CA2078876A1 - Preparation of low molecular weight cellulose esters - Google Patents
Preparation of low molecular weight cellulose estersInfo
- Publication number
- CA2078876A1 CA2078876A1 CA 2078876 CA2078876A CA2078876A1 CA 2078876 A1 CA2078876 A1 CA 2078876A1 CA 2078876 CA2078876 CA 2078876 CA 2078876 A CA2078876 A CA 2078876A CA 2078876 A1 CA2078876 A1 CA 2078876A1
- Authority
- CA
- Canada
- Prior art keywords
- cellulose
- anhydride
- cellulose ester
- mixture
- group
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B3/00—Preparation of cellulose esters of organic acids
- C08B3/06—Cellulose acetate, e.g. mono-acetate, di-acetate or tri-acetate
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B3/00—Preparation of cellulose esters of organic acids
- C08B3/02—Catalysts used for the esterification
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B3/00—Preparation of cellulose esters of organic acids
- C08B3/22—Post-esterification treatments, including purification
- C08B3/24—Hydrolysis or ripening
Abstract
A process is disclosed for the preparation of low molecular weight, high hydroxyl cellulose esters ideally suited for use in coating applications. The new synthetic procedure involves treating a cellulose polymer with trifluoroacetic acid, a mineral acid, an acyl or aryl anhydride in an appropriate carboxylic solvent followed by, optionally, in situ hydrolysis. Typical reaction times for conversion to a triester are 5 to 30 minutes while typical hydrolysis times for far hydrolyzed mixed esters range from 4 to 7 hours. Molecular weight loss occurs during formation of the cellulose triester permitting concentrated reaction mixtures and easier isolation of the product ester.
Description
;
PREPARATION OF LOW MOLECULAR WEIGHT CELLU~OSE ESTERS
Field of Invention This invention relates to the preparation 4~
cellulose esters. In one aspect, it relates to the preparation of cellulose triesters. In another aspect, it relates to the preparation of cellulose esters with a degree of substitution (DS) less than three. In yet another aspect, it relates to the preparation of low molecular weight cellulose esters.
Backqround_of the Invention Cellulose esters are of great commercial importance. Cellulose acetates, for example, are used in cigarette filters and as photographic film baseO
Other cellulose esters, e.g., cellulose propionates, cellulose butyrates, cellulose acetate propionates, or cellulose acetate butyrates, have found widespread use in cosmetics, plastics, and pharmaceuticals.
Furthermore, cellulose esters, in particular, cellulose mixed esters having low molecular weight and high hydroxyl content, have high commercial utility as coatings resins (P.M. Cook, U.S. Patent 4,839,230 (1989)). These low molecular weight and high hy~roxyl 25 ~ containing cellulose esters provide for high solids to liquid ratios in coating formulations, provide reactive sites ~or crosslinking reactions, and suitable ~unctionality for derivatization of the cellulose polymer. Therefore, an improved process for the production of cellulose esters suitable for coating applica~ions would be of considerable commercial importance.
, It is well known in the art that cellulose ~triesters, for example cellulose triacetate (DS = 3; the dégree oX substitution is de~ined as the number o~ acyl :~
.
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groups per anhydroglucose ri~g), can he prepared by treating preactivated cellulose with a mixture of sulfuric acid, acetic acid, and acetic anhydride (H~LoB~
Gray and C.J. Staud, U.S. Patent 1~683~347 (1928))o Cellulose triacetate is not suitable for all uses and, consequently, is often hydrolyzed to a cellulose acet~te with a degree of substitution of 0.6-2.8 (C.J. Malm;
U.S. Patent 1~984~147 (1934); C.R. Fordyce, U.S. Patent
PREPARATION OF LOW MOLECULAR WEIGHT CELLU~OSE ESTERS
Field of Invention This invention relates to the preparation 4~
cellulose esters. In one aspect, it relates to the preparation of cellulose triesters. In another aspect, it relates to the preparation of cellulose esters with a degree of substitution (DS) less than three. In yet another aspect, it relates to the preparation of low molecular weight cellulose esters.
Backqround_of the Invention Cellulose esters are of great commercial importance. Cellulose acetates, for example, are used in cigarette filters and as photographic film baseO
Other cellulose esters, e.g., cellulose propionates, cellulose butyrates, cellulose acetate propionates, or cellulose acetate butyrates, have found widespread use in cosmetics, plastics, and pharmaceuticals.
Furthermore, cellulose esters, in particular, cellulose mixed esters having low molecular weight and high hydroxyl content, have high commercial utility as coatings resins (P.M. Cook, U.S. Patent 4,839,230 (1989)). These low molecular weight and high hy~roxyl 25 ~ containing cellulose esters provide for high solids to liquid ratios in coating formulations, provide reactive sites ~or crosslinking reactions, and suitable ~unctionality for derivatization of the cellulose polymer. Therefore, an improved process for the production of cellulose esters suitable for coating applica~ions would be of considerable commercial importance.
, It is well known in the art that cellulose ~triesters, for example cellulose triacetate (DS = 3; the dégree oX substitution is de~ined as the number o~ acyl :~
.
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groups per anhydroglucose ri~g), can he prepared by treating preactivated cellulose with a mixture of sulfuric acid, acetic acid, and acetic anhydride (H~LoB~
Gray and C.J. Staud, U.S. Patent 1~683~347 (1928))o Cellulose triacetate is not suitable for all uses and, consequently, is often hydrolyzed to a cellulose acet~te with a degree of substitution of 0.6-2.8 (C.J. Malm;
U.S. Patent 1~984~147 (1934); C.R. Fordyce, U.S. Patent
2~129~052 (1938)~ Such a process requires dilute reaction mixtures, long reaction times, and requires isolation o~ the high boiling by-pxoduct acetic acid from the dilute reaction mixture.
In U.S. Patent 1~880~808 (1932), H.T. Clarke and -~
C.J. Malm disclose the use of chloro, bromo, or alkoxy containing acetyl anhydrides as an impelling reagent (i.e., an anhydride which promotes esterification without contributing any groups to the ester produced~
in the esterification of cellulose with fatty acidsO In a typical procedure, cellulose was treated with an ~: 20 excess (1.9-9.1 equivalents per hydroxyl) of the impelling reagent, the appropriate fatty acid, and a -catalyst. After the required reaction time, the product was isolated by precipitation into a nonsolven~. Such a process typically requires a large excess o~ the 25 - -impelling reagent and produces only the cellulose _ triester. Eurthermore, isolation of the high boiling impelling acid from a dilute solution which also contain~ the esterifying fatty acid is required.
Similar work disclosed by H.T. Clarke and C.J. Malm (U.S. ~atents 1,690,620 (1928); 1,690,621 (1928);
1,698,048 (lg29); 1,~98,049 ~1929)) as well as by C.J.
Malm and G.D. Hiatt (U.S. Patent 2,172,250 ~1939)) su~fer from the same shortcomings described above.
E.J. Bourn~, M. Stacey, J.C. Tatlow, and J.M.
Tedder (J. Chem. Soc. 1949, 2976-2g79) have disclosed .' ' . ' ~' ' . ' ,, '' ' ' : '. .
'': ' ' : ' ' . '. ' , .' . ' ' :' . "' , ' ....
-: -- 3 --the use of trifluoroacetic anhydride (TFAA) as an impelling reagent in the acetylation of cellulose and amylose with acetic acid. By their process, a large excess of TFAA (8.4 equivalents/hydroxyl) was required in order to obtain satisfactory yields of the triester.
A process for preparing cellulose acetates with a degree of substitution of 0.6-2.8 was not described. Work disclosed by K.S. Barclay, E.J. Bourne, M. Stacey~ and M. Webb (J. Chem. Soc. 1954, 1501-1505), T. Morooka, - 10 M. Norimoto, T. Yamadaj N. Shiraishi (J. Appl. PolymO
Sci. 1984, 29, 3981-3990), and T. Yamagishi, T. Fukuda, T. Miyamoto, J. Watanabe (Polym. Bulletin 1988, 20, 373-377) suffer from the same shortcomings described above.
In U.S. Patent Application Serial No. 495,186 filed March 19, 1990, C.M. Buchanan teaches the use of trifluoroacetic anhydride and acyl anhydride as an effective means for preparing cellulose triesters as well as less than ~ully substituted cellulose esters~
By this proeess, smaller amounts of the impelling reagent are required (typically 0.5-1.0 equivalents~
hydroxyl~ to obtain high molecular weight c~llulose ester derivati~es with a degree of substitution ranging ~rom 0.5 to 3Ø
25 - -- In U.S. Patent 3,617,201 ~1971), R.J. Beral et alO
describe a process in which cellulose fiber is treated with TFAA and a carboxylic acid in an inert solvent (ben~ene) to produce a cellulose ester with a low deqree of substitution (0.1-0.3) suitable for use in cellulose textiles. In this process, the cellulose ~ibers are not disrupted since the reaction medium remains ` heterogeneous throughout. U.S~ Patent 3,097,051 (R~Ho Wadë! 1963) and S.U. Patent 1,047,908 (O.S. Bludova, N.I. Klenkova, A.P. Sokorenko, 1983) teach similar processes.
5~B~TITIJTE ~3HE~
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US-A-1,645,915 describes a process o~ making est~rs of organic acids such as cellulose acetate by treating - cellulosic material with an acylating agent, such as acetic anhydride, the action of which is catalyzed by means of one or more of the compounds, M(Cl04)~ in which M, the positive part, or ion, is less positive than sodium and potassium in the electro-potential scaleO
The valence of M is indicated by ~. M represents not only any metal, (except the alkali metals) which fo~ms a perchlorate, but also hydrogen, the ammonium group~ and many organic bases which form perchlorates.
US-A-2,629,716 describes the use of trifluoroacetic acid as a catalyst in the preparation of esters ~rom monomeric or polymeric alcohols and especially of its catalytic activity in the preparation of cellulose acetate.
There is, therefore, a need for a process whiGh provides both cellulose triesters and high hydroxyl ~ cellulose esters having low molecular weight. The ;;; 20 process must provide for fast esterification and hydrolysis rates. The process should not require an impelling reagent or excessive amounts of mineral acidsO
It is desirable that degradation of the cellulose polymer occux in the initial stages of the reaction 25 ~~ thereby permitting concentrated reaction mixtures. The _ process must allow for practical reaction temperatures as well as for easy and practical product and carboxylic acid recovery.
SummarY of the Invention Accordingly, we have discovered a process for the preparation of low molecular w~ight cellulose esters which meets the needs of the cellulose art.
