルオキシフェニル）−１，３，５−トリアジンからなる紫外線吸収剤を３重量％練り込んでおいた。
また該ポリカーボネート積層シートの被覆層の厚みは、被覆層用押出機からの吐出量を調整することによって両面ともに３０μｍにした。
【００４４】
このようにして得られたポリカーボネート積層シートは外観がよく、不安定流による積層界面の乱れ模様等は全く見られなかった。結果を表１に示す。
【００４５】
【実施例２〜４】
被覆層用ポリカーボネートの粘度を表１に示すように変更した以外は、実施例１と同様に行った。得られたポリカーボネート積層シートはいづれも外観良好であった。結果を表１に示す。
【００４６】
【比較例１〜３】
被覆用ポリカーボネートの粘度を表１に示すように変更した以外は、実施例１と同様に行った。得られたポリカーボネート積層シートの外観は、いづれも不安定流による積層界面の乱れ模様、特に押出方向に沿って縦筋模様が発生していた。結果を表１に示す。
【００４７】
【比較例４】
被覆層用ポリカーボネートとして２８０℃で１００ｃｍ^-1のせん断速度における溶融粘度が１５００Ｐａ・ｓのポリカーボネートを用い、かつ被覆層用押出機からの吐出量を調整することによって被覆層の積層厚みを両面ともに３００μｍにした以外は実施例１と同様に行った。得られたポリカーボネート積層シートの外観は特開平８−２２４８４８号公報にあるように不安定流による積層界面の乱れもなくきれいなものであったが、被覆層に多量に配合された紫外線吸収剤によって初期着色が大きく問題である。結果を表１に示す。
【００４８】
【比較例５】
基板及び被覆層に用いるポリカーボネートの粘度を、表１に示す通り極端に低いものを用いて実施例１と同様に行った。粘度が低すぎて、シーティングが全くできなかった。
【００４９】
【比較例６】
基板及び被覆層に用いるポリカーボネートの粘度を、表１に示す通り極端に高いものを用いて実施例１と同様に行った。粘度が高すぎるため押出機内で溶融できず押出不可能であった。
【００５０】
【比較例７〜８】
被覆層用押出機からの吐出量を調整することによって被覆層の積層厚みを両面ともに５μｍまたは３００μｍにした以外は実施例１と同様に行った。
被覆層積層厚みが５μｍにしようとすると、均一な被覆層の形成が困難で外観不良になるばかりか、被覆層での紫外線吸収効果が小さく基材層ポリカーボネートが紫外線に曝されてしまい、耐候変色が発生した。また被覆層積層厚みが３００μｍの場合、外観は良好であったが、被覆層に多量に配合された紫外線吸収剤によって初期着色が大きく問題である。結果を表１に示す。
【００５１】
【比較例９〜１０】
被覆層ポリカーボネートにあらかじめ配合する２，４−ジフェニル−６−（２−ヒドロキシ−４−ヘキシルオキシフェニル）−１，３，５−トリアジンからなる紫外線吸収剤の量を１重量％、もしくは３０重量％にした以外は実施例１と同様に行った。いづれの場合も外観は良好であったが、紫外線吸収剤が１重量％では被覆層での紫外線吸収効果が小さく基材層ポリカーボネートが紫外線に曝されてしまい、耐候変色が発生した。また３０重量％の場合、耐候変色は確かにないものの、初期着色が大きく問題である。結果を表１に示す。
【００５２】
【表１】

