JPH0445102A - Production of emulsion polymer and emulsion polymer obtained by the same production - Google Patents

Abstract

PURPOSE:To obtain the subject polymer, having a high elongation ratio at low temperatures and useful for coatings, etc., by using a monomer capable of providing a polymer having a low glass transition point thereof in the initial period of polymerization and further a monomer capable of affording a polymer having a high glass transition point in the end of the polymerization, enhancing the weight ratio of an emulsifying agent with time and carrying out emulsion polymerization. CONSTITUTION:(A) A polymerizable unsaturated monomer capable of providing a polymer having -60 to +10 deg.C glass transition temperature (Ta) thereof is fed to a reaction system in the initial period of polymerization reaction and (B) a polymerizable unsaturated monomer capable of affording a polymer having 0-100 deg.C glass transition temperature (Tb) and (Tb-Ta)>=10 deg.C is further fed to the reaction system in the end of the polymerization reaction. The polymerizable unsaturated monomers are subjected to emulsion polymerization in the presence of water and an emulsifying agent. In the process, the polymerization is carried out under conditions such that the weight ratio of the emulsifying agent to the sum thereof and the polymers of the polymerizable unsaturated monomers in the reaction system may be enhanced with the elapsed time of the polymerization reaction. Thereby, the objective polymer composed of particles having a soft inner layer and a rigid surface layer with a particle diameter within the range of 0.3-3.0mu, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing emulsion polymers, and more particularly, to a method for producing emulsion polymers, and more particularly, by controlling the morphology and size of the particles, a considerable elongation rate can be achieved at low temperatures. The present invention relates to a method for producing an emulsion polymer suitable as a material for a coating composition that exhibits the same properties and has excellent stain resistance.

(Prior art) Currently, various emulsion polymers are used for a wide range of purposes, but the amount of emulsion polymers used as coating materials has increased in recent years, and Various advanced requirements are becoming stronger.

For example, in the case of single-layer elastic paints for construction, the film has a considerable elongation rate at low temperatures of around -10°C, and the film surface has low stickiness at room temperature, making it difficult for dust and other dirt to adhere to it. Therefore, it is desired to develop an emulsion polymer that satisfies this requirement.

Conventionally, in order to increase the elongation rate at low temperatures in synthetic resin emulsion paints, it has been common practice to use emulsion polymers with a resin composition with a low glass transition temperature, or to incorporate large amounts of plasticizers. However, in these cases, satisfactory quality in terms of stain resistance cannot be obtained, and in the end, depending on these methods, it is difficult to simultaneously satisfy elongation at low temperatures and stain resistance.

One possible way to solve this problem is to create an emulsion polymer consisting of particles with different resin compositions in the inner layer and the surface layer. (Tokuko Showa 5l-46555
Emulsion polymerization methods applying conventionally known methods such as ) can be considered. When synthesizing emulsion polymers consisting of particles with a so-called multilayer structure using these polymerization methods, conventional methods have been used to distribute hard components in the inner layer of the particles and soft components in the surface layer in order to improve film-forming properties. The components supplied to the reaction system are often adjusted.

However, the dry film obtained from the emulsion polymer synthesized by this method does not have sufficient stain resistance because soft components appear on the surface. In addition, with the intention of obtaining a film with sufficient stain resistance, an emulsion polymer was synthesized by adjusting the components supplied to the reaction system so that the soft component was distributed in the inner layer and the hard component was distributed in the surface layer. However, the resulting emulsion polymer has a considerably high minimum film forming temperature (MFT) (and requires a large amount of coalescent when used in coating applications, making it difficult to form a film that is practically satisfactory). It is difficult to create.

(Means for Solving the Problems) In view of the above points, the present inventors conducted intensive research and found that the inner layer is soft, the surface layer is hard, and the particle size is 0.3 to 3.0.
Emulsion polymers with so-called large particle diameters in the μm range are
The MFT is lower than that of normal particle sizes, which eliminates the interpressure associated with film formation, and the elongation rate is high at low temperatures (and it is possible to obtain a film with excellent stain resistance at room temperature). The inventors also discovered that emulsion polymers having these characteristics can be produced by the method described below, leading to the completion of the present invention.

