The subject of the present invention is an anti-fouling- agent for the polymerization of olefinic chloride monomers.

The polyvinyl alcohol molecule may be considered as a linear polymer having lateral chains made up of secondary alcoholic functional groups, said secondary alcoholic groups are therefore subject to giving all the characteristic reactions of alcohols, among which is the esterification reaction.

The greater part of recent studies and processes in use on esterified compounds of polyvinylic alcohol have specific applications, the most important of which are photographic processes where the scope is to prepare transparent films having adequate physical properties and which, at the same time, contain groups suitable for coupling with dyes.

The present invention refers to a production method of polyvinyl alcohol esters having mono or polyamminic derivatives of benzoic acid; the resulting product may be considered a polyester or an aro atiac polyamino.

It is known that during the polymerization process in the reactors for the production of PVC-S substantial incrustations are deposited which have the following main inconveniences:

- considerable maintenance to eliminate the incrustations with consequent interruption of production;

- pollution of the product because a number of pieces of incrustation end up in the respective polymerized product with consequent complaints from the user and scrapping of the products; - hinders both the productive system and the regularity of the respective supplies.

The damage is even more, obvious if one considers that the greater part of the incrustations have different colours and

therefore the resulting products are irremediably down-graded.

The chemical-physical properties of the polyesters do not strictly regard us whereas the properties of the aromatic polyaminos have in recent years found an application as anti-dirtying agents in the polymerization reactors of the ole ins.

However the results have not been very satisfying due to the scarce anti-incrusting efficacy and to the colouring of the formed crust which pollutes the resulting products when it flakes.

The scope of the present invention is to eliminate the above-mentioned inconveniences.

According to the present invention, a film or coating of amino benzoic esters of polyvinyl alcohol with more or less acetyl is applied on the internal surfaces of the reactor, and the same to be said of all those parts of the reactor such as: the blades and agitater shaft, the thermometric probes, the condenser, the wave-breaking blades, etc.

The best results have been obtained when the protective film of polyviayl alcohol aminobenzoic esters has been created by spraying.

Obviously the system of application is not limiting as the following systems may also be used: a steam suspension or systems of electrostatic deposit or other, not excluding the manual applications also by brush.

According to the invention the best result is obtained by washing the applied product with water. In this way the product, which is insoluble in water, precipitates on the walls and the surplus part is washed away. An extremely fine, superficial coating which is practically transparent is thus obtained which can be used for several productive phases. The aromatic polyamino deposited on the reactor walls in minimum quantities does not influence in any way the polymerization

- -

reaction; on the other hand, it protects the walls and the parts which are in contact with the means of reaction and avoids troublesome and costly phenomena of polymer deposit. The mechanism by which the aromatic polyaminos prevent the polymer deposit on the internal parts of the reactor during the polymerization of an olefinic monomer in the presence of an olesoluble catalyst, that is, soluble in the same monomer, is still not clear. However, it can be preconized that a free radical in phase of expansion is destroyed by the a inic group instead of depositing itself on the metal wall; in fact, the anti-oxidant activity of the a inos is well known. The system of application according to the invention is as follows:

- the product in organic solution from 0.05 to 5% of active substance is applied on the respective surfaces to be protected;

- the surfaces thus treated are then washed with water.

- the polymerization charge of the polyvinyl chloride in liquid suspension (PVC-S) is then carried out.

The structure of the aminos proposed as per the present invention is as follows:

CH ₂ - CH CH p - CH - CH - CH -

0 OH

0

I ^■

0 = C 0 = C

Where R1,R2,R3 can be H or NH with at least one of the groups substituted by NH 2

The ratios of V, "n" and "p" to each other depend on the original polyvinyl alcohol and on the degree of- re-esterification to which the polyvinyl alcohol is subjected. It is obvious that in this situation the sum and the ratios of

II ^■ mmi"l , 'l _n nt"l, I"!p-,"" to each other also determine the water solubility of the finished product while the good protective capacity on the wall is determined by the number of aminic groups present. The reaction scheme to obtain the product which is the subject of the present invention is as follows:

R' " ₂ m+n

CH - OH R"' <CΩ _-- > ^ Cl

CH _Λ R" R"

CH - O C - CH with R'.R'SR'" equal to -H or NO

II In which' at least σie of the substituted o groups is -NO

Therefore the resulting product will be:

m

The polynitrobenzoil esters of the polyvinyl alcohol is then reduced by triethylammonium-for ate in the presence of palladium as catalyst.

