Polyvinyl alcohol resin containing acetoacetyl group, and method for producing polyvinyl alcohol resin containing acetoacetyl group

Abstract

The present invention provides an acetoacetyl-containing polyvinyl alcohol resin having less fluctuation in acetoacetyl content in each particle size range as described below. An acetoacetyl-containing polyvinyl alcohol resin is a powdered acetoacetyl-containing polyvinyl alcohol resin having a distribution of acetoacetyl content in which the ratio of the highest acetoacetyl content to the lowest acetoacetyl content (highest acetoacetyl content / lowest acetoacetyl content) is less than 1.2 among the acetoacetyl content in each particle size range of less than 105 μm, 105 μm or more and less than 177 μm, 177 μm or more and less than 600 μm.

Description

Technical Field

[0001] The present invention relates to a polyvinyl alcohol resin containing acetoacetyl groups and a method for producing the same. The polyvinyl alcohol resin has a structural unit having acetoacetyl groups and has a small fluctuation in the content of the structural unit in each particle size range. Background Art

[0002] It is known that the acetoacetyl-containing polyvinyl alcohol resin obtained by acetoacetylation of a polyvinyl alcohol resin can obtain excellent water resistance due to its high reactivity with various cross-linking agents (hereinafter, "polyvinyl alcohol resin" is sometimes referred to as "PVA", "acetoacetylation" is referred to as "AA-ization", and "acetoacetyl-containing polyvinyl alcohol resin" is referred to as "AA-ized PVA").

[0003] In the past, from the viewpoint of improving the qualities of AA-treated PVA, such as transparency and long-term stability, an AA-treated PVA having an acetoacetylation degree ratio (AA degree ratio) set to a specific range has been proposed, wherein the acetoacetylation degree ratio is obtained by classifying particles of the AA-treated PVA into various particle size ranges, measuring the content of structural units having acetoacetyl groups in each particle size range (hereinafter, "the content of structural units having acetoacetyl groups" may sometimes be referred to as "acetoacetyl content" or "AA degree"), and dividing the highest AA degree by the lowest AA degree (Patent Document 1).

[0004] In addition, as a method for producing the above-mentioned AA-modified PVA, a method has been proposed, in which PVA whose swelling degree and dissolution rate are adjusted to a specified range is swollen in acetic acid, and the swollen PVA is reacted with diketene to produce the desired AA-modified PVA (Patent Document 1).

[0005] As another method for producing AA-modified PVA, for example, a method has been proposed in which PVA is swelled in acetic acid and the swollen PVA is reacted with acetoacetate to produce a desired AA-modified PVA (Patent Document 2).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 9-110925

[0009] Patent Document 2: U.S. Patent No. 5719231 Summary of the invention

[0010] Problem that the invention aims to solve

[0011] In recent years, there is a demand for higher quality AA-based PVA, and further improvements are sought. For example, when the AA degree of each particle size range in the AA-based PVA fluctuates, there are problems such as differences in the temperature range of dissolution due to the AA degree, and uneven dissolution. In addition, when the AA degree of each particle size range in the AA-based PVA fluctuates, there are problems such as not being able to obtain homogeneous AA-based PVA when the particles of the AA-based PVA are classified into each particle size range during transportation, and therefore, there is a demand to improve the fluctuation.

[0012] However, the AA-modified PVA disclosed in Patent Documents 1 and 2 does not sufficiently suppress the fluctuation of the AA degree in each particle size range, and cannot be said to be sufficiently homogeneous. In addition, the AA-modified PVA disclosed in Patent Documents 1 and 2 does not sufficiently reduce the amount of fine particles contained in the AA-modified PVA, and therefore, there is room for improvement from the perspective of quality improvement.

[0013] That is, in the method of swelling PVA in acetic acid and reacting the swollen PVA with diketene as in the production method disclosed in Patent Document 1, the reaction rate is relatively fast, and therefore, the fluctuation of the degree of AA in each particle size range cannot be sufficiently suppressed, and a sufficiently homogeneous AA-formed PVA cannot be obtained, and an AA-formed PVA with a sufficiently reduced amount of fine particles cannot be obtained. Furthermore, in the method of using diketene as in the production method disclosed in Patent Document 1, the risk caused by the acute toxicity inherent in diketene is high, and there is also room for improvement from the viewpoint of safety.

[0014] On the other hand, the method disclosed in Patent Document 2 does not use diketene and is therefore excellent from the perspective of safety. However, this method cannot sufficiently suppress the fluctuation of the degree of AA in each particle size range. In fact, it is impossible to obtain AA-adapted PVA with a sufficiently homogeneous degree of AA-adapted and AA-adapted PVA with a sufficiently reduced amount of fine particles.

[0015] Solutions for solving problems

[0016] In view of the above situation, the present inventors have repeatedly conducted in-depth research and found that the above problems can be solved by controlling the distribution of the acetoacetyl content in each specific particle size range to a specific range. In addition, it was found that the above problems can be solved by a method for producing AA-based PVA having a specific swelling step using acetoacetate and the AA-based PVA obtained by the production method.

