RU2405008C2 - Aqueous emulsion and use thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: aqueous emulsion contains resin (A) based on polyvinyl alcohol in amount of 0.1-30 wt %, containing a 1,2-diol component in a side chain and having average degree of polymerisation from 50-500, and polymer (B) obtained via emulsion polymerisation of at least one unsaturated monomer selected from a monomer with an ethylene bond and a diene-type monomer and in the presence of resin (A) as an emulsifying agent and in the presence of an initiator.

EFFECT: emulsion is characterised by excellent stability of emulsion polymerisation during preparation and has excellent resistance to mechanical effects, stability during freezing, prolonged resistance to high temperatures, excellent water-resistant adhesion properties and ability to redispersion.

5 cl, 1 tbl, 6 ex

Description

FIELD OF TECHNOLOGY

The present invention relates to an aqueous emulsion, in particular to an aqueous emulsion, which is characterized by excellent stability of the emulsion polymerization process upon receipt of the specified emulsion and has excellent resistance to mechanical stress, stability upon freezing, long-term resistance to high temperatures and excellent adhesive properties not affected by moisture, while the specified emulsion can be turned into a powder by removing water, which when repeated spergirovanii in water forms an emulsion having an excellent resistance to mechanical impacts. The present invention also relates to a redispersible powder resin and adhesive material obtained using said aqueous emulsion.

BACKGROUND

A resin based on polyvinyl alcohol (hereinafter polyvinyl alcohol is often referred to by the abbreviation PVA) has so far been successfully used as a dispersion stabilizer in the emulsion polymerization of vinyl acetate monomers and acrylic acid monomers.

In addition, the possibility of using various modified PVA-based resins is being studied in order to obtain an aqueous emulsion with improved resistance to mechanical stress, stability during freezing, and resistance to high temperatures. For example, aqueous emulsions have been proposed that include an aqueous emulsion containing a PVA-based polymer with a terminal mercapto group, a surfactant, and a polymer containing predominantly an ethylenically unsaturated monomer as the monomer units, with an average particle diameter of said emulsion being 0.3 μm or less (see, for example, patent document 1). An aqueous emulsion is also known in which a PVA-based resin having a blocking degree [η] of more than 0.6 and a saponification degree of more than 0.95 mol% and containing active hydrogen in the molecule adheres to the surface of the polymer particles (see, for example, patent document 2). In addition, an acrylic acid-based copolymer emulsion is known to be prepared using an amide-modified PVA as a protective colloidal stabilizer (see, for example, Patent Document 3).

Patent Document 1: JP-A-2003-171567

Patent Document 2: JP-A-2003-277419

Patent Document 3: JP-A-2004-018692

DESCRIPTION OF THE INVENTION

OBJECT OF THE PRESENT INVENTION

As a result of a detailed study of the above known methods, the authors of the present invention found the following. Despite the fact that all of these aqueous emulsions have significantly improved resistance to mechanical stress and stability during freezing, the resistance of such emulsions to high temperatures and the time during which the emulsions exhibit this stability can be improved in order to meet market requirements. In particular, there is a need for an aqueous emulsion having excellent resistance to mechanical stress and stability during freezing, and an additionally increased resistance to long-term exposure to high temperatures.

WAYS TO SOLVE THE PROBLEM

As a result of the study conducted by the authors of the present invention, it was found that an aqueous emulsion containing a resin (A) based on PVA, which in turn contains a 1,2-diol component in the side chain and has an average degree of polymerization from 50 to 2500, and polymer (B) comprising at least one unsaturated monomer selected from a monomer unsaturated in the type of ethylene bond and a diene-based monomer meets the task. Thus, the present invention has been completed.

The specified PVA-based resin (A) containing a 1,2-diol component in the side chain is preferably a PVA-based resin (A) containing as a structural unit a 1,2-diol of the general formula (1):

In this formula, each of the groups R ¹ , R ² and R ³ independently represents a hydrogen atom or an alkyl group, and R ⁴ represents a single bond or alkylene group containing from 1 to 3 carbon atoms, which may contain an alkyl group.

In addition, polymer (B) is preferably a polymer obtained by emulsion polymerization of at least one unsaturated monomer selected from an ethylenically unsaturated monomer and a diene-based monomer in the presence of an emulsifier-based resin (A) PVA.

Advantages of the Invention

The aqueous emulsion according to the present invention is characterized by excellent stability of the emulsion polymerization process, resulting in the preparation of said emulsion, excellent stability during freezing and resistance to high temperatures. The proposed emulsion can also be turned into a powder by removing water. When re-dispersed, this emulsion also has satisfactory resistance to mechanical stress. In addition, an adhesive material having excellent waterproof adhesive properties is obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

Below is a detailed description of the PVA resin (A) used according to the present invention, containing a 1,2-diol component in the side chain.

The PVA-based resin (A) used according to the present invention is a PVA-based resin containing a 1,2-diol component in the side chain. In particular, said resin may be a PVA-based resin containing, as a structural unit, a 1,2-diol of the following general formula (1):

In the compound of the indicated general formula (1), each of R ¹ , R ² and R ³ independently represents hydrogen or an alkyl group. The alkyl group is not limited to any particular alkyl group. However, an alkyl group containing from 1 to 4 carbon atoms is preferred, such as a methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl group. Said alkyl group may contain a substituent, for example a halogen, a hydroxyl group, an ester group, a carboxyl group, a sulfo group and the like, if necessary. R ⁴ represents a single bond or alkylene group containing from 1 to 3 carbon atoms, which may contain an alkyl group.

Methods for producing said PVA resin are not limited to any particular methods. However, it is preferable to obtain a resin using the method according to which the saponification of a copolymer based on a vinyl ester monomer and a compound of the general formula (2) is carried out:

In the compound of general formula (2), R ¹ , R ² , R ³ and R ⁴ are the same as defined for the compound of general formula (1). Each of R ⁵ and R ⁶ independently represents hydrogen or R ⁷ —CO—, where R ⁷ represents an alkyl group, preferably a methyl, propyl, butyl, hexyl or octyl group, wherein said alkyl group may contain a substituent, for example, halogen, a hydroxyl group, an ester group, a carboxyl group, a sulfo group and the like, as appropriate.

