JPH0586753B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to a film-like laminate that can be used as a lid material for thermal adhesion, etc., and more specifically, a film-like laminate that can be used as a lid material for a container made of crystallized or molecularly oriented polyester. In particular, the present invention relates to a film-like laminate that has easy-open properties that have extremely high practical value and has heat-resistant dimensional stability that can withstand heat sterilization. [Prior Art] Tray-shaped or cup-shaped molded bodies obtained by thermoforming sheets made of polyester, particularly polyethylene terephthalate, are widely used as food or beverage containers. In particular, polyethylene terephthalate (sometimes abbreviated as PET) composition sheets containing polyolefin resin are used.
Molded products obtained by thermoforming PET under conditions that can crystallize it have excellent heat resistance (Japanese Patent Application Laid-Open No.
62660) and can be used as a heat-resistant container that can be cooked in an oven (sometimes called ovenable). Furthermore, molded products obtained by thermoforming biaxially stretched PET films have excellent heat resistance and strength and can be used for various containers (see Japanese Patent Laid-Open Publication No. 38216/1983). However, such techniques provide
In PET containers, the PET molecules are in a crystallized or oriented state, resulting in extremely poor thermal adhesion, making it difficult to thermally bond (sometimes called heat sealing) the lid material. It has its drawbacks. Furthermore, after filling food, etc. and heat-sealing the lid material, if heat sterilization such as hot water sterilization (boiling sterilization) or steam heat sterilization (sometimes called retort sterilization) is performed, the lid material and the container will not adhere to each other. It has the disadvantage that the strength is further reduced, and an improvement has been desired. [Objective of the Invention] The present invention has been made against the background of the above circumstances, and its object is to obtain a material that is in a crystalline state or a molecularly oriented state and that can be thermally bonded when used as a lid material for a PET container. The object of the present invention is to provide a film-like laminate which has easy-open properties and can withstand heat sterilization. [Structure of the Invention] As a result of extensive research into film-like laminates for polyester containers that do not have the above-mentioned drawbacks, the present inventors have found that if a specific copolymer polyester is laminated onto a specific film-like material, the drawbacks can be avoided. We have discovered that this can be improved, and have arrived at the present invention. That is, in the present invention, a thin layer of copolymerized polyester is laminated on one or both sides of a film-like material serving as a base material. The copolyester of the thin layer is (a) a thermoplastic polyester with a melting point of 100 to 200°C, and (b) an aliphatic dicarboxylic acid having 4 or more carbon atoms, preferably 6 to 10 carbon atoms. (preferably a linear dicarboxylic acid) or an ester-forming derivative thereof, copolymerized with 5 mol% or more per acid component; (c) More preferably, 50 mol% or more of the acid component is terephthalic acid. and/or isophthalic acid,
and 50 mol% or more of the glycol component is ethylene glycol, tetramethylene glycol, neobentyl glycol, or a mixed glycol thereof, and the film-like material serving as the base material is polyethylene terephthalate, polycarbonate, or a mixture thereof. unstretched or at least 1
A film-like laminate characterized by being an axially oriented film. The copolymerized polyester used in the present invention has a melting point of
It is copolymerized at 100 to 200°C with 5 mol% or more of an aliphatic dicarboxylic acid component having 4 or more carbon atoms. This copolymerized polyester has a melting point of
