JPH0149722B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves suspending an aqueous monomer solution in an inert and hydrophobic liquid and polymerizing it therein in the presence of a polymerization initiator and a specific protective colloid to form beads. The present invention relates to a method for producing bead-shaped polymers from water-soluble ethylenically unsaturated monomers by reverse-phase suspension polymerization to obtain (spherical) polymerization products.

The use of a reversed-phase suspension polymerization method to produce spherical polymers from water-soluble ethylenically unsaturated monomers is known from Japanese Patent Publication No. 10644/1983 and Japanese Patent Application Laid-open No. 1082/1982. . In order to carry out this method it is important to properly select a suitable protective colloid. This protective colloid stabilizes the W/O suspension and influences the particle size of the polymer. Known protective colloids include sorbitan fatty acid esters such as sorbitan monostearate and sorbitan monopalmitate, and fatty acid monoglycerides such as stearic acid monoglyceride. During polymerization, the aqueous phase of the W/O dispersion becomes viscous, and the suspended water-containing polymer remains somewhat sticky even after polymerization. Therefore, during the polymerization or during subsequent steps such as azeotropic dehydration following the polymerization, the polymer particles stick to each other. In extreme cases, this phenomenon can even cause all the polymers to stick together and form a lump on the stirrer and vessel walls. The known protective colloids have the disadvantage that they do not prevent the formation of films on the walls of the polymerization apparatus and on the surfaces of the stirrers. Furthermore, when reverse phase suspension polymerization is carried out using known protective colloids, such as sorbitan fatty acid esters, the resulting polymer becomes a very fine powder with a particle size of 100 μm or less. Therefore, dust countermeasures are required when handling powder. Also, when dissolving powder, “Mamako”
This phenomenon easily occurs and dissolution becomes extremely difficult.

As a result of intensive research, the present inventors found that 1 to 20 wt% of α,
By using a reaction product grafted with β-unsaturated polyhydric carboxylic acid or its anhydride or a low molecular weight monoolefin polymer oxidized to a final acid value of 10 to 100, the particle size can be reduced. It has been found that a large polymer can be obtained and the above-mentioned drawbacks can be solved, and the present invention has been achieved.

That is, the present invention is a reverse-phase suspension polymerization method in which an aqueous monomer solution is suspension-polymerized in a polymerization-inert and hydrophobic liquid using a water-soluble radical polymerization initiator to obtain a spherical polymerization product. A reaction product obtained by grafting 1 to 20 wt% of α,β-unsaturated polyhydric carboxylic acid or its anhydride to a monoolefin polymer having an acid value of 750 to 10,000, or a monoolefin polymer having an acid value of 10 to 10. The present invention provides a method for producing a bead-shaped polymer from a water-soluble ethylenically unsaturated monomer, characterized in that the product obtained by oxidizing the monomer to 100% is used as a protective colloid.

In the present invention, as the inert and hydrophobic liquid that is the dispersion medium of the W/O type dispersion, any liquid can be used, in principle, as long as it does not participate in polymerization and does not mix with water. Preferred are aliphatic, alicyclic and aromatic hydrocarbons, halogenated hydrocarbons, or mixed solutions thereof.

According to the present invention, all water-soluble ethylenically unsaturated monomers are polymerized into bead-like (spherical) polymers by reverse phase suspension polymerization. Examples of the water-soluble monomers include (meth)acrylic acid, (meth)acrylates (sodium salts, ammonium salts, etc.), (meth)acrylamide and N-substituted (meth)acrylamides, 2-(meth) Examples include acryloylethanesulfonic acid, 2-(meth)acryloylethanesulfonate, styrenesulfonic acid, styrenesulfonate, dimethylaminoethyl (meth)acrylate, and their quaternary ammonium salts. It is also possible to use two or more types of mer. Furthermore, if necessary, these monomers can be copolymerized with a water-soluble crosslinking agent having two or more polymerizable unsaturated groups. The monomer concentration in the aqueous monomer solution can vary within a wide range and is generally 15-80 wt%. This upper limit depends, inter alia, on the solubility of the monomers, but the lower limit is generally not lower than the above-mentioned value for economic reasons.

