MXPA97008702A - Anti-incrustation agent for reinforcing polymerizac reactors - Google Patents

Abstract

The object of the invention is to provide an anti-caking agent for coating the polymerization reactors for monomers, of the liquid types, obtained by means of the condensation of naphthols with an aldehyde crosslinking product, characterized in that: to obtain the condensate, a hydrosulfite is used; contains hydrosulfite and / or bisulfite and / or bisulfite radicals, the condensate is made in such a way that in the absence of oxygen it is in the form of a transparent liquid color

Description

RNTI-INCRUSTATION AGENT FOR COATING POLYMERIZATION REACTORS TECHNICAL FIELD The present invention relates to an anti-fouling agent for coating polymerization reactors. Anti-fouling agents for polymerization reactors are already well known in the prior art.

TECHNICAL BACKGROUND In the present technique there are also different types of anti-fouling agents for each type of polymer. For example, the ani-incrustation agent for the production of vimlo chloride is not the same as that used in the reactor for the production of polystyrene or that used for the production of acrylic polymers, etc. This is in fact needed in the storage of different products with all the consequences of high maintenance costs. In addition, even reactors must be specifically dedicated to only one type of reaction, resulting in increased costs.

DESCRIPTION OF THE INVENTION A first aim of this invention is to make an anti-fouling agent that operates well in any type of polymerization reactor and for most of the varied types of different materials, therefore for vinyl chloride, as well as for styrene and acrylic polymers , etc. In the specific case of vimlo chloride, for example, it is known that in the reactors a substantial deposit of scale is formed which have as main disadvantages: a consistent maintenance to remove the scale with consequent interruption of production, opening the reactor and, therefore, with high amounts of emissions of monomeric vinyl chloride (VCM) gaseous into the atmosphere; - contamination of the resulting product as some of the encrusting parts pass to the respective polyrneized product with the consequent worsening in the quality and complaints of the users; - definitive obstacles in the productive system and in ecological problems for the areas in which industrial plants of polyvinyl chloride (P.V.C.) operate. This problem exists for virtually all types of polymerizations. In addition, the anti-fouling products intended to coat the surfaces of the respective reactors are of a bluish or dark brown color almost black, whereby the particles that are detached from the crust, contaminate the polymer obtained (for example, polyvinyl chloride). obtained) of the reactor in the form of black dots, which for example in the finished products worsens the qualitative aspect of the same product. In addition, it should be noted that the material particles that are detached from the crust of the wall, end in the reaction product, constituting the contamination of the same, generally dealing with toxic products. In the prior art, the technique of condensation or polycondensation of naphthols with aldheidic crosslinking product (eg, forrnaldehyde, and others), to obtain anti-fouling products is known. For this purpose, it refers to - U5-A-3669946 (filed in the United States on August 31, 1970 and described on June 13, 1972), which suggests the use of formaldehyde and mixed ketone, naphthol, etc. materials. , and also alpha-naphthylaniline and nigrosine. This technique predivulgates the general concept of formation of condensed anti-fouling agents that start from the combination of formaldehyde and naphthols. - U5-A-3825434 of June 23, 1974, describes an anti-fouling agent for the polymerization of vmilo chloride, obtained from the condensation of phenol with formaldehyde, where obviously by definition in the patent the product obtained is always classified as belonging to the family of phenol-for aldehyde or polyarylphenol. - US-, 068, 059 (filed on February 17, 1977, published January 10, 1978) further explains the importance of using anti-fouling agents, products that in their chemical structure contain one or more of the following groups: -OH; -C00H; S03H and S03Na. These groups are usually fixed to an aromatic nucleus. - EP-fl-0052421 discloses a process for obtaining an anti-fouling product that differs from the fact that formaldehyde is reacted with effective 1-naphthol (alpha-naphthol) in the nuclear positions 2 and 4 are not replaced and the Nuclear position 3 is not replaced or have a substitute that is not a strong electron attractant to obtain a condensate. It is also appropriate to note that the use of naphthols is already suggested in US-A-3669946, so it is obvious to use 1-naphthol in the above procedure in place of the phenols as mentioned. Even in this case, the product obtained according to chemistry should always be considered as belonging to the polyarylphenol family. 