JP2000272001A - Aliphatic polyester-based biaxially oriented film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an aliphatic polyester-based biaxially oriented film capable of obtaining the biaxially oriented film in which processing suitability is excellent in the case of performing printing, laminating and bag making or the like, by raising uniformity of molecular orientation in the inside of the film and to provide a film obtained by this method. SOLUTION: A nonorientated film consists of aliphatic polyester in which a main repeating unit is a formula -O-CHR-CO- (R shows-H or 1-3C alkyl group), as a main component. In the method for producing a biaxially orientated film having a sequential biaxially orientating process in which the nonorientated film is orientated in the longitudinal direction and thereafter orientated in the lateral direction, orientation in the longitudinal direction is performed in a range of temperature not lower than glass transition temperature (Tg)+20 deg.C of aliphatic polyester and not higher than low temperature crystallization temperature (Tc)+20 deg.C and in separation of at least two stages so that the combined draw ratio in the longitudinal direction becomes 2.0-4.5 times.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は、脂肪族ポリエステ
ル系二軸延伸フィルムの製造方法およびその製造方法に
より得られるフィルムに関するものである。得られる脂
肪族ポリエステル系二軸延伸フィルムは、主に生鮮食
品、加工食品、医薬品、医療機器、電子部品等の包装用
フィルムに利用される。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a biaxially stretched aliphatic polyester film and a film obtained by the method. The obtained aliphatic polyester-based biaxially stretched film is mainly used as a packaging film for fresh foods, processed foods, pharmaceuticals, medical devices, electronic components, and the like.

【０００２】[0002]

【従来の技術】従来、ポリ乳酸をはじめとする脂肪族ポ
リエステル系フィルムは、自然環境下に棄却された場合
に分解すること、例えばポリ乳酸フィルムは土壌中にお
いて自然に加水分解したのち微生物によって無害な分解
物となることを特徴として開発されてきた。このような
脂肪族ポリエステル系フィルムは、自然界で分解させる
ことを優先して開発が進められ、このため、本来、脂肪
族ポリエステルが持つ優れた特性を十分に引き出すこと
ができていなかった。すなわち、フィルムの配向・結晶
化が進むことにより、加水分解や微生物による分解が抑
制されるために、フィルム製膜時にフィルムの配向・結
晶化を抑制する必要があり、強度や熱寸法安定性が不十
分なものとなっていた。2. Description of the Related Art Conventionally, aliphatic polyester films such as polylactic acid are decomposed when discarded in a natural environment. For example, polylactic acid films are harmless by microorganisms after being naturally hydrolyzed in soil. It has been developed to be a decomposed product. Such aliphatic polyester-based films have been developed with a priority on decomposing in the natural world, and therefore, originally, the excellent properties of aliphatic polyesters could not be sufficiently brought out. That is, as the orientation and crystallization of the film progress, hydrolysis and decomposition by microorganisms are suppressed, so it is necessary to suppress the orientation and crystallization of the film during film formation, and the strength and thermal dimensional stability are reduced. Was inadequate.

【０００３】これに対し、フィルムの配向性や結晶化度
を向上させて、強度や熱寸法安定性を改善する試みがな
されている。例えば、特開平７−２０７０４１号公報に
は、ポリ乳酸系重合体からなり、面配向度ΔＰが３．０
×１０^-3以上であり、かつフィルムを昇温したときの結
晶融解熱量ΔＨｍと昇温中の結晶化により発生する結晶
化熱量ΔＨｃとの差（ΔＨｍ−ΔＨｃ）が２０Ｊ／ｇ以
上であるポリ乳酸系フィルムが開示されている。On the other hand, attempts have been made to improve strength and thermal dimensional stability by improving the orientation and crystallinity of a film. For example, Japanese Patent Application Laid-Open No. 7-207041 discloses a method comprising a polylactic acid-based polymer having a plane orientation degree ΔP of 3.0.
× 10 ⁻³ or more, and a difference (ΔHm−ΔHc) between the heat of crystal fusion ΔHm when the film is heated and the heat of crystallization ΔHc generated by crystallization during the temperature rise is 20 J / g or more. A lactic acid based film is disclosed.

【０００４】[0004]

【発明が解決しようとする課題】しかしながら、このよ
うなフィルムは、全体としての強度や熱寸法安定性が改
善されているものの、フィルム内の分子配向の均一性を
高める工夫がなされていないため、生鮮食品、加工食
品、医薬品、医療機器、電子部品等の包装用フィルムと
して用いる場合、包装用途のフィルムとして必要である
印刷工程やラミネート工程において平面性の悪化が生じ
て、しわが発生するなど、加工適性に問題があることが
明らかになった。However, although such a film has improved overall strength and thermal dimensional stability, it has not been devised to improve the uniformity of molecular orientation in the film. When used as a packaging film for fresh foods, processed foods, pharmaceuticals, medical equipment, electronic components, etc., flatness deteriorates in the printing process and lamination process required as a film for packaging use, and wrinkles are generated. It became clear that there was a problem in workability.

【０００５】また、このような脂肪族ポリエステル系フ
ィルムは、一般に、未延伸フィルムを縦方向に一段で延
伸し、ついで横方向に延伸する逐次二軸延伸方法等によ
り製造されるが、この方法で製造した二軸延伸フィルム
は、その幅方向に物性の分布（不均一）が生じやすいこ
とが知られている。このため、例えば、当該二軸延伸フ
ィルムを前述の包装用フィルムとして用いる場合、製袋
時における表裏のフィルムの配向の向きが異なり易く、
製袋時に熱を受けた場合や製袋後の加熱処理の際に、し
わの発生や袋のねじれ現象が発生するなどの問題があっ
た。[0005] Such an aliphatic polyester film is generally produced by a sequential biaxial stretching method in which an unstretched film is stretched in one step in the machine direction and then in the transverse direction. It is known that the produced biaxially stretched film tends to have a distribution (non-uniformity) of physical properties in the width direction thereof. For this reason, for example, when the biaxially stretched film is used as the packaging film described above, the orientation of the front and back films during bag making tends to be different,
There were problems such as generation of wrinkles and twisting of the bag when receiving heat during bag making or during heat treatment after bag making.

