JP3592799B2 - Method for molding polylactic acid-based polymer, polylactic acid-based molded article, and polylactic acid-based molded article - Google Patents
Method for molding polylactic acid-based polymer, polylactic acid-based molded article, and polylactic acid-based molded article Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
- Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics
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Description
【０００１】
【発明の属する技術分野】
本発明は、寸法安定性に優れかつ自然環境下で分解する、ポリ乳酸系重合体の成形方法およびポリ乳酸系成形物に関する。
【０００２】
【従来の技術】
各種商品の展示包装用に広く用いられているブリスター加工品や飲料水等を入れるボトルはポリ塩化ビニル、ポリエチレン、ポリスチレン、ポリエチレンテレフタレート等のプラスチック樹脂が使用されている。しかし、これらの樹脂は化学的、生物的に安定なため自然環境下に放置されてもほとんど分解されることなく残留、蓄積される。そして、自然環境中に散乱して動植物の生活環境を汚染するだけでなく、ゴミとして埋められた場合にもほとんど分解せずに残り、埋立地の寿命を短くするという問題がある。
【０００３】
このため、これらの問題を生じない自然分解性を有する重合体からなる材料が要求されており、実際多くの研究、開発が行われている。その一例としてポリ乳酸が注目されている。ポリ乳酸は土壌中において自然に加水分解が進行し土中に原形が残らず、微生物により無害な分解物となる。
【０００４】
【発明が解決しようとする課題】
現在、ポリ乳酸を用いて成形物を得る方法が検討されており、特開平６−２３８２８号およびに特開平６−１２２１４８号に衝撃強さ、透明性および成形性を改良した、ポリ乳酸からなる成形物が開示されている。
【０００５】
ところで、ブリスター加工品やボトル等のプラスチック容器は高温にさらされると、収縮することがあり、容器の内容物が飛び出す等の問題が生じてしまう。そこで、上述したプラスチック容器には寸法安定性が要求されることがある。すなわち、ポリ乳酸を用いた成形物を広い分野で使用していくためには、寸法安定性を付与することが大切である。
【０００６】
そこで、本発明の課題は寸法安定性に優れたポリ乳酸系重合体の成形方法およびポリ乳酸系成形物を提供することにある。
【０００７】
【課題を解決するための手段】
本発明の要旨は、Ｌ−体とＤ−体との組成比が１００：０〜９４：６または６：９４〜０：１００であるポリ乳酸系重合体からなる一次成形物を所望する形状に成形して二次成形物を得た後、前記二次成形物をポリ乳酸系重合体のガラス転移温度Ｔｇから融点Ｔｍの温度範囲に保持することを特徴とするポリ乳酸系重合体の成形方法である。異なる本発明の要旨は、Ｌ−体とＤ−体との組成比が１００：０〜９４：６または６：９４〜０：１００であるポリ乳酸系重合体からなるシートあるいは中空体を、所望する形状に成形した後、前記重合体のガラス転移温度Ｔｇから融点Ｔｍの温度範囲で熱処理して得られるポリ乳酸系成形物である。
【０００８】
【発明の実施の形態】
本発明に用いられるポリ乳酸系重合体とは、ポリ乳酸または乳酸と他のヒドロキシカルボン酸との共重合体、もしくはこれらの混合物であり、本発明の効果を阻害しない範囲で他の高分子材料を混入できる。
【０００９】
乳酸としてはＬ−乳酸、Ｄ−乳酸があり、ヒドロキシカルボン酸としてはグリコ−ル酸、３−ヒドロキシ酪酸、４−ヒドロキシ酪酸、３−ヒドロキシ吉草酸、４−ヒドロキシ吉草酸、６−ヒドロキシカプロン酸などが代表的に挙げられる。
