JP2006052300A - Biaxially stretched polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially stretched polyester film having good film formation stability and good hand cutting properties and suitable as a constituent material of a packaging material for an industrial material, a medicine, a sanitary material, a food, etc. <P>SOLUTION: The biaxially stretched polyester film is characterized as having ≥125°C crystallization temperature (Tc) of the film and ≤80 N end tearing resistance value in both the longitudinal direction and the width direction of the film. Furthermore, the film is a laminated film having at least 2 polyester layers. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a film excellent in hand cutting properties and suitable as a constituent material for packaging materials such as industrial materials, pharmaceuticals, sanitary materials, and foods.

  Conventionally, it has often been required that packaging materials such as industrial materials, pharmaceuticals, sanitary materials, foods, etc. have good hand cutting properties. There is a big merit that it is easy to take out. Examples of such a material having a hand cutting property include cellophane, a so-called moisture-proof cellophane in which cellophane is coated with a vinyl chloride-vinyl acetate copolymer, and a film in which cellophane is coated with vinylidene chloride (K-coated cellophane). Yes. In addition, cellophane is being used more frequently because it has the advantage that cellophane has excellent transparency and the contents can be easily confirmed.

  Cellophane, moisture-proof cellophane, or K-coated cellophane has excellent hand-cutting properties, but the film characteristics change depending on humidity, the printing characteristics are poor, and the basic quality thickness fluctuation is much larger than that of polyester film There is a drawback. In addition, the cellophane base material is expensive, and there is a concern about supply in the future. Furthermore, K-coated cellophane is difficult to use due to environmental considerations (possibility of generation of dioxins during combustion).

  Polyester film, on the other hand, is used as a packaging material due to its excellent properties such as mechanical properties, dimensional stability, heat resistance, water resistance, and transparency. Has a problem. As a method for solving the above drawbacks, 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). ) Etc. have been proposed.

  However, in the above prior art, the method of aligning in the uniaxial direction can be easily cut linearly in the alignment direction but is difficult to cut in other directions, and the method of copolymerizing a large amount of diethylene glycol component is inherently achieved by copolymerization. The characteristic is lost. Furthermore, the method using a low molecular weight polyester resin is not practical because it easily causes troubles in film breakage in the stretching step.

  There has been proposed a method in which a copolyester described in Patent Documents 4 and 5 is used and a layer whose orientation is disrupted is interposed. However, when a sealant layer such as polyethylene is extrusion laminated, a film is formed by heat of the sealant layer. Crystallizes and the film whitens.

Japanese Patent Publication No.55-8551 Japanese Patent Publication No. 56-50692 Japanese Patent Publication No.55-20514 Japanese Patent Publication No. 5-104618 Japanese Patent Application No. 2002-371183

  The present invention is intended to solve the above-mentioned conventional problems, and it is an object of the present invention to provide a film with good hand cutting properties that can replace current packaging materials such as cellophane, moisture-proof cellophane, or K-coated cellophane. It is what.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be easily solved by a film having a specific configuration, and have completed the present invention.

  That is, the gist of the present invention is a biaxial stretching characterized in that the crystallization temperature (Tc) of the film is 125 ° C. or more, and the end row resistance values in the longitudinal direction and the width direction of the film are both 80 N or less. It exists in the polyester film.

Hereinafter, the present invention will be described in detail.
The polyester referred to in the present invention refers to a polymer containing an ester group obtained by polycondensation from a dicarboxylic acid and a diol or from a hydroxycarboxylic acid. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and the diol includes ethylene glycol and 1,4-butane. Examples include diol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol and the like, and examples of hydroxycarboxylic acid include p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. be able to. As the production method, for example, a transesterification reaction is carried out between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or an aromatic dicarboxylic acid and a glycol are directly esterified to form a substantially aromatic compound. A method is employed in which a bisglycol ester of a dicarboxylic acid or a low polymer thereof is formed and then polycondensed by heating under reduced pressure.

  Typical examples of such a polymer include polyethylene terephthalate and polyethylene-2,6-naphthalate. These polymers may be homopolymers or may be a copolymer of the third component.

The polybutylene terephthalate referred to in the present invention refers to a polymer containing an ester group obtained by polycondensation from terephthalic acid as an acid component and 1,4-butanediol as a glycol component. Such a polymer may be a homopolymer or a copolymer of the third component.
The copolyester referred to in the present invention is represented by a polyester in which the acid component is terephthalic acid and isophthalic acid and the glycol component is ethylene glycol. Furthermore, other copolymer components may be copolymerized.

