Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-12-03
2002-06-11
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S198000, C524S199000, C524S589000, C524S591000, C524S839000, C524S840000, C528S044000, C528S069000
Reexamination Certificate
active
06403702
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for the preparation of one-shot polyurethane cast elastomers containing liquid, diurethane non-migrating plasticizers. This process comprises reacting via the one-shot process an organic polyisocyanate, an isocyanate-reactive polyol component, and at least one chain extender and/or crosslinking agent in the presence of a liquid diurethane plasticizer.
Plasticizers are generally used in plastics (i.e., PVC) to adjust hardness, flexibility, and processing characteristics. Plasticizers are also used in some commercial polyurethane elastomer formulations to provide products exhibiting higher flexibility, lower hardness, and lower rebound resulting in increased energy absorption. However, these products can potentially embrittle over time due to migration of the plasticizer. Plasticizers that have a minimal effect on hardness and physical properties, and which are non-migrating are desirable for polyurethane elastomers prepared by a one-shot cast elastomer process.
Diurethanes are known and described as suitable stabilizing additives for sealing compounds in, for example, U.S. Pat. No. 4,824,888 and as plasticizers for polyurethane based sealing and adhesive compositions in U.S. Pat. No. 5,525,654.
U.S. Pat. No. 4,824,888 discloses diurethanes corresponding to one of the general formulas:
R
1
—NH—CO—O—R
2
—O—CO—NH—R
1
(I)
R
3
—O—CO—NH—R
4
—NH—CO—OR
3
(II)
wherein:
R
1
: represents a C
3
-C
22
alkyl radical, a C
7
C
22
aralkyl radical, preferably C
7
-C
22
phenylalkyl or C
8
-C
22
alkylphenyl alkyl or a phenyl radical;
R
2
: represents the residue of a difunctional polypropylene glycol having a number average molecular weight of from 1000 to 4000;
R
3
: represents the residue of a monofunctional polypropylene glycol monoalkyl (preferably C
1
-C
6
monoalkyl) ether having a number average molecular weight of from 500 to 2000; and
R
4
: represents a C
4
-C
36
alkylene group, a diaryl methane group, preferably diphenylmethane or ditolylmethane, or a tolylidene group;
as stabilizing additives in sealing compounds based on isocyanate-terminated prepolymers of difunctional and trifunctional polyether or polyester polyols and/or polyvinylchloride swellable copolymers of vinyl chloride with monomers from the group vinyl acetate, vinyl propionate, alkyl acrylates. These diurethanes are reaction products of monofunctional alcohols and diisocyanates. In particular, the monoalcohols are monofunctional polypropylene glycol monoalkyl ethers having a molecular weight of about 500 to 2000. These diurethanes are also suitable stabilizing agents for isocyanate-terminated polyurethane prepolymers, and for polyvinyl chloride homopolymer or copolymer plastisols. Disclosed are diurethanes prepared by reaction of diols with monoisocyanates and diurethanes prepared from symmetrical diisocyanates with polyether monoalcohols.
Moisture curing sealing and/or adhesive compositions based on alkoxysilane-terminated polyurethanes which contain diurethanes as plasticizers are described by U.S. Pat. No. 5,525,654. These diurethanes are prepared from either diol mixtures and monofunctional isocyanates wherein substantially all the free hydroxyl groups are reacted, or from diisocyanates and monofunctional alcohols wherein substantially all the free isocyanate groups are reacted.
Other urethane plasticizers are disclosed in, for example, U.S. Pat. Nos. 4,123,413 and 4,482,408. The urethane plasticizers of U.S. Pat. No. 4,123,413 correspond to one of three general formulas, and are prepared by reaction of an alcohol or a phenol with an isocyanate, from amines and chloroformates, or from chloroformamides and alcohols or phenols in the presence of acid binding agents.
