JPS60206803A - Production of emulsion polymer - Google Patents

Abstract

PURPOSE:To obtain a monodispersible large-particle diameter emulsion polymer low in the formation of coagulants during polymerization, by emulsion-polymerizing a polymerizable unsaturated monomer absorbed by a specified aqueous polymer dispersion in the presence of an emulsifier and a redox radical polymerization initiator. CONSTITUTION:An aqueous polymer dispersion containing a seed polymer containing 10-100wt% low-MW compound of an MW of 200-10,000 (e.g., styrene) or an aqueous polymer dispersion containing absorbed organic compound having a solubility in water <=0.001wt% (e.g., hexane) is allowed to absorb 10-400 per volume of the polymer, of a polymerizable unsaturated monomer (e.g., vinyl acetate). Next, this is emulsion-polymerized in the presence of a redox radical polymerization initiator (e.g., hydroperoxide) in water containing an emulsifier (sodium lauryl sulfate) in a concentration below its critical micelle concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a novel method for producing emulsion polymers. More specifically, the present invention relates to a method for producing a monodisperse emulsion polymer with large particle size.

Technical Background In recent years, as the uses of emulsion polymers have expanded, various performances have come to be required. One of the important properties is the particle size of the polymer. It is known that a large particle size is good for improving fluidity and achieving high solids content, and for a base latex for resins, a large particle size is also good from the viewpoint of impact resistance.

Prior Art The currently available method for obtaining emulsion polymers with large particle size is polymerization in the presence of an electrolyte, but there is a limit to the amount of electrolyte that can be added, which makes it difficult to control the particle size. There is also a limit to the diameter.

Further, the remaining electrolyte poses problems such as lowering the water resistance of the latex film. Another method is to use strong stirring during polymerization to coagulate and fuse several particles to obtain an emulsion polymer with a large particle size. There is a problem that the particle size distribution is extremely wide and it is difficult to obtain an emulsion polymer with uniform particles.

One way to obtain monodisperse emulsion polymers with large particle size is to gradually enlarge and polymerize kneaded latex.
The emulsifier and monomer must be added in stages, making the process complicated.

Methods for producing monodisperse emulsion polymers with large particle diameters include the invention disclosed in JP-A No. 54-97582 and the invention disclosed in JP-A No. 54-12628.
No. 826288 was invented.

JP-A No. 54-97582 discloses that by adding a chain transfer agent during polymerization, a polymer with a molecular weight much lower than that of a normal monomer latex is synthesized, and this is used as a seed polymer. A method of absorbing and polymerizing soluble unsaturated monomers is disclosed. However, in this method, the commonly used oil-soluble initiators and water-soluble initiators have drawbacks such as generation of coagulated substances and generation of new particles, and it is difficult to obtain monodispersed emulsion polymers with large particle size and a good yield in a stable manner. difficult.

In addition, JP-A No. 54-126288 states that in the first step, the water solubility is 10'''2Vt H,
Organic compounds smaller than 0 are absorbed into the camphor tree polymer, and in the second step, a somewhat water-soluble monomer, which is 100 times the volume of the seed polymer, is absorbed to form swollen particles of the monomer. After forming the polymerization initiator, a water-soluble initiator such as potassium persulfate or azoisobutyronitrile (AIBN
) has been disclosed, and a method is disclosed in which the particles are polymerized while maintaining their particle shape. However, with an oil bath initiator, even the monomer phase that does not swell the seed polymer is polymerized as it is, resulting in the formation of a coagulated product with many wrinkles and a decrease in yield.

In addition, with persulfate, even if the emulsifier concentration is below the critical micelle formation level, the propagating radicals in the aqueous phase will continue to act as the emulsifier, and so-called soap-free emulsion polymerization will proceed partially or completely, resulting in the shape of the swollen particles. There is a drawback that it cannot be maintained.

Purpose of the Invention In view of the above-mentioned current situation, the present inventors have conducted extensive research with the aim of obtaining a monodisperse emulsion polymer with large particle diameters that generates less coagulum and new particles during polymerization. As a result, we have arrived at the present invention.

Structure of the Invention The present invention provides a seed polymer containing from 100% by weight of a low molecular weight compound having a molecular weight of 200 to 10,000. The aqueous polymer dispersion containing stones has a solubility in water of o, o.
A nonaqueous polymer dispersion is used to absorb a nonaqueous polymer dispersion in which the M organic compound is absorbed in an amount of 10 to 400 times (preferably 20 to 2') the volume of the polymer Q.
This is a method for producing an emulsion polymer characterized in that a redox-based radical polymerization initiator is used entirely at an emulsifier concentration below the critical micelle concentration in the method of polymerizing after absorbing an amount (OO times).

The configuration of the present invention will be explained in detail below.

