FR2471854A1 - Heat weldable cellular material esp. polyurethane - contg. a uniformly distributed powder of a heat weldable material fixed by a fine grain powder with thermo-adhesive properties - Google Patents

Abstract

Sheets and tapes of high frequency weldable synthetic cellular material are comprised of a reticulated cellular material contg. a powdered synthetic material which is weldable at high frequency, uniformly distributed by means of a fine grained powder with thermal adhesive properties. Pref. cellular material is flexible polyurethane foam; the high frequency weldable material is polyamides, PVC, polyvinylidene chloride, polyvinyl acetate, or copolymers of these; and the material with thermal adhesive properties is polyethylene, EVA, PVC, polyvinylidene chloride, polyvinyl acetate, or mixts. of these. The prods. can be welded by high frequency techniques to other synthetic materials, synthetic leather, etc., as paddings and stuffings e.g. in the prodn. of upholstered articles, cushions, automobile trim, furniture, etc.

Description

 The invention relates to sheets and strips of foam or cellular synthetic material, preferably flexible polyurethane foams, which can be welded by high frequency, as well as a method for their production.

There has been a great need, for a long time now, for plates and strips of alveolar synthetic materials or foams, in particular those of polyurethane, which can be welded by high frequency, which can be used in particular for padding and which can therefore be used even under fairly large thickness .

For example, attempts have been made to use, directly during the production of foam materials, directly weldable modified polyols. The addition in the manufacture of synthetic foams or cellular materials, of synthetic materials weldable by high frequency such as polyvinyl chloride (PCV), polyacrylonitrile (PA), polyacetals and polyacetates, did not lead either to the desired results . By impregnating or after-spraying the foam materials with dispersions of synthetic material, for example dispersions of PCV, polyvinyl acetate (PAV) and PA, the desired results are not obtained either. Attempts have also been made to after-shoot the cellular materials with fibrous synthetic materials so as to make them weldable by high frequency. None of the products used in the prior art give entirely satisfactory results. In particular, their possibility of use in high frequency welding is limited to more or less special conditions. Special typhic solutions are described in patents DE 1 903 667, 1 913 209 and 1 929 352.

 Patent DE 2,116,092 discloses the means of making high-frequency weldable strips of cellular polyurethane by mechanically deforming the cellular material and applying the welding aid to a material at the latest when the latter is in the state deformed Thanks to the process described by said patent, it is possible to introduce synthetic powder weldable by high frequency, on the surface as well as in the pores of the cellular material, adjacent to the surface.

To implement this method, a special apparatus is required which has the role of ensuring, by expensive mechanical means, the uniform distribution of the powder on the surface of the foam material. It is obvious without further explanation that, according to this method, it is only possible to treat very thin strips because the welding can be carried out exclusively in the surface regions of the strip of cellular material.

The object of the invention is to provide plates and strips of alveolar synthetic material which can be welded by high frequency and which can be used in any thickness and practically universally, being easy to handle.

In particular, it is necessary to obtain foam materials which can be welded by high frequency, preferably flexible polyurethane foam materials which can be used for padding purposes and which can be welded during manufacture to any other materials used. in padding, the welds must meet, mechanically and optically, all the requirements of modern industrial products.

 Surprisingly, this problem is solved by virtue of the fact that crosslinked cellular materials are used, which are introduced into them in a uniformly distributed manner, powders of synthetic material weldable # by high frequency, and which fixes these powders using a fine-grained powder having iron-on properties. To manufacture these plates or strips of cellular material weldable by high frequency according to the invention, or else # one begins by projecting uniformly onto the #nets, in the crosslinked foam material, a fine-grained powder having iron-on properties (tacky by fusion) and then the powder of aynthetic material weldable by high frequency is introduced uniformly, or else a powder is uniformly introduced and optionally heated of synthetic material # weldable by high frequency uniformly sprinkled with fine grain powder having iron-on properties.

Crosslinked cellular materials are known. These are cellular materials in which the cell walls have been practically completely eliminated so that they are only formed from the network-shaped skeleton. or net system. They can be obtained in the usual way starting from cellular materials, by mechanical, chemical or thermal treatment. Until now, the application of crosslinked cellular materials has been limited to special fields such as the treatment of flowing fluids, the modification of mechanical, acoustic and electrical waves, and special packaging.

