http://rdf.ncbi.nlm.nih.gov/pubchem/patent/NO-125633-B
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| Predicate | Object |
|---|---|
| assignee | http://rdf.ncbi.nlm.nih.gov/pubchem/patentassignee/MD5_7995660796c354a2881371a7406bf6dd |
| classificationCPCAdditional | http://rdf.ncbi.nlm.nih.gov/pubchem/patentcpc/B01J2219-185 http://rdf.ncbi.nlm.nih.gov/pubchem/patentcpc/B01J2219-182 http://rdf.ncbi.nlm.nih.gov/pubchem/patentcpc/B01J2219-1946 |
| classificationCPCInventive | http://rdf.ncbi.nlm.nih.gov/pubchem/patentcpc/C08F259-04 http://rdf.ncbi.nlm.nih.gov/pubchem/patentcpc/B01J8-36 http://rdf.ncbi.nlm.nih.gov/pubchem/patentcpc/B01J8-382 http://rdf.ncbi.nlm.nih.gov/pubchem/patentcpc/C08F14-06 |
| classificationIPCInventive | http://rdf.ncbi.nlm.nih.gov/pubchem/patentipc/B01J8-38 http://rdf.ncbi.nlm.nih.gov/pubchem/patentipc/B01J8-36 http://rdf.ncbi.nlm.nih.gov/pubchem/patentipc/C08F2-44 http://rdf.ncbi.nlm.nih.gov/pubchem/patentipc/C08F2-34 http://rdf.ncbi.nlm.nih.gov/pubchem/patentipc/C08F2-00 http://rdf.ncbi.nlm.nih.gov/pubchem/patentipc/C08F14-00 http://rdf.ncbi.nlm.nih.gov/pubchem/patentipc/C08F14-06 http://rdf.ncbi.nlm.nih.gov/pubchem/patentipc/C08F259-04 |
| filingDate | 1967-08-23-04:00^^<http://www.w3.org/2001/XMLSchema#date> |
| inventor | http://rdf.ncbi.nlm.nih.gov/pubchem/patentinventor/MD5_263ea37216f3262d6a5728214d2dcf7e |
| publicationDate | 1972-10-09-04:00^^<http://www.w3.org/2001/XMLSchema#date> |
| publicationNumber | NO-125633-B |
| abstract | The present invention relates to a process for the polymerization and / or copolymerization of vinyl chloride in the gas phase. The methods hitherto used for the polymerization of vinyl chloride, namely suspension, emulsion and bulk processes, all have in common that they are carried out in the liquid phase. . In all these processes, the reaction mass formed by a liquid phase consists of. end of the monomer and optionally a diluent in which the monomer is in a more or less fine dispersion. However, these processes have several disadvantages. Polymers obtained by means of suspension and emulsion processes thus have altered properties due to various contaminants added to the polymerization medium. Resins obtained by these methods have a transparency which is insufficient for certain applications. On the other hand, these methods cause the formation. of crusts in polymerization autoclaves, which is associated with major disadvantages, especially as regards the polymerization yield, and causes a contamination of finished products. In addition, the formation of these reductions requires extensive purification of the polymerization autoclave. It is especially this crust formation in the polymerization reactors which has delayed the use of continuous industrial processes for polymerizing vinyl chloride. Furthermore, the polymers obtained by the liquid phase process must be separated from the liquid phase and dried, while the monomer should often be purified after has been recycled to the polymerization reactor. Attempts have been made to eliminate some of these disadvantages by reducing the volume of the liquid phase present during the polymerization. According to French patents 1,087,197 and 1,117,753, in the absence of a solvent and a diluent, a mixture of liquid monomers and powdered polymers is polymerized, the ratio of the solid to the liquid phase always being controlled in such a way that the reaction mass retains its powdery nature.However, this method is associated with serious disadvantages of a technological and economic nature. Namely, it is necessary to carry out the polymerization in the presence of enormous amounts of powdered polymers (1/4 to 1/3 of the reactor volume) in order for the reaction mixture to retain its powdery character, while using small amounts of monomers to be polymerized. For example, polymer powders present in the reactor must have a rather large particle size, preferably a size between 0.1 and 2 mm. Furthermore, the polymer granules should be porous to facilitate the absorption of liquid monomers. Finally, the process requires continuous addition of the catalyst throughout the polymerization to ensure that the polymerization proceeds. However, the polymer produced under these conditions is heavily contaminated with catalyst residues. By studying the prior art, it can be seen that although one was aware of the disadvantages associated with the presence of a liquid phase during the polymerization of vinyl chloride and has tried to eliminate these disadvantages of reducing the volume of. this phase, however, it has always been assumed that the presence of a flow-. It is now found that it is possible to carry out the polymerization of vinyl chloride under such conditions that