WO1999058622A1

WO1999058622A1 - Rapid-curing adhesive composition

Info

Publication number: WO1999058622A1
Application number: PCT/US1999/010338
Authority: WO
Inventors: Jiang Wan; Takeshi Kamikaseda
Original assignee: National Starch And Chemical Investment Holding Corporation
Priority date: 1998-05-12
Filing date: 1999-05-12
Publication date: 1999-11-18
Also published as: EP1040174A1; AU3899099A

Abstract

A rapid-curing adhesive composition is provided which comprises liquid component (A) and (B). The liquid component (A) consists essentially of an aqueous solution or dispersion containing: (a) a water soluble polymer having a carboxyl group and a hydroxyl group in the molecule thereof; and (b) an aqueous polymer having at least one of a primary amino group and a secondary amino group in the molecule thereof. The liquid component (B) consists essentially of an aqueous solution or dispersion containing (c) a water soluble aldehyde compound. The rapid-curing adhesive composition of the present invention can quickly exhibit its initial adhesive strength, and is superior in penetration property, post-curing adhesive strength and water resistance. More specifically, when the liquid components (A) and (B) are respectively applied on two mating surfaces and the surfaces are brought into contact with each other, the aqueous polymer (component (b)) in the liquid component (A) instantaneously reacts with the water soluble aldehyde compound (component (c)) in the liquid component (B) to give a gel. The gel has a small molecular weight and, hence, has a proper elasticity and viscosity thereby to readily penetrate into the surfaces. The intact water soluble polymer (component (a)) in the liquid component (A) also readily penetrates into the surfaces. Further, a gelation reaction between the water soluble polymer (component (a)) and the water soluble aldehyde compound (component (c)) starts thereby to polymerize the gel in the mating surfaces. The two-step gelation allows the adhesive composition to exhibit its initial adhesive strength in a short time and to have an excellent penetration property and high post-curing adhesive strength.

Description

RAPID-CURING ADHESIVE COMPOSITION

BACKGROUND OF THE INVENTION The present invention relates to a rapid-curing adhesive composition and, more particularly, to a rapid-curing two-part adhesive composition of separate application type

DESCRIPTION OF THE INVENTION

In the lumber industry and the like, rapid-curing adhesives have been desired in an attempt at continuous mass production of laminates and the like utilizing a conveyor system in a production line One exemplary rapid-curing adhesive is a cyanoacrylate instantaneous adhesive which, however, is not suitable for practical applications because of its high cost Heretofore, the following two-part adhesive compositions (1 ) to (4) of separate application type have been proposed which are superior in practicality

(1 ) An adhesive composition comprising (I) a first liquid component consisting essentially of a urea resin adhesive, and (II) a second liquid component consisting essentially of a mixture of an aqueous solution of a polymer such as polyvinyl alcohol and a strong acid such as phosphoric acid or the like

(2) An adhesive composition comprising (I) a first liquid component consisting essentially of an aqueous solution of a soluble protein having an amide bond in the molecule thereof or an aqueous solution of a synthetic polymer having an imide group in the molecule thereof, and (II) a second liquid component consisting essentially of an aqueous solution of a water soluble dialdehyde compound, as disclosed in Japanese Patent Publication No SHOU 63-17871 (1988)

(3) An adhesive composition comprising (I) a first liquid component consisting essentially of at least one of an aqueous solution and an aqueous emulsion which contains a polymer having an acetoacetyl group in the molecule thereof, and (II) a second liquid component consisting essentially of an aqueous solution of a hydrazine compound, as disclosed in Japanese Patent Publication No HEI 1-60192 (1989)

(4) An adhesive composition comprising (I) a first liquid component consisting essentially of an aqueous polymer resin having a primary ammo group or a secondary ammo group in the molecule thereof, and (II) a second liquid component consisting essentially of an aldehyde compound, as disclosed in Japanese Patent Laid- Open No HEI 3-281683 (1991 )

However, the adhesive compounds (1 ) to (4) have the following drawbacks The composition (1 ) has not come into wide use, because the acid (e.g , phosphoric acid) is liable to accelerate aging of the urea resin adhesive and reduce the strength of a wood material

