Method for obtaining combustible textile structures based on nitrocellulose, combustible textile structures, and combustible objects containing same

Abstract

The present invention relates to a method for obtaining a highly flammable combustible textile structure that comprises: a) producing a nitrocellulose collodion; b) manufacturing at least one nitrocellulose filament via spinning extrusion of the collodion produced in step a), with the at least one nitrocellulose filament passing into and through at least one nitrocellulose coagulation bath; c) sizing the at least one nitrocellulose filament obtained in step b) by passing it into and through an aqueous solution containing a sizing agent; d) spin-drying and drying the at least one sized nitrocellulose filament obtained in step c), and winding same; e) manufacturing a textile forming a textile structure by knitting, weaving or braiding with at least one sized nitrocellulose filament obtained in step d); f) chemically treating the textile structure obtained in step e) in order to desize the at least one sized constituent nitrocellulose filament, and then drying same.

Description

[0001] Process for obtaining combustible textile structures based on nitrocellulose, combustible textile structures and combustible objects containing them.

[0002] Field of invention

[0003] The technical field of the invention is that of technical textiles manufactured by knitting, weaving or braiding filaments obtained by spinning a pasty mixture. The technical textiles of the invention form highly flammable combustible structures which may, for example, be suitable for containers, structural reinforcements or assembly parts in the civil and military fields.

[0004] State of the art

[0005] The production of nitrocellulose filaments and wound or coated structures using nitrocellulose filaments is well known in the prior art and described in the 1950s-1970s, in particular in patent applications US 3,256,371, US 3,745,927, US 2,991,168 and US 3,304,867.

[0006] US Patent 2,991,168 describes nitrocellulose filaments and their method of production. The composition of the filaments is about 79.9% to 99% nitrocellulose having a nitrogen content of 12.6% to 13.25%, and about 0.5% to 2.5% stabilizer, 0% to 19.5% nitroglycerin, 0% to 9% dinitrotoluene, and 0% to 5% plasticizer. The plasticizer may be an energetic plasticizer such as triethylene glycol dinitrate (TEGN) or diethylene glycol dinitrate (DEGN). These conventional nitrocellulose filaments are classified in the dry state as hazard division 1.3.

[0007] Filaments or bundles of filaments are obtained by dry spinning or wet spinning processes with spinning machines that are conventionally used, for example, for spinning viscose filaments. The filaments are wound (circumferentially or helically) or twisted (in a Z or S twist) around a core (made of cardboard, wood, plastic, metal, etc.) and impregnated with a binder to obtain combustible structures. They can also be cut into short strands (typically 12 to 50 mm) and hot-pressed, in the form of a slurry in the presence of a binding agent and / or a plasticizer, to obtain strips. The strips are then superimposed and dried to form a nonwoven fabric similar to paper to obtain a structure.

[0008] The coating (also called "sizing") of nitrocellulose filaments with starch, polyvinyl alcohol, polyacrylic acid and styrene polymers or other coating agents identical to those used for drawn glass fiber filaments is incidentally cited in US patent 3,745,927. These coatings are therefore cited in analogy with the field of glass fibers. The glass fiber coatings give the fibers lubricating properties (creep during the molding phase of the resin matrix), and adhesion with the resin matrix for the reinforcement of resins for SMC (Sheet Molding Compound) prepregs as described in patent application EP 0 004 816. It is therefore understood that US patent 3,745,927 cites nitrocellulose filament coatings with reference to obtaining structures by laminating or molding strands or tow.US Patent 3,745,927 does not comment on the impact on the combustion properties of the coating of the nitrocellulose filaments.

[0009] US Patent 3,745,927 also incidentally cites the reinforcement of nitrocellulose structures with nitrocellulose filament fabrics. US Patent 3,304,867 similarly cites the use of textile machines for obtaining nitrocellulose filament fabrics or structures.

[0010] Whether for coated nitrocellulose filaments or nitrocellulose filament fabrics or the use of textile machines with nitrocellulose filaments, US patents 3,745,927 and US patents 3,304,867 do not give any examples and these are only prospective descriptions.

