JP2005272481A - Aqueous emulsion and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous emulsion excellent in polymerization stability and shelf stability, and a redispersible powder. <P>SOLUTION: The aqueous emulsion is obtained by polymerizing an acrylic monomer in the presence of an acetoacetate group-containing polyvinyl alcohol, where the acetoacetate group-containing polyvinyl alcohol has a block character [η] of 0.3-0.6, a saponification degree of at least 97 mol% and an acetoacetic esterification degree of 0.01-1.5 mol%, and the value obtained by dividing the maximum value by the minimum value of the respective average acetoacetic esterification degree for each of the acetoacetate group-containing polyvinyl alcohol fractionated by the particle size of 44-74, 74-105, 105-177, 177-297, 297-500 and 500-1680 μm is 1.0-3.0. The redispersible powder is obtained by drying the aqueous emulsion. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aqueous emulsion excellent in polymerization stability and standing stability. More specifically, in the present invention, particles having a small difference in the degree of acetoacetate esterification by particle size and a high block property of acetoacetate group-containing polyvinyl alcohol are attached to the surface of polymer particles made of an acrylic monomer. The present invention relates to an aqueous emulsion as a dispersoid, and a redispersible powder obtained by drying the aqueous emulsion. The aqueous emulsion and redispersible powder of the present invention can be used as an adhesive such as particle board or an admixture for cement and mortar.

  Conventionally, polyvinyl alcohol (hereinafter referred to as PVA) has been used as a protective colloid agent in order to impart mechanical stability and freeze stability to an acrylic aqueous emulsion. However, although the mechanical stability and freezing stability of the emulsion are improved, the polymerization stability is insufficient. In particular, polymerization can be performed at a high concentration where the resin content in the emulsion exceeds 50% by weight. There wasn't. Therefore, when PVA is used as a protective colloid agent for an acrylic aqueous emulsion, the resin content in the emulsion needs to be 50% by weight or less, which is problematic in terms of productivity. In addition, the resulting emulsion has insufficient stability and has a problem of thickening with time.

  Also, vinyl acetate-based or acrylic-based aqueous emulsions and redispersible powders obtained by drying aqueous emulsions are used for mixing with cement and mortar. However, when such an emulsion is mixed, there is a problem that the fluidity of cement and mortar deteriorates with time and the workability decreases.

  Therefore, when PVA is used as a protective colloid agent for an acrylic aqueous emulsion, the development of a PVA protective colloid agent that can polymerize the resin content in the emulsion even at a high concentration of 50% by weight or more, and cement mortar There has been a demand for the development of an aqueous emulsion and a redispersible powder that do not deteriorate the workability even when mixed.

  As a countermeasure, it has been proposed to use acetoacetate group-containing polyvinyl alcohol as an emulsifying dispersant, which is described in many patent documents. For example, Patent Document 1 discloses a method for producing an acetoacetate group-containing PVA (hereinafter referred to as AA-PVA). When AA PVA was fractionated into particle sizes of 44 to 74, 74 to 105, 105 to 177, 177 to 297, 297 to 500, and 500 to 1680 μm, the degree of acetoacetate esterification (hereinafter referred to as AA degree) AA-PVA in which the value obtained by dividing the maximum value of 1.0 by 3.0 is 1.0 to 3.0 is excellent in transparency and stability when used as an aqueous solution, and is suitable as an emulsion dispersion stabilizer. It is described.

  Patent Document 2 contains active hydrogen groups such as acetoacetate group, mercapto group, diacetone acrylamide group, block character [η] is larger than 0.6, and saponification degree is 95.0 mol%. Disclosed is an aqueous emulsion in which higher and less blocky PVA is attached to a polymer, and is obtained by drying the emulsion, as well as the mechanical stability, freezing stability and high-temperature storage stability of the resulting aqueous emulsion. It is stated that the mechanical stability of the redispersible powder is good. Furthermore, an example in which the polymerization is performed so that the resin concentration in the emulsion is 50% by weight is also described.

  Patent Document 3 discloses a highly blocky PVA containing an acetoacetate group or a mercapto group and having a block character [η] of 0.3 to 0.6, an ethylenically unsaturated monomer and / or A powder obtained by adhering to a polymer comprising a diene monomer is disclosed. The obtained powder is said to be excellent in redispersibility, and the physical properties of the cement mixed therewith are also good. Furthermore, an example in which the polymerization is performed so that the resin concentration in the emulsion is 50% by weight is also described.

  However, in recent years, it has been desired that the emulsion is polymerized at a resin concentration as high as possible from the viewpoint of improving the productivity. In the aqueous emulsion described in the above-mentioned patent document, the polymerization was performed with the resin concentration in the emulsion being 50% by weight or more. In such cases, problems such as insufficient polymerization stability and generation of coarse particles, and insufficient standing stability and thickening of the emulsion have occurred.

  In addition, when the aqueous emulsion and redispersible powder described in the above-mentioned patent document are mixed with cement or mortar, workability is good when cement or mortar is used immediately after mixing, but it takes time after mixing. In the case of use, the fluidity of cement or mortar is lowered, and the workability is lowered.

Japanese Patent Laid-Open No. 09-110925 JP 2003-277419 A JP 2002-060406 A

  An object of the present invention is to provide an aqueous emulsion excellent in polymerization stability and standing stability, an adhesive (composition), and a redispersible powder.

  The present invention relates to an aqueous emulsion obtained by polymerizing an acrylic monomer in the presence of acetoacetate group-containing polyvinyl alcohol, wherein the block character [η] of the acetoacetate group-containing polyvinyl alcohol is 0. 0.3 to 0.6, saponification degree is 97 mol% or more, acetoacetic acid esterification degree is 0.01 to 1.5 mol%, and 44 to 74, 74 to 105, 105 to 177, 177 to 297 The maximum value of the average acetoacetate esterification degree (hereinafter abbreviated as acetoacetate esterification degree) of each of the acetoacetate group-containing polyvinyl alcohols fractionated into particle sizes of 297 to 500 and 500 to 1680 μm is the minimum value. It is related with the aqueous emulsion whose value divided by 1.0-3.0.

  Preferred embodiments of the present invention include the following.

  It is preferable that the polymer has a pH of 3 to 8 and is produced by polymerizing an acrylic monomer.

  The polymer is preferably produced by polymerizing an acrylic monomer using persulfate as a polymerization initiator.

  It is preferable that the glass transition temperature of a polymer is 10-80 degreeC.

  The polymer is preferably produced by copolymerizing an acrylic monomer with an acetoacetate group-containing ethylenically unsaturated monomer.

  The aqueous emulsion preferably contains 1-1000 ppm of iron compound.

  The present invention also relates to an adhesive composition comprising the aqueous emulsion.

  In particular, it is preferable that the adhesive composition contains an isocyanate-based crosslinking agent.

  The present invention relates to an adhesive for particle board and an adhesive for medium fiber board (MDF) comprising the adhesive composition.

  Furthermore, the present invention relates to a powder obtained from the aqueous emulsion.

  According to the present invention, an aqueous emulsion excellent in polymerization stability and standing stability, and a redispersible powder can be obtained. Further, the aqueous emulsion and redispersible powder of the present invention are excellent as an adhesive such as particle board and an admixture for cement and mortar.

  The aqueous emulsion of the present invention is an aqueous emulsion obtained by polymerizing an acrylic monomer in the presence of AA-PVA, and the block character [η] of the acetoacetate group-containing polyvinyl alcohol is 0.00. 3 to 0.6, saponification degree is 97 mol% or more, acetoacetic acid esterification degree is 0.01 to 1.5 mol%, and 44 to 74, 74 to 105, 105 to 177, 177 to 297, The maximum value of the degree of acetoacetate esterification (hereinafter sometimes referred to as AA degree) of the acetoacetate group-containing polyvinyl alcohol separated into particle sizes of 297 to 500 and 500 to 1680 μm is the minimum value. Is an aqueous emulsion having a value divided by 1.0 to 3.0.

