KR100497457B1 - Precoating Type Adhesive Composition - Google Patents

Abstract

The present invention (A) (A1) at least one polymerization accelerator; (A2) at least one compound having at least one polymerizable double bond at its terminal or side chain thereof; (A3) a suspension consisting of a mixture of at least one acidic substance dissolved in water and then acidic, (A4) an aqueous binder having emulsifying capacity and insoluble in water by the acidic substance (A3), and (B) The present invention relates to an adhesive composition for precoating screws, comprising microcapsules containing at least one polymerization initiator. Also provided is a method of producing the adhesive composition.

Description

Precoating Type Adhesive Composition

The present invention relates to a precoated adhesive composition for forming an adhesive layer on the helically engaged surface of screws such as screws, bolts and nuts to provide threading fixing function and adhesion. More specifically, the present invention relates to a liquid adhesive composition which is applied in the form of a liquid material to the helically engaging surfaces of screws such as screws, bolts and nuts to form a clearly solid layer having bonding capacity.

A known precoated thread fixing adhesive applied to a spirally engaging surface (thread) of a spirally engaging member such as a screw, a bolt, a nut, and the like, comprising: an organic solvent or water which is a solvent; Microcapsules comprising a reactive adhesive; And a composition composed of a binder resin are known from Japanese Patent Publication (So) 52-46339, Japanese Patent Application Laid-Open No. 2-308876, and Japanese Patent Application Laid-Open No. 53-11883. In addition, Japanese Patent Laid-Open No. 57-192476 discloses a thread fixing adhesive, comprising: a polymer monomer; Microcapsules comprising a polymerization initiator; Polymerization promoters; And an aqueous binder of an ethylene / maleic anhydride copolymer. In addition, Japanese Patent Laid-Open No. 7-331187 discloses a monomer polymerizable as a thread fixing adhesive; Water-resistant microcapsules comprising a polymerization initiator; Polymerization promoters; And an aqueous binder of a water-soluble polyacetal resin.

Since the pre-coated adhesive composition disclosed in these citations is generally in a liquid state, in order to form an adhesive layer on the spirally engaging surface of bolts,

(1) applying a liquid precoated adhesive composition to the surface of the adherend such as a bolt; And

(2) The process of drying the coated precoated adhesive composition thus prepared to form a solid layer clearly is required.

Application of the precoated adhesive composition in step (1) has previously been performed, for example, by spray coating the liquid precoated adhesive composition onto the adherend, or by coating the adherend with the adhesive composition. It was achieved by immersing the adherend in the air or by using the coating apparatus described in Japanese Utility Model Publication No. Hei 2-43504 and Japanese Utility Model Publication No. 63-4532. Also in the case of step (2), it was a common embodiment to allow the coated adherend to stand at room temperature to naturally dry, or to heat to the extent that the polymerizable adhesive is not reacted to promote drying.

However, among the microencapsulated adhesives known to date, those which are each microencapsulated, or which include a microencapsulated reactant and a reaction initiator (curing agent), can be obtained by using a large amount of microcapsules. As pointed out in 331187, even with good storage stability as a liquid adhesive, it is disadvantageous in that the production cost is increased. This also results in insufficient adhesion since the amount of microcapsules, ie the amount of reactant used, is limited.

Among microencapsulated adhesives containing water-soluble binders, those containing easily water-soluble aqueous binders are disadvantageous in that they require a lot of time to dry after being applied to the bolts. This decreases productivity. In order to solve these difficulties, as disclosed in Japanese Unexamined Patent Application Publication No. Hei 5-140514, an aqueous binder exhibiting an appropriate water solubility is selected to emulsify the precoated adhesive composition, and the emulsified adhesive composition is adhered. It improves a drying characteristic by apply | coating to. However, such a precoated adhesive composition has a high viscosity in liquid form, which is disadvantageous in that it is difficult to control the amount of adhesion to the adherend when the coating is performed by immersing the adherend in the adhesive composition. Thus, if a diluent is added to the precoated adhesive composition to control its viscosity, it causes problems such as a drop in adhesion, which is one of the original intended properties of the precoated adhesive composition. Also, although this emulsified solution of the precoated adhesive composition quickly forms a solid surface layer, its moisture tends to remain therein as drying proceeds on the surface. This takes a lot of time to dry the membrane. In addition, shrinkage of the formed layer, accompanied by drying, creates voids inside the formed layer or worsens the appearance of the formed layer.

