EP3656753B1 - Method for preparing composite pyrotechnical products - Google Patents

Method for preparing composite pyrotechnical products Download PDF

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Publication number
EP3656753B1
EP3656753B1 EP19211106.0A EP19211106A EP3656753B1 EP 3656753 B1 EP3656753 B1 EP 3656753B1 EP 19211106 A EP19211106 A EP 19211106A EP 3656753 B1 EP3656753 B1 EP 3656753B1
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fillers
type
energetic
cross
advantageously
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German (de)
French (fr)
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EP3656753A1 (en
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Jérôme LAFARGE
Nancy Desgardin
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ArianeGroup SAS
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ArianeGroup SAS
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    • C—CHEMISTRY; METALLURGY
    • C06—EXPLOSIVES; MATCHES
    • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
    • C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
    • C06B45/04—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive
    • C06B45/06—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive the solid solution or matrix containing an organic component
    • C06B45/10—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive the solid solution or matrix containing an organic component the organic component containing a resin
    • C06B45/105—The resin being a polymer bearing energetic groups or containing a soluble organic explosive

Definitions

  • the present invention falls within the field of solid propulsion. More specifically, it relates to a process for preparing composite pyrotechnic products (composite solid propellants) and composite pyrotechnic products (composite solid propellants) capable of being obtained by said process. Said composite pyrotechnic products (composite solid propellants) are particularly suitable for the propellant loadings of strategic or tactical missiles.
  • the composite pyrotechnic products in question contain a high rate of energetic charges (of nitramine type) in an energetic binder (comprising an energetic polymer (of the polyglycidyl azide (PAG) type) crosslinked and plasticized with at least one energetic plasticizer.
  • an energetic binder comprising an energetic polymer (of the polyglycidyl azide (PAG) type) crosslinked and plasticized with at least one energetic plasticizer.
  • the process in question is a process by analogy, the products in question are of known type. However, said products retain the signature of their preparation process which involves an original crosslinking system. Despite the substitution of this original crosslinking system for the crosslinking system of the prior art, they exhibit interesting mechanical properties and the thermal protection (PT) / binder / product assemblies also exhibit interesting peel properties (they are sufficiently robust. to respond to firing requests).
  • PT thermal protection
  • EP 0 576 326 discloses a pyrotechnic composition comprising a polyhydroxyl terminated glycidyl azide, at least one polyisocyanate, an energetic plasticizer and an oxidizing filler. It also discloses that the preferred polyisocyanates are a mixture of an aliphatic trimer with an aromatic polymer, showing an average NCO group functionality of 2.7 and an NCO: OH ratio close to 1: 1.
  • CMR substance Carcinogenic, Mutagenic (or genotoxic) and toxic for Reproduction (or reprotoxic)
  • the inventors wished to find a substitute for it; more precisely, they wished to identify an efficient crosslinking system (leading to a composite propellant with suitable properties, with the same constituent ingredients, except therefore the crosslinking system, and this under the same preparation conditions), free of CMR substance.
  • the overall functionality corresponds to the functionality of the crosslinking system consisting of a mixture of polyisocyanates aliphatic.
  • the overall functionality of the crosslinking system is equal to: [(average functionality (di-NCO) * mol number (di-NCO)) / (mol number (di-NCO) + mol number (tri-NCO) )] + [(average functionality (tri-NCO) * mol number (tri-NCO)) / (mol number (di-NCO) + mol number (tri-NCO)].
  • the process in question is a process by analogy which is implemented, in a conventional manner (see the above steps) with the majority of the conventional constituent ingredients of a composite pyrotechnic product of the type sought (see above), except therefore for the crosslinking system.
  • this difference is in no way insignificant with regard to the properties sought for the final product and the bonding properties of said final product.
  • the oligomers of the crosslinking agents of the aliphatic polyisocyanate type of the invention are advantageously homopolymers and / or oligomerization products of the urethdione and / or allophanate type.
  • the crosslinking agents consist of a mixture of aliphatic polyisocyanates, based on the one hand on polyisocyanates without or with urethdione or allophanate structural units having an average functionality greater than 2.1 and less than 3.0, and based, on the other hand, on polyisocyanates having an average functionality greater than 3.0, and preferably greater than 3.0 and less than 4.0.
  • the aliphatic polyisocyanates of the invention advantageously have the same isocyanate unit.
  • said same isocyanate unit is hexamethylene 1,6-diisocyanate (HMDI or HDI) or isophoronediisocyanate (IPDI), and more preferably hexamethylene 1,6-diisocyanate (HMDI or HDI) ).
  • said crosslinking agents consist of a mixture of aliphatic polyisocyanates, based on the one hand on polyisocyanates with units of urethdione or allophanate structure having a functionality of approximately 2.5 and based, on the other hand, on polyisocyanates of homopolymers of hexamethylene 1,6-diisocyanate (HMDI or HDI) having a functionality of about 3.5.
  • HMDI hexamethylene 1,6-diisocyanate
  • the bridging ratio Rp (NCO / OH) of said crosslinking agents corresponds to the ratio by number of isocyanate functions (NCO) and of hydroxy functions (OH) originating from PAG.
  • This bridging ratio Rp (NCO / OH) preferably varies from 1.0 to 1.4, more preferably from 1.1 to 1.3, and even more preferably is equal to 1.2.
  • the overall functionality of said crosslinking system preferably varies from 2.5 to 3.0, and even more preferably from 2.6 to 3.0.
  • the energetic polymer selected as precursor of the binder of the products of the invention is therefore a polyazide, a poly glycidyl azide (PAG) which has terminal hydroxyl functions (a hydroxytelechelic PAG); hence 1) its energetic properties and 2) its ability to be crosslinked with polyisocyanate type crosslinking agents.
  • Said polymer has an adequate molecular weight (in particular, with reference to its consistency (liquid) and to the consistency of its mixture with essentially the fillers and with reference to the relative content of the crosslinked binder in crosslinking agents, number-average molecular weight included between 700 and 3000 g / mol, advantageously between 1700 and 2300 g / mol.
  • the organic energy charges are of the nitramine type. They are advantageously chosen from charges of hexogen (RDX), octogen (HMX), hexanitrohexaazaisowurtzitane (CL 20), and mixtures thereof. Very advantageously they consist of hexogen charges (RDX).
  • the at least one energetic plasticizer very advantageously consists of a mixture of butanetriol trinitrate (BTTN) and trimethylolethane trinitrate (TMETN).
  • Said at least one stabilizer of said at least one energy plasticizer is generally chosen from aromatic amines, epoxidized fatty acid esters and mixtures thereof. It is advantageously chosen from 2-nitrodiphenylamine (2-NDPA), N-methylparanitroaniline (MNA) and their mixtures.
  • oxidizing charges can in particular consist of potassium perchlorate charges.
  • fillers can be present, in the absence of reducing fillers, at a low content. More generally, they are present with reducing fillers, such as aluminum fillers.
  • At least one additive can in particular be chosen from crosslinking catalysts, ballistic catalysts, processing aids, anti-glare and binder / fillers binding agents. Such additives conventionally enter into the composition of propellants.
  • a second subject of the invention relates to a composite pyrotechnic product containing organic energetic charges of nitramine type in a plasticized binder, said plasticized binder comprising at least one polyazide of glycidyl with terminal hydroxyl functions, the number-average molecular mass of which is between 700 and 3000 g / mol, crosslinked via its hydroxyl functions by aliphatic polyisocyanates, at least one energetic plasticizer and at least one stabilizer of said at least one energetic plasticizer, capable of being obtained by the preparation process of the invention.
  • the binder crosslinking system (“diisocyanate” + “triisocyanate”) (see the tested crosslinking systems described below) was then added to said homogeneous paste according to the protocol described below.
  • the "diisocyanate” was introduced first, then left stirring for 10 minutes at 40 ° C, then the “triisocyanate” was then added, stirring the medium for 20 minutes.
  • a sample of each of the propellant pastes thus prepared was taken for the determination of pot life.
  • the pot life of a propellant paste is evaluated by measuring the change in the viscosity of said paste over time. It is expressed as the time (in hours) to reach a viscosity of 1.5 kPa.s. It is more or less critical depending on the quantities of dough prepared.
  • each of the prepared propellant pastes was then poured into a suitable structure and then subjected to the following heat treatment: baking for 21 days at a temperature of 40 ° C. At the end of the heat treatment, crosslinked propellants were obtained.
  • the mechanical properties of said propellants were determined by subjecting a series of five test pieces (a long CRB test piece (of the "JANAF” type, having the following measurements: useful thickness 6.9 mm, total length 91.3 mm, length of the narrowed portion 83 mm, thickness of said narrowed portion 9.1 mm)) of said propellants to simple tensile tests and recording the corresponding tensile curves.
  • the precursor paste of the Azalane® propellant of the prior art was obtained according to the above protocol using the crosslinking system below.
  • Cross-linking system Isonate® M143 (Dow Chemical): aromatic isocyanate (CMR), marketed by the company Covestro, containing a high percentage of 4,4'-diphenylmethane diisocyanate (MDI) (monomer (free) (70% free MDI), exhibiting a average functionality of 2.17 and a low viscosity of 39 mPa.s at 25 ° C according to standard MDI-01-02), + Desmodur® N3300 (Covestro): aliphatic isocyanate, marketed by the company COVESTRO, containing homopolymers of hexamethylene 1,6-diisocyanate (HMDI or HDI), containing an amount of free HMDI less than 0.15% by mass, exhibiting an average functionality of 3.5, and a viscosity of 3000 mPa s at 23 ° C according to DIN EN ISO 3219.
  • MDI 4,4'-diphenylmethane diisocyanate
  • Table 2 The results presented in Table 2 are comparative results with respect to the Azalane® reference. All these results are lower than the Azalane® reference made up of the mixture of Isonate® M143 and Desmodur® N3300. The% negative for the elongation tests and for the stress tests correspond to the percentage of level losses compared to the Azalane® reference, these degradations are low when it is indicated "in the dispersion", which means that they do not differ from the results obtained for the Azalane® reference (except for the uncertainty).
  • the pot life of the propellant pastes of the invention with Desmodur® N3400 and Desmodur® XP2860 is greater than 24 hours.

