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
  • C08F220/00—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
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/12—Esters of monohydric alcohols or phenols
  • C08F220/14—Methyl esters, e.g. methyl (meth)acrylate
• • 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
  • C08F2/22—Emulsion 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
  • C08F2/00—Processes of polymerisation
  • C08F2/38—Polymerisation using regulators, e.g. chain terminating agents, e.g. telomerisation

Definitions

• the present invention relates to a method for the formation of polymers by emulsion polymerisation and in particular to the formation of polymers under miniemulsion conditions.
• Emulsion polymerisation is widely used as a commercial process to produce a variety of latexes for a range of industries. Emulsion polymerisation processes are typically used to produce high molecular weight polymers, however, in recent times the advantage of generating much lower molecular weights for specific product applications has become evident.
• Catalytic chain transfer has been shown to be a highly effective synthetic tool for reducing molecular weight in free-radical solution/bulk polymerisation and emulsion polymerisation.
• Limitations to the use of catalytic chain transfer agents in emulsion polymerisation reactions have been identified in the prior art. Firstly, such polymerisation reactions result in a loss of catalytic activity with time. This has.
• the initial monomer droplet size of about 100 nm is much smaller than conventional emulsion polymerisation, which is about 1 ⁇ m in size. Due to this size difference, particle nucleation occurs predominantly in the monomer droplets as opposed to creating a new particle phase. Disclosure of Invention
• the present invention consists in a method of forming a polymer, the method comprising: a) forming a miniemulsion including i) a monomer. ii) a non-aqueous solution including a cobalt-containing chain transfer agent, and iii) an aqueous solution; and b) reacting the miniemulsion in the presence of an initiator for a time sufficient to form the polymer.
• the initiator for the polymerisation reaction can be included in the reaction prior to the formation of the miniemulsion or in the miniemulsion.
• a variety of monomers may be used in the present invention, including methacrylate derivatives, acrylate derivatives, acrylic acid, ⁇ - hydroxymethylacrylates, methacrylonitrile. ⁇ -hydroxymethylacrylonitrile, styrene and styrene derivatives.
• Methacrylate derivatives may be selected from, methyl methacrylate (MMA). ethyl methacrylate. n -butyl methacrylate. i-butyl methacrylate, benzyl methacrylate, methacrylic acid and 2- hydroxyethyl methacrylate.
• MMA methyl methacrylate
• ethyl methacrylate n -butyl methacrylate.
• i-butyl methacrylate benzyl methacrylate
• methacrylic acid and 2- hydroxyethyl methacrylate.
• the styrene derivative is ⁇ -methyl styrene. It will be appreciated,
• cobalt-containing chain transfer agents with varying hydrophobicity may be employed in the present invention.
• Suitable chain transfer agents are ones that are able to partition equally between the oil and water phase or those that reside primarily in the oil phase.
• An example of a suitable cobalt-containing chain transfer agent able to reside equally between the oil and water phase is cobaloxime boron fluoride (COBF) ( Figure 1).
• a suitable chain transfer agent able to reside exclusively in the oil phase is tetraphenyl cobaloxime boron fluoride (COPhBF) ( Figure 1).
• the catalyst is present in a concentration of between 1 to 25 ppm.
• the aqueous solution may consist of a surfactant in deionised water.
• a surfactant selected from anionic. cationic and non-ionic surfactants may be used in the present invention either singularly or in combination.
• the surfactant is sodium dodecylsulfate (SDS).
• SDS sodium dodecylsulfate
• An initiator is included in the reaction either prior to the formation of the miniemulsion or in the miniemulsion.
• a variety of initiators capable of generating free radicals in an aqueous or organic phase may be used in the present invention. Suitable initiators include peroxides, persulfates. azo initiators and redox initiator systems.
• Preferable persulfate initiators include potassium persulfate (KPS).
• azo initiators include azobisisobutyronitrile (AIBN). azobiscyanovaleric acid and azobis(2-amidinopropane)dihydrochloride (Vazo V50TM).
• redox initiators include a redox couple from which each member is selected from iron catalysts, sodium metabisulfite and sodium formaldehyde sulfonate. Particularly preferred are initiators that generate oxygen centred radicals such as, persulfates and peroxides.
• the concentration of the initiator used will depend on many variables including temperature, monomer and other reaction conditions. The appropriate concentrations to be used falls within the skill of a formulator of polymers.
• AIBN produces carbon-centred radicals while KPS produces oxygen centred radicals.
• KPS is preferably predissolved in water and added in the miniemulsion at the reaction temperature.
• the emulsion may be stabilised by the presence of a highly water- insoluble compound (hydrophobe).
• hydrophobe a highly water- insoluble compound
• the hydrophobe is preferably contained in the non-aqueous solution.
• the hydrophobe may be selected from a variety of alkanes and fatty alcohols, however, it will be appreciated that a suitable hydrophobe can be selected from a wide variety of other species.
• the alkane is hexadecane and the fatty alcohol is cetyl alcohol