[0011] The prior art is therefore limited to the use of nitrocellulose filaments by winding or laminating to obtain combustible structures. The use of textile machines to manufacture textiles forming highly flammable combustible textile structures based on nitrocellulose filaments is certainly suggested but is not described and put into practice. Indeed, the mechanical stresses in traction and friction on the filaments during manufacturing with textile machines are prohibitive in the case of nitrocellulose filaments classified in risk division 1.3 due to the risks of pyrotechnic ignition.

[0012] Furthermore, in the textile field, we are aware of new developments in so-called "technical" textiles which find their application in the clothing (cut-resistant gloves, protective jackets), sports (sailing, canoeing, nets, etc.), medical (orthosis, dressings, surgical implants, etc.), transport (hose, filters, etc.), construction (insulation, roofing, window protection, etc.), agriculture (reflectors, nets, etc.), industry (conveyor belts, filters, flexible pipes, sheathing, sealing gaskets, grinding discs, packaging, etc.) sectors. We are also aware of new textile processes known as "integral" or "three-dimensional (3D)" or "seamless" for obtaining textile structures that can be obtained with a single filament. These processes, using digital design and manufacturing tools, allow, in particular, the reduction of costs and manufacturing times without producing raw material waste.They are notably implemented in the field of clothing, for example by the company 3D-Tex, or in sports, by the company VisionKnit for the manufacture of Kevlar-Polyester canoes, or the company Horse Pilot for the manufacture of riding clothes and boots, or in an exploratory way in the field of art architecture at the Delft University of Technology in the Netherlands. Many 3D structure manufacturing machines are commercially available, notably those proposed by the company Mayer & Cie (Germany), the company Santoni (Italy) or the company Sintelli (China). The manufactured structures are made of natural plant fibers (cotton, jute, linen, etc.) or animal fibers (wool, silk), synthetic fibers (aramid, polyester, etc.) or inorganic fibers (carbon, glass, etc.).Industrial mastery of 3D manufacturing of textile structures is therefore established and could be advantageously implemented to obtain highly flammable combustible textile structures. However, the mechanical constraints applied to the filaments by the implementation of these processes are high and incompatible with their use with pyrotechnic materials, such as dry nitrocellulose filaments described in the prior art.

[0013] It is to the credit of the inventors to have developed a process for obtaining highly flammable combustible textile structures based on nitrocellulose filaments using textile machines, in particular machines for manufacturing three-dimensional textile structures also known as integral or seamless. This process allows the use of textile manufacturing machines in safety with regard to the pyrotechnic risk with nitrocellulose filaments for obtaining highly flammable combustible textile structures.

[0014] Summary of the invention

[0015] The present invention relates, according to a first aspect, to a method for obtaining a highly flammable combustible textile structure composed of one or more nitrocellulose filaments.

[0016] The textile structures of the invention are generally made up of several knitted and / or woven and / or braided nitrocellulose filaments, but may also, in the case of an integral textile manufacturing process, be made up of a single nitrocellulose filament. The process for obtaining a highly flammable combustible nitrocellulose textile structure according to the invention comprises: a) producing a nitrocellulose collodion, b) manufacturing at least one nitrocellulose filament (generally several) using an extrusion process by spinning the collodion carried out in step a), with passage of the at least one nitrocellulose filament into and through at least one nitrocellulose coagulation bath, c) sizing the at least one nitrocellulose filament obtained in step b) by passage into and through an aqueous solution containing a water-soluble polymeric sizing agent,d) spinning and drying the at least one sized nitrocellulose filament obtained in step c), and winding it, e) manufacturing a textile forming a textile structure by knitting, weaving or braiding with at least one sized nitrocellulose filament obtained in step d), f) chemical treatment of the textile structure obtained in step e) for desizing the at least one filament composing it, then drying it.,

[0017] The at least one sized nitrocellulose filament obtained in step d) of the process is phlegmatized in combustion by the sizing coating and therefore suitable for being wound and used safely without risk of ignition with textile machines. The combustion characteristics of the at least one filament obtained in step d) are equivalent to those of a cotton-type cellulosic filament (see Table 8).

