Hydroxyl functional monomers, their preparation and their use in preparing polyurethanes

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 in general, and in particular to the formation of hydroxyl functional monomers 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. EP-A-280815 discloses the preparation of a range of hydroxyalkyl carbamates from cyclic carbonates and alkylene diamines. Polyurethane polyols suitable as high solids coatings, inks and adhesives may be prepared from these carbamates. US 4704446 discloses polyurethanes prepared from poly (alkylene ether) urethane polyols blended with suitable short- and long-chained polyols prior to reaction with a polyisocyanate. SUMMARY OF THE INVENTION The present invention provides a process for the preparation of a polyurethane which includes a desired backbone of a dimer acid, which comprises selecting a compound (NH₂)₂-D wherein D represents the backbone of a dimer acid, reacting said compound with a cyclic carbonate to produce the desired urethane polyol, and reacting said polyol with one or more diisocyanates or polyisocyanates. 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-0 361 950, entitled "BIOSTABLE SEGMENTED ALIPHATIC POLYURETHANES AND PROCESSES FOR THEIR PREPARATION". DESCRIPTION OF THE INVENTION In some applications requiring elastoplastic polyurethanes, inclusion of a dimer acid backbone in the "soft" segments of segmented polyurethanes has been found particularly desirable. The dimer acids as the term is used herein are described and discussed in the book "The Dimer Acids", edited by Edward C. Leonard, published by Humko Sheffield Chemical , 1975. Dimer acids are the reaction product of a Diels-Alder addition or other coupling process of two aliphatic, unsaturated, predominantly 18 carbon fatty acids. Dimer acids take the form of single ring, double ring or branched chain structures predominantly having two carboxylic acid functionalities. Dimer acid based products commercially available include dimer isocyanate, dimer amine, and dimerol. All three are produced beginning with dimer acid, and include the 36 carbon dimer acid backbone. Representing the 36 carbon dimer acid backbone as "D", the formula for dimerol is HO-D-OH, the formula for dimer isocyanate is OCN-D-NCO, and the formula for dimer amine is H₂N-D-NH₂. While dimerol may be reacted with diisocyanates to produce polyurethanes, dimer amine is presently more readily obtainable. Dimer acids and derivatives thereof are available from Humko Sheffield Chemical Operation of Kraftco Corporation, U.S.A. Whilst there is some variability in the nature of the preparations available, it is well within the scope of a man skilled in the art to establish the suitability of a particular preparation for his purposes using simple experimentation. 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, and Examples 1 and 2 are illustrative of this aspect. Example 1 268.2 grams (1.00 eq.) of dimer amine and 89.0 grams (1.01 eq.) of ethylene carbonate (converted to a liquid by warming) were weighed into a nitrogen purged jar. A magnetic stirring bar was placed in the jar and it was covered. The mixture was warmed with stirring on a magnetic hot plate. The mixture cleared within 30 minutes and its viscosity rose. The mixture was stirred a total of 3 hours while the temperature was maintained between 70-90°C. Infrared spectroscopy indicated that the carbonate absorption (1800cm⁻¹) had disappeared while being replaced by the expected urethane carbonyl peak (1700cm⁻¹). The product of Example 1, bis-hydroxyethyl dimer urethane (hereafter BHEDU diol) is useful in the preparation of a variety of polymers. The formula for BHEDU diol is HO-CH₂-CH₂-OOC-NH-D-NH-COO-CH₂-CH₂-OH, in which "D" represents the hydrocarbon backbone of dimer acid. In particular, it is useful in production of ether and ester free polyurethanes as disclosed in our above-mentioned co-pending application of even date herewith EP-A-0 361 950 One example of a polyurethane produced employing the diol of Example 1 is set forth in Example 2, below. Example 2 29.1 grams (.10 Eq.) of dimer diisocyanate were mixed with 7.4 grams (.125 Eq.) of 1,6-hexane diol and 8.9 grams (.025 Eq.) of BHEDU diol. The covered mixture was placed into a 121°C (250°F) oven until the solid 1,6-hexane diol melted. At that point, the mixture was removed from the oven and stirred for 10 minutes, and a drop of dibutyltin dilaurate was added to catalyze the reaction. The mixture was stirred until thickening indicated that the reaction was well underway. The covered mixture was returned to a 121°C (250°F) oven for 3 hours. After removing the mixture from the oven, 20.0 grams (.15 Eq.) of 4,4-diisocyanatodicyclohexlmethane (Desmodur-W®, produced by Mobay, Inc.) and 4.5 grams (.10 Eq.) of 1,4-butane diol were added to the mixture and stirred. The covered mixture was returned to the 121°C (250°F) oven for 2 minutes, and removed and stirred until thickening indicated that polymerization was well underway. The covered mixture was returned to the oven overnight to complete the cure. The resultant product is a solid elastoplastic polyurethane having an ultimate tensile strength of 3710 p.s.i., 100% secant modulus of 1613 p.s.i., 388% elongation at break and Shore hardness of 88A. The polyurethane produced is believed useful as an insulator for implantable electrical leads and/or as a coating or other functional portion of an implantable medical device. The general method disclosed in Example 1 is also applicable to other polyamines to produce polyols including diols appropriate for use in production of polyurethanes and other polymers.

Claims: A process for the preparation of a polyurethane which includes a dimer acid moiety D, which comprises selecting a compound (NH₂)₂-D, wherein D represents the hydrocarbon backbone of a dimer acid, reacting said compound with a cyclic carbonate to produce the desired urethane diol, and reacting said diol with one or more diisocyanates or polyisocyanates. A process as claimed in Claim 1 wherein the urethane diol is formed before polyurethane formation. A process as claimed in Claim 1 or Claim 2 wherein the cyclic carbonate is ethylene carbonate. A urethane diol having the formula: HO-CH₂-CH₂-OOC-NH-D-NH-COO-CH₂-CH₂-OH, wherein D represents the hydrocarbon backbone of dimer acid. A process for the preparation of a urethane diol as claimed in Claim 4 which comprises reacting a compound (NH₂)₂-D wherein D is as defined in Claim 4 with ethylene carbonate. A process for preparing a polyurethane as claimed in Claim 1 or Claim 2 wherein the urethane diol produced is a urethane diol as claimed in Claim 4 which is then reacted with one or more diisocyanates or polyisocyanates. A process for preparing a polyurethane wherein a urethane diol as claimed in Claim 4 is reacted with one or more diisocyanates or polyisocyanates. A process for preparing a segmented polyurethane which includes the hydrocarbon of dimer acid which comprises reacting dimer amine with ethylene carbonate to produce a urethane diol, and reacting said diol with one or more diisocyanates or polyisocyanates.

Inventors: COURY ARTHUR J, HOBOT CHRISTOPHER M, COURY, ARTHUR J., HOBOT, CHRISTOPHER M.
Applicants: MEDTRONIC INC, MEDTRONIC, INC.
Application year: 1989
Main classification: C07C271
IPC codes: C08G18, C08G71, C07C271