【００１０】
ポリ乳酸系重合体の構成単位には、乳酸の構造単位がＬ−乳酸であるポリ（Ｌ−乳酸）、構造単位がＤ−乳酸であるポリ（Ｄ−乳酸）さらにはＬ−乳酸とＤ−乳酸の共重合体であるポリ（ＤＬ−乳酸）がある。また、これらの混合体もある。
【００１１】
重合法には縮重合法、開環重合法など公知のいずれの方法を採用することができる。例えば、縮重合法ではＬ−乳酸またはＤ−乳酸あるいはこれらの混合物を直接脱水宿重合して任意の組成を持ったポリ乳酸を得ることができる。
【００１２】
また、開環重合法では乳酸の環状２量体であるラクチドを、必要に応じて重合調整剤等を用いながら、選ばれた触媒を使用してポリ乳酸を得ることができる。ラクチドにはＬ−乳酸の２量体であるＬ−ラクチド、Ｄ−乳酸の２量体であるＤ−ラクチド、さらにＬ−乳酸とＤ−乳酸からなるＤＬ−ラクチドがあり、これらを必要に応じて混合して重合することにより任意の組成、結晶性をもつポリ乳酸を得ることができる。
【００１３】
分子量増大を目的として少量の鎖延長剤、例えば、ジイソシアネート化合物、エポキシ化合物、酸無水物などを使用できる。重合体の重量平均分子量の好ましい範囲としては６万から７０万であり、この範囲を下回る場合は実用物性がほとんど発現されず、上回る場合には、溶融粘度が高すぎ成形加工性に劣る。射出成形には、分子量が少ないものが適している。
【００１４】
また、成形加工性、成形物の物性を調整する目的で、可塑剤、滑剤、無機フィラー、紫外線吸収剤などの添加剤、改質剤を添加することも可能である。
【００１５】
共重合体ではＬ−乳酸構造単位とＤ−乳酸構造単位の割合で結晶性、融点が異なり、本発明に使用されるポリ乳酸系重合体の混合比率は成形用の材料としては、Ｌ−乳酸とＤ−乳酸との組成比が１００：０〜９４：６または６：９４〜０：１００とする。この範囲に入れば、後述するが、ガラス転移温度Ｔｇから融点Ｔｍの温度範囲で熱処理することにより、結晶性の高い二次成形物を得ることができる。
【００１６】
成形物の成形方法を説明する。まず、上述した乳酸系重合体を用いて、シートあるいは中空体（一次成形物）を製造し、次いで加熱加工して所望の形状に成形して二次成形物を得る。加熱加工とはいわゆる熱成形法であり、具体的には真空成形、圧空成形、真空圧空成形、プラグアシスト成形、雌雄型成形、ブロー成形等がある。
【００１７】
一次成形物としては、具体的には溶融押出あるいはプレス成形によるシートやプレート、射出成形等によって作られる中空状の成形物（パリソン）等があげられる。
【００１８】
一次成形物として使用するシートの製造方法は、例えば、ポリ乳酸系重合体を水分を除去した後、押出機にて溶融押出を行う。溶融温度は組成によって変化することや重合体の熱分解も考慮して適宜選択することが好ましい。実際には１４０℃から２５０℃の温度範囲が選ばれる。
【００１９】
Ｔダイより押し出してキャスティングドラム（冷却ドラム）に接触させてシート状にする。キャスティングロールの好ましい温度範囲は重合体のガラス転移温度Ｔｇ以下である。ガラス転移温度Ｔｇより高いとポリマーがキャスティングドラムに粘着し、引き取れない。さらには、結晶化が促進されて球晶が発達してしまい、所望する形状に相当する成形物を得にくい。
【００２０】
シートから二次成形物を得るにあたり、成形以前にシートをガラス転移温度Ｔｇ以上になるよう予熱して軟化させる。次いで所望する形状の金型に密着させて二次成形物を得た後、熱処理を行って成形物を得る。
【００２１】
熱処理を行う方法は特に限定はされないが通常、金型の中で行われる。
熱処理の温度は二次成形物を得る際の金型の温度と同じ場合と、異なる場合とがあるが、いずれにせよ、寸法安定性に優れた成形物を得るためには、ガラス転移温度Ｔｇから融点Ｔｍの温度範囲で行う。
【００２２】
本発明でいう熱処理とは、二次成形物をガラス転移温度Ｔｇから融点Ｔｍの温度範囲に保持する。好ましくは、９０℃から融点Ｔｍの範囲に保持する。上記範囲に保持する時間は、熱処理の温度によって異なるが、３秒以上の熱処理を施すことが好ましい。二次成形物の結晶化度を増大させ、
