JP3181766B2 - Redispersible acrylic emulsion powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a redispersible acrylic resin emulsion powder obtained by pulverizing an acrylic resin emulsion obtained by using a polymer obtained by polymerizing a polymerizable emulsifier as a protective colloid.

[0002]

2. Description of the Related Art A redispersible synthetic resin emulsion powder is
Manufactured by spray-drying a synthetic resin emulsion, it is a powder compared to a synthetic resin emulsion, so it is easy to handle and convenient to transport.When used, the powder is added to water and stirred to make it into water. Because of its re-dispersing ability, it is used in a wide range of applications, such as adhesives, binders for paints, and admixtures in cement products. However, most of what is known as a synthetic resin emulsion powder was a vinyl acetate polymer or a copolymer thereof, that is, a vinyl acetate resin emulsion powder. And the vinyl acetate resin has a weak point that it is inferior in alkali resistance. On the other hand, acrylic resin emulsions have better alkali resistance than vinyl acetate resins. However, acrylic resin emulsions need to be manufactured using surfactants as emulsifiers, and emulsion powders obtained by spray drying acrylic resin emulsions using these surfactants as emulsifiers are redispersed in water. There is no sex. However, there is also a problem when emulsion polymerization is performed using a protective colloid. For example, an acrylic monomer is easily grafted on PVA. PVA grafted with an acrylic monomer has reduced hydrophilicity and reduced protective colloid ability. Therefore, various measures have to be taken to produce a good emulsion. Such problems often do not occur with other monomers. For example, in the case of vinyl acetate, a good emulsion can be obtained because grafting on PVA is suppressed by acetaldehyde present in the monomer.

Accordingly, the present inventor has disclosed a method for obtaining an emulsion powder having good redispersibility by spray-drying an acrylic resin emulsion using a PVA-based water-soluble protective colloid, as disclosed in JP-A-4-185606 and JP-A-4-185607.
The invention was proposed. In addition, melamine formaldehyde sulfonate condensate (JP-B-51-46126), vinylpyrrolidone-vinyl acetate copolymer (JP-B 4-5932)
4), isobutylene maleic anhydride copolymer (JP-A-4-288335), phenol formaldehyde sulfonate condensate (JP-A-3-56536), seratin,
Special protective colloid such as dextrin (Japanese Patent Publication 3-549)
73), polycarboxylic acids (JP-A-62-129356)
And so on. However, when these water-soluble substances are used, the water resistance in a wet state becomes poor, so that a disadvantage that adhesiveness is deteriorated occurs, which is not preferable. When a large amount of substances other than the acrylic resin are added, the performance of the acrylic resin is deteriorated.

[0004]

However, redispersible acrylic resin emulsion powder cannot be obtained by emulsion polymerization using a surfactant, and water resistance is poor when a PVA-based water-soluble protective colloid is used. The inventors have studied other emulsion polymerization methods. In addition, the use of polymerizable emulsifiers resulted in poor redispersibility of the resulting emulsion powder, as did the use of surfactants. As a result, the present inventors succeeded in solving the problem and completed the present invention.

[0005]

Means for Solving the Problems The present invention provides a method for spray-drying an emulsion obtained by emulsion-polymerizing a polymerizable polymerizable emulsifier as a protective colloid and presenting the emulsifier in an amount of 2 to 40% by weight based on an acrylic monomer. 2. The redispersible acrylic resin emulsion powder obtained by the above method 2. The redispersible acrylic resin emulsion powder according to item 1, wherein the protective colloid is a homopolymer of a polymerizable emulsifier 3. The protective colloid is polymerizable 3. The redispersible acrylic resin emulsion powder according to item 1, which is a copolymer of an emulsifier, an acrylic monomer and a monoethylenically unsaturated carboxylic acid or a salt thereof 4. The polymerizable emulsifier is ethylenically unsaturated 1 or 2 selected from sulfonic acid, ethylenically unsaturated sulfuric acid, and salts thereof
Item 4. The redispersible acrylic resin emulsion powder according to any one of Items 1 to 3 above. 5. 5. The redispersible acrylic resin emulsion powder according to any one of items 1 to 4, wherein the polymerizable emulsifier polymer as a protective colloid is a polymer having a molecular weight of 1,000 to 500,000. 6. The emulsion according to any one of claims 1 to 5, wherein the emulsion obtained by using the polymerizable emulsifier polymer is an emulsion obtained by copolymerizing an acrylic monomer and a copolymerizable monomer. Redispersible acrylic resin emulsion powder. 7. The emulsion obtained using the polymerizable emulsifier polymer is a copolymer emulsion obtained by copolymerizing 50 to 100% by weight of an acrylic monomer and 50 to 0% by weight of a copolymerizable monomer. Item 7. The redispersible acrylic resin emulsion powder according to any one of Items 6 to 6. 8. Item 8. The redispersible acrylic resin emulsion powder according to any one of Items 1 to 7, wherein the emulsion particles are particles crosslinked with a functional monomer. About.