That is, the present invention emulsion polymerizes a polymerizable unsaturated monomer in the presence of water and an emulsifier, so that the inner layer is soft, the surface layer is hard, and the particle size is in the range of 0.3 to 3.0 μm. A method for producing an emulsion polymer consisting of certain particles, comprising: (a) a polymerizable unsaturated monomer (A) supplied to the reaction system at the initial stage of the polymerization reaction; T
a) is -60 to 10°C, and the polymerizable unsaturated monomer (B) supplied to the reaction system in the latter stage of the polymerization reaction is (B)
The glass transition temperature (Tb) of the polymer is 0 to 100°C, and Tb-Ta is 210°C. The present invention relates to a method for producing an emulsion polymer, characterized in that the weight ratio of the emulsifier to the sum of the saturated monomers and the polymer increases as the polymerization reaction progresses, and an emulsion polymer obtained by the method.

Here, unless otherwise specified, "particle diameter" refers to what is measured by the following method. That is, Jo
Disk Centrifug manufactured by yce-Loeb1
Measure the particle size distribution using an e (MK-m type) particle size distribution analyzer, and the value of the particle size where the maximum peak appears in the obtained particle size distribution curve is defined as the "particle size" here. handle.

Here, to explain the glass transition temperature (Ta) of the polymer of the polymerizable unsaturated monomer (A) in more detail, the polymerizable unsaturated monomer (A) is monomer M.

Consisting of Mz, Ms..., the weight fraction of each is C,, C,, C,..., and the homopolymers of the respective monomers P+, P2, Ps..., The glass transition temperatures expressed in absolute terms are T, , T, respectively.

Ta..., Ta is expressed by equation (1).

I C, C2C3 = -10-10-+... (1) Ta TI T2 Ta The polymer of monomer (A) is monomer MI M2
, Ms..., and Ta indicates the glass transition temperature of the copolymer. Ta is sometimes referred to as the glass transition temperature of the monomer (A).

The glass transition temperature (Tb) of the polymer of monomer (B) is also the same as above.

Among the methods of the present invention, (a) is a means for producing polymer particles having a morphology in which the inner layer is soft and the surface layer is hard. That is, supplying a polymerizable unsaturated monomer with a relatively low glass transition temperature at the initial stage of polymerization,
At this time, a soft polymer that is to become the center layer component of the polymer particles is produced. Subsequently, a polymerizable unsaturated monomer with a higher glass transition temperature is supplied to form a hard polymer, and this hard polymer extends outside the region of the previously formed soft polymer. It is possible to produce polymer particles with structures arranged in the shell.

It is a means to Although it is difficult to obtain such relatively large polymer particles by normal emulsion polymerization, method (b) of the present invention makes it possible to produce larger polymer particles than in the normal case. It is an emulsion polymerization method that allows
Moreover, it is compatible with a method for producing polymer particles having a soft internal layer morphology and a hard surface layer morphology.

In other words, by keeping the weight ratio of the emulsifier to the sum of the polymerizable unsaturated monomer and the unsaturated monomer in the reaction system relatively low at the initial stage of polymerization, the number of polymer particles produced can be reduced. However, the size of the finally produced polymer particles can be increased. Furthermore, by increasing the ratio of the emulsifier in the reaction system as the reaction progresses, it is possible to prevent a decrease in the dispersion stability of the polymer particles, which is a concern as the particle phase fraction increases.

In the present invention, it is necessary to perform both (a) and (b) above. As a specific method, for example, the following method can be mentioned.

