Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
1996-12-16
2001-05-08
Kuhns, Allan R. (Department: 1732)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C264S122000, C264S489000, C264S916000
Reexamination Certificate
active
06228478
ABSTRACT:
The invention relates to a method of manufacturing a composite foam, having acoustic properties, from foam flakes, a composite foam manufactured by the method and the use of such a composite foam.
The manufacture of composite foam from foam flakes has been known in practice for a considerable time, for example for the in-house processing (recycling) of remainder or waste materials arising in the course of production. This processing—of material per se of only one kind—poses no problems apart from the possible different colours of the foam flakes, so long as no particular demands are made of the production process and the desired properties of the product.
In a known procedure according to EP-B1-0 031 425 foam (foamed material) flakes are wetted with an aqueous dispersion and/or an aqueous solution which contains dispersed or dissolved components for attaining particular characteristics, and the mixture is cured together with a binding agent which is such as to form polyurethane. By means of this manner of manufacture, the thermal formability, the possibility of high frequency welding and the fire-resistance properties are intended to be improved, as well as further characteristics and effects achieved. The method is, however, relatively complex, in particular time consuming, and employs prepolymers and heat which must be supplied either in the oven or by means of a hot air blower. In the subsequent drying in a drying chamber, the curing time for the parts is about two hours, it being possible to reduce this by the employment of hot air to as little as 15 minutes. By means of the addition of dissolved solids, such as for example colour pigments, it is intended that the end product should be given a uniform appearance.
However, no teaching is given to the skilled man in the relevant technical field which enables him to combine foam flakes of differing sizes, differing origins and/or differing material compositions, to a composite foam. Likewise, no indication is given as to how the quantity of binding agent to be used and other supplemental materials such as separator or release agents can be reduced without making worse the mechanical and physical characteristic values of the composite foam of foam flakes, in particular with regard to acoustic characteristics.
This is, however, of significance and of increasing importance. Because of the conventional manufacture of such molded part in molds, the consumption of release agent for achieving removability from the mold should be as little as possible, for reasons of environmental protection. Because of the possible future duty of the manufacturer to take back old motor vehicles, for example, there will in future be additional large quantities of foam materials, for example from seat cushioning and sound insulation, in addition to the usual quantities of residual materials from production, which will have to be re-processed.
It is therefore the object of the invention to further develop the known method so that despite lesser quantities of binding agent and despite the employment of foam flakes of differing sizes, differing origin and/or differing material composition, composite foams can be achieved the mechanical properties of which are comparable with those composite foams manufactured in accordance with the present technology and additionally have sound insulation characteristics.
In accordance therewith, foam flakes of various origins and/or various compositions are combined in accordance with per se know techniques to different molded parts in an energy and cost-saving method, whereby by embedding such parts in new parts of foam, preferably of polyurethane foam, subsequent recycling—of material of one kind—is favoured, even when the composite foam and the newly manufactured polyurethane foam are employed together as acoustic spring within a mass-spring-system. The acoustically effective mass of this system is in such a case conventionally formed by means of a sound damping heavy layer of per se conventional art, as flexibly yielding as possible.
The binding agent, which is added in only low weight-percent proportions, is inactive at room temperature and provides for a very good wetting of the foam flakes which even after the wetting can be conveyed (transported) and dosed well. As a result of this kind of pre-treatment of the foam flakes, a continuous manufacture of molded parts of composite foam is possible. For curing, (water) steam is used, with subsequently applied vacuum or partial vacuum and/or supplied hot air, in order to accelerate the drying and curing process. Instead of steam, microwave energy may be employed.
The method of manufacturing composite foam out of foam flakes and with reduced addition of binding agent, in accordance with the present invention, will be described below with reference to two examples.
Two charges of foam flakes of differing origin and composition are available. The first 10 charge originates from production residue from the manufacture of light polyurethane foam having a density, after forming in the closed mold, of about 60 to 80 kg/m
3
. By means of sieving, foam flake components having edge lengths of 6, 8, 12 and 15 mm are made available. The foam flakes of the second charge originate from recovered foam seat cushions of vehicles. These foam flakes had a substantially uniform edge length of the order of 8 mm. In preliminary trials concerning the wetting of the foam flakes with a polyurethane dispersion binding agent and the subsequent process steps of conveying (transporting) and dosing, it was determined that foam flakes with edge lengths of the order of 8 mm showed optimal results.
In the first example, of the first charge only those foam flakes with edge length of 8 mm are selected and mixed with those of the second charge. The foam flakes from the two charges are combined, each 50 parts by weight, to a mixture and wetted with a binding agent. As binding agent there is employed an aqueous binding agent mixture of NCO-prepolymer with blocked isocyanate groups which contained a polyamide component having primary and/or secondary (cyclo)aliphatically bound amino groups.
The polyurethane dispersion binding agent was diluted with water in the ratio 1:1 parts by weight. Of this solution, and referred to the weight of the foam flakes employed, 20 weight % were put to use in the examples.
For manufacturing the composite foam of foam flakes, after the wetting, the foam flakes were drawn into a dosing reservoir by means of vacuum, and from here blown into a mold bed using overpressure, via two injectors, the mold bed having the dimensions 550×308×25 mm. For 30 seconds steam was flowed through the mold bed at a pressure of 4 bar and a temperature of 153° C. The steam temperature may by varied within the range from 120 to 180° C., preferably in the range from 140 to 160° C. Subsequently, vacuum was applied to draw off the residual moisture, from vapours out of the composite foam. The lower temperature limit of 120° C. arises because only from this temperature is the aqueous binding agent with the blocked isocyanate groups capable of reaction, and the upper temperature limit arises because at higher temperatures thermal decomposition would set in.
In the second example exclusively foam flakes, which are of one kind in terms of origin, from the first charge are employed likewise with a uniform edge length of the order of 8 mm. In this case also, the same polyurethane dispersion binding agent was diluted with water 1:1 parts by weight and of this solution, referred to the weight of the foam flakes, 20 weight % were applied to the foam flakes for wetting. The further process steps corresponded to those of the first example.
For the determination of the optimum set time for the flow through of steam and the application of vacuum, preliminary experiments have likewise being carried out. Both parameters were varied so that mechanical characteristic values as good as possible were provided. With the preferred steam temperature range (140 to 160° C.), the steam through-flow times were in ran
Kittel Christoph
Kliwer Carsten
Kuhns Allan R.
Marshall O'Toole Gerstein Murray & Borun
Stankiewicz GmbH
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