SE432103B - PROCEDURE FOR PREPARING DISPERSIONS OF POLYMERS OR COPOLYMERS OF VINYL ACETATE - Google Patents

Description

7713139-9 a) a reducing system, formed by sodium formaldehyde sulphoxylate and water in an amount significantly exceeding the stoichiometric amount, b) an acetate and / or a sulphate of an element of the eighth group of the Periodic Table, in particular iron and cobalt and in particular cobalt , c) a mixture (oxidizing mixture) formed by an oxidizing system composed of water-soluble peroxides, in particular hydrogen peroxide or alkali metal or alkaline earth metal persulphates, hydrogen peroxide being preferred in the presence of a bicarbonate and / or an alkali metal or alkaline earth metal metal acetate, in particular bicarbonate and / or sodium or potassium acetate, d) a chain transfer agent consisting of an aldehyde, in particular formaldehyde, propionaldehyde or crotonaldehyde, e) a protective colloid consisting of polyvinylpyrrolidone, methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose or hydroxymethylcellulose polyvinyl alcohol, the latter being obtained by either acidic or alkaline alcohol lysis, and f) a surfactant consisting of sodium or potassium dodecylbenzenesulfonate or a polyglycol ether of nonylphenol.

The process according to the invention comprises the following successive steps: a) In the polymerization vessel, in addition to water, the whole amount of the reducing system, the whole amount of acetate and / or sulphate of the element from the eighth group of the periodic table, the whole amount of chain transfer agent and the whole amount of protective colloid are first introduced. , while only a part of the total amount of monomer (vinyl acetate and optionally monomer esters is added in an amount corresponding to 10-70% of the total weight of the mixture, preferably 25-45% by weight; b) in the reaction vessel charged according to point a) is gradually and continuously added a mixture consisting of the oxidizing system and the bicarbonate and / or acetate of an alkali or alkaline earth metal, the reaction vessel being maintained at a temperature between 25 and 6500; C) when the monomer or monomers added according to a) have almost completely reacted, the remaining monomer or monomers are added gradually and continuously while the addition of the mixture indicated in step b) is maintained with unchanged speed, maintaining a temperature of at least 60 ° C.

This stepwise process leads to the formation of two different particle generations, the first of which is obtained at a lower temperature between 25 and 65 ° C and has a high content of protective colloid and a relatively variable particle diameter distribution, while the second is obtained at a higher, but constant temperature and has a narrower particle size distribution.

This heterogeneous character of the particles is particularly valuable in the production of adhesives, in which a certain part of the polymer particles must migrate into the pores of the adhesive-bearing element during a gluing process while other particles remain on the outside of the surface and account for the binding effect of the polymer.

Another important feature of the process according to the invention is the possibility of producing dispersions with high viscosity values and exceptionally constant viscosity despite dilution.

This property, together with the rheological properties and the good resistance to shear stress, is particularly important for dispersions to be used for binders and water-based paints.

Another interesting feature of the process according to the invention is that by varying the amounts of monomers charged initially and continuously during the process, emulsions with varying degrees of polydispersity and thus varying viscosity levels can be obtained while maintaining the advantageous process and product properties.

It has also surprisingly been found that the process according to the invention also entailed reduced reactant deposits on the reactor.

Any traces of incrustations can be removed by washing only with water at low pressure. Other notable advantages are the increase in the efficiency of the polymerization process, which is quantitatively of the order of 40-50%.

As stated above, the process of the present invention can be used to prepare dispersions starting from vinyl acetate and / or carboxylic acid esters. Esters of unsaturated carboxylic acids which have given particularly satisfactory results are: butyl maleate, ethylhexyl maleate, alkyl acrylate, where the number of carbon atoms of the alkyl group is less than 12.

The invention will now be further elucidated by means of a number of embodiments.

Example 1 - Comparative Example In a 16-liter stainless steel polymerization reactor equipped with a stirrer and reflux condenser, the following mixture was introduced, the quantity data relating to 100 parts of monomer: Vinyl acetate 100 parts Water, 95 parts Partially saponified polyvinyl alcohol ( alkaline alcoholysis) 13.5 parts Sodium dodecylbenzene sulfonate 0.5 parts Hydrogen peroxide (35%) 0.35 parts All the above ingredients together with 20 parts vinyl acetate were heated in the reactor to 68 ° C, and the polymerization was carried out with the addition of residual vinyl acetate for 4 hours at a reaction temperature of 68-70 ° C.

