JPH03220279A - Preparation of synthetic rubber latex adhesive - Google Patents

Abstract

PURPOSE:To prepare the title adhesive having an improved structural viscosity, high flowability, and excellent coatability on a roll coater by specifying the features of polymer particles of a copolymer latex prepared from butadiene, a vinyl monomer, and a reactive monomer. CONSTITUTION:Polymer particles of a copolymer latex prepared from butadiene, a vinyl monomer (e.g. styrene), and a reactive monomer (e.g. 2-hydroxyethyl methacrylate) are irregularly shaped with a mean particle size of 0.2-0.5mum.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to vinyl acetate emulsion, vinyl acetate acrylic copolymer emulsion, and vinyl acetate ethylene emulsion, which are used in large quantities in the plywood, woodworking, civil engineering, paper, and textile fields. The present invention relates to a method for producing a synthetic rubber latex adhesive that imparts excellent fluidity to a copolymer emulsion.

More specifically, the present invention relates to a method for producing a synthetic rubber latex adhesive in which the biggest drawback of synthetic rubber latex adhesives, namely thixotropic viscosity, is brought closer to Newtonian viscosity with excellent fluidity. .

[Conventional technology]

Despite the fact that synthetic rubber latex has adhesive properties equivalent to or better than vinyl acetate emulsions, it is used in the plywood, paper, and textile processing fields where roll coaters are used as the adhesive application method. The number of usage examples was extremely low.

The background to this is that synthetic rubber latex generally has a lower viscosity than vinyl acetate emulsions, so it was necessary to increase the viscosity by some method.

The biggest drawback of this thickened product is that it exhibits strong thixotropic viscosity behavior, and the viscosity decreases significantly due to liquid transfer onto the roll coater and rotational friction of the rolls, making it extremely difficult to apply a predetermined amount of adhesive. It had been.

[Problem to be solved by the invention]

As a means to solve this problem, synthetic rubber latex,
In addition to the addition of water-soluble polymers such as polyvinyl alcohol, hydroxyethyl cellulose, carboxy cellulose, and carboxy methyl cellulose used in vinyl acetate emulsions, viscosity improvement by adding surfactant-based thickeners, that is, Newtonian Although attempts have been made to impart fluidity close to viscosity, none of them have been satisfactory as the viscosity is significantly different from that of vinyl acetate emulsions.

Means for Solving Problem C) As a result of intensive studies, the present inventors have found that the average particle diameter of synthetic rubber latex is in the range of 0.2 to 0.5 microns,
We have also found that using synthetic rubber latex with irregular particle shapes, adjusting the pH of the latex to a range of 3 to 7, and thickening it with partially saponified polyvinyl alcohol is extremely effective in solving the above problem. The present invention has now been completed.

That is, the present invention provides: (1) a copolymer latex consisting of butadiene, a vinyl monomer, and a reactive monomer, the average particle diameter of which is in the range of 0.2 to 0.5 microns, and the particle shape is irregular; A method for producing a synthetic rubber latex adhesive characterized by:

(2) 0 reactive monomers in 100 parts by weight of total monomers
．． A method for producing a synthetic rubber latex adhesive according to item (1) above, in which 5 to 20 parts by weight are copolymerized.

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

(4) The synthetic rubber latex adhesive according to item (1) above, wherein the reactive monomer is introduced dividedly or continuously within a range of at least 0 to 50% polymer conversion based on the total weight of the monomer. manufacturing method.

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

(6) Item (1) above, characterized in that 1 to 20 parts by weight of partially saponified polyvinyl alcohol having a degree of polymerization of 50 to 2,500 is blended as a solid content 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, acrylonitrile, etc., and styrene is preferably used.

The copolymerization ratio of butadiene and vinyl monomer is 1 by weight.
A range of 0:90 to 90:10 is appropriate, preferably a range of 30:70 to 70:30.

If the butadiene copolymerization ratio is less than 10 parts by weight, the copolymer becomes hard and the adhesive strength decreases, which is not preferable. If the amount is more than 90 parts by weight, the stability during emulsion polymerization will be significantly reduced, and the copolymer will be soft, making it less practical as an adhesive.