The adhesive composition (2) cures through a crosslinking reaction between the soluble protein or the synthetic polymer in the first liquid component and the water soluble dialdehyde compound in the second liquid component However, the crosslinking reaction is thermally reversible, presenting a durability problem The adhesive composition (2), after having cured, has a high adhesive strength because of its high gelation rate and a great hardness of the resulting gel, but is inferior in adherent penetration property into a body to be adhered, resulting in an unsatisfactory adhesive reliability (impact resistance) Further, the high gelation rate shortens the allowable time between the step of bonding mating surfaces and the pressing step, also presenting a workability problem

The adhesive composition (3) which employs the aqueous solution of the polymer having an acetoacetyl group in the molecule thereof is inferior in shelf life, and shows a defect in a point of high pH dependence in the crosslinking reaction thereof Since the adhesive composition (3) has a low gelation rate, development of its initial adhesive strength is retarded In addition, the adhesive composition (3), after having cured, exhibits low adhesive strength because the resulting gel has not become hard Further, the composition (3) has insufficient water resistance because number of its crosslinking point in the molecule is very few The adhesive composition (4) has a high gelation rate, which shortens the allowable time between the step of bonding mating surfaces and the pressing step, presenting a workability problem In addition, the adhesive composition, after having cured, exhibits insufficient water resistance Therefore, the adhesive composition is used only for limited scope of applications As described above, there has not been provided a rapid-curing adhesive composition which can quickly exhibit its initial adhesive strength and its superior in adherent penetration property, post-curing adhesive strength and water resistance, and development of such an adhesive composition has been desired In view of the foregoing, it is an object of the present invention to provide a rapid- curing adhesive composition which can quickly exhibit its initial adhesive strength and which is superior in adherent penetration property, post-curing adhesive strength and water resistance

SUMMARY OF THE INVENTION

The inventors of the present invention have made intensive studies to obtain a rapid-curing adhesive composition which can quickly exhibit its initial adhesive strength and which is superior in adherent penetration property, post-curing adhesive strength and water resistance In the course of the studies, the inventors have found that quick exhibition of the initial adhesive strength and the superior adherent penetration property can be ensured where the gelation rate is moderate and the resulting gel has an elasticity, while the high water resistance can be ensured where number of the crosslinking point of the molecule is kept much more As a result of further research and development, the inventors have accomplished the present invention In accordance with the present invention, there is provided a rapidOcuπng adhesive composition which comprises liquid components (A) and (B) The liquid component (A) consists essentially of an aqueous solution or dispersion containing (a) a water soluble polymer having a carboxyl group and a hydroxyl group in the molecule thereof, and (b) an aqueous polymer having at least one of a primary ammo group and a secondary ammo group in the molecule thereof The liquid component (B) consists essentially of an aqueous solution or dispersion containing (c) a water soluble aldehyde compound

When the liquid components (A) and (B) are respectively applied onto two mating surfaces and the surfaces are brought into abutting relationship, the specific aqueous polymer (component (b)) in the liquid component (A) instantaneously reacts with the water soluble aldehyde compound (component (c)) in the liquid component (B) to give a gel The gel has a small molecular weight and, hence, has sufficient elasticity and viscosity thereby to readily penetrate into the surfaces of the body to applied The intact water soluble polymer (component (a)) in the liquid component (A) also readily penetrates into the surfaces Further, a gelation reaction between the water soluble polymer (component (a)) and the water soluble aldehyde compound (component (c)) starts thereby to polymerize the gel in the mating surfaces The two-step gelation allows the adhesive composition to exhibit its initial adhesive strength in a short time and to have high adherent penetration property and high post-curing adhesive strength Moreover, the water soluble polymer (component (a)) and the aqueous polymer (component (b)) have functional groups including a carboxyl group, a hydroxyl group, a primary ammo group and a secondary ammo group, so that the cured composition has an increased number of crosslinking points. As a result, the cured composition exhibits high water resistance with higher crosslinking density

Further, where the liquid component (A) contains (d) at least one of a synthetic resin emulsion and a rubber latex in addition to the water soluble polymer (component (a)) and the aqueous polymer (component (b)), adhesion of the adhesive composition to various materials and toughness of the materials can be enhanced Still further, where the liquid component (B) contains (e) a crosslinking agent in addition to the water soluble aldehyde compound (component (c)), the gelation reaction between the liquid components (A) and (B) can be accelerated Thus, the adhesive composition can exhibit its initial adhesive strength in a shorter time Moreover, the post- curing water resistance and heat resistance can be improved by the crosslinking