The protective colloid of the present invention is a reaction product obtained by grafting 1 to 20 wt% of α,β-unsaturated polyhydric carboxylic acid or its anhydride to a low molecular weight monoolefin polymer, or a reaction product with an acid value of 10 to 100 in the final product. A low molecular weight monoolefin polymer is used, which is oxidized to have a carbonyl group and a carboxyl group introduced into the molecule. Examples of the monoolefin polymer include polyethylene, polypropylene, polybutene, and ethylene-propylene copolymer, and preferably polyethylene, polypropylene,
It is an ethylene-propylene copolymer and contains substantially no double bonds. These have a molecular weight of about 750-10,000, preferably 1,000-5,000. The present invention excludes diene polymers such as polybutadiene. This is because when such a polymer is used, the polymer particles produced by the production method of the present invention are sticky, resulting in poor workability during use. What is important in the present invention is to graft α,β-unsaturated polyhydric carboxylic acid or its anhydride to the monoolefin polymer, or to oxidize the monoolefin polymer with air or use an oxidizing agent (ozone, periodic acid, etc.). The purpose is to give the monoolefin polymer an affinity for water by introducing a carboxyl group into the molecule. α,β-unsaturated polycarboxylic acids or their anhydrides used for modifying low molecular weight monoolefin polymers include α,β-unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, and itaconic acid. , maleic anhydride, citraconic anhydride,
Mention may be made of anhydrides of α,β-unsaturated dicarboxylic acids such as itaconic anhydride, preferably maleleic anhydride. In the present invention, it does not matter whether the monoolefin polymer modified in this way is in an acid anhydride state or in a partially or completely ring-opened state when used. Protective colloid against dispersion medium
It is used in an amount of 0.01 to 10 wt%, preferably 0.05 to 5.0 wt%.

In the present invention, the ratio of the amounts of aqueous monomer solution and dispersion medium can be varied over a wide range. Generally, a small amount of dispersion medium is advantageous in that a large amount of monomer can be charged per batch in the reactor, but it becomes difficult to remove heat generation. Therefore, a normal capacity ratio between 1:1 and 1:4 is appropriate.

For the polymerization of the monomers, water-soluble radical polymerization initiators, such as peroxides, hydroperoxides, azo compounds, etc., are used in known amounts. These initiators can be used as a mixture or can be used as a redox initiator. In this way, a spherical polymer is obtained, which may be separated from the dispersion medium by means such as tilting, filtration, or centrifugation and then dried, or the polymer may be dried by directly distilling off the dispersion medium and water. You can also get In the present invention, the bead-shaped (spherical) polymer means particles having a size of 0.5 to 5 mm and consisting of small particles having a center particle diameter of 100 to 350 μm or a group of small particles in which many of these particles are attached to each other.

An advantage of the process according to the invention is that no or only a very small amount of film formation is observed, especially on the polymerization equipment and equipment, and another advantage is that the particle size is significantly improved by the addition of the protective colloid, and dust and This means that the "mamako" phenomenon during dissolution is almost no longer observed.

The present invention will be specifically explained below using Examples and Comparative Examples. The protective colloids used in the Examples are listed below.

Protective colloid A: 150 g of high-density polyethylene wax (molecular weight 2200, density 0.97) equipped with a stirring bar
Pour into a 300ml flask and heat in an oil bath to melt.
Replace with nitrogen at 150℃. Next, 25g of maleic anhydride,
Add 5g of benzoyl peroxide one by one and heat to 150°C.
Let it react for 1 hour. After the reaction is complete, stir for 5 mm.
Unreacted maleic anhydride was removed by keeping in Hg vacuum for 1 hour. The acid value of this product was 63.

Protective colloid B: 150 g of low density polyethylene wax (molecular weight 2000, density 0.93), 6 g maleic anhydride and 3 g t-butylcumyl peroxide were reacted in the same manner as protective colloid A. The acid value of this product was 28.

Protective colloid C: A commercially available modified polyethylene wax to which maleic anhydride has been added (Mitsui Petrochemicals Hi-wax 1105A, molecular weight 1400, density 0.94, acid value 60) Protective colloid D: A commercially available product to which maleic anhydride has been added. Modified polyethylene wax (Mitsui Petrochemical Hi-wax2203A, molecular weight 2700, density 0.94, acid value 30) Protective colloid E: Polypropylene wax (molecular weight 3000, density 0.89) 150g and maleic anhydride 15
g and 3 g of benzoyl peroxide at 160°C.
After reacting for a period of time, the same procedure as for protective colloid A was carried out. The acid value of this product was 53.

Protective colloid F: 150 g of ethylene-propylene copolymer (molecular weight 2000, density 0.92), 6 g of maleic anhydride, and 3 g of t-butylcumyl peroxide were reacted at 160°C for 4 hours, and then operated in the same manner as protective colloid A. . The acid value of this product was 35.

Protective colloid G: Commercially available air-oxidized polyethylene wax (Mitsui Petrochemicals Hi--
wax 4202E, molecular weight 2600, density 0.94, acid value 18) Example 1 Place 230 ml of n-hexane in a 500 ml four-necked round-bottomed flask equipped with a stirrer, reflux condenser, dropping funnel, and nitrogen gas inlet tube, and add protection. 2.3 g of colloid A was added and dispersed. After blowing in nitrogen gas to drive out dissolved oxygen, the temperature was raised to 65°C to dissolve the protective colloid. Separately, in an Erlenmeyer flask, 30 g of acrylic acid was dissolved in 40 g of ion-exchanged water while cooling with ice from the outside.
After neutralizing with 13.4 g of 98% caustic soda, 0.1 g of potassium persulfate was added and dissolved, and nitrogen gas was blown in to remove oxygen present in the aqueous solution. The contents of the Erlenmeyer flask were added to a four-necked flask and dispersed, and the internal temperature of the flask was maintained at 60 to 65°C for 1 hour to carry out polymerization. The hexane was distilled off under reduced pressure, and the remaining swollen polymer portion was dried under reduced pressure at 80°C to obtain spherical particles with a center particle size of 100 to 350μ. The deposit in the tank was only 0.5 g.

