Thermosensitive recording materials such as thermal paper have printed indicia of high quality on the back thereof printed on a backcoating. This backcoating also incorporates an optically variable compound which provides a security feature.

The present invention relates to thermosensitive recording materials with high quality images preprinted thereon.
Direct thermal paper is a thermosensitive recording material on which print or a design is obtained without an ink ribbon by the application of heat energy thereto. Direct thermal paper comprises a base sheet, a base coating and a thermosensitive coating with color forming chemicals that respond to heat.
The most common type of thermosensitive coating used on direct paper is the dye-developing type system. This typically comprises a colorless dye (color former), a bisphenol or an acidic material (color developer) and sensitizer. These solid materials are reduced to very small particles by grinding and incorporated into a coating formulation along with any optional additives such as pigments, binders and lubricants. The coating formulation is then applied to the surface of a support system, typically a base sheet and base coating. The color is formed by application of heat to the thermosensitive coating to melt and interact the three color producing materials.
Thermal printing on thermosensitive recording materials provides a number of advantages over printing on plain paper using inked ribbons. One advantage is that thermal printers are less noisy than impact printers. With fewer mechanical operations, thermal printers are believed to be more reliable than impact printers. There are some compromises which must be made when switching from bond paper to thermal paper because the color producing components require special handling and conditions.
To replace plain paper receipt rolls, it is often desirable that the thermal paper also provides security features and preprinted information such as store logos, advertisements, rules and regulations, etc. It is also desirable that this preprinted indicia be of high quality.
By adding features to thermal paper, care must be taken not to pre-react the reactive components within the thermosensitive coating of the thermal paper or prevent the formation of an image on the thermal paper when passed through a thermal printer. Certain chemical factors can adversely affect and degrade the performance of the thermosensitive coatings and should be avoided such as some organic solvents, plasticizers, amines and certain oils.
The use of ink with optically variable compounds as a security measure is well known. Optically variable compounds change color or reflect a unique wavelength in response to a change in ambient conditions such as exposure to a light source other than ambient light or a change in ambient temperature. Optically variable compounds as defined herein include fluorescent compounds and photochromic compounds which respond to infrared or ultraviolet light, thermochromic compounds which change color at different temperatures and near infrared fluorescent (NIRF) compounds which reflect radiation in the near-infrared range. Examples of fluorescent compounds include those described in U.S. Pat. Nos. 4,153,593, 4,328,332 and 4,150,997. Examples of thermochromic compounds are described in U.S. Pat. Nos. 4,425,161; 5,427,415; 5,500,040; 5,583,223; 5,595,955; 5,690,857; 5,826,915; 6,048,347; and 6,060,428. Examples of near infra-red compounds (NIRF) include those described in U.S. Pat. Nos. 5,292,855; 5,423,432 and 5,336,714. The use of fluorescent compounds as a security feature for thermosensitive recording materials is described in U.S. Pat. No. 5,883,043. The use of NIRF compounds as a security feature for thermosensitive recording materials is described in U.S. Pat. No. 6,060,426, assigned to the assignee as the present invention.
To protect thermal paper from environment conditions, and premature coloration from handling, a number of developments have been made. One is to produce a barrier or protection on top of the thermal coating as disclosed in U.S. Pat. Nos. 4,370,370; 4,388,362; 4,424,245; 4,44,819; 4,507,669 and 4,551,738. A U.V. cured silicone acrylate/methacrylate protective coating for a thermosensitive layer is described in U.S. Pat. No. 4,604,635.
U.S. Pat. No. 5,595,955 discloses coating a latent image comprising a thermochromic ink on the reverse side of thermal paper with a thin protective layer.
The present invention provides a thermosensitive recording material such as thermal paper, comprising a base sheet, an optional base coating, a thermosensitive coating on the top surface of the base sheet or the optional base coating, a backcoating on the side of the base sheet opposite the thermosensitive coating and a printed image on the top surface of the backcoating. The backcoating has incorporated therein a fluorescent compound, a thermochromic compound, a photochromic compound, or a near infrared fluorescent compound (NIRF).
When used as a security feature, the amount of NIRF compound within the backcoating must be sufficient to be sensed by a photon detector operating in the near infrared region of 650 nm to 2500 nm. For a photochromic or fluorescent compound to provide a security feature, the amount of these compounds within the backcoating must be sufficient to generate a latent image when exposed to infrared or ultraviolet light. To provide a security feature, the amount of thermochromic compound within the backcoating must be sufficient to generate or eliminate an image when exposed to temperatures greater than ambient temperature.
The backcoating containing the fluorescent compound, photochromic compound, thermochromic compound and/or NIRF compound can be a U.V., infrared or electron beam cured coating or an air dried coating such as a flexographic or lithographic coating. The backcoating is preferably U.V. cured. This will eliminate the exposure of reactive components within the thermosensitive coating to heat which can cause the reactive components to prematurely color. The backcoat provides a medium in which the optically variable compounds will provide their security function while shielding the reactive components of the thermosensitive coatings from these optically variable compounds. This shielding will preserve the activity of the optically variable compounds as well as the activity of any reactive components within the thermosensitive coating of the thermal paper so that the thermosensitive coating will still generate color when exposed to heat.
In certain embodiments, two or more optically variable compounds can be present in the backcoating to provide two modes of security. For example, optically variable compounds responsive to ultraviolet light can be combined with NIRF compounds which are responsive to near-infrared radiation. In alternative embodiments, the backcoating can overcoat a separate image of a security ink. This requires an additional printing step and is not preferred.
The backcoating can be applied by conventional coating processes such as flexography, gravure, wet-offset printing, letter press and relief printing and where necessary cured by air drying or U.V., infrared or electron beam curing techniques. Following the cure of the backcoating, an image is printed over the backcoating by conventional printing techniques such as flexography, gravure, wet-offset printing, letter press and relief printing.
The thermosensitive recording media of the present invention have a base sheet and a thermosensitive coating positioned on one side of the base sheet. Optionally, a base coating is positioned between the thermosensitive coating and the base sheet. Conventional base sheets and base coatings can be used in the thermosensitive recording materials of the present invention. The base sheet can comprise those materials used in conventional thermosensitive recording materials and at least includes those derived from synthetic and natural fibers such as cellulose (natural) and polyester (synthetic) fibers. The base coating is typically comprised of an inert pigments and binders and provides a smooth surface for the thermosensitive coating. The base sheet and base coatings must not contain any reactive elements which will prematurely color the thermosensitive coating or cause the loss of the color forming properties of the thermosensitive coating.