【０００６】そこで、本発明の目的は、フィルム内の分
子配向の均一性を高めることで、印刷、ラミネート、製
袋等を行う際の加工適性が優れた二軸延伸フィルムを得
ることができる脂肪族ポリエステル系二軸延伸フィルム
の製造方法、及び当該方法により得られるフィルムを提
供することにある。Accordingly, an object of the present invention is to improve the uniformity of molecular orientation in a film to obtain a biaxially stretched film having excellent workability in printing, laminating, bag making, and the like. An object of the present invention is to provide a method for producing an aromatic polyester-based biaxially stretched film and a film obtained by the method.

【０００７】[0007]

【課題を解決するための手段】本発明者らは、前記課題
を解決すべく、脂肪族ポリエステル系二軸延伸フィルム
の製造に採用されていた逐次二軸延伸方法について鋭意
検討を重ねた結果、縦方向の延伸工程を、特定の温度範
囲内で、しかも少なくとも二段階に分けて行うことによ
り、上記目的が達成できることを見出し、更に検討を加
えて本発明を完成するに至った。Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive studies on a sequential biaxial stretching method employed for producing an aliphatic polyester-based biaxially stretched film. It has been found that the above-mentioned object can be achieved by performing the stretching step in the longitudinal direction within a specific temperature range and in at least two steps, and has completed the present invention after further studies.

【０００８】即ち、本発明の製造方法は、主たる繰り返
し単位が一般式−Ｏ−ＣＨＲ−ＣＯ−（ＲはＨまたは、
炭素数１〜３のアルキル基を示す）である脂肪族ポリエ
ステルを主成分としてなる未延伸フィルムを、縦方向に
延伸した後に横方向に延伸する逐次二軸延伸工程を有す
る脂肪族ポリエステル系二軸延伸フィルムの製造方法に
おいて、前記縦方向の延伸を、前記脂肪族ポリエステル
のガラス転移温度（Ｔｇ）＋２０℃以上、低温結晶化温
度（Ｔｃ）＋２０℃以下の温度範囲内で、少なくとも二
段階に分けて、縦方向の総合倍率が２．０〜４．５倍と
なるように行うことを特徴とする。ここで、低温結晶化
温度（Ｔｃ）とは、温度を昇温していく際、ポリマーが
結晶化する温度を指す。That is, in the production method of the present invention, the main repeating unit is represented by the general formula -O-CHR-CO- (R is H or
Aliphatic polyester-based biaxial having a sequential biaxial stretching step in which an unstretched film mainly comprising an aliphatic polyester having 1 to 3 carbon atoms) is stretched in the longitudinal direction and then in the transverse direction. In the method for producing a stretched film, the stretching in the longitudinal direction is divided into at least two steps within a temperature range of a glass transition temperature (Tg) of the aliphatic polyester + 20 ° C. or more and a low-temperature crystallization temperature (Tc) + 20 ° C. or less. The total magnification in the vertical direction is 2.0 to 4.5 times. Here, the low-temperature crystallization temperature (Tc) indicates a temperature at which the polymer crystallizes when the temperature is increased.

【０００９】上記において、前記縦方向の延伸が、各段
階の延伸工程間のフィルム温度を前記Ｔｇ以上に維持し
つつ行うものであることが好ましい。In the above, it is preferable that the stretching in the longitudinal direction is performed while maintaining the film temperature at or above the Tg between the stretching steps in each step.

【００１０】前記脂肪族ポリエステルとしては、後述の
如く種々のものが挙げられるがポリ乳酸であることが好
ましい。As the above-mentioned aliphatic polyester, various ones can be mentioned as described later, and polylactic acid is preferable.

【００１１】一方、本発明の脂肪族ポリエステル系二軸
延伸フィルムは、上記いずれかに記載の製造方法により
得られる脂肪族ポリエステル系二軸延伸フィルムであっ
て、配向主軸の最大歪みが３０度以下、厚み方向の屈折
率（Ｎｚ）が１．４４０〜１．４５５であり、１２０℃
における熱収縮率が５％以下のものである。ここで、配
向主軸の最大歪み、Ｎｚ、及び熱収縮率は、実施例にお
ける評価方法で測定される値を指す。On the other hand, the aliphatic polyester-based biaxially stretched film of the present invention is an aliphatic polyester-based biaxially stretched film obtained by any one of the above-described production methods, wherein the maximum distortion of the main orientation axis is 30 ° or less. , The refractive index (Nz) in the thickness direction is 1.440 to 1.455, and 120 ° C.
Is less than 5%. Here, the maximum strain, Nz, and heat shrinkage of the orientation main axis indicate values measured by the evaluation method in the examples.

【００１２】上記において、長手方向の屈折率（Ｎｘ）
から幅方向の屈折率（Ｎｙ）を差し引いた値（Ｎｘ−Ｎ
ｙ）が−０．０２０〜０であることが好ましい。ここ
で、Ｎｘ、Ｎｙは、実施例における評価方法で測定され
る値を指す。In the above, the refractive index in the longitudinal direction (Nx)
(Nx-N) obtained by subtracting the refractive index (Ny) in the width direction from
It is preferred that y) is -0.020 to 0. Here, Nx and Ny indicate values measured by the evaluation method in the example.

【００１３】［作用効果］本発明の製造方法によると、
実施例の結果が示すように、フィルム内の分子配向の均
一性を高めることで、印刷、ラミネート、製袋等を行う
際の加工適性が優れた脂肪族ポリエステル系二軸延伸フ
ィルムを製造することができる。つまり、縦方向の延伸
工程を、特定の温度範囲内で、しかも少なくとも二段階
に分けて行うことにより、一段で行う場合に比べて、フ
ィルム内の分子配向の均一性を高めることができ、その
結果、加熱を伴う加工において、フィルムの歪が生じに
くくなり、加工適性が改善されると考えられる。[Effects] According to the production method of the present invention,
As the results of the examples show, by increasing the uniformity of molecular orientation in the film, printing, laminating, producing an aliphatic polyester-based biaxially stretched film excellent in workability when performing bag making and the like. Can be. In other words, by performing the stretching process in the longitudinal direction within a specific temperature range, and at least in two steps, the uniformity of molecular orientation in the film can be improved as compared with the case of performing in one step. As a result, in processing involving heating, it is considered that distortion of the film hardly occurs and processing suitability is improved.