 However, it has been found that these crosslinked cellular materials are also very suitable for being transformed into plates and bands which can be welded by high frequency. For this purpose, -in crosslinked cellular materials which are generally not weldable by high frequency, uniformly are introduced.

powders of synthetic material weldable by high frequency.

this can be done in a particularly easy way by simply and uniformly semaabt the powder of synthetic material on the cellular material, the quantities of excess emerging.

through the skeleton of nets, below the plate or strip. So that the plates and bands can be transported and stored and so that the uniform distribution is not compromised again afterwards, it is necessary to fix the particles of the powder of synthetic material which can be welded to the threads of the cellular material According The invention is achieved by means of a fine-grained powder having fusible properties (sticky by fusion). This fine-grained powder can either be introduced before the introduction of the weldable synthetic powder into the cellular material, or introduce it at the same time as the synthetic material powder, in a single operation, by sprinkling beforehand with fine-grained powder, the synthetic material powder. these powders of synthetic material, in a way "breaded", are already fixed by simple heating to the threads of the crosslinked synthetic material without otherwise modifying its mechanical and optical properties. The plates and strips thus obtained can then be welded at will. thanks to.

conventional high-frequency welding machines, - the most diverse materials can also be welded together
in one operation. A particular advantage of products according to
the invention is that they can be made and put in
works without difficulty even in thicknesses exceeding 5 mm.

In the process according to patent DE 2,116,092 already cited, it is necessary, if the
layer thicknesses exceed 5mm, apply welding aus
so well on the upper side than on the lower side, which leads in
practice at notable expense supplements. According to the invention, one can
make weldable even sheets and strips of foam material having
thicknesses from 10 to 20 mm.

As crosslinked cellular materials, it is possible in principle to envisage
all cellular materials but in practice, we prefer polyu
flexible cellular rethannes, in particular based on polyesters and
of polyethers. As high weldable synthetic powders
frequency, polyamides, PCV, polychlo are used in particular
vinylidene rure, polyvinyl acetate, copolymer products
rization and mixtures of these bodies. The grain sizes can be from 100 to 500 tu, preferably from 100 to 300 sort. It should be noted here that the grain sizes must be less than the pore size of the crosslinked synthetic materials, since otherwise penetration and flow are no longer possible. The crosslinked cellular materials generally have 5 to 30 cells! Cm, preferably 14 at 22 cells / cm. The bulk density of these cellular materials is 15 to 60 g / l, preferably 25 to 45 g / l. The powders of synthetic material weldable by high frequency are contained in the finished product at a rate of 20 to 200% of the weight of the cellular material. Preferably, quantities of 50 to 150% by weight are used. To fix the powders of synthetic material which can be welded by high frequency, use is made of fine-grained powders having fusible properties. These powders can be formed from polyethylene, ethylene vinyl acetate copolymer, polyamides, PVC, polyvinylidene chloride, polyvinyl acetate tPAV> copolymerization products and mixtures of these bodies.

The particle size must be from 1 to 100 μm, preferably from 5 to 60 but must have a clear difference, of about a power of ten, with the grain size of the powders of synthetic weldable material. The melting point of fine-grained powders with fusible properties must be between 40 and 120 ° C., preferably between 60 and 80 ° C. Powder is used at a rate of 1 to 30% and preferably from 5 to 15% of the weight of the powders of synthetic material weldable by high frequency.

To ensure sufficient fixation of the powders of synthetic material weldable by high frequency to the skeleton of nets of the crosslinked cellular materials, it is possible to start from the preheated cellular material or else to heat it each time after the introduction of the pulverulent substances. The heating can be ensured for example by means of infrared rays, hot air, gas, steam but also by high frequency, insofar as the fine grain powder with fusible properties is excitable by high frequency.

According to a preferred embodiment, the fine grain powder with fusible properties is sprayed onto the powder of synthetic material which can be welded by high frequency and in this somewhat "breaded" form, the powder is introduced uniformly into the crosslinked foam material. By heating, the powder of synthetic material which can be welded by high frequency is only fixed superficially to the threads by sintering. However, unlike adhesives, solvents, dispersions, etc., foreign matter is not introduced into the foam material influencing the welding process or the quality of the final product.

