JP2002187963A - Biaxially oriented polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a biaxially oriented polyester film showing excellent releasability even after repeated use, use after a molding process, and use under a water atmosphere, and further exhibiting a stable performance with a small dispersion, and having excellent releasability. SOLUTION: This biaxially oriented polyester film comprises a film consisting of a polyester comprising an ethylene terephthalate unit and/or an ethylene phthalate unit as a principal constituting component, the melting point of the film being 180-270 deg.C, the film comprising carnauba wax of 0.1-2 wt.% (X wt.%) and a germanium element (Y ppm) of an amount satisfying the equation; 10X<=Y<=80.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially stretched polyester film having excellent releasability, and in particular, excellent releasability even after repeated use, use after molding, and use under a water atmosphere. The present invention relates to a biaxially stretched polyester film which exhibits stable and stable performance with small variations.

[0002]

2. Description of the Related Art Polyester films are used for various purposes because of their excellent properties. However, polyester has a poor releasability due to its molecular skeleton, and a technique of coating a surface with a release component is generally used to impart releasability. However, this method has disadvantages such as a decrease in performance when the surface is deformed by processing, and a decrease in performance when repeatedly used due to insufficient strength of the coat layer itself. Furthermore, the adhesion between the release layer and the polyester layer is poor, so that there is a problem that the performance is significantly reduced after use in a water atmosphere or after treatment such as retort or boiling. It has been proposed to solve the latter problem by providing a primer layer or reacting two components in a coat layer with a catalyst or the like, but this is not only unsuitable for use in food applications, but also reduces productivity. There was a problem. It has been difficult to stably satisfy the performance under various use conditions as described above.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems of the prior art, and to provide excellent use even after repeated use, use after molding, and use in a water atmosphere. An object of the present invention is to provide a biaxially stretched polyester film that exhibits releasability and exhibits stable performance with small variations and excellent releasability.

[0004]

The biaxially stretched polyester film of the present invention for this purpose is a film composed of a polyester containing ethylene terephthalate units and / or ethylene naphthalate units as a main component. A biaxially stretched polyester film characterized by having a melting point of 180 to 270 ° C, containing 0.1 to 2% by weight of carnauba wax, and containing an amount of germanium element satisfying the following formula (1). 10X ≦ Y ≦ 80 Formula (1) X: Carnauba wax content (% by weight) Y: Germanium element content in the film (pp
m)

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The biaxially stretched polyester film of the present invention comprises a polyester having an ethylene terephthalate unit and / or an ethylene naphthalate unit as a main constituent.

In the present invention, the polyester containing ethylene terephthalate units and / or ethylene naphthalate units as a main component is a polyester containing at least 70 mol% of ethylene terephthalate units and / or ethylene naphthalate units. Is preferably 85% by mol or more from the viewpoint of
It is preferably at least mol%.

Further, another dicarboxylic acid component and / or a glycol component may be copolymerized. As the dicarboxylic acid component, for example, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-
Aliphatic ring such as aromatic dicarboxylic acid such as sodium sulfoisophthalic acid and phthalic acid, aliphatic dicarboxylic acid such as oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid and fumaric acid, and cyclohexyne dicarboxylic acid An oxycarboxylic acid such as an aromatic dicarboxylic acid and p-oxybenzoic acid can be used.

On the other hand, as the glycol component, for example,
Propanediol, butanediol, pentanediol
And aliphatic glycols such as cyclohexanedimethanol, aromatic glycols such as bisphenol A and bisphenol S, and diethylene glycol. Incidentally, two or more of these dicarboxylic acid components and glycol components can be used in combination.

Further, as long as the effects of the present invention are not impaired, a polyfunctional compound such as trimellitic acid, trimesic acid, and trimethylolpropane can be copolymerized with the polyester or copolymerized polyester used in the present invention.

In the present invention, components which are preferably copolymerized in a small amount are components such as butanediol, diethylene glycol, polyethylene glycol, cyclohexanedimethanol, sebacic acid, adipic acid, dimer acid, isophthalic acid and naphthalenedicarboxylic acid.

In the present invention, the melting point of the film needs to be 180 to 270 ° C. from the viewpoints of heat resistance and productivity. The temperature is preferably from 220 to 265 ° C, more preferably from 246 to 260 ° C.

In the present invention, the surface free energy is preferably 20 to 20 from the viewpoints of mold release, handling, and productivity.
It is preferably 40 mN / m, more preferably 3 mN / m.
0 to 38 mN / m. Surface free energy is 20m
When it is lower than N / m, problems such as deviation of the end face due to winding of the film may occur.

