EP4617252A1 - Drop set for initiating a gas-generating charge - Google Patents

Abstract

The present invention relates to a liquid-applied ignition composition for a system for providing a pyrotechnic energy release, comprising a pyrotechnic material embedded in a matrix which reacts pyrotechnically at a material-specific reaction temperature, wherein the matrix is formed by a water-dispersible organic polymer.

Description

The present invention relates to a liquid-applied igniter composition for a system for providing a pyrotechnic energy release, as well as to such a system for providing a pyrotechnic energy release. Such a system comprises, for example, a pyrotechnic separating device or a fast-acting actuation mechanism, e.g., for an emergency exit or fire door. Furthermore, the present invention relates to a liquid-applied dispersion for forming an igniter composition. Finally, the present invention also relates to a manufacturing method for a liquid-applied igniter composition.

Systems for providing pyrotechnic energy release may comprise a pyrotechnic drive with, for example, an electrical or thermal trigger and an actuating mechanism that can be pyrotechnically operated by the pyrotechnic drive, such as a capping mechanism or an accelerable piston. For example, the pyrotechnic drive comprises an ignition charge housed in a housing that can be initiated by an electrical trigger unit. The trigger unit may be designed as an electrical ignition bridge carrier according to EP 0248977 A1 The ignition bridge carrier comprises a glass or ceramic body inserted into a metallic outer ring, into which the current-conducting contact sections are embedded and on the side of which an ignition bridge is formed facing the ignition charge. A current pulse heats the ignition bridge and initiates the ignition charge, resulting in a pyrotechnic reaction. It is known to supplement such a trigger element with an additional charge. to supplement by arranging another pyrotechnic substance in such a way that the pyrotechnic conversion of the ignition charge affects the additional charge in order to generate a pyrotechnic gas expansion which is used for an intended purpose of the system, such as accelerating a piston or a cutting mechanism.

A powder-based ignition charge has proven to be disadvantageous for various applications, as the pyrotechnic implementation could not be ensured reliably enough when the system is exposed to external conditions with very low temperatures and/or high accelerations, for example, as in the aerospace industry.

Another known alternative is to apply the ignition charge in a pressed form to the glass feedthrough, also called the ignition bridge carrier. However, from a manufacturing perspective, the production of the ignition bridge has proven difficult.

Furthermore, it is also already known from the prior art to apply the primer charge in a matrix that is liquid at the time of processing, as a so-called drip-coating, to the glass feedthrough supporting the ignition bridge. After curing, in particular through evaporation of the solvent of the liquid matrix, the primer charge is evenly embedded in the matrix. It is known to use PMMA (polymethyl methacrylate) as the matrix material, which can first be dissolved in a sufficient amount of the solvent, which can be n-butyl acetate, to ensure, on the one hand, a uniform distribution of the primer charge therein and, on the other hand, a reproducible drip-coating of the primer charge.

This process presents several problems. Firstly, the resulting droplet is very viscous and difficult to accurately dose using a dispensing system. Secondly, it has been determined that after curing, the resulting droplet exhibits significant shrinkage of up to 30% of its total volume. This, in turn, results in the droplet detaching from the surface of the glass feedthrough, making it difficult to fix the droplet. is significantly weakened. This results in reduced mechanical stability, which can lead to failure during functional testing, meaning the system cannot reliably fulfill its intended function.

Furthermore, disadvantages have been identified during storage, especially at low temperatures of, for example, -40°C. These can lead to a further weakening of the fixation of the drip set to the glass feedthrough or to a complete detachment of the drip set.

An object of the present invention is to overcome the disadvantages of the prior art, in particular to provide a liquid-applicable drip set for a system for pyrotechnic energy release, which can be dosed more precisely and/or has better mechanical properties, in particular with regard to the strength and longevity of the fixation to a surface.

The problem is solved by the subject matter of independent claim 1.

The object is achieved in particular by a liquid-applied ignition composition for a system for providing pyrotechnic energy release, comprising a pyrotechnic material embedded in a matrix that undergoes pyrotechnic conversion at a material-specific conversion temperature. According to the invention, the matrix is formed by a water-dispersible organic polymer.

