JP2004358798A - Laminated biaxially stretched polyester film excellent in easy cutting properties - Google Patents
Laminated biaxially stretched polyester film excellent in easy cutting properties Download PDFInfo
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- JP2004358798A JP2004358798A JP2003159495A JP2003159495A JP2004358798A JP 2004358798 A JP2004358798 A JP 2004358798A JP 2003159495 A JP2003159495 A JP 2003159495A JP 2003159495 A JP2003159495 A JP 2003159495A JP 2004358798 A JP2004358798 A JP 2004358798A
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- crystalline polyester
- film
- polyester
- layer
- laminated
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- 238000005520 cutting process Methods 0.000 title claims abstract description 27
- 229920006267 polyester film Polymers 0.000 title claims abstract description 21
- 229920000728 polyester Polymers 0.000 claims abstract description 109
- 238000002844 melting Methods 0.000 claims abstract description 56
- 230000008018 melting Effects 0.000 claims abstract description 45
- 238000002425 crystallisation Methods 0.000 claims abstract description 15
- 230000008025 crystallization Effects 0.000 claims abstract description 15
- 230000032798 delamination Effects 0.000 claims description 12
- 239000010410 layer Substances 0.000 description 58
- 238000000034 method Methods 0.000 description 43
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 22
- -1 polyethylene terephthalate Polymers 0.000 description 20
- 229920001225 polyester resin Polymers 0.000 description 15
- 239000004645 polyester resin Substances 0.000 description 15
- 238000010030 laminating Methods 0.000 description 12
- 238000007334 copolymerization reaction Methods 0.000 description 11
- 238000004519 manufacturing process Methods 0.000 description 10
- 229920005989 resin Polymers 0.000 description 10
- 239000011347 resin Substances 0.000 description 10
- 229920000139 polyethylene terephthalate Polymers 0.000 description 9
- 239000005020 polyethylene terephthalate Substances 0.000 description 9
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 description 8
- 238000009998 heat setting Methods 0.000 description 8
- QQVIHTHCMHWDBS-UHFFFAOYSA-N isophthalic acid Chemical compound OC(=O)C1=CC=CC(C(O)=O)=C1 QQVIHTHCMHWDBS-UHFFFAOYSA-N 0.000 description 8
- 239000002253 acid Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 7
- 239000013078 crystal Substances 0.000 description 7
- 229920000298 Cellophane Polymers 0.000 description 6
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 6
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 6
- ADCOVFLJGNWWNZ-UHFFFAOYSA-N antimony trioxide Chemical compound O=[Sb]O[Sb]=O ADCOVFLJGNWWNZ-UHFFFAOYSA-N 0.000 description 6
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 238000006116 polymerization reaction Methods 0.000 description 6
- ARCGXLSVLAOJQL-UHFFFAOYSA-N trimellitic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C(C(O)=O)=C1 ARCGXLSVLAOJQL-UHFFFAOYSA-N 0.000 description 6
- 239000003795 chemical substances by application Substances 0.000 description 5
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- FJKROLUGYXJWQN-UHFFFAOYSA-N 4-hydroxybenzoic acid Chemical compound OC(=O)C1=CC=C(O)C=C1 FJKROLUGYXJWQN-UHFFFAOYSA-N 0.000 description 4
- VZCYOOQTPOCHFL-OWOJBTEDSA-N Fumaric acid Chemical compound OC(=O)\C=C\C(O)=O VZCYOOQTPOCHFL-OWOJBTEDSA-N 0.000 description 4
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 4
- 239000002390 adhesive tape Substances 0.000 description 4
- WNLRTRBMVRJNCN-UHFFFAOYSA-N adipic acid Chemical compound OC(=O)CCCCC(O)=O WNLRTRBMVRJNCN-UHFFFAOYSA-N 0.000 description 4
- QMKYBPDZANOJGF-UHFFFAOYSA-N benzene-1,3,5-tricarboxylic acid Chemical compound OC(=O)C1=CC(C(O)=O)=CC(C(O)=O)=C1 QMKYBPDZANOJGF-UHFFFAOYSA-N 0.000 description 4
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 description 4
- WERYXYBDKMZEQL-UHFFFAOYSA-N butane-1,4-diol Chemical compound OCCCCO WERYXYBDKMZEQL-UHFFFAOYSA-N 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
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- 230000001771 impaired effect Effects 0.000 description 4
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 239000000155 melt Substances 0.000 description 4
- 238000004806 packaging method and process Methods 0.000 description 4
- XNGIFLGASWRNHJ-UHFFFAOYSA-N phthalic acid Chemical compound OC(=O)C1=CC=CC=C1C(O)=O XNGIFLGASWRNHJ-UHFFFAOYSA-N 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- CYIDZMCFTVVTJO-UHFFFAOYSA-N pyromellitic acid Chemical compound OC(=O)C1=CC(C(O)=O)=C(C(O)=O)C=C1C(O)=O CYIDZMCFTVVTJO-UHFFFAOYSA-N 0.000 description 4
- CXMXRPHRNRROMY-UHFFFAOYSA-N sebacic acid Chemical compound OC(=O)CCCCCCCCC(O)=O CXMXRPHRNRROMY-UHFFFAOYSA-N 0.000 description 4
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 description 4
- YIMQCDZDWXUDCA-UHFFFAOYSA-N [4-(hydroxymethyl)cyclohexyl]methanol Chemical compound OCC1CCC(CO)CC1 YIMQCDZDWXUDCA-UHFFFAOYSA-N 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 230000032050 esterification Effects 0.000 description 3
- 238000005886 esterification reaction Methods 0.000 description 3
- 230000004927 fusion Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 229920000092 linear low density polyethylene Polymers 0.000 description 3
- 239000004707 linear low-density polyethylene Substances 0.000 description 3
- 238000000465 moulding Methods 0.000 description 3
- DNIAPMSPPWPWGF-VKHMYHEASA-N (+)-propylene glycol Chemical compound C[C@H](O)CO DNIAPMSPPWPWGF-VKHMYHEASA-N 0.000 description 2
- YPFDHNVEDLHUCE-UHFFFAOYSA-N 1,3-propanediol Substances OCCCO YPFDHNVEDLHUCE-UHFFFAOYSA-N 0.000 description 2
