Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/42—Block-or graft-polymers containing polysiloxane sequences
  • C08G77/445—Block-or graft-polymers containing polysiloxane sequences containing polyester sequences
  • C08G77/448—Block-or graft-polymers containing polysiloxane sequences containing polyester sequences containing polycarbonate sequences
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
  • C08G18/46—Polycondensates having carboxylic or carbonic ester groups in the main chain having heteroatoms other than oxygen
  • C08G18/4692—Polycondensates having carboxylic or carbonic ester groups in the main chain having heteroatoms other than oxygen containing silicon
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/61—Polysiloxanes

Definitions

• the present invention generally relates to silicon-based polycarbonates, processes for their preparation and their use in the synthesis of copolymers, in particular segmented copolymers such as polyurethanes for biomedical applications.
• Polysiloxane-based polymers especially polydimethyl siloxane (PDMS) exhibit characteristics such as low glass transition temperatures, good thermal, oxidative and hydrolytic stabilities and low surface energies. These properties would be desirable in the macrodiol-derived component of a segmented copolymer. In addition, they display good compatibility with biological tissues and fluids and low toxicity. For these reasons, PDMS has found particular application in the construction of medical devices, especially implantable devices. However, polymers derived from PDMS do not generally exhibit good tensile properties such as flexural strength or abrasion resistance.
• Suitable macrodiols would retain the advantages of silicon-based polymers such as flexibility, low temperature performance, stability and in some cases biocompatibility.
• the disadvantages of poor mechanical properties will preferably be avoided so that the silicon-based macrodiols can form part of materials which can be used in various demanding applications, particularly the biomedical field.
• R,, R 2 , R 3 , R 4 , R 5 , Re, R g and R 9 are same or different and selected from hydrogen or an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical;
• A is an endcapping group; n, y and z are integers of 0 or more; and x is an integer of 0 or more.
• alkenyl denotes groups formed from straight chain, branched or mono- or poly-cyclic alkenes including ethylenically mono- or poly-unsaturated alkyl or cycloalkyl groups as defined above, preferably C 2 . 12 alkenyl.
• alkenyl examples include vinyl, allyl, 1-methylvinyl, butenyl, iso-butenyl, 3-methyl-2-butenyl, 1- pentenyl, cyclopentenyl, 1-methyl-cyclopentenyl, 1-hexenyl, 3-hexenyl, cyclohexenyl, 1-heptenyl, 3 heptenyl, 1-octenyl, cyclooctenyl, 1-nonenyl, 2-nonenyl, 3-nonenyl, 1-decenyl, 3-decenyl, 1,3-butadienyl, 1 ,4-pentadienyl, 1,3-cyclopentadienyl, 1,3- hexadienyl, 1,4-hexadienyl, 1,3-cyclohexadienyl, 1,4-cyclohexadienyl, 1,3- cycloheptadienyl, 1,3,5-cycl
• aryl denotes single, polynuclear, conjugated and fused residues of aromatic hydrocarbons.
• aryl include phenyl, biphenyl, terphenyl, quaterphenyl, phenoxyphenyl, naphthyl, tetrahydronaphthyl, anthracenyl, dihydroanthracenyl, benzanthracenyl, dibenzanthracenyl, phenanthrenyl and the like.
• heterocyclyl denotes mono- or poly-cyclic heterocyclyl groups containing at least one heteroatom selected from nitrogen, sulphur and oxygen.
• Suitable divalent linking groups for R 7 include O, S and NR wherein R is hydrogen or an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical.
• endcapping group is used herein in its broadest sense and includes reactive functional groups or groups containing reactive functional groups.
• Suitable examples of reactive functional groups are alcohols, carboxylic acids, aldehydes, ketones, esters, acid halides, acid anhydrides, amines, imines, thio, thioesters, sulphonic acid and expoxides.
• the reactive functional group is an alcohol or an amine, more preferably an alcohol.
• a preferred polycarbonate is a compound of the formula (I) wherein A is OH which is a polycarbonate macrodiol of the formula (la):
• R, to Rg, n, y, x and z are as defined in formula (I) above.
• the present invention also provides a process for preparing the silicon-based polycarbonate macrodiol of the formula (la) as defined above which includes reacting a source of carbonate with either:
• Suitable carbonate compounds include cyclic carbonates such as alkylene carbonates for example ethylene or propylene carbonate and linear carbonates such as dialkyl or diaryl carbonates, for example, dimethyl carbonate, diethyl carbonate or diphenyl carbonate.
• the source of carbonate has a low molecular weight because of the ease of removal of the condensation by-product from the reaction mixture.
