JP2916190B2 - Method for producing synthetic rubber latex adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a vinyl acetate emulsion, a vinyl acetate acrylic copolymer emulsion, and a vinyl acetate ethylene which are used in large quantities in the fields of plywood, woodwork, civil engineering, paper and textiles. The present invention relates to a method for producing a synthetic rubber latex-based adhesive having excellent fluidity similar to that of a copolymer emulsion.

More specifically, the viscosity which is the biggest disadvantage of synthetic rubber latex adhesives, that is, thixotropic viscosity,
The present invention relates to a method for producing a synthetic rubber latex-based adhesive which is close to Newtonian viscosity having excellent fluidity.

[Conventional technology]

Synthetic rubber latex has the same or better characteristics as vinyl acetate emulsions in terms of adhesive performance, but is used in the plywood, paper, and fiber processing fields using a roll coater as an adhesive application method. Was very low.

This is because synthetic rubber latex generally has a lower viscosity than a vinyl acetate emulsion, so that it was necessary to increase the viscosity by some method.

This thickened material shows strong thixotropic viscous behavior, has a significant viscosity decrease due to liquid transfer onto a roll coater, and the rotational friction of the roll, and the biggest disadvantage is that it is extremely difficult to apply a predetermined amount of adhesive. It had been.

[Problems to be solved by the invention]

As a means for solving this problem, surfactants such as polyvinyl alcohol, hydroxyethyl cellulose, carboxycellulose, and carboxymethylcellulose used in vinyl acetate emulsions are added to synthetic rubber latex, Studies have been made to improve the viscosity by adding a thickener, that is, to impart fluidity close to the Newtonian viscosity, but none of them has been satisfactory because there is a large difference from the viscosity of the vinyl acetate emulsion.

[Means for solving the problem]

The present inventors have conducted intensive studies and found that the average particle diameter of the synthetic rubber latex is in the range of 0.2 to 0.5 μm, and that the particle shape is irregular, and the latex pH is in the range of 3 to 7. It has been found that the use of partially saponified polyvinyl alcohol to increase the viscosity is extremely effective in solving the above problem, and the present invention has been completed.

That is, the present invention is characterized in that (1) a copolymer latex comprising butadiene, a vinyl monomer and a reactive monomer, has a polymer average particle diameter in the range of 0.2 to 0.5 μm and has an irregular particle shape. Of producing a synthetic rubber latex adhesive.

(2) 0.5 parts of reactive monomer in 100 parts by weight of all monomers
The method for producing a synthetic rubber latex-based adhesive according to the above item (1), wherein the adhesive is copolymerized by 20 to 20 parts by weight.

(3) The method for producing a synthetic rubber latex adhesive according to the above (1), wherein the reactive monomer is a hydroxyl group and a carboxyl group.

(4) The synthetic rubber latex-based adhesive according to the above (1), wherein the reactive monomer is divided or continuously introduced at least in a range of a polymer conversion rate of 0 to 50% of the total monomer weight. Production method.

(5) The method for producing a synthetic rubber latex adhesive according to the above (1), wherein the pH of the copolymer latex is in the range of 3 to 7.

(6) The above item (1), wherein 1 to 20 parts by weight of a partially saponified polyvinyl alcohol having a polymerization degree of 50 to 2500 as a solid content is blended with respect to 100 parts by weight of the solid content of the copolymer latex. This is a method for producing a synthetic rubber latex adhesive.

Examples of the vinyl monomer used in the present invention include styrene, α-methylstyrene, methyl methacrylate, methyl acrylate, and acrylonitrile, and styrene is preferably used.

The copolymerization ratio of butadiene and vinyl monomer is expressed by weight.
A range of 10:90 to 90:10 is suitable, preferably 30:70 to 7
A range of 0:30 is appropriate.

If the butadiene copolymerization ratio is less than 10 parts by weight, the copolymer becomes hard and the adhesive strength is undesirably reduced. When the amount is more than 90 parts by weight, stability at the time of emulsion polymerization is remarkably reduced, and at the same time, the copolymer is soft and lacks practicality in terms of function as an adhesive.

The reactive monomer used in the present invention means a hydroxyl group and a carboxyl group, and examples of the hydroxyl group include allyl alcohol, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, and 2-hydroxypropyl. Examples thereof include propyl acrylate and monoallyl ether of a polyhydric alcohol, and are preferably 2-hydroxyethyl methacrylate.

As the carboxyl group, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid,
Examples include itaconic acid and maleic acid half ester, and preferably itaconic acid.