[0017] That is, the first main purpose of the present invention is a polyvinyl alcohol-based resin containing acetoacetyl groups, which is a powdered polyvinyl alcohol-based resin containing acetoacetyl groups and has an acetoacetyl content distribution in which the ratio of the highest acetoacetyl content to the lowest acetoacetyl content (highest acetoacetyl content / lowest acetoacetyl content) in the acetoacetyl content in each particle size range of less than 105 μm, greater than 105 μm and less than 177 μm, greater than 177 μm and less than 600 μm, and greater than 600 μm is less than 1.2.

[0018] The second gist of the present invention is an acetoacetyl group-containing polyvinyl alcohol-based resin, which is a powdery acetoacetyl group-containing polyvinyl alcohol-based resin, wherein the content of particles having a particle size of less than 105 μm is 6% by weight or less of the entire particles.

[0019] In the acetoacetyl group-containing polyvinyl alcohol-based resin of the first aspect, the content of particles having a particle size of less than 105 μm is 6% by weight or less of the entire particles.

[0020] The third main purpose of the present invention is a method for producing a polyvinyl alcohol-based resin containing an acetoacetyl group, which is a method for producing a powdered polyvinyl alcohol-based resin containing an acetoacetyl group, and the method comprises the following steps: a step of swelling the polyvinyl alcohol-based resin in a solvent having an amide group; and a step of reacting the swollen polyvinyl alcohol-based resin with acetoacetate.

[0021] The fourth main purpose of the present invention is a method for producing a polyvinyl alcohol-based resin containing acetoacetyl groups, which is a method for producing a powdered polyvinyl alcohol-based resin containing acetoacetyl groups, and the method comprises the following steps: mixing the polyvinyl alcohol-based resin with a solvent to swell the polyvinyl alcohol-based resin to a swelling degree greater than 2.5; and reacting the swollen polyvinyl alcohol-based resin with acetoacetate.

[0022] Effects of the Invention

[0023] According to the present invention, an AA-modified PVA having a uniform AA degree in each particle size range can be provided. Since the AA-modified PVA has a small AA degree distribution and is homogeneous, regardless of the particle size, it is expected that an AA-modified PVA with stable quality can be obtained safely.

[0024] Furthermore, according to the present invention, since AA-modified PVA having a small content of fine particles can be provided, it can be expected that AA-modified PVA having stable quality can be obtained safely. DETAILED DESCRIPTION

[0025] Hereinafter, the present invention will be described in detail. However, the following description is an example of an embodiment of the present invention, and the present invention is not limited to the following description unless exceeding the gist thereof.

[0026] The AA-modified PVA of one embodiment of the present invention is a powdered AA-modified PVA having an acetoacetyl content distribution in which the ratio of the highest acetoacetyl content to the lowest acetoacetyl content (highest acetoacetyl content / lowest acetoacetyl content) in each acetoacetyl content in each particle size range of less than 105 μm, greater than 105 μm and less than 177 μm, greater than 177 μm and less than 600 μm, and greater than 600 μm is less than 1.2.

[0027] The AA-modified PVA according to another embodiment of the present invention is a powdered AA-modified PVA, wherein the content of particles having a particle size of less than 105 μm is 6% by weight or less of the entire particles.

[0028] (AA-PVA)

[0029] First, the AA-modified PVA of the present invention is described. The AA-modified PVA of the present invention is obtained by introducing acetoacetyl groups (AA groups) into PVA obtained by saponifying a polyvinyl ester resin as a polymer of a vinyl ester monomer, and is a PVA having AA groups in the side chains. The AA-modified PVA of the present invention has a structural unit represented by the following formula (1), and in addition to the structural unit having an AA group represented by formula (1), it has a vinyl alcohol structural unit and also has a vinyl acetate structural unit as an unsaponified portion.

[0030]

[0031] Examples of the vinyl ester monomers used as the raw materials include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl versatate, and the like. From the perspective of economic efficiency, vinyl acetate is preferably used.

[0032] The above-mentioned vinyl ester monomers are usually used alone, but saponified products of copolymers with monomers copolymerizable with the above-mentioned vinyl ester monomers (comonomers) may also be used. Examples of such comonomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene, hydroxyl-containing α-olefins such as 3-butene-1-ol, 4-pentene-1-ol, 5-hexene-1-ol, and 3,4-dihydroxy-1-butene, and derivatives thereof such as acylates, and unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undecylenic acid, and salts thereof, and monoesters or dialkyl esters thereof. Esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as diacetone acrylamide, acrylamide and methacrylamide, olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid or their salts, alkyl vinyl ethers, dimethyl allyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, vinyl compounds such as glycerol monoallyl ether, substituted vinyl acetates such as isopropenyl acetate and 1-methoxyvinyl acetate, vinylidene chloride, 1,4-diacetoxy-2-butene, 1,4-dihydroxy-2-butene, vinylene carbonate, etc.

