JPH0737126B2 - Polyester film with good adhesion - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyester film having good adhesiveness.

(Prior Art) A polyester film is obtained by molding a polymer compound obtained by condensing terephthalic acid as an acid and ethylene glycol or diethylene glycol as an alcohol into a film. BACKGROUND ART A polyester film is colorless and transparent, has good weather resistance, and has high strength, and is therefore widely used for packaging articles.

However, the polyester film has the drawback of having poor adhesive strength. That is, polyester films have limited use because it is difficult to bond themselves to each other. In addition, it is difficult to bond the polyester film to other films, which makes it difficult to form a laminated film. Furthermore, even if an attempt is made to print on a polyester film, the adhesiveness with printing ink is not good, so that the application is limited in the field of packaging film. Therefore, attempts have been made to improve the adhesiveness of the polyester film.

As a method for improving the adhesiveness of the polyester film, an electric discharge treatment method and a coextrusion method with another resin are known. Among them, the discharge treatment method is a method in which a high voltage strain force is applied to the polyester film to change the properties of the film surface. Although this method requires a large amount of equipment, it has not been possible to sufficiently improve the adhesive strength.
In addition, the co-extrusion method is a method of simultaneously extruding polyester and another resin and superimposing them on each other, but in this method, what is used as the other resin together with polyester is a problem. This attempt was not successful enough because no other suitable resin could be chosen.

(Problems to be Solved by the Invention) The present invention is intended to improve the adhesiveness of a polyester film by attaching another resin to the surface of the polyester film. In addition, as the other resin, one which is colorless and transparent, has good weather resistance, has a strong adhesive force to the surface of the polyester film, and has a sufficient adhesive force to other objects, is selected and used. is there.

(Means for Solving the Problems) This invention uses a copolymer composed of at least three kinds of monomers of vinyl chloride, α-olefin and glycidyl methacrylate as a resin attached to the surface of a polyester film. It is intended to improve the adhesiveness of the polyester film by attaching the film of this copolymer to the surface of the polyester film.

The present invention provides a polyester film having good adhesion, which is formed by forming a copolymer of vinyl chloride, α-olefin and glycidyl methacrylate on the surface of the polyester film.

The copolymer used in this invention is vinyl chloride (hereinafter,
VC) and α-olefin (hereinafter referred to as OL),
It is a copolymer of three kinds of monomers with glycidyl methacrylate (hereinafter referred to as GM). Of these, VC and GM are each a single compound, but only OL can use several compounds. For example, ethylene, propylene, butylene, etc. can be used. Although only one kind of compound can be used, a plurality of kinds of compounds can be mixed and used. Of these, ethylene and propylene are preferable.

VC is a gas with a boiling point of -13.9 ° C. VC itself easily polymerizes to form a vinyl chloride polymer, and also easily polymerizes with other monomers to form a vinyl chloride copolymer. These polymers are widely used as colorless and transparent synthetic resins.

GM is the formula It is a liquid having a boiling point of 189 ° C. GM
It is known to polymerize itself and to copolymerize with other monomers such as VC or OL to produce a synthetic resin.

In this invention, a copolymer of three kinds of monomers of VC, OL and GM is used. The copolymerization ratio is, by weight, VC = 97-
70%, CL 2-20%, GM 1-10%. this house,
The OL was set to 2-20% because when the OL is less than 2%, the copolymer becomes difficult to dissolve in the solvent, and when it exceeds 20%, the adhesiveness of the copolymer decreases. is there. Also, GM
If the GM is less than 1%, the adhesiveness of the copolymer will be inferior, and if it exceeds 10%, the adhesiveness of the copolymer to the polyester film will be inferior. Not only that, but the thermal stability of the copolymer becomes worse. Also, VC is 97-70%, because VC is the main
This is to improve the adhesiveness and weather resistance of the copolymer.

The copolymer used in the present invention may be a copolymer obtained by adding a small amount of another monomer in addition to the above-mentioned three kinds of monomers. As another monomer, vinyl acetate,
Examples thereof include vinyl esters such as vinyl stearate, alkyl vinyl ethers, esters of acrylic acid or methacrylic acid, and vinylidene chloride. These other monomers must be 10% by weight or less based on the whole copolymer.

To make a copolymer, these monomers are mixed to make a mixture of monomers and this is polymerized. When mixing the monomers, GM is liquid at room temperature and VC and OL are gases at room temperature, so these three are mixed under pressure.
Various methods can be used to copolymerize the mixture thus obtained. For example, various methods such as a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, a solution polymerization method and a precipitation polymerization method can be used. Among them, the suspension polymerization method and the precipitation polymerization method are preferable.

The following is a brief description of the polymerization method, taking the suspension polymerization method as an example. First, an aqueous medium is prepared by adding a dispersant such as partially saponified polyvinyl alcohol, methyl cellulose, polyvinyl pyrrolidone in water, and a surfactant such as sodium lauryl sulfate and sorbitan monostearate. Separately from this, an oil-soluble peroxide such as benzoyl peroxide, lauroyl peroxide, or α, α′-azobisisobutyronitrile, α, α′-azobis-2 is added to the monomer mixture under pressure. An azo compound such as 4,4-dimethylvaleronitrile is added to prepare a monomer mixture to be polymerized. Then, the monomer mixture is dispersed in an aqueous medium and heated to accelerate the polymerization. After the polymerization has proceeded in this way, the polymerization system is cooled to lower the temperature and stop the polymerization reaction. Then, the copolymer produced in the dispersion is obtained.

