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The invention concerns EPS cαtibination foam pieces, a procedure for manufacturing same, and their use. In particular, the invention concerns EPS combination foam pieces, and manufacturing thereof, which are composed of mixtures of EPS granules and a foarrH Lke binding ^" 10 agent.

It is known in the art to mix EPS p:refoami_τg ccrmpound (EPS-cell- forming polystyrene) in the form of discrete granules and ccπiponents producing polyurethane foam in manufacturing various products, e.g. 15 mattresses, by die casting. The difficulty has then been that the separate granules rise in the die or mould to the surface layer. The EPS globules are easily damaged by the high mould teirtperature (>100°C) .

20 m the Japanese Patent No. 56-120326(A), a problem solution is dis¬ closed in which the reaction tørπperature cannot rise to such great height that the EPS globules would suffer damage. In said procedure, a box mould is used which is open on one side. The mould is filled with EPS granules and the open side of the mould is closed with a

25 net which locks the EPS globules in place. The substance mix forming polyurethane foam is then poured into the mould. About 40% of the volume within the mould will then be available to be occupied by the polyurethane foam that is formed in the mould.

30 τtιe net is removed after the product has hardened. One of the draw¬ backs of this procedure is that therein is needed a mould, and a net in said mould. For this reason the procedure is in actual practice restricted mainly to the manufacturing of rectangular pieces. Further¬ more, it is not possible by this procedure to manufacture lαngi-

3 tudinally continuous products, nor laminated products.

One of the objects of the present invention is an EPS combination foam piece which is free from the drawbacks described. The EPS com¬ bination foam piece of the invention is characterized in that it consists of an EPS polystyrene sheet or shaped piece with spacious structure and viiich has been impregnated with a free-flowing foam¬ like binding agent vfaich fills the free spaces between the polystyrene granules and solidifies therein.

It is thus understood that in the EPS αarribinaticn foam piece of the invention is used an EPS sheet or shaped piece with spacious structure which has open spaces amounting to between 10 and 30% of the total volume. A sheet or shaped piece with spacious structure is here understood to mean a finished sheet or shaped piece made in a way known in itself in the art, by foaming in a mould, of EPS granules. Such a product contains EPS granules cemented to each other, and it is self-coherent, in contrast to the loose EPS granules used in the above-cited Japanese Patent No. 56-120326(A) . The EPS sheet or shaped piece may also have the shape of a continuous web, and thus the invention also encompasses EPS combination foam products which are continuous in the longitudinal direction.

For binding agent, one may according to the invention use organic or inorganic hardening, foam-forming substances. The prerequisite is imposed on the binding agent that it will not corrode polystyrene, and that its foam-producing ∞mponents in combination constitutes a free-flowing substance mix filling the spaces between the polystyrene globules and foaming and hardening in said spaces between globules. The density of the binding agent has to be high enough (>30 kg/cm ³ ) to afford adequate mechanical properties and cold-endurance of the foam that is produced. The binding agent may have open-cell or closed- cell structure.

The contribution of the binding agent to the ESP combination foam piece of the invention is advantageously less than 30% by volume. Hereby no such great amounts of heat are liberated at curing that damage to the EPS granules would incurred. The low temperature also

entails the advantage that the shrinkage occurring as the piece cools will be less.

The task of the binding agent is to fill and reinforce the EPS foam pieces and in special instances, e.g. in multi-ply s ^* tructures, to attach the surface laminations directly in one single work step to the EPS combination foam piece serving as core material.

Suitable binding agents are, for instance: polyurethane resins, epoxy resins, and phenolic resins. A recαrπmendable binding agent is polyurethane.

The EPS c nbinatiαn foam piece of the invention presents good heat resistance, that is, it tolerates teπperatures higher than normal, without shrinkage. Particularly in those instances in which an open- cell binding agent foam is used, the thermal expansion of the products is _. less than that of a conventional closed-cell, dense EPS sheet. Compared with equivalent foamed products which have been formed exclusively of the binding agent used in the product, the EPS cαiibi- nation foam product is considerably less expensive to manufacture. When used as a packaging material, the EPS combination foam product of the invention presents shock absorbing properties which are close to those of"the best polyethylene foam.

