JP2008138106A - Method for producing hydrophilic polymer suspension - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a hydrophilic polymer suspension being free from agglomeration among polymer particles and giving a polymer product of a reduced content of a residual solvent. <P>SOLUTION: The method for producing a hydrophilic polymer suspension comprises adding a displacement solvent to a suspension containing water-containing hydrophilic polymer particles having a water content of 1.5-10.0 wt.% based on the polymer weight (the weight of the polymer left after the solvent and the water are removed from the polymer particles) and a hydrophobic solvent and distilling off the hydrophobic solvent from the mixture. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a useful process for producing hydrophilic polymer suspensions.

  Currently, various hydrophilic polymers are produced in various industrial fields. Among them, production methods such as reverse phase suspension polymerization and dispersion polymerization are used. In the reverse phase suspension polymerization method and the dispersion polymerization method, the monomer component, the crosslinking agent, and the polymerization initiator are uniformly dissolved, and water or the like is added as necessary, in a hydrophobic solvent in which the dispersant is uniformly dissolved or dispersed. Mix and perform the polymerization reaction.

The reaction product obtained by the reverse phase suspension polymerization method or the dispersion polymerization method is in the form of a suspension (slurry) containing the hydrophobic solvent used in the reaction, and is replaced with a solvent other than the polymerization solvent as necessary. For example, in Patent Document 1, in a reverse-phase polymerization reaction using a hydrophobic solvent, after the polymerization reaction, the hydrophobic solvent is distilled off, and after adding the hydrophilic solvent, the hydrophobic solvent is distilled again. A method for producing hydrophilic polymer particles is disclosed. However, in the solvent replacement operation, there is a problem that the polymers are aggregated or the hydrophobic solvent remains in the polymer product after the replacement.
JP 2002-201211 A

  An object of the present invention is to provide a method for producing a hydrophilic polymer suspension that prevents aggregation of polymers and reduces the amount of remaining hydrophobic solvent in the polymer suspension product.

  In the present invention, a substitution solvent is added to a suspension of hydrous hydrophilic polymer particles having a water content of 1.5 to 10.0% by weight relative to the polymer weight (the polymer weight obtained by removing the solvent and water from the polymer particles) and the hydrophobic solvent. Provided is a method for producing a hydrophilic polymer suspension in which a hydrophobic solvent is distilled off after the addition.

  According to the method of the present invention, aggregation of polymers can be prevented and the residual amount of hydrophobic solvent in the polymer suspension product can be reduced.

[Hydrophilic polymer]
As the hydrophilic polymer of the present invention, (i) a cationic group-containing vinyl monomer such as an amino group, an ammonium group, a pyridyl group, an imino group, or a betaine structure and / or a salt thereof (hereinafter referred to as a cationic monomer), (b) ) Hydrophilic nonionic group-containing vinyl monomers (hereinafter referred to as nonionic monomers) such as hydroxy groups, amide groups, ester groups, ether groups, (c) Anions such as carboxy groups, sulfonic acid groups, and phosphoric acid groups Examples thereof include polymers obtained from one or more monomers selected from functional group-containing vinyl monomers and / or salts thereof (hereinafter referred to as anionic monomers), preferably one or more cationic monomers and one or more nonionics. It is a polymer obtained from a functional monomer.

  The hydrophilic polymer of the present invention preferably has a cross-linked structure with a cross-linkable vinyl monomer having at least two reactive unsaturated groups in the molecule (hereinafter referred to as cross-linkable monomer). In addition, other vinyl monomers that can be copolymerized with the monomers (a) to (c) can also be copolymerized.

<(I) Cationic monomer>
(A) As the cationic monomer, (meth) acrylic acid ester or (meth) acrylamide having a dialkylamino group having 2 to 44 carbon atoms, styrene having a dialkylamino group having 2 to 44 carbon atoms, vinylpyridine, Acid neutralized products of monomers having amino groups such as N-vinyl heterocyclic compounds, vinyl ethers or the like, and these monomers are alkyl halides (1 to 22 carbon atoms), benzyl halides, alkyls (1 to 18 carbon atoms). Or examples include monomers such as those quaternized with aryl (6 to 24 carbon atoms) sulfonic acid or dialkyl sulfate (2 to 8 total carbon atoms), diallyl-type quaternary ammonium salts, vinyl monomers having a betaine structure, and the like. . Among these cationic monomers, amino group and ammonium group-containing monomers are preferable, and quaternary ammonium salt monomers are more preferable.