The thermosensitive coating is preferably of the dye-developing type. Particularly suitable dye developer systems are those wherein the reactive dyes are colorless or white colored and become dark colored when melted or exposed to color developer. Such dyes typically are basic substances which become colored when oxidized by acidic compounds or bisphenol compounds. In these dye-developer systems, sensitizers are typically mixed with the dyes to form a blend with a reduced melting point. This reduces the amount of heat necessary to melt the dye and obtain reaction with the color developer. The components of the thermosensitive coating are often determined by the operating temperature of the thermal printer to be used. The operating temperature of conventional thermal printers varies widely, typically within the range of from 50xc2x0 C. to 250xc2x0 C. A well-known dye that operates in this range is identified in the art as xe2x80x9cODB-IIxe2x80x9d. A preferred color developer is bisphenol A and a preferred sensitizer is M-terphenyl. One skilled in the art can readily determine the melting point necessary for desired application and select a dye and developer accordingly, or select a conventional thermal paper with a thermosensitive coating on one side.
The thermosensitive coating can vary in composition as is conventionally known in the art, including the encapsulation of components therein and the use of protective layers thereon to prevent premature coloration during handling. These thermosensitive coatings can be applied by conventional methods using conventional equipment.
Color formers suitable for use in the coating formulations that form the thermosensitive recording materials of this invention are leuco dyes. Leuco dyes are colorless or light-colored basic substances, which become colored when oxidized by acidic substances. Examples of leuco dyes that can be used herein are leuco bases of triphenylmethane dyes represented by formula I in U.S. Pat. No. 5,741,592. Specific examples of such dyes are: 3,3-bis(p-dimethylaminophenyl)-phthalide, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (Crystal Violet Lactone), 3,3-bis(p-dimethylaminophenyl)-6-diethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide, and 3,3-bis(p-dibutylaminophenyl)-phthalide.
Leuco bases of floran dyes represented by formula II in U.S. Pat. No. 5,741,592, are also suitable. Some examples of these fluoran dyes are:
3-cyclohexylamino-6-chlorofluoran, 3-(Nxe2x80x94N-diethylamino)-5-methyl-7-(N,N-Dibenzylamino)fluoran, 3-dimethylamino-5,7-dimethylfluoran and 3-diethylamino-7-methylfluoran. Other suitable fluoran dyes include: 3-diethylamino-6-methyl-7-chlorofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, and 2-[3,6-bis(diethylamino)-9-(0-chloroanilino)xanthylbenzoic acid lactam].
Also suitable are lactone compounds represented by formula III in U.S. Pat. No. 5,741,592 and the following compounds:
3-(2xe2x80x2-hydroxy-4xe2x80x2-dimethylaminophenyl)-3-(2xe2x80x2[-methoxy-5xe2x80x2-chlorophenyl)phthalide, 3-(2xe2x80x2-hydroxy-4xe2x80x2-dimethylaminophenyl)-3-(2xe2x80x2-methoxy-5xe2x80x2-nitrophenyl-phthalide, 3-(2xe2x80x2-hydroxy-4xe2x80x2-diethylaminophenyl)-3-(2xe2x80x2-methoxy-5xe2x80x2-methylphenyl)phthalide, and 3-(2xe2x80x2-methoxy-4xe2x80x2-dimethylaminophenyl)-3-(2xe2x80x2-hydroxy-4xe2x80x2-diethylaminophenhl)-3-(2xe2x80x2-methoxy-5xe2x80x2-methylphenyl)phthalide, and 3-(2xe2x80x2-methoxy-4xe2x80x2-dimethylaminophenyl)-3-(2xe2x80x2-hydroxy-4xe2x80x2-chloro-5xe2x80x2-methylphenyl)-phthalide.
There are many substances which change the color of the dyes by oxidizing them and function as developers. Color developers suitable for the coating formulations and thermosensitive recording materials of this invention are phenol compounds, organic acids or metal salts thereof and hydroxybenzoic acid esters. Preferred color developers are phenol compounds and organic acids which melt at about 50xc2x0 C. to 250xc2x0 C. and are sparingly soluble in water. Examples of suitable phenol compounds include 4,4xe2x80x2-isopropylene-diphenol (bisphenol A), p-tert-butylphenol, 2-4-dinitrophenol, 3,4-dichlorophenol, p-phenylphenol, 4,4-cyclohexylidenediphenol, 2,2-bis(4xe2x80x2-hydroxyphenyl)-n-heptane and 4,4xe2x80x2-cylcohexylidene phenol. Useful examples of organic acid and metal salts thereof include 3-tert-butylsalicyclic acid, 3,5-tert-butylsalicyclic acid, 5-a-methylbenzylsalicylic acid and salts thereof of zinc, lead, aluminum, magnesium or nickel.
Sensitizers or thermosensitivity promoter agents are preferably used in the thermal papers of the present invention to give a good color density. The exact mechanism by which the sensitizer helps in the color forming reaction is not well known. It is generally believed that the sensitizer forms a eutectic compound with one or both of the color forming compounds. This brings down the melting point of these compounds and thus helps the color forming reaction take place at a considerably lower temperature. Some of the common sensitizers which are suitable are fatty acid amide compounds such as acetamide, stearic acid amide, linolenic acid amide, lauric acid amide, myristic acid amide, methylol compounds or the above mentioned fatty acid amides such as methylene-bis(stearamide), and ethylenebis(stearamide), and compounds of p-hydroxybenzoic acid esters such as methyl p-hydroxybenzoate, n-propyl p-hydroxybenzoate, isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate.
The backcoating for printing on the reverse side of thermosensitive recording medium preferably has a thickness of from 0.05 to 2.0 mils. It should be recognized however that higher thicknesses will not affect the chemical activity of the thermosensitive coating on the thermosensitive recording media. In addition, higher thicknesses will not affect the ability of the backcoating to accept print. The above range is preferred from the standpoint of cost and efficiency.
Flexographic and lithographic printing methods are preferred for applying the backcoating on the thermosensitive recording medium. Other suitable techniques include gravure, letter press and relief printing which does not require temperatures above 50xc2x0 to 65xc2x0 C. Once applied the backcoating preferably does not require temperatures in excess of 125xc2x0 F. (about 50xc2x0 C.) to cure. The backcoat can vary significantly from a U.V. or visible light cured polymer coating to an electron beam cured polymer coating, to a heat cured polymer coating cured at temperatures of up to 125xc2x0 F., to a condensed polymer coating which dries at ambient temperature in air. This backcoat serves to protect the thermosensitive layer from the optically variable compounds incorporated therein when the thermosensitive recording medium is stored on a continuous roll rolled onto itself or is stored as stacked sheets.
