JPH04132705A - Production of hydrophilic fine grain - Google Patents

Abstract

PURPOSE:To obtain fine grains having excellent water absorption in drying and antistatic properties after film forming by (co)polymerizing an acrylamide (derivative) with p-styrene sulfonic acid (salt), (meth)acrylic acid (salt), etc., in a water-miscible organic solvent, etc., in the presence of a soluble resin. CONSTITUTION:In a water-miscible organic solvent or a mixed solvent of water- miscible organic solvent/water, a homogeneous polymerization of a monomer soluble in the above-mentioned solvent(s) and selected from (A) an acrylic amide (derivative), (B) p-styrene sulfonic acid (salt) and (C) (meth)acrylic acid (salt) or copolymerization of (D) a vinyl compound [preferably styrene (derivative), (meth)acrylic acid ester, (meth)acrylonitrile or maleic acid (derivative)] polymerizable with the monomers of the components A to C is carried out in the presence of a resin soluble to the above-mentioned organic solvent to provide the aimed fine grains.

Description

[Detailed description of the invention]

[00011

[Industrial application field]

The present invention relates to a method for producing a water-soluble polymer in the form of fine particles, and compared to conventional water-soluble polymer solutions, the clay content of the dispersion is significantly reduced because the polymer is dispersed in the form of fine particles. By doing so, it is possible to produce and use water-soluble polymers in a highly concentrated state while maintaining fluidity. [0002] Furthermore, when making a water-soluble polymer dispersed at a high concentration into an aqueous solution in water, it is sufficient to simply dilute the dispersion,
This eliminates the need for the conventional process of dissolving powdered polymers. Examples of aqueous polymers that can be used include various water-soluble polymers such as polyacrylamide, which is used as a polymer flocculant, polyacrylic acid, which is used as a dispersant, and sodium polystyrene sulfonate, which is used as an antistatic agent. Since both polymers and their copolymers are manufactured in the form of highly concentrated fine particles, it is possible to transport high molecular weight polymers with low viscosity, and they can be used as is, for example, as a coating liquid. This has the advantage that it only needs to be diluted when used underwater. [0003] Further, in the present invention, by imparting a crosslinked structure to the fine particles, it is possible to maintain the original shape even in water, and the applications include, for example, fillers for liquid chromatography, matting agents, spacers, medical care. It can be applied to carriers for diagnostic drugs and other applications. Furthermore, by appropriately adjusting the degree of crosslinking in the fine particles,
It is also possible to form highly water-absorbent fine particles, which can be applied to highly water-absorbent sheet materials and inkjet recording materials. [0004]

[Conventional technology]

Although water-soluble polymers are used in a wide range of industrial fields in the form of aqueous solutions, they are supplied in the form (i
) an aqueous solution, (ii) a dry powder, or (iii) an emulsion dispersed in a hydrocarbon medium. [0005] In the aqueous solution state of (i), in the case of a high molecular weight water-soluble polymer solution, the viscosity of the solution increases significantly even when the concentration is low, making it difficult to transport the solution, and the concentration per solid content increases during transportation. There were problems such as high transportation costs. or,
Even when a water-soluble polymer solution is applied as a coating liquid, it is necessary to evaporate a large amount of water, and furthermore, the viscosity of the coating liquid is too high, which often causes various problems. [0006] When the water-soluble polymer is made into dry powder (ii),
The drying process usually requires a large amount of thermal energy, and redissolving the powder in water also requires a large amount of thermal energy and time. [0007] In recent years, as in (iii), so-called reverse-phase emulsion polymerization or reverse-phase suspension polymerization, in which a water-soluble polymer is produced in an emulsion state in a hydrocarbon medium, etc., has been carried out on an industrial scale. Water-soluble polymers have come to be supplied in the form of emulsions dispersed in oil, but in this case, when redissolving the water-soluble polymer emulsion in water, it is necessary to use an organic solvent that is immiscible with water. need to be removed, creating a difficult problem in terms of toxicity or flammability. [0008] When using a water-soluble polymer as a coating liquid, there are often problems such as the viscosity of the coating liquid becoming too high and compatibility when used in combination with other water-soluble polymers. Although it has sometimes been attempted to lower the viscosity and improve the compatibility by lowering the molecular weight of the polymer, undesirable results such as deterioration of the physical properties of the film after film formation are often observed. In order to solve these problems, it is necessary to form water-soluble polymers into fine particles, achieve low viscosity despite high molecular weight, and make coating liquids that can be mixed with other water-soluble polymers. is possible, but until now there has been no method to achieve this. Furthermore, by crosslinking a water-soluble polymer, it is possible to impart water resistance or water absorption, for example, but making the crosslinked polymer itself into an aqueous solution would significantly increase the liquid viscosity, making it difficult to use as a coating liquid. was practically impossible. [0009]

