WO2017104671A1 - Method for producing aqueous synthetic resin emulsion, method for producing reemulsifiable synthetic resin powder, method for producing polymer cement mortar, aqueous synthetic resin emulsion, and reemulsifiable synthetic resin powder - Google Patents

Abstract

Provided is a method for producing an aqueous synthetic resin emulsion having a high solids fraction concentration and low viscosity with which it is possible to obtain a reemulsifiable synthetic resin powder having excellent workability after reemulsification. A method for producing an aqueous synthetic resin emulsion for emulsion polymerizing a polymerization component [1] in the presence of a polyvinyl alcohol resin, wherein the method for producing an aqueous synthetic resin emulsion contains a hydrophobic monomer having a solubility in 20°C water of 0.1% or less in a quantity of 30 wt% or more relative to the entire polymerization component [1] and conducts emulsion polymerization while continuously adding the total amount of polymerization component [1] in an aqueous medium.

Description

Method for producing aqueous synthetic resin emulsion, method for producing re-emulsifiable synthetic resin powder, method for producing polymer cement mortar, aqueous synthetic resin emulsion and re-emulsifiable synthetic resin powder

The present invention relates to a method for producing an aqueous synthetic resin emulsion, a method for producing a re-emulsifiable synthetic resin powder, a method for producing a polymer cement mortar, an aqueous synthetic resin emulsion and a re-emulsifiable synthetic resin powder. Aqueous synthetic resin emulsion suitable for production of emulsifiable synthetic resin powder and suitable for mixing with cement to form polymer cement, re-emulsifiable synthetic resin powder obtained by pulverizing the same, production method thereof, and polymer The present invention relates to a method for producing cement mortar.

Conventionally, a general re-emulsifiable synthetic resin powder obtained by spray-drying an emulsion containing water is easier to handle and transport than an emulsion containing water, with no risk of freezing. It is used in various applications. For example, it is effectively used as mortar or concrete by mixing with cement to form polymer cement. In particular, since re-emulsifiable synthetic resin powder is a powder, it can be premixed, and can be pre-mixed with cement etc. at an optimal mixing ratio in advance, and immediately without mixing with cement at the construction site. Widely used because it can be used.

For example, in the following Patent Document 1, a polyvinyl alcohol resin [I] having a specific structure includes at least one monomer (A) of an acrylic monomer and a styrene monomer and a specific functional group-containing monomer (B). Disclosed are an aqueous synthetic resin emulsion for cement mortar admixture, in which a synthetic resin as a copolymer component is dispersed and stabilized, and a re-emulsifiable aqueous synthetic resin emulsion powder for cement mortar admixture obtained by drying the emulsion. In addition, it is described that when these are used as a cement mortar admixture, good fluidity and workability are exhibited, there is little variation in physical properties, and adhesion strength is improved.
Patent Document 2 listed below discloses a re-emulsifiable synthetic resin powder for polymer cement containing a re-emulsifiable synthetic resin powder (A) containing a synthetic resin having a specific glass transition temperature and inorganic fine particles (B) containing silicon. A composition and a polymer cement mortar using the composition are disclosed, and the anti-blocking property of the re-emulsifiable synthetic resin powder and the strength, elongation, and fluidity after cement mixing are excellent in a good balance. Are listed.

JP 2009-35470 A JP 2014-15386 A

However, in Patent Document 1 and Patent Document 2, since the initial polymerization in which a part of the monomer component is previously polymerized is performed in the emulsion polymerization step, the average particle diameter of the resin particles becomes relatively small. There was a tendency for the viscosity of the resulting aqueous synthetic resin emulsion to increase. If the aqueous synthetic resin emulsion has a high viscosity, spray clogging tends to cause clogging of the spray, and uniform spray spraying is difficult, which makes stable production difficult. On the other hand, when the viscosity is lowered by diluting with water so as to be suitable for spraying, the solid content concentration of the sprayed droplets is lowered, so that there is a problem that energy efficiency is deteriorated such as raising the drying temperature.

In addition, re-emulsifiable synthetic resin powder obtained by pulverizing a high-viscosity aqueous synthetic resin emulsion tends to increase in viscosity even when re-dispersed in water. The resulting polymer cement mortar has a high slurry viscosity, resulting in problems such as poor coating properties and poor coating appearance. Although it is possible to adjust the fluidity of the mortar by adding water with emphasis on workability, there is a concern that the performance (bending strength, compressive strength, adhesion strength, etc.) of the polymer cement mortar will be insufficient. there were.

The present invention has been made in view of the above circumstances, and since it has a high solid content concentration and a low viscosity, an aqueous synthetic resin emulsion capable of obtaining an emulsion powder excellent in workability after re-emulsification with high production efficiency. It is an object of the present invention to provide a method for producing a re-emulsifiable synthetic resin powder and a method for producing a polymer cement mortar.

However, as a result of repeated earnest studies in view of such circumstances, the present inventors have used a large amount of hydrophobic monomer in a method for producing an aqueous synthetic resin emulsion in which a polymerization component is emulsion-polymerized in the presence of a polyvinyl alcohol-based resin. By carrying out emulsion polymerization while continuously adding the entire amount of the polymerization components to the aqueous medium without performing initial polymerization, an aqueous synthetic resin emulsion having a high solid content concentration and a low viscosity can be obtained. The inventors have found that a re-emulsifiable synthetic resin powder can be efficiently produced, and completed the present invention.

In general, in emulsion polymerization, it is preferable to perform initial polymerization in which a part of a polymerization component is preliminarily performed from the viewpoint of promoting reaction while growing particles and easily controlling reaction heat. In this method, the initial polymerization is not carried out and the whole amount of the components is continuously added.
In the case of initial polymerization, a fine “seed particle” is formed by polymerizing a part of the polymerization component, and the resin particle grows based on this, so that the particle diameter of the obtained resin particle is In contrast with the seed particles produced in the present invention, the polymerization component is continuously added without performing the initial polymerization as described above, while the viscosity of the emulsion is increased relatively. Since droplets containing a sufficiently large polymerization component (preferably a pre-emulsion formed by pre-emulsifying the polymerization component) itself undergo a polymerization reaction to form resin particles, the resulting resin particles have a relatively large particle size. It is assumed that the viscosity of the emulsion can be lowered.