Examples of the compounds of formula (2) include 3,4-dihydroxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-hydroxy-1-butene, 4-acyloxy-3-hydroxy-1-butene , 3,4-diacyloxy-2-methyl-1-butene, 4,5-dihydroxy-1-pentene, 4,5-diacyloxy-1-pentene, 4,5-dihydroxy-3-methyl-1-pentene, 4 , 5-diacyloxy-3-methyl-1-pentene, 5,6-dihydroxy-1-hexene and 5,6-diacyloxy-1-hexene. Among these compounds, a compound is preferred in which each of R ¹ , R ² and R ³ is hydrogen, R ⁴ is a single bond, and each of R ⁵ and R ⁶ is R ⁷ —CO—, where R ⁷ is is an alkyl group, that is, 3,4-diacyloxy-1-butene is preferable because it has excellent copolymerizability and is convenient from a technological point of view. Particularly preferred is a compound in which R ⁷ represents a methyl group, i.e. 3,4-diacetoxy-1-butene.

It should be noted that 3,4-diacetoxy-1-butene manufactured by Eastman Chemical Company and Across Inc. available for sale.

Examples of vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, valeric acid vinyl ester, vinyl butyrate, trimethylacetic acid vinyl ester, capric acid vinyl ester, lauric acid vinyl ester, vinyl stearate, and vinyl benzoate. From the point of view of economic feasibility, vinyl acetate is preferred among these compounds.

According to the present invention, other monomers suitable for the purposes of the present invention may be copolymerized in an amount of from about 0.5 to 10 mol%. Examples of such monomers include olefins, for example ethylene, propylene, isobutylene, α-octene, α-dodecene and α-octadecene; unsaturated acids, for example acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid and their salts or mono- or dialkyl esters of these acids; nitriles, for example acrylonitrile and methacrylonitrile; amides such as diacetone acrylamide, acrylamide and methacrylamide; olefin sulfonic acids, for example ethylene sulfonic acid, allyl sulfonic acid and metal sulfonic acid, and their salts; alkyl vinyl ethers; dimethylallyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride, polyoxyalkylene (meth) allyl ether, for example polyoxyethylene (meth) allyl ether and polyoxypropylene (meth) allyl ether; polyoxyalkylene (meth) acrylate, for example polyoxyethylene (meth) acrylate and polyoxypropylene (meth) acrylate; polyoxyalkylene (meth) acrylamide, for example polyoxyethylene (meth) acrylamide and polyoxypropylene (meth) acrylamide; polyoxyethylene (1- (meth) acrylamido-1,1-dimethylpropyl) ether, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine and polyoxypropylene vinylamine.

Examples of such compounds further include the monomer having a cationic group, such as chloride, N-akrilamidometiltrimetilammoniya chloride, N-akrilamidoetiltrimetilammoniya chloride, N-akrilamidopropiltrimetilammoniya chloride, 2-acryloxyethyltrimethylammonium chloride, 2-metakriloksietiltrimetilammoniya chloride, 2-hydroxy-3-metakriloiloksipropiltrimetilammoniya, alliltrimetilammoniya chloride, metalltrimethylammonium, 3-butentrimethylammonium chloride, dimethyldiallylammonium chloride and diethyl diallylammonium chloride; an acetoacetyl group-containing monomer, ethylene carbonate, vinyl ethylene carbonate, isopropenyl acetate and 1-methoxy vinyl acetate.

The copolymerization of the above vinyl ester-based monomer with a compound of formula (2) (and possibly other monomers as well) can be carried out in accordance with known methods without particular restrictions, for example, by bulk polymerization, solution polymerization, suspension polymerization, dispersion polymerization or emulsion polymerization. Typically, polymerization is carried out in solution.

Methods for adding monomer during copolymerization are not limited to any specific methods; any desired methods can be applied, for example, one-time addition, part-by-part addition and continuous addition. However, it is preferable to carry out the polymerization by adding the monomer dropwise from the point of view that in this case a uniform distribution of the compound of formula (2) in the molecular chain of the polyvinyl ester-based polymer is ensured. In particular, a HANNA-based polymerization process is preferred.

Examples of solvents suitable for use in copolymerization generally include lower alcohols, such as methanol, ethanol, isopropyl alcohol, n-propanol and butanol, and ketones, such as acetone and methyl ethyl ketone. Under industrial conditions, methanol is preferably used.

The amount of solvent used can be selected based on a given degree of polymerization of the copolymer, taking into account the chain transfer constant for a given solvent. For example, in the case where the solvent is methanol, the amount of said solvent can be selected from a range of from about 0.01 to 10 (mass ratio) for the ratio S (solvent) / M (monomer), preferably from about 0.05 to 3 (mass ratio).

In copolymerization, a polymerization catalyst is used. Examples of the polymerization catalyst include known radical polymerization catalysts such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide and lauryl peroxide, and low temperature active polymerization catalysts such as azobisdimethylvaleronitrile and azobismethoxymethylvaleronitrile. The amount of polymerization catalyst used cannot be unambiguously determined without taking into account the specifics of the process, since it varies depending on the type of catalyst. However, the amount of said catalyst can be selected by any one depending on the polymerization rate. For example, in the case of the use of azoisobutyronitrile or acetyl peroxide, said amount is preferably from 0.01 to 0.2 mol%, particularly preferably from 0.02 to 0.15 mol%, based on the vinyl ester monomer.

The copolymerization reaction can be carried out at a temperature of from 30 ° C. to approximately the boiling point, depending on the solvent used and the pressure. More specifically, the copolymerization can be carried out at a temperature in the range from 35 to 150 ° C, preferably from 40 to 75 ° C.

