JP5306137B2 - Method for producing foamed polylactic acid resin particles for in-mold foam molding - Google Patents
Method for producing foamed polylactic acid resin particles for in-mold foam molding Download PDFInfo
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本発明は、二次発泡粒子の潰れを防止して型内発泡成形性に優れた型内発泡成形用ポリ乳酸系樹脂発泡粒子（以下「ポリ乳酸系樹脂発泡粒子」と略することがある）を製造することができる型内発泡成形用ポリ乳酸系樹脂発泡粒子の製造方法に関する。 The present invention is a polylactic acid-based resin foamed particle for in-mold foam molding that is excellent in in-mold foam moldability by preventing crushing of secondary foamed particles (hereinafter sometimes abbreviated as “polylactic acid-based resin foamed particles”). It is related with the manufacturing method of the polylactic acid-type resin expanded particle for in-mold foam molding which can manufacture.
ポリ乳酸系樹脂は、天然に存在する乳酸を重合されて得られた樹脂であり、自然界に存在する微生物によって分解可能な生分解性樹脂であると共に、常温での機械的特性についても優れており、更に、近年の環境意識の高まりと原油高騰などから石油を原料とする合成樹脂に代わる合成樹脂として注目を集めている。 Polylactic acid resin is a resin obtained by polymerizing naturally occurring lactic acid. It is a biodegradable resin that can be decomposed by microorganisms existing in nature, and has excellent mechanical properties at room temperature. Furthermore, due to the recent increase in environmental awareness and the rise in crude oil prices, it has attracted attention as a synthetic resin that replaces synthetic resins made from petroleum.
ポリ乳酸系樹脂は、一般に、Ｄ−乳酸及び／又はＬ−乳酸を重合させるか、或いは、Ｌ−ラクチド、Ｄ−ラクチド及びＤＬ−ラクチドからなる群から選ばれた一又は二以上のラクチドを開環重合させることによって製造されている。 The polylactic acid resin generally polymerizes D-lactic acid and / or L-lactic acid, or opens one or more lactides selected from the group consisting of L-lactide, D-lactide and DL-lactide. Manufactured by ring polymerization.
又、ポリ乳酸系樹脂発泡粒子を発泡させてポリ乳酸系樹脂発泡成形体を製造する方法としては、型内発泡成形が提案されている。上記型内発泡成形とは、ポリ乳酸系樹脂発泡粒子を金型内に充填し、熱水や水蒸気などの熱媒体によってポリ乳酸系樹脂発泡粒子を加熱して発泡させ、ポリ乳酸系樹脂発泡粒子の発泡圧によって発泡粒子同士を融着一体化させて所望形状を有するポリ乳酸系樹脂発泡成形体を製造する方法である。 Further, in-mold foam molding has been proposed as a method for producing a polylactic acid resin foamed molded body by foaming polylactic acid resin foamed particles. The above-mentioned in-mold foam molding is a method in which polylactic acid resin foam particles are filled in a mold, and the polylactic acid resin foam particles are heated and foamed with a heat medium such as hot water or water vapor to produce polylactic acid resin foam particles. This is a method for producing a polylactic acid resin foamed molded article having a desired shape by fusing and integrating foamed particles with each other by the foaming pressure.
そして、ポリ乳酸系樹脂発泡粒子を発泡させて得られるポリ乳酸系樹脂発泡成形体の発泡倍率の向上及び成形性の改善について種々の技術が開示されている。例えば、特許文献１には、ポリ乳酸系発泡成形体の製造において、ポリ乳酸系樹脂粒子に炭素数３−６の炭化水素系発泡剤を含浸させてポリ乳酸系発泡性粒子を得、該ポリ乳酸系発泡性粒子を発泡させてポリ乳酸系発泡粒子とした後に、二酸化炭素を該ポリ乳酸系発泡粒子に付与した二酸化炭素含有ポリ乳酸系発泡粒子を型内成形することを特徴とするポリ乳酸系発泡成形体製造時の成形性を向上させる方法が開示されている。 And various techniques are disclosed about the improvement of the expansion ratio of the polylactic acid-type resin foaming molding obtained by foaming a polylactic acid-type resin foaming particle, and the improvement of a moldability. For example, in Patent Document 1, in the production of a polylactic acid-based foamed molded article, polylactic acid-based resin particles are impregnated with a hydrocarbon foaming agent having 3 to 6 carbon atoms to obtain polylactic acid-based foamable particles. Polylactic acid characterized by foaming lactic acid-based expandable particles into polylactic acid-based expanded particles and then molding in-mold carbon dioxide-containing polylactic acid-based expanded particles having carbon dioxide added to the polylactic acid-based expanded particles A method for improving moldability at the time of production of a foamed molded article is disclosed.
しかしながら、ポリ乳酸系粒子に二酸化炭素を含浸させるにあたって、密閉容器内にその容器内圧力が０．１ＭＰａ以上で且つ２．０ＭＰａ未満となるように二酸化炭素を瞬時に供給しており、密閉容器内の二酸化炭素による昇圧速度が極めて高くなっている。 However, when impregnating the polylactic acid-based particles with carbon dioxide, carbon dioxide is instantaneously supplied into the sealed container so that the pressure in the container is 0.1 MPa or more and less than 2.0 MPa. The pressure increase rate due to carbon dioxide is extremely high.
従って、ポリ乳酸系粒子が二酸化炭素による急激な圧力上昇によって潰れてしまう虞れがあり、特に、ポリ乳酸系粒子が高発泡倍率である場合にはその現象が顕著であり、その結果、二酸化炭素含有ポリ乳酸系発泡粒子の型内発泡成形時における発泡性が低下し、得られる発泡成形体の外観が低下するという問題点を有している。 Therefore, there is a possibility that the polylactic acid-based particles may be crushed by a sudden pressure increase due to carbon dioxide, and this phenomenon is particularly remarkable when the polylactic acid-based particles have a high expansion ratio. There is a problem that the foamability of the contained polylactic acid-based foamed particles during foam molding is reduced, and the appearance of the resulting foamed molded article is lowered.
又、特許文献２には、生分解性ポリエステルを主成分とする予備発泡ビーズを、（１）４５℃〜９０℃の温度で処理した後、（２）０．１０５ＭＰａ〜１．０ＭＰａの圧力下に保持する生分解性発泡ビーズの製造方法が開示されている。 In Patent Document 2, pre-expanded beads mainly composed of biodegradable polyester are treated at (1) a temperature of 45 ° C. to 90 ° C., and (2) under a pressure of 0.105 MPa to 1.0 MPa. A method for producing biodegradable foam beads held in a container is disclosed.
そして、段落番号〔００４３〕には、工程（２）の加圧方法として瞬時又は時間をかけての何れでもよいことが記載されているものの、実施例をみると、オートクレーブ内に一気（瞬時）に所定圧力まで加圧している。又、段落番号〔００４５〕には、工程（２）の加圧条件として処理温度を３０〜５０℃に維持することが好ましいことが記載されている。 And although paragraph number [0043] describes that the method of pressurization in step (2) may be either instantaneous or time-consuming, in the example, it is immediately in the autoclave (instant) To a predetermined pressure. Further, paragraph [0045] describes that it is preferable to maintain the treatment temperature at 30 to 50 ° C. as the pressurizing condition in the step (2).
しかしながら、オートクレーブ内に空気を瞬時に所定圧力まで加圧していることから、上述と同様に、オートクレーブ内の昇圧速度が極めて高くなっており、予備発泡ビーズが急激な圧力上昇によって潰れてしまう虞れがある。 However, since air is instantaneously pressurized to a predetermined pressure in the autoclave, the pressure increase rate in the autoclave is extremely high as described above, and the pre-expanded beads may be crushed by a sudden pressure increase. There is.
更に、工程（２）の加圧時に処理温度を３０〜５０℃に維持すると、ポリ乳酸系樹脂の結晶化の進行と共に予備発泡ビーズの収縮が発生し、得られる生分解性発泡ビーズの型内発泡成形性が低下し、得られる発泡成形体の外観が低下するという問題を有している。 Furthermore, if the treatment temperature is maintained at 30 to 50 ° C. during the pressurization in the step (2), the shrinkage of the pre-expanded beads occurs with the progress of crystallization of the polylactic acid resin, and the resulting biodegradable expanded beads are within the mold. There exists a problem that foam moldability falls and the external appearance of the obtained foaming molding falls.
本発明は、二次発泡粒子の潰れを防止しながら、二次発泡粒子に内圧を付与して型内発泡成形性に優れた型内発泡成形用ポリ乳酸系樹脂発泡粒子を製造することができる型内発泡成形用ポリ乳酸系樹脂発泡粒子の製造方法を提供する。 The present invention can produce polylactic acid resin foamed particles for in-mold foam molding excellent in in-mold foam moldability by applying an internal pressure to the secondary foamed particles while preventing collapse of the secondary foamed particles. A method for producing foamed polylactic acid-based resin particles for in-mold foam molding is provided.
本発明の型内発泡成形用ポリ乳酸系樹脂発泡粒子の製造方法は、ポリ乳酸系樹脂を押出発泡させて得られた一次発泡粒子を二次発泡させて二次発泡粒子とし、この二次発泡粒子に不活性ガスを温度０〜２５℃、昇圧速度０．０１〜０．１ＭＰａ／分の条件下にてゲージ圧力０．１〜１．６ＭＰａとなるまで加圧供給して上記二次発泡粒子に上記不活性ガスを含浸させることを特徴とする。 The method for producing foamed polylactic acid resin particles for in-mold foam molding according to the present invention is obtained by subjecting primary foamed particles obtained by extrusion foaming of polylactic acid resin to secondary foam to obtain secondary foamed particles. The secondary foamed particles are obtained by pressurizing and supplying an inert gas to the particles at a temperature of 0 to 25 ° C. and a pressure increase rate of 0.01 to 0.1 MPa / min until the gauge pressure is 0.1 to 1.6 MPa. Is impregnated with the above inert gas.