That is, the gist of the present invention is a method for producing an aqueous synthetic resin emulsion in which a polymerization component is emulsion-polymerized in the presence of a polyvinyl alcohol-based resin, and the hydrophobic monomer has a solubility in water at 20 ° C. of 0.1% or less. In an aqueous synthetic resin emulsion, wherein the emulsion polymerization is carried out while continuously adding the entire amount of the polymerization component to an aqueous medium. is there.

The present invention also provides a method for producing a re-emulsifiable synthetic resin powder obtained by drying the aqueous synthetic resin emulsion, a method for producing a polymer cement mortar characterized by using these, and further an aqueous synthetic resin emulsion, It also relates to emulsifying synthetic resin powder.

According to the method for producing an aqueous synthetic resin emulsion of the present invention, an aqueous synthetic resin emulsion having a high solid content concentration and a low viscosity can be obtained. The resin powder can be produced, and the resulting re-emulsifiable synthetic resin powder and the aqueous synthetic resin emulsion obtained by re-emulsifying the resin powder have good fluidity and workability when used as a cement mortar admixture. As a cement mortar application, it is very useful as a modifying agent for repair mortars, base preparation coating materials, self-leveling materials, tile bonding mortars, and gypsum-based materials.

Hereinafter, the configuration of the present invention will be described in detail, but these show examples of desirable embodiments, and the present invention is not limited to these contents.

[Method for producing aqueous synthetic resin emulsion]
The method for producing an aqueous synthetic resin emulsion of the present invention comprises emulsion polymerization of a polymerization component (hereinafter, the polymerization component used in the present invention is referred to as “polymerization component [I]”) in the presence of a polyvinyl alcohol-based resin. Yes, the emulsion polymerization is carried out while continuously adding the entire amount of the polymerization component [I] to the aqueous medium.

As the polymerization component [I], for example, at least one monomer component of an acrylic monomer, a styrene monomer, and a vinyl ester monomer is preferably contained as a main component. In the present invention, the main component means to occupy 50% by weight or more of the whole, and includes the case where the whole consists of only the main component.

Examples of the acrylic monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) ) Acrylate, cyclohexyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, stearyl (meth) acrylate and other aliphatic (meth) acrylates, and phenoxy (meth) acrylate and other aromatic (meth) Acrylate, trifluoroethyl (meth) acrylate, and the like. Among them, an aliphatic (meth) acrylate having an alkyl group having 1 to 18 carbon atoms, particularly 1 to 10 carbon atoms is preferable. Or 2 or more types can be used.
In the present invention, (meth) acrylate means acrylate or methacrylate.

Examples of the styrene monomer include styrene and α-methylstyrene. These may be used alone or in combination of two or more.

Examples of the vinyl ester monomers include linear or branched vinyl esters of monocarboxylic acids having 2 to 12 carbon atoms. Specific examples include vinyl formate, vinyl acetate, and vinyl propionate. , Vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl versatate, vinyl 2-ethylhexanoate and the like. These may be used alone or in combination of two or more.

Further, it may contain a functional group-containing monomer, such as a glycidyl group-containing monomer, an allyl group-containing monomer, a hydrolyzable silyl group-containing monomer, an acetoacetyl group-containing monomer, or two vinyl groups in the molecular structure. The monomer which has the above, a hydroxyl-group containing monomer, etc. are mentioned.

Examples of the glycidyl group-containing monomer include glycidyl (meth) acrylate, glycidyl (meth) allyl ether, 3,4-epoxycyclohexyl (meth) acrylate, and the like. Among these, glycidyl (meth) acrylate is particularly preferable from the viewpoints of little variation in physical properties and improvement of the adhesive strength when wet.

Examples of the allyl group-containing monomer include monomers having two or more allyl groups such as triallyloxyethylene, diallyl maleate, triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane, allyl glycidyl ether, and allyl acetate. Etc. Of these, allyl glycidyl ether is preferred from the viewpoint of adhesive strength when wet.

Examples of the hydrolyzable silyl group-containing monomer include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, vinylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxy. Examples thereof include propylmethyldimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltriethoxysilane, and γ-methacryloxypropylmethyldiethoxysilane. Among these, vinyltrimethoxysilane is preferable from the viewpoint of improving water resistance and improving the adhesive strength to the base or the old mortar surface.

Examples of the acetoacetyl group-containing monomer include acetoacetate vinyl ester, acetoacetate allyl ester, diacetoacetate allyl ester, acetoacetoxyethyl (meth) acrylate, acetoacetoxyethyl crotonate, acetoacetoxypropyl (meth) acrylate, acetoacetoxy Examples thereof include propyl crotonate and 2-cyanoacetoacetoxyethyl (meth) acrylate. Of these, acetoacetoxyethyl (meth) acrylate is preferred from the viewpoints of particularly little variation in physical properties and, in addition, improvement in water resistance and improvement in adhesion strength to the base and old mortar surface.

Examples of the monomer having two or more vinyl groups in the molecular structure include divinylbenzene, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, ethylene glycol di (meth) acrylate, 1,2-propylene glycol di ( (Meth) acrylate, 1,3-propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, tri Examples include methylolpropane tri (meth) acrylate and allyl (meth) acrylate.

Examples of the hydroxyl group-containing monomer include (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Of these, 2-hydroxyethyl methacrylate is preferred from the viewpoint of protective colloidal action during emulsion polymerization and improved miscibility with cement mortar blends.

In the present invention, from the viewpoint of improving the water-resistant compressive strength and water-resistant bending strength, the polymerization component [I] is a hydrophobic monomer having a solubility in water at 20 ° C. of 0.1% or less (hereinafter simply referred to as “hydrophobic monomer”). )) As an essential component, and its content must be 30% by weight or more, preferably 40% by weight, based on the entire polymerization component [I]. Above, more preferably 50% by weight or more, particularly preferably 70% by weight or more. The upper limit is usually 100% by weight or less. If the content of the hydrophobic monomer is too small, the water-resistant compressive strength and water-resistant bending strength of the mortar are undesirably lowered.

