IE45992B1

IE45992B1 - Preparation of dispersions

Info

Publication number: IE45992B1
Application number: IE2367/77A
Authority: IE
Original assignee: Anic Spa
Priority date: 1976-11-22
Filing date: 1977-11-22
Publication date: 1983-01-26
Also published as: SE432103B; NO150318C; NO150318B; EG12967A; TR19944A; DE2752102A1; DE2752102C2; FR2392042B1; DK516177A; CH629227A5; ES464654A1; AT363683B; LU78551A1; PT67300A; FI63247B; NO773948L; FI63247C; GB1567704A; IE45992L; FI773416A

Abstract

To prepare vinyl ester dispersions having improved rheological and adhesive properties by emulsion polymerisation, an oxidising system together with an alkali metal salt is added in a first stage to a mixture consisting of a part of the vinyl monomers, a large excess of a reducing system, a salt of a metal from group VIII of the periodic table and other ingredients, maintaining the temperature between 25 DEG C and 65 DEG C, whereas, in the second and last stage carried out at a constant temperature not below 60 DEG C, the remainder of the monomers and more oxidising system are added.

Description

This invention relates to a process for the preparation of dispersions of polymers or copolymers of ethylenically unsaturated esters and/or esters of unsaturated carboxylic acids.

For example, the invention relates to the dispersion polymerisation of vinyl acetate, either alone or together with other monomers such as vinyl monomers and/or alkyl, aryl or cycloalkyl esters of unsaturated mono or bicarboxylic acids having from 3 to 15 carbon atoms.

The polymerisation of vinyl acetate alone or with the mono10 mers referred to above usually takes place according to the known art at a temperature of 65°C - 70°C, which is to the boiling point of the monomer. Such a temperature is initially attained by heating with a steam jacket. Higher reaction temperatures can be attained by carrying out the polymerisation under a slight pressure. Thus, short reaction times are obtained but the pro-245992 ducts are of a poor quality, especially those which are intended for use in the adhesive industry.

It has now surprisingly been found that it is possible to overcome the defects of the known art while obtaining products of a high quality by polymerising at lower temperatures, within considerably shorter times and without the initial heating of the reactants.

According to the present invention, there is provided a process for the preparation of a dispersion, which comprises polymerising an ethylenically unsaturated ester and/or an ester of an unsaturated carboxylic acid in a reaction mixture comprising (1) water, (2) as a reducing agent, sodium formaldehyde sulphoxylate, (3) an acetate and/or sulphate of an element of Group VIII of the Periodic Table, (4) an oxygen-evolving system com15 prising (a) a water-soluble peroxide and (b) a bicarbonate and/or acetate of an alkali metal or alkaline earth metal, (5) an aldehydic chain-transfer agent and (6) a protective colloid, the reducing agent being used in stoichiometric excess amount relative to the oxygen-evolving system and the polymerisation being ef20 fected in two stages in the first of which the oxygen-evolving system is initially absent and only 10 to 70% by weight Of the total amount of the ester is used, and in the second of which the oxygen-evolving system is present and the remaining 90 to 30% by weight of the ester is used.

The preferred acetates and sulphates of elements of Group V111 of the Periodic Table are those of iron and, in particular, cobalt. As is known, the elements of Group V111 of the Periodic Table are iron, cobalt nickel and the platinum group metals. -345992 The preferred- water-soluble peroxides are hydrogen peroxide and alkali metal or alkaline-earth metal persulphates, and the preferred bicarbonates and acetates are those of sodium and potassium, The preferred chain-transfer agents are formaldehyde, propion-aldehyde and crotonaldehyde, and the preferred protective colloids are polyvinylpyrrolidone, methycellulose, hydroxyethylcellulose, hydroxymethylcelluose, polyvinyl alcohol obtained by acidic alcoholysis, and polyvinyl alcohol obtained by alkaline alcoholysis. The reaction mixture may further comprise a surfac10 tant, the preferred surfactants being sodium and pot~ssium dodecylbenesulphonate and polyglycol ethers of nonylphenol.