Description

La présente invention s'inscrit dans le domaine de la propulsion solide. Elle a plus précisément pour objet un procédé de préparation de produits pyrotechniques composites (propergols solides composites) et les produits pyrotechniques composites (propergols solides composites) susceptibles d'être obtenus par ledit procédé. Lesdits produits pyrotechniques composites (propergols solides composites) conviennent tout particulièrement pour les chargements propulsifs de missiles stratégiques ou tactiques.The present invention falls within the field of solid propulsion. More specifically, it relates to a process for preparing composite pyrotechnic products (composite solid propellants) and composite pyrotechnic products (composite solid propellants) capable of being obtained by said process. Said composite pyrotechnic products (composite solid propellants) are particularly suitable for the propellant loadings of strategic or tactical missiles.

Les produits pyrotechniques composites en cause renferment un fort taux de charges énergétiques (de type nitramine) dans un liant énergétique (comprenant un polymère énergétique (du type polyazoture de glycidyle (PAG)) réticulé et plastifié avec au moins un plastifiant énergétique.The composite pyrotechnic products in question contain a high rate of energetic charges (of nitramine type) in an energetic binder (comprising an energetic polymer (of the polyglycidyl azide (PAG) type) crosslinked and plasticized with at least one energetic plasticizer.

Le procédé en cause est un procédé par analogie, les produits en cause sont de type connu. Lesdits produits gardent toutefois la signature de leur procédé de préparation qui fait intervenir un système de réticulation original. Ils présentent, malgré la substitution de ce système de réticulation original au système de réticulation de l'art antérieur, des propriétés mécaniques intéressantes et les assemblages protection thermique (PT)/lieur/produit présentent également des propriétés de pelage intéressantes (ils sont suffisamment robustes pour répondre aux sollicitations de tir).The process in question is a process by analogy, the products in question are of known type. However, said products retain the signature of their preparation process which involves an original crosslinking system. Despite the substitution of this original crosslinking system for the crosslinking system of the prior art, they exhibit interesting mechanical properties and the thermal protection (PT) / binder / product assemblies also exhibit interesting peel properties (they are sufficiently robust. to respond to firing requests).

L'homme du métier connait les procédés de préparation de produits pyrotechniques renfermant des charges énergétiques (type RDX, HMX, CL-20, ADN) dans un polymère énergétique réticulé (plastifié par au moins un plastifiant énergétique), de type polyazoture de glycidyle (PAG) réticulé via ses fonctions hydroxyle téléchéliques avec au moins un agent de réticulation de type polyisocyanate. A ce sujet, on peut notamment se référer à l'enseignement de la demande de brevet FR 3 027 598 .Those skilled in the art are familiar with the processes for preparing pyrotechnic products containing energetic charges (RDX, HMX, CL-20, DNA type) in a crosslinked energetic polymer (plasticized by at least one energetic plasticizer), of the glycidyl polyazide type ( PAG) crosslinked via its telechelic hydroxyl functions with at least one polyisocyanate type crosslinking agent. On this subject, reference may in particular be made to the teaching of the patent application FR 3 027 598 .

EP 0 576 326 divulgue une composition pyrotechnique comprenant un polyazoture de glycidyle à terminaisons hydroxyles, au moins un polyisocyanate, un plastifiant énergétique et une charge oxydante. Il divulgue aussi que les polyisocyanates préférés sont un mélange d'un trimère aliphatique avec un polymère aromatique, montrant une fonctionalité moyenne en groupe NCO de 2,7 et un rapport NCO:OH voisin de 1:1. EP 0 576 326 discloses a pyrotechnic composition comprising a polyhydroxyl terminated glycidyl azide, at least one polyisocyanate, an energetic plasticizer and an oxidizing filler. It also discloses that the preferred polyisocyanates are a mixture of an aliphatic trimer with an aromatic polymer, showing an average NCO group functionality of 2.7 and an NCO: OH ratio close to 1: 1.

A ce jour, pour l'obtention de produits présentant des propriétés mécaniques intéressantes et d'assemblages protection thermique (PT)/lieur/produit présentant des propriétés de pelage intéressantes (voir ci-dessus), on a coutume d'utiliser, en mélange, des agents de réticulation de deux types :

  • un « diisocyanate » aromatique : le 4,4'-diisocyanate de diphénylméthane (MDI), renfermant un fort pourcentage de monomère (MDI) libre, notamment celui commercialisé par la société Dow Chemical sous la dénomination Isonate® M143 (renfermant 70% en masse de monomère libre, présentant une fonctionnalité moyenne de 2,17 et une viscosité (selon la norme MDI-01-02) à 25°C de 39 MPa.s), et
  • un « triisocyanate » aliphatique : le trimère du 1,6-diisocyanate d'hexaméthylène (HDI), renfermant une large proportion d'homopolymères dudit 1,6-diisocyanate d'hexaméthylène (HDI) et une faible proportion de monomère (HDI) libre, notamment celui commercialisé par la société Covestro sous la dénomination Desmodur® N3300 (renfermant moins de 0,15% en masse de monomère libre), présentant une fonctionnalité moyenne de 3,5 et une viscosité (selon la norme DIN EN ISO 3219 à 23°C de 3000 mPa.s).
To date, to obtain products exhibiting interesting mechanical properties and thermal protection (PT) / binder / product assemblies exhibiting interesting peel properties (see above), it is customary to use, as a mixture , crosslinking agents of two types:
  • an aromatic “diisocyanate”: diphenylmethane 4,4′-diisocyanate (MDI), containing a high percentage of free monomer (MDI), in particular that marketed by the company Dow Chemical under the name Isonate® M143 (containing 70% by mass of free monomer, exhibiting an average functionality of 2.17 and a viscosity (according to standard MDI-01-02) at 25 ° C of 39 MPa.s), and
  • an aliphatic “triisocyanate”: the trimer of hexamethylene 1,6-diisocyanate (HDI), containing a large proportion of homopolymers of said hexamethylene 1,6-diisocyanate (HDI) and a small proportion of free monomer (HDI) , in particular that marketed by the company Covestro under the name Desmodur® N3300 (containing less than 0.15% by mass of free monomer), exhibiting an average functionality of 3.5 and a viscosity (according to DIN EN ISO 3219 to 23 ° C of 3000 mPa.s).

Le procédé de préparation de produits pyrotechniques en question, avec utilisation de ces deux types d'agent de réticulation, est illustré dans les exemples ci-après. Les performances obtenues (en termes de propriétés mécaniques et de propriétés de pelage) sont chiffrées.The process for preparing pyrotechnic products in question, using these two types of crosslinking agent, is illustrated in the examples below. The performances obtained (in terms of mechanical properties and peel properties) are quantified.

Dans la mesure où le « diisocyanate » aromatique ci-dessus est désormais classé substance CMR (Cancérogène, Mutagène (ou génotoxique) et toxique pour la Reproduction (ou reprotoxique)), les inventeurs ont souhaité lui trouver un substitut ; ils ont plus précisément souhaité identifier un système de réticulation performant (conduisant à un propergol composite aux propriétés adéquates, avec les mêmes ingrédients constitutifs, hormis donc le système de réticulation, et ceci dans les mêmes conditions de préparation), exempt de substance CMR.Insofar as the aromatic “diisocyanate” above is now classified as a CMR substance (Carcinogenic, Mutagenic (or genotoxic) and toxic for Reproduction (or reprotoxic)), the inventors wished to find a substitute for it; more precisely, they wished to identify an efficient crosslinking system (leading to a composite propellant with suitable properties, with the same constituent ingredients, except therefore the crosslinking system, and this under the same preparation conditions), free of CMR substance.

