Method of manufacturing a stiffening fabric exhibiting adhesive properties when exposed to head and polymer fusible at elevated temperature

Description of the invention

The present invention relates to a method for the production of a heat-adhesive stiffening fabric whereby dots of heat-melting polymer are applied to the right side of a stiffening fabric substrate selected from textile and non-woven substrates, and the left side of the stiffening fabric substrate is bombarded. electrons.

The present invention relates to the field of heat-sticking stiffening fabrics, which are substrates, spun yarns or non-woven materials, on one side of which dots of heat-melting polymer are applied, which are then able to adhere to the piece of clothing to be reinforced by applying some pressure. on hot. More particularly, the invention relates to a method of producing such a stiffening fabric using electron bombardment to locally alter the melting point and / or the viscosity of a heat melting polymer; it also relates to a heat-melting polymer specially developed for carrying out the above-mentioned method.

Of all the problems encountered in the field of heat-sticking stiffening fabrics, one of the most difficult to solve is the risk of piercing the substrate of the heat-sticking stiffening fabric when applied by heat pressure to the piece of clothing to be reinforced. Indeed, the temperature selected to effect this hot deposition must allow the polymer point to be fused so that the polymer so melted can spread and adhere to the fibers or filaments on the surface of the piece of clothing. Often, however, this distribution of the polymer does not only take place at the surface, but rather that the polymer melt escapes through the fibers or filaments and appears on the other side of the backing of the stiffening fabric. This has no effect on aesthetics, except where the stiffening fabric is to be visible to form the back side of the garment. In any event, the effect of this perforation is to locally increase the stiffness of the stiffening fabric, and hence of the garment, which may be contrary to the intended effect. It can also cause sticking on the lining fabrics, such as the lining and some of the wool fabrics on the wrong side, resulting in a deterioration in the quality of the garment.

To overcome this difficulty, a certain embodiment of a heat-sticking stiffening fabric has already been presented, the points of heat-melting polymer of which comprise two superimposed layers, i.e. a first layer in contact with the right side of the stiffening fabric substrate and a second layer located precisely. over the first. Of course, the components of the two layers are determined such that, when the piece of clothing is applied by heat pressure, only the heat-melting polymer of the second layer reacts to the temperature. Diffusion of the heat-melting polymer in this case can only take place towards the piece of clothing, it is impossible to diffuse towards the base of the stiffening fabric as the first layer serves as a barrier in some way.

In practice, such a technique with two overlapping layers has certain drawbacks, in particular the difficulty in carrying out the superimposition of the two layers and the risk of delamination of the two layers.

To remedy these disadvantages, the Applicant has previously proposed in French Patent FR 2 606 603 the use of chemical agents acting on a heat melting polymer to alter the chemical structure, at least partially or at least at the interface with the stiffening fabric substrate, such way, to prevent the heat-melting polymer from sticking to the backing of the heat and / or pressure and / or steam stiffening fabric. Chemical agents capable of altering the chemical structure of the heat melting polymer include at least a reactive substance and at least a reactive agent capable of initiating, providing, promoting the reaction between the reactive substance and the heat melting polymer.

The contact between the reactive substance and the heat-melting polymer is brought into contact either by mixing the two elements, which are then applied as dots as a homogeneous mixture, to the backing of the stiffening fabric, or by applying the reactive substance to the backing of the stiffening fabric before applying the stiffening fabric. polymer points (then devoid of reactive substance). Heat supply, ultraviolet radiation and electron bombardment are mentioned among the reactive agents.

PL 212 674 B1

The Applicant has also proposed in EP 0 855 146 A1 a method in which dots made of heat-melting polymers of average thickness E, containing a radical activator, are applied to the right side of a stiffening fabric substrate, and one of the sides of the substrate is bombarded. electrons, regulating the depth of electron penetration at points made of a polymer melting under the influence of heat, yes, to change the physicochemical properties of the heat-melting polymer, selected from the melting point and viscosity, in the thickness "e" with respect to the average thickness "E".

The purpose of the radical activator is to generate free radicals that enable the initiation of the polymerization reaction on the activator of the polymer melting under the influence of heat. It is therefore not, in the strict sense, a reactive substance in the sense referred to in French Patent Specification No. FR 2 606 603.

