Reactive compositions with an extended pot life

Details Reactive compositions with an extended pot life Reactive compositions with an extended pot life

1997-08-07

2003-09-23

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...

C528S066000, C528S079000, C427S388100, C427S389000, C427S389900, C427S393500

Reexamination Certificate

active

06624282

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to reactive compositions based on NCO prepolymers and polyol chain extenders having an extended pot life at room temperature and a high reactivity at elevated temperature, as well as the use of these compositions to coat substrates of any type, principally flexible substrates such as textiles and leather.
Solvent-free or low-solvent reactive compositions based on NCO prepolymers are known. Such compositions are prepared by mixing a ketoxime-blocked NCO pre-polymer based on an aromatic polyisocyanate with a polyamine chain extender, followed by curing the composition by heat treatment (which results in splitting off the ketoxime) and optionally evaporating the solvent. Reactive compositions of this type used for coating flexible substrates are described, for example, in German Offenlegungsschrift 2,902,090.
Reactive compositions based on ketoxime-blocked prepolymers of aliphatic poly-isocyanates are also known. E.g., European Patent Application 65,688. However, they require substantially longer curing times than the systems based on aromatic polyisocyanates, which is the reason that reactive systems based on aliphatic poly-isocyanates have not previously been used widely in industry.
During curing of the two systems described above, the ketoxime splits off, which means that the waste air must be treated even if the systems do not contain solvents. Furthermore, blocking of free NCO groups leads to additional urethane groups and thus to an increase in the viscosity of the compositions, which in most cases must be compensated for by adding solvents.
The object of the present invention was, therefore, to provide reactive compositions based on NCO prepolymers that overcome the disadvantages of the prior art. It has now surprisingly been found that this object can be achieved by choosing specific polyols as chain extenders.
SUMMARY OF THE INVENTION
The present invention accordingly provides reactive compositions comprising
(A) an NCO prepolymer based on aliphatic and/or cycloaliphatic polyisocyanates and having an NCO content of 1 to 8 wt. % (preferably 2 to 4 wt. %) based on the aliphatic and/or cycloaliphatic polyisocyanate and a monomeric polyisocyanate content of less than 2 wt. % (preferably less than 0.5 wt. %) (quantities in each case being relative to component (A)),
(B) an amine-free chain extender comprising at least 50 equivalent percent (preferably at least 80 equivalent percent), relative to the NCO-reactive groups of the chain extender, of compounds melting between 50° and 160° C. and having the formula (I)
HO—X—Y—X—OH  (I)
 wherein
Y denotes methylene, ethylene, —C≡C—, 1,4-, 1,3-, or 1,2-cyclohexylene, or 1,4-, 1,3-, or 1,2-phenylene, and
X denotes methylene, —OCH
2
CH
2
— (wherein oxygen is bonded to group Y), or 1,4-, 1,3-, or 1,2-cyclohexylene, and
(C) 0 to 20 wt. % (preferably 0 to 15 wt. %), relative to component (A), of inert organic solvents,
wherein the equivalent ratio of the free NCO groups of component (A) to the NCO-reactive groups of component (B) is 0.90 to 1.35 (preferably 1 to 1.25).
DETAILED DESCRIPTION OF THE INVENTION
The most preferred compound of formula (I) is 1,4-bis(2-hydroxy-ethoxy)benzene.
As used hereinafter, the expression “mean molecular weights” is understood to mean number average molecular weights.
The use of 1,4-bis(2-hydroxyethoxy)benzene as a structural element for polyurethanes is known. See I. S. Lin., J. Biranowski, D. H. Lorenz,
Adv. Urethane Sci. Technol.,
8, 105-117 (1981); B. L. Williams, L. Weissbein, A. Singh,
Rubber Age,
57-65 (1968); and S. A, Iobst, H. W. Cox,
J. Appl. Polym. Sci.
23, 2513-2527 (1979).
In addition, compounds of formula (I) have already been recommended in individual cases as a chain extender for reactions involving NCO prepolymers. Cf. U.S. Pat. No. 4,119,594. This patent, however, concerns reactive systems using prepolymers based on aromatic polyisocyanates and accordingly cannot contribute to achieving the above-mentioned object.
