GB2099722A

GB2099722A - High frequency-weldable foam panels

Info

Publication number: GB2099722A
Application number: GB8117830A
Authority: GB
Original assignee: Sinter Ltd
Current assignee: Sinter Ltd
Priority date: 1981-06-10
Filing date: 1981-06-10
Publication date: 1982-12-15

Abstract

The panels or sheets consist of reticulated foam such as polyurethane into which uniformly distributed high frequency-weldable mouldable resin has been introduced and bonded by a finely divided powder having hot melt- adhesive properties. The mouldable resin may be polyamides, polyvinyl chloride, polyvinylidene chloride, or polyvinyl acetate. The bonding material may be polyethylene, ethylene/vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, or polyvinyl acetate.

Description

SPECIFICATION High frequency-weldable foam panels The present invention relates to high frequencyweldable panels and sheeting of plastic foam, preferably of soft polyurethane foams, and to processes for the manufacture of such panels and sheeting.

There has for a long time been a great need for high frequency-weldable panels and sheeting of plastic foams, especially of polyurethane foam, which can, in particular, be employed for cushioning purposes and can therefore also be employed in substantial thicknesses. For example, attempts have been made to employ, even at the stage of manufacture of the foam, modified polyols which would be directly weldable. The use of high frequency-weldable plastics such as PVC, polyamides, polyacetals and polyacetates in the manufacture of the foam has also not led to the desired results. The subsequent impregnating or spraying of the foams with plastic dispersions, for example of PVC, polyvinyl acetate and polyamide, has also not given the desired results. Attempts have also been made subsequently to needlepunch foams with fibrous plastics so as to render the foams high-frequency weldable.All the products hitherto used in the prior art fail to give completely satisfactory results. In particular, the usability of the product in high frequency welding has been restricted to more or less specific conditions. Typical specific solutions of the problem are described in German Patent Specifications 1,903,667, 1,913,209 and 1,929,352.

German Patent Specification 2,116,092 discloses that polyurethane foam sheeting can be made high frequency-weldable by mechanically deforming the foam and applying the welding auxiliary to the foam not later than when the foam is in the deformed state. By using the process described in the said publication it is possible to introduce high frequency-weldable plastic powder into both the surface of the foam and the pores adjoining the surface. To carry out this process, a special device is necessary, which is intended to ensure uniform distribution of the powder on the surface of the foam but is mechanically complicated. It will readily be appreciated that using this process only very thin sheeting can be treated, since the welding can only take place in the surface zones of the foam sheeting.

It is an object of the present invention to provide high frequency-weldable panels and sheeting of plastic foam, which can be employed in any thickness and are easily handled and virtually universally usable. In particular, it is an object to provide high frequency-weldable foams, preferably based on soft polyurethane foams, which can be employed for cushioning purposes and can, during fabrication, be welded to any other material employed in cushioning, the welds conforming, mechanically and visually, to all demands made of modern industrial products.

This object has been achieved, surprisingly, by using reticulated foams and introducing high frequency-weldable plastic powders in uniform distribution into these foams and fixing these powders by means of a finely divided powder having hot melt-adhesive properties. The manufacture of these high frequency-weldable plastic panels or sheetings according to the invention is effected either by first dusting the web system in the reticulated foam uniformly with the finely divided powder having hot melt-adhesive properties and then uniformly introducing the high frequency-weldable plastic powder, or uniformly introducing into the foam, if appropriate with heating, a high frequency-weldable plastic powder which has been uniformly dusted with a finely divided powder having hot melt-adhesive properties.

Reticulated foams are known. These are foams in which the cell walls have been virtually completely removed so that the foams only consist of the residual network-like skeleton or web system. They can be obtained in a conventional manner from foams by mechanical, chemical or thermal treatment. The use of reticulated foams has hitherto been restricted to special fields such as the treatment of flowing media, the modification of mechanical, acoustic and electrical vibrations, and special packaging.

