CS276393B6 - Process of vinyl chloride homopolymerization or copolymerization - Google Patents

Description

(57)

Homopolymerization or copolymerization of vinyl chloride is carried out in the presence of at least one free radical initiator and at least one suspending agent. The process consists in wetting the internal walls of the reactor and all parts coming into contact with the polymerization medium prior to polymerization with an organic salt solution or suspension. The anionic portion of the salt is derived from aliphatic dicarboxylic acids of 6 to 16 carbon atoms, benzenepolycarboxylic acids and aromatic sulfo acids, the cationic portion is derived from an ec-naphthyl amine or nigrosine B. The process prevents the formation of incrustations on the internal walls and other parts of the reactor coming into contact with a polymerization medium.

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G3 276 393-6

The present invention relates to a process for the homopolymerization or copolymerization of vinyl chloride in an aqueous suspension.

Aqueous suspension polymerization is a commonly used process for producing halogen-containing vinyl monomer polymers.

The process consists in polymerization. % of monomer or monomer in a stirred aqueous medium and in the presence of one or more suspending agents and one or more polymerization initiators which act as a free radical generating source. Both suspending agents used are both synthetic, melt natural polymers having protective colloid properties, such as partially hydrolyzed polyvinyl acetate, cellulose ethers, gelatin, esters of scitrite and lauric acid, stearic acid and other substances.

Organic peroxides such as lauroyl peroxide, benzoyl peroxide, isopropyl peroxydicarbonates, acetylcyclohexylsulfonyl peroxide, perers such as tertiary butylperneodecanoate], azo compounds such as azobisisobutyronitrile, dimethylvaleronitrile and dimethylvaleronitrile and dimethylvaleronitrile and dimethylvaleronitrile and dimethylvaleronitrile and dimethylvaleronitrile and dimethylvaleronitrile and dimethylvaleronitrile and dimethylvaleronitrile and dimethylvaleronitrile and dimethylvaleronitrile and dimethylvaleronitrile and dimethylvaleronitrile and dimethylvaleronitrile, respectively.

The polymerization is conveniently carried out by a batch process in a reactor equipped with a paddle stirrer and optionally baffles.

During polymerization, especially when a steel reactor is used, polymer deposits, commonly referred to as incrustations, are formed which adhere very strongly to the reactor surface, agitator and baffles.

Incrustations cause a number of negative phenomena. In particular, poor thermal conductivity of the incrustations causes difficulties in the exchange of heat between the reaction medium and the external cooling wall, and these difficulties increase with the growth of the surface area of the incrustations and its thickness during polymerization.

This implies that the productivity of the reactor decreases because it is operated at a lower polymerization rate than would be possible without incrustations. In addition, it may happen that some of these incrustations separate during the time required for polymerization and contaminate the polymer, thereby deteriorating its quality, resulting in difficulty in melting and different morphologies.

Furthermore, to carry out the subsequent polymerization, the reactor must be cleaned at the end of each run, such purification being carried out manually. solvents or a stream of water.

These cleaning operations are very complex, heavy and cause an increase in the time the reactor remains inoperative. In addition, it is necessary to have access to the interior of the autoclave and therefore it is not possible to operate according to the reactor shutdown technology with the necessary cleaning at each termination of the polymerization; such technology would provide a source of environmental pollution that would have to be eliminated.

Various tests were carried out to prevent or avoid the formation of deposits. For example, in British Patent No. 1 29 '145 it is proposed that all parts and walls that may come into contact with a vinyl monomer to be polymerized be coated before the polymerization reaction begins with a coating composition which may consist of one or more of the following: said compounds: an organic compound containing a nitrogen atom such as azo group, nitro group, nitroso group, azomethines, azines, amine compounds, an organic compound containing a sulfur atom, quinone, ketone, aldehyde, a 6-carbon alcohol, surfactants based on cationic and anionic compounds, indigoid type dyes, sulfide dyes, nitro dyes, thiolol dyes, quinol dyes, diazo dyes and the like.