寸法安定性を付与することができる。
【００２３】
用途によっては透明性の高い成形物を必要とする。透明性の高い成形物を得るためには、一次成形物を比較的低温（ガラス転移温度Ｔｇ付近）で予熱した後、熱処理を行う。これにより球晶の成長を抑えることができ、透明性に優れ、かつ、寸法安定性に優れた成形物を得ることができる。
【００２４】
シートである一次成形物から成形物を得る場合を上述したが、他の一次成形物、例えば、中空体であるパリソンから成形物を得る場合も同様である。
【００２５】
【実施例】
以下に実施例を述べるが、本発明はこれに限定されるものではない。尚、述べる測定値は次に示すような条件で測定を行って求めた。
【００２６】
（１）ガラス転移温度Ｔｇおよび融解温度Ｔｍ
パ−キンエルマ−社製示差走査熱量計ＤＳＣ−７を用い、ポリ乳酸系重合体１０ｍｇをＪＩＳ−Ｋ７１２２に基づいて、昇温速度１０℃／分で昇温したときのサ−モグラムからガラス転移温度Ｔｇおよび融解温度Ｔｍをに求めた。
【００２７】
（２）容積保持率
成形品を２０ｃｍ×２０ｃｍの箱状ステンレス製金網内に入れ８０℃の温水中に５分間浸漬した。浸漬後、成形品に水を充填して、その水をメスシリンダーで計りとって収縮後の容量（Ｖ１）を調べ、浸漬前の容量（Ｖ０）と比較して容積保持率を算出した。
【００２８】
容積保持率（％）＝（Ｖ１／Ｖ０）×１００
（実施例１）
Ｌ−乳酸とＤ−乳酸との組成比が９８：２で、ガラス転移温度Ｔｇは５８℃、融解温度Ｔｍは１７５℃、重量平均分子量１８０，０００であるポリ乳酸重合体を、水分除去のため乾燥空気を送りながら１２０℃で３時間乾燥した。このポリ乳酸重合体を６０ｍｍφ単軸エクストルーダーにて２１０℃でＴダイより押し出し、キャスティングロール（ロール温度５８℃）にて急冷して、厚み約４００μｍの透明なポリ乳酸重合体からなるシート（一次成形物）を得た。ポリ乳酸重合体の押出性は良好であった。
【００２９】
２５０ｍｍ×２５０ｍｍに切り出した約４００μｍ厚の上記ポリ乳酸シート（一次成形物）を、三和興業社製熱成形機（ＰＬＡＶＡＣ−ＦＥ３６ＰＨ型）に装着した後、シートを赤外線ヒーターで６８℃に予熱した。当該ポリ乳酸シートの下から金型を持ち上げプラグでシートを上から金型底から３ｍｍまで押し込んだ後、金型内を真空にして、シートをコップ状に成形して、二次成形物を得た。この時、金型温度は７０℃である。
【００３０】
上記二次成形物を引続き金型温度７０℃で、真空吸引しながら３０秒保持して、熱処理を施した。その後、金型内の熱成形品に水を噴霧して冷却し、コップ状の成形物を金型より取り出した。
【００３１】
（実施例２）
二次成形物を得る際の金型温度を１００℃、熱処理を行う際の金型温度を１００℃、熱処理時間を２０秒とした以外は、実施例１と同様にしてコップ状のポリ乳酸系成形物を製造した。
【００３２】
（実施例３）
二次成形物を得る際の金型温度を７０℃、熱処理を行う際の金型温度を１６０℃、熱処理時間を１０秒とした以外は、実施例１と同様にしてコップ状のポリ乳酸系成形物を製造した。
【００３３】
（実施例４）
Ｌ−乳酸とＤ−乳酸との組成比が９４：６で、ガラス転移温度Ｔｇは５７℃、融解温度Ｔｍは１５２℃、重量平均分子量１３０，０００であるポリ乳酸重合体から、実施例１と同様の方法でシートを得た。
【００３４】
上記ポリ乳酸シートから二次成形物を得る際の金型温度を５０℃、熱処理を行う際の金型温度を１００℃、熱処理時間を２０秒とした以外は、実施例１と同様にしてコップ状のポリ乳酸系成形物を製造した。
【００３５】
（比較例１）
二次成形物を得る際の金型温度を５０℃、熱処理を行う際の金型温度を５０℃、熱処理時間を６０秒とした以外は、実施例１と同様にしてコップ状のポリ乳酸系成形物を製造した。
【００３６】
（比較例２）
二次成形物を得る際の金型温度を７０℃、熱処理を行う際の金型温度を１９０℃、熱処理時間を１０秒とした以外は、実施例１と同様にしてコップ状ポリ乳酸系成形物を製造した。
