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
1997-09-03
2001-06-05
Sergent, Rabon (Department: 1711)
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...
C252S182200, C252S182290, C524S720000, C524S728000, C528S045000, C528S048000, C528S049000, C560S115000, C560S158000, C560S330000, C560S332000, C560S355000, C564S034000, C564S044000, C564S045000, C564S060000
Reexamination Certificate
active
06242530
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to new blocked polyisocyanates, which have been stabilized against thermal yellowing, and to their use in one-component polyurethane stoving lacquers.
2. Description of the Prior Art
Blocked polyisocyanates are used in one-component polyurethane (1C-PUR) stoving lacquers, especially for automotive clearcoats and coil coating lacquers. In these applications only a very slight thermal yellowing of the lacquers is allowable, even during accidental or unwanted overstoving of the coating composition.
The blocking agent has an effect on the thermal yellowing of blocked isocyanates. Blocking agents that produce only a very slight thermal yellowing are known and include dimethyl pyrazole and 1,2,4-triazole. Both blocking agents have specific disadvantages however. The first blocking agent is relatively expensive, while the second cannot be used for all applications. For example, when 1,2,4-triazole is used to block the most industrially important lacquer polyisocyanates based on HDI, the resulting products have a high tendency to crystallize, which makes them unsuitable for lacquer applications.
Butanone oxime would also be a particularly suitable blocking agent due to its cost and performance if the thermal yellowing that it produces could be significantly reduced.
Stabilizing agents that significantly reduce the thermal yellowing caused also by butanone oxime are known, e.g., from U.S. Pat. No. 5,216,078 and EP-A 654,490, and the commercially available product Luchem HA-R 100 stabilizer from Elf-Atochem):
(Molecular Weight 242)
An object of the present invention is to provide butanone oxime-blocked isocyanates which have improved resistance to thermal yellowing and which may be obtained in an economical and technically easy and reliable manner.
This object may be achieved in accordance with the present invention as described hereinafter.
SUMMARY OF THE INVENTION
The present invention relates to (cyclo)aliphatic polyisocyanates which have a content of blocked and unblocked isocyanate groups (calculated as NCO) of 5 to 25 wt. %, in which at least 95% of the isocyanate groups are present in a form blocked with blocking agents, and which also contain the following stabilizing compounds:
A) 0.1 to 5.0 wt. % of amines having a structural unit corresponding to formula (I) which does not contain any hydrazide units
B) optionally 0.1 to 8.0 wt. % of hydrazides having a structural unit correspond to formula (II)
and
C) 0 to 5.0 wt. % of stabilizers other than A) and B).
The present invention also relates to the use of the blocked polyisocyanates according to the invention as crosslinking agents for organic polyhydroxyl compounds in 1C-PUR stoving lacquers, especially for automotive clearcoats and coil coating lacquers.
REFERENCES:
patent: 4178279 (1979-12-01), Uhrhan et al.
patent: 4983738 (1991-01-01), Kazmierczak et al.
patent: 5043372 (1991-08-01), MacLeay
patent: 5132387 (1992-07-01), Baron et al.
patent: 5142001 (1992-08-01), Yasuda et al.
patent: 5173560 (1992-12-01), Gras et al.
patent: 5216078 (1993-06-01), Cook et al.
patent: 5232988 (1993-08-01), Venham et al.
patent: 5379947 (1995-01-01), Williams et al.
patent: 5504178 (1996-04-01), Shaffer et al.
patent: 5510443 (1996-04-01), Shaffer et al.
patent: 5523377 (1996-06-01), König et al.
patent: 475003 (1992-03-01), None
Engbert Theodor
Konig Eberhard
Noble Karl-Ludwig
Bayer Aktiengesellschaft
Gil Joseph C.
Roy Thomas W.
Sergent Rabon
LandOfFree
Stabilized blocked isocyanates and their use in polyurethane... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Stabilized blocked isocyanates and their use in polyurethane..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stabilized blocked isocyanates and their use in polyurethane... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2491756