Although according to the present invention, the proportion of the compound of formula (2) in the copolymer is not limited to any particular value, it can be set depending on the amount of 1,2-diol to be introduced, as indicated below.

Next, the resulting copolymer is saponified. During saponification, the resulting copolymer is dissolved in alcohol or a water-alcohol medium, and then saponification is carried out using an alkaline catalyst or an acid catalyst. Examples of said alcohol include methanol, ethanol, propanol and tert-butanol, with methanol being particularly preferred. The concentration of the copolymer in alcohol can be selected based on the viscosity of the system. However, said concentration is usually selected from a range of 10 to 60% by weight. Examples of the catalysts used in the saponification include an alkaline catalyst such as an alkali metal hydroxide and alcoholate, for example sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate and lithium methylate, and an acid catalyst such as sulfuric acid, hydrochloric acid, nitric acid, methanesulfonic acid, zeolite and cation exchange resin.

The amount of saponification catalyst used can be selected in accordance with the saponification method, a predetermined degree of saponification, etc. However, in the case of using an alkaline catalyst, a suitable ratio of said catalyst is usually from 0.1 to 30 mmol, preferably from 2 to 17 mmol, based on 1 mol of the total content of the vinyl ester monomer and the compound of formula (2).

In the preparation of a resin (A) based on PVA containing a 1,2-diol component in the side chain by saponification of the indicated vinyl ester monomer copolymer and a compound of the formula (2), the vinyl ester monomer ester group and the ester group in the compound formulas (2) are simultaneously converted to hydroxyl groups. An advantage of the above process for producing PVA resin (A) is the absence of the formation of an undesirable by-product, such as dimethyl carbonate, typically formed when using vinylethylene carbonate.

In the PVA-based resin (A) thus obtained, the content of the 1,2-diol component located in the side chain of the molecule of said resin is not limited to any particular value. However, it is preferable that said content is from 1 to 15 mol% (more preferably from 1 to 12 mol%, particularly preferably from 2 to 10 mol%, in particular from 2 to 8 mol%). Too low a 1,2-diol component is undesirable, since the result and advantages of the present invention are not fully achieved. Too high a content of said 1,2-diol is also undesirable, since the unsaturated monomer reduces the stability of the polymerization of the emulsion.

The PVA resin (A) according to the present invention should have an average degree of polymerization (determined in accordance with JIS K6726) from 50 to 2500 (from 100 to 1700, particularly preferably from 100 to 1000, in particular from 200 to 500). A PVA resin having an average degree of polymerization below 50 is not suitable since it is difficult to obtain such a PVA resin on an industrial scale. Conversely, a PVA-based resin having a too high average degree of polymerization is not suitable because the viscosity of the resulting aqueous emulsion is too high and the polymerization stability decreases during the emulsion polymerization process.

Said PVA-based resin (A) is preferably a resin in which the content of residual ester groups that have not been saponified is 15 mol% or less (more preferably 10 mol% or less). Too high a content of residual ester groups is undesirable, since the polymerization stability during the emulsion polymerization process is significantly reduced, and there may be cases when the target aqueous emulsion is not formed.

The content of residual ester groups in the resin (A) based on PVA is expressed as the ratio (mol%) of the number of unsaponified groups to the number of ester groups in the composition of the vinyl ester monomer and ester groups in the compound of formula (1).

The following is a description of polymer (B).

Polymer (B) is a polymer obtained by polymerizing at least one unsaturated monomer selected from an ethylene bond-containing monomer and a diene-based monomer. Examples of an ethylene bond-containing monomer and a diene-based monomer generally include monomers often used for emulsion polymerization, such as a vinyl ester-based monomer, an acrylic acid or its ester-based monomer, and a diene-based monomer. Examples of other monomers include olefin-based monomer, acrylamide-based monomer, acrylonitrile-based monomer, styrene-based monomer, vinyl ether-based monomer, and allyl-based monomer.

Examples of vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl ester of valerianic acid, vinyl butyrate, vinyl isobutyrate, vinyl ester of trimethylacetic acid, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate acetate, vinyl isatropate, 1-vinyl versatate acetate. Examples of monomers based on acrylic acid or its esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl ( meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate and (meth) acrylic acid. Examples of diene monomers include butadiene-1,3,2-methylbutadiene-1,3 or 2,3-dimethylbutadiene-1,3 and 2-chlorobutadiene-1,3.

Examples of olefin monomers include olefin monomers such as ethylene, propylene, 1-butene and isobutene, and halogenated olefins such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride. Examples of acrylamide-based monomers include (meth) acrylamide, N-methylolacrylamide, N, N-dimethylacrylamide, acrylamido-2-methylpropanesulfonic acid and diacetone acrylamide. Examples of acrylonitrile-based monomers include (meth) acrylonitrile. Examples of styrene-based monomers include styrene and α-methyl styrene. Examples of vinyl ethers include methyl vinyl ether, n-propyl vinyl ether, iso-propyl vinyl ether, n-butyl vinyl ether, iso-butyl vinyl ether, tert-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether. Examples of allyl-based monomers include allyl acetate and allyl chloride.

Other examples include compounds containing a carboxy group, for example fumaric acid, maleic acid (anhydride), itaconic acid (anhydride) and trimellitic acid anhydride and its esters; compounds containing a sulfo group such as ethylene sulfonic acid, allyl sulfonic acid, metal sulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid; vinylsilane compounds such as vinyltrimethoxysilane; isopropenyl acetate and 3- (meth) acrylamidopropyltrimethylammonium chloride.

Among these compounds, monomers based on (meth) acrylic acid or its esters, styrene-containing monomers based on the indicated acid, and butadiene-containing monomers based on the indicated acid are preferable from the point of view of the stability of the aqueous emulsion to alkalis.

