CA1047033A - Process for producing organic acid esters of cellulose - Google Patents

Abstract

PROCESS FOR PRODUCING ORGANIC ACID ESTERS

OF CELLULOSE

ABSTRACT

A process for producing organic acid esters of cellulose, in an efficient and rapid manner, which includes confricating cellulose in the presence of esterification chemicals, the confrication step providing the major driving force in conducting the esterification reaction; the cellulose acetate is especially useful in fibrous form in the textile industry as textile fibers.

Description

Background of the Invention As ~tated in the Encyclopedia of Polymer Science and Technology, volume 3, page 325 (1972), "Cellulose i~ a polyhydroxy compound and is therefore capable of reacting with such reagents as organic acids, anhydrides, and acid chlorides to form organic e~ters. Theoretically, (cellulose) esters of almost any organic acicl can be prepared, ..."
For example, cellulose acetate, the most important commercial cellulose e~ter, has been conventionally prepared by treat-ment of cellulose pulps in batch-wise operations with acetic acid and acetic anhydride, catalyzed by a mineral acid such as sulfuric acid.
A detailed history of organic cellulose esters is provided on pages 325-354 of the above identified Polymer Encyclopedia volume.
~ urthermore, volume 4 of Kirk Obhmer Encyclopedia of Chemical Technology, pages 632 to 637 (1970), sets forth additional background material on cellulose acetate, cellu-lose acetate propionate, and cellulose acetate butyrate, respectively.
The respective cellulose and cellulose triacetate molecules are pictured on page 329 of the previously described Polymer Encyclopedia article. In ordex to prepare a cellu-lose acetate for use in its main application, i.e., fibers for the textile industry, a product having an acetyl content of from about 37% to about 41% must be prepared. Another way of characterizing the cellulose acetate product is by using the term "degree of substitution" (DS). The degree of sub- -stitution (DS) is defined as the average number of hydroxyl groups substituted, of the three hydroxyl groups available for substitutlon in the anhydro glucose units. For ex~mple, ~0~7~3 so-called cellulose triacetate has an acetyl content of 43.5% and a degree of substitution of about 2.8-3Ø
Two types of acetylation reactions have been suggested for preparing cellulose esters. The first is homogeneous or fibrous esterification. In the homogeneous process, which is by far the major means by which cellulose acetate is produced commercially, an excess of acetic acid and acetic anhydride are employed to form cellulose tri-acetate having a DS of at least 2.8~ The cellulose tri-aceta~e produced is in solution in the form of a dope, i.e.,a viscous, usually clear, cellulose acetate solution, pre-ferably ree of fibers. In order to prepare the desired cellulose ester product having the requisite lower degree of substitution, the cellulose triacetate dope is hydrolyzed by increasing the water content by about 5% to 10%.
As described on pages 337-341 of the ~ncyclopedia of Polymer Science and Technology articla cited above, the major commercial process for the preparation o cellulose acetate is the solution or homogeneous acetylation process.
me most commonly used catalyst in this process is, of course~
sulfuric acid. The Encyclopedia article goes on to state the esterification reaction to produce the triester contem-plate~ adding cellulose and acetic acid to an acetylation mixture where, after the cellulose has been ~wollen and acti-vated, a small portion of the sulfuric acid catalyst is added to initiate cleavage of the cellulose chain. At this point, the mixture is cooled and cold acetic anhydride is added thereto, thus causing any water in the system to be reacted by the acetylation mechanism. The mixture is then further cooled and the acetylation reaction initiated by adding the remainder of the sulfuric acid catalyst. The reaction temperature i8 regulated to gradually increa~e to 7~33 90 -95 F. during an interval of about 1.5 to 2 hours to produce the aforementioned cellulose triester dope. A
60% to 75% mixture of acetic acid and water is then added to t~rminate the acetylation reaction at the requisite vis-cosity by destroying the excess anhydride present in the system. This termination step may require about an hour to complete. If the triester is a desired product, the catalyst i5 then neutralized and removed. If, however, the hydrolyzed lower D.S. product is desired, such as secondary cellulose acetate, the sulfuric acid concenkration is gener-ally reduced to the desired level for conducting the reaction, the temperature is adjusted, and the batch is transferred to an hydrolysis vessel where the cellulose solution is all~wed to hydrolyze at constant temperature until desired acetyl value, as previously discussed, is reached. The cellulose acetate is then re~overed by various known techniques.
