JP4820493B2 - Polylactic acid resin composition - Google Patents

Description

【００１３】
【化４】

【００１４】
【発明の実施の形態】
以下に本発明の内容を詳細に説明する。
本発明のポリ乳酸系樹脂組成物においてポリ乳酸系樹脂には、乳酸ホモポリマーの他、乳酸コポリマー、またはこれらと他のポリマーとのブレンドポリマーを含むものである。
【００１５】
上記ポリ乳酸系樹脂におけるＬ−乳酸単位、Ｄ−乳酸単位の構成モル比Ｌ／Ｄは１００／０〜０／１００のいずれであってもよいが、高い融点を得るにはＬ−乳酸あるいはＤ−乳酸いずれかの単位を９０モル％以上、さらに高い融点を得るにはＬ−乳酸あるいはＤ−乳酸いずれかの単位を９５モル％以上含むことが好ましい。特に、高結晶性という点で、Ｌ−乳酸が多い方が好ましい。
【００１６】
乳酸コポリマーは、乳酸モノマーまたはラクチドと共重合可能な他の成分とが共重合されたものである。このような他の成分としては、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、およびこれらの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。
【００１７】
上記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。
【００１８】
上記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サイ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等のエーテルグリコール等が挙げられる。
【００１９】
上記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等が挙げられる。
上記ラクトンとしては、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−バレロラクトン等挙げられる。
【００２０】
上記ポリ乳酸系樹脂においてブレンドできる他のポリマーとしては、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、およびこれらの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。
【００２１】
上記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。
【００２２】
上記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サイ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等のエーテルグリコール等が挙げられる。
【００２３】
上記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等が挙げられる。
上記ラクトンとしては、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−バレロラクトン等挙げられる。
【００２４】
ポリ乳酸は従来公知の方法で合成することができる。すなわち、特開平７−３３８６１号公報、特開昭５９−９６１２３号公報、高分子討論会予稿集４４巻、3198-3199 頁に記載のような乳酸からの直接脱水縮合、または乳酸環状二量体ラクチドの開環重合によって合成することができる。開環重合では、より高分子量のものを得ることができる。
【００２５】
直接脱水縮合を行なう場合、Ｌ−乳酸、Ｄ−乳酸、ＤＬ−乳酸、またはこれらの混合物のいずれの乳酸を用いても良い。また、開環重合を行なう場合においても、Ｌ−ラクチド、Ｄ−ラクチド、ＤＬ−ラクチド、メソ−ラクチドまたはこれらの混合物のいずれのラクチドを用いても良い。
ラクチドの合成、精製および重合操作は、例えば米国特許４０５７５３７号明細書、Polymer Bulletin, 14, 491-495 (1985)、および Makromol Chem., 187, 1611-1628 (1986) 等の文献に様々に記載されている。
【００２６】
この重合反応に用いる触媒は特に限定されるものではないが、公知の乳酸重合用触媒を用いることができる。例えば、乳酸スズ、酒石酸スズ、ジカプリル酸スズ、ジラウリン酸スズ、ジパルミチン酸スズ、ジステアリン酸スズ、ジオレイン酸スズ、α−ナフトエ酸スズ、β−ナフトエ酸スズ、オクチル酸スズ等の有機スズ系化合物、粉末スズ、酸化スズ； 亜鉛末、ハロゲン化亜鉛、酸化亜鉛、有機亜鉛系化合物； テトラプロピルチタネート等のチタン系化合物； ジルコニウムイソプロポキシド等のジルコニウム系化合物； 三酸化アンチモン等のアンチモン系化合物； 酸化ビスマス(III) 等のビスマス系化合物； 酸化アルミニウム、アルミニウムイソプロポキシド等のアルミニウム化合物等を挙げることができる。これらの中でも、スズまたはスズ化合物からなる触媒が活性の点から特に好ましい。これら触媒の使用量は、一般にラクチド１００重量部に対して０．００１〜５重量部程度である。
【００２７】
重合反応は、上記触媒の存在下、触媒種によっても異なるが通常１００〜２００℃の温度で行うことができる。また、特開平７−２４７３４５号公報に記載のような２段階重合を行うことも好ましい。
【００２８】
本発明においては、ポリ乳酸中の残存ラクチド含有量は１重量％以下であることが望ましい。ラクチド含有量が１重量％以下の場合に、得られる熱可塑性樹脂本来の物性が充分発揮されるからである。
【００２９】
本発明の組成物は前記一般式（Ｉ）または一般式（II）で示されるレブリン酸化合物のうち少なくとも一種を含む。
【００３０】