Dans un tel contexte, ils proposent donc un procédé de préparation de produits pyrotechniques composites, procédé par analogie mais utilisant un système de réticulation original, exempt de substance CMR. Ledit procédé de préparation constitue le premier objet de la présente invention. Il comprend :

  1. a) la mise à disposition des ingrédients constitutifs dudit produit pyrotechnique composite, lesdits ingrédients constitutifs comprenant (a priori essentiellement, voire exclusivement) :
    • au moins un polyazoture de glycidyle à fonctions terminales hydroxyle, dont la masse moléculaire moyenne en nombre est comprise entre 700 et 3000 g/mol,
    • au moins un plastifiant énergétique,
    • au moins un stabilisant dudit au moins un plastifiant énergétique,
    • des charges énergétiques organiques de type nitramine,
    • des agents de réticulation de type polyisocyanate,
    • éventuellement des charges additionnelles choisies parmi des charges oxydantes et des mélanges de charges oxydantes et de charges réductrices,
    • éventuellement au moins un additif, dont au moins un catalyseur de réticulation ;
  2. b) la constitution d'une pâte homogène, renfermant tous les ingrédients constitutifs du produit pyrotechnique recherché (l'homme du métier n'ignore pas qu'en référence au problème de la vie de pot de ladite pâte homogène, lesdits agents de réticulation de type polyisocyanate sont ajoutés le plus tard possible (avant la coulée)) ;
  3. c) la coulée de ladite pâte homogène obtenue dans au moins une structure ; et
  4. d) le traitement thermique de ladite pâte homogène coulée dans ladite au moins une structure.
In such a context, they therefore propose a process for preparing composite pyrotechnic products, a process by analogy but using an original crosslinking system, free of CMR substance. Said preparation process constitutes the first object of the present invention. He understands :
  1. a) the provision of the constituent ingredients of said composite pyrotechnic product, said constituent ingredients comprising (a priori essentially, or even exclusively):
    • at least one glycidyl polyazide with hydroxyl terminal functions, the number-average molecular mass of which is between 700 and 3000 g / mol,
    • at least one energetic plasticizer,
    • at least one stabilizer of said at least one energy plasticizer,
    • organic energetic charges of nitramine type,
    • polyisocyanate type crosslinking agents,
    • optionally additional charges chosen from oxidizing charges and mixtures of oxidizing charges and reducing charges,
    • optionally at least one additive, including at least one crosslinking catalyst;
  2. b) the constitution of a homogeneous paste, containing all the constituent ingredients of the desired pyrotechnic product (those skilled in the art are aware that, with reference to the problem of the pot life of said homogeneous paste, said crosslinking agents of polyisocyanate type are added as late as possible (before casting));
  3. c) casting said homogeneous paste obtained in at least one structure; and
  4. d) heat treatment of said homogeneous paste cast in said at least one structure.

De façon caractéristique, ledit procédé est mis en œuvre avec des agents de réticulation qui consistent en des polyisocyanates aliphatiques :

  • existant, pour plus de 99,6% en masse, avantageusement plus de 99,7% en masse, sous la forme d'oligomères et, pour moins de 0,4% en masse, avantageusement moins de 0,3% en masse, sous la forme d'au moins un monomère libre,
  • présentant une fonctionnalité globale de 2,1 à 3,0, et utilisés en une quantité qui assure un rapport de pontage Rp(NCO/OH) compris entre 0,9 et 1,5.
Characteristically, said process is carried out with crosslinking agents which consist of aliphatic polyisocyanates:
  • existing, for more than 99.6% by mass, advantageously more than 99.7% by mass, in the form of oligomers and, for less than 0.4% by mass, advantageously less than 0.3% by mass, in the form of at least one free monomer,
  • exhibiting an overall functionality of 2.1 to 3.0, and used in an amount which provides an Rp (NCO / OH) bridging ratio of between 0.9 and 1.5.

Au sens de l'invention, la fonctionnalité globale correspond à la fonctionnalité du système de réticulation constitué d'un mélange de polyisocyanates aliphatiques. En particulier, la fonctionnalité globale du système de réticulation est égale à : [(fonctionnalité moyenne (di-NCO) * nombre de mol (di-NCO)) / (nombre mol (di-NCO) + nombre mol (tri-NCO))] + [(fonctionnalité moyenne (tri-NCO) * nombre mol (tri-NCO)) / (nombre mol (di-NCO) + nombre mol (tri-NCO)].For the purposes of the invention, the overall functionality corresponds to the functionality of the crosslinking system consisting of a mixture of polyisocyanates aliphatic. In particular, the overall functionality of the crosslinking system is equal to: [(average functionality (di-NCO) * mol number (di-NCO)) / (mol number (di-NCO) + mol number (tri-NCO) )] + [(average functionality (tri-NCO) * mol number (tri-NCO)) / (mol number (di-NCO) + mol number (tri-NCO)].

Comme indiqué ci-dessus, le procédé en cause est un procédé par analogie qui est mis en œuvre, de façon conventionnelle (voir les étapes ci-dessus) avec la majorité des ingrédients constitutifs conventionnels d'un produit pyrotechnique composite du type recherché (voir ci-dessus), hormis donc le système de réticulation. L'homme du métier conçoit que cette différence n'est en rien anodine au regard des propriétés recherchées pour le produit final et de collage dudit produit final. En effet, en sélectionnant des « diisocyanates », non CMR, faiblement plus visqueux (450 mPa.s), contenant donc un taux d'oligomères fonctionnels plus important, il est apparu possible de compenser la baisse de réactivité par une diffusion fortement limitée de ces agents de réticulation du propergol vers le lieur (explication a posteriori), ce qui est a priori favorable à une meilleure tenue mécanique de l'assemblage PT/lieur/propergol.As indicated above, the process in question is a process by analogy which is implemented, in a conventional manner (see the above steps) with the majority of the conventional constituent ingredients of a composite pyrotechnic product of the type sought (see above), except therefore for the crosslinking system. Those skilled in the art will understand that this difference is in no way insignificant with regard to the properties sought for the final product and the bonding properties of said final product. Indeed, by selecting "diisocyanates", non CMR, slightly more viscous (450 mPa.s), therefore containing a higher level of functional oligomers, it appeared possible to compensate for the drop in reactivity by a strongly limited diffusion of these agents for crosslinking the propellant towards the linker (explanation a posteriori), which is a priori favorable to better mechanical strength of the PT / linker / propellant assembly.

Les oligomères des agents de réticulation de type polyisocyanate aliphatique de l'invention sont avantageusement des homopolymères et/ou des produits d'oligomérisation de type uréthdione et/ou allophanate.The oligomers of the crosslinking agents of the aliphatic polyisocyanate type of the invention are advantageously homopolymers and / or oligomerization products of the urethdione and / or allophanate type.

Selon une variante avantageuse de l'invention, les agents de réticulation consistent en un mélange de polyisocyanates aliphatiques, à base d'une part de polyisocyanates sans ou avec unités de structure uréthdione ou allophanate présentant une fonctionnalité moyenne supérieure à 2,1 et inférieure à 3,0, et à base, d'autre part, de polyisocyanates présentant une fonctionnalité moyenne supérieure à 3,0, et de préférence supérieure à 3,0 et inférieure à 4,0.According to an advantageous variant of the invention, the crosslinking agents consist of a mixture of aliphatic polyisocyanates, based on the one hand on polyisocyanates without or with urethdione or allophanate structural units having an average functionality greater than 2.1 and less than 3.0, and based, on the other hand, on polyisocyanates having an average functionality greater than 3.0, and preferably greater than 3.0 and less than 4.0.

Les polyisocyanates aliphatiques de l'invention présentent avantageusement le même motif isocyanate. Selon un mode de réalisation préféré, ledit même motif isocyanate est le 1,6-diisocyanate d'hexaméthylène (HMDI ou HDI) ou l'isophoronediisocyanate (IPDI), et plus préférentiellement le 1,6-diisocyanate d'hexaméthylène (HMDI ou HDI).The aliphatic polyisocyanates of the invention advantageously have the same isocyanate unit. According to a preferred embodiment, said same isocyanate unit is hexamethylene 1,6-diisocyanate (HMDI or HDI) or isophoronediisocyanate (IPDI), and more preferably hexamethylene 1,6-diisocyanate (HMDI or HDI) ).

Ainsi, selon une variante encore plus avantageuse de l'invention, lesdits agents de réticulation consistent en un mélange de polyisocyanates aliphatiques, à base d'une part de polyisocyanates avec unités de structure uréthdione ou allophanate présentant une fonctionnalité d'environ 2,5 et à base, d'autre part, de polyisocyanates d'homopolymères du 1,6-diisocyanate d'hexaméthylène (HMDI ou HDI) présentant une fonctionnalité d'environ 3,5.Thus, according to an even more advantageous variant of the invention, said crosslinking agents consist of a mixture of aliphatic polyisocyanates, based on the one hand on polyisocyanates with units of urethdione or allophanate structure having a functionality of approximately 2.5 and based, on the other hand, on polyisocyanates of homopolymers of hexamethylene 1,6-diisocyanate (HMDI or HDI) having a functionality of about 3.5.

Le rapport de pontage Rp(NCO/OH) desdits agents de réticulation correspond au rapport en nombre des fonctions isocyanate (NCO) et des fonctions hydroxy (OH) provenant du PAG. Ce rapport de pontage Rp(NCO/OH) varie de préférence de 1,0 à 1,4, plus préférentiellement de 1,1 à 1,3, et encore plus préférentiellement est égal à 1,2.The bridging ratio Rp (NCO / OH) of said crosslinking agents corresponds to the ratio by number of isocyanate functions (NCO) and of hydroxy functions (OH) originating from PAG. This bridging ratio Rp (NCO / OH) preferably varies from 1.0 to 1.4, more preferably from 1.1 to 1.3, and even more preferably is equal to 1.2.

La fonctionnalité globale dudit système de réticulation (i.e. de l'ensemble desdits agents de réticulation) varie de préférence de 2,5 à 3,0, et encore plus préférentiellement de 2,6 à 3,0.The overall functionality of said crosslinking system (i.e. of all of said crosslinking agents) preferably varies from 2.5 to 3.0, and even more preferably from 2.6 to 3.0.