  AA-modified PVA is obtained by introducing an acetoacetate group into PVA. As the PVA used as a raw material, a saponified product obtained by saponifying a polyvinyl acetate solution with an alkali or an acid or a derivative thereof is used. Further, a copolymer of vinyl acetate and a monomer copolymerizable with vinyl acetate is used. A saponified product obtained by saponifying a polymer can be used as long as the object of the present invention is not impaired.

  Saponification is carried out by dissolving a polymer such as polyvinyl acetate in an alcohol or hydrous alcohol and using an alkali catalyst or an acid catalyst. Examples of the alcohol include methanol, ethanol, propanol, tert-butanol and the like, and methanol is particularly preferably used. The concentration of the polymer in the alcohol is appropriately selected depending on the viscosity of the system, but is usually selected from the range of 10 to 60% by weight. Catalysts used for the saponification include sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate, alkali metal hydroxides such as lithium methylate, alkali catalysts such as alcoholate; sulfuric acid, Examples include acid catalysts such as hydrochloric acid, nitric acid, metasulfonic acid, zeolite, and cation exchange resin. The amount of the saponification catalyst used is appropriately selected depending on the saponification method, the target degree of saponification, and the like. When an alkali catalyst is used, it is usually 0.1 to 30 mmol, preferably 1 mol relative to 1 mol of PVA. Is suitably 2 to 17 mmol. The reaction temperature for the saponification reaction is not particularly limited, but is preferably 10 to 60 ° C, more preferably 20 to 50 ° C.

  The conditions that the raw material PVA should have include saponification degree, average polymerization degree, 1,2-glycol bond amount, swelling degree, elution rate, particle size, and the like, which will be described in order below.

  The degree of saponification of PVA is 97-100 mol%, in particular 97-99.5 mol%. If the degree of saponification is less than 97 mol%, the stability of the emulsion during polymerization is extremely lowered, making it difficult to obtain the desired aqueous emulsion.

  The average degree of polymerization of PVA is not particularly limited, but is preferably 50 to 2000, more preferably 100 to 1500, and particularly preferably 100 to 600. It is difficult to industrially produce a PVA having a degree of polymerization of less than 50. On the other hand, if it exceeds 2000, the viscosity of the emulsion becomes too high or the polymerization stability of the emulsion is lowered, which is not preferable.

  Furthermore, the 1,2-glycol bond amount of PVA is preferably 1.5 mol% or more, more preferably 1.6 to 2.2 mol%, and 1.6 to 1.8 mol%. More preferably. When the 1,2-glycol bond amount is less than 1.5 mol%, the temperature dependence of the emulsion viscosity is increased, and the emulsion polymerization stability may be lowered, which is not preferable.

The 1,2-glycol bond amount is determined from the measured value of ¹ H-NMR. First, after saponification, thoroughly washed with methanol, then PVA dried under reduced pressure at 90 ° C. for 2 days was dissolved in DMSO-D ₆ to a concentration of 5% by weight, and a sample with a few drops of trifluoroacetic acid was added. , By using 400 MHz ¹ H-NMR (AVANCE DPX-400, manufactured by Bruker) under the following conditions.
Temperature: 80 ° C
Flip angle: 45 ° Pulse repetition time: 10 sec
Integration count: 16 times

When sodium 3- (trimethylsilyl) propionate is used as a reference substance, the peak derived from methine in the vinyl alcohol unit is 3.2 to 4.0 ppm (integrated value A), and the peak derived from one methine having a 1,2-glycol bond. Is assigned to 3.25 ppm (integral value B), and the 1,2-glycol bond amount can be calculated by the following formula.
1,2-glycol bond amount (mol%) = B / A × 100

  The degree of swelling of PVA is adjusted to be 1.0 or more, preferably 1.0 to 500, and more preferably 3.0 to 200. If the degree of swelling is less than 1.0, it is difficult to obtain an AA-PVA having an AA degree distribution of 1.0 to 3.0. On the other hand, if the degree of swelling is too high, the stirring load becomes too high during production, which is not preferable.

The degree of swelling of PVA is defined by the following formula.
Swelling degree = (C−D) / D
Here, C added 270 g of water to 30 g of PVA, allowed to stand at 25 ° C. for 24 hours, filtered with suction at a vacuum degree of 100 mmHg for 10 minutes, and then remained on the filter paper (No. 2) to absorb water-swelled PVA. Represents weight (g). D represents a weight (g) when the water-absorbed and swollen PVA is dried at 105 ° C. to become a constant weight.

  The elution rate of PVA is adjusted to 3.0% by weight or more, preferably 3.0 to 97.0% by weight, and more preferably 5.0 to 60.0% by weight. When the elution rate is less than 3.0% by weight, it is difficult to obtain an acetoacetate group-containing polyvinyl alcohol having an AA degree distribution of 1.0 to 3.0. Moreover, when the elution rate is too high, when PVA is converted to acetoacetate, PVA resin adheres to the side wall of the reaction vessel, the stirring load during the reaction increases, and the reaction temperature is not uniform, There is a high possibility that the uniformity of distribution among particles of acetoacetate groups (hereinafter sometimes referred to as AA groups) is impaired.

In addition, the elution rate of PVA is defined by the following formula.
Dissolution rate (% by weight) = (E / 30) × 100
Here, E is obtained by adding 270 g of water to 30 g of PVA, leaving it at 25 ° C. for 24 hours, and then filtering off water and volatile components from the filtrate obtained by filtering for 10 minutes with a vacuum of 100 mmHg. Represents the weight (g) of the non-volatile component.

  In order to adjust the swelling degree and elution rate of PVA, there are methods such as heat treatment while allowing PVA to stand or flow and adjusting the crystallinity, but the volatile matter can be adjusted. The fluidized heat treatment method is preferred.

  The particle size of PVA is preferably 20 to 5000 μm, and more preferably 44 to 1680 μm. If the particle size is less than 20 μm, the particles are likely to be fused by heat of reaction, and further post-treatment such as washing and drying becomes difficult, which is not preferable. On the other hand, when the particle size exceeds 5000 μm, the contact between the PVA particles and the diketene used in the AA reaction becomes non-uniform, which is not preferable. The particle size of the PVA can be adjusted by adjusting with a standard sieve or air classification after the production of the PVA.

  PVA may contain several weight percent of alcohols, esters or moisture used in the production, but these react with the diketene, consume the diketene and reduce the reaction rate of the diketene. It is preferable to use it after reducing it as much as possible by the pressure reduction operation.

  Examples of a method for introducing an acetoacetate group into PVA include a method of reacting PVA with diketene, a method of reacting PVA with acetoacetate, etc., but the production process is simple and AA is of good quality. From the viewpoint of obtaining PVA, it is preferable to produce the PVA by a method in which PVA and diketene are reacted. Furthermore, the method of reacting PVA and diketene is also preferred in that the amount of diketene used is small and the reaction yield of diketene is improved. Hereinafter, although the method to make this PVA and diketene react is demonstrated, it is not limited to this.

  As a method of reacting PVA and diketene, a method of directly reacting PVA with liquid or gaseous diketene, an organic acid is adsorbed and occluded in PVA in advance, and then liquid or gaseous diketene is reacted in an inert gas atmosphere. A method of spraying and reacting, a method of spraying and reacting a mixture of an organic acid and liquid diketene on PVA, and the like are used.

  When uniformly adsorbing and absorbing liquid diketene on the PVA by means such as spraying, it is preferable to continue stirring or fluidization for a predetermined time at 20 to 120 ° C. in an inert gas atmosphere. .

  Moreover, when making gaseous diketene react with PVA, contact temperature becomes like this. Preferably it is 30-250 degreeC, More preferably, you may be 50-200 degreeC. Although it is preferable that the diketene gas is brought into contact with the PVA at a temperature at which the diketene gas does not liquefy and the diketene partial pressure, it is not a problem that a part of the gas becomes droplets. The contact time may be appropriately selected from the range of 1 minute to 6 hours depending on the contact temperature, that is, it may be long when the temperature is low and short when the temperature is high. In the case of supplying diketene gas, diketene gas alone may be supplied, or a mixed gas of diketene gas and inert gas may be supplied. The temperature may be raised after the PVA absorbs the diketene gas, but it is preferable to contact the gas after the PVA is heated.

