JP4248088B2 - Method for producing granular vinyl polymer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a granular vinyl polymer having a very low content of residual monomers and impurities.
[0002]
[Prior art]
In recent years, there has been an increasing demand for special paints that use an organic solvent having a low boiling point, such as acetone and ethyl acetate, and have an acid group-containing vinyl polymer as a main film-forming component. Since acetone, ethyl acetate, and the like have low boiling points, it is difficult to produce an acid group-containing vinyl polymer in ordinary solution polymerization using these as solvents. Accordingly, the present situation is that a solid acid group-containing vinyl polymer is usually produced by some method and dissolved in a solvent such as acetone or ethyl acetate. As a solid acid group-containing vinyl polymer, a polymer produced by removing a solvent after solution polymerization has been generally used until now. However, the production cost and removal required for processes such as solvent removal and pulverization are common. In recent years, a method for directly producing a granular acid group-containing vinyl polymer by suspension polymerization has begun to be adopted due to the raw material cost of the solvent to be used or environmental problems.
[0003]
[Problems to be solved by the invention]
However, when a granular acid group-containing granular vinyl polymer is produced by suspension polymerization, an unreacted monomer may remain, and its odor may be a problem. Further, when an acid group-containing vinyl polymer is produced by suspension polymerization, a slight amount of emulsion polymerization occurs in parallel in water, and high acid value and / or high molecular weight emulsified fine particles are easily produced as by-products as impurities. Have Since it is difficult to completely wash and remove such emulsified fine particles, when an acid group-containing granular vinyl polymer produced by suspension polymerization is dissolved in an organic solvent, an insoluble matter is generated, which is colorless and transparent. In some cases, a solution could not be obtained.
[0004]
An object of the present invention is to provide a method for producing a granular vinyl polymer having a very small content of residual monomers and impurities.
[0005]
[Means for Solving the Problems]
Therefore, as a result of intensive studies to solve the above problems, the present inventors have found a method for producing an acid group-containing granular vinyl polymer that solves the above problems, thereby completing the present invention. That is, the method for producing an acid group-containing granular vinyl polymer of the present invention is characterized in that a surfactant is added together with a water-soluble polymerization initiator after the polymerization exotherm during suspension polymerization reaches a maximum value. Is.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the constituent component of the granular vinyl polymer obtained in the present invention include (meth) acrylic acid, 2- (meth) acryloxyethyl hexahydrophthalic acid, 2- (meth) acryloxypropyl hexahydrophthalic acid, 2- (meth) acryloxyethyltetrahydrophthalic acid, 2- (meth) acryloxypropyltetrahydrophthalic acid, 5-methyl-2- (meth) acryloxyethylhexahydrophthalic acid, 2- (meth) acryloxyethylphthalate Acid, 2- (meth) acryloxypropylphthalic acid, 2- (meth) acryloxyethyl oxalic acid, 2- (meth) acryloxypropyl oxalic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, sorbic acid, etc. And acid group-containing monomers such as carboxyl group-containing vinyl monomers. These may be used singly or in combination of two or more, but methacrylic acid is particularly preferable.
[0007]
In addition to the above acid group-containing monomers, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, (meth) acrylic (Meth) acrylic acid alkyl esters such as t-butyl acid, 2-ethylhexyl (meth) acrylate, n-lauryl (meth) acrylate, n-stearyl (meth) acrylate, cyclohexyl (meth) acrylate, N- Maleimide derivatives such as phenylmaleimide, N-cyclohexylmaleimide, N-butylmaleimide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (meth) 4-hydroxybutyl acrylate, 6-hydroxyhexyl (meth) acrylate, etc. Vinyl polymerizable monomer having a hydroxyalkyl group, acrolein, diacetone acrylamide, formyl styrene, vinyl alkyl ketone, (meth) acrylamide pivalin aldehyde, diacetone (meth) acrylate, acetonyl acrylate, 2-hydroxypropyl acrylate Toacetyl acetate, acetoacetoxyethyl (meth) acrylate, butanediol-1,4-acrylate-acetyl acetate, vinyl monomer having aldehyde group or carbonyl group of acrylamide methyl anisaldehyde, (meth) acrylamide, crotonamide, N- Amide group-containing vinyl monomers such as methylolacrylamide, epoxy group-containing vinyl monomers such as allyl glycidyl ether and glycidyl (meth) acrylate Chromatography, styrene, can be mentioned α- aromatic vinyl monomers methyl styrene, a nitrile group-containing vinyl monomers such as acrylonitrile, olefinic monomers such as butadiene. These can be appropriately selected and used as necessary.
