JP4038673B2 - Polylactic acid-based expandable resin particles and foamed molded products - Google Patents
Polylactic acid-based expandable resin particles and foamed molded products Download PDFInfo
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- JP4038673B2 JP4038673B2 JP2003066564A JP2003066564A JP4038673B2 JP 4038673 B2 JP4038673 B2 JP 4038673B2 JP 2003066564 A JP2003066564 A JP 2003066564A JP 2003066564 A JP2003066564 A JP 2003066564A JP 4038673 B2 JP4038673 B2 JP 4038673B2
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- Prior art keywords
- polylactic acid
- foaming
- resin particles
- foaming agent
- mass
- Prior art date
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- 229920000747 poly(lactic acid) Polymers 0.000 title claims description 91
- 239000004626 polylactic acid Substances 0.000 title claims description 91
- 239000002245 particle Substances 0.000 title claims description 80
- 229920005989 resin Polymers 0.000 title claims description 77
- 239000011347 resin Substances 0.000 title claims description 77
- 238000005187 foaming Methods 0.000 claims description 71
- 239000004088 foaming agent Substances 0.000 claims description 62
- RGSFGYAAUTVSQA-UHFFFAOYSA-N Cyclopentane Chemical compound C1CCCC1 RGSFGYAAUTVSQA-UHFFFAOYSA-N 0.000 claims description 56
- 239000011342 resin composition Substances 0.000 claims description 40
- DMEGYFMYUHOHGS-UHFFFAOYSA-N heptamethylene Natural products C1CCCCCC1 DMEGYFMYUHOHGS-UHFFFAOYSA-N 0.000 claims description 28
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 claims description 20
- JVTAAEKCZFNVCJ-REOHCLBHSA-N L-lactic acid Chemical compound C[C@H](O)C(O)=O JVTAAEKCZFNVCJ-REOHCLBHSA-N 0.000 claims description 14
- NNPPMTNAJDCUHE-UHFFFAOYSA-N isobutane Chemical compound CC(C)C NNPPMTNAJDCUHE-UHFFFAOYSA-N 0.000 claims description 10
- QWTDNUCVQCZILF-UHFFFAOYSA-N isopentane Chemical compound CCC(C)C QWTDNUCVQCZILF-UHFFFAOYSA-N 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 8
- IJDNQMDRQITEOD-UHFFFAOYSA-N sec-butylidene Natural products CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 claims description 8
- 229930182843 D-Lactic acid Natural products 0.000 claims description 7
- JVTAAEKCZFNVCJ-UWTATZPHSA-N D-lactic acid Chemical compound C[C@@H](O)C(O)=O JVTAAEKCZFNVCJ-UWTATZPHSA-N 0.000 claims description 7
- 229940022769 d- lactic acid Drugs 0.000 claims description 7
- 239000007900 aqueous suspension Substances 0.000 claims description 6
- AFABGHUZZDYHJO-UHFFFAOYSA-N dimethyl butane Natural products CCCC(C)C AFABGHUZZDYHJO-UHFFFAOYSA-N 0.000 claims description 5
- 238000010097 foam moulding Methods 0.000 claims description 5
- 239000001282 iso-butane Substances 0.000 claims description 5
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 15
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 12
- 238000004519 manufacturing process Methods 0.000 description 12
- 239000006260 foam Substances 0.000 description 11
- 238000005470 impregnation Methods 0.000 description 11
- 238000003860 storage Methods 0.000 description 11
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerol Natural products OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 9
- -1 aliphatic glycols Chemical class 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 6
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 230000009471 action Effects 0.000 description 5
- 239000002270 dispersing agent Substances 0.000 description 5
- 210000000497 foam cell Anatomy 0.000 description 5
- 230000009477 glass transition Effects 0.000 description 5
- 239000004094 surface-active agent Substances 0.000 description 5
- 239000004604 Blowing Agent Substances 0.000 description 4
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 4
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 4
- 239000001273 butane Substances 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
- 235000014113 dietary fatty acids Nutrition 0.000 description 4
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- 229930195729 fatty acid Natural products 0.000 description 4
- 235000011187 glycerol Nutrition 0.000 description 4
- 239000002667 nucleating agent Substances 0.000 description 4
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- UQDJGEHQDNVPGU-UHFFFAOYSA-N serine phosphoethanolamine Chemical compound [NH3+]CCOP([O-])(=O)OCC([NH3+])C([O-])=O UQDJGEHQDNVPGU-UHFFFAOYSA-N 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- 238000005273 aeration Methods 0.000 description 3
- 229920006167 biodegradable resin Polymers 0.000 description 3
- 125000004432 carbon atom Chemical group C* 0.000 description 3
