JPH10330719A - Adhesive composition and bonding therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive composition having good adhesion to poorly bondable plastics, especially fluororesins and being excellent in especially boiling- water resistance and resistance to weather discoloration by mixing a polyester resin with an epoxy-modified polybutadiene and an oxazoline-group-containing polymer. SOLUTION: This composition comprises 60-98 wt.% polyester resin (a) having an acid value of 3-30, a number-average molecular weight of 10,000-50,000 and a glass transition temperature of 60-98 wt.%, 1-25 wt.% epoxy-modified polybutadiene (b) and 1-25 wt.% polymer (c) containing at least two oxazoline groups in the molecule. Component (b) is a polybutadiene having at least two epoxy groups in the molecule. Component (c) is desirably a polymer of an acrylic type. This composition can be desirably used to bond a metal or a synthetic resin to a plastic film. Desirably, a fluoro resin film is used after it is subjected to surface activation treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive composition, particularly to an adhesive composition having excellent adhesiveness, boiling water resistance and weathering resistance, and a bonding method using the adhesive.

[0002]

2. Description of the Related Art Fluororesins are excellent in chemical resistance and stain resistance. Therefore, they are useful in a wide variety of fields by improving the surface properties of substrates by bonding them to surfaces of metals and plastics. Material can be provided. But,
Conventionally, various types of adhesives have been commercially available, but very few have excellent adhesiveness to fluorine resins. Japanese Patent Application Laid-Open No. 7-238270 discloses a method of bonding a fluororesin in which a fluororesin whose surface is activated by corona discharge treatment is bonded using an adhesive composed of a polyester resin having an epoxy-modified end and a polyisocyanate. doing. However, this adhesive is insufficient as an adhesive in that it has insufficient boiling water resistance and is inferior in weather discoloration resistance.
JP-A-4-266984 discloses an adhesive composition containing a polyester, an isocyanate and, if necessary, an epoxy resin. This adhesive has been developed for bonding a metal material and a synthetic resin, and has excellent boiling water resistance, but does not provide sufficient adhesive strength to a fluororesin. As described above, an adhesive having sufficient adhesiveness to a plastics resin, particularly a fluororesin, and having excellent boiling water resistance and weather discoloration resistance has not been obtained.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an adhesive having good adhesion to plastics having poor adhesion, especially to fluororesin, and particularly excellent in boiling water resistance and weather discoloration resistance. is there.

[0004]

According to the present invention, there are provided (a) an acid value of 3 to 30, a number average molecular weight of 10,000 to 50,000,
Polyester resin 6 having a glass transition temperature of -30 to 30 ° C
0 to 98% by weight, (b) epoxy-modified polybutadiene 1
To 25% by weight, and (c) 1 to 25% by weight of a polymer containing two or more oxazoline groups per molecule. The present invention also relates to a method for bonding a metal or synthetic resin and a plastics film, particularly a fluororesin film, using the above-mentioned adhesive composition. In particular, according to the present invention, a fluororesin film is disposed between a discharge electrode and a counter electrode, the average electric field strength represented by applied voltage / electrode distance is 30 to 200 KV / cm, and the pulse width is 1 μs.
The present invention also relates to the above bonding method, wherein the surface is activated by corona discharge generated by applying a high voltage having a pulse frequency of 20 pps or more.

The above-mentioned adhesive composition of the present invention has excellent adhesiveness to plastics, especially fluororesins, which have been extremely difficult to adhere due to poor wettability of the adhesive due to low surface activity. Excellent in boiling water resistance and weather discoloration resistance.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester resin (a) which is a component of the adhesive of the present invention has an acid value of 3 to 30, a number average molecular weight of 10,000 to 50,000, and a glass transition temperature of-.
30-30 ° C. The polyester resin preferably has an acid value of 4 to 20, and a number average molecular weight of 15,000 to 30,0.
00, the glass transition temperature is -20 to 20 ° C. When the acid value is less than 3, the reaction with the epoxy group of the component (b) and the oxazoline group of the component (c) is not sufficiently performed, and the desired adhesive performance cannot be obtained. The number average molecular weight is 1
If it is less than 0000, stable adhesiveness cannot be obtained, while if it is more than 50,000, production becomes difficult. When the glass transition temperature is lower than −30 ° C., the cohesive strength of the adhesive is reduced. On the other hand, when the glass transition temperature is higher than 30 ° C., the internal stress becomes too large, and sufficient adhesive strength cannot be obtained.

Such a polyester resin can be produced from a polycarboxylic acid or its anhydride and a polyhydric alcohol by a usual polycondensation reaction. Examples of polycarboxylic acids that can be used include phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, and fumaric acid. Succinic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, hymic anhydride, trimellitic anhydride, methylcyclohexenetricarboxylic anhydride,
Acid anhydrides such as pyromellitic anhydride are exemplified.

