JPS6345754B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of applying a two-component rubber latex adhesive to enhance initial bond strength. The issue of environmental protection from the viewpoint of air pollution prevention and occupational safety and health is a social requirement, and regulations are becoming stricter over the years. In this context, the regulation of solvents is moving from qualitative to quantitative regulations, and toward regulating the total amount of solvents. In response to this situation, industries such as adhesives, pressure-sensitive adhesives, paints, and printing inks are trying to limit the use of large amounts of organic solvents and make the materials used non-polluting. New research is being carried out in the field of mold adhesives and hot melt adhesives. As an example, it is well known that water-based adhesives using emulsion latex and the like have been developed and are used in large quantities in the building materials and interior materials industries, the packaging industry, the automobile industry, and the like. Furthermore, water-based adhesives using water-soluble polymers are widely used in the packaging industry, wallpaper manufacturing, paper processing industry, and general household use. The advantage of water-based adhesives is that they do not cause pollution problems;
No fire hazard, simple manufacturing equipment,
Examples include low manufacturing cost, resource saving, hygienic and easy to use. On the other hand, the biggest drawback of these water-based adhesives is that they dry slowly, but in view of the above-mentioned advantages, the shift from adhesive systems using organic solvents to water-based adhesive systems can be said to be the trend of the times. The slow drying time of water-based adhesives compared to solvent-based adhesives is mainly due to the difference in evaporation rate between water and organic solvents, but in the paint industry it is relatively easy to transition from organic solvent-based paints to water-based paints. It is. The reason for this is that in the case of paint, the painted surface is exposed to the atmosphere and water evaporates easily, so slow drying is not a major drawback. This is due to the early onset of the anchoring effect. On the other hand, in the case of adhesive systems, the purpose is to form an adhesive film between two adherend materials and simultaneously bond them together to demonstrate their usefulness as a new material. This results in the disadvantage that water trapped between the materials does not easily volatilize. FIG. 1 is illustrated to facilitate understanding of these processes. This drawing shows step-by-step the process by which the adhesive layer forms an adhesive film when bonding materials using an emulsion latex-based water-based adhesive. The material 1 is coated with an emulsion latex adhesive and is bonded to another adherend material 2, where 3 represents rubber or resin particles in the adhesive, and 4 represents water. (B) shows a state in which water gradually evaporates and particles come into contact with each other.
In (c), the water further evaporates and the particles are deformed to become fused particles 3'. (d) All the particles are fused together, and there are no boundaries between the particles, forming a continuous film 3''. As shown in Figure 1 above, in the case of a water-based adhesive using emulsion or latex, An adhesive film is formed only when the water evaporates and the particles fuse together.In the case of water-soluble adhesives that use polymers dissolved in water, such as polyvinyl alcohol, once the water evaporates, the adhesive film forms. Although a film remains, in the case of emulsions or latexes there is an additional step of particle fusion, and the practical bonding mechanism is completed only after the adhesive film is formed.In contrast, in the case of paints, A paint film is formed and the purpose is achieved in the same way as with adhesives, but even before a paint film is formed, the wettability of the adherend material is a practical property (initial adhesion). There is no particular problem if the following conditions are satisfied.In the case of adhesives, the role of adhering to another adherend material is to provide usefulness as a new material, so in many cases there is a gap between the adherend materials. Adhesives are often actively stressed and required to withstand that stress, which is where the difficulty lies with adhesives compared to paints. The biggest disadvantage of using water-based adhesives is poor drying properties due to the slow evaporation rate of water, which results in a long time to form an adhesive film, that is, a long film-forming time. The problem with this drawback is that it cannot withstand practical stresses such as shearing and peeling immediately after adhering to the interface between the adhesive layer and the adherend material.
When only compressive force is applied to the adhesive layer immediately after adhesion, a continuous film of adhesive is formed, which can sufficiently withstand actual stresses such as shearing and peeling. Taking advantage of this fact, emulsion type adhesives have been used in large quantities in the architecture, building materials, and other industries.
In other words, compressive force is applied to the bonded objects at room temperature,
After pressing and curing until a continuous adhesive film is completely formed, the adhesive is released and used for practical use. Although the time required to form an adhesive film, that is, the film-forming time, can be somewhat shortened by increasing the temperature, there is a limit to the shortening of the pressing time. In the case of emulsion-based adhesives, it is difficult to form a continuous film unless the water completely evaporates.
For example, at high temperatures of 100°C or higher, water may boil and bubbles may form in the adhesive film. On the other hand, in the case of latex-based adhesives, even if some water remains,