A pyrotechnic reaction can be understood as a specific reaction of the pyrotechnic material in which a controlled combustion or explosion occurs. Suitable pyrotechnic materials include primary explosives, as well as those described in the publication EP 1 890 986 B1 , which includes the international patent application WO 2006/128910 which are to be incorporated by reference into the disclosure content of the present invention.

A "copolymer" according to the present invention is understood to mean a polymer consisting of at least two different monomer units Preferably, a copolymer according to the invention comprises at least 2, 5, 10, 50, 100, 500, 1000 or more repeating units of the at least two different monomer units. A copolymer comprises a substance, in particular a chain-like substance, which is obtainable or obtained as a product from a polymerization reaction between at least two different monomer molecules. The term "polymer" usually refers to large molecules, for example molecules with a molecular weight greater than 1000 D, preferably greater than 5000 D, i.e. macromolecules composed of a large number of repeating smaller chemical units, in particular monomer units.

In an exemplary embodiment of the present invention, the polymer comprises a vinyl ester copolymer. In this context, a vinyl ester copolymer according to the present invention comprises both a polymer comprising a vinyl ester monomer unit and at least one other monomer unit different therefrom, and a product from a polymerization reaction, in particular from a radical polymerization reaction, between a vinyl ester monomer molecule and at least one other monomer molecule different therefrom.

According to the present invention, the term "vinyl ester monomer" refers to a monomer unit having the chemical formula (I). where R is an alkyl, preferably a C _1-8 alkyl, more preferably an alkyl selected from the group consisting of methyl, ethyl, and propyl. R is preferably methyl.

The term "alkyl" refers to any straight or branched carbon group, such as methyl, ethyl, isopropyl, n-propyl, 2-butyl, isobutyl, n-butyl, pentyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-Methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1-ethyl-1-methylpropyl, or 1-ethyl-2-methylpropyl. Alkyl preferably refers to a carbon group having—unless otherwise stated—1 to 8 (C _1-8 alkyl), in particular 1 to 6 (C _1-6 alkyl), and preferably 1 to 4 (C _1-4 alkyl) carbon atoms. In some embodiments, methyl is preferred.

Examples of a vinyl ester monomer are a vinyl acetate monomer, vinyl propionate monomer, vinyl butyrate monomer, vinyl valerate monomer and vinyl hexanoate monomer and mixtures thereof.

In a particularly preferred embodiment according to the present invention, the at least one other monomer unit and/or at least one other monomer molecule does not comprise an acrylate monomer unit.

According to the present invention, the term "vinyl acrylate monomer" refers to a monomer unit having the chemical formula (II). where R is an alkyl, preferably a C _1-6 alkyl, more preferably a methyl.

In a preferred embodiment according to the present invention, the vinyl ester monomer unit and/or the monomer molecule comprises 2 to 6 carbon atoms, in particular vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate and vinyl hexanoate or a mixture thereof.

For example, vinyl ester copolymer, vinyl acetate copolymer, vinyl propionate copolymer, vinyl butyrate copolymer, vinyl valerate copolymer and vinyl hexanoate copolymer or a mixture thereof.

In a preferred embodiment, the vinyl ester copolymer according to the present invention comprises a vinyl acetate copolymer, in particular the vinyl ester copolymer consists of a vinyl acetate copolymer.

According to an exemplary development, the proportion of vinyl ester monomers in the vinyl ester copolymer is at least 10 wt.%, preferably at least 20 wt.%, preferably at least 30 wt.%, preferably at least 40 wt.%, preferably at least 50 wt.%, preferably at least 60 wt.%, preferably at least 70 wt.%, preferably at least 80 wt.%, preferably at least 90 wt.%, in each case based on the total weight of the vinyl ester copolymer.

In a particularly preferred embodiment according to the present invention, the at least one other monomer unit and/or at least one other monomer molecule comprises an ethylene monomer unit. In this context, the vinyl ester copolymer according to the invention comprises a vinyl ester and an ethylene copolymer.

For example, vinyl ester and ethylene copolymer, vinyl acetate and ethylene copolymer, vinyl propionate and ethylene copolymer, vinyl butyrate and ethylene copolymer, vinyl valerate and ethylene copolymer and vinyl hexanoate and ethylene copolymer or a mixture thereof.