If the temperature is lower than 100°C, the adhesive strength with the PET container will drop significantly during heat sterilization, which is not preferable. If the melting point is higher than 200° C., it is not preferable because lamination with a film-like material is difficult or the heat-sealing temperature is too high, resulting in significant deformation or embrittlement of the heat-bonded portion of the PET container. Next, in the copolymerized polyester of the present invention, the aliphatic dicarboxylic acids having 4 or more carbon atoms in the copolymerization component include, for example, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, etc. These are linear dicarboxylic acids, and adipic acid is particularly preferred because it has excellent adhesive strength. Aliphatic dicarboxylic acids having 3 or less carbon atoms cannot be used as lid materials because of their weak adhesive strength. The copolymerization ratio of the dicarboxylic acid needs to be 5 mol% or more to develop adhesive strength, and the upper limit is determined by its melting point, but if it exceeds 50 mol%, the melting point will drop to 100°C or less, making it inappropriate. . Dicarboxylic acid components other than aliphatic dicarboxylic acid components include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid,
Aromatic dicarboxylic acids such as diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylsulfone dicarboxylic acid, etc.; Alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hexahydroisophthalic acid, etc.; p-β-hydroxyethoxy Examples include one or more components of other difunctional carboxylic acids such as oxyacids such as benzoic acid, p-oxybenzoic acid, ε-oxycaproic acid, and the like. Especially 50 mol% of terephthalic acid and/or isophthalic acid
It is preferable that it is above because appropriate rigidity can be obtained. Glycol components include ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentyl glycol, diethylene glycol, 1,1-cyclohexane dimethylol, 1,4-cyclohexane dimethylol, 2,2 - selected from one or more of bis(4-β-hydroxyethoxyphenyl)propane, bis(4-βhydroxyethoxyphenyl)sulfone, etc., especially ethylene glycol and/or neopentyl glycol and /or Tetramethylene glycol is preferable since it has good adhesive strength. The intrinsic viscosity of this copolymerized polyester resin is
If it is lower than 0.5, the adhesive strength with the container body during heat sealing, for example, becomes weak, which is not preferable. Although there is no particular upper limit to the intrinsic viscosity, if it is too high, production becomes difficult, so it is preferable to take this point into consideration when determining the intrinsic viscosity of the polymer used. In the present invention, the above-mentioned composition is laminated on at least one surface of a film-like object, and the method of lamination is such that the composition dissolved and dispersed in a solvent is coated on at least one surface of the film-like object, and then the solvent is removed. Examples include a method of removing by evaporation, a method of extruding a molten composition onto a thin film and cooling and solidifying it while being pressed with a roll, and a co-extrusion method. The thickness of the composition layer (adhesive layer) may normally be selected so that the adhesive strength is appropriate, and is preferably, for example, 50 μm or less, particularly around 10 μm. The film-like material on which the adhesive layer is laminated in the present invention is
Any material may be used as long as it can be laminated, but preferably a thermoplastic resin film such as polyester or a metal foil such as aluminum foil is used. In particular, films made by biaxially stretching PET and further heat-setting, polycarbonate films, polyarylate films, etc. have good adhesion when laminated with the copolyester, and
It is preferable because it has good dimensional stability during heat sterilization at ℃. In the case of a PET film, it may be a non-oriented film in which other polyesters such as polybutylene terephthalate and polyarylate or polycarbonate are mixed in an amount within 30% by weight. The preferred thickness of the film-like material varies depending on the material of which the film is made, but it should be such that the temperature of the sealing surface rises to a temperature that produces adhesive strength in a short period of time (for example, within 3 seconds) when heat sealing is performed. For example, in the case of polyester film, it is 300μ or less, and in the case of aluminum foil, it is 100μ.