On page 340 of the Encyclopedia of Polymer Science and Technology description, a more detailed di~cussion of the intricacies of acetylation is provided. More specifically, in the previously described conventional cellulose acetate process, the acetic acid is employed as a ~olvent for the cellulose triester during the reaction, the acetic anhydride being the esterifying agent and, at the same time, reacting with any water formed during the est0rifica~ion process.
Critical to the formation of a uni~orm cellulose acetate product i`Q a uniform distribution of the sulfuric acid catalyst with respect to the cellulose molecule. H~Wever, since the sulfation reaction between the cellulose and the sulfuric acid is much faster than the acetylation reaction, the sulfuric acid combines completely, but not necessarily uniformly, with the cellulose immediately after the addition of the acetic anhydride. Therefore, control of the kinetics . . .
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of both the sulfation and subsequent acetylation reactions, respectively, to produce a uniform cellulose triester produck is difficalt, at best. Accordingly, the prior art has pro-vided means for chemically driving and controling the sul-fation and acetylation reaction kinetics. In the aforemen-tioned conventional cellulose acetate formation process, for example, acetic anhydride ac~s as the driving force for chemically controling the ~inetics of the respective sulfa-tion and acetylation reactions. This i9 accomplished by the use of an excessive amount of expensive acetic anhydride to form the cellulose triacetate product while meticulously controling the reaction parameters over an inordinately long time period. By employing this tedious, step-wise method, i.e., activation of the cellulose molecule with sulfuric acid followed by acetylation employing acetic anh~dride, the requisite uniform cellulose triester dope will, hopefully, be produced. as stated on lines 14-16 of page 340, of the Polymer ~ncyclopedia article, "Proper correlation o the initial speed of reaction, maximum temperature, and total time of esterification are important in pxoduction control and in obtaining a fiber-free clear solution of cellulose triacetate in acetic acid."
The above peculiarities of the cellulose acetyla~
tion reaction are said to be due to several factors. First, all of the cellulose hydroxyl groups may not be available for reaction because crystallinity or insolubility of the cellulose hinders acces~ of the reagent to the hydroxyl groups. Second, excessive amounts of degradive side reactions mu~t cause cleavage of the cellulose chains resulting in undesirable, nonuniform products having un~atisfactory physi-cal and chemical pxoperties. In the past, the degradation reactions have been controled by lowering the temperature 16J1~7~)33 and allowing the acetylation reaction to continue for long periods of time. Third, the rates of esterification of the primary hydroxyl groups of the cellulose molecule, as com-pared with the secondary hydroxyl groups, are di~erent. As shown by C. J. Malm et alO in the Journal of the American Chemical Society, Volume 75, pages 80-84 (1953), the uncatalyzed reactions of cellulose with acetic anhydride indicate that primary hydroxyl groups reacted ten times as ; fast as the secondary. Furthermore, when the reactions were catalyzed with sulfuric acid, the primary hydroxyl groups reacted two and one-half times as fast. This is a further important reason as to why the cellulose ace~ate ~ormation reaction cannot be~readily controled~
The proposed heterogeneous formation of cellulose acetate is accomplished topichemically without dissolving the cellulose fibers. Furthermore, a product having an ~
optimum degree of substitution for acetone solubility (2~2-2.6) ~ 7~ ' `
can theoretiaally be produced by this proce~s in a direct manner, without going to the cellulose triester, thereby further reducing the need for employment of large, excess amounts of acetic acid and acetic anhydride. Until now, how-ever, an economical process for producing uniformly substituted, heterogeneous cellulose esters, preferably in a direct manner, has not been commercially success~ul.
