NO150516B - PROCEDURE FOR POLYMERIZATION OF VINYL CHLORIDE - Google Patents

Description

The present invention relates to an improved method for the polymerization of vinyl chloride or a mixture of

monomers, consisting mainly of vinyl chloride, in the presence of a polymerization initiator in a polymerization reactor, and whereby the deposition of polymer shell on the inner walls of the polymerization reactor and the surfaces of an agitator as well as other parts, which come into contact with the monomer or monomers, can be effectively prevented.

Known methods for the production of vinyl chloride polymer include suspension polymerization, emulsion polymerization, solution polymerization, gas phase polymerization and bulk polymerization. These conventional polymerization methods have the disadvantage of

pe that polymerization scale is deposited on the surfaces and walls of the polymerization reactor and other parts including agitator blades, which parts come into contact with the monomer> and this results in a reduced yield of polymer product as well as a reduced cooling effect in the case of the polymerization reactor. Furthermore, the shell deposit on the surfaces tends to loosen and so-

is led to enter the polymer product, and this results in a lower product quality. Furthermore, all scale deposits must be removed after each polymerization run, and this requires a lot of work time,

which in turn results in reduced productivity. In addition, the work with shell removal involves a health problem because the monomeric vinyl chloride has cancer-causing properties.

In order to prevent such unwanted polymer shell deposition on the inner walls and other surfaces of the polymerization reactor, it has been proposed to coat these surfaces with an amine compound, a quinone compound, an aldehyde compound or another polar organic compound (cf. U.S. patent 3.669946) .

This method is, however, applicable when it comes to suspension ion polymerization, but it is not suitable when it comes to other types of polymerization. Nevertheless, the method used in suspension polymerization is only effective in connection with homopolymerization of vinyl chloride, whereby one can. avoid polymer shell formation even after a significant number of polymerization runs. In general, however, the former is known

procedure disadvantageous when:

(1) a copolymerization of vinyl chloride with a copolymerizable monomer or copolymerizable monomers shall be carried out; (2) an emulsifier is added to the polymerization mixture to aid dispersion; (3) an acyl peroxide such as benzoyl peroxide or lauroyl peroxide is used as the polymerization initiator; and (4) the polymerization is carried out in the presence of certain process additives such as lubricants and stabilizers, e.g. lauric acid, stearic acid, lauryl sulphonate, stearyl sulphonate and salts thereof.

It has therefore been a primary purpose of the present invention to provide a method for the polymerization of vinyl chloride or a mixture of monomers consisting essentially of

lig of vinyl chloride in the presence of a polymerization initiator in a polymerization reactor, and whereby the deposition of polymer shell on the inner walls of the polymerization reactor and other surfaces, which come into contact with the monomer or monomers, essentially can. is prevented regardless of the type of polymerization.

Another purpose of the present invention has been to provide a method for the polymerization of vinyl chloride or a mixture of monomers, which essentially consists of vinyl chloride, and by which vinyl chloride polymer of high quality can easily be produced.

A further object of the present invention has been to provide a method for the production of a polyvinyl chloride resin or a copolymer resin consisting essentially of vinyl chloride, and whereby the production efficiency of the polymerization process can be improved.

With the method according to the present invention, the above-mentioned objectives have been achieved by coating the inner walls of the aforementioned polymerization reactor and other surfaces, which come into contact with the monomer or monomers, with a coating material that contains in the at least one electron donor compound selected from "Solvent Black-. 7", diaminonaphthalene,, "Solvent Orange 14", ethylenediamine, "Basic Green 4", "Solvent Black 5", indulin, azulene, thiophenol, "Solvent Black 3" , ethanolamine and morpholine and at least one electron acceptor compound selected from "Solvent Red 1", • Solvent Red 49", "Acid Black 2"", "Acid Brown 14", "Mordant Black 11", p-benzoquinone, " Acid Red 27", "Solvent Red 26", diphenoquinone, phenol and diphenyl acid dg p-benzoxinone.

In the method according to the present invention, the deposition can

of polymer shell on the inner walls of the polymerization reactor, the agitator blades and other parts, which come into contact with monomer or monomers., are essentially eliminated. Furthermore, the present method is advantageous as it is effective in connection with any type of polymerization, i.e. , suspension polymerization, emulsion polymerization, solution polymerization or mass polymerization, yes also when it comes to copolymerization of a monomer mixture consisting essentially of vinyl chloride as well as in homopolymerization of vinyl chloride.

