RU2802416C2 - Bulletproof product based on films supplied with a matrix - Google Patents

Abstract

FIELD: military.

SUBSTANCE: invention relates to a method for manufacturing a bulletproof product, which includes the steps: a) stacking a stretchable plate of ultra-high molecular weight polyethylene (UHMWPE) and a stretchable continuous film of polymer as an organic matrix material with the formation of a plate-film stack, where a continuous polymer film is used as an organic matrix material and is not a UHMWPE film, b) stretching the plate-film stack obtained in step a) at a temperature below the melting point of the UHMWPE stretch plate to a draw ratio of at least 2, whereby a UHMWPE film with an organic matrix material is provided, wherein a UHMWPE film is co-stretched with a polymer film as an organic matrix material, c) superposing a plurality of films provided according to step b) to form a layer of films, d) stacking at least two layers of films obtained according to step c) and forming a sheet, e) stacking a plurality of sheets obtained according to step d), forming a stack of sheets, and f) consolidating the sheets before and/or after stacking according to step e) by applying pressure and optional heating. The invention also relates to a bulletproof product that can be obtained by using the claimed method.

EFFECT: invention provides ballistic resistant articles containing films with low amounts of matrix with good adhesion and wear resistance properties, and which combine high ballistic performance with low surface weight and good stability.

15 cl, 7 ex, 2 tbl

Description

The present invention relates to a bulletproof product comprising films provided with an organic matrix material and methods for its manufacture.

Bulletproof articles containing films are known in the art.

EP 1627719 describes a bulletproof article primarily composed of ultra-high molecular weight polyethylene, which includes a plurality of unidirectionally oriented polyethylene sheets arranged crosswise at an angle with respect to each other and attached to each other in the absence of any resin, adhesive matrix, or the like.

WO 2009/109632 describes a bulletproof molded article comprising a compressed stack of sheets containing tapes and an organic matrix material, where the direction of the tapes within the compressed stack is not unidirectional, where the stack contains 0.2-8 wt.%. organic matrix material. The matrix material may be provided in liquid form or as a film. However, the small amount of matrix material used makes the use of film less preferable.

Although the reference material mentioned above describes bulletproof products with adequate properties, there is still room for improvement.

In particular, when using UHMWPE films, the presence of the matrix plays a critical role in ensuring that the films adhere to each other during processing and application. However, too much matrix can negatively impact the ballistic performance of the bulletproof product. Therefore, it is important to minimize the amount of matrix. One way to minimize the matrix material, as described, is to apply the matrix material intermittently, only to discrete points on the surface of the films. For example, WO 2009/109632 describes the application of a matrix material in the form of a mesh, where the mesh is a non-continuous polymer film, that is, a polymer film with holes, since this makes it possible to provide small masses of matrix material.

However, intermittent application of the matrix material results in zones of film with different adhesive properties. In addition, the presence of uneven matrix distribution over the surface of the films can result in poor wear resistance, since UHMWPE films tend to form fibrils during processing and during application in areas free of matrix material, which is undesirable from an aesthetic and performance point of view.

Thus, there is a need for bulletproof products containing films with low amounts of matrix with good adhesive and wear-resistant properties, and that combine high ballistic performance with low surface weight and good stability. The present invention provides such an article.

In one embodiment, the present invention relates to a bulletproof product comprising a stack of sheets, where the sheets include at least two layers of ultra-high molecular weight polyethylene (UHMWPE) films provided with an organic matrix material, wherein the continuous film of polymer as the organic matrix material is not a UHMWPE film, wherein the UHMWPE films are provided on at least 95% of at least one of their surfaces with a continuous film of polymer as the organic matrix material, wherein the UHMWPE films have a thickness of 10-100 microns, and the organic matrix polymer film has a thickness of 0.1-3 microns wherein the weight percentage of the organic matrix polymer relative to the total weight of the organic matrix polymer and the ultra-high molecular weight polyethylene is from 0.1 to 3 wt%, and where the sheets in the stack are subject to consolidation, where the orientation of the polymer molecules in a continuous film of the polymer as the organic matrix material in the first film direction is different from the orientation of the polymer molecules in a continuous film of polymer in the second film direction, where the first film direction and the second film direction are at an angle of 90°.

The present invention therefore relates to a bulletproof article, such as a hard bulletproof article or a soft bulletproof article, comprising a stack of sheets, wherein the sheets include at least two layers of ultra-high molecular weight polyethylene (UHMWPE) films provided with an organic matrix material, and wherein the sheets in the stack are subjected to consolidation.

UHMWPE films provide at least 95% of at least one of their surfaces with a continuous film of polymer as an organic matrix material. The matrix polymer is not UHMWPE.

In addition, UHMWPE films have a thickness of 10-100 microns, and organic matrix polymer film has a thickness of 0.1-3 microns. In addition, the weight percentage of the organic matrix polymer relative to the total weight of the organic matrix polymer and ultra-high molecular weight polyethylene is from 0.1 to 3% by weight.

In the bulletproof article of the present invention, a large area of at least one of the surfaces of the UHMWPE films is coated with a continuous thin layer of organic matrix material. This allows the use of very small amounts of organic matrix material while providing good adhesion to the UHMWPE films and protecting the UHMWPE films from fibril formation, which improves the wear resistance of the bulletproof article, for example, during production, processing or use.

The orientation of polymer molecules in a continuous film of polymer as an organic matrix material in a first film direction is different from the orientation of polymer molecules in a continuous film of polymer in a second film direction, where the first film direction and the second film direction are at an angle of 90°. The orientation of the polymer in the organic matrix material can be determined, for example, by polarized Fourier transform infrared (FT-IR) spectroscopy using the dichroism coefficient. The dichroism coefficient is the ratio between the absorptions measured with radiation polarized in a first direction (eg, the film drawing direction) and with radiation polarized in a second direction perpendicular to the first direction. The wavelength at which this coefficient is determined differs for different polymers. For polyethylene matrix material, for example, wavelengths of 720 and 730 nm can be used. If a polyethylene matrix is used, the measurement should be designed so that only the polyethylene matrix is measured and not the UHMWPE film. This can be achieved using methods known to one skilled in the art, for example, by attenuated total reflection (ATR) measurements using a Ge crystal. The difference in the orientation of the polymer molecules is generally due to the method of making the film, where the first direction corresponds to the direction of drawing of the film, and the second direction corresponds to a direction perpendicular to the direction of drawing. The effect is especially pronounced when the bulletproof product is manufactured by the method according to the invention, where the matrix film is produced by a technology in which it is co-stretched with a UHMWPE film.

In addition, the bulletproof products described in this document have good ballistic characteristics. Their ballistic performance can even be improved relative to similar bulletproof products based on UHMWPE films with higher amounts of matrix. Moreover, to achieve similar ballistic characteristics, the product according to the invention requires less weight than a product with higher amounts of matrix, which advantageously allows for lighter bulletproof products.

The present invention also relates to a method for making a bulletproof article. In particular, a method for manufacturing a bulletproof product includes the steps of:

a) stacking a stretchable plate of ultra-high molecular weight polyethylene (UHMWPE) and a stretchable continuous film of polymer as an organic matrix material to form a plate-film stack, wherein the continuous film of polymer as an organic matrix material is not a UHMWPE film,

b) stretching the plate-film stack obtained in step a) at a temperature below the melting point of the UHMWPE stretch plate to a draw ratio of at least 2, whereby providing a UHMWPE film with an organic matrix material, while having the UHMWPE film subjected to joint stretching with a polymer film as an organic matrix material,

c) combining the plurality of films provided according to step b) to obtain a layer of films,

d) stacking at least two layers of films obtained according to step c) to obtain a sheet,

e) stacking a plurality of sheets obtained according to step d) to obtain a stack of sheets, and

f) consolidating the sheets before and/or after stacking according to step e) by applying pressure and optionally heating.