- 210000004027 cell Anatomy 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 150000002430 hydrocarbons Chemical class 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N methyl pentane Natural products CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 244000005700 microbiome Species 0.000 description 3
- 229920001228 polyisocyanate Polymers 0.000 description 3
- 239000005056 polyisocyanate Substances 0.000 description 3
- 239000000454 talc Substances 0.000 description 3
- 229910052623 talc Inorganic materials 0.000 description 3
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 150000001338 aliphatic hydrocarbons Chemical class 0.000 description 2
- SCABKEBYDRTODC-UHFFFAOYSA-N bis[2-(2-butoxyethoxy)ethyl] hexanedioate Chemical compound CCCCOCCOCCOC(=O)CCCCC(=O)OCCOCCOCCCC SCABKEBYDRTODC-UHFFFAOYSA-N 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- NEHMKBQYUWJMIP-UHFFFAOYSA-N chloromethane Chemical compound ClC NEHMKBQYUWJMIP-UHFFFAOYSA-N 0.000 description 2
- 238000007872 degassing Methods 0.000 description 2
- DOIRQSBPFJWKBE-UHFFFAOYSA-N dibutyl phthalate Chemical compound CCCCOC(=O)C1=CC=CC=C1C(=O)OCCCC DOIRQSBPFJWKBE-UHFFFAOYSA-N 0.000 description 2
- CZZYITDELCSZES-UHFFFAOYSA-N diphenylmethane Chemical compound C=1C=CC=CC=1CC1=CC=CC=C1 CZZYITDELCSZES-UHFFFAOYSA-N 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000003063 flame retardant Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 239000012299 nitrogen atmosphere Substances 0.000 description 2
- WWZKQHOCKIZLMA-UHFFFAOYSA-N octanoic acid Chemical compound CCCCCCCC(O)=O WWZKQHOCKIZLMA-UHFFFAOYSA-N 0.000 description 2
- FDPIMTJIUBPUKL-UHFFFAOYSA-N pentan-3-one Chemical compound CCC(=O)CC FDPIMTJIUBPUKL-UHFFFAOYSA-N 0.000 description 2
- 229920000728 polyester Polymers 0.000 description 2
- 238000006116 polymerization reaction Methods 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 239000001294 propane Substances 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000002562 thickening agent Substances 0.000 description 2
- URAYPUMNDPQOKB-UHFFFAOYSA-N triacetin Chemical compound CC(=O)OCC(OC(C)=O)COC(C)=O URAYPUMNDPQOKB-UHFFFAOYSA-N 0.000 description 2
- DEIGXXQKDWULML-UHFFFAOYSA-N 1,2,5,6,9,10-hexabromocyclododecane Chemical compound BrC1CCC(Br)C(Br)CCC(Br)C(Br)CCC1Br DEIGXXQKDWULML-UHFFFAOYSA-N 0.000 description 1
- VEORPZCZECFIRK-UHFFFAOYSA-N 3,3',5,5'-tetrabromobisphenol A Chemical compound C=1C(Br)=C(O)C(Br)=CC=1C(C)(C)C1=CC(Br)=C(O)C(Br)=C1 VEORPZCZECFIRK-UHFFFAOYSA-N 0.000 description 1
- MKXAREWNUVZNTJ-UHFFFAOYSA-N 5-acetyl-7-butyl-6-hydroxyundecane-4,5,6-tricarboxylic acid Chemical compound CCCCC(CCCC)(C(O)=O)C(O)(C(O)=O)C(CCCC)(C(C)=O)C(O)=O MKXAREWNUVZNTJ-UHFFFAOYSA-N 0.000 description 1
- 241000251468 Actinopterygii Species 0.000 description 1
- MQIUGAXCHLFZKX-UHFFFAOYSA-N Di-n-octyl phthalate Natural products CCCCCCCCOC(=O)C1=CC=CC=C1C(=O)OCCCCCCCC MQIUGAXCHLFZKX-UHFFFAOYSA-N 0.000 description 1
- QSJXEFYPDANLFS-UHFFFAOYSA-N Diacetyl Chemical group CC(=O)C(C)=O QSJXEFYPDANLFS-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 235000019482 Palm oil Nutrition 0.000 description 1
- 229920000331 Polyhydroxybutyrate Polymers 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000007933 aliphatic carboxylic acids Chemical class 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- BJQHLKABXJIVAM-UHFFFAOYSA-N bis(2-ethylhexyl) phthalate Chemical compound CCCCC(CC)COC(=O)C1=CC=CC=C1C(=O)OCC(CC)CCCC BJQHLKABXJIVAM-UHFFFAOYSA-N 0.000 description 1
- ZFMQKOWCDKKBIF-UHFFFAOYSA-N bis(3,5-difluorophenyl)phosphane Chemical compound FC1=CC(F)=CC(PC=2C=C(F)C=C(F)C=2)=C1 ZFMQKOWCDKKBIF-UHFFFAOYSA-N 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical class OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 1
- 150000001860 citric acid derivatives Chemical class 0.000 description 1
- 238000004581 coalescence Methods 0.000 description 1
- 239000003240 coconut oil Substances 0.000 description 1
- 235000019864 coconut oil Nutrition 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 239000012024 dehydrating agents Substances 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 125000001033 ether group Chemical group 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 150000004665 fatty acids Chemical class 0.000 description 1
- RMBPEFMHABBEKP-UHFFFAOYSA-N fluorene Chemical compound C1=CC=C2C3=C[CH]C=CC3=CC2=C1 RMBPEFMHABBEKP-UHFFFAOYSA-N 0.000 description 1
- 235000013305 food Nutrition 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 239000001087 glyceryl triacetate Substances 0.000 description 1
- 235000013773 glyceryl triacetate Nutrition 0.000 description 1