The sheets and strips of cellular material according to the invention can be worked without difficulty with a large number of other materials. for example, it is possible to double surfaces with one or more layers and to weld together plastic sheets as well as textiles with the cellular material or others at will. The products thus obtained can advantageously be used for upholstery, for example in the manufacture of upholstered furniture, automobile seats and interior equipment of automobiles. However, they are also suitable for the production of mattresses and cushions and can be worked, for example, with artificial leather and textiles to obtain high quality end products.

In the manufacture of lined products, the process can be simpli fied and made practical if, for example, the alveolar material already lined is passed on one side under a vibrating distributor, by uniformly distributing the powder of synthetic material sprinkled with fine-grained powder and proportioning it as much as possible in such a way that the projected quantity is barely sufficient to cover the fillets of synthetic material but that the excess does not accumulate, or only in small quantities, on the doubled underside . After this application of "breaded" powder, the material is heated and the synthetic powder is attached to the threads. Heating can be carried out in a particularly simple way by means of infrared rays.

 Then, if desired, the second surface of the foam can also be lined with a fabric. The product thus obtained is very suitable for upholstery of furniture and automobile seats.

Claims (9)

 1. Plates and bands of high frequency weldable cellular synthetic material, characterized in that they are formed of a crosslinked cellular material into which a powder of high frequency weldable synthetic material has been introduced, uniformly distributed and fixed to the using a fine-grained powder with iron-on properties  2 plates and strips according to claim 1, characterized in that they are formed of flexible cellular polyurethanes  3 Plates and strips according to either of Claims 1 and 2, characterized in that the powder of synthetic material weldable by high frequency is formed from polyamides, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, of copolymerization products and mixtures of these bodies  40 Plates and strips according to one of claims 1 to 3, characterized in that the fine-grain powder having iron-on properties is formed from polyethylene, ethylene / vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride , polyvinyl acetate, copolymerization products and mixtures of these bodies 5 Plates and strips according to one of claims 1 to a, characterized in that the fine-grain powder with fusible properties has grain sizes from 1 to 100 µm, preferably from 5 to 60 µm.  6 Strips and strips according to one of claims 1 to 5, characterized in that the powder of synthetic material weldable by high frequency has grain sizes of 100 to 500 µm, preferably 100 to 300 vm, but greater d '' at least a power of ten to fine grain powder with fusible properties  7 plates and strips according to one of claims 1 to 6, characterized in that the crosslinked alveolar synthetic material comprises 5 to 30 and preferably 14 to 22 cells / cm and has a density of 15 to 60 g / l , preferably 25 to 45 g / l. 8. Plates and strips according to one of claims 1 to 7, characterized in that the fine-grained powder with fusible properties melts between 40 and 1200C, preferably between # 60 and 80oc.  9. Plates and strips according to one of claims 1 to 8, characterized in that the powder of synthetic material weldable by high frequency is present in an amount of 20 to 200X} and preferably from 50 to 150% of the weight of the cross-linked cellular synthetic material.  10. Plates and strips according to one of claims 1 to 9, characterized in that the fine-grain powder with fusible properties is present in an amount of 1 to 30% and preferably from 5 to 15% by weight of the powder high frequency weldable synthetic material. 11. A method of manufacturing plates or strips of synthetic material which can be welded by high frequency, characterized in that, in a crosslinked cellular material, the system of threads is firstly uniformly dusted with a fine-grained powder. iron-on properties and then a powder of synthetic material which can be welded at high frequency is uniformly introduced.  12. A method of manufacturing plates or strips of synthetic material weldable by high frequency, characterized in that, in a crosslinked cellular material, a powder of synthetic material weldable by high frequency is uniformly introduced uniformly dusted with a fine grain powder with iron-on properties and which are heated. 13. Method according to one of claims 11 or 12, characterized in that one starts from the preheated crosslinked foam material.  14. Method according to one of claims 11 or 12, characterized in that the pulverulent material is heated each time after the introduction of the pulverulent substances.  15. Method according to Il'lune of claims 11 to 14, characterized in that it is heated using infrared rays, hot air, gas, steam or by high frequency.