<(B) Nonionic monomer>
As the nonionic monomer (b), vinyl alcohol, (meth) acrylic acid ester or (meth) acrylamide having a hydroxyalkyl group (1 to 8 carbon atoms), (meth) acrylic acid ester of polyhydric alcohol, (meta ) Acrylamide, alkyl (1-8 carbon atoms) (meth) acrylamide, dialkyl (2-8 total carbon atoms) (meth) acrylamide, diacetone (meth) acrylamide, N-vinyl cyclic amide, alkyl (1-8 carbon atoms) Examples thereof include (meth) acrylic acid ester having a group and (meth) acrylamide having a cyclic amide group. Preferred examples include (meth) acrylamide monomers, (meth) acrylic acid esters having the above hydroxyalkyl (C 1-8) groups, and (meth) acrylic acid esters of the above polyhydric alcohols.

<(C) Anionic monomer>
(C) as an anionic monomer, a carboxylic acid monomer having a polymerizable unsaturated group and / or an acid anhydride thereof (when one monomer has two or more carboxyl groups); a polymerizable unsaturated group And sulfonic acid monomers having a polymerizable unsaturated group. The anionic group may be neutralized to an arbitrary degree of neutralization with a basic substance. In this case, all anionic groups in the polymer or some anionic groups thereof form a salt.

  Here, as a cation in the salt, an ammonium ion, a trialkylammonium ion having 3 to 54 carbon atoms (for example, trimethylammonium ion or triethylammonium ion), a hydroxyalkylammonium ion having 2 to 4 carbon atoms, and a total carbon number of 4 to 4 8 dihydroxyalkylammonium ions, trihydroxyalkylammonium ions having 6 to 12 carbon atoms in total, alkali metal ions, alkaline earth metal ions, and the like. Neutralization may be performed by neutralizing the monomer or neutralizing the polymer.

  Among these, preferably, the above-mentioned polymerizable unsaturated group-containing carboxylic acid monomer and / or acid anhydride thereof (provided that one monomer has two or more carboxyl groups), the above-mentioned polymerizable monomers. Examples thereof include sulfonic acid monomers having an unsaturated group.

<Crosslinkable monomer>
As the crosslinkable monomer, (meth) acrylic acid esters of polyhydric alcohols, acrylamides, divinyl compounds, polyallyl compounds, (meth) acrylic acid esters of unsaturated alcohols, and the like are used.

  Among these crosslinkable monomers, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, divinylbenzene, pentaerythritol triallyl ether, and pentaerythritol tetraallyl ether are preferable.

<Other monomers>
Examples of other vinyl monomers that can be copolymerized with the monomers (a) to (c) constituting the hydrophilic polymer of the present invention include (meth) acrylic acid derivatives.

<Hydrophilic polymer>
The hydrophilic polymer used in the present invention preferably comprises one or more monomers selected from the above (a) to (c) as essential constituent monomers, but other monomers copolymerizable with these monomers. Can also be copolymerized. In all monomers, the total amount of monomers (A) to (C) is preferably 70 to 100% by weight, more preferably 85 to 100% by weight.

  The hydrophilic polymer of the present invention preferably contains a crosslinkable monomer as a constituent monomer, and the amount of the crosslinkable monomer is preferably 0.005 to 5% by weight based on the total monomers, and 0.01 to 1. More preferred is 0% by weight.

