JP7549525B2 - Styrenic biaxially oriented sheet and container using same - Google Patents
Styrenic biaxially oriented sheet and container using same Download PDFInfo
- Publication number
- JP7549525B2 JP7549525B2 JP2020214799A JP2020214799A JP7549525B2 JP 7549525 B2 JP7549525 B2 JP 7549525B2 JP 2020214799 A JP2020214799 A JP 2020214799A JP 2020214799 A JP2020214799 A JP 2020214799A JP 7549525 B2 JP7549525 B2 JP 7549525B2
- Authority
- JP
- Japan
- Prior art keywords
- styrene
- copolymer
- mass
- biaxially oriented
- sheet
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 claims description 201
- 229920001577 copolymer Polymers 0.000 claims description 137
- 239000000178 monomer Substances 0.000 claims description 66
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 claims description 31
- PEEHTFAAVSWFBL-UHFFFAOYSA-N Maleimide Chemical compound O=C1NC(=O)C=C1 PEEHTFAAVSWFBL-UHFFFAOYSA-N 0.000 claims description 22
- 235000013305 food Nutrition 0.000 claims description 17
- HIDBROSJWZYGSZ-UHFFFAOYSA-N 1-phenylpyrrole-2,5-dione Chemical group O=C1C=CC(=O)N1C1=CC=CC=C1 HIDBROSJWZYGSZ-UHFFFAOYSA-N 0.000 claims description 13
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical group O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 claims description 13
- 238000004806 packaging method and process Methods 0.000 claims description 10
- 229920001893 acrylonitrile styrene Polymers 0.000 claims description 6
- SCUZVMOVTVSBLE-UHFFFAOYSA-N prop-2-enenitrile;styrene Chemical compound C=CC#N.C=CC1=CC=CC=C1 SCUZVMOVTVSBLE-UHFFFAOYSA-N 0.000 claims description 6
- 229920006249 styrenic copolymer Polymers 0.000 claims description 4
- 230000000977 initiatory effect Effects 0.000 claims description 2
- 239000003921 oil Substances 0.000 description 33
- 238000000034 method Methods 0.000 description 23
- 238000011156 evaluation Methods 0.000 description 22
- 229920005989 resin Polymers 0.000 description 15
- 239000011347 resin Substances 0.000 description 15
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 12
- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 description 11
- 238000005259 measurement Methods 0.000 description 11
- 238000006116 polymerization reaction Methods 0.000 description 10
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 9
- 239000004793 Polystyrene Substances 0.000 description 9
- 239000000463 material Substances 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- 229920002223 polystyrene Polymers 0.000 description 9
- 239000000243 solution Substances 0.000 description 9
- -1 2-ethylhexyl Chemical group 0.000 description 7
- 239000006096 absorbing agent Substances 0.000 description 7
- YNQLUTRBYVCPMQ-UHFFFAOYSA-N Ethylbenzene Chemical compound CCC1=CC=CC=C1 YNQLUTRBYVCPMQ-UHFFFAOYSA-N 0.000 description 6
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 6
- 238000005227 gel permeation chromatography Methods 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 239000008268 mayonnaise Substances 0.000 description 6
- 235000010746 mayonnaise Nutrition 0.000 description 6
- 239000003963 antioxidant agent Substances 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- 229920001971 elastomer Polymers 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 238000000465 moulding Methods 0.000 description 4
- 230000003014 reinforcing effect Effects 0.000 description 4
- 239000005060 rubber Substances 0.000 description 4
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 4
- FCKXGFANXSHGAW-DTXPUJKBSA-N (2s)-n,n'-bis[(2s)-1-(2-chloro-4-nitroanilino)-1-oxo-3-phenylpropan-2-yl]-2-hydroxybutanediamide Chemical compound C([C@H](NC(=O)C[C@H](O)C(=O)N[C@@H](CC=1C=CC=CC=1)C(=O)NC=1C(=CC(=CC=1)[N+]([O-])=O)Cl)C(=O)NC=1C(=CC(=CC=1)[N+]([O-])=O)Cl)C1=CC=CC=C1 FCKXGFANXSHGAW-DTXPUJKBSA-N 0.000 description 3
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 description 3
- 240000007594 Oryza sativa Species 0.000 description 3
- 235000007164 Oryza sativa Nutrition 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 239000004798 oriented polystyrene Substances 0.000 description 3
- 235000006408 oxalic acid Nutrition 0.000 description 3
- 230000000379 polymerizing effect Effects 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 239000011342 resin composition Substances 0.000 description 3
- 235000009566 rice Nutrition 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 125000003011 styrenyl group Chemical group [H]\C(*)=C(/[H])C1=C([H])C([H])=C([H])C([H])=C1[H] 0.000 description 3
- FVQMJJQUGGVLEP-UHFFFAOYSA-N (2-methylpropan-2-yl)oxy 2-ethylhexaneperoxoate Chemical compound CCCCC(CC)C(=O)OOOC(C)(C)C FVQMJJQUGGVLEP-UHFFFAOYSA-N 0.000 description 2
- VSAWBBYYMBQKIK-UHFFFAOYSA-N 4-[[3,5-bis[(3,5-ditert-butyl-4-hydroxyphenyl)methyl]-2,4,6-trimethylphenyl]methyl]-2,6-ditert-butylphenol Chemical compound CC1=C(CC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)C(C)=C(CC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)C(C)=C1CC1=CC(C(C)(C)C)=C(O)C(C(C)(C)C)=C1 VSAWBBYYMBQKIK-UHFFFAOYSA-N 0.000 description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- QRUDEWIWKLJBPS-UHFFFAOYSA-N benzotriazole Chemical compound C1=CC=C2N[N][N]C2=C1 QRUDEWIWKLJBPS-UHFFFAOYSA-N 0.000 description 2
- 239000012964 benzotriazole Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000012662 bulk polymerization Methods 0.000 description 2
- 238000011088 calibration curve Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000010828 elution Methods 0.000 description 2
- 238000001125 extrusion Methods 0.000 description 2
- 125000001841 imino group Chemical group [H]N=* 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 239000004611 light stabiliser Substances 0.000 description 2
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 2
- QUAMTGJKVDWJEQ-UHFFFAOYSA-N octabenzone Chemical compound OC1=CC(OCCCCCCCC)=CC=C1C(=O)C1=CC=CC=C1 QUAMTGJKVDWJEQ-UHFFFAOYSA-N 0.000 description 2
- QADJHAOXTKCYFT-UHFFFAOYSA-N octyl 3-(3-octoxy-3-oxopropyl)sulfanylpropanoate Chemical compound CCCCCCCCOC(=O)CCSCCC(=O)OCCCCCCCC QADJHAOXTKCYFT-UHFFFAOYSA-N 0.000 description 2
- NFHFRUOZVGFOOS-UHFFFAOYSA-N palladium;triphenylphosphane Chemical compound [Pd].C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1.C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1.C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1.C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1 NFHFRUOZVGFOOS-UHFFFAOYSA-N 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- ZQBAKBUEJOMQEX-UHFFFAOYSA-N phenyl salicylate Chemical compound OC1=CC=CC=C1C(=O)OC1=CC=CC=C1 ZQBAKBUEJOMQEX-UHFFFAOYSA-N 0.000 description 2
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- YGSDEFSMJLZEOE-UHFFFAOYSA-N salicylic acid Chemical compound OC(=O)C1=CC=CC=C1O YGSDEFSMJLZEOE-UHFFFAOYSA-N 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 229920003048 styrene butadiene rubber Polymers 0.000 description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- DTGKSKDOIYIVQL-WEDXCCLWSA-N (+)-borneol Chemical group C1C[C@@]2(C)[C@@H](O)C[C@@H]1C2(C)C DTGKSKDOIYIVQL-WEDXCCLWSA-N 0.000 description 1
- ZOKCNEIWFQCSCM-UHFFFAOYSA-N (2-methyl-4-phenylpent-4-en-2-yl)benzene Chemical compound C=1C=CC=CC=1C(C)(C)CC(=C)C1=CC=CC=C1 ZOKCNEIWFQCSCM-UHFFFAOYSA-N 0.000 description 1
- VNFXPOAMRORRJJ-UHFFFAOYSA-N (4-octylphenyl) 2-hydroxybenzoate Chemical compound C1=CC(CCCCCCCC)=CC=C1OC(=O)C1=CC=CC=C1O VNFXPOAMRORRJJ-UHFFFAOYSA-N 0.000 description 1
- KMHAFDJFHSEAHT-UHFFFAOYSA-N 1,1-bis(2,3-ditert-butylphenyl)-2,2-bis(hydroxymethyl)propane-1,3-diol dihydroxyphosphanyl dihydrogen phosphite Chemical compound OP(O)OP(O)O.C(C)(C)(C)C=1C(=C(C=CC1)C(O)(C(CO)(CO)CO)C1=C(C(=CC=C1)C(C)(C)C)C(C)(C)C)C(C)(C)C KMHAFDJFHSEAHT-UHFFFAOYSA-N 0.000 description 1
- UOZNXGJVAWDLQK-UHFFFAOYSA-N 1-(2,3-dimethylphenyl)pyrrole-2,5-dione Chemical compound CC1=CC=CC(N2C(C=CC2=O)=O)=C1C UOZNXGJVAWDLQK-UHFFFAOYSA-N 0.000 description 1
- KPQOXMCRYWDRSB-UHFFFAOYSA-N 1-(2-chlorophenyl)pyrrole-2,5-dione Chemical compound ClC1=CC=CC=C1N1C(=O)C=CC1=O KPQOXMCRYWDRSB-UHFFFAOYSA-N 0.000 description 1
- LJDGDRYFCIHDPX-UHFFFAOYSA-N 1-(2-methoxyphenyl)pyrrole-2,5-dione Chemical compound COC1=CC=CC=C1N1C(=O)C=CC1=O LJDGDRYFCIHDPX-UHFFFAOYSA-N 0.000 description 1
- QYOJZFBQEAZNEW-UHFFFAOYSA-N 1-(2-methylphenyl)pyrrole-2,5-dione Chemical compound CC1=CC=CC=C1N1C(=O)C=CC1=O QYOJZFBQEAZNEW-UHFFFAOYSA-N 0.000 description 1
- BQTPKSBXMONSJI-UHFFFAOYSA-N 1-cyclohexylpyrrole-2,5-dione Chemical compound O=C1C=CC(=O)N1C1CCCCC1 BQTPKSBXMONSJI-UHFFFAOYSA-N 0.000 description 1
- NVZWEEGUWXZOKI-UHFFFAOYSA-N 1-ethenyl-2-methylbenzene Chemical compound CC1=CC=CC=C1C=C NVZWEEGUWXZOKI-UHFFFAOYSA-N 0.000 description 1
- JZHGRUMIRATHIU-UHFFFAOYSA-N 1-ethenyl-3-methylbenzene Chemical compound CC1=CC=CC(C=C)=C1 JZHGRUMIRATHIU-UHFFFAOYSA-N 0.000 description 1
- BAWHYOHVWHQWFQ-UHFFFAOYSA-N 1-naphthalen-1-ylpyrrole-2,5-dione Chemical compound O=C1C=CC(=O)N1C1=CC=CC2=CC=CC=C12 BAWHYOHVWHQWFQ-UHFFFAOYSA-N 0.000 description 1
- NQDOCLXQTQYUDH-UHFFFAOYSA-N 1-propan-2-ylpyrrole-2,5-dione Chemical compound CC(C)N1C(=O)C=CC1=O NQDOCLXQTQYUDH-UHFFFAOYSA-N 0.000 description 1
- DABFKTHTXOELJF-UHFFFAOYSA-N 1-propylpyrrole-2,5-dione Chemical compound CCCN1C(=O)C=CC1=O DABFKTHTXOELJF-UHFFFAOYSA-N 0.000 description 1
- QEDJMOONZLUIMC-UHFFFAOYSA-N 1-tert-butyl-4-ethenylbenzene Chemical compound CC(C)(C)C1=CC=C(C=C)C=C1 QEDJMOONZLUIMC-UHFFFAOYSA-N 0.000 description 1
- YEKDUBMGZZTUDY-UHFFFAOYSA-N 1-tert-butylpyrrole-2,5-dione Chemical compound CC(C)(C)N1C(=O)C=CC1=O YEKDUBMGZZTUDY-UHFFFAOYSA-N 0.000 description 1
- MEZZCSHVIGVWFI-UHFFFAOYSA-N 2,2'-Dihydroxy-4-methoxybenzophenone Chemical compound OC1=CC(OC)=CC=C1C(=O)C1=CC=CC=C1O MEZZCSHVIGVWFI-UHFFFAOYSA-N 0.000 description 1
- OCSIKZYSDOXRPA-UHFFFAOYSA-N 2,2-bis(hydroxymethyl)-3-octadecylhenicosane-1,3-diol dihydroxyphosphanyl dihydrogen phosphite Chemical compound OP(O)OP(O)O.C(CCCCCCCCCCCCCCCCC)C(O)(C(CO)(CO)CO)CCCCCCCCCCCCCCCCCC OCSIKZYSDOXRPA-UHFFFAOYSA-N 0.000 description 1
- YYFJBFQNTPRKOS-UHFFFAOYSA-N 2,2-bis(hydroxymethyl)hexadecane-1,3-diol dihydroxyphosphanyl dihydrogen phosphite Chemical compound OP(O)OP(O)O.C(CCCCCCCCCCCC)C(O)C(CO)(CO)CO YYFJBFQNTPRKOS-UHFFFAOYSA-N 0.000 description 1
- ZXDDPOHVAMWLBH-UHFFFAOYSA-N 2,4-Dihydroxybenzophenone Chemical compound OC1=CC(O)=CC=C1C(=O)C1=CC=CC=C1 ZXDDPOHVAMWLBH-UHFFFAOYSA-N 0.000 description 1
- JLZIIHMTTRXXIN-UHFFFAOYSA-N 2-(2-hydroxy-4-methoxybenzoyl)benzoic acid Chemical compound OC1=CC(OC)=CC=C1C(=O)C1=CC=CC=C1C(O)=O JLZIIHMTTRXXIN-UHFFFAOYSA-N 0.000 description 1
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- ZMWRRFHBXARRRT-UHFFFAOYSA-N 2-(benzotriazol-2-yl)-4,6-bis(2-methylbutan-2-yl)phenol Chemical compound CCC(C)(C)C1=CC(C(C)(C)CC)=CC(N2N=C3C=CC=CC3=N2)=C1O ZMWRRFHBXARRRT-UHFFFAOYSA-N 0.000 description 1
- LHPPDQUVECZQSW-UHFFFAOYSA-N 2-(benzotriazol-2-yl)-4,6-ditert-butylphenol Chemical compound CC(C)(C)C1=CC(C(C)(C)C)=CC(N2N=C3C=CC=CC3=N2)=C1O LHPPDQUVECZQSW-UHFFFAOYSA-N 0.000 description 1
- WXHVQMGINBSVAY-UHFFFAOYSA-N 2-(benzotriazol-2-yl)-4-tert-butylphenol Chemical compound CC(C)(C)C1=CC=C(O)C(N2N=C3C=CC=CC3=N2)=C1 WXHVQMGINBSVAY-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- QSRJVOOOWGXUDY-UHFFFAOYSA-N 2-[2-[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propanoyloxy]ethoxy]ethoxy]ethyl 3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propanoate Chemical compound CC(C)(C)C1=C(O)C(C)=CC(CCC(=O)OCCOCCOCCOC(=O)CCC=2C=C(C(O)=C(C)C=2)C(C)(C)C)=C1 QSRJVOOOWGXUDY-UHFFFAOYSA-N 0.000 description 1
