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
  • C08F2/12—Polymerisation in non-solvents
  • C08F2/16—Aqueous medium

Definitions

• the present invention relates to a process for the polymerization of vinyl halide monomers such as vinyl chloride in aqueous dispersion.
• polymerization in aqueous dispersion polymerization in aqueous emulsion or aqueous suspension (including aqueous microsuspension), optionally in the presence of colloids such as polyvinyl alcohol and/or surfactants.
• This deposit which varies in thickness, hardness and degree of adhesion to the metal is composed of polymer in several different physical forms.
• the main type particularly from the standpoint of routine cleaning, is a hard film over the whole surface of the reactor. The thickness of this film varies from batch to batch but is normally a few thousandths of an inch thick.
• the other types are hard or soft lumps which accumulate locally in the reactor or powder which is more generally distributed. The soft lumps are composed of material that has escaped the washing out process and are comparatively easy/to remove.
• the hard lumps are believed to originate as soft material that has been allowed to stay in the reactor for more than one batch or simply by polymerization of vinyl chloride in an area of very high or very low agitation, i.e.
• a process for the polymerization of vinyl halide monomers in aqueous dispersion which process is characterized by the addition of a composition comprising metal ions.
• the metal ions are those derived from the metals of Groups Ib to VIIb inclusive, and Group VIII, but are preferably selected from the group consisting of chromium, copper, cobalt, nickel, tungsten, molybdenum, and manganese. Ferric and ferrous ions are also effective but may lead to contamination of the product polymer.
• compositions of our invention can be applied to the internal surfaces of the polymerization reactor, we prefer to add the compositions to the polymerization reaction medium. It is a particular advantage of our process that the composition can be added to the reaction medium without opening the reactor.
• the reactors used for the polymerization do not need to be opened between each polymerization cycle, either to remove adhering build-up, or to apply or remove anti-build-up coatings.
• composition comprising these ions is not narrowly critical. We have found for example that good results may be obtained using an aqueous solution of the ion in the form of simple salts such as for example, nitrates, sulphates and acetates. Particularly good results are obtained using the chlorides.
• the ion may also be in the form of complex ions such as amine complexes or complexes of the metallic ion with polyethers.
• compositions comprising these metal ions are cuprous chloride, cupric sulphate, nickelous chloride cobaltous chloride,chromic chloride, manganese sulphate and ammonium molybdate.
• Oxide compositions for example chrominum trioxide and tungsten trioxide, may conveniently be dissolved in dilute acids such as hydrochloric and sulphuric acids.
• the composition comprises copper, nickel, and cobalt ions, and most preferably the composition comprises chromium ions.
• Compositions comprising two or more of the said metal ions may also be used.
• metal ion can beadded to the reactor contents during the polymerization, we prefer to add the metal ion at or before the start of the polymerization reaction. It is a surprising feature of the process of our invention that small or catalytic amounts of the metal ions are effective in inhibiting build-up. The actual amount is not narrowly critical and we have found good results may be obtained if the amounts added are in the range from 0.001% to 0.1% w/w based on the monomer content in the polymerization.
• additives known to suppress build-up may also be added to the autoclave.
• the metal ion is added to the reaction mixture prior to the polymerization and during the polymerization a solution of a hydroquinone or a quinone, such as benzoquinone or naphthoquinone, is injected into the reaction mixture.
• a solution of a hydroquinone or a quinone such as benzoquinone or naphthoquinone
• the concentration of hydroquinone or quinone is less than 0.02 to 0.03% w/w based on the monomer content, since above this level the polymerization reaction may be inhibited.
• the operating conditions for polymerization according to the process of the present invention may be those customarily used.
• the temperature is generally below 110°C and typically between 40 and 80°C and the pressure generally below 15 kg/cm 2 .
• Compositions of metal ions of our invention comprising bromides are preferably used in polymerization processes carried out at temperatures below 60°C.
• vinyl halide monomers those monomers polymerizable by free-radical polymerization which are olefinically unsaturated in the alpha position and substituted by at least one halogen atom. These monomers are preferably selected from substituted derivatives of ethylene and contain only two carbon atoms. Examples of such monomers include vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, chlorotrifluoroethylene and tetrafluoroethylene. The invention is preferably applied to the polymerization of fluorine- or chlorine-containing vinyl monomers, especially vinyl chloride.