[0006]

The first feature of the present invention is that the spray-dried acrylic resin emulsion is an emulsion obtained by emulsion polymerization in the presence of a special protective colloid. According to the study of the present inventor, in order to obtain an acrylic resin emulsion powder having excellent redispersibility, an acrylic monomer such as an acrylate ester and / or a methacrylate ester or a monomer copolymerizable therewith is used. When emulsion polymerization is carried out, the presence of a protective colloid is indispensable.

The present inventor believes that the acrylic resin particles generated during the emulsion polymerization form a bond with the protective colloid, which has an excellent effect on the redispersibility of the resin powder. Also, especially when spray drying of the resin emulsion, the water-soluble protective colloid inhibits the fusion of acrylic resin particles with each other, and the acrylic resin particles are individually present in the powder after spray drying, so that the powder is It is believed that when stirred in water, the acrylic resin particles are dispersed by the water-soluble protective colloid and exhibit excellent redispersibility. According to the study of the present inventor, the surfactant has no effect of protecting the acrylic resin particles such as a water-soluble protective colloid from fusing, and the acrylic resin particles fuse with each other during spray drying.
It was clarified that secondary particles were formed, and thus the acrylic resin powder did not show any redispersibility.

The fact that the presence of a water-soluble protective colloid is indispensable at the time of emulsion polymerization is essential even when the same amount of a water-soluble protective colloid is added to an acrylic resin emulsion obtained using a surfactant as an emulsifier. It is clear from no effect. Even after adding a water-soluble protective colloid,
The mere presence of the water-soluble protective colloid in the water does not combine with the emulsion particles and does not prevent the acrylic resin particles from fusing together during spray drying to form secondary particles. The acrylic resin emulsion powder of the present invention exhibits excellent redispersibility with a small amount of protective colloid, and is re-emulsified to almost the original emulsion state by adding the powder to water and stirring, similar to the acrylic resin emulsion. Can be used.

The acrylic monomers used in the present invention include acrylates having 1 to 12 carbon atoms in the alkyl group and methacrylates having 1 to 12 carbon atoms in the alkyl group. Examples of monomers copolymerized with these include aromatic vinyl compounds such as styrene and methylstyrene, vinyl acetate, vinyl esters of saturated carboxylic acids branched at the α-position, acrylic acid, methacrylic acid, itaconic acid, and crotonic acid. , Unsaturated carboxylic acids such as, vinyl phosphate, acrylonitrile, acrylamide and N-methylol acrylamide, glycidyl methacrylate, 2 hydroxyalkyl acrylate, alkoxyethyl acrylate, vinyl triethoxysilane, vinyl (2-methoxyethoxy) silane, vinyl trisacetoxy Examples include functional monomers such as silane and polyfunctional silane monomers such as γ-methacryloxypropyltrimethoxysilane, and ethylene, vinyl chloride, and vinylidene chloride. Divinyl compound, di (meth) acrylate compound, tri (meth) acrylate compound, tetra (meth)
Monomers having two or more polymerizable unsaturated groups, such as acrylate compounds, diallyl compounds, triallyl compounds, and tetraallyl compounds are also used. Specifically, for example, divinylbenzene, divinyl adipate, ethylene glycol di (meth) acrylate, 1,3-butyl di (meth) acrylate, triethylene glycol di (meth)
Acrylate, trimethylolpropane tri (meth) acrylate, diallyl phthalate, triallyl dicyanurate, tetraallyl ethoxyethane and the like can be mentioned.

When a monomer having a functional group is used, the emulsion particles are crosslinked, so that crosslinked emulsion particles can be obtained. This crosslinked emulsion has high water resistance and improved strength. The amount of the copolymerizable monomer used is 50% or less of the acrylic monomer. If the amount of these monomers exceeds 50% of the acrylic monomer, the characteristics of the acrylic resin are lost, and the effect of the present invention is reduced.

A second feature of the present invention lies in the protective colloid used. The protective colloid used in the present invention is a polymer obtained by polymerizing one or two or more anionic, cationic, or nonionic polymerizable emulsifiers. The polymerizable emulsifier used to form such a protective colloid includes the following.

