JP2004083710A - Polyester resin foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester resin foam based on a copolyester, excellent in biodegradability and hydrolysis resistance and also mechanical properties including compression and tensile properties. <P>SOLUTION: This polyester resin foam 0.03-0.2 g/cm<SP>3</SP>in apparent density and 0.3-10 mm in thickness is based on a resin 90-150°C in melting point containing ≥50 wt.% of the copolyester containing, as the main dicarboxylic acid component unit, adipic acid component unit and/or succinic acid component unit. <P>COPYRIGHT: (C)2004,JPO

Description

【００３７】
上記歪量γ（ｔ）を一定応力σｃで割って得られた値をクリープコンプライアンスＪ（ｔ）といい、下記（２）式で定義される。
【数２】
Ｊ（ｔ）＝γ（ｔ）／σｃ　　　　　（２）
【００３８】
クリープコンプライアンスＪ（ｔ）は、歪量γ（ｔ）と同様に最初は急激に増加するが経時と共になだらかに増加し、充分な時間が経過すると時間に対して直線的に変化するようになる（図１に示す）。該直線状に変化するようになったクリープコンプライアンスＪ（ｔ）は、下記（３）式で表すことができる。
【数３】
Ｊ（ｔ）＝Ｊ_０＋ｔ／η　　　　　　　（３）
【００３９】
本明細書における平衡コンプライアンス（Ｊ_０）は、前記（３）式におけるＪ_０として与えられる。即ち、クリープコンプライアンスＪ（ｔ）を縦軸に、時間ｔを横軸にプロットした図において、クリープコンプライアンスＪ（ｔ）の直線部分を時間ｔ＝０に外挿したときの時間ｔ＝０における切片として与えられる。
【００４０】
本発明において使用するポリエステル共重合体を含み、特定の融点、１９０℃での特定の平衡コンプライアンス（Ｊ_０）を有する樹脂は、例えば、該樹脂中に５０重量％以上含まれるポリエステル共重合体のジカルボン酸成分単位のテレフタル酸成分単位とアジピン酸成分単位とのモル比を変えることなどにより調製することができる。また、該ポリエステル共重合体に上記多官能化合物を導入したり、エーテル結合を導入すること、電子線照射、有機過酸化物等によりゲルが発生しない程度の微架橋構造を導入することにより平衡コンプライアンスが目的の値を示すものとすることができる。但し、本発明においては発泡体を構成する樹脂の合成方法、改質方法、物性調整方法等は特に限定されるものではない。
【００４１】
本発明において特定される平衡コンプライアンス及び引張弾性率の値を満足する樹脂として、具体的には、ビーエーエスエフ社製のポリエチレンテレフタレートアジペート『Ｅｃｏｆｌｅｘ　ＦＢＸ７０１１』（テレフタル酸成分単位とアジピン酸成分単位とのモル比が４２：５８）を選択することができる。
【００４２】
尚、本発明で使用する上記ポリエステル共重合体は、発泡体を構成する樹脂中に、７０重量％〜１００重量％含まれることが好ましい。また、当然のことながら、発泡体を構成する樹脂が上記ポリエステル共重合体１００重量％からなる場合、上記ポリエステル共重合体が特定の平衡コンプライアンス（Ｊ_０）や特定の引張弾性率を有するものでなければならない。
【００４３】
本発明の発泡体（Ａ）、（Ｂ）は、上記樹脂を押出発泡することによって得られる。該押出発泡法としては、例えば、上記基材樹脂を押出機内で加熱溶融、混練し、更に高温高圧下で物理発泡剤を注入、混練して発泡性溶融樹脂組成物とした後、押出機先端に設けられた環状ダイを通して大気圧下に押出して筒状に発泡させ、この筒状発泡体を押出方向に沿って切り開いて発泡シートとする方法、環状ダイを通して大気圧下に押出して筒状に発泡させ、この筒状発泡体をロールで挟圧して、筒状発泡体の内面同士を接着させ板状発泡体とする方法、該発泡性溶融樹脂組成物をフラットダイを通して押出して板状発泡体とする方法、該発泡性溶融樹脂組成物を異形ダイを通して押出して種々の異なる断面積形状の発泡体とする方法が挙げられる。
【００４４】
また、必要に応じて押出機とダイの間にアキュームレーターを設置してもよい。アキュームレーターを設置することにより、吐出速度を飛躍的に増大させることができるので、小さな押出機であっても、高発泡倍率、高厚みの本発明発泡体、特に板状、長尺状の発泡体を得るさいに好適である。
【００４５】
本発明の発泡体（Ａ）、（Ｂ）の製造においては、基材樹脂中に必要に応じて気泡調整剤を添加することができる。気泡調整剤としては、タルク、シリカ等の無機粉末や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或いは重炭酸ナトリウムとの反応混合物等が挙げられる。気泡調整剤の添加量は基材樹脂１００重量部当たり３重量部以下が好ましい。
【００４６】
又、必要に応じて基材樹脂に所期の目的を妨げない範囲の量の収縮防止剤、帯電防止剤、耐候剤、滑剤、酸化防止剤、着色剤等の各種添加剤を配合することもできる。更に、タルク、シリカ、炭酸カルシウム、クレー、ゼオライト、アルミナ、硫酸バリウム等を無機充填剤として添加することもできる。これら無機充填剤の添加量は樹脂と他の添加剤等を合計した総重量の４０重量％を上限とすることが好ましい。上記無機充填剤は平均粒径が１〜７０μｍのものが好ましい。無機充填剤を添加すると得られた発泡体の耐熱性が向上するとともに、発泡体を焼却する際の燃焼カロリーを更に低下させることができる。
【００４７】
又、本発明の発泡体（Ａ）、（Ｂ）の製造においては、基材樹脂中に炭素数が１８〜２４の飽和脂肪酸アミドおよび炭素数が１８〜２４の不飽和脂肪酸アミドの群から選択される１種以上を添加することが好ましい。これらの飽和脂肪酸や不飽和脂肪酸アミドを添加すると、生分解性発泡シートは特有のベタベタ感がなくなり、滑り性が良くなり、ポリエチレン樹脂発泡シートのような滑らかな感触を有するものとなる。上記飽和脂肪酸としては、例えばステアリン酸アミド、アラキン酸アミド、ベヘン酸アミド、リグノゼン酸アミド等が挙げられ、不飽和脂肪酸アミドとしては、例えばエルカ酸アミド、ブラシジン酸アミド、セトレイン酸アミド、アラキドン酸アミド、ステアロール酸アミド等が挙げられる。尚、飽和脂肪酸や不飽和脂肪酸アミドの好ましい添加量は、基材樹脂１００重量部に対して０．１〜２．０重量部である。
【００４８】
以下において、本発明の発泡体（Ａ）及び（Ｂ）についてさらに詳述する。
（発泡体（Ａ））
発泡体（Ａ）の見掛け密度は、０．０３〜０．２ｇ／ｃｍ^３であり、好ましくは０．０４〜０．１２ｇ／ｃｍ^３である。見掛け密度が０．０３ｇ／ｃｍ^３未満の発泡体を得ようとすると、収縮等が発生し、良好な発泡体が得られない。また機械的物性が低すぎて、実用上の使用で耐えうるものではない。その見掛け密度が０．２ｇ／ｃｍ^３を超えると、発泡体の感触は硬くなり、用途によっては緩衝性が不充分となることがある。
発泡体（Ａ）の厚みは、０．３〜１０ｍｍであり、好ましくは０．５〜７ｍｍである。厚みが０．３ｍｍ未満であると、緩衝性、強度が低すぎて、実用上の使用で耐えうるものではない。一方、その厚みが１０ｍｍを超えるものは、フラットダイの下流側に連続する成形具をとりつけた特殊な構造の装置により製造しなければならず、通常の環状ダイによる製造自体が困難であり、環状ダイにより厚みが１０ｍｍを超えるものが得られたとしても、マンドレルカール等の歪が残留しやすく、例えば包装材料としては使用しにくいものとなる。
