Polysiloxane polyols and segmented polyurethanes manufactured therefrom

Abstract: By reacting polyamines with ethylene carbonate, hydroxyethyl urethane diols and polyols are produced. These diols and polyols are particularly useful for the synthesis of polyurethanes by reaction with diisocyanates or polyisocyanates.

Description: This invention relates to the formation of hydroxyl functional monomers having polysiloxane groups in the backbone and which are useful in the synthesis of polyurethanes. Synthesis of polyurethanes by reacting isocyanates and alcohols is well known to the art. Typically, long or medium chain diols or polyols are used to provide the "soft" segments of segmented polyurethanes. These polyols generally consist of hydroxyl terminated polyethers or polyesters. Reaction of these polyols with polyisocyanates produces polyether or polyester urethanes, respectively. Short chain polyols are often reacted with polyisocyanates to form the "hard" segments of segmented polyurethanes. Unfortunately, commercial availability of polyols appropriate for use in the synthesis of polyurethanes is somewhat limited. However, certain polyamines having backbones appropriate for polymer synthesis are more readily available. They may be reacted with polyisocyanates, to form polyureas. However, reactions between polyamines and polyisocyanates are often too fast to allow for commercially feasible production. Moreover, polyureas generally have limited thermal processability. SUMMARY OF THE INVENTION The present invention provides a process of producing novel urethane polyols, particularly hydroxyethyl urethane polyols, which term herein includes diols, from readily available polyamines, including diamines. In our process, a compound A n -M, in which M represents a polysiloxane moiety, A represents a primary or secondary amine group and n is a number greater than or equal to 2, is reacted with a cyclic e.g. ethylene carbonate to produce the desired polyols. These polyols are then readily and controllably reacted with polyisocyanates, including diisocyanates to produce novel polyurethanes. Ether and ester free polyols according to the present invention are believed to have great potential in the preparation of polyurethanes for use in biomedical applications. Such polyurethanes and their preparation are described in detail in our copending EP-A-0361950 entitled "BIOSTABLE SEGMENTED ALIPHATIC POLYURETHANES AND PROCESSES FOR THEIR PREPARATION". DESCRIPTION OF THE INVENTION By suitable choice of polyamine, the invention allows for inclusion of a variety of polymer backbones in polyurethanes, especially segmented polyurethanes. Examples of such amines A n -M include polydimethyl siloxane (PDMS), a silicone polymer available from Petrarch Systems with aminopropyl termination (PDMS diamine). The present invention allows any desired polyamine which is free of ethylene carbonate-reactive functional groups (other than amines) to be converted to urethane polyols of the invention, and then to be incorporated in polyurethanes. The polyols produced may be reacted with one or more polyisocyanates, including diisocyanates, to produce the polyurethanes. The following non-binding Examples help illustrate the invention. Long chain diamines and the diols produced therefrom are particularly useful in fabricating the "soft" segments of segmented polyurethanes. Examples 1 and 2 are illustrative of this aspect. Short chain diamines and the diols produced therefrom are useful in producing the "hard" segments of segmented polyurethanes. Examples 4-7 of EP-A-0361950 are illustrative of this aspect. Example 1 403 grams (.300 Eq.) of aminopropyl terminated polydimethylsiloxane (Petrarch Systems) and 26.64 grams (.303 Eq.) of ethylene carbonate were combined in a reaction vessel previously dried with a purge of nitrogen. The ethylene carbonate was added first, then the diprimary amine. The mixture was initially incompatible. The mixture was stirred and heated on a magnetic hot plate at ambient temperature. The temperature was gradually increased from 40°C to 105°C over the first hour of heating and stirring. The temperature was gradually reduced to 60°C over the next hour, and the heating element was turned off after 2 hours of stirring. The mixture was stirred for an additional 3 hours at room temperature. Infrared spectroscopy performed on samples of the resultant liquid indicated that the expected reaction had taken place to produce a urethane diol. PDMS diamine has the general formula H 2 N-(CH 2 ) 3 -PDMS-(CH 2 ) 3 -NH 2 . The formula for the resultant diol (PDMS urethane diol) is HO-CH 2 -CH 2 -OOC-NH-(CH 2 ) 3 -PDMS-(CH 2 ) 3 -NH-COO-CH 2 -CH 2 -OH in which "PDMS" represents polydimethylsiloxane. Example 2 5.7 grams (.004 Eq.) of the PDMS urethane diol prepared according to Example 1 were added to 28.62 grams (.196 Eq.) of 9-hydroxymethyl octadecanol and 26.6 grams (.200 Eq.) of 4,4-diisocyanatodicyclohexylmethane (Desmodur-W®, produced by Mobay, Inc.). The reactants were mixed together in a beaker, and stirred. The mixture was then placed into a 121°C (250°F) vacuum oven for 10 minutes. The mixture was then removed, stirred for an additional 10 minutes and replaced in the oven for an additional 15 minutes. The mixture was then removed, stirred for 5 minutes and catalyzed with 1 drop of dibutyltin dilaurate. The mixture was stirred until thickening of the mixture made further stirring impossible. The mixture was placed back in the oven overnight to complete the cure. Samples of the material were compression molded at 215.6°C (420°F). The resulting polyurethane had ultimate tensile strength of 23.2x10 6 Pa, yield strength 20.4x10 6 Pa at 7% elongation and 215% elongation at break. The polyurethane is a solid elastoplastic believed useful either as a coating, sheet or molded plastic.

