US3512536A - Smoking material of oxidized cellulosic material and method of making same - Google Patents

Description

Uted States Patent SMOKING MATERIAL 0F OXIDIZED CELLULOSIC MATERIAL AND METHOD OF MAKING SAME Theodore S. Briskin and Geoffrey R. Ward, Beverly Hills, Calif., assignors to Sutton Research Corporation, Los Angeles, Calif., a corporation of Delaware No Drawing. Continuation-impart of applications Ser. No.

595,622, Nov. 21, 1966, and Ser. No. 674,994, Oct. 12,

1967. This application July 17, 1968, Ser. No. 745,418

Int. Cl. A24b 15/00; C08b 15/02 US. Cl. 131-2 14 Claims ABSTRACT OF THE DISCLOSURE The preparation of a smoking product from cellulosic material by oxidation of cellulosic material with nitrogen dioxide and pre-treatment or post-treatment with a liquid solvent medium to extract residual lignins, waxes, oils, grease, gums and natural resins from the cellulosic material, and which may include the step of setting the oxidized cellulose to minimize dissolution in aqueous medium by treatment with alcoholic solution or acidulated aqueous medium. The effective solvents includeketones, esters, ethers, acetone, benzene, toluene, xylene and dimethyl sulfoxide.

This is a contiuuation-in-part of our copending applications Ser. No. 595,622, filed Nov. 21, 1966, now Pat.

' No. 3,447,539 and entitled Smoking Products, and Ser.

No. 674,994, filed Oct. 12, 1967, and entitled Smoking Products and Process for Making Such Products.

As used herein, the term smoking products is meant to refer to and to include filler material embodied in cigarettes, cigars and for use with pipes and the like, and mixtures thereof with various proportions of tobacco and including cigarette papers and wrappers used in the preparation of such cigars and cigarettes, and it includes cigarettes, cigars and the like products manufactured with such filler materials and wrappers.

In the aforementioned copending applications, description is made of the preparation of a smoking product suitable for use in cigarettes, cigars or with pipes wherein the smoking product is prepared of relatively pure cellulosic materials subjected to selective oxidation with liquid nitrogen dioxide to convert preferably more than 90% of the methylol groups in the cellulosic molecule to yield a product which can be referred to as an oxycellulose of polyuronic acid. The oxidation reaction product is further processed by removal of liquid nitrogen dioxide by vaporization and preferably by washing the oxidized cellulosic product with water and/or alcohol and/or acetone or other solvent for removal of solubilized foreign material, including oils, Waxes, latices and the like, which contribute undesirably to the taste and aroma when used as a smoking product in accordance with the practice of this invention.

As further described in the aforementioned copending applications, the oxidized and cleansed cellulosic derivative is further processed by a reduction reaction with borohydrides of an alkali or alkaline earth metal such as sodium or lithium borohydride for reduction of such nitrogen compounds, quinones, ketones, aldehydes and unsaturates as otherwise have a tendency to impart undesirable aroma and taste as the smoking product is burned. The product before or after reduction can be subjected to additional oxidation with a dilute peroxide solution as a means for eliminating further groupings which impart undesirable aroma or taste to the product.

The resulting smoking product is then formulated with mineralizing agents such as oxalates, glycolates, diglycolates, lactates, pivalates or tannates of such metals as calcium, magnesium, lithium, potassium, barium or strontium, preferably introduced to form the salt internally in the cellulosic derivative for purposes of providing desired ashing characteristics. Instead of forming the described salts internally in the cellulosic derivatives, limited beneficial characteristics can be achieved by external application of such mineralizing agents. As described, the desired internal introduction is achieved by first wetting the cellulosic derivative with metal cation in dilute solution for absorption into the cellulosic derivative followed by exposure to the acid anion in solution to precipitate the metal salt in situ in the cellulosic material.

The treated cellulosic derivatives can be further processed to improve the burning, glow and smoking characteristics by formulation to include a potassium salt, such as potassium oxalate or by the addition of rubidium or cesium in the form of compounds thereof in amounts within the range of 0.1% to 10% by weight but preferably less than 1% by weight, as described in the co pending application Ser. No. 623,528, filed Mar. 16, 1967, and entitled Smoking Products and Process for their Manufacture. Smoke generators for improving the appearance of the smoke generated by the product can be introduced as by the introduction of various fatty acids, esters, ethers and the like and the aroma and pH characteristics can be achieved by the addition of vol-atilizable alkalyzing material such as ammonium oxalate and the like.

