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

Abstract

The present invention relates to a method for obtaining a highly flammable combustible textile structure which comprises: a) producing a nitrocellulose collodion, b) manufacturing at least one nitrocellulose filament by extrusion by spinning the collodion produced 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 sizing agent, d) spinning and drying the at least 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. Figure 1.,

Description

Title of the invention: Process for obtaining combustible textile structures based on nitrocellulose, combustible textile structures and combustible objects containing them. Field of invention

[0001] 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. State of the art

[0002] 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.

[0003] US Patent 2,991,168 describes nitrocellulose filaments and their method of production. The composition of the filaments is approximately 79.9% to 99% nitrocellulose having a nitrogen content of 12.6% to 13.25%, and approximately 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 of the triethylene glycol dinitrate (TEGN) or diethylene glycol dinitrate (DEGN) type. These conventional nitrocellulose filaments are classified in the dry state in hazard division 1.3.

[0004] The filaments or bundles of filaments are obtained by dry spinning or wet spinning processes with spinning machines which 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 non-woven fabric similar to paper to obtain a structure.

[0005] 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. Glass fiber coatings give the fibers lubricating properties (fining 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 nitrocellulose filaments.

[0006] 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.

[0007] 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 3,304,867 do not give any examples and these are only prospective descriptions.

[0008] 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.

[0009] Furthermore, in the textile field, we know the new developments of so-called "technical" textiles which find their application in the sectors of 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.). We also know the new textile processes called "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 sport. 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 exploratory in the field of art architecture at the Delft University of Technology in the Netherlands. Many 3D structure manufacturing machines are commercially available, including those offered 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 the 3D manufacturing of textile structures is therefore established and could be advantageously implemented to obtain highly flammable combustible textile structures.However, the mechanical stresses applied to the filaments by the implementation of these methods are high and incompatible with their use with pyrotechnic materials, such as dry nitrocellulose filaments described in the prior art.

[0010] 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 respect to the pyrotechnic risk with nitrocellulose filaments for obtaining highly flammable combustible textile structures. Summary of the invention

[0011] 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.

[0012] The textile structures of the invention are generally made up of several knitted and / or woven and / or braided nitrocellulose filaments, but can also, in the case of an integral textile manufacturing process, be made up of a single nitrocellulose filament.

[0013] The method for obtaining a highly flammable combustible nitrocellulose textile structure according to the invention comprises:

[0014] a) the production of a nitrocellulose collodion,

[0015] b) the manufacture of at least one nitrocellulose filament (generally several) according to 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,

[0016] c) sizing the at least one nitrocellulose filament obtained in step b) by passing it into and through an aqueous solution containing a water-soluble polymeric sizing agent,

[0017] d) wringing and drying the at least one sized nitrocellulose filament obtained in step c), and its winding,

[0018] e) manufacturing a textile forming a textile structure by knitting, weaving or braiding with at least one sized nitrocellulose filament obtained in step d),

[0019] f) the chemical treatment of the textile structure obtained in step e) for the desizing of at least one filament composing it, then its drying.

[0020] 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 cellulose filament (see table 8).

[0021] 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.

[0022] The invention also relates to the intermediate products and the final product obtained by the process of the invention:

[0023] - the at least one sized nitrocellulose filament, and the coil obtained by the steps a), b), c), and d) of the method of the invention;

[0024] - the textile structure composed of at least one sized nitrocellulose filament obtained in step e) of the process of the invention;

[0025] - 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;

[0026] - objects containing a textile structure of the invention.

[0027] The flammability characteristics given in Table 1 can be attributed to the products produced during the implementation of the method of the invention:

[0028] [Tables 1] Process steps Products Flammability characteristics a Nitrocellulose collodion Hazard division 3 (flammable liquid) b Wet nitrocellulose filament Hazard Division 4.1 (flammable solid) c and d Dry sized nitrocellulose filament Equivalent to those of a cotton-type cellulosic material e Textile structure composed of one or more dry sized nitrocellulose filaments Equivalent to those of a cotton-type cellulosic material f Textile structure composed of one or more desized nitrocellulose filaments Highly flammable consisting of at least one nitrocellulose filament of Hazard Division 1.3 (*)

[0029] *: by analogy of the combustion characteristics with a nitrocellulose filament conventional dry. Brief description of the figures

[0030] [Fig. 1] schematically represents a device for implementing steps a) to d) of the method of the invention.