先ず、本発明で用いられるポリ乳酸系樹脂について説明する。本発明で用いられるポリ乳酸系樹脂は、一般に市販されているポリ乳酸系樹脂を用いることができ、具体的には、Ｄ−乳酸及びＬ−乳酸をモノマーとして共重合させるか、Ｄ−乳酸又はＬ−乳酸の何れか一方をモノマーとして重合させるか、或いは、Ｄ−ラクチド、Ｌ−ラクチド及びＤＬ−ラクチドからなる群より選ばれた一又は二以上のラクチドを開環重合させることによって得ることができ、何れのポリ乳酸系樹脂であってもよい。 First, the polylactic acid resin used in the present invention will be described. As the polylactic acid resin used in the present invention, commercially available polylactic acid resins can be used. Specifically, D-lactic acid and L-lactic acid are copolymerized as monomers, or D-lactic acid or It can be obtained by polymerizing any one of L-lactic acid as a monomer or ring-opening polymerization of one or more lactides selected from the group consisting of D-lactide, L-lactide and DL-lactide. Any polylactic acid resin can be used.
そして、ポリ乳酸系樹脂を製造するに際して、モノマーとしてＤ体とＬ体とを併用した場合においてＤ体若しくはＬ体のうちの少ない方の光学異性体の割合が５モル％未満である場合、又は、モノマーとしてＤ体若しくはＬ体のうちの何れか一方の光学異性体のみを用いた場合、即ち、上記ポリ乳酸系樹脂が、その構成モノマー成分としてＤ体及びＬ体の双方の光学異性体を含有し且つＤ体又はＬ体のうちの少ない方の光学異性体の含有量が５モル％未満であるか、或いは、構成モノマー成分としてＤ体又はＬ体のうちの何れか一方の光学異性体のみを含有している場合は、得られるポリ乳酸系樹脂は、その結晶性が高くなり融点が高くなる一方、モノマーとしてＤ体とＬ体とを併用した場合においてＤ体又はＬ体のうちの少ない方の割合が５モル％以上である時は、少ない方の光学異性体が増加するにしたがって、得られるポリ乳酸系樹脂は、その結晶性が低くなり、やがて非結晶となる。 And when producing a polylactic acid-based resin, when the D isomer and L isomer are used in combination as a monomer, the proportion of the lesser optical isomer of the D isomer or L isomer is less than 5 mol%, or In the case where only one of the optical isomers of D-form or L-form is used as a monomer, that is, the polylactic acid-based resin has both D-form and L-form optical isomers as its constituent monomer components. And the content of the smaller optical isomer of D-form or L-form is less than 5 mol%, or any one of the D-form or L-form optical isomer as a constituent monomer component In the case where only the D-form or L-form is used as a monomer, the polylactic acid resin obtained has a higher crystallinity and a higher melting point. The smaller percentage When it mol% or more, according to the optical isomer is increased the smaller the resulting polylactic acid-based resin, its crystallinity decreases, the eventually amorphous.
従って、本発明では、構成モノマー成分としてＤ体及びＬ体の双方の光学異性体を含有し且つＤ体又はＬ体のうちの少ない方の光学異性体の含有量が５モル％未満であるポリ乳酸系樹脂か、或いは、構成モノマー成分としてＤ体又はＬ体のうちの何れか一方の光学異性体のみを含有しているポリ乳酸系樹脂を用いることが好ましい。このようなポリ乳酸系樹脂を用いることによって、得られるポリ乳酸系樹脂発泡粒子の耐熱性を高いものとすることができる。 Therefore, in the present invention, a polymorphism containing both D-form and L-form optical isomers as a constituent monomer component and the content of the smaller of the D-form and L-form is less than 5 mol%. It is preferable to use a lactic acid-based resin or a polylactic acid-based resin containing only one optical isomer of either D-form or L-form as a constituent monomer component. By using such a polylactic acid-based resin, the heat resistance of the obtained polylactic acid-based resin expanded particles can be increased.
更に、Ｄ体とＬ体をモノマーとして併用して重合させて得られたポリ乳酸系樹脂としては、Ｄ体又はＬ体のうちの何れか少ない方の光学異性体の割合が４モル％未満であるモノマーを重合させて得られたポリ乳酸系樹脂が好ましく、Ｄ体又はＬ体のうちの何れか少ない方の光学異性体の割合が３モル％未満であるモノマーを重合させて得られたポリ乳酸系樹脂がより好ましく、Ｄ体又はＬ体のうちの何れか少ない方の光学異性体の割合が２モル％未満であるモノマーを重合させて得られたポリ乳酸系樹脂が特に好ましい。 Furthermore, the polylactic acid-based resin obtained by polymerizing the D-form and the L-form in combination as a monomer has a ratio of the smaller optical isomer of the D-form or the L-form of less than 4 mol%. A polylactic acid resin obtained by polymerizing a certain monomer is preferred, and a polylactic acid resin obtained by polymerizing a monomer in which the proportion of the optical isomer, whichever is smaller, of D-form or L-form is less than 3 mol% A lactic acid-based resin is more preferable, and a polylactic acid-based resin obtained by polymerizing a monomer in which the ratio of the optical isomer, which is the smaller of either the D-form or the L-form, is less than 2 mol% is particularly preferred.
即ち、構成モノマー成分としてＤ体及びＬ体の双方の光学異性体を含有し且つＤ体又はＬ体のうちの少ない方の光学異性体の含有量が４モル％未満であるポリ乳酸系樹脂が好ましく、構成モノマー成分としてＤ体及びＬ体の双方の光学異性体を含有し且つＤ体又はＬ体のうちの少ない方の光学異性体の含有量が３モル％未満であるポリ乳酸系樹脂がより好ましく、構成モノマー成分としてＤ体及びＬ体の双方の光学異性体を含有し且つＤ体又はＬ体のうちの少ない方の光学異性体の含有量が２モル％未満であるポリ乳酸系樹脂が更に好ましい。 That is, a polylactic acid-based resin containing both optical isomers of D-form and L-form as a constituent monomer component, and the content of the smaller optical isomer of D-form or L-form is less than 4 mol%. Preferably, a polylactic acid-based resin that contains both D-form and L-form optical isomers as a constituent monomer component, and the content of the smaller of the D-form and L-form is less than 3 mol%. More preferably, a polylactic acid resin containing both D isomer and L isomer as constituent monomer components, and the content of the lesser of the D isomer and L isomer being less than 2 mol% Is more preferable.
そして、構成モノマー成分としてＤ体及びＬ体を含有するポリ乳酸系樹脂は、Ｄ体又はＬ体のうちの何れか少ない方の光学異性体の割合が少なくなればなる程、ポリ乳酸系樹脂は、その結晶性のみならず融点も上昇する。よって、発泡粒子を金型内に充填して発泡させて得られる発泡成形体の耐熱性も向上し、発泡成形体は高い温度であってもその形態を維持することができる。従って、発泡成形体を金型から高い温度のまま取り出すことが可能となって発泡成形体の金型内における冷却時間が短縮され、発泡成形体の生産効率を向上させることもできる。 And as for the polylactic acid-type resin which contains D body and L body as a constituent monomer component, the ratio of the optical isomer of the smaller one of D body or L body decreases, and the polylactic acid resin becomes In addition to its crystallinity, the melting point increases. Therefore, the heat resistance of the foamed molded product obtained by filling the foamed particles in the mold and foaming is improved, and the foamed molded product can maintain its form even at a high temperature. Therefore, the foamed molded product can be taken out from the mold at a high temperature, the cooling time in the mold of the foamed molded product is shortened, and the production efficiency of the foamed molded product can be improved.
ここで、ポリ乳酸系樹脂中におけるＤ体又はＬ体の含有量は以下の方法によって測定することができる。ポリ乳酸系樹脂を凍結粉砕し、ポリ乳酸系樹脂の粉末２００ｍｇを三角フラスコ内に供給した後、三角フラスコ内に１Ｎの水酸化ナトリウム水溶液３０ミリリットルを加える。そして、三角フラスコを振りながら６５℃に加熱してポリ乳酸系樹脂を完全に溶解させる。しかる後、１Ｎ塩酸を三角フラスコ内に供給して中和し、ｐＨが４〜７の分解溶液を作製し、メスフラスコを用いて所定の体積とする。 Here, the content of D-form or L-form in the polylactic acid-based resin can be measured by the following method. The polylactic acid-based resin is freeze-pulverized and 200 mg of the polylactic acid-based resin powder is supplied into the Erlenmeyer flask, and then 30 ml of a 1N sodium hydroxide aqueous solution is added to the Erlenmeyer flask. Then, the polylactic acid resin is completely dissolved by heating to 65 ° C. while shaking the Erlenmeyer flask. Thereafter, 1N hydrochloric acid is supplied into the Erlenmeyer flask to neutralize it, a decomposition solution having a pH of 4 to 7 is prepared, and a predetermined volume is obtained using a volumetric flask.