【００１４】前記縦方向の延伸が、各段階の延伸工程間
のフィルム温度を前記Ｔｇ以上に維持しつつ行うもので
ある場合、フィルム内の分子配向の均一性をより高める
ことができ、フィルムの加工適性もより優れたものとな
る。In the case where the stretching in the longitudinal direction is performed while maintaining the film temperature between the stretching steps in each step at or above the Tg, the uniformity of molecular orientation in the film can be further improved, and Processing suitability is also improved.

【００１５】また、前記脂肪族ポリエステルのうちポリ
乳酸は、成形性、耐熱性、コストなどの総合的な面か
ら、本発明において好適に使用される。[0015] Of the aliphatic polyesters, polylactic acid is preferably used in the present invention from the comprehensive aspects such as moldability, heat resistance and cost.

【００１６】一方、本発明の脂肪族ポリエステル系二軸
延伸フィルムによると、フィルム内の分子配向の均一性
の指標となる、配向主軸の最大歪みが３０度以下である
ことに加え、面配向度の指標となる厚み方向の屈折率
（Ｎｚ）が１．４４０〜１．４５５であり、熱寸法変化
の指標となる熱収縮率が５％以下であるため、フィルム
内の分子配向の均一性を高めつつ、加熱を伴う加工時に
おけるフィルムの歪等の影響をより低減することができ
る。On the other hand, according to the aliphatic polyester-based biaxially stretched film of the present invention, the maximum distortion of the main orientation axis, which is an index of the uniformity of molecular orientation in the film, is not more than 30 degrees, The refractive index (Nz) in the thickness direction as an index of 1.44 to 1.455 and the thermal shrinkage rate as an index of the thermal dimensional change is 5% or less. It is possible to further reduce the effects of film distortion and the like during processing involving heating.

【００１７】また、長手方向の屈折率（Ｎｘ）から幅方
向の屈折率（Ｎｙ）を差し引いた値（Ｎｘ−Ｎｙ）が−
０．０２０〜０である場合、加熱を伴う加工におけるフ
ィルムの平面性や、フィルムの厚みの均一性がより高い
ものとなり、加工適性がより優れたものとなる。The value (Nx-Ny) obtained by subtracting the refractive index (Ny) in the width direction from the refractive index (Nx) in the longitudinal direction is-
When it is 0.020-0, the flatness of the film and the uniformity of the thickness of the film in the processing involving heating become higher, and the processing suitability becomes more excellent.

【００１８】[0018]

【発明の実施の形態】以下、本発明について詳細に説明
する。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

【００１９】本発明に用いる一般式−Ｏ−ＣＨＲ−ＣＯ
−（ＲはＨまたは炭素数１〜３のアルキル基）を主たる
繰り返し単位とする脂肪族ポリエステルとは、例えばポ
リ乳酸、ポリグリコール酸、ポリ（２−オキシ酪酸）等
のα−オキシ酸の重合体を挙げることができるが、これ
らに限定されるものではない。また、脂肪族ポリエステ
ルは、これらの単独でも良く、或いは混合物、共重合体
を使用してもかまわない。なお、脂肪族ポリエステルを
構成するα−オキシ酸等の不斉炭素を有するモノマー
は、Ｌ−体、ＤＬ−体、Ｄ−体のいずれの光学異性体で
も良く、またそれら異性体の混合物でも良い。これら脂
肪族ポリエステルは、対応するα−オキシ酸等の脱水環
状エステル化合物を開環重合する方法等、公知の方法で
製造することが出来る。The general formula -O-CHR-CO used in the present invention
The aliphatic polyester having-(R is H or an alkyl group having 1 to 3 carbon atoms) as a main repeating unit is, for example, a polymer of α-oxyacid such as polylactic acid, polyglycolic acid and poly (2-oxybutyric acid). Although coalescence can be mentioned, it is not limited to these. The aliphatic polyester may be used alone, or a mixture or a copolymer thereof may be used. The monomer having an asymmetric carbon such as α-oxy acid constituting the aliphatic polyester may be an optical isomer of L-form, DL-form or D-form, or may be a mixture of these isomers. . These aliphatic polyesters can be produced by a known method such as a method of ring-opening polymerization of a corresponding dehydrated cyclic ester compound such as α-oxy acid.

【００２０】また、前記脂肪族ポリエステルは、重量平
均分子量が、通常、１万〜５０万程度のものである。１
万未満であると、得られたフィルムの物性が著しく劣
り、且つ、分解速度が速すぎ本発明の目的を達し得な
い。また、フィルム製造時の押出し性、二軸延伸性も低
下することから重量平均分子量は１万以上である必要が
ある。これらを考慮すれば重量平均分子量は５万以上と
するのが好ましい。一方、重量平均分子量が５０万以上
の高粘度重合体になると溶融押出しが困難になるという
問題がある。これらを考慮すれば重量平均分子量は３０
万以下とするが好ましい。The aliphatic polyester generally has a weight average molecular weight of about 10,000 to 500,000. 1
If it is less than 10,000, the physical properties of the obtained film are remarkably inferior, and the decomposition rate is too high to achieve the object of the present invention. In addition, since the extrudability and biaxial stretchability during film production are also reduced, the weight average molecular weight needs to be 10,000 or more. In consideration of these, the weight average molecular weight is preferably set to 50,000 or more. On the other hand, a high viscosity polymer having a weight average molecular weight of 500,000 or more has a problem that melt extrusion becomes difficult. Considering these, the weight average molecular weight is 30.
It is preferably set to 10,000 or less.

【００２１】本発明の製造方法に供される、実質的に未
延伸フィルムは、前記脂肪族ポリエステルを主成分とす
るものであり、通常、押出成形法により成形される。当
該フィルムを押出成形する方法は、公知のＴ−ダイ法、
インフレーション法等を適用できる。押出し温度は、通
常、用いる脂肪族ポリエステルの融解温度（Ｔｍ）〜Ｔ
ｍ＋７０℃の範囲、より好ましくは、Ｔｍ＋２０℃〜Ｔ
ｍ＋５０℃の範囲である。押出し温度が低すぎると押出
し安定性が得難く、また過負荷に陥りやすい。また逆に
高すぎるとポリマーの分解が激しくなるので好ましくな
い。本発明で用いる押出機のダイは、環状または線状の
スリットを有するものでよい。ダイの温度は押出温度範
囲と同じ程度で良い。The substantially unstretched film used in the production method of the present invention contains the aliphatic polyester as a main component and is usually formed by an extrusion method. The method of extruding the film is a known T-die method,
An inflation method or the like can be applied. The extrusion temperature is usually from the melting temperature (Tm) of the aliphatic polyester used to T.
m + 70 ° C., more preferably Tm + 20 ° C. to T
m + 50 ° C. If the extrusion temperature is too low, it is difficult to obtain extrusion stability, and it is easy to fall into overload. Conversely, if the temperature is too high, the decomposition of the polymer becomes severe, which is not preferable. The die of the extruder used in the present invention may have an annular or linear slit. The temperature of the die may be as high as the extrusion temperature range.

