JPH0784576B2 - Adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Purpose of the invention [Industrial field of application] The present invention relates to a one-pack type adhesive, which has a particularly high adhesion rate, is a room temperature curable type, and has excellent oil resistance. The present invention also relates to a multifunctional adhesive composition having good coatability by forming an aqueous composition having a long pot life and a viscosity that does not change with time.

Since this adhesive composition can be finished to a dry touch, it is suitable as a screw loosening preventive adhesive or a laminate type laminate adhesive.

[Conventional technology]

Conventionally, as a one-pack type room temperature curable adhesive that cures rapidly, anaerobic mainly composed of a monomer having an acryloyl group and / or a methacryloyl group (hereinafter referred to as “(meth) acrylate monomer”). Curable compositions have been used.

[Problems to be solved by the invention]

Conventional anaerobic curable compositions are compositions that remain oily when in contact with air or oxygen and that cure rapidly when shielded from air or oxygen.

For this reason, before curing, curing accelerators such as oily (meth) acrylate monomers, peroxides, or amines may cause unstable pot life that is highly dependent on the risk of chemical injury and the oxygen concentration in the atmosphere. However, there are drawbacks such as coating properties, selectivity of the adherend, unsatisfactory oil resistance, or coating failure due to inadequate viscosity.

(B) Structure of the Invention [Means for Solving Problems] The present invention is partially saponified polyvinyl alcohol 40 to 99% by weight.
And a (meth) acrylate monomer emulsified in water with a polymer mixture consisting of 60 to 1% by weight of water-soluble nylon,
An adhesive composition comprising an encapsulated organic peroxide and a reducing agent that forms a redox system with the organic peroxide.

[(Meth) acrylate monomer emulsified in water]

The emulsification method of the (meth) acrylate monomer in the present invention is as follows.

The partially saponified polyvinyl alcohol used at this time preferably has a saponification degree of 70 to 98 mol% and an average degree of polymerization of 1000 to 2000. The range of this range is the emulsifying power of the (meth) acrylate monomer in water. Is excellent. It is preferable that the water-soluble nylon used together contains a dimethylamino group, a sulfonamide group or a sodium-carboxylate group, has a glass transition temperature of -55 ° C to + 70 ° C, and has a large dissolving power in water. , Which has an emulsifying power for the (meth) acrylate monomer and an excellent adhesive power for a metal surface.

If the (meth) acrylate monomer is gradually added to the aqueous solution in which both are mixed under stirring, the emulsion is easily emulsified.

The mixing ratio of the two is extremely important for the method of the present invention, and the following effects were confirmed. That is, it is necessary that the partially saponified polyvinyl alcohol is contained in the mixture in an amount of 40 to 99% by weight. When it exceeds 99% by weight, the (meth) acrylate monomer is emulsified, applied to the adherend, and after drying, the film formed on the upper layer surface is poor in flexibility or is not flexible over time. descend. For example, when using this as an adhesive to prevent screws from loosening, the film may peel off or the tightening torque may increase when tightening the nut.
Not only does this hinder handling, but the pot life and gasoline resistance of the adhesive performance are also reduced. On the other hand, when the amount is less than 40% by weight, the strength of the formed film is low and the tackiness is observed.
Furthermore, the initial adhesive strength is low. At the same time, the pot life of the adhesive performance is insufficient. A more preferable content of partially saponified polyvinyl alcohol is 60 to 95% by weight. Emulsification (meta)
It is preferred to use 2 to 15 parts by weight of a mixture of partially saponified polyvinyl alcohol and water-soluble nylon and 50 to 250 parts by weight of pure water with respect to 100 parts by weight of the acrylate monomer. The produced emulsion is 5,000 to 20,000 cps at 20 rpm by a B-type viscometer.
And the (meth) acrylate monomer is 2 to
It is preferably dispersed in oil droplets with a diameter of 10μ.

