DE3815397A1 - Autoclave coating - Google Patents

Abstract

To prevent the formation of polymer deposits on the wall or internal fittings of autoclaves during the free-radical polymerisation of ethylenically unsaturated compounds, a mixture is applied comprising two components, A and B. Component A is an epoxy resin or epoxy precondensate, preferably a polyglycidyl ether or polyglycidyl ester. Component B comprises aromatic or heterocyclic compounds having at least one primary or two secondary amino groups and, preferably, further polar substituents which act, on the one hand, as curing agent for the epoxy resin and, on the other hand, as inhibitors of the formation of deposits. The mixture is applied in solution or suspension and is cured at from 10 to 120@C.

Description

The invention relates to an autoclave coating for Ver Prevention of the formation of polymer coatings on the autoclave used in the radical polymerization ethylenically and saturated compounds.

In the production of polymers ethylenically unsaturated compounds, for example in the radical Polymerization of homopolymers or copolymers of vinyl chloride are formed in the course of the polymerization at the coming in contact with the reaction mixture, surface Chen of the autoclave or on the autoclave internals poly merisate coverings. These polymeric wall coverings cannot are further processed and therefore reduce the polymer station yield. Furthermore, these coverings lead to deterioration product quality, as they change during the Detach polymerization and in the polymerization product Cause specks. The polymer coatings on the Autokla walls and fittings also hinder the removal of the Heat of polymerization over the autoclave wall, whereby un more economical longer reaction times, as well as an uncon trolled course of the reaction and thus a risk to the Operational safety must be accepted.

Such coverings and incrustations are therefore unavoidable to remove. This is usually done by spraying  the autoclave with high pressure water. This allows however only remove the slightly adherent polymer coverings nen, while the remaining residues in the following An rates lead to increased deposit formation. Therefore, the Reactor are opened after a few approaches and under elaborate safety precautions by hand Spatula to be cleaned. Do this cleaning work at uneconomically long downtimes and are on problematic due to the environmental hazard from the remaining VC. In addition, with the cleaning work with the Spatula injuries or roughening of the autoclave walls do not avoid, which in turn leads to an intensified crust education in the following approaches.

Because of this problem, a variety of procedures were developed, all of which had the objective that Bil Formation of such polymer coatings during the polymerization reduce or prevent.

From DE-C 22 39 942 (US-A 38 42 055) it is known that Autoclave walls and internals during the polymerization spray to prevent the formation of incrustations other.

It is also known to avoid polymer deposits the autoclave walls with insoluble organic compound coatings containing polar groups. At these connections are, for example, orga African dyes such as nigrosine black (GB-A 15 62 290) or Polycondensates such as polyimines, amines or phenols, the ge are possibly networked (US-A 30 55 876). The effect however, these coatings are unsatisfactory; moreover if they detach from the wall, they will discolor the Pro ducts and negatively affect the course of polymerization  (Coarsening of the grain, reduction of the thermal load speed of the polymer).

DE-A 27 03 280 (US-A 41 43 097) describes a process ren, in which the autoclave walls with derivatives of Benzthia zol-2-one hydrazone, which is in a carrier material, e.g. on Alkyd or epoxy resin base, embedded, coated will. A disadvantage of this method is that the effect substance is only physically bound in the carrier material and is therefore easily washed out. In addition, the manufacture (exact mixing ratio of epoxy, hardener, active substance stamping) and storage (short pot life) of the coating material problematic.

Okada et al. (US-A 43 55 141) describe an autoclave coating which is produced in a complex reaction lasting several hours by condensation of a phenol-formaldehyde precondensate with NH ₂ - or NO ₂ -substituted aromatics. The auto klav must be re-coated before each polymerization batch.

In US-A 43 20 215 a coating is claimed those by condensation of optionally substituted Ortho-dihydroxyaromatics with aldehydes is produced. The Coating agent must also in this process a reaction that lasts several hours, before it is applied to the autoclave wall.

Englin et al. (EP-A 8 887, US-A 42 62 109) claim one Mixture of an epoxy resin and a special condensate, that by reacting an aliphatic amine with a aromatic amine and an aromatic hydroxy compound, also in a separate reaction with distillation and Drying operations.  

