JP3048728B2 - Easy adhesion 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 an easy-adhesive polyester film, and more particularly to a biaxially oriented polyester film used for producing a laminate film in which a polyolefin is laminated on one side or both sides by an extrusion lamination method. The present invention also relates to an easily-adhesive polyester film having excellent adhesion to polyolefin.

[0002]

2. Description of the Related Art Laminated films obtained by heating and melting polyethylene at a high temperature of about 300.degree. C. and extruding them into a curtain and bonding them to a biaxially oriented polyester film are widely used mainly for packaging materials.

The purpose of extrusion lamination is to produce a new material in which polyethylene and polyester films are integrated by supplementing their properties, and the adhesion between the two is the most important property in the processing. is there.

However, polyethylene has its structure

[0005]

Embedded image

[0006] As shown by the non-polar and inert
It is a polymer with extremely poor adhesion. Further, the biaxially oriented polyester film is a film having high cohesiveness on the surface and poor adhesion since the surface thereof is highly crystallographically oriented.

Therefore, as a method for improving the adhesion between the two, polyethylene is melt-extruded at a high temperature of about 300 ° C., the surface is oxidized in an air gap to impart polarity, and an anchor agent is added to the biaxially oriented polyester film. A method of performing a contact promoting treatment by coating is used.

As the anchoring agent, an isocyanate-based (urethane-based), polyethyleneimine-based, organic titanate-based, polybutadiene-based anchoring agent is used, and these anchoring agents are biaxial just before extrusion lamination of polyethylene. It is applied online on an oriented polyester film.

Therefore, there is a need for a facility for applying and drying the anchor agent in the laminating step, and there is a drawback that the anchor agent that can be used is limited by the capability of the drying facility.

By the way, in recent years, such an on-line anchor agent coating has been omitted to simplify the process,
There is also a need to eliminate restrictions on usable anchor agents. Off-line coating is a method to respond to this, but isocyanate-based, polyethyleneimine-based, and polybutadiene-based anchoring agents that have been conventionally used have poor blocking resistance, and a biaxially oriented polyester film coated with the anchoring agent is used. When the film is wound into a roll, a problem occurs in that the films adhere to each other (blocking), and it is practically difficult to use the film.

Also, widely used isocyanate-based (urethane-based) anchor agents show excellent adhesiveness when anchored online immediately before lamination, but have poor adhesiveness when applied off-line and laminated over time. However, sufficient adhesiveness is not exhibited.

[0012]

SUMMARY OF THE INVENTION The present inventor has solved the above problem and has developed an easily adhesive film useful for producing a laminate film of a polyolefin and a biaxially oriented polyester film by an extrusion lamination method. As a result of intensive research, the present invention has been achieved.

An object of the present invention is to provide a biaxially oriented polyester which has excellent adhesion to a polyolefin by extrusion lamination without sticking (blocking) between films when the film is wound into a roll after the application of the anchor agent. To provide a film.

[0014]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
According to the present invention, on one or both sides of a biaxially oriented polyester film, the general formula YR ₁ Si (OR) ₃ (where R is a methyl group or an ethyl group, R ₁ is a lower alkylene group, and Y is an organic functional group) The thickness of the cured silane coupling agent represented by the formula
This is achieved by an easily adherent polyester film for polyolefin extrusion lamination, comprising a first layer of 0.2 μm and a second layer of polyethyleneimine having a thickness of 0.003 to 0.05 μm provided thereon.

The polyester in the present invention is a crystalline linear saturated polyester produced from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof, and specifically, polyethylene terephthalate. , Polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, poly (1,4-cyclohexylene dimethylene terephthalate) and the like. Further, a copolymer in which some of these components are substituted with other components, or a mixture with polyalkylene glycol or another resin may be used.

The polyester may contain a lubricant, for example, inorganic fine particles such as calcium carbonate, kaolin, silica, and titanium oxide, and / or precipitated fine particles of catalyst residue for controlling the surface roughness.