In addition, Japanese Patent Laid-Open No. 57-192476 discloses, as a thread fixing adhesive, a polymerizable monomer; Microcapsules comprising a polymerization initiator; Polymerization promoters; And an aqueous binder of an ethylene / maleic anhydride copolymer. However, this composition also forms a liquid substance in an emulsion state similar to the composition. Therefore, its moisture tends to remain inside the resulting solid surface layer. In addition, the storage stability of the emulsified liquid composition itself is lowered, or the adhesion may be lowered when the reactive material is modified in the dried coating layer.

The present invention aims to solve the above problem. That is, the object of the present invention is to have good storage stability in liquid form before being applied to the bolts while maintaining its essential properties, namely adhesion and sealing properties, and also to have good workability when applied onto adherends such as bolts, It is to provide a pre-coated adhesive composition that provides good stability of the reactive material even after being applied to form a coating layer that is apparently solid.

It is a further object of the present invention to have a solid such as bolts in solids as high as possible, having a viscosity that is not so high and which can be easily applied to the adherend by an immersion coating method, thereby providing good mass productivity. It is to provide a pre-coated adhesive composition comprising the active ingredient as an adhesive to be applied).

Other objects and effects of the present invention will become apparent from the following description.

The above object of the present invention

(A) (A1) at least one polymerization promoter;

(A2) at least one compound having at least one polymerizable double bond at its terminal or side chain thereof;

(A3) at least one acidic substance which is dissolved in water and then becomes acidic; And

(A4) a suspension having an emulsifying capacity and comprising a mixture of aqueous binders insolubilized in water by an acidic substance (A3); And,

(B) is achieved by providing a threaded precoating adhesive composition comprising microcapsules comprising at least one polymerization initiator.

The invention also

(a) (A1) at least one polymerization promoter;

(A2) at least one compound having at least one polymerizable double bond at its terminal or side chain thereof; And

(A3) preparing a mixture comprising at least one acidic substance which is dissolved in water and then becomes acidic;

(b) each of the mixtures prepared in step (a) is formed on its surface by mixing with an aqueous binder (A4) which has an emulsifying capacity and is insoluble in water by an acidic substance (A3) while stirring to effect emulsification. Preparing a suspension comprising emulsified particles having a water insoluble layer; And

(c) mixing the suspension with a microcapsule comprising at least one polymerization initiator to obtain an adhesive composition.

In step (c), microcapsules comprising at least one polymerization initiator are added to the suspension to be dispersed. Thus, a uniform suspension is provided. Compared with conventional emulsion type adhesive compositions, this suspended structure allows the viscosity of the adhesive composition to be kept at a lower value, while allowing the nonvolatile content to be maintained. Therefore, the amount applied to the adherend can be controlled by the adhesive composition of the present invention.

The polymerization promoter (A1) for use in the present invention may be, but is not limited to, all known polymerization promoters such as amine compounds and sulfide compounds. Examples of polymerization of the polymerization accelerator include tertiary amines such as N, N-dimethyl-p-toluidine, and sulfides such as 3-oxo-2,3-dihydrobenzisothiazole-1,1-dioxide. Among these, particularly preferred polymerization promoters are 2-hydroxyethyl-p-toluidine, N, N-dimethyl-p-toluidine, and N, N-dihydroxyethyl-p-toluidine, N, N-dihydroxymethyl- derivatives thereof such as p-toluidine and N-ethyl-N-hydroxyethyl-p-toluidine. Ferrocene compounds are also effective.

Compounds (A2) comprising at least one polymerizable double bond at its terminal or side chain thereof may be compounds known to date, such as compounds comprising a (meth) acryloyl group at their terminal (s) or side chain (s) thereof. Can be. Among them, preferred compounds are those having a water solubility of 10% by weight or less. Specific examples of these compounds include 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, epoxidized bisphenol A di (meth) acrylate, 1, 3-butanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, neopentyl di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and diisocyanate and glycol and hydroxyalkyl (meth) There is a polyurethane polyfunctional (meth) acrylate obtained by reaction with an acrylate. Among these, bisphenol A (meth) acrylate is especially preferable.