Examples of the (meth) acrylate monomer used in the present invention include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and tetrahydrofurfuryl (meth). Acrylate, 2-hydroxyethyl (meth) acrylate, allyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, morpholyl (meth) acrylate, glycidyl (meth) acrylate, methoxyethyl (meth) acrylate, n-butoxyethyl (meth ) Acrylate, sulfopropyl (meth) acrylate, 2-hydroxyethylacryloyl phosphite, acetoxyethyl (meth) acrylate, and methyl (carb) (meth) acrylate, etc. Or ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,3-butanediol di (meth)
Polyester di (meth) acrylate, epoxidized bisphenol A di (meth) acrylate, epoxidized bisphenol A and ethylene glycol or diethylene glycol obtained by polyesterification reaction by dehydration condensation of acrylate, polybasic acid, polyol and (meth) acrylic acid Alternatively, a di (meth) acrylate obtained from a condensate of triethylene glycol and (meth) acrylic acid, a di (meth) acrylate such as a polyurethane di (meth) acrylate obtained from diisocyanate, glycol and hydroxyalkyl (meth) acrylate, Further, a compound part containing two or more (meth) acrylate structures obtained from glycerin, trimethylolpropane, pentaerythritol, etc. and (meth) acrylic acid can be mentioned. There can be used as a mixed manner of two or more. Particularly, in order to increase the adhesive strength, it is preferable to use a mono (meth) acrylate having a hydroxyl group, a sulfonic acid group, or an amino group, and to improve heat resistance or chemical resistance, an alkylene ether bond is used. The use of di- or tri (meth) acrylate is preferred.

To emulsify (meth) acrylate monomer in water,
It is also possible to use partially saponified polyvinyl alcohol and water-soluble nylon in accordance with the method of the present invention while simultaneously mixing other polymers. For example, in order to improve the film-forming ability, acrylic acid ester resin, vinyl acetate copolymer or methyl vinyl ether copolymer, polyvinylpyrrolidone, styrene or ethylene with 20% to 50% by weight of acrylic acid is used. Examples thereof include copolymers with maleic acid or acrylic acid, or water-soluble copolymers such as urea-formalin copolymers, acrylic ester resins, urethane resins, chloroprene polymers, or butadiene-acrylonitrile copolymers. The emulsion polymer of can also be used.

[Encapsulated organic peroxide]

The hydrophobic powdery or liquid organic peroxide can be easily encapsulated by using the coacervation method or the interfacial polymerization method.

When the coacervation method is used, a method of applying a gelatin-arabic gum coating can be mentioned, but in order to improve water resistance, after coacervation, a prepolymer of urea-formalin-melamine is allowed to be present in the interface. The so-called two-step encapsulation method, in which the polymerization is continued, is preferred.

In the case of finely powdered organic peroxide, it is preferable to adopt the interfacial polymerization method. Specifically, the organic polymer is used in the urea-formalin prepolymer obtained by the methylolation reaction at pH 7.5 to 9. A method of suspending the peroxide, gradually lowering the pH to 2-3, maintaining the reaction temperature at 35 to 40 ° C., and encapsulating the polymer while precipitating the produced polymer in the peroxide powder by the methyleneation reaction is available. It is suitable.

In the method of the present invention, the powder size of the capsule is 20 to 100 because of the stability when mixed with the (meth) acrylate monomer emulsified in water and the necessity of breaking the capsule during the bonding operation.
μm is preferable, and the content of peroxide in the capsule is
10-60% by weight is preferred.

As the organic peroxide used in the present invention, hydroperoxide, ketone peroxide, dialkyl peroxide, peroxy ester, diacyl peroxide or the like can be used, but in particular, benzoyl peroxide or I prefer the turtle oil peroxide.

The amount of the encapsulated organic peroxide used is preferably 0.2 to 3 parts by weight based on 100 parts by weight of the (meth) acrylate monomer.

