JP2012057074A - Resin powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin powder, excellent in blocking resistance, re-dispersibility, and excellent in water resistance, preservation stability and the like after being re-dispersed.SOLUTION: The resin powder is obtained by drying an aqueous emulsion containing: a polymer (A) as a dispersoid having at least one unsaturated monomer unit selected from an ethylenic unsaturated monomer and a diene-based monomer; and a vinyl alcohol-based polymer (B) as a dispersant having a group represented by formula (I) at a terminal. (In the formula, R represents a hydrogen atom or an OM group; and M represents a hydrogen atom, an alkali metal atom, a 1/2 alkaline earth metal atom or an ammonium group).

Description

  The present invention relates to a resin powder having excellent dispersibility in water.

  An aqueous emulsion in which polymer fine particles are dispersed in an aqueous medium is used in a wide range of applications such as an admixture for cement or mortar, an adhesive, and a binder for paints, but contains about 50% by weight of water as a medium. Therefore, the transportation cost is high, and there is a problem in processing the container after use. Therefore, there is a demand for a resin powder that is transported in the form of a powder and that is easily dispersed in water by adding water and stirring at the time of use.

  As a resin powder having dispersibility in water, a vinyl ester heavy polymer obtained by spray drying an aqueous emulsion obtained by emulsion polymerization of a vinyl ester monomer using polyvinyl alcohol as a dispersant. Spray an aqueous emulsion obtained by emulsion polymerization of a (meth) acrylate monomer or diene monomer using a coalescent powder (Patent Document 1) or a low molecular surfactant as a dispersant. (Meth) acrylate polymer powders and diene polymer powders obtained by drying are known. However, all of these resin powders have a problem that they are not sufficiently dispersible in water. Patent Document 2 discloses a synthetic resin having high redispersibility in water obtained by spray-drying an aqueous emulsion containing a vinyl alcohol polymer having 1,2 glycol bonds of 1.7 mol% or more as a dispersant. Although an emulsion powder is disclosed, the vinyl alcohol polymer has a problem that it must be produced at a higher temperature than a normal vinyl alcohol polymer.

Japanese Patent Laid-Open No. 4-185606 JP 2001-342260 A

  An object of the present invention is to solve the above-mentioned problems, and to provide a resin powder which is excellent in blocking resistance and redispersibility, and excellent in water resistance and storage stability even when redispersed.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that a polymer (A) having at least one unsaturated monomer unit selected from an ethylenically unsaturated monomer and a diene monomer (A) Is a dispersoid, and a vinyl alcohol polymer (B) having a group represented by the following general formula (I) at its terminal (hereinafter, “vinyl alcohol polymer” may be abbreviated as “PVA”). The present inventors have found that a resin powder obtained by drying an aqueous emulsion having a dispersant as a dispersant is suitable for the purpose, and completed the present invention.

（式中、Ｒは水素原子またはＯＭ基を表し、Ｍは、水素原子、アルカリ金属原子、１／２アルカリ土類金属原子またはアンモニウム基を表す。）

(In the formula, R represents a hydrogen atom or an OM group, and M represents a hydrogen atom, an alkali metal atom, a 1/2 alkaline earth metal atom, or an ammonium group.)

  In the present invention, it is preferable that the polymer (A) is a (meth) acrylic acid ester polymer, and the viscosity average degree of polymerization of PVA (B) is 500 or more. Moreover, it is also preferable that a polymer (A) is a diene polymer and the viscosity average degree of polymerization of PVA (B) is 100 or more. Furthermore, the present invention provides at least one unsaturated monomer selected from ethylenically unsaturated monomers and diene monomers in a dispersion medium mainly containing water, using PVA (B) as a dispersion stabilizer. Also included is a method for producing the above resin powder, in which an aqueous emulsion is produced by polymerization and the aqueous emulsion is spray-dried.

  The resin powder of the present invention is excellent in water redispersibility and blocking resistance, and the emulsion obtained by redispersing in water is excellent in water resistance and storage stability.