Thus, cellulose acetate, as well as other higher acid esters, are still, for the most part, produced in batch-wise operations requiring considerable time, u~ing relativaly large ~mounts of exce~s anhydride. Thus, the above standard conventional procedure, ag well as requiring a high capital investment owing to the need for extensive equipment to main-tain the cellulose and reactants during the tedious formation process, also requires a high material cost owing to the , . . . . .
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~7~33 necessity for using exce~sive amount of expensive organic anhydrides.
Various patents describe complex processes for making organic acid esters of cellulo~e~ For Example, U. S. 2,966,485 to Laughlin et al. relates to th~ production of cellulose esters employing a eries of at least four successive reaction æones in an attempt to form uniform homogenaous prod-~ct. In British Patents 740,171 and 802,863 to Societe Rhodiaceta, tubular esterification zones are pro-vided for conducting the requisite ~sterification reaction.
In U. S. 2,778,820 to Clevy et al. and U~ S. 2,854,446 to Robin et al., cellulose fibers, which have been previously beaten at low consistency, are employed as the cellulose feed stream for subsequent cellulose ester formation. Other patents, such as U. S. 3,525,734 to Rajon, d scribe complex processes for acetylation and/or hydrolysis in producing cellulose acetate including modifie~ catalyst systems, the addition of stabilizers, or by providing other addi~ional steps to an already lengthy formation procedure. Other sys-20 tems, such as described in U. S. 3,273,807 to Wright, provide a process for premixing conditioning fluid, such as acetic acid, with cellulose fiber solids to facilitate the produc-tion of fluffed pulp, the respective fibers being individually coated with conditioning fluid. In this case, a refiner is used to perform the premixing function.
Summary of the Invention The present invention relates to an esterification process employed in the rapid and efficient production of organic acid esters of cellulose, which includes employing a confrication step as the predominant means for providing penetration of the esterification chemicals throughout the cellulose in a uniformly distributed and controled manner, , ~ L~47~)33 without unwanted de~radation of the confricated product formed.
"Confrication" is defined, for purposes of this invention, as high energy, frictional interaction of a cellulose-containing reaction ~ystem, including cellulose fibers and all or part of the chemicals required for esteri-fication, the cellulose fibers and esterification chemicals being maintained in intimate contact with each other. More specifically, the chemicals which are employed with the cellulose for con~rication in a high energy reactor include an organic reagent and an esterification catalyst. ~he con-frication step can be conducted in the absence o~ an organic acid anhydride reactant. Moreover, all or part of the anhydride reaction can be provided during the confrication step and/or at a subsequent point in the reaction sequence.
By employing the above confrication step, the esterification chemicals, and, if present, the organic acid anhydride, rapidly and substantially completely penetrate i~
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and are uniformly distributed throuyhout, the cellulose fiber ~ -20 ~tructure without unwanted deyradation thereof. In contra- -~
distinction, the prior art processes provide for topichemical treatment of the cellulose by mixing, wetting, or condition-ing. In ~hese topichemical treatment~, esteri~ication i8 ~ ;~
~lowly advanced chemically ~rom layer-to-layer throughout ;~
the cellulose structure as opposed to the rapid, uniform penetration which occurs when the confrication step of the present invention i5 employed. Thus, prior art proce~se~, by their nature, are inefficient, cumbersome, and difficult to control. Purthermore, in order to attain the requisite uniformity commexcially required of the subject cellulose esters, such as cellulose acetate, cellulose diacetate, and cellulose triacetate, the prior art esterification reactions ., , :: , ' 1~7~33 must be closely monitored with respect to temperature during the entire formation procedure, excessive amounts of anhyd-ride and extensively long periods of time being a prerequis-ite to forming the desired product.
Quite unexpectedly, when the process of the present invention is employed, the requisite organic acid esters of cellulose can be rapidly and continuously formed, the need to harness the subject exothermic esterification in order to maintain uniformity and control degradation and molecular weight of the reaction product being substantially diminished by employing the subject controled esterification. More specifically, when the process of this invention is employed, the above described confrication step can be conducted either at atmospheric or super-atmospheric reaction conditions, respectively, and at ambient or elevated temperatures. In ~;