Examples of acidic substances (A3) which are dissolved in water and then acidic for use in the present invention are many compounds such as phosphorous esters and phosphate esters. Specific examples of preferred acidic materials are (meth) acrylate acid phosphates (e.g., light ester PA (meth) acrylics, including reactive double bonds at their ends or side chains thereof, available from Kyoeisha Fat Chemical Co., Ltd.). Rate); Kayamer PM-1, Kayamer PM-2 and Kayamer PM-21 available from Nippon Kayaku Co., Ltd .; And JPA-514 available from Johoku Chemical Co., Ltd .; Aliphatic or aromatic carboxylic acids, anhydrides and carboxyl group-containing (meth) acrylates (eg, containing carboxyl groups at their ends and double bonds at their molecules) available from Kyoeisha Fat Chemical Co., Ltd. HOA-MS (2-acryloyloxyethylsuccinic acid), HOA-MPL (2-acryloyloxy ethylphthalic acid), HOA-MPE (2-acryloyloxyethyl-2-hydroxyethylphthalic acid), HO- MS (2-methacryloyloxyethylsuccinic acid) and HO-MPL (2-methacryloxyethylphthalic acid); Aronix M5400 and Aronix M5500 available from Toa Gosei Chemical Industry Co., Ltd .; Shin-nakamura Chemical Co. NK esters A-SA (β-acryloyloxyethylhydrogen succinate) and SA (β-methacryloyloxyethylhydrogen succinate) available from, Ltd., maleic anhydride and maleic acid.

If a substance containing a double bond in the molecule is used as the acidic substance (A3), it may substitute all or a suitable portion of the polymerizable monomer (A2). However, if the acidic substance does not contain a double bond in its molecule, it is not possible to achieve a solid bond of screws such as screws and bolts, which is the main intended purpose of the present invention, with such an acidic aqueous binder (A4). Will need to be added in an amount sufficient to insolubilize in water to form a suspension. In general, the addition amount of the acidic substance (A3) which is dissolved in water and then becomes acidic can be suitably selected as long as the intended purpose of using the acidic substance (A3) can be achieved. That is, the amount is not particularly limited because the aqueous binder (A4) is insolubilized in water to form a water insoluble layer. However, acidic substances (A3) are generally used in amounts of up to 20% by weight, based on the total weight of the suspension (A) and microcapsules (B). By controlling the amount of acid added, the degree of suspension formation can be controlled. This makes it possible to freely adjust the viscosity of the resulting suspension. If the precoated adhesive composition is used to be applied to an adherend such as a bolt by an immersion method, the viscosity of the adhesive composition may be adjusted with a diluent or the like to control the amount of the composition attached to the adherend. However, if the adhesive composition is diluted too much, it causes problems such as deterioration of adhesion, which is one of the original objects of the present invention. Therefore, the nonvolatile content of the adhesive composition should be kept high. To be standard, the suspension preferably has a viscosity of 50 to 500 cps and a nonvolatile content of 40 to 60% by weight.

Examples of the aqueous binder (A4) which comes into contact with the acidic substance forming the water insoluble layer include alkali metal salts of alginic acid, ammonium salts of alginic acid, alkali metal salts of pectic acid, ammonium salts of pectic acid, alkali metal salts of polyacrylic acid, and polyacrylic acid. Ammonium salts, alkali metal salts of polyacrylic acid esters, ammonium salts of polyacrylic acid esters, alkali metal salts of carboxymethyl (or carboxyethyl) cellulose, ammonium salts of carboxymethyl (or carboxyethyl) cellulose and alkali metal salts of silicic acid. However, the present invention is not limited to these materials. In the present invention, these various aqueous binders can be used. Among them, particularly preferred aqueous binders are sodium polyacrylate resin and sodium alginate resin which impart high adhesion to the adherend and easily form a suspension.

Aqueous binders also form water insoluble layers by the action of metal ions such as calcium, magnesium, iron and copper. In the present invention, all metal salts which can be dissolved in component (A3) can be used as a source of metal ions. Examples are calcium lactate, calcium chloride, magnesium chloride, potassium carbonate, potassium phosphate, aluminum chloride, iron chloride and copper chloride.

If water insolubilization occurs markedly, aggregation tends to occur while the suspension is produced. Suitable aqueous binders different from component (A4) can be used in the formulation to relieve water insolubilization and to cause adhesion to certain metals. Specific examples of such aqueous binders are polyvinyl alcohol and water soluble polyacetal resins.

The polymerization initiator to be encapsulated in the microcapsules for use in the present invention may be a peroxide compound, a hydroperoxide compound, a perester compound, a peramide compound, and the like. Preferably, the polymerization initiator is a peroxide compound, more preferably a diacyl peroxide compound. The wall material forming the wall of the microcapsules may be an aldehyde resin or a urea resin. Examples of aldehyde resins are urea-formaldehyde resins and melamine / formaldehyde resins. Examples of urea resins include polyurea resins and polyurethane resins. Among them, particularly preferred urea resins are melamine resins. The particle size of the microcapsules is appropriately determined according to the shape and size of the adherend to which the adhesive composition is applied. For example, when the adhesive composition is applied to a bolt or nut, the particle size of the microcapsules may vary within a range of several micrometers to about 300 μm, depending on the size of the threads of the bolts. When peroxides, usually in the form of solid particles such as benzoyl peroxide (BPO), are used as the polymerization initiator, microcapsules with layers formed along the surface of the powder can be obtained even if spherical microcapsules cannot be obtained. Since the benzoyl peroxide powder itself is poorly soluble in water, the use of these can dramatically increase the retention of the adhesive composition.

