JP4205404B2 - Polylactic acid resin composition, molded article, and plasticizer for polyester resin - Google Patents

Description

【００１６】
（式中、Ｒ₁は炭素数３〜１０の３価の基であり、Ｒ₂、Ｒ₃はそれぞれ炭素数２〜１０のアシル基である。）
【００１７】
【化８】

【００１８】
（式中、Ｒ₄は炭素数４〜１０の４価の基であり、Ｒ₅、Ｒ₆、Ｒ₇はそれぞれ炭素数２〜１０のアシル基である。）
【００１９】
また、本発明は上記ポリ乳酸系樹脂組成物を含む成形品、並びに上記一般式（１）又は（２）で示される化合物のうちの少なくとも一種を含むことを特徴とするポリエステル樹脂用可塑剤を提供する。
【００２０】
【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。
【００２１】
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、又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。
【００２２】
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−乳酸のいずれかの単位を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−乳酸のいずれかの単位を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。
【００２３】
上記ポリ乳酸系樹脂における相対粘度（ηｒｅｌ）は２．５〜４．２であることが成形性の面から好ましく、特に２．７〜４．０であることが好ましい。
【００２４】
乳酸コポリマーは、乳酸モノマー又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、ラクトンなど、及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などが挙げられる。
【００２５】
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、イソフタル酸などが挙げられる。
【００２６】
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などのエーテルグリコールなどが挙げられる。
【００２７】
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などが挙げられる。
【００２８】
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−又はγ−ブチロラクトン、ピバロラクトン、δ−バレロラクトンなど挙げられる。
【００２９】
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、ラクトンなど、及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などが挙げられる。
【００３０】
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、イソフタル酸などが挙げられる。
【００３１】
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などのエーテルグリコールなどが挙げられる。
【００３２】
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などが挙げられる。
【００３３】
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−又はγ−ブチロラクトン、ピバロラクトン、δ−バレロラクトンなど挙げられる。
【００３４】
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、又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。
【００３５】
直接脱水縮合を行なう場合、Ｌ−乳酸、Ｄ−乳酸、ＤＬ−乳酸、又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−ラクチド又はこれらの混合物のいずれのラクチドを用いても良い。
【００３６】
ラクチドの合成、精製及び重合操作は、例えば米国特許４０５７５３７号明細書、Polymer Bulletin, 14, 491-495(1985)、及びMakromol Chem., 187, 1611-1628(1986)などの文献に様々に記載されている。
【００３７】
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、オクチル酸スズなど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などのチタン系化合物；ジルコニウムイソプロポキシドなどのジルコニウム系化合物；三酸化アンチモンなどのアンチモン系化合物；酸化ビスマス（ＩＩＩ）など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などのアルミニウム化合物などを挙げることができる。これらの中でも、スズ又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。
【００３８】
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。
【００３９】
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。
【００４０】
本発明においては、ポリ乳酸中の残存モノマー（ラクチド）含有量は１重量％以下であることが望ましい。モノマー（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。
【００４１】
本発明のポリ乳酸樹脂組成物は、下記一般式（１）又は（２）で示される化合物のうちの少なくとも一種を含むものである。
【００４２】
【化９】

【００４３】
一般式（１）において、Ｒ₁は炭素数３〜１０の３価の基であり、好ましくは窒素、酸素及び硫黄原子から選択されるヘテロ原子を含んでいてもよい、飽和又は不飽和の脂肪族、脂環式、又は芳香族の、炭素数３〜１０の３価の炭化水素基である。このような基として、例えば、下記式
【００４４】
【化１０】

【００４５】
の基などが挙げられる。この中でも、Ｒ₁が下記式（３）
【００４６】
【化１１】

【００４７】
で示される基のいずれかであるのがより好ましい。
【００４８】
一般式（１）で示される化合物においては、化合物中にレブリノイル基があることで、ポリ乳酸系樹脂との相溶性及び化合物の耐熱性が向上する。
【００４９】
また、Ｒ₂、Ｒ₃はそれぞれに炭素数２〜１０のアシル基である。本発明において、炭素数２〜１０のアシル基としては、炭素数２〜１０の、−Ｏ−又は−（Ｃ＝Ｏ）−を含んでいてもよいアシル基、特に−Ｏ−又は−（Ｃ＝Ｏ）−を含んでいてもよい、炭素数２〜１０の、アルキルカルボニル（アセチル、プロピオニル、ブチリル、イソブチリル、２−メチルブチリル、２−エチルブチリル、３，３−ジメチルブチリル、ペンタノイル、４−メチルペンタノイル、ヘキサノイル、２−メチルヘキサノイル、２−エチルヘキサノイル、ヘプタノイル、オクタノイル、ノナノイル、デカノイル、イソバレリル、ピバロイルなどの、飽和カルボン酸から誘導されるアシル基；メトキシアセチル、メトキシプロピオニル、エトキシアセチルなどの、−Ｏ−を含むアシル基；レブリノイル、ピルビノイル、４−アセチルブチリノイル、２−オキソペンタノイル、７−オキソノナノイルなどの、−ＣＯ−を含むアシル基など）；シクロアルキルカルボニル（シクロプロピルカルボニル、シクロブチルカルボニルなど）；アリールカルボニル（ベンゾイルなど）；ヘテロアリールカルボニル（ピリジルカルボニル、フロイルなど）、特に好ましくはレブリノイル基を挙げることができる。式（１）の化合物においては、Ｒ₂、Ｒ₃が全てレブリノイル基であるとさらに化合物の耐熱性が向上するので好ましい。レブリノイル基の数が多いほど、ポリ乳酸系樹脂との相溶性が向上し、ブリードアウトが防止される傾向にある。また、この化合物添加による樹脂の耐熱性への影響が少ない。
【００５０】
【化１２】

