NO761167L - - Google Patents

Description

.Inner coated reaction vessel.

The present invention relates to a container for polymerization reaction with a coating on the inner surfaces, which results from the application of a coating composition, the primary component of which contains a polyaromatic amine with a straight or branched chain, dissolved in an aqueous solution of a 1 ka in ime tallium hydroxide. During the polymerization of olefin monomers such as vinyl halides, vinylidene halides and vinylidene monomers with at least one end group CH2 = cd and mixtures thereof, in the presence of this coating^, significant polymer build-up on the inner surfaces of the reaction vessel is avoided. Several coatings or batches of polymer can also be carried out in the internally coated reaction container without this being opened between the coatings, which thus prevents the release of unreacted monomer into the atmosphere.

Chemical processes of various types are usually carried out in large, stirred containers which are often provided with auxiliary equipment such as screens, heat transfer coils, which enable heat to be added to or removed from the container contents, etc. In many cases, however, such progress ' ways unfortunate deposits on the apparatus surfaces, with which the reaction mixture comes into contact. Such deposits interfere with the effective transfer of heat to and from the interior of the container. These deposits also have a tendency to be destroyed and partially break into pieces, which leads to contamination of the reaction mixture and products produced therefrom. This problem is particularly prevalent in polymerization type reactions as the deposits or "build-up" of solid polymer on the reaction supernatants not only interfere with heat transfer, but also reduce productivity and adversely affect polymer quality.

This problem is particularly serious in the commercial production of polymers or copolymers of vinyl- and vinyl-. idene halides, when polymerized alone or together with other vinylidene monomers with an end group CH2=CC^ or with polymerizable olefin monomers. In the commercial production of vinyl chloride polymers, for example, these are usually formed in the form of separate particles by polymerization in aqueous suspension systems. When using such a polymerization system, the vinyl chloride and other comonomers, when such are used, are kept

in the form of small separated drops - by using a suspending agent and stirring. When the reaction is finished, the resulting polymer is washed and dried. These polymerization reactions in water-suspension systems are usually carried out under pressure in metal reactors equipped with screens and high-speed stirrers. However, these suspension systems are unstable and during the polymerization reaction, vinyl chloride polymer builds up on the internal surfaces of the polymerization reactor, including the surfaces of the screens or led plates and tubes. This polymer build-up must obviously be removed as it leads to further formation of polymer build-up, which in turn leads to a crust which adversely affects the heat transfer and contaminates the polymer that is formed.

The nature of the accumulated polymer or the insoluble deposit on the walls of the reactor is such that in the past, in the commercial production of polymers, as described, it has been the practice that after each completed polymerization reaction someone is allowed to enter the reactor and scrape away the polymer the construction from the walls and the screens and the stirrer. Such treatment is not only expensive - both in terms of labor costs and downtime for the reactor - but also presents potential health hazards. While various previously proposed methods for reducing the amount of polymer build-up on the polymerization reactor surfaces, e.g. cleaning with solvents, various hydraulic and mechanical reactor cleaners and the like, none have been shown to be the final solution to the removal of polymer build-up. In other words, these various methods and devices have done an acceptable job, but there is still room for improvement in this area, especially from an economic point of view.

A coating composition for reactors containing a condensation polymer of m-phenylenediamine and resdrcinol is already known, see Norwegian patent application no. 753157 - The coating is applied to the reactor surfaces from a solution thereof in an organic solvent. This coating composition has proven more than satisfactory for the intended purpose. However, experience has shown that it would be more practical and economical with a coating that could be applied to the surfaces from an aqueous solution.

It has been shown that if a reaction vessel is coated in advance on its inner surfaces with a suitable coating, unwanted polymer build-up on these surfaces can be significantly reduced and in certain cases completely removed by polymerization of olefin monomers in the reactor. It has now been shown that when a reactor's inner surfaces are coated with a coating composition comprising a polyaromatic with a straight or branched chain and dissolved in an aqueous solution of alkali metal hydroxide, the polymer accumulation on the reactor's surface is substantially removed. Due to the nature of the coating composition, it can be placed on the inner surfaces of the reactor without the reactor having to be opened, which thus provides a closed polymerization system. In the case of polymerization of olefin monomers, this takes place in an aqueous polymerization medium which

■is kept in constant contact with the coated surfaces throughout the polymerization reaction.

According to the present invention, a film or a coating of a polyaromatic amine is placed on the inner surfaces of a polymerization reactor or a polymerization container by only bringing the surfaces into contact with an aqueous solution of the polyaromatic amine's alkali metal salt. All exposed surfaces in the interior of the reactor, apart from the walls, such as screens, stirrers etc., are also treated in a similar way. - As the aqueous alkali metal hydroxide solution has been applied to the surfaces, the polymerization medium can be introduced into the reactor and the reaction started without it being necessary to dry the surfaces before the introduction of. the polymerization medium. The

■ is however appropriate and the best results are obtained when, after the application of the polyaromatic amine to the inner surfaces of the reactor, the surfaces are sprayed with water or the reactor is filled with water and drained, 'whereby surprisingly' leaving on the surfaces a densely adherent coating or film which

is not affected by the polymerization medium in the sense that its intended function is prevented from being achieved, namely the prevention of polymer build-up on the surfaces.