Hereinafter, the resin powder of the present invention will be described in detail.
Examples of the ethylenically unsaturated monomer constituting the polymer (A) contained in the resin powder of the present invention include olefins such as ethylene, propylene, and isobutene; vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, and the like. Vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl versatic acid, vinyl pivalate; acrylic acid and its salts; methyl acrylate, ethyl acrylate, n-propyl acrylate, acrylic acid i Acrylic esters such as propyl, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid and salts thereof; methyl methacrylate, Ethyl methacrylate, methacrylic acid n Methacrylic acid esters such as propyl, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate; acrylonitrile, methacrylonitrile Nitriles such as allyl compounds such as allyl acetate and allyl chloride; acrylamide derivatives such as acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, and N-methylolacrylamide; methacrylamide, N -Methacrylamide derivatives such as methyl methacrylamide, N-ethyl methacrylamide, N-methylol methacrylamide; styrene, α-methyl styrene, p-methyl styrene Styrene monomers such as phonic acid and its sodium and potassium salts; trimethyl- (3-acrylamido-3,3-dimethylpropyl) -ammonium chloride, 3-acrylamidopropyltrimethylammonium chloride, 3-methacrylamidopropyltrimethylammonium chloride , Quaternary ammonium salts such as hydroxypropyltrimethylammonium chloride methacrylate, hydroxypropyltrimethylammonium chloride acrylate; N- (3-allyloxy-2-hydroxypropyl) dimethylamine, N- (4-allyloxy-3-hydroxybutyl) Examples include amines such as diethylamine or quaternary salts thereof; N-vinylpyrrolidone and the like. Among these monomers, acrylic acid esters and methacrylic acid esters are preferable. That is, the polymer (A) is preferably a (meth) acrylic acid ester polymer from the viewpoints of weather resistance, transparency, flexibility, and the like. Examples of the diene monomer include butadiene, isoprene, chloroprene and the like. A polymer (A) may be comprised only from 1 type among these monomers, and may be comprised from 2 or more types.

  The PVA (B) contained in the resin powder of the present invention has a group represented by the above general formula (I) at the terminal.

Examples of the alkali metal atom represented by M include a sodium atom and a potassium atom. Examples of the ½ alkaline earth metal atom represented by M include a ½ magnesium atom and a ½ calcium atom. When M is a ½ alkaline earth metal atom, the remaining ½ alkaline earth metal atom (that is, the remaining bond of the divalent alkaline earth metal atom) is oxygen in the general formula (I). atom, an oxygen atom in the following general formula (II), may be combined with P (H ₂ O ₂₎ or the like.

（ただし、Ｍは水素原子、アルカリ金属原子、１／２アルカリ土類金属原子またはアンモニウム基を表す。）

(However, M represents a hydrogen atom, an alkali metal atom, a 1/2 alkaline earth metal atom, or an ammonium group.)

  PVA (B) may contain a group represented by the general formula (II) in the main chain.

  The degree of saponification of PVA (B) is not particularly limited, but is preferably 40 to 99.99 mol%, more preferably 50 to 99.9 mol%, and more preferably 60 to 99.5 mol% from the viewpoint of water solubility and the like. Further preferred. In addition, the saponification degree of PVA is a value obtained by measuring according to JIS-K6726.

Although there is no restriction | limiting in particular about the viscosity average degree of polymerization (P) of PVA (B), 100-3000 are preferable and 300-2000 are more preferable. When the viscosity average degree of polymerization is less than 100, the redispersibility of the resulting resin powder may be lowered, and when it exceeds 3000, industrial production of the PVA may be difficult. Here, when said polymer (A) is a (meth) acrylic acid ester-type polymer, 500-2500 are preferable and, as for the viscosity average polymerization degree of PVA (B), 500-1500 are more preferable. Moreover, when a polymer (A) is a diene polymer, 100-2000 are preferable and, as for the viscosity average polymerization degree of PVA (B), 100-1500 are more preferable. The PVA (B) may be a blend of two or more PVA having different degrees of polymerization. In this case, it is preferable to adjust the blend ratio and the like so that the viscosity average degree of polymerization of the blend falls within the above range. The viscosity average degree of polymerization (P) of PVA (B) is measured according to JIS-K6726. That is, after re-saponifying and purifying the PVA, it is obtained by the following equation from the intrinsic viscosity [η] measured in water at 30 ° C.

P = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}

The viscosity average degree of polymerization may be simply referred to as the degree of polymerization.

  The production method of PVA (B) is not particularly limited as long as the obtained PVA has a group represented by the general formula (I) at the end, but for example, vinyl ester monomers are present in the presence of a compound containing phosphorus. It can be produced by a method comprising a step of radical polymerization under the step and a step of saponifying the obtained polymer.

  Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl palmitate, Examples include vinyl stearate, vinyl oleate, vinyl benzoate, etc. Among them, vinyl acetate is most preferable.

  Compounds containing phosphorus include hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, magnesium hypophosphite, ammonium hypophosphite and hydrates thereof. Examples of the compound include sodium hypophosphite or a hydrate thereof, which is the most inexpensive industrially.

  There is no restriction | limiting in particular in the usage-amount of the compound containing phosphorus, What is necessary is just to set suitably according to the quantity of group represented by general formula (I) to introduce | transduce into PVA (B). As for the usage-amount of the compound containing phosphorus, 0.001-30 weight part is preferable with respect to 100 weight part of vinyl ester monomers.

  The polymerization of the vinyl ester monomer can be performed in a solvent such as an alcohol solvent or without a solvent.

  As a polymerization method used for the polymerization of the vinyl ester monomer, any of batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization may be used. As the polymerization method, any known method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method can be used. Among them, a bulk polymerization method or a solution polymerization method in which polymerization is performed without a solvent or an alcohol solvent is suitably employed, and an emulsion polymerization method is employed for the purpose of producing a copolymer having a high degree of polymerization. As the alcohol solvent, methanol, ethanol, n-propanol or the like can be used, but is not limited thereto. These solvents can be used in combination of two or more. As the initiator used for the polymerization, conventionally known azo initiators, peroxide initiators, redox initiators and the like are appropriately selected according to the polymerization method. As the azo initiator, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4- Dimethyl valeronitrile) and the like, and peroxide initiators include perisopropyl compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate; t-butyl Perester compounds such as peroxyneodecanate, α-cumylperoxyneodecanate, and t-butylperoxydecanate; acetylcyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, etc. Is mentioned. Furthermore, the initiator can be combined with potassium persulfate, ammonium persulfate, hydrogen peroxide, or the like to form an initiator. Moreover, as a redox-type initiator, what combined said peroxide and reducing agents, such as sodium hydrogen sulfite, sodium hydrogencarbonate, tartaric acid, L-ascorbic acid, Rongalite, is mentioned. In addition, when the polymerization of the vinyl ester monomer is performed at a high temperature, coloring of PVA due to the decomposition of the vinyl ester monomer may be seen. It is safe to add an antioxidant such as tartaric acid to the polymerization system in an amount of 1 to 100 ppm (relative to the vinyl ester monomer).

  0-200 degreeC is preferable and the temperature employ | adopted when superposing | polymerizing a vinyl ester-type monomer has more preferable 30-140 degreeC. When the polymerization temperature is lower than 0 ° C., a sufficient polymerization rate cannot be obtained, which is not preferable. Moreover, when the temperature which superposes | polymerizes is higher than 200 degreeC, since it becomes difficult to obtain target PVA, it is unpreferable. As a method for controlling the temperature employed in the polymerization to 0 to 200 ° C., for example, a method of balancing the heat generated by the polymerization and the heat radiation from the surface of the reactor by controlling the polymerization rate. In addition, a method of controlling by an external jacket using an appropriate heating medium can be mentioned, but the latter method is preferable from the viewpoint of safety.

