DE19831706A1 - Use of maleic acid ester in emulsion polymerization gives minimal coagulation due to the resulting good shear and electrolyte resistance - Google Patents

Abstract

Emulsion polymerization process involves uses maleic acid ester to give minimal coagulation. Emulsion polymerization process involves using maleic acid ester of formula (I) as copolymerizable emulsifier: R<1>OOC-CH=CH-COO-(BO)z(PO)y(EO)xR<2> (I) R<1> = 6-24C alkyl or alkylene; R<2> = 1-4C alkyl; BO = butylene oxide; PO = propylene oxide; EO = ethylene oxide; x, y and z = 1-100 and at least one is different.

Description

Field of the Invention

The invention is in the polymer sector and relates to a process for emulsion poly merization using new copolymerizable emulsifiers and the use of special maleic acid esters as emulsifiers in emulsion polymerization.

State of the art

As emulsifiers for emulsion polymerization, olefinic double bonds containing polyme various ionic or nonionic emulsifiers have been described e.g. B. alkylarylsulfonates, nonylphenol ethoxylates and ethylene oxide / propylene oxide block copolymers, [Techn. Brochure RES / VVX / 4 (G), 3rd edition, 1976, publisher: Shell-Chemie], α-sulfofett acid esters [DE-A1 33 39 407], tertiary hydroxyalkylamines [DE-A 33 37 640], addition products of Ethylene oxide on aliphatic vicinal diols with 8 to 25 carbon atoms, [DE-A1 33 19 782], poly ethylene oxysulfonates [EP-A 0 026 932] and fatty alkyl hydroxysulfonates [DE-A1 39 19 961].

The aforementioned surfactants show various when used in emulsion polymerization Disadvantage. So z. B. the polyethylene oxysulfonates in them containing aqueous systems strong foam formation and are also difficult to manufacture. In contrast, oleyl sulfates are Low-foaming, however, they are saponification-stable only when heavily buffered in the alkaline pH range; at They tend to store longer than dilute solutions at neutral to slightly acidic pH values Saponification ("post-acidification"). Other surfactants, e.g. B. alkylarylsulfonates and nonylphenol ethoxylates not or only poorly biodegradable, penetrate into the polymers formed and deteriorate in this way their shear and electrolyte stability. Also from the prior art Non-ionic acrylic and methacrylic acid esters known, but easy in emulsion polymerization form undesirable homopolymers. If such emulsifiers are incorporated into the polymer, obtained a partially soluble product that results in unstable latices.

The complex object of the present invention was therefore to produce a method to provide polymers based on unsaturated, polymerizable monomers, with the help of polymers, especially latices, which are characterized by a special shear and Characterize electrolyte resistance and a minimum of coagulum. The procedure should also continue be practically foam-free and neither to form unwanted volatile substances (VOC: voilatil organic compounds) still lead to proportions of homopolymers of the emulsifier.

Description of the invention

The invention relates to a process for the preparation of polymers by emulsion polymerization of unsaturated monomers, which is characterized in that maleic acid esters of the formula (I) are used as copolymerizable emulsifiers,

R ¹ OOC-CH = CH-COO- (BO) _z (PO) _y (EO) _x R ² (I)

in which R ^{1 stands} for a linear or branched alkyl and / or alkenyl radical with 6 to 24 carbon atoms, R ² for an alkyl radical with 1 to 4 carbon atoms, BO for a butylene oxide unit, PO for a propylene oxide unit and EO for an ethylene oxide unit and the Numbers x, y and z independently of one another represent 0 or numbers from 1 to 100, with the proviso that at least one of the numbers x, y and z is different from 0.

Surprisingly, it was found that the use of the special copolymerizable emulsions leads in the process according to the invention to polymers which are characterized by a special shear and Characterized electrolyte stability and a particularly low coagulum content. In a preferred one Embodiment of the invention, latices are obtained, which in turn are additionally characterized by a special water resistance and stability against temperature fluctuations and where no migration of the emulsifier into the film can be determined. Another benefit of the whole process is also that it is virtually foam-free and the formation of volatile organic Substances is reliably avoided. Since the emulsifier is incorporated quantitatively into the polymer, with its use also has no problems related to biodegradability. The Furthermore, maleic acid esters show practically no tendency to homopolymerize.