Although the monomer containing an ethylene bond and the diene monomer can be polymerized separately, a mixture of two or more of these monomers can, of course, also be polymerized (copolymerized).

The following is a description of the process for producing an aqueous emulsion according to the present invention.

To obtain an aqueous emulsion, methods such as emulsion polymerization and a method followed by emulsification can be used. The first of these methods, that is, emulsion polymerization, can be carried out in accordance with (i) the traditional emulsion polymerization method, according to which the unsaturated monomer containing an ethylene bond and / or the diene monomer are added simultaneously or continuously in the presence of water, PVA-based resins and a polymerization catalyst, and then heated and stirred; or (ii) in accordance with an emulsion polymerization method, according to which an dispersion solution (pre-emulsion) obtained by mixing and dispersing an unsaturated monomer containing an ethylene bond and / or a diene monomer in an aqueous solution of a PVA-based resin is added; the specified addition is carried out simultaneously or continuously in the presence of water, a resin based on PVA and a polymerization catalyst, and then the specified solution is heated and mixed.

The amount of PVA-based resin (A) used varies slightly depending on the type of resin, the resin content in the emulsion, etc. However, in the General case, it is preferable that the amount of the specified resin ranged from 0.1 to 30 wt.% (More preferably from 1 to 25 wt.%, Particularly preferably from 2 to 20 wt.%) Based on the total weight of the reaction system involved in emulsion polymerization. An amount of resin of less than 0.1 wt.% Is undesirable since it is difficult to maintain polymer particles in a stable emulsified state. Conversely, an amount of resin of more than 30 wt.% Is undesirable, since the emulsion viscosity becomes too high, which leads to a decrease in processability and too low water resistance.

As the polymerization initiator, potassium persulfate, ammonium persulfate, potassium bromate and the like are generally used, individually or in combination with sodium hydrosulfite. In addition, a water-soluble redox system such as hydrogen peroxide / tartaric acid, hydrogen peroxide / iron salt, hydrogen peroxide / ascorbic acid / iron salt, hydrogen peroxide / rongalite or hydrogen peroxide / rongalit / iron salt can be used as a polymerization initiator . In particular, a catalyst containing an organic peroxide and a redox system such as Kayabutyl B or Kayabutyl A-50C (both of which are manufactured by Kayaku Akzo Co., Ltd.) can be used.

Methods for adding a polymerization initiator are not limited to any particular methods. You can, for example, use the method according to which the entire amount of the polymerization initiator is added at a time at the beginning of the process, or the method according to which the polymerization initiator is added continuously during the polymerization.

In the above emulsion polymerization, a water-soluble polymer, a nonionic surfactant or an anionic surfactant can also be used as a dispersion stabilizer.

Examples of the water-soluble polymer include PVA different from the above PVA-based resin (A), for example, unmodified PVA, PVA containing a carboxyl group, formylated PVA, acetalized PVA, butyralized PVA, urethaneised PVA, and PVA esterified with an acid, for example, sulfonic acid or carboxylic acid and a saponified copolymer of a vinyl ester and a monomer copolymerizable with said ester. Examples of a vinyl ester copolymerizable monomer include olefins such as ethylene, butylene, isobutylene, α-octene, α-dodecene and α-octadecene; unsaturated acids, such as acrylic acid, methacrylic acid, cretonic acid, maleic acid, maleic anhydride and itaconic acid, or its salts, or mono- or dialkylated esters; nitriles such as acrylonitrile and methacrylonylryl; amides such as acrylamide, diacetone acrylamide and methacrylamide; olefin sulfonic acid, for example ethylene sulfonic acid, allyl sulfonic acid and metal sulfonic acid, and its salts; alkyl vinyl ethers, vinyl ketone, N-vinyl pyrrolidone, vinyl chloride and vinylidene chlorides.

Examples of a water-soluble polymer other than the above PVA include cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, aminomethylhydroxypropyl cellulose acid, aminomethylhydroxypropyl cellulose acid, aminomethyl hydroxy cellulose cellulose, and polyvinylpyrrolidone, polyacrylic acid or its salts, polymethacrylic acid or its salts, polyacryl mide, polymethacrylamide, a copolymer of vinyl acetate and an unsaturated acid such as maleic acid, maleic anhydride, acrylic acid, methacrylic acid, itaconic acid, fumaric acid and crotonic acid, a copolymer of styrene and one of the above unsaturated acids, a copolymer of vinyl ether and one of the above unsaturated acids and salts or esters of the above copolymers.

Examples of nonionic surfactants include, for example, compounds such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol, polyoxyethylene ester and polyhydric alcohol, polyhydric alcohol and fatty acid ester and hydroxyethylene / hydroxypropylene block polymer.

Examples of anionic surfactants include higher alcohol sulfate, an alkali metal salt of a higher fatty acid, polyoxyethylene ether and alkyl phenol sulfate, alkyl benzene sulfonate, a condensed naphthalene sulfonate and formalin compound, alkyl diphenyl ether sulfonate, dialkyl sulfosuccinate and higher alcohol salt.

In addition, you can also use a plasticizer, such as phthalic acid ester or phosphoric acid ester, and a pH adjuster, such as sodium carbonate, sodium acetate or sodium phosphate.

The average particle diameter of the polymer is preferably 200 nm or more (more preferably 300 nm or more). By adjusting the average particle diameter to 200 nm or more, an emulsion is obtained having a minimum film formation temperature (MTOP) of 10 ° C or more. Such an emulsion has a high resistance to mechanical stress.

The average particle diameter in this case means the numerical value of the average particle diameter (Dn) measured using a DLS-700 dynamic light scattering photometer manufactured by Otsuka Electronics Co., Ltd. under the following conditions and calculated using a histogram.

Conditions for obtaining a sample for measurements

The emulsion (EM) was diluted with water passed through an ion-exchange filter so as to obtain a 0.05 wt.% Aqueous solution.

