CS203963B2 - Suppression method for polymer flakes settling out on polymeration vessel surface - Google Patents

Description

The invention relates to a process for the suspension polymerization of vinyl chloride or mixtures of vinyl monomers containing at least 50% vinyl chloride.

Suspension polymerization of vinyl chloride is usually carried out in an aqueous medium containing

(1) a suspending agent, for example synthetic or natural polymers, which serve as protective colloids, such as partially saponified polyvinyl acetate, cellulose ethers or gelatin, a solid dispersing agent, such as calcium carbonate, magnesium carbonate, barium sulfate, titanium dioxide and aluminum oxide;

2) a catalyst, for example organic peroxides such as dilauryl peroxide, dibenzoyl peroxide, isopropylperoxydicarbonate and acetylcyclohexylsulfonyl peroxide, azo compounds such as azobisisobutyronitrile or dimethylvaleronitrile.

In carrying out the polymerization, an aqueous medium containing the above substances and additives is placed in a polymerization vessel equipped with a stirrer and cooling jacket. The temperature inside the vessel is maintained at 30-60 ° C and the aqueous medium is vigorously stirred. In this case, as is well known, polymer scales are deposited on the inner walls of the vessel, reducing polymer yield and cooling capacity of the polymerization vessel. Also, the polymer deposited in the form of scales on the walls of the container of the product may mix, resulting in a deterioration in the physical properties of the product. The deposition of scales of the polymer also results in a slowing of the operation of the polymerization apparatus, since scales removal is laborious and takes a long time. The deposition of polymer scales on the walls of the container, which is increasing in size over time, is one of the major factors that prevents the polymerization from being carried out continuously. Numerous ways have been suggested to overcome these difficulties, but no satisfactory results have been achieved so far. Each method has its own advantages and disadvantages.

When the vinyl chloride polymer is to be produced in bulk, the capacity of the polymerization vessel needs to be increased. In this case, however, the wall surface does not grow in proportion to the volume of the container and the heat dissipation area is therefore too small. It has therefore been proposed to equip the polymerization vessel with a condenser to intensify the cooling and stirring of the reaction system. However, during operation, polymer scales often deposit on the inner walls of the conduit connecting the portion of the polymerization vessel in which the gas phase and the condenser are located, as well as on the inner walls of the condenser where the capacitor comes into contact with the monomer, Moreover, the quality of the polymer produced is deteriorating and the entire polymerization process is compromised. It has therefore been found that this process is unsuitable for suspension polymerization.

SUMMARY OF THE INVENTION The present invention provides a process for the suspension polymerization of vinyl chloride, which has the advantage over the prior art processes that virtually no scales of polymer are deposited on the walls of the polymerization vessel.

Another advantage of the invention is that the rate of polymerization increases so that polyvinyl chloride can be produced in bulk. The polymerization according to the invention does not cause scaling, but does not impair the processability of the product, the particle size distribution, the initial color and the thermal stability of the product.

The invention is based on the discovery that in the slurry polymerization of vinyl chloride or a vinyl monomer mixture containing vinyl chloride as the main component in an aqueous medium containing a suspending agent and an oil soluble catalyst, the above advantages are achieved by providing the inner walls of the polymerization vessel and the stirring vanes and / or the condenser provided with the container, coated with at least one compound selected from the group of polar organic compounds including nitrogen-containing organic compounds, such as compounds containing azo groups, nitro groups, azomethine groups and azine rings and amino groups; sulfur-containing organic compounds such as those containing thiocarbonyl residues, thioether residues, and thioalcohol residues; ketones; aldehydes; alcohols containing at least 6 carbon atoms; carboxylic acids containing at least 6 carbon atoms; from the group of organic dyes such as azine dyes, i.e. azines, oxazines and thiazines containing oxygen, sulfur or nitrogen atoms, quinone dyes, azo dyes, phthalocyanine dyes and aniline black: and / or in the group of inorganic pigments such as chrome yellow or zinc white.