前記一般式（Ｉ）においてＲ₁は水素，アルキル基またはアリール基を表す。
【００３１】
尚、Ｒ₁が水素の場合は、樹脂組成物中の未反応多価アルコールと反応してエステルを形成することで、可塑剤としての役割を果たし得るが、R₁がアルキル基，アリール基の場合、残留多価アルコールが少なくても、効果を発揮するので好ましい。この場合、残留多価アルコールは、後述するように、少ないほど良い。
【００３２】
アルキル基としては例えば、炭素総数１〜12までの置換または無置換のアルキル基が好ましい。このようなアルキル基として具体的に、メチル、エチル、プロピル、イソプロピル、ブチル、イソブチル、ペンチル、２，２−ジメチルプロピル、ヘキシル、ヘプチル、２−エチルヘキシル、オクチル、ノニル、デシル、メトキシメチル、ベンジル、ベンジルオキシメチル、ｐ−メトキシベンジルオキシメチル、（４−メトキシフェノキシ）メチル、ｔ−ブトキシメチル、ジメチルシリルオキシメチル、２−メトキシエトキシメチル、2,2,2-トリクロロエトキシメトキシメチル、アリル基等が挙げられる。
【００３３】
アリール基としてはフェニル、p-メトキシフェニル、p-メチルフェニル、p-エチルフェニル、p-エトキシフェニル、p-クロロフェニル基等が挙げられる。
【００３４】
これらのうち、エチル、プロピル、イソプロピル、ブチル、イソブチル、ペンチル、２，２−ジメチルプロピル、ヘキシル、メトキシメチル、２−エチルヘキシルが導入の容易さ、安定性、相溶性などの点から好ましい。
【００３５】
これらの化合物は、レブリン酸と、上記のアルキル基またはアリール基を有するアルコールとを脱水縮合するなどして容易に合成することができる。ここで未反応のレブリン酸やアルコールが残留しても差し支えないが、過剰に含まれるとエステル交換反応などを起こし成形物の物性を著しく損なうことがある。そのために未反応物は少ない方がよい。具体的には酸価とヒドロキシル基価の合計が５０ｍｇ−ＫＯＨ／ｇ以下であることが望ましい。
【００３６】
前記一般式（II）においてＲ₂はアルキレン基またはアリーレン基を表す。
【００３７】
アルキレン基としては例えば、炭素総数１〜１２までの置換または無置換のアルキレン基が好ましい。より具体的には、エチレン、トリメチレン、テトラメチレン、ペンタメチレン、ヘキサメチレン、２,２−ジメチルトリメチレン、ヘプタメチレン、オクタメチレン、１−イソプロピル−２，２−ジメチルトリメチレン、ノナメチレン、デカメチレンなどが挙げられる。
【００３８】
アリーレン基としてはｏ−フェニレン、ｍ−フェニレン、ｐ−フェニレンなどが挙げられる。
【００３９】
これらのうち、テトラメチレン、ペンタメチレン、ヘキサメチレン、２,２−ジメチルトリメチレンが導入の容易さ、安定性、相溶性などの点から好ましい。
【００４０】
これらの化合物も同様に、レブリン酸と、上記のアルキレン基，アリーレン基を有するアルコールとを脱水縮合するなどして容易に合成することができる。ここで未反応のレブリン酸やアルコール、モノエステルなどが残留しても差し支えないが、少ない方がよい。具体的には酸価とヒドロキシル基価の合計が５０ｍｇ−ＫＯＨ／ｇ以下であることが望ましい。
【００４１】
一般式（Ｉ）または一般式（II）で示されるレブリン酸化合物は、単独または併用して用いられるが、その合計量は、ポリ乳酸系樹脂の合計量１００重量部に対し１〜１００重量部であることが好ましく、更に好ましくは５〜７０重量部、特に好ましくは、１０〜５０重量部である。
【００４２】
本発明の組成物においては、本発明の成形品，フィルム，シート等を製造するに際して通常必要とされる、酸化防止剤、熱安定剤、光安定剤、着色剤、帯電防止剤、滑剤、難燃剤、発泡剤、充填剤、抗菌・抗カビ剤等の各種添加剤を、必要に応じて配合することもできる。
【００４３】
本発明のレブリン酸化合物や上記添加剤を配合する方法は、特に制限されるものではなく、従来公知の方法によって行うことができる。例えば、ミルロール、バンバリ−ミキサー、スーパーミキサー、単軸あるいは二軸押出機等を用いて混合混練すればよい。
【００４４】
成形品の機械的強度は成形品の使用目的によっても異なるが、一般に引張強度１５〜４０ＭＰａ、破断伸び１０〜３００％が好ましい。本発明のレブリン酸化合物を加えることにより、弾性率の低下と破断伸びの増加が起こるが、それに伴う強度低下により成形品が破損しやすくなるため、ある程度の強度が必要である。
【００４５】
本発明のポリ乳酸系樹脂に配合される前記一般式（Ｉ）、一般式（II）で示される化合物は、樹脂組成物に十分な柔軟性を与えると共に、十分な柔軟性を与え得る量を配合しても樹脂の透明性を損ねることがない。従って、この樹脂組成物から得られる成形品は、柔軟で強靭なものであり、かつ成形品の透明性の低下、滲み出しなどの問題がない。
【００４６】
本発明の成形品，フィルム，シートは、それぞれ、本発明のポリ乳酸系樹脂組成物を用いて、通常の方法により製造することができる。
【００４７】
【実施例】
以下に実施例を挙げて、本発明を具体的に説明するが、これに限定されるものではない。
【００４８】
（樹脂組成物の評価方法）
引張破断強度と引張破断伸度はJIS K7113に、曲げ弾性率はJIS K7171に従って測定した。また、ガラス転位点（Ｔｇ）はＤＳＣにより測定した。
【００４９】
（合成例（ａ））
窒素雰囲気下、還流冷却器、分水管、撹拌機、温度計を備えたフラスコにレブリン酸1509g（13mol）と2-エチルヘキサノール1862ｇ（14.3mol）、キシレン3000ｇおよびp-トルエンスルホン酸4g（0.02mol）を加え、常圧下140℃に保ち、生成水を系外に除去しながら4時間反応をおこなった。反応終了後冷却し水1000ｇを加え水洗を行った。静置分相後、水相を取り除いた後、エバポレータにてキシレンを減圧留去し、レブリン酸2エチルヘキシル2835ｇを得た。
【００５０】
【化５】