- KLIZOTJVECGYSJ-UHFFFAOYSA-N 2-[2-[3-(benzotriazol-2-yl)-5-(2-phenylpropan-2-yl)phenyl]propan-2-yl]phenol Chemical compound C=1C(N2N=C3C=CC=CC3=N2)=CC(C(C)(C)C=2C(=CC=CC=2)O)=CC=1C(C)(C)C1=CC=CC=C1 KLIZOTJVECGYSJ-UHFFFAOYSA-N 0.000 description 1
- SKMNWICOBCDSSQ-UHFFFAOYSA-N 2-[4-[3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoyloxy]-2,2,6,6-tetramethylpiperidin-1-yl]ethyl 3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoate Chemical compound CC(C)(C)C1=C(O)C(C(C)(C)C)=CC(CCC(=O)OCCN2C(CC(CC2(C)C)OC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)(C)C)=C1 SKMNWICOBCDSSQ-UHFFFAOYSA-N 0.000 description 1
- 125000003229 2-methylhexyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])(C([H])([H])[H])C([H])([H])* 0.000 description 1
- IKEHOXWJQXIQAG-UHFFFAOYSA-N 2-tert-butyl-4-methylphenol Chemical compound CC1=CC=C(O)C(C(C)(C)C)=C1 IKEHOXWJQXIQAG-UHFFFAOYSA-N 0.000 description 1
- BQARUDWASOOSRH-UHFFFAOYSA-N 2-tert-butylperoxypropan-2-yl hydrogen carbonate Chemical compound CC(C)(C)OOC(C)(C)OC(O)=O BQARUDWASOOSRH-UHFFFAOYSA-N 0.000 description 1
- PYSRRFNXTXNWCD-UHFFFAOYSA-N 3-(2-phenylethenyl)furan-2,5-dione Chemical compound O=C1OC(=O)C(C=CC=2C=CC=CC=2)=C1 PYSRRFNXTXNWCD-UHFFFAOYSA-N 0.000 description 1
- QRLSTWVLSWCGBT-UHFFFAOYSA-N 4-((4,6-bis(octylthio)-1,3,5-triazin-2-yl)amino)-2,6-di-tert-butylphenol Chemical compound CCCCCCCCSC1=NC(SCCCCCCCC)=NC(NC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)=N1 QRLSTWVLSWCGBT-UHFFFAOYSA-N 0.000 description 1
- STEYNUVPFMIUOY-UHFFFAOYSA-N 4-Hydroxy-1-(2-hydroxyethyl)-2,2,6,6-tetramethylpiperidine Chemical compound CC1(C)CC(O)CC(C)(C)N1CCO STEYNUVPFMIUOY-UHFFFAOYSA-N 0.000 description 1
- JLBJTVDPSNHSKJ-UHFFFAOYSA-N 4-Methylstyrene Chemical compound CC1=CC=C(C=C)C=C1 JLBJTVDPSNHSKJ-UHFFFAOYSA-N 0.000 description 1
- DBOSBRHMHBENLP-UHFFFAOYSA-N 4-tert-Butylphenyl Salicylate Chemical compound C1=CC(C(C)(C)C)=CC=C1OC(=O)C1=CC=CC=C1O DBOSBRHMHBENLP-UHFFFAOYSA-N 0.000 description 1
- UWSMKYBKUPAEJQ-UHFFFAOYSA-N 5-Chloro-2-(3,5-di-tert-butyl-2-hydroxyphenyl)-2H-benzotriazole Chemical compound CC(C)(C)C1=CC(C(C)(C)C)=CC(N2N=C3C=C(Cl)C=CC3=N2)=C1O UWSMKYBKUPAEJQ-UHFFFAOYSA-N 0.000 description 1
- WEFMTVNJCFTOFQ-UHFFFAOYSA-N 6-decoxybenzo[c][2,1]benzoxaphosphinine Chemical compound C1=CC=C2P(OCCCCCCCCCC)OC3=CC=CC=C3C2=C1 WEFMTVNJCFTOFQ-UHFFFAOYSA-N 0.000 description 1
- 229920002126 Acrylic acid copolymer Polymers 0.000 description 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical group N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
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- 229920000049 Carbon (fiber) Polymers 0.000 description 1
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- GHKOFFNLGXMVNJ-UHFFFAOYSA-N Didodecyl thiobispropanoate Chemical compound CCCCCCCCCCCCOC(=O)CCSCCC(=O)OCCCCCCCCCCCC GHKOFFNLGXMVNJ-UHFFFAOYSA-N 0.000 description 1
- MUXOBHXGJLMRAB-UHFFFAOYSA-N Dimethyl succinate Chemical compound COC(=O)CCC(=O)OC MUXOBHXGJLMRAB-UHFFFAOYSA-N 0.000 description 1
- 229920000181 Ethylene propylene rubber Polymers 0.000 description 1
- CERQOIWHTDAKMF-UHFFFAOYSA-M Methacrylate Chemical compound CC(=C)C([O-])=O CERQOIWHTDAKMF-UHFFFAOYSA-M 0.000 description 1
- MWCLLHOVUTZFKS-UHFFFAOYSA-N Methyl cyanoacrylate Chemical compound COC(=O)C(=C)C#N MWCLLHOVUTZFKS-UHFFFAOYSA-N 0.000 description 1
- GYCMBHHDWRMZGG-UHFFFAOYSA-N Methylacrylonitrile Chemical compound CC(=C)C#N GYCMBHHDWRMZGG-UHFFFAOYSA-N 0.000 description 1
- GHAZCVNUKKZTLG-UHFFFAOYSA-N N-ethyl-succinimide Natural products CCN1C(=O)CCC1=O GHAZCVNUKKZTLG-UHFFFAOYSA-N 0.000 description 1
- HDFGOPSGAURCEO-UHFFFAOYSA-N N-ethylmaleimide Chemical compound CCN1C(=O)C=CC1=O HDFGOPSGAURCEO-UHFFFAOYSA-N 0.000 description 1
- CFLSGXYCBKVRJB-UHFFFAOYSA-N P(OC1=C(C(=CC=C1)CCCCCCCCC)CCCCCCCCC)OCCCCCCCC Chemical compound P(OC1=C(C(=CC=C1)CCCCCCCCC)CCCCCCCCC)OCCCCCCCC CFLSGXYCBKVRJB-UHFFFAOYSA-N 0.000 description 1
- 239000006002 Pepper Substances 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 235000016761 Piper aduncum Nutrition 0.000 description 1
- 235000017804 Piper guineense Nutrition 0.000 description 1
- 244000203593 Piper nigrum Species 0.000 description 1
- 235000008184 Piper nigrum Nutrition 0.000 description 1
- 239000005062 Polybutadiene Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 1
- 239000006087 Silane Coupling Agent Substances 0.000 description 1
- 229920000147 Styrene maleic anhydride Polymers 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229920000122 acrylonitrile butadiene styrene Polymers 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
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- SODJJEXAWOSSON-UHFFFAOYSA-N bis(2-hydroxy-4-methoxyphenyl)methanone Chemical compound OC1=CC(OC)=CC=C1C(=O)C1=CC=C(OC)C=C1O SODJJEXAWOSSON-UHFFFAOYSA-N 0.000 description 1
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- 239000004917 carbon fiber Substances 0.000 description 1
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- 125000002704 decyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- PWWSSIYVTQUJQQ-UHFFFAOYSA-N distearyl thiodipropionate Chemical compound CCCCCCCCCCCCCCCCCCOC(=O)CCSCCC(=O)OCCCCCCCCCCCCCCCCCC PWWSSIYVTQUJQQ-UHFFFAOYSA-N 0.000 description 1
- WNAHIZMDSQCWRP-UHFFFAOYSA-N dodecane-1-thiol Chemical compound CCCCCCCCCCCCS WNAHIZMDSQCWRP-UHFFFAOYSA-N 0.000 description 1
- MCPKSFINULVDNX-UHFFFAOYSA-N drometrizole Chemical compound CC1=CC=C(O)C(N2N=C3C=CC=CC3=N2)=C1 MCPKSFINULVDNX-UHFFFAOYSA-N 0.000 description 1
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- 238000005516 engineering process Methods 0.000 description 1
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 238000010528 free radical solution polymerization reaction Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
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- 229920005669 high impact polystyrene Polymers 0.000 description 1
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- 239000004615 ingredient Substances 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 239000010445 mica Substances 0.000 description 1
- 229910052618 mica group Inorganic materials 0.000 description 1
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- 238000002156 mixing Methods 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 125000004108 n-butyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
- SEEYREPSKCQBBF-UHFFFAOYSA-N n-methylmaleimide Chemical compound CN1C(=O)C=CC1=O SEEYREPSKCQBBF-UHFFFAOYSA-N 0.000 description 1
- 239000002736 nonionic surfactant Substances 0.000 description 1
- 150000001451 organic peroxides Chemical class 0.000 description 1
- DXGLGDHPHMLXJC-UHFFFAOYSA-N oxybenzone Chemical compound OC1=CC(OC)=CC=C1C(=O)C1=CC=CC=C1 DXGLGDHPHMLXJC-UHFFFAOYSA-N 0.000 description 1
- FJKROLUGYXJWQN-UHFFFAOYSA-N papa-hydroxy-benzoic acid Natural products OC(=O)C1=CC=C(O)C=C1 FJKROLUGYXJWQN-UHFFFAOYSA-N 0.000 description 1
- 229960000969 phenyl salicylate Drugs 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 229920002857 polybutadiene Polymers 0.000 description 1
- 239000003505 polymerization initiator Substances 0.000 description 1
- 229920006327 polystyrene foam Polymers 0.000 description 1
- 229920005990 polystyrene resin Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 1
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- FZYCEURIEDTWNS-UHFFFAOYSA-N prop-1-en-2-ylbenzene Chemical compound CC(=C)C1=CC=CC=C1.CC(=C)C1=CC=CC=C1 FZYCEURIEDTWNS-UHFFFAOYSA-N 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
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- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- CXVGEDCSTKKODG-UHFFFAOYSA-N sulisobenzone Chemical compound C1=C(S(O)(=O)=O)C(OC)=CC(O)=C1C(=O)C1=CC=CC=C1 CXVGEDCSTKKODG-UHFFFAOYSA-N 0.000 description 1
- 239000000454 talc Substances 0.000 description 1
- 229910052623 talc Inorganic materials 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- LVEOKSIILWWVEO-UHFFFAOYSA-N tetradecyl 3-(3-oxo-3-tetradecoxypropyl)sulfanylpropanoate Chemical compound CCCCCCCCCCCCCCOC(=O)CCSCCC(=O)OCCCCCCCCCCCCCC LVEOKSIILWWVEO-UHFFFAOYSA-N 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- MZHULIWXRDLGRR-UHFFFAOYSA-N tridecyl 3-(3-oxo-3-tridecoxypropyl)sulfanylpropanoate Chemical compound CCCCCCCCCCCCCOC(=O)CCSCCC(=O)OCCCCCCCCCCCCC MZHULIWXRDLGRR-UHFFFAOYSA-N 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- 229920003169 water-soluble polymer Polymers 0.000 description 1
- 238000004383 yellowing Methods 0.000 description 1
Landscapes
- Wrappers (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
Description
本発明は、スチレン系二軸延伸シート及びそれを用いた容器に関する。 The present invention relates to a styrene-based biaxially oriented sheet and a container using the same.
ポリスチレンからなる二軸延伸シート（以下、「ポリスチレン二軸延伸シート」と記載する）は、透明性、及び剛性に優れることから、食品包装用容器をはじめ、各種成形容器として広く利用されている。一方でポリスチレン二軸延伸シートは耐熱性に劣るため、前記二軸延伸シートからなる成形品を容器本体や蓋材として用いた容器を電子レンジで加熱した場合、変形が生じる場合がある。
ポリスチレン二軸延伸シートの耐熱性を改良することを目的に、スチレン－（メタ）アクリル酸共重合体やスチレン－無水マレイン酸共重合体等の耐熱性スチレン樹脂を用いた、ポリスチレン系樹脂シートが提案されている（例えば、特許文献１～２等）。
A biaxially oriented sheet made of polystyrene (hereinafter, referred to as "biaxially oriented polystyrene sheet") is excellent in transparency and rigidity, and is therefore widely used as various molded containers, including food packaging containers. However, since the biaxially oriented polystyrene sheet has poor heat resistance, when a molded product made of the biaxially oriented sheet is used as a container body or a lid material and heated in a microwave oven, deformation may occur.
For the purpose of improving the heat resistance of biaxially oriented polystyrene sheets, polystyrene-based resin sheets using heat-resistant styrene resins such as styrene-(meth)acrylic acid copolymers and styrene-maleic anhydride copolymers have been proposed (for example, Patent Documents 1 and 2, etc.).
ところで、電子レンジで加熱される食品の中には、油を多く含むものがある。このような食品を内包した容器を電子レンジで加熱した場合、（１）食品の熱が容器に伝達して容器の温度が上昇する、（２）食品に含まれる油が容器を構成する樹脂に浸透して樹脂が可塑化する、といった原因により、容器に局所的に収縮応力が発生して容器に穴が開いたり、容器が大きく変形したりする場合がある。このような現象は、１０００Ｗを超えるような高出力の電子レンジで食品を加熱した場合により顕著となる。そのため、食品包装用の容器には、高出力の電子レンジで加熱しても、穴あきや変形が生じない、高い耐熱性及び耐油性が要求されている。前述の特許文献１～２に記載のポリスチレン系樹脂シートから得られた容器は、耐熱性及び耐油性が十分ではない。 Some foods heated in microwave ovens contain a lot of oil. When a container containing such food is heated in a microwave oven, (1) the heat of the food is transferred to the container, causing the temperature of the container to rise, and (2) the oil contained in the food penetrates the resin that constitutes the container, causing the resin to plasticize. This may cause localized shrinkage stress in the container, causing holes in the container, or the container to become significantly deformed. This phenomenon is more pronounced when the food is heated in a high-power microwave oven, such as one that exceeds 1000 W. Therefore, food packaging containers are required to have high heat resistance and oil resistance so that they do not become holed or deformed even when heated in a high-power microwave oven. The containers obtained from the polystyrene resin sheets described in the above-mentioned Patent Documents 1 and 2 do not have sufficient heat resistance and oil resistance.