That is, it stably emulsifies a polymerizable unsaturated monomer in the presence of water and an emulsifier to create a first monomer pre-emulsion, and emulsifies another polymerizable unsaturated monomer in the presence of water and an emulsifier. a second monomer pre-emulsion is stably emulsified in the presence of is an emulsion polymerization method in which a polymerizable unsaturated monomer is supplied from a second supply source to a first supply source, and at this time, the polymerizable unsaturated monomer is emulsion polymerized in the reaction system, (a) the first The polymerizable unsaturated monomer (
A), the glass transition temperature (Ta) of the polymer of (A) is -
60 to 10°C, and the polymerizable unsaturated monomer (B) in the monomer pre-emulsion supplied to the reaction system from the first supply source at the end of the polymerization reaction is the polymer of (B). has a glass transition temperature (Tb) of 0 to 100°C, and T
(b) The weight ratio of the emulsifier in the first monomer pre-emulsion to the polymerizable unsaturated monomer in the same pre-emulsion is higher than that in the second monomer pre-emulsion. The polymerizability in the monomer pre-emulsion supplied from the first source to the reaction system is lower than the polymerization ratio of the emulsifier in the same braemulsion to the sexually unsaturated monomer, and according to (a) and (b) above, This is a method in which the composition of unsaturated monomers and emulsifiers is continuously changed over time of the polymerization reaction.

The emulsion polymer particles produced by the above method are characterized by having a multilayer structure and at the same time being larger in size than conventional particles. Conventional multilayer structure emulsion polymers generally have a particle diameter (d) of 0.3 μm or less, and the morphology of the film after film formation is usually a repetition of units of this size (#d). On the other hand, since the emulsion polymer particles of the present invention have a large size, the repeat unit size of the morphology of the film after film formation becomes thicker.As a result, it is expected that performance not seen before can be exhibited. As a result of various studies, the present inventors found that these emulsion polymers have the above-mentioned properties, which we believe is due to the film morphology in which the size of the repeating unit is large.

The emulsion polymer of the present invention is characterized by a large particle size, which ranges from 0.3 to 3.0 μm, preferably from 0.3 μm to 3.0 μm.
4 to 230 μm, more preferably 0.5 to 1.0 μm
It is.

The polymerizable unsaturated monomer used in the method of the present invention is not particularly limited as long as it is commonly used in emulsion polymerization. Specific examples include methyl (meth)acrylate,
Ethyl (meth)acrylate, butyl (meth)acrylate, lauryl (meth)acrylate, (meth)acrylic acid-
Acrylics such as 2-ethylhexyl, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate or glycidyl (meth)acrylate. various esters of acid or methacrylic acid;
Various amides such as (meth)acrylamide or N-methylol (meth)acrylamide; various carboxyl group-containing monomers such as acrylic acid, methacrylic acid, maleic acid or fumaric acid; dimethylaminoethyl (meth)acrylate or diethylaminopropylene Various dialkylamino group-containing monomers such as vinyl(meth)acrylate; vinyl halides or vinylidene halides such as vinyl chloride vinylidene chloride or vinylidene fluoride; various aromatic vinyls such as styrene, α-methylstyrene or vinyltoluene. Compounds; various vinyl esters such as vinyl acetate or vinyl propionate; various conjugated dienes such as butadiene or isoprene; various polyhydric carboxylic acid anhydride-containing monomers such as maleic anhydride or itaconic anhydride; ethylene ,
Mention may be made of aliphatic monoolefins such as propylene or butene; or unsaturated nitriles such as acrylonitrile or methacrylonitrile. These materials can be used alone or in combination of two or more.

Further, the emulsifier used in the method of the present invention is not particularly limited as long as it is commonly used in emulsion polymerization, but specifically, anionic surfactants and nonionic surfactants such as those shown below may be used. , cationic surfactants and mixtures thereof can be used. Examples of anionic surfactants include various fatty acid salts, higher alcohol sulfate ester salts, alkylbenzene sulfonates, dialkyl sulfosuccinates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl phenyl ether sulfates, polyoxyethylene Examples include polyoxybrobylene glycol ether sulfate and polycarboxylic acid type polymeric surfactants. Nonionic surfactants include polyoxyethylene alkyl ether,
Examples include polyoxyethylene alkylphenyl ether, sorbitan fatty acid ester, polyoxyethylene fatty acid ester, and polyoxyethylene/polyoxybrobylene block copolymer. Furthermore, examples of the cationic surfactant include alkylamine salts, quaternary ammonium salts, and the like. The amount of these emulsifiers used is 0.0% based on the total amount of polymerizable unsaturated monomers.
Suitably, the amount is in the range of 0.01 to 10% by weight, preferably 0.1 to 5% by weight.

