IE42687B1 - Process for the continuous manufacture of polymers and copolymers of vinyl chloride - Google Patents

Abstract

Homopolymers and copolymers of vinyl chloride containing at least 85 % by weight of polymerised vinly chloride units are prepared continuously in aqueous emulsion. The polymerisation is carried out in the presence of water-soluble catalysts which form free radicals, polymerisation auxiliaries and 1.5 to 3 % by weight of an emulsifier mixture. The emulsifier mixture comprises a) alkali metal and/or ammonium salts of sulphosuccinic diesters and b) alkali metal and/or ammonium salts of alkylsulphonic acids and/or of alkylarylsulphonic acids of the type and composition defined in Claim 1. The dried polymers obtained are particularly suitable for the preparation of plastisols.

Description

PROCESS FOR THE CONTINUOUS MANUFACTURE OF POLYMERS AND COPOLYMERS OF VINYL CHLORIDE PATENT APPLICATION BY (71) HOECHST AKTIENGESELLSCHAFT, A JOINT STOCK COMPANY ORGANIZED AND EIXSTING UNDER THE LAWS OF THE FEDERAL REPUBLIC OF GERMANY, OF 6230 FRANKFURT/MAIN 80, FEDERAL REPUBLIC OF GERMANY. 24n The present invention provides a process for the continuous manufacture of homo- and copolymers of vinyl chloride containing at least 85% by weight (relative to the total polymer) of polymerized vinyl chloride in the presence of water-soluble catalysts and an emulsifier mixture of salts of sulfosuccinic acid diesters and alkylsulfonic acids or alkylarylsulfonic acids. The polymers obtained and dried are especially suitable for the manufacture Of pastes (plastisols).

German Auslegeschrift No. 1,119,513 proposes the use of alkali metal salts of sulfosuccinic acid diesters as emulsifiers in the continuous manufacture of vinyl chloride homo- and copolymers. Thus, stable latices are obtained having a solids content of about 45%. The dry * I polymers yield, pastes having an especially low paste viscosity which rises only slowly on storage. However, the thermostability of these pastes is insufficient for modern paste processing. Emulsifiers such as alkylsulfates, sulfonates or alkylarylsulfonates are said to be unfit for this polymerization process for the manufacture of low viscosity pastes.

It is known from German Auslegeschrift No. 1,271,403 that vinyl chloride polymers suitable for the manufacture of plastisols may be prepared by polymerization of vinyl chloride in agueous emulsion by the seed technique in the presence of a water-soluble persalt as catalyst and an emulsifier mixture which is added continuously throughout the duration of the polymerization. The emulsifier mixture consists of an alkali metal alkylsulfate, an alkali metal salt of sulfonated alkylnaphthalenes and alkyl-benzenes, or an alkali metal salt of sulfonated paraffins and an alkali metal or ammonium salt of an ester of sulfosuccinic acid.

This batch method involves previous preparation of a seed latex whioh is complicated, time-consuming and generally permits the preparation only of latices having a maximum solids content of about 35%, that is, a poorer space-time yield of polymer than in the continuous process without using a seed latex, and often causes problems because of the sensitivity of the latex to shearing forces.

The present invention is based on the observation that emulsifier mixtures consisting of alkali metal salts or ammonium salts of sulfosuccinic acid diesters and alkylsulfonic and alkylarylsulfonic acids may be advantageously used for the continuous polymerization of vinyl chloride in aqueous emulsion, in contrast to the suggestions made in German Auslegeschrift No. 1,119,513, when specific mixing ratios are observed.