  A particularly preferred hydrophilic polymer is obtained by radical polymerization using at least one cationic monomer of (a), at least one nonionic monomer of (b) and a crosslinkable monomer as essential constituent monomers. It is what

[Hydrophilic hydrophilic polymer particles]
The method for producing water-containing hydrophilic polymer particles having a water content of 1.5 to 10.0% by weight with respect to the polymer weight in the present invention is not particularly limited, but the polymer particles are suspended from the viewpoint of improving productivity and handling properties. A production method obtained in the form of a liquid such as a liquid (slurry) or in the form of a paste is preferred, and in particular, using the above monomers (a) to (c) and optionally a crosslinkable monomer, preferably a radical polymerization initiator (for example In the presence of a peroxide or an azobis compound such as 2,2-azobisisobutyronitrile), a reverse phase polymerization method using a hydrophobic solvent (for example, suspension polymerization method, dispersion polymerization method, emulsion weight) A method is preferred in which the polymerization is carried out by a combination method, etc., and the water content is adjusted to the above range by further dehydration.

  Specifically, a monomer and an initiator are uniformly mixed in an aqueous solution, and then mixed with a hydrophobic solvent. If necessary, a dispersant is used. Next, this mixture is preliminarily dispersed or pre-emulsified with a high-pressure homogenizer or a line mixer, and then polymerized by raising the temperature under an inert gas such as nitrogen. The polymerization initiation temperature varies depending on the monomer, but is usually about 40 to 90 ° C., and the reaction time is about 1 to 24 hours.

  The hydrophobic solvent used in the production of hydrous hydrophilic polymer particles is a solvent having a solubility at 25 ° C. of 1% by weight or less in 100 g of water. Specific examples of these hydrophobic solvents include hydrocarbon solvents such as hexane, cyclohexane, heptane, octane, benzene, toluene, xylene, and ethylbenzene, halogenated hydrocarbon solvents such as carbon tetrachloride and dichloroethane, and isobar. Mineral oil or the like is used. Of these, hydrocarbon solvents are preferably used as the hydrophobic solvent, and hexane and cyclohexane are more preferable. The solvent amount is preferably 1 to 20 times by weight, more preferably 1 to 10 times by weight based on the total amount of monomers.

  Dispersants used in the production of hydrous hydrophilic polymer particles include sorbitan monostearate, sorbitan monopalmitate, polyvinyl alcohol, methylcellulose, ethylcellulose, hydroxycellulose, carboxymethylcellulose, carboxyethylcellulose, sugar ester (Mitsubishi Chemical Foods Co., Ltd.) Product name), polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, alkyl trimethyl ammonium chloride, dialkyl dimethyl ammonium chloride, alkyl sulfate, polyoxyethylene alkyl ether sulfate, etc. These dispersants may be used alone or in combination. Among these, sorbitan monostearate and sugar ester are preferable from the viewpoint of dispersion stability. The amount of these dispersants used is preferably 0.3 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the total monomers.

  As the polymerization initiator used for the production of the hydrous hydrophilic polymer particles, a radical polymerization initiator is preferably used. For example, a peroxide, an organic or inorganic peracid or a salt thereof, or an azobis compound that is uniformly dissolved in the monomer component. The redox type | system | group by a single or combination with a reducing agent is mentioned. Typical examples thereof include t-butyl peroxide, t-amyl peroxide, cumyl peroxide, acetyl peroxide, propionyl peroxide, benzoyl peroxide, benzoylisobutyryl peroxide, laurylyl peroxide, t-butyl hydroperoxide, cyclohexyl hydroperoxide, tetralin hydroperoxide, t-butyl peracetate, t-butyl perbenzoate, bis (2-ethylhexyl peroxydicarbonate), 2,2′-azobisiso Butyronitrile, phenylazotriphenylmethane, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (2- (5-methyl-2-imidazolin-2-yl) dihydrochloride Salt, sodium persulfate , Potassium persulfate, ammonium persulfate, hydrogen peroxide, persulfates and tertiary amines such as triethylamine, triethanolamine, diethylaniline, etc. Among these, t-butyl peroxide, Benzoyl peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (2- (5-methyl-2-imidazoline- 2-yl) dihydrochloride, sodium persulfate, potassium persulfate or ammonium persulfate alone or combinations of these persulfates with tertiary amines such as triethylamine, triethanolamine or dimethylaniline are preferred. The amount of initiator used is high enough to increase the degree of polymerization of the main polymer chain and not crosslink. From the viewpoint of reducing the chain ratio to make it difficult to dissolve in water or a hydrophobic solvent, increasing the reaction rate of the polymerization reaction, and reducing the amount of residual monomers, preferably 0.01 parts per 100 parts by weight of the total monomers. -5 parts by weight, more preferably 0.5-3 parts by weight, particularly preferably 0.1-1 part by weight.