[0012] The polymerizable emulsifier anionic there allyl alcohol derivatives such as sodium allyl <br/> sulfonic Ho phosphate. Such a polymerizable emulsifier is disclosed, for example, in JP-B-49-4.
6291, JP-A-58-203960, 62-1048
02, JP-A-4-53802. Further sodium sulfopropyl methacrylate, 2-accession <br/> Riruamido - 2 acrylic acid derivatives such as methyl propane sulfonic Ho phosphate and salts thereof are also used. These polymerizable emulsifiers are described, for example, in JP-B-46-12472 and JP-A-54-1982.
144317, and JP-A-55-11525. In addition, JP-A-46-34894 and JP-B-51-4
4157, JP-A-51-30284, JP-B-56-29
657, etc .;
1-444157, JP-A-51-30284, JP-B-56
And maleic acid derivatives described in US Pat. JP-A-51-30285, JP-A-51-302
84, etc., which have a sulfonic acid group or a sulfuric acid group, such as fumaric acid derivatives, styrene derivatives such as vinylstyrenesulfonic acid or salts thereof, and ethylene derivatives such as vinylsulfonic acids or salts thereof. You.
Examples of nonionics include JP-A-56-20007, JP-A-56-28208, JP-A-55-73747 and JP-A-5-73747.
Methacryl derivatives described in JP-A-5-41684 and JP-A-54-129081, and JP-B-46-34894.
And the like. Itaconic acid derivatives described in US Pat.

[0013] As the cationic type, JP-A-55-982
For example, methacryl group derivatives described in No. 01 and the like are used. These substances are used as an emulsifier per se, and are known to be polymerized in a polymer in emulsion polymerization to exhibit an emulsion stabilizing effect.However, a polymer obtained by polymerizing this polymerizable emulsifier is used as a protective colloid. Acting as is what was previously not known at all. One of such polymerizable emulsifiers may be polymerized, and for example, a plurality of anionic ones may be polymerized. Polymerization may be carried out by combining anionic and nonionic, and cationic and nonionic.

The monomers copolymerizable with these polymerizable emulsifiers include acrylates having 1 to 12 carbon atoms in the alkyl group and 1 to 1 carbon atoms in the alkyl group.
Two methacrylic acid esters, aromatic vinyl compounds such as styrene, vinyl acetate, vinyl esters of unsaturated carboxylic acids branched at the α-position, acrylic acid, methacrylic acid,
Unsaturated monomers such as itaconic acid, crotonic acid, maleic acid and fumaric acid, acrylonitrile, acrylamide, methacrylamide, N-methylolacrylamide, glycidyl methacrylate, functional monomers such as 2hydroxyalkyl acrylate and methacrylate,
In addition, ethylene, vinyl chloride and the like are used.

Since the protective colloid affects the viscosity of the emulsion, the molecular weight is adjusted so that the viscosity is such that spray drying can be carried out well. Alcohols such as methanol, ethanol and butanol as molecular weight regulators. Carbon atom 2 such as acetone, MEK, cyclohexane, acetophenone, acetaldehyde, propionaldehyde, n-butyraldehyde, furfural, benzaldehyde, etc.
8 amino acids, dodecyl mercaptan, lauryl mercaptan, normal Mel captan, 2-ethylhexyl thioglycolate, thioglycolic acid, may be used one or more mercaptans such as thioglycerol. Suitable polymerizable emulsifier polymers have a molecular weight of 1,0
00 to 500,000, preferably 10,000 to 2
00,000.

The amount of the protective colloid used is 2 to 40 parts by weight, preferably 3 to 8 parts by weight, based on 100 parts by weight of the monomer. By spray-drying an emulsion produced by emulsion polymerization of the above-mentioned monomer in the presence of a protective colloid obtained by polymerizing a polymerizable emulsifier, redispersibility in water is good, and redispersibility and film A protective colloid-based redispersible acrylic resin emulsion powder having excellent properties is obtained. Although a surfactant can be used in combination, emulsification must be mainly made of protective colloid.

As the emulsion polymerization method, a usual emulsion polymerization method is applied, and the emulsion polymerization method is carried out by a batch emulsion polymerization method, a monomer drop emulsion polymerization method, an emulsion monomer drop emulsion polymerization method, or the like.
As the polymerization initiator for emulsion polymerization, potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, peroxides such as butyl peroxide, and Redox polymerization initiator in which these peroxides and a reducing agent are combined Is used.