The present invention therefore provides a process for the manufacture of a vinyl chloride homo- or copolymer having at least 85% by weight (relative to the polymer) of polymerized vinyl chloride units, which comprises polymerizing in a continuous flow the monomer(s) in aqueous emulsion in the presence of a water-soluble catalyst, from 1.5 to 3% by weight (relative to the monomer(s)) of an emulsifier mixture composed of: (a) from 95 to 65% by weight (relative to the mixture) of an alkali metal or ammonium salt of a sulfosuccinic acid diester, a 0.05% aqueous solution of which, free from any other salts, has a surface tension in a Traube stalagmometer of at most 32 dyne ./cm, or a mixture thereof, and (b) from 5 to 35% by weight (relative to the mixture) of an alkali metal or ammonium salt of an alkylsulfonic acid having from 10 to 18 carbon atoms in the alkyl radical and/or an alkylarylsulfonic acid having a total of from 6 to 16 carbon atoms in the alkyi radical(s), or a mixture thereof; and one or more other polymerization auxiliaries, and subsequently drying the polymer obtaihed.

The polymerisation in a continuous flow is carried out in known manner by continuously feeding the monomer(s) together with aqueous solutions of the emulsifiers and the catalyst to a stirred reaction zone and withdrawing continuously a corresponding amount of an aqueous emulsion of the polymerized monomers from the reaction zone at the same time. .

When using less than 1.5% by weight of emulsifier mixture, the latices obtained generally no longer have sufficient processing stability, in which case coagulates are formed. When.using more than 3% by weight of emulsifier mixture, the polymers obtained have less favourable properties, especially lower transparency, sensitivity to water and physiological tolerance.

Polymerization is preferably carried out in the presence of from 1.8 to 2.4% by weight (relative to the monomer(s)) of the emulsifier mixture. - 5 An emulsifier mixture containing less than 5% by weight of component (b) results in practically no improvement in the thermostability of the polymer. With more than 35% by weight of component (b), however, considerable increase of the paste viscosity is observed. Especially good results are obtained when the emulsifier mixture contains from 10 to 25% by weight of component (b), and 9075% by weight of component (a).

As component (a) of the emulsifier mixture used according to the present invention, there may be used all alkali metal and/or ammonium salts of sulfosuccinic acid diesters the 0.05% aqueous solutions of which, free from foreign salts, have a surface tension in a Traube stalagmometer of at most 32 dyne/cm, for example the alkali metal and/or ammonium salts, especially the sodium salts, of bis-lsononyl-sulphosuccinate, bis-isodecyl-sulphosuccinate, bistridecyl-sulphosuccinate and isodecylalkylsulphosuccinate.

Salts of sulfosuccinic acids esterified with two different alcohol components may also be used, as well as mixtures of salts of different sulfosuccinic acid esters.

Component (b) of the emulsifier mixture may be for example an alkali metal and/or ammonium salt,especially the sodium salt, of an alkylsulfonic acid having from 10 to 18 carbon atoms, preferably from 12 to 16 carbon atoms in the alkyl group. Preferred acids are sulfonic acid group-containing saturated, branched and linear alkanes in which at least 80% by weight of the alkanesulfonic acids have from 12 to 16 carbon atoms. Especially preferred are those alkanesulfonic acids containing at least 80% by weight of alkylsulfonic acids each having from 14 to 16 carbon atoms in the alkyl group.

Component (b) may also be an alkali metal and/or . ammonium salt, especially the sodium salt, of an alkylarylsulfonic acid having a total of from 6 to 16 carbon atoms in the alkyl radical(s), and preferably those alkylarylsulfonic aqids the aryl group of which is substituted by one or more alkyl radicals which may be identical or different and all the alkyl substituents on one aryl group have together from 8 to 12 carbon atoms. Preferred aryl radicals are the phenyl and naphthyl radicals. Examples of preferred acids are dibutylnaphthalenesulfonic acid, and, especially, dodecylbenzenesulfonic acid. In addition, mixtures of different salts of sulfonic acids may be used.