  When the vinyl ester monomer is polymerized, it may be copolymerized with other monomers as long as the gist of the present invention is not impaired. Examples of monomers copolymerizable with vinyl ester monomers include α-olefins such as ethylene, propylene, n-butene, and isobutylene; acrylic acid and its salts; methyl acrylate, ethyl acrylate, and acrylic acid n. Acrylic esters such as -propyl, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid and Salts thereof: methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate , Octadecyl methacrylate, etc. Methacrylic acid esters; Acrylamide; N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salt, acrylamide-2-methylpropanesulfonic acid and its salt, acrylamidopropyl Acrylamide derivatives such as dimethylamine and salts thereof or quaternary salts thereof, N-methylolacrylamide and derivatives thereof; methacrylamide; N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and salts thereof, methacrylamidepropyl Methacrylamide derivatives such as dimethylamine and salts thereof or quaternary salts thereof, N-methylol methacrylamide and derivatives thereof; Quaternary ammonium salts such as (3-acrylamide-3,3-dimethylpropyl) -ammonium chloride; N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i- Vinyl ethers such as butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; Nitriles such as acrylonitrile and methacrylonitrile; Halogenated vinyls such as vinyl chloride, vinyl bromide and vinyl fluoride; Vinylidene chloride and fluoride Vinylidene halides such as vinylidene; tetrafluoroethylene; allyl compounds such as allyl acetate and allyl chloride; unsaturated vinyl sulfonate and sodium allyl sulfonate N-vinylamides such as N-vinylformamide and N-vinylacetamide; Unsaturated dicarboxylic acids such as maleic acid, itaconic acid and fumaric acid and their salts, anhydrides or esters thereof; Vinyltrimethoxysilane and the like Of vinyl silyl compounds: polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, polyoxyethylene (meth) acrylic amide, polyoxypropylene (meth) acrylic amide, polyoxyethylene (1- (meth) acrylamide -1,1-dimethylpropyl) ester, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether and other oxyalkylene groups Mer; isopropenyl acetate and the like.

  In the polymerization of the vinyl ester monomer, the polymerization may be carried out in the presence of a chain transfer agent within the range not impairing the gist of the present invention for the purpose of adjusting the degree of polymerization of the obtained PVA. . Chain transfer agents include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol, n-dodecanethiol and 3-mercaptopropionic acid; tetrachloromethane, bromotrichloro Halides such as methane, trichlorethylene, and perchlorethylene are listed. In addition, thiol compounds such as thiol acetic acid and mercaptopropionic acid can be used to introduce a functional group to the terminal of PVA.

  By polymerization of a vinyl ester monomer in the presence of a phosphorus-containing compound, a vinyl ester (co) polymer incorporating a phosphorus-containing compound at the terminal is obtained.

  For the saponification reaction of vinyl ester polymers, alcoholysis or hydrolysis using a conventional basic catalyst such as sodium hydroxide, potassium hydroxide or sodium methoxide or an acidic catalyst such as p-toluenesulfonic acid. Reaction can be applied. Examples of the solvent that can be used in this reaction include alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene and toluene; These can be used alone or in combination of two or more. Among them, it is convenient and preferable to perform the saponification reaction using methanol or a methanol / methyl acetate mixed solution as a solvent and sodium hydroxide as a catalyst.

  According to the above method, the PVA having the group represented by the general formula (I) at the terminal and the group represented by the general formula (I) at the terminal and represented by the general formula (II) PVA having groups in the main chain can be obtained as a mixture.

  In PVA (B), the modification amount of the group represented by the general formula (I) is preferably 0.01 to 18 mol%. If it is less than 0.01 mol%, the degree of polymerization may exceed 3000, the productivity of the PVA may be reduced, and the utility may be impaired. When it exceeds 18 mol%, since the polymerization degree of PVA (B) may be less than 10, productivity may be reduced and practicality may be impaired.

  The resin powder of the present invention contains at least one unsaturated monomer selected from the above ethylenically unsaturated monomers and diene monomers in a dispersion medium mainly containing water using PVA (B) as a dispersion stabilizer. It is produced by polymerizing a monomer to produce an aqueous emulsion, and further spray-drying the aqueous emulsion.

  The polymerization initiator used in the polymerization is not particularly limited, and various types can be used. For example, a polymerization initiator such as potassium persulfate, ammonium persulfate, hydrogen peroxide, t-butyl hydroperoxide alone, Or it can be used as a redox polymerization initiator in combination with various reducing agents. Examples of the method of adding the initiator include a method of adding all at once in the initial stage and a method of adding continuously as the polymerization progresses.