【００５３】
【発明の効果】
本発明によって、被覆するポリカーボネート層の厚みが薄くても層間流動不安定現象がなく、積層界面が平滑で外観の優れた耐候性ポリカーボネート積層シートを提供することができ、ポリカーボネートシートの更なる用途拡大が期待できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a weather-resistant polycarbonate laminated sheet having a good appearance.
[0002]
[Prior art]
Polycarbonate sheet is excellent in impact resistance, transparency, flame resistance, etc. and various materials such as building materials represented by window materials, carport roofing materials, veranda waist plates, road materials such as transparent soundproof plates, railway vehicle materials, etc. It is used in the field and its use is expected to expand in the future.
[0003]
However, the polycarbonate sheet has poor weather resistance, and particularly when used in places exposed to ultraviolet rays such as outdoors, optical performance such as yellowing and loss of transparency, mechanical properties such as tensile strength and impact resistance, etc., are problematic. It was.
In general, a UV absorber is blended as a method for improving weather resistance. Polycarbonate sheet, as a unique technology, coats the polycarbonate sheet surface with a polycarbonate thin film containing a large amount of UV absorber. In recent years, many methods for forming a laminated sheet have been proposed. Examples thereof include Japanese Patent Publication No. 3-54626, Japanese Patent Publication No. 6-41162, and Japanese Patent Application Laid-Open No. 6-31493. A coextrusion method is often used as a method for producing these laminated sheets.
[0004]
This co-extrusion method is disclosed in many patents and documents such as Japanese Patent Publication No. 50-6860, Plastics, 24, 9 (Mar. 1973), Plastics Age, 21, 71 (Sept. 1975). ing.
When a laminated sheet is formed by coextrusion, it is important to control the surface of the sheet and control the lamination interface as in the case of normal sheet forming.
[0005]
W. J. et al. Schrenk, N.M. L. Bradley, T .; Alfredy, H .; Maack, Polym. Eng. & Sci. , 18, 620 (1978) describes that an unstable phenomenon occurs between layers during coextrusion. This phenomenon is called the interlaminar flow instability phenomenon. Even if the sheet with the interlaminar flow instability phenomenon is smooth, the unstable flow pattern is clearly visible when viewed through the sheet, especially like a polycarbonate sheet. When transparency is a feature, commercial value is reduced.
[0006]
In order to prevent the interlayer flow instability phenomenon occurring at the lamination interface, the above-mentioned literatures can be used to equalize the viscosity of the resins to be laminated, greatly increase the viscosity of the resin to be coated on the outside, or conversely to coat the outside. It is described that the flow of the lamination interface can be theoretically stabilized by greatly reducing the viscosity of the resin.
However, in practice, even if polycarbonates having the same viscosity are laminated by coextrusion, it is difficult to obtain a sheet having a smooth laminated interface and an excellent appearance.
[0007]
JP-A-8-224848 discloses that the viscosity of the outer layer is preferably at least 50 Pa · s, preferably 100 to 2000 Pa · s lower than the viscosity of the base sheet.
However, when co-extrusion lamination was actually performed by this method, when the outer layer exceeded 200 μm, a polycarbonate sheet having an excellent appearance as described in the publication was obtained. However, when the lamination thickness was 200 μm or less, it was still due to the difference in viscosity. It was difficult to obtain a sheet having an excellent external appearance due to the phenomenon of instability of the interlaminar flow at the lamination interface.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide a weather-resistant polycarbonate laminate sheet having no interlayer flow unstable phenomenon even when the polycarbonate layer to be coated is thin, having a smooth laminate interface and excellent appearance.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present inventors have intensively studied, and as a result, the resin hardly flows in the vicinity of the wall surface of the molding die, and exhibits fluidity as if the viscosity was increased. The viscosity difference was 100 cm ⁻¹ at 280 ° C. It was found to be 10 Pa · s or more and less than 50 Pa · s in terms of melt viscosity at the shear rate. It was also found that the closer to the molding die wall, the stronger the influence of the apparent viscosity difference, and the influence was exerted up to a depth of about 200 μm. As a result, it has been found that even when coextrusion lamination molding is performed using a resin having the same viscosity, an interlayer flow instability phenomenon occurs.
[0010]
That is, the present invention relates to a polycarbonate composition containing 2 to 20% by weight of an ultraviolet absorber on one or both sides of a substrate made of a polycarbonate having a melt viscosity of 500 to 3000 Pa · s at a shear rate of 100 cm ⁻¹ at 280 ° C. It is a polycarbonate laminated sheet provided with a coating layer having a thickness of 10 to 200 μm, wherein the difference in melt viscosity between the polycarbonate of the substrate and the coating layer composition is 10 to 50 Pa · s.
[0011]
Hereinafter, the present invention will be described in detail.
The polycarbonate used for the board | substrate and coating layer of this invention has the principal chain which consists of a repeating unit represented by the following general formula.
[0012]
[Chemical 1]

[0013]
(In the formula, Ar is a divalent aromatic residue, and examples thereof include phenylene, naphthylene, bifinylene, pyridylene, and those represented by the following general formula.)
[0014]
[Chemical formula 2]