In suspension polymerization of vinyl chloride, the polymer scales usually deposit on the inner walls of the polymer because the monomer is first adsorbed on the inner walls of the polymerization of the vessel, which is then subsequently polymerized. The monomer adsorption on the inner walls of the polymerization vessel appears to be because the wall surface is uneven, or because the wall surface is activated by the corrosion caused by halogen ions formed during the polymerization.

In the present invention, it has been found that the deposition of scales of the polymer is prevented when the surfaces on which the scales tend to settle are coated with one or more of the aforementioned organic or inorganic substances. For this purpose, a very small amount of coating material is sufficient, which, moreover, does not impair the physical properties of the vinyl chloride polymer to be prepared, so that polymerization is very advantageous and can be carried out continuously. When carrying out the process according to the invention, it is not necessary to use large amounts of suspending agent or agents, as is customary in this case, to prevent scale buildup. The resulting product has many advantageous properties.

When the polymerization is carried out in a polymerization vessel equipped with a condenser, the surface of the condenser, where the scales are usually deposited, should be treated in the same manner as above. This prevents the condenser from clogging and increases its efficiency. The function of the capacitor is to remove latent heat from the polyvinyl chloride particles by evaporating the vinyl chloride monomer which evaporates directly from the particles, thus preventing them from overheating. As a result, the polyvinyl chloride obtained has a uniform and suitable polymerization step.

The coating, which according to the invention is formed on the inner walls of the apparatus using the above-mentioned substances, is very thin. In forming the coating, the substances are used in the form of a solution or together with diluents. The coating is provided on the surface of the inner walls of the vessels, the mixing vane and the partition where polymer scales may be deposited. When the condenser is located in a portion of the polymerization vessel that is in contact with the gas phase, or when it is located outside the vessel and attached to the polymerization vessel, it is most preferred that the inner surface of the condenser and the conduit connecting the condenser to the polymerization vessel are treated in the same way. It is not necessary to apply the substance in a thick layer. The layer thickness should preferably be such that the substance consumption is at least 0.001 g / m ² . If the coating is thinner, that is to say when the amount is less than 0.001 g / m ² , the treatment effect is not very long lasting. If the polymerization vessel is to be operated for a long period of time, it cannot be expected that the scaling of the polymer will be prevented. There is no upper limit to the coating thickness unless the coating has an adverse effect on the properties of the polyvinyl chloride produced. Thus, the coating may correspond, for example, to an amount of 1 g / m ² or may be thicker.

In the polymerization of vinyl chloride according to the invention, it is preferred that a small amount of the above-mentioned organic substance or substances or alkaline substance (s) and / or some kind of inorganic oxygen compound is added to the mother liquid phase. In other words, it is preferable to add to the mother liquor a small amount of substance (s) (several to 100 ppm) which has been used to coat the inner walls of the vessel in which the polymerization is carried out. The addition of this substance reduces the possibility of dissolving the coating agents on the walls in the aqueous or oil phase present in the polymerization vessel203963

S Bě. In addition, this additive collects on the surface of the suspended particles and further prevents deposition of scales of the polymer.

If the alcohols or carboxylic acid have an alkali metal or alkaline earth metal either before or during the polymerization in an amount such that the pH of the liquid at the end of the polymerization is at least 6 or preferably at least 8, this prevents the deposition of polymer scales even more intensively. However, when partially saponified polyvinyl acetate is used as the suspending agent in the polymerization, the addition of the base results in further saponification of the polyvinyl acetate. This has an adverse effect on the particle size distribution of the polyvinyl chloride produced. In this case, the base should only be added when the vinyl chloride conversion reaches at least several%. When the walls of the polymerization vessel are made of metal, the addition of an inorganic oxygen compound to the mother liquor is effective. The addition of potassium dichromate or potassium permanganate as the compound to the aqueous medium prior to the start of polymerization will further enhance the protective effect of these inorganic compounds deposited on the walls or other parts of the polymerization vessel against scaling of the polymer.

The addition of several ppm to several tens of ppm of oxygenated compound to the liquid is effective. If the amount used is outside these limits, the substance has an adverse effect on the particle distribution and the quality of the polyvinyl chloride produced.