The resulting product is suitable for use as a smoking product alone or in admixture with tobacco to produce a smoking product having good taste, good aroma and good appearance. a

As the cellulosic raw material, use can be made of various forms of cellulose, such as wood pulp, alphacellulose, flax, fibrous carbohydrates, seaweed carbohydrates, bamboo filaments, cotton filaments, hemp, straw, refined paper, rice paper, filamentous gums and even plants and plant leaves and the like fibrous or sheet materials from which non-carbohydrate components have been separated, all of which is hereinafter referred to as cellulosic material.

It is preferred to make use of a purified cellulosic material from which various of the sugars, proteins, chlorophylls, flavones, colors, lignins, oils, waxes, resins and latices have been removed since these lend considerably to the undesirable odor and taste from the smoking product.

Purified cellulose is unsatisfactory for use as a smoking product from the standpoint of taste, aroma and burning characteristics. This is believed to stem from the acids and aldehydes that are evolved upon pyrolysis of the cellulose. It has been found that many of the defects of pure cellulose can be greatly alleviated by conversion of the methylol groups to carboxyl groups to produce a product which readily pyrolyzes with complete burning of the cellulosic molecule into water vapor, and oxidation products of carbon such as carbon dioxide and low molecular weight compounds which readily volatilize. Thus the object is to achieve selective oxidation of the cellulosic material to convert methylol groups, primarily the methylol groups containing the C carbon, to carboxyl groups, preferably with better than conversion. There is no objection to further oxidation beyond by conversion of secondary hydroxyl groups as on C and C to monoand diketo groups so long as clevage does not occur.

It has been found that liquid nitrogen dioxide yields an oxidation reaction that has the desired selectivity and that complete Wetting of the cellulosic materials can be achieved almost instanteously with liquid nitrogen dioxide with the result that the oxidation reaction takes place substantially uniformly throughout the cross-section of the cellulosic material and at a much more rapid rate whereby a more uniformly and more completely oxidized product is obtained in less time. Furthermore, liquid nitrogen dioxide, when used in the proportions most suitable for the practice of this invention, quenches and immediately dissipates heat generated by the exothermic reaction so as to avoid the formation of hot spots or non-uniformity in the reactions.

It has been found that the course of the oxidation reaction and the treatment of the oxidized cellulosic material can be influenced by a number of very important factors which cannot be translated into reactions with gaseous nitrogen dioxide but which can be employed in the oxidation of the cellulosic material with liquid nitrogen dioxide thereby greatly to enhance the oxidation process including increase in reaction rate, increase in the amount of conversion, uniformity of oxidation, as well as purification and subsequent treatment of the oxidized reaction product, as will hereinafter appear.

In our copending application Ser. No. 745,221 filed concurrently herewith and entitled A Smoking Product and Method of Preparation, description is made of the oxidation of a cellulosic material by suspension in liquid nitrogen dioxide in the ratio of 1 part by weight cellulosic material to to 1000 parts by weight liquid nitrogen dioxide and preferably 1 part by weight cellulosic material to 25 to 50 parts by weight of liquid nitrogen dioxide. The reaction therein is carried out at a temperature within the range of 15 to 65 C. and at an autogenous pressure when the reaction temperature exceeds 21 C. (boiling point of nitrogen dioxide, N 0

In our copending application Ser. No. 745,135 filed concurrently herewith and entitled Preparation of Smoking Product of Cellulose Derivatives and Process, description is made of the selective oxidation of cellulosic material wherein the oxidation reaction, including reaction rate and the amount of conversion, is materially improved by formulation of the oxidation reaction medium to contain up to 8% by weight of water in the liquid nitrogen dioxide system and by carrying out the reaction at elevated temperature above 15 C. and preferably within the range of 20 to 45 (3., depending somewhat upon the amount of moisture present in the reaction medium, whereby the reaction medium is rendered relatively non-electrically conductive so that the presence of water in the reaction medium will not result in attack or degradation of the cellulosic material to be oxidized and wherein the formulation to include aqueous medium in the reaction of liquid nitrogen dioxide operates also to adjust the specific gravity of the reaction medium in the direction towards the specific gravity of the cellulosic material whereby suspension of the cellulosic material in the reaction medium is easier to achieve and maintain. The result is a more rapid and uniform oxidation reaction of the cellulosic material to produce a better product at a more rapid rate.

It has been found that nitro groups and foreign materials such as lignins, waxes, oils, grease, natural resins and the like are to be found in the oxidized cellulosic materials, the amounts depending somewhat upon the source or composition of the cellulosic raw material. However, amounts as little as 0.1% by weight are noticeable by way of an undesirable odor and taste that is contributed to the product when smoked in a cigarette, cigar or pipe. As a result, it is desirable to effect further treatment of the cellulosic material before and/ or preferably after oxidation to remove lignins, waxes, oils, grease, resins, latex and the like undesirable impurities.

