JP4761916B2 - Polylactic acid resin foam molding - Google Patents

Polylactic acid resin foam molding Download PDF

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JP4761916B2
JP4761916B2 JP2005294918A JP2005294918A JP4761916B2 JP 4761916 B2 JP4761916 B2 JP 4761916B2 JP 2005294918 A JP2005294918 A JP 2005294918A JP 2005294918 A JP2005294918 A JP 2005294918A JP 4761916 B2 JP4761916 B2 JP 4761916B2
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克典 西嶋
孝明 平井
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Sekisui Kasei Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/22—After-treatment of expandable particles; Forming foamed products
    • C08J9/228—Forming foamed products
    • C08J9/232—Forming foamed products by sintering expandable particles
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
    • C08J9/14—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent organic
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/16—Making expandable particles
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/14—Saturated hydrocarbons, e.g. butane; Unspecified hydrocarbons
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones

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Description

本発明は、優れた耐熱性及び機械的強度を有するポリ乳酸系樹脂発泡成形体に関する。   The present invention relates to a polylactic acid resin foam molded article having excellent heat resistance and mechanical strength.

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いることから注目を集めている。   Polylactic acid resin is a resin obtained by polymerizing naturally occurring lactic acid, is a biodegradable resin that can be decomposed by microorganisms existing in nature, and has excellent mechanical properties at room temperature. It attracts attention.

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.

そして、得られるポリ乳酸系樹脂は、該ポリ乳酸系樹脂中に含有されるＤ体成分或いはＬ体成分の含有比率によって物性、特に結晶性が変化し、具体的には、Ｄ体成分或いはＬ体成分のうちの少ない方の光学異性体の割合が多くなるにしたがってポリ乳酸系樹脂の結晶性が低下し、やがて非結晶性となる。   The obtained polylactic acid-based resin changes in physical properties, particularly crystallinity, depending on the content ratio of the D-form component or L-form component contained in the polylactic acid-based resin. As the proportion of the smaller optical isomer of the body components increases, the crystallinity of the polylactic acid resin decreases and eventually becomes amorphous.

一方、型内発泡成形は、ポリ乳酸系樹脂発泡粒子を金型内に充填し、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ポリ乳酸系樹脂発泡粒子の表面を溶融させると共に発泡させ、隣接するポリ乳酸系樹脂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が、ポリ乳酸系樹脂発泡粒子の結晶化度が高いと発泡粒子の耐熱性が高く、融着性に優れた型内発泡成形品を得ることが困難になる。従って、ポリ乳酸系樹脂発泡粒子、及び、ポリ乳酸系樹脂型内発泡成形体を製造するポリ乳酸系樹脂としては、型内発泡成形時における発泡粒子同士の融着性の点からＬ体或いはＤ体比率が高く、結晶性の低いポリ乳酸系樹脂を使用している例が殆どである。   On the other hand, in-mold foam molding, the polylactic acid resin foam particles are filled in a mold, and the polylactic acid resin foam particles are heated by a heat medium such as water vapor to melt the surface of the 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 fusing together adjacent polylactic acid resin foamed particles, but the polylactic acid resin foamed particles have a high degree of crystallinity. In addition, it is difficult to obtain an in-mold foam-molded product having high heat resistance of the expanded particles and excellent fusing property. Accordingly, the polylactic acid resin foam particles and the polylactic acid resin for producing the polylactic acid resin in-mold foam molded article are L-form or D-form from the viewpoint of the fusion property of the foam particles during in-mold foam molding. In most cases, a polylactic acid resin having a high body ratio and low crystallinity is used.

具体的には、特許文献１には、Ｌ体とＤ体のモル比が９５／５〜６０／４０、又は４０／６０〜５／９５であるポリ乳酸にイソシアネート基≧２．０当量／モルのポリイソシアネート化合物を該ポリ乳酸に対して０．５〜５重量％配合し反応させた樹脂組成物を所定条件で熟成させてなる樹脂組成物が提案され、そして、上記樹脂組成物から粒子を製造し、この粒子に発泡剤及び発泡助剤を含浸させ、得られた発泡性粒子を予備発泡させて予備発泡粒子を製造し、この予備発泡粒子を金型に充填して発泡させて所望形状を有する成形体を成形することが開示されている。   Specifically, Patent Document 1 discloses that an isocyanate group ≧ 2.0 equivalents / mol in polylactic acid having a molar ratio of L-form to D-form of 95/5 to 60/40, or 40/60 to 5/95. A resin composition obtained by aging under a predetermined condition a resin composition obtained by mixing 0.5 to 5% by weight of the polyisocyanate compound with respect to the polylactic acid and reacting the same is proposed, and particles are formed from the resin composition. The particles are impregnated with a foaming agent and a foaming auxiliary agent, and the resulting foamable particles are pre-foamed to produce pre-foamed particles. The pre-foamed particles are filled into a mold and foamed to obtain a desired shape. It is disclosed to form a molded body having the following.

しかしながら、上記ポリ乳酸系樹脂は、そのＬ体成分又はＤ体成分のうちの少ない方の光学異性体成分のモル比が５モル％以上であり、ポリ乳酸系樹脂は結晶性が低いか或いは非結晶性であって耐熱性に劣り、得られる成形体の耐熱性はせいぜい５０℃程度であって、実用上の使用には問題点があった。   However, the polylactic acid-based resin has a molar ratio of the smaller optical isomer component of the L-form component or the D-form component of 5 mol% or more, and the polylactic acid-based resin has low crystallinity or is not non-crystalline. It is crystalline and inferior in heat resistance, and the resulting molded article has a heat resistance of about 50 ° C. at most, which is problematic for practical use.

又、特許文献２には、加熱速度２℃／ｍｉｎでの示差走査熱量測定における吸熱量（Ｒｅｎｄｏ）が１０Ｊ／ｇ以上のポリ乳酸系樹脂を基材樹脂とし、加熱速度２℃／ｍｉｎでの示差走査熱量測定における発熱量（Ｂｅｘｏ）と吸熱量（Ｂｅｎｄｏ）との比及び差が所定範囲内にある発泡粒子を用いた型内発泡成形体の製造方法が開示されている。 Patent Document 2 discloses that a polylactic acid resin having an endotherm (R endo ) in differential scanning calorimetry at a heating rate of 2 ° C./min as a base resin and a heating rate of 2 ° C./min. A method for producing an in-mold foam molded article using foamed particles in which the ratio and difference between the heat generation amount (B exo ) and the heat absorption amount (B endo ) in differential scanning calorimetry is within a predetermined range is disclosed.

しかしながら、上記型内発泡成形体の製造方法では、型内発泡成形体に耐熱性を付与するために養生工程を要しており、生産効率が悪いといった問題点の他に、型内発泡成形体の耐熱性も９０℃が上限であって決して満足のできるものではなかった。   However, in the above-mentioned method for producing an in-mold foam molded article, a curing process is required to impart heat resistance to the in-mold foam molded article. The upper limit of the heat resistance was 90 ° C., which was not satisfactory.

更に、特許文献３には、温度１９０℃、剪断速度１００ｓｅｃ-1における溶融粘度が１×１０2 〜１×１０5 Ｐａ・ｓで且つ所定条件下における示差走査熱量測定で得られた結晶融解熱量ΔＨｍ及び所定の結晶融解熱量に達する温度差が所定温度以上であるポリ乳酸系樹脂からなる無架橋のポリ乳酸系樹脂発泡性粒子が開示されている。 Further, Patent Document 3 discloses that the melting viscosity at a temperature of 190 ° C. and a shear rate of 100 sec −1 is 1 × 10 2 to 1 × 10 5 Pa · s and obtained by differential scanning calorimetry under a predetermined condition. Non-crosslinked polylactic acid resin expandable particles made of a polylactic acid resin having a temperature difference reaching ΔHm and a predetermined amount of heat of crystal melting equal to or higher than a predetermined temperature are disclosed.

しかしながら、上記ポリ乳酸系樹脂発泡性粒子で用いられているポリ乳酸系樹脂は結晶化度が高く、型内発泡成形に際し、発泡粒子同士を融着させるために、融点の異なるポリ乳酸系樹脂を三種或いはそれ以上用いて、その最も低融点のポリ乳酸系樹脂の融点以上に加熱する必要があった。そのため、型内発泡成形時の加熱温度を１４１〜１６１℃としなければならないことから、加熱時の蒸気圧を０．３６〜０．６２ＭＰａ程度まで上げる必要があり、高圧に耐え得る特殊な成形機が必要である上に、加熱時に必要とする水蒸気の量も多大なものであるという問題点があった。   However, the polylactic acid resin used in the above-mentioned polylactic acid-based resin expandable particles has a high degree of crystallinity, and in order to fuse the expanded particles with each other during in-mold foam molding, polylactic acid resins having different melting points are used. Using three or more kinds, it was necessary to heat to the melting point of the polylactic acid resin having the lowest melting point. Therefore, since the heating temperature at the time of in-mold foam molding must be 141 to 161 ° C., it is necessary to increase the vapor pressure at the time of heating to about 0.36 to 0.62 MPa, and a special molding machine that can withstand high pressure In addition, there is a problem that the amount of water vapor required at the time of heating is enormous.

しかも、上述のように、ポリ乳酸系樹脂の融点に近い高温の水蒸気を用いて加熱発泡させていることから、得られるポリ乳酸系樹脂発泡成形体は収縮を生じて外観性に乏しいばかりか、融着性も低く機械的強度が低いと共に、耐熱性の点においても熱湯に耐えることができる程度に過ぎないものであった。   Moreover, as described above, since it is heated and foamed using high-temperature steam close to the melting point of the polylactic acid-based resin, the resulting polylactic acid-based resin foam molded article is not only poor in appearance due to shrinkage, The meltability was low and the mechanical strength was low, and the heat resistance was only enough to withstand hot water.

特開２０００−１７０３７号公報JP 2000-17037 A 特開２００５−８７７６号公報JP 2005-8776 A 特開２００２−２０５２５号公報JP 2002-20525 A

本発明は、優れた耐熱性及び機械的強度を有するポリ乳酸系樹脂発泡成形体に関する。   The present invention relates to a polylactic acid resin foam molded article having excellent heat resistance and mechanical strength.

本発明のポリ乳酸系樹脂発泡成形体は、ポリ乳酸系樹脂発泡粒子を型内発泡成形して得られたポリ乳酸系樹脂発泡成形体であって、１５０℃での加熱寸法変化率が５％未満であり、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と共に、上記ポリ乳酸系樹脂における融点（ｍｐ）と動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔとが下記式１を満たすことを特徴とする。
（ポリ乳酸系樹脂の融点（ｍｐ）−４０℃）
≦（交点における温度Ｔ）≦ポリ乳酸系樹脂の融点（ｍｐ）・・・式１ The polylactic acid resin foam molded article of the present invention is a polylactic acid resin foam molded article obtained by in-mold foam molding of polylactic acid resin foamed particles, and the heating dimensional change rate at 150 ° C. is 5%. The polylactic acid-based resin contains both D-form and L-form optical isomers as constituent monomer components, and the content of the lesser of the D-form and L-form is 5 It is less than mol%, or contains only one optical isomer of D-form or L-form as a constituent monomer component, and has a melting point (mp) and dynamic viscosity in the polylactic acid resin. The temperature T at the intersection of the storage elastic modulus curve and the loss elastic modulus curve obtained by the elastic measurement satisfies the following formula 1 .
(Melting point of polylactic acid resin (mp) -40 ° C)
≦ (temperature T at the intersection) ≦ melting point of polylactic acid resin (mp) Formula 1

上記ポリ乳酸系樹脂発泡成形体を構成するポリ乳酸系樹脂は下記化１で示され、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。   The polylactic acid-based resin constituting the polylactic acid-based resin foam molded article is represented by the following chemical formula 1, and is copolymerized with D-lactic acid and L-lactic acid as monomers, or either D-lactic acid or L-lactic acid Any polylactic acid resin can be obtained by polymerizing as a monomer or by ring-opening polymerization of one or more lactides selected from the group consisting of D-lactide, L-lactide and DL-lactide It may be.

Figure 0004761916
Figure 0004761916

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 and the L-form are used together, the polylactic acid-based resin obtained has a higher crystallinity, while the D-form and the L-form are used in combination as a monomer. Is more than 5 mol% When that is, according to the optical isomer is increased the smaller the resulting polylactic acid-based resin, its crystallinity decreases, the eventually amorphous.

従って、本発明のポリ乳酸系樹脂発泡成形体では、耐熱性に優れたものとするために、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。   Therefore, in order to make the polylactic acid-based resin foam molded article of the present invention excellent in heat resistance, it contains both D-form and L-form optical isomers 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 It is preferable to use a polylactic acid resin.

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。従って、ポリ乳酸系樹脂発泡成形体の耐熱性も向上し、ポリ乳酸系樹脂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、金型から高い温度のまま取り出すことが可能となってポリ乳酸系樹脂発泡成形体の金型内における冷却時間を短縮することができ、ポリ乳酸系樹脂発泡成形体は優れた生産性を有する。   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 polylactic acid-based resin foamed molded product is also improved, and the polylactic acid-based resin foamed molded product can maintain its form even at a high temperature, and can be taken out from the mold at a high temperature. Thus, the cooling time in the mold of the polylactic acid resin foamed molded product can be shortened, and the polylactic acid resin foamed molded product has excellent productivity.