any case, this is totally contrary to the prior art teach-ings, wherein meticulous regulation o the entire esterifica-~, ~
tion reaction is mandatory if commercial cellulose esters are to be produced.
Thus, while the aforementioned conventional prior art process requires temperature to be maintained at less than about 95 F., during the course of the entire reaction, in order to produce a cellulose ester product having the required physical and chemical properties, temperatures up to about the boiling point of the organic reagent, at a$mos-p heric pressure, and above the boiling point of the organic reagent at corresponding super-atmospheric pressures, can be employed in the subject proces~. It is further provided herein t'nat the ~ubjsct controled esterification can be com-pletPd in a period of at least about 0.5 hour, and preferably in at least about 0.25 hour, and more preferably in a period of at least about 0.1 hour, each of the above ime periods 10~7~33 being measured Erom the point at which the cellulose-containing reaction system, ln the absence or in the eresence of an organic acid anhydride, is subjPct to the subject con-frication.
A reduction in the D.S. of the cellulose ester product is required, after completion of the subject esteri-fication, the esterified cellulosic product formed is then subjected to hydrolysis, using conventional techniques known in the prior art, thereby producing the requisite organic acid esters of cellulose by removing some of the acyl groups formed during the above esteriication formation.
In any event, the overall amount of organic acid anhydride reactant can in many instances be significantly ~ ~ .
reduced to a level well below that which is required for ~ ~
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conventional cellulose ester formation. Alternatively, the anhydride can be substantially eliminated from the reaction scheme. However, in this latter case, the cellulose esters produced have a much broader D.S. range as compared to the above conventional materials, significantly lower D.S. values being encompassed thereby.
Brie-f-DescriPtion of the Draw ng , Figure 1 is a schematic view in hlock form of a process flow diagram illustrating the formation of organic acid esters of cellulose according to the present invention.
Det~iled DescriPtion_of the Invention Referring now to Figure 1, a cellulose feed system 2 is employed, at high consistency, and is comprised of cellu-lose fibers and water. Suitable materials from which the cellulose can be derived for use herein include the usual species of coniferous pulp wood such as spruce, hemlock, fir, pinQ, and the like; deciduous pulp wood such as poplar, birch, ~: ', ' ' ' . ' 7~
cottonwood, alder, etc.; and fibrous plants used in paper-making exemplified ~y cereal straws, corn stalks, bagasse, grasses, and the like.
Individual fibers are separated from the lignin lamella, i.e., the adhesive-like substa~ce which hinds the Eibers together and surrounds the multi~b layers of the cellu-lose in its natural state, by conventional means, such as chemical pulping. The above feed should preferably be cellulosic pulp of a~ least 90 G~ brightness points, having a preferred alpha~cellulose content of at least 85%, and more prefer~bly of at least 90%. Conventional processes require a 92~-96% alpha-cellulose range.
"Consistency", as used herein, refers to the percent by weight on a dry basis of the fibers in the feed. Cellu-lose feed, which is normally prepared as an aqueous mixture, is dewatered and reduced to a high consistency so that the respective fibar surfaces are in intimate contact. Con-sistencies ranging from about 10% to 60%, and preferably from about 15% to 35%, are advantageously employedO
Since high consistency cellulosic fibers, in the usual instance, are in a semifluid state, they are generally considered nonpumpable. Therefore, a device capable of transporting a relatively immobile mixture, such as a screw conveyor, or other like means, can be used to charge the high consistency cellulose to high energy reactor 10.
Reactor 10 can be any device capable of confricating -cellulose feed system 2 and esterification chemicals 3 to produce a confricated, organic acid ester of cellulose 7.
As previously discussed, this ~tep urnishes the predominant means for producing chemical penetration of the esterifica-tion chemicals 3, and, if present, organic acid anhydride reactant 6, throughout the cellulose feed fibers in a : -- 10 --, :

