MXPA00007493A

MXPA00007493A - Carboxylated cellulose esters

Info

Publication number: MXPA00007493A
Application number: MXPA/A/2000/007493A
Authority: MX
Inventors: Benedict Moonsang Lee; Chungming Kuo; Jessica Poseydowty; Larry Gerald Curtis
Original assignee: Eastman Chemical Company
Priority date: 1998-02-06
Filing date: 2000-07-31
Publication date: 2001-07-31

Abstract

A process for preparing a carboxylated cellulose ester from oxidized cellulose is described. The carboxylated cellulose esters have improved solvent solubility and coating resin compatibility when compared to cellulose esters made from regular grade cellulose. The process comprises activating the oxidized cellulose with water. The activated oxidized cellulose is then dehydrated by displacing the water with acetic acid and optionally displacing at least some of the acetic acid with butyric acid or propionic acid. After dehydration the activated cellulose is reacted with an esterifying reagent in the presence of a catalyst at about 0°C. The temperature is gradually increased to a level sufficient to complete reaction and to obtain an intrinsic viscosity ranging from about 0.2 to about 1.6 dl/g. The reacted solution is then hydrolyzed to obtain a hydroxyl content ranging from about 0.05 to about 1.0. The catalyst is neutralized with a neutralizing agent and the solution is optionally filtered and the carboxylated cellulose ester is then precipitated with a precipitating agent. The invention also relates to carboxylated cellulose esters prepared by the process described above as well as high solids coating compositions containing carboxylated cellulose esters made by the above process.

Description

CARBOXYLATE CELLULOSE ESTERS DESCRIPTION OF THE INVENTION The invention relates to a process for preparing a carboxylated cellulose ester from oxidized cellulose. The carboxylated cellulose esters of the invention can be formulated into coating compositions having a very high solids content ie, greater than 45%. A carboxylated cellulose ester prepared by the process of the invention shows improved compatibility with coating resins and is soluble in a wider range of solvents than conventional cellulose esters. Cellulose esters are used in various applications such as filter tow, pharmaceutical coatings, ink compositions, molded articles and industrial coatings. Thus, methods for their economic preparation are clearly desirable. Coating compositions ordinarily employ cellulose esters that often exhibit relatively low solids contents, i.e., the compositions require excessive amounts of solvents, which presents difficulties with respect to time. of drying, evaporation of solvent and other environmental interests. Although, cellulose esters transported in solvents can transport desirable properties to coatings, Recent trends towards the decrease of the volatile organic compound (VOC) of the coating formulations have reduced the use of solvents, and with that the cellulose esters transported in solvents. Additionally, ordinary cellulose esters exhibit limited compatibility with some kinds of polymeric materials. One way to improve the compatibility of the cellulose esters is to add carboxylic acid groups to the cellulose ester. A process for carboxylating the cellulose ester has been described by I.D. Sand in "The Properties and Applications of Ozonolyzed Cellulose Acétate Butyrate," Polymer Material Science Engineerig, 1987, p. 57-63. In this process the hydroxyl groups of cellulose acetate butyrate are oxidized in the presence of ozone to produce a carboxylated or oxidized cellulose acetate butyrate. According to Sand, carboxylated cellulose acetates butyrate have a lower molecular weight than conventional non-carboxylated cellulose acetates butyrate. As a result, cellulose acetate butyrates carboxylates are soluble in a wider range of solvents and are compatible with a wider range of resins than cellulose acetate butyrates. Unfortunately, however, in addition to the carboxyl group, the ozone treatment described by Sand also generates peroxide, aldehyde and ketone functional groups in the cellulose Similarly, European Patent Application No. 138, 703, describes a process for preparing carboxylated cellulose esters by the reaction of a cellulose ester with ozone. However, as in the process described by Sand, in the process described for this European Patent Application, functional groups of peroxide, aldehyde and acetone are generated in the cellulose esters in addition to the carboxyl group. Thus, there remains a need to develop cellulose esters which can be formulated into high solids coating compositions that meet current VOC requirements, while maintaining solvent solubility and coating resin compatibility. The carboxylated cellulose esters of the invention respond to this need. Surprisingly it has been discovered that when a carboxylated cellulose ester is prepared from oxidized cellulose, the carboxylated cellulose ester can be formulated into high solids coating compositions and exhibits improved coating compatibility and solvent solubility compatibility. Accordingly, the invention relates to a process for making carboxylated cellulose esters from oxidized cellulose. In the process of the invention, the oxidized cellulose is activated with water. Activated oxidized cellulose is it then dehydrates by displacing the water with acetic acid and optionally displacing at least some of the acetic acid with butyric acid or propionic acid. After dehydration the activated cellulose is reacted with a steamer reagent in the presence of a catalyst at an initial temperature of about 0 ° C. The temperature is gradually increased to a level sufficient to complete the reaction and obtain an intrinsic viscosity in a range of about 0.2 to about 1.6 dl / g. The reaction solution was then hydrolyzed to obtain a hydroxyl content ranging from about 0.05 to about 1.0 The catalyst is neutralized with a neutralizing agent and the solution is optionally filtered.The carboxylated cellulose ester is then precipitated with an agent The invention also relates to a carboxylated cellulose ester obtained by the process described above, such carboxylated cellulose esters can be formulated into coating compositions having a high solids content, preferably greater than 45%. , of having improved solubility in solvents and compatibility of coating resin, the carboxylated cellulose ester made by the process of the invention is an excellent pigment dispersing agent and provides rheology control in metal lamella coating. In another embodiment, the invention relates to pigment dispersions, metal and wood coating compositions and ink compositions comprising carboxylated cellulose esters prepared by the above processes. The invention also relates to substrates coated with the carboxylated cellulose ester prepared by the above process. The additional objects and advantages of the invention are discussed in the detailed description that follows, and will be obvious from that description, or can be learned by practicing the invention. It should be understood that this summary and the following detailed description are exemplary and explanatory only and are not intended to restrict the invention. The invention relates to a process for making a carboxylated cellulose ester from oxidized cellulose. The carboxylated cellulose esters which can be prepared by the invention include, for example, carboxylated cellulose acetate, carboxylated cellulose acetate butyrate and carboxylated cellulose acetate propionate. Any initial material of oxidized cellulose can be used to prepare the cellulose esters j¡ ^^ carboxylated of the invention. For example, the initial oxidized cellulose material for use in the process of the invention can be obtained from Rayonier in Jesup, Georgia. Alternatively, the oxidized cellulose can be formed by oxidizing cellulose materials by conventional methods which are well known in the art. For example, the cellulose materials can be bleached with an oxidizing agent such as hypochlorite. Preferably, the carboxyl content of the oxidized cellulose materials is at least about 30 meq / kg, more preferably ranging from about 47 to about 77 meq / kg. In the process of the invention, the oxidized cellulose is activated with water, preferably with demineralized water. Generally, oxidized cellulose is available as a sheet that can be broken into small, thin pieces and activated by soaking in water. Once the pieces are fully inflated, they can be further broken into smaller pieces in a mixer, such as, for example, an EBERBACH® industrial mixer. The oxidized cellulose activated by water is then dehydrated by washing with acetic acid to displace the water with acetic acid. Depending on the desired cellulose ester, the water-activated cellulose can be further washed with butyric acid or propionic acid to displace the acetic acid with butyric or propionic acid, thereby obtaining cellulose acetate butyrate or cellulose acetate propionate respectively. If the desired carboxylated cellulose ester is cellulose acetate, the activated cellulose is washed only with acetic acid. After the dehydration step, the activated cellulose is reacted with an esterifying reagent in the presence of a catalyst at an initial temperature of about 0 ° C. The esterifying reagent is selected from acetic acid, propionic acid, butyric acid, its anhydrides and mixtures thereof. The esterifying reagent is present in an amount in the range of about 10.0 moles to about 3.0 moles relative to one mole of the anhydrous glucose unit of the cellulose. The selection of the esterifying reagent is governed by the desired carboxylated cellulose ester. For example, if cellulose acetate is desired, the esterifying reagent may be acetic acid and / or acetic anhydride. Similarly, if the cellulose acetate butyrate is desired, the esterifying reagent may be a mixture of acetic acid and / or acetic anhydride and butyric acid and / or butyric anhydrides. When a mixture of esterifying reagents is used, the preferred amount of acetic acid or anhydride ranges from about 0.1 to 3.0 moles and the preferred amount of butyric acid or propionic acid or anhydrides thereof ranges from about 0.6 to about 6.0 moles.

