JP3733729B2 - Polyester film - Google Patents

Description

【表２】

【表３】

【表４】

【表５】

【００５４】
【発明の効果】
本発明のポリエステルフイルムは熱接着性、保香性だけでなくラミネート加工性に優れており、工材、包材用途のフイルムとして好適に使用することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyester film, and more particularly to a polyester film suitable for heat-bonding with another film for packaging and industrial use, or for heat-sealing in flexible packaging.
[0002]
[Prior art]
Conventionally, as a film used in heat bonding and heat sealing applications, a polyolefin film is typical, and it has been preferably used because of its high heat sealing strength and low temperature sealing properties. On the other hand, the film has the disadvantages that it easily adsorbs fat and oil components and perfume components and easily changes the scent and taste of the contents. In addition, even in cases where biaxially stretched PET films are used as industrial and packaging materials, olefinic films are used as the heat-adhesive layer and heat seal layer to form packaging materials that are environmentally easy to recycle. In that respect, there is also a desire to make most of the structure polyester.
[0003]
In order to solve these requirements, for example, as disclosed in Japanese Examined Patent Publication No. 61-22631, a low-melting polyester is coextruded and heat-treated at a temperature equal to or higher than the melting point of the low-melting polyester after biaxial stretching. A method for obtaining an axially stretched polyester film, a method for obtaining an unstretched film in which a specific copolymerized polyester component is blended as disclosed in JP-A-8-231836, and JP-A-5-208472 blends an ionomer resin with polyester. There is a method, but heat sealability and fragrance retention are improved, but the biaxially stretched polyester film with the heat seal layer does not have sufficient heat seal strength, and the unstretched film changes with time when it is thinned. The elongation drop due to the remarkably occurs, tearing and tearing when slitting after actually forming the film, There is a problem that arises tear and tearing at the time of laminate-processing.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a polyester film that not only has excellent fragrance retention and thermal adhesiveness but also does not break during handling.
[0005]
[Means for Solving the Problems]
An object of the present invention described above is that polyester B having a melting point of 150 to 230 ° C. is formed on at least one surface of a film comprising polyester A having an intrinsic viscosity of 0.7 to 1.5 having an ethylene terephthalate unit of 60% by weight or more. A polyester film formed by laminating a film having a plane orientation coefficient of 0 to 0.05, an elongation of 100% or more after 5 days at 40 ° C., and a thickness of the polyester film Can be achieved by a polyester film characterized by being 5 to 40 μm .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, good aroma retention can be obtained by using polyester A in which 60% by weight or more of the structural units are ethylene terephthalate units. Polyester is a polymer composed of a dicarboxylic acid component and a glycol component. Examples of the dicarboxylic acid component include terephthalic acid, ishiphthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenoxyethanedicarboxylic acid, and 5-sodium. Aromatic dicarboxylic acids such as sulfoisophthalic acid and phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other alicyclic dicarboxylic acids such as cyclohexyne dicarboxylic acid Examples thereof include oxycarboxylic acids such as acid and p-oxybenzoic acid. Of these dicarboxylic acid components, terephthalic acid is preferred from the viewpoints of heat resistance and cost performance. On the other hand, examples of the glycol component include aliphatic glycols such as ethylene glycol, propanediol, pentanediol, hexanediol and neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, aromatic glycols such as bisphenol A and bisphenol S, and the like. Is mentioned. Among these glycol components, ethylene glycol, cyclohexanedimethanol, and 1,3-propanediol are preferable, but if a large amount of cyclohexanedimethanol and 1,3-propanediol is used, the fragrance retention is lowered. Two or more of these acid components and glycol components may be used in combination.
[0007]
In particular, in order to improve the mechanical properties without deteriorating the taste properties, it is preferable to contain 3 or more and less than 35% by weight of the 1,3-propanediol component in the glycol component.
[0008]
Furthermore, the thing which does not contain a butanediol residue substantially is preferable in terms of taste characteristics.
[0009]
Moreover, as long as the effect of this invention is not inhibited, you may copolymerize polyfunctional compounds, such as trimellitic acid, trimesic acid, a trimethylol propane, to copolyester.