En référence aux ingrédients constitutifs (autres que lesdits agents de réticulation) du produit pyrotechnique composite préparé selon le procédé de l'invention, on peut, de façon nullement limitative, préciser ce qui suit.With reference to the constituent ingredients (other than said crosslinking agents) of the composite pyrotechnic product prepared according to the process of the invention, it is possible, in no way limiting, to specify the following.

Le polymère énergétique sélectionné comme précurseur du liant des produits de l'invention est donc un polyazoture, un polyazoture de glycidyle (PAG) qui présente des fonctions terminales hydroxyle (un PAG hydroxytéléchélique) ; d'où 1) ses propriétés énergétiques et 2) sa capacité à être réticulé avec des agents de réticulation de type polyisocyanate. Ledit polymère a une masse moléculaire adéquate (notamment, en référence à sa consistance (liquide) et à la consistance de son mélange avec essentiellement les charges et en référence à la teneur relative du liant réticulé en agents de réticulation, masse moléculaire moyenne en nombre comprise entre 700 et 3000 g/mol, avantageusement entre 1700 et 2300 g/mol. Notons incidemment ici que le « un » polyazoture de glycidyle (= polymère précurseur du liant) doit se lire « au moins un » polyazoture de glycidyle dans tout le présent texte. En effet, il est nullement exclu du cadre de l'invention qu'un mélange d'au moins deux polyazotures de glycidyle (présentant des masses moléculaires (entre 700 et 3000 g/mol) et/ou des taux de ramification différents) soit utilisé comme polymère précurseur du liant des produits de l'invention.The energetic polymer selected as precursor of the binder of the products of the invention is therefore a polyazide, a poly glycidyl azide (PAG) which has terminal hydroxyl functions (a hydroxytelechelic PAG); hence 1) its energetic properties and 2) its ability to be crosslinked with polyisocyanate type crosslinking agents. Said polymer has an adequate molecular weight (in particular, with reference to its consistency (liquid) and to the consistency of its mixture with essentially the fillers and with reference to the relative content of the crosslinked binder in crosslinking agents, number-average molecular weight included between 700 and 3000 g / mol, advantageously between 1700 and 2300 g / mol. Incidentally, it should be noted here that the “one” poly glycidyl azide (= polymer precursor of the binder) should read “at least one” poly glycidyl azide throughout the present In fact, it is in no way excluded from the scope of the invention that a mixture of at least two glycidyl polyazides (having molecular masses (between 700 and 3000 g / mol) and / or different branching rates) or used as precursor polymer for the binder of the products of the invention.

Les charges énergétiques organiques sont de type nitramine. Elles sont avantageusement choisies parmi des charges d'hexogène (RDX), d'octogène (HMX), d'hexanitrohexaazaisowurtzitane (CL 20), et leurs mélanges. Très avantageusement elles consistent en des charges d'hexogène (RDX).The organic energy charges are of the nitramine type. They are advantageously chosen from charges of hexogen (RDX), octogen (HMX), hexanitrohexaazaisowurtzitane (CL 20), and mixtures thereof. Very advantageously they consist of hexogen charges (RDX).

Le au moins un plastifiant énergétique est généralement de type nitrate et/ou nitramine. Il est avantageusement choisi parmi :

  • les esters nitriques, tels que le dinitrate de diéthylène glycol (DEGDN), le dinitrate de triéthylène glycol (TEGDN), le trinitrate de butanetriol (BTTN), le trinitrate de triméthyloléthane (TMETN), la nitroglycérine et leurs mélanges ;
  • les nitramines, telles qu'un mélange de 2,4-dinitro-2,4-diazapentane, de 2,4-dinitro-2,4-diazahexane et de 3,5-dinitro-3,5-diazaheptane, les nitrato éthyl nitramines, notamment la méthyl-2-nitratoéthyl nitramine (méthylNENA) et l'éthyl-2-nitratoéthyl nitramine (éthylNENA), et leurs mélanges ; et
  • les mélanges desdits esters nitriques et nitramines.
The at least one energetic plasticizer is generally of the nitrate and / or nitramine type. It is advantageously chosen from:
  • nitric esters, such as diethylene glycol dinitrate (DEGDN), triethylene glycol dinitrate (TEGDN), butanetriol trinitrate (BTTN), trimethylolethane trinitrate (TMETN), nitroglycerin and mixtures thereof;
  • nitramines, such as a mixture of 2,4-dinitro-2,4-diazapentane, 2,4-dinitro-2,4-diazahexane and 3,5-dinitro-3,5-diazaheptane, nitrato ethyl nitramines, in particular methyl-2-nitratoethyl nitramine (methylNENA) and ethyl-2-nitratoethyl nitramine (ethylNENA), and mixtures thereof; and
  • mixtures of said nitric esters and nitramines.

Le au moins un plastifiant énergétique consiste très avantageusement en un mélange de trinitrate de butanetriol (BTTN) et de trinitrate de triméthyloléthane (TMETN).The at least one energetic plasticizer very advantageously consists of a mixture of butanetriol trinitrate (BTTN) and trimethylolethane trinitrate (TMETN).

Ledit au moins un stabilisant dudit au moins un plastifiant énergétique est généralement choisi parmi les amines aromatiques, les esters d'acide gras époxydés et leurs mélanges. Il est avantageusement choisi parmi la 2-nitrodiphénylamine (2-NDPA), la N-méthylparanitroaniline (MNA) et leurs mélanges.Said at least one stabilizer of said at least one energy plasticizer is generally chosen from aromatic amines, epoxidized fatty acid esters and mixtures thereof. It is advantageously chosen from 2-nitrodiphenylamine (2-NDPA), N-methylparanitroaniline (MNA) and their mixtures.

Outre les charges énergétiques organiques de type nitramine, des charges additionnelles choisies parmi des charges oxydantes et des mélanges de charges oxydantes et de charges réductrices peuvent être présentes. Les charges oxydantes peuvent notamment consister en des charges de perchlorate de potassium. De telles charges peuvent être présentes, en l'absence de charges réductrices, à une faible teneur. Plus généralement, elles sont présentes avec des charges réductrices, telles des charges d'aluminium.Besides the organic energetic charges of nitramine type, additional charges chosen from oxidizing charges and mixtures of oxidizing charges and reducing charges may be present. The oxidizing charges can in particular consist of potassium perchlorate charges. Such fillers can be present, in the absence of reducing fillers, at a low content. More generally, they are present with reducing fillers, such as aluminum fillers.

En sus des ingrédients constitutifs identifiés ci-dessus (et des agents de réticulation, éléments clés originaux de la présente invention, discutés plus avant), on peut utiliser d'autres ingrédients constitutifs et notamment au moins un additif. Un tel au moins un autre additif peut notamment être choisi parmi les catalyseurs de réticulation, les catalyseurs balistiques, les auxiliaires de fabrication, les anti-lueurs et les agents de liaison liant/charges. De tels additifs entrent conventionnellement dans la composition des propergols.In addition to the constituent ingredients identified above (and crosslinking agents, original key elements of the present invention, discussed further before), it is possible to use other constituent ingredients and in particular at least one additive. Such at least one other additive can in particular be chosen from crosslinking catalysts, ballistic catalysts, processing aids, anti-glare and binder / fillers binding agents. Such additives conventionally enter into the composition of propellants.

Selon un mode de mise en œuvre préféré, l'étape b) du procédé de l'invention (étape de constitution de la pâte homogène à couler), comprend, avec les ingrédients constitutifs du produit pyrotechnique recherché mis à disposition :

  • b1) la constitution, à une température comprise entre 35 et 55°C, sous agitation, d'un mélange (prémix) comprenant ledit au moins un polyazoture de glycidyle à fonctions terminales hydroxy (PAG-diol), dont la masse moléculaire moyenne en nombre est comprise entre 700 et 3000 g/mol, ledit au moins un plastifiant énergétique et ledit au moins un stabilisant dudit au moins un plastifiant énergétique ;
  • b2) la constitution d'une pâte homogène, renfermant tous les ingrédients constitutifs du produit pyrotechnique composite recherché, par:
    • b21) incorporation, dans ledit mélange, maintenu sous agitation, à une température comprise entre 35 et 55°C, des charges énergétiques organiques de type nitramine (si seul type de charges énergétiques présentes : «Azalane® ») et des autres ingrédients constitutifs dudit produit pyrotechnique composite, non introduits à l'étape b), qui comprennent éventuellement lesdites charges oxydantes et charges réductrices, et au moins un additif, à l'exception d'un quelconque agent de réticulation ;
    • b22) agitation de la pâte résultante, sous vide partiel, à une température comprise entre 35 et 55°C ;
    • b23) incorporation dans ladite pâte, maintenue, sous vide partiel et sous agitation, à une température comprise entre 35 et 55°C, desdits agents de réticulation de type polyisocyanate ;
      le au moins un catalyseur de réticulation étant éventuellement ajouté à l'étape b21) et/ou à l'étape b23) ci-dessus ; et
    • b24) nouvelle agitation sous vide partiel pour l'obtention de ladite pâte homogène, renfermant tous les ingrédients constitutifs du produit pyrotechnique recherché.
According to a preferred embodiment, step b) of the method of the invention (step of constituting the homogeneous paste to be poured), comprises, with the constituent ingredients of the desired pyrotechnic product made available:
  • b1) the constitution, at a temperature of between 35 and 55 ° C, with stirring, of a mixture (premix) comprising said at least one polyazide of glycidyl with terminal hydroxy functions (PAG-diol), of which the average molecular mass in number is between 700 and 3000 g / mol, said at least one energetic plasticizer and said at least one stabilizer of said at least one energetic plasticizer;
  • b2) the constitution of a homogeneous paste, containing all the constituent ingredients of the desired composite pyrotechnic product, by:
    • b21) incorporation, in said mixture, kept under stirring, at a temperature between 35 and 55 ° C, organic energetic charges of nitramine type (if only type of energetic charges present: “Azalane®”) and other constituent ingredients of said composite pyrotechnic product, not introduced in step b), which optionally comprise said oxidizing charges and reducing charges, and at least one additive, with the exception of any crosslinking agent;
    • b22) stirring the resulting paste, under partial vacuum, at a temperature between 35 and 55 ° C;
    • b23) incorporation into said paste, maintained, under partial vacuum and with stirring, at a temperature between 35 and 55 ° C., of said polyisocyanate type crosslinking agents;
      the at least one crosslinking catalyst optionally being added in step b21) and / or in step b23) above; and
    • b24) new stirring under partial vacuum to obtain said homogeneous paste, containing all the constituent ingredients of the desired pyrotechnic product.

