Method for preparing styrene-acrylic copolymers aqueous dispersions

FIELD: chemical industry, chemical technology, polymers.

SUBSTANCE: invention relates to a method for preparing aqueous polymer dispersions of the multipurpose designation. Method for preparing an aqueous dispersion of styrene-acryl copolymer is carried out by preliminary emulsifying a mixture of acrylic monomers with styrene in the presence of emulsifying agent and the following aqueous-emulsion co-polymerization of the reaction mixture in the presence of initiating agent. Monomer mixture comprises additionally acrylamide, and method involves using ammonium persulfate and hydrogen peroxide as an initiating agent. Method involves the successive fractionally dosing feeding ammonium persulfate for two stages followed by addition of a mixture of polymethylsiloxane of molecular mass 55-1000 Da and iron sulfate in their mass ratio = (25-35):1 to the reaction mixture at stirring, cooling the reaction mass and its neutralization to pH = 5-6. Invention provides preparing the stable aqueous polymeric dispersion with diminished size of particles. Invention provides enhancing strength and water resistance of film prepared on its base.

EFFECT: improved preparing method.

1 tbl, 3 ex

 

The invention relates to the chemistry of polymers, and in particular to methods of obtaining water styrene-acrylic polymer dispersions, which are widely used in various industries, such as film-forming agents for paints and varnishes, petlevoj, plasters, glues, adhesives for wood, paper, textiles; as a binder in the manufacture of paper, molded; as a binder in the construction industry, in particular as additives to concrete, construction adhesives, building solutions.

The above multi-purpose water dispersion of styrene-acrylic copolymer leads to increased requirements to the quality of its products, primarily low content of residual monomers, the increased stability of the dispersion, and a high level of cohesion and adhesion properties to various materials (metal, wood, stone, paper, textiles), as well as other high performance properties, such as elasticity, mechanical strength, water-resistant films and coatings based on it.

A known method of reducing the content of residual monomers in aqueous dispersions of polymers in the process of obtaining them is their depolymerization by introducing an additional amount of initiator after the end of the main polymerization process. Describe the method of obtaining aqueous dispersions of (meth)acrylic (co)polymers by emulsion polymerization of the pre-emulsified monomers in the presence of water-soluble redox systems the basis of peroxides followed by depolymerization in the presence of additional redox system (Japan's bid No. 54-6089, CL 08 F 2/02, epubl).

At the stage of preliminary emulsification to prepare a mixture containing monomers (for example, methyl methacrylate, butyl acrylate, Acrylonitrile and acrylic acid), emulsifier, water and a redox system containing a potassium persulfate and sodium metabisulfite. As an emulsifier, a mixture of dodecylbenzenesulfonate sodium and ethoxylated Nonylphenol. The correlation of phases monomers: water in the emulsion is 1:1,45.

The first main stage polymerization is carried out by dosingthe mixture in the reactor, containingthis mixture, when 60-75°C for 1 h Then add 30 minutes additional amount of methyl methacrylate and specified redox system and continue the reaction until completion of polymerization.

In the second stage of polymerization of the polymer mixture is cooled to 45-50°add in another redox system containing a peroxide tert-butyl and ascorbic acid, and incubated for about 1 h to Receive the aqueous dispersion of a copolymer with the following content of residual monomers: metalmetal elata 0,013%, of butyl acrylate 0,035% and Acrylonitrile 0,021%.

The described method allows to reduce the content of residual monomers. However, this comes at the expense of introduction of the initiator on the primary stage of polymerization and additional Stora stage depolymerization, which complicates the process.

Due to the specified multi-purpose such polymer dispersion should provide a high degree of penetration of the material into the surface with low porosity (less than 1 Ám). Usually the best penetration into porous substrates, provide solutions of polymers in organic solvents. Dispersion polymers generally having a sufficiently large size particles do not penetrate into the porous substrate to a depth necessary to achieve high adhesion and strength complex paintwork.