(Seed polymer) The t-type polymer with improved swelling ability used in the present invention is emulsion polymerized in whole or in part under conditions that produce a low molecular weight product with a shorter chain length than that obtained by ordinary emulsion polymerization. Examples of the method include a method of directly synthesizing t% of a low molecular weight monodisperse polymer, such as styrene, by soap-free emulsion polymerization using a molecular weight regulator.

Other methods of obtaining certain polymers with swelling ability include using low-molecular weight substances that are difficult to dissolve in water, under special conditions (such as increasing the apparent water solubility of poorly water-soluble compounds due to the presence of acetone, or increasing the criticality of emulsifiers). How to diffuse the aquarium and absorb it into polymer particles (such as soluble by using micelle concentration or higher)?
can be mentioned. In this method, low molecular weight fvIJ having a solubility in water of 0.001 weight ft or less is used.
You can use anything as long as it is of good quality. Companions such as hexane, heptane, octane, 1-chlordodecane, stearyl methacrylate, dioctyl adipate, 1 and lauroyl peroxide, dioctanoyl peroxide, etc. can be diffused into the polymer particles to improve the swelling ability of m-type polymers. 1 can be obtained.

The molecular weight of the birch polymer may be within the range of 200-10,000, and is particularly preferably within the range of 200-5,000.

Molecular kka14 moderators include n-dodecylmercaptan, t-dodecylmercaptan, 1-butanethiol,
1-Prenethiol, carbon tetrachloride, etc. can be used.

As the monomer for producing the seed polymer, any monomer that can produce monodisperse particles can be used.

Specific examples of such monomers include aromatic vinyl monomers such as styrene, vinyl esters such as vinyl acetate,
Examples include unsaturated nitriles such as acrylonitrile, ethylenically unsaturated carboxylic acid alkyl esters such as methyl methacrylate, and conjugated diolefins such as butadiene. may be used in appropriate amounts.

(Polymerizable monomer) Examples of the polymerizable premature compound that can be used in the present invention include aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene, halogenated styrene, and divinylbenzene; Vinyl esters such as vinyl acetate and vinyl propionate, unsaturated nitriles such as acrylonitrile, methyl acrylate, methyl methacrylate,
Ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate,
Examples include ethylenically unsaturated carboxylic acid alkyl esters such as lauryl acrylate, lauryl methacrylate, ethylene glycol diacrylate, and ethylene glycol dimethacrylate.

Conjugated diolefins such as mata, butadiene, and imprene can also be used.

Acrylamide P1 methacrylamide, glycidyl acrylate, glycidyl methacrylate, N-
Methylol acrylamide, N-methylolmethacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, diallyl phthalate, allyl acrylate, allyl methacrylate, etc. can also be used depending on the purpose. Also, acrylic acid,
Depending on the safety, methacrylic acid, itaconic acid, fumaric acid, etc. may be used in a proportion that does not inhibit swelling polymerization.

The above monomers can be used alone or in combination of two or more.

10 to 40 of the volume of these polymerizable premature body polymers
Swollen particles are obtained by absorbing into the seed polymer a factor of 0, preferably 20 to 200 times.

(Emulsifier) Examples of the emulsifier for polymerization used in the present invention include sodium dodecylbenzenesulfonate, sodium lauryl sulfate,
Anionic emulsifiers such as sodium dioctyl sulfosuccinate, disodium dodecyl diphenyl ether disulfonate, polyoxyethylene alkyl ether,
Common emulsifiers include nonionic emulsifiers such as polyoxyethylene alkylphenyl ether. The amount of emulsifier to be used is such that the concentration of the emulsifier in the aqueous phase is lower than the critical micelle concentration in a state where the seed polymer is swollen with the monomer.

If polymerization occurs at a concentration higher than the critical micelle concentration, polymerization will start even within the micelles, resulting in the production of new particles with small diameters. Therefore, monodisperse particles with a large particle size cannot be obtained, which is not suitable for the purpose of the present invention.

C polymerization initiator).

In the present invention, a redox initiator that is a combination of a peroxide and a reducing agent shown below is used.

Preferred peroxides that are one component of the polymerization initiator used in the present invention include organic peroxides such as cumene hydrono-oxide, diinzolobylpenzenehydro-oxide, and amenthanohydro-peroxide. At least one kind is selected from peroxide and hydrogen peroxide.

Other reducing agents include L-ascorbic acid,
Select at least one substance with reducing power, such as ferrous sulfate, glucose, sodium bisulfite, and sodium formaldehyde sulfoxylate.

Oxidizing agents that are somewhat water-soluble, such as Hi-P oxide, tend to cause redox more easily than oil-soluble oxidants such as dialkyl oxide and diacyl peroxide. There is.

As the oxidizing agent is persulfate, the initiator section is 0803-
Those with sharp, growing radicals that act as emulsifiers tend to form micelles and create new particles.

