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
• • 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
  • C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
  • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
  • C08F20/42—Nitriles
  • C08F20/44—Acrylonitrile
• • 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
  • C08F12/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring
  • C08F12/02—Monomers containing only one unsaturated aliphatic radical
  • C08F12/04—Monomers containing only one unsaturated aliphatic radical containing one ring
  • C08F12/06—Hydrocarbons
  • C08F12/08—Styrene
• • 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
  • C08F2/18—Suspension polymerisation
• • 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
  • C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
  • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
  • C08F20/10—Esters
  • C08F20/12—Esters of monohydric alcohols or phenols
• • 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
  • C08F291/00—Macromolecular compounds obtained by polymerising monomers on to macromolecular compounds according to more than one of the groups C08F251/00 - C08F289/00

Definitions

• the present invention relates to a process for the continuous production of particulate homopolymers and copolymers using the technique of microsuspension polymerization.
• Polymerization in a disperse system such as an emulsion or a suspension is a technically proven process for the production of particulate polymers.
• Important products of such processes are polyvinyl acetate, polyvinyl chloride and polytetrafluoroethylene.
• the use of particularly finely dispersed monomers is sought in the industrial manufacturing process. Therefore, methods such as the miniemulsion or microsuspension process, both of which allow the intermediate production and polymerization of such particularly finely dispersed monomers, are becoming increasingly important.
• the mixture of one or more monomers and a stabilizing suspending aid - protective colloids or surfactant emulsifiers are usually used - is subjected to very high shear forces in water, which leads to the formation of a very high shear force fine emulsion of droplets with a diameter of about 0.1-2 ⁇ m leads.
• microsuspension This emulsion, hereinafter referred to as microsuspension, is then mixed with a hydrophobic radical polymerization initiator in a second step and, after heating to the required reaction temperature, polymerized to particles of a diameter of approximately 0.1-50 ⁇ m (see, for example, . 'Handbuch der Technischen Polymerchemie', VCH Verlagsgesellschaft mbH, Weinheim, 1993, p. 450).
• emulsion, suspension and terms derived therefrom such as mini-emulsion, microsuspension, emulsify, suspend and others are used differently in the literature in connection with polymerizations. This can lead to unclear descriptions.
• emulsion, suspension and microsuspension polymerization see 'Handbuch der Technischen Polymer-Chemie', VCH Verlagsgesellschaft mbH, Weinheim, 1993, p. 316 and p. 450.
• microsuspension is understood to mean the finished, finely divided mixture of the substances to be polymerized.
• Emulsifying means to convert the mixture of the substances to be polymerized into a microsuspension.
• EP-B 0 443 609 discloses a microsuspension process in which various monomers are emulsified in water using a high-speed stirrer which generates very high shear forces. The total amount of the microsuspension is then converted into the polymer with a particle size of 5-50 ⁇ m diameter in a stirred tank in a batchwise process.
• DE-A 196 33 626 which is older and has not been published in advance, proposes the polymerization of a microsuspension of, inter alia, (meth) acrylic acid derivatives and of further (meth) acrylic acid and styrene derivatives which can optionally be used as comonomers.
• a microsuspension of, inter alia, (meth) acrylic acid derivatives and of further (meth) acrylic acid and styrene derivatives which can optionally be used as comonomers.
• only part of the microsuspension containing monomer is placed in the stirred tank reactor and the rest is metered in continuously as the reaction proceeds.
• the continuous polymerization in mini-emulsions here means a continuously stirred tank reactor to which a mini-emulsion generated in a tubular pre-reactor is metered in continuously.
• the object of the present invention is to provide an industrially feasible method for the polymerization of microsuspensions. different monomers in a continuously operated tubular reactor while avoiding the disadvantages of the prior art.
• the solution to the problem is based on the known processes for the production of particulate homopolymers or copolymers of at least one polymerizable monomer using the technique of microsuspension polymerization at a temperature of at least 0 ° C. in the presence of at least one hydrophobic radical polymerization initiator.
• the invention is based on the known processes for the production of particulate homopolymers or copolymers of at least one polymerizable monomer using the technique of microsuspension polymerization at a temperature of at least 0 ° C. in the presence of at least one hydrophobic radical polymerization initiator.