At the present time in connection with the tightening of requirements of ecological safety of construction works extremely relevant is the use of a complex of a water-dispersible materials, including primers, deep penetration, strengthen cement and concrete substrate and improve the quality of application of finishing coats of paint (increase coverage and improve the appearance of the coating, in particular when refinishing old substrates (the restoration work. In addition, the use of dispersions of copolymers with small particle size in the formulation of paints and varnishes for finishing works in construction, coating and other applications will improve the continuity of the film, to increase the resistance and service life of the coatings.

To obtain a film-forming method set forth in A.S. No. 197171, with the aim of increasing the adhesion properties of coatings using acrylamide or methacrylamide. The resulting copolymer also contains a reduced amount of coagulate. However, the copolymer obtained in this way contains a significant amount of residual monomers (0,1-0,2%), and the particle size of the dispersion is 180-250 nm.

From RU 2171813, 10.08.2001 known method of preparation of stable aqueous dispersions of polymers by radical polymerization ethanobotany monomers (vinyl aromatic hydrocarbons, such as styrene, α,β-monomethylethanolamine mono - and dicarboxylic acids, such as acrylic acid, methacrylic acid, their amides, esters of (meth)acrylic acid) according to the method of the suspension or emulsion polymerization in the presence of one or more colloids with a molecular weight ≤500000, containing

a) at least 20 wt.% Monomeric units containing sulfoxylate or sulphonate group,

b) 480 wt.% Monomeric units, containing N - methylol - or N-alkoxymethyl group,

C) 0.1 to 20 wt.% hydrophobic monomer unit from the group of water-insoluble ethanobotany compounds and hydrophobic end groups of residues initiators or molecules, regulators, and the number, expressed in wt.%, stated in terms of the total weight of the copolymer and the part containing sulfoxylate/sulphonate groups of monomer units, optionally up to 50 wt.%, in terms of the weight amount of monomer units (a)may be substituted containing carboxyl groups managerseminare g) or containing amide groups of the Monomeric units d).

Thus obtained polymer dispersion does not contain clots and has the following characteristics: solids content material 55,2-56,1%, pH of 4.8, the size of the particles 330-440 nm, the viscosity 5450 MPa·C.

From RU 2076109, 27.03.1997, a method of obtaining aqueous dispersions of polymers by emulsification (meth)acrylic monomers or mixtures thereof with vinyl monomers with subsequent emulsion polymerization in the presence of a radical initiator, according to which the emulsification is carried out at a mass ratio of monomer: water of 1:0.1 to 0.7, in the presence as an emulsifier anionic compounds of General formula I: R-O(CH2-CH2O)nHO3IU

where X Is S, P, M-K, Na, NH4;

when R is alkyl n=1-13, R-alkylphenyl, dialkylphenol n=6-30, or its mixture with nonionic compound of General formula II:

R-O(CH2CH2O)n- H

where R is alkylphenyl, dialkylphenol n=6-100, containing at least 0.4% by weight of monomers of the compounds of formula I, when a total content of emulsifiers of at least 0.5% by weight of monomers. Examples of emulsifiers used in the known above-mentioned method, are anionic compound is a sodium or potassium salt of laurylsulfate (n=1-13), ammonium salt sulfoacetaldehyde (di)of Nonylphenol (n=6-12, 12-30), ammonium salt tridesilon-fetoxilate (n=10), ammonium salt potatogrowing of Nonylphenol (n=6), as non-ionic compounds use ethoxylated nonylphenols (n=12,100), ethoxylated dinonylphenol (n=6-20). The amount of emulsifier depends on the composition in liberatoaa system and the effectiveness of the emulsifier and 0.5-10 wt.%.