From the above, it is appropriate to select hydroperoxide or hydrogen peroxide as the oxidizing agent.

EXAMPLES Examples and comparative examples are given below to provide a more detailed explanation of the present invention. Naturally, the present invention is not limited to the following examples.

Parts and percentages are parts by weight and percentages by weight, respectively.

[Example 1] 1000 parts of water, 0.5 parts of sodium lauryl sulfate, 3 parts of potassium persulfate, 2 parts of t-dodecyl mercaptan, and 100 parts of styrene were smoothed and placed in a reactor purged with nitrogen gas, and heated to 80°C. The temperature was raised and the reaction was carried out for 8 hours.

As a result, a monodisperse emulsion with a styrene polymerization rate of 99% or higher, a stable particle size of 0.25 IIm, and a monodisperse emulsion was obtained.

Take 11 parts of this as a seed emulsion, add 0.145 parts of sodium lauryl sulfate, 2 parts of 1-chlordodecane, and further add 3 parts of acetone to increase the water solubility of 1-chlordodecane. did.

After stirring for 2 hours at 25-30°C and absorbing the 1-chlordodecane into the seed polymer, the acetone was removed by vacuum evaporation. Take this seed solution in a reaction container and add 1 1/2 ounces of water.
90ftlL Nuthylene 100 parts, ferrous sulfate 0.002
1 part, 0.02 part of ethylenediaminetetraacetic acid cII, 0.2 part of Ly Scorch ym, 0.02 part of hydrosulfide, and 0.1 part of cumene hydroperoxide,
The mixture was stirred at 40°C. The monomer is quickly absorbed into the seed polymer and becomes swollen particles with a uniform particle size of 1 μm or more.
The emulsifier concentration was 2.6 m mol/l, lower than the critical micelle concentration, and the initiation of polymerization in the micelles was slow, so no new particles were generated, and the swollen particles maintained their shape even as the polymerization proceeded. . After 8 hours, a highly stable emulsion polymer was obtained in which the polymerization rate of the monomers was 90% or more and the generation of coagulated products was 10% or less of the monomers charged.

When the emulsion polymer was examined using an electron microscope, it was found that a monodisperse emulsion was formed with particles having a diameter of 1.1 μm and almost no new particles being generated.

[Example 2] Emulsion 1 was combined in exactly the same manner as in Example 1 except that 0.05 part of formaldehydna (l) ramsulfoxyler) was used instead of using 2 parts of ■・-Ascorby7MO in Example 1. I got it.

When the emulsion polymer was examined using an electron microscope, a monodisperse emulsion was obtained in which the particle diameter was 1.1 μm and almost no new particles were generated.

[Example 3] Instead of using the monodisperse emulsion with a diameter of 25 μm as the self-emulsion in Example 1, the monodisperse polystyrene particles of 1 and 10 μm synthesized in Example 1 were used as the seed emulsion. An emulsion polymer was obtained in exactly the same manner as in Example 1.

When the emulsion polymer was examined using an electron microscope, a monodisperse emulsion was obtained in which the particle diameter was 4.95 mounds and almost no new particles were generated.

[Example 4] An emulsion polymer was obtained in exactly the same manner as in Example 1 except that 2 parts of hexane was used instead of 2 parts of 1-chlordodecane in Example 1.

By heating the produced emulsion polymer to 80°C, hexa/ could be removed from the particles.

When the emulsion polymer was examined using an electron microscope, a monodisperse emulsion was obtained in which the particle diameter was 1.1 μm and almost no new particles were generated.

[Example 5] 1000 parts of water, 0.5 parts of sodium lauryl sulfate, 3 parts of potassium persulfate, 20 parts of t-dodecylmercaptan, and 100 parts of styrene were placed in a reactor that had been purged with nitrogen gas in advance, and the temperature was raised to 80°C. The mixture was allowed to react for 8 hours. As a result, an emulsion containing 11# of styrene having a polymerization rate of 90% or more, a stable particle size of 0.28 μm, and a monodisperse molecular weight of less than 1000 at 10% or more was obtained. Take 33 parts of this as a seed emulsion, add 0.2 parts of sodium lauryl sulfate, 120 parts of water, and 2 parts of styrene.
0 parts and 80 parts of butyl acrylate were added and stirred at 40°C to absorb the monomer into the seed particles.

In 50 parts of water, 0.002 parts of ferrous sulfate, 0.02 parts of ethylenediaminetetraacetic acid, and 0.1 parts of L-ascorbic acid were added.
parts, sodium dithionite 0.02 parts, hydrogen peroxide 0
．． 0.05 parts was dissolved and added to the previous 7-mer swollen particle solution.

Polymerization was allowed to proceed at 40°C, and after 8 hours, a highly stable emulsion polymer was obtained in which the monomer polymerization rate was 90% or more and the generation of coagulum was 5% or less.

