Low fogging polyester polyurethane foams

The present invention provides 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: (i) (a) at least one hydroxy acid; or (ii) (b) at least one diacid; and (c) at least one diol or polyol; or (iii) (a) at least one hydroxy acid; (b) at least one diacid; and (c) at least one diol or polyol wherein said reactants cannot combine to provide a cyclic ester comprising a 12 to 14 member ring.

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: 
(i) (a) at least one hydroxy acid, generally an aliphatic hydrocarboxylic 
acid; 
(ii) (b) at least one diacid, generally an aliphatic dicarboxylic acid: and 
(c) at least one diol or polyol, generally an aliphatic diol or polyol; or 
(iii) (a) at least one hydroxy acid, generally an aliphatic hydrocarboxylic 
acid; and 
(b) at least one diacid, generally an aliphatic dicarboxylic acid; and 
(c) at least one diol or polyol, generally an aliphatic diol or polyol 
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: 
(i) (a) at least one hydroxy acid; or 
(ii) (b) at least one diacid; and 
(c) at least one diol or polyol; or 
(iii) (a) at least one hydroxy acid; 
(b) at least one diacid; and 
(c) at least one diol or polyol 
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: 
(i) (a) at least one hydroxy acid; or 
(ii) (b) at least one diacid; and 
(c) at least one diol or polyol; or 
(iii) (a) at least one hydroxy acid; 
(b) at least one diacid; 
(c) at least one diol or polyol 
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 of water, catalyst and 
surfactant. 
In a third aspect of the present invention there is provided a motor car 
trim component comprising a low fogging polyester polyurethane foam 
according to the first aspect and a method of manufacture thereof. 
In the course of investigations the applicant has discovered that the 13 
membered ring of the DEG/adipate product appears to be at the optimum 
thermodynamics for the formation of a cyclic ester. Any alteration to 
larger or smaller ring size reduces the amount of cyclic ester. For 
example with a polybutylene glycol/adipic acid combination, which will 
form a 12 membered ring by-product, the cyclic ester equilibrium is 0.35 
weight % compared with the diethylene glycol adipate where the cyclic 
ester equilibrium is 1 to 1.1 weight %. A 16 membered ring or more and a 
10 membered ring or below has been found to have such a low equilibrium 
amount of cyclic ester that the cyclic ester does not cause significant 
fogging. 
For example succinic acid/diethylene glycol (11 membered cyclic ester); 
adipic acid/ethylene glycol (10 member cyclic ester) and dodecanedioic 
acid/diethylene glycol (19 member cyclic ester) have cyclic ester contents 
approaching zero and produce polyester polyurethane foam which Goes not 
cause significant fogging on the windscreen of a car. Foams made from 
these three exemplified esters, while being non-fogging, give essentially 
different physical properties to that of DEG/adipate. It has been found, 
however, that by blending polyethylene glycol and ethylene glycol in 
appropriate ratios, the physical properties of the polyester polyurethane 
foam based on an adipate polyester polyol can be made to approximate those 
of a foam based on diethylene glycol adipate, but the foam produces 
negligible fogging on the windscreen. 
To provide polyester polyols for use in preparing the polyurethane foam of 
the present invention, suitable combinations of: 
(i) (a) at least one hydroxy acid; or 
(ii) (b) at least one diacid; and 
(c) at least one polyol or diol; or 
(iii) (a) at least one hydroxy acid; 
(b) at least one diacid: and 
(c) at least one diol or polyol 
are selected to ensure that cyclic esters are not formed with 12 to 14 
member rings and preferably are not formed with 11 to 15 member rings. 
Suitable components include: 
(i) and (iii) 
(a) is preferably an aliphatic hydroxycarboxylic acid, more preferably a 
C.sub.7 or longer hydroxy-straight chain aliphatic carboxylic acid; 
(ii) and (iii) 
(b) is preferably a dicarboxylic acid, more preferably an aliphatic 
dicarboxylic acid such as a dimer acid or more preferably a straight chain 
aliphatic dicarboxylic acid such as succinic acid, adipic acid, azelaic or 
dodecanedioic acid; 
(c) is preferably an aliphatic diol or polyol, preferably a poly(C.sub.1-4) 
alkylene glycol especially polyethylene glycol, poly-1-methylethylene 
glycol or polypropylene glycol. 
