A PROCESS FOR PRODUCING INSULATING PADDING

Abstract: This process comprises the steps of mixing fibres, such as polyester or other fibres, with silicone treated fibres of various nature and origin to produce, after carding, a web (1) of mixed fibres which is then treated, on one face, with a mixture (1) of sticky plastic bonding agents and subse­ quently pressed through a calender (4) having two or more suitably heated cylinders (4′, 4″) which reduces the thick­ ness of the web (1) itself. At the output of the cylinders (4′, 4″) of the calender (4) the product (1) remains, for a short time, adhering with its sticky surface to the corresponding cylinder (4′), thus being subjected to a slight expansion process which causes the formation of air pockets (5).

Description: The present invention relates to a process for the production of insulating padding in synthetic or other fibres and usable for clothing or furnishings in general, and in particular in the manufacture of windcheater jackets, and to padding obtained by means of this process. Currently, windcheater jackets are provided with a padding of insulating material which increases their natural insulating characteristics. This padding usually comprises layers of synthetic fibres forming a cohered fabric - (non woven fabric). In general, the fibres used are polypropylene or polyester although other fibres may also be used. For use in clothing it is preferable that the padding be as thin and flexible as possible both for practical and for aesthetic reasons, whilst at the same time maintaining a high thermal insulation value. For the purpose of obtaining reduced thickness, traditional wadding of very low weight per Square metre (40, 50 or 60 g/m²) is currently produced; another attempt to obtain a thin padding is made by stitching otherwise conventional wadding. This latter operation, although it causes a limited squashing of the padding to make it thinner, also significantly hardens it, thereby limiting the softness and flexibility of padded articles, in which it is used. Even so, layers of padding obtained in this way have only relatively low values of thermal insulation and do not have the necessary characteristics of finish. Moreover, it is important to note that the insulation of the layers of the padding is determined, among other things, by the correct ratio between the density of the wadding and the quantity of air trapped between the fibres. Consequently, if it is desired to obtain products having a high thermal insulation value using only conventional techniques, it is necessary to increase considerably the weight and therefore the thickness of the starting material. This, however, leads to an unwanted increase in the volume of the produce, such as to prejudice the line of the finished product, for example, a windcheater jacket. The US 3,879,257 document discloses a method for producing fibrous webs comprising web preparing steps substantially corresponding to the introductory part of Claims 1. The US 4,304,817 document, moreover, discloses a three-ingredients polyester fiberfill which can be made and processed conveniently into bolts using conventional textile machinery, which bolts are reduced to the desired thickness by needle punching the two sides of the bolt. The present invention seeks therefore to eliminate this disadvantage by providing a process for the production of padding which will allow padding having high insulation values to be produced with low thickness; even heavy weight padding may be produced by the process of the invention in very reduced thicknesses in comparison with conventional padding or stitched wadding of equivalent insulation value. According to one aspect of the present invention, therefore, there is provided a process for the production of padding in synthetic or other fibres, having the feature of the characterizing part of Claim 1. Among the many advantages of the process of the present invention are the fact that it produces a padding which is compact and the nap of which is well secured on both faces and which therefore does not lose fibres through the fabric. A further advantage of the process of the present invention is that it produces a padding which, for the same thermal insulation value as conventional padding, has a noticeably smaller thickness. In performing the process of the invention, by suitably regulating the pressure and the temperature of the cylinders, desired and adjustable reduction in thickness of the starting material can be obtained, and simultaneously, by the effect of the adhesion of the plastic side of the layer upon separation from the cylinder there takes place a slight reinflation which creates an "air chamber" or air pocket in the material. It is important to note that the formation of this air chamber or air pocket is also favoured by the presence of the silicone treated fibres which are therefore slippery. The process of the present invention makes it possible to reduce the thickness of heavy weight paddings, that is, paddings having very high weight per square metre, down to a low thickness value. Another advantage of the invention lies in the fact that it is possible by means of the calendering operation, to produce padding of selected thickness, from a given starting material, by appropriately varying the temperature and pressure of the