Analysis data Solid 50.5% Viscosity 225000 cp pH 4.4 Sediment 180 ppm Mechanical stability sufficient Removed incrustations 520 g Viscosity after dilution (25 parts water) 500 cp Resistance to freezing-melting process poor Resistance to mechanical stress poor Durability 7% Durability about 5000 Å 75% "30000 Å 18%" 10000 Å a few lumps 10 15 20 25 30 35 7715139 ~ 9 5 Example gel 2 The experiment was based on the following mixture: Vinyl acetate 100 parts Water 95 "Partially saponified polyvinyl alcohol (alkaline alcoholysis) 7, Sodium formaldehyde sulfoxylate 0.35 "Propionaldehyde 0.14" Cobalt acetate 0.003 "35% hydrogen peroxide 0.3" Sodium bicarbonate 0.14 "At the start of the experiment the reactor was charged with water, the polyvinyl alcohol previously dissolved in water, the sodium formaldehyde sulfoxylate, propionaldehyde, cobalt acetate and 40 parts of vinyl acetate. Thereafter, gradual addition of the hydrogen peroxide and bicarbonate was started. The remaining vinyl acetate was fed at 55 ° C for two hours, during which time the reaction temperature was kept below 80 ° C.

Analysis data Solid 50.7% viscosity 37000 cp pH 4.5 Sediment ll0 ppm Mechanical stability In very good Removed incrustations 20 g viscosity after dilution (25 parts water) 6500 cp Resistance to freezing-melt process very good Resistance to mechanical stress very good Viscosity unchanged Shelf life very good, unchanged viscosity Particle size 40% approx. 5000 Å 60% less than 5000 Å no lumps Example gel 3 The following starting mixture was used in the experiment: Vinyl acetate 100 parts Water 95 parts 10 15 20 25 30 35 * 70713139- 9 6 Polyvinylpyrrolidone (K90) Sodium dodecylbenzene sulfonate Sodium formaldehyde sulphoxylate Cobalt acetate 35% hydrogen peroxide Sodium bicarbonate 7 parts 0.4 parts 0.15 parts 0.0035 parts 0.3 parts 0.16 parts The test was carried out in the same manner as in Example 2 at a reaction temperature not exceeding 80 ° C.

Assay data_ Solid 50.6% Viscosity 17000 cp pH 4.45 Sediment 40 ppm_ Mechanical sability very good Removed incrustations 25 g Resistance to freezing melt process very good Shelf life very good Particle size 60% approx. 10000 Å 40% "5000 Å no lumps Example 4 In this experiment the following starting mixture was used: Vinyl acetate 100 parts Water 90 parts Methylcellulose (400 cp) 3 parts Sodium dodecylbenzenesulfonate 0.25 parts Nonylphenol polyglycol ether 0.5 parts Propionaldehyde 0.2 parts Cobalt acetate 0.0025 parts Sodium formaldehyde sulfoxylate 35% Dalalate 25 parts D18 hydrogen peroxide 0.35 parts Sodium bicarbonate 0.15 parts The reactor was charged directly with water, the methylcellulose, the sodium dodecylbenzenesulfonate and the nonylphenol polyglycol ether, all said components being previously dissolved in water, the propionaldehyde, the sodium formaldehyde sulfoxylate and the vinyl phthylate. 20 25 30 35 7713139-9 7 Thereafter, gradual addition of water is started the teperoxide and sodium bicarbonate, and when the reaction started, the remaining vinyl acetate and dibutyl phthalate began to feed while maintaining the reaction temperature at a temperature below 60 ° C.