【００２２】本発明では、前記未延伸フィルムを縦方向
に延伸し、ついで横方向に延伸する逐次二軸延伸方法に
より、脂肪族ポリエステル系二軸延伸フィルムを製造す
る。その際、縦方向の延伸を、脂肪族ポリエステルのガ
ラス転移温度（Ｔｇ）＋２０℃以上、低温結晶化温度
（Ｔｃ）＋２０℃以下の温度範囲内で、少なくとも二段
階に分けて、縦方向の総合倍率２．０〜４．５倍となる
ように行う。In the present invention, an aliphatic polyester-based biaxially stretched film is produced by a sequential biaxial stretching method in which the unstretched film is stretched in the machine direction and then in the transverse direction. At that time, the stretching in the longitudinal direction is divided into at least two stages within a temperature range of the glass transition temperature (Tg) of the aliphatic polyester + 20 ° C. or more and the low-temperature crystallization temperature (Tc) + 20 ° C. or less. This is performed so that the magnification becomes 2.0 to 4.5 times.

【００２３】縦方向の延伸温度が、Ｔｇ＋２０℃より低
いと、通常、縦方向の延伸を一段で製膜した場合と同
様、製膜後のフィルムの幅方向における物性差が大きく
なる。また、延伸温度が、Ｔｃ＋２０℃を超えると、厚
み均一性や得られたフィルムの機械的強度が低下し好ま
しくない。When the stretching temperature in the machine direction is lower than Tg + 20 ° C., the difference in physical properties in the width direction of the film after the film formation becomes large, as in the case where the machine is formed in one step in the machine direction. On the other hand, when the stretching temperature exceeds Tc + 20 ° C., the thickness uniformity and the mechanical strength of the obtained film are undesirably reduced.

【００２４】縦方向の延伸は少なくとも二段階に分ける
が、たとえば前段と後段の二段階に分けて、前段、後段
とも延伸温度をＴｇ＋２０〜Ｔｃ＋１０℃程度にするの
がより好ましい。The stretching in the longitudinal direction is divided into at least two stages. For example, it is more preferable to divide the stretching into two stages, a former stage and a latter stage, and to set the stretching temperature to about Tg + 20 to Tc + 10 ° C. in both the former and latter steps.

【００２５】また、縦方向の延伸における、各段階（二
段階の場合は前段と後段）の中間時における温度を、一
旦、Ｔｇ未満に冷却すると、得られるフィルムの幅方向
における物性差の低減効果が少なくなるため、中間時の
温度は、Ｔｇ以上にしておくのが好ましい。Further, once the temperature at the middle of each stage (the former stage and the latter stage in the case of two stages) in the longitudinal stretching is cooled to less than Tg, the effect of reducing the physical property difference in the width direction of the obtained film is reduced. Therefore, the temperature at the intermediate time is preferably set to Tg or more.

【００２６】また、縦方向の延伸倍率は、各段階の倍率
を合わせた総合倍率として２．０〜４．５倍にする。縦
方向の延伸の総合倍率が２．０倍に満たない場合には、
厚み均一性の良いフィルムは得られず、また機械的強度
等の物性の向上も乏しい。一方、縦方向の総合倍率が
４．５倍を超える場合には、フィルムの幅方向の物性差
が大きくなる傾向があり好ましくない。The stretching ratio in the longitudinal direction is 2.0 to 4.5 times as a total ratio obtained by combining the ratios of the respective stages. When the total magnification of the longitudinal stretching is less than 2.0 times,
A film having good uniformity in thickness cannot be obtained, and improvement in physical properties such as mechanical strength is also poor. On the other hand, if the total magnification in the vertical direction exceeds 4.5 times, the difference in physical properties in the width direction of the film tends to increase, which is not preferable.

【００２７】なお、縦方向の延伸を、たとえば前段と後
段の二段階に分けた場合、前段と後段の、それぞれ倍率
は、特に制限されないが、前段を１．０５〜３倍程度、
後段を１．０５〜３倍程度に調整し、総合倍率として２
〜４．５倍とするのが好ましい。When the stretching in the longitudinal direction is divided into, for example, two stages of a former stage and a latter stage, the respective magnifications of the former stage and the latter stage are not particularly limited.
Adjust the latter stage to about 1.05 to 3 times, and set the total magnification to 2
It is preferably set to 4.5 times.

【００２８】縦方向の延伸速度は、各段階のいずれの場
合も、厚み方向の屈折率（Ｎｚ）及び熱収縮率を所定の
範囲とするために、通常、１００００％／分以上、さら
に好ましくは１５０００％／分以上、特に好ましくは２
００００％／分以上である。The stretching speed in the longitudinal direction is usually 10,000% / min or more, and more preferably in order to keep the refractive index (Nz) and the heat shrinkage in the thickness direction within predetermined ranges in each of the steps. 15000% / min or more, particularly preferably 2
0000% / min or more.

【００２９】縦方向の延伸に続く、横方向の延伸は、各
種の手段を採用できる。延伸温度は、通常、Ｔｇ＋１０
〜Ｔｇ＋７０℃であり、延伸速度は、１０００％／分以
上が好ましい。また、横方向の延伸は、一段階で行って
もよく、多段階に分けて行っても良い。また、横方向の
延伸倍率は最終的には少なくとも３倍以上であることが
好ましく、特に好ましくは、３．５倍以上である。For the stretching in the horizontal direction following the stretching in the longitudinal direction, various means can be adopted. The stretching temperature is usually Tg + 10
To Tg + 70 ° C., and the stretching speed is preferably 1000% / min or more. The stretching in the horizontal direction may be performed in one stage or may be performed in multiple stages. Further, the stretching ratio in the transverse direction is preferably at least 3 times or more, and particularly preferably 3.5 times or more.