The weight ratio of the emulsifier to the sum of the polymerizable unsaturated monomer and the polymer of the polymerizable unsaturated monomer in the reaction system must be increased as the reaction progresses. Therefore, the emulsifier is supplied so that this value increases more at the end of the reaction than at the beginning of the reaction, and the increase rate is suitably in the range of 1.5 to 500 times, preferably 2 to 100 times. .

In the present invention, a polymerizable unsaturated monomer is emulsion polymerized in a reaction system, and a polymerization initiator is generally used at that time. The polymerization initiator is not particularly limited as long as it is commonly used in emulsion polymerization, but specific examples include water-soluble inorganic peroxides such as hydrogen peroxide; potassium persulfate, ammonium persulfate, etc. Persulfates: organic peroxides such as cumene hydroperoxide, benzoyl peroxide, -butyl hydroperoxide, di-t-butyl peroxide; azo-based starting materials such as azobisisobutyronitrile, azobiscyanovaleric acid These radical polymerization initiators can be used alone or in combination of two or more. The amount used is preferably 0.1 to 2% by weight based on the total amount of polymerizable unsaturated monomers.

Note that redox polymerization may be carried out by using the above peroxide-based polymerization initiator together with a metal ion or a reducing agent as a polymerization initiator.

These polymerization initiators can be supplied by charging an aqueous solution or dispersion of the polymerization initiator into the reactor in advance;
A method in which a polymerizable unsaturated monomer or a monomer pre-emulsion is blended, a method in which an aqueous solution or aqueous dispersion of a polymerization initiator is fed into a reactor simultaneously with a polymerizable unsaturated monomer,
Alternatively, these methods can be used in combination. Furthermore, after the supply of the polymerizable unsaturated monomer is completed, a portion of the polymerization initiator may be supplied to the reactor as an additional catalyst.

The amount of water used in the present invention is 10 to 300% by weight, preferably 10 to 300% by weight based on the total amount of polymerizable unsaturated monomers.
A range of 100% by weight is suitable.

In the present invention, in addition to the above-mentioned polymerizable unsaturated monomers, emulsifiers, polymerization initiators, and water, chain transfer agents such as mercaptans, and buffers such as sodium bicarbonate and sodium acetate are optionally used. etc. may also be used. These additives can be supplied, for example, by charging them into the reactor in advance, or by mixing them into a polymerizable unsaturated monomer or polymer pre-emulsion and feeding it into the reactor. can be done.

In the method of the present invention, the feed rate of the polymerizable unsaturated monomer to the reaction system may be appropriately selected depending on the monomer used, the polymerization initiator, the polymerization temperature, etc. This is the speed at which the entire amount is completely fed into the reaction system over 1 to 10 hours. When supplying a polymerizable unsaturated monomer into the reaction system, a monomer pre-emulsion is created by stably emulsifying the polymerizable unsaturated monomer in the presence of water and an emulsifier.
This monomer pre-emulsion may be fed into the reaction system. A monomer pre-emulsion can be easily obtained, for example, by first mixing an emulsifier and water and then mixing the polymerizable unsaturated monomer with stirring.

The polymerization temperature of the reaction system is not particularly limited, but is usually 10 to 1
00°C, preferably 30 to 80°C.

(Effects of the Invention) By using the method of the present invention, an emulsion polymer consisting of particles having a soft inner layer, a hard surface layer, and an average particle diameter in the range of 0.3 to 3.0 μm can be produced. I can do it.

The emulsion polymer obtained by the method of the present invention can be used as a paint, a powder, a sealant, a caulking agent, a backing agent for carpets, etc. This emulsion polymer is
Since it has the above-mentioned morphology and is composed of particles having a relatively large size, it is possible to more clearly reflect the characteristics of the layer structure in the film performance compared to conventional multi-layer structure latex.

(Examples) The present invention will be specifically described below based on Examples. Note that the scope of the present invention is not limited only to these examples.

The viscosity was measured using a B-type viscometer (60 rpm).

The particle size was measured using the method described in Note 1), and the minimum film forming temperature was measured using Nippon Rigaku Kogyo Co., Ltd.
A minimum film-forming temperature measurement device manufactured by Kogyo Co., Ltd. was used. In addition, “
Parts" and "%" are by weight.