[0018] The at least one desized nitrocellulose filament constituting the textile structure obtained in step f) is classified in risk division 1.3 by equivalence of its combustion characteristics (see table 8) with those of a conventional dry nitrocellulose filament obtained directly by drying after step b) of the process.

[0019] The invention also relates to the intermediate products and the final product obtained by the process of the invention:

[0020] - the at least one sized nitrocellulose filament, and the coil obtained by steps a), b), c), and d) of the process of the invention;

[0021] - the textile structure composed of at least one sized nitrocellulose filament obtained in step e) of the process of the invention;

[0022] - the highly flammable combustible textile structure obtained in step f) by desizing (washing) the textile structure composed of at least one sized nitrocellulose filament obtained in step e) of the process; - the objects containing a textile structure of the invention.

[0023] The flammability characteristics given in Table 1 can be attributed to the products produced during the implementation of the method of the invention:

[0024] Table 1 *: by analogy of the combustion characteristics with a conventional dry nitrocellulose filament.

[0025] Brief description of the figures

[0026] Figure 1 schematically represents a device for implementing steps a) to d) of the method of the invention. Figure 2 shows a view of dry sized nitrocellulose filaments obtained in step d) before winding the method according to example 1.

[0027] Figure 3 shows coils of dry sized nitrocellulose filaments obtained in step d) of the process according to Example 1.

[0028] Figure 4 shows a pyrotechnic textile structure obtained in step f) of the process according to example 1.

[0029] Description of the invention

[0030] In the context of this application, pyrotechnic material means materials classified in hazard division 1 within the meaning of the UN GHS classification (UN Globally Harmonized System of Classification and Labelling of Chemicals), more specifically in division 1.3 for combustible pyrotechnic materials. Non-pyrotechnic material means flammable solid materials classified in hazard division 4 and flammable liquid materials classified in hazard division 3 within the meaning of the UN GHS classification. In addition, filaments are defined as very long threads (greater than ten meters up to ten kilometers) obtained by spinning a pasty mixture (for example, a viscous collodion). Textiles are defined as products obtained by knitting, weaving or braiding filaments. Textile structures are defined as functional structures formed by a textile.

[0031] In the context of the present application, the terms "sizing", "coating" and "coating" may be used interchangeably. Similarly, the terms "de-sizing" and "washing" may be used interchangeably.

[0032] The present invention therefore relates, according to one aspect, to a method for obtaining a textile forming a highly flammable combustible textile structure by textile manufacturing with at least one nitrocellulose filament.Said method comprises the following steps: a) producing a nitrocellulose collodion, b) manufacturing at least one nitrocellulose filament (generally several) according to an extrusion process by spinning the collodion carried out in step a), with passage of the at least one nitrocellulose filament in and through at least one nitrocellulose coagulation bath, c) sizing the at least one nitrocellulose filament obtained in step b) by passage in and through an aqueous solution containing a water-soluble polymeric sizing agent, d) spinning and drying the at least one sized nitrocellulose filament obtained in step c) and winding it, e) manufacturing a textile forming a textile structure by knitting, weaving or braiding with at least one sized nitrocellulose filament obtained in step d), f) chemically treating the textile structure obtained in step e) for the desizing of at least one filament composing it, then its drying.

[0033] According to another aspect, the present invention relates to a method for obtaining at least one sized nitrocellulose filament, which comprises: a) producing a nitrocellulose collodion; b) manufacturing at least one nitrocellulose filament according to an extrusion method by spinning the collodion carried out in step a), with passage of the at least one nitrocellulose filament in and through at least one nitrocellulose coagulation bath; c) sizing the at least one nitrocellulose filament obtained in step b) by passage in and through an aqueous solution containing a water-soluble polymeric sizing agent; d) spinning and drying the at least one sized nitrocellulose filament obtained in step c).

[0034] According to another aspect, the present invention relates to a method of obtaining a highly flammable combustible textile structure which comprises:

[0035] (i) knitting, weaving or braiding at least one sized nitrocellulose filament obtained according to the process described above;

[0036] (ii) the chemical treatment of the textile structure obtained in step (i) for the desizing of at least one sized nitrocellulose filament composing it, then its drying.