【００３０】また、縦方向および横方向の延伸後の、縦
・横の面積倍率は、厚み均一性の良いフィルムが得ら
れ、機械的強度等の物性の向上もよいことから、９倍以
上に延伸することが好ましく、特に１２倍以上に延伸す
るのが好ましい。The area ratio in the vertical and horizontal directions after stretching in the vertical and horizontal directions is 9 times or more, since a film having good uniformity in thickness can be obtained and physical properties such as mechanical strength can be improved. The film is preferably stretched, and particularly preferably stretched 12 times or more.

【００３１】さらに、脂肪族ポリエステル系二軸延伸フ
ィルムは、前記二軸延伸後に熱固定を行うのが、熱収縮
率を小さくする上で好ましい。熱固定温度は、１４５℃
〜融点が好ましい。Further, the biaxially stretched aliphatic polyester film is preferably heat-set after the biaxial stretching in order to reduce the heat shrinkage. Heat setting temperature is 145 ℃
~ Melting point is preferred.

【００３２】かかる本発明の脂肪族ポリエステル系二軸
延伸フィルムは製造工程において共押出し法やコーティ
ング法によって積層してもよい。また、本発明の二軸延
伸フィルムは、表面エネルギーを向上する目的で、コロ
ナ処理、プラズマ処理や火炎処理等を施しても良い。The biaxially stretched aliphatic polyester film of the present invention may be laminated by a coextrusion method or a coating method in the production process. Further, the biaxially stretched film of the present invention may be subjected to a corona treatment, a plasma treatment, a flame treatment or the like for the purpose of improving the surface energy.

【００３３】なお、本発明の脂肪族ポリエステルには、
公知の添加剤を必要に応じて含有させることができる。
例えば、滑剤、ブロッキング防止剤、熱安定剤、酸化防
止剤、帯電防止剤、耐光剤、耐衝撃性改良剤などを含有
させてもよい。但し、本発明の脂肪族ポリエステル系二
軸延伸フィルムは、ヒートシール層を形成された後にお
いても、透明で内容物が見える必要があるので、添加剤
はヒートシール層を形成される前においても高い透明性
を維持できるものを用いる。The aliphatic polyester of the present invention includes
Known additives can be contained as needed.
For example, a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a lightfast agent, an impact resistance improver, and the like may be contained. However, the aliphatic polyester-based biaxially stretched film of the present invention, even after the heat seal layer is formed, it is necessary to be transparent and the contents can be seen, so the additive is also formed before the heat seal layer is formed. Use a material that can maintain high transparency.

【００３４】なお、前記滑剤としては、シリカ、二酸化
チタン、タルク、カオリナイト等の金属酸化物、炭酸カ
ルシウム、リン酸カルシウム、硫酸バリウム等の金属の
塩または架橋ポリスチレン樹脂、架橋アクリル樹脂、シ
リコン樹脂、架橋ポリエステル樹脂等の有機ポリマーか
らなる粒子等の脂肪族ポリエステル系ポリマーに対し不
活性な粒子が例示される。Examples of the lubricant include metal oxides such as silica, titanium dioxide, talc and kaolinite; salts of metals such as calcium carbonate, calcium phosphate and barium sulfate; crosslinked polystyrene resins; crosslinked acrylic resins; silicone resins; Particles which are inert to aliphatic polyester-based polymers such as particles made of an organic polymer such as a polyester resin are exemplified.

【００３５】これらの滑剤は、いずれか一種を単独で用
いてもよく、また２種以上を併用してもよい。使用する
滑剤の平均粒子径は、０．０１〜３. ０μｍが好まし
く、特に好ましいのは０．０５〜２．５μｍである。脂
肪族ポリエステルに対する滑剤の含有量は、フィルムの
透明性および滑り性を両立するために、０．００５〜２
重量％であることが好ましく、特に好ましくは０．０１
〜１重量％以下である。One of these lubricants may be used alone, or two or more thereof may be used in combination. The average particle size of the lubricant used is preferably 0.01 to 3.0 μm, particularly preferably 0.05 to 2.5 μm. The content of the lubricant relative to the aliphatic polyester is 0.005 to 2 in order to achieve both transparency and slipperiness of the film.
% By weight, and particularly preferably 0.01% by weight.
１1% by weight or less.

【００３６】また、滑剤は、透明性と滑り性を両立する
為には、２種以上を併用することが好ましい。特に、フ
ィルムの製膜時に延伸応力により変形する滑剤粒子（た
とえば架橋ポリスチレン、架橋アクリル等の架橋度の低
い有機粒子、一次粒子の凝集体であるシリカ等の無機滑
剤）とフィルム製膜時の応力で変形しない通常の滑剤粒
子（無機粒子、Ｔｇまたは架橋度の高い有機粒子や無機
粒子）を併用することが好ましい。It is preferable to use two or more lubricants in order to achieve both transparency and slipperiness. In particular, lubricant particles (eg, organic particles having a low degree of crosslinking, such as cross-linked polystyrene and cross-linked acryl, and inorganic lubricants such as silica, which are aggregates of primary particles) that are deformed by stretching stress during film formation, and stress during film formation. It is preferable to use ordinary lubricant particles (inorganic particles, Tg, or organic or inorganic particles having a high degree of crosslinking) which do not deform.

【００３７】こうして得られる本発明の脂肪族ポリエス
テル系二軸延伸フィルムは、フィルムの幅方向の物性差
が小さく、配向主軸の歪みの最大値が３０度以下である
のが好ましい。好ましくは２５度以下、特に好ましくは
２０度以下である。配向主軸の歪みの最大値が３０度を
超えると、印刷工程やラミネート工程、ヒートシール工
程時においてフィルムが加熱された時にフィルムに歪み
が生じ、多色の印刷を実施する場合に色ずれが発生、あ
るいは袋においては袋のねじれ現象が発生するため好ま
しくない。The aliphatic polyester-based biaxially stretched film of the present invention thus obtained preferably has a small difference in physical properties in the width direction of the film and a maximum value of distortion of the main orientation axis of 30 ° or less. It is preferably at most 25 degrees, particularly preferably at most 20 degrees. When the maximum value of the distortion of the orientation main axis exceeds 30 degrees, the film is distorted when the film is heated in a printing process, a laminating process, and a heat sealing process, and color misregistration occurs when performing multicolor printing. Or, in the case of a bag, the twisting of the bag occurs, which is not preferable.