【００４９】
発泡体（Ａ）の引張伸びは、好ましくは２００％以上であり、更に好ましくは３００〜９００％である。引張伸びが２００％未満であると、被包装材の形状への追従性が悪く、しっかり包装できないばかりか、被包装材のコーナー部や鋭利な部分で亀裂が発生しやすい。尚、上記発泡体（Ａ）の引張伸びは、発泡体の押出方向（ＭＤ）と発泡体の押出方向と直交する幅方向（ＴＤ）の各々の値の内、少なくとも一方が上記範囲内であればよいが、ＭＤ及びＴＤの値が共に上記範囲内であることが更に好ましい。
【００５０】
発泡体（Ａ）の引張弾性率は、好ましくは１〜３０ＭＰａであり、更に好ましくは１〜５ＭＰａである。該引張弾性率が１ＭＰａ未満であると、少ない荷重でも底付等が発生し、緩衝性が不充分となる虞がある。一方、引張弾性率が大きすぎると柔軟性が不十分になるおそれがある。尚、上記発泡体（Ａ）の引張弾性率は、発泡体の押出方向（ＭＤ）と発泡体の押出方向と直交する幅方向（ＴＤ）の各々の値の内、少なくとも一方が上記範囲内であればよいが、ＭＤ及びＴＤの値が共に上記範囲内であることが更に好ましい。
【００５１】
また、発泡体（Ａ）の引張強さは、好ましくは０．８ＭＰａ以上であり、更に好ましくは１〜５ＭＰａである。尚、引張強さの上限は概ね３０ＭＰａである。該引張強さが０．８ＭＰａ未満であると、発泡体の引張物性が不充分となる虞がある。尚、上記発泡体（Ａ）の引張強さは、発泡体の押出方向（ＭＤ）と発泡体の押出方向と直交する幅方向（ＴＤ）の各々の値の内、少なくとも一方が上記範囲内であればよいが、ＭＤ及びＴＤの値が共に上記範囲内であることが更に好ましい。
【００５２】
発泡体（Ａ）の平均気泡径は好ましくは０．２〜２．５ｍｍであり、更に好ましくは０．３〜２．０ｍｍである。発泡体の平均気泡径が０．２ｍｍ未満であると、発泡体製造時にセルが連通して収縮等が発生し、良好な発泡体が得られ難い。また得られたとしてもコルゲートがきつく発生し、取り扱いにくいものとなる虞がある。一方、平均気泡径が２．５ｍｍを超えると、セルの膜が厚くなり柔軟性に欠けた感触となり、また外観も悪化する虞がある。
【００５３】
発泡体（Ａ）の連続気泡率は好ましくは０〜７０％であり、更に好ましくは０〜６０％であり、特に好ましくは０〜４０％である。連続気泡率が、７０％を超えると柔軟性は高まるが、圧縮強さは低下するため、重量物を包装した場合、特に厚みが３〜１０ｍｍのものについては底付等が発生する虞がある。但し、厚みが３ｍｍ未満の場合は、連続気泡率が７０％を超えるものと、そうでないものとの物性的な差は殆ど見られない。
【００５４】
発泡体（Ａ）はトレー等の成形型等により、加熱成形を行うことができる。
【００５５】
（発泡体（Ｂ））
発泡体（Ｂ）の見掛け密度は、０．０３５〜０．２５ｇ／ｃｍ^３であり、好ましくは０．０４〜０．２０ｇ／ｃｍ^３である。その密度が０．０３５ｇ／ｃｍ^３未満であると、均一な気泡の発泡体を製造することが難しく、また、連続気泡率の高い発泡体となり、収縮してしまい良好な発泡体が得られない。一方、０．２５ｇ／ｃｍ^３を超えると、断熱性、軽量性おいて不十分である。
【００５６】
発泡体（Ｂ）の押出方向に対する垂直断面の面積は５ｃｍ^２以上である。５ｃｍ^２未満では、生産効率が悪く、また、使用される用途が限定されてしまう。その面積の上限値は特に制約されないが、通常、５０００ｃｍ^２程度である。尚、発泡体（Ｂ）の厚みは０．５ｃｍ以上、更に１ｃｍ以上が好ましい。
【００５７】
発泡体（Ｂ）の厚み方向（ＺＤ）に対する圧縮強さは、好ましくは１〜５０ｋＰａ、更に好ましくは５〜３５ｋＰａである。圧縮強さが１ｋＰａ未満のものは、圧縮強さが低すぎ用途によっては発泡体の変形が大きくなり過ぎる可能性がある。一方、５０ｋＰａを超えるものは、圧縮強さが高すぎるため用途によって柔軟性に劣る場合がある。つまり、１〜５０ｋＰａの範囲のものは、底付きしにくく、柔軟性のある発泡体となる。
【００５８】
また、発泡体（Ｂ）の厚み方向（ＺＤ）に対する圧縮弾性率は好ましくは０．１〜６ｋＰａ、更に好ましくは０．５〜４ｋＰａである。圧縮弾性率が０．１ｋＰａ未満のものは実用上、柔らかすぎることがあり、６ｋＰａを超えると実用上、硬い感触のものとなる。つまり、０．１〜６ｋＰａの範囲のものは、適度に柔らかい従来のものにはない特有の感触の発泡体となる。
【００５９】
発泡体（Ｂ）の平均気泡径は、０．２〜５ｍｍであることが好ましい。０．２ｍｍ未満では、発泡体製造時に収縮等が発生し、良好な発泡体が得られない虞があり。５ｍｍを超えると、気泡膜が厚くなり過ぎ、外観が悪く、また柔軟性の悪いものとなる可能性がある。
【００６０】
発泡体（Ｂ）の連続気泡率は、適度に高い圧縮強さ等の機械的物性のものを得るという点から、連続気泡率は好ましくは０〜７０％であり、更に好ましくは０〜６０％であり、特に好ましくは０〜４０％である。一方、さほど圧縮強さ等の機械的物性の要求されない用途に関しては、本発明発泡体のゴム状弾性に係る物性を充分に発揮させ更に柔軟性を兼備させるために該連続気泡率が７０％を超えるものとすることが好ましい。
【００６１】
【実施例】
以下、実施例を挙げて本発明を更に詳細に説明する。
【００６２】
各実施例及び参考例で使用した樹脂の溶融特性等を以下に記す。
（１）実施例１〜１０の基材樹脂
ＢＡＳＦ社製　Ｅｃｏｆｌｅｘ　ＦＢＸ７０１１（テレフタル酸成分単位とアジピン酸成分単位とのモル比が４２：５８）
・メルトインデックス（ＭＩ）（１９０℃、２．１６ｋｇｆ）　５．６ｇ／１０ｍｉｎ
・メルトテンション（１９０℃）　０．８ｇｆ
・融点（Ｔｍ）（ＪＩＳ　Ｋ７１２１）　１１６℃
・密度　　　　　　　　　　　　　１．２５ｇ／ｃｍ^３
・Ｊ_０　　　　　　　　　　　　　　２．４５×１０^−４Ｐａ^−１
・引張弾性率　　　　　　　　　　５３ＭＰａ
【００６３】
（２）参考例１、３の基材樹脂
昭和高分子社製　ビオノ−レ　♯１９０３
・ＭＩ（１９０℃、２．１６ｋｇｆ）　３．６ｇ／１０ｍｉｎ
・メルトテンション（１９０℃）　５．６ｇｆ
・Ｔｍ（ＪＩＳ　Ｋ７１２１）　　１１２℃
・密度　　　　　　　　　　　　　１．２６ｇ／ｃｍ^３
【００６４】
（３）参考例２の基材樹脂
日本ユニカー社製　低密度ポリエチレン　ＤＦＤＪ６７７５
・ＭＩ（１９０℃、２．１６ｋｇｆ）　０．２ｇ／１０ｍｉｎ
・メルトテンション（１９０℃）　１８．０ｇｆ
・Ｔｍ（ＪＩＳ　Ｋ７１２１）　　１１０℃
・密度　　　　　　　　　　　　　０．９２ｇ／ｃｍ^３
【００６５】
実施例１、２及び参考例１、２
上記基材樹脂と、気泡核剤としてタルクを第一押出機に投入し、加熱溶融混練し、発泡剤としてイソブタン／ノルマルブタン＝３／７（重量比）の混合物を押出機中に圧入し、さらに混練させ発泡性溶融樹脂とする。次いでクロスバーによって連結された第二押出機にて所定の樹脂温度まで発泡性溶融樹脂を冷却し、押出機先端に取付けた環状ダイスから大気中に円筒状に押出発泡させ、これをマンドレル上に引取り冷却固化させ円筒状発泡体とし、これを一箇所切り開きシート状発泡体を得た。発泡剤添加量、タルク添加量、押出発泡時の樹脂温度は、表２に示した通りである。
【００６６】
実施例１、２においては、得られた発泡体を加熱真空成形することにより、１５０ｍｍ×１２０ｍｍ　深さ３０ｍｍ（底面１１５ｍｍ×９５ｍｍ）のヤケや賦形不良のない、良好なトレーを得た。該加熱真空成形の条件としては、三和興業（株）製ＦＥ−３６型単発成形機を使用し、該成形機の加熱設定を上ヒーター２００Ｖ×（３００Ｗ×ヒーター４０枚＝１２ＫＷ）で出力３０％、下ヒーター２００Ｖ×（８００Ｗ×６枚＝４．８ＫＷ）で出力４０％とした。