The reactive hexamer 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,
Examples include 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, monoallyl ether of polyhydric alcohol, and 2-hydroxyethyl methacrylate is preferred.

Further, examples of the carboxyl group include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, itaconic acid and hismaleic acid half ester, and preferably itaconic acid.

The copolymerization ratio of this reactive monomer is suitably in the range of 0.5 to 20 parts by weight, preferably 2 to 10 parts by weight, when the total of all monomers, that is, butadiene, vinyl monomer 1, and reactive monomer is 100 parts by weight. Parts by weight range.

If the copolymerization ratio of the reactive monomer is less than 0.5 parts by weight, it will not be effective in improving the desired thixotropic viscosity, and if it is more than 20 parts by weight, the emulsion polymerization rate and stability will be significantly reduced. , it lacks practicality in manufacturing.

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

When the copolymerization ratio of hydroxyl groups in the reactive monomer is 1 or less,
It has no effect on increasing the average particle diameter of the polymer or making the particle shape irregular, and it is difficult to improve thixotropic viscosity.
If it is 5 or more, the average particle diameter of the polymer becomes too large, and the emulsion polymerization rate and stability are significantly reduced, making production extremely difficult.

The polymer average particle diameter of the copolymerized latex of the present invention is 0
．． The range of 2 to 0.5 microns is appropriate, preferably the range of 0.2 to 0.3 microns, and the shape of the polymer is irregular, that is, while ordinary latex polymer particles are spherical, It is essential that it be in the shape of a daruma.

If the average particle diameter of the polymer is 0.2 microns or less and it is spherical, it will not have the same effect on thixotropic viscosity improvement, and
．． If the diameter is 5 microns or more and the shape is spherical, the emulsion polymerization time will be significantly longer and the polymerization stability will be impaired, and it will be difficult to increase the viscosity by adding a thickener, making it impractical. In addition, regarding the average particle diameter of the polymer, irregularly shaped particles, that is, spherical particles, also lack practicality for the same reason.

The above-mentioned irregular shape, that is, daruma-like particles, is the following magnification: 4
As shown in the drawing of an electron microscope taken at 0,000 times magnification, it is a particle-shaped object in which two latex particles are fused together, and the upper and lower parts of the particle are formed by one particle each. Assuming that, when expressed as the ratio of the particle radius of the upper part and the lower part (or the lower part and the upper part), l : is suitably in the range of 10 to 3:4, preferably in the range of 1:3 to 2:3.

Further, the length ratio of the vertical and horizontal (larger diameter) lengths of the daruma-like particles is in the range of 1:0.4 to 1:0.95, preferably in the range of 1:0°7 to 170.9. Appropriate.

If this particle radius ratio is less than 1:10, that is, the upper (or lower) particle diameter is small, there is no effect on thixotropic viscosity improvement, and if it is more than 3:4, a large amount of It is necessary to use a functional group monomer, making it extremely difficult to ensure polymerization stability and lacking in practicality.

Further, the ratio of the vertical and horizontal lengths of the daruma-shaped particles is 1:
95 or more, that is, when the ratio of length to width is close to 1,
It has no effect on thixotropic viscosity improvement, and
: If it is less than 0.4, it becomes difficult to maintain polymerization stability and it lacks practicality.

The copolymer latex of the present invention having a polymer average particle size in the range of 0.2 to 0.5 microns and having irregular particle size shapes can be copolymerized with butadiene and vinyl monomers as main monomers. It can be obtained by administering a reactive monomer at the beginning of emulsion polymerization.

That is, the conversion rate of total monomer weight to polymer is 0 to 5.
It can be obtained within the range of 0% by dividing or continuously administering the reactive monomer.

More specifically, at the initial charging stage, that is, immediately after raising the temperature, part of the raw monomers butadiene and vinyl monomer and a hydroxyl monomer among the reactive monomers are charged,
After starting emulsion polymerization, the carboxyl group-containing monomer is dividedly or continuously administered together with the remaining butadiene and vinyl monomers to obtain particles with an average particle size of 0.2 to 0.5 microns and a particle shape. A copolymer latex with a uniform shape in the shape of a doll is obtained.

