Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1999-10-08
2002-07-09
Wilson, James O. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S037000, C536S038000
Reexamination Certificate
active
06417345
ABSTRACT:
TECHNICAL ART
The present invention relates to a method for producing acetylated pyroxylin (or, in another parlance, cellulose acetate nitrate) used as starting materials for explosives, paints, etc.
BACKGROUND ART
Acetylated pyroxylin, in which heat resistance is imparted to pyroxylin (or, in another parlance, nitrocellulose), is obtained by dissolving pyroxylin in a suitable organic solvent for an acetylation reaction with anhydrous acetic acid, etc. in the presence of a suitable catalyst, and precipitating the reaction product in water or an alcohol, followed by filtration and washing with water, etc. (see JP-A's 56-82849 and 8-277301).
Acetylated pyroxylin is also obtained by dispersing pyroxylin in a suitable dispersing medium for an acetylation reaction with anhydrous acetic acid in the presence of a suitable catalyst while the pyroxylin is maintained in a fibrous (solid phase) state, and filtering the reaction product, followed by water washing, etc. (see Japanese Patent Application No. 10-195292).
Usually, the starting pyroxylin is provided as alcohol-wetted pyroxylin which is wetted with alcohols such as ethanol and/or isopropanol. This is because dry pyroxylin is very dangerous due to its expressiveness, and so must be handled in a water- or alcohol-wetted state. Usually, however, the alcohol-wetted pyroxylin is used because the water-wetted pyroxylin for explosive or paint purposes is disadvantageous for the reason that water is less susceptible to mixing with other solvents.
Originally, pyroxylin is available in a water-wetted state upon production. To convert this to alcohol-wetted pyroxylin, the water must be replaced by alcohols such as ethanol and/or isopropanol for filtration. Thus, the alcohol-wetted pyroxylin is more expensive than the water-wetted pyroxylin.
In one conventional acetylated pyroxylin production method, such expensive alcohol-wetted pyroxylin is used as the starting material. The alcohols contained in the pyroxylin are first replaced by toluene, etc. Then, the pyroxylin is filtered for removal of the alcohols to avert any reaction between the alcohols and anhydrous acetic acid acting as an acetylating agent. Finally, the pyroxylin is allowed to react with anhydrous acetic acid for acetylation.
In another conventional acetylated pyroxylin production method, water-wetted pyroxylin is first directly dissolved in a solvent such as acetone. Then, an acetylating agent, i.e., anhydrous acetic acid is charged in the solution for an acetylation reaction. However, a problem with this method is that the water in the water-wetted pyroxylin reacts with the acetylating agent or anhydrous acetic acid to yield acetic acid; that is, the efficiency of using anhydrous acetic acid becomes worse, resulting in cost increases.
In yet another conventional acetylated pyroxylin production method, water-wetted pyroxylin is first dried for water removal to avert any reaction between the water and an acetylating agent, i.e., anhydrous acetic acid. Then, the dried pyroxylin is subjected to a similar acetylation reaction as mentioned above. However, a problem with this method is that the use of the dried pyroxylin gives rise to the risk of pyroxylin explosion, etc.
DISCLOSURE OF THE INVENTION
As a result of intensive studies, the inventors have found that water-wetted pyroxylin can be pretreated for a safe acetylation reaction, and so have accomplished the instant invention. It is therefore one object of the invention to provide a method for producing acetylated pyroxylin with safety yet at low cost using inexpensive water-wetted pyroxylin rather than expensive alcohol-wetted pyroxylin.
Thus, the present invention provides a method for producing acetylated pyroxylin by permitting an acetylating agent and a catalyst to act on pyroxylin, characterized in that water-wetted pyroxylin is dehydrated in the presence of a nonalcoholic non-solvent for pyroxylin, and the acetylating agent is then permitted to act on dehydrated pyroxylin.
One aspect of the invention is embodied as follows.