  Other copolymer components include acid components such as adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid and other aliphatic dicarboxylic acids, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1 , 5-naphthalene dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, anthracene dicarboxylic acid, and other aromatic carboxylic acids. Examples of the alcohol component include aliphatic diols such as diethylene glycol, propylene glycol, neopentyl glycol, butanediol, pentanediol and hexanediol, and polyalkylene glycols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol. . These may be used alone or in combination of two or more.

  The film of the present invention is preferably a film having a laminated structure having a polyester layer (A layer) having a melting point of 240 ° C. or lower and a polyester layer (B layer) containing a butylene terephthalate unit. The melting point of the polyester layer (B) is preferably higher than that of the polyester layer (A), and specifically, the melting point is preferably 10 ° C. or higher.

It is essential that the polyester layer (A) has a butylene terephthalate unit. At this time, in order to improve the tearability, the melting temperature of the polyester layer (A) is higher than the melting start temperature in the heat treatment step after uniaxial stretching, preferably the melting point. When the above heat treatment is performed, sufficient tearability can be obtained.
The thickness of the polyester layer (B) is preferably 8 μm or less or 50% or less.

  By containing fine particles in the polyester film of the present invention, workability in the film winding process, coating process, vapor deposition process, and the like can be improved. These fine particles include inorganic particles such as calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, lithium phosphate, magnesium phosphate, calcium phosphate, lithium fluoride, aluminum oxide, silicon oxide, kaolin, acrylic resin, guanamine resin, etc. Although there may be mentioned organic particles and precipitated particles obtained by making catalyst residuals into particles, the present invention is not limited to these. The particle size and amount of these particles can be appropriately determined according to the purpose. The fine particles to be contained may be a single component, or two or more components may be used simultaneously.

  The method of blending each particle with the raw material polyester is not particularly limited, and for example, a method of adding each particle to the polyester polymerization step or a method of melt-kneading the raw material polyester and each particle is suitable. In addition, various stabilizers, lubricants, antistatic agents, and the like can be added as appropriate.

In the film of the present invention, at least two kinds of the above-mentioned polyester raw materials are supplied to, for example, a well-known melt extrusion apparatus represented by a separate extruder, and heated to a temperature equal to or higher than the melting point of each polymer to be melted. Next, the molten polymer is laminated while being extruded from a slit-shaped die, and is rapidly cooled and solidified in a rotating cooling drum shape so as to have a temperature equal to or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. This sheet is obtained by stretching in a biaxial direction to form a film and heat-setting. In this case, the stretching method may be sequential biaxial stretching or simultaneous biaxial stretching. Moreover, you may extend | stretch longitudinally and / or a horizontal direction again before or after performing heat setting as needed. In the present invention, in order to obtain sufficient dimensional stability and waist as a packaging material, the draw ratio is preferably 9 times or more, more preferably 12 times or more as the area magnification.

  The heat treatment temperature after stretching in the present invention is preferably not less than the melting start temperature of the polyester layer (A), preferably not less than the melting point. Sufficient tearability may not be obtained if the heat treatment is performed at a temperature lower than the melting start temperature of the polyester layer (A).

  The crystallization temperature (Tc) of the polyester film of the present invention is 125 ° C. or higher, preferably 130 ° C. or higher. When the crystallization temperature is lower than 125 ° C, the transparency after extrusion lamination of the sealant layer is deteriorated, and it is not suitable as a packaging material.

  The end row resistance of the polyester film of the present invention is 80 N or less, preferably 5 to 60 N in both the longitudinal direction and the width direction of the film. When the end row resistance exceeds 80 N, sufficient hand cutting performance cannot be obtained. If the edge resistance is 5 N or less, the film is too hand-cut, and may break when the film is processed with high tension.

  The thickness of the polyester film in this invention is 9-50 micrometers normally, Preferably it is 12-38 micrometers.

  The film printed on the polyester film of the present invention and then laminated with a sealant layer can be used as a packaging material with good hand cutting properties in order to increase the intentionality. Further, even if the sealant layer is extrusion laminated, the transparency is not impaired, and it can be used as a transparent packaging material with good hand cutting properties. A typical example is a medicine sachet packaging. In addition, the gas barrier film obtained by depositing a barrier layer made of metal or metal oxide on the polyester film of the present invention by vapor deposition or coating an existing barrier layer is used as a gas barrier packaging material with good hand cutting properties. can do. Laminated aluminum foil can also be used as a gas barrier packaging material with good hand cutting properties.

  According to the present invention, it is possible to supply a polyester film that is excellent in processability and mechanical properties, and has good hand cutting properties that do not impair transparency even when a sealant layer is extrusion laminated.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method and the processing method of a sample in an Example and a comparative example are as follows. Further, “parts” in Examples and Comparative Examples represents “parts by weight”.