次に、分解溶液を０．４５μｍのメンブレンフィルターで濾過した後、液体クロマトグラフを用いて分析し、得られたチャートに基づいてＤ体及びＬ体由来のピーク面積から面積比を存在比としてＤ体量及びＬ体量を算出する。そして、上述と同様の要領を５回繰り返して行い、得られたＤ体量及びＬ体量をそれぞれ相加平均して、ポリ乳酸系樹脂のＤ体量及びＬ体量とした。 Next, after the decomposition solution is filtered through a 0.45 μm membrane filter, it is analyzed using a liquid chromatograph. Based on the obtained chart, the area ratio is calculated from the peak area derived from D-form and L-form as D Calculate body weight and L body weight. Then, the same procedure as described above was repeated 5 times, and the obtained D-form amount and L-form amount were arithmetically averaged to obtain the D-form amount and L-form amount of the polylactic acid resin.
ＨＰＬＣ装置（液体クロマトグラフ）：日本分光社製 商品名「PU-2085 Plus型システ
ム」
カラム：住友分析センター社製 商品名「SUMICHIRAL OA5000」(4.6ｍｍφ×250ｍｍ)
カラム温度：２５℃
移動相：２ｍＭCuSO4水溶液と２−プロパノールとの混合液
(CuSO4水溶液:2-プロパノール(体積比)＝95:5)
移動相流量：１．０ミリリットル／分
検出器：ＵＶ ２５４ｎｍ
注入量：２０マイクロリットル
HPLC system (liquid chromatograph): “PU-2085 Plus type system” manufactured by JASCO Corporation
Column: Product name “SUMICHIRAL OA5000” (4.6 mmφ × 250 mm) manufactured by Sumitomo Analysis Center
Column temperature: 25 ° C
Mobile phase: Mixed solution of 2 mM CuSO 4 aqueous solution and 2-propanol
(CuSO 4 aqueous solution: 2-propanol (volume ratio) = 95: 5)
Mobile phase flow rate: 1.0 ml / min Detector: UV 254 nm
Injection volume: 20 microliters
そして、ポリ乳酸系樹脂を押出発泡させて一次発泡粒子を製造する方法としては、汎用の方法を用いることができ、例えば、ポリ乳酸系樹脂及び発泡剤を押出機に供給して溶融混練し、押出機の先端に取り付けたノズル金型から押出発泡させ、ノズル金型から押出された直後の押出発泡体を連続的に回転刃によって切断した後に直ちに冷却するポリ乳酸系樹脂発泡粒子の製造方法が挙げられる。 And, as a method of producing the primary foamed particles by extrusion foaming the polylactic acid-based resin, a general-purpose method can be used, for example, supplying the polylactic acid-based resin and the foaming agent to the extruder, melt kneading, There is a method for producing polylactic acid resin foamed particles which is extruded and foamed from a nozzle mold attached to the tip of an extruder, and immediately cooled after the extruded foam immediately after being extruded from the nozzle mold is cut by a rotary blade. Can be mentioned.
発泡剤としては、従来から汎用されているものが用いられ、例えば、アゾジカルボンアミド、ジニトロソペンタメチレンテトラミン、ヒドラゾイルジカルボンアミド、重炭酸ナトリウムなどの化学発泡剤；プロパン、ノルマルブタン、イソブタン、ノルマルペンタン、イソペンタン、ヘキサンなどの飽和脂肪族炭化水素、ジメチルエーテルなどのエーテル類、塩化メチル、１，１，１，２−テトラフルオロエタン、１，１−ジフルオロエタン、モノクロロジフルオロメタンなどのフロン、二酸化炭素、窒素などの物理発泡剤などが挙げられ、ジメチルエーテル、プロパン、ノルマルブタン、イソブタン、二酸化炭素が好ましく、プロパン、ノルマルブタン、イソブタンがより好ましく、ノルマルブタン、イソブタンが特に好ましい。なお、発泡剤は、単独で用いられても二種以上が併用されてもよい。 As the blowing agent, those conventionally used are used. For example, chemical blowing agents such as azodicarbonamide, dinitrosopentamethylenetetramine, hydrazoyldicarbonamide, sodium bicarbonate; propane, normal butane, isobutane, normal Saturated aliphatic hydrocarbons such as pentane, isopentane, hexane, ethers such as dimethyl ether, chlorofluorocarbons such as methyl chloride, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, monochlorodifluoromethane, carbon dioxide, Examples thereof include physical blowing agents such as nitrogen, dimethyl ether, propane, normal butane, isobutane and carbon dioxide are preferred, propane, normal butane and isobutane are more preferred, and normal butane and isobutane are particularly preferred. In addition, a foaming agent may be used independently or 2 or more types may be used together.
そして、押出機に供給される発泡剤量としては、少ないと、一次発泡粒子を所望発泡倍率まで発泡させることができないことがある一方、多いと、発泡剤が可塑剤として作用することから溶融状態のポリ乳酸系樹脂の粘弾性が低下し過ぎて発泡性が低下し良好な一次発泡粒子を得ることができず或いは一次発泡粒子の発泡倍率が高過ぎて結晶化度を制御できなくなる場合があるので、ポリ乳酸系樹脂１００重量部に対して０．１〜５重量部が好ましく、０．２〜４重量部がより好ましく、０．３〜３重量部が特に好ましい。
When the amount of the foaming agent supplied to the extruder is small, the primary foamed particles may not be foamed to the desired foaming ratio. On the other hand, when the foaming agent is large, the foaming agent acts as a plasticizer. The viscoelasticity of the polylactic acid-based resin may be too low and foamability may be deteriorated to obtain good primary expanded particles, or the expansion ratio of the primary expanded particles may be too high to control the crystallinity. Therefore, 0.1-5 weight part is preferable with respect to 100 weight part of polylactic acid-type resin, 0.2-4 weight part is more preferable, 0.3-3 weight part is especially preferable.
次に、得られた一次発泡粒子に不活性ガスを含浸させた上で二次発泡させて二次発泡粒子とする。このように、一次発泡粒子を二次発泡させて二次発泡粒子とすることによって高発泡倍率のポリ乳酸系樹脂発泡成形体を得ることができる。なお、上記不活性ガスとしては、例えば、二酸化炭素、窒素、ヘリウム、アルゴンなどが挙げられ、二酸化炭素が好ましい。 Next, the obtained primary expanded particles are impregnated with an inert gas and then subjected to secondary expansion to obtain secondary expanded particles. In this way, a polylactic acid resin foamed molded article having a high expansion ratio can be obtained by secondary foaming of the primary foamed particles into secondary foamed particles. Examples of the inert gas include carbon dioxide, nitrogen, helium, and argon, and carbon dioxide is preferable.
一次発泡粒子に不活性ガスを含浸させる方法としては、例えば、常圧以上の圧力を有する不活性ガス雰囲気下に一次発泡粒子を置くことによって一次発泡粒子中に不活性ガスを含浸させる方法が挙げられる。例えば、オートクレーブや耐圧タンクなどの開閉自在に密閉可能な密閉容器内に一次発泡粒子を供給し、密閉容器内を常圧以上の圧力を有する不活性ガス雰囲気下とする方法や、密閉容器内を不活性ガス雰囲気とした上で、密閉容器内に一次発泡粒子を供給し、密閉容器内に不活性ガスを加圧状態で供給して密閉容器内を常圧以上の圧力を有する不活性ガス雰囲気とする方法などが挙げられる。 Examples of the method of impregnating the primary expanded particles with the inert gas include a method of impregnating the primary expanded particles with the inert gas by placing the primary expanded particles in an inert gas atmosphere having a pressure equal to or higher than normal pressure. It is done. For example, a method in which primary foam particles are supplied into an airtight container that can be opened and closed, such as an autoclave and a pressure tank, and the inside of the airtight container is placed in an inert gas atmosphere having a pressure higher than normal pressure, An inert gas atmosphere in which the primary expanded particles are supplied into the sealed container and the inert gas is supplied in a pressurized state in the sealed container, and the sealed container has a pressure higher than normal pressure. And the like.
そして、一次発泡粒子に不活性ガスを含浸させる時の不活性ガスの温度は−４０〜２５℃が好ましく、−１０〜２０℃がより好ましい。これは、不活性ガスの温度が低いと、不活性ガスの温度を下げるための設備を必要とし、生産コストが高くなることがあるからである。一方、不活性ガスの温度が高いと、一次発泡粒子への不活性ガスの含浸量が低くなり、一次発泡粒子に充分な発泡性を付与することができないことがあると共に、一次発泡粒子の結晶化が促進され、得られるポリ乳酸系樹脂発泡粒子の型内発泡成形性が低下することがあるからである。 And, the temperature of the inert gas when impregnating the primary expanded particles with the inert gas is preferably -40 to 25 ° C, and more preferably -10 to 20 ° C. This is because if the temperature of the inert gas is low, equipment for lowering the temperature of the inert gas is required, which may increase the production cost. On the other hand, when the temperature of the inert gas is high, the amount of the inert gas impregnated into the primary foamed particles becomes low, and sufficient foamability may not be imparted to the primary foamed particles. This is because the formation of the polylactic acid-based resin foamed particles may deteriorate and the in-mold foam moldability of the resulting polylactic acid-based resin foamed particles may deteriorate.
又、一次発泡粒子に不活性ガスを含浸させる時の密閉容器のゲージ圧力は０．２〜１．６ＭＰａが好ましく、０．２８〜１．２ＭＰａがより好ましい。不活性ガスが二酸化炭素である場合には、一次発泡粒子に不活性ガスを含浸させる時の密閉容器のゲージ圧力は０．２〜１．５ＭＰａが好ましく、０．２５〜１．２ＭＰａがより好ましい。これは、圧力が低いと、一次発泡粒子への不活性ガスの含浸量が低くなり、一次発泡粒子に充分な発泡性を付与することができず、得られるポリ乳酸系樹脂発泡粒子の型内発泡成形性が低下することがあるからである。 Further, the gauge pressure of the sealed container when the primary expanded particles are impregnated with the inert gas is preferably 0.2 to 1.6 MPa, and more preferably 0.28 to 1.2 MPa. When the inert gas is carbon dioxide, the gauge pressure of the sealed container when impregnating the primary expanded particles with the inert gas is preferably 0.2 to 1.5 MPa, more preferably 0.25 to 1.2 MPa. . This is because, when the pressure is low, the amount of inert gas impregnated in the primary foamed particles is low, and sufficient foamability cannot be imparted to the primary foamed particles. It is because foam moldability may fall.