Examples of compounds that can be used to coat the walls of a polymerization vessel, stirrer and / or condenser include the following:

Polar organic compounds which may be used in the process of the invention, as mentioned above, include compounds containing one or more kinds of atoms or groups with unpaired electrons, such as oxygen, nitrogen or sulfur atoms. These compounds include nitrogen - containing organic compounds selected from the group consisting of azo groups, nitro groups, nitroso groups, azomethine residues and amino groups such as azomethane, azobenzene, nitrobenzene, nitrosobenzene, monoaminomononitroazobenzene, pyrazine, pyridine, thiazine, oxazine,. ), aniline, benzanlline, ethylenediaminetetraacetic acid (EDTA), α-naphthylamine, ethanolamine, diethanolamine, methylene blue, nigrosine black, oil black and spirit black, glue, organic compounds containing sulfur atoms, selected from the group of compounds containing thiocarbonyl radicals, thioether radicals, thioalcohol radicals such as thioglycolic acid, thiourea, thiocarbanic acid, thiocarbamic acid, thiobenzoic acid, various thioethers and mercaptans of the general formula RSR ', where R and R' are the same or different; quinones such as parabenzoquinone; aldehydes such as formaldehyde, acetaldehyde and benzaldehyde; ketones such as acetone; alcohols containing at least 6 carbon atoms, such as cetyl alcohol and octyl alcohol; carboxylic acids containing at least 6 carbon atoms, such as stearic acid.

When only 1 to 5 carbon atoms are added to the liquid, satisfactory results are not obtained. Anionic and nonionic surfactants are also polar organic compounds of a special type and are effective in reducing deposition of polymer scales, but the length of their alkyl residues is limited. The upper limit of the length of these alkyl radicals is about 18 carbon atoms. The polar organic compounds used should be inert to the polymerization. Meizi dyes which can be used in the process of the invention include azo dyes such as water-soluble monoazo and polyazo dyes, metal azo dyes, naphthol dyes (azoic and inactive azoic dyes and dispersible azo dyes; anthraquinone dyes such as anthraquinone acid dyes, anthraquinone cypher dyes, anthron vat dyes, alizarin dyes, dispersible anthraquinone dyes, indigoid dyes such as Brilliant Indigo B, Indanthrene red violet RH and Indanthrene printing black B; sulfur dyes such as Sulfur blue F. Β B. and Sulfur black B; phthalocyanine pigments such as copper phthalocyanine compound and non-metal phthalocyanine compounds; diphenylmethane and triphenylmethane dyes; nitro dyes, nitron dyes, thlazole dyes; xanthene dyes; acridine dyes; azine dyes; oxazine dyes; thiazine dyes; benzoquinone dyes; Inorganic pigments which may also be used include chromium yellow, zinc yellow, ZTO chromium zinc, minimum, powdered iron oxides and zinc white.

Various fixatives may be used to fix these dyes or pigments to the container wall surface. Examples of such fixatives are natural and synthetic polymers such as glue, gelatin, cellulose derivatives, polyvinyl alcohol and polyacrylic acid, polystyrene and polyvinyl chloride; thermosets such as shellac resins, phenolic resins, alkyd resins, epoxy resins, urethane resins and Chinese wood oil; alcohols such as methanol, isopropyl alcohol and cetyl alcohol; organic acids such as acetic acid, p-toluenesulfonic acid and rosin; ketones such as acetone; aromatic hydrocarbons such as toluene, benzene and xylene; esters such as ethyl acetate, butyl acetate and dioctyl phthalate; and water. as additive, one or more substances may be used simultaneously.

The process of the invention can be used for the suspension polymerization of vinyl chloride in the presence of any suspending agent. Examples of suspending agents include polyvinyl alcohol, polyvinyl acetate, vinyl acetate-maleic anhydride copolymer, styrene-maleic anhydride copolymer, polyacrylic acid, gelatin, starch, and cellulose derivatives such as methylcellulose, hydroxymethylcellulose and carboxymethylcellulose.

