JP4042206B2 - Film and sheet comprising polylactic acid composition - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、少なくとも３０℃の温度範囲にわたって、動的粘弾性の温度依存性に関する試験（ＪＩＳ−Ｋ７１９８Ｂ法）での貯蔵弾性率（Ｅ′）が６×１０6 Ｐａ以下で安定しているポリ乳酸組成物よりなるフィルム及びシートに関する。
【０００２】
【従来の技術】
近年、自然環境保護の見地から、自然環境中で分解する生分解樹脂重合体およびその成形品が求められ、ポリ乳酸などの脂肪族ポリエステル等の自然分解性樹脂の研究が活発に行われている。
【０００３】
ポリ乳酸は、光学活性中心を有する乳酸の重縮合体である。ポリ乳酸は、このポリマーを構成する乳酸の光学純度によりその結晶性が異なる。
光学純度が高いポリ乳酸すなわち結晶性の高いポリ乳酸は、５０℃以下の領域ではガラス状態で弾性率は高いが、ガラス転移温度を超えるとゴム状態に変わり弾性率が下がる。その転移領域を超えると次第に結晶化し再び弾性率が上がり、ゴム状態が維持されない。
【０００４】
一方、光学純度が低いポリ乳酸すなわち非晶性のポリ乳酸は、５０℃以下の領域ではガラス状態で弾性率は高いが、ガラス転移温度を超えるとゴム状態が維持できず大きく弾性率が低下し、 加工性に劣る。
【０００５】
単一ポリマーでは光学純度を微細に調整しても、弾性率の温度依存性についてゴム状平坦部を得ることが難しいことは既に知られている（高分子学会予稿集、第４６巻、第１４号、３８６５〜３８６６ページ（１９９７））。そのため、単一ポリマーでは、成形加工時の加工温度域が狭いなど加工性が低い。 また、接着剤あるいは粘着剤として利用しにくい。
このような現状において、成形加工性に優れたポリ乳酸が要望されていた。
【０００６】
【発明が解決しようとする課題】
そこで、本発明の目的は、生分解性樹脂であるポリ乳酸であって、成形加工性に優れたポリ乳酸組成物よりなるフィルム及びシートを提供することにある。
【０００７】
【課題を解決するための手段】
本発明者らは鋭意検討の結果、結晶性の異なる２種のポリ乳酸をブレンドすることにより、動的粘弾性の温度依存性に関する試験（ＪＩＳ−Ｋ７１９８Ｂ法）の貯蔵弾性率（Ｅ′）が６０℃以上で安定したゴム状平坦部を有する組成物が得られることを見出し、本発明に到達した。
【０００８】
すなわち、本発明は、光学純度が８０％以上である高結晶性ポリ乳酸（Ａ）と、光学純度が５４％以上８０％未満である低結晶性または非晶性ポリ乳酸（Ｂ）とを、（Ａ）／（Ｂ）＝１０／９０〜９０／１０の重量割合で含み、動的粘弾性の温度依存性に関する試験（ＪＩＳ−Ｋ７１９８Ｂ法）での貯蔵弾性率が、少なくとも３０℃の温度範囲にわたって、６×１０6 Ｐａ以下で安定しているポリ乳酸組成物よりなるフィルム又はシートである。
ここで、「６×１０6 Ｐａ以下で安定」とは、前記貯蔵弾性率が、６×１０6 Ｐａ以下で、±０．５×１０6 Ｐａの範囲で安定していることを意味する。
【０００９】
また、ポリ乳酸の成形加工性の観点から、少なくとも３０℃の温度範囲にわたって、貯蔵弾性率（Ｅ′）が安定していることが必要である。好ましくは３５℃以上の温度範囲にわたって、貯蔵弾性率（Ｅ′）が安定していることである。
【００１０】
このように、貯蔵弾性率（Ｅ′）の温度依存性曲線にいわゆる「ゴム状平坦部」を有することにより、本発明において用いるポリ乳酸組成物は、生分解性を有するのみならず、熱可塑性エラストマーとしてフィルム又はシートなどの用途にも適するものとなる。
【００１１】