The backcoating may contain additives such as resins binders, pH stabilizers, U.V. stabilizers, surfactants, color pigments and defoamers provided they do not pre-react the thermosensitive layer. The nature of the additives will depend on the end use of the backcoating. Suitable binder components of the backcoating include: polyvinyl chloride polymers, polyvinyl acetate polymers, vinyl chloride-vinyl acetate copolymers, polyvinyl alcohol polymers, polyethylene polymers, polypropylene polymers, polyacetal polymers, ethylene-vinyl acetate copolymers, ethylene alkyl(meth)acrylate copolymers, ethylene-ethylacetate copolymers, polystyrene, styrene copolymers, polyamides, ethylcelluloses, epoxy resins, polyketone resins, polyurethane resins, polyvinyl butryl polymers, styrene butadiene rubbers, nitrile rubbers, acrylic rubbers, polypropylene rubber, ethylene alkyl(meth)acrylate copolymers, styrene-alkyl(meth)acrylate copolymers, acrylate acid-ethylene-vinyl acetate tert polymers, saturated polyester polymers and sucrose benzoate. To obtain emulsions of polymers which are insoluble or partially soluble, the resin is typically ground to submicron size. U.S. Pat. No. 5,843,864 describes some of the suitable synthetic resin binders and suitable cellulose binders with synthetic wax are described in U.S. Pat. No. 4,740,495.
Suitable U.V. cured backcoatings are the coatings described in U.S. Pat. No. 4,886,744. Most free radical initiated polymerizations can be suitably cured with the use of a free radical initiator that is responsive in the U.V. range. These U.V. cured backcoatings may also contain additives such as U.V. absorbers and light stabilizers. Employing the U.V. cured backcoating allows for rapid drying. U.S. Pat. No. 5,158,924 also describes ultraviolet curing resins which are suitable for backcoatings and include urethane resins, epoxy resins, organosiloxane resins, polyfunctional acrylate resins, melamine resins, thermoplastic resins having high softening points such as fluorine plastics, silicone resins and polycarbonate resins. A specific example of a urethane acrylate-type U.V. curing resin is UNIDIC C7-157 made by Dianippon Ink and Chemicals Inc.
The optically variable compound that can be incorporated within this coating can include fluorescent compounds, photochromic compounds, thermochromic compounds and NIRF compounds. The fluorescent compounds and photochromic compounds typically respond to infrared or ultraviolet light. Representative inks which fluoresce include those described in U.S. Pat. Nos. 4,153,593; 4,328,332 and 4,150,997. Representative photochromic compounds are disclosed by Takahashi et al. in U.S. Pat. No. 5,266,447.
Photochromic compounds which change color when exposed to U.V. light can be used. Suitable photochromic compounds include the spiro compounds of formula V disclosed by Takahashi in U.S. Pat. No. 5,266,447. These include spiro oxazine compounds, spiropyran compounds, and thiopyran compounds of the formulae in cols. 5-6 of U.S. Pat. No. 5,266,447. Other examples of suitable photochromic compounds include the benzopyran compounds disclosed by Kumar in U.S. Pat. No. 5,429,774, the benzothioxanone oxides disclosed by Fischer in U.S. Pat. No. 5,177,218 the dinitrated spiropyrans disclosed by Hibino et al. in U.S. Pat. No. 5,155,230, the naphthacenequinones disclosed by Fischer et al. in U.S. Pat. No. 5,206,395 and U.S. Pat. No. 5,407,885, the naphthopyran compounds disclosed by Knowles in U.S. Pat. No. 5,384,077, the spiro (indoline) naphthoxazine compounds disclosed by VanGemert in U.S. Pat. No. 5,405,958, the ring compounds disclosed by Tanaka et al. in U.S. Pat. No. 5,106,988 and the spiro-benzoxazine compounds disclosed by Rickwood et al. in U.S. Pat. No. 5,446,151. Mixtures of such compounds are preferred and are available commercially from such sources as Color Change Corp. of Shaumburg, and Chromatic Technologies Inc. of Colorado Springs, Colo.
Suitable fluorescent pigments and dyes include the fluorescent resins produced in U.S. Pat. No. 4,328,332 from trimelitic anhydrides and propylene glycol with zinc acetate catalyst. Representative water soluble fluorescent dye components are fluorescein and eosine dyes and blaze orange 122-8524-A (manufactured by Dyco Color Corp. of Cleveland, Ohio).
The concentration of the fluorescent and/or photochromic pigment within the backcoating used on the thermal paper and method to this invention can vary widely. In general, the optical effect can be developed in most thermal papers with the fluorescent dye or photochromic pigment component present in an amount which ranges from 1 to 50% by weight and preferably in an amount of 1 to 15% by weight.
Suitable NIRF compounds are typically employed in polyester based and polyester amide based coatings. Examples of suitable NIRF compounds are described in U.S. Pat. Nos. 5,292,855; 5,423,432 and 5,336,714. Suitable NIRF compounds include pthalocyanines, napthalocyanines squaraines with are covalently bonded to halometals. NIRF compounds typically provide a security measure that is responsive to wavelengths in the near infrared region of 650 nm to 2500 nm. The NIRF pigment particles are solids and typically comprise a polymer or copolymer which is either admixed with NIRF compounds or the NIRF compounds are copolymerized with other active monomers, oligomers or polymers to form a copolymer. The amount of NIRF compound within the ink formulation typically falls within in the range of 0.1 ppm to 1000 ppm, based on dry components of the ink. Typical amounts fall within the range of 0.5 ppm to 300 ppm with amounts of 1 ppm to 100 ppm often being most preferred.
The thermochromic compounds suitable for use in the backcoating are selected to provide a security measure that is responsive to temperatures above ambient temperature (above 20xc2x0 C.) and below the temperature of activation of the thermosensitive recording medium (typically about 60xc2x0 C.). One class of preferred thermochromic compounds are active at temperatures in the range of 21xc2x0 C. to 40xc2x0 C., (about 70xc2x0 F. to 100xc2x0 F.). The compounds may be responsive to temperatures above this range but heating the thermosensitive recording medium to temperatures above this range will activate most conventional thermosensitive layers. One or more xe2x80x9csensitizersxe2x80x9d may be added to the backcoating to control the temperature at which the color change occurs. Examples of suitable sensitizer compounds for the thermochromic compounds include carboxylic acids, acid amides, hydroxides, alcohols, esters and phenols. The thermochromic compounds are preferably stable to air, sunlight, and fluorescent light.
When a flexographic process is employed to deposit the backcoating, the thermochromic compounds are preferably soluble dispersible or emulsifiable in water to provide xe2x80x9cwater basedxe2x80x9d formulations or inks. When a lithographic process is employed to deposit the thermochromic compounds, it can be used in a hydrophobic or oil based formulation or ink, provided it is compatible with the backcoating. Water-based or U.V. cured formulations are preferred to avoid the use of solvents that may prereact the thermosensitive layer or cause the loss of color forming properties of the thermosensitive layer.