The techniques presented in the two documents cited above have various drawbacks. According to French Patent No. FR 2 606 603, when the reactive substance is applied to the backing of the stiffening fabric prior to the application of the polymer dots, the reaction that takes place after the application of heat, ultraviolet radiation or electron bombardment takes place at the interface between the reactive substance and the polymer. melting under the influence of heat. This reaction therefore only takes place at a reduced thickness. In all other cases, the reactive substance of French Patent No. FR 2 606 603 or the radical agent of European Patent No. EP 0 855 146 A1 is mixed with the heat-melting polymer before the dots are applied to the backing of the stiffening fabric. This mixture is usually made by dispersing the polymer in the form of a pasty mass, the reactive substance or radical agent being then incorporated like any other formulation product. In order to obtain an even more homogeneous mixture, according to European Patent No. EP 0 855 146 A1, a mixture of a heat-melting polymer and a radical activator is first prepared, the mixture is subjected to successive melting, extrusion and grinding operations to obtain a powder that is used it is as it is to be coated or it is diluted, to then prepare an aqueous dispersion in the form of a pasty mass for applying the polymer dots to the backing of the stiffening fabric. However, whatever the homogeneity of the mixture, at each point applied to the aforementioned backing of the stiffening fabric there is always a heat melting polymer on the one hand which provides the adhesive function which is necessary for the support of the stiffening fabric substrate on the piece of clothing to be reinforced, and on the other hand reactive substance or radical agent that provides a reactive function under the influence of reactive agents, such as heat supply, ultraviolet radiation and electron bombardment, especially the latter as it relates to a radical agent.

In the particular case of a method for producing a heat-stick fabric that uses electron bombardment to alter the chemical structure of a heat-melting polymer, the presence of a radical agent presents some difficulties. When an aqueous dispersion in the form of a pasty mass is used in the technique of applying polymer dots, it is important that the ingredients making up the pasty formulation are water-soluble in order to obtain a good stability of the pasty mass over time. The products useful as free radicals are largely water-insoluble, at least in the proportions in which they are used in preparing an aqueous dispersion, which may cause the pasty mass to be relatively unstable over time. Moreover, the products useful as radical agents are generally in the form of liquids with boiling points, which may optionally be compatible with the temperatures used under the operating conditions used when the dots are applied to the stiffening fabric substrate. Thus, in this case, partial evaporation of the radical agent may take place, resulting in loss or even loss of reactivity to electron bombardment. Finally, it is also noted that since the products useful as free radicals are mostly low molecular weight monomers, their behavior in admixture with a heat melting polymer is comparable to that of a plasticizer. This behavior can change the melt viscosity of the heat-melting polymer, it can create quality problems, coating problems, and it can also change the mechanical strength properties relevant to the polymer and thus affect the adhesive parameters.

The aim of the applicant was to present a method of producing a heat-sticking stiffening fabric in which electro-bombardment is used.

In order to change the chemical structure of the heat-melting polymer, which reduces the aforementioned drawbacks.

This object is fully achieved by the method according to the invention.

The present invention relates to a method for the production of a heat-adhesive stiffening fabric whereby dots of heat-melting polymer are applied to the right side of a stiffening fabric substrate selected from textile and non-woven substrates, and the left side of the stiffening fabric substrate is bombarded. electrons, characterized by the fact that points made of a polymer that melts under the influence of heat, are based on at least one functional polymer containing functional groups that can react with free radicals resulting from electron bombardment and / or are themselves free radical generators under the influence of electron bombardment, moreover, the depth of electron penetration at polymer points is controlled to obtain self-crosslinking higher of said functional polymer at a thickness constrained "e" relative to the average thickness "E" of the polymer dots.

Preferably, the heat melting polymer dots are based on at least one functional polymer whose functional groups include ethylenically unsaturated functional groups, for example of the acrylate, methacrylate, allyl, acrylate, vinyl ether, styrene, maleic or fumaric types.

Preferably the heat melting polymer dots are based on at least one functional polymer whose functional groups contain unstable units which have lower bond energies than conventional carbon-carbon or carbon-hydrogen bonds.

More preferably, the labile unit is a carbon-chlorine, C-Cl, or SH thiol bond.

Yes, the above-mentioned disadvantages of a mixture of a heat melting polymer and a radical agent are eliminated, since it is the heat melting polymer itself that performs both the adhesion function and the electron bombardment function.

The heat-melting polymer for the heat-adhering stiffener fabric is specially developed for use in the process of the invention. This heat melting polymer is characterized by containing functional groups which can react with free radicals upon electron bombardment and / or to be free radical generators themselves upon electron bombardment.

According to a first embodiment of the invention, these functional groups of the polymer include ethylenically unsaturated functional groups, for example of the acrylate, methacrylate, allyl, acrylamide, vinyl ether, styrene, maleic or fumaric type.

According to a second embodiment of the invention, the aforementioned functional groups of the polymer contain unstable units, i.e. units which have lower binding energies than conventional carbon-carbon or carbon-hydrogen bonds. As an example of a labile unit, a carbon-chlorine C-Cl bond or a SH thiol bond can be mentioned.

The heat-melting functional polymers according to the invention are prepared according to two possible methods. According to the first method, monomers containing a functional group or functional groups which can react with free radicals under electron bombardment and / or are themselves free radical generators under electron bombardment are added directly to the reaction medium of the polymer synthesis. According to a second method, the already formed heat-melting polymer is started and then converted by grafting the desired functional groups onto its polymer structure by known grafting techniques.

The location of the functional group along the polymer chain significantly influences the reactivity of the functional polymer under the influence of electron bombardment as well as the structure of the obtained mesh network. The functional group may be located at the end of the chain, it may be incorporated along the chain, or it may furthermore be located on branches or strains along the main polymer chain.