- 238000005469 granulation Methods 0.000 description 1
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- IQPQWNKOIGAROB-UHFFFAOYSA-N isocyanate group Chemical group [N-]=C=O IQPQWNKOIGAROB-UHFFFAOYSA-N 0.000 description 1
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- 229920000609 methyl cellulose Polymers 0.000 description 1
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- NIHNNTQXNPWCJQ-UHFFFAOYSA-N o-biphenylenemethane Natural products C1=CC=C2CC3=CC=CC=C3C2=C1 NIHNNTQXNPWCJQ-UHFFFAOYSA-N 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 235000019198 oils Nutrition 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- 239000002540 palm oil Substances 0.000 description 1
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- XNGIFLGASWRNHJ-UHFFFAOYSA-N phthalic acid Chemical class OC(=O)C1=CC=CC=C1C(O)=O XNGIFLGASWRNHJ-UHFFFAOYSA-N 0.000 description 1
- 239000002984 plastic foam Substances 0.000 description 1
- 239000005015 poly(hydroxybutyrate) Substances 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
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- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 1
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 1
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 1
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- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229940080264 sodium dodecylbenzenesulfonate Drugs 0.000 description 1
- BDHFUVZGWQCTTF-UHFFFAOYSA-M sulfonate Chemical compound [O-]S(=O)=O BDHFUVZGWQCTTF-UHFFFAOYSA-M 0.000 description 1
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- PAPBSGBWRJIAAV-UHFFFAOYSA-N ε-Caprolactone Chemical compound O=C1CCCCCO1 PAPBSGBWRJIAAV-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Biological Depolymerization Polymers (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、ポリ乳酸系発泡性樹脂粒子に関する。より詳細には、発泡助剤としてシクロペンタンを用いることにより、発泡倍率の経時安定性に優れ、保存後も優れた発泡倍率を維持することができるポリ乳酸系発泡性樹脂粒子に関する。
【０００２】
【従来の技術】
軽量性、緩衝性および成形加工性により、プラスチック発泡成形品が広く使用されており、その用途も、家電製品用等の梱包材、建築用ボードおよび断熱ブロック、魚箱等の断熱容器、即席食品用のカップ類、土木工事における埋設ブロック等、様々な分野にわたる。従来の発泡成形品は主としてポリスチレン、ポリオレフィン等を原料としてなるが、これらは燃焼カロリーが高いため焼却時に焼却炉を傷め、また埋立処理をしても自然に分解しないので、使用後の後処理が非常に困難であった。また、処理されずに投棄された発泡成形品は、河川や海洋の汚染等、自然態系へ悪影響を及ぼす場合もあり、大きな社会問題となっている。
【０００３】
後処理に関する問題を解決した発泡成形品として、近年、生態系中で分解する生分解性樹脂からなる発泡成形品の開発が試みられている。その成形品に使用される候補の生分解性樹脂としては例えば、微生物の体内で合成されるポリヒドロキシブチレート系樹脂、脂肪族グリコールと脂肪族カルボン酸からなるポリエステルまたはカプロラクトンを主成分とするポリエステル系樹脂等が挙げられる。しかしながら前者は、製造に微生物を用いるため純度が低い上に極めて生産性が悪く、利用が制限される。また後者は、原料が安価な石油や天然ガスであるため生産性は良好であるけれども、結晶性でかつガラス転移点が低いため発泡成形品の材料としては実用性に乏しい。
【０００４】
これらの問題を解決したものとして、ポリ乳酸系樹脂を主成分とした発泡性樹脂粒子から製造した発泡成形品が注目されている。この発泡成形品は、微生物により殆ど分解されるため処理に際して環境への悪影響が少なく、また安価で生産性が高いため実用的でもある。
【０００５】
ところで、発泡成形品の製造には表面伸び、ハイサイクル性が求められており、これに伴い発泡性樹脂粒子には、高倍率に発泡し、省エネルギー性（低蒸気圧成形可能）であるものが望まれている。そのため発泡性樹脂粒子は、通常、プロパン、ブタン、ペンタン等の揮発性の発泡剤が添加されている。加えて、発泡をさらに容易にするために発泡助剤も添加されている。発泡助剤は、予備発泡に際してポリ乳酸の軟化を促進することで発泡倍率を高め、予備発泡時間を短縮することができる。
【０００６】
発泡性樹脂粒子に用い得るポリ乳酸系樹脂組成物としては、例えば、Ｌ体とＤ体のモル比が９５／５〜６０／４０または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質量％配合し反応させてなり、該樹脂組成物の保有水分を１００〜１００００ｐｐｍの範囲に保持しながら２０〜６０℃の温度で熟成し、熟成後の溶融粘度がメルトインデックス値（ＭＩ）で５以下であるものが知られている（例えば、特許文献１、特許文献２および特許文献３参照）。また、このポリ乳酸系樹脂組成物に発泡剤を含浸させることにより発泡性樹脂粒子を製造し得ることも報告されている。係る発泡剤の含浸工程は非水系で行われている。
【０００７】
また、Ｌ体とＤ体のモル比が９５／５〜６０／４０であり、Ｌ体とＤ体からなる実質的に非晶性のポリ乳酸を主体とする発泡性樹脂粒子であって、予め増粘剤と発泡核剤としてのタルクを１〜２０質量％混合、分散させた非晶性ポリ乳酸系樹脂組成物に低沸点有機化合物を含浸させてなり、さらに発泡性樹脂粒子の表面に高級脂肪酸またはその金属塩、エステル、アミドから選ばれた化合物を０．０１〜１質量％配合して得られるものが知られている（例えば、特許文献４参照）。この発泡性樹脂粒子もまた非水系において発泡剤が含浸されるものである。
【０００８】
さらに、Ｌ体とＤ体のモル比が５／９５〜４０／６０であり、実質的に非晶性のポリ乳酸に増粘剤と発泡核剤を加えて生分解性樹脂組成物を製造し、該樹脂組成物に発泡助剤と炭素数３〜４の炭化水素化合物である発泡剤を含浸させて粒子を製造し、そして該粒子を５０〜１０５℃の水蒸気で１０〜３００秒熱処理することからなる、ポリ乳酸系発泡性樹脂粒子の製造方法が知られている（例えば、特許文献５参照）。この製造方法では、発泡剤として炭素数５のペンタンを使用すると、発泡倍率を大きくするけれども同時に発泡セル径もまた大きくし、満足な発泡成形品が得られないために好ましくないとされている。また、発泡剤に加えて、好ましくはメタノール、エタノール、アセトンから選ばれた化合物である発泡助剤の使用が不可欠であり、これらの発泡助剤を用いない場合には、高発泡倍率で微細かつ均一な発泡セルを達成する発泡性樹脂粒子が得られないと報告されている。
【０００９】
【特許文献１】
特開２０００−１７０３７公報
【特許文献２】
特開２０００−１７０３８公報
【特許文献３】
特開２０００−１７０３９公報
【特許文献４】
特開２００１−９８１０４公報
【特許文献５】
特開２００１−１６４０２７公報
【００１０】
【発明が解決しようとする課題】
ここで、ポリ乳酸系樹脂組成物に発泡剤を含有させて発泡性樹脂粒子を製造する工程を非水系で行った場合、以下の問題が生じる。
１）非水系の場合、発泡剤等は直接に樹脂粒子に含浸させることとなるが、含浸を効率良く行うために樹脂粒子の温度をそのガラス転移温度以上に上昇させる必要がある。しかしながらガラス転移温度以上では、樹脂粒子の軟化および発泡剤の膨潤により、樹脂粒子同士が付着し易くなる。付着により生じた集塊物は、発泡成形を行うときの送粒中に詰まる等の問題を引き起こす。また、集塊物が多くなると、発泡剤の含浸中に樹脂粒子が全て固まる惧れもあり大きな問題となる。２）特許文献５に開示されるように、発泡剤としてペンタン以上に高級な炭化水素系化合物を用いると、発泡セル径が大きくなる等の問題が生じ満足な発泡成形品を得ることができない。従って、使用可能な発泡剤は炭素数３〜４の炭化水素系化合物に限定される。
３）樹脂粒子中の発泡セル数を多くし、均一かつ小さくする目的で、タルクに代表される発泡核剤を用いる必要がある。平均粒子径が３μｍ以下の発泡核剤を２〜１０質量％添加しないと、発泡時に適当な発泡セル径を得ることはできない。
【００１１】