DETAILED DESCRIPTION OF THE INVENTION The present invention will hereinafter be described in detail A rapid-curing adhesive composition according to the present invention includes specific liquid components (A) and (B) The liquid component (A) consists essentially of an aqueous solution or dispersion containing (a) a water soluble polymer having a carboxyl group and a hydroxyl group in the molecule thereof, and (b) an aqueous polymer having at least one of a primary ammo group and a secondary ammo group in the molecule thereof The water soluble polymer (component (a)) in the liquid component (A) is not particularly limited as long as it is water soluble Examples of specific water soluble polymers include a carboxylated polyvmyl alcohol and a carboxylated methyl cellulose (CMC) The carboxylated polyvmyl alcohol to be used is not specifically limited One exemplary carboxylated polyvmyl alcohol may be prepared by first copolymeπzing vinyl acetate with an unsaturated acid such as maleic acid, itaconic acid, acrylic acid or methacrylic acid and then saponifying the resulting copolymer The polymerization degree and saponification degree of the resulting polymer are not particularly limited

Proportions of carboxyl groups and hydroxyl groups in the component (a) is not specifically limited, but are each preferably not less than 0 5 mol% of the total component (a)

The aqueous polymer (component (b)) to be contained along with the component (a) in the liquid component (A) is not particularly limited as long as it is aqueous (i e water soluble or emulsifiable) Examples of the aqueous polymer include polyamines, polyamide amines and compounds having as a side chain at least one of a primary ammo group and a secondary ammo group These may be used either alone or in combination Among these compounds, those having a sufficient water solubility may be used as the aqueous polymer (component (b)) as it is, while those not having water solubility are emulsified with a surfactant or the like for use as the aqueous polymer (component (b))

Examples of specific polyamines include polyethylene imine, polypropylene imine and polyamines obtained by reacting polyfunctional amines such as 1 ,2-ethylene diamine or ammonia with polyfunctional epoxy compounds

Examples of specific polyamide amines include those obtained through a condensation reaction between polybasic acids such as adipic acid and polyfunctional amines such as 1 ,2-ethylene diamine Examples of the compound having a side chain of at least one of a primary ammo group and a secondary ammo group include acrylamine, vinylamine and allylamine More specific examples thereof include (1 ) acrylamine obtained by modifying some of carboxyl groups in a carboxyl-containmg acrylic resin with an alkylene imine and modifying the remaining carboxyl groups with a base such as tπethylamine for solubihzation thereof, as disclosed in U S Patent No 4,221 ,885, (2) an emulsion of acrylamine with a primary ammo group or a secondary ammo group which is obtained by modifying a carboxyl- containmg emulsion with an alkylene imine, as disclosed in U S Patent No 3,467,611 , (3) an emulsion of acrylamine with a primary ammo group which is obtained by reacting an emulsion containing carbonyl groups (limited to aldehyde and keto groups) with a hydrazine derivative, such as hydrazine hydrate, having at least two residual hydrazine groups in the molecule thereof, as disclosed in Japanese Patent Laid-Open Nos SHOU 54-110248 (1979) and SHOU 62-72742 (1987), and (4) vinylamine having a primary ammo group, as disclosed in Japanese Patent Laid-Open No SHOU 61-51006 (1986) Proportions of primary am o groups and secondary ammo groups in the component (b) are not particularly limited, but are each preferably not less than 1 % by weight of the total component (b)

In the liquid component (A) of the rapid-curing adhesive composition of the present invention, the component (a) and the component (b) are present in a weight ratio of (a)/(b) = 1/0 1 to 1/10, more preferably (a)/(b) = 1/0 2 to 1/5, on a solids basis If the weight ratio is out of the aforesaid range, the initial adhesive strength of the adhesive composition may be reduced

The liquid component (A) may contain (d) at least one of a synthetic resin emulsion and a rubber latex in addition to the components (a) and (b) Adhesion of the adhesive composition to various materials and toughness of the materials can be enhanced by using the liquid component (A) containing the component (d) as well as the components (a) and (b) The synthetic resin emulsion to be contained as the component (d) is not particularly limited, but examples thereof include an emulsion of vinyl acetate, emulsions of copolymers of vinyl acetate with unsaturated acids such as acrylic acid, maleic acid, fumaπc acid and crotonic acid and esters of these acids, emulsions of ethylene-vinyl acetate copolymers, emulsions of styrene-acrylate copolymers and emulsions of acrylate copolymers These may be used either alone or in combination Examples of the rubber latex to be contained as the component (d) include a styrene- butadiene latex, a butadiene-acrylonitrile latex, a chloroprene latex and a butyl rubber latex These may be used either alone or in combination