In the present invention, excellent releasability can be exhibited even after repeated use, use after molding and use in a water atmosphere, and from the viewpoint of hygiene in use in packaged food applications and the like, It is necessary to add carnauba wax, and it is particularly preferable to use purified carnauba wax. The amount of the carnauba wax compound or the like added in the film is preferably 0.1 to 2% by weight, more preferably 0.2 to 0.9% by weight, and particularly preferably 0.3 to 2% by weight.
0.8% by weight. Further, it is necessary to contain a germanium element in an amount satisfying the following formula (1) from the viewpoint of improving wax dispersibility, improving mold release performance, and suppressing contamination in the process. 10X ≦ Y ≦ 80 Formula (1) X: Carnauba wax content (% by weight) Y: Germanium element content in the film (pp
m)

The method of adding carnauba wax to the polyester in the present invention includes the steps of improving the dispersibility of carnauba wax and exhibiting stable performance and suppressing contamination in the step of forming a film. The method of adding in the following polymerization step is preferable. (1) A method in which carnauba wax is added during polymerization of polyester. (2) Master pellets containing a large amount of carnauba wax (carnauba wax master polyester)
Is produced by polymerization, and the master pellets and a polyester containing no or a small amount of carnauba wax (diluting polyester) are mixed at a predetermined ratio and kneaded. In the present invention, when producing a polyester to which carnauba wax is added, it is particularly necessary to polymerize using a germanium catalyst from the viewpoint of improving the dispersibility, and the germanium element is represented by the above formula (1). It is necessary that it is contained in an amount specified by
The content is 80 ppm, more preferably 30 to 60 ppm.

The film configuration of the biaxially stretched polyester film of the present invention may of course be a single layer or a laminated configuration. A / B in the case of a stacked configuration
, Three layers of A / B / A or A / B / C, or a multilayer structure of more than three layers, and the laminate thickness ratio can be set arbitrarily. / B. Here, the layer A is a layer of the film of the present invention (Claim 1) containing carnauba wax, and the layers B and C are other film layers. In particular, the layer A to which the wax is added preferably has a thickness of 1/30 to 1/2, more preferably 1/20 to 1/3.
In this case, the content of the carnauba wax in the layer B is from 0 to 0.
Preferably it is less than 2% by weight.

The film of the present invention can be suitably used for processing applications, particularly for forming and food packaging applications in which bending or drawing is performed by 10% or more. In particular, it is suitable for applications that are used by being bonded to a metal plate.

When the film of the present invention is used for forming, the biaxially stretched film has a plane orientation coefficient (fn) of 0.1.
It is preferable to be in the range of 08 to 0.15. When the plane orientation coefficient is smaller than the above range, the impact resistance is deteriorated, and in such a range, the laminability to a metal or another polymer film becomes good, and the moldability is also excellent. From the viewpoint of impact resistance and tear resistance, the plane orientation coefficient is more preferably in the range of 0.120 to 0.145.

In the present invention, biaxial stretching is required in view of heat resistance, printability, chemical resistance, and impact resistance after processing. The method of biaxial stretching may be any of simultaneous biaxial stretching, sequential biaxial stretching, and tubular stretching, with simultaneous biaxial stretching and sequential biaxial stretching being particularly preferred.

In the present invention, the intrinsic viscosity of the film is preferably from 0.5 to 1 dl / g, more preferably from 0.55 to 0.8 dl / g, particularly from the viewpoint of processability, heat resistance and productivity. Is 0.55 to 0.7.

In producing the polyester used in the present invention, a reaction catalyst can be used. As the reaction catalyst, for example, alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds,
For example, a phosphorus compound or the like can be used as a coloring inhibitor, such as a titanium compound.In any stage before the completion of the production of the polyester, an antimony compound or a germanium compound as a polymerization catalyst may be added. preferable. Such methods include:
For example, taking a germanium compound as an example, a method of adding a germanium compound powder as it is, or a method of adding a germanium compound to a glycol component which is a starting material of a polyester as described in JP-B-54-22234. Can be dissolved and added.