[0015]
(In the formula, Ar ¹ and Ar ² are each an arylene group. For example, they represent groups such as phenylene, naphthylene, biphenylene, pyridylene, and Y represents an alkylene group or a substituted alkylene group represented by the following general formula, or —O—, It is a divalent group such as —CO—, —S—, —SO ₂ —, —CO ₂ —, —CON (R ¹ ) —, and (R ¹ is the same as above).
[0016]
[Chemical 3]

[0017]
(Wherein R ¹ , R ² , R ³ and R ⁴ are each a hydrogen atom, a lower alkyl group, a cycloalkyl group, an aryl group or an aralkyl group, optionally substituted with a halogen atom or an alkoxy group. , K is an integer of 3 to 11, and the hydrogen atom in Chemical Formula 4 may be substituted with a lower alkyl group, an aryl group, a halogen, or the like.
Examples of these divalent aromatic residues include those having the following general formula.
[0018]
[Formula 4]

[0019]
[Chemical formula 5]

[0020]
Wherein R ⁵ and R ⁶ are each hydrogen, halogen, C ₁ -C ₁₀ alkyl group, C ₁ -C ₁₀ alkoxy group, C ₁ -C ₁₀ cycloalkyl group or phenyl group. When R is an integer of 4 and m is 2 to 4, each R ⁵ may be the same or different, and when n is 2 to 4, each R ⁶ may be the same or different.
Especially, what is represented by the following general formula is preferable. In particular, those containing 85 mol% or more of a repeating unit having this as Ar are preferable.
[0021]
[Chemical 6]

[0022]
Further, the polycarbonate in the present invention may contain a trivalent or higher aromatic residue as a copolymerization component, or may contain an aliphatic or aromatic ester component as a copolymerization component.
As the molecular structure at the -terminal of the polycarbonate in the present invention, one or more terminal groups selected from a hydroxy group, an aryl carbonate group and an alkyl carbonate group can be bonded. Examples of the aryl carbonate terminal group and alkyl carbonate terminal group include those having the following general formula.
[0023]
[Chemical 7]

[0024]
(In the formula, Ar ³ is a monovalent aromatic residue, and the aromatic ring may be substituted, or a linear or branched alkyl group having 1 to 20 carbon atoms.)
Specific examples include those of the following general formula.
[0025]
[Chemical 8]

[0026]
[Chemical 9]