【００３８】また、本発明の脂肪族ポリエステル系二軸
延伸フィルムの１２０℃における熱収縮率は、５％以下
であるのが好ましい。より好ましくは３％以下である。
熱収縮率が５％を超えると、印刷工程においては印刷ず
れが発生し、ヒートシール時にはしわが発生するため好
ましくない。The thermal shrinkage at 120 ° C. of the biaxially stretched aliphatic polyester film of the present invention is preferably 5% or less. It is more preferably at most 3%.
If the heat shrinkage exceeds 5%, printing misalignment occurs in the printing process, and wrinkles occur during heat sealing, which is not preferable.

【００３９】さらに、本発明の脂肪族ポリエステル系二
軸延伸フィルムの厚み方向の屈折率（Ｎｚ）は、１．４
４０〜１．４５５である必要があり、好ましくは１．４
４５〜１．４５５である。Ｎｚが１．４４０未満では、
フィルムを製膜する工程において破断が発生しやすくな
る。一方、１．４５５を超えると、印刷やラミネート工
程等でフィルムが加熱された場合に、平面性の乱れが発
生するため好ましくない。Further, the thickness direction refractive index (Nz) of the aliphatic polyester-based biaxially stretched film of the present invention is 1.4.
It should be 40 to 1.455, preferably 1.4.
45 to 1.455. When Nz is less than 1.440,
Breakage is likely to occur in the process of forming a film. On the other hand, if it exceeds 1.455, when the film is heated in a printing or laminating step, the planarity is disturbed, which is not preferable.

【００４０】本発明における脂肪族ポリエステル系二軸
延伸フィルムの長手方向の屈折率（Ｎｘ）から幅方向の
屈折率（Ｎｙ）を差し引いた値（Ｎｘ−Ｎｙ）は、−
０．０２０〜０が好ましく、特に好ましくは−０．０１
５〜０である。（Ｎｘ−Ｎｙ）が−０．０２０未満で
は、印刷やラミネート工程等でフィルムが加熱された場
合に、フィルムの搬送張力により引き伸ばされ、印刷ず
れや波うちが発生し平面性が悪化するため好ましくな
い。また、（Ｎｘ−Ｎｙ）が０を超えると、厚みむらが
大きくなりやすい。The value (Nx-Ny) obtained by subtracting the refractive index (Ny) in the width direction from the refractive index (Nx) in the longitudinal direction of the biaxially stretched aliphatic polyester-based film in the present invention is-
0.020 to 0 is preferable, and particularly preferably -0.01.
5 to 0. When (Nx-Ny) is less than -0.020, when the film is heated in a printing or laminating step or the like, the film is stretched due to the transport tension of the film, and printing deviation or wavy occurs to deteriorate the flatness. Absent. When (Nx−Ny) exceeds 0, the thickness unevenness tends to increase.

【００４１】[0041]

【実施例】以下、実施例、比較例を挙げて本発明の内容
及び効果を具体的に説明するが、本発明は、その要旨を
逸脱しない限り以下の実施例に限定されるものではな
い。なお、以下の実施例、比較例における物性の評価方
法は以下の通りである。EXAMPLES Hereinafter, the contents and effects of the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to the following examples unless departing from the gist thereof. The methods for evaluating physical properties in the following examples and comparative examples are as follows.

【００４２】（１）配向主軸の歪みの最大値 フィルム形状がロール状の場合は長手方向に１０００ｍ
ｍ、幅方向には全幅を切り出し、シート状サンプルの場
合は試料形状に内接する面積最大の長方形を描き、該長
方形の頂点と２辺を共有する１００ｍｍ四方の正方形を
４つの頂点から切り出し、各々の配向主軸をマイクロ波
によって求めた。最初に測定した点の分子配向角を０度
としたときに、他の三点の配向角が最も差の大きいもの
からその差の絶対値を最大値として求めた。マイクロ波
による主軸の配向角を測定するために、神崎製紙( 株)
製の分子配向計（ＭＯＡ−２００１Ａ）を用いた。(1) Maximum value of the distortion of the main orientation axis When the film shape is a roll shape, 1000 m in the longitudinal direction
m, cut out the entire width in the width direction, in the case of a sheet-shaped sample, draw a rectangle with the largest area inscribed in the sample shape, cut out a square of 100 mm square sharing two sides with the vertices of the rectangle from four vertices, Was measured by microwave. Assuming that the molecular orientation angle of the point measured first is 0 degree, the absolute value of the difference was determined as the maximum value from the one with the largest difference in the orientation angles of the other three points. In order to measure the orientation angle of the main axis by microwave, Kanzaki Paper Co., Ltd.
Molecular orientation meter (MOA-2001A) was used.

【００４３】（２）熱収縮率 一辺１００ｍｍの正方形にきったフィルムの対角線の交
点を中心に直径５０ｍｍの円を描き、１２０℃に加熱し
た熱風乾燥機中に無荷重の状態で３０分放置した後取り
出し、デジタイザーによって寸法変化を読み取り、対角
線の交点をとおる収縮の最大位置の長さ（Ｂ）から下式
により求めた。(2) Heat Shrinkage Ratio A film having a diameter of 50 mm was drawn around the intersection of the diagonal lines of a square film having a side of 100 mm and left in a hot-air dryer heated to 120 ° C. for 30 minutes without load. It was taken out afterwards, the dimensional change was read by a digitizer, and it was determined from the length (B) of the maximum position of contraction through the intersection of the diagonal lines by the following formula.

【００４４】１２０℃の熱収縮率（％）＝（５０−Ｂ）
／５０×１００ （３）厚み方向、長手方向および幅方向の屈折率（Ｎ
ｚ、Ｎｘ、Ｎｙ） 株式会社アタゴ製アッベ屈折計１Ｔを用いて、それぞれ
の屈折率を測定した。Heat shrinkage at 120 ° C. (%) = (50−B)
/ 50 × 100 (3) Refractive index in the thickness direction, longitudinal direction and width direction (N
z, Nx, Ny) Each refractive index was measured using an Abbe refractometer 1T manufactured by Atago Co., Ltd.

