GB2078763A - A Bonding Method Using an alpha - cyanoacrylate Adhesive - Google Patents

Abstract

A bonding method comprises interposing an adhesive assistant, composed of a hardening accelerator for accelerating hardening of an alpha - cyanoacrylate adhesive and a flexible support member to which said hardening accelerator is attached, between a first bonding member and a second bonding member. An alpha - cyanoacrylate adhesive is applied to the bonding faces or the adhesive assistant and the first bonding member is bonded to the second bonding member through the adhesive assistant.

Description

SPECIFICATION A Bonding Method Using an cr-cyanoacrylate Adhesive This invention relates to a bonding method using an ez-cyanoacrylate adhesive and, particularly, to a method of temporary attachment useful in the building industry.

a-cyanoacrylate adhesive, which is considered to be an instantaneous adhesive, is a blockade type adhesive, wherein ionic polymerization begins rapidly due to water in the air or water absorbed in the surface of the object to be bonded, by which almost all materials except certain kinds of plastics can be bonded. Therefore, it is recommended for use when rapid bonding is required.

However, where the surface of the object to be bonded is uneven or is absorbent, such as a porous surface, it is impossible to use this adhesive directly for bonding, because it has a low viscosity.

This fact prevents the adhesive being used in cases of bonding, i.e., temporary attachment, of concrete surfaces, mortar surfaces, plaster surfaces, or wood surfaces to like surfaces, or to faced plywoods, tiles, glass (such as a mirror) or other wall materials. Consequently, the adhesive has scarcely been used in the building industry, because bonding surfaces are perpendicular in many cases.

On the other hand, in the building industry, it is often required to carry out temporary attachment and pressing for instantaneous bonding. For example, in the case of attachment of cladding materials, such as decoration plates, plaster plates, and mirrors, by adhesion to concrete or mortar wail surfaces, hitherto an epoxy resin adhesive has been applied thereto, followed by temporarily attaching the cladding material to the wall surface by means of nails or an adhesive tape until complete adhesion is obtained. However, in the case of using nails, splits are sometimes caused, nail marks are left, or nailing may be impossible, according to the materials used. In the latter case, sufficient adhesive strength cannot be obtained. Accordingly, there has been a need for a convenient method for forming strong temporary attachments.

Prior art methods of using a-cyanoacrylate adhesives include a method which comprises processing a bonding surface of wood with a quaternary ammonium salt (Japanese Patent Publication No. 1 685/77) and a method which comprises preliminarily applying a primer composed of a sealant and a hardening accelerator to the bonding surface (Japanese Patent Application (OPI) No. 40027/78) (the term "OPI" as used herein refers to a "published unexamined Japanese patent application").

However, these methods are difficult to adapt to the above-described uses in the building industry because, for example, the processing is troublesome, and the instantaneous adhesion is damaged in the case of using an adhesive containing a filler (having an increased viscosity).

As a result of extensive studies into the use of an a-cyanoacrylate adhesive in the building industry, and particularly, for temporary attachment, a bonding method has been developed in accordance with this invention in which a flexible material to which a hardening accelerator is attached is interposed between the bonding surfaces of first and second bonding members to be joined by the a-cyanoacrylate adhesive.

More particularly, this invention relates to a method of bonding a first bonding member (typically having an uneven or porous surface, such as a decoration plate) to a second bonding member (also typically having an uneven or porous surface, such as a concrete wall surface), wherein an adhesive assistant, composed of a flexible support member, which is easily adaptable to the bonding faces of the first and second bonding members and absorbs and holds the -cyanoacrylate adhesive, such as absorbent cotton, and a hardening accelerator attached to the support member is placed on one or more parts of the bonding faces, a small amount of an ez-cyanoacrylate adhesive (typically one or a few drops) is applied to the adhesive assistant or the bonding faces, and by contact through the adhesive assistant the first and second bonding members are attached. Thus the flexible support member is instantaneously fixed by the adhesive such that it conforms to the shape of the surfaces of the members being bonded, i.e., the first and second bonding members, namely, the shape of the bonding faces and the gaps between the bonding faces, whereby both members are bonded simultaneously to firmly attach them to each other.