3P-A-5-230 112 refers to a condensation product based on an aromatic amine and aromatic hydroxyl compounds and is prepared with the use of reaction termites. In particular, it is suggested to use an ileol solution of 4-arn? Nodifen? Larn na and 7-d? H? Drox? Naphthalene heated in the presence of p-benzoquinone (catalyst) for a certain period combined with an aqueous solution of Rongalite, stirred for a certain period to give a condensation product. These latter products have the disadvantage of providing, in contact with oxygen, a dark brown or dark blue almost black product, and not always being suitable for use in polymerization sectors with different materials. In particular, the latter is worse than the previous ones because Rongalite is used to terminate the reaction to give a condensation product. The product of condensation is one of the causes that gives the product dark brown or dark blue almost black, because the condensed particles are of a visible size and produce in the suspension a dark bluish color. Obviously, this dark bluish color gives the resulting polished product a visible contamination. The reaction is difficult to control and leads to crosslinked products insoluble in aqueous alkaline solution (condensation). In addition, the coating of the reactor with these anti-fouling compounds (anti-fouling agents) is easily consumed by dispersing the same in the reaction material, contaminating it with color and with toxicity. In addition, it should be noted that these anti-fouling agents are of low efficiency, or however require a massive deposit of scale on the wall, to avoid certain uses, such as health and food, where the required product limits contamination in the finished product are decidedly lower, etc. However, to obtain good antifouling efficiency, they must be deposited on the wall in large quantities which also affects the cost. The color of the anti-fouling agents of the known art is dark and can be hardly appreciated by the user because it looks like 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 something much more severe is what was already mentioned, that during the reaction particles of crust are detached and mixed with the polymer. Since these crust parts are black, it is obvious that there is a qualitative worsening of the product. The purpose of the present invention is to pump 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 that once applied to the reactor wall was substantially colorless. It is known that to whiten an aromatic product, co-dyes or, for example, sodium hydrosulfite or potassium hydrosulfite are used. The inventors fear the idea of translating this principle of banal bleaching into the manufacture of anti-fouling agents to obtain * the desired colorless product. Attempts to use hydrosulphite together with formaldehyde and 1-naphthol have given negative results because the resulting condensate always remains bluish in color, tending to form deposits even when driving in the absence of oxygen, for example, in the presence of my oxygen. When proceeding with the investigation, it was thought to avoid the reaction between formaldehyde and 1-naphthol in order to avoid the use of formaldehyde as such and the use of an aldehyde product that nevertheless allows to obtain a colorless condensate product. After numerous experiments, it was found that the best product to combine with 1-naphthol is Rongalinte. The result was surprising and the content condensed product was perfectly colorless. In the tests of anti-fouling in the polyvinyl chloride reactors surprising results were obtained both for yield, quality and production, being able to be used also by means of the production of other polymers. Rongalite is the commercial name of a common product that is chemically defined as forrnaldehyde-sodium sulphoxylate or sodium hydroxymetansulfmate, with the formula: 0 = • ONa CH2OH This product can be obtained by reacting hydrosulfite with formaldehyde and therefore the result is no longer a formaldehyde. Therefore, for this reaction the condensed product was no longer dark bluish or even black, and obviously due to the primary reaction of 1-naphthol with formaldehyde was inhibited, contrary to the teachings of the anti-fouling production of the prior art. In conclusion, it was discovered that an interlacing-aldehyde agent should be used, characterized in that it was obtained by means of an aldehyde and hydrosulfite reaction. Using this sulfoxylate in a mixture, sodium hydroxy methane sulfinate, with 1-naphthol in the proportions by weight of 1 to 1.5, in aqueous solution of 10% to 40%, and bringing the solution to a temperature between 70 ° and 95 ° C. in an atmosphere of nitrogen, to an alkaline environment (pH 11-13), therefore, a condensate product of a clear transparent color was obtained, completely reaching the predetermined purpose and without reducing the quality of the product, and in fact improving it. The product condensed in this way is physically obtained from a clear, transparent appearance but if it is left for a certain time in the presence of air, it oxidizes it slightly, tending toward a greenish-blue color. However, the surprise is that, if the contact with oxygen is interrupted, the product returns to its original appearance, transparent clear. This physical behavior proves that a completely new product has been achieved structurally different compared to the products of the prior art, where this physical phenomenon can not be observed. From the chemical and spectroscopic analyzes, several hypotheses have been postulated about the structural 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 in the condensate. of a reducing activity, probably due to the presence of a reducing radical. In short, in accordance with the most probable deductions, it must be treated with a bisulfitic adduct of the prirner