Un deuxième objet de l'invention concerne un produit pyrotechnique composite renfermant des charges énergétiques organiques de type nitramine dans un liant plastifié, ledit liant plastifié comprenant au moins un polyazoture de glycidyle à fonctions terminales hydroxyle, dont la masse moléculaire moyenne en nombre est comprise entre 700 et 3000 g/mol, réticulé via ses fonctions hydroxyle par des polyisocyanates aliphatiques, au moins un plastifiant énergétique et au moins un stabilisant dudit au moins un plastifiant énergétique, susceptible d'être obtenu par le procédé de préparation de l'invention.A second subject of the invention relates to a composite pyrotechnic product containing organic energetic charges of nitramine type in a plasticized binder, said plasticized binder comprising at least one polyazide of glycidyl with terminal hydroxyl functions, the number-average molecular mass of which is between 700 and 3000 g / mol, crosslinked via its hydroxyl functions by aliphatic polyisocyanates, at least one energetic plasticizer and at least one stabilizer of said at least one energetic plasticizer, capable of being obtained by the preparation process of the invention.

Selon un mode de réalisation préféré, ledit au moins un polyazoture de glycidyle à fonctions terminales hydroxyle réticulé du produit pyrotechnique composite de l'invention est un réseau tridimensionnel essentiellement formé d'unités structurelles :

  • de type A : dont le précurseur consiste en ledit au moins polyazoture de glycidyle à fonctions terminales hydroxyle, et
  • de type B : dont les précurseurs consistent en lesdits oligomères du polyisoicyanate(s) aliphatique(s).
According to a preferred embodiment, said at least one polycarbonate with crosslinked hydroxyl terminal functions of the composite pyrotechnic product of the invention is a three-dimensional network essentially formed of structural units:
  • of type A: the precursor of which consists of said at least glycidyl polyazide with hydroxyl terminal functions, and
  • of type B: the precursors of which consist of said oligomers of the aliphatic polyisoicyanate (s).

La composition du produit pyrotechnique composite de l'invention (propergol solide composite), exprimée en pourcentages massiques, renferme généralement :

  • de 50 à 70%, avantageusement de 55 à 65%, desdites charges énergétiques organiques de type nitramine,
  • de 9 à 14% dudit polymère énergétique réticulé (via le système de réticulation original),
  • de 10 à 30%, avantageusement de 15 à 25%, dudit au moins un plastifiant énergétique, et
  • de 0 à 10%, avantageusement de 0,1 à 10%, d'au moins un additif.
The composition of the composite pyrotechnic product of the invention (composite solid propellant), expressed in percentages by mass, generally contains:
  • from 50 to 70%, advantageously from 55 to 65%, of said organic energetic charges of nitramine type,
  • from 9 to 14% of said crosslinked energetic polymer (via the original crosslinking system),
  • from 10 to 30%, advantageously from 15 to 25%, of said at least one energetic plasticizer, and
  • from 0 to 10%, advantageously from 0.1 to 10%, of at least one additive.

On se propose ci-après d'illustrer l'art antérieur de l'invention, les démarches des inventeurs et l'invention présentement en cause.It is proposed below to illustrate the prior art of the invention, the approaches of the inventors and the invention presently in question.

EXEMPLES :EXAMPLES: Protocole de préparation des propergols :Propellant preparation protocol:

Dans un réacteur double enveloppe chauffé à 40°C, on a introduit le polymère précurseur du liant (PAG, 7,5% de Mn égale à 1685 g/mol, commercialisé par la société Eurenco), puis les plastifiants (BTTN/TMETN dans un ratio 30/70 = 16,54%) et les agents de stabilisation (MNA/2NDPA : 0,55%) desdits plastifiants. Apres introduction de tous les composants, le mélange a été agité durant 8 h par un bullage d'azote pour l'homogénéiser et le sécher à une température de 40°C.In a jacketed reactor heated to 40 ° C, the precursor polymer of the binder (PAG, 7.5% of Mn equal to 1685 g / mol, sold by the company Eurenco) was introduced, then the plasticizers (BTTN / TMETN in a ratio of 30/70 = 16.54%) and the stabilizing agents (MNA / 2NDPA: 0.55%) of said plasticizers. After introducing all the components, the mixture was stirred for 8 h by bubbling nitrogen through to homogenize it and dry it at a temperature of 40 ° C.

On a ensuite introduit ce mélange dans un malaxeur et coulé sur celui-ci la poudre d'aluminium (Al : 17,5%) et les catalyseurs de réticulation (triphényl bismuth (50 ppm) et DBTL (5 ppm)). Le mélange a été agité durant 15 minutes à 40°C. Une première partie des charges énergétiques organiques (HMX) a ensuite été introduite dans ledit mélange, puis le perchlorate d'ammonium (PA : 8%) par portion, ainsi que le reste des charges énergétiques (total de HMX : 47,5%). Après chaque portion introduite, le milieu a été agité pendant 15 minutes à 40°C L'agitation a ensuite été poursuivie pendant 2h30, toujours à la température de 40°C et sous un vide de 10 mm de Hg (qui permet le dégazage du milieu), pour l'obtention d'une pâte homogène.This mixture was then introduced into a kneader and the aluminum powder (Al: 17.5%) and the crosslinking catalysts (triphenyl bismuth (50 ppm) and DBTL (5 ppm)) were poured thereon. The mixture was stirred for 15 minutes at 40 ° C. A first part of the organic energy charges (HMX) was then introduced into said mixture, then the ammonium perchlorate (PA: 8%) per portion, as well as the rest of the energy charges (total of HMX: 47.5%) . After each portion introduced, the medium was stirred for 15 minutes at 40 ° C. The stirring was then continued for 2 h 30 min, still at the temperature of 40 ° C and under a vacuum of 10 mm Hg (which allows the degassing of the medium), to obtain a homogeneous paste.

Le système de réticulation du liant (« diisocyanate » + « triisocyanate ») (voir les systèmes de réticulation testés décrits ci-après) a alors été ajouté à ladite pâte homogène selon le protocole décrit ci-après. Le « diisocyanate » a été introduit en premier, puis laissé sous agitation pendant 10 minutes à 40°C, puis le « triisocyanate » a ensuite été ajouté, en agitant le milieu pendant 20 minutes.The binder crosslinking system (“diisocyanate” + “triisocyanate”) (see the tested crosslinking systems described below) was then added to said homogeneous paste according to the protocol described below. The "diisocyanate" was introduced first, then left stirring for 10 minutes at 40 ° C, then the "triisocyanate" was then added, stirring the medium for 20 minutes.

On a ainsi préparé des lots de 800 g de pâte de propergol.Batches of 800 g of propellant paste were thus prepared.

On a prélevé un échantillon de chacune des pâtes de propergol ainsi préparées pour la détermination de la vie de pot. La vie de pot d'une pâte de propergol est évaluée par la mesure de l'évolution de la viscosité de ladite pâte au cours du temps. Elle est exprimée comme le temps (en heure) pour atteindre une viscosité de 1,5 kPa.s. Elle est plus ou moins critique selon les quantités de pâte préparée.A sample of each of the propellant pastes thus prepared was taken for the determination of pot life. The pot life of a propellant paste is evaluated by measuring the change in the viscosity of said paste over time. It is expressed as the time (in hours) to reach a viscosity of 1.5 kPa.s. It is more or less critical depending on the quantities of dough prepared.

Le reste de chacune des pâtes de propergol préparées a alors été coulé dans une structure adaptée puis soumis au traitement thermique ci-après : cuisson pendant 21 jours à une température de 40°C. A l'issu du traitement thermique, on a obtenu des propergols réticulés.The remainder of each of the prepared propellant pastes was then poured into a suitable structure and then subjected to the following heat treatment: baking for 21 days at a temperature of 40 ° C. At the end of the heat treatment, crosslinked propellants were obtained.

Les objectifs étaient d'appréhender les propriétés mécaniques et les propriétés de collage des propergols ainsi préparés.The objectives were to understand the mechanical properties and the bonding properties of the propellants thus prepared.