Maleic acid ester

The maleic acid esters to be used as emulsifiers in the process according to the invention are known substances which can be obtained by the relevant processes of preparative organic chemistry. A process for their preparation consists, for example, in a first stage of maleic acid and an end-capped polyglycol ether of the formula (II),

HO- (BO) _z (PO) _y (EO) _x R ² (II)

in which R ² , BO, PO, EO, x, y and z have the meanings from formula (I), in a molar ratio of 1: 0.9 to 1: 1.1 at temperatures in the range from 80 to 120 ° C. bring to reaction from 4 to 6 h, continuously remove the water of reaction, and condense the partial ester formed with a fatty alcohol of the formula (III),

R ¹ OH (III)

in which R ^{1 represents} a linear or branched alkyl and / or alkenyl radical having 6 to 24 carbon atoms. The molar ratio of partial ester to alcohol can again be 1: 0.9 to 1: 1.1, the reaction temperature is usually 80 to 120 ° C, the reaction time 4 to 8 h. It has proven to be advantageous to catalyze the esterification by adding small amounts of acid (e.g. sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid) and to separate off the water of reaction continuously at reduced pressure. In this context, it should also be noted on the printed publication Polym. Bull. (Berlin), 33, 133 (1994).

Typical examples of emulsifiers that can be used for the purposes of the process according to the invention are maleic acid esters, which are derived from fatty alcohols such as. B. capronic alcohol, caprylic alcohol, 2-ethylhexyl alcohol, capric alcohol, lauryl alcohol, isotridecyl alcohol, myristyl alcohol, cetyl alcohol, palmoleyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, elaidyl alcohol, petro selinyl alcohol, linolyl alcohol, elaoleyl alcohol, brassol alcohol, linoleyl alcohol, alcohol alcohol derive technical mixtures. Preferred emulsifiers of the formula (I) are those in which R ^{1 represents} an alkyl radical having 12 to 18 carbon atoms and R ^{2 represents} a methyl radical. On the other hand, the maleic acid esters can be derived from ethylene / propylene / butylene oxide copolymers, which are available on the market under the Pluronics® brand. If emulsifiers with predominantly hydrophobic properties are desired, it is advisable to reduce the proportion of ethylene oxide against propylene oxide or butylene oxide units. Emulsifiers of the formula (I) are preferably used in which x and y independently of one another represent numbers from 1 to 20, in particular x stands for numbers from 2 to 10 and y stands for numbers from 15 to 18 and z is 0. The copolymerizable emulsifiers are usually used in amounts of 0.1 to 25, preferably 1 to 20 and in particular 5 to 10% by weight, based on the sum of the monomers.

Monomers

The maleic esters of the general formula (I) to be used according to the invention are suitable as Emulsifiers in the emulsion polymerization of almost all technically important, essentially union water-insoluble monomers, but preferably acrylic and vinyl compounds. Typical Examples of these monomers are vinyl aromatics, e.g. B. styrene, divinylbenzene or vinyltoluene, poly merizable olefins and diolefins such as propene, butadiene or isoprene, esters of acrylic or meth acrylic acid with linear or branched alcohols with 1 to 18 carbon atoms, in particular from Alcohols with 1 to 8 carbon atoms and - particularly preferably - methyl esters, ethyl esters and butyl esters thereof, vinyl esters of acids having 2 to 12 carbon atoms, in particular Vinyl acetate, vinyl propionate, vinyl 2-ethylhexanate and vinyl laurate, vinyl alkyl ether with 1 to 8 carbons atomic alkyl groups, vinyl chloride, vinylidene chloride and the like; the pre mentioned monomers can in the presence of the copolymerizable to be used according to the invention Emulsifiers homopolymerized or with other of the compounds mentioned from the above List are copolymerized. Furthermore, copolymerizations can be carried out at which up to 50 wt .-% further, partially or completely water-soluble monomers involved are, e.g. B. acrylonitrile, methacrylonitrile, half esters of maleic or fumaric acid with 1 to 8 carbon atoms men, acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid and / or itaconic acid.