The preparation method of the precoated adhesive composition according to the present invention is described below. In more detail, components (A1), (A2) and (A3) are premixed. The mixture obtained is then mixed with an aqueous binder (A4). In this method, components (A1), (A2) and (A3) are temporarily emulsified with the aqueous binder (A4). The water-soluble acidic substance (A3) inside the emulsion particles is then eluted gradually from the particle interface resulting in a sudden pH change and ion exchange at the particle interface. This may cause the aqueous binder (A4) to be insolubilized in water to form a layer on the surface of the emulsion particles. Due to the layer formation on the surface of the emulsion particles, the emulsion particles can clearly become solid. Thus, a suspension is produced. The term "emulsion" as used herein means a liquid-liquid dispersion in which the liquid medium is dispersed and emulsified in the liquid medium. As used herein, the term "suspension" means a liquid-solid dispersion in which solids are dispersed in a liquid medium.

The amount of the microcapsules (B) and the amount of the polymerization promoter (A1) including the polymerization initiator based on the addition amount of the compound (A2) including the polymerizable double bond is the amount of the compound (A2) including the polymerizable double bond. It may be appropriately selected so long as it is sufficient to polymerize and cure. The microcapsules (B) comprising a polymerization initiator and the polymerization promoter (A1) are preferably added in a slight excess so that the stability of the compound (A2) comprising a polymerizable double bond cannot be impaired. Examples of preferred mixing ratios of these components include 30 to 50 parts by weight of a compound (A2) including a polymerizable double bond, 10 to 30 parts by weight of an aqueous binder (A4), and microcapsules (B) 1 to 5 including a polymerization initiator. By weight, and 0.5 to 5 parts by weight of the polymerization promoter (A1) are mixed with 50 parts by weight of water to prepare a suspension. The effective amount of the polymerization initiator contained in the microcapsules (B) may vary depending on the type of material constituting the microcapsule wall or the type of polymerization initiator to be encapsulated, but is generally based on the weight of the microcapsule (B). 30 to 90% by weight.

In the present invention, various additives may be additionally used as necessary. For example, when filler is added to and used in the adhesive composition, the amount of addition enhances the bonding properties of the adhesive composition, e.g. the ability to bond the bolts when the composition is applied to the bolts, and microcapsules (B) when tightening the bolts. It is suitably chosen so that it will burst easily. The addition amount of the filler is preferably 1 to 10 parts by weight per 100 parts by total amount of components (A1), (A2), (A3), (A4) and (B). The type of filler is not particularly limited, but in order to achieve the above object, the filler is preferably in the form of scales or needles. The particle diameter of the filler can be adjusted to 100 μm or less so that the composition can be applied to the bolts without causing any problems.

The precoated adhesive composition of the present invention may further include a well-known polymerization inhibitor or a chelating agent for stabilizing the compound (A2) containing a polymerizable double bond. Specific examples of polymerization inhibitors are hydroquinone, benzoquinone, naphthoquinone and anthraquinone. Particular examples of chelating agents are the sodium salts of β-diketones, ethylenediaminetetraacetic acid and ethylenediaminetetraacetic acid.

In addition, plasticizers, pigments, dyes, diluents, antifoaming agents, mildewproofing agents, rust inhibitors, pH adjusting agents and other additives known in the art may be impaired in the precoated adhesive composition of the present invention. It may be added by any suitable means. However, since the pH adjusting agent is likely to affect the suspension formation and the stability of the suspension, the amount of the pH adjusting agent needs to be adjusted.

In the present invention, colloidal silica is effectively used to maintain the stability of the suspension thus produced. This is because the addition of the colloidal silica solution (A5) after the suspension is produced causes the deposition of the colloidal silica on the surface of the suspension particles. An example of a solvent for use in the colloidal silica solution (A5) is water. The colloidal silica solution (A5) once deposited can no longer be dispersed again, thus enhancing the stability of the suspended particles.

The application method for the bolts of the precoated adhesive composition of the present invention is described below. The suspension thus prepared may be applied with an automatic coater or brush coater or with a spirally engaged surface of bolts by immersing the adherend in a container filled with the suspension. The adherend coated with the suspension is left at room temperature or treated in a heating furnace to evaporate the moisture in the suspension to form an apparently dried coating on the spirally engaging portion of the bolt.