このようなポリ乳酸組成物は、光学純度が８０％以上である高結晶性ポリ乳酸（Ａ）と、光学純度が５４％以上８０％未満である低結晶性または非晶性ポリ乳酸（Ｂ）とからなるポリ乳酸組成物であり、生体内吸収性や生分解性などの特徴を有する。
【００１２】
本発明において、ポリ乳酸（Ａ）及びポリ乳酸（Ｂ）は、実質的にＬ−乳酸及び／又はＤ−乳酸由来のモノマー単位のみで構成されるポリマーである。ここで「実質的に」とは、本発明の効果を損なわない範囲で、Ｌ−乳酸又はＤ−乳酸に由来しない、他の共重合モノマー単位を含んでいても良いという意味である。ポリ乳酸（Ａ）及びポリ乳酸（Ｂ）中における他の共重合モノマー単位は、一般に２０モル％程度までの量が好ましい。
【００１３】
このような他の共重合モノマー成分としては、乳酸モノマー又はラクチドと共重合可能な他のモノマー成分であり、２個以上のエステル結合形成性の官能基を持つジカルボン酸、多価アルコール、ヒドロキシカルボン酸、ラクトン等； 及びこれら種々の構成成分より成る各種ポリエステル、各種ポリエーテル、各種ポリカーボネート等が挙げられる。
【００１４】
ジカルボン酸としては、コハク酸、アジピン酸、アゼライン酸、セバシン酸、テレフタル酸、イソフタル酸等が挙げられる。
【００１５】
多価アルコールとしては、ビスフェノールにエチレンオキシドを付加反応させたものなどの芳香族多価アルコール、エチレングリコール、プロピレングリコール、ブタンジオール、ヘキサンジオール、オクタンジオール、グリセリン、ソルビタン、トリメチロールプロパン、ネオペンチルグリコールなどの脂肪族多価アルコール、ジエチレングリコール、トリエチレングリコール、ポリエチレングリコール、ポリプロピレングリコールなどのエーテルグリコール等が挙げられる。
【００１６】
ヒドロキシカルボン酸としては、グリコール酸、ヒドロキシブチルカルボン酸、その他特開平６−１８４４１７号公報に記載されているもの等が挙げられる。
【００１７】
ラクトンとしては、グリコリド、ε−カプロラクトングリコリド、ε−カプロラクトン、β−プロピオラクトン、δ−ブチロラクトン、β−またはγ−ブチロラクトン、ピバロラクトン、δ−バレロラクトン等が挙げられる。
【００１８】
ポリ乳酸（Ａ）及びポリ乳酸（Ｂ）の製造方法としては、既知の任意の重合方法を採用することができる。最も代表的に知られているのは、乳酸の無水環状二量体であるラクチドを開環重合する方法（ラクチド法）であるが、乳酸を直接縮合重合しても構わない。重合反応には、通常オクチル酸スズ等の有機スズ化合物が用いられる。
【００１９】
また、ポリ乳酸（Ａ）及びポリ乳酸（Ｂ）の分子量としては、重量平均分子量で、５０，０００〜１，０００，０００の範囲が好ましい。かかる範囲を下回ると機械特性等が十分発現されず、上回る場合は加工性に劣る傾向がある。
【００２０】
ポリ乳酸が、Ｌ−乳酸に由来するモノマー単位のみからなる場合又はＤ−乳酸に由来するモノマー単位のみからなる場合には、重合体は結晶性で高融点を有し、本発明において、高結晶性ポリ乳酸（Ａ）として用いられる。
【００２１】
また、Ｌ−乳酸、Ｄ−乳酸由来のモノマー単位の比率（Ｌ／Ｄ比と略称する）を変化させることにより、ポリ乳酸（Ａ）の結晶性・融点を自在に調節することができるので、用途に応じ、実用特性を制御することが可能になる。
【００２２】
一方、ポリ乳酸が、ポリマーを構成する乳酸の光学純度が低い場合には、重合体は結晶性が低いか、あるいは融点をもたず、本発明において、低結晶性または非晶性ポリ乳酸（Ｂ）として用いられる。
【００２３】