Preferred thermochromic compounds have excellent thermal stability with little light absorption in the visible light region, i.e., they impart little or no color to coatings and substrates to which they are applied. Preferably, they are transparent or invisible to the naked viewing eye under ambient light at ambient temperature (about 20xc2x0 C.). Suitable thermochromic compositions include those described in U.S. Pat. Nos. 5,292,855; 5,423,432; 5,336,714; 5,461,136; 5,397,819; 5,703,229; 5,614,088; 5,665,151; 5,503,904; 4,425,161; 5,427,415; 5,500,040; 5,583,223; 5,959,955; 5,690,857; 5,826,915; 5,048,837 and 6,060,428. These include the conventional electron donors/electron accepting combinations known in the art. Examples of electron donor compounds are described in U.S. Pat. No. 4,425,161 and include diarylphthalides, such as crystal violet lactone, polyarylcarbinols, leucoauramines, Rhodamine B lactams, indolines, spiropyrans and fluorans. Examples of electron-acceptor compounds are also described in U.S. Pat. No. 4,425,161 and include triazol compounds, thioureas, phenols, phenol resins, benzolthiozols, carboxylic acids and metal salts thereof, and phosphorous esters and metal salts thereof.
Suitable commercially available thermochromic printing inks which activate at temperatures in the range of 21xc2x0 to 51xc2x0 C. include 744020TC (thermochromic blue), 744010TC (thermochromic turquoise), 744027TC (thermochromic yellow), 734010TC (thermochromic rose), 724010TC (thermochromic orange), 754027TC (thermochromic green) sold by SICPA Securink Corp. Springfield, Va. Included are the thermochromic inks which lose color when heated, i.e., change from a color to clear. This includes the compounds 138000TC5 (rose/clear) and 178002TC (Blue/clear) available from SICPA Securink Corp. which are active at 1xc2x0 C.-12xc2x0 C. Marks and images made of these compounds are colorless at ambient temperature and change color when cooled. The compound 178002TC (Blackclear) from SICPA Securink Corp. is active at 27xc2x0 C.-36xc2x0 C. Compounds from SICPA Securink Corp. which are active at 22xc2x0 C.-31xc2x0 C. include: 128001TC (orange/clear), 1384175TC (rose/clear), 150015TC (green/clear), 148003TC (blue/clear), 17800TC (black/clear), 14001TCBR (blue/red) and 128001TCY (orange/yellow). Compounds from SICPA Securink Corp. which are active at 24xc2x0 C.-33xc2x0 C. include: 118000TC (yellow/clear), 128002TC (orange/clear), 138103TC (vermillion/clear), 15002TC (green/clear), 14001TC (blue/clear), 14000TCBR (blue/red) and 128001TCY (orange/yellow). Compounds from SICPA Securink Corp. which are active at 24xc2x0 C.-33xc2x0 C. include: 11800TC (yellow/clear), 128002TC (orange/clear), 138103TC (vermillion/clear), 15002TC (green/clear), 14001TC (blue/clear), 14000TCBR (blue/red) and 128002TC (orange/yellow). Compounds from SICPA Securink Corp. which are active at 32xc2x0 C.-41xc2x0 C. include: 13001TC (rose/clear), 148002TC (blue/clear), 178001TC (black/clear) and 178002TCBR (blue/red).
Preferred thermochromic compositions are microencapsulated within the backcoat. The microcapsules can be dispersed in a slurry, preferably a neutral aqueous slurry and can be dried to a powder. The encapsulant can vary in composition and includes epoxy resins and polyurea resins. Microencapsulation can be performed by any conventional technique such as interfacial polymerization as described in U.S. Pat. Nos. 3,429,827 and 3,167,602 and in-situ polymerization as described in British Patent No. 989264, coacervation from an aqueous slurry as described in U.S. Pat. Nos. 2,800,457 and 3,116,206, suspension coating as described in U.S. Pat. No. 3,202,533 and spray drying as described in U.S. Pat. No. 3,016,308. The microcapsules can be of a conventional size but are typically about 30 microns or less.
The thermochromic compositions can be employed in the backcoating formulations in amounts of from 1% to about 50% by weight of the solids within the backcoating formnulation. Preferred levels range from about 5% to about 40% by weight of the microencapsulated thermochromic composition, based on the total weight of solids in the backcoating formulation.
Preferably, a special apparatus is not needed to detect the presence of a thermochromic composition and simply rubbing the mark or image with a finger will generate the color shift. Devices which will excite the thermochromic compositions include incandescent light sources, hot air dryers, resistance heaters and other radiant energy sources that emit heat or infrared radiation. Preferred heat sources are those which heat the surface of the thermosensitive compound to a temperature above ambient temperature but less than the temperature of activation of the thermosensitive layer, i.e. about 21xc2x0 C. to 51xc2x0 C. The thermochromic compounds typically have a defined temperature range at which the color shift is actuated. For example, thermochromic inks with actuation temperatures in the following ranges are commercially available.
1xc2x0 to 12xc2x0 C.
22xc2x0 to 31xc2x0 C.
24xc2x0 to 33xc2x0 C.
27xc2x0 to 36xc2x0 C.
32xc2x0 to 41xc2x0 C.
The carrier or vehicle used for the backcoating formulation preferably dries or cures at a temperature below 50xc2x0 C. If the formulation is for flexographic printing, aqueous based formulations are preferred. The aqueous vehicles which dry by gelation, polymerization or solidification are suitable as are water miscible organic solvents which do not pre-react the thermosensitive layer. The aqueous based carrier may contain a dispersing agent to help solubilize the optically variable compounds within the backcoat formulation. The backcoat formulation preferably has a viscosity which is below 500 cps and preferably in the range of about 5 to 100 cps at 25xc2x0 C., for flexographic printing. For flexographic printing, a solids content of 40-60 wt % is preferred. For UV cured backcoatings, a tack within the range of 10-20 at 1200 rpm and 90xc2x0 F. is preferred.
The backcoating may contain an optional pigment or dye which does not interfere with the optical properties of the optically variable ink. Examples may include carbon blacks, cadmium, primrose, cobalt oxide, nickel oxide, etc. When used, the pigment or dye preferably comprises from 0.01 to 10 wt % of the backcoating, based on solids.
Thermal papers which contain security features as a separate image overcoated by the backcoating can be prepared by methods similar to methods with the security feature within the backcoating as described above but with an additional printing step.
The backcoating applied to the thermosensitive recording material may contain more than one security feature provided by a different optically variable compound or by the binder of the backcoating. For example, the fluorescent compounds may be combined with NIRF compounds, thermochromic compounds or photochromic compounds and the binder may provide a water mark or a water repellant image once cured.
The binder component of the backcoating employed in the thermal papers of this invention may be a water repelling agent such as acrylic polymers and copolymers or it may contain a separate water repelling agent such as a silicone resin in an amount of 0.5 to 10 wt % based on total solids. This water repelling agent may provide an additional security for the thermal paper obtained. The water repellant agent is used in amounts efficient to provide a dry image with a surface tension less than 35 dynes preferably between 20 to 30 dynes. Water has a surface tension of 70 dynes. The binder may also dry to provide a pseudo water mark when applied in a pattern.
