JP3137450B2 - Laminated polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated polyester film having excellent adhesiveness, especially heat sealability, and excellent heat resistance and mechanical properties. And a laminated polyester film having excellent heat sealing properties and high sealing strength.

[0002]

2. Description of the Related Art
A film used for a packaging material or the like is generally a polyolefin-based resin film such as polyethylene. However, these polyolefin-based resin films have substantially good heat sealing properties, but have many drawbacks such as low mechanical properties, low heat resistance, poor gas barrier properties, and a unique odor. Therefore, in recent years, in recent years, it is often unsuitable for applications requiring the above-mentioned physical properties as many packaging materials, including food packaging, and the actual use of such materials is not limited. On the other hand, a polyester resin film represented by a polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) resin exhibits stable properties over a wide temperature range, and is strong and excellent in dimensional stability and oil resistance. It is drawing attention as a packaging material. In particular, the PBT film has a high crystallization rate, so that it does not need to be subjected to a special heat treatment after biaxial stretching or film formation, so that mechanical properties, heat resistance, dimensional stability,
A film with excellent gas barrier properties and oil resistance is obtained,
It is suitable for applications requiring these physical properties. However, crystalline polyester films such as PBT are inferior in heat-sealing properties, require high temperatures for heat-sealing, and have a narrow range of sealing temperatures, requiring not only strict condition control in the sealing process, but also sealing. However, they have problems such as extremely low sealing strength and have many advantages as a packaging film, but their use has been limited. As a method for solving such a problem, for example, Japanese Patent Application Laid-Open No. 3-149253 proposes a method in which a PBT resin is mixed with a polycarbonate resin to increase the heat sealing temperature range and improve the heat sealing property. In addition, a method of lowering the sealing temperature by using a copolyester having a large amount of comonomer units introduced as a component constituting the polyester, expanding the sealing temperature range, and compensating for the heat sealing property can be considered.
As described above, a polyester film in which a large amount of copolymer units are introduced or in which a large amount of other resin components are blended has improved heat sealability, but loses crystallinity, and has heat resistance, mechanical properties, and oil resistance of the material itself. The properties and the like are lowered, and the original advantage as the crystalline polyester is lost, which is also not preferable.

[0003]