The exact mechanism by which the film or coating of polyaromatic amine functions to prevent the build-up or accumulation of polymer shell on the inner surfaces of the reaction vessel is not entirely clear, but it is believed to be a free radical scavenging mechanism or free radical scavenging mechanism. It is believed that this is because aromatic diamines, for example, are known to destroy free radicals, such as their well-known activities as antioxidants. By destroying the free radicals of the coating or film of polyaromatic amine, the polymerization on the inner surfaces of the reactor is thus prevented.

The polyaromatic amines which are suitable for carrying out the present invention are produced by means of a condensation reaction of two or more of the compounds indicated below, or by self-condensation reaction of some of the compounds indicated in the following and containing, at least one group' -OH and at least one group -NH2.' Such reactions are generally carried out under heating in the presence of an acidic catalyst. The polyaromatic amines formed in this way have the following general formula: where A, B and C are either:

H

t where and R|j are defined below and R,- denotes -N-, or an alkylene or alkylidene group with straight or branched

chain and with 1-5 carbon atoms and where A, B and C can be the same or different and each repeating unit can be the same or different, and R2 denotes either -H, -OH, -NH2 or:

and may be the same or different, R^ denotes -H, halogen

or an alkyl group with 1-8 carbon atoms and may be equal or

■different, R^ denotes -H, -OH, -NH2 or an alkyl group with 1-8 carbon atoms and can be the same or different, x denotes

.an integer with the value 1-20 and y denotes an integer with the value 0-20. When a trifunctional compound is used, e.g. trihydroxybenzenes, branched chains will be obtained, which thus gives a branched polyaromatic amine; and

where A and B denote either:

where-R-^, R^ and R^ have the same meaning as in formula (A) and where

A and B may be the same or different and each repeating unit may be the same or different, R, denotes -H, -OH, -MH2 or:

R2 denotes -H or:

x denotes an integer with the value 1-4 and y denotes an integer with the value 1-15.

Compounds which are generally applicable in the production of olearomatic amines used according to the present invention are (a) polyaminobenzenes of the formula: where FL denotes -H, -NH2, -OH-or an alkyl group with at least 1-8 carbon atoms and R2 denotes - H, halogen or an alkyl group, as defined for R 1 , e.g. o-, m- and p-phenylenediamines, diamino-■toluene or diaminoxylenes, diaminophenols, triaminobenzenes, -toluenes and -xylenes, ethyl-, propyl-, butyl- and pentyl-di- and triaminobenzenes, etc. , where the most suitable compounds are those in which R1 is -H and R2 is -H, methyl or ethyl, (-b) polyvalent phenols of the formula:

where Rybet denotes -H, -NH2, -OH or an alkyl group with 1-8 carbon atoms and Rj_|denotes -H', -OH, halogen or an alkyl group as defined for R^,- e.g. catechol, resorcinol, chlorresorcinol, hydroquinone, phloroglucinol, pyrogallol, etc., dihydroxytoluenes and -xylenes, trihydroxytoluenes and -xylenes, ethyl-, propyl-, butyl- and pentyl-di- and trihydroxybenzenes and the like, as

the most suitable compounds are those where in R-, is -H and R^ is

■ -H or -OH, (c) aminophenols and alkyl-substituted aminophenols with the formula:

where R^ is -H, -NH,-,,- -OH or an alkyl group with 1-8 carbon atoms and Rg is -H, -NH2, halogen or an alkyl group as defined for R^, e.g. o-, m- and p-aminophenyls, diamino- and triamino-phenols,. methyl, ethyl, propyl, butyl and pentylamino and dd-aminophenols and the like, the most suitable compounds being those in which R^ is -H and Rg is -H or -NH2, and (d) diphenylamines, alkyl substituted diphenylamines and other compounds with the formula:

H

where R is -N- or an alkyl group with a straight or branched chain and with 1-5 carbon atoms and R^, R2,- R^. and R 2 can each be -H, -NH 0 , . -OH, halogen or an alkyl group with 1-8 carbon atoms and whereby at least two represent -NH2, -OH or one of each, e.g. bisphenol A and the like, the most suitable compounds being those in which and R[( is -OH or -NH2 and R2 and R^ are -H.

The halogen in the formulas given above can be

chlorine, bromine, iodine or fluorine.