  The amount of PVA (B) used in the above polymerization is not particularly limited, but is preferably 0.5 to 100 parts by weight, more preferably 1 to 50 parts by weight, based on 100 parts by weight of the monomer used. More preferred is 30 parts by weight. When the amount of PVA (B) used is less than 0.5 parts by weight, the polymerization stability is lowered, and the mechanical stability and chemical properties of the aqueous dispersion obtained by adding the obtained resin powder to water are reduced. There is a possibility that the stability may be lowered and the strength of the film may be lowered. On the other hand, when the amount of PVA (B) used exceeds 100 parts by weight, the viscosity at the time of polymerization increases, and it may be difficult to remove reaction heat or the water resistance of the film may be reduced. Examples of the method for adding PVA (B) include a method of adding all at once in the initial stage, and a method of adding a part in the initial stage and continuously adding the polymerization process. In the polymerization, in addition to PVA (B), conventionally known nonionic, anionic, cationic and amphoteric surfactants, various PVA other than PVA (B), water-soluble polymers such as hydroxyethyl cellulose May be used in combination.

  As a method of adding monomers in polymerization, a method of adding all at once in the initial stage, a method of adding a part of the monomers in the initial stage, and a method of adding the remainder continuously as the polymerization progresses, a dispersing agent is used. A method in which a monomer previously emulsified in water is continuously added.

  In the polymerization, a chain transfer agent can also be added. As the chain transfer agent, a compound having a mercapto group is preferable from the viewpoint of chain transfer efficiency. Examples of the compound having a mercapto group include alkyl mercaptans such as n-octyl mercaptan, n-dodecyl mercaptan and t-dodecyl mercaptan, 2-mercaptoethanol, and 3-mercaptopropionic acid. The addition amount of the chain transfer agent is preferably 5 parts by weight or less with respect to 100 parts by weight of the monomer. When the chain transfer agent exceeds 5 parts by weight, the polymerization stability is lowered, the molecular weight of the resulting polymer is remarkably lowered, and the film properties may be lowered.

  The resin powder of the present invention can be obtained by drying the aqueous emulsion obtained by the above polymerization. Examples of the drying method include spray drying, heat drying, blow drying, freeze drying, and the like. Among these, spray drying is preferable. Examples of the spraying method include a disk type and a nozzle type. Examples of the heat source for drying include hot air and heated steam. As the drying conditions, it is preferable to set the conditions of the size and type of the spray dryer, the concentration of the aqueous emulsion, the viscosity, and the flow rate so that a sufficiently dried powder can be obtained at a drying temperature of 40 to 150 ° C. . The volatile content of the resin powder may be about the equilibrium water content, specifically 3 wt% or less is preferable, and 2 wt% or less is more preferable.

  In order to further improve the redispersibility in water, a water-soluble additive can be added to the resin powder of the present invention. The water-soluble additive is preferably added to the aqueous emulsion before spray drying. The amount of the water-soluble additive used is set so as not to adversely affect the physical properties such as water resistance of the resin powder. Examples of water-soluble additives include PVA, hydroxyethyl cellulose, methyl cellulose, starch derivatives, polyvinyl pyrrolidone, polyethylene oxide, water-soluble alkyd resins, water-soluble phenol resins, water-soluble urea resins, water-soluble melamine resins, water-soluble naphthalene sulfonic acid resins, Water-soluble polymers such as water-soluble amino resins, water-soluble polyamide resins, water-soluble acrylic resins, water-soluble polycarboxylic acid resins, water-soluble polyester resins, water-soluble polyurethane resins, water-soluble polyol resins, and water-soluble epoxy resins. .

  Moreover, it is preferable to add an antiblocking agent (anti-caking agent) to the resin powder of the present invention in order to improve storage stability and redispersibility in water. The anti-blocking agent may be added to the resin powder obtained by spray drying and mixed uniformly, but it is preferably added to the aqueous emulsion before spray drying. As the antiblocking agent, fine inorganic powder having an average particle size of 0.1 to 10 μm is preferable. Examples of the inorganic powder include calcium carbonate, clay, anhydrous silicic acid, aluminum silicate, white carbon, talc, and alumina white. Organic fillers can also be used. 20 weight% or less is preferable with respect to a synthetic resin powder, and, as for the usage-amount of an antiblocking agent, 0.2 to 10 weight% is more preferable.