【００５１】
一般式（２）において、Ｒ₄は炭素数４〜１０の４価の基であり、好ましくは炭素数４〜１０の４価の、飽和又は不飽和の脂肪族炭化水素基である。例えば、下記式
【００５２】
【化１３】

【００５３】
で示される、炭素数４〜８の４価の、直鎖又は分岐鎖状のアルカンテトライル基などが挙げられる。この中でも、Ｒ₄が下記式（４）
【００５４】
【化１４】

【００５５】
で示される基のいずれかであることがより好ましい。
【００５６】
一般式（２）で示される化合物においては、化合物中にレブリノイル基があることで、ポリ乳酸系樹脂との相溶性及び化合物の耐熱性が向上する。
【００５７】
また、Ｒ₅、Ｒ₆、Ｒ₇はそれぞれに炭素数２〜１０のアシル基である。本発明において、炭素数２〜１０のアシル基としては、炭素数２〜１０の、−Ｏ−又は−（Ｃ＝Ｏ）−を含んでいてもよいアシル基、特に−Ｏ−又は−（Ｃ＝Ｏ）−を含んでいてもよい、炭素数２〜１０の、アルキルカルボニル（アセチル、プロピオニル、ブチリル、イソブチリル、２−メチルブチリル、２−エチルブチリル、３，３−ジメチルブチリル、ペンタノイル、４−メチルペンタノイル、ヘキサノイル、２−メチルヘキサノイル、２−エチルヘキサノイル、ヘプタノイル、オクタノイル、ノナノイル、デカノイル、イソバレリル、ピバロイルなどの、飽和カルボン酸から誘導されるアシル基；メトキシアセチル、メトキシプロピオニル、エトキシアセチルなどの、−Ｏ−を含むアシル基；レブリノイル、ピルビノイル、４−アセチルブチリノイル、２−オキソペンタノイル、７−オキソノナノイルなどの、−ＣＯ−を含むアシル基など）；シクロアルキルカルボニル（シクロプロピルカルボニル、シクロブチルカルボニルなど）；アリールカルボニル（ベンゾイルなど）；ヘテロアリールカルボニル（ピリジルカルボニル、フロイルなど）、特に好ましくはレブリノイル基を挙げることができる。本発明の式（２）の化合物においては、Ｒ₅、Ｒ₆、Ｒ₇が全てレブリノイル基であるとさらに化合物の耐熱性が向上する。レブリノイル基の数が多いほど、ポリ乳酸系樹脂との相溶性が向上し、ブリードアウトが防止される傾向にある。また、この化合物添加による樹脂の耐熱性への影響が少ない。
【００５８】
前記一般式（１）又は（２）で示される化合物は、多価アルコールと、レブリン酸及びその他の脂肪酸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品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価の合計が３０mgＫＯＨ／g以下であることが望ましい。好ましくは、２０mgＫＯＨ／g以下、さらに好ましくは、１０mgＫＯＨ／g以下である。
【００５９】
一般式（１）又は（２）で示される化合物は、１種を単独で又は２種以上を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。好ましくは５〜７０重量部、より好ましくは１０〜５０重量部である。
【００６０】
本発明の成形品は、成形体、フィルム、シート、繊維を含む成形品を表し、これら成形品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・抗カビ剤などの各種添加剤を、必要に応じて配合することもできる。
【００６１】
本発明の可塑剤や上記添加剤をポリ乳酸系樹脂と混合する方法には、特に制限はなく、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、バンバリーミキサー、スーパーミキサー、単軸あるいは二軸押出機などを用いて混合混練すればよい。
【００６２】
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。前記一般式（１）又は（２）で示される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。
【００６３】
本発明のポリ乳酸系樹脂に配合される前記一般式（１）又は（２）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、このポリ乳酸系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、ブリードアウトなどの問題がない。
【００６４】
本発明の成形品（成形体、フィルム、シートや繊維）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。
【００６５】
また本発明に用いられる前記一般式（１）又は（２）の化合物は、ポリエステル樹脂用の可塑剤として有用である。
【００６６】
【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、本発明はこれの実施例により何ら限定されるものではない。
【００６７】
（分析方法）
＜酸価及びヒドロキシル価＞
合成例で得られた化合物の酸価及びヒドロキシル価は、ＪＩＳ Ｋ ００７０（１９９２）に従って測定した。
【００６８】
＜ポリ乳酸中の残存モノマー含有量＞
試料を濃度１０mg／mLとなるようクロロホルムに溶解させ、クロロホルムを溶媒としてＧＰＣ分析を行い、ポリスチレン換算で分子量１０００以下の成分割合から、残存するモノマー含有量（重量％）を算出した