また、非水系で製造されるポリ乳酸系発泡性樹脂粒子の場合、メタノール、エタノールのような低級脂肪族アルコール、アセトン、メチルエチルケトン、ジエチルケトンのような低級脂肪族ケトン、トルエン等の発泡助剤を用いる必要があるが、これらの発泡助剤を用いると、発泡助剤が発泡剤の揮散を促進して、発泡剤が時間と共に樹脂粒子中から逸散してしまう。そして発泡剤の逸散は樹脂粒子の発泡倍率の低下を招くので、従来のポリ乳酸系発泡性樹脂粒子は長期間の保存に適さず、輸送等に大変不都合であった。
【００１２】
本発明は、以上の事情を背景としてなされたものであって、その課題とするところは、保存後にも高い発泡倍率を保ち、発泡成形後に微細で均一性の高い発泡セルを形成することができるポリ乳酸系発泡性樹脂粒子を提供することにある。並びに、本発明の他の課題は、かように優れた該発泡性樹脂粒子を使用して得られるポリ乳酸系発泡成形品の提供にある。
【００１３】
【課題を解決するための手段】
本発明者等は、上記の課題を解決すべく鋭意研究を行った結果、発泡剤含浸の過程でノルマルブタン、イソブタン、ノルマルペンタン、イソペンタン等を発泡剤として用い、かつシクロペンタンを発泡助剤として用いるとき、発泡剤の逸散を抑制することができ、かつ高発泡倍率の成形品を得ることを見出し、本発明を完成するに至った。
【００１４】
従って、本発明は、ポリ乳酸系樹脂組成物に、水懸濁系で、発泡剤および発泡助剤を含浸させてなり、前記発泡助剤はシクロペンタンであることを特徴とするポリ乳酸系発泡性樹脂粒子に関する。
本発明の好ましい態様は、前記発泡助剤の含有量は、前記ポリ乳酸系樹脂組成物１００質量部に対して、２．５〜５．５質量部であることを特徴とする前記ポリ乳酸系発泡性樹脂粒子に関する。
本発明の他の好ましい態様は、前記ポリ乳酸系樹脂組成物は、Ｄ−乳酸、Ｌ−乳酸またはこれらの混合物由来の構造単位を５０％以上含有するポリ乳酸系樹脂と、該ポリ乳酸系樹脂１００質量部に対して０．１〜５０質量部の層状ケイ酸塩を含んでなることを特徴とする前記ポリ乳酸系発泡性樹脂粒子に関する。
本発明のさらなる好ましい態様は、前記発泡剤は、イソブタン、ノルマルブタン、イソペンタンおよびノルマルペンタンからなる群より選択されることを特徴とする前記ポリ乳酸系発泡性樹脂粒子に関する。
また本発明は、前記ポリ乳酸系発泡性樹脂粒子を予備発泡させ、次いでそれを発泡成形して得られる発泡成形品に関する。
【００１５】
本発明のポリ乳酸系発泡性樹脂粒子は、ポリ乳酸系樹脂組成物が含有する発泡剤の含有量の経時変化が少なく、保管や輸送を行う際に大変有用なものとなる。例えば、メタノールを発泡助剤として用いた従来のポリ乳酸系発泡性樹脂粒子の場合、１０日間室温で放置するだけで発泡剤の含有量は半分近くまで減少し、これに伴い発泡倍率も低下する。ポリ乳酸系発泡性樹脂粒子の輸送を考えるとさらに高温下の状況が想定され、従来のポリ乳酸系発泡性樹脂粒子では大変不都合であると考えられる。これに対して、シクロペンタンを発泡助剤として用いた本発明のポリ乳酸系発泡性樹脂粒子の場合、ガラス転移温度以下の条件であれば発泡剤の逸散はほとんど無い。
【００１６】
【発明の実施の形態】
本発明は、ポリ乳酸系樹脂組成物に発泡助剤としてシクロペンタンを添加していることが特徴である。シクロペンタンは、予備発泡に際してポリ乳酸の軟化を促進することで発泡倍率を高め、予備発泡時間を大幅に短縮することもできる。また発泡成形時にも低蒸気圧で融着性の良い発泡成形品を得ることができるので、全体として省エネルギーの面でも大幅に改善される。
【００１７】
ポリ乳酸系発泡性樹脂粒子中に存在する発泡助剤の量は、ポリ乳酸系樹脂組成物１００質量部に対して、０．１〜１０．０質量部の範囲であることが好ましく、２．５〜５．５質量部がさらに好ましい。シクロペンタンの含有量が０．１質量部以下の場合、シクロペンタンのポリ乳酸系樹脂組成物に対する軟化作用が弱すぎ、発泡助剤としての効果を発揮できずに満足な発泡倍率の発泡粒子を得ることができない。他方、シクロペンタンの含有量が１０．０質量部を超える場合、シクロペンタンのポリ乳酸系樹脂組成物に対する軟化作用が強すぎるため、ポリ乳酸系発泡性樹脂粒子の収縮が生じ、結果として高い倍率の発泡性粒子を得ることが難しい。
【００１８】
本発明におけるポリ乳酸系樹脂組成物には様々な種類のものを用いることができる。なかんずく、Ｄ−乳酸、Ｌ−乳酸またはこれらの混合物由来の構造単位を５０％以上含有するポリ乳酸系樹脂と、該ポリ乳酸系樹脂１００質量部に対して０．１〜５０質量部の層状ケイ酸塩を含んでなるポリ乳酸系樹脂組成物を用いるのが好ましい。このポリ乳酸系樹脂組成物は、層状ケイ酸塩を添加したことにより、発泡成形性に優れたレオロジー特性を有するものとなり、さらにこれから製造した発泡成形品は良好な耐熱性および機械的強度を備えることとなる。
【００１９】
前記発泡剤としては、プロパン、イソブタン、ノルマルブタン、イソペンタン、ノルマルペンタン、ヘキサン等の脂肪族炭化水素系化合物、および塩化メチル、フルオレン等のハロゲン化脂肪族炭化水素系化合物を好ましく利用できる、これらの発泡剤は単独で用いることができ、また２種類以上の組み合わせで用いてもよい。しかしながら、発泡剤を含浸した後のポリ乳酸系樹脂組成物中の内部に含まれる水分を除去する際に発泡剤の逸散が少ないという観点から、発泡剤としてブタン、イソブタン、ペンタン、イソペンタンを用いることがより好ましい。ポリ乳酸系発泡性樹脂粒子中の発泡剤の含有量は、所望の発泡倍率により変化するが、３〜２５質量％、好ましくは５〜１５質量％である。
【００２０】
本発明のポリ乳酸系発泡性樹脂粒子は、発泡剤および発泡助剤に加え、可塑剤、難燃剤等を含有することができる。
可塑剤としては、アセチルトリブチルクエン酸等のクエン酸エステル、トリアセチン、グリセリンジカプリルモノアセチル、グリセリンモノカプリルジアセチル等のグリセリン脂肪酸エステル、フタル酸ジブチル、フタル酸ジオクチル等のフタル酸エステル、アジピン酸ジオクチル等の脂肪酸エステル、トリエチレングリコールジアセチル、アジピン酸ジブトキシエトキシエチル、椰子油、パーム油等が使用できる。特にクエン酸エステルやグリセリン脂肪酸エステルが好ましい。さらに可塑剤を多量に添加する場合には、アジピン酸ジブトキシエトキシエチルやトリエチレングリコールジアセチル等のエーテル基を有する可塑剤を併用することが好ましい。
難燃剤としては、ヘキサブロモシクロドデカン、テトラブロモビスフェノールＡ等が挙げられる。
【００２１】
本発明のポリ乳酸系発泡性樹脂粒子は、ポリ乳酸系樹脂組成物中に水を媒体とした水懸濁系で発泡剤および発泡助剤を含浸することにより製造できる。また、水懸濁系において、加熱下および高圧下において発泡剤および発泡助剤の含浸を行うことができる。含浸温度は通常、ポリ乳酸系樹脂組成物のガラス転移温度以上で選択され、例えば７０〜１１０℃の含浸温度では、０．５〜３時間の含浸時間で十分な含浸を行うことができる。
水懸濁系でポリ乳酸に発泡剤等の含浸を行う場合には、媒体となる水中に、分散を助け樹脂同士の合一を防ぐ目的で、分散剤や界面活性剤を添加することができる。分散剤や界面活性剤としては、通常一般的に使用されるものが用いられる。例えば、分散剤としては、ポリビニルアルコール、ポリビニルピロリドン、メチルセルロース等が用いられ、界面活性剤としては、ドデシルベンゼンスルホン酸ナトリウム、α−オレフィンスルホン酸ナトリウム等が用いられる。
【００２２】
発泡剤を含浸した後のポリ乳酸系発泡性樹脂粒子中に存在する微孔には水分が含まれている。この水分を所定量以下に減少させる必要があるが、これは表面水分を遠心分離工程等で脱水した組成物のペレットを５〜４０℃の乾燥空気中で５〜４８時間、通風状態に保つ（エアレーションする）ことによって行うことができる。その他、真空乾燥機による乾燥、脱水剤を用いる乾燥等によっても可能である。
【００２３】
【実施例】
以下の実施例により本発明をより詳しく説明する。但し、実施例は本発明を説明するためのものであり、いかなる方法においても本発明を限定することを意図しない。
【００２４】
本実施例における評価は以下のようにして行った。
・ポリ乳酸系発泡性樹脂粒子中の発泡剤および発泡助剤の含有量測定
試料約０．２ｇを精秤した後、該試料をトルエン中に溶解し、該溶液についてガスクロマトグラフィーを行って発泡剤および発泡助剤の含有量を測定した。
・発泡倍率
ポリ乳酸系発泡性樹脂粒子を、８５〜９５℃の水蒸気により３０秒間加熱して予備発泡させた。得られた予備発泡粒子の体積をメスシリンダーで測定して発泡倍率を求めた。
【００２５】
ポリ乳酸系発泡性樹脂粒子の製造１（試料番号１〜１０）
ポリ乳酸（カーギルダウ社製Ｎａｔｕｒｅ Ｗｏｒｋｓ、重量平均分子量：１９８０００、数平均分子量：１１５０００）１００質量部に対し、層状ケイ酸塩を４質量部添加して二軸押出機（池貝製ＰＣＭ−３０、ダイス直径４ｍｍ×３孔）を用いて溶融混練し、得られたストランドを粉砕機によりペレット化してポリ乳酸系樹脂組成物を得た。水懸濁系にこれらを分散させ、発泡剤としてペンタン（ノルマル／イソ＝７５／２５）および発泡助剤としてシクロペンタンを含浸させてポリ乳酸系発泡性樹脂粒子を得た。発泡剤および発泡助剤のほかに分散剤および界面活性剤をも添加した。含浸は、攪拌機付きオートクレーブ中で９０℃で約１時間保持することによって行った。
ポリ乳酸系発泡性樹脂粒子の製造２（試料番号１１）
ポリ乳酸系発泡性樹脂粒子の製造１と同様にして得たペレット化されたポリ乳酸系樹脂組成物を攪拌機付きオートクレーブに入れ、発泡剤としてペンタン（ノルマル／イソ＝６７／３３）および発泡助剤としてメタノールを添加した。温度８０〜９０℃で２時間保持することによって、発泡剤の含浸を行った。
各試料についての発泡剤と発泡助剤の添加割合を表１に示す。
【表１】
各試料について、発泡性樹脂粒子の製造直後にエアレーションを行い、発泡助剤の含有量、発泡剤の含有量および発泡倍率を測定した。次いで、発泡性樹脂粒子を室温で１０日間保存し、保存後の発泡剤の含有量および発泡倍率を測定した。
結果を表２に示す。含有量はポリ乳酸系樹脂組成物を１００とした質量部である。
【表２】
試料２および３（本発明の実施例）は、シクロペンタンを比較的少量含有するものである。これらの試料は１０日後であっても発泡剤の逸散は生じなかったが、シクロペンタンの含有量が比較的少ないため、試料１と同様、ポリ乳酸系樹脂組成物の軟化作用が小さく、発泡倍率は比較的低めであった。
試料４、５および６（本発明の実施例）は、２．５〜５．５質量部のシクロペンタンを発泡助剤として含有するものである。これらの試料では予備発泡においてポリ乳酸系樹脂組成物の軟化が促進されて高倍率の予備発泡粒子が得られ、試料２および３よりも好ましかった。また、含浸後にポリ乳酸系発泡性樹脂粒子を室温にて１０日間保存したが、発泡剤の逸散は見られなかった。