[0037] According to another aspect, the present invention relates to a method of manufacturing an object comprising a highly flammable combustible textile structure, which comprises obtaining a highly flammable combustible textile structure according to the method described above.

[0038] The collodions produced in step a) to obtain filaments to be extruded consist of a nitrocellulose base and a solvent. The cellulose base comprises nitrocellulose, a plasticizer, a solvent, and optionally one or more additives. Collodions of this type are described in patent application FR 3 117 399 and are classified in risk division 3 (flammable liquid).

[0039] Nitrocellulose advantageously has a nitrogen content ranging from 10.7% to 13.8%. It is nitrocellulose of grade A (10.7% to 11.3%) or AM (11.3% to 11.8%) or E and CA2 (11.8 to 12.3%), or gun cotton (> 12.3%) or a mixture of several nitrocelluloses of the same grades and / or different grades. This range covers both nitrocelluloses for industrial applications (A, AM, E, CA2) and those for military applications (gun cotton).

[0040] Examples of plasticizers include: phthalates, centralites, diethyl succinate, adipates, triacetin, organic phosphates, citrates, triethylene glycol, glycol esters, castor oil, fusel oil, glycerol-based molecules, tetrahydrofurfuryl oleate, pentaerythrityl tetrabenzoate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, trioctanoate, methyldinitramine, camphor, sucrose acetate isobutyrate, sucrose benzoatesulfoamides, urea resin, acrylic resin, polyethylene adipate-polyethylene glycol amphiphilic block copolymer, epoxidized and ethoxylated plasticizer, trioctyl trimellitate, dioctyl malate or bis(2-ethylhexyl) malate, cardanol, dimethylacetamide, butylphthalimide isopropylphthalimide, alkyl polyvinyl ethers, crosslinked polyesters, poly(E-caprolactone), urethanes and their mixtures.

[0041] The solvent is conventional: alcohols, ethers, acetates as well as ketones, for example acetone, an acetate, ether, ethanol and their mixtures, for example a double solvent of the acetone / butyl acetate type or of the ethyl lactate / butyl acetate type, or ethyl acetate alone or ethyl lactate alone. The stabilizer is of the conventional type, it can be chosen for example from alpha tocopherol, alpha ionone, polybutadiene, akardyte, 2-nitrodiphenylamine (2NDPA), l,3-diethyl-l,3-diphenyl urea (centrality I), l,3-dimethyl-l,3-diphenyl urea (centrality II), and l-methyl-3-ethyl-l,3-diphenyl urea (centrality III), and their mixtures.

[0042] The additives are typically selected from anti-adhesive agents (e.g., silicone type), anti-glare agents, antioxidants, colorants, surfactants, anti-caking agents, anti-UV agents (e.g., benzophenone or diamyl phenol type) and mixtures thereof.

[0043] In one embodiment, the viscosity of the collodion is adjusted to ensure its implementation by the extrusion-spinning process for obtaining filaments by adjusting the nitrocellulose / solvent(s) ratio according to the intrinsic viscosity of the nitrocellulose. This adjustment makes the collodion suitable for implementation by the extrusion-spinning processes. The degree of polymerization of the nitrocellulose used in the context of the invention corresponds to viscosities according to the ISO 14446 standard of 1 to 12, preferably of 1 to 7. The viscosity of the collodion, fixed by the nitrocellulose base / solvent ratio, for its implementation by the process of the invention is advantageously between 140 and 1000 Pa.s, measured at 20°C. In this viscosity range, the process of the invention can be implemented at room temperature, therefore without heating the reservoir containing the collodion and the extrusion nozzle.It is nevertheless possible to condition the collodion in a temperature range between 16°C and 26°C to adjust its viscosity optimally for the implementation of the process.

[0044] The collodion is advantageously formulated to result in a dry extract (after evaporation of the solvent) of 10% to 80% of the mass of the collodion, preferably, in a dry extract of 35% to 50%. Thus, according to one embodiment, the collodion contains the following constituents, expressed as a mass percentage:

[0045] - about 8% to about 60% nitrocellulose,

[0046] - about 1% to about 40% of at least one plasticizer,

[0047] - about 0.2% to about 2% of at least one stabilizing additive,

[0048] - 0% to approximately 0.5% of at least one additive,

[0049] - approximately 20% to approximately 90% of at least one solvent, the sum of the quantities of these constituents being equal to 100%.