[Problem to be solved by the invention]

An object of the present invention is to provide a method for producing a hydrophilic polymer in the form of fine particles, and to provide a method for selectively producing a hydrophilic polymer having a shape of fine particles with an average particle size of at most 10 microns or less. be. [0010]

[Means to solve the problem]

As monomers that form such fine particles, acrylamide and its derivatives, p-styrenesulfonic acid and its salts, (meth)acrylic acid and their salts, etc. are used alone or in copolymers of these monomers, or in combination with other monomers. It is formed into fine particles as a copolymer of This is a method in which a hydrophilic polymer is formed as fine particles by allowing a polymer to exist and polymerizing the above monomers. [0011] That is, the present invention provides the following (a) which is soluble in these solvents in a water-miscible organic solvent or a mixed solvent of water-miscible organic solvent/water in the presence of a resin soluble in these solvents. ~(c
) Homopolymerization of monomers selected from ) or the following (a) ~
This is a method for producing hydrophilic fine particles characterized by copolymerizing monomers selected from (d). (a) acrylamide and its derivatives, (b) p-styrenesulfonic acid and its salts, (c) (meth)acrylic acid and its salts, (d) copolymerizable with the monomers (a) to (c) above. Vinyl compounds, [0012] Such polymerization methods are dispersion poly
This method is called erization or dispersion polymerization method, and is generally used to polymerize monomers that are soluble in solvents in their monomer state, but become insoluble in solvents by polymerization, using an appropriate polymer dispersant. It is characterized by being carried out in the presence of. In this method, before polymerization starts, the reaction mixture is generally a homogeneous system in which all of the reaction mixture is dissolved in a solvent, and as the polymerization progresses, it becomes a heterogeneous system in which the produced polymer precipitates. At this time, the presence of a polymer that is added in advance to the system as a dispersion stabilizer is extremely important; in the absence of such a polymer, the polymer is usually recovered as a low molecular weight precipitate, resulting in fine particles as referred to in the present invention. Usually it is not possible to obtain. [0013] In the present invention, a hydrophilic monomer is polymerized together with a suitable polymer dispersion stabilizer in a water-miscible organic solvent or in a mixed solvent of this and water, and the resulting polymer exhibits low solubility in these solvents. By taking advantage of this fact, it can be precipitated into fine particles, and by using a non-aqueous solvent, it can be easily copolymerized with other hydrophobic monomers. In addition, during polymerization, for example, by copolymerizing a crosslinkable monomer having two or more polymerizable vinyl groups in the molecule other than the monomers selected from (a) to (d), hydrophilic monomers having a particulate crosslinked structure can be used. This also makes it possible to produce synthetic particles. Examples of crosslinkable monomers having two or more polymerizable vinyl groups in the molecule include methylene bisacrylamide, (meth)acrylic acid vinyl ester, divinylbenzene, ethylene glycol di(meth)acrylate, and the like. [0014] On the other hand, one method for producing a hydrophilic resin in the form of particles is, for example, dispersing or suspending a monomer aqueous solution in an aliphatic hydrocarbon, aromatic hydrocarbon, or halogenated hydrocarbon solvent such as n-hexane. There are reverse-phase suspension polymerization methods that are carried out in a turbid state, but such methods require the removal of organic solvents that are not compatible with water, and in terms of size, for example, 10 μm as referred to in the present invention. It has been difficult to selectively obtain the following fine particles with uniform particle diameters. [0015] Since the present invention uses an organic solvent that is compatible with water, it is possible to use the system in which the generated wood-philic polymer fine particles are dispersed as is, or to separate the fine particles by centrifugation or the like. is also possible. Alternatively, the polymerization solution can be used in a state in which the organic solvent is heated and the fine particles are dissolved or semi-dissolved in water. Depending on the degree of intraparticle crosslinking, it is possible to arbitrarily control the state from a state in which the particles are completely dissolved in water to a state in which the hydrophilic polymer fine particles maintain their shape even in water. [0016] In the present invention, by using a suitable polymer as a dispersion stabilizer, fine particles made of a hydrophilic polymer can be produced stably in a water-miscible organic solvent or a mixed solvent of this and water using a hydrophilic monomer. The solubility of monomers or dispersion stabilizers is poor before the start of force-dried polymerization, which is used to synthesize