In DE-A 34 05 436 (US-A 46 61 569) the coating the autoclave wall with an oligomer, preferably from Bisphenol A diglycidyl ether and, for example, one more Substituted aromatics, including hydroxybenzoe acid or aminosalicylic acid, claimed. In a particular of the preferred embodiment, these oligomers in Mixture with bisphenol A diglycidyl ether on the wall wear. This leads to the formation of polymer chains and thus to improve the adhesion of the coating. Disadvantageous this procedure is complex to manufacture the coating. In a reaction lasting several hours, one ethanolic solution of bisphenol A diglycidyl ether added ethanolic solution of the respective reactant and then stirred. Then the ethanol is removed distilled and the oligomer isolated. To apply on the autoclave wall must ge in ethanol again solves that will eventually harden on the autoclave vein wall is evaporated again.

The object of the invention was therefore a coating for To make available, on the one hand, the polymer attachment effectively inhibited, i.e. hydrophilizing and radical has hibernating functional groups; for two Excellent metal adhesion around the contact to prevent product minimization and a continuous driving style without renewing the coating between the individual approaches. But above all, it should Simply add coating from common commercial products places and without any intermediate to be synthesized levels get along.

Surprisingly, this was achieved by commercially available epoxy resins or epoxy precondensates in Ge mixed with components applied, on the one hand as a hardener  act for the epoxy resins and thus good mechanical egg guarantee properties of the coating, and secondly still have a radical inhibiting effect and thus the formation of Wall incrustations can effectively inhibit.

The invention relates to an autoclave coating for Prevention of the formation of polymer deposits on the car clave wall in the radical polymerization ethylenically unsaturated compounds, characterized in that for coating two components A and B in solution or Suspension in an organic solvent or water, or Mixtures of which are applied to the autoclave wall and the application is cured at 10 to 120 ° C, component A being polyglycidyl ether, Polyglycidyl esters or mono- or di-oxirane-substituted aliphatic or cycloaliphatic alkene oxides or mixtures is about and component B is an aromatic or an O-, N- or S-heterocycle, as direct substituents or in alkyl side chains at least one primary or two secondary Amino groups, and preferably further amino, hydroxyl, Mercapto, ether, carboxyl, sulfonyl or nitro groups carries, or represents mixtures of such compounds, the quantitative ratio of components A and B so ge is chosen that an epoxy unit in component A 0.5 up to 2 N-H bonds in component B.

The polyglycidyl ethers mentioned as component A are included for example diglycidyl ethers such as bisphenol A diglycidyl ether, Bisphenol-F-diglycidyl ether, butanediol or hexanediol di glycidyl ether or the diglycidyl ether of hydroquinone or Catechins. Bisphenol-A diglycidyl is preferred ether used.  

Examples of diglycidyl esters are tetra or hexahydro phthalic acid diglycide ester. Aliphatic or cycloaliphatic Alkene oxides such as 3,4-epoxycyclohexyloxirane can also can be used as component A.

Higher-functional epoxides can also be used as component A. such as triglycidyl ethers such as 4-aminophe nol triglycid ether and triglycid isocyanurate, or tetragly cidethers such as diaminodiphenylmethane tetragly cidether. Triglycid isocyanurate or Di aminodiphenylmethane tetraglycidether used.

Examples of component B are aniline and anilinderi vate, such as 2-, 3- or 4-aminophenol; ortho, meta or para-anisidine; ortho-, meta- or para-toluidine; the ver various dimethoxyanilines, 3-methoxy-4-nitroaniline, 2- Aminophenol-4-sulfonic acid, ortho-, meta- or para-nitro aniline; Aminoacetophenone, anthranilic acid, 4-dimethylamino aniline or 4-aminosalicylic acid.

Component B can also differ from multinuclear aromatics derived, such as 1-naphthylamine, 2-naphthylamine, 1- Naphthylamine-2-sulfonic acid, 1-naphthylamine-3,6-disulfonic acid, 1-amino-5-naphtol-7-sulfonic acid or 1-aminoanthraquinone.

He is also suitable for use as component B. terocycles such as 2-, 3- or 4-aminopyridine; 2-aminopyridine-3- carboxylic acid, 8-aminoquinoline, 2-amino-6-hydroxypyridine, 2- Amino-4-methylthiazole.

Examples of compounds having multiple amino groups are ortho-, meta- or para-phenylenediamine; Naphtalin-1,8-di amine, 4-methyl-1,2-phenylenediamine, 1,4-diaminoantachinone, 4,4'-diaminodiphenylmethane.  