Specific examples of the hydrophobic monomer having a solubility in water of 20 ° C. of 0.1% or less include the following.
Acrylic monomers; for example, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, lauryl (meth) acrylate, Alkyl groups such as octyl (meth) acrylate and stearyl (meth) acrylate having 4 or more carbon atoms, preferably 6 to 18 (meth) acrylates, especially aliphatic (meth) acrylates, aromatics such as phenoxy acrylate (Meth) acrylate, trifluoroethyl methacrylate and the like can be mentioned.
Styrene monomers; for example, styrene, α-methylstyrene and the like.
Vinyl monomers; for example, vinyl laurate, vinyl stearate, vinyl versatate and the like.

Among the hydrophobic monomers, aliphatic (meth) acrylate monomers and styrene monomers having an alkyl group having 4 or more carbon atoms are preferably used, and styrene, n-butyl (meth) acrylate, 2-ethylhexyl are particularly preferable. It is preferable to use (meth) acrylate.
The hydrophobic monomers can be used alone or in combination of two or more.

In the present invention, in particular, styrene is contained as the hydrophobic monomer, and the content ratio of styrene with respect to the whole hydrophobic monomer is preferably 80% by weight or less, particularly preferably 70% by weight or less, more preferably 60% by weight. It is as follows. On the other hand, the lower limit of the styrene content is particularly preferably 30% by weight or more, and more preferably 40% by weight or more.
When the styrene content is more than 80% by weight, there may be a problem that the weather resistance is deteriorated such as polymer deterioration or discoloration due to ultraviolet rays. On the other hand, when the styrene content ratio is 30% by weight, it is preferable from the viewpoint of superior water resistance.

The polyvinyl alcohol resin used in the present invention (hereinafter sometimes referred to as “PVA resin”) is used for the purpose of imparting dispersion stability of the pre-emulsion during polymerization and to the resulting aqueous synthetic resin emulsion. In addition to imparting stability, the re-emulsifiable synthetic resin powder obtained by spray-drying the emulsion is used for the purpose of facilitating re-dispersion in water.

The average saponification degree of the PVA-based resin is preferably 70 mol% or more, particularly preferably 80 mol% or more, and further preferably 85 mol% or more. On the other hand, the upper limit of the average saponification degree is preferably 99.9 mol%, particularly preferably 99.5 mol%, further preferably 99.0 mol%.
If the average degree of saponification is too low, it is difficult for the polymerization to proceed stably, and even if the polymerization is completed, the storage stability of the emulsion tends to be lowered. If it is too high, the re-emulsifiable synthetic resin powder is re-emulsified. Tend to be difficult.

The average saponification degree can be obtained according to the saponification degree calculation method described in JIS K 6726.

In addition, the average degree of polymerization of the PVA resin is preferably 50 or more, particularly preferably 100 or more, and further preferably 200 or more. On the other hand, the upper limit of the average degree of polymerization is preferably 3,000, particularly preferably 2,000, and more preferably 1,000.
If the average degree of polymerization is too low, the protective colloid ability at the time of emulsion polymerization is insufficient and the polymerization tends not to proceed stably, and if it is too high, the reaction system becomes unstable due to thickening at the time of polymerization and dispersion. There is a tendency for stability to decrease.

The average degree of polymerization can be determined according to the method for calculating the average degree of polymerization described in JIS K 6726.

In the present invention, PVA or a modified PVA resin modified with various modified species can be used as the PVA resin, and the amount of modification is usually 20 mol% or less, preferably 15 mol% or less, more preferably. Is 10 mol% or less. In addition, as a lower limit, it is 0.01 mol%.

Examples of the modified PVA resin include an anion modified PVA resin modified with an anionic group such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group, and a cation modified with a cationic group such as a quaternary ammonium group. Modified PVA resin, modified PVA resin modified with various functional groups such as acetoacetyl group, diacetone acrylamide group, mercapto group, silanol group, etc., and PVA system having 1,2-diol bond in the side chain Examples thereof include resins.

In the present invention, the use amount of the PVA-based resin is preferably 20 parts by weight or less, particularly preferably 10 parts by weight or less, and still more preferably 7 parts by weight with respect to 100 parts by weight of the polymerization component [I] described above. It is as follows. On the other hand, the upper limit of the amount of PVA resin used is preferably 0.01 parts by weight, particularly preferably 0.1 parts by weight, and more preferably 0.5 parts by weight.
If the amount of the PVA resin used is too small, the emulsifying power becomes insufficient during emulsion polymerization, the dispersion stability of the polymerization component tends to decrease, and the polymerization stability tends to decrease. The viscosity of the synthetic resin emulsion tends to increase and the stability tends to decrease.

In the present invention, the PVA resin is usually made into an aqueous solution using an aqueous medium, and this is used in the process of emulsion polymerization. Examples of such an aqueous medium include water or an alcoholic solvent mainly composed of water, preferably water.

The content ratio (solid content) of the PVA resin in the aqueous solution is preferably 5 to 30% by weight from the viewpoint of ease of handling.

As a method of emulsion polymerization, it is necessary to perform emulsion polymerization while continuously adding the entire amount of the polymerization component [I] to an aqueous medium in the presence of a PVA-based resin. A medium and a PVA-based resin are charged, the temperature is raised, and the entire amount of the polymerization component [I] is continuously added dropwise to allow polymerization.
Examples of the aqueous medium include water and alcoholic solvents mainly composed of water, preferably water.

In the present invention, a pre-emulsion is prepared by previously emulsifying and dispersing the total amount of the polymerization component [I] in an aqueous medium in the presence of a PVA-based resin, and the total amount of the pre-emulsion is continuously contained in the aqueous medium. It is preferable to carry out emulsion polymerization while adding.

As a method for preparing such a pre-emulsion, for example, a method of dropping the polymerization component [I] while stirring an aqueous solution of a PVA resin can be mentioned. As a stirring device at that time, a known dispersing machine such as a stirring mixer with a stirring blade, a static mixer, a bipro mixer, or a homogenizer can be used. Among these, stirring mixing with a stirring blade is preferable.

In the present invention, it is necessary to carry out emulsion polymerization while continuously adding the entire amount of the polymerization component [I] (or the pre-emulsion) to an aqueous medium.
Here, the emulsion polymerization while continuously adding the whole amount means that the emulsion polymerization is carried out while continuously adding the whole amount without performing the initial polymerization. This means an emulsification method different from the method of emulsion polymerization by dropping the remaining components after polymerization.