CH ₂ CH-OH

HC0 ₂ H Pd/C

CH

O ET ₃ N

II

CH - O - ϋ - CH ,

CH R' R"

CH - O - C <o R"'

R' m

CH

CH-OH

CH

O

II

CH - O - C - CH

CH R R

I 1 , 2 i ιι

CH - O - C - <_ O _> ^" R

R, R m

¹ 2

Which is the formula of the product according to the present invention.

Which results as the formula of the product as per the present invention.

The following experimental examples are given: Example 1. A PVC-S polymerization reaction, without the application of an anti-fouling product, is conducted in a 1,500 lit. stainless steel reactor, with the following charging formula:

- H 0/CVM = 1,3

- Primary suspending agent PVA 40/78 = 0.05% CVM + Hydroxy-propyl-methyl-cellulose 0.03% CVM

- Lauroil peroxide = 0.02% CVM - dimerisitylperoxide 0.07% CVM

- Reaction temperature = 55°C

- Pressure decrease from start to finish of polymerization reaction = 3.5 bar. After the reaactor has been drained and rinsed with water, a film of deposit which is clearly visible and difficult to detach can be observed after cooling.

After removal and weighing, the weight results as 100 grams.

Example 2. A solution of nitrobenzoyl-chloride in dimethylformamide maintained at a temperature of 20°C is placed in a flask equipped with agitator, thermometer, condenser and with an adequate thermoregulation system.

A solution of 10% polyvinyl alcohol having a degree of hydrolysis equal to 79% mole OH in dimethylformamide in slowly added while under agitation.

The agitation continues for approx. 6 hours with simultaneous separation of the gaseous hydrochloric acid which develops from the reaction mixture. Upon completion of the esterification reaction (disappearance of the development of the gaseous HC1, the remaining solution is dispersed in approx. 20 times the value of H 0 maintained under energetic agitation.

A polymer, white in colour, precipitates and upon "UV" and

"ITRO"" elementary analysis (analysis under ultraviolet and infrared rays), shows itself to be of the p-NO -benzoic (Paranitrobenzoic) esters of the original, partially acetylised, polyvinyl alcohol.

The polymer thus obtained is dissolved in acetone (ratio 1:10) after drying.

The following are added to the solution thus obtained, 2.9 mole of triethyla ine and 2.2 mole of formic acid and then 0.1% of palladium on granular coal in respect 'to the monomeric residues of the polyvinyl alcohol. CO and H develop for approx. 3-6 hours. The reaction is completed in 18 hours at the boiling temperature of the acetone.

Upon completion of the reaction the product is removed and the palladium on the coal is recovered.

The acetonic solution is already ready for industrial uses such as anti-deposit agent, as previously described.

For analytic purposes, the product must be precipitated, washed with water and dried. Whether it is in solution or in the dried state, the product results light-sensitive and easily oxidizable with the formation of various black-bluish, oxidization sub-products.

The yield in reduction is practically quantitative. Example 2-1. The product obtained from the above-mentioned example is dissolved at 0.8% p/v in 95% ethyl alcohol and 10 parts % p/v of paratoluen-sulfonic (99% strength) are added to the solution thus obtained. This mixture is ready for application at any temperature and by any means to the internal parts of the PVC-S polymerization reactor.

The excess of the product present on the said reactor must ^" be removed with water which in addition to washing the surfaces also provides for the fundamental precipitation and fixing of

the anti-crust product as per the present invention.

Indicatively, 30 ml of solution are used per mq. of the reactor's surface. Example 2.2. In the same reactor, after a thorough cleaning and application of the solution as per example 2-1, the same polymerization charge described as per the characteristics of the present invention has been repeated.

After draining and washing the reactor, the walls and all the internal parts of the same result perfectly absent from any sort of deposit, and upon analysis of- the PVC-S obtained not even a minimum trace of the product used as anti-crust agent can be noticed. Observations Whereas in example 1 it is necessary to stop the productive cycle of the reactor every 4-5 reactions for a radical cleaning and dis-incrustation, this operation is not necessary with example 2 of the present invention. At the most, the restoration of the coating as described in the same example is necessary.