[0008]
In the vinyl-type polymer of this invention, it is preferable to contain the unit which consists of the above-mentioned acid group containing monomer in 1-50 mass%. This tends to make it difficult for emulsion impurities to be generated during suspension polymerization by setting the unit consisting of the acid group-containing monomer to 1% by mass or more. This is because it tends to proceed stably. More preferably, it is the range of 5-35 mass%.
[0009]
Moreover, it is preferable that the acid value of the vinyl polymer of this invention is the range of 5-350 mgKOH / g. This is because when the acid value is 5 mgKOH / g or more, emulsion impurities tend not to be generated during suspension polymerization, and when the acid value is 350 mgKOH / g or less, suspension polymerization proceeds stably. It is because it is in a tendency. Preferably, it is the range of 30-250 mgKOH / g.
[0010]
The dispersant used in the suspension polymerization in the present invention can be appropriately selected and used as necessary. For example, poly (meth) acrylic acid alkali metal salt or (meth) acrylic acid and (meth) Examples include an alkali metal salt of a copolymer of methyl acrylate, polyvinyl alcohol having a saponification degree of 70 to 100%, methyl cellulose, and the like. These can be used alone or in combination of two or more.
[0011]
In the suspension polymerization in the present invention, the amount of the dispersant used is preferably in the range of 0.001 to 10% by mass in the aqueous suspension. This is because when the amount of the dispersant is 0.001% by mass or more, the dispersibility at the time of polymerization tends to be good, and when it is 10% by mass or less, the dehydrated granular vinyl polymer is obtained. This is because the property and the drying property tend to be good. More preferably, it is the range of 0.01-1 mass%.
[0012]
As a method for suspension polymerization in the present invention, the above-mentioned dispersant is dissolved alone or in combination of two or more in water, a monomer, an oil-soluble polymerization initiator, and a chain transfer agent as necessary are added, and the monomer is stirred while stirring. -Is preferably dispersed in droplets of about 0.05 to 1 mm and polymerization is carried out under heating.
[0013]
Examples of the oil-soluble polymerization initiator used during suspension polymerization include azo initiators such as azobisisobutyronitrile and organic peroxide initiators such as benzoyl peroxide. Examples of the chain transfer agent include mercaptans such as n-dodecyl mercaptan, α-methylstyrene dimer, and the like.
[0014]
The polymerization temperature is not particularly limited, but is preferably in the range of 50 to 100 ° C. from the viewpoint of dispersion stability and reaction time during suspension polymerization.
[0015]
In the present invention, it is further necessary to add a water-soluble polymerization initiator after the polymerization exotherm during suspension polymerization reaches the maximum value. As a result, a granular vinyl polymer having a very small content of residual monomer and impurities can be produced.
[0016]
The reason for this is not clear, but by adding a water-soluble polymerization initiator, the residual monomer is reduced and the dispersion stability of the emulsified fine particles produced as a by-product is improved, which is added to the granular vinyl polymer. This is considered to be difficult to be taken in as an impurity.
[0017]
However, if a water-soluble polymerization initiator is added before the polymerization exotherm of suspension polymerization reaches its maximum value, an extremely large amount of emulsion is generated during suspension polymerization. This is not preferable because the solvent solubility tends to decrease.