Examples of the continuous addition method include a method in which the polymerization component [I] is dropped into an aqueous medium using a dropping funnel or a rotary pump.

The dropping speed may be adjusted under conditions generally considered as continuous dropping, and may be appropriately adjusted in consideration of the reactivity of the polymerization component used, the amount of polymerization initiator used, the reaction temperature, etc. Specifically, for example, the dropping interval is usually within 10 seconds, preferably within 5 seconds, and the amount of one dropping is usually 2% by weight or less, preferably 1% by weight or less of the total monomer amount.
The dropping interval and the amount of one dropping may be uniform or non-uniform.

It is also preferable to provide a certain aging period after the entire amount of the polymerization component [I] is dropped.

Emulsion polymerization conditions can be appropriately selected according to the type of polymerization component, polymerization scale, etc., but the temperature conditions during the reaction are usually usually 40 ° C. or higher, particularly preferably 60 ° C. or higher. . The upper limit of the temperature condition during the reaction is usually 90 ° C, particularly preferably 80 ° C.

Further, it is preferable to stir at the time of emulsion polymerization, and the stirrer at that time can be the same as that used for the preparation of the pre-emulsion, and stirring mixing with a stirring blade is particularly preferable.

Usually, in emulsion polymerization, a polymerization initiator is preferably used, and a polymerization regulator, an auxiliary emulsifier, a plasticizer, and the like can be used as necessary.

The polymerization initiator is not particularly limited as long as it can be used for ordinary emulsion polymerization. Examples thereof include inorganic peroxides such as potassium persulfate, sodium persulfate, and ammonium persulfate; organic peroxides, azo-based initiators, Examples thereof include peroxides such as hydrogen oxide and butyl peroxide; and redox polymerization initiators obtained by combining these with reducing agents such as acidic sodium sulfite and L-ascorbic acid. Two or more of these may be used in combination.
In the present invention, among these, it is preferable to use an inorganic peroxide from the viewpoint of easy polymerization without adversely affecting the film physical properties and strength enhancement, and ammonium persulfate and potassium persulfate are particularly preferable.

As a method of adding a polymerization initiator, it is possible to use a method of adding in a lump at an initial stage or a method of adding in a divided manner with the progress of polymerization, etc. The method of adding to a reaction can, the method of dripping continuously with a polymerization component, etc. can be used.

The amount of the polymerization initiator used varies depending on the type of polymerization component used and the polymerization conditions, but is usually 0.01 parts by weight or more, preferably 0.5 parts by weight or more, based on 100 parts by weight of the polymerization component [I] It is. Moreover, the upper limit of the usage-amount is 5 weight part normally, Preferably it is 3 weight part.

The polymerization regulator can be appropriately selected from known ones. Examples of such a polymerization regulator include a chain transfer agent and a buffer.

Examples of the chain transfer agent include alcohols such as methanol, ethanol, propanol and butanol; aldehydes such as acetaldehyde, propionaldehyde, n-butyraldehyde, furfural and benzaldehyde; and dodecyl mercaptan, lauryl mercaptan, normal mercaptan, thiol And mercaptans such as glycolic acid, octyl thioglycolate, and thioglycerol. These may be used alone or in combination of two or more.

Examples of the buffer include sodium acetate, ammonium acetate, dibasic sodium phosphate, and sodium citrate. These may be used alone or in combination of two or more.

The auxiliary emulsifier is not particularly limited as long as it can be usually used for emulsion polymerization. For example, anionic, cationic, and nonionic surfactants, water-soluble polymers having protective colloid ability other than PVA-based resins, And water-soluble oligomers.

Examples of the surfactant include anionic surfactants such as sodium lauryl sulfate and sodium dodecylbenzenesulfonate, and nonionic surfactants such as those having a pluronic structure and those having a polyoxyethylene structure. Agents. Moreover, the reactive surfactant which has a radically polymerizable unsaturated bond in a structure can also be used as a surfactant. These may be used alone or in combination of two or more.

The use of the above-mentioned surfactant has the effect of making the emulsion polymerization proceed smoothly, making it easy to control (effect as an emulsifier), and suppressing the generation of coarse particles and block-like substances generated during the polymerization. However, if many of these surfactants are used as emulsifiers, the graft rate tends to decrease. For this reason, when using surfactant, it is preferable that the usage-amount is an auxiliary | assistant amount with respect to PVA-type resin, ie, reduce as much as possible.

Examples of water-soluble polymers having protective colloid ability other than PVA-based resins include hydroxyethyl cellulose, polyvinyl pyrrolidone, methyl cellulose and the like. These may be used alone or in combination of two or more. These are effective in that the viscosity is changed by changing the stability of the emulsion and the particle size of the emulsion. However, since the water resistance of the film may be lowered depending on the amount used, it is desirable to use a small amount when used.

As the water-soluble oligomer, for example, a polymer having a hydrophilic group such as a sulfonic acid group, a carboxyl group, a hydroxyl group, and an alkylene glycol group is preferable, and a polymer or copolymer having a degree of polymerization of about 10 to 500 is particularly preferable. It is given to. Specific examples of the water-soluble oligomer include amide copolymers such as 2-methacrylamide-2-methylpropanesulfonic acid copolymer, sodium methacrylate-4-styrenesulfonate copolymer, styrene / maleic acid copolymer, and the like. Examples include polymers, melamine sulfonic acid formaldehyde condensates, poly (meth) acrylates, and the like. Furthermore, specific examples include a monomer having a sulfonic acid group, a carboxyl group, a hydroxyl group, an alkylene glycol group or the like, a water-soluble oligomer obtained by copolymerizing a radical polymerizable reactive emulsifier in advance alone or with another monomer, and the like. It is done. These may be used alone or in combination of two or more.

As the plasticizer, an adipate plasticizer, a phthalic acid plasticizer, a phosphoric acid plasticizer, or the like can be used.

Thus, the aqueous synthetic resin emulsion is produced by the production method of the present invention, that is, the method of emulsion polymerization in the presence of the PVA resin while continuously adding the entire amount of the polymerization component [I] to the aqueous medium. be able to.
The resulting aqueous synthetic resin emulsion is one in which synthetic resin particles are dispersed and stabilized in an aqueous medium by a PVA resin.