Claims: A process for the preparation of a polyurethane which includes a polysiloxane moiety M, which comprises selecting a compound A n -M wherein M represents the polysiloxane moiety, A represents a primary or secondary amine group and n is a number greater than or equal to 2, reacting said compound with a cyclic carbonate to produce the desired urethane polyol, and reacting said polyol with one or more diisocyanates or polyisocyanates. A process as claimed in Claim 1 wherein in the compound A n -M, n represents 2 and a urethane diol is formed before polyurethane formation. A process as claimed in Claim 1 or Claim 2 wherein in the compound A n -M, M represents a polysiloxane moiety. A process as claimed in any of Claims 1 to 3 wherein the cyclic carbonate is ethylene carbonate. Urethane polyols having the general formula (HO-CH 2 -CH 2 -OOC-NX) n -M, wherein M represents a polysiloxane polymer backbone, NX represents the residue of a primary or secondary amine group and n represents a number equal to or greater than 2. A urethane diol having the formula: HO-CH 2 -CH 2 -OOC-NH-(CH 2 ) 3 -(PDMS)-(CH 2 ) 3 -NH-COO-CH 2 - CH 2 -OH, in which PDMS represents polydimethylsiloxane. A process for the preparation of a urethane polyol as claimed in Claim 5 or Claim 6 which comprises reacting a compound A n -M wherein M is as defined in Claim 5, A is a primary or secondary amine group and n is a number greater than or equal to 2 with ethylene carbonate. A process for preparing a polyurethane as claimed in any of Claims 1 to 4 wherein the urethane polyol produced is a urethane polyol as claimed in Claim 5 or Claim 6 which is then reacted with one or more diisocyanates or polyisocyanates. A process for preparing a polyurethane wherein a urethane polyol as claimed in Claim 5 or Claim 6 is reacted with one or more diisocyanates or polyisocyanates. A process as claimed in Claim 1 wherein the polyurethane includes a polydimethylsiloxane backbone, comprising the steps of: reacting amino terminated polydimethylsiloxane with ethylene carbonate to produce a urethane diol; and reacting the urethane diol produced in the previous step with one or more diisocyanates or polyisocyanates to produce a polyurethane.

Inventors: COURY ARTHUR J, HOBOT CHRISTOPHER M, COURY, ARTHUR J., HOBOT, CHRISTOPHER M.
Applicants: MEDTRONIC INC, MEDTRONIC, INC.
Application year: 1989
Main classification: C08G18
IPC codes: C08G18, C08G71