  The resin powder of the present invention can be blended with various additives other than those described above depending on the application. For example, when used as an admixture for cement and mortar, an AE agent, a water reducing agent, a fluidizing agent, a water retention agent, a thickening agent, a waterproofing agent and the like are added. When used in an adhesive, a viscosity improver, a water retention agent, a tackifier, a thickener and the like are added. When used in a coating binder, a viscosity improver, a thickener, a pigment dispersant, a stabilizer and the like are added.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In Examples and Comparative Examples, “parts” and “%” both mean weight.

Production Example 1
(Production of PVA-1)
200 g of methanol and 1.0 g of sodium phosphinate monohydrate were charged into a reactor to prepare a methanol solution of sodium phosphinate monohydrate. Next, 1200 g of vinyl acetate was charged into the reactor, and the inside of the reactor was purged with nitrogen by bubbling nitrogen gas. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 0.5 g of 2,2′-azobisisobutyronitrile was added to the reactor to initiate polymerization. The polymerization temperature was maintained at 60 ° C. during the polymerization. After 4 hours, when the polymerization rate reached 30%, the polymerization was stopped by cooling. Next, unreacted vinyl acetate was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate (PVAc). The PVAc solution adjusted to 25% was saponified by adding NaOH methanol solution (10% concentration) so that the alkali molar ratio (number of moles of NaOH / number of moles of vinyl acetate unit in PVAc) was 0.015. After adding the alkaline solution, a gel was formed in about 8 minutes. This was pulverized with a pulverizer and allowed to stand at 40 ° C. for 1 hour to proceed with saponification, and then 1000 g of methyl acetate was added to remain. The alkali was neutralized. After confirming the completion of neutralization using a phenolphthalein indicator, a white solid was obtained by filtration, 4000 g of methanol was added thereto, and the mixture was left to wash at room temperature for 3 hours. After the above washing operation was repeated three times, the white solid obtained by centrifugal drainage was left in a dryer at 65 ° C. for 2 days to obtain PVA-1. This polymer had a viscosity average polymerization degree of 1500 and a saponification degree of 96.0 mol%.

The modification amount of the group represented by the general formula (I) of the obtained PVA-1 was determined by ¹ H-NMR as follows. The obtained PVA-1 was purified by Soxhlet extraction with methanol for 48 hours, then dissolved in d ₆ -DMSO, and analyzed using ¹ H-NMR (JEOL GX-500) of 500 MHz. Peaks (7.5 to 7.7 ppm and 6.5) derived from protons attached to phosphorus of the group represented by the formula (I) and the area α of the peak derived from chain methylene (1.1 to 1.9 ppm). The amount of modification of the group represented by the general formula (I) was calculated from the area β of 3 to 6.6 ppm) using the following formula. In PVA-1, the modification amount of the group represented by the general formula (I) was 0.05 mol%. The results are shown in Table 1.

Modification amount of group represented by general formula (I) (mol%) = {(peak area β) / ((peak area α) / 2 + (peak area β))} × 100

Production Examples 2-5
PVA-3 was prepared in the same manner as in Production Example 1 except that the saponification conditions such as the charge amount of vinyl acetate, methanol and sodium phosphinate monohydrate, and the molar ratio of sodium hydroxide to the vinyl acetate unit during saponification were changed. , PVA-5, PVA-6 and PVA-8 were obtained. The results are shown in Table 1.

