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
1995-03-21
2001-02-20
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...
C524S589000, C528S073000
Reexamination Certificate
active
06191212
ABSTRACT:
SUMMARY OF THE INVENTION
This invention relates to a moisture-curing hotmelt adhesive containing:
a) polyurethane prepolymers, with a content of NCO groups of 0.16 to 0.84 moles of NCO groups per kg of prepolymer, obtainable by reaction of crystalline polyester polyols having a number average molecular weight in the range from 2000 to 10,000, optionally in admixture with liquid and/or amorphous polyester polyols and/or polyether polyols having a number average molecular weight in the range from 500 to 10,000, with isocyanates having a functionality of more than 1 and
b) diisocyanates trimerized to isocyanurates.
STATEMENT OF RELATED ART
Moisture-curing or moisture-crosslinking hotmelt adhesives based on polyurethanes are normally prepared in one step from polyols and isocyanates having a functionality of more than 1, i.e. containing more than one NCO group per isocyanate molecule, with an excess of NCO groups based on free OH groups in the polyols. The molecular weight of the prepolymers obtained is dependent upon the functionality of the polyols and isocyanates used, an increase in functionality resulting in an increase in molecular weight. Although a relatively high functionality of the polyols and isocyanates leads to relatively high tensile shear strengths of the bonds established with the moisture-curing hotmelt adhesives, the viscosity of the prepolymers increases at the same time exponentially with their molecular weight. Accordingly, there are narrow limits to improvements in tensile shear strength by the use of polyols and isocyanates of relatively high functionality.
Another disadvantage of the moisture-curing hotmelt adhesives known from the prior art with an excess of the generally liquid isocyanates lies in the fact that the isocyanates have a substantial vapor pressure at the temperatures in the region of 130° C. at which moisture-curing hotmelt adhesives are normally processed, so that special protective measures have to be taken during processing.
DETAILED DESCRIPTION OF THE INVENTION
Object of the Invention
The problem addressed by the present invention was to improve the processing and performance properties of typical moisture-curing hotmelt adhesives and, more particularly, to increase the mechanical strength of the bond without any adverse effect on the viscosity of the hotmelt adhesive, its open time or its initial strength.
DESCRIPTION OF PREFERRED EMBODIMENTS
The isocyanurates present in the moisture-curing hotmelt adhesives according to the invention have a such a low vapor pressure, even at typical hotmelt processing temperatures, that the above-mentioned protective measures during processing are no longer necessary or do not to be taken to the same extent as before.
The moisture-curing hotmelt adhesives according to the invention may contain typical additives familiar to one skilled in the art. Typical examples of such additives are fillers, tackifiers and plasticizers. They may also contain typical catalysts which accelerate curing of the hotmelt adhesives, for example metal catalysts, such as dibutyl tin dilaurate, amine catalysts, such as dimorpholine diethyl ether and the like.
Crystalline polyester polyols in the context of the invention are those which are solid and at least partly crystallized at room temperature, for example solid partly crystalline polyester polyols having a degree of crystallization of more than 30%, as measured with X-rays in accordance with Neff, Grundlagen und Anwendung der Röntgenfeinstruktur [Title in English: Fundamentals and Applications of X-ray Fine Structure], (Verlag R. Oldenbourg, München, 1959), page 320. Typical examples are the commercially available DYNACOLL® types RP 320, 340, 350 and 360.
Liquid polyester polyols are, for example, those which are liquid at 20° C. and have a glass temperature below 0° C. Typical examples are the DYNACOLL® types 210, 220, 230 and 250.
Amorphous polyester polyols are solid at ambient temperature and have a glass temperature above 0° C., for example the DYNACOLL® types RP 110, 130 and 140.
In one preferred embodiment of the invention, the polyurethane prepolymers have a content of NCO groups of 0.22 to 0.72 moles of NCO groups per kg of prepolymer.
Polyester polyols or polyether polyols and isocyanates are normally reacted in quantities corresponding to an NCO:OH ratio of 3.5:1 to 1.4:1 and preferably 3:1 to 1.7:1.
In another advantageous embodiment of the invention, the crystalline polyester polyols, liquid and/or amorphous polyester polyols and polyether polyols have an OH functionality of 1.8 to 2.7 and, more particularly, 2. The OH functionality is the number average of free OH groups per polyester polyol or polyether polyol molecule.
In another advantageous embodiment of the invention, the isocyanates have an NCO functionality of 1.8 to 2.7 and, more particularly, 2. Isocyanates such as these are commercially available compounds.
In another advantageous embodiment of the invention, the number average molecular weights of the crystalline polyester polyols are in the range from 3000 to 7000, the number average molecular weights of the liquid and/or amorphous polyester polyols are in the range from 1500 to 5000 and the number average molecular weights of the polyether polyols are in the range from 1500 to 5000.
In another advantageous embodiment of the invention, the crystalline polyester polyols are condensation products of glycols selected from the group consisting of ethylene glycol, butylene glycol, hexamethylene glycol and decamethylene glycol and dicarboxylic acids selected from the group consisting of oxalic acid, suberic acid, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid and hexahydrophthalic acid (cis and trans forms).
Crystalline polyester polyols in the form of condensation products of hexamethylene glycol or decamethylene glycol and adipic acid are particularly preferred.
In another advantageous embodiment of the invention, the liquid and/or amorphous polyester polyols are condensation products of polyols from the group consisting of ethylene glycol; polyethylene glycol, for example diethylene glycol, triethylene glycol, tetraethylene glycol and the like; propylene glycol; polypropylene glycol, for example dipropylene glycol, tripropylene glycol and the like; butylene glycol; neopentyl glycol; hexamethylene glycol; decamethylene glycol; bisphenol A; reaction products of bisphenol A with ethylene oxide and/or propylene oxide; glycerol and pentaerythritol with dicarboxylic acids from the group consisting of adipic acid, maleic acid, phthalic acid and isophthalic acid. Liquid and/or amorphous polyester polyols obtainable by condensation of mixtures of the above-mentioned polyols and dicarboxylic acids are also suitable. Liquid and/or amorphous polyester polyols, which are condensation products of glycols from the group consisting of ethylene glycol, diethylene glycol and neopentyl glycol with the dicarboxylic acids mentioned, are particularly preferred.
In another advantageous embodiment of the invention, the polyether polyols are selected from the group consisting of polyethylene glycol, polypropylene glycol and polytetramethylene glycol, including copolymers thereof. Physical mixtures of the above-mentioned glycols may also be used.
In another advantageous embodiment of the invention, the isocyanates having a functionality of more than 1 are selected from the group consisting of diphenylmethane-4,4′-diisocyanate,diphenylmethane-2,4′-diisocyanate,hydrogenation products of the above-mentioned diisocyanates, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and naphthylene-1,5-diisocyanate, including technical mixtures thereof.
In another advantageous embodiment of the invention, the diisocyanates trimerized to isocyanurates are derived from diisocyanates selected from the group consisting of diphenylmethane-4,4′-diisocyanate, diphenylmethane-2,4′-diisocyanate, hydrogenation products of the above-mentioned diisocyanates, tolylene-2,4-diisocyanat
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Niland Patrick D.
LandOfFree
Moisture-curing hotmelt adhesives does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Moisture-curing hotmelt adhesives, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Moisture-curing hotmelt adhesives will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2607952