In accordance with the above, in the bulletproof product and method described herein, a UHMWPE film is co-stretched with a polymer film as an organic matrix material.

The process step of drawing the plate-film stack to provide the UHMWPE film co-stretched with the organic matrix polymer film allows for the production of a low amount and low thickness of the organic matrix material in combination with a large and continuous coverage of the UHMWPE films with the organic matrix material.

EP 0721021 describes a method for introducing functional groups into polyethylene material. In particular, this document describes a method for continuously producing a polyethylene material by rolling a film of ultra-high molecular weight polyethylene or a film-like material and then drawing the rolled material, wherein the film is a thermoplastic resin including at least one additive selected from a coloring agent, an impact stabilizing agent atmospheric conditions, an antistatic agent, a hydrophilicity agent, an adhesion promoter and a dyeability agent are laminated to the film material in a rolling step. This method makes it easy to dye a polyethylene material having high strength and high modulus of elasticity and give it weather resistance and other desirable properties. However, this document does not describe or suggest such materials for use in bulletproof products. Also, this document does not describe products that have a low organic matrix content along with good adhesive and wear-resistant properties.

Detailed Description of the Invention

The bulletproof product described herein comprises a stack of sheets, wherein the sheets comprise at least two layers of UHMWPE films provided with an organic matrix material.

In the context of the description of the present invention, the term film means an object whose length, that is, the largest dimension of the object, is greater than the width, that is, the second smallest dimension of the object, and the thickness, that is, the smallest dimension of the object, the width being the queue is greater than the thickness. For purposes of describing the present invention, UHMWPE film is considered to have two film surfaces, that is, an upper and lower plane, defined by the film's length and width dimensions.

The ratio between the length and width of the film is typically at least 10:1. Depending on the width of the film, this ratio may be greater, for example at least 100:1 or at least 1000:1. The maximum ratio is not critical to the present invention. As a common value, a maximum length to width ratio of 1,000,000:1 may be mentioned.

The ratio between width and thickness is generally more than 10:1, in particular more than 50:1, and even more so more than 100:1. The maximum ratio between width and thickness is not critical for the present invention. It is usually no more than 10,000:1.

The ultra-high molecular weight polyethylene (UHMWPE) for the film described herein has a mass average molecular weight (Mw) of at least 300,000 grams/mol, more of at least 500,000 grams/mol, more of 1×10 ⁶ gram/mol to 1×10 ⁸ gram/mol.

The weight average molecular weight (Mw) can be determined according to ASTM B 6474-99 at 160°C using 1,2,4-trichlorobenzene (TCB) as a solvent. Appropriate chromatography equipment (eg, PL-GPC220 from Polymer Laboratories) including a high temperature sample acquisition device (eg, PL-SP260) can be used. This system is calibrated using sixteen polystyrene standards (Mw/Mn <1.1) in the molecular weight range 5×10 ³ -8×10 ⁶ g/mol.

Molecular weight distribution can also be determined using melt viscometry. Before measurement, a polyethylene sample to which 0.5 wt.% was added. antioxidant, such as IRGANOX 1010, to prevent degradation by thermal oxidation, is first sintered at 50°C and 20 bar. Disks of 8 mm diameter and 1 mm thickness made from sintered polyethylenes are rapidly heated (at a rate of approximately 30°C/min) to a value well above the equilibrium melting point in a rheometer under a nitrogen atmosphere. The disk, for example, can be kept at 180°C for two hours or more. Slippage between the sample and the rheometer disks can be detected using an oscilloscope. During dynamic experiments, two output signals coming from the rheometer, i.e., one signal corresponding to the sinusoidal strain and the other signal corresponding to the response voltage, are continuously monitored using an oscilloscope. The response voltage of a precisely sinusoidal shape, which can be achieved at low values of deformation force, is an indicator of the absence of slippage between the sample and the disks.

Rheometric measurements can be made using a parallel plate rheometer such as the Rheometrics RMS 800 from TA Instruments. TA Intruments' Orchestrator Software, which uses the Mead algorithm, can be used to determine the molar mass and molar mass distribution based on modulus versus frequency data obtained from the polymer melt. These data are recorded under isothermal conditions at temperatures between 160 and 220°C. To achieve a good fit to the data, a range of angular frequencies from 0.001 to 100 rad/s and a constant strain in the linear viscoelastic region from 0.5 to 2% should be selected. Temperature-time superposition is used at a standard temperature of 190°C. Stress relaxation experiments can be performed to measure the elastic modulus at frequencies below 0.001 (rad/s). In these stress relaxation experiments, a single temporary strain (step strain) is applied to a polymer melt and maintained on the sample at a fixed temperature, and the time-dependent stress decay is recorded.

The UHMWPE film described herein typically may be free of polymer solvent due to its manufacturing process, which will be described in more detail below. To a greater extent, UHMWPE films may typically have a polymer solvent content of less than 0.05 wt%, especially less than 0.025 wt%, more generally less than 0.01 wt%.

UHMWPE films are supplied with a continuous polymer film.

The general purpose of the polymer film is to act as an organic matrix material providing UHMWPE films with at least one adhesion surface. For example, in the bulletproof product described herein, UHMWPE films are bonded together by at least an organic matrix polymer film. In addition, the polymer film reliably ensures that the UHMWPE film does not undergo fibril formation during processing and use, which improves the wear resistance of the UHMWPE film and bulletproof products containing it. The polymer (film) is also referred to herein as an organic matrix polymer (film).

The continuous polymer film reliably ensures that there is a uniform distribution of the organic matrix material over the surface of the UHMWPE films, in other words, the UHMWPE film does not have gaps in the coating made of the organic matrix material. Due to this, the adhesive and wear-resistant properties of the UHMWPE film are uniform over its entire surface.

The organic matrix polymer film preferably has a melting point lower than the melting temperature of the UHMWPE film.

Organic matrix polymer film can have the same chemical composition as UHMWPE film. Alternatively, a polymer with a different chemical composition can be used as the organic matrix material.

Examples of suitable organic matrix materials include polymers such as thermoplastic elastomers. Suitable thermoplastic elastomers include polyurethanes, polyvinyls, polyacrylates, block copolymers, and mixtures thereof. In one embodiment, the thermoplastic elastomer is a block copolymer of styrene and an alpha-olefin comonomer. Suitable comonomers include C4-C12 alpha-olefins such as ethylene, propylene and butadiene. Specific examples include polystyrene-polybutadiene-polystyrene (SBS) or polystyrene-polyisoprene-polystyrene (SIS). Such polymers are commercially available, for example, under the trade name Kraton or Styroflex.

Polyolefin-based films may be preferred as the organic matrix material. These polyolefins include polypropylene; polyethylene such as high density polyethylene (HDPE), low density polyethylene (LDPE), median density polyethylene (MDPE), linear low density polyethylene (LLDPE); ethylene-α-olefin copolymers such as ethylene-propylene copolymers and ethylene-vinyl acetate copolymers; or combinations thereof.

Preferably, the organic matrix polymer film is a polyethylene film, preferably an LDPE film or an HDPE film. Such films have the same chemical composition as UHMWPE film, and this advantageously allows for easier recycling of organic matrix material-equipped UHMWPE films and bulletproof products made from them. In addition, polyethylene has good adhesive properties and is perfectly compatible with UHMWPE.

An organic matrix polymer film (also referred to herein as a matrix film) is provided on at least 95% of at least one of the surfaces of the UHMWPE film. In particular, the matrix film may cover at least 97% of at least one of the surfaces of the UHMWPE film, a greater extent of at least 99%, and an even greater extent of at least 99.5%. In one embodiment, 100% of at least one of the surfaces of the UHMWPE film may be covered with a matrix film.