Specifically, cellulose triesters (i.e., cellulose ~ ~ T~ ~F~T
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. -- 5 esters having a DS of about 3) are rapidly prepared by contacting:
(~) a cellulose pol~mer having a degree of substitu~ion less than that of the product cellulose ester (i.e., less than about 3) and also having a molecular weight greater than that of the product cellulose ester, (b) trifluoroacetic acid, (c) at least one acyl anhydride of the formula R/ ~o/ ~ 1 wherein each of R and Rl is, independently, H, a straight chain alkyl, branched chain alkyl, aryl, or substituted aryl, and (d) a mineral acid, in the presence o~ a solubilizing amount of a solvent and under conditions such that the desired cellulose ester is formed (such process will alternatively be referred to herein as the "triesterification process"~
1` To prepare cellulose esters with a DS of less than about 3, the cellulose triester formed by the above-described process is suhjected to a second step " (hereinafter alternatively re~erred to herein as the "hydrolysis step") in which the cellulose triester (i.e., cellulose ester with a DS of about 3) is.
contacted with a suf~icient amount of a reactive - hydrolysis solvent under conditions to form the desired cellulosa ester with a DS higher than the cellulose polymer used as a starting material ~or the triesterification process.
Det~iled Description of the Invention : In accordance with the present invention, typical cellulose esters produced by the process of the . . .
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: -- 6 --- invention are Cl to C20 esters of cellulose, have the`................. desired DS, have a lower molecular weight than the cellulose polymer starting material, and comprise repeating units of the 6tructure:
:-~` \ \ CH20R4 RO ~ OR
. _ 3 ~ ~ `
wherein R2, R3, and R~ are selected separately from thegroup consisting of: hydrogen, straight chain alkanoyl, . branched alkanoyl, aroyl, and heteroaroyl. The ~ alkanoyl, aroyl, and heteroaroyl moieties typically contain up to 20 carbon atoms, more typically up to 6 carbon atoms. Preferred cellulose esters produced by the process of the invention include cellulose triacetate, cellulose tripropionate, cellulose tributyrate, cellulose acetate, cellulose propionatef cellulose butyrate, cellulose acetate propionate, and .: cellulose acetate butyrate.
The cellulose polymer used as a starting ~aterial : for preparing the cellulose triester can be cellulose, a secondary cellulose ester, or a mixture thereof.
Examples of secondary cellulose esters include cellulose _ acetate, cellulose propionate, and cellulose butyrate, and are described in U.S. Pat~nt 1,984,147.
The cellulose esters useful in the present inv2ntion as starting materials have at least 2 anhydroglucose rings and typically have between 2 and 5,000 anhydroglucose rings; also, such polymers typically have an inherent viscosity (I.V.) o~ about 1.0 to 3.0 deciliters~gram as ~easured at a temperature of 25C for 0.25 gram sample in ~00 ml of a 60~40 by weight sol~tion of phenol~tetrachloroethane. As these I.V.
values indicake, such polymers have a molecular weight ..
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greater than the product cellulose ester; typical number average molecular weight values range from l.o to 10.0 X 105.
The product cellulose esters produced by the process of this invention typically have an inh~rent viscosity (I.V.) of about 0.2 to about 0.6 deciliters/gram as measured at a temperature of 250C
for 0.25 gram sample in 100 ml of a 60~40 by weight solution of phenol/tetrachloroethane and a number average molecular weight of less than about 1.0 X 105.
The DS of the cellulose polymer starting material for the triesterification process is preferably 0 to about 2.9.
As is known in the art, the theoretical maximum DS .
for a cellulose ester is 3. However, due to normal error of standard analytical techniques, the maximum DS
will vary experimentally, for example an error of plus or minus 3 percent is common. When the term "about" is used herein to describe a given DS, it is contemplated that this analytical error will be taken into account as well as minor actual deviations in the DS of the particular cellulose ester. Therefore, it is contemplated that the term "about 3" when referring to a given DS means a measured range of 2.9 to 3.1, preferably 2.95 to 3.05.
Typical anhydrides suitable for the practice of the pFesent invention are..:o.f.the structure:
- R/ b ~1 -:
wherein each of R and R~ is, independently, selected - from the group consisting o~ hydrogen, a straight chain alkyl, a branched chain alkyl,- aryi or substituted aryl.
In the acyl anhydride molecule, typical straighk chain alkyl groups contain 1 to 20 carbon atoms, typical . :
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branched chain alkyl groups have 3 to 20 carbon atoms, and typical aryl groups have 6 to 12 carbon atoms.
` Substituted aryl groups are typically substituted with 1, 2 or 3 substituents such as lower alkyl (i.e., alkyl groups having 1 to 3 carbon atoms), halo (i.e., ~, Br, Cl or I), and lower alkoxy (i.e., alkoxy groups having 1 to 3 carbon atoms). It is preferred that the acyl anhydride is symmetrical, i.e., that R and R1 are the same.
Exemplary acyl anhydrides useful in the present invention are, but are not limited to, acetic anhydride, propionic anhydride, isobutyric anhydride, butyric anhydride, trimethylacetic anhydride, ~aleric anhydride, hexanoic anhydride, nonanoic anhydride, benzoic anhydride, or a mixture thereof. The most preferred acyl anhydrides include acetic anhydride, propionic anhydride, butyric anhydride, or a mixture thereofO
The mineral acid useful as component (d) in the present invention can be any strong mineral acid which~
when combined with trifluoroacetic acid (TFA), promotes rapid esterification, hydrolysis, and moleculax weight loss. Examples of such mineral acids include sulfuric acid, hydrochloric acid, Mg(Cl04)2 and HCl04. 0~ course, mixtures of two or more mineral acids are contemplated for use in the present invention.
_ In the process of preparing the cellulose triester lQ the amount of component (b) (i . 2., the TFA) is preferably about 0.25 to 1.0 equivalents per hydroxyl~
more preferably about 1.0 equivalents; the amount of component (c) is preferably at least 1.0 equiYalent per hydroxyl, more preferably about }.7 equivalents; and the amount of component (d) is preferably about 0.0001 to 0.01 equival2nts per hydroxyl; more pxefPrably about - 0.008 equivalents~
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.'i`' -- 9 _ .''.' , - Conditions suitable for the formation o~ celluloi~e esters can vary widely. The temperature typically ~ varies from ambient to the temperature at which the - mixture begins to reflux; typically about 20C to about 150~C. More preferably, the temperature is 700C.
Those skilled in the art readily recognize that contact time and acyl anhydride reactivity are interdependent. For example, acylation with a mixture of propionic anhydride and acetic anhydride requires a contact time as little as 5 minutes~ When acylating the same wood pulp with a mixture of butyric acid and acetic anhydrid~, a contact time of 30 minutes may be requiredO
Those skilled in the art understand that the flat period (i.e., the period of time after ~ormation of the cellulose triester and beginning of hydrolysis during which polymer degradation is occurring) can vary widelyO
Accordingly, a broad flat period for the process of the ~- invention is about 1 minute to about 120 minutes. A
, more preferred ~lat period is about 5 minutes to about ^~ 20 30 minutes.
Thu~, the total reaction period of time (i.e., including the period ~or acylation, flat period, and hydrolysis period) can vary from about 0.5 to about 25 hours. A preferred total reaction period is about 4 to 2~--about 8 hours.
The mixture of the TFA and the mineral acid in the : ." _ .
triesteri~ication process essentially acts as a .... . . ......
ca~alyst. In addition, the mineral acid functions to degrade the ceflulose polymer. By utilizing a mineral acid in th~ triesterification process, molecular weight loss occurs during ~ormation of the cellulose triester which permits more concentrated reaction mixtures and thereby easier isolation of the product cellulose ester.
For the triesterification process said solvent is typically a carboxylic acid having 1 to 20 carbon atoms, , SUÇ~S~ E S~ , .
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dimethylformamide, dimethylsulfoxide, or a mixture thereof; howe~er, excess acyl anhydride can be used as solvent. The carboxylic acid can optionally be substituted with halogen atoms such as F, Br, and C1~ an example of such a substituted carboxylic acid is trifluoroacetic acid. Preferred is a carboxylic acid, Pspecially the particular carboxylic acid corresponding to the acyl anhydride(s) employed, or, in the case of mixed esters, corresponding to the least reactive acyl anhydride.
If a carboxylic acid is used as a reaction solvent, the acid can contribute to the reaction (i.e., act as a reactant) if the particular carboxylic acid used has a corresponding anhydride that is more reactive than the acyl anhydride employed as reactant (c).
The reactive hydrolysis solvent for the hydrolysis step is typically a polar solvent such as an n-alkanol having 1 to 4 carbon atoms, water, a branched chain alkanol having 3 to 4 carbon atoms, an aryl alkanol having 7 to 12 carbon atoms, and a mixture thereo~O
` Preferred reactive hydrolysis solvents include methanol, ethanol, n-propanol, n-butanol, isopropyl alcohol, benzyl alcohol, water, or a mixture thereofO
Most preferred are methanol and water, or a mixture 25 -thereof.
For the hydrolysis step, the preferred amount of reactive hydrolysis solvent is from about 1 volume % to that amount which results in the desired product precipitating from solution. It is more preferred that the amount of reactive hydrolysis solvent is from about 5 to about 15 volume %.
Preferred reaction conditions for the hydrolysis : step include a temperature range from ambient to the temperature at which the mixture begins to reflux (typically 20C to 150C) and a reaction time of about ~' .
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o.s hours to about 24 hours. Most preferred reaction conditions are a temperature of 70OC and a reaction time of about 4 hours to about 7 hours.
The cellulose triester formed by the triesteri,,fi-cation process can be isolated and~or purified byconventional means known in the art such as by precipitation into a nonsolvent, distillation, or by spray drying (and, if desired, subjected to the hydrolysis step). Alternatively, the cellulose triester can be hydrolyzed directly in the reaction medium without the need for any special purification or isolation steps. After hydrolysis, the desired cellulose ester can be isolated and purified by conventional means known in the art such as by a nonsolvent precipitation, distillation, or by spray drying. , , The preferred cellulose esters produ~ed after khe hydrolysis step are substantially the same as produced by the triesterification process except that the DS is ' 20 lower. Thus, preferred products produced by the hydrolysis step include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.
Typical desired products produced after the 25 '~hydrolysis step of the invention have a DS o~ about 0O5 " _to about 2.85, more typically about 1.9 to about 2.3 for mixed esters, the 4s refer~ to the combined DS).