In view of the above problems, the present inventors have developed a film having mechanical properties (strength, flexibility), heat resistance, oil resistance, etc., and having good heat sealability. As a result of diligent studies to obtain a specific polyester resin film as a substrate, the above-mentioned problems are solved by laminating another specific polyester resin film on at least one surface thereof, and processing and use at high temperature Thus, a laminated film which is excellent in mechanical properties, gas barrier properties and heat sealing properties and is suitable as a material for food packaging has been completed. That is, the present invention mainly comprises an aromatic dicarboxylic acid residue as the acid component, and 1,4 as the diol component.
-A polyester copolymer mainly composed of butanediol residues, having a heat of crystallization (ΔH) of 10 joules / gram (J / g) or more, and a tensile modulus of 3000 to 10,000 kgf
/ Cm ² , a polyester film (B) made of an amorphous or low-crystalline polyester copolymer having a heat of crystallization (ΔH) of less than 10 J / g on at least one surface of the base layer crystalline polyester film (A). It is a laminated polyester film obtained by laminating. (However, the heat of crystallization (ΔH) is
The amount of heat (peak area) generated at the crystallization temperature when the sample melted and held at 250 ° C for 3 minutes at a rate of 10 ° C / min using a scanning differential calorimeter (DSC) and the weight of the measured sample Is a value calculated from. The film (A) serving as the base layer constituting the laminated film of the present invention needs to have excellent mechanical properties and heat resistance, and also have excellent gas and odor barrier properties. Therefore, the polyester constituting the base layer (A) is a crystalline polyester copolymer mainly composed of an aromatic dicarboxylic acid residue as an acid component and mainly composed of a 1,4-butanediol residue as a diol component. The heat of crystallization (ΔH) showing the property is 10 J / g or more. The above-mentioned polyester easily crystallizes at the time of film formation, and crystallizes without needing special heat treatment after biaxial stretching and film formation, and desired physical properties can be obtained. Examples of the main aromatic dicarboxylic acid component constituting the polyester of the base film (A) of the present invention include a terephthalic acid residue and a 2,6-naphthalenedicarboxylic acid residue.
Particularly, it is preferably a terephthalic acid residue. The diol component is a copolymer mainly composed of 1,4-butanediol residues. Further, the base layer film (A) of the present invention preferably has a moderate flexibility, and for this purpose, it is necessary that the tensile elastic modulus is 3000 to 10000 kgf / cm ² , and preferably 3000 to 8000 kgf / cm 2. ²
The tensile modulus of the base layer film (A) can be arbitrarily selected from the above range depending on the purpose of use of the laminated film, etc. However, if it is too low, it is often too flexible and disadvantageous. If it exceeds 10,000 kgf / cm ² , flexibility is poor, and it is often unfavorable. Further, the melting point of the polyester resin constituting the base layer film (A) is preferably from 160 to 215 ° C, particularly preferably from 180 to 215 ° C, from the viewpoint of heat resistance. In order to satisfy the crystallinity (heat of crystallization ΔH), tensile modulus, and melting point of the base layer film (A), the aromatic dicarboxylic acid residue and 1,4- It is preferable that the polyester copolymer is obtained by introducing a small amount of another acid component and / or a diol component in addition to the main component consisting of a butanediol residue. Preferred as such a copolymer component are, for example, isophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and tapsic acid as the acid component.
_{-OOC- (CH 2) n -COO- (} n is 4 to 40) are exemplified aliphatic dicarboxylic acids having the structure. In addition, a long-chain branched aliphatic dicarboxylic acid having 20 to 40 carbon atoms having a branched chain such as dimer acid or partially having an unsaturated bond can be mentioned. In addition, as the diol component as the other copolymer component, ethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol,
1,6-hexanediol, neopentyl glycol, decamethylene glycol, cyclohexanedimethanol,
Examples thereof include cyclohexanediol and polyoxyalkylene glycol. In particular, in the case of the present invention, adipic acid, sebacic acid, azelaic acid, and dodecanedicarboxylic acid are preferred as the copolymerization component constituting the base layer polyester resin (A) because heat resistance, flexibility and impact resistance are improved. Among them, dodecanedicarboxylic acid is most preferred.

The amount of the copolymer component introduced is such that its crystallinity is not less than 10 g / J as heat of crystallization, and its tensile modulus is 3000
It is limited to an amount to maintain the ~10000kgf / cm ^2. In general, when the amount of the above-mentioned copolymer component is small, the crystallinity (ΔH) is improved, and the tensile elasticity is improved to reduce the flexibility. When the amount is too large, the crystallinity (ΔH), melting point and tensile elasticity are increased. Etc., and the strength, heat resistance, etc., which are the objects of the present invention, are undesirably reduced. The copolymer component of the PBT-based polyester and the amount thereof for satisfying the requirements of the base layer film (A) of the present invention such as ΔH and tensile elastic modulus are easily determined from the above viewpoint. For example, when the copolymer component is a copolyester composed of dodecanedicarboxylic acid, 5
~ 25 mol%.