In a particularly preferred embodiment, the vinyl ester copolymer comprises a vinyl acetate and ethylene copolymer, in particular the vinyl ester copolymer consists of a vinyl acetate and ethylene copolymer.

According to an exemplary development, the proportion of the ethylene monomer unit in the vinyl ester copolymer is at least 10 wt.%, preferably at least 20 wt.%, preferably at least 30 wt.%, preferably at least 40 wt.%, preferably at least 50 wt.%, preferably at least 60 wt.%, preferably at least 70 wt.%, preferably at least 80% by weight, preferably at least 90% by weight, each based on the total weight of the vinyl ester copolymer.

In a particularly preferred embodiment, the vinyl ester copolymer according to the present invention comprises or consists of ADHESIN A 7032.

A processable, not yet cured matrix of the present invention can be formed from the polymer of the present invention and water. The ignition composition of the invention comprises the matrix of the present invention and a pyrotechnic material. In a particularly preferred embodiment of the invention, the pyrotechnic material is embedded in the matrix.

The term "water" as used in the present application includes both tap water and deionized water, in particular deionized water with a conductivity of at most 0.06 µS · cm ^-1 .

In a preferred embodiment, the processable matrix according to the present invention has a vinyl ester copolymer concentration of, for example, 15 wt.% to 45 wt.%, or, more preferably, 20 wt.% to 40 wt.%, or, more preferably, 25 wt.% to 35 wt.%, or even more preferably, 30 wt.%, in each case based on the total weight of the matrix. In this context, the matrix according to the present invention has a water concentration of, for example, 85 wt.% to 55 wt.%, or, more preferably, 80 wt.% to 60 wt.%, or, more preferably, 75 wt.% to 65 wt.%, or even more preferably, 70 wt.%, in each case based on the total weight of the matrix in the as-processed state. The term "as-processed state," as used herein, refers to the state prior to curing in which the materials are still processable or applicable.

In this context, the cured primer composition according to the present invention may, for example, contain 65 wt% to 85 wt% or, more preferably, 70 wt% to 80 wt% or even more preferably 75 wt% pyrotechnic material according to the present invention, in each case based on the total weight of the ignition charge. In this context, in another preferred embodiment, the ignition charge according to the present invention may comprise, for example, 35 wt.% to 15 wt.% or, more preferably, 30 wt.% to 20 wt.% or even more preferably 25 wt.% of the cured matrix according to the present invention, in each case based on the total weight of the cured ignition charge.

In a preferred embodiment, the primer charge is designed to shrink by less than 10%, in particular by less than 7.5% or less than 5%, upon curing. The term "shrinkage" is to be understood particularly in connection with the curing of the liquid-applied primer charge, e.g., through evaporation of the solvent, and refers to the reduction in the volume or mass of the primer charge during the curing or evaporation process. As a result, the primer charge according to the present invention is mechanically stable and/or characterized by high mechanical flexibility. Furthermore, due to the low shrinkage, the primer charge detaches less from the substrate.

Due to the physical and chemical properties of the above-described composition, the primer composition according to the present invention is more reliable than conventional primers, such as primers in a PMMA matrix, even under extreme conditions such as low temperatures. The following section will demonstrate that the primer composition according to the invention exhibits higher wetting power, adheres better to the surface of a substrate, and undergoes much less physical change during curing, particularly significantly less shrinkage.

A further advantage of the present invention was identified as the pronounced flexibility of the matrix, particularly compared to a PMMA-containing matrix known from the prior art. Samples of the matrix materials with diameters of 38 mm and thicknesses of approximately 1.5 mm were prepared experimentally. After curing, the samples were subjected to a force-displacement test. In this test, a chisel with rounded edges was pressed into the PMMA specimen. It was observed that a penetration depth of 0.5 mm required five to ten times the force required.

For example, the ignition charge exhibits high mechanical stability, being designed to withstand the mechanical stresses encountered during storage, transport, and standardized testing of the entire system (such as the impact force following a free fall from a height of at least 12 m and/or an acceleration of several thousand g), as well as during use. In contrast, conventional matrix materials, such as those containing PMMA, are more brittle and therefore detach from the carrier material and/or shatter.