【００５１】
（合成例（ｂ））
窒素雰囲気下、還流冷却器、分水管、撹拌機、温度計を備えたフラスコにレブリン酸1509g（13mol）とイソデカノール2235g（14.3mol）、キシレン3000ｇおよびp-トルエンスルホン酸4g（0.02mol）を加え、常圧下140℃に保ち、生成水を系外に除去しながら4時間反応をおこなった。反応終了後冷却し水1000ｇを加え水洗を行った。静置分相後、水相を取り除いた後、エバポレータにてキシレンを減圧留去し、レブリン酸イソデシル3140ｇを得た。
【００５２】
【化６】

【００５３】
（合成例（ｃ））
窒素雰囲気下、還流冷却器、分水管、撹拌機、温度計を備えたフラスコにレブリン酸1974g（17mol）と１，４−ブタンジオール721g（8mol）、キシレン3000ｇおよびp-トルエンスルホン酸4g（0.02mol）をを加え、常圧下140℃に保ち、生成水を系外に除去しながら4時間反応をおこなった。反応終了後冷却し水1000ｇを加え水洗を行った。静置分相後、水相を取り除いた後、エバポレータにてキシレンを減圧留去し、ブタンジオールレブリン酸ジエステル2176ｇを得た。
【００５４】
【化７】

【００５５】
（合成例（ｄ））
窒素雰囲気下、還流冷却器、分水管、撹拌機、温度計を備えたフラスコにレブリン酸1974g（17mol）と１，６−ヘキサンジオール944g（8mol）、キシレン3000ｇおよびp-トルエンスルホン酸4g（0.02mol）を加え、常圧下140℃に保ち、生成水を系外に除去しながら4時間反応をおこなった。反応終了後冷却し水1000ｇを加え水洗を行った。静置分相後、水相を取り除いた後、エバポレータにてキシレンを減圧留去し、ヘキサンジオールレブリン酸ジエステル2388ｇを得た。
【００５６】
【化８】

【００５７】
（合成例（ｅ））
窒素雰囲気下、還流冷却器、分水管、撹拌機、温度計を備えたフラスコにレブリン酸1974g（17mol）とネオペンチルグリコール833g（8mol）、キシレン3000ｇおよびp-トルエンスルホン酸4g（0.02mol）をを加え、常圧下140℃に保ち、生成水を系外に除去しながら4時間反応をおこなった。反応終了後冷却し水1000ｇを加え水洗を行った。静置分相後、水相を取り除いた後、エバポレータにてキシレンを減圧留去し、ネオペンチルグリコールレブリン酸ジエステル2283ｇを得た。
【００５８】
【化９】