The copolymerization ratio of the present reactive monomer is appropriately 0.5 to 20 parts by weight, preferably 2 to 10 parts by weight when the total of all monomers, i.e., butadiene, vinyl monomer, and the reactive monomer is 100 parts by weight. Range.

If the copolymerization ratio of the reactive monomer is less than 0.5 part by weight, there is no effect on the intended thixotropic viscosity improvement, and if it is more than 20 parts by weight, the emulsion polymerization rate and stability are significantly reduced, and Lack of practicality.

The copolymerization ratio of the hydroxyl group and the carboxyl group of the reactive monomer is, by weight ratio, hydroxyl group: carboxyl group = 1: 5 to 5:
1, preferably in the range of 1: 1 to 1: 2.

In the reactive monomer, when the copolymerization ratio of the hydroxyl group is 1 or less, there is no effect on the enlargement of the average particle diameter of the polymer and the deformation of the particle shape, and it is difficult to improve the thixotropic viscosity. The particle size becomes too large,
The emulsion polymerization rate and stability are remarkably reduced, which makes production extremely difficult.

Polymer average particle diameter of the copolymer latex of the present invention,
A range of 0.2-0.5 microns is suitable, preferably 0.2
It is essential that the diameter of the latex polymer is in the range of about 0.3 micron and that the shape of the polymer is irregular, that is, the latex polymer particles are spherical, whereas the latex polymer particles are spherical.

The average particle size is shown in photographs taken with an electron microscope (40,0 magnification).
The length in the vertical direction of the dharma-shaped particles of (00) was measured and measured with a measure.

If the polymer average particle size is 0.2 microns or less and spherical, there is no effect on thixotropic viscosity improvement,
When the particle diameter is 5 μm or more, the emulsion polymerization time becomes extremely long and the polymerization stability is impaired. On the other hand, it is difficult to increase the viscosity by adding a thickener, which is not practical. Further, in the above-mentioned average particle diameter of the polymer, the irregular shape, that is, the darma-like particle is also lacking in practicality for the same reason.

The above-mentioned variant, that is, dalma-shaped particles,
As shown in the electron microscope drawing taken at 40,000x,
A particle having a darma-like shape in which two latex particles are fused, and assuming that the upper and lower parts of the darma are each one particle, the particle radius of the upper and lower (or lower and upper) particles When expressed by the ratio of 1:10 to 3: 4, preferably
A range of 1: 3 to 2: 3 is appropriate.

Further, the ratio of the length of the dalma-like particles to the side (the larger diameter) is in the range of 1: 0.4 to 1: 0.95, preferably 1: 0.7 to 1: 0.
A range of 9 is appropriate.

When the ratio of the particle radii is 1:10 or less, that is, when the upper (or lower) particle diameter is small, there is no effect on thixotropic viscosity improvement, and when the ratio is 3: 4 or more, a large amount at the beginning of emulsion polymerization. It is necessary to use a functional group monomer of the formula (1), and it becomes extremely difficult to secure the polymerization stability, and this is not practical.

In addition, the ratio of the vertical length of the dalma-shaped particles is 1:
When it is 95 or more, that is, when the ratio of the horizontal length is close to 1, there is no effect on thixotropic viscosity improvement, and 1: 0.4
In the following cases, the polymerization stability becomes difficult and lacks practicality.

The polymer average particle size of the present invention is in the range of 0.2 to 0.5 microns, and the particle size of the copolymer latex is irregular,
In the copolymerization with butadiene and vinyl monomer, which are main monomers, it is obtained by administering a reactive monomer at the beginning of emulsion polymerization.

That is, the conversion ratio of the total monomer weight to the polymer is 0 to 0.
It can be obtained by dividing or continuously administering the reactive monomer within the range of 50%.

More specifically, at the stage of initial charging, that is, immediately after the temperature rise, a part of butadiene and vinyl monomer which are main monomers and a hydroxyl monomer in the reactive monomer are charged, emulsion polymerization is started, and then the remaining butadiene is reacted. By dividing or continuously administering a monomer having a carboxyl group in combination with a vinyl monomer, a copolymer latex having an average particle diameter of 0.2 to 0.5 μm and a uniform particle shape having a particle shape of Dharma can be obtained.

When the hydroxyl monomer was initially charged, that is, not administered immediately after the temperature was raised, or the carboxyl group monomer was not administered within the range of 0 to 50% of the conversion rate of the total monomer weight to the polymer, the fixed particles were not obtained. Polymer particles having a uniform diameter and irregular shape, that is, a Dharma-like shape, cannot be obtained, and a desired copolymer latex having improved thixotropic properties cannot be obtained.