The molecular weight and the degree of condensation of the polyaromatic amine depend on the ratio in which the reactants are bound, the time and temperature of the heating, and that of the catalyst. type and concentration. When two or more compounds are reacted together, they are usually used in approximately equal molar amounts. In order for the product obtained to be soluble in aqueous alkali metal hydroxide solutions, however, there must be sufficient hydroxyl groups present on the aromatic nuclei. It is therefore appropriate to use such quantities of starting materials and to choose the reaction conditions so that a polyaromatic amine is obtained with a maximum number of molecules, which are terminated at both ends with hydroxy groups. On the other hand, if R^ and R2 are. equal to -NH 2 , a sufficient amount of the groups R^ and R^ being hydroxy to provide the necessary solubility. It has been found that approx. 2 or more groups -OH are required at a molecular weight of 1000. It is the degree of acidity of such hydroxy groups that increases the solubility of the polyaromatic amine in aqueous alkali metal hydroxide solutions, e.g., sodium hydroxide solutions.

The molecular weight can be further regulated by application

■of small amounts of monofunctional compounds. One can e.g. use small amounts of an aromatic monoamine or a phenol to encapsulate the polymerization and thereby regulate the molecular weight. Polyaromatic amines with a higher molecular weight than approx. 250 is satisfactory to use according to the present invention. The upper limit of molecular weight will vary depending on it

special compound or the special compounds used in the production of the polyaromatic amine. It is sufficient to state that the particular polyaromatic amine should have a molecular weight such that it is workable and soluble in the aqueous

alkali metal.hydroxide solution so that it can be easily applied to the inner surfaces of the reactor. It has been shown that polyaromatic amines with a molecular weight of approx. 250 - approx. 1000 is most suitable.

While all described polyaromatic amines are useful in the practice of the present invention, particularly suitable polyaromatic amines are those obtained when an aromatic diamine and a. polyhydric phenol is brought to react with each other. Usually these compounds are reacted together in an approximately equimolar ratio. However, an excess of either the diamine or the phenol can be used. The only difference is that when an excess of polyhydric phenol is used, polyaromatic amines are obtained which have a somewhat higher softening point than those prepared in the presence of an excess of aromatic diamine. While some of the polyaromatic amines usable according to the present invention do not have a specific melting point, it has been shown that among the solid polyaromatic amines there are those with a wt softening point ■ of approx. 65 to over 150°C most satisfactory.

The softening point of the polyaromatic amine, as used here, is determined in the following way: the polyaromatic amine is melted and cast in a split aluminum mold to form a cube having a side of 12.7 mm. The mold is cooled, the cube is removed and allowed to cool carefully. The cube is then attached to a thermometer ball by heating the ball to a temperature beyond the expected melting point, after which the ball is placed on the side of the cube and then allowed to cool to 35°C. The thermometer with attached cube is introduced into a mercury bath which has been pre-heated to 35°C. The introduction takes place so that the upper surface or side of the cube comes 13 mm below the mercury surface. The mercury-silver bath is then heated at a rate of 4°C/min. The softening point is determined as the temperature at which, when the cube is moved upwards, it just breaks through the mercury surface. It should be observed that the cube should crawl up onto the thermometer and should not "shoot up". This is achieved by precisely regulating the rate of temperature rise in the mercury bath.

It should be repeated that many polyaromatic amines, which can be used in the practice of the present invention, have no definite softening point, but are viscous, flowable materials which are normally solid at room temperature. When these polyaromatic amines are dissolved in an aqueous alkali metal hydroxide solution and deposited on the internal surfaces of a reactor, however, they leave a water-soluble monomer film on these surfaces, whereby the object of the present invention is achieved.

When the specified compounds are self-condensed or reacted with one or more other compounds, an acid catalyst is used. It has been found that HC1 is the most effective catalyst. Other suitable catalysts can also be used, e.g. eg ... methanesulfonic acid, benzenesulfonic acid, sulfanilic acid, phosphoric acid, iodine, benzenedisulfonic acid, hydrogen bromide. (HBr), hydrogen iodide (HI), aluminum chloride and the like. The concentration of the catalyst will vary depending on the particular catalyst used. However, it has been shown that a catalyst concentration of approx. 0.005 - approx. 0.20 mol per mole compound, which self-condenses, or per mole of amino compound, when one or more compounds are caused to react, is satisfactory. It

however, the amount of catalyst used is not critical in some cases.

The temperature during the reaction of the compounds, either individually or with others, will vary depending on the reaction time and the desired molecular weight of the final product. You can, for example, heat the reaction components quickly to 315°C and then maintain this temperature for different periods of time. The reaction components can also be heated to various temperatures above 300°C and immediately cooled. When this latter method is used, the reaction time is defined as 0 hours. The reaction temperature will therefore vary from approx. 150 to approx.

l60°C and the reaction time will vary from approx. 0 to approx. 3 hours. One

A suitable reaction temperature range is 175-330°C and a reaction time of 0-1 hour. It is of course clear that the particular time and temperature chosen depends on the catalyst used and the desired final molecular weight of the polymerized amine.