[0010]
In the present invention, it is important that the intrinsic viscosity of the polyester A is 0.7 to 1.5, preferably 0.75, in order to improve impact resistance, fragrance retention, and aging resistance. It is 1.3 or more and particularly preferably 0.8 or more and 1.2 or less. If the intrinsic viscosity is large, the probability of molecular entanglement is increased, and not only the impact resistance and aging resistance are improved, but also it is considered that adsorption of aroma components hardly occurs. On the other hand, if the intrinsic viscosity is large, the heat sealability may be lowered.
[0011]
Here, the intrinsic viscosity is obtained by dissolving a polymer in o-chlorophenol and measuring the relative viscosity at 25 ° C.
[0012]
In the present invention, not only the film having a thickness of 5 to 40 μm is important in terms of reducing the fragrance retention and the weight of the packaging material, but also being resistant to tearing and tearing since it is a thin film film. It was found that troubles due to tearing and tearing can be greatly reduced when the breaking elongation of the film after aging at 40 ° C. for 5 days is 100% or more.
[0013]
In order to improve the elongation at break of the film after the lapse of time, it is effective to increase the plane orientation coefficient, but on the other hand, there is a disadvantage that the heat sealability is lowered, and the biaxially stretched PET film is a laminated film. Even if a copolymerized PET is laminated on top and processed at a melting point or higher, the heat sealing force is disadvantageous in that it is difficult to increase due to cleavage. In the present invention, it has been found that heat treatment of the film to 100 to 180 ° C. is effective as a method for increasing the elongation at break even in a state where the plane orientation coefficient of polyester A is low and cleaving is difficult to occur. Such heat treatment improves the aging resistance of the film and drastically reduces film tearing . The heat treatment temperature is particularly preferably 110 to 150 ° C., and roll heat treatment, hot air heat treatment, radiation heat treatment, hot water heat treatment and the like can be used. These methods may be used in combination . The heat treatment time is 1 to 30 seconds , preferably 1 to 15 seconds. In this case, the film crystallinity is preferably 0 to 10%, more preferably 0 to 5%, and particularly preferably 0 to 3% in order to improve mechanical properties. Here, the crystallinity x is obtained by x = {(ρ−1.335) /0.12} × 100 based on the density ρ obtained by the density gradient method.
[0014]
In the present invention, the plane orientation coefficient [fn] obtained from the refractive index (Nx, Ny, Nz) in the longitudinal direction, the width direction, and the thickness direction measured using an Abbe refractometer using sodium D-line (wavelength 589 nm) as a light source. = {(Nx + Ny) / 2} -Nz] is important to be 0 to 0.05. When the plane orientation coefficient fn exceeds 0.05, the heat seal strength is lowered or the thermal dimensional stability is lowered.
[0015]
Furthermore, laminated polyester B having a melting point of 150 to 230 ° C. on at least one surface of the polyester A in terms of achieving both the heat seal strength and with lapse time properties. Polyester B is preferably a copolymer of polyethylene terephthalate and isophthalic acid, diethylene glycol, polyalkylene glycol, cyclohexane dimethanol and the like. Polyester B may be single-sided, but may be laminated on both sides in terms of curling resistance.
[0016]
The thickness of the polyester B is preferably 1 to 15 μm, particularly preferably 3 to 10 μm.
[0017]
The polyester film in the present invention may be substantially unstretched or stretched, but is preferably unstretched from the viewpoint of heat sealability.
[0018]
In addition, the polyester of the present invention improves the handleability and scratch resistance of the film, and also improves the adhesion between the printing layer composed of ink and other films and the B layer and prevents blocking. The surface roughness Ra is preferably 0.01 μm or more and 3 μm or less. The method of setting the surface roughness Ra to 0.01 μm or more and 3 μm or less, preferably 0.02 μm or more and 1 μm or less is not particularly limited, but a method of incorporating particles into polyester and a method of transferring with a ground drum are preferable. Specifically, it is preferable that 0.001 to 50% by weight of inorganic particles and / or organic particles having an average particle diameter of 0.001 to 8 μm, or internal particles generated in the polymerization system is contained, and further the average It is preferable that 0.005 to 3 wt% of inorganic particles and / or organic particles having a particle diameter of 0.1 to 5 μm is contained. Inorganic particles and / or organic particles include, for example, wet and dry silica, colloidal silica, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay and the like, and styrene, silicone, acrylic acid, etc. And organic particles having the above as a constituent component. Among them, there can be mentioned 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. As the internal particles, those produced by a known method in which an alkali metal compound, an alkaline earth metal compound or the like is added to the reaction system and a phosphorus compound is further added can be used. Two or more kinds of these inorganic particles and / or organic particles may be used in combination.
