US3669924A - Stabilized polyvinyl nitrate and process - Google Patents

Stabilized polyvinyl nitrate and process Download PDF

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Publication number
US3669924A
US3669924A US857234A US3669924DA US3669924A US 3669924 A US3669924 A US 3669924A US 857234 A US857234 A US 857234A US 3669924D A US3669924D A US 3669924DA US 3669924 A US3669924 A US 3669924A
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solution
solvent
pvn
parts
polyvinylnitrate
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US857234A
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Eduard Daume
Jurg Breitenmoser
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Rheinmetall Air Defence AG
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Werkzeugmaschinenfabrik Oerlikon Buhrle AG
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
    • C08J3/09—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in organic liquids
    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
    • C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
    • C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids

Definitions

  • ABSTRACT A novel stabilized polyvinylnitrate and a process for the production thereof including the precipitation of the compound from organic solutions containing same.
  • the present invention relates to stabilized polyvinylnitrate (PVN), and to methods for producing same.
  • fuels for rocket motors In the development of fuels for rocket motors, it is endeavored to produce fuel compositions which are as energyrich as possible, in order thereby to be ableto deliver large payloads with small volumes of fuel.
  • double-base fuels In the field of solid-fuel rockets, the so-called double-base" fuels are mainly used to this end. They consist essentially of a mixture of nitrocellulose and nitroglycerine, to which additives are admixed for modifying the combustion properties.
  • inorganic oxidizing agents such as ammonium perchlorate, ammonium nitrate as well as metal powder may also be admixed to these fuels in order to increase the energy content thereof.
  • the so-called composite fuels are also known, which are substantially based on the use of inorganic oxidizing agents with organic bonding agents.
  • These bonding agents are for example polybutadiene, polyurethane, polysultide, polyester and the like.
  • the oxidizing agents are mixed with the still fluid organic components for producing these fuels and are subsequently subjected to a curing process, this resulting in a solid resilient mass of predeterrninated fonn.
  • Metal powder may also be added to these fuels in order to increase the energy content thereof.
  • hydrochloric acid When using ammonium perchlorate as oxidizing agent, gaseous hydrochloric acid is produced which forms heavy fumes particularly when the atmosphere is damp.
  • the hydrochloric acid is also disadvantagous due to its corrosive effect on the ground installa tion.
  • metal powder in particular aluminum or magnesium, also increases the formation of smoke since the corresponding metal oxides are produced during combustion.
  • High-energy fuels which do not present these disadvantages of smoke formation and the corrosive effect on ground installations, may be produced, on the basis of the present invention, from stabilized polyvinylnitrate.
  • This purely synthetically produceable material has good thermoplastic properties and may be gelatinized with many organic nitric esters or other known plasticizers. In this form, it is capable of absorbing larger amounts of known explosives in pure or mixed form, such as for example trimethylenetrinitroamine, nitropenta, trotyl or even ammonium nitrate. From such mixtures, propellants may be formed, which deliver completely smoke-less combustion products and high specific impulses.
  • Polyvinyl nitrate was already under consideration in the 40's as component in fuels and explosives, but its use in this field has, up to the present, not been able to penetrate.
  • the main disadvantage is stated to be the difficulty in the stabilization process. PVN decomposes more or less quickly during storage and/or heating.
  • Polyvinylnitrate may be produced by nitration (esterification) of polyvinyl alcohol with pure concentrated nitric acid or with a so-called mixed acid, consisting of concentrated nitric acid and concentrated sulfuric acid. Nitration (ester-iiication) is preferably carried out at 0 C. The polyvinyl nitrate formed is thereby completely or partly soluble in the nitrating acid depending upon the selected excess thereof. After nitration, the product is precipitated in water. During this precipitation process, a considerable heat of dilution is produced, which causes the polyvinylnitrate precipitating in the water to coagulate.
  • the particle size of the polyvinyl nitrate formed may be relatively well controlled according to the conditions of precipitation, an acid inclusion cannot be avoided.
  • the conventional methods used in the explosives and fuel industry for washing out the nitration product formed and subsequently treating with alkaline agents such as sodium bicarbonate or ammonium bicarbonate and the like do not lead to the target, since the included acid cannot be reached by the alkalis. It was also proposed to treat the polyvinylnitrate with an alkaline solvent-water mixture and in this way to remove the residual acid. Also, this method does not produce good stability values. Finally, it is known that it was attempted to dissolve the polyvinylnitrate in acetone and to reprecipitate the lacquer solution after its neutralization in water.
