JP2635076B2 - Method for producing maleic anhydride copolymer particles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing maleic anhydride copolymer particles, and more particularly, to an adhesive, a dispersant, an emulsion stabilizer, a binder, and a sustained release. The present invention relates to a method for obtaining maleic anhydride copolymer particles useful as a pharmaceutical composition, a paper sizing agent, a cement admixture, and the like as spherical and uniform primary particles.

[Problems to be solved by conventional technology and invention]

Conventionally, various types of maleic anhydride copolymers have been developed, for example, adhesives for wood and paper, binders for paints and inks, dispersants such as inorganic pigments, stabilizers for emulsion polymerization, and paper sizes. Although it is used for applications such as additives and cement admixtures, it is particularly useful as a cement admixture that maintains the fluidity of concrete for a long time, so-called anti-slump loss agent.

Among such maleic anhydride copolymers, conventionally, a water-soluble salt of an olefin-maleic anhydride copolymer has been known as a cement admixture (JP-A-51-101024).
For example, JP-A-60-16851 and JP-A-61-26543 disclose a copolymer of an olefin having 2 to 8 carbon atoms and maleic anhydride itself as a cement compound. It has been shown that the addition of the cement compound can maintain the fluidity of the cement composition for a long time and also keep the fluidity constant, thereby significantly improving the workability and workability of the cement composition. Cement particles in a cement composition generally lose their fluidity gradually due to chemical agglomeration due to hydration reaction and physical agglomeration due to interparticle attractive force. If you add
The copolymer is hydrolyzed by alkali eluted from the cement, becomes water-soluble, and gradually dissolves in water from the surface (slow release action) to exhibit cement dispersibility. It is estimated to be retained for a long time.

In this method, the balance between the rate of slump loss due to chemical and physical agglomeration of cement particles and the rate of hydrolysis of the maleic anhydride copolymer is most important in order to prevent slump loss of the cement composition. It is considered to be an important factor.

The hydrolysis rate of the copolymer depends on its molecular weight and particle size. The copolymer useful as a slump loss inhibitor preferably has a molecular weight in the range of 500 to 20,000. On the other hand, the particle size is desirably in the range of 0.1 to 1,000 μm, particularly preferably in the range of 0.1 to 10 μm.

However, a maleic anhydride copolymer having such a particle size is difficult to obtain by a usual method, and usually has a particle size of 20 μm to
Since it is obtained as an agglomerate or lump of several millimeters, it is necessary to reduce the particle size to a desired particle size by a wet or dry pulverization method. However, pulverizing to such a particle size requires a large amount of energy, even if the pulverization is performed by a wet sand mill or the like, for example, and causes an increase in manufacturing cost. Furthermore, since the copolymer particles obtained by the pulverization method are amorphous and have a very wide particle size distribution, it is difficult to control the above-mentioned sustained release rate constantly. When used as an additive,
For example, it is stored in a water slurry state, but particles having a large particle diameter are settled, causing a problem that the quality is not uniform.

For these reasons, it is desired that the copolymer particles have a uniform shape (for example, spherical) and a narrow particle size distribution.

On the other hand, as a method for obtaining a copolymer of maleic anhydride and an olefin or a styrene-based monomer as described above, many methods by precipitation polymerization have been proposed. This is a method in which polymerization is carried out in a solvent that can dissolve the monomer but does not dissolve the polymer, and obtains the polymer as a powder, granules, or a lump. As the solvent, acetone, lower ketones such as methyl ethyl ketone, lower esters such as methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, methyl propionate, benzene, xylene, toluene, ethylbenzene, n- or t-butylbenzene, Aromatic solvents such as isopropylbenzene, hydrocarbon solvents such as hexane and ligroin, and mixtures thereof are used.

The inventors of the present invention have actually studied using these solvents. According to the precipitation polymerization using these polymerization solvents, the following disadvantages were respectively observed.

That is, when lower ketones such as acetone are used,
The solvent itself has a strong polarity and dissolves a part of the produced copolymer.As a result, the yield is low, the amount of deposits on the reactor wall is large, and the obtained particles have an irregular coagulation size of 30 to several 100 μm. It was a collective.

Next, when an ester solvent such as isopropyl acetate or butyl acetate is used as shown in JP-B-49-6396 and JP-A-61-91208, the deposits on the reactor There were many. In this case, when an attempt was made to obtain a copolymer having an average molecular weight of 100,000 or more, formation of particles having a particle size of about 1 μm was observed. It became an aggregate.

Further, when an aromatic solvent such as ethylbenzene is used, as seen in JP-A-60-99110, the solubility of the copolymer is reduced, so that the amount of adhesion to the reactor wall is certainly small. However, the obtained copolymer was an amorphous aggregate having a particle size of 20 to 50 μm, and a pulverizing means was necessary to use the copolymer as described above.