【００５９】
合成例（a）〜（e）までの物性
【００６０】
【表１】

【００６１】
実施例１〜10
ポリ乳酸と合成例（ａ）〜（ｅ）のレブリン酸化合物を、表２に示す割合で混合し、押出機（KCK製 KCK80×2-50VEX）シリンダー設定温度１６０〜２１０℃の条件にて混合混練し、本発明の樹脂組成物を製造し、ペレット化した。このペレットを４０℃で１０時間減圧乾燥した後、射出成形機（日精樹脂工業製 PS60E9ASE）を用いて１８０℃でJIS K7113の１号試験片（厚さ３ｍｍ）を作製し、本発明の成形品とした。引張試験および曲げ試験を行い、柔軟性を測定した。
【００６２】
比較例１
実施例１〜１０で用いたものと同じポリ乳酸を６０℃で１０時間減圧乾燥した後、射出成形機を用いて１９０℃でJIS K7113の２号試験片（厚さ３ｍｍ）を作製し、引張試験および曲げ試験を行い、柔軟性を測定した。
【００６３】
比較例２〜３
実施例１〜１０で用いたものと同じポリ乳酸と各可塑剤とを表３に示す割合で混合し、押出機シリンダー設定温度１６０〜２１０℃の条件にてペレット化した。このペレットを４０℃で１０時間減圧乾燥した後、射出成形機を用いて１８０℃でJIS K7113の１号試験片（厚さ３ｍｍ）を作製し、引張試験および曲げ試験を行い、柔軟性を測定した。
【００６４】
【表２】

【００６５】
【表３】

【００６６】
比較例１，２は引張破断伸度が小さく柔軟性があるとは言えなかった。比較例３では柔軟性はあるが経時で可塑剤が滲み出し外観が悪かった。実施例では引張破断伸度が大幅に向上し、曲げ弾性率が低下したことにより柔軟性が向上していることが分かった。また、実施例の中でもとくに、合成例（ｂ）および（ｄ）を添加した樹脂が引張破断伸度、曲げ弾性率から柔軟性が大幅に向上したと言える。また経時でブリードアウトすることもなく外観も良好であった。
【００６７】
【発明の効果】
本発明に係るポリ乳酸系樹脂組成物は、柔軟性を付与した組成物であり、さらには、Ｔダイ成形、インフレーション成形に適した組成物である。従来品に比べ少ない添加量で柔軟性を付与することができ、また安全性も向上する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polylactic acid resin composition and a molded product thereof. More specifically, the present invention relates to a polylactic acid resin composition having excellent flexibility and safety, and having excellent decomposability after use, and a molded product thereof.
[0002]
[Prior art]
In general, resins such as polyethylene, polypropylene, soft polyvinyl chloride, and polyethylene terephthalate are listed as resins having excellent flexibility, heat resistance, and water resistance, and are used in garbage bags, packaging bags, and the like. However, since these resins increase the amount of dust when discarded after use, and are hardly decomposed in the natural environment, they remain in the ground semi-permanently even if they are buried. In addition, the discarded plastics cause problems such as damage to the landscape and destruction of the living environment of marine life.
[0003]
On the other hand, polylactic acid and copolymers of lactic acid and other aliphatic hydroxycarboxylic acids, polyesters derived from aliphatic polyhydric alcohols and aliphatic polycarboxylic acids, etc., as thermoplastic resins and biodegradable polymers Has been developed.
[0004]
These biodegradable polymers, when placed in soil or seawater, begin to degrade in a few weeks in a moist environment and disappear in about one to several years. Furthermore, the decomposition product has the property of becoming carbon dioxide and water. In particular, polylactic acid has recently been manufactured in a large amount and at low cost by the fermentation method of L-lactic acid as a raw material, and has a fast decomposition rate in compost, resistance to mold, and odor resistance to foods. It has been expected to expand its field of use because of its excellent characteristics such as properties and coloring resistance.
[0005]
However, polylactic acid has high rigidity and is not a suitable resin for applications that require flexibility such as films and packaging materials.
[0006]
In general, as techniques for softening a resin, methods such as (1) addition of a plasticizer, (2) copolymerization, and (3) blending of soft polymers are known. However, in the methods (1) and (2), even if sufficient flexibility can be imparted, the glass transition temperature of the resin composition is lowered, and as a result, it is crystallized and hardened due to a normal environmental temperature. In the case of the method in which the physical properties are changed or the method of adding a plasticizer is used, there are problems such as bleeding out of the plasticizer. Furthermore, some plasticizers are not sufficiently safe, and in particular, there are many cases where the use as a food packaging material is limited.
[0007]
Compared with vinyl chloride resin, polylactic acid has a limited compatibility with good plasticizers, such as tributyl acetylcitrate, but the plasticizing effect on the amount added is not sufficient, and safety However, it may be limited depending on the application.
[0008]
On the other hand, in the method (3), considering biodegradability which is one of the problems, the resin to be blended is limited to a biodegradable resin having flexibility. Examples of such a resin include polybutylene succinate, polyethylene succinate, polycaprolactone and the like, which have already been disclosed in JP-A-8-245866 and JP-A-9-111107.
[0009]
However, in this method, it is necessary to add a large amount (for example, 60 parts by weight or more in the case of polybutylene succinate) in order to impart sufficient flexibility (elastic modulus is 1000 MPa or less) to the polylactic acid resin composition. As a result, the above-mentioned characteristics of polylactic acid are impaired. As described above, it has been difficult to improve the flexibility without impairing the characteristics of polylactic acid using conventional techniques.
[0010]
[Problems to be solved by the invention]
Accordingly, the object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a compound that is excellent in compatibility with the polylactic acid resin and plasticizing efficiency, and has no problems such as a decrease in transparency of the molded product and bleeding. Another object of the present invention is to provide a polylactic acid-based resin composition from which a flexible and tough molded product can be obtained.
[0011]
[Means for Solving the Problems]
As a result of intensive studies on polylactic acid, the present inventors have obtained a sufficient plasticizing effect in a small amount by using a specific compound having good compatibility with polylactic acid, and without impairing transparency. The present inventors have found a polylactic acid-based resin composition that satisfies the above-mentioned problems with excellent safety and completed the present invention. That is, the polylactic acid-based resin composition of the present invention is characterized by containing polylactic acid and at least one of the compounds represented by the following general formula (I) or general formula (II).
[0012]
[Chemical 3]