If it is difficult to obtain a uniform solution, a necessary amount of other solvent (such as water) may be added to aid dissolution. [0017] The polymer used as the dispersion stabilizer can generally be used as long as it is soluble in the polymerization medium, but it is preferable that the polymer has a certain degree of adsorption ability for the generated hydrophilic polymer fine particles. In this sense, polymers such as polyvinylpyrrolidone, polyvinyl acetate and partially saponified products thereof, polyvinyl alcohol, and polymethacrylic acid are effective, but a wide variety of other polymers can also be used. [0018] As the water-miscible organic solvent, it is particularly preferable to use alcohols such as methanol, ethanol, infropanol, butanol. In addition, various organic solvents such as acetone, ketones such as methyl ethyl ketone, dioxane, methyl ethyl ketone, and tetrahydrofuran can be used. It is possible. The ratio of these water-miscible organic solvents to water is
It is important to set the monomer mixture within a range that dissolves it, and to set the mixing ratio so as to at least partially insolubilize the potash-forming polymer. [0019] It is also possible to copolymerize various monomers for the purpose of modifying the surface or interior of the fine particles obtained by the present invention. For example, hydrophilic fine particles having such functional groups can be easily produced by copolymerizing monomers having acid or basic groups. Also in the copolymerization of hydrophobic monomers,
By using a water-miscible organic solvent, it is often possible to obtain homogeneous resin fine particles with no particularly large difference in composition ratio. [00201 Monomers used in the present invention include acrylamide,
Like sodium p-styrene sulfonate and sodium 2-acrylamido-2-methylpropanesulfonate, they are soluble in water-miscible organic solvents or mixed solvents with water in the monomer state, but when polymerized, Although monomers that are insoluble in the medium are polymerized, various monomers can also be introduced as copolymerization components. [0021] For example, a self-crosslinking monomer such as N-methylolacrylamide, a hydrophobic monomer such as styrene or (meth)acrylic acid ester, or (meth)acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, etc. A basic monomer such as N,N-dimethylaminoethyl (meth)acrylate or a monomer having a reactive group such as chloromethylstyrene can be copolymerized. At this time, if a large amount of a component which excessively increases the solubility of the resulting polymer in alcohol is introduced as a copolymerizable monomer, particle formation may be impaired and it may be difficult to obtain stable and fine particles. In such cases, it is also possible to form fine particles by adding another solvent for the purpose of reducing the solubility of the produced polymer. [0022] Also, by adding other reactive reagents after forming the microparticles,
It is also possible to change the particle composition; for example, acrylamide microparticles can be formed by the method according to the invention and then converted into polyacrylate microparticles by alkaline hydrolysis. [0023] The fine particles formed in the present invention can be stably dispersed by themselves in a water-miscible organic solvent or in a mixed solvent with water, so they can be used as they are, or they can be used after being diluted with water, etc. It is also possible to do so. Alternatively, depending on the application, it can be used in the form of a powder or water dispersion after removing the water-miscible organic solvent. [0024] When a film is formed using only the fine particle dispersion system according to the present invention as a coating material, cracking or curling of the film may occur due to volume shrinkage. A good film can be formed by adding a water-soluble polymer with good properties. [0025]