Example 1 The polymerization reactor consisted of a reactor (2ρ flask) equipped with a stirrer, thermometer and reflux condenser, a first monomer pre-emulsion source equipped with a stirrer, a second monomer pre-emulsion source equipped with a stirrer. The system consists of a monomer pre-emulsion supply source, a catalyst solution supply source, piping connecting these, and three pumps. The reactor and the first supply source were connected by piping, and a pump was installed in the middle.

Separately, the reactor and the catalyst solution supply source were connected by piping, and a pump was installed in the middle. Further, the first monomer pre-emulsion supply source and the second monomer pre-emulsion supply source were connected by piping, and a pump was installed in the middle.

A reactor was charged with 240 parts of deionized water and heated to a temperature of 70°C. A first monomer pre-emulsion consisting of the following formulation was prepared in a first source.

Deionized water 167 parts Nucol 271A Note 2) 1.40 parts Nucol 1
120 Note 3) 0.67 part styrene
132 parts 2-ethylhexyl acrylate 360 parts Methyl methacrylate 1
81 parts acrylic acid 6.73 parts t
-Butyl hydroperoxide Note 4) 2.50 parts A second monomer pre-emulsion consisting of the following formulation was prepared in a second source.

Deionized water 109 parts Nucol 271A Note 2) 40.7 parts Nucol 11
20 Note 3) 19.5 parts styrene
132 parts 2-ethylhexyl acrylate 270 parts Methyl methacrylate 27
0 parts acrylic acid 6.73 parts t-
Butyl hydroperoxide Note 4) 2.50 parts The glass transition temperature of the polymerizable unsaturated monomer in the above first monomer pre-emulsion is 0.4°C, and the glass transition temperature of the polymerizable unsaturated monomer in the above first monomer pre-emulsion is 0.4°C. The glass transition temperature of the polymerizable unsaturated monomer therein is 20.4°C.

A catalyst solution consisting of the following formulation was prepared in a catalyst solution source.

Sodium formaldehyde sulfonate 8.0 parts Deionized water 40.0 parts The first monomer pre-emulsion was fed from the first source to the reactor at a constant rate over a period of 5 hours. At the same time, 55% of the second monomer pre-emulsion is transferred from the second source to the first source.
The feed was carried out at a constant rate over time, and the first source was kept stirring during the feed period to ensure that sufficient mixing occurred at all times. At the same time, catalyst solution was pumped into the reactor from a catalyst solution source at a constant rate over a period of 5 hours.

During the above operation, 70 parts of the reactor were kept at 2° C. and stirring was continued. After the introduction of the monomer pre-emulsion and catalyst solution was completed, 70 parts of the reactor were kept at 2° C. for 1 hour and stirring was continued. During that period, 7.50 parts of Rongalite aqueous solution consisting of 1.60 parts of sodium formaldehyde sulfonate and 5.90 parts of deionized water and 1.60 parts of t-butyl hydroperoxide were added into the reactor in three portions. te15
Inserted at minute intervals.

After the above operation is completed, the reactor is cooled, and 12.7 parts of 25% ammonia water is added to the reactor.
1 and 2.00 parts of Suraoff 72N Note 6) were charged into the reactor, and then stirred for 10 minutes. The contents of the reactor were then filtered through a 300 mesh silk cloth. The obtained latex had a solid content concentration of 68.9% and a viscosity of 1650CP.
S, pH 9-1, particle size 0.55 μm, minimum film forming temperature 7
It was ℃.

Comparative Example 1 The same polymerization reaction apparatus as in Example 1 was used. The following formulation was used as the first monomer pre-emulsion.

Deionized water 167 parts Nucol 271A Note 2) 1.40 parts Nucol 11
20 Note 3) 0.67 parts styrene
132 parts 2-ethylhexyl acrylate 270 parts Methyl methacrylate 27
0 parts acrylic acid 6.73 parts t-
Butyl hydroperoxide Note 4) 2.50 parts The following formulation was used as the second monomer pre-emulsion.