このように、ポリ乳酸の結晶性は、ポリマーを構成する乳酸の光学純度と密接に関連する。前記高結晶性ポリ乳酸（Ａ）は、光学純度８０％以上であり、好ましくは光学純度９０％以上である。前記低結晶性または非晶性ポリ乳酸（Ｂ）は、光学純度５４％以上８０％未満であり、好ましくは光学純度の上限７０％未満である。
【００２４】
ポリ乳酸の光学純度（以下ＯＰと略称する）は次式で計算される。
ＯＰ（％）＝１００×（［Ｌ］−［Ｄ］）／（［Ｌ］＋［Ｄ］） 又は、
ＯＰ（％）＝１００×（［Ｄ］−［Ｌ］）／（［Ｌ］＋［Ｄ］）
ここで、［Ｌ］はポリ乳酸のＬ−乳酸モル濃度、［Ｄ］はポリ乳酸のＤ−乳酸モル濃度を表わす。
【００２５】
また、ポリ乳酸の結晶性は、プラスチックの転移温度測定方法（ＪＩＳ−Ｋ７１２１）による融点における融解熱量にも関係する。例えば、高結晶性ポリ乳酸（Ａ）については、この融解熱量が１０Ｊ／ｇ以上であることが好ましく、１２Ｊ／ｇ以上であることがより好ましい。低結晶性または非晶性ポリ乳酸（Ｂ）については、この融解熱量が１０Ｊ／ｇ未満であることが好ましく、非晶性の場合には、融点は観測されない。
【００２６】
本発明において用いるポリ乳酸組成物は、高結晶性ポリ乳酸（Ａ）と低結晶性または非晶性ポリ乳酸（Ｂ）を、（Ａ）／（Ｂ）＝１０／９０〜９０／１０の重量割合で含んでいる。このような混合割合の中から、使用目的に応じて最適の割合を選択することができる。
【００２７】
結晶性の異なるポリ乳酸（Ａ）とポリ乳酸（Ｂ）との混合方法や混合装置は、特に限定されないが、連続的に処理できるものが工業的に有利で好ましい。
例えば溶融混合法の場合は、ポリ乳酸（Ａ）とポリ乳酸（Ｂ）を同時に単軸又は二軸押出し混練機に供給し溶融混合した後、ペレット化して良い。溶融押出し温度としては、使用する生分解性樹脂の融点及び混合比率を考慮して、適宜選択するが、通常１００〜２５０℃の範囲である。
【００２８】
この混合ペレットを用いて、常法により、射出成型品、押出し成型品、真空圧空成型品、ブロー成型品、フィルム、シート、ラミネート、容器、各種部品、その他の成型品を得ることができる。あるいは、一旦ペレット化することなく、溶融混合した後、直接成型することも可能である。
【００２９】
本発明におけるポリ乳酸組成物には、必要に応じて、従来公知の可塑剤、酸化防止剤、熱安定剤、光安定剤、紫外線吸収剤、顔料、着色剤、各種フィラー、帯電防止剤、離型剤、香料、滑剤、難燃剤、発泡剤、充填剤、抗菌・抗カビ剤、核形成剤等の各種添加剤を配合しても良い。
【００３０】
本発明において用いるポリ乳酸組成物は、前記貯蔵弾性率（Ｅ′）が、少なくとも３０℃の温度範囲にわたって、６×１０6 Ｐａ以下で安定し、貯蔵弾性率（Ｅ′）の温度依存性曲線にいわゆる「ゴム状平坦部」を有するので、生分解性を有するのみならず、成形加工性に優れる熱可塑性エラストマーとして、フィルム又はシートなどの用途にも適する。
【００３１】
【実施例】
以下、実施例により本発明をさらに具体的に説明する。
実施例において、重合体の重量平均分子量（Ｍｗ）はＧＰＣ分析によるポリスチレン換算値で示す。動的貯蔵弾性率（Ｅ′）の測定は、動的粘弾性の温度依存性に関する試験（ＪＩＳ−Ｋ７１９８Ｂ法）に準じて行った。また、融点及びその溶融吸熱量は走査型示差熱量計（ＤＳＣ）により、昇温速度５℃／ｍｉｎ．にて測定した。またポリ乳酸の光学純度は高速液体クロマトグラフィー（ＨＰＬＣ）により定量した。
【００３２】
［実施例１］
結晶性の高いポリ乳酸（（株）島津製作所製「ラクティ」、ＯＰ＝９８．０％、以下ＰＬＡ１と称する）２０重量％と、非晶性のポリ乳酸（（株）島津製作所製「ラクティ」、ＯＰ＝５４．０％、以下ＰＬＡ２と称する）８０重量％とをドライブレンドし、１８０℃の二軸混錬押出機にて平均５分間溶融混合し、口金よりストランド状に押出し、水冷後、切断しポリ乳酸組成物（以下ＰＬＡ３と称する）のチップＣ１を得た。