• the process is then characterized in that the microsuspension is produced continuously or batchwise, the polymerization takes place in at least 50% of the conversion in a tubular reactor, the process products have an average particle diameter d 50 of less than 50 ⁇ m and the tubular reactor consists of one Pipe or hose with a ratio of length to diameter (L / D) of at least 20.
• Suitable monomers for this are, for example, (meth) acrylic acid, (meth) acrylamide, (meth) acrylonitrile, alkyl (meth) acrylates, butadiene, isoprene, alkylene oxides, styrene, substituted styrenes, vinyl acetate and vinyl chloride.
• Alkyl (meth) acrylates are esters of (meth) acrylic acid with linear Ci- C 32 - or branched C 3 -C understand 32 alkyl radicals, in particular methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl or 2-ethylhexyl .
• alkyl radicals can be unsubstituted or substituted by functional groups, for example by hydroxyl, amino, ether, epoxy, sulfonic acid groups or by chlorine.
• Preferred monomers having such functional groups in the alkyl group are 2-hydroxyethyl acrylate, 2-hydroxyethyl, 3-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, Ethyldiglykolacrylat, tert-butylaminoethyl methacrylate, diethylaminoethyl acrylate, n-Butoxymethylaminomethacrylat, glycidyl methacrylate, 2-acrylamido-2-methyl - Propanesulfonic acid and 3-chloro-2-hydroxypropyl acrylate.
• monomers with polar, acidic or basic groups makes the polymers suitable
• the microsuspension of only one monomer is used in the polymerization step, homopolymers are formed.
• the microsuspension of a further monomer or a monomer mixture can be fed into the tubular reactor, so that this Monomers or these monomers are partially polymerized or polymerized in shell form on the polymer particles formed first. This process can also be repeated several times with other monomers or mixtures of different compositions in order to obtain particles with several shells.
• Additional monomers can also be metered in without prior preparation of a microsuspension by metering in the monomers or monomer mixture, water, suspending agent and, if appropriate, other additives directly. It is also possible to first transfer the previously formed polymer to another tubular reactor and then to start metering in at least one further monomer.
• Suitable comonomers are bi- and polyfunctional monomers, for example butadiene, isoprene, divinyl esters of dicarboxylic acids such as succinic and adipic acid, diallyl and divinyl ethers, and bis-acrylic and bis-methacrylic acid esters of bifunctional alcohols such as ethylene glycol and butane-1,4-diol, 1,4-divinylbenzene and triallyecyanurate.
• the acrylic and methacrylic acid esters of allyl alcohol and the acrylic acid esters of tricyclodecenyl alcohol (dihydrodicyclopentadienyl acrylate) are particularly suitable.
• the tubular reactor can also be operated in the form of a circulation reactor, the microsuspension in the tubular reactor being circulated and polymerized. Part of the already polymerized microsuspension is continuously removed from the circuit and an equivalent part of new microsuspension is metered in.
• the ratio between the amount of microsuspension that passes through a pipe cross-section in a certain time interval and the amount of microsuspension that is metered into the cycle reactor in the same time interval is generally greater than 5, preferably greater than 10 and particularly preferably greater than 20.
• tubular reactor is understood to mean both a circulation reactor and a non-circulation-operated reactor.
• the tubular reactor can be filled with elements which ensure better radial mixing.
• Raschig rings, baffles or other internals and static mixers are suitable as elements.
• a better radial mixing can also be achieved by a so-called pulsing mode of operation of the reactor.
• This usually means a pulsating feeding of the microsuspension into the tubular reactor.
• a pulsating driving style with a feed rate of once in 30 seconds to ten times in one second is preferred, in particular from once in 2 seconds to five times in one second.
• the average residence time of the microsuspension in the tubular reactor depends, inter alia, on the monomers to be polymerized and is usually between 10 minutes and 10 hours, preferably between 10 minutes and 4 hours.
• the dimensions of the tubular reactor depend on the desired properties of the particulate polymers to be produced.