[0018]
The addition timing of the water-soluble polymerization initiator is suspension polymerization because it is necessary to stabilize the dispersion after the granular vinyl polymer is formed and before the by-produced emulsified fine particles are incorporated into the granular vinyl polymer. It is preferable that the polymerization exotherm is within 1 hour from the time when the polymerization exotherm shows the maximum value, and the polymerization temperature is preferably added in the temperature range of 50 to 100 ° C. from the viewpoint of stabilizing the dispersion of the emulsified fine particles.
[0019]
Examples of the water-soluble polymerization initiator used in the present invention include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2 '-Azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, etc. An azo-type initiator etc. can be mentioned. These can be used alone or in combination of two or more. Among them, persulfate, particularly sodium persulfate is preferable.
[0020]
The addition amount of the water-soluble polymerization initiator is preferably in the range of 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the granular vinyl polymer. This is because when the addition amount of the water-soluble polymerization initiator is 0.01 parts by mass or more, the residual monomer tends to be efficiently reduced. This is because the dispersion stability of the coalesce tends not to be impaired. More preferably, it is the range of 0.02-0.2 mass part.
[0021]
In order to further reduce the influence of mixing of emulsified fine particles by-produced in the suspension polymerization in the present invention, it is preferable to add a surfactant together with the water-soluble polymerization initiator.
[0022]
Examples of the surfactant include anionic surfactants such as sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl (phenyl) ether sulfate, sodium dialkylsulfosuccinate, and polyoxyethylene alkyl (phenyl) ether. Nonionic surfactants, sodium salts of (meth) acrylic acid polyoxyethylene sulfate, sodium salts of alkylallylsulfosuccinate, anionic polymerizable surfactants such as glycerol allyl nonylphenyl polyoxyethylene ammonium sulfate ether Nonionic polymerizable surfactants such as polyoxyethylene alkylbenzene (meth) acrylate, glyceryl allyl nonylphenyl polyethylene glycol ether, poly (meth) acrylate alkali Metal salts, alkali metal salts of copolymers of (meth) acrylic acid and methyl (meth) acrylate, polymer alcohols such as 70-100% saponification degree polyvinyl alcohol and methylcellulose, etc. Can be mentioned. These can be used alone or in combination of two or more. Among them, anionic surfactants, particularly sodium polyoxyethylene alkyl (phenyl) ether sulfate is preferable.
[0023]
The addition amount of the surfactant is preferably in the range of 0.1 to 3 parts by mass with respect to 100 parts by mass of the granular vinyl polymer. This is because the dispersion stability of the emulsified fine particles tends to be increased by setting the addition amount of the surfactant to 0.1 parts by mass or more, and by setting it to 3 parts by mass or less, foaming of the suspension can be suppressed. It is because it is in a tendency. More preferably, it is the range of 0.2-1 mass part.
[0024]
The target granular vinyl polymer can be obtained by, for example, filtering, washing and drying an aqueous suspension of the polymer obtained by the production method of the present invention.
[0025]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. The non-volatile content and the acid value are measured by the following methods.
[0026]
Nonvolatile content: A sample of about 5 g was weighed in an aluminum dish, heated and dried at 105 ° C. for 2 hours, then weighed again, and obtained by the following formula.
[0027]
Nonvolatile content (mass%) = (sample weight after drying) / (sample weight before drying) × 100
[0028]
Acid value: About 2 g of vinyl polymer was weighed and dissolved by adding 50 g of solvent (acetone / ethanol = 50/50), and then phenol with 0.2 N potassium hydroxide (ethanol solution). Titration was carried out based on the discoloration point of ruphthalein, and the number of mg of KOH necessary for neutralizing 1 g of the vinyl polymer was determined by the following formula.