In the esterification step, when the carboxylated cellulose acetate butyrate is the desired cellulose ester, the degree of substitution of the butyryl groups can vary from about 0.5 to about 2.95 and the degree of substitution of the acetyl groups can vary from about 0.4 to approximately 2.95. Similarly, when the carboxylated cellulose acetate propionate is desired, the degree of substitution of the propyl groups may vary from about 0.5 to about 2.95 and the degree of substitution of acetyl groups may vary from about 0.4 to about 2.95. Preferably, the carboxylated cellulose acetate butyrates and propionates according to the invention, the degree of substitution of propionate or butyrate ranges from about 1 to about 2.5 and the preferred degree of acetate substitution ranges from about 0.4 to about 1.6. The carboxylated cellulose acetates prepared by the above process generally have a degree of substitution of acetyl groups ranging from about 2.0 to about 2.95. Suitable catalysts useful in the process of the invention include esterification catalysts known in the art. Sulfuric acid is preferred, although other catalysts such as perchloric acid, zinc chloride, titanium alkoxides, sulfate salts, Sulfamic acid, methanesulfonic acid or mixtures thereof may also be used. Preferably, the intrinsic viscosity of a carboxylated cellulose ester obtained from the process of the invention ranges from about 0.2 to about 1.6, more preferably, from about 0.2 to about 0.9 dl / g. The preferred intrinsic viscosity is obtained by adjusting the reaction time and temperature. For example, the initial reaction temperature is maintained at about 0 ° C. The temperature is then gradually increased to a level sufficient to complete the reaction and to obtain the desired viscosity. After the activated cellulose is reacted, the esterified carboxylated cellulose can be hydrolyzed to obtain a degree of substitution of hydroxyl groups which preferably ranges from about 0.05 to about 1.0. The hydrolysis ratio can be controlled by the temperature and catalyst concentration with higher temperatures and catalyst concentrations that increase the hydrolysis ratio. Preferred hydrolysis reactions can be performed with the 90:10 mixture of acetic acid / water in the presence of acid catalyst at temperatures ranging from about 30 ° C to about 70 ° C. The extension of the hydrolysis can also be increased by adding more acetic acid / water mixture * • go ' in the sequential stages. When the desired degree of substitution of the hydroxyl group in the carboxylated cellulose ester is achieved, the hydrolysis is stopped by neutralizing the catalyst in the solution of the reaction step. Methods for monitoring the degree of substitution of hydroxyl groups are known in the art and include, for example, IR, NMR, and gas chromatography by pyrolysis. The neutralizing agent can be any basic component. Examples of suitable neutralizing agents include, but are not limited to, magnesium acetate, calcium acetate, sodium acetate, pyridine or mixtures thereof. The period of time to achieve the desired degree of substitution can be predetermined by methods known in the art. Once the desired degree of hydrolysis has been achieved, the solution can be filtered by methods known in the art. Filtering, however, is not always necessary. The carboxylated cellulose ester is then precipitated from the reaction solution by the conventional methods known in the art. A preferred precipitating agent for the precipitation of the carboxylated cellulose ester is an aqueous acetic acid, more preferably, a 10% solution of acetic acid. For carboxylated cellulose esters having a high degree of substitution of hydroxyl groups, the alcohols soluble in Water such as methanol, isopropanol, and ethanol help facilitate precipitation if the ester is not soluble in it. The preferred alcohol is isopropanol. If desired, the carboxylated cellulose ester can be further purified by washing with water to remove other acids and salts. Optionally, the carboxylated cellulose ester can be dried, for example, to obtain a powder. In another embodiment, the invention relates to various carboxylated cellulose esters made by the process described above. Such carboxylated cellulose esters include, for example, carboxylated cellulose acetate, carboxylated cellulose acetate butyrate, carboxylated cellulose acetate propionate, carboxylated cellulose propionate butyrate and carboxylated cellulose acetate propionate butyrate. Preferred carboxylated cellulose esters include, for example, carboxylated cellulose acetate, carboxylated cellulose acetate butyrate and carboxylated cellulose acetate propionate.