In the liquid component (A), the component (d) is preferably present in an amount of not greater than 10 parts by weight, more preferably 1 to 5 parts by weight, per one part by weight of the aqueous solution or dispersion containing the components (a) and (b) on a solids basis If the amount of the component (d) exceeds 10 parts by weight, the proportions of carboxyl groups and hydroxyl groups in the component (a) and primary ammo groups and secondary ammo groups in the component (b) are relatively reduced, so that the crosslinking density of the cured adhesive composition may be lowered Therefore, sufficient effects cannot be expected for the acceleration of the exhibition of the initial adhesive strength and the improvement of the water resistance

The liquid component (A) of the rapid-curing adhesive component of the present invention can be prepared, for example, by fully mixing the component (a) with the component (b) with stirring until a viscous mixture is obtained Then, as required, the component (d) is mixed with the resulting mixture The liquid component (B) of the rapid-curing adhesive composition to be used along with the liquid component (A) consists essentially of an aqueous solution or dispersion containing (c) a water soluble aldehyde compound The water soluble aldehyde compound (component (c)) to be contained in the liquid component (B) is not particularly limited, but is preferably a compound or a hydrate thereof which virtually has an aldehyde group when being dissolved in a solvent such as water or an alcohol Examples thereof include monoaldehyde compounds, dialdehyde compounds, paraformaldehyde (linear polymer of formaldehyde), dialdehyde starch and 2,3-dιhydroxy- 1 ,4-dιoxane, among which the dialdehyde compounds are particularly preferred These may be used either alone or in combination Exemplary monoaldehyde compounds include formaldehyde, acetaldehyde and the like Exemplary dialdehyde compounds include glyoxal, malondialdehyde, succmdialdehyde, glutardialdehyde, pimelmdialdehyde, subeπndialdehyde, among which glyoxal is particularly preferred

The liquid component (B) of the rapid-curing adhesive composition of the present invention may contain (e) a crosslinking agent in addition to the component (c) By using the liquid component (B) containing the component (e) as well as the component (c), a gelation reaction between the liquid components (A) and (B) can be accelerated for quick exhibition of the initial adhesive strength, and the post-curing water resistance and heat resistance can be improved by the crosslinking Usable as the crosslinking agent (component (e)) are those which can crosslink the functional groups of the water soluble polymer (component (a)) and the aqueous polymer (component (b)), i e , at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, a primary ammo group and a second ammo group The crosslinking agent is preferably miscible with the component (c) without any reaction therewith, and capable of promoting the crosslinking reaction which proceeds in parallel to the gelation reaction when two mating surfaces are brought into contact with each other after the liquid components (A) and (B) are respectively applied onto the mating surfaces Examples of specific crosslinking agents include polyepoxy compounds such as polyepoxides of polyols

The liquid component (B) may further contain additives such as a colorant, a surface active agent and a viscosity controller, as required, which do not adversely affect the water soluble aldehyde compound (component (c))

The liquid component (B) can be prepared, for example, by dissolving the water soluble aldehyde compound (component (c)) and any of the aforesaid optional compounds in a solvent such as water or an alcohol The rapid-curing adhesive composition thus obtained is used, for example, in the following manner First, the liquid components (A) and (B) are respectively applied onto two mating surfaces The mating surfaces are brought into contact with each other, followed by pressing The adhesive composition can exhibit a sufficient adhesive strength within 30 seconds to several minutes at room temperature Thus, the rapid-curing adhesive composition of the present invention cures, exhibiting its initial adhesive strength in a shorter time Therefore, the resulting produce can be released from pressure in a very short time The product is allowed to stand for complete curing of the adhesive composition, which finally exhibits a high adhesive strength The product can be subjected to a machining operation such as a cutting operation immediately after being released from pressure In general, aqueous adhesive compositions should be subjected to the pressing at room temperature for a very long time to obtain a sufficient final adhesive strength On the contrary, the rapid-curing adhesive composition of the present invention quickly develops its initial adhesive strength as described above and, therefore, exhibits a sufficient final adhesive strength after the short-time pressing and curing