The coating solution of polyaromatic amine is prepared commercially using heat and stirring, if necessary. The polyaromatic amine is dissolved in a suitable aqueous alkali metal hydroxide solution to such an extent that the solids content of the coating solution does not prevent it from being sprayed onto the inner surfaces of the reactor through permanently mounted spray nozzles. Usually, a coating solution with a substance content of polyaromatic amine of approx. 0.1 - approx. 20.0% by weight satisfactory. However, the dry matter content depends on the molecular weight of the polyaromatic amine, i.e. the dry matter content should in certain cases be greater than 20.0% by weight or less than 0.1% by weight. Additives can also be used in the coating solution, if desired, e.g. softeners, stabilizers, lubricants or fillers, etc. When additives are used,

■ of course there is a suitable setting of the coating dissolution's dry matter f content'.

The aqueous alkali metal hydroxide solutions used in the production of the present coating solutions,

are those made from a metal in group IA of the periodic table.' Such hydroxides as sodium hydroxide, lithium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide and francium hydroxide are included. Aqueous solutions of other compounds can also be used, e.g. aqueous solutions of quaternary amines such as tetraalkylammonium hydroxy

der et al., or other alkali metal salts, such as phosphates, e.g. trisodium phosphate, etc. It has been found that an important point is that the chosen compound in aqueous solution must have a sufficiently high basicity or pH, usually approx. 12.4 or above. It is believed, however, that certain compounds with a lower pH' than 12.4 should be usable according to the invention.

The temperature of the aqueous alkali metal hydroxide solution, when the polyaromatic amine is dissolved therein, is not critical. Usually a temperature of approx. 0 - approx. 100°C satisfactory. Stirring during the dissolution of the polyaromatic amine is desirable and in certain cases necessary when the polyaromatic amine has a high molecular weight. To achieve desired results, the concentration of the alkali metal hydroxide in the aqueous solution can be varied between approx. 0.1% by weight and approx. 25.0% by weight. Suitable concentration of alkali metal hydroxide is. 0.5-5.0% by weight.

As pointed out, the coating solution is usually applied to the internal reactor surfaces by spraying. However, it is also possible to apply the coating solution by filling the reactor, after which it is drained, but spraying is the most practical and economical application method. After spraying the coating solution on the internal surfaces and draining the reactor, the polymerization reaction can be started immediately without further treatment of the surfaces. However, it has been shown that the best results are achieved when, after the application of the coating solution on the surfaces of the reactor, the surfaces are sprayed with water and the reactor is drained before coating the reactor with polymerization mixture. The present coating works equally well on glass as on metal surfaces such as stainless steel etc.

The spraying of the coating solution on the inner surfaces of the reactor with water is considered to have a non-dissolving agent effect, causing the polyaromatic amine to precipitate and adhere to the reactor surfaces. This is believed to be the case as it has been shown that the polyaromatic amine is brought out of solution by dilution with water of the aqueous alkali metal hydroxide coating solution. While the exact adhesion mechanism of the coating on the surface does not

is known with certainty, it is believed to involve some type of 'electrical force or absorption between the reactor surfaces

and the polyaromatic amine..1 in any case, the present coating composition eliminates significant polymer build-up on the reactor surfaces and the small polymer build-up, if any in

all that may enter is of the sandy type which has such a nature that it can be easily removed from the reactor surfaces. The polymer build-up to be avoided is. the one referred to as "paper build-up", as this type of build-up is very difficult to remove and usually requires hand scraping or high-pressure spraying with. water or other liquid. In any case, must. the reactor is opened for cleaning, which naturally allows the release of unreacted vinyl chloride into the atmosphere.

According to the present invention, several polymerizations can take place in a coated reactor before its surfaces have to be recoated. However, this has been shown to happen quickly and it is appropriate to coat the inner surfaces of the reactor after each polymerization in it. This has the definite advantage that it essentially eliminates emissions of unreacted monomer vapors into the surrounding atmosphere, which emissions under the current regulations must be kept to a minimum. As pointed out earlier, it is possible to reach all the inner surfaces of the reactor with spray nozzles which are permanently mounted at suitable points in the reactor. After each completed polymerization and after the reactor has been drained, the internal surfaces are sprayed with water and the reactor is flushed. The coating solution is sprayed onto the surfaces and the reactor is drained of excess solution in such a way that the solution can possibly be led to a recovery system. The surfaces are then sprayed with water and the flowing liquid is diverted or possibly recovered. The reactor is then coated with polymerization medium and components in the usual way and the polymerization reaction is started. This cycle is repeated after each polymerization without opening the reactor.

After each application of coating composition to the inner surfaces of the reaction vessel and spraying of these with water, the reaction to be carried out in the apparatus can be started immediately whereby no special modification of the process technique is required due to the presence of the coating. The use of a reaction container which is internally coated according to the invention does not, moreover, adversely affect the heat stability or other physical and chemical properties of the polymers produced therein.