ポリスチレン系樹脂シートの耐油性を改良する方法として、例えば、特許文献３～５には、親水性高分子や熱可塑性エマルジョンの塗膜をポリスチレン系樹脂シートの上に形成することが提案されている。しかしながら、高出力の電子レンジで加熱する用途においては、十分な耐熱性、及び耐油性が得られない。 As a method for improving the oil resistance of polystyrene-based resin sheets, for example, Patent Documents 3 to 5 propose forming a coating film of a hydrophilic polymer or a thermoplastic emulsion on the polystyrene-based resin sheet. However, sufficient heat resistance and oil resistance cannot be obtained for applications in which the sheet is heated in a high-output microwave oven.
本発明は、耐熱性及び耐油性に優れたスチレン系二軸延伸シート及びそれを用いた容器を提供することを目的とする。さらに詳しくは、高出力の電子レンジで加熱しても変形や穴あきが生じにくい、高い耐熱性及び耐油性を備える食品包装用容器を提供できる、スチレン系二軸延伸シートを提供することを目的とするものである。 The present invention aims to provide a styrene-based biaxially oriented sheet with excellent heat resistance and oil resistance, and a container using the same. More specifically, the present invention aims to provide a styrene-based biaxially oriented sheet that can provide a food packaging container with high heat resistance and oil resistance, and is resistant to deformation and hole formation even when heated in a high-power microwave oven.
上記課題に対して、本願発明者らは鋭意検討した結果、特定の単量体単位を含むスチレン系共重合体（Ａ）、（Ｂ）を含み、かつ熱収縮開始温度が特定の温度以上であるスチレン系二軸延伸シートであれば、上記の全ての課題を解決できることを見出し、本発明を完成させるに至った。
すなわち、本発明は以下の態様を有する。
［１］シアン化ビニル単量体単位を含むスチレン系共重合体（Ａ）と、マレイミド系単量体単位を含むスチレン系共重合体（Ｂ）と、を含むスチレン系二軸延伸シートであって、前記スチレン系二軸延伸シートの長さ方向及び幅方向の熱収縮開始温度が１０７℃以上である、スチレン系二軸延伸シート。
［２］前記スチレン系二軸延伸シートの総質量に対して、前記スチレン系共重合体（Ａ）を６０～９５質量％含み、前記スチレン系共重合体（Ｂ）を５～４０質量％含む、［１］に記載のスチレン系二軸延伸シート。
［３］前記スチレン系共重合体（Ａ）が、アクリロニトリル－スチレン共重合体である、［１］または［２］に記載のスチレン系二軸延伸シート。
［４］前記マレイミド系単量体単位が、Ｎ－フェニルマレイミド単位を含む、［１］から［３］のいずれか一項に記載のスチレン系二軸延伸シート。
［５］前記スチレン系共重合体（Ｂ）中の前記Ｎ－フェニルマレイミド単位の割合が、前記スチレン系共重合体（Ｂ）の総質量に対して、３５～５５質量％である、［４］に記載のスチレン系二軸延伸シート。
［６］前記スチレン系共重合体（Ｂ）が、無水マレイン酸単位を含む、［１］から［５］のいずれか一項に記載のスチレン系二軸延伸シート。
［７］前記スチレン系共重合体（Ｂ）が、スチレン－Ｎ－フェニルマレイミド－無水マレイン酸共重合体を含む、［６］に記載のスチレン系二軸延伸シート。
［８］前記スチレン－Ｎ－フェニルマレイミド－無水マレイン酸共重合体が、さらにアクリロニトリル単位を含む、［７］に記載のスチレン系二軸延伸シート。
［９］［１］から［８］のいずれか一項に記載のスチレン系二軸延伸シートからなる容器。
［１０］食品包装用である、［９］に記載の容器。
As a result of intensive research into the above-mentioned problems, the inventors of the present application have found that a styrene-based biaxially oriented sheet containing styrene-based copolymers (A) and (B) containing specific monomer units and having a heat shrinkage onset temperature of a specific temperature or higher can solve all of the above-mentioned problems, and have thus completed the present invention.
That is, the present invention has the following aspects.
[1] A styrene-based biaxially oriented sheet comprising a styrene-based copolymer (A) containing a vinyl cyanide monomer unit and a styrene-based copolymer (B) containing a maleimide monomer unit, the styrene-based biaxially oriented sheet having a heat shrinkage onset temperature of 107°C or higher in the length direction and width direction.
[2] The styrene-based biaxially oriented sheet according to [1], wherein the styrene-based copolymer (A) is 60 to 95% by mass and the styrene-based copolymer (B) is 5 to 40% by mass, based on the total mass of the styrene-based biaxially oriented sheet.
[3] The styrenic biaxially stretched sheet according to [1] or [2], wherein the styrenic copolymer (A) is an acrylonitrile-styrene copolymer.
[4] The styrene-based biaxially stretched sheet according to any one of [1] to [3], wherein the maleimide-based monomer unit contains an N-phenylmaleimide unit.
[5] The styrene-based biaxially stretched sheet according to [4], wherein the ratio of the N-phenylmaleimide unit in the styrene-based copolymer (B) is 35 to 55 mass% with respect to the total mass of the styrene-based copolymer (B).
[6] The styrene-based biaxially oriented sheet according to any one of [1] to [5], wherein the styrene-based copolymer (B) contains maleic anhydride units.
[7] The styrene-based biaxially stretched sheet according to [6], wherein the styrene-based copolymer (B) contains a styrene-N-phenylmaleimide-maleic anhydride copolymer.
[8] The styrene-based biaxially stretched sheet according to [7], wherein the styrene-N-phenylmaleimide-maleic anhydride copolymer further contains acrylonitrile units.
[9] A container made of the styrene-based biaxially oriented sheet according to any one of [1] to [8].
[10] The container according to [9], which is for food packaging.
本発明によれば、耐熱性及び耐油性に優れたスチレン系二軸延伸シート及びそれを用いた容器を提供できる。 The present invention provides a styrene-based biaxially oriented sheet with excellent heat resistance and oil resistance, and a container using the same.
以下、本発明を詳細に説明するが、本発明は以下の態様に限定されるものではない。
［スチレン系二軸延伸シート］
本発明に係るスチレン系二軸延伸シートは、シアン化ビニル単量体単位を含むスチレン系共重合体（Ａ）と、マレイミド系単量体単位を含むスチレン系共重合体（Ｂ）と、を含むスチレン系二軸延伸シートであって、前記スチレン系二軸延伸シートの長さ方向及び幅方向の熱収縮開始温度が１０７℃以上であることを特徴とする。このようなスチレン系二軸延伸シート（以下、単に「延伸シート」と記載することもある）は、耐熱性及び耐油性に優れている。そのため、本発明に係るスチレン系二軸延伸シートからなる容器は、食品等の内容物を内包して高出力の電子レンジで加熱しても、穴あきや変形が生じにくい。なお、本明細書において「二軸延伸シート」とは、無延伸シートを、長さ方向及び幅方向に逐次延伸又は同時に延伸した、樹脂シートのことを意味する。
The present invention will be described in detail below, but the present invention is not limited to the following embodiments.
[Styrene-based biaxially oriented sheet]
The styrene-based biaxially stretched sheet according to the present invention is a styrene-based biaxially stretched sheet containing a styrene-based copolymer (A) containing a vinyl cyanide monomer unit and a styrene-based copolymer (B) containing a maleimide monomer unit, characterized in that the heat shrinkage start temperature in the length direction and width direction of the styrene-based biaxially stretched sheet is 107°C or higher. Such a styrene-based biaxially stretched sheet (hereinafter sometimes simply referred to as "stretched sheet") has excellent heat resistance and oil resistance. Therefore, a container made of the styrene-based biaxially stretched sheet according to the present invention is unlikely to be perforated or deformed even if it contains contents such as food and is heated in a high-power microwave oven. In this specification, the "biaxially stretched sheet" means a resin sheet obtained by sequentially or simultaneously stretching an unstretched sheet in the length direction and width direction.
本発明に係るスチレン系二軸延伸シートの長さ方向及び幅方向の熱収縮開始温度は１０７℃以上である。前記熱収縮開始温度の上限は特に限定されない。好ましい態様においては、前記熱収縮開始温度は１０７℃以上１３０℃以下であってもよく、１１０～１２３℃であってもよい。なお、本明細書において、「スチレン系二軸延伸シートの長さ方向」とは、延伸シートを成形する際の樹脂の流れ方向（ＭＤの方向）を意味する。また、「スチレン系二軸延伸シートの幅方向」とは、前記長さ方向に対して直交する方向を意味する。本明細書においては、スチレン系二軸延伸シートの長さ方向を「ＭＤ方向」と記載し、「幅方向」を「ＴＤ方向」と記載することもある。
本発明における、延伸シートのＭＤ方向及びＴＤ方向の熱収縮開始温度は、具体的には以下の方法で測定した値を意味する。
＜熱収縮開始温度の測定方法＞
熱収縮応力測定機（テスター産業（株）製、製品名：「ＴＰ－５０１」）を用いて測定する。具体的には、作製した二軸延伸シートを、１５０ｍｍ（ＭＤ方向）×１５ｍｍ（ＴＤ方向）に切り出して測定サンプルを調製する。前記延伸シートのサンプルを、チャック間距離１００ｍｍとなるように前記測定器のチャック部分で把持して、９０℃以下の油浴に浸漬させる。その後、油浴の温度を０．５℃／分の昇温速度で、９０℃から１４０℃まで昇温させる。この際、延伸シートのＭＤ方向又はＴＤ方向に熱収縮が発生して、熱収縮応力が０．０５ＭＰａ以上に達した時の温度を、ＭＤ方向又はＴＤ方向の熱収縮開始温度とする。
The heat shrinkage start temperature in the length direction and width direction of the styrene-based biaxially stretched sheet according to the present invention is 107°C or more. The upper limit of the heat shrinkage start temperature is not particularly limited. In a preferred embodiment, the heat shrinkage start temperature may be 107°C or more and 130°C or less, or may be 110 to 123°C. In this specification, the "length direction of the styrene-based biaxially stretched sheet" means the flow direction (MD direction) of the resin when forming the stretched sheet. In addition, the "width direction of the styrene-based biaxially stretched sheet" means a direction perpendicular to the length direction. In this specification, the length direction of the styrene-based biaxially stretched sheet may be referred to as the "MD direction", and the "width direction" may be referred to as the "TD direction".
In the present invention, the heat shrinkage initiation temperatures in the MD and TD directions of the stretched sheet specifically refer to values measured by the following method.
<Method for measuring heat shrinkage starting temperature>
The measurement is performed using a heat shrinkage stress measuring instrument (manufactured by Tester Sangyo Co., Ltd., product name: "TP-501"). Specifically, the produced biaxially stretched sheet is cut into a size of 150 mm (MD direction) x 15 mm (TD direction) to prepare a measurement sample. The stretched sheet sample is held by the chuck portion of the measuring instrument so that the chuck distance is 100 mm, and immersed in an oil bath of 90°C or less. Thereafter, the temperature of the oil bath is increased from 90°C to 140°C at a heating rate of 0.5°C/min. At this time, the temperature at which heat shrinkage occurs in the MD or TD direction of the stretched sheet and the heat shrinkage stress reaches 0.05 MPa or more is defined as the heat shrinkage start temperature in the MD or TD direction.
（スチレン系共重合体（Ａ））
本発明に係るスチレン系二軸延伸シートは、シアン化ビニル単量体単位を含むスチレン系共重合体（Ａ）（以下、単に「共重合体（Ａ）」と記載する）を含む。スチレン系二軸延伸シートが共重合体（Ａ）を含むことにより、耐油性が良好となり、レンジ加熱時に穴あきが発生しにくい。なお、本明細書において、「スチレン系共重合体」とは、スチレン系単量体単位を含む共重合体を意味する。すなわち、「共重合体（Ａ）」は、単量体単位として、少なくともスチレン系単量体単位と、シアン化ビニル単量体単位とを含む。
スチレン系二軸延伸シート中の共重合体（Ａ）の含有量は、スチレン系二軸延伸シートの総質量に対して、６０～９５質量％が好ましく、６５～８５質量％がより好ましく、６５～７５質量％が特に好ましい。共重合体（Ａ）の含有量が前記範囲内であれば、スチレン系二軸延伸シートの耐熱性及び耐油性が向上しやすくなる。なお、「スチレン系二軸延伸シートの総質量」とは、スチレン系二軸延伸シートを構成する樹脂組成物の総質量のことを意味する。
(Styrene-based copolymer (A))
The styrene-based biaxially oriented sheet according to the present invention contains a styrene-based copolymer (A) (hereinafter simply referred to as "copolymer (A)") containing a vinyl cyanide monomer unit. The styrene-based biaxially oriented sheet contains copolymer (A), which improves oil resistance and makes it less likely to develop holes during heating in a microwave oven. In this specification, "styrene-based copolymer" means a copolymer containing a styrene-based monomer unit. That is, "copolymer (A)" contains at least a styrene-based monomer unit and a vinyl cyanide monomer unit as monomer units.
The content of copolymer (A) in the styrene-based biaxially oriented sheet is preferably 60 to 95% by mass, more preferably 65 to 85% by mass, and particularly preferably 65 to 75% by mass, based on the total mass of the styrene-based biaxially oriented sheet. If the content of copolymer (A) is within the above range, the heat resistance and oil resistance of the styrene-based biaxially oriented sheet are likely to be improved. Note that the "total mass of the styrene-based biaxially oriented sheet" means the total mass of the resin composition constituting the styrene-based biaxially oriented sheet.
スチレン系単量体単位を構成するスチレン系単量体としては、例えば、スチレン、α－メチルスチレン、ｐ－メチルスチレン、ｏ－メチルスチレン、ｍ－メチルスチレン、エチルスチレン、ｐ－ｔ－ブチルスチレン等が挙げられる。これらスチレン系単量体は、１種単独で用いられてもよく、２種以上を併用してもよい。このうち、スチレンを含むことが好ましい。
共重合体（Ａ）中のスチレン系単量体単位の割合は、共重合体（Ａ）の総質量に対して、６０～９０質量％であることが好ましく、６５～８０質量％であることがより好ましく、６８～７６質量％がさらに好ましい。スチレン系単量体単位の割合が前記範囲内であれば、延伸シートの色相が良好となりやすい。
Examples of styrene monomers constituting the styrene monomer units include styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene, and p-t-butylstyrene. These styrene monomers may be used alone or in combination of two or more. Among these, it is preferable to use styrene.