[0050] The collodion to be extruded advantageously contains the following constituents, expressed as a mass percentage:

[0051] - about 24% to about 54% nitrocellulose,

[0052] - about 1% to about 40% of at least one plasticizer,

[0053] - about 0.3% to about 1% of at least one stabilizing additive,

[0054] - 0% to approximately 0.5% of at least one additive,

[0055] - approximately 35% to approximately 50% of at least one solvent, the sum of the quantities of these constituents being equal to 100%.

[0056] Collodion can be prepared as follows: in a tank (mixer type), the raw materials of the collodion are added and stirred. This step lasts between ten minutes and 4 hours, the duration depending on the selected formulation and the desired homogeneity of the collodion. The collodion is then filtered if necessary to remove impurities from the raw materials. This preparation is conveyed, if necessary, via a pump or via an endless screw or by gravity, to tanks to carry out a debubbling step (degassing) at atmospheric pressure or under vacuum (relative pressure lowered to between 0.05 and 5 bars). This pressure is maintained between 30 minutes and 4 hours to obtain a mixture without any bubbles. The collodion is conditioned at temperature in a tank so as to maintain its constant viscosity during the extrusion.The tank may also include an agitator to ensure the homogeneity of the collodion.

[0057] In the process of the invention, the masses of collodion used are approximately 8 kg per batch on a pilot scale as in the example given below and up to approximately 50 kg per batch on an industrial scale.

[0058] Step b) of the process of the invention for obtaining at least one nitrocellulose filament (generally several filaments) is carried out in a conventional manner, for example according to that described in US patent 3,256,371. The at least one nitrocellulose filament is obtained by wet spinning of the nitrocellulose collodion from step a) conveyed to an extrusion die by a pump. The diameter of the at least one orifice of the extrusion die is typically between 10 μm and 500 μm, preferably between 50 μm and 400 μm. To obtain several filaments, the extrusion die may comprise up to 1000 orifices on the pilot scale of the example given below and up to approximately 3000 orifices on an industrial scale. The volume flow rate of material at the outlet of the die is approximately 200 mL / h to approximately 450 mL / h on a pilot scale as in the example given below and up to approximately 1250 mL / h on an industrial scale.

[0059] The at least one nitrocellulose filament leaving the extrusion die passes directly into and through at least one aqueous bath known as a coagulation bath so as to set the filamentary material and remove any solvent present. The aqueous bath is an organic aqueous solution. When the structural setting liquid of the coagulation bath is a coagulation liquid composed of an organic aqueous solution, it contains a mixture of alcohol with water and optionally a ketone and / or an acetate, preferably with the following mass percentages for the various constituents:

[0060] - about 30% to about 99% alcohol,

[0061] - 0% to about 50% of a ketone,

[0062] - 0% to about 50% of an acetate,

[0063] - approximately 1% to approximately 70% water, the sum of the quantities of these constituents being equal to 100%.

[0064] Advantageously, the alcohol is isopropanol or ethanol, preferably isopropanol, the ketone is butanone or acetone, preferably acetone, the acetate may be methyl acetate or ethyl acetate, preferably ethyl acetate. When the structural setting liquid is composed of alcohol and water, the alcohol / water proportions are typically from about 50 / 50 to about 70 / 30 by volume.

[0065] The drawing ratio (ratio of the speed at the outlet of the coagulation bath with the speed at the outlet of the extrusion die) of the at least one filament is between approximately 0.5 and approximately 2, typically 0.8.

[0066] The at least one filament then passes into and through one or more washing baths consisting of water. The at least one wet nitrocellulose filament thus produced is classified in hazard division 4.1. Conventional industrial textile spinning machines can be used for this step b). The at least one filament leaving the washing bath(s) has a breaking stress of between approximately 90 MPa and approximately 150 MPa.