The a-cyanoacrylate adhesive used in the present invention typically comprises an a-cyanoacrylate monomer represented by the formula

wherein R represents an alkyl group having from 1 to 1 6 carbon atoms, a cycloalkyl group, a cyclohexyl group, an alkenyl group, a cycloalkenyl group, a phenyl group, an allyl group, etc., as an adhesive component. An adhesive containing a very small amount of SO2 as a stabilizer, an anionic and radical polymerization inhibitor, such as hydroquinone, and esters as plasticizers can be effectively used, also.

Although a thickener may be used, if it is used in a very small amount, it is not preferred to do so, because it reduces the instantaneous adhesion property and permeation into the flexible support member.

The adhesive assistant used in the present invention is composed of a hardening accelerator, for accelerating hardening of the a-cyanoacrylate adhesive, and a support member by which the hardening accelerator is supported by attachment, fixing, adsorption, or chemically bonding (referred to collectively as "attachment", hereinafter).

The support member is formed of a flexible material which is adaptable to fit between gaps, uneven surfaces, and various shapes when interposed or inserted between a first bonding member and a second bonding member and which effectively holds the hardening accelerator It also effectively holds the adhesive by rapid permeation of the adhesive into the flexible support member when the adhesive is applied thereto, by which contact of the adhesive with the hardening accelerator is effectively carried out and the support member is solidified to bond the first bonding member to the second bonding member and to fill up the gaps between them. For example, cotton goods such as absorbent cotton or cotton towel, which easily change shape when compressed are suitably used.In addition, flax, wool, rayon, acetate, polyester, nylon, vinylon (i.e., polyvinyl alcohoi synthetic fiber), glass fiber and other organic or inorganic natural or synthetic fibers can be used instead of cotton.

Furthermore, any form of support material may be used, such as cotton wool, cloth, tape, felt, sheet, non-woven web, string, provided it is flexible and easily adaptable to uneven surfaces, effectively holds the hardening accelerator, and effectively holds the a-cyanoacrylate adhesive by rapid permeation.

Accordingly, it is possible to use materials composed of continuous open cell foams which easily change shape, such as sponge or urethane foamed goods. Filter paper and pulps, etc., also can be used.

As the hardening accelerator, it is possible to use any compound which initiates or accelerates anionic polymerization of a ct-cyanoacrylate. As known hardening accelerators, there are, for example, hydroxides of alkali metals such as lithium, sodium, or potassium, compounds of these alkali metals with mono-, di- or tri-basic acids such as hydrochloric acid, sulfuric acid or phosphoric acid or organic acids such as acrylic acid or acetic acid oxides and hydroxides of alkaline earth metals such as magnesium or calcium metal soaps composed of organic acids such as naphthenic acid and cobalt, vanadium, manganese, lead or iron amines such as monoethanolamine, diethanolamine, triethanolamine, amylamine, ethylhydrazine or hexamethylenediamine basic compounds containing at least one primary, secondary, tertiary, or quaternary nitrogen atom in the molecule.

Since they each have a different ability of hardening the cg-cyanoacrylate adhesive, they can be used by selecting the kind and the amount thereof according to the nature of the support member or by combining with a fixing agent or permeating agent, etc., according to the purpose of use.

The adhesive assistant according to the present invention is preferably produced by a method which comprises dissolving one or more of the above-described hardening accelerators in water or an organic solvent, dipping a support member such as absorbent cotton in the resulting solution, dehydrating (or removing the solvent) in a state that molecules of the hardening accelerator attach to the surface of fibers, and drying in air. The dehydration is preferably carried out by a centrifugal separator, etc., such that the attached hardening accelerator is firmly attached thereto. In the case of using an organic solvent, removal thereof is carried out in a conventional manner.Further, it is possible not only physically to attach (fixing, absorption) the hardening accelerator to the support member but also to chemically bond the accelerator to the support member such as the case of alkali cellulose.

The above-described solution of the hardening accelerator may also contain, if desired, assistants such as a fixing agent for ensuring attachment of the hardening accelerator to the support fibers, a permeating agent for improving permeation of the hardening accelerator into the fibers, and a chemical for improving permeation and holding the ct-cyanoacrylate adhesive. As a fixing agent, carboxymethyl cellulose (CMC) or derivatives thereof such as dimethylcarboxymethyl cellulose sodium salt, acrylic acid esters, polyacrylic acid and salts thereof, can be used, according to the type of support member and hardening accelerator used.As a permeating agent, surface active agents, for example Noigen 1 30T (trade name) can be used, but materials having both functions (i.e., fixing agent and permeating agent), such as sodium polyacrylate or dimethylcarboxymethyl cellulose sodium salt may also be used.