一方、圧力が高いと、得られる二次発泡粒子の結晶化度が上昇し、得られるポリ乳酸系樹脂発泡粒子の熱融着性が低下し、得られるポリ乳酸系樹脂発泡成形体の機械的強度が低下することがあるからである。 On the other hand, when the pressure is high, the degree of crystallinity of the resulting secondary foamed particles increases, the heat-fusibility of the resulting polylactic acid-based resin foamed particles decreases, and the resulting polylactic acid-based resin foamed molded article has mechanical properties. This is because the strength may decrease.
更に、一次発泡粒子に不活性ガスを含浸させる時間は、２０分〜２４時間が好ましく、１〜１８時間がより好ましく、３〜８時間が特に好ましい。不活性ガスが二酸化炭素である場合には、一次発泡粒子に不活性ガスを含浸させる時間は２０分〜２４時間が好ましい。これは、含浸時間が短いと、一次発泡粒子に不活性ガスを充分に含浸させることができないからである。一方、含浸時間が長いと、ポリ乳酸系樹脂発泡粒子の製造効率が低下するからである。 Furthermore, the time for impregnating the primary expanded particles with the inert gas is preferably 20 minutes to 24 hours, more preferably 1 to 18 hours, and particularly preferably 3 to 8 hours. When the inert gas is carbon dioxide, the time for impregnating the primary expanded particles with the inert gas is preferably 20 minutes to 24 hours. This is because if the impregnation time is short, the primary expanded particles cannot be sufficiently impregnated with the inert gas. On the other hand, when the impregnation time is long, the production efficiency of the polylactic acid-based resin expanded particles is lowered.
このように、一次発泡粒子に不活性ガスを−４０〜２５℃で且つ密閉容器内のゲージ圧力０．２〜１．６ＭＰａの圧力下にて含浸させることによって、一次発泡粒子の結晶化度の上昇を抑えつつ、発泡性を向上させることができる。 Thus, by impregnating the primary foamed particles with an inert gas at −40 to 25 ° C. and a gauge pressure of 0.2 to 1.6 MPa in a sealed container, the crystallinity of the primary foamed particles is improved. While suppressing the rise, the foamability can be improved.
上述のようにして一次発泡粒子に不活性ガスを含浸させた上で二次発泡させて高発泡倍率の二次発泡粒子とする。なお、一次発泡粒子を加熱する加熱媒体としては、特に限定されないが、乾燥した空気が好ましい。 As described above, the primary expanded particles are impregnated with an inert gas and then subjected to secondary expansion to obtain secondary expanded particles having a high expansion ratio. The heating medium for heating the primary expanded particles is not particularly limited, but dry air is preferable.
一次発泡粒子を発泡させて二次発泡粒子とする際の加熱温度としては、高いと、得られる二次発泡粒子の結晶化度が上昇して、得られるポリ乳酸系樹脂発泡粒子同士の熱融着性が低下し、得られるポリ乳酸系樹脂発泡成形体の機械的強度及び外観性が低下するので、７０℃未満が好ましい。 When the heating temperature when foaming the primary foamed particles to obtain the secondary foamed particles is high, the crystallinity of the resulting secondary foamed particles increases, and the resulting polylactic acid resin foamed particles are thermally fused. Less than 70 ° C. is preferred because the adhesiveness is lowered and the mechanical strength and appearance of the resulting polylactic acid resin foamed molded article are lowered.
次に、二次発泡粒子に不活性ガスを含浸させて型内発泡成形用ポリ乳酸系樹脂発泡粒子を製造する。なお、不活性ガスとしては、例えば、二酸化炭素、窒素、ヘリウム、アルゴンなどが挙げられ、二酸化炭素が好ましい。一次発泡粒子に含浸させた不活性ガスと、二次発泡粒子に含浸させる不活性ガスとは同一であっても相違していてもよいが、同一であることが好ましい。 Next, the secondary foamed particles are impregnated with an inert gas to produce polylactic acid resin foamed particles for in-mold foam molding. In addition, as an inert gas, a carbon dioxide, nitrogen, helium, argon etc. are mentioned, for example, A carbon dioxide is preferable. The inert gas impregnated in the primary expanded particles and the inert gas impregnated in the secondary expanded particles may be the same or different, but are preferably the same.
二次発泡粒子に不活性ガスを含浸させる方法を説明する。先ず、オートクレーブや耐圧タンクなどの開閉自在に密閉可能な密閉容器内に二次発泡粒子を供給し、密閉容器内に不活性ガスを常圧にて供給して、二次発泡粒子を常圧の不活性ガス雰囲気下に置く。なお、密閉容器内に予め不活性ガスを供給して密閉容器内を常圧の不活性ガス雰囲気とした上で、密閉容器内に二次発泡粒子を供給して、二次発泡粒子を常圧の不活性ガス雰囲気下に置いてもよい。 A method for impregnating the secondary expanded particles with an inert gas will be described. First, the secondary foam particles are supplied into an airtight container that can be opened and closed, such as an autoclave or a pressure tank, and an inert gas is supplied into the airtight container at normal pressure, so that the secondary foam particles are at normal pressure. Place under an inert gas atmosphere. In addition, after supplying an inert gas into the sealed container in advance to create an inert gas atmosphere at normal pressure in the sealed container, the secondary expanded particles are supplied into the sealed container to It may be placed under an inert gas atmosphere.
しかる後、密閉容器内に不活性ガスを加圧状態にて供給し、密閉容器内の二次発泡粒子に不活性ガスを含浸させる。密閉容器内に不活性ガスを供給する際、密閉容器内の圧力の昇圧速度が０．０１〜０．１ＭＰａ／分となるように、好ましくは、昇圧速度が０．０１〜０．０９５ＭＰａ／分となるように、より好ましくは、昇圧速度が０．０１〜０．０９ＭＰａ／分となるように、密閉容器内に不活性ガスを供給する。なお、密閉容器内の昇圧速度は、０．０１〜０．１ＭＰａ／分となるように調整されておれば、一定であっても変化してもよい。 Thereafter, an inert gas is supplied into the sealed container in a pressurized state, and the secondary expanded particles in the sealed container are impregnated with the inert gas. When supplying the inert gas into the sealed container, the pressure increasing rate is preferably 0.01 to 0.095 MPa / min so that the pressure increasing rate of the pressure in the sealed container is 0.01 to 0.1 MPa / min. More preferably, the inert gas is supplied into the sealed container so that the pressure increase rate is 0.01 to 0.09 MPa / min. In addition, as long as the pressurization speed | rate in an airtight container is adjusted so that it may become 0.01-0.1 MPa / min, you may change even if it is constant.
密閉容器内の圧力の昇圧速度が小さいと、二次発泡粒子に不活性ガスを含浸させるのに要する時間が長くなり過ぎてポリ乳酸系樹脂発泡粒子の製造効率が低下するからである。 This is because if the pressure increase rate of the pressure in the sealed container is small, the time required for impregnating the secondary foamed particles with the inert gas becomes too long and the production efficiency of the polylactic acid-based resin foamed particles decreases.
一方、密閉容器内の圧力の昇圧速度が大きいと、二次発泡粒子は二回の発泡によって比較的高発泡倍率となっていることから、密閉容器内の急激に大きくなる圧力に二次発泡粒子が耐えきれなくなり、その結果、二次発泡粒子が潰れてしまい、得られるポリ乳酸系樹脂発泡粒子の型内発泡成形性が低下し、得られるポリ乳酸系樹脂発泡成形体の機械的強度及び外観性が低下するからである。 On the other hand, if the pressure increase rate of the pressure in the sealed container is large, the secondary foamed particles have a relatively high foaming ratio due to foaming twice, so that the secondary foamed particles are rapidly increased in pressure in the sealed container. As a result, the secondary foamed particles are crushed, the in-mold foam moldability of the obtained polylactic acid resin foamed particles is lowered, and the mechanical strength and appearance of the resulting polylactic acid resin foam molded article This is because the sex is lowered.
即ち、密閉容器内の圧力の昇圧速度を０．０１〜０．１ＭＰａ／分となるように調整することにより、密閉容器内の二次発泡粒子に不活性ガスを含浸させて二次発泡粒子の内圧を増加させながら、密閉容器内の圧力を徐々に増加させており、よって、二次発泡粒子が不活性ガスによる圧力によって押し潰れることはなく、二次発泡粒子に不活性ガスが安定的に且つ確実に含浸される。 That is, by adjusting the pressure increase rate of the pressure in the sealed container to be 0.01 to 0.1 MPa / min, the secondary foamed particles in the sealed container are impregnated with an inert gas to While increasing the internal pressure, the pressure in the sealed container is gradually increased, so that the secondary expanded particles are not crushed by the pressure of the inert gas, and the inert gas is stably added to the secondary expanded particles. And it is surely impregnated.