【Example】

The present invention will be explained in more detail with reference to Examples below. [0026] Example 1 35 g of acrylamide, 2
-acrylamido-2-methylpropanesulfonic acid 15
g, 2 g of styrene and 1 g of N-methylolacrylamide were added, and further 7 g of polyvinylpyrrolidone and 150 g of ethanol were added, followed by heating and stirring at 70°C. Approximately 30
After purging with nitrogen, 5 g of AIBNo was added to start polymerization. The product was a stable white emulsion consisting of 0.2 μm monodisperse microparticles. [0027] Example 2 When 50 ml of a 10% aqueous sodium hydroxide solution was added dropwise to the emulsion obtained in Example 1 at 40°C, generation of ammonia was observed along with neutralization of sulfonic acid groups, indicating that it was due to hydrolysis of the acrylamide component. Generation of sodium acrylate units was confirmed. At this time, no aggregation of particles was observed, and almost no change in particle diameter was observed. [0028] Example 3 Similarly to Example 1, sodium p-styrene sulfonate 6
150 g of ethanol and 70 g of water were added to 0 g of polyvinylpyrrolidone and 6.5 g of polyvinylpyrrolidone, and the mixture was heated and stirred at 75° C. under a nitrogen atmosphere. A stable white emulsion was obtained by adding 7 g of AIB No. and heating and stirring for about 5 hours. The particles were stable particles with a particle size of about 2 to 5 μm. [0029] Example 4 In the same manner as in Example 1, 60 g of acrylamide, 5 g of methacrylic acid, 5 g of chloromethylstyrene, and 6 g of polyvinylpyrrolidone were dissolved in 180 g of isopropanol, and 7 g of
6 g of AIBNo was added and polymerized at 0°C. A stable white emulsion was produced. The particles were stable and had a particle diameter of 1 μm or less. [0030] Example 5 In Example 1, polyvinylpyrrolidone-vinyl acetate copolymer (7
: Polymerization was carried out in exactly the same manner except that the same weight of 3) was used, and a stable fine particle dispersion was similarly obtained. The particle size is 10. It was below um. [0031] Example 6 In Example 1, in the same manner as in Example 6, partially saponified polyvinyl acetate was used instead of polyvinylpyrrolidone to obtain a white emulsion which was polymerized and was stable like the mold. The particles were stable and had a particle size of 5 μm or less. [0032] Example 7 In the same manner as in Example 1, 60 g of sodium p-styrene sulfonate, 6 g of vinyl methacrylate, and 7 g of polyvinylpyrrolidone were mixed with 170 g of ethanol and 80 g of water.
6 g of AIBNo was added thereto at 75° C. under a nitrogen atmosphere and polymerized. The product was stable fine particles with an average particle size of 0.2 μm. [0033] Example 8 In the same manner as in Example 1, 50 g of methacrylic acid, 0.5 g of divinylbenzene and 7 g of polyvinylpyrrolidone were dissolved in 200 g of isopropanol, and neutralized with a 10% aqueous sodium hydroxide solution while cooling. . 5 g of AIBNo was added at 75° C. under a nitrogen atmosphere to initiate polymerization to obtain a white emulsion. The particles were stable and had a particle size of 5 μm or less. [0034] Example 9 Acrylamide (AM
) 50g, polyvinylpyrrolidone PVP (molecular weight approx. 9
5 g), 150 g of ethanol, and 50 g of distilled water were added and dissolved at 0° C. under a nitrogen stream. The solution temperature was increased to 65° C. and azobisisobutyronitrile (AIBM) 0.
Polymerization was started by adding 5 g, and heating and stirring were continued for about 1 hour. When the particle size of the product was measured in ethanol using Coulter N4 (manufactured by Coulter Electronics), it was found to be monodisperse polyacrylamide particles with a particle size of 1.18 μm. This product immediately dissolved in water, and as a result of molecular weight measurement by GPC, the weight average molecular weight was 150,000. [0035] Example 10 Polymerization was carried out in the same manner as in Example 1 using the composition shown in Clothing 1 below, and stable polyacrylamide fine particles could be obtained in each case. [0036]