Examples of polyhydric alcohols that can be used include:
Ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol, neopentyl glycol hydroxypivalate, bisphenol A hydroxide, phenol dihydroxypropyl Ether, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol and the like can be mentioned. The material and production method of the polyester resin used in the present invention are not particularly limited as long as it has the above-mentioned physical properties. However, from the viewpoint of the stability of the adhesive composition, it is preferable that the polyhydric alcohol used as the material is a linear alcohol. On the other hand, as a production method, it is preferable in terms of synthesis to introduce an acid group by reacting a hydroxyl group terminal with carboxylic anhydride.

[0009] The polyester resin is contained in the adhesive composition of the present invention in a proportion of 60 to 98% by weight, preferably 70 to 90% by weight. If the amount of the polyester is less than 60% by weight, the adhesiveness of the adhesive is impaired. On the other hand, when the content is more than 98% by weight, the amount of the other resin to be added becomes small, and the adhesion in the normal state and after the boiling water test becomes insufficient.

The epoxy-modified polybutadiene (b), which is another component of the adhesive of the present invention, is a polybutadiene having two or more epoxy groups in one molecule. Preferably, it is a polybutadiene having three or more epoxy groups. The polybutadiene has a number average molecular weight of 500-1.
0,000, preferably 1,000-2,000.
When the number average molecular weight is higher than 10,000, a problem occurs in workability, and when the number average molecular weight is lower than 500, a problem in adhesiveness may occur. These epoxy-modified polybutadienes can be obtained by epoxidizing polybutadiene, and are available as "Nisseki polybutadiene E" (trade name) manufactured by Nippon Petrochemical Co., Ltd.

[0011] By blending the epoxy-modified polybutadiene, the epoxy group reacts with the carboxyl group at the terminal of the polyester to give elasticity to the adhesive, thereby improving the properties of the adhesive after curing. The epoxy-modified polybutadiene is contained in the adhesive composition in an amount of 1 to 25% by weight, preferably 5 to 25% by weight.
It is incorporated in an amount of 15% by weight. When the amount of the epoxy-modified polybutadiene is less than 1% by weight, the adhesiveness after the boiling water resistance test decreases, and when it exceeds 25% by weight, the normal state adhesiveness decreases.

The polymer (c) containing an oxazoline group, which is the third component of the adhesive composition of the present invention, contains two or more, preferably three or more oxazoline groups in one molecule of the polymer. The polymer having an oxazoline group (c) has a number average molecular weight of 1,500 to 10,000, preferably 3,000.
0 to 8,000. As the polymer (c) containing an oxazoline group, an acrylic type polymer is preferable. Such an oxazoline group-containing acrylic polymer can be obtained, for example, by copolymerizing an oxazoline group-containing ethylenically unsaturated monomer with another ethylenically unsaturated monomer. It is available as the "Epocross" (trade name) series.

Adhesion is improved by blending an oxazoline group-containing polymer. The oxazoline group-containing polymer (c) is blended in the adhesive composition in an amount of 1 to 25% by weight, preferably 5 to 15% by weight. When the amount of the oxazoline group-containing polymer is less than 1% by weight, the normal state adhesiveness decreases, and when it exceeds 25% by weight, the adhesiveness after the boiling water resistance test decreases.

In the adhesive composition of the present invention, other than the above-mentioned indispensable components, the following other components can be blended as required. For example, when the adherend is a polypropylene resin, it is preferable to add a polypropylene powder or a chlorinated polypropylene resin in order to improve adhesion. When glass is the adherend, it is preferable to add a silane coupling agent for the same purpose. On the other hand, when the material obtained by the bonding method using the adhesive of the present invention is used for applications requiring heat resistance, it is preferable to add a heat-resistant polymer such as polyimide or phenol resin. In addition, in order to extend the pot life of the adhesive, an amine compound may be added for the purpose of neutralizing the carboxyl group in the component of the present invention. In order to improve weather resistance, an ultraviolet absorber, a hindered amine light stabilizer, an antioxidant, and the like may be added. Further, a solvent such as alcohol (for example, methanol, ethanol, propanol, butanol, etc.), a hydrocarbon or an ester as a diluent for adjusting the coating viscosity, and a surface adjusting agent for adjusting the coating workability may be added. Can be. Further, it may contain a coloring agent such as a pigment or a dye, a surfactant, a suspending agent, a lubricant, a wetting agent, a thickener, a defoaming agent, a corrosion inhibitor and the like depending on the use.

The adhesive of the present invention can be obtained by mixing the polyester resin, epoxy-modified polybutadiene, oxazoline group-containing polymer, and other components, which are the constituent components, at a predetermined weight ratio. In addition, mixing is generally performed at room temperature, but heating may be performed as long as the viscosity does not cause any problem during coating.

