Process for preparing a flexible polyurethane foam

Details Process for preparing a flexible polyurethane foam Process for preparing a flexible polyurethane foam

2002-07-18

2003-06-17

Cooney, Jr., John M. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Cellular products or processes of preparing a cellular...

C521S130000, C521S170000

Reexamination Certificate

active

06579912

ABSTRACT:

FIELD OF INVENTION
The present invention is related to a process for preparing a flexible polyurethane foam and to such foams having specific properties. More specifically, the present invention is related to a process for preparing a flexible polyurethane foam using a polyoxyethylene polyoxypropylene polyol having special properties and a polyisocyanate having a high 4,4′-diphenylmethane diisocyanate (4,4′-MDI) content.
BACKGROUND OF THE INVENTION
Processes for preparing flexible foams from polyols having a high oxyethylene (EO) content and a polyisocyanate having a high 4,4′-MDI content have been disclosed in EP 547765. The examples shown in EP 547765 give low density foams with a low resilience.
Co-pending application WO 00/55232 discloses a process for making a moulded polyurethane material, like a flexible polyurethane foam, by reacting 4,4′-diphenylmethane diisocyanate, a polyol having a high oxyethylene content and water.
Pending PCT patent application PCT/EP01/00553 is related to a process for making moulded flexible polyurethane foams, using a polyisocyanate-reactive composition comprising 80-100% by weight of a polyether polyol having an average nominal functionality of 2-6, an average equivalent weight of 750-5000, an average molecular weight of 2000-10000, an oxyethylene content of 60-90% by weight and a primary hydroxyl content of 70-100%.
Surprisingly, it has been found that when a special class of polyols is used stable foams can be made which show a high resilience at low density, have low recession and/or a low hysteresis loss and more open cells. Foams when made in a mould can be easily demoulded even if no external mould release agent is applied after the first moulding has been made.
Foams can be made more easily because the viscosity of the raw material is low. Further the formulation latitude is wider and in general foam properties remain acceptable at lower densities.
SUMMARY OF THE INVENTION
Therefore, the present invention is concerned with a process for preparing a flexible polyurethane foam having an apparent overall density of 15-150 kg/m
3
comprising reacting a polyisocyanate and an isocyanate-reactive composition in the presence of water, wherein the reaction is conducted at an isocyanate index of 50 to 130, the polyisocyanate consists of a) 80-100% by weight of diphenylmethane diisocyanate comprising at least 40%, preferably at least 60% and most preferably at least 85% by weight of 4,4′-diphenylmethane diisocyanate and/or a derivative of said diphenylmethane diisocyanate which derivative has an NCO value of at least 20% by weight (polyisocyanate a), and b) 20-0% by weight of another polyisocyanate (polyisocyanate b), and wherein the isocyanate-reactive composition consists of a) 10-100 and preferably 30-100 and most preferably 50-100% by weight of a polyether polyol (polyol a)) having an average nominal functionality of 2-8, an average equivalent weight of 750-5000, an average molecular weight of 2000-12000, an oxyethylene (EO) content of 20-90% by weight calculated on the weight of the polyether polyol, a melting enthalpy, |&Dgr;Hm|, of at least 30 J/g and a melting temperature, Tm, of 4° C. or more, excluding such polyols having an oxyethylene content of 60-90% by weight and a primary hydroxyl content of 70-100% and excluding such polyols having an oxyethylene content of at least 50% by weight and being random polyoxyethylene polyoxypropylene polyols and b) 90-0 and preferably 70-0 and most preferably 50-0% by weight of one or more other isocyanate-reactive compounds (isocyanate-reactive compound b)) excluding water.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is concerned with a process for preparing a flexible polyurethane foam having an apparent overall density of 15-150 kg/m
3
comprising reacting a polyisocyanate and an isocyanate-reactive composition in the presence of water, wherein the reaction is conducted at an isocyanate index of 50 to 130, the Page 4 of 17 polyisocyanate consists of a) 80-100% by weight of diphenylmethane diisocyanate comprising at least 40%, preferably at least 60% and most preferably at least 85% by weight of 4,4′-diphenylmethane diisocyanate and/or a derivative of said diphenylmethane diisocyanate which derivative has an NCO value of at least 20% by weight (polyisocyanate a), and b) 20-0% by weight of another polyisocyanate (polyisocyanate b), and wherein the isocyanate-reactive composition consists of a) 10-100 and preferably 30-100 and most preferably 50-100% by weight of a polyether polyol (polyol a)) having an average nominal functionality of 2-8, an average equivalent weight of 750-5000, an average molecular weight of 2000-12000, an oxyethylene (EO) content of 20-90% by weight calculated on the weight of the polyether polyol, a melting enthalpy, |&Dgr;Hm|, of at least 30 J/g and a melting temperature, Tm, of 4° C. or more, excluding such polyols having an oxyethylene content of 60-90% by weight and a primary hydroxyl content of 70-100% and excluding such polyols having an oxyethylene content of at least 50% by weight and being random polyoxyethylene polyoxypropylene polyols and b) 90-0 and preferably 70-0 and most preferably 50-0% by weight of one or more other isocyanate-reactive compounds (isocyanate-reactive compound b)) excluding water.
The foams have an apparent overall density of 15-150 kg/m
3
(ISO845), preferably of 25-60 kg/m
3
and a resilience (ISO 8307) of 45-80% and preferably of 50-80% and most preferably of 55-80%.
In the context of the present invention the following terms have the following meaning:
1) isocyanate index or NCO index or index:
 the ratio of NCO-groups over isocyanate-reactive hydrogen atoms present in a formulation, given as a percentage:
[
NCO
]
×
100
[
active
⁢
 