The polymerization is carried out in aqueous emulsion in the presence of from for example 0.001 to 1% by weight, preferably from 0.01 to 0.3% by weight, relative to the monomer(s), of a radical forming water-soluble catalyst. Suitable catalysts are persulfates such as potassium, sodium and ammonium persulfates, hydrogen peroxide, tert.-butylhydroperoxide, peroxydiphosphates and other water-soluble peroxides, as well as mixtures of different catalysts. These catalysts may be used in the presence of from 0.001 to 1% by weight, relative to the monomer(s), of one or more reducing substances suitable for the formation of a redox catalyst system, for example sulfites,.bisulfites, dithionites, thiosulfates and aldehyde sulfoxylates such as sodium formaldehyde sulfoxylate. Optionally, the polymerization may be carried out in the presence of soluble metal salts, for 43687 - 7 example salts of copper, silver, iron, nickel, cobalt or chromium. The amount of these metal salts should be corresponding to 0.05 to 10 parts of the metal-cation of the salt per one million parts of the monomer(s) which are to be polymerised in the presence of the salt.

Besides catalysts and emulsifiers, the polymerization may be carried out in the presence of buffer substances, for example alkali metal acetates, borax, alkali metal phosphates, alkali metal carbonates, ammonia or ammonium salts of carboxylic acids, as well as molecular weight regulators, for example aliphatic aldehydes having from 2 to 4 carbon atoms, halogenated hydrocarbons, for example di- or trichloroethylene, chloroform, bromoform and methylene chloride, and mercaptans.

Monomers suitable for copolymerization with vinyl chloride are for example olefins such as ethylene and propylene, vinyl esters ot linear or branched carboxylic acids, which acids have from 2 to 20, preferably 2 to 4 carbon atoms, such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl-2-ethyl-hexoate; vinyl and vinylidene halides such as vinyl fluoride, vinylidene fluoride, or vinylidene chloride; vinyl ethers; unsaturated acids such as maleic, fumaric, acrylic and methacrylic acids and the mono- or diesters thereof with mono- or dialcohols having from 1 to 10 carbon atoms, and maleimide and the N-substitution products thereof having aromatic, cycloaliphatic and optionally branched aliphatic substituents.

After polymerization, there may be added further substances for stabilizing the polymers obtained after drying to a powder or for Improving their processing - 8 properties, for example mono-, di- or trifatty acid esters of polyhydric alcohols such as sorbitol, pentaerythritol, glycerol and di-glycerol.

The polymerization is generally carried out at a temperature of from 35 to 80°C, preferably from 40 to 7O°C, at a conversion rate of from 89 to 95%, preferably from 91 to 93% relative to the monomer(s) used. The conversion percentage, in the case of continuous emulsion polymerization, is advantageously determined by the unit weight, measured as described below. The conversion rates correspond to about the following unit weights: 89% of conversion = 90 g/2 liters of unit weight, 91% of conversion = 110 g/2 liters of unit weight, 93% of conversion = 140 g/2 liters of unit weight, and 95% of conversion = 190 g/2 liters of unit weight.

The liguor/monomer ratio is advantageously chosen in such a manner that there are obtained latices having solids contents of from about 40 to 48%, preferably 43 to 46%.

After complete polymerization and elimination of the substantial amount of unreacted monomer, the polymer is generally separated by evaporation of the water, for example in a spray-dryer. Optionally, the latex may be liberated before drying from part of the aqueous liquor by physical methods, for example ultrafiltration.

The process of the present invention permits the manufacture of vinyl chloride homo- or copolymers especially suitable for processing with plasticizers to pastes (plastisols), and is distinguished by very low paste viscosity and excellent thermostability, while utilizing the technical advantages of continuous emulsion - 9 polymerization and maintaining emulsifier costs relatively low. The thermostability of the polymers so obtained is substantially increased as compared to the indications of German Auslegeschrift No. 1,119,513.

Also compared to the process of this German Auslegeschrift a definite K value of the polymer is obtained with the emulsifier mixture according to the invention at higher temperature and therefore also a higher throughput rate, and thus a space-time yield increased by 30 to 100% is attained.

As compared to the batchwise process using a seed latex according to German Auslegeschrift No. 1,271,403, the improvement of space-time yield is from 70 to 250%, and moreover, the paste viscosity is considerably lower.