Suitable combinations may include the following 
______________________________________ 
(b) (c) ring number 
______________________________________ 
succinic acid diethylene 11 
glycol 
adipic acid ethylene glycol 
10 
adipic acId pentaerythritol 
11 
adipic acid polyethylene 19 
glycol 200 
azelaic acid pentaerythritol 
14 
azelaic acid diethylene glycol 
16 
dodecanedioic diethylene 19 
acid glycol 
dimer acid polyethylene 25 or above 
glycol 400 
______________________________________ 
A polyethylene glycol HO(CH.sub.2 CH.sub.2 O).sub.n H will combine with 
adipic acid to produce a cyclic ester of ring size 3n+7, which will thus 
meet the requirements of the present invention for n.gtoreq.3. By blending 
polyethylene glycol and ethylene glycol and reacting the blend with adipic 
acid, and preferably a suitable polyol to provide the required degree of 
branching and cross linking, such as pentaerythritol, thereby to produce a 
polyester polyol, it is possible to produce a polyester polyurethane foam 
based on that polyester polyol which has physical properties approximating 
to those of the conventional diethylene glycol/adipate based polyester 
polyurethane foam. A preferred blend is a blend of polyethylene glycol 200 
and ethylene glycol in the ratio of from 4:1 to 2:1 parts by weight, 
preferably 7:2 to 3:1 parts by weight, more preferably 720 to 730 parts by 
weight of polyethylene glycol to 225 parts by weight of ethylene glycol. 
It will be appreciated that other combinations may be selected providing 
that the reactants do not produce cyclic esters with ring sizes within the 
excluded range. 
The selected reactants may be reacted in known manner by a chemically 
catalysed reaction at elevated temperature with removal of water. 
Alternatively, they may be reacted by an enzymatic polyester 
polymerisation process as described in our co-pending applications 
92/25054.7 and 92/25030.7, that is to say reaction in the presence of a 
lipase in the presence or absence of an organic solvent. 
The reactive carboxylic acid groups and reactive hydroxy groups of the 
reactants are generally present in substantially equal numbers or with a 
slight excess of hydroxy groups to provide a hydroxy-terminated polyester 
(a polyester polyol). Preferably the acid groups and hydroxyl groups are 
present in a molar ratio of 1:1 to 1:1.1. 
The resultant polyester polyol may be converted to a polyurethane foam in 
known manner by mixing with a diisocyanate, water, which reacts with the 
diisocyanate generating carbon dioxide to produce a foam, suitable 
catalysts, and one or more surfactants to control the cell structure of 
the foam. Optionally, flame retardants may be included. 
A suitable diisocyanate is toluene diisocyanate, which may consist of a 
blend of isomers, typically 80/20 2,4-toluene diisocyanate/2,6-toluene 
diisocyanate or 65/35 2,4-toluene diisocyanate/2,6-toluene diisocyanate. 
The known catalysts include amine type catalysts such as n-ethyl 
morpholine, dimethyl benzylamine, dimethyl cetylamine, 
dimethylcyclohexylamine. Additionally organo-metallic catalysts, such as 
stannous octoate, may be used as co-catalysts. 
The types and amounts of catalysts are selected in known manner to balance 
the reactions that take place between the polyol and the isocyanate and 
between the water and the isocyanate. Surfactants, which may for example 
be organic or silicone based such as Fomrez M66-86A (Witco) and L532 
(Union Carbide) may be used to stabilise the cell structure, to act as 
emulsifiers and to assist in mixing. Where the polyester polyurethane foam 
is required to be flame retarded, flame retardants, for example flame 
retardants of the chlorinated phosphate type such as tris 
1,3-dichloropropylphosphate and tris monochloro isopropyl phosphate, may 
be incorporated. 
The polyester polyurethane foams of the present invention find use in the 
manufacture of shaped and moulded articles, and fabric laminated articles, 
particularly for use in motor vehicles. The polyurethane foams of the 
present invention have low fogging characteristics showing essentially no 
fogging. These foams preferably have a fogging value F not less than about 
70% reflectance and preferably approaching 100% reflectance when measured 
in accordance with Fogging Characteristics Din 75-201-A. Polyester 
polyurethane foams according to the present invention may find application 
in other areas where low levels of volatile components, in particular 
cyclic esters, are desirable,

The following examples illustrate the invention and are not intended to 
limit the scope thereof. 
EXAMPLE 1 
A round bottom flask equipped with a stirrer, thermometer, condenser and 
nitrogen inlet tube was charged with 3300 parts of azelaic acid, 74.9 
parts of pentaerythritol and 1975 parts of diethylene glycol. The minute 
was heated in a current of nitrogen to a temperature of 225.degree. C., 
water of reaction starting to distil out at about 150.degree. C. The 
reaction as continued at 225.degree. C. until an acid number of less than 
2 was achieved. About 4718 parts of a product was obtained having a 
hydroxyl number of 53 and a viscosity of about 19,000 cps at 25.degree. C. 