If the hydroxyl monomer is not administered at the initial charge, i.e., immediately after the temperature rise, or if the carboquine monomer is not administered within the range of 0 to 50% conversion of total monomer weight to polymer, a constant particle It has a uniform diameter and irregular shape, that is, a daruma-like shape. Polymer particles cannot be obtained, and the desired copolymer latex with improved thixotroviscosity cannot be obtained.

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

If the pH is below 3, the mechanical stability of the copolymer latex is impaired, and aggregates are generated during liquid transfer using a gear pump, rotary pump, etc., or on a coating machine such as a roll coater, making it impractical.

On the other hand, when the pH is set to 7 or more, the thixotropic properties are not improved when a thickener is added, and it becomes difficult to impart fluidity similar to that of a vinyl acetate emulsion.

The copolymer latex of the present invention can be easily adjusted to any viscosity by incorporating partially saponified polyvinyl alcohol, and its thickened product exhibits fluidity similar to that of a vinyl acetate emulsion.

The polyvinyl alcohol used in the present invention is a saponified product with a degree of saponification (mol %) of 86 to 91, and a degree of polymerization in the range of 50 to 2,500, which is preferable for delicate viscosity adjustment work. It is preferable to use one having a degree of polymerization of 500 to 1,700.

The amount of 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 ranges from 1 to 211 parts, preferably from 2 to 1
It is in the range of 0 parts by weight.

If the amount of polyvinyl alcohol blended is less than 1 part by weight, it lacks thickening properties, and if it is more than 20 parts by weight, the thickened product will become highly viscous and paste-like, causing problems in liquid transfer during coating work. This leads to a decrease in the solid content on the adhesion side, making it impractical.

When using the above-mentioned polyvinyl alcohol, it is convenient to use an aqueous solution prepared by dissolving it in water to a concentration of 10 to 20% by weight.

As described above, in the method for producing a synthetic rubber Latinx adhesive of the present invention, in the copolymerization of the main monomers butadiene and vinyl monomers with the reactive monomer, by using the reactive monomer at the initial stage of emulsion polymerization, By adjusting the pH to a weakly acidic range and blending partially saponified polyvinyl alcohol, the polymer particles become enlarged and the particle shape becomes irregular, which is a disadvantage of conventional synthetic rubber Latinx adhesives. Thixotropic viscosity can be greatly improved, and its practical value is extremely high, especially as an adhesive for plywood, woodworking, paper, and textile fields where adhesives are applied using a roll coater.

〔Example〕

Next, the present invention will be specifically explained using Examples and Comparative Examples, but the present invention is not limited thereto.

In addition, in the following, unless otherwise specified, parts or percentages are based on weight.

Examples 1-5 In a 3J2 autoclave with a stirrer, distilled water 710
g, 2 g of potassium sulfate, 0.5 g of sodium dodecylbenzenesulfonate, and 5 g of potassium persulfate, and the container was sealed.
Adjust the autoclave internal pressure to 5 kg/c with gauge pressure using nitrogen.
T! After conducting a leak test for 5 minutes, the pressure was reduced to 500 aHg.

After repeating this operation twice, perform 250RP in a nitrogen stream.
The mixture was stirred at a rotational speed of M, and the temperature was raised to 65°C.

Next, under each polymer conversion rate condition shown in Table 1,
Monomers are administered in divided doses, and after all monomers have been administered,
The remaining monomers were completely reacted.

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

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

This latex was filtered through a 100-mesh wire mesh, and the resin characteristic values were measured, as shown in Table 3.

In addition, regarding the synthetic rubber latex obtained from Examples 1 to 5, particles were photographed using an electron microscope (magnification: 40.000) and the shapes were confirmed. The ratio of the upper part to the lower part of the daruma shape is within the range of 1:3 to 2:3, and the ratio of the length and width of the daruma shape is also 1:04 to 1:0.95. It was within range.

A representative electron micrograph (40.000 magnification) of the synthetic rubber latex obtained in Example 1 of the present invention is shown in FIG. 1 of the drawings.

Next, the synthetic rubber latex obtained in Examples 1 to 5 was
The pH was adjusted to 5.0 with a 0% potassium hydroxide aqueous solution.