The pH of the copolymer latex of the present invention is adjusted to a range of 3 to 7 using an alkaline salt such as aqueous ammonia, potassium hydroxide, and sodium hydroxide. Preferably
The pH is in the range of 4-6.

When the pH is 3 or less, the mechanical stability of the copolymer latex is impaired, and aggregates are generated during liquid transfer using a gear pump, a rotary pump or the like, or on a coating machine such as a roll coater, which is not practical.

On the other hand, when the pH is 7 or more, the thixotropic property at the time of blending the thickener is not improved, and it is difficult to impart fluidity similar to a vinyl acetate emulsion.

The copolymer latex of the present invention can be easily adjusted to an arbitrary viscosity by blending the partially saponified pyrivinyl alcohol, and the thickened product exhibits fluidity similar to that of a vinyl acetate emulsion.

The polyvinyl alcohol used in the present invention is a saponified product having a saponification degree (mol%) of 86 to 91 and a polymerization degree in a range of 50 to 2500. It is preferable to use one having a degree of polymerization of 500 to 1700.

The amount of the polyvinyl alcohol used in the present invention is based on 100 parts by weight of the solid content of the copolymer latex.
The solid content is in the range of 1 to 20 parts by weight, preferably 2 to 10 parts by weight.
It is in the range of parts by weight.

If the blending amount of polyvinyl alcohol is less than 1 part by weight, the viscosity is lacking, and if it is more than 20 parts by weight, the thickened material becomes highly viscous and becomes a paste, which hinders the liquid transfer during the coating operation, This leads to a decrease in the solid content of the adhesive and lacks practicality.

In the use of the polyvinyl alcohol, it is convenient to use an aqueous solution which has been previously dissolved in water to a concentration of 10 to 20% by weight.

As described above, the method for producing a synthetic rubber latex-based adhesive of the present invention uses a reactive monomer in the initial stage of emulsion polymerization in the copolymerization of a reactive monomer with butadiene and a vinyl monomer as main monomers. The polymer particles were enlarged and the shape of the particles was deformed, the pH was adjusted to a weakly acidic range, and the addition of partially saponified polyvinyl alcohol was a disadvantage of the conventional synthetic rubber latex adhesive. The thixotropic viscosity can be greatly improved, and the practical value is extremely high especially as an adhesive for plywood, woodwork, paper and textile fields in which an adhesive is applied using a roll coater, and its significance is great.

〔Example〕

Next, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these.

In the following, parts and percentages are by weight unless otherwise specified.

Examples 1 to 5 In a 3 l autoclave with a stirrer, 710 g of distilled water, 2 g of potassium sulfate, 0.5 g of sodium dodecylbenzenesulfonate,
5 g of potassium persulfate was charged and sealed, and the internal pressure of the autoclave was adjusted to 5 kg / cm ² by gauge pressure with nitrogen, and after performing a leak test for 5 minutes, the pressure was reduced to 500 mmHg.

After repeating this operation twice, the mixture was stirred at a rotation speed of 250 RPM in a nitrogen stream, and heated to 65 ° C.

Then, the monomers were dividedly administered under the conditions of the polymer conversion rate shown in Table 1, and after the administration of all the monomers was completed, the remaining monomers were completely reacted.

The time required from the first monomer administration to the end of the polymerization was 22 hours.

After completion of the reaction, the mixture was cooled to 30 ° C. to obtain a synthetic rubber latex of the present invention.

This latex was filtered through a 100-mesh wire gauze, and the resin characteristic values were measured.

In addition, particles of the synthetic rubber latex obtained from Examples 1 to 5 were photographed with an electron microscope photograph (magnification: 40,000), and the shape was confirmed. The ratio of the upper and lower dalmas is in the range of 1: 3 to 2: 3, and the ratio of the height and width of the dharma is also in the range of 1:04 to 1: 0.95. Was.

FIG. 1 shows a representative electron micrograph (magnification: 40,000) of the synthetic rubber latex obtained in Example 1 of the present invention.

Next, the synthetic rubber latex obtained in Examples 1 to 5,
The pH was adjusted to 5.0 with a 20% aqueous potassium hydroxide solution.

200 g of the synthetic rubber latex is collected in a 300 cc beaker and, with stirring, a 20% partially saponified polyvinyl alcohol prepared in advance (Kuraray Co., Ltd., trade name Kuraray Povar 205, polymerization degree 500, degree of saponification) (Mol% 88)) 15
g, gradually added to thicken.