By space-time yield, there is to be understood the amount of polymer which can be produced within a unit of time (for example 1 year) in a specific space for the polymerization, and it is hereinafter indicated in tons 3 per year per m (on the basis of 8000 manufacturing hours per year).

Because of their low paste viscosity, the polymers manufactured according to the present invention are especially suitable for the manufacture of pastes having a high filler content and/or a high polymer content.

The articles manufactured therefrom are distinguished by lower tack, decreased dust adsorption, improved mechanical properties and less abrasion (for example of floor coatings applied by spreading processes).

The following Examples illustrate the invention.

The various values were determined as follows! K-value according to German Industrial Standard lo DIN 53 726.

Unit weight: shortly after the outlet orifice of the vessel where the continuous polymerization is carried out, there is mounted a discharge opening having a diameter of 15 mm which can be closed. The latex under pressure is discharged and foams because of its content of unpolymerized monomer. As soon as the foam current has become uniform, it is allowed to flow into a metal receptacle which has been previously weighed and contains exactly 2 liters when filled to the rim. When the receptacle is completely filled, the over ranging foam is skimmed over the rim and the receptacle is weighed at once. The weight gain is the unit weight in g/2 liters.

Thermostability: formulation: 100 parts of polymer di-ethylhexylphthalate (DOP) part barium stabilizer* cadmium * *(barium and cadmium salts of an acid mixture of p-tert.butylbenzoic acid and branched aliphatic carboxylic acids having frcm 9 to 11 carbon atoms).

DOP and the two stabilizers are stirred, and the polyvinyl chloride is added uniformly within 3 minutes.

The mixture is then homogenized for 12 minutes by means of a cross-blade agitator of Jahnke & Kunkel turning at 750 rpm. Samples of a drop of the paste so obtained per tube are introduced into several test tubes, and the tubes are introduced into an oil bath heated at 170°G + O.2°C. In a preliminary test, the time (minutes) is evaluated which has passed until a distinct yellow-brown 43687 - 11 discolouration of the samples occurs. For the genuine measurement, 10 charged tubes are introduced into the oil bath, and 5 minutes before the time found out in the preliminary test the first tube is taken off the bath and another tube every further minute, so that the time passing until the first distinct appearance of the yellowbrown discolouration is more exactly measured. The stabilizer system is chosen in such a manner that a relatively sharp, reproducible color change occurs.

Paste viscosity; 80 g of diethylhexylphthalate are introduced into a beaker having a capacity of 400 ml, subsequently 60 g of polymer are stirred in within 3 minutes at 500 rpm, and a further 60 g of polymer within the next 3 minutes at 760 rpm. Agitation is continued for 10 minutes at 750 rpm, and subsequently, the mixture is warmed at 20°C for 60 minutes. After this time, the viscosity of a sample is measured in Pascals (Pas) by means of a rotation viscometer (Rotavisco of Messrs.

Haake) at a shearing gradient of 40 sec \ After having charged the measuring chamber of the apparatus, 15 more minutes must have passed before measuring, in order to ensure an exact adjustment of the temperature to 20°C.

In analogous manner, a further sample is measured after 24 and 96 hours. The original mixture is maintained at 20° C during the total time of measurement.

The Examples 1 to 7 and Comparative Tests I to III were carried out as follows: Monomers or monomer mixture, a 2% aqueous solution of potassium persulfate and an aqueous solution of the emulsifier or emulsifiers are introduced continuously, but separately, into a vertically positioned autoclave - 12 having a capacity of 10 m3 and being provided with a blade agitator ih its upper part. 1.16 kg of emulsifier solution and 0.05 kg of persulfate solution are added per kg of monomer. The concentration of the emulsifier solution is chosen in such a manner that 2% by weight of total emulsifier are present in the reaction mixture.

The temperature of the reaction mixture is maintained constant. The polymer emulsion (latex) formed is discharged from the lower part of the autoclave while measuring the unit weight.

