JPH10219220A - Aqueous adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous adhesive excellent in water-resistant adhesion, boiling water-resistant adhesion and heat-resistant adhesion and good in pot life by including a specific proportions of an aqueous polymer emulsion and a specified modified polyvinyl alcohol. SOLUTION: This aqueous adhesive is obtained by formulating (A) an aqueous polymer emulsion containing a polymer of an ethylenically unsaturated monomer as a dispersoid (e.g. an ethylene-vinyl acetate-based copolymer emulsion) and (B) a modified polyvinyl alcohol having at least one kind of a functional group selected from a primary or secondary amino group in the molecule in the weight ratio A/B of (100/0.1) to (100/100). For example, the component A is obtained by carrying out emulsion polymerization of the ethylenically unsaturated monomer in the presence of a dispersion stabilizer for the emulsion polymerization, an initiator, etc., and the component B is obtained by copolymerizing the ethylenically unsaturated monomer having the primary or secondary amino group with vinyl acetate and saponifying the obtained copolymer. The aqueous adhesive is especially useful as the adhesive for a plywood.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based adhesive, and more particularly to a water-based adhesive, an adhesive for woodworking, an adhesive for plywood, an adhesive for paper, etc. More particularly, the present invention relates to an aqueous adhesive suitable as an adhesive for plywood.

[0002]

2. Description of the Related Art Conventionally, aqueous polymer emulsions have been widely used as adhesives for wood, paper, plastic and the like. However, in recent years, as the demand for the durability of the adhesive product has increased, improvement of the water resistance, boiling resistance and heat resistance of the aqueous adhesive has been strongly desired. Under such circumstances, many attempts have been made to introduce a crosslinkable group into the aqueous polymer emulsion, and the durability of the adhesive has been dramatically improved. For example, recently, a method of introducing an acetoacetyl group into an aqueous polymer emulsion has been studied,
Although a remarkable improvement in water resistance has been reported, the pot life is poor due to the extremely high reactivity of the acetoacetyl group itself, and severe restrictions are imposed when a third component is added to form a composition. In addition, many methods for introducing a carboxyl group into an aqueous emulsion and adding a polyfunctional crosslinking agent that reacts with the carboxyl group to the aqueous emulsion have been studied. However, also in this case, it is difficult to balance water resistance and storage viscosity stability (pot life).

[0003]

Under such circumstances, the present invention provides a water-based adhesive having excellent water-resistant adhesive strength, boiling-resistant adhesive strength, heat-resistant adhesive strength, and a good pot life. The purpose is to do so.

[0004]

The object of the present invention is to provide (A) an aqueous polymer emulsion and (B) a modified polyvinyl alcohol having at least one functional group selected from primary or secondary amino groups in the molecule, A) / (B)
(Weight ratio of solid content) is 100 / 0.1 to 100/100
This is achieved by providing an aqueous adhesive that is

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous polymer emulsion (A) constituting the aqueous adhesive of the present invention is an aqueous polymer emulsion in which the dispersoid obtained by ordinary emulsion polymerization is a polymer of an ethylenically unsaturated monomer. Can be used. Here, preferred examples of the ethylenically unsaturated monomer include ethylene, propylene, olefins such as isobutylene, vinyl chloride, vinyl fluoride, vinylidene chloride, halogenated olefins such as vinylidene fluoride, vinyl formate, vinyl acetate, and the like. Vinyl esters such as vinyl propionate and vinyl versatate; acrylic acids such as acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and 2-hydroxyethyl acrylate Methacrylates such as esters, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, 2-hydroxyethyl methacrylate, dimethyl acrylate Ethyl, dimethylaminoethyl methacrylate and quaternary products thereof, and acrylamides such as acrylamide, methacrylamide, N-methylolacrylamide, N, N-dimethylacrylamide, acrylamide-2-methylpropanesulfonic acid and its sodium salt. Monomers, styrene, α-methylstyrene, p-styrenesulfonic acid and styrene monomers such as sodium and potassium salts, other N-vinylpyrrolidone and the like, butadiene, isoprene,
Diene monomers such as chloroprene can be mentioned, and these can be used alone or as a mixture of two or more. Among these, particularly preferred aqueous polymer emulsions include vinyl ester (co) polymer emulsions represented by ethylene-vinyl acetate copolymer emulsions and the like, and (meth) acrylate ester (co) polymers. Emulsions and styrene-butadiene copolymer emulsions.