product of the reaction that is formed between 1-naphthol and Rongalite. The product applied on the surface of the reactor in an atmosphere devoid of oxygen, after drying, gives an opaque white opaque color, contrary to the dark color of the anti-fouling agents present. Therefore, the results 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. Advantageously it has been found that the best preservation is by means of pressure of the container with neutral gas, preferably nitrogen. Equally advantageous it was discovered that the most effective containers are glass or, even better, polyethylene terephthalate "PET" (in such a way that the containers do not contaminate and are completely recirculated). With the use of the container in "PET" (flexible container), another important physical behavior was discovered: when a 1 liter bottle, for example, of the product is opened in accordance with the present invention before hermetically closed and that, given the transparency it is transparently visible, leaving the bottle open for a few minutes at a time, the contained product is obscured; - closing a bottle again after the product is obscured, it is noted that the flexible PET bottle retracts slightly. This could be justified in that the product destroys all the oxygen that remained in the air that is contained in the bottle before opening it and when it has been closed. After that the product returns to a clear transparent color as before, as if nothing had happened. This proves that the product is self-protecting or self-reconstituting in its original appearance, with the condition, however, that it stays away from contact with air. The product preserved as such remains unchanged, of a light color, and in the experiment of application on the wall of the reactor * (obviously in the presence of inert gas) the anti-fouling agent is deposited on the wall as a thin layer which, As mentioned earlier, it becomes colorless and transparent. Advantageously it has been 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 spraying water vapor at high temperature. Spraying the product with water vapor at elevated temperature (as high as possible) gives the maximum adhesion result. Since the reaction of polymerization in the reactor lasts on average from 4 to 6 hours, it is evident that this time and in the absence of oxygen, there are no substantial degradations of the product, and consequently irnometric decays, so once the The polymerization reaction has been completed and once the percentage of anti-fouling agent is integrated into the polished mass, it will not suffer any significant contamination and degradation. Instead, in the prior art using previously known anti-fouling products, it is feared that the reactor will be completely washed and emptied of any minimum amount of product residue applied to the wall as an anti-fouling agent, with this new product, it is possible to send the reactor rinse to the tank 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 chloride polymerization reactors. monomepco vinyl with the technique named by the experts of the sector-horn of closed main hole. Since Rongalite can also be prepared with a molar excess of hydrosulphite, even using this product, a condensate of analogous or improved performance (largely condenser reducing) is obtained. In this case, as in the previous ones, the activity of the product always occurs from the presence of bisulfate derivatives and in particular of bisulfate radicals present in the condensate, this characteristic clearly distinguishes the new product from that of the prior art, and in particular with reference to the resulting structure of the condensed product, this is identified as innovative by the presence of a carbon atom interposed between the aromatic ring and the sulfomco salified group. It is also proved that other naphthols with more or less similar results can be used instead of 1-naphthol. Obviously, for the aforementioned purpose rather than to cause the formaldehyde to react with the sodium hydrosulfite to obtain Rongalite, the formaldehyde could be reacted with potassium hydrosulfite obtaining an equally effective product to be used for the formation of the condensate. However, it is important that the hydrosulfite prevents evolution of the reaction to stable condensed forms. From the experiments, it is also proved that the aqueous support can be replaced by other supports, for example, acetone, obtaining satisfactory results, if not better (in addition to the cost). Equally advantageous, it has been discovered that the same results are obtained with the same advantages, if not better, by using an alcohol as a vehicle and in particular: methyl alcohol, which, although it is advantageous in terms of cost, has the same effect. disadvantage of being toxic, but completely compatible with the polyvinyl chloride reaction used by this vehicle; ethyl alcohol, which has the advantage of not being toxic, and is completely compatible with the reaction of polyvinyl chloride used by this vehicle. -Isopropyl alcohol, with substantially equivalent results. The fundamental characteristic, however, is always to have a clear transparent colored appearance in the absence of clean liquid oxygen. For clarity purposes, a substantial, almost colorless appearance may vary from opalescent white to light yellow, light ivory, light ocher or light beige to clear limits to give the liquid the appearance of clean water.