While the present invention is illustrated in more detail in the following with reference to suspension polymerization of vinyl chloride, it is clear that the device and method can also be applied to dispersion, emulsion or suspension polymerization of any polymerizable, ethylenic, unsaturated monomer or monomers when unwanted polymer build-up occurs. Examples of such monomers are other vinyl halides and vinylidene halides, such as vinyl bromide, vinylidene chloride

■ etc.', vinylidene monomers-with at least one end group CH^-CCI , such as esters of acrylic acid, e.g. methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, cyanoethyl acrylate and the like, vinyl acetate, esters of methacrylic acid such as methyl methacrylate, butyl methacrylate and the like; styrene and styrene derivatives including α-methylstyrene, vinyl toluene, chlorostyrene, vinyl naphthalene, diolefins, including butadiene, isoprene, chloroprene etc.; and mixtures of some of these types of monomers and other vinylidene monomers that are copolymerizable therewith, and other vinylidene monomers of known types. However, the present invention is particularly suitable in connection with suspension polymerization of vinyl chloride, either alone or in admixture with one or more other vinylidene monomers with at least one end group CF^-C^, which are copolymerizable thus in such large quantities as approx. 80% by weight or more, calculated on the weight of the monomer mixture, as the polymer build-up in the reaction vessel is a particularly difficult problem here: In the present invention, the polymerization process is usually carried out at a temperature of approx. 0 - approx. 100°C depending on the particular monomer or monomers being polymerised. However, it is appropriate to use temperatures of approx. 40 - approx. 70°C as polymers with

the most suitable properties are formed at these temperatures. The polymerization reaction time will normally vary from approx. 2 to approx.

15 hours. '

The polymerization process can be carried out by self-pressure, although higher pressure than atmospheric pressure up to 10 atmospheres or more can be used with some advantage in the case of more volatile monomers. Pressure above atmospheric pressure is also used with such monomers which have the necessary volatilities at reaction temperatures which allow reflux cooling of the reaction mixture.

The polymerization method can further be carried out using the technique with a full reactor, i.e. the reaction container is completely filled with the polymerization medium and kept in this way during the reaction through the constant addition thereto of water or additional supplemental liquid containing the monomer or monomers in the same proportion as with the initiation. Upon addition of a certain predetermined amount of liquid, the polymerization reaction is usually terminated by the addition of a quick-stopping agent. The need for liquid addition is due to the shrinkage in the volume of the reaction medium, which is achieved by transferring the monomer or monomers to the polymer state.

For gradation of the different coatings, as specifically stated in the execution examples, a gradation scale has been created with regard to paper-like and sandy structure, as described.. An uncoated reactor In which normal amounts of the two types of structure occur , a rating of 1.5 is given - A rating below 1.0 is good or a definite improvement. In other words, the gradation 0.0 is perfect, etc.

The invention is described in more detail in the following examples in which all parts and percentages are expressed as parts by weight or % by weight, if nothing else is indicated.

Example I

The polyaromatic amine was prepared by reacting m-phenylenediamine (m-PDA) with resorcinol (Res.) in equinolar amounts. HCl was used as catalyst.

Resorcinol and m-phenylenediamine were mixed beforehand and introduced into a three-necked round-bottomed flask.' The HCl catalyst was added and heating started from room temperature up to 315°C as quickly as possible. The coating melted at approx. 60-70°C. When most of the solid had melted, a stream of nitrogen gas was introduced into the melt through a dip tube, which caused agitation of the mixture. The reaction mixture was held at 315°C for 0.5 hours. The heating was then terminated and a stream of air was directed over the flask. When the temperature

had fallen to'250<Q>C, the batch was rapidly cooled by being poured into a mixture of ice. and water while stirring. The polyaromatic amine was then filtered off and air-dried at room temperature. The melting point of the polyaromatic amine or resin was 111°C.

The polyaromatic amine was then dissolved in 0.25N NaOH to form a 1.5% by weight coating solution. The inner surfaces of the reactor were coated with this solution and then rinsed with water. The following composition was then introduced into the reactor in the usual way:

xtil. 89% hydrolyzed polyvinyl acetate di-s-butyl peroxydicarbonate The reaction was carried out with a full reactor, i.e. a sufficient amount of water was added to fill the reactor, and at a temperature of 57°C with stirring. The reaction was continued while adding water as the mixture shrank due to polymer formation, so that the reactor was kept full. The reaction was interrupted after the addition of 400 g of water. The contents of the reactor were removed in the usual way and the internal surfaces judged according to the specified method for grading the surfaces. Degree- ■ . the ratio was as follows: paper build-up 0.0 and sand build-up (on top of the stirring paddles) 0.1. It is clear that the coated reactor was vastly superior to the control reactor or the uncoated reactor which had a rating of 1.5.

