JPH11209412A - Preparation of polymer emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a preparation process of a high solid content emulsion having a low viscosity and a good stability which process enables a polymerization of a high seed efficiency. SOLUTION: In a preparation process of a polymer emulsion in which at least one ethylenically unsaturated monomer is added in the presence of a seed emulsion, I) the weight of the ethylenically unsaturated monomer is not less than 4 times of that of the seed emulsion; II). The polymerization temperature ( deg.C) is not less than [T-30( deg.C)] (T is the glass transition temperature of either polymer having a higher glass transition temperature between the polymer in the seed emulsion and the polymer resulted from the polymerization of the ethylenic unsaturated monomer); III) The solid content concentration of the final polymer emulsion is not less than 50 wt.% and the viscosity of the emulsion is not more than 5,000 cP.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-productivity polymer emulsion having a high solid content and a low viscosity.

[0002]

2. Description of the Related Art A polymer obtained by salting out and drying a polymer emulsion is widely used in the fields of rubber industry and plastic industry.

[0003] High solid differentiation of polymer emulsions is strongly desired from the viewpoint of improving productivity. However, simply increasing the solids content leads to an increase in the viscosity of the emulsion, and its production causes a great problem in terms of heat removal and fouling of the polymerization reactor. It is known that in order to solve this problem, the width of the particle size distribution should be increased while increasing the particle size of the particles in the emulsion.
Various methods have been proposed for that purpose.

[0004] It is also known that in emulsion polymerization, the sequential addition of emulsion method enables the production of an emulsion having a wide particle size distribution, but this is because the micelles in the emulsion supplied in the latter half of the polymerization are not sufficiently dispersed. It is based on the inability to grow. However, it is difficult to produce particles having a highly controlled morphology having a multilayer structure by this method.

Therefore, particles having a multilayer structure are generally produced by a multi-stage polymerization method using a seed polymerization method or the like. High solid differentiation of an emulsion by a seed polymerization method is disclosed in JP-A-61-252203 by polymerizing a monomer mixture containing an ethylenic monomer having a carboxyl group to form a seed emulsion, and then adding a basic compound. A method has been proposed in which a high-concentration latex is obtained by adding and polymerizing an ethylenic monomer in the absence of a surfactant. In this method, the weight ratio of the added monomer to the weight of the polymer in the seed emulsion (hereinafter referred to as seed efficiency) is low, and a large amount of the seed emulsion is required for the finally obtained emulsion. Is not so good.

[0006]

According to the method for producing a high solid content emulsion known so far, it is difficult to obtain a high solid content emulsion which is polymerized with high seed efficiency and has low viscosity and good stability. there were.

An object of the present invention is to provide a method for producing a high solid content emulsion which can be polymerized with high seed efficiency and has low viscosity and good stability.

[0008]

The gist of the present invention is to provide a method for producing a polymer emulsion in which one or more ethylenically unsaturated monomers are added and polymerized in the presence of a seed emulsion. The weight of the ethylenically unsaturated monomer added is 4% of the weight of the polymer in the seed emulsion.
II) The polymerization temperature t (° C.) is (T-30 (° C.)) or higher (where T is the glass transition temperature of the polymer in the seed emulsion or the ethylenically unsaturated monomer to be added). The higher the glass transition temperature (° C.) of the polymer obtained by polymerization of the monomer, the higher the glass transition temperature (° C.), the higher the solid content of the polymer emulsion obtained is 50% by weight or more. Has a viscosity of 50
A method for producing a polymer emulsion, which is not more than 00 cP.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The seed emulsion used in the present invention does not particularly limit the composition of the polymer and the method for producing the seed emulsion such as emulsion polymerization and mechanical emulsification. Specific examples thereof include emulsions of silicone, polybutadiene, polyurethane, polytetrafluoroethylene, and the like, in addition to poly (meth) acrylate and polystyrene emulsion. Since seed polymerization is easier when the total surface area of the particles per unit weight of the seed emulsion is larger, it is preferable that the number average particle diameter of the seed emulsion be smaller. Specifically, the thickness is preferably 0.5 μm or less, more preferably 0.3 μm or less, and most preferably 0.15 μm or less. It is. Further, the number average particle diameter of the seed emulsion is preferably 0.01 μm or more.

