JPH089710B2 - Latex for water-based adhesive - Google Patents

Description

TECHNICAL FIELD The present invention relates to a binder for water-based adhesives, and more particularly to a carboxy-modified butadiene-based copolymer latex that imparts excellent water-resistant adhesive strength to water-based adhesives.

[Conventional technology]

Water-based adhesives that use butadiene-based copolymer latex as a binder (water-based adhesives) are used to bond ceramic tiles (Japanese Patent Publication No. 58-33274), floor materials such as carpets, cushion floors, and PVC tiles ( U.S. Pat. No. 3,625,807), adhesion of wood (JP-A-52-77146),
Adhesion of veneer decorative thin plates and decorative paper (JP-A-58-183772),
Adhesion of plywood (JP-A-58-11571, JP-A-58-84875)
No.), adhesion of boards (Japanese Patent Publication No. 48-1824), adhesion of corrugated cardboard (Japanese Patent Publication No. 58-180570), adhesion of leather and laminates of various films (Japanese Patent Publication No. 60-11759), backing material for carpet. It is widely used in a wide range of applications such as adhesion of rubber and adhesion of fibers and rubber.

As the butadiene-based copolymer latex, carboxy-modified styrene / butadiene copolymer latex is often used, but in the adhesive for ceramic tile,
It is described in JP-B-58-33274 that a styrene / butadiene copolymer latex having a large proportion of carboxyl groups and soluble in an alkaline region can also be used.

The performance required for the above-mentioned water-based adhesive is excellent adhesive strength and initial adhesiveness, but in addition to these performances, water-resistant adhesive strength (wet adhesive strength or water resistance) is often required. It is said that

As a method for obtaining an excellent water-resistant adhesive strength, when a water-based adhesive is dried by heating, a method of adding a compound having heat reactivity to a butadiene-based copolymer latex (Japanese Patent Application Laid-Open No. SHO 61-242242)
58-7467, JP-A-58-183772, JP-A-52-7716,
JP-A-53-119939, etc.) is overwhelmingly large, and in the case of drying at room temperature, a method in which a tackifier resin is dissolved in an organic solvent and / or a plasticizer in a butadiene-based copolymer latex is added. Kosho 60-11759, Japanese Examined Sho 48-1824,
JP-A-58-152074, etc.) is generally known.

[Problems to be solved by the invention]

However, the method of adding a compound having heat reactivity is easy to obtain an aqueous adhesive having excellent water-resistant adhesive strength, lack of stability over time of the aqueous adhesive, or used in a relatively short time, It has a drawback that it must be used as a two-pack type. On the other hand, the latex-based adhesive used in the case of drying at room temperature has a good temporal stability of the welding agent, but the water-resistant adhesive strength is not sufficient. In particular, the butadiene-based copolymer latex water-based adhesive used for adhering tiles in places where there is a lot of contact with water or warm water, such as bathrooms and shower rooms, does not sag even when the adhesive is applied to the vertical surface Since it requires a high viscosity to prevent the tiles from slipping even when pasted to a tile, a relatively large amount of a thickener (water-soluble polymer) that lowers the water-resistant adhesive strength is included, making it suitable for use. I can't stand it. Although the use of an alkali-soluble latex that also functions as a thickener has been proposed as described above, the amount of thickener used can be significantly reduced, but the latex polymer can dissolve in water. Since it is easy to do, only adhesives with low water-resistant adhesive strength can be obtained.

An object of the present invention is to provide a specific carboxy-modified butadiene copolymer latex-based water-based adhesive which has high water-resistant adhesive strength and can be applied to adhesion of ceramic tiles such as bathrooms and shower rooms.