[0031] [Fig.2] shows a view of dry sized nitrocellulose filaments obtained in step d) before winding in the process according to example 1.

[0032] [Fig.3] shows coils of dry sized nitrocellulose filaments obtained in step d) of the process according to example 1.

[0033] [Fig.4] shows a pyrotechnic textile structure obtained in step f) of the process according to example 1. Description of the invention

[0034] In the context of the present application, pyrotechnic material is understood to mean materials classified in risk division 1 within the meaning of the UN GHS classification (UN Globally Harmonized System of Classification and Labeling of Chemicals), more particularly in division 1.3 for combustible pyrotechnic materials. Non-pyrotechnic material is understood to mean flammable solid materials classified in risk division 4 and flammable liquid materials classified in risk division 3 within the meaning of the UN GHS classification. In addition, filaments are defined as very long threads (greater than about ten meters up to about ten kilometers) obtained by spinning a pasty mixture (for example a viscous collodion). Textile is defined as products obtained by knitting, weaving or braiding filaments. Textile structure is defined as functional structures formed by a textile.

[0035] 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.

[0036] The present invention therefore relates, according to a first 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:

[0037] a) the production of a nitrocellulose collodion,

[0038] b) the manufacture of at least one nitrocellulose filament (generally several) according to 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,

[0039] c) sizing the at least one nitrocellulose filament obtained in step b) by passing it into and through an aqueous solution containing a water-soluble polymeric sizing agent,

[0040] d) wringing and drying the at least one sized nitrocellulose filament obtained in step c) and its winding,

[0041] e) manufacturing a textile forming a textile structure by knitting, weaving or braiding with at least one sized nitrocellulose filament obtained in step d),

[0042] f) the chemical treatment of the textile structure obtained in step e) for the desizing of at least one filament composing it, then its drying.

[0043] The collodions produced in step a) for obtaining 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).

[0044] The nitrocellulose advantageously has a nitrogen content ranging from 10.7% to 13.8%. This 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 powder 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 (powder cotton).

[0045] Examples of plasticizers that may be mentioned are: phthalates, centrals, 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, amphiphilic polyethylene adipate-polyethylene glycol 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), methanes and mixtures thereof.

[0046] 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 even ethyl acetate alone or ethyl lactate alone.

[0047] The stabilizer is of 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 mixtures thereof.

[0048] The additives are typically chosen from anti-adhesive agents (of the silicone type, for example), anti-glare agents, antioxidants, colorants, surfactants, anti-agglomeration agents, anti-UV agents (for example of the benzophenone or diamyl phenol type) and mixtures thereof.

[0049] 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.

[0050] 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%.

[0051] Thus, according to one embodiment, the collodion contains the following constituents, expressed as a mass percentage:

[0052] - about 8% to about 60% nitrocellulose,

[0053] - about 1% to about 40% of at least one plasticizer,

[0054] - about 0.2% to about 2% of at least one stabilizing additive,

[0055] - 0% to about 0.5% of at least one additive,

[0056] - about 20% to about 90% of at least one solvent,

[0057] the sum of the quantities of these constituents being equal to 100%.

[0058] The collodion to be extruded advantageously contains the following constituents, expressed as a mass percentage:

[0059] - about 24% to about 54% nitrocellulose,

[0060] - about 1% to about 40% of at least one plasticizer,

[0061] - about 0.3% to about 1% of at least one stabilizing additive,

[0062] - 0% to about 0.5% of at least one additive,

[0063] - about 35% to about 50% of at least one solvent,

[0064] the sum of the quantities of these constituents being equal to 100%.