The proportion of the styrene-based monomer units in the copolymer (A) is preferably 60 to 90% by mass, more preferably 65 to 80% by mass, and even more preferably 68 to 76% by mass, based on the total mass of the copolymer (A). When the proportion of the styrene-based monomer units is within the above range, the hue of the stretched sheet tends to be good.
シアン化ビニル単量体単位を構成するシアン化ビニル単量体としては、例えば、アクリロニトリル、メタクリロニトリル、シアノ（メタ）アクリレート等が挙げられる。これらシアン化ビニル単量体は、１種単独で用いられてもよく、２種以上を併用してもよい。このうち、耐油性がより向上しやすい観点から、シアン化ビニル単量体としては、アクリロニトリルを含むことが好ましい。
共重合体（Ａ）中のシアン化ビニル単量体単位の割合は、共重合体（Ａ）の総質量に対して、１０～４０質量％であることが好ましく、１８～３５質量％であることがより好ましく、２４～３２質量％であることがさらに好ましい。シアン化ビニル単量体単位の割合が前記範囲内であれば、延伸シートの色相、シート外観、製膜性がより良好となりやすい。
Examples of the vinyl cyanide monomer constituting the vinyl cyanide monomer unit include acrylonitrile, methacrylonitrile, and cyano(meth)acrylate. These vinyl cyanide monomers may be used alone or in combination of two or more. Among these, it is preferable that the vinyl cyanide monomer contains acrylonitrile, from the viewpoint of easier improvement of oil resistance.
The proportion of the vinyl cyanide monomer unit in the copolymer (A) is preferably 10 to 40 mass%, more preferably 18 to 35 mass%, and even more preferably 24 to 32 mass%, based on the total mass of the copolymer (A). When the proportion of the vinyl cyanide monomer unit is within the above range, the hue, sheet appearance, and film formability of the stretched sheet tend to be better.
共重合体（Ａ）は、必要に応じて、スチレン系単量体単位とシアン化ビニル単量体単位以外の単量体単位（その他の単量体単位（ｘ））を含んでいてもよい。その他の単量体単位（ｘ）としては、ビニル系単量体単位が挙げられ、例えば、（メタ）アクリル酸、無水マレイン酸、メチル（メタ）アクリレート、エチル（メタ）アクリレート、ｎ－ブチル（メタ）アクリレート、２－メチルヘキシル（メタ）アクリレート、２－エチルヘキシル（メタ）アクリレート、デシル（メタ）アクリレート、ジシクロペンタニル（メタ）アクリレート、イソボルニル（メタ）アクリレート等の（メタ）アクリレート等が挙げられる。これらは、１種単独で用いられてもよく、２種以上を併用してもよい。なお、「（メタ）アクリル酸」は、アクリル酸及びメタクリル酸を意味する。また、「（メタ）アクリレート」は、アクリレート及びメタクリレートを意味する。
共重合体（Ａ）がその他の単量体単位（ｘ）を含む場合、共重合体（Ａ）の総質量に対して、１０質量％未満であることが好ましく、１～５質量％であることがより好ましい。
The copolymer (A) may contain a monomer unit (other monomer unit (x)) other than the styrene-based monomer unit and the vinyl cyanide monomer unit, as necessary. Examples of the other monomer units (x) include vinyl-based monomer units, such as (meth)acrylic acid, maleic anhydride, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-methylhexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate. These may be used alone or in combination of two or more. The term "(meth)acrylic acid" refers to acrylic acid and methacrylic acid. The term "(meth)acrylate" refers to acrylate and methacrylate.
When the copolymer (A) contains other monomer units (x), the content of such units is preferably less than 10% by mass, more preferably 1 to 5% by mass, based on the total mass of the copolymer (A).
共重合体（Ａ）は、アクリロニトリル－スチレン共重合体であることが好ましい。すなわち、本発明に係るスチレン系二軸延伸シートは、アクリロニトリル－スチレン共重合体を含むことが好ましい。共重合体（Ａ）がアクリロニトリル－スチレン共重合体であれば、耐熱性及び耐油性がより向上しやすくなる。アクリロニトリル－スチレン共重合体中の、アクリロニトリル単位及びスチレン単位の好ましい割合は、前述のシアン化ビニル単量体単位及びスチレン系単量体単位と同じである。 The copolymer (A) is preferably an acrylonitrile-styrene copolymer. That is, the styrene-based biaxially oriented sheet according to the present invention preferably contains an acrylonitrile-styrene copolymer. If the copolymer (A) is an acrylonitrile-styrene copolymer, the heat resistance and oil resistance are more likely to be improved. The preferred ratio of acrylonitrile units and styrene units in the acrylonitrile-styrene copolymer is the same as the vinyl cyanide monomer units and styrene-based monomer units described above.
共重合体（Ａ）は、シアン化ビニル単量体と、スチレン系単量体とを含む単量体混合物、好ましくは、アクリロニトリルとスチレンとを重合して得られる。重合方法としては特に限定されないが、臭気を低減しやすい観点から、塊状連続重合が好ましい。
１つの態様においては、共重合体（Ａ）は、複数の共重合体の混合物であってもよい。この場合、各共重合体を任意の方法で重合したのち、複数の共重合体を混合して共重合体（Ａ）としてもよい。
The copolymer (A) is obtained by polymerizing a monomer mixture containing a vinyl cyanide monomer and a styrene-based monomer, preferably acrylonitrile and styrene. The polymerization method is not particularly limited, but from the viewpoint of easily reducing odor, bulk continuous polymerization is preferred.
In one embodiment, the copolymer (A) may be a mixture of multiple copolymers. In this case, each copolymer may be polymerized by any method, and then the multiple copolymers may be mixed to obtain the copolymer (A).
塊状連続重合としては公知の方法を採用することができる。このうち、エチルベンゼン、トルエン、メチルエチルケトン等の溶剤を単量体混合物１００質量部に対して、１０～４０質量部添加して重合を行うことが好ましい。また、重合時に、従来公知の有機過酸化物、分子量調整剤等を必要に応じて添加することができる。
重合温度は、８０～１７０℃が好ましく、１００～１６０℃であることがより好ましい。
A known method can be used for the bulk continuous polymerization. Among these, it is preferable to carry out the polymerization by adding 10 to 40 parts by mass of a solvent such as ethylbenzene, toluene, or methyl ethyl ketone to 100 parts by mass of the monomer mixture. Furthermore, during the polymerization, a conventionally known organic peroxide, a molecular weight modifier, or the like can be added as necessary.
The polymerization temperature is preferably from 80 to 170°C, and more preferably from 100 to 160°C.
共重合体（Ａ）の重量平均分子量（Ｍｗ）は、５０，０００～２５０，０００であることが好ましく、１００，０００～２００，０００であることがより好ましい。共重合体（Ａ）のＭｗが５０，０００～２５０，０００であれば、延伸シートの強度が良好となりやすい。また、製膜性も良好となりやすい。また、共重合体（Ａ）のＭｗと数平均分子量（Ｍｎ）との比である多分散度（Ｍｗ／Ｍｎ）は、２．０～３．０が好ましく、２．１～２．５であることがより好ましい。共重合体（Ａ）の多分散度が２．０～３．０であれば、延伸シートの強度が低下しにくく、耐油性もより良好となりやすい。なお、共重合体（Ａ）のＭｗ及びＭｎはＧＰＣ（ゲルパーミエーションクロマトグラフィ）により、ポリスチレン換算によって算出した値を指す。具体的には、以下の条件で測定した値を指す。
＜共重合体（Ａ）のＭｗ及びＭｎの測定方法＞
装置：Ｓｈｏｄｅｘ（株）製、製品名：「Ｓｈｏｄｅｘ ＳＹＳＴＥＭ－２１」
カラム：ＰＬｇｅｌ ＭＩＸＥＤ－Ｂ
測定温度：４０℃
溶媒：テトラヒドロフラン
流量：１．０ｍＬ／分
検出方法：ＲＩ
サンプル濃度：０．２質量％
注入量：１００μＬ
検量線：標準ポリスチレン（Ｐｏｌｙｍｅｒ Ｌａｂｏｒａｔｏｒｉｅｓ製）
The weight average molecular weight (Mw) of the copolymer (A) is preferably 50,000 to 250,000, more preferably 100,000 to 200,000. If the Mw of the copolymer (A) is 50,000 to 250,000, the strength of the stretched sheet is likely to be good. Also, the film formability is likely to be good. Also, the polydispersity (Mw/Mn), which is the ratio of the Mw to the number average molecular weight (Mn) of the copolymer (A), is preferably 2.0 to 3.0, more preferably 2.1 to 2.5. If the polydispersity of the copolymer (A) is 2.0 to 3.0, the strength of the stretched sheet is unlikely to decrease, and the oil resistance is likely to be better. The Mw and Mn of the copolymer (A) refer to values calculated in terms of polystyrene by GPC (gel permeation chromatography). Specifically, they refer to values measured under the following conditions.
<Method of measuring Mw and Mn of copolymer (A)>
Apparatus: Shodex Co., Ltd., product name: "Shodex SYSTEM-21"
Column: PLgel MIXED-B
Measurement temperature: 40°C
Solvent: Tetrahydrofuran Flow rate: 1.0 mL/min Detection method: RI
Sample concentration: 0.2% by mass
Injection volume: 100 μL
Calibration curve: Standard polystyrene (manufactured by Polymer Laboratories)
共重合体（Ａ）のＪＩＳ Ｋ ７２０６ Ｂ５０法の条件で測定したビカット軟化温度（ＶＳＴ）は、１００～１２０℃であることが好ましく、１０５～１１５℃であることがより好ましく、１０７～１１０℃であることがさらに好ましい。共重合体（Ａ）のＶＳＴが前記範囲内であれば、製膜性が良好となりやすい。 The Vicat softening temperature (VST) of copolymer (A) measured under the conditions of JIS K 7206 B50 method is preferably 100 to 120°C, more preferably 105 to 115°C, and even more preferably 107 to 110°C. If the VST of copolymer (A) is within the above range, the film-forming properties are likely to be good.
（スチレン系共重合体（Ｂ））
本発明に係るスチレン系二軸延伸シートは、マレイミド系単量体単位を含むスチレン系共重合体（Ｂ）（以下、単に「共重合体（Ｂ）」と記載する）を含む。スチレン系二軸延伸シートが共重合体（Ｂ）を含むことにより、延伸シートの耐熱性及び耐油性が向上する。本明細書において、「共重合体（Ｂ）」は、単量体単位として、少なくともスチレン系単量体単位と、マレイミド系単量体単位とを含む。
スチレン系二軸延伸シート中の共重合体（Ｂ）の含有量は、スチレン系二軸延伸シートの総質量に対して、５～４０質量％が好ましく、１５～３５質量％がより好ましく２５～３５質量％が特に好ましい。共重合体（Ｂ）の含有量が前記範囲内であれば、スチレン系二軸延伸シートの耐熱性及び耐油性がより向上しやすくなる。
(Styrene-based copolymer (B))
The styrene-based biaxially stretched sheet according to the present invention contains a styrene-based copolymer (B) (hereinafter simply referred to as "copolymer (B)") containing a maleimide-based monomer unit. When the styrene-based biaxially stretched sheet contains copolymer (B), the heat resistance and oil resistance of the stretched sheet are improved. In this specification, "copolymer (B)" contains at least a styrene-based monomer unit and a maleimide-based monomer unit as monomer units.
The content of the copolymer (B) in the styrene-based biaxially oriented sheet is preferably 5 to 40 mass%, more preferably 15 to 35 mass%, and particularly preferably 25 to 35 mass%, based on the total mass of the styrene-based biaxially oriented sheet. When the content of the copolymer (B) is within the above range, the heat resistance and oil resistance of the styrene-based biaxially oriented sheet are more likely to be improved.
共重合体（Ｂ）に含まれる、スチレン系単量体単位を構成するスチレン系単量体としては、共重合体（Ａ）と同じものが挙げられ、好ましい例もまた同じである。スチレン系単量体は、１種単独で用いられてもよく、２種以上を併用してもよい。このうち、スチレンを含むことが好ましい。
共重合体（Ｂ）中のスチレン系単量体単位の割合は、共重合体（Ｂ）の総質量に対して、４０～６０質量％であることが好ましく、４５～５５質量％であることがより好ましく、４７～５３質量％であることがさらに好ましい。スチレン系単量体単位の割合が前記範囲内であれば、延伸シートの外観が良好となりやすい。
The styrene monomer constituting the styrene monomer unit contained in the copolymer (B) may be the same as that of the copolymer (A), and the preferred examples are also the same. The styrene monomer may be used alone or in combination of two or more kinds. Among these, it is preferable to contain styrene.
The proportion of the styrene-based monomer units in the copolymer (B) is preferably 40 to 60 mass%, more preferably 45 to 55 mass%, and even more preferably 47 to 53 mass%, based on the total mass of the copolymer (B). When the proportion of the styrene-based monomer units is within the above range, the appearance of the stretched sheet tends to be good.
