US3482578A - Preparation of smoking product from cellulosic material and processes in treatment thereof - Google Patents

Description

United States Patent Int. Cl. A24b /00 US. Cl. 1312 9 Claims ABSTRACT OF THE DISCLOSURE The preparation of a smoking product in the form of a cellulose derivative which has been selectively oxidized with liquid nitrogen dioxide, with or without water, and with or without gaseous oxygen in which the oxidation reaction product is treated with anhydrous liquid nitrogen dioxide for the removal of solubles.

This is a continuation-in-part of our copending applications Ser. No. 595,622, filed Nov. 21, 1966, 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 wrapers 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 or 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 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, strontium, preferably introduced to form the salt internally in the cellulosic derivative for purposes of providing desired 3,482,578 Patented Dec. 9, 1969 ashing characteristics. Instead of forming the described salts internally in the cellulosic derivative, 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 l% by weight, as described in the copending 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 volatilizable 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.

This application will be addressed to the process for treatment of the cellulosic material with liquid nitrogen dioxide for selective oxidation of methylol groups in forming an oxidized cellulosic derivative which is more suitable for use as a smoking product than the purified cellulose and which finds excellent use in the preparation of a smoking product.

The features of this invention reside in the conversion of a cellulosic material to a product which is desirable for use in smoking and which finds wide acceptance as a smoking product from the standpoint of taste, aroma, appearance, burning characteristics and relative absence of harmful ingredients or undesirable reaction products.

As the cellulosic raw material, use can be made of various forms of cellulose, such as Wood pulp, straw, alpha-cellulose, flax, fibrous carbohydrates, seaweed carbohydrates, bamboo filaments, cotton filaments, hemp, refined paper, rice paper, filamentous gums and even plants and plant leaves and the like fibrous 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 contribute undesirable odors and tastes to 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 breakup of the cellulosic molecule into water vapor, and oxidation products of carbon such as carbon dioxide and low molecular weight compounds which readily volatilize 01f. Thus the object is to achieve selective oxidation of the cellulosic material to convert methylol groups, especially 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 cleavage does not occur.

Selective oxidation without degradation of the cellulosic material is difi'icult to achieve with oxidizing agents such as peroxides, hypochlorites, permanganates, dichromates and the like. On the other hand, such selective oxidation for use in preparation of a smoking product from such cellulosic materials can be achieved with nitrogen dioxide.

Gaseous nitrogen dioxide has been found to be impractical for this purpose since the resulting oxidation reaction is too slow and difficulty is experienced in achieving complete access to the entire cross-section of the cellulose derivative with gaseous nitrogen dioxide with the result that it is difficult to achieve high conversion at a commercial rate and conversion is not uniform thereby to produce an undesirable product for smoking. Further, the reaction of oxidation of the cellulosic matetrial is an exothermic reaction that is accompanied by the generation of heat which is not easily dissipated with the use of gaseous nitrogen dioxide. As a result, hot spots can develop in various areas of the treated material to cause degradation and occasional conflagration of the cellulosic material.

On the other hand, 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 instantaneously 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 lesser time. Furthermore, liquid nitrogen dioxide, when used in the proportions most suitable for the practice of this invention, operates as a quench immediately to dissipate 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 ease of purification and subsequent treatment of the oxidized reaction product, as will hereinafter appear.

In our copending application filed concurrently herewith 745,221 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 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 filed concurrently herewith 745,135 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 to 45 C., depending somewhat upon the amount of moisture present in the reaction medium, whereby the re action medium is rendered relatively non-electrically conductive so that the presence of water in the reaction me dium 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.

In our copending application filed concurrently herewith 745,134 and entitled Cellulosic Smoking Product and Method in the Preparation of Same, description is made of the selective oxidation of cellulosic material with liquid nitrogen dioxide, with or without water, and in which a molecular oxygen containing gas is introduced into the reaction medium during the reaction for reconversion of formed nitrous acid to nitric acid and nitric oxide to nitrogen dioxide, and for entering into the oxidation reaction in the presence of liquid nitrogen dioxide.

It has been found that small amounts of lignins, waxes, oils, and other hydrocarbons remain in the cellulosic material, even when highly purified in the preparation of pulp, paper and the like raw materials for use in the preparation of a smoking product. Such lignins, waxes, oils, resins and the like burn with an acrid odor and give bad taste when allowed to remain in the smoking product. During the oxidation of the cellulosic material, as in the manners described in the aforementioned copending applications and in the previously mentioned copending applications filed concurrently herewith, such lignins, waxes, oils, resins and the like are at least in part converted to oxidation products which detract from the aroma and taste of the prepared smoking product. As a result, it is desirable to effect removal of as much as such undesirable materials as possible from the cellulosic material before oxidation and to remove as much of such material as possible from the oxidation reaction product after the oxidation reaction has been completed. It is desirable to achieve such results as economically as possible and without introducing other undesirable factors into the process which might interfere with utilization of the oxidation reaction product in the preperation of a smoking material.