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。先ず、ポリ乳酸系樹脂をクロロホルムに溶解させて、ポリ乳酸系樹脂の濃度が１０ｍｇ／ミリリットルのクロロホルム溶液を作製する。次に、旋光計を用いて２５℃にて波長５８９ｎｍの偏光をクロロホルム溶液に照射して、クロロホルム溶液の比旋光度を測定する。   Here, the content of D-form or L-form in the polylactic acid-based resin can be measured by the following method. First, a polylactic acid resin is dissolved in chloroform to prepare a chloroform solution having a polylactic acid resin concentration of 10 mg / ml. Next, the chloroform solution is irradiated with polarized light having a wavelength of 589 nm at 25 ° C. using a polarimeter, and the specific rotation of the chloroform solution is measured.

一方、モノマーとしてＤ体のみを用いて重合して得られたポリ乳酸系樹脂、或いは、モノマーとしてＬ体のみを用いて重合して得られたポリ乳酸系樹脂について、上述と同様の要領で比旋光度を測定してもよいが、この比旋光度は、通常、既に測定されており、Ｄ体のみを用いて重合して得られたポリ乳酸系樹脂は＋１５６°、モノマーとしてＬ体のみを用いて重合して得られたポリ乳酸系樹脂は−１５６°とされている。   On the other hand, the polylactic acid resin obtained by polymerization using only the D isomer as the monomer, or the polylactic acid resin obtained by polymerizing using only the L isomer as the monomer, was compared in the same manner as described above. Although the optical rotation may be measured, this specific optical rotation is usually already measured. The polylactic acid resin obtained by polymerization using only D-form is + 156 °, and only L-form is used as a monomer. The polylactic acid-based resin obtained by polymerization using it is set to −156 °.

そして、下記式に基づいてポリ乳酸系樹脂中におけるＤ体成分又はＬ体成分の量を算出することができる。
Ｄ体成分量（モル％）＝１００×｛クロロホルム溶液の比旋光度−（−１５６）｝
／｛１５６−（−１５６）｝
Ｌ体成分量（モル％）＝１００−（Ｄ体成分量） And the quantity of D body component or L body component in polylactic acid-type resin is computable based on a following formula.
D-form component amount (mol%) = 100 × {specific rotation of chloroform solution − (− 156)}
/ {156-(-156)}
L-form component amount (mol%) = 100- (D-form component amount)

ところが、後述するように、ポリ乳酸系樹脂発泡粒子は押出発泡によって製造することが好ましいことから、ポリ乳酸系樹脂としては、押出発泡に適したものを選択することが好ましく、具体的には、ポリ乳酸系樹脂として、融点（ｍｐ）と、動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔとが下記式１を満たすポリ乳酸系樹脂を用いる。
（ポリ乳酸系樹脂の融点（ｍｐ）−４０℃）
≦（交点における温度Ｔ）≦ポリ乳酸系樹脂の融点（ｍｐ）・・・式１ However, as described later, since the polylactic acid-based resin foamed particles are preferably produced by extrusion foaming, it is preferable to select a polylactic acid-based resin that is suitable for extrusion foaming. Specifically, As a polylactic acid resin, a melting point (mp) and a polylactic acid resin obtained by dynamic viscoelasticity measurement and having a temperature T at the intersection of a storage elastic modulus curve and a loss elastic modulus curve satisfy the following formula 1. using Ru.
(Melting point of polylactic acid resin (mp) -40 ° C)
≦ (temperature T at the intersection) ≦ melting point of polylactic acid resin (mp) Formula 1

ここで、動的粘弾性測定にて得られた貯蔵弾性率は、粘弾性において弾性的な性質を示す指標であって、発泡過程における気泡膜の弾性の大小を示す指標であり、発泡過程において、気泡膜の収縮力に抗して気泡を膨張させるのに必要な発泡圧の大小を示す指標である。   Here, the storage elastic modulus obtained by the dynamic viscoelasticity measurement is an index indicating elastic properties in the viscoelasticity, and is an index indicating the elasticity of the bubble film in the foaming process. This is an index indicating the magnitude of the foaming pressure required to expand the bubbles against the contraction force of the bubble film.

即ち、ポリ乳酸系樹脂の動的粘弾性測定にて得られた貯蔵弾性率が低いと、気泡膜が伸長された場合、気泡膜が伸長力に抗して収縮しようとする力が小さく、ポリ乳酸系樹脂発泡粒子の製造に必要とする発泡圧によって発泡膜が容易に伸長してしまう結果、気泡膜が過度に伸長してしまい破泡を生じる一方、ポリ乳酸系樹脂の動的粘弾性測定にて得られた貯蔵弾性率が高いと、気泡膜に伸長力が加わった場合、伸長に抗する気泡膜の収縮力が大きく、ポリ乳酸系樹脂発泡粒子の製造に必要とする発泡圧で一旦、気泡が膨張したとしても、温度低下などに起因する経時的な発泡圧の低下に伴って気泡が収縮してしまう。   That is, if the storage elastic modulus obtained by the dynamic viscoelasticity measurement of the polylactic acid-based resin is low, when the cell membrane is stretched, the force that the cell membrane attempts to contract against the stretching force is small. As a result of the expansion of the foamed film easily due to the foaming pressure required for the production of lactic acid resin foamed particles, the foamed film expands excessively, resulting in bubble breakage, while measuring the dynamic viscoelasticity of the polylactic acid resin When the storage elastic modulus obtained in (2) is high, when the expansion force is applied to the cell membrane, the contraction force of the cell membrane against the expansion is large, and once the expansion pressure required for the production of the polylactic acid resin expanded particles is reached. Even if the bubbles expand, the bubbles contract as the foaming pressure decreases with time due to a temperature drop or the like.

又、動的粘弾性測定にて得られた損失弾性率は、粘弾性において粘性的な性質を示す指標であって、発泡過程における気泡膜の粘性を示す指標であり、発泡過程において、気泡膜をどの程度まで破れることなく伸長させることができるかの許容範囲を示す指標であると同時に、発泡圧によって所望大きさに気泡を膨張させた後、この膨張した気泡をその大きさに維持する能力を示す指標でもある。   The loss elastic modulus obtained by dynamic viscoelasticity measurement is an index indicating the viscous property in viscoelasticity, and is an index indicating the viscosity of the bubble film in the foaming process. This is an index indicating the allowable range of how much can be expanded without breaking, and at the same time, the ability to expand the bubbles to the desired size by the foaming pressure and then maintain the expanded bubbles at that size It is also an indicator that indicates.

即ち、ポリ乳酸系樹脂の動的粘弾性測定にて得られた損失弾性率が低いと、ポリ乳酸系樹脂発泡粒子の製造に必要とする発泡圧によって気泡膜が伸長された場合、気泡膜が容易に破れてしまう一方、ポリ乳酸系樹脂の動的粘弾性測定にて得られた損失弾性率が高いと、発泡力が気泡膜によって熱エネルギーに変換されてしまい、ポリ乳酸系樹脂発泡粒子の製造時に気泡膜を円滑に伸長させることができず、気泡を膨張させることができない。   That is, if the loss elastic modulus obtained by the dynamic viscoelasticity measurement of the polylactic acid-based resin is low, when the cell membrane is expanded by the foaming pressure required for the production of the polylactic acid-based resin expanded particles, On the other hand, if the loss elastic modulus obtained by the dynamic viscoelasticity measurement of the polylactic acid resin is high, the foaming force is converted into thermal energy by the cell membrane, and the polylactic acid resin expanded particles The bubble membrane cannot be extended smoothly during production, and the bubbles cannot be expanded.

このように、ポリ乳酸系樹脂を発泡させてポリ乳酸系樹脂発泡粒子を製造するにあたっては、発泡過程において、ポリ乳酸系樹脂は、ポリ乳酸系樹脂発泡粒子を得るために必要とされる発泡圧によって気泡膜が破れることなく適度に伸長するための弾性力、即ち、貯蔵弾性率を有している必要があると共に、上記発泡圧によって気泡膜が破れることなく円滑に伸長し、所望大きさに膨張した気泡をその大きさに発泡圧の経時的な減少にかかわらず維持しておくための粘性力、即ち、損失弾性率を有している必要がある。   As described above, in producing polylactic acid resin foamed particles by foaming polylactic acid resin, in the foaming process, the polylactic acid resin has a foaming pressure required to obtain polylactic acid resin foamed particles. It is necessary to have an elastic force for stretching the bubble film appropriately without breaking, i.e., a storage elastic modulus, and the bubble film can be smoothly stretched without breaking by the foaming pressure, to a desired size. It is necessary to have a viscous force, that is, a loss elastic modulus, for maintaining the expanded bubble in its size regardless of the decrease in the foaming pressure with time.

つまり、押出発泡工程において、ポリ乳酸系樹脂の貯蔵弾性率及び損失弾性率の双方が押出発泡に適した値を有している必要があり、このような押出発泡に適した貯蔵弾性率及び損失弾性率を押出発泡工程においてポリ乳酸系樹脂に付与するために、動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔ（以下「貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔ」ということがある）とポリ乳酸系樹脂の融点（ｍｐ）とが下記式１を満たすことが好ましく、より好ましくは式２を満たすように、特に好ましくは式３を満たすように調整することによって、ポリ乳酸系樹脂の貯蔵弾性率及び損失弾性率をそれらのバランスをとりながら押出発泡に適したものとしてポリ乳酸系樹脂の押出発泡性を良好なものとし、ポリ乳酸系樹脂発泡粒子を安定的に製造することができる。   That is, in the extrusion foaming process, both the storage elastic modulus and loss elastic modulus of the polylactic acid-based resin need to have values suitable for extrusion foaming, and the storage elastic modulus and loss suitable for such extrusion foaming. In order to impart elastic modulus to the polylactic acid resin in the extrusion foaming process, the temperature T (hereinafter referred to as “storage elastic modulus curve”) at the intersection of the storage elastic modulus curve and the loss elastic modulus curve obtained by dynamic viscoelasticity measurement. And the melting point (mp) of the polylactic acid resin preferably satisfies the following formula 1, more preferably so as to satisfy the formula 2. By adjusting so as to satisfy Formula 3, the storage elastic modulus and loss elastic modulus of the polylactic acid resin are suitable for extrusion foaming while balancing them, and the extrusion foamability of the polylactic acid resin is good And things, the polylactic acid-based resin foamed particles can be produced stably.

〔ポリ乳酸系樹脂の融点（ｍｐ）−４０℃〕
≦交点における温度Ｔ≦ポリ乳酸系樹脂の融点（ｍｐ）・・・式１ [Melting point of polylactic acid resin (mp) −40 ° C.]
≦ Temperature at the intersection T ≦ Melting point of polylactic acid resin (mp) Formula 1

〔ポリ乳酸系樹脂の融点（ｍｐ）−３５℃〕
≦交点における温度Ｔ≦〔ポリ乳酸系樹脂の融点（ｍｐ）−１０℃〕・・・式２ [Melting point of polylactic acid resin (mp) -35 ° C.]
≦ Temperature at the intersection T ≦ [Melting point of polylactic acid resin (mp) −10 ° C.] Formula 2

〔ポリ乳酸系樹脂の融点（ｍｐ）−３０℃〕
≦交点における温度Ｔ≦〔ポリ乳酸系樹脂の融点（ｍｐ）−２０℃〕・・・式３ [Melting point of polylactic acid resin (mp) -30 ° C.]
≦ Temperature at the intersection T ≦ [Melting point of polylactic acid resin (mp) −20 ° C.] Formula 3

更に、ポリ乳酸系樹脂の動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔとポリ乳酸系樹脂の融点（ｍｐ）とが上記式１を満たすように調整するのが好ましい理由を下記に詳述する。   Furthermore, the temperature T and the melting point (mp) of the polylactic acid resin obtained at the intersection of the storage elastic modulus curve and the loss elastic modulus curve obtained by dynamic viscoelasticity measurement of the polylactic acid resin satisfy the above formula 1. The reason why it is preferable to make such adjustment will be described in detail below.

先ず、ポリ乳酸系樹脂の動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔが、ポリ乳酸系樹脂の融点（ｍｐ）よりも４０℃を越えて低い場合には、押出発泡時におけるポリ乳酸系樹脂の損失弾性率が貯蔵弾性率に比して大き過ぎるために、損失弾性率と貯蔵弾性率とのバランスが崩れてしまう虞れがある。   First, the temperature T at the intersection of the storage elastic modulus curve and the loss elastic modulus curve obtained by dynamic viscoelasticity measurement of the polylactic acid resin exceeds 40 ° C. than the melting point (mp) of the polylactic acid resin. If it is low, the loss elastic modulus of the polylactic acid resin at the time of extrusion foaming is too large compared to the storage elastic modulus, so that the balance between the loss elastic modulus and the storage elastic modulus may be lost.

そこで、ポリ乳酸系樹脂の損失弾性率に適した発泡力、即ち、ポリ乳酸系樹脂の粘性に合わせた発泡力とすると、ポリ乳酸系樹脂の弾性力にとっては発泡力が大き過ぎてしまい、気泡膜が破れて破泡を生じて良好なポリ乳酸系樹脂発泡粒子を得ることができず、逆に、ポリ乳酸系樹脂の貯蔵弾性率に適した発泡力、即ち、ポリ乳酸系樹脂の弾性に合わせた発泡力とすると、ポリ乳酸系樹脂の粘性力にとっては発泡力が小さく、ポリ乳酸系樹脂が発泡しにくくなり、やはり良好なポリ乳酸系樹脂発泡粒子を得ることができない。   Therefore, if the foaming force suitable for the loss elastic modulus of the polylactic acid-based resin, that is, the foaming force matched to the viscosity of the polylactic acid-based resin, the foaming force is too large for the elastic force of the polylactic acid-based resin. The film is broken and bubbles are broken, and good polylactic acid resin expanded particles cannot be obtained. Conversely, the foaming force suitable for the storage elastic modulus of the polylactic acid resin, that is, the elasticity of the polylactic acid resin is reduced. If the combined foaming force is used, the foaming force is small for the viscosity force of the polylactic acid-based resin, and the polylactic acid-based resin is difficult to foam, so that good polylactic acid-based resin expanded particles cannot be obtained.