そして、密閉容器内に不活性ガスを加圧状態にて供給する際の不活性ガスの温度は、低いと、二次発泡粒子に不活性ガスを充分に含浸させることができず、高いと、二次発泡粒子を構成しているポリ乳酸系樹脂の結晶化が進行し、得られるポリ乳酸系樹脂発泡粒子の熱融着性が低下して、ポリ乳酸系樹脂発泡粒子を用いて得られたポリ乳酸系樹脂発泡成形体の機械的強度や外観が低下するので、０〜２５℃に限定され、５〜２０℃が好ましい。 And if the temperature of the inert gas when supplying the inert gas in a sealed container in a pressurized state is low, the secondary expanded particles cannot be sufficiently impregnated with the inert gas, and if high, The polylactic acid resin constituting the secondary expanded particles was crystallized, and the heat-fusible property of the obtained polylactic acid resin expanded particles was lowered. Since the mechanical strength and appearance of the polylactic acid resin foamed molded article are lowered, it is limited to 0 to 25 ° C, and preferably 5 to 20 ° C.
又、密閉容器内への不活性ガスの加圧供給は、密閉容器内のゲージ圧力が０．１〜１．６ＭＰａとなるまで行われる。密閉容器内への不活性ガスの加圧供給が密閉容器内のゲージ圧力が０．１ＭＰａ未満にて終了すると、二次発泡粒子に不活性ガスを充分に含浸させることができない。一方、密閉容器内への不活性ガスの加圧供給が密閉容器内のゲージ圧力が１．６ＭＰａを越えて行われると、二次発泡粒子が不活性ガスの圧力によって押し潰されてしまう虞れがある。 Further, the pressurized supply of the inert gas into the sealed container is performed until the gauge pressure in the sealed container becomes 0.1 to 1.6 MPa. If the pressurized supply of the inert gas into the sealed container is completed when the gauge pressure in the sealed container is less than 0.1 MPa, the secondary expanded particles cannot be sufficiently impregnated with the inert gas. On the other hand, when the pressurized supply of the inert gas into the sealed container is performed with the gauge pressure in the sealed container exceeding 1.6 MPa, the secondary expanded particles may be crushed by the pressure of the inert gas. There is.
上述の条件で二次発泡粒子に不活性ガスを含浸させることによって、二次発泡粒子が不活性ガスの圧力によって押し潰されることなく、二次発泡粒子に不活性ガスを含浸させることができ、得られる型内発泡成形用ポリ乳酸系樹脂発泡粒子は優れた発泡性を有し、型内発泡成形時にポリ乳酸系樹脂発泡粒子同士の融着性が向上し、得られるポリ乳酸系樹脂発泡成形体は優れた機械的強度及び外観を有する。 By impregnating the secondary expanded particles with the inert gas under the above-described conditions, the secondary expanded particles can be impregnated with the inert gas without being crushed by the pressure of the inert gas, The obtained polylactic acid-based resin foamed particles for in-mold foam molding have excellent foamability, and the fusion property between the polylactic acid-based resin foamed particles is improved at the time of in-mold foam molding. The body has excellent mechanical strength and appearance.
得られたポリ乳酸系樹脂発泡粒子の三次発泡性は、低いと、ポリ乳酸系樹脂発泡粒子を用いて型内発泡成形を行った場合にポリ乳酸系樹脂発泡粒子同士の熱融着が不充分となり、得られるポリ乳酸系樹脂発泡成形体の機械的強度及び外観が低下することがあるので、２．５以上が好ましく、２．６〜３．５がより好ましい。 If the tertiary foamability of the obtained polylactic acid-based resin expanded particles is low, the thermal fusion between the polylactic acid-based resin expanded particles is insufficient when in-mold foam molding is performed using the polylactic acid-based resin expanded particles. Thus, since the mechanical strength and appearance of the obtained polylactic acid resin foam molded article may be lowered, 2.5 or more is preferable, and 2.6 to 3.5 is more preferable.
なお、ポリ乳酸系樹脂発泡粒子の三次発泡性は下記の要領で測定された値をいう。先ず、ポリ乳酸系樹脂発泡粒子の嵩密度Ｄ1を後述の要領で測定する。次に、ポリ乳酸系樹脂発泡粒子を９０℃の水に５秒間に亘って浸漬してポリ乳酸系樹脂発泡粒子を発泡させた後に４０℃にて５時間に亘って乾燥させて三次発泡粒子を得る。この三次発泡粒子の嵩密度Ｄ2を後述の要領で測定し、下記式に基づいて算出することができる。
三次発泡性＝Ｄ1／Ｄ2
The tertiary foamability of the polylactic acid resin foamed particles refers to a value measured in the following manner. First, measure the bulk density D 1 of the polylactic acid-based resin foamed particles in the manner described below. Next, the polylactic acid-based resin expanded particles are immersed in water at 90 ° C. for 5 seconds to foam the polylactic acid-based resin expanded particles, and then dried at 40 ° C. for 5 hours to obtain the tertiary expanded particles. obtain. The bulk density D 2 of the tertiary foamed particles measured in the manner described below, it can be calculated based on the following equation.
Tertiary foamable = D 1 / D 2
次に、上述のようにして得られた型内発泡成形用ポリ乳酸系樹脂発泡粒子を用いて型内発泡成形によってポリ乳酸系樹脂発泡成形体を製造することができる。具体的には、ポリ乳酸系樹脂発泡粒子を金型のキャビティ内に充填して加熱し、ポリ乳酸系樹脂発泡粒子を発泡させることによって、ポリ乳酸系樹脂発泡粒子を発泡させて得られる発泡粒子同士をそれらの発泡圧によって互いに融着一体化させると共にポリ乳酸系樹脂の結晶化度を上昇させて、融着性及び耐熱性に優れた所望形状を有するポリ乳酸系樹脂発泡成形体を得ることができる。 Next, a polylactic acid resin foam molded article can be produced by in-mold foam molding using the polylactic acid resin foamed particles for in-mold foam molding obtained as described above. Specifically, foamed particles obtained by foaming polylactic acid-based resin foamed particles by filling polylactic acid-based resin foamed particles in a mold cavity and heating the foamed polylactic acid-based resin foamed particles To obtain a polylactic acid resin foam molded article having a desired shape excellent in fusion property and heat resistance by fusing together with each other by their foaming pressure and increasing the crystallinity of the polylactic acid resin. Can do.
なお、金型内に充填したポリ乳酸系樹脂発泡粒子の加熱媒体としては、特に限定されず、水蒸気の他に、熱風、温水などが挙げられるが、６０〜１００℃の水を用いることが好ましい。これは、水は、液体状であって比熱が大きいことから、温度が低くても金型内のポリ乳酸系樹脂発泡粒子に発泡に必要な高い熱量を充分に付与することができるからである。 The heating medium for the polylactic acid-based resin foam particles filled in the mold is not particularly limited, and examples include hot air and hot water in addition to water vapor, but it is preferable to use water at 60 to 100 ° C. . This is because water is in a liquid state and has a large specific heat, so that a high amount of heat necessary for foaming can be sufficiently imparted to the polylactic acid resin foamed particles in the mold even at a low temperature. .
加熱媒体として用いる水の温度は、低いと、金型内に充填したポリ乳酸系樹脂発泡粒子の発泡が不充分となりポリ乳酸系樹脂発泡粒子同士の熱融着性が低下して得られるポリ乳酸系樹脂発泡成形体の機械的強度や外観性が低下することがある一方、高いと、水を高圧状態としなければならず、ボイラーなどの大掛かりな設備を要するので、６０〜１００℃が好ましく、７０〜９９℃がより好ましく、８０〜９８℃が特に好ましい。 If the temperature of the water used as the heating medium is low, the polylactic acid resin foam particles filled in the mold are insufficiently foamed and the polylactic acid obtained by reducing the heat-fusibility between the polylactic acid resin foam particles On the other hand, the mechanical strength and appearance of the resin-based resin molded article may be reduced. On the other hand, if it is high, water must be in a high pressure state, and large equipment such as a boiler is required. 70-99 degreeC is more preferable and 80-98 degreeC is especially preferable.
金型内に充填したポリ乳酸系樹脂発泡粒子に６０〜１００℃の水を供給してポリ乳酸系樹脂発泡粒子を加熱する方法としては、特に限定されず、例えば、(1)従来から用いられている型内発泡成形機において水蒸気の代わりに６０〜１００℃の水を金型内に供給する方法、(2)ポリ乳酸系樹脂発泡粒子を充填した金型を、６０〜１００℃の水中に浸漬してポリ乳酸系樹脂発泡粒子に水を供給する方法などが挙げられ、複雑な形状の金型であっても金型全体、即ち、ポリ乳酸系樹脂発泡粒子を全体的に均一に加熱、発泡させることができることから、上記(2)の方法が好ましい。 The method of heating the polylactic acid resin expanded particles by supplying water at 60 to 100 ° C. to the polylactic acid resin expanded particles filled in the mold is not particularly limited. For example, (1) conventionally used A method of supplying 60-100 ° C. water in place of water vapor into the mold in the in-mold foam molding machine, and (2) a mold filled with polylactic acid-based resin expanded particles in water at 60-100 ° C. Examples include a method of immersing and supplying water to the polylactic acid-based resin expanded particles, and even when the mold has a complicated shape, the entire mold, that is, the polylactic acid-based resin expanded particles is heated uniformly throughout. The method (2) is preferred because it can be foamed.
そして、６０〜１００℃の水でポリ乳酸系樹脂発泡粒子を加熱して型内発泡成形を行った後、金型内に形成されたポリ乳酸系樹脂発泡成形体を冷却した上で金型を開放して所望形状を有するポリ乳酸系樹脂発泡成形体を得ることができる。 And after heating the polylactic acid-based resin foamed particles with water at 60 to 100 ° C. to perform in-mold foam molding, after cooling the polylactic acid-based resin foam molded body formed in the mold, the mold is A polylactic acid-based resin foam molded body having a desired shape can be obtained by opening.