試料７、８および９（本発明の実施例）は、シクロペンタンを比較的多量で含有するものである。これらの試料では発泡剤は逸散せず、よって発泡倍率の経時的低下は見られなかったが、予備発泡に際して軟化作用が強すぎるため、発泡後の収縮があった。
試料１０（本発明の範囲外の比較例）は、発泡剤を使用せず、シクロペンタンのみを用いたものである。この試料では、シクロペンタンが樹脂粒子中に多量に含浸されているものの、予備発泡粒子の発泡倍率は高くならなかった。
試料１１（本発明の範囲外の比較例）は、発泡助剤としてメタノールを用いたものである。発泡助剤としてシクロペンタンを用いた試料２〜１０についてはいずれも１０日間の保存後に発泡剤の逸散は確認できなかったのに対して、この試料では１０日間で約半分の発泡剤が逸散し、これに伴い発泡倍率も低下した。
【００２７】
ポリ乳酸系発泡性樹脂粒子の製造３（試料番号１２〜１６）
市販のＬ−乳酸およびＤ−乳酸をそれぞれ酢酸エチルで再結晶化して精製した。精製したＬ−乳酸およびＤ−乳酸をＤ体比率が１０モル％となるように混合し、これに錫含有量が１０ｐｐｍとなるように触媒のオクチル酸錫を添加し、攪拌機付きオートクレーブ中で、減圧脱気した後、窒素雰囲気下で重合させた。反応終了後、オートクレーブより生成物を取り出し、次いで水分含有量が１０００ｐｐｍ以下になるまで乾燥させた後、粘度増加剤として官能基２．８当量のジフェニルメタンポリイソシアネートを生成物に対して１質量％配合した。得られた配合物を二軸混練機に供給し、回転数１００ｒｐｍ、溶融温度１８０℃、滞留時間３〜５分、吐出量１０ｋｇ／時の条件下で反応混練した後、ダイスより押出カットして、直径約１ｍｍの粒子としてポリ乳酸系樹脂組成物を得た。なお、得られたポリ乳酸系樹脂組成物のＭＩ値は０．２であった。
得られたポリ乳酸系樹脂組成物に、発泡剤としてブタン（ノルマル／イソ＝６７／３３）および発泡助剤としてシクロペンタンを含浸させてポリ乳酸系発泡性樹脂粒子を得た。発泡剤および発泡助剤のほかに分散剤および界面活性剤をも添加した。含浸は、攪拌機付きオートクレーブ中で９０℃で約１時間保持することによって行った。
ポリ乳酸系発泡性樹脂粒子の製造４（試料番号１７）
市販のＬ−乳酸およびＤ−乳酸をそれぞれ酢酸エチルで再結晶化して精製した。精製したＬ−乳酸およびＤ−乳酸をＤ体比率が１０モル％となるように混合し、これに錫含有量が１０ｐｐｍとなるように触媒のオクチル酸錫を添加し、撹拌機付きオートクレーブ中で、減圧脱気した後、窒素雰囲気下で重合させた。反応終了後、オートクレーブより生成物を取り出し、次いで水分含有量が１０００ｐｐｍ以下になるまで乾燥させた後、生成物に対して、タルクを３質量％、粘度増加剤として官能基２．８等量のジフェニルメタンポリイソシアネートを１質量％配合した。得られた配合物を二軸混練機に供給し、回転数１００ｒｐｍ、溶融温度１８０℃、滞留時間３〜５分、吐出量１０ｋｇ／時の条件下で反応混練した後、ダイスより押出カットして、直径約１ｍｍの粒子としてポリ乳酸系樹脂組成物を得た。なお、得られたポリ乳酸系樹脂組成物のＭＩ値は０．２であった。
得られたペレット化されたポリ乳酸系樹脂組成物を攪拌機付きオートクレーブに入れ、発泡剤としてブタン（ノルマル／イソ＝６７／３３）および発泡助剤としてアセトンを添加した。温度８０〜９０℃で２時間保持することによって、発泡剤の含浸を行った。
各試料についての発泡剤と発泡助剤の添加割合を表３に示す。
【表３】
各試料について、発泡性樹脂粒子の製造直後にエアレーションを行い、発泡助剤の含有量、発泡剤の含有量および発泡倍率を測定した。次いで、発泡性樹脂粒子を室温で１０日間保存し、保存後の発泡剤の含有量および発泡倍率を測定した。結果を表４に示す。含有量はポリ乳酸系樹脂組成物を１００とした質量部である。
【表４】
試料１３（本発明の実施例）は、シクロペンタンを比較的少量含有するものである。この試料は１０日後であっても発泡剤が逸散せず、よって発泡倍率の経時的低下は見られなかったが、シクロペンタンの含有量が比較的少ないため、ポリ乳酸系樹脂組成物の軟化作用が小さく、発泡性樹脂粒子の発泡倍率は比較的低めであった。
試料１４（本発明の実施例）は、２．５〜５．５質量部のシクロペンタンを発泡助剤として含有するものである。この試料では予備発泡においてポリ乳酸系樹脂組成物の軟化が促進されて試料２よりも高倍率の予備発泡粒子が得られた。また、室温にて１０日間保存した後にも発泡剤の逸散は見られなかった。
試料１５（本発明の実施例）は、シクロペンタンを比較的多量に含有するものである。この試料では発泡剤は逸散しなかったが、予備発泡に際して軟化作用が強く、発泡後の収縮が大きいため、発泡倍率が低かった。
試料１６（本発明の範囲外の比較例）は、発泡剤を使用せず、シクロペンタンのみを用いたものである。この試料では、シクロペンタンが樹脂粒子中に多量に含浸されているものの、予備発泡粒子の発泡倍率は高くならなかった。
試料１７（本発明の範囲外の比較例）は、発泡助剤としてアセトンを用いたものである。発泡助剤としてシクロペンタンを用いた試料１３〜１６についてはいずれも１０日間の保存後に発泡剤の逸散は確認できなかったのに対して、この試料では１０日間で半分以上の発泡剤が逸散し、これに伴い発泡倍率も大きく低下した。
【００２９】
【発明の効果】
本発明のポリ乳酸系発泡性樹脂粒子では、発泡助剤としてシクロペンタンを含浸させたことにより、発泡性樹脂粒子中に含まれる発泡剤が逸散せず、長期にわたる保存後にも優れた発泡性を維持することができる。即ち、発泡倍率の経時変化が良好であり、保存や輸送に都合の良いポリ乳酸系発泡性樹脂粒子となる。また、本発明のポリ乳酸系発泡性樹脂粒子から製造した発泡成形品は、発泡セル数が多く、発泡セルの寸法は均一かつ小さい。加えて、本発明のポリ乳酸系発泡性樹脂粒子の発泡性は良好であるので、予備発泡時間を大幅に短縮することができ、低蒸気圧で融着性の良い発泡成形品とすることができ、その製造が全体として省エネルギーとなる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to polylactic acid-based expandable resin particles. More specifically, the present invention relates to polylactic acid-based expandable resin particles that are excellent in stability over time of the expansion ratio and can maintain an excellent expansion ratio after storage by using cyclopentane as a foaming aid.
[0002]
[Prior art]
Plastic foam molded products are widely used due to their light weight, shock-absorbing properties and moldability, and their uses are also used for packaging materials for household appliances, building boards and insulation blocks, insulation containers such as fish boxes, and instant foods. Covers various fields such as cups for construction, buried blocks in civil engineering. Conventional foamed moldings are mainly made of polystyrene, polyolefin, etc., but these burn high in calories and damage the incinerator at the time of incineration. It was very difficult. In addition, foamed molded articles that are discarded without being treated may cause adverse effects on natural systems, such as pollution of rivers and oceans, and are a major social problem.
[0003]
In recent years, attempts have been made to develop a foam molded article made of a biodegradable resin that can be decomposed in an ecosystem as a foam molded article that solves problems relating to post-treatment. Examples of candidate biodegradable resins used in the molded article include polyhydroxybutyrate resins synthesized in the body of microorganisms, polyesters composed of aliphatic glycols and aliphatic carboxylic acids, or polyesters mainly composed of caprolactone. Based resins and the like. However, since the former uses microorganisms for production, its purity is low and productivity is extremely poor, and its use is limited. The latter has good productivity because the raw material is cheap oil or natural gas, but is poor in practicality as a material for foam-molded articles because it is crystalline and has a low glass transition point.