The urethane plasticizer of U.S. Pat. No. 4,482,408 is octyidecylbutyl urethane and is prepared by reacting an equimolar mixture of octyidecyl isocyanate and n-butyl alcohol. This urethane plasticizer is a mono-urethane described as a straight-chain, saturated, carbamic acid ester and is suitable as a plasticizer for propellant compositions with problems of plasticizer migration which typically occur during propellant storage.
Useful diurethane plasticizers according to the present invention are based on asymmetrical diisocyanates and monoalcohols or mixtures of monoalcohols. They are prepared by either adding the alcohols to the asymmetric diisocyanates or by addition of the diisocyanates to the monofunctional alcohol(s). The diurethane plasticizers are liquid at 25° C. and usually exhibit low viscosity. The resulting diurethanes do not contain any free hydroxyl- or isocyanate-groups, and thus they are non-reactive and can be added to either isocyanates or polyols to form stable mixtures.
The use of these diurethane plasticizers in one-shot cast elastomers has several important benefits:
1) Addition to either the polyol or the isocyanate composition allows one to adjust the mix ratio very favorably, i.e., to adjust a 1:1.5 ratio to an easier to process ratio of 1:1.
2) Addition to either the polyol or the isocyanate compositions allows one to adjust the viscosities of the two components very favorably, i.e., to obtain viscosities which are similar which facilitates the mixing process.
3) Unmodified polyisocyanates that contain no urethane, allophanate, urea, or biuret groups are usually very incompatible with polyol compositions due to major differences in surface energy (i.e., polarity). Addition of the diurethane containing plasticizers according to the invention to either the polyisocyanate or both the polyisocyanate and polyol side of one-shot elastomer formulations helps to overcome these incompatibility problems and thus facilitates mixing.
Although it is possible in one-shot elastomer formulations to meter the single components separately and mix them, i.e., in a reactor or mixhead, it is preferred to combine the diurethane containing plasticizer with the polyisocyanate and/or the polyol/chain extender blend prior to mixing the isocyanate and the isocyanate reactive polyol components.
Besides the processing advantages diurethane plasticizers provide in one-shot polyurethane elastomer formulations, they do not show any substantial migration or lower the physical properties of the final polyurethane elastomer upon aging to the extent observed in state of the art non-urethane group containing plasticizers. As a result, the high performance properties of one-shot polyurethane elastomers are effected minorly upon aging when diurethane containing plasticizers are used in the formulation.
SUMMARY OF THE INVENTION
This invention relates to a process for the preparation of one-shot polyurethane cast elastomers containing liquid, diurethane non-migrating plasticizers. This process comprises reacting, via the one-shot process,
(A) at least one organic polyisocyanate component,
(B) at least one isocyanate-reactive component, and
(C) at least one chain extender and/or crosslinking agent, in the presence of
(D) a liquid diurethane plasticizer having a viscosity of less than about 50,000 mPa·s, preferably less than 15,000 mPa·s, at 50° C. Suitable liquid diurethane plasticizers comprise the reaction product of:
(1) an asymmetrical diisocyanate component having an NCO group content of about 32.0 to about 48.3%, a functionality of about 2.0, and having a viscosity of less than 1000 mPa·s at 25° C., preferably less than about 100 mPa·s; and
(2) at least one monoalcohol having a molecular weight of about 100 to about 1,000, preferably of about 128 to about 720, and an OH number of about 56 to about 560, preferably of about 78 to about 438.
A preferred asymmetrical diisocyanate component comprises an isomeric mixture of diphenylmethane diisocyanate containing at least about 20% (preferably from 40 to 70) by weight of the 2,4′-isomer, less than about 80% (preferably about 30-60%) by weight of the 4,4′-isomer, and about 0 to about 5% (preferably no more than about 2%) by weight of the 2,2′-isomer.
DETAILED DESCRIPTION OF THE INVENTION
Suitable organic polyisocya
Markusch Peter H.
Pantone Richard S.
Bayer Corporation
Brown N. Denise
Gil Joseph C.
Niland Patrick D.
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