[0065] Collodion can be prepared in the following way: 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 in order 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 in order 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 ensuring the homogeneity of the collodion.

[0066] 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.

[0067] 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. For obtaining 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 the scale industrial. 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.

[0068] The at least one nitrocellulose filament which leaves the extrusion die passes directly into and through at least one aqueous bath called a coagulation bath so as to set the filamentary material and to 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 different constituents:

[0069] - about 30% to about 99% alcohol,

[0070] - 0% to about 50% of a ketone,

[0071] - 0% to about 50% of an acetate,

[0072] - about 1% to about 70% water,

[0073] the sum of the quantities of these constituents being equal to 100%.

[0074] 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 about 50 / 50 to about 70 / 30 by volume.

[0075] 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.

[0076] 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. Industrial spinning machines for conventional textiles can be used for this step b).

[0077] The at least one filament leaving the washing bath(s) has a breaking stress of between approximately 90 MPa and approximately 150 MPa.

[0078] 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 the 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. These are, for example, polyvinyl alcohol (PVA), carbomethylcelluloses (CMC), polyacrylates, water-soluble polyethers such as polyethylene glycol (PEG) or water-soluble polyesters. For the PVA sizing agent, the weighted molar mass Mw is between approximately 25,000 and approximately 195,000 g / mol, typically 31,000 g / mol with a partial hydrolysis rate of between approximately 88 and approximately 98% and having a viscosity of approximately 4 to approximately 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 rate of the sizing agent on the filament is between approximately 0.3 and approximately 10% of the mass of the filament.

[0079] 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 (generally several) reels.

[0080] 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.

[0081] For step e), the coil(s) of coated 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 coated nitrocellulose filament(s) is phlegmatized in combustion and can be compared in terms of its flammability to a conventional cellulosic structure (for example cotton), equal to the at least one sized nitrocellulose filament composing it. The use of dry sized nitrocellulose filaments (phlegmatized in combustion by the sizing coating) on ​​a textile machine therefore does not generate any risk of ignition.

[0082] 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 coated nitrocellulose filament(s) constituting it. The chemical treatment for desizing textile filaments sized with a water-soluble polymer is well known in the skilled person. 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 between approximately 10 and approximately 70°C. The duration of impregnation of said textile structure in the desizing impregnation bath obviously depends on the mass and volume of the structure, it is typically greater than approximately 5s. Said structure is then dried at controlled ambient temperature (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.

[0083] 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. Example

[0084] An example of implementation of the process of the invention and of the products obtained according to this process is given below.

[0085] Step a): Production of a nitrocellulose collodion.

[0086] The composition of the collodion used for implementing step a) of the process is given in table 2.

[0087] [Tables2] Collodion Components % by mass Nitrocellulose Base Nitrocellulose Type E7 30 Fusel Oil 25 Solvent Ethyl Acetate 45 Total 100

[0088] 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.

[0089] The viscosity of the collodion measured using a Brookfield RVT mobile viscometer No. 7 at 2.5 rpm is 500 Pa.s at a temperature of 20°C.

[0090] The collodion of Table 2 when directly dried by evaporation of the solvent leads to a dry product whose mass rates are given in Table 3.

[0091] [Tables3] % by mass Nitrocellulose type E7 54.5 Fusel oil 45.5 % by mass residual of the quantity of solvent constituting the collodion remaining in the dry structure Residual solvent <2%

[0092] The device used for the following steps b) to d) of spinning, sizing and winding is shown in [Fig.l].

[0093] Step b): Manufacture of nitrocellulose filaments.

[0094] The conditions for implementing step b) of the process for obtaining nitrocellulose filaments of the invention with reference to [Fig.l] are given in table 4.

