MXPA97009640A - Anti-incrustation agents for polymerization reactor coatings - Google Patents

Abstract

A process for the production of an anti-incrustation agent for coating the monomer polymerization reactors is characterized, characterized in that said anti-fouling product is obtained by means of the reaction between the sodium salt of the hydroxymethanesulfinic acid with naphthol

Description

ANTI-INCRUSTATION AGENTS FOR POLYMERIZATION REACTOR COATINGS TECHNICAL FIELD The object of this invention is a process for the production of anti-incrustator for coating polymerization reactors. Anti-fouling agents for polymerization reactors are already known in the prior art.

TECHNICAL BACKGROUND In the most advanced technique currently there are also different types of anti-incrustation agents for each type of polymer. For example, the anti-fouling agent for the production of vinyl chloride is not the same as that used in the reactor for the production of polystyrene or for the production of acrylic polymers, etc. This fact requires the storage of different products with all the consequences of high handling costs. In addition, even reactors should be specifically targeted only at one type of reaction, resulting in increased costs.

DESCRIPTION OF THE INVENTION The first purpose of this invention is to make an anti-incrustator that works well in any type of polymerization reactor and for most of the varied types of different materials, therefore for polystyrene as well as acrylic polymers, ABS, polyurethane, PVC, etc. In the specific case of polymerization of vinyl chloride in suspension or emulsion, for example, it is known that in the reactors a substantial deposit of scale is formed having as main disadvantages: a consistent maintenance to remove the scale with consequent interruption of the production , by opening the reactor and therefore high amounts of gaseous vinyl monomer chloride (VCM) emissions into the atmosphere: - contamination of the resulting product as some of the scale parts pass to the respective polymerized product with the consequent worsening in quality and complaints by users; In short, there are obstacles both in the productive system and in ecological problems for the areas in which the industrial plants of polyvinyl chloride (P.V.C.) operate. This problem practically exists for all types of polymerizations.

In addition, the anti-fouling products intended to coat the surfaces of the respective reactors *: are bluish or dark brown almost black, so that the particles that are detached from the crust, contaminate the polymer obtained (for example, chloride of polyvinyl obtained) from the reactor ba or the form of black dots which, for example, in the finished products worsens the qualitative aspect of said product. In addition, it should be noted that the particles of material that are detached from the crust of the wall end in the product in reaction, constituting the contamination of the ism, generally dealing with toxic products. In the prior art, the technique of condensation or polycondensation of naphthols and phenol with an aldehyde crosslinking product (eg, formaldehyde and others) is known to obtain anti-fouling products. For this purpose reference is made to: - US-A-3669946 (filed in the United States on August 31, 1970, described June 13, 1972), which suggests the use of formaldehyde and mixed ketone bodies, naphthol, etc. . and also alpha-naftilamma and nigrosma. This teaching pre-divides the general concept of forming anti-fouling condensate that starts from formaldehyde with derivatives of phenols and naphthols. - US-A-3825434 (July 23, 1974) describes an anti-fouling agent for the polymerization of vinyl chloride, obtained from the condensation of phenol with formaldehyde, wherein obviously for definition in this patent the product obtained it is always classified as belonging to the family of phenol-formaldehyde or polyarylphenol. • US-4,06T, 059 (filed on February 17, 1977, published January 10, 1978) further explains the importance of using as anti-incrustants, products that in their chemical structure contain one or more of the following groups : -OH; -COOH; SO3H and S? 3Na. These groups are generally used to an aromatic nucleus. EP-A-0052421 discloses a process for obtaining an anti-fouling product formed with formaldehyde which is made to react with 1-naphthol (alpha-naphthol), in which the nuclear positions 2 and 4 are not replaced and the position Nuclear 3 is not replaced or has a substitute that is not strongly electron attractor to obtain a condensate. Even in this case, the product obtained according to the chemistry must always be considered as belonging to the polyarylphenol family. These latter products have the disadvantage of supplying a dark brown or dark blue almost black product, and are not always suitable for use in polymerization sectors with different materials.