- QFGCFKJIPBRJGM-UHFFFAOYSA-N 12-[(2-methylpropan-2-yl)oxy]-12-oxododecanoic acid Chemical class CC(C)(C)OC(=O)CCCCCCCCCCC(O)=O QFGCFKJIPBRJGM-UHFFFAOYSA-N 0.000 description 2
- JAHNSTQSQJOJLO-UHFFFAOYSA-N 2-(3-fluorophenyl)-1h-imidazole Chemical compound FC1=CC=CC(C=2NC=CN=2)=C1 JAHNSTQSQJOJLO-UHFFFAOYSA-N 0.000 description 2
- VPWNQTHUCYMVMZ-UHFFFAOYSA-N 4,4'-sulfonyldiphenol Chemical compound C1=CC(O)=CC=C1S(=O)(=O)C1=CC=C(O)C=C1 VPWNQTHUCYMVMZ-UHFFFAOYSA-N 0.000 description 2
- 229940090248 4-hydroxybenzoic acid Drugs 0.000 description 2
- IAYPIBMASNFSPL-UHFFFAOYSA-N Ethylene oxide Chemical class C1CO1 IAYPIBMASNFSPL-UHFFFAOYSA-N 0.000 description 2
- 101150015738 Fev gene Proteins 0.000 description 2
- 239000002202 Polyethylene glycol Substances 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 2
- 102100037681 Protein FEV Human genes 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- KDYFGRWQOYBRFD-UHFFFAOYSA-N Succinic acid Natural products OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 description 2
- ZJCCRDAZUWHFQH-UHFFFAOYSA-N Trimethylolpropane Chemical compound CCC(CO)(CO)CO ZJCCRDAZUWHFQH-UHFFFAOYSA-N 0.000 description 2
- XDODWINGEHBYRT-UHFFFAOYSA-N [2-(hydroxymethyl)cyclohexyl]methanol Chemical compound OCC1CCCCC1CO XDODWINGEHBYRT-UHFFFAOYSA-N 0.000 description 2
- LUSFFPXRDZKBMF-UHFFFAOYSA-N [3-(hydroxymethyl)cyclohexyl]methanol Chemical compound OCC1CCCC(CO)C1 LUSFFPXRDZKBMF-UHFFFAOYSA-N 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 239000001361 adipic acid Substances 0.000 description 2
- 235000011037 adipic acid Nutrition 0.000 description 2
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 description 2
- HNEGQIOMVPPMNR-IHWYPQMZSA-N citraconic acid Chemical compound OC(=O)C(/C)=C\C(O)=O HNEGQIOMVPPMNR-IHWYPQMZSA-N 0.000 description 2
- 229940018557 citraconic acid Drugs 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- QYQADNCHXSEGJT-UHFFFAOYSA-N cyclohexane-1,1-dicarboxylate;hydron Chemical compound OC(=O)C1(C(O)=O)CCCCC1 QYQADNCHXSEGJT-UHFFFAOYSA-N 0.000 description 2
- 150000001991 dicarboxylic acids Chemical class 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000001530 fumaric acid Substances 0.000 description 2
- 230000009477 glass transition Effects 0.000 description 2
- 235000011187 glycerol Nutrition 0.000 description 2
- 150000002334 glycols Chemical class 0.000 description 2
- XXMIOPMDWAUFGU-UHFFFAOYSA-N hexane-1,6-diol Chemical compound OCCCCCCO XXMIOPMDWAUFGU-UHFFFAOYSA-N 0.000 description 2
- 239000004310 lactic acid Substances 0.000 description 2
- 235000014655 lactic acid Nutrition 0.000 description 2
- 239000005001 laminate film Substances 0.000 description 2
- 238000003475 lamination Methods 0.000 description 2
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 description 2
- 239000011976 maleic acid Substances 0.000 description 2
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical compound O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 description 2
- HNEGQIOMVPPMNR-NSCUHMNNSA-N mesaconic acid Chemical compound OC(=O)C(/C)=C/C(O)=O HNEGQIOMVPPMNR-NSCUHMNNSA-N 0.000 description 2
- LVHBHZANLOWSRM-UHFFFAOYSA-N methylenebutanedioic acid Natural products OC(=O)CC(=C)C(O)=O LVHBHZANLOWSRM-UHFFFAOYSA-N 0.000 description 2
- HNEGQIOMVPPMNR-UHFFFAOYSA-N methylfumaric acid Natural products OC(=O)C(C)=CC(O)=O HNEGQIOMVPPMNR-UHFFFAOYSA-N 0.000 description 2
- RXOHFPCZGPKIRD-UHFFFAOYSA-N naphthalene-2,6-dicarboxylic acid Chemical compound C1=C(C(O)=O)C=CC2=CC(C(=O)O)=CC=C21 RXOHFPCZGPKIRD-UHFFFAOYSA-N 0.000 description 2
- SLCVBVWXLSEKPL-UHFFFAOYSA-N neopentyl glycol Chemical compound OCC(C)(C)CO SLCVBVWXLSEKPL-UHFFFAOYSA-N 0.000 description 2
- 235000006408 oxalic acid Nutrition 0.000 description 2
- 239000005022 packaging material Substances 0.000 description 2
- WXZMFSXDPGVJKK-UHFFFAOYSA-N pentaerythritol Chemical compound OCC(CO)(CO)CO WXZMFSXDPGVJKK-UHFFFAOYSA-N 0.000 description 2
- 229920001707 polybutylene terephthalate Polymers 0.000 description 2
- 229920001223 polyethylene glycol Polymers 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 229920001451 polypropylene glycol Polymers 0.000 description 2
- 229920000166 polytrimethylene carbonate Polymers 0.000 description 2
- 239000000565 sealant Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- PAPBSGBWRJIAAV-UHFFFAOYSA-N ε-Caprolactone Chemical compound O=C1CCCCCO1 PAPBSGBWRJIAAV-UHFFFAOYSA-N 0.000 description 2
- 229920008790 Amorphous Polyethylene terephthalate Polymers 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000012790 adhesive layer Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 230000003078 antioxidant effect Effects 0.000 description 1
- 239000002216 antistatic agent Substances 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- CDQSJQSWAWPGKG-UHFFFAOYSA-N butane-1,1-diol Chemical compound CCCC(O)O CDQSJQSWAWPGKG-UHFFFAOYSA-N 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- 239000003484 crystal nucleating agent Substances 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 238000009820 dry lamination Methods 0.000 description 1
- 235000013305 food Nutrition 0.000 description 1
- 229920001903 high density polyethylene Polymers 0.000 description 1
- 239000004700 high-density polyethylene Substances 0.000 description 1
- DLINORNFHVEIFE-UHFFFAOYSA-N hydrogen peroxide;zinc Chemical compound [Zn].OO DLINORNFHVEIFE-UHFFFAOYSA-N 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000011256 inorganic filler Substances 0.000 description 1
- 229910003475 inorganic filler Inorganic materials 0.000 description 1
- 229920001684 low density polyethylene Polymers 0.000 description 1
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- 229910052751 metal Inorganic materials 0.000 description 1
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- 239000012785 packaging film Substances 0.000 description 1