Examples of the germanium compound include germanium dioxide, germanium hydroxide containing water of crystallization, or germanium alkoxide compounds such as germanium tetramethoxide, germanium tetraethoxide, germanium tetrabutoxide, germanium ethylene glycoloxide, and germanium phenolate. And germanium phenoxide compounds such as germanium β-naphtholate, phosphorus-containing germanium compounds such as germanium phosphate and germanium phosphite, and germanium acetate. Among them, germanium dioxide is preferable. As the antimony compound, for example, antimony oxide such as antimony trioxide, antimony acetate and the like can be used. As the titanium compound, an alkyl titanate compound such as tetraethyl titanate and tetrabutyl titanate is preferably used.

Next, a case where germanium dioxide is added as a germanium compound when producing polyethylene terephthalate will be described as an example. The terephthalic acid component and the ethylene glycol are subjected to a transesterification or esterification reaction, and then a germanium dioxide and a phosphorus compound are added, followed by a polycondensation reaction under a high temperature and a reduced pressure until a constant diethylene glycol content is obtained. Get united. Further, preferably, the obtained polymer is subjected to a solid-phase polymerization reaction under reduced pressure or an inert gas atmosphere at a temperature equal to or lower than its melting point to reduce the content of acetoadheride to obtain a predetermined intrinsic viscosity and a carboxyl end group. And the like.

In the present invention, from the viewpoint of improving the compatibility with carnauba wax, the amount of the carboxyl terminal group of the polyester is preferably 25 to 55 equivalents / ton,
It is more preferably from 30 to 50 equivalents / ton, particularly preferably from 35 to 45 equivalents / ton.

The polyester in the present invention preferably has a diethylene glycol content of 0.01 to 4% by weight, more preferably 0.01 to 3% by weight, particularly preferably 0.01 to 2% by weight. It is desirable to maintain good hygiene and maintain good hygiene even after lapse of time or after undergoing heat history during processing. Further, an antioxidant may be added in an amount of 0.0001 to 1% by weight. Further, diethylene glycol may be added during the production of the polymer as long as the properties are not impaired.

In order to improve hygiene, the content of acetaldehyde in the film is preferably 30 pp.
m or less, more preferably 25 ppm or less, particularly preferably 20 ppm or less. As a method for reducing the content of acetaldehyde in the film to 30 pm or less, for example, in order to remove acetaldehyde generated by thermal decomposition when producing the polyester by a polycondensation reaction or the like, the polyester is subjected to a reduced pressure or an inert gas atmosphere. Under the method of heat treatment at a temperature below the melting point of the polyester, preferably a method of solid-phase polymerization of the polyester under a reduced pressure or an inert gas atmosphere at a temperature of 150 ℃ or more, using a vacuum vented extruder Melt extrusion of a polymer, when the polymer is melt-extruded, the extrusion temperature should be within + 30 ° C., preferably + 2 ° C. of the high melting polymer side.
A method of extruding at 5 ° C. within a short period of time, preferably within an average residence time of 1 hour or the like may be used.

As a method for producing a biaxially stretched polyester film in the present invention, for example, after drying each polyester as required, it is supplied to a known melt extruder, extruded into a sheet shape from a slit die, and then statically extruded. An unstretched sheet is obtained by bringing it into close contact with the casting drum by a method such as application of electricity and cooling and solidifying it. The stretching method may be either simultaneous biaxial or sequential biaxial stretching, but the unstretched sheet is stretched in the longitudinal direction and width direction of the film and heat-treated to obtain a film having a desired degree of plane orientation. Preferably, a tenter method is preferred in terms of film quality.After stretching in the longitudinal direction, a sequential biaxial stretching method in which the film is stretched in the width direction, a simultaneous biaxial stretching method in which the film is stretched almost simultaneously in the longitudinal direction and the width direction. Is desirable. The stretching magnification is 1.5 to 4.0 times in each direction, preferably 1.8 to 4.0.
It is 4.0 times. Either the stretching ratio in the longitudinal direction or the stretching direction in the width direction may be increased, and may be the same.

The stretching speed is from 1,000% / min to 20%.
It is desirable that the stretching temperature is 0.000% / min.
Any temperature can be used as long as the temperature is equal to or higher than the glass transition temperature of the polyester and equal to or lower than [glass transition temperature + 80 ° C.]. Further, the film is subjected to a heat treatment after the biaxial stretching, and this heat treatment can be carried out by any conventionally known method, such as in an oven or on a heated roll. The heat treatment temperature can be usually any temperature from 120 ° C to 245 ° C, but is preferably from 120 to 240 ° C. Further, the heat treatment time can be arbitrarily set, but it is usually preferable to perform the heat treatment for 1 to 60 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction. Further, re-stretching may be performed once or more in each direction, and then heat treatment may be performed.

