JPH05202214A - Polyester film having good bondability - Google Patents

Abstract

PURPOSE:To provide a polyester film for extrusion laminating with a polyolefin which film has high anti-blocking property and excellent adhesion to the polyolefin. CONSTITUTION:The title film, which is for use in extrusion laminating with a polyolefin, comprises a biaxially oriented polyester film and, formed on one or both sides thereof, a thin cured film of a silane coupling agent represented by the formula YR1Si(OR)3 (wherein R is methyl or ethyl, R1 is a lower alkylene, and Y is an organic functional group).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily adhesive polyester film, and more specifically, a biaxially oriented polyester film having a polyolefin film laminated on one side or both sides thereof is used for producing by an extrusion laminating method. The present invention also relates to an easily-adhesive polyester film having excellent adhesiveness with polyolefin.

[0002]

2. Description of the Related Art A laminated film obtained by heating and melting polyethylene at a high temperature of about 300 ° C., extruding it in a curtain shape and adhering it to a biaxially oriented polyester film is widely used mainly for packaging materials.

The purpose of extrusion laminating is to produce a new material in which polyethylene and polyester film are integrated to provide complementary properties, and the adhesion between the two is the most important characteristic in the process. is there.

However, polyethylene has a structure

[0005]

[Chemical 1]

[0006] Since it is non-polar and inactive,
It is a polymer with extremely poor adhesion. Further, the biaxially oriented polyester film is also a film having high surface cohesiveness and poor adhesiveness because its surface is highly crystallographically oriented.

Therefore, as a method of improving the adhesiveness between the two, polyethylene is melt extruded at a high temperature of about 300 ° C. to oxidize the surface in the air gap to impart polarity, and an anchor agent is added to the biaxially oriented polyester film. The method of coating and performing contact promotion treatment is adopted.

As the anchor agent, isocyanate type (urethane type), polyethyleneimine type, organic titanate type, polybutadiene type and the like anchor agents are used, and these anchor agents are biaxial immediately before extrusion lamination of polyethylene. Coated online on oriented polyester film.

Therefore, there is a drawback that a facility for coating and drying the anchor agent is required in the laminating step, and the capability of the drying facility limits the usable anchor agent.

By the way, in recent years, the process of simplifying the process has been attempted by omitting such an online coating of the anchor agent.
In addition, there is a demand for eliminating restrictions on usable anchor agents. As a method for responding to this, there is offline coating, but conventionally used isocyanate-based, polyethyleneimine-based, polybutadiene-based, etc. anchoring agents have poor blocking resistance, and a biaxially oriented polyester film coated with the anchoring agent is used. When rolled up into a roll, the film sticks to each other (blocks), which is practically difficult to use.

Further, widely used isocyanate type (urethane type) anchoring agents show excellent adhesiveness when anchored online immediately before lamination, but when applied offline and laminated after a lapse of time, the adhesiveness decreases. However, sufficient adhesiveness is not expressed.

[0012]

DISCLOSURE OF THE INVENTION The present inventors intend to solve the above problems and develop an easily-adhesive film useful for producing a laminate film of a polyolefin and a biaxially oriented polyester film by an extrusion laminating method. As a result of intensive research, the present invention has been achieved.

An object of the present invention is a biaxially oriented polyester film which does not have sticking (blocking) between the films when it is wound into a roll after being coated with an anchoring agent and which provides excellent adhesion with polyolefin by extrusion lamination. To provide.

[0014]

The object of the present invention is to:
According to the present invention, one or both sides of a biaxially oriented polyester film has the general formula YR ₁ Si (OR) ₃ (wherein R is a methyl group or an ethyl group, R ₁ is a lower alkylene group, and Y is an organic functional group. And a cured thin film of a silane coupling agent represented by the formula (1).

The polyester in the present invention is a crystalline linear saturated polyester produced from an aromatic dibasic acid or its ester-forming derivative and a diol or its ester-forming derivative, and specifically, polyethylene terephthalate. Preferred examples include polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, and poly (1,4-cyclohexylene dimethylene terephthalate). Further, it may be a copolymer in which a part of these is substituted with another component, or a mixture with a polyalkylene glycol or another resin.

In order to control the surface roughness, the polyester may contain a lubricant, for example, inorganic fine particles such as calcium carbonate, kaolin, silica, titanium oxide, and / or fine particles for depositing catalyst residues.