• the choice of the suitable reactor dimension depends, inter alia, on the polymerization rate of the monomers, on the shape of the tube and on the mode of operation of the reactor. In a cycle mode of operation, the ratio L / D is generally between 50 and 1000 and is therefore to be chosen smaller than in a non-cycle mode of operation.
• the choice of the reactor material depends on the type of monomers to be polymerized.
• Non-metallic materials for example polytetrafluoroethylene, and metallic, for example steels according to DIN 17440, which can be coated on the inside, for example with enamel or polymers, in particular with fluorine-containing polymers, are preferred.
• the tubular reactor can be tempered by immersing it in a heat-transfer medium or preferably having a double jacket filled with a heat-transfer medium.
• suitable media are, for example, water, brine, oils and other liquids.
• the temperature selected for the polymerization in the tubular reactor essentially depends on the type of monomers and polymerization initiators used and is generally between 0 and 140 ° C., preferably between 20 and 130 ° C.
• the tubular reactor can also be operated with a temperature program.
• the Polymerization started at a temperature of 70 ° C and ended at 100 ° C.
• the polymerization takes place at least 60%, in particular at least 80%, in the tubular reactor.
• the part of the monomers which have not yet reacted completely or completely polymerize out after leaving the tubular reactor provided the suspension is still at a temperature which is sufficient for the polymerization.
• the polymers can, if desired, be easily separated from the unreacted monomers and, if appropriate, from the other constituents of the suspension, for example by spray drying or by coagulation and drying.
• the polymers produced by the process according to the invention have an average particle diameter d 50 , which is preferably between 0.03 and 50 ⁇ m, in particular between 0.1 and 30 ⁇ m.
• the mean particle diameter can be determined by taking light or electron microscopic images and then measuring and counting the particles. Another method is Fraunhofer laser diffraction.
• Suitable suspending aids are those water-soluble compounds which are able to coat the fine monomer droplets and the polymer particles formed therefrom and in this way to protect them from undesired coagulation.
• These include, for example, cellulose derivatives, such as carboxyl and hydroxymethyl cellulose, poly-N-vinylpy ⁇ olidin, polyvinyl alcohol and polyethylene oxide, anionic polymers such as polyacrylic acid and their copolymers and cationic polymers such as poly-N-vinylimidazole in concentrations of preferably 0.02 to 5 % By weight, based on the total mass of the microsuspension.
• Emulsifiers such as the alkali salts of aryl and alkyl sulfonic acids and of aryl and alkyl carboxylic acids, for example sodium stearate, potassium stearate, sodium oleate and potassium oleate, and also ethoxylated or propoxylated alcohols and phenols. These emulsifiers are also used in concentrations of preferably 0.02 to 5% by weight, based on the total mass of the microsuspension.
• polyvinyl alcohols with a degree of hydrolysis of less than 96 mol%, preferably between 60 and 94 mol%, in particular between 65 and 92 mol%.
• the preferred polyvinyl alcohols have a viscosity of 1 to 100 mPa / s, in particular 2 to 60 mPa / s, measured as a 4% strength by weight solution in water at 20 ° C. according to DIN 53015.
• colloidal silica in concentrations of 0.2 to 5% by weight, based on the total amount of the microsuspension.
• the microsuspension is added or at least one further monomer Addition of at least one further monomer.
• This step can be repeated several times in order to obtain polymers with a multi-layer structure.
• copolymers can also be prepared in such a way that after the polymerization of a monomer or monomer mixture, the polymer thus prepared is transferred to a second crude reactor, and then at least one further monomer is metered in.
• stirred tank reactor is used instead of one second tube reactor possible, as well as the reverse procedure, that is, first of all, preparation of a polymer in a stirred tank reactor and then metering in of at least one further monomer in a tube reactor.
• the transition from the core to the shell or the transition from one shell to the next shell is sharper the more completely a monomer is already polymerized before the metering in of at least one further monomer as such or in the form of a microsuspension is started.
• the particle morphology can also be influenced by appropriate selection of the monomers and the reactor conditions. For example, newly fed monomers can not only polymerize shell-like onto the already polymerized particles of a previously used other monomer type, but also polymerize into these particles to a considerable extent, so that the core-shell structure is less pronounced.