As mentioned above, the organic matrix polymer film is continuous. Accordingly, in the case where the organic matrix polymer film does not cover the entire surface of the UHMWPE film, that is, the coverage is less than 100%, the surface area of the UHMWPE film that is not covered by the organic matrix film will generally be found at the edges along the length of the UHMWPE film.

Generally, the coating of a UHMWPE film with a continuous organic matrix polymer film is determined by the width of the UHMWPE stretch plate and the organic matrix polymer stretch film used in preparing the organic matrix material-equipped UHMWPE film, which is described in more detail below. Thus, coating the surface of a UHMWPE film with an organic matrix polymer film can be determined simply. Additionally, if this is the case, the areas of the UHMWPE film that are not coated with the organic matrix polymer film can be recognized by a clear difference in appearance when compared with the coated areas and identifying a demarcation line. Thus, the proportion of total coverage can be easily determined, for example, as the ratio of the covered width to the total width.

Provided that at least one of the surfaces of the UHMWPE film is coated with an organic matrix polymer film, the second surface of the UHMWPE film may be free of organic matrix material, or it may also be coated with an organic matrix polymer film. If its UHMWPE is coated with an organic matrix polymer film, the organic matrix polymer film is preferably provided on at least 95% or at least 97%, 99%, 99.5% or even 100% of the second surface of the UHMWPE film. However, it may be preferable that the second surface of the UHMWPE film be free of organic matrix material. Such films will make it possible to provide bulletproof articles with a lower amount of organic matrix material than, for example, films coated on both sides with an organic matrix material.

In the bulletproof product described herein, the UHMWPE films have a thickness of 10-100 microns, especially 20-80 microns, more commonly 30-70 microns, and even more 40-65 microns. The organic matrix polymer film has a thickness of 0.1-3 microns, in particular 0.15-2.5 microns, more generally 0.2-2 microns, even more 0.4-1.5 microns.

As a result of the presence of such a thin layer of organic matrix material, the performance degradation of the UHMWPE film is minimal. In particular, bulletproof products containing films described herein have excellent ballistic properties despite having an organic matrix polymer film (which is typically a low ballistic material) covering a large surface area of the UHMWPE film (which is is a material with high ballistic characteristics).

In the bulletproof article described herein, the weight percentage of the organic matrix polymer relative to the total weight of the organic matrix polymer and ultra-high molecular weight polyethylene is from 0.1 to 3% by weight, especially from 0.15 to 2.5% by weight, and may preferably be from 0.2 to 2% by weight, or even from 0.5 to 1.5% by weight. The inventors have unexpectedly discovered that small amounts of organic matrix material can be advantageously used in bulletproof articles provided that the UHMWPE films have a high coverage of the organic matrix material. Also surprisingly, such small amounts of organic matrix materials can be obtained using the method described herein, in which a UHMWPE film is co-stretched with a polymer film as the organic matrix material.

Advantageously, due to the low amount of organic matrix polymer, bulletproof articles containing films disclosed herein have a reduced amount of low performance materials, which, combined with a fine and uniform distribution of the organic matrix polymer, contributes to the performance characteristics of the bulletproof articles.

The UHMWPE films provided with an organic matrix material described herein may have a width of at least 2 mm, in particular at least 10 mm, more particularly at least 20 mm. The width of the film is not critical and can, as a rule, be no more than 500 mm.

The physical properties of UHMWPE films provided with an organic matrix material described herein are very similar or even the same as the physical properties of UHMWPE films that are not provided with an organic matrix polymer film. In particular, such UHMWPE films typically have high tensile strength, high tensile modulus and high energy consumption, reflected in the high energy required for tensile elongation.

In one embodiment, the tensile strength of UHMWPE films provided with an organic matrix material is at least 1.2 GPa, more at least 1.5 GPa, more at least 1.8 GPa, even to an even greater extent, at least 2.0 GPa. In one embodiment, the tensile strength of these films is at least 2.0 GPa, in particular at least 2.5 GPa, more at least 3.0 GPa, even more at least 4 GPa. Tensile strength can be determined according to ATM D7744-11.

In one embodiment, UHMWPE films provided with an organic matrix material have a tensile modulus of at least 50 GPa. More specifically, the films may have a tensile modulus of at least 80 GPa, more of at least 100 GPa, more of at least 120 GPa, even more of at least 140 GPa, or at least 150 GPa. This elastic modulus can be determined according to ASTM D7744-11.

In one embodiment, UHMWPE films provided with an organic matrix material have a tensile energy at break of at least 20 J/g, in particular at least 25 J/g. In yet another embodiment, the tapes have a tensile energy at break of at least 30 J/g, in particular at least 35 J/g, more of at least 40 J/g, more of at least 50 J/g. Tensile energy at break can be determined according to ASTM D7744-11 (calculated by integrating the energy per unit mass under the stress-strain curve).

UHMWPE films provided with an organic matrix material used in the present invention can have high strength combined with high linear density. In this application, linear density is expressed in dtex. This means the mass in grams for 10,000 meters of film. In one embodiment, the film according to the invention has a denier of at least 3000 dtex, in particular at least 5000 dtex, more of at least 10,000 dtex, even more of at least 15,000 dtex, or even less at least 20,000 dtex, in combination with the above-specified strengths of at least 2.0 GPa, in particular at least 2.5 GPa, more, at least 3.0 GPa, even more, at least at least 3.5 GPa, and even more so, at least 4 GPa.

In the bulletproof product described herein, the sheets comprise at least two layers of ultra-high molecular weight polyethylene (UHMWPE) films provided with an organic matrix material. In particular, the sheets may contain at least 3, at least 4 or at least 6 film layers, and at most 20, at most 15 or at most 10 film layers. Sheets containing two layers of films may be preferred.

The orientation of UHMWPE films provided with an organic matrix material within a layer of films can preferably be unidirectional. For example, the films can be arranged in parallel to form a layer.

UHMWPE films provided with an organic matrix material may be partially overlapped within a layer or may be aligned without an overlap region between adjacent films, for example, the films may be in butting contact or there may be small gaps between adjacent films. By small gaps we mean that less than 5% of the surface area of the layer corresponds to gaps. It may be preferable that the films are arranged in abutting contact without significant gaps between adjacent films, for example, less than 0.5% of the surface area of the layer corresponds to gaps.

Optionally, the orientation of the films in one layer may be at an angle to the orientation of the films in the adjacent layer. The angle between the orientation of films in one layer and the orientation of films in an adjacent layer may be from 45 to 135 degrees, or from 60 to 120 degrees, or from 85 to 95 degrees, or about 90 degrees. In a particular embodiment, the orientation of the films in one layer may be parallel to the orientation of the films in alternating layers. In yet another embodiment, the orientation of the films in one layer may be at an angle relative to the orientation of the films in alternating layers. What is said above regarding the angle between adjacent layers also applies to the angle between alternating layers.

Layers of unidirectionally oriented films that are angled relative to each other may be within the same sheet or in adjacent sheets. For example, the sheet may contain at least two layers of unidirectionally oriented films that are angled to each other (eg, have a 0-90 structure). The sheet may also contain at least two layers of unidirectionally oriented films that are parallel to each other (having a 0-0 structure). Such sheets may have, in particular, a briquette structure, where the films of one layer are parallel to the films of another layer, but are located offset within it. A sheet with a 0-0 structure may be at an angle with respect to an adjacent sheet that also has a 0-0 structure. The sheet may also contain at least four layers of unidirectionally oriented films. These layers may be parallel to each other in groups of two, and said groups of two may be at an angle with respect to each other (for example, forming a 0-0-90-90 structure), or the layers may be at an angle with respect to adjacent layers (for example, form a 0-90-0-90 structure). Sheets containing two layers of 0-90 structure or four layers of 0-90-0-90 structure may be preferred.