【００６７】
実施例３、４
表２に示す発泡剤量等以外は、実施例１、２と同様にして押出機先端に取り付けた環状ダイスから大気中に円筒状に押出発泡させた。続いて円筒状発泡体の内面が圧着可能な状態にあるうちに挟圧ロールで挟み込み発泡体の内面を接着して平板状発泡体とした。
【００６８】
尚、実施例２及び実施例４においては、発泡体見掛け密度の小さな発泡体を得やすくする事を目的として、有機過酸化物（日本油脂製、パークミルＤＭ４０）を基材樹脂１００重量部に対し０．０５重量部の割合となるように第一押出機に投入し、発泡性溶融樹脂の溶融張力及び粘度の向上を図った。尚、実施例２、４で得られた発泡体を加熱プレスにて溶融脱泡したものの平衡コンプライアンス（１９０℃）は各々２．７３×１０^−４Ｐａ^−１、２．７１×１０^−４Ｐａ^−１であった。
【００６９】
実施例１〜４、参考例１、２にて得られた発泡体の物性等を表２に併せて示した。
【００７０】
【表２】

【００７１】
実施例５、６
実施例１と同様の樹脂と、気泡調整剤としてタルクを混合した原料を、口径４０ｍｍの押出機に供給して加熱、混練して溶融樹脂とした後、さらに物理発泡剤としてイソブタンを押出機内の樹脂中に圧入混練して発泡性溶融物とした後、該発泡性溶融物を押出機と連結した口径９０ｍｍのアキュームレーターに充填し、次にアキュームレーターから発泡性溶融物を射出するとともに、クリアー３ｍｍ、長さ８０ｍｍのフラットダイから押出して、良好な板状の押出発泡体を得た。発泡剤添加量、タルク添加量、押出発泡時の樹脂温度は、表３に示した通りである。
【００７２】
実施例７
発泡体の連続気泡率を低くすることを目的とし、実施例２と同様に過酸化物を使用し基材樹脂を増粘させた以外は、実施例５と同様にして行い、良好な板状の押出発泡体を得た。発泡剤添加量、タルク添加量、押出発泡時の樹脂温度は、表３に示した通りである。尚、実施例７で得られた発泡体を加熱プレスにて溶融脱泡したものの平衡コンプライアンスは２．８０×１０^−４Ｐａ^−１であった。
【００７３】
実施例８
２．５ｃｍ角の角柱ダイスを用いた以外は、実施例５と同様にして行い、良好な円柱の押出発泡体を得た。発泡剤添加量、タルク添加量、押出発泡時の樹脂温度は、表３に示した通りである
【００７４】
参考例３
参考例１と同様の樹脂を用い、実施例３と同様の方法にて、良好な発泡体を得た。発泡剤添加量、タルク添加量、押出発泡時の樹脂温度は、表３に示した通りである。
【００７５】
実施例５〜８、参考例３にて得られた発泡体の物性等を表３に併せて示した。
【表３】

【００７６】
実施例９、１０
基材樹脂１００重量部に対して、エルカ酸アミド０．５重量部、実施例２，４と同様に発泡体の見掛け密度を小さくするために有機化酸化物（日本油脂製、パークミルＤ）を０．０５重量部添加したことと、表４に示す発泡剤量等以外は、実施例１、２と同様にしてシート状発泡体を得た。発泡剤添加量、タルク添加量、押出発泡時の樹脂温度は、表４に示した通りである。実施例９、１０にて得られたシート状発泡体の物性等を表４に併せて示した。
尚、実施例９、１０にて得られたシート状発泡体は、感触が滑らかで、静止摩擦係数が実施例１の１．５０に対して、１．０３（実施例９）、１．２０（実施例１０）と小さかった。
【００７７】
【表４】

【００７８】
尚、表２、３、４における物性の測定法及び評価の方法は下記のとおりである。
〔発泡体の引張伸び、引張弾性率及び引張強さ〕
押出方向（ＭＤ）及び幅方向（ＴＤ）について各々ＪＩＳ　Ｋ　６７６７（１９７６）記載のダンベル状１号形の試験片を作成し、万能試験機を用いて、試験速度５００ｍｍ／ｍｉｎ、チャック間距離５０ｍｍの条件でＪＩＳ　Ｋ　６７６７Ａ法に準拠して引張破断試験を行った。尚、発泡体の引張弾性率を算出するための計算式は、前述の基材樹脂の引張弾性率を算出するための計算式を用いて、平行部分の長さＣ＝４ｃｍにて算出した。
【００７９】
〔発泡体の圧縮強さ〕
厚み方向についてＪＩＳ　Ｋ　７２２０（１９８３）に準拠して標準試験片（試験片幅及び長さ１００ｍｍ、試験片高さ５０ｍｍ）を使用し、試験速度５ｍｍ／分にて測定を行い、２５％変形時の値を用い、２５％圧縮強さとした。
【００８０】
〔発泡体の圧縮弾性率〕
厚み方向についてＪＩＳ　Ｋ　７２２０（１９８３）に準拠して標準試験片（試験片幅及び長さ１００ｍｍ、試験片高さ５０ｍｍ）を使用し、試験速度５ｍｍ／分にて測定を行い圧縮弾性率を求めた。
【００８１】
〔連続気泡率〕
発泡体の連続気泡率は、発泡体サンプルの見掛けの体積：Ｖａ（ｃｍ^３）、発泡体サンプルの真の体積：Ｖｘ（ｃｍ^３）、発泡体サンプルの重量：Ｗ（ｇ）、発泡体サンプルの基材樹脂の密度：ρ（ｇ／ｃｍ^３）とから求められる。上記発泡体の見掛けの体積とは、発泡体サンプルの外寸から求められる見掛けの体積であり、発泡体の真の体積とは、発泡体サンプルを構成している基材樹脂の容積と、発泡体サンプル内の独立気泡部分の気泡全容積との和である。よって連続気泡化した気泡の体積百分率（連続気泡率）は、下記（４）式により求められる。
【数４】
連続気泡率（％）＝（Ｖａ−Ｖｘ）×１００／（Ｖａ−Ｗ／ρ）・・・（４）
発泡体の真の体積は上記サンプルを、ＡＳＴＭ　Ｄ−２８５６−７０［１９７６再認定］（手順Ｃ）に準じ、空気比較式比重計を用いて求めた。
【００８２】
〔平均気泡径〕
ＡＳＴＭ　Ｄ３５７６−７７に基づき求めた。但し、最終的に０．６１６にて割り算する操作は行わず、基準線と交わる気泡数（個）を数え、得られた気泡数（個）で基準線の長さ（ｍｍ）を割り算出することにより求めた値である。
【００８３】
〔見掛け密度〕
ＪＩＳ　Ｋ７２２２（１９８５）に基づき求めた。但し、該ＪＩＳにおいて試験片は５０ｃｍ^３以上とするとあるが、５０ｃｍ^３以上の試験片を切り出せない場合は、５０ｃｍ^３未満の試験片を使用してもかまわない。
【００８４】
〔静摩擦係数測定方法〕
ＪＩＳ　Ｐ８１４７（傾斜方法）に基づき求めた。但し、試験片の測定条件は、以下の通りである。
試験片：幅１００ｍｍ、長さ２５０ｍｍ
おもり：底部サイズ（７０ｍｍ×３５ｍｍ）、重量（２００ｇ）、水平時底面にかかる圧力（０．００８ｋｇ／ｃｍ^２）、傾斜速度：３．０度／秒
【００８５】
〔生分解性〕
得られた発泡体から切り出した試験片を土に埋めて土中分解性試験を行い、３０週経過後の重量減少量が７０重量％以上のものを良好とした。
【００８６】
【発明の効果】
本発明のポリエステル系樹脂発泡体は、生分解性、耐加水分解性に優れると共に、引張等の機械的物性において優れ、柔軟性及び緩衝性において従来の生分解性樹脂発泡体では達成することのできなかった優れた特性を有するものであり、家電包装材、クッション材その他各種用途の材料として極めて有用である。
また、本発明の発泡体は、気泡構造、外観及び物性において優れた、シート状、板状、棒状等の良好な発泡体である。したがって、優れた特性を有する該基材樹脂の特性を充分に引出すことを可能にし、更に有効に活用することができる。
【図面の簡単な説明】
【図１】クリープコンプライアンスＪ（ｔ）と時間との関係の一例を示すグラフである。
【図２】引張弾性率の算出方法の説明図で仮定荷重とチャート長さの関係の一例を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polyester-based resin foam having excellent biodegradability and hydrolysis resistance and excellent properties in mechanical properties such as compression and tension, and a method for producing the same.