[0006] Emulsion polymerization dispersion stabilizers for emulsion polymerization of ethylenically unsaturated monomers include conventionally known anionic, cationic, amphoteric and nonionic surfactants, and radical polymerizable surfactants in the molecule. Low molecular surfactants such as reactive surfactants having a double bond, and conventionally known polyvinyl alcohols, also modified with carboxyl group, modified with sulfonic acid group, modified with cationic group, modified with thiol group, modified with oxyalkylene group, acetoacetate Various modified polyvinyl alcohols such as acetyl group modification, water-soluble cellulose derivatives such as hydroxymethyl cellulose, and substantially water-soluble polymer compounds such as poly (meth) acrylate can be used.

When the above aqueous polymer emulsion is produced by emulsion polymerization, conventionally known initiators (hydrogen peroxide, persulfate, water-soluble azo initiator V-50, etc.) may be used alone or in Rongalit, tartaric acid, etc. , L-ascorbic acid, used in combination with reducing substances such as ferrous chloride,
As the emulsion polymerization method, a conventionally known polymerization method such as a monomer batch charging method, a monomer sequential addition method, and a monomer emulsion addition method can be used. However, the aqueous polymer emulsion (A) of the present invention is not limited to the above production method.

The aqueous polymer emulsion (A) of the present invention can be obtained by emulsion polymerization of an ethylenically unsaturated monomer in an aqueous medium as described above, and can be prepared by various polymerization methods. A polymer obtained by mechanically post-emulsifying the union with an aqueous medium using various emulsion dispersion stabilizers, or having a water-soluble functional group (carboxyl group, amino group, sulfonic acid group, etc.) in the molecule obtained by various polymerization methods It also includes those obtained by self-emulsifying a polymer in an aqueous medium. Examples of these aqueous polymer emulsions include a polyurethane emulsion, a polyolefin emulsion, an epoxy emulsion, and a polyester emulsion. As the aqueous emulsion (A) used in the present invention, an aqueous polymer emulsion obtained by the above method or the like may be used alone, but if necessary, two or more kinds may be used in combination.

The (B) modified polyvinyl alcohol having at least one functional group selected from primary or secondary amino groups in the molecule, which constitutes the aqueous adhesive of the present invention, has a primary or secondary amino group in the molecule. There is no particular limitation as long as it is a modified polyvinyl alcohol-based polymer containing a group. The modified polyvinyl alcohol-based polymer having this functional group can be obtained by various methods, for example, 1. An ethylenically unsaturated monomer having a primary amino group or a secondary amino group or a primary A method in which an ethylenically unsaturated monomer having a functional group capable of forming an amino group or a secondary amino group (such as vinyl formamide) and vinyl acetate are copolymerized and then saponified, 2. Allyl glucidyl ether, etc. And a mercaptan having an amino group (such as 2-aminothiophenol or 2-aminoethanethiol) as a side chain epoxy group of a polymer comprising a monomer having an epoxy group and vinyl acetate.
A saponification method after an addition reaction using a catalyst as a catalyst, 3. a compound having a functional group capable of reacting with a hydroxyl group of polyvinyl alcohol in a molecule and having a primary or secondary amino group in a polyvinyl alcohol polymer. And the like. Furthermore, it can be obtained by a method of polymerizing an ethylenically unsaturated monomer having a primary amino group or a secondary amino group in the presence of a polyvinyl alcohol-based polymer having a mercapto group. In this case, a polyvinyl alcohol-based block polymer is obtained. The modified polyvinyl alcohol-based polymer obtained by the above two methods is preferred.