EP. .0598537 (Shin-Etsu Chem. Co. Ltd) (DI) discloses a polymer scale prevention agent for use in the polymerization of a monomer having an ethylenically unsaturated double bond, comprising an alkaline solution containing: (A) ) a condensation product of (Al) a compound of hydronaphthalene and (A-2) an aldehyde compound and (B) an inorganic colloid. EP-A-0052421 (1C1) (D3) describes a polymerization process of vinyl chloride carried out in aqueous suspension in which the polymerization is carried out in a polymerization reactor having a suppressive coating adherently deposited on the internal surfaces thereof. of accumulation (anti-fouling agent) comprising a product having accumulation suppressive activity formable by the condensation reaction of 1-naphthol and formaldehyde. JP-A-05 230112 (Shinetsu Chem. Ind. CO. Ltd) (D2) discloses agents that prevent the formation of scale and coated reactors for the polymerization of vinyl monomers using the agents. In the cited example it is mentioned that a solution of IleOH of 4 g of 4-aminodi phenylamine and 10 g of 2,7-dihydroxynaphthalene was heated in the presence of 2 g of p-benzoquinone (catalyst) for 15 hours at 50 ° (supposedly 50 ° C), and then combined with 4 g of Rongalite, and stirred for 5 hours to give a condensation product. The reaction to producing this scale preventing agent is difficult to control and leads to crosslinked products insoluble in alkaline aqueous solution, the product being dark and clearly constituting a contaminant of the polymer in reaction, when applied as an anti-fouling coating. incrustations in the reactor wall. In addition, the coating of the reactor with these anti-scalers is easily consumed by dispersing in the reaction material, contaminating it with color and toxicity. In addition, it should be noted that these anti-inclinators are of low efficiency or, however, require a massive deposit of scale on the wall, to avoid some uses, such as health and food, where the required product limits pollutant in the finished product are decidedly minor, etc. In order to obtain a good antifouling efficiency, however, they must be deposited on the wall in high quantities which also influence the costs. The color of the anti-incrustators of the known art is dark and unappreciated by the user also because it makes one think of a polluting product. The dark color of the product leads to a crust on the wall, also of dark color (blackish) and this does not allow to see final application defects. But much more serious is the aforementioned, that during the reaction scab particles are detached and mixed with the polymer. Since these parts of the crust are black, it is obvious that there is a qualitative worsening of the product. The purpose of the present invention is to obviate the aforementioned disadvantages and in particular to obviate the dark color of the product and the scale that will form on the wall of the reactor. The inventors originally intended to make an anti-fouling product which, once applied to the reactor wall, was substantially colorless. It is known that to whiten an aromatic product, for example dyes, sodium hydrosulfite or potassium hydrosulfite is used. Attempts to make colorless with hydrosulfite the condensate of formaldehyde and 1-naphthol have given negative results because the condensate always remains bluish black, tending to form deposits even when driving in the absence of oxygen, for example, in the presence of nitrogen. As the investigation progressed, it was thought to avoid the reaction between formaldehyde and 1-naphthol to replace it with a toxic substance and capable of forming a colorless product. After innumerable experiments, it was found that the best product can be obtained by combining 1-naphthol with hydroxymethansulfinic acid. The result was surprising and the product obtained was perfect colorless. In the tests of an + i -mcrus + acion in the polymerization reactors of the products described above, surprising results were obtained in terms of yield, quality and production. The hydroxy methanesulphonic acid is identified with the following formula: 0 CH20H The best solution of the invention is achieved by using hydroxy ethansulfinic acid mixed with -naphthol in the proportions by weight of 1 to 1.5, in an aqueous solution of 10 to 40% and bringing the temperature of the solution between 70 ° and 95 ° C. in a nitrogen atmosphere, alkaline environment (pH 1.1-13); a clear transparent colorless product was obtained, which completely reached the predetermined purpose and without reducing the quality of the product, in fact improving it. The resulting product is physically clear, transparent, but if left in the presence of air for a certain period it is slightly oxidized leading to a blue-green color. However, the surprise is that, if the contact with oxygen is interrupted, the product reverts to its original transparent clear appearance. This physical behavior proves that a completely new and structurally different product has been obtained compared to products of the prior art, where this physical phenomenon could not be observed. Based on chemical and spectroscopic analyzes, several hypotheses have been formulated about the nature of the product, and even if the structure is not completely certain, it is believed that the reversibility of the phenomenon could be linked to the presence of a radical in the product, which depending on the oxygen concentrations may or may not bind to the molecular structure of the primary compound. In short, according to the most probable deductions, it must be treated with a bisulphitic adduct of the first product that is formed in the reaction between 1-naphthol and hydroxy methanesulphonic acid. The product applied on the surface of the reactor in an atmosphere devoid of oxygen, after drying, results in a white, opaque, opaque color, contrary to the dark color of the anti-incrustants herein. The results therefore have been surprisingly good. To maintain the transparent appearance of the liquid product before application on the wall, in accordance with the present invention, it is stored in oxygen-impermeable containers. It has been discovered that the best preservation is by means of pressure to contain with neutral gas, preferably nitrogen. Equally advantageous, it was discovered that most effective containers are made of glass or better still of polyethylene + ereftalat-or "PET" (in such a way that the containers do not contaminate and are completely reccrculable). With the use of the container in "PET" (flexible container), another important physical behavior was discovered: when a one liter bottle, for example, of the product according to the present invention being closed + closed + closed and opened the transparency is visibly transparent, leaving the bottle open to the air for a few minutes, the contaminated product becomes dark; closing the bottle again after the product has darkened, you notice that the bottle in flexible "PET" shrinks slightly. This could be justified in that the product destroys all the oxygen that has remained in the air that is contained in the bottle previously opened and now closed; In addition, the product returns to a clear transparent color as before, as if nothing had happened. This proves that the product self-protects or self-reconstitutes in its original appearance, with the condition, however, that it stays away from contact with air. The product preserved as such therefore remains unchanged, light in color, and in the experimentation of the application on the wall of the reactor (obviously in the presence of inert gas), the anti-fouling agent is deposited on the wall as an extract The thin one that was mentioned before becomes colorless and transparent. Advantageously, it was discovered that the application on the wall of the reactor must be done not only in the absence of oxygen, but also by means of high temperature water vapor spraying. Spraying the product with water vapor at high temperature results in maximum adhesion. Since the reaction of polymerization in the reactor lasts on average from 4 to 6 hours, it is evident that in that time and in the absence of oxygen, there are no substantial degradations of the product, and consequently colorimetric degradations.; therefore, once the polymerization reaction has been completed and once the smaller percentage of antifouling is integrated into the polymerized mass, it will not suffer significant contamination and degradation. Instead, although in the prior art using the previously known anti-fouling products, the reactor had to be completely washed and drained of every minimum amount of product residue applied to the wall as an anti-incrustator, with this new product it is possible to send the reactor rinse to the collection tank of the aqueous suspensions of the obtained polymer without requiring additional rejection discharges, thus realizing a complete and effective and above all economic technology of loading and unloading of polymerization reactors with the known technique by industry experts as closed main hole. Since hydroxy ethanesulfinic acid is also used with an excess of molar hydrosulphite, even using this product ee obtains a condensate of analogous or improved performance (largely reducing conditions). Both in this case and in the previous one, the activity of the product always occurs from the presence of bisulfate derivatives and in particular of bisulfite radicals present in the derivative; this feature clearly distinguishes the new product from the prior art and in particular with reference to the resulting structure of the derived product; This is identified as innovative by the presence of a carbon atom interposed between the aromatic rings and bound to a sulfonic group. It was also proved that other naphthols with more or less regular results can be used instead of 1-naphthol.