[0002]
[Prior art]
BACKGROUND ART Conventionally, polyethylene resin foam sheets have been widely used as cushioning packaging materials for home electric appliances and the like. However, although the polyethylene resin foam sheet is excellent in flexibility and cushioning property, it is often used with reinforcement by laminating a resin film or the like because of insufficient tensile properties. Further, since most uses of the polyethylene resin foam sheet are disposable, in recent years, biodegradability has been required for disposable plastic packaging materials as an environmental problem.
[0003]
Thus, Japanese Patent Application Laid-Open No. Hei 10-152572 by the present applicant describes an extruded foam sheet made of an aliphatic polyester resin having a specific melt viscosity and melt tension. However, the biodegradable foam sheet in the publication has a lower tensile elongation, a higher elastic modulus, and an insufficient flexibility as compared with the polyethylene resin foam sheet. Due to such a thing, even if the home appliance is packaged, the cushioning packaging material has a poor conformability to the shape of the home appliance, cracks are generated immediately, and the surface of the packaged object may be damaged. Was not satisfactory enough.
[0004]
In addition, polyethylene resin foam boards and polyethylene resin rod-like foams have been used as buffering packaging materials and the like, but those having biodegradability have not been commercialized. The mechanical properties are inferior to expensive urethane foams, and new applications are expected by further improving the mechanical properties. Although it is possible to obtain a biodegradable foamed board by the technique described in the above-mentioned Japanese Patent Application Laid-Open No. H10-152572, the mechanical properties such as compression are insufficient as in the case of a polyethylene resin foamed board. Was.
[0005]
On the other hand, Japanese Unexamined Patent Publication No. 10-505620 discloses a biodegradable polyester copolymer of an aromatic polycarboxylic acid, an aliphatic polycarboxylic acid, and a polyol. There is a description about the use as a material for members. JP-T-10-508640 discloses a biodegradable polyester copolymer having a branched structure of adipic acid, terephthalic acid and C2 to C6-alkanediol. The polymer is described for use in foam production.
[0006]
However, although the above publication describes that the biodegradable polyester copolymer can be used for producing a foam, there is no specific example of the foam, and whether a practically usable foam may be obtained. It is unknown and leaves room for intensive research.
[0007]
[Problems to be solved by the invention]
The present invention provides a polyester-based resin foam having excellent properties in mechanical properties such as compression, tension, and the like, as well as excellent biodegradability and hydrolysis resistance using a polyester copolymer as a base resin, and a method for producing the same. The task is to provide.
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, have completed the present invention.
That is, the polyester resin foam of the present invention contains at least 50% by weight of a polyester copolymer containing a terephthalic acid component unit and an adipic acid component unit and / or a succinic acid component unit as main dicarboxylic acid component units, The apparent density of the base resin having a melting point of 90 to 150 ° C. is 0.03 to 0.2 g / cm.³And a polyester resin foam having a thickness of 0.3 to 10 mm (hereinafter, also simply referred to as foam (A)).
[0009]
Further, the polyester resin foam of the present invention contains 50% by weight or more of a polyester copolymer containing a terephthalic acid component unit and an adipic acid component unit and / or a succinic acid component unit as main dicarboxylic acid component units, The apparent density of the base resin having a melting point of 90 to 150 ° C. is 0.035 to 0.25 g / cm.³The area of the cross section perpendicular to the extrusion direction is 5 cm²The above polyester resin foam (hereinafter, also simply referred to as foam (B)).
[0010]
In the foams (A) and (B), the polyester copolymer preferably contains a butanediol component unit as a main diol component unit.
[0011]
In the foams (A) and (B), the open cell ratio is preferably 70% or less.
The foam (A) preferably has a tensile elongation of 200% or more and a tensile modulus of 1 to 30 MPa.
The foam (B) is preferably a plate-like foam having a compressive strength in the thickness direction of 1 to 50 kPa and a compressive elasticity of 0.1 to 6 kPa.
[0012]
In the foams (A) and (B), the molar ratio of the terephthalic acid component unit to the adipic acid component unit and / or the succinic acid component unit is preferably from 20:80 to 50:50.
In the foams (A) and (B), the base resin is selected from the group consisting of saturated fatty acid amides having 18 to 24 carbon atoms and unsaturated fatty acid amides having 18 to 24 carbon atoms. It is preferable to contain at least one of these.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
The polyester-based resin foam of the present invention comprises a polyester copolymer containing (i) a terephthalic acid component unit and (ii) an adipic acid component unit and / or a succinic acid component unit as main dicarboxylic acid component units in an amount of 50%. The base resin is one containing not less than 70% by weight, preferably not less than 70% by weight, and more preferably not less than 85% by weight.
[0014]
The polyester copolymer used in the present invention is produced by a method of polycondensing a dicarboxylic acid component and a diol component, a transesterification reaction of a polyester homopolymer and / or a polyester copolymer, or the like. The dicarboxylic acid component and the diol component of the polyester copolymer used in the present invention will be described in detail. As the dicarboxylic acid component, dicarboxylic acid or an ester-forming derivative thereof can be used. Examples of the ester-forming derivative include ester derivatives such as dimethyl ester and diethyl ester, salts such as diammonium salts, and acid halides such as dichloride.
[0015]
In the polyester copolymer, the main dicarboxylic acid component units are (i) a terephthalic acid component unit and (ii) an adipic acid component unit and / or a succinic acid component unit, and the molar ratio thereof is 20:80 to 50. : 50 is preferable, and 30:70 to 45:55 is more preferable from the viewpoint that a material having a lower density and a higher thickness can be obtained and biodegradability is excellent. If the molar ratio is other than 20:80 to 50:50, the desired physical property or biodegradability may not be obtained.
[0016]
The above (ii) adipic acid component unit and / or succinic acid component unit includes (ii-1) a case consisting only of adipic acid component unit, (ii-2) a case consisting only of succinic acid component unit, and (ii) -3) When it is composed of adipic acid component unit and succinic acid component unit, there are three types. The molar ratio of (i) the terephthalic acid component unit to (ii) the adipic acid component unit and / or the succinic acid component unit is as follows: (i) the terephthalic acid component unit and the above (ii-1) to (ii- It means that it is preferable that any one of 3) satisfies the relationship of the above molar ratio.
[0017]
Further, the meaning that the main dicarboxylic acid component unit is (i) a terephthalic acid component unit and (ii) an adipic acid component unit and / or a succinic acid component unit means that (i) a terephthalic acid component unit; and (ii) (Iii) In addition to the adipic acid component unit and / or the succinic acid component unit, (iii) another dicarboxylic acid component unit may be contained in an amount of 30 mol% or less, preferably 20 mol% or less.
[0018]
Other dicarboxylic acid component units include phthalic acid, isophthalic acid, 4,4′-diphenyldicarboxylic acid, 3,4′-diphenyldicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, Component units derived from aromatic dicarboxylic acids such as 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid or anhydrides thereof, or ester-forming derivatives thereof, or glutaric acid A component unit derived from an aliphatic dicarboxylic acid such as pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid or an anhydride thereof, or an ester-forming derivative thereof, or 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, decalin dical Emissions acids, alicyclic dicarboxylic acids or their anhydrides such such tetralindicarboxylic acids, or can include constituent units derived from an ester-forming derivative thereof.
[0019]
On the other hand, the diol component unit includes ethylene glycol, propylene glycol, trimethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, Component units derived from aliphatic diols such as 5-pentadiol and 1,6-hexanediol, or 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,6-cyclohexanediol and the like Component units derived from an alicyclic diol or component units derived from an aromatic diol such as bisphenol A can be mentioned. Among them, ethylene glycol, 1,2-propanediol, and 1,3-propanediol , 1,2-butanediol, 1,4- Is the component unit is preferably derived from butanediol. In particular, the main diol component unit is preferably a butanediol component unit. The meaning that the main diol component unit is a butanediol component unit means that in addition to the butanediol component unit, another diol component unit may be contained in an amount of 30 mol% or less, preferably 20 mol% or less. That is.