[0029]
Acid value (mgKOH / g) = A × 0.2 × f × 56.1 / Sample mass A: titration (ml), f: titer of 0.2N potassium hydroxide solution
[ Reference Example 1 ]
In a polymerization apparatus capable of heating and cooling, 200 parts by mass of deionized water and 0.6 parts by mass of polyvinyl alcohol (saponification degree 80%, polymerization degree 1,700) are added and stirred to completely dissolve the polyvinyl alcohol. Then, stirring was stopped once, 50 parts by mass of methyl methacrylate, 10 parts by mass of styrene, 25 parts by mass of n-butyl methacrylate, 10 parts by mass of ethyl acrylate, and 5 parts by mass of methacrylic acid were added and stirred again. 0.3 parts by mass of ronitrile and 1 part by mass of n-dodecyl mercaptan were added, the temperature was raised to 75 ° C., the reaction temperature was maintained at 75-80 ° C. for 2 hours, and the maximum value of the exothermic polymerization was confirmed. After 30 minutes, 0.05 part by weight of sodium persulfate was added, the temperature was raised to 90 ° C., and this state was maintained for 2 hours to complete the reaction. The obtained aqueous suspension was filtered and washed with a nylon filter cloth having an opening of 45 μm, and then the filtrate was dried at 40 ° C. for 16 hours to obtain a granular vinyl polymer. The obtained vinyl polymer had a non-volatile content of 99.2%, an acid value of 31.3 mgKOH / g, little odor, and its 30% by mass ethyl acetate solution was colorless and transparent and in a good state.
[0031]
[ Reference Example 2 ]
In a polymerization apparatus capable of heating and cooling, 200 parts by mass of deionized water and 0.6 parts by mass of polyvinyl alcohol (saponification degree 80%, polymerization degree 1,700) are added and stirred to completely dissolve the polyvinyl alcohol. Then, once stirring was stopped, 45 parts by mass of methyl methacrylate, 30 parts by mass of n-butyl methacrylate, 10 parts by mass of styrene, 10 parts by mass of 2-ethylhexyl acrylate, 5 parts by mass of methacrylic acid were added and stirred again. Add 0.3 parts by weight of azobisisobutyronitrile and 0.7 parts by weight of n-dodecyl mercaptan, raise the temperature to 75 ° C., maintain the reaction temperature at 75-80 ° C. for 2 hours, The maximum value was confirmed, 30 minutes later, 0.3 parts by mass of sodium persulfate was added, the temperature was raised to 90 ° C., and this state was maintained for 2 hours to complete the reaction. The obtained aqueous suspension was filtered and washed with a nylon filter cloth having an opening of 45 μm, and the filtrate was dried at 40 ° C. for 16 hours to obtain a granular vinyl polymer. The obtained vinyl polymer had a non-volatile content of 99.5%, an acid value of 31.4 mgKOH / g, little odor, and its 30% by mass methyl ethyl ketone solution was colorless and transparent and in a good state.
[0032]
[ Reference Example 3 ]
In a polymerization apparatus capable of heating and cooling, 200 parts by mass of deionized water and 0.6 parts by mass of polyvinyl alcohol (saponification degree 80%, polymerization degree 1,700) are added and stirred to completely dissolve the polyvinyl alcohol. Then, once stirring was stopped, 20 parts by mass of methyl methacrylate, 30 parts by mass of styrene, 15 parts by mass of n-butyl acrylate and 35 parts by mass of methacrylic acid were added and stirred again, 3 parts by mass of benzoyl peroxide and α-methylstyrene. 1 part by weight of dimer was added, the temperature was raised to 85 ° C., the reaction temperature was maintained at 85 to 90 ° C. for 2 hours, the maximum value of the polymerization exotherm was confirmed, and 2,2′-azobis (2 -Amidinopropane) After adding 0.02 part by weight of dihydrochloride, the temperature was raised to 95 ° C., and this state was maintained for 2 hours to complete the reaction. The obtained aqueous suspension was filtered and washed with a nylon filter cloth having an opening of 45 μm, and the filtrate was dried at 40 ° C. for 16 hours to obtain a granular vinyl polymer. The obtained vinyl polymer had a non-volatile content of 99.3%, an acid value of 215.2 mgKOH / g, little odor, and its 30% by mass acetone solution was colorless and transparent and in a good state.