It has been found that removal of such waxes, lignings, oils, resins and the like from the cellulosic raw material, without introducing additional problems to oxidation with liquid nitrogen dioxide, or without increasing the number of steps or the amount of work in the preparation of a smoking product therefrom, can be achieved in accordance with one important concept of this invention by pretreatment of the cellulosic raw material with anhydrous liquid nitrogen dioxide, generally having the formula N 0 Such anhydrous liquid nitrogen dioxide operates to dissolve out waxes, lignins, oils and the like to effect removal from the cellulosic raw material in reparation of the raw material for the described selective oxidation. Pro-treatment with anhydrous liquid nitrogen dioxide offers a number of plus factors in that all of the anhydrous liquid nitrogen dioxide need not be removed from the cellulosic material since the cellulosic material is subsequently to be reacted for selective oxidation in the presence of liquid nitrogen dioxide.

Further, such lignins, waxes, oils, resins and the like organic substances, as are extracted from the cellulosic raw material by the anhydrous liquid nitrogen dioxide, can be precipitated from solution by addition or dilution of the treating liquid with small amounts of aqueous medium followed by cooling. This then results in a purified liquid nitrogen dioxide which finds use as the reaction medium for the subsequent selective oxidation of the treated cellulosic raw material. For this purpose, it is not necessary to make use of such amounts of anhydrous liquid nitrogen dioxide as in the selective oxidation reaction for suspension of the cellulosic material therein. In fact, it is sufficient if the anhydrous liquid nitrogen dioxide used in pre-treatment to dissolve out waxes, lignins, oils, resins and the like impurities is employed in an amount within the range of five to fifty times the weight of the cellulosic raw material and preferably in an amount within the range of ten to twenty-five times the weight of the cellulosic raw material.

Impurities dissolved in the anhydrous liquid nitrogen dioxide are rendered insoluble by the addition of water in an amount within the range of 0.5% to by weight of the liquid nitrogen dioxide and preferably in an amount within the range of 1% to 4% by weight. Cooling to a temperature of 5 C. to 0 C. is then employed until an acid liquor settles out, containing the organic impurities. When precipitation for separation of impurities is effected by the addition of water in the amounts described, the supernatant liquid can be used without further modification as the oxidizing medium for selective oxidation of the treated cellulosic material. Since pre-treatment is usually carried out with an amount of anhydrous liquid nitrogen dioxide considerably less than that employed in the oxidation reaction, use can be made of substantially all of the recovered nitrogen dioxide in formulating the oxidizing medium with the further addition of liquid nitrogen dioxide to provide the volumetric ratio described in the copending applications filed concurrently herewith.

It has been found further that lignins, waxes and the like impurities remaining in the cellulosic raw material become even more accessible to the selective oxidation reaction and that some of the oxidation products thereof become soluble in anhydrous liquid nitrogen dioxide. Thus it is another important concept of this invention immediately to follow the selective oxidation reaction with treatment by anhydrous liquid nitrogen dioxide after the reaction medium has been separated and before an evaporative drying or a water rinse or wash. A water wash or rinse following immediately after separation of the oxidizing solution from the cellulosic materials operates to precipitate the lignins, waxes, and the like reaction products thereof to be dissolved out while in their most accessible state for removal from the oxidized cellulosic material to be processed into a smoking product.

p A further and particularly important reason for rinsing the oxidized cellulosic material with anhydrous nitrogen dioxide, at the end of the oxidation reaction period, is to remove moist nitrogen dioxide and an acid liquor consisting of nitric and nitrous acid which tends to absorb on the oxidized cellulosic material.

In between the stages of draining ofr" the nitrogen dioxide reaction medium and rinsing the oxidized material with water, some degree of evaporation is inevitable and on a production scale, an evaporation stage is very desirable to reduce loss of nitrogen dioxide.

In the absence of the anhydrous nitrogen dioxide rinse, acid liquor builds up on the oxidized cellulosic material, due to its relatively low volatility, and causes degradation and weakening of the material during the evaporation stage. A rinse with anhydrous nitrogen dioxide immediately after draining off the nitrogen dioxide reactant substantially precludes this possibility.

It is sufiicient if the post-treatment is carried out with substantially anhydrous liquid nitrogen dioxide employed in an amount'corresponding to 1 part by volume anhydrous liquid nitrogen dioxide to 0.5 to 5 parts by volume of the oxidized cellulosic material and preferably at a temperature between 5 C. and C. Temperatures below 5 C. are less capable of dissolving the acid liquor.

As in the described pre-treatment, recovery of the liquid nitrogen'dioxide used in the described post-treatment of the oxidized cellulosic material can be efl ected by the addition of aqueous medium followed by cooling to precipitate out an acid liquor containing dissolved impurities, preferably by the addition of water in amounts previously described. The resulting supernatant liquid can be used to make up all or part of the oxidizing medium for the selective oxidation reaction of the cellulosic raw material.

It will be understood that the inventive concepts reside either in the pre-treatment and/or the post-treatment but in the preferred practice both the pre-treatment and posttreatment are employed. The extent to which the anhydrous nitrogen dioxide is truly anhydrous is such that it contains substantially less water than the nitrogen dioxide at the end of the oxidation reaction.