[0033] Furthermore, examples of the comonomer include polyoxyethylene (meth)propylene ether, polyoxyethylene (meth)acrylamide, polyoxypropylene (meth)acrylamide, polyoxyethylene (meth)acrylate, polyoxypropylene (meth)acrylate, polyoxyethylene (1-(meth)acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine and other polyoxyalkylene group-containing monomers. The monomers containing cationic groups include N-acrylamide methyl trimethyl ammonium chloride, N-acrylamide ethyl trimethyl ammonium chloride, N-acrylamide propyl trimethyl ammonium chloride, 2-acryloyloxy ethyl trimethyl ammonium chloride, 2-methacryloyloxy ethyl trimethyl ammonium chloride, 2-hydroxy-3-methacryloyloxy propyl trimethyl ammonium chloride, allyl trimethyl ammonium chloride, methyl allyl trimethyl ammonium chloride, 3-butene trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, diethyl diallyl ammonium chloride, etc. In the present invention, (meth) acrylic acid refers to acrylic acid or methacrylic acid, and (meth) acrylate refers to acrylate or methacrylate.

[0034] The amount of the comonomer introduced is appropriately set depending on the type of the monomer, but is usually 10 mol% or less, particularly 5 mol% or less. If the amount is too large, water solubility and chemical resistance may be impaired, which is not preferred.

[0035] In addition, in the case of ordinary PVA, the main chain bonding mode is mainly 1,3-diol bond, and the content of 1,2-diol bond is about 1.5 to 1.7 mol%, but by setting the polymerization temperature when polymerizing vinyl ester monomers to a high temperature, it is also possible to use one with a content of 1.7 to 3.5 mol%.

[0036] The content of the structural unit having an AA group in the AA-modified PVA (the degree of AA modification) is usually 0.1 to 20 mol%, more preferably 0.3 to 15 mol%, more preferably 1 to 10 mol%, and particularly preferably 3 to 8 mol%. If the content of the structural unit having an AA group is too small, the water resistance tends to decrease, and if the content is too large, the AA groups react with each other due to long-term storage in a high temperature and high humidity environment to form a cross-linked structure, and the water solubility tends to decrease.

[0037] The above-mentioned AA degree can be obtained, for example, by nuclear magnetic resonance spectroscopy or the like. Specifically, it is not limited to the following method, for example, it can be obtained by 1 The ratio of the peak area derived from the acetoacetyl group appearing at 2.2 ppm in H-NMR to the peak area derived from the CH2 unit of PVA was calculated.

[0038] In the present invention, the distribution of acetoacetyl content in each particle size range (AA degree distribution) is expressed by dividing the highest AA degree by the lowest AA degree (AA degree ratio) when measuring the AA degrees of each AA degree of each AA PVA in each particle size range (highest acetoacetyl content / lowest acetoacetyl content).

[0039] The value of the AA degree distribution in one embodiment of the present invention is less than 1.2. Specifically, the AA degree distribution value calculated based on the AA degree of each AA-treated PVA after screening using sieves with apertures of 105 μm, 177 μm, and 600 μm is less than 1.2, preferably less than 1.15, and more preferably less than 1.13. There is no particular restriction on the lower limit, but the closer it is to 1, the more the effect of the present invention is obtained, so it is preferred.

[0040] More specifically, the particles of the AA-modified PVA include: a first particle group consisting of particles having a particle size of less than 105 μm, a second particle group consisting of particles having a particle size of 105 μm or more and less than 177 μm, a third particle group consisting of particles having a particle size of 177 μm or more and less than 600 μm, and a fourth particle group consisting of particles having a particle size of 600 μm or more. The AA-modified PVA has the following AA degree distribution: the acetoacetyl content (A) of the first particle group is 105 μm or more, and the acetoacetyl content (A) of the first particle group is 105 μm or more, and the acetoacetyl content (A) of the first particle group is 105 μm or more, and the acetoacetyl content (A) of the second particle group is 105 μm or more, and the acetoacetyl content (A) of the second particle group is 105 μm or less, and the acetoacetyl content (A) of the third particle group is 105 μm or less, and the acetoacetyl content (A) of the fourth particle group is 105 μm or less, and the acetoacetyl content (A) of the first ... 1 ) [mol %], the acetoacetyl content of the second particle group (A 2 ) [mol %], the acetoacetyl content of the third particle group (A3 ) [mol %] and the acetoacetyl content of the fourth particle group (A 4 ) [mol %], the highest acetoacetyl content (A H ) relative to the lowest acetoacetyl content (A L )[mol%] of [mol%] content ratio (A H / A L ) is less than 1.2〔A H / A L <1.2〕. It should be noted that a particle group refers to an aggregate of a plurality of particles.

[0041] In addition, the acetoacetyl content (A 1 ) [mol %] and the acetoacetyl content of the fourth particle group (A 4 ) [mol %], the content ratio of the relatively high acetoacetyl content to the relatively low acetoacetyl content (relatively high acetoacetyl content / relatively low acetoacetyl content) is preferably less than 1.15, more preferably less than 1.13, particularly preferably less than 1.1, and particularly preferably less than 1.08. There is no particular restriction on the lower limit, which is 1.