Example 2 The procedure was carried out in the same manner as in Example 1, except that cyclohexane was used as the dispersion medium and a protective colloid was used as the protective colloid.
When 1.86 g of B was used, spherical particles with a center particle size of 100 to 350 μm were obtained. The amount of deposits in the tank was 0.7g.

Example 3 In the polymerization reactor of Example 1, 230 ml of heptane,
2.3g of protective colloid C was added. On the other hand, in an Erlenmeyer flask, add 20 g of acrylamide and 12.6 g of sodium acrylate.
An aqueous monomer solution was prepared using 76 g of ion-exchanged water, and 0.1 g of ammonium persulfate was added and dissolved in this solution, followed by polymerization in the same manner as in Example 1.
The deposit in the tank is 0.8g, and the center particle size is 100~
It was a spherical polymer with a diameter of 350μ.

Example 4 The procedure was carried out in the same manner as in Example 3, except that when 1.8 g of protective colloid D was used as the protective colloid, the central particle size was
Spherical particles of 100-350μ were obtained. The deposit in the tank was only 0.5 g.

Comparative Example 1 The procedure was carried out in the same manner as in Example 1, except that 3.6 g of oleic acid monoglyceride was used as the protective colloid, and the deposit in the tank was 10.5 g, which was a 5-10 mm granular polymer made up of fine particles gathered together. It was hot.

Comparative Example 2 The procedure was as in Example 1, except that 1.8 g of sorbitan monostearate was used as the protective colloid.
The deposit in the tank weighed 5.3 g and was a polymer with very small particles (median particle size 5-50 microns).

Example 5 The procedure was carried out in the same manner as in Example 1, except that 30 g of sodium styrene sulfonate was dissolved in 60 g of ion-exchanged water as an aqueous monomer solution, and 0.1 g of potassium persulfate was added.
When 2.3 g of protective colloid C was used, spherical particles with a center particle size of 100 to 350 μm were obtained. The amount of deposit in the tank was 0.5g.

Example 6 230 ml of benzene was placed in the polymerization reactor of Example 1.
Contains 2.2g of protective colloid F. On the other hand, in an Erlenmeyer flask, an aqueous monomer solution was prepared with 30 g of acrylamide, 0.03 g of N,N'-methylenebisacrylamide, and 46 g of ion-exchanged water, and 0.1 g of t-butyl hydroperoxide was added and dissolved in this solution. Polymerization was carried out in the same manner. Deposits in the tank are 0.9
g, 1 to 3 mm in which small particles are gathered together
It was a spherical polymer.

Example 7 The procedure was carried out in the same manner as in Example 1, except that an aqueous monomer solution prepared by dissolving 25 g of 2-methacryloylethyltrimethylammonium chloride in 50 g of ion-exchanged water and further adding 0.05 g of ammonium persulfate was used. When 1.92 g of protective colloid G was used, a spherical polymer with a size of 0.3 to 5 mm and made up of small particles was obtained. The amount of deposits in the tank was 0.6g.

Example 8 The procedure was carried out in the same manner as in Example 1, except that 2.2 g of protective colloid E was used as the protective colloid and 230 ml of carbon tetrachloride was used as the dispersion medium.The deposit in the tank was 0.8 g, and small particles were gathered together. A spherical polymer with a diameter of 1 to 3 mm was obtained.

When the polymers obtained in Examples 1 to 8 and Comparative Examples 1 to 2 were dispersed and dissolved in water, the polymers of Examples 1 to 8 according to the present invention had extremely good dispersibility and almost no dust was observed. I couldn't help it. On the contrary, in the polymers of Comparative Examples 1 and 2, "baby eggs" were generated during dispersion, making it difficult to disperse, and the amount of dust was extremely noticeable.

Claims (1)

[Claims] 1. In a reversed-phase suspension polymerization method in which an aqueous monomer solution is subjected to suspension polymerization in a polymerization-inert and hydrophobic liquid using a water-soluble radical polymerization initiator to obtain a spherical polymerization product. , a reaction product in which 1 to 20 wt% of α,β-unsaturated polycarboxylic acid or its anhydride is grafted to a monoolefin polymer with a molecular weight of 750 to 10,000, or a monoolefin polymer whose acid value is finally 1. A method for producing a bead-shaped polymer from a water-soluble ethylenically unsaturated monomer, characterized in that the product obtained by oxidizing the monomer to have a molecular weight of 10 to 100 is used as a protective colloid. 2. The method for producing a bead-shaped polymer from a water-soluble ethylenically unsaturated monomer according to claim 1, wherein the protective colloid is a reaction product of a monoolefin polymer and maleic anhydride.