マレイミド系単量体単位を構成するマレイミド系単量体としては、例えば、マレイミド、Ｎ－メチルマレイミド、Ｎ－エチルマレイミド、Ｎ－プロピルマレイミド、Ｎ－イソプロピルマレイミド、Ｎ－シクロヘキシルマレイミド、Ｎ－フェニルマレイミド、Ｎ－トルイルマレイミド、Ｎ－キシリールマレイミド、Ｎ－ナフチルマレイミド、Ｎ－ｔ－ブチルマレイミド、Ｎ－オルトクロルフェニルマレイミド、Ｎ－オルトメトキシフェニルマレイミド等が挙げられる。これらは、１種単独で用いられてもよく、２種以上を併用してもよい。このうち、マレイミド系単量体としては、マレイミド、又はＮ－フェニルマレイミドを含むことが好ましい。マレイミド系単量体単位が、Ｎ－フェニルマレイミドを含む場合、マレイミド系単量体単位中のＮ－フェニルマレイミド単位の割合は、延伸シートの耐熱性向上、および黄色味抑制の観点から、マレイミド系単量体単位の総質量に対して、３５～５０質量％が好ましく、４０～４５質量％がより好ましい。１つの態様においては、マレイミド系単量体単位は、Ｎ－フェニルマレイミド単位のみから構成されていてもよい。
共重合体（Ｂ）中のマレイミド系単量体単位の割合は、共重合体（Ｂ）の総質量に対して、３５～６０質量％であることが好ましく、３８～５５質量％であることがより好ましく、４０～５２質量％であることがさらに好ましい。マレイミド系単量体単位の割合が前記範囲内であれば、耐熱性がより向上しやすく、かつ延伸シートの色相がより良好となりやすい。
共重合体（Ｂ）がＮ－フェニルマレイミド単位を含む場合、共重合体（Ｂ）中のＮ－フェニルマレイミドの割合は、共重合体（Ｂ）の総質量に対して、３５～５５質量％が好ましく、４０～５２質量％であることがより好ましい。
Examples of maleimide monomers constituting the maleimide monomer unit include maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-toluylmaleimide, N-xylylmaleimide, N-naphthylmaleimide, N-t-butylmaleimide, N-orthochlorophenylmaleimide, and N-orthomethoxyphenylmaleimide. These may be used alone or in combination of two or more. Of these, the maleimide monomer preferably contains maleimide or N-phenylmaleimide. When the maleimide monomer unit contains N-phenylmaleimide, the proportion of the N-phenylmaleimide unit in the maleimide monomer unit is preferably 35 to 50 mass %, more preferably 40 to 45 mass %, based on the total mass of the maleimide monomer units, from the viewpoints of improving the heat resistance of the stretched sheet and suppressing yellowing. In one embodiment, the maleimide monomer unit may be composed only of the N-phenylmaleimide unit.
The proportion of the maleimide monomer units in copolymer (B) is preferably 35 to 60 mass%, more preferably 38 to 55 mass%, and even more preferably 40 to 52 mass%, based on the total mass of copolymer (B). When the proportion of the maleimide monomer units is within the above range, heat resistance is more likely to be improved and the hue of the stretched sheet is more likely to be improved.
When the copolymer (B) contains an N-phenylmaleimide unit, the proportion of N-phenylmaleimide in the copolymer (B) is preferably 35 to 55 mass%, and more preferably 40 to 52 mass%, based on the total mass of the copolymer (B).
共重合体（Ｂ）は、必要に応じて、スチレン系単量体単位とマレイミド系単量体単位以外の単量体単位を含んでいてもよい。前記単量体単位としては、前述のその他の単量体単位（ｘ）が挙げられる。このうち、耐熱性がより向上しやすい観点から、その他の単量体単位（ｘ）としては、無水マレイン酸単位を含むことが好ましい。共重合体（Ｂ）がその他の単量体単位（ｘ）を含む場合、共重合体（Ｂ）の総質量に対して、１０質量％未満であることが好ましく、１～８質量％であることがより好ましい。また、共重合体（Ｂ）が無水マレイン酸単位を含む場合、共重合体（Ｂ）の総質量に対する無水マレイン酸単位の割合は、０．１～２質量％が好ましく、０．３～１．１質量％がより好ましい。無水マレイン酸単位の割合が前記範囲内であれば、共重合体（Ａ）と共重合体（Ｂ）との相溶性が良好となりやすい。 The copolymer (B) may contain a monomer unit other than the styrene-based monomer unit and the maleimide-based monomer unit, if necessary. Examples of the monomer unit include the other monomer unit (x) described above. Among these, from the viewpoint of easier improvement of heat resistance, it is preferable that the other monomer unit (x) contains a maleic anhydride unit. When the copolymer (B) contains the other monomer unit (x), it is preferable that the other monomer unit (x) contains less than 10% by mass, more preferably 1 to 8% by mass, based on the total mass of the copolymer (B). Furthermore, when the copolymer (B) contains the maleic anhydride unit, the ratio of the maleic anhydride unit to the total mass of the copolymer (B) is preferably 0.1 to 2% by mass, more preferably 0.3 to 1.1% by mass. If the ratio of the maleic anhydride unit is within the above range, the compatibility between the copolymer (A) and the copolymer (B) is likely to be good.
共重合体（Ｂ）は、スチレン－Ｎ－フェニルマレイミド－無水マレイン酸共重合体を含むことが好ましい。共重合体（Ｂ）がスチレン－Ｎ－フェニルマレイミド－無水マレイン酸共重合体を含むことにより、延伸シートの耐熱性及び耐油性がより向上しやすくなる。
共重合体（Ｂ）中の、スチレン－Ｎ－フェニルマレイミド－無水マレイン酸共重合体の割合は、共重合体（Ｂ）の総質量に対して、９０～１００質量％が好ましく、９２～１００質量％がより好ましい。好ましい態様においては、共重合体（Ｂ）は、スチレン－Ｎ－フェニルマレイミド－無水マレイン酸共重合体であってもよい。
The copolymer (B) preferably contains a styrene-N-phenylmaleimide-maleic anhydride copolymer, which makes it easier to improve the heat resistance and oil resistance of the stretched sheet.
The proportion of the styrene-N-phenylmaleimide-maleic anhydride copolymer in the copolymer (B) is preferably 90 to 100 mass%, more preferably 92 to 100 mass%, based on the total mass of the copolymer (B). In a preferred embodiment, the copolymer (B) may be a styrene-N-phenylmaleimide-maleic anhydride copolymer.
前記スチレン－Ｎ－フェニルマレイミド－無水マレイン酸共重合体は、さらにアクリロニトリル単位を含んでいてもよい。スチレン－Ｎ－フェニルマレイミド－無水マレイン酸共重合体がアクリロニトリル単位を含む場合、その割合は、共重合体（Ａ）と共重合体（Ｂ）との相溶性が悪化しにくく、かつ外観をより良好とする観点から、前記共重合体の総質量に対して、１０質量％未満であることが好ましく、０～８質量％であることがより好ましい。 The styrene-N-phenylmaleimide-maleic anhydride copolymer may further contain acrylonitrile units. When the styrene-N-phenylmaleimide-maleic anhydride copolymer contains acrylonitrile units, the proportion of the acrylonitrile units is preferably less than 10% by mass, and more preferably 0 to 8% by mass, based on the total mass of the copolymer, from the viewpoint of preventing the compatibility between copolymer (A) and copolymer (B) from deteriorating and improving the appearance.
共重合体（Ｂ）は、マレイミド系単量体と、スチレン系単量体とを含む単量体混合物とを重合して得られる。共重合体（Ｂ）は、スチレン、Ｎ－フェニルマレイミド、無水マレイン酸及び、必要に応じてアクリロニトリルを重合して得られるものであってもよい。
１つの態様においては、共重合体（Ｂ）は、複数の共重合体の混合物であってもよい。この場合、各共重合体を任意の方法で重合したのち、複数の共重合体を混合して共重合体（Ｂ）としてもよい。
The copolymer (B) is obtained by polymerizing a monomer mixture containing a maleimide monomer and a styrene monomer, and may be obtained by polymerizing styrene, N-phenylmaleimide, maleic anhydride, and, if necessary, acrylonitrile.
In one embodiment, the copolymer (B) may be a mixture of multiple copolymers. In this case, each copolymer may be polymerized by any method, and then the multiple copolymers may be mixed to obtain the copolymer (B).
重合方法としては、例えば、溶液重合、塊状重合を用いることができる。 Polymerization methods that can be used include, for example, solution polymerization and bulk polymerization.
共重合体（Ｂ）の重量平均分子量（Ｍｗ）は、５０，０００～１５０，０００であることが好ましく、８０，０００～１４０，０００であることがより好ましい。共重合体（Ｂ）のＭｗが前記範囲内であれば、外観が良好となりやすい。また、共重合体（Ｂ）の多分散度（Ｍｗ／Ｍｎ）は、２．０～３．０が好ましく、２．３～２．８がより好ましい。共重合体（Ｂ）の多分散度が前記範囲内であれば、共重合体（Ａ）への相溶性が良好となりやすい。なお、共重合体（Ｂ）のＭｗ及びＭｎはＧＰＣ（ゲルパーミエーションクロマトグラフィ）により、ポリスチレン換算によって算出した値を指す。具体的には、前述の共重合体（Ａ）と同様の条件で測定することができる。 The weight average molecular weight (Mw) of copolymer (B) is preferably 50,000 to 150,000, more preferably 80,000 to 140,000. If the Mw of copolymer (B) is within the above range, the appearance is likely to be good. The polydispersity (Mw/Mn) of copolymer (B) is preferably 2.0 to 3.0, more preferably 2.3 to 2.8. If the polydispersity of copolymer (B) is within the above range, the compatibility with copolymer (A) is likely to be good. The Mw and Mn of copolymer (B) refer to values calculated in terms of polystyrene by GPC (gel permeation chromatography). Specifically, they can be measured under the same conditions as those for copolymer (A) described above.
共重合体（Ｂ）のＭＦＲ（Ｍｅｌｔ Ｆｌｏｗ Ｒａｔｅ）は、１．０～１００ｇ／１０分であることが好ましく、３～７０ｇ／１０分であることがより好ましい。共重合体（Ｂ）のＭＦＲが前記範囲内であれば、外観が良好となりやすい。なお、前記ＭＦＲは２６５℃、９８Ｎの荷重条件下で、ＪＩＳ Ｋ ７２１０に従って測定した値のことを指す。 The MFR (Melt Flow Rate) of copolymer (B) is preferably 1.0 to 100 g/10 min, and more preferably 3 to 70 g/10 min. If the MFR of copolymer (B) is within the above range, the appearance tends to be good. The MFR is a value measured according to JIS K 7210 under conditions of 265°C and a load of 98 N.
（その他成分）
本発明に係るスチレン系二軸延伸シートは、共重合体（Ａ）と共重合体（Ｂ）以外のその他の樹脂を含んでいてもよい。その他の樹脂としては、例えば、共重合体（Ａ）、（Ｂ）以外のスチレン系共重合体、ハイインパクトポリスチレン、ＡＢＳ樹脂、ＡＥＳ樹脂、スチレン－ブタジエンブロック共重合体樹脂等のゴム強化樹脂等が挙げられる。延伸シートがその他の樹脂を含む場合、透明性、耐熱性の観点から、延伸シートの総質量に対して、３質量％未満であることが好ましい。
(Other ingredients)
The styrene-based biaxially stretched sheet according to the present invention may contain other resins in addition to the copolymer (A) and the copolymer (B). Examples of other resins include styrene-based copolymers other than the copolymers (A) and (B), high impact polystyrene, rubber-reinforced resins such as ABS resins, AES resins, and styrene-butadiene block copolymer resins. When the stretched sheet contains other resins, the amount of the other resins is preferably less than 3% by mass with respect to the total mass of the stretched sheet from the viewpoints of transparency and heat resistance.
また、延伸シートは、必要に応じて、紫外線吸収剤、光安定剤、酸化防止剤、滑剤、可塑剤、着色剤、帯電防止剤、難燃剤、鉱油等のその他添加剤、ガラス繊維、カーボン繊維、アラミド繊維等の補強繊維、タルク、シリカ、マイカ、炭酸カルシウム等の充填剤等を含むことができる。これらは１種単独で用いられてもよく、２種以上を併用してもよい。 The stretched sheet may also contain, as necessary, other additives such as ultraviolet absorbers, light stabilizers, antioxidants, lubricants, plasticizers, colorants, antistatic agents, flame retardants, and mineral oils, reinforcing fibers such as glass fibers, carbon fibers, and aramid fibers, and fillers such as talc, silica, mica, and calcium carbonate. These may be used alone or in combination of two or more.
紫外線吸収剤としては、例えば、２－（５’－メチル－２’－ヒドロキシフェニル）ベンゾトリアゾ－ル、２－（５’－ｔ－ブチル－２’－ヒドロキシフェニル）ベンゾトリアゾ－ル、２－［２’－ヒドロキシ－３’，５’－ビス（α、α－ジメチルベンジル）フェニル］ベンゾトリアゾ－ル、２－（３’，５’－ジ－ｔ－ブチル－２’－ヒドロキシフェニル）ベンゾトリアゾ－ル、２－（３’－ｔ－ブチル－５’－メチル－２’－ヒドロキシフェニル）－５－クロロベンゾトリアゾ－ル、２－（３’，５’－ジ－ｔ－ブチル－２’－ヒドロキシフェニル）－５－クロロベンゾトリアゾ－ル、２－（３’，５’－ジ－ｔ－アミル－２’－ヒドロキシフェニル）ベンゾトリアゾ－ル、２－［３’－（３”，４”，５”，６”－テトラヒドロ・フタルイミドメチル）－５’－メチル－２’－ヒドロキシフェニル］ベンゾトリアゾ－ル、２，２’－メチレンビス［４－（１，１，３，３－テトラメチルブチル）－６－（２Ｈ－ベンゾトリアゾ－ル－２－イル）フェノ－ル］等のベンゾトリアゾ－ル系紫外線吸収剤；２－エトキシ－２’－エチル蓚酸ビスアニリド、２－エトキシ－５－ｔ－ブチル－２’－エチル蓚酸ビスアニリド、２－エトキシ－４’－イソデシルフェニル蓚酸ビスアニリド等の蓚酸アニリド系紫外線吸収剤；２－ヒドロキシ－４－ｎ－オクトキシベンゾフェノン、２，４－ジヒドロキシベンゾフェノン、２－ヒドロキシ－４－メトキシベンゾフェノン、２－ヒドロキシ－４－メトキシ－５－スルホベンゾフェノン、２，２’－ジヒドロキシ－４－メトキシベンゾフェノン、２，２’－ジヒドロキシ－４，４’－ジメトキシベンゾフェノン、２－ヒドロキシ－４－メトキシ－２’－カルボキシベンゾフェノン等のベンゾフェノン系紫外線吸収剤；フェニルサリシレ－ト、ｐ－ｔ－ブチルフェニルサリシレ－ト、ｐ－オクチルフェニルサリシレ－ト等のサリチル酸系紫外線吸収剤；２－エチルヘキシル－２－シアノ－３，３’－ジフェニルアクリレ－ト、エチル－２－シアノ－３，３’－ジフェニルアクリレ－ト等のシアノアクリレ－ト系紫外線吸収剤；ルチル型酸化チタン、アナタ－ゼ型酸化チタン、アルミナ、シリカ、シランカップリング剤、チタン系カップリング剤等の表面処理剤で処理された酸化チタン等の酸化チタン系紫外線安定剤等が挙げられる。これらは１種単独で用いられてもよく、２種以上を併用してもよい。 Examples of ultraviolet absorbers include 2-(5'-methyl-2'-hydroxyphenyl)benzotriazole, 2-(5'-t-butyl-2'-hydroxyphenyl)benzotriazole, 2-[2'-hydroxy-3',5'-bis(α,α-dimethylbenzyl)phenyl]benzotriazole, 2-(3',5'-di-t-butyl-2'-hydroxyphenyl)benzotriazole, 2-(3'-t-butyl-5'-methyl-2'-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3',5'-di-t-butyl-2'-hydroxyphenyl)-5-chlorobenzotriazole, benzotriazole-based ultraviolet absorbers such as 2-(3',5'-di-t-amyl-2'-hydroxyphenyl)benzotriazole, 2-[3'-(3",4",5",6"-tetrahydrophthalimidomethyl)-5'-methyl-2'-hydroxyphenyl]benzotriazole, and 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole-2-yl)phenol]; 2-ethoxy-2'-ethyl oxalic acid bisanilide, 2-ethoxy-5-t-butyl oxalic acid anilide-based ultraviolet absorbers such as 2-ethyl-2'-ethyl oxalic acid bisanilide and 2-ethoxy-4'-isodecylphenyl oxalic acid bisanilide; benzophenones such as 2-hydroxy-4-n-octoxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, and 2-hydroxy-4-methoxy-2'-carboxybenzophenone; Examples of such ultraviolet ray absorbing agents include: salicylic acid ultraviolet ray absorbing agents such as phenyl salicylate, p-t-butylphenyl salicylate, and p-octylphenyl salicylate; cyanoacrylate ultraviolet ray absorbing agents such as 2-ethylhexyl-2-cyano-3,3'-diphenylacrylate and ethyl-2-cyano-3,3'-diphenylacrylate; and titanium oxide ultraviolet ray stabilizers such as rutile titanium oxide, anatase titanium oxide, alumina, silica, titanium oxide treated with a surface treating agent such as a silane coupling agent or a titanium coupling agent. These may be used alone or in combination of two or more.