In the present invention, the aqueous synthetic resin emulsion obtained by emulsion polymerization is typically milky white, and the average particle size of the synthetic resin particles in the aqueous synthetic resin emulsion is 0.2 μm or more. The thickness is preferably 0.3 μm or more. Further, the upper limit of the average particle diameter is preferably 2 μm, and particularly preferably 1.5 μm. If the average particle size of the synthetic resin particles is too large, the polymerization stability tends to decrease, and if it is too small, the viscosity of the aqueous synthetic resin emulsion tends to be too high.

The average particle diameter can be measured by a conventional method, for example, a laser analysis / scattering particle size distribution analyzer “LA-950S2” (manufactured by Horiba, Ltd.).

In addition, the glass transition temperature (Tg) of the synthetic resin particles in the aqueous synthetic resin emulsion obtained by the production method of the present invention is preferably −40 ° C. or higher, particularly preferably −30 ° C. or higher, and further preferably. Is −20 ° C. or higher. The upper limit of the glass transition temperature (Tg) is preferably 30 ° C, particularly preferably 20 ° C, and further preferably 10 ° C. If the glass transition temperature is too high, the effect of the resin as an adhesive cannot be exhibited sufficiently at low temperatures, and if it is too low, the compressive strength and the bending strength tend to decrease.
The glass transition temperature is calculated from the Fox equation represented by the following Equation 1.

In addition, the glass transition temperature at the time of setting it as the homopolymer of the monomer which comprises a synthetic resin is normally measured with a differential scanning calorimeter (DSC).

The viscosity at 23 ° C. of the aqueous synthetic resin emulsion obtained by the production method of the present invention is preferably 100 mPa · s or more, particularly preferably 300 mPa · s or more, and further preferably 500 mPa · s or more. On the other hand, the upper limit of the viscosity is preferably 5,000 mPa · s, particularly preferably 3,000 mPa · s, and further preferably 2,000 mPa · s. If the viscosity is too high or too low, the aqueous synthetic resin emulsion tends to be difficult to powder.
The viscosity is measured with a B-type viscometer.

The solid content concentration of the aqueous synthetic resin emulsion obtained by the production method of the present invention is preferably 30% by weight or more, particularly preferably 35% by weight or more, and further preferably 40% by weight or more. On the other hand, the upper limit of the solid content concentration is preferably 60% by weight, particularly preferably 55% by weight, and further preferably 50% by weight. If the solid content concentration is too low, the production efficiency when pulverizing the aqueous synthetic resin emulsion is lowered, and if it is too high, the aqueous synthetic resin emulsion tends to be difficult to pulverize.

In the present invention, various additives may be further added to the aqueous synthetic resin emulsion after emulsion polymerization as necessary. Examples of such additives include organic pigments, inorganic pigments, water-soluble additives, pH adjusters, preservatives, and antioxidants.

Thus, when the aqueous synthetic resin emulsion obtained by the production method of the present invention is used as it is, it is preferably adjusted to a solid content concentration of usually 40 to 60% by weight.

[Method for producing re-emulsifiable synthetic resin powder]
By drying the aqueous synthetic resin emulsion obtained by the above production method, the re-emulsifiable synthetic resin powder according to the present invention is obtained. The re-emulsifiable synthetic resin powder has a function of emulsifying again by mixing with water, and can be effectively used for, for example, polymer cement.

Examples of the method for drying the aqueous synthetic resin emulsion include spray drying, freeze drying, and hot air drying after coagulation. Among these, spray drying is preferable from the viewpoint of production cost, energy saving, and continuous productivity.

In the case of spray drying, the spraying method can be implemented by a disk type, nozzle type, or the like. Examples of the heat source for spray drying include hot air and heated steam. The conditions for spray drying can be appropriately selected according to the size and type of the spray dryer, the nonvolatile content of the synthetic resin emulsion, the viscosity, the flow rate, and the like. The temperature for spray drying is usually preferably 80 ° C. or higher, more preferably 120 ° C. or higher. Further, the upper limit of the spray drying temperature is preferably 180 ° C, more preferably 160 ° C.
If the drying temperature is too low, it takes time to dry and the productive efficiency tends to decrease. If it is too high, the resin itself tends to be altered by heat.

Specifically, for example, an aqueous synthetic resin emulsion is continuously supplied from a nozzle of a spray dryer, and the mist is dried with warm air to be powdered. In some cases, it is also possible to preheat the adjusted spray liquid before spraying, continuously supply it from the nozzle, and dry the atomized liquid with warm air to form a powder. Heating increases the drying speed and enables highly non-volatile differentiation of the spray liquid as the viscosity of the spray liquid decreases, contributing to a reduction in production costs.

Further, in order to further improve the re-emulsification property of the re-emulsifiable synthetic resin powder in water, a water-soluble additive can be blended. Usually, a water-soluble additive is mix | blended with the aqueous synthetic resin emulsion before drying. The blending amount is 2 to 50 parts by weight with respect to 100 parts by weight of the nonvolatile content of the aqueous synthetic resin emulsion before drying. If the amount is too small, there is a tendency that the re-emulsification property to water cannot be sufficiently improved. If the amount is too large, the water re-emulsification property to water is greatly improved, but the water resistance of the film is lowered and expected. There is a tendency that the physical properties to be exhibited cannot be exhibited.

Examples of the water-soluble additive include PVA resins, hydroxyethyl celluloses, methyl celluloses, polyvinyl pyrrolidone, starches, dextrins, water-soluble alkyd resins, water-soluble amino resins, water-soluble acrylic resins, and water-soluble polycarboxylic acids. Examples thereof include water-soluble resins such as acid resins and water-soluble polyamide resins. These may be used alone or in combination of two or more. Among these, PVA-based resins are preferable. As the PVA-based resins, the same PVA-based resins as those described above can be used, and a portion of unmodified PVA or a completely saponified product, a portion of various modified PVA or a completely saponified product, and a combination thereof. good.

