JPH09104715A - Method for coagulating polymer latex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain an excellent effect of growing the particles of a polymer latex containing particles of diameters as small as a specified value or below by adding a plurality of surfactants and an acid to the latex and neutralizing the acidified latex with an alkaline substance. SOLUTION: To a small-particle-diameter latex such as a polybutadiene latex having a particle diameter of 800Å or below and produced by emulsion polymerization, an emulsifier having surface activity stable under acidic conditions and comprising 0.02-0.2 pt.wt. per 100 pts.wt. polymer, anionic surfactant (e.g. sodium alkylbenzenesulfonate), about 0.001-0.006 pt.wt., per 100 pte.wt. polymer, nonionic surfactant (e.g. polyoxyethylene alkyl ether), etc., is added and mixed. The pH of the emulsion is adjusted to about 6 or below by adding at least one member selected from among hydrochloric acid, acetic acid, etc., thereto. The acidified emulsion is then neutralized with an alkaline substance (e.g. KOH) to obtain a polymer latex having a bimodal distribution with a particle diameter of 800Å or above, especially about 1,500-7,000Å.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for aggregating a polymer latex, and particularly to agglomerating a polymer latex for obtaining a polymer latex containing large-sized particles stably in a short time without producing coagulated particles as a by-product in the aggregating step. Regarding the method.

[0002]

2. Description of the Related Art Resins obtained by emulsion polymerization using rubber latex as a substrate are often important as engineering plastics. The main examples thereof are ABS resins obtained by graft polymerization of styrene and acrylonitrile onto polybutadiene, Examples thereof include ASA resin in which styrene and acrylonitrile are graft-polymerized with butyl acrylate.

Generally, a polymer containing grafted rubber particles as a component changes its physical properties depending on the graft polymerization method, but the physical properties of the polymer also change greatly by changing the particle size and distribution of the rubber matrix particles, so that it is suitable. It is well known that it is necessary to use a rubber matrix having a particle size and a distribution state.

For example, in the case of ABS resin, it is generally difficult to obtain good physical properties unless the particle diameter is at least 2500 Å or more, and it is preferable that particles of 5000 Å or more are contained at all.

[0005]

However, the production of polymer particles having such a large particle size by emulsion polymerization leads to a marked decrease in the polymerization rate, as easily derived from the general theory of emulsion polymerization. Therefore, it is industrially disadvantageous.

Various methods for aggregating small particle size polymer latex have been known so far. For example, US Pat. Nos. 2,446,101 and 2,49.
No. 4,002 discloses a method in which ammonium chloride is added to a latex. However, in the method of aggregating using such a water-soluble salt, the effect is small, so that the particle size enlargement effect is In order to increase it, a large amount must be added. Moreover, it is necessary to add a large amount of emulsifier in order to re-stabilize the polymer latex after aggregation.

Further, these low molecular weight components added in large amounts in the aggregating step may cause problems in stability in the subsequent steps, and may remain in the final polymer to impair the quality of the product, which is not preferable. .

US Pat. No. 3,281,386,
No. 3,551,370 and No. 3,652,
No. 721 proposes a method of aggregating latex particles by deactivating the surfactant activity of the emulsifier with acetic acid or acetic anhydride. However, in this method, the step of adding an acid to the latex is the most unstable, and the coagulated particles (aggregate until the particles reach 10 μm or more, enlarge and become an emulsified state) at the interface where the added acid diffuses in the latex. Is an irreversible particle and often produces (hereinafter referred to as "coagulam"), and it is necessary to make the concentration of the acid sufficiently low in order to prevent the formation of such particles. This is a disadvantageous method because not only the final latex concentration decreases, but also the effect of increasing the particle size itself decreases.

On the other hand, a method using a so-called polymer flocculant having a hydrophilic group and a hydrophobic group in one molecule is disclosed in US Pat. No. 3,049,500 and US Pat. No. 3,056,758.
No. 3,330,795, No. 3,330
288,741 and JP-B-46-14539
No. 1993.

In these methods, the polymer flocculant is used as it is or after being partially modified and used alone or in combination with a specific salt.

However, the method using a polymer flocculant requires a long time for the flocculation step, the particle size is not enlarged so much, it is difficult to stop the flocculation, and the latex after flocculation is stored. It has a major drawback that the particle size changes.

[0012] By the way, the methods currently used industrially include a method using a high-pressure homogenizer and a method of adding a solvent having a good affinity for the polymer latex. In the case of the former, Latex particles having a uniform particle size cannot be obtained because only a part of the latex particles are aggregated. In the latter case, the solvent needs to be distilled off as a pre-stage of the graft polymerization, and there is much room for improvement.

[0013]

The object of the present invention is to stabilize a polymer latex containing particles of both small particle size and large particle size uniformly in a short aggregation time without forming a coagulum in the aggregation process. It is to provide an industrially advantageous aggregation method that can be obtained.