The adhesive composition of the present invention is generally used as an aqueous dispersion such as an emulsion or an organic solvent or water / water.
It can be used as a solution dissolved in an organic mixed solvent.

In order to bond a metal or synthetic resin, which is a material to be bonded, to a plastic film, the above-mentioned adhesive is applied to the surface of the material to be bonded and / or the plastic film, and after both are joined, heating is performed if necessary. . Any conventional means such as brush coating, roll coating, spray coating and the like can be used for applying the adhesive. Note that it is preferable to use a so-called dry lamination method in which the solvent is evaporated after the application of the adhesive, followed by lamination. In this dry lamination method, the heating for evaporating the solvent is performed at 60 to 180 ° C. when the substrate is a plastic film or a synthetic resin, and when the substrate is a metal, the heating is performed at 140 ° C.
~ 250 ° C is suitable.

Materials to be bonded include cold-rolled steel sheets, stainless steel sheets, aluminum steel sheets, galvanized steel sheets, aluminum / galvanized steel sheets, zinc / nickel-plated steel sheets, and other metal sheets, polyolefins, and maleic anhydride-modified. Polyolefins, ethylene-vinyl acetate copolymers, polyvinyl chloride and ethylene-acrylic copolymers, resins such as various fluororesins, ceramics, and various other materials such as decorative boards, glass, cloth, non-woven fabric, cushioning materials Is exemplified.

Examples of the plastics film which can be adhered with the adhesive of the present invention include films of polyolefin resin, polyester resin, polyamide resin, polyvinyl chloride resin, polyvinylidene chloride resin, fluorine resin, and almost all other synthetic resins. it can. Above all, the adhesive of the present invention exhibits a characteristic for bonding a fluororesin film which has not been sufficiently adhesive with a conventional adhesive.

Examples of the fluororesin film include ethylene-tetrafluoroethylene copolymer, polyvinyl fluoride, tetrafluoroethylene-perfluoroether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer and the like. . While these fluororesin films can be bonded to the above-mentioned material to be bonded using the adhesive of the present invention as they are, preferably,
It is preferable that the surface of the fluororesin film is modified by an activation treatment before use.

The method of activating the fluororesin film is not limited, and examples thereof include flame treatment, chemical treatment such as sodium etching, corona discharge treatment, sputtering treatment, and reduced pressure plasma treatment. An activation treatment method that achieves particularly favorable results when used in combination with the adhesive of the present invention is a corona discharge plasma treatment using a pulsed high voltage. As such a corona discharge plasma treatment method by applying a high voltage pulse, a corona discharge treatment method described in Japanese Patent Application No. 8-223528 can be used. Specifically, as a pulse high voltage applied between the discharge electrode and the counter electrode, the peak value is 10 to 300 KV, preferably 4 to 300 KV.
0-200 KV, more preferably 50-120 KV, and a repetition frequency of 20 pps or more, preferably 20-20
00 pps, more preferably 100-1000 pps,
The pulse width is 1 μsec or more, preferably 1 to 10 μsec.
c, more preferably 2 to 5 μsec, and the distance between the electrodes is 30.
mm, preferably 10 to 30 mm, and the average electric field strength represented by applied voltage (peak value) / electrode distance is 30 KV / c.
m or more, preferably 40 to 180 KV / cm.

[0022]

The present invention will be described more specifically with reference to the following examples. [Preparation of Adhesive] Examples 1 to 5, Comparative Examples 1 to 9 (a) Polyester resin at a ratio shown in Tables 1 and 2,
(B) Polybutadiene resin and (c) oxazoline group-containing resin were blended to prepare adhesives of Examples 1 to 5 (Table 1) and Comparative Examples 1 to 9 (Table 2). Commercially available components (a), (b), and (c) were used in this example. The polyester resin "KA-2072M" is a product from Arakawa Chemical Co., Ltd., and has a number average molecular weight Mn of 2
4,000, glass transition point Tg is -1 ° C, acid value is 7.8, and “KA-2072A” is manufactured by Arakawa Chemical Co.,
Mn is 30,000, Tg is -2 ° C, and acid value is 2.0. "E-1" used as an epoxy-modified polybutadiene
800-6.5 "is a product of Nippon Petrochemical Co., Ltd. and has an epoxy equivalent of 246. "B-1000" is a product of Nippon Petrochemical Co., Ltd. and is a polybutadiene homopolymer containing no epoxy group. "Epocross RS-1205T" used as the oxazoline group-containing resin is a product of Nippon Shokubai Co., Ltd. and is an acrylic polymer having an oxazoline group equivalent of 550, which is obtained by copolymerizing a vinyl polymerizable monomer having an oxazoline group. Based on the solid content shown in Tables 1 and 2, the adhesive was mixed at room temperature, and then mixed with ethyl acetate to obtain a viscosity suitable for application (solid content of 20 to
(30% by weight).