The cellulose esters produced by the triesterifica-tion process ~optionally followed by the hydrolysis step) have low molecular weight. Typical molecular weight ranges of cellulose esters produced by the ' , process of the present inventio~ have a number average molecular weight (~) of about 0.01 X 10S to about l.0 X 105, a weight average molecular weight ~r~) of abou~ 0.02 X 103,to about 2.0 X 105, and a Z average `:
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molecular weight (~) of about 0. 04 X 105 to about 4. 0 X 105. Preferred molecular weight ranges are an of about 0.2 X 105 to about 0.6 X 105, a MW of about 0.6 X 105 to about 1.0 X 105, and a ~ of about 0.3 X 105 ` 5 to about 3.0 X 105. The ratio o~ M~ is preferably about 1.0 to about 2.0, with about 1.4 to about 1.9 being more preferred.
As is well known in the art, I.V. values are related to molecular weight. The I.V. of the product - 10 cellulose ester produced by the triesterification process toptionally followed by the hydrolysis step) is typically about 0.2 to about 0.6, preferably about 0O3 to about 0.4 deciliters/gram as measured at a temperature of 25C for 0.25 gram sample in 100 ml of a 60/40 by weight solution of phenol/tetrachloroethaneO
Some products produced after the hydrolysis step, especially high hydroxyl (i.e., low DS), mixed esters, will be soluble in n-propylacetate tn-PrOAc), acetone~
~` CHCl3, ethanol, tetrahydrofuran (THF), and dimethylsulfoxide (DMS0).
The following examples are to illustrate the invention but should not be interpreted as a limitation thereon.
.-.
2~ -- EXAMPLES
In the following examples, water activated ." ._ cellulose was prepared by mechanically blending the ceIlulose with water. The excess water was removed by filtration. Résidual water was removed by washing the damp cellulose with the carboxylic acid which corr~sponds to an acyl group being attached to the c~llulose polymer. The activated cellulose was loaded into a flask equipped ~or mechanical stirring. To the cellulose was added a mixture o~ acyl anhydride (5) and a catalyst consisting of TFA and a mineral acid such as ., .
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~' ~ ' ~ , ' ' '' ' i , ' , , , "`' sulfuric acid. The reactor was then heated to 70~Co The reaction mixture was stirred until a cleax solu.tion - was obtained which is the indicated contact time ~or formation of the triester. After formation of the - 5 triester, the reaction mixture was maintained at 70c for a period of time to allow degradation of the pol~mer (i.e., a flat period) before adding a hydrolysis solution to the reaction mixture. The reaction was stirred for the indicated time(s) before isolating the product by addition of a nonsolvent. The TFA, the carboxylic acid(s), and the unconsumed acyl anhydride(s) can be recovered from the reaction mixture before the addition of a nonsolvent. Also, the TFA and carboxylic acids can be recovered from the ~iltrate ~ollowing precipitation by distillation techniques familiar to those skilled in the art. Alternatively, the TFA, the carboxylic acid(s), and the unconsumed acyl anhydride(s) can be isolated by spray drying techniques familiar to those skilled in the art. The results in the examples indicate yields of isolated, well-characterized products. The products were typically characterized by proton NMR spectroscopy, inherent viscosity, gel permeation chromatography (values are reported in polystyrene equivalents), and other methods familiar to 2~--those skilled in the art. The abbreviations used herein have the following meanings: TFA is trifluoroacetic acid, TFAA is trifluoroacetic anhydride, NMR is nuclear ......
magnetic resonance, Pr DS is propionyl degree of substitution, ~c DS is acetyl degree of substitution, TCE is tetrachloroethane, GPC is gel permeation chromatography, DMF is dimethylformamide, T~F is tetrahydrofuran, DMSO is dimethylsulfoxide, n-PrOAc is propy;l acetate, and CAB is ceIlulose acetate butyrate.
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.~ Reagents set forth below were subjected to the ~` standard procedure described above under the indicated reaction conditions. The result, in terms of identity and yield of the desired cellulose ester, and key analyses of the product, are also set f orth below~
Starting Cellulosic Cellulose Weight (g) 50 Equivalents of 1.0 TFA/hydroxyl Equivalents of 0.008 H2SO4/hydroxyl : Acyl Anhydride Acetic Anhydride Equivalents/hydroxyl 0.03 20 Acyl Anhydride Propionic Anhydride Equivalents/hydroxyl 1.7 Carboxylic Acid Propionic Acid Weight (g) 107 : 25 . Hydrolysis Mixture 76.5 g water Contact ~ime (min) 10 30 Flat Period (min) 30 HydrolysisPr DS Ac DS I.V.
~ Time (h~ (IH NMR) !IH NMR~ .(Phenol~TCE) ; 0 3.00 0.05 0.35 2.0 2.59 0.03 0.37 --.. ... .. .
4.0 2.24 0.02 0.39 .
5.0 2.06 0.01 0.41 ~.0 1.93 0.01 0.42 : 7.0 1.84 0.01 0.42 7.8 1.70 0.01 . 0.44 . - - .
This exa~ple demonstrates that a catalyst system consisting o~ TFA~H2SO4 rapidly promotes the .
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In U.S. Patent 1~880~808 (1932), H.T. Clarke and -~
C.J. Malm disclose the use of chloro, bromo, or alkoxy containing acetyl anhydrides as an impelling reagent (i.e., an anhydride which promotes esterification without contributing any groups to the ester produced~
in the esterification of cellulose with fatty acidsO In a typical procedure, cellulose was treated with an ~: 20 excess (1.9-9.1 equivalents per hydroxyl) of the impelling reagent, the appropriate fatty acid, and a -catalyst. After the required reaction time, the product was isolated by precipitation into a nonsolven~. Such a process typically requires a large excess o~ the 25 - -impelling reagent and produces only the cellulose _ triester. Eurthermore, isolation of the high boiling impelling acid from a dilute solution which also contain~ the esterifying fatty acid is required.
Similar work disclosed by H.T. Clarke and C.J. Malm (U.S. ~atents 1,690,620 (1928); 1,690,621 (1928);
1,698,048 (lg29); 1,~98,049 ~1929)) as well as by C.J.
Malm and G.D. Hiatt (U.S. Patent 2,172,250 ~1939)) su~fer from the same shortcomings described above.
E.J. Bourn~, M. Stacey, J.C. Tatlow, and J.M.
Tedder (J. Chem. Soc. 1949, 2976-2g79) have disclosed .' ' . ' ~' ' . ' ,, '' ' ' : '. .
'': ' ' : ' ' . '. ' , .' . ' ' :' . "' , ' ....
-: -- 3 --the use of trifluoroacetic anhydride (TFAA) as an impelling reagent in the acetylation of cellulose and amylose with acetic acid. By their process, a large excess of TFAA (8.4 equivalents/hydroxyl) was required in order to obtain satisfactory yields of the triester.
A process for preparing cellulose acetates with a degree of substitution of 0.6-2.8 was not described. Work disclosed by K.S. Barclay, E.J. Bourne, M. Stacey~ and M. Webb (J. Chem. Soc. 1954, 1501-1505), T. Morooka, - 10 M. Norimoto, T. Yamadaj N. Shiraishi (J. Appl. PolymO
Sci. 1984, 29, 3981-3990), and T. Yamagishi, T. Fukuda, T. Miyamoto, J. Watanabe (Polym. Bulletin 1988, 20, 373-377) suffer from the same shortcomings described above.
In U.S. Patent Application Serial No. 495,186 filed March 19, 1990, C.M. Buchanan teaches the use of trifluoroacetic anhydride and acyl anhydride as an effective means for preparing cellulose triesters as well as less than ~ully substituted cellulose esters~
By this proeess, smaller amounts of the impelling reagent are required (typically 0.5-1.0 equivalents~
hydroxyl~ to obtain high molecular weight c~llulose ester derivati~es with a degree of substitution ranging ~rom 0.5 to 3Ø
25 - -- In U.S. Patent 3,617,201 ~1971), R.J. Beral et alO
describe a process in which cellulose fiber is treated with TFAA and a carboxylic acid in an inert solvent (ben~ene) to produce a cellulose ester with a low deqree of substitution (0.1-0.3) suitable for use in cellulose textiles. In this process, the cellulose ~ibers are not disrupted since the reaction medium remains ` heterogeneous throughout. U.S~ Patent 3,097,051 (R~Ho Wadë! 1963) and S.U. Patent 1,047,908 (O.S. Bludova, N.I. Klenkova, A.P. Sokorenko, 1983) teach similar processes.
5~B~TITIJTE ~3HE~
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US-A-1,645,915 describes a process o~ making est~rs of organic acids such as cellulose acetate by treating - cellulosic material with an acylating agent, such as acetic anhydride, the action of which is catalyzed by means of one or more of the compounds, M(Cl04)~ in which M, the positive part, or ion, is less positive than sodium and potassium in the electro-potential scaleO
The valence of M is indicated by ~. M represents not only any metal, (except the alkali metals) which fo~ms a perchlorate, but also hydrogen, the ammonium group~ and many organic bases which form perchlorates.
US-A-2,629,716 describes the use of trifluoroacetic acid as a catalyst in the preparation of esters ~rom monomeric or polymeric alcohols and especially of its catalytic activity in the preparation of cellulose acetate.
There is, therefore, a need for a process whiGh provides both cellulose triesters and high hydroxyl ~ cellulose esters having low molecular weight. The ;;; 20 process must provide for fast esterification and hydrolysis rates. The process should not require an impelling reagent or excessive amounts of mineral acidsO
It is desirable that degradation of the cellulose polymer occux in the initial stages of the reaction 25 ~~ thereby permitting concentrated reaction mixtures. The _ process must allow for practical reaction temperatures as well as for easy and practical product and carboxylic acid recovery.
SummarY of the Invention Accordingly, we have discovered a process for the preparation of low molecular w~ight cellulose esters which meets the needs of the cellulose art.
Specifically, cellulose triesters (i.e., cellulose ~ ~ T~ ~F~T
, .. , :., . : -.::.: ',',,: ' ' '~. .' ' :'' , . ' '' . :' . :. . : : :' ' : : :
,- : . . . . . .
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. -- 5 esters having a DS of about 3) are rapidly prepared by contacting:
(~) a cellulose pol~mer having a degree of substitu~ion less than that of the product cellulose ester (i.e., less than about 3) and also having a molecular weight greater than that of the product cellulose ester, (b) trifluoroacetic acid, (c) at least one acyl anhydride of the formula R/ ~o/ ~ 1 wherein each of R and Rl is, independently, H, a straight chain alkyl, branched chain alkyl, aryl, or substituted aryl, and (d) a mineral acid, in the presence o~ a solubilizing amount of a solvent and under conditions such that the desired cellulose ester is formed (such process will alternatively be referred to herein as the "triesterification process"~
1` To prepare cellulose esters with a DS of less than about 3, the cellulose triester formed by the above-described process is suhjected to a second step " (hereinafter alternatively re~erred to herein as the "hydrolysis step") in which the cellulose triester (i.e., cellulose ester with a DS of about 3) is.
contacted with a suf~icient amount of a reactive - hydrolysis solvent under conditions to form the desired cellulosa ester with a DS higher than the cellulose polymer used as a starting material ~or the triesterification process.