  In the method of reacting PVA and diketene using an organic acid, the organic acid is most preferably acetic acid, but propionic acid, butyric acid, isobutyric acid, and the like can also be used. The amount of the organic acid to be used is preferably an amount within the limit that can be adsorbed and occluded by the PVA in the reaction system, in other words, an amount that does not exist the organic acid separated from the PVA in the reaction system. Specifically, it is appropriate that 0.1 to 80 parts by weight, preferably 0.5 to 50 parts by weight, and particularly preferably 5 to 30 parts by weight of an organic acid coexist with 100 parts by weight of PVA. If the amount is less than 0.1 parts by weight, it is difficult to obtain the effect of the present invention. On the other hand, if the amount exceeds 80 parts by weight, a product having an excessive degree of organic acid and a non-uniform AA degree can be easily obtained. There is a tendency to increase.

  In order to uniformly adsorb and occlude the organic acid on the PVA, a method of spraying the organic acid alone on the PVA, a method of dissolving the organic acid in an appropriate solvent, and spraying it can be used.

  As the catalyst used for introducing the acetoacetate group, basic compounds such as sodium acetate, potassium acetate, primary amine, secondary amine and tertiary amine are effective. The amount of the catalyst may be smaller than that of a known reaction method, and is preferably 0.1 to 5.0% by weight with respect to PVA. Since PVA usually contains sodium acetate, there is often no need to add a catalyst. If the amount of catalyst is too large, side reaction of diketene is likely to occur, which is not preferable. In order to suppress the consumption of diketene due to moisture in PVA and improve the reaction rate of diketene, a small amount of acid anhydride such as acetic anhydride may be present.

  As a reaction apparatus for carrying out the AA conversion, an apparatus capable of heating and equipped with a stirrer is sufficient. For example, a kneader, a Henschel mixer, a ribbon blender, other blenders, and a stirring / drying apparatus can be used.

  When AA-PVA used in the present invention is fractionated into particle sizes of 44 to 74, 74 to 105, 105 to 177, 177 to 297, 297 to 500, and 500 to 1680 μm, the degree of acetoacetate esterification A value obtained by dividing the maximum value among them by the minimum value (AA degree distribution) is set to 1.0 to 3.0. This value is preferably 1.0 to 2.0, more preferably 1.0 to 1.5. When the AA degree distribution exceeds 3.0, when AA PVA is dissolved in water, a small amount of undissolved material is present, transparency is lowered, or when AA PVA is stored as an aqueous solution for a long period of time. Viscosity increases. Further, after the AA-PVA is stored as a powder for a long period of time, the viscosity when it is made into an aqueous solution becomes higher than the viscosity when the powder immediately after production is made into an aqueous solution, and the object of the present invention cannot be achieved.

  As described above, the AA degree distribution is obtained by separating AA PVA into particle sizes of 44 to 74, 74 to 105, 105 to 177, 177 to 297, 297 to 500, and 500 to 1680 μm, and then each AA. The degree of conversion is calculated from the amount of alkali consumed by neutralization titration, and is calculated by dividing the maximum value of AA degree by the minimum value. However, when the particle size distribution of the AA-PVA is narrow and falls within a specific particle size portion, and only a single AA degree value is calculated, the AA degree degree distribution is set to 1.0.

  Here, the particle size of 44 to 74 μm means a particle size screened by 350 mesh (44 μm) on a standard wire mesh and 200 mesh (74 μm) pass, and 74 to 105 μm means 200 mesh (74 μm). ) The particle size screened by the 145 mesh (105 μm) pass is 105 to 177 μm. The particle size screened by the 145 mesh (105 μm) on and 80 mesh (177 μm) pass is 177 to 297 μm is a particle size screened by 80 mesh (177 μm) on, 48 mesh (297 μm) pass, and 297-500 μm is 48 mesh (297 μm) on, screened by 32 mesh (500 μm) pass The particle size of 500-1680 μm is 32 mesh. Interview (500 [mu] m) on, means a particle size which is screened by 10.5 mesh (1680μm) pass.

  The method for obtaining AA-modified PVA having an AA-degree distribution as described above is not particularly limited. For example, a method for adjusting the swelling degree, particle size, etc. of PVA as a raw material to a specific range, Examples include a method of removing a particle size fraction having a high AA degree and a low particle size fraction, and a method of adjusting the average AA degree of AA PVA to a low level. It is practical to adjust the particle size.

  The AA degree is 0.01 to 1.5 mol%, preferably 0.05 to 1.0 mol%. When the AA degree is less than 0.01 mol%, the water resistance and mechanical strength of the emulsion are insufficient, which is not preferable. On the other hand, if it exceeds 1.5 mol%, the polymerization stability of the acrylic emulsion is insufficient, which is not preferable.

  Moreover, the block character [η] of AA-PVA needs to be 0.3 to 0.6, and it is difficult to industrially manufacture PVA having such a block character of less than 0.3. When the block character exceeds 0.6, emulsion polymerization stability and redispersibility are poor, and it is difficult to achieve the object of the present invention.

The block character [η] is a peak [(OH, OH) dyad = 46-49 ppm absorption, (OH, OR) dyad, based on the methylene carbon moiety found in the range of 40-49 ppm as measured by ¹³ C-NMR. = 43.5-45.5 ppm absorption, (OR, OR) dyad = 40-43 ppm absorption, where OR represents O-acetic acid group and / or O-acetoacetic acid group] It is a value calculated from the following formula.
[Η] = (OH, OR) / 2 (OH) (OR)
Here, (OH, OR), (OH), and (OR) are all calculated as mole fractions. Further, (OH) is the degree of saponification (molar fraction) calculated from the integral ratio of ¹³ C-NMR, and (OR) shows the molar fraction of acetic acid group and acetoacetic acid group at that time.

  The degree of saponification of AA-modified PVA is 97 to 100 mol%, preferably 97.5 to 99.5 mol%. If the degree of saponification is less than 97 mol%, the stability of the emulsion during polymerization is extremely lowered, making it difficult to obtain the desired aqueous emulsion.

In addition, the saponification degree of AA-ized PVA is calculated by the following formula.
Saponification degree of AA-PVA (mol%) =
100-Amount of residual acetate group (mol%)-Acetoacetate group amount (mol%)

  The aqueous emulsion of the present invention can be obtained by emulsion polymerization of an acrylic monomer in the presence of the AA-PVA.

  As acrylic monomers, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-methacrylic acid 2- Methacrylic acid esters such as ethylhexyl, dodecyl methacrylate, and octadecyl methacrylate, acrylic acid esters, methacrylic acid, and the like can be used. An acrylic monomer may be used independently and may be used in mixture of 2 or more types. Moreover, the following monomers can be used together in the range which does not inhibit the objective of this invention. Vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl versatate Dimers such as butadiene-1,3,2-methylbutadiene, 1,3 or 2,3-dimethylbutadiene-1,3, 2-chlorobutadiene-1,3; ethylene, propylene, 1 -Olefin monomers such as butene and isobutene; halogenated olefin monomers such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; methacrylamide, N-methylolacrylamide, N, N-dimethylacrylamide, Acrylamide-2-methylpropanesulfonic acid, diace Acrylamide monomers such as polyacrylamide; Nitrile monomers such as methacrylonitrile; Styrene monomers such as styrene and α-methylstyrene; Methyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl Vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, vinyl ether of stearyl vinyl ether; and allyl monomers such as allyl acetate and allyl chloride can be used. In addition, carboxyl group-containing compounds such as fumaric acid, maleic anhydride, itaconic anhydride, trimetic acid, and esters thereof; ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methyl Sulfonic acid group-containing compounds such as propanesulfonic acid; vinylsilane compounds such as vinyltrimethoxysilane; isopropenyl acetate, 3-methacrylamidopropyltrimethylammonium chloride, 3,4-diacetoxybutene, vinylethylene carbonate, etc. can also be used. .