Thereafter, the bolts with the apparently dried coating on the helically engaged portions are tightened to the nuts to form a polymerization initiator emanating from the ruptured microcapsules (B) and a polymerizable double bond exuding from the aqueous binder (A4). As the compound (A2) to be contained is polymerized rapidly by the polymerization accelerator (A1) and cured, the bolt is fixed to the nut.

The present invention will be described in more detail with reference to the following examples and comparative examples, but should not be construed as being limited thereto. Prior to describing the examples, Comparative Examples 1 to 3 will be described.

Comparative Example 1

Precoated adhesive compositions were prepared with the following components and proportions thereof.

Component (A1):

0.2 parts by weight of dimethyl-p-toluidine

Component (A2):

50 parts by weight of bisphenol A epoxy acrylate

(Available from BPE-4, Shin-nakamura Chemical Co., Ltd.)

Component (A4):

10 parts by weight of a water-soluble sodium polyacrylate binder

(Available from Cogum HW-7, Showa Highpolymer Co., Ltd.)

Component (B):

Microcapsules containing polymerization initiator: 3 parts by weight

(Microcapsules: with walls made of melamine / formaldehyde resin; contains 70% by weight of BPO)

(i) A mixed solution X of the components (A1) and (A2) was prepared.

(Ii) Subsequently, 10 parts by weight of the component (A4) and water-soluble polyacetal (KW-10, available from Sekisui Chemical Co., Ltd.) were mixed with 30 parts by weight of water and dissolved therein to prepare an aqueous solution Y.

(Iii) The said component (B) was added and dispersed in 25 weight part of water, and the aqueous solution Z was produced. Subsequently, the mixture X was added to the aqueous solution Y while stirring to prepare an emulsion solution. Subsequently, the aqueous solution Z prepared above was added to the emulsion solution with stirring to obtain a precoated adhesive composition (Comparative Sample 1).

Comparative Example 2

Precoated adhesive compositions were prepared with the following components and proportions thereof.

Component (A1):

0.2 parts by weight of 2-hydroxyethyl-p-toluidine

Component (A2):

50 parts by weight of bisphenol A epoxy acrylate

(Available from BPE-200, Shinnakamura Chemical Co., Ltd.)

Component (A4):

10 parts by weight of a water-soluble sodium polyacrylate binder

(Available from HW-7, Showa Highpolymer Co., Ltd.)

Component (B):

Microcapsules containing polymerization initiator: 3 parts by weight

(Microcapsules: with walls made of melamine / formaldehyde resin; contains 70% by weight of BPO)

(i) A mixed solution X of the components (A1) and (A2) was prepared.

(Ii) The above component (A4) was mixed with 30 parts by weight of water and dissolved in it to prepare an aqueous solution Y.

(Iii) The said component (B) was added and dispersed in 25 weight part of water, and the aqueous solution Z was produced. Subsequently, the mixture X was added to the aqueous solution Y while stirring to prepare an emulsion solution. Subsequently, the above-prepared aqueous solution Z was added to the emulsion solution with stirring to obtain a precoated adhesive composition (Comparative Sample 2).

Comparative Example 3

Precoated adhesive compositions were prepared with the following components and proportions thereof.

Component (A1):

0.2 parts by weight of 2-hydroxyethyl-p-toluidine

Component (A2):

50 parts by weight of bisphenol A epoxy acrylate

(Available from BPE-200, Shinnakamura Chemical Co., Ltd.)

Component (A4):

10 parts by weight of a water-soluble sodium alginate binder

(20% aqueous solution)

Component (B):

Microcapsules containing polymerization initiator: 3 parts by weight

(Microcapsules: with walls made of melamine / formaldehyde resin; contains 70% by weight of BPO)

Etc:

10 parts by weight of the adhesive donating aqueous binder

(Available from Gosenol GM-14, Nippon Synthetic Chemical Industry Co., Ltd .; 4% aqueous solution)

(i) A mixed solution X of the components (A1) and (A2) was prepared.

(Ii) The component (A4) and the adhesive donor aqueous binder were mixed with 30 parts by weight of water and dissolved therein to prepare an aqueous solution Y.

(Iii) The said component (B) was added and dispersed in 25 weight part of water, and the aqueous solution Z was produced. Subsequently, the mixture X was added to the aqueous solution Y while stirring to prepare an emulsion solution. Subsequently, the above-prepared aqueous solution Z was added to this emulsion solution while stirring to obtain a precoated adhesive composition (comparative sample 3).