The invention also concerns a procedure for manufacturing EPS combi¬ nation foam pieces, said procedure being characterized in that an EPS polystyrene foam piece with spacious structure is iπpregnated with a foamable, free-flowing binding agent which fills the free spaces between EPS granules and hardens therein.

Application of the binding agent to the EPS foam piece is accαπplished simply, fcy adding a free-flowing substance mixture which forms foam- like binding agent, upon the foamed piece, whereby it will be absorbed in the spaces between the EPS granules, while at the same time foaming sets in. This mode of application is advantageous when shaped pieces are being manufactured and the impregnated foamed piece is advaiv-

tageously kept in the mould during the curing time of the binding agent if the product being manufactured has a peculiar shape. Binding agent application may, when manufacturing laminated products, also be between the lamination layers, whereby absorption of the binding agent, its foaming and cemeriting-on of the surface laminations all take place in one work step.

The handling of an EPS foam sheet is simple because the EPS globules remain interlocked without need to use any mould. Binding agent application may be accomplished e.g. in a press, or even on ccntiπucus-cperation iπpregnation lines which are used in manufac¬ turing laminated products. Since the structure of the EPS piece is uniform and the volumetric contribution of the globules is 70 to 90%, the reaction heat will not raise the ten*perature of the product to such height that any collapse of EPS globules need be feared. This also entails the advantage that the cycle times are shorter than in the case of semi-hard integral foam applications, and that the shrinkage, which is an established problem, will be less.

Application of the binding agent may also take place at the point of use of the final product, e.g. in connection with the manufacturing of building construction elements or when lagging roofs of buildings on site.

ihe EPS combination foam products of the invention may be applied e.g. as lagging, or insulation, sheets or for footfall attenuation, when the binding agent foam component is soft, e.g. polyurethane, or to serve as insulation panel when a hard binding agent component is used. In the latter case it is advantageous to use also surface lamination, whereby a hi -strer-gth laminated sheet structure is obtained in applications at a building site.

Products which are pressed into shape f om sheet material may be manuf ctured by combining a surface lamination with the polystyrene in conjunction with the polyurethane addition. This enables finished products, e.g. lagging sheets appropriate for the ceiling of a car

body, to be manufactured in one work step, using cold tools.

The invention is now described in detail, referring to an advantageous embodiment of the invention, presented in the figures of the attached drawings, yet to which the invention is not meant to be exclusively confined.

Fig. 1 presents graphically certain characteristics of the EPS combi¬ nation foam piece of the invention.

Fig. 2 presents an embodiment of the EPS combination foam piece of the invention, in schematic section.

m Fig. 1 has been plotted the peak deceleration 6, as a function of static stress in kPa, and the impact attenuation factor C, as a function of work capacity in kJ/m ³ .

In Fig. 2, the ceiling cladding sheet of the invention in general has been indicated with reference numeral 10. In this embodiment example, the ceiling cladding sheet 10 comprises a surface lamination 11 serving attachment, and a cladding surface lamination 12. The cellular polystyrene (EPS) sheet with spacious structure inside the laminated structures 11 and 12 has been denoted with reference numeral 13 and the binding agent foam, with 14.

The invention is illustrated with the aid of the following examples.

Example 1

Upon an ESP sheet with spacious structure of 50 mm thickness and with particle size about 10 mm, density about 10-15 g/dm ³ arώ empty (free space) volume about 25%, a polyol/isocyanate mixture was applied which had soft foam starting time about 15 seconds and free density about 20 g/dm ³ . The sheet was kept between polyethylene foils under a small weight. The combination foam product thus produced had density 34 g/dm ³ , and its impact attenuation factor was markedly superior to

that of an ESP sheet with equivalent density, as can be seen in Fig.

1, where the deceleration and impact attenuation factors of EPS sheet, of the EPS combination foam product of the invention and of a polyethylene foam product have been compared.

Example 2

A ceiling cladding sheet for a car body was manufactured in that upon an EPS sheet with spacious structure of 10 mm thickness and with particle size abcut 5 mm, density abcut 15 g/dm ³ and empty volume about 10%, a polyol/isocyanate mixture was applied "which had soft foam (rigid) starting time about 60 seconds and free density about 40 g/dm ³ . The sheet was placed between surface laminations, in a press. The core material (combination product or foam) of the multi-ply sheet thus produced had density about 40 o dm ³ , i.e., 400 g/m ² . Fig. 2 is a general representation of the structure of this sheet.