Measurement conditions on the "DLS-700"

Set the aperture (⌀ 0.1 to ⌀ 0.2) and the ND filter (ND50 to ND25) in such a way as to provide a sample rate per second (CPS) (light energy) of 5000 to 12000, and measurement carried out under the following conditions:

SAMPLING TIME (standard time): 40 μs

ACCUM. TIMES (accumulation time) (amount of integration): 100 times

CORRE CH (set value for convergence of the correlation function): 256

In order to further increase the resistance of the polymerization and the resistance of the emulsion to mechanical stresses, it is preferable to co-use a water-soluble polymerization inhibitor in an amount of from 10 to 500 ppm (more preferably from 10 to 200 ppm) based on the amount of PVA-based monomer with resin (A) as an emulsifier .

A water soluble polymerization inhibitor is not limited to any particular compound. Examples of said inhibitor include a thiocyanic acid salt, a nitrous acid salt, and a water-soluble sulfur-containing organic compound. Examples of the thiocyanic acid salt include ammonium thiocyanate, zinc thiocyanate, sodium thiocyanate, potassium thiocyanate and aluminum thiocyanate. Examples of the nitrous acid salt include sodium nitrite, potassium nitrite, ammonium nitrite, calcium nitrite, silver nitrite, strontium nitrite, cesium nitrite, barium nitrite, magnesium nitrite, lithium nitrite and dicyclohexylammonium nitrite. Examples of a water-soluble sulfur-containing organic compound include a hydroxyl substituted mercaptan, for example mercaptoethanol, monothiopropylene glycol and thioglycerol; mercaptocarboxylic acid, such as thioglycolic acid, thiohydracrylic acid, thiolactic acid and thiomaleic acid; amino substituted mercaptan such as thioethanolamine; nitro-substituted mercaptan such as β-nitroethyl mercaptan; a divalent mercapto group containing a hydroxyl group as a substituent, such as 1,2-dithioglycerol and 1,3-dithioglycerin; dimercaptoketones, such as 1,3-dimercaptoacetone; dimercaptocarboxylic acid, such as β, β-dithioisobutyric acid; hydroxyl-substituted sulfide such as thioglycol; hydroxyl-substituted sulfide such as thiodiglycol; sulfide carboxylic acid such as thiodiglycolic acid, β, β-thiodipropionic acid and thiodimactic acid; an aldehyde-substituted sulfide such as β-methylthiopropionic aldehyde; amino substituted sulfide such as β-aminoethyl sulfide; nitro-substituted sulfide such as β-nitroethyl sulfide; and a mercapto-substituted sulfide such as β-mercaptoethyl sulfide. The rate of addition of the indicated water-soluble polymerization inhibitor, expressed in units of the degree of conversion of the acrylic monomer during the polymerization, is preferably from 5 to 75%. If the addition of this inhibitor is carried out before the degree of conversion of the monomer reaches 5%, the dispersion of the polymerized system deteriorates, which leads to the formation of an acrylic-based emulsion containing a larger number of large particles. On the other hand, the addition of this inhibitor after the degree of conversion of the monomer reaches 75% is undesirable from the point of view of the inhibitory effect on the formation of large particles in acrylic emulsions and to increase the resistance of the emulsion to mechanical stress.

In the case of adding a water-soluble polymerization inhibitor, the polymerization initiator is preferably oil soluble. Preferably, said initiator is pre-dissolved in the monomer, since it is effective in inhibiting the formation of large particles.

Said oil-soluble polymerization initiator is not limited to any particular compounds. Examples of said initiator include peroxydicarbonate, such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate; a peroxy ester such as tert-butyl peroxyneodecanoate and α-cumyl peroxyneodecanoate; peroxide, such as acetylcyclohexylsulfonyl peroxide; and an azo compound such as azobis-isobutyronitrile, azobis-2,4-dimethylvaleronitrile and azobis- (4-methoxy-2,4-dimethylvaleronitrile).

Depending on the specific task, a combination of any nonionic surfactant, such as polyoxyethylene and alkyl ether, such as polyoxyethylene alkylphenol and polyhydric ester can also be used; cationic surfactants, such as salts of higher alkylamines, and other various surfactants suitable for use in emulsion polymerization, as described above. You can also mix these surfactants in advance for subsequent use for emulsification. In addition, a pH adjuster such as phthalic acid ester, sodium acetate or sodium phosphate can also be used in combination.

If necessary and depending on the specific application, additives for various purposes can be added to the target aqueous emulsion. Examples of these additives include a crosslinking agent, an additive that provides increased water-resistant properties, a pigment, a dispersant, an anti-foaming additive; oil solution, viscosity modifier, tackifier, thickener, water-retaining agent, fiber softening agent, leveling agent and antistatic agent.

Thus obtained aqueous emulsion has excellent resistance to mechanical stress, stability during freezing and resistance to high temperatures. The resulting emulsion can be successfully used, for example, as an additive to cement / mortar, as a coating material based on cement / mortar, as a starting material for civil engineering, coating material, adhesive material, adhesive adhesive material (adhesive material, pressure sensitive), fiber treatment agent, paper processing agent, inorganic binder, resin modifier, e.g. vinyl chloride, fi sation / stabilizing viscous soil such as sludge and industrial waste, removable coating material for surface protection and for cosmetic purposes.

Particularly preferred of these applications are the use as an additive to cement / mortar, a cement / mortar based coating material, a starting material for civil engineering purposes, a coating material, and the like. The advantage of this aqueous emulsion when used for the indicated purpose is its resistance to mechanical stress. In addition, it is particularly preferable to use said aqueous emulsion as an adhesive material or an adhesive adhesive material (pressure sensitive adhesive material); while the advantage of this emulsion is its excellent water resistance and adhesive / adhesive properties. Examples of suitable bonding materials include wood, paper, plastic and fibers.