[Table 1] No, IAMI PVP 1EtOHIWater
1 particle diameter (g) l (g) l (g
) l (g) l (μm)1 5
0 1.25 1502 50 2.50
150 3 50 5.00 1504 50 1
0.00 150 5 10 5.00 125 6 25 5.00 1257 50
5.00 1258 75 5.00
125 9 25 5.00 200 10 25 5.00 17550 1.
31 50 1.20 50 1.18 50 1.03 75 0.88 75 1.06 75 1.22 75 2.40 0 0.34 25 0.55 [0037] Example 11 Same as Example 1, 20 g of acrylamide, 5.0 g of N,N-methylenebisacrylamide (MBAM) and 5.0 g of polyvinylpyrrolidone were dissolved in 125 g of ethanol and 75 g of distilled water, and 2 g of AIBNo.
Polymerization was started by adding , and heating and stirring was continued at 70° C. for 1 hour. The product was almost monodisperse fine particles with a particle size of 1.10 μm, and did not swell even in water. [0038] Example 12 In the same manner as in Example 1, 24 g of acrylamide, MBA
Polymerization was started by dissolving 50 g of Mlg and PVP in 125 g of ethanol and 75 g of distilled water, and adding 02 g of AIBN at 65°C, followed by heating and stirring at 70°C for 1 hour. The particle size in ethanol was 1.03 μm, but in water the particle size doubled to about 2.1 μm, indicating that the particles absorbed water and swelled. [0039] Example 13 In the same manner as in Example 1, 50 g of acrylic acid was dissolved in 150 g of ethanol and 50 g of distilled water, and 25% ammonium water was added dropwise to the solution while cooling at room temperature for neutralization. Thereafter, 5 g of PVPl was added and dissolved at 40°C, and then 5 g of AIBNO was added and polymerization was carried out at 70°C for 1.5 hours. The product has a particle size of 1.
The particles were stable fine particles with a diameter of 0 μm, and by diluting them in water, an aqueous ammonium polyacrylate solution with a molecular weight of 100,000 was obtained. [0040] Example 14 In the same manner as in Example 1, a mixed solvent of 150 g of ethanol and 50 g of distilled water containing 48 g of acrylic acid was neutralized with ammonium water, and then 2 g of divinylbenzene and 2.
5 g was added and uniformly dissolved at 40°C. AIB at 65℃
5 g of No. No. was added, and the mixture was heated and stirred at this temperature for about 2 hours to obtain crosslinked polyacrylic acid fine particles. [0041] Example 15 In the same manner as in Example 1, polyvinylpyrrolidone (K-9
0) 5 g and 49 g of acrylamide 1 g of methylene bisacrylamide were dissolved in 75 g of methyl ethyl ketone, 50 g of ethanol, and 75 g of distilled water, and AIB was prepared at 70°C.
Polymerization was started by adding No. 5. After about 1 hour, the mixture was cooled to room temperature, and the particles were separated by centrifugal sedimentation and dried. A powder having a particle size of about 1 μm was obtained. [0042]

【Effect of the invention】

The fine particles obtained in the present invention are polymer electrolytes with a crosslinked structure, and have water absorption properties during drying or after film formation.
Antistatic properties etc. can be obtained.

Claims (5)

[Claims] Claim 1: In a water-miscible organic solvent or a water-miscible organic solvent/water mixture, in the presence of a resin soluble in these solvents, the following (a) to ( A method for producing hydrophilic fine particles, characterized by carrying out homopolymerization of a monomer selected from c) or copolymerization of a monomer selected from the following (a) to (d). (a) acrylamide and its derivatives, (b) p-styrenesulfonic acid and its salts, (c) (meth)acrylic acid and its salts, (d) copolymerizable with the monomers (a) to (c) above. vinyl compound, 2. A claim in which the resin soluble in a water-miscible organic solvent or a water-miscible organic solvent/water mixture is polyvinylpyrrolidone, polyvinyl acetate, partially saponified polyvinyl acetate, polyvinyl alcohol, or polymethacrylic acid. 1. The method for producing hydrophilic fine particles according to 1. 3. The method for producing hydrophilic fine particles according to claim 1, wherein a crosslinking monomer having at least two or more polymerizable double bonds in the molecule is contained together with the monomer selected from (a) to (d). 4. The method for producing hydrophilic fine particles according to claim 1, wherein the monomer (d) is selected from styrene and its derivatives, (meth)acrylate (meth)acrylonitrile, maleic acid and its derivatives. 5. The method for producing hydrophilic fine particles according to claim 1, wherein the water-miscible organic solvent is selected from alcohol, ketone, dioxane, and tetrahydrofuran.