Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1994-12-15
1996-06-25
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521130, 521131, 521133, G08J 900
Patent
active
055300324
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method for the production of integral skin foam from a liquid skeleton substance which is foamed up by at least one inert, non-flammable gas which is set free by energy supply.
BACKGROUND ART
One such type of method is known from DE 32 26 818 A1. During this known method conventional devices are used for the measurement of gas and gas loading. After a measurement of density of a mixture sample which was taken from a machine container, or in a bypass the gas loading done at another position is controlled on the basis of this measurement. The addition of the gas occurs also in a bypass, for example, parallel to a return pipe-line coming from a mixer casing in the vicinity of a machine tank. The gas addition in the bypass is done by a capillary tube introduced into the pipe-line and a Venturi-tube. The control of gas loading can be done manually or with the help of a computer. The application of the Venturi-principle makes this known method difficult to control because the amount of gas loading is heavily dependent on an interface tension between liquid and gas, wherein high interface tension means small bubbles of the absorbed gas in the liquid and wherein low interface tension means large bubbles of the absorbed gas. In addition to that the known method working according to the Venturi-principle is high energy consuming because the flow in the pipe, in which the Venturi-device is situated, must have a high speed, so that the gas loading resulting according to the type of a water jet blast can function at all. Finally it is disadvantageous in the case of the known method, that relatively high quantities of foaming agent, among others hydrocarbon fluids, are necessary.
Another known method is, for example, mechanical frothing. In this case foaming agent, air and gelling agent are fed to a plastic serving as a skeleton substance and a homogeneous mixture is produced by a mixer (vide A.M. Wittfoth, Kunststofftechnisches Worterbuch, Carl Hanser Verlag Munchen Wien, Part 3, page 146, 1978). The mixture is then poured into a mould. In a subsequent heating operation the mixture expands and solidifies, so that a foamed product is produced. Therein a foaming agent in the form of azo or diazo-compounds is always added, which sets free N.sub.2 or CO.sub.2, when the foaming agent decomposes under gas formation in the heating operation subsequent to the mixing and thus leads to the foaming up of the skeleton substance and to the formation of foam. In the case of some foaming agents no heating process is necessary, as they decompose even at room temperature. However, even here normally a heating process is conducted afterward in order to cure the foam.
Again there are other methods for the production of foam from plastic, e.g. the one-shot process, which is also called direct process, or the two-step process. Therein either foaming agents or liquid solvents are admixed to a plastic to be foamed up. The foaming agents decompose at a certain temperature under gas formation and thus foam up the plastic by forming cavities within the plastic. In the case of production of foams by adding volatile solvents these are admixed to the plastic during the polymerisation, whereby spaces filled with solvent are created, which become cavities after the evaporation of the solvent.
Foams are produced from polystyrene, polycarbonates or polyurethanes, for example, wherein the production of foams from polyurethanes has the greatest technical importance and such foams find use in upholstery, mattresses or wrappings, for example.
Most of the known methods have the disadvantage, that during the use of foaming agents free from chlorofluorocarbons (CFC), like n-pentane, for example, with air there are easily produced very highly inflammable air-gas mixtures. These air-gas mixtures develop not only in the production phase of the foams, but also during aging of the foams afterward, during which the residual foaming agent is set free from the foam. Production companies for foams which handle such type
REFERENCES:
patent: 5034424 (1991-07-01), Wenning et al.
patent: 5086078 (1992-02-01), Harclerode et al.
patent: 5096933 (1992-03-01), Volkert
patent: 5110837 (1992-05-01), Harclerode et al.
Derwent's Abstract No. 87-148657/21, Week 8721, Abstract of SU, A2, 1260235 (Petrol Gas Ind. Res.), Sep. 30, 1986.
A. M. Wittfoht, "Plastics Technical Dictionary", Part 3: Reference Volume, Carl Hanser Verlag Munchen Wien, p. 147, (1978).
Jurgen Falbe and Manfred Regitz, "Rompp Chemie Lexikon", 9th Edition, pp. 4802-4803, (1992).
Derwent's Abstract No. 8218994E/10, Abstract of JP 8093901, (Tiejin KK), Feb. 2, 1982.
Poschl Gunter
Wayand Hans-Jurgen
Foelak Morton
PPV-Verwaltungs-AG
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