Having described the basic concepts of this invention, the following examples are given by Way of illustration, but not by way of limitation, of the practice of this invention.

EXAMPLE 1 A highly purified commercial grade of wood pulp is first treated with equal parts by weight of anhydrous liquid nitrogen dioxide to effect solution of soluble lignins, waxes, oils, resins and the like materials which are soluble in the liquid nitrogen dioxide.

The anhydrous liquid nitrogen dioxide is separated from the pulp. After water washing, the pulp is then formed in the conventional manner into a thin paper and shredded into strands of about 2 mm. width. The shredded paper is then introduced into a reaction vessel with one hundred times its weight of liquid nitrogen dioxide. Reaction is carried out for six to eight days at a temperature of about 20 C. and atmospheric pressure until at least of the methylol groups on C have been oxidized. During the reaction, a slow stream of air is passed through the nitrogen dioxide to convert any nitric oxide by-product back into nitrogen dioxide.

The liquid reactant is then drained from the reaction vessel and the remaining oxidized cellulosic derivative is warmed under mild vacuum to volatilize otf nitrogen dioxide and the derivative is then copiously washed with aqueous medium for the removal of water solubles.

The anhydrous liquid nitrogen dioxide used in the pretreatment of the cellulosic raw material is diluted with about 2% by weight of water and cooled to 5 C. to precipitate out lignins, waxes and the like insolubilized components in the form of an acid liquor.

EXAMPLE 2 A highly purified Wood pulp is fabricated into thin paper, formed into strands of about 2 mm. width and loaded into a pressure vessel with liquid nitrogen dioxide containing 2% by weight water and in which the liquid reaction medium is introduced in the ratio of 1 part by weight pulp to 25 parts by weight of the liquid oxidizing medium. The reaction medium is heated to a temperature within the range of 25 to 40 C. and the reaction is carried out under a pressure of about 35 to 50 p.s.i. for 24 hours.

Upon completion of the selective oxidation reaction, the liquid oxidizing medium is separated from the oxidized cellulose reaction product and then the latter is treated with a volume of anhydrous liquid nitrogen dioxide corresponding to one-half the weight of the oxidized cellulosic material to dissolve out the solubilized lignins, waxes, oils and resins and their oxidized reaction products and to wash out the spent nitrogen dioxide.

The anhydrous liquid nitrogen dioxide is separated from the treated oxidized cellulosic derivative and the latter is heated to volatilize 01f nitrogen dioxide and then it is washed copiously with water to remove water solubles, or preferably used forthwith in further treatment with mineralizing solutions.

The anhydrous liquid nitrogen dioxide separated in the post-treatment of the oxidized cellulosic material can be diluted with a small amount of water within the range of 2% to 5% by weight and cooled to 5 C. whereby lignins, oils, waxes and resins dissolved in the anhydrous liquid nitrogen dioxide will be precipitated as an acid liquor to enable separation.

The separated anhydrous liquid nitrogen dioxide can be used to form a part of the reaction medium used in the selective oxidation of more cellulosic raw material.

7 EXAMPLE 3 Purified wood pulp is given a pre-treatment with an equal volume of anhydrous liquid nitrogen dioxide to dissolve out lignins, waxes, oils, resins and the like soluble materials. The anhydrous liquid nitrogen dioxide is separated from the treated pulp and diluted with 2% by weight of water and cooled to -5 C. to precipitate out waxes, lignins, oils and resins which separate as an acid liquor.

The supernatant liquid from which the insolubles have been removed is then introduced with sufficient amounts of additional liquid nitrogen dioxide containing about 2% by weight of water into a reaction vessel with the pre-treated wood pulp in amounts corresponding to 1 part by weight of wood pulp to parts by weight of the liquid reaction medium. The oxidation reaction is carried out at a temperature of about 25 to C.

After completion of the reaction, the liquid reaction medium is drained from the reaction vessel for separation from the oxidized cellulosic material.

The treated cellulosic material is subjected to a posttreatment with an equal volume of anhydrous liquid nitrogen dioxide further to dissolve out lignins, waves, oils and resins remaining in the cellulosic material and oxidized reaction products which may become soluble in the anhydrous liquid nitrogen dioxide, As in the pretreatment, the anhydrous liquid nitrogen dioxide is sep arated from the cellulosic oxidation reaction product and it may be diluted with 2% by weight of water and cooled to -5 C. to precipitate out dissolved impurities extracted from the oxidized cellulosic material. The supernatant liquid from the post-treatment can be used as a part of the liquid oxidizing medium employed in the selective oxidation reaction of more cellulosic material.

The post-treated oxidized cellulosic material is then heated to elevated temperature to volatilize gaseous oxides of nitrogen and then the material is copiously washed with water to remove water solubles, if desired.

The product resulting from the treatments described in Examples 1 to 3 will exhibit improved smoking characteristics from the standpoint of taste and aroma as compared to the cellulosic material prior to the described treatments. It is preferred, however, further to process the oxidized