The reason why polymer shell deposition is avoided by the present method is believed to be due to the mechanism that a mixture of one of the aforementioned electron-donating compounds and one of the aforementioned electron-accepting compounds forms an e-t charge transfer complex, which is effective - for the purpose, ■pg which differs from the usually used coating compounds such as amines, quinones and aldehydes. the surface does not absorb shell-forming molecules that occur in the polymerization mixture.

The usable electron donor compounds in the method according to the present invention include Solvent Black 7, diamino-naphthalene, Solvent Orange 14, ethylenediamine, Basic Green 4, Solvent Black 5, indulin, azulene, thiophenol, Solvent Black 3", ethanolamine and morpholine.

The useful electron acceptor compounds in the method of the present invention include "Solvent Red 1", "Solvent Red 49", "Acid Black 2", "Acid Brown 14", "Mordant Black 11", p-benzoquinone, "Aeid Red 27" , "Solvent Red 26", diphenoquinorr, phenol and diphenyl acid and p-benzoquinone^

In the present method, at least one of the mentioned electron donor compounds and at least one of the mentioned electron acceptor compounds are mixed in a simple way by dissolving or dispersing them together in a suitable medium. It is also possible to dissolve or disperse these separately themselves, so that the two solutions or dispersions obtained are mixed. Such a dissolution or dispersion is usually carried out at room temperature, or sometimes below 0°C or above 50°C, and, if desired, under irradiation with light. The light used is usually visible or ultraviolet light, which comes from a fluorescent lamp or mercury lamp.

Examples of media in which said electron-donating and electron-accepting compounds can be dissolved or dispersed are water; ethers such as tetrahydrofuran and diisopropyl ether; alcohols such as methanol, ethanol and propanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; hydrocarbons such as benzene, toluene, xylene and hexane; chlorinated hydrocarbons such as methylene chloride, carbon tetrachloride and trichlorethylene; and aprotic solvents such as dimethylformamide, dimethylacetamide, dimethylsulfoxide and acetonitrile. These mentioned media are used separately or in combination.

According to the present invention, a good effect is achieved with regard to preventing the deposition of polymer shells when the mixing ratio of the electron donor compound and the electron acceptor compound is between 1:5 and 5:1 (weight ratioj.

The quantity ratios in the mixture of the electron donor and electron acceptor compounds that are applied to the inner walls of the polymerization reactor and other parts that come into contact with the monomer or monomers are unchanged in relation to the quantities used in previously known methods, and whereby conventional coating materials are used. I.e. that a satisfactory effect is achieved with regard to preventing polymer shell deposition when the mixtures are applied. on the surfaces in a quantitative ratio--which corresponds to . at least 0.001 g/m 2 coated surface,, However, it is recommended that the thus coated surfaces be washed with water to remove any excess of coating material, which could eventually come loose and enter the polymer product.

Furthermore, the effect with regard to preventing the deposition of polymer shell can be enhanced by adding one or more alkaline substances such as oxides, hydroxides, carbonates, phosphates, bicarbonates. ■' silicates and carboxylates of alkali metals, alkaline earth metals and ammonium to the polymerization mixture. In this case, however, it is preferred that the amount of such additives is less than 1% by weight, calculated on the monomer or monomers, so that the quality of the polymer obtained will not be impaired, and so that the polymerization reaction is not disturbed.

The method according to the present invention is effective in all types of polymerization of vinyl chloride, i.e. suspension polymerisation, solution and mass polymerisation. The method according to the present invention is also not limited by polymerization conditions such as polymerization temperatures and agitation conditions or by the type of additives that are added to the polymerization mixture, e.g. suspending agents such as partially saponified polyvinyl alcohol and methyl cellulose, anionic emulsifiers such as sodium lauryl sulfate, sodium dodecylbenzene sulfonate and sodium dioctyl sulfosuccinate, nonionic emulsifiers such as sorbitan monolaurate and polyoxyethylene alkyl ether, chain transfer agents such as trichloroethylene and mercaptans and initiators such as diidopropyl peroxydicarbonate, lauroyl peroxide and dimethylvaleronitrile. The effect of the method according to the present invention is not affected by the presence of certain additives such as fillers (e.g. calcium carbonate and titanium dioxide), stabilizers (e.g. tribasic lead sulphate, calcium stearate and dibutyltin laurate), lubricants (e.g. rice wax and stearic acid) and plasticizers (e.g. dioctyl phthalate and dibutyl phthalate).