又、ポリ乳酸系樹脂の動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔが、ポリ乳酸系樹脂の融点（ｍｐ）よりも高いと、押出発泡時におけるポリ乳酸系樹脂の貯蔵弾性率が損失弾性率に比して大き過ぎるために、上述と同様に損失弾性率と貯蔵弾性率とのバランスが崩れてしまう虞れがある。   Further, when the temperature T at the intersection of the storage elastic modulus curve and the loss elastic modulus curve obtained by the dynamic viscoelasticity measurement of the polylactic acid resin is higher than the melting point (mp) of the polylactic acid resin, Since the storage elastic modulus of the polylactic acid-based resin at the time of foaming is too large compared to the loss elastic modulus, the balance between the loss elastic modulus and the storage elastic modulus may be lost as described above.

そこで、ポリ乳酸系樹脂の貯蔵弾性率に適した発泡力、即ち、ポリ乳酸系樹脂の弾性に合わせた発泡力とすると、ポリ乳酸系樹脂の粘性力にとっては発泡力が大き過ぎてしまい、気泡膜が破れて破泡を生じ良好なポリ乳酸系樹脂発泡粒子を得ることができず、逆に、ポリ乳酸系樹脂の損失弾性率に適した発泡力、即ち、ポリ乳酸系樹脂の粘性に合わせた発泡力とすると、ポリ乳酸系樹脂の弾性力にとっては発泡力が小さく、ポリ乳酸系樹脂が発泡力で一旦、発泡したとしても、経時的な発泡力の低下に伴って気泡が収縮してしまって、やはり良好なポリ乳酸系樹脂発泡粒子を得ることができない。   Therefore, if the foaming force suitable for the storage elastic modulus of the polylactic acid-based resin, that is, the foaming force matched to the elasticity of the polylactic acid-based resin, the foaming force is too large for the viscosity force of the polylactic acid-based resin, The film is broken and bubbles are broken, and good polylactic acid resin foam particles cannot be obtained. Conversely, the foaming force suitable for the loss elastic modulus of the polylactic acid resin, that is, the viscosity of the polylactic acid resin is adjusted. If the foaming force is high, the foaming force is small for the elastic force of the polylactic acid-based resin. Even if the polylactic acid-based resin foams once due to the foaming force, the bubbles shrink as the foaming force decreases over time. In other words, good polylactic acid resin expanded particles cannot be obtained.

そして、ポリ乳酸系樹脂の動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔと、ポリ乳酸系樹脂の融点（ｍｐ）とが上記式１を満たすように調整する方法としては、ポリ乳酸系樹脂の重量平均分子量が高くなるにしたがって、ポリ乳酸系樹脂の動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔが高くなることから、ポリ乳酸系樹脂の重合時に反応時間或いは反応温度を調整することによって、得られるポリ乳酸系樹脂の重量平均分子量を調整する方法、押出発泡前に或いは押出発泡時にポリ乳酸系樹脂の重量平均分子量を増粘剤や架橋剤を用いて調整する方法が挙げられる。   Then, the temperature T at the intersection of the storage elastic modulus curve and the loss elastic modulus curve obtained by the dynamic viscoelasticity measurement of the polylactic acid resin and the melting point (mp) of the polylactic acid resin are expressed by the above equation 1. As a method of adjusting so as to satisfy, as the weight average molecular weight of the polylactic acid resin increases, the storage elastic modulus curve and the loss elastic modulus curve obtained by the dynamic viscoelasticity measurement of the polylactic acid resin Since the temperature T at the intersection becomes high, a method for adjusting the weight average molecular weight of the obtained polylactic acid resin by adjusting the reaction time or reaction temperature during polymerization of the polylactic acid resin, before extrusion foaming or extrusion foaming A method of adjusting the weight average molecular weight of the polylactic acid resin sometimes using a thickener or a crosslinking agent is mentioned.

このような観点から、ポリ乳酸系樹脂の重量平均分子量は、１４０，０００〜３００，０００が好ましく、１５０，０００〜２７０，０００がより好ましく、１６０，０００〜２５０，０００が特に好ましい。更に、ポリ乳酸系樹脂の分子量分布（重量平均分子量Ｍｗ／数平均分子量Ｍｎ）は、３．２〜１０が好ましく、３．４〜９がより好ましく、３．６〜８が特に好ましい。   From such a viewpoint, the weight average molecular weight of the polylactic acid-based resin is preferably 140,000 to 300,000, more preferably 150,000 to 270,000, and particularly preferably 160,000 to 250,000. Furthermore, the molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of the polylactic acid-based resin is preferably 3.2 to 10, more preferably 3.4 to 9, and particularly preferably 3.6 to 8.

この他に、Ｌ体の比率がＤ体の比率に比して大きいモノマーから得られたポリ乳酸系樹脂の場合、Ｄ体の比率が増加するにつれてポリ乳酸系樹脂の融点（ｍｐ）が低下することから、モノマー中のＤ体の比率を調整することによってポリ乳酸系樹脂の融点（ｍｐ）を調整し、ポリ乳酸系樹脂の動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔと、ポリ乳酸系樹脂の融点（ｍｐ）とが上記式１を満たすように調整する方法が挙げられる。   In addition, in the case of a polylactic acid resin obtained from a monomer in which the ratio of the L isomer is larger than that of the D isomer, the melting point (mp) of the polylactic acid resin decreases as the D isomer ratio increases. From the above, the storage modulus curve and loss obtained by adjusting the melting point (mp) of the polylactic acid resin by adjusting the ratio of D-form in the monomer and by measuring the dynamic viscoelasticity of the polylactic acid resin There is a method in which the temperature T at the intersection with the elastic modulus curve and the melting point (mp) of the polylactic acid resin are adjusted so as to satisfy the above formula 1.

ここで、ポリ乳酸系樹脂の融点（ｍｐ）は下記の要領で測定されたものをいう。即ち、ＪＩＳ Ｋ７１２１：１９８７に準拠してポリ乳酸系樹脂の示差走査熱量分析を行い、得られたＤＳＣ曲線における融解ピークの温度をポリ乳酸系樹脂の融点（ｍｐ）とする。なお、融解ピークの温度が複数個ある場合には、最も高い温度とする。   Here, the melting point (mp) of the polylactic acid resin is measured in the following manner. That is, the differential scanning calorimetry of the polylactic acid resin is performed in accordance with JIS K7121: 1987, and the melting peak temperature in the obtained DSC curve is defined as the melting point (mp) of the polylactic acid resin. When there are a plurality of melting peak temperatures, the highest temperature is set.

又、ポリ乳酸系樹脂の動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔは下記の要領で測定されたものをいう。即ち、ポリ乳酸系樹脂を９．３３×１０4 Ｐａの減圧下にて８０℃で３時間に亘って乾燥する。このポリ乳酸系樹脂を該ポリ乳酸系樹脂の融点よりも４０〜５０℃だけ高い温度に加熱した測定プレート上に載置して窒素雰囲気下にて５分間に亘って放置し溶融させる。 Further, the temperature T at the intersection of the storage elastic modulus curve and the loss elastic modulus curve obtained by the dynamic viscoelasticity measurement of the polylactic acid-based resin is the one measured in the following manner. That is, the polylactic acid resin is dried at 80 ° C. for 3 hours under a reduced pressure of 9.33 × 10 4 Pa. This polylactic acid-based resin is placed on a measurement plate heated to a temperature higher by 40 to 50 ° C. than the melting point of the polylactic acid-based resin, and allowed to stand for 5 minutes in a nitrogen atmosphere to melt.

次に、直径が２５ｍｍの平面円形状の押圧板を用意し、この押圧板を用いて測定プレート上のポリ乳酸系樹脂を押圧板と測定プレートとの対向面間の間隔が１ｍｍとなるまで上下方向に押圧する。そして、押圧板の外周縁からはみ出したポリ乳酸系樹脂を除去した後、５分間に亘って放置する。   Next, a flat circular pressure plate having a diameter of 25 mm is prepared, and the polylactic acid resin on the measurement plate is moved up and down until the distance between the opposing surfaces of the pressure plate and the measurement plate becomes 1 mm. Press in the direction. And after removing the polylactic acid-type resin which protruded from the outer periphery of a press plate, it is left to stand for 5 minutes.

しかる後、歪み５％、周波数１ｒａｄ／秒、降温速度２℃／分、測定間隔３０秒の条件下にて、ポリ乳酸系樹脂の動的粘弾性測定を行って貯蔵弾性率及び損失弾性率を測定する。次に、横軸を温度とし、縦軸を貯蔵弾性率及び損失弾性率として、貯蔵弾性率曲線及び損失弾性率曲線を描く。なお、貯蔵弾性率曲線及び損失弾性率曲線を描くにあたっては、測定温度を基準として互いに隣接する測定値同士を直線で結ぶ。   Thereafter, the dynamic viscoelasticity measurement of the polylactic acid resin is performed under the conditions of 5% strain, frequency 1 rad / sec, temperature drop rate 2 ° C./min, and measurement interval 30 sec to determine the storage elastic modulus and loss elastic modulus. taking measurement. Next, a storage elastic modulus curve and a loss elastic modulus curve are drawn with the horizontal axis as temperature and the vertical axis as storage elastic modulus and loss elastic modulus. In drawing the storage elastic modulus curve and the loss elastic modulus curve, the measurement values adjacent to each other are connected with a straight line based on the measurement temperature.

そして、得られた貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔを上記グラフから読み取ることによって得ることができる。なお、貯蔵弾性率曲線と損失弾性率曲線とが複数箇所において互いに交差する場合は、貯蔵弾性率曲線と損失弾性率曲線との複数の交点における温度のうち最も高い温度を、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔとする。   And it can obtain by reading the temperature T in the intersection of the obtained storage elastic modulus curve and loss elastic modulus curve from the said graph. When the storage modulus curve and the loss modulus curve intersect each other at a plurality of locations, the highest temperature among the temperatures at the plurality of intersections of the storage modulus curve and the loss modulus curve is defined as the storage modulus curve. It is set as the temperature T in the intersection with a loss elastic modulus curve.

又、動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔは、Reologica Instruments A.B 社から商品名「DynAlyser DAR-100」 にて市販されている動的粘弾性測定装置を用いて測定することができる。   The temperature T at the intersection of the storage elastic modulus curve and the loss elastic modulus curve obtained by dynamic viscoelasticity measurement is a dynamic value commercially available from Reologica Instruments AB under the trade name “DynAlyser DAR-100”. It can be measured using a mechanical viscoelasticity measuring device.

ポリ乳酸系樹脂の動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔでの弾性率、即ち、貯蔵弾性率又は損失弾性率は、低いと、発泡中のポリ乳酸系樹脂の粘弾性が低くなり、気泡膜が発泡圧によって破れて破泡を生じることがある一方、高いと、発泡圧によって気泡膜を伸長させて気泡を所望大きさに膨張させることができず、発泡が不安定になることがあるので、１．０×１０3 〜１．０×１０5 Ｐａが好ましく、５．０×１０3 〜９．０×１０4 Ｐａがより好ましく、１．０×１０4 〜８．０×１０4 Ｐａが特に好ましい。 The elastic modulus at the temperature T at the intersection of the storage elastic modulus curve and the loss elastic modulus curve obtained by the dynamic viscoelasticity measurement of the polylactic acid resin, that is, the storage elastic modulus or the loss elastic modulus is low. While the foamed polylactic acid resin has low viscoelasticity, the foam film may be broken by foaming pressure to cause foam breakage. On the other hand, when the foam is high, the foam film is expanded by the foaming pressure to expand the foam to the desired size. 1.0 × 10 3 to 1.0 × 10 5 Pa is preferable, and 5.0 × 10 3 to 9.0 × 10 4 Pa is more preferable. 1.0 × 10 4 to 8.0 × 10 4 Pa is particularly preferable.

なお、ポリ乳酸系樹脂の動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔでの弾性率（貯蔵弾性率又は損失弾性率）は、ポリ乳酸系樹脂の重合時に反応時間或いは反応温度を調整することによって、ポリ乳酸系樹脂の重量平均分子量を調整する方法、押出発泡前に或いは押出発泡時にポリ乳酸系樹脂の重量平均分子量を増粘剤や架橋剤を用いて調整する方法が挙げられる。   The elastic modulus (storage elastic modulus or loss elastic modulus) at temperature T at the intersection of the storage elastic modulus curve and the loss elastic modulus curve obtained by dynamic viscoelasticity measurement of the polylactic acid resin is polylactic acid. A method of adjusting the weight average molecular weight of the polylactic acid resin by adjusting the reaction time or reaction temperature during polymerization of the resin, the viscosity average molecular weight of the polylactic acid resin before or during extrusion foaming, The method of adjusting using a crosslinking agent is mentioned.

