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
2001-07-16
2002-09-03
Lambkin, Deborah C. (Department: 1626)
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
Reexamination Certificate
active
06444778
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for the production of uretdione polyisocyanates and coating compositions and polyurethane plastics containing these uretdione polyisocyanates.
2. Description of the Prior Art
The production of polyisocyanates having uretdione groups by catalytic dimerization and optionally simultaneous trimerization (generic term: oligomerization) of monomeric aliphatic or cycloaliphatic diisocyanates is known. The advantages and disadvantages of the various dimerizing catalysts or catalyst systems are discussed at length in literature (cf. e.g. J. Prakt. Chem. 336 (1994) 185-200, EP-A 569 804, EP-A 572 995, EP-A 645 411, EP-A 780 377, U.S. Pat. Nos. 5,315,004, 5,461,135, WO 97/45399 and WO 99/07765).
Tertiary phosphines, like tributyl phosphine, are the most important dimerizing catalysts for producing light-coloured polyisocyanates containing uretdione groups on an industrial scale. The resulting polyisocyanates are characterized by extraordinarily low viscosities and consequently are preferred as crosslinker components for low-solvent ‘high-solids’ coating compositions and also completely solvent-free coating compositions.
A substantial disadvantage of the uretdione polyisocyanates produced by catalysis with tertiary phosphines, however, is that they are not sufficiently stable with regard to breaking back down into free diisocyanates. Even at temperatures below the thermal decomposition temperature of uretdione structures, which are known to be thermally labile, for example at 50° C., these products tend to release considerable quantities of monomeric starting diisocyanates over time. The maximum concentration of 0.5 wt.-% of volatile monomeric diisocyanates, which must be adhered to for safe handling of lacquer polyisocyanates, can be exceeded under these conditions after only a few days, and usually after 3 to 4 weeks.
It is an object of the present invention to provide a new, improved, dimerization process, which produces uretdione polyisocyanates in which the content of monomeric starting diisocyanates does not increase significantly when stored for long periods at high temperatures. This object was achieved with the process according to the invention.
SUMMARY OF THE INVENTION
The present invention relates to a process for the production of polyisocyanates containing uretdione groups comprising the steps of oligomerizing a portion of the isocyanate groups of a starting diisocyanate with aliphatically and/or cycloaliphatically bonded isocyanate groups in the presence of a tertiary phosphine, terminating the oligomerization reaction at a desired oligomerization level and removal of the non-converted excess starting diisocyanate by extraction or thin-layer distillation, characterized in that the oligomerization reaction is carried out in the presence of ureas of formula (I) and/or amides of formula (II),
wherein
R
1
, R
2
and R
3
represent independently of one another a hydrogen atom, a saturated or unsaturated aliphatic or cycloaliphatic, an optionally substituted aromatic or araliphatic group, which may contain up to 18 carbon atoms and optionally up to 3 hetero atoms selected from oxygen, sulfur, nitrogen,
R
4
has the meaning given for R
1
to R
3
or represents the group
wherein X represents a divalent, optionally branched, aliphatic or cycloaliphatic group with up to 12 carbon atoms, and R
1
has the meaning given above,
or
R
1
, R
2
and R
3
in formula (I), and
R
1
and R
4
in formula (II) in combination with each other together with the nitrogen atoms of the urea or amide group, and optionally a further nitrogen atom or an oxygen atom can also form heterocyclic rings with 3 to 6 carbon atoms.
The invention also relates to polyurethane plastics prepared from the polyisocyanates containing uretdione groups produced according to this process. The invention also relates to a crosslinker component for binders or binder components with groups, which are reactive with isocyanate groups prepared from the polyisocyanates containing uretdione groups produced according to this process. Optionally, the polyisocyanates containing uretdione groups produced according to this process can be used while blocked with blocking agents.