⁢
 
⁢
hydrogen
]
⁢
(
%
)
.
 In other words the NCO-index expresses the percentage of isocyanate actually used in a formulation with respect to the amount of isocyanate theoretically required for reacting with the amount of isocyanate-reactive hydrogen used in a formulation.
 It should be observed that the isocyanate index as used herein is considered from the point of view of the actual foaming process involving the isocyanate ingredient and the isocyanate-reactive ingredients. Any isocyanate groups consumed in a preliminary step to produce modified polyisocyanates (including such isocyanate-derivatives referred to in the art as prepolymers) or any active hydrogens consumed in a preliminary step (e.g. reacted with isocyanate to produce modified polyols or polyamines) are not taken into account in the calculation of the isocyanate index. Only the free isocyanate groups and the free isocyanate-reactive hydrogens (including those of the water) present at the actual foaming stage are taken into account.
2) The expression “isocyanate-reactive hydrogen atoms” as used herein for the purpose of calculating the isocyanate index refers to the total of active hydrogen atoms in hydroxyl and amine groups present in the reactive compositions; this means that for the purpose of calculating the isocyanate index at the actual foaming process one hydroxyl group is considered to comprise one reactive hydrogen, one primary amine group is considered to comprise one reactive hydrogen and one water molecule is considered to comprise two active hydrogens.
3) Reaction system: a combination of components wherein the polyisocyanates are kept in one or more containers separate from the isocyanate-reactive components.
4) The expression “polyurethane foam” as used herein refers to cellular products as obtained by reacting polyisocyanates with isocyanate-reactive hydrogen containing compounds, using foaming agents, and in particular includes cellular products obtained with water as reactive foaming agent (involving a reaction of water with isocyanate groups yielding urea linkages and carbon dioxide and producing polyurea-urethane foams) and with polyols, aminoalcohols and/or polyamines as isocyanate-reactive compounds.
5)

Affiliated with

Also associated with

Rating

Process for preparing a flexible polyurethane foam does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for preparing a flexible polyurethane foam, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for preparing a flexible polyurethane foam will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3102146