It is preferable that it is below. In addition, in order to improve heat seal strength and blocking properties, inorganic particles with an average particle size of 20μ or less,
For example, SiO ₂ , TiO ₂ , CaCO ₃ , Fe ₂ O ₃ , Al ₂ O ₃ ,
It may be dispersed in CaO, MgO, etc., a mixture thereof, or a copolymerized polyester, or it may contain a stabilizer to improve melt stability. [Effects of the Invention] The film-like laminate of the present invention has excellent heat-sealing properties, retort resistance, oil resistance, etc., and can be used as a lid material film that can be easily opened, especially for crystallized heat-resistant PET containers. . [Example] The present invention will be explained in detail with reference to Examples below. The measurement conditions for the main physical property values are as follows. (1) Intrinsic viscosity [IV]; 35 in 0-chlorophenol or phenol/tetrachloroethane mixed solvent
Measured at °C. (2) Density [ρ]: Measured at 25°C using a density gradient tube made of carbon tetrachloride and n-heptane. (3) Softening point (SP): Based on the Vikatsuto softening point measurement method. (4) Easy ovenability: Lay the sample cut to 15 mm width on the sample to be bonded so that the adhesive layer is in the middle, and heat seal it at a predetermined temperature and pressure for a predetermined time using a heat sealer with a 5 mm wide heating part. After the sealed portion had cooled to room temperature, the adhesive strength was measured. The adhesive strength was evaluated as follows. Strength 1.0-3.0Kg/15mm...Good ○ 0.5-1.0〃...Slightly poor△ 0-0.5〃...Poor × (5) Melting point [Tm]; Differential calorimeter (DSC-20 model manufactured by Seiko Electronics Co., Ltd.) ) at a heating rate of 20℃/mm. If a melting point peak did not appear on DSC, measurement was performed using a micro melting point measuring device (Model MP manufactured by Yanagimoto Seisakusho). Examples 1 to 8 and Comparative Examples 1 to 9 (Molding of laminates) Copolymerized polyesters having the composition ratios shown in Table 1 (melt viscosity measured at 200°C with a Koka type float tester of about 600 to 3000 poise) The copolymerized polyester (copolymerized polyester) is fed to a twin-screw extruder equipped with a die for sheet extrusion at the tip, and the copolymerized polyester is polymerized to a thickness of approximately 30 μm.
sheet was extruded. The sheet was laminated in a molten state on top of a separately prepared biaxially stretched PET film (stretching ratio 3.5 x 3.5 times, heat setting temperature 220°C, wall thickness 75μ, density 1.42g/cm ³ ), and the molten sheet A Teflon sheet was further laminated on the upper surface of the sheet, which was then supplied between water-cooled rolls, and cooled and solidified while being pressed by the rolls. After the sheet was cooled, the Teflon sheet was peeled off and the copolyester was laminated onto the stretched PET film to obtain a film-like laminate. (Formation of crystalline PET containers) PET with an intrinsic viscosity (IV) of 1.12 (dried at 160°C for 5 hours) is added to 97wt% with a melt index (MI) of 1.3.
After blending LLDPE (linear low-density polyethylene) at a ratio of 3 wt%, it was fed to an extruder with a 30 mm screw diameter equipped with a die for sheet extrusion at the tip. Extruder cylinder setting temperature 240~280
The extruded sheet was melt-kneaded under the conditions of 0.degree. The density of the sheet was 1.32 g/cm ³ (substantially amorphous), and the IV of PET in the sheet was 0.92. This sheet is engraved into mold A using Asano Laboratory's FC-IAPA-W type compressed air/vacuum forming machine.
A concave tray type with a height of 135 mm, a width of 58 mm, and a depth of 18 mm.
A convex tray mold with a height of 133 mm, a width of 56 mm, and a depth of 18 mm was used as mold B, and the heating sheet surface temperature was 160 to 180.
℃, contact time with mold A 5 seconds, temperature of mold B 20~
Vacuum forming was carried out under the conditions of 50°C and a contact time with mold B of 15 seconds. The tray thus obtained has a density of 1.36
It was a crystallized PET tray of g/cm ³ (crystallinity about 30%). This PET tray can be heated for 230 minutes in the oven.
It had good heat resistance with almost no shrinkage or deformation when heat treated at ℃ for 10 minutes. The film-like laminate thus obtained and the crystallization
A 15 mm wide rectangular sample was cut out from the PET tray and thermally bonded with a heat sealer. The thermally bonded sample was (a) allowed to cool to room temperature, (b) immersed in hot water of 95 to 98°C for 1 hour, and (c) treated in a retort sterilizer at 120°C under steam pressure for 30 minutes, Adhesive strength was measured using a tensile tester. The results are shown in Table-1. As is clear from Table 1, the laminate of the present invention having the composition of Example 6 was good in all respects except for some problems in retort resistance, whereas the laminate of Comparative Examples 1 to
All compositions of No. 9 could not be thermally bonded. For reference, the above amorphous extruded sheet (density
1.32 g/cm ³ ), the compositions of Comparative Examples 1 to 9 also showed good adhesive strength. From this,
It was confirmed that the laminate of the present invention has particularly good thermal adhesion to crystalline PET.