The biaxially oriented polyester film of the present invention can be produced by a conventionally known method. For example, the above polyester is dried and then melted, and a die (for example, T
(Die, I-die, etc.) onto a cooling drum and quenched into an unstretched film, stretched in the biaxial direction, and heat-fixed. The thickness of the film is not particularly limited, but is 12 to 25.
0 μm is preferred.

In the present invention, the cured thin film provided on one side or both sides of the biaxially oriented polyester film is a cured thin film of a silane coupling agent. This silane coupling agent is a compound represented by the following general formula: YR ₁ Si (OR) ₃ (where R is a methyl group or an ethyl group, R ₁ is a lower alkylene group, and Y is an organic functional group). In the above formula, the lower alkylene group of R ₁ is particularly preferably a propylene group, and the organic functional group of Y is particularly preferably an amino group or a glycidyl group. It should be understood that the amino group includes a substituted amino group such as an N-β (aminoethyl) amino group [H ₂ NCH ₂ CH ₂ NH—]. Specific examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyltriethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β ( Aminoethyl)
γ-aminopropyltrimethoxysilane and the like are preferably exemplified. These can be used alone or in combination of two or more.

The silane coupling agent is preferably used after being partially hydrolyzed as an aqueous liquid, and the aqueous liquid is applied to one or both surfaces of a polyester film, and then subjected to a heat treatment to form a cured thin film. .
By this heat treatment, the water solvent is removed, and the curing reaction (self-condensation reaction) of the partial hydrolyzate proceeds. The processing temperature is preferably 180 ° C. or higher from the viewpoint of curing reactivity.

The aqueous solution of the silane coupling agent may be applied in a usual application step, that is, a step of applying the biaxially stretched and heat-set polyester film separately from the production step of the film. However, when a heat treatment of 180 ° C. or more, which is preferable for a curing reaction, is performed in the coating in this step, the polyester film is liable to be wrinkled due to heat shrinkage, and the oligomer is deposited on the film surface to make the film cloudy. Therefore, coating during the polyester film manufacturing process is preferable. In particular, it is preferable to apply an aqueous coating solution to one or both surfaces of the polyester film before the crystal orientation is completed in this step.

Here, the polyester film before the completion of the crystal orientation is an unstretched film obtained by hot-melting a polyester to form a film as it is; a non-stretched film in a longitudinal direction (longitudinal direction) or a transverse direction (width). Uniaxially stretched film oriented in one of two directions; furthermore, a film stretched and oriented at a low magnification in two directions, that is, longitudinally and laterally (finally re-stretched in the longitudinal or transverse direction to obtain oriented crystallization. (The biaxial film before completion).

The solid content of the above coating solution is usually 30% by weight or less, more preferably 10% by weight or less. The coating amount is 0.5 to ²⁰ g, preferably 1 to 10 g, per m ² of the running film.

The coating thickness is preferably from 0.005 to 0.2 μm, more preferably from 0.01 to 0.1 μm. When the coating thickness is less than 0.005 μm, sufficient adhesiveness is not exhibited, while when the coating thickness exceeds 0.2 μm, no further effect of improving the adhesiveness is observed, which is not preferable.

As a coating method, any known coating method can be applied. For example, a roll coating method, a gravure coating method, a roll brushing method, a spray coating method, an air knife coating method, an impregnation method, a curtain coating method, or the like may be applied alone or in combination.

The polyester film to which the coating liquid has been applied and before the completion of the crystal orientation is dried and led to steps such as stretching and heat setting. For example, a vertically uniaxially stretched polyester film coated with an aqueous liquid is guided to a stenter, and is horizontally stretched and heat-set. During this time, the coating liquid is dried and thermally cured.

Conditions for oriented crystallization of the polyester film,
For example, stretching, heat setting, and the like can be performed under conditions conventionally accumulated by those skilled in the art.

The aqueous liquid contains an anionic surfactant,
A cationic surfactant; a necessary amount of a surfactant such as a nonionic surfactant can be added and used. As such a surfactant, the surface tension of the aqueous coating solution is 40 dyne.
/ Cm or less, which promotes wetting to the polyester film. For example, polyoxyethylene alkylphenyl ether, polyoxyethylene-fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, fatty acid metal soap, alkyl sulfate, Examples thereof include alkyl sulfonates, alkyl sulfosuccinates, quaternary ammonium chloride salts, and alkylamine hydrochlorides.