Furthermore, with the present invention, an excellent effect can be achieved not only by homopolymerization of vinyl chloride, but also by copolymerization of vinyl chloride with one or more monomers that are copolymerizable with vinyl chloride, e.g. vinyl esters, vinyl ethers, acrylonitrile, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, maleic acid, maleic acid esters, maleic anhydride, furmaric acid, furmaric acid esters, aromatic vinyl monomers, vinyl halides with the exception of vinyl chloride, vinylidene halides and olefins.

The present invention shall be further illustrated by means of the following examples.

Example . 1

•Different coating solutions were prepared by mixing the electron-donor compounds and the electron-acceptor compounds in the solvents, as shown in Table I, at room temperature under agitation for 3 hours, after which filtration was carried out in order to obtain a concentration of 1% by weight calculated on the solvent.

Each coating solution, which was thus obtained, was applied to the surfaces of the inner walls of a 1,000-liter stainless steel polymerization reactor in a quantity ratio that corresponded to 0.1 g/m 2 (calculated as dry matter). The thus treated surfaces were then dried and washed with water.

Then, 500 kg of deionized water, 0.5 kg of hydroxypropyl methyl cellulose, 0.5 kg of sorbitan monolaurate, 200 g of dimethylvaleronitrile and 200 kg of vinyl chloride were charged into the polymerization reactor, after which the polymerization was carried out at 57°C for 10 hours. After completion of the polymerization, the amount of polymer shell deposition on the surfaces was determined with the results given in the same table.

Example 2

Coating solution was prepared by mixing "Solvent Black 3" as electron donor and "Acid Black 2" as electron acceptor in different proportions (weight ratio) in certain solvents under special conditions, as indicated in Table II, after which filtration was carried out in order to obtain a concentration of 1% by weight calculated on the solvent.

Each coating solution thus obtained was applied to the surfaces of the inner walls of a 1,000-liter stainless steel polymerization reactor as well as to the agitator blades in a density ratio corresponding to 0.1 g/m 2 (as dry matter). The thus treated surfaces were then dried and washed with water. Next, 500 kg of deionized water, 0.5 kg of partially saponified polyvinyl alcohol, 100 g of diisopropyl peroxydicarbonate and 200 kg of vinyl chloride were charged into the polymerization reactor, after which the polymerization was carried out at 57°C for 10 hours under agitation at a speed of 100 rpm. After completion of polymerization the amount of polymer shell deposition on the surfaces was determined, and the results are given in Table II.

Conditions (a): Both compounds were together in the solvent under agitation for 3 hours at room temperature.

(b) : Same conditions as (a) except for

that the temperature was 0°C.

(c) : Same conditions as (a) except for

that the temperature was 90°C.

(d) : Of each compound, a solution was formed using the solvent under agitation for 3 hours at room temperature, and the 2 solutions obtained were combined. (e) : Same conditions as (a) with the exception that

irradiation with UV-lvs was added.

(f): Same conditions as (a) with the exception that the agitation period lasted 1 hour.

Example 3

By using the coating solution from trial No. 28 in Example 2, the surface of the inner walls of a 1000-liter stainless steel polymerization vessel as well as the agitator, which had paddle-type blades, and which was 600 mm in diameter ^coated with an amount corresponding to 0.1 g/m 2, calculated as dry matter. The thus treated surfaces were then dried and washed with water.

Then, 100 kg of vinyl chloride, 200 kg of deionized water and certain amounts of additives together with certain amounts of polymerization initiator and dispersant, as indicated in Table III, were added to the polymerization reactor, after which the polymerization was carried out at 57°C for 10 hours under an agitation speed at 100 revolutions per minute. After completion of the polymerization, the amount of polymer shell deposited on the surfaces was determined. The results appear in table III under the heading "Present invention".