Further, it is possible to control hardening time by combining these additives with the hardening accelerator, because some of these additives accelerate or retard the hardening of the a-cyanoacrylate adhesive. Table 1 (a) shows examples of results obtained by carrying out adhesion tests for various bonding members. As is obvious from the results, in the process of the present invention, an adhesive strength (tensile shear strength) of about 10 kg/cm2 or more was obtained in the cases wherein at least one of the bonding members had a porous absorbent surface, such as an asbestos slate or plywood, which is in striking contrast to the lack of adhesion in the case of not using the adhesive assistant.

Moreover, in all cases except that of iron-iron bonding, the tensile shear strength test resulted in destruction of one or both of the bonding members. Accordingly, it is apparent that the method of this invention is effective in bonding objects having an uneven or porous face, because the weight of the bonded objects can be sufficiently supported not only for temporary bonding, but also for conventional adhesion.

The results shown in Table 1 (a) were obtained as follows. An adhesive assistant having the composition shown in Table 1 (a) was thinly spread on an edge part of the second bonding member (test piece), 2 drops of the sr-cyanoacrylate adhesive (Alteco EE, trade name, produced by Alpha Giken Co.) were applied (by dropping) on edge parts of the first bonding member (test piece), and the first and second bonding members were lightly pressed together for 1 to 3 seconds to bond them. After a lapse of 2 hours after bonding, the strength in a normal state was measured according to JIS K-6850.

Further, in Table 1 (b), the expression "fuming property" refers to whether fumes (of unreacted substances and others) are generated by reaction heat when the adhesive hardens, which becomes a criterion of conclusion of the hardening. In the following tables, the occurrence of fuming is shown in the column of fuming property by the mark o.

Thus, in the case of bonding wall materials such as plaster boards or decoration plywoods, etc., to wall face of concrete, etc., temporary fixing can be carried out easily and surely by a method comprising placing few pieces of the adhesive assistent having a size, e.g., of a red bean or a soybean on a part between the bonding members, particularly, on the circumferential part, after applied an epoxy resin adhesive or another adhesive, dropping one or few drops of the a-cyanoacrylate adhesive thereon, and lightly pressing them together for a few seconds.

Table 1 (a) With Adhesive Assistant First Bonding Second Bonding Tensile Without Member Member Shear Adhesive (thickness m/m) (thickness m/m) Strength Observation Testing Assistant (kg/cm2) Iron plate Asbestos slate (3.2) 15.7 The base of the asbestos slate is broken. No bonding (coarse face) (1.5) Iron plate Plywood (5.5) 29.5 The surface of the plywood (interface) " (coarse face) (1.5) peels off.

Iron plate Non-combustible 16.6 The base of the non-combustible decora- " (coarse face) (1.5) decoration plate tion plate is broken.

(4.2) Iron plate Iron plate 150.0 (coarse face) (1.5) (coarse face) (1.5) Non-combustible Plywood (5.5) 9.6 The surface of the plywood (interface) " decoration plate peels off.

(4.2) Non-combustible Asbestos slate (3.2) 9.0 The base of the asbestos slate is broken. " decoration plate (4.2) Mortar (20) Plywood (5.6) 8.0 The interface between the materials is " broken.

Mortar (20) Non-combustible 12.0 The interface between the materials is decoration plate) broken.