For spray drying, ordinary spray drying in which a fluid is sprayed and dried can be used. Depending on the type of spraying, there are a disk type and a nozzle type, and any type is used. Also, as the heat source, hot air, heated steam, or the like is used. Drying conditions may be selected depending on the size and type of the spray dryer, the concentration, viscosity, flow rate, and the like of the emulsion. The drying temperature is suitably from 100 ° C. to 150 ° C., and it is preferable to set other drying conditions so as to obtain a sufficiently dried powder within the range of the drying temperature. 100
When the temperature is lower than 150 ° C., sufficient drying is not performed. When the temperature is higher than 150 ° C., it is not preferable because the acrylic resin is deteriorated by heat. Drying needs to be performed sufficiently, and excess water tends to aggregate and block the acrylic resin emulsion powder.

In order to further improve the redispersibility of the protective colloid-based redispersible acrylic resin emulsion powder of the present invention in water, a water-soluble additive may be added. The water-soluble additive has the advantage of being uniformly mixed when added to the emulsion before spray drying and spray dried. The amount of the water-soluble additive used is also related to the amount of the water-soluble protective colloid used in the production of the emulsion, and the solid content of the water-soluble protective colloid and the water-soluble additive relative to the emulsion solid before spray drying. Is preferably 5 to 50% by weight. 5
If it is less than 5% by weight, redispersibility in water cannot be said to be sufficient, and
When the content is 0% by weight or more, the water resistance and the like are remarkably reduced, and the properties become close to those of the water-soluble resin, and the characteristics as an emulsion powder are lost.

As the water-soluble additive, a water-soluble polymer compound is preferable, and it is used as the above-mentioned water-soluble protective colloid. Polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, starch derivatives, polyvinylpyrrolidone, polyethylene oxide, etc., as well as water-soluble alkyd resin, water-soluble phenol resin, water-soluble urea resin, water-soluble melamine resin, water-soluble guanamine resin, water-soluble naphthalene Sulfonic acid resin, water-soluble amino resin, water-soluble polyamide resin, water-soluble acrylic resin, water-soluble polycarboxylate, water-soluble polyester resin, water-soluble polyurethane resin, water-soluble polyol resin,
A water-soluble epoxy resin is also used.

In the present invention, depending on the use of the protective colloid-based redispersible acrylic resin emulsion powder, various additives used for the use may be blended. For example, viscosity improvers for adhesives, water retention agents,
Fiber softeners, thickeners, and smoothing agents for fiber finishing use, such as viscosity improvers, thickeners, pigment dispersants, and stabilizers for binders for paints and binderies for aqueous inks, such as tackifiers and thickeners. An AE agent, a water reducing agent, a fluidizing agent, a water retention agent, a thickening agent, a waterproofing agent, etc. in addition and use to cement, mortar, etc., such as an antistatic agent, are also used as appropriate.

In order to improve the storage stability of the protective colloid-based redispersible acrylic resin emulsion powder of the present invention,
It is preferred to use anti-caking agents. The storage stability of the emulsion powder refers to a tendency that the powders adhere to each other during storage and agglomerate and block, and the softer the resin, the stronger the tendency to block and the storage stability is poor. Further, a core-shell structure can be obtained by polymerizing the emulsion particles by dividing the monomer composition into two stages. For example, the first stage has a soft composition and the second stage does not use a new emulsifier so that no new particles are generated.
The polymer is produced by adsorbing a hard monomer on the polymer particles generated in the first step. By adopting the core-shell structure in this manner, the shell can be hardened and the anti-blocking property can be increased.

The anti-binder may be added to the spray-dried emulsion powder and mixed uniformly. However, when the emulsion is spray-dried, the emulsion is sprayed in the presence of the anti-binder, for example, simultaneous spraying. This is preferable in that uniform mixing can be performed and the anti-caking effect is obtained. As the anti-binder, fine inorganic powders are preferable, and calcium carbonate, clay, anhydrous silicic acid, aluminum silicate, white carbon, talc, alumina white, and the like are used. In particular, the average particle diameter is about 0.01 to 0.1. 5 μm anhydrous silicic acid, aluminum silicate, calcium carbonate and the like are preferred. The amount of the anti-binder used is not particularly limited, but is preferably used in the range of 2 to 20% by weight based on the emulsion powder.
If the content is less than 2% by weight, the effect of using the anti-binding agent cannot be obtained,
If the content is 20% by weight or more, the content of the inorganic powder becomes excessively large, and the characteristics of the emulsion powder are lost. Organic fillers can also be used. next,
The present invention will be described specifically with reference to examples.