[Means for solving problems]

A latex forming a dry film having good water resistance was studied, paying attention to the fact that the water-resistant adhesive strength of the water-based adhesive is greatly affected by the water resistance of the dry film of the butadiene-based copolymer latex used as the binder. However, the use of a latex forming a film whose strength hardly decreases even when contacted with water, but the water-resistant adhesive strength of the water-based adhesive was slightly improved, but it did not reach the target level. Therefore, as a result of diligently investigating factors affecting the water-resistant adhesive strength in addition to the water resistance of the latex film, besides the above, the water-resistant strength retention rate of the latex dry film has a certain level or more, and further, it does not dissolve in the alkaline region. When a carboxy-modified butadiene-based copolymer that has a certain amount of viscosity and has a certain particle diameter and polymer composition and is lubricious in an alkaline region is used, the water-resistant adhesive strength of the adhesive can be significantly improved. It turned out and reached the present invention.

That is, in the present invention, the polymer composition is unsaturated carboxylic acid 5
% To 30% by weight, butadiene 10% to 80% by weight and the balance 100% by weight of other copolymerizable monomers
In the latex of the copolymer, the latex viscosity of 45% solid content at pH 10 is 10 ³ cps to 10 ⁷ cps, the particle diameter of the dispersion copolymer is 500 Å to 2200 Å, and the copolymer particles are in the alkaline range. The present invention relates to a carboxy-modified butadiene-based copolymer latex for water-based adhesives, which is lubricious and has a water-resistant strength retention of the latex dry film of 10% or more.

The Lotex of the present invention has a solid content of 45% (nonvolatile content when dried at 130 ° C. for 30 minutes) in an alkaline range (pH 10).
When adjusted to 10 ³ cps to 10 ⁷ cps (value measured at 25 ° C using a BH type viscometer, No. 7 spindle, provided that the viscosity is 5 × 10 ₄ c
If it is less than ps, the viscosity should be 20 rpm, and if it is 5 × 10 ⁴ cps or more, the viscosity should be 2 rpm. 10 ³ c
If it is less than ps, the viscosity of the adhesive is low, and in order to obtain a highly viscous adhesive that can also be applied to the adhesion of ceramic tiles, more thickener will be added, and high water-resistant adhesive strength will be obtained. Not desirable. When the latex viscosity exceeds 10 ⁷ cps, the viscosity of the adhesive tends to increase with time, which is not preferable. Further, if the water resistant strength retention of the latex dry film is less than 10%, an adhesive having a high water resistant adhesive strength aimed at by the present invention cannot be obtained, which is not preferable. Further, when the average particle diameter of latex (value measured by a light scattering method) exceeds 2200Å, the viscosity tends to gradually increase in an alkaline region, and the change in viscosity diameter of the adhesive becomes large, which is not preferable. The average particle size of the latex is preferably small, but it is difficult to stably produce a latex having a particle size of about 500Å or less by the emulsion polymerization method.

Heretofore, there is no known copolymer latex usually used for this type of latex diameter aqueous adhesive and having the performance of the present invention, but about 5 to 30% by weight of unsaturated carboxylic acid,
A copolymer latex having a composition of about 10 to 80% by weight of butadiene and the balance of other copolymerizable monomers in a total amount of 100% by weight can have the performance targeted by the present invention. .

As the unsaturated carboxylic acid, itaconic acid, fumaric acid,
Acrylic acid, methacrylic acid, maleic acid and its half-esters can be mentioned, but acrylic acid or maleic acid half-esters and methacrylic acid are preferably used because a copolymer film having a high water resistance retention rate can be easily obtained. . If the amount of unsaturated carboxylic acid used is less than 5% by weight, the viscosity in the alkaline range is low, which is not preferable, and if it exceeds 30% by weight, the water resistance retention rate of the latex dry film is low, which is not preferable. What is the water resistant strength retention rate of the dry film of latex? About 1 mm of latex (45% solid content) of pH 10 is placed on a glass plate or an iron plate coated with Teflon.
Copolymer film obtained by coating with a thickness film caster and gradually drying (more than 24 hours) at a temperature higher than the minimum film formation temperature. Tensile strength (tensile speed) after soaking in water for 24 hours. (10 mm / mm) is measured, divided by the tensile strength of the film before being immersed in water, and multiplied by 100.