substantially complete, uniformly distributed and controled manner, without unwanted degradation of the confricated product formed. For example, cellulose feed system 2 can be introduced into an area formed within high energy reactor 10, the area including means for confricating feed ~ystem 2 and esterification chemicals 3, respectively. More spe cifically, the confricating means can, for example, compri e a pair of opposed surfaces forming a work space therebe~ween, ;~
the opposed surfaces being capable of providing the requi~
ite amount of confricating energy to the cellulose feed system 2 and esterification chemicals 3 passing within the work space. This provides substantial penetr~tion and ~ ;
uniform distribution of the esterification chemical~ through- ;
out the cellulose fibexs. Typically, a single- or double-revolving disc refiner is employed as a high energy reactor ~ ;~
10. A double-disc refiner, for instance, can be the same refiner, in principle, as the one disclosed in U. S. Patents

2,214,704 and 2,568,783, respectively. Operation of a refiner such as the Bauer 415, in the mechanical sense, is more specifically described in the aforementioned patents ; and in Example 1 of this application. In a similar manner, confricated product 7, or the product from ~econdary reactor 8, can be provided to high energy reactor 9 ~or fur-ther confrication. This latter confrication step can be conducted in the absence or presence of additional amounts of esterification chemicals.
Confricated product 7 can be directly recovered or hydrolyzed employing ~onventional techniques or, as will be hereinafter described, can be ~urther reacted with an organic acid anhydride in secondary reactor 8, or can be further con-fricated in high energy reactor 9.

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The amount of energy imparted to the high con-sistency cellulose ~ystem 2 must be of sufficient magnitude to provide confrication. The power input and feed rate~ of the cellulose can therefore be controled, depending on the type and quality of the cellulose fibers, so that a given amount of energy can be imparted to the fibers. For instance, about 8 horsepower days per ton of air-dried pulp (HPD/T~, the daily horsepower re~uired to produce one ton -~
of pulp per pass through the high energy reactor~s), and pxeferably about 15 HPD/~, and an upper energy level of about 40 NPD/~, and preferably 25 HPD/T, can be exPmplarily employed.
In producing the subject organic acid ester, esterification chemicals 3 are added ~o high energy reactor 10 along with the cellulose feed system 2. Typically, esterification chemicals 3 comprise an organic acid reagent 4 and esterification catalyst 5. Regarding the organic acid reagent 4, lower alkyl organic acids, either individually or combinations thereof, such as propionic acid, butyric acid, and acetic acid~ are most often employed since higher alkyl organic acid reagents generally react too 510wly.
Acetic acid is preferred, however, for use herein. Esteri-fication catalyst 5 can also be added to high energy reactor lO as a component of esterification chemicals 3. Although other cataly~ts have been proposed, a mineral acid catalyst, and more particularly sul~uric acid, has attained the most widespread u~e in catalyzing cellulose e terification reactions.
A~ previously ~tated, the con~rication step can be conducted in the presence or absence of organic acid anhyd-ride reactant 6 employing only the aforementioned feed system 2 and esterification chemicals 3, respectively, in forming - ~2 -. ' , ' , ~47~33 a confricated organic acid ester of cellulose 7O There-after, in a particular emhodiment of this invention, organic acid anhydride 6 can be chemically combined with the previou~ly formed confricated cellulose ester product 7 to produce a substantially complete and esterified organic acid ester of cellulose. The amount of anhydride 6 employed, in any case, is dependent for the mo~t part on reaction conditions, the amount of water present, and the degree of substitution desired. However, since the anhydride reactant is quite costly with respect to the ;~
other material~ employed, a minimum amount should be added in order to maintain the commercial feasibility of the esterification process.
In a further alternative embodiment, varying amounts of organic acid anhydride 6 can be added along ; with the cellulose feed 3ystem 2, to high energy reactor 10. Further amounts of organic acid anhydride 6, if desired, may be also added to secondary reactor 8 fox reaction with confricated cellulose ester product 7, as previously described.
As in the case of esterification chemicals 3, the anhydride reactant 6 on reaction in the high energy reactor 10, substantially penetrates, and is uniformly di~tributed throughout, the confricated cellulosic product.
~ower alkyl organic acid anhydride, individually or com-binations thereof, such as propionic anhydride, butyric anhydride, and acetic anhydride, are, again, typically ernployed since higher organic acid anhydride generally ; reacts too slowly.
~he conditions of temperature and/or pressure at which the con~rication step is conducted does not require the degree sf meticulous regulation present in conventional , ..... .