• the silicon-based diols of the formula (II) may be obtained as commercially available products. For example 1 ,3-bishydroxypropyl- 1 , 1 ,3 ,3-tetramethyldisiloxane and l,3-bishydroxybutyl-l,l,3,3-tetramethyldisiloxane are available from Shin Etsu or Silar Laboratories. Others can be prepared by using the appropriate disilane compounds and hydroxy terminated olefinic compounds using a hydrosilylation reaction 4 . It will be appreciated that the diol of formula (II) can be used separately or as a mixture containing two or more structurally different diols in the preparation of the polycarbonates according to the present invention. The presence of silicon or siloxy radicals in the diol imparts hydrophobic and flexibility characteristics which results in improved elastomeric and degradation resistance in copolymers produced from these polycarbonates.
• non-silicon based diols of the formula (III) can be used in combination with the silicon-based diols of the formula (II) for the preparation of polycarbonates.
• the non-silicon based diol is an aliphatic dihydroxy compound, such as, alkylene diols, for example, 1,4-butanediol, 1,6- hexanediol, diethyleneglycol, triethyleneglycol, 1,4-cyclohexanediol or 1,4- cyclohexanedimethanol.
• polycarbonates having a broad range of properties can be prepared by choosing different ratios of the two diols.
• the process for preparing the polycarbonate is preferably a transesterif ⁇ cation similar to that described in US 4,131,731 which is carried out in the presence of a transesterif ⁇ cation catalyst.
• suitable catalysts include those disclosed in US 4,105,641 such as stannous octoate and dibutyl tin dilaurate.
• the present invention further provides a copolymer which includes a silicon-based polycarbonate segment of the formula (lb):
• a polyurethane elastomeric composition which includes a silicon-based polycarbonate segment of the formula (lb) defined above.
• the polyurethane elastomeric compositions of the present invention may be prepared by any suitable known technique.
• a preferred method involves mixing the polycarbonate and a chain extender and then reacting this mixture with a diisocyanate.
• the initial ingredients are preferably mixed at a temperature in the range of about 45 to about 100°C, more preferably about 60 to about 80°C.
• a catalyst such as dibutyl tin dilaurate at a level of about 0.001 to about 0.5 wt % based on the total ingredients may be added to the initial mixture.
• the mixing may occur in conventional apparatus or within the confines of a reactive extruder or continuous reactive injection molding machine.
• the polyurethanes may be prepared by the prepolymer method which involves reacting a diisocyanate with the polycarbonate to form a prepolymer having terminally reactive diisocyanate groups. The prepolymer is then reacted with a chain extender.
• the polyurethane elastomeric composition of the present invention may be further defined as comprising a reaction product of:
• the diisocyanate is selected from 4,4'-methylenediphenyl diisocyanate (MDI), methylene bis (cyclohexyl) diisocyanate (H 12MDI), p-phenylene diisocyanate (p-PDI), trans-cyclohexane-1, 4-diisocyanate (CHDI) or a mixture of the cis and trans isomers, 1 ,6-hexamethylene diisocyanate (DICH), 2,4-toluene diisocyanate (2,4- TDI) or its isomers or mixtures thereof, p-tetramethylxylene diisocyanate (p-TMXDI) and m-tetramethylxylene diisocyanate (m-TMXDI). MDI is particularly preferred.
• MDI 4,4'-methylenediphenyl diisocyanate
• H 12MDI methylene bis (cyclohexyl) diisocyanate
• the chain extender is preferably selected from 1, 4-butanediol, 1, 6- hexanediol, 1, 8-octanediol, 1,9-nonanediol, 1,10-decanediol 1,4-cyclohexane dimethanol, p-xyleneglycol, 1,4-bis (2-hydroxyethoxy) benzene and 1,12- dodecanediol.
• 1, 4-butanediol is particularly preferred.
• a particularly preferred polyurethane elastomeric composition of the present invention comprises a reaction product of:
• An advantage of the incorporation of the polycarbonate segment is the relative ease of processing of the polyurethane by conventional methods such as extrusion, injection and compression moulding without the need of added processing waxes.
• conventional polyurethane processing additives such as catalysts, antioxidants, stablisers, lubricants, dyes, pigments, inorganic and/or organic fillers and reinforcing materials can be incorporated into the polyurethane during preparation.
• Such additives are preferably added to the polycarbonate.
• the polycarbonate, diisocyanate and chain extender may be present in certain proportions.
• the preferred level of hard segment (i.e., diisocyanate and chain extender) in the composition is about 30 to about 60 wt %, more preferably 40 to 50 wt%.
• the polyurethane elastomeric composition of the present invention is particularly useful in preparing materials having good mechanical properties, in particular biomaterials.
• a material having improved mechanical properties, clarity, processability and/or degradation resistance comprising a polyurethane elastomeric composition which includes a polycarbonate segment of the formula (lb) defined above.
• the present invention also provides use of the polyurethane elastomeric composition defined above as a material having improved mechanical properties, clarity, processability and/or degradation resistance.
• the present invention further provides the polyurethane elastomeric composition defined above when used as a material having improved mechanical properties, clarity, processability and/or degradation resistance.
• the mechanical properties which are improved include tensile strength, tear strength, abrasion resistance, Durometer hardness, flexural modulus and related measures of flexibility or elasticity.