If the amount is less than 0.2 parts by weight, the adhesive performance will not be exhibited. On the other hand, if the amount exceeds 3 parts by weight, an excessive amount will be introduced as a foreign substance and the adhesive ability will be deteriorated.

[Reducing agent forming redox system with organic peroxide]

The compound can be used by adding it during the emulsification process of the (meth) acrylate monomer and simultaneously emulsifying it, or encapsulating it and mixing it with the composition.

Specific examples of the compound include copper, cobalt, manganese, and other organic acid salts, ethylenethiourea, and tetramethylthiourea for organic hydroperoxides or peroxyesters when they correspond to organic peroxides used at the same time. Hydrophobic mercapto compounds such as 2-mercapobenzimidazole, hydrazine, 2-hydroxyethylhydrazine, hydrazine derivatives such as benzoylhydrazine, sodium p-toluenesulfinate, L-ascorbic acid, or triethylenediamine.

For diacyl peroxide, dimethylaniline, dimethyl-p-toluidine, diethyl-p-toluidine, N, N dimethyl-p-anisidine, O-sulfobenzoic acid imide, mercaptoethanol, thiomalic acid, thioglycolic acid, thiol Water-soluble mercapto compounds such as lactic acid, α-thiobutyric acid, mercaptoethylamine, or O- or m-thiosalicylic acid are preferably used.

The amount of the compound used is (meth) acrylate monomer 100.
It is preferred to use 0.1 to 2 parts by weight with respect to parts by weight.

When it is less than 0.1 part by weight, the redox reaction is weak,
When it exceeds 2 parts by weight, it does not lose the balance of the redox reaction mechanism and the adhesive ability decreases, which is not suitable.

[Other substances that can be adopted in the adhesive composition of the present invention]

For the purpose of improving the properties of the adhesive composition, for example, in order to impart thixotropy, talc, silica, alumina, calcium carbonate, or a glass microballoon having a particle size of 10 to 30 μm is used, and a long pot life property is obtained. In order to maintain the following, hydroquinone, methylhydroquinone, 2,4
-Dinitroanisole, 2,6-ditertiary butyl p
-Cresol or a water-soluble chelating agent can be used.

[Work]

The adhesive composition of the present invention retains an aqueous system during coating on the adherend, and after drying, the peroxide, which is the main catalyst system, is encapsulated. The body does not undergo an effective reaction and forms an oil layer on the surface of the adherend,
In addition, a dry touch film is formed on the surface of the polymer which is present in the metal.

However, during the bonding work, the capsule is destroyed by simply rubbing or applying pressure on the surface of the adherend, and the peroxide is eluted in the (meth) acrylate monomer, and at the same time with the reducing agent present in the vicinity. When they come into contact with each other, the curing reaction is started to exert the adhesive ability.

At this time, the partially saponified polyvinyl alcohol and the water-soluble nylon coexist as the film-forming polymer according to the conditions constituting the adhesive composition of the present invention, whereby the redox reaction is appropriately controlled and the adhesion rate is increased. Despite this, the flexibility of the coating applied to the adherend, that is, the pot life is maintained for a long period of time, and this coating has excellent oil resistance to gasoline, engine oil, etc. is there.

〔Example〕

Next, examples and comparative examples will be given in order to more specifically describe the present invention.

Example 1 (Production of Encapsulated Benzoyl Peroxide) In order to encapsulate benzoyl peroxide with a urea-formalin resin, a urea-formalin prepolymer was first synthesized by the following method.

350 g of 37% by weight aqueous formalin solution in one flask,
Charged 131 g of urea and 1.7 g of triethanolamine to 300 r
Stir at 70 ° C for 2 hours at pm to react, pH 8.1 and B
A prepolymer having a viscosity of 8.3 cps at 20 rpm in a Brookfield viscometer was obtained.