• crosslinking monomers are polymerized to form a core or a shell, then reaction, i.e. polymerizable C-C double bonds remain, onto which a further monomer can be grafted in the next polymerization step.
• reaction i.e. polymerizable C-C double bonds remain, onto which a further monomer can be grafted in the next polymerization step.
• Such grafting reactions are known to the person skilled in the art.
• radical polymerization initiators Compounds which form free radicals are suitable as radical polymerization initiators, provided they are oil-soluble. These include peroxides, azo compounds and compounds with labile CC bonds. If such monomers are to be polymerized that spontaneously tend to polymerize at elevated temperature, the addition of a radical polymer sationsinitiators be waived. This group of monomers includes in particular styrene and its derivatives.
• peroxides those with a ratio of carbon to oxygen of greater than 3 to 1, such as dilauryl peroxide, dibenzoyl peroxide, diacetyl peroxidicarbonate, dimyristil peroxidicarbonate and bis- (3,5,5-trimethylhexanoyl) peroxide, in particular dilauryl peroxide, are preferred.
• azo compounds 2,2'-azobis (isobutyronitrile) and 2,2'-azobis (2-methylbutyronitrile) are preferred.
• 3,4-dimethyl-3,4-dipherrylhexane and 2,3-dimethyl-2,3-diphenylbutane are preferably used.
• polymerization initiators are used in an amount of 0.05 to 4% by weight, based on the amount of the monomer, preferably 0.1 to 2% by weight, in particular 0.3 to 1.0% by weight. Of course, this quantity does not apply if the monomer is also the initiator. Mixtures of the polymerization initiators mentioned can also be used.
• the polymerization initiator can be added as such, but preferably as a solution, emulsion or suspension, either to the mixture to be emulsified to form a microsuspension, to the already prepared microsuspension or to the microsuspension to be polymerized in the crude reactor.
• Organic solvents such as benzene, toluene, xylene, ethylbenzene, cyclohexane and the monomers themselves are suitable as the solvent or as the liquid phase for the polymerization initiator.
• the mixture to be emulsified or the already prepared microsuspension can be more than 0.1% by weight, preferably more than 1% by weight, in particular more than 5% by weight, of at least one solid in dissolved, swollen or suspended form are added.
• These solids can be polymers, coloring and ferromagnetic pigments as well as other substances such as minerals.
• carbon black black particulate polymers are produced, which are used in particular as copier toners.
• the use of ferromagnetic pigments leads to the formation of particulate polymers with ferromagnetic properties.
• Such polymers are particularly suitable for the production of magnetic tapes and magnetic foils.
• additives which influence the product properties can also be added in the process according to the invention, depending on the desired properties of the polymers.
• - molecular weight regulators for example t-dodecyl mercaptan or 2-
• Buffers to regulate the pH value for example citrate buffers, disodium hydrogen phosphate and sodium dihydrogen phosphate, inhibitors which simultaneously inhibit the process of microsuspension polymerization which is an undesirable competitive reaction
• Emulsion polymerization in which essentially undesirable smaller polymers are formed, is suppressed, for example chromium (VI) salts, in particular potassium and sodium dichromate.
• VI chromium
• microsuspension used in the process according to the invention is made up of monomer, suspending agent, water and, if appropriate, the others Solid and other additives specified above and optionally polymerization initiator prepared by allowing very high shear forces to act on the mixture of these substances. Methods for being able to exert very high shear forces are known to the person skilled in the art.
• stirrers and homogenizers examples are: Laboratory dissolver Dispermat, VMA-Getzmann, Reichshof, DE
• the microsuspension is usually produced at room temperature, but can also be carried out at a lower or higher temperature, depending on the type of monomers and other substances.
• the stirrers are usually operated at speeds between 1000 and 25000 revolutions per minute (rpm), preferably between 2000 and 15000 rpm, with a stirring time which can be between 0.1 seconds and several hours.
• the amount of water in which the monomers and the suspending aids are dispersed is usually from 15 to 95% by weight, preferably from 35 to 85% by weight, and particularly preferably from 40 to 75% by weight, based in each case on the total Monomers, water and suspending agents.