[0004]
As a solution to these problems, a foam-molded article produced from expandable resin particles mainly composed of a polylactic acid resin has attracted attention. This foam-molded product is practically practical because it is almost decomposed by microorganisms and has little adverse effect on the environment during processing, and is inexpensive and highly productive.
[0005]
By the way, in the production of foam molded products, surface elongation and high cycleability are required, and as a result, foamable resin particles are foamed at a high magnification and have energy saving properties (low vapor pressure molding is possible). It is desired. Therefore, volatile foaming agents such as propane, butane and pentane are usually added to the foamable resin particles. In addition, a foaming aid is added to further facilitate foaming. The foaming auxiliary agent can increase the expansion ratio by promoting the softening of polylactic acid at the time of preliminary foaming, and shorten the preliminary foaming time.
[0006]
Examples of the polylactic acid-based resin composition that can be used for the expandable resin particles include polylactic acid having an L-form to D-form molar ratio of 95/5 to 60/40 or 40/60 to 5/95, an isocyanate group. ≧ 2.0 equivalents / mole of polyisocyanate compound is blended and reacted in an amount of 0.5 to 5% by mass with respect to the polylactic acid, while maintaining the water content of the resin composition in the range of 100 to 10,000 ppm. It is known that aging is performed at a temperature of ˜60 ° C., and the melt viscosity after aging is 5 or less in terms of melt index value (MI) (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3). It has also been reported that expandable resin particles can be produced by impregnating the polylactic acid resin composition with a foaming agent. The step of impregnating the foaming agent is performed in a non-aqueous system.
[0007]
The molar ratio of L-form to D-form is 95/5 to 60/40, and is a foamable resin particle mainly composed of substantially amorphous polylactic acid composed of L-form and D-form, An amorphous polylactic acid resin composition in which 1 to 20% by mass of talc as a thickener and a foaming nucleating agent is mixed and dispersed is impregnated with a low-boiling organic compound. A compound obtained by blending 0.01 to 1% by mass of a compound selected from fatty acids or their metal salts, esters and amides is known (see, for example, Patent Document 4). These expandable resin particles are also impregnated with a foaming agent in a non-aqueous system.
[0008]
Furthermore, the molar ratio of L-form and D-form is 5/95 to 40/60, and a biodegradable resin composition is produced by adding a thickener and a foam nucleating agent to substantially amorphous polylactic acid. And impregnating the resin composition with a foaming aid and a foaming agent, which is a hydrocarbon compound having 3 to 4 carbon atoms, to produce particles, and heat treating the particles with water vapor at 50 to 105 ° C. for 10 to 300 seconds. There is known a method for producing polylactic acid-based expandable resin particles comprising (for example, see Patent Document 5). In this manufacturing method, when pentane having 5 carbon atoms is used as a foaming agent, the foaming ratio is increased, but the foamed cell diameter is also increased, and a satisfactory foamed molded product cannot be obtained. In addition to the foaming agent, it is essential to use a foaming aid that is preferably a compound selected from methanol, ethanol, and acetone. When these foaming aids are not used, the foaming agent is fine and has a high expansion ratio. It has been reported that expandable resin particles that achieve uniform foam cells cannot be obtained.
[0009]
[Patent Document 1]
JP 2000-17037 A [Patent Document 2]
JP 2000-17038 A [Patent Document 3]
JP 2000-17039 A [Patent Document 4]
JP 2001-98104 A [Patent Document 5]
Japanese Patent Laid-Open No. 2001-164027
[Problems to be solved by the invention]
Here, when the step of producing a foamable resin particle by adding a foaming agent to the polylactic acid-based resin composition is performed in a non-aqueous system, the following problems occur.
1) In the case of a non-aqueous system, the foaming agent or the like is directly impregnated into the resin particles. However, in order to efficiently perform the impregnation, it is necessary to raise the temperature of the resin particles above the glass transition temperature. However, above the glass transition temperature, the resin particles tend to adhere to each other due to softening of the resin particles and swelling of the foaming agent. The agglomerate generated by the adhesion causes problems such as clogging during the granulation when foam molding is performed. In addition, when the agglomerate is increased, all the resin particles may be hardened during the impregnation with the foaming agent, which is a serious problem. 2) As disclosed in Patent Document 5, if a higher hydrocarbon compound than pentane is used as the foaming agent, problems such as an increase in the foamed cell diameter occur and a satisfactory foamed molded product cannot be obtained. Accordingly, usable blowing agents are limited to hydrocarbon compounds having 3 to 4 carbon atoms.
3) It is necessary to use a foam nucleating agent represented by talc for the purpose of increasing the number of foamed cells in the resin particles to be uniform and small. Unless 2 to 10% by mass of a foam nucleating agent having an average particle diameter of 3 μm or less is added, an appropriate foam cell diameter cannot be obtained at the time of foaming.
[0011]
In the case of polylactic acid-based foamable resin particles produced in a non-aqueous system, a foaming aid such as lower aliphatic alcohols such as methanol and ethanol, lower aliphatic ketones such as acetone, methyl ethyl ketone, and diethyl ketone, and toluene. Although it is necessary to use these foaming aids, the foaming aid promotes the volatilization of the foaming agent, and the foaming agent dissipates from the resin particles over time. Dissipation of the foaming agent causes a reduction in the expansion ratio of the resin particles, so that the conventional polylactic acid-based expandable resin particles are not suitable for long-term storage and are very inconvenient for transportation.
[0012]
The present invention has been made against the background of the above circumstances, and the problem is that a high expansion ratio can be maintained even after storage, and fine and highly uniform foam cells can be formed after foam molding. The object is to provide polylactic acid-based expandable resin particles. In addition, another object of the present invention is to provide a polylactic acid-based foam molded article obtained by using the excellent foamable resin particles.
[0013]
[Means for Solving the Problems]
As a result of diligent research to solve the above problems, the present inventors have used normal butane, isobutane, normal pentane, isopentane, etc. as a blowing agent in the process of impregnation with a blowing agent, and cyclopentane as a blowing aid. When used, it has been found that a foaming agent can be prevented from escaping and a molded product having a high expansion ratio can be obtained, and the present invention has been completed.
[0014]
Accordingly, the present invention provides a polylactic acid-based foaming composition characterized in that a polylactic acid-based resin composition is impregnated with a foaming agent and a foaming aid in a water suspension system, and the foaming aid is cyclopentane. Relates to a conductive resin particle.
In a preferred embodiment of the present invention, the content of the foaming assistant is 2.5 to 5.5 parts by mass with respect to 100 parts by mass of the polylactic acid resin composition. The present invention relates to expandable resin particles.
In another preferred embodiment of the present invention, the polylactic acid resin composition comprises a polylactic acid resin containing 50% or more of a structural unit derived from D-lactic acid, L-lactic acid, or a mixture thereof, and the polylactic acid resin. The present invention relates to the polylactic acid-based expandable resin particle, comprising 0.1 to 50 parts by mass of layered silicate with respect to 100 parts by mass.
In a further preferred aspect of the present invention, the foaming agent is selected from the group consisting of isobutane, normal butane, isopentane, and normal pentane.
The present invention also relates to a foam-molded product obtained by pre-foaming the polylactic acid-based foamable resin particles and then foam-molding it.
[0015]
The polylactic acid-based expandable resin particles of the present invention have very little change over time in the content of the foaming agent contained in the polylactic acid-based resin composition, and are very useful for storage and transportation. For example, in the case of conventional polylactic acid-based foamable resin particles using methanol as a foaming aid, the foaming agent content is reduced to almost half just by leaving it at room temperature for 10 days, and the foaming ratio is also lowered accordingly. . Considering the transportation of the polylactic acid-based expandable resin particles, a situation at a higher temperature is assumed, and the conventional polylactic acid-based expandable resin particles are considered to be very inconvenient. On the other hand, in the case of the polylactic acid-based expandable resin particles of the present invention using cyclopentane as a foaming aid, there is almost no dissipation of the foaming agent under the condition of the glass transition temperature or lower.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is characterized in that cyclopentane is added as a foaming aid to the polylactic acid resin composition. Cyclopentane can increase the expansion ratio by promoting softening of polylactic acid at the time of preliminary foaming, and can greatly shorten the preliminary foaming time. In addition, since a foam molded article having a low vapor pressure and good fusion property can be obtained at the time of foam molding, the overall energy saving is greatly improved.
