Patent Application
20240125580
The present invention concerns a stab proof material in roll form and a method and plant for the production thereof.
More specifically, the present invention refers to a material used as a base for the production of articles provided with ballistic protection, in particular for the production of bullet-proof vests also having a given level of stab proof protection (against stab or spike).
The field of personal protection, as meant in this document, is characterized by the use of a wide range of materials, with the aim of responding especially to specific requirements in terms of ballistic performance and resistance to stabbing, but also to requirements commonly known and considered important according to market surveys, such as flexibility, optimization of manufacturing waste, etc.
A ballistic solution for “soft armoring”, as the functional part of a bullet-proof vest is called, is composed of many layers of different types of materials, each of which contributes totally or partially to one or more functions.
The list of materials used to compose a ballistic solution is very long and the combination of said materials is optimized especially thanks to a trial-and-error approach where the first test is defined on the basis of a starting database.
The products used include: aramid fabrics, polyethylene fabrics, aramid unidirectionals, polyethylene unidirectionals, aramid felts, metallic mesh, metallic plates, barriers with metallic or ceramic flakes, laminates made of resins/films on aramid or polyethylene fabrics, Multi Threat Penetration (MTP) sheets, i.e. sheet products provided with both ballistic and stab proof properties.
Alongside purely ballistic materials are types of products that can add a given level of stab proof protection to the vest, called stab proof products.
The stab proof materials analogous to the one described here are in general produced by means of a four-stage process:
The resulting product is a finite number of semi-rigid flat sheets with ballistic and stab proof properties determined by various factors: choice of the fabric, matrix, percentage by weight of the latter with respect to the fabric, chemical composition and degree of interpenetration of the matrix with it.
Manufacture of the end product consists in cutting said sheets, and if necessary other materials to be used in combination, according to the shape of a bullet-proof vest, in accordance with the guidelines of the relevant reference standard, and making up the vest according to an arrangement of the layers designed to meet the relevant performance requirements.
The publication US 2016/0281272 A1 describes a composite material for ballistic applications, which comprises a bimodal binder.
The aim of the present invention is to provide a production system of a fiber-reinforced and pre-impregnated composite material, a so-called pre-preg, which is innovative and alternative with respect to the conventional coating/lamination systems.
Within this aim, an object of the invention is to provide a system that makes available a product in roll form which enables all manufacturers, not equipped with infrastructures for shaping a large number of flat sheets, to work with MTP materials in the same way as they work with fabrics, unidirectionals, etc.
Another object of the invention is to provide a system that allows waste optimization, using the same templates, by making available a continuous roll instead stead of single pieces.
A further object of the present invention is to provide a high versatility in defining the configuration of the end product and a consequent significant reduction in costs.
These and further objects, which will become clearer below, are achieved by a stab proof material in roll form and a method and plant for the production thereof, as claimed in the appended claims.
Further characteristics and advantages of the subject of the present invention will become clearer from an examination of the description of a preferred but non-exclusive embodiment of the invention, illustrated by way of non-limiting example in the attached drawings, in which:
The laminate 10 is composed of a base fabric 3, on the surface of which the matrix 12 is deposited, formed of the micrometric powder 2 in a dry state; the latter is melted, compacted over the same fabric 3 and not only adheres to it but also interpenetrates it. In this case the object illustrated in
In order to achieve this object, a further pressure melting stage is carried out also on the other face of the fabric, with analogous deposition of micrometric powder and pressure melting, to form an amorphous, i.e. non-crystalline, thermoplastic matrix, well interpenetrated inside the fabric.
With particular reference to the numerical symbols of the above-mentioned figures, the composite material production method, according to the invention, is carried out by means of a plant schematically illustrated in
According to the present invention, a starting amorphous thermoplastic matrix is obtained from the pressure melting treatment of a micrometric powder 2 which is distributed over the whole surface of both faces of a textile structure, in particular an aramid fabric 3 as it is unwound over a conveyor belt 4, by means of a powder scattering station 5.
This deposition is followed by entry of the material into the heart of the production line, formed of a system of double belts in contact, split into two sections, by means of which the material is conveyed along the line: a first hot section 6 and a second relatively cold section 7.