EXAMPLE 2 
This example incorporates a dimer acid. Typically these dimer acids contain 
mixtures of C18 monomer, dimer and trimer acids. Preferably the dimer 
acids content should be at least 70%. Examples of suitable commercial 
dimer acids include Unidyme 18 (Union Camp Chemicals Ltd.), Pripol 1017 
(Unichema) and Empol 1018 (Henkel) etc. 
A round bottom flask equipped with a stirrer, thermometer, condenser and 
nitrogen inlet tube was charged with 4000 parts of Unidyme 18 dimer acid, 
19.4 parts of pentaerythritol, 545.1 parts of polyethylene glycol 400 and 
807.6 parts of diethylene glycol. The mixture was heated in a current of 
nitrogen to a temperature of 225.degree. C., water of reaction starting to 
distil out at about 150.degree. C. The reaction was continued at 
225.degree. C. until an acid number of less than 2 was achieved. About 
5123 parts of a product was obtained having a hydroxyl number of 53 and a 
viscosity of about 19,000 cps at 25.degree. C. 
EXAMPLE 3 
A round bottom flask equipped with a stirrer, thermometer, condenser and 
nitrogen inlet tube was charged with 2700 parts of adipic acid, 74.5 parts 
of pentaerythritol, 605.2 parts of monoethylene glycol and 1952.7 parts of 
polyethylene glycol 200. The mixture was heated in a current of nitrogen 
to a temperature of 225.degree. C., water of reaction starting to distil 
out at about 150.degree. C. The reaction was continued at 225.degree. C. 
until an acid number of less than 2 was achieved. About 4668 parts of a 
product was obtained having a hydroxyl number of 53 and a viscosity of 
about 19,000 cps at 25.degree. C. 
EXAMPLE 4 (EXAMPLE FOR COMISON) 
A round bottom flask equipped with a stirrer, thermometer, condenser and 
nitrogen inlet tube was charged with 2900 parts of adipic acid, 117.5 
parts trimethylol propane and 2185 parts of diethylene glycol. The mixture 
was heated in a current of nitrogen to a temperature of 225.degree. C., 
water of reaction starting to distil out at about 150.degree. C. The 
reaction was continued at 225.degree. C. until an acid number of less than 
2 was achieved. About 4487 parts of a product was obtained having a 
hydroxyl number of 53 and a viscosity of about 19,000 cps at 25.degree. C. 
EXAMPLE 5 
A comparison of polyester polyurethane foams formulated from polyester 
polyols of Examples 1 to 4 by reaction with 80/20 toluene diisocyanate 
shows the following properties. Polyester polyurethane foams based on the 
polyester polyols of Examples 1 to 3 provide good results (high percentage 
reflection values) when subjected to the test method of DIN 75.201-A 
"Determination of the windscreen fogging characteristics of trim materials 
in motor vehicles--Reflectance Method". Polyester polyurethane foams based 
on Example 4 (standard polyethylene glycol adipate foams) produce poor 
results (low percentage reflection value) when subjected to the same test 
method. The physical properties of polyurethane foam based on the 
polyester polyol of Example 3, a polyethylene glycol/monoethylene 
glycol/adipic acid derived polyester polyol are similar to the standard 
diethylene glycol/adipic acid derived polyester polyurethane foam based on 
the polyester polyol of Example 5, but the Example 3 based foam has 
improved fogging properties. 
EXAMPLE 6 
A round bottom flask equipped with a stirrer, thermometer, condenser and 
nitrogen inlet tube was charged with 3000 parts of adipic acid, 87.3 parts 
of pentaerythritol, 667 parts of monoethylene glycol and 2152 parts of 
tetraethylene glycol. The mixture was heated in a current of nitrogen to a 
temperature of 225.degree. C., water of reaction starting to distil out at 
about 150.degree. C. The reaction was continued at 225.degree. C. until an 
acid number of less than 2 was achieved. About 4866 parts of a product 
were obtained having a hydroxyl number of 54 and a viscosity of about 
17,000 cps at 25.degree. C. 
EXAMPLE 7 
A round bottom flask equipped with a stirrer, thermometer, condenser and 
nitrogen inlet tube was charged with 3000 parts of adipic acid, 67.5 parts 
of pentaerythritol, 667.5 parts of monoethylene glycol and 1615.5 parts of 
triethylene glycol. The mixture was heated in a current of nitrogen to a 
temperature of 225.degree. C., water of reaction starting to distil out at 
about 150.degree. C. The reaction was continued at 225.degree. C. until an 
acid number of less than 2 was achieved. About 4345 parts of a product 
were obtained having a hydroxyl number of 51 and a viscosity of about 
20,800 cps at 25.degree. C.