The latex has a solids content of about 45% by weight, it is mechanically stable and may be pumped by means of rotary pumps. It is spray-dried, the dry polymer is sorted out, the particles having a size above about 35 microns are ground to a mean secondary particle size of.from 10 to 12 microns and subsequently joined again with the finely distributed product sorted out.

K value,paste viscosity and thermostability of this latter joint product are measured, and the values obtained are listed in the following Table, in which I, II, III are comparative tests according to continuous polymerization process 1 to 7 are examples according to this invention VC is vinyl chloride VAc is vinyl acetate al is the sodium salt of bis-isodecyl-sulphosuccinate a2 is the sodium salt of bis-isononyl-sulphosuccinate bl is the sodium salt of an alkylsulfonic acid mixture containing 80% by weight (relative to the mixture) of alkylsulfonic acids having from 14 to 16 carbon atoms in the alkyl groups, b2 is the sodium salt of the dodecylbenzenesulfonic acid.

All percentages are by weight, relative to the monomer used - 13 n Ό I (0 H tfl Q) Γ0 Φ C >i U g •H ο I 4 -μ to n Φ H fi & to 1 ft) 01 ft •rl *—· h X > Φ ’Cf 4J CM Φ «Ρ ¢4 «Ρ •H ft) W to ft) 0 4Ϊ cu 0 r-1 φ >ι·Ρ •Ρ ω -H ra r~l Ql fi fi JJ Cn rd •Η Ή CM CJ Φ X. B tr Monomers Emulsifiers Emulsifier Polymer ft · e u id Bi >< +> C fl JS M •rl BI 0 X O -rt rl -rl Ε υ ? a o ts III 2 % al 100/0 48 160 29 5.80 6.50 8.60 “ 310 Comparative tests using a seed latex according to the batchwise process of German Auslegeschrift No. 1,271,403.

Test A A mixture of 5.2 parts of seed latex containing a vinyl chloride homopolymer and prepared according to the following description, having a solids content of 29% and a particle diameter of about 0.2 micron, of 195 parts of water and 0.15 parts of sodium bicarbonate is introduced into an autoclave of stainless super-refined steel, provided with an agitator and laving a capacity of 600 1.

By evacuation and flushing with nitrogen, the air is eliminated from the reactor, and subsequently, 0.15 parts of sodium bisulfite and 30 parts of vinyl chloride are added. The contents are heated to 50°C, and the poly nerization is started by continuously feeding-in of 0.03 parts of potassium persulfate dissolved in water. After about 1 hour, 120 parts of vinyl chloride and a solution if-1.12 parts of emulsifier a 1 in 22.5 parts of water ire fed in continuously.

These solutions are continuously fed in during the ;otal time of reaction, which proceeds generally for 6 to 5 hours. When the pressure in the reactor is decreased :o 4 bars over-pressure, a further 0.3 part of emulsifier t 1 is added and the contents of the reactor are coo Led. ?he remaining monomer is discharged, the emulsion is ipray-dried and ground to a mean secondary particle size if from 10 to 12 microns, A total of 0,95% by weight relative to the vinyl chloride Used) of emulsifier a 1 s used, emulsifier mixing ratio being 100/0. 'aste viscosity: after 1 hour 6.3 Pas, after 24 hours - 15 8.00 Pas. K value: 74.

Test B Operations are as in Test A, but an emulsifier mixture of 1.14 parts of emulsifier a 1 and 0.28 part of emulsifier b 1 is used. The total amount of emulsifier is 0.95% by weight (relative to the vinyl chloride used), emulsifier mixing ratio: 80/20.

Paste viscosity: after 1 hour 5.9 Pas, after 24 hours 7.9 Pas. K value: 74. 1° Test C Operations are as in Test A, but an emulsifier mixture of 0.71 part of emulsifier a 1 and 0.71 part of emulsifier b 1 is used. The total amount of emulsifier mixture is again 0.95% by weight, relative to the vinyl chloride used, emulsifier mixing ratio: 50/50.