~(~47~333 esterifica-tion processes. Therefore, confrication can be carried O-lt at a temperature up to the boiling point of organic acid reagent 4, at atmospheric pressure, and above the boiling point of organic acid reagent 4, at correspond- ;
ing super-atmospheric pressure. For example, if the organic acid reagen-t employed is acetic acid, under atmospheric conditions, the confrication energy in the high energy reactor 10 can be up to about 118 C. (the boiling point o~
acetic acid).
In the subject controlled esterification process, an organic acid ester of cellulose, which is substituted in a substantially uniformly distributed manner, is efficiently and rapidly producedO The time required to complete the above esterification, as previously stated, is measured from the point at which the cellulose reaction system 2, -~
in the absence or in the presence of an organic acid anhyd-~ ride, is subjected to confrication in high energy reactor -~ 10. Specifically, the time required to complete the con-trolled esterification, as previously set forth, is at least about 0.5 hour, and preferably in at least about 0.25 hour, and more preferably in at least about 0.1 hour.
Exam~le 1 As an illustration of the process of the present invention for forming organic acid esters of cellulose, in an efficient and rapid manner, including the subject controlled esterification reaction, the following experiments were con-ducted.
(A) 10.0 pounds of a high alpha, acetate grade, cellulose pulp and 0.7 pound of water were premixed with 20 pounds of acetic acid, and fed into a Bauer 415 refiner where they were confricated for a period of 2 minutes, at a power input of 12 HPD/T. A solution of 20 pounds of . ~ .
' ' " ' ' ~47~3 acetic acid ~nd 0.3 pound of sulfuric acid were metered, over the course of the above 2 minute~' confrication period, to the center duct or eye of a 24-inch double-disc Bauer 415 high consistency refiner into a working space for~ed between a pair of rotatable discs. Each of the discs carried a ~ '!
movably mounted, roughened surface, refining plate section. ;~
The nominal consistency of the cellulose-containing reaction system formed, measured at the exit of the refiner, was about 19.6%. The discs, in this case, are rotatable in opposite directions, about a fixed, common axis by suitable power means. The roughened surfaces were in r~latively high motion with respect to each other and were operated at ~ ;
a predetermined power input level of about 12 ~PD/~ so that the desired degree of confrication was maintained therein.
To produce the energy required for confrication, the relative movement between the two surfaces will vary depending upon the type of apparatus employed. In general, if the discs operate in opposed directions, the surfaces will operate at a relative tangential velocity of no less than about 1000 ft/minute, and the rotation will be about a fixed axis to obvia~e relative gyratory movement which causes ball-ing of the fibers. When one of the surfaces is stationary, however, the relative tangential velocity of the surface~
will preferably be at least 5000 ft/minute. Wher2 both sur-~aces are moving in opposite directions, a relative tangential velocity of at least 15,000 ft/minute is preferred. Under all conditions, the velocity between the refiner surfaces should be sufficiently great so as to impart sufficient energy to the fibers to effect confrication and, at the same time, provide sufficient energy to move the fiber~ through the refiner. The two surfaces bet~een which the pulp is txeated should preferably be roughened by providing ' '. , 1~47q~
projections of such character as to engage the high consistency pulp.
Although the average operating pressure imparted by the refiner s~rfaces on the cellulosic fibers may vary, an average pressure of between 5 to 20 pounds/in will be sufficient to produce a pulp of desired physical and chemical properties.
The pulp then is moved rapidly and continuously in a single pass through the work space, in a direction away O from the point of introduction, toward the point of dis~
charge, the cellulose acetate product being rapidly formed therein.
From the confricated product formed, six 765-gram -samples, each containing about 150 grams of cellulose, 600 grams of acetic acid, 5.4 grams of sulfuric acid, and 10.2 grams of water, were added to a cooled solution (at a temperature of about 0 - 5 C.) of 445.5 grams of acetic anhydride, 300 grams of acetic acid, and 5.4 grams of sulfuric acid. The mixtures were stirred and the cellulose quickly went into solution in a time of about 15 minutes. The product formed was cellulose triacetate.
(B) The process described in (A) of this example was repeated, except that in addition to the cellulose, water and acetic acid, a solution of 0.48 pound of sulfuric acid and 20 pounds of acetic anhydride was also pumped into the eye of the refiner over the course of the 2-minute confrica-tion period. The consistency in the refiner during this run was about 19.5%. Three samples of 512 grams each were added to cold solutions of 400 grams of acetic acid, 97 grams of acetic anhydride, and 2.4 grams of sulfuric acid. The cellu-lose triacetate formation reaction began so rapidly that the ~ 7~33;~ ~
confricated product was beginning to turn to acetate dope as it exited the refiner, in a period o~ time o~ at least 0.1 hour.