[0027]
Among these, a phenyl carbonate group, a pt-butylphenyl carbonate group, a p-cumylphenyl carbonate group, and the like are preferable. Further, the ratio of the hydroxyl group terminal to the other terminal is preferably 1/100 or more, and more preferably 1/40 or more.
The hydrolyzable chlorine contained in the polycarbonate in the present invention is preferably 1 ppm or less, more preferably 0.5 ppm or less. When the amount exceeds 1 ppm, it is exposed to a high temperature for a long time such as during molding and is colored, and the transparency that is characteristic of polycarbonate is lost.
[0028]
In the production of the polycarbonate in the present invention, a method of reacting an aromatic dihydroxy compound and a carbonate precursor, for example, an interfacial polymerization method (phosgene) in which an aromatic dihydroxy compound and phosgene are reacted in the presence of a sodium hydroxide aqueous solution and a methylene chloride solvent. Method), a transesterification method (melting method) in which an aromatic dihydroxy compound and diphenyl carbonate are reacted, and a method in which a crystallized carbonate prepolymer is solid-phase polymerized (Japanese Patent Laid-Open Nos. 1-158033, 1-271426, and 3-68627). ) And the like.
[0029]
The viscosity of the polycarbonate used for the substrate is 500 to 3000 Pa · s, preferably 700 to 2800 Pa · s, more preferably 1000 to 2500 Pa · s in terms of melt viscosity at a shear rate of 100 cm ⁻¹ at 280 ° C.
If the melt viscosity is 500 Pa · s or less, it is difficult to take the sheet in a sheet shape. Conversely, if the viscosity exceeds 3000 Pa · s, an excessive load is applied to the molding machine, which makes extrusion molding difficult.
[0030]
It has been shown in the prior art that the viscosity of the polycarbonate used for the coating layer is the same as that of the substrate polycarbonate to prevent the interlayer flow instability phenomenon and to obtain a laminated sheet having a good appearance. However, in actual coextrusion lamination molding, an interlayer flow instability phenomenon occurs even if the same polycarbonate is coextrusion lamination molding. This is because the resin does not flow easily near the mold wall surface, and it exhibits fluidity as if the viscosity has increased. The inventors have found that this is the cause. As a result of further investigation, it was found that the above-mentioned apparent viscosity difference was 10-50 Pa · s at a shear rate of 100 cm ⁻¹ at 280 ° C., and the viscosity of the coating layer polycarbonate was lowered by this viscosity difference in advance. It was found that the phenomenon of instability of the interlaminar flow can be prevented. That is, the viscosity of the polycarbonate used for the coating layer is 10 to 50 Pa · s, preferably 20 to 40 Pa · s in terms of melt viscosity at a shear rate of 100 cm ⁻¹ at 280 ° C. with respect to the viscosity of the base layer polycarbonate. Low is important for preventing a laminar flow instability, smoothing the lamination interface, and obtaining a laminated sheet having a good appearance.
[0031]
When the difference is less than 10 Pa · s, an interlayer flow instability phenomenon occurs due to the above-described reason, and the laminated interface is disturbed, resulting in poor appearance and loss of commercial value.
On the other hand, when the difference in viscosity exceeds 50 Pa · s, when the thickness of the coating layer exceeds 200 μm, a polycarbonate sheet having an excellent appearance is obtained as disclosed in JP-A-8-224848. However, when the lamination thickness is 200 μm or less, the interlayer flow instability phenomenon of the lamination interface as in the prior art occurs due to the difference in viscosity between the base layer and the coating layer resin, and the lamination interface is smooth and has an appearance. It is difficult to obtain an excellent sheet.
[0032]
Various additives may be blended with the polycarbonate in the present invention as necessary, for example, heat stabilizers, antioxidants, weathering agents, ultraviolet absorbers, mold release agents, lubricants, antistatic agents, plasticizers, other resins. And polymers such as rubber, pigments, dyes, fillers, reinforcing agents, flame retardants and the like.
These additives and the like may be added while the polycarbonate after polymerization is in a molten state, and after pelletizing the polycarbonate, the additive may be added and remelted and kneaded. You may add in the middle of shaping | molding.
[0033]
The coating layer polycarbonate contains 2 to 20% by weight, preferably 3 to 10% by weight, more preferably 3 to 5% by weight of an ultraviolet absorber for improving weather resistance. If it is less than 2% by weight, there is no effect of improving weather resistance, and the laminated sheet will turn yellow when exposed to ultraviolet rays or the like. If it exceeds 20% by weight, the weather resistance is very effective, but the coloring by the UV absorber is conspicuous and the commercial value is lost.
[0034]
Examples of the ultraviolet absorber blended in the coating layer polycarbonate include benzotriazole compounds, benzophenone compounds, hydroxyphenyltriazine compounds, salicylic acid phenyl ester compounds, and the like.