Alternatively, the bonding of two mating surfaces may be achieved in the following manner After the liquid component (B) is preliminary applied onto one of the mating surfaces and dried, the liquid component (A) is applied onto the other surface and the mating surfaces are brought into abutting relationship The rapid-curing adhesive composition of the present invention, though being of two-part separate application type, is superior in workability like a one-part adhesive It is also possible that, after the liquid component (B) is preliminary applied onto one of two mating surfaces and dried, the liquid component (A) is applied onto the same surface and the mating surfaces are brought into abutting relationship Therefore, woodworking operations, for example, can be performed on a continuous conveyor system with the use of the rapid-curing adhesive composition of the present invention

Examples and comparative examples of the present invention will hereinafter be described In these examples and comparative examples, the parts and the percentages are given by weight, unless otherwise specified

EXAMPLE 1 First, 60 parts of a 15% aqueous solution of carboxylated polyvmyl alcohol (KM618 available from Kuraray Co , Ltd ) was mixed with 9 parts of polyethylene imine (100% solids, EPOMINE SP003 available from Nippon Shokubai Kagaku Kogyo Co , Ltd ) with stirring to give a viscous mixture, which was used as the liquid component (A). A 15% aqueous solution of glyoxal was prepared, which was used as the liquid component

(B).

COMPARATIVE EXAMPLE 1 An aqueous solution of a synthetic polymer having an imide group was prepared in the following manner, and used as the liquid component (A). More specifically, 200 parts of a maleimide resin (ISOBAM 304 available from Kuraray Co., Ltd.) was dissolved in 50 parts of 20% aqueous ammonia, and then 650 parts of water was added thereto. Further, the pH of the resulting mixture was adjusted at 7 by adding 10% hydrochloric acid thereto. The resulting solution was used as the liquid component (A). A 15% aqueous solution of glyoxal was prepared as in Example 1 , and used as the liquid component (B).

COMPARATIVE EXAMPLE 2 An aqueous solution of a polymer having an acetoacetyl group was prepared in the following manner, and used as the liquid component (A). More specifically, a 20% aqueous solution of acetoacetylated polyvinyl alcohol (GOSEFIMER Z200 available from Nippon Gosei Kagaku Kogyo K.K.) was prepared, which was used as the liquid component (A). A 15% aqueous solution of dihydrazide adipate was prepared, which was used as the liquid component (B). The adhesive compositions (liquid components (A) and (B)) thus obtained in

EXAMPLE 1 and COMPARATIVE EXAMPLES 1 and 2 were each tested in the following manner for determination of the compression shear adhesive strength thereof. The results are shown in TABLE 1.

The compression shear adhesive strength of each of the adhesive compositions was determined in accordance with the "Testing methods for strength properties of adhesives in shear by compression loading" specified by JIS K 6852. More specifically, two test strips (25mm X 30 mm X 10 mm) of birch were prepared for each test sample. The liquid component (A) was applied in an amount of about 200g/m2 onto a mating surface of one of the test strips, while the liquid component (B) was applied in an amount of about 50g/m2 onto a mating surface of the other test strip In turn, the test strips were joined together with their mating surfaces brought into contact with each other, and pressed with a pressure of about 10kg/cm2 for a predetermined period After being released from the pressure, the resulting test sample was allowed to stand for curing of the adhesive composition The compression shear adhesive strength of the adhesive composition was measured after 5-mιnute curing and after 24-hour curing These operations were all performed at 20°C. The values of compression shear adhesive strength shown in TABLE 1 are mean values obtained with three test samples It is noted that a higher wood fracture rate indicates a more excellent penetration property of an adhesive composition

TABLE 1

Note The percentages in parentheses indicate the wood fracture rates after 24-hour curing

As can be understood from TABLE 1 , the adhesive composition of EXAMPLE 1 exhibited higher levels of compression shear adhesive strength than the adhesive compositions of COMPARATIVE EXAMPLES 1 and 2 The test samples employing the composition of EXAMPLE 1 had a wood failure rate of 100% after the 24-hour curing, while the test samples employing the compositions of COMPARATIVE EXAMPLES 1 and 2 had a wood failure rate of 0% Therefore, the adhesive composition of EXAMPLE 1 is superior in the adhesive reliability to the compositions of COMPARATIVE EXAMPLES 1 and 2 EXAMPLES 2 TO 8 For preparation of adhesive compositions of EXAMPLES 2 to 8, ingredients were mixed with stirring in accordance with the formulations shown in TABLE 2 to give viscous mixtures, which were each used as the liquid component (A). A 15% aqueous solution of glyoxal was prepared as in EXAMPLE 1 , and used as the liquid component (B).