【００３３】
得られたチップＣ１のＤＳＣを測定した結果、 ガラス転移温度は４９℃、結晶化温度は１３７．５℃、融点は１７０℃、融解熱量は１２．２Ｊ／ｇであった。また、ＧＰＣを測定した結果、重量平均分子量は、９２，０００であった。
チップＣ１を８０℃で真空乾燥し、 絶乾状態にした後、金型温度を２５℃に保ち、射出成形により名刺大プレート（１ｍｍ厚）を得た。
得られた１ｍｍ厚の名刺大プレートを１０ｍｍ×５０ｍｍの短冊状に切り出し、 動的粘弾性の温度依存性に関する試験（ＪＩＳ Ｋ７１８７Ｂ法）での動的貯蔵弾性率（Ｅ′）を測定した。
【００３４】
［比較例１］
実施例１で用いたＰＬＡ１のＤＳＣを測定した結果、ガラス転移温度は５９℃、結晶化温度は９７℃、融点は１７３℃、融解熱量は４７．１Ｊ／ｇであった。また、ＧＰＣを測定した結果、重量平均分子量は、１４３，０００であった。
ＰＬＡ１を８０℃で真空乾燥し、 絶乾状態にした後、金型温度を２５℃に保ち、射出成形により名刺大プレート（１ｍｍ厚）を得た。
得られた１ｍｍ厚の名刺大プレートを１０ｍｍ×５０ｍｍの短冊状に切り出し、 実施例１と同様に動的貯蔵弾性率を測定した。
【００３５】
［比較例２］
実施例１で用いたＰＬＡ２のＤＳＣを測定した結果、ガラス転移温度は４７℃、結晶化温度及び融点は観測されなかった。また、ＧＰＣを測定した結果、重量平均分子量は、１１５，０００であった。
ＰＬＡ２を４０℃で真空乾燥し、 絶乾状態にした後、金型温度を２５℃に保ち、射出成形により名刺大プレート（１ｍｍ厚）を得た。 成形加工性も良好であった。
得られた１ｍｍ厚の名刺大プレートを１０ｍｍ×５０ｍｍの短冊状に切り出し、 実施例１と同様に動的貯蔵弾性率を測定した。
【００３６】
動的貯蔵弾性率（Ｅ′）の測定結果を図１に示す。 この結果より、実施例１では、１００℃から１３５℃の間で動的貯蔵弾性率が１×１０6 Ｐａ付近で安定しており、ゴム状平坦部が観測された。
比較例１では、８０℃以上で弾性率が高くなり、また比較例２では、８０℃以上で弾性率が徐々に低下して、いずれも１０5 〜１０7 Ｐａにゴム状平坦部は観測されなかった。
【００３７】
【発明の効果】
本発明では、光学純度が８０％以上である高結晶性ポリ乳酸（Ａ）と、光学純度が５４％以上８０％未満である低結晶性または非晶性ポリ乳酸（Ｂ）とを、（Ａ）／（Ｂ）＝１０／９０〜９０／１０の重量割合で含み、少なくとも３０℃の温度範囲にわたって、６×１０6 Ｐａ以下で安定し、貯蔵弾性率（Ｅ′）の温度依存性曲線にいわゆる「ゴム状平坦部」を有する安定したポリ乳酸組成物を用いる。このポリ乳酸組成物は、成型加工性に優れ、ポリ乳酸を使用した生分解性プラスチック製品の利用分野を広げることができ、このポリ乳酸組成物よりなるフィルム又はシートが提供される。
【図面の簡単な説明】
【図１】 動的貯蔵弾性率の測定結果を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention is a polycrystal having a storage elastic modulus (E ′) of 6 × 10 6 Pa or less in a test (JIS-K7198B method) relating to temperature dependence of dynamic viscoelasticity over a temperature range of at least 30 ° C. It relates to film and sheet made of acid composition.