The biaxially oriented polyester film of the present invention can be produced by a conventionally known method. For example, the polyester is dried and then melted, and a die (for example, T
It can be produced by extruding from a die, an I-die or the like) onto a cooling drum to rapidly cool it into an unstretched film, stretching the unstretched film biaxially, and further heat-setting. The thickness of the film is not particularly limited, but is 12 to 25
0 μm is preferable.

In the present invention, the cured thin film provided on one side or both sides of the biaxially oriented polyester film is a cured film of a silane coupling agent. This silane coupling agent is a compound represented by the following general formula YR ₁ Si (OR) ₃ (wherein 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 general formula, the lower alkylene group for R ₁ is particularly preferably a propylene group, and the organic functional group for Y is particularly preferably an amino group or a glycidyl group. It should be understood that the above amino group includes a substituted amino group such as 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 use 1 type (s) or 2 or more types.

The silane coupling agent is preferably used as an aqueous liquid after being partially hydrolyzed, and the cured liquid can be formed by applying the aqueous liquid to one or both surfaces of the polyester film and further subjecting it to heat treatment. ..
By this heat treatment, the water solvent is removed and the curing reaction (self-condensation reaction) of the partial hydrolyzate proceeds. The treatment temperature is preferably 180 ° C. or higher in view of curing reactivity.

The aqueous solution of the silane coupling agent may be applied in a usual applying step, that is, a step of applying the biaxially stretched heat-fixed polyester film separately from the step of producing the film. However, when the coating in this step is heat-treated at 180 ° C. or higher, which is preferable for the curing reaction, the polyester film tends to have wrinkles due to heat shrinkage, and oligomers are deposited on the surface of the film to make the film cloudy. Therefore, coating in the polyester film manufacturing process is preferable. In particular, it is preferable to apply the aqueous coating liquid to one or both sides of the polyester film before the crystal orientation is completed in this step.

Here, the polyester film before the crystal orientation is completed is an unstretched film obtained by heat-melting polyester into a film as it is; an unstretched film in the longitudinal direction (longitudinal direction) or the lateral direction (width). Uniaxially-stretched film oriented in one of the two directions (direction), and further oriented in a low-magnification stretch direction in both the longitudinal and transverse directions (finally reoriented in the longitudinal or transverse direction for oriented crystallization). It includes a biaxial film before completion).

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

The coating thickness is preferably 0.02 to 0.5 μm, more preferably 0.03 to 0.3 μm. When the coating thickness is less than 0.02 μm, sufficient adhesiveness is not exhibited, while when the coating thickness exceeds 0.5 μm, sticking (blocking) between the films tends to occur when wound on a roll, 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 and a curtain coating method may be applied individually or in combination.

The polyester film coated with the coating liquid and before the completion of the crystal orientation is dried and introduced into a process such as stretching and heat setting. For example, a longitudinally uniaxially stretched polyester film coated with an aqueous liquid is introduced into a stenter and laterally stretched and heat set. During this time, the coating liquid is dried and heat-cured.

Oriented crystallization conditions of polyester film,
For example, the stretching, heat setting and the like can be carried out under the conditions conventionally accumulated by those skilled in the art.

Such an aqueous liquid contains an anionic surfactant,
Cationic surfactants; surfactants such as nonionic surfactants may be added in a necessary amount and used. As such a surfactant, the surface tension of the aqueous coating solution is 40 dyne.
It is preferable that it can be lowered to not more than 10 cm / cm 2 and accelerate the wetting of 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, alkyl amine hydrochloric acid and the like. Furthermore, in the range where the effects of the present invention are not lost, for example, antistatic agents, ultraviolet absorbers, pigments,
Other additives such as an organic filler, an inorganic filler, a lubricant and an antiblocking agent can be mixed.

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

For example, polyethylene is heated and melted at about 300 ° C. and slit die (for example, T die, I die, etc.)
Is extruded as a heat-melt film, and the biaxially oriented polyester film that has been subjected to an easy-adhesion treatment in advance is pressed and bonded between the pressure rubber roll and the cooling metal roll, and then the cooling film is cooled and solidified by the cooling roll and peeled from the surface of the cooling roll. By winding, a laminated film of polyethylene and a biaxially oriented polyester film can be manufactured.

As the polyolefin in the present invention,
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, and more preferably in the range of 20,000 to 40,000. Also,
Melt pool rate (MFR), which is a practical property of LDPE
(ASTM D-1238) is preferably in the range of 0.5 to 10, and more preferably in the range of 1 to 9. Furthermore, swelling ratio (SR) (ASTMD-12
38) is preferably 1.2 to 2.0, more preferably 1.4 to 1.9.