Preferably, the oxygen-evolving system is continuously fed to the reaction mixture during the first and second stages, and, in the second stage, the remaining 90 to 30% by weight of the ester is continuously fed to the reaction mixture.

In one embodiment, the process of the invention comprises the following steps: (a) feeding into a polymerisation vessel, in addition to water, firstly the entire reducing agent, all of the acetate and/ or sulphate of the element of Group VIII of the periodic Table, all of the chain-transfer agent and all of the protective colloid, the monomer (vinyl acetate and/or other monomers as defined above) being added only in an amount of 10-70% by weight, preferably 25%· 45% by weight, of the total amount; (b) feeding to reaction vessel, charged with the above ingredients, in a continuous and gradual manner, the oxygenevolving system and maintaining within the reaction vessel a -445992 temperature of from 25°C to 65°C; and (c) feeding, shortly before the completion of the reaction of the monomer or monomers added in step (a), the remaining monomer or monomers gradually and continuously while at the same time continuing to feed gradually and with the same rate of flow as in step (b) the oxygen-evolving system, the temperature being kept at 60°C or above.

This operational sequence is conducive to the formation of two generations of particles, the first, formed at the lower temperature of from 25°C to 65°C, having a high content of a protecting colloid and wide particle size distribution, and the second, formed at the higher temperature, having a narrow particle size distribution.

The heterogeneous character of the particles is particularly useful in the production of adhesives, since during assembly of the pieces to be joined together by the adhesive, a portion of the polymer particles must migrate towards the interior of the porous pieces whereas the other particles must remain stuck to the outside surface, thus encouraging the adhesive action of the adhesive.

Another favourable feature of the process according to the invention is that the dispersions obtained usually have a high viscosity which undergoes little change upon dilution. These properties of the dispersions, together with their rheological properties and their resistance to shear stresses, which also are usually high, are desirable when the dispersions are to be used as adhesives or as water-based paints. -545992 It is interesting to note that by appropriately varying the amounts of monomer in the initial charge and in the feed stream, emulsions having various degrees of poly-dispersability and thus various viscosities, but still retaining their other properties, are obtained.

It has also been surprisingly found that by the process according to the invention a substantial reduction of reactor soiling may be achieved. The removal of possible traces of incrustations can be effected by merely washing with water at a low pressure.

Also, an increase of the efficiency of the polymerisation process by as much as 40% - 50% may be achieved.

As indicated above, the process according to the invention can be applied to the preparation of dispersions from ethylenically unsaturated esters and/or carboxylic acid esters. Vinyl acetate has been given as a typical ethylenically unsaturated ester, it is the one which is most used commercially at present. Examples of other ethylenically unsaturated esters are vinylpropionate and vinyl laurate. Examples of esters of unsaturated carboxylic acids are butyl maleate, ethylhexyl maleate, and alkyl acrylates wherein the number of carbon atoms of the alkyl radical is less than 12.

The invention will now be illustrated by the following Examples: EXAMPLE 1 (Comparison) A 16-litre stainless steel polymerisation reactor, equipped with stirrer and reflux condenser, was used. For polymerisation, -645992 the following components, per 100 parts of monomer, were used: Parts Vinyl acetate 100 Water 95 Partially saponified polyvinyl alcohol (alkaline alcoholysis) 13.5 Sodium dodecylbenzene-sulphonate 0.5 Hydrogen peroxide (35%) 0.35 All of the above components, apart from 80 parts of the vinyl acetate, were heated to 68°C and added to the reactor. Polymerisation was carried out for 4 hours at a reaction temperature of 68°C - 70°C, the remaining 80 parts of vinyl acetate being added during polymerisation. The resulting dispersion had the following properties: Solid matter content 50.5% Viscosity 22,500 centipoise PH 4.4 Sediment 180 ppm (parts per million) Mechanical stability sufficient Removed incrustations 520 grams Viscosity after dilution (25 parts of water) 500 centipoise Resistance to freeze-thaw cycles poor Resistance to mechanical stresses poor Storage life sufficient Particle size distribution 7% at about 5000 J? 75% at.about 30000 A -7- 18% at about 10000 8 A few clumps EXAMPLE 2 The following components were used: f PARTS Vinyl acetate 100 Water 95 Partially saponified polyvinyl alcohol (alkaline alcoholysis 7.5 Sodium formaldehyde sulphoxylate 0.35 Propionaldehyde 0.14 Cobalt acetate 0.003 Hydrogen peroxide (35%) 0.3 Sodium bicarbonate 0.14 At the outset, the water, the polyvinyl alcohol (dissolved in water), the sodium formaldehyde sulphoxylate, the propionaldehyde, the cobalt acetate and 40 parts of the vinyl acetate were added to the reactor. Then, the hydrogen peroxide and the bicarbonate were added in increments. At 55°C, the remaining vinyl acetate was added over a period of 2 hours, the reaction temperature being meanwhile maintained below 80°C. The dispersion obtained had the following properties.