The first section 6 applies to the powder 2 a temperature ranging from 100 to 250° C. and a pressure from 0.1 N/cm2 to 200 N/cm2, preferably 160-250° C. and 10-200 N/cm2, according to the chemical-physical characteristics of the powder used, functional to the formation of said surface amorphous thermoplastic matrix 12, which is then incorporated in the thickness of the fabric 3, by pressure melting of the powder 2 over the latter. The film or the matrix 12 totally interpenetrates the fibers of said fabric 3, thus forming a flexible pre-preg 10 wound in the form of a roll 13 (
The second section 7 facilitates detachment of the material from the belts, by cooling to a temperature preferably below the melting or glass transition temperature of the film 12.
The double belt system comprises an upper belt 8 and a lower belt 9 and, according to the present invention, the thermoplastic matrix 12 is totally interpenetrated inside the fabric 3, with the desired basis weight obtained according to the speed of the line and the settings of the scattering head 5.
Inside the fabric 3 impregnated with thermoplastic resin, a phenomenon of fiber-interlocking occurs, which joins and compacts the weft and warp threads of the fabric 3, giving the composite improved resistance to cutting or stabbing.
According to the invention, the fabric 3 is a fabric for ballistic application made of para-aramid, glass, polyethylene (UHMWPE) or polypropylene fibers with denier from 220 to 3300 dtex.
The thermoplastic matrix 2 is obtained from a powder preferably based on polyesters, polyethers, polyolefins, polyvinyl butyral, polyurethanes, polyamides, polyimides and any derivatives or combinations thereof, having powder diameter distribution ranging from 0.1 to 750 μm.
The powder scattering system 5 associated with the double belt system, according to the invention, allows a choice totally free of constraints regarding the amount of powder 2 added to the support 3.
The present invention, in fact, allows the basis weight of the powder 2 to be adjusted from 20 to 250 g/m2, in one single step.
The laminate 10 deriving from the present invention provides a flexible product in roll form which enables all the end manufacturers, not equipped with infrastructures for shaping flat sheets, to work with MTP materials in the same way as they work with fabrics, unidirectionals, etc. In fact, according to the invention, the laminate 10 is collected at the end of the production line in the form of a roll 13.
The stab proof product in roll form, obtained according to the present invention, has performance analogous to the conventional sheets, made from similar components, but thanks to the special architecture and to its nature, the product made according to the present invention can be used with a much lower number of layers.
This gives it a further significant economic advantage compared to the conventional products.
The following Table 1 shows a comparative example, relative to aramid fabrics with different matrixes, matrix weight percentage, from standard technology and the technology according to the invention.
According to the present invention, stab proof products in roll form with analogous performances can be produced from the following components:
In practice it has been found that the invention achieves the intended aim and objects.
The laminate according to the present invention is obtained by means of a technology substantially different from a conventional coating/lamination and offers a number of substantial advantages.
The present invention provides a considerable versatility in definition of the product configuration. At least the following aspects should be considered.
The thermosetting resins used in ballistics, which are water- or solvent-based, are used in such a way as to determine a resin content to obtain optimized performances of the subsequently molded product.
The basis weight can be chosen on a continuous scale, however above given amounts (from 20 gsm to approximately 80 gsm) the control over the process in order to obtain uniform impregnation becomes very difficult in terms of controlling evaporation of the solvent or the water. Above the limit indicated, the formation of bubbles and the residual stickiness make the outgoing product unmanageable and unusable.
For this reason, whenever is possible, multiple impregnation steps are used, with consequent significant increase in costs.
On the other hand, the present invention allows adjustment of the basis weight from 20 up to 250 g/m2 in one single step, requiring at the most an optimization of the process parameters (usually a simple temperature increase of a few degrees centigrade), since the absence of solvents results in the absence of problems connected with the formation of bubbles and with a high level of stickiness.
In the same way, coupling on two sides by means of a conventional system can be a difficult and expensive operation, whereas with the present invention the coupling on two sides can be carried out easily and with a limited increase in costs since the use of appropriate thermoplastic powders allows a choice of temperatures and pressures in section 6 which, during coating on the second side, do not alter what has already been deposited on the opposite side.
The conventional thermoplastic-based systems are made from films with specific basis weight (most commonly 50-100 g/m2, sometimes 25-75-125 g/m2), a limiting factor with regard to the choice of the matrix content which often does not allow simultaneous adoption of the best fabric and choice of the optimal resin content to meet a required performance.
With the process of the present invention this limitation is overcome, since basis weights from 20 to 250 g/m2 can be chosen without gaps on a continuous basis.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021000005624 | Mar 2021 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2022/052040 | 3/8/2022 | WO |