It is possible to form a continuous film. In the case of emulsion adhesives, they are usually cured at room temperature for more than one day, and under pressure for at least half a day, but as this increases the total production cost, in many cases they are cured at room temperature after pressing. is the current situation. On the other hand, in the case of an adhesive that uses a large amount of organic solvent, it can sufficiently withstand the actual initial stress even if another adherend material is bonded immediately after the adhesive is applied to the adherend material. Therefore, in order to convert adhesives that use large amounts of organic solvents to non-polluting water-based adhesives, adhesive strength must be strong enough to withstand the initial stress of practical use.
So-called initial adhesive strength is an essential condition. However, to date, no water-based adhesive has been developed that satisfies the initial adhesive strength for practical use, and in that sense it does not meet social demands. However, it is clear from the above explanation of the adhesion mechanism of water-based adhesives that it is extremely difficult to develop an adhesive that satisfies this requirement. The present inventors have tackled this problem and, as a result of repeated research, have been able to grasp the beginnings of a method of applying a water-based adhesive that is satisfactory both in terms of initial adhesive strength and final adhesive strength. Next, we will explain how we obtained the application method for this newly developed water-based adhesive. The following four methods were investigated in advance to improve the initial adhesive strength of emulsion or latex-based water-based adhesives. A method of improving initial adhesion by forcibly drying the adhesive after applying it to promote water evaporation and the formation of an adhesive film. A method for enhancing initial adhesion by adding a water-soluble polymer to utilize the tackiness of the polymer. A method of enhancing initial adhesion by adding an auxiliary agent to improve the speed of forming an adhesive film (film formation). By adding certain adjuvants, the initial adhesion can be improved by forming an adhesive film in a short time, separating the water layer from the film, and making it easier for the water to evaporate more freely. How to enhance it. Although we have carried out research on each of the above items, we found that method (1) increases production costs and is impractical, and method (2) does not improve initial adhesion as much as expected, and final adhesion (water resistance, humidity). The auxiliary agents used in the method are plasticizers and film-forming auxiliaries, such as phthalate ester plasticizers, high boiling point solvents, butyl cellosolve, butyl cellosolve acetate, butyl carbitol, butyl carbitol acetate,
carbitol acetate, hexyl glycol,
Although Texanol and the like have been used, the rate of water evaporation was still not accelerated and the initial adhesion did not improve as expected. This method is based on a special idea discovered by the inventors during the research stage.The principle behind this method is to form a film on the colloid surface by adding a certain kind of film-forming agent to an aqueous adhesive containing emulsion or latex. The potential of the colloid is lowered to cause the colloid to condense. It has been found that water molecules contained in emulsions or latexes have a slow rate of evaporation, but if only the aqueous layer is separated, the rate of evaporation is surprisingly accelerated. The aqueous adhesive composition used in the present invention is composed of a combination of an aqueous adhesive mainly composed of rubber latex (Part A) and a film forming agent (Part B) for forming a film from the adhesive. It is a fast-curing, two-component water-based adhesive that quickly removes moisture and forms a film between adhered materials to increase initial adhesive strength. Next, examples of formulations for Parts A and B are shown. For Part A, ingredients are added to the formulation of a general rubber latex adhesive to make the adhesive film particularly sticky at the initial stage of adhesion. Although modified, the present invention is not limited to this example in practice. Part A: Part by weight Rubber latex 100 Phenolic and/or terpene resin emulsion 20-60 Rosin derivative or petroleum hydrocarbon resin emulsion 5-20 Water-soluble polymer 2-10 Anti-aging agent 2 Dispersant 1 Pigment (inorganic or Organic type) 20-100 Film-forming agent 2-5 Vulcanizing agent and vulcanization accelerator 10-20 Water Appropriate amount Agent B: parts by weight Film-forming agent 10-20 Water 80-90 Film-forming agent adopted in the present invention can be selected from the following classes of chemicals that lower colloid surface potential, which are classified as quaternary ammonium salts, silicates, and weakly acidic promoters, specifically lauryltrimethylammonium chloride, stearyltrimethylammonium chloride. , distearyldimethylammonium chloride, alkylbenzyldimethylammonium chloride, sodium silicate, potassium silicate, ammonium sulfate, ammonium nitrate, ammonium chloride, and the like. Among these, in view of economic efficiency, it is appropriate to use weakly acidic accelerators such as ammonium sulfate and ammonium nitrate alone or in combination with some quaternary ammonium salts. For example, apply a two-component adhesive with the above composition to a non-porous painted steel plate at 150 to 200 g.
On the painted surface of agent A applied at a coating rate of g/m ² ,
When Agent B is evenly sprayed at a coating rate of about 10 g/m ² , Agent A immediately begins to form a film, forming a uniform continuous film. The phenolic resin or petroleum resin in Part A improves the tackiness of the adhesive film.
After spraying the B agent, the porous adherend material can be bonded together within 30 seconds to obtain sufficient initial adhesive strength. In the case of only agent A, it takes about 10 minutes to stand at a temperature of 20±2° C. and a relative humidity of 65±5% until sufficient initial adhesive strength is developed. The time required for a two-component adhesive consisting of Parts A and B to develop sufficient initial adhesion is approximately 1/20 of the time required for Part A only.