[0013]
[Formula 4]

[0014]
DETAILED DESCRIPTION OF THE INVENTION
The contents of the present invention will be described in detail below.
In the polylactic acid-based resin composition of the present invention, the polylactic acid-based resin includes a lactic acid homopolymer, a lactic acid copolymer, or a blend polymer of these and other polymers.
[0015]
The structural molar ratio L / D of the L-lactic acid unit and D-lactic acid unit in the polylactic acid-based resin may be any of 100/0 to 0/100. To obtain a high melting point, L-lactic acid or D -In order to obtain 90 mol% or more of any unit of lactic acid and a higher melting point, it is preferable to contain 95 mol% or more of either unit of L-lactic acid or D-lactic acid. In particular, a higher amount of L-lactic acid is preferable in terms of high crystallinity.
[0016]
The lactic acid copolymer is obtained by copolymerizing a lactic acid monomer or other component copolymerizable with lactide. Examples of such other components include dicarboxylic acids having two or more ester bond-forming functional groups, polyhydric alcohols, hydroxycarboxylic acids, lactones, etc., and various polyesters and various polyesters composed of these various components. Examples include ether and various polycarbonates.
[0017]
Examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid.
[0018]
Examples of the polyhydric alcohol include aromatic polyhydric alcohols such as those obtained by addition reaction of ethylene oxide with bisphenol, ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, glycerin, sorbitan, trimethylolpropane, neopentyl. Examples include aliphatic polyhydric alcohols such as glycol, ether glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol.
[0019]
Examples of the hydroxycarboxylic acid include glycolic acid and hydroxybutylcarboxylic acid.
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.
[0020]
Other polymers that can be blended in the polylactic acid-based resin include dicarboxylic acids having two or more ester bond-forming functional groups, polyhydric alcohols, hydroxycarboxylic acids, lactones, and the like, and various components thereof. Examples include various polyesters, various polyethers, and various polycarbonates.
[0021]
Examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid.
[0022]
Examples of the polyhydric alcohol include aromatic polyhydric alcohols such as those obtained by addition reaction of ethylene oxide with bisphenol, ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, glycerin, sorbitan, trimethylolpropane, neopentyl. Examples include aliphatic polyhydric alcohols such as glycol, ether glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol.
[0023]
Examples of the hydroxycarboxylic acid include glycolic acid and hydroxybutylcarboxylic acid.
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.
[0024]
Polylactic acid can be synthesized by a conventionally known method. That is, direct dehydration condensation from lactic acid or lactic acid cyclic dimer as described in JP-A-7-33861, JP-A-59-96123, Polymer Proceedings Proceedings Vol. 44, pages 3198-3199 It can be synthesized by ring-opening polymerization of lactide. In the ring-opening polymerization, a higher molecular weight can be obtained.
[0025]
When performing direct dehydration condensation, any lactic acid of L-lactic acid, D-lactic acid, DL-lactic acid, or a mixture thereof may be used. Also, in the case of carrying out ring-opening polymerization, any lactide of L-lactide, D-lactide, DL-lactide, meso-lactide or a mixture thereof may be used.
The synthesis, purification and polymerization operations of lactide are variously described in documents such as US Pat. No. 4,057,537, Polymer Bulletin, 14, 491-495 (1985), and Makromol Chem., 187, 1611-1628 (1986). Has been.
[0026]
Although the catalyst used for this polymerization reaction is not particularly limited, a known catalyst for lactic acid polymerization can be used. For example, organic tin compounds such as tin lactate, tin tartrate, dicaprylate, dilaurate, dipalmitate, tin distearate, dioleate, α-naphthoate, β-naphthoate, and octylate Zinc powder, zinc halide, zinc oxide, organic zinc compounds; titanium compounds such as tetrapropyl titanate; zirconium compounds such as zirconium isopropoxide; antimony compounds such as antimony trioxide; Examples thereof include bismuth compounds such as bismuth oxide (III); aluminum compounds such as aluminum oxide and aluminum isopropoxide. Among these, a catalyst made of tin or a tin compound is particularly preferable from the viewpoint of activity. The amount of the catalyst used is generally about 0.001 to 5 parts by weight with respect to 100 parts by weight of lactide.
[0027]
The polymerization reaction can be usually performed at a temperature of 100 to 200 ° C. in the presence of the catalyst, although it varies depending on the catalyst type. It is also preferable to carry out two-stage polymerization as described in JP-A-7-247345.
[0028]
In the present invention, the residual lactide content in the polylactic acid is desirably 1% by weight or less. This is because when the lactide content is 1% by weight or less, the original physical properties of the obtained thermoplastic resin are sufficiently exhibited.
[0029]
The composition of the present invention contains at least one levulinic acid compound represented by the general formula (I) or the general formula (II).
[0030]
In the general formula (I), R ₁ represents hydrogen, an alkyl group or an aryl group.
[0031]
When R ₁ is hydrogen, it can serve as a plasticizer by reacting with an unreacted polyhydric alcohol in the resin composition to form an ester, but R ₁ is an alkyl group or an aryl group. In this case, even if there is little residual polyhydric alcohol, the effect is exhibited, which is preferable. In this case, the less residual polyhydric alcohol, the better as will be described later.
[0032]