光安定剤としては、例えば、ビス（２，２，６，６－テトラメチル－４－ピペリジル）セバケ－ト、ビス（１，２，２，６，６－ペンタメチル－４－ピペリジル）セバケ－ト、コハク酸ジメチル・１－（２－ヒドロキシエチル）－４－ヒドロキシ－２，２，６，６－テトラメチルピペリジン重縮合物、ポリ［［６，（１，１，３，３－テトラメチルブチル）アミノ－１，３，５－トリアジン－２，４－ジイル］［（２，２，６，６－テトラメチル－４－ピペリジル）イミノ］－ヘキサメチレン－［（２，２，６，６－テトラメチル－４－ピペリジル）イミノ〕］、１－［２－［３－（３，５－ジ－ｔ－ブチル－４－ヒドロキシフェニル）プロピオニルオキシ］エチル］－４－［３－（３，５－ジ－ｔ－ブチル－４－ヒドロキシフェニル）プロピオニルオキシ］－２，２，６，６－テトラメチルピペリジン等が挙げられる。これらは１種単独で用いられてもよく、２種以上を併用してもよい。 Examples of light stabilizers include bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, dimethyl succinate/1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly[[6,(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidyl)imino]-hexamethylene-[(2,2,6,6-tetramethyl-4-piperidyl)imino]], 1-[2-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, etc. These may be used alone or in combination of two or more.
酸化防止剤としては、例えば、トリエチレングリコ－ル－ビス［３－（３－ｔ－ブチル－５－メチル－４－ヒドロキシフェニル）プロピオネ－ト］、２，４－ビス（ｎ－オクチルチオ）－６－（４－ヒドロキシ－３，５－ジ－ｔ－ブチルアニリノ）－１，３，５－トリアジン、ペンタエリスリチルテトラキス［３－（３，５－ジ－ｔ－ブチル－４－ヒドロキシフェニル）プロピオネ－ト］、オクタデシル－３－（３，５－ジ－ｔ－ブチル－４－ヒドロキシフェニル）プロピオネ－ト、２，２－チオビス（４－メチル－６－ｔ－ブチルフェノ－ル）及び１，３，５－トリメチル－２，４，６－トリス（３，５－ジ－ｔ－ブチル－４－ヒドロキシベンジル）ベンゼン等のフェノ－ル系酸化防止剤；ジトリデシル－３，３’－チオジプロピオネ－ト、ジラウリル－３，３’－チオジプロピオネ－ト、ジテトラデシル－３，３’－チオジプロピオネ－ト、ジステアリル－３，３’－チオジプロピオネ－ト、ジオクチル－３，３’－チオジプロピオネ－ト等の硫黄系酸化防止剤；トリスノニルフェニルホスファイト、４，４’－ブチリデン－ビス（３－メチル－６－ｔ－ブチルフェニル－ジ－トリデシル）ホスファイト、（トリデシル）ペンタエリスリト－ルジホスファイト、ビス（オクタデシル）ペンタエリスリト－ルジホスファイト、ビス（ジ－ｔ－ブチルフェニル）ペンタエリスリト－ルジホスファイト、ビス（ジ－ｔ－ブチル－４－メチルフェニル）ペンタエリスリト－ルジホスファイト、ジノニルフェニルオクチルホスフォナイト、テトラキス（２，４－ジ－ｔ－ブチルフェニル）１，４－フェニレン－ジ－ホスフォナイト、テトラキス（２，４－ジ－ｔ－ブチルフェニル）４，４’－ビフェニレン－ジ－ホスフォナイト、１０－デシロキシ－９，１０－ジヒドロ－９－オキサ－１０－ホスファフェナンスレン等の燐系酸化防止剤等が挙げられる。これらは１種単独で用いられてもよく、２種以上を併用してもよい。 Examples of antioxidants include triethylene glycol bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl phenol-based antioxidants such as 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 2,2-thiobis(4-methyl-6-t-butylphenol), and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene; ditridecyl-3,3'-thiodipropionate, dilauryl-3,3'-thiodipropionate, ditetradecyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, sulfur-based antioxidants such as dioctyl-3,3'-thiodipropionate and dioctyl-3,3'-thiodipropionate; trisnonylphenyl phosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl)phosphite, (tridecyl)pentaerythritol diphosphite, bis(octadecyl)pentaerythritol diphosphite, bis(di-t-butylphenyl)pentaerythritol diphosphite, bis(di Examples of phosphorus-based antioxidants include tetrakis(2,4-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, dinonylphenyl octyl phosphonite, tetrakis(2,4-di-t-butylphenyl)1,4-phenylene diphosphonite, tetrakis(2,4-di-t-butylphenyl)4,4'-biphenylene diphosphonite, and 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene. These may be used alone or in combination of two or more.
本発明に係るスチレン系二軸延伸シートには、必要に応じて、公知の補強ゴムが含まれていてもよい。補強ゴムとしては、例えば、ブタジエンゴム、スチレン－ブタジエンゴム、（メタ）アクリル酸メチル－ブタジエン－スチレンゴム、エチレン－プロピレンゴム等が挙げられる。これらは、１種単独で用いられてもよく、２種以上を併用してもよい。延伸シートが補強ゴムを含む場合、透明性の観点から、延伸シートの総質量に対して、１０質量％未満であることが好ましい。 The styrene-based biaxially stretched sheet according to the present invention may contain a known reinforcing rubber, if necessary. Examples of reinforcing rubber include butadiene rubber, styrene-butadiene rubber, methyl (meth)acrylate-butadiene-styrene rubber, and ethylene-propylene rubber. These may be used alone or in combination of two or more. When the stretched sheet contains reinforcing rubber, it is preferable that the amount of the reinforcing rubber is less than 10% by mass relative to the total mass of the stretched sheet, from the viewpoint of transparency.
［スチレン系二軸延伸シートの製造方法］
本発明に係る延伸シートの製造方法としては、共重合体（Ａ）、共重合体（Ｂ）、及び必要に応じてその他の成分を押出機に投入して溶融混錬し、その後ダイ（好ましくはＴダイ）から押出して無延伸シートを作成する。無延伸シートの厚みは、包装容器として好適な厚みの点で、１．０～２．０ｍｍ、好ましくは１．４～１．９ｍｍとすることができる。その後、無延伸シートを、二軸方向に、逐次又は同時に延伸することにより延伸シートを製造することができる。
延伸方法としては、例えば、二軸延伸機を用いて無延伸シートを延伸する方法等、従来公知の方法を採用することができる。
ＭＤ方向への延伸倍率としては、２～４倍が好ましく、２．５～３倍であることがより好ましい。また、ＴＤ方向への延伸倍率としては、２～４倍が好ましく、２．５～３倍であることがより好ましい。なお、前記の延伸倍率は、無延伸シートのＭＤ方向の長さ及びＴＤ方向の長さを基準とした場合の倍率（すなわち、無延伸シートのＭＤ方向及びＴＤ方向の長さを「１」とした場合の倍率）である。
延伸シートの厚みは本発明の効果を有する限り特に限定されないが、例えば、０．１５～０．３５ｍｍの範囲、より好ましくは０．２０～０．３０ｍｍの範囲とすることができる。
溶融混錬時の温度としては、２２０～３００℃が好ましく、２４０～２８０℃がより好ましい。
延伸時の温度としては、１４０～１６０℃が好ましく、１４５～１５５℃がより好ましい。また、延伸速度は、配向緩和応力の観点から、２０～４０ｍｍ／秒であることが好ましく、２５～３５ｍｍ／秒であることがより好ましい。
[Method of manufacturing styrene-based biaxially stretched sheet]
In the method for producing the stretched sheet according to the present invention, the copolymer (A), the copolymer (B), and other components as necessary are fed into an extruder, melt-kneaded, and then extruded through a die (preferably a T-die) to produce an unstretched sheet. The thickness of the unstretched sheet may be 1.0 to 2.0 mm, preferably 1.4 to 1.9 mm, in terms of a thickness suitable for a packaging container. The unstretched sheet is then stretched biaxially, either sequentially or simultaneously, to produce a stretched sheet.
As the stretching method, a conventionally known method such as a method of stretching an unstretched sheet using a biaxial stretching machine can be used.
The stretching ratio in the MD direction is preferably 2 to 4 times, and more preferably 2.5 to 3 times. The stretching ratio in the TD direction is preferably 2 to 4 times, and more preferably 2.5 to 3 times. The stretching ratio is based on the length in the MD direction and the length in the TD direction of the unstretched sheet (i.e., the stretching ratio when the length in the MD direction and the length in the TD direction of the unstretched sheet are set to "1").
The thickness of the stretched sheet is not particularly limited as long as it maintains the effects of the present invention, but it can be, for example, in the range of 0.15 to 0.35 mm, and more preferably in the range of 0.20 to 0.30 mm.
The temperature during melt kneading is preferably from 220 to 300°C, and more preferably from 240 to 280°C.
The temperature during stretching is preferably 140 to 160° C., more preferably 145 to 155° C. From the viewpoint of orientation relaxation stress, the stretching speed is preferably 20 to 40 mm/sec, more preferably 25 to 35 mm/sec.
延伸シートのＭＤ方向の最大配向緩和応力は、０．１～０．６ＭＰａであることが好ましく、０．１～０．５ＭＰａであることがより好ましい。また、延伸シートのＴＤ方向の最大配向緩和応力は、０．２～０．７ＭＰａであることが好ましく、０．２～０．６ＭＰａであることがより好ましい。ＭＤ方向及びＴＤ方向の最大配向緩和応力が前記範囲内であれば、熱収縮開始温度がより好適な範囲となりやすい。また、最大配向緩和応力のＭＤ方向とＴＤ方向の比（ＭＤ／ＴＤ）は、０．５～１．５であることが好ましく、０．６～１．０であることがより好ましい。なお、前記最大配向緩和応力は、ＡＳＴＭ Ｄ１５４０の条件に従って測定した値を指す。 The maximum orientation relaxation stress in the MD direction of the stretched sheet is preferably 0.1 to 0.6 MPa, more preferably 0.1 to 0.5 MPa. The maximum orientation relaxation stress in the TD direction of the stretched sheet is preferably 0.2 to 0.7 MPa, more preferably 0.2 to 0.6 MPa. If the maximum orientation relaxation stresses in the MD and TD directions are within the above ranges, the heat shrinkage onset temperature tends to be in a more suitable range. The ratio of the maximum orientation relaxation stress in the MD direction to the TD direction (MD/TD) is preferably 0.5 to 1.5, more preferably 0.6 to 1.0. The maximum orientation relaxation stress refers to a value measured according to the conditions of ASTM D1540.
ＡＳＴＭ－Ｄ３４２０に従って測定される、本発明に係る延伸シートのフィルムインパクト強度は、１．８～２．５ｍｍ／Ｊであることが好ましい。 The film impact strength of the stretched sheet of the present invention, measured according to ASTM-D3420, is preferably 1.8 to 2.5 mm/J.
本発明に係る延伸シートは、必要に応じて、食品等の内包物と接触する側のシート表面に、防曇剤を塗工してもよい。 If necessary, the stretched sheet of the present invention may be coated with an anti-fogging agent on the surface of the sheet that comes into contact with the contents such as food.
防曇剤を塗工する場合は、例えば、ポリスチレン系二軸延伸シートの防曇剤として従来公知のものを採用することができる。例えば、非イオン性界面活性剤、ポリビニルアルコ－ル及びその共重合体、ポリビニルピロリドン及びその共重合体、水溶性高分子等を延伸シートの表面に塗工してもよい。またその塗工量については特に限定されず、例えば、１０～１５０ｍｇ／ｍ２の範囲で任意に調整することができる。また塗工方法は、従来公知の方法を採用することができる。 When applying an anti-fogging agent, for example, a conventionally known anti-fogging agent for a polystyrene biaxially oriented sheet can be used. For example, a non-ionic surfactant, polyvinyl alcohol and its copolymer, polyvinylpyrrolidone and its copolymer, water-soluble polymer, etc. may be applied to the surface of the stretched sheet. The amount of application is not particularly limited and can be adjusted to any amount within the range of, for example, 10 to 150 mg/ m2 . A conventionally known method can be used as the application method.
［容器］
本発明に係るスチレン系二軸延伸シートは、公知の手法により容器とすることができる。例えば、真空成型や圧空成形等の方法によって容器とすることができる。具体的には、熱板加熱式圧空成形により型再現性の良好な成形品を得ることができる。本発明における「容器」には、内容物を収納するための本体容器の他、前記本体容器と嵌合可能な蓋材も含まれる。
本発明に係るスチレン系二軸延伸シートからなる容器は、耐熱性及び耐油性に優れるため、食品包装用の容器、特に電子レンジで加熱される食品包装用容器として好適に用いることができる。なお、当然ながら本発明の延伸シートから得られる容器は、その用途が食品包装用途に限定されるわけではない。
[container]
The styrene-based biaxially oriented sheet according to the present invention can be made into a container by a known method. For example, it can be made into a container by a method such as vacuum molding or pressure molding. Specifically, a molded product with good shape reproducibility can be obtained by hot plate heating pressure molding. The "container" in the present invention includes not only a main container for storing contents, but also a lid material that can be fitted to the main container.