TABLE 2

*1 KM618 (15% solids) available from Kuraray Co Ltd

*2 EPOMINE SP003 (100% solids) available from Nippon Shokubai Co Ltd

*3 SUMIKAFLEX 400 (55% solids) available from Sumitomo Chemical Co , Ltd

The compression shear adhesive strength of each of the adhesive compositions (liquid components (A) and (B)) thus prepared in EXAMPLES 2 to 8 was determined in the same manner as described above The results are shown in TABLE 3 In COMPARATIVE EXAMPLE 3, an emulsion of ethylene-vinyl acetate copolymer resin (55% solids, SUMIKAFLEX 400 available from Sumitomo Chemical Co , Ltd ) as used in EXAMPLES 6 to 8 was applied in an amount of about 200g/m2 onto a mating surface of one of two test strips, and the liquid composition (B) was not applied onto a mating surface of the other test strip Then, the test strips were joined together

TABLE 3

As can be understood from TABLE 3, the adhesive compositions of EXAMPLES 2 to 8 each exhibited higher levels of compression shear adhesive strength than the adhesive composition of COMPARATIVE EXAMPLE 3 The test samples employing the compositions of EXAMPLES 2 to 8 had a wood fracture rate of 100% after the 24-hour curing, while the test samples employing the composition of COMPARATIVE EXAMPLE 3 had a wood fracture rate of 0% Therefore, the adhesive compositions of EXAMPLES 2 to 8 are superior in the adhesive reliability to the composition of COMPARATIVE EXAMPLE 3

EXAMPLES 9 TO 15 For preparation of adhesive compositions of EXAMPLES 9 to 15, ingredients were mixed with stirring in accordance with the formulations shown in TABLE 4 to give viscous mixtures, which were each used as the liquid component (A) A 20% aqueous solution of glutaraldehyde was prepared, which was used as the liquid component (B) TABLE 4

*1 KIKKOLATE ULV (15% solids) available from Nichinn Chemical Industries Ltd

*2 TOMIDE 296 (100% solids) available from Tohto Kasei Co Ltd

*3 Lx438C (55% solids) available from Nippon Zeon Co , Ltd

The compression shear adhesive strength of each of the adhesive compositions

(liquid components (A) and (B)) thus prepared in EXAMPLES 9 to 15 was determined in the same manner as described above The results are shown in TABLE 5 In COMPARATIVE EXAMPLE 4, a styrene-butadiene copolymer latex (55% solids, Lx438C available from Nippon Zeon Co , Ltd ) as used in EXAMPLES 13 to 15 was applied in an amount of about 200g/m2 onto a mating surface of one of two test strips, and the liquid composition (B) was not applied onto a mating surface of the other test strip Then, the test strips were joined together

TABLE 5

Note The percentages in parentheses indicate the wood fracture rates after 24-hour curing.

As can be understood from TABLE 5, the adhesive compositions of EXAMPLES 9 to 15 each exhibited higher levels of compression shear adhesive strength than the adhesive composition of COMPAF ATIVE EXAMPLE 4. The test samples employing the compositions of EXAMPLE 9 to 15 had a wood fracture rate of 100% after the 24-hour curing, while the test samples employing the composition of COMPARATIVE EXAMPLE 4 had a wood fracture rate of 0%. Therefore, the adhesive compositions of EXAMPLES 9 to 15 are superior in the adhesive reliability to the composition of COMPARATIVE EXAMPLE 4.