The backcoating may cover the entire back surface of the base sheet of the thermal paper or it may only cover a portion of the base sheet. Where the backcoating provides a pseudo water mark or a waterproof image, the backcoating does not cover the entire base sheet.
An image is printed on the backcoating by a conventional printing technique such as flexography, lithography, gravure, letter press, relief printing or ink jet printing which does not require the application of heat or high temperatures (less than 65xc2x0 C.), including U.V., electron beam and infrared cures. The technique employed is preferably identical to the printing method employed to apply the backcoating to the base sheet. Most conventional inks are suitable for providing the image provided they do not contain components which react with the thermosensitive layer. Suitable pigments include carbon blacks, cadmium, primrose, cobalt oxide, nickel oxide, etc. The carrier and binder employed in the ink is preferably identical to that used to apply the backcoating to the ensure compatibility. With such inks, high quality images with high gloss, referred to in the art as xe2x80x9cmagazine qualityxe2x80x9d images can be produced.
Without further elaboration is believed that one skilled in the art can using the proceeding description utilize the present invention to its fullest extent. The entire disclosure of all applications, patents, publications, cited above and below are herein incorporated by reference.


A tree harvesting cable saw includes an elongated flexible cable that has a plurality of tubular cutting links located at spaced intervals thereon with reversible drive means for driving the cable saw in either direction of its length. Each cutting link has an axial opening for receiving the cable and a continuous cutting edge on each end extending circumferentially around the entire cable and being spaced therefrom so that the cable can be driven in either direction and sever a tree. The cable saw is supported on a frame through a drive pulley and a driven pulley and is driven by a reversible motor. Preferably, the frame is movable between positions so that the cable saw can be forced through a standing tree to sever the tree adjacent its base.

Numerous types of mechanical logging equipment have been proposed and usually these include some type of cutting mechanism for severing the tree at its base. The most common type of cutter that has been used, particularly in large tree harvesting apparatus is the shear cutter wherein a pair of shear blades are pivoted on a frame and are moved between open and closed positions through drive means, usually in the form of a fluid ram. One of the problems with a shear cutter is that physical force is required to force the sharp edge of the shear through the base of the tree and results in splitting the tree trunk during the severing operation. An example of this type of shear mechanism is disclosed in U.S. Pat. No. 3,575,222.
Another type of cutter that has been proposed is what is commonly referred to as a rotary cutter which is rotated about its own axis and is moved across the base of the tree through some drive mechanism for severing the tree. An example of this type of mechanism is disclosed in U.S. Pat. No. 3,902,538. The problem with the rotary cutter is that initially such cutting units are fairly expensive and also require daily sharpening which decreases the production time and increases the cost per severed tree.
A third type of cutting mechanism is what is commonly referred to as a chain saw which may be mounted on a frame that is movable with respect to a tree. One of the problems encountered with this type of cutting device is that the cutting elements tend to dull rather quickly and are subjected to damage. Another disadvantage is that the cutting apparatus must be rotated in the same direction.
Another type of cutting apparatus that has been known for many years is what is commonly referred to as a cable saw wherein a flexible cable supports a plurality of cutting elements. Examples of this type of saw are disclosed in U.S. Pat. Nos. 641,129; 1,457,761; 1,903,518; 2,043,603; 2,752,964; and 3,958,332.

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A licensing method includes the steps of establishing a licensing vendor; providing an imaging device that uses an imaging media in forming printed images on print media, the imaging media including an initial supply amount of an imaging substance; associating a usage license with at least one of the imaging device and the imaging media, the usage license defining a first usage threshold at which a consumer is prompted to acquire a new license; and providing a license monitoring mechanism communicatively coupled with the imaging device, the license monitoring mechanism performing the steps of tracking an amount of usage of the imaging media by the imaging device; determining whether the amount of usage of the imaging media by the imaging device has reached a usage threshold; and upon reaching the usage threshold, then prompting the consumer to acquire the new license from the licensing vendor.

1. Field of the Invention
The present invention relates to renewing an available imaging substance supply for use by an imaging device, and, more particularly, to a licensing method for use with an imaging device and/or imaging media.
2. Description of the Related Art
An imaging device typically has associated therewith an imaging media, such as for example, an ink supply tank, an ink jet cartridge, a toner tank, or electrophotographic process (EP) cartridge, that stores a supply of an imaging substance, such as for example ink or toner, that is consumed during an imaging process. Examples of such an imaging device include an ink jet printer and/or copier, or an electrophotographic printer and/or copier. During imaging with the imaging device, the amount of the imaging substance is depleted. Thus, eventually, once the imaging substance supply of the imaging media is exhausted, the imaging media is either discarded or is re-filled. In either event, the consumer must provide a new supply of imaging substance in order to continue imaging. Typically, the new supply of imaging substance is acquired by the purchase of additional imaging substance, or the purchase of an entirely new imaging media. In either case, the purchasing process can inconvenience the consumer due to inherent delays in the purchasing process. For example, even when a vendor has the item, i.e., imaging substance or imaging media, in stock, the consumer either must go to the vendor to obtain the desired item, or await the delivery of the desired item. Also, proper disposal of spent imaging media can be an inconvenience to a consumer.
What is needed in the art is a licensing method for use with an imaging device and/or imaging media, wherein a consumer can "renew" an available supply of imaging substance, while reducing or avoiding the traditional inconveniences incurred by a consumer following exhaustion of the available imaging substance from the imaging media.

Licensing method for use with an imaging device


A managment station responds to an HTTP request for device discovery by spawning a device discovery task that creates a linked list and first broadcasts UDP based requests out on a subnetwork for devices on the same subnetwork to respond. Device information from responding network devices is stored in a linked list. This process is repeated until a specified length of time has expired. Then a second broadcast request is sent out that includes a list of printers that have responded so that they will nor keep responding. The list is updated by responses until there are no more responses. Any nodes in the linked list that still only have a network address are upadated by sending a unicast SNMP request those network addresses in order to get the additional information. The data from the linked list is sent back to the HTTP client.

The present invention relates to locating devices on a network, and more particularly to allowing a network device to locate other network devices on the same sub-network.
Some users of devices residing on a network find it desirable to locate all or a class of other devices on the network. For example, a user may wish to have a list of all the printers of a certain brand, along with information about those printers that are on the same sub-network. Typically, a network device would perform such a search using a network communications method (protocol) such as Simple Network Management Protocol (SNMP).
A network device typically searches for other devices on the network by sending (User Datagram Protocol) UDP messages to the sub-network and then waiting for particular responses from network devices that are listening on the same sub-network. The network device that sends out the request is typically called a management station and a device responding to such a request is typically referred to as a network agent.