Furthermore, when a hydrocarbon solvent such as hexane is used, maleic anhydride does not dissolve, so that polymerization is not performed uniformly, and a bulk polymer is obtained even when reacted in a heterogeneous phase, which is difficult to handle. Met.

In addition, a method using a mixed solvent (Japanese Patent Publication No. 49-16551)
Publication) has been proposed, but it is difficult to obtain the present copolymer as primary particles.

On the other hand, a method in which a dispersant is present in such a polymerization solvent to carry out precipitation polymerization has been proposed. Examples of the dispersant include a copolymer of an α-olefin having 20 or more carbon atoms and maleic anhydride (JP-B-62-5927), and a copolymer of an α-olefin having 2 to 8 carbon atoms and maleic anhydride. Half ester or half amide (JP-A-51-95489) and ethylene-vinyl ester copolymer (JP-A-54-95489).
No. 156092), although the amount of adhering to the reactor wall is certainly reduced, the copolymer has a particle diameter of 10 to several tens of μm, and it has not yet been possible to obtain only fine particles of 10 μm or less with a high yield.

[Object of the invention]

An object of the present invention is to provide a copolymer of maleic anhydride and a vinyl monomer copolymerizable with maleic anhydride in a spherical shape, with a monodisperse particle size distribution, and without forming an aggregate, Is about 10
An object of the present invention is to provide a method for obtaining primary particles having a size of μm or less.

Another object of the present invention is to prevent the polymer from adhering to the reactor walls, stirring blades, etc. in the precipitation polymerization of maleic anhydride and a vinyl monomer copolymerizable therewith. An object of the present invention is to provide a method by which coalesced particles can be obtained in high yield.

[Means for solving the problem]

The present inventors have conducted intensive studies in order to solve the above-described problems of the prior art, and as a result, when copolymerizing maleic anhydride and a vinyl monomer copolymerizable therewith, the presence of a specific compound It has been found that the above objects can be achieved by precipitation polymerization below, and the present invention has been completed.

That is, in the present invention, when maleic anhydride and styrene or isobutylene (hereinafter, referred to as comonomer) are copolymerized, these monomers are dissolved, but the obtained copolymer is dissolved in a solvent in which the copolymer is not dissolved. The present invention provides a method for producing maleic anhydride copolymer particles, wherein radical polymerization is carried out in the presence of a cellulose ester or a cellulose ether used as a dispersant.

In the present invention, an oil-soluble monomer is mainly used as the comonomer. However, acrylic acid, methacrylic acid, 2-hydroxy Polymerization can also be carried out by appropriately coexisting a hydrophilic vinyl monomer such as ethyl (meth) acrylate, (meth) acrylamide, or vinylpyrrolidone.

In the present invention, the molar ratio between maleic anhydride and the copolymer (when two or more kinds are used, the total amount thereof) is 1/2.
~ 2/1 is desirable, more preferably 1 /
It is in the range of 1.2 to 1.2 / 1.

Solvents used in the present invention that dissolve maleic anhydride and the comonomer but do not dissolve the resulting copolymer include benzene, xylene, toluene, ethylbenzene, n- or t-butylbenzene, and isopropylbenzene. And aromatic ester solvents such as methyl acetate, ethyl acetate, isopropyl acetate, and methyl propionate. These solvents may be used alone or in combination of two or more. Alkylbenzenes such as benzene and ethylbenzene are preferred. The amount of these solvents is preferably such that the resulting copolymer has a concentration of 5 to 35% by weight.

As the cellulose ester or cellulose ether used as a dispersant in the present invention, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, methyl cellulose, ethyl cellulose, propyl Cellulose, hydroxyethylcellulose, benzylcellulose, ethylhydroxyethylcellulose, carboxymethylcellulose, cyanoethylcellulose and the like are preferable, and those which are particularly easily soluble in the solvent used are preferable. However, ethyl cellulose is preferred.

In the present invention, maleic anhydride and a vinyl monomer copolymerizable therewith are copolymerized by a precipitation polymerization method using the above-mentioned cellulose ester or cellulose ether as a dispersant.

The cellulose derivative has a weight average molecular weight (polystyrene or sodium polysterenesulfonate) of 1,00 as determined by gel permeation chromatography.
Those with 0-800,000 are suitable, preferably 10,000-25
It is a thing of 0,000. Cellulose derivatives having a molecular weight of less than 1,000 or more than 800,000 have no effect as a dispersant when synthesizing a maleic anhydride copolymer.

The used amount of the above-mentioned cesulose derivative is maleic anhydride 10
The amount is preferably 0.05 to 20 parts by weight based on 0 polymerization parts. When the amount is less than 0.05 part by weight, the effect as a dispersant is poor.On the other hand, even when the amount is more than 20 parts by weight, the effect as a dispersant is not particularly improved, and the performance of the obtained copolymer particles is impaired. Is not preferred.