- 238000005240 physical vapour deposition Methods 0.000 description 1
- 229920006122 polyamide resin Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920013716 polyethylene resin Polymers 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
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- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000012748 slip agent Substances 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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Images
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、透明性、耐熱性、バリヤー性等を失うことなく実用面の特性を維持し、良好な引裂き性を具備した包装用フィルムやテープ用フィルムとして有用な積層二軸延伸ポリエステルフィルムに関する。
【０００２】
【従来の技術】
従来から、切断性の優れたフィルムとしては、セロハンが知られている。セロハンは、その優れた透明性と易切断性、ひねりシワ固定性等の特性により各種包装材料、粘着テープ用として重用されている。しかし、一方ではセロハンは吸湿性を有する為に特性が季節により変動し、一定の品質のものを常に供給することは困難であった。
【０００３】
一方、ポリエチレンテレフタレートの二軸延伸フィルムからなる包装袋や粘着テープなどは、強靭性、耐熱性、耐水性、透明性、寸法安定性などの優れた特長を有しているが、反面、切断しにくく、包装用袋の口を引裂き難い欠点や、粘着テープが切り難い欠点、さらにひねり固定性が劣る為にひねり包装用に用いることができない等の欠点があった。ポリエチレンテレフタレートフィルムの厚みを薄くすると、易切断性は容易に改善されるが、通常４μｍ以下の極薄にしなければならない。このようなフィルムは生産や二次加工においてハンドリング性能が極端に低下するため、フィルムの厚みを薄くすることなしに、易切断性を付与する技術が種々検討されてきた。
【０００４】
上記問題を解決する方法として、一軸方向に配向させたポリエステルフィルム（特許文献１）、ジエチレングリコール成分などを共重合させたもの（特許文献２）、低分子量のポリエステル樹脂を用いるもの（特許文献３）、さらに融点の異なる二種のポリエステルフィルムからなる積層フィルムにおいて、低融点層が実質的に非晶構造となるような製法により得られたフィルム（特許文献４）などが提案されている。
【０００５】
しかしながら、上記従来技術において、特許文献１の一軸方向に延伸させたフィルムは、配向方向へは直線的に容易に切れるが配向方向以外には切れ難いものである。また特許文献２のジエチレングリコール成分などを多量に共重合させたフィルムは、共重合によりポリエチレンテレフタレート本来の特性が失われるという欠点を有している。更に、特許文献３の低分子量のポリエステル樹脂を用いたフィルムは、溶融張力が小さくなりすぎるためにフィルムの溶融成形においてドローダウンなどのトラブルが発生しやすかったり、延伸工程での膜破れのトラブルが発生しやすく工業的な生産は困難であった。
【０００６】
一方、特許文献４の積層フィルムは、低融点ポリエステル層が比較的低強度の非晶状態となるような条件を採用し、かつ強度保持層である高融点ポリエステル層を可能な限り薄く成形することで、フィルムの厚みを減じることなく、強度特性をセロファンに近づけることが可能となるという利点がある。
しかし、特許文献４に提案された構成では、実質的に高融点ポリエステル層の強度特性が積層フィルムの易切断性に大きく影響する。すなわち高融点ポリエステル層単独の強度が高いと積層フィルム全体の強度が増加し、易切断性の改良効果が低下するという特徴を有している。特許文献４の実施例１および２では、高融点ポリエステルの固有粘度が一般的に包装用途において用いられている程度の値（０．６２）であるため、その強度と破断伸度が比較的高く、手で切断する際にフィルムが伸びやすく、開封性がセロファンに比較して劣るという問題があった。さらに、特許文献４に記載された方法では、積層フィルムの層間剥離強度が低く、例えばフィルムを手で引き裂いた場合に層間剥離が生じ、カットラインが乱れてしまうという問題があった。すなわち、このようなフィルムからなる製袋品を開封すると、いわゆる股開きが生じ、内容物の飛散が起こりやすいという問題があった。
【０００７】
【特許文献１】
特公昭５５−８５５１号公報
【特許文献２】
特公昭５６−５０６９２号公報
【特許文献３】
特公昭５５−２０５１４号公報
【特許文献４】
特開平５−１０４６１８号公報
【０００８】
【発明が解決しようとする課題】
本発明はセロハンの有する特性のうち特に易切断性に注目し、従来の改良されたポリエステル系フィルムよりもさらに易切断性に優れたフィルムを提供することを目的としたものである。
【０００９】
【課題を解決するための手段】
本発明者らは、鋭意検討を行った結果、融点の異なる二種以上の結晶性ポリエステルからなる積層二軸延伸ポリエステルフィルムにおいて、従来単独では製膜困難と考えられていた範囲の低い固有粘度のポリエステルを強度支持層である高融点ポリエステル樹脂層として使用し、また低融点ポリエステル樹脂層として比較的高い固有粘度のポリエステルを用いつつ、低融点ポリエステル樹脂層が実質的に非晶状態となるような製法をとることで、溶融成形性に優れ、かつ積層フィルムの厚みを減じることなく易切断性が改良され、かつ生産性の高いフィルムが得られることを見出し本発明に至った。本発明の要旨は以下のとおりである。
（１）下記▲１▼〜▲３▼を満たす結晶性ポリエステル（Ａ）と結晶性ポリエステル（Ｂ）とからそれぞれ構成されたフィルム層を少なくとも一層ずつ有する積層フィルムであって、積層フィルムが下記▲４▼〜▲５▼を満たすことを特徴とする易切断性に優れた積層二軸延伸ポリエステルフィルム。
▲１▼結晶性ポリエステル（Ｂ）の融点が、結晶性ポリエステル（Ａ）の融点より２５℃以上低い。
▲２▼結晶性ポリエステル（Ａ）の固有粘度が０．４０〜０．５５である。
▲３▼結晶性ポリエステル（Ｂ）の固有粘度が０．６０〜０．９０である。
▲４▼結晶性ポリエステル（Ａ）層の厚み割合が全厚みに対し１０〜５０％である。
▲５▼結晶性ポリエステル（Ｂ）層の結晶化指数Ｑが０．２以下である。
（２）結晶性ポリエステル（Ａ）層と結晶性ポリエステル（Ｂ）層の層間剥離強度が１．０Ｎ／ｃｍ以上であることを特徴とする（１）記載の積層二軸延伸ポリエステルフィルム。
（３）積層フィルムの厚みが８〜３０μｍであり、かつ積層フィルムの引張強度が２０〜１２０ＭＰａであること特徴とする（１）または（２）に記載の積層二軸延伸ポリエステルフィルム。
【００１０】
【発明の実施の形態】
以下、本発明について詳細に説明する。
本発明において用いられる結晶性ポリエステル（Ａ）としては通常融点が２００℃以上、好ましくは２２０℃以上のものが用いられ、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリプロピレンテレフタレート、ポリエチレン−２，６−ナフタレートを主骨格とするものが用いられる。中でもポリエチレンテレフタレートを主骨格とするポリエステル樹脂が好適に用いられる。このような結晶性ポリエステル樹脂には、必要とされる特性が損なわれない限り他の共重合成分が共重合されていてもよい。
【００１１】
共重合に用いられる酸変性成分としては、イソフタル酸、フタル酸、２，６−ナフタレンジカルボン酸、５−ナトリウムスルホイソフタル酸、シュウ酸、コハク酸、アジピン酸、セバシン酸、ドデカン二酸、ダイマー酸、無水マレイン酸、マレイン酸、フマール酸、イタコン酸、シトラコン酸、メサコン酸、シクロヘキサンジカルボン酸などのジカルボン酸や、４−ヒドロキシ安息香酸、ε−カプロラクトン、乳酸などのオキシカルボン酸や、トリメリット酸、トリメシン酸、ピロメリット酸などの多官能化合物などが挙げられる。これらの酸変性成分は単独で用いてもよいし、２種以上を混合して用いてもよい。
【００１２】
また、共重合に用いられるジオール変性成分として、１，３−プロパンジオール、１，４−ブタンジオール、ネオペンチルグリコール、１，４−シクロヘキサンジメタノール、１，３−シクロヘキサンジメタノール、１，２−シクロヘキサンジメタノール、１，６−へキサンジオール、ポリエチレングリコール、ポリプロピレングリコール、ポリテトラメチレングリコール、ビスフェノールＡやビスフェノールＳのエチレンオキシド付加体などのグリコールや、トリメチロールプロパン、グリセリン、ペンタエリスリトールなどの多官能化合物などが挙げられる。これらのジオール変性成分は単独で用いてもよいし、２種以上を混合して用いてもよい。
【００１３】
本発明において用いられる結晶性ポリエステル（Ａ）の２０℃における固有粘度は０．４０〜０．５５であることが必要であり、０．４０〜０．５０であることが好ましい。結晶性ポリエステル（Ａ）の固有粘度をこの範囲に限定することにより、従来よりも優れた易切断性を有する積層フィルムを提供することができる。固有粘度がこれより大きいと、易切断性が損なわれるため好ましくない。また固有粘度がこれより小さいと、溶融成形が困難となったり、フィルムの強度や伸度が低下しすぎるため好ましくない。
【００１４】
本発明において用いられる結晶性ポリエステル（Ｂ）は、後述した理由により、結晶性ポリエステル（Ａ）よりも２５℃以上低い融点を有する結晶性ポリエステルであることが必要である。結晶性ポリエステル（Ｂ）の具体例として、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリプロピレンテレフタレート、ポリエチレン−２，６−ナフタレートを主骨格とし、他の共重合成分が共重合されたものが挙げられる。
【００１５】
共重合に用いられる酸変性成分としては、イソフタル酸、フタル酸、２，６−ナフタレンジカルボン酸、５−ナトリウムスルホイソフタル酸、シュウ酸、コハク酸、アジピン酸、セバシン酸、ドデカン二酸、ダイマー酸、無水マレイン酸、マレイン酸、フマール酸、イタコン酸、シトラコン酸、メサコン酸、シクロヘキサンジカルボン酸などのジカルボン酸や、４−ヒドロキシ安息香酸、ε−カプロラクトン、乳酸などのオキシカルボン酸や、トリメリット酸、トリメシン酸、ピロメリット酸などの多官能化合物などが挙げられる。これらの酸変性成分は単独で用いてもよいし、２種以上を混合して用いてもよい。
【００１６】
また、共重合に用いられるジオール変性成分として、１，３−プロパンジオール、１，４−ブタンジオール、ネオペンチルグリコール、１，４−シクロヘキサンジメタノール、１，３−シクロヘキサンジメタノール、１，２−シクロヘキサンジメタノール、１，６−へキサンジオール、ポリエチレングリコール、ポリプロピレングリコール、ポリテトラメチレングリコール、ビスフェノールＡやビスフェノールＳのエチレンオキシド付加体などのグリコールや、トリメチロールプロパン、グリセリン、ペンタエリスリトールなどの多官能化合物などが挙げられる。これらのジオール変性成分は単独で用いてもよいし、２種以上を混合して用いてもよい。
【００１７】
本発明に用いられる結晶性ポリエステル（Ｂ）は、結晶性ポリエステル（Ａ）と同等の共重合成分からなる共重合体であってもよいし、また異なる共重合成分からなる共重合体であってもよい。
【００１８】
本発明において用いられる結晶性ポリエステル（Ｂ）の２０℃における固有粘度は０．６０〜０．９０であることが必要であり、０．６８〜０．８０であることが好ましい。本発明においては積層フィルムを構成する高融点ポリエステル（Ａ）層の固有粘度が比較的小さく、（Ａ）層単独では溶融成形が困難であるため、積層フィルムのもう一方の構成成分である低融点ポリエステル（Ｂ）層の固有粘度は比較的高いものを用いる必要がある。結晶性ポリエステル（Ｂ）層の固有粘度が０．６０未満であると溶融張力が低下し、積層フィルムの溶融成形が困難となるため好ましくない。また０．９０より大きいと溶融押出時の負荷が大きくなるため好ましくない。
【００１９】
本発明において用いられる結晶性ポリエステル（Ａ）と（Ｂ）のガラス転移温度に特に制限はないが、共押出、共延伸という製法を採用する上で両者のガラス転移温度の差の絶対値が４０℃以下であることが好ましい。この値が４０℃より大きいと、共延伸をおこなう延伸温度において、どちらか一方のポリエステルの延伸が困難となり、延伸が不均一となるため好ましくない。
【００２０】