As the polymerization catalyst, peroxides such as oil-soluble hydroperoxides, diacyl peroxides such as dibenzoyl peroxide, dilauroyl peroxide, and other radical-forming catalysts such as azobisisobutyronitrile, which form azonitrile radicals, may be used; in this case, the reaction is carried out under normal stirring and at a temperature of from 20 to 70 ° C.

The process according to the invention can be used not only for the polymerization of vinyl chloride, but also for its copolymerization. Vinyl monomers that are copolymerizable with vinyl chloride include vinyl esters, vinyl ethers, acrylic and methacrylic acid and their esters, maleic and fumaric acid and their esters and anhydrides, vinyl aromatic compounds, vinylidene halides and olefins.

The following examples serve to illustrate the invention in greater detail, but do not limit the invention in any way.

He did

The inner surface of the 1000 L stainless steel polymerization vessel and the outer surface of the paddle stirrer (0 600 millimeters) equipped with the polymerization vessel were uniformly coated with the various compounds listed in Table 1 in an amount of 0.005 g / m ² . Either the compounds as such or a solution in a small amount of benzene or ethanol are used for coating. The coated surface is then dried and 200 kg of vinyl chloride, 500 kg of pure water, 200 g of methyl cellulose and 200 g of dilauroyl peroxide are introduced into the polymerization vessel. The stirrer is operated at 100 rpm and the temperature is raised to 57 ° C with stirring. At this temperature the vinyl chloride is polymerized for 16 hours. The amounts of polymer scales deposited in the liquid phase contacting portion of the polymerization vessel are shown in Table 1. These amounts are considerably lower than when the polymerization vessel and agitator were not coated with any of the compounds. A tube condenser consisting of a plurality of tubes having a total exchange area of 1 m ² is also connected to the polymerization vessel, in a portion of the vessel in contact with the gas phase. The amount of scales deposited in the capacitor is also considerably reduced. There will be no clogging of the capacitors.

Table 1

Try Compound applied Quantity of deposited polymer scales number for walls of polymerization vessel and other parts On parts in contact with the liquid phase (gj On parts in contact with the gas phase (g) Total amount of scales (G) and b C d E

1 aniline 1.5 0.5 2,0 2 formaldehyde 3 2 5 3 thioglycolic acid 1.1 0.4 1.5 4 azobenzene 2.5 0.5 3.0 5 nitrobenzene 7 3 10 6 nltrosobenzene 5 3 8 7 pyrazine 2.5 0.5 3 8 pyridine 3 1 4 9 thiazine 2.5 0.5 3 10 morpholine 2.5 0.5 3 11 benzalaniline 3.5 1.5 5 12 methylthioether 5 2 7 13 thiourea 5 1 6

and b C d E 14 methylene blue 0.7 0.3 1 15 Dec alizarin yellow 1.3 0.2 1.5 16 yellow Fast light yellow G 0 0 0 17 nigrosin black 0 0 0 18 Oil black 0 0 0 19 Dec Spirit black 0 0 0 20 May Indanthrene golden yellow-RX 0 0 0 21 Alizarin red V2A 0 0 0 22nd gray Indanthrene gray-X 0 0 0 23 blue Oil blue-G extra . 0 0 0 24 parabenzoquinone 5 1 6 25 glue 2 1 3 26 monoaminonitrosobenzene 0.3 0.2 0.5 27 Mar: cetylalkohol 5 5 10 28 stearic acid 7 8 15 Dec 29 octylalcohol 10 3 13 30 acetone 8 2 10 31 aniline black 0 0 0 32 0 500 200 700 Example 2 oil yellow G 'in the quantities shown in Table 2. The procedure is exactly the same This is done in a container so treated as in of Example 1, except that on 2. Carry out in a container so treated internal walls of the polymerization vessel polymerization of vinyl chloride. Quantity will save- chadlo Apply EDTA, α-naphthylamine, thlomo- properties of polyvinyl- crime, phthalocyanine blue or yellow “Fast chloride are shown in Table 2.