In this context, in an exemplary embodiment, the cured primer charge is flexible and/or can be mechanically processed, in particular partially mechanically removed, while adhering to a surface without causing damage. The flexibility of the cured primer charge prevents, for example, chipping or crumbling.

In a further exemplary embodiment, the ignition charge according to the present invention is characterized by unrestricted adhesion to the surface of the carrier material at temperatures of down to -40°C, or more preferably down to -45°C, or even more preferably down to -50°C. In other words, the ignition charge adheres reliably and/or for a long period of time to the surface of the carrier material even under the specified conditions. The surface of the carrier material according to the present invention comprises, in particular, a metal surface, such as a steel, nickel, chromium, or tantalum surface, and/or a glass or ceramic surface. A pyrotechnic propulsion device comprising the ignition charge according to the present invention exhibits a lower failure rate under extreme climatic conditions, particularly during storage at temperatures well below 0°C.

In a further exemplary embodiment, the ignition charge is designed to have a metal surface, such as a steel, nickel, chromium or tantalum surface, and/or to wet a glass or ceramic surface, especially at a relative humidity of at least 40%, preferably 50%. Wetting of the surface refers in particular to the ability of the liquid igniter to distribute evenly over the surface and, in particular, to form a coherent layer.

In a further preferred embodiment, the ignition charge according to the present invention is free from a lacquer coating, in particular a lacquer coating that is applied after the ignition charge has hardened.

According to a further preferred embodiment, the ignition charge is designed to be applied by means of a dosing device, in particular one operated by compressed air, wherein in particular the dosing device has a cannula with an inner diameter of less than 1 mm, in particular of less than 0.8 mm or of approximately 0.6 mm.

According to a further aspect of the present invention, which can be combined with the preceding aspects and exemplary embodiments, a liquid-applicable dispersion is provided for a system for providing a pyrotechnic energy release. The dispersion according to the invention comprises a water-dispersible organic polymer, such as a vinyl ester copolymer, water, and a pyrotechnic material that undergoes pyrotechnic reaction at a material-specific reaction temperature. In the context of a water-dispersed polymer, the term "dispersion" can refer to a homogeneous mixture in which the water-dispersible organic polymer is dispersed in the water in the form of small particles or molecules. This mixture is formed by dispersing the polymer in water, with the polymer molecule typically being present in finely divided form.

According to a further aspect of the present invention, the dispersion is low-viscosity. "Low-viscosity" refers in particular to a low viscosity. Viscosity is a measure of the flowability or viscosity of a fluid, with a low-viscosity fluid having low viscosity and flowing easily.

According to an exemplary embodiment of the present invention, the water-dispersible organic polymer comprises a vinyl ester copolymer, in particular a vinyl acetate copolymer.

According to a further exemplary embodiment of the present invention, the water-dispersible organic polymer comprises a vinyl ester copolymer comprising, in particular consisting of, a vinyl acetate and ethylene copolymer.

In a preferred embodiment, the dispersion according to the present invention has a polymer concentration of, for example, 15 wt% to 45 wt%, or, more preferably, 20 wt% to 40 wt%, or, more preferably, 25 wt% to 35 wt%, or even more preferably 30 wt%, in each case based on the total weight of the polymer and the water. In this context, the matrix according to the present invention has a water concentration of, for example, 85 wt% to 55 wt%, or, more preferably, 80 wt% to 60 wt%, or, more preferably, 75 wt% to 65 wt%, or even more preferably 70 wt%, in each case based on the total weight of the polymer and the water.

In an exemplary embodiment according to the present invention, the vinyl ester copolymer and/or the monomer molecules that have not reacted to form the vinyl ester copolymer are water-dispersible. The term "water-dispersible," as used in this application, is understood to mean something capable of forming a homogeneous liquid mixture or dispersion with water.

According to a further exemplary embodiment, the dispersion has a viscosity at room temperature of at most 2 Pa s, in particular of at most 1.8 Pa s or at most 1.5 Pa s. It has been found that the dispersion with the specified viscosity, in particular up to the specified viscosity limit, is particularly advantageous for the purposes of the invention, especially with regard to the dosage of the ignition charge on the surface to be applied.