It has now been found that the success of the present invention can be promoted by ensuring that the compound of formula (I) is heterogeneous with respect to the remaining components of the reactive composition (i.e., particularly component (A) and optionally the proportion of component (B) that is not a compound of formula (I)). Particularly favorable results are achieved if the compound of formula (I) is present in solid form under the mixing condition (i.e., at temperatures of up to 50° C.). In this respect, the present invention differs from the process of U.S. Pat. No. 4,086,214, which teaches that heterogeneity between the chain extender and higher molecular weight polyol should be avoided by a preliminary reaction with part of the isocyanate.
A reaction mixture is considered to be heterogeneous if the compound of formula (I) is present in an amount exceeding 50% in the form of particles having a mean particle size of more than 1 &mgr;m. The mean particle size is the particle size above and below which 50 wt. % of the particles are present.
Preferred NCO prepolymers (A) have specific number average molecular weights of 500 to 10,000 (preferably 700 to 8000).
The NCO prepolymers (A) can be prepared by reacting organic polyisocyanates (a) with NCO-reactive compounds (b). Suitable organic polyisocyanates (a) include aliphatic and cycloaliphatic polyisocyanates. Preferred polyisocyanates (a) are compounds of the formula Q(NCO)
n
having a mean molecular weight below 800, wherein n is a number from 2 to 4 and Q is an aliphatic C
4
-C
12
hydrocarbon group or a cycloaliphatic C
6
-C
15
hydrocarbon group, for example, diisocyanates from the series 4,4′-diisocyanatodicyclohexylmethane, 3-isocyanatomethyl-3,3,5-trimethylcyclohexylisocyanate (isophorone diisocyanate, or IPDI), tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), 2-methylpentamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate (THDI), dodecamethylene diisocyanate, 1,4-diisocyanatocyclohexane, 4,4′-diisocyanato-3,3′-dimethyldicyclohexylmethane, 4,4′-diisocyanatodicyclohexylpropane-(2,2), 3-isocyanatomethyl-1-methyl-1-isocyanatocyclohexane (IMCI), 1,3-diisocyanato-4-methylcyclohexane, 1,3-diisocyanato-2-methylcyclohexane, and &agr;,&agr;,&agr;′,&agr;′-tetramethyl-m- or -p-xylylene diisocyanate (TMXDI), as well as mixtures consisting of these compounds.
It is preferred to use 4,4′-diisocyanatodicyclohexylmethane, especially industrial grade 4,4′-diisocyanatodicyclohexylmethane containing 10 to 50 wt. % (preferably 15 to 20 wt. %) of trans,trans-4,4′-diisocyanatodicyclohexylmethane.
For special applications, other polyisocyanates may also be used in amounts of up to 10 equivalent percent relative to the NCO groups of the total polyisocyanates (a), as described, for example, in
Methoden der organischen Chemie
(Houben-Weyl), Vol. 14/2, Georg Thieme-Verlag, Stuttgart, 1963, pages 61 to 70, and W. Siefken in
Liebigs Annalen der Chemie,
562, pages 75 to 136. It is particularly preferred, however, to use only aliphatic and/or cycloaliphatic diisocyanates, especially 4,4′-diisocyanatodicyclohexylmethane, as the sole polyisocyanate.
Particularly preferred NCO-reactive compounds (b) are polyols. Higher molecular weight hydroxyl compounds and, to a lesser extent, also lower molecular weight hydroxyl compounds may be used as polyols.
Higher molecular weight hydroxyl compounds include the hydroxy polyesters, hydroxy polyethers, hydroxy polythioethers, hydroxy polyacetals, hydroxy polycarbonates, and dimeric fatty alcohols and/or ester amides conventionally used in polyurethane chemistry, each having mean molecular weights of 400 to 8000 (preferably those compounds with mean molecular weights of 500 to 6500). Hydroxy polyethers, hydroxy polyesters, and hydroxy polycarbonates are particularly preferred. Polyols conventionally used in polyurethane chemistry having molecular weights of 62 to 399 may be used as lower molecular weight polyhydroxyl compounds, for exam

Affiliated with

Also associated with

Rating

Reactive compositions with an extended pot life does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Reactive compositions with an extended pot life, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reactive compositions with an extended pot life will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3024784