そして、本発明のポリ乳酸系樹脂発泡成形体における１５０℃での加熱寸法変化率は、大きいと、ポリ乳酸系樹脂発泡成形体を構造部材や断熱材などに用いた場合に歪みや隙間が生じ易くなるので、５％未満に限定され、３％未満が好ましく、１％未満がより好ましい。   If the polylactic acid resin foam molding of the present invention has a large rate of change in heating at 150 ° C., distortion or gaps will occur when the polylactic acid resin foam molding is used as a structural member or a heat insulating material. Since it becomes easy, it is limited to less than 5%, less than 3% is preferable, and less than 1% is more preferable.

なお、ポリ乳酸系樹脂発泡成形体における１５０℃での加熱寸法変化率は、ＪＩＳ Ｋ６７６７に準拠して測定されたものをいう。具体的には、ポリ乳酸系樹脂発泡成形体を、ＪＩＳ Ｋ７１００に規定された標準温湿度状態、即ち、２３℃、相対湿度５０％に維持された恒温恒湿室内に２４時間に亘って放置した後、ポリ乳酸系樹脂発泡成形体から縦１５０ｍｍ×横１５０ｍｍで厚さは発泡成形体の厚みのままの試験片を切り出す。   In addition, the heating dimensional change rate at 150 ° C. in the polylactic acid-based resin foam molded article refers to that measured in accordance with JIS K6767. Specifically, the polylactic acid resin foamed molded product was left in a standard temperature and humidity state specified in JIS K7100, that is, a constant temperature and humidity chamber maintained at 23 ° C. and 50% relative humidity for 24 hours. Thereafter, a test piece having a length of 150 mm × width of 150 mm and a thickness of the foamed molded product is cut out from the polylactic acid resin foamed molded product.

次に、上記試験片の上面中央部に、３本の直線を５０ｍｍ間隔で互いに平行な状態に縦方向に沿って描くと共に、３本の直線を５０ｍｍ間隔で互いに平行な状態に横方向に沿って描く。そして、試験片の上面中央部に描いた６本の直線の長さを測定し、６本の直線の長さの相加平均値を算出し、加熱前寸法Ｌ1 とする。 Next, at the center of the upper surface of the test piece, three straight lines are drawn along the vertical direction in parallel with each other at intervals of 50 mm, and the three straight lines are parallel with each other at intervals of 50 mm along the horizontal direction. Draw. Then, the lengths of the six straight lines drawn at the center of the upper surface of the test piece are measured, and an arithmetic average value of the lengths of the six straight lines is calculated and set as the dimension L 1 before heating.

しかる後、上記試験片を１５０℃に保持した熱風循環式乾燥機内に水平状態に放置して２２時間に亘って加熱した後に熱風循環式乾燥機から取り出し、続いて、試験片をＪＩＳ Ｋ７１００に規定された標準温湿度状態、即ち、２３℃、相対湿度５０％に維持された恒温恒湿室内に１時間に亘って放置する。   Thereafter, the test piece is left in a hot air circulation dryer maintained at 150 ° C. in a horizontal state and heated for 22 hours, then removed from the hot air circulation dryer, and then the test piece is specified in JIS K7100. In a constant temperature and humidity room maintained at 23 ° C. and 50% relative humidity for 1 hour.

次に、上記試験片の上面中央部に描いた６本の直線の長さを測定し、６本の直線の長さの相加平均値を算出し、加熱後寸法Ｌ2 とし、下記式４に基づいて、１５０℃での加熱寸法変化率を算出する。 Next, the lengths of the six straight lines drawn at the center of the upper surface of the test piece are measured, the arithmetic average value of the lengths of the six straight lines is calculated, and is defined as a dimension L 2 after heating. Based on the above, the heating dimensional change rate at 150 ° C. is calculated.

Figure 0004761916
Figure 0004761916

又、本発明のポリ乳酸系樹脂発泡成形体における加熱速度５℃／分での示差走査熱量測定による発熱量は、１０Ｊ／ｇ未満が好ましく、３Ｊ／ｇ未満がより好ましい。このように、ポリ乳酸系樹脂発泡成形体における加熱速度５℃／分での示差走査熱量測定による発熱量を所定量未満とすることによって、ポリ乳酸系樹脂発泡成形体に優れた耐熱性を付与することができる。   Further, the calorific value by differential scanning calorimetry at a heating rate of 5 ° C./min in the polylactic acid resin foam molded article of the present invention is preferably less than 10 J / g, and more preferably less than 3 J / g. In this way, the polylactic acid resin foamed molded product is provided with excellent heat resistance by setting the calorific value by differential scanning calorimetry at a heating rate of 5 ° C./min to less than a predetermined amount. can do.

ここで、ポリ乳酸系樹脂発泡成形体における加熱速度５℃／分での示差走査熱量測定による発熱量は、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、５℃／分の加熱速度にて昇温させながら測定されたＤＳＣ曲線から発熱量（Ｊ／ｇ）を算出することができる。   Here, the calorific value obtained by differential scanning calorimetry at a heating rate of 5 ° C./min in the polylactic acid resin foamed molded product conforms to the measurement method described in JIS K7121 using a differential scanning calorimeter (DSC). The calorific value (J / g) can be calculated from the DSC curve measured while raising the temperature at a heating rate of ° C / min.

次に、上記ポリ乳酸系樹脂発泡成形体の製造方法について説明する。はじめに、ポリ乳酸系樹脂発泡成形体の製造に用いられるポリ乳酸系樹脂発泡粒子の製造方法について説明する。   Next, the manufacturing method of the said polylactic acid-type resin foam molding is demonstrated. First, the manufacturing method of the polylactic acid-type resin expanded particle used for manufacture of a polylactic acid-type resin foam molding is demonstrated.

先ず、ポリ乳酸系樹脂を押出機に供給して発泡剤の存在下にて溶融混練した後、押出機の先端に取り付けた金型から押出発泡させる。この押出発泡させて得られた押出発泡体の形態は、特に限定されず、ストランド状、シート状などが挙げられるが、ストランド状が好ましい。これらの発泡体を粒子状に切断することでポリ乳酸系樹脂発泡粒子が得られる。   First, a polylactic acid resin is supplied to an extruder and melt-kneaded in the presence of a foaming agent, and then extruded and foamed from a mold attached to the tip of the extruder. The form of the extruded foam obtained by extrusion foaming is not particularly limited, and examples thereof include a strand shape and a sheet shape, and a strand shape is preferable. By cutting these foams into particles, polylactic acid-based resin foamed particles can be obtained.

又、上記発泡剤としては、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。   Further, as the foaming agent, those conventionally used are used, for example, chemical foaming agents such as azodicarbonamide, dinitrosopentamethylenetetramine, hydrazoyldicarbonamide, sodium bicarbonate; propane, normal butane, Saturated aliphatic hydrocarbons such as isobutane, normal pentane, isopentane, hexane, ethers such as dimethyl ether, chlorofluorocarbons such as methyl chloride, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, monochlorodifluoromethane, Examples thereof include physical blowing agents such as carbon dioxide and 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、ポリ乳酸系樹脂発泡体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ポリ乳酸系樹脂発泡体を得ることができなかったり或いはポリ乳酸系樹脂発泡体の発泡倍率が高過ぎる場合があるので、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。   If the amount of the foaming agent supplied to the extruder is small, the polylactic acid resin foam may not be foamed to the desired foaming ratio, whereas if it is large, the foaming agent acts as a plasticizer. When the melted polylactic acid resin is too low in viscoelasticity and foamability is reduced and a good polylactic acid resin foam cannot be obtained, or the expansion ratio of the polylactic acid resin foam is too high Therefore, the amount is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 4 parts by weight, and particularly preferably 0.3 to 3 parts by weight with respect to 100 parts by weight of the polylactic acid resin.

なお、押出機には気泡調整剤が添加されることが好ましいが、気泡調整剤の多くは、ポリ乳酸系樹脂発泡体の結晶核剤として作用するため、ポリ乳酸系樹脂の結晶化を促進しない気泡調整剤を用いることが好ましく、このような気泡調整剤としては、ポリテトラフルオロエチレン粉末、アクリル樹脂で変性されたポリテトラフルオロエチレン粉末が好ましい。そして、ポリテトラフルオロエチレン粉末、及び、アクリル樹脂で変性されたポリテトラフルオロエチレン粉末は、ポリ乳酸系樹脂の結晶化を殆ど促進することなく、ポリ乳酸系樹脂発泡体の気泡の微細化を図ることができる。   In addition, it is preferable that a bubble regulator is added to the extruder, but since many of the bubble regulators act as a crystal nucleating agent for the polylactic acid resin foam, crystallization of the polylactic acid resin is not promoted. It is preferable to use a bubble regulator, and as such a bubble regulator, polytetrafluoroethylene powder or polytetrafluoroethylene powder modified with an acrylic resin is preferred. The polytetrafluoroethylene powder and the polytetrafluoroethylene powder modified with an acrylic resin aim to make the bubbles of the polylactic acid resin foam finer without substantially promoting crystallization of the polylactic acid resin. be able to.

又、押出機に供給される気泡調整剤の量としては、少ないと、ポリ乳酸系樹脂発泡体の気泡が粗大となり、得られるポリ乳酸系樹脂発泡成形体の外観が低下することがある一方、多いと、ポリ乳酸系樹脂を押出発泡させる際に破泡を生じてポリ乳酸系樹脂発泡体の独立気泡率が低下することがあるので、ポリ乳酸ポリ乳酸系樹脂１００重量部に対して０．０１〜３重量部が好ましく、０．０５〜２重量部がより好ましく、０．１〜１重量部が特に好ましい。   Moreover, as the amount of the air conditioner supplied to the extruder, if the amount is small, the bubbles of the polylactic acid resin foam may become coarse, and the appearance of the resulting polylactic acid resin foam molded product may be reduced. If the amount is too large, foam breakage may occur when the polylactic acid resin is extruded and foamed, and the closed cell ratio of the polylactic acid resin foam may decrease. It is preferably 01 to 3 parts by weight, more preferably 0.05 to 2 parts by weight, and particularly preferably 0.1 to 1 part by weight.

なお、押出機には、本発明のポリ乳酸系樹脂発泡成形体の物性を損なわない範囲内において、着色剤、滑剤、劣化防止剤、帯電防止剤、難燃剤などの添加剤を添加してもよい。   Note that additives such as a colorant, a lubricant, a deterioration preventing agent, an antistatic agent and a flame retardant may be added to the extruder as long as the physical properties of the polylactic acid resin foam molded article of the present invention are not impaired. Good.

又、上記押出機としては、従来から汎用されている押出機であれば、特に限定されず、例えば、単軸押出機、二軸押出機、複数の押出機を連結させたタンデム型の押出機が挙げられ、タンデム型の押出機が好ましい。   The extruder is not particularly limited as long as it is a conventionally used extruder. For example, a single-screw extruder, a twin-screw extruder, and a tandem extruder in which a plurality of extruders are connected. A tandem type extruder is preferable.

そして、押出機内において発泡剤と共に溶融混練されて発泡剤が分散されたポリ乳酸系樹脂は、押出機の先端に取り付けられた金型から押し出されると直ちに発泡してポリ乳酸系樹脂押出発泡体となる。   The polylactic acid resin melt-kneaded with the foaming agent in the extruder and the foaming agent is dispersed is immediately foamed when extruded from a mold attached to the tip of the extruder, and the polylactic acid resin extruded foam Become.

押出機に取り付ける金型としては、特に限定されないが、ポリ乳酸系樹脂を押出発泡させて均一微細な気泡を形成できる金型が好ましく、このような金型としては、ノズル金型が好ましく、ノズルを複数有するマルチノズル金型がより好ましい。   The mold attached to the extruder is not particularly limited, but a mold capable of forming uniform fine bubbles by extrusion foaming a polylactic acid-based resin is preferable. As such a mold, a nozzle mold is preferable, and a nozzle A multi-nozzle mold having a plurality of is more preferable.

マルチノズル金型のノズルの出口直径は、小さいと、押出圧力が高くなりすぎて押出発泡が困難となることがある一方、大きいと、ポリ乳酸系樹脂発泡粒子の径が大きくなって金型への充填性が低下するので、０．２〜２ｍｍが好ましく、０．３〜１．６ｍｍがより好ましく、０．４〜１．２ｍｍが特に好ましい。   If the outlet diameter of the nozzle of the multi-nozzle mold is small, the extrusion pressure may become too high and extrusion foaming may become difficult. Therefore, 0.2 to 2 mm is preferable, 0.3 to 1.6 mm is more preferable, and 0.4 to 1.2 mm is particularly preferable.

更に、押出機の先端に取り付けた金型から押出発泡させる際のポリ乳酸系樹脂の樹脂温度は、下記式５を満たすことが好ましく、下記式６を満たすことがより好ましい。
（貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔ＋４０℃）≦樹脂温度
≦（貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔ＋９０℃）・・・式５
（貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔ＋５０℃）≦樹脂温度
≦（貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔ＋８０℃）・・・式６ Furthermore, the resin temperature of the polylactic acid-based resin when extrusion foaming from a mold attached to the tip of the extruder preferably satisfies the following formula 5, and more preferably satisfies the following formula 6.
(Temperature T + 40 ° C. at intersection of storage modulus curve and loss modulus curve) ≦ Resin temperature ≦ (Temperature T + 90 ° C. at intersection of storage modulus curve and loss modulus curve) Equation 5
(Temperature T + 50 ° C. at the intersection of the storage modulus curve and the loss modulus curve) ≦ Resin temperature ≦ (Temperature T + 80 ° C. at the intersection of the storage modulus curve and the loss modulus curve) Equation 6

これは、ポリ乳酸系樹脂の樹脂温度が低いと、フラクチャーが発生してポリ乳酸系樹脂発泡体の外観性が低下し或いは押出負荷が大きくなり過ぎて押出機から押出発泡させることが困難となることがある一方、高いと、ポリ乳酸系樹脂の溶融粘度が低くなり過ぎて良好なポリ乳酸系樹脂発泡体を得ることができないことがあるからである。   This is because, when the resin temperature of the polylactic acid-based resin is low, fracture occurs and the appearance of the polylactic acid-based resin foam deteriorates or the extrusion load becomes too large to be extruded and foamed from the extruder. On the other hand, if it is high, the melt viscosity of the polylactic acid resin becomes too low, and a good polylactic acid resin foam may not be obtained.