However, in the tests performed by the present inventors, it was clear that treatment of the walls and other parts of the reactor that come into contact with a liquid or gaseous monomer during polymerization with one or more of the above compounds is not entirely effective in all cases and in all forms. polymerization. .

It is an object of the present invention to provide a simple and effective method of preventing or eliminating

CS 276 393 B6 to avoid the formation of incrustations inside the steel reactors used in the polymerization of vinyl chloride in aqueous suspension.

It is another object of the present invention to provide a method for preparing vinyl chloride polymers in aqueous suspension without formation of encrustations. This eliminates the need for granulometric distribution of the particles, which impairs the initial color and thermal stability of the polymer.

Homopolymerization or copolymerization of vinyl chloride is carried out in the presence of one or more suspending agents and one or more free radical initiators. The process according to the invention is characterized in that the inner walls of the polymerization reactor and all parts coming into contact with the polymerization medium are moistened before the start of the polymerization reaction with an organic salt solution or suspension. The anionic moiety is derived from C 6 to C 16 aliphatic dicarboxylic acids, benzenepolycarboxylic acids and aromatic sulfo acids, the cationic moiety is derived from 6 6-naphthylamine or nigrosine B.

Preferably, an organic salt may be used, the anionic portion of which is derived from adipic acid, trimesic acid and p-toluenesulfonic acid. Methanol, ethanol or acetone are used as solvent or diluent of the organic salt. The minimum amount of organic salt used for application to the reactor walls and the parts in contact with the polymerization medium is greater than 0.005 g / m 2 of exposed area.

The inner walls of the polymerization reactor are either metal or glass. The solution or suspension of the organic salt used has a pH in the range of 0 to 2.

To prepare a solution or suspension of an organic salt may be used in any suitable solvent or diluent such as methanol, ethanol, \ ^r ODA, acetone, a mixture of water and acetone and the like.

Examples of characteristic anions that can be used to prepare the organic salt used in the process of the present invention are anions derived from adipic acid, citric acid, oxalic acid, trimesic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, abietic acid, o- toluenesulfonic acid, m-toluenesulfonic acid, benzenesulfonic acid, trimellitic acid, phthalic acid, terephthalic acid, tartaric acid, pyromellitic acid, benzoic acid, propionic acid, butyric acid, caproic acid and the like.

Examples of characteristic cations that can be used to prepare the organic salts used in the process of this invention are those derived from oC-naphthylamine, aniline, m-toluenediamine, pyrrole, imidazole, pyrazole, pyrazine, pyriraidine, pyridazine, indole, indazole, purine, quinoline, phenanthroline, phenanthridine, carbazole, phenazine, piperazine, piperidine, organic dyes containing a group of the formula = H-, = MH or -HH ₀ such as nigrosine and the like.

The organic salt used in the present process of the invention is preferably obtained by dissolving the basic compound in a selected solvent and then neutralizing the free groups = N-, = HH and / or -NHg by adding an organic acid.

According to the invention, the organic salt is applied as a thin layer on the surface of the reactor, on the stirrer blades and the baffles, if present, by coating by wetting or evenly spraying the salt solution on the surfaces mentioned above.

Said treatment is also carried out on the walls of the condenser and the piping which is connected to the polymerization reactor, if present.

The amount of salt required to achieve an anti-settling effect is very small. In practice, an amount of greater than 0.005 g / m 2 is preferably used, since when working at an amount less than the threshold value, the anti-settling effect may not be safe.

Conversely, there is no upper limit for the amount used for coating, provided that no negative effects on the properties of the polymer occur. Amounts greater than 1 g / m 2 may also be used.

OS 276,393 B6

The process according to the invention can be used in the polymerization of halogen-containing vinyl monomers in aqueous suspension.