【００６９】
＜樹脂の相対粘度：ηｒｅｌ＞
フェノール／テトラクロロエタン＝６０／４０（質量比）の混合溶媒に試料を１ｇ／ｄＬの濃度になるように溶解し、２０℃でウベローデ粘度管を用いて相対粘度を測定した。
【００７０】
＜Ｌ−体の測定＞
ポリマーを加水分解させ、１．０Ｎ（０．０４ｇ／ml）メタノール性水酸化ナトリウム溶液を溶媒として高速液体クロマトグラフィー（ＨＰＬＣ：島津製 ＬＣ１０ＡＤ型）を使ってＬ−体の比率を求めた。
【００７１】
（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 Ｋ ７１１３（１９９５）に、曲げ弾性率はＪＩＳ Ｋ ７１７１（１９９４）に従って測定した。ガラス転移点（Ｔｇ）はＤＳＣ（島津製作所製 ＤＳＣ−５０）により測定した。また、試験片を室温で放置した５日後の状態を目視で判断し、下記の４段階で評価した。
◎：透明
○：若干濁っているがほとんど透明
△：白濁しているが透けている
×：白濁し、不透明
【００７２】
（使用した樹脂）
Ｌ−体比率９５．５モル％、相対粘度（ηｒｅｌ）３．９５、モノマー含有量０．３重量％のポリ乳酸を使用した。
【００７３】
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、グリセリン９２ｇ（１mol）、レブリン酸１１６ｇ（１mol）、トルエン３００ｇ、ｐ−トルエンスルホン酸１．９ｇ（０．０１mol）を加え、常圧下１１５℃に保ち、生成水を系外に除去しながら３時間反応させた。次いで、酢酸カリウム１．９６ｇ（０．０２mol）を加えた後、無水酢酸２０４ｇ（２mol）を加えて１００℃で４時間反応させた。反応終了後冷却し、水３００ｇを加え水洗した。静置分相し、水相を取り除いた後、エバポレータにてトルエンを減圧留去し、グリセリンモノレブリネートジアセテート２５２．６ｇを得た。この化合物の酸価とヒドロキシル価を表１に示す。
【００７４】
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グリセリン９２ｇ（１mol）、レブリン酸３４８ｇ（３mol）、トルエン３００ｇ、ｐ−トルエンスルホン酸１．９ｇ（０．０１mol）を加え、常圧下１１５℃に保ち、生成水を系外に除去しながら６時間反応させた。反応終了後冷却し、水３００ｇを加え水洗した。静置分相し、水相を取り除いた後、エバポレータにてトルエンを減圧留去し、グリセリントリレブリネート３６４．２ｇを得た。この化合物の酸価とヒドロキシル価を表１に示す。
【００７５】
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トリメチロールプロパン１３４（１mol）、レブリン酸３４８ｇ（３mol）、トルエン５００ｇ、ｐ−トルエンスルホン酸１．９ｇ（０．０１mol）を加え、常圧下１１５℃に保ち、生成水を系外に除去しながら６時間反応させた。反応終了後冷却し、水５００ｇを加え水洗した。静置分相し、水相を取り除いた後、エバポレータにてトルエンを減圧留去し、トリメチロールプロパントリレブリネート３９６．８ｇを得た。この化合物の酸価とヒドロキシル価を表１に示す。
【００７６】
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ペンタエリスリトール１３６ｇ（１mol）、レブリン酸１１６ｇ（１mol）、トルエン５００ｇ、ｐ−トルエンスルホン酸１．９ｇ（０．０１mol）を加え、常圧下１１５℃に保ち、生成水を系外に除去しながら４時間反応させた。次いで、酢酸カリウム１．９６ｇ（０．０２mol）を加え、さらに無水酢酸３０６ｇ（３mol）を加えた後、１００℃で４時間反応させた。反応終了後冷却し、水５００ｇを加え水洗した。静置分相し、水相を取り除いた後、エバポレータにてトルエンを減圧留去し、ペンタエリスリトールモノレブリネートトリアセテート３３６．５ｇを得た。この化合物の酸価とヒドロキシル価を表１に示す。
【００７７】
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ペンタエリスリトール１３６ｇ（１mol）、レブリン酸４６４ｇ（４mol）、トルエン５００ｇ、ｐ−トルエンスルホン酸１．９ｇ（０．０１mol）を加え、常圧下１１５℃に保ち、生成水を系外に除去しながら６時間反応させた。反応終了後冷却し、水５００ｇを加え水洗した。静置分相し、水相を取り除いた後、エバポレータにてトルエンを減圧留去し、ペンタエリスリトールテトラレブリネート５０７．４ｇを得た。この化合物の酸価とヒドロキシル価を表１に示す。
【００７８】
合成例（ｆ）
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エリスリトール１２２ｇ（１mol）、レブリン酸４６４ｇ（４mol）、トルエン５００ｇ、ｐ−トルエンスルホン酸１．９ｇ（０．０１mol）を加え、常圧下１１５℃に保ち、生成水を系外に除去しながら６時間反応させた。反応終了後冷却し、水５００ｇを加え水洗した。静置分相し、水相を取り除いた後、エバポレータにてトルエンを減圧留去し、ペンタエリスリトールテトラレブリネート４９２．４ｇを得た。この化合物の酸価とヒドロキシル価を表１に示す。
【００７９】
【表１】