Furthermore, as the monomer, in addition to the acrylic monomer, use of an acetoacetate group-containing ethylenically unsaturated monomer improves adhesion when using the resulting aqueous emulsion as an adhesive. Is preferable. The acetoacetate group-containing ethylenically unsaturated monomer may be produced by a known method, for example, by the following method.
(1) A diketene is reacted with a functional group-containing ethylenically unsaturated monomer such as a hydroxyl group, an amide group, a urethane group, an amino group, or a carboxyl group to produce an acetoacetate group-containing ethylenically unsaturated monomer. . As such a functional group-containing ethylenically unsaturated monomer, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, 2-hydroxy-3-chloropropyl acrylate, and the like can be used. The reaction can be carried out in the absence of a catalyst, but the reaction should be carried out in the presence of a tertiary amine, acid (such as sulfuric acid), basic salt (such as sodium acetate), or organometallic compound (such as dibutyltin laurate). You can also.
(2) The functional group-containing ethylenically unsaturated monomer and the acetoacetate are transesterified to produce an acetoacetate group-containing ethylenically unsaturated monomer. The reaction is preferably performed in the presence of a transesterification catalyst such as calcium acetate, zinc acetate or lead oxide.

  The glass transition temperature (Tg) of a polymer composed of an acrylic monomer and an acetoacetate group-containing ethylenically unsaturated monomer is preferably 10 to 80 ° C, more preferably 30 to 80 ° C. Preferably, it is 50-80 degreeC. When Tg is less than 10 ° C., the heat and pressure resistance and the adhesive strength when used as an adhesive are insufficient. On the other hand, if the Tg exceeds 80 ° C., the film forming property of the adhesive layer becomes unfavorable. When two or more monomers are used, it is preferable to adjust the composition ratio of the monomers so that the Tg of the copolymer falls within such a temperature range.

The Tg (° C.) of the copolymer obtained when two or more monomers are used can be calculated by the following equation. The following formula is such that when the total amount of the monomers X and Y is 100 mol%, the monomer X is x mol% and the monomer Y is y mol%. An example of the use is shown.
1 / (copolymer Tg + 273)
= (X / 100) × (1 / (Tg of homopolymer of monomer X + 273)
+ (Y / 100) × (1 / (Tg of homopolymer of monomer Y + 273)

  The aqueous emulsion of the present invention is prepared by adding an acrylic monomer temporarily or continuously in the presence of water, AA-PVA, and a polymerization initiator, followed by heating and stirring.

  The concentration of the acrylic monomer is preferably 10 to 70% by weight of the whole system, and more preferably 45 to 60% by weight. If the amount is less than 10% by weight, the industrial productivity is not met and the productivity is lowered. If the amount exceeds 70% by weight, the emulsion polymerization cannot proceed stably, and a good emulsion cannot be obtained.

  The amount of AA-modified PVA used varies slightly depending on the type and the resin content of the emulsion, but is usually preferably 0.1 to 30% by weight, and preferably 1 to 25% by weight based on the whole reaction system. More preferably, it is more preferably 2 to 20% by weight. If the blending amount is less than 0.1% by weight, it is difficult to maintain the polymer particles in a stable emulsified state. Conversely, if the blending amount exceeds 30% by weight, the emulsion viscosity will increase excessively and workability will decrease. Absent.

  As the polymerization initiator, potassium persulfate, ammonium persulfate, potassium bromate and the like are usually used alone or in combination with acidic sodium sulfite. Water-soluble redox polymerization initiators such as hydrogen peroxide-tartaric acid, hydrogen peroxide-iron salt, hydrogen peroxide-ascorbic acid-iron salt, hydrogen peroxide-longalit, hydrogen peroxide-longalit-iron salt Is also used. Specifically, a catalyst composed of an organic peroxide and a redox system such as “Kayabutyl B” (manufactured by Kayaku Akzo) or “Kayabutyl A-50C” (manufactured by Kayaku Akzo) can also be used. Among them, it is preferable to use a persulfate because the graft polymerization between the acrylic monomer and the AA-PVA is promoted and the polymerization stability is improved. Of the persulfates, ammonium persulfate is particularly preferred. The method for adding the polymerization initiator is not particularly limited, and a method of adding all at once in the initial stage, a method of adding continuously with the progress of polymerization, or the like can be employed.

  During polymerization, it is preferable to maintain the pH at 3.0 to 8.0 from the viewpoint of improving the polymerization stability of the emulsion. More preferably, it is pH 3.5-6.0, More preferably, it is pH 4.0-6.0. If the pH is less than 3.0, the polymerization stability of the emulsion becomes insufficient. On the other hand, when the pH is too high, the polymerization rate is extremely lowered, which is not preferable. In order to maintain the pH within the above range, it is preferable to add a buffer before and / or during the polymerization. When it is added during the polymerization, it may be added in portions or continuously. Although it does not specifically limit as a buffering agent, Sodium acetate, potassium acetate, sodium carbonate, sodium phosphate, etc. can be used. In particular, it is preferable to use an aqueous sodium acetate solution.

  Furthermore, it is preferable to add an iron compound to the emulsion polymerization system because the controllability of emulsion polymerization can be further improved, aggregation or the like hardly occurs during emulsion polymerization, and the polymerization stability is remarkably improved. The iron compound is not particularly limited, but at least one iron compound selected from iron oxide, ferrous chloride, ferrous sulfate, ferric chloride, ferric nitrate or ferric sulfate is preferably used. Among them, ferric chloride is particularly preferably used.

  The amount of the iron compound added is preferably 1 to 1000 ppm, more preferably 5 to 200 ppm, and particularly preferably 5 to 100 ppm based on the aqueous emulsion after emulsion polymerization. When the amount of iron compound added is less than 1 ppm, the effect of addition is poor. Conversely, when the amount exceeds 1000 ppm, the resulting emulsion and the film obtained from the emulsion may be colored. The water resistance tends to decrease, which is not preferable.

  The iron compound is preferably added before emulsion polymerization, but may be added during emulsion polymerization or at the end of emulsion polymerization.

  In the emulsion polymerization, a water-soluble polymer, a nonionic active agent, an anionic active agent, a cationic active agent, etc. can be used in combination as an emulsion dispersion stabilizer.

  Examples of water-soluble polymers include non-modified PVA other than AA-modified PVA, carboxyl group-containing PVA, PVA formalized product, acetalized product, butyralized product, urethanized product, esterified product with sulfonic acid, carboxylic acid, etc., vinyl Examples thereof include a saponified product of a copolymer of an ester and a monomer copolymerizable with a vinyl ester. Monomers copolymerizable with vinyl esters include olefins such as ethylene, butylene, isobutylene, α-octene, α-dodecene, α-octadecene, acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride , Unsaturated acids such as itaconic acid, salts thereof, mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide, diacetone acrylamide and methacrylamide, ethylene sulfonic acid, allyl sulfonic acid, meta Examples thereof include olefin sulfonic acids such as allyl sulfonic acid, or salts thereof, alkyl vinyl ethers, vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, and vinylidene chloride.

  In addition, cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxybutyl methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, aminomethyl hydroxypropyl cellulose, aminoethyl hydroxypropyl cellulose, starch, tragacanth, pectin, Glue, alginic acid or its salt, gelatin, polyvinylpyrrolidone, polyacrylic acid or its salt, polymethacrylic acid or its salt, polyacrylamide, polymethacrylamide, vinyl acetate and maleic acid, maleic anhydride, acrylic acid, methacrylic acid, itacone Copolymers of unsaturated acids such as acid, fumaric acid, crotonic acid, styrene and unsaturated acids Polymers, copolymers of vinyl ether and the unsaturated acid and the like salts or esters of the copolymer can also be used as a water-soluble polymer.

  Nonionic activators include, for example, polyoxyethylene-alkyl ether type, polyoxyethylene-alkylphenol type, polyoxyethylene-polyhydric alcohol ester type, ester of polyhydric alcohol and fatty acid, oxyethylene / oxypropylene block Examples include polymers.

  Examples of anionic activators include higher alcohol sulfates, higher fatty acid alkali salts, polyoxyethylene alkylphenol ether sulfates, alkylbenzene sulfonates, naphthalene sulfonate formalin condensates, alkyl diphenyl ether sulfonates, and dialkyl sulfosuccinates. And higher alcohol phosphoric acid ester salts.