The modified polyvinyl alcohol having at least one functional group selected from primary or secondary amino groups in the molecule of the present invention may have a functional group other than primary or secondary amino groups in the molecule. Also, even if it has another monomer as a copolymerization component, there is no problem as long as the effects of the present invention are not impaired. Here, the other monomer components include ethylene, isobutylene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, (anhydrous) fumaric acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, allylsulfonic acid, Ryl sulfonic acid, vinyl sulfonic acid,
Acrylamide-2-methylpropanesulfonic acid, methacrylamide-2-methylpropanesulfonic acid, sulfopropyl acrylate, sulfopropyl methacrylate and their alkali salts, acrylamide, methacrylamide, trimethyl- (3-acrylamido-3-dimethylpropyl ) -Ammonium chloride, ethyl vinyl ether, butyl vinyl ether, N-vinyl pyrrolidone,
Examples include vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, and tetrafluoroethylene. Further, those having a functional group at the terminal obtained by polymerizing a vinyl ester monomer such as vinyl acetate in the presence of a thiol compound such as thiolacetic acid or mercaptopropionic acid may be used.

The content of the primary amino group or the secondary amino group in the modified polyvinyl alcohol having at least one functional group selected from primary or secondary amino groups in the molecule of the present invention is not particularly limited, and the content is not limited. May be appropriately selected according to the reaction conditions, but is usually from 0.1 to 30 mol%, preferably from 0.5 to 25 mol%, as a monomer unit containing the functional group.
Mol%. If the amount of the functional group is less than 0.1 mol%, the effect of introducing the functional group may not be sufficiently exhibited, while if it exceeds 30 mol%, the inherent properties of polyvinyl alcohol may not be sufficiently exhibited. In addition, the degree of polymerization of the modified polyvinyl alcohol having this functional group varies depending on the purpose of use and cannot be uniquely determined, but is preferably 100 or more, particularly 200 to 8000.
Is more preferred. The saponification degree of the modified polyvinyl alcohol is not particularly limited, but is preferably 50 mol% or more, and more preferably 80 to 99.9 mol%.

The aqueous adhesive of the present invention comprises (A) an aqueous polymer emulsion and (B) a modified polyvinyl alcohol having at least one functional group selected from primary or secondary amino groups in the molecule; / (B) (weight ratio of solid content) is 100 / 0.1 to 100/100.
When the ratio of (B) is smaller than (A) / (B) = 100 / 0.1, the main effects of the present invention are water-resistant adhesive strength,
Boil resistance and heat resistance are not sufficiently exhibited. on the other hand,
When the ratio of (B) is larger than (A) / (B) = 100/100, water-resistant adhesive strength, boiling adhesive strength, and heat-resistant adhesive strength are not sufficiently exhibited, and the pot life of the adhesive is deteriorated. It is not preferable because there is. A preferable range of (A) / (B) is 100 / 0.2 to 100/70.

The method for producing the aqueous adhesive of the present invention is not particularly limited, but generally, (A) an aqueous polymer emulsion and (B) at least one kind selected from primary or secondary amino groups in the molecule. It is produced by mixing under stirring an aqueous solution in which modified polyvinyl alcohol having a functional group is dissolved in water. Further, the water-based adhesive of the present invention, if necessary, in order to adjust its drying property, setting property, viscosity, film forming property, etc., various organic solvents such as toluene, perchrene, dichlorobenzene, trichlorobenzene, starch, etc. , Denatured starch, oxidized starch, sodium alginate,
Water-soluble polymers such as carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, maleic anhydride-isobutene copolymer, maleic anhydride-styrene copolymer, maleic anhydride-methylvinyl ether copolymer, and urea-formalin-based condensation resin, Thermosetting resins such as melamine-folimarin-based condensation resin, urea-melamine-folimarin-based condensation resin, phenol-folimarin-based condensation resin, resorcin-formalin-based condensation resin, and clay, kaolin, talc, calcium carbonate, wood powder, etc. Fillers, fillers such as flour, pigments such as titanium oxide, or other additives such as defoaming agents, dispersants, antifreeze agents, preservatives, and rust preventives.