(1) Method for measuring film thickness Ten films were stacked, the thickness was measured by a micrometer method, and the result was divided by 10 to obtain an average value to obtain the film thickness.

(2) Method for measuring the thickness of the laminated polyester layer The film piece was fixed with an epoxy resin and then cut with a microtome, and the cross section of the film was observed with a transmission electron micrograph. Two of the cross-sections are observed in parallel with the film surface, and the interface is observed by light and dark. The distance between the two interfaces and the film surface was measured from 10 photographs, and the average value was defined as the laminated thickness.

(3) Measurement Method of Melting Start Temperature and Melting Point Melting start temperature (Tim) and melting point (Tpm) were measured using a Perkin-Elmer differential scanning calorimeter DSC7 type. The DSC measurement conditions are as follows. That is, 6 mg of the sample film was set in a DSC apparatus, melted and held at 300 ° C. for 5 minutes, and then rapidly cooled with liquid nitrogen. The rapidly cooled sample was heated from 0 ° C. at a rate of 10 ° C./min, and the melting point was detected according to how to read the DSC curve of JIS K7121.

(4) Measuring method of crystallization temperature The crystallization temperature (Tc) was measured using a Perkin-Elmer differential scanning calorimeter DSC7 type. The DSC measurement conditions are as follows. That is, 6 mg of the sample film was set in a DSC apparatus, the rapidly cooled sample was heated from room temperature at a rate of 10 ° C./min, and the crystallization temperature was detected according to the DSC curve reading of JIS K7121.

(5) Measuring method of end row resistance The average value was made into end row resistance value by the measuring method of JIS C2318-1975.

(6) Measuring method of hand tearability It was evaluated according to the following criteria whether the film was torn by hand without making a cut. Evaluation was performed with respect to the longitudinal direction (MD) and the width direction (TD), respectively.

Evaluation A: Can be easily torn by hand Evaluation B: Can be relatively easily torn by hand Evaluation C: Can not be easily torn by hand

(7) Haze Measurement Method According to JIS K7136, the haze of the film was measured with a haze meter NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

(8) Method for judging transparency after extrusion lamination A film was produced by extrusion laminating 40 μm of low density polyethylene (LDPE) on the film. The produced laminate film was made into a bag with a three-side seal wrapping machine, and whether the contents of the bag could be confirmed was evaluated for transparency after extrusion lamination according to the following criteria.

Evaluation ○: The contents can be easily confirmed. Evaluation ×: The contents cannot be easily confirmed.

The polyester raw materials used in the following examples and comparative examples were produced by the following method.
<Method for producing polyester 1>
The terephthalic acid was used as the dicarboxylic acid component, and 1.4 butanediol was used as the polyhydric alcohol component, and it was produced by a conventional melt polycondensation method. The intrinsic viscosity ([η]) of this polyester raw material was 0.80 dl / g. The polyester film obtained from the raw material had a melting start temperature (Tim) of 213 ° C. and a melting point (Tpm) of 222 ° C.

<Method for producing polyester 2>
The dicarboxylic acid components were isophthalic acid and terephthalic acid, and the polyhydric alcohol components were ethylene glycol, respectively. The isophthalic acid content in the dicarboxylic acid component was 22 mol%. The intrinsic viscosity ([η]) of this polyester raw material was 0.69 dl / g. The polyester film obtained from this raw material had a melting start temperature (Tim) of 175 ° C. and a melting point (Tpm) of 196 ° C.

<Method for producing polyester 3>
The dicarboxylic acid components were isophthalic acid and terephthalic acid, and the polyhydric alcohol components were ethylene glycol, respectively. The isophthalic acid content in the dicarboxylic acid component was 15 mol%. The intrinsic viscosity ([η]) of this polyester raw material was 0.69 dl / g. The polyester film obtained from this raw material had a melting start temperature (Tim) of 198 ° C. and a melting point (Tpm) of 220 ° C.

<Method for producing polyester 4>
A polyester chip having an intrinsic viscosity ([η]) of 0.69 dl / g was obtained by a conventional melt polycondensation method using terephthalic acid as the dicarboxylic acid component and ethylene glycol as the polyhydric alcohol component, respectively. The polyester film obtained from this raw material had a melting start temperature (Tim) of 242 ° C. and a melting point (Tpm) of 254 ° C.