[0042] In addition, the acetoacetyl content (A 3 ) [mol %] and the acetoacetyl content of the fourth particle group (A 4 ) [mol %], the content ratio of the relatively high acetoacetyl content to the relatively low acetoacetyl content (relatively high acetoacetyl content / relatively low acetoacetyl content) is preferably less than 1.15, more preferably less than 1.13, particularly preferably less than 1.1, and particularly preferably less than 1.08. There is no particular restriction on the lower limit, which is 1.

[0043] It should be noted that the classification of each particle size in the present invention refers to the use of sieves with apertures of 105μm, 177μm, and 600μm, and the sieving is divided into: 105μm aperture passing; 177μm aperture passing and 105μm aperture on the sieve; 600μm aperture passing and 177μm aperture on the sieve; 600μm aperture on the sieve.

[0044] The average particle size of the powdered AA-based PVA obtained by the present invention is usually 50 to 2000 μm, preferably 100 to 1700 μm, more preferably 200 to 1500 μm, and particularly preferably 400 to 1000 μm. If the average particle size is too small, it tends to form lumps during dissolution, and if it is too large, it tends to take a long time to dissolve.

[0045] The average particle size refers to the particle size at which the cumulative value of the powder particle size distribution obtained from each weight becomes 50% by weight, when sieved using sieves with pore sizes of 105μm, 177μm, and 600μm to separate the powdered AA-based PVA into particles passing through the 105μm pore size; particles passing through the 177μm pore size and on the 105μm sieve; particles passing through the 600μm pore size and on the 177μm sieve; and particles on the 600μm pore size.

[0046] In the AA-modified PVA of one embodiment of the present invention, the content of particles having a particle size of less than 105 μm is preferably 6% by weight or less, more preferably 5% by weight or less, and particularly preferably 3% by weight or less of the total particles. There is no particular lower limit, but the closer to 0% by weight, the better.

[0047] In another embodiment of the present invention, the content of particles with a particle size of less than 105 μm in the AA-modified PVA is 6% by weight or less. That is, a powdered AA-modified PVA has a content of particles with a particle size of less than 105 μm of 6% by weight or less relative to the total content of particles with a particle size of less than 105 μm and particles with a particle size of more than 105 μm (100% by weight: total particles). The content of particles with a particle size of less than 105 μm is preferably 5% by weight or less, and more preferably 4% by weight or less. There is no particular restriction on the lower limit, but the closer to 0% by weight, the better.

[0048] In another embodiment of the present invention, the content of the particles of the AA-modified PVA having a particle size of less than 177 μm is not particularly limited, but is preferably 18 wt% or less, more preferably 15 wt% or less, and particularly preferably 12 wt% or less. There is no particular lower limit, but the closer to 0 wt%, the better.

[0049] The saponification degree of the AA-modified PVA of the present invention is the same as the saponification degree of the PVA used as a raw material described later.

[0050] The average polymerization degree of the AA-modified PVA of the present invention (according to JIS K6726) is usually 300 to 4000, particularly preferably 400 to 2000, and further preferably 500 to 1500. If the average polymerization degree is too low, water resistance tends to decrease, while if it is too high, viscosity tends to increase, making it difficult to handle.

[0051] (Method for producing AA-modified PVA)

[0052] The method for producing the AA-modified PVA of the present invention is not particularly limited. From the viewpoint of making the value of the AA degree distribution fall within the above-mentioned suitable range and obtaining an AA-modified PVA with a small content of fine particles, the production method preferably includes a step of causing the PVA serving as a raw material (hereinafter sometimes referred to as "raw material PVA") to undergo an ester exchange reaction with acetoacetate in a swollen state.

[0053] Specifically, the method for producing AA-modified PVA of the present invention is preferably a method comprising the steps of swelling the raw material PVA with a solvent, using acetoacetate as a substrate, and further performing an ester exchange reaction with a catalyst.

[0054] The saponification degree of the raw material PVA used in the present invention (according to JIS K6726) is usually 75 to 99.9 mol%, more preferably 80 to 99.5 mol%, particularly preferably 85 to 99.3 mol%. If the saponification degree is too low, the solubility in water tends to decrease, which is not preferred.

[0055] The average polymerization degree (according to JIS K6726) of the raw material PVA used in the present invention is preferably 200 to 4000, more preferably 400 to 3500, and still more preferably 500 to 3000. If the average polymerization degree is too low, water resistance tends to decrease, while if it is too high, viscosity tends to increase and handling tends to become difficult.

[0056] The viscosity of a 4 wt % aqueous solution of the raw material PVA used in the present invention at 20° C. (according to JIS K6726) is usually 1.5 to 100 mPa·s, preferably 4 to 80 mPa·s, and more preferably 5 to 70 mPa·s. If the viscosity of the 4 wt % aqueous solution is too high, the viscosity tends to increase and become difficult to handle, while if the viscosity of the 4 wt % aqueous solution is too low, the water resistance tends to decrease.