The method for aggregating a polymer latex of the present invention contains two or more kinds of surfactants and has a particle size of 800Å.
An acid is added to the small particle size polymer latex obtained by the emulsion polymerization method, which is then agglomerated, and then neutralized with an alkaline substance, thereby aggregating a polymer latex having a bimodal distribution with a particle size of 800 Å or more. It is a method to let.

The small particle diameter polymer latex having a particle size of 800 Å or less used in the present invention is produced by a conventional emulsion polymerization using two or more kinds of surfactants and is not particularly limited as a surfactant. For example, a carboxylic acid group and an alkali metal are used. Anionic surfactants such as potassium laurate, sodium oleate, mixed fatty acid potassium, potassium rosinate alkylbenzene sulfonate, and phenylethoxy sulfate are used.

Further, nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, sorbitan fatty acid ester and glycerin fatty acid ester can be used. The kind is not particularly limited, but preferably a combination of an anionic surfactant and a nonionic surfactant gives good results, and the anionic surfactant is 0.02 per 100 parts by weight of the polymer.
To 0.2 parts by weight, preferably 0.05 to 0.15 parts. The amount of the nonionic surfactant is 0.001 to 0.006 part, preferably 0.002 to 0.005 part.

In the present invention, the small particle size polymer latex means a polymer latex having a particle size of 1,500 Å or less, which is generally called a small particle size. The particle size of the small particle size polymer latex is not particularly limited because it is selected from the viewpoint of industrial advantage that is produced by emulsion polymerization for a short time and the particle size enlargement effect in the aggregation step, but is not limited to 500Å to 1,
000Å is preferable.

The component of the small particle size polymer latex is not particularly limited, but for example, a soft polymer latex such as polybutadiene latex, polystyrene-butadiene copolymer latex, polyacrylonitrile-butadiene copolymer latex, and polybutyl acrylate latex is preferable. It is also possible to use a hard polymer latex such as polystyrene latex or polyacrylonitrile-styrene copolymer latex.

In the present invention, it is preferable to add an emulsifier having acidity and good surface-active ability in advance before adding an acid to the small particle size polymer latex. The emulsifier used for this purpose may be one having an acid group having a higher ionization constant than the below-mentioned acid, for example, as an emulsifier composed of a sulfonic acid group and an alkali metal salt, sodium alkylbenzene sulfonate, Sodium alkylnaphthalene sulfonate, potassium alkyl diphenyl ether sulfonate, sodium lauryl sulfate, etc., and anionic surfactants such as potassium laurate having sodium salt of carboxylic acid group and alkali metal, sodium oleate, mixed fatty acid potassium, potassium rosinate, etc. Anionic surfactants such as sodium alkylbenzene sulfonate and phenylethoxy sulfate are used.

Further, nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, sorbitan fatty acid ester and glycerin fatty acid ester can be used. The kind is not particularly limited, but preferably a combination of an anionic surfactant and a nonionic surfactant gives good results, and the amount of the anionic surfactant is 0.0 per 100 parts by weight of the polymer.
2 to 0.2 parts by weight, preferably 0.05 to 0.15 parts by weight. Nonionic surfactant is 0.001-0.006
Parts, preferably 0.002 to 0.005 parts.

If the amount added is too small, coagulum tends to occur in the acid addition step, and if too large, the particle size enlargement effect tends to decrease. The emulsifier may be added at the time of polymerizing the small particle size polymer latex or after the polymerization.

The small particle size polymer latex is aggregated and enlarged, and the bimodal enlarged particle size polymer latex is a polymer latex having a particle size of about 1,500Å to 7,000Å.

The acid added for aggregation and enlargement may be any acid having an ionization constant higher than that of the acid group of the emulsifier which is acidic and has a reduced surface activity, such as sulfuric acid or hydrochloric acid.
A strong acid such as sulfonic acid and a weak acid such as maleic acid, itaconic acid and acetic acid may be used alone or in combination of two or more. However, the concentration is preferably as high as possible within the range where coagulum is not generated in the aggregation step.

The amount of the acid added to the small particle size polymer latex varies depending on the type and amount of the emulsifier used, but is not particularly limited, but the pH of the polymer latex is not limited.
Is preferably 6 or less.

When the concentration of the small particle size polymer latex used in the present invention is too high, coagulum is generated in the step of adding an acid, and when it is too low, the particle size enlarging effect tends to be small. However, the concentration range is not particularly limited because it varies depending on the type and concentration of the acid used, and the type and addition amount of the emulsifier having acidic and good surface-active ability, but for industrial purposes such as productivity, latex is used. 30% by weight or more based on the total weight is preferred.

Examples of the alkaline substance used for stabilizing the bimodal enlarged particle size polymer latex include sodium hydroxide, potassium hydroxide and ammonium hydroxide. The amount added is appropriate to neutralize the acid added in the coagulation step, and if the concentration is too high, coagulum is formed in the addition step, so it is preferably 15% or less based on the total weight of the latex. .