In the present invention, the second layer provided on the first layer made of the cured thin film of the silane coupling agent is a thin layer made of polyethyleneimine. This polyethyleneimine can be obtained by polymerizing ethyleneimine by a known method, and its molecular weight is preferably in the range of 1,000 to 10,000, more preferably in the range of 1,500 to 5,000.

Such polyethyleneimine is easily dissolved in water or an organic solvent. Therefore, the coating solution for the second layer can be prepared by dissolving polyethyleneimine in water or an organic solvent, but is preferably dissolved in water or a mixed solvent of water and an organic solvent, particularly a lower alcohol. The solid concentration of the coating solution is usually 20% by weight or less, and 10% by weight.
The following is preferred. Further, the content is preferably 0.2 to 10% by weight.

The thickness of the second layer is 0.003-0.05 μm
m, preferably 0.005 to 0.03 μm. If the thickness is less than 0.003 μm, sufficient adhesiveness cannot be obtained. On the other hand, if the thickness exceeds 0.05 μm, sticking (blocking) between the films tends to occur when the films are wound into a roll, which is not preferable.

As the coating method, any known coating method can be applied as in the case of the first layer.

As in the case of the first layer, the coating solution for the second layer may be applied to the polyester film during the production process, particularly to the polyester film before the completion of the crystal orientation. It may be carried out in the step of applying the film separated from the manufacturing process of the film to the prepared polyester film.

The biaxially oriented polyester film thus obtained has excellent blocking resistance and can be wound into a roll. Furthermore, it has excellent adhesion to polyolefin, and can be easily laminated to polyolefin by a conventionally known extrusion lamination method.

For example, polyethylene is heated and melted at about 300 ° C. and slit die (for example, T die, I die, etc.)
Extruded as a hot-melt film from, and bonded and bonded between a biaxially oriented polyester film that has been subjected to easy adhesion processing in advance and a rubber roll for pressing and a cooling metal roll, then cools and solidifies the molten film with a cooling roll, By peeling and winding, a laminated film of polyethylene and a biaxially oriented polyester film can be produced.

The polyolefin in the present invention includes
Polyethylene, especially high pressure low density polyethylene (LDP)
E) is preferably used. The number average molecular weight of LDPE is preferably in the range of 10,000 to 50,000, more preferably in the range of 20,000 to 40,000. Also,
Melt Plate (MFR), a practical property of LDPE
(ASTM D-1238) is preferably in the range of 0.5 to 10, more preferably 1 to 9. Swelling Ratio (SR) (ASTMD-12
38) is preferably from 1.2 to 2.0, and more preferably from 1.4 to 1.9.

As polyethylene, besides LDPE,
Depending on the application, linear low density polyethylene (LLDPE),
High density polyethylene (HDPE) is also used.

The laminated film of the polyolefin and the biaxial polyester film thus produced has excellent adhesiveness between the two, and can be widely used for packaging and the like.

[0038]

The present invention will be described below in detail with reference to examples. In the examples, “parts” means “parts by weight”.
Further, the blocking resistance and adhesiveness of the easily adhesive-treated film were evaluated by the following methods.

1. Adhesive density 0.919 g / cm ³ , melt plate (MF
R) 7.0 g / 10 min, swelling ratio (S
R) 30 1.75 low density polyethylene (LDPE)
The mixture was heated and melted at 5 ° C., extruded from a slit die (T die) into a film having a thickness of 30 μm after cooling, and then biaxially oriented polyester film, a pressure rubber roll and
After pressure bonding between metal rolls cooled to ° C., they were cooled and solidified by the cooling rolls, and peeled and wound up from the cooling roll surface.

The adhesive strength is indicated by the peel strength (g / 25 mm) when the polyethylene and the biaxially oriented polyester film of the laminate film thus obtained are peeled in the T-shaped direction by an Instron type tensile tester. I do.