  After completion of the reaction, the temperature in the tank is raised and dehydration is performed. In the dehydration operation, moderate water is left in the polymer particles so that the remaining water content in the polymer particles falls within the above range. If the amount of residual water in the polymer particles is large, polymer particle aggregates in the product paste after the hydrophobic solvent is distilled off increase. On the other hand, if the amount of water remaining in the polymer particles is small, the amount of the hydrophobic solvent remaining in the polymer particles increases after the hydrophobic solvent is removed again, causing a hydrophobic solvent odor to remain in the product.

  From these viewpoints, the residual water content in the polymer with respect to the polymer weight after completion of the dehydration operation (the weight excluding the solvent and water in the polymer from the polymer particles) is 10.0% by weight or less, and 8.0% by weight or less. preferable. Moreover, it is 1.5 weight% or more, and 2.0 weight% or more is preferable.

  The temperature in the tank in the dehydration operation is about 60 to 100 ° C., and may be performed under a reduced pressure of about 10 to 100 kPa as necessary. The time for the dehydration operation is about 0.5 to 20 hours. When the hydrophobic solvent is also distilled from the reaction tank in the dehydration operation, water and the hydrophobic solvent are separated by stationary separation etc. outside the reaction tank, and the separated hydrophobic solvent is continuously added to the tank during the dehydration operation. Is preferable from the viewpoint of preventing aggregation of polymer particles.

  The volume average particle size of the hydrophilic polymer in the hydrophobic solvent after dehydration is preferably 50 μm or less, and more preferably 1 to 30 μm.

[Method for producing hydrophilic polymer suspension]
In the method for producing a hydrophilic polymer suspension of the present invention, a substitution solvent is added to a suspension of water-containing hydrophilic polymer particles and a hydrophobic solvent in which the water content with respect to the polymer weight is adjusted to 1.5 to 10.0% by weight. Then, the hydrophobic solvent is distilled off. Here, the substitution solvent refers to a solvent other than water and a hydrophobic solvent used for polymerization.

  Examples of the hydrophobic solvent used here include those having a solubility at 25 ° C. of 1% by weight or less in 100 g of water described in the above-mentioned “Hydrophilic hydrophilic polymer particles” column. In addition, the suspension of the hydrous hydrophilic polymer particles and the hydrophobic solvent is a dehydration obtained by continuously refluxing the hydrophobic solvent to the tank during the dehydration operation according to the method for producing the hydrous hydrophilic polymer particles. Polymer suspensions that have been terminated are preferred.

  The ratio of the water-containing hydrophilic polymer particles and the hydrophobic solvent in the suspension is not particularly limited as long as the water-containing hydrophilic polymer particles are suspended in the hydrophobic solvent, but is 10 to 70% by weight (weight of the water-containing hydrophilic polymer particles). / (Hydrophilic hydrophilic polymer particle weight + hydrophobic solvent weight) × 100) is preferable, and 15 to 50% by weight is more preferable.

  The substitution solvent added to the suspension of the hydrous hydrophilic polymer particles and the hydrophobic solvent is preferably at least one selected from polyhydric alcohols, surfactants and fats and oils.