Propriétés mécaniques :Mechanical properties :

Les propriétés mécaniques desdits propergols ont été déterminées en soumettant une série de cinq éprouvettes (une éprouvette CRB longue (de type « JANAF », présentant les mensurations ci-après : épaisseur utile 6,9 mm, longueur totale 91,3 mm, longueur de la partie rétrécie 83 mm, épaisseur de ladite partie rétrécie 9,1 mm)) desdits propergols à des essais de traction simple et en enregistrant les courbes de traction correspondantes.The mechanical properties of said propellants were determined by subjecting a series of five test pieces (a long CRB test piece (of the "JANAF" type, having the following measurements: useful thickness 6.9 mm, total length 91.3 mm, length of the narrowed portion 83 mm, thickness of said narrowed portion 9.1 mm)) of said propellants to simple tensile tests and recording the corresponding tensile curves.

Les essais ont été réalisés à + 20°C sous une traction de 50 mm/min.The tests were carried out at + 20 ° C. under a traction of 50 mm / min.

Les paramètres déterminés à partir de telles courbe de traction, ont été :

  • E = le module d'Young (MPa),
  • Sm = la contrainte maximale avant rupture (MPa), et
  • em = l'allongement avant rupture (= la déformation maximale liée à la contrainte maximale avant rupture) (%), et
  • le pelage = la tenue mécanique sur assemblage PT/lieur/propergol (daN/cm) (norme AFNOR T70-367).
The parameters determined from such traction curves were:
  • E = Young's modulus (MPa),
  • Sm = the maximum stress before failure (MPa), and
  • em = the elongation before failure (= the maximum strain related to the maximum stress before failure) (%), and
  • peeling = mechanical strength on PT / binder / propellant assembly (daN / cm) (AFNOR T70-367 standard).

Le test de pelage, mis en œuvre à température ambiante avec des bandes adhésives, permet de quantifier la force d'arrachement qu'il est nécessaire d'exercer pour séparer le lieur du propergol (une amorce de pelage est réalisée manuellement et la partie décollée est mise en traction à 90° à une vitesse de 50 mm/min ; le critère qualité impose d'avoir une valeur minimale de 1,3, plutôt de 1,5 daN/cm) et de qualifier le type de rupture. Plusieurs types de rupture sont possibles :

  • Type 0 : rupture pure à l'interface (lieur /propergol). Ce type de rupture traduit un manque d'adhésion ;
  • Type 1 : rupture pure à l'interface (lieur /propergol) avec traces de propergol sur le lieur. Ce type de rupture n'est pas satisfaisant dans la mesure où il traduit un manque de cohésion du propergol au voisinage de l'interface ;
  • Type 2 : rupture avec arrachement (« en continu », sur une faible profondeur) de propergol au voisinage de l'interface. Ce type de rupture traduit un affaiblissement du propergol au voisinage de l'interface ;
  • Type 3 : rupture cohésive dans le propergol. C'est ce type de rupture qui est recherché.
The peel test, carried out at room temperature with adhesive strips, makes it possible to quantify the tearing force that is necessary to exert to separate the binder from the propellant (a peel primer is carried out manually and the part detached is put in tension at 90 ° at a speed of 50 mm / min; the quality criterion requires having a minimum value of 1.3, rather 1.5 daN / cm) and qualifying the type of failure. Several types of rupture are possible:
  • Type 0: pure rupture at the interface (linker / propellant). This type of rupture reflects a lack of adhesion;
  • Type 1: pure rupture at the interface (binder / propellant) with traces of propellant on the binder. This type of failure is not satisfactory insofar as it reflects a lack of cohesion of the propellant in the vicinity of the interface;
  • Type 2: rupture with tearing (“continuous”, over a shallow depth) of propellant near the interface. This type of failure reflects a weakening of the propellant in the vicinity of the interface;
  • Type 3: cohesive rupture in the propellant. It is this type of rupture that is sought after.

EXEMPLE DE L'ART ANTERIEUR :EXAMPLE OF THE PRIOR ART:

La pâte précurseur du propergol Azalane® de l'art antérieur a été obtenue selon le protocole ci-dessus en utilisant le système de réticulation ci-après.The precursor paste of the Azalane® propellant of the prior art was obtained according to the above protocol using the crosslinking system below.

Système de réticulation :
Isonate® M143 (Dow Chemical) : isocyanate aromatique (CMR), commercialisé par la société Covestro, renfermant un pourcentage élevé de 4,4'-diisocyanate de diphénylméthane (MDI) (monomère (libre) (70% MDI libre), présentant une fonctionnalité moyenne de 2,17 et une faible viscosité de 39 mPa.s à 25°C selon la norme MDI-01-02),
+
Desmodur® N3300 (Covestro) : isocyanate aliphatique, commercialisé par la société COVESTRO, renfermant des homopolymères du 1,6-diisocyanate d'hexaméthylène (HMDI ou HDI), contenant une quantité de HMDI libre inférieure à 0,15% en masse, présentant une fonctionnalité moyenne de 3,5, et une viscosité de 3000 mPa·s à 23°C selon la norme DIN EN ISO 3219.Cross-linking system:
Isonate® M143 (Dow Chemical): aromatic isocyanate (CMR), marketed by the company Covestro, containing a high percentage of 4,4'-diphenylmethane diisocyanate (MDI) (monomer (free) (70% free MDI), exhibiting a average functionality of 2.17 and a low viscosity of 39 mPa.s at 25 ° C according to standard MDI-01-02),
+
Desmodur® N3300 (Covestro): aliphatic isocyanate, marketed by the company COVESTRO, containing homopolymers of hexamethylene 1,6-diisocyanate (HMDI or HDI), containing an amount of free HMDI less than 0.15% by mass, exhibiting an average functionality of 3.5, and a viscosity of 3000 mPa s at 23 ° C according to DIN EN ISO 3219.

Les quantités d'Isonate® M143 et de Desmodur® N3300 sont déterminées grâce au rapport de pontage Rp = nombre de fonctions NCO/nombre de fonctions OH, en respectant le réglage suivant :

  • Rp « di-NCO » + Rp « tri-NCO » = 1,2, et
  • Rp « di-NCO » / Rp « tri-NCO » = 1.
The quantities of Isonate® M143 and Desmodur® N3300 are determined using the bridging ratio Rp = number of NCO functions / number of OH functions, respecting the following setting:
  • Rp "di-NCO" + Rp "tri-NCO" = 1.2, and
  • Rp "di-NCO" / Rp "tri-NCO" = 1.

Les propriétés mécaniques des éprouvettes obtenues sont présentées dans le Tableau 1 ci-après. [Table.1] Propriétés mécaniques sur éprouvettes CRB longues (de type « JANAF ») et pelage sur assemblage PT/lieur/propergol après 21 jours de cuisson à 40°C E (MPa) Sm (MPa) em (%) Pelage (daN/cm) Référence Azalane® 4,1 ± 0,5 0,68 ± 0,03 32 ± 4 1,0 ± 0,1 The mechanical properties of the test pieces obtained are presented in Table 1 below. [Table.1] Mechanical properties on long CRB specimens (of the "JANAF" type) and peeling on PT / binder / propellant assembly after 21 days of baking at 40 ° C E (MPa) Sm (MPa) em (%) Peel (daN / cm) Reference Azalane® 4.1 ± 0.5 0.68 ± 0.03 32 ± 4 1.0 ± 0.1

EXEMPLES COMPARATIFS :COMPARATIVE EXAMPLES:

Des essais de substitution de l'Isonate® M143 par des « monomères » diisocyanates non CMR (toujours en combinaison avec le Desmodur® N3300) ont été réalisés. Le but de ces exemples comparatifs était d'observer la réactivité de ces « monomères » diisocyanates en fonction de leur structure, et les propriétés mécaniques qui en découlaient.Tests for the substitution of Isonate® M143 by non-CMR diisocyanate “monomers” (still in combination with Desmodur® N3300) were carried out. The aim of these comparative examples was to observe the reactivity of these diisocyanate “monomers” as a function of their structure, and the resulting mechanical properties.

Les « monomères » diisocyanates non CMR testés sont des monomères purs de fonctionnalité 2, vendus par la société Aldrich, et qui ne sont pas CMR. Ces « monomères » sont les suivants :

  • l'isophorone diisocyanate (IPDI),
  • le 4,4'-diicyclohexylméthane diisocyanate (MDCI),
  • l'α,α,α',α'-tétraméthyl-1,3-xylylène diisocyanate (TMXDI),
  • le 1,8-octaméthylène diisocyanate,
  • le 1,4-cyclohexylène diisocyanate (1,4-CHDI),
  • le 1,4-phénylène diisocyanate, et
  • le 1,6-diisocyanate d'hexaméthylène (HMDI ou HDI).
The non-CMR diisocyanate “monomers” tested are pure monomers with functionality 2, sold by the company Aldrich, and which are not CMR. These “monomers” are as follows:
  • isophorone diisocyanate (IPDI),
  • 4,4'-diicyclohexylmethane diisocyanate (MDCI),
  • α, α, α ', α'-tetramethyl-1,3-xylylene diisocyanate (TMXDI),
  • 1,8-octamethylene diisocyanate,
  • 1,4-cyclohexylene diisocyanate (1,4-CHDI),
  • 1,4-phenylene diisocyanate, and
  • hexamethylene 1,6-diisocyanate (HMDI or HDI).