A stack of sheets of a bulletproof product described herein may contain at least 2 sheets, in particular at least 4, at least 10 or at least 20 sheets, and not more than 1000 sheets, and preferably not more than 500 sheets or no more than 250 sheets. The number of sheets depends on the number of film layers within one sheet and the required level (class) of protection, characterized by ballistic resistance. The appropriate number of layers and sheets can be determined by one skilled in the art.

The bulletproof products described in this document have sheets in a stack that are consolidated.

The sheets as such can be consolidated (individually, for example, before stacking, which is described in detail below), or the entire stack of sheets can be consolidated (sheets taken together, that is, after stacking, which is also described in detail below) . If you are consolidating sheets as such, you do not need to consolidate the entire stack, but you can consolidate the entire stack. In this way, the sheets can be consolidated before and after stacking, that is, individually and stacked as a unit.

The term consolidated as used herein means that the UHMWPE films in layers of sheets or stacks of sheets are firmly and tightly attached to each other by an organic matrix material. Accordingly, in one embodiment, the bulletproof product comprises sheets that are individually consolidated, that is, at least two layers of UHMWPE films provided with an organic matrix material present in the sheet are firmly and tightly attached to each other. In another embodiment, a stack of sheets for a bulletproof article is consolidated as a single unit, that is, layers of UHMWPE films provided with an organic matrix material within the sheet and adjacent sheets are firmly and tightly attached to each other.

The sheets or stack of sheets can be consolidated by applying pressure and optionally heat, as is known in the art and will be discussed in more detail below.

The stack of sheets described herein can be used as such as a bulletproof article or can be further processed into a bulletproof article. For example, a stack of individually consolidated sheets described herein can be used, for example, as a bulletproof article for soft ballistic protection applications. A stack of sheets consolidated as a single unit described herein can be used, for example, as a bulletproof product for hard ballistic protection applications.

In addition, the stack of sheets can be stitched along the peripheral edges or placed in a support bag in order to meet the requirements of a bulletproof product.

Alternatively or additionally, the stack of sheets may be combined with stacks or sheets of other ballistic-resistant materials, such as non-woven unidirectional layers (UDs) or woven webs of UHMWPE fiber, aramid fiber, or aramid copolymer fiber.

Alternatively or additionally, the stack of sheets may be shaped to provide the bulletproof article with a specific shape, such as a helmet, a single curved panel, a double curved panel, or a multiple curved panel.

Alternatively or additionally, the stack of sheets may be used in combination with other ballistic materials, such as ceramic or steel impact absorbing face materials. In a particular embodiment, the stack of sheets may be co-shaped with such ballistic materials, as explained in more detail below.

The present invention further relates to a method for making a bulletproof article described herein, comprising the steps of

a) stacking a stretchable plate of ultra-high molecular weight polyethylene (UHMWPE) and a stretchable continuous film of polymer as an organic matrix material to form a plate-film stack,

b) drawing the plate-film stack obtained in step a) at a temperature below the melting temperature of the UHMWPE stretch plate until a draw ratio of at least 2 is achieved, whereby providing a UHMWPE film with an organic matrix material, thereby obtaining a UHMWPE film, subjected to co-stretching with a polymer film as an organic matrix material,

c) combining the plurality of films provided according to step b) to obtain a layer of films,

d) stacking at least two layers of films obtained according to step c) to obtain a sheet,

e) stacking a plurality of sheets obtained according to step d) to obtain a stack of sheets, and

f) consolidating the sheets before and/or after stacking according to step e) by applying pressure and optionally heating.

The stack of sheets produced by the method described herein may itself meet the requirements for a bulletproof article or may be further processed to form a bulletproof article.

The present invention relates to bulletproof articles produced by such methods.

In the method described herein, UHMWPE films provided with an organic matrix material are prepared by stacking a stretchable UHMWPE plate with a stretchable continuous film of polymer as the organic matrix material (step a) and exposing the thus obtained plate-film stack to at the drawing stage (stage b).

The term "stretchable" means that the plate or film can be subjected to the drawing step. Drawing can be achieved either by rolling or stretching or any combination thereof. Rolling can be carried out in one or several stages. Stretching can be carried out in one or more stages. The plate-film stack can be subjected to, for example, a draw ratio of at least 2, without significantly affecting the integrity of the film, for example, by breaking or tearing in the length direction of the film. It is believed that the presence of microscopic voids in the film formed during drawing does not affect the integrity of the film.

Laying of the stretchable continuous polymer film can be performed on a stretchable UHMWPE sheet, preferably obtained by solid state processing, as described in more detail below. In particular, a stretchable UHMWPE plate that can be used in the present invention can be manufactured by solid state processing of UHMWPE, where the method includes compacting UHMWPE powder into a plate, optionally rolling, and further optionally stretching the resulting densified plate , preferably under conditions such that at no point in time during the processing of the polymer is its temperature raised to a value above its melting point. Suitable methods for solid state processing of UHMWPE are known in the art and do not require further explanation here. Reference should be made, for example, to WO2009/109632, WO2009/153318 and WO2010/079172.

The starting material for making such UHMWPE films may be highly unintertwined UHMWPE. Shear modulusG _N immediately after melting at 160°C is a measure of the degree of intertwining of polymer chains. In particular, the starting polymer may have a shear modulusG _N , determined immediately after melting at 160°C, being not more than 1.4 MPa, in particular not more than 1.0 MPa, in most cases not more than 0.9 MPa, in even more cases not more than 0.8 MPa, and even to an even greater extent, no more than 0.7 MPa. The expression "immediately after melting" means that the elastic modulus is determined immediately after the polymer is melted, in particular within 15 seconds after the polymer melts. For this polymer melt, the elastic modulus typically increases from 0.6 to 2.0 MPa after a few hours.G _N is the shear modulus of elasticity in the high elasticity plateau region. It is related to the average molecular weight between the interweaves (Me_e), which in turn is inversely proportional to the weave density. In a thermodynamically stable melt with a uniform distribution of weaves, M_e can be calculated fromG _N using formulaG _N =g _N ρ R T/M_e, Whereg _N represents a numerical coefficient set to 1, rho (ρ) represents the density in g/cm³, R is the universal gas constant, and T is the absolute temperature in degrees K. A low elastic modulus thus corresponds to large stretches of the polymer between weaves, and thus a low degree of weave. This method is based on the results of a study on changes in weave formation, which is described in: Rastogi, S., Lippits, D., Peters, G., Graf, R., Yefeng, Y. and Spiess, H., entitled “Heterogeneity in Polymer Melts from Melting of Polymer Crystals”, Nature Materials, 4(8), 1st August 2005, 635-641; and the master's thesis by Lippits, D.R., entitled “Controlling melting kinetics of polymers; route to new melt state”, Eindhoven University of Technology, dated March 6, 2007, ISBN 978-90-386-0895-2.

Such unintertwined polyethylene can be produced using a polymerization process where ethylene is polymerized in the presence of a single site catalyst at a temperature below the crystallization temperature of the polymer, such that the polymer crystallizes immediately upon formation. Suitable methods for producing polyethylene used in the present invention are known in the art. For example, reference must be made to international publication WO01/21668 and US patent US20060142521.