In the present invention, precipitation polymerization is carried out in the above-mentioned solvent in the presence of the cellulose derivative and the radical polymerization initiator according to a conventional method.

Radical polymerization initiators include peroxides such as cumene hydroperoxide, t-butyl hydroperoxide, benzoyl peroxide, diisopropyl peroxycarbonate, lauroyl peroxide, t-butylperoxybenzoate, potassium persulfate, and ammonium persulfate. , 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile)
And the like, but are not particularly limited thereto.

The use amount of these polymerization initiators is preferably from 0.1 to 20 mol% based on maleic anhydride.

The cellulose derivative is preferably present in the reaction system from the beginning of the polymerization, but the polymerization initiator and the monomer are:
They may be added all at once in the early stage of the polymerization, or may be added gradually as the polymerization proceeds.

The polymerization temperature is selected according to the decomposition temperature of the polymerization initiator to be used and the boiling point of the solvent to be used.
The reaction is carried out at a temperature of 0 ° C, preferably 40 to 100 ° C. If the polymerization temperature is too low, the polymerization rate will decrease. If the polymerization temperature is too high, the produced copolymer will easily adhere to the reactor wall or become bulky.

The time of the polymerization reaction is appropriately set usually in the range of 1 to 15 hours.

The reaction may be carried out under a pressurized state, or may be carried out under normal pressure while dropping the comonomer as it is or as a solution, or while blowing monomer on a gas.

In this way, by performing precipitation polymerization in the presence of a specific cellulose derivative, the desired maleic anhydride copolymer particles can be obtained.

The average molecular weight of the copolymer is usually about 200,000 or less, but the molecular weight can be adjusted by setting conditions such as the monomer concentration, the amount of the initiator used, and the polymerization temperature, and a commonly used chain transfer agent such as lauryl mercaptan, It is also possible to carry out the polymerization in the presence of a sulfur compound such as sulfur, a nitrogen compound such as an aromatic amine or an aliphatic amine, or a halogen compound such as chloroform or carbon tetrachloride.

In the present invention, when the molecular weight of the target copolymer is relatively small, that is, the particle shape of the copolymer is liable to be deformed, adhere to the reactor wall, the yield is easily reduced, and the like. , 0
This is particularly useful when it is desired to set the value to 00 or less.

When observed with an electron microscope, the maleic anhydride copolymer particles obtained by the method of the present invention are spherical in all parts, and are almost monodisperse in particle size distribution. The size of the obtained particles varies depending on the type of the solvent, the type and amount of the cellulose derivative used, the reaction conditions, and the like, but is usually in the range of 0.1 to 3 μm.

In addition, the particles obtained by the present invention are almost primary particles and are used for the intended purpose as they are, for example, even if there is some aggregation at a high temperature, or dispersed in water,
Alternatively, it can be returned to the original primary particles by very simple crushing.

〔The invention's effect〕

As described above, according to the method of the present invention,
The maleic anhydride copolymer can be obtained as primary particles that are spherical, have a substantially monodispersed particle size distribution, and do not form aggregates.

Furthermore, according to the present invention, the copolymer particles can be obtained in high yield by eliminating the adhesion to the reactor wall and the stirring blade. This makes it possible to easily produce the copolymer particles having a relatively low molecular weight, which has been conventionally difficult.

Therefore, the cost can be reduced by improving the yield, and for the use as a slump loss inhibitor for concrete, etc. as mentioned in the present invention, the complicated granulation by the conventional pulverization method, a great deal of In addition to solving the problem of energy loss, excellent performance stability can be provided.

Furthermore, for other applications, such as pigment dispersants, emulsion and latex emulsion stabilizers, binders for paints and inks, paper sizing agents, sustained release drug compositions, and the like,
Dissolution, neutralization, and the like are easily performed, and workability and performance stability can be significantly improved.

[Examples] Hereinafter, the present invention will be described specifically with reference to Examples.
The present invention is not limited to only these examples. In the examples, “parts” is “parts by weight”.