during the polymerization there is never a liquid phase in the polymerization medium and that this mode of operation allows to avoid all the above-mentioned disadvantages. The present invention relates to a process for the polymerization and / or copolymerization of vinyl chloride in the presence of powdered catalysts, optionally in the presence of inert solids, preferably powdered polyvinyl chloride, and the polymerization is carried out with gaseous monomers. at a pressure lower than the saturated vapor pressure of the vinyl chloride at the polymerization temperature, and in the complete absence of the liquid phase. brought to a temperature sufficient to initiate the decomposition of the catalyst, gaseous vinyl chloride is introduced. The pressure prevailing in the autoclave may vary, but it should always be lower than the saturated vapor pressure of vinyl chloride at the polymerization temperature, so that never during the polymerization a liquid phase is present in the reaction medium. The polymer obtained forms a white powder which does not need drying. However, it is preferred to carry out the polymerization in the presence. of a solid, powdered or granular substance which is inert under the polymerization conditions and which is introduced in advance. This solid mainly serves as a dispersion phase for the catalyst. The increased dispersion of the catalyst significantly improves the polymer yield. This solid phase can have any character provided that it does not constitute or does not contain a polymerization-inhibiting material. Asbestos, silicon dioxide, perlite, etc. may be used in particular. form or in granular form and in particular polyvinyl chloride or a resin which it is desired to mix with the polyvinyl chloride formed. Preferably, a resin with very fine granulometry is selected. The amount of the solid phase previously introduced into the polymerization reactor may vary, and the ratio of the solid phase to the polymerized monomer is not critical. To ensure normal productivity in the reactors, the amount of the pre-introduced resin is kept as low as possible. One of the advantages of the process according to the invention is that it allows the use of a very small amount of the starting resin, because the polymerization leads to the formation of new granules and not to the increase of the pre-introduced granules. As catalysts for polymerization in the gas phase can be used. all catalysts or all preformed catalyst systems commonly used for the polymerization of vinyl chloride and in particular catalysts which form free radicals. For example. one can use, alone or in combination, organic peroxides, such as lauroyl peroxide, benzoyl peroxide, peroxide carbonates, azo-bisisobutyronitrile, tert. butyl perpivalate, etc. The amount used of the catalyst is preferably between 0.01 and 5% by weight relative to the monomer or monomers used. Stirring of the reaction medium has a great influence on the polymerization yield. The solid material in the polymerization reactor is therefore subjected to constant stirring by means of stirrers which are suitably selected and operated at precisely determined velocities. Preferably stirrers of the kind used for mixing are selected. and homogenize powdered products, namely "belt mixers". (ribbon blender), frame stirrers, stirrers with wiping blades, etc. Although the method according to the invention can be used in particular. to polymerize vinyl chloride, it can also be used for copolymerization of vinyl chloride with other monomers, e.g. vinyl acetate,. ethylene, propylene, etc. It has also been found that by means of the process according to the invention it is possible to obtain resins with improved stability by introducing in the solid starting phase powdered stabilizers provided that they do not hinder the polymerization reaction. According to an embodiment of the invention, powdered stabilizers can also be used as catalyst supports, such as fatty acid salts and in particular calcium, lead, barium, cadmium stearates, etc. These methods ensure better dispersion of the stabilizer within the resin, and thereby better efficiency of the stabilizer. The process according to the invention is of great economic value. as it is easy to perform. Due to the absence of a liquid phase. in the reaction medium, the resins obtained do not require drying. In addition, the unconverted monomer or monomers can be recovered in gaseous form and immediately recycled to the polymerization reactor without any subsequent purification process. Another and very important advantage of the process according to the invention is the absence of crusts in the polymerization reactor. All these characteristic features of the process according to the invention and