  Examples of the cationic activator include higher alkylamine salts.

  Furthermore, in the emulsion polymerization, a plasticizer such as phthalate ester or phosphate ester, a pH adjuster such as sodium carbonate, sodium acetate, or sodium phosphate can be used in combination.

  The polymerization temperature is preferably 70 to 90 ° C, more preferably 75 to 85 ° C. If it is less than 70 degreeC, the graft polymerization of an acryl-type monomer and AA-ized PVA is not accelerated | stimulated, superposition | polymerization stability falls and it is unpreferable. If the temperature exceeds 90 ° C., the protective colloid of AA-PVA is deteriorated, and emulsion polymerization is difficult to proceed stably.

  The average particle diameter of the polymer particles is preferably 200 nm or more, and more preferably 300 nm or more. By adjusting the average particle diameter to 200 nm or more, an emulsion having a minimum film-forming temperature (MFT) of 10 ° C. or more is obtained, and mechanical stability is improved.

  The average particle diameter here is a number average particle diameter (Dn) measured under the following conditions using a dynamic light scattering photometer “DLS-700” manufactured by Otsuka Electronics Co., Ltd. and calculated by the histogram method. Point to.

(sample)
The emulsion is diluted with ion-exchanged water to a 0.05 wt% aqueous solution.
(Measurement condition)
The slit switching knob (Φ0.1 to Φ0.2) and the ND filter knob (ND50 to ND25) are adjusted so that the CPS value (light quantity) is 5000 to 12000, and measurement is performed under the following conditions.
SAMPLING TIME (reference clock): 40 μsec
ACUUM. TIME (number of integration): 100 times CORRE. CH (set value for converging the correlation function): 256

  Moreover, the powder excellent in redispersibility can be obtained by removing a water | moisture content from the aqueous emulsion of this invention. The method for removing water is not particularly limited, and spray drying, heat drying, blast drying, freeze drying, drying by pulse shock wave, drying by a belt press dehydrator, etc. can be used. Drying is preferably performed. For spray drying, a normal spray dryer for spraying and drying a liquid can be used. Depending on the type of spraying, there are a disk type and a nozzle type, and any type is used. Hot air or heated steam is used as the heat source.

  The spray drying conditions are appropriately selected depending on the size and type of the spray dryer, the emulsion concentration, the viscosity, the flow rate, and the like. The drying temperature is preferably 80 to 150 ° C, more preferably 100 to 140 ° C. When the drying temperature is less than 80 ° C., the film cannot be sufficiently dried. When the drying temperature exceeds 150 ° C., the polymer is deteriorated by heat.

  In addition, since the redispersible powder may be agglomerated and aggregated and blocked during storage, an anti-caking agent is preferably used in order to improve storage stability. The anti-caking agent may be added to the emulsion powder after spray drying and mixed uniformly. However, when the emulsion is spray-dried, the emulsion may be sprayed in the presence of the anti-caking agent. It is preferable from the point of being able to carry out, and the point of the caking prevention effect. It is particularly preferred to spray and dry both at the same time.

  As the anti-caking agent, fine inorganic powder is preferable, and examples thereof include calcium carbonate, clay, anhydrous silicic acid, aluminum silicate, white carbon, talc, and alumina white. In particular, silicic anhydride, aluminum silicate, calcium carbonate and the like having an average particle diameter of about 0.01 to 0.5 μm are preferable. Although the usage-amount of an anti-caking agent is not specifically limited, 2-20 weight% is preferable with respect to a powder.

  The aqueous emulsion and redispersible powder of the present invention are useful as paper processing agents, adhesives, paints, fiber processing agents, cosmetics, civil engineering and building materials, pressure-sensitive adhesives (pressure-sensitive adhesives), and in particular, cement and mortar. It is very useful as an admixture for woodworking and as an adhesive for woodworking.

  When the aqueous emulsion or redispersible powder of the present invention is used in an adhesive composition, the adhesive composition includes, in addition to the aqueous emulsion and redispersible powder, water-soluble polymers such as PVA, polyvalent isocyanate compounds, and the like. A crosslinking agent, water-proofing agent, pigment, dispersant, antifoaming agent, oil agent, viscosity modifier, tackifier, thickener, water retention agent and the like can be contained. Among these, a crosslinking agent is particularly important. Examples of the crosslinking agent include melamine, acetoguanamine, benzoguanamine, urea, alkylated methylolurea, alkylated methylolmelamine, acetoguanamine, a condensate of benzoguanamine and formaldehyde, diethylenetriamine, and triethylene. Amines such as tetramine, tetraethylenepentamine, trimethylhexamethylenediamine, polyetherdiamine, and other aliphatic amines, metaxylenediamine, aromatic amines such as diaminodiphenylmethane, amine adducts, and modified amines such as polyamidoamine; formaldehyde, acetaldehyde , Monoaldehydes such as propionaldehyde, butyraldehyde, glyoxal, glutandialdehyde, malondialdehyde, succi Aldehydes such as dialdehydes such as dialdehyde, maleidialdehyde, phthaldialdehyde; hydrazine, hydrazine hydrard, hydrazine hydrochloride, sulfuric acid, nitric acid, nitrous acid, phosphoric acid, thiocyanic acid, carbonic acid and other inorganic salts and formic acid, Organic salts such as oxalic acid, monosubstituted hydrazine such as methyl, ethyl, propyl, butyl and allyl, asymmetric disubstituted such as 1,1-dimethyl, 1,1-diethyl and 4-n-butyl-metal, And hydrazine compounds such as symmetric disubstituted compounds such as 1,2-dimethyl, 1,2-diethyl and 1,2-diisopropyl; polymers composed of monomers such as vinylformamide, N-allylformamide, acrylformamide, or the like Monomer, vinyl acetate, styrene, methyl (meth) acrylate Formamide group-containing compounds such as copolymers with tolylene diisocyanate, hydrogenated tolylene diisocyanate, adducts of trimethylolpropane-tolylene diisocyanate, triphenylmethane triisocyanate, methylene bis-4-phenylmethane triisocyanate, methylene bis Isocyanate compounds such as isophorone diisocyanate, methylene bis-4-phenylmethane triisocyanate, ketoxime block product of methylene bisisophorone diisocyanate; aluminum acetate, copper acetate, aluminum chloride, copper chloride, lead chloride, cobalt chloride, iron (III) chloride, Examples thereof include polyvalent metal ions such as aluminum sulfate and iron (III) sulfate. In addition, a compound containing a zirconyl-based compound such as basic zirconyl chloride or zirconyl ammonium carbonate, a titanium tetrachloride, a methylol group, or an alkoxymethyl group-containing compound can also be used.

  For example, when an aqueous emulsion is used, the aqueous emulsion is preferably contained in an adhesive composition containing a crosslinking agent or the like in an amount of 10 to 98% by weight, more preferably 40 to 90% by weight. If it is less than 10% by weight, the adhesive strength is lowered and the drying time is prolonged, which is not preferable. If it exceeds 98% by weight, workability may be deteriorated or a predetermined adhesive strength may not be obtained.

  The adhesive composition of the present invention can be used for corrugated cardboard, interleaf paper, paper tube, wood, plywood, structural veneer laminate (LVL), particle board, laminated wood, fiberboard, etc. It can be used as an agent. In particular, in the particle board obtained by applying an adhesive made of a thermosetting resin such as urea resin or melamine resin as a woodworking adhesive to a piece of wood (chip), forming it into a plate shape, and hot pressing molding, Although VOC problems such as acetaldehyde and formalin have become particularly obvious and become a social problem, the use of the adhesive composition of the present invention as an adhesive for the application does not cause such a problem. Very useful in terms.

  The particle board using the adhesive composition of the present invention as an adhesive is obtained by applying the main agent composed of the aqueous emulsion and cross-linking agent of the present invention or the main component composed of the redispersible powder, cross-linking agent and water of the present invention to a piece of wood. It is manufactured by forming and hot pressing.