Table 2

Try number Used compound 0 g / m ² 0.001 g / m ² 0.005 g / m ² 1 g / m ² 33 EDTA Scale amount (g) Particle size distribution 700 100 ALIGN! 1 1

[through sieve with holes 0.147 mm (%)] 50.5 50.7 49.3 49.9 Thermal stability Good Good Good Good Initial coloring good good good good Admixtures (pieces) 15 Dec 13 17 20 May N-naphthylamine Quantity of scales (g) 700 90 0.7 0.6 Particle size distribution (sieve with 0.147 mm /% sieve) 50.5 51.0 49.2 47.1 Thermal stability good ' Good Good enough Initial coloring good good good bad enough Admixtures (pieces) 15 Dec 18 16 poorly 12 thiourea Quantity of scales (g) 700 130 3 2.5 Particle size distribution (sieve with 0.147 mm /% sieve) 50.5 51.0 50.1 47.9 Thermal stability Good Good Good enough Initial coloring good good good bad enough Admixtures (pieces) 15 Dec 14 17 poorly 19 Dec phthalocyanate Quantity Scales (g) 700 70 1 1,2 blue Particle size distribution (sieve with 0.147 mm /% sieve) 50.5 49.2 49.7 51.0 Thermal stability Good Good Good enough Initial coloring good good good bad poorly Admixtures (pieces) 15 Dec 20 May 18 30

Attempt number

Used compound 0 g / m ² 0.001 g / m ² 0.005 g / m ² 1 g / m ² yellow Fast oil Quantity of scales (g) 700 70 1.5 0.8 yellow G Particle size distribution [sieve with 0.147 mm (%) sieves] 50.5 49.7 49.5 50.0 Thermal stability Good Good Good enough Initial coloring good good good bad enough Admixtures (pieces) 15 Dec 19 Dec 13 poorly 18

Example 3

The inner surface of a 1000 L stainless steel polymerization vessel, the outer surface of a paddle stirrer (0 600 mm) and one of the baffles provided with the polymerization vessel were each coated with the compounds listed in Table 3 in an amount of 0.005 g / m ² , the surface dries. 200 kg of vinyl chloride, 500 kg of pure water, 200 g of methylcellulose and 60 g of dimethylvaleronitrile are introduced into the vessel, together with 10 ppm of the same compound as that used for the wall coating. The stirrer was operated at a speed of 100 rpm and the polymerization was carried out at 57 ° C for 16 hours. Then the polymer is removed (1 batch) and further polymerizations are carried out every 16 hours until a "icing" of the polymer is apparent on the walls of the polymerization vessel as compared to the exposed surface, so that it becomes apparent that the next batch deposition of scales, or until the amount of scales is greater than 1 g. The results are shown in Table 3.

Table 3

Experiment Compound number thioglycolic acid aniline alizarin yellow nigrosin black black Oil black black Spirit black thiazine chrome yellow

Example 4

Similar experiments were carried out as in Example 3, except that compounds other than those used to coat the reactants were added to the reactants.

Number of consecutive batches

Added Coated to the surface Added and applied to the surface 1 3 5 1 2 4 1 4 6 1 10 15 Dec 1 10 15 Dec 1 10 15 Dec 1 7 12 - 2 -

the inner walls of the polymerization vessel and other parts. The number of consecutive batches before scales start to precipitate and the physical properties of the polymers obtained are shown in Table 4.

0 3 9 6 4

Table 4 Try number Compound used Added compound Number of consecutive compounds added Compounds added and loaded 46 thioglycolic acid nigrosin black 5 6 47 aniline nigrosin black 2 5 48 nigrosin black thiazine 10 15 Dec 49 Oil black Spirit black 10 15 Dec 50 Spirit black aniline 10 13 51 thiazine nigrosin black 7 12 52 Try 0 0 -> Table 4 - continued Physical properties of polymer number W> '·' Particle size distribution Thermal stability [through sieve with holes 0.147 mm /%) Initial coloring Admixtures (pieces) 46 45 - 56 Good good 10—15 47 45 - 56 Good good 12 - 16 48 42 - 53 Good good 16 - 20 49 44 - 58 Good good 10 - 18 50 45-55 Good good 10 - 20 51 42 - 54 Good good 10 - 16 52 42 - 58 Good bad enough 10 - 20 Example 5 in an amount 100 ppm a 1000 ppm. Počet po

consecutive batches prior to starting experiments similar to experiments No. 48 for scaling and physical properties of up to 50 in Example 4, but the additives used with the obtained polymers are shown in the table.