(4.2) Table 1(b) Amount of Support Attachment Fuming Member Accelerator Assistant Solvent {%} Property Absorbent Diethanolamine Noigen Water 11.3 o cotton 50 g 130T2.5g 450g 809 Accordingly, the finish is good because nails are not required for the bonding. Further, the temporary fixing of materials to which nails cannot be applied, such as glasses, mirrors or tiles, can be easily carried out without the occurrence of accidental separation, as may occur in the case of using adhesive tapes, and thus working efficiency is increased without soiling the hands. In addition, the size of the adhesive assistant used is not limited, and the adhesive assistant can be used for not only temporary attachment, but also conventional adhesion.In this case, the fault of the a-cyanoacryiate adhesive that it is not suitable for bonding many kinds of materials can be overcome, and it can be applied to not only the uneven faces or porous faces but also to smooth bonding faces. Particularly, in case of bonding tiles with a mortar, it was the case hitherto that only a few rows could be applied per day because of collapse due to self-weight. However, according to the process of the present invention, the whole face can be finished within one day. Moreover, it greatly contributes to the building industry, because, for example, crosspieces can be bonded to a concrete face, after which decoration plywoods can be nailed on the crosspieces.

The following Table 2 shows results of testing the properties of adhesive assistants produced using 80 g of absorbent cotton as a support member, and various kinds of hardening accelerators and fixing agents, wherein the fuming property was evaluated, and the time until fuming began is shown.

The fuming property was visually observed by putting a piece of the processed absorbent cotton (adhesive assistant) on an iron plate, and then dropping 2 drips of the same adhesive as in Table 1. In case of a low degree of fuming or no fuming (which are shown as A and x, respectively, in the Table, wherein the hardening proceeds slowly), the time until fuming was measured as the time taken for the processed absorbent cotton ta increase in density and is shown in parenthesis. Furthermore, as the acrylic emulsion in the Tables, Acryset (PK-542) (solid content: 39.6% pH: 7.1) produced by Nippon Shokubai Co., was used.

Table 2 Fuming Property Amount of Hardening Time Attachment Fixing Agent (g) Accelerator (g) Solvent (g) Fuming (seconds) (%) Natural Dimethylcarboxy 3 Sodium carbonate 60 Water 780 o 8-10 32.5 material cellulose (anhydrous salt) sodium salt Emulsion Acrylic acid 20 Sodium carbonate 45 Water 200 x (15-20) ester (10 hydrate) Emulsion Acrylic acid 50 Hexamethylene- 25.4 Water 450 x (20) 15.8 ester tetramine Polymer Sodium 50 Sodium carbonate 136.2 Water 314 # (30) 8.6 salt polyacrylate (10 hydrate) Vegetable Linseed oil 50 Diethanolamine 2.5 Toluene 350 o 12 oil Cobalt naphthenate 0.25 MEK 100 Ethanal 50 Polyglycol Polypropylene 5 Calcium stearate 10 Water 10 o 5-7 glycol Table 3 and Table 4 show the results of the same fuming test as described above in relation to Table 2 for processed adhesive assistants composed of various types of support members.In Table 3, the support member was dipped in a solution prepared by dissolving 60 g of sodium carbonate as a hardening accelerator and 3 g of dimethylcarboxymethyl cellulose sodium salt as a fixing agent in 780 g of water, and thereafter the support member was dried. In Table 4, the support member was dipped in a solution prepared by dissolving 5 g of diethanolamine as a hardening accelerator and 0.25 g of Noigen 1 30T as a permeating agent in 495 g of water and, thereafter, the support member was dried.