[0005] Next, the other film layer (B) constituting the laminated film of the present invention is intended especially for the purpose of supplementing the heat sealing property, and therefore it is necessary to have excellent heat sealing workability. is there. That is, it is desirable that the heat sealable temperature is appropriate, the temperature range is large, and the sealing strength is high. In addition, it has good affinity with the base film (A) and good adhesion to the base film (A) when laminated, and a difference in shrinkage when laminated with the base film (A). It is necessary not to cause deformation and distortion due to In particular, from the viewpoint of heat sealing properties, it is desirable that heat sealing can be performed at a sealing temperature of 180 ° C. or less, preferably at a sealing temperature of 160 ° C. or less. Such a property is that at least ΔH is 10 J / as a constituent material of the film layer (B).
It has been confirmed that the above object is achieved by using an amorphous or low-crystalline polyester having a weight of less than 5 g, preferably 5 J / g or less. Therefore, polyesters having a ΔH of 10 J / g or more, such as the above-mentioned base layer polyester resin (A), have poor heat sealability and are not preferred as the seal layer (B). As the polyester constituting the surface layer (B), generally, a polyester copolymer in which an acid component or a diol component, or both components are copolyesters composed of two or more kinds, and a relatively large amount of the copolymer component is introduced. This is achieved by using The constituent components of the polyester copolymer need not be particularly limited.For example, the acid component is selected from various aromatic dicarboxylic acids or alicyclic carboxylic acids, and aliphatic dicarboxylic acids, and the diol component is ethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol,
Aliphatic glycols such as neopentyl glycol, 1,6-hexanediol and decamethylene glycol, cycloaliphatic glycols such as cyclohexanedimethanol and cyclohexanediol, or ethoxylated bisphenol A;
It can be selected from aromatic diols such as ethoxylated bisphenol S and polyoxyalkylene glycols such as polyoxyethylene glycol and polytetramethylene glycol. As described above, the value of ΔH of the polyester copolymer generally has a constant changing tendency depending on the type of the component and the amount of the copolymer component, and if the type is constant, the value tends to decrease as the amount of the copolymer component increases. ΔH is 10 J / g as the (B) layer film.
It is not difficult for a person skilled in the art to obtain a polyester copolymer satisfying the following requirements, and the polyester copolymer can be easily selected by measuring ΔH of a commercially available polyester copolymer resin. In particular, a polyester copolymer preferable for forming the surface layer (B) is a polyethylene terephthalate-based copolymer or a polybutylene terephthalate-based copolymer containing a relatively large amount of a comonomer component. Isophthalic acid (about 25 mol% or more based on the total acid component), isophthalic acid copolymerized polyethylene terephthalate resin composed of ethylene glycol as the diol component, or ethylene glycol and cyclohexane dimethanol (the total diol component composed of only terephthalic acid) Cyclohexane dimethanol copolymerized polyethylene terephthalate resin comprising about 25 to 40 mol% of diol), or terephthalic acid and isophthalic acid (about 25 mol% or more based on all acid components) as acid components, and 1,4-butane as diol component Isophthalic acid copolymerized polybutylene terephthalate resin consisting ol. Even if the polyester resin alone has a ΔH exceeding 10 J / g, if the ΔH is less than 10 J / g as a polyester composition (alloy) containing another resin having an effect of lowering the crystallinity of the polyester resin, It can be used as the layer (B) of the present invention. As a specific example, a PBT resin having an ΔH of 10 J / g or more mixed with a polycarbonate resin which is an amorphous resin, and melt-kneaded to have a ΔH of less than 10 J / g is the present invention. It can be preferably used as the surface film (B). A single-layer film consisting only of the surface film (B) can be sealed at a relatively low temperature, but (B) is originally amorphous because of its characteristic amorphous property, and thus has sufficient heat resistance and mechanical properties. In addition to not being able to satisfy the requirements, a single layer tends to melt and cut due to heat applied only to the seal part during sealing, and the shrinkage increases, and the edge of the seal part along the so-called seal edge line With the base film (A) having the specific heat of crystallization and having a specific tensile modulus of elasticity. Lamination is also effective from the viewpoint of sealability. As described above, the present invention is characterized by laminating both the films (A) and (B) each having the specific requirements, thereby providing a film having the above-mentioned overall effect. It is a thing.

Various additives can be added to the base film (A) and the surface film (B) as long as the above-mentioned basic performance is not lost. For example, antistatic agents such as aliphatic glycerides, metal salts of alkyl benzene sulfonic acids and metal salts of alkyl sulfonic acids, organic slip agents such as fatty acid amides, slip agents such as inorganic particles, hindered phenol-based, phosphorus-based, and thioether-based heat Stabilizer,
Weathering stabilizers such as antioxidants, ultraviolet absorbers, metal benzoates, metal ethylene (meth) acrylate copolymers,
Known additives, such as a metal nucleating agent such as diphenyl phosphate metal salt and boron nitride, and a coloring agent such as dye and pigment, may be added to one or both of them according to the purpose.