Examples of benzotriazole compounds include 2- (5-methyl-2-hydroxyphenyl) -2H-benzotriazole and 2- [2-hydroxy-3,5-bis (α, αdimethylbenzyl) phenyl] -2H-benzotriazole. 2- (2′-hydroxy-5′-t-octylphenyl) benzotriazole, 2,2-methylenebis [4- (1,1,3,3-tetramethylenebutyl) -6- (2H-benzotriazole- 2-yl) phenol], etc., and examples of the benzophenone compounds include 2-hydroxy-4-octoxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxy-4′-chlorobenzophenone, 2, 2-dihydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4,4′-dimeth Shi benzophenone.
[0035]
Examples of the ultraviolet absorber comprising a hydroxyphenyltriazine compound include 2,4-diphenyl-6- (2-hydroxy-4-methoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6 (2-hydroxy-4-ethoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-propoxyphenyl) -1,3,5-triazine, 2,4- Diphenyl-6- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3,5-triazine 2,4-diphenyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydro Ci-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-benzyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl -6- (2-hydroxy-4- (2-butoxyethoxy) phenyl) -1,3,5-triazine, 2,4-di-p-toluyl-6- (2-hydroxy-4-methoxyphenyl)- 1,3,5-triazine, 2,4-di-p-toluyl-6- (2-hydroxy-4-ethoxyphenyl) -1,3,5-triazine, 2,4-di-p-toluyl-6 -(2-hydroxy-4-propoxyphenyl) -1,3,5-triazine, 2,4-di-p-toluyl-6- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine 2,4-di-p-to Yl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3,5-triazine, 2,4-di-p-toluyl-6- (2-hydroxy-4-octyloxyphenyl) -1, 3,5-triazine, 2,4-di-p-toluyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4-di-p-toluyl-6 (2-hydroxy-4-benzyloxyphenyl) -1,3,5-triazine, 2,4-di-p-toluyl-6- (2-hydroxy-4- (2-hexyloxyethoxy) phenyl) -1 , 3,5-triazine and the like, and salicylic acid phenyl ester ultraviolet absorbers include para-t-butylphenyl salicylic acid ester, para-octylphenyl salicylic acid ester and the like. The
[0036]
Of these, UV absorbers composed of benzotriazole compounds and hydroxyphenyltriazine compounds which are less volatile are more preferred.
The thickness of the coating layer polycarbonate layer is 10 to 200 μm, preferably 20 to 100 μm, more preferably 30 to 50 μm.
If the laminated thickness is less than 10 μm, it becomes difficult to coat with a uniform thickness, the effect of improving the weather resistance is small, and in order to improve the weather resistance, it is necessary to add a large amount of UV absorber, so UV absorption The coloring by the agent is conspicuous and the commercial value is lost. When the laminated thickness exceeds 200 μm, coloring becomes conspicuous under the influence of the ultraviolet absorber and the commercial value is lost.
[0037]
The method for producing the polycarbonate laminated sheet of the present invention is preferably a coextrusion method.
Moreover, there is no restriction | limiting in particular about the thickness of the whole polycarbonate laminated sheet, It can design freely with the thickness of 0.5-20 mm with the capability of an extruder.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
Evaluation of each item was measured by the following method.
(1) The appearance was visually inspected of the produced polycarbonate laminated sheet.
(2) For the initial coloring, the yellowness immediately after forming the laminated sheet was measured according to JIS K 7105. When the yellowness exceeds 4, coloring can be clearly seen visually.
[0039]
The case where the yellowness was less than 4 was evaluated as initial coloring ◎, that is, the initial coloring was small, and conversely, the case where the yellowness was 4 or more was evaluated as initial coloring x, that is, the initial coloring was large.
(3) For weather resistance, use Sunshine Super Long Life Carbon with Sunshine Weather Meter manufactured by Suga Test Instruments, and expose the test specimen for 3000 hours under the condition of a constant temperature of 63 ° C and a cycle of 2 hours without rain and 18 minutes of rain. did.
[0040]
Changes in yellowness and haze (cloudiness value) before and after exposure were measured according to JISK 7103.
Yellowness (ΔYI) = (Yellowness before exposure) − (Yellowness before exposure)
When the yellowing value is large, it means that the yellowish color is darker (colored) than the initial value, and when this yellowing degree exceeds 4, it is clearly seen visually.
[0041]
Haze difference (ΔH%) = (Haze after exposure) − (Haze before exposure)
When the haze difference value is large, it means that the haze is larger than the initial value. When this haze difference exceeds 2, the loss of transparency is clearly seen visually.
When the yellowing degree is less than 4 and the haze difference is less than 2, that is, neither yellowing nor clouding occurs, the weather resistance is ◎, and when the yellowing degree is 4 or more or the haze difference (ΔH%) is 2 or more, that is, yellowing The case where it was clouded or clouded was evaluated as weather resistance x.
[0042]
[Example 1]
A polycarbonate having a melt viscosity of 1650 Pa · s at a shear rate of 100 cm ⁻¹ at 280 ° C. is used as the polycarbonate for the substrate, and a polycarbonate having a melt viscosity of 1590 Pa · s at a shear rate of 100 cm ⁻¹ at 280 ° C. as the polycarbonate for the coating layer. A two-layer, three-layer polycarbonate laminated sheet having a thickness of 8 mm was prepared using a coextrusion sheet prototype.
