WO1995001402A1 - Procede de revetement par polymerisation suivant une oxydoreduction - Google Patents

Procede de revetement par polymerisation suivant une oxydoreduction Download PDF

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Publication number
WO1995001402A1
WO1995001402A1 PCT/GB1994/001275 GB9401275W WO9501402A1 WO 1995001402 A1 WO1995001402 A1 WO 1995001402A1 GB 9401275 W GB9401275 W GB 9401275W WO 9501402 A1 WO9501402 A1 WO 9501402A1
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WO
WIPO (PCT)
Prior art keywords
polymerisation
monomer
polymer
coated
coating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1994/001275
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English (en)
Inventor
Hermann Block
Keith Moray Blackwood
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BTG International Ltd
Original Assignee
British Technology Group Ltd
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Filing date
Publication date
Application filed by British Technology Group Ltd filed Critical British Technology Group Ltd
Publication of WO1995001402A1 publication Critical patent/WO1995001402A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • C08F271/00—Macromolecular compounds obtained by polymerising monomers on to polymers of nitrogen-containing monomers as defined in group C08F26/00

Definitions

  • This invention relates to coated solids and the preparation and use of such solids and is particularly, but not exclusively, concerned with coated polymers useful as a dispersed phase in the preparation of electrorheological fluids.
  • Electrorheological fluids are suspensions of a solid dispersed phase in a liquid continuous phase which exhibits an increase in flow resistance on application of an electric field. Research is in continual progress with a view to improving both the dispersed and continuous phases of electrorheological fluids : see, for example, UK Patents Nos. 1501635, 1570234, 2100740, 2119392 and 2153372. However, the mechanisms by which electrorheological phenomena occur are still not fully understood.
  • the present invention seeks to provide for the preparation of improved solids for use as the dispersed phase in electrorheological fluids or for use in other situations where it is desirable to modify the surface properties cf materials.
  • the present invention comprises a polymerisation process initiated by a polymeric redox initiator and the resulting products of such a process.
  • the invention includes a process for the preparation of a coated solid substrate in which polymerisation of at least one coating monomer is carried out in the presence of surfaces of a polymer capable itself of acting as the redox initiator for the polymerisation of the monomer.
  • polymer used herein comprises homopolymers and co-polymers.
  • the invention also includes coated solids prepared by such a process and electrorheological fluids incorporating such solids.
  • the polymer acting as the redox initiator is suitably a polymer having internal redox capability as exhibited by polyaniline and described, for example, by MacDiarmid ei aj . ., Mol. Cryst. Liq. Cryst., 1985, HI, 173-180.
  • Examples of other materials having internal redox capability are polymers of substituted anilines e.g. the toluidines and anisidines, and polymers of diphenylamines and pyrroles. Structures of such typical polymers are illustrated in Figure 1.
  • the coating monomer may be any vinyl monomer which can be polymerised in solution or suspension in the presence of a redox initiator, such as an alkene monomer, for example styrene or an unsaturated ester monomer such as methyl methacrylate or vinyl acetate.
  • a redox initiator such as an alkene monomer, for example styrene or an unsaturated ester monomer such as methyl methacrylate or vinyl acetate.
  • the longer chain alkyl methacrylates containing up to 20 carbon atoms in the alkyl group e.g. lauryl methacrylate provide steric stabilisation of the substrate particles and are therefore preferred. Mixtures of coating monomers may be employed.
  • the polymer acting as the redox initiator may have any convenient form of surface but is preferably present in particulate form so that the product coated comprises coated particles. It is also contemplated within the scope of the present invention that the redox polymer may be present as a coating on a further material, such as a non-redox initiating polymer e.g., polyethylene or nylon, or an inorganic material such as carbon or glass fibres, so that the polymer acts as a substrate for deposition of a layer of polymerised monomer. It will be appreciated that, in this way, it is possible to provide a wide range of coated solids in which the properties of the solid are modified by the coating.
  • the intrinsic conductivity of polyaniline can be maintained by provision of a surface coating of, for example, polystyrene, the more insulating nature of which ensures that the bulk conductivity of a dispersion in which such a coated solid is used remains low.
  • the process of the invention may be used to apply an insulating coating to a conductive substrate such as carbon fibres.
  • the solid redox initiator polymer or composite is added to liquid monomer and after heating to effect polymerisation of the latter the excess monomer is removed.