525g of the above prepolymer and 440g of pure water were placed in a 2 beaker and stirred with a homogenizer at 5000rpm with a 1N hydrochloric acid aqueous solution 10c.
The pH was brought to 2.2 by addition of c. 26 g of fine powder of benzoyl peroxide (average particle size 20 μm) was added, the temperature was raised to 40 ° C., and the reaction was continued for 6 hours. During this time, 300 cc and 100 cc of pure water were added at the 4th and 6th hours, respectively, to prevent a rapid increase in viscosity. After that, reduce the stirring number to 40 ℃ × 2000
The reaction was continued under the conditions of rpm × 12 hours to obtain a slurry-like encapsulated benzoyl peroxide.

This was a powder having a urea-formalin resin film content of 85.4% by weight and a polynuclear average particle size of 50 μm.

(Adjustment of Adhesive Composition) 860 g of pure water in 2 beakers, 82.4 g of Gohsenol GM-14 (partially saponified polyvinyl alcohol having a saponification degree of 86 mol% and an average degree of polymerization of 1400, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), AQ-Nylon A-90 (water-soluble nylon, glass transition temperature 15 ℃,
Toray Co., Ltd.) 20.6 g was charged to prepare an aqueous solution, and then stirred with a homogenizer at 2000 rpm to obtain NK BPE-200.
(2,2 bis [4- (methacryloxy-3-diethoxy) phenyl] propane, manufactured by Shin-Nakamura Chemical Co., Ltd.) 1030 g,
Dimethyl paratoluidine (5.2 g) was added and stirring was continued for 2 hours to obtain an aqueous emulsion. This emulsion had emulsion particles with an average particle size of 4 μm, and had a viscosity of 12000 cps at 20 rpm with a B type viscometer.

70.5 g of benzoyl peroxide encapsulated in the emulsion (content of benzoyl peroxide 10.3 g.
g) was mixed with stirring to obtain a water-based adhesive composition.

(Coating of the adhesive composition on the bolt screw) Uniformly apply 0.2 g of the aqueous adhesive composition obtained so that the groove of the yellow chromate screw with a diameter of 8 m / m and a length of 40 m / m is filled. Then, it was dried at 60 ° C. for 30 minutes to obtain an adhesive tightening type screw on which a resin film having a tack-free surface was formed and the adhesive composition was applied.

(Adhesion Performance Evaluation Test) 1. Adhesion Test The above-mentioned coated screw was tightened with a nut of the same material at a torque of 230 kgf · cm, and the starting return torque after standing at 23 ° C. for 24 hours was measured.

2. Adhesive performance pot life test After the above-mentioned coated screws were heated at 40 ° C for 60 days, they were tightened with a torque of 230 kgf · cm and the starting return torque after leaving them at 23 ° C for 24 hours. It was measured.

3. Gasoline resistance test The above coated screws were tightened with a torque of 230 kgf · cm, immersed in gasoline at 40 ° C for 7 days, and the starting return torque immediately after taking out was measured.

The results of these tests are shown in Table 1.

Examples 2 to 8 and Comparative Examples 1 to 2 In Example 1, a redox system is formed with a (meth) acrylate monomer, a film-forming polymer, an organic peroxide, or the organic peracid. The type and amount of the reducing agent to be used are changed as shown in Table 1, and other conditions are shown in Table 1 together with the test results when the same operation as in Example 1 was performed.

(C) Effect of the Invention The adhesive composition of the present invention is water-based and has good coatability because the main component of the catalyst is encapsulated, and also has an adhesive ability after being applied to an adherend. The film maintains a stable redox-catalyst system for a long period of time, is dry-touch, and is excellent in oil resistance, and thus is suitable for storage and transportation of adherends.

Claims (1)

[Claims] 1. A monomer having an acryloyl group and / or a methacryloyl group emulsified in water with a polymer mixture comprising 40 to 99% by weight of partially saponified polyvinyl alcohol and 60 to 1% by weight of water-soluble nylon, encapsulation. An adhesive composition comprising the organic peroxide and a reducing agent that forms a redox system with the organic peroxide.