The term halogen-containing vinyl monomers as used in this specification and the appended claims is meant to include all monomers that can be polymerized by free radical initiated polymerization having a terminal olefinic unsaturation and containing at least one halogen atom as a substituent. These monomers are preferably derivatives of ethylene, which may include, but are not limited to, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, chlorotrifluoroethylene, tetrafluoroethylene and the like. Chlorine-containing vinyl monomers are particularly preferred, and in particular vinyl chloride.

The term polymerization as used herein and the appended subject matter includes both the homopolymerization and copolymerization of two or more halogen-containing vinyl monomers between them, or one or more such monomers with one or more other monomers which they are copolymerizable with them.

Examples of other monomers are vinyl ethers such as vinyl acetate, acrylic esters such as methyl acrylate and glycidyl acrylate, unsaturated diesters such as dibutyl maleate, allyl esters such as allyl acetate, unsaturated amides such as acrylamide, styrene, substituted styrene, οί-olefin. is ethylene or propylene and the like.

The present invention is preferably used for polymerization to produce polymers containing at least 50 mol%, preferably more than 80 mol%, vinyl chloride.

The anti-fouling effect which occurs with the organic salt in the process according to the invention is independent of the type of suspending agent used.

Specifically, copolymers of vinyl acetate with vinyl alcohol or other types of alcohols, cellulose and / or cellulose ethers, polymers or copolymers containing acidic functions, glycerol esters and / or sorbitol and other substances, either alone or in combination with one another, may be used. The amount of such suspending agents usually ranges from 0.01 to 1% by weight, based on the monomer or monomers present.

Any initiator may be used in the slurry polymerization process of the present invention provided that they are compatible with the other substances present in the polymerization medium.

Among the known initiators, products from the group of alkyl peroxides, peresters and percarbonates have proved to be particularly interesting in practice.

In addition to the suspending agent and the polymerization initiator, the polymerization mixture may contain several other additives which are selected from those commonly used in aqueous suspension polymerization, such as stabilizers, molecular weight regulators, buffer systems, and so on.

The polymerization conditions correspond to those usually used in an aqueous suspension polymerization process. The polymerization is usually carried out batchwise and the reactor internal coating is normally applied after each polymerization batch.

In this way, it is possible to maintain, for an indefinite period of time, all internal parts of the polymerization reactor and all parts that come into contact with the polymerization medium in perfect order.

In order that this invention may be more fully understood and practiced, the following non-limiting examples illustrate the invention.

In the examples, all parts are by weight unless otherwise indicated.

Examples 1 to 12

A 1500 liter polymerization reactor equipped with a paddle stirrer was sprayed onto the inner walls and stirrer to coat the solution shown in Table 1 with 720 liters of water, 480 kg of vinyl chloride, 675 g of lauryl peroxide, 96 g.

CS 276 393 tertiary butylcyclohexylperoxydicarbonate, 480 g vinyl acetate-maleic anhydride copolymer having a molecular weight of 1 200 000 and containing 52 mole acetate and 48 mol% maleic anhydride, and 960 g of vinyl acetate-allyl alcohol copolymer having a number molecular weight Mn 6,000 and 8.5% hydroxyl content ·

The temperature of the polymerization mass rises up to 54 ° C. After 10 hours, the polymerization product is removed and the polymerization operation is repeated until the reactor has to be cleaned due to the excessive presence of deposits that are carried out chemically or manually or with a stream of water.

The manual removal of deposits shows that the total weight of the resulting incrustations after cleaning is about 1 kg.

If the polymerization operation exceeds ten without the need for purification, then the reactor is cleaned after the tenth batch and the weight of the collected incrustations is determined.

Table 1 lists the number of polymerization operations carried out prior to manual cleaning and the weight of the incrustation collected as a function of the type of solution used to treat the reactor walls.