本発明の型内発泡成形用ポリ乳酸系樹脂発泡粒子の製造方法は、上述の如く、二次発泡粒子に所定条件にて不活性ガスを含浸させているので、二次発泡粒子が不活性ガスの圧力によって押し潰されることなく二次発泡粒子に不活性ガスを含浸させることができ、よって、得られる型内発泡成形用ポリ乳酸系樹脂発泡粒子は優れた発泡性を有しており、この型内発泡成形用ポリ乳酸系樹脂発泡粒子を用いて得られたポリ乳酸系樹脂発泡成形体は優れた機械的強度及び外観を有している。 In the method for producing foamed polylactic acid resin particles for in-mold foam molding of the present invention, as described above, the secondary foamed particles are impregnated with an inert gas under predetermined conditions. The secondary foamed particles can be impregnated with an inert gas without being crushed by the pressure of the pressure, and thus the obtained polylactic acid-based resin foamed particles for in-mold foam molding have excellent foaming properties. A polylactic acid resin foam molded article obtained using the polylactic acid resin foamed particles for in-mold foam molding has excellent mechanical strength and appearance.
又、上記型内発泡成形用ポリ乳酸系樹脂発泡粒子の製造方法において、ポリ乳酸系樹脂として、構成モノマー成分としてＤ体及びＬ体の双方の光学異性体を含有し且つＤ体又はＬ体のうちの少ない方の光学異性体の含有量が５モル％未満であるポリ乳酸系樹脂か、或いは、構成モノマー成分としてＤ体又はＬ体のうちの何れか一方の光学異性体のみを含有しているポリ乳酸系樹脂を用いて場合には、得られるポリ乳酸系樹脂発泡粒子は、その結晶性が高くて耐熱性に優れている。 Further, in the above method for producing foamed polylactic acid-based resin particles for foam molding, the polylactic acid-based resin contains both optical isomers of D-form and L-form as constituent monomer components, and D-form or L-form Either the polylactic acid resin in which the content of the smaller optical isomer is less than 5 mol%, or only one optical isomer of D-form or L-form as a constituent monomer component When the polylactic acid resin used is used, the resulting polylactic acid resin foamed particles have high crystallinity and excellent heat resistance.
従って、得られる型内発泡成形用ポリ乳酸系樹脂発泡粒子は、型内発泡成形において、優れた発泡性及び熱融着性を発揮し、得られるポリ乳酸系樹脂発泡成形体は、外観性、耐熱性及び機械的強度に優れている。 Therefore, the obtained polylactic acid-based resin foamed particles for in-mold foam molding exhibit excellent foamability and heat-fusibility in in-mold foam molding, and the resulting polylactic acid-based resin foam molded article has an appearance property, Excellent heat resistance and mechanical strength.
本発明において、発泡粒子の嵩密度、ポリ乳酸系樹脂発泡粒子の収縮率及び結晶化度、並びに、ポリ乳酸系樹脂発泡成形体の外観は下記の要領によって測定されたものをいう。 In the present invention, the bulk density of the expanded particles, the shrinkage rate and crystallinity of the expanded polylactic acid resin particles, and the appearance of the expanded polylactic acid resin molded product are those measured according to the following procedures.
（発泡粒子の嵩密度）
発泡粒子の嵩密度は、ＪＩＳ Ｋ６９１１：１９９５年「熱硬化性プラスチック一般試験方法」に準拠して測定されたものをいう。即ち、ＪＩＳ Ｋ６９１１に準拠した見掛け密度測定器を用いて測定し、下記式に基づいて発泡粒子の嵩密度を測定した。
(Bulk density of expanded particles)
The bulk density of the expanded particles refers to that measured in accordance with JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. That is, it measured using the apparent density measuring device based on JISK6911, and measured the bulk density of the expanded particle based on the following formula.
発泡粒子の嵩密度（ｇ／ｃｍ3）
＝〔試料を入れたメスシリンダーの質量（ｇ）−メスシリンダーの質量（ｇ）〕
／〔メスシリンダーの容量（ｃｍ3）〕
Bulk density of expanded particles (g / cm 3 )
= [Mass of measuring cylinder with sample (g) -Mass of measuring cylinder (g)]
/ [Capacity of measuring cylinder (cm 3 )]
（ポリ乳酸系樹脂発泡粒子の収縮率）
二次発泡粒子の嵩密度Ｄ3を上述の要領で測定した。次に、二次発泡粒子に不活性ガスを含浸させて得られたポリ乳酸系樹脂発泡粒子を１時間に亘って放置した後、ポリ乳酸系樹脂発泡粒子の嵩密度Ｄ4を上述の要領で測定し、下記式に基づいて収縮率を算出した。
収縮率（％）＝１００×（Ｄ4−Ｄ3）／Ｄ3
(Shrinkage of polylactic acid resin expanded particles)
The bulk density D 3 of the secondary foamed particles was measured in the manner described above. Next, after leaving the polylactic acid-based resin expanded particles obtained by impregnating the secondary expanded particles with an inert gas for 1 hour, the bulk density D 4 of the polylactic acid-based resin expanded particles is set as described above. The shrinkage rate was calculated based on the following formula.
Shrinkage rate (%) = 100 × (D 4 −D 3 ) / D 3
（ポリ乳酸系樹脂発泡粒子の連続気泡率）
ポリ乳酸系樹脂発泡粒子の連続気泡率は下記の要領で測定される。先ず、体積測定空気比較式比重計の試料カップを用意し、この試料カップの８０％程度を満たす量のポリ乳酸系樹脂発泡粒子の全重量Ａ（ｇ）を測定する。次に、上記ポリ乳酸系樹脂発泡粒子全体の体積Ｂ（ｃｍ3）を比重計を用いて１−１／２−１気圧法により測定する。なお、体積測定空気比較式比重計は、例えば、東京サイエンス社から商品名「１０００型」にて市販されている。
(Open cell ratio of polylactic acid resin foamed particles)
The open cell ratio of the polylactic acid-based resin expanded particles is measured in the following manner. First, a sample cup of a volumetric air comparison type hydrometer is prepared, and the total weight A (g) of polylactic acid resin expanded particles in an amount satisfying about 80% of the sample cup is measured. Next, the volume B (cm 3 ) of the whole polylactic acid-based resin expanded particles is measured by a 1-1 / 2-1 atmospheric pressure method using a hydrometer. The volumetric air comparison type hydrometer is commercially available, for example, from Tokyo Science Co. under the trade name “1000 type”.
続いて、金網製の容器を用意し、この金網製の容器を水中に浸漬し、この水中に浸漬した状態における金網製の容器の重量Ｃ（ｇ）を測定する。次に、この金網製の容器内に上記ポリ乳酸系樹脂発泡粒子を全量入れた上で、この金網製の容器を水中に浸漬し、水中に浸漬した状態における金網製の容器とこの金網製容器に入れたポリ乳酸系樹脂発泡粒子の全量とを併せた重量Ｄ（ｇ）を測定する。 Subsequently, a wire mesh container is prepared, the wire mesh container is immersed in water, and the weight C (g) of the wire mesh container in the state immersed in the water is measured. Next, after all the polylactic acid-based resin expanded particles are put in the wire mesh container, the wire mesh container is immersed in water, and the wire mesh container and the wire mesh container are immersed in water. The weight D (g) of the total amount of the polylactic acid-based resin expanded particles put in the container is measured.
そして、下記式に基づいてポリ乳酸系樹脂発泡粒子の見掛け体積Ｅ（ｃｍ3）を算出し、この見掛け体積Ｅと上記ポリ乳酸系樹脂発泡粒子全体の体積Ｂ（ｃｍ3）に基づいて下記式によりポリ乳酸系樹脂発泡粒子の連続気泡率を算出することができる。なお、水１ｇの体積を１ｃｍ3 とした。
Ｅ＝Ａ＋（Ｃ−Ｄ）
連続気泡率（％）＝１００×（Ｅ−Ｂ）／Ｅ
Then, the apparent volume E (cm 3 ) of the polylactic acid-based resin expanded particles is calculated based on the following formula, and the following formula is calculated based on this apparent volume E and the volume B (cm 3 ) of the entire polylactic acid-based resin expanded particles. Thus, the open cell ratio of the polylactic acid-based resin expanded particles can be calculated. The volume of 1 g of water was 1 cm 3 .
E = A + (CD)
Open cell ratio (%) = 100 × (EB) / E
（ポリ乳酸系樹脂発泡粒子の結晶化度）
ポリ乳酸系樹脂発泡粒子の結晶化度は、示差走査熱量計（ＤＳＣ）を用いてＪＩＳ Ｋ７１２１に記載の測定方法に準拠して１０℃／分の昇温速度にて昇温しながら測定された１ｍｇ当たりの冷結晶化熱量及び１ｍｇ当たりの融解熱量に基づいて下記式により算出することができる。
(Crystallinity of polylactic acid resin foamed particles)
The degree of crystallinity of the polylactic acid-based resin expanded particles was measured using a differential scanning calorimeter (DSC) while raising the temperature at a rate of temperature increase of 10 ° C./min according to the measurement method described in JIS K7121. It can be calculated by the following formula based on the amount of cold crystallization per 1 mg and the amount of heat of fusion per 1 mg.