The heat-melting functional polymer of the present invention must necessarily have the adhesive or adhesive properties necessary for its intended use on a heat-adhering stiffening fabric. Moreover, it should be able to functionalize either during its synthesis or by subsequent transformation as stated previously. It is therefore especially of the type of polyethylene (PE), copolyamide (coPA), polyester (Pes), polyurethane (PU), copolyamide

Block ether block (PBAX). By way of non-limiting examples, with regard to the polyamide-type backbone, the functional groups are placed at the end of the chain; as for the backbone of the polyethylene type, the functional groups are located on the branches along the main chain; with the backbone of the polyester type, the functional groups are included along the main chain; As for the polyurethane type backbone, the functional groups are grafted along the main chain.

Of course, the heat-melting functional polymer of the invention is selected to accommodate the use limitations of the heat-sticking stiffener fabric, limitations that vary depending on the techniques used.

Particularly with regard to its presentation, it should be possible to provide the polymer in the form of a powder resistant to disintegration with a grain size of 10 to 200 µm, or it should also be possible to supply the polymer as granules if the technique used is of the hot melt type.

When the application of the polymer dots is carried out on the basis of an aqueous dispersion in the form of a pasty mass, the polymer must of course be suitable for such aqueous dispersion.

When application is carried out in the form of a coating, the functional groups which the heat-melting polymer contains must be stable at the coating temperature, given that, according to the technique used, this temperature may be up to 150 to 225 ° C. This thermal stability is necessary to prevent the functional groups from causing uncontrolled self-crosslinking to start. This thermal stability can be improved by incorporating an antioxidant into a heat melting functional polymer.

The melting point of the non-electron bombarded functional polymer should typically be between 70 and 150 ° C, given that the same self-crosslinked polymer has a higher melting point due to electron bombardment.

The heat-melting functional polymer is, depending on the application, machine-washable, resistant to dry cleaning with a chlorine-containing solvent and resistant to steam.

According to one embodiment, the functional polymer has a polyethylene-type skeleton and contains methacrylate-type functional groups. To obtain this functional polymer, the starting material is made from a low percentage ethylene monomer, on the order of 3% by weight, of acrylic acid. This initial polyethylene type polymer contains acid functional groups (- C - OH)

II

O related to the carbon chain. This is in particular the EAA polymer represented by Dow Chemical under the name Primacor 3150. This starting polymer is esterified with an epoxy-type compound of the formula:

H \

C = /

H presented by Aldrich under the name GMA in stoichiometric proportion. A functional polymer is obtained with the formula:

,., [CH₂ - CH₂ - CH₂ - CH - CH₂ - CH₂

C = 0

AND

OH

<img file="PL212674B1_D0001.tif" />

<img file="PL212674B1_D0002.tif" />

whose methacrylate functional groups contain ethylenic unsaturation, which can cause self-crosslinking of the polymer on itself, thanks to free radicals formed by the influence of electrons during electron bombardment. It is especially about electron bombardment carried out at a power of at least 70 kV with a dose of 10 to 100 kGray on the left side

The backing of a stiffening fabric the right side of which comprises dots formed with the functional polymer. The power and the retained dose make it possible to limit the action of electrons on the thickness e of the limited thickness of the average of the superimposed points. Thus, self-crosslinking of the functional polymer takes place only at that point thickness e, at the base of the above-mentioned point, i.e. the thickness which is in contact with the substrate of the stiffening fabric. The self-cross-linked polymer has a melting point higher than that of the non-cross-linked functional polymer so that when the stiffening fabric is applied to the product to be reinforced, the self-cross-linked base of the polymer point will leak less than the rest of the point, thus avoiding perforation.

There may be second and third examples of functional polymers with a skeleton of the polyethylene type. In a second embodiment of the invention, the functional groups are of the styrene type. The starting polymer is obtained from ethylene monomer and in the order of 10% by weight of hydroxyethyl methacrylate. It may be the EHEMA polymer presented by Neste Chemical under the number NRT 354. It reacts with an isopropenyl compound having the formula:

<img file="PL212674B1_D0003.tif" />

presented by the American Cyanamid company with the general formula:

under the name TMI to give a functional polymer

<img file="PL212674B1_D0004.tif" />

In a third embodiment of the invention, the functional groups are of the acrylate type. The starting polymer is obtained from ethylene monomer and in the order of 16% by weight of vinyl alcohol. It may be the EVOH polymer presented by Bayer under the number Levasint S-31. It reacts with the compound with acrylic acid to give a functional polymer of the general formula:

<img file="PL212674B1_D0005.tif" />

In all cases, the operational conditions of the various reactions used are determined so as to obtain a functional polymer that has the appropriate proportion of functional groups to obtain the desired result, namely to bring, under the influence of electrons, to a localized

The rise in melting point is caused by self-crosslinking of the above-mentioned functional polymer and which moreover corresponds to the conditions required for the application to a stiffening fabric of the heat-sticking substrate onto which the functional polymer dots are applied.