To obtain the copolymer is first prepared monomer emulsion with a ratio of phases monomers: water = 1:0,1-0,7. As acrylic monomers using methyl acrylate, acrylate, butyl acrylate, 2-ethyl-hexylaniline, acrylic acid, as methacrylic monomers is methyl methacrylate, methylolmethacrylamide, methacrylic acid, as a vinyl - styrene, vinylize is at. The prepared emulsion of monomers is metered into the reactor for 1.5-2 hours and simultaneously serves the polymerization initiator (sodium persulfate or potassium). The temperature of copolymerization depends on the initiator used.

There is a method allows to obtain a styrene-acrylic dispersion with a low content of residual monomers (0,005-0,01%), stable to electrolytes, as well as to mechanical impact. The description is not given data on the particle size, however when playing this way were obtained polymer dispersion with a particle size of 150-200 nm. This known method is the closest to the claimed as the invention method.

The technical objective of the claimed invention to provide a stable aqueous polymer dispersion with reduced particle size, increased strength and water resistance of the films obtained on its basis.

The goal of the project is achieved in that in the method of obtaining a water dispersion of styrene-acrylic copolymer by pre-emulsification mixture of acrylic monomers with styrene in the presence of emulsifier and the subsequent emulsion copolymerization reaction mixture in the presence of the initiator as an initiator, a mixture of ammonium persulfate and hydrogen peroxide, when this is carried out after ovately fractional dosed feed initiator, then under stirring, the reaction mixture was injected mixture of polyorganosiloxane with a molecular weight of 500-1000, and iron sulfate at a mass ratio of 25-35:1, cooled the reaction mass is neutralized to pH 5-6.

In the method according to the invention as the acrylic monomer mixture, composed, for example, from (meth)acrylic acid ester (meth)acrylic acid (methyl methacrylate, butyl acrylate, methyl acrylate, acrylate, methacrylamide, acrylamide.

As the emulsifier in the implementation of the method according to the invention using, for example, etclromano fatty alcohols with C8-C36alkyl groups and the degree of amoxilonline (EA-degree) from 3 to 50; ethoxylated mono-, di-, and dialkylphenol with4-C10alkyl groups and the degree of EO from 3 to 50; alkali metal salts of di-C4-C12alilovic esters sulfonterol acid. Acceptable salts of alkali metals and ammonium C8-C12of alkyl sulphates, ethoxylated alkanols with C12-C18alkyl group and with a degree in EE from 30 to 50, C12-C18alkylsulfonyl,9-C18alkylarylsulphonate and sulfonates of ethoxylated linear and branched C8-C36alilovic alcohols with a degree in EE from 3 to 50. In addition to the above compounds can be used, for example, with the offer of sodium salts of isomeric alkylsulfonic acids With 11-C18or ammonium salt of sulfuric acid ester of a mixture of polyethylene glycol ethers of ALKYLPHENOLS of the General formula:

R-C6H5-O-(CH2CH2O)n-SO3NH4where R is alkyl (C8-C10, n=10-12, produced in industry under the name of emulsifier C-10.

As polyorganosiloxanes with a molecular mass of 500 to 1000 is used, for example, polymethylsiloxane: product PMS-500, PG-4A and other

In the process according to the invention, the mass ratio of monomer (or mixture of monomers) and water is approximately 1:0,16-0,19;

The following examples illustrate but do not limit the invention.

Example 1. Cook the mixture for 59.7 g of butyl acrylate, 57,1 g of styrene, 3.13 g of acrylic acid, 5,78 g of 30%aqueous solution of acrylamide, of 3.96 g of a mixture of sodium salts of isomeric alkylsulfonic acids With11-C18as an emulsifier and 19.5 demineralized water. Mixing lead for 30 min to obtain a homogeneous emulsion. In a reactor equipped with a stirrer, thermometer, dozirovocnami craters, download 30.0 g of demineralized water, 0.5 g of ammonium persulfate, stirred until complete dissolution of the initiator, then at a temperature (80±2)°C for 1 h metered mixture prepared emulsion 0.7 g of ammonium persulfate. Then charged to the reactor 0.25 g of 30%RA the creators of hydrogen peroxide and increase the mixer rotation speed of 100 rpm, then in the reaction mixture of 0.85 g of polymethylsiloxane PG-4A (molecular weight 800) and 0.025 g of ferric sulfate and keep stirring for 1 h after exposure of the reaction mass is then cooled by Stripping with nitrogen to a temperature of (40±2)°and the mixture is neutralized with triethanolamine with ammonia water in the ratio of 1:1 to pH 5-6.