The carboxylated cellulose acetates made by the process described above have a degree of substitution of hydroxyl groups ranging from about 0.05 to about 1.0, a degree of substitution of acetyl groups ranging from about 2.0 to about 2.95 and an intrinsic viscosity ranging from about 0.2 to about 1.6 dl / g, more preferably, from about 0.2 to about 0.9 dl / g. The carboxylated cellulose acetate propionates made by the process according to the invention have a degree of substitution of hydroxyl groups ranging from about 0.05 to about 1.0; a degree of substitution of propyl groups ranging from about 0.5 to about 2.95; a degree of substitution of acetyl groups ranging from about 0.4 to about 2.95; and an intrinsic viscosity ranging from about 0.2 to about 1.6 dl / g more preferably, from about 0. to about 0.9 dl / g. The carboxylated cellulose acetate butyrates prepared by the process according to the invention have a degree of substitution of hydroxyl groups ranging from about 0.05 to about 1.0; a degree of substitution of butyryl groups ranging from about 0.5 to about 2.95; a degree of substitution of acetyl groups ranging from about 0.4 to about 2.95; and an intrinsic viscosity ranging from about 0.2 to about 1.6 dl / g, more preferably, from about 0.2 to about 0.9 dl / g. Preferably, the carboxylated cellulose acetate propionates and / or butyrates prepared in accordance with invention have a degree of substitution of propionate or butyrate which ranges from about 1 to about 2.5 and a preferred degree of substitution of acetate which varies from about 0.4 to about 1.6. The carboxylated cellulose esters obtained by the process described above can be used in a variety of coating compositions such as architectural coatings, maintenance coatings, industrial coatings, automotive coatings, textile coatings, inks, adhesives, and coatings for metal, paper, wood and plastics. Accordingly, the invention relates to such coating compositions comprising a carboxylated cellulose ester of the invention. The carboxylated cellulose esters of the invention can be incorporated into those coating compositions in the same way as known cellulose esters and used with the conventional components and / or additives of such compositions. The coating compositions can be transparent or pigmented. Coating compositions containing carboxylated cellulose esters are known in the art and are described, for example, in European Patent Application No. 138,703, the disclosure of which is incorporated herein by reference. A coating composition according to invention may comprise water, a solvent, a pigment (organic or inorganic) and / or other additives and fillers known in the art. Such additives or fillers include, but are not limited to, leveling agents, rheology, and flow control, such as silicones, fluorocarbons, urethanes or cellulosics; extenders; coalescent auxiliary reagents, such as those described in U.S. Patent No. 5,349,026, the disclosure of which is incorporated herein by reference; agents to opacify; dispersing and wetting agents for pigments and surfactants; ultraviolet (UV) absorbers; UV light stabilizers; coloring pigments; defoaming and defoaming agents; anti-sedimentation, anti-pollution and incorporation agents; anti-skim agents; anti-flood and antiseparation agents, fungicides and mildeucides; corrosion inhibitors; thickening agents; plasticizing agents, hardeners; or coalescing agents. Specific examples of such additives can be found in Raw Materials Index, published by the National Paint and Coatings Association, 1500 Rhode Island Avenue, N.W., Washington, D.C. 20005, the description of which is incorporated herein by reference. The carboxylated cellulose esters obtained by the process described above can be used to make coating formulations that have a very high solids content. Actually, coating formulations with a solids content greater than 45% can be obtained. Additionally, the carboxylated cellulose esters obtained by the process described above show improved compatibility with the resin coatings and solubility over a wider range of coating solvents. A carboxylated cellulose ester prepared by the process of the invention is compatible with a number of solvents. These solvents include, but are not limited to, methanol; methylene chloride; diacetone alcohol; lower alkanoic acids, such as formic acid, acetic acid; and propionic acid; lower alkyl ketones, such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, and methyl n-amyl ketone; esters, 'such as methyl acetate, ethyl acetate, isopropyl acetate, n-propyl acetate, n-butyl acetate, ethylhexyl acetate, isobutyl acetate, 2-butoxy-ethyl acetate, l-acetate methoxy-2-propyl, 2-ethoxy-ethyl acetate, ethyl-3-ethoxy propionate, isobutyl isobutyrate and 2,4,4-trimethyl-1,3-pentanediol monoisobutyrate; ethers such as ethylene glycol butyl ether, propylene glycol propyl ether, 2-ethoxyethanol, 2-propoxyethane and 2-butoxyethanol, and mixtures thereof. Also, mixtures of solvents, such as mixtures of toluene and / or xylene with ethanol and mixtures of ethanol with esters such as ethyl acetate, l-methoxy-2-propyl acetate and the like can be used. Of course, the above list is not intended to be exhaustive, although it is indicative of the diversity of solvents that may be employed in conjunction with the carboxylated cellulose esters of the invention. The carboxylated cellulose esters made by the process of the invention are compatible with a wide range of resinous materials such as those used in the coating and ink compositions. The classes of resins with which the carboxylated cellulose esters are compatible include, but are not limited to, thermoplastic acrylics, thermoset acrylics, silicone resins, alkyd resins, ordinary cellulose esters, urea formaldehyde resins, melamine resins, urethanes , nitrocellulose, unsaturated polyester resins and other thermosetting resins. A coating formulation containing the carboxylated cellulose ester of the invention can be applied to a variety of surfaces, substrates, or articles, eg, paper; plastic; metal; such as steel and aluminum; wood; gypsum earthenware; concrete; brick; masonry; or galvanized sheet. The type of surface, substrate, or article to be coated generally determines the type of used coating formulation. The coating formulation can be applied using means known in the art. For example, a coating formulation can be applied by spraying, by brush, roller or any other application method to coat a substrate. In metal coatings, the solid level of the formulation significantly influences the orientation of the metal foil, which is manifested by observing the coating at different lighting angles and verifying the change in apparent brightness commonly referred to as "flapping". As the level of solids increases, the orientation of the foil becomes more random causing an uneven appearance and luster. Typical metal coating formulations require about 20 to about 30 percent carboxylated cellulose ester to achieve a satisfactory metal foil orientation. However, a carboxylated cellulose ester of the invention can be formulated into metallic coating compositions, which also contain no more than 5 percent, based on the solids of the resin, of carboxylated cellulose esters and still having satisfactory metal foil orientation. Thus, another embodiment of the invention relates to a metal coating composition comprising from about 5% to about 30% of a carboxylated cellulose ester made by the process according to the invention and from about 30% to about 70% of film forming materials. A carboxylated cellulose ester of the invention is also useful as a main component that forms film in both of the cured and uncured finishes of wood coatings. Accordingly, the invention also relates to wood finishes of the cured type comprising about 10 weight percent of a carboxylated cellulose ester prepared by the process of the invention, about 20 weight percent of an alkyd resin, about 2 to about 5 weight percent of a melamine resin, about 5 to about 7.5 weight percent of a urea formaldehyde resin, a relatively small amount of a silicone resin and a solvent system comprising suitable solvents such such as xylene, toluene, ethanol, n-butyl alcohol, and methyl ethyl ketone. Opacifying agents such as SYLOID® 83 and SYLOID® 378 can also be used. A carboxylated cellulose ester prepared by the process according to the invention can be formulated into ink formulations. Here, the carboxylated cellulose ester functions as a means to disperse the pigments in the ink and also serves as a main resin forming film. So, another modality of invention relates to ink compositions comprising from about 30 to about 70% by weight of a carboxylated cellulose ester, from about 30 to about 70% by weight of an ink pigment and a solvent present in an amount effective to provide an suitable viscosity to apply the ink composition under the desired conditions. The carboxylated cellulose ester is preferably selected from carboxylated cellulose acetate, carboxylated