The content of butadiene in the latex copolymer is about 10
A range of -80 wt% is preferred. If it is less than 10%, even if a solvent or plasticizer is present in the adhesive, it is difficult to form a film at low temperatures, and sufficient adhesive strength cannot be obtained in winter, and if it exceeds 80% by weight, the film strength is low and the adhesive strength is low. Is extremely low, which is not preferable. Other copolymerizable monomers include aromatic vinyl monomers such as styrene, α-methylstyrene and vinyltoluene, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-methacrylate.
Acrylic ester or methacrylic acid ester such as ethylhexyl acrylate, 2-ethylhexyl methacrylate, acrylonitrile, methacrylonitrile, glycidyl methacrylate, 2-hydroxyethyl acrylate, acrylamide, methacrylamide, N
Examples thereof include vinyl compounds having an epoxy group such as methylol acrylamide and N-butoxymethyl acrylamide, a hydroxyl group, an amide group, and a methylol group.

The copolymer latex used in the present invention can be obtained by a conventional known emulsion polymerization method, but 10 to 90% by weight of a monomer containing 1 to 10% by weight of an unsaturated carboxylic acid (based on all monomers) (based on all monomers) Emulsion polymerization), and then
A preferred method is emulsion polymerization of 10 to 90% by weight of a monomer having a relatively high proportion of unsaturated carboxylic acid of 4 to 20% by weight in the presence of the copolymer latex. The particles of the copolymer latex obtained from the above monomer composition and polymerization method are considered to form a different layer structure in which more carboxylic acids are present in the surface layer than in the inner layer, and the latex particles are alkali-soluble in the alkaline region. It is considered that, unlike the latex particles, the particles do not completely dissolve but swell and exhibit a high latex viscosity, and that the dried film has a high water resistant strength retention rate. A latex having the performance of the present invention can be obtained by selecting the type and level of the unsaturated carboxylic acid also by a method of emulsion-polymerizing all the monomers to be blended in one step. Its performance is inferior in comparison.

In the present invention, it is essential to use the above-mentioned copolymer latex as a binder, but if necessary, chlorobrene latex, natural rubber latex, ordinary carboxy-modified butadiene latex, acrylic latex, ethylene-vinyl acetate system. Latex, ethylene-vinyl chloride latex and the like can also be used in combination. When an aqueous adhesive is prepared using the butadiene-based copolymer latex of the present invention, a solvent and / or a plasticizer, a tackifying resin, a filler and a thickener are usually used together. The tackifying resin is used for the purpose of imparting initial adhesiveness to the adhesive, and a thermoplastic resin having a softening point (ring and ball method: JIS K-2531) of about 30 ° C to 180 ° C is preferable, and specifically, Rosin, for example
Examples thereof include modified rosin and derivatives thereof, terpene-based resins, aliphatic hydrocarbon resins, aromatic hydrocarbon resins, phenol-based resins, xylene resins and coumarone-indene resins. The solvent and / or the plasticizer is used mainly for dissolving or swelling the tackifying resin and / or the copolymer latex to enhance the initial adhesiveness of the adhesive. For example, the solvent is an aromatic substance such as benzene or toluene. Examples thereof include group-based solvents, naphthene-based and paraffin-based solvents, ketones, and esters.Plasticizers include phthalic acid esters such as dioctyl phthalate and dibutyl phthalate, and high-boiling petroleum fractions. it can.