In one embodiment, the organic matrix material-equipped UHMWPE films used in the present invention have high molecular orientation, as evidenced by their X-ray diffraction (XRD) pattern. In one embodiment of the present invention, the UHMWPE films have a single-plane orientation parameter Φ (200/110) equal to at least 3. The single-plane orientation parameter Φ (200/110) is defined as the ratio between the areas of the 200 and 110 peaks in the XRD pattern of the sample film, which is due to the reflection geometry. The single-plane orientation parameter (200/110) provides information about the degree of orientation of the crystal planes 200 and 110 relative to the film surface. For a film sample with a high single-plane orientation (200/110), the planes of the crystal 200 are highly oriented parallel to the film surface. It has been found that high uniplanar orientation is generally accompanied by high elastic modulus, high tensile strength and high tensile energy at break. The ratio between peak areas 200 and 110 for a sample with statistically oriented crystallites is about 0.4. However, UHMWPE films that may be preferably used may have 200 index crystallites that are oriented predominantly parallel to the film surface, resulting in a higher peak area ratio of 200/110, and therefore a higher single-plane orientation parameter. This parameter may be defined as described in WO2009/109632.

UHMWPE films may preferably have a single-plane orientation parameter (200/110) of at least 4, more of at least 5, or at least 7. Higher values, such as values of at least 10 or even at least 15 may be particularly preferred. The theoretical maximum value for this parameter is infinite if the area of peak 10 is zero.

The stretchable continuous film of polymer may be laid on a UHMWPE stretch plate obtained immediately after compaction, on a UHMWPE stretch plate obtained after the compacted plate has been rolled, or on a UHMWPE stretch plate obtained after the compacted plate has been rolled and stretched. Thus, prior to stacking, the UHMWPE stretch plate can be partially stretched by rolling and optional stretching.

The draw ratio obtained by the rolling step may be at least 2, in particular at least 4, at least 5 or at least 6 and not more than 12, not more than 10 or not more than 8. The draw ratio obtained at the stage of partial stretching, may be at least 2, in particular at least 4, at least 5 or at least 6, and not more than 12, not more than 10 or not more than 8. The stretch ratio is defined as the cross-sectional area of the UHMWPE stretch plate as it enters the rolling or stretching stage divided by the cross-sectional area of the UHMWPE stretch plate as it leaves the rolling or stretching stage.

The UHMWPE stretch plate used herein may preferably have a thickness of 50-3000 microns, especially 75-2500 microns, more particularly 100-2250 microns.

In one embodiment of the present invention, a plate-film stack is formed by stacking a stretchable continuous polymer film onto a UHMWPE stretch plate that is formed prior to exposing the compressed UHMWPE plate during the rolling step. In this embodiment, the UHMWPE stretch plate may preferably have a thickness of 500-3000 microns, especially 1000-2500 microns, and even more 1250-2250 microns.

In yet another embodiment, a plate-film stack is formed by stacking a stretchable continuous polymer film onto a stretchable UHMWPE plate obtained after exposing the compressed UHMWPE plate to the rolling step but before subjecting it to the stretching step. In this embodiment, the UHMWPE stretch plate may preferably have a thickness of 200-1200 microns, especially 300-1000 microns, and even more 400-800 microns.

In yet another embodiment, the plate-film stack is formed by stacking a stretchable continuous polymer film onto a UHMWPE stretch plate obtained after subjecting the rolled plate to at least one stretching step. In this embodiment, the UHMWPE stretch plate may preferably have a thickness of 50-500 microns, especially 75-300 microns, and even more 100-200 microns.

The stretchable polymer film as an organic matrix material in the context of this document may preferably have a thickness of 4-25 microns, in particular 5-15 microns, even more 6-10 microns.

Providing exposure to the plate-film stack during the drawing stage provides several advantages. For example, the organic matrix material can be applied to a UHMWPE stretch plate as a stretchable polymer film using films that, despite the resulting low amounts of organic matrix material, are relatively thick at the start of the process. This method provides the improvement that the original stretch matrix films are easier to work with than thinner films (eg, easier to lay over UHMWPE films). In addition, the very thin films produced by the process described herein are not commercially available because they are difficult to produce and handle. In addition, the drawing process produces a good bond between the organic matrix polymer film and the UHMWPE film.

A particular advantage of applying a stretch polymer film to a UHMWPE stretch plate that has not yet been rolled is that the plate-film stack can be exposed to a higher stretch ratio (by applying stress to the plate-film stack as in the step rolling and at the stretching stage), and a maximum reduction in the thickness of the organic matrix polymer film can be achieved.

The width of the UHMWPE stretch plate when it enters the process according to the invention is not a critical value. It can be, for example, at least 1 cm, in particular at least 5 cm, more particularly at least 10 cm. Typically, the maximum width can be no more than 150 cm.

The use of a continuous organic matrix polymer film generally provides a continuous coating of the UHMWPE film with the organic matrix material.

The organic matrix polymer stretch film can be laid on top of the UHMWPE stretch plate in parallel to maximize the coverage of the UHMWPE film with the organic matrix material.

The stretch continuous organic matrix polymer film used in the stack will generally not be wider than the UHMWPE stretch sheet to avoid the presence of excess organic matrix material. To reliably provide a large coverage of the UHMWPE film with the organic matrix polymer film, it may be preferable that the width of the organic matrix polymer stretch film is at least 90% of the width of the UHMWPE stretch plate. More specifically, the width of the organic matrix polymer stretch film may be at least 95%, or at least 99%, or even at least 99.5% of the width of the UHMWPE stretch sheet. In one embodiment, the width of the organic matrix polymer stretch film matches the width of the UHMWPE stretch plate.

Stretchable organic matrix polymer films are commercially available or can be provided by known methods. For example, these films can be produced by extrusion blown or film extrusion, methods that are well known in the art.

The plate-film stack stretching step is carried out at a temperature below the melting point of the UHMWPE stretch plate. The drawing step is typically carried out at a temperature at least 1°C below the melting temperature of the UHMWPE stretch plate under process conditions. Depending on the nature of the UHMWPE polymer, the temperature may be lower, for example at least 3°C or even at least 5°C below the melting temperature of the UHMWPE stretch plate under process conditions. The temperature of the drawing step is thus usually determined in accordance with the melting temperature of the UHMWPE stretch plate.

The melting point of an organic matrix polymer stretch film (or softening point for organic matrix materials that do not have a melting point, such as block copolymers such as SIS) is generally lower than the melting point of a UHMWPE stretch sheet. In particular, the melting point or softening temperature for an organic matrix polymer film can generally be 5-50°C lower than the melting point of a UHMWPE film, in particular 10-45°C, more generally 15-30 °C.

The drawing step may be carried out at a temperature below the melting temperature of the stretchable organic matrix polymer film, or, provided that the temperature is maintained below the melting temperature of the stretchable UHMWPE sheet, at a temperature above the melting temperature of the stretchable organic matrix polymer film. It may be preferable to conduct the stretching step at a temperature above the melting point of the stretchable organic matrix polymer film so as to prevent the matrix polymer film from tearing during stretching and thereby reliably ensure uniform distribution of the matrix polymer on the UHMWPE film.

As is known to one skilled in the art, the melting point of polymers can depend on the constraints under which they are placed. This means that the melting temperature under process conditions may vary from case to case. However, the melting point can be easily defined as the temperature at which the strain in the process drops sharply. The unconstrained melting temperature for the UHMWPE stretch plate and the organic matrix polymer stretch film can be determined by one skilled in the art, for example, using DSC (differential scanning calorimetry). Specifically, DSC can be carried out in nitrogen, in a temperature range from +30 to +180°C and at a temperature rise rate of 10°C/minute. The maximum of the largest endothermic peak in the range from 80 to 170°C is regarded here as the melting point.

Typically, the drawing step is carried out at a temperature no more than 30°C below the melting temperature of the UHMWPE stretch plate under process conditions, in particular no more than 20°C, in particular no more than 15°C below melting temperature of the polymer under process conditions.

The draw ratio applied to the plate-film stack in the method according to the invention is at least 2, in particular at least 6, or at least 10, or at least 20, or at least 28, or even at least at least 100, or at least 150.

The draw ratio is defined as the cross-sectional area of the plate-film stack as it enters the drawing stage divided by the cross-sectional area of the organic matrix material-equipped UHMWPE film as it leaves the drawing stage.