Example 1
A glass container equipped with a reflux condenser, a dropping funnel, a thermometer, a nitrogen inlet, and a stirrer was charged with 8 parts of PVA-1 obtained in Production Example 1 and 90 parts of ion-exchanged water, and completely at 95 ° C. Dissolved. The pH of the obtained PVA aqueous solution was adjusted to 4 with dilute sulfuric acid, and 10 parts of vinyl acetate was added while stirring at 150 rpm. Next, after the system was purged with nitrogen, the temperature was raised to 60 ° C. After adding 5 parts of 5% aqueous tartaric acid solution, 0.5% aqueous hydrogen peroxide solution was continuously added to initiate emulsion polymerization. 90 parts of vinyl acetate was continuously added over 2 hours, and after 3 hours from the start of polymerization, the polymerization was terminated when the residual vinyl acetate concentration became 1% or less, and the solid content concentration was stable at 50.4%. A polyvinyl acetate emulsion was obtained. A part of the obtained emulsion was subjected to a water resistance test described later. A mixture of 100 parts of the same emulsion and 80 parts of water, and 3% silicic acid fine powder (average particle size 2 μm) based on the solid content in the emulsion were separately sprayed separately into hot air at 100 ° C. By drying, a resin powder having an average particle size of 60 μm was obtained.

  Using the obtained resin powder, the following physical properties were evaluated. The results are shown in Table 2.

[Blocking resistance]
The resin powder was put in a container, and a state when it was allowed to stand at 20 ° C. and 65% RH for 10 days under a load of 25 g / cm ² was observed.

○ Almost no blocking.
Δ Partial lump is generated due to blocking.
X The whole becomes a lump by blocking.
-Resin powder cannot be obtained.

[Redispersibility]
80 parts of ion-exchanged water is added to 100 parts of resin powder, and the aqueous dispersion obtained by sufficiently stirring with a stirrer is filtered through a 200-mesh stainless steel wire mesh, and the filtration residue is dried at 105 ° C. for 5 hours. The proportion of was measured.

Filtration residue (%) = (filter residue after drying / emulsion powder weight used for redispersion) × 100

[Film-forming properties]
The aqueous dispersion for evaluation of redispersibility was cast on a glass plate at 50 ° C. and dried to obtain a film. The obtained film was observed and evaluated according to the following criteria.

○ Uniform and strong.
△ Uniform but fragile.
X A uniform film cannot be obtained.
-Resin powder cannot be obtained. Alternatively, an aqueous dispersion cannot be obtained.

[water resistant]
The aqueous dispersion for evaluation of redispersibility (after pulverization) was cast on a glass plate at 20 ° C. and dried to obtain a film. One sheet was used for measuring the weight of the film before immersion (represented by the suffix t), and the other sheet was immersed in water at 20 ° C. for 24 hours. The water absorption rate and elution rate were calculated from the weight of the film before and after immersion as follows and used as water resistance indicators. The water absorption and elution rate were calculated in the same manner for the aqueous emulsion (before pulverization) obtained after polymerization.

Dissolution rate (%) = [1- (W1d / W0d)] × 100
Water absorption (%) = [(W1w / W1d) -1] × 100
However,
W0d = W0w × (Wtd / Wtw)

W0d: absolute dry weight of the film before immersion.
W0w: Weight of the film before dipping W1d: Absolute dry weight of the film after dipping.
W1w: Weight of the film after immersion. The surface water is wiped off with gauze from the immersed film and weighed.

Wtd: absolute dry weight of the film for weight measurement.
Wtw: Weight of the film for weight measurement.

Absolutely dry weight: Weight when the film is dried at 105 ° C. until the weight does not change.

Comparative Example 1
A polyvinyl acetate emulsion and a resin powder were obtained and evaluated in the same manner as in Example 1 except that PVA-2 shown in Table 1 was used as a dispersant instead of PVA-1. The results are shown in Table 2.

Example 2
A glass container equipped with a reflux condenser, a dropping funnel, a thermometer, a nitrogen inlet, and a stirrer was charged with 5 parts of PVA-3 obtained in Production Example 2 and 90 parts of ion-exchanged water, and completely at 95 ° C. Dissolved. The pH of the obtained PVA aqueous solution was adjusted to 4 with dilute sulfuric acid, and 10 parts of methyl methacrylate, 10 parts of n-butyl acrylate and 0.1 part of n-dodecyl mercaptan were added while stirring at 150 rpm. Next, after the system was purged with nitrogen, the temperature was raised to 70 ° C. Polymerization was initiated by adding 5 parts of 1% strength potassium persulfate. Over a period of 2 hours, a mixture of 40 parts of methyl methacrylate, 40 parts of n-butyl acrylate and 0.4 part of n-dodecyl mercaptan was continuously added, and after 3 hours from the start of polymerization, the conversion rate was 99.6%. At this point, the polymerization was terminated, and a stable methyl methacrylate-n-butyl acrylate copolymer emulsion having a solid content concentration of 52.2% was obtained. Resin powder was obtained and evaluated in the same manner as in Example 1. The results are shown in Table 3.