[0019]
More preferably, the wetting tension of the A layer and / or the B layer is 48 dyne / cm or more, particularly preferably 50 dyne / cm or more. The method for increasing the wetting tension is not particularly limited, and examples thereof include flame treatment, chemical treatment, discharge treatment, coating treatment with polyester, and the like for the A layer and / or the B layer. Among them, the method of treating the surface with corona discharge is preferable because the adhesion with ink is improved. The corona discharge treatment may be performed in air, nitrogen or carbon dioxide gas, and a mixture thereof. For example, treatments described in JP-A-1-20236, JP-B-57-30854 and the like are preferable. The intensity at the time of corona discharge treatment is expressed as an E value. E value = W / (D / V). W is the processing intensity (W), D is the processing width (m), and V is the film speed (m / min). The E value is preferably 20 to 60 W / m, and more preferably 25 to 55 W / m.
[0020]
Moreover, the polyester film in this invention may differ in the catalyst and carboxyl terminal group amount in each layer. When recovering the film edge, it is preferable from the viewpoint of heat sealability to recover the polyester B layer to the polyester A layer.
[0021]
Furthermore, it is preferable to laminate a layer made of a metal and / or metal oxide on the polyester film of the present invention since the gas barrier property after the bag forming process is improved. It was found that when vapor-deposited on a sealant film having excellent mechanical properties as in the present invention, the gas barrier property is greatly improved because lamination is performed after applying a printing process to a conventional biaxially stretched film. .
[0022]
In addition, laminating the biaxially stretched polyester film of the present invention and a plane orientation coefficient of 0.10 to 0.17 through an adhesive layer is heat resistance as a packaging material in order to make most of the composition polyester. It is preferable because it is excellent in recoverability.
[0023]
The film of the present invention can be formed using any conventionally known method.
[0024]
Next, the film production method of the present invention will be described, but the present invention is not limited to this.
[0025]
Polyethylene A (polyethylene terephthalate (IV = 1.0, melting point 250 ° C.) as polyester A and cyclohexanedimethanol 30 mol% copolymerized polyethylene terephthalate (IV = 0.80, melting point 198 ° C.) as polyester B are separately extruded in a biaxial vent type. It is usually melted and fed to a machine (the temperature of the extruder is set to melting point + 35 ° C.), filtered through a 30 μm cut filter, and then laminated into two layers with a feed block (lamination ratio 1: 3 (A: B)) After being discharged from the base, a cast film is obtained by cooling and solidifying with a ground cooling drum so that the B layer becomes the drum surface by electrostatic application (7 kV). The obtained film is heat-treated with a roll at 130 ° C. for 10 seconds, rapidly cooled to 25 ° C., and subjected to corona discharge treatment on both sides to obtain a film.
[0026]
In the present invention, a biaxially stretched polyester film having a plane orientation coefficient of 0.10 to 0.17 is laminated on the above-mentioned polyester film via an adhesive layer, for example, a lid for an A-PET (unstretched polyethylene terephthalate sheet) container, It can be suitably used for flexible packaging. As the adhesive layer, polyurethane resin, acrylic resin or the like can be used, and adhesion between films is improved and heat sealability can be maintained.
[0027]
Furthermore, in producing the film of the present invention, additives such as an antioxidant, a plasticizer, an antistatic agent, a weathering agent, and a terminal blocking agent can be used as necessary.
[0028]
【Example】
Hereinafter, the present invention will be described in detail by way of examples. The characteristics of the polyester film were measured and evaluated by the following methods.
[0029]
(1) The polyester melting point film was measured with a differential scanning calorimeter (DSC-2 type, manufactured by Perkin Elmer Co.) at a temperature increase rate of 20 ° C./min. Samples whose melting point was difficult to measure were obtained by crystallizing the sample.
[0030]
(2) Polyester intrinsic viscosity Polyester was dissolved in orthochlorophenol and measured at 25 ° C.
[0031]
(3) The resin is removed from the average particle diameter film by a plasma low-temperature ashing method to expose the particles. The processing conditions are selected such that the resin is incinerated but the particles are not damaged. This was observed with a scanning electron microscope for 5,000 to 10,000 particles, and a particle image was obtained from the equivalent circle diameter by an image processing apparatus.