It has now been found that these reticulated foams are also exceptionally suitable for conversion to high frequency-weldable panels and sheeting. For this purpose, high frequencyweldable plastic powders are uniformly introduced into the reticulated foams, which as a rule are not per se high frequency-weldable. This introduction can be effected in a particularly easy manner simply by evenly sprinkling the plastic powder onto the foam, with excess amounts issuing again underneath the panel or sheeting by passing through the web structure. In order to make the panels and sheeting transportable and storable and avoid the risk of the uniform distribution being subsequently disturbed again, it is necessary to fix the particles of the weldable plastic powder to the webs of the foam.According to the invention, this is done by means of a finely divided powder having hot melt-adhesive properties. This finely divided powder can either be introduced into the foam before introducing the weldable plastic powder or be introduced in a single step together with the plastic powder, by first dusting the plastic powder with the finely divided powder. These dusted plastic powders are fixed to the webs of the reticulated foam merely by simple warming, without thereby changing the other mechanical properties, and the visual properties, of the foam.

The panels and sheeting thus obtained can then be welded in any desired manner by means of conventional high frequency-welding equipment, and even the most diverse materials can be welded to one another in one step. A particular advantage of the products according to the invention is that they can be manufactured, and processed, without difficulties even in thicknesses of more than 5 mm. In the process according to German Patent Specification 2,11 6,092, if the thickness of the material is more than 5 mm, both the upper face and the lower face must be provided with welding auxiliaries, and this, in practice, leads to considerable additional costs.

According to the invention, even foam panels and sheeting in thicknesses of 10 to 20 mm can be rendered weldable.

The reticulated foams which can be used are in principle all foams, but in practice soft polyurethane foams, especially based on polyesters and polyethers, are preferred. The high frequency-weldable plastic powders employed are in particular polyamides, PVC, polyvinylidene chloride, polyvinyl acetate, copolymers and mixtures of these. The particle sizes can be 100 to 500 ym, but particle sizes of 100 to 300 ym are preferred. It is to be borne in mind that the particle sizes must be less than the pore sizes of the reticulated foams, since otherwise penetration into, and trickling through, the foam is no longer possible. The reticulated foams in general have 5 to 30 cells per cm, 14 to 22 cells per cm being preferred. The density of these foams is 1 5 to 60, preferably 25 to 45, g/l.The high frequencyweldable plastic powders are present in the finished product in amounts of 20 to 200% by weight, based on the weight of the foam.

Preferably, amounts of 50 to 150% by weight are employed. To fix the high frequency-weldable plastic powders, finely divided powders having hot melt-adhesive properties are employed. These powders can consist of polyethylene, ethylene/vinyl acetate copolymers, polyamides, PVC, polyvinylidene chlirde, polyvinyl acetate, copolymers and mixtures of these. The particle size should be from 1 to 100, preferably from 5 to 60, ym, but there should be a distinct difference in size, of about one power of ten, from the particle size of the weldable plastic powder.The melting point of the finely divided powder having hot meltadhesive properties should be between 40 and 1200 C, preferably between 60 and 800 C. These powders are employed in amounts of 1 to 30, preferably 5 to 15. % by weight relative to the weight of the high frequency-weldable plastic powders. To ensure adequate fixing of the high frequency-weldable plastic powders to the web structure of the reticulated foams, it is possible either to start from preheated foam or in each case to heat the material after introduction of the pulverulent substances. Heating can be, for example, by infrared, hot air, gases or steam, but also by high frequency, if the finely divided powder having hot melt-adhesive properties can also be activated by high frequency.In a preferred embodiment, the high frequency-weldable plastic powder is dusted with the finely divided powder having hot melt-adhesive properties and is uniformly introduced, in this dusted form, into the reticulated foam. The heating merely sinters the high frequency-weldable plastic powder superficially onto the webs. In contrast to the use of adhesives, solvents, dispersions and the like, however, no foreign materials which influence the welding process or influence the quality of the end product are introudced into the foam.

The foam panels and sheeting according to the invention can, without difficulties, be processed conjointly with a large number of other materials.