  • the reaction is therefore a heterogeneous reaction producing a surface effect. This ensures that the polymer is deposited over the surface of the initiating polymer, and in the context of ER fluid formulations, further markedly improves the bulk resistivity of such fluids by electrically insulating the particles.
  • the invention may be seen as a process of modifying the surface of an electrorheologically functional polymer characterised in that the polymer is one capable of acting as a redox initiator of polymerisation and is modified by polymerisation of an olefinically unsaturated monomer at the polymer surface.
  • the preparation can alternatively be effected in aqueous emulsion, using, if necessary, a suitable surfactant such as
  • Triton X-100 to maintain the emulsion. After completion of polymerisation, the coated solid is then dried to an extent necessary for the intended subsequent use.
  • a coated solid such as styrene-coated polyaniline for use as the dispersed phase of an electrorheological fluid, it is desirable to obtain as end product a dry non-agglomerated solid capable of good dispersion in the intended continuous phase of the fluid.
  • Suitable continuous phases may be provided by silicone oils, transformer oils or a liquid ester such as diethyl phthalate.
  • Suitable drying techniques include azeotropic drying in the presence of benzene or toluene.
  • the preparation can be effected in a non-aqueous solvent, such as hexane or heptane.
  • a non-aqueous solvent such as hexane or heptane.
  • the presence of a surfactant is not required and the drying problems of aqueous systems are obviated.
  • the coated solid after filtration, can be dispersed in a suitable continuous phase such as silicone oil or diethyl phthalate.
  • suitable continuous phase such as silicone oil or diethyl phthalate.
  • the choice of solvent is determined by the need for a material which is a non-solvent for the polymeric redox initiator and coated product but a solvent or dispersant for the monomer.
  • the conditions of polymerisation can vary widely dependent on the nature of the polymeric redox initiator and the monomer and on the intended use of the coated solid. Further co-monomeric materials may be employed to modify the properties of the coating. Variables such as reaction time, temperature and concentration of the starting components will be adjusted to achieve optimum yield commensurate with evenness and desired coating thickness. Suitable temperatures range from 40°C to 70°C preferably 50°C.
  • the pH will also be critical factor in that the extent of base "doping" of the polyaniline redox initiator affects the conductivity of the coated solid and, ultimately, the yield strength of the electrorheological fluid.
  • the pH of the polyaniline is adjusted to pH 8 to 12, suitably about pH 10. Conversion to the base form of polymer may in some cases be carried out before the coating monomer is grafted on to the substrate particles e.g. for aniline polymers but in others it should be carried out after the coating step e.g. for poly-toluidines.
  • Lauryl methacrylate was extracted with 1M sodium hydroxide solution, washed with water and then dried over anhydrous sodium sulphate.
  • the poly(o-toluidine hydrochloride) was suspended in excess of this monomer (lg to 20cm * --) in a pyrex tube and after degassing the tube was sealed under vacuum.
  • the reaction mixture in the tube was heated to 50°C and reaction allowed to continue until the required level of polymer had formed, typically around 100% weight gain in 24 hours.
  • the solid was then collected by filtering and washed with methanol , dried under vacuum for 12 hours at 50°C.
  • Figure 2 illustrates the effect of varying polymerisation time on the % weight gain of the substrate polymer particles.
  • this material required conversion to a more basic form. Typically this was achieved by immersing the powder in excess pH 5 phosphate buffer (250ml per g) and leaving for 12 hours after which the base form was filtered off, extracted with water overnight and finally vacuum dried for 48 hours at 50 ⁇ C. c ) ER Fluid Performance of coated polv(o-toluidine)
  • Table 1 shows a comparison of the performance in terms of static yield stress and current density of pH 5 polydauryl methacrylate ) coated and uncoated poly(o-toluidine) dispersed in 20cS silicone oil at 0.2 volume fraction of solid.
  • Coated Uncoated Coated Uncoated 800 0.15 0.5 0.50 1 .25
  • polyCaniline can be successfully coated in the base form. This conversion was achieved by dispersing the hydrochloride in distilled water and the pH of the dispersion was adjusted to pHIO using 1M sodium hydroxide. The solution volume was doubled with a borate based pHIO buffer solution and the system left to equilibrate overnight. The solid was then collected by filtration and washed with water before being extracted for 12 hours with water and dried under vacuum for 48 hours at 50°C. b) Coating of polyCaniline)
  • Table 2 below shows a comparison of the performance of pH 10 polyCstyrene) coated and uncoated polyCaniline) dispersed in 20cS silicone oil at 0.2 volume fraction of solids. Table 2.