When the aqueous emulsion or redispersible powder of the present invention is used as the main agent, the amount of formaldehyde released from the particle board is remarkably reduced to a level of E ₀ type (0.5 mg / l) or less stipulated in JIS A5908. In addition to being able to suppress, the adhesion performance can be maintained at a high level that clears the P type, and the adhesion durability can be improved.

  When the adhesive of the present invention is used for the production of particle board, an appropriate amount of a wax emulsion for imparting water resistance may be added in addition to the main component adhesive component. In the manufacturing process, as the adhesive, MDI may be used for the core layer, and the adhesive of the present invention may be used for the front and back layers. When MDI is used for the front and back layers, not only does the MDI stick to the hot plate in hot pressing, but the workability is impaired, and the surface properties of the particle board are impaired, so the adhesive of the present invention is used as the adhesive for the front and back layers. Embodiments are preferred.

  The fiber board (fiber board) using the adhesive of the present invention is a generic term for plate-like products molded from wood fibers as the main raw material, and insulation board (soft fiber board, IB) depending on the density of the board. , Medium density fiberboard (medium fiberboard, MDF) and hardboard (hard fiberboard, HB).

  Fiber is made by mechanically defibrating chips cooked under high temperature and pressure with a refiner. There are a wet method and a dry method for producing fiberboard, and the wet method is a method using a large amount of water as a medium from defibration to forming.

  The adhesive of the present invention can be used for any fiber board of IB, MDF, and HB, but is particularly preferably used in MDF and HB, and more preferably used in MDF.

MDF is mainly manufactured by a dry method. The adhesive of the present invention is added to the dried fiber to make a mat, and hot pressed to obtain a board having a density of 0.35 to 0.80 g / cm ³ . For example, when the aqueous emulsion of this invention is contained in the adhesive agent to be used, the density | concentration of the aqueous emulsion in an adhesive agent becomes like this. Preferably it is 10 to 98 weight%, More preferably, it is 40 to 98 weight%. If it is less than 10% by weight, the adhesive strength is lowered, which is not preferable. If it exceeds 98% by weight, workability may be deteriorated or a predetermined adhesive strength may not be obtained. Moreover, the addition amount of the adhesive of this invention is 4 to 20 weight% with respect to a fiber, Preferably, it is 6 to 15 weight%.

  The fiber is dried while being blown at a low temperature with a flash dryer. There are a method of adding an adhesive immediately before drying (blow-in method) and a method of adding with a blender after drying. In the blow-in method, after the fiber made by the refiner enters the small-diameter high-pressure pipe and then enters the large-diameter pipe of the dryer, the pressure suddenly drops, and the fiber is turbulent at the outlet. This is a method in which an adhesive is evenly applied to the fiber by utilizing the scattering effect. If the temperature is increased and drying is attempted in a short time, there are problems such as pre-curing of the adhesive and lower tack as compared with mechanical blending.

  The board side surface of the MDF obtained using the adhesive of the present invention is dense and perpendicular to the surface, and the surface is smooth and has good workability and printability. Used for furniture, cabinets, building foundations (floors, interior walls, roofs) and construction parts.

  Further, the core layer may be used as strand particles in which fibers are deposited on the front and back layers and simultaneously pressed using a vapor jet press.

  The adhesive of the present invention can also be used for the production of plywood.

  As a plywood, a three-ply plywood obtained by polymerizing three face materials is known as a building material. A three-ply plywood using the adhesive of the present invention can be produced by a method similar to the conventional method. That is, the adhesive of the present invention is applied to both surfaces of the intermediate surface material, and a surface material having the same size as the intermediate surface material is superposed on the front and back surfaces of the surface material. A predetermined number of sheets (100 to 150 sheets) are superposed and pressure is applied by a cold press apparatus at room temperature to allow the adhesive to become familiar (cold pressing step). Thereafter, the plywood is taken out one by one, and the plywood is heated and heated by a hot press device, and the plywood is pressed and fixed (hot press process). For example, when the aqueous emulsion of the present invention is contained in the adhesive, the concentration of the aqueous emulsion in the adhesive is preferably 30 to 80%, more preferably 40 to 75%. If it is less than 10%, the adhesive strength decreases, which is not preferable. If it exceeds 80% by weight, workability may be deteriorated or a predetermined adhesive strength may not be obtained.

  When using the aqueous emulsion or redispersible powder of the present invention as an admixture for cement or mortar, for example, when using a redispersible powder, considering the physical properties of the resulting cured product, 100 parts by weight of cement or mortar The amount is preferably 5 to 30 parts by weight, and more preferably 10 to 30 parts by weight. Considering an economical aspect, 5 to 15 parts by weight is preferable, and 8 to 12 parts by weight is more preferable.

  As a method of mixing an aqueous emulsion and redispersible powder into cement or mortar, a method of mixing (compounding) with cement or mortar in advance, a method of mixing (compounding) with water in advance, cement or mortar, water, And a method of mixing the aqueous emulsion and the redispersible powder at the same time.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In the examples and comparative examples, “parts” represent “parts by weight”.

Production Example 1: Production of AA PVA (a) PVA (degree of saponification 99.5 mol%, degree of polymerization 1280) was heat-treated at 80 ° C for 60 minutes at the time of drying in the final step of production, particle size 63 to 1680 μm, A PVA powder having a swelling degree of 3.5 and an elution rate of 12.1% by weight was obtained. Using the obtained PVA powder as a raw material, 444 parts were charged into a kneader having an internal volume of 7 l, and 100 parts of acetic acid was added thereto to swell. While stirring at a rotation speed of 20 rpm, the temperature was raised to 60 ° C., and then a mixed solution of 8 parts of diketene and 32 parts of acetic acid was added dropwise over 4 hours, and the mixture was further reacted for 30 minutes. After completion of the reaction, the mixture was washed with 500 parts of methanol and then dried at 70 ° C. for 6 hours to obtain AA-modified PVA (a) having a degree of AA conversion of 0.50 mol% (diketene conversion: 50 mol%). From the obtained AA-modified PVA, 6 types of fractions were taken out using 7 types of sieves, and the AA conversion was measured.
44-74 μm: 0.58 mol%,
74 to 105 μm: 0.56 mol%,
105-177 μm: 0.53 mol%,
177-297 μm: 0.50 mol%,
297-500 μm: 0.47 mol%,
500 to 1680 μm: 0.42 mol%
Met. The AA degree distribution (maximum AA degree / lowest AA degree) was 1.4, the block character [η] was 0.55, and the saponification degree was 99.0 mol%.

Production Example 2: Production of AA-modified PVA (b) PVA (degree of saponification 98.0 mol%, degree of polymerization 1280) was heat-treated at 80 ° C. for 60 minutes during the final step of production to produce a particle size of 63 to 1680 μm. A PVA powder having a swelling degree of 3.5 and an elution rate of 12.1% by weight was obtained. Except using this PVA powder, it operated similarly to manufacture example 1, and obtained AA-ized PVA (b) of AA degree of 0.50 mol% (diketene conversion rate 50 mol%). AA conversion is
44-74 μm: 0.58 mol%,
74 to 105 μm: 0.55 mol%,
105-177 μm: 0.52 mol%,
177 to 297 μm: 0.49 mol%,
297-500 μm: 0.46 mol%,
500 to 1680 μm: 0.42 mol%
Met. Further, the AA degree distribution (maximum AA degree / lowest AA degree) was 1.4, the block character [η] was 0.54, and the saponification degree was 97.5 mol%.

Production Example 3: Production of AA-modified PVA (c) PVA (degree of saponification 99.0 mol%, degree of polymerization 1280) was subjected to a heat treatment at 105 ° C for 120 minutes during the final step of production to produce a particle size of 63 to 1680 µm, A PVA powder having a swelling degree of 0.8 and an elution rate of 2.7% by weight was obtained. Except using this PVA powder, it operated similarly to manufacture example 1, and obtained AA-ized PVA (c) of AA degree of conversion 0.45 mol% (diketene conversion 45 mol%). AA conversion is
44-74 μm: 0.77 mol%,
74 to 105 μm: 0.62 mol%,
105-177 μm: 0.52 mol%,
177-297 μm: 0.40 mol%,
297 to 500 μm: 0.29 mol%,
500-1680 μm: 0.18 mol%
Met. The AA degree distribution (maximum AA degree / lowest AA degree) was 4.3, the block character [η] was 0.54, and the saponification degree was 98.5 mol%.