  Polyhydric alcohols include dihydric alcohols such as tetraethylene glycol, polyethylene glycol, and propylene glycol, trihydric alcohols such as trimethylolpropane, and tetrahydric or higher alcohols such as diglycerin, triglycerin, polyglycerin, pentaerythritol, and sorbitol. Is mentioned. Examples of the surfactant include anionic surfactants such as polyoxyethylene alkyl ether sulfate, and nonionic surfactants such as polyoxyethylene alkyl ether and glycerin fatty acid ester. Examples of the fats and oils include fatty oils or fats typified by fatty acid glycerin esters, and waxes. These may be used alone or in combination. Of these substitution solvents, polyhydric alcohols, particularly polyethylene glycol are preferred.

  The property of the substitution solvent is preferably 30 ° C. or more, more preferably 50 ° C. or more, from the viewpoint of combining the three components of polymer particles / hydrophobic solvent / substitution solvent with good removal of the hydrophobic solvent from the polymer particles. preferable. In addition, the boiling point of the substitution solvent is preferably such that the boiling point difference from the hydrophobic solvent is larger because the hydrophobic solvent can be easily distilled off. Accordingly, the boiling point at normal pressure of the substitution solvent is preferably 101 ° C. or higher, more preferably 110 ° C. or higher.

  The addition amount of the substitution solvent is 10 to 70% by weight (hydrophilic polymer particle weight / (hydrophilic polymer particle weight + substitution solvent weight) × 100) from the viewpoint of improving the fluidity of the polymer suspension after solvent substitution. Is preferable, and 20 to 50 weight% is more preferable.

  After the substitution solvent is added, the temperature in the tank is raised and the hydrophobic solvent is distilled off. The temperature in the tank is preferably about 60 to 100 ° C., and if necessary, it may be distilled off under reduced pressure of about 10 to 100 kPa. The distillation time is about 0.5 to 20 hours. When the hydrophobic solvent is distilled off, a suspended hydrophilic polymer is obtained.

  The amount of the hydrophobic solvent in the hydrophilic polymer suspension produced by the production method of the present invention is preferably less than 2000 ppm, and more preferably 0 to 1000 ppm.

<Production Example 1 of Hydrous Polymer Particles>
In a 300 LSUS reaction vessel, 18.3 kg of dimethylaminoethyl methacrylate diethylsulfate quaternized product (effective content 90%), N, N-dimethylacrylamide 15.8 kg, polyethylene glycol dimethacrylate (EO 14 mol adduct) 0 .006 kg, 0.12 kg 2,2-azobis (2-amidinopropane) dihydrochloride as initiator, 45.2 kg water, 133 kg cyclohexane as hydrophobic solvent, 0.3 kg sugar ester as dispersant, homomixer After being emulsified and dispersed with the like, the temperature in the reaction vessel was raised to 57 ° C. under an inert gas such as nitrogen, and a polymerization reaction was performed for 3 hours.

  After completion of the reaction, the temperature in the tank was set to 85 ° C., and cyclohexane and water were distilled from the reaction tank to perform a dehydration operation. The fraction was condensed in a condenser and then allowed to stand and separate into water and cyclohexane. The separated cyclohexane was continuously refluxed to the tank during the dehydration operation, and only the aqueous layer was distilled off from the tank. The total distilled water was 45.0 kg. After the dehydration operation, the residual water content in the polymer with respect to the polymer weight in the reaction vessel was 6.2% by weight. Here, the polymer weight is a weight obtained by removing the solvent and water from the reaction product. The volume average particle diameter of the polymer particles was 3.9 μm. The volume average particle diameter was measured with LS-230 (Laser diffraction scattering particle size distribution analyzer: manufactured by Coulter).

<Production Example 2 of Hydrous Polymer Particles>
Polymerization and dehydration were carried out in the same manner as in Production Example 1 except that the amount of water distilled off by dehydration was changed to 46.1 kg. After the dehydration operation, the residual water content in the polymer with respect to the polymer weight in the reaction vessel was 2.9% by weight. The volume average particle diameter of the polymer particles was 3.8 μm.

<Production Example 3 of Hydrous Polymer Particles>
Polymerization and dehydration were carried out in the same manner as in Production Example 1 except that the amount of water distilled off by dehydration was changed to 43.7 kg. After the dehydration operation, the residual water content in the polymer with respect to the polymer weight in the reaction vessel was 10.2% by weight. The volume average particle diameter of the polymer particles was 3.5 μm.