It could be shortened to the following. Further, even when the coating amount of agent B was increased beyond the specified value, no significant difference was observed in the time required to develop sufficient initial adhesive strength, and on the contrary, there was a tendency for the tackiness of the adhesive film to decrease. When using the water-based adhesive of the present invention, there is no significant difference in the time it takes to develop sufficient initial adhesive strength even if the environmental temperature of the coating operation is low; however, the adhesive strength of the adhesive film increases as the temperature increases. We obtained increasing results. The deposited materials used in the present invention require that at least one of them be a porous substrate. As is generally said in the case of solvent-based adhesives, it is the adhesive film that is responsible for the final adhesive strength and does not contain any volatile components. Therefore, there is a need for an adhering material that is convenient for volatilization of volatile components. The porous adhesive materials herein specifically include wood, paper, woven fabrics, non-woven fabrics, welts, foamed substrates such as polyurethane foam, polyethylene foam, and the like. Conventionally, regarding the application method of two-component adhesive, A.
Since the performance as an adhesive can only be achieved when the agent and agent B are evenly mixed manually or mechanically, the method of applying the adhesive to the adherend after mixing is generally adopted.
It had the disadvantage of having to work under unfavorable conditions such as limited pot life due to mixing. Furthermore, the properties of the adhesive may change due to mixing, such as an increase in the viscosity of the adhesive or the beginning of hardening, which may impede painting operations. When using a coating device, it is necessary to continue dispensing without stopping the device, and the adhesive that is being dispensed outside of the time when it is actually being applied to non-adhesive materials cannot be reused, so it must be carefully disposed of, such as discarding it. There was a disadvantage. The water-based adhesive of the present invention satisfies the performance as an adhesive with only agent A as in the previous stage, but
By adding the agent, it is possible to develop initial adhesive strength in a short period of time. The use of agent B also has the advantage of increasing the final adhesive strength as an adhesive. However, since the two-component water-based adhesive used in the present invention has remarkable fast curing properties, it is necessary to mix parts A and B in advance and then apply the adhesive, as with conventional two-part water-based adhesives. Can not. The method of applying the two-component mixed water-based adhesive consisting of Parts A and B according to the present invention uses a spray device such as an airless sprayer or an air sprayer, and each agent is ejected into a mist that is atomized in a space. After the two liquids are automatically mixed and applied to both joint surfaces of the adherend material, the adherend material is pasted, or agent A is applied to one of the joint surfaces of the adherend material by an appropriate means, e.g. Apply with a spray, spatula, brush, roll, etc., and apply B on the other side of the bonded material.
The purpose of adhesion can be achieved by applying the adhering material after each application of the agent by suitable means as well. Furthermore, either agent A or agent B is applied to the bonding surface of the adherend materials by an appropriate means, and then the other agent of agent A or agent B is applied to the same surface, and then the adhesion is performed. Materials can also be attached. The amount of agent B applied is approximately 1/20 of that of agent A, which is sufficient to achieve the desired purpose.
Even if an operation mode in which only agent B is applied separately is adopted, the application operation can be done instantaneously, and there is no particular problem economically. Next, examples of the present invention will be shown. Example 1 This example shows a prescription example for Agents A and B. Part A: Part by weight Chloroprene latex 100 Terpene-modified phenolic resin emulsion (resin content 40%) 60 Rosin resin emulsion (resin content 40%) 20 Methyl cellulose 3% aqueous solution 5 Part B: Ammonium sulfate 20 Water 80 Example 2 In this example, A coating method using in-air mixing of aqueous adhesives (Part A and Part B) sprayed by a spray gun according to the invention will be explained with reference to A and B of FIG. A is a drawing showing that spray 1' from spray gun 1 that sprays agent A and spray 2' from spray gun 2 that sprays agent B are mixed in the air and coated on one adherend material. Then, after spraying coating on other adherend materials in the same manner, adhesion is performed by pasting and adhering both adherend materials. B is a drawing showing that the B agent spray 12 sucked by the spray from the spray gun 11 that ejects the A agent becomes a mixed spray 13 in the air and is painted on the adherend material 14; Adhesion is performed by applying another adherend material. Arrows indicate the direction of drug introduction. Example 3 This example shows the spraying, brushing,
Apply to the bonding surface of the adherend materials using a suitable device such as a trowel, spatula, roll, etc., and then apply the other of Agent B or Agent A to the same surface. is formed, and another adherend material is adhered onto the surface for adhesion. Next, the water-based adhesive according to the present invention in Example 1, Part A and Part A + Part B (used at 5% with respect to A) were applied by the method of Example 2 or 3, and the open time was 1.5 minutes and 1 minute. Table 1 shows the initial adhesive strength in each case. In the case of cotton canvas/cotton canvas, the coating method in Table 1 shows the case where the A and B agents of Example 2A were mixed and sprayed simultaneously in a space and applied to both sides of the adherend material. In the case of water-resistant veneer/water-resistant veneer, the method of Example 3 was used in which agent A was first applied using a combing iron, and then agent B was immediately applied on the same surface using the same combing iron.