The water-based adhesive of the present invention can be used for various woods, plywood,
It has excellent water, boiling and heat resistant adhesion to particle board, paper, fiber, non-woven fabric, etc.
It is used in applications such as woodworking adhesives, plywood adhesives, paperworking adhesives, paper tube adhesives, fiber treatment agents, and nonwoven fabric binders. In particular, when the aqueous adhesive of the present invention is used as an adhesive for plywood processing, a modified polyvinyl alcohol that absorbs formalin generated from plywood laminated with a formalin-based condensation resin adhesive and has an amino group by the formalin is used. The effect of further improving the water-resistant adhesiveness and the boiling-resistant adhesiveness due to the cross-linking of the polyester resin is observed. Therefore, it is suitably used for bonding plywood, bonding plywood / decorative paper, bonding plywood / wallpaper, bonding plywood / sticking board, bonding plywood / wood products, and the like. Here, as the formalin-based condensation resin adhesive, urea-formalin-based condensation resin adhesive, melamine-formalin-based condensation resin adhesive, urea-melamine-formalin-based condensation resin adhesive, phenol-formalin-based condensation resin adhesive And a resorcin-formalin-based condensation resin adhesive.

The method of bonding various substrates using the water-based adhesive of the present invention is not particularly limited, and a conventional coating method such as hand coating or roll coating may be applied in a coating amount suitable for the purpose and the substrate. An adhesive is applied and bonded. Although the bonding (or pressing) temperature is not particularly limited, it is usually performed at room temperature or higher.

[0016]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following Examples and Comparative Examples, “parts” and “%” mean on a weight basis unless otherwise specified. Further, the performance of the obtained adhesive composition as an adhesive for woodworking and an adhesive for plywood was evaluated in the following manner.

(1) Performance as an adhesive for woodworking Wood / wood (birch wood) adhesion test A specimen was prepared under the following conditions, and the adhesion was measured. [Adhesion conditions] Adherend material: birch / birch (mass), water content 8% Coating amount: 150 g / m ² (both sides coated) Deposition time: 1 minute Pressing conditions: 20 ° C., 24 hours, pressure 10 kg / cm ² [Measurement conditions] Compressive shear adhesive strength is measured according to JIS K-6852 Normal strength: Measured as it is after curing for 7 days at 20 ° C Water resistance: 20 ° C, cured for 7 days After immersion in water for 3 hours, measured in a wet state Resistance to warm water: After curing for 7 days at 20 ° C., the test piece was immersed in warm water at 60 ° C. for 3 hours, then cooled in 20 ° C. water and left wet Measured in condition

(2) Performance as a Plywood Adhesive Plywood / Plywood Adhesion Test A specimen was prepared under the following conditions, and the adhesion was evaluated. [Adhesion conditions] Adhering material: Plywood obtained by laminating using urea-formalin-based condensed resin adhesive (P1) Plywood obtained by laminating using aqueous vinyl urethane-based adhesive (P2) Coating amount: 150 g / M ² (single-side coating) Deposition time: 1 minute Pressing conditions: 20 ° C., 20 minutes, pressure 6 kg / cm ² [Measurement conditions] Heat-resistant peeling: 20 ° C., curing for 3 days, and drying with hot air at 60 ° C. for 3 hours. Observe the peeling state of the bonding surface in the case. Hot water immersion peeling: After curing at 20 ° C. for 3 days, immersion in hot water at 70 ° C. for 2 hours, and then drying with hot air at 60 ° C. for 3 hours, the peeled state of the adhesive surface was observed. Boiling water immersion peeling: After curing at 20 ° C. for 3 days, immersing in boiling water for 4 hours, and then performing hot air drying at 60 ° C. for 3 hours, the state of peeling of the bonded surface was observed.

(3) Viscosity Stability Test of Adhesive Changes in viscosity after 30 days when the adhesive was left at 5 ° C. and 50 ° C. were observed.