[0002]
[Prior art]
In recent years, from the viewpoint of protecting the natural environment, biodegradable resin polymers that decompose in the natural environment and molded articles thereof have been demanded, and research on natural degradable resins such as aliphatic polyesters such as polylactic acid has been actively conducted. .
[0003]
Polylactic acid is a polycondensate of lactic acid having an optically active center. Polylactic acid has different crystallinity depending on the optical purity of lactic acid constituting this polymer.
Polylactic acid with high optical purity, that is, polylactic acid with high crystallinity, has a high elastic modulus in the glass state in the region of 50 ° C. or lower, but when it exceeds the glass transition temperature, it changes into a rubber state and the elastic modulus decreases. When the transition region is exceeded, it gradually crystallizes and the elastic modulus increases again, and the rubber state is not maintained.
[0004]
On the other hand, polylactic acid with low optical purity, that is, amorphous polylactic acid, has a high elastic modulus in the glassy state at a temperature of 50 ° C. or lower, but when the glass transition temperature is exceeded, the rubbery state cannot be maintained and the elastic modulus is greatly reduced. Inferior in workability.
[0005]
It is already known that it is difficult to obtain a rubber-like flat portion with respect to the temperature dependence of the elastic modulus even if the optical purity is finely adjusted with a single polymer (Proceedings of the Society of Polymer Science, Vol. 46, No. 14). No., 3865-3866 (1997)). Therefore, a single polymer has low processability such as a narrow processing temperature range during molding. Further, it is difficult to use as an adhesive or a pressure-sensitive adhesive.
Under such circumstances, polylactic acid having excellent molding processability has been demanded.
[0006]
[Problems to be solved by the invention]
An object of the present invention is a polylactic acid is a biodegradable resin, is to provide a film and sheet made of excellent polylactic acid composition moldability.
[0007]
[Means for Solving the Problems]
As a result of intensive studies, the inventors of the present invention have obtained a storage elastic modulus (E ′) of a test on temperature dependence of dynamic viscoelasticity (JIS-K7198B method) by blending two kinds of polylactic acids having different crystallinity. The inventors have found that a composition having a rubber-like flat portion that is stable at 60 ° C. or higher can be obtained, and reached the present invention.
[0008]
That is, the present invention provides a highly crystalline polylactic acid (A) having an optical purity of 80% or more and a low crystalline or amorphous polylactic acid (B) having an optical purity of 54% or more and less than 80% . (A) / (B) = 10/90 to 90/10 in a weight ratio, and a storage elastic modulus in a test for temperature dependence of dynamic viscoelasticity (JIS-K7198B method) is at least 30 ° C. It is a film or sheet made of a polylactic acid composition that is stable at 6 × 10 6 Pa or less.
Here, “stable at 6 × 10 6 Pa or less” means that the storage elastic modulus is 6 × 10 6 Pa or less and is stable within a range of ± 0.5 × 10 6 Pa.
[0009]
In addition, from the viewpoint of moldability of polylactic acid, it is necessary that the storage elastic modulus (E ′) is stable over a temperature range of at least 30 ° C. Preferably, the storage elastic modulus (E ′) is stable over a temperature range of 35 ° C. or higher.
[0010]
Thus, by having a so-called “rubbery flat portion” in the temperature dependence curve of the storage elastic modulus (E ′), the polylactic acid composition used in the present invention has not only biodegradability but also thermoplasticity. It becomes also suitable for the film or sheet of any applications as an elastomer.
[0011]
Such a polylactic acid composition includes a highly crystalline polylactic acid (A) having an optical purity of 80% or more, and a low crystalline or amorphous polylactic acid (B) having an optical purity of 54% or more and less than 80%. The polylactic acid composition is composed of the following, and has characteristics such as in vivo absorbability and biodegradability.