そして、押出機から押出発泡されたポリ乳酸系樹脂押出発泡体を冷却して、ポリ乳酸系樹脂押出発泡体の結晶化が進行するのを抑制する。   And the polylactic acid-type resin extrusion foam extruded and foamed from the extruder is cooled, and it suppresses that crystallization of a polylactic acid-type resin extrusion foam advances.

上記ポリ乳酸系樹脂押出発泡体の冷却方法としては、押出発泡されたポリ乳酸系樹脂押出発泡体の結晶化度の上昇を速やかに停止できる方法が好ましく、具体的には、押出機から押出発泡されたポリ乳酸系樹脂押出発泡体を水面に浮かせて冷却する方法、押出機から押出発泡されたポリ乳酸系樹脂押出発泡体に水などを霧状に吹き付ける方法、低温に温度調節された冷却板上に、押出機から押出発泡されたポリ乳酸系樹脂押出発泡体を接触させることによって冷却させる方法、押出機から押出発泡された押出発泡体に冷風などの冷却された気体を吹き付ける方法などが挙げられる。なお、ポリ乳酸系樹脂押出発泡体を水面に浮かせて冷却する場合は、水温は０〜４５℃に調整することが好ましい。   As the method for cooling the polylactic acid-based resin extruded foam, a method capable of quickly stopping the increase in crystallinity of the extruded and foamed polylactic acid-based resin is preferable. A method of cooling the extruded polylactic acid resin foam by floating it on the water surface, a method of spraying water or the like onto the extruded polylactic acid resin foam foamed from an extruder, a cooling plate whose temperature is adjusted to a low temperature On top of this, there is a method of cooling by bringing a polylactic acid resin extruded foam extruded from an extruder into contact, a method of blowing a cooled gas such as cold air onto an extruded foam extruded from an extruder, etc. It is done. In addition, when making a polylactic acid-type resin extrusion foaming body float on the water surface and cooling, it is preferable to adjust water temperature to 0-45 degreeC.

ポリ乳酸系樹脂押出発泡体を粒子状に切断する切断機としては、ペレタイザーやホットカット機などが挙げられ、又、切断機の切断方法としては、ドラムカッタ式やファンカッタ式があるが、ポリ乳酸系樹脂押出発泡体の切断時にポリ乳酸系樹脂押出発泡体に割れや欠けが発生しにくいことから、ファンカッタ式の切断方法を用いることが好ましい。なお、上記では、ポリ乳酸系樹脂押出発泡体の冷却後に、ポリ乳酸系樹脂押出発泡体を切断する場合を説明したが、押出機から押出発泡させると同時にポリ乳酸系樹脂押出発泡体を切断して粒子状とした後に、ポリ乳酸系樹脂発泡粒子を冷却するようにしてもよい。   Examples of the cutting machine that cuts the extruded polylactic acid resin into particles include a pelletizer and a hot-cut machine. The cutting methods of the cutting machine include a drum cutter type and a fan cutter type. It is preferable to use a fan-cutter-type cutting method because cracking and chipping are less likely to occur in the extruded polylactic acid resin foam when cutting the extruded lactic acid resin foam. In the above description, the case where the polylactic acid resin extruded foam is cut after cooling the polylactic acid resin extruded foam has been described. However, the polylactic acid resin extruded foam is cut simultaneously with the extrusion foaming from the extruder. Then, the polylactic acid resin foamed particles may be cooled after being made into particles.

このようにして得られたポリ乳酸系樹脂発泡粒子の嵩密度は、小さいと、ポリ乳酸系樹脂発泡粒子の連続気泡率が上昇して、型内発泡成形における発泡時にポリ乳酸系樹脂発泡粒子に必要な発泡力を付与することができない虞れがある一方、大きいと、得られるポリ乳酸系樹脂発泡粒子の気泡が不均一となって、型内発泡成形時におけるポリ乳酸系樹脂発泡粒子の発泡性が不充分となることがあるので、０．０３〜０．５ｇ／ｃｍ3 が好ましく、０．０５〜０．４ｇ／ｃｍ3 がより好ましく、０．０７〜０．３ｇ／ｃｍ3 が特に好ましい。 If the bulk density of the polylactic acid-based resin expanded particles obtained in this way is small, the open cell ratio of the polylactic acid-based resin expanded particles increases, and the polylactic acid-based resin expanded particles become foamed during foaming in in-mold foam molding. On the other hand, there is a possibility that the necessary foaming force cannot be imparted. On the other hand, if it is large, the resulting foam of the polylactic acid resin foamed particles becomes uneven, and foaming of the polylactic acid resin foamed particles during in-mold foam molding 0.03 to 0.5 g / cm 3 is preferable, 0.05 to 0.4 g / cm 3 is more preferable, and 0.07 to 0.3 g / cm 3 is particularly preferable. preferable.

又、上記ポリ乳酸系樹脂発泡粒子の粒子径は、小さいと、型内発泡成形時にポリ乳酸系樹脂発泡粒子の発泡性が低下することがある一方、大きいと、型内発泡成形時に金型内へのポリ乳酸系樹脂発泡粒子の充填性が低下することがあるので、１．０〜５．０ｍｍが好ましく、２．０〜４．０ｍｍがより好ましい。   In addition, if the particle diameter of the polylactic acid-based resin expanded particles is small, the foamability of the polylactic acid-based resin expanded particles may be reduced at the time of in-mold foam molding. Since the filling property of the polylactic acid-based resin foamed particles may be lowered, 1.0 to 5.0 mm is preferable, and 2.0 to 4.0 mm is more preferable.

ポリ乳酸系樹脂押出発泡体がストランド状であり、このストランド状のポリ乳酸系樹脂押出発泡体をその長さ方向に所定間隔毎に切断してポリ乳酸系樹脂発泡粒子を製造した場合、各ポリ乳酸系樹脂発泡粒子の切断面における最も長い直径（長径）及び最も短い直径（短径）の平均値をポリ乳酸系樹脂発泡粒子の直径とし、上記と同様の理由から、ポリ乳酸系樹脂発泡粒子の直径は１．０〜５．０ｍｍが好ましく、２．０〜４．０ｍｍがより好ましい。又、各ポリ乳酸系樹脂発泡粒子における切断面に直交する方向の長さは、短いと、ポリ乳酸系樹脂発泡粒子全体に対する切断面の破断気泡の割合が相対的に増加してポリ乳酸系樹脂発泡粒子の発泡性が低下することがある一方、長いと、型内発泡成形時にポリ乳酸系樹脂を金型内に充填する際の充填性が低下することがあるので、２．０〜５．０ｍｍが好ましく、２．０〜４．０ｍｍがより好ましい。   When the polylactic acid-based resin extruded foam is in the form of a strand and the strand-shaped polylactic acid-based resin extruded foam is cut at predetermined intervals in the length direction, The average value of the longest diameter (major axis) and the shortest diameter (minor axis) at the cut surface of the lactic acid-based resin expanded particles is defined as the diameter of the polylactic acid-based resin expanded particles. For the same reason as described above, the polylactic acid-based resin expanded particles The diameter of is preferably 1.0 to 5.0 mm, and more preferably 2.0 to 4.0 mm. In addition, when the length of each polylactic acid resin expanded particle in the direction orthogonal to the cut surface is short, the ratio of the broken cells of the cut surface relative to the entire polylactic acid resin expanded particle is relatively increased, and the polylactic acid resin On the other hand, the foamability of the foamed particles may be lowered. On the other hand, when the foamed particles are long, the fillability at the time of filling the polylactic acid-based resin into the mold at the time of in-mold foam molding may be lowered. 0 mm is preferable, and 2.0 to 4.0 mm is more preferable.

そして、上記ポリ乳酸系樹脂発泡粒子の結晶化度は、高いと、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低下することがあるので、３０％未満が好ましく、３〜２８％がより好ましく、５〜２６％が特に好ましい。   And when the crystallinity degree of the said polylactic acid-type resin expanded particle is high, since the meltability of polylactic acid-type resin expanded particles may fall at the time of in-mold foam molding, less than 30% is preferable, 3 28% is more preferable, and 5 to 26% is particularly preferable.

ここで、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５℃／分の昇温速度にて昇温しながら測定された１ｍｇ当たりの発熱量及び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。   Here, the degree of crystallinity of the polylactic acid-based resin expanded particles is measured while using a differential scanning calorimeter (DSC) in accordance with the measuring method described in JIS K7121 at a temperature rising rate of 5 ° C./min. The calorific value per 1 mg and the heat of fusion per mg measured can be calculated by the following formula.

Figure 0004761916
Figure 0004761916

このように、得られるポリ乳酸系樹脂発泡粒子の結晶化度を３０％未満に調整することによって、ポリ乳酸系樹脂発泡粒子の融着性を確保し、型内発泡成形時におけるポリ乳酸系樹脂発泡粒子同士の融着性を良好なものとすることができる。   Thus, by adjusting the degree of crystallinity of the obtained polylactic acid-based resin expanded particles to less than 30%, the fusion property of the polylactic acid-based resin expanded particles is ensured, and the polylactic acid-based resin at the time of in-mold foam molding The fusibility between the expanded particles can be improved.

又、このポリ乳酸系樹脂発泡粒子から更に高発泡倍率に発泡したポリ乳酸系樹脂発泡粒子を得ることができる。具体的には、上記ポリ乳酸系樹脂を圧力容器内に供給し、この圧力容器内にガスを圧入してポリ乳酸系樹脂発泡粒子にガスを含浸させて、ポリ乳酸系樹脂発泡粒子に高い発泡性を付与し、この発泡性を付与されたポリ乳酸系樹脂発泡粒子を攪拌しながら６０〜８０℃の熱風で加熱することで更に高発泡倍率に発泡したポリ乳酸系樹脂発泡粒子が得られる。なお、上記ガスとしては、例えば、二酸化炭素、窒素、空気などが挙げられ、二酸化炭素が好ましい。   Moreover, the polylactic acid-based resin expanded particles expanded at a higher expansion ratio can be obtained from the polylactic acid-based resin expanded particles. Specifically, the polylactic acid-based resin is supplied into a pressure vessel, and a gas is injected into the pressure vessel to impregnate the polylactic acid-based resin expanded particles with gas. The polylactic acid-based resin expanded particles expanded to a higher expansion ratio can be obtained by heating the expanded foamed polylactic acid-based resin particles with hot air at 60 to 80 ° C. while stirring. In addition, as said gas, a carbon dioxide, nitrogen, air etc. are mentioned, for example, A carbon dioxide is preferable.

ポリ乳酸系樹脂発泡粒子にガスを含浸させる際のガス圧は、低いと、ポリ乳酸系樹脂発泡粒子に充分な発泡性を付与させることができない一方、高いと、ポリ乳酸系樹脂発泡粒子の発泡性が向上し過ぎて、ポリ乳酸系樹脂発泡粒子を加熱、発泡させた際に破泡を生じる虞れがあるので、ゲージ圧０．５〜３ＭＰａが好ましく、ゲージ圧１．０〜２．０ＭＰａがより好ましい。   If the gas pressure when impregnating the polylactic acid resin expanded particles with gas is low, sufficient foamability cannot be imparted to the polylactic acid resin expanded particles. On the other hand, if the gas pressure is high, foaming of the polylactic acid resin expanded particles Therefore, the gauge pressure is preferably 0.5 to 3 MPa, and the gauge pressure is 1.0 to 2.0 MPa because there is a possibility that foaming may occur when the polylactic acid resin foamed particles are heated and foamed. Is more preferable.

更に、ポリ乳酸系樹脂発泡粒子にガスを含浸させる時間は、１時間以上が好ましく、２時間以上がより好ましい。又、ポリ乳酸系樹脂発泡粒子にガスを含浸させる温度は、０〜４０℃が好ましく、１０〜３０℃がより好ましい。   Furthermore, the time for impregnating the polylactic acid resin expanded particles with gas is preferably 1 hour or longer, and more preferably 2 hours or longer. Moreover, 0-40 degreeC is preferable and, as for the temperature which impregnates polylactic acid-type resin expanded particle with gas, 10-30 degreeC is more preferable.

又、ポリ乳酸系樹脂発泡粒子の加熱に際して、水蒸気や水分を多く含んだ熱風を用いると、ポリ乳酸系樹脂発泡粒子の結晶化度が上昇し易く、ポリ乳酸系樹脂発泡粒子の型内発泡成形時に、ポリ乳酸系樹脂発泡粒子同士の融着性が低下する虞れがあるため好ましくない。   Also, when heating polylactic acid resin foamed particles, if hot air containing a lot of water vapor or moisture is used, the degree of crystallinity of the polylactic acid resin foamed particles tends to increase, and in-mold foam molding of the polylactic acid resin foamed particles is performed. Sometimes, the fusion between the polylactic acid-based resin expanded particles may be lowered, which is not preferable.