Place 20 pieces of this synthetic rubber latex in a 300cc beaker.
Collect 0 g and, while stirring, add 20% of the previously prepared
15 g of partially saponified polyvinyl alcohol (trade name: Tararebovar 205, manufactured by Kuraray Co., Ltd., degree of polymerization 500, degree of saponification (mol% 88)) was gradually added to increase the viscosity.

The viscosity properties of this synthetic rubber latex thickened product were measured by the method shown below, and the results are shown in Table 5.

Ino 1 Toyotafuchi foot removal (a) Viscosity BM type rotational viscometer, No. 3 spindle, rotation speed 6O
The temperature was adjusted to 25°C under the measurement conditions of rpm.

The viscosity of the synthetic rubber latex thickened product of the present invention was measured, and c
Displayed in ps.

(b) Thixotropy, resistance (hereinafter abbreviated as Tr value) According to the measurement conditions in (a) above, the viscosity at 6 rpm was 6
The value divided by the viscosity of Orpm was expressed as TI (1).

A high 7M value indicates good fluidity.

(c) Spreadability using a roll coater The synthetic rubber latex thickened product is rolled up using a roll coater type gum up tester manufactured by Kumagai Riki ■, using a pink up roll that rolls up the adhesive from a tank by rotation, and a pink up roll for adjusting the amount of application. The distance between the non-driven transfer rolls was adjusted so that they barely touched each other.

Next, the thickened synthetic rubber latex was placed in the adhesion subtank, and the pick-up roll was rotated at a rotation speed of 78 RPM, and the state of transfer to the transfer roll and the state of rotation of the transfer roll were observed and displayed as shown below.

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

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

×...The rotation of the transfer roll was irregular and there was a slip phenomenon, and the amount of transfer was extremely small.

Comparative Examples 1 to 4 Synthetic rubber latexes having the characteristic values shown in Table 4 were obtained in the same manner as in Examples according to the monomer division method shown in Table 2.

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

Comparative Example 5 All conditions were as in Example except that the pH of the synthetic rubber latex obtained in Example 1 was 7.5, and the results of measuring the viscosity characteristics are shown in Table 5.

*Measurement table using electron micrographs Table 5 [Effects of the invention] The synthetic rubber latex adhesive of the present invention has improved thixotropic properties, that is, structural viscosity, which was the biggest drawback of conventional synthetic rubber latex adhesives. It is clear from Table 5 that it has greatly improved fluidity and roll coatability comparable to vinyl acetate emulcidin polymerized using a water-soluble polymer as a core.

[Brief explanation of drawings]

FIG. 1 is an electron micrograph of the synthetic rubber latex obtained in Example 1 of the present invention.

Claims (1)

[Scope of Claims] 1. A copolymer latex consisting of butadiene, a vinyl monomer, and a reactive monomer has an average particle diameter in the range of 0.2 to 0.5 microns, and the particle shape is irregular. A method for producing a synthetic rubber latex adhesive characterized by: 2. 0 reactive monomers in 100 parts by weight of total monomers
．． The method for producing a synthetic rubber latex adhesive according to claim 1, wherein 5 to 20 parts by weight are copolymerized. 3. The particle shape looks like two latex particles fused together.
An object having a daruma-like shape, assuming that the upper and lower parts of the daruma shape are each one particle, and expressed as the ratio of the particle radius of the upper part and the lower part (or the lower part and the upper part), it is 1:10 ~ 3
The method for producing a synthetic rubber latex adhesive according to claim 1, wherein the adhesive is in the range of :4. 4. The method for producing a synthetic rubber latex adhesive according to claim 1, wherein the reactive monomer is a hydroxyl group and a carboxyl group. 5. The synthetic rubber latex adhesive according to claim 1, wherein the reactive monomer has a polymer conversion rate of at least 0 to 50% of the total monomer weight, and is introduced in portions or continuously. manufacturing method. 6. The method for producing a synthetic rubber latex adhesive according to claim 1, wherein the pH of the copolymer latex is in the range of 3 to 7. 7. The synthesis according to claim 1, wherein 1 to 20 parts by weight of partially saponified polyvinyl alcohol having a degree of polymerization of 50 to 2,500 is blended as a solid content to 100 parts by weight of the solid content of the copolymer latex. Method for manufacturing rubber latex adhesive.