[0007] The thickness of the laminated polyester film of the present invention should be appropriately set according to the application, but is usually in the range of 5 to 1000 µm. The ratio between the base layer (A) and the surface layer (B) depends on the total thickness, but (A):
It is generally preferred that (B) be from 95 to 40: 5 to 60.
When the layer (A) is too small, there is a problem in strength and heat resistance. On the contrary, in the opposite case, the heat sealing strength is not sufficient, and neither is preferable.

The method for producing the laminated polyester film of the present invention is not particularly limited, and it can be prepared by applying a generally known method for producing a laminated film. For example, one (A) film is prepared by a T-die method or the like, and the other layer (B) is melt-extruded and laminated thereon, (A) and (B) both resins are co-extruded, and dry lamination is performed. Any method such as a wet lamination method can be applied. In particular, in the laminated polyester film of the present invention, both the base layer film (A) and the surface layer film (B) are chemically similar in chemical structure to polyester resin and have good affinity, so that a multi-manifold die, a multi-feed block die, etc. By using the co-extrusion method, a laminated film having good appearance and properties can be obtained without using an adhesive, which is advantageous in terms of production efficiency and economy. In the preparation of the laminated film of the present invention, the desired effect can be obtained by crystallization of the (A) layer film without performing stretching or special heat treatment, but further effects can be obtained. Therefore, (A) the layer film or the laminated film may be subjected to such a treatment. The laminated film of the present invention is obtained by laminating a surface layer film (B) on at least one side of a base layer film (A), and may have both sides as a (B) layer if necessary. Alternatively, one side may be a film (B) and another resin film may be laminated on the other side as needed. Further, an aluminum foil or the like may be laminated as a barrier layer. Also, the laminated polyester film of the present invention may be embossed if necessary,
Surface processing such as sand mat processing and satin finishing may be performed. In the sealing process of the laminated film of the present invention, one sheet is folded or two sheets are overlapped so that the layer (B) is in contact, and the peripheral portion is heat-pressed and sealed with a normal heat sealer to easily form a bag. After the contents are filled, the opening side can be similarly sealed and sealed.

[0009]

The laminated film of the present invention is excellent in mechanical properties, heat resistance, oil resistance, gas barrier properties, etc., has good heat sealability and seal strength, and has comprehensively required characteristics as a packaging material. Particularly, it is suitable as a packaging material for foods and the like that require heat resistance.

[0010]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. The characteristic values and evaluation methods in the following examples and comparative examples are as follows. 1. Measurement of heat of crystallization (ΔH) Using a scanning differential calorimeter DSC-7, manufactured by PerkinElmer, hold at 250 ° C for 3 minutes, and then cool at a rate of 10 ° C / min. ΔH (J / g) was calculated from the peak area at (T _c ) and the weight of the measurement sample. 2. Tensile modulus Dumbbell-type test piece with a distance of 40 mm between the marked lines (thickness 50 μm, width 10
mm) was set in a tensile tester (Orientec® RTM-100), a tensile test was performed at a tensile speed of 100 mm / min, and the initial elastic modulus was measured. 3. Tensile strength and elongation of the laminated film In the same manner as above, a tensile test was performed at a tensile speed of 500 mm / min, and the strength and elongation at break were measured. 4. Seal strength A laminated film heat-sealed with a seal width of 10 mm is cut to a width of 15 mm in a direction perpendicular to the seal line, and both ends are fixed with the seal part in the center using a tensile tester RTM-100 manufactured by Orientec Co., Ltd. At a speed of 300 mm / min, and the seal strength was measured. 5. Heat resistance The same heat-sealed laminated film as in 4 above (width 15m
m) is suspended in a closed container by applying a load of 10 g to one end of the container. The container is heated and pressurized with steam, and retorted at 121 ° C for 30 minutes. Ranked. Excellent; no change in film and seal part. Good; slight change in color tone (whitening) and shape change (wrinkle, warpage, etc. due to shrinkage) in film and seal part. Poor; significant change in color tone and shape. Δ of polyester constituting base film layer (A) and seal layer (B) used in Examples and Comparative Examples
H, constituent components, and tensile modulus are as shown in Tables 1 and 2.