なお、ポリ乳酸系樹脂発泡成形体の実用性からすると、ポリ乳酸系樹脂発泡粒子の嵩密度は、低いほど好ましいが、嵩密度が低くなるにしたがって、得られるポリ乳酸系樹脂発泡成形体の耐熱性が低下していく傾向にある。従って、高発泡倍率化させたポリ乳酸系樹脂発泡粒子の嵩密度は、０．０２〜０．１ｇ／ｃｍ3 が好ましく、０．０２２〜０．０６６ｇ／ｃｍ3 がより好ましく、０．０２８〜０．０５ｇ／ｃｍ3 が特に好ましい。 In view of the practicality of the polylactic acid resin foam molded article, the lower the bulk density of the polylactic acid resin foamed particles, the better. However, as the bulk density decreases, the heat resistance of the resulting polylactic acid resin foam molded article Tend to decline. Therefore, the bulk density of the polylactic acid-based resin foamed particles obtained by a high expansion ratio of is preferably 0.02~0.1g / cm 3, more preferably 0.022~0.066g / cm 3, 0.028~ 0.05 g / cm 3 is particularly preferred.

なお、ポリ乳酸系樹脂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、下記式に基づいてポリ乳酸系樹脂発泡粒子の嵩密度を測定した。   The bulk density of the polylactic acid-based resin expanded particles refers to those 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 polylactic acid-type resin expanded particle based on the following formula.

ポリ乳酸系樹脂発泡粒子の嵩密度（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 (g / cm 3 ) of foamed polylactic acid resin
= [Mass of measuring cylinder with sample (g) -Mass of measuring cylinder (g)]
/ [Capacity of measuring cylinder (cm 3 )]

このようにして製造されたポリ乳酸系樹脂粒子は、型内発泡成形機により所望の形状のポリ乳酸系樹脂発泡成形体に成形される。即ち、ポリ乳酸系樹脂発泡粒子を、型内発泡成形機の雌雄金型間に形成され且つ密閉し得ないキャビティ内に充填して水蒸気などの加熱媒体で加熱し、型内発泡成形す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ポリ乳酸系樹脂発泡成形体を得ることができる。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、水蒸気の他に、熱風などが挙げられるが、効率的に成形を行い、発泡成形体の結晶化を促進させ耐熱性を付与させるためには水蒸気が最も有効である。   The polylactic acid resin particles thus produced are molded into a polylactic acid resin foam molded body having a desired shape by an in-mold foam molding machine. That is, polylactic acid-based resin expanded particles are filled in a cavity that cannot be sealed and formed between male and female molds of an in-mold foam molding machine, heated with a heating medium such as water vapor, and subjected to in-mold foam molding. By increasing the crystallinity of the lactic acid-based resin, it is possible to obtain a polylactic acid-based resin foam molded article having excellent fusion and heat resistance. In addition to steam, hot air can be used as the heating medium for the polylactic acid resin foamed particles filled in the mold, but it can be efficiently molded to promote crystallization of the foamed molded product and has high heat resistance. Water vapor is most effective for imparting.

具体的には、ポリ乳酸系樹脂発泡粒子をＥＰＳ成形機などの汎用の型内発泡成形機におけるそれぞれにドレン排出機構を含有する雌雄金型間に形成されたキャビティ内に充填する。しかる後、一方の金型側からキャビティ内に、ゲージ圧０．０１〜０．０５ＭＰａ（温度にして１０１〜１１０℃）の水蒸気を５〜３０秒間に亘って吹き込んで、ポリ乳酸系樹脂発泡粒子間に存在する空気をドレン排出口から外部に排出すると共に、ポリ乳酸系樹脂発泡粒子を加熱、発泡させ、次に、他方の金型側からもキャビティ内にゲージ圧０．０１〜０．０５ＭＰａ（温度にして１０１〜１１０℃）の水蒸気を２〜２０秒間に亘って吹き込んで、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粒子同士を加熱融着一体化させる。なお、一方の金型側からキャビティ内に水蒸気を圧入する際に、他方の金型側からキャビティ内を真空吸引してもよい。   Specifically, polylactic acid-based resin foam particles are filled into cavities formed between male and female molds each containing a drain discharge mechanism in a general-purpose in-mold foam molding machine such as an EPS molding machine. Thereafter, water vapor of a gauge pressure of 0.01 to 0.05 MPa (temperature of 101 to 110 ° C.) is blown into the cavity from one mold side for 5 to 30 seconds, and polylactic acid resin expanded particles The air present between them is discharged to the outside from the drain outlet, and the polylactic acid resin foamed particles are heated and foamed. Next, the gauge pressure of 0.01 to 0.05 MPa is also entered into the cavity from the other mold side. Water vapor (at a temperature of 101 to 110 ° C.) is blown in for 2 to 20 seconds to foam the polylactic acid-based resin expanded particles, and the polylactic acid-based resin expanded particles are integrated by heat fusion. Note that when the water vapor is pressed into the cavity from one mold side, the inside of the cavity may be vacuumed from the other mold side.

続いて、両型のドレン弁を閉じた状態で雌雄金型の双方の金型からキャビティ内にゲージ圧０．０２〜０．１５ＭＰａ（温度にして１０３〜１２５℃）の水蒸気を１０〜３０秒間に亘って吹き込み、発泡粒子同士の融着率を更に向上させると共に発泡粒子の結晶化度を向上させてポリ乳酸系樹脂発泡成形体を製造することができる。   Subsequently, water vapor with a gauge pressure of 0.02 to 0.15 MPa (temperature of 103 to 125 ° C.) is injected into the cavity from both the male and female molds with the drain valves of both molds closed for 10 to 30 seconds. It is possible to produce a polylactic acid-based resin foamed molded article by blowing the resin and further improving the fusion rate between the foamed particles and improving the crystallinity of the foamed particles.

又、本発明で得られるポリ乳酸系樹脂発泡成形体の融着率は、６０％以上とすることができる。特に融着率７０％以上のポリ乳酸系樹脂発泡成形体は外観及び機械的強度に特に優れている。なお、ポリ乳酸系樹脂発泡成形体の融着率は、下記の要領で測定されたものをいう。先ず、ポリ乳酸系樹脂発泡体の表面に一対の長辺の中心同士を結ぶ直線に沿ってカッターナイフで深さ約３ｍｍの切り込み線を入れた後、この切り込み線に沿って発泡成形体を手で二分割し、その破断面における発泡粒子について、粒子内で破断している粒子の数（ａ）と、粒子同士の境界面で破断している粒子の数（ｂ）とを数え、
融着率（％）＝〔（ａ）／｛（ａ）＋（ｂ）｝〕×１００
に代入して得られた値を融着率（％）とした。 In addition, the fusion rate of the polylactic acid resin foam molded article obtained in the present invention can be 60% or more. In particular, a polylactic acid resin foam molded article having a fusion rate of 70% or more is particularly excellent in appearance and mechanical strength. In addition, the fusion rate of a polylactic acid-type resin foaming molding means what was measured in the following way. First, a cutting line having a depth of about 3 mm is made with a cutter knife along a straight line connecting the centers of a pair of long sides on the surface of the polylactic acid resin foam, and then the foamed molded body is handed along the cutting line. And for the foamed particles in the fracture surface, count the number of particles broken within the particles (a) and the number of particles broken at the interface between the particles (b),
Fusing rate (%) = [(a) / {(a) + (b)}] × 100
The value obtained by substituting for is the fusion rate (%).

雌雄金型の双方の金型からキャビティ内に吹き込む水蒸気の圧力は、低いと、発泡粒子同士の融着率が向上しないと共に、発泡粒子の結晶化度も向上せず耐熱性に優れたポリ乳酸系樹脂発泡成形体を得ることができないことがある一方、高いと、ポリ乳酸系樹脂発泡粒子の温度上昇が急激なものとなり、ポリ乳酸系樹脂発泡粒子の結晶化度の上昇がポリ乳酸系樹脂発泡粒子の溶融速度に追いつかず、ポリ乳酸系樹脂発泡粒子が融けてしまい、得られるポリ乳酸系樹脂発泡成形体に収縮が生じることがあるので、ゲージ圧０．０２〜０．１５ＭＰａ（温度にして１０３〜１２５℃）が好ましく、ゲージ圧０．０６〜０．１５ＭＰａ（温度にして１１０〜１２５℃）がより好ましい。ここでの加熱を充分に行うことでポリ乳酸系樹脂発泡成形体の示差走査熱量測定における発熱量を低く抑えることができる。   If the pressure of the water vapor blown into the cavity from both the male and female molds is low, the fusion rate between the foamed particles will not improve, and the crystallinity of the foamed particles will not improve, and polylactic acid with excellent heat resistance In some cases, it is not possible to obtain a resin-based resin foam molded product. On the other hand, when the temperature is high, the temperature of the polylactic acid-based resin expanded particles increases rapidly, and the crystallinity of the polylactic acid-based resin expanded particles increases. Since the polylactic acid resin foamed particles may not be able to keep up with the melting rate of the foamed particles, and the resulting polylactic acid resin foamed molded product may shrink, the gauge pressure is 0.02 to 0.15 MPa (at the temperature). 103 to 125 ° C.) and a gauge pressure of 0.06 to 0.15 MPa (temperature of 110 to 125 ° C.) is more preferable. By sufficiently heating here, the calorific value in the differential scanning calorimetry of the polylactic acid resin foam molded article can be kept low.

なお、型内発泡成形するにあたっては、得られたポリ乳酸系樹脂発泡粒子に更にガスを含浸させてもよい。ポリ乳酸系樹脂発泡粒子にガスを含浸させる要領は、ガス圧及びガスを含浸させる時間が異なること以外は前記と同様の要領で行われる。   In addition, when performing in-mold foam molding, the obtained polylactic acid resin foamed particles may be further impregnated with gas. The procedure for impregnating the polylactic acid-based resin expanded particles with gas is performed in the same manner as described above except that the gas pressure and the time for impregnation with the gas are different.

このようにポリ乳酸系樹脂発泡粒子の発泡性を向上させることにより、型内発泡成形時における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更に優れた機械的強度を有する。   Thus, by improving the foamability of the polylactic acid-based resin expanded particles, the fusion property between the polylactic acid-based resin expanded particles at the time of in-mold foam molding is improved. Has excellent mechanical strength.

このような場合、ポリ乳酸系樹脂発泡粒子にガスを含浸させる際のガス圧は、低いと、ポリ乳酸系樹脂発泡粒子に充分にガスを含浸させることができず、ポリ乳酸系樹脂発泡粒子の発泡力を充分に向上させることができない一方、高いと、ポリ乳酸系樹脂発泡粒子の発泡力が向上し過ぎて、ポリ乳酸系樹脂発泡粒子を発泡させた際に破泡を生じ或いは型内発泡成形時の冷却時間が延びる虞れがあるので、０．２〜２．０ＭＰａが好ましく、０．５〜１．０ＭＰａがより好ましい。   In such a case, if the gas pressure when impregnating the polylactic acid-based resin expanded particles with gas is low, the polylactic acid-based resin expanded particles cannot be sufficiently impregnated with gas. While the foaming power cannot be improved sufficiently, if it is too high, the foaming power of the polylactic acid resin foamed particles will be improved too much, causing foam breakage when foaming the polylactic acid resin foamed particles, or foaming in the mold Since there is a possibility that the cooling time at the time of molding may be extended, 0.2 to 2.0 MPa is preferable, and 0.5 to 1.0 MPa is more preferable.

ポリ乳酸系樹脂発泡粒子にガスを含浸させる時間は、１時間以上が好ましく、２時間以上がより好ましい。又、ポリ乳酸系樹脂発泡粒子にガスを含浸させる温度は、０〜４０℃が好ましく、１０〜３０℃がより好ましい。   The time for impregnating the polylactic acid-based resin expanded particles with gas is preferably 1 hour or longer, and more preferably 2 hours or longer. Moreover, 0-40 degreeC is preferable and, as for the temperature which impregnates polylactic acid-type resin expanded particle with gas, 10-30 degreeC is more preferable.

又、本発明では、ポリ乳酸系樹脂発泡成形体の見掛け密度は０．０２〜０．２ｇ／ｃｍ3 が好ましい。具体的には、ポリ乳酸系樹脂発泡成形体の用途によって適宜、調整され、住宅の壁断熱材としては０．０２５〜０．０５ｇ／ｃｍ3 が好ましく、自動車構造材などでは０．０６〜０．２ｇ／ｃｍ3 が好ましい。なお、ポリ乳酸系樹脂発泡成形体の見掛け密度は、ＪＩＳ Ｋ６７６７：１９９９「発泡プラスチック及びゴム−見掛け密度の測定」に記載の方法で測定されたものをいう。 In the present invention, the apparent density of the polylactic acid resin foamed molded article is preferably 0.02 to 0.2 g / cm 3 . Specifically, it is appropriately adjusted depending on the use of the polylactic acid resin foamed molded article, and is preferably 0.025 to 0.05 g / cm 3 as a wall insulating material for a house, and 0.06 to 0 for an automobile structural material or the like. .2 g / cm 3 is preferred. In addition, the apparent density of the polylactic acid-based resin foam molded article refers to that measured by the method described in JIS K6767: 1999 “Measurement of foamed plastic and rubber-apparent density”.

