Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1999-07-16
2002-06-18
Geist, Gary (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S063000, C536S064000, C536S068000, C536S069000, C536S070000, C536S124000
Reexamination Certificate
active
06407224
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a catalytic system for cellulose acylation and to processes for producing said catalytic system and its application for cellulose acylation and synthesis of acetone-soluble primary cellulose acetates.
The aforesaid catalytic system incorporates as the base an adduct of sulfuric acid and N,N-dimethylacetamide. There is no direct reference to the presence or formation of this adduct in the reaction medium for producing cellulose esters. At the same time, a number of patents describe nonindustrial processes for synthesis of cellulose esters, wherein this adduct may be formed and may function as a specific catalyst. Such processes are recommended for carrying into effect an accelerated process of cellulose acetylation at high temperatures, with the maintaining of a high degree of polymerization of the product obtained.
Cellulose esters produced with the use of this catalytic system are used in traditional fields, e.g., for producing artificial fibers, cigarette stick, cine and photographic materials, commercial and household-use plastics, lacquers and varnishes, surface-coating materials, and for other applications.
2. The Prior Art
U.S. Pat. No. 2,705,710 discloses a cellulose acetylation process which, (since no direct reference is given in this patent) incorporates formation of an adduct of sulfuric acid with N,N-dialkylamide (DAA) selected from the group consisting of N,N-dimethylformamide (DMFA), N,N-diethylformamide (DEFA), N,N-dimethylacetamide (DMAA), and N,N-diethylacetamide (DEAA). This adduct is dissolved in a large quantity of the respective amide. The inventors have to use a large proportion of amide (450 moles per mole of sulfuric acid) which enables one to suppress an excessively high-temperature dissociation of the adduct into free sulfuric acid and amide, thereby retaining an increased degree of polymerization of the cellulose triacetate being synthesized. This, however, results in too high an acetylation module and therefore complicates the process of regeneration of a mixture of a large number of solvents (acetic acid and N,N-dialkylamide).
Fraizy, U.S. Pat. No. 2,536,634 discloses a method for cellulose acetylation wherein cellulose is first treated with acetic acid, acetic anhydride and sulfuric acid. It is then treated with an acetylating mixture comprising acetic anhydride and sulfuric acid. 30.0 minutes later compounds of a basic character and used for partial or complete neutralization of sulfuric acid are added to the reaction medium. In particular, acetic acid is added, and this acid comprises acetamide in terms of 1.0 mole of acetamide per 1.0-2.0 moles of sulfuric acid.
The Fraizy method has the following disadvantages which do not permit to:
(a) implement commercial procedures with very low module, about 3.0 since the module used in the Fraizy method which is considerably higher, approximately 8.0-10.0 can not be reduced due to relatively low temperatures at the acetylation stage, at which temperatures only the Fraizy method can be implemented;
(b) produce cellulose acetates having a higher degree of polymerization since in this method at the beginning of cellulose treatment with the acetylating mixture (within the first 30 minutes), when the reaction proceeds in the presence of the total amount of sulfuric acid, the degree of cellulose polymerization decreases to a considerable extent; and
(c) control the degree of substitution of cellulose acetates during the acetylation process and to obtain acetone-soluble primary cellulose acetates, since this prior art method can not use large enough quantities of sulfuric acid required for achieving the specific goals.
U.S. Pat. No. 2,976,277 describes a process for producing primary acetone-soluble cellulose acetates, using a titanium compound as the catalyst, wherein a “homogeneous” acetylation mechanism takes place. A disadvantage inherent in this process resides in that acetylation is conducted in the medium of acetic anhydride with a high module of acetylation equal to 13, the amount of acetic anhydride used being more than 7 times that required according to theory. In addition, the process is conducted at rather high temperatures equal to 136° C.-137° C.
One prior art process for producing primary low-substituted cellulose esters is described in Japanese Patent 57-35451. This process features homogeneous cellulose acylation conditions (in a cellulose solution in N,N-dimethylacetamide with lithium chloride), and the resultant formation of low-substituted cellulose esters, including cellulose acetate soluble in an acetone-water mixture, the acetylation module being about 40. This prior art process, however, fails to produce primary acetone-soluble cellulose acetates and features a complicated process of regeneration of a mixture of great amounts of solvents, i.e., N,N-dimethylacetamide and acetic acid.
One more prior art process for producing acetone-soluble primary cellulose acetates is known (
Chemical Abstracts,
V. 52, No. 14, Jul. 25, 1958, p. 14169a), wherein the process is conducted in a medium containing acetic acid and acetic anhydride, with a much lower acetylation module than specified above, that is, 8 at a temperature of below 33° C. According to this prior art process, cellulose acetylation is carried out in the presence of a large amount of free sulfuric acid, i.e., 20%-45% of the weight of cellulose. A disadvantage of the process is a relatively low degree of polymerization of the resultant product, that is, 160, as well as comparatively high acetylation module equal to 8.
Soviet Union Patent No. 1,237,671 discloses a process for producing primary cellulose acetates in a medium of N,N-dimethylformamide and used as the catalyst is a mixture called a “complex” by the inventors, comprising 600-800 wt.pt. of N,N-dimethylformamide and 20-40 wt.pt. of sulfuric acid. Primary cellulose acetates are produced as follows: the parent cellulose is activated with this “complex” at 60° C.-80° C. for one hour, whereupon acetylation is carried out in the presence of this “complex”. The resultant product is subjected to desulfation, the catalyst is neutralized, and the end product is extracted by a conventional technique. The end product is acetone-soluble and has a specific viscosity of 0.36-0.68. Disadvantages of the process reside in a high acetylation module equal to 10 and a complicated process of regeneration of a mixture of a great amount of solvent, i.e., N,N-dimethylformamide and acetic acid. In addition, this prior art patent contains an inexact information about the composition of the “complex” used, which is apparently a solution of the adduct of N,N-dimethylformamide and sulfuric acid in N,N-dimethylformamide.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a catalytic system which is capable of synthesizing cellulose esters with a minimized acylation module equal to 3-7, preferably 3.0-5.0, in a medium of a lower fatty acid-anhydride of a lower fatty acid.
The foregoing object is accomplished due to the provision of a catalytic system for cellulose acylation, said system comprised in an acylating mixture composition and comprising an adduct of sulfuric acid with N,N-dimethylacetamide as well as free sulfuric acid or free N,N-dimethylacetamide with the following mole ratio of the components:
adduct of sulfuric acid
1.00
with N,N-dimethylacetamide
free sulfuric acid, max., or
0.49
free N,N-dimethylacetamide, max.
0.40.
The principal component of the catalytic system of the invention is an adduct, i.e., an equimolar complex compound of sulfuric acid with N,N-dimethylacetamide.
It has now been discovered that this complex in a catalytic system with free sulfuric acid incorporates an N-cation, and the use of free N,N-dimethylacetamide in the catalytic system of the invention results in formation of a complex containing both an N-cation and O-cation at a time, whereas the N-cation alone is present in an equimolecular system.
It has also been discovered that an adduct with an N-cation is
Bondar Valentin Ananievich
Grishin Eduard Pavlovich
Mironov Dmitry Petrovich
Shamolin Anatoly Ivanovich
Collard & Roe P.C.
Geist Gary
Nauchno-prozvodstvennaya firma “Efiry Tselljulosy”
White Everett
LandOfFree
Catalytic system for cellulose acylation process for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Catalytic system for cellulose acylation process for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Catalytic system for cellulose acylation process for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2982423