Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
  • C08F2/002—Scale prevention in a polymerisation reactor or its auxiliary parts
  • C08F2/004—Scale prevention in a polymerisation reactor or its auxiliary parts by a prior coating on the reactor walls

Definitions

• a film or coating of a water-soluble dye is applied to the interior surfaces of a polymerization reactor or vessel by merely contacting said surfaces with an aqueous solution of said dye.
• all exposed surfaces in the interior of the reactor, other than the walls, such as the baffles, agitator, and the like, are also treated in like manner.
• the surfaces are sprayed with water or the reactor is filled with water and drained, thereby surprisingly, leaving on said surfaces a tightly .adhering coating or film of the dye, which is not affected by the polymerization.medium in the sense of preventing it from achieving its assigned function, namely, the prevention of polymer buildup on said surfaces.
• dyes suitable in the practice of the present invention are those which contain in their chemical structure one or more of the following radicals: -COONa, -COOH, -SO 3 H, and -SO 3 Na, which radicals may be the same or different on any one dye structure.
• radicals may be the same or different on any one dye structure.
• These groups or radicals are usually attached to an aromatic nucleus. While other groups or radicals are present in most of the dyes, the above-named radicals are necessary for water solubility.
• the classes of dyes with one or more of said radicals are the azo dyes, suchasmonoazo and polyazo dyes; metal-containing azo dyes; mordant dyes; pyrazolones; stilbene dyes; phenols, naphthols; acid anthraquinone dyes; thiazoles; nitro dyes; xanthenes; and solubilized vat dyes, such as indigoids and anthraquinoids.
• the natural ionic dyes are also useful in the practice of the present invention.
• ionic dyes is meant the acridines, azines, oxazines and the thiazines.
• the natural ionic dyes exist as salts in the dry state and all have a heterocyclic ring system in their structure which is positively charged.
• the above-named dyes having one or more of the indicated radicals in their chemical structure there may be named 4-(p-nitrophenylazo)Resorcinol, Direct Blue 2B, Alizarin, Alizarin Yellow R, Alizarin Red S, Orange G, Phenolphthalein, Naphthol Yellow S, Congo Red, Eriochrome Black T. Tartrazine, Alizarin Irisol R, and Indigosol O.
• the ionic dyes there may be named Celestine Blue, Acridine Orange NO, Saframine T, Rhodamine 6G, Meldola's Blue, and Methylene Blue.
• the dye coating solution is made by conventional methods,.using ' heat and agitation where necessary.
• the dye is dissolved in water, preferably demineralized, to an extent such that the solids content of the coating solution does not prevent it being sprayed on the inner surfaces of the reactor through spray nozzles mounted permanently thereon.
• a coating solution having a solids content of water-soluble dye in the range of about 0.1% to about 20.0% by weight is satisfactory.
• the solids content depends upon the molecular weight of the water-soluble dye. That is, the solids content could, in certain instances, be greater than 20.0% or less than 0.1% by weight.
• additives may be employed in the coating solution, if desired, suchasplasticizers, stabilizers, lubricants, or fillers, and the like. Of course, when additives are employed, suitable adjustment in thesolids content of the coating solution is made.
• the preferred concentration of the dye in the coating solution is from 0.1% to 5.0% by weight.
• the temperature of the water when the dye is dissolved therein is not critical. Usually a temperature in the range of about 5°C. to about 100°C. is satisfactory. Agitation during dissolution of the dye is desirable.
• the coating solution is usually applied to the inner reactor surfaces by spraying. However, it is also possible to apply the coating solution by flooding the reactor and then draining, or by brushing or painting on the reactor surfaces, but spraying is the most practical and economical method of application. After spraying the coating solution on the inner surfaces and draining the reactor, the surfaces are sprayed with water and the reactor drained prior to charging the reactor with the polymerization mix.
• the present coating works well on glass or metal surfaces, such as stainless steel, and the like.
• the spraying of the coating solution on the inner surfaces of the reactor with water is believed to have a nonsolvent effect causing the dye to precipitate and adhere to the reactor surfaces. While the exact adhesion mechanism of the coating to the surface is not known for certain, it is believed to involve some type of electrical force or adsorption between the reactor surfaces and the dye. At any rate, the coating composition of the present invention does substantially eliminate polymer buildup on the reactor surfaces and what little polymer buildup, if any, that may occur, is of the "sandy" type which is of such a nature that it is readily removable from the reactor surfaces.