(1) A method for producing acetylated pyroxylin by permitting an acetylating agent and a catalyst to act on pyroxylin, characterized in that water-wetted pyroxylin is dehydrated in the presence of a nonalcoholic non-solvent for pyroxylin, and the acetylating agent is then permitted to act on dehydrated pyroxylin.
(2) The method according to (1) above, characterized in that said acetylating agent is anhydrous acetic acid.
(3) The method according to (1) or (2) above, characterized in that for said dehydration, said water-wetted pyroxylin is dispersed in a dispersing medium comprising said nonalcoholic non-solvent for pyroxylin, and then distilled.
(4) The method according to (3) above, characterized in that said dispersing medium is an aromatic hydrocarbon having 6 to 8 carbon atoms.
(5) The method according to (1) or (2) above, characterized in that for said dehydration, said nonalcoholic non-solvent for pyroxylin is added to said water-wetted pyroxylin as a replacing agent, and said water-wetted pyroxylin is filtered.
(6) The method according to (5) above, characterized in that said replacing agent is an aromatic hydrocarbon having 6 to 8 carbon atoms.
(7) The method according to (5) above, characterized in that said replacing agent is a mixture of an aromatic hydrocarbon having 6 to 8 carbon atoms and a nonalcoholic hydrophilic solvent, said mixture having a composition incapable of dissolving pyroxylin therein.
(8) The method according to (7) above, characterized in that said mixture is a mixture of said aromatic hydrocarbon having 6 to 8 carbon atoms and acetic acid at a weight ratio of 40/60 to 95/5.
(9) The method according to (5) above, characterized in that said replacing agent is an aromatic hydrocarbon having 6 to 8 carbon atoms, with a surface active agent added thereto.
(10) The method according to any one of (4) and (6) to (9) above, characterized in that said aromatic hydrocarbon is toluene.
Another aspect of the invention is embodied as follows.
(11) The method according to any one of (1) to (10) above, characterized in that said water-wetted pyroxylin has a water content of 23 to 50% by weight provided that a total weight of said water-wetted pyroxylin is 100% by weight.
(12) The method according to any one of (1) to (11) above, characterized in that said water-wetted pyroxylin has a water content of 25 to 35% by weight provided that a total weight of said water-wetted pyroxylin is 100% by weight.
(13) The method according to any one of (1) to (12) above, characterized in that said non-solvent for pyroxylin is a nonalcoholic solvent, said solvent being substantially incapable of dissolving pyroxylin therein.
(14) The method according to any one of (1) to (13) above, characterized in that said non-solvent for pyroxylin is a nonalcoholic solvent, said solvent being substantially incapable of dissolving pyroxylin therein and a liquid at up to 110° C.
(15) The method according to (3) above, characterized in that said dispersing medium is a hydrocarbon.
(16) The method according to (3) or (15) above, characterized in that said dispersing medium is selected from a group consisting of aliphatic hydrocarbons, alicyclic hydrocarbons and aromatic hydrocarbons.
(17) The method according to (3), (15) or (16) above, characterized in that said dispersing medium is selected from a group consisting of benzene, toluene, ethylbenzene and xylene.
(18) The method according to any one of (3) and (15) to (17) above, characterized in that said dispersing medium is used in an amount that, on a weight basis, is 5 to 80 times as large as a net weight or weight upon drying of pyroxylin.
(19) The method according to any one of (3) and (15) to (17) above, characterized in that said dispersing medium is used in an amount that, on a weight basis, is 8 to 40 times as large as a net weight or weight upon drying of pyroxylin.
(20) The method according to any one of (3) and (15) to (19) above, characterized in that for said dehydration, distillation is effected under reduced pressure.
(21) The method according t
Kamei Noboru
Tanaka Tokuji
Yabune Hideo
Armstrong Westerman & Hattori, LLP
Daicel Chemical Industries Ltd.
Maier Leigh C.
Wilson James O.
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