【００８０】
実施例１〜１２
ポリ乳酸と合成例（ａ）〜（ｆ）で得られた化合物を、表２に示す割合で混合し、押出機（ＫＣＫ製 ＫＣＫ８０×２−５０ＶＥＸ）で、シリンダー設定温度１６０〜２１０℃の条件にて混合混練し、本発明のポリ乳酸系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 Ｋ ７１１３の１号試験片（厚さ３mm）及びＪＩＳ Ｋ ７１７１の標準試験片を作製し、引張試験及び曲げ試験を行い、柔軟性を測定した。
【００８１】
比較例１
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 Ｋ ７１１３の１号試験片（厚さ３mm）及びＪＩＳ Ｋ ７１７１の標準試験片を作製し、引張試験及び曲げ試験を行い、柔軟性を測定した。
【００８２】
比較例２〜４
ポリ乳酸と表３に示す可塑剤とを各割合で混合し、押出機で、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 Ｋ ７１１３の１号試験片（厚さ３mm）及びＪＩＳ Ｋ ７１７１の標準試験片を作製し、引張試験及び曲げ試験を行い、柔軟性を測定した。
【００８３】
【表２】

【００８４】
【表３】

【００８５】
比較例１、２は引張破断伸度が小さく柔軟性がなかった。比較例３、４では柔軟性はあるが、経時で可塑剤がブリードアウトし外観が悪くなった。
【００８６】
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、実施例の中でも特に、合成例（ａ）及び（ｂ）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ている。また経時でブリードアウトすることもなく外観も透明で良好であった。
【００８７】
【発明の効果】
本発明に係るポリ乳酸系樹脂組成物を用いることで柔軟性及び透明性、安全性、生分解性に優れた成形品が得られる。[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a polylactic acid resin composition, a molded product thereof, andpolyesterThe present invention relates to a plasticizer for resin. More specifically, it is excellent in flexibility and safety, and further after use, a polylactic acid resin composition excellent in degradability, and a molded product thereof, andpolyesterThe present invention relates to a plasticizer for resin.
[0002]
[Prior art]
In general, resins having excellent flexibility, heat resistance, and water resistance include resins such as polyethylene, polypropylene, soft polyvinyl chloride, and polyethylene terephthalate, and are used in garbage bags and packaging bags. 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]
In contrast, polymers that are biodegradable with thermoplastic resins include polylactic acid, copolymers of lactic acid and other aliphatic hydroxycarboxylic acids, polyesters derived from aliphatic polyhydric alcohols and aliphatic polycarboxylic acids, etc. 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 produced 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 fields of use because of its excellent characteristics such as colorability and color resistance.
[0005]
However, polylactic acid has a high rigidity, and it is difficult to say that it is an appropriate resin for applications that require flexibility such as films and packaging materials.
[0006]
In general, as a technique 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 by 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]
Polylactic acid has a limited compatible plasticizer as compared with vinyl chloride resin, and examples thereof include tributyl acetylcitrate. (For example, refer to Patent Document 1). However, it cannot be said that the plasticizing effect with respect to the added amount is sufficient, and the safety 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. (For example, see Patent Documents 2 and 3)
[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.
[0010]
Moreover, although there exists an example (for example, refer patent document 4) which uses glycerol diacetomonocaprylate as a plasticizer, heat resistance is inadequate and a use will be limited.
As described above, it has been difficult in the prior art to improve flexibility without impairing the characteristics of polylactic acid.
[0011]
[Patent Document 1]
Japanese Patent Laid-Open No. 8-034913
[Patent Document 2]
JP-A-8-245866
[Patent Document 3]
JP-A-9-111107
[Patent Document 4]
JP 2002-060604 A
[0012]
[Problems to be solved by the invention]
  Therefore, 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 out. A polylactic acid-based resin composition containing a flexible and tough molded product, a molded product containing the composition, andpolyesterThe object is to provide a plasticizer for resin.
[0013]
[Means for Solving the Problems]
As a result of intensive studies on the polylactic acid resin, the present inventors have found that the specific compound has good compatibility with the polylactic acid resin and has a sufficient plasticizing effect even in a small amount. As a result, it was found that a polylactic acid-based resin composition satisfying the above-mentioned problems without sacrificing transparency and excellent in safety was obtained, and the present invention was completed.
[0014]
  That is, the present invention relates to a polylactic acid resin and at least one of the compounds represented by the following general formula (1) or (2)., 1 to 100 parts by weight per 100 parts by weight of the polylactic acid resinA polylactic acid-based resin composition is provided.
[0015]
[Chemical 7]