【００３７】
（比較例３）
実施例４で使用したシートから二次成形物を得る際の金型温度を５０℃、熱処理を行う際の金型温度を５０℃、熱処理時間を６０秒とした以外は、実施例１と同様にしてコップ状のポリ乳酸系成形物を製造した。
【００３８】
（比較例４）
Ｌ−乳酸とＤ−乳酸との組成比が９３：７で、ガラス転移温度Ｔｇは５７℃、融解温度Ｔｍは１２５℃、重量平均分子量１１０，０００であるポリ乳酸重合体から、実施例１と同様の方法でポリ乳酸シートを得た。
【００３９】
上記シートから二次成形物を得る際の金型温度を１００℃、熱処理を行う際の金型温度を１００℃、熱処理時間を３０秒とした以外は、実施例１と同様にしてコップ状のポリ乳酸系成形物を製造した。
【００４０】
尚、実施例３，４と比較例２とは、二次成形物を得る際の金型温度と熱処理を行う際の金型温度とが異なり、他は同じである。
【００４１】
表１に上記実施例１〜４および比較例１〜４で得られたコップ状のポリ乳酸系成形物におけるＬ−乳酸とＤ−乳酸との組成比、ガラス転移温度Ｔｇ、融点Ｔｍ、熱処理温度、熱処理時間を示した。また、表１に各コップ状のポリ乳酸系成形物の容積保持率を示した。
【００４２】
【表１】
実施例２，３は容積保持率が９５％を越しており、高温の溶液を充填する場合に優れている。
【００４３】
一方、比較例１，３，４は容積保持率が７０％未満であり、ブリスター加工品やボトル等のプラスチック容器として使用するには不十分である。
また、比較例２は熱処理によりコップ状の成形物が溶解してしまった。
【００４４】
上記実施例はＬ−乳酸がＤ−乳酸より多い場合を示しているが、Ｄ−乳酸がＬ−乳酸より多い場合にも同様の結果を得ている。
【００４５】
【発明の効果】
上述したように本発明によれば、ポリ乳酸系成形物に寸法安定性を付与できるので、ポリ乳酸を用いた成形物をブリスター加工品やボトル等のプラスチック容器として広い分野で使用することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for molding a polylactic acid-based polymer which is excellent in dimensional stability and decomposes in a natural environment, and a polylactic acid-based molded article.
[0002]
[Prior art]
Plastic resins such as polyvinyl chloride, polyethylene, polystyrene, and polyethylene terephthalate are used for blister products and bottles for drinking water, which are widely used for display and packaging of various products. However, since these resins are chemically and biologically stable, they remain and accumulate without being substantially decomposed even when left in a natural environment. In addition, there is a problem that not only are they scattered in the natural environment to pollute the living environment of animals and plants, but also they are hardly decomposed even when buried as garbage, thereby shortening the life of the landfill.