As polyethylene, in addition to LDPE,
Linear low density polyethylene (LLDPE), depending on the application
High density polyethylene (HDPE) is also used.

The laminated film of the polyethylene and the biaxial polyester film thus produced is
It has excellent adhesiveness between the two and can be widely used for packaging applications.

[0033]

EXAMPLES The present invention will be described in detail below with reference to examples.

In the examples, "part" means "part by weight". The blocking resistance and adhesiveness of the easily-adhesive-treated film were evaluated by the following methods.

1. Adhesiveness Density 0.919 g / cm ³ , melt pool rate (MF
R) 7.0 g / 10 min, swelling ratio (S
R) 1.75 low density polyethylene (LDPE) 30
It is melted by heating at 5 ° C. and extruded from a slit die (T die) into a film shape so that the thickness after cooling is 30 μm, a biaxially oriented polyester film, a pressure rubber roll, and 20
After pressure bonding between the metal rolls cooled to ℃, it was cooled and solidified by the cooling rolls, and peeled and wound from the surface of the cooling rolls.

The laminated film polyethylene and the biaxially oriented polyester film thus obtained were peeled in the T-shape by an Instron type tensile tester, and the peel strength (g / 25 mm) was used to indicate the adhesive strength. To do.

2. Blocking resistance A 50 μm-thick biaxially stretched polyester film having a thickness of 250 m / m was wound on a 1000 m roll and then kept in a thermo-hygrostat at 45 ° C. × 70% RH for 72 hours. .. After completion of this treatment, the film was allowed to stand at room temperature for 72 hours, and then the state of sticking (blocking) between the films of the roll sample was examined. The results are shown below. ◯: No blocking observed Δ: Some blocking tendency was observed ×: Blocking was observed

[0038]

Examples 1-4 and Comparative Examples 1-2 Polyethylene terephthalate having an intrinsic viscosity of 0.65 measured in 35 ° C. O-chlorophenol (containing 0.2% lubricant) on a rotating cooling drum maintained at 20 ° C. Melt-extruded to obtain an unstretched film having a thickness of 650 μm, and then stretched 3.5 times in the machine axis direction (longitudinal direction), and then 90 parts of the silane coupling agent component and nonionic surfactant (polyoxy An aqueous solution containing 10 parts of ethylene nonyl phenyl ether) was applied to one side of the uniaxially stretched film by the kiss coating method so that the coating thickness became the value shown in Table 1. Continue to 105
The film was stretched 3.9 times in the transverse direction at 0 ° C. and further heat treated at 210 ° C. to obtain a 50 μm-thick polyester film coated with an easily adhesive layer.

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

[0040]

Comparative Example 3 Example 1 except that the application of the aqueous liquid is omitted.
A biaxially stretched polyester film was obtained in the same manner as above.

A 10% ethanol solution of the silane coupling agent shown in Table 1 was applied to one surface of this biaxially stretched film by a kiss coat method so that the applied thickness was 0.1 μm, and 1
It was dried and cured at 30 ° C.

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

[0043]

Comparative Example 4 Example 1 except that the application of the aqueous liquid is omitted.
A biaxially stretched polyester film was obtained in the same manner as above.

This polyester film is not subjected to any surface treatment. The results of evaluation of the polyethylene adhesion of this film are shown in Table 1.

[0045]

[Table 1]

As is clear from Table 1, the easily-adhesive polyester films of the examples have excellent adhesiveness to polyethylene during extrusion lamination, and there is no sticking between the films when wound into a roll, and there is no blocking resistance. It is a film with excellent properties.

[0047]

EFFECTS OF THE INVENTION According to the present invention, a biaxially oriented polyester which does not have sticking (blocking) between films when coated in a roll after application of an anchoring agent and gives excellent adhesion to polyolefin by extrusion lamination. A film can be provided.

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Claims (3)

[Claims] 1. A biaxially oriented polyester film having one or both of the general formulas YR ₁ Si (OR) ₃ (wherein R is a methyl group or an ethyl group, R ₁ is a lower alkylene group, and Y is an organic functional group). ) An easily-adhesive polyester film for polyolefin extrusion lamination, which is provided with a cured thin film of a silane coupling agent represented by (4). 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 is formed by applying a partial hydrolyzate of a silane coupling agent on one side or both sides of a polyester film and then heat-curing at 180 ° C. or higher. An easily adhesive polyester film for polyolefin extrusion lamination according to 1.