As the PVA-based resins, PVA having an average saponification degree of 85 mol% or more is preferable, and PVA having 87 mol% or more is particularly preferable. Moreover, as an upper limit of an average saponification degree, it is preferable that it is 99.5 mol%, and it is more preferable that it is 95 mol%. When the average saponification degree is too small, the water resistance of the resulting polymer cement mortar tends to be remarkably lowered, and when it is too large, the re-emulsification property to water tends to be lowered.

The average degree of polymerization is preferably 50 or more, more preferably 200 or more, and further preferably 300 or more. Further, the upper limit of the average degree of polymerization is preferably 3,000, more preferably 2,000, and still more preferably 600. If the average degree of polymerization is too small, the water resistance tends to decrease, and if it is too large, the re-emulsification property tends to decrease.

Thus, the re-emulsifiable synthetic resin powder of the present invention is obtained.

The re-emulsifiable synthetic resin powder of the present invention may further contain an anti-sticking agent, a water reducing agent, a dispersing agent, a mortar fluidization accelerator, a water repellent, an antioxidant, a rust inhibitor and the like.
The anti-sticking agent can be contained in the aqueous synthetic resin emulsion, mixed in the resin emulsion powder after spray drying, or sprayed from a nozzle different from the aqueous synthetic resin emulsion at the time of spray drying. .

[Aqueous synthetic resin emulsion obtained by re-emulsification]
The re-emulsifiable synthetic resin powder can be re-emulsified by adding the aqueous medium to obtain an aqueous synthetic resin emulsion. The aqueous synthetic resin emulsion obtained by this re-emulsification can exhibit the same effects as the aqueous synthetic resin emulsion prior to the re-emulsifiable synthetic resin powder.

[Polymer cement composition / Polymer cement mortar]
The re-emulsifiable synthetic resin powder thus obtained can be used as a polymer cement composition by blending with cement, and can be used as mortar or concrete by further blending water, sand or gravel. When water is added to the polymer cement composition, the re-emulsifiable synthetic resin powder is re-emulsified to regenerate the aqueous synthetic resin emulsion.

Examples of the cement include ordinary Portland cement, alumina cement, early-strength Portland cement, ultra-early strong Portland cement, medium heat Portland cement, low heat Portland cement, sulfate-resistant Portland cement, blast furnace cement, fly ash cement, silica cement, and the like. Among them, Portland cement is preferable from the viewpoint of workability.

The blending amount of the cement is preferably 3 parts by weight or more, more preferably 30 parts by weight or more with respect to 100 parts by weight of the re-emulsifiable synthetic resin powder. Moreover, the upper limit of the cement content is preferably 500 parts by weight, and more preferably 350 parts by weight.

The amount of water used as mortar or concrete is preferably 50% by weight or less, more preferably 30% by weight or less, based on the total amount of the polymer cement composition.

Further, the amount of sand and gravel when used as mortar or concrete is preferably 30% by weight or more, more preferably 50% by weight or more based on the total amount of the polymer cement composition. The upper limit of the amount of the above sand / gravel is preferably 300 parts by weight, and more preferably 150 parts by weight.

The polymer cement composition may include a cement water reducing agent or fluidizing agent (for example, lignin-based, naphthalene-based, melamine-based, carboxylic acid-based, etc.), shrinkage reducing agent (for example, glycol ether-based). , Polyether, etc.), anti-chilling agents (eg, calcium chloride, etc.), waterproofing agents (eg, stearic acid, etc.), rust inhibitors (eg, phosphates, etc.), viscosity modifiers (eg, methylcellulose, hydroxyethylcellulose, Polyvinyl alcohol, etc.), dispersants (eg, polycarboxylic acid-based, inorganic phosphorus-based, etc.), antifoaming agents (eg, silicon-based, mineral oil-based, etc.), preservatives, reinforcing agents (eg, steel fibers, glass fibers, synthetic materials) Fiber, carbon fiber, etc.) can be used alone or in combination of two or more.

When preparing a polymer cement mortar using a polymer cement composition, as in general mortar, add essential and optional components, add an appropriate amount of water, and then use a kneader or the like. And kneading.

The polymer cement mortar is usually used by adjusting the flow value to 170 ± 5 mm in the test of JIS R 5201 according to the procedure of JIS A 6203.
When the re-emulsifiable synthetic resin powder obtained by the production method of the present invention is used, it can be adjusted to a desired flow value by blending a small amount of water compared to the re-emulsifiable synthetic resin powder obtained by the conventional production method. Furthermore, the re-emulsifiable synthetic resin powder obtained by the production method of the present invention is excellent in coatability because it can be adjusted to a desired flow value without adding an additive such as a water reducing agent. You can say that. In general, a large amount of water to be blended is not preferable because the curing rate is lowered or the strength of the resulting cured product is lowered.

The polymer cement composition thus obtained exhibits good fluidity and workability when mixed with cement mortar, and is excellent in adhesion to the old mortar surface and the resin coating surface. In addition, there is little variation in physical properties, and in addition, there are excellent effects such as improvement in adhesive strength. These polymer cement compositions are used as cement mortar admixtures, such as repair mortars, base preparation coating materials, self-leveling materials, tile adhesive mortars, mortar sealers / primers, mortar curing agents, and gypsum-based materials. It is useful as an agent, and further useful for civil engineering and building materials, glass fiber sizing agents, flame retardants, and the like.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the examples, “parts” and “%” mean weight basis.

<Experimental example 1>
[Preparation of pre-emulsion]
To the flask, 5 parts of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Gohsenol GL-03) and 49 parts of water were added and dissolved sufficiently at 80 ° C. for 1 hour, cooled to room temperature, and then styrene 46 And 54 parts of butyl acrylate were added, and stirring was continued for 30 minutes with a turbine blade to emulsify to prepare a pre-emulsion.

[Production of aqueous synthetic resin emulsion]
52 parts of water and 1 part of sodium acetate were added to a separable flask equipped with a paddle type stirring blade, a reflux condenser, a dropping funnel and a thermometer, and the temperature in the flask was raised to 80 ° C. while stirring at 150 rpm. Next, 3 parts of 10% aqueous solution of ammonium persulfate was added to the flask, and then 154 parts of the pre-emulsion prepared above and 4.6 parts of 10% aqueous solution of ammonium persulfate were dropped from the dropping funnel over 5 hours, followed by polymerization reaction. Went. Subsequently, aging was carried out at 80 ° C. for 2 hours, during which time 3.5 parts of 10% aqueous solution of ammonium persulfate was added in three portions to complete the reaction, cooled to room temperature, non-volatile content 48.7%, viscosity 2 940 mPa.s. s (Brookfield viscometer BM 12 rpm, 23 ° C.) aqueous synthetic resin emulsion was obtained.