Paste viscosity; after 1 hour 5.8 Pas, after 24 hours 7.7 Pas. K value: 74.

Test D 156 kg of seed latex of a vinyl chloride homo20 polymer, previously prepared according to the following description) having, a solids content of 29% and a particle size of 0.2 microns, 5850 kg of water and 4.5 kg of sodium bicarbonate are introduced into an autoclave 3 of super-refined steel having a capacity of 12.m and 25 provided with an agitator. After elimination of the air, 4.5 kg of sodium bisulfite, 900 kg of vinyl chloride and, continuously, a solution containing 900 g of potassium persulfate are fed in, and the reactor contents are heated to 50°C. After 1 hour, 3600 kg of vinyl chloride are added continuously and subsequently a solution of 26.9 kg - 16 of emulsifier a 1 and 6.7 kg of emulsifier b 1 in 675 liters of water.

The polymerization, up to a pressure of 4 bars in the reactor, proceeds for 6 to 7 hours at a temperature of the cooling water of about 20°C. Towards the end of the polymerization, an emulsifier mixture of 7.2 kg of emulsifier a 1 and 1.8 kg of emulsifier b 1 is added in order to stabilize the latex. The remaining monomer is discharged and the latex obtained is spray-dried and ground. The total amount of emulsifier mixture is 0.85% by weight, relative to the vinyl chloride used* emulsifier mixing ratio: 80/20.

Paste viscosity: after 1 hour 5.7 Pas, after 24 hours 7.6 Pas. K value: 74.

Space-time yield* 245 tons-a-year/m3.

Claims (8)

1. CIAIMS:1. A process for the manufacture of a vinyl chloride homo or copolymer having at least 85% by weight (relative to the polymer) of polymerized vinyl chloride units, which comprises polymerizing in a continuous flow the monomer(s) in aqueous emulsion in the presence of a water-soluble catalyst, from 1.5 to 3% by weight (relative to the monomer(s)) of an emulsifier mixture composed of (a) from 95 to 65% by weight (relative to the mixture) of an alkali metal or ammonium salt of a sulfosuccinic acid diester, a 0.05% aqueous solution of which, free from any other salts, has a surface tension in a Trauble stalagmometer of at most 32 dyne/cm, or a mixture thereof, and (b) from 5 to 35% by weight (relative to the mixture) of an alkali metal or ammonium salt of an alkylsulfonic acid having from 10 to 18 carbon atoms in the alkyl radical and/or an alkylarylsulfonic acid having a total of from 6 to 16 carbon atoms in the alkyl radical(s), or a mixture thereof; and one or more other polymerization auxiliaries and subsequently drying the polymer obtained.

2. A process as claimed in claim 1, wherein polymerization is carried out in the presence of from 1.8 to 2.4% by weight (relative to the monomer(s)) of the emulsifier mixture.

3. A process as claimed in claim 1 or claim 2, wherein the emulsifier mixture contains from 90 to 75% by weight (relative to the mixture) of component (a) and from 10 to 25% by weight (relative to the mixture) of component (b).

4. A process as claimed in any one of claims 1 to 3, wherein the emulsifier mixture contains an alkali metal or ammonium salt of the bis-isodecyl-sulpho succin ate.

5. A process as claimed in any one of claims 1 to 4, wherein the emulsifier mixture contains an alkali metal or ammonium salt of an alkylsulfonic acid mixture consisting of more than 80% by weight of alkylsulfonic acids each having from 14 to 16 carbon atoms in the alkyl group.

6. A process as claimed in any one of claims 1 to 4, wherein the emulsifier mixture contains an alkali metal or ammonium salt of dodecylbenzenesulfonic acid.

7. A process as claimed in claim 1 carried out substantially as described in any one of Examples 1 to 7 herein.

8. A vinyl chloride homo- or copolymer containing at least 85% by weight (relative to the polymer) of polymerized vinyl chloride units, whenever obtained by a process as claimed in any one of Claims 1 to 6.