本発明において用いられる結晶性ポリエステル（Ａ）と（Ｂ）は、本発明の効果を阻害しない範囲で、公知の各種添加剤、例えば結晶核剤、スリップ剤、無機フィラー、ピニング剤、酸化防止剤、帯電防止剤などを含んでいてもよい。また、結晶性ポリエステル（Ａ）と（Ｂ）には、必要とされる特性が損なわれない範囲において他の高分子成分が含まれていてもよい。これらの高分子成分は分子論的に相溶であっても、非相溶であっても構わない。
【００２１】
本発明の積層フィルムは、結晶性ポリエステル（Ａ）と結晶性ポリエステル（Ｂ）とを少なくとも一層ずつ有することが必要である。積層ポリエステルフィルムの具体的な層構成に特に限定はないが、Ａ／Ｂなどの２種２層構成をはじめ、Ａ／Ｂ／Ａ、Ｂ／Ａ／Ｂなどの２種３層構成、Ａ／Ｂ／Ａ／Ｂ／Ａ、Ｂ／Ａ／Ｂ／Ａ／Ｂなどの２種５層構成など任意の構成が挙げられる。結晶性ポリエステル（Ａ）層が最外層になるように構成した積層フィルムは、これに接着剤を介してポリエチレン層を積層して用いた場合に、ヒートシール時の外層融着がなく、また耐薬品性に優れるため、Ａ／Ｂ／Ａが好ましい構成として挙げられる。
【００２２】
本発明の積層フィルムにおいては、結晶性ポリエステル（Ａ）層の厚みの、積層フィルムの全厚みに対する割合は１０〜５０％であることが必要であり、さらには１５〜４５％であることが好ましい。結晶性ポリエステル（Ａ）層の厚みが全厚みの５０％を超えると、積層フィルムの強度が高くなり易切断性が低下したり、低粘度層の増加によって溶融張力が低下し安定的な溶融成形が困難となるため好ましくない。また結晶性ポリエステル（Ａ）層の厚みが全厚みの１０％未満の場合、結晶性ポリエステル（Ａ）層の寄与により得られる積層フィルムの耐熱性、力学的特性および良好な延伸性、厚み精度が損なわれたり、積層フィルムにおける結晶性ポリエステル（Ａ）層単独の厚み精度をコントロールすることが困難となるため好ましくない。
【００２３】
本発明の積層フィルムは、次式（１）で規定される結晶化指数Ｑが０．２以下であることが必要であり、０．１以下、さらに０．０５以下であることが好ましい。
Ｑ＝（｜ΔＨｍＢ｜−｜ΔＨｃＢ｜）／｜ΔＨｍＢ｜・・・（１）
ただしΔＨｍＢおよびΔＨｃＢはそれぞれ、示差走査型熱量計によって積層フィルムを２０℃から高融点側の結晶性ポリエステル（Ａ）の融点＋２０℃まで昇温速度１０℃／ｍｉｎで昇温した際に観測される、低融点側の結晶性ポリエステル（Ｂ）に由来する結晶融解熱量および発熱結晶化熱量を示す。式（１）においてＱが小さいことは積層ポリエステル内における低融点側の結晶性ポリエステル（Ｂ）が、第１回目の昇温過程において結晶化可能な部分を有する、すなわち結晶化可能な非晶性部分をより多く有していることを意味する。低融点側の結晶性ポリエステル（Ｂ）の非晶性が大きいほど、積層ポリエステル全体の強度が低下するため、厚みを減じることなく易切断性が向上するため好ましい。結晶化指数Ｑが０．２より大きい場合は、低融点側の結晶性ポリエステル（Ｂ）層の配向結晶化の寄与により、積層フィルムの易切断性が低下するため好ましくない。
【００２４】
上記のような結晶化指数Ｑを有する（Ｂ）層を積層フィルムに形成する方法として、例えば特開平５−１０４６１８号公報に記載の方法と類似の方法を採用することができる。すなわち二軸延伸工程後に積層フィルムを低融点側の結晶性ポリエステル（Ｂ）の融点より５℃以上高く、かつ高融点側の結晶性ポリエステル（Ａ）の融点より５℃以上低い温度で熱固定処理を行う方法などが挙げられる。このような方法をとることによって、二軸延伸によって生じた結晶性ポリエステル（Ａ）層の配向結晶化構造を大きく損なうことなく熱固定処理を行い、そして二軸延伸によって生じた結晶性ポリエステル（Ｂ）の配向結晶化構造のみを、解配向、結晶融解させ、結果として積層フィルム全体が配向結晶化している場合よりも、易切断性の改善された積層フィルムが得られる。熱固定温度がこの温度範囲より低いと、低融点ポリエステル（Ｂ）層の結晶融解および解配向効果が十分に得られず、積層フィルムの易切断性改良効果が低下するため好ましくない。またこの温度範囲より高いと、高融点結晶性ポリエステル（Ａ）層においても結晶融解および解配向が起こり、二軸延伸フィルムの生産が困難となるため好ましくない。
【００２５】
通常、工業的に生産性の高い二軸延伸ポリエステルフィルムの製法においては、熱セット炉長と生産速度の関係から熱固定に利用できる時間は通常数秒から十数秒の範囲に限定される。したがって、このような短時間内に結晶性ポリエステル（Ｂ）を結晶融解、解配向させるためには、熱固定温度は結晶性ポリエステル（Ｂ）の融点より可能な限り高いことが好ましい。一方、熱固定温度の上限としては高融点側の高結晶性ポリエステル（Ａ）の融点近傍の温度が挙げられ、通常は融点より５℃低い温度以上で熱固定処理を行うことは困難である。よって、本発明の積層フィルムを工業的に容易に得るためには、結晶性ポリエステル（Ａ）と（Ｂ）の融点差が大きいほど好ましい。このような観点から、本発明に用いられる結晶性ポリエステル（Ｂ）は、結晶性ポリエステル（Ａ）よりも２５℃以上低い融点を有することが必要であり、さらには３０℃以上低い融点を有することが好ましい。
【００２６】
本発明の積層フィルムにおいては、積層フィルムにおける層間剥離強度が１．０Ｎ／ｃｍ以上であることが好ましく、さらに１．２Ｎ／ｃｍ以上であることが好ましい。ここでいう層間剥離強度とは温度２０℃、湿度６５％ＲＨの環境下、幅１５ｍｍの試料片を用い、結晶性ポリエステル（Ａ）層および結晶性ポリエステル（Ｂ）層間を速度３００ｍｍ／ｍｉｎでＴ型剥離した際に計測されるＴ型剥離強度（試料片の幅１ｃｍあたりに換算した剥離強力。単位Ｎ／ｃｍ）のことをいう。本発明のごとく積層フィルムの一方の構成成分である結晶性ポリエステル（Ａ）層に比較的低分子量のポリエステルを用いることにより、従来よりも層間剥離強度が改善される。層間剥離強度がこれより小さいと、手でフィルムを切断した際に層間剥離が生じやすく、その結果切断後のカットラインが乱れ、例えば製袋品などを開封する際に内容物の飛散を招きやすいため好ましくない。
【００２７】
本発明の積層フィルムの厚みは８〜３０μｍの範囲、さらには１０〜２５μｍの範囲にあることが好ましい。厚みが８μｍより小さい場合、生産工程や、印刷などの二次加工工程においてしわ、切断などのトラブルが生じ易いため好ましくない。また厚みが３０μｍより大きい場合、本発明に記載の積層フィルム構成によっても、フィルムに易切断性を付与することが困難となるため好ましくない。
【００２８】
本発明の積層フィルムは上記の厚み範囲内にあって、かつＪＩＳ Ｋ ６７３２に準じて測定された引張強度が２０〜１２０ＭＰａ、さらには３０〜１１０ＭＰａであることが好ましい。引張強度がこれより大きいと、上記の厚み範囲にある積層フィルムに十分な易切断性を付与することが困難となるため好ましくない。また引張強度がこれより小さいと、積層フィルムの生産や二次加工においてフィルムの切断トラブルが起こりやすくなるため好ましくない。本発明においては積層フィルムの厚みを適度な範囲にコントロールしつつ、かつフィルムの引張強度を従来の技術よりも低下させることで、生産や二次加工において良好なハンドリング性を付与しつつ、かつ易切断性に優れた積層フィルムを提供できる点で、従来の技術に優っている。
【００２９】
本発明の積層フィルムには必要に応じて、他の高分子素材、例えば高密度ポリエチレン樹脂、低密度ポリエチレン樹脂、直鎖状低密度ポリエチレン樹脂、変性ポリエチレン樹脂、ポリプロピレン樹脂、変性ポリプロピレン樹脂、ポリアミド樹脂、ポリエステル樹脂、および／またはそれらからなるフィルムを、接着剤層の存在下または非存在下に少なくとも一層以上積層してもよい。積層する方法としてはドライラミネート法、押出ラミネート法、熱ラミネート法など任意の公知の方法が挙げられる。
【００３０】
本発明の積層フィルムには必要に応じて、無機膜、例えば二酸化珪素、アルミナ、二酸化亜鉛、またはこれらの混合物などからなる層を積層してもよい。積層する方法としては物理蒸着法、化学蒸着法など任意の公知の方法が挙げられる。
【００３１】
本発明の積層フィルムには必要に応じて、金属膜、例えばアルミニウムからなる層を積層してもよい。積層する方法として例えば蒸着法、ドライラミネート法など任意の公知の方法が挙げられる。
【００３２】
本発明の積層フィルムには必要に応じて、紙からなる層を積層してもよい。積層する方法として例えばドライラミネート法、押出ラミネート法、熱ラミネート法など任意の公知の方法が挙げられる。
【００３３】
結晶性ポリエステル（Ａ）層と結晶性ポリエステル（Ｂ）層とを積層する方法として、複数の押出機等の中で、別々に樹脂を溶融し、ダイス出口から押出して未延伸フィルムに成形し、次いで未延伸フィルム同士を加温状態でラミネートする方法が好適な例として挙げられる。別の方法としては一方の未延伸フィルムの表面に、他方の溶融フィルムを溶融ラミネートする方法が挙げられる。さらに別の方法としては共押出し法により積層した状態でダイス出口より押出してフィルムを成形する方法が挙げられる。
【００３４】
次に本発明の積層フィルムの製造法の一例を説明する。十分に乾燥した結晶性ポリエステル（Ａ）及び結晶性ポリエステル（Ｂ）をそれぞれ別の２台の押出機に供給し、溶融押出しし、複合アダプターを通過させ、２種２層（Ａ／Ｂ）または２種３層（Ａ／Ｂ／Ａ）としてＴダイのダイオリフィスからシート状に押出し吐出する。ダイオリフィスから吐出された軟化状態にあるシートは、例えば静電ピニング法など公知の冷却法により冷却ドラムに密着、冷却される。
続いて、得られた未延伸シートを９０〜１４０℃の温度で、通常、縦横それぞれ３．０〜５．０倍の延伸倍率で二軸延伸する。延伸温度が９０℃未満であると均質な延伸フィルムを得ることができない場合があり、１４０℃を超えると、結晶性ポリエステル樹脂の結晶化が促進されて延伸が不均一となったり、透明性が悪くなる場合がある。また、延伸倍率が３．０倍未満であると、十分な配向効果が得られないために力学特性に劣り、また５．０倍を超えると延伸が困難になるため好ましくない。
二軸延伸されたフィルムは、続いて、結晶性ポリエステル（Ｂ）層の融点＋５℃以上、結晶性ポリエステル（Ａ）層の融点−５℃以下の温度で熱処理される。熱処理温度が高すぎるとフィルムが溶断するため好ましくない。
なお、二軸延伸方法としては、テンター同時二軸延伸法、ロールとテンターによる逐次二軸延伸方法、あるいはチューブラー法のいずれでもよい。
【００３５】
【実施例】
以下、実施例により本発明を説明する。実施例および比較例における評価の方法と使用したポリエステル樹脂は以下のとおりである。
【００３６】
〔端裂抵抗および端裂伸度の測定〕
端裂抵抗は、ＪＩＳ Ｃ ２３１８ ６．３．４項に準じ、積層フィルムのＭＤ方向について測定した。また試料の破断点における変形率（％）により端裂伸度を評価した。
【００３７】
〔引張強度の測定〕
引張強度はＪＩＳ Ｋ ６７３２に準じ、積層フィルムのＭＤ方向について測定した。
【００３８】
〔層間剥離強度の測定〕
積層フィルムの片面に接着剤（（ａ）主剤：大日本インキ化学工業社製ディックドライＬＸ６３Ｆ、（ｂ）硬化剤：大日本インキ化学工業社製ＫＰ−９０、（ｃ）酢酸エチル、（ａ）／（ｂ）／（ｃ）＝１／１２／１０（質量比））を塗布、８０℃、１５秒間熱風乾燥して溶媒を蒸発させたのち、直鎖状低密度ポリエチレンシーラント（東セロ社製ＴＵＸＦＣＳ＃５０：厚み５０μｍ）をドライラミネートした。ドライラミネートサンプルより幅１５ｍｍ、長さ１４０ｍｍのサンプルを切り出し、２０℃、６５％ＲＨの環境下、引張速度３００ｍｍ／ｍｉｎの速度でＴ型剥離を行い、剥離強度を測定した（単位Ｎ／ｃｍ）。剥離後の試料厚みを測定することにより、試料の剥離界面を判定したところ、本実施例、比較例の全てのサンプルで結晶性ポリエステル樹脂（Ａ）層と結晶性ポリエステル樹脂（Ｂ）層の間で剥離しており、これらの剥離強度をもって層間剥離強度とした。
【００３９】
〔結晶化指数の測定〕
積層フィルムより約５ｍｇの試料をサンプリングし、島津製作所社製示差走査熱量計ＤＳＣ−６０を用い下記の方法で測定した。試料を２０℃から２７０℃まで１０℃／ｍｉｎの昇温速度で昇温した際の、低融点側の結晶性ポリエステル（Ｂ）に由来する発熱ピークの面積より結晶化熱量ΔＨｃＢ（Ｊ／ｇ）を、また低融点側の結晶性ポリエステル（Ｂ）に由来する吸熱ピークより結晶融解熱量ΔＨｍＢ（Ｊ／ｇ）を測定した。ピーク面積の算出にあたっては、ピーク温度に対して低温側のベースラインと高温側のベースラインにおけるオフセット温度を結んだ直線をピーク部のベースラインとして用いた（図１）。各測定値より結晶化指数Ｑを計算した。
【００４０】
〔手切れ性の評価〕
１００ｍｍ角に切り出された積層フィルムサンプルをフィルムのＴＤ方向に両手で引き裂くことによりフィルムのハンドカット性能を３段階で評価した。容易に手で引き裂けたものを○、やや抵抗が高かったが引き裂きは可能なものを△、手で引き裂くのが困難であったものを×とした。
【００４１】
〔製袋品の開封安定性〕