The container made of the styrene-based biaxially oriented sheet according to the present invention has excellent heat resistance and oil resistance, and therefore can be suitably used as a food packaging container, particularly as a food packaging container to be heated in a microwave oven. However, the use of the container obtained from the oriented sheet according to the present invention is not limited to food packaging.
以下、実施例を示して本発明を詳細に説明するが、本発明は以下の記載によって限定されるものではない。 The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following description.
共重合体（Ａ）及び（Ｂ）における、Ｍｗ、Ｍｎ、ＶＳＴ、ＭＦＲ及び単量体組成比は以下に示す方法によって測定した。
＜重量平均分子量（Ｍｗ）及び数平均分子量（Ｍｎ）＞
重量平均分子量算出はＧＰＣ（ゲルパーミエーションクロマトグラフィー）測定で行った。条件を下記に示す。
装置：Ｓｈｏｄｅｘ（株）製、製品名：「ＳＹＳＴＥＭ－２１」
カラム：ＰＬｇｅｌ ＭＩＸＥＤ－Ｂ
温度：４０℃
溶媒：テトラヒドロフラン
流量：１．０ｍＬ／分
検出：ＲＩ
濃度：０．２質量％
注入量：１００μｌ
検量線：標準ポリスチレン（Ｐｏｌｙｍｅｒ Ｌａｂｏｒａｔｏｒｉｅｓ社製）を用い、溶離時間と溶出量の関係を分子量と変換して各種平均分子量を求めた。
The Mw, Mn, VST, MFR and monomer composition ratio of the copolymers (A) and (B) were measured by the methods described below.
<Weight average molecular weight (Mw) and number average molecular weight (Mn)>
The weight average molecular weight was calculated by GPC (gel permeation chromatography) measurement under the following conditions.
Apparatus: Shodex Co., Ltd., product name: "SYSTEM-21"
Column: PLgel MIXED-B
Temperature: 40°C
Solvent: Tetrahydrofuran Flow rate: 1.0 mL/min Detection: RI
Concentration: 0.2% by mass
Injection volume: 100 μl
Calibration curve: Using standard polystyrene (Polymer Laboratories), the relationship between elution time and elution amount was converted into molecular weight to determine various average molecular weights.
＜ビカット軟化温度（ＶＳＴ）＞
５０Ｎ荷重下、ＪＩＳ Ｋ ７２０６ Ｂ５０法に従い測定した。
<Vicat Softening Temperature (VST)>
Measurement was carried out under a load of 50 N in accordance with JIS K 7206 B50 method.
＜ＭＦＲ＞
２６５℃、９８Ｎ荷重条件下で、ＪＩＳ Ｋ ７２１０に従い測定した。
<MFR>
The measurement was performed in accordance with JIS K 7210 under conditions of 265° C. and a load of 98 N.
＜単量体組成比：熱分解ガスクロマトグラフィ＞
熱分解装置：日本分析工業（株）製 製品名：「ＪＰＳ－２２０」
熱分解温度：５９０℃
ガスクロマトグラフィ：ヒューレットパッカード社製 製品名：「５８９０ＳＥＲＩＥＳＩ」
カラム：微極性カラム アジレント・テクノロジー（株）製、製品名：「ＤＢ－５」
キャリアガス：Ｈｅ 圧力２ｐｓｉ
温度条件：５０℃で５分間保持した後、１８℃／分で２５０℃まで昇温し、２５０℃で７分間保持
検出：ＦＩＤ
共重合体（Ａ）、（Ｂ）のサンプルを０．３ｍｇ秤量して上記の条件で測定した。検出された成分のピーク面積比から単量体組成比を決定した。
<Monomer composition ratio: pyrolysis gas chromatography>
Pyrolysis equipment: Japan Analytical Industry Co., Ltd. Product name: "JPS-220"
Thermal decomposition temperature: 590℃
Gas chromatograph: Hewlett-Packard, product name: "5890SERIESI"
Column: slightly polar column, manufactured by Agilent Technologies, product name: "DB-5"
Carrier gas: He pressure 2 psi
Temperature conditions: held at 50°C for 5 minutes, then heated to 250°C at 18°C/min, and held at 250°C for 7 minutes Detection: FID
0.3 mg of each sample of copolymers (A) and (B) was weighed out and measured under the above conditions. The monomer composition ratio was determined from the peak area ratio of the detected components.
［共重合体（Ａ－１）の製造］
連続式の塊状重合にて作製した。反応器として完全混合槽型撹拌槽を１基使用し、３０Ｌの容量で重合を行った。スチレン６０質量％、アクリロニトリル２２質量％、エチルベンゼン１８質量％の原料溶液を作製し、反応器に９．５Ｌ/ｈの流量で連続的に供給した。また、原料溶液に対して、重合開始材としてｔ－ブチルパーオキシイソプロピルモノカーボネートを１６０ｐｐｍ、連鎖移動剤としてｎ－ドデシルメルカプタンを４００ｐｐｍの濃度となるよう、原料溶液の供給ラインに連続的に添加した。反応器の反応温度は１４５℃となるよう調整した。反応器から連続的に取り出された共重合体を含む溶液を、予熱器付き真空脱揮槽に供給し、未反応のスチレン及びアクリロニトリル、エチルベンゼンを分離した。脱揮槽内の共重合体の温度が２３５℃となるように予熱器の温度を調製した。また、脱揮槽内の圧力は０．４ｋＰａとした。ギヤーポンプにより真空脱揮槽から共重合体を抜出し、ストランド状に押出して冷却水にて冷却後、切断してペレット状の共重合体（Ａ－１）を得た。共重合体（Ａ－１）の構成単位は、スチレン単位が７３．５質量％、アクリロニトリル単位が２６．５質量％であった。また、重量平均分子量は１４６，０００であった。また、ＶＳＴは１０７℃であった。共重合体（Ａ－１）の詳細を表１に示す。
[Production of Copolymer (A-1)]
It was prepared by continuous bulk polymerization. One complete mixing type stirring tank was used as the reactor, and polymerization was carried out with a volume of 30 L. A raw material solution of 60 mass% styrene, 22 mass% acrylonitrile, and 18 mass% ethylbenzene was prepared and continuously supplied to the reactor at a flow rate of 9.5 L/h. In addition, t-butylperoxyisopropyl monocarbonate as a polymerization initiator and n-dodecyl mercaptan as a chain transfer agent were continuously added to the supply line of the raw material solution so that the concentration of the raw material solution was 160 ppm and 400 ppm, respectively. The reaction temperature of the reactor was adjusted to 145 ° C. The solution containing the copolymer continuously taken out from the reactor was supplied to a vacuum devolatilization tank equipped with a preheater, and unreacted styrene, acrylonitrile, and ethylbenzene were separated. The temperature of the preheater was adjusted so that the temperature of the copolymer in the devolatilization tank was 235 ° C. In addition, the pressure in the devolatilization tank was set to 0.4 kPa. The copolymer was extracted from the vacuum devolatilizer tank by a gear pump, extruded in the form of a strand, cooled with cooling water, and cut to obtain copolymer (A-1) in the form of pellets. The constituent units of copolymer (A-1) were 73.5% by mass of styrene units and 26.5% by mass of acrylonitrile units. The weight average molecular weight was 146,000. The VST was 107° C. Details of copolymer (A-1) are shown in Table 1.
［共重合体（Ａ－２）～（Ａ－３）の製造］
単量体混合物中のアクリロニトリル及びスチレンの比率を変更した以外は、共重合体（Ａ－１）と同様の方法にて、共重合体（Ａ－２）～（Ａ－３）を調製した。共重合体（Ａ－２）～（Ａ－３）の詳細を表１に示す。
[Production of Copolymers (A-2) to (A-3)]
Copolymers (A-2) to (A-3) were prepared in the same manner as for copolymer (A-1), except that the ratio of acrylonitrile and styrene in the monomer mixture was changed. Details of copolymers (A-2) to (A-3) are shown in Table 1.
［共重合体（Ｂ－１）の製造］
攪拌機を備えた容積約１２０Ｌのオートクレーブに、スチレン４２質量部、アクリロニトリル１０質量部、無水マレイン酸４質量部、２，４－ジフェニル－４－メチル－１－ペンテン０．６質量部、メチルエチルケトン２７質量部を仕込み、気相部を窒素ガスで置換した後、撹拌しながら４０分かけて９２℃まで昇温した。昇温後９２℃を保持しながら、無水マレイン酸２１質量部と、ｔ－ブチルパーオキシ－２－エチルヘキサノエート０．１５質量部とを、メチルエチルケトン８５質量部に溶解した溶液、及びスチレン２０質量部を、４．５時間かけて連続的にオートクレーブに添加した。更に、無水マレイン酸を含む前記溶液を添加終了後、ｔ－ブチルパーオキシ－２－エチルヘキサノエート０．０２質量部をメチルエチルケトン９質量部に溶解した溶液及びスチレン３質量部を３０分かけて連続的に添加した。添加後、１２０℃に昇温し、３０分反応させて重合を終了させた。その後、重合液にアニリン２３質量部、トリエチルアミン０．４質量部を加え１４０℃で７時間反応させた。反応終了後のイミド化反応液をベントタイプスクリュー式押出機に投入し、揮発分を除去してペレット状のマレイミド系共重合体（Ｂ－１）を得た。共重合体（Ｂ－１）は、スチレン単位５２質量％、アクリロニトリル単位８質量％、Ｎ－フェニルマレイミド単位３９質量％、無水マレイン酸単位１質量％であり、重量平均分子量Ｍｗは８０，０００、多分散度（Ｍｗ／Ｍｎ）は２．４であった。また、ＭＦＲ（２６５℃、９８Ｎ）は７０ｇ／１０ｍｉｎであった。共重合体（Ｂ－１）の詳細を表２に示す。
[Production of Copolymer (B-1)]
In an autoclave with a volume of about 120 L equipped with a stirrer, 42 parts by mass of styrene, 10 parts by mass of acrylonitrile, 4 parts by mass of maleic anhydride, 0.6 parts by mass of 2,4-diphenyl-4-methyl-1-pentene, and 27 parts by mass of methyl ethyl ketone were charged, and the gas phase was replaced with nitrogen gas, and then the temperature was raised to 92 ° C. over 40 minutes while stirring. After the temperature was raised to 92 ° C., a solution in which 21 parts by mass of maleic anhydride and 0.15 parts by mass of t-butylperoxy-2-ethylhexanoate were dissolved in 85 parts by mass of methyl ethyl ketone, and 20 parts by mass of styrene were continuously added to the autoclave over 4.5 hours. Furthermore, after the addition of the solution containing maleic anhydride was completed, a solution in which 0.02 parts by mass of t-butylperoxy-2-ethylhexanoate was dissolved in 9 parts by mass of methyl ethyl ketone and 3 parts by mass of styrene were continuously added over 30 minutes. After the addition, the temperature was raised to 120°C, and the polymerization was terminated by reacting for 30 minutes. Thereafter, 23 parts by mass of aniline and 0.4 parts by mass of triethylamine were added to the polymerization solution and reacted at 140°C for 7 hours. The imidization reaction solution after the reaction was charged into a vent-type screw extruder, and volatile matter was removed to obtain a pellet-shaped maleimide copolymer (B-1). The copolymer (B-1) had 52% by mass of styrene units, 8% by mass of acrylonitrile units, 39% by mass of N-phenylmaleimide units, and 1% by mass of maleic anhydride units, a weight average molecular weight Mw of 80,000, and a polydispersity (Mw/Mn) of 2.4. The MFR (265°C, 98N) was 70g/10min. Details of the copolymer (B-1) are shown in Table 2.
［共重合体（Ｂ－２）～（Ｂ－４）の製造］
共重合体（Ｂ－２）は、アニリンの添加量を調整して無水マレイン酸のマレイミドへの転化率を調整したこと、α－メチルスチレンダイマーを添加してＭｗを調整したこと以外は、共重合体（Ｂ－１）と同様の方法にて調製した。また、共重合体（Ｂ－３）～（Ｂ－４）は、マレイミドへの転化率、Ｍｗの調整、及びアクリロニトリルを添加しなかったこと以外は、共重合体（Ｂ－１）と同様の方法にて調製した。共重合体（Ｂ－２）～（Ｂ－４）の詳細を表２に示す。
[Production of Copolymers (B-2) to (B-4)]
Copolymer (B-2) was prepared in the same manner as copolymer (B-1), except that the conversion rate of maleic anhydride to maleimide was adjusted by adjusting the amount of aniline added, and Mw was adjusted by adding α-methylstyrene dimer. Copolymers (B-3) to (B-4) were prepared in the same manner as copolymer (B-1), except that the conversion rate to maleimide, Mw were not adjusted, and acrylonitrile was not added. Details of copolymers (B-2) to (B-4) are shown in Table 2.