DETAILED DESCRIPTION OF THE INVENTION
The starting compounds for the process according to the invention include diisocyanates with aliphatically and/or cycloaliphatically bonded isocyanate groups, in particular those of the molecular weight range 140 to 400. Examples include 1,4-diisocyanatobutane, 1,6-diisocyanatohexane (HDI), 2-methyl-1,5-diisocyanatopentane, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3- and 1,4-diisocyanatocyclohexane, 1,3- and 1,4-bis-(isocyanatomethyl)-cyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (isophorone diisocyanate, IPDI), 4,4′-diisocyanatodicyclohexylmethane, 1-isocyanato-1-methyl-4(3)isocyanatomethylcyclohexane, bis-(isocyanatomethyl)-norbornane and 1,3- and 1,4-bis-(2-isocyanato-prop-2-yl)-benzene (TMXDI) as well as mixtures of such diisocyanates. These diisocyanates may be obtained by phosgenation or by phosgene-free processes, for example, thermal splitting of urethanes. Preferred starting compounds are HDI and/or IPDI.
Suitable catalysts for the process according to the invention include tertiary organic phosphines of formula (III)
wherein
R
5
, R
6
and R
7
independently of one another represent an alkyl or cycloalkyl group with up to 10, preferably 2 to 8 carbon atoms, an aralkyl group with 7 to 10, preferably with 7 carbon atoms, or an optionally alkyl-substituted aryl group with 6 to 10, preferably 6 carbon atoms, provided that at most one of the groups represents an aryl group and at least one of the groups represents an alkyl or cycloalkyl group, or wherein
R
5
and R
6
together with the phosphorus atom, form a heterocyclic ring with 4 to 6 atoms, R
7
representing an alkyl group with up to 4 carbon atoms,
or mixtures of such tertiary phosphines.
Suitable tertiary phosphines include triethylphosphine, dibutylethylhosphine, tri-n-propylphosphine, triisopropylphosphine, tri-tert-butylphosphine, tribenzyl-phosphine, dicyclopentylbutylphosphine, tricyclopentylphosphine, benzyldimethyl-phosphine, dimethylphenyl-phosphine, tri-n-butylphosphine, triisobutylphospine, triamylphosphine, trioctylphosphine or butyl-phosphacyclopentane.
The above-mentioned trialkylphosphines are preferred as catalysts for the process according to the invention. More preferred catalysts are tributylphosphine and/or trioctylphosphine.
These catalysts are generally used in a quantity of 0.01 to 5 wt.-%, preferably 0.1 to 3 wt.-%, based on the quantity of starting diisocyanate used.
Optionally, suitable co-catalysts can be used with the catalysts mentioned for the process according to the invention. Suitable co-catalysts include in particular low-molecular weight mono- or polyvalent aliphatic alcohols, preferably those in the molecular weight range 32 to 200. Those include, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, n-hexanol, 2-ethyl-1-hexanol, 1-methoxy-2-propanol, ethylene glycol, propylene glycol, the isomeric butane diols, hexane diols, or octane diols, and diethylene glycol, dipropylene glycol, 2-ethyl-1,3-hexane diol, 2,2,4-trimethylpentane diol, glycerine, trimethylolpropane or mixtures of such alcohols.
These co-catalysts are used in the process according to the invention, if at all, in quantities of up to 5 wt.-%, preferably from 0.5 to 3 wt.-%, based on the quantity of starting diisocyanate used.
The actual co-catalysts are the urethanes formed by the reaction of the co-catalysts with the starting diisocyanate. Therefore, instead of the alcohols mentioned, their urethanes obtained separately by reaction with isocyanates are also suitable as co-catalysts.
According to the invention, the oligomerization reaction is carried out in the presence of special stabilizers. These are ureas of formula (I) and/or amides of formula (II),
w
Halpaap Reinhard
Laas Hans-Josef
Mager Dieter
Bayer Aktiengesellschaft
Gil Joseph C.
Lambkin Deborah C.
Roy Thomas W.
LandOfFree
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