Production Example 4: Production of AA-modified PVA (d) 100 parts of a methanol solution of polyvinyl acetate obtained by solution polymerization (average polymerization degree 1440: measured according to JIS K6726 after complete saponification of polyvinyl acetate) A kneader equipped with a cooler was charged, the temperature was raised, and when refluxing began, 0.5 part of sulfuric acid was charged as a catalyst and saponification was carried out for 17 hours. Thereafter, neutralization with sodium hydroxide was performed to stop saponification, washing was repeated with methanol, and then dried to obtain PVA having a saponification degree of 96.0 mol% (residual acetate group 4.0 mol%). It was.

During the final drying process of the PVA production, heat treatment was performed at 80 ° C. for 60 minutes to obtain a PVA powder having a particle size of 63 to 1680 μm, a swelling degree of 3.8, and an elution rate of 14.0%. Except using this PVA powder, it operated similarly to manufacture example 1, and obtained AA-ized PVA (d) of AA degree of 0.50 mol% (diketene conversion rate 50 mol%). AA conversion is
44-74 μm: 0.72 mol%,
74 to 105 μm: 0.66 mol%,
105 to 177 μm: 0.51 mol%,
177 to 297 μm: 0.47 mol%,
297 to 500 μm: 0.44 mol%,
500-1680 μm: 0.40 mol%
Met. The AA degree distribution (maximum AA degree / lowest AA degree) was 1.8, the block character [η] was 0.80, and the saponification degree was 95.5 mol%.

Production Example 5: Production of acetoacetate group-containing ethylenically unsaturated monomer 150 parts of 2-hydroxyethyl methacrylate was added, 0.05 part of triethylamine was added as a catalyst for the diketene addition reaction, and the temperature was raised to 60 ° C. 96.9 parts (equivalent to 2-hydroxyethyl methacrylate) was added dropwise with stirring over 2 hours. The reaction was further continued for 5 hours to acetoacetate the hydroxyl group of 2-hydroxyethyl methacrylate to obtain acetoacetate 2-hydroxyethyl methacrylate in which all of the hydroxyl groups of 2-hydroxyethyl methacrylate were acetoacetate. It was.

Example 1
In a separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer, 80 parts of water, 10 parts of AA-PVA (a), 0.02 part of sodium acetate as a pH adjuster, ferric chloride as an iron compound 0.002 part (10 ppm with respect to the aqueous emulsion after emulsion polymerization), monomer (methyl methacrylate / n-butyl acrylate = 80/20 (weight ratio)), Tg of homopolymer of methyl methacrylate is 105 And when the Tg of the homopolymer of n-butyl acrylate is −54 ° C., 10 parts of the obtained copolymer is calculated, and the temperature in the flask is adjusted to 60 ° C. while stirring. Raised. Meanwhile, while replacing the inside of the flask with nitrogen gas, 5 parts of a 1% by weight aqueous ammonium persulfate solution was added to initiate polymerization. The pH in the system before the start of polymerization was 5.8. After initial polymerization for 30 minutes, the remaining 90 parts of the monomer was added dropwise over 4 hours, and 1 part of a 5% by weight aqueous ammonium persulfate solution was added 5 times every hour for polymerization. Simultaneously with the aqueous ammonium persulfate solution, 1 part of a 5 wt% aqueous sodium acetate solution was added 5 times every hour. Then, after aging at 75 ° C. for 1 hour, the mixture was cooled to obtain an emulsion I of a methyl methacrylate / n-butyl acrylate copolymer having a solid content of 55% by weight. The pH in the system during the polymerization was maintained in the range of 4.2 to 5.8, and the pH of the finally obtained emulsion I was 4.8.

  About the obtained emulsion I, the coarse particle amount and the thickening ratio were evaluated as follows.

(Rough particle amount)
The resulting aqueous emulsion is diluted with water, filtered through a 100 mesh wire mesh, the resin content remaining on the wire mesh is dried at 105 ° C. for 3 hours, the weight of the resin content is measured, and the following equation is obtained.
Coarse particle amount (% by weight) = (weight of dry resin on wire mesh / solid weight of emulsion) × 100

(Thickening ratio)
The obtained aqueous emulsion was stored at 25 ° C., and the change in viscosity was measured with a BROOKFIELD type viscosity system (rotor No. 4, rotation speed: 10, 25 ° C.), and obtained from the following formula.
Thickening ratio = viscosity of emulsion after 30 days storage at 25 ° C./viscosity of emulsion immediately after polymerization

  The obtained aqueous emulsion I had a coarse particle amount of 0.0005% by weight and a thickening ratio of 1.02.

  5 wt% of silicic acid fine powder (anti-caking agent) was added to the solid content of the aqueous emulsion I and spray-dried in hot air at 120 ° C. to obtain a redispersible powder i.

  Regarding the aqueous emulsion I, the wood adhesion performance was evaluated as follows. The results are shown in Table 4.

(Wood adhesion performance)
5 parts of an isocyanate compound (MDI, isocyanate group amount: 6.71 × 10 ⁻³ mol / g) was added to 100 parts of the emulsion to obtain an adhesive composition. A hip wrap material (Betula Maximowicziana REGAL, average air dry specific gravity 0.70, moisture content 9% by weight) was used as a test material, and a single lap tensile shear type test piece was prepared. The applied amount was 280 g / m ² , the pressing pressure was 1 MPa, the pressing was performed at 20 ° C. for one day, and then the pressure was released. Thereafter, heating treatment was performed at 20 ° C. for 7 days and at 120 ° C. for 2 hours. The adhesion test was carried out at a load rate of 10 mm / min after being immersed in water at 20 ° C. for one day under normal conditions. The test was performed 5 times and the average value was taken.

  Further, the redispersible powder i was evaluated for miscibility with mortar as follows. The results are shown in Table 5.

(Mortar mixing test)
In accordance with JIS A-6203, a polymer cement mortar was produced by mechanical kneading. The mixing ratio of mortar was set to normal Portland cement / Toyoura quartz sand / redispersible powder / water = 500/1500/50/375 (weight ratio). The slump value immediately after mechanical kneading and the change in the slump value after the mortar was stored at 25 ° C. for 30 minutes were evaluated as the fluidity of the mortar. When the value is small, the fluidity is deteriorated and the workability is deteriorated.

Example 2
The monomer composition was methyl methacrylate / n-butyl acrylate / acetoacetylated 2-hydroxyethyl methacrylate = 64/16/20 (weight ratio) (acetylated 2-hydroxyethyl methacrylate homopolymer Tg 55 When the temperature was set to ° C., the same operation as in Example 1 was carried out except that the calculated copolymer Tg was adjusted to 57 ° C., and methyl methacrylate / n-butyl acrylate having a solid content of 55% by weight. / Emulsion II of acetoacetylated 2-hydroxyethyl methacrylate copolymer was obtained. The obtained emulsion II had a pH of 4.8, a coarse particle amount of 0.001% by weight, and a thickening ratio of 1.1. Redispersible powder ii was prepared in the same manner as in Example 1, and the wood adhesion performance of aqueous emulsion II and the miscibility of redispersible powder ii with mortar were evaluated. The results are shown in Tables 4 and 5.

Example 3
Except for using AA-modified PVA (b), the same operation as in Example 1 was performed to obtain an emulsion III of a methyl methacrylate / n-butyl acrylate copolymer having a solid content of 55% by weight. The pH of Emulsion III was 4.8, the amount of coarse particles was 0.0005% by weight, and the thickening ratio was 1.02. Redispersible powder iii was prepared in the same manner as in Example 1, and the wood adhesion performance of aqueous emulsion III and the miscibility of redispersible powder iii with mortar were evaluated. The results are shown in Tables 4 and 5.