Det~iled Description of the Invention : In accordance with the present invention, typical cellulose esters produced by the process of the . . .
:` , . .
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: -- 6 --- invention are Cl to C20 esters of cellulose, have the`................. desired DS, have a lower molecular weight than the cellulose polymer starting material, and comprise repeating units of the 6tructure:
:-~` \ \ CH20R4 RO ~ OR
. _ 3 ~ ~ `
wherein R2, R3, and R~ are selected separately from thegroup consisting of: hydrogen, straight chain alkanoyl, . branched alkanoyl, aroyl, and heteroaroyl. The ~ alkanoyl, aroyl, and heteroaroyl moieties typically contain up to 20 carbon atoms, more typically up to 6 carbon atoms. Preferred cellulose esters produced by the process of the invention include cellulose triacetate, cellulose tripropionate, cellulose tributyrate, cellulose acetate, cellulose propionatef cellulose butyrate, cellulose acetate propionate, and .: cellulose acetate butyrate.
The cellulose polymer used as a starting ~aterial : for preparing the cellulose triester can be cellulose, a secondary cellulose ester, or a mixture thereof.
Examples of secondary cellulose esters include cellulose _ acetate, cellulose propionate, and cellulose butyrate, and are described in U.S. Pat~nt 1,984,147.
The cellulose esters useful in the present inv2ntion as starting materials have at least 2 anhydroglucose rings and typically have between 2 and 5,000 anhydroglucose rings; also, such polymers typically have an inherent viscosity (I.V.) o~ about 1.0 to 3.0 deciliters~gram as ~easured at a temperature of 25C for 0.25 gram sample in ~00 ml of a 60~40 by weight sol~tion of phenol~tetrachloroethane. As these I.V.
values indicake, such polymers have a molecular weight ..
. . .
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.. . . . . ... - .. . .
- . .. . . .
greater than the product cellulose ester; typical number average molecular weight values range from l.o to 10.0 X 105.
The product cellulose esters produced by the process of this invention typically have an inh~rent viscosity (I.V.) of about 0.2 to about 0.6 deciliters/gram as measured at a temperature of 250C
for 0.25 gram sample in 100 ml of a 60~40 by weight solution of phenol/tetrachloroethane and a number average molecular weight of less than about 1.0 X 105.
The DS of the cellulose polymer starting material for the triesterification process is preferably 0 to about 2.9.
As is known in the art, the theoretical maximum DS .
for a cellulose ester is 3. However, due to normal error of standard analytical techniques, the maximum DS
will vary experimentally, for example an error of plus or minus 3 percent is common. When the term "about" is used herein to describe a given DS, it is contemplated that this analytical error will be taken into account as well as minor actual deviations in the DS of the particular cellulose ester. Therefore, it is contemplated that the term "about 3" when referring to a given DS means a measured range of 2.9 to 3.1, preferably 2.95 to 3.05.
Typical anhydrides suitable for the practice of the pFesent invention are..:o.f.the structure:
- R/ b ~1 -:
wherein each of R and R~ is, independently, selected - from the group consisting o~ hydrogen, a straight chain alkyl, a branched chain alkyl,- aryi or substituted aryl.
In the acyl anhydride molecule, typical straighk chain alkyl groups contain 1 to 20 carbon atoms, typical . :
.
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branched chain alkyl groups have 3 to 20 carbon atoms, and typical aryl groups have 6 to 12 carbon atoms.
` Substituted aryl groups are typically substituted with 1, 2 or 3 substituents such as lower alkyl (i.e., alkyl groups having 1 to 3 carbon atoms), halo (i.e., ~, Br, Cl or I), and lower alkoxy (i.e., alkoxy groups having 1 to 3 carbon atoms). It is preferred that the acyl anhydride is symmetrical, i.e., that R and R1 are the same.
Exemplary acyl anhydrides useful in the present invention are, but are not limited to, acetic anhydride, propionic anhydride, isobutyric anhydride, butyric anhydride, trimethylacetic anhydride, ~aleric anhydride, hexanoic anhydride, nonanoic anhydride, benzoic anhydride, or a mixture thereof. The most preferred acyl anhydrides include acetic anhydride, propionic anhydride, butyric anhydride, or a mixture thereofO
The mineral acid useful as component (d) in the present invention can be any strong mineral acid which~
when combined with trifluoroacetic acid (TFA), promotes rapid esterification, hydrolysis, and moleculax weight loss. Examples of such mineral acids include sulfuric acid, hydrochloric acid, Mg(Cl04)2 and HCl04. 0~ course, mixtures of two or more mineral acids are contemplated for use in the present invention.
_ In the process of preparing the cellulose triester lQ the amount of component (b) (i . 2., the TFA) is preferably about 0.25 to 1.0 equivalents per hydroxyl~
more preferably about 1.0 equivalents; the amount of component (c) is preferably at least 1.0 equiYalent per hydroxyl, more preferably about }.7 equivalents; and the amount of component (d) is preferably about 0.0001 to 0.01 equival2nts per hydroxyl; more pxefPrably about - 0.008 equivalents~
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.'i`' -- 9 _ .''.' , - Conditions suitable for the formation o~ celluloi~e esters can vary widely. The temperature typically ~ varies from ambient to the temperature at which the - mixture begins to reflux; typically about 20C to about 150~C. More preferably, the temperature is 700C.
Those skilled in the art readily recognize that contact time and acyl anhydride reactivity are interdependent. For example, acylation with a mixture of propionic anhydride and acetic anhydride requires a contact time as little as 5 minutes~ When acylating the same wood pulp with a mixture of butyric acid and acetic anhydrid~, a contact time of 30 minutes may be requiredO
Those skilled in the art understand that the flat period (i.e., the period of time after ~ormation of the cellulose triester and beginning of hydrolysis during which polymer degradation is occurring) can vary widelyO
Accordingly, a broad flat period for the process of the ~- invention is about 1 minute to about 120 minutes. A
, more preferred ~lat period is about 5 minutes to about ^~ 20 30 minutes.
Thu~, the total reaction period of time (i.e., including the period ~or acylation, flat period, and hydrolysis period) can vary from about 0.5 to about 25 hours. A preferred total reaction period is about 4 to 2~--about 8 hours.
The mixture of the TFA and the mineral acid in the : ." _ .
triesteri~ication process essentially acts as a .... . . ......
ca~alyst. In addition, the mineral acid functions to degrade the ceflulose polymer. By utilizing a mineral acid in th~ triesterification process, molecular weight loss occurs during ~ormation of the cellulose triester which permits more concentrated reaction mixtures and thereby easier isolation of the product cellulose ester.
For the triesterification process said solvent is typically a carboxylic acid having 1 to 20 carbon atoms, , SUÇ~S~ E S~ , .
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dimethylformamide, dimethylsulfoxide, or a mixture thereof; howe~er, excess acyl anhydride can be used as solvent. The carboxylic acid can optionally be substituted with halogen atoms such as F, Br, and C1~ an example of such a substituted carboxylic acid is trifluoroacetic acid. Preferred is a carboxylic acid, Pspecially the particular carboxylic acid corresponding to the acyl anhydride(s) employed, or, in the case of mixed esters, corresponding to the least reactive acyl anhydride.
If a carboxylic acid is used as a reaction solvent, the acid can contribute to the reaction (i.e., act as a reactant) if the particular carboxylic acid used has a corresponding anhydride that is more reactive than the acyl anhydride employed as reactant (c).
The reactive hydrolysis solvent for the hydrolysis step is typically a polar solvent such as an n-alkanol having 1 to 4 carbon atoms, water, a branched chain alkanol having 3 to 4 carbon atoms, an aryl alkanol having 7 to 12 carbon atoms, and a mixture thereo~O
` Preferred reactive hydrolysis solvents include methanol, ethanol, n-propanol, n-butanol, isopropyl alcohol, benzyl alcohol, water, or a mixture thereofO
Most preferred are methanol and water, or a mixture 25 -thereof.
For the hydrolysis step, the preferred amount of reactive hydrolysis solvent is from about 1 volume % to that amount which results in the desired product precipitating from solution. It is more preferred that the amount of reactive hydrolysis solvent is from about 5 to about 15 volume %.
Preferred reaction conditions for the hydrolysis : step include a temperature range from ambient to the temperature at which the mixture begins to reflux (typically 20C to 150C) and a reaction time of about ~' .
.~ . , .
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o.s hours to about 24 hours. Most preferred reaction conditions are a temperature of 70OC and a reaction time of about 4 hours to about 7 hours.
The cellulose triester formed by the triesteri,,fi-cation process can be isolated and~or purified byconventional means known in the art such as by precipitation into a nonsolvent, distillation, or by spray drying (and, if desired, subjected to the hydrolysis step). Alternatively, the cellulose triester can be hydrolyzed directly in the reaction medium without the need for any special purification or isolation steps. After hydrolysis, the desired cellulose ester can be isolated and purified by conventional means known in the art such as by a nonsolvent precipitation, distillation, or by spray drying. , , The preferred cellulose esters produ~ed after khe hydrolysis step are substantially the same as produced by the triesterification process except that the DS is ' 20 lower. Thus, preferred products produced by the hydrolysis step include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.
Typical desired products produced after the 25 '~hydrolysis step of the invention have a DS o~ about 0O5 " _to about 2.85, more typically about 1.9 to about 2.3 for mixed esters, the 4s refer~ to the combined DS).
The cellulose esters produced by the triesterifica-tion process ~optionally followed by the hydrolysis step) have low molecular weight. Typical molecular weight ranges of cellulose esters produced by the ' , process of the present inventio~ have a number average molecular weight (~) of about 0.01 X 10S to about l.0 X 105, a weight average molecular weight ~r~) of abou~ 0.02 X 103,to about 2.0 X 105, and a Z average `:
.
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molecular weight (~) of about 0. 04 X 105 to about 4. 0 X 105. Preferred molecular weight ranges are an of about 0.2 X 105 to about 0.6 X 105, a MW of about 0.6 X 105 to about 1.0 X 105, and a ~ of about 0.3 X 105 ` 5 to about 3.0 X 105. The ratio o~ M~ is preferably about 1.0 to about 2.0, with about 1.4 to about 1.9 being more preferred.