[0012]
In the present invention, polylactic acid (A) and polylactic acid (B) are polymers composed substantially only of monomer units derived from L-lactic acid and / or D-lactic acid. Here, “substantially” means that other copolymerizable monomer units not derived from L-lactic acid or D-lactic acid may be included as long as the effects of the present invention are not impaired. The amount of other copolymerizable monomer units in the polylactic acid (A) and the polylactic acid (B) is generally preferably up to about 20 mol%.
[0013]
Such other copolymerizable monomer components include other monomer components copolymerizable with lactic acid monomer or lactide, and dicarboxylic acids, polyhydric alcohols, hydroxycarboxylic acids having two or more ester bond-forming functional groups. Examples include acids, lactones, and the like; and various polyesters, various polyethers, and various polycarbonates composed of these various components.
[0014]
Examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid.
[0015]
Polyhydric alcohols include aromatic polyhydric alcohols such as those obtained by addition reaction of bisphenol with ethylene oxide, ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, glycerin, sorbitan, trimethylolpropane, neopentyl glycol, etc. And aliphatic glycols, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, and other ether glycols.
[0016]
Examples of the hydroxycarboxylic acid include glycolic acid, hydroxybutylcarboxylic acid, and those described in JP-A-6-184417.
[0017]
Examples of the lactone include glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, δ-valerolactone, and the like.
[0018]
As a method for producing the polylactic acid (A) and the polylactic acid (B), any known polymerization method can be employed. Most representatively known is a method of ring-opening polymerization of lactide, which is an anhydrous cyclic dimer of lactic acid (lactide method), but lactic acid may be directly subjected to condensation polymerization. In the polymerization reaction, an organic tin compound such as tin octylate is usually used.
[0019]
Moreover, as molecular weight of polylactic acid (A) and polylactic acid (B), the range of 50,000-1,000,000 is preferable at a weight average molecular weight. Below this range, the mechanical properties and the like are not sufficiently expressed, and when it exceeds, the processability tends to be inferior.
[0020]
When the polylactic acid is composed only of monomer units derived from L-lactic acid or only composed of monomer units derived from D-lactic acid, the polymer is crystalline and has a high melting point. It is used as soluble polylactic acid (A).
[0021]
In addition, the crystallinity and melting point of polylactic acid (A) can be freely adjusted by changing the ratio of monomer units derived from L-lactic acid and D-lactic acid (abbreviated as L / D ratio). Practical characteristics can be controlled according to the application.
[0022]
On the other hand, when polylactic acid has low optical purity of lactic acid constituting the polymer, the polymer has low crystallinity or does not have a melting point, and in the present invention, low crystalline or amorphous polylactic acid ( B).
[0023]
Thus, the crystallinity of polylactic acid is closely related to the optical purity of lactic acid constituting the polymer. The highly crystalline polylactic acid (A) has an optical purity of 80% or higher, preferably an optical purity of 90% or higher. The low crystalline or amorphous polylactic acid (B) has an optical purity of 54% or more and less than 80%, preferably an upper limit of optical purity of less than 70%.
[0024]
The optical purity (hereinafter abbreviated as OP) of polylactic acid is calculated by the following equation.
OP (%) = 100 × ([L] − [D]) / ([L] + [D]) or
OP (%) = 100 × ([D] − [L]) / ([L] + [D])
Here, [L] represents the L-lactic acid molar concentration of polylactic acid, and [D] represents the D-lactic acid molar concentration of polylactic acid.
[0025]
The crystallinity of polylactic acid is also related to the heat of fusion at the melting point according to the plastic transition temperature measurement method (JIS-K7121). For example, for the highly crystalline polylactic acid (A), the heat of fusion is preferably 10 J / g or more, and more preferably 12 J / g or more. For the low crystalline or amorphous polylactic acid (B), the heat of fusion is preferably less than 10 J / g, and in the case of amorphous, no melting point is observed.
[0026]
The polylactic acid composition used in the present invention comprises a high crystalline polylactic acid (A) and a low crystalline or amorphous polylactic acid (B) in a weight of ( A) / (B) = 10/90 to 90/10. Includes by percentage. From such a mixing ratio, an optimal ratio can be selected according to the purpose of use.
[0027]
The mixing method and mixing apparatus of polylactic acid (A) and polylactic acid (B) having different crystallinity are not particularly limited, but those that can be continuously processed are industrially advantageous and preferable.