  • the process according to the invention comprises the steps of a. providing a solution of raw acid containing polyvinylnitrate in an organic solvent,
  • step (c) introducing said purified solution of step (c) into a hot precipitating bath in which said organic solvent is insoluble or only partially soluble, whereby said solvent is stripped and stabilized polyvinylnitrate is precipitated,and whereby the rate of introduction of said purified solution corresponds to the stripping rate of said solvent so that steady-state conditions are maintained, and whereby a solvent is selected in step (a) the pure boiling point of which or the azeotropic boiling point of which with the precipitating bath is below the boiling point of the pure precipitating bath.
  • aqueous precipitating baths such solvents are preferably used in the PVN-solution which form with the water an azeotrope with minimum boiling point, this usually being immediately the case when using solvents which are not or only partially miscible with water.
  • solvents are esters and ketones, such as ethyl and butyl acetate or methylethylketone and methylisobutylketone. Ethyl acetate is preferred.
  • PVN starting product a direct product of nitration of polyvinyl alcohol after precipitation with water, filtration and washing-out with water until neutrality is reached, is advantageously used.
  • This product can immediately be dissolved in humid state without drying, e.g. in ethylacetate.
  • an alkaline agent e.g. NaOH, NaHCO or Na CQ or other alkali metal hydroxides, carbonates or bicarbonates
  • weakly basizity or slightly alkaline as used herein is to be understood as comprising pH values in the range of about 7 to about 9, preferably between about 7 and about 8.5.
  • the neutralized or slightly alkaline PVN solution is separated from the salts formed, i.e. generally from the alkali-nitrates or their solution, if an aqueous neutralizing solution was used.
  • the solution is generally allowed to stand and the separation of the salts or the salt solution is awaited. The separation usually occurs by itself after a short time, the supernatant PVN solution has clarified and may be drawn off for further processing. If it ap pears advantageous, the PVN solution may be subjected to a post-sedimentation, e. g. by centrifugation.
  • a percent by weight solution of PVN in ethyl acetate is for example particularly suitable.
  • the content of the solutions will vary depending upon the molecular weight or viscosity of the crude PVN. Too strongly diluted solutions represent volumes which are difficult to handle, while too concentrated solutions are very viscous and are difficult to neutralize.
  • the solution may be diluted after neutralization.
  • Solutions which are more diluted than those described above generally produce purer products. After dilution, the solid content of the solution is advantageously assayed, e.g. by evaporating a sample until it is dry. Before precipitation, a stabilizer for the PVN may be added to the solution, preferably 2- nitrodiphenylamine; however, the process according to the present invention mainly consists in a stabilization by purifying the PVN.
  • the precipitating bath used consists, in the simplest case, of water. However, it has proved advantageous if the precipitating bath contains certain additives which increase the quality, i.e. in particular the stability, of the precipitating PVN. Also coming into question in particular are surface active agents, preferably such of anion-active nature, e.g. the sodium salt of disulfonated dodecyldiphenyloxide; electrolytes, e.g. sodium sulfate; pH regulators, preferably for adjusting or maintaining slightly basic conditions, e.g. sodium bicarbonate; protective colloids, e.g. bone glue, etc.
  • surface active agents preferably such of anion-active nature, e.g. the sodium salt of disulfonated dodecyldiphenyloxide
  • electrolytes e.g. sodium sulfate
  • pH regulators preferably for adjusting or maintaining slightly basic conditions, e.g. sodium bicarbonate
  • protective colloids e.g. bone glue, etc.
  • the PVN solution contains a solvent or solvent mixture which is partially miscible with water, it is recommended to saturate the precipitating bath with this solvent or mixture or to add so much to these liquids that saturation practically occurs at precipitation temperature.
  • the boiling temperature of such a precipitating bath corresponds to the temperature at which the continuous precipitating process proceeds.
  • the precipitating bath is preferably strongly stirred at least during the introduction of the PVN solution, perhaps with the aid of a vibrator-mixer. In this way, a uniform and fine precipitation is obtained.
  • a polyvinylnitrate purified in this way produced from polyvinyl alcohol with a saponification number of 99 mole to which 0.5 percent 2-nitrodiphenylamine were added, is thermally stable and satisfies for example the Heat-Test according to US-MIL-Standard at 120 C. in 65 min., at l34.5 C. in 25 min. and the Abel-Test at C. in 40 min.
  • This product has an explosion heat of 909 cal/g and a combustion heat of 2,963 cal/g.
  • EXAMPLE 1 20.4 parts of crude humid polyvinylnitrate, produced by the nitration (ester-ification) of a polyvinylalcohol with a saponification number of about 99 mole and an approximate molecular weight of 100,000 (Mowiol N -99 sold by Farbwerke Hoechst AG), subsequent dilution with water and filtration (water content about 50 percent by weight) were dissolved in 40.8 parts of ethyl acetate. (The crude product contains nitrating acid still included therein. It would therefore be senseless to determine the nitrogen content.)