[0027]

EXAMPLES The method of the present invention will now be described in detail with reference to examples. In Examples and Comparative Examples, "part" means part by weight and "%" means% by weight.

Example 1 Butadiene Monomer 100
Parts, deionized water 150 parts, potassium oleate 3.0
Parts, sodium sulfate 0.3 parts, potassium persulfate 0.2
Parts, 0.20 parts of tert-lead decyl mercaptan, and 0.18 parts of potassium hydroxide were placed in a pressure vessel equipped with a stirrer, the temperature was raised to 60 ° C., and polymerization was started.

After the initiation of the polymerization, when the polymerization rate was 65%, 5 parts of deionized water in which 0.1 part of potassium persulfate was dissolved was added to the pressure vessel to raise the polymerization temperature to 65 ° C. Polymerization time 1
Polymerization rate 95% in 3 hours, average particle size 800Å, solid content 4
A polybutadiene latex of 0.1% and a viscosity of 200 centipoise was obtained. This is designated as latex A.

Next, latex A was added with organic sulfonic acid soda (trade name "TAMOL-SN TR", manufactured by Rohm and Haas Co.) in an amount of 0.1 parts by weight per 100 parts by weight of latex A.
15 parts by weight of polyoxyethylenenolyl phenyl ether (trade name "Emulgel 999S", manufactured by Kao)
02 parts by weight was added, and after stirring for 5 minutes, 2 parts by weight of acetic acid was added.

Then, 2 parts by weight of potassium hydroxide was added to obtain a stable latex.

This latex is a bimodal latex having a particle size peak of 1500Å and 7000Å, does not form a coagulum and has a solid content of 40%.
It was a high-concentration latex. 1 as the weight fraction
The 500Å was 70% by weight and the 7,000Å was 30% by weight.

(Example 2) 100 parts by weight of latex A produced in the same manner as in Example 1 was mixed with polyoxyethylenenolyl phenyl ether (trade name "Emulgel 999".
S ", manufactured by Kao) was used, and a stable latex was obtained by the same formulation as in Example 1. The latex was a bimodal particle size latex having beaks at 1,500Å and 7,000Å. The weight fraction of 1,500Å was 60% by weight, and that of 7,000Å was 40% by weight. Coagulam was a high-concentration latex with a solid content of 40% without by-products.

COMPARATIVE EXAMPLE 1 100 parts by weight of latex A produced in the same manner as in Example 1 was mixed with 0.15 parts by weight of organic sulfonic acid soda (trade name "TAMOL-SN TR", manufactured by Rohm and Haas Co.). After addition, and stirring for 5 minutes, 2 parts by weight of acetic acid was added. Then, 2 parts by weight of potassium hydroxide was added to obtain a stable latex. The average particle size of this latex was a latex having a monomodal particle size distribution with a peak at 2,500Å.

(Comparative Example 2) 100 parts by weight of latex A produced in the same manner as in Example 1 was mixed with polyoxyethylenenolyl phenyl ether (trade name "Emulgen 999S",
(Manufactured by Kao) was added in an amount of 0.002 parts by weight, and the mixture was stirred for 5 minutes, and then 2 parts by weight of acetic acid was added. Then, 2 parts by weight of potassium hydroxide was added to obtain a stable latex. The average particle size of this latex was a latex having a monomodal particle size distribution having a peak at 3,000Å.

[0036]

According to the present invention as described above,
It is possible to obtain the effect that the coagulum is not generated in the coagulation process and the particle size of the polymer latex is large. Moreover, even if the aggregation time is short, it is possible to stably agglomerate a bimodal polymer latex containing particles having both a large particle size and a small particle size, which is advantageously applied on an industrial scale. be able to.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Matsuda, Ube City, Yamaguchi Prefecture Obi Ubi, Yamaguchi Prefecture 14 No. 525, Okiyama, Ube Plant, Ube Plant (72) Inventor Junhisa Akaboshi Ube City, Ube City, Yamaguchi Prefecture No. 14 of 525, Okinoyama Ube factory

Claims (4)

[Claims] 1. A small particle size polymer latex obtained by an emulsion polymerization method, which comprises two or more kinds of surfactants and has a particle size of 800 Å or less, is added with an acid to coagulate, and then neutralized with an alkaline substance. , Which results in a particle size of 800Å
A method for aggregating a polymer latex having the above bimodal distribution. 2. The method according to claim 1, wherein an emulsifier having a good surface-active ability under acidic conditions is added before adding an acid to the small particle size polymer latex. 3. The method according to claim 1, wherein the acid is one or a mixture of two or more of strong acids such as sulfuric acid, hydrochloric acid and sulfonic acid and weak acids such as maleic acid, itaconic acid and acetic acid. 4. The method according to claim 1, wherein the alkaline substance is sodium hydroxide, potassium hydroxide, or ammonium hydroxide.