As previously described, the rapid-curing adhesive composition of the present invention comprises the liquid components (A) and (B). The liquid component (A) consists essentially of the aqueous solution or dispersion containing the water soluble polymer (component (a)) having a carboxyl group and a hydroxyl group in the molecule thereof and the aqueous polymer (component (b)) having at least one of a primary amino group and a secondary amino group in the molecule thereof. The liquid component (B) consists essentially of the aqueous solution or dispersion containing the water soluble aldehyde compound (component (c)). The rapid-curing adhesive composition of the present invention can exhibit its initial adhesive strength quickly, and is superior in penetration property, post-curing adhesive strength and water resistance. More specifically, when the liquid components (A) and (B) are respectively applied onto two mating surfaces and the surfaces are brought into contact with each other, the aqueous polymer (component (b)) in the liquid component (A) instantaneously reacts with the water soluble aldehyde compound (component (c)) in the liquid component (B) to give a gel. The gel has a small molecular weight and, hence, has a proper elasticity and viscosity thereby to readily penetrate into the surfaces. The intact water soluble polymer (component (a)) in the liquid component (A) also readily penetrates into the surfaces. Further, a gelation reaction between the water soluble polymer (component (a)) and the water soluble aldehyde compound (component (c)) starts thereby to polymerize the gel on the mating surfaces. The two-step gelation allows the adhesive composition to exhibit its initial adhesive strength in short time and to have a high penetration property and a high post-curing adhesive strength. Moreover, the water soluble polymer (component (a)) and the aqueous polymer (component (b)) have functional groups including carboxyl groups, hydroxyl groups, so that the cured composition has a increased number of crosslinking points. As a result, the cured composition exhibits a high water resistance with a higher crosslinking density.

Further, where the liquid component (A) contains at least one (component (d)) of the synthetic resin emulsion and the rubber latex in addition to the water soluble polymer (component (a)) and the aqueous polymer (component (b)), adhesion of the adhesive composition to various materials and toughness of the materials can be enhanced.

Still further, where the liquid component (B) contains the crosslinking agent (component (e)) in addition to the water soluble aldehyde compound (component (c)), the gelation reaction between the liquid components (A) and (B) can be accelerated. Thus, the adhesive composition quickly exhibits its initial adhesive strength. Moreover, the post- curing water resistance and heat resistance can be improved by the crosslinking.

As described above, the rapid-curing adhesive composition of the present invention can quickly develop its initial adhesive strength, so that the press time can be shortened for improvement of the productivity. Further, the adhesive composition has a high post-curing adhesive strength and an excellent adherent penetration property. Particularly, the adhesive composition has a high post-curing adhesive strength and an excellent adherent penetration property. Particularly, the adhesive composition readily penetrates into a wood adherent (this is indicated by the high wood fracture rate). Thus, the adhesive composition is superior in adhesive reliability. In addition, the adhesive composition has a high water resistance and, therefore, can be used for bonding various types of materials, for example, wood materials such as lumber, chip boards and hardboards; inorganic materials such as slates and calcium silicate plates; plastic materials such as melamine resin decorative sheets, bakelite plates and foamed polystyrene boards; and paper materials such as corrugated boards, paper boards and craft paper sheets. Therefore, the adhesive composition will find extensive application in woodworking, furniture assembly, paper article manufacturing. For example, the adhesive composition may be used for plane- and edge-bonding of flush panels, fancy plywood, pre-fab panels, laminates and the like, for bonding of tenons, dowels, miters, butts and corner wood pads, and for production of corrugated boards, laminated paper sheets, paper pipes, paper bags and the like.

Claims

What is claimed:

1. A rapid-curing adhesive composition comprising liquid components (A) and (B), the liquid component (A) comprising an aqueous solution or dispersion containing: (a) a water soluble polymer having a carboxyl group and a hydroxyl group in a molecule thereof; and

(b) an aqueous polymer having at least one of a primary amino group and a secondary amino group in a molecule thereof, the liquid component (B) comprising an aqueous solution or dispersion containing:

(c) a water soluble aldehyde compound.

2. The rapid-curing adhesive composition of Claim 1 , wherein the water soluble polymer of the component (a) and the aqueous polymer of the component (b) are present in the liquid component (A) in a weight ratio of (a)/(b) = 1/0.1 to 1/10 on a solids basis.

3. The rapid-curing adhesive composition of Claim 1 , wherein the liquid component

(A) further comprises:

(d) at least one of a synthetic resin emulsion and a rubber latex, which is present in an amount of not greater than 10 parts by weight per one part by weight of the aqueous solution or dispersion containing the components (a) and (b) on a solids basis.

4. The rapid-curing adhesive composition of Claim 1 , wherein the liquid component

(B) further comprises: (e) a crosslinking agent that reacts with at least one of the functional groups contained in the water soluble polymer of the component (a) and the aqueous polymer of the component (b).