The copolymer thus obtained is colorless and transparent, and has a sufficient film-forming ability by itself. Further, this copolymer is easily dissolved in a wide range of solvents and dissolves to form a low viscosity solution. Further, this copolymer has a large adhesive force to other substances. Moreover, the copolymer is stable to heat and light and has sufficient weather resistance. Therefore, this copolymer is suitable for forming a coating layer.

In the present invention, the copolymer obtained as described above is formed as a thin film on the surface of the polyester film. In order to form a thin film, first, this copolymer is dissolved in a solvent. Examples of the solvent include aliphatic ketones such as methyl ethyl ketone and methyl isobutyl ketone, ethyl acetate, acetic acid-
Esters such as n-butyl, chlorinated hydrocarbons such as chlorobenzene and methylene chloride, aromatic ketones such as cyclohexanone, cyclic ethers such as tetrahydrofuran dioxane, aromatic hydrocarbons such as benzene, toluene and xylene. A class etc. can be used. Only one kind of these solvents may be used, or two or more kinds of solvents may be mixed and used. The copolymer is dissolved in these solvents to form a solution in the range of 10-50% by weight.

In the present invention, the solution of the copolymer thus obtained is applied to the surface of the polyester film, and the solvent is volatilized to form the copolymer on the surface of the polyester film. To apply the solution, the polyester film may be dipped in the solution, the solution may be cast on the polyester film, the solution may be sprayed on the polyester film, and other applicators may be used. Alternatively, it may be applied with a bar coder or the like. Volatilization of the solvent accelerates this by sending warm air over the coating. The air temperature at that time must not be too high.

The film thus obtained is a laminate of a polyester film and a copolymer film, and since the polyester film therein has high strength, it is a tough film as a whole. Further, the obtained film has a copolymer of VC, OL and GM on its surface,
Since the copolymer is colorless and transparent, the film as a whole is beautiful and colorless and transparent. Moreover, since the copolymer is strongly adhered to the polyester film, the obtained film does not peel off. In addition, since the polyester film and the copolymer film have good weather resistance, the obtained film is hard to deteriorate and is kept in a beautiful state for a long time. Furthermore, since the copolymer has sufficient adhesion to other objects, the obtained film has the printing ink firmly adhered to this surface, which makes it suitable for printing accordingly, and also to this surface. Suitable for pasting other things. Thus, the film according to the present invention exhibits value as a polyester film having good adhesiveness. That is, it can be expected to have a wide range of uses, such as one that can be easily printed on the surface and one that is suitable for lamination with a vinyl chloride resin, a vinylidene chloride resin, or a metal foil.

Next, the advantages of the film according to the present invention will be specifically described with reference to Examples and Comparative Examples. In the following, simply parts or% means parts by weight or% by weight, respectively.

Example 1 In this example, as a copolymer, VC was 92%, ethylene was 5% and GM was 3%, and the average degree of polymerization was 700.
I used the one. This copolymer is dissolved in methyl ethyl ketone to make a 15% solution, and this solution is applied onto a stretched polyester film with a bar coater and dried,
A 5-10 micron thick copolymer film was formed on a polyester film.

The bonding strength of the bonded film thus obtained was examined by a tape peeling test. In the test, a cellophane adhesive tape was attached to the surface of the copolymer film, rubbed while pressing firmly with the thumb 5 times, and then the tape was gradually separated at first and then rapidly separated to peel off the copolymer film. I checked the condition. Since the copolymer film was integrated with the polyester film without peeling off, it was found that the bonding strength was high.

Further, printing ink was separately applied onto the laminated film and the printability was examined. As printing ink, polyamide (polyamide 40E manufactured by Sanyo Kasei Co., Ltd.) 16%, nitrocellulose (SS / 1/4 manufactured by Daicel Co., Ltd.) 3%, titanium oxide (JR-701 manufactured by Teikoku Chemical Co., Ltd.) 30%, A composition having 29% toluene, 17% isopropyl alcohol, and 6% ethyl acetate was used, and this was coated on the surface of the copolymer with a bar coder. The thickness of the printing ink was 5-10 microns. In order to confirm the adhesive strength of the printing ink thus formed, the above-mentioned tape peeling test was conducted. As a result, it was found that the printing ink was strongly adhered to the film without being peeled off by the cellophane adhesive tape.

From the above, it was confirmed that the film of the present invention has good adhesiveness.

Example 2 This example was carried out in the same way as Example 1, but only the copolymer was changed.

A copolymer having a composition of 90% VC, 7% propylene and 3% GM and an average degree of polymerization of 500 was used.

As in Example 1, the above copolymer was used as a film and formed on a polyester film, and its bonding strength was measured. Further, printing ink was applied onto the laminated film in the same manner as in Example 1, and the adhesive strength of the printing ink was measured. As a result, it was found that neither the copolymer nor the printing ink was peeled off.

Comparative Example In this comparative example, the printing ink used in Example 1 was directly applied onto a polyester film, assuming that no copolymer was used. The coating was performed in exactly the same manner as in Example 1.

A cellophane adhesive tape was attached onto the applied printing ink, and a tape peeling test was conducted in the same manner as in Example 1. The result was that the printing ink came off. Therefore, it was confirmed that the adhesiveness was not sufficient.

Claims (3)

[Claims] 1. A polyester film having good adhesion, which is formed by forming a film of a copolymer of vinyl chloride, α-olefin and glycidyl methacrylate on the surface of a polyester film. 2. The copolymer is a copolymer of 97-70% by weight of vinyl chloride, 2-20% by weight of α-olefin and 1-10% by weight of glycidyl methacrylate. The polyester film according to claim 1. 3. The copolymer is dissolved in methyl ethyl ketone
The polyester film according to claim 1 or 2, which is prepared as a 10 to 50% by weight solution and applied onto a polyester film and dried.