JPH01266114A - Latex composition - Google Patents

Abstract

PURPOSE:To produce the title composition which is excellent in stability and dispersibility in a matrix with the amount of an emulsifying agent to be used reducible substantially without using any surface active agent, an anti-foaming agent, etc. at all, by subjecting styrene monomer and butadiene monomer to emulsion polymerization in the presence of a specific compound. CONSTITUTION:Styrene monomer and butadiene monomer as essential components are subjected to emulsion polymerization in the presence of a high- molecular naphthalene sulfonate/formalin condensate having an average degree of condensation of 10-18 and/or a melamine/sulfonate compound, thereby producing a latex composition. According to the above process, the amount of an emulsifying agent which causes foaming or the like can be substantially decreased, and a latex composition which is excellent in chemical and mechanical stability and also in dispersibility into a matrix can be produced without using any surface active agent, an anti-foaming agent, etc. which are used conventionally and cause foaming and lowering of the performance of the product.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a latex composition, and more specifically to a styrene-butadiene latex composition that is blended into cement, asphalt, paper processing, calcium silicate moldings, etc. It is about things.

(Prior Art) Synthetic rubber latex has been used for many purposes such as cement, concrete, sealing materials, and paper processing. For example, when an emulsion containing styrene-butadiene latex (SBR latex), acrylic acid compound, vinyl acetate, etc. is mixed into cement mortar as a modifier for a cement mortar molded product, the resulting molded product has good bending strength, water resistance, and adhesion. It is known that various properties such as elasticity are improved, and various synthetic rubber latexes and synthetic resin emulsions have been developed for such uses.

In particular, it has recently been discovered that in addition to having good adhesion, SBR latex is particularly effective in preventing carbonation caused by carbon dioxide gas, which is thought to be one of the causes of early deterioration of cement and concrete. There is a tendency for the use ratio of SBR latex to increase for this purpose.

When such SBR-based latex is used as a modifier for cement or concrete, polyvalent metal ions such as calcium ions and aluminum ions eluted from cement and other various aggregates and Because it is required to be chemically stable and stable against mechanical shearing forces such as crosstalk, a large amount of nonionic or cationic surfactant is usually added to SBR latex. efforts have been made to stabilize the situation.

(Problems to be Solved by the Invention) However, when using a large amount of such surfactants, S E-3
When mixed with R-based latex, foaming may be amplified during mixing, or a large amount of antifoaming agent etc. must be used in order to suppress foaming, resulting in a decrease in strength due to porosity in the case of cement mortar molded bodies. This has led to various problems such as poor water resistance and slow curing speed, resulting in a decrease in the performance of the resulting target product.

(Means to Solve the Problem) Therefore, the present inventors conducted intensive studies to solve the problem, and found that a latex composition obtained by emulsion polymerization in the presence of a specific compound, It is possible to significantly reduce the amount of emulsifiers that cause foaming, etc., and there is no need to use conventionally used surfactants and antifoaming agents, etc., which can cause foaming and deterioration of product performance. They discovered this and arrived at the present invention.

That is, an object of the present invention is to provide a latex composition that has excellent chemical and mechanical stability as well as excellent dispersibility in a matrix.

The purpose is to emulsion polymerize styrene monomer and butadiene monomer as essential components in the presence of a naphthalene sulfonate formalin high condensate and/or melamine sulfonate compound with an average degree of condensation of 10 to /r. This can be easily achieved using a latex composition characterized by:

The present invention will be explained in detail below.

In the present invention, a styrene monomer and a butadiene monomer are used as essential components, but a third component monomer such as an unsaturated carboxylic acid or an unsaturated carboxylic acid ester may also be used. The unsaturated carboxylic acid is not particularly limited as long as it is used in the production of normal latex, such as acrylic acid, methacrylic acid,
Examples include itaconic acid, fumaric acid, maleic acid, and crotonic acid.

Further, as unsaturated carboxylic acid esters, esters of the above-mentioned carboxylic acids having carbon number/~v, preferably carbon number/, 2 are usually used, and specifically, methyl acrylate,
Examples include ethyl acrylate, methyl methacrylate, and ethyl methacrylate.

The latex composition of the present invention is obtained by emulsion polymerizing each of the above monomers in the presence of a naphthalene sulfonate formalin high condensate and/or a melamine sulfonate having an average degree of condensation in the range of 10-/♂. The presence of such specific compounds is extremely important.

The naphthalene sulfonate formalin high condensate has an average degree of condensation in the range of 70 to /I, preferably l/ to /I.
It is preferable to use a salt in the range of j, and as the salt, it is preferable to use an alkali metal salt, preferably a sodium salt.Specifically, "Mighty/jθ" manufactured by Kako Co., Ltd., "rNP-to" manufactured by FDJ Policy Bussan Co., Ltd., etc. can be mentioned.

Naphthalene sulfonate formalin low condensates, which have been conventionally used as dispersants for emulsion polymerization and have an average degree of condensation of less than 10, are preferable because they have high foaming properties and low dispersing ability, and furthermore, economically the dispersing effect decreases. Without,
If the average degree of condensation is greater than /I, the cost will be high and a significant improvement in effectiveness will not yet be observed, which is not preferable.