[0020]
Further, the polyester copolymer has a molecular end sealed by a component unit derived from a monofunctional compound such as a small amount of benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid, methoxypolyethylene glycol, or the like. Is also good. Further, it may contain a small amount of a component unit derived from a polyfunctional compound such as trimellitic acid, pyromellitic acid, trimesic acid, glycerin, pentaerythritol and the like. Further, the polyester copolymer used in the present invention can be various modified products. As such modified products, conventionally known modified products, for example, Japanese Patent Application Laid-Open No. 10-508640, Japanese Patent Application Laid-Open No. 10-508645, Japanese Patent Application Laid-Open No. 10-508647, Japanese Patent Application Laid-Open No. 10-512006, Japanese Patent Application Laid-Open No. Modified compounds described in each gazette such as JP-A-11-500761, JP-A-11-511767, JP-A-11-500762, JP-A-11-500157, and JP-T-2000-504355 can be exemplified.
[0021]
As the polymer other than the above-mentioned polyester copolymer which can be contained in the base resin, any polymer can be used as long as it does not inhibit the object and effects of the present invention. In addition, as the polymer other than the polyester copolymer, an aliphatic polyester such as polylactic acid, polybutylene succinate, polybutylene adipate, polybutylene succinate adipate, or the like is preferable. What was mixed or copolymerized with the polymer can be used as the base resin.
[0022]
In the present invention, the melting point of the base resin containing 50% by weight or more of the polyester copolymer is 90 to 150 ° C. If the melting point is too high, the flexibility of the resulting foam will be insufficient. On the other hand, when the melting point is too low, extrusion foaming when obtaining a foam is particularly difficult, and the heat resistance of the obtained foam is insufficient.
[0023]
In the present specification, the melting point of the base resin is measured based on JIS K7121 (1987). That is, the melting point of the base resin is the temperature at the peak apex obtained from the second DSC curve obtained by differential scanning calorimetry.
The second DSC curve obtained by the differential scanning calorimetry of the base resin referred to in the present invention means that 1 to 5 mg of the base resin is heated to 220 ° C. by a differential scanning calorimeter at a rate of 10 ° C./min. Then, the temperature is lowered from 220 ° C. to 30 ° C. at a rate of 10 ° C./min. Thereafter, the DSC curve obtained by raising the temperature to 220 ° C. again at a rate of 10 ° C./min is referred to as a second DSC curve.
Further, in the present invention, when two or more peak apexes appear in the base resin, the peak apex temperature of the peak having the widest peak area is defined as the melting point.
[0024]
The foams (A) and (B) of the present invention are obtained by melting the polyester copolymer, preferably under high temperature and high pressure, mixing the melt with a foaming agent, and extruding and foaming in a low pressure zone. Examples of the foaming agent used in such a case include an inert gas, a saturated aliphatic hydrocarbon, a saturated alicyclic hydrocarbon, an aromatic hydrocarbon, a halogenated hydrocarbon, an ether, and a ketone. These may be used alone or in combination of two or more. Used. Specifically, carbon dioxide, nitrogen, methane, ethane, normal butane, isobutane, normal pentane, isopentane, neopentane, normal hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane Dimethylbutane, methylcyclopropane, cyclopentane, 1,1-dimethylcyclopropane, cyclohexane, methylcyclopentane, ethylcyclobutane, 1,1,2-trimethylcyclopropane, benzene, 1,1,1,2-tetrafluoroethane , 1,1-zirfluoroethane, 1,1,1,2,2-pentafluoroethane, trichlorotrifluoroethylene, dichlorotetrafluoroethylene, dimethyl ether, 2-ethoxyethanol, acetone, ethyl methyl ketone, acetylacetone and the like. Ceremony It is. Further, a chemical foaming agent can be used as the foaming agent. Examples of such a chemical blowing agent include azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate and the like.
[0025]
These foaming agents can be used by being appropriately mixed. The amount of the foaming agent used varies depending on the type of the foaming agent, the desired expansion ratio of the foam, and the like. However, the standard of the amount of the foaming agent used is 1 kg of the base resin in the case of an organic physical foaming agent such as normal butane. Is used in an amount of 0.05 to 3 mol. If the amount of the foaming agent is less than 0.05 mol, the foam is low foaming, so there is no cost advantage, and only a foam having poor heat insulating properties can be obtained. If the amount exceeds 3 mol, the gas seal in the die is unstable. And a good foam may not be obtained.
[0026]
Examples of the blowing agent used to obtain the foam of the present invention include physical blowing agents, especially organic physical blowing agents such as saturated aliphatic hydrocarbons, saturated alicyclic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons. It is preferable to use a foaming agent containing, because a good foam having a small apparent density can be efficiently obtained. Further, as the organic physical foaming agent, a saturated aliphatic hydrocarbon or a halogenated hydrocarbon is preferable. Particularly, normal butane and / or isobutane are preferred. The content of the organic physical blowing agent in the blowing agent containing the organic physical blowing agent is preferably 50 to 100% by weight based on 100% by weight of the total amount of the blowing agent.
[0027]
In the foams (A) and (B) of the present invention, not only the above polyester copolymer is used alone, but also polybutylene succinate, polyethylene succinate, polybutylene succinate adipate, polycaprolactone, polylactic acid One or more biodegradable resins such as polybutylene succinate carbonate, polyhydroxybutyrate, polyvinyl alcohol, and cellulose acetate can be used. In this case, the biodegradable resin is preferably mixed at a ratio of less than 40% by weight with respect to 100% by weight of the resin constituting the foam.
[0028]
The foams (A) and (B) of the present invention contain 50% by weight of the above-mentioned polyester copolymer and have an equilibrium compliance (J) in dynamic viscoelasticity measurement.₀) Is 1.8 × 10^-4Pa^-1Above, preferably 2.0 × 10^-4~ 1.5 × 10^-3Pa^-1It is obtained by extruding and foaming a base resin having a melting point of 90 to 150 ° C.
[0029]
Further, the tensile modulus of the base resin is preferably 100 MPa or less, and more preferably 20 to 80 MPa.
By using a resin having a tensile modulus of 100 MPa or less, the physical properties related to the rubber-like elasticity specific to the foam of the present invention are particularly excellent.
[0030]
In the present specification, the tensile modulus is a value measured according to JIS K7113 (1995) and calculated by the following equation (1). However, the shape of the test piece was a No. 2 type test piece (thickness 1.1 mm, length C of the parallel portion of the test piece: 3.3 (cm)) described in JIS K7113 (1995), and the test speed was 50 mm / min. I do. The test piece was formed by a hot press heated to 230 ° C. using a jig having a thickness of 1.1 mm and press-molding for 5 minutes to form a resin plate having a thickness of 1.1 mm. The plate was processed into a predetermined test piece shape, and the condition was adjusted for 48 hours or more at a temperature of 23 ° C. and a relative humidity of 50%. Depending on the type of resin, air bubbles may be contained in the obtained resin plate due to water absorption of the resin at the time of hot pressing for forming the resin plate, but in such a case, the resin is placed in a vacuum oven at 150 ° C. Using a sufficiently dried resin, such as drying for 10 hours, a resin plate containing no air bubbles is prepared again to obtain a test piece.
[0031]
(Equation 1)
Tensile modulus (MPa) = Δσ / Δε (1)
here,
Δσ = load corresponding to the straight line between points AB in FIG. 2 “assumed load” (kgf) / [width D of test piece parallel part: (cm) × thickness I of test piece parallel part: (cm)]
Δε = [Chart moving distance “chart length” (cm) × [test speed (mm / min) / chart speed (mm / min)] corresponding to the straight line between points A and B in FIG. 2] / parallel test piece Part length: C (cm)
FIG. 2 is a graph showing a tensile load curve obtained at the time of measuring the tensile modulus.
[0032]
The equilibrium compliance of the resin (J₀) Is 1.8 × 10^-4Pa^-1If it is less than 3, the foaming property becomes insufficient, and although the foam is obtained, it is difficult to adjust the apparent density and thickness of the foam according to the purpose, and the appearance may be insufficient. .