[0016]
(Wherein R₁Is a trivalent group having 3 to 10 carbon atoms and R₂, R_ThreeAre each an acyl group having 2 to 10 carbon atoms. )
[0017]
[Chemical 8]

[0018]
(Wherein R_FourIs a tetravalent group having 4 to 10 carbon atoms, and R_Five, R₆, R₇Are each an acyl group having 2 to 10 carbon atoms. )
[0019]
  Moreover, this invention contains at least 1 type of the molded article containing the said polylactic acid-type resin composition, and the compound shown by the said General formula (1) or (2), It is characterized by the above-mentioned.polyesterA plasticizer for resin is provided.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The contents of the present invention will be described in detail below.
[0021]
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.
[0022]
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 any 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.
[0023]
The relative viscosity (ηrel) in the polylactic acid-based resin is preferably 2.5 to 4.2 from the viewpoint of moldability, and particularly preferably 2.7 to 4.0.
[0024]
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, and the like, and various polyesters and various polyesters composed of these various components. Examples include ether and various polycarbonates.
[0025]
Examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid.
[0026]
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.
[0027]
Examples of the hydroxycarboxylic acid include glycolic acid and hydroxybutylcarboxylic acid.
[0028]
Examples of the lactone include glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, and δ-valerolactone.
[0029]
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.
[0030]
Examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid.
[0031]
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.
[0032]
Examples of the hydroxycarboxylic acid include glycolic acid and hydroxybutylcarboxylic acid.
[0033]
Examples of the lactone include glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, and δ-valerolactone.
[0034]
Polylactic acid can be synthesized by a conventionally known method. That is, direct dehydration condensation from lactic acid or lactic acid cyclic dimer lactide as described in JP-A-7-33861, JP-A-59-96123, Polymer Science Society Proceedings Vol. 44, 3198-3199. Can be synthesized by ring-opening polymerization. In the ring-opening polymerization, a higher molecular weight can be obtained.
[0035]
When direct dehydration condensation is performed, 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.
[0036]
The synthesis, purification and polymerization operations of lactide are variously described in the literature such as US Pat. No. 4,057,537, Polymer Bulletin, 14, 491-495 (1985), and Makromol Chem., 187, 1611-1628 (1986). Has been.
[0037]
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, octylate Tin powder, tin oxide; 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 active.
Particularly preferred.
[0038]
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.
[0039]
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.
[0040]
In the present invention, the residual monomer (lactide) content in the polylactic acid is desirably 1% by weight or less. This is because when the monomer (lactide) content is 1% by weight or less, the original properties of the obtained thermoplastic resin are sufficiently exhibited.
[0041]
The polylactic acid resin composition of the present invention contains at least one of the compounds represented by the following general formula (1) or (2).
[0042]
[Chemical 9]

[0043]
In the general formula (1), R₁Is a trivalent group having 3 to 10 carbon atoms, preferably a saturated or unsaturated aliphatic, alicyclic or aromatic group which may contain a heteroatom selected from nitrogen, oxygen and sulfur atoms These are trivalent hydrocarbon groups having 3 to 10 carbon atoms. As such a group, for example, the following formula
[0044]
[Chemical Formula 10]

[0045]
And the like. Among these, R₁Is the following formula (3)
[0046]
Embedded image

[0047]
Is more preferably any one of the groups represented by
[0048]
In the compound represented by the general formula (1), the levulinoyl group in the compound improves the compatibility with the polylactic acid resin and the heat resistance of the compound.
[0049]
R₂, R_ThreeAre acyl groups having 2 to 10 carbon atoms. In the present invention, the acyl group having 2 to 10 carbon atoms is an acyl group having 2 to 10 carbon atoms which may contain —O— or — (C═O) —, in particular —O— or — (C ═O) —, which may contain an alkylcarbonyl having 2 to 10 carbon atoms (acetyl, propionyl, butyryl, isobutyryl, 2-methylbutyryl, 2-ethylbutyryl, 3,3-dimethylbutyryl, pentanoyl, 4-methyl) Acyl groups derived from saturated carboxylic acids such as pentanoyl, hexanoyl, 2-methylhexanoyl, 2-ethylhexanoyl, heptanoyl, octanoyl, nonanoyl, decanoyl, isovaleryl, pivaloyl; methoxyacetyl, methoxypropionyl, ethoxyacetyl, etc. An acyl group containing -O-; levulinoyl, pyruvinoyl, 4-acetyl Butylinoyl, 2-oxopentanoyl, 7-oxononanoyl, etc., including -CO- containing acyl groups); cycloalkylcarbonyl (cyclopropylcarbonyl, cyclobutylcarbonyl, etc.); arylcarbonyl (benzoyl, etc.); heteroarylcarbonyl (pyridyl) Carbonyl, furoyl, etc.), particularly preferably a levulinoyl group. In the compound of formula (1), R₂, R_ThreeIs a levulinoyl group because the heat resistance of the compound is further improved. The greater the number of levulinoyl groups, the better the compatibility with the polylactic acid resin and the tendency to prevent bleed out. In addition, the addition of this compound has little effect on the heat resistance of the resin.
[0050]
Embedded image