[0033]
[ Example 1 ]
In a polymerization apparatus capable of heating and cooling, 200 parts by mass of deionized water and 0.6 parts by mass of polyvinyl alcohol (saponification degree 80%, polymerization degree 1,700) are added and stirred to completely dissolve the polyvinyl alcohol. Then, once stirring was stopped, 50 parts by mass of methyl methacrylate, 30 parts by mass of n-butyl methacrylate, 10 parts by mass of 2-ethylhexyl acrylate and 10 parts by mass of methacrylic acid were added and stirred again, and 1 part by mass of lauroyl peroxide. And 0.5 parts by mass of octyl thioglycolate were added, the temperature was raised to 75 ° C., the reaction temperature was maintained at 75-80 ° C. for 2 hours, the maximum value of the polymerization exotherm was confirmed, and 30 minutes later After adding 0.05 part by weight of ammonium persulfate and 1 part by weight of sodium polyoxyethylene alkyl ether sulfate, the temperature was raised to 90 ° C., and this state was maintained for 2 hours. The reaction was terminated. The obtained aqueous suspension was filtered and washed with a nylon filter cloth having an opening of 45 μm, and the filtrate was dried at 40 ° C. for 16 hours to obtain a granular vinyl polymer. The obtained vinyl polymer had a nonvolatile content of 99.1%, an acid value of 62.0 mgKOH / g, little odor, and its 30% by mass acetone solution was colorless and transparent, and was in a good state.
[0034]
[Comparative Example 1]
In a polymerization apparatus capable of heating and cooling, 200 parts by mass of deionized water and 0.6 parts by mass of polyvinyl alcohol (saponification degree 80%, polymerization degree 1,700) are added and stirred to completely dissolve the polyvinyl alcohol. Then, stirring was stopped once, 50 parts by mass of methyl methacrylate, 10 parts by mass of styrene, 25 parts by mass of n-butyl methacrylate, 10 parts by mass of ethyl acrylate, and 5 parts by mass of methacrylic acid were added and stirred again. 0.3 parts by mass of ronitrile and 1 part by mass of n-dodecyl mercaptan were added, the temperature was raised to 75 ° C., the reaction temperature was maintained at 75-80 ° C. for 2 hours, and the maximum value of the exothermic polymerization was confirmed. Thereafter, the temperature was raised to 90 ° C., and this state was maintained for 2 hours to complete the reaction. The obtained aqueous suspension was filtered and washed with a nylon filter cloth having an opening of 45 μm, and the filtrate was dried at 40 ° C. for 16 hours to obtain a granular vinyl polymer. The obtained vinyl polymer had a non-volatile content of 98.5% and an acid value of 30.8 mg KOH / g, but had a strong residual monomer odor, and slight turbidity was observed in the 30% by mass ethyl acetate solution. Insoluble matter settled out.
[0035]
【The invention's effect】
The method for producing a granular vinyl polymer of the present invention suppresses the content of residual monomers and emulsified fine particles as impurities, and has good odor and solubility in various organic solvents of the obtained granular vinyl polymer. It is very useful for industry.

Claims (4)

A method for producing an acid group-containing granular vinyl polymer , comprising adding a surfactant together with a water-soluble polymerization initiator after a polymerization exotherm during suspension polymerization reaches a maximum value. The method for producing an acid group-containing granular vinyl polymer according to claim 1, wherein the acid group-containing granular vinyl polymer contains a carboxyl group-containing vinyl monomer unit. The method for producing an acid group-containing granular vinyl polymer according to claim 1, wherein the acid value of the acid group-containing granular vinyl polymer is in the range of 5 to 350 mgKOH / g. 2. The acid group-containing granular vinyl polymer according to claim 1, wherein the addition timing of the water-soluble polymerization initiator and the surfactant is within one hour from the time when the suspension polymerization exotherm shows the maximum value. Manufacturing method.