As the alkyl group, for example, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms is preferable. Specific examples of such alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, 2,2-dimethylpropyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, methoxymethyl, benzyl, Benzyloxymethyl, p-methoxybenzyloxymethyl, (4-methoxyphenoxy) methyl, t-butoxymethyl, dimethylsilyloxymethyl, 2-methoxyethoxymethyl, 2,2,2-trichloroethoxymethoxymethyl, allyl group, etc. Can be mentioned.
[0033]
Examples of the aryl group include phenyl, p-methoxyphenyl, p-methylphenyl, p-ethylphenyl, p-ethoxyphenyl, and p-chlorophenyl groups.
[0034]
Of these, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, 2,2-dimethylpropyl, hexyl, methoxymethyl, and 2-ethylhexyl are preferred from the viewpoint of ease of introduction, stability, compatibility, and the like.
[0035]
These compounds can be easily synthesized by dehydrating condensation of levulinic acid and the alcohol having the above alkyl group or aryl group. Here, unreacted levulinic acid or alcohol may remain, but if it is excessively contained, a transesterification reaction or the like may occur and the physical properties of the molded product may be significantly impaired. Therefore, it is better that there are few unreacted substances. Specifically, the total of the acid value and the hydroxyl group value is desirably 50 mg-KOH / g or less.
[0036]
In the general formula (II), R ₂ represents an alkylene group or an arylene group.
[0037]
As the alkylene group, for example, a substituted or unsubstituted alkylene group having 1 to 12 carbon atoms in total is preferable. More specifically, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, 2,2-dimethyltrimethylene, heptamethylene, octamethylene, 1-isopropyl-2,2-dimethyltrimethylene, nonamethylene, decamethylene, etc. Can be mentioned.
[0038]
Examples of the arylene group include o-phenylene, m-phenylene, and p-phenylene.
[0039]
Among these, tetramethylene, pentamethylene, hexamethylene, and 2,2-dimethyltrimethylene are preferable from the viewpoint of ease of introduction, stability, compatibility, and the like.
[0040]
Similarly, these compounds can also be easily synthesized by dehydration condensation of levulinic acid and the above alcohol having an alkylene group or an arylene group. Here, unreacted levulinic acid, alcohol, monoester and the like may remain, but it is preferable that the amount is less. Specifically, the total of the acid value and the hydroxyl group value is desirably 50 mg-KOH / g or less.
[0041]
The levulinic acid compound represented by the general formula (I) or the general formula (II) is used alone or in combination, and the total amount thereof is 1 to 100 parts by weight with respect to 100 parts by weight of the total amount of the polylactic acid resin. It is preferably 5 to 70 parts by weight, more preferably 10 to 50 parts by weight.
[0042]
In the composition of the present invention, an antioxidant, a heat stabilizer, a light stabilizer, a colorant, an antistatic agent, a lubricant, a difficult agent, which are usually required in producing the molded article, film, sheet, etc. of the present invention. Various additives such as a flame retardant, a foaming agent, a filler, an antibacterial / antifungal agent and the like can be blended as necessary.
[0043]
The method of blending the levulinic acid compound of the present invention and the above additives is not particularly limited, and can be performed by a conventionally known method. For example, mixing and kneading may be performed using a mill roll, a Banbury mixer, a super mixer, a single screw or a twin screw extruder, or the like.
[0044]
The mechanical strength of the molded product varies depending on the purpose of use of the molded product, but generally a tensile strength of 15 to 40 MPa and a breaking elongation of 10 to 300% are preferable. Addition of the levulinic acid compound of the present invention causes a decrease in elastic modulus and an increase in breaking elongation, but the molded product tends to be damaged due to the accompanying decrease in strength, and therefore a certain level of strength is required.
[0045]
The compound represented by the general formula (I) and the general formula (II) blended in the polylactic acid resin of the present invention is provided in an amount that provides sufficient flexibility and sufficient flexibility to the resin composition. Even if it mix | blends, the transparency of resin is not impaired. Therefore, a molded product obtained from this resin composition is flexible and tough, and there are no problems such as a decrease in transparency and bleeding of the molded product.
[0046]
The molded article, film, and sheet of the present invention can be produced by ordinary methods using the polylactic acid resin composition of the present invention.
[0047]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
[0048]
(Evaluation method of resin composition)
The tensile strength at break and tensile elongation at break were measured according to JIS K7113, and the flexural modulus was measured according to JIS K7171. The glass transition point (Tg) was measured by DSC.
[0049]
(Synthesis Example (a))
In a nitrogen atmosphere, a flask equipped with a reflux condenser, water separator, stirrer and thermometer was charged with 1509 g (13 mol) of levulinic acid, 1862 g (14.3 mol) of 2-ethylhexanol, 3000 g of xylene and 4 g of p-toluenesulfonic acid (0.02 mol). ) And kept at 140 ° C. under normal pressure, and the reaction was carried out for 4 hours while removing the generated water from the system. After completion of the reaction, the reaction mixture was cooled and 1000 g of water was added and washed with water. After the stationary phase separation, the aqueous phase was removed, and xylene was distilled off under reduced pressure using an evaporator to obtain 2835 g of 2-ethylhexyl levulinate.
[0050]
[Chemical formula 5]