[0003]
For this reason, there is a demand for a material made of a polymer having a natural degradability that does not cause these problems, and much research and development have actually been carried out. As one example, polylactic acid has attracted attention. Polylactic acid is naturally hydrolyzed in soil, remains in the original form in soil, and becomes a harmless degradation product by microorganisms.
[0004]
[Problems to be solved by the invention]
At present, a method for obtaining a molded product using polylactic acid is being studied. Japanese Patent Application Laid-Open Nos. 6-23828 and 6-122148 disclose a polylactic acid having improved impact strength, transparency and moldability. Moldings are disclosed.
[0005]
By the way, a plastic container such as a blister product or a bottle may be shrunk when exposed to a high temperature, which causes a problem such as popping out the contents of the container. Therefore, the above-mentioned plastic container may be required to have dimensional stability. That is, in order to use a molded article using polylactic acid in a wide field, it is important to impart dimensional stability.
[0006]
Therefore, an object of the present invention is to provide a method for molding a polylactic acid-based polymer having excellent dimensional stability and a polylactic acid-based molded article.
[0007]
[Means for Solving the Problems]
The gist of the present invention is to form a primary molded product of a polylactic acid-based polymer having a composition ratio of L-form and D-form of 100: 0 to 94: 6 or 6:94 to 0: 100 into a desired shape. After molding to obtain a secondary molded product, the secondary molded product is maintained in a temperature range from the glass transition temperature Tg to the melting point Tm of the polylactic acid-based polymer. It is. A different gist of the present invention is to provide a sheet or hollow body made of a polylactic acid-based polymer having a composition ratio of L-form and D-form of 100: 0 to 94: 6 or 6:94 to 0: 100. A polylactic acid-based molded product obtained by forming the polymer into a shape to be formed and then heat-treating the polymer in a temperature range from the glass transition temperature Tg to the melting point Tm.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The polylactic acid-based polymer used in the present invention is polylactic acid or a copolymer of lactic acid and another hydroxycarboxylic acid, or a mixture thereof, and other polymer materials as long as the effects of the present invention are not impaired. Can be mixed.
[0009]
Lactic acid includes L-lactic acid and D-lactic acid, and hydroxycarboxylic acids include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid and 6-hydroxycaproic acid And the like.
[0010]
The structural units of the polylactic acid-based polymer include poly (L-lactic acid) in which the structural unit of lactic acid is L-lactic acid, poly (D-lactic acid) in which the structural unit is D-lactic acid, and L-lactic acid and D-lactic acid. There is poly (DL-lactic acid) which is a copolymer of lactic acid. There are also mixtures thereof.
[0011]
As the polymerization method, any known method such as a condensation polymerization method and a ring-opening polymerization method can be employed. For example, in the polycondensation method, L-lactic acid or D-lactic acid or a mixture thereof can be directly subjected to dehydration polymerization to obtain polylactic acid having an arbitrary composition.
[0012]
In the ring-opening polymerization method, lactide, which is a cyclic dimer of lactic acid, can be used to obtain polylactic acid by using a selected catalyst while using a polymerization regulator and the like as necessary. Lactide includes L-lactide which is a dimer of L-lactic acid, D-lactide which is a dimer of D-lactic acid, and DL-lactide composed of L-lactic acid and D-lactic acid. By mixing and polymerizing, polylactic acid having any composition and crystallinity can be obtained.
[0013]
For the purpose of increasing the molecular weight, a small amount of a chain extender, for example, a diisocyanate compound, an epoxy compound or an acid anhydride can be used. The preferred range of the weight average molecular weight of the polymer is from 60,000 to 700,000. If it is below this range, practical physical properties are hardly exhibited, and if it is above this range, the melt viscosity is too high and molding processability is poor. Those having a low molecular weight are suitable for injection molding.
[0014]
In addition, additives such as plasticizers, lubricants, inorganic fillers, and ultraviolet absorbers, and modifiers can be added for the purpose of adjusting the molding processability and the physical properties of the molded product.
