JPH06313162A - Adhesive for metal covered with film - Google Patents

Abstract

PURPOSE:To obtain the subject adhesive capable of lowering the temperature at which a synthetic resin film is bonded to a metal plate and improved in adhesion, by using a specified modified polyester resin, an isocyanate compound and an epoxy resin as the constituents. CONSTITUTION:100 pts.wt. thermoplastic polyester having a weight-average molecular weight of 10,000 to 50,000 and a glass transition temperature of 50-90 deg.C is reacted with 0.1-3 pts.wt. aziridine compound to give a modified polyester resin. 100 pts.wt. of this resin is mixed with 5-50 pts.wt. isocyanate compound, 10-50 pts.wt. epoxy resin, and if necessary, 1-8 pts.wt. vinyl chloride/ vinyl acetate copolymer and 1-5 pts.wt. coupling agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive for coating a synthetic resin film on a metal plate such as a steel plate or an aluminum plate at a low temperature.

[0002]

2. Description of the Related Art It is widely practiced to coat a surface of a steel sheet such as a cold-rolled steel sheet or a zinc plated steel sheet with a film made of various synthetic resins to improve appearance and durability. Vinyl chloride resin film (hereinafter PV
C film) is widely used because of its excellent workability and physical properties. As the adhesive used for bonding the PVC film and the steel sheet, a polyester-based adhesive is mainly used from the viewpoint of adhesive strength and workability.

[0003]

However, when the above polyester-based adhesive is used, it is applied to a steel sheet and then heat-treated at a high temperature (190 to 220 ° C.), and then PV.
It is necessary to coat C film or the like. Therefore, especially when a thin film is used, the film is likely to be deformed due to high temperature and spoil the appearance, and conversely, if the heat treatment under the above-mentioned bonding conditions is performed at low temperature, the adhesive strength becomes insufficient and the steel plate and the synthetic resin film are insufficient. There is a drawback in that the adhesive properties such as peel strength between them are poor. The above problems similarly occur in metal plates such as aluminum plates.

[0004]

SUMMARY OF THE INVENTION The present invention provides a film-coated metal adhesive having excellent adhesive properties even under low-temperature adhesive conditions.
Based on a modified polyester resin obtained by adding 0.1 to 3 parts by weight of an aziridine compound to 100 parts by weight of a thermoplastic polyester resin and reacting it, 5 to 50 parts by weight of an isocyanate compound and an epoxy compound are added to 100 parts by weight of this modified polyester resin. A film-coated metal adhesive comprising a composition containing 10 to 50 parts by weight of a resin. Further preferred embodiments of the present invention will be clarified in the following description.

Hereinafter, the present invention will be described in detail by taking an example of steel plate adhesion. In the description, "part" indicating the addition ratio means part by weight. The adhesive of the present invention is based on a modified polyester resin obtained by reacting 100 parts of a thermoplastic polyester resin with 0.1 to 3 parts of an aziridine compound.

The thermoplastic polyester resin used herein refers to a saturated polyester resin obtained by condensation of a dicarboxylic acid and a polyhydric alcohol, having a weight average molecular weight of 10,000 to 50,000 and a glass transition temperature of 50.
Those in the range of to 90 ° C are preferable.

Examples of the dicarboxylic acid component include aromatic carboxylic acids such as terephthalic acid and isophthalic acid; aliphatic dicarboxylic acids such as succinic acid, adipic acid and sebacic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. Can be mentioned.

Examples of the polyhydric alcohol component include ethylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol and the like.

The aziridine compound is a compound containing an aziridinyl group in its structure, and is diphenylmethane-bis-4,4'-N, N'-diethylurea, 2-
(1-aziridinyl) ethyl methacrylate and the like can be mentioned.

The aziridine compound is added to the polyester resin in the range of 0.1 to 3 parts, preferably 0.5 to 1.5 parts, and reacted in a solution. If the number of added parts is less than 0.1 part, no improvement in peel strength is observed, and if it exceeds 3 parts, part of the peel strength is lowered, which is inconvenient. Even if only this modified polyester resin is used, it is sufficient as an adhesive for film-coated metals, but it is effective to add other components in order to improve low temperature adhesion.

That is, 5 to 50 parts, preferably 10 to 30 parts of an isocyanate compound and 10 to 50 parts of an epoxy resin are added to 100 parts of the modified polyester resin to obtain low temperature treatment conditions (150 to 170 ° C.). ), It is possible to obtain an adhesive having a peel strength equivalent to that under high temperature conditions (190 to 220 ° C.) (hereinafter, this adhesive will be referred to as adhesive-1).

Examples of the isocyanate compound include a tolylene diisocyanate compound, a diphenylmethane diisocyanate compound, and a tris (isocyanatephenyl) thiophosphate compound, but the diphenylmethane diisocyanate compound is preferable from the viewpoint of peel strength under low temperature conditions. . If the number of added parts is less than 5 parts, no improvement in peel strength is observed, and if it exceeds 50 parts, the peel strength under low temperature conditions decreases.

The epoxy resin particularly contributes to the improvement of corrosion resistance. From the viewpoint of improving the corrosion resistance, the bisphenol type is preferable, and when the number of added parts is outside the above range, the improvement of the corrosion resistance is not recognized.

If the vinyl chloride-vinyl acetate copolymer is added to the above-mentioned adhesive-1 in an amount of 1 to 8 parts, preferably 3 to 5 parts, per 100 parts of the modified polyester resin, the peel strength at low temperature treatment is further improved. Improve (hereinafter, this adhesive is referred to as adhesive-2). The above vinyl chloride-vinyl acetate copolymer is a vinyl chloride monomer containing 3 to 2 vinyl acetate.
5% by weight is polymerized.