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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)
  • Macromolecular Compounds Obtained By Forming Nitrogen-Containing Linkages In General (AREA)
  • Lubricants (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

On prépare des solides recouverts d'une couche, lesquels sont appropriés, par exemple, pour être utilisés comme phase dispersée d'un fluide électrorhéologique, en effectuant une polymérisation d'au moins un monomère de revêtement en présnce des surfaces d'un polymère capable d'agir lui-même comme initiateur de l'oxydoréduction servant à la polymérisation du monomère.
PCT/GB1994/001275 1993-06-29 1994-06-14 Procede de revetement par polymerisation suivant une oxydoreduction Ceased WO1995001402A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9313408.8 1993-06-29
GB939313408A GB9313408D0 (en) 1993-06-29 1993-06-29 Redox polymerisationcoating process

Publications (1)

Publication Number Publication Date
WO1995001402A1 true WO1995001402A1 (fr) 1995-01-12

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PCT/GB1994/001275 Ceased WO1995001402A1 (fr) 1993-06-29 1994-06-14 Procede de revetement par polymerisation suivant une oxydoreduction

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GB (2) GB9313408D0 (fr)
WO (1) WO1995001402A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3139410B2 (ja) 1997-04-15 2001-02-26 富士ゼロックス株式会社 グラフト重合方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0455224A2 (fr) * 1990-05-02 1991-11-06 Tomoegawa Paper Co. Ltd. Dérivés de polyaniline et procédé pour leur préparation
EP0512926A1 (fr) * 1991-05-07 1992-11-11 Alcatel N.V. Polyanilines conductrices auto-dopées et leur procédé de préparation

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3410494A1 (de) * 1984-03-22 1985-10-03 Basf Ag, 6700 Ludwigshafen Verfahren zur herstellung von polypyrrol-pfropfpolymerisaten
GB8908825D0 (en) * 1989-04-19 1989-06-07 Block Hermann Electrorheological fluid
US4990279A (en) * 1989-04-21 1991-02-05 Hercules Incorporated Electrorheological fluids
US4992192A (en) * 1989-04-21 1991-02-12 Hercules Incorporated Electrorheological fluids

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0455224A2 (fr) * 1990-05-02 1991-11-06 Tomoegawa Paper Co. Ltd. Dérivés de polyaniline et procédé pour leur préparation
EP0512926A1 (fr) * 1991-05-07 1992-11-11 Alcatel N.V. Polyanilines conductrices auto-dopées et leur procédé de préparation

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
MACDIARMID ET AL.: "Polyaniline : interconversion of metallic and insulating forms", MOLECULAR CRYSTALS AND LIQUID CRYSTALS, vol. 121, 1985, pages 173 - 180 *

Also Published As

Publication number Publication date
GB2279355A (en) 1995-01-04
GB9411890D0 (en) 1994-08-03
GB9313408D0 (en) 1993-08-11

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