[0017]
The amount of the foaming aid present in the polylactic acid-based expandable resin particles is preferably in the range of 0.1 to 10.0 parts by mass with respect to 100 parts by mass of the polylactic acid-based resin composition. 5 to 5.5 parts by mass is more preferable. When the content of cyclopentane is 0.1 parts by mass or less, the softening action of cyclopentane on the polylactic acid resin composition is too weak, and the foamed particles having a satisfactory expansion ratio cannot be exhibited as the foaming aid. Can't get. On the other hand, when the content of cyclopentane exceeds 10.0 parts by mass, the softening action of cyclopentane on the polylactic acid resin composition is too strong, resulting in shrinkage of the polylactic acid foamable resin particles, resulting in high magnification. It is difficult to obtain expandable particles.
[0018]
Various kinds of polylactic acid resin compositions in the present invention can be used. In particular, a polylactic acid resin containing 50% or more of structural units derived from D-lactic acid, L-lactic acid or a mixture thereof, and 0.1 to 50 parts by mass of layered silica with respect to 100 parts by mass of the polylactic acid resin. It is preferable to use a polylactic acid resin composition comprising an acid salt. This polylactic acid resin composition has rheological properties excellent in foam moldability due to the addition of the layered silicate, and the foam molded product produced therefrom has good heat resistance and mechanical strength. It will be.
[0019]
As the blowing agent, aliphatic hydrocarbon compounds such as propane, isobutane, normal butane, isopentane, normal pentane, and hexane, and halogenated aliphatic hydrocarbon compounds such as methyl chloride and fluorene can be preferably used. A foaming agent can be used independently and may be used in combination of 2 or more types. However, butane, isobutane, pentane, and isopentane are used as the foaming agent from the viewpoint of less dissipation of the foaming agent when removing moisture contained in the polylactic acid resin composition impregnated with the foaming agent. It is more preferable. The content of the foaming agent in the polylactic acid-based expandable resin particles varies depending on the desired expansion ratio, but is 3 to 25% by mass, preferably 5 to 15% by mass.
[0020]
The polylactic acid-based expandable resin particles of the present invention can contain a plasticizer, a flame retardant and the like in addition to the foaming agent and the foaming aid.
Examples of the plasticizer include citrate esters such as acetyltributylcitric acid, glycerol fatty acid esters such as triacetin, glycerol dicapryl monoacetyl, glycerol monocapryl diacetyl, phthalate esters such as dibutyl phthalate and dioctyl phthalate, and dioctyl adipate. Fatty acid esters, triethylene glycol diacetyl, dibutoxyethoxyethyl adipate, coconut oil, palm oil and the like can be used. Particularly preferred are citric acid esters and glycerin fatty acid esters. Further, when a large amount of plasticizer is added, it is preferable to use a plasticizer having an ether group such as dibutoxyethoxyethyl adipate or triethylene glycol diacetyl in combination.
Examples of the flame retardant include hexabromocyclododecane and tetrabromobisphenol A.
[0021]
The polylactic acid-based expandable resin particles of the present invention can be produced by impregnating a polylactic acid-based resin composition with a foaming agent and a foaming aid in a water suspension system using water as a medium. Further, in a water suspension system, impregnation with a foaming agent and a foaming aid can be performed under heating and high pressure. The impregnation temperature is usually selected above the glass transition temperature of the polylactic acid resin composition. For example, at an impregnation temperature of 70 to 110 ° C., sufficient impregnation can be performed with an impregnation time of 0.5 to 3 hours.
When polylactic acid is impregnated with a foaming agent in an aqueous suspension system, a dispersant or a surfactant can be added in the medium water for the purpose of helping dispersion and preventing coalescence of the resins. . As the dispersant and the surfactant, those generally used in general are used. For example, polyvinyl alcohol, polyvinyl pyrrolidone, methyl cellulose or the like is used as the dispersant, and sodium dodecylbenzene sulfonate, sodium α-olefin sulfonate or the like is used as the surfactant.
[0022]
The micropores present in the polylactic acid-based foamable resin particles after impregnated with the foaming agent contain moisture. It is necessary to reduce this moisture to a predetermined amount or less. This is because the pellet of the composition obtained by dehydrating the surface moisture in a centrifugal separation step or the like is kept in a ventilation state for 5 to 48 hours in 5 to 40 ° C. dry air ( Aeration). In addition, drying by a vacuum dryer, drying using a dehydrating agent, or the like is also possible.
[0023]
【Example】
The following examples illustrate the invention in more detail. However, the examples are for illustrating the present invention and are not intended to limit the present invention in any way.
[0024]
Evaluation in this example was performed as follows.
-About 0.2 g of the sample for measuring the content of the foaming agent and foaming aid in the polylactic acid-based foamable resin particles is precisely weighed, and then the sample is dissolved in toluene and foamed by gas chromatography on the solution. The contents of the agent and the foaming aid were measured.
-Foaming ratio Polylactic acid-based foaming resin particles were pre-foamed by heating with 85-95 ° C water vapor for 30 seconds. The volume of the pre-expanded particles obtained was measured with a graduated cylinder to determine the expansion ratio.
[0025]
Production 1 of polylactic acid-based expandable resin particles (sample numbers 1 to 10)
4 parts by mass of layered silicate is added to 100 parts by mass of polylactic acid (Natural Works, manufactured by Cargill Dow, weight average molecular weight: 198000, number average molecular weight: 115000), and a twin screw extruder (Ikegai PCM-30, dice) The resulting strand was pelletized by a pulverizer to obtain a polylactic acid-based resin composition. These were dispersed in a water suspension system, and impregnated with pentane (normal / iso = 75/25) as a foaming agent and cyclopentane as a foaming aid to obtain polylactic acid-based foamable resin particles. In addition to the foaming agent and foaming aid, a dispersant and a surfactant were also added. Impregnation was carried out by holding at 90 ° C. for about 1 hour in an autoclave equipped with a stirrer.
Production 2 of polylactic acid-based expandable resin particles (Sample No. 11)
The pelletized polylactic acid-based resin composition obtained in the same manner as in Production 1 of polylactic acid-based expandable resin particles is placed in an autoclave equipped with a stirrer, and pentane (normal / iso = 67/33) and a foaming aid as a foaming agent. As methanol was added. The foaming agent was impregnated by maintaining the temperature at 80 to 90 ° C. for 2 hours.
Table 1 shows the ratio of the foaming agent and the foaming assistant added for each sample.
[Table 1]
For each sample, aeration was performed immediately after the production of the expandable resin particles, and the content of the foaming aid, the content of the foaming agent, and the expansion ratio were measured. Next, the expandable resin particles were stored at room temperature for 10 days, and the content of the foaming agent and the expansion ratio after storage were measured.
The results are shown in Table 2. Content is the mass part which made the polylactic acid-type resin composition 100.
[Table 2]
Samples 2 and 3 (Examples of the present invention) contain a relatively small amount of cyclopentane. These samples did not dissipate the foaming agent even after 10 days. However, since the content of cyclopentane was relatively small, the softening action of the polylactic acid resin composition was small and the foaming was similar to that of Sample 1. The magnification was relatively low.
Samples 4, 5 and 6 (Examples of the present invention) contain 2.5 to 5.5 parts by mass of cyclopentane as a foaming aid. In these samples, the softening of the polylactic acid-based resin composition was promoted in the pre-expansion to obtain high-magnification pre-expanded particles, which was preferable to the samples 2 and 3. Further, after the impregnation, the polylactic acid-based expandable resin particles were stored at room temperature for 10 days, but no dissipation of the foaming agent was observed.