[0015]
The copolymer has different crystallinity and melting point depending on the ratio of L-lactic acid structural unit to D-lactic acid structural unit, and the mixing ratio of the polylactic acid-based polymer used in the present invention is L-lactic acid as a molding material. And the composition ratio of D-lactic acid to 100: 0 to 94: 6 or 6:94 to 0: 100. If it falls within this range, a secondary molded product having high crystallinity can be obtained by performing heat treatment in a temperature range from the glass transition temperature Tg to the melting point Tm, as described later.
[0016]
A method for forming a molded product will be described. First, a sheet or a hollow body (primary molded product) is manufactured using the above-described lactic acid-based polymer, and then heated and formed into a desired shape to obtain a secondary molded product. The heat processing is a so-called thermoforming method, and specifically includes vacuum forming, pressure forming, vacuum pressure forming, plug assist forming, male and female mold forming, blow molding and the like.
[0017]
Specific examples of the primary molded product include a sheet or plate formed by melt extrusion or press molding, and a hollow molded product (parison) formed by injection molding or the like.
[0018]
As a method for producing a sheet used as a primary molded product, for example, after extruding water from a polylactic acid-based polymer, melt extrusion is performed by an extruder. It is preferable that the melting temperature be appropriately selected in consideration of the fact that it varies depending on the composition and the thermal decomposition of the polymer. In practice, a temperature range of 140 ° C. to 250 ° C. is selected.
[0019]
It is extruded from a T-die and brought into contact with a casting drum (cooling drum) to form a sheet. The preferred temperature range of the casting roll is below the glass transition temperature Tg of the polymer. If the temperature is higher than the glass transition temperature Tg, the polymer sticks to the casting drum and cannot be removed. Further, crystallization is promoted and spherulites develop, and it is difficult to obtain a molded product having a desired shape.
[0020]
In order to obtain a secondary molded product from the sheet, the sheet is preheated and softened to a glass transition temperature Tg or higher before molding. Next, after being brought into close contact with a mold having a desired shape to obtain a secondary molded product, heat treatment is performed to obtain a molded product.
[0021]
The method for performing the heat treatment is not particularly limited, but is usually performed in a mold.
The temperature of the heat treatment may or may not be the same as the temperature of the mold used to obtain the secondary molded product. In any case, in order to obtain a molded product having excellent dimensional stability, the glass transition temperature Tg To a melting point Tm.
[0022]
The heat treatment referred to in the present invention is to maintain the secondary molded product in a temperature range from the glass transition temperature Tg to the melting point Tm. Preferably, it is kept in the range from 90 ° C. to the melting point Tm. The time for maintaining the above range depends on the temperature of the heat treatment, but it is preferable to perform the heat treatment for 3 seconds or more. Increase the crystallinity of the secondary molded product,
Dimensional stability can be imparted.
[0023]
Some applications require highly transparent moldings. In order to obtain a molded product having high transparency, the primary molded product is preheated at a relatively low temperature (around the glass transition temperature Tg) and then heat-treated. Thereby, growth of spherulites can be suppressed, and a molded article having excellent transparency and excellent dimensional stability can be obtained.
[0024]
Although the case where the molded article is obtained from the primary molded article which is a sheet has been described above, the same applies to the case where the molded article is obtained from another primary molded article, for example, a parison which is a hollow body.
[0025]
【Example】
Examples will be described below, but the present invention is not limited thereto. Note that the measured values described were obtained by performing measurements under the following conditions.
[0026]
(1) Glass transition temperature Tg and melting temperature Tm
Using a differential scanning calorimeter DSC-7 manufactured by Perkin Elmer, a glass transition temperature was obtained from a thermogram obtained when 10 mg of a polylactic acid-based polymer was heated at a rate of 10 ° C./min based on JIS-K7122. Tg and melting temperature Tm were determined.
[0027]
(2) Volume Retention The molded product was placed in a 20 cm × 20 cm box-shaped stainless steel wire mesh and immersed in warm water at 80 ° C. for 5 minutes. After immersion, the molded product was filled with water, and the water was measured with a measuring cylinder to check the volume after shrinkage (V1), and compared with the volume before immersion (V0) to calculate the volume retention rate.