In the biaxially oriented polyester film of the present invention, it is preferable to use internal particles, inorganic particles, and organic particles in the film in order to improve the releasability, handleability and processability. The content of the inorganic particles and / or the organic particles contained in the film is preferably 0.02 to 5% by weight, more preferably 0.03 to 4% by weight.
It is. Among them, it is preferable to use so-called external particles such as inorganic particles and / or organic particles having an average particle diameter of 0.01 to 10 μm. In particular, when used as a film for the inner surface of a can, it is preferable that inorganic particles and / or organic particles having an average particle size of 0.1 to 5 μm are added. As a method of depositing internal particles, for example,
61556, JP-A-51-12860, JP-A-53-41355, JP-A-54-90397
And the technology described in Japanese Patent Application Publication No. Furthermore, Japanese Unexamined Patent Publication No.
It can also be used in combination with other particles such as JP-A-5-20496 and JP-A-59-204617.

It is not preferable to use particles having an average particle diameter of more than 10 μm, since defects in the film are likely to occur. As the inorganic particles and / or organic particles,
For example, inorganic particles such as wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, and clay, and styrene, silicone, acrylic acid, etc. Organic particles and the like. Among these, inorganic particles such as wet and dry colloidal silica and alumina, and organic particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene, and the like as constituent components can be exemplified. Two or more of these internal particles, inorganic particles and / or organic particles may be used in combination.

The biaxially stretched polyester film of the present invention contains additives such as an antistatic agent, a heat stabilizer, an antioxidant, a crystal nucleating agent, a weathering agent, and an ultraviolet absorber in an amount that does not impair the object of the present invention. Can be used. In addition, surface irregularities such as embossing and sand matting, or surface treatments such as corona discharge treatment, plasma treatment, and alkali treatment may be performed as necessary. Further, if the film of the present invention does not inhibit the desired effect of the present invention, the other surface of the surface exhibiting releasability may be provided with an easy-adhesion treatment agent, an antistatic agent, a water vapor / gas barrier agent (polyvinylidene chloride). Etc.), adhesives, adhesives, flame retardants, ultraviolet absorbers, matting agents, pigments, dyes, etc. may be coated or printed, such as aluminum, aluminum oxide,
Shields metals and their compounds, such as silicon oxide and palladium,
Vacuum deposition may be performed for the purpose of water vapor / gas barrier, surface conductivity, infrared reflection, and the like, and the purpose and method are not limited to the above.

[Measurement and evaluation methods of physical properties and characteristics]
Methods for measuring and evaluating physical properties and characteristics used in the description of the present invention or the examples described later will be described. (1) Melting point (Tm), glass transition temperature (Tg) Measured using a differential scanning calorimeter DSC2 (manufactured by PerkinElmer). 10 mg of the sample was collected under a nitrogen stream.
The mixture was kept at 0 ° C. for 5 minutes and then quenched with liquid nitrogen.
In the process of raising the temperature of the obtained sample at a rate of 10 ° C./min, a specific heat change peak based on a transition from a glass state to a rubber state is read, and this temperature is defined as a glass transition temperature (Tg), and an endothermic peak temperature based on crystal melting. Was taken as the melting point (Tm). (2) Carboxyl end group content The film was treated with ortho-cresol / chloroform (weight ratio 7).
/ 3) at 95 ° C and the potential difference was measured with an alkali. (3) Elongation The elongation was measured according to ASTM-D-882-81 (Method A).

(4) Plane Orientation Coefficient (fn) Using sodium D line as a light source, the refractive index (Nx, Ny, N
z) was measured and determined by the following equation. fn = (Nx + Ny) / 2-Nz (5) Intrinsic viscosity Polyester was dissolved in orthochlorophenol and 25
Measured in ° C. (6) Surface free energy Measured according to JIS K-6788. The measurement temperature was 23 ° C. and the humidity was 65%. (7) Release Property A 20 × 50 mm cellophane tape was attached to the film, the surface free energy Sf2 after peeling was measured, and the difference ΔSf (mN / m) from the surface free energy Sf1 of the original film was measured. It was determined as follows. Class A: 0-1 Class B: 1-2 Class C: 2-3 Class D: 3-5 Class E: more than 5

(8) Peelability A mold having a height of 30 mm and a width of 200 mm × 200 mm was heated to 150 ° C. to perform transfer in-mold molding and evaluated as follows. ：: Smoothly obtained without any adhesion to the mold. ×: There is a portion that adheres to the mold. (9) Non-adhesive properties Non-adhesive properties are as follows: film, egg, meat and flour 3: 2: 1
Into a packed beaker containing
The mixture was retorted at 30 ° C. for 30 minutes, taken out, and the amount of adhesion to the film was determined according to the following. Class A: 0 to 5% Class B: 5 to 10% Class C: 10 to 20% Class D: 20 to 50% Class E: 50 to 100%

[0034]

The present invention will be described below by way of examples.