Example 4
Except that no ferric chloride was added, the same operation as in Example 1 was performed to obtain an emulsion IV of a methyl methacrylate / n-butyl acrylate copolymer having a solid content of 55% by weight. The pH of Emulsion IV was 4.8, the amount of coarse particles was 0.002% by weight, and the thickening ratio was 1.1. Redispersible powder iv was prepared in the same manner as in Example 1, and the wood adhesion performance of aqueous emulsion IV and the miscibility of redispersible powder iv with mortar were evaluated. The results are shown in Tables 4 and 5.

Comparative Example 1
Except for using AA-modified PVA (c), the same operation as in Example 1 was performed to obtain an emulsion X of a methyl methacrylate / n-butyl acrylate copolymer having a solid content of 55% by weight. The pH of the emulsion X was 4.8, the amount of coarse particles was 0.85% by weight, and the thickening ratio was 5.5. A redispersible powder x was prepared in the same manner as in Example 1, and the wood emulsion performance of the aqueous emulsion X and the miscibility of the redispersible powder x with a mortar were evaluated. The results are shown in Tables 4 and 5.

Comparative Example 2
The same as Comparative Example 1 except that the polymerization monomer composition was adjusted to methyl methacrylate / n-butyl acrylate = 45/55 (weight ratio) (calculated Tg of the resulting copolymer was −3 ° C.). Operation was performed to obtain an emulsion Y of a methyl methacrylate / n-butyl acrylate copolymer having a solid content of 55% by weight. The pH of Emulsion Y was 4.8, the amount of coarse particles was 1.05% by weight, and the thickening ratio was 6.0. A redispersible powder y was prepared in the same manner as in Example 1, and the wood emulsion performance of the aqueous emulsion Y and the miscibility of the redispersible powder y with a mortar were evaluated. The results are shown in Tables 4 and 5.

Comparative Example 3
Except for using AA-modified PVA (d), the same operation as in Example 1 was performed to obtain an emulsion Z of a methyl methacrylate / n-butyl acrylate copolymer having a solid content of 55% by weight. The pH of emulsion Z was 4.8, the amount of coarse particles was 0.55% by weight, and the thickening ratio was 3.8. The redispersible powder z was prepared in the same manner as in Example 1, and the wood emulsion performance of the aqueous emulsion Z and the miscibility of the redispersible powder z with the mortar were evaluated. The results are shown in Tables 4 and 5.

Example 5
An adhesive comprising aqueous emulsion II (100 parts) prepared in Example 2, 10 parts of an isocyanate compound (MDI, isocyanate group amount: 6.71 × 10 ⁻³ mol / g) and 2 parts of a wax emulsion was prepared. It apply | coated so that it might become the following ratios per particle board of 3'x6 'size. That is, it was applied to a piece of wood (chip) so that the surface layer of the particle board was 30 to 32 parts by weight with respect to 100 parts by weight of the piece of wood, and the part to be the core layer was 15 to 16 parts by weight. Thereafter, hot pressing (temperature: 160 to 170 ° C., time: 8 to 10 minutes, pressure: 30 to 31 kgf / cm ² ) was performed by hot pressing to obtain a particle board. Emission of formaldehyde from particle board is definitely clear levels E ₀ type, adhesion performance was also cleared levels of P-type.

Example 6
An adhesive comprising aqueous emulsion II (100 parts) prepared in Example 2, 10 parts of an isocyanate compound (MDI, isocyanate group amount: 6.71 × 10 ⁻³ mol / g) and 2 parts of a wax emulsion was prepared. It apply | coated as an adhesive for front and back layers so that it might become the following ratios per particle board of 3'x6 'size. In addition, an isocyanate compound (MDI, isocyanate group amount: 6.71 × 10 ⁻³ mol / g) was used as an adhesive for the core layer. That is, the surface layer of the particle board is applied to 1500 parts by weight of wood chips at a ratio of 30 to 32 parts by weight with respect to 100 parts by weight of the chip (chip), and the part of the particle board is 100 pieces of wood. After applying and forming to 1800 parts by weight of the wood chip for core layer at a ratio of 8 parts by weight with respect to parts by weight, hot pressing (temperature: 160 to 170 ° C., time: 8 to 10 minutes, pressure: 30) A particle board was obtained by hot-press molding at ˜31 kgf / cm ² ). Emission of formaldehyde from particle board is definitely clear levels E ₀ type, adhesion performance was also cleared levels of P-type.

Example 7
An adhesive comprising aqueous emulsion II (100 parts) prepared in Example 2, 10 parts of an isocyanate compound (MDI, isocyanate group amount: 6.71 × 10 ⁻³ mol / g) and 2 parts of a wax emulsion was prepared. The adhesive was applied to the following ratio per 3 ′ × 6 ′ size MDF. That is, in the dried fiber, the surface layer is 9 to 12 parts by weight with respect to 100 parts by weight of the fiber, and the core layer is 6 to 9 parts with respect to 100 parts by weight of the fiber. Was applied to form a mat, and hot pressed (temperature: 160 to 170 ° C., time: 8 to 10 minutes, pressure: 50 kgf / cm ² ) to obtain MDF. The amount of formaldehyde released from the MDF reliably cleared the level of the E ₀ type, and the adhesion performance also cleared the level of the P type.

Example 8
An adhesive comprising aqueous emulsion II (100 parts) prepared in Example 2, 10 parts of an isocyanate compound (MDI, isocyanate group amount: 6.71 × 10 ⁻³ mol / g) and 2 parts of a wax emulsion was prepared. It apply | coated as an adhesive for front and back layers so that it might become the following ratios per MDF of 3'x6 'size. In addition, an isocyanate compound (MDI, isocyanate group amount: 6.71 × 10 ⁻³ mol / g) was used as an adhesive for the core layer. That is, the surface layer of the MDF is applied to 1500 parts by weight of the fiber at a ratio of 9 to 12 parts with respect to 100 parts by weight of the fiber, and the part to be the core layer is based on 100 parts by weight of the fiber. After coating and forming on 1800 parts by weight of the core layer fiber at a ratio of 8 parts by weight, heat is applied with a hot press (temperature: 160 to 170 ° C., time: 8 to 10 minutes, pressure: 50 kgf / cm ² ). The MDF was obtained by press molding. The amount of formaldehyde released from the MDF reliably cleared the level of the E ₀ type, and the adhesion performance also cleared the level of the P type.

Claims (11)

An aqueous emulsion of a polymer obtained by polymerizing an acrylic monomer in the presence of acetoacetate group-containing polyvinyl alcohol, wherein the block character [η] of the acetoacetate group-containing polyvinyl alcohol is 0. 3 to 0.6, saponification degree is 97 mol% or more, acetoacetic acid esterification degree is 0.01 to 1.5 mol%, and 44 to 74, 74 to 105, 105 to 177, 177 to 297, A value obtained by dividing the maximum value of the average degree of acetoacetate esterification of each of the acetoacetate group-containing polyvinyl alcohols divided into particle sizes of 297 to 500 and 500 to 1680 μm by the minimum value is 1.0 to 3.0. Is an aqueous emulsion. The aqueous emulsion according to claim 1, wherein the polymer is produced by polymerizing an acrylic monomer at a pH of 3 to 8. The aqueous emulsion according to claim 1 or 2, wherein the polymer is produced by polymerizing an acrylic monomer using persulfate as a polymerization initiator. The aqueous emulsion according to claim 1, 2 or 3, wherein the polymer has a glass transition temperature of 10 to 80 ° C. The aqueous emulsion according to claim 1, 2, 3 or 4, wherein the polymer is produced by copolymerizing an acrylic monomer and an acetoacetic acid group-containing ethylenically unsaturated monomer. The aqueous emulsion according to claim 1, 2, 3, 4, or 5 containing 1 to 1000 ppm of an iron compound. An adhesive composition comprising the aqueous emulsion according to claim 1, 2, 3, 4, 5 or 6. The adhesive composition of Claim 7 containing an isocyanate type crosslinking agent. An adhesive for particle board comprising the adhesive composition according to claim 7 or 8. An adhesive for medium-sized fiberboard comprising the adhesive composition according to claim 7 or 8. A powder obtained from the aqueous emulsion according to claim 1, 2, 3, 4, 5 or 6.