The maximum stretch ratio, as a rule, corresponds to the highest stretch ratio that can be achieved without compromising the integrity of the plate-film stack and will depend on the properties of the original stretchable materials and the process conditions. Typically, the plate-film stack is drawn to its maximum or to a level as close as possible to its maximum. One skilled in the art can readily determine such a maximum for a given system. As an example, the stretch ratio may be no more than 400, no more than 300, or no more than 200.

In general, the extent to which the plate-film stack is stretched in the drawing step may depend on the extent to which the original UHMWPE stretch plate was stretched, if at all stretched, in any of the rolling and stretching stages used in its production .

In general, the lower the draw ratio of the original UHMWPE stretch wafer (which is achieved during its production), the higher the draw ratio that can be applied during stretching of the wafer-film stack.

The degree of drawing may also depend on the number of drawing steps, such as rolling and stretching steps. Generally, the greater the number of drawing steps, the greater the degree of stretch that can be achieved. In general, the drawing in step b) can be carried out in at least two drawing stages or at least three drawing stages.

Drawing can be carried out using a combination of rolling and/or stretching steps. If rolling is carried out, then rolling of the plate-film stack can be carried out in at least two stages or even in at least three stages. If stretching is carried out, the stretching of the plate-film stack may be carried out in at least two stages or even in at least three stages.

It may be preferable to maximize the stretch ratio of the plate-film stack so as to minimize the amount and thickness of the organic matrix polymer film covering the UHMWPE film. This can be achieved, for example, by stretching a plate-film stack obtained by stacking an organic matrix polymer stretch film onto a UHMWPE stretch plate that was obtained after rolling a compacted UHMWPE plate (without undergoing any partial stretch steps), where the draw ratio at the mentioned rolling stage is, for example, 2-6. For example, the stretch ratios achieved for a plate-film stack at the drawing stage, using such a UHMWPE stretch plate as a starting point, are 20-50. Cumulative draw ratios of the final UHMWPE film provided with organic matrix material are 80-300. Higher slab-film stack stretch ratios can be achieved by stretching a slab-film stack obtained by stacking an organic matrix polymer stretch film onto a UHMWPE stretch slab that has not been pre-stretched, such as that obtained directly after compacting the UHMWPE powder into UHMWPE plate when carrying out the technological process in the solid state. For example, the draw ratios achieved for a plate-film stack in the drawing step, using such a UHMWPE stretch plate as a starting point, can be 80-300, which would correspond to the total draw ratio of the final UHMWPE film provided with the organic matrix material.

It has been found that stacking a stretch film of an organic matrix polymer on a stretch UHMWPE plate and allowing the plate-film stack to stretch advantageously results in a co-stretched film where the ballistic properties of the UHMWPE film remain unaffected, i.e., are comparable to the ballistic properties of the film , obtained using similar rolling/stretching steps in the absence of an organic matrix polymer film. In addition, the method described herein provides very good control of the distribution of the organic matrix polymer film on the surface of the UHMWPE film.

In addition, the use of UHMWPE films, which are equipped with an organic matrix material, greatly simplifies the production of bulletproof products. In particular, since the UHMWPE films adhere to each other due to the presence of the organic matrix polymer film, it is not necessary to independently provide the organic matrix material and include the application of the organic matrix material in the method of making bulletproof articles.

UHMWPE films that are provided with an organic matrix material according to step b) of the process described herein may be referred to as co-stretched films.

The method described herein further includes combining a plurality of films provided in step b) to form a layer of films (step c).

The co-stretched films may preferably be aligned in parallel, thereby forming a layer of unidirectionally oriented co-stretched films or, in other words, thereby providing a unidirectional orientation of UHMWPE films provided with an organic matrix material within the layer of films.

Films can be overlapped in parallel. Because of this, the organic matrix material present in the overlapping zone of the films can promote adhesion of the films to each other.

Alternatively, and in some embodiments preferably, the films are aligned in parallel so that they do not overlap, for example the films may be in abutting contact or there may be small gaps between adjacent films, preferably the films are arranged in an abutting contact without significant gaps between adjacent films, as described above regarding the bulletproof product. In this way, layers are obtained that have a uniform thickness, that is, free from overlapping areas.

The method described herein further includes stacking at least two layers of films obtained according to step c) to form a sheet (step d).

The sheets can be produced by combining a plurality of co-stretched films to form a first layer of films and stacking a second layer of films on top of the first layer by combining a plurality of co-stretched films directly on top of the first layer, resulting in a sheet of two layers of films .

Additional layers of films may be stacked in a similar manner to form a sheet of, for example, at least 3, 4, 6 or more layers, as described above with respect to the bulletproof product. The stacking can be carried out to provide the desired orientation of the films in one layer relative to the orientation of the films in the adjacent layer, as described in detail above.

For example, co-stretched films can be arranged in a row on top of a first layer of co-stretched films to form a second layer of co-stretched films such that the orientation of the films in the first layer matches the orientation of the films in the second layer, that is, the films in the first and the second layers will be parallel to each other in a 0-0 structure. In a particular embodiment, the films of the second layer are arranged offset relative to the films of the first layer in a so-called briquette structure.

Alternatively, the co-stretched films may be stacked on top of the first layer of co-stretched films to form a second layer of co-stretched films such that the orientation of the films in the first layer is at an angle with respect to the orientation of the films in the second layer. Regarding preferred orientation angles, reference is made to what is described above with respect to the bulletproof article. For example, a sheet with at least two layers in a 0-90 structure may be provided.

Additional layers of co-stretched films may be stacked to secure such structures until a sheet with the desired number of layers is obtained.

The method described herein further includes stacking a plurality of sheets obtained according to step d) to form a stack of sheets. The sheets may be stacked in the same manner as described above with respect to stacking layers of co-stretched films, whereby sheets are formed during stacking. Alternatively, the sheets may be individually preformed and then stacked on top of each other. Sheet stacking can be done to achieve the desired orientation of the films within the stack. For example, two sheets with a 0-90 structure can be stacked to provide a stack structure of 0-90-0-90. Alternatively, two sheets with a 0-0 structure can be stacked perpendicularly to provide a stack structure of 0-0-90-90. Additional sheets may be stacked to secure such structures within the stack until a stack with the desired number of sheets is obtained.

The method described herein further includes consolidating the sheets before and/or after stacking according to step e) by applying pressure and optionally heating. Thus, the sheets may be individually consolidated prior to stacking and/or the stack of sheets may be consolidated as a unit after stacking.

The sheet or stack of sheets can be consolidated by applying pressure and optional heat, as is known in the art. For example, a sheet or stack of sheets may be placed in a press and pressed.

The sheet or stack of sheets may be compressed by applying a pressure of, for example, at least 0.1 MPa. A maximum pressure of not more than 50 MPa may be mentioned. The pressure to be applied is expected to reliably produce a bulletproof article with adequate properties.

The use of pressure may be sufficient to initiate adhesion of the UHMWPE films in a sheet or stack of sheets to each other through the organic matrix material. However, if necessary, the temperature during pressing may be selected such that the temperature of the organic matrix material is brought to a level above its softening or melting point if necessary to initiate the matrix to assist in adhesion of the films and/or sheets to each other.

The required pressing time and pressing temperature may depend on the nature of the UHMWPE films and organic matrix material and on the thickness of the sheet or stack of sheets to be consolidated, and can be readily determined by one skilled in the art.