積層フィルムの片面に接着剤（（ａ）主剤：大日本インキ化学工業社製ディックドライＬＸ６３Ｆ、（ｂ）硬化剤：大日本インキ化学工業社製ＫＰ−９０、（ｃ）酢酸エチル、（ａ）／（ｂ）／（ｃ）＝１／１２／１０（質量比））を塗布、８０℃、１５秒間熱風乾燥して溶媒を蒸発させたのち、直鎖状低密度ポリエチレンシーラント（東セロ社製ＴＵＸＦＣＳ＃３０：厚み３０μｍ）をドライラミネートした。得られたラミネートフィルムを４０℃、４８時間エージング処理した。得られたラミネートフィルムから１００ｍｍ×１００ｍｍの試料片を二枚切り出し、ＭＤ、ＴＤ方向をそろえて重ね合わせ四方ヒートシール袋を作製した。このシール袋をＴＤ方向に手で引裂いた際に、直線的なカットラインで開封されたものを○、結晶性ポリエステル（Ａ）層と結晶性ポリエステル（Ｂ）層の間で層間剥離が生じ、カットラインが大きく乱れ、股開き状態となったものを×とした。
【００４２】
〔ポリエステル樹脂〕
ＰＥＴ１：
ユニチカ社製ポリエチレンテレフタレート樹脂ＤＡＢＲ、固有粘度０．４７、融点２５６℃。
ＰＥＴ２：
ユニチカ社製ポリエチレンテレフタレート樹脂ＤＨＣＢＲ、固有粘度０．６７、融点２５６℃。
ＰＥＴ３：
ユニチカ社製ポリエチレンテレフタレート樹脂ＣＧ０ＢＲＤ、固有粘度０．５４、融点２５６℃。
【００４３】
ＩＰＥＴ１：
グリコール成分としてエチレングリコールと、酸成分としてテレフタル酸、共重合比１１ｍｏｌ％のイソフタル酸をエステル化槽に仕込み、２４０℃で４時間反応させ、エステル化物を得た。次に、三酸化アンチモン触媒下、１．３ｈＰａの減圧下、３００℃で溶融重合し、固有粘度が０．６７になるように重合時間を調整して、融点２１１℃のポリエステル樹脂ＩＰＥＴ１を得た。
【００４４】
ＩＰＥＴ２：
上記ＩＰＥＴ１と同様にして溶融重合し、固有粘度が０．５８になるように重合時間を調整して、融点２１１℃のポリエステル樹脂ＩＰＥＴ２を得た。
【００４５】
ＡＰ１：
グリコール成分としてエチレングリコールと、酸成分としてテレフタル酸、共重合比１ｍｏｌ％のトリメリット酸、および共重合比５ｍｏｌ％のイソフタル酸をエステル化槽に仕込み、２４０℃で４時間反応させ、エステル化物を得た。次に、三酸化アンチモン触媒下、１．３ｈＰａの減圧下、３００℃で溶融重合し、固有粘度０．５０、融点２３２℃のポリエステル樹脂ＡＰ１を得た。
【００４６】
ＢＤＰＥＴ
グリコール成分としてエチレングリコールと共重合比４７ｍｏｌ％のブタンジオール、酸成分としてテレフタル酸をエステル化槽に仕込み、２４０℃で４時間反応させ、エステル化物を得た。次に、三酸化アンチモン触媒下、１．３ｈＰａの減圧下、３００℃で溶融重合し、固有粘度０．６７、融点１８０℃のポリエステルＢＤＰＥＴを得た。
【００４７】
ＡＰＥＴ：
イーストマンケミカル社製ＥＡＳＴＥＲ ９９２１（エチレングリコールと１，４−シクロヘキサンジメタノール３．４ｍｏｌ％、およびテレフタル酸を共重合したポリエステル）固有粘度０．８０、融点２３４℃。
【００４８】
実施例１
結晶性ポリエステル（Ａ）としてＰＥＴ１、結晶性ポリエステル（Ｂ）としてＩＰＥＴ１を各々温度２７０℃で別々の押出機により溶融し、この溶融体を複合アダプターで合流させた後にＴダイより押出し、冷却ドラムで急冷してＡ／Ｂ／Ａ構成の３層の未延伸積層フィルムを得た。この時、延伸後の積層ポリエステルフィルムにおいて結晶性ポリエステル（Ａ）層および結晶性ポリエステル（Ｂ）層の厚み構成が２μｍ／８μｍ／２μｍの割合になるように各押出機の吐出量を調整した。
未延伸積層フィルムをまずロール延伸法により縦方向に約９０℃で３．５倍、次いでテンター延伸法により横方向に約１１０℃で３．８倍に延伸した後、横方向に３％の弛緩を行いつつ２２０℃の温度で約５秒間熱処理を行った。さらにフィルムを冷却した後、巻取機によりロール状に巻き取り、表１に示した厚み構成を有する積層二軸延伸ポリエステルフィルムを得た。このフィルムの評価結果を表１に示した。
【００４９】
実施例２〜６、比較例１〜５
結晶性ポリエステル（Ａ）と結晶性ポリエステル（Ｂ）の種類、またＡ／Ｂ／Ａの厚み構成を表１のように変更した以外は実施例１と同様にして積層二軸延伸ポリエステルフィルムを得た。このフィルムの評価結果を表１に示した。
【００５０】
【表１】
実施例１〜６の積層フィルムは、手切れ性と開封安定性に優れたものであった。一方、比較例１と２の積層フィルムは、結晶性ポリエステル（Ａ）の固有粘度が高いため、それぞれ引張強度が高く、易切断性に劣るものであり、また積層フィルムの剥離強度は低いものであった。また比較例３の積層フィルムは、結晶性ポリエステル（Ａ）の厚み比率が高いため、さらに比較例４の積層フィルムは、結晶性ポリエステル（Ｂ）の融点が結晶性ポリエステル（Ａ）の融点より２５℃以上低くないので、熱固定工程において結晶融解が生じず、結晶化指数Ｑが高くなったため、それぞれのフィルムは引張強度が高く、易切断性に劣るものであった。比較例５の積層フィルムは結晶性ポリエステル（Ｂ）の固有粘度が低いために、ドローダウンにより未延伸フィルムの製膜が困難であった。
【００５２】
【発明の効果】
本発明のごとく、融点の異なる二種のポリエステルを積層した二軸延伸フィルムにおいて、各樹脂の層厚みの比率、固有粘度を特定の範囲に限定することにより、積層フィルムの層間剥離強度が改善され、従来の技術に比して易切断性に優れ、かつ溶融成形が容易な積層ポリエステルフィルムを得ることができる。その結果、手切れ性のみならず開封時のカットラインの安定性にすぐれ、かつ加工性のバランスに優れたポリエステルフィルムを得ることができる。本発明の方法によれば、食品をはじめとする、医薬品、日用品、コスメティックスなどの包装材料や粘着テープとして有用な手切れ性に優れたフィルムを工業的かつ容易に提供することが可能である。
【図面の簡単な説明】
【図１】示差走査型熱量計によって観察される結晶融解熱量（ΔＨｍＢ）と結晶化熱量（ΔＨｃＢ）を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laminated biaxially stretched polyester film useful as a packaging film or tape film that maintains practical properties without losing transparency, heat resistance, barrier properties, and the like and has good tearability.
[0002]
[Prior art]
Conventionally, cellophane has been known as a film having excellent cutting properties. Cellophane is widely used for various packaging materials and adhesive tapes due to its excellent transparency, easy cutting property, twist wrinkle fixability and the like. However, on the other hand, since cellophane has hygroscopicity, its characteristics fluctuate depending on the season, and it has been difficult to always supply a certain quality.
[0003]
On the other hand, packaging bags and adhesive tapes made of polyethylene terephthalate biaxially stretched film have excellent features such as toughness, heat resistance, water resistance, transparency, and dimensional stability. There are disadvantages such as difficulty in tearing the mouth of the packaging bag, difficulty in cutting the adhesive tape, and inability to use for twist packaging due to poor twist fixability. When the thickness of the polyethylene terephthalate film is reduced, the easy-cutting property is easily improved, but usually it must be extremely thin 4 μm or less. Since such a film has extremely low handling performance in production and secondary processing, various techniques for imparting easy cutting properties without reducing the thickness of the film have been studied.
[0004]
As a method for solving the above problems, a polyester film oriented in a uniaxial direction (Patent Document 1), a copolymerized diethylene glycol component (Patent Document 2), or a low molecular weight polyester resin (Patent Document 3) Furthermore, a film (Patent Document 4) obtained by a manufacturing method in which a low melting point layer has a substantially amorphous structure in a laminated film composed of two kinds of polyester films having different melting points has been proposed.
[0005]
However, in the above prior art, the film stretched in the uniaxial direction of Patent Document 1 is easily cut linearly in the alignment direction but difficult to cut in other directions than the alignment direction. Moreover, the film which copolymerized the diethylene glycol component of patent document 2 in large quantities has the fault that the original characteristic of a polyethylene terephthalate is lost by copolymerization. Furthermore, the film using the low molecular weight polyester resin of Patent Document 3 has a low melt tension, so that troubles such as drawdown are likely to occur in the melt molding of the film, and there is a problem of film breakage in the stretching process. It was easy to generate and industrial production was difficult.
[0006]
On the other hand, the laminated film of Patent Document 4 adopts conditions such that the low-melting polyester layer is in a relatively low strength amorphous state, and the high-melting polyester layer that is a strength holding layer is formed as thin as possible. Thus, there is an advantage that the strength characteristics can be brought close to cellophane without reducing the thickness of the film.