[0043]
The polycarbonate for coating layer was previously kneaded with 3% by weight of an ultraviolet absorber composed of 2,4-diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3,5-triazine.
Moreover, the thickness of the coating layer of the polycarbonate laminated sheet was adjusted to 30 μm on both sides by adjusting the discharge amount from the coating layer extruder.
[0044]
The polycarbonate laminated sheet obtained in this way had a good appearance, and there was no turbulence pattern or the like at the lamination interface due to unstable flow. The results are shown in Table 1.
[0045]
[Examples 2 to 4]
The same procedure as in Example 1 was performed except that the viscosity of the polycarbonate for the coating layer was changed as shown in Table 1. All of the obtained polycarbonate laminated sheets had good appearance. The results are shown in Table 1.
[0046]
[Comparative Examples 1-3]
The same procedure as in Example 1 was performed except that the viscosity of the coating polycarbonate was changed as shown in Table 1. As for the appearance of the obtained polycarbonate laminated sheet, in each case, a disordered pattern of the laminated interface due to an unstable flow, particularly a vertical streak pattern occurred along the extrusion direction. The results are shown in Table 1.
[0047]
[Comparative Example 4]
As the polycarbonate for the coating layer, a polycarbonate having a melt viscosity of 1500 Pa · s at a shear rate of 100 cm ⁻¹ at 280 ° C. is used, and the thickness of the coating layer is adjusted to 300 μm on both sides by adjusting the discharge amount from the extruder for the coating layer. The procedure was the same as in Example 1 except that. The appearance of the obtained polycarbonate laminate sheet was clean without disturbance of the laminate interface due to unstable flow as disclosed in JP-A-8-224848, but it was initially treated with an ultraviolet absorber mixed in a large amount in the coating layer. Coloring is a big problem. The results are shown in Table 1.
[0048]
[Comparative Example 5]
As shown in Table 1, the viscosity of the polycarbonate used for the substrate and the coating layer was extremely low, and the same procedure as in Example 1 was performed. The viscosity was too low for sheeting at all.
[0049]
[Comparative Example 6]
As shown in Table 1, the viscosity of the polycarbonate used for the substrate and the coating layer was extremely high, and the same procedure as in Example 1 was performed. Since the viscosity was too high, it could not be melted in the extruder and could not be extruded.
[0050]
[Comparative Examples 7-8]
The same procedure as in Example 1 was performed except that the thickness of the coating layer was changed to 5 μm or 300 μm on both sides by adjusting the discharge amount from the coating layer extruder.
If the thickness of the coating layer is set to 5 μm, it is difficult to form a uniform coating layer, resulting in poor appearance, and the UV absorption effect in the coating layer is small, and the base material layer polycarbonate is exposed to UV rays, resulting in weather discoloration. There has occurred. Further, when the coating layer lamination thickness is 300 μm, the appearance is good, but the initial coloring is a big problem due to the ultraviolet absorber mixed in a large amount in the coating layer. The results are shown in Table 1.
[0051]
[Comparative Examples 9 to 10]
The amount of the ultraviolet absorber composed of 2,4-diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3,5-triazine, which is previously blended with the coating layer polycarbonate, is 1% by weight or 30% by weight. The procedure was the same as in Example 1 except that. In any case, the appearance was good, but when the UV absorber was 1% by weight, the UV absorption effect in the coating layer was small and the base layer polycarbonate was exposed to UV rays, resulting in weathering discoloration. In the case of 30% by weight, although weathering discoloration is certainly not present, initial coloring is a big problem. The results are shown in Table 1.
[0052]
[Table 1]

[0053]
【The invention's effect】
According to the present invention, even if the polycarbonate layer to be coated is thin, there is no interlayer flow instability phenomenon, it is possible to provide a weather-resistant polycarbonate laminate sheet with a smooth lamination interface and excellent appearance, and further expansion of the use of the polycarbonate sheet Can be expected.

Claims (1)

Thickness of a coating layer made of a polycarbonate composition containing 2 to 20% by weight of an ultraviolet absorber on one or both sides of a substrate made of polycarbonate having a melt viscosity of 500 to 3000 Pa · s at a shear rate of 100 cm ⁻¹ at 280 ° C. It is a polycarbonate laminated sheet provided at 10 to 200 μm, the melt viscosity of the coating layer composition is lower than the polycarbonate of the substrate, and the difference in melt viscosity between the polycarbonate of the substrate and the coating layer composition is 10 to 50 Pa · s. Polycarbonate laminate sheet characterized by