（実施例１）
共重合体（Ａ－１）（樹脂組成物の総質量に対して７０質量％）と、共重合体（Ｂ－１）（樹脂組成物の総質量に対して３０質量％）とを、同方向二軸押出機（東芝機械（株）製、製品名：「ＴＥＭ－３５Ｂ」、有効長（Ｌ／Ｄ）：３２）を用いて、シリンダー温度２６０℃、フィード量２０ｋｇ／ｈｒ、スクリュー回転数２００ｒｐｍの条件にて溶融混錬しペレット化した。得られたペレットをスクリュー径が４０ｍｍの単軸押出機を用いて、２４０℃、７０ｒｐｍで溶融混錬し、Ｔダイを通して、厚み１．５ｍｍの無延伸シートを得た。得られた無延伸シートを、二軸延伸機を用いて、延伸温度１４７℃、延伸速度３０ｍｍ／秒、ＭＤ方向の延伸倍率２．６倍、ＴＤ方向の延伸倍率２．６倍で逐次延伸して、二軸延伸シートを得た。得られた二軸延伸シートの熱収縮開始温度を以下の方法で測定した。実施例１の二軸延伸シートのＭＤ方向及びＴＤ方向の熱収縮開始温度はいずれも１１７℃であった。また、得られた二軸延伸シートのＭＤ方向及びＴＤ方向の最大配向緩和応力、シート外観、色見、耐熱性、及び耐油性を以下の条件で測定した。結果を表３に示す。なお、表３における「製膜性」とは、Ｔダイ押出による製膜の可否を評価したものである。すなわち、Ｔダイ押出により製膜できたものを「合格」とし、製膜できなかったものを「不合格」として評価した。
＜熱収縮開始温度の測定方法＞
熱収縮応力測定機（テスター産業（株）製、製品名：「ＴＰ-５０１」）を用いて、測定した。具体的には、二軸延伸シートを１５０ｍｍ（ＭＤ方向）×１５ｍｍ（ＴＤ方向）に切り出して測定サンプルを調製した。前記延伸シートのサンプルを、チャック間距離１００ｍｍとなるように前記測定器のチャック部分で把持して、９０℃以下の油浴に浸漬させた。その後、油浴の温度を０．５℃／分の昇温速度で、９０℃から１４０℃まで昇温させた。この際、延伸シートのＭＤ方向又はＴＤ方向に熱収縮が発生して、熱収縮応力が０．０５ＭＰａ以上に達したときの温度を、ＭＤ方向又はＴＤ方向の熱収縮開始温度とした。
Example 1
Copolymer (A-1) (70% by mass relative to the total mass of the resin composition) and copolymer (B-1) (30% by mass relative to the total mass of the resin composition) were melt-kneaded and pelletized using a same-direction twin-screw extruder (manufactured by Toshiba Machine Co., Ltd., product name: "TEM-35B", effective length (L/D): 32) under conditions of a cylinder temperature of 260 ° C., a feed rate of 20 kg/hr, and a screw rotation speed of 200 rpm. The obtained pellets were melt-kneaded at 240 ° C. and 70 rpm using a single-screw extruder with a screw diameter of 40 mm, and passed through a T-die to obtain an unstretched sheet having a thickness of 1.5 mm. The obtained unstretched sheet was sequentially stretched using a biaxial stretching machine at a stretching temperature of 147 ° C., a stretching speed of 30 mm/sec, a stretch ratio of 2.6 times in the MD direction, and a stretch ratio of 2.6 times in the TD direction to obtain a biaxially stretched sheet. The heat shrinkage start temperature of the obtained biaxially stretched sheet was measured by the following method. The heat shrinkage onset temperatures in both the MD and TD directions of the biaxially oriented sheet of Example 1 were 117°C. The maximum orientation relaxation stress in the MD and TD directions of the obtained biaxially oriented sheet were also measured under the following conditions. The results are shown in Table 3. Note that "film formability" in Table 3 refers to an evaluation of whether or not a film could be formed by T-die extrusion. That is, those that could be formed into a film by T-die extrusion were evaluated as "passed", and those that could not be formed into a film were evaluated as "failed".
<Method for measuring heat shrinkage starting temperature>
The measurement was performed using a heat shrinkage stress measuring instrument (manufactured by Tester Sangyo Co., Ltd., product name: "TP-501"). Specifically, a biaxially stretched sheet was cut into a size of 150 mm (MD direction) x 15 mm (TD direction) to prepare a measurement sample. The stretched sheet sample was held by the chuck part of the measuring instrument so that the chuck distance was 100 mm, and immersed in an oil bath of 90°C or less. Thereafter, the temperature of the oil bath was increased from 90°C to 140°C at a heating rate of 0.5°C/min. At this time, the temperature at which heat shrinkage occurred in the MD or TD direction of the stretched sheet and the heat shrinkage stress reached 0.05 MPa or more was defined as the heat shrinkage start temperature in the MD or TD direction.
＜最大配向緩和応力の測定＞
熱収縮応力測定器（テスター産業（株）製、製品名：「ＴＰ－５０１」）を用いて、ＡＳＴＭ Ｄ１５４０の条件に従って測定した。具体的には、二軸延伸シートを１５０ｍｍ（ＭＤ方向）×１５ｍｍ（ＴＤ方向）に切り出して測定サンプルを調製した。前記延伸シートサンプルを、チャック間距離１００ｍｍとなるように前記測定器のチャック部分で把持して、１５０℃の湯浴に浸漬させた。この際、延伸シートのＭＤ方向またはＴＤ方向に熱収縮が発生して、熱収縮応力が最大となったときの荷重を、ＭＤ方向又はＴＤ方向の最大配向緩和応力とした。
<Measurement of maximum orientation relaxation stress>
Measurements were performed under the conditions of ASTM D1540 using a heat shrinkage stress measuring instrument (manufactured by Tester Sangyo Co., Ltd., product name: "TP-501"). Specifically, a measurement sample was prepared by cutting a biaxially stretched sheet into a size of 150 mm (MD direction) x 15 mm (TD direction). The stretched sheet sample was held by the chuck portion of the measuring instrument so that the chuck distance was 100 mm, and immersed in a water bath at 150°C. At this time, the load at which heat shrinkage occurred in the MD or TD direction of the stretched sheet and the heat shrinkage stress became maximum was taken as the maximum orientation relaxation stress in the MD or TD direction.
＜シート外観の評価＞
延伸シートのシート外観を視認性により評価した。具体的には、４００ｍｍ×４００ｍｍの大きさの延伸シート５枚を目視で評価し、延伸シート全体の厚みムラの有無を確認した。また、以下の評価基準に沿って評価し、良評価以上を合格（シート外観が良好である）とした。
（評価基準）
優：厚みムラがなく視認性が良好であった。
良：延伸シートの一部に、厚みムラにより視認性が低下している箇所があった。
不可：厚みムラにより、延伸シート全体の視認性が悪かった。
<Evaluation of seat appearance>
The appearance of the stretched sheet was evaluated by visibility. Specifically, five stretched sheets each having a size of 400 mm x 400 mm were visually evaluated to check for unevenness in thickness throughout the stretched sheet. The sheet was also evaluated according to the following evaluation criteria, and a good rating or better was deemed to pass (good sheet appearance).
(Evaluation Criteria)
Excellent: There was no unevenness in thickness and visibility was good.
Good: There were some parts of the stretched sheet where visibility was reduced due to uneven thickness.
Poor: Visibility of the entire stretched sheet was poor due to uneven thickness.
＜色見の評価＞
延伸シートの色見を、色差計（コニカミノルタ（株）製、製品名：「分光測色計ＣＭ－２５００ｄ」）を用いて評価した。具体的には、厚さ０．２５ｍｍの延伸シート６枚を重ね合わせて、厚み１．５ｍｍのシートサンプルを作成し、ＳＣＩ法の条件でサンプルの色見を評価した。また、以下の評価基準に沿って評価し、良評価以上を合格（黄色味が少ないため色相が良好である）とした。
優：ｂ＊の値が１０以下である。
良：ｂ＊の値が１０超１５以下である。
不可：ｂ＊の値が１５超である。
<Color evaluation>
The color of the stretched sheet was evaluated using a color difference meter (Konica Minolta, Inc., product name: "Spectrophotometer CM-2500d"). Specifically, six stretched sheets with a thickness of 0.25 mm were stacked together to prepare a sheet sample with a thickness of 1.5 mm, and the color of the sample was evaluated under the conditions of the SCI method. In addition, the evaluation was performed according to the following evaluation criteria, and a rating of good or better was considered to be a pass (the hue is good because there is little yellowness).
Excellent: the b * value is 10 or less.
Good: the b * value is more than 10 and 15 or less.
Unacceptable: b * value is greater than 15.
＜耐熱性及び耐油性の評価＞
延伸シートを熱板成形機（(株）脇坂エンジニアリング製、製品名：「ＨＰＴ－４００Ａ」）にて、熱板温度１４５℃、金型温度９０℃の条件で成形して、容器の蓋材を得た。次に、厚み２．４ｍｍの発泡スチレン（ＰＳＰ）系シートから成形された本体容器を準備し、前記本体容器内に麻婆丼４５０ｇ（（株）セブン－イレブン・ジャパン製、商品名：「花椒の香り広がる！麻婆丼」）を内包した。前記麻婆丼１０ｇを、蓋材の内容物側の表面に均一に付着させた後、前記蓋材を本体容器と嵌合させた。その後、１５００Ｗの電子レンジで２分間加熱して、蓋材の状態を以下の評価基準に沿って評価した。また、良評価以上を合格（耐熱性及び耐油性に優れる）とした。
優：蓋材に変形及び穴あきがない。
良：蓋材が僅かに変形したが、穴あきはない。
不可：蓋材が大きく変形し、かつ穴あきが発生した。
<Evaluation of heat resistance and oil resistance>
The stretched sheet was molded in a hot plate molding machine (manufactured by Wakisaka Engineering Co., Ltd., product name: "HPT-400A") under conditions of a hot plate temperature of 145°C and a mold temperature of 90°C to obtain a container lid material. Next, a main container molded from a 2.4 mm thick polystyrene foam (PSP) sheet was prepared, and 450 g of mapo rice bowl (manufactured by Seven-Eleven Japan Co., Ltd., product name: "Mapo rice bowl with the aroma of pepper!") was placed in the main container. 10 g of the mapo rice bowl was uniformly attached to the surface of the lid material on the content side, and the lid material was fitted to the main container. Thereafter, the lid material was heated in a 1500 W microwave oven for 2 minutes, and the condition of the lid material was evaluated according to the following evaluation criteria. In addition, a good evaluation or better was determined to be pass (excellent heat resistance and oil resistance).
Excellent: The lid material is free of deformation and holes.
Good: The lid is slightly deformed, but there are no holes.
Unacceptable: The lid material was significantly deformed and holes were formed.
＜耐油性の評価：マヨネーズ付着試験＞
より過酷な条件での耐油性を以下の方法で評価した。
延伸シートの中央部を５０ｍｍ×５０ｍｍの大きさに切り出し、マヨネーズを９か所にそれぞれ１ｇずつ付着させて評価シートを作成した。この評価シートを各３枚ずつ作製し、前述の耐熱性及び耐油性の評価と同条件で作成した容器蓋の内側に貼り付けた。次に、前述の耐熱性及び耐油性の評価と同条件で作成した容器本体に水３００ｇを入れ、３枚の評価シートを貼り付けた容器蓋を嵌合させ、１５００Ｗの電子レンジで９０秒間加熱した。その後、評価シートの変形度合いを以下の評価基準に沿って評価した。また、良評価以上を合格とした。
優：マヨネーズ付着部分２７箇所中、評価シートの変形箇所が１０箇所未満であった。
良：マヨネーズ付着部分２７箇所中、評価シートの変形箇所が１０箇所以上２０箇所未満であった。
不可：マヨネーズ付着部分２７箇所中、評価シートの変形箇所が２０箇所以上であった。
<Evaluation of oil resistance: mayonnaise adhesion test>
The oil resistance under more severe conditions was evaluated by the following method.
The center of the stretched sheet was cut into a size of 50 mm x 50 mm, and 1 g of mayonnaise was attached to each of 9 places to create an evaluation sheet. Three sheets of each evaluation sheet were created and attached to the inside of a container lid created under the same conditions as the above-mentioned evaluation of heat resistance and oil resistance. Next, 300 g of water was placed in a container body created under the same conditions as the above-mentioned evaluation of heat resistance and oil resistance, and the container lid with the three evaluation sheets attached was fitted and heated for 90 seconds in a 1500 W microwave oven. Thereafter, the degree of deformation of the evaluation sheet was evaluated according to the following evaluation criteria. In addition, a good evaluation or better was considered to be a pass.
Excellent: Of 27 areas with mayonnaise on the evaluation sheet, less than 10 areas were deformed.
Good: Of 27 areas with mayonnaise attached, the evaluation sheet was deformed in 10 or more but less than 20 areas.
Unacceptable: Deformation of the evaluation sheet occurred in 20 or more of the 27 areas where mayonnaise was attached.
［実施例２～８及び比較例１］
共重合体（Ａ）、（Ｂ）の割合及び無延伸シートの厚みを表３に示す通りとした以外は、実施例１と同様の方法にて延伸シートを作成した。また各例の延伸シートについて、実施例１と同様の方法で、熱収縮開始温度、最大配向緩和応力、シート外観、色見、耐熱性、及び耐油性を評価した。結果を表３に示す。
[Examples 2 to 8 and Comparative Example 1]
Stretched sheets were prepared in the same manner as in Example 1, except that the ratios of copolymers (A) and (B) and the thicknesses of the unstretched sheets were as shown in Table 3. The stretched sheets of each example were evaluated for heat shrinkage onset temperature, maximum orientation relaxation stress, sheet appearance, color, heat resistance, and oil resistance in the same manner as in Example 1. The results are shown in Table 3.
表３に示す通り、本発明の構成を満たす実施例１～８の延伸シートから得られた容器（蓋材）は、耐熱性及び耐油性に優れていた。すなわち、食品を内包した状態で高出力の電子レンジで加熱しても、容器の変形や穴あきが生じにくかった。また、マヨネーズを直接付着させた状態で高出力の電子レンジで加熱した場合でも変形箇所が少なく、耐油性に非常に優れていた。一方、本発明の構成を満たさない延伸シートから得られた比較例１の容器（蓋材）は、高出力の電子レンジで加熱した際に穴あき及び変形が生じた。以上の結果から、本発明のスチレン系二軸延伸シートは、耐熱性及び耐油性に優れており、高出力の電子レンジで加熱しても変形や穴あきが生じにくい食品包装用容器を提供できることが確認された。
As shown in Table 3, the containers (lids) obtained from the stretched sheets of Examples 1 to 8 satisfying the constitution of the present invention were excellent in heat resistance and oil resistance. That is, even when the container was heated in a high-power microwave oven with food inside, deformation and hole formation were unlikely to occur. In addition, even when the container was heated in a high-power microwave oven with mayonnaise directly attached thereto, there were few deformations, and the oil resistance was very excellent. On the other hand, the container (lid) of Comparative Example 1 obtained from the stretched sheet not satisfying the constitution of the present invention was perforated and deformed when heated in a high-power microwave oven. From the above results, it was confirmed that the styrene-based biaxially stretched sheet of the present invention has excellent heat resistance and oil resistance, and can provide a food packaging container that is unlikely to deform or develop holes even when heated in a high-power microwave oven.
Claims (9)
マレイミド系単量体単位を含むスチレン系共重合体（Ｂ）と、を含むスチレン系二軸延伸シートであって、
前記スチレン系二軸延伸シートの長さ方向及び幅方向の熱収縮開始温度が１０７℃以上であり、
前記スチレン系二軸延伸シートの総質量に対して、前記スチレン系共重合体（Ａ）を６０～９５質量％含み、前記スチレン系共重合体（Ｂ）を５～４０質量％含む、スチレン系二軸延伸シート。 A styrene-based copolymer (A) containing vinyl cyanide monomer units;
A styrene-based biaxially stretched sheet comprising a styrene-based copolymer (B) containing a maleimide-based monomer unit,
The styrene-based biaxially oriented sheet has a heat shrinkage initiation temperature in the length direction and width direction of 107° C. or more ,
A styrene-based biaxially oriented sheet comprising 60 to 95% by mass of the styrene-based copolymer (A) and 5 to 40% by mass of the styrene-based copolymer (B) relative to the total mass of the styrene-based biaxially oriented sheet.
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