【００４５】（４）加工適性 各実施例、比較例で得られた積層熱可塑性フィルムの上
にグラビアインキ（ラミエース６１白二液タイプ、東洋
インキ製造（株）製）をグラビア印刷して印刷インキ層
を形成し、次いで接着剤ＡＤ５８５／ＣＡＴ−１０（東
洋モートン社製）を２ｇ／ｍ² 塗布した後、常法に従っ
て厚み６０μｍの未延伸ポリプロピレンフィルム（Ｐ１
１２０、東洋紡績製）をドライラミネート法にて貼り合
わせてシーラント層を設け、脂肪族ポリエステル系フィ
ルム積層体を得た。この工程においてフィルム積層体の
状態を観察し、下記三段階で評価した。(4) Processing Suitability Gravure ink (Lamiace 61 white two-liquid type, manufactured by Toyo Ink Mfg. Co., Ltd.) is gravure printed on the laminated thermoplastic film obtained in each of the examples and comparative examples, and the printing ink is printed. After forming a layer and then applying 2 g / m ^{2 of an} adhesive AD585 / CAT-10 (manufactured by Toyo Morton Co., Ltd.), a 60 μm-thick unstretched polypropylene film (P1
120, manufactured by Toyobo Co., Ltd.) by a dry lamination method to form a sealant layer to obtain an aliphatic polyester film laminate. In this step, the state of the film laminate was observed and evaluated according to the following three steps.

【００４６】 ○：フィルムの状態良好 △：しわおよび印刷ずれが若干発生 ×：平面性悪化が見られ、しわおよび印刷ずれ問題あ
り。：: Good film condition Δ: Slight wrinkles and print misregistration ×: Deterioration of flatness is observed, and there are wrinkles and print misregistration problems.

【００４７】実施例１ 重量平均分子量が８．３万のポリ−Ｌ−乳酸１００重量
部に対し、表面突起を形成するための滑剤として平均粒
子径１．６５μｍの凝集体シリカ粒子を０．０８重量部
添加した樹脂組成物を、Ｔダイ付き口径３０ｍｍ押出機
を使用して、樹脂組成物温度２０５℃で押出した後、２
０℃のチルロールで冷却し、厚さ３００μｍの未延伸フ
ィルムを得た。未延伸フィルムのガラス転移温度（Ｔ
ｇ）は６１℃、低温結晶化温度（Ｔｃ）は１２５℃であ
った。Example 1 Aggregate silica particles having an average particle diameter of 1.65 μm as a lubricant for forming surface projections were added in an amount of 0.08 to 100 parts by weight of poly-L-lactic acid having a weight average molecular weight of 83,000. The resin composition added by weight was extruded at a resin composition temperature of 205 ° C. using a 30 mm diameter extruder with a T-die.
It was cooled with a chill roll at 0 ° C. to obtain an unstretched film having a thickness of 300 μm. Glass transition temperature of unstretched film (T
g) was 61 ° C, and the low temperature crystallization temperature (Tc) was 125 ° C.

【００４８】複数本のセラミックロールにより未延伸フ
ィルム温度を９７℃に予熱し、ロール間で２５０００％
／分の延伸速度で縦方向に１．４５倍延伸し、その後、
フィルム温度を８５℃に保温しつつ、更に９８℃で２．
７倍縦方向に２段階に分け縦延伸を行った。次いで、テ
ンター式延伸機で横方向に８０℃で３．８倍延伸した
後、１５５℃で熱固定した後、１３４℃で３％横弛緩処
理を行い、厚さ２０μｍの二軸延伸フィルムを得た。表
１にその物性及び評価結果を示す。The temperature of the unstretched film is preheated to 97 ° C. by a plurality of ceramic rolls, and 25,000%
/1.5 times in the machine direction at a drawing speed of / min.
1. While maintaining the film temperature at 85 ° C, further at 98 ° C.
The film was stretched longitudinally in two stages in the longitudinal direction at 7 times. Next, the film is stretched 3.8 times in the transverse direction at 80 ° C. with a tenter-type stretching machine, heat-set at 155 ° C., and then subjected to a 3% transverse relaxation treatment at 134 ° C. to obtain a biaxially stretched film having a thickness of 20 μm. Was. Table 1 shows the physical properties and evaluation results.

【００４９】比較例１ 実施例１において、縦方向の延伸を延伸温度６７℃、延
伸倍率３．２倍となるように一段延伸で実施した以外は
実施例１とまったく同様の方法で二軸延伸フィルムを得
た。表１にその物性及び評価結果を示す。Comparative Example 1 Biaxial stretching was performed in exactly the same manner as in Example 1 except that the stretching in the longitudinal direction was performed in one-step stretching at a stretching temperature of 67 ° C. and a stretching ratio of 3.2. A film was obtained. Table 1 shows the physical properties and evaluation results.

【００５０】参考例 実施例１において、熱固定温度を１３８℃で実施した以
外は実施例１とまったく同様の方法で二軸延伸フィルム
を得た。表１にその物性及び評価結果を示す。Reference Example A biaxially stretched film was obtained in the same manner as in Example 1 except that the heat setting temperature was 138 ° C. Table 1 shows the physical properties and evaluation results.

【００５１】実施例２ 実施例１において、熱固定温度を１５０℃で実施した以
外は実施例１とまったく同様の方法で二軸延伸フィルム
を得た。表１にその物性及び評価結果を示す。Example 2 A biaxially stretched film was obtained in the same manner as in Example 1, except that the heat setting temperature was 150 ° C. Table 1 shows the physical properties and evaluation results.

【００５２】実施例３ 実施例１において、縦延伸の前段と後段の中間時にフィ
ルム温度を、一旦５４℃まで冷却した以外は実施例１と
まったく同様の方法で二軸延伸フィルムを得た。表１に
その物性及び評価結果を示す。Example 3 A biaxially stretched film was obtained in exactly the same manner as in Example 1 except that the film temperature was once cooled to 54 ° C. in the middle of the former stage and the latter stage of longitudinal stretching. Table 1 shows the physical properties and evaluation results.

