Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2001-11-26
2003-01-14
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...
C521S111000, C521S112000, C521S117000, C521S122000, C521S170000, C521S174000
Reexamination Certificate
active
06506810
ABSTRACT:
RELATED APPLICATIONS
This application claim priority to German application No. 100 59 057.8, filed Nov. 28, 2000, herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to the use of mixtures of organofunctionally modified polysiloxanes with branched alcohols in the production of flexible polyurethane foams.
2. Description of Related Art
Polysiloxane-polyoxyalkylene block copolymers, hereinafter referred to as polyether siloxanes, are used in the production of polyurethane foams. They make it possible to obtain a uniform, fine pore structure and stabilize the foam during the production process.
However, depending on the production process and depending on what further raw materials are used, an unsatisfactory cell structure is obtained in some cases. For example, the use of polyols having a high polypropylene oxide content frequently tends to give a coarser cell structure.
The equipment used can also lead to an irregular or coarse cell structure, for example when using low-pressure mixing heads or when the raw materials are simply mixed by stirring at atmospheric pressure.
The use of alternative blowing agents, in particular CO
2
, also places particularly high demands on the polyether siloxane in respect of achieving a fine-pored cell structure. Owing to the advantageous ecological balance, this liquid CO
2
technology has become increasingly important in the past years. In this process, pressurized CO
2
is used as blowing gas in addition to the CO
2
formed by chemical reaction of the isocyanates used with water. This technology is described, for example, in EP-A-0 645 226. However, the introduction of this technology has shown that the spontaneous foaming of the pressurized CO
2
on discharge of the reaction mixture places increased demands on the cell formation characteristics of the components used in the foam formulation. This can also be explained by the isocyanate/water reaction, which previously commenced slowly over a period of several seconds, leading only to slow saturation of the liquid phase with gas and thus the slow formation of gas bubbles, viz. the cream phase of the foam.
This previously slow process which forms the basis for the morphological properties, i.e. cell count and cell size distribution of the resulting foam is now compressed into fractions of a second, namely the time required by the raw materials to pass from the pressurized mixing bead of a foaming machine and the adjoining discharge device to the ambient pressures of one atmosphere. This results, in a manner similar to shaving foam from a spray can, to spontaneous formation of a foam due to vaporization of liquid CO
2
. The defects which occurred in such foams were nonuniform, sometimes enlarged cells within the foam structure, and the use of suitable foam stabilizers can be useful for minimizing these defects. Nevertheless, there is often the problem, depending on boundary conditions (pressure, raw material temperatures, use of solids in the formulation), of stabilizers which are well-suited according to the present state of the art, e.g. as described in U.S. Pat No. 5,357,018 or U.S. Pat. No. 5,321,051, not producing fully defect-free foams.
In principle, the cell structure can be made finer by increasing the amount of polyether siloxane used, but there is limited latitude for achieving this increase, firstly because of the accompanying phenomenon of overstabilization which then occurs and can lead to a high proportion of closed cells, in extreme cases even to shrinkage of the foam, and secondly because of the associated unfavorable economics.
In principle, the use of additives to polyether siloxanes or flexible foam formulations for increasing the fineness of the cells is already known.
EP-A-0 900 811 describes the use of cyclic carbonates as agents for increasing the fineness of the cells in flexible foam formulations. However, the cyclic carbonates are effective only in amounts of the same order of magnitude as the polyether siloxane and additionally have the disadvantage of being volatile components which vaporize from the finished foam.
EP-A-0 976 781 described the combined use of polyether siloxanes and salts of organic acids. The cells become finer even at low concentrations, but the solubility of the salts is relatively limited so that the use of water as cosolvent becomes necessary. The use of such combinations is therefore restricted to hydrolysis-stable polyether siloxanes. Furthermore, water contributes to the blowing reaction with isocyanates and may, depending on the concentration used, have to be taken into account in the formulation calculation.
U.S. Pat. No. 4,520,160 describes a process for preparing polyether siloxanes in the presence of fatty alcohols. The latter prevent gel formation during the preparation. The resulting products are preferably used as emulsifiers in cosmetic applications. The document also mentions the in-principle possibility, documented by means of an example, of use in polyurethane foams, but liquid CO
2
applications are not mentioned. The use of the product described has, according to this document, no negative influence on the applications mentioned. On the basis of the information provided, the experiment described using a mixture of a polyether siloxane having an SiC structure and isostearyl alcohol gives an open-celled foam whose properties are equal to or better than a foam resulting from a comparative experiment in which isopropyl alcohol is used in place of isostearyl alcohol. Specific criteria for the assessment are not mentioned. In particular, no information on cell structure is given. The foam is only described by the characterization “good foam”. Analysis of the example leaves the question of which class of polyurethane compounds is being addressed largely open, since, for example, the polyol type is not defined. The catalyst employed is the organotin compound dibutyltin dilaurate (DBTDL) which could indicate an HR slabstock application. DBTDL is frequently used in flexible foam applications exclusively in HR slabstock and not in conventional slabstock; the latter application requires tin octoate as catalyst. DBTDL is additionally employed in the production of rigid foams and also of elastomers/shoe soles, or classes of polyurethane different from flexible foams.
Our attempts to repeat the example lead not to a flexible foam but to a prepolymer-like elastomer without foam character. The use of a defined amount of water and amine catalysts would be absolutely necessary for producing a flexible foam.
Neither water nor amine catalyst are mentioned in the example; the product is thus not a flexible foam. The foam parameters described for the products of the experiment, e.g. foam height and air permeability, are thus not comprehensible.
The present invention relates to formulations for producing flexible polyurethane foams, by which are meant both conventional flexible polyether foams and flexible polyether foams produced with the aid of liquid CO
2
technology.
Conventional flexible polyether foams are produced using as catalyst, apart from a tertiary amine, at least one of the following:
a) a metal salt of an organic acid, for example an alkali metal, alkaline earth metal, Al, Sn, Pb, Mn, Co, Bi or Cu salt of an organic acid such as octanoic acid, ricinoleic acid, acetic acid, oleic acid, lauric acid or hexanoic acid;
b) alkoxides and phenoxides of various metals, e.g. Ti(OR)
4
, Sn(OR)
4
, Sn(OR)
2
, Al(OR)
3
, where R are alkyl or aryl radicals;
c) chelate complexes of various metals with acetylacetone, benzoylacetone, trifluoroacetylacetone, ethyl acetoacetate, salicylaldehyde, cyclopentanone-2-carboxylate, acetylacetonimine, bisacetylacetone alkylenimines, salicylaldimine and the like, with possible metals being Be, Mg, Zn, Cd, Pb, Ti, Zr, Sn, As, Bi, Cr, Mo, Mn, Fe, Co, Ni or ions such as MoO
2
++
and UO
2
++
and the like;
d) acidic metal salts of strong acids, e.g. iron chloride, tin chloride, antimony trichloride and bismuth chloride or nitrate.
The polyols s
Borgogelli Rob
Eyrisch Oliver
Cooney Jr. John M.
Goldschmidt AG
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