Example 2. Prepare a mixture of 45.7 g of butyl acrylate, to 61.2 g of styrene, of 2.53 g of acrylic acid, 6,12 g of 30%aqueous solution of acrylamide, of 4.2 g of emulsifier C-10 and 21.5 demineralized water. Mixing lead for 30 min to obtain a homogeneous emulsion. In a reactor equipped with a stirrer, thermometer, metering craters, download 30.0 g of demineralized water, 0.45 g of ammonium persulfate, stirred until complete dissolution of the initiator, then at a temperature (80±2)°C for 1 h metered mixture prepared emulsion 0.4 g of ammonium persulfate. Then charged to the reactor 0.25 g of 30%aqueous hydrogen peroxide solution and increase the mixer rotation speed of 100 rpm, and then the reaction mixture was added 0.625 g of polymethylsiloxane PMS-500 and 0.025 g of ferric sulfate and keep stirring for 1 h Then the process is carried out analogously to example 1.

Example 3. Cook the mixture to 58.2 g of butyl acrylate, 43,5 g of styrene, 5,67 g of acrylic acid, 5,78 g of 30%aqueous solution of acrylamide, 5,96 g of emulsifier is From-10 and 18.7 demineralized water. Mixing lead for 30 min to obtain a homogeneous emulsion. In a reactor equipped with a stirrer, thermometer, metering craters, download 30.0 g of demineralized water, 0.5 g of ammonium persulfate, stirred until complete dissolution of the initiator, then at a temperature (80±2)°C for 1 h metered mixture prepared emulsion with 0.75 g of ammonium persulfate. Then charged to the reactor 0.25 g of 30%aqueous hydrogen peroxide solution and increase the mixer rotation speed of 100 rpm, and then the reaction mixture was added 0,875 g polymethylsiloxane PMS-500 and 0.025 g of ferric sulfate and keep stirring for 1 h Then the process is carried out analogously to example 1.

Properties of the resulting polymer dispersions and films based on them are given in the table.

Table
Name of indicatorValue
the placeholderother No. 1Ave No. 2Ave No. 3
Mass fraction of non-volatiles, %50505050
Mass fraction of residual monomers, %0,0050,0050,0050,005
Resistance to mechanical impact (14 is is. rpm)stablestablestablestable
Resistance to the action of electrolytes (10%HaCl)stablestablestablestable
Particle size, nm200503050
Water absorption of the film, %:

- after 1 hour

after 24 hours


9,3

39,7


5,8

17,8


5,0

18,0


5,3

10,3
The film strength at break, MPa4,210,511,39,8

Thus, as shown by the method according to the invention to obtain a stable aqueous dispersion of styrene-acrylic copolymer having good film-forming properties and provides good penetration ability in relation to porous materials, good adhesion and strength properties.

A method of obtaining a water dispersion of styrene-acrylic copolymer by pre-emulsification mixture of acrylic monomers with styrene in the presence of emulsifier and the subsequent emulsion copolymerization reaction mixture in presets the following initiator, wherein the Monomeric mixture further comprises acrylamide, and as an initiator using ammonium persulfate and hydrogen peroxide, that you are carrying out sequential fractional dosed supply of ammonium persulfate in two steps, and then the hydrogen peroxide, then with stirring, the reaction mixture was injected mixture of polymethylsiloxane with a molecular weight of 500-1000, and iron sulfate in their mass ratio of 25-35:1, cooled the reaction mass is neutralized to pH=5-6.



 

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1 tbl, 15 ex

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