【００５３】[0053]

【表１】 表１の結果が示すように、実施例の製造方法によると、
配向主軸の最大歪が小さく、フィルム内の分子配向の均
一性が高くなっており、同時に熱収縮率、Ｎｚ、Ｎｘ−
Ｎｙも適切な範囲内であるため、ラミネート加工時の加
工適性が優れた脂肪族ポリエステル系二軸延伸フィルム
を製造することができる。[Table 1] As shown in the results of Table 1, according to the manufacturing method of the example,
The maximum strain of the orientation main axis is small, the uniformity of the molecular orientation in the film is high, and the heat shrinkage, Nz, Nx-
Since Ny is also within an appropriate range, an aliphatic polyester-based biaxially stretched film having excellent workability during lamination can be produced.

───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.⁷ 識別記号 ＦＩ テーマコート゛(参考） Ｂ２９Ｌ 7:00 (72)発明者 小田 尚伸 福井県敦賀市東洋町10番24号 東洋紡績株 式会社総合研究所敦賀分室内 (72)発明者 奥平 正 滋賀県大津市堅田二丁目１番１号 東洋紡 績株式会社総合研究所内 Ｆターム(参考） 3E086 AD01 BA02 BA15 BA33 BB90 CA01 CA17 CA18 CA22 CA25 CA27 CA28 CA31 4F071 AA43 AF31 AF52 AH04 BB08 BC01 BC17 4F210 AA24 AB17 AE01 AG01 QA02 QA03 QC05 QD04 QD13 QW07 QW12 4J002 BC032 BG002 CF002 CF181 CP002 DE136 DE236 DG046 DH046 DJ016 DJ036 DJ046 FD040 FD060 FD070 FD100 FD170 GG02 ──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 7:00 (72) Inventor Naoshin Oda 10-24 Toyocho, Tsuruga-shi, Fukui Toyobo Co., Ltd. Research Institute Tsuruga Branch (72) Inventor Tadashi Okuhira 2-1-1 Katata, Otsu-shi, Shiga F-term in Toyobo Co., Ltd. Research Laboratory (reference) 3E086 AD01 BA02 BA15 BA33 BB90 CA01 CA17 CA18 CA22 CA25 CA27 CA28 CA31 4F071 AA43 AF31 AF52 AH04 BB08 BC01 BC17 4F210 AA24 AB17 AE01 AG01 QA02 QA03 QC05 QD04 QD13 QW07 QW12 4J002 BC032 BG002 CF002 CF181 CP002 DE136 DE236 DG046 DH046 DJ016 DJ036 DJ046 FD040 FD060 FD070 FD100 FD100

Claims (5)

【特許請求の範囲】[Claims] 【請求項１】 主たる繰り返し単位が一般式−Ｏ−ＣＨ
Ｒ−ＣＯ−（ＲはＨまたは、炭素数１〜３のアルキル基
を示す）である脂肪族ポリエステルを主成分としてなる
未延伸フィルムを、縦方向に延伸した後に横方向に延伸
する逐次二軸延伸工程を有する脂肪族ポリエステル系二
軸延伸フィルムの製造方法において、 前記縦方向の延伸を、前記脂肪族ポリエステルのガラス
転移温度（Ｔｇ）＋２０℃以上、低温結晶化温度（Ｔ
ｃ）＋２０℃以下の温度範囲内で、少なくとも二段階に
分けて、縦方向の総合倍率が２．０〜４．５倍となるよ
うに行うことを特徴とする脂肪族ポリエステル系二軸延
伸フィルムの製造方法。(1) a main repeating unit represented by the general formula -O-CH
A sequential biaxial stretching in which an unstretched film mainly composed of an aliphatic polyester which is R-CO- (R represents H or an alkyl group having 1 to 3 carbon atoms) is stretched in a longitudinal direction and then in a transverse direction. In the method for producing an aliphatic polyester-based biaxially stretched film having a stretching step, the stretching in the longitudinal direction is performed at a temperature equal to or higher than a glass transition temperature (Tg) of the aliphatic polyester + 20 ° C. and a low temperature crystallization temperature (T
c) An aliphatic polyester-based biaxially stretched film, which is performed at least in two steps within a temperature range of + 20 ° C. or lower so that the total magnification in the longitudinal direction is 2.0 to 4.5 times. Manufacturing method. 【請求項２】 前記縦方向の延伸が、各段階の延伸工程
間のフィルム温度を前記Ｔｇ以上に維持しつつ行うもの
である請求項１記載の脂肪族ポリエステル系二軸延伸フ
ィルムの製造方法。2. The method for producing an aliphatic polyester-based biaxially stretched film according to claim 1, wherein the stretching in the longitudinal direction is performed while maintaining the film temperature between the stretching steps in each step at or above the Tg. 【請求項３】 前記脂肪族ポリエステルがポリ乳酸であ
る請求項１または２記載の脂肪族ポリエステル系二軸延
伸フィルムの製造方法。3. The method for producing an aliphatic polyester-based biaxially stretched film according to claim 1, wherein the aliphatic polyester is polylactic acid. 【請求項４】 請求項１〜３いずれかに記載の製造方法
により得られる脂肪族ポリエステル系二軸延伸フィルム
であって、配向主軸の最大歪みが３０度以下、厚み方向
の屈折率（Ｎｚ）が１．４４０〜１．４５５であり、１
２０℃における熱収縮率が５％以下である脂肪族ポリエ
ステル系二軸延伸フィルム。4. An aliphatic polyester-based biaxially stretched film obtained by the production method according to any one of claims 1 to 3, wherein a maximum distortion of an orientation main axis is 30 degrees or less, and a refractive index (Nz) in a thickness direction. Is 1.440 to 1.455, and 1
An aliphatic polyester-based biaxially stretched film having a heat shrinkage of 5% or less at 20 ° C. 【請求項５】 長手方向の屈折率（Ｎｘ）から幅方向の
屈折率（Ｎｙ）を差し引いた値（Ｎｘ−Ｎｙ）が−０．
０２０〜０である請求項４記載の脂肪族ポリエステル系
二軸延伸フィルム。5. A value (Nx−Ny) obtained by subtracting a refractive index (Ny) in a width direction from a refractive index (Nx) in a longitudinal direction is −0.05.
The aliphatic polyester-based biaxially stretched film according to claim 4, wherein the number is from 020 to 0.