• the polymer buildup to be avoided is what is referred to as "paper buildup" since this type of buildup is very difficult to remove and usually requires hand scraping or a high pressure jet stream of water or other liquid. In either event, the reactor must be opened in order to clean the same which, of course, allows the escape into the atmosphere of unreacted monomer, such as vinyl chloride, which is to be-avbided.
• polymerizations may be run in a coated reactor before having to recoat the surfaces thereof.
• I have found it expeditious, and it is preferred, to coat the internal surfaces of the reactor after each polymerization run therein.
• the spray nozzles permanently mounted at strategic points'on the reactor, it is possible to reach all inner surfaces thereof without opening the reactor.
• the inner surfaces are sprayed with water and the reactor flushed.
• the coating solution is sprayed on the surfaces and the reactor is drained of the excess solution in such a way that the solution can be sent to a recovery system, if desired.
• the reaction to be carried out in the equipment may be commenced immediately, no particular modification of processing techniques being required due to the presence of the coating. Further, utilization of the internally coated reaction vessel of the present invention does not adversely affect the heat stability or other physical and chemical properties of the polymers produced therein.
• the polymerization process is usually conducted at a temperature in the range of about 0°C. to about 100°C. depending upon the particular monomer or monomers being polymerized. However, it is preferred to employ temperatures in the range of about 40°C. to about 70°C., since, at these temperatures polymers having the most beneficial properties are produced.
• the time of the polymerization reaction will normally vary from about 2 to about 15 hours.
• the polymerization process may be carried out at autogenous pressures although superatmospheric pressures of up to 10 atmospheres or more may be employed with some advantage with the more volatile monomers.
• Superatmospheric pressures may also be employed with those monomers having the requisite volatilities at reaction temperatures permitting reflux cooling of the reaction mixture.
• the polymerization process may be carried out utilizing a full reactor technique. That is, the reaction vessel is completely filled with the polymerization medium and kept that way throughout the reaction by constant addition thereto of water or additional make-up liquid containing the monomer or monomers in the same proportion as at start-up. Upon the addition of a certain predetermined about of liquid, the polymerization reaction is terminated, usually by the addition thereto of a short-stopping agent. The necessity for the addition of liquid is due to the shrinkage in volume of the reaction medium produced by the conversion of the monomer or monomers to the polymeric state.
• a rating scale was devised with respect to paper and sandy buildup, as referred to above.
• an uncoated reactor the inner surfaces of which are uncleaned or solvent cleaned, will have both types of buildup and is given a rating of 1.5. Any rating below 1.0 is good or a definite improvement. In other words, 0.0 rating is perfect, and so on.
• the rating on an uncoated reactor after three charges is 1.3. This is used as the control in the Example hereinafter.
• the coating solution after application to the internal surfaces of the reactor, does not have to be dried. Being able to employ water solutions not only has economic advantages, but also eliminates the need for using chemical solutions resulting in ease of handling.
• Coating of the internal surfaces of the polymerization reactor substantially reduces, and in many cases, practically eliminates polymer buildup on said surfaces during the polymerization reaction and thus results in increased production over a unit period of time.
• a little polymer buildup does accumulate on the interior surfaces, it is not of the hard, rough, difficult- to-remove type and is easily removed without employing the difficult tedious scraping methods that are presently necessary in the art.
• the present invention enables one to operate a closed polymerization system, which in the case of vinyl chloride polymerization, it has the advantage of reducing the parts per million of vinyl chloride in the atmosphere of the plant drastically and to a point that meets the new Governmental Regulations. Numerous other advantages of the present invention will be apparent to those skilled in the art.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polymerisation Methods In General (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

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• 1978
  • 1978-06-16 JP JP7228078A patent/JPS548690A/ja active Granted
  • 1978-06-19 EP EP78100189A patent/EP0000166A1/de not_active Withdrawn

Patent Citations (4)

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