The viscosity of the synthetic rubber latex thickened material was measured by the method described below, and the results are shown in Table-5.

Viscosity Characteristic Measurement Method (a) Viscosity The temperature was adjusted to 25 ° C with a BM type rotational viscometer under the measurement conditions of No. 3 spindle and rotation speed of 60 rpm.

Measure the viscosity of the synthetic rubber latex thickener of the present invention,
Displayed in cps.

(B) Thixotropic property (hereinafter abbreviated as TI value) According to the measurement conditions of (a) above, the viscosity at 6 rpm is 60 rpm
The value obtained by dividing the viscosity by the viscosity was shown as a TI value.

Larger TI values indicate better fluidity.

(C) Coatability with a roll coater The synthetic rubber latex thickened material is rolled up from a tank using a roll coater type gum-up tester manufactured by Kumagai Riki Co., Ltd. The distance between the non-driven transfer rolls was barely adjusted.

Then put the thickened synthetic rubber latex in the adhesive tank, rotate the pickup roll at a rotation speed of 78 RPM,
The transfer state to the transfer roll and the rotation state of the transfer roll were observed and displayed as follows.

…: The rotation of the transfer roll was smooth, uniform and a large amount of transfer was observed.

Δ: The rotation of the transfer roll is smooth, but the transfer amount is low.

×: Transfer roller rotation is irregular and there is a slip phenomenon.
In addition, the transfer amount is extremely small.

Comparative Examples 1 to 4 Synthetic rubber latex having the characteristic values shown in Table 4 was obtained in the same manner as in the Examples, according to the method for dividing monomers shown in Table 2.

Next, the pH was adjusted and the viscosity was increased in the same manner as in the examples, and the results of measuring the viscosity characteristics are shown in Table-5.

Comparative Example 5 Except that the pH of the synthetic rubber latex obtained in Example 1 was changed to 7.5, the conditions were all the same as those in Example, and the measurement results of the viscosity characteristics thereof are shown in Table-5.

[Effect of the Invention] The synthetic rubber latex-based adhesive of the present invention has a thixotropic property, which is the biggest defect of the conventional synthetic rubber latex-based adhesive, that is, the structural viscosity is greatly improved, and the water-soluble polymer is a core. It is clear from Table-5 that the polymer has fluidity comparable to that of a vinyl acetate emulsion polymerized as a polymer and applicability by a roll coater.

[Brief description of the drawings]

FIG. 1 is an electron micrograph of the particle structure of a synthetic rubber latex obtained according to Example 1 of the present invention.

Claims (7)

(57) [Claims] 1. A terpolymer latex comprising butadiene, a vinyl monomer and a vinyl monomer having a reactive group, wherein the vinyl monomer having a reactive group is added at an early stage of emulsion polymerization to thereby increase the average particle diameter of the polymer. A method for producing a synthetic rubber latex-based adhesive, characterized in that a copolymer latex having a particle size in the range of 0.2 to 0.5 micron and having a particle shape is obtained. 2. The method for producing a rubber latex adhesive according to claim 1, wherein 0.5 to 20 parts by weight of a vinyl monomer having a reactive group is copolymerized in 100 parts by weight of all monomers. 3. A particle having a Dharma-like shape in which two latex particles are fused, and the upper and lower portions of the Dharma are assumed to be one particle each, and the upper and lower portions are assumed to be one. Expressed as the ratio of the particle radii (or lower and upper), 1:10
2. The method for producing a synthetic rubber latex-based adhesive according to claim 1, wherein the adhesive is in the range of from 3: 4. 4. The method for producing a synthetic rubber latex adhesive according to claim 1, wherein the reactive groups are a hydroxyl group and a carboxyl group. 5. The method according to claim 1, wherein the vinyl monomer having a reactive group is at least in the range of 0 to 50% of the conversion of the polymer based on the total weight of the monomers, and is introduced in a divided or continuous manner. A method for producing a synthetic rubber latex-based adhesive. 6. The method according to claim 1, wherein the pH of the copolymer latex is in the range of 3 to 7. 7. The method according to claim 1, wherein 1 to 20 parts by weight of a solid content of partially saponified polyvinyl alcohol having a polymerization degree of 50 to 2500 is blended with respect to 100 parts by weight of the solid content of the copolymer latex. A method for producing the synthetic rubber latex-based adhesive according to the above.