[0057] As the solvent used in the step of swelling the raw material PVA of the present invention, any solvent can be used without particular limitation as long as it can dissolve the acetoacetate used in the transesterification reaction with PVA and swell PVA. For example, organic acids having at least one carboxyl group and compounds having an amide group (a solvent having an amide group) can be cited. Specifically, carboxylic acids such as formic acid, acetic acid, propionic acid, and butyric acid; lactam compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone (NMP), N-methyl-2-piperidone, N-methylcaprolactam, N-acetylpyrrolidone, and N-ethyl-2-pyrrolidone; urea derivatives such as 1,3-dimethyl-2-imidazolidinone (DMI), tetramethylurea, N,N-dimethylvinylurea, and N,N'-dimethylpropyleneurea (DMPU); and amide compounds such as hexamethylphosphoramide, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N,N',N'-tetramethylmalonamide, N,N-diethylacetamide, N,N-dimethylpropionamide, N,N-dimethylisobutyramide, and N-methylformamide. Among them, compounds having an amide group (solvents having an amide group) are preferred, 2-pyrrolidone, N-methyl-2-pyrrolidone, N,N'-dimethylpropyleneurea are more preferred, and N-methyl-2-pyrrolidone is particularly preferred. It should be noted that these solvents can be used alone or in any combination and ratio. Use two or more.

[0058] The above-mentioned solvent is usually used in an amount of 10 to 300 parts by weight, preferably 40 to 250 parts by weight, and particularly preferably 70 to 200 parts by weight relative to 100 parts by weight of the raw material PVA. When the amount of the above-mentioned solvent is too much, there is a tendency for PVA to dissolve, and a re-precipitation process is required. In addition, when the amount of the above-mentioned solvent is too small, there is a tendency for the swelling degree of PVA to become insufficient, which becomes a cause of a decrease in reaction speed and uneven reaction.

[0059] The swelling degree of the raw material PVA is preferably evaluated by the volume swelling degree (the rate of increase in volume before and after swelling). For example, the swelling degree of the raw material PVA is expressed by the volume ratio of the volume (A) of the PVA before swelling to the volume (B) of the PVA after swelling [(B) / (A)].

[0060] More specifically, for example, after adding 200 g of PVA of known volume (A) to the reaction apparatus described later, 200 g of solvent (S) is added dropwise, and the volume (B) of PVA is measured when the mixture is uniformly heated and stirred at 91° C. for 1 hour, and the swelling degree [(B) / (A)] is calculated. It should be noted that the swelling degree [(B) / (A)] when N-methyl-2-pyrrolidone (NMP) is used as the solvent (S) is 3.45, and the swelling degree [(B) / (A)] when acetic acid is used as the solvent (S) is 2.5.

[0061] The method for measuring the above volumes (A) and (B) is not particularly limited, and a measuring instrument such as a measuring cylinder can be generally used. It should be noted that the swollen state refers to a state in which the swelling degree [(B) / (A)] is greater than 1.0.

[0062] The swelling degree [(B) / (A)] in the step of swelling the raw material PVA of the present invention is preferably greater than 2.5 and less than 10, more preferably greater than 2.8 and less than 7.5, and particularly preferably greater than 3.0 and less than 5.0. When the swelling degree is too high, there is a tendency for PVA to dissolve, and a re-precipitation step is required, which is not preferred. When the swelling degree is too low, the swelling degree of PVA becomes insufficient, and therefore, there is a tendency to cause a decrease in reaction speed and uneven reaction. In addition, AA groups will self-crosslink with each other, which is not preferred.

[0063] As the acetoacetate used in the step of reacting the swollen PVA with the acetoacetate of the present invention, for example, methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, sec-butyl acetoacetate, tert-butyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, stearyl acetoacetate, benzyl acetoacetate, phenyl acetoacetate, etc. can be mentioned. The carbon number of the alkyl group of the acetoacetate is preferably 1 to 10, and more preferably 1 to 5. Among these, methyl acetoacetate and tert-butyl acetoacetate are particularly preferred. These can be used alone or in any combination and ratio. Use two or more.

[0064] The above-mentioned acetoacetate is usually used in an amount of 0.1 to 100 parts by weight, preferably 0.5 to 85 parts by weight, and particularly preferably 1 to 75 parts by weight relative to 100 parts by weight of the raw material PVA. When the amount of acetoacetate is too much, there is a tendency to hinder the swelling of PVA, which becomes a cause of a decrease in reaction rate and uneven reaction. In addition, when the amount of acetoacetate is too little, there is a tendency for the chemical equilibrium to shift to the reactant side, which becomes a cause of a decrease in reaction rate.