cellulose acetate butyrate, carboxylated cellulose acetate propionate or a mixture thereof. Preferably, the composition of the ink of the invention comprises 45 to 70% by weight of at least one carboxylated cellulose ester prepared by the process according to the invention. The ink compositions of the invention may also contain common ink additives depending on the need for particular ink or printing method. Such ink additives include, but are not limited to, wetting agents, leveling agents, rheology additives, additives to promote resolubility / rewetting in the press, coalescing aids, pigment wetting agents, dispersing agents, surfactants, waxes, defoaming agents. , antifoaming agents and modifying polymers. The concentration of the pigments depends on the particular pigment employed and the color and degree of coating desired in the composition of the ink. Pigments that are useful in the ink compositions of the invention are those well known in the art and are described, for example in Kirk-Othmer Encyclopedia of Chemical Technology, 2d Ed., Vol. 11, pp. 613-615, the description of which is incorporated herein by reference. Solvents useful in the ink compositions of the invention are also well known in the art and are described, for example, in Kirk-Othmer Encyclopedia of Chemical Technology, 2d Ed., Vol. 11, p. 621-623, the description of which is incorporated herein by reference. Preferred solvents include ethanol, ethyl acetate, isopropanol, diacetone alcohol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and mixtures thereof. As a further aspect, a carboxylated cellulose ester prepared by the process according to the invention is useful as a pigment dispersing agent. Methods for dispersing pigments are known and taught in the art, for example, in European Patent Application No. 138,703, the description of which is incorporated herein by reference. In a conventional dispersion type a carboxylated cellulose ester, such as carboxylated cellulose acetate butyrate, are mixed with an organic or inorganic pigment and the mixture is then processed in a suitable apparatus such as a double roller mill, during processing, frictional heat and / or heat provided from an external source causes the carboxylated cellulose ester to soften and subsequently disperse in the pigment. In this way, expensive pigments can be easily dispersed in the coating formulations, thereby providing a high coloring power and good transparency while using a minimum amount of the pigment. Other methods for dispersing pigments include, but are not limited to, solution methods, ball mill, stone mill, Kady mill and sand mill. In these methods, the carboxylated cellulose ester is dissolved in a suitable solvent, pigment is added and the mixture is mixed in a mill for up to 48 hours. The dispersion of the resulting solution can be used to disperse pigments in lacquers, paints, automotive coatings, etc. Accordingly, the invention also relates to a method for dispersing a pigment comprising dissolving a carboxylated cellulose ester made by the process described above in a solvent and adding a pigment to the carboxylated cellulose ester / solvent mixture. Preferably, the weight ratio of the pigment to the carboxylated cellulose ester ranges from about 20:80 to about 60:40. He The pigment and the carboxylated cellulose ester / solvent mixture are mixed under conditions sufficient to disperse the pigment. Typical pigments used with carboxylated cellulose ester obtained by the process according to the invention include perylenes, quinacridones, phthalocinanines, iron oxides, and carbon blacks. The wide compatibility of the carboxylated cellulose esters prepared by the process of the invention allows the pigment dispersions described above to be used with a wide variety of polymers, thus making the dispersions useful in many paint and ink formulations. The practice of the invention is described in the following examples, which should not be construed to limit the invention in any way. EXAMPLES The solubility of cellulose acetate butyrates was determined by dissolving the ester in coating solvents such as methyl isobutyl ketone (MIBK), methyl n-amyl ketone (MAK), n-butyl acetate, ethylene glycol butyl ether (EASTMAN® EB), ethyl 3-ethoxypropionate (EASTMAN® EEP), propylene glycol propyl ether (PP), isobutyl isobutyrate (EASTMAN® IBIB), 2, 2, 4-trimethyl-l, 3-pentanediol monoisobutyrate. (TEXANOL®), a mixture of ketone (EASTMAN® C-ll), a mixture of aromatic and olefinic solvents (AROMATIC 100 and 150), 2-ethylhexyl acetate and n-propyl acetate. These solubilities were compared with those of non-commercial carboxylated cellulose esters CAB381-2BP, CAB381-0.1, CAB381-0.5, CAB321-1, CAB321-0.1, CAB171-15S and CAB531-1 available from Eastman Chemical Company. The compatibilities of cellulose acetate butyrate with alkyd resin coatings such as CARGIL 74-7455 and CARGIL 052-7711 available from McWorter, formerly known as Cargill, Inc., of Carpentersville, IL and polyisocyanate (Bayer 's DESMODUR HL) also were determined. Some of the samples of cellulose acetate butyrate were tested for the application of the metallic coating base of the original equipment manufacturer (OEM). A few formulations were prepared for spray application tests on metal plates. Sprayed metal plates were subjectively classified for orientation and appearance of the metal foil. EXAMPLE 1 A 20 gram sample of an oxidized cellulose containing 77 meq / kg carboxyl groups was broken into small pieces and soaked in demineralized water overnight. The soaked cellulose was broken into smaller pieces by processing the material in an EBERBACH® industrial mixer. After draining the water using a suction glass filter, the oxidized cellulose activated with water is washed a few times with acetic acid and then with butyric acid a few times. The esterifying reagent was prepared by mixing 47 grams of butyric acid including the residual amount with the oxidized cellulose activated by water, 6.2 grams of acetic anhydride and 50.6 grams of butyric anhydride. As a catalyst, 0.68 grams of 8% sulfuric acid was added. The esterifying reagent and the catalyst were added to the oxidized cellulose activated by water and placed in a round bottom flask with a stirrer. The flask was placed in an ice bath which maintained the bath temperature at about 0 ° C. After maintaining the bath temperature at about 0 ° C for 4 hours, the bath temperature gradually rose to room temperature, and finally rose to 50 ° C to complete the esterification reaction. A mixture of 19 grams of acetic acid and 19 grams of water was added to the solution and the bath temperature was raised to 60 ° C for hydrolysis. When the desired degree of hydrolysis was achieved, the catalyst in the solution was neutralized by adding 1.5 grams of magnesium acetate dissolved in aqueous acetic acid solution. The solution was filtered and then precipitated in a 10 percent aqueous solution of acetic acid and dried. This cellulose ester is referred to as Sample No. 1. The results of the Analytical test are shown in the Table 1 TABLE 1 * DS = degree of substitution To determine the compatibility of this carboxylated cellulose ester with the CARGIL 74-7455 alkyd compound, three samples were prepared in which the carboxylated cellulose ester and the CARGIL 74-7455 were dissolved in MIBK in various relationships as set forth in Table 2 The level of total solids in the solution remained approximately 10 percent. Compatibility was determined by the clarity of the dry film of these mixtures on a glass plate. The results are set forth in Table 2 TABLE 2 These results show that carboxylated cellulose acetate (CAB) butyrate made from oxidized cellulose was compatible with the alkyd resin of CARGIL 74-7455. EXAMPLE 2 A carboxylated cellulose ester was made with 0 grams of the same oxidized cellulose used in Example 1. The process was similar to that described in Example 1, but the esterifying reagent was prepared by mixing 80 grams of butyric acid including the amount residual with cellulose, 8.3 grams of acetic anhydride and 62.7 grams of butyric anhydride. The reaction bath temperature was maintained at 0 ° C for 2 hours, and then gradually rose to 35 ° C. The rest of the process steps were the same as those of Example 1. This cellulose ester is referred to as Sample No. 2. A cellulose acetate butyrate was made using a regular grade PLACETATE F® cellulose following the same process as that of the previous sample made of oxidized cellulose. The solution, after neutralization through medium glass frit filter to eliminate the excessive amount of fiber. This cellulose ester is referred to as Sample No. 3. The analytical results of these two cellulose acetates butyrate are given in Table 3. TABLE 3 Sample No. 2, made of oxidized cellulose, showed good compatibility with the alkyds, but Sample No. 3, made of regular grade cellulose, was incompatible with the alkyds based on the observation of cast films of the mixtures in MIBK solvents. .