Table 5

Try number Applied compound Added compound Amount of compound added 0 100 ppm 1000 ppm 53 nigrosin black thiazine Number of consecutive batches before scales start to precipitate Particle size distribution 10 15 Dec 15 Dec (sieve drop) with holes 0.147 mm /% J 51.2 51.5 53.5 Thermal stability Initial Good Good bad coloring good good poorly Admixtures (pieces) 20 May 20 May 25 54 aniline nigrosin black Number of consecutive batches before scales start to precipitate Particle size distribution 2 5 5 (sieve with holes) 0.147 mm /%) 49.0 50.0 51.6 Thermal stability Initial Good Good bad coloring good good poorly Admixtures (pieces) 15 Dec 18 20 May

203983

Example 6

In a 1000 L stainless steel polymerization vessel equipped with a paddle stirrer (800 mm) and a septum were placed 200 kg of vinyl chloride, 500 kg of pure water, 200 g of methyl cellulose and 100 g of azobisisobutyronitrile together with the compounds listed in Tables 6 and 0. The base was run at 100 rpm and polymerization was carried out at 57 ° C.

Prior to polymerization, the surface of the inner walls of the polymerization vessel, the outer surface of the blades and the baffle were uniformly coated with the compounds listed in Table 6 in an amount of 0.005 g / m ² . Either the compounds as such or a solution in a small amount of benzene are used to form the coating. The resulting coating was dried. The amount of polymer scales deposited and the physical properties of the polymers obtained are shown in Table 6.

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Example 7

In a 1000 L stainless steel polymerization vessel equipped with a paddle stirrer (0 600 mm) and a septum, 200 kg of vinyl chloride, 500 kg of pure water, 200 g of partially saponified polyvinyl acetate, 30 g of isopropyl peroxydicarbonate and 10 ppm of nigrosine black are placed. The stirrer is run at 100 rpm and polymerization is performed at 57 ° C.

Prior to polymerization, the surface of the inner walls of the polymerization vessel, the outer surface of the blades, and the septum were evenly coated with 0.005 g / m ^{2 of} Spirit black dissolved in a small amount of benzene. An aqueous NaOH solution was used as the base. The influence of the amount of base used and the manner of its addition on the reaction rate, the amount of deposited scales of the polymer and the physical properties of the polymers are shown in Table 7.

Table 7

Attempt number 63 64 65 66 67 68 Amount of base (NaOH) relative to. to the amount of vinyl chloride 0.01% 0.01% 0.01% Add time At the same time, 1 h. After start 1.5—4 h principles water reaction after the start of the reaction Number of batches before scaling begins 25 23 22nd pH of the mother liquor after polymerization 7—9 7—9 7—9 Particle size distribution sieve with holes (mm) 0.246 0.147 0,246 0,147 0.246 0.147 Drawdown (%) 80.3 21.2 99.2 47.3 99.8 53.4 Initial coloring good good good Reaction time* yj = 60% η = 170% η = ^! 88% throw. 12 9.5 9 Attempt number 69 70 71 72 73 74 Amount of base (NaOH) based on the amount of vinyl chloride 0.01% 0.001% 0.1% Add time 3 h At the same time, At the same time, principles reaction water water Number of batches before scaling begins 18 18 30 pH of mother liquor after polymerization 7—9 5 10—11 Particle size distribution Sieve with holes (mm) 0.246 0.147 0,246 0,147 0.246 0.147 Drawdown (%) 99.9 54.0 93.4 30.1 65.1 13.8 Initial coloring good good bad enough Reaction time* η = (90%) η = 90% η = 50% throw. 9 9.5 20 May

* Below the reaction time is the time required to achieve the above-mentioned conversion value.

