Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2000-09-29
2002-08-20
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C607S009000, C623S002420, C623S003290, C623S018110, C623S926000
Reexamination Certificate
active
06437073
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present invention relates to non-elastomeric polyurethane compositions based on silicon-containing chain extenders characterised by high flexural modulus, high glass transition and heat distortion temperatures. These polyurethane compositions are useful for applications requiring high impact resistance, flexural strength, and other structural properties similar to engineering thermoplastics, and in particular for use in above ambient temperature end-use environments.
Polyurethanes represents a broad class of materials formed by reacting chemical compounds bearing functional groups such as isocyanate and hydroxyl. A wide range of polymers with a variety of properties ranging from elastomers to rigid materials can be prepared by selecting a suitable combination of reagents in various proportions. Of these materials, polyurethane elastomers formed by reacting a polyol (typical molecular weight 500 to 4000) with a diisocyanate and a chain extender (low molecular weight diol of molecular weight less than 500), form an important class of commercially useful materials. The methods of synthesis and studies on structure property relationships of these materials are abundant in the polyurethane literate
1
.
The polyurethanes formed by reacting only the chain extender and the diisocyanate are generally very rigid with high flexural modulus, and are often difficult to process due to high melting temperatures. For example, a polyurethane prepared from a common diisocyanate 4,4′-methylenediphenyldiisocyanate (MDI) and 1,4-butanediol (BDO) generally melts at temperatures above 210° C. which is well above the thermal decomposition temperature of the urethane linkage
2
. Further, such materials are generally very brittle and have poor mechanical properties. Alternatively, harder grades of polyurethane elastomers prepared using a relatively lower proportion of the polyol component usually have a low heat distortion temperatures, primarily due to the presence of the polyol component, usually with a glass transition below ambient temperature.
Development of polyurethane compositions with high flexural modulus combined with high heat distortion temperatures and thermal processability would provide a new range of rigid materials with strength required for applications in high temperature end-use environments.
The hard polyurethane compositions disclosed in U.S. Pat. No. 4,101,529 are made by reacting polyisocyanates with mixtures of cycloaliphatic diols and low molecular weight diol chain extenders such as ethylene glycol and low molecular weight active hydrogen containing materials such as trimethylolpropane, and optionally a polymeric polycaribonate diol. These compositions are characterised by heat distortion temperature of at least 88° C. (measured by ASTM D-648 at 264 psi) and hardness of at least 75 Shore D. Similarly, U.S. Pat. No. 4,808,690 discloses polyurethane compositions with high heat distortion temperatures that are highly cross-linked, and are made by reacting a polyisocyanate prepolymer and a polyhydric alcohol having from 2 to 8 hydroxyl groups in combination with a polyester polyol. Such polyurethanes are expected to be difficult to thermally process due to their highly cross-linked nature.
U.S. Pat. No. 4,822,827 describes thermoplastic polyurethane compositions with high glass transition temperatures based on reacting a polyisocyanate and a particular combination of chain extenders including cycloalkane diol, optionally in the presence of a minor amount of high molecular weight polyol. It is also disclosed that only certain members of the new polymers are optically clear.
The compositions disclosed in U.S. Pat. No. 4,101,529, U.S. Pat. No. 4,393,186, U.S. Pat. No. 4,808,690 and U.S. Pat. No. 4,822,827 all contain a polyol for example polyester, polycarbonate or polyether as part of the polyurethane structure. This would make the prior art compositions susceptible to possible degradation under oxidative and hydrolytic environments, particularly high temperature environments which may limit their applications. Development of new polyurethane compositions which are free of segments derived from polyols while overcoming most of the disadvantages of the prior art compositions, would broaden the applications of these materials to areas such as medical devices and implants.
Accordingly, a requirement exists to develop polyurethanes which are easily processable and have a high flexural modulus, high heat distortion temperature, optical clarity, and resistance to degradation.
According to one aspect, the present invention provides a non-elastomeric polyurethane composition which includes a chain extender of the general formula (1)
wherein
R
1
, R
2
, R
3
, R
4
, R
5
and R
6
are the same or different and selected from an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical;
R
7
is a divalent linking group or an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical; and
n is 0 or greater, preferably 2 or less.
The term “non-elastomeric” in the present context refers to polyurethanes having a % elongation of up to about 200%, generally up to about 100%.
The term “chain extender” in the present context means any compound having at least two functional groups per molecule capable of reacting with the isocyanate group and generally in the molecular weight range 60 to about 500, more preferably 60 to about 450.
Preferably, the chain extender of formula (1) has a molecular weight of about 500 or less.
The hydrocarbon radical for substituents R
1
, R
2
, R
3
and R
4
may include alkyl, alkenyl, alkynyl, aryl and heterocyclyl radicals. It will be appreciated that the equivalent radicals may be used for substituents R
5
, R
6
and R
7
except that the reference to alkyl, alkenyl and alkynyl should be to alkylene, alkenylene and alkynylene, respectively. In order to avoid repetition, only detailed definitions of alkyl, alkenyl and alkynyl are provided hereinafter.
The term “alkyl” denotes straight chain, branched or mono- or poly-cyclic alkyl, preferably C
1-12
alkyl or cycloalkyl. Examples of straight chain and branched alkyl include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, amyl, isoamyl, sec-amyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, pentyl, hexyl, 4-methylpentyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 1,1-dimethylbutyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 1,2,2-trimethylpropyl, 1,1,2-trimethylpropyl, heptyl, 5-methylhexyl, 1-methylhexyl, 2,2-dimethylpentyl, 3,3-dimethylpentyl, 4,4-dimethylpentyl, 1,2-dimethylpentyl, 1,3-dimethylpentyl, 1,4-dimethylpentyl, 1,2,3-trimethylbutyl, 1,1,2-trimethylbutyl, 1,1,3-methylbutyl, octyl, 6-methylheptyl, 1-methylheptyl, 1,1,3,3-tetramethylbutyl, nonyl, 1-, 2-, 3-, 4-, 5-, 6- or 7-methyloctyl, 1-, 2-, 3-, 4- or 5-ethylheptyl, 1-, 2- or 3-propylhexyl, decyl, 1-, 2-, 3-, 4-, 5-, 6-, 7- and 8-methylnonyl, 1-, 2-, 3-, 4-, 5- 3- or 4-propylheptyl, undecyl 1-, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-methyldecyl 3-, 4-, 5-, 6- or 7-ethylnonyl, 1-, 2-, 3-, 4- or 5-propyloctyl, 1-, 2-butylheptyl, 1-pentylhexyl, dodecyl, 1-, 2-, 3-, 4-, 5-, 6-, 7-, 8-, 9- or 10-methylundecyl, 1-, 2-, 3-, 4-, 5-, 6, 7- or 8-ethyldecyl, 1-, 2-, 3-, 4-, 6-propylnonyl, 1-, 2-, 3- or 4-butyloctyl, 1,2-pentylheptyl and the like. Examples of cyclic alkyl include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl and the like.
The term “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. Examples of alkenyl 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-deceny
Adhikari Raju
Gunatillake Pathiraja A.
McCarthy Simon John
Mejis Gordon Francis
Aortech Biomaterials PTY Ltd.
Gorr Rachel
Schwegman Lundberg Woessner & Kluth P.A.
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