Claims (7)

NOVELTY OF THE INVENTION CLAIMS 1. - A liquid anti-fouling agent for coating polymerization reactors for ordinary, obtained by means of the condensation of naphthols with an interlayer-aldehyde product characterized in that: to obtain the condensate, a reaction is carried out in a basic environment of hydrosulfite and compound of formaldehyde combined with 1-naphthol; contains hydrosulfite and / or bisulfite and / or bisulfite radicals; it is in the form of clear transparent colored liquid; and it is stored in the absence of oxygen. 2. A liquid anti-fouling agent for coating the polymerization reactors according to claim 1, further characterized in that it contains an equal amount of hydrosulfite and / or bisulfite and / or bisulfite radicals in such a way that: absence of oxygen, it is of clear transparent color, in presence of oxygen, it turns greenish or dark bluish color; and if the contact with oxygen is interrupted, it reverts to its original appearance. 3. A liquid anti-fouling agent for coating the polymerization reactors according to claim 1, further characterized by containing sodium hydrosulfite. 4. - A liquid anti-fouling agent for coating the polymerization reactors according to claim 1, further characterized by the fact that it contains potassium hydrosulfite. 5. A liquid anti-fouling agent for coating the polymerization reactors according to claim 1, further characterized by the fact that it is packed in oxygen-impermeable containers. 6. A liquid anti-fouling agent for coating the polymerization reactors according to claim 1, further characterized by the fact that it is packed in oxygen-impermeable containers under pressure in inert gas. 7. A liquid anti-fouling agent for coating the polymerization reactors according to claim 1, further characterized by the fact that it is packed in oxygen-impermeable containers under nitrogen pressure. 8. An anti-fouling agent for coating the polymerization reactors according to claim 1, characterized in that it is packed in oxygen-impermeable containers, said containers made of polyethylene terephthalate (PET). 9. A liquid anti-fouling agent for coating the polymerization reactors according to claim 1, further characterized by the fact of being

1. 7 packed in oxygen-impermeable containers, the polyethylene terephthalate (PET) containers being made transparent. 10. A liquid anti-fouling agent for coating the polymerization reactors according to the preceding claims, characterized in that it is in an aqueous support. 11. An antifouling liquid agent for coating the polymerization reactors according to the preceding claims, characterized in that they are an acetone support. 1

2. A liquid anti-fouling agent for coating the polymerization reactors according to the preceding claims, characterized in that it is in an alcoholic support. 1

3. A liquid antifouling agent for coating the polymerization reactors according to the preceding claims, characterized in that it contains acetone. 1

4. A liquid anti-fouling agent for coating the polymerization reactors according to the preceding claims, characterized in that it contains methyl alcohol. 1

5. A liquid anti-fouling agent for coating the polymerization reactors according to the preceding claims, characterized in that it contains ethyl alcohol. 1

6. A liquid anti-fouling agent for coating the polymerization reactors according to the preceding claims, characterized in that it contains isopropyl alcohol. 1

7. A liquid anti-fouling agent made by reacting hydroxy methane sulfonate with a mixture of 1-naphthol and polyvinyl alcohol having a degree of hydrolysis greater than 99% OH and the molecular weight is between 70,000 and 90,000.