[0051]
In the general formula (2), R_FourIs a tetravalent group having 4 to 10 carbon atoms, preferably a tetravalent saturated or unsaturated aliphatic hydrocarbon group having 4 to 10 carbon atoms. For example, the following formula
[0052]
Embedded image

[0053]
And a tetravalent, linear or branched alkanetetrayl group having 4 to 8 carbon atoms and the like. Among these, R_FourIs the following formula (4)
[0054]
Embedded image

[0055]
Is more preferably any one of the groups represented by
[0056]
In the compound represented by the general formula (2), the levulinoyl group in the compound improves the compatibility with the polylactic acid resin and the heat resistance of the compound.
[0057]
R_Five, R₆, R₇Are acyl groups having 2 to 10 carbon atoms. In the present invention, the acyl group having 2 to 10 carbon atoms is an acyl group having 2 to 10 carbon atoms which may contain —O— or — (C═O) —, in particular —O— or — (C ═O) —, which may contain an alkylcarbonyl having 2 to 10 carbon atoms (acetyl, propionyl, butyryl, isobutyryl, 2-methylbutyryl, 2-ethylbutyryl, 3,3-dimethylbutyryl, pentanoyl, 4-methyl) Acyl groups derived from saturated carboxylic acids such as pentanoyl, hexanoyl, 2-methylhexanoyl, 2-ethylhexanoyl, heptanoyl, octanoyl, nonanoyl, decanoyl, isovaleryl, pivaloyl; methoxyacetyl, methoxypropionyl, ethoxyacetyl, etc. An acyl group containing -O-; levulinoyl, pyruvinoyl, 4-acetyl Butylinoyl, 2-oxopentanoyl, 7-oxononanoyl, etc., including -CO- containing acyl groups); cycloalkylcarbonyl (cyclopropylcarbonyl, cyclobutylcarbonyl, etc.); arylcarbonyl (benzoyl, etc.); heteroarylcarbonyl (pyridyl) Carbonyl, furoyl, etc.), particularly preferably a levulinoyl group. In the compound of the formula (2) of the present invention, R_Five, R₆, R₇When all are levulinoyl groups, the heat resistance of the compound is further improved. The greater the number of levulinoyl groups, the better the compatibility with the polylactic acid resin and the tendency to prevent bleed out. In addition, the addition of this compound has little effect on the heat resistance of the resin.
[0058]
The compound represented by the general formula (1) or (2) can be easily synthesized by dehydration condensation of a polyhydric alcohol, levulinic acid and other fatty acids. Here, unreacted 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, it is desirable that the sum of the acid value and the hydroxyl value is 30 mg KOH / g or less. Preferably, it is 20 mgKOH / g or less, More preferably, it is 10 mgKOH / g or less.
[0059]
  The compounds represented by the general formula (1) or (2) are used singly or in combination of two or more, but the total amount is 1 with respect to 100 parts by weight of the total amount of the polylactic acid resin. ~ 100 parts by weight. GoodPreferably 5 to 70 parts by weight,ThanPreferably it is 10-50 weight part.
[0060]
The molded product of the present invention represents a molded product including a molded product, a film, a sheet, and a fiber, and is usually required in manufacturing these molded products, an antioxidant, a heat stabilizer, a light stabilizer, a colorant, Various additives such as an antistatic agent, a lubricant, a flame retardant, a foaming agent, a filler, an antibacterial / antifungal agent and the like can be blended as necessary.
[0061]
The method for mixing the plasticizer of the present invention and the above additives with the polylactic acid resin 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, and the like.
[0062]
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. By adding the compound represented by the general formula (1) or (2), the modulus of elasticity and the elongation at break increase, but the molded product is easily damaged by the accompanying strength reduction, so that some strength is obtained. is necessary.
[0063]
The compound represented by the general formula (1) or (2) blended in the polylactic acid-based resin of the present invention is blended in an amount capable of imparting sufficient flexibility to the resin composition. However, the transparency of the resin is not impaired. Therefore, a molded product obtained from this polylactic acid-based resin composition is flexible and tough, and there are no problems such as a decrease in transparency of the molded product and bleeding out.
[0064]
The molded article (molded article, film, sheet or fiber) of the present invention can be produced by a usual method using the polylactic acid resin composition of the present invention.
[0065]
  The compound of the general formula (1) or (2) used in the present invention ispolyesterUseful as a plasticizer for resins.
[0066]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples.
[0067]
(Analysis method)
<Acid value and hydroxyl value>
The acid value and hydroxyl value of the compound obtained in the synthesis example were measured according to JIS K 0070 (1992).
[0068]
<Residual monomer content in polylactic acid>
The sample was dissolved in chloroform to a concentration of 10 mg / mL, GPC analysis was performed using chloroform as a solvent, and the residual monomer content (wt%) was calculated from the component ratio of molecular weight 1000 or less in terms of polystyrene.
[0069]
<Relative viscosity of resin: ηrel>
The sample was dissolved in a mixed solvent of phenol / tetrachloroethane = 60/40 (mass ratio) to a concentration of 1 g / dL, and the relative viscosity was measured at 20 ° C. using an Ubbelohde viscometer.
[0070]
<Measurement of L-body>
The polymer was hydrolyzed, and the ratio of L-isomer was determined using high-performance liquid chromatography (HPLC: LC10AD, manufactured by Shimadzu Corporation) using 1.0N (0.04 g / ml) methanolic sodium hydroxide solution as a solvent.
[0071]
(Evaluation method of resin composition)