Consolidation can be carried out at a compaction temperature above the softening or melting temperature of the organic matrix material (i.e. organic matrix polymer film) and below the melting temperature of UHMWPE films. In the case where the pressing is carried out at such a temperature, it may be preferable to cool the compressed material (i.e., sheet or stack of sheets) also under pressure, whereby a predetermined minimum pressure will be maintained during cooling at least until the temperature at in which the structure of a sheet or stack of sheets can no longer relax at atmospheric pressure. Determining such a temperature for each individual case is within the competence of a person skilled in the art. When applicable, it is preferable to conduct cooling at a specified minimum pressure to achieve a temperature at which the organic matrix material is substantially or completely solidified or crystallized and which is below the relaxation temperature of the UHMWPE film. The pressure during cooling does not need to be the same as the pressure used for consolidation. During cooling, the pressure can be monitored to maintain appropriate pressure values to compensate for the reduction in pressure caused by shrinkage of the sheet or stack of sheets in the press.

The consolidation described above can be carried out in a static press or using a continuous process. Suitable continuous processes include lamination, calendering and double belt pressing.

The method described herein provides a stack of sheets that, as such, can meet the requirements for a bulletproof product, or can be further processed into a bulletproof product.

For example, whether the sheets are consolidated as such or a stack of sheets is consolidated as a unit, additional steps in the method described herein may include placing the stack of sheets in a support bag or stitching along the peripheral edges of the stack of sheets.

Other additional steps may include, for example, combining the stack of sheets with stacks or sheets of other bulletproof materials, such as nonwoven unidirectional layers (UDs) or woven webs of UHMWPE fiber, aramid fiber, or aramid copolymer fiber.

Alternatively or additionally, additional steps may include shaping the stack of sheets to provide the bulletproof article with a specific shape, such as a helmet shape, a single curved panel, a double curved panel, or a multiple curved panel.

Alternatively or additionally, additional steps may include combining the sheet stack with other ballistic materials, such as ceramic or steel impact absorbing face materials. In a specific embodiment, the method may include shaping the stack of sheets together with such ballistic materials, for example, using vacuum consolidation, so that the stack of sheets takes the shape of this additional ballistic material, that is, a preformed ceramic or steel impact-resisting facing material.

The present invention also relates to bulletproof articles produced by the manufacturing methods described herein.

The present invention is further illustrated by the following examples, which are not intended to be limiting or limiting of the invention.

EXAMPLES

General methods

The modulus of elasticity of UHMWPE films and co-tensile UHMWPE films can be determined according to ASTM D7744/D7744M-11, Standard Test Methods for Tensile Testing of High Strength Polyethylene Tapes, taking into account the description of ASTM D76 for Tensile Testing Machines for Textiles and implementation of the ASTM D1776 standard for conditioning and testing textile materials.

The thickness of the UHMWPE film and the co-stretched UHMWPE film can be determined using a digital readout micrometer, such as the one commercially available from Mitutoyo. The thickness is measured at at least three positions along the width of the film and the average is taken.

While the stack is being consolidated in the press, a thermocouple is inserted into the middle of the stack. The temperature that is measured is defined as the internal temperature (the temperature inside the material).

Example 1

An HDPE film having a thickness of 6 microns and a melting point of 128°C is laid on top of a 320 micron thick UHMWPE stretch plate made by compacting UHMWPE powder into a UHMWPE plate and rolling the UHMWPE plate to a draw ratio of 5. The plate-film stack is drawn by stretching at a temperature above melting point of HDPE and below the melting point of UHMWPE. The draw ratio of the plate-film stack is 36. This results in a UHMWPE film equipped with an organic matrix material with a total draw ratio of 5×36=180 and an overall average thickness of about 43 microns, including an HDPE layer that has an average thickness of about 1 micron. The surface coverage of UHMWPE film with organic matrix material is 96%. The weight percentage of the organic matrix polymer relative to the total weight of the organic matrix polymer and UHMWPE is 1.5% by weight. The modulus of elasticity of UHMWPE film provided with organic matrix material is 186.3 N/tex.

Example 2

An HDPE film having a thickness of 6 microns and a melting point of 128°C is stacked on top of a 170 micron thick UHMWPE plate made by compacting UHMWPE powder into a UHMWPE plate, rolling the UHMWPE plate to a draw ratio of 5, and stretching the rolled sheet to a combined draft ratio of 20. The plate-film stack is drawn by stretching at a temperature above the melting point of HDPE and below the melting point of UHMWPE. The draw ratio of the plate-film stack is 6. This results in a film with a total draw ratio of 20×6=120 and an overall average thickness of about 58 microns, including an HDPE layer that has an average thickness of about 2 microns. The surface coverage of UHMWPE film with organic matrix material is 95%. The weight percentage of the organic matrix polymer relative to the total weight of the organic matrix polymer and UHMWPE is 3 wt%. The modulus of elasticity of UHMWPE film provided with organic matrix material is 166.9 N/tex.

Example 3

An LDPE film having a thickness of 10 microns and a melting point of 115°C is laid on top of a 320 micron thick UHMWPE plate made by compacting UHMWPE powder into a UHMWPE plate and rolling the UHMWPE plate to a draw ratio of 5. The plate-film stack is drawn by stretching at a temperature above melting point of LDPE and below melting point of UHMWPE. The draw ratio of the plate-film stack is 36. This results in a film with a total draw ratio of 5×36=180 and an overall average thickness of about 44 microns, including an LDPE layer that has an average thickness of about 1 micron. The surface coverage of UHMWPE film with organic matrix material is 95%. The weight percentage of the organic matrix polymer relative to the total weight of the organic matrix polymer and UHMWPE is 2% by weight. The modulus of elasticity of UHMWPE film provided with organic matrix material is 183 N/tex.

Example 4

The first 0-90 cross-ply sheet (Sheet A) is produced using a Meyer laboratory laminator. Three rolls of film with a width of 133 mm, obtained as described above in example 1, are placed on an unwinding installation. These films are fed into the laminator with a minimum gap between the films, so that the three films are parallel in the joint contact, but without overlapping, producing a bottom layer of '0 degree' films. On top of this '0 degree' layer, three films of the same width and length of 40 cm, produced in the same way as in example 1, are placed perpendicular to the '0 degree' layer immediately before entering the laminator, producing a layer of '90 degree' films. Films in the ‘90 degree’ layer are manually placed to achieve minimal overlap. After lamination, a consolidated sheet with a cross-layer arrangement of the 0-90 type is obtained, which is wound on a winding installation.

In the second stage, a second 0-90 cross-ply sheet (sheet B) is produced using the same laminator as described above for sheet A, except that instead of three films of 133 mm width, four films are fed into the laminator, two of which are 66.5mm wide, and two of which are 133mm wide.

In the third stage, cross-layer sheet A and cross-layer sheet B are unwound and fed into the laminator simultaneously to produce and consolidate the 0-90-0-90 cross-sheet web. The consolidated web with a cross arrangement of sheets is wound on a winding installation.

Comparative example 1

In a comparative example, UHMWPE produced under similar conditions with similar mechanical properties as in Example 1 is used, however, in the absence of HDPE or LDPE stacked on the surface of the film, so no matrix is co-stretched with the UHMWPE film. UHMWPE films have a thickness of 45 microns, a width of 133 mm and a total draw ratio of 180, and a modulus of elasticity of 184 N/tex. These films are also used to produce a 0-90-0-90 cross-layer sheet in the same manner as described above for sheet C of Example 4, except that the HDPE film having a thickness of 6 microns and a melting point 128°C, placed between each layer of films to reliably ensure adhesion of all adjacent layers. The weight percentage of the organic matrix polymer relative to the total weight of the organic matrix polymer and UHMWPE is 15% by weight.

Example 5

Using the same laminator setup as in Example 4, a roll of UD sheet with a 0-0 structure is obtained. The three films described in Example 1, 133 wide, are unwound to produce the first layer of '0 degree' films. On top of this layer of films, four films are fed into the laminator, two films of which at the side of the layer are 66.5 mm wide instead of 133 mm, producing a second layer of '0 degree' films parallel to but angled to the first layer of '0 degree' films ', obtaining a consolidated sheet with a briquette-like structure (UD 0-0). The UD 0-0 sheet is wound on a winding machine. A portion of this UD 0-0 sheet is cut to obtain a sheet 40 cm long.