Example II

The procedure according to e.g. I was followed in the preparation of the polyaromatic amine except that H^PO^ was used as catalyst instead of HC1 and the temperature raised

to 270°C and then stopped. The obtained condensation product of m-PDA and Res. had a softening point of 65°C. The polyaromatic amine was then dissolved in 0.25 N NaOH to form a 1.5% solution. The coating solution was placed on the inner surfaces of the reactor and then rinsed with water. Same

polymerization composition•and the same reaction conditions as

in ex. I was used. After the polymerization and after removing the contents from the reactor, the internal surfaces were extremely clean, whereby the grades were: paper build-up 0.0 and sand build-up 0.05. Example III

The polyaromatic amine was prepared by condensation of n-PDA (0.2 mol) and bisphenol A (BPA) (0.4 mol) in the presence of HCl (0.02 mol) as catalyst. The temperature of the reaction mixture was raised to 200°C and held here for 0.5. hours. Heating and stirring were then stopped and the reaction product was withdrawn. After cooling, the reaction product was a dark brown, sticky resin. ' The softening point was too low to be determined. The product was then dissolved in 0.25N NaOH to form a 1.5% solution. This solution was placed on the reactor surfaces and then rinsed with water. The composition and method according to e.g. I was used in the subsequent polymerization reaction. After removal of the contents from the reactor, the surfaces were graded to 0.0 for paper build-up, and 1.0 • for sandy build-up.

Example IV'

The polyaromatic amine used was the self-condensation product of m-aminophenol. 54.5 g of m-aminophenol (0.5 mol) was introduced into a three-necked flask with a round bottom and provided with a thermometer and a short air cooler. A magnetic stirrer was used. 4.2 ml of HCl catalyst (0.05 mol) were added and the heating started. The reaction medium was heated to 175°C and held at this temperature for 4 hours. After completion of heating and cooling, the product formed was a black, sticky resin with a softening point too low to be determined. The product was then dissolved in 0.25N NaOH to form a 1.5% coating solution, which was placed on the reactor surfaces and rinsed with water. The reactor was coated with the composition according to ex. I'and polymerized. in the same way. After the removal of the contents of the reactor, the overflow was extremely clean with a grading of 0.0 for paper build-up and 0.0 for sandy build-up.

Example V

The polyaromatic amine was prepared by a condensation reaction of 3 components, namely 0.5 mol of m-phenylenediamine

(m-PDA), 0.5 mol resorcinol (Res.) and 0.5 mol p-aminophenol (PAP).

The reactants were fused together with stirring. 6.2 ml of HCl was added and the mixture heated to 250°C at which temperature a sample was removed and a hard resin formed at room temperature. The contents were precipitated and on cooling a dark colored brittle resin was formed which had a softening point of 78°C. The polyaromatic amine formed in this way was then dissolved in 0.5N NaOH to form a 1.5% coating solution which was placed on the reactor surfaces and rinsed with water. Again the reactor was coated with the composition according to ex. I, and was polymerized under the conditions stated therein. After emptying the reactor, the surfaces were very good with only a few spots of paper-like and sandy build-up. The gradations were 0.2 for paper build-up and -0.2 for sandy build-up.

Example VI

The polyaromatic amine was prepared by a condensation reaction of four components in the following amounts:

The reactants were mixed in a beaker and then transferred to a

.reaction flask. 2.5 mL of HCl was added and heating was started. The reaction mixture was stirred as soon as possible. It turned out that the reaction product solidified on cooling when a

temperature of 260°C had been achieved. The contents were then extracted

and cooled. The polyaromatic amine was a hard, brittle, dark red

resin and had a softening point of 68°C. The resin was then dissolved in 0.5N NaOH to form a 1.5% coating solution. The solution was placed on the reactor surfaces and

then rinse with water. Same polymerization method and composition as in ex. - You were used again. After the contents of the reactor had been removed, it was observed that the surfaces were in very good condition and free of build-up. The ratings were 0.0 for paper build-up and 0.0 for sandy build-up.

Example VII

A halogenated component was used; Thus, 0.15 mol of m-PDA (16.2 g) and 0.15 mol of 3-chloro-resorcinol (21.7 g) were used, which were introduced into a reaction flask. Then 1.3 ml.HCl was added and heating was started. • The temperature was brought to 275°C and the heating interrupted. The product was very viscous and could only be poured with difficulty at 275°C. In the cooled state, the cold, resin-like polyaromatic amine resembled coke. The softening point was too high to be achieved. Sufficient of the product was added to 0.5N NaOH to form a 1.5% solution. However, not everything was dissolved

.and the total dissolved product solids was 0.6%. The solution was applied to the reactor surfaces and rinsed with water. The polymerization method and composition according to e.g. You were exploited. After complete polymerization and removal of the contents from the reactor, the internal surfaces were examined and it was found

to be in very good condition. The ratings were 0.0. for paper build-up bg 0.0 for sandy build-up.