Analysis data Solid 55.5% Viscosity 13500 cp pH 4.5 Sediment 42 ppm Mechanical stability very good Resistance to freezing melt process very good Abrasion resistance in humid environment very good Resistance to saponifier good Durability very good P Particle size 60% approx 5000 Å 40% less than 5000 Å no lumps Removed incrustations 37 g Example 5 The following starting material was used in the experiment: Vinyl acetate 100 parts Dibutyl maleate 25 parts Water 80 parts Hydroxyethylcellulose 3 parts Nonylphenol polyglycol ether 2 parts Sodium dodecylbenzenesulfonate 0.3 parts Vinylsulfonyl 0,5 parts Crotonaldehyde 0.07 parts Acetaldehyde 0.10 parts 35% hydrogen peroxide 0.55 parts Methanol 10 parts, Sodium bicarbonate 0.25 parts All the above ingredients except the hydrogen peroxide and sodium bicarbonate were introduced into the reactor at the same time. 7713139-9 8 was gradually set according to the thermal level in the reactor. The polymerization was carried out at a maximum temperature of 7000.

Assay data Solid 56.3% Viscosity 12500 cp pH 4.2 Sediment 110 ppm Mechanical stability very good Resistance to freezing melt process very good Resistance to abrasion in humid environment good Resistance to saponifying agent Good Durability very good Particle size 70% approx 5000 Å 30% less than 5000 Å No lumps particle size Removed incrustations 42 g Example 6 '_ The experiment was based on the following mixture: Vinyl acetate' 100 parts Water- 87 parts Partially saponified polyvinyl alcohol (acid alcoholysis) 7.5 parts Sodium formaldehyde sulphoxylate 0.35 parts Propionaldehyde 0.14 parts Cobalt acetate 0.003 parts 35% hydrogen peroxide 0.3 parts Sodium bicarbonate 0.12 parts The experiment was carried out in the same manner as given for Example 2, Analysis data in which the reaction temperature was not allowed to exceed 75 ° C.

Solid 53.5% viscosity 27000 cp pH 4.7 Sediment 65 ppm Mechanical stability very good Removed incrustations 18 g 10 15 20 25 30 35 9 Viscosity after dilution (25 parts water) Resistance to mechanical stress Durability Resistance to freezing melt process Particle size Example 7 7713139-9 4400 cp very good - very good very good 70% about 5000 Å 30% less than 5000 Å no lumps The following starting mixture was used in the experiment: Vinyl acetate Water Partially saponified polyvinyl alcohol (alkaline alcoholysis) Sodium formaldehyde sulphoxylate Propionaldehyde Cobalt acetate 35% hydrogen acetate Sodium bicarbonate 100 parts 95 parts 7.5 parts' 0.32 parts 0.12 parts 0.003 parts 0.28 parts 0.17 parts The experiment was carried out in the same manner as in Example 2. The reaction temperature was maintained at about 70 ° C.

Analysis data Solid Substance Viscosity pH Sediment Mechanical stability Removed incrustations Viscosity after dilution (25 parts water) Resistance to mechanical stress Resistance to freezing melt process Particle size 49.9% 79000 cp 4.5 115 ppm very good 31 g 8200 cp very good very good 30 % approx 5000 Å 70% less than 5000 Å no lumps l0 15 20 25 30 35 40 77§1313.9-9 10 Example 8 In this example the following starting mixture was used: Vinyl acetate Water Partially saponified polyvinyl alcohol (alkaline alcoholysis) Sodium formaldehyde sulphoxylate Propionaldehyde Cobalt acetate 35% hydrogen peroxide Sodium bicarbonate 100 parts 95 parts 7.5 parts 0.32 parts 0.12 parts 0.03 parts 0.28 parts 0.17 parts The experiment was carried out in the same way as in Example 2, except that 50 parts of vinyl acetate were introduced at the start and 50 parts were added gradually thereafter. The reaction temperature was 70 ° C.

Analytical data Solid Viscosity pH Seditment Mechanical stability Removed incrustations Viscosity after dilution (25 parts water) Resistance to mechanical stress Resistance to freezing melt process Durability Particle size Example 9 50.3% 50000 cp 4.7 95 ppm very good 27 g 5800 cp very good very good 40% about 5000 Å 50% less than 5000 Å no lumps In this example the following starting mixture was used: Vinyl acetate Water Partially saponified polyvinyl alcohol (alkaline alcoholysis) Sodium formaldehyde sulphoxylate Propionaldehyde Cobalt acetate 100 parts 270 parts 12 parts 0.35 parts 0.12 parts 0.03 parts 5 l0 l5 20 25 30 35 40 7715139-'9 ll 0.30 parts 0.19 parts 35% hydrogen peroxide Sodium bicarbonate The experiment was carried out in the same manner as in Example 2, the reaction temperature not exceeding 7000.