Solid matter content 50.7% Viscosity 37,000 centipoise pH 4.5 Sediment 110 ppm -845992 Mechanical stability very good Removed incrustations 20 grams Viscosity upon dilution in 25 parts of water 6,500 cps. Resistance to free-thaw cycles very good Resistance to mechanical stresses very good Viscosity unaltered Storage life very good, viscosity unaltered. Particle size distribution 40% at about 5,000 A 60% at less · 5,000 A Ho clumps.

EXAMPLE 3 The following components were used: Parts Vinyl acetate 100 Water 95 Polyvinylpyrrolidone (K90) 7 Sodium dodecylbenzenesulphonate 0.4 Sodium formaldehyde sulphoxylate 0.15 Cobalt acetate 0.0035 Hydrogen peroxide (35%) 0.3 Sodium bicarbonate 0.16 The procedure used was the same as that of Example 2, with a reaction temperature not exceeding 80°C.. The dispersion obtained had the following properties: -945993 Solid matter content 50.6% Viscosity 17,000 cps PH 4.45 Sediment 40 ppm Mechanical stability very good Removed- incrustations 25 grams Resistance to free-thaw cycles very good Storage life very good Particle size distribution 60% at about 10,000 A 40% at about 5,000 A no clumps. EXAMPLE 4 The following components were used: Parts Vinyl acetate 100 Water' 90 Methylcellulose (400 cps) 3 Sodium dodecylbenzene sulphonate 0.25 Nonylphenol polyglycol ether 0.5 Propionaldehyde 0.2 Cobalt acetate 0.0025 Sodium formaldehyde sulphoxylate 0.18 Dibutylphthalate 25 Hydrogen peroxide (35%) 0.35 Sodium bicarbonate 0.15 The raethylcellulose, the sodium dodecylbenzene sulphonate and the nonylphenol polyglycol ether, all dissolved in water, the -1045992 propionaldehyde, the sodium formaldehyde sulphoxylate, 30% of the vinyl acetate, the dibutylphthalate and the water were added to the reactor. Then, the hydrogen peroxide and the sodium bicarbonate were added in increments as the reaction has been primed. The remaining vinyl acetate and the dibutyl phthalate were added, the reaction temperature being maintained at about fi0°C, The dispersion had the following properties: Solid matter content Viscosity PH Sediment Mechanical stability Resistance to freeze-thaw cycles Abrasion resistance in moist environment Resistance to saponifying agents Storage life Particle size distribution Removed incrustations .5% 13,500 cps 4.4 ppm very good very good very good good very good 60% at0about 5,000 A 40% at less than 5,000 8 no clumps 37 grams.

EXAMPLE 5 The following components were used: -1145992 Parts Vinyl acetate 100 Dibutyl maleate 25 Water 80 Hydroxyethylcellulose 3 Nonylphenol polyglycol ether 2 Sodium dodecylbenzene sulphonate 0.3 Vinyl sulphonate 0.15 Sodium formaldehyde sulphoxylate 0.6 Crotonaldehyde 0.07 Acetaldehyde , . 0.10 Hydrogen peroxide (35%) 0.55 Methanol 10 Sodium bicarbonate 0.25 All of the,above components, with the exception of the hydrogen peroxide and the sodium bicarbonate which were added in increments during polymerisation according to the thermal level of the reaction, were added to the reactor. Polymerisation was carried out at a maximum temperature of 70°C. The dispersion 20 obtained had the following properties.

