Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B1/00—Preparatory treatment of cellulose for making derivatives thereof, e.g. pre-treatment, pre-soaking, activation
  • C08B1/02—Rendering cellulose suitable for esterification
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B1/00—Preparatory treatment of cellulose for making derivatives thereof, e.g. pre-treatment, pre-soaking, activation
  • C08B1/02—Rendering cellulose suitable for esterification
  • C08B1/04—Rendering cellulose suitable for esterification for the preparation of cellulose nitrate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B5/00—Preparation of cellulose esters of inorganic acids, e.g. phosphates
  • C08B5/02—Cellulose nitrate, i.e. nitrocellulose

Definitions

• a lene ⁇ 6 Claims ABSTRACT OF THE DISCLOSURE A process of nitration of cellulose.
• the process includes first impregnating cellulose with a chlorinated aliphatic solvent and then subjecting it to nitration using a nitrating bath comprising concentrated nitric acid and chlorinated aliphatic solvent.
• the quantity of nitric acid in the nitrating bath being less than or equal to 50% and the nitration temperature being to 45 C.
• the invention further provides a process for the preparation of pure, stable microcrystalline nitrocellulose.
• Present methods for making nitrocelluolse generally consist in nitrating cellulose in a sulphonitric mixture.
• nitrate cellulose by means of a nitric acid/methylene chloride mixture in excess.
• the nitration ratios R are very high (in the order of 100 to 300) and more often lead to a partial gelatinization of the nitrocellulose.
• the cellulose to be nitrated must be in a subdivided form, giving rise to the necessity for preliminary operations, such as opening of the cotton used.
• An object of the present invention is to provide an improved method for the nitration of cellulose which minimizes or removes the aforesaid disadvantages.
• the cellulose to be nitrated is first impregnated with a chlorinated aliphatic solvent and then subjected to nitration by means-of a nitrating bath composed of concentrated nitric acid, a chlorinated aliphatic solvent and, optionally, a strong dehydrating agent, using a nitration ratio of 10 to 50, a nitric acid content in the nitrating bath less than or equal to 50% its tates Patent 3,534,l3 Patented 0st. 13, 1970 ice b.w., and a nitration temperature of 0 to C.; after nitration the nitrocellulose obtained is recovered, after having been stabilized, if required.
• Methylene chloride, chloroform, carbon tetrachloride or the like, or a mixture of these solvents are particularly suitable as the chlorinated aliphatic solvent.
• the preferred solvent is methylene chloride.
• Phosphorus pentoxide, sulphur trioxide, oleum, acetic anhydride and the like can be mentioned as suitable strong dehydrating agents.
• the preferred dehydrating agent is phosphorus pentoxide.
• the presence of a strong dehydrating agent in the nitrating bath is necessary in the case where it is desired to obtain a nitrocellulose which has a nitrogen content which is higher than 13.8.
• celluloses of very varied constitution and origin, such as cotton linters, wood pastes, hydrolyzed celluolses, hydrocelluloses;
• nitrating celluloses which are in forms other than the sub-divided form, such as floss, threads, linen, paper, cotton, shavings, while keeping the original form;
• PRELIMINARY IMPREGNATION This is fulfilled by bringing a cellulose in any form and of any kind into contact with a chlorinated aliphatic sol vent. It can be fulfilled, for example, continuously by sprinkling or intermittently by soaking.
• Impregnation can be easily carried out in a liquid bath at ordinary temperatures. Its duration varies according to the type of cellulose used and its form (from 30' seconds to several minutes). It can equally be effected in the vapour phase.
• the amount of the chlorinated aliphatic solvent should be between 1 and 6 times the amount of the cellulose to be nitrated. An amount of more than 6 would give a composition of the nitration bath which would risk division into 2 phases during nitration. An amount lower than 1 could lead to heterogeneity of the impregnation and to a risk of gelatinization of certain badly-impregnated parts of the cellulose.
• NITRATION This is fulfilled by bringing the cellulose, which has previously been impregnated with the aliphatic chlorinated solvent, into contact with the nitrating bath.
• the latter is composed of concentrated nitric acid with additions of a chlorinated aliphatic solvent and possibly a strong dehydrating agent.
• the reaction which can be carried out continuously or intermittently, is effected in known manner.