Analysis data Solid 36.5% Viscosity 34000 cp pH 4.6 Sediment 46 ppm Mechanical stability very good Removed incrustations 30 g Viscosity after dilution (25 parts water) 5700 cp Resistance to mechanical stress very good Durability very good Resistance to freezing melt process very good Particle size 50% about 5000 Å 50% less than 5000 Å no lumps Example 10 In this example the following starting mixture was used: Vinyl acetate 100 parts Water 135 parts Hydroxyethylcellulose 4 parts Polyglycol ether 2.5 parts Sodium dodecylbenzenesulfonate 0.3 parts Vinyl sulfonate 0.2 parts Sodium formaldehyde sulfoxylate , 52 parts Vinyl versatate 40 parts Propionaldehyde 0.25 parts 35% hydrogen peroxide 0.3 parts Sodium bicarbonate 0.2 parts Methanol 10 parts The reactor was charged with the above ingredients, with at the start only one third of the vinyl acetate, vinyl versatate and propionaldehyde being added. Then the addition of the bicarbonate and hydrogen peroxide was started. At a temperature of 600, the addition of the remaining vinyl versatate, vinyl acetate and propionaldehyde was started and the reaction temperature was maintained at a temperature not exceeding SOOC. When the reaction was complete, cooling took place and water and methanol (1: 1) were added.

Analysis data Solid _ 51.2% Viscosity 2800 cp pH 4.4 Sediment 8.0 ppm Mechanical stability very good Resistance to freezing melt process very good Resistance to abrasion in humid environment very good Resistance to saponifying agents very good Durability in accelerated aging tests very good Viscosity unchanged

Claims (7)

7713139-9 PATENT REQUIREMENTS 1. Process for the preparation of dispersions of polymers or copolymers of vinyl acetate by polymerization of vinyl acetate or vinyl acetate and esters of unsaturated carboxylic acids (nmnomer esters), characterized in that l) for polymerization a starting mixture is used which vinyl acetate and optionally monomer esters and water also comprise a) a reducing system composed of sodium formaldehyde sulfoxylate and water, b) an acetate and / or sulfate of an element of the eighth group of the periodic table, c) an oxidizing mixture of water-soluble peroxides in the presence of a bicarbonate and / or acetate of an alkali or alkaline earth metal, d) a chain transfer agent which is an aldehyde, e) a protective colloid and f) surfactants, and 2) the polymerization is carried out by a) in the polymerization vessel introducing in addition to water the whole amount of the reducing system according to a) above, the whole amount of acetate and / or sulphate of the element from the periodic table's eight group according to b) above, the whole amount of the chain transfer agent according to d) and the whole amount of protective colloid according to e), while adding only a part of the total amount of monomer (vinyl acetate and possibly monomer esters) in an amount corresponding to lÜ-70% of the total weight of the mixture, preferably 25-45% by weight; b) thereafter in the polymerization vessel gradually continuously introducing a mixture consisting of the oxidizing system of bicarbonate and / or acetate of an alkali or alkaline earth metal according to c) above, the reaction vessel being maintained at a temperature between 25 and GSOC; c) after the monomer or monomers added in accordance with a) above have almost completely reacted, add the remaining monomers and any monomer esters gradually and continuously while maintaining the addition of the mixture indicated in step b) above with 77Å13139-9. unchanged speed, maintaining a temperature of at least 60 ° C. 2. A method according to claim 1, characterized in that the element from the eighth group of the periodic table is iron or cobalt. 3. A process according to claim 1, characterized in that the oxidizing system is composed of hydrogen peroxide and potassium or sodium bicarbonate and / or acetate. 4. A process according to claim 1, characterized in that the oxidizing system is composed of alkali metal or alkaline earth metal persulphates as water-soluble peroxides. 5. A process according to claim 1, characterized in that the chain transfer agent is acetataldehyde, propionaldehyde or crotonaldehyde. Process according to Claim 1, characterized in that the protective colloid is polyvinylpyrrolidone, methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose or polyvinyl alcohol, the latter being obtained by either acidic or alkaline alcoholysis. IN Process according to Claim 1, characterized in that the surfactant is sodium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate or nonylphenol polyglycol ethers.