[0032]
When the particles are internal particles, the polymer cross-section is cut to create an ultrathin section having a thickness of about 0.1 to 1 μm, and photographs are taken at a magnification of about 5000 to 20000 using a transmission electron microscope (10 sheets: 25 cm × 25 cm). ) The average dispersion diameter of the internal particles was calculated from the equivalent circle diameter.
[0033]
(4) Film surface roughness (centerline average roughness Ra, maximum roughness Rt)
The surface roughness was measured using a high precision thin film level difference measuring instrument ET-10 manufactured by Kosaka Laboratory. The conditions were as follows, and the average value of 20 measurements was taken as the value.
[0034]
・ Tip tip radius: 0.5μm
-Stylus load: 5mg
・ Measurement length: 1mm
・ Cutoff value: 0.08mm
The definitions of Ra and Rt are shown in, for example, “Measurement / Evaluation Method of Surface Roughness” by Jiro Nara (General Technology Center, 1983).
[0035]
(5) Wetting tension (γ)
This was performed according to JIS K-6768. The following three types of standard solutions were used according to the surface tension.
[0036]
30 dyne / cm ≦ γ <56 dyne / cm: JIS K-6768 standard solution 56 dyne / cm ≦ γ <72 dyne / cm: ammonia water 72 dyne / cm ≦ γ: sodium hydroxide aqueous solution (6) Elongation at 40 ° C. and relative humidity 80% After leaving the film for 5 days, using a Tensilon (tensile tester), the tensile elongation at 300 mm / min, the width is 10 mm, the sample length is 50 mm, and the room temperature is the elongation at break according to ASTM-D-882-81 (Method A). (%) Was measured in the longitudinal direction and the width direction of the film, and each value was obtained by n number 5, and all values were averaged.
[0037]
(7) The frequency of tearing or tearing when laminating a biaxially stretched PET film (12 μm, plane orientation coefficient 0.158) via an adhesive to a film one month after film formation is as follows: (Roll tension 1 kg / cm, laminating speed 20 m / min, adhesive: solvent urethane adhesive).
[0038]
Class A: No trouble in 5 hours Class B: One trouble in 5 hours Class C: Two or more troubles in 5 hours (8) Heat seal strength Heat-sealing by changing the temperature of the above laminated film with an impulse sealer After that, the seal strength was measured with a Tensilon under the condition of 180 ° (15 mm width, pulling speed 300 mm / min).
[0039]
(9) The fragrance-retaining polyester film was left in contact with a fragrance aqueous solution (d-limonene 30 ppm aqueous solution) (contact area: 500 cm ² ) at 40 ° C. for 14 days, and then 30 ° C. at the glass transition temperature of the thermoplastic resin A + 5 ° C. The components that were heated in a nitrogen stream for a minute and driven away were subjected to gas chromatography to determine the amount of d-limonene adsorbed per gram of film and evaluate the taste characteristics.
[0040]
(10) Oxygen permeability and water vapor permeability were measured after laminating the gas barrier deposited film. The oxygen transmission rate was measured using an oxygen transmission rate measuring apparatus (manufactured by Modern Control, OX-TRAN100) according to ASTM D-3985. The measurement conditions are a temperature of 23 ° C. and a relative humidity of 80%.
[0041]
The water vapor transmission rate was measured at a temperature of 40 ° C. and a relative humidity of 90% using a water vapor transmission rate meter according to ASTM F-1249.
[0042]
Example 1
Polyester A as polyethylene terephthalate (IV = 1.0, melting point 247 ° C.), Polyester B as cyclohexanedimethanol 30 mol% copolymerized polyethylene terephthalate (IV = 0.80, melting point 194 ° C., crosslinked polystyrene particles (average particle diameter 6 μm, 0.1 wt%)) was fed and melted into separate twin-screw vent type extruders (the temperature of the extruder was set at the melting point + 35 ° C), filtered through a 30 µm cut filter, and then fed into two layers with a feed block After laminating (lamination ratio is 1: 3 (A: B)) and discharging from a normal die, it is cooled and solidified by a ground cooling drum so that the B layer becomes the drum surface by electrostatic application (7 kV) and cast. Get the film. The obtained film is heat-treated for 10 seconds with a roll at 130 ° C., rapidly cooled to 25 ° C., and subjected to corona discharge treatment (E = 35) on both sides to obtain a film. The physical properties of the two-layer laminated film thus obtained are shown in Table 1. The degree of crystallinity was 0.5%. As can be seen from the table, the laminate processability was good and the bag opening was also good.