Examination of the emulsion polymer using an optical microscope revealed that a monodisperse emulsion was formed with particle diameters of 0.9 μm and almost no new particles.

[Comparative Example 1] Same as Example 1 except that 0.7 part of potassium persulfate was used for polymerization at 70°C using a redox-based polymerization initiator as the initiator in Example 1. An emulsion polymer was obtained in exactly the same manner.

When the emulsion polymer was examined with an electron microscope, it was found that 1.0 μm particles were produced by retaining the swollen particles, and 0.29 μm particles were produced by fresh soap-free emulsion polymerization (i.e., two types of particles). was found to be included. The proportion of new particles was 10% or more by weight.

[Comparative Example 2] Instead of polymerizing at 40°C using a redox polymerization initiator as the initiator in Example 1, 0.8% of AIBN was used.
An emulsion polymer was obtained in exactly the same manner as in Example 1, except that the emulsion polymer was polymerized at 70°C.

Although monodisperse particles of 1.1 μm were obtained without the generation of new particles, more than 10% of the charged particles were coagulated due to bulk polymerization of the monomer phase.

[Comparative Example 3] In Example 1, sodium lauryl sulfate e0.14
An emulsion polymer was obtained in exactly the same manner as in Example 1 except that 1.5 parts were used instead of 5 parts.

When the emulsion polymer was examined with an electron microscope, it was found that it contained two types of particles: 1.0 μm particles that were formed by holding the swollen particles, and 0.18 μm particles that were formed by newly starting polymerization in the micelles. I found out that I can wear it. The proportion of small particles was more than 5% by weight.

Effect of the invention The effects of the present invention are listed below.

(Since the 11 redox initiator is used, the shape of the swollen monomer particles is maintained as is, and a monodisperse emulsion polymer with large particle size can be obtained.

(2) When the present invention is compared with a method in which an oil-soluble initiator is absorbed into swollen monomer particles and polymerized, a high molecular weight polymer is easily obtained in the present invention.

(3) In the present invention, since polymerization can be carried out at a relatively low temperature, for example, 60° C. or lower, a compound with a low boiling point can be used as the poorly water-soluble substance to be preabsorbed into the seed polymer. If, for example, 1-chlordodecane, which has a high boiling point, is used as a poorly water-soluble substance, 0.5 to 20 parts of it will remain in the final polymer particles.
1. It may have a confusing effect on the physical properties of the polymer. There is also the problem of odor. Therefore, after the product is obtained, it is desirable that the poorly water-soluble substance can be easily vaporized and removed by heating under reduced pressure. desirable. However, if the boiling point of the poorly water-soluble substance is lower than the polymerization temperature, the water-repellent substance will vaporize and be removed from the system during polymerization, resulting in the disadvantage that the shape of the swollen monomer particles will no longer be maintained. .

For example, hexane has a low solubility in water and works well as a poorly water-soluble substance, but its boiling point is approximately 69°C, and
It is difficult to carry out polymerization while maintaining the shape of the swollen monomer particles using a thermally decomposable radical polymerization initiator that is commonly used and requires a polymerization temperature of 90°C. Therefore, by using the redox initiator of the present invention, polymerization can be performed at a low temperature, so a poorly water-soluble substance with a relatively low boiling point can be used, and this poorly water-soluble substance can be easily removed after polymerization. You can also get the unexpected effect of being able to do it.

(4) Monodisperse emulsion polymers with a size of 0.3 to 5 μm cannot be produced by normal methods, but monomers can be absorbed into a seed polymer with improved swelling ability and polymerized while maintaining the shape of the swollen particles (i.e. The present invention) has made this possible for the first time.

Applicant: Japan Synthetic Rubber Co., Ltd. Agent: Patent Attorney, Benita Saneo

Claims (3)

[Claims] (1) Molecular weight as a seed polymer is 200 to 10,000
Aqueous polymer dispersion containing 10-100% by weight of low molecular weight compounds or having a solubility in water of 0.001% by weight
In the method described below, using an aqueous polymer dispersion that has absorbed an organic compound, a polymerizable unsaturated monomer is absorbed in an amount of 10 to 400 times the volume of the polymer, and then polymerized. A method for producing an emulsion polymer, characterized in that a redox yarn radical 1 initiator is used at an emulsifier oIk degree below a micelle concentration. (2) The seed polymer absorbs the polymerizable unsaturated monomer and contains 90% by weight or more of particles with an average particle diameter of 0.3 to 5 mm and a size within ±20% of the average particle diameter. A method for producing an emulsion polymer according to claim 1. (3) The method for producing an emulsion polymer according to claim 1, wherein the peroxide of the redox polymerization initiator is hydromonooxide or hydrogen peroxide.