  • the solution obtained was mixed, with stirring, with a 5 percent by weight aqueous solution of NaHCO until the CO evolution had stopped and the mixture had a pH-value of 7 to 7.5. To this end, 1.5 parts of the NaHCO solution were necessary. After the mixture had been allowed to stand for 20 minutes, two layers had formed. The upper organic layer was separated off. 1.0 parts thereof were dried in vacuo, and the residue amounted to 0.2 parts. The neutralized PVN solution was therefore still 20 percent by weight. By the addition of 50 parts of ethyl acetate, an about 10 percent by weight PVN solution was produced. 0.05 parts of Z-nitrodiphenylamine were added to this solution.
  • a four-necked, round-bottomed flask with distilling attachment and cooler, thermometer, dropping funnel and agitator is charged with parts of an aqueous solution, which contains 1 part of disodium dodecyldiphenyloxide disulfonate, 2.5 parts of sodium sulfate, 0.4 parts of sodium bicarbonate, 2 parts of bone glue and 5 parts of ethyl acetate.
  • the agitator (vibrator-mixer) is set into action and the flask is heated until the contents thereof are boiling (about 71 C.).
  • the above described PVN solution is made to drop in. Heating of the flask and speed of feed-in are regulated so that the liquid level in the flask remains practically constant.
  • EXAMPLE 2 26.0 parts of crude, humid polyvinylnitrate, produced by the nitration (esterification) of a polyvinylalcohol. with a saponification number of about 98 mole and an approximate molecular weight of 41,000 (Mowiol N 50-98" sold by Hoechst AG), subsequent dilution with water and filtration (water content about 40 percent), were dissolved in 36.4 parts of methylethylketone. The solution obtained was mixed, with stirring, in a 5 percent by weight aqueous NaHCO solution, until the CO, stopped forming and the mixture had a pH-value of 7. To this end, 2.5 parts of the NaHCO solution were necessary.
  • EXAMPLE 10 Components, percent by weight n, (ll. PVN AN lhN (lvw.
  • EXAMPLE 6 Components, percent by weight 1100, Stability 6
  • a four-necked roundbottomed flask with distillating attachment and cooler, thermometer, dropping funnel and agitator is charged with 100 parts of an aqueous solution which contains 1 part of disodium dodecyldiphenyloxydisulfonate, 2.5 parts of sodium sulfate, 0.4 parts of sodium bicarbonate, 2 parts of bone glue and 5 parts of methylethylketone.
  • the agitator (vibrator-mixer) is set into action and the flask is heated until the contents thereof are boiling (about 74 C). immediately after the beginning of boiling, the above described PVN solution is made to drop in. Heating of the flask and rate of feed-in are controlled so that the liquid level in the flask remains practically constant.
  • water as outer phase, may be replaced by another liquid compound in which PVN is not soluble.
  • Suitable solvents which form the inner phase with the dissolved PVN, should not or only partly be soluble in the outer phase. Their boiling point must be lower than that of the outer phase.
  • PVN Polyvinlynitrate, stabilized according to the invention What we claim is:
  • a process for preparing a stabilized polyvinylnitrate from a crude starting material comprising the steps of a. providing a solution of raw acid containing polyvinylnitrate in an organic solvent,
  • step (c) introducing said purified solution of step (c) into a hot aqueous precipitating bath in which said organic solvent is insoluble or only partially soluble, whereby said solvent is stripped and stabilized polyvinylnitrate is precipitated, and whereby the rate of introduction of said purified solution corresponds to the stripping rate of said solvent so that steady-state conditions are maintained, and whereby a solvent is selected in step (a) the pure boiling point of which or the azeotropic boiling point of which with the precipitating bath is below the boiling point of the pure precipitating bath.
  • step (b) is carried out by using an aqueous neutralizing solution of an alkali metal hydroxide, bicarbonate or carbonate.
  • step (b) is carried out by using an aqueous neutralizing solution of NaHCO,,.
  • step (a) a solvent is used selected from the group comprising an ester and a ketone at most partially miscible with water.
  • step (a) ethyl acetate is used as a solvent.
  • a process as in claim 1 further comprising the step of diluting the solutions of step (b) with the same solvent as used in step a) 7.
  • a process as in claim 1 in which a solution of about 20 parts by weight of crude polyvinylnitrate in about 80 parts by weight of ethyl acetate is prepared in step (a), and further comprising the dilution of the neutralized solution of step (b) with ethyl acetate to a concentration of about 10 percent by weight of polyvinyl nitrate.
  • step (c) 2-nitrodiphenylamine as a stabilizing agent.
  • step (d) is selected from the group comprising pure water and an aqueous medium containing at least one additive of the group consistir ifoTelectrolytes, protection colloids and pH regulators.
  • step (d) A process as in claim 1 in which an aqueous precipitating bath is used in step (d) which has been previously saturated with the organic solvent of step (a) in the range between normal room temperature and the azeotropic boiling point.