Co-emulsifiers

Furthermore, it is also possible to use the maleic acid esters to be used according to the invention in combination with other known nonionic co-emulsifiers. This can lead to dispersions with increased stability, e.g. B. against shear forces, temperature influences and electrolytes. The co-emulsifiers are added in amounts of 0.5 to 5, preferably 1 to 3% by weight, based on monomers. It is possible to submit the co-emulsifiers together with the emulsifiers at the beginning of the polymerization or to meter them in during the course of the polymerization. Another variant provides for a pre-emulsion to be produced using or co-using the co-emulsifiers and to be metered in during the course of the polymerization. It is also possible to stabilize the dispersions obtained using the acrylic acid and / or meth acrylic acid esters according to the invention by adding co-emulsifiers to them. Typical examples of suitable nonionic co-emulsifiers are:

• - Linear, branched, cyclic, saturated and unsaturated alkyl polyglycol ethers, especially fatty alcohol alcohol polyglycol ether;
• - Mono-, di- and trialkylaryl polyglycol ethers, in particular octyl and nonylphenol polyglycol ethers, di nonylphenol polyglycol ether, triisobutylphenol polyglycol ether;  
• - Aryl polyglycol ether, e.g. B. reaction products of phenol with 3 to 10 moles of ethylene oxide;
• - Polyglycol ethers of hydroxyalkanols, e.g. B. according to DE-A1 33 19 782;
• - End-capped alkyl or alkylaryl polyglycol ethers, e.g. B. according to DE-A1 35 30 301 and DE-A1 36 43 896;
• - Carboxylic acid polyglycol esters, especially fatty acid polyglycol esters;
• - Fatty acid alkanolamide-ethylene oxide adducts, in particular adducts of ethylene oxide with coconut fat acid monoethanolamide;
• - ethylene oxide / propylene oxide block polymers;
• - ethoxylated sorbitan esters, especially sorbitan monolaurate + 20 EO;
• - ethoxylated fatty amines.

The maleic acid esters of the formula (I) to be used according to the invention can also be used together with Protective colloids are used. Typical examples of such protective colloids are complete or partially saponified homo- and / or copolymers of vinyl acetate, e.g. B. partially saponified polyvinyl acetate, or fully saponified copolymers of vinyl acetate and vinyl ethers. Preferred copolymers have 1 to 4 carbon atoms in the ether part of the polyvinyl ether. Other protective colloids can be derived from polysaccharides. For example, cellulose ethers such as hydroxyethyl cellulose, Hydroxypropyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose or mixed cellulose ether suitable. Polyacrylamide and its copolymers with acrylic acid, acrylic are also suitable nitrile or acrylic esters. Also condensation products from naphthalenesulfonic acid and formaldehyde or other water-soluble formaldehyde resins, especially urea-formaldehyde resins, can be used be applied. After all, casein, gelatin, gum arabic and natural starch are Substituted starch derivatives such as hydroxyethyl starch are suitable protective colloids.

Emulsion polymerization

The using the maleic acid ester of the general formula (I) in the first step of Ver In practice, aqueous dispersions to be prepared usually have 15 to 75% by weight. polymerized monomers (dry residue) in water or water / water-soluble organic Solvents. The range from 20 to 60% by weight of dry residue is preferred; however are for special applications also aqueous dispersions with less than 15 wt .-% dry residue producible. In the aforementioned processes for emulsion polymerization, other conventional ones can also be used Polymerization aids are used, in particular initiators, for. B. inorganic Peroxidver bonds such as potassium or ammonium persulfate or hydrogen peroxide; still organic per oxide compounds or organic azo compounds, insofar as these are used for emulsion polymerization are usable. The initiators are used in conventional amounts, i.e. H. from 0.05 to 2% by weight, preferably from 0.1 to 0.5% by weight. Other suitable auxiliaries are buffer substances, e.g. B. sodium  hydrogen carbonate, sodium pyrophosphate or sodium acetate, in amounts of up to 2% by weight can be placed. Accelerators such as formaldehyde sulfoxylate can also be used. Furthermore, conventional molecular weight regulators used in emulsion polymerization, e.g. B. Butenol or organic thio compounds such as mercaptoethanol, thioglycolic acid, octyl mercaptan or tert-dodecyl mercaptan can be used. For the implementation of the Polymerisa tion processes come different, usually used in emulsion polymerization Methods considered, e.g. B. a total template of all reactants, a monomer feed or an emul inflow. In general, the temperature of the polymerization medium is in a range from 40 to 100, in particular 50 to 90 ° C. A range is expediently used as the pH value between 3 and 9 adhered to, however thanks to the unsaponifiability of the sulfonate groups with the inventions compounds according to the invention also permit emulsion polymerization at lower pH values. The aforementioned possible process variants for emulsion polymerization are more expedient as in coolable and heatable, provided with stirrers and temperature measuring containers, for. B. in Stirring pressure vessels. It is also possible to use coil reactors or so-called loop reactors. When the polymerization is complete, the polymer dispersion expediently cooled and removed from the reactor via screening devices. If the reaction products should be isolated as solid products, the polymer dispersion is used moderately precipitated or spray dried. However, direct use of the at is preferred the polymerizations obtained dispersions as binders for paints, adhesives, paper coating masses and other coating agents. Additional conditions for processes for emulsion poly merization using the methacrylic acid esters to be used according to the invention NEN formula (I) can be adapted by the person skilled in the art in a conventional manner to the respective requirements or be chosen freely. General expertise in the field of emulsion polymerization results, for example, from A. Schmidt, Methods of Organic Chemistry (Houben-Weyl), 4. Edition, Vol. E 20, Macromolecular Substances, Part 1, pp. 227-268, Stuttgart (1987).