in particular the absence of crusts in the reactor make the process particularly suitable for continuous work. This constitutes a very important advantage, because today no other satisfactory method is known which allows to polymerize vinyl chloride continuously. The essential characteristic feature of the invention which makes it possible to achieve this result is the continuous formation of new polymer granules, since it is clear that if the polymerization only led to an increase in the existing granulate, it would not be possible to carry it out for a long time and in no case continuously. Another characteristic feature of the continuous implementation of the process is that the polymerization can be continued for a relatively long time without the need to add new catalyst. On the other hand, the resins obtained have a relatively high degree of purity and thereby excellent transparency. This is mainly associated with the fact that no foreign matter, emulsifier, pesticide, protective colloid, etc. contaminates the polymerized polymer. Another characteristic feature of the invention is the possibility of easily obtaining low molecular weight resins under a pressure which is considerably lower than that. pressure required by the usual suspension, emulsion or mass processes. Despite their bulk density after stamping (0.7 - 0.8 kg / dm 3), the resins produced by the process also have excellent absorption properties when The following are some embodiments. EXAMPLE 1.1 g of lauroyl peroxide is introduced as a fine powder into a 3-liter autoclave subjected to continuous stirring by means of a stirrer with wiping paddles. The speed of the stirrer is 125 rpm. The autoclave is heated to 58 ° C and maintained at this temperature throughout the polymerization. Gaseous vinyl chloride is then introduced in such a way that the pressure in the autoclave is 8 kg / cm 2. The polymerization reaction begins and a pressure drop is found which is compensated by the introduction of gaseous vinyl chloride regulated in such a way that a constant pressure is maintained. 8 kg / cm 2. After 1 hour of polymerization, the autoclave is cooled, unconverted vinyl chloride is degassed and 31 g of white, powdered polyvinyl chloride are recovered which do not require drying. EXAMPLE 2. The polymerization of vinyl chloride is carried out in the presence of powdered polyvinyl chloride. homogenized mixture of 100 g of powdered polyvinyl chloride and 1 g of lauroyl peroxide. The catalyst on the support is stirred continuously during the polymerization by means of a stirrer with wiping paddles rotating at a speed of 125 rpm. gaseous vinyl chloride is introduced. The prevailing pressure in the autoclave is 8 kg / cm 2. the beginning of the polymerization reaction can be ascertained by a pressure drop. The pressure is maintained at 8 kg / cm 2 by successive introduction of gaseous vinyl chloride. After 5 hours of reaction, the introduction of gaseous vinyl chloride is stopped and 500 g of white powdered polyvinyl chloride are recovered which can be used as such without drying. EXAMPLES 3- by the method and under the conditions described in Example 2, but the catalysts used are the various compounds listed in the following Table 1. All the resins prepared have similar properties. They have excellent transparency and the bulk density after stamping is 0.7 - 0.8 kg / dm 3. No crusts are formed in the polymerization autoclave. EXAMPLE 9. The polymerization of vinyl chloride is carried out in the presence of a stabilizer dispersed in the solid starting material. A homogenized mixture of 100 g of powdered polyvinyl chloride, 1 g of lauroyl peroxide and 1 g of calcium stearate is introduced into the autoclave. The autoclave is heated to 58 ° C and stirred continuously by means of an agitator with wiping paddles, which rotates at 125 rpm. Gaseous vinyl chloride is introduced into the autoclave and the pressure is maintained at 8 kg / cm 2 during the polymerization by successive introduction of gaseous vinyl chloride. The polymerization is stopped after 9 hours 30 minutes, and 688 g of dry polyvinyl chloride are recovered whose thermal stability in an oil bath at 160 ° C is 20/30 minutes. The thermal stability of a polyvinyl chloride prepared according to Example 2 is 10-20 minutes. EXAMPLE 10. A copolymerization of vinyl chloride and propylene is carried out. A homogeneous mixture of 100 g of polyvinyl chloride and 3 g of lauroyl peroxide is introduced into the autoclave. The mixture is stirred continuously by means of a stirrer with wiping paddles rotating at 125 rpm. Then a mixture of constant ratio is introduced into the autoclave. of 626 parts vinyl chloride and 10 parts propylene. In the autoclave. a pressure of 8.8 kg / cm 2 prevails. After an 11% hour reaction, the polymerization is stopped. After degassing of the unconverted monomers, 725 g of a vinyl chloride / propylene copolymer containing are recovered. 