At the second stage of lamination, the roll with the UD 0-0 sheet is unwound and fed into the laminator. Cut sheets 40 cm long are placed perpendicularly on top of the UD 0-0 roll immediately before feeding into the laminator, with the formation and consolidation of the web with a cross arrangement of sheets like a 0-0-90-90 briquette. A consolidated web with a cross arrangement of sheets like a briquette 0-0-90-90 is wound on a winding installation.

Comparative example 2

In a comparative example, UHMWPE produced under similar conditions and with similar mechanical properties as in Example 1 is used, however, in the absence of HDPE or LDPE on the surface of the film, so no matrix is co-stretched with the UHMWPE film. UHMWPE films have a thickness of 45 microns, a width of 133 mm and a total draw ratio of 180, and a modulus of elasticity of 184 N/tex. These films are used to produce cross-sheet webs similar to the 0-0-90-90 briquette described in Example 5, where HDPE film having a thickness of 6 microns and a melting point of 128°C is placed between each layer of films to ensure reliable adhesion all adjacent layers. The weight percentage of the organic matrix polymer relative to the total weight of the organic matrix polymer and UHMWPE is 15% by weight.

Test results - stacks of individually consolidated sheets

The cross-layer sheets described above in Example 4, Comparative Example 1, Example 5 and Comparative Example 2 were cut into sheets measuring 40 x 40 cm. A number of sheets were stacked to achieve a surface weight of 3.1 kg/m ² . The stacks are sewn together at the corners. 5 stacks are made from each sample. Each stack is shot 8 times with a Remington (9mm) weapon. v50 is determined based on data from all 40 shots by fitting a logistic curve. The results are presented in Table 1.

Table 1 Example v50 (m/sec) Example 5 (0-0-90-90) 433 Comparative example 2 417 Example 4 (0-90-0-90) 551 Comparative example 1 491

Samples of the invention with UHMWPE films co-stretched with a matrix material (Examples 4 and 5) show improved performance compared to Comparative Examples (1 and 2), where the samples have a similar sheet structure, but the matrix material is added between the sheets of UHMWPE films instead to be co-stretched with UHMWPE films.

Test results - stacks consolidated as a whole

The cross-layer sheets described above in Example 4 and Comparative Example 1 were cut into sheets measuring 40 x 40 cm. The sheets were stacked until the required surface weight (which is shown in Table 2) was achieved. The stacks are pressed at a pressure of 55 bar and an internal temperature of 135°C. Flat plates are evaluated in accordance with NATO standardization agreement Stanag 2920 using 1.1 g fragmentation simulator type projectiles and v50 is determined. The results are presented in Table 2.

table 2 Material Surface mass (kg/ ^m2 ) v50 (m/sec) Comparative Example 1 7.2 772 Comparative Example 1 7.9 829 Example 4 7.45 854

The sample according to the invention (Example 4) clearly shows the best ballistic performance with the highest v50 value.

Claims (26)

1. A method for manufacturing a bulletproof product, including the stages: a) stacking a stretchable slab of ultra-high molecular weight polyethylene (UHMWPE) and a stretchable continuous film of polymer as the organic matrix material to form a slab-film stack, where the continuous film of polymer as the organic matrix material is not a UHMWPE film, b) stretching the plate-film stack obtained in step a) at a temperature below the melting temperature of the UHMWPE stretch plate to a draw ratio of at least 2, whereby providing a UHMWPE film with an organic matrix material in which the UHMWPE film is co-stretched with a polymer film as an organic matrix material, c) combining the plurality of films provided according to step b) to obtain a layer of films, d) stacking at least two layers of films obtained according to step c) to obtain a sheet, e) stacking a plurality of sheets obtained according to step d) to obtain a stack of sheets, and f) consolidating the sheets before and/or after stacking according to step e) by applying pressure and optionally heat. 2. The method of claim 1, wherein the stretchable UHMWPE sheet has a thickness of 50-3000 microns, and the stretchable continuous organic matrix polymer film has a thickness of 4-25 microns. 3. The method according to any one of claims 1, 2, in which the melting temperature of the stretchable organic matrix polymer film is lower than the melting temperature of the stretchable UHMWPE plate, and the stretching in step b) is carried out at a temperature higher than the melting temperature of the stretchable organic matrix polymer film. 4. Method according to any one of claims 1 to 3, wherein the draw ratio in step b) is at least 6, or at least 10, or at least 20, or at least 28, or at least 100, or at least 150. 5. Method according to any one of claims 1 to 4, wherein the drawing in step b) is carried out in at least two drawing stages or at least three drawing stages. 6. The method according to any one of claims 1 to 5, comprising consolidating the individual sheet obtained according to step d) before stacking, by applying pressure and, optionally, heat to the sheet. 7. A method according to any one of claims 1 to 6, comprising consolidating the stack of sheets obtained in step e) as a single unit, after stacking, by applying pressure to the stack of sheets and, optionally, heating. 8. A bulletproof product containing a stack of sheets, wherein the sheets include at least two layers of ultra-high molecular weight polyethylene (UHMWPE) films provided with an organic matrix material, wherein the UHMWPE films are provided on at least 95% of at least one of their surfaces with a continuous film of polymer as an organic matrix material, wherein the continuous film of polymer as an organic matrix material is not a UHMWPE film, wherein the UHMWPE films have a thickness of 10-100 microns, and the organic matrix polymer film has a thickness of 0.1-3 microns, and the weight percentage of the organic matrix polymer relative to the total weight of the organic matrix polymer and ultra-high molecular weight polyethylene is from 0.1 to 3 wt. %, And, where the sheets in the stack are subject to consolidation, wherein the orientation of the polymer molecules in the continuous film of the polymer as an organic matrix material in the first film direction is different from the orientation of the polymer molecules in the continuous film of the polymer in the second film direction, and the first film direction and the second film direction are at an angle of 90°, and the first film direction corresponds to the drawing direction during film production. 9. The bulletproof product of claim 8, wherein the UHMWPE films are provided with a continuous film of polymer on at least 97%, or at least 99%, or at least 99.5% of at least one of their surfaces. 10. The bulletproof product according to claim 8 or 9, wherein the weight percentage of the organic matrix polymer relative to the total weight of the organic matrix polymer and ultra-high molecular weight polyethylene is from 0.15 to 2.5 wt. %, or from 0.2 to 2 wt. %, or from 0.5 to 1.5 wt. %. 11. The bulletproof product according to any one of the preceding claims 8 to 10, wherein the organic matrix polymer film is a polyethylene film, in particular a low-density polyethylene film or a high-density polyethylene film. 12. Bulletproof product according to any one of the preceding claims 8-11, in which the UHMWPE films have a thickness of 20-80 microns, in particular 30-70 microns, and the organic matrix polymer film has a thickness of 0.15-2.5 microns, in particular 0.2-2 microns, and to a greater extent 0.4-1.5 microns. 13. The bulletproof article according to any one of the preceding claims 8 to 12, wherein the orientation of the UHMWPE films provided with the organic matrix material within a layer of films is unidirectional, and, optionally, the orientation of the films in one layer is at an angle to the orientation of the films in the adjacent layer particularly at an angle of 45 to 135 degrees, or 60 to 120 degrees, or 85 to 95 degrees, or approximately 90 degrees. 14. The bulletproof product according to any one of the preceding claims 8 to 13, wherein the sheets are individually consolidated. 15. The bulletproof product according to any one of the preceding claims 8 to 14, wherein the stack of sheets is consolidated as a single unit.