cylinders. The invention can be put into practice in various different ways, one example of the way the invention may be put into practice is described hereinbelow with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a practical example of this process; Figure 2 is a diagram illustrating the relative insulating values of padding formed according to the invention and two different prior art paddings of the same thickness; and Figure 3 is a graph illustrating the variations of the insulating value with thickness of the materials to which Figure 2 relates. With reference to the drawings, the process of the invention for the production of padding provides for the mixture of polyester or other fibres with silicone treated fibres of different nature and origin. This mixture of fibres is formed, by means of carding machines (not illustrated) into a layer 1, which is resin bonded with a mixture of bonding agents for the purpose of making it more compact and for fixing the nap. More specifically, two mixtures of bonding agents are used: the first is a sticky plastic bonding agent 2 which, when polymerised, creates a very soft and elastic film on one side of the wadding; on the other side, there is sprayed another type of bonding agent 3, of different nature, which is not sticky. The product which results from this is a soft and bulky layer; however, for the requirements of fashion or for other requirements, there exists the necessity of having the product in layers of high weight per square metre, and, therefore of high insulation value but with reduced thickness. The process of the present invention is continued by passing the layer of wadding 1', produced as described above, through a calender, generally indicated 4, composed of two or more cylinders 4', 4", heated to selected temperatures. In particular, and preferably, one of the cylinders 4' is completely smooth and metal, whilst the other 4" or the others (if there are more than two) is or are clad with a material of different nature, which is or are not smooth. By suitably adjusting the pressure and the temperature, and putting the layer with the plastic side towards the coated cylinder 4', it is possible to obtain the desired and adjustable reduction in thickness and, simultaneously, by the effect of the adhesion of the plastic side of the layer itself during separation of the layer from the cylinder 4, there occurs a slight reinflation which creates an "air chamber" or air pockets under the plastic surface of the layer. The said calender 4 could alternatively be constituted by entirely metal cylinders, or other non-clad materials to achieve the same adhesion effect upon separation of the layer from the cylinder in contact with the sticky plastic surface as it passes through the calender, since the presence of a layer, however thin, of sticky adhesive bonding agent, on one face of the layer, makes this latter adhere, at least over a certain section, to the corresponding cylinder 4'. In practice, the slight expansion of the compressed material, which is substantially controllable by varying the calendering parameters causes the formation of zones of discontinuities, in the material itself, which reduce the specific weight of the material and increase its thermal resistance. From this fact it will be appreciated that the product thus obtained is able to offer a high thermal insulation value without by this presenting excessive thicknesses. The table set out below by way of example illustrates a comparison of dimensional characteristics and weights of three products, produced, starting from layers of superimposed cohered fibres of polyester and using two prior art techniques and the process invention; From what has been explained above and from observation of the attached figures, the great functionality and practicality in use which characterises the padding of synthetic fibres obtained by means of the process constituting the subject of the present invention will be apparent.

Claims: A process for the production of padding in synthetic or other fibres, comprising the steps of: preparing a mixture of fibres of polyester or other, with silicone treated fibres of diverse nature and origin; forming a web (1) from such mixture by means of carding machines; characterized in that said process further comprises the steps of applying to one side of the web (1) a layer (2) comprising a mixture of adhesives of sticky plastic consistency which, when polymerised, create a very soft and elastic film; applying to the other side of the web (1) another type of adhesive of difference nature, which is not sticky; and passing the thus coated web through a calender (4) composed of two or more cylinders (4', 4"), heated to a selected temperature. A process for the production of padding, according to Claim 1, characterized by the fact that, one of the cylinders (4") of the said calender, is completely smooth and metallic, whilst the other (4') os clad with a material of different nature, which is not smooth. A process for the production of padding, according to Claim 1, characterized in that the cylinders (4', 4") of the calender (4) are both non-clad, entirely metal cylinders.

Inventors: SINISCALCHI, LUCIANO
Applicants: FISI FIBRE SINTETICHE S.P.A.
Application year: 1984
Main classification: D04H1
IPC codes: B32B38, D04H1, A41D31, B32B37