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  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Molecular Biology (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
US857234A 1968-09-19 1969-09-11 Stabilized polyvinyl nitrate and process Expired - Lifetime US3669924A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH1404268A CH504482A (de) 1968-09-19 1968-09-19 Verfahren zur Stabilisierung von Polyvinylnitrat

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3965081A (en) * 1974-01-21 1976-06-22 The United States Of America As Represented By The Secretary Of The Army Isotactic and syndiotactic polyvinyl nitrates and processes for their formation
US4023996A (en) * 1973-08-09 1977-05-17 Societe Nationale Des Poudres Et Explosifs Moldable compositions comprising polyvinyl nitrate
US4039640A (en) * 1973-08-09 1977-08-02 Societe Nationale Des Poudres Et Explosifs Moldable compositions comprising polyvinyl nitrate
US4347087A (en) * 1978-12-22 1982-08-31 Societe Nationale Des Poudres Et Explosifs Granular propellant powder based on nitrocellulose, oily nitrate ester and polyvinyl nitrate, and process

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2118487A (en) * 1936-07-15 1938-05-24 Du Pont Process for preparing polyvinyl nitrate

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2118487A (en) * 1936-07-15 1938-05-24 Du Pont Process for preparing polyvinyl nitrate

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4023996A (en) * 1973-08-09 1977-05-17 Societe Nationale Des Poudres Et Explosifs Moldable compositions comprising polyvinyl nitrate
US4039640A (en) * 1973-08-09 1977-08-02 Societe Nationale Des Poudres Et Explosifs Moldable compositions comprising polyvinyl nitrate
US3965081A (en) * 1974-01-21 1976-06-22 The United States Of America As Represented By The Secretary Of The Army Isotactic and syndiotactic polyvinyl nitrates and processes for their formation
US4347087A (en) * 1978-12-22 1982-08-31 Societe Nationale Des Poudres Et Explosifs Granular propellant powder based on nitrocellulose, oily nitrate ester and polyvinyl nitrate, and process

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CH504482A (de) 1971-03-15
DE1938902A1 (de) 1970-03-26
DE1938902B2 (de) 1977-06-02
SE348742B (de) 1972-09-11

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