For example, in the case of the melt mixing method, the polylactic acid (A) and the polylactic acid (B) may be simultaneously fed to a single-screw or twin-screw extrusion kneader and melt mixed, and then pelletized. The melt extrusion temperature is appropriately selected in consideration of the melting point and mixing ratio of the biodegradable resin to be used, but is usually in the range of 100 to 250 ° C.
[0028]
Using this mixture pellets, by a conventional method, injection molding, extrusion molding, vacuum-pressure molding, blow molding, full Irumu, sheets, laminates, containers, each seed components, to obtain the other molding it can. Alternatively, once without pelletization, after melt mixing, Ru possible der be molded directly.
[0029]
In the polylactic acid composition of the present invention, conventionally known plasticizers, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, pigments, colorants, various fillers, antistatic agents, release agents are optionally added. Various additives such as a mold, a fragrance, a lubricant, a flame retardant, a foaming agent, a filler, an antibacterial / antifungal agent, and a nucleating agent may be blended.
[0030]
In the polylactic acid composition used in the present invention, the storage elastic modulus (E ′) is stable at 6 × 10 6 Pa or less over a temperature range of at least 30 ° C., and the temperature dependence curve of the storage elastic modulus (E ′). because it has a so-called "rubber-like flat portion" in not only biodegradable, thermoplastic elastomer excellent in moldability, also suitable for the film or sheet of any application.
[0031]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
In the examples, the weight average molecular weight (Mw) of the polymer is shown as a polystyrene conversion value by GPC analysis. The dynamic storage elastic modulus (E ′) was measured according to a test (JIS-K7198B method) on the temperature dependence of dynamic viscoelasticity . Also, the melting point and by their melting endotherm is a differential scanning calorimeter (DSC), heating rate 5 ° C. / min. Measured with The optical purity of polylactic acid was quantified by high performance liquid chromatography (HPLC).
[0032]
[Example 1]
Highly crystalline polylactic acid (“Lacty” manufactured by Shimadzu Corporation, OP = 98.0%, hereinafter referred to as PLA1) and 20% by weight of amorphous polylactic acid (“Lacty” manufactured by Shimadzu Corporation) , OP = 54.0%, hereinafter referred to as PLA2) 80% by weight, melt blended for 5 minutes on average in a 180 ° C. twin-screw kneading extruder, extruded into a strand form from the die, water-cooled, The chip C1 of the polylactic acid composition (hereinafter referred to as PLA3) was obtained by cutting.
[0033]
As a result of measuring DSC of the obtained chip C1, the glass transition temperature was 49 ° C., the crystallization temperature was 137.5 ° C., the melting point was 170 ° C., and the heat of fusion was 12.2 J / g. Moreover, as a result of measuring GPC, the weight average molecular weight was 92,000.
The chip C1 was vacuum-dried at 80 ° C. to make it completely dry, then the mold temperature was kept at 25 ° C., and a business card large plate (1 mm thickness) was obtained by injection molding.
The obtained 1 mm thick business card large plate was cut into a strip of 10 mm × 50 mm, and the dynamic storage elastic modulus (E ′) was measured by a test on the temperature dependence of dynamic viscoelasticity (JIS K7187B method).
[0034]
[Comparative Example 1]
As a result of measuring DSC of PLA1 used in Example 1, the glass transition temperature was 59 ° C., the crystallization temperature was 97 ° C., the melting point was 173 ° C., and the heat of fusion was 47.1 J / g. Moreover, as a result of measuring GPC, the weight average molecular weight was 143,000.
PLA1 was vacuum-dried at 80 ° C. to make it completely dry, and then the mold temperature was kept at 25 ° C. to obtain a large business card plate (1 mm thick) by injection molding.
The obtained 1 mm thick business card large plate was cut into a strip of 10 mm × 50 mm, and the dynamic storage elastic modulus was measured in the same manner as in Example 1.
[0035]
[Comparative Example 2]
As a result of measuring DSC of PLA2 used in Example 1, the glass transition temperature was 47 ° C., and the crystallization temperature and the melting point were not observed. Moreover, as a result of measuring GPC, the weight average molecular weight was 115,000.