It has been found further that the highly oxidized cellulosic material is subject to solution in aqueous medium during subsequent washing and treating operations and that some deterioration can take place when the oxidized cellulosic material is not stabilized or set.

This application is addressed to the treatment of cellulosic material, preferably after selective oxidation with nitrogen dioxide to set the oxidized cellulosic material to militate against solution of the oxidized cellulose in aqueous medium during subsequent washing and/or processing steps, and more important, to effect removal of impurities remaining in the oxidized material which might contribute an undesirable odor or taste to the smoking product, When used in a cigarette, cigar, pipe or the like.

An important concept of this invention resides in the treatment of the cellulosic material before and/ or preferably after the selective oxidation reaction with a volatilizable organic solvent system and under conditions to effect dissolution of lignins, waxes, oils, grease, natural gums and resins and the like impurities from the cellulosic material. For this purpose, it is preferred to make use of a ketone, such as acetone, methyl ethyl ketone, methyl amyl ketone and the like, or good solvents for such lignins, waxes, oils, grease and natural resins such as dimethyl sulfoxide, benzene, toluene, xylene, ethers and esters.

Treatment to effect extraction is made by suspension of the cellulosic material in an amount of solvent liquids at least five times the weight of the cellulosic material and preferably ten to one hundred times the weight of the cellulosic material. While extraction can be carried out at ambient temperature, in the preferred practice of the invention, the extraction is carried out at elevated temperature up to slightly below the boiling point temperature for the solvent system but not above C.

When, in the preferred practice of the invention, the treatment with the described solvent system is carried out after selective oxidation with liquid nitrogen dioxide, it is desirable to include a small amount of chalk, calcium carbonate, or other alkali or alkaline earth metal carbonate and the like substances which will not introduce undesirable impurities into the treated cellulosic material. The calcium carbonate, chalk or the like material takes up nitric acid remaining in the oxidized cellulosic material and can be washed out with the acetone or solvent to effect removal from the smoking product. When the calculations are based upon chalk or calcium carbonate, it will be sufficient if such material is present in suspension in the solvent system in an amount up to 1% by weight and preferably in an amount within the range of 0.01% to 0.1% by weight. Time is not of the essence since treatment under the conditions described can be based upon countercurrent flow for extraction between the cellulosic material and the solvent system but extraction on a batch principle is more desirable for leaching the solubles from the cellulosic material. It is sufficient if the extraction is allowed to take place over one minute but longer times within the range of 5 to 30 minutes are preferred. More than 30 minutes can be used but removal of much more of the impurities is not secured such that longer times serve no useful purpose, and in the higher range of temperatures, damage may occur.

When the treatment is applied as a pre-treatment before selective oxidation of the cellulosic material with liquid nitrogen dioxide, the formulation need not include chalk, calcium carbonate and the like since nitro groups have not yet been introduced by the selective oxidation with nitrogen dioxide.

Treatment of the oxidized cellulosic material to set the derivative and to stabilize the oxidized cellulose against solubilization in aqueous medium during subsequent treatments can be effected by wetting the oxidized cellulose with an alcoholic solution or with acidnlated water having a pH below 5 and preferably within the range of 3 to 4. The described treatment, when employed, should precede the treatment with acetone or other solvent. but it should follow the selective oxidation of the cellulosic material.

As the alcohol, use can be made of methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, amyl alcohol and the like lower alkyl alcohols. The alcoholic component is preferably employed as an dized cellulosic material in aqueous medium.

Treatments with alcoholic aqueous systems can be made in the ratio of one part by weight oxidized cellulosic material to 1 to 50 parts by weight alcoholic solution and preferably 1 part by weight of the oxidized cellulosic material to 5 to 20 parts by weight of the alcoholic solution. Treatment to stabilize the oxidized cellulosic material can be etfected at room temperature or above room temperature but at a temperature less than the boiling point of the alcohol and preferably. at a temperature within the range of to 30 C.

When use is made of acidulated aqueous medium to stabilize the oxidized cellulosic material, it is preferred to elfect acidulation of the aqueous medium with gaseous carbon dioxide. Other acids can be employed but it is preferred either to use an organic acid corresponding to the acid components of the salts later to be produced or introduced into the oxidized cellulosic material such as oxalic acid, glycolic acid, pivalic acid, and the like, or use can be made of an inorganic acid which does not introduce undesirable groupings that require subsequent removal. Treatment by acidulated aqueous medium can be carried out in a countercurrent flow principle or by immersion of the oxidized cellulosic material in 1 to 10 times its weight of the acidulated aqueous medium.