When used as an adhesive material, the aqueous emulsion according to the present invention, taken separately, can be used as an adhesive one-component material. The composition of this aqueous emulsion is usually controlled so that the resin concentration in said emulsion is preferably 20 wt.% Or more, and more preferably 45 wt.% Or more.

If the resin concentration is less than 20 wt.%, Then in some cases drying takes place for a longer time, or the specified aqueous emulsion is excessively absorbed in bonded materials such as wood, which can lead to a decrease in adhesion, which is undesirable.

The aqueous emulsion according to the present invention can be converted into a re-dispersible powdery synthetic resin by removing water from said emulsion. Methods for removing water are not limited to any specific methods. Examples of such methods include spray drying, heat drying, blow drying, freeze drying and pulsed shock drying. In industry, spray drying is preferred.

For spray drying, a conventional spray drying apparatus in which the liquid is sprayed and dried can be used. Examples of such settings, depending on the type of spraying, include a disk type setting and a nozzle type setting, and any of these types can be used. As a source of heat, you can use hot air, heating steam, etc.

Drying conditions are selected in accordance with the size and type of spray drying apparatus, concentration, viscosity and flow rate of the aqueous emulsion, etc. A suitable drying temperature is from 80 to 150 ° C. If the drying temperature is less than 80 ° C, drying is insufficient. If the drying temperature is more than 150 ° C, changes in the polymer may occur under the influence of heat. Both of these cases are not preferred. More preferred is a drying temperature of from 100 to 140 ° C.

The possibility of clumping of particles of a re-dispersible powdery synthetic resin and their aggregation during storage with the formation of blocks is not ruled out. Therefore, it is preferable to use an anti-clumping agent to improve storage stability. This anti-clumping agent can be added to the emulsion powder obtained after spray drying and mixed to ensure uniform distribution. However, it is preferable that during spray drying, the emulsion is sprayed in the presence of an anti-clumping agent, which allows for uniform mixing and prevents clumping. Especially preferred is the simultaneous spraying of the emulsion and the anti-clumping agent during drying.

The anti-clumping agent is preferably an inorganic powder of fine particles. Examples of this agent include calcium carbonate, clay, silicic anhydride, aluminum silicate, carbon black, talc and white corundum. Particularly preferred are silicic anhydride, aluminum silicate, calcium carbonate and the like, each of which has an average particle diameter of from about 0.01 to about 0.5 microns. The amount of anti-clumping agent used is not limited to any particular value. However, preferably this amount is from 2 to 20 wt.% Based on the powder of the emulsion.

In this way, a re-dispersible powdery synthetic resin is obtained. By adding the powder of said resin to water and stirring this mixture, the powder can easily be converted back to the emulsion. Thus obtained re-dispersed emulsion can be used in the same way as the original emulsion, and it also has high resistance to mechanical stress.

Like an aqueous emulsion, a dispersible powdery synthetic resin is suitable for use, for example, as an additive to cement / mortar, cement / mortar based coating material, civil engineering starting material, coating material, adhesive material, adhesive adhesive material (pressure sensitive adhesive material), fiber treatment agent, paper processing agent, binder for inorganic materials and for cosmetic purposes. In particular, the re-dispersible powdery synthetic resin according to the present invention can advantageously be used as an additive for cement or mortar. An explanation of the indicated application is given below.

When used as an additive for cement or construction mixtures, the above powder resin is preferably used in an amount of about 20 mass fractions (from 5 to 30 mass fractions, more preferably from 10 to 30 mass fractions) per 100 mass fractions of cement in terms of the properties of the obtained cured material etc. From the point of view of economic feasibility, it is preferable to use the specified powdered resin in an amount of about 10 mass fractions (from 5 to 15 mass fractions, more preferably from 8 to 12 mass fractions).

Examples of methods for adding said powdered synthetic resin include a method in which the resin is mixed with cement (added to cement) beforehand; the method according to which the resin is pre-mixed with water (added to water); and a method according to which the resin is simultaneously mixed with cement and water.

EXAMPLES

Below the invention will be explained in detail with reference to Examples. However, the present invention is not limited to the following Examples.

Hereinafter “%” means mass percent, unless otherwise indicated.

Production Example 1: PVA-based resin (A1)

800 g of vinyl acetate, 1200 g of methanol and 96 g (6 mol%) of 3,4-diacetoxy-1-butene were added to a reaction vessel equipped with a reflux condenser, dropping funnel and stirrer. To this mixture was added azobis-isobutyronitrile in an amount of 0.6 mol% (based on the added vinyl acetate). The mixture was heated with stirring in a stream of nitrogen to initiate polymerization. When the polymerization degree of vinyl acetate reached 95%, m-dinitrobenzene and methanol were added in predetermined quantities to dilute and cool the mixture and complete the polymerization. Then, the remaining unreacted vinyl acetate monomer was removed from the system by sparging through a system of methanol vapors. Thus, a solution of the copolymer in methanol was obtained.

Then this solution was diluted with methanol to a concentration of 50%. This solution was placed in a kneading machine and a 2% solution of sodium hydroxide in methanol was added to it in an amount of 10 mmol per 1 mol of the total amount of vinyl acetate and 3,4-diacetoxy-1-butene in the copolymer, maintaining the solution temperature at 40 ° C. for saponification. During saponification, the saponification product precipitated. At the moment when the precipitate took the form of particles, it was separated by filtration. The precipitate was sufficiently washed with methanol and dried in a hot air dryer to obtain a PVA-based resin (A1).

The obtained PVA-based resin (A1) was examined for the content of the residual ester group by determining the spent amount of alkali necessary for the hydrolysis of residual vinyl acetate and 3,4-diacetoxy-1-butene. As a result, it was found that the amount of residual ester group was 2.5 mol%. The average degree of polymerization was determined in accordance with JIS K 6726, which was found to be 300. The content of the structural unit based on 1,2-diol was determined by calculation after completion of saponification and subsequent analysis by ¹ H-NMR; it was found to be 5.9 mol%. For the NMR analysis, an AVANCE DPX400 instrument manufactured by Bruker Japan Co., Ltd. was used.

