Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-11-27
2004-05-25
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...
C252S182260, C252S182270, C252S182280, C560S079000, C560S093000, C568S583000, C568S606000, C568S619000, C568S623000, C521S163000, C521S164000, C521S167000, C521S172000, C521S173000
Reexamination Certificate
active
06740686
ABSTRACT:
The present invention relates to a process for the manufacture of a polyurethane foam by reaction of a polyol with a polyisocyanate, in which process a tertiary amine is used as catalyst and in which process an expansion agent or foaming agent, such as water, for example, is used.
It is well known to use one or more tertiary amines to catalyze a first reaction: that of at least one polyol with at least one polyisocyanate. Furthermore, in the case where water is used as foaming agent, the tertiary amine(s) is (are) capable of catalyzing a second reaction: that of water with the free isocyanate functional groups, which reaction results in the evolution of carbon dioxide gas which serves for the expansion of the foam. Several known techniques exist for the preparation of polyurethanes. According to a first technique, at least one polyetherpolyol and/or at least one polyesterpolyol is reacted with at least one polylisocyanate, so as to obtain a prepolymer comprising free isocyanate groups, and then the prepolymer obtained is reacted with an additional amount of polyol(s). Another well known technique is the so-called “one shot” technique, where all the ingredients are introduced, separately or selectively premixed according to their compatibility, into the mixing head.
The known tertiary amines can promote the first reaction and/or the second reaction to variable extents. When one of the reactions is not catalyzed or is insufficiently catalyzed, it is then necessary to use another catalyst for the other reaction. This other catalyst can be an organometallic derivative, such as stannous octoate or dibutyltin dilaurate, known for preferentially catalyzing the isocyanate polyol reaction. The use is therefore being attempted of tertiary amines which satisfactorily catalyze both reactions. It is known to use tertiary amines, such as N-ethylmorpholine, dimethylbenzylamine, triethylene-diamine and hexadecyldimethylamine, these tertiary amines being introduced as such into the reaction mixture.
However, these tertiary amines have a disadvantage: they are volatile, have a very unpleasant amine smell and are often toxic. As most of the tertiary amine(s) remains in the foam in the free state, the foam prepared has an undesirable smell and gives off toxic vapors. Furthermore, the handling of tertiary amines during the manufacture of polyurethane foam demands specific precautions in order to meet safety standards.
In order to overcome the above disadvantages, the use has been proposed (paper by Savoca, Franson and Louie, UTECH'92 Conference Proceedings, p. 309-315 and U.S. Pat. No. 4,433,170) of less volatile amines with a high molecular weight, however, the ratio by weight of the tertiary amine functional group with respect to the weight of the molecule becomes low and the reactivity of the catalyst decreases. Furthermore, these amines are more expensive, they often still have an unpleasant smell and they often have a reactivity which is too different from that of standard amines, which is not very acceptable to foam producers.
Furthermore, it has also been proposed (paper by Diblitz and Hoell, UTECH'92 Conference Proceedings, p. 80-85) to attach the tertiary amine catalyst to free isocyanate functional groups. To this end, a tertiary amine, for example a hydroxylated tertiary amine, which reacts with the isocyanate functional groups during the preparation of the polyurethane is added to the reaction mixture. However, in this case, it is still necessary to handle polluting amines at the stage of preparation of the foam and precautions are still necessary to meet safety standards.
The preparation of a polyurethane by reaction of at least one polyesterpolyol with at least one polyisocyanate is well known. This polyesterpolyol is conventionally prepared by reaction of an acid reactant having a functionality at least equal to 2, such as adipic acid, with at least one polyol with a functionality equal to 2, such as diethylene glycol, subsequently denoted by P2, and at least one polyol with a functionality at least equal to 3, such as trimethylolpropane, glycerol or pentaerythritol, subsequently denoted by P3. FR-A-2 747 389 discloses the manufacture of specific polyesterpolyols, capable of being used in the manufacture of polyurethane foams, which do not exhibit fogging when they are used in the passenger compartment of a vehicle. According to this patent, the polyol P2 comprises monoethylene glycol and optionally a branched glycol with a functionality equal to 2 and the polyol P3 is a polyoxyalkylenated polyol which is, inter alia, obtained from triethanolamine or from triisopropanolamine. In the preparation of the polyurethane foams disclosed in FR-A-2 747 389, a separate tertiary amine catalyst, dibutylbenzylamine according to the examples, is still added.
According to the present invention, it has been found that, when the polyesterpolyol is prepared from at least one polyol P3 which is a polyoxyalkylenated polyol obtained by oxyalkylenation of a tertiary polyalkanolamine and when it is thus “amine”, it is no longer essential, during the manufacture of the polyurethane foam, to separately add a tertiary amine as catalyst or, that to say the least, the amount of separate tertiary amine to be added is markedly reduced. This is because it has been found that the amine polyesterpolyol defined above has an autocatalytic effect, that is to say that it has both a reactive role and a catalyst role.
Throughout the text of the present patent application, the term “polyalkanolamine” has generically denoted an alkanolated amine which can be either a polyalkanolmonoamine or a polyalkanolpolyamine.
In a first embodiment, the tertiary polyalkanolamine is a polyamine, at least one amine group and preferably all the amine groups of which is (are) tertiary and is (are) substituted by identical or different C
1
-C
6
alkanol radicals.
In a second embodiment, the tertiary polyalkanolamine is a tertiary monoamine substituted by identical or different C
1
-C
6
alkanol radicals.
Generally, according to the present invention, it has been found that an amine polyesterpolyol in which is inserted at least one such polyoxyalkylenated polyalkanolamine had, by itself, a catalytic effect for the formation of polyurethane foams. It acts mainly on the foaming reaction in the presence of water and to a certain extent on the reaction of the polyol with an isocyanate, known as gelling. Consequently, it is possible not to use any other amine catalyst, only a small amount of catalyst of the organometallic type optionally being able to be added in order to accelerate the gelling reaction and to obtain a foam which does not collapse.
According to the invention, the tertiary amine is introduced during the polyesterification process into at least one polyesterpolyol used for the manufacture of the polyurethane: it is thus included or inserted in the said polyesterpolyol; the result of this is that:
the risks of evolution of tertiary amine during the manufacture of the polyurethane are avoided and, consequently, there is neither a problem of odor nor a problem of toxicity on the foam production site; problems of pollution during the production of the foam are thus avoided and certain specific precautions for meeting safety standards do not have to be taken;
foams are obtained which do not have an amine smell and are less toxic. In particular, a source of fogging when the foam is used in the passenger compartment of a motor vehicle is thus avoided and, furthermore, when polyesterpolyols, such as those disclosed in FR-A-2 747 389, not comprising volatile cyclic dimers are employed, the foam does not result in any fogging.
The subject matter of the present invention is consequently a process for the manufacture of a polyurethane foam by reaction of at least one polyesterpolyol and of at least one polyisocyanate in the presence of a foaming agent and of a catalyzing agent, such a polyesterpolyol having been obtained beforehand by reaction of an acid reactant A, comprising at least one aliphatic or aromatic polyacid with a funct
Dumont Remy
Ghesquiere Denis
Cooney Jr. John M.
Crompton Corporation
Dilworth Michael P.
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