Example 8

To. 1000 L stainless steel polymerization flasks equipped with a paddle stirrer [600 mm &lt; 3 &gt; and a septum were placed with 200 kg vinyl chloride, 500 kg pure water, 200 g partially saponified polyvinyl acetate and 100 g azobisisobutyronitrile together with 10 ppm additive and 1 ppm oxidizing agent The mixer runs at 100 rpm and polymerization is carried out at 57 ° C. Prior to polymerization, the surface of the inner walls of the polymerization vessel, the outer surface of the blades and the baffle were uniformly coated with the compounds listed in Table 8 in an amount of 0.005 g / m ² . Either the compounds as such or a solution in small amounts of toluene or methanol are used to form the coating. The coated surfaces are dried. Two hours after the start of polymerization, 0.01% NaOH was added. The amounts of deposited scales of the polymer having the physical properties of the polymers obtained are shown in Table 8.

Table 8

Attempt number 75 76 77 78 79 80 Applied Spirit nigrosin nigrosin compound Added black black methylene black nigrosin compound 0 blue black NaOH added Oxidative No Yes Potassium dichromate Yes agent Number of batches prior to initiation of excretion No Yes No Yes No Yes scales Properties 10 15 Dec 23 30 25 35 sieve with 0.147 mm holes 46 40— 41— 40— 41— 40— Drawdown (° / o) 45 45 42 45 43 Thermal stability Good Good Good Good Good Good Initial coloring good good good good good good Admixtures 15 Dec 15— 12— 12— 14— 11— (pieces) 20 May 16 16 18 19 Dec

Note: If partially saponified polyvinyl acetate is used in the above experiments, NaOH is added during the polymerization.

Attempt number 81 82 83 84 85 86

Applied phthalocyanine phthalocyanine phthalocyanine compound blue blue blue Added 0 phthalocyanine aniline compound blue NaOH added Yes No Yes Oxidative cerium sulphate agent No Yes No Yes No Yes Number of batches before by initiating excretion scales 10 17 7 12 14 19 Dec Properties sieve with 0.147 mm holes 41— 43— 46— 40— 41- 40— Drawdown (%) 46 55 55 55 46 46 Thermal stability Good Good Good Good good Good Initial coloring good good good good Good good Admixtures 13- 13- 10— 10— 16- 17— (pieces) 17 17 20 May 17 18 21

Attempt number

Coated NaOH added Oxidizing agent Number of bags before scaling begins Properties sieve with 0.147 millimeters (% j) Thermal stability Initial color Additions (pieces) black Spirit black 0 0

45—56 good good

18—25 phthalocyanine blue 0 0 good good

Example 9

The same polymerization vessel as that used in Example 1 was fed with liquid methylcellulose and vinyl chloride via a metering pump in the amounts listed below and the prescribed amount of catalyst (azobisisobutyronitrile) using a metering pump for small amounts. The reaction liquid is transferred to the product reservoir at a self-pressure control valve. The polymerization was carried out for 60 hours. The amount of scales deposited on the walls of the polymerization vessel and other parts at the end of the polymerization is shown in Table 9. Before Polya b c d

e f

WITH

clean water 160 kg / h methylcellulose 80 g / h Oil black 0.08 g / h (as a suspension in aqueous toluene) Na ₂ Cr ₂ O7 0.08 g / h NaOH 8 g / h vinyl chloride 80 kg / hr azobisisobutyronitril 30 g / h

For the measurement, the surface of the inner walls of the polymerization vessel is evenly coated with oil black or nigrosine black in an amount of 0.005 g / m ^2, and 10 ppm oil black and 1 ppm Na 2 CrCl 2 based on vinyl chloride are added to the polymerization system. To maintain the pH of the reaction liquid in the range of 7-8, NaOH is also added to the reactants approximately 0.01% (based on vinyl chloride charged). The anti-scaling additives are added either as a solution or a suspension in pure water.