Table 1

The solution used Compound Solvent Number operations Deposit weight (g) 1 - - 1 3 000 2 adipic acid methanol 1 2 500 3 trimesic acid methanol 1 2 500 4 p-toluenesulfonic acid methanol 1 1 500 5 Nigrosin B methanol 1 1 500 6 06-naphthylamine methanol 1 2 200 7 salt of adipic acid and <6-naphthylamine methanol 5 1 100 8 a salt of trimesic acid and 4-naphthylamine methanol 4 1 200 9 a salt of p-toluenesulfonic acid and α-naphthylamine methanol 6 900 10 salt of adipic acid and Nigrosin B methanol 8 1 000 1 1 salt of trimesic acid and Nigrosin B methanol 10 100 ALIGN! 12 p-toluenesulfonic acid salt and Nigrosin B methanol 10 tracks

Examples 13 to 15

The standard of Example 1 was repeated, replacing 480 g of vinyl acetate-maleic anhydride copolymer and 960 g of vinyl acetate-allyl alcohol copolymer with a mixture of 960 g vinyl acetate-vinyl alcohol copolymer having a viscosity limit of 20 ml / g, 30% hydrolysis, and the index n is 0.35, and 750 g of another vinyl acetate-vinyl alcohol copolymer having a viscosity limit of 66.5 ml / g is 72% hydrolyzed and the index n is 0.40.

Table 2 shows the number of polymerization operations performed prior to manual cleaning and the weight of the incrustation collected as a function of the type of solution used to treat the reactor walls.

Table 2

The solution used Compound Solvent Number operations Deposit weight (g) 13 adipic acid and N-naphthyl amine salt methanol 4 1 300 14 a salt of trimesic acid and N-naphthylamine methanol  4 1 300 15 Dec p-toluenesulfonic acid salt and Nigrosin B methanol 10 tracks

S 276,393 B6

Examples 16 to 18

The embodiments of Example 1 are repeated, replacing 480 g of vinyl acetate-maleic anhydride copolymer and 960 g of vinyl acetate-allyl alcohol copolymer with 400 g of methylhydroxypropylcellulose having a methyl group content of 28% and a hydroxypropyl group content of 5% and 750 g of vinyl acetate copolymer with vinyl alcohol, which _t has a viscosity limit of 20 ral / g, is 55% hydrolyzed and the index n equals 0.35 ·

Table 3 shows the number of polymerization operations carried out prior to manual cleaning and the weight of the collected incrustations, as a function of the type of solution used to treat the reactor walls.

Table 3

Solution used Number of deposits

Compound _ ___ _ Solvent ____ operations _____ weight_ (g)

The salt of adipic acid and α-naphthyl amine methanol 4 1 100 1 'trimesic acid and t-naphthylamine salt methanol 4 1 100 18 salt of p-toluenesulfonic acid and Nigrosin B methanol 10 tracks Examples 19 to 22 The embodiments of Example 1 are repeated, where 480 g of vinyl acetate copolymer with an-

maleic hydride and 960 g of vinyl acetate-allyl alcohol copolymer are replaced.

160 g of the same vinyl acetate-maleic anhydride copolymer, 200 g of vinyl acetate-vinyl alcohol copolymer having a viscosity limit of 20 ml / g, are 25% hydrolyzed and an index n of 0.40, and 250 g of sorbitan monostearate.

Table 4 shows the number of polymerization operations carried out prior to manual cleaning and the weight of the incrustation collected as a function of the type of solution used to treat the reactor walls.

Table 4

Solution used Number of deposits

Compound Solvent operations weight (g) 19 Dec adipic acid salt and t-naphthylamine methanol 5 1 300 20 May a salt of trimesic acid and N-naphthylamine methanol 6 1 000 21 salt of trimesic acid and Uigrosin B methanol 10 tracks 22nd p-toluenesulfonic acid salt and Nigrosin B methanol 10 tracks

Examples 23 to 25

The embodiments of Example 1 were repeated, but 96 g of tertiary butyl cyclohexyl peroxydicarbonate was replaced with 22 g of lauroyl peroxide.