[0011]

[Table 1]

Note) * 1 TP: terephthalic acid residue DD: dodecanedicarboxylic acid residue SA: sebacic acid residue AA: adipic acid residue IP: isophthalic acid residue 1,4 BD: 1,4-butanediol residue Group

[0013]

[Table 2]

Note) * 1 TP: Terephthalic acid residue IP: Isophthalic acid residue 1,4 BD: 1,4-butanediol EG: Ethylene glycol residue CD: Cyclohexane dimethanol residue * 2 PC: Polycarbonate resin Examples 1 to 14 and Comparative Examples 1 to 14 Tables 1 and 2 were obtained by using a co-extrusion film forming machine in which two extruders A and B were connected to one co-extrusion die (two-layer multi-manifold die: die width 150 mm). (A) and (B) are supplied to the extruders A and B, respectively.
It was co-extruded from a die and immediately cooled and solidified with a cooling roll set at 30 ° C. to prepare a co-extruded film having a combination of two layers (A) and (B) shown in Tables 3 to 5. Each extruder was set at a temperature about 20 ° C. higher than the melting point of each resin and melt-extruded, and the screw rotation speed of the two extruders was adjusted to adjust the thickness of the laminated film and the thickness of both laminated resins (A). : The ratio (% by weight) of (B) was adjusted. Next, the various evaluations were performed on the laminated film. The heat sealing was performed by superposing the surface films (B) on each other, using a heat sealer manufactured by Tester Sangyo Co., Ltd., at a sealing pressure of 1 kg / cm ² for 1 sec, using a flat seal bar, and a seal width of 10 mm. Tables 3 to 5 show the combinations of the resins (A) and (B) used and the evaluation results. For comparison, the (A) layer and the (B) layer were each independently evaluated, and the (A) and (B) layers were also evaluated as a laminated film that did not satisfy the requirements of the present invention. Tables 3 to 5 also show the results.

[0015]

[Table 3]

[0016]

[Table 4]

[0017]

[Table 5]

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-218830 (JP, A) JP-A-4-151246 (JP, A) JP-A-63-81042 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (4)

(57) [Claims] (1) a terephthalic acid residue as an acid component;
And isophthalic acid, adipic acid, sebacic acid,
A few selected from jellyic acid and dodecanedicarboxylic acid
A diol consisting of at least one dicarboxylic acid residue
Polybut having 1,4-butanediol residue as a main component
It is composed of a tylene terephthalate-based polyester copolymer and has a heat of crystallization (ΔH) of 10 joules / gram (J /
g) or more, and at least one surface of the base layer crystalline polyester film (A) having a tensile modulus of 3000 to 10,000 kgf / cm ² , having an amorphous or low crystallinity having a heat of crystallization (ΔH) of less than 10 J / g. A laminated polyester film obtained by laminating a polyester film (B) comprising a conductive polyester copolymer. (However, the heat of crystallization (ΔH) is generated at the crystallization temperature when the temperature of a sample melted and held at 250 ° C for 3 minutes at a rate of 10 ° C / min is lowered using a scanning differential calorimeter (DSC). This is a value calculated from the amount of heat (peak area) to be measured and the weight of the measurement sample.) 2. A base layer crystalline polyester film (A)
The laminated polyester film according to claim 1, wherein the melting point of the polyester film is 160 to 215 ° C. 3. The copolymerized polyester film (B) comprises:
Terephthalic acid residue as main acid component, 1,4-butanedi
All and / or diol mainly composed of ethylene glycol
Polyester as a component and containing another ester-forming component
3. The laminated polyester film according to claim 1, comprising a tercopolymer. 4. The copolymerized polyester film (B) comprises:
1,4-butylene terephthalate copolymer and / or
The main component is a tylene terephthalate copolymer.
Claims comprising a resin composition containing a carbonate-based resin
Item 4. The laminated polyester film according to any one of Items 1 to 3 .