As the ethylenically unsaturated monomer used in the present invention, those generally used for emulsion polymerization can be used. Specifically, methyl (meth) acrylate,
Ester of acrylic acid or methacrylic acid such as ethyl (meth) acrylate and butyl (meth) acrylate; vinyl halides such as vinyl chloride; aromatic vinyls such as styrene; vinyl cyanides such as acrylonitrile;
Vinyl esters such as vinyl acetate can be used.

In the present invention, a monomer containing a carboxyl group, such as (meth) acrylic acid, which is generally used for producing a high solid content emulsion, is not necessarily required. In order to produce a high solid content emulsion from a small amount of the seed emulsion, the larger the amount of the ethylenically unsaturated monomer to be added to the weight of the polymer in the seed emulsion, the better. preferable. If the amount of the ethylenically unsaturated monomer is less than four times the weight of the polymer in the seed emulsion, a large amount of the seed emulsion is required to produce a high solids emulsion, resulting in poor productivity.

In the present invention, it is preferable to add a surfactant when polymerizing the ethylenically unsaturated monomer. This surfactant is a usual anionic or nonionic surfactant or a mixture thereof. Specifically, there are fatty acid soaps, alkyl sulfonates, alkyl aryl sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl aryl sulfates, etc. in the anionic type, and polyoxyethylene alkyl aryl sulfates in the nonionic type. Examples include ethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene sorbitan fatty acid ester, and oxyethylene oxypropylene block polymer. The preferred addition amount of these surfactants is 0.05 to 4% by weight based on the ethylenically unsaturated monomer.

The polymerization catalyst used in the polymerization of the ethylenically unsaturated monomer in the present invention is a compound that generates a radical by heat or a reducing substance, and examples thereof include peroxides and persulfates. Examples thereof include t-butyl hydroperoxide, cumene hydroperoxide, isopropylcumyl hydroperoxide, potassium persulfate, and ammonium persulfate. The amount is usually 0.1 to 1% by weight based on the ethylenically unsaturated monomer.
Used. Further, a redox catalyst is more preferable in that the polymerization rate can be increased, and specific examples thereof include a combination of ferrous sulfate, sodium aldehyde sulfoxylate, and hydroperoxides.

[0014] Additives commonly used in emulsion polymerization, such as chain transfer agents, buffers, stabilizers, etc., can be used as well. Also, an emulsifying aid such as hexadecane may be used, but is not always necessary.

What is important in the present invention is the temperature at which the ethylenically unsaturated monomer is added, that is, the polymerization temperature, and there is no particular limitation on the rate of addition of the monomer.

The polymerization temperature t (° C.) is the higher of the glass transition temperature of the polymer constituting the seed emulsion or the glass transition temperature of the polymer obtained by polymerizing the ethylenically unsaturated monomer to be added. When the temperature is T (° C.), it is necessary that t ≧ T−30 (° C.), preferably t ≧ T−15 (° C.), and more preferably t ≧ T (° C.)
It is. If the polymerization temperature is much lower than T, fine particles will be formed during the polymerization, which will increase the emulsion viscosity. The glass transition temperature of the polymer does not need to be an actually measured value. If it is composed of one type of monomer, the literature value may be used as it is. If it is composed of two or more types of monomers, it is calculated as a random copolymer. The value obtained may be used.