[Production of re-emulsifiable synthetic resin powder]
After adding 20 parts of 20% aqueous solution of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., GOHSENOL GL-05) to 100 parts by weight of the obtained aqueous synthetic resin emulsion, an anti-caking agent (trade name INCOMP SE-SUPER) was added. In the presence of 14 parts of Palentaler Minerals GmbH & Co KG), it was dried while spraying in an air current atmosphere at 140 ° C. to obtain a resin powder (re-emulsifiable synthetic resin powder).

<Comparative Example 1>
[Preparation of pre-emulsion]
A pre-emulsion was prepared in the same manner as in Example 1.
[Production of aqueous synthetic resin emulsion]
52 parts of water and 1 part of sodium acetate were added to a separable flask equipped with a paddle type stirring blade, a reflux condenser, a dropping funnel and a thermometer, and the temperature in the flask was raised to 80 ° C. while stirring at 150 rpm. Next, 3 parts of a 10% aqueous solution of ammonium persulfate is added to the flask, and 15.4 parts of the pre-emulsion prepared above (10% of the total amount of polymerization monomers) are added all at once, and initial polymerization is performed for 60 minutes. Then, 138.6 parts of pre-emulsion and 4.6 parts of 10% aqueous solution of ammonium persulfate were dropped from the dropping funnel over 5 hours to carry out a polymerization reaction. Subsequently, aging was carried out at 80 ° C. for 2 hours, during which time 3.5 parts of 10% aqueous solution of ammonium persulfate was added in three portions to complete the reaction, cooled to room temperature, non-volatile content 48.6%, viscosity 6, 390 mPa.s. s (Brookfield viscometer BM 12 rpm, 23 ° C.) aqueous synthetic resin emulsion was obtained.
[Production of re-emulsifiable synthetic resin powder]
Using the obtained aqueous synthetic resin emulsion, a resin powder (re-emulsifiable synthetic resin powder) was obtained in the same manner as in Example 1.

<Comparative Example 2>
[Preparation of pre-emulsion]
A pre-emulsion was prepared in the same manner as in Example 1.
[Production of aqueous synthetic resin emulsion]
52 parts of water and 1 part of sodium acetate were added to a separable flask equipped with a paddle type stirring blade, a reflux condenser, a dropping funnel and a thermometer, and the temperature in the flask was raised to 80 ° C. while stirring at 150 rpm. Next, 3 parts of a 10% ammonium persulfate aqueous solution was added to the flask, and 3.1 parts of the pre-emulsion prepared above (2% of the total amount of the polymerization monomer) was added all at once, and initial polymerization was performed for 60 minutes. Subsequently, 150.9 parts of pre-emulsion and 4.6 parts of 10% aqueous solution of ammonium persulfate were dropped from the dropping funnel over 5 hours to carry out the polymerization reaction. Subsequently, aging was carried out at 80 ° C. for 2 hours, during which time 3.5 parts of 10% aqueous solution of ammonium persulfate was added in three portions to complete the reaction, cooled to room temperature, non-volatile content 49.1%, viscosity 34, 600 mPa.s. s (Brookfield viscometer BM 12 rpm, 23 ° C.) aqueous synthetic resin emulsion was obtained.
[Production of re-emulsifiable synthetic resin powder]
Using the obtained aqueous synthetic resin emulsion, an attempt was made to produce a re-emulsifiable synthetic resin powder in the same manner as in Example 1, but the viscosity was high and spray spraying was impossible.

<Comparative Example 3>
[Preparation of pre-emulsion]
A pre-emulsion was prepared in the same manner as in Example 1.
[Production of aqueous synthetic resin emulsion]
52 parts of water and 1 part of sodium acetate were added to a separable flask equipped with a paddle type stirring blade, a reflux condenser, a dropping funnel and a thermometer, and the temperature in the flask was raised to 80 ° C. while stirring at 150 rpm. Next, 3 parts of a 10% aqueous solution of ammonium persulfate was added to the flask, and 7.7 parts of the pre-emulsion prepared above (5% of the total amount of the polymerization monomer) was added all at once, and initial polymerization was performed for 30 minutes. Thereafter, pre-emulsion 146.3 and 4.6 parts of 10% aqueous solution of ammonium persulfate were dropped from the dropping funnel over 5 hours to carry out a polymerization reaction. Subsequently, aging was performed at 80 ° C. for 2 hours, during which time 3.5 parts of 10% aqueous solution of ammonium persulfate was added in three portions to complete the reaction, cooled to room temperature, non-volatile content 49.1%, viscosity 26, 200 mPa.s. s (Brookfield viscometer BM 12 rpm, 23 ° C.) aqueous synthetic resin emulsion was obtained.
[Production of re-emulsifiable synthetic resin powder]
Using the obtained aqueous synthetic resin emulsion, an attempt was made to produce a re-emulsifiable synthetic resin powder in the same manner as in Example 1, but the viscosity was high and spray spraying was impossible.

<Comparative Example 4>
[Preparation of pre-emulsion]
A pre-emulsion was prepared in the same manner as in Example 1.
[Production of aqueous synthetic resin emulsion]
52 parts of water and 1 part of sodium acetate were added to a separable flask equipped with a paddle type stirring blade, a reflux condenser, a dropping funnel and a thermometer, and the temperature in the flask was raised to 80 ° C. while stirring at 150 rpm. Next, 3 parts of a 10% aqueous solution of ammonium persulfate was added to the flask, and 15.4 parts of the pre-emulsion prepared above (10% of the total amount of polymerization monomers) were added all at once, and initial polymerization was performed for 10 minutes. After that, 138.6 parts of pre-emulsion and 4.6 parts of 10% aqueous solution of ammonium persulfate were added dropwise from the dropping funnel over 5 hours. However, the reaction became unstable in the middle, and a good polymerization reaction could not be performed. A synthetic resin emulsion could not be obtained.