[0067] For step c), the at least one nitrocellulose filament from step b) is coated with an aqueous sizing liquid containing a sizing agent in solution. This coating (sizing) step is carried out using a kiss roll or by passing through an impregnation bath or by spraying. The sizing agent material in solution in the sizing bath is chosen so that after drying it phlegmatizes the combustion of said at least one nitrocellulose filament and so that it is soluble in a non-solvent for nitrocellulose, more particularly water-soluble. This type of sizing agent of the water-soluble (co)polymer type is known from the prior art, and in particular described in patent application FR 2 998 309. It involves, for example, polyvinyl alcohol (PVA), carboxymethylcelluloses (CMC), polyacrylates, water-soluble polyethers such as, for example, polyethylene glycol (PEG) or water-soluble polyesters.For the PVA sizing agent, the weighted molar mass Mw is between about 25,000 and about 195,000 g / mol, typically 31,000 g / mol with a partial hydrolysis rate between about 88 and about 98% and having a viscosity of about 4 to about 10 mPa.s in solution at 4% by mass with water, for example PVA conventionally called PVA 4-88. The diameter of a sized filament is typically about a hundred micrometers. The thickness of the peripheral sizing layer around a nitrocellulose filament is typically one tenth to one hundredth of a micrometer. The mass content of the sizing agent on the filament is between about 0.3 and about 10% of the mass of the filament.

[0068] Step d) consists of wringing and drying the at least one sized nitrocellulose filament obtained in step c) so as to dry it by evaporation of the water and other residual solvents. After drying, the at least one dry sized nitrocellulose filament has combustion properties (see Table 8) comparable to those of cellulose filaments (for example cotton). The at least one dry sized nitrocellulose filament is then wound to obtain one or more (usually several) reels.

[0069] The implementation of steps b) to d) allows production of nitrocellulose filaments typically at a speed of approximately 5 m / min to approximately 10 m / min on a pilot scale as in the example given below and at approximately 100 m / min on an industrial scale, i.e. approximately 2 kg / h on an industrial scale. For step e), the spool(s) of sized nitrocellulose filament(s) obtained in step d) is / are placed on a textile knitting, weaving or braiding machine to obtain a textile forming a textile structure. The textile structure obtained with the dry sized nitrocellulose filament(s) is phlegmatized in combustion and can be compared in terms of its flammability to a classic cellulose structure (for example cotton), equal to the at least one sized nitrocellulose filament composing it.The use of dry sized nitrocellulose filaments (phlegmatized during combustion by the sizing coating) on ​​a textile machine therefore does not create any risk of ignition.

[0070] For step f), the textile structure obtained in step e) is subjected, by impregnation in an aqueous bath, to a chemical treatment to desize the sized nitrocellulose filament(s) constituting it. The chemical treatment for desizing textile filaments sized with a water-soluble polymer is well known to those skilled in the art. In the context of the present invention, it is carried out with water which is a non-solvent for nitrocellulose. For example, the desizing treatment is carried out by impregnating said textile structure with hot water at a temperature of between approximately 10 and approximately 70°C. The duration of impregnation of said textile structure in the desizing impregnation bath naturally depends on the mass and volume of the structure; it is typically greater than approximately 5 seconds.Said structure is then dried at controlled ambient conditions (temperature, atmosphere, humidity, evaporated solvent content) in order to eliminate residual solvents, it is exposed to a temperature between approximately 18 and approximately 60°C in an oven for a given time. After this desizing and drying step, the textile structure is highly flammable, consisting of dry nitrocellulose filaments whose combustion properties are equivalent to those of conventional dry nitrocellulose filaments classified in risk division 1.3 which have not undergone the sizing and desizing steps of the process (see example and table 8). The highly flammable textile structures obtained at the end of the process of the invention are suitable, for example, for containers, structural reinforcements or assembly parts in the civil and military fields.

[0071] They can be integrated into objects, in particular military or civilian pyrotechnic objects intended to operate by combustion, such as the propulsion units of shells for tube weapons or for rockets and missiles, propellant hunting cartridges, airbag gas generators, pyrotechnic valves, thermal fuses.