Deionized water 109 parts Nucol 271A Note 2) 40.7 parts Nucol 11
20 Note 3) 19.5 parts styrene
132 parts 2-ethylhexyl acrylate 360 parts Methyl methacrylate 18
1 part acrylic acid 6.73 parts t-
Butyl hydroperoxide Note 4) 2.50 parts The glass transition temperature of the polymerizable unsaturated monomer in the above first monomer pre-emulsion is 20.4°C, and the second monomer pre-emulsion The glass transition temperature of the polymerizable unsaturated monomer therein is 0.4°C.

A latex was synthesized using the above monomer pre-emulsion and performing the same operation as in Example 1. The obtained latex had a solid content concentration of 68.9% and a viscosity of 1426 cp.
s, pH 9.2, particle size 0.65 μm, minimum film forming temperature 1
The temperature was 4°C.

Note 1) Disk C manufactured by Joyce-Loeb1
The particle size distribution is measured using an entrifuge (MK-III type) particle size distribution analyzer, and the value of the particle size where the maximum peak appears in the obtained particle size distribution curve is
Treated as "particle size" here.

Note that the measurement conditions were that the spin liquid was water at 10 to 20 m℃;
The rotation speed of the disk is 2000 to 6000 rpm,
The temperature was 10 to 30°C, the sample dispersion medium was a mixed solution of methanol and deionized water (1:1 by volume), the sample dispersion concentration was O, 1 to 1.0% by weight, and the injection amount of the sample dispersion was 0.1~
It is assumed to be 1.0 mj2.

Note 2) Anionic surfactant manufactured by Nippon Nyukazai Co., Ltd. Note 3) Nonionic surfactant manufactured by Nippon Nyukazai Co., Ltd. Note 4) 70% aqueous solution Note 5) Antifoaming agent manufactured by Mudenka Kogyo Co., Ltd. 6) Preservative manufactured by Shikinichi Yakuhin Kogyo Co., Ltd.

Claims (4)

[Claims] (1) From particles with a soft inner layer, a hard surface layer, and a particle size in the range of 0.3 to 3.0 μm, obtained by emulsion polymerization of a polymerizable unsaturated monomer in the presence of water and an emulsifier. A method for producing an emulsion polymer comprising: (a) a polymerizable unsaturated monomer (A) supplied to the reaction system at the initial stage of the polymerization reaction;
a) is -60 to 10°C, and the polymerizable unsaturated monomer (B) supplied to the reaction system at the end of the polymerization reaction is (B)
The glass transition temperature (Tb) of the polymer is 0 to 100°C, and Tb-Ta≧10°C, and (b) regarding the supply of the emulsifier to the reaction system, the polymerizability in the reaction system is A method for producing an emulsion polymer, characterized in that the weight ratio of the emulsifier to the sum of the unsaturated monomer and the polymer is increased as the polymerization reaction progresses. (2) A first monomer pre-emulsion is created by stably emulsifying a polymerizable unsaturated monomer in the presence of water and an emulsifier, and another polymerizable unsaturated monomer is emulsified in the presence of water and an emulsifier. the first monomer pre-emulsion is stably emulsified in the presence of is supplied from a second supply source to a first supply source, and at this time, a polymerizable unsaturated monomer is emulsion polymerized in a reaction system, comprising: The polymerizable unsaturated monomer (
A) is when the glass transition temperature (Ta) of the polymer (A) is -
60 to 10°C, and the polymerizable unsaturated monomer (B) in the monomer pre-emulsion supplied to the reaction system from the first supply source at the end of the polymerization reaction is the polymer of (B). has a glass transition temperature (Tb) of 0 to 100°C, and T
b-Ta≧10°C, and (b) the weight ratio of the emulsifier in the first monomer pre-emulsion to the polymerizable unsaturated monomer in the same pre-emulsion is such that the weight ratio of the emulsifier in the second monomer pre-emulsion is is lower than the weight ratio of emulsifier to polymerizable unsaturated monomer in the same pre-emulsion, and according to (a) and (b) above, the monomer pre-emulsion supplied from the first source to the reaction system is 2. The method for producing an emulsion polymer according to claim 1, wherein the composition of the polymerizable unsaturated monomer and the emulsifier is continuously changed over time of the polymerization reaction. (3) An emulsion polymer obtained by the method according to claim 1. (4) An emulsion polymer obtained by the method according to claim 2.