Type and quantity of substances added to the polymerization vessel:

Reaction conditions:

Stirring: 600 mm 0 paddles, 100 rpm Reaction temperature: 57 ° C

Table 9

Attempt number 89 90 ⁹¹ 92 Loaded compound black nigrosin 0 nigrosin Time elapsed before Oil black black a_ * í ·. »· black by starting scales excretion Amount of deposits 60 60 15 Dec 60 scales (g) After interrupting the polymerization, a plurality of scales deposited in the portion in contact ~ 0 ~ 0 2000 ~ 0 with gas phase the quantity of scales deposited in the part in contact with ~ 0 ~ 0 1500 ~ 0 liquid phase ~ 0 ~ 0 500 ~ 0

In experiment No. 92, a 0.5 m ² exchange capacitor is attached to the polymerization vessel in the portion in contact with the vinyl chloride gas. The amount of condensate returned (liquid vinyl chloride) is 50 kg / h. Even in this case, the amount of scales deposited on the vessel walls and on the capacitor walls is practically zero.

Claims (6)

SUBJECT A method for suppressing the deposition of polymer scales on a surface of a polymerization vessel in contact with a monomer or monomer mixture during suspension polymerization of vinyl chloride or a mixture of vinyl monomers containing vinyl chloride in an aqueous polymerization mixture comprising a suspending agent and an oil-soluble catalyst; prior to polymerization, a coating of a compound selected from the group of polar organic compounds which are azo compounds, nitro compounds, nitroso compounds, compounds containing azomethine groups or azine rings, amines, compounds containing thiocarbonyl residues, compounds containing thioether residues and thioalcohols, quinones, aldehydes, ketones alcohols having at least 6 carbon atoms and carboxylic acids having at least 6 carbon atoms, anionic and nonionic surfactants with alkyl radicals containing up to 18 carbon atoms; from the group of organic dyes which are water-soluble monoazo dyes, water-soluble polyazo dyes, metal-containing azo dyes, naphthol dyes and dispersible azo dyes, anthraquinone dye dyes, anthraquin dye dyes, anthron dye dyes, alizarin dyes, and dispersible anigo, Indanthrene red violet RH and Indanthrene printing black B, sulfur dyes such as Sulfur blue F. Β. B. and sulfur black B, phthalocyanine dyes, for example phthalocyanine-copper compounds or metal-free phthalocyanine compounds; or from the group of inorganic pigments, which are chromium yellow, zinc yellow, zinc chromate ZTO, minium, powdered iron oxide and zinc white or mixtures of said compounds, with a thickness corresponding to their consumption of at least 0.001 g / m ² surface area. 2. A process according to claim 1, wherein the alizarin dyes are alizarin yellow or alizarin red V2A. 3. The method of claim 1, wherein: YNALEZU that azoethane, azobenzene and monoaminonitrosobenzene are used as azo compounds; nitrosobenzene is used as nitro compounds; the cyclic azides used are compounds of the group comprising pyrazine, pyridine, thiazine, oxazine, methylene blue, nigrosine black, oil black, spirit black; amines used include aniline, benzalaniline, ethylenediaminotetraacetic acid, α-naphthylamine, ethanol amine, diethanolamine and glues; as thiocarbonyl-containing compounds, thioglycolic acid, thiocarbamic acid, thiocarbanilic acid, and thiobenzoic acid are used; thiourea and dimethylthioether are used; as thioalcohols, mercaptans of the general formula R —S —R‘‘ are used R and R‘ are alkyl radicals; p-benzoquinone is used as quinones; aldehydes used are compounds selected from the group consisting of formaldehyde, acetaldehyde and benzaldehyde; acetone is used as the ketones; cetyl alcohol or octyl alcohol is used as the alcohol and stearic acid is used as the carboxylic acid. 4. The process of claim 1 wherein up to 100 ppm of the coating compound is added to the polymerization mixture, monomer or polymerization mixture and monomer. 5. A process as claimed in any one of claims 1 to 4, wherein a base is added to the polymerization mixture in an amount such that the pH of the polymerization mixture at the end of the polymerization is at least 6. 6. A process as claimed in any one of claims 1 to 5, wherein an additive selected from the group consisting of permanganic acid salts, dichromates and cerium sulfate is added to the polymerization mixture.