[0072] Example

[0073] An example of implementation of the process of the invention and of the products obtained according to this process is given below.

[0074] Step a): Production of a nitrocellulose collodion.

[0075] The composition of the collodion chosen for the implementation of step a) of the process is given in table 2.

[0076] Table 2

[0077] The fusel oil incorporated in the collodion corresponds to the commercial reference W249715 from the company Sigma Aldrich and listed by the CAS number 8013-75-0.

[0078] The viscosity of collodion measured using a Brookfield RVT mobile viscometer No. 7 at 2.5 rpm is 500 Pa.s at a temperature of 20°C.

[0079] The collodion in Table 2 when directly dried by evaporation of the solvent leads to a dry product whose mass rates are given in Table 3.

[0080] Table 3

[0081] The device used for the following steps b) to d) of spinning, sizing and winding is shown in Figure 1.

[0082] Step b-): Manufacture of nitrocellulose filaments.

[0083] The conditions for implementing step b) of the process for obtaining nitrocellulose filaments of the invention with reference to Figure 1 are given in Table 4. Table 4

[0084] *: mass fraction 70% isopropanol / water 30%

[0085] Step c): Sizing the wet nitrocellulose filaments. Step c) of sizing the wet nitrocellulose filaments produced in step b) of the example is described below.

[0086] The sizing material for implementing step c) of the process is polyvinyl alcohol known under the reference PVA 4-88 marketed by the company Sigma Aldrich under the reference 81381. The characteristics of this material are given in table 5.

[0087] Table 5

[0088] The conditions for implementing step c) of the process of the invention with reference to Figure 1 are given in Table 6. A kiss roll is used to coat the wet nitrocellulose filaments produced in step b) with the sizing material. The lick roll rotates in its lower part in an aqueous bath containing 2% by mass of the sizing material.

[0089] Table 6

[0090] Step d): Spinning and drying of the sized nitrocellulose filaments and winding.

[0091] The conditions for implementing step d) of spinning and drying the sized nitrocellulose filaments produced in step c) and then winding according to the present example are given in table 7 with reference to figure 1.

[0092] Table 7

[0093] At the end of this step d), the dry sized nitrocellulose filaments (figure 2) have a diameter of 97.8 ± 3.9 pm (for comparison, dry nitrocellulose filaments obtained using the same process without sizing have a diameter of 97.9 ± 3.3 pm). Coils consisting of a bundle of 15 dry sized nitrocellulose filaments obtained at the end of this step d) are shown in figure 3.

[0094] The bundle of 15 filaments has a breaking stress of approximately 95 MPa for an elongation at break of approximately 16% which makes it suitable for use on a textile machine.

[0095] Step e): Manufacture of a textile forming a textile structure.

[0096] The coils of dry sized nitrocellulose filaments (phlegmatized by combustion) obtained in step d) were mounted on a multiaxial circular textile machine comprising 72 spindles to obtain the braided textile structure shown in Figure 4.

[0097] Step f): Desizing of the textile structure.

[0098] The desizing treatment of the dry sized nitrocellulose filaments forming the textile structure obtained in step e) for the final production of a highly flammable combustible textile structure is carried out by impregnating the textile structure obtained in step e) in a hot water bath at a temperature of 40°C for 30 s.

[0099] The textile structure is then extracted from the aqueous bath and dried in an oven at room temperature to obtain a highly flammable combustible textile structure. The filaments constituting the textile structure at the output of step f) of the process have combustion characteristics equivalent to conventional dry nitrocellulose filaments classified in hazard division 1.3 (see table 8).

[0100] Combustion test results:

[0101] Combustion tests (Table 8) were carried out on dry sized nitrocellulose filaments obtained in step d) of the example and on the sized and then dry desized nitrocellulose filaments according to step f) of the example. The combustion rate of the dry sized nitrocellulose filaments is approximately 5 times lower than that of the dry desized filaments. The phlegmatization effect of combustion by sizing the nitrocellulose filaments is therefore clearly observed.