The tensile strength at break and tensile elongation at break were measured according to JIS K 7113 (1995), and the flexural modulus was measured according to JIS K 7171 (1994). The glass transition point (Tg) was measured by DSC (DSC-50, manufactured by Shimadzu Corporation). Moreover, the state after 5 days which left the test piece at room temperature was judged visually, and evaluated according to the following 4 levels.
A: Transparent
○: Slightly cloudy but almost transparent
Δ: Cloudy but transparent
×: cloudy and opaque
[0072]
(Resin used)
Polylactic acid having an L-isomer ratio of 95.5 mol%, a relative viscosity (ηrel) of 3.95, and a monomer content of 0.3% by weight was used.
[0073]
Synthesis example (a)
Under a nitrogen atmosphere, in a flask equipped with a reflux condenser, a water separator, a stirrer, and a thermometer, glycerin 92 g (1 mol), levulinic acid 116 g (1 mol), toluene 300 g, p-toluenesulfonic acid 1.9 g (0.01 mol) ) And maintained at 115 ° C. under normal pressure, and reacted for 3 hours while removing generated water out of the system. Next, 1.96 g (0.02 mol) of potassium acetate was added, 204 g (2 mol) of acetic anhydride was added, and the mixture was reacted at 100 ° C. for 4 hours. After completion of the reaction, the reaction mixture was cooled, and 300 g of water was added and washed with water. After stationary phase separation and removal of the aqueous phase, toluene was distilled off under reduced pressure using an evaporator to obtain 252.6 g of glycerin monolevulinate diacetate. The acid value and hydroxyl value of this compound are shown in Table 1.
[0074]
Synthesis example (b)
Under a nitrogen atmosphere, in a flask equipped with a reflux condenser, a water separator, a stirrer, and a thermometer, 92 g (1 mol) of glycerin, 348 g (3 mol) of levulinic acid, 300 g of toluene, 1.9 g (0.01 mol) of p-toluenesulfonic acid Was maintained at 115 ° C. under normal pressure, and the reaction was carried out for 6 hours while removing the produced water from the system. After completion of the reaction, the reaction mixture was cooled, and 300 g of water was added and washed with water. After stationary phase separation and removal of the aqueous phase, toluene was distilled off under reduced pressure using an evaporator to obtain 364.2 g of glycerol trilevulinate. The acid value and hydroxyl value of this compound are shown in Table 1.
[0075]
Synthesis example (c)
Under a nitrogen atmosphere, in a flask equipped with a reflux condenser, a water separator, a stirrer, and a thermometer, trimethylolpropane 134 (1 mol), 348 g (3 mol) levulinic acid, 500 g toluene, 1.9 g p-toluenesulfonic acid (0. 01 mol) was added, kept at 115 ° C. under normal pressure, and allowed to react for 6 hours while removing generated water out of the system. After completion of the reaction, the reaction mixture was cooled, and 500 g of water was added and washed with water. After stationary phase separation and removal of the aqueous phase, toluene was distilled off under reduced pressure with an evaporator to obtain 396.8 g of trimethylolpropane trilevulinate. The acid value and hydroxyl value of this compound are shown in Table 1.
[0076]
Synthesis example (d)
Under a nitrogen atmosphere, a flask equipped with a reflux condenser, a water pipe, a stirrer, and a thermometer was charged with 136 g (1 mol) of pentaerythritol, 116 g (1 mol) of levulinic acid, 500 g of toluene, and 1.9 g (0.01 mol) of p-toluenesulfonic acid. ) And maintained at 115 ° C. under normal pressure, and reacted for 4 hours while removing generated water out of the system. Next, 1.96 g (0.02 mol) of potassium acetate was added, and 306 g (3 mol) of acetic anhydride was further added, followed by reaction at 100 ° C. for 4 hours. After completion of the reaction, the reaction mixture was cooled, and 500 g of water was added and washed with water. After stationary separation and removal of the aqueous phase, toluene was distilled off under reduced pressure with an evaporator to obtain 336.5 g of pentaerythritol monolevulinate triacetate. The acid value and hydroxyl value of this compound are shown in Table 1.
[0077]
Synthesis example (e)
Under a nitrogen atmosphere, a flask equipped with a reflux condenser, a water pipe, a stirrer, and a thermometer was charged with 136 g (1 mol) of pentaerythritol, 464 g (4 mol) of levulinic acid, 500 g of toluene, and 1.9 g (0.01 mol) of p-toluenesulfonic acid. ) And maintained at 115 ° C. under normal pressure and allowed to react for 6 hours while removing generated water out of the system. After completion of the reaction, the reaction mixture was cooled, and 500 g of water was added and washed with water. After stationary phase separation and removal of the aqueous phase, toluene was distilled off under reduced pressure using an evaporator to obtain 507.4 g of pentaerythritol tetralevulinate. The acid value and hydroxyl value of this compound are shown in Table 1.
[0078]
Synthesis example (f)
In a nitrogen atmosphere, a flask equipped with a reflux condenser, a water separator, a stirrer, and a thermometer was charged with 122 g (1 mol) of erythritol, 464 g (4 mol) of levulinic acid, 500 g of toluene, and 1.9 g (0.01 mol) of p-toluenesulfonic acid. Was maintained at 115 ° C. under normal pressure, and the reaction was carried out for 6 hours while removing the produced water from the system. After completion of the reaction, the reaction mixture was cooled, and 500 g of water was added and washed with water. After stationary phase separation and removal of the aqueous phase, toluene was distilled off under reduced pressure using an evaporator to obtain 492.4 g of pentaerythritol tetralevulinate. The acid value and hydroxyl value of this compound are shown in Table 1.
[0079]
[Table 1]