2% propylene. The K number measured on a solution in dichloroethane is 57.5, while K-. the number of polyvinyl chloride produced under the same working conditions is 59. EXAMPLES 11, 12, 13. For the sake of comparison, it was for 1 hour at 58 ° C in a 3-. liter autoclave performed a polymerization test accordingly. by the method described in French patent 1,087,197 and in accordance with the invention. In the first two experiments, 200 ml of vinyl chloride were polymerized in the presence of 500 g of polyvinyl chloride. In it. In the first of these experiments (Example 11), the most favorable conditions were used for carrying out the first method using porous polyvinyl chloride having a granulometry between 0.1 and 0.2 mm. The second experiment (Example 12) was carried out in the presence of fine and dense polyvinyl chloride which is particularly suitable for carrying out the process in gas. phase. A non-porous polyvinyl chloride having a granulometry between 63 and 88 microns was used here. A gas phase polymerization test was then carried out on wood. by means of the method according to the invention (experiment 13) by ar-. both with the same resin as in Example 12, but only with 100 g of solid resin introduced initially. After the polymerization, the granulometric composition of the polyvinyl chlorides obtained was determined. The results are shown in Table II. In experiments 11 and 12 carried out in accordance with the method described in French Patent No. 1,087,197, no new granulate is formed, but there is a densification and an increase of the originally introduced polyvinyl chloride granulate. In contrast, the results of Example 13 undoubtedly show that new granules of polyvinyl chloride are formed and in particular a large amount of granules which are smaller than the smallest starting grade. zero of polyvinyl chloride. EXAMPLES 14 AND 15. The following examples will show advantages of the process. according to the present invention compared with the process according to French patent 1,087,197. In a first comparative experiment (Example 14) vinyl chloride is polymerized according to the above-mentioned French patent, i.e. liquid vinyl chloride is polymerized in the presence of porous polyvinyl chloride. Into the polymerization autoclave containing 600 g of porous polyvinyl chloride identical to that used in Example 11 is introduced 200 g of liquid vinyl chloride in which 1 g of lauroyl peroxide is dissolved. south. The temperature in the autoclave is brought to 59 ° C. In the autoclave, a pressure of 8.95 kg / cm 2 prevails. After 1 hour of polymerization, the pressure drops to 7.9 kg / cm 2. Every hour, the pressure in the autoclave is restored successively. to introduce 40 ml of liquid vinyl chloride in which a catalyst is dissolved in an amount of 0.5 g / l. After 9 hours of polymerization, 343 g of polyvinyl chloride are recovered. Without further addition of catalyst, it has been found. that the reaction stops after a few hours and that the polyvinyl chloride obtained has mediocre properties. The pressure difference {/ \ ^ P) for 1 hour is given in the following Table III. It can be seen that these differences diminish over time, which. shows that the reaction rate decreases. In another experiment, the polymerization of vinyl chloride is carried out. in the gas phase, but under conditions identical to those described in the first experiment, i.e. in the presence of 600 g of porous polyvinyl chloride in which 1 g of lauroyl peroxide is dispersed at a temperature of 59 ° C. However, no further catalyst is introduced. amount during the polymerization. The pressure in the autoclave is maintained at 8 kg / cm 2 by successive introductions of gaseous vinyl chloride. After 5 hours of polymerization 441 g of supplementary polyvinyl chloride are recovered and after 12 hours 1,150 kg of polyvinyl chloride. constant and that approximately 100 g of vinyl chloride are polymerized per It can thus be seen that the process for gas phase polymerization according to the invention allows to polymerize vinyl chloride continuously without further addition of the catalyst, while the process according to French patent 1,087,197 requires constant addition of catalyst throughout the polymerization, and even with this addition allows it does not continue the reaction for longer than 8 hours. |
| priorityDate | 1966-08-29-04:00^^<http://www.w3.org/2001/XMLSchema#date> |
| type | http://data.epo.org/linked-data/def/patent/Publication |
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