As is well known in the art, I.V. values are related to molecular weight. The I.V. of the product - 10 cellulose ester produced by the triesterification process toptionally followed by the hydrolysis step) is typically about 0.2 to about 0.6, preferably about 0O3 to about 0.4 deciliters/gram as measured at a temperature of 25C for 0.25 gram sample in 100 ml of a 60/40 by weight solution of phenol/tetrachloroethaneO
Some products produced after the hydrolysis step, especially high hydroxyl (i.e., low DS), mixed esters, will be soluble in n-propylacetate tn-PrOAc), acetone~
~` CHCl3, ethanol, tetrahydrofuran (THF), and dimethylsulfoxide (DMS0).
The following examples are to illustrate the invention but should not be interpreted as a limitation thereon.
.-.
2~ -- EXAMPLES
In the following examples, water activated ." ._ cellulose was prepared by mechanically blending the ceIlulose with water. The excess water was removed by filtration. Résidual water was removed by washing the damp cellulose with the carboxylic acid which corr~sponds to an acyl group being attached to the c~llulose polymer. The activated cellulose was loaded into a flask equipped ~or mechanical stirring. To the cellulose was added a mixture o~ acyl anhydride (5) and a catalyst consisting of TFA and a mineral acid such as ., .
., .
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~' ~ ' ~ , ' ' '' ' i , ' , , , "`' sulfuric acid. The reactor was then heated to 70~Co The reaction mixture was stirred until a cleax solu.tion - was obtained which is the indicated contact time ~or formation of the triester. After formation of the - 5 triester, the reaction mixture was maintained at 70c for a period of time to allow degradation of the pol~mer (i.e., a flat period) before adding a hydrolysis solution to the reaction mixture. The reaction was stirred for the indicated time(s) before isolating the product by addition of a nonsolvent. The TFA, the carboxylic acid(s), and the unconsumed acyl anhydride(s) can be recovered from the reaction mixture before the addition of a nonsolvent. Also, the TFA and carboxylic acids can be recovered from the ~iltrate ~ollowing precipitation by distillation techniques familiar to those skilled in the art. Alternatively, the TFA, the carboxylic acid(s), and the unconsumed acyl anhydride(s) can be isolated by spray drying techniques familiar to those skilled in the art. The results in the examples indicate yields of isolated, well-characterized products. The products were typically characterized by proton NMR spectroscopy, inherent viscosity, gel permeation chromatography (values are reported in polystyrene equivalents), and other methods familiar to 2~--those skilled in the art. The abbreviations used herein have the following meanings: TFA is trifluoroacetic acid, TFAA is trifluoroacetic anhydride, NMR is nuclear ......
magnetic resonance, Pr DS is propionyl degree of substitution, ~c DS is acetyl degree of substitution, TCE is tetrachloroethane, GPC is gel permeation chromatography, DMF is dimethylformamide, T~F is tetrahydrofuran, DMSO is dimethylsulfoxide, n-PrOAc is propy;l acetate, and CAB is ceIlulose acetate butyrate.
. .
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.
~;
.~ Reagents set forth below were subjected to the ~` standard procedure described above under the indicated reaction conditions. The result, in terms of identity and yield of the desired cellulose ester, and key analyses of the product, are also set f orth below~
Starting Cellulosic Cellulose Weight (g) 50 Equivalents of 1.0 TFA/hydroxyl Equivalents of 0.008 H2SO4/hydroxyl : Acyl Anhydride Acetic Anhydride Equivalents/hydroxyl 0.03 20 Acyl Anhydride Propionic Anhydride Equivalents/hydroxyl 1.7 Carboxylic Acid Propionic Acid Weight (g) 107 : 25 . Hydrolysis Mixture 76.5 g water Contact ~ime (min) 10 30 Flat Period (min) 30 HydrolysisPr DS Ac DS I.V.
~ Time (h~ (IH NMR) !IH NMR~ .(Phenol~TCE) ; 0 3.00 0.05 0.35 2.0 2.59 0.03 0.37 --.. ... .. .
4.0 2.24 0.02 0.39 .
5.0 2.06 0.01 0.41 ~.0 1.93 0.01 0.42 : 7.0 1.84 0.01 0.42 7.8 1.70 0.01 . 0.44 . - - .
This exa~ple demonstrates that a catalyst system consisting o~ TFA~H2SO4 rapidly promotes the .
~3~Bs r~ E S~
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esterification of cellulose with propionic anhydride and acetic anhydride to provide a triester, provldes ~or rapid degradation of the cellulose polymer, and gives : excellent rates of hydrolysis.
: . 5 Reagents set forth below were subjected to ~he standard procedure described above under the indicated reaction conditions. The result, in terms of identity lo and yield of the desired cellulose ester, and key analyses of the product, are also set forth below.
Starting Cellulosic Cellulose Weight (g) 50 15 Equivalents of 1.0 TFA/hydroxyl Equivalents of 0.008 ; Mg(Cl04)~hydroxyl Acyl Anhydride Acetic Anhydride Equivalents/hydroxyl 0.03 .~ Acyl Anhydride Propionic Anhydride : 25 Equivalents/hydroxyl 1.7 : Carboxylic Acid Propionic Acid Weight (g) 86 30 Hydrolysis ~ixture 76.5 g water Contact Time (min) 7 - Flat Period (min) g 39.-. . . . .. ..
Hyd~olysis Pr DS Ac DS I.V.
Time th) (IH NMR) ~lH NMR~ Lphenol~TcE) 0 3.05 0.04 0.54 1.0 2.77 0.04 0.3~
1.8 2.51 0002 . 0.34.
3.3 2.16 0.00 0.36 5.3 1.79 0.01 0.38 6.3 1.59 0.00 0.39 ~;lJB~
. .. , ....... . . . , . . . ~ . .. . . . .
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- . ~ ` ~ . ` .: . . .
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,. . . . . . . . ` ..
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This example demonstrakes that a catalyst system consisting of TFA~Mg(Cl04)2 rapidly promotes the esterification of cellulose with propionic anhydride and acetic anhydride to provide a triester, proYides ~or rapid degradation of the cellulose polymer, and gives excellent rates of hydrolysis.
Reagents set forth below were subjected to the standard procedure described above under the indicated reaction conditions. The result, in terms of identity and yield of the desired cellulose ester, and key analyses of the product, are also set forth belowO
.
~, .
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Starting Cellulosic Cellulose Weight (g) 50 -~ Equivalents of 1.0 TFA~hydroxyl E~uivalents of 0.008 H2SO4/hydroxyl 10 Acyl Anhydride Acetic Anhydride Equivalents/hydroxyl 0.03 Acyl Anhydride Propionic Anhydride Equivalents/hydroxyl 1.7 Carboxylic Acid Propionic Acid Weight (g) 75 Hydrolysis Mixture 76.5 g water Contact Time (min) 5 Flat Period (min) 30 25 Hydrolysis Time (h) 4.5 DS Pr(lH NMR) 2.08 . DS Ac(lH NMR) O.02 GPC M~ = O.4 X 105; M~ = 0~7 X
105;
(DMF~LiBr, ~ = 0.4 X 105; ~ = 1092 Polystyrene equivalents) IV (Phenol~TCE) 0.33 '~ , Solubility Data Soluble in organic solvents
~ . ' .
:,~',. .' . /; :'.
: . I f~,, :.
. .
esterification of cellulose with propionic anhydride and acetic anhydride to provide a triester, provldes ~or rapid degradation of the cellulose polymer, and gives : excellent rates of hydrolysis.
: . 5 Reagents set forth below were subjected to ~he standard procedure described above under the indicated reaction conditions. The result, in terms of identity lo and yield of the desired cellulose ester, and key analyses of the product, are also set forth below.
Starting Cellulosic Cellulose Weight (g) 50 15 Equivalents of 1.0 TFA/hydroxyl Equivalents of 0.008 ; Mg(Cl04)~hydroxyl Acyl Anhydride Acetic Anhydride Equivalents/hydroxyl 0.03 .~ Acyl Anhydride Propionic Anhydride : 25 Equivalents/hydroxyl 1.7 : Carboxylic Acid Propionic Acid Weight (g) 86 30 Hydrolysis ~ixture 76.5 g water Contact Time (min) 7 - Flat Period (min) g 39.-. . . . .. ..
Hyd~olysis Pr DS Ac DS I.V.
Time th) (IH NMR) ~lH NMR~ Lphenol~TcE) 0 3.05 0.04 0.54 1.0 2.77 0.04 0.3~
1.8 2.51 0002 . 0.34.
3.3 2.16 0.00 0.36 5.3 1.79 0.01 0.38 6.3 1.59 0.00 0.39 ~;lJB~
. .. , ....... . . . , . . . ~ . .. . . . .
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- . ~ ` ~ . ` .: . . .
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This example demonstrakes that a catalyst system consisting of TFA~Mg(Cl04)2 rapidly promotes the esterification of cellulose with propionic anhydride and acetic anhydride to provide a triester, proYides ~or rapid degradation of the cellulose polymer, and gives excellent rates of hydrolysis.
Reagents set forth below were subjected to the standard procedure described above under the indicated reaction conditions. The result, in terms of identity and yield of the desired cellulose ester, and key analyses of the product, are also set forth belowO
.
~, .
' -.. ' , , 5~ -3~
... . . . . . . .
.. .. ..
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' ': . ' ','' , , ~ ' . ': . .
.
-. . .. . ;: : - . : .
... . . . . .
-, .. .
: . , :
Starting Cellulosic Cellulose Weight (g) 50 -~ Equivalents of 1.0 TFA~hydroxyl E~uivalents of 0.008 H2SO4/hydroxyl 10 Acyl Anhydride Acetic Anhydride Equivalents/hydroxyl 0.03 Acyl Anhydride Propionic Anhydride Equivalents/hydroxyl 1.7 Carboxylic Acid Propionic Acid Weight (g) 75 Hydrolysis Mixture 76.5 g water Contact Time (min) 5 Flat Period (min) 30 25 Hydrolysis Time (h) 4.5 DS Pr(lH NMR) 2.08 . DS Ac(lH NMR) O.02 GPC M~ = O.4 X 105; M~ = 0~7 X
105;
(DMF~LiBr, ~ = 0.4 X 105; ~ = 1092 Polystyrene equivalents) IV (Phenol~TCE) 0.33 '~ , Solubility Data Soluble in organic solvents
4~ . . ... such as n-PrOAc, acetone~
CHCl3, THF, alcohol, and DMSO
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: . . ,, . - , . . .