Samples 7, 8 and 9 (Examples of the present invention) contain a relatively large amount of cyclopentane. In these samples, the foaming agent did not dissipate, and thus the foaming ratio did not decrease with time, but the softening action was too strong during the pre-foaming, so there was shrinkage after foaming.
Sample 10 (a comparative example outside the scope of the present invention) does not use a foaming agent and uses only cyclopentane. In this sample, although the resin particles were impregnated with a large amount of cyclopentane, the expansion ratio of the pre-expanded particles did not increase.
Sample 11 (a comparative example outside the scope of the present invention) uses methanol as a foaming aid. In all of Samples 2 to 10 using cyclopentane as a foaming aid, no dissipation of foaming agent was confirmed after storage for 10 days, whereas in this sample, about half of the foaming agent was lost in 10 days. As a result, the expansion ratio also decreased.
[0027]
Production 3 of polylactic acid-based expandable resin particles (sample numbers 12 to 16)
Commercially available L-lactic acid and D-lactic acid were purified by recrystallization from ethyl acetate. Purified L-lactic acid and D-lactic acid were mixed so that the D-form ratio would be 10 mol%, and then tin octylate as a catalyst was added so that the tin content would be 10 ppm. In an autoclave equipped with a stirrer, After degassing under reduced pressure, polymerization was performed in a nitrogen atmosphere. After completion of the reaction, the product is taken out from the autoclave, and then dried until the water content is 1000 ppm or less. Then, 2.8 equivalents of diphenylmethane polyisocyanate as a viscosity increasing agent is blended in 1% by mass with respect to the product. did. The obtained blend was supplied to a twin-screw kneader, reacted and kneaded under the conditions of a rotation speed of 100 rpm, a melting temperature of 180 ° C., a residence time of 3 to 5 minutes, and a discharge rate of 10 kg / hour, and then extrusion-cut from a die. A polylactic acid resin composition was obtained as particles having a diameter of about 1 mm. The obtained polylactic acid resin composition had an MI value of 0.2.
The resulting polylactic acid resin composition was impregnated with butane (normal / iso = 67/33) as a foaming agent and cyclopentane as a foaming aid to obtain polylactic acid-based foamable resin particles. In addition to the foaming agent and foaming aid, a dispersant and a surfactant were also added. Impregnation was carried out by holding at 90 ° C. for about 1 hour in an autoclave equipped with a stirrer.
Production 4 of polylactic acid-based expandable resin particles (Sample No. 17)
Commercially available L-lactic acid and D-lactic acid were purified by recrystallization from ethyl acetate. Purified L-lactic acid and D-lactic acid were mixed so that the D-form ratio was 10 mol%, and then tin octylate as a catalyst was added so that the tin content was 10 ppm, and the mixture was stirred in an autoclave equipped with a stirrer. After degassing under reduced pressure, polymerization was performed under a nitrogen atmosphere. After completion of the reaction, the product was taken out from the autoclave and then dried until the water content became 1000 ppm or less. Then, 3% by mass of talc and 2.8 equivalents of functional group as a viscosity increasing agent were used with respect to the product. 1% by mass of diphenylmethane polyisocyanate was blended. The obtained blend was supplied to a twin-screw kneader, reacted and kneaded under the conditions of a rotation speed of 100 rpm, a melting temperature of 180 ° C., a residence time of 3 to 5 minutes, and a discharge rate of 10 kg / hour, and then extrusion-cut from a die. A polylactic acid resin composition was obtained as particles having a diameter of about 1 mm. The obtained polylactic acid resin composition had an MI value of 0.2.
The obtained pelletized polylactic acid resin composition was placed in an autoclave equipped with a stirrer, and butane (normal / iso = 67/33) as a foaming agent and acetone as a foaming aid were added. The foaming agent was impregnated by maintaining the temperature at 80 to 90 ° C. for 2 hours.
Table 3 shows the ratio of the foaming agent and the foaming aid added for each sample.
[Table 3]
For each sample, aeration was performed immediately after the production of the expandable resin particles, and the content of the foaming aid, the content of the foaming agent, and the expansion ratio were measured. Next, the expandable resin particles were stored at room temperature for 10 days, and the content of the foaming agent and the expansion ratio after storage were measured. The results are shown in Table 4. Content is the mass part which made the polylactic acid-type resin composition 100.
[Table 4]
Sample 13 (an example of the present invention) contains a relatively small amount of cyclopentane. In this sample, the foaming agent did not dissipate even after 10 days. Therefore, the foaming ratio did not decrease over time, but the content of cyclopentane was relatively small, so the polylactic acid resin composition was softened. The action was small, and the expansion ratio of the expandable resin particles was relatively low.
Sample 14 (an example of the present invention) contains 2.5 to 5.5 parts by mass of cyclopentane as a foaming aid. In this sample, the softening of the polylactic acid-based resin composition was promoted in the pre-expansion, and pre-expanded particles having a higher magnification than that of the sample 2 were obtained. Also, no foaming agent was lost after storage at room temperature for 10 days.
Sample 15 (an example of the present invention) contains a relatively large amount of cyclopentane. In this sample, the foaming agent did not dissipate, but the foaming ratio was low because of the strong softening effect during prefoaming and large shrinkage after foaming.
Sample 16 (Comparative Example outside the scope of the present invention) does not use a foaming agent and uses only cyclopentane. In this sample, although the resin particles were impregnated with a large amount of cyclopentane, the expansion ratio of the pre-expanded particles did not increase.
Sample 17 (a comparative example outside the scope of the present invention) uses acetone as a foaming aid. In any of Samples 13 to 16 using cyclopentane as a foaming aid, no dissipation of the foaming agent was confirmed after storage for 10 days, whereas in this sample, more than half of the foaming agent was lost in 10 days. As a result, the expansion ratio was greatly reduced.
[0029]
【The invention's effect】
In the polylactic acid-based expandable resin particles of the present invention, by impregnating cyclopentane as a foaming aid, the foaming agent contained in the expandable resin particles does not dissipate and has excellent foamability even after long-term storage Can be maintained. That is, the change in expansion ratio with time is good, and the polylactic acid-based expandable resin particles are convenient for storage and transportation. In addition, the foam molded product produced from the polylactic acid-based expandable resin particles of the present invention has a large number of foam cells, and the dimensions of the foam cells are uniform and small. In addition, since the foamability of the polylactic acid-based expandable resin particles of the present invention is good, the pre-foaming time can be greatly shortened, and a foamed molded product having a low vapor pressure and good fusibility can be obtained. The manufacturing process is energy saving as a whole.
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| JP4473517B2 (en) * | 2003-03-25 | 2010-06-02 | ユニチカ株式会社 | Thermoplastic resin foam having fine bubbles and method for producing the same |
| JP4664106B2 (en) * | 2005-03-31 | 2011-04-06 | 株式会社ジェイエスピー | Method for producing foamed polylactic acid resin particles |
| JP4697861B2 (en) * | 2005-03-31 | 2011-06-08 | 株式会社ジェイエスピー | Polylactic acid-based resin foamed particles and polylactic acid-based resin in-mold foam molding |
| KR101050338B1 (en) * | 2007-03-29 | 2011-07-19 | 세키스이가세이힝코교가부시키가이샤 | Polylactic acid-based resin foamed particles for in-mold foam molding, a method for producing the same, and a method for producing a polylactic acid-based resin foamed molded article |
| US20120009420A1 (en) | 2010-07-07 | 2012-01-12 | Lifoam Industries | Compostable or Biobased Foams |
| US8962706B2 (en) | 2010-09-10 | 2015-02-24 | Lifoam Industries, Llc | Process for enabling secondary expansion of expandable beads |
| JP2022027146A (en) * | 2020-07-31 | 2022-02-10 | 株式会社リコー | Foam, foam sheet, product, and method for producing foam |
| CN114920976A (en) * | 2022-06-13 | 2022-08-19 | 安徽瑞鸿新材料科技有限公司 | Preparation method of degradable polylactic acid foaming particles |
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