Examples of components B in which the reactive amino group in the side chain are tyrosine, mescaline, py ridoxamine, dopamine, 3,4-dihydroxybenzylamine, noradrenaline.

To produce the coating composition, the Components A and B in an organic solvent or water or mixtures thereof dissolved or suspended. From the comm Components A and B can be made separately those that are combined before coating. The compo However, parts A and B can also be used in whole or in part Mixture in the respective solvent or solvent amount be mixed or suspended.

Preferably one goes in the preparation of the solutions or Suspensions so that first separate solutions or Suspensions of A and B in a molar concentration of 0.05 to 1 mol / l are produced and these two Lö solutions or suspensions combined shortly before coating will. The quantitative ratios of A and B selected so that in the recipe, which is ultimately based on the Autoclave wall and the internals is applied to a Epoxy unit in component A 0.5 to 2 NH bonds of Component B are coming.

If necessary, the combined solutions can be adjusted to pH values from 7 to 12, preferably from 9 to 12, for example by adding (earth) alkali metal hydroxide, such as NaOH, Ca (OH) ₂ or KOH, before application.

Suitable solvents or suspension media are water or organic solvents, mixtures of water and or ganic solvent or mixtures of various organi shear solvent. As organic solvents preference is given to polar solvents which are free from amino, imino,  amido or imido functional groups are preferred boil at a maximum of 120 ° C. Are particularly preferred Propanone, butan-2-one, n- and iso-propanol and in particular Ethanol, methanol and tetrahydrofuran (THF).

Before applying the coating to the autoclave wall it is advantageous to remove these from adhering polymer residues and to get rid of other impurities. This is more common wise by mechanical cleaning, treatment with solution agents, acids, oxidizing agents or high pressure water. The The coating composition is applied by means of common methods, such as by litigation cleaning, spraying or rinsing the autoclave. Subsequently is used to remove the solvent and harden the Coating for preferably 30 to 120 minutes before heated preferably 10 to 120 ° C. The coating is made before preferably all in contact with the reaction mixture upcoming surfaces. Are next to the autoclave wall this, for example, internals such as pipes, valves, Baffles, sensors, pressure compensation vessels, coolers and Tank neck.

Before the polymerization begins, the treated areas chen, preferably rinsed with water. After renewed Drying the treated reactor surfaces can do this treatment if necessary be repeated. Usually enough however, the unique coating completely.

Due to the very good liability of the fiction appropriate coating on the inner surfaces of the Polymerisa tion reactor there is no need to renew the coating between the individual polymerization batches. It is sufficient rather, loosen the container by rinsing with water  Free polymer residues and the coating first to renew after 20 to 70 reaction cycles. The Be Layering systems do not show any dissolution or detachment rend the polymerization, so that neither the polymerization product is still contaminated.

The method according to the invention can be based on a number of Monomers are applied in bulk or in aqueous Medium after the suspension, emulsion or microsuspen sion processes are produced. As examples are here the styrenes, acrylic and methacrylic esters, vinyl esters, vinyl halides and vinylidene halides and mixtures thereof called. The method according to the invention is particularly suitable for the homo-, co- and graft copolymerization of vinyl chloride. The polymers can in the usual way and Worked up way, for example, the ent standing suspensions, dispersions or latices or poly degassed, filtered, coagulated in the usual way, dried or stabilized.

The following examples serve to further explain the Invention. They represent preferred embodiments of the Er invention without restricting it.

Implementation of the coating and polymerization in the Examples and comparative examples:  

The tests were carried out in a 1 liter steel autoclave with an impeller stirrer. For pre-cleaning, the autoclave was filled with THF and stirred at 80 ° C for 3 hours. The THF was drained and this treatment with DMSO repeated. Finally, the autoclave was rinsed with deionized water and dried at 60 ° C. The autoclave was coated with the components given in the examples (comparative examples 1, 2 without coating). To remove the solvents and to harden the coating, heating was continued at 90 ° C. for one to two hours. For the polymerization, the autoclave was treated with 450 parts of deionized water, 0.2 part of dilauroyl peroxide, 0.5 part of di acetyl peroxodicarbonate and 16.4 parts of a 5.5% solution of a partially saponified polyvinyl acetate (viscosity approx. 5 mPa.s in 4% solution in H ₂ O, saponification number approx. 270).