[0028]
Volume retention (%) = (V1 / V0) × 100
(Example 1)
A polylactic acid polymer having a composition ratio of L-lactic acid and D-lactic acid of 98: 2, a glass transition temperature Tg of 58 ° C., a melting temperature Tm of 175 ° C., and a weight average molecular weight of 180,000 was used to remove water. It dried at 120 degreeC for 3 hours, sending dry air. This polylactic acid polymer was extruded from a T-die at 210 ° C. with a 60 mmφ single-screw extruder, quenched by a casting roll (roll temperature: 58 ° C.), and a sheet (primary) made of a transparent polylactic acid polymer having a thickness of about 400 μm was prepared. Molded article). The extrudability of the polylactic acid polymer was good.
[0029]
The above-mentioned polylactic acid sheet (primary molded product) having a thickness of about 400 μm cut into a size of 250 mm × 250 mm was mounted on a thermoforming machine (PLAVAC-FE36PH type) manufactured by Sanwa Kogyo Co., Ltd., and the sheet was preheated to 68 ° C. with an infrared heater. . After lifting the mold from the bottom of the polylactic acid sheet and pushing the sheet from the top to 3 mm from the bottom of the mold with a plug, the inside of the mold is evacuated and the sheet is formed into a cup to obtain a secondary molded product. Was. At this time, the mold temperature is 70 ° C.
[0030]
The secondary molded product was kept at a mold temperature of 70 ° C. for 30 seconds while being vacuum-sucked, and heat-treated. Thereafter, the thermoformed product in the mold was sprayed with water and cooled, and the cup-shaped molded product was taken out from the mold.
[0031]
(Example 2)
A cup-shaped polylactic acid system was prepared in the same manner as in Example 1 except that the mold temperature when obtaining the secondary molded product was 100 ° C, the mold temperature when performing the heat treatment was 100 ° C, and the heat treatment time was 20 seconds. Moldings were produced.
[0032]
(Example 3)
A cup-shaped polylactic acid system was obtained in the same manner as in Example 1 except that the mold temperature when obtaining the secondary molded product was 70 ° C, the mold temperature when performing the heat treatment was 160 ° C, and the heat treatment time was 10 seconds. Moldings were produced.
[0033]
(Example 4)
From the polylactic acid polymer having a composition ratio of L-lactic acid and D-lactic acid of 94: 6, a glass transition temperature Tg of 57 ° C., a melting temperature Tm of 152 ° C. and a weight average molecular weight of 130,000, Example 1 was used. A sheet was obtained in the same manner.
[0034]
A cup was prepared in the same manner as in Example 1 except that the mold temperature when obtaining a secondary molded product from the polylactic acid sheet was 50 ° C, the mold temperature when performing heat treatment was 100 ° C, and the heat treatment time was 20 seconds. A polylactic acid-based molded article was produced.
[0035]
(Comparative Example 1)
A cup-shaped polylactic acid system was obtained in the same manner as in Example 1, except that the mold temperature when obtaining the secondary molded product was 50 ° C, the mold temperature when performing the heat treatment was 50 ° C, and the heat treatment time was 60 seconds. Moldings were produced.
[0036]
(Comparative Example 2)
A cup-shaped polylactic acid-based molding was performed in the same manner as in Example 1, except that the mold temperature when obtaining the secondary molded product was 70 ° C, the mold temperature when performing the heat treatment was 190 ° C, and the heat treatment time was 10 seconds. Was manufactured.
[0037]
(Comparative Example 3)
Same as Example 1 except that the mold temperature when obtaining the secondary molded product from the sheet used in Example 4 was 50 ° C., the mold temperature when performing the heat treatment was 50 ° C., and the heat treatment time was 60 seconds. Thus, a cup-shaped polylactic acid-based molded product was produced.