Solid matter content 56.3% Viscosity 12,500 cps PH 4.2 Sediment 110 ppm Mechanical stability very good Resistance to freeze-thaw cycles very good Resistance to abrasion in moist environment good Resistance tq saponifying agents good Storage life very good .15 9 9 2 Particle size distribution 70% at about 5000 & 30% at less than 5,000 ft no clumps Removed incrustations 42 grams.

EXAMPLE 6 The following components were used: Parts Vinyl acetate 100 Water 87 Partially saponified polyvinyl alcohol (acidic alcoholysis) 7.5 Sodium formaldehyde sulphoxylate 0.35 Propionaldehyde 0.14 Cobalt acetate 0.003 Hydrogen peroxide (35%) 0.3 Sodium bicarbonate 0.12 The procedure was the same as in Example 2, the reaction temperature not exceeding 75°C. The dispersion obtained has the following properties: Solid matter content 53.5% Viscosity 27,000 cps PH 4.7 Sediment 66 ppm Mechanical stability very good Removed incrustations 18 grams Viscosity after dilution in 25 parts of water 4,400 cps. -1.3 £5992 ' Resistance to mechanical stresses Storage life Resistance to freeze-thaw cycles Particle size distribution very good very good very good 70% at about 5,000 8 30% at less than 5,000 8 No clumps.

EXAMPLE 7 The following components were used Vinyl acetate Water Partially saponified polyvinyl alcohol (alkaline alcoholysis) Sodium formaldehyde sulphoxylate Propion aldehyde Cobalt acetate Hydrogen peroxide (35%) Sodium bicarbonate Parts 100 7.5 0.32 0.12 0.003 0.28 0.17 The procedure was the same as in Example 2. The reaction temperature was maintained at about 70°C. The dispersion obtained had the following properties: Solid matter content Viscosity PH Sediment 49.9% 79,000 cps 4.5 115 ppm -1445992 Mechanical stability very good Removed incrustations 31 grams Viscosity after dilution in 25 parts of water 8,200 cps Resistance to mechanical stresses very good Storage life very good Resistance to freeze-thaw cycles very good Particle size distribution 30¾ at about 5,000 5 70% at less 0 than 5,000 A No clumps.

EXAfIPLE S The following components were used: Parts Vinyl acetate 100 Water 95 Partially saponified polyvinyl alcohol (alkaline alcoholysis) 7.5 Sodium formaldehyde sulphoxylate 0.32 Propionaldehyde 0.12 Cobalt acetate 0.03 Hydrogen peroxide (35%) 0.28 Sodium bicarbonate 0.17 The procedure was the same as in Example 2, but 50 parts of vinyl acetate were introduced initially and 50 parts added -154599 2 continuously thereafter. The reaction, temperature was 70°C. The dispersion obtained had the following properties: Solid matter. content Viscosity PH Sediment Mechanical stability Removed incrustations Viscosity after dilution in 25 parts of water Resistance to mechanical stresses Resistance to freeze-thaw cycles Storage life Particle size distribution 50.3% 50,000 cps 4.7 ppm very good 27 grams ,800 cps very good very good very good 40% at about 5,000 S. 50% at less than 5,000 J? no clumps.

EXAMPLE 9 The following components were used Parts Vinyl acetate 100 Water 270 Partially saponified polyvinyl alcohol (alkaline alcoholysis) 12 Sodium formaldehyde sulphoxylate 0.35 Propion aldehyde 0.12 -1S45992 Cobalt acetate Hydrogen peroxide (35%) Sodium bicarbonate The procedure was the same as in Example 2 temperature not exceeding 70°C. The dispersion the following properties : Solid matter content Viscosity PH Sediment Mechanical stability Removed incrustations Viscosity after dilution in 25 parts of water Resistance to mechanical stresses Storage life Resistance to freeze-thaw cycles Particle size distribution EXAMPLE 10 The following components were added: Vinyl acetate 0.03 0.30 0.19 with a reaction obtained had 36.5% 34,000 cps 4.6 ppm very good 30 grams ,700 cps very good very good very good 50% at about 5,000 £ 50% at less than 5,000 J? no clumps.