UDP is a protocol that offers a limited amount of service when messages are exchanged between network devices in a network that uses the Internet Protocol (IP). A persistent problem is the loss of information packets due to congestion in the network or the receiving device, whether a management station or agent. Congestion essentially is the existence of interfering messages. One way this problem can occur, for example, is when responses from network agents arrive as a result of the UIDP broadcast message from the management station and they are initially received by the on-board Ethernet driver. This driver executes at a high priority intercepting every packet that arrives. If the packet has the expected frame type then the packet is ready to be delivered to the IP layer of the network stack. The IP task, which is running at a lower priority than the Ethernet driver, needs to accept as many packets as possible from the Ethernet driver. The total buffer area for the IP task is finite and the buffer for the Ethernet driver is also finite. Available buffer space depends on how fast the application task that is executing UDP routines can read and consume the data. Since both the IP task and the UDP level task run at a lower priority than the Ethernet Driver and total buffer space of the Ethernet driver is limited, the management station will not be able to read all the UDP based response packets that arrive at the on-board Ethernet driver. This approach of using UDP alone prevents an exhaustive and reliable search of the network since some request or response packets can be lost.
Service Location Protocol (SLP), described in the Internet Request For Comments document 2165 (RFC 2165), is one protocol that may be used instead of, or to supplement UDP based SNMP broadcast and responses. SLP provides a means to send in the broadcast request a list of devices that have already responded such that those who have already responded will not do so again. However, using SLP would result in slower and more cumbersome location of devices on the network because of it""s complexity and lack of specialization.
A second problem also exists when attempting to locate or find devices with no IP address. Prior approaches using IP multicasting require registration with the router and therefore do not provide a complete solution.
What is desired is a system for network device location that provides a faster and more exhaustive search which supplements the basic UDP broadcast and responses in order to reliably receive response packets from network agents or devices, and to uniquely identify those devices without relying on their IP address.
Accordingly, the present invention provides a faster, more exhaustive search and supplements the basic UDP broadcast and responses in order to receive and read more response packets from network agents. The present invention provides an approach to achieve device location discovery based on a MAC (media access channel) address even though the IP address is not known.
The invention employs a unicast (HTTP) request that is sent on a network to a device, such as a printer, with a known location and that device discovers other devices with unknown network locations. The device with the known location returns a web page to the user showing its status, with links to the other discovered devices. The user can then select the link to one of the newly discovered devices and view the web page of the selected device.
A device implementing this invention responds to an HTTP request for device discovery by spawning a device discovery task that broadcasts a SNMP over UDP based request out on a sub-network for devices to respond. When responses are received they are parsed and the device information such as network address, name, status, version and model is added to a list of discovered devices. Any responses from devices outside a specified class of devices, such as those not of a certain brand, are disregarded. The task waits for the responses until a specified amount of time has expired.
Then a device location protocol (DLP) over UDP broadcast request is sent out that includes a list of devices, such as printers, that have responded. The request is that only devices not on the list respond. Responses are then parsed and the responding device""s network address is added to the list of responding devices. This process is repeated until there are no more responses.
The management station may use unicast SNMP requests to the devices in the list to learn additional information about those devices which have an assigned IP address. The data from the linked list is then copied into a (Hypertext Markup Language) HTML buffer to be sent to the HTTP client that sent the original request.
These aspects, advantages, and other novel features of the present invention are apparent from the following detailed description when read in conjunction with the appended claims and attached drawings.


An acrylic fingernail removal strip having a foil strip with adhesive on each end. An absorbent pad element is affixed to the center portion, allowing the user to apply acetone onto the absorbent pad and wrap the removal strip about the finger nail to be removed, thereby causing the nail to be soaked in solvent and not the entire hand.

1. Field of the Invention
The present invention relates generally to artificial fingernail extensions and, more particularly, to an apparatus in kit form that aids in the removal of artificial acrylic nails.
2. Description of the Related Art
One of the luxuries enjoyed by many women that relates to beauty or salon type indulgences is the manicure. During these procedures the finger nails are cut, shaped, cleaned, painted and polished to provide for a beautiful appearance of the fingernails and surrounding area. For those women whose fingernails are not long enough or of the proper shape or texture, artificial nails made of an acrylic material remain the first option of choice after natural nails. While these artificial nails are every bit as beautiful when properly prepared and applied, they do have several drawbacks. One of these drawbacks is the removal process, in which the fingers are soaked in acetone for up to a half an hour to dissolve the adhesive used to hold the acrylic nail to the natural nail. This extended soaking time often leads to cuticle damage, nail damage, and skin irritation.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention. The following patents disclose a device for removing artificial fingernails:
U.S. Pat. No. 5,823,203 issued in the name of Carroll et al.;
U.S. Pat. No. 5,609,166 issued in the name of Walker; and
U.S. Pat. No. 5,388,597 issued in the name of Smith et al.
U.S. Pat. No. 5,613,506 issued in the name of Kurokawa discloses a device for removing a manicure coating.
U.S. Pat. No. 4,644,966 issued in the name of Ferrari discloses a fingernail treatment arrangement.
U.S. Pat. No. 4,510,954 issued in the name of Miller discloses a method and apparatus for automatically removing fingernail polish.
U.S. Pat. No. 4,466,452 issued in the name of Ferrari discloses a fingernail treatment arrangement.
U.S. Pat. No. 4,321,936 issued in the name of Chaconas, which discloses a nail polish remover, as well as in other related references, disclose element of the basic concept as the present invention. However, other elements in combination are different enough as to make the present combination unique and unanticipated in the art.
Consequently, there is a need for a means by which artificial nails can be removed in a quick and easy manner without the drawbacks normally associated with common removal procedures.
Therefore, it is an object of the invention to indicate a device of the type disclosed above which avoids the disadvantages inherent in the state of the art. In particular, the device is to allow removal of nails without soaking, and to allow the user to perform other tasks while eliminating long term damage associated with soaking of fingers in containers of acetone.
Briefly described according to the preferred embodiment of the present invention, an apparatus in kit form is provided that aids in the removal of artificial acrylic nails. A few drops of acetone are placed on the nail along with a few drops on a cotton pad. The pad is then placed on the nail where it is secured and encased with a strip of metal foil. The foil is wrapped around the nail and secured to itself, as well as the finger, with an adhesive strip. The foil also allows for heat retention which aids the acetone in the removal process. This process is repeated for the remaining fingers. In approximately 15 to 20 minutes the foil, the cotton ball as well as the artificial acrylic nail can be removed easily. During the 15 to 20 minute waiting time, the user can perform other tasks without being tethered to a container of acetone, as would be required by the conventional method of nail removal.
The use of the present invention allows for the quick, easy and efficient removal of artificial acrylic nails without the drawbacks normally associated with such products.