The tackifier resin, solvent and plasticizer may be emulsified with an anionic emulsifier or a nonionic emulsifier, and may be mixed with the latex and / or the filler, but the tackifier resin and the solvent and / or the plasticizer are mixed beforehand. However, it is better to mix it with a latex and / or a filler prepared by emulsifying in water with an anionic emulsifier or a nonionic emulsifier, or mixing the resin solution directly with the latex and / or the filler in the adhesive. The amount of the emulsifier is small and preferred. The addition of a thickener has the effect of imparting a desired adhesive viscosity to the adhesive, as well as imparting water retention to the adhesive to prevent abrupt drying and prolonging the open time (tile sticking possible time). Examples of the thickener include methyl cellulose, carboxymethyl cellulose, high molecular weight sodium polyacrylate and alkali-soluble latex.

Although calcium carbonate is preferably used as the filler because it is inexpensive, inorganic fillers such as clay, talc, titanium oxide and silica sand, or organic fillers such as pulp and various resin powders can also be used.

The proportion of these components is 50 to 500 parts by weight of the filler, 10 to 200 parts by weight of the tackifying resin, 1 to 100 parts by weight of the solvent and / or the plasticizer, and the thickening agent with respect to 100 parts by weight (solid content) of the Kyo Polymer latex. The range of 0.2 to 2.0 parts by weight of the agent is preferable because it has the necessary adhesive strength, water-resistant adhesive strength, initial adhesiveness, coating workability (high thixotropy), and viscosity stability over time as an adhesive for ceramic tiles.

In addition to the copolymer latex of the present invention, a phosphorus dispersant such as sodium tripolyphosphate and sodium hexametaphosphate and a low molecular weight sodium polyacrylate filler dispersant, caustic, caustic soda, a neutralizing agent such as aqueous ammonia, various antiaging agents A preservative, an antifreeze, a cross-linking agent, etc. can be added as required.

The water-based adhesive obtained by using the copolymer latex of the present invention can be suitably used for adhesion of ceramic tiles that require high water-resistant adhesive strength, but flooring materials and base materials such as carpets, cushion floors and PVC tiles. It can also be used for bonding a wide range of similar materials and different materials such as bonding with wood, bonding wood with each other, bonding boards, bonding wood with plastic, veneer, veneer, and metal.

〔The invention's effect〕

The carpoxy-modified butadiene of the present invention having a specific particle size and a polymer composition, which does not dissolve in an alkaline region but swells without swelling and thickens to a certain viscosity or more, and the water-resistant retention rate of the dry film is higher than a certain amount. The water-based adhesive obtained using the system copolymer latex has excellent water-resistant adhesive strength,
It can be suitably used for adhesive applications such as attaching ceramic tiles in bathrooms and shower rooms.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to examples.
The present invention is not limited to the following examples. In addition,% and part shown below mean a weight% and a weight part.

Example 1 62 parts of ion-exchanged water and 0.5 part of sodium lauryl sulfate were added to a pressure reactor equipped with a stirrer whose temperature was controlled by replacing nitrogen, and the temperature was raised to 80 ° C. Then, an aqueous solution prepared by dissolving 0.12 parts of caustic soda, 0.35 parts of sodium sulphate and 0.2 parts of sodium lauryl sulphate in 12 parts of ion-exchanged water, and 50.2 parts of the monomer for the first stage polymerization and the chain transfer agent shown in Example 1 were used. Gradually added and polymerized over 2 hours. Then, 50.4 parts of the monomer for second-stage polymerization and chain transfer agent shown in Example 1 of Table 1 were used for 2 hours, and 12 parts of ion-exchanged water and sodium sulfate were added.
An aqueous solution consisting of 35 parts, 0.2 part of sodium lauryl sulfate and 0.12 part of caustic soda was further added for 3 hours for polymerization. Next, the residual monomer was removed by steam stripping to obtain the copolymer latex of Example 1. The reaction rate of the monomer was 98% and the particle size was 1340Å. Adjust this copolymer latex to 45% solids, pH 10 (caustic soda),
When the viscosity was measured, it was 400,000 cps. Also, a copolymer latex of pH 10 was coated on a glass plate with a 1 mm caster, dried at 25 ° C. for 24 hours to prepare a film, and the tensile strength of the film was measured to be / 72 Kg / cm ² . The tensile strength of the wet film after further immersing the film in water for 24 hours was 30 Kg / cm ² , and the water resistant strength retention rate was 17.4%.