• the improved resistance to degradation includes resistance to free radical, oxidative, enzymatic and/or hydrolytic processes and to degradation when implanted as a biomaterial.
• an in vivo degradation resistant material which comprises the polyurethane elastomeric composition defined above.
• the polyurethane elastomeric composition may also be used as a biomaterial.
• biomaterial is used herein in its broadest sense and refers to a material which is used in situations where it comes into contact with the cells and/or bodily fluids of living animals or humans.
• the polyurethane elastomeric composition is therefore useful in manufacturing medical devices, articles or implants.
• the present invention still further provides medical devices, articles or implants which are composed wholly or partly of the polyurethane elastomeric composition defined above.
• the medical devices, articles or implants may include cardiac pacemakers and defibrillators, catheters, cannulas, implantable prostheses, cardiac assist devices, heart valves, vascular grafts, extra-corporeal devices, artificial organs, pacemaker leads, defibrillator leads, blood pumps, balloon pumps, A-V shunts, biosensors, membranes for cell encapsulation, drug delivery devices, wound dressings, artificial joints, orthopaedic implants and soft tissue replacements.
• the siloxane component of the polyurethane elastomeric composition by virtue of its dielectric properties will provide opportunities for use in electronic and electrical components and insulation.
• the present invention extends to the use of the polyurethane elastomeric composition defined above in the manufacture of devices or articles.
• the present invention also provides devices or articles which are composed wholly or partly of the polyurethane elastomeric composition defined above.
• the invention will now be described with reference to the following examples. These examples are not to be construed as limiting the invention in any way.
• Fig. 1 shows differential scanning calorimetry (DSC) thermograms of polycarbonate macrodiols (a) 1,6-hexandiol based commercial polycarbonate, (b) macrodiol of Example 2 and (c) macrodiol of Example 1 ; and Fig. 2 shows DSC thermograms demonstrating well phase separated morphologies of polyurethanes based on silicon containing macrodiols (i) PU- 1 based on a commercial polycarbonate macrodiol, (ii) PU-2 from macrodiol in Example 2 and (iii) PU-3 from macrodiol in Example 1.
• DSC differential scanning calorimetry
• the reaction mixture was heated to 180°C under a nitrogen flow while maintaining a vacuum of 140 mmHg over a period of about 4h.
• the reaction temperature was raised to 190°C while increasing the vacuum to 50 mmHg and the reaction was continued for 2 more hours. During this period, the vacuum was reduced to 10 mmHg, stepwise. About 75% of the total distillate was collected during the second stage.
• the temperature was raised to 200°C, the vacuum reduced to 5 mmHg with the nitrogen flow stopped and the reaction was continued for a further 30 min. The reaction was stopped at the end of the third stage by removing the flask from the heating bath and allowing to cool to room temperature under ambient pressure.
• the progress of the polymerisation reaction was monitored by analysing a sample of the crude product by 1H-NMR spectroscopy and by size exclusion chromatography.
• the product polymer was a pale yellow viscous liquid. Yield of the crude polymer was 44.5g.
• the crude macrodiol was dissolved in dichloromethane to make a 15 % solution and treated with charcoal to remove coloured impurities as well as the catalyst residues.
• the macrodiol obtained after evaporating the dichloromethane from the filtered solution was further purified by washing with boiling water to remove traces of ethylene glycol and unreacted ethylene carbonate. Boiling water (200 ml) was added to the polymer and stirred for 10 min, allowed to settle and the water was decanted off. This process was repeated three times.
• the final polymer was then dried at 80°C under vacuum (0J mmHg) for 15 h. The final yield was 40 g.
• the molecular weight of the macrodiol based on the hydroxyl number was 1220.
• the macrodiol was also analysed by DSC and the results are shown in Fig. 1.

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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)
• Polyesters Or Polycarbonates (AREA)
• Silicon Polymers (AREA)
• Polyurethanes Or Polyureas (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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• 1997
  • 1997-05-26 AU AUPO7002A patent/AUPO700297A0/en not_active Abandoned
• 1998
  • 1998-05-20 AT AT98922507T patent/ATE224419T1/de not_active IP Right Cessation
  • 1998-05-20 JP JP50000399A patent/JP4593694B2/ja not_active Expired - Fee Related
  • 1998-05-20 DE DE69808076T patent/DE69808076T2/de not_active Expired - Lifetime
  • 1998-05-20 BR BR9809474-2A patent/BR9809474A/pt not_active Application Discontinuation
  • 1998-05-20 EP EP98922507A patent/EP0984997B1/en not_active Expired - Lifetime
  • 1998-05-20 WO PCT/AU1998/000375 patent/WO1998054242A1/en not_active Ceased
  • 1998-05-20 CN CN98805443A patent/CN1257520A/zh active Pending
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• 2002
  • 2002-08-14 US US10/219,732 patent/US7026423B2/en not_active Expired - Lifetime

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