Examples 3-4, Comparative Examples 2-3
A methyl methacrylate-n-butyl acrylate copolymer emulsion and resin powder were obtained and evaluated in the same manner as in Example 2 except that various dispersants shown in Table 3 were used instead of PVA-3. . The results are shown in Table 3.

Example 5
A pressure-resistant autoclave equipped with a nitrogen inlet and a thermometer was charged with 100 parts of a 4% aqueous solution of PVA-6 obtained in Production Example 4, adjusted to pH 4 with dilute sulfuric acid, and further 60 parts of styrene and t-dodecyl. 1 part of mercaptan was charged. Next, after replacing the system with nitrogen, 40 parts of butadiene was injected from a pressure gauge and the temperature was raised to 70 ° C. Polymerization was started by adding 10 parts of 2% ammonium persulfate. The internal pressure was 4.5 kg / cm ² before the start of polymerization, but decreased to 0.3 kg / cm ² after 20 hours. The polymerization rate at this time was 99.4%, and a stable styrene-butadiene copolymer emulsion having a solid content of 49.3% was obtained. Resin powder was obtained and evaluated in the same manner as in Example 1. The results are shown in Table 4.

Example 6 and Comparative Examples 4 to 5
A styrene-butadiene copolymer emulsion and a resin powder were obtained and evaluated in the same manner as in Example 5 except that various dispersants shown in Table 4 were used instead of PVA-6. The results are shown in Table 4.

Example 7
A pressure-resistant autoclave equipped with a nitrogen inlet and a thermometer was charged with 80 parts of a 6.25% aqueous solution of PVA-8 obtained in Production Example 5, and the pH was adjusted to 3.5 with dilute sulfuric acid. Prepared the department. Next, after the system was purged with nitrogen, the temperature was raised to 60 ° C. Ethylene was injected to 45 kg / cm ² and 5 parts of a 5% strength Rongalite aqueous solution was added, and then a 0.4% strength aqueous hydrogen peroxide solution was continuously added to initiate polymerization. Three hours later, when the vinyl acetate concentration reached 1.0%, the polymerization was terminated to obtain a stable ethylene-vinyl acetate copolymer emulsion having a solid content concentration of 55.3%. Resin powder was obtained and evaluated in the same manner as in Example 1. The results are shown in Table 5.

Comparative Example 6
An ethylene-vinyl acetate copolymer emulsion and a resin powder were obtained and evaluated in the same manner as in Example 7 except that PVA-9 shown in Table 1 was used as a dispersant instead of PVA-8. The results are shown in Table 5.

Claims (4)

A polymer (A) having at least one unsaturated monomer unit selected from ethylenically unsaturated monomers and diene monomers is used as a dispersoid, and a group represented by the following general formula (I): Resin powder obtained by drying an aqueous emulsion having the vinyl alcohol polymer (B) at the end as a dispersant.

(In the formula, R represents a hydrogen atom or an OM group, and M represents a hydrogen atom, an alkali metal atom, a 1/2 alkaline earth metal atom, or an ammonium group.)   The resin powder according to claim 1, wherein the polymer (A) is a (meth) acrylic acid ester polymer, and the vinyl alcohol polymer (B) has a viscosity average polymerization degree of 500 to 2500.   The resin powder according to claim 1, wherein the polymer (A) is a diene polymer, and the vinyl alcohol polymer (B) has a viscosity average polymerization degree of 100 to 2,000.   Polymerizing at least one unsaturated monomer selected from an ethylenically unsaturated monomer and a diene monomer in a dispersion medium mainly containing water using the vinyl alcohol polymer (B) as a dispersion stabilizer. The method for producing a resin powder according to any one of claims 1 to 3, wherein an aqueous emulsion is produced, and the aqueous emulsion is further spray-dried.