An adhesive was prepared with the following composition using this copolymer latex (pH 7.0, adjusted to 48% solid content).

The tile adhesive strength and water resistant adhesive strength of the prepared adhesive were measured under the following conditions.

Adhesive strength After applying 625g / m ² (wet) of adhesive with a comb iron on the back of a ceramic tile (Danto, 75mm × 75mm × 5mm) (open time 0 minutes), another identical piece The back surface of the tile was attached to the tile-coated surface (shifted by 1 cm), a load of 500 g was applied for 1 minute, and the tile was cured at 25 ° C. for 7 days. The compressive shear strength (speed 20 mm / min) of the cured sample was measured to determine the adhesive strength.

Water resistant adhesive strength Adhesive strength measurement sample (after curing for 7 days) 24 in water
After soaking for a period of time, the compressive shear strength was measured to determine the water resistant adhesive strength.

Table 1 shows the results of the adhesive strength and the water resistant adhesive strength obtained by measuring under the above conditions.

Examples 2 to 5 By the same method as in Example 1, the monomers having the formulations shown in Table 1 were emulsion polymerized to obtain a copolymer latex having an average particle size of about 1400Å. Table 1 shows the results of measuring the latex viscosity and the water resistant strength retention of the latex film of the obtained latex. An adhesive (nonvolatile content 70%, pH 10) having the composition shown in Example 1 was prepared using these copolymer latexes, and the adhesive strength and the water resistant adhesive strength were measured. The results are shown in Table 1.

Example 6 A reactor similar to that of Example 1 was charged with 75 parts of deionized water and 0.2 parts.
Part of sodium lauryl sulfate was added and the temperature was raised to 80 ° C. Then 25 parts of deionized water, 0.25 parts of caustic soda, 0.7 parts
5 parts of sodium sulphate and 0.2 parts of sodium lauryl sulphate
Gradually added over time. At the same time, the monomers and chain transfer agents shown in Example 6 of Table 1 were added and polymerized for 4 hours. Then, the residual monomer was removed by steam stripping to obtain a copolymer latex of Example 6 having an average particle size of 1780Å. About this copolymer latex, Example 1 except that latex viscosity, latex film tensile strength and underwater tensile strength, and 2 parts of a thickener were used.
An adhesive was prepared with the same raw material composition as above, and the adhesive strength and water resistant adhesive strength were measured. Table 1 shows the results.

Comparative Example 1, Comparative Example 2 and Comparative Example 5 Polymerization methods similar to those in Example 6 were used to prepare monomer compositions of Comparative Example 1 and Comparative Example 2 and Comparative Example 5 shown in Table 2, each of about 1700.
A copolymer latex having an average particle size of Å was obtained. Table 2 shows the results of measuring the viscosity (pH 10, 45% solid content), the tensile strength of the film and the water-resistant tensile strength of these copolymer latexes. Then, using the copolymer latex having a low latex viscosity obtained in Comparative Example 1 and Comparative Example 2, the same raw material blending ratio and preparation conditions as in Example 1 except that the adhesive nonvolatile content was 75% and the amount of the thickener was 2.0 parts. An adhesive having substantially the same viscosity as in Example 1 was prepared, and the adhesive strength and water resistant adhesive strength were measured. The results are shown in Table 2. In the case of the copolymer latex obtained in Comparative Example 5, an adhesive having substantially the same viscosity as in Example 1 was prepared with the same raw material composition as in Example 1 except that 2 parts of the thickener was used. The adhesive strength and water resistant adhesive strength were measured. The results are shown in Table 2.