Pour ces essais, les propergols ont été préparés selon le protocole exposé ci-dessus, en respectant le réglage suivant :

  • Rp « di-NCO » + Rp « tri-NCO » = 1,2, et
  • Rp « di-NCO » / Rp « tri-NCO » = 1,
le but étant de s'approcher « au plus près » des propergols de la référence Azalane® constitué d'Isonate® M143 et de Desmodur® N3300.For these tests, the propellants were prepared according to the protocol described above, respecting the following setting:
  • Rp "di-NCO" + Rp "tri-NCO" = 1.2, and
  • Rp “di-NCO” / Rp “tri-NCO” = 1,
the aim being to get “as close as possible” to the propellants of the Azalane® reference consisting of Isonate® M143 and Desmodur® N3300.

Les résultats sont présentés dans le Tableau 2 ci-après. [Table.2] Propriétés mécaniques sur éprouvettes CRB longues (de type « JANAF ») et pelage sur assemblage PT/lieur/propergol après 21 jours de cuisson à 40°C ΔE (%) ΔSm(%) Δem (%) Pelage* (daN/cm) Référence Azalane® - - - 1,0 ± 0,1 (2) IPDI -36 -27 Dans la dispersion 0,7 (2) Propriétés mécaniques non stabilisées après 21 jours de cuisson Dégradation des propriétés mécaniques et du pelage MDCI -45 -32 Dans la dispersion 0,5 (1) TMXDI -64 -49 24 0,4 (2) 1,8-octaméthylène diisocyanate -12 -10 Dans la dispersion 0,4 (2) Propriétés mécaniques stabilisées après 21 jours de cuisson Propriétés mécaniques un peu plus faibles que la référence Dégradation au pelage 1,4-CHDI -14 -16 Dans la dispersion 0,4 (2) 1,4-phénylène diisocyanate -10 -14 Dans la dispersion 0,3 (1) HMDI ou HDI -10 Dans la dispersion Dans la dispersion 0,5(1) * Les valeurs entre parenthèses indiquent le type de rupture lors du test de pelage. The results are presented in Table 2 below. [Table.2] Mechanical properties on long CRB specimens (of the "JANAF" type) and peeling on PT / binder / propellant assembly after 21 days of baking at 40 ° C ΔE (%) ΔSm (%) Δem (%) Peel * (daN / cm) Reference Azalane® - - - 1.0 ± 0.1 (2) IPDI -36 -27 In the dispersion 0.7 (2) Mechanical properties not stabilized after 21 days of cooking Degradation of mechanical properties and peeling MDCI -45 -32 In the dispersion 0.5 (1) TMXDI -64 -49 24 0.4 (2) 1,8-octamethylene diisocyanate -12 -10 In the dispersion 0.4 (2) Mechanical properties stabilized after 21 days of cooking Mechanical properties a little lower than the reference Degradation on peeling 1,4-CHDI -14 -16 In the dispersion 0.4 (2) 1,4-phenylene diisocyanate -10 -14 In the dispersion 0.3 (1) HMDI or HDI -10 In the dispersion In the dispersion 0.5 (1) * The values in brackets indicate the type of breakage during the peel test.

Les résultats présentés au Tableau 2 sont des résultats comparatifs par rapport à la référence Azalane®. Tous ces résultats sont inférieurs à la référence Azalane® constitué du mélange Isonate® M143 et Desmodur® N3300. Les % négatifs pour les tests d'élongations et pour les tests de contraintes correspondent au pourcentage de pertes de niveaux par rapport à la référence Azalane®, ces dégradations sont faibles lorsqu'il est indiqué « dans la dispersion », ce qui signifie qu'ils ne diffèrent pas des résultats obtenus pour la référence Azalane® (à l'incertitude près).The results presented in Table 2 are comparative results with respect to the Azalane® reference. All these results are lower than the Azalane® reference made up of the mixture of Isonate® M143 and Desmodur® N3300. The% negative for the elongation tests and for the stress tests correspond to the percentage of level losses compared to the Azalane® reference, these degradations are low when it is indicated "in the dispersion", which means that they do not differ from the results obtained for the Azalane® reference (except for the uncertainty).

Ces résultats montrent une variation des propriétés mécaniques en fonction de la structure du diisocyanate, et que l'HMDI reste le meilleur remplaçant à l'Isonate® M143, malgré un impact négatif sur le pelage. Notamment, certains desdits « monomères » diisocyanates (IPDI, MDCI et TMXDI) ont induit une baisse notable des propriétés mécaniques du propergol, se caractérisant notamment par une diminution de la contrainte Sm. Même avec 10 jours de cuisson supplémentaires, les propriétés mécaniques ainsi que le pelage n'étaient pas satisfaisants.These results show a variation in mechanical properties depending on the structure of the diisocyanate, and that HMDI remains the best replacement for Isonate® M143, despite a negative impact on the coat. Notably, some said diisocyanate “monomers” (IPDI, MDCI and TMXDI) induced a notable drop in the mechanical properties of the propellant, characterized in particular by a decrease in the Sm stress. Even with an additional 10 days of cooking, the mechanical properties as well as the coat were not satisfactory.

Les propriétés mécaniques des propergols obtenus avec les autres diisocyanates (1,4-phénylène diisocyanate, 1,8-octaméthylène diisocyanate, 1,4-CHDI et HMDI ou HDI), bien que plus basses que la référence, restaient dans la dispersion des mesures obtenues pour la référence Azalane®. Cependant, une dégradation notable du pelage a été observée avec chacun de ces « monomères ».The mechanical properties of the propellants obtained with the other diisocyanates (1,4-phenylene diisocyanate, 1,8-octamethylene diisocyanate, 1,4-CHDI and HMDI or HDI), although lower than the reference, remained in the dispersion of the measurements. obtained for the Azalane® reference. However, noticeable coat degradation was observed with each of these "monomers".

Ces travaux ont mis en évidence la difficulté à trouver un grade non CMR aussi performant que l'Isonate® M143.This work highlighted the difficulty in finding a non-CMR grade as efficient as the Isonate® M143.

EXEMPLES DE L'INVENTION :EXAMPLES OF THE INVENTION:

Pour les essais illustrant l'invention, les propergols ont été préparés selon le protocole exposé ci-dessus en utilisant dans le système de réticulation, en lieu et place de l'Isonate® M143 :

  • soit le Desmodur® N3400 (Covestro) : mélange de produits d'oligomérisation avec unités de structure uréthdione du HMDI, ayant un taux de HMDI (monomère libre) très faible (moins de 0,3% en masse), présentant une fonctionnalité moyenne de 2,5, une viscosité de 150 mPa.s à 23°C (méthode M014 - ISO - 3219/A.3), et un taux de NCO de 21,8%,
  • soit le Desmodur® XP2860 « à base de HMDI » (Covestro) : mélange de produits d'oligomérisation type allophanate du HMDI ayant un taux de HMDI (monomère libre) très faible (moins de 0,16% en masse), présentant une fonctionnalité moyenne de 2,5, une viscosité de 484 mPa.s élevée à 23°C (méthode M014 - ISO -3219/A.3), et un taux de NCO de 20%.
For the tests illustrating the invention, the propellants were prepared according to the protocol described above using in the crosslinking system, instead of Isonate® M143:
  • or Desmodur® N3400 (Covestro): mixture of oligomerization products with urethdione structural units of HMDI, having a very low level of HMDI (free monomer) (less than 0.3% by mass), exhibiting an average functionality of 2.5, a viscosity of 150 mPa.s at 23 ° C (method M014 - ISO - 3219 / A.3), and an NCO rate of 21.8%,
  • or Desmodur® XP2860 “based on HMDI” (Covestro): mixture of allophanate type oligomerization products of HMDI having a very low level of HMDI (free monomer) (less than 0.16% by mass), exhibiting a functionality average of 2.5, a viscosity of 484 mPa.s high at 23 ° C (method M014 - ISO -3219 / A.3), and an NCO rate of 20%.

On résume dans le Tableau 3 ci-après les informations des systèmes de réticulation utilisés dans les exemples de l'invention. [Table.3] Nom commercial Fournisseur % monomère Fonctionnalité moyenne Viscosité à 25°C (mPas.s) Référence : Isonate® M143 Dow Chemical 70% MDI 2,17 39* HMDI Aldrich 100% HMDI 2 3 Desmodur® N3400 Covestro 0,23% HMDI 2,5 152** Desmodur® XP2860 Covestro 0,08% HMDI 2.5 484** * Norme de viscosité : MDI-01-02
** Norme de viscosité : DIN EN ISO 3219/A.3 The information on the crosslinking systems used in the examples of the invention is summarized in Table 3 below. [Table.3] Trade name Provider % monomer Average functionality Viscosity at 25 ° C (mPas.s) Reference: Isonate® M143 Dow Chemical 70% MDI 2.17 39 * HMDI Aldrich 100% HMDI 2 3 Desmodur® N3400 Covestro 0.23% HMDI 2.5 152 ** Desmodur® XP2860 Covestro 0.08% HMDI 2.5 484 ** * Viscosity standard: MDI-01-02
** Viscosity standard: DIN EN ISO 3219 / A.3

Les taux d'introduction des « diisocyanates » et « triisocyanates » ont été réglés pour atteindre des niveaux d'allongement et de contrainte similaires à ceux de la référence Azalane®, en ajustant :

  • le rapport de pontage pour avoir :
    Rp « di-NCO » + Rp « tri-NCO » = 1,2, et
  • la fonctionnalité globale pour atteindre celle de la référence Azalane® : 2,69.
The rates of introduction of “diisocyanates” and “triisocyanates” were adjusted to achieve levels of elongation and stress similar to those of the Azalane® reference, by adjusting:
  • the bypass ratio to have:
    Rp "di-NCO" + Rp "tri-NCO" = 1.2, and
  • the overall functionality to reach that of the Azalane® reference: 2.69.