本発明のポリ乳酸系樹脂発泡成形体は、ポリ乳酸系樹脂発泡粒子を型内発泡成形して得られたポリ乳酸系樹脂発泡成形体であって、１５０℃での加熱寸法変化率が５％未満であることを特徴とするので、優れた耐熱性を有しており高温における加熱寸法変化率が低いので、耐熱性が求められる用途に広く用いることができる。   The polylactic acid resin foam molded article of the present invention is a polylactic acid resin foam molded article obtained by in-mold foam molding of polylactic acid resin foamed particles, and the heating dimensional change rate at 150 ° C. is 5%. Since it is characterized by being less than, it has excellent heat resistance and has a low rate of dimensional change in heating at high temperatures. Therefore, it can be widely used in applications requiring heat resistance.

そして、ポリ乳酸系樹脂発泡粒子が、ポリ乳酸系樹脂を押出機に供給して発泡剤の存在下にて溶融混練し押出発泡して押出発泡体を製造し、この押出発泡体を粒子状に切断して得られたものである場合には、従来のようにポリ乳酸系樹脂粒子を一旦、作製し、このポリ乳酸系樹脂粒子に発泡剤を含浸させて予備発泡させる場合と異なり、型内発泡成形前のポリ乳酸系樹脂発泡粒子の結晶化度の上昇を防止することができ、ポリ乳酸系樹脂発泡粒子は融着性を良好に維持しており、このような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更に優れた機械的強度を有する。   Then, the polylactic acid-based resin expanded particles are supplied to the extruder, melt-kneaded in the presence of a foaming agent, extruded and foamed to produce an extruded foam, and the extruded foam is made into particles. In the case of a product obtained by cutting, unlike the conventional case in which polylactic acid resin particles are once prepared, the polylactic acid resin particles are impregnated with a foaming agent and pre-foamed. The increase in crystallinity of the polylactic acid resin expanded particles before foam molding can be prevented, and the polylactic acid resin expanded particles maintain good fusion properties. Such polylactic acid resin expanded particles The polylactic acid-based resin foam molded article obtained by using has a further excellent mechanical strength.

（実施例１）
一段目となる口径５０ｍｍの単軸押出機と二段目となる口径６５ｍｍの単軸押出機とを接続管を介して接続してなるタンデム型の押出機を用意した。 Example 1
A tandem type extruder in which a single-screw extruder having a diameter of 50 mm serving as the first stage and a single-screw extruder having a diameter of 65 mm serving as the second stage were connected via a connecting pipe was prepared.

そして、上記タンデム型の押出機の一段目の押出機に、結晶性のポリ乳酸系樹脂（ユニチカ社製 商品名「ＴＥＲＲＡＭＡＣ ＨＶ−６２００」、融点：１６７．４℃、Ｄ体比率：１．５重量％、Ｌ体比率：９８．５重量％、動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔ：１３９．５℃、動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点の温度Ｔにおける弾性率（貯蔵弾性率又は損失弾性率）：４．２３×１０4 Ｐａ）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重量部を供給して２２０℃にて溶融混練した。なお、図１に、ポリ乳酸系樹脂の動的粘弾性測定にて得られた、貯蔵弾性率曲線及び損失弾性率曲線を示した。 Then, a crystalline polylactic acid resin (trade name “TERRAMAC HV-6200” manufactured by Unitika Co., Ltd., melting point: 167.4 ° C., D-form ratio: 1.5 is added to the first stage extruder of the tandem type extruder. % By weight, L-form ratio: 98.5% by weight, temperature T at the intersection of storage elastic modulus curve and loss elastic modulus curve obtained by dynamic viscoelasticity measurement: 139.5 ° C., dynamic viscoelasticity measurement obtained in the elastic modulus at a temperature of T intersections of the loss modulus curve and storage elastic modulus curve (storage modulus or loss modulus) as 4.23 × 10 4 Pa) 100 parts by weight of nucleating agent 0.1 parts by weight of polytetrafluoroethylene powder (trade name “Fluon L169J” manufactured by Asahi Glass Co., Ltd.) was supplied and melt-kneaded at 220 ° C. In addition, in FIG. 1, the storage elastic modulus curve and the loss elastic modulus curve obtained by the dynamic viscoelasticity measurement of polylactic acid-type resin were shown.

続いて、第一押出機の途中から、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０．７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。   Subsequently, in the middle of the first extruder, a polylactic acid-based polylactic acid in a molten state so that butane comprising 35% by weight of isobutane and 65% by weight of normal butane is 0.7 parts by weight with respect to 100 parts by weight of the polylactic acid-based resin. It was press-fitted 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一段目の押出機から接続管を介して二段目の押出機に連続的に供給した。溶融状態のポリ乳酸系樹脂を二段目の押出機にて樹脂温度２００℃に冷却した後、二段目の押出機の先端に取り付けたマルチノズル金型の各ノズルから押出発泡させてストランド状のポリ乳酸系樹脂押出発泡体を製造した。   Thereafter, the molten polylactic acid-based resin was continuously supplied from the first-stage extruder to the second-stage extruder via a connecting pipe. After the molten polylactic acid resin is cooled to a resin temperature of 200 ° C. by a second stage extruder, it is extruded and foamed from each nozzle of a multi-nozzle mold attached to the tip of the second stage extruder. A polylactic acid-based resin extruded foam was produced.

続いて、ストランド状のポリ乳酸系樹脂押出発泡体を冷却水槽内の水面上に浮かせて冷却した。なお、冷却水槽内の水温は、２０℃であった。   Subsequently, the strand-like polylactic acid resin extruded foam was floated on the water surface in the cooling water tank and cooled. In addition, the water temperature in a cooling water tank was 20 degreeC.

なお、マルチノズル金型は、出口直径が１．０ｍｍのノズルが１５個、配設されており、ランド部の長さは７ｍｍであった。又、マルチノズル金型のノズルから押出発泡させた際の樹脂温度は、二段目の押出機の先端部と金型との間にブレーカープレートを挿入し、このブレーカープレートの中心部に熱電対を挿入することによって測定した。   The multi-nozzle mold was provided with 15 nozzles having an exit diameter of 1.0 mm, and the land portion had a length of 7 mm. The resin temperature when extrusion foaming from the nozzle of the multi-nozzle mold is such that a breaker plate is inserted between the tip of the second stage extruder and the mold, and a thermocouple is placed in the center of the breaker plate. Was measured by inserting.

そして、ストランド状のポリ乳酸系樹脂押出発泡体を充分に水切りした後、このポリ乳酸系樹脂押出発泡体をファンカッタ式のペレタイザーを用いて切断してポリ乳酸系樹脂発泡粒子（Ａ）を得た。なお、得られたポリ乳酸系樹脂発泡粒子（Ａ）は、その嵩密度が０．１７ｇ／ｃｍ3 で、長さが平均３．５ｍｍ、直径が平均２．３ｍｍで、結晶化度は１７．２％であった。 Then, after sufficiently draining the strand-like polylactic acid resin foam, the polylactic acid resin foam is cut using a fan cutter type pelletizer to obtain polylactic acid resin foam particles (A). It was. The obtained polylactic acid resin expanded particles (A) had a bulk density of 0.17 g / cm 3 , an average length of 3.5 mm, an average diameter of 2.3 mm, and a crystallinity of 17.7. 2%.

次に、このポリ乳酸系樹脂発泡粒子（Ａ）を１０リットルの圧力容器に入れ密閉し、この圧力容器内に二酸化炭素を０．５ＭＰａの圧力にて圧入して２５℃にて２時間に亘って放置してポリ乳酸系樹脂発泡粒子に二酸化炭素を含浸させた。   Next, the polylactic acid-based resin expanded particles (A) are put in a 10-liter pressure vessel and sealed, and carbon dioxide is injected into the pressure vessel at a pressure of 0.5 MPa, and then at 25 ° C. for 2 hours. Then, the polylactic acid resin expanded particles were impregnated with carbon dioxide.

続いて、圧力容器から、与圧されたポリ乳酸系樹脂発泡粒子を取り出し、このポリ乳酸系樹脂粒子を直ちに型内成形機の、それぞれにドレン排出機構を備えた雌雄金型間に形成されたキャビティ内に充填して、キャビティ内に雌金型側からゲージ圧０．０２ＭＰａ（温度にして１０３℃）の水蒸気で１５秒間に亘って吹き込み、ポリ乳酸系樹脂発泡粒子間の空気を雄型のドレン排出口から排出しながらポリ乳酸系樹脂発泡粒子を加熱、発泡させ、次に、キャビティ内に雄金型側からゲージ圧０．０２ＭＰａ（温度にして１０３℃）の水蒸気を１０秒間に亘って吹き込み、ポリ乳酸系樹脂発泡粒子を加熱、発泡させた。   Subsequently, the pressurized polylactic acid-based resin expanded particles were taken out from the pressure vessel, and the polylactic acid-based resin particles were immediately formed between the male and female molds each having a drain discharge mechanism of the in-mold molding machine. The inside of the cavity was filled, and water was blown into the cavity from the female mold side with water vapor with a gauge pressure of 0.02 MPa (temperature of 103 ° C.) for 15 seconds, and the air between the polylactic acid resin expanded particles was blown into the male mold. The polylactic acid resin foamed particles are heated and foamed while being discharged from the drain outlet, and then water vapor with a gauge pressure of 0.02 MPa (temperature of 103 ° C.) is supplied into the cavity from the male mold side for 10 seconds. Blowing was performed to heat and foam the polylactic acid resin foamed particles.

次に、両型のドレン弁を閉じた状態で雌雄金型の双方側からキャビティ内にゲージ圧０．０８ＭＰａ（温度にして１１６℃）の水蒸気を２０秒間に亘って吹き込んでポリ乳酸系樹脂発泡粒子を更に加熱した。そして、雌雄金型を水で充分に冷却した後に、キャビティ内から、縦３００ｍｍ×横４００ｍｍ×厚み２０ｍｍの直方体形状のポリ乳酸系樹脂発泡成形体を取り出した。   Next, with both types of drain valves closed, water vapor with a gauge pressure of 0.08 MPa (temperature of 116 ° C.) is blown into the cavity from both sides of the male and female molds for 20 seconds to foam the polylactic acid resin. The particles were further heated. Then, after the male and female molds were sufficiently cooled with water, a rectangular parallelepiped polylactic acid-based resin foam molded body having a length of 300 mm × width of 400 mm × thickness of 20 mm was taken out from the cavity.

このポリ乳酸系樹脂発泡成形体を４０℃の恒温室にて２４時間乾燥した後に見掛け密度を測定したところ、０．１６ｇ／ｃｍ3 であった。ポリ乳酸系樹脂発泡成形体は、収縮もなく外観性は良好で融着率は８０％であった。 This polylactic acid resin foamed molded article was dried in a constant temperature room at 40 ° C. for 24 hours, and then the apparent density was measured to find that it was 0.16 g / cm 3 . The polylactic acid-based resin foam molded article had no shrinkage and good appearance and had a fusion rate of 80%.

（実施例２）
実施例１で得られたポリ乳酸系樹脂発泡粒子（Ａ）を１０リットルの圧力容器内に入れ密閉し、この圧力容器内に二酸化炭素を１．０ＭＰａの圧力にて圧入して２５℃にて６時間に亘って放置してポリ乳酸系樹脂発泡粒子に二酸化炭素を含浸させた。 (Example 2)
The polylactic acid resin expanded particles (A) obtained in Example 1 were sealed in a 10 liter pressure vessel, and carbon dioxide was injected into the pressure vessel at a pressure of 1.0 MPa at 25 ° C. The polylactic acid resin foamed particles were impregnated with carbon dioxide for 6 hours.

次いで、圧力容器から、二酸化炭素を含浸させたポリ乳酸系樹脂発泡粒子を取り出し、直ちに攪拌機付きの除湿熱風乾燥機に供給し、ポリ乳酸系樹脂発泡粒子を攪拌しながら７０℃の熱風で１８０秒間に亘って加熱して発泡させて、高発泡倍率のポリ乳酸系樹脂発泡粒子を得た。なお、得られた高発泡倍率のポリ乳酸系樹脂発泡粒子は、その嵩密度が０．０４２ｇ／ｃｍ3 で、結晶化度は１８．６％であった。 Next, the polylactic acid resin foam particles impregnated with carbon dioxide are taken out of the pressure vessel, and immediately supplied to a dehumidifying hot air dryer with a stirrer, and the polylactic acid resin foam particles are stirred for 180 seconds with hot air at 70 ° C. The mixture was heated and foamed to obtain expanded foamed polylactic acid resin particles having a high expansion ratio. The obtained foamed polylactic acid resin particles with a high expansion ratio had a bulk density of 0.042 g / cm 3 and a crystallinity of 18.6%.

次に、高発泡倍率のポリ乳酸系樹脂発泡粒子を１０リットルの圧力容器内に入れ密閉し、この圧力容器内に二酸化炭素を０．５ＭＰａの圧力にて圧入して２５℃にて２時間に亘って放置してポリ乳酸系樹脂発泡粒子に二酸化炭素を含浸させた。   Next, polylactic acid-based resin expanded particles having a high expansion ratio are put in a 10 liter pressure vessel and sealed, and carbon dioxide is injected into the pressure vessel at a pressure of 0.5 MPa for 2 hours at 25 ° C. Then, the polylactic acid resin foamed particles were impregnated with carbon dioxide.