Comparative Example 3 and Comparative Example 4 Emulsion polymerization was performed using the monomers and chain transfer agents shown in Table 2 by the same polymerization method as in Example 1, and the copolymerization weights of Comparative Example 3 and Comparative Example 4 having an average particle size of about 1300Å were obtained. A combined latex was obtained. The results of measuring the latex viscosity, the film tensile strength and the film water resistant tensile strength are shown in Table 2. Next, using the copolymer latex of Comparative Example 3, an adhesive was prepared under the same raw material composition and conditions as in Example 1, and the adhesive strength and water resistant adhesive strength were measured. However, since the viscosity of the copolymer latex of Comparative Example 3 in the alkaline region was very high, the nonvolatile content of the adhesive was set to 68% and an adhesive was prepared without using a thickener. Since the copolymer latex of Comparative Example 4 had a low viscosity in the alkaline region, 2 parts of the thickener was used in the same manner as in Comparative Examples 1 and 2 to prepare an adhesive with a nonvolatile content of 75%. The adhesive strength and water resistant adhesive strength were measured. The measured results are shown in Table 2.

From the results of Table 1 and Table 2, the adhesive for ceramics made from a copolymer latex having a high viscosity above a certain level in an alkaline region and having a water resistant strength retention rate of which the dry film is above a certain level is high. It is recognized that it has both adhesive strength and very high water resistant adhesive strength.

Example 7 In the polymerization of Example 1, the amount of the emulsifier (sodium lauryl sulfate) added before the start of the polymerization was changed from 0.5 parts to 0.2 parts by the same monomer composition, the same polymerization conditions and the same polymerization method as in Example 1, and 1850Å A copolymer latex having an average particle size was obtained. This copolymer latex has a solid content of 45% and a pH of
It was adjusted to 10 (neutralizer: caustic soda) and the viscosity was measured to be 2.8 × 10 ⁵ cps. Then, using the copolymer latex obtained in this example, an adhesive was prepared with the same raw material composition as in Example 1 except that the amount of thickener was changed to 1.2 parts, and the initial viscosity and room temperature were maintained for 2 weeks at room temperature. The viscosity after standing was measured together with the adhesive of Example 1. Table 3 shows the results.

Comparative Example 6 In the polymerization for obtaining the copolymer latex of Example 1, the amount of the emulsifier (sodium lauryl sulfate) added before the initiation of the polymerization was changed.
The same monomer composition as in Example 1 except that 0.5 part was changed to 0.03 part, and the amount of the emulsifier (sodium lauryl sulfate) added in the first-stage polymerization and the second-stage polymerization was changed from 0.2 part to 0.1 part, A copolymer latex having an average particle size of 2400Å was obtained according to the polymerization conditions and the polymerization method. The copolymer latex was adjusted to have a solid content of 45% and a pH of 10 (neutralizing agent: caustic soda), and the viscosity was measured and found to be 1.6 × 10 ⁵ cps. Then, using the copolymer latex obtained in this comparative example, an adhesive was prepared with the same raw material composition as in Example 1 except that the amount of thickener was changed to 1.5 parts, and the initial viscosity and room temperature were maintained for 2 weeks at room temperature. The viscosity after standing was measured. Table 3 shows the results.

As shown in Table 3, the viscosity of the adhesive changes with time as the particle size of the latex increases, and when the latex having the average particle size of 2400Å of Comparative Example 7 is used, the viscosity of the adhesive increases remarkably with time. It is sticky and apparently undesirable.

Claims (1)

[Claims] 1. A polymer composition having an unsaturated carboxylic acid content of 5% by weight.
~ 30 wt%, butadiene 10 wt% ~ 80 wt% and a total 100 wt% copolymer latex consisting of the other copolymerizable monomers, the latex viscosity of 45% solids at pH 10 10 ³ cps to 10 ⁷ cps, the dispersion copolymer has a particle size of 500Å to 2200Å, the copolymer particles are lubricious in an alkaline region, and the latex dry film has a water resistance retention rate of 10%. The above is a carboxyl-modified butadiene-based copolymer latex for an aqueous adhesive, which is characterized by the above.