【table】

[Table] Examples 9 to 13 and Comparative Examples 10 to 11 Adhesive strength was investigated in the same manner as in Example 1 except that the composition of the copolymerized polyester was changed. The results are shown in Table-2. From Table 2, it was found that the composition ratio of aliphatic dicarboxylic acid was preferably 5 to 50 mol%, particularly 10 to 40 mol%. Reference Examples 1 to 3 Ethylene vinyl acetate (EVR) as adhesive layer
The table below shows examples of the results of examining thermal adhesion properties when using polyolefin, polyolefin, and polyamide resins.
Shown in 2. Materials such as EVA have poor heat resistance,
Furthermore, those made of olefin or polyamide had poor thermal adhesion.

[Table] Example 14 and Comparative Example 12 Example 1 and Comparative Example 1 except that a 100μ polycarbonate film was used as the film material.
We conducted a similar study. The results were the same as in Example 1 and Comparative Example 1. Examples 15 and 16 and Comparative Examples 13 and 14 Further studies were carried out in the same manner as in Example 1 or Comparative Example 1, except that a 125μ thick non-oriented PET film and a 40μ thick aluminum foil were used. The results were the same as in Example 1 and Comparative Example 1. Comparative Examples 15 and 16 A study was conducted in the same manner as in Example 1 except that a polypropylene sheet with a wall thickness of 100 μm and a nylon 6 sheet were used as the film-like material, but the adhesion with the copolymerized polyester layer was poor and the laminate I couldn't get it. Example 17 and Comparative Example 17 (Formation of biaxially oriented PET container) A PET sheet of IV0.7 was biaxially stretched (magnification 2.5×
2.5) After that, a stretched PET film with a wall thickness of 150 μm that had been heat-set at 220° C. was air-formed using the pressure mold/vacuum forming machine described above to obtain a biaxially oriented PET container. After heating the film to 220℃ using a hot plate,
The above-mentioned mold A with a compressed air pressure of 6 kg/cm ² G and a mold temperature of 100° C. was used. Except for using Example 14 as the laminate and using the above biaxially oriented PET container as the PET container,
The same study as in Example 1 and Comparative Example 1 was conducted. The results obtained were the same as in Example 1 and Comparative Example 1. As is clear from the above examples, the film-like laminate of the present invention has good heat sealability and heat sterilization resistance compared to crystalline PET or oriented PET, and is excellent as a lid material that can be used in an easy oven. be.

Claims (1)

[Scope of Claims] 1 A laminate comprising a thin layer laminated on at least one surface of a film-like material serving as a base material, the thin layer being a polyester whose main components are aromatic dicarboxylic acid and glycol. obtained by copolymerizing a part of the dicarboxylic acid component with an aliphatic dicarboxylic acid having 4 or more carbon atoms and/or its ester-forming derivative in an amount of 5 mol % or more based on the acid component.
A film-like laminate comprising a thermoplastic copolymer polyester having a melting point of 100 to 200°C. 2. The film-like laminate according to claim 1, wherein the film-like material is an unoriented or oriented film containing polyethylene terephthalate, polycarbonate, or a mixture thereof as a main component. 3. The copolymerized polyester contains 50 mol% or more of terephthalic acid and/or isophthalic acid as an acid component, and 50 mol% or more of at least one of ethylene glycol, tetramethylene glycol, and neopentyl glycol as a glycol component. , and the aliphatic dicarboxylic acid and/or its ester-forming derivative is a linear dicarboxylic acid having 6 to 10 carbon atoms. laminate.