• polymerization is meant both the homopolymerization of the vinyl halide monomers and the copolymerization with each other or with other comonomers copolymerizable therewith.
• vinyl esters such as vinyl acetate, acrylic esters such as methyl acrylate and butyl methacrylate, acrylic nitriles such as acrylonitrile and methacrylonitrile, unsaturated diesters such as diethyl maleate, allyl esters such as allyl acetate, ⁇ -olefines such as ethylene and propylene, vinyl ethers and styrene compounds.
• the process according to the invention may be employed in any polymerization technique where the monomer(s) is dispersed in the form of droplets in a liquid aqueous phase.
• the monomer(s) may be dispersed in the form of droplets in a liquid aqueous phase.
• it may be used for polymerization in aqueous emulsion in which case any suitable emulsifying agent such as sodium lauryl sulphonate or sodium dodecyl benzene sulphonate and non-ionic emulsifying agents may be used.
• the process of the invention is also most applicable to polymerization in aqueous suspension and microsuspension.
• Any suitable dispersing agent may be used for polymerization in aqueous suspension, and particularly finely dispersed solids, gelatin, polyvinyl acetates of various degrees of hydrolysis, water-soluble cellulosic ethers and polyvinyl pyrrolidones. These dispersing agents can be used together with surface-active agents if desired.
• the amount employed may vary widely and is generally between 0.05 and 1.5% by weight calculated on the amount of water used.
• Any suitable free-radical polymerisation initiator that is monomer-soluble may be used for polymerization in aqueous suspension.
• these include peroxy compounds such as di-tertiary-butyl peroxide, lauroyl peroxide and acetyl cyclohexyl sulphonyl peroxide, t-butyl perpivalate,azo compounds such azo-bis-isobutyronitrile and 2,2'-azo-bis-2,4-dimethyl-valeronitrile,and boron alkyls.
• Monomer-soluble free-radical polymerization initiators that are particularly suitable for use in the process according to the invention are the dialkyl peroxydicarbonates whose alkyl radicals contain up to 20 carbon atoms, such as diethyl peroxydicarbonate, diisopropyl peroxydicarbonate and di(tertiarybutyl-cyclohexyl)peroxydicarbonate, and 2,2'-azo-bis-2,4-dimethylvaleronitrile and azo-bis-isobutyronitrile. These initiators may be used in conventional quantities - generally speaking from 0.01 to 1% by weight calculated on monomer.
• Polymerization in homogenised aqueous dispersion comprises mechanically homogenising an aqueous dispersion of the monomer or monomers in the presence of a surface-active agent (for example by subjecting it to a violent shearing action), and polymerizing the homogenised dispersion in the presence of an initiator that is monomer soluble.
• emulsifying agents and monomer-soluble initiators can be used for polymerization in microsuspension such as for example an ionic emulsifying agent like sodium dodecylbenzenesulphonate, and peroxide initiators of the dialkanoyl peroxide type, e.g. lauroyl peroxide.
• an ionic emulsifying agent like sodium dodecylbenzenesulphonate
• peroxide initiators of the dialkanoyl peroxide type e.g. lauroyl peroxide.
• the aqueous dispersions may contain one or more additives that are normally employed in conventional processes for polymerization in aqueous dispersion.
• additives include particle size regulators, molecular weight regulators, stabilisers, plasticisers, colouring agents, reinforcing agents and processing aids.
• the polymerization medium may also contain one or more substances which themselves inhibit polymerization build-up.
• a stainless steel pressure vessel of 7 litres nominal capacity equipped with heating and cooling means was charged with 3500 ml of demineralized water, 2.4 g of a peroxydicarbonate catalyst and 1.75 g polyvinyl alcohol (partially hydrolyzed polyvinyl acetate). The contents of the vessel were stirred and the air above the liquid was removed by evacuation. Vinyl chloride monomer (3000 g) was added to the evacuated vessel and the contents were heated to 56°C. The temperature was maintained until pressure drop indicated the end of the reaction of polymerization.