Disclosed is a process for producing reactive cellulose for use in the manufacture of cellulose acetate having superior clarity by mercerizing hardwood cellulosic material and reacting it with an hydroxyalkylating agent to a degree of molar substitution ranging from 0.04 to 0.15 per anhydroglucose unit in cellulose.

This invention relates to a process for the modification of cellulose and particularly to a process for the preparation of reactive cellulosic hardwood pulp to make cellulose acetate with superior properties.
Considerable effort has been expended to improve the reactivity of cellulose so as to decrease the manufacturing costs of cellulose derivatives. One known approach to achieving such a goal is the treatment of cellulosic pulp in the presence of an alkali with an alkylene oxide to produce a trace substituted hydroxyethylated pulp. Such a process was disclosed, for example, by J. L. Riley in Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives, edited by A. F. Turbak, ACS Symposium Series 58, ACS, Washington, D.C. page 149 (1977). While some improvement in reactivity has been achieved by this reaction, the improvement was not sufficient to economically justify its use. The process, for example, does not improve the reactivity of cellulose in xe2x80x9clow catalystxe2x80x9d acetylation processes, widely used for the preparation of cellulose acetate.
The treatment of cellulose with alkali under xe2x80x9cmercerizing conditionsxe2x80x9d is a well known procedure which converts cellulose from its native form, cellulose I, to a more thermodynamically stable, less crystalline form, cellulose II. The critical concentration of the caustic solution (weight % of the solution of sodium hydroxide or, less often, potassium hydroxide) necessary for mercerization is dependent upon both temperature and type of cellulose. However, in general, the caustic solution strength for mercerizing conditions at ambient temperatures will be more than 5%, and usually about 6-16%. For a given caustic concentration, mercerization occurs more readily at low temperatures than high. At a given temperature, such as 0xc2x0 C., a greater caustic concentration is required to mercerize a prehydrolyzed kraft pulp than a sulfite pulp, for example. The conditions (temperature, caustic concentration) required to mercerize various cellulosic materials are well known.
Because it is less crystalline and more amorphous, mercerized cellulose would presumably be more readily accessible to reagents. Unfortunately, mercerized pulps are relatively inert to acetylation as a consequence of structural collapse in the interfibrillar spaces upon drying. Thus, the prior art initially taught that just enough alkali should be used to refine cellulose during alkaline bleaching stages, but that the caustic amount and temperatures used should be insufficient to produce mercerizing conditions in the production of acetate grade pulps.
Early attempts to improve cellulose reactivity by hydroxyalkylation scrupulously avoided mercerizing conditions. Such conditions are well known and well defined in the cellulose industry. See, for example, Pulping Processes, S. A. Rydholm, Interscience Publishers, 1965, pages 143-145. In the alkylene oxide treatment of cellulose disclosed in the above identified publication by J. L. Riley, only a 2% solution of sodium hydroxide, based on pulp, was used to promote the reaction at ambient temperatures. This is well below the concentration of sodium hydroxide necessary for mercerizing pulp.
A prior attempt to produce a modified cellulose pulp which would be reactive in low catalyst acetylation reactions is described in U.S. Pat. No. 4,399,275. It focused on the use of softwood cellulose pulps. According to the process of U.S. Pat. No. 4,399,275, softwood cellulose is mercerized in conventional fashion to convert cellulose I to cellulose II and then alkylene oxides are reacted with the mercerized softwood pulp fibers. The patentee discovered that the alkylene oxides appeared to xe2x80x9cwedge openxe2x80x9d the mercerized softwood fibers, so that they did not collapse upon drying and, as a result, maintained a high level of reactivity in subsequent low catalyst acetylation processes.
Propylene oxide was found to be the preferred alkylene oxide for making mercerized softwood fibers which are reactive in low catalyst acetylation processes with desirable properties being achieved with hydroxypropoxy group (xe2x80x94OC3H6OH) content range of 3.6 to 5.7%, corresponding to a degree of molar substitution (d.s.) of 0.08 to 0.13 per anhydroglucose unit in cellulose.
Although the softwood cellulosic materials produced according to U.S. Pat. No. 4,399,275 were extremely reactive in acetylation reactions, it was found that to achieve commercially acceptable haze levels for most products, mercerized softwood pulp had to be reacted with undesirably large amounts of alkylene oxide. For example, at least 15% by weight of propylene oxide based on oven-dried (o.d.) pulp weight was required to achieve acceptable cellulose acetate properties. In order to achieve substantially improved triacetate haze values, it was determined that treatment with about 20% by weight propylene oxide based on o.d. pulp weight was necessary. Further, the modified cellulose pulps produced according to this patent were so highly reactive in known low catalyst acetylation processes as to require special cooling equipment to slow down the acetylation reaction to avoid damaging conditions.
Because of the special processing equipment required to moderate the acetylation reaction for alkylene oxide modified softwood pulps, and because of the relatively large amounts of alkylene oxide required to produce softwood pulps which would enable the manufacture of cellulose acetate products having desirable low haze levels, commercial interest never developed in the process of U.S. Pat. No. 4,399,275.
Accordingly, there exists a need for a modified cellulose pulp which is reactive to acetylation using standard low catalyst acetylation processes, but which is not so reactive in such processes as to require special equipment to moderate the acetylation reaction. Further, it would be desirable if such a modified cellulose pulp could be made without consuming large amounts of expensive reagents as to make the manufacture of such pulp cost prohibitive. Finally, the acetylation of a modified cellulose pulp should yield cellulose acetate products having low haze levels, so that they will be suitable for use in commercial applications having stringent haze requirements, such as in viewing screens for flat panel monitors.
It is accordingly a primary object of the present invention to provide a process for the preparation of modified cellulose having only moderate acetylation reactivity, specifically reactivity that is similar to that expected from a standard acetate wood pulp.
It is an additional object of this invention to provide a process for producing cellulosic pulps which will significantly improve the properties of cellulose acetate derived from them.
It is a more specific object of this invention to provide a cellulosic wood pulp which might improve levels of cellulose acetate production and reduce costs to manufacture superior cellulose acetate products when compared, for example, to use of alternate cellulosic materials such as high purity cotton linters.
The foregoing and other objects of the invention are achieved by the preparation of reactive cellulose by mercerizing hardwood cellulosic material, and reacting the mercerized hardwood cellulose with an hydroxyalkylating agent to a molar degree of substitution of the cellulose ranging from about 0.04 to about 0.15 per anhydroglucose unit in cellulose, the degree of substitution being insufficient to render the cellulose appreciably soluble in water, and recovering the substantially water insoluble product. The hardwood sources which are suitable for use in the invention are woods such as gum, maple, oak, eucalyptus, poplar, beech and aspen.