得られたポリ乳酸系樹脂発泡粒子を直ちに、実施例１と同様の要領で型内発泡成形してポリ乳酸系樹脂発泡成形体を得た。このポリ乳酸系樹脂発泡成形体を４０℃の恒温室にて２４時間乾燥した後に見掛け密度を測定したところ、０．０４１ｇ／ｃｍ3 であった。ポリ乳酸系樹脂発泡成形体は、収縮もなく外観性は良好で融着率は８０％であった。 The obtained polylactic acid resin foamed particles were immediately subjected to in-mold foam molding in the same manner as in Example 1 to obtain a polylactic acid resin foam molded article. When the apparent density was measured after drying this polylactic acid-based resin foam molded article in a constant temperature room at 40 ° C. for 24 hours, it was 0.041 g / cm 3 . The polylactic acid-based resin foam molded article had no shrinkage and good appearance and had a fusion rate of 80%.

（比較例１）
ポリ乳酸系樹脂として、結晶性のポリ乳酸系樹脂（ユニチカ社製 商品名「ＴＥＲＲＡＭＡＣ ＴＥ−４０００」、融点：１７０．３℃、Ｄ体比率：１．４重量％、Ｌ体比率：９８．６重量％、動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔ：１０５．５℃、動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点の温度Ｔにおける弾性率（貯蔵弾性率又は損失弾性率）：１．１７×１０5 Ｐａ）を用い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粒子を得た。 (Comparative Example 1)
As the polylactic acid resin, crystalline polylactic acid resin (trade name “TERRAMAC TE-4000” manufactured by Unitika Ltd.), melting point: 170.3 ° C., D-form ratio: 1.4% by weight, L-form ratio: 98.6 Weight%, temperature T at the intersection of storage elastic modulus curve and loss elastic modulus curve obtained by dynamic viscoelasticity measurement: 105.5 ° C., storage elastic modulus curve obtained by dynamic viscoelasticity measurement Polylactic acid resin foaming in the same manner as in Example 1 except that the elastic modulus (storage elastic modulus or loss elastic modulus) at the temperature T at the intersection of the elastic modulus curve and the loss elastic modulus curve is 1.17 × 10 5 Pa). Particles were obtained.

しかしながら、押出機から押出発泡させて得られたストランド状のポリ乳酸系樹脂押出発泡体は、気泡破れによる収縮が激しく、良好なポリ乳酸系樹脂発泡粒子を製造することができなかった。   However, the strand-like polylactic acid-based resin extruded foam obtained by extrusion foaming from an extruder is severely shrunk due to bubble breakage, and good polylactic acid-based resin expanded particles cannot be produced.

（比較例２）
ポリ乳酸系樹脂として、結晶性のポリ乳酸系樹脂（島津製作所社製 商品名「ＬＡＣＴＹ９０３１」、融点：１３２．９℃、Ｄ体比率：８．４重量％、Ｌ体比率：９１．６重量％、動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔ：１１０．０℃、動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点の温度Ｔにおける弾性率（貯蔵弾性率又は損失弾性率）：９．５４×１０4 Ｐａ）を用い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粒子を得た。なお、得られたポリ乳酸系樹脂発泡粒子は、その嵩密度が０．１６ｇ／ｃｍ3 で、長さが平均３．５ｍｍ、直径が平均２．４ｍｍで、結晶化度は２．１％であった。 (Comparative Example 2)
As a polylactic acid resin, a crystalline polylactic acid resin (trade name “LACTY9031” manufactured by Shimadzu Corporation, melting point: 132.9 ° C., D-form ratio: 8.4 wt%, L-form ratio: 91.6 wt% The temperature T at the intersection of the storage modulus curve and the loss modulus curve obtained by dynamic viscoelasticity measurement: 110.0 ° C., the storage modulus curve and the loss obtained by dynamic viscoelasticity measurement Polylactic acid resin expanded particles in the same manner as in Example 1 except that the elastic modulus at the temperature T at the intersection with the elastic modulus curve (storage elastic modulus or loss elastic modulus): 9.54 × 10 4 Pa) was used. Got. The obtained polylactic acid-based resin expanded particles had a bulk density of 0.16 g / cm 3 , an average length of 3.5 mm, an average diameter of 2.4 mm, and a crystallinity of 2.1%. there were.

次に、上記ポリ乳酸系樹脂発泡粒子を１０リットルの圧力容器内に入れ密閉し、この圧力容器内に二酸化炭素を０．５ＭＰａの圧力にて圧入して２５℃にて６時間に亘って放置してポリ乳酸系樹脂発泡粒子に二酸化炭素を含浸させた。   Next, the polylactic acid-based resin expanded particles are put in a 10-liter pressure vessel and sealed, and carbon dioxide is injected into the pressure vessel at a pressure of 0.5 MPa and left at 25 ° C. for 6 hours. Then, the polylactic acid resin expanded particles were impregnated with carbon dioxide.

続いて、圧力容器から上記ポリ乳酸系樹脂発泡粒子を取り出し、直ちに型内発泡成形機の、それぞれにドレン排出機構を備えた雌雄金型間に形成されたキャビティ内に充填して、キャビティ内に雌金型側からゲージ圧０．０２ＭＰａ（温度にして１０３℃）の水蒸気で１０秒間に亘って吹き込み、ポリ乳酸系樹脂発泡粒子間の空気を雄型のドレン排出口から排出しながらポリ乳酸系樹脂発泡粒子を加熱、発泡させ、次に、キャビティ内に雄金型側からゲージ圧０．０２ＭＰａ（温度にして１０３℃）の水蒸気を７秒間に亘って吹き込み、ポリ乳酸系樹脂を加熱、発泡させた。   Subsequently, the polylactic acid-based resin expanded particles are taken out from the pressure vessel, and immediately filled in cavities formed between the male and female molds each having a drain discharge mechanism of the in-mold foam molding machine. A polylactic acid system is blown in from a female mold side with water vapor at a gauge pressure of 0.02 MPa (temperature: 103 ° C.) for 10 seconds, and the air between the polylactic acid resin foamed particles is discharged from the male drain outlet. The foamed resin particles are heated and foamed, and then steam with a gauge pressure of 0.02 MPa (temperature of 103 ° C.) is blown into the cavity from the side of the male mold for 7 seconds to heat and foam the polylactic acid resin. I let you.

次に、両型のドレン弁を閉じた状態で、雌雄金型の双方側からキャビティ内にゲージ圧０．０６ＭＰａ（温度にして１１０℃）の水蒸気を１２秒間に亘って吹き込んでポリ乳酸系樹脂発泡粒子を更に加熱した。そして、雌雄金型を水で充分に冷却した後に、キャビティ内から、縦３００ｍｍ×横４００ｍｍ×厚み２０ｍｍの直方体形状のポリ乳酸系樹脂発泡成形体を取り出した。   Next, with both types of drain valves closed, a water vapor of 0.06 MPa (temperature: 110 ° C.) is blown into the cavity from both sides of the male and female molds for 12 seconds to form a polylactic acid resin. The expanded particles were further heated. Then, after the male and female molds were sufficiently cooled with water, a rectangular parallelepiped polylactic acid-based resin foam molded body having a length of 300 mm × width of 400 mm × thickness of 20 mm was taken out from the cavity.

このポリ乳酸系樹脂発泡成形体を４０℃の恒温室にて２４時間乾燥した後に見掛け密度を測定したところ、０．１４ｇ／ｃｍ3 であった。ポリ乳酸系樹脂発泡成形体は、収縮もなく外観性は良好で融着率は９０％であった。 When the apparent density was measured after drying this polylactic acid-based resin foam molded article in a constant temperature room at 40 ° C. for 24 hours, it was 0.14 g / cm 3 . The polylactic acid-based resin foam molded article had no shrinkage and good appearance and had a fusion rate of 90%.

得られたポリ乳酸系樹脂発泡成形体の１５０℃での加熱寸法変化率（表１では単に「加熱寸法変化率」と表した）、融着率及び結晶化度、並びに、加熱速度５℃／分での示差走査熱量測定によるポリ乳酸系樹脂発泡成形体の発熱量（表１では「ＤＳＣ発熱量」と表した）を測定し、その結果を表１に示した。なお、比較例２のポリ乳酸系樹脂発泡成形体は、加熱寸法変化率の測定の際に溶融してしまい原型をとどめておらず耐熱性を有していなかった。   The resulting polylactic acid-based resin foamed molded article has a heating dimensional change rate at 150 ° C. (simply expressed as “heating dimensional change rate” in Table 1), a fusion rate and a crystallinity, and a heating rate of 5 ° C. / The calorific value (expressed as “DSC calorific value” in Table 1) of the polylactic acid resin foamed molded article by differential scanning calorimetry in minutes was measured, and the results are shown in Table 1. In addition, the polylactic acid-based resin foamed molded article of Comparative Example 2 melted during measurement of the heating dimensional change rate and did not retain the original shape and did not have heat resistance.

Figure 0004761916
Figure 0004761916

実施例１で用いられたポリ乳酸系樹脂の動的粘弾性測定にて得られた、貯蔵弾性率曲線及び損失弾性率曲線を示したグラフである。2 is a graph showing a storage elastic modulus curve and a loss elastic modulus curve obtained by dynamic viscoelasticity measurement of the polylactic acid resin used in Example 1. FIG.

Claims (7)

ポリ乳酸系樹脂発泡粒子を型内発泡成形して得られたポリ乳酸系樹脂発泡成形体であって、１５０℃での加熱寸法変化率が５％未満であり、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と共に、上記ポリ乳酸系樹脂における融点（ｍｐ）と動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔとが下記式１を満たすことを特徴とするポリ乳酸系樹脂発泡成形体。
（ポリ乳酸系樹脂の融点（ｍｐ）−４０℃）
≦（交点における温度Ｔ）≦ポリ乳酸系樹脂の融点（ｍｐ）・・・式１ A polylactic acid resin foam molded article obtained by in-mold foam molding of polylactic acid resin foamed particles, wherein a heating dimensional change rate at 150 ° C. is less than 5% , and the polylactic acid resin is The constituent monomer component contains both D-isomer and L-isomer optical isomers, and the content of the lesser of the D-isomer and L-isomer is less than 5 mol%, or the constituent monomer component Storage modulus curve obtained by measuring only the optical isomer of either D-form or L-form as well as the melting point (mp) and dynamic viscoelasticity of the polylactic acid resin. And a temperature T at the intersection of the loss elastic modulus curve satisfy the following formula 1 .
(Melting point of polylactic acid resin (mp) -40 ° C)
≦ (temperature T at the intersection) ≦ melting point of polylactic acid resin (mp) Formula 1 １５０℃での加熱寸法変化率が１％未満であることを特徴とする請求項１に記載のポリ乳酸系樹脂発泡成形体。   The polylactic acid resin foamed molded article according to claim 1, wherein a heating dimensional change rate at 150 ° C is less than 1%. ポリ乳酸系樹脂発泡粒子が、ポリ乳酸系樹脂を押出機に供給して発泡剤の存在下にて溶融混練し押出発泡して押出発泡体を製造し、この押出発泡体を粒子状に切断して得られたものであることを特徴とする請求項１又は請求項２に記載のポリ乳酸系樹脂発泡成形体。   Polylactic acid resin foamed particles are supplied to an extruder, melted and kneaded in the presence of a foaming agent, extruded and foamed to produce an extruded foam, and the extruded foam is cut into particles. The polylactic acid-based resin foam-molded article according to claim 1 or 2, wherein the polylactic acid-based resin foam molded article is obtained. ポリ乳酸系樹脂発泡粒子同士の融着率が６０％以上であることを特徴とする請求項１乃至請求項３の何れか１項に記載のポリ乳酸系樹脂発泡成形体。   The polylactic acid resin foamed molded article according to any one of claims 1 to 3, wherein the fusion rate between the polylactic acid resin foamed particles is 60% or more. 加熱速度５℃／分での示差走査熱量測定によるポリ乳酸系樹脂発泡成形体の発熱量が１０Ｊ／ｇ未満であることを特徴とする請求項１乃至請求項４の何れか１項に記載のポリ乳酸系樹脂発泡成形体。   The calorific value of the polylactic acid-based resin foam molding by differential scanning calorimetry at a heating rate of 5 ° C / min is less than 10 J / g, according to any one of claims 1 to 4. Polylactic acid resin foam molding. 加熱速度５℃／分での示差走査熱量測定によるポリ乳酸系樹脂発泡成形体の発熱量が３Ｊ／ｇ未満であることを特徴とする請求項１乃至請求項４の何れか１項に記載のポリ乳酸系樹脂発泡成形体。   The calorific value of the polylactic acid-based resin foam molding by differential scanning calorimetry at a heating rate of 5 ° C / min is less than 3 J / g, according to any one of claims 1 to 4. Polylactic acid resin foam molding. ポリ乳酸系樹脂における動的粘弾性測定にて得られた、貯蔵弾性率曲線と損失弾性率曲線との交点における温度Ｔでのポリ乳酸系樹脂の弾性率が１．０×１０3 〜１．０×１０5 Ｐａであることを特徴とする請求項１乃至請求項６の何れか１項に記載のポリ乳酸系樹脂発泡成形体。 The elastic modulus of the polylactic acid resin at a temperature T at the intersection of the storage elastic modulus curve and the loss elastic modulus curve obtained by dynamic viscoelasticity measurement in the polylactic acid resin is 1.0 × 10 3 to 1. It is 0x10 < 5 > Pa, The polylactic acid-type resin foam molding of any one of Claim 1 thru | or 6 characterized by the above-mentioned.
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