Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1996-09-20
1998-01-27
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521173, C08G 1834, C08G 1836
Patent
active
057123209
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to polyester polyurethane foams with low fogging characteristics and methods for their manufacture.
Polyester polyurethane foams may be produced by reaction of a polyester polyol and a diisocyanate in the presence of suitable catalysts in known manner as hereinafter described. The characteristics of the resulting polyester polyurethane foam depend at least in part on those of the polyester polyol.
The polyester polyol may be a polyester comprising or consisting as repeating units residues of: acid;
(iii) (a) at least one hydroxy acid, generally an aliphatic hydrocarboxylic acid; and
The polyester polyol may be formed by reacting: (i) (a); or (ii) (b) and (c): or (iii)(a) and (b) and (c) under known conditions as further described below to produce polyesters with terminal hydroxy units. These processes are accompanied by the formation of quantities of unwanted by-products in the form of cyclic esters.
Polyester polyurethane foams are used in the production of shaped, moulded and fabric laminated articles in, for example, the car industry. For automobile applications the polyester polyol is typically diethylene glycol adipate, which may be formed by reacting in known manner adipic acid diethylene glycol and generally also a polyol, such as trimethylol propane to provide a degree of branching and cross linking. The cyclic acid by-product of an adipic acid molecule with a diethylene glycol molecule is a 13 membered ring cyclic ester. This is a waxy solid melting at around 60.degree. C., which readily sublimes. The 13 membered cyclic ester is found in diethylene glycol adipate polyesters at about 1 to 1.1% by weight. It is known that cyclic esters may be removed by high vacuum distillation at 250.degree. C., but readily reform at these temperatures to the equilibrium level of 1 to 1.1 weight %.
When present in polyester polyurethane foam based on diethylene glycol/adipic acid incorporated into automobile trim components such as headliners, sun visors and so forth, this volatile 13 membered ring volatilises from the polyester polyurethane foam, and subsequently deposits on, for example, the car windscreen as an oily film. This phenomenon is known as fogging.
In an effort to solve this problem, attempts have been made to seek to remove the 13 membered cyclic ester from commercial diethylene glycol polyadipate polyester polyurethane foam by passing the polyester polyol through a wipe film apparatus at 1 mm Hg and 250.degree. C. very quickly and cooling to less than 100.degree. C. quickly so that the cyclic ester is removed, but does not have a chance to reform.
Two dimer based polyester polyols are described in a leaflet from Unichema International dated May 1991: PRIPLAST 3191, described as a liquid, slightly branched dimer based polyester; and PRIPLAST 2038, described as a slightly branched dimer based polyester. These are said by Unichema to be mainly used for flexible foam. Flexible polyester polyurethane foams based on these polyesters are said to exhibit low fogging properties, making them suitable for automotive applications. Flexible foam formulations based on these polyesters are said to be different from the standard diethylene glycol adipate polyesters.
According to the present invention there is provided a polyester polyurethane foam with low fogging characteristics comprising the product of reaction of a polyester polyol and a diisocyanate wherein said polyester polyol comprises as repeating units residues of the following reactants:
wherein said reactants cannot combine to provide a cyclic ester comprising a 12 to 14 member ring.
In a second aspect of the present invention there is provided a method of manufacturing a polyester polyurethane foam with low fogging characteristics comprising:
forming a polyester polyol by reacting:
wherein said reactants are selected such that they cannot combine to provide a cyclic ester comprising a 12 to 14 member ring;
forming a polyester polyurethane foam by reacting the thus formed polyester polyol with a diisocyanate in the presence
REFERENCES:
patent: 4049592 (1977-09-01), Marans et al.
patent: 4605729 (1986-08-01), Barnes et al.
patent: 5112940 (1992-05-01), Korte
Unichema International Leaflet entitled "Dimer based polyester polyols for the polyurethane industry" Pub. May, 1991.
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