• the residual gas was vented off and the slurry of polyvinyl chloride in water was dropped down through the bottom valve.
• the lid was opened and the remaining loose polymer was rinsed with water and the firm deposition of the polymer inside the autoclave was examined.
• the total weight of the deposit constituted 0.6% w/w of the vinyl chloride monomer charged to the autoclave.
• Example 1 The pressure vessel of Example 1 was thoroughly cleaned free from all deposit, washed and dried. The charging procedure of Example 1 was repeated and 5 minutes after vinyl chloride addition, a solution of 0.22 g of copper chloride dihydrate (0.003% w/w copper ion on vinyl chloride charge) in 35 mls water was injected into the polymerization mixture. When reaction was on temperature for an hour 0.25 g of hydroquinone, in 35 mls of water were injected and the reaction was finished as described in
• Example 1 The pressure vessel of Example 1 was thoroughly cleaned free from all deposit, washed and dried. Nickel chloride (0.4 g; 0.003% w/w nickel ion on vinyl chloride) was added to the water charge and the procedure of Example 1 repeated.
• the autoclave walls and roof were virtually free from build-up. Very little easily removed deposit was found on the shaft and around the gland. The overall amount of build-up was ca. 0.02% w/w of the initial monomer charge.
• cuprous polyether complex was prepared as follows:
• Example 1 The pressure vessel of Example 1 was thoroughly cleaned free from all deposit, washed and dried. The charging procedure of Example 1 was repeated followed by two consecutive injections of 35 ml of aqueous solution of the cuprous/polyether solution prepared above, and 5 mls of 0.43 g triethylenetetramine solution in alcohol. The general process of Example 1 was repeated. After polymerization the autoclave walls, roof and paddle were virtually clean from any build-up. Firmly attached polymer deposit was situated only around the shaft. The overall amount of hard build-up was ca. 0.2% w/w of the monomer charge.
• Example 1 The pressure vessel of Example 1 was thoroughly cleaned free from all deposit, washed and dried. A solution of nickel chloride hexahydrate and tetraethylenepentamine (1:1 w/w) in water (50 w) was sprayed on the internal surfaces of the vessel which had been preheated to 60°C. After 5 min drying the surfaces were resprayed and dried again. Then the reactor was left at 60 to 70°C for 30 min. Nickel chloride hexahydrate (1 g, 0.008% w/w nickel ion on vinyl chloride) was added to the water charge and the procedure of Example 1 repeated.
• Nickel chloride hexahydrate (1 g, 0.008% w/w nickel ion on vinyl chloride
• the autoclave walls and roof were free from build-up except for a few small patches of skin build-up on top of the autoclave. Some seed-like build-up was found on the shaft and around the gland.
• the pressure vessel of ⁇ Example 1 was thoroughly cleaned free from all deposit, washed and dried.
• the vessel was heated to 70°C, sprayed with a 2% w/w solution of hydroquinone and tetraethylenepentamine (1:1) in a mixture (1:1) of water and ethanol and kept at 60 to 80°C for 30 min. All surfaces were then washed with cold water. Copper chloride dihydrate .7 g, 0.011% w/w copper ion on vinyl chloride) was added to the water charge and the procedure of Example 1 repeated.
• the autoclave walls were free from build-up. Few patches of build-up film were found on the shaft and paddle. The overall amount of build-up was a negligible .02% w/w of the initial monomer charge.
• Example 6 The procedure of Example 6 was repeated except that the solutions of hydroquinone/tetraethylenepentamine and copper chloride, respectively, were replaced by:
• Example 1 The pressure vessel of Example 1 was thoroughly cleaned free from all deposit, washed and dried. Nickel chloride hexahydrate (0.39 g, 0.0032% w/w nickel ion on vinyl chloride) and copper chloride dihydrate (0.22 g, 0.0035% w/w copper ion on vinyl chloride) was added to the water charge and the procedure of Example 1 repeated.
• the autoclave walls and lid were clean and shiny.
• the paddle was partly covered by skin build-up. A few loosely attached lumps and some powdery build-up was found around the shaft and glands.