In the closed reactor was by repeated evacuation and venting with nitrogen largely displaces the air. After 225 parts of vinyl chloride had been pressed in at ei ner stirrer speed of 400 rpm and a reaction temperature polymerization at 61 ° C. After a pressure drop of 3 bar, about 3 hours after the start of heating, the reaction became by cooling and distilling off the unreacted mono meren ended. The PVC suspension was filtered and the Polymer yield after drying determined by weighing. The K- The value was around 64. After rinsing the autoclave with Water followed the next polymerization after the same Method.

After a sequence of 4 such approaches the amount of PVC-An accumulated after the series was determined Baking on the inner reactor wall by boiling the Autoclave with tetrahydrofuran at 90 ° C for one or two Hours. After distilling off the solvent and the The residue amount was dried by the residue Weighing determined.  

The reactor was used to remove residue residues Start of a new series with an additional hour at 90 ° C DMSO cleaned.

The type of coating composition and the one used quantities and the percentage of polymer caking the reactor wall in the individual examples or ver Similar examples are shown in Table 1.

Example 1:

1.4 g of 4-aminophenol were dissolved in 70 g of ethanol at room temperature. At the same time, a solution of 3.6 g of an epoxy resin composed of bisphenol A and epichlorohydrin (MW 370) in 30 g of ethanol was prepared at 40 ° C. The solutions were then combined and made alkaline with 0.5 ml of 2N NaOH. The autoclave wall was coated with the resulting solution. After a series of 4 polymerizations, the wall had 0.15 parts (0.02% by weight) of polymer caking.

Examples 2 to 10:

Carried out analogously to Example 1; instead of a single one Amine was partially in solution 2 (Examples 2 and 5) Mixture of different amines or a mixture of amine and Epoxy (Example 6) used. In Examples 8-10 no alkali was added. The exact re recipes and the degree of polymeric deposits on the Autoclave walls are listed in Table 1.

Examples 11 to 13

Carried out analogously to the previous examples. However, the polymerization formulation was changed by adding 20 mg Na ₂ HPO ₄ × H ₂ O and 30 mg NaHCO ₃ .

Comparative Examples 1 and 2:

A series of 4 polymerizations according to the above procedure writing was carried out without any autoclave coating guided. The series in comp. Ex. 1 led to 5.1 parts (0.5 % By weight) wall caking; the series of comp. ex. 2 even resulted 13.4 parts (1.7% by weight) of polymeric wall encrustation.

Comparative Example 3:

The reactor was analogous to DE-A 34 05 436 (Example 23) coated and the coating for one hour at 95 ° C. burned. After a series of 4 approaches there were 0.14 parts (0.02% by weight) polymeric wall encrustation present.

Comparative Examples 4 and 5:

Execution analogous to the previous comparative examples. However, the polymerization formulation was changed by adding 20 mg Na ₂ HPO ₄ × H ₂ O and 30 mg NaHCO ₃ .

Claims (5)

1. Autoclave coating to prevent the formation of polymer deposits on the autoclave wall in the radial polymerization of ethylenically unsaturated compounds, characterized in that for coating two components A and B in solution or suspension in an organic solvent or water, or mixtures thereof on the autoclave wall applied, and the application is cured at 10 to 120 ° C,
where component A is polyglycidyl ether, polyglycidyl ester or mono- or di-oxirane-substituted aliphatic or cycloaliphatic alkene oxides or mixtures thereof, and component B is an aromatic or an O-, N- or S-heterocycle which carries at least one primary or two secondary amino groups and preferably further amino, hydroxyl, mercapto, ether, carboxyl, sulfonyl or nitro groups as direct substituents or in alkyl side chains, or represents mixtures of such compounds,
the quantitative ratio of components A and B is chosen such that 0.5 to 2 NH bonds in component B come to an epoxy unit in component A. 2. Autoclave coating according to claim 1, characterized records that as component A a diglycidyl ether or Diglycidyl ester is used. 3. Autoclave coating according to claim 1, characterized records that as component A triglycid isocyanurate or a diaminodiphenylmethane tetraglycidyl ether is set.   4. Autoclave coating according to claim 1, 2, 3 or 4, because characterized in that components A and B in Solution or suspension, at a concentration of 0.05 up to 1.0 mol / l. 5. autoclave coating according to claim 1, 2, 3, 4 or 5, characterized in that the components A and B in alkaline solution or suspension for coating be applied.