Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-03-01
2003-07-08
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...
C252S182250, C252S182270, C521S130000
Reexamination Certificate
active
06590008
ABSTRACT:
The instant invention relates to a process for making low density foams. It also relates to a specific polyol composition and to a reaction system that are useful in the said process.
For flexible polyurethane foams, low density means cost effectiveness. Thus, low density is a target, that should however not be obtained with detrimental effects on the foam properties. Physical blowing, using carbon dioxide for example, is known to reduce foam density, but is associated with processing difficulties as well as the need for additional equipment.
U.S. Pat. No. 5,686,502 discloses foams obtained through a one-shot process, where the polyol comprises a first polyol which is a poly(oxyalkylene)triol which is chain terminated with oxypropylene (PO)and a second polyol which is either (i) a poly(oxyalkylene)diol terminated with EO, or (ii) a polyfunctional polyol terminated with PO. The thus obtained foams are hydrophylic. The densities obtained in the examples vary between 13 and 20 kg/m
3
. There is no mention of the resilience.
U.S. Pat. No. 5,420,170 discloses foams that are visco-elastic which are prepared by reacting a specific polyol composition. The polyol composition comprises a block PO/EO polyol having an OH value of 14 to 65, 2 to 9% of tipped EO and a functionality of 2.3 to 2.8 and a di-or tri-functional PO/EO polyol having an OH value of 20 to 80 and 60 to 85% of EO (preferably up to 20% as tipped EO). The resulting foams are visco-elastic and do not exhibit any ball rebound (for densities obtained in the examples of about 70-77 kg/m
3
).
U.S. Pat. No. 4,833,176 discloses a process comprising reacting a polyisocyanate with a polyol at a NCO index below 70. The polyol may vary; examples comprise mixtures of a low EO-content polyol and high EO content polyol.
EP-A-0 845 485 discloses a process for preparing flexible foams comprising reacting a polyisocyanate with a polyol, where the polyol is a specific polyol composition. Said polyol composition comprises: (i) a polyetherpolyol having a functionality of 2.5-6.0, which is a PO/EO polyol with 15% or less of EO; (ii) a polyetherpolyol having a functionality of 1.8-2.5, which is an all-PO polyol; (iii) a polyetherpolyol having a functionality of 1.8-6.0 and having an EO content of at least 50 wt %. The respective amounts of components (i), (ii) and (iii) are as follows: (i) 15-70%, (ii) 30-80%, and (iii) 3-15%, based on the combined weights of the polyols.
U.S. Pat. No. 5,594,097 discloses a polyol comprising PO and EO, having an OH value of 16-45, a primary hydroxyl content of at least 50%, an EO content of 21-49%, and having a structure of the type PO-(PO/EO)-EO, where the tipped EO content is 10-20%. This specific polyol is said to be usable in combination with other polyols. All examples, however, relate to polyol compositions comprised solely of this specific polyol. Also, while a relatively low density is obtained, (i) there is no disclosure of the resilience values and (ii) there are processing difficulties and bad compression set when the EO-enriched polyol is used as the main polyol.
None of the above documents teaches or suggests the instant invention.
The following way of describing polyols is used in the present application: A PO-EO polyol is a polyol having first a PO block attached to the initiator followed by an EO block. A PO-PO/EO polyol is a polyol having first a PO block and then a block of randomly distributed PO and EO. A PO-PO/EO-EO polyol is a polyol having first a PO block then a block of randomly distributed PO and EO and then a block of EO. A PO-EO polyol is a polyol having first a PO block and then an EO block. In the above descriptions only one tail of a polyol is described (seen from the initiator); the nominal hydroxy functionality will determine how many of such tails will be present.
The present invention provides a process that surprisingly affords a resilient flexible polyurethane foam having a good stability (low recession) and the advantages of EO enriched polyol as the main polyol (i.e. density reduction) without having the drawbacks (i.e. negative impact on mechanical properties, like tensile strength, elongation and tear strength).
The invention thus provides a polyol composition comprising:
b1) a polyoxyethylene-polyoxypropylene polyol, having an average nominal hydroxyl functionality of 2-6 where the EO is present as tipped EO, the EO content being between 10-25% by weight based on the weight of the polyol
b2) a polyoxyethylene-polyoxypropylene polyol, having an average nominal hydroxy functionality of 2-6, where the EO is present as tipped EO and random EO, the total EO content being between 20-50% and the tipped EO content being between 10-20%, both by weight based on the weight of the polyol
b3) a polyol, having an average nominal hydroxy functionality of 2-6, and comprising EO and optionally PO where the EO is present as random EO, the EO content being at least 50% by weight based on the weight of the polyol
these polyols b1, b2 and b3 being present according to the following proportions, based on the combined weights of b1, b2 and b3, b1: 60-97 wt %, b2: 3-40 wt %, b3: 0-25 wt %.
Unless otherwise stated amounts of EO and PO in a polyol are indicated hereinafter as % by weight based on the weight of the polyol.
The invention thus provides a process for preparing a flexible polyurethane foam at an NCO index of 70-120 and preferably of 70-105 by reacting
a) a polyisocyanate;
b1) a polyoxyethylene-polyoxypropylene polyol, having an average nominal hydroxyl functionality of 2-6 where the EO is present as tipped EO, the EO content being between 10-25%;
b2) a polyoxyethylene-polyoxypropylene polyol, having an average nominal hydroxy functionality of 2-6, where the EO is present as tipped EO and random EO, the total EO content being between 20-50%, the tipped EO content being between 10-20%,
b3) a polyol, having an average nominal hydroxy functionality of 2-6, and comprising EO and optionally PO where the EO is present as random EO, the EO content being at least 50%,
these polyols b1, b2 and b3 being present according to the following proportions, based on the combined weights of b1, b2 and b3, b1: 60-97 wt %, b2: 3-40 wt %, b3: 0-25 wt %;
c) water; and
d) additives and auxiliaries known per se.
The invention finally relates to a reaction system comprising A) a polyisocyanate and B) an isocyanate-reactive component comprising the polyol of the invention and water, as well as to a reaction system comprising A) a polyisocyanate prepolymer obtained by reacting the polyisocyanate with part of the polyol composition of the invention, and B) an isocyanate-reactive component comprising the remainder of the polyol composition of the invention and water.
In the context of the present invention the following terms, if and whenever they are used, have the following meaning:
1) isocyanate index or NCO 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 quasi or semi-prepolymers and prepolymers) or any active hydrogens 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, if used) present at the actual foaming stage are taken into account.
2) The expression “isocyanate-reactive hydroge
Parfondry Alain
Yu Jianming
Huntsman International LLC
Pillsbury & Winthrop LLP
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