[0051]
(Synthesis Example (b))
In a nitrogen atmosphere, add 1509 g (13 mol) of levulinic acid, 2235 g (14.3 mol) of isodecanol, 3000 g of xylene, and 4 g (0.02 mol) of p-toluenesulfonic acid to a flask equipped with a reflux condenser, water separator, stirrer, and thermometer. The reaction was carried out for 4 hours while maintaining the atmospheric pressure at 140 ° C. and removing the produced water out of the system. After completion of the reaction, the reaction mixture was cooled and 1000 g of water was added and washed with water. After the stationary phase separation, the aqueous phase was removed, and xylene was distilled off under reduced pressure using an evaporator to obtain 3140 g of isodecyl levulinate.
[0052]
[Chemical 6]

[0053]
(Synthesis Example (c))
In a nitrogen atmosphere, a flask equipped with a reflux condenser, a water pipe, a stirrer and a thermometer was charged with 1974 g (17 mol) of levulinic acid, 721 g (8 mol) of 1,4-butanediol, 3000 g of xylene and 4 g of p-toluenesulfonic acid (0.02). mol) was added, kept at 140 ° C. under normal pressure, and reacted for 4 hours while removing the generated water from the system. After completion of the reaction, the reaction mixture was cooled and 1000 g of water was added and washed with water. After the stationary phase separation, the aqueous phase was removed, and then xylene was distilled off under reduced pressure using an evaporator to obtain 2176 g of butanediol levulinic acid diester.
[0054]
[Chemical 7]