La vie de pot des pâtes de propergol de l'invention avec Desmodur® N3400 et Desmodur® XP2860 est supérieure à 24 heures.The pot life of the propellant pastes of the invention with Desmodur® N3400 and Desmodur® XP2860 is greater than 24 hours.

Les propriétés mécaniques et les niveaux de pelage sont présentés dans le Tableau 4 ci-après. [Table.4] Propriétés mécaniques sur éprouvettes CRB longues (de type « JANAF ») et pelage sur assemblage PT/lieur/propergol après 21 jours de cuisson à 40°C E (MPa) Sm (MPa) em (%) Pelage* (daN/cm) Référence Azalane® 4,6 0,69 27 1,0 ± 0,1 (2) Comparatif avec HMDI** -10% Dans la dispersion Dans la dispersion 0,5 (1) Invention avec Desmodur® N3400 4,6 0,64 26 1,0 (2) Invention avec Desmodur® XP2860 4,7 0,68 32 1,1 (2) * Les valeurs entre parenthèses indiquent le type de rupture lors du test de pelage
** Voir les résultats présentés au Tableau 2 The mechanical properties and the peel levels are presented in Table 4 below. [Table.4] Mechanical properties on long CRB specimens (of the "JANAF" type) and peeling on PT / binder / propellant assembly after 21 days of baking at 40 ° C E (MPa) Sm (MPa) em (%) Peel * (daN / cm) Reference Azalane® 4.6 0.69 27 1.0 ± 0.1 (2) Comparison with HMDI ** -10% In the dispersion In the dispersion 0.5 (1) Invention with Desmodur® N3400 4.6 0.64 26 1.0 (2) Invention with Desmodur® XP2860 4.7 0.68 32 1.1 (2) * The values in brackets indicate the type of breakage during the peel test
** See the results presented in Table 2

On observe une augmentation notable du pelage caractérisant la bonne tenue mécanique de l'assemblage PT/lieur/propergol comparativement au résultat obtenu avec le monomère HMDI.A notable increase in the peel is observed, characterizing the good mechanical strength of the PT / linker / propellant assembly compared to the result obtained with the HMDI monomer.

Le système de réticulation de l'invention présente les avantages suivants :

  • une alternative non CMR qui permet de remplacer l'Isonate® M143 (CMR),
  • des propriétés mécaniques et une tenue mécanique de l'assemblage PT/lieur/propergol préservées,
  • l'absence d'impact défavorable sur la faisabilité et la performance énergétique, et
  • une facilité de mise en œuvre à l'échelle industrielle.
The crosslinking system of the invention has the following advantages:
  • a non-CMR alternative which replaces the Isonate® M143 (CMR),
  • mechanical properties and mechanical strength of the PT / binder / propellant assembly preserved,
  • the absence of an unfavorable impact on feasibility and energy performance, and
  • ease of implementation on an industrial scale.

Claims (16)

  1. A process for preparing a composite pyrotechnic product comprising:
    a) providing the constituent ingredients of said composite pyrotechnic product, said constituent ingredients comprising:
    - at least one hydroxyl-terminated polyglycidyl azide, the number-average molecular weight of which is comprised between 700 and 3000 g/mol,
    - at least one energetic plasticizer,
    - at least one stabilizer of said at least one energetic plasticizer,
    - organic energetic fillers of the nitramine type,
    - cross-linking agents of the polyisocyanate type,
    - optionally additional fillers selected from oxidizing fillers and mixtures of oxidizing and reducing fillers,
    - optionally at least one additive, including at least one cross-linking catalyst;
    b) the constitution of a homogeneous paste, containing all the constituent ingredients of the desired pyrotechnic product;
    c) casting the resulting homogeneous dough into at least one structure; and
    d) heat treatment of said homogeneous paste cast in said at least one structure;
    characterized in that said cross-linking agents consist of aliphatic polyisocyanates:
    - existing, for more than 99.6% by mass, advantageously more than 99.7% by mass, in the form of oligomers and, for less than 0.4% by mass, advantageously less than 0.3% by mass, in the form of at least one monomer,
    - having an overall functionality of 2.1 to 3.0, and
    - used in an amount that ensures a bridging ratio Rp(NCO/OH) of 0.9 to 1.5.
  2. The process as claimed in claim 1, wherein said oligomers are homopolymers and/or urethdione and/or allophanate oligomerization products.
  3. The process as claimed in claim 1 or 2, characterized in that said cross-linking agents consist of a mixture of aliphatic polyisocyanates, based on the one hand on polyisocyanates without or with urethdione or allophanate structural units having an average functionality of greater than 2.1 and less than 3.0, and based on the other hand on polyisocyanates having an average functionality of greater than 3.0, and preferably greater than 3.0 and less than 4.0.
  4. The process as claimed in any one of claims 1 to 3, characterized in that said aliphatic polyisocyanates have the same isocyanate unit.
  5. The process as claimed in claim 4, characterized in that the same isocyanate unit is hexamethylene 1,6-diisocyanate (HMDI or HDI) or isophoronediisocyanate (IPDI), and preferably hexamethylene 1,6-diisocyanate (HMDI or HDI).
  6. The process as claimed in claim 4 or 5, characterized in that said cross-linking agents consist of a mixture of aliphatic polyisocyanates, based on the one hand on polyisocyanates with urethdione or allophanate structural units having an average functionality of about 2.5 and based, on the other hand, on polyisocyanates of homopolymers of hexamethylene 1,6-diisocyanate (HMDI or HDI) having an average functionality of about 3.5.
  7. The process as claimed in one of claims 1 to 6, characterized in that the bridging ratio Rp(NCO/OH) of said cross-linking agents is from 1.0 to 1.4, preferably from 1.1 to 1.3, and more preferentially is equal to 1.2.
  8. The process as claimed in one of claims 1 to 7, characterized in that the overall functionality of said cross-linking agents is from 2.5 to 3.0, and preferably from 2.6 to 3.0.
  9. The process as claimed in one of claims 1 to 8, characterized in that the number-average molecular weight (Mn) of the hydroxyl-terminated polyglycidyl azide is comprised between 1700 and 2300 g/mol.
  10. The process as claimed in one of claims 1 to 9, characterized in that said organic energetic fillers are selected from hexogen (RDX), octogen (HMX), hexanitrohexaazaisowurtzitane (CL 20) fillers, and mixtures thereof, and in that advantageously they consist of hexogen (RDX) fillers.
  11. The process as claimed in any one of claims 1 to 10, characterized in that said at least one energetic plasticizer is of the nitrate and/or nitramine type;
    in that said at least one energetic plasticizer is advantageously selected from:
    - nitric esters, such as diethylene glycol dinitrate (DEGDN), triethylene glycol dinitrate (TEGDN), butanetriol trinitrate (BTTN), trimethylolethane trinitrate (TMETN), nitroglycerin and mixtures thereof;
    - nitramines, such as a mixture of 2,4-dinitro-2,4-diazapentane, 2,4-dinitro-2,4-diaza-hexane and 3,5-dinitro-3,5-diazaheptane, nitrato ethyl nitramines, in particular methyl-2-nitratoethyl nitramine (methylNENA) and ethyl-2-nitratoethyl nitramine (ethylNENA), and mixtures thereof; and
    - mixtures of said nitric esters and nitramines;
    in that said at least one energetic plasticizer very advantageously consists of a mixture of butanetriol trinitrate (BTTN) and trimethylolethane trinitrate (TMETN).
  12. The process as claimed in any one of claims 1 to 11, characterized in that said at least one stabilizer of said at least one energetic plasticizer is selected from aromatic amines, epoxidized fatty acid esters and mixtures thereof, and in that said at least one stabilizer of said at least one energetic plasticizer is advantageously selected from 2-nitrodiphenylamine (2-NDPA), N-methylparanitroaniline (MNA) and mixtures thereof.
  13. The process as claimed in any one of claims 1 to 12, characterized in that said constituent ingredients comprise oxidizing fillers, advantageously ammonium perchlorate fillers, and reducing fillers, advantageously aluminum fillers.
  14. The process as claimed in any one of claims 1 to 13, characterized in that said constituent ingredients comprise at least one additive, in particular selected from cross-linking catalysts, ballistic catalysts, processing aids, antiflash agents and binder/filler binding agents.
  15. A composite pyrotechnic product containing organic energetic fillers of the nitramine type in a plasticized binder, said plasticized binder comprising at least one hydroxyl-terminated polyglycidyl azide, the number-average molecular mass of which is between 700 and 3000 g/mol, cross-linked via its hydroxyl functions by aliphatic polyisocyanates, at least one energetic plasticizer and at least one stabilizer for said at least one energetic plasticizer, obtainable by the preparation process as claimed in any one of the preceding claims.
  16. The composite pyrotechnic product as claimed in claim 15, wherein said at least one cross-linked hydroxyl-terminated polyglycidyl azide is a three-dimensional network consisting essentially of structural units:
    - of type A: the precursor of which consists of said at least one hydroxyl-terminated polyglycidyl azide, and
    - of type B: the precursors of which consist of said aliphatic polyisocyanate oligomers.
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