Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1994-06-22
2002-07-16
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C156S331700, C181S288000, C181S290000, C181S294000, C521S051000, C521S170000, C521S914000
Reexamination Certificate
active
06420447
ABSTRACT:
The invention relates to a visco-elastic damping foam with an adhesive surface for adhesion coupling to vibrating surfaces for solid-borne sound absorption.
Extremely varied polyurethane soft foamed materials are known for sound-insulation which, however, unlike the foamed material according to the invention, are not suitable for sound deadening (anti-drumming). DE-AS 19 23 161 and DE-OS 28 35 329 describe foamed materials filled with minerals which, because of their high density of 500 to 1,250 kg/m
3
, enable good sound blocking. Sound-deadening (anti-drumming) of sheet metal is, however, not possible with these materials since the loss factor of these foamed materials is too low.
DE-PS 27 56 622 focuses on the manufacture of foamed materials with high loss factors, but the method described, namely the impregnation of open-pored polyurethane foamed materials or PVC foamed materials with visco-elastic materials, for example polyolefins containing inorganic fillers or organic resins or waxes, involves considerable outlay.
It is known from DE-OS 37 10 731.3 that polyurethane soft foamed materials with adhesive properties can be obtained when a polyisocyanate or a polyisocyanate prepolymer is reacted with polyols or mixtures thereof present in excess, whilst keeping an NCO index of ≦80. The sub-cross-linking of isocyanate and polyol is used in order to arrive at the desired surface properties. The foamed materials able to be produced according to this state of the art however have the disadvantage that the mechanical characteristic values turn out unfavourably as compared to foamed materials based on two-component polyurethane which are produced with the stoichiometric ratio.
Consequently the object of the invention is to provide a visco-elastic foamed material, which is produced on the basis of polyurethane in stoichiometrically balanced quantities of polyol and isocyanate with the usual additives. This visco-elastic foamed material produced thus has adhesive surfaces for adhesion coupling to vibrating surfaces and has the required characteristics for sound-proofing. For the lining or covering material itself, this concerns the loss factor d
2
, according to DIN 53 440, and the modulus of elasticity E
2
.
This object is achieved according to the invention in that the isocyanate is reacted in stoichiometric quantities with at least two polyols, preferably of the polyether type, which are incompatible with one another. The two polyols are able to be mixed together, but only because of their high viscosity or syrupy consistency. They are however incompatible with one another because they separate completely after some time. The process of separation occurs relatively slowly because it has to “work” against the viscosity.
The polyether polyols used are characterised by a hydroxyl number ≦100 and are produced on the basis of approximately 75% ethylene oxide in the presence of a starter. Common polyether polyols are based for example on 15 to 20% ethylene oxide. Mixtures of these two types of polyether polyol are incompatible with one another. Polyether polyols produced on a high ethylene oxide basis are used according to the state of the art as cell openers, at approximately 0.5% to 5% relative to the total mixture. Compositions according to the present invention contain clearly greater quantities in contrast to this, for example 50%.
The polyether polyol produced on a low ethylene oxide basis tends to be more reactive than the polyol on a high ethylene oxide basis which therefore accumulates on the outer surfaces. The reaction in the foamed part occurs in a stoichiometrically balanced manner. No sub-cross-linking takes place, rather the adhesive surface is based surprisingly on the action of functional groups. The adhesiveness achieved according to the invention is produced with a functionality of the polyether polyol on a high ethylene oxide basis of 2 to 4.
In the exothermal reaction of polyols with isocyanate a higher temperature is produced, when filling the tool, in the inner core zones of the part being produced than at the outer regions or on the surfaces. The heat quickly dissipates over the surface of the tool. Because of the low temperature in the surface region of the foamed part being produced, the reaction speed is reduced there, as a result of which the separation of the at least two polyols which are incompatible with one another begins.
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Advances in Polyurethane Technology, edited by Buist and H. Gudgeon, p. 196. Elsevier Pub. Co. Ltd., London (1970).
Polyurethane Technology, edited by Bruins, p. 4, Interscience Publishers, New York (1969).
Burak Gerhard
Kittel Christoph
Kliwer Carsten
Peters Cornelia
Scully Scott Murphy & Presser
Sergent Rabon
Stankiewicz GmbH
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