[0055]
(Synthesis Example (d))
In a nitrogen atmosphere, a flask equipped with a reflux condenser, a water pipe, a stirrer, and a thermometer was charged with 1974 g (17 mol) of levulinic acid, 944 g (8 mol) of 1,6-hexanediol, 3000 g of xylene and 4 g of p-toluenesulfonic acid (0.02). mol) was added, kept at 140 ° C. under normal pressure, and reacted for 4 hours while removing the generated water from the system. After completion of the reaction, the reaction mixture was cooled and 1000 g of water was added and washed with water. After the stationary phase separation, the aqueous phase was removed, and xylene was distilled off under reduced pressure using an evaporator to obtain 2388 g of hexanediol levulinic acid diester.
[0056]
[Chemical 8]

[0057]
(Synthesis example (e))
In a nitrogen atmosphere, add 1974 g (17 mol) of levulinic acid, 833 g (8 mol) of neopentyl glycol, 3000 g of xylene, and 4 g of p-toluenesulfonic acid (0.02 mol) to a flask equipped with a reflux condenser, water separator, stirrer, and thermometer. Was maintained at 140 ° C. under normal pressure, and the reaction was carried out for 4 hours while removing the generated water from the system. After completion of the reaction, the reaction mixture was cooled and 1000 g of water was added and washed with water. After the stationary phase separation, the aqueous phase was removed, and then xylene was distilled off under reduced pressure using an evaporator to obtain 2283 g of neopentyl glycol levulinic acid diester.
[0058]
[Chemical 9]

[0059]
Physical properties of synthesis examples (a) to (e)
[Table 1]

[0061]
Examples 1-10
Polylactic acid and the levulinic acid compounds of Synthesis Examples (a) to (e) are mixed in the proportions shown in Table 2, and mixed under conditions of an extruder (KCK KCK80 × 2-50VEX) cylinder set temperature 160 to 210 ° C. By kneading, the resin composition of the present invention was produced and pelletized. This pellet was dried under reduced pressure at 40 ° C. for 10 hours, and then a JIS K7113 No. 1 test piece (thickness 3 mm) was produced at 180 ° C. using an injection molding machine (PS60E9ASE manufactured by Nissei Plastic Industries). It was. Tensile and bending tests were performed to measure flexibility.
[0062]
Comparative Example 1
The same polylactic acid as that used in Examples 1 to 10 was dried under reduced pressure at 60 ° C. for 10 hours, and then a JIS K7113 No. 2 test piece (thickness 3 mm) was prepared at 190 ° C. using an injection molding machine. Tests and bending tests were performed to measure flexibility.
[0063]
Comparative Examples 2-3
The same polylactic acid as used in Examples 1 to 10 and each plasticizer were mixed in the ratio shown in Table 3, and pelletized under the conditions of an extruder cylinder set temperature of 160 to 210 ° C. This pellet was dried under reduced pressure at 40 ° C. for 10 hours, then a JIS K7113 No. 1 test piece (thickness 3 mm) was prepared at 180 ° C. using an injection molding machine, and subjected to a tensile test and a bending test to measure flexibility. did.
[0064]
[Table 2]

[0065]
[Table 3]

[0066]
Comparative Examples 1 and 2 were small in tensile elongation at break and could not be said to be flexible. In Comparative Example 3, there was flexibility, but the plasticizer oozed out over time and the appearance was poor. In the examples, it was found that the tensile elongation at break was greatly improved, and the flexibility was improved due to the decrease in flexural modulus. Further, it can be said that, among the examples, the resin added with the synthesis examples (b) and (d) has greatly improved flexibility from the tensile elongation at break and the flexural modulus. Also, the appearance was good without bleeding out over time.
[0067]
【The invention's effect】
The polylactic acid-based resin composition according to the present invention is a composition imparted with flexibility, and is a composition suitable for T-die molding and inflation molding. Flexibility can be imparted with a smaller amount of addition than conventional products, and safety is also improved.

Claims (5)

A polylactic acid resin composition comprising at least one compound represented by the following general formula (I) or general formula (II).

The polylactic acid-based resin composition according to claim 1, comprising 1 to 100 parts by weight of at least one of the compounds represented by the general formula (I) or (II) with respect to 100 parts by weight of the polylactic acid-based resin. A film comprising the polylactic acid resin composition according to claim 1. A sheet comprising the polylactic acid resin composition according to claim 1. A molded article comprising the polylactic acid-based resin composition according to claim 1.