[0043]
Examples 2-5
The heat treatment conditions, copolymerization component, and surface wettability were changed, and after obtaining a film by the same method as in Example 1, the film physical properties were examined. Tables 1 to 3 show the results.
[0044]
In Example 2, polyester B was laminated on both sides and subjected to corona discharge treatment (E = 40), and good results were obtained.
[0045]
In Example 3, when the heat treatment condition was changed to 110 ° C. for 10 seconds, the elongation after aging decreased, and the workability decreased as shown in Table 1.
[0046]
In Example 4, when the intrinsic viscosity of polyester A was set to 0.78, the workability decreased and the heat seal strength also decreased.
[0047]
In Example 5, when the draw between the cast and the roll was adjusted so that the plane orientation coefficient was 0.02, the workability was particularly good.
[0048]
Example 6
When an aluminum oxide vapor deposition layer having a thickness of 20 nm was formed on the PET surface of Example 1, the gas barrier properties after processing were 0.4 g / m ² · day and 0.6 ml / m ² · day.
[0049]
Example 7
In Example 1, as polyester B, polypropylene terephthalate (20% by weight) (melting point 224 ° C., IV = 0.85) obtained from 1,3-propylene glycol and terephthalic acid and isophthalic acid 10 mol% copolymer polyethylene terephthalate ( A film was obtained in the same manner except that a blend of IV = 0.80, melting point 233 ° C., containing crosslinked polystyrene particles (average particle diameter 6 μm) was used. The obtained film had particularly good heat sealability.
[0050]
Comparative Example 1
When Example 1 was formed without heat treatment, the obtained film was greatly deteriorated in laminate processability. Further, when forming the transparent deposition layer in the same manner as in Example 6, the gas barrier properties after processing was ^{1.0g / m 2 · day, 1.3ml} / m 2 · day.
[0051]
Comparative Example 2
Isophthalic acid copolymerized polyethylene terephthalate having a melting point of 210 ° C. (0.2% by weight of silica particles having an average particle diameter of 1 μm) is coextruded with PET and stretched at 90 ° C. by 3.2 times and 3.2 times at 220 ° C. When heat-fixed with the copolymer PET, the thickness of the copolymerized PET was 3 μm, but the heat sealability was lowered.
[0052]
Comparative Example 3
Adipic acid 20 mol% copolymerized PBT (IV = 0.8) and isophthalic acid 13 mol% copolymerized PET (IV = 0.65) were mixed at 2: 8 and extruded at 270 ° C. Obtained. The obtained film was inferior in processability and aroma retention.
[0053]
[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[0054]
【The invention's effect】
The polyester film of the present invention is excellent not only in thermal adhesiveness and fragrance retention properties but also in laminate processability, and can be suitably used as a film for use as a construction material or a packaging material.

Claims (6)

Polyester obtained by laminating a film made of polyester B having a melting point of 150 to 230 ° C. on at least one surface of a film comprising polyester A having an intrinsic viscosity of 0.7 to 1.5 having an ethylene terephthalate unit of 60% by weight or more. The plane orientation coefficient of the polyester film is 0 to 0.05, the elongation after aging for 5 days at 40 ° C. is 100% or more, and the thickness is 5 to 40 μm. Characteristic polyester film. 2. The polyester film according to claim 1, wherein the glycol component of polyester A contains a 1,3-propanediol component in an amount of 3 to 35% by weight. The polyester film according to claim 1 or 2, wherein the polyester A contains substantially no butanediol residue. Polyester film according to any one of claims 1 to 3, wherein the at least one surface of a surface roughness Ra of 0.01μm or more 3μm or less. A polyester film obtained by laminating a layer made of a metal and / or a metal oxide on the polyester film according to any one of claims 1 to 4 . A polyester film obtained by laminating the polyester film according to any one of claims 1 to 5 and a biaxially stretched polyester film having a plane orientation coefficient of 0.10 to 0.17 via an adhesive layer.