[0065] The catalyst used in the step of reacting the swollen PVA with acetoacetate of the present invention can be used without particular limitation as long as it is a catalyst commonly used in transesterification reactions. For example, Bronsted organic acids, Bronsted inorganic acids, Lewis inorganic acids, Lewis organic bases, and combinations thereof can be used. Specifically, for example, as Bronsted organic acids, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, benzoic acid, phthalic acid, gallic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, malic acid, citric acid, and aconitic acid can be mentioned; as Bronsted inorganic acids, sulfuric acid, nitric acid, phosphoric acid, boric acid, hydrofluoric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, and partial esters thereof can be mentioned; as Lewis inorganic acids, sodium acetate, potassium acetate, magnesium acetate, calcium acetate, zinc acetate, lithium trifluoromethanesulfonate, magnesium trifluoromethanesulfonate, zinc trifluoromethanesulfonate, ytterbium trifluoromethanesulfonate, zinc diacetylacetonate, zirconium tetraacetylacetonate, dioctyltin, and tetrabutoxytitanium can be mentioned; as Lewis organic bases, primary amines, secondary amines, tertiary amines, pyridines, primary phosphines, secondary phosphines, and tertiary phosphines can be mentioned.

[0066] The above-mentioned catalyst is usually used in an amount of 0.01 parts by weight or more, preferably 0.05 parts by weight or more, and more preferably 0.1 parts by weight or more, relative to 100 parts by weight of the raw material PVA. If the amount of the above-mentioned catalyst is less than 0.01 parts by weight, the reaction tends to be slow. In addition, preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and particularly preferably 3 parts by weight or less can be used. If the amount of the catalyst exceeds 10 parts by weight, it is economically disadvantageous and there is a tendency to make it difficult to remove the catalyst, so it is not preferred.

[0067] The reaction apparatus used in the transesterification reaction in the present invention is preferably an apparatus capable of heating and equipped with a stirrer, and for example, a kneader, a Henschel mixer, a ribbon mixer, and various mixers can be used.

[0068] In addition, in the process of swelling the raw material PVA, a solvent can be added by dripping. The dripping time is arbitrary and also depends on the capacity of the reaction scale and the cooling equipment, but as the lower limit, it is preferably more than 0.1 hour, more preferably more than 0.5 hour, and particularly preferably more than 1.0 hour. If the dripping time is more than 0.1 hour, the swelling property of PVA becomes more uniform. In addition, as the upper limit, it is preferably less than 6 hours, more preferably less than 3 hours, and particularly preferably less than 2 hours. From the viewpoint of productivity, it is preferably less than 6 hours to suppress the imparting of unnecessary heat.

[0069] In addition, in the above-mentioned reaction apparatus, the temperature at which the swollen PVA and the acetoacetate are reacted is not particularly limited, but as a lower limit, it is preferably 60°C or higher, more preferably 70°C or higher, and particularly preferably 80°C or higher. If it is 60°C or higher, the reaction rate tends to be faster, which is preferred from the viewpoint of productivity. In addition, as an upper limit, it is preferably 120°C or lower, more preferably 100°C or lower, and particularly preferably 95°C or lower. If it is 120°C or lower, it tends to be easy to suppress the self-crosslinking of AA groups, so it is preferred.

[0070] In addition, in the process of reacting the swollen PVA with acetoacetate of the present invention, when adding acetoacetate, it can be added dropwise. The dropping time of the above-mentioned acetoacetate is arbitrary and depends on the reaction scale and the capacity of the cooling equipment, but as a lower limit, it is preferably more than 0.5 hours, more preferably more than 1 hour, and particularly preferably more than 2.0 hours. If the dropping time is more than 0.5 hours, it is preferred from the perspective of maintaining the swelling degree of PVA and being able to react. In addition, as an upper limit, it is preferably less than 8 hours, more preferably less than 6 hours, and particularly preferably less than 5 hours. If it is less than 8 hours, it is preferred from the perspective of productivity.

[0071] The reaction time in the transesterification step is not particularly limited, but is preferably 1 hour or more, more preferably 2 hours or more, as a lower limit, and preferably 10 hours or less, more preferably 6 hours or less, as an upper limit.

[0072] After the transesterification reaction, a washing step of washing with a washing solvent of an alcohol having 1 to 3 carbon atoms is performed, and further a drying step is performed to remove the solvent. As the alcohol having 1 to 3 carbon atoms used in the washing step, specifically, ethanol, methanol, and n-butanol can be cited. They can be used alone or in any combination and ratio. Among them, methanol is preferably used from the perspective of low boiling point and less energy required for removal.

[0073] In addition, the drying time in the drying process can be appropriately selected in consideration of the above-mentioned temperature and pressure conditions, and further in consideration of the weight of the object to be treated, and is preferably set in the range of 0.5 to 10 hours. In addition, the temperature of the above-mentioned drying treatment can also be appropriately selected, and is preferably set in the range of 20 to 80°C.

[0074] Examples of uses of the AA-modified PVA of the present invention obtained in this manner include various uses shown in the following (1) to (10).

[0075] (1) Molding related: fibers, films, sheets, pipes, catheters, leak-proof films, temporary coating films, chemical laces, water-soluble fibers, etc.