Example VIII

Here. was o-aminophenol self-condensed. 54.5 g o-aminophenol (1.0 mol) was introduced into the reaction flask. 4.2 ml of HCl catalyst (0.05 mol) was added and heating started. The reaction medium was heated to 175°C with stirring as soon as the coating was sufficiently liquid to permit this. The temperature was maintained at 175°C for four hours. The reaction product was then poured off and allowed to cool. The cooled •product was a black, sticky tar and consequently the softening point' was too low to be determined. The product was then dissolved in 0.5N NaOH to form a 1.5% ig coating solution. The solution was then placed on the surfaces of the polymerization reactor and rinsed with water. The reactor was coated with the composition according to Example I and polymerized according to Example I. After removing the contents from the reactor, the surfaces were found to be very clean with the grades 0.0 for paper build-up and 0.0 for sandy build-up.

Example IX

That in e.g. In prepared polyaromatic amines, namely the condensation reaction product of m-PDA and resorcinol, was dissolved in 0.25N potassium hydroxide in sufficient quantity to provide

bringing a 1.5% coating solution. The solution was placed on the reactor surfaces and then rinsed with water. The polymerization reaction was carried out as in ex. I. After the removal of the contents from the reactor, the surfaces were free of paper build-up and only small pieces of sandy build-up were scattered on the screen and the agitator shaft and vanes. The ratings were 0.0 for paper structure and 0.5 for sandy structure.

Example X

The polyaromatic amine was prepared by condensation of 2,4-toluenediamine monohydrochloride and resorcinol without the use of catalyst as sufficient mende.HCl using the monohydrochloride form was present for catalysis

of the reaction. The two components were mixed in a beter 1 in the following quantities:

100 g of 2,4-toluenediamine monohydrochloride

69.3 g resorcinol

After mixing, the mixture was transferred to a three-necked round bottom flask and heating was started with stirring. The mixture was then heated to 250°C over 2.5 hours and the contents then removed. On cooling, the reaction product became a hard, brittle resin with a softening point of 129°C. The product was dissolved in 0.5N NaOH to form a 1.5% solution. The solution was then applied to the reactor surfaces and rinsed with water. The composition and procedure in ex. I was used in the subsequent polymerization reaction. After removing the contents from the reactor, the surfaces were graded to 0.0 for paper build-up and 0.2 for sandy build-up.

Coating the internal surfaces of the polymerization reactor according to the present invention significantly reduces and in many cases practically eliminates the polymer build-up on the surfaces during the polymerization reaction and thus leads to increased production per unit of time.. In those cases where a small amount of polymer build-up accumulates on the inner surfaces, it is not of the hard, raw type, which is difficult to remove and is easily removed without the use of the difficult, time-consuming scraping methods that are necessary today. Of greater importance is that the present invention enables operation in a closed or closed polymerization system which, in the case of vinyl chloride polymerization, has the advantage that

.it drastically reduces the number of parts of vinyl chloride per millininon i

1 the factory atmosphere.

With any of the polyaromatic amines described and using the method of any of the examples, the cycle is repeated at each. batch without opening the polymerization device. This is achieved by using spray nozzles which are placed in the roof of the reaction vessel or polymerization device, whereby the coating solution • is sprayed onto the internal surfaces, drained and possibly recovered, and whereby water is sprayed through the same nozzle and

performs drainage, after which the polymerization mixture is introduced.

After polymerization, the contents are removed and the interior is rinsed with water using the spray nozzles. The cycle is then repeated without opening the reactor.

Claims (22)