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Claims (13)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for forming organic acid esters of cellulose, in an efficient and rapid manner, which includes a controled esterification reaction comprising confricating cellulose, at high consistency, in the presence of esteri-fication chemicals, to form a confricated cellulose ester product, said confrication step including high energy, frictional interaction of said cellulose and esterification chemicals, respectively, which are maintained in relatively intimate contact one with the other, and furnishing the predominant means for providing penetration of said esteri-fication chemicals for distribution throughout the cellulose, without substantial degradation of the confricated cellulose ester product formed.

2. The process of claim 1, wherein said cellulose is chemically combined with an organic acid anhydride reactant, said anhydride substantially penetrating, and being distri-buted throughout, said cellulose.

3. The process of claim 1, wherein said organic acid anhydride is present during said confrication step, said anhydride reactant substantially penetrating, and being distributed throughout, the cellulose.

4. The process of claim 3, wherein said confricated cellulose product formed during said confrication step is further reacted with an organic acid anhydride reactant.

5. The process of claim 1, wherein said esterifi-cation chemicals comprise an organic acid reagent and esterification catalyst.

6. The process of claim 2, wherein super-atmospheric pressure is maintained during said confrication step.

7. The process of claim 6, wherein the temperature is maintained above the boiling point of said organic acid reagent during said confrication step.

8. The process of claim 2, wherein the time required to efficiently and rapidly form said organic acid esters of cellulose is less than about 0.5 hour.

9. The process of claim 8, wherein the formation time is less than about 0.1 hour.

10. The process of claim 5, wherein the organic acid reagent is acetic acid and the esterification catalyst is sulfuric acid.

11. The process of claim 2, wherein the organic acid anhydride reactant is acetic anhydride.

12. A process for rapidly forming organic acid esters of cellulose which comprises the steps of:
a) introducing cellulose, at high consistency, and esterification chemicals into an area formed within a high energy reactor, said area including means for confricating said high-consistency cellu-lose in the presence of said esterification chemicals; and b) confricating said cellulose and esterification chemicals, respectively, said confrication step including the high energy, frictional interaction of said cellulose and esterification chemicals which are maintained at relatively intimate contact one with the other, said resultant confricated product being characterized in that said esterifica-tion chemicals have substantially penetrated, and are uniformly distributed throughout, said cellulose.

13. The process of claim 12, wherein said confricating means comprises a pair of opposed surfaces forming a work space therebetween, said opposed surfaces being capable of imparting the requisite amount of confrication energy to said cellulose passing within the confines of said work space.