Example 1 Both chips of polyesters A and B were produced by the usual method under the conditions shown in Table 1. After mixing the obtained chips at the ratios shown in Table 1, 1
Extruder I (main layer) and vacuum extruder at 80 ° C for 3 hours
II (sub-layer), and after discharging from the normal mouthpiece,
It was cooled and solidified by a mirror-surface cooling drum while applying static electricity (7 kv) to obtain an unstretched film. This unstretched film is
Stretched 3.4 times in the longitudinal direction at 105 ° C, cooled to 40 ° C, preheated at 95 ° C for 5 seconds, stretched 3.2 times in the width direction at 115 ° C, and relaxed at 210 ° C 5
%, And heat-treated for 5 seconds to obtain a biaxially stretched polyester film having a thickness of 15 μm shown in Table 1. As shown in Table 1, it was confirmed that excellent characteristics were exhibited.

Examples 2 to 4 Biaxially stretched polyester films were obtained in the same manner as in Example 1 except that the composition of the polyester chips, the mixing ratio of the polyester chips, and the like were changed according to Table 1. As shown in Table 1, it was confirmed that excellent characteristics were exhibited.

(Comparative Examples 1 and 2) A biaxially stretched polyester film was obtained in the same manner as in Example 1 except that the composition of the polyester chips, the mixing ratio of the polyester chips, and the like were changed as shown in Table 1. The resulting film had poor properties.

[0038]

[Table 1] The symbols in the table are as follows. PET: polyethylene terephthalate PET / I: isophthalic acid copolymerized polyethylene terephthalate

[0039]

According to the present invention, excellent releasability is exhibited even after repeated use, use after molding, and use under a water atmosphere, and stable release performance with little variation is exhibited. A biaxially stretched polyester film having excellent moldability can be obtained.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C08J 3/22 C08J 3/22 C08K 3/08 C08K 3/08 5/101 5/101 C08L 67/02 C08L 67/02 F-term (reference) 3E086 AB01 AD01 BA02 BA15 BA35 BB71 BB90 CA03 4F070 AA47 AC06 AC14 AC15 AC20 AC36 AC42 AC43 AE17 FA03 FB03 FC05 4F071 AA45 AA46 AB06 AB18 AB25 AC05 AC09 AC10 AE22 AH04 BA01 BA01 BB08 AT01 BC01 BC01 BA04 BA06 BA07 BA10A BA10B BA10D EJ38A EJ38B GB15 GB23 JL14 4J002 CF061 CF081 DA117 DE047 EC077 EG047 EH036 EJ077 FD010 FD166 FD207 GG02

Claims (7)

[Claims] 1. A film comprising a polyester having an ethylene terephthalate unit and / or an ethylene naphthalate unit as a main constituent, wherein the film has a melting point of 180 to 270 ° C. and a carnauba wax of 0.1 to 2%. A biaxially stretched polyester film, which contains an amount of germanium in an amount satisfying the following formula (1) by weight. 10X ≦ Y ≦ 80 Formula (1) X: Carnauba wax content (% by weight) Y: Germanium element content in the film (pp
m) 2. A surface free energy of 20 to 40 mN /
The biaxially stretched polyester film according to claim 1, wherein m is m. 3. A film produced from a polyester obtained by diluting a master polyester containing 20 to 80 ppm of germanium element and 1 to 5% by weight of carnauba wax. Biaxially stretched polyester film. 4. The biaxially stretched polyester film according to claim 1, wherein the amount of the carboxyl terminal group is 30 to 50 equivalents / ton. 5. A biaxially laminated film comprising two or more layers, wherein at least one surface of the film layer is the polyester film according to any one of claims 1 to 4. Stretched polyester film. 6. The biaxially stretched polyester film according to claim 1, which is used for food packaging. 7. The biaxially stretched polyester film according to claim 1, wherein the polyester film is used by being attached to a metal plate.