Synthesis Example of Modified Polyvinyl Alcohol Having at least One Functional Group Selected from Primary or Secondary Amino Group in Molecule Synthesis Example 1 In a reactor equipped with a stirrer, a reflux condenser, a nitrogen inlet, and a thermometer. And 405 parts of a vinyl acetate monomer, 11 parts of allyl glycidyl ether and 30 parts of methanol, and degassed by bubbling nitrogen gas for 15 minutes. Separately, an initiator solution prepared by dissolving 4.5 parts of 2,2-azoisobutyronitrile in 15 parts of methanol was prepared, and nitrogen was replaced by bubbling with nitrogen gas. Start raising the temperature of the reactor.
Then, a separately prepared initiator solution was added to initiate polymerization. Polymerization was carried out at 60 ° C. for 4 hours, and the polymerization was stopped by cooling. At this time, the solid content concentration was 54.8%. Subsequently, unreacted vinyl acetate monomer was removed while occasionally adding methanol at 30 ° C. under reduced pressure to obtain a methanol solution of polyvinyl acetate copolymer (concentration: 44.5%). This copolymer was a polyvinyl acetate copolymer containing 2.1 mol% of allyl glycidyl ether units (epoxy groups) and having a viscosity average molecular weight of 80 × 10 ³ . Next, a methanol solution of the polyvinyl acetate copolymer having an epoxy group obtained above (concentration: 44.5%) was placed in a reactor equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer.
After 100 parts were weighed and nitrogen gas was bubbled for 15 minutes, a solution prepared by dissolving 8.0 parts of 2-aminothiophenol and 0.03 part of sodium hydroxide in 48 parts of methanol was charged. After reacting at 50 ° C. for 2 hours with stirring, 40
After cooling to ° C., 40 parts of a 10% strength methanol solution of sodium hydroxide was added to perform saponification. The mixture was allowed to stand at 40 ° C. for 5 hours, pulverized, neutralized by adding 8 parts of acetic acid, subjected to Soxhlet extraction with methanol for 48 hours, and then dried at 60 ° C. for 20 hours or more to obtain a modified polyvinyl alcohol. The modified polyvinyl alcohol (PVA-1)
2.1 mol% of aniline groups were introduced, the vinyl alcohol content was 97.0 mol%, and the polymerization degree was 1,000.

Example 1 Ethylene-vinyl acetate copolymer emulsion (OM-4200 manufactured by Kuraray, solid content concentration 55%, Em-1) 100
Parts, 15% aqueous solution of PVA-1 of Synthesis Example 1
Parts were added to prepare an aqueous adhesive. Using this water-based adhesive, the above-mentioned (1) performance as an adhesive for woodworking,
(2) Performance as an adhesive for plywood, (3) Viscosity stability test of the adhesive. The results are shown in Tables 1 to 4.

Example 2 400 g of ion-exchanged water was placed in a 1-liter glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet.
g, PVA (degree of polymerization 1750, degree of saponification 88.5 mol)
%) And completely dissolved at 95 ° C. Next, after cooling this PVA aqueous solution and replacing with nitrogen, 40 g of vinyl acetate was charged while stirring at 140 rpm, the temperature was raised to 60 ° C., and then polymerization was started in the presence of a hydrogen peroxide / tartaric acid redox initiator system. . After 15 minutes from the start of the polymerization, 360 g of vinyl acetate was continuously added over 3 hours to complete the polymerization. A polyvinyl acetate emulsion (Em-2) having a solid content of 48.5% was obtained. 5 parts of dibutyl phthalate was added to and mixed with 100 parts by weight of this emulsion, and a 15% aqueous solution of PVA-1 of Synthesis Example 1 was added.
Parts were added to prepare an aqueous adhesive. The same test as in Example 1 was performed using this water-based adhesive. Table 1 shows the results.
It is shown in FIG.