Table 3 Fuming Property Support Member Amount Attachment Fuming Time Material Raw Material Source % (seconds) Absorbent Cotton Miyake Menko. 32.5 o 5-6 cotton (cellulose) The Japanese Pharmacopoeia, 450 g Lot No. 540330 Surface mat Glass fiber Asahi Fiber Glass, 29.0 o 5-6 SM-3603-E 60 g/m2 Nonwoven web Polyester fiber Toray Acstar 3.9 o 5-6 Spanbond 100 g/m2 Sponge swab Urethane foamed Marketing goods 102.5 o 5-6 material (domestic) 30x100x150 m/m Table 4 Fuming Property Support Material Amount of Attachment Time Material Raw Material Source {%J Fuming (seconds) Cotton cloth Cotton Marketing goods 10 o less than 3 (towel) Flax string Flax Marketing goods 8 o less than 3 Nonwoven web Polyester fiber Toray Acstar 4 o less than 3 100 g/m2 Filter paper Pulp Toyo Roshi, 3.5 o less than 3 No. 5B 9c Table 5 Dehydration by Centrifugal Seperator Dried Fuming Tensile Welght Property Shear Hardening Support Time Weight in Air Time Strength Accelerator Assistant Solvent Member (sec) (g) (g) Fuming (sec) (kg/cm2) Diethanol- 25 g Permeating agent 1.25 g Water 475 g Absorbent 30 149 87 o 3 16.1 amine Noigen 130T cotton (DEA 5%) 80 g Diethanol- 50 g Permeating agent 2.5 g Water 450 g " 30 139 89 o 2-2.5 10.8 amine Noigen 130T (DEA 10%) Diethanol- 75 g Permeating agent 5.0 g Water 425 g " 30 156 98 o 1 12.2 amine Noigen 130T (DEA 15%) Sodium 136.2 g Fixing agent 50 g Water 314 g " 30 380 87 # (30) 25 carbonate 1 % Aqueous 60 303 10 hydrate solution of 90 269 sodium polyacrylate Ammonium 37.1 g Fixing agent 50 g Water 413 g " 30 390 160 o 12 40.2 carbonate 1% Aqueous 60 237 solution of 90 201 sodium polyacrylate Cobalt 50 g - Toluene 450 g " Squeezing - 113 o 10 38 naphthenate by hands Lead 12.5 g - Toiuene 487.5 g " Squeezing - 91 o 14 32.2 naphthenate by hands Diethanol- 2.5 g Fixing agent 50 g Toluene 350 g " - 365 - o 12 22.6 amine Linseed oil by hands Cobalt 0.25 g MEK 100 g " naphthenate Ethanot 50 g Results of measuring adhesive strength (tensile shear strength) of adhesive assistants prepared using 80 g of absorbent cotton as a support member and various kinds of hardening accelerators and assistants are shown in Table 5. The absorbent cotton was used in an amount of 80 g. The measuring conditions and others were the same as the case of Table 1 (a), except that the adhesive used was one drop and the temporary pressing (lightly pressing the bonding faces by hand) was carried out for the time shown in the fuming property. Further, the content of the hardening accelerators other than diethanolamine (DEA) was based on DEA 10%, which was equimolar (0.476 mol) to the molar amount of DEA 10%. The yield (shown in Table 5 was "Dried Weight in Air (g)") was measured 24 hours after dehydration and drying in air.

It is obvious from the above-described results that adhesion can be carried out in from one second to several tens of seconds according to the process of the present invention, irrespective of the unevenness or absorbance of the bonding faces, but it is also possible to achieve the required adhesion in a range of from several minutes to ten odd minutes by appropriate selection of the hardening accelerator.

Claims (9)

Claims

1. A bonding method comprising interposing an adhesive assistant, composed of a hardening accelerator for accelerating hardening of an a-cyanoacrylate adhesive and a flexible support member to which said hardening accelerator is attached, between a first bonding member and a second bonding member, applying an a-cyanoacrylate adhesive to the bonding faces or the adhesive assistant, and bonding the first bonding member to the second bonding member through the adhesive assistant.

2. A bonding method as claimed in Claim 1, wherein the adhesive assistant is placed on a part of the bonding face.

3. A bonding method as claimed in Claim 2, wherein the adhesive assistant is placed on a circumferential part of the bonding face.

4. A bonding method as claimed in any preceding Claim, wherein at least one of the first bonding member and the second bonding member has a porous face, an absorbent face, or an uneven face.

5. A bonding method as claimed in any preceding Claim, wherein the hardening accelerator is selected from an alkali metal hydroxide, a compound of alkali metal with a mono-, di or tri-basic acid organic acid, an alkaline earth metal oxide, an alkaline earth metal hydroxide, a metal soap, an amine, and a basic compound containing at least one primary, secondary, tertiary or quarternary nitrogen atom in the molecule.

6. A bonding method as claimed in any preceding Claim, wherein the flexible support member is selected from cotton, flax, wool, rayon, acetate, polyester, nylon, vinylon, glass fiber, sponge, urethane foamed goods, filter paper, and pulp.

7. A bonding method as claimed in any preceding Claim, wherein the flexible support member is in a form of cotton wool, cloth, tape, felt, sheet, nonwoven web, or string.

8. A bonding method as claimed in Claim 1, substantially as hereinbefore described.

9. A pair of members bonded together by a method as claimed in any preceding Claim.