Subsequently, each of the compositions prepared in Comparative Examples 1 to 3 (Comparative Samples 1 to 3) was then subjected to zinc chromate plated steel bolts (M of 10 mm (diameter), 1.5 mm of P (pitch), 25 mm of L (effective spiral). Length)) was applied with a coating width of 22 to 24 mm from the top of the thread, followed by drying at a temperature of 80 ° C. for 20 minutes to obtain precoated bolts (comparative samples 1 to 3).

<Example 1>

Precoated adhesive compositions were prepared with the following components and proportions thereof.

Component (A1):

0.2 parts by weight of dimethyl-p-toluidine

Component (A2):

50 parts by weight of bisphenol A epoxy acrylate

(Available from BPE-4, Shinnakamura Chemical Co., Ltd.)

Component (A3):

Methacrylic acid phosphate 3 parts by weight

(Available from JPA-514, Johoku Chemical Co., Ltd.)

Component (A4):

10 parts by weight of a water-soluble sodium polyacrylate binder

(Available from Cogum HW-7, Showa Highpolymer Co., Ltd.)

Component (B):

Microcapsules containing polymerization initiator: 3 parts by weight

(Microcapsules: with walls made of melamine / formaldehyde resin; contains 70% by weight of BPO)

(i) A mixed solution X 'of the components (A1), (A2) and (A3) was prepared.

(Ii) 10 parts by weight of the component (A4) and water-soluble polyacetal (KW-10, available from Sekisui Chemical Co., Ltd.) were mixed with 30 parts by weight of water and dissolved therein to prepare an aqueous solution Y.

(Iii) The said component (B) was added and dispersed in 25 weight part of water, and the aqueous solution Z was produced. The mixture X 'was then slowly added to aqueous solution Y with stirring to prepare a suspension. Subsequently, the above-prepared aqueous solution Z was added to this suspension with stirring to obtain a precoated adhesive composition (sample 1).

<Example 2>

Precoated adhesive compositions were prepared with the following components and proportions thereof.

Component (A1):

0.2 parts by weight of 2-hydroxyethyl-p-toluidine

Component (A2):

50 parts by weight of bisphenol A epoxy acrylate

(Available from BPE-200, Shinnakamura Chemical Co., Ltd.)

Component (A3):

1 part by weight of maleic anhydride

Component (A4):

10 parts by weight of a water-soluble sodium polyacrylate binder

(Available from HW-7, Showa Highpolymer Co., Ltd.)

Component (B):

Microcapsules containing polymerization initiator: 3 parts by weight

(Microcapsules: with walls made of melamine / formaldehyde resin; contains 70% by weight of BPO)

Colloidal silica:

10 parts by weight (available from Adelite AT-300, Asahi Denka Kogyo K.K.)

(i) A mixed solution X 'of the components (A1), (A2) and (A3) was prepared.

(Ii) The above component (A4) was mixed with 30 parts by weight of water and dissolved in it to prepare an aqueous solution Y.

(Iii) The said component (B) was added and dispersed in 25 weight part of water, and the aqueous solution Z was produced. The mixture X 'was then slowly added to aqueous solution Y with stirring to prepare a suspension. Subsequently, 10 parts by weight of the colloidal silica shown above was added with stirring. The resulting aqueous solution Z was then added to the resulting mixture with stirring to give a precoated adhesive composition (sample 2).

<Example 3>

Precoated adhesive compositions were prepared with the following components and proportions thereof.

Component (A1):

0.2 parts by weight of 2-hydroxyethyl-p-toluidine

Component (A2):

50 parts by weight of bisphenol A epoxy acrylate

(Available from BPE-200, Shinnakamura Chemical Co., Ltd.)

Component (A3):

1 part by weight of methacrylate phosphate

(Available from Kayamer PM-1, Nippon Kayaku Co., Ltd.)

Component (A4):

10 parts by weight of a water-soluble sodium alginate binder

(20% aqueous solution)

Component (B):

Microcapsules containing polymerization initiator: 3 parts by weight

(Microcapsules: with walls made of melamine / formaldehyde resin; contains 70% by weight of BPO)

Colloidal silica:

10 parts by weight (available from Adelite AT-300, Asahi Denka Kogyo K.K.)

(i) A mixed solution X 'of the components (A1), (A2) and (A3) was prepared.

(Ii) The above component (A4) was mixed with 30 parts by weight of water and dissolved in it to prepare an aqueous solution Y.

(Iii) The said component (B) was added and dispersed in 25 weight part of water, and the aqueous solution Z was produced. The mixture X 'was then slowly added to aqueous solution Y with stirring to prepare a suspension. Subsequently, 10 parts by weight of the colloidal silica shown above was added with stirring. Subsequently, the above-prepared aqueous solution Z was added to the mixture with stirring to obtain a precoated adhesive composition (sample 3).