Production Example 2: PVA Resin (A2)

800 g of vinyl acetate, 1200 g of methanol and 64 g (4 mol%) of 3,4-diacetoxy-1-butene were added; for the polymerization in the same manner as in Production Example 1, 0.4 mol% (based on added vinyl acetate) of azobis-isobutyronitrile was used. The degree of polymerization of vinyl acetate was 96%.

Then, saponification, washing and drying were carried out in the same manner as in Production Example 1, except that the amount of sodium hydroxide added changed to 8 mmol per 1 mol of the total content of vinyl acetate and 3,4-diacetoxy-1-butene in the copolymer. Thus, a resin (A2) based on PVA was obtained.

The obtained PVA-based resin (A2) had a residual ester group content of 6.0 mol% and an average degree of polymerization of 350. The content of the 1,2-diol-based structural unit in said resin was 4.0 mol%.

Production Example 3: PVA Resin (A3)

800 g of vinyl acetate, 1200 g of methanol and 24 g (1.5 mol%) of 3,4-diacetoxy-1-butene were added; for the polymerization (in the same manner as in Production Example 1), 0.5 mol% (based on added vinyl acetate) of azobis-isobutyronitrile was used. The degree of polymerization of vinyl acetate was 95%.

Then, saponification, washing and drying were carried out in the same manner as in Production Example 1. Thus, PVA-based resin (A3) was obtained.

The obtained PVA-based resin (A3) had a residual ester group content of 2.2 mol% and an average degree of polymerization of 450. The content of the structural unit based on 1,2-diol was 1.5 mol%.

Production Example 4: PVA Resin (A4)

1000 g of vinyl acetate, 900 g of methanol and 16 g (0.8 mol%) of 3,4-diacetoxy-1-butene were added; for the polymerization (in the same manner as in Production Example 1), 0.4 mol% (based on added vinyl acetate) of azobis-isobutyronitrile was used. The degree of polymerization of vinyl acetate was 92%.

Then, saponification, washing and drying were carried out in the same manner as in Production Example 1, except that the resin concentration was changed and was 40%, and the amount of added sodium hydroxide changed and was 7 mmol per 1 mol of the total vinyl acetate content and 3,4-diacetoxy-1-butene in a copolymer. Thus, a resin (A4) based on PVA was obtained.

The resulting PVA-based resin (A4) had a residual ester group content of 2.5 mol% and an average degree of polymerization of 750. The content of the structural unit based on 1,2-diol was 0.7 mol%.

Production Example 5: PVA Resin (A5)

The concentration of the methanol solution of polyvinyl acetate (with an average degree of polymerization determined according to JIS K6726 after complete saponification of polyvinyl acetate equal to 300) obtained by polymerization in solution was set to 50%. This solution was placed in a kneading machine, and a 2% methanol solution of sodium hydroxide was added thereto in an amount of 10 mmol per 1 mol of the vinyl acetate-based structural unit in the polymer, while the temperature of the solution was maintained at 40 ° C for saponification. In the course of saponification, the saponification product precipitated. At the moment when this precipitate took the form of particles, it was separated by filtration. The precipitate was sufficiently washed with methanol and dried in an oven with hot air. Thus, a resin (A5) based on PVA was obtained, which had a residual ester group content of 2.8 mol%.

Production Example 6: PVA Resin (A6)

1500 g of vinyl acetate, 75 g of methanol and 30 g (1.0 mol%) of 3,4-diacetoxy-1-butene were added; for polymerization in the same manner as in Production Example 1, 0.0015 mol% (based on added vinyl acetate) of azobis-isobutyronitrile was used.

Then, saponification, washing and drying were carried out in the same manner as in Production Example 1, except that the resin concentration was changed to 20% and the amount of sodium hydroxide added changed to 10 mmol per 1 mol of the total vinyl acetate content and 3,4-diacetoxy-1-butene in a copolymer. Thus, a resin (A6) based on PVA was obtained.

The obtained PVA-based resin (A6) had a residual ester group content of 2.4 mol% and an average degree of polymerization of 2900. The content of the structural unit based on 1,2-diol was 1.0 mol%.

Example 1

In an interchangeable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer, 83 parts of water, 12 parts of PVA-based resin (A1) obtained in Example 1, 0.02 parts of sodium acetate as a pH regulator and 18 hours were added. monomers intended for polymerization (methyl methacrylate / n-butyl acrylate = 60/40 (mass ratio)). The temperature in the flask was raised to 60 ° C with stirring. During heating, 5 parts of a 1% aqueous solution of ammonium persulfate were added, while replacing the atmosphere in the flask with nitrogen gas to initiate polymerization. Initial polymerization was carried out for 30 minutes. To carry out the polymerization of the remaining monomer, 102 parts of the monomer were added dropwise over 4 hours and 5 parts of a 1% aqueous solution of ammonium persulfate was added in four doses at 1 hour intervals. After that, the mixture was kept at 75 ° C for 1 hour, and then cooled to obtain an aqueous emulsion of methyl methacrylate / n-butyl acrylate copolymer. This emulsion had a solids content of 55%.

The aqueous emulsion obtained above was evaluated by the following properties. The results are shown in the Table.

Polymerization Resistance

The resulting emulsion was diluted with water and filtered through a 100 mesh metal sieve. The large particles remaining on the metal sieve were dried at 105 ° C for 3 hours and their dry weight (X g) was determined. The number of large particles (%) was calculated using the following equation and used as an indicator of the polymerization stability.