Parts 100 Water 135 Hydroxyethylcellulose 4 A polyglycol ether 2.5 Sodium dodecylbenzene sulphonate 0.3 Vinyl sulphonate 0.2 Sodium formaldehyde sulphoxylate 0.52 Vinyl versatate 40 Propion aldehyde 0.25 Hydrogen peroxide (35%) 0.3% Sodium bicarbonate 0.2 Methanol 10 All the ingredients were added to the reactor except that only one third of the vinyl acetate, the vinyl versatate and the propionaldehyde were added. Then, the feed of bicarbonate and hydrogen peroxide was started. At a temperature of 60°C, the remaining vinyl versatate, vinyl acetate and propionaldehyde were initially fed and the reaction temperature was maintained at 80°C or below. On completion of the reaction and upon cooling a 1:1 mixture of methanol and water was added. The dispersion obtained had the following properties:

Claims

1. A process for the preparation of a dispersion, which comprises polymerising an ethylenically unsaturated ester and/ or an ester of an unsaturated carboxylic acid in a reaction mixture comprising (1) water, (2) as a reducing agent, sodium formaldehyde sulphoxylate, (3) an acetate and/or sulphate of an element of Group V111 of the Periodic Table, (4) an oxygenevolving system comprising (a) a water-soluble peroxide and (b) a bicarbonate and/or acetate of an alkali metal or alkaline earth metal, (5) an aldehydic chain-transfer agent and (6) a protective colloid, the reducing agent being used in a stoichiometric excess amount relative to the oxygen-evolving system, and the polymerisation being effected in two stages in the first of which the oxygen-evolving system is initially absent and only 10 to 70% by weight of the total amount of the ester is used, and in the second of which the oxygen-evolving system is present and the remaining 90 to 30% by weight of the ester is used.

2. A process according to claim 1, wherein the oxygenevolving system is continuously fed to the reaction mixture during the first and second stages, and wherein, in the second stage, the remaining 90 to 30?, by weight of the ester is con-19 4599 2 tinuously fed to the reaction mixture.

3. A process according to claim 1 or 2, wherein the acetate and/or sulphate of an element of Group VI11 of the Periodic Table is an acetate and/or sulphate of iron or cobalt.

4. 5 4. A process according to any of claims 1 to 3, wherein the'^eroxTdSTsT^arog'en peroxide, 1 and wherein the bicarbonate and/or acetate is a bicarbonate and/or acetate of sodium or potassium. 5. A process according to any „of ciaimisT ' to. 3, wherein 1θ the peroxide is a persulphate of an alkali metal or an alkaline earth metal, or hydrogen peroxide. -_______ ..&?

5. 6. A process according to-any of claims 1 to 5, wherein the chain-transfer agent is acetaldehyde, propionaldehyde or crotonaldehyde. 15

6. 7. A process according to any of claims 1 to 6, wherein the protective colloid is polyvinylpyrrolidone, methyl cellulose, hydroxyethylcellulose, hydroxymethylcellulose, or polyvinyl elcohol obtained by acidic or alkaline alcolholysis.

7. 8. A process according to any of claims 1 to 7, wherein 2o the reaction mixture further comprises a surfactant.

8. 9. A process according to claim 8, wherein the surfactant is sodium dodecylbenzenesulphonate, potassium dodecylben-2045992 zenesulphonate, or a polyglycol ether of nonylphenol.

9. 10. A process according to any of claims 1 to 9, wherein from 25 to 45% by weight of the total amount of ester is used in the first stage. 5

10. 11. Λ process according to any of claims 1 to 10, wherein the ester is copolymerised with at least one other monomer copolymerisable therewith.

11.

12. A process for the preparation of a dispersion, substantially as described in any of the foregoing Examples 2 to 10 10

13. A dispersion when prepared by a process according to any of claims 1 to 12.