Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2001-08-17
2003-09-02
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S060000, C528S061000, C528S062000, C528S063000, C528S059000, C528S064000, C528S065000
Reexamination Certificate
active
06613864
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to polyurethane polymers. More particularly, it relates to reaction injection molded (RIM) polyurethane polymers.
DESCRIPTION OF THE PRIOR ART
Polyurethane polymers are useful in a variety of elastomeric applications. In automobile applications, the advantages of replacing metal and other heavy materials with polyurethane materials are well known. For example, these polymers offer lightweight and corrosion resistant alternatives that can significantly affect cost and performance. Suitable automobile applications include fascia and body panels. The manufacture of molded shoe soles is an example of how isocyanate-based polymers are useful for small molding application.
Unfortunately, the use of polyurethane polymers is not always trouble-free. When filled polyurethane articles are exposed to humid conditions and then exposed to high temperatures, they can exhibit surface defects. This is a particular concern with automobile body parts which are subject to temperatures exceeding 350° F. (177° C.). Polyurethane parts containing too much water can exhibit a surface defect known in the automobile industry as blistering.
Blistering occurs when absorbed moisture absorbed interacts with the polymer to produce gas and the gas accumulates in the part to form a gas pocket. If the surface defect is severe, the entire part may be rejected. As a result, there is a loss in raw materials and production efficiency as well as an increase in waste and scrap materials.
Obvious solutions to the blistering problem include avoiding exposure of the polymeric part to humid conditions or high temperatures. Unfortunately these solutions are not always feasible or desirable. Controlling the humidity in every phase of part's production can be expensive. Heat curing can impart desirable properties to polyurethane parts. Heat can aid in curing paint finishes, thereby improving production rates. Additionally, a polyurethane part may be attached to another article that requires high temperature exposure.
An alternative solution to the blistering problem is to introduce hydrophobic segments into the polymeric backbone. U.S. Pat. No. 4,301,110, issued to Cuscurida, et al., teaches preparing RIM elastomers from a poly(oxybutyleneoxyethylene) glycol, an aromatic polyisocyanate, and a chain extending agent. Unfortunately, polyols having secondary hydroxyls can have a reactivity that differs from polyols having primary hydroxyls. This reactivity difference is often undesirable in many applications.
Similarly, U.S. Pat. No. 5,317,076, issued to Primeaux, II, discloses preparation of RIM elastomers from an amine-terminated poly(oxybutyleneoxyethylene) glycol. The amine catalyzes the reaction as well as reacts with the polyisocyanate. While the amine-terminated polyol has improved reactivity in comparison to polyols only having secondary hydroxyls, it will unfortunately have more catalytic activity than polyols having primary hydroxyls.
It is desirable to prepare polyurethane polymers that do not blister upon exposure to humidity followed by exposure to elevated temperatures. But, it is also desirable to prepare polyurethane polymers from formulations having reactivity similar to that of traditional formulations.
SUMMARY OF THE INVENTION
According to the present invention, a polyurethane composition useful for the manufacture of an elastomeric part is provided. The polyurethane composition comprises a polyisocyanate prepolymer and an active hydrogen containing compound, wherein from about 10 to about 60 percent by weight of the composition is a butylene oxide adduct and from about 70 to about 100 percent by weight of the butylene oxide adduct is present in the polyisocyanate prepolymer. A method for preparing a polyurethane polymer from the polyurethane composition is also provided. Also, a method for preparing polyurethane polymer article from the polyurethane composition is provided.
DESCRIPTION OF THE INVENTION
In the preferred embodiment of the present invention, the polyurethane composition comprises a polyisocyanate prepolymer and an active hydrogen containing compound, wherein from about 10 to about 60 percent by weight of the composition is a butylene oxide adduct and from about 70 to about 100 percent by weight of the butylene oxide adduct is present in the polyisocyanate prepolymer. The present invention is useful for preparing polyurethane polymeric parts.
In the present invention, polyurethane polymer can refer to a polyurethane compound, a polyurea compound, or mixtures thereof A polyurethane compound can be obtained by the reaction of a polyol with a polyisocyanate, wherein the polyol is the active hydrogen containing compound. A polyurea compound can be obtained by the reaction of an amine with a polyisocyanate, wherein the amine is the active hydrogen containing compound. A polyurethane compound or polyurea compound can contain both urethane and urea functionality, depending on what compounds are included in the A and/or B-side formulations. For the purposes of the present application, no further distinction will be made herein between the polyurethane compounds and polyurea compounds. The term “polyurethane polymer” will be used generically to describe a polyurethane compound, a polyurea compound, and mixtures thereof.
Suitable polyisocyanate prepolymers have an NCO content of from 5 to 40 weight percent, preferably from 15 to 30 weight percent. These prepolymers are the reaction products of polyisocyanates and active hydrogen containing compounds such as lower molecular weight diols or triols. Primarily, the active hydrogen containing compounds are multivalent and derived mostly from butylene oxide. The polyisocyanate is present in stoichiometric excess so that the prepolymer retains isocyanate functionality.
The polyisocyanate component of the prepolymer of the present invention can be advantageously selected from organic polyisocyanates, modified polyisocyanates, isocyanate-based prepolymers, and mixtures thereof. These can include aliphatic and cycloaliphatic isocyanates, but multifunctional and particularly difunctional aromatic isocyanates are preferred. Preferred are 2,4- and 2,6-toluenediisocyanate (TDI) and the corresponding isomeric mixtures; 4,4′-, 2,4′- and 2,2′-diiphenylmethane-diisocyanate (MDI) and the corresponding isomeric mixtures; mixtures of 4,4′-, 2,4′- and 2,2′-MD1 and polyphenyl polymethylene polyisocyanates (PMDI); and mixtures of PMDI and TDI.
Also useful with the present invention are aliphatic and cycloaliphatic isocyanate compounds such as 1,6-hexamethylene-diisocyanate; 1-isocyanato-3,5,5-trimethyl-1-3-isocyanatomethyl-cyclohexane; 2,4- and 2,6-hexahydrotoluenediisocyanate. The corresponding isomeric mixtures 4,4′-, 2,2′- and 2,4′-dicyclohexylmethanediisocyanate can also be used. Isophorone diisocyanate can also be used with the present invention.
Also advantageously used for the polyisocyanate component of the prepolymer of the present invention are the so-called modified multifuictional isocyanates, that is, products which are obtained through chemical reactions of the above polyisocyanates. Exemplary polyisocyanates contain esters, ureas, biurets, allophanates, carbodiimides, uretonimines, and urethane groups. Polyisocyanates containing carbodiimide groups and/or uretonimine groups having an isocyanate group (NCO) content of from 10 to 40 weight percent, more preferably from 20 to 35 weight percent, can also be used. These include, for example, polyisocyanates based on 4,4′-, 2,4′- and/or 2,2′-MDI and the corresponding isomeric mixtures, 2,4- and/or 2,6-TD1 and the corresponding isomeric mixtures; mixtures of MDI and PMDI and mixtures of TDI and PMDI and/or diphenylmethane diisocyanates.
Even more preferred for use in the present invention are: (i) polyisocyanates having an NCO content of from 8 to 40 weight percent containing carbodiimide groups and/or urethane groups, from 4,4′-MDI or a mixture of 4,4′- and 2,4′-MDI; (ii) prepoly
Arnold Kenneth B.
James Allan
Porter James R.
Dow Global Technologies Inc.
Gorr Rachel
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