Having described the basic concepts of this invention, examples will now be given by way of illustration, but not by way of limitation, of the practice of this invention.

EXAMPLE 1 Cellulosic raw material in the form of purified wood pulp is introduced into a vessel with ten times its weight of acetone and the materials are allowed to remain in contact one with the other for a period of 30 minutes while being maintained at a temperature of about 25 C. The-acetone solution is drained from the cellulose pulp for separation and the remaining product is heated to volatilize off any remaining acetone.

The treated produce from which lignins, waxes, oils, grease, natural resins and the like have been leached by the acetone is then subjected to oxidation with liquid nitrogen dioxide by introduction into a reaction vessel with twenty-five times its weight of liquid nitrogen dioxide. The materials are maintained in the reaction vessel at a temperature maintained at about 25 C. under autogeneous pressure for about six to eight days. Thereafter the liquid nitrogen dioxide is drained from the vessel for separation from the oxidized cellulosic material. The oxidized .cellulosic material is then rinsed with anhydrous liquid nitrogen dioxide, dried by evaporation, and then washed with water and dried to produce the oxidized cellulosic material suitable .for use in the preparation of a smoking product.

EXAMPLE 2 Thin paper formed of purified wood pulp is cut into fine strips of about 2 mm. in width and introduced into a reaction vessel with about one hundred times its weight of liquid nitrogen dioxide containing 1 /2% by weight water. Oxidation reaction is carried out for two days at a temperature of about 30 C. With constant recirculation of the oxidizing medium to maintain the materials in a constant state of agitation.

Upon completion of the oxidation reaction, the liquid oxidizing medium is drained from the reactor and the product is heated to volatilize nitrogen oxides and the product is washed with water, until free of mineral acids, and then dried.

The washed and dried oxidized cellulosic material is introduced into a vessel with twenty-five times its volume of acetone and the materials are maintained in contact one with the other with constant agitation for a period of 20 to 30 minutes whereby the acetone leaches nitrates, oils, Waxes, grease, natural resins which might remain as residuals in the oxidized cellulosic material.

Upon completion of the leaching reaction, the solvent liquids are drained for separation from the oxidized cel' lulosic material and then the materials are heated to elevated temperature for removal of the volatiles.

EXAMPLE 3 Cellulosic pulp in the form of paper is oxidized with liquid nitrogen dioxide, as in Example 2, and the oxidized cellulosic material, without water washing, is then introduced into a vessel with twenty times its weight of acetone containing 0.05% by weight chalk. The materials are allowed to remain in the reaction vessel for 30 minutes at 25 C. whereby the chalk absorbs nitrates and the acetone leaches impurities such as oils, grease, waxes, lignins, natural resins and gums from the oxidized cellulosic material. The liquid component is separated from the oxidized cellulosic material by drainage and the oxidized cellulosic material is washed with water and dried.

EXAMPLE 4 Cellulosic pulp in the form of thin strips of paper is oxidized with liquid nitrogen dioxide as in Examples 1 and 2.

The oxidized cellulosic material, after separation of the liquid nitrogen dioxide, is introduced into a vessel with ten times its weight of a 50% ethyl alcohol solution in water. The materials are allowed to remain in contact one with the other for a short period of time or about 10 to 15 minutes and the alcoholic solution is drained. The resulting stabilized oxidized cellulosic material is introduced into a vessel with thirty times its weight of benzene and the materials, maintained in a constant state of agitation, are heated to a temperature of about 30 C. for 30 to 60 minutes and then the benzene solution is treated for separation from the oxidized cellulosic material and the latter is then dried.

EXAMPLE 5 Purified cellulose wood pulp in the form of a thin paper cut into strips is subjected to pre-treatment with acetone as-in Example 1. The cellulosic material, after removal of the acetone, is subjected to selective oxidation with liquid nitrogen dioxide as in Examples 1 and 2 and the oxidized cellulose material is subjected to a post-treatment with acetone as in Example 2.

EXAMPLE 6 The process of Example 4 is repeated except that instead of setting the oxidized cellulosic material for stabilization with aqueous alcoholic solution, stabilization of theoxidized cellulosic material is efiected by introducing the oxidized cellulosic material into a vessel with thirty times its volume of water and then bubbling gaseous carbon dioxide through the system to maintain a state of agitation and to acidulate the water whereby the oxidized cellulosic material becomes stabilized and set.