• the water content of the concentrated nitric acid used should preferably be lower than 6% b.w. when using methylene chloride as the chlorinated aliphatic solvent, taking into account the terniary miscibility diagram (Water-nitric acid-CH Cl).
• methylene chloride as the chlorinated aliphatic solvent
• nitric acid in the total nitration bath it is advisable to limit the amount of nitric acid in the total nitration bath (impregnated chlorinated aliphatic solvent included) to a value less than or equal to 50%, so as to eliminate any risks of gelatinization.
• the nitration ratio must be more than 10 and, particularly, from 10 to 50.
• the temperature of nitration can very between and 45 C. Thus the reaction can easily be conducted at the reflux boiling point of the reaction mixture.
• the nitrocellulose is dried, rinsed in a chlorinated aliphatic solvent to recover the nitric acid which is impregnated therein and then immersed in water; the chlorinated aliphatic solvent is then recovered by distillation.
• the finishing operations must include alcohol stabilization followed by rinsing in twice-changed water and then by rinsing in alcohol in the cold state. The latter is eliminated by boiling under agitation, for example.
• nitrocelluloses thus obtained are immediately stable and have practically the same degree of polymerization as the original cellulose. They likewise keep the same fine structure.
• Regulation of the nitrogen content between 0 an 13.8 is easily done by varying the nitration ratio of to 50 and the nitric acid content in the mixture of nitric acidwater-chlorinated aliphatic solvent at between 0 and 50%.
• nitrocelluloses with a nitrogen content of more than 13.8 between 13.8 and 14.14
• a strong dehydrating agent into the nitration bath.
• the dehydrating agent will also be capable of use for the manufacture of nitrocellulose with a nitrogen content of less than 13.8.
• Another use of the invention concerns the preparation of a pure, stable, microcrystalline nitrocellulose which is especially used as a source of atomic vapour for analysis by spectrophotometry of atomic absorption.
• EXAMPLE 1 304 g. of phosphorus pentoxide, 1000 cc. of methylene chloride and then 460 g. of 99% nitric acid were introduced into a nitration reactor. A mixture of 500 cc. of methylene chloride and 162 g. of hydrolyzed cellulose with a polymerisation degree of 135 was then stirred in.
• the reagents and the reactor had previously been cooled to 5 C. After admixing the reagents, the temperature rose to about +25 C. The mixture was left to react for 30 minutes, whilst being stirred.
• the nitrocellulose obtained was dried and then rinsed in methylene chloride.
• a dried specimen had a nitrogen content of 14.0 and a polymerization degree of 130.
• EXAMPLE 3 A eucalyptus paste in the form of 5 mm. squares cut into sheets 0.9 mm. thick weighing 700 g./m. was stirred in a reactor with 6 times its weight of methylene chloride. 99% nitric acid diluted by methylene chloride was poured in whilst maintaining strong agitation, until the nitric acid content was 24.5% in the bath of nitric acid-methylene chloride and the nitration yield 35.5. The mixture was left to react for 30 minutes at C. under agitation. Anitrocellulose with a nitrogen content of 12.0 was obtained.
• EXAMPLE 5 A cloth woven with fine cotton threads of long fibres in a width of 15 mm. was impregnated with twice its own weight of methylene chloride and then nitrated for 30 minutes at C. in a bath of 99% nitric acid-methylene chloride. The amount of nitric acid in the nitration bath was and the nitration ratio was 45. A nitrated cloth 0.30 mm. thick with a nitrogen content of 13.0 was obtained.
• the tensile strength for a test piece 1 cm. in size was 11 kg. for the non-nitrated cloth and 10.5 kg. for the nitrated cloth.
• Such a method of analysis is based on the fact that an atomic vapour absorbs radiation in a wavelength which is specific to the cation contained in the vapour.
• the liquid containing the cation to be measured is usually atomized in the flame of a Bunsen-burner.
• molecular dissociation and then the change to the atomic state is caused by the gas evolving from the combustion of a nitrocellulose base powder, and the samples to be measured are either impregnated or simply mixed with the powder.
• Such a method can be used on much smaller specimens and the specimens to be measured do not have to be made into a solution.
• the nitrocellulose powder must simultaneously have several properties:
• the rate of combustion of the test sample must be as constant as possible (by radiation and convection, the length of combustion has an effect on the temperature of the gases); furthermore, this rate is a function of the nitrogen content of the powder;
• Impregnation of the powder by the measuring liquid must be as even as possible in order to avoid at the heart of the mass preferential concentrations of the cations to be measured, which can cause dispersion effects, the consequence of which would be to completely falsify the result by default;