（ポリ乳酸系樹脂発泡成形体の外観）
ポリ乳酸系樹脂発泡成形体の外観を目視観察して下記基準に基づいて判断した。
○：ポリ乳酸系樹脂発泡粒子の伸びが良く、ポリ乳酸系樹脂発泡成形体の発泡粒子間に
凹凸が見られない。
×：ポリ乳酸系樹脂発泡粒子の伸びが悪く、ポリ乳酸系樹脂発泡成形体の発泡粒子間に
凹凸が見られる。
(Appearance of polylactic acid resin foam molding)
The appearance of the polylactic acid resin foamed molded article was visually observed and judged based on the following criteria.
○: Polylactic acid-based resin expanded particles have good elongation, and no irregularities are observed between the expanded particles of the polylactic acid-based resin expanded molded article.
X: The elongation of the polylactic acid-based resin expanded particles is poor, and unevenness is observed between the expanded particles of the polylactic acid-based resin expanded molded article.
（実施例１）
結晶性のポリ乳酸系樹脂（ユニチカ社製 商品名「ＴＥＲＲＡＭＡＣ ＨＶ−６２５０Ｈ」、融点（ｍｐ）：１６９．１℃、Ｄ体比率：１．２モル％、Ｌ体比率：９８．８モル％）１００重量部及び気泡調整剤としてポリテトラフルオロエチレン粉末（旭硝子社製 商品名「フルオンＬ１６９Ｊ」）０．１重量部を口径が６５ｍｍの単軸押出機に供給して溶融混練した。なお、単軸押出機内において、ポリ乳酸系樹脂を始めは１９０℃にて溶融混練した後に２２０℃まで昇温させながら溶融混練した。
Example 1
Crystalline polylactic acid resin (trade name “TERRAMAC HV-6250H” manufactured by Unitika Ltd., melting point (mp): 169.1 ° C., D-form ratio: 1.2 mol%, L-form ratio: 98.8 mol%) 100 parts by weight and 0.1 part by weight of a polytetrafluoroethylene powder (trade name “Fluon L169J” manufactured by Asahi Glass Co., Ltd.) as a foam regulator were supplied to a single screw extruder having a diameter of 65 mm and melt-kneaded. In the single screw extruder, the polylactic acid resin was first melt-kneaded at 190 ° C. and then melt-kneaded while raising the temperature to 220 ° C.
次に、単軸押出機の途中から、イソブタン３５重量％及びノルマルブタン６５重量％からなるブタンをポリ乳酸系樹脂１００重量部に対して１．０重量部となるように溶融状態のポリ乳酸系樹脂に圧入してポリ乳酸系樹脂中に均一に分散させた。 Next, in the middle of the single-screw extruder, a polylactic acid-based polylactic acid in a molten state so that butane composed of 35% by weight isobutane and 65% by weight normal butane is 1.0 part by weight with respect to 100 parts by weight of the polylactic acid-based resin. The resin was pressed into the resin and uniformly dispersed in the polylactic acid resin.
しかる後、溶融状態のポリ乳酸系樹脂を冷却した後、単軸押出機の前端に取り付けた出口部の直径が１．０ｍｍのノズルを２０個有しているマルチノズル金型の各ノズルから剪断速度７６３９ｓｅｃ-1でポリ乳酸系樹脂を押出発泡させ、押出発泡された直後のポリ乳酸系樹脂押出発泡体を所定長さ毎にカッターを用いて切断した後に冷却して一次発泡粒子を得た。得られた一次発泡粒子の粒子径は２．０〜３．０ｍｍであった。 Thereafter, after cooling the molten polylactic acid resin, shearing is performed from each nozzle of the multi-nozzle mold having 20 nozzles having a diameter of 1.0 mm at the outlet portion attached to the front end of the single screw extruder. The polylactic acid resin was extruded and foamed at a speed of 7639 sec −1 , and the polylactic acid resin extruded foam immediately after the extrusion foaming was cut with a cutter for each predetermined length, and then cooled to obtain primary expanded particles. The particle diameter of the obtained primary expanded particles was 2.0 to 3.0 mm.
そして、得られた一次発泡粒子を１０リットルの開閉自在な密閉容器内に供給して常圧下にて密閉容器内の空気を二酸化炭素と完全に置換した上で密閉し、この密閉容器内の二酸化炭素を２０℃に維持した上で、密閉容器内に２０℃の二酸化炭素を密閉容器内のゲージ圧力１．０ＭＰａにて圧入し、一次発泡粒子に二酸化炭素を５時間に亘って含浸した。 Then, the obtained primary foamed particles are supplied into a 10-liter openable / closable sealed container, and the air in the sealed container is completely replaced with carbon dioxide under normal pressure. After maintaining the carbon at 20 ° C., carbon dioxide at 20 ° C. was injected into the sealed container at a gauge pressure of 1.0 MPa in the sealed container, and the primary foamed particles were impregnated with carbon dioxide for 5 hours.
一次発泡粒子を密閉容器から取り出して、一次発泡粒子を直ちに撹拌機付きの熱風乾燥機に供給し、一次発泡粒子を撹拌しながら６５℃の乾燥した熱風で３分間に亘って加熱して発泡させ、粒径が３．５〜５．０ｍｍ、嵩密度が０．０４９ｇ／ｃｍ3、結晶化度が２３．２％の二次発泡粒子を得た。 The primary foam particles are taken out from the sealed container, and the primary foam particles are immediately supplied to a hot air dryer with a stirrer, and the primary foam particles are heated and foamed with hot air dried at 65 ° C. for 3 minutes while stirring. Secondary expanded particles having a particle size of 3.5 to 5.0 mm, a bulk density of 0.049 g / cm 3 , and a crystallinity of 23.2% were obtained.
次に、開閉自在な密閉容器を別に用意し、この密閉容器内に二次発泡粒子を供給した後、密閉容器内の空気を常圧にて二酸化炭素に完全に置換した。しかる後、密閉容器を密閉し、この密閉容器内の二酸化炭素を１８℃に維持した上で、密閉容器内に１８℃の二酸化炭素を密閉容器内の圧力の昇圧速度が０．０１ＭＰａ／分となるように加圧状態で供給し、密閉容器内のゲージ圧力が０．６ＭＰａとなった時点で密閉容器内への二酸化炭素の供給を停止した。そして、密閉容器内への二酸化炭素の供給を停止してから３時間に亘って放置して二次発泡粒子に二酸化炭素を含浸させて型内発泡成形用ポリ乳酸系樹脂発泡粒子を得た。 Next, an airtight container that can be freely opened and closed was prepared, and after the secondary expanded particles were supplied into the airtight container, the air in the airtight container was completely replaced with carbon dioxide at normal pressure. Thereafter, the sealed container is sealed, and the carbon dioxide in the sealed container is maintained at 18 ° C., and then the pressure increase rate of the pressure in the sealed container is set to 0.01 MPa / min. In a pressurized state, the supply of carbon dioxide into the sealed container was stopped when the gauge pressure in the sealed container reached 0.6 MPa. Then, after the supply of carbon dioxide into the sealed container was stopped, it was left for 3 hours to impregnate the secondary foamed particles with carbon dioxide to obtain polylactic acid resin foamed particles for in-mold foam molding.
得られたポリ乳酸系樹脂発泡粒子を金型の縦３０ｍｍ×横３００ｍｍ×高さ３００ｍｍの直方体形状のキャビティ内に充填した。そして、加熱水槽内に８５℃に維持された水を溜め、この加熱水槽内の水中にポリ乳酸系樹脂発泡粒子を充填した金型を完全に１分間に亘って浸漬して、金型の供給口を通じて、金型のキャビティ内に充填したポリ乳酸系樹脂発泡粒子に水を供給し、ポリ乳酸系樹脂発泡粒子を加熱、発泡させてポリ乳酸系樹脂発泡粒子同士を熱融着一体化させた。 The obtained polylactic acid-based resin foamed particles were filled into a rectangular parallelepiped-shaped cavity having a length of 30 mm, a width of 300 mm, and a height of 300 mm. Then, water maintained at 85 ° C. is stored in the heated water tank, and a mold filled with polylactic acid resin foam particles is completely immersed in the water in the heated water tank for 1 minute to supply the mold. Water was supplied to the foamed polylactic acid resin filled in the cavity of the mold through the mouth, and the foamed polylactic acid resin was heated and foamed so that the polylactic acid resin foamed particles were fused together. .
次に、加熱水槽内から金型を取り出した。そして、別の冷却水槽に２０℃に維持された水を溜め、この冷却水槽内に金型を完全に５分間に亘って浸漬して、金型内のポリ乳酸系樹脂発泡成形体を冷却した。金型を冷却水槽から取り出して金型を開放して直方体形状のポリ乳酸系樹脂発泡成形体を得た。得られたポリ乳酸系樹脂発泡成形体は、非常に優れた外観を有していた。 Next, the mold was taken out from the heated water tank. And the water maintained at 20 degreeC was stored in another cooling water tank, and the metal mold | die was completely immersed in this cooling water tank over 5 minutes, and the polylactic acid-type resin foaming molding in a metal mold | die was cooled. . The mold was taken out from the cooling water tank, and the mold was opened to obtain a rectangular parallelepiped polylactic acid resin foam molded product. The obtained polylactic acid resin foamed molded article had a very excellent appearance.