By conducting the polymerization under the above-mentioned polymerization temperature conditions, it becomes possible to produce a high solid content emulsion with high seed efficiency. The higher the solids concentration of the polymer, the better, but the viscosity of the emulsion increases accordingly. The solid concentration is preferably 50% by weight, more preferably 55% by weight or more. The viscosity of the polymer emulsion is 5000 cP
If it is less than or equal to, it is sufficiently fluid, and if it is less than 1000 cP, liquid transfer with a pump or the like can be performed smoothly, so that it is more preferable.

Hereinafter, the present invention will be described by way of examples. Evaluation of the polymer emulsion was performed by the following method.

Solid content concentration: About 1 g of a polymer emulsion was collected and dried at 170 ° C. for 2 hours, and the evaporation residue was expressed in terms of% by weight.

Number average particle size: Electrophoretic light scattering photometer EL
It was measured by S-800 (Otsuka Electronics Co., Ltd.).

Viscosity: The viscosity of the polymer emulsion at 25 ° C. was measured with a B-type viscometer at a rotation speed of 60 rpm.

[0022]

EXAMPLES Production Example 1 Production of seed emulsion 3 g of sodium dodecylbenzenesulfonate and 700 of water
g of methyl methacrylate in a separable flask containing
00 g and t-butyl hydroperoxide 1.2 g were charged, and the temperature was heated to 50 ° C. Next, ferrous sulfate 0.
004 g, ethylenediaminetetraacetic acid disodium salt 0.1 g.
012 g, sodium aldehyde sulfoxylate
An aqueous solution in which 5 g was dissolved in 50 g of water was added to carry out polymerization.

The obtained emulsion has a solid content of 30.
At 1% by weight, the number average particle size was 80 nm.

The seed emulsion and the ethylenically unsaturated monomer are methyl (poly) methacrylate (glass transition temperature 1
(05 ° C.).

Example 1 167 g of the seed emulsion of Production Example 1 was placed in a pressure-resistant reactor.
An aqueous solution in which 420 g of water, 0.0001 g of ferrous sulfate, 0.0003 g of disodium ethylenediaminetetraacetate, and 2.0 g of sodium aldehyde sulfoxylate were dissolved in 50 g of water was charged, and the temperature was heated to 80 ° C. Next, 50 g of methyl methacrylate in which 0.2 g of t-butyl hydroperoxide was dissolved was added. After addition, polymerization starts, but after holding for about 30 minutes, 12.
60 g of a 5% by weight aqueous solution of sodium dodecylbenzenesulfonate was added. Hereinafter, the temperature was controlled at 80 ° C. 800 g of methyl methacrylate was added at a constant rate over 1 hour, and after the completion of the dropwise addition, the mixture was maintained for 1 hour to complete the polymerization.

The obtained emulsion has a solid content of 55.
This was a uniform emulsion having a weight-average particle diameter of 1 nm, a number average particle diameter of 220 nm and a viscosity of 66 cP.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that the polymerization temperature in Example 1 was 65 ° C. As a result, the viscosity of the emulsion increased to 10,000 cP or more before the solid content concentration reached 50% by weight during the addition of the monomer. Therefore, stirring was stopped, and a stable emulsion could not be obtained.

[0028]

According to the present invention, the solid content concentration is 50% by weight.
The above low viscosity emulsion can be produced with high seed efficiency. Then, by spray-drying the high solid content emulsion, a powder useful as a resin modifier can be efficiently produced.

Claims (1)

[Claims] 1. A method for producing a polymer emulsion in which one or more ethylenically unsaturated monomers are added and polymerized in the presence of a seed emulsion; The weight is 4 times the weight of the polymer in the seed emulsion.
II) The polymerization temperature t (° C.) is (T-30 (° C.)) or higher (where T is the glass transition temperature of the polymer in the seed emulsion or the ethylenically unsaturated monomer to be added). The higher the glass transition temperature (° C.) of the polymer obtained by polymerization of the monomer, the higher the glass transition temperature (° C.), the higher the solid content of the polymer emulsion obtained is 50% by weight or more. Has a viscosity of 50
A method for producing a polymer emulsion, which is not more than 00 cP.