[0076] (2) Adhesives: Adhesives for wood, paper, aluminum foil, plastic, etc., adhesives, rewetting agents, adhesives for non-woven fabrics, adhesives for various building materials such as gypsum boards and fiberboards, adhesives for various powder granulation, additives for cement and mortar, hot-melt adhesives, pressure-sensitive adhesives, fixatives for anionic coatings, etc.

[0077] (3) Coating agent related: transparent coating agent for paper, pigment coating agent for paper, internal sizing agent for paper, sizing agent for fiber products, warp paste, fiber processing agent, leather finishing agent, coating, antifogging agent, metal preservative, brightener for galvanizing, antistatic agent, conductive agent, temporary coating, etc.

[0078] (4) Blending agents for hydrophobic resins: antistatic agents and hydrophilicity imparting agents for hydrophobic resins, additives for composite fibers, films, and molded products, etc.

[0079] (5) Suspension and dispersion stabilizers: Pigment dispersion stabilizers for coatings, inks, water-based colorants, adhesives, etc.; dispersion stabilizers for suspension polymerization of various vinyl compounds such as vinyl chloride, vinylidene chloride, styrene, (meth)acrylate, vinyl acetate, etc.

[0080] (6) Emulsification and dispersion stabilizers: emulsifiers for emulsion polymerization of various acrylic monomers, ethylenically unsaturated compounds, butadiene compounds, post-emulsifiers for hydrophobic resins such as polyolefins and polyester resins, epoxy resins, paraffin wax, asphalt, etc.

[0081] (8) Thickener related: thickeners for various aqueous solutions, emulsions, oil drilling fluids, etc.

[0082] (9) Flocculants related: Flocculants for underwater suspended matter and dissolved matter, water filters for pulp and slurry, etc.

[0083] (9) Exchange resins and related products: ion exchange resins, chelate exchange resins, ion exchange membranes, etc.

[0084] (10) Others: soil conditioners, photosensitizers, photoresist resins, etc.

[0085] Example

[0086] Below, enumerate embodiment and comparative example, the present invention is further described in detail.It should be noted that, the following embodiment is for describing the present invention in detail and is shown, as long as it does not violate its purpose, the present invention is not limited to the following embodiment.It should be noted that, in the example, "part" refers to weight basis.

[0087] (Example 1)

[0088] 200 parts of raw material PVA (saponification degree 99.1 mol%, viscosity of 4 wt% aqueous solution at 20°C 13.3 mPa·s, average degree of polymerization 1200) and 0.83 parts of sodium acetate as a reaction catalyst were put into a kneader heated to 91°C, and 200 parts of N-methyl-2-pyrrolidone (NMP) were added dropwise for 1 hour under stirring conditions at a rotation speed of 20 rpm to swell the raw material PVA (volume swelling degree 3.45). After that, 142 parts of tert-butyl acetoacetate (t-BAA) were added dropwise for 3 hours while maintaining the same rotation speed and the same temperature, and the reaction was further performed for 4 hours. After the reaction was completed, it was washed with methanol and dried at 40°C under vacuum for 3 hours to obtain powdered AA-modified PVA1 (average degree of polymerization 1200, AA degree 4.7 mol%, average particle size 437 μm).

[0089] (Comparative Example 1)

[0090] 100 parts of raw material PVA (saponification degree 99.1 mol%, viscosity of 4 wt% aqueous solution at 20°C 13.3 mPa·s, average degree of polymerization 1200) and 0.83 parts of sodium acetate as a reaction catalyst were put into a kneader heated to 91°C, 30 parts of acetic acid were added, and the raw material PVA was swollen (volume swelling degree 1.85) under stirring conditions of a rotation speed of 20 rpm. Then, 5 parts of diketene were added dropwise over 3 hours under the conditions of a rotation speed of 20 rpm and a temperature of 60°C, and the reaction was further carried out for 1 hour. After the reaction was completed, it was washed with methanol and dried at 70°C for 12 hours under vacuum to obtain powdered AA-modified PVA2 (average degree of polymerization 1200, AA degree 5.2 mol%, average particle size 231 μm).

[0091] (Comparative Example 2)

[0092] 200 parts of raw material PVA (saponification degree 99.1 mol%, viscosity of 4 wt% aqueous solution at 20°C 13.3 mPa·s, average degree of polymerization 1200) and 0.83 parts of sodium acetate as a reaction catalyst were put into a kneader heated to 91°C, 200 parts of acetic acid were added thereto, and the raw material PVA was swollen (volume swelling degree 2.5) under stirring conditions of a rotation speed of 20 rpm. Then, 142 parts of tert-butyl acetoacetate were added dropwise over 3 hours under the conditions of a rotation speed of 20 rpm and a temperature of 91°C, and the reaction was further carried out for 4 hours. After the reaction was completed, it was washed with methanol and dried at 40°C under vacuum for 3 hours to obtain powdered AA-modified PVA3 (average degree of polymerization 1200, AA degree 2.7 mol%, average particle size 306 μm).