• Example 1 The pressure vessel of Example 1 was thoroughly cleaned free from all deposit, washed and dried. The charging procedure of Example 1 was repeated and 5 min after vinyl chloride addition a solution of 0.78 g nickel chloride hexahydrate (0.006% w/w nickel ion on vinyl chloride) in 21.3 ml of water and 1 ml of concentrated hydrochloric acid was injected into the polymerisation mixture.
• the autoclave surfaces were covered by a film of a light build-up with lumps on the shaft and in the gland area.
• the amount of build-up was 0.5% w/w on the initial monomer charge.
• Example 9 The procedure of Example 9 was repeated except that ;he solution of nickel chloride was replaced by a solution of manganese chloride tetrahydrate (0.48 g) in 14 ml water (0.004% w/w manganese ion based on vinyl chloride). After the reaction the internal surfaces of the vessel were inspected and the amount of residual build-up was similar to that observed in Example 9.
• Example 1 The pressure vessel of Example 1 was thoroughly cleaned free from all deposit, washed and dried. The charging procedure of Example 1 was repeated and 5 min after vinyl chloride addition a solution of 0.22 g of copper chloride dihydrate (0.003% w/w copper ion based on vinyl chloride) in 10 ml of water and .5 ml concentrated hydrochloric acid was injected into the polymerisation mixture.
• Example 3 The procedure of Example 3 was repeated except that the nickel chloride was replaced by 0.22 g of copper chloride dihyrate. After the polymerization reaction was completed the internal surfaces of the vessel were inspected and found to be substantially free of build-up. The total amount of build-up was ca. 0.03% w/w of the initial monomer charge. This build-up was mainly restricted to a film around the top edge of the vessel.
• Example 12 The procedure of Example 12 was repeated except that the solution of .22 g of copper chloride dihydrate in water was injected into the polymerisation mixture 5 min after charging the vinyl chloride. The amount of build-up on the internal surfaces of the polymerization vessel after the reaction was completed was similar to that obtained in Example 9.
• Example 1 The pressure vessel of Example 1 was thoroughly cleaned free from all deposit, washed and dried.
• Manganese chloride tetrahydrate .(0.4 g; 0.004% w/w manganese ion on vinyl chloride) was dissolved in the polyether referred to hereinbefore and the solution injected into the autoclave 5 min after the vinyl chloride was charged.
• a light skin of build-up covered the internal walls and lid of the vessel. A somewhat heavier build-up deposit was found on the paddle, shaft and around the gland. The amount of deposit was ca. 0.07% w/w on the initial charge of the monomer.
• Example 1 The procedure of Example 1 was followed except that copper chloride (0.5 g dihydrate; 0.006% w/w copper ion on vinyl chloride) was added to the water charge.
• copper chloride 0.5 g dihydrate; 0.006% w/w copper ion on vinyl chloride
• Example 15 The procedure of Example 15 was repeated except that the copper chloride was replaced by 0.75 g of cobaltous chloride hexahydrate (0.006% w/w cobalt ion on vinyl chloride).
• Example 15 The procedure of Example 15 was repeated except that the copper chloride was replaced by 0.6 g of cupric acetate monohydrate (0.006% copper ion on vinyl chloride). No retardation or inhibition of the polymerization reaction occurred as compared to a control run.
• Example 15 The procedure of Example 15 was repeated except that the copper chloride was replaced by a solution of 1.55 g of chromyl chloride (0.017% w/w chromium ion on vinyl chloride) prepared by dissolving 1 g of chromium tioxide in 3.4 ml of 32% w/w hydrochloric acid and diluting to 100 ml with water.
• chromyl chloride (0.017% w/w chromium ion on vinyl chloride) prepared by dissolving 1 g of chromium tioxide in 3.4 ml of 32% w/w hydrochloric acid and diluting to 100 ml with water.
• the internal walls of the vessel including the lid and paddle and shaft, were very shiny and completely free from any build-up;

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• 1978
  • 1978-06-30 DE DE7878300113T patent/DE2860931D1/de not_active Expired
  • 1978-06-30 EP EP78300113A patent/EP0000430B1/fr not_active Expired

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