[0095] [Tables4] Ref. to Figure 1 Process step b) Adjustment parameters s Values ​​Al Die and collodion extrusion nozzle Number of orifices Diameter of orifices Mass flow rate 15,200 pm 245 mL / h B1 Coagulation bath Volume Composition Temperature Drawing rate 70 L Isopropanol / water * 20°C 0.8 RI Roller Speed ​​7 m / min B2 Washing bath no. 1 Volume Composition Temperature 60 L Water ~ 20°C R2 Roller Speed ​​7.5 m / min B3 Washing bath no. 2 Volume 60 L Composition Temperature Water ~ 20°C R3 Roller Speed ​​7.7 m / min

[0096] *: mass fraction 70% isopropanol / water 30%

[0097] Step c): Sizing of the wet nitrocellulose filaments.

[0098] Step c) of sizing the wet nitrocellulose filaments produced in step b) of the example is described below.

[0099] 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.

[0100] [Tables5] Characteristics of the sizing material MW values ​​31,000 g / mol % hydrolysis 88% Standard viscosity at a concentration of 4% mass in water 4 mPa.s

[0101] The conditions for implementing step c) of the process of the invention with reference to [Fig.l] 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.

[0102] [Tableauxô] Ref. to Figure 1 Step c) of the process Adjustment parameters Values ​​Ml Licking roller Sizing bath Temperature Rotation speed 98% water / 2% PVA ~ 20°C 20 rpm

[0103] Step d): Spinning and drying of the sized nitrocellulose filaments and winding.

[0104] 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 [Fig.l].

[0105] [Tables7] Ref. to Figure 1 Step d) of the process Adjustment parameters Values Tl Temperature-regulated tunnel Temperature Length ~ 20°C 180 cm R4 and R5 Motorized heating rollers Temperature Speed ​​Exposure time at filament temperature 80°C 7.8 m / min ~ 20 s R6 Motorized roller Speed ​​7.8 m / min B Reel Winding speed 7.8 m / min

[0106] At the end of this step d), the dry sized nitrocellulose filaments ([Fig.2]) have a diameter of 97.8 ± 3.9 pm (for comparison, dry nitrocellulose filaments obtained according to 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 [Fig.3].

[0107] 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.

[0108] Step e): Manufacture of a textile forming a textile structure.

[0109] 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 [Fig.4],

[0110] Step D: Desizing of the textile structure.

[0111] 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.

[0112] 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 outlet of step f) of the process have combustion characteristics equivalent to conventional dry nitrocellulose filaments classified in risk division 1.3 (see table 8).

[0113] Results of combustion tests:

[0114] Combustion tests (Table 8) were carried out on dry sized nitrocellulose filaments obtained in step d) of the example and on the dry sized and then 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.

[0115] 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. The desizing operation of the sized nitrocellulose filaments according to the process of the invention therefore makes it possible to restore the original combustion properties of dry pyrotechnic nitrocellulose filaments.

[0116] [Tables8] Type of filament Combustion speed Dry sized nitrocellulose filament (step d) 42 mm / s Dry desized nitrocellulose filament (step f) 225 mm / s Dry unsized nitrocellulose filament (Hazard Division 1.3) 225 mm / s

[0117] 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 of Table 2.

[0118] These results obtained on filaments are transposed to a textile structure of the invention based on nitrocellulose filaments, as shown in [Fig.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. Process according to claim 1, in which the collodion contains the following constituents, expressed as a mass percentage: - 8% to 60% of 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% of alcohol, - 0% to 50% of a ketone, - 0% to 50% of an acetate, - 1% to 70% of water, the sum of the quantities of these constituents being equal to 100%.

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11. Method according to one of claims 1 to 3, in which the water-soluble polymeric sizing agent is a polyvinyl alcohol, a carbomethylcellulose polymer, a polyacrylate, a water-soluble polyether or a water-soluble polyester. 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. 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. Sized nitrocellulose filament obtained by steps a), b), and c) of the process according to claim 1. Spool of shrunken nitrocellulose filament(s) obtained by step d) of the method according to claim 1. Textile structure consisting of at least one sized nitrocellulose filament according to claim 7. 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. An object containing a highly flammable combustible textile structure according to claim 10.

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