[0093] (Grading method)

[0094] AAized PVA1 was classified into various particle size ranges using sieves with apertures of 105 μm, 177 μm, and 600 μm as specified in JIS Z8815. Specifically, AAized PVA1 was classified using the above sieves into: AAized PVA containing a particle group consisting of particles with a particle size of less than 105 μm, AAized PVA containing a particle group consisting of particles with a particle size of 105 μm or more and less than 177 μm, AAized PVA containing a particle group consisting of particles with a particle size of 177 μm or more and less than 600 μm, and AAized PVA containing a particle group consisting of particles with a particle size of 600 μm or more. AAized PVA2 and 3 were classified in the same manner.

[0095] (Determination of AA degree in each particle size range)

[0096] The AA degree of each AA-modified PVA classified into each particle size range was measured using a nuclear magnetic resonance device "Ascend 400 (400 MHz), AVANCE III 400, Cryo-probe" manufactured by Bruker. Specifically, each AA-modified PVA was dissolved in DMSO-d6 (dimethyl sulfoxide-D6) (concentration 4%) and measured under the conditions of 16 cumulative times and 50°C. 1 The AA degree was calculated from the ratio of the peak area derived from the acetoacetyl group appearing at 2.2 ppm in H-NMR to the peak area derived from the CH2 unit of PVA, and the AA degree distribution was determined from the AA degree calculated for each particle size range.

[0097] (Measurement of average particle size)

[0098] Use sieves with pore sizes of 105μm, 177μm, and 600μm to sieve into the following categories: particles passing through the pore size of 105μm; particles passing through the pore size of 177μm and on the pore size of 105μm; particles passing through the pore size of 600μm and on the pore size of 177μm; and particles on the pore size of 600μm. The particle size at which the cumulative value of the powder particle size distribution obtained from each weight becomes 50% by weight is approximated by an exponential function to calculate the average particle size.

[0099] As shown in Table 1, in Example 1, the AA degree of AA-treated PVA classified into a particle size of less than 105 μm was the highest, and the AA degree of AA-treated PVA classified into a particle size of 177 μm or more and less than 600 μm was the lowest, and the value of the AA degree distribution was 1.09.

[0100] On the other hand, in Comparative Example 1, the AA degree of AA-modified PVA classified into a particle size of less than 105 μm was the highest, and the AA degree of AA-modified PVA classified into a particle size of 600 μm or more was the lowest, and the value of the AA degree distribution was 1.53.

[0101] In Comparative Example 2, the AA degree of AA-treated PVA classified into a particle size of less than 105 μm was the highest, and the AA degree of AA-treated PVA classified into a particle size of 600 μm or more was the lowest, and the value of the AA degree distribution was 1.4.

[0102] [Table 1]

[0103]

[0104] *1: tert-Butyl acetoacetate

[0105] *2: N-methyl-2-pyrrolidone

[0106] *3: Content of structural units having AA groups in AA-modified PVA

[0107] *4: Highest AA degree / Lowest AA degree

[0108] The weight of the AA-based PVA in each particle size range was measured, and the total weight of each particle size range was set to 100 weight %, and the particle size distribution (weight %) was calculated. The results are shown in Table 2.

[0109] [Table 2]

[0110]

[0111] *1: tert-Butyl acetoacetate

[0112] *2: N-methyl-2-pyrrolidone

[0113] As shown in Table 2, it was confirmed that in Example 1, the content of particles classified into particles with a particle size of less than 105 μm was sufficiently reduced, whereas in Comparative Examples 1 and 2, the content of particles classified into particles with a particle size of less than 105 μm was not sufficiently reduced.

[0114] According to the present invention, since diketene is not used, AA-modified PVA can be safely produced, and the AA-modified PVA produced using acetoacetate has a uniform distribution of AA degrees in each particle size range, so that AA-modified PVA with stable quality can be obtained.

[0115] According to the present invention, since diketene is not used, AA-modified PVA can be safely produced, and since the content of fine particles smaller than 105 μm in AA-modified PVA produced using acetoacetate is small, excellent quality AA-modified PVA can be obtained.

[0116] Although the specific modes of the present invention are shown in the above embodiments, the above embodiments are merely examples and are not to be interpreted as limiting. Those skilled in the art can make various obvious modifications within the scope of the present invention.

Claims

1. A method for producing a powdery acetoacetyl-containing polyvinyl alcohol-based resin, wherein: The production method comprises the following steps: a step of swelling a polyvinyl alcohol-based resin in a solvent having an amide group until the swelling degree is greater than 2.5; and a step of reacting the swollen polyvinyl alcohol-based resin with acetoacetate. In the powdered polyvinyl alcohol-based resin containing acetoacetyl groups obtained by the manufacturing method, the content of particles with a particle size of less than 105 μm is less than 6 weight % of the total particles, and the distribution of the acetoacetyl content in each particle size range of less than 105 μm, greater than 105 μm and less than 177 μm, greater than 177 μm and less than 600 μm, and greater than 600 μm (highest acetoacetyl content / lowest acetoacetyl content) is less than 1.2.

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