EXAMPLE 3 A carboxylated cellulose acetate butyrate was prepared using the same oxidized cellulose as in Example 1. One hundred fifty grams of the oxidized cellulose were reacted with an esterifying reagent composed of 352.5 grams of butyric acid (total), 46.5 grams of acetic anhydride, 379.5 grams of butyric anhydride. As catalyst, 6.18 grams of 98 percent sulfuric acid was added. The reaction was maintained at about 0 ° C for 5 hours, and then the temperature was gradually raised to 40 ° C to complete the esterification. After the esterification was complete, a mixture of 142.5 grams of acetic acid, and 142.5 grams of water was added for hydrolysis. The hydrolysis was carried out at 60 ° C for 15 hours. The solution was filtered through an ordinary glass frit filter and precipitated in a 10 percent acetic acid solution. This cellulose ester is referred to as Sample No. 4. The analytical results of this carboxylated cellulose ester are given in Table 4. TABLE.

The solubility of Sample No. 4 of carboxylated cellulose ester was determined by dissolving the carboxylated cellulose ester in solvents of commonly used organic coatings. The solubilities of sample No. 4 and CAB531-1, a commercially available non-carboxylated cellulose acetate butyrate, were compared. These results are set forth in Table 5. TABLE 5 I: Insoluble, S: Soluble, PS: Partly Soluble.