Subsequently, each of the compositions prepared in Examples 1 to 3 (Samples 1 to 3) was then subjected to zinc chromate plated steel bolts (M (diameter) of 10 mm, P (pitch) of 1.5 mm, L of 25 mm (effective spiral length) The threaded portion of)) was applied with a coating width of 22 to 24 mm from the top of the thread, followed by drying at a temperature of 80 ° C. for 20 minutes to obtain precoated bolts (Examples 1 to 3).

The compositions and precoated bolts obtained in Comparative Examples 1-3 and Examples 1-3 were evaluated for the following properties. The results are shown in Table 1.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Nonvolatile content (110 ℃, 2 hours) 45% ^-1 ) - 45% - - Viscosity 1 (BL, 60 rpm) 6,250 3,500 2,500 358 220 190 Viscosity 2 (BL, 6 rpm) 7,600 4,800 3,000 420 240 210 Thixotropy ratio (ratio of viscosity 1 / viscosity 2) 1.22 1.37 1.20 1.17 1.09 1.10 Breaking torque ²⁾ (Tighten to 300kgfcm, cured for 24 hours) 375 390 350 370 380 360 Note: The symbol "-" indicates no measurement. 2) average value over 5 times

<Measurement of Nonvolatile Content and Viscosity>

Comparative Samples 1-3 and Samples 1-3 were evaluated for nonvolatile content (110 ° C., 2 hours) and viscosity (cps) with a BL viscometer (60 rpm and 6 rpm) to determine their structural viscosity rate. Was measured.

Torque Test

Each of the obtained precoated bolts was fitted to a nut, tightened to 300 kgf · cm, left for 24 hours, and the breaking torque was measured when released.

For Comparative Sample 1 and Sample 1, before mixing with component (B), each composition was examined for the formation of the suspension by scanning electron micrographs and for fluidity characteristics with a rheometer. Investigation of suspension formation by scanning electron micrograph was performed as follows. Comparative Sample 1 and Sample 1 were each diluted 50-fold with purified water to give a solution which was then immediately frozen. The frozen solution was metallized with gold, and SEM photographs of the test bodies thus prepared, frozen in solution, were taken to observe the state of the suspension.

<Suspension formation>

It was observed that Comparative Sample 1 had frozen resin distributed like cobwebs around the oil droplets and monomers dispersed in oil droplets by the surface activity of the aqueous binder. Thus, the inventors have found that the sample has a resin distributed around the oil droplets in the form of a liquid emulsion. On the other hand, Sample 1 had an aqueous binder formed with a poorly water soluble film on the surface of the oil droplets. Thus, core-shell oil droplets were formed which act as solids. There was also only water around the oil droplets, demonstrating that the oil droplets remain sufficiently suspended. This indicates that water can be easily evaporated off during drying.

<Measured by flowmeter>

The inventors have found that when measured at a shear rate lowered below the measurement range by a BL viscometer, Sample 1 itself shows an increased viscosity that is difficult to drip. When measured at a shear rate of 1/10 to 100 seconds ^{−1 that} is optimal for coating, Sample 1 exhibits a low viscosity to facilitate application to the adherend. Samples immersed and coated on the adherend exhibit a high fixed viscosity such that they are prevented from dripping themselves. In contrast, Comparative Sample 1 was diluted with water to adjust to approximately the same viscosity as Sample 1 and then measured with a rheometer. However, the sample did not show a significant increase in fixed viscosity even at reduced shear rates. Thus, it was confirmed that this sample was easily dipped.

The bolts obtained in Example 1 and Comparative Example 2 were observed for the appearance of the coating formed by the spinning machine. As a result, the bolt of Example 1 was observed to have a uniform smooth coating layer formed on its surface with sufficient thickness. In contrast, it was observed that the bolts of Comparative Example 1 had a reduced film thickness due to lack of solids content and thus caused wrinkles on the surface of the coating layer.

According to the present invention, the use of a suspension system having a solid material dispersed in a liquid medium can yield a precoated adhesive having a high non-volatile content and reduced viscosity suitable for immersion coating. The use of this suspension system provides a precoated adhesive composition that is applied to the adherend and exhibits enhanced internal drying capacity during drying. In addition, after drying, the precoated threaded screw thus obtained can be stored for a long time.

The use of a suspension system also provides an adhesive composition with a higher non-volatile content compared to the emulsion system, while its viscosity can be suppressed to a lower value. Because of its fluidity, the suspension has a low viscosity and can therefore be easily applied to the adherend by the dipping method. If the adherend is removed from the suspension, the suspension can be difficult to drop. In addition, by using a suspension system, surface drying can be suppressed and the internal drying ability can be enhanced. Thus, the coating layer can be formed along the valley of the screw without damaging the appearance.