• miniemulsion polymerisation is that highly water insoluble ingredients are present directly in the monomer droplets which are the locus of polymerisation, whereas in conventional emulsion polymerisation, monomer and other reaction components need to diffuse from the droplets via the water phase to the locus of the reaction (the particles). This can be exploited by dissolving highly water insoluble chain transfer agents directly into the monomer droplets, the loci of the reaction.
• a miniemulsion can be formed in a variety of ways. Preferably it is formed from an emulsion by ultrasonification or high shear mixing at room temperature. In order to provide optimum polymerisation conditions, care should be taken at all steps to exclude oxygen from the system as the chain transfer agents are generally sensitive to oxygen once in solution.
• the cobalt-containing chain transfer agent is dissolved in the non-aqueous solution comprising the monomer which were preferably degassed by freeze- pump-thaw cycles, usually about three cycles.
• the monomer solution is transferred via a cannula to the aqueous solution, which has preferably been deoxygenated by purging with an inert gas, for example argon, for one hour, and initial emulsification is achieved using, for example, a magnetic stirrer.
• the miniemulsion may be generated by. for example, ultrasonification of the emulsion for approximately fifteen minutes using an ultrasonic bath.
• reaction of the miniemulsion occurs in the same vessel in which the miniemulsion is formed.
• the reactions may take place at any suitable temperature.
• a temperature range of about 40 to 80°C has been found to be particularly suitable.
• the reaction is controlled isothermally at about 65 °C and ambient pressure in a flask fitted with a nitrogen purge and a magnetic stirrer. Samples may be removed periodically for conversion (by gravimetry) and molecular weight analyses. Typically, reaction times are two to four hours. It will be appreciated, however, that the reaction time will vary depending on the polymer being formed.
• the present invention consists in a polymer prepared by the method according to the first aspect of the present invention.
• Figure 1 shows structures of the chain transfer agents cobaloxime boron fluoride (COBF) and tetraphenyl cobaloxime boron fluoride (COPhBF).
• Figure 2 is a graph showing dependence of M,, vs conversion on the concentration of catalyst (COBF and COPhBF) for AIBN initiated runs.
• Figure 3 is a graph showing dependence of conversion vs time on the concentration of catalyst (COBF and COPhBF) for AIBN initiated runs.
• Figure 4 is a graph showing dependence of M ⁇ vs conversion on the concentration of catalyst (COBF and COPhBF) for KPS initiated runs.
• Figure 5 is a graph showing dependence of conversion vs time on the concentration of catalyst (COBF and COPhBF) for KPS initiated runs.
• miniemulsion polymerisation of methyl methacrylate using two different initiators (AIBN and KPS) and two different cobalt- containing chain transfer agents (COBF and COPhBF) have been described.
• the recipes for the miniemulsion polymerisation reactions carried out according to Examples 2 to 5 and 7 to 8 are outlined in Tables 1 and 2.
• the miniemulsion was formed by the following procedure.
• the surfactant sodium dodecylsulfate (SDS). was dissolved in deionised water that was previously deoxygenated by purging with argon for one hour.
• the cobalt-containing chain transfer agent was dissolved in a non-aqueous solution comprising methyl methacrylate (MMA) and the hydrophobe (hexadecane). that were previously degassed by three freeze-pump-thaw cycles.
• the monomer solution was transferred via a cannula to the aqueous solution and initial emulsification was achieved using a magnetic stirrer.
• the miniemulsion was generated by ultrasonification of the emulsion for fifteen minutes using an ultrasonic bath.
• AIBN AIBN was used as initiator, it was added to the aqueous phase with the SDS. prior to the formation of the emulsion.
• KPS KPS was used as the initiator, it was predissolved in water prior to the miniemulsion at room temperature.
• Molecular weight distributions may be measured by size exclusion chromatography (SEC) on a modular system, comprising an autoinjector. guard column, two mixed bed columns (60 cm mixed C and 30 cm mixed E.
• SEC size exclusion chromatography
• the eluent may be tetrahydrofuran at 1 mL/min.
• COPhBF appears to be a more effective catalyst than COBF under these conditions. This can easily be explained by the relative solubilities of the chain transfer agents in the two phases. It has been shown that COBF partitions approximately equally between the oil and water phase. Thus for the same overall catalyst concentration, the COBF concentration in the locus of polymerisation is less than the COPhBF concentration which resides exclusively in the oil phase.

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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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• 1997
  • 1997-05-08 AU AUPO6696A patent/AUPO669697A0/en not_active Abandoned
• 1998
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  • 1998-05-08 CA CA002288933A patent/CA2288933A1/en not_active Abandoned
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  • 1998-05-08 KR KR1019997010331A patent/KR20010012378A/ko not_active Withdrawn
  • 1998-05-08 EP EP98918990A patent/EP0980392A4/de not_active Withdrawn
  • 1998-05-08 JP JP54755198A patent/JP2001523290A/ja active Pending
  • 1998-05-08 WO PCT/AU1998/000337 patent/WO1998050436A1/en not_active Ceased
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