However, in the configuration proposed in Patent Document 4, the strength characteristics of the high-melting polyester layer substantially affect the easy-cutability of the laminated film. That is, when the strength of the high melting point polyester layer alone is high, the strength of the whole laminated film is increased, and the effect of improving the easy cutting property is lowered. In Examples 1 and 2 of Patent Document 4, since the intrinsic viscosity of the high-melting polyester is a value (0.62) that is generally used in packaging applications, its strength and elongation at break are relatively high. When cut by hand, there was a problem that the film was easy to stretch, and the openability was inferior to cellophane. Furthermore, the method described in Patent Document 4 has a problem that the delamination strength of the laminated film is low. For example, when the film is torn by hand, delamination occurs and the cut line is disturbed. That is, when a bag-made product made of such a film is opened, there is a problem that so-called crotch opening occurs and the contents are easily scattered.
[0007]
[Patent Document 1]
Japanese Patent Publication No.55-8551
[Patent Document 2]
Japanese Patent Publication No. 56-50692
[Patent Document 3]
Japanese Patent Publication No.55-20514
[Patent Document 4]
Japanese Patent Laid-Open No. 5-104618
[0008]
[Problems to be solved by the invention]
The present invention aims to provide a film that is more easily cut than conventional polyester-based films by paying particular attention to easy cutting among the characteristics of cellophane.
[0009]
[Means for Solving the Problems]
As a result of intensive studies, the inventors of the present invention, in a laminated biaxially stretched polyester film composed of two or more crystalline polyesters having different melting points, have a low intrinsic viscosity in a range that was conventionally considered difficult to form alone. The polyester is used as a high-melting polyester resin layer which is a strength support layer, and a polyester having a relatively high intrinsic viscosity is used as a low-melting polyester resin layer, while the low-melting polyester resin layer is substantially in an amorphous state. By taking the production method, the inventors found that a film having excellent melt moldability, improved easy cutting without reducing the thickness of the laminated film, and high productivity can be obtained. The gist of the present invention is as follows.
(1) A laminated film having at least one film layer composed of crystalline polyester (A) and crystalline polyester (B) satisfying the following (1) to (3), wherein the laminated film is A laminated biaxially stretched polyester film excellent in easy cutting characteristics characterized by satisfying 4 ▼ to 5).
(1) The melting point of the crystalline polyester (B) is 25 ° C. or more lower than the melting point of the crystalline polyester (A).
(2) The intrinsic viscosity of the crystalline polyester (A) is 0.40 to 0.55.
(3) The intrinsic viscosity of the crystalline polyester (B) is 0.60 to 0.90.
(4) The thickness ratio of the crystalline polyester (A) layer is 10 to 50% with respect to the total thickness.
(5) The crystallization index Q of the crystalline polyester (B) layer is 0.2 or less.
(2) The laminated biaxially stretched polyester film according to (1), wherein the delamination strength between the crystalline polyester (A) layer and the crystalline polyester (B) layer is 1.0 N / cm or more.
(3) The laminated biaxially stretched polyester film according to (1) or (2), wherein the laminated film has a thickness of 8 to 30 μm and the laminated film has a tensile strength of 20 to 120 MPa.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
As the crystalline polyester (A) used in the present invention, those having a melting point of 200 ° C. or higher, preferably 220 ° C. or higher are used, and polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, and polyethylene-2,6-naphthalate are mainly used. A skeleton is used. Of these, polyester resins having polyethylene terephthalate as the main skeleton are preferably used. Such a crystalline polyester resin may be copolymerized with other copolymerization components as long as required properties are not impaired.
[0011]
Examples of acid-modifying components used for copolymerization include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid , Maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, cyclohexanedicarboxylic acid and other dicarboxylic acids, 4-hydroxybenzoic acid, ε-caprolactone, lactic acid and other oxycarboxylic acids, and trimellitic acid And polyfunctional compounds such as trimesic acid and pyromellitic acid. These acid-modifying components may be used alone or in combination of two or more.
[0012]
Further, as diol-modifying components used for copolymerization, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2- Cyclohexanedimethanol, 1,6-hexanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, glycols such as ethylene oxide adducts of bisphenol A and bisphenol S, and polyfunctional compounds such as trimethylolpropane, glycerin, pentaerythritol Etc. These diol-modified components may be used alone or in combination of two or more.
[0013]
The intrinsic viscosity at 20 ° C. of the crystalline polyester (A) used in the present invention needs to be 0.40 to 0.55, preferably 0.40 to 0.50. By limiting the intrinsic viscosity of the crystalline polyester (A) to this range, it is possible to provide a laminated film having an easy-to-cut property superior to that of the prior art. If the intrinsic viscosity is larger than this, it is not preferable because easy cutting properties are impaired. On the other hand, if the intrinsic viscosity is smaller than this, melt molding becomes difficult, and the strength and elongation of the film are excessively lowered.
[0014]
The crystalline polyester (B) used in the present invention needs to be a crystalline polyester having a melting point that is 25 ° C. lower than the crystalline polyester (A) for the reasons described later. Specific examples of the crystalline polyester (B) include those in which polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, and polyethylene-2,6-naphthalate are main skeletons and other copolymerization components are copolymerized.
[0015]
Examples of acid-modifying components used for copolymerization include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid , Maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, cyclohexanedicarboxylic acid and other dicarboxylic acids, 4-hydroxybenzoic acid, ε-caprolactone, lactic acid and other oxycarboxylic acids, and trimellitic acid And polyfunctional compounds such as trimesic acid and pyromellitic acid. These acid-modifying components may be used alone or in combination of two or more.
[0016]
Further, as diol-modifying components used for copolymerization, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2- Cyclohexanedimethanol, 1,6-hexanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, glycols such as ethylene oxide adducts of bisphenol A and bisphenol S, and polyfunctional compounds such as trimethylolpropane, glycerin, pentaerythritol Etc. These diol-modified components may be used alone or in combination of two or more.
[0017]
The crystalline polyester (B) used in the present invention may be a copolymer composed of copolymer components equivalent to the crystalline polyester (A), or a copolymer composed of different copolymer components. Also good.
[0018]
The intrinsic viscosity at 20 ° C. of the crystalline polyester (B) used in the present invention is required to be 0.60 to 0.90, and preferably 0.68 to 0.80. In the present invention, since the intrinsic viscosity of the high-melting polyester (A) layer constituting the laminated film is relatively small and it is difficult to melt-mold the layer (A) alone, the low melting point which is the other component of the laminated film. The polyester (B) layer must have a relatively high intrinsic viscosity. If the intrinsic viscosity of the crystalline polyester (B) layer is less than 0.60, the melt tension is lowered, and it becomes difficult to melt-mold the laminated film. On the other hand, if it is larger than 0.90, the load at the time of melt extrusion increases, which is not preferable.
[0019]
The glass transition temperatures of the crystalline polyesters (A) and (B) used in the present invention are not particularly limited, but the absolute value of the difference between the glass transition temperatures of the two methods is 40 when adopting the coextrusion and costretching methods. It is preferable that it is below ℃. When this value is larger than 40 ° C., it is not preferable because either one of the polyesters becomes difficult to be stretched at the stretching temperature at which co-stretching is performed, and stretching becomes nonuniform.
[0020]
The crystalline polyesters (A) and (B) used in the present invention are various known additives such as a crystal nucleating agent, a slip agent, an inorganic filler, a pinning agent, and an antioxidant as long as the effects of the present invention are not impaired. Further, it may contain an antistatic agent or the like. The crystalline polyesters (A) and (B) may contain other polymer components as long as the required properties are not impaired. These polymer components may be molecularly compatible or incompatible.
[0021]
The laminated film of the present invention needs to have at least one layer of the crystalline polyester (A) and the crystalline polyester (B). The specific layer structure of the laminated polyester film is not particularly limited, but includes two kinds and two layers such as A / B, two kinds and three layers such as A / B / A, B / A / B, and A / B. Arbitrary structures, such as 2 types 5 layer structure, such as B / A / B / A and B / A / B / A / B, are mentioned. The laminated film configured so that the crystalline polyester (A) layer is the outermost layer has no outer layer fusion at the time of heat sealing when it is used by laminating a polyethylene layer via an adhesive. Since it is excellent in chemical properties, A / B / A is mentioned as a preferred configuration.
[0022]
In the laminated film of the present invention, the ratio of the thickness of the crystalline polyester (A) layer to the total thickness of the laminated film needs to be 10 to 50%, and more preferably 15 to 45%. . If the thickness of the crystalline polyester (A) layer exceeds 50% of the total thickness, the strength of the laminated film will increase and the easy-cut property will decrease, or the melt tension will decrease due to the increase in the low-viscosity layer, and stable melt molding Is not preferable because it becomes difficult. When the thickness of the crystalline polyester (A) layer is less than 10% of the total thickness, the heat resistance, mechanical properties, good stretchability, and thickness accuracy of the laminated film obtained by the contribution of the crystalline polyester (A) layer are This is not preferable because it is difficult to control the thickness accuracy of the crystalline polyester (A) layer alone in the laminated film.
[0023]
The laminated film of the present invention needs to have a crystallization index Q defined by the following formula (1) of 0.2 or less, preferably 0.1 or less, and more preferably 0.05 or less.
Q = (| ΔHmB | − | ΔHcB |) / | ΔHmB | (1)
However, ΔHmB and ΔHcB are each observed when the temperature of the laminated film is raised from 20 ° C. to the melting point of the crystalline polyester (A) on the high melting point side + 20 ° C. at a heating rate of 10 ° C./min by a differential scanning calorimeter. 2 shows the amount of heat of crystal melting and the amount of heat of crystallization derived from the crystalline polyester (B) on the low melting point side. The small Q in the formula (1) means that the low-melting-point crystalline polyester (B) in the laminated polyester has a crystallizable portion in the first temperature raising process, that is, a crystallizable amorphous property. It means having more parts. The higher the amorphous property of the low-melting-point crystalline polyester (B), the lower the strength of the entire laminated polyester. When the crystallization index Q is larger than 0.2, it is not preferable because the easy cutting property of the laminated film is lowered due to the orientation crystallization of the crystalline polyester (B) layer on the low melting point side.