<Production Example 4 of Hydrous Polymer Particles>
Polymerization and dehydration were carried out in the same manner as in Production Example 1 except that the amount of water distilled off by dehydration was changed to 46.6 kg. After the dehydration operation, the residual water content in the polymer with respect to the polymer weight in the reaction vessel was 1.3% by weight. The volume average particle diameter of the polymer particles was 3.6 μm.

Example 1
To the cyclohexane suspension of the water-containing polymer obtained in Production Example 1, 50 kg of polyethylene glycol (PEG 1540: manufactured by Sanyo Chemical Industries, Ltd.) is added, the temperature in the tank is set to 80 ° C., and under reduced pressure (40 kPa) Cyclohexane was distilled off. When the distillation of cyclohexane could not be visually confirmed (the amount of residual cyclohexane was about 1.6% by weight), the degree of vacuum was changed to 26.7 kPa, and the cyclohexane was further distilled off for 10 hours. The amount of residual cyclohexane in the obtained suspension composition was 420 mg / kg (ppm). The residual cyclohexane amount was extracted with methyl acetate and measured by gas chromatography (internal standard method). Further, the amount of aggregates in the obtained suspension composition was measured and found to be 1.8% by weight. The amount of agglomerates was calculated from the amount of polymer remaining on the wire mesh and the weight of the polymer excluding the solvent and water before passing through the wire mesh through a wire mesh having an opening of 2 mm.

Example 2
The same operation as in Example 1 was performed except that the cyclohexane suspension of the water-containing polymer obtained in Production Example 1 was changed to the cyclohexane suspension of the water-containing polymer obtained in Production Example 2. The amount of residual cyclohexane in the obtained suspension composition was 590 mg / kg. It was 0.3 weight% when the amount of aggregates in the obtained suspension-like composition was measured.

Comparative Example 1
The same operation as in Example 1 was performed, except that the cyclohexane suspension of the water-containing polymer obtained in Production Example 1 was changed to the cyclohexane suspension of the water-containing polymer obtained in Production Example 3. The amount of residual cyclohexane in the obtained suspension composition was 240 mg / kg. When the amount of aggregates in the obtained suspension composition was measured, it was 19%, and a large amount of aggregates were produced.

Comparative Example 2
The same operation as in Example 1 was performed, except that the cyclohexane suspension of the water-containing polymer obtained in Production Example 1 was changed to the cyclohexane suspension of the water-containing polymer obtained in Production Example 4. The amount of residual cyclohexane in the obtained suspension composition was 2900 mg / kg, and the amount of residual cyclohexane was large. When the amount of aggregates in the obtained suspension composition was measured, it was 0.1%.

  The results of Examples 1 and 2 and Comparative Examples 1 and 2 are summarized in Table 1.

Claims (6)

  After adding a substitution solvent to a suspension of hydrous hydrophilic polymer particles having a water content of 1.5 to 10.0% by weight with respect to the polymer weight (the polymer weight obtained by removing the solvent and water from the polymer particles) and the hydrophobic solvent, A method for producing a hydrophilic polymer suspension in which a hydrophobic solvent is distilled off.   The process according to claim 1, wherein the hydrous hydrophilic polymer particles are obtained by reverse phase suspension polymerization.   The process according to claim 1 or 2, wherein the water-containing hydrophilic polymer particles are obtained by dehydration after polymerization.   The production method according to claim 1, wherein the hydrophobic solvent is a hydrocarbon solvent.   The production method according to claim 1, wherein the substitution solvent is at least one selected from polyhydric alcohols, surfactants and fats and oils.   The hydrophilic polymer has at least one of a cationic group-containing vinyl monomer and / or a salt thereof, at least one of a hydrophilic nonionic group-containing vinyl monomer, and at least two reactive unsaturated groups in the molecule. The method according to any one of claims 1 to 5, which is obtained by radical polymerization using a crosslinkable vinyl monomer as an essential constituent monomer.