[0033]
On the other hand, the equilibrium compliance (J₀) Is 1.5 × 10^-3Pa^-1When it exceeds, it may be difficult to obtain a material having a small apparent density, and when a foam having a large cross-sectional area such as a plate or a rod is obtained, dimensional stability such as shrinkage of the molded body after extrusion foaming is obtained. It is necessary to carefully consider the curing conditions in consideration of the nature. From the viewpoint that the foaming property can be further improved, the open cell ratio of the obtained foam can be further reduced, and the cushioning property, compressive strength, and the like associated with them can be improved,₀Is 2.0 × 10^-4~ 1.5 × 10^-3Pa^-1It is preferable that
[0034]
In this specification, the equilibrium compliance (J₀) Is measured by a dynamic viscoelasticity meter (Dynamic Analyzer SR200 manufactured by Rheometrics Scientific F.E.).
[0035]
Equilibrium compliance (J₀The measurement of ()) is specifically performed as follows.
First, a disk sample having a diameter of 25 mm is prepared from a measurement sample resin plate having a thickness of about 2 mm obtained by press-molding a resin by a hot press at a temperature of 230 ° C. for 5 minutes. Next, this sample was sandwiched between parallel plates having a diameter of 25 mm of a dynamic viscoelasticity measuring apparatus, heated to 190 ° C., left under a nitrogen atmosphere for about 10 minutes, and then adjusted to an interval of 1.4 mm. Then, the molten resin protruding from the parallel plate is removed. Next, the upper parallel plate is rotated so as to apply a constant stress σc of 100 Pa to the sample melted in the nitrogen atmosphere, and the time lapse of the strain amount γ (t) based on the time t = 0 when the constant stress σc is started to be applied. Measure the change. The amount of strain γ (t) rapidly increases at first but gradually increases with time, and changes linearly with time after a sufficient time has elapsed.
The apparatus settings of the dynamic analyzer SR200 were set as shown in Table 1, and the equilibrium compliance (J₀) Is calculated by the automatic function on the device.
[0036]
[Table 1]

[0037]
The value obtained by dividing the strain amount γ (t) by the constant stress σc is called creep compliance J (t) and is defined by the following equation (2).
(Equation 2)
J (t) = γ (t) / σc (2)
[0038]
The creep compliance J (t) rapidly increases at first like the strain amount γ (t), but gradually increases with time, and changes linearly with time after sufficient time has passed ( Shown in FIG. 1). The creep compliance J (t) that changes linearly can be expressed by the following equation (3).
(Equation 3)
J (t) = J₀+ T / η (3)
[0039]
The equilibrium compliance (J₀) Is J in the equation (3).₀Given as That is, in a diagram in which the creep compliance J (t) is plotted on the vertical axis and the time t is plotted on the horizontal axis, the intercept at the time t = 0 when the linear portion of the creep compliance J (t) is extrapolated to the time t = 0. Given as
[0040]
Including the polyester copolymer used in the present invention, a specific melting point, a specific equilibrium compliance at 190 ° C. (J₀) Can be prepared, for example, by changing the molar ratio of the terephthalic acid component unit and the adipic acid component unit of the dicarboxylic acid component unit of the polyester copolymer contained in the resin in an amount of 50% by weight or more. it can. Equilibrium compliance can be obtained by introducing the above polyfunctional compound into the polyester copolymer, introducing an ether bond, or introducing a micro-crosslinked structure that does not generate a gel due to electron beam irradiation, organic peroxide or the like. Indicates the target value. However, in the present invention, the method of synthesizing the resin constituting the foam, the method of modifying the resin, and the method of adjusting the physical properties are not particularly limited.
[0041]
Specific examples of the resin satisfying the equilibrium compliance and the tensile modulus specified in the present invention include polyethylene terephthalate adipate “Ecoflex @ FBX7011” (manufactured by BSF Ltd.) (molar of terephthalic acid component unit and adipic acid component unit). Ratio of 42:58) can be selected.
[0042]
The polyester copolymer used in the present invention is preferably contained in the resin constituting the foam in an amount of 70% by weight to 100% by weight. When the resin constituting the foam is composed of 100% by weight of the polyester copolymer, it is needless to say that the polyester copolymer has a specific equilibrium compliance (J).₀) Or a specific tensile modulus.
[0043]
The foams (A) and (B) of the present invention are obtained by extrusion foaming the above resin. As the extrusion foaming method, for example, the base resin is heated and melted and kneaded in an extruder, and a physical foaming agent is further injected and kneaded under high temperature and high pressure to form a foamable molten resin composition. Extruded under atmospheric pressure through an annular die provided to foam into a cylindrical form, this tubular foam is cut open along the extrusion direction to form a foamed sheet, extruded under atmospheric pressure through an annular die into a cylindrical shape Foaming, pressing the cylindrical foam with a roll, bonding the inner surfaces of the cylindrical foam to each other to form a plate-like foam, extruding the foamable molten resin composition through a flat die, and forming a plate-like foam. And a method in which the foamable molten resin composition is extruded through a deformed die to form foams having various cross-sectional shapes.
[0044]
Further, an accumulator may be provided between the extruder and the die as needed. By installing an accumulator, the discharge speed can be dramatically increased. Therefore, even in a small extruder, the foam of the present invention having a high expansion ratio and a high thickness, in particular, a plate-like or long-form foam can be obtained. Suitable for obtaining body.
[0045]
In the production of the foams (A) and (B) of the present invention, an air conditioner can be added to the base resin as required. Examples of the foam control agent include inorganic powders such as talc and silica, acid salts of polycarboxylic acids, and reaction mixtures of polycarboxylic acids with sodium carbonate or sodium bicarbonate. The added amount of the cell regulator is preferably 3 parts by weight or less per 100 parts by weight of the base resin.
[0046]
In addition, various additives such as anti-shrinkage agents, antistatic agents, weathering agents, lubricants, antioxidants, and coloring agents may be added to the base resin as needed, in an amount not to impair the intended purpose. it can. Further, talc, silica, calcium carbonate, clay, zeolite, alumina, barium sulfate and the like can be added as an inorganic filler. The upper limit of the amount of the inorganic filler added is preferably 40% by weight of the total weight of the resin and other additives. The inorganic filler preferably has an average particle size of 1 to 70 μm. When the inorganic filler is added, the heat resistance of the obtained foam is improved, and the calorie burned when the foam is incinerated can be further reduced.
[0047]
In the production of the foams (A) and (B) of the present invention, the base resin is selected from the group consisting of saturated fatty acid amides having 18 to 24 carbon atoms and unsaturated fatty acid amides having 18 to 24 carbon atoms. It is preferable to add at least one of the following. When these saturated fatty acids or unsaturated fatty acid amides are added, the biodegradable foamed sheet does not have a specific sticky feeling, has improved slipperiness, and has a smooth feel like a polyethylene resin foamed sheet. Examples of the above-mentioned saturated fatty acids include stearic acid amide, arachidic amide, behenic acid amide, lignosenic acid amide and the like, and examples of the unsaturated fatty acid amides include erucic acid amide, brassic acid amide, setreic acid amide, arachidonic acid amide And stearolamide. The preferred amount of the saturated fatty acid or unsaturated fatty acid amide is 0.1 to 2.0 parts by weight based on 100 parts by weight of the base resin.
[0048]
Hereinafter, the foams (A) and (B) of the present invention will be described in more detail.
(Foam (A))
The apparent density of the foam (A) is 0.03 to 0.2 g / cm.³And preferably 0.04 to 0.12 g / cm³It is. Apparent density is 0.03g / cm³If an attempt is made to obtain a foam having a size of less than 1, shrinkage or the like occurs, and a good foam cannot be obtained. Also, the mechanical properties are too low and cannot be tolerated in practical use. Its apparent density is 0.2g / cm³If it exceeds, the foam will have a hard feel and may have insufficient cushioning properties depending on the application.
The thickness of the foam (A) is 0.3 to 10 mm, preferably 0.5 to 7 mm. When the thickness is less than 0.3 mm, the cushioning property and the strength are too low, so that it cannot be used in practical use. On the other hand, when the thickness exceeds 10 mm, it must be manufactured by a device having a special structure in which a continuous forming tool is attached to the downstream side of the flat die. Even if a die having a thickness exceeding 10 mm is obtained by a die, distortion such as mandrel curl is likely to remain, which makes it difficult to use, for example, as a packaging material.
[0049]
The tensile elongation of the foam (A) is preferably 200% or more, and more preferably 300 to 900%. If the tensile elongation is less than 200%, the ability to follow the shape of the material to be packaged is poor, so that not only the package cannot be firmly packed, but also cracks are likely to occur at corners and sharp parts of the material to be packaged. The tensile elongation of the foam (A) is such that at least one of the values in the extrusion direction (MD) of the foam and the width direction (TD) orthogonal to the extrusion direction of the foam is within the above range. It suffices that both the MD and TD values are within the above ranges.