.. . . . . . . .
- . . . . .. . . ..
~ - 18 -. . , This example demonstrates that a catalyst system :- consisting of TFA~H2SO4 can be used to obtain a CAP mixed .,"! ester with high hydroxyl content and low molecular weight. This mixed ester gives high solids to liquid ratios in organic solvents such as n-propyl acetate ,: t25~
Reagents set ~orth below were subjected to the standard procedure described above under the indicated reaction conditions. The result, in terms of identity and yield of the desired cellulose ester, and key analyses of the product, are also set forth below.
15 Starting Cellulosic Cellulose Weight tg~ 50 Equivalents of 1.0 TFA~hydroxyl .. 20 Equivalents of 0.008 ,. H2SO4~hydroxyl Y Acyl Anhydride Acetic Anhydride 25 Equivalents~hydroxyl 0.03 . Acyl Anhydride Butyric Anhydride Equivalents~hydroxyl 1.7 3~ --Carboxylic Acid Butyric Acid Weight (g) 75 .,, _ . Hydrolysis Mixture 76.5 g water .. -- . . . ..... .
; 35 Contact Time (min) 15 . Flat Period (min) 30 :
~ .
.
:
.- :
.~`. .
. , .
.
~ ;q ;~ ~ ~
: .
:,~ , , . . . . :
:: . . . , . .. : --: ~ :. : .: .
.- . , - - .-' . : :: : - : , ' : ' .: ~ :- : . - . . . .
'~3~ . .
HydrolysisBu DS Ac DS I.V.
Time (h)~IH NMR) (IH NMR) (Phenol/TCE) 0 3.02 0.07 0.40 2.0 2.74 0.06 0.37 4.0 2.43 0.0~ 0.36
CHCl3, THF, alcohol, and DMSO
~. ' .
~
.. . . . . . . .
... . . . . . . .
... . , , ,.. ., .... . . . . ~
. . . . . . .. . . . . ..
.. . ... . . .
.~ . . .
- . . . . . .
: . . ,, . - , . . .
.. . . . . . . .
- . . . . .. . . ..
~ - 18 -. . , This example demonstrates that a catalyst system :- consisting of TFA~H2SO4 can be used to obtain a CAP mixed .,"! ester with high hydroxyl content and low molecular weight. This mixed ester gives high solids to liquid ratios in organic solvents such as n-propyl acetate ,: t25~
Reagents set ~orth below were subjected to the standard procedure described above under the indicated reaction conditions. The result, in terms of identity and yield of the desired cellulose ester, and key analyses of the product, are also set forth below.
15 Starting Cellulosic Cellulose Weight tg~ 50 Equivalents of 1.0 TFA~hydroxyl .. 20 Equivalents of 0.008 ,. H2SO4~hydroxyl Y Acyl Anhydride Acetic Anhydride 25 Equivalents~hydroxyl 0.03 . Acyl Anhydride Butyric Anhydride Equivalents~hydroxyl 1.7 3~ --Carboxylic Acid Butyric Acid Weight (g) 75 .,, _ . Hydrolysis Mixture 76.5 g water .. -- . . . ..... .
; 35 Contact Time (min) 15 . Flat Period (min) 30 :
~ .
.
:
.- :
.~`. .
. , .
.
~ ;q ;~ ~ ~
: .
:,~ , , . . . . :
:: . . . , . .. : --: ~ :. : .: .
.- . , - - .-' . : :: : - : , ' : ' .: ~ :- : . - . . . .
'~3~ . .
HydrolysisBu DS Ac DS I.V.
Time (h)~IH NMR) (IH NMR) (Phenol/TCE) 0 3.02 0.07 0.40 2.0 2.74 0.06 0.37 4.0 2.43 0.0~ 0.36
5.0 2.36 0.03 0.37
6.0 2.28 0.03 0.35
7.0 2.12 0.02 0.40 This example demonstrates that a catalyst system consisting of TFA~H2SO4 rapidly promotes the esterification of cellulose with butyric anhydride and acetic anhydride to provide a triester, provides for rapid degradation of the cellulose polymer, and gives excellent rates of hydrolysis.
. :
Reagents set forth below were subjected to the standard procedure described above under t~e indicated reaction conditions. The result, in terms of identity and yield of the desired cellulose ester, and key analyses of the product, are also set forth below.
.
'.,,,' '-- -. ~' :
.
.
. - ; .
.. . . .
: : , : , ., ;. . .
. . - ~
.
Starting Cellulosic Cellulose Weight (g) 50 Equivalents of 1.0 TFA/hydroxyl Equivalents of 0.008 H2SO4/hydroxyl 10 Acyl Anhydride Acetic Anhydride Equivalents/hydroxyl 0.07 Acyl Anhydride Butyric Anhydride Equivalents/hydroxyl 1.7 Carboxylic Acid Butyric Acid Weight (g) 75 ~:
Hydrolysis Mixture 76.5 g water ; 20 Contact Time (min) 25 Flat Period (min) 30 25 Hydrolysis Time (h) 7 DS Bu(lH NMR) 2.18 . DS Ac(~H NMR) 0.06 GPC ~ = 0.5 X 105; MW = loO X
105;
(DMF/LiBr, ~ = 1.5 X 105; M~ = 1.45 Polystyrene eguivalents) IV (Phenol~TCE) 0.39 Solubility Data Solubl~ in organic solvents 40 - - such as n-PrOAc, acetone, CHCl3, THF, alcohol, and DMSO
, , ;
, .
EE~
~ : .
~ . , .
. .
............
. . .
:' r~
'~'.i .-,, 1,,~
This example demonstrateS that a catalyst syste~
consisting of TFA~H2SO4 can be used to obtain a CAB m.i~ed ester with high hydroxyl content and low molecular weight. This mixed ester gives high solids to liquid ratios in organic solvents such as n-propyl acetate (25%).
. .
EXAMPLE 6 ~ :
Reagents set forth below were sub~ected to the standard procedure described above under the indicated reaction conditions. The result, in terms of identity and yield of the desired cellulose ester, and key analyses of the product, are also set forth belowO
~, , .
.~ ." _ ' .
..
. .
T~TF~
: , . ~ .. , ` , . . . . . . .
... . , . : `
.. ... : ` ., ; . .. , . : , .- . . . . ` . . . .
.. . . , ~ . . . .
. : ` ~. `: ` ` ` ,:
- .. ` ' . : ` . ` . `, .. .. .
. , . . . . . . . , . ~ , .
.; .
"~
,:'.: (.:,~.'.;;
starting Cellulosic Cellulose weight (g) 50 Equivalents of 1.5 TFAA~hydroxyl .
Acyl Anhydride Acetic Anhydride Equivalents/hydroxyl 0.15 10 Acyl Anhydride Propionic Anhydride Equivalents/hydroxyl 1.7 Carboxylic Acid Propionic Acid Weight (g) 152 Hydrolysis Mixture 76.5 g water, 152 g Propionlc Acid Contact Time (min) 1080 . 20 :.
Reaction Temperature 55C :
, ..
" . . . . ... . ..
.
.
.-. ;
sU~3 ~
... ... . . .
.~ . ~ , . .
. ,, ~ , .
' ' . .:
' ' ' . ', :
r; .
~' '.
~ydrolysis Pr DS Ac DS I~Vo Time (h) (IH NMR) (IH NMR) (Phenol~TCE~
0 3.04 0.09 1.44 2.2 2.90 0.08 1.37 - 54.7 2.63 0.10 1.37 7.2 2.46 0.08 1.38 This example differs from the standard procedure in that the sulfuric acid was omitted, T~AA was substituted for TFA, and the reaction was at 55~C. The result is a - longer contact time, slower hydrolysis rate, and higher molecular weights as illustrated by I.V.
With reference to Example 1, this example :.
demonstrates the critical role of sulfuric acid and ~ 15 illustrates how the process of this invention differs ; fro~ a process devoid of sulfuric acid and ~FA.
EXAMPLE 7 (Comparative) ` Reagents set forth below were subjected to the 0 standard procedure described above under the indicat@d réaction conditions. The result, in terms of idsntity and yield of the desired cellulose ester, and key analyses of the product, are also set forth below.
.
" _ ..... . . . ... . . .
. ' ' .. .
~' .
- - -, ': ' ; . . , . . , : ~ , . .. :- , . . . . .
: . . : .. . ~ . , ., :,. , . : . . . -: . , , , :
.. . - !
` '`.: `-.
. - 24 -`
Starting Cellulosic Cellulose Weight (g) 5 . Equivalents of . 0.8 TFA/hydroxyl Acyl Anhydride Acetic Anhydride Equivalents/hydroxyl 2.1 10 Carboxylic Acid Acetic Acid Weight (g) 30 Contact Time (m.in) 10320 15 Reaction Temperature 55C
Product Cellulose Triacetate Degree of Substitution 3.02 (From IH NMR) Intrinsic Viscosity 1.74 (Phenol~TCE) GPC (DMF, Polystyrene ~ = 25.7 X 104; Mw = 4O4 X
equivalents) ~ = 7.6 X 105; M~ = 170 ... . .
: This example differs from the standard procedure in that the sulfuric acid was omitted and the reaction was at 55 C.
With reference to Examples 1 and 6, this example demonstxates the critical role of sulfuric acid and . ..illustrates how the process o~ this invention dif~ers from a process using TFA but devoid o~ sulfuric acid.
.
......
E~AMPLE 8 (Comparative) Reagents set forth below were subjected to the standard procedure described above under the indicated reaction conditions. The result, in terms of identity and yield of the desired cellulose ester, and key - ana~yses o~ the product, are also set forth below.
.. .. : : . ~ . . . .
. - ,, : .- . , . . ~ :
, .. ~: . .. . . .
,. . .- ., .,, . ~,.. . .
.. - . . . . .. . ..
Starting CellulosiC Cellulose Weight (g) 50 Equivalents of 1.0 TFA/hydroxyl Equivalents of H2S04/ 0.008 hydroxyl 10 Carboxylic Acid Acetic Acid Weight (g) 1.9 Carboxylic Acid Propionic Acid Weight tg) 230 contact Time (min) 1510 DS (From IH NMR) No Reaction ; This example differs from the standard procedure in that the appropriate molar amount of carboxylic acid was substituted for the acyl ~nhydrides.
With reference to Example l, this example demonstrates the critical role of acyl anhydrides and illustrates an aspect of how this process differs from i~i; that taught by H.T. Clar~e and C.J. Malm (U.SO Pat2nt 1,880,80~ (1932)).