Prior to use, component (A) is generally mixed with about 1-5% of microcapsules (B) comprising a polymerization initiator. The adhesive composition thus prepared is applied to the bolt and then dried. Because of their suspension form, the adhesive composition can hardly be dripping and thus provide an improved appearance after drying. Also, since the emulsion particles are clearly solid and the aqueous binder originally dissolved in the solution forms a layer on the surface of the emulsion particles, the solution from which the emulsion particles have been removed does not contain an aqueous binder therein. Water can thus be easily evaporated away from the interior of the adhesive composition, and the adhesive composition tends to be less dry at its surface. Thus, the adhesive composition of the present invention has excellent drying properties suitable for mass production. In addition, according to the present invention, the coating layer formed of the adhesive composition is somewhat isolated even after the monomer or oligomer is dried. Thus, the composition applied to the bolts has a very high stability, thus allowing the storage of precoated bolts over a long period of time.

As above, the conversion to the liquid suspension allows for the provision of adhesive compositions having increased concentrations and reduced viscosities. This improves the dip coating properties of the adhesive composition and provides a dry layer having an improved appearance. Thus, the adhesive composition produced exhibits improved drying capacity and productivity. In addition, by forming the poorly water-soluble layer, the emulsion particles are in a liquid state that can be stored for a long time even in a suspension system containing a polymerization initiator.

While the present invention has been described in detail with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope thereof.

Claims (16)

(A) (A1) at least one polymerization promoter; (A2) at least one compound having at least one polymerizable double bond at its terminal or side chain thereof; (A3) at least one acidic substance which is dissolved in water and then becomes acidic; And (A4) a suspension having an emulsifying capacity and comprising a mixture of aqueous binders insoluble in water by said acidic material (A3); And, (B) An adhesive composition for precoating screws comprising a microcapsule comprising at least one polymerization initiator. The adhesive composition according to claim 1, wherein the compound (A2) comprises a compound having a water solubility of 10 wt% or less. The adhesive composition according to claim 2, wherein the compound having a water solubility of 10 wt% or less is bisphenol A (meth) acrylate. The adhesive composition of claim 1, wherein the acidic material (A3) comprises (meth) acrylate acid phosphate. The method according to claim 1, wherein the acidic material (A3) (a) aliphatic carboxylic acids terminus in the molecule and having a polymerizable double bond; (b) aromatic carboxylic acids having terminal carboxyl groups in the molecule and having polymerizable double bonds; And, (c) An adhesive composition comprising at least one compound selected from the group consisting of carboxyl group-containing (meth) acrylates. The adhesive composition of claim 1, wherein the aqueous binder (A4) comprises a binder that is solubilized in water by alkali salt dipping. The adhesive composition according to claim 6, wherein the aqueous binder (A4) is sodium polyacrylate resin or sodium alginate resin. The adhesive composition according to claim 1, wherein the polymerization accelerator (A1) comprises a tertiary amine. The adhesive composition according to claim 1, wherein the polymerization accelerator (A1) comprises modified dimethyl-p-toluidine. The adhesive composition of claim 1, wherein the wall of the microcapsules (B) comprises a water resistant melamine resin. The adhesive composition according to claim 1, wherein the polymerization initiator contained in the microcapsules (B) comprises a solid diacyl peroxide. The adhesive composition of claim 1, wherein the suspension (A) has a viscosity of 50 to 500 cps and a nonvolatile content of 40 to 60% by weight. The adhesive composition according to claim 1, wherein the mixture constituting the suspension (A) further comprises a colloidal silica solution (A5). (a) (A1) at least one polymerization promoter; (A2) at least one compound having at least one polymerizable double bond at its terminal or side chain thereof; And (A3) preparing a mixture comprising at least one acidic substance which is dissolved in water and then becomes acidic; (b) the mixture prepared in step (a) is mixed with an aqueous binder (A4) which has an emulsifying capacity and is insoluble in water by an acidic substance (A3) while stirring to carry out emulsification, respectively on its surface. Preparing a suspension comprising emulsified particles having a water insoluble layer formed; And (c) mixing the suspension with a microcapsule comprising one or more polymerization initiators to obtain an adhesive composition. The method of claim 14, further comprising adding a colloidal silica solution (A5) to the suspension prepared in step (b) and coating the surface of the water insoluble layer therewith. The process according to claim 14, wherein the water insolubilization of the aqueous binder (A4) takes place by ion exchange with the acidic material (A3).