According to a further aspect of the present invention, which can be combined with the preceding aspects and exemplary embodiments, a method for producing an ignition charge, in particular according to the invention, is provided, in which the ignition charge is formed by curing a dispersion, in particular according to the invention, of a water-dispersible organic polymer, in particular a vinyl ester copolymer, water, and a pyrotechnic material. According to an exemplary development, a low-viscosity dispersion is used.

The term "curing," as used in the present application, can refer to a process in which the dispersion according to the present invention hardens to form the primer composition according to the invention. This process can, in particular, be a physical reaction, such as solvent evaporation.

According to a preferred embodiment, curing occurs through water evaporation. In this context, the dispersion has a higher water concentration than the primer charge before curing. Furthermore, the dispersion has a vinyl ester copolymer concentration in the range of 7 wt.% to 8 wt.%, a water concentration in the range of 17 wt.% to 18 wt.%, and/or a pyrotechnic material concentration in the range of 74 wt.% to 76 wt.%, each based on the total weight of the dispersion.

It has proven advantageous for the dispersion to be thin and thus suitable for application using a dosing device, particularly one powered by compressed air. The thin consistency allows for better handling of the dosing system.

In a further preferred embodiment of the method according to the present invention, the ignition charge is applied by means of a dosing device, in particular one powered by compressed air. The dosing device has, in particular, a cannula with an inner diameter of less than 1 mm, in particular less than 0.8 mm or approximately 0.6 mm.

In a further preferred embodiment of the method according to the present invention, the primer charge is cured after application, in particular after application to a surface, in particular a metal surface, such as a steel, nickel, chromium, or tantalum surface, and/or a glass or ceramic surface. According to an exemplary development, the primer charge is designed such that curing occurs by evaporation and that the primer charge adheres to the surface after curing.

In a further preferred embodiment according to the present invention, the dispersion shrinks upon curing by less than 10%, in particular by less than 7.5% or by less than 5%, in each case based on the total volume of the applied dispersion. Due to the constant volume during curing, the primer composition according to the present invention maintains better contact with the surface. The term "shrinkage" is to be understood particularly in connection with the curing or evaporation of the liquid-applied primer composition and refers to the reduction in the volume or mass of the primer composition during the curing or evaporation process.

In particular, the primer composition uses water as the solvent instead of an organic solvent. It has been found that water evaporates more slowly in air than the previously used organic solvent. This, along with the chemical and physical properties and resulting increased flexibility of the water-dispersible polymer used, results in less change in the shape and volume of the primer composition during curing, allowing shrinkage of less than 10% to be achieved according to the present invention. This also prevents dangerous explosive residues from remaining in the cannula.

According to a further aspect of the present invention, which can be combined with the preceding aspects and exemplary embodiments, a system for providing a pyrotechnic energy release is provided. The system according to the invention comprises an ignition charge according to the invention and a A fast-acting, particularly pyrotechnically operable, actuating mechanism associated with the ignition charge. The actuating mechanism may comprise or be a pyrotechnic separating device or an actuating mechanism, e.g., for an emergency exit or fire door.

The system according to the invention can, for example, comprise a pyrotechnic drive with an electrical trigger and an actuating mechanism that can be pyrotechnically operated by the pyrotechnic drive, such as a capping mechanism or an accelerable piston. For example, the pyrotechnic drive comprises an ignition charge accommodated in a housing and designed according to the invention, which can be initiated by an electrical trigger unit. The trigger unit can be designed as an electrical ignition bridge carrier according to EP 0248977 A1 The ignition bridge carrier can comprise a glass or ceramic body embedded in a metallic outer ring, into which conductive contact sections are embedded, and an ignition bridge is formed on the side facing the ignition charge. A current pulse can heat the ignition bridge and initiate the ignition charge, resulting in a pyrotechnic reaction.

Furthermore, the system can have an additional charge, which is realized by arranging a further pyrotechnic substance in such a way that the pyrotechnic conversion of the ignition charge according to the invention affects the additional charge in order to generate a pyrotechnic gas expansion, which is used for an intended purpose of the system, such as for accelerating a piston or a cutting mechanism.