Table 5 shows the weight of the incrustations that were collected. This weight is a function of the type of solution used to treat the reactor walls.

Table 5

The solution used

Compound Solvent Number operations Deposit weight (g) 23 salt of adipic acid and Nigrosin B methanol 8 950 24 salt of trimesic acid and Nigrosin B methanol 10 tracks 25 p-toluenesulfonic acid salt and Kigrosin B methanol 10 tracks

Example 26

The same results as shown in Tables 1 and 5 are obtained when copolymerization of a monomer mixture consisting of 87 wt. % vinyl chloride and 13 wt. vinyl acetate

CS 276 393 B6

under the same working conditions as in Examples 1 to i 2 and 32 to 37. Examples 27 to 29 The embodiment of Example 15 is repeated except that are the difference values pH of aqueous suspension. Table 6 shows the number of operations and the mass collected incrustations as a function in solution. Table 6 The solution used Number sediment Compound Solvent oH ouerací weight (g) 27 salt of p-toluenesulfonic acid and Nigrosine 3 methanol 2 10 tracks 28 salt of p-toluenesulfonic acid and Nigrosine 3 methanol 6 10 tracks 29 p-toluenesulfonic acid salt and Nigrosin 3 methanol 10 ίο tracks Examples 30 and 31 The embodiment of Example 15 is repeated except that is used different types solvents for the preparation of a salt solution. Table 7 shows the number of operations and the mass collected incrustations as a function of the solvent type. Table 7 The solution used Number Sediment Compound Solvent operations weight (p) Salt of p-toluenesulfonic acid and Nigrosine 3 ethanol "in tracks 31 p-toluenesulfonic acid salt and Nigrosin S acetone 10 tracks Examples 32 and 33 The embodiment of Example 1 is repeated except that glass poles are used.

measuring reactor of 500 liters capacity, equipped with a rotating stirrer, the inner walls of which are coated with a spray solution of the type shown in Table 8. 225 liters of water, 150 kg of vinyl chloride, 21 g of lauroyl peroxide and 30 g of tertiary butylcyclohexylperoxydicarbonate 50 E of vinyl acetate-maleic anhydride copolymer, 62.5 g of vinyl acetate-vinyl alcohol copolymer having a viscosity limit of about 20 ml / g is 25% hydrolyzed and the index n equals 0.4, and 78 g of sorbitan monosuearate .

Table 8 shows the number of polymerization operations carried out prior to manual cleaning and the weight of the incrustation collected as a function of the type of solution used to treat the reactor walls.

Table 8

Solution used Number of deposits,

Compound 3 solvent operation weight (g) salt of trimesic acid and Nigrosin B methanol 10 feet salt of p-toluenesulfonic acid and Nigrosine 3 methanol 10 feet

CS 276 393 B6

PATENT CLAIMS

Claims (4)

A process for the homopolymerization or copolymerization of vinyl chloride in the presence of one or more free radical initiators and one or more suspending agents, characterized in that the inner walls of the polymerization reactor and all parts in contact with the polymerization medium are moistened before starting the polymerization reaction with a solution or suspension an organic salt of which the anionic moiety is derived from aliphatic dicarboxylic acids having 6 to 16 carbon atoms, benzenepolycarboxylic acids and aromatic sulfo acids, the cationic moiety being derived from α-naphthyl amine or nigrosine B. 2. Process according to claim 1, characterized in that organic salts are used whose anionic part is derived from adipic acid, trimesic acid and p-toluenesulfonic acid. 3. The process according to claim 1, wherein the solvent or diluent of the organic salt is methanol, ethanol or acetone. 4. The process of claim 1 wherein the minimum amount of organic salt used for application to the reactor walls and portions in contact with the polymerization medium is greater than 0.005 g / m &lt; 2 &gt; of exposed area.