[0024]

【Example】

(A) Preparation of Protective Colloid A solution having the composition shown in Table 1 was polymerized and adjusted in a 500 ml four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a dropping funnel. I got

[0025]

[Table 1]

[0026] (Note) EREMINOR JS2 (Sanyo Kasei Co., Ltd. polymerization emulsifiers) Adekaria SE-10N (Asahi Denka Kogyo Co., Ltd. polymerization emulsifiers) Aku-alone RN-50 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. polymerizable Emulsifier) Gohsenol GL05 (polyvinyl alcohol manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) So. Na. Sodium vinyl sulfonate St. So. Na. Sodium styrene sulfonate Ac. M. So. Na. Acrylic San'a Mi de 2 methylpropanesulfonic acid sodium Lau. Su. Na. Sodium lauryl sulfate

(B) Preparation of Emulsion The above protective colloids A to Q were heated to an internal temperature of 70 ° C., and 1.5 parts by weight of a 10% aqueous sodium persulfate solution was added to each of them. Parts by weight and 50 parts by weight of butyl acrylate were added dropwise over about 2 hours. During that time, 2.5 parts by weight of a 12% aqueous sodium persulfate solution was added in portions during and after the dropwise addition. After completion of the dropwise addition, stirring was continued for about 2 hours while maintaining the internal temperature at 72 to 75 ° C. After the polymerization reaction was completed, the mixture was cooled to obtain an emulsion shown in Table 2.

[0028]

[Table 2]

(Note) M. A: Methyl methacrylate B. A: butyl acrylate The obtained polymer dispersion had no coagulated product and had a solid content of 50%.
It was a milky white resin dispersion having a weight percentage of 100 cp and a viscosity of 100 cp. 100 parts by weight of the polymer dispersion and 100 parts by weight of water were uniformly mixed to obtain a dispersion.

(C) Example The dispersion and fine silica powder in an amount of 5% based on the solid content of the dispersion are separately sprayed simultaneously in hot air at 120 ° C. and dried to obtain an average particle diameter of 70 μm. Resin powder was obtained.

[0031]

[Table 3]

(Note) 100 weights of agitated powder were mixed with 10 parts of deionized water.
It was added to 0 parts by weight and sufficiently stirred by a stirrer to confirm the following. Redispersibility:…: The most dispersed liquid is uniform and the sedimentation of the resin is slight. X: The most dispersed liquid is separated into two layers of a transparent layer and a precipitated resin powder. Viscosity: measure the viscosity of re-dispersion with a B-type viscometer. Film forming property:…: A uniform film is obtained, and a tough film is obtained. X: No film was obtained. Water resistance: The emulsion redispersed on a glass plate is applied to a dry film thickness of 0.2 mm, and after drying, the glass plate is placed horizontally on a newspaper. Next, water drops are dropped on the film on the glass plate, and the time until the film is whitened and the characters (8-point type hiragana) on the newspaper cannot be read is measured.

[0033]

According to the present invention, the re-emulsifiability is good and an emulsion substantially identical to the original emulsion can be formed. In addition, the water resistance is improved in each step as compared with an acrylic emulsion using a conventional protective colloid.

Claims (8)

(57) [Claims] 1. A polymer of a polymerizable emulsifier is used as a protective colloid, and the emulsifier is 2 to 40% by weight based on the acrylic monomer.
A redispersible acrylic resin emulsion powder obtained by spray drying an emulsion polymerized in the presence of an emulsion. 2. The redispersible acrylic resin emulsion powder according to claim 1, wherein the protective colloid is a homopolymer of a polymerizable emulsifier. 3. The redispersible acrylic resin emulsion powder according to claim 1, wherein the protective colloid is a copolymer of a polymerizable emulsifier, an acrylic monomer and a monoethylenically unsaturated carboxylic acid or a salt thereof. . 4. A polymerizable emulsifier selected from ethylenically unsaturated sulfonic acid, ethylenically unsaturated sulfuric acid and salts thereof.
4. The redispersible acrylic resin emulsion powder according to claim 1, wherein the powder is at least two. 5. The polymerizable emulsifier polymer as a protective colloid is a polymer having a molecular weight of 1,000 to 500,000.
The redispersible acrylic resin emulsion powder according to any one of claims 1 to 4. 6. The emulsion according to claim 1, wherein the emulsion obtained using the polymerizable emulsifier polymer is an emulsion obtained by copolymerizing an acrylic monomer and a copolymerizable monomer. Item 8. The redispersible acrylic resin emulsion powder described in the above item. 7. A copolymer obtained by copolymerizing 50 to 100% by weight of an acrylic monomer and 50 to 0% by weight of a copolymerizable monomer in an emulsion obtained using a polymerizable emulsifier polymer. The redispersible acrylic resin emulsion powder according to any one of claims 1 to 6, which is an emulsion. 8. The redispersible acrylic resin emulsion powder according to claim 1, wherein the emulsion particles are particles crosslinked with a functional monomer.