[0038]
(Comparative Example 4)
From the polylactic acid polymer having a composition ratio of L-lactic acid and D-lactic acid of 93: 7, a glass transition temperature Tg of 57 ° C., a melting temperature Tm of 125 ° C. and a weight average molecular weight of 110,000, Example 1 was used. A polylactic acid sheet was obtained in the same manner.
[0039]
A cup-shaped resin was obtained in the same manner as in Example 1 except that the mold temperature when obtaining the secondary molded product from the sheet was 100 ° C, the mold temperature when performing the heat treatment was 100 ° C, and the heat treatment time was 30 seconds. A polylactic acid-based molded product was produced.
[0040]
Note that Examples 3 and 4 and Comparative Example 2 are different from each other in the mold temperature when obtaining the secondary molded product and the mold temperature when performing the heat treatment, and are otherwise the same.
[0041]
Table 1 shows the composition ratio of L-lactic acid and D-lactic acid, glass transition temperature Tg, melting point Tm, and heat treatment temperature in the cup-shaped polylactic acid-based molded products obtained in Examples 1 to 4 and Comparative Examples 1 to 4. , Heat treatment time. Table 1 shows the volume retention of each cup-shaped polylactic acid-based molded product.
[0042]
[Table 1]
Examples 2 and 3 have a volume retention ratio of more than 95%, and are excellent when filling a high-temperature solution.
[0043]
On the other hand, Comparative Examples 1, 3, and 4 have a volume retention of less than 70%, which is insufficient for use as a plastic container such as a blister product or a bottle.
In Comparative Example 2, the cup-shaped molded product was dissolved by the heat treatment.
[0044]
Although the above example shows a case where L-lactic acid is more than D-lactic acid, similar results are obtained when D-lactic acid is more than L-lactic acid.
[0045]
【The invention's effect】
As described above, according to the present invention, dimensional stability can be imparted to a polylactic acid-based molded product, so that a molded product using polylactic acid can be used in a wide field as a plastic container such as a blister processed product or a bottle. .
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16889095A JP3592799B2 (en) | 1995-07-04 | 1995-07-04 | Method for molding polylactic acid-based polymer, polylactic acid-based molded article, and polylactic acid-based molded article |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16889095A JP3592799B2 (en) | 1995-07-04 | 1995-07-04 | Method for molding polylactic acid-based polymer, polylactic acid-based molded article, and polylactic acid-based molded article |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0912748A JPH0912748A (en) | 1997-01-14 |
| JP3592799B2 true JP3592799B2 (en) | 2004-11-24 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16889095A Expired - Lifetime JP3592799B2 (en) | 1995-07-04 | 1995-07-04 | Method for molding polylactic acid-based polymer, polylactic acid-based molded article, and polylactic acid-based molded article |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3592799B2 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6908652B1 (en) | 1996-09-18 | 2005-06-21 | Cryovac, Inc. | Poly(lactic acid) in oxygen scavenging article |
| EP1422044B1 (en) * | 2001-07-19 | 2010-10-13 | Toyo Seikan Kaisha, Ltd. | Molded object obtained through stretching and thermal fixing and process for producing the same |
| JP2003253009A (en) | 2002-03-06 | 2003-09-10 | Unitika Ltd | Polylactic acid based molded product and production method therefor |
| JP4808367B2 (en) * | 2003-03-06 | 2011-11-02 | ユニチカ株式会社 | Method for producing polylactic acid-based molded body |
| JP2005330008A (en) * | 2005-04-13 | 2005-12-02 | Mitsubishi Plastics Ind Ltd | Film case |
| JP4916149B2 (en) * | 2005-09-09 | 2012-04-11 | 花王株式会社 | Method for producing composite molded body |
| JP2007283557A (en) * | 2006-04-13 | 2007-11-01 | Seiko Epson Corp | Liquid container |
-
1995
- 1995-07-04 JP JP16889095A patent/JP3592799B2/en not_active Expired - Lifetime
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| Publication number | Publication date |
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| JPH0912748A (en) | 1997-01-14 |
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