The invention has been described in detail with particular reference to pxe~erred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and ., - scope of the invention. All of the U.S. patents cited --in the specification a~ incorporated herein by 35 reference in their entirety. -, -.
'~" '''''" ' '' ,'.' '':", '',', ',";''" ~',,,',.' ., " '''', ' " ''"' " ' '' ''' , ' .,: , ., , ' ' , ' ' . ' , ' ' ' . , ' , ' , ' ' ' , . , ,' . , ' " ' ;'', ' ' , ' "' '," ,' ,,' . :' '' , ' .' ,.. . ', " '~'' ' ' ' ~ ' . ' ' ' , " ' , . ' .' . . '' ' ' ' , - , ' ' :: ~ , : .' . ' . . ' ' ' ' ' .' . . .
' : - :~ ~ ' - . , . ' . ' ' ~', ' . ' . . , ' ' ' ,. ' ' ".' ' ' ' . , , . : ' . . .
. :
Reagents set forth below were subjected to the standard procedure described above under t~e indicated reaction conditions. The result, in terms of identity and yield of the desired cellulose ester, and key analyses of the product, are also set forth below.
.
'.,,,' '-- -. ~' :
.
.
. - ; .
.. . . .
: : , : , ., ;. . .
. . - ~
.
Starting Cellulosic Cellulose Weight (g) 50 Equivalents of 1.0 TFA/hydroxyl Equivalents of 0.008 H2SO4/hydroxyl 10 Acyl Anhydride Acetic Anhydride Equivalents/hydroxyl 0.07 Acyl Anhydride Butyric Anhydride Equivalents/hydroxyl 1.7 Carboxylic Acid Butyric Acid Weight (g) 75 ~:
Hydrolysis Mixture 76.5 g water ; 20 Contact Time (min) 25 Flat Period (min) 30 25 Hydrolysis Time (h) 7 DS Bu(lH NMR) 2.18 . DS Ac(~H NMR) 0.06 GPC ~ = 0.5 X 105; MW = loO X
105;
(DMF/LiBr, ~ = 1.5 X 105; M~ = 1.45 Polystyrene eguivalents) IV (Phenol~TCE) 0.39 Solubility Data Solubl~ in organic solvents 40 - - such as n-PrOAc, acetone, CHCl3, THF, alcohol, and DMSO
, , ;
, .
EE~
~ : .
~ . , .
. .
............
. . .
:' r~
'~'.i .-,, 1,,~
This example demonstrateS that a catalyst syste~
consisting of TFA~H2SO4 can be used to obtain a CAB m.i~ed ester with high hydroxyl content and low molecular weight. This mixed ester gives high solids to liquid ratios in organic solvents such as n-propyl acetate (25%).
. .
EXAMPLE 6 ~ :
Reagents set forth below were sub~ected to the standard procedure described above under the indicated reaction conditions. The result, in terms of identity and yield of the desired cellulose ester, and key analyses of the product, are also set forth belowO
~, , .
.~ ." _ ' .
..
. .
T~TF~
: , . ~ .. , ` , . . . . . . .
... . , . : `
.. ... : ` ., ; . .. , . : , .- . . . . ` . . . .
.. . . , ~ . . . .
. : ` ~. `: ` ` ` ,:
- .. ` ' . : ` . ` . `, .. .. .
. , . . . . . . . , . ~ , .
.; .
"~
,:'.: (.:,~.'.;;
starting Cellulosic Cellulose weight (g) 50 Equivalents of 1.5 TFAA~hydroxyl .
Acyl Anhydride Acetic Anhydride Equivalents/hydroxyl 0.15 10 Acyl Anhydride Propionic Anhydride Equivalents/hydroxyl 1.7 Carboxylic Acid Propionic Acid Weight (g) 152 Hydrolysis Mixture 76.5 g water, 152 g Propionlc Acid Contact Time (min) 1080 . 20 :.
Reaction Temperature 55C :
, ..
" . . . . ... . ..
.
.
.-. ;
sU~3 ~
... ... . . .
.~ . ~ , . .
. ,, ~ , .
' ' . .:
' ' ' . ', :
r; .
~' '.
~ydrolysis Pr DS Ac DS I~Vo Time (h) (IH NMR) (IH NMR) (Phenol~TCE~
0 3.04 0.09 1.44 2.2 2.90 0.08 1.37 - 54.7 2.63 0.10 1.37 7.2 2.46 0.08 1.38 This example differs from the standard procedure in that the sulfuric acid was omitted, T~AA was substituted for TFA, and the reaction was at 55~C. The result is a - longer contact time, slower hydrolysis rate, and higher molecular weights as illustrated by I.V.
With reference to Example 1, this example :.
demonstrates the critical role of sulfuric acid and ~ 15 illustrates how the process of this invention differs ; fro~ a process devoid of sulfuric acid and ~FA.
EXAMPLE 7 (Comparative) ` Reagents set forth below were subjected to the 0 standard procedure described above under the indicat@d réaction conditions. The result, in terms of idsntity and yield of the desired cellulose ester, and key analyses of the product, are also set forth below.
.
" _ ..... . . . ... . . .
. ' ' .. .
~' .
- - -, ': ' ; . . , . . , : ~ , . .. :- , . . . . .
: . . : .. . ~ . , ., :,. , . : . . . -: . , , , :
.. . - !
` '`.: `-.
. - 24 -`
Starting Cellulosic Cellulose Weight (g) 5 . Equivalents of . 0.8 TFA/hydroxyl Acyl Anhydride Acetic Anhydride Equivalents/hydroxyl 2.1 10 Carboxylic Acid Acetic Acid Weight (g) 30 Contact Time (m.in) 10320 15 Reaction Temperature 55C
Product Cellulose Triacetate Degree of Substitution 3.02 (From IH NMR) Intrinsic Viscosity 1.74 (Phenol~TCE) GPC (DMF, Polystyrene ~ = 25.7 X 104; Mw = 4O4 X
equivalents) ~ = 7.6 X 105; M~ = 170 ... . .
: This example differs from the standard procedure in that the sulfuric acid was omitted and the reaction was at 55 C.
With reference to Examples 1 and 6, this example demonstxates the critical role of sulfuric acid and . ..illustrates how the process o~ this invention dif~ers from a process using TFA but devoid o~ sulfuric acid.
.
......
E~AMPLE 8 (Comparative) Reagents set forth below were subjected to the standard procedure described above under the indicated reaction conditions. The result, in terms of identity and yield of the desired cellulose ester, and key - ana~yses o~ the product, are also set forth below.
.. .. : : . ~ . . . .
. - ,, : .- . , . . ~ :
, .. ~: . .. . . .
,. . .- ., .,, . ~,.. . .
.. - . . . . .. . ..
Starting CellulosiC Cellulose Weight (g) 50 Equivalents of 1.0 TFA/hydroxyl Equivalents of H2S04/ 0.008 hydroxyl 10 Carboxylic Acid Acetic Acid Weight (g) 1.9 Carboxylic Acid Propionic Acid Weight tg) 230 contact Time (min) 1510 DS (From IH NMR) No Reaction ; This example differs from the standard procedure in that the appropriate molar amount of carboxylic acid was substituted for the acyl ~nhydrides.
With reference to Example l, this example demonstrates the critical role of acyl anhydrides and illustrates an aspect of how this process differs from i~i; that taught by H.T. Clar~e and C.J. Malm (U.SO Pat2nt 1,880,80~ (1932)).
The invention has been described in detail with particular reference to pxe~erred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and ., - scope of the invention. All of the U.S. patents cited --in the specification a~ incorporated herein by 35 reference in their entirety. -, -.
'~" '''''" ' '' ,'.' '':", '',', ',";''" ~',,,',.' ., " '''', ' " ''"' " ' '' ''' , ' .,: , ., , ' ' , ' ' . ' , ' ' ' . , ' , ' , ' ' ' , . , ,' . , ' " ' ;'', ' ' , ' "' '," ,' ,,' . :' '' , ' .' ,.. . ', " '~'' ' ' ' ~ ' . ' ' ' , " ' , . ' .' . . '' ' ' ' , - , ' ' :: ~ , : .' . ' . . ' ' ' ' ' .' . . .
' : - :~ ~ ' - . , . ' . ' ' ~', ' . ' . . , ' ' ' ,. ' ' ".' ' ' ' . , , . : ' . . .
Claims (35)
1. A process for preparing cellulose esters having a degree of substitution of 3 and a number average molecular weight of less than 1.0 X 105 comprising contacting the following:
(a) a cellulose polymer having a degree of substitution less than that of the product cellulose ester and molecular weight greater than that of the product cellulose ester, (b) trifluoroacetic acid, (c) at least one acid anhydride of the formula:
wherein each of R and R1 is, independently, H, a straight chain alkyl groups containing 1-20 carbon atoms, a branched chain alkyl groups having 3 to 20 carbon atoms, aryl having 6 to 12 carbon atoms, or substituted aryl having 6 to 12 carbon atoms, and having substituents selected from the group consisting of alkyl groups having 1 to 3 carbon atoms, halo, and lower alkoxy groups having 1 to 3 carbon atoms, and (d) a mineral acid;
in the presence of a solubilizing amount of a solvent and under conditions such that the desired cellulose ester is formed wherein the amount of component (b) is 0.25 to 1.0 equivalents per hydroxyl, the amount of component (c) is at least equivalent per hydroxyl, and the amount of component (d) is 0.0001 to 0.01 equivalents per hydroxyl.
(a) a cellulose polymer having a degree of substitution less than that of the product cellulose ester and molecular weight greater than that of the product cellulose ester, (b) trifluoroacetic acid, (c) at least one acid anhydride of the formula:
wherein each of R and R1 is, independently, H, a straight chain alkyl groups containing 1-20 carbon atoms, a branched chain alkyl groups having 3 to 20 carbon atoms, aryl having 6 to 12 carbon atoms, or substituted aryl having 6 to 12 carbon atoms, and having substituents selected from the group consisting of alkyl groups having 1 to 3 carbon atoms, halo, and lower alkoxy groups having 1 to 3 carbon atoms, and (d) a mineral acid;
in the presence of a solubilizing amount of a solvent and under conditions such that the desired cellulose ester is formed wherein the amount of component (b) is 0.25 to 1.0 equivalents per hydroxyl, the amount of component (c) is at least equivalent per hydroxyl, and the amount of component (d) is 0.0001 to 0.01 equivalents per hydroxyl.
2. The process of Claim 1 wherein component (a) is a cellulose polymer having a degree of substitution of 0 to 2.9 and is selected from the group consisting of cellulose, a secondary cellulose ester, and a mixture thereof.
