Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-04-12
2003-09-09
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, C521S133000, C521S137000, C521S160000, C521S904000
Reexamination Certificate
active
06617369
ABSTRACT:
The instant invention relates to a process for making visco-elastic foams. It also relates to reaction systems that are useful in the said process, as well as specific polyols blends.
Visco-elastic foams are usually produced from a polyol blend comprising a rigid polyol having an OH value of 180-400. This provides drawbacks. The first problem is that this rigid polyol is usually all PO, thus with only secondary hydroxy groups, thus less reactive. The second drawback is that this rigid polyol leads to highly crosslinked foams, thus with lower mechanical properties (tear strength and elongation are quite low). The third drawback is that the flow quality is poor (due to an early network formation).
U.S. Pat. No. 4,839,397 discloses a foam with insulation properties obtained at an index below 80, which is adhesive, has a high density and a loss factor of at least 0.4. The visco-elastic adhesive foams are notably produced from a polyol blend such as 48 parts of polyol PO/EO, OH value 42, molecular weight 4000, 26 parts PPG, OH value 250, molecular weight 450 and 6 parts of polyol PO/EO, OH value 28, as a cell regulator.
U.S. Pat. No. 5,847,014 discloses a process for making a foam from a polyol blend comprising notably a standard polyol, a non-tertiary amine polyol and amine/alcohol.
WO-A-9816567 discloses a foam obtained from a polyol mixture comprising 30-70% of a polyol having a high primary hydroxy content and 70-30% of a rigid polyol having a molecular weight in the range of 300 to 1000.
The instant invention aims at solving these problems and at providing easy processable visco-elastic foams without resort to hard polyol.
The instant invention also aims at providing a flexible polyurethane foam which exhibits a low compression set, a very low resilience (good damping), a good tear strength, a very high elongation and a high loss factor.
The instant invention also aims at providing a system of wide range of processability (wide range of 2,4′/4,4′ ratio for MDI), of low viscosity for the ingredient streams (which would be especially useful for making mouldings for sound insulation, and which could be used on state-of-the-art polyurethane machinery).
The invention thus provides a one-shot or prepolymer process for preparing a visco-elastic polyurethane foam at an NCO index of 70-120 by reacting:
a) a polyisocyanate composition;
b1) a polyoxyethylene-polyoxypropylene polyol, having an average nominal hydroxy functionality of 2-6, where the EO is present as tipped EO and/or random EO, the total EO content being at least 50% by weight;
b2) a polyoxyethylene-polyoxypropylene polyol, having an average nominal hydroxy functionality of 2-6, where the EO is present as tipped EO and/or random EO, the total EO content being between 20-50% by weight, having a primary hydroxy content of at least 50% calculated on the amount of primary and secondary hydroxyl groups;
b3) a polyoxyethylene-polyoxypropylene polyol, having an average nominal hydroxyl functionality of 2-6, having a primary hydroxy content of at least 50% calculated on the amount of primary and secondary hydroxyl groups, and having an EO content of from 10 to 20% by weight;
b4) a polyalkyleneglycol having an average molecular weight from 100 to 1200;
these polyols b1, b2, b3 and b4 being reacted according to the following proportions, based on the combined weights of b1, b2, b3 and b4, b1: 30-85 wt %, b2: 5-65 wt %, b3: 5-40 wt %, b4: 0-50 wt %;
c) water; and
d) additives and auxiliaries known per se;
and where the polyisocyanate prepolymer has an NCO value above 20% by weight in case the prepolymer process is used.
The invention also relates to a specific polyol composition comprising the three or four above polyols according to specific ratios.
The invention also relates 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:
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N
C
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%
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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) 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 hydroxyl and amine hydrogen atoms present in the reactive compositions in the form of polyols, polyamines and/or water; 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 or secondary 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 polyisocyanate component is kept in a container separate from the isocyanate-reactive components.
4) The expression “polyurethane foam” as used herein generally 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).
5) The term “average nominal hydroxyl functionality” is used herein to indicate the average functionality (number of hydroxyl groups per molecule) of the polyol composition on the assumption that this is the average functionality (number of active hydrogen atoms per molecule) of the initiator(s) used in their preparation although in practice it will often be somewhat less because of some terminal unsaturation. The average equivalent weight of a polyol is the average molecular weight divided by this average nominal hydroxyl functionality.
6) The term “average” is used to indicate an average by number.
7) The term “visco-elastic foams” are intended to designate those foams having a resilience of at most 40%, as measured according to ISO 8307.
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 (see
Parfondry Alain
Yu Jianming
Cooney Jr. John M.
Huntsman International LLC
Peffer Nicole
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