Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-01-15
2004-08-31
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S170000
Reexamination Certificate
active
06784219
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to polyurethane cast elastomers based on 2,3,5,6-tetramethyl-1,4-diisocyanatobenzene (also known as “durene diisocyanate”), their preparation and their use for the production of moldings exposed to high mechanical stresses.
Polyurethane cast elastomers (PU elastomers) have been known for a long time and are described in numerous patent and literature publications.
An overview of PU elastomers, their properties and uses is given, for example, in Kunststoff-Handbuch, Volume 7, Polyurethane, 3rd revised edition, 1993, edited by Prof. Dr. G. W. Becker and Prof. Dr. D. Braun (Carl-Hanser-Verlag, Munich, Vienna).
For the preparation of polyurethane elastomers with high-quality mechanical properties, 1,5-diisocyanatonaphthalene (1,5-NDI) has proven to be an isocyanate unit suitable for such elastomers.
Because 1,5-NDI is not easy to handle due to its relatively high melting point, attempts to replace 1,5-NDI with cheaper diisocyanates that are easier to handle without losing the favorable properties of PU elastomers based on 1,5-NDI continue to be made.
In this connection, German Offenlegungsschriften DE 19 627 907; 19 628 145; and 19 628 146 describe attempts to replace 1,5-NDI with other diisocyanates that are said to be suitable for providing compact or cellular PU elastomers with a comparably favorable profile of mechanical properties.
Both when 1,5-NDI is used as an isocyanate component for PU elastomers and when the diisocyanates proposed in the above-mentioned German Offenlegungsschriften (i.e., 4,4′-stilbene diisocyanate, 3,3′-dimethoxy-4,4′-diisocyanato-diphenyl and 1,4-phenylene-diisocyanate) are used with at least one additional aromatic diisocyanate chosen from the group of toluene-diisocyanate and diphenylmethane-diisocyanate, the color stability of the elastomers can not yet be regarded as satisfactory.
Moreover, an improvement in the storage stability of prepolymers based on the above-mentioned isocyanate components when the polyurethane cast elastomers are prepared by the prepolymer process is also required.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide new polyurethane cast elastomers having increased color stability, combined with high-quality mechanical properties.
It is also an object of the present invention to provide PU cast elastomers with good properties that are inexpensive to prepare.
It is another object of the present invention to provide prepolymers from which polyurethane cast elastomers may be produced that have a high storage stability, which results in a longer, particularly user-friendly processing time.
These and other objects which will be apparent to those skilled in the art are accomplished by using durene diisocyanate to produce the NCO-terminated pre-polymers and/or cast polyurethane elastomer.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to polyurethane elastomers (PU elastomers) prepared from
a) at least one higher molecular weight polyhydroxyl compound having an average molecular weight of from about 500 to about 6,000 and a functionality of at least 2,
b) 2,3,5,6-tetramethyl-1,4-diisocyanatobenzene (durene diisocyanate) and
c) at least one low molecular weight chain-lengthening and/or crosslinking agent having at least two hydroxyl groups and an average molecular weight of from about 18 to about 800.
Higher molecular weight hydroxyl compounds preferably used in the process of the present invention include those hydroxyl compounds having an average molecular weight of from about 800 to about 4,000, most preferably from about 1,000 to about 3,500.
Suitable higher molecular weight polyhydroxy compounds include, in principle, any of the polyhydroxyl compounds which are used in polyurethane chemistry. Polyether polyols, polyester polyols and polycarbonates containing hydroxyl groups are preferred.
The polyester, polyether and polycarbonate polyols can be employed either individually or in a mixture with one another. Suitable polyester, polyether and polycarbonate polyols which can be used for producing the PU elastomers according to the invention are listed in detail, for example, in DE 19 627 907, at pages 4 and 5.
Polyester components which are preferably employed are those which are produced from succinic acid or adipic acid and ethylene glycol, diethylene glycol, 1,4-butanediol or 1,6-hexanediol. Those polyesters produced from adipic acid and ethylene glycol are particularly preferred.
Polyoxytetramethylene glycols are the preferred polyether polyols.
The chain-lengthening and crosslinking agents which can be employed in the practice of the present invention include any of the chain-lengthening and crosslinking agents known from polyurethane chemistry. These chain lengthening and crosslinking agents generally have an average molecular weight of from about 18 to about 800, preferably from 18 to 400, most preferably from 60 to 300. These chain lengthening and crosslinking agents may be derived, for example, from alkanediols, dialkylene glycols and polyoxyalkylene glycols (chain-lengthening agents) and 3- or 4-hydric alcohols and oligomeric polyoxyalkylene polyols with a functionality of 3 to 6 (crosslinking agents). In this connection, reference is again made to DE-A-19 627 907, pages 5 and 6 which describes such agents in greater detail. Chain-lengthening and crosslinking agents which are particularly preferably employed include: ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, hydro-quinone bis(2-hydroxyethyl) ether, 1,1,1-tris(hydroxymethyl)-n-propane and water.
The chain-lengthening and crosslinking agents can, of course, be employed individually or in a mixture with one another. The specific chain-lengthening, crosslinking agents and higher molecular weight polyhydroxyl compounds used are selected on the basis of the desired profile of mechanical properties of the PU elastomers to be prepared.
The PU elastomers of the present invention based on durene diisocyanate can be obtained both as compact elastomers and in cellular form.
To establish the mechanical properties, for example, the hardness, in the PU elastomers, the amounts of the reactants can be varied over a wide range of ratios. The elastomer hardness increases as the content of difunctional chain-lengthening and at least trifunctional crosslinking agents in the PU elastomer is increased. The amounts of the reactants necessary to achieve the desired hardness can be determined experimentally in a simple manner. To prepare compact PU elastomers, it is preferred that the higher molecular weight polyol (component a)) be used in an amount of from about 30 to about 96 wt. % (based on the total weight of the reactive components), more preferably from about 55 to about 90 wt. %; the 2,3,5,6-tetramethyl-1,4-diisocyanatobenzene (component b)) be used in an amount of from about 5 to about 40 wt. % (based on the total weight of the reactive components), preferably from about 10 to 25 wt. %; and the crosslinking and/or chain extending agent (component c)) be used in an amount of from about 0.5 to 30 wt. % (based on the total weight of the reactive components), preferably from about 1 to 20 wt. %.
For the preparation of PU elastomers with a cellular structure, the amount of component a) is generally from about 46 to about 96 wt. % (based on the total weight of the reactive components), preferably from about 65 to about 90 wt. %; the amount of component b) is 5 to 40 wt. % (based on the total weight of the reactive components), preferably from about 10 to about 25 wt. %; and the amount of component c) is from about 0.1 to 20 wt. % (based on the total weight of the reactive components), preferably from about 0.2 to about 10 wt. %.
The conventional additives of polyurethane chemistry can, of course, also be incorporated into the PU elastomers according to the present invention. Examples of such additives include: surface-active substances, fillers, flameproofing agents, nucleating agents, oxidation retardants, stabilizers, lubricants and mold rel
Heitkämper Peter
Jost Klaus
Mayer Eduard
Münzmay Thomas
Wagner Joachim
Bayer Aktiengesellschaft
Gil Joseph C.
Gorr Rachel
Mrozinski, Jr. John E.
LandOfFree
Polyurethane cast elastomers based on durene diisocyanate does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyurethane cast elastomers based on durene diisocyanate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyurethane cast elastomers based on durene diisocyanate will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3346133