In addition to the above-mentioned adhesive-1 or adhesive-2, 1-5 parts, preferably 2-part, of a silane-based or titanium-based coupling agent is added per 100 parts of the modified polyester resin.
When it is added in the range of 3 parts, the peel strength at low temperature is further improved. In these adhesives, there is no improvement in peel strength under low-temperature bonding conditions when the amount is less than the above range, and when the amount exceeds the range, the adhesive properties such as peel strength deteriorate.

In order to improve the peel strength at a low temperature, di-n-butyltin dilaurate,
An isocyanate curing catalyst such as tetra-n-butyltin, tetramethylbutanediamine, 1,8-diaza-bicyclo [5,4,0] undecene-7 may be added.

The adhesive described above is used by dissolving it in an organic solvent such as methyl ethyl ketone or toluene in a range of about 5 to 30% by weight, and has a film thickness after drying of 0.5 to about 5 on a steel plate.
Apply so that the thickness is about 4 μm. The heat treatment temperature after coating may be a steel plate surface temperature of about 150 to 170 ° C., which can significantly lower the treatment temperature as compared with the conventional film-coated metal adhesive requiring treatment of about 190 to 200 ° C. it can.

As the metal plate to which the adhesive of the present invention is applied, various steel plates such as hot rolled steel plate, cold rolled steel plate, molten zinc plated steel plate, tin plated steel plate and stainless steel plate and aluminum plate can be used. You may use it after applying.

The synthetic resin film is 0.1
A vinyl chloride resin having a thickness of about 1.0 mm and an olefin film such as polyethylene and polypropylene can be used, and may be used after surface treatment such as corona treatment. Next, the effects of the present invention will be clarified by examples.

[0020]

【Example】

(Examples 1 to 5 and Comparative Examples 2 to 7) Toluene / methyl ethyl ketone (2/1) was added to each formulation shown in Tables 1 and 2.
Was dissolved in to prepare an adhesive. The obtained adhesive was applied to one side of a zinc plated steel plate by a Meyer bar coater so that the film thickness after drying would be 2 μm. Then, dry and heat the coated surface with an infrared heater heating furnace,
While keeping the steel plate surface at 150 and 170 ° C., immediately using a roll laminator, a PVC film (thickness: 0.18
mm) was coated with a linear pressure of 10 kg / cm, and cooled to obtain a sample.

Comparative Example 1 An adhesive prepared by adding an isocyanate compound and an epoxy resin to a general-purpose polyester resin not modified with aziridine and dissolving it with toluene / methyl ethyl ketone (2/1) was used as an adhesive.
Similarly, a PVC film was coated at 0 ° C to prepare a sample.

(Comparative Examples 8 and 9) A commercially available polyester adhesive was used as an adhesive for film-coated metal, and the steel sheet surface temperature after application of the adhesive was 170 ° C. and 200 ° C. The film was coated to give a sample.

The materials in Tables 1 and 2 are as follows. 1) Polyester resin: A thermoplastic polyester resin having an acid component of terephthalic acid and isophthalic acid (molar ratio 50:50) and a glycol component of ethylene glycol and neopentyl glycol (molar ratio 45:55) (secondary transition temperature 67 ° C.). ) 2) Modified polyester resin ... The above polyester resin 1
A resin obtained by adding 0.8 part of 3- (1-aziridinyl) propionate as an aziridine compound to 00 parts and reacting it in a solution 3) Isocyanate compound ... Polymethylene polyphenyl polyisocyanate 4) Epoxy resin ... Diglycidyl ether.
Bisphenol A 5) Vinyl chloride-vinyl acetate copolymer 8% by weight vinyl acetate content 6) Coupling agent 6-γ-glycidoxypropylmethoxysilane

The results of performance tests conducted on the obtained samples are also shown in Tables 1 and 2. The performance test method is as follows. 1) Peel strength According to JISK-6744, the peel strength at room temperature was measured by a 180 degree peel test. 2) Water resistance to boiling The sample was immersed in boiling water for 5 hours and the peel strength was measured. In addition, in terms of peeling strength, those in which the PVC film did not peel at all were rated as (◯).

[0025]

[Table 1]

[Table 2]

From the results shown in Table 1, it can be seen that the examples using the adhesive of the present invention have excellent performance as film-coated steel sheets even when they are laminated at a low temperature. On the other hand, in Comparative Example 1 in which the polyester resin not modified with aziridine was used, the adhesiveness was insufficient even under the high temperature treatment condition even if the isocyanate compound and the epoxy resin were blended.

Further, it can be seen that Comparative Examples 8 to 9 using the conventional film-coated metal adhesives also require high temperature conditions and are inferior in performance. Further, in Comparative Examples 2 to 7 in which the ratio of the blended composition was not preferable, the performance was poor.

[0028]

According to the adhesive of the present invention, the adhesive condition of the synthetic resin film to the steel plate can be kept at a low temperature, and
It has excellent adhesive properties and is highly applicable as an adhesive for film-coated metals.

Claims (3)

[Claims] 1. A modified polyester resin prepared by reacting 100 parts by weight of a thermoplastic polyester resin with 0.1 to 3 parts by weight of an aziridine compound, and 100 parts by weight of the modified polyester resin with 5 to 100 parts by weight of an isocyanate compound. An adhesive for film-coated metals, which comprises a composition containing 50 parts by weight and 10 to 50 parts by weight of an epoxy resin. 2. The adhesive for film-coated metals according to claim 1, which is composed of a mixture in which 1 to 8 parts by weight of a vinyl chloride-vinyl acetate copolymer is further added to 100 parts by weight of the modified polyester resin. 3. An adhesive for film-coated metals, which comprises a composition in which 1 to 5 parts by weight of a coupling agent is added to 100 parts by weight of a modified polyester resin in addition to the adhesive according to claim 1 or 2.