[0080]
Examples 1-12
Polylactic acid and the compounds obtained in Synthesis Examples (a) to (f) were mixed in the proportions shown in Table 2, and the conditions of the cylinder set temperature of 160 to 210 ° C. were used with an extruder (KCK 80 × 2-50VEX manufactured by KCK). Were mixed and kneaded to produce the polylactic acid resin composition of the present invention and pelletized. The pellets were dried under reduced pressure at 40 ° C. for 10 hours, and then at 180 ° C. using an injection molding machine (PS60E9ASE manufactured by Nissei Plastic Industries), a JIS K 7113 No. 1 test piece (thickness 3 mm) and a standard test piece of JIS K 7171. Were prepared, subjected to a tensile test and a bending test, and the flexibility was measured.
[0081]
Comparative Example 1
After polylactic acid was dried under reduced pressure at 60 ° C. for 10 hours, a JIS K 7113 No. 1 test piece (thickness 3 mm) and a standard test piece of JIS K 7171 were prepared at 190 ° C. using an injection molding machine. A bending test was performed to measure the flexibility.
[0082]
Comparative Examples 2-4
Polylactic acid and the plasticizer shown in Table 3 were mixed at various ratios, and pelletized with an extruder at a cylinder set temperature of 160 to 210 ° C. After the pellets were dried under reduced pressure at 40 ° C. for 10 hours, JIS K 7113 No. 1 test piece (thickness 3 mm) and JIS K 7171 standard test piece were prepared at 180 ° C. using an injection molding machine. A bending test was performed to measure the flexibility.
[0083]
[Table 2]

[0084]
[Table 3]

[0085]
In Comparative Examples 1 and 2, the tensile elongation at break was small and there was no flexibility. In Comparative Examples 3 and 4, there was flexibility, but the plasticizer bleeded out over time and the appearance deteriorated.
[0086]
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, among the examples, the resin added with the synthesis examples (a) and (b) has greatly improved flexibility from the tensile elongation at break and the flexural modulus. Moreover, it did not bleed out over time and the appearance was transparent and good.
[0087]
【The invention's effect】
By using the polylactic acid resin composition according to the present invention, a molded article excellent in flexibility, transparency, safety and biodegradability can be obtained.

Claims (5)

A polylactic acid resin composition comprising 1 to 100 parts by weight of at least one compound represented by the following general formula (1) or (2) with respect to 100 parts by weight of a polylactic acid resin.

(In the formula, R ₁ is a trivalent group having 3 to 10 carbon atoms, and R ₂ and R ₃ are each an acyl group having 2 to 10 carbon atoms.)

(In the formula, R ₄ is a tetravalent group having 4 to 10 carbon atoms, and R ₅ , R ₆ and R ₇ are each an acyl group having 2 to 10 carbon atoms.) The polylactic acid-based resin composition according to claim 1, wherein, in the general formula (1), R ₁ is any one of groups represented by the following formula (3).

The polylactic acid-based resin composition according to claim 1, wherein, in the general formula (2), R ₄ is any one of groups represented by the following formula (4).

The molded article containing the polylactic acid-type resin composition in any one of Claims 1-3 . A plasticizer for a polyester resin, comprising at least one of compounds represented by the following general formula (1) or (2).

(In the formula, R ₁ is a trivalent group having 3 to 10 carbon atoms, and R ₂ and R ₃ are each an acyl group having 2 to 10 carbon atoms.)

(In the formula, R ₄ is a tetravalent group having 4 to 10 carbon atoms, and R ₅ , R ₆ and R ₇ are each an acyl group having 2 to 10 carbon atoms.)