• nitrocelluloses do not allow a nitrogen content to be attained which is sufiiciently constant to be conveniently utilizable. Moreover, their method of manufacture introduces a certain number of cations which would consequently be undesirable.
• Such a nitrocellulose becomes very useful as a source of atomic vapour in atomic absorption spectrophotometry after one or more stabilization treatments, according to the invention, in ethyl alcohol at boiling point, the object of which is to remove all the fibres of weakly-nitrated cellulose.
• the ratio of alcoholznitrocellulose in the course of this treatment is more than 1, preferably being about 2:1 to 3:1.
• Such treatment is followed, after drying and cooling teh mass of stabilized nitrocellulose, by a certain number of rinses in twice-exchanged water and then in ethyl alcohol in the cold state, with drying taking place after each washing.
• Nitration 304 g. of phosphorus pentoxide, 1000 cc. of methylene chloride and then 460 g. of 99% nitric acid were introduced into a nitration reactor in order to form the nitrating bath.
• the reagents and the reactor had previously been cooled to 5 C. After mixing the reagents, the temperature rose to about +25 C. The mixture was left to react for 30 minutes under agitation.
• nitrocellulose obtained was dried and rinsed in methylene chloride in order to obtain nitrocellulose (280 g.) which had a nitrogen content of 14.0 and a degree of polymerisation of 130.
• Stabilization 100 g. of the nitrocellulose already obtained was treated for an hour with 200 cc. of ethyl alcohol at the boiling point in atmospheric pressure. This treatment was followed by drying in vacuum, after which a new stabilization was effected with 200 cc. of 95% ethyl alcohol at the boiling point for an hour at atmospheric pressure; the nitrocellulose thus stabilized was again dried under vacuum and cooled to ambient temperature.
• the homogeneity of the product according to the in vention is determined as a function of the error made in measuring the absorption by the flame of a microcrystalline nitrocellulose, in perfectly defined experimental conditions, of the radiation given out by a given metallic element, in this case copper (wavelength 3247 A.).
• the stability of the product according to the invention is illustrated by the Taliani test carried out on samples of microcrystalline nitrocellulose with a nitrogen content of 13.5% having been stabilized with ethyl alcohol at the boiling point for different periods of time:
• a process of nitration of cellulose which comprises impregnating cellulose with a chlorinated aliphatic solvent in a weight ratio of solventzcellulose of about 1:1 to 6:1, and then subjecting said impregnated cellulose to nitration using a nitrating bath comprising concentrated nitric acid and chlorinated aliphatic solvent, the quantity of nitric acid in the nitrating bath being no greater than 50% and the nitration temperature to 45 C.
• a process according to claim 1 for the preparation of pure, stable microcrystalline nitrocellulose wherein the resultant nitrated cellulose is subjected to a stabilization treatment in ethyl alcohol at the boiling point using an alcoholtnitrocellulose ratio of more than 1 and the stabilized nitrocellulose is cooled, dried and Washed in twiceexchanged Water, under mechanical agitation, at a temperature of about 10 to C., using a nitrocellulose: water ratio of about 1:5 to 1:50 and is finally dried and Washed in cold ethyl alcohol using an alcoholznitrocellulose ratio of about 2:1 to 5:1.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Biochemistry (AREA)
• Materials Engineering (AREA)
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• Life Sciences & Earth Sciences (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)
• Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)

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Citations (4)

• 1968
  • 1968-05-29 FR FR153338A patent/FR94575E/fr not_active Expired
  • 1968-12-11 GB GB58976/68A patent/GB1220299A/en not_active Expired
  • 1968-12-11 BE BE725302D patent/BE725302A/xx unknown
  • 1968-12-12 LU LU57536D patent/LU57536A1/xx unknown
  • 1968-12-17 SE SE17256/68A patent/SE341265B/xx unknown
  • 1968-12-18 ES ES361611A patent/ES361611A1/es not_active Expired
  • 1968-12-18 US US784950A patent/US3534018A/en not_active Expired - Lifetime
  • 1968-12-19 NL NL686818328A patent/NL138963B/xx not_active IP Right Cessation
  • 1968-12-19 CH CH1893768A patent/CH507315A/fr not_active IP Right Cessation
  • 1968-12-19 DE DE19681815809 patent/DE1815809A1/de not_active Withdrawn

Patent Citations (4)

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