Example 3 400 g of ion-exchanged water was placed in a 1-liter glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet.
g, a nonionic surfactant (Nonipol 200, manufactured by Sanyo Chemical Industries), 12 g, and an anionic surfactant (Sandet BL,
2 g (manufactured by Sanyo Chemical Industries) was charged and dissolved. Next, after replacing with nitrogen, 5 g of n-butyl acrylate and 5 g of methyl methacrylate were charged while stirring at 140 rpm, and the temperature was raised to 70 ° C., and 10 g of a 5% aqueous solution of ammonium persulfate was added to initiate polymerization. 15 minutes after the start of polymerization, n-acrylic acid
A mixture of 190 g of butyl and 190 g of methyl methacrylate was added continuously over 2 hours to complete the polymerization. Poly (n-acrylic acid) having a solid content of 46.5%
Butyl / methyl methacrylate) emulsion (Em-
3) was obtained. An aqueous adhesive was prepared by adding 10 parts of a 15% aqueous solution of PVA-1 of Synthesis Example 1 to 100 parts by weight of this emulsion. The same test as in Example 1 was performed using this water-based adhesive. The results are shown in Tables 1 to 4.

Example 4 Ethylene-vinyl acetate copolymer emulsion (Em-
1) 90 parts, polyurethane emulsion (Hydran HW-311 manufactured by Dainippon Ink and Chemicals, solid content concentration 45%, E
m-4) 10 parts and 10 parts of a 15% aqueous solution of PVA-1 of Synthesis Example 1 were added to prepare an aqueous adhesive. The same test as in Example 1 was performed using this water-based adhesive. The results are shown in Table 1.

Example 5 Ethylene-vinyl acetate copolymer emulsion (Em-
1) 100 parts, 15% aqueous solution 1 of PVA-1 of Synthesis Example 1
Parts were added to prepare an aqueous adhesive. The same test as in Example 1 was performed using this water-based adhesive. Table 1 shows the results.
It is shown in FIG.

Example 6 Ethylene-vinyl acetate copolymer emulsion (Em-
1) 100 parts, 15% aqueous solution of PVA-1 of Synthesis Example 1
An aqueous adhesive was prepared by adding 00 parts. The same test as in Example 1 was performed using this water-based adhesive. The results are shown in Tables 1 to 4.

Comparative Example 1 Ethylene-vinyl acetate copolymer emulsion (Em-
1) The same test as in Example 1 was performed using 100 parts. The results are shown in Tables 1 to 4.

Comparative Example 2 Ethylene-vinyl acetate copolymer emulsion (Em-
1) To 100 parts, 400 parts of a 15% aqueous solution of PVA-1 of Synthesis Example 1 was added to prepare an aqueous adhesive. The same test as in Example 1 was performed using this water-based adhesive. The results are shown in Tables 1 to 4.

Comparative Example 3 In place of the modified polyvinyl alcohol of Example 1, unmodified polyvinyl alcohol (polymerization degree 1000, saponification degree 98.
An aqueous adhesive was prepared in the same manner as in Example 1 except that 2 mol% of PVA-2) was used, and the same test as in Example 1 was performed. The results are shown in Tables 1 to 4.

Example 7 A vinylamine group-containing PVA obtained by copolymerizing vinyl formamide and vinyl acetate in place of the modified polyvinyl alcohol of Example 1 and then saponifying (polymerization degree 1050, saponification degree 98.5%) A water-based adhesive was prepared in the same manner as in Example 1 except that the modified amount of vinylamine group was 3.0 mol% and PVA-3) was used, and the same test as in Example 1 was performed. The results are shown in Tables 1 to 4.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

The water-based adhesive of the present invention has excellent standing viscosity stability, water-resistant adhesive strength, boiling-resistant adhesive strength, and heat-resistant adhesive strength, and is suitable for woodworking adhesives, plywood adhesives, and papers. It is suitably used as an adhesive or the like. It is particularly effective as an adhesive for plywood laminated with a formalin-based condensation resin adhesive.

Claims (2)

[Claims] 1. An aqueous polymer emulsion comprising: (A) an aqueous polymer emulsion; and (B) a modified polyvinyl alcohol having at least one functional group selected from primary or secondary amino groups in the molecule, wherein (A) / (B) (solid Weight ratio of 10)
An aqueous adhesive having a ratio of 0 / 0.1 to 100/100. 2. An adhesive for plywood comprising the aqueous adhesive according to claim 1.