3. The process of Claim 1 wherein component (c) is selected from the group consisting of acetic anhydride, propionic anhydride, isobutyric anhydride, butyric anhydride, trimethylacetic anhydride, valeric anhydride, hexanoic anhydride, nonanoic anhydride, benzoic anhydride, and a mixture thereof.
4. The process of Claim 1 wherein component (c) is selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, and a mixture thereof.
5. The process of Claim 1 carried out at 20°C to 150°C
for 5 to 30 minutes.
for 5 to 30 minutes.
6. The process of Claim 1 wherein said solvent is selected from the group consisting of a carboxylic acid having 1 to 20 carbon atoms, dimethyl-formamide, dimethylsulfoxide, and a mixture thereof.
7. The process of Claim 1 wherein said solvent is acetic acid.
8. The process of Claim 1 wherein R and R1 are the same.
9. The process of Claim 1 including the additional step of isolating, after reaction, the desired product by the addition of a precipitating amount of a nonsolvent, distillation, or by spray drying.
10. The process of Claim 1 wherein component (d) is selected from the group consisting of hydrochloric acid, Mg(C104)2, HC104, and a mixture thereof.
11. The process of Claim 1 wherein the product cellulose ester has a Mn of 0.01 X 105 to 1.0 X 105, a Mw of 0.02 X 105 to 2.0 X 105, a Mz of 0.04 X 105 to 4.0 X 105, and a ratio of Mw/Mn of 1.0 to 2Ø
12. The process of Claim 1 wherein the product cellulose ester has a Mn of 0.2 X 105 to 0.6 X 105, a Mw of 0.6 X 105 to 1.0 X 105, a Mz of 0.3 X 105 to 3.0 X 105, and a ratio of Mw/Mn of 1.5 to 1.9.
13. The process of Claim 1 wherein the product cellulose ester is cellulose triacetate, cellulose tributyrate, cellulose tripropionate, cellulose acetate butyrate, cellulose acetate propionate, and said product cellulose ester has an inherent viscosity of 0.2 to 0.6 as measured at a temperature of 25°C for a 0.25 gram sample in 100 ml of a 60/40 by weight solution of phenol/tetrachloroethane.
14. A process for preparing a cellulose ester having a degree of substitution of less than 3 and a number average molecular weight of less than 1.0 X 105 comprising:
(A) contacting (a) a cellulose polymer having a degree of substitution of less than 3, (b) trifluoroacetic anhydride, (c) at least one acyl anhydride of the formula:
wherein each or R and R1 is, independently, H, a straight chain alkyl, a branched alkyl, aryl, or substituted aryl, and (d) a mineral acid, in the presence of a solubilizing amount of a solvent and under conditions such that a cellulose ester is formed having a degree of substitution of 3 and a molecular weight less than that of the cellulose polymer of step (A)(a), and (B) contacting the cellulose ester formed by step (A) with a sufficient amount of a reactive hydrolysis solvent under conditions to form the desired cellulose ester which has a degree of substitution higher than the original cellulose polymer of step (A)(a).
(A) contacting (a) a cellulose polymer having a degree of substitution of less than 3, (b) trifluoroacetic anhydride, (c) at least one acyl anhydride of the formula:
wherein each or R and R1 is, independently, H, a straight chain alkyl, a branched alkyl, aryl, or substituted aryl, and (d) a mineral acid, in the presence of a solubilizing amount of a solvent and under conditions such that a cellulose ester is formed having a degree of substitution of 3 and a molecular weight less than that of the cellulose polymer of step (A)(a), and (B) contacting the cellulose ester formed by step (A) with a sufficient amount of a reactive hydrolysis solvent under conditions to form the desired cellulose ester which has a degree of substitution higher than the original cellulose polymer of step (A)(a).
15. The process of Claim 14 wherein for step (A), component (a) is a cellulose polymer having a degree of substitution of 0 to 2.9 and is selected from the group consisting of cellulose, a secondary cellulose ester, and a mixture thereof.
16. The process of Claim 14 wherein for step (A) component (c) is selected from the group consisting of acetic anhydride, propionic anhydride, isobutyric anhydride, butyric anhydride, trimethylacetic anhydride, valeric anhydride, hexanoic anhydride, nonanoic anhydride, benzoic anhydride, and a mixture thereof.
17. The process of Claim 14 wherein for step (A), the amount of component (b) is 0.25 to 1.0 equivalents per hydroxyl, the amount of component (c) is at least 1 equivalent par hydroxyl, and the amount of component (d) is 0.0001 to 0.01 equivalents per hydroxyl.
18. The process of Claim 14 wherein for step (A), component (c) is selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, and a mixture thereof.
19. The process of Claim 14 wherein step (A) is carried out at 20°C to 150°C for 5 to 30 minutes.
20. The process of Claim 14 wherein said reactive hydrolysis solvent is selected from the group consisting of an n-alkanol having 1 to 4 carbon atoms, water, a branched chain alkanol having 3 to 4 carbon atoms, an aryl alkanol having 7 to 12 carbon atoms, and a mixture thereof.
21. The process of Claim 14 wherein said reactive hydrolysis solvent is selected from the group consisting of methanol, ethanol, n-propanol, n-butanol, isopropyl alcohol, benzyl alcohol, and water.
22. The process of Claim 14 wherein said reactive hydrolysis solvent is selected from the group consisting of methanol, water, and a mixture thereof.
23. The process of Claim 14 wherein the amount of reactive hydrolysis solvent is from 1 volume % to that amount which results in the desired product precipitating from solution.
,
,
24. The process of Claim 14 wherein the amount of reactive hydrolysis solvent is from 5 to 15 volume %.
25. The process of Claim 14 wherein step (B) is carried out at a temperature from 20°C to 150°C for 0.5 to 24 hours.
26. The process of Claim 14 wherein the cellulose ester formed by step (B) has a degree of substitution of from 0.5 to 2.85.
27. The process of Claim 14 wherein the solvent for step (A) is selected from the group consisting of a carboxylic acid having 1 to 20 carbon atoms, dimethylformamide, dimethylsulfoxide, and a mixture thereof.
28. The process of Claim 14 wherein the solvent for step (A) is acetic acid.
29. The process of Claim 14 wherein R and R1 are the same.
30. The process of Claim 14 including the additional step of isolating, after reaction, the desired product by the addition of a precipitating amount of a nonsolvent, distillation, or spray drying.
31. The process of Claim 14 wherein the mineral acid for step (A) is selected from the group consisting of hydrochloric acid, Mg(C104)2, HC104, and a mixture thereof.
32. The process of Claim 14 wherein the cellulose ester produced by step (A) has a Mn of 0.01 X 105 to 1.0 X 105, a Mw of 0.02 X 105 to 2.0 X 105, a Mz of 0.04 X 105 to 4.0 X 105, and a ratio of Mw/Mn of 1.0 to 2Ø
33. The process of Claim 14 wherein the cellulose ester produced by step (A) has a Mn of 0.2 X 105 to 0.6 X 105, a Mw of 0.6 X 105 to 2.0 X 105, a Mz of 0.3 X 105 to 3.0 X 105, and a ratio of Mw/Mn n of 1.5 to 1.9.
34. The process of Claim 14 wherein the final product cellulose ester is cellulose acetate, cellulose butyrate, cellulose propionate, cellulose acetate butyrate, cellulose acetate propionate, and said product cellulose ester has an inherent viscosity of 0.2 to 0.6 as measured at a temperature of 25°C
for a 0.25 gram sample in 100 ml of a 60/40 by weight solution of phenol/tetrachloroethane.
for a 0.25 gram sample in 100 ml of a 60/40 by weight solution of phenol/tetrachloroethane.
35. The process of Claim 14 wherein the total reaction period is 0.5 to 25 hours.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US509,535 | 1983-06-30 | ||
| US50953590A | 1990-04-16 | 1990-04-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2078876A1 true CA2078876A1 (en) | 1991-10-17 |
Family
ID=24027033
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2078876 Abandoned CA2078876A1 (en) | 1990-04-16 | 1991-04-12 | Preparation of low molecular weight cellulose esters |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0525082A1 (en) |
| JP (1) | JPH05507302A (en) |
| CA (1) | CA2078876A1 (en) |
| WO (1) | WO1991016356A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6667397B2 (en) * | 2000-08-25 | 2003-12-23 | Eastman Chemical Company | Methods of preparing disaccharide and trisaccharide C6-C12 fatty acid esters with high alpha content and materials therefrom |
| US7893138B2 (en) | 2003-03-14 | 2011-02-22 | Eastman Chemical Company | Low molecular weight carboxyalkylcellulose esters and their use as low viscosity binders and modifiers in coating compositions |
| GB0516154D0 (en) * | 2005-08-05 | 2005-09-14 | Ntnu Technology Transfer As | Carbon membranes |
| CN104277122B (en) * | 2013-07-11 | 2016-08-10 | 南通醋酸纤维有限公司 | Direct synthesis method of cellulose esters being dissolved in acetone and products thereof |
| KR101540155B1 (en) * | 2013-10-14 | 2015-07-28 | 주식회사 씨티씨 | Triacetyl cellulose film with improved transparency and method of producing the same |
| ES2908713T3 (en) * | 2017-12-04 | 2022-05-03 | Lg Chemical Ltd | Process for producing the composition for forming the active layer of the gas separation membrane, the composition for forming the active layer of the gas separation membrane produced thereby, the process for manufacturing the gas separation membrane and the gas separation membrane |
| CN110642954B (en) * | 2019-09-20 | 2021-06-29 | 万华化学集团股份有限公司 | Method for preparing cellulose acetate butyrate with high hydroxyl content |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1645915A (en) * | 1926-09-23 | 1927-10-18 | Eastman Kodak Co | Process of making cellulose esters of organic acids |
| US2629716A (en) * | 1948-07-07 | 1953-02-24 | Du Pont | Preparation and hydrolysis of esters |
| JPS6017441B2 (en) * | 1981-07-10 | 1985-05-02 | ダイセル化学工業株式会社 | New method for producing cellulose acetate |
-
1991
- 1991-04-12 WO PCT/US1991/002557 patent/WO1991016356A1/en not_active Application Discontinuation
- 1991-04-12 JP JP91508370A patent/JPH05507302A/en active Pending
- 1991-04-12 EP EP91908621A patent/EP0525082A1/en not_active Withdrawn
- 1991-04-12 CA CA 2078876 patent/CA2078876A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| EP0525082A1 (en) | 1993-02-03 |
| JPH05507302A (en) | 1993-10-21 |
| WO1991016356A1 (en) | 1991-10-31 |
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