<Method for producing polyester 5>
Intrinsic viscosity containing 0.18 part of amorphous silica having an average particle size of 2.5 μm by a conventional melt polycondensation method using terephthalic acid as the dicarboxylic acid component and ethylene glycol as the polyhydric alcohol component, respectively ( A polyester chip having [η]) of 0.69 dl / g was obtained. The polyester film obtained from this raw material had a melting start temperature (Tim) of 242 ° C. and a melting point (Tpm) of 254 ° C.

<Method for producing polyester 6>
After 25 parts of polyester 1, 50 parts of polyester 2 and 25 parts of polyester 4 were blended, they were melt kneaded with a twin screw extruder to obtain chips. The amount of polybutylene terephthalate contained in the polyester 8 was 25%, and the isophthalic acid content in the dicarboxylic acid component was 11 mol%. The polyester film obtained from this raw material had a melting start temperature (Tim) of 195 ° C. and a melting point (Tpm) of 217 ° C.

<Method for producing polyester 7>
After 25 parts of polyester 1 and 75 parts of polyester 3 were blended, they were melt kneaded with a twin screw extruder to obtain chips. The amount of polybutylene terephthalate contained in the polyester 7 was 25%, and the content of isophthalic acid in the dicarboxylic acid component was 11 mol%. The melting start temperature (Tim) of the polyester film obtained from this raw material was 185 ° C., and the melting point (Tpm) was 216 ° C.

<Method for producing polyester 8>
25 parts of polyester 1 and 75 parts of polyester 3 were blended. The amount of polybutylene terephthalate contained in the polyester 8 was 25%, and the amount of isophthalic acid in the dicarboxylic acid was 11 mol%. The polyester film obtained from this raw material had a melting start temperature (Tim) of 195 ° C. and a melting point (Tpm) of 217 ° C.

  Polyester 5 and polyester 6 pellets are melted in separate single-screw extruders, and using a laminated die, polyester 5 (layer B) / polyester 6 (layer A) / polyester 5 (layer B) 2 types 3 The layer-laminated polyester resin was extruded onto a cooling drum having a surface temperature of 30 ° C. and quenched to obtain an unstretched film having a thickness of about 250 μm. Next, the film was stretched 3.5 times in the longitudinal direction at 70 ° C., and then subjected to a preheating step in the tenter, 4.4 times transverse stretching at 80 ° C., and heat treatment at 230 ° C. for 5 seconds to form a laminate having a thickness of 16 μm. A polyester film was obtained. The thickness configuration of the B layer / A layer / B layer was 1 μm / 14 μm / 1 μm. The properties of the obtained film are shown in Table 1 below. This film had good hand cutting properties, and the transparency of the laminate film was also good.

  A laminated polyester film was prepared in the same manner as in Example 1 except that polyester 7 was used as the raw material for the A layer. The properties of the obtained film are shown in Table 1 below. This film had good hand cutting properties, and the transparency of the laminate film was also good.

  A laminated polyester film was prepared in the same manner as in Example 1 except that polyester 8 was used as the raw material for layer A and the heat treatment temperature after transverse stretching was 235 ° C. The properties of the obtained film are shown in Table 1 below. This film had good hand cutting properties, and the transparency of the laminate film was also good.

  A laminated polyester film was prepared in the same manner as in Example 1 except that the thickness configuration of the B layer / A layer / B layer of the polyester film was changed to 5 μm / 20 μm / 5 μm. The properties of the obtained film are shown in Table 1 below. This film had good hand cutting properties, and the transparency of the laminate film was also good.

(Comparative Example 1)
A laminated polyester film was prepared in the same manner as in Example 1 except that the heat treatment temperature after transverse stretching was 220 ° C. The properties of the obtained film are shown in Table 2 below. Although this film had good hand cutting properties, the transparency of the laminate film was not good.

(Comparative Example 2)
A laminated polyester film was prepared in the same manner as in Example 1 except that polyester 3 was used as the raw material for layer A and the heat treatment temperature after transverse stretching was 220 ° C. The properties of the obtained film are shown in Table 2 below. Although this film had good hand cutting properties, the transparency of the laminate film was not good.

(Comparative Example 3)
A laminated polyester film was prepared in the same manner as in Example 1 except that polyester 4 was used as the raw material for layer A and the heat treatment temperature after transverse stretching was 220 ° C. The properties of the obtained film are shown in Table 2 below. Although this film had good transparency of the laminate film, it had poor hand cutting properties.

  The film of the present invention can be suitably used as a constituent material for packaging materials such as industrial materials, pharmaceuticals, sanitary materials, and foods.

Claims (1)

A biaxially stretched polyester film characterized in that the crystallization temperature (Tc) of the film is 125 ° C. or more, and the end-row resistance values in the longitudinal direction and the width direction of the film are both 80 N or less.