[0050]
The tensile modulus of the foam (A) is preferably 1 to 30 MPa, more preferably 1 to 5 MPa. If the tensile modulus is less than 1 MPa, bottoming or the like may occur even with a small load, and the cushioning property may be insufficient. On the other hand, if the tensile modulus is too large, the flexibility may be insufficient. The tensile modulus of the foam (A) is such that at least one of the values in the extrusion direction (MD) of the foam and the width direction (TD) orthogonal to the extrusion direction of the foam is within the above range. However, it is more preferable that the values of MD and TD both fall within the above ranges.
[0051]
Further, the tensile strength of the foam (A) is preferably 0.8 MPa or more, and more preferably 1 to 5 MPa. The upper limit of the tensile strength is approximately 30 MPa. If the tensile strength is less than 0.8 MPa, the tensile properties of the foam may be insufficient. The tensile strength of the foam (A) is such that at least one of the values in the extrusion direction (MD) of the foam and the width direction (TD) orthogonal to the extrusion direction of the foam is within the above range. However, it is more preferable that the values of MD and TD both fall within the above ranges.
[0052]
The average cell diameter of the foam (A) is preferably from 0.2 to 2.5 mm, more preferably from 0.3 to 2.0 mm. If the average cell diameter of the foam is less than 0.2 mm, the cells communicate with each other during the production of the foam, causing shrinkage and the like, and it is difficult to obtain a good foam. Moreover, even if it is obtained, the corrugate may be tightly generated and may be difficult to handle. On the other hand, if the average cell diameter exceeds 2.5 mm, the cell membrane becomes thick, resulting in a feel lacking in flexibility, and the appearance may be deteriorated.
[0053]
The open cell ratio of the foam (A) is preferably 0 to 70%, more preferably 0 to 60%, and particularly preferably 0 to 40%. When the open cell ratio exceeds 70%, the flexibility increases, but the compressive strength decreases. Therefore, when packing a heavy object, bottoming may occur particularly in the case of a thickness of 3 to 10 mm. . However, when the thickness is less than 3 mm, there is almost no difference in physical properties between those having an open cell ratio of more than 70% and those having no open cell ratio.
[0054]
The foam (A) can be subjected to heat molding using a mold such as a tray.
[0055]
(Foam (B))
The apparent density of the foam (B) is 0.035 to 0.25 g / cm.³And preferably 0.04 to 0.20 g / cm³It is. Its density is 0.035 g / cm³If it is less than 1, it is difficult to produce a foam having uniform cells, and the foam has a high open cell ratio, and shrinks, so that a good foam cannot be obtained. On the other hand, 0.25 g / cm³When it exceeds, the heat insulating property and the lightness are insufficient.
[0056]
The area of the cross section perpendicular to the extrusion direction of the foam (B) is 5 cm.²That is all. 5cm²If it is less than 1, the production efficiency is poor, and the application to be used is limited. Although the upper limit of the area is not particularly limited, it is usually 5000 cm.²It is about. The thickness of the foam (B) is preferably 0.5 cm or more, more preferably 1 cm or more.
[0057]
The compressive strength in the thickness direction (ZD) of the foam (B) is preferably 1 to 50 kPa, more preferably 5 to 35 kPa. If the compression strength is less than 1 kPa, the compression strength is too low, and depending on the application, the deformation of the foam may be too large. On the other hand, if it exceeds 50 kPa, the compressive strength is too high, and the flexibility may be poor depending on the use. In other words, a foam in the range of 1 to 50 kPa hardly bottoms out and becomes a flexible foam.
[0058]
Further, the compression modulus in the thickness direction (ZD) of the foam (B) is preferably 0.1 to 6 kPa, and more preferably 0.5 to 4 kPa. If the compression elastic modulus is less than 0.1 kPa, it may be too soft for practical use, and if it exceeds 6 kPa, it will be practically hard. That is, a foam in the range of 0.1 to 6 kPa is a moderately soft foam having a unique feel not found in the conventional foam.
[0059]
The average cell diameter of the foam (B) is preferably 0.2 to 5 mm. If it is less than 0.2 mm, shrinkage or the like may occur during the production of the foam, and a good foam may not be obtained. If it exceeds 5 mm, the bubble film may be too thick, resulting in poor appearance and poor flexibility.
[0060]
The open cell ratio of the foam (B) is preferably 0 to 70%, more preferably 0 to 60%, from the viewpoint of obtaining mechanical properties such as moderately high compressive strength. And particularly preferably 0 to 40%. On the other hand, for applications in which mechanical properties such as compressive strength are not so required, the open cell ratio is preferably 70% in order to sufficiently exhibit the physical properties related to the rubber-like elasticity of the foam of the present invention and to further have flexibility. It is preferred to exceed.
[0061]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
[0062]
The melting characteristics and the like of the resin used in each of Examples and Reference Examples are described below.
(1) Base resin of Examples 1 to 10
"Ecoflex" FBX7011 manufactured by BASF (molar ratio of terephthalic acid component unit to adipic acid component unit is 42:58)
・ Melt index (MI) (190 ° C, 2.16 kgf) @ 5.6 g / 10 min
・ Melt tension (190 ℃) 0.8gf
Melting point (Tm) (JIS K7121) 116 ° C
・ Density 1.25g / cm³
・ J₀2.45 × 10^-4Pa^-1
・ Tensile modulus 53MPa
[0063]
(2) Base resin of Reference Examples 1 and 3
Showa Polymer Co., Ltd. Bionole 1903
・ MI (190 ° C, 2.16 kgf) @ 3.6 g / 10 min
・ Melt tension (190 ° C) 5.6gf
・ Tm (JIS K7121) 112 ℃
・ Density 1.26g / cm³
[0064]
(3) Base resin of Reference Example 2
Nippon Unicar Ltd. Low Density Polyethylene DDFJ675
・ MI (190 ° C, 2.16kgf) @ 0.2g / 10min
・ Melt tension (190 ° C) @ 18.0gf
・ Tm (JIS K7121) 110 ℃
・ Density 0.92g / cm³
[0065]
Examples 1 and 2 and Reference Examples 1 and 2
The base resin and talc as a cell nucleating agent are charged into a first extruder, heated and kneaded, and a mixture of isobutane / normal butane = 3/7 (weight ratio) as a blowing agent is pressed into an extruder, It is further kneaded to obtain a foamable molten resin. Next, the foamable molten resin is cooled to a predetermined resin temperature by a second extruder connected by a crossbar, and is extruded and foamed into a cylindrical shape into the atmosphere from an annular die attached to the extruder tip, and this is placed on a mandrel. The cylindrical foam was taken out, cooled, and solidified, cut into one portion, and a sheet-like foam was obtained. The amount of the foaming agent added, the amount of talc added, and the resin temperature during extrusion foaming are as shown in Table 2.
[0066]
In Examples 1 and 2, the obtained foam was heated and vacuum-formed to obtain a good tray free from burns and shaping defects of 150 mm × 120 mm 30 mm (bottom 115 mm × 95 mm). As the conditions for the heating vacuum forming, a FE-36 single-shot forming machine manufactured by Sanwa Kogyo Co., Ltd. was used, and the heating setting of the forming machine was set to an upper heater of 200 V × (300 W × 40 heaters = 12 KW) with an output of 30. %, The output was 40% with the lower heater 200V × (800W × 6 sheets = 4.8KW).
[0067]
Examples 3 and 4
Except for the amount of the foaming agent shown in Table 2, in the same manner as in Examples 1 and 2, a cylindrical die was extruded and foamed into the atmosphere from an annular die attached to the extruder tip. Subsequently, while the inner surface of the cylindrical foam was in a state capable of being press-bonded, the inner surface of the foam was sandwiched by a pressing roll and adhered to obtain a flat foam.
[0068]
In Examples 2 and 4, an organic peroxide (manufactured by NOF Corporation, Park Mill DM40) was added to 100 parts by weight of the base resin for the purpose of easily obtaining a foam having a small apparent density. The mixture was charged into the first extruder so as to have a ratio of 0.05 part by weight to improve the melt tension and the viscosity of the foamable molten resin. The foams obtained in Examples 2 and 4 were melted and defoamed by a hot press, and the equilibrium compliance (190 ° C.) was 2.73 × 10 3 each.^-4Pa^-12.71 × 10^-4Pa^-1Met.
[0069]
Table 2 also shows the properties and the like of the foams obtained in Examples 1 to 4 and Reference Examples 1 and 2.