• the microsuspension is produced either batchwise or continuously.
• the mixture of the substances to be emulsified is processed in a container with one of the stirrers or homogenizers mentioned above to form the microsuspension.
• the homogenizer can also be arranged parallel to the container and the mixture is then circulated through the homogenizer.
• the substances to be emulsified are fed continuously to the homogenizer, and the microsuspension formed is then also fed continuously to the tubular reactor.
• the continuous preparation of the microsuspension can also be carried out in such a way that only a part of the microsuspension is fed to the tubular reactor and the rest passes through the homogenizer again.
• This circular mode of operation is particularly recommended if the absolute droplet size or the size distribution of the droplets should be unsatisfactory with a single throughput through the homogenizer.
• microsuspensions of high and uniform quality Separate the area-intensive, discontinuous production of the microsuspension from the actual polymerization and feed the microsuspension to the tube reactor as required.
• the particulate polymers are dispersed in water and, if necessary, can be spray-dried directly or, after separation of the aqueous phase, for example by sieving, filtering, decanting or centrifuging, can be dried further in the customary manner, for example by warm air or with the help of a power dryer.
• this polymer-containing dispersion which generally has a viscosity of 100-500 mPa / s, can also be further processed as such.
• the method according to the invention enables a stable, i.e. Operation without blockage of the reactor. This also applies to very long operating times of the tubular reactor, which are a multiple of the average residence time of the microsuspension in the tubular reactor.
• the microsuspension used does not tend to show signs of coagulation under the chosen reaction conditions.
• the homopolymers and copolymers prepared according to the invention have good performance properties. They are used, for example, as additives for thermoplastic molding compositions, as constituents of copier toners, paper and leather auxiliaries, coatings for magnetic tapes and magnetic foils, and as coloring and coating components.
• Acrylonitrile, butyl acrylate, dihydrodicyclopentadienyl acrylate and styrene are products of BASF AG, Ludwigshafen, DE and were used without further purification.
• the Mowiol ® polyvinyl alcohols are products of Hoechst AG, Frankfurt am Main, DE.
• the first number after the brand name indicates the viscosity of a 4 wt. -% solution of the polyvinyl alcohol in water at 20 ° C in [mPa / s], measured according to DIN 53015.
• the second number characterizes the degree of hydrolysis of the polyvinyl alcohol in mol%.
• the polymerization initiators are commercially available products.
• the metering rate was 500 ml / h.
• the temperature of the reactor contents was kept at 75 ° C. using a water bath. After an average residence time of 20 minutes in the tubular reactor, the polymerized suspension was collected.
• the tubular reactor was operated for a total of 5 hours and 45 minutes under these conditions. The suspension showed no coagulum and the tubular reactor showed no signs of clogging.
• the solids content was 33% by weight.
• the average particle diameter d 50 was 2.5 ⁇ m.
• Example 2 To prepare a copolymer, the experiment from Example 1 was repeated and the suspension containing butyl acrylate polymer thus prepared was metered into a second crude reactor which had the same dimensions and the same material composition as that in Example 1. At a temperature of 75 ° C., the two given below were given Mixtures A and B are metered in separately in a continuous manner. The metering rate was chosen so that the weight ratio of mixture B to polybutyl acrylate was 20 to 80.
• the polymerized suspension was collected.
• the crude reactor was operated for a total of 5 hours under these conditions.
• the suspension showed no coagulum and the crude reactor showed no signs of constipation.
• the average particle diameter d 50 was 2 ⁇ m.

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Citations (2)

• 1997
  • 1997-04-28 DE DE19717877A patent/DE19717877A1/de not_active Withdrawn
• 1998
  • 1998-04-24 WO PCT/EP1998/002429 patent/WO1998049204A1/de not_active Application Discontinuation
  • 1998-04-24 KR KR19997009937A patent/KR20010012124A/ko not_active Application Discontinuation
  • 1998-04-24 JP JP54658698A patent/JP2001522394A/ja active Pending
  • 1998-04-24 EP EP98925480A patent/EP0977783A1/de not_active Withdrawn
  • 1998-04-24 CN CN98804549A patent/CN1253568A/zh active Pending

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