Using the re-emulsifiable synthetic resin powder obtained in Example 1 and Comparative Example 1, the re-emulsification property and the fluidity of the polymer cement mortar were evaluated by the following methods.

<Re-emulsification of resin powder>
To 100 parts of deionized water, 100 parts of a re-emulsifiable aqueous synthetic resin emulsion powder was added with stirring, and then re-emulsified by stirring for 10 minutes at 1000 rpm. The viscosity of this re-emulsified liquid at Brookfield viscometer BM 12 rpm, 23 ° C. was measured. The evaluation criteria are as follows. The results are shown in Table 2.
(Evaluation criteria)
A: The viscosity of the re-emulsified emulsion solution is 3,000 mPa.s. Less than s Δ: The viscosity of the re-emulsified emulsion solution is 3,000 mPa.s. s or more and 5,000 mPa.s. Less than s x: The viscosity of the re-emulsified emulsion solution is 5,000 mPa.s. s or more

<Flowability of polymer cement mortar>
In accordance with JIS A6203, re-emulsifiable synthetic resin powder and various components are blended as shown in Table 1 below, and water is added until the polymer cement mortar conforms to the specified flow value: 170 ± 5 mm to produce a polymer cement mortar. did.
Table 1 shows the flow value of the polymer cement mortar at each amount of water added.

Water / cement (%) was determined for the polymer cement mortar that had been watered until the flow value specified in JIS A6203 was satisfied, and was evaluated according to the following criteria. The results are shown in Table 2.
(Evaluation criteria)
○ ・ ・ ・ Water / cement is less than 80% × ・ ・ ・ Water / cement is 80% or more

As shown in Table 2, the synthetic resin emulsion of Example 1 obtained by the production method of the present invention has a low viscosity, and the emulsifiable synthetic resin powder obtained by drying the emulsion has excellent re-emulsification properties. It turns out that the fluidity | liquidity of the cement mortar which uses this is favorable.

On the other hand, the synthetic resin emulsion of Comparative Example 1 obtained by a production method different from the production method of the present invention and the monomer polymerization method has a high viscosity, and the re-emulsifiable synthetic resin powder obtained by drying the emulsion is The viscosity after emulsification was also high and inferior in re-emulsification.
Moreover, as can be seen from the results of Tables 1 and 2, the polymer cement mortar using the re-emulsifiable synthetic resin powder obtained by drying the synthetic resin emulsion obtained by the production method of Comparative Example 1 The amount of water equal to 1 cannot be adjusted to the specified flow value in JIS A 6203, and more water must be added to adjust the flow value to the specified flow value. It turns out that it is inferior to fluidity | liquidity compared with the re-emulsifiable synthetic resin powder obtained by drying the synthetic resin emulsion obtained by the manufacturing method of Example 1. If the amount of water in the polymer cement mortar is large, the curing rate of the polymer cement is lowered and the strength of the resulting cured product is lowered, so that the practicality is inferior.

In addition, since the synthetic resin emulsions obtained by the production methods of Comparative Examples 2 and 3 have a high viscosity, re-emulsifiable synthetic resin powders cannot be obtained. In the production method of Comparative Example 4, the polymerization stability is poor, A synthetic resin emulsion could not be obtained.

According to the method for producing an aqueous synthetic resin emulsion of the present invention, an aqueous synthetic resin emulsion having a high solid content and a low viscosity can be obtained. Therefore, an emulsion powder having excellent workability after re-emulsification can be obtained with high production efficiency. The re-emulsifiable synthetic resin powder obtained by the production method of the re-emulsifiable synthetic resin powder of the present invention and the aqueous synthetic resin emulsion obtained by re-emulsifying this are good when used as a cement mortar admixture. It exhibits excellent fluidity and workability and is very useful as a modifier for cement mortar applications, such as for repair mortars, undercoating materials, self-leveling materials, tile adhesive mortars, and gypsum-based materials.

Claims (8)

1. A method for producing an aqueous synthetic resin emulsion in which a polymerization component is emulsion-polymerized in the presence of a polyvinyl alcohol resin,
   A hydrophobic monomer having a solubility in water at 20 ° C. of 0.1% or less is 30% by weight or more based on the whole polymerization component,
   A method for producing an aqueous synthetic resin emulsion, wherein emulsion polymerization is carried out while continuously adding the total amount of the polymerization components to an aqueous medium.
2. Containing styrene as the hydrophobic monomer having a solubility in water of 20 ° C. of 0.1% or less,
   The content of this styrene is 80% by weight or less based on the whole hydrophobic monomer having a solubility in water at 20 ° C. in the polymerization component of 0.1% or less. A method for producing an aqueous synthetic resin emulsion.
3. In the presence of the polyvinyl alcohol resin, the entire amount of the polymerization component is emulsified and dispersed in the aqueous medium to prepare a pre-emulsion, and the total amount of the pre-emulsion is continuously added to the aqueous medium while performing emulsion polymerization. A method for producing an aqueous synthetic resin emulsion according to claim 1 or 2.
4. The method for producing an aqueous synthetic resin emulsion according to any one of claims 1 to 3, wherein the viscosity of the aqueous synthetic resin emulsion is 100 to 5000 mPa · s and the solid content concentration is 30 to 60%.
5. A method for producing a re-emulsifiable synthetic resin powder, comprising drying the aqueous synthetic resin emulsion obtained by the production method according to any one of claims 1 to 4.
6. A method for producing a polymer cement mortar, wherein the re-emulsifiable synthetic resin powder obtained by the production method according to claim 5 is used.
7. An aqueous synthetic resin emulsion obtained by polymerizing a polymerization component containing 30% by weight or more of a hydrophobic monomer having a solubility in water at 20 ° C. of 0.1% or less,
   Styrene-containing as the hydrophobic monomer,
   The content of the styrene is 80% by weight or less based on the entire hydrophobic monomer,
   An aqueous synthetic resin emulsion characterized by a viscosity of 100 to 5,000 mPa · s and a solid content concentration of 30 to 60%.
8. A re-emulsifiable synthetic resin powder obtained from the aqueous synthetic resin emulsion according to claim 7.