For example, it is possible to apply single-layer or multi-iayer laminations, and to weld both plastic sheets and textiles to the foam, with or without additional layers, as desired. The products thus obtained can preferentially be used for cushioning, for example in the manufacture of upholstered furniture, motor vehicle seats and internal fitments of motor vehicles. They are however also suitable for the manufacture of mattresses and loose cushions and can, for example, be processed together with imitation leather and textiles to give high quality end products.

In the manufacture of laminated products, the manufacturing process can be simplified and carried out in a particularly practical manner by sprinkling the plastic powder, which has been uniformly dusted with finely divided powder, into the foam, for example by means of a vibratory plate dispenser, the foam having already been laminated on one side, and controlling the amount of plastic powder, as far as possible, so that the amount sprinkled onto the foam just suffices to cover the foam webs, with little or no excess collecting against the laminated lower face. After the application of this dusted powder, the material is heated, the plastic powder thereby being fixed to the webs. Heating can be effected particularly simply by means of infrared. Thereafter, if desired, a fabric can also be laminated onto the second face of the foam. The product thus obtained is outstandingly suitable for upholstering of furniture and car seats.

Claims

1. High frequency-weldable panels and sheeting of plastic foam, characterised in that they consist of a reticulated foam, into which uniformly distributed high frequency-weldable plastic powder has been introduced and fixed by means of a finely divided powder having hot meltadhesive properties.

2. High frequency-weldable panels and sheeting according to Claim 1, characterised in that reticulated soft polyurethane foams are employed.

3. High frequency-weldable panels and sheeting according to Claim 1 or 2, characterised in that the high frequency-weldable plastic powder consists of polyamides, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, copolymers and mixtures of these.

4. High frequency-weldable panels and sheeting according to Claims 1 to 3, characterised in that the finely divided powder having hot meltadhesive properties consists of polyethylene, ethylene/vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, copolymers and mixtures of these.

5. High frequency-weldable panels and sheeting according to Claims 1 to 4, characterised in that the finely divided powder having hot meltadhesive properties has particle sizes of 1 to 100, preferably 5 to 60, #m.

6. High frequency-weldable panels and sheeting according to Claims 1 to 5, characterised in that the high frequency-weldable plastic powder has particle sizes of 100 to 500, preferably 100 to 300, Mm, but is coarser by at least one power of ten than the finely divided powder having hot melt-adhesive properties.

7. High frequency-weldable panels and sheeting according to Claims 1 to 6, characterised in that the reticulated plastic foam has 5 to 30, preferably 14 to 22, cells per cm and has a density of 15 to 60, preferably 25 to 45, girl.

8. High frequency-weldable panels and sheeting according to Claims 1 to 7, characterised in that the finely divided powder having hot meltadhesive properties melts at 40#1200 C, preferably 60#800 C.

9. High frequency-weldable panels and sheeting according to Claims 1 to 8, characterised in that the high frequency-weldable plastic powder is present in amounts of 20 to 200, preferably 50 to 1 50, % by weight of the reticulated plastic foam.

10. High frequency-weldable panels and sheeting according to Claims 1 to 9, characterised in that the finely divided powder having hot meltadhesive properties is present in amounts of 1 to 30, preferably 5 to 15, % by weight relative to the weight of the high frequency-weldable plastic powder,

1 1. Process for the manufacture of high frequency-weldable foam panels or sheeting, characterised in that either a) first the web system of a reticulated foam is uniformly dusted with a finely divided powder having hot melt-adhesive properties and thereafter a high frequency-weldable plastic powder is uniformly introduced, or b) a high frequency-weldable plastic powder which has been uniformly dusted with a finely divided powder having hot melt-adhesive properties is uniformly introduced into a reticulated foam, if appropriate with heating.

12. Process according to Claim 11, characterised in that preheated, reticulated foam is used as the starting material and/or heating is applied in each case after the introduction of the pulverulent substances.

13. Process according to Claims 1 1 and 12, characterised in that heating is effected with infrared, hot air, gases, steam or high frequency.