[Table] Below, Agents A and B were mixed and sprayed in a space on cotton canvas/cotton canvas, cotton canvas/painted steel plate, and gypsum board/painted steel plate by the method of Example 2A, and applied to both sides of the adhered materials. The adhesive strength after 7 days of adhesion is shown when first applying agent A and then agent B to cotton canvas/painted steel plate, gypsum board/painted steel plate, and lauan plywood/lauan plywood with the brush of Example 3. ―
Shown in 2.

[Table] Example 4 For 100 parts by weight of an acrylic ester copolymer (trade name "Cemedine EM305" manufactured by Cemedine Co., Ltd.) as the A agent, the substances listed in Table 3 were added as the B agent. It was applied to both bonding surfaces of the adherend material by mixing and spraying in the space described in Example 2A in such proportions as parts by weight, and was adhered. For comparison, the adhesive strength using only agent A was also measured. The results are shown in Table 4.

【table】

【table】

[Table] Example 5 100 parts by weight of agent A described in Example 4 and 10 parts by weight of a 30% polyethyleneimine aqueous solution 1) as agent B were applied to the adherend material by the method described in Table 5. and pasted it together. The results are shown in Table-5. The materials to be adhered to were a combination of synthetic resin board and felt, and experiments were conducted in which the A and B agents were applied on the same surface and on different surfaces.

[Table] The substances and test methods described in the examples are as follows. 1 Nippon Shokubai Kagaku Kogyo Co., Ltd. Epomin P-1000 2 Adhesive application method A agent ← B agent Apply B agent immediately after applying A agent, and take an open time. When applying agents A and B to separate surfaces, after applying agent B to one adherend material, immediately apply agent A to the other adherend material and allow an open time. 3. Initial Adhesive Strength After 0.5 minutes of open time, the adhesive was bonded and immediately subjected to a peel test at room temperature, with a tensile speed of 200 mm/min, and the felt material was passed if it broke.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional explanatory diagram for explaining the adhesion process of adherend materials using a general emulsion latex water-based adhesive, and A, B, C, and D show the progressing stages of adhesion. FIG. 2 is an explanatory diagram showing a specific example of mixing and spraying to show how to apply the two-component water-based adhesives A and B according to the present invention. 1 is a spray gun that sprays agent A, 1' is a spray thereof, 2 is a spray gun that sprays agent B, 2' is a spray thereof,
3 is one adherend material, 11 is a spray gun that sprays agent A, and 12 is B that is sucked and sprayed by 11.
A spray device for spraying the agent, 13 indicates a mixed spray, and 14 indicates one adherent material.

Claims (1)

[Claims] 1 Consists of a combination of a water-based adhesive whose main component is rubber latex and a film-forming agent for forming a film with the adhesive, which quickly removes moisture during adhesion and forms a film between the adhered materials. In a method for applying a two-component water-based adhesive to enhance initial adhesive strength, the water-based adhesive is applied to one of the bonding surfaces of the adherend material,
Applying the film forming agent to the other bonding surface of the adherend material,
Next, an adherend material is pasted, or one of the water-based adhesive or the film-forming agent is applied to the joint surface of the adherend material, and then the other of the water-based adhesive or the film-forming agent is applied. After applying on the same joint surface,
After applying the adherend material to both bonding surfaces of the adherend material by pasting the adherend material or by mixing and spraying the water-based adhesive and the film forming agent in a space,
A method characterized by pasting an adherend material.