1. Method for substantially removing the polymer build-up on the internal surfaces of a polymerization vessel, characterized in that a coating solution of a polyaromatic amine is applied to these surfaces. with a straight or branched chain and with a higher molecular weight. than approx. 250, solved in one. aqueous alkali metal hydroxide solution, where the polyaromatic amine has the formula: where A, B and C denote either: where R is ■5 or an alkylene or alkylidene group with a straight or branched chain and with 1-5 carbon atoms, or: and where' A3 B and C can be the same or different, and each repeating unit can be the same or different, and R2 represents either -H, -OH, -NH"2 or: and may be the same or different, R^ denotes'-H,' halogen or an alkyl group with -1-8 carbon atoms and may be the same or different, R^ denotes -H, -OH, -NH2 or an alkyl group with 1-8 carbon atoms and may be the same or different, x denotes et integer with the value 1-20 and y denotes an integer with the value 0-20, or where A and B have the same meaning as in (A), R^' , R1, R^ and R^ have same meaning as i-(A), R 2 .denotes -H or: • x denotes an integer with the value 1-4 and y denotes an integer with the value 1-15. 2. Method according to claim 1, characterized in that the polyaromatic amine has the formula (A). 3- Method according to claim 1, characterized in that the polyaromatic amine has the formula (B). 4. Method according to claim 1, characterized in that the polyaromatic amine is the reaction product of a polyaminobenzene with the formula: .where -H denotes -NH2, -OH or an alkyl group with 1-8 carbon atoms and R2 denotes -H, halogen or an alkyl group, as defined for R^, and a polyhydric phenol of the formula: where R^ denotes -H, -NH2, -OH or an alkyl group' with 1-8 carbon atoms, and R^ denotes -H, halogen or an alkyl group, as defined for Rv. 3 5. Method according to claim 1, characterized in that the polyaromatic amine is the reaction product of polyaminobenzene with the formula: where R 1 denotes -H, . -NH2, -OH or an alkyl group with 1-8 carbon atoms and R2 -denotes -H, halogen or an alkyl group, as defined for R-^, and a diphenylamine, alkyl-substituted diphenyl-'amine or another compound with the formula: where R denotes =ller' an alkylene or alkylidene group with a straight or branched chain and with 1-5 carbon atoms, and R-1, R2, R3 and Ri| each can be -H, -NH2, -OH, halogen or an alkyl group with 1-8 carbon atoms, with at least one of the groups representing -OH.' 6. Method according to claim 1, characterized in that the polyaromatic amine is the reaction product of a polyaminobenzene with the formula: where. R denotes -H, -NH2, -OH or an alkyl group with 1-8 carbon atoms, and R2 denotes -H, halogen or an alkyl group, as defined for R-^, and an aminophenol or, an alkyl substituted aminophenol of the formula: where R^ denotes -H, - -Nh'2, -OH or an alkyl group with 1-8 carbon atoms and Rg denotes -H, -NH2 -, halogen or a. alkyl group as defined for Rr . 5 7. Method according to claim 1, characterized by . that the polyaromatic amine is the reaction product of an aminophenol or an alkyl-substituted aminophenol with the formula: where R,- denotes -H3 -NH2 , -OH or an alkyl group with 1-8 carbon atoms, and Rg denotes -H, -NH2 , halogen or -an alkyl group as defined for R^, and a diphenylamine, alkyl-substituted diphenylamine or a other connection with the formula: ■ where R denotes or an alkylene or alkylidene group with a straight or branched chain and with 1-5 carbon atoms and R-^, R2 , R^ and R^ can each be -H, -NH2 , -OH, halogen or an alkyl group . with 1-8 carbon atoms, at least one of these groups being -OH or -NH 2 . 8. Method according to claim 1, characterized in that the polyaromatic amine is the reaction product of a polyhydric phenol with the formula: where R^ denotes -H, -MH2, -OH or an alkyl group with 1-8 carbon atoms, and Rj denotes -H, halogen or an alkyl group as defined for' Rj, and a diphenylamine or alkyl-substituted diphenylamine or another compound with the formula: where R denotes or one-alkylene or alkylidene group with a straight or branched chain and with 1-5 carbon atoms, and R^ , R? and .Rjj can each be -H, -NI^, -OH, halogen or an alkyl group with 1-8 carbon atoms, at least one of these groups being -NH2. 9. - Method according to any one of claims 1-8, characterized in that the coating solution contains approx. 0.10 - approx. 20.0% by weight polyaromatic amine. 10. Method according to any one of claims 1-9, characterized in that the alkali metal hydroxide is sodium hydroxide. . 11. Method according to claims 1-9, characterized in that the alkali metal hydroxide is potassium hydroxide. 12. Method according to any one of claims 1-9, characterized in that the alkali metal hydroxide is lithium hydroxide. 13. Method according to claims 1-12, characterized in that it. polyaromatic amines have a molecular weight of approx. 250 - approx. 1000. 14. Method according to claim 1, characterized in that the polyaromatic amine is the reaction product of m-phenylenediamine and resorcinol. 15- Method according to claim 1, characterized in that the polyaromatic amine is the reaction product of m-phenylenediamine and bisphenol A. 16. Process according to claim 1, characterized in that the polyaromatic amine is the reaction product of 0-phenylenediamine and -resorcinol. 17. Process according to claim 1, characterized in that the polyaromatic amine is a self-condensed aminophenol. 18. Method according to claim 14, characterized in that the alkali metal hydroxide is sodium hydroxide. 19. Method according to claim 18, characterized in that the sodium hydroxide concentration in the aqueous solution is approx. 0.1 - approx. 25.0% by weight. 20.. Method according to claim 19, characterized in that the coating solution contains approx. 0.10 - approx. 20.0% by weight polyaromatic amine. 21. Method, according to any one of claims 1-20, characterized in that the polyaromatic amine has a softening point of approx. 65 - approx. 150°C. 22. Process according to claim 1, characterized in that the polyaromatic amine is a reaction product of m-phenylenediamine, resorcinol and p-aminophenol. 23- Method according to claim 1. characterized in that the polyaromatic amine is a reaction product ■ .duct of m-phenylenediamine, resorcinol, phloroglucinol and m-aminophenol-24. Process according to claim 1, characterized in that the polyaromatic amine is a self-condensed reaction product containing at least one group -OH and at least one group -NHp.