PLA2 was vacuum-dried at 40 ° C. to make it completely dry, and then the mold temperature was kept at 25 ° C. to obtain a large business card plate (1 mm thick) by injection molding. Molding processability was also good.
The obtained 1 mm thick business card large plate was cut into a strip of 10 mm × 50 mm, and the dynamic storage elastic modulus was measured in the same manner as in Example 1.
[0036]
The measurement result of the dynamic storage elastic modulus (E ′) is shown in FIG. From this result, in Example 1, the dynamic storage elastic modulus was stable in the vicinity of 1 × 10 6 Pa between 100 ° C. and 135 ° C., and a rubber-like flat portion was observed.
In Comparative Example 1, the elastic modulus increases at 80 ° C. or higher, and in Comparative Example 2, the elastic modulus gradually decreases at 80 ° C. or higher, and a rubber-like flat portion is observed at 10 5 to 10 7 Pa in all cases. There wasn't.
[0037]
【The invention's effect】
In the present invention, a highly crystalline polylactic acid (A) having an optical purity of 80% or more, and a low crystalline or amorphous polylactic acid (B) having an optical purity of 54% or more and less than 80% , (A ) / (B) = 10/90 to 90/10 in a weight ratio, stable at 6 × 10 6 Pa or less over a temperature range of at least 30 ° C., and a temperature dependence curve of storage elastic modulus (E ′) A stable polylactic acid composition having a so-called “rubbery flat portion” is used. This polylactic acid composition is excellent in moldability, and can be used in biodegradable plastic products using polylactic acid, and a film or sheet made of this polylactic acid composition is provided.
[Brief description of the drawings]
FIG. 1 is a graph showing measurement results of dynamic storage elastic modulus.
Claims (6)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| JP13132498A JP4042206B2 (en) | 1998-04-23 | 1998-04-23 | Film and sheet comprising polylactic acid composition |
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| JP13132498A JP4042206B2 (en) | 1998-04-23 | 1998-04-23 | Film and sheet comprising polylactic acid composition |
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| JPH11302521A JPH11302521A (en) | 1999-11-02 |
| JP4042206B2 true JP4042206B2 (en) | 2008-02-06 |
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Cited By (1)
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|---|---|---|---|---|
| EP4361205A1 (en) | 2022-10-31 | 2024-05-01 | Ricoh Company, Ltd. | Foamed polylactic acid sheet, method of manufacturing foamed polylactic acid sheet, and product |
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| JP2004204128A (en) * | 2002-12-26 | 2004-07-22 | Mitsubishi Plastics Ind Ltd | Polylactic acid polymer composition for thermoforming, polylactic acid polymer sheet, and thermoformed product using the sheet |
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| DE602005021860D1 (en) * | 2004-02-26 | 2010-07-29 | Mitsubishi Plastics Inc | BIODEGRADABLE WRAPPING FOIL |
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| JP2009013407A (en) * | 2007-06-06 | 2009-01-22 | Mitsubishi Plastics Inc | Heat-shrinkable film, molding using the film, heat-shrinkable label, and vessel attached with the molding or the label |
| JP4724737B2 (en) * | 2008-10-03 | 2011-07-13 | 三菱樹脂株式会社 | Injection molded body |
| JP4669890B2 (en) * | 2008-10-06 | 2011-04-13 | 三菱樹脂株式会社 | Method for producing thermoformed body |
| JP2010143995A (en) * | 2008-12-17 | 2010-07-01 | Wintech Polymer Ltd | Polyester resin composition and molded article thereof |
| US10669417B2 (en) | 2013-05-30 | 2020-06-02 | Cj Cheiljedang Corporation | Recyclate blends |
| WO2015149029A1 (en) | 2014-03-27 | 2015-10-01 | Metabolix, Inc. | Highly filled polymer systems |
| EP3214106B1 (en) * | 2016-03-03 | 2019-01-23 | PURAC Biochem BV | Non-reactive hot-melt adhesive with lactide-based copolymer |
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Cited By (1)
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| EP4361205A1 (en) | 2022-10-31 | 2024-05-01 | Ricoh Company, Ltd. | Foamed polylactic acid sheet, method of manufacturing foamed polylactic acid sheet, and product |
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