2. Blocking resistance A biaxially stretched polyester film having a thickness of 50 μm subjected to an easy adhesion treatment was wound up on a 1000 m roll at a width of 250 m / m, and then kept in a thermo-hygrostat at 45 ° C. × 70% RH for 72 hours. . After the completion of this treatment, the roll sample was left at room temperature for 72 hours, and the state of sticking (blocking) between the films of the roll sample was examined. The results are shown in the following evaluation. ：: Blocking is not recognized Δ: Some tendency of blocking is recognized X: Blocking is recognized

[0042]

Examples 1-5 Polyethylene terephthalate (containing 0.2% lubricant) having an intrinsic viscosity of 0.65 measured in O-chlorophenol at 35 ° C. was melt-extruded on a rotating cooling drum maintained at 20 ° C. and had a thickness of 650 μm. And stretched 3.5 times in the machine axis direction (longitudinal direction), and then 90 parts of the silane coupling agent component shown in Table 1 and a nonionic surfactant (polyoxyethylene nonylphenyl ether) 10 The aqueous solution containing
The coating was applied to one surface of the uniaxially stretched film so that the coating thickness became the value shown in Table 1. 2. Later at 105 ° C. in the lateral direction.
Stretched 9 times and heat-treated at 210 ° C to a thickness of 50 µm
A silane coupling agent-coated polyester film was obtained.

Further, an ethanol solution of polyethyleneimine was applied to the treated surface by a kiss coat method so that the applied thickness became the value shown in Table 1, and dried at 120 ° C.

Table 1 shows the results of evaluating the obtained biaxially stretched polyester film for blocking resistance and adhesiveness.

[0045]

Comparative Examples 1-2 The silane coupling agent-coated polyester was prepared in the same manner as in Example 1 except that the application of polyethyleneimine was omitted and the amount of the silane coupling agent applied was changed as shown in Table 1. I got a film.

Table 1 shows the evaluation results of the blocking resistance and the adhesiveness of this film.

[0047]

Comparative Examples 3 and 4 Biaxial stretching with polyethyleneimine coating was carried out in the same manner as in Example 1, except that the application of the silane coupling agent was omitted and the amount of polyethyleneimine applied was changed as shown in Table 1. A polyester film was obtained.

Table 1 shows the evaluation results of the blocking resistance and the adhesiveness of this film.

[0049]

Comparative Example 5 A biaxially stretched polyester film was obtained in the same manner as in Example 1, except that the application of the silane coupling agent and polyethyleneimine was omitted. This polyester film has not been subjected to any surface treatment.

Table 1 shows the results of evaluation of the adhesiveness of this film.

[0051]

[Table 1]

As is evident from Table 1, the easily adhesive polyester films of the examples have excellent adhesion to polyethylene during extrusion lamination, do not stick to each other when wound into a roll, and have anti-blocking properties. It is a film with excellent properties.

[0053]

According to the present invention, a biaxially oriented polyester which does not stick to each other (blocking) when wound into a roll after the application of an anchoring agent and gives excellent adhesion to polyolefin by extrusion lamination. A film can be provided.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 B29C 47/06 C08J 7/04 B05D 1/00-7/26

Claims (3)

(57) [Claims] 1. A biaxially oriented polyester film on one or both sides of a general formula YR ₁ Si (OR) ₃ (where R is a methyl or ethyl group, R ₁ is a lower alkylene group, and Y is an organic functional group) The thickness of the cured silane coupling agent represented by the formula
An easily adhesive polyester film for polyolefin extrusion lamination, comprising a first layer of 0.2 μm and a second layer of polyethyleneimine having a thickness of 0.003 to 0.05 μm provided thereon. 2. The easily adhesive polyester film for polyolefin extrusion lamination according to claim 1, wherein the organic functional group Y in the general formula is an amino group or a glycidyl group. 3. The cured thin film of the first layer is formed by applying a partial hydrolyzate of a silane coupling agent on one or both sides of a polyester film, and then performing a heat curing treatment at 180 ° C. or higher. 2. The easily adhesive polyester film for polyolefin extrusion lamination according to claim 1.