The hydroxyalkylating agents useful in the invention are generally the alkylene oxides, including ethylene, propylene and butylene oxides and halogen substituted alkylene oxides such as epichlorohydrin. Benefits of the invention are achieved with about 2.0% to about 5.5% by weight hydroxyalkoxy (xe2x80x94OCnH2nOH) group content on the cellulose. This corresponds to a degree of molar substitution per anhydroglucose unit in cellulose of from about 0.04 to about 0.15. Because introduction of hydroxypropoxy (xe2x80x94OC3H6OH) groups using propylene oxide is more efficient in promoting the benefits of the invention, and also represents a safer, less costly process, it is a preferred alkylene oxide for use in the invention. For propylene oxide, benefits can be expected in about the 2.5 to 4.0% hydroxypropoxy (xe2x80x94OC3H6OH) group content range which corresponds to a degree of molar substitution of about 0.055 to 0.09 per anhydroglucose unit in cellulose.
It is principally in the substitution ranges set forth above for hardwoods that fiber inactivation resulting from the mercerization process is overcome. This has been observed as a marked reduction in the haze levels of cellulose acetate dopes produced with the reactive cellulose pulps of the invention and also in a marked reduction of color in the acetate dopes.
In the practice of the invention, the hardwood cellulosic pulp may be pretreated with NaOH which acts both to mercerize the pulp and as a catalyst for the reaction of cellulose with alkylene oxides. Normally, hydroxyalkylation will be conducted at the same caustic solution concentration as the mercerizing reaction, although it need not. Solution concentrations from 1 to 40% may be used for hydroxyalkylation. Certain bleaching and refining operations for cellulosic pulps involve a cold caustic extraction stage utilizing from 6 to 16% caustic solution at ambient temperatures (about 5xc2x0 to about 40xc2x0 C.) to extract hemicelluloses. During the cold caustic extraction stage, mercerization occurs. It has been found that reactive cellulosic pulps of acetylation quality may be produced by combining into one integral operation the cold caustic extraction stage using mercerizing conditions with alkylene oxide modification of the pulp.
In theory from 6 to 40% caustic solution may be used to mercerize the pulp. In practice, however, a preferred method of carrying out the present invention is to first conduct a cold caustic extraction using from 8 to 20%, and preferably 10 to 16%, caustic solution at a temperature of from 15xc2x0 to 35xc2x0 C., preferably 23xc2x0 to 25xc2x0 C., at a low consistency (weight of pulp per total weight of pulp slurry) of from 1 to 10%, preferably about 3%. The pulp slurry should then be dewatered to a high consistency of from about 10 to over 50%, preferably over 25%, using a centrifuge and/or press and then reacted with an alkylene oxide in the gas phase (25xc2x0 C. for ethylene oxide, 50xc2x0 C. for propylene oxide) before rinsing and further processing In industrial practice, the consistency should be increased as high as possible (to about 50% or more) to minimize side reactions of alkylene oxides with water. During reaction with alkylene oxide, the caustic concentration should preferably remain at the mercerizing level, i.e., at 6 to 40%, preferably 8 to 20% caustic. A cold caustic refining process, of the type which typically may be used in the practice of the present invention, is more fully disclosed in U.S. Pat. No. 3,148,106. Reference to the foregoing patent should be made for a more complete description of such a refining process.
A wide variety of hardwood cellulosic material, principally pulps, are useful in the practice of the present invention, including both prehydrolyzed kraft and sulfite pulps. While the process is preferably combined with a refining operation, the process is nevertheless useful for both bleached and unbleached pulps. The invention is particularly useful for the preparation of acetate grade pulps. However, the reactive pulps of the invention may be used for the manufacture of other cellulose derivatives and plastics, including other cellulose esters and cellulose ethers such as ethyl cellulose.
Conventional acetylation processes used for the preparation of cellulose acetate involve both high and low acid catalyst reactions. The present process leads to acetate quality pulps which are reactive in both high and low catalyst processes. The reactive cellulosic pulps of the invention show substantially improved acetate filterability levels compared to standard acetylation grade pulps. Thus, cellulosic pulps prepared in accordance with the invention can lead to significantly improved levels of acetate production.
When a hardwood prehydrolyzed kraft pulp was mercerized by cold caustic extraction using 10% NaOH, followed by reaction with 10% propylene oxide (PO) based on o.d pulp, and the fibers were subjected to low catalyst acetylation after washing and drying, the reaction rates of the modified pulp were found to be substantially the same as normal hardwood prehydrolyzed kraft acetate pulp. Further, the triacetate and diacetate haze values of treated pulp were found to be far superior to those of a standard hardwood acetate grade wood pulp (e.g., Sulfatate H-J, a prehydrolyzed kraft pulp available from Rayonier Performance Fibers Division of Jesup, Ga.). Color values were also superior.
These results were highly surprising since much faster reactivity was expected based on U.S. Pat. No. 4,399,275, and the haze and color values achieved with the hardwood pulp were much better than were achieved with softwood pulp in that patent.
The same procedure was evaluated utilizing 16% NaOH, and reaction with 10% PO, and the resulting product gave even better haze values, and similar reactivities. The triacetate haze values achieved with 16% NaOH mercerization were as low as the clarity values generally obtained when cotton linters are used to make cellulose acetate.
Control pulps mercerized with both 10 and 16% NaOH cold caustic extractions, but not PO modified, gave triacetate haze results that were poor.
Reaction with levels of PO in the 10-15% range gave haze results that were far better than Sulfatate-H-J, a standard hardwood acetate pulp which is generally regarded as one of the best acetate pulps in the industry.
It was surprisingly found that at equivalent PO treatment levels of mercerized pulps, softwoods give much higher acetate reactivity, but much higher haze levels; whereas, similar treatment of hardwood pulps gives acetylation times that are much more normal, but with superb haze results. The latter have considerable market value, and were achieved at levels of PO treatment which were more economic than the higher PO treatment levels which are necessary to achieve modified softwood pulps with acceptable haze values. Excellent benefits are clearly obtained in the 2.9-3.7% hydroxypropoxy content range (d.s. of 0.064-0.082) with no significant improvements observed for moving to higher levels of substitution. This favorably contrasts with d.s. levels of 0.08-0.13 required to achieve benefits utilizing softwoods.
The very low triacetate haze (or clarity) values achieved utilizing hardwood pulp in accordance with the invention are equivalent to those from cotton linters pulp. Due to the excellent triacetate clarity values of cotton linters, compared to those attainable from commercial wood cellulose acetate pulps, cotton linters have been the preferred source material for premium acetate end-use markets, such as liquid crystal displays (LCDs). The PO modified, mercerized hardwood pulps according to the invention can compete in this market and also in manufacture of high quality triacetate film for professional photography.
Another benefit of using the modified hardwood pulps of the invention is that they react faster than cotton linters in low catalyst acetylation reactions.
The below examples are illustrative of the process of the present invention.

Alkylene oxide modified hardwood cellulose