Polyurethanes obtained from hydroxyalkanoates and isocyanates

Details Polyurethanes obtained from hydroxyalkanoates and isocyanates Polyurethanes obtained from hydroxyalkanoates and isocyanates

2001-07-13

2004-06-22

Short, Patricia A. (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S450000, C525S938000, C528S080000, C528S085000, C528S904000

Reexamination Certificate

active

06753384

ABSTRACT:

BACKGROUND OF THF INVENTION
The present invention relates to polyurethanes and to products containing or formed from polyurethanes, such as foams, elastomers, adhesives, coatings, textiles, and the like.
In general, the raw materials for preparing polyurethanes are polyisocyanates, polyols, diamines, catalysts, additives, and blocking agents. The polyisocyanates are either aliphatic, like hexamethylene diisocyanates, isophorone diisocyanate, and 4,4′-diisocyanate dicyclo hexylmethane, or the polyisocyanates can be aromatic, like 2,4-toluene diisocyanate, 1,5-naphthalene diisocyanate, and 4,4′-methylene diphenyl diisocyanate. The polyols are typically polyethers, such as propylene glycol and trimethylolpropane combined with sucrose or polyesters, or ethylene glycol, 1,2-propanediol, 1,4-butenediol, and diethylene glycol combined with glycerol. Polyethers are typically used to produce flexible and rigid foams and polyesters are typically used to produce elastomers, flexible foams, and coatings. Lewis acids and Lewis bases are typically used as catalysts. Additives, which can be present, are typically polysiloxane-polyether, carbodiamide piperazine, chloro-fluoro-hydrocarbons, and phosphorous and nitrogen containing compounds.
U.S. Pat. No. 4,324,880 to Dhein et al. describes the formation of a lacquer from the transesterification reaction of PHB with a polyhydroxycompound such a trimethylol propane or pentaerythritol in the presence of dibutyl tin oxide to produce a reaction product having a hydroxyl number between 50 and 400. No description of the reaction product is given. However, because an excess of PHB was used relative to the polyhydroxycompound, one would expect that the resultant product is predominantly the n-ester, where n is the number of hydroxyl groups present in the polyhydroxy compound. Because the reaction product is ill defined one could expect significant variability in the final lacquer product.
U.S. Pat. No. 5,352,763 to Yamaguchi et al. describes the formation of an oligomer having the general structure (ABA)
n
X where A is a polyhydroxyalkanoate oligomer and B is a difunctional coupling agent and X is a di-isocyanate compound. Reaction conditions are similar to those described in U.S. Pat. No. 4,324,880 with the reactants being the alkylester of the (R) 3-hydroxyalkanoate and a smaller molar contribution of the diol “B” coupling agent.
U.S. Pat. No. 5,665,831 to Neuenschwander et al. describes biodegradable block copolymers containing two distinct copolymer blocks. One of the copolymer blocks is obtained from the transesterification of poly (R) 3 hydroxybutyrate (or poly (R) 3 hydroxybutyrate co (R) 3 hydroxyvalerate) with ethylene glycol using similar reaction conditions described in U.S. Pat. Nos. 4,324,880 and 5,352,763.
In all three patents, the descriptions indicate that the resulting diol ester contains terminal secondary hydroxyl groups on the chiral carbon atoms from the (R) hydoxyalkanoate moiety. Because both terminal hydroxyl groups have the same reactivity, i.e., secondary hydroxyl group, then subsequent reactions with for instance, an isocyanate group will occur with equal frequency at both ends of the oligomer.
In the present invention, the hydroxyl terminated hydroxyalkanoate derivatives preferably have hydroxyl terminal groups with different functionalities. This significantly changes the subsequent reaction methodology when combined with polyisocyanate molecules to form polyurethanes. By modifying the reaction conditions, the present invention generates unique polyurethane structures with enhanced physical properties.
While there are a variety of polyurethanes available, there is a need to form polyurethanes which have the capability of being biodegradable or can be easily recycled. In addition, there is a need to provide polyurethanes which preferably have improved flexibility and/or improved hydrophobicity.
SUMMARY OF THF PRESENT INVENTION
A feature of the present invention is to provide polyurethanes which are biodegradable.
Another feature of the present invention is to provide polyurethanes which can be recycled.
A further feature of the present invention is to provide polyurethanes having improved physical properties, such as improved flexibility and/or improved hydrophobicity.
Additional features and advantages of the present invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and obtained by means of the elements and combinations particularly pointed out in the written description and appended claims.
To achieve these and other advantages, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention relates to a polyurethane obtained by the reaction of at least one isocyanate containing material and at least one compound having at least two hydrogen atoms and capable of reacting with isocyanate groups, such as a hydroxyl-containing material, wherein the compound contains a thermally decomposable or a biodegradable hydroxyalkanoate. The hydroxyl-containing material preferably has hydroxyl terminal groups with different functionalities.
The present invention further relates to foams, elastomers, coatings, adhesives, and textiles containing the above-described polyurethane.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide a further explanation of the present invention, as claimed.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The present invention relates to polyurethanes and products made from or containing polyurethanes. The present invention also relates to methods of making polyurethanes.
For purposes of the present invention, the polyurethane can be a polyurethane obtained by the reaction of a) at least one isocyanate containing material and b) at least one compound containing at least two hydrogen atoms and capable of reacting with isocyanate groups. The compound containing at least two hydrogen atoms contains, as part of the compound, a biodegradable or a thermally decomposable hydroxyalkanoate. As a result, the polyurethane is preferably at least partially biodegradable and/or thermally decomposable.
For purposes of the present invention, the polyurethane of the present invention can be linear or cross-linked. The polyurethane can be any type of polyurethane such as, but not limited to, castable, millable, thermoplastic, cellular, sprayable, poromeric (e.g., porous), fibrous, and the like. These various types of polyurethanes can be formed using the components of the present invention along with the knowledge of those skilled in the art with respect to making these particular types of polyurethanes. For instance, a linear polyurethane is typically prepared by reacting a hydroxyl-containing group with an aliphatic diisocyanate. Castable polyurethanes are typically obtained by extending hydroxyl-containing compounds with diisocyanate to yield an isocyanate-terminated prepolymer. Glycol or diamine chain extenders can then be used to bring about further chain extension. Typically, a slight excess of diisocyanate is normally employed and this enables the crosslinking to occur at the urethane or urea group.
The molecular weight of the polyurethane can be any molecular weight and depends upon the products used to form the polyurethane. Strictly as an example, the molecular weight of the polyurethane can be from about 20,000 to about 200,000. Other molecular weight ranges can be obtained.
The isocyanate containing material can typically be a polyisocyanate. Preferably, the isocyanate containing material contains at least two isocyanate groups per molecule. The polyisocyanates can be any polyisocyanate traditionally used in the formation of polyurethanes. These polyisocyanates can be modified or unmodified versions. Preferably, the polyisocy

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