The features disclosed in the above description and the claims may be important both individually and in any combination for the realization of the invention in the various embodiments.

Claims (15)

Liquid-applied ignition composition for a system for providing a pyrotechnic energy release, comprising a pyrotechnic material embedded in a matrix which reacts pyrotechnically at a material-specific reaction temperature, characterized in that the matrix is formed by a water-dispersible organic polymer. Ignition charge according to claim 1, characterized in that the polymer comprises a vinyl ester copolymer. Ignition charge according to one of the preceding claims, characterized in that the vinyl ester copolymer comprises a vinyl acetate copolymer, and/or that the vinyl ester copolymer comprises, in particular consists of, a vinyl acetate and ethylene copolymer. Ignition charge according to one of the preceding claims, characterized by a concentration of the pyrotechnic material of 70 wt.% to 80 wt.% and/or a matrix concentration of 30 wt.% to 20 wt.%. Ignition charge according to one of the preceding claims, characterized in that the ignition charge is free from a lacquer coating, in particular applied after the ignition charge has hardened. Ignition charge according to one of the preceding claims, characterized in that the ignition charge is designed to shrink by less than 10% during hardening. Ignition charge according to one of the preceding claims, characterized in that the ignition charge is flexible and/or non-destructively adhering to a surface and can be mechanically processed, in particular partially mechanically removed. Ignition charge according to one of the preceding claims, characterized by unrestricted adhesion at a temperature of up to -40°C to a surface, in particular a metal surface, such as a steel, nickel, chromium and tantalum surface, and/or a glass or ceramic surface. Ignition charge according to one of the preceding claims, characterized in that the ignition charge is designed to wet a metal surface, such as a steel, nickel, chromium and tantalum surface, and/or a glass or ceramic surface, in particular at a relative humidity of at least 40%, preferably 50%, and/or that the ignition charge is designed to be applied by means of a dosing device, in particular one operated by compressed air, wherein in particular the dosing device has a cannula with an inner diameter of less than 1 mm, in particular of less than 0.8 mm or of approximately 0.6 mm. A liquid-applicable dispersion for forming an ignition charge, in particular according to one of the preceding claims, for a system for providing a pyrotechnic energy release, comprising a water-dispersible organic polymer, such as a vinyl ester copolymer, water, and a pyrotechnic material which reacts pyrotechnically at a material-specific reaction temperature, characterized in that the dispersion is of low viscosity. Dispersion according to claim 10, characterized in that the water-dispersible organic polymer comprises a vinyl ester copolymer, such as a vinyl acetate copolymer, and/or that the water-dispersible organic polymer has a concentration of 20 wt.% to 40 wt.% in water, and/or that the water is deionized water, in particular deionized water preferably with a conductivity of at most 0.06 µS × cm ^-1 , and/or that the water-dispersible organic polymer comprises a vinyl ester copolymer which comprises, in particular consists of, a vinyl acetate and ethylene copolymer. Dispersion according to one of claims 10 or 11, characterized by a viscosity at room temperature of at most 2 Pa·s, in particular of at most 1.8 Pa·s or at most 1.5 Pa·s. Method for producing an ignition charge designed in particular according to one of claims 1 to 9, in which the ignition charge is formed by curing a dispersion designed in particular according to one of claims 10 to 12 from a vinyl ester copolymer, water and a pyrotechnic material. Method according to claim 13, in which the dispersion is liquid, in particular by means of a metering device, in particular one operated by compressed air, wherein in particular the metering device comprises a cannula with an inner diameter of less than 1 mm, in particular of less than 0.8 mm or of approximately 0.6 mm, is applied, wherein in particular the ignition charge is cured after application, in particular application to a surface, in particular a metal surface, such as a steel, nickel, chromium and/or tantalum surface, and/or a glass or ceramic surface, wherein in particular the water contained evaporates during curing and/or the ignition charge adheres to the surface after curing, and/or wherein the ignition charge shrinks by less than 10% during curing. System for providing a pyrotechnic energy release, comprising an ignition charge designed according to one of claims 1 to 9 and an actuating mechanism associated with the ignition charge, in particular one operable pyrotechnically.