[0023]

[Table 1]

[0024]

[Table 2]

[Adhesion Test] Examples 1 to 5 and Comparative Example 1
As described in Tables 1 and 2, plastic films were bonded to various materials to be bonded using the adhesives obtained in Nos. 1 to 9 above. In bonding, an adhesive is applied to a plate-like material to be bonded with a bar coater so that a dry film thickness is about 7 μm, and a temperature of 150 ° C. when the material to be bonded is 80 ° C. when the material to be bonded is a synthetic resin. , The plastic films were immediately superimposed, and the joined body was passed through a silicone rubber roller and pressed at a pressure of 5 kg / cm ² to obtain an adhesive composite. A part of the plastic film was subjected to a discharge treatment under the following conditions to activate the surface. [Discharge treatment] Discharge portion length of discharge electrode: 300 mm, repetition frequency: 370 pps, pulse peak value: 80 KV, pulse width: 2 μsec, maximum average electric field intensity: 100 KV / cm, processing speed: 6 m
/ Min PVC dielectric thickness: 7 mm The bonded composite was allowed to stand at room temperature for 24 hours, and then tested for adhesion, boiling water resistance and weather discoloration resistance by the following methods.
The results are shown in Tables 1 and 2.

Evaluation Method [Normal Adhesion] The composite for evaluation was cut to a width of 1 cm, and the 180 degree peel strength was measured at a tensile speed of 50 mm / min. [Adhesiveness after boiling water test] The evaluation composite was placed in boiling water for 1 hour.
Soak for 0 hours. After being taken out of the water and left to dry at room temperature for one day and night, the same adhesion test as in the normal state is performed. [Weather Discoloration Resistance] The composite for evaluation was prepared using Weatherometer 10
The test was performed for 00 hours, and after standing for one day and night, the discoloration of the sample was visually evaluated. In the table, ○ indicates that the discoloration is small, and X indicates that the discoloration is remarkable.

[0027]

By using the adhesive of the present invention, it has become possible to obtain a strong bond between a fluororesin film and a metal, a synthetic resin or the like, which has not been able to obtain sufficient adhesiveness in the past. It has the characteristics of being excellent in boiling water resistance and weather discoloration resistance. The use of this adhesive facilitates the production of various composites utilizing the properties of the fluororesin.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Osamu Katayama 19-17 Ikedanakacho, Neyagawa-shi, Osaka Japan Paint Co., Ltd.

Claims (9)

[Claims] (A) an acid value of 3 to 30, a number average molecular weight of 10,000 to 50,000, and a glass transition temperature of -30 to
An adhesive comprising 60 to 98% by weight of a polyester resin at 30 ° C, (b) 1 to 25% by weight of an epoxy-modified polybutadiene, and (c) 1 to 25% by weight of a polymer having two or more oxazoline groups per molecule. Composition. 2. The adhesive composition according to claim 1, wherein the epoxy-modified polybutadiene is a polybutadiene containing two or more epoxy groups in one molecule. 3. The adhesive composition according to claim 1, wherein the polymer containing an oxazoline group is an acrylic type polymer. 4. A method for bonding a metal or synthetic resin to a plastic film using the adhesive composition according to claim 1. 5. The plastic film is selected from the group consisting of ethylene-tetrafluoroethylene copolymer, polyvinyl fluoride, tetrafluoroethylene-perfluoroether copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer. The bonding method according to claim 4, wherein the bonding method is a resin film. 6. A fluororesin film is disposed between a discharge electrode and a counter electrode, the average electric field strength expressed by applied voltage / electrode distance is 30 to 200 KV / cm, and the pulse width is 1 μs.
6. The bonding method according to claim 5, wherein the surface is activated by corona discharge generated by applying a high voltage having a pulse frequency of 20 pps or more. 7. The metal is cold-rolled steel plate, stainless steel plate,
The bonding method according to claim 4, wherein the bonding method is selected from the group consisting of an aluminum plate, a galvanized steel plate, a zinc / nickel plated steel plate, and an aluminum / galvanized steel plate. 8. The synthetic resin comprises a polyolefin resin, a maleic anhydride-modified polyolefin resin, an ethylene-vinyl alcohol copolymer resin, an ethylene-vinyl acetate copolymer resin, a polyvinyl chloride resin, and an ethylene-acryl copolymer resin. The bonding method according to claim 4, wherein the bonding method is selected from the group. 9. The bonding method according to claim 4, wherein the synthetic resin is a fluororesin surface-treated by the method according to claim 5.