The number of large particles (%) = [(X (g) / (mass of solid in the emulsion (g)] × 100

Resistance to mechanical stress

When using the Maron tester manufactured by Yasuda-Seiki-Seisakusho Ltd. Measurements were taken under the following conditions:

Resin Content: 20%

Used amount: 50 g

Rotational speed: 100 rpm (± 20)

Time: 10 minutes

Load: 40 kgf

The emulsion that was tested was filtered through an 80 mesh metal sieve and the dry weight of the aggregates was measured on a metal sieve W (g). The amount of aggregates formed (%) was determined using the following equation. The indicated amount was evaluated based on the following criteria.

The number of aggregates obtained (%) = (W (g)) / [(50 (g)) × (resin content in the emulsion (20%))] × 100

And ... (the number of aggregates formed) <0.10

B ... 0.10 ≤ (number of aggregates formed) <1.00

С ... 1.00 ≤ (number of aggregates formed)

Freeze Stability

50 g of the resulting emulsion was placed in a 100 ml polymer container, and this container was kept in the freezer at -15 ° C for 16 hours to freeze the emulsion. After that, the container was kept in a thermostat chamber at 25 ° C for 8 hours, so that the emulsion melted. This cycle was repeated and the number of cycles was calculated in which the emulsion does not return to the emulsified state upon melting, i.e., it begins to separate after solidification into solid and water. The specified parameter was evaluated based on the following criteria.

And ... 10 times or more

AT …. 4 to 9 times

C ... 3 times or less

Resistance to high temperatures

300 g of the resulting emulsion were placed in a 450 ml mayonnaise jar. The viscosity of the emulsion was measured at 25 ° C (V ₀ ) using a BROOKFIELD type viscometer. The emulsion was kept in a thermostat chamber at 60 ° C for 10 days, and then the viscosity was measured at 25 ° C (V ₂₀ ). The ratio between these viscosities (V ₂₀ / V ₀ ) was determined.

Moisture-free adhesive properties

The resulting emulsion was applied to a paper base for a roll of paper in an amount of 30 g / m ² . Immediately after this, it was applied to another paper base for a roll of paper and rolled three times with a hand roller, and then the assembly was held at room temperature for 24 hours. The adhesion test specimen was immersed in water at 30 ° C for 24 hours, and then the degree of adhesion was examined. A sample was evaluated according to the following criteria:

And ... the destruction of the bonded material

B ... partial destruction of the material to be bonded

C ... lag

Resistance to re-dispersed emulsion to mechanical stress

To the emulsion obtained, a finely divided powder of silicic anhydride (anti-clumping agent) was added in an amount of 5 wt.% Based on the solids content in the emulsion. The mixture was dried by spraying in a stream of hot air (120 ° C) to obtain a re-dispersible powder resin. 20 parts of the obtained resin powder were added to 80 parts of deionized water and the mixture was stirred to obtain a re-dispersed emulsion. The mechanical stability of the obtained reconstituted emulsion was evaluated as described above.

Examples 2-4

Aqueous emulsions were obtained in the same manner as in Example 1, except that we used air defense resins (A2-A4) obtained according to Production Examples 2-4. Assessment of these aqueous emulsions was carried out in a similar manner. The results are shown in the Table.

Comparative Examples 1 and 2

Aqueous emulsions were obtained in the same manner as in Example 1, except that the PVA-based resins (A5 and A6) obtained according to Production Examples 5 and 6 were used. These aqueous emulsions were evaluated in a similar manner. The results are shown in the Table.

The present invention is described in detail with reference to specific options for its implementation, while it is obvious to a person skilled in the art that various possible changes and modifications are also within the scope of the present invention.

This application is based on the Japanese patent application filed September 29, 2004 (application No. 2004-283771) and the Japanese patent application filed September 29, 2005 (application No. 2005-283200), the contents of which are incorporated into this description by links.

INDUSTRIAL APPLICABILITY

The aqueous emulsion according to the present invention is characterized by excellent stability of emulsion polymerization leading to the production of said emulsion, and has excellent resistance to mechanical stress, stability when frozen, resistance to long-term exposure to high temperatures, adhesive properties not affected by moisture, etc. In addition, this emulsion can be turned into a powder by removing water. Since the obtained powdery resin, when redispersed in water, forms an emulsion with excellent mechanical resistance, the proposed aqueous emulsion and powdery resin obtained from the specified aqueous emulsion are suitable for use as an additive to cement / mortar, a coating material based on cement / mortar, source material for civil engineering purposes, coating material, adhesive material, adhesive adhesive material (cu pressure-sensitive adhesive material), fiber treatment agent, plain paper processing agent, inkjet paper processing agent, inorganic binder, cosmetics, and the like. In particular, the proposed emulsion is particularly suitable for use as an additive to cement or mortar.

Claims (5)

1. An aqueous emulsion containing:
resin (A) based on polyvinyl alcohol in an amount of from 0.1 to 30 wt.%, containing a structural block of 1,2-diol in the side chain and having an average degree of polymerization from 50 to 500; and
polymer (B), which is a polymer obtained by emulsion polymerization of at least one unsaturated monomer selected from a monomer containing an ethylene bond and a diene type monomer, in the presence of polyvinyl alcohol-based resin (A) as an emulsifier in the presence of an initiator, while the specified structural block of 1,2-diol corresponds to the General formula (1):

where each of R ¹ , R ² and R ³ independently represents a hydrogen atom or an alkyl group, and R ⁴ represents a single bond or alkylene group containing from 1 to 3 carbon atoms, possibly substituted by a methyl group; and the solid content in the emulsion is from 20 to 50 wt.%. 2. The aqueous emulsion according to claim 1, characterized in that the content of the specified structural block of 1,2-diol in the resin (A) based on polyvinyl alcohol is from 1 to 15 mol.%. 3. An aqueous emulsion according to any one of claims 1 or 2, characterized in that said unsaturated monomer containing an ethylene bond is an acrylic based monomer. 4. The re-dispersible powder resin obtained by removing water from an aqueous emulsion according to any one of claims 1 to 3. 5. An adhesive containing an aqueous emulsion according to any one of claims 1 to 3.