[0024]
As a method for forming the layer (B) having the crystallization index Q as described above on the laminated film, for example, a method similar to the method described in JP-A-5-104618 can be employed. That is, after the biaxial stretching step, the laminated film is heat-set at a temperature 5 ° C. or more higher than the melting point of the low-melting crystalline polyester (B) and 5 ° C. or lower than the melting point of the high-melting crystalline polyester (A). The method of performing etc. is mentioned. By adopting such a method, a heat-setting treatment is performed without greatly damaging the oriented crystallization structure of the crystalline polyester (A) layer generated by biaxial stretching, and the crystalline polyester (B Only the oriented crystallized structure of) is subjected to de-orientation and crystal melting, and as a result, a laminated film with improved easy cutting properties can be obtained as compared with the case where the whole laminated film is oriented and crystallized. When the heat setting temperature is lower than this temperature range, the crystal melting and deorientation effects of the low melting point polyester (B) layer cannot be sufficiently obtained, and the effect of improving the easy cutting property of the laminated film is lowered, which is not preferable. If the temperature is higher than this temperature range, crystal melting and deorientation also occur in the high-melting crystalline polyester (A) layer, and production of a biaxially stretched film becomes difficult.
[0025]
Usually, in the production method of a biaxially stretched polyester film with high industrial productivity, the time available for heat setting is usually limited to a range of several seconds to several tens of seconds from the relationship between the heat setting furnace length and the production speed. Therefore, in order to crystallize and disorient the crystalline polyester (B) within such a short time, the heat setting temperature is preferably as high as possible as compared with the melting point of the crystalline polyester (B). On the other hand, the upper limit of the heat setting temperature includes a temperature in the vicinity of the melting point of the high crystalline polyester (A) on the high melting point side, and it is usually difficult to perform the heat setting treatment at a temperature of 5 ° C. or lower than the melting point. Therefore, in order to easily obtain the laminated film of the present invention industrially, it is preferable that the difference in melting point between the crystalline polyesters (A) and (B) is large. From such a viewpoint, the crystalline polyester (B) used in the present invention needs to have a melting point lower by 25 ° C. or more than the crystalline polyester (A), and further has a melting point lower by 30 ° C. or more. Is preferred.
[0026]
In the laminated film of the present invention, the delamination strength in the laminated film is preferably 1.0 N / cm or more, and more preferably 1.2 N / cm or more. The delamination strength here refers to a sample piece having a width of 15 mm under an environment of a temperature of 20 ° C. and a humidity of 65% RH, and the T between the crystalline polyester (A) layer and the crystalline polyester (B) layer at a speed of 300 mm / min. T-type peel strength measured at the time of mold peeling (peeling strength converted per 1 cm width of the sample piece, unit N / cm). By using a relatively low molecular weight polyester for the crystalline polyester (A) layer which is one of the components of the laminated film as in the present invention, the delamination strength is improved as compared with the prior art. If the delamination strength is lower than this, delamination is likely to occur when the film is cut by hand, and as a result, the cut line after the cutting is disturbed, and for example, the contents are likely to be scattered when opening a bag-making product. Therefore, it is not preferable.
[0027]
The thickness of the laminated film of the present invention is preferably in the range of 8 to 30 μm, more preferably in the range of 10 to 25 μm. When the thickness is less than 8 μm, troubles such as wrinkling and cutting are liable to occur in the production process and the secondary processing process such as printing. Moreover, when thickness is larger than 30 micrometers, since it becomes difficult to provide easy cutability to a film also by the laminated | multilayer film structure as described in this invention, it is unpreferable.
[0028]
The laminated film of the present invention is in the above thickness range, and the tensile strength measured according to JIS K 6732 is preferably 20 to 120 MPa, more preferably 30 to 110 MPa. When the tensile strength is larger than this, it is difficult to impart sufficient easy cutting property to the laminated film in the above thickness range, which is not preferable. On the other hand, if the tensile strength is less than this, it is not preferable because troubles in cutting the film are likely to occur in the production of the laminated film and the secondary processing. In the present invention, while controlling the thickness of the laminated film to an appropriate range and lowering the tensile strength of the film from the conventional technology, it is easy to provide good handling properties in production and secondary processing. It is superior to conventional technology in that it can provide a laminated film with excellent cutting properties.
[0029]
If necessary, the laminated film of the present invention may have other polymer materials such as high density polyethylene resin, low density polyethylene resin, linear low density polyethylene resin, modified polyethylene resin, polypropylene resin, modified polypropylene resin, polyamide resin. , Polyester resin, and / or a film comprising them may be laminated at least in the presence or absence of an adhesive layer. As a method for laminating, any known method such as a dry laminating method, an extrusion laminating method, or a thermal laminating method may be mentioned.
[0030]
If necessary, the laminated film of the present invention may be laminated with an inorganic film, for example, a layer made of silicon dioxide, alumina, zinc dioxide, or a mixture thereof. As a lamination method, any known method such as physical vapor deposition or chemical vapor deposition may be used.
[0031]
If necessary, the laminated film of the present invention may be laminated with a metal film, for example, a layer made of aluminum. As a lamination method, for example, any known method such as a vapor deposition method or a dry lamination method may be used.
[0032]
If necessary, a layer made of paper may be laminated on the laminated film of the present invention. As a method of laminating, for example, any known method such as a dry laminating method, an extrusion laminating method, or a thermal laminating method may be mentioned.
[0033]
As a method of laminating the crystalline polyester (A) layer and the crystalline polyester (B) layer, in a plurality of extruders, etc., the resins are melted separately, extruded from the die outlet and formed into an unstretched film, Next, a preferred example is a method of laminating unstretched films in a heated state. Another method includes a method of melt laminating the other molten film on the surface of one unstretched film. Still another method includes a method of forming a film by extruding from a die outlet in a state of being laminated by a co-extrusion method.
[0034]
Next, an example of the manufacturing method of the laminated film of this invention is demonstrated. The sufficiently dried crystalline polyester (A) and crystalline polyester (B) are fed to two separate extruders, melt extruded, passed through a composite adapter, two types of two layers (A / B) or It is extruded and discharged in the form of a sheet from the die orifice of a T die as two types and three layers (A / B / A). The softened sheet discharged from the die orifice is closely attached to the cooling drum and cooled by a known cooling method such as an electrostatic pinning method.
Subsequently, the obtained unstretched sheet is biaxially stretched at a temperature of 90 to 140 ° C., usually at a stretching ratio of 3.0 to 5.0 times in the longitudinal and lateral directions. If the stretching temperature is less than 90 ° C, a homogeneous stretched film may not be obtained. If the stretching temperature exceeds 140 ° C, crystallization of the crystalline polyester resin is promoted and stretching becomes nonuniform, It may get worse. Further, if the draw ratio is less than 3.0 times, a sufficient orientation effect cannot be obtained, so that the mechanical properties are inferior, and if it exceeds 5.0 times, stretching becomes difficult, which is not preferable.
The biaxially stretched film is subsequently heat treated at a temperature of the melting point of the crystalline polyester (B) layer + 5 ° C. or higher and the melting point of the crystalline polyester (A) layer−5 ° C. or lower. If the heat treatment temperature is too high, the film will melt, which is not preferable.
The biaxial stretching method may be any of a tenter simultaneous biaxial stretching method, a sequential biaxial stretching method using a roll and a tenter, or a tubular method.
[0035]
【Example】
Hereinafter, the present invention will be described by way of examples. Evaluation methods and polyester resins used in Examples and Comparative Examples are as follows.
[0036]
(Measurement of end resistance and end elongation)
The end resistance was measured in the MD direction of the laminated film according to JIS C 2318 6.3.4. Further, the end crack elongation was evaluated by the deformation rate (%) at the breaking point of the sample.
[0037]
(Measurement of tensile strength)
The tensile strength was measured in the MD direction of the laminated film according to JIS K 6732.
[0038]
[Measurement of delamination strength]
Adhesive on one side of the laminated film ((a) Main agent: Dick Dry LX63F manufactured by Dainippon Ink and Chemicals, (b) Curing agent: KP-90 manufactured by Dainippon Ink and Chemicals, (c) Ethyl acetate, (a) / (B) / (c) = 1/12/10 (mass ratio)), dried with hot air at 80 ° C. for 15 seconds to evaporate the solvent, and then linear low density polyethylene sealant (TUXFCS manufactured by Tosero) # 50: 50 μm thick) was dry laminated. A sample having a width of 15 mm and a length of 140 mm was cut out from the dry laminate sample, and T-type peeling was performed at a tensile rate of 300 mm / min in an environment of 20 ° C. and 65% RH, and the peeling strength was measured (unit: N / cm). . When the peeling interface of the sample was determined by measuring the thickness of the sample after peeling, between the crystalline polyester resin (A) layer and the crystalline polyester resin (B) layer in all the samples of this example and the comparative example. The peel strength was defined as the peel strength.
[0039]
(Measurement of crystallization index)
A sample of about 5 mg was sampled from the laminated film and measured by the following method using a differential scanning calorimeter DSC-60 manufactured by Shimadzu Corporation. The amount of heat of crystallization ΔHcB (J / g) from the area of the exothermic peak derived from the crystalline polyester (B) on the low melting point side when the sample was heated from 20 ° C. to 270 ° C. at a rate of 10 ° C./min. The heat of crystal fusion ΔHmB (J / g) was measured from the endothermic peak derived from the low melting point crystalline polyester (B). In calculating the peak area, a straight line connecting the offset temperature between the low temperature side baseline and the high temperature side baseline with respect to the peak temperature was used as the peak portion baseline (FIG. 1). The crystallization index Q was calculated from each measured value.
[0040]
[Evaluation of hand cutting properties]
The hand cut performance of the film was evaluated in three stages by tearing a laminated film sample cut into a 100 mm square with both hands in the TD direction of the film. Those that were easily torn by hand were rated as ◯, those that were somewhat resistant but could be torn were marked by Δ, and those that were difficult to tear by hand were marked as ×.