As the melamine sulfonic acid compound, a formalin condensate of an alkali metal melamine sulfonic acid salt, a melamine resin sulfonate, etc. are used, and specifically, a product name such as "NL Hiro O0o" manufactured by Hozoris Bussan Co., Ltd. can be mentioned.

As a method for producing the latex composition of the present invention, first, styrene monomer:butadiene monomer (weight ratio (wt%)) =
≠ ~ ♂: Adjusted to a ratio of 6 to 2, the above naphthalene sulfonate formalin high condensate and/or melamine sulfonate was added to 100 parts by weight of the total amount of styrene monomer and butadiene monomer -12 parts by weight, preferably 2-7
4tj to 70°C, j-/j in an aqueous solution by adding parts by weight
Emulsion polymerization is carried out in about hours.

At that time, it is preferable to add a surfactant having a micelle-forming ability as an emulsifier in an amount at least exceeding the critical micelle concentration. In particular, the emulsifier is preferably a nonionic emulsifier with an anion group added to the end, and specifically a polyoxyethylene alkyl phenyl ether sulfate emulsifier is used. ” etc.

The emulsifier is preferably used in o, i -s parts by weight based on 100 parts by weight of the total amount of styrene monomer and butadiene monomer.

Furthermore, if a sounionic emulsifier is used as an emulsifier, the mechanical stability will be poor, and if a completely anionic emulsifier is used, the chemical stability will be poor, which is not preferable.

In addition, when using a third component monomer other than styrene monomer and butadiene monomer, the total amount of styrene monomer and butadiene monomer ioo parts by weight during the above emulsion polymerization, It may be blended in a proportion of 0.2 to 20 parts by weight, preferably 0.2 to is parts by weight.

(Examples) Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited thereto.

Example 1-2 The composition shown in Table 7 was placed in a polymerization tank at 60°C.
The reaction was carried out for 2 hours to produce a latex composition of the present invention.

(Table 7) Example 1 Example 2 (Parts by weight) (Parts by weight) Polyoxyethylene alkyl 03 0.3
Phenyl ether sodium sulfate A+) 3
-0 B←)
-Hiro・Deionized water 12θ /20・
Styrene to 6゜・Butadiene ≠OhiroQ-Methyl methacrylate 3-・Methacrylic acid
- potassium persulfate 0.3 0.3+)
Naphthalenesulfonic acid sodium formalin high condensate (
average degree of condensation to-ts) ("Mighty/rOJ (chemical industry)
) Old 0 melamine sulfonic acid soda formalin condensate (r
NL≠000 J (Hozorisu Bussan)) Comparative Examples 1 to 3 The compositions shown in Table 2 were polymerized in the same manner as in Examples/- to obtain latex. In the case of comparative example (Table 2)
A latex composition was prepared by adding and mixing the stabilizer and antifoaming agent shown in .

(Table 2) Comparative Example 1 Comparative Example 2 Comparative Example 3 (Parts by weight) (II) (II) Soda/tertiary sodium phosphate o3 o, g
-・・Deionized water /20 /20
120・Styrene t,o to
t.

・Butadiene Hiro0 HiroO≠O・Methyl methacrylate − −3・Potassium persulfate 0,2 0,2 0.3 [Hereafter, added after polymerization] Table 2 continued Comparative example 1 Comparative example 2 Comparative example 3 (・Polyoxyethylene nonylphenylny -≠ -chill ("Emargenta l/" (chemical industry)) ・Silicone antifoaming agent ("Antifoam - / -AFEJ")
(Dow Corning)) Reference Examples Cement mortar molded bodies were obtained using the latex compositions obtained in Examples and Comparative Examples. As a method for producing a cement mortar molded body, cement, sand, latex, and water were mixed at the following mixing ratios.

(Mixing ratio) Cement/sand (silica sand No. 7) -//3 (weight ratio) Cement/latex =/10. / (solid content equivalent; weight ratio) Cement/water = i7o, ? (Weight ratio) The physical properties of this cement mortar molded body are shown in Table 3.

(Table 3) In addition, carbon fiber (“Dialead” t =
As a result of mixing J mm (Mitsubishi Kasei), Example/2
Compared to the comparative example, the carbon fibers were clearly dispersed better, and almost no undispersed lumps were found.

(Effects) The latex obtained by the present invention has a high ability to disperse particles, etc., so it is particularly suitable for use in cement mortar, concrete mixing, calcium silicate moldings, etc. where the matrix is particulate. Even when fillers such as fibers are added, they promote their dispersion, giving an excellent composite. As the dispersant (water-reducing agent) in the latex is adsorbed to the matrix particles, the latex itself is also uniformly dispersed in the matrix, making it possible to improve efficiency and effectiveness with a small amount of rubber.

Claims (2)

[Claims] (1) Styrene monomer and butadiene monomer as essential components are emulsion polymerized in the presence of a naphthalene sulfonate formalin high condensate and/or melamine sulfonate compound having an average degree of condensation of 10 to 18. A latex composition characterized by: (2) The latex composition according to claim 1, which contains a polyoxyethylene alkyl phenyl ether sulfate emulsifier.