[0070]
[Table 2]

[0071]
Examples 5 and 6
The same resin as in Example 1 and a raw material obtained by mixing talc as a cell regulator were supplied to an extruder having a diameter of 40 mm, heated and kneaded to obtain a molten resin, and isobutane was further added as a physical foaming agent in the extruder. After press-kneading and kneading into a resin to form a foamable melt, the foamable melt is charged into a 90 mm-diameter accumulator connected to an extruder, and then the foamable melt is injected from the accumulator and cleared. The sheet was extruded from a flat die having a length of 3 mm and a length of 80 mm to obtain a good plate-like extruded foam. The amount of the foaming agent added, the amount of talc added, and the resin temperature during extrusion foaming are as shown in Table 3.
[0072]
Example 7
Performed in the same manner as in Example 5 except that the purpose of reducing the open cell ratio of the foam was to increase the viscosity of the base resin by using a peroxide in the same manner as in Example 2. To obtain an extruded foam. The amount of the foaming agent added, the amount of talc added, and the resin temperature during extrusion foaming are as shown in Table 3. The equilibrium compliance of the foam obtained in Example 7 melted and defoamed by a hot press was 2.80 × 10^-4Pa^-1Met.
[0073]
Example 8
Except having used the 2.5 cm square prism dice, it carried out similarly to Example 5, and obtained the favorable cylindrical extruded foam. The amount of the foaming agent added, the amount of talc added, and the resin temperature during extrusion foaming are as shown in Table 3.
[0074]
Reference Example 3
Using the same resin as in Reference Example 1, a good foam was obtained in the same manner as in Example 3. The amount of the foaming agent added, the amount of talc added, and the resin temperature during extrusion foaming are as shown in Table 3.
[0075]
Table 3 also shows the properties and the like of the foams obtained in Examples 5 to 8 and Reference Example 3.
[Table 3]

[0076]
Examples 9 and 10
To 100 parts by weight of the base resin, 0.5 parts by weight of erucamide was used. In order to reduce the apparent density of the foam as in Examples 2 and 4, an organic oxide (Park Mill D, manufactured by NOF Corporation) was used. A sheet-like foam was obtained in the same manner as in Examples 1 and 2, except that 0.05 part by weight was added, and the amount of the foaming agent shown in Table 4. The amount of the foaming agent added, the amount of talc added, and the resin temperature during extrusion foaming are as shown in Table 4. Table 4 also shows the physical properties and the like of the sheet foams obtained in Examples 9 and 10.
The sheet foams obtained in Examples 9 and 10 had a smooth feel and a static friction coefficient of 1.03 (Example 9) and 1.20 compared to 1.50 of Example 1. (Example 10) was small.
[0077]
[Table 4]

[0078]
The methods for measuring and evaluating physical properties in Tables 2, 3, and 4 are as follows.
(Tensile elongation, tensile modulus and tensile strength of foam)
For each of the extrusion direction (MD) and the width direction (TD), a dumbbell-shaped No. 1 test piece described in JIS K6767 (1976) was prepared, and the test speed was 500 mm / min and the distance between chucks was 50 mm using a universal testing machine. A tensile rupture test was carried out in accordance with JIS K6767A under the following conditions. In addition, the calculation formula for calculating the tensile elastic modulus of the foam was calculated using the above-described calculation formula for calculating the tensile elastic modulus of the base resin, with the length C of the parallel portion being 4 cm.
[0079]
[Compressive strength of foam]
In the thickness direction, a standard test piece (test piece width and length 100 mm, test piece height 50 mm) is used in accordance with JIS K 7220 (1983), and measurement is performed at a test speed of 5 mm / min. And a 25% compressive strength.
[0080]
(Compressive modulus of foam)
Using a standard test piece (test piece width and length 100 mm, test piece height 50 mm) in the thickness direction according to JIS K 7220 (1983), measure at a test speed of 5 mm / min to determine the compression modulus. Was.
[0081]
(Open cell rate)
The open cell ratio of the foam was determined by measuring the apparent volume of the foam sample: Va (cm).³), True volume of foam sample: Vx (cm³), Weight of foam sample: W (g), density of base resin of foam sample: ρ (g / cm)³). The apparent volume of the foam is the apparent volume determined from the outer dimensions of the foam sample, and the true volume of the foam is the volume of the base resin constituting the foam sample and the foam volume. This is the sum of the closed cell portion and the total cell volume in the body sample. Therefore, the volume percentage (open cell rate) of the cells that have been made into open cells can be obtained by the following equation (4).
(Equation 4)
Open cell ratio (%) = (Va−Vx) × 100 / (Va−W / ρ) (4)
The true volume of the foam was determined using an air-comparison hydrometer according to ASTM No. D-2856-70 [1976 recertified] (Procedure C).
[0082]
(Average bubble diameter)
It was determined based on ASTM D3576-77. However, the operation of finally dividing by 0.616 is not performed, the number of bubbles (pieces) intersecting with the reference line is counted, and the length (mm) of the reference line is calculated by dividing the obtained number of bubbles (pieces). This is the value obtained from the above.
[0083]
[Apparent density]
It was determined based on JIS K7222 (1985). However, the test piece is 50 cm in the JIS.³Although it is said that it is above, 50 cm³When the above test piece cannot be cut out, 50 cm³It is permissible to use a test piece of less than.
[0084]
(Static friction coefficient measurement method)
It was determined based on JIS P8147 (inclination method). However, the measurement conditions of the test piece are as follows.
Test piece: width 100 mm, length 250 mm
Weight: bottom size (70 mm x 35 mm), weight (200 g), pressure applied to the bottom surface when horizontal (0.008 kg / cm)²), Tilt speed: 3.0 degrees / second
[0085]
(Biodegradable)
A test piece cut out from the obtained foam was buried in soil to perform a soil degradability test, and those having a weight loss of 70% by weight or more after 30 weeks were evaluated as good.
[0086]
【The invention's effect】
The polyester resin foam of the present invention is excellent in biodegradability and hydrolysis resistance, and is excellent in mechanical properties such as tension, and can be achieved with conventional biodegradable resin foam in flexibility and buffering property. It has excellent characteristics that could not be obtained, and is extremely useful as a packaging material for home appliances, a cushion material, and other materials for various uses.
In addition, the foam of the present invention is a good foam such as a sheet, a plate, and a rod having excellent cell structure, appearance, and physical properties. Therefore, it is possible to sufficiently draw out the characteristics of the base resin having excellent characteristics, and it is possible to more effectively utilize the characteristics.
[Brief description of the drawings]
FIG. 1 is a graph showing an example of the relationship between creep compliance J (t) and time.
FIG. 2 is an explanatory diagram of a method of calculating a tensile elasticity, and is a graph showing an example of a relationship between an assumed load and a chart length.

Claims (8)

As a main dicarboxylic acid component unit, a polyester resin containing at least 50% by weight of a polyester copolymer containing a terephthalic acid component unit and an adipic acid component unit and / or a succinic acid component unit, and is composed of a base resin having a melting point of 90 to 150 ° C. apparent density 0.03~0.2g / cm ^3, polyester resin foam thickness 0.3 to 10 mm. As a main dicarboxylic acid component unit, a polyester resin containing at least 50% by weight of a polyester copolymer containing a terephthalic acid component unit and an adipic acid component unit and / or a succinic acid component unit, and is composed of a base resin having a melting point of 90 to 150 ° C. A polyester resin foam having an apparent density of 0.035 to 0.25 g / cm ³ and an area of a cross section perpendicular to the extrusion direction of 5 cm ² or more. The polyester resin foam according to claim 1 or 2, wherein the polyester copolymer contains a butanediol component unit as a main diol component unit. The polyester resin foam according to any one of claims 1 to 3, wherein an open cell ratio of the foam is 70% or less. The polyester resin foam according to claim 1, wherein the foam has a tensile elongation of 200% or more and a tensile modulus of 1 to 30 MPa. The polyester resin foam according to claim 2, wherein the foam is a plate-like foam having a compressive strength in the thickness direction of 1 to 50 kPa and a compressive elasticity of 0.1 to 6 kPa. The polyester resin foam according to any one of claims 1 to 6, wherein the molar ratio of the terephthalic acid component unit to the adipic acid component unit and / or the succinic acid component unit is 20:80 to 50:50. The base resin contains at least one selected from the group consisting of saturated fatty acid amides having 18 to 24 carbon atoms and unsaturated fatty acid amides having 18 to 24 carbon atoms. Polyester resin foam according to any one of the above.

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