Industrial applicability

The maleic acid esters to be used according to the invention can be polymerized easily and completely together with olefinic monomers, where they promote the formation of a foam-free and homogeneous emulsion. Another object of the invention therefore relates to the use of maleic acid esters of the formula (I),

R ¹ OOC-CH = CH-COO- (BO) _z (PO) _y (EO) _x R ² (I)

in which R ^{1 stands} for a linear or branched alkyl and / or alkenyl radical with 6 to 24 carbon atoms, R ² for an alkyl radical with 1 to 4 carbon atoms, BO for a butylene oxide unit, PO for a propylene oxide unit and EO for an ethylene oxide unit and the Numbers x, y and z independently of one another represent 0 or numbers from 1 to 100, with the proviso that at least one of the numbers x, y and z is different from 0, as copolymerizable emulsifiers in the emulsion polymerization of unsaturated monomers.

Examples Production of the dispersions Example 1: Copolymerization of a vinyl acetate / tert-monocarboxylic acid vinyl ester mixture

The monocarboxylic acid vinyl ester was a commercially available mixture of a vinyl ester of isomeric synthetic, saturated, essentially tertiary monocarboxylic acids with a chain length of C ₁₀ , described in the technical brochure AES / VVX / 4 (G), 3rd edition, October 1976, publisher : Shell-Chemie, and is referred to below with the abbreviation VeoVa 10, which is also used there. The copolymerization was carried out in a closed, heatable 2 l flat ground cup with V4A anchor stirrer (stirring speed 100 to 150 rpm), storage vessels and reflux condenser. The following reaction components were first prepared separately:
Component I: 191.5 g of fully demineralized water, 1.3 g of maleic acid ester of the formula (I) with R ¹ = lauryl, R ² = methyl, x = 3, y = 17 and z = 0, 0.5 g of potassium peroxodisulfate (starter ) and 0.2 g borax (buffer).
Component II: 282.3 g of fully demineralized water, 0.8 g of maleic acid ester of the formula (I) with R ¹ = lauryl, R ² = methyl, x = 3, y = 17 and z = 0.17.1 g of nonylphenol + 30 EO (70 wt .-% AS, co-emulsifier), 1.9 g of potassium peroxodisulfate and 2.1 g of borax.
Component III: 330.1 g vinyl acetate, 143.5 g VeoVa 10 and 4.8 g acrylic acid.

23.9 g of ammonium carbonate solution (10% by weight) were used to adjust the pH. The Component 1 was placed in the reaction vessel. The vessel was stirred with stick for 30 min rinsed fabric and then heated to 80 ° C. During the heating phase was in the template a pre-emulsion was prepared by mixing component III while stirring component II inflicted. After an internal temperature of the reactor of 80 ° C was reached, the pre-emulsion metered in within a period of 2 to 2.5 hours. After the addition had ended, the tem temperature maintained at 80 ° C for a further 2 hours. The dispersion was then cooled; the The pH was adjusted to about 7 with the 10% by weight ammonium carbonate solution.

Example 2: Preparation of an ethyl acrylate / acrylic acid copolymer

The following components were initially manufactured:
Component I: 662.6 g of fully demineralized water, 3.2 g of maleic acid ester of the formula (I) with R ¹ = lauryl, R ² = methyl, x = y = 0 and y = 17, 0.4 g of NaOH (cookies), dissolved in 8.7 demineralized water;
Component II: 0.5 g ammonium peroxodisulfate, dissolved in 8.7 g demineralized water;
Component III: 8.0 g of hydrogen peroxide (30% by weight);
Component IV: 290.9 g of ethyl acrylate and 9.0 g of acrylic acid.