Example-1 A stirrer, a gas introduction tube, a thermometer, and a cooling tube were provided, and a 607 part of toluene, 68.6 parts of maleic anhydride, and ethyl cellulose [manufactured by Hercules Co., Ltd.] were placed in a 1-separable flask equipped with a gas bag at the end of the cooling tube. Ethyl cellulose N-7,
An ethoxyl content of 48% and a molecular weight of 62,000 (in terms of polystyrene)] of 3.4 minutes were added, and the mixture was heated to 70 ° C. with stirring in a nitrogen atmosphere. 6.8 parts of 2,2'-azobisisobutyronitrile were added as a polymerization initiator, and then isobutylene gas was introduced into the solution from a gas cylinder through a separately prepared cylinder. While maintaining the reaction temperature at 70 ° C., 45 parts (molar ratio to maleic anhydride: 1.14) of isobutylene gas were continuously blown in over 3 hours. After starting the introduction of isobutylene gas,
Since the solution becomes cloudy immediately and the gas bag does not inflate,
It was found that the gas was efficiently absorbed into the solution, and that the polymerization reaction was occurring. After completion of gas blowing, the mixture was aged at that temperature for 2 hours under stirring, and then cooled. The slurry reaction solution containing the polymer precipitate was taken out, filtered and dried to obtain 106 parts of a polymer white powder. The yield based on the charged maleic anhydride was as high as 98.1%. When the separable flask from which the reaction solution was taken out was inspected, little adhesion of the polymer was found on the inner wall of the container or the stirring blade.

Further, the obtained polymer was dispersed in water and neutralized with an equivalent amount of NaOH to obtain an aqueous solution, and the molecular weight was measured by gel permeation chromatography.
It was 4,200 (in terms of sodium polystyrene sulfonate).

On the other hand, when the obtained polymer powder was observed with an electron microscope, it was found to be fine spherical monodispersed particles. Further, the polymer powder was dispersed in water, and the particle size and the particle size distribution were measured using a light transmission type centrifugal sedimentation particle size distribution analyzer (SACP-3 manufactured by Shimadzu Corporation). A single peak appeared, indicating that little aggregate was formed.

Example-2 A method similar to that of Example-1 except that ethylcellulose N-200 manufactured by Hercules Inc. [ethoxyl content 48%, molecular weight 216,000 (in terms of polystyrene)] was used instead of ethylcellulose N-7 in Example-1. The polymerization was carried out.

As a result, 105 parts of isobutylene and maleic anhydride copolymer powder were obtained, the yield was 97.8%, and no adhesion of polymer was observed on the inner wall of the reactor and the stirring blade. or,
The obtained polymer particles were monodisperse particles of 0.2 μm.

Example 3 Instead of the isobutylene gas of Example 1, styrene 7 was used.
The procedure was performed in the same manner as in Example 1, except that 2.8 parts (molar ratio to maleic anhydride: 1.0) was continuously added dropwise over 3 hours.

139 parts of a white powder were obtained (yield 985), which was an alternating copolymer of styrene and maleic anhydride. No adhesion of the polymer to the inner wall of the reactor or the stirring blade was observed. When the molecular weight and the particle diameter were analyzed in the same manner as in Example 1, the weight average molecular weight was 13,100, the particle diameter was 0.4 μm, and the particles were monodisperse particles having almost no aggregate.

Comparative Example-1 In Example-1, precipitation polymerization of isobutylene and maleic anhydride was performed without adding ethylcellulose. After the completion of the polymerization, the slurry-like reaction liquid was taken out, filtered and dried to obtain 76.5 parts of a white powder of a polymer. The yield based on the charged maleic anhydride was low at 71%. When the separable flask from which the reaction solution was taken out was inspected, a large amount of the polymer adhered to the inner wall of the solution and the stirring blade, and the weight was measured by scraping off the adhered substance, and it was 29 parts.

When the molecular weight of the powder polymer obtained in the same manner as in Example 1 was measured, the weight-average molecular weight was 12,200, and the molecular weight was almost the same as that of Example 1. Not seen at all,
Almost 20 to 100 μm in irregular mass.

Comparative Example 2 Precipitation polymerization was carried out using a half ester (weight average molecular weight 10,000) of a copolymer of isobutylene and maleic anhydride represented by the following formula in place of ethyl cellulose in Example 1.

As a result of performing the same operation as in Example 1, adhesion to the reactor wall and the stirrer was relatively small, and it was 6.4 parts. However, when the obtained polymer powder was observed with an electron microscope, no particle formation was observed at all, and it was again an amorphous mass of 30 to 100 μm.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-204910 (JP, A) JP-A-51-95489 (JP, A) JP-B-62-6567 (JP, B1) JP-B-62 5927 (JP, B1)

Claims (2)

(57) [Claims] When a copolymer of maleic anhydride and styrene or isobutylene is used, the monomer is dissolved, but the resulting copolymer is not dissolved in a solvent in which cellulose ester or cellulose ester used as a dispersant is used. A method for producing maleic anhydride copolymer particles, wherein radical polymerization is performed in the presence of cellulose ether. 2. A copolymer of maleic anhydride and styrene or isobutylene, which dissolves these monomers but does not dissolve the obtained copolymer in a solvent in which ethyl cellulose used as a dispersant is present. A method for producing maleic anhydride copolymer particles, comprising performing radical polymerization below.