[0041]
[Opening stability of bag products]
Adhesive on one side of the laminated film ((a) Main agent: Dick Dry LX63F manufactured by Dainippon Ink and Chemicals, (b) Curing agent: KP-90 manufactured by Dainippon Ink and Chemicals, (c) Ethyl acetate, (a) / (B) / (c) = 1/12/10 (mass ratio)), dried with hot air at 80 ° C. for 15 seconds to evaporate the solvent, and then linear low density polyethylene sealant (TUXFCS manufactured by Tosero) # 30: 30 μm thick) was dry laminated. The obtained laminate film was aged at 40 ° C. for 48 hours. Two 100 mm × 100 mm sample pieces were cut out from the obtained laminate film and aligned in the MD and TD directions to produce a four-side heat-sealed bag. When this seal bag is torn by hand in the TD direction, the one opened by the linear cut line is ○, delamination occurs between the crystalline polyester (A) layer and the crystalline polyester (B) layer, The case where the cut line was greatly disturbed and the crotch was in an open state was rated as x.
[0042]
[Polyester resin]
PET1:
Unitika polyethylene terephthalate resin DABR, intrinsic viscosity 0.47, melting point 256 ° C.
PET2:
Unitika polyethylene terephthalate resin DHCBR, intrinsic viscosity 0.67, melting point 256 ° C.
PET3:
Unitika polyethylene terephthalate resin CG0BRD, intrinsic viscosity 0.54, melting point 256 ° C.
[0043]
IPET1:
Ethylene glycol as a glycol component, terephthalic acid as an acid component, and isophthalic acid having a copolymerization ratio of 11 mol% were charged in an esterification tank and reacted at 240 ° C. for 4 hours to obtain an esterified product. Next, melt polymerization was performed at 300 ° C. under a reduced pressure of 1.3 hPa under an antimony trioxide catalyst, and the polymerization time was adjusted so that the intrinsic viscosity was 0.67, whereby a polyester resin IPET1 having a melting point of 211 ° C. was obtained. .
[0044]
IPET2:
In the same manner as in the above-mentioned IPET1, melt polymerization was carried out, and the polymerization time was adjusted so that the intrinsic viscosity was 0.58.
[0045]
AP1:
Ethylene glycol as a glycol component, terephthalic acid as an acid component, trimellitic acid having a copolymerization ratio of 1 mol%, and isophthalic acid having a copolymerization ratio of 5 mol% are charged into an esterification tank and reacted at 240 ° C. for 4 hours to obtain an esterified product. Obtained. Next, melt polymerization was performed at 300 ° C. under a reduced pressure of 1.3 hPa under an antimony trioxide catalyst to obtain a polyester resin AP1 having an intrinsic viscosity of 0.50 and a melting point of 232 ° C.
[0046]
BDPET
Ethylene glycol as a glycol component and butanediol having a copolymerization ratio of 47 mol% and terephthalic acid as an acid component were charged in an esterification tank and reacted at 240 ° C. for 4 hours to obtain an esterified product. Next, melt polymerization was performed at 300 ° C. under a reduced pressure of 1.3 hPa under an antimony trioxide catalyst to obtain a polyester BDPET having an intrinsic viscosity of 0.67 and a melting point of 180 ° C.
[0047]
APET:
Eastman Chemical Co., Ltd. EASTER 9921 (polyester copolymerized with ethylene glycol, 1,4-cyclohexanedimethanol, 3.4 mol%, and terephthalic acid) Inherent viscosity 0.80, melting point 234 ° C.
[0048]
Example 1
PET1 as the crystalline polyester (A) and IPET1 as the crystalline polyester (B) were melted by separate extruders at a temperature of 270 ° C., and these melts were merged with a composite adapter, extruded from a T die, and cooled with a cooling drum. Quenching was performed to obtain a three-layer unstretched laminated film having an A / B / A configuration. At this time, the discharge amount of each extruder was adjusted so that the thickness configuration of the crystalline polyester (A) layer and the crystalline polyester (B) layer in the laminated polyester film after stretching was in a ratio of 2 μm / 8 μm / 2 μm.
An unstretched laminated film is first stretched 3.5 times at about 90 ° C in the machine direction by roll stretching, then 3.8 times at about 110 ° C in the transverse direction by the tenter stretching method, and then relaxed by 3% in the transverse direction. Then, heat treatment was performed at a temperature of 220 ° C. for about 5 seconds. Further, after the film was cooled, it was wound into a roll by a winder, and a laminated biaxially stretched polyester film having the thickness configuration shown in Table 1 was obtained. The evaluation results of this film are shown in Table 1.
[0049]
Examples 2-6, Comparative Examples 1-5
A laminated biaxially stretched polyester film was obtained in the same manner as in Example 1 except that the types of the crystalline polyester (A) and the crystalline polyester (B) and the thickness structure of A / B / A were changed as shown in Table 1. It was. The evaluation results of this film are shown in Table 1.
[0050]
[Table 1]
The laminated films of Examples 1 to 6 were excellent in hand cutting properties and opening stability. On the other hand, since the laminated films of Comparative Examples 1 and 2 have high intrinsic viscosity of the crystalline polyester (A), the tensile strength is high and the easy-cut property is poor, and the peel strength of the laminated film is low. there were. Moreover, since the laminated film of Comparative Example 3 has a high thickness ratio of the crystalline polyester (A), the laminated film of Comparative Example 4 further has a melting point of the crystalline polyester (B) of 25 than the melting point of the crystalline polyester (A). Since the temperature was not lower than ° C., crystal melting did not occur in the heat setting step, and the crystallization index Q was high. Therefore, each film had high tensile strength and poor cutability. Since the laminated film of Comparative Example 5 had a low intrinsic viscosity of the crystalline polyester (B), it was difficult to form an unstretched film by drawdown.
[0052]
【The invention's effect】
As in the present invention, in a biaxially stretched film in which two kinds of polyesters having different melting points are laminated, the delamination strength of the laminated film is improved by limiting the ratio of the layer thickness of each resin and the intrinsic viscosity to a specific range. Thus, it is possible to obtain a laminated polyester film that is excellent in easy cutting properties and easy to melt-mold as compared with conventional techniques. As a result, it is possible to obtain a polyester film that is excellent not only in hand cutting properties but also in the stability of the cut line at the time of opening and excellent in workability balance. According to the method of the present invention, it is possible to provide industrially and easily a film having excellent hand cutting properties useful as packaging materials such as foods, pharmaceuticals, daily necessities, cosmetics and the like and adhesive tapes.
[Brief description of the drawings]
FIG. 1 is a graph showing a heat of crystal fusion (ΔHmB) and a heat of crystallization (ΔHcB) observed by a differential scanning calorimeter.
Claims (3)
▲１▼結晶性ポリエステル（Ｂ）の融点が、結晶性ポリエステル（Ａ）の融点より２５℃以上低い。
▲２▼結晶性ポリエステル（Ａ）の固有粘度が０．４０〜０．５５である。
▲３▼結晶性ポリエステル（Ｂ）の固有粘度が０．６０〜０．９０である。
▲４▼結晶性ポリエステル（Ａ）層の厚み割合が全厚みに対し１０〜５０％である。
▲５▼結晶性ポリエステル（Ｂ）層の結晶化指数Ｑが０．２以下である。A laminated film having at least one film layer composed of a crystalline polyester (A) and a crystalline polyester (B) satisfying the following (1) to (3), wherein the laminated film comprises the following (4) to (4) A laminated biaxially stretched polyester film excellent in easy cutting, characterized by satisfying (5).
(1) The melting point of the crystalline polyester (B) is 25 ° C. or more lower than the melting point of the crystalline polyester (A).
(2) The intrinsic viscosity of the crystalline polyester (A) is 0.40 to 0.55.
(3) The intrinsic viscosity of the crystalline polyester (B) is 0.60 to 0.90.
(4) The thickness ratio of the crystalline polyester (A) layer is 10 to 50% with respect to the total thickness.
(5) The crystallization index Q of the crystalline polyester (B) layer is 0.2 or less.
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| WO2006087795A1 (en) * | 2005-02-18 | 2006-08-24 | Toyo Boseki Kabushiki Kaisha | Easy-to-tear polyester resin film |
| JP2008031273A (en) * | 2006-07-28 | 2008-02-14 | Toyobo Co Ltd | Biaxially stretched polyester film |
| JP2009214355A (en) * | 2008-03-09 | 2009-09-24 | Mitsubishi Plastics Inc | Biaxially oriented laminated polyester film |
| WO2020067193A1 (en) * | 2018-09-28 | 2020-04-02 | ユニチカ株式会社 | Polyester film, and method for manufacturing same |
| CN114015097A (en) * | 2021-11-05 | 2022-02-08 | 衢州市闻天化工有限公司 | Heat insulation composite film for building materials and preparation process thereof |
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| JP2001191407A (en) * | 2000-01-07 | 2001-07-17 | Mitsubishi Plastics Ind Ltd | Polylactic acid film |
| JP2002337290A (en) * | 2001-05-16 | 2002-11-27 | Toyobo Co Ltd | Laminated polyester film |
| JP2002337269A (en) * | 2001-05-16 | 2002-11-27 | Toyobo Co Ltd | Laminated polyester film and packaging bag using the same |
| JP2002337285A (en) * | 2001-05-16 | 2002-11-27 | Toyobo Co Ltd | Laminated polyester film |
| JP2002337289A (en) * | 2001-05-16 | 2002-11-27 | Toyobo Co Ltd | Laminated polyester film and packaging bag using the same |
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| WO2006087795A1 (en) * | 2005-02-18 | 2006-08-24 | Toyo Boseki Kabushiki Kaisha | Easy-to-tear polyester resin film |
| JP2008031273A (en) * | 2006-07-28 | 2008-02-14 | Toyobo Co Ltd | Biaxially stretched polyester film |
| JP2009214355A (en) * | 2008-03-09 | 2009-09-24 | Mitsubishi Plastics Inc | Biaxially oriented laminated polyester film |
| WO2020067193A1 (en) * | 2018-09-28 | 2020-04-02 | ユニチカ株式会社 | Polyester film, and method for manufacturing same |
| EP3858887A4 (en) * | 2018-09-28 | 2022-06-22 | Unitika Ltd. | Polyester film, and method for manufacturing same |
| CN114015097A (en) * | 2021-11-05 | 2022-02-08 | 衢州市闻天化工有限公司 | Heat insulation composite film for building materials and preparation process thereof |
| CN114015097B (en) * | 2021-11-05 | 2022-08-30 | 衢州市闻天化工有限公司 | Heat insulation composite film for building materials and preparation process thereof |
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