8.0 g of concentrated ammonia water were used to adjust the pH. Component I was presented in the reaction vessel described in Example 1. The reaction vessel was with for 30 min Flushed with nitrogen and then heated to 80 ° C. Solution II was added at 70 ° C. Component IV was produced during the heating phase. When reaching a reactor component IV was metered in over a period of 50 to 60 min. After a further 10 minutes, component III was added. Then the temperature kept at 86 to 87 ° C for a further 40 min. The dispersion obtained was cooled; the pH was adjusted to about 8 with concentrated ammonia.

Examples 3 and 4

Examples 1 and 2 were each repeated with corresponding amounts of a maleic acid ester of the formula (I) in which R ^{1 was} C _12/18 cocoalkyl, R ^{2 was} methyl, x was 5, y was 10 and z was 2.

Example 5

Example 1 was repeated, but a maleic acid ester of the formula (I) was used as component II in which R ^{1 was} C _12/18 cocoalkyl, R ^{2 was} methyl, x was 5, y was 10 and z was 2.

Application engineering assessment

• (a) Coagulum content after manufacture. The finished dispersion was tared Perlone sieve bags from Schwegmann filled with a mesh size of 80 µm. The sieve bag with Coagulate present was dried at 105 ° C. for 24 h and the coagulate by difference weighing determined.
• (b) Dry content. The determination was carried out using a dry residue determination scale (Fa. Sartorius), type 709301. The solids content was determined at step 7 and a drying time of 20 minutes. The initial weight was approx. 5 g.
• (c) Viscosity. The viscosity was determined using the Brookfield viscometer type RVT at 25 ° C (spindle 1, 20 rpm).
• (d) Minimum film formation temperature (MFT). The determination was made with a film formation and Block point tester from Coesfeld according to DIN 53 787.
• (e) Mechanical stability. The mechanical stability of the dispersion was assessed using a Klaxon stirrer type HM 5 UB 2 with the addition of 0.25% by weight of the defoamer Dehydran P4 tested. The amount of coagulum is given in% by weight.

The results are summarized in Table 1.  

Table 1

Application engineering characterization

Claims (6)

1. A process for the preparation of polymers by emulsion polymerization of unsaturated monomers, characterized in that maleic acid esters of the formula (I) are used as copolymerizable emulsifiers,
R ¹ OOC-CH = CH-COO- (BO) _z (PO) _y (EO) _x R ² (I)
in which R ^{1 stands} for a linear or branched alkyl and / or alkenyl radical with 6 to 24 carbon atoms, R ² for an alkyl radical with 1 to 4 carbon atoms, BO for a butylene oxide unit, PO for a propylene oxide unit and EO for an ethylene oxide unit and the Numbers x, y and z independently of one another represent 0 or numbers from 1 to 100, with the proviso that at least one of the numbers x, y and z is different from 0. 2. The method according to claim 1, characterized in that one uses emulsifiers of the formula (I) in which R ^{1 is} an alkyl radical having 12 to 18 carbon atoms and R ^{2 is} a methyl radical. 3. Process according to claims 1 or 2, characterized in that the emulsifiers Formula (I) in which x and y independently of one another represent numbers from 1 to 20 and z 0 means. 4. The method according to at least one of claims 1 to 3, characterized in that the copolymerizable emulsifiers in amounts of 0.1 to 25 wt .-% - based on the sum of Monomers - used. 5. The method according to at least one of claims 1 to 4, characterized in that Uses monomers selected from the group consisting of acrylic and / or Vinyl compounds. 6. Use of maleic acid esters of the formula (I),
R ¹ OOC-CH = CH-COO- (BO) _z (PO) _y (EO) _x R ² (I)
in which R ^{1 stands} for a linear or branched alkyl and / or alkenyl radical with 6 to 24 carbon atoms, R ² for an alkyl radical with 1 to 4 carbon atoms, BO for a butylene oxide unit, PO for a propylene oxide unit and EO for an ethylene oxide unit and the Numbers x, y and z independently of one another represent 0 or numbers from 1 to 100, with the proviso that at least one of the numbers x, y and z is different from 0, as copolymerizable emulsifiers in the emulsion polymerization of unsaturated monomers.