The cellulosic materials treated with solvent to eiiect removal of waxes, oils, grease, lignins, natural resins and the like find utility as smoking products having improved aroma and taste by comparison with cellulosic materials in the absence of such treatment. The cellulosic products resulting from the selective oxidation of cellulosic materials with liquid nitrogen dioxide followed by leaching with acetone or other solvent system, with or without the addition of chalk, also find use as a smoking product having odor and taste characteristics much improved over the cellulosic material prior to oxidation or after oxidation without the leaching treatment. However, it is preferred further to process the treated oxidized cellulosic materials of this invention by modification to include a mild reduction reaction with borohydrides, as described in our copending application filed concurrently herewith and entitled Method for Preparation of Smoking Product with Selective Reduction following Selective Oxidation, or to effect the addition of agents to improve the characteristics of the smoking product as by the addition of mineralizing agents, such as calcium oxalate and the like to improve the ashing characteristics, addition of agents for controlling burning and glow, such as potassium, cesium or rubidium salts; agents to improve color and neutralizing agents-such as ammonium, ammonium hydroxide or amine salts, and the like modifiers.

It will be apparent from the foregoing that we have provided a simple and efiicient means for treatment of cellulosic materials to improve their utilization as a smoking product for use in cigarettes, cigars or pipes.

It will be understood that changes may be made in the details of formulation and operation without departing from the spirit of the invention.

We claim:

1. In the method of preparing a smoking product of cellulosic material, the steps of selectively oxidizing the cellulosic material by reaction with nitrogen dioxide, treating the cellulosic material as a pre-treatment before or as a post-treatment after oxidation or both by soaking the cellulosic material in a liquid solvent medium selected from the group consisting of ketone, ester, ether, acetone, benzene, toluene, xylene and dimethyl sulfoxide and in which organic impurities in the cellulosic material selected from the group consisting of lignins, waxes, oils, grease, gums, natural resins and latex are soluble, separating the liquid solvent medium from the treated cellulosic material, and then drying the treated cellulosic material.

2. The method as claimed in claim 1 in which the treatment with the liquid solvent medium is carried out at a temperature within the range of ambient temperature to 3. The method as claimed in claim 1 in which the liquid solvent medium and the cellulosic material are present in the ratio of 1 part by weight of the cellulosic material to at least 5 parts by weight of the liquid solvent medium.

4. The method as claimed in claim 1 in which the liquid solvent medium is present in an amount ten to one hundred times the weight of the cellulosic material.

5. The method as claimed in claim 1 in which the treatment with the liquid solvent medium is continued for a time up to 30 minutes.

6. In the method of preparing a smoking product of cellulosic material, the steps of selectively oxidizing the cellulosic material by reaction with nitrogen dioxide, treating the cellulosic material as a pretreatment before or as a post-treatment after oxidation or both by soaking the cellulosic material in a liquid solvent medium in which organic impurities in the cellulosic material selected from the group consisting of lignins, waxes, oils, grease, gums,

, of the liquid solvent medium.

8. The method as claimed in claim 7 in which the com pound is present in an amount within the range of 0.01% to 0.1% by weight of the liquid solvent medium.

9. In the method of preparing a smoking product of cellulosic material, the steps of selectively oxidizing the cellulosic material by reaction with nitrogen dioxide, treating the cellulosic material as a pretreatment before or as a post-treatment after oxidation or both by soaking the cellulosic material in a liquid solvent medium in which organic impurities in the cellulosic material selected from the group consisting of lignins, waxes, oils, grease, gums, natural resins and latex are soluble, separating the liquid solvent medium from the treated cellulosic material, and then drying the treated cellulosic material, and which includes the step, after oxidation of the cellulosic material but before post-treatment with the liquid solvent medium, of setting and stabilizing the oxidized cellulosic material by soaking the oxidized cellulosic material in an acidulated aqueous medium having a pH of less than 5.

10. The method as claimed in claim 9 in which the pH of the acidulated aqueous medium is within the range of 3 to 4.

11. The method as claimed in claim 9 in which the acidulated aqueous medium comprises water through which carbon dioxide is bubbled.

12. A smoking product formed of a cellulosic material oxidized with nitrogen dioxide and treated by the method of claim 1.

113. A smoking product formed of a cellulosic material oxidized with nitrogen dioxide and treated by the method of claim 9. a

14. A smoking product formed of a cellulosic material oxidized with nitrogen dioxide and treated by the method of claim 6.

References Cited UNITED STATES PATENTS 3,364,200 1/1968 Ashton et al 260-212 3,236,669 2/1966 Williams 260-212 FOREIGN PATENTS 702,918 2/1965 Canada.

MELVIN D. REIN, Primary Examiner US. Cl. X.R. 131-140; 260-212