Claims (11)

NOVELTY OF THE INVENTION CLAIMS

1. A process for the production of an anti-fouling agent for coating the monomer polymerization reactors, wherein said anti-fouling product is obtained by means of the reaction between the sodium salt of hydroxymethansulfinic acid with naf + ol, characterized in that the product is obtained using hydroxymetansulinic acid mixed with 1-naphthol in proportions by weight of 1 to 1.5, in an aqueous solution of 10 to 40% and bringing the solution temperature between 70 ° and 95 ° C in an atmosphere of nitrogen and alkaline environment of pH 11-13, to obtain a clear transparent product, the process carried out in such a way that the resulting product is clearly transparent in the absence of contact with oxygen.

2. A process for the production of an anti-fouling agent for coating polymerization reactors according to the preceding claims, further characterized in that sodium hydrosulfite is added to the reaction.

3. A process for the production of an anti-fouling agent for coating polymerization reactors according to the preceding claims, further characterized in that potassium hydrosulfite is added to the reaction.

4. A process for the production of an anti-fouling agent for coating polymerization reactors according to the preceding claims, further characterized in that the product containing hydrosulfite is added in such a way that the hydrosulfite prevents the evolution of the reaction towards stable condensed forms.

5. A process for the production of an anti-fouling agent for coating polymerization reactors according to the preceding claims, further characterized in that the product obtained is stored in oxygen-impermeable containers.

6. A process for the production of an anti-fouling agent for coating polymerization reactors according to the preceding claims, further characterized in that the product obtained is stored in oxygen-impermeable containers by means of inert gas pressure.

7. A process for the production of an antifouling agent for coating polymerization reactors according to the preceding claims, further characterized in that the product obtained is kept in oxygen-impermeable containers by means of nitrogen pressure. Process for the production of an anti-fouling agent for coating polymerization reactors according to the preceding claims, further characterized in that the product obtained is stored in oxygen-impermeable containers by means of pressure in nitrogen by means of the use of polyethylene terephthalate containers ( PET). 9. A process for the production of an anti-fouling agent for coating polymerization reactors according to the preceding claims, further characterized in that the product obtained is stored in oxygen-impermeable containers by means of nitrogen pressure by the use of transparent polyethylene terephthalate (PET) containers. 10. An anti-fouling product in the form of a liquid to be applied on the walls of a polymerization reactor, obtained in accordance with the method of the preceding claims wherein said anti-fouling product is obtained by means of the reaction between the sodium salt of hydroxymetansulfinic acid with naphthol following at least the process of claim 1, characterized in that it contains bisulfite and / or hydrosulfite radicals; it supposes the following characteristic: in the absence of oxygen, it is of a clear transparent color and in the presence of oxygen acquires a greenish or dark blue color; and if the contact with oxygen is interrupted, it reverts to its original appearance. 11. An anti-fouling product in liquid form for application on the walls of a polymerization reactor, obtained in accordance with the method of the preceding claims, further characterized in that anti-fouling product is obtained by reaction between the salt of sodium hydroxymethanesulfinic acid with 1-naphthol.