For comparison, the same work operations as indicated above were repeated with the exception that the coating solution was a solution of "Solvent Black. 7" alone. The amount of polymer shell was determined and the results are given in the same table under the heading "Comparison".

For further comparison, trial No. 52, shown in

the table, carried out in a similar way with the exception that no coating solution was used. The result, i.e. the amount of polymer shell deposition in this experiment is given in the same table.

Notes:

(1) In experiment no. 43, a monomer mixture consisting of 85 kg of vinyl chloride and 15 kg of vinyl acetate was used instead of the vinyl chloride that was used in the other experiments. (2) In experiment no. 44, a monomer mixture consisting of 95 kg of vinyl chloride and 5 kg of vinyl acetate was used.

(3) In experiment no. 51, the speed during agitation was 30.

(4) In the table, DVN means dimethylvaleronitrile; LPO

means lauroyl peroxide; BPO means benzoyl peroxide;

IPP means diisopropyl peroxydicarbonate; PVA means partially saponified polyvinyl alcohol; HPMC means hydroxypropyl methyl cellulose S.L.S means sodium lauryl sulfate; ABOUT. means cetyl alcohol and DOP means dioctyl phthalate.

Example 4 - The coating solution from experiment no. 28, example 2, was applied to the surfaces of the inner walls of a 5-litre stainless steel polymerisation ion reactor as well as the agitator blades in a quantity ratio corresponding to 0.1 g/m 2. The thus treated surfaces were then dried and washed with water. Next, 1800 g of vinyl chloride, 2700 g of deionized water, 0.1 g of partially saponified polyvinyl alcohol, 0.1 g of sodium stearate and 0.03 g of dimethylvaleronitrile were added to the polymerization reactor, after which polymerization was carried out at 57°C in the presence of a specific alkaline substance which were added in amounts and at times indicated in Table IV. Polymerization runs were repeated with the same polymerization reactor until polymer scale deposition on the coated surfaces was found to exceed 1 g/m or observed with the naked eye. The number of polymerization runs, before just such a polymerization run where polymer shell deposition was observed, was recorded. The results appear in Table IV.

Example 5

Coating solution from test no. 28 in example 2 was applied to the surface of the inner walls of 2 polymerization reactors, whereby one was a 2-liter stainless steel vertical-type reactor and the other was a 4-liter horizontal-type stainless steel reactor , as well as other parts that come into contact with the monomer, and then in a quantity ratio that corresponded to 0.1 g/m . The coated surfaces were dried and then washed with water. Next, 800 g of vinyl chloride and 0.4 g of dimethylvaleronitrile were added to the first 2-liter polymerization reactor, followed by polymerization at 60° C. for 2 hours with an agitation speed of .9.00. The resulting reaction mixture was transferred to the second 4-liter polymerization reactor, where 800 g of vinyl chloride and 0.4 g of dimethylvaleronitrile were added, in order to carry out a further polymerization at 57°C for 10 hours and with a speed of 100 during the agitation .

The polymer shell deposition on the surface of each polymerization reactor was determined as indicated in Table V.

For comparison, a similar experiment was carried out without using the coating solution or using a coating solution consisting of "Solvent Black" alone. The results are shown in the same table.

Claims (2)

1. Process for the polymerization of vinyl chloride or a mixture of monomers consisting mainly of vinyl chloride in the presence of a polymerization initiator in a polymerization reactor, characterized in that before the polymerization, and optionally after washing with water, coating the inner walls of said polymerization reactor and other surfaces, which come into contact with the monomer or monomers, with coating material containing at least one electron donor compound selected from "Solvent Black 7", diaminonaphthalene, "Solvent Orange 14", ethylenediamine, "Basic Green 4", "Solvent Black 5", indulin, azulene, thiophenol, "Solvent Black 3", ethanolamine and morpholine and'at least one electron acceptor compound selected from "Solvent Red 1", " Solvent Red 49", "Acid Black 2", Acid Brown 14", "Mordant Black 11", p-benzoquinone, "Acid Red 27", "Solvent Red 26", diphenoquinone, phenol and diphenyl acid and p-benzoquinone. 2. Method according to claim 1, characterized in that a coating material is used which contains said electron donor compound and said electron acceptor compound in a weight ratio from 1:5 to 5:1.