[0102] For comparison, measurements were carried out on dry pyrotechnic nitrocellulose filaments classified in risk division 1.3 which had not undergone steps e) (sizing) and f) (desizing) of the process. The combustion rate obtained is identical to that measured on the desized filaments after step f) of the process (see Table 8). The desizing operation of the nitrocellulose filaments sized according to the process of the invention therefore makes it possible to restore the original combustion properties of dry pyrotechnic nitrocellulose filaments.

[0103] Table 8 The dry desized filaments at the end of step f) of the process of the invention therefore have combustion properties similar to those of the filaments obtained directly by spinning and drying the collodion in Table 2.

[0104] These results obtained on filaments are transposed to a textile structure of the invention based on nitrocellulose filaments, as shown in Figure 4, obtained according to the process of the invention.

Claims

Claims 1. A method for obtaining a highly flammable combustible textile structure which comprises: a) producing a nitrocellulose collodion; b) manufacturing at least one nitrocellulose filament using a collodion spinning extrusion process carried out in step a), with passage of the at least one nitrocellulose filament into and through at least one nitrocellulose coagulation bath; c) sizing the at least one nitrocellulose filament obtained in step b) by passage into and through an aqueous solution containing a water-soluble polymeric sizing agent; d) spinning and drying the at least one sized nitrocellulose filament obtained in step c), and winding it; e) manufacturing a textile forming a textile structure by knitting, weaving or braiding with at least one sized nitrocellulose filament obtained in step d);f) the chemical treatment of the textile structure obtained in step e) for the desizing of at least one sized nitrocellulose filament composing it, then its drying.; 2. Method according to claim 1, in which the collodion contains the following constituents, expressed as a mass percentage: - 8% to 60% nitrocellulose, - 1% to 40% of at least one plasticizer, - 0.2% to 2% of at least one stabilizing additive, - 0% to 0.5% of at least one additive, - 20% to 90% of at least one solvent, the sum of the quantities of these constituents being equal to 100%.

3. Method according to one of claims 1 and 2, in which the coagulation bath is composed of an organic aqueous solution, containing the following constituents, expressed as a mass percentage: - 30% to 99% alcohol, - 0% to 50% of a ketone, - 0% to 50% of an acetate, - 1% to 70% water, the sum of the quantities of these constituents being equal to 100%.

4. Method according to one of claims 1 to 3, in which the water-soluble polymeric sizing agent is a polyvinyl alcohol, a carboxymethylcellulose polymer, a polyacrylate, a water-soluble polyether or a water-soluble polyester.

5. Method according to one of claims 1 to 4, in which the mass rate of the sizing agent on the filament is between 0.3 and 10% relative to the mass of the filament.

6. Method according to one of claims 1 to 5, in which the desizing treatment according to step f) is carried out by impregnating the textile structure with hot water at a temperature between 10 and 70°C.

7. Sized nitrocellulose filament obtained by steps a), b), and c) of the process according to claim 1.

8. Spool of sized nitrocellulose filament(s) obtained by step d) of the process according to claim 1.

9. Textile structure consisting of at least one sized nitrocellulose filament according to claim 7.

10. Highly flammable combustible textile structure obtained by applying step f) of the method according to claim 1 to a textile structure according to claim 9.

11. Object containing a highly flammable combustible textile structure according to claim 10.

12. Process for obtaining at least one sized nitrocellulose filament, which comprises: a) producing a nitrocellulose collodion; b) manufacturing at least one nitrocellulose filament using a collodion spinning extrusion process carried out in step a), with passage of the at least one nitrocellulose filament into and through at least one nitrocellulose coagulation bath; c) sizing the at least one nitrocellulose filament obtained in step b) by passage into and through an aqueous solution containing a water-soluble polymeric sizing agent; d) spinning and drying the at least one sized nitrocellulose filament obtained in step c).

13. A process for obtaining a highly flammable combustible textile structure which comprises: (i) knitting, weaving or braiding at least one sized nitrocellulose filament obtained according to the process of claim 12; (ii) the chemical treatment of the textile structure obtained in step (i) for the desizing of at least one sized nitrocellulose filament composing it, then its drying.

14. A method of manufacturing an object containing a highly flammable combustible textile structure, which comprises obtaining a highly flammable combustible textile structure according to the method of claim 13.

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