（実施例２）
密閉容器内に二次発泡粒子を供給した後、密閉容器内の空気を常圧にて二酸化炭素に完全に置換した。しかる後、密閉容器を密閉し、この密閉容器内の二酸化炭素を１８℃に維持した上で、密閉容器内に１８℃の二酸化炭素を密閉容器内の圧力の昇圧速度が０．０１ＭＰａ／分となるように加圧状態で供給し、密閉容器内のゲージ圧力が１．５ＭＰａとなった時点で密閉容器内への二酸化炭素の供給を停止した。そして、密閉容器内への二酸化炭素の供給を停止してから３時間に亘って放置して二次発泡粒子に二酸化炭素を含浸させて型内発泡成形用ポリ乳酸系樹脂発泡粒子を得たこと以外は実施例１と同様にしてポリ乳酸系樹脂発泡成形体を得た。得られたポリ乳酸系樹脂発泡成形体は、非常に優れた外観を有していた。
(Example 2)
After supplying the secondary expanded particles into the sealed container, the air in the sealed container was completely replaced with carbon dioxide at normal pressure. Thereafter, the sealed container is sealed, and the carbon dioxide in the sealed container is maintained at 18 ° C., and then the pressure increase rate of the pressure in the sealed container is set to 0.01 MPa / min. In a pressurized state, the supply of carbon dioxide into the sealed container was stopped when the gauge pressure in the sealed container reached 1.5 MPa. Then, after the supply of carbon dioxide into the closed container was stopped, it was allowed to stand for 3 hours to impregnate the secondary foamed particles with carbon dioxide to obtain polylactic acid resin foamed particles for in-mold foam molding. Except for this, a polylactic acid resin foamed molded article was obtained in the same manner as in Example 1. The obtained polylactic acid resin foamed molded article had a very excellent appearance.
（実施例３）
密閉容器内に二次発泡粒子を供給した後、密閉容器内の空気を常圧にて二酸化炭素に完全に置換した。しかる後、密閉容器を密閉し、この密閉容器内の二酸化炭素を２０℃に維持した上で、密閉容器内に２０℃の二酸化炭素を密閉容器内の圧力の昇圧速度が０．０９ＭＰａ／分となるように加圧状態で供給し、密閉容器内のゲージ圧力が０．６ＭＰａとなった時点で密閉容器内への二酸化炭素の供給を停止した。そして、密閉容器内への二酸化炭素の供給を停止してから３時間に亘って放置して二次発泡粒子に二酸化炭素を含浸させて型内発泡成形用ポリ乳酸系樹脂発泡粒子を得たこと以外は実施例１と同様にしてポリ乳酸系樹脂発泡成形体を得た。得られたポリ乳酸系樹脂発泡成形体は、非常に優れた外観を有していた。
(Example 3)
After supplying the secondary expanded particles into the sealed container, the air in the sealed container was completely replaced with carbon dioxide at normal pressure. Thereafter, the sealed container is sealed, and the carbon dioxide in the sealed container is maintained at 20 ° C., and then the pressure increase rate of the pressure in the sealed container is set to 0.09 MPa / min. In a pressurized state, the supply of carbon dioxide into the sealed container was stopped when the gauge pressure in the sealed container reached 0.6 MPa. Then, after the supply of carbon dioxide into the closed container was stopped, it was allowed to stand for 3 hours to impregnate the secondary foamed particles with carbon dioxide to obtain polylactic acid resin foamed particles for in-mold foam molding. Except for the above, a polylactic acid resin foamed molded article was obtained in the same manner as in Example 1. The obtained polylactic acid resin foamed molded article had a very excellent appearance.
（実施例４）
密閉容器内に二次発泡粒子を供給した後、密閉容器内の空気を常圧にて二酸化炭素に完全に置換した。しかる後、密閉容器を密閉し、この密閉容器内の二酸化炭素を５℃に維持した上で、密閉容器内に５℃の二酸化炭素を密閉容器内の圧力の昇圧速度が０．０９ＭＰａ／分となるように加圧状態で供給し、密閉容器内のゲージ圧力が０．６ＭＰａとなった時点で密閉容器内への二酸化炭素の供給を停止した。そして、密閉容器内への二酸化炭素の供給を停止してから３時間に亘って放置して二次発泡粒子に二酸化炭素を含浸させて型内発泡成形用ポリ乳酸系樹脂発泡粒子を得たこと以外は実施例１と同様にしてポリ乳酸系樹脂発泡成形体を得た。得られたポリ乳酸系樹脂発泡成形体は、非常に優れた外観を有していた。
Example 4
After supplying the secondary expanded particles into the sealed container, the air in the sealed container was completely replaced with carbon dioxide at normal pressure. Thereafter, the sealed container is sealed, and the carbon dioxide in the sealed container is maintained at 5 ° C., and then the pressure increase rate of the pressure in the sealed container is set to 0.09 MPa / min. In a pressurized state, the supply of carbon dioxide into the sealed container was stopped when the gauge pressure in the sealed container reached 0.6 MPa. Then, after the supply of carbon dioxide into the closed container was stopped, it was allowed to stand for 3 hours to impregnate the secondary foamed particles with carbon dioxide to obtain polylactic acid resin foamed particles for in-mold foam molding. Except for the above, a polylactic acid resin foamed molded article was obtained in the same manner as in Example 1. The obtained polylactic acid resin foamed molded article had a very excellent appearance.
（比較例１）
密閉容器内に二次発泡粒子を供給した後、密閉容器内の空気を常圧にて二酸化炭素に完全に置換した。しかる後、密閉容器を密閉し、この密閉容器内の二酸化炭素を２０℃に維持した上で、密閉容器内に２０℃の二酸化炭素を密閉容器内の圧力の昇圧速度が０．３ＭＰａ／分となるように加圧状態で供給し、密閉容器内のゲージ圧力が１．０ＭＰａとなった時点で密閉容器内への二酸化炭素の供給を停止した。そして、密閉容器内への二酸化炭素の供給を停止してから３時間に亘って放置して二次発泡粒子に二酸化炭素を含浸させて型内発泡成形用ポリ乳酸系樹脂発泡粒子を得たこと以外は実施例１と同様にしてポリ乳酸系樹脂発泡成形体を得た。得られたポリ乳酸系樹脂発泡粒子は収縮が大きく、更に、得られたポリ乳酸系樹脂発泡成形体は、収縮を生じてしまい外観が悪かった。
(Comparative Example 1)
After supplying the secondary expanded particles into the sealed container, the air in the sealed container was completely replaced with carbon dioxide at normal pressure. Thereafter, the sealed container is sealed, and the carbon dioxide in the sealed container is maintained at 20 ° C., and then the carbon dioxide at 20 ° C. is pressurized into the sealed container at a pressure increase rate of 0.3 MPa / min. Thus, the supply of carbon dioxide into the sealed container was stopped when the gauge pressure in the sealed container reached 1.0 MPa. Then, after the supply of carbon dioxide into the closed container was stopped, it was allowed to stand for 3 hours to impregnate the secondary foamed particles with carbon dioxide to obtain polylactic acid resin foamed particles for in-mold foam molding. Except for this, a polylactic acid resin foamed molded article was obtained in the same manner as in Example 1. The obtained polylactic acid-based resin expanded particles had large shrinkage, and further, the obtained polylactic acid-based resin foamed molded article contracted and had a poor appearance.
（比較例２）
密閉容器内に二次発泡粒子を供給した後、密閉容器内の空気を常圧にて二酸化炭素に完全に置換した。しかる後、密閉容器を密閉し、この密閉容器内の二酸化炭素を３５℃に維持した上で、密閉容器内に３５℃の二酸化炭素を密閉容器内の圧力の昇圧速度が０．０６ＭＰａ／分となるように加圧状態で供給し、密閉容器内のゲージ圧力が０．６ＭＰａとなった時点で密閉容器内への二酸化炭素の供給を停止した。そして、密閉容器内への二酸化炭素の供給を停止してから３時間に亘って放置して二次発泡粒子に二酸化炭素を含浸させて型内発泡成形用ポリ乳酸系樹脂発泡粒子を得たこと以外は実施例１と同様にしてポリ乳酸系樹脂発泡成形体を製造しようとしたが、密閉容器内に二酸化炭素を供給中に二次発泡粒子に潰れが発生すると共に、二次発泡粒子を構成しているポリ乳酸系樹脂の結晶化が進行してしまい、ポリ乳酸系樹脂発泡成形体を得ることができなかった。
(Comparative Example 2)
After supplying the secondary expanded particles into the sealed container, the air in the sealed container was completely replaced with carbon dioxide at normal pressure. Thereafter, the sealed container is sealed, and the carbon dioxide in the sealed container is maintained at 35 ° C., and then the carbon dioxide at 35 ° C. is pressurized into the sealed container at a pressure increase rate of 0.06 MPa / min. In a pressurized state, the supply of carbon dioxide into the sealed container was stopped when the gauge pressure in the sealed container reached 0.6 MPa. Then, after the supply of carbon dioxide into the closed container was stopped, it was allowed to stand for 3 hours to impregnate the secondary foamed particles with carbon dioxide to obtain polylactic acid resin foamed particles for in-mold foam molding. Except for the above, an attempt was made to produce a polylactic acid-based resin foamed molded article in the same manner as in Example 1, but the secondary foamed particles were crushed while carbon dioxide was being supplied into the sealed container, and the secondary foamed particles were constituted. Crystallization of the polylactic acid based resin progressed, and a polylactic acid based resin foamed molded article could not be obtained.
得られた型内発泡成形用ポリ乳酸系樹脂発泡粒子の収縮率、連続気泡率、結晶化度及び三次発泡性、並びに、ポリ乳酸系樹脂発泡成形体の外観を上述の要領で測定し、その結果を表１に示した。 The shrinkage ratio, open cell ratio, crystallinity and tertiary foamability of the obtained polylactic acid resin foamed particles for in-mold foam molding, and the appearance of the polylactic acid resin foam molded article were measured as described above. The results are shown in Table 1.
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