* Propylene glycol propyl ether. As shown in Table 5, Sample 4 of carboxylated cellulose ester made of oxidized cellulose was easily soluble in EASTMAN®EB, EASTMAN®IBIB, propylene glycol propyl ether (PP), however, CAB531-1, was not soluble in EASTMAN ®EB or PP and was only partially soluble in EASTMAN®IBIB. EXAMPLE 4 Carboxylated cellulose ester was prepared as in Example 1, except that the molar ratio of acetic and butyric anhydride in the esterifying reagent was changed from 1: 5 to 1: 4, but the total amount was kept at 1.9 moles. The hydrolysis conditions also changed for these samples to increase the DS hydroxyl numbers. This cellulose ester is referred to as Samples No. 5 and No. 6. The hydrolysis conditions of these samples are set forth in Table 6.

TABLE 6 After hydrolysis, the solutions were filtered through an ordinary glass frit filter and precipitated in a 10 percent acetic acid solution. The carboxylated cellulose esters were washed thoroughly and dried. The analytical results of these carboxylated cellulose esters are set forth in Table 7 TABLE 7 The solubilities of Samples No. 5 and No. 6 were determined by dissolving the carboxylated cellulose esters in commonly used organic coating solvents. The solubility in organic solvents of these carboxylated cellulose esters revealed that they were more readily soluble in a wide range of solvents than commercial non-carboxylated cellulose esters. The solubility of the carboxylated cellulose esters of Samples Nos. 5 and 6 were compared with commercially available non-carboxylated cellulose acetate butyrate, CAB 531-1. The results are set forth in Table 8. TABLE 8 I: Insoluble, S: soluble, PS: Partly Soluble * Propylene glycol propyl ether. As shown in Table 8, cellulose acetates butyrate made from oxidized cellulose were easily soluble in EASTMAN®EB, EASTMAN®IBIB, propylene glycol propyl ether (PP), while commercial non-carboxylated CAB 531-1 was not soluble in EASTMAN® IBIB or PP and was only partially soluble in EASTMAN® IBIB. EXAMPLE 5 In this example, basecoat formulations were prepared using the cellulose esters of samples No. 5 and 6 and various commercially available cellulose acetate butyrates. The formulations comprised polyester, cellulose ester, melamine coatings such as RESIMENE 755®, available from Monsanto Chemical Company, SILBERLINE® 5245 (65% aluminum foil and 35% mineral spirits), PTSA catalyst (p-toluenesulfonic acid) and a combination of solvents of covering. The specific formulations are set forth in Table 9. TABLE 9 These formulations were sprayed onto metal plates which were dried in an oven. The sprayed panels are subjectively judged by experts for appearance and orientation of the metal foil by methods known in the art and described by J. Meister in "Circulation Reductions Specular Reflectance of Metallic Automotive Points," Polymers, 38 (2), pp. 638-639, Sept. 1997. The results of the evaluation of Sample No. 5 and commercial cellulose acetate butyrate are given in Table 10.

TABLE 10 The evaluation revealed that the use of carboxylated cellulose ester from Sample 5 in place of the comparable commercial cellulose acetate butyrate resulted in a 27.8% increase in the solids level, with a total solids level of 49.2%, and a Improved performance of panel spraying. This increase in the level of solids is clearly beneficial since a higher level of solids is required to reduce the amount of volatile organic compounds (VOC) during the spraying operation. EXAMPLE 6 Samples of carboxylated cellulose of 100 grams of the same oxidized cellulose used in Example 1 were prepared. The molar ratio of acetic anhydride and butyric anhydride is changed to about 3: 1, instead of the 1: 4 ratio used in the Example 4. The esterifying reagent was made with 235.0 grams of butyric acid, 141.7 grams of acetic anhydride and 73.0 grams of butyric anhydride and 3.45 grams of 98 percent sulfuric acid. Temperature Initial bathing water was maintained at approximately 0 ° C, and gradually increased to 65 ° C over a period of 6.5 hours. The hydrolysis was carried out in two stages by adding the first mixture of acetic acid solution / g 142 g / 142 g and after 16 hours of hydrolysis at 55 ° C, adding the second mixture of acetic acid / water solution 60 g / 60 g running for 4 more hours The remaining stages were similar to those of the previous examples. This cellulose ester is referred to as Sample No. 7. The analytical results of these samples are set forth in Table 11. TABLE 11 The solubility of the carboxylated cellulose ester of sample No. 7 was determined by dissolving the Commercial cellulose having similar compositions was not soluble in some of the same organic solvents.

As shown in these examples, these carboxylated cellulose acetates butyrate can be made in various combinations of ratios of acetyl DS / DS butyryl, I.V. and carboxyl contents without changing their performance characteristics in organic solvent solubility and alkyd compatibility when compared to commercial cellulose acetate butyrates. These examples demonstrated that adding carboxylated cellulose acetate butyrate to metal coating formulations increases the level of solids, while maintaining satisfactory operation in the orientation and appearance of the metal foil. The coating formulations exemplified above were prepared with polyester resins, but similar performance is expected in acrylic resin formulations. carboxylated cellulose in solvents of commonly used organic coatings. The results are shown in Table 12 including the solubilities of three commercial non-carboxylated cellulose esters having similar properties. TABLE 12 I: Insoluble, S: Soluble, PS: Partly Soluble.

* Propylene glycol propyl ether. The carboxylated cellulose ester of Sample No. 7 made of oxidized cellulose was easily soluble in EASTMAN® EEP, propylene glycol, propyl ether (PP), n-butyl acetate, and EASTMAN® MAK while the acetate esters of

Claims

CLAIMS 1. A process for making a carboxylated cellulose ester of oxidized cellulose characterized in that it comprises the following steps: (I) activating the oxidized cellulose with water; (II) dehydrating the activated oxidized cellulose by displacing the water with acetic acid and optionally displacing at least some of the acetic acid with butyric acid or propionic acid; (III) reacting the activated cellulose with a steamer reagent in the presence of a catalyst at a temperature of about 0 ° C; (IV) gradually increasing the temperature to a level sufficient to complete the reaction and to obtain an intrinsic viscosity ranging from about 0. to about 1.6 dl / g; (V) hydrolyzing the reaction solution to obtain a degree of substitution of hydroxyl groups ranging from about 0.05 to about 1.0; (VI) neutralizing the catalyst with a neutralizing agent; (VII) optionally filtering the solution; and (VIII) precipitating the solution with a precipitating agent to precipitate the carboxylated cellulose ester.
2. The process according to claim 1, characterized in that the esterifying reagent is acetic acid, propionic acid, butyric acid, acetic anhydride, propionic anhydride, butyric anhydride or a mixture thereof. 3. The process in accordance with the claim 1, characterized in that the esterifying reagent is present in an amount ranging from about 10.0 moles to about
3.0 moles relative to one mole of anhydrous glucose bound cellulose.
4. The process according to claim 1, characterized in that the carboxylated cellulose ester is carboxylated cellulose acetate.
5. The process according to claim 1, characterized in that: (a) the carboxylated cellulose ester is carboxylated cellulose acetate butyrate; (b) the acetic acid is displaced with at least some of the butyric acid; and (c) the esterifying reagent comprises from about 0.1 to about 3 moles of acetic anhydride and from about 6.0 to 0.6 moles of butyric anhydride. 6. The conformity process in claim 1, characterized in that: (a) the carboxylated cellulose ester is carboxylated cellulose acetate propionate; (b) the acetic acid is displaced with at least some propionic acid; and (c) the esterifying reagent comprises from about 0.1 to about 3 moles of acetic anhydride and from about
6.0 to about 0.1 moles of propionic anhydride.
7. The process according to claim 1, characterized in that the catalyst is sulfuric acid, perchloric acid, zinc chloride, titanium alkoxide, a sulfate salt, sulphonic acid, methanesulfonic acid or a mixture thereof and wherein the Neutralizing agent is magnesium acetate, calcium acetate, sodium acetate, pipdin or a mixture thereof.
8. The process according to claim 1, characterized in that the intrinsic viscosity ranges from about 0.2 to about 0.9 dl / g and wherein the degree of substitution of the hydroxyl groups ranges from about 0.05 to about 1.0.
9. The process according to claim 1, characterized in that the oxidized cellulose has a carboxyl content of at least 30 meq / kg.
10. The process according to claim 13, characterized in that the oxidized cellulose has a carboxyl content ranging from about 47 to about 77 meq / kg.
11. The carboxylated cellulose acetate butyrate prepared by the process according to claim 5, characterized in that it has a degree of hydroxyl group substitution ranging from about 0.05 to about 1.0; a degree of substitution of butyryl groups ranging from about 0.05 to about 2.95; a degree of substitution of acetyl groups ranging from about 0.5 to about 2.95; and an intrinsic viscosity ranging from about 0.2 to about 1.6 dl / g.
12. The carboxylated cellulose acetate propionate prepared by the process according to claim 6, which has a degree of substitution of hydroxyl groups ranging from about 0.05 to about 1.0; a degree of substitution of propyl groups ranging from about 0.5 to about 2.95; a degree of substitution of acetyl groups ranging from about 0.5 to about 2.95; and an intrinsic viscosity ranging from about 0.2 to about 1.6 dl / g.
13. The carboxylated cellulose acetate prepared by the process according to claim 4, which has a varying degree of substitution of hydroxyl groups from about 0.05 to about 1.0; a degree of substitution of acetyl groups ranging from about 2.0 to about 2.95; and an intrinsic viscosity ranging from about 0.2 to about 1.6 dl / g.
14. The coating composition characterized in that it comprises a carboxylated cellulose ester prepared by the process according to claim 1.
15. The coating composition according to claim 14, characterized in that the recomposition of coating is a coating composition of metal, an ink composition, a textile coating composition or an adhesive composition.
16. The coating composition according to claim 15, characterized in that the solids content is at least about 45%.
17. The coating composition according to claim 16, characterized in that the coating composition is a metal coating composition comprising from about 5 to about 30% by weight of the carboxylated cellulose ester and from about 30 to 70% by weight. weight of a material that forms film.
18. The metal coating composition of according to claim 17, further characterized in that it comprises an additive selected from the group consisting of a leveling agent, a rheology agent, a flow control agent, an opacifying agent, a wetting agent, a dispersing agent, ultraviolet absorbers (UV ), a UV light stabilizer, a defoaming agent, an antifoaming agent, an anti-settling agent, an anti-sinking agent, an incorporation agent, an antisleaving agent, an anti-flooding agent, an antiseparation agent, a fungicide, a mildeucide, a corrosion inhibitor, a thickening agent, a plasticizer, a hardening agent, a coalescing agent, and mixtures thereof.
19. The metal coating composition according to claim 18, characterized in that the carboxylated cellulose ester is selected from the group consisting of a carboxylated cellulose acetate, a carboxylated cellulose acetate butyrate, a carboxylated cellulose acetate propionate, or a mixture of them.
20. A coating composition according to claim 16, characterized in that the coating composition is an ink composition comprising: (i) from about 30 to about 70% by weight of the carboxylated cellulose ester; (ii) from about 30 to about 70% by weight of an ink pigment; (m) a solvent present in an amount effective to provide a suitable viscosity for applying the ink composition under the desired conditions. The ink composition according to claim 20, characterized in that the solvent is selected from the group consisting of ethanol, ethyl acetate, isopropanol, diacetone alcohol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and mixtures thereof. The ink composition according to claim 20, further characterized in that it comprises an additive selected from the group consisting of a wetting agent, a leveling agent, a rheology agent, a coalescence aid, a wetting agent, a dispersing agent , a surfactant, a wax, a defoaming agent, an antifoaming agent, a modifying polymer, and mixtures thereof. 23. The method for dispersing a pigment characterized in that it comprises the following steps: (i) dissolving the carboxylated cellulose ester made by the process according to claim 1, in a solvent; (ii) adding a pigment to the carboxylated cellulose ester / solvent mixture; (? ü) mix the pigment / cellulose ester carboxylated / solvent mixture under conditions sufficient to disperse the pigment. 4. The pigment dispersion made by the process according to claim 23, characterized in that the weight ratio of the pigment to the carboxylated cellulose ester varies from about 20:80 to about 60:40. SUMMARY A process for preparing a carboxylated cellulose ester from oxidized cellulose is described. The carboxylated cellulose esters have solvent solubility and improved resin coating compatibility when compared to cellulose esters made of regular grade cellulose. The process comprises the activation of the oxidized cellulose with water. The activated oxidized cellulose is then dehydrated by displacing the water with acetic acid and optionally displacing at least some of the acetic acid with butyl or propionic acid. After dehydration the activated cellulose is reacted with an esterifying reagent in the presence of a catalyst at about 0 ° C. The temperature is gradually increased to a level sufficient to complete the reaction and to obtain an intrinsic viscosity in the range of about 0.2 to about 1.6 dl / g. The solution that was reacted was then hydrolyzed to obtain a hydroxyl content in the range of about 0.05 to about 1.0. The catalyst is neutralized with a neutralizing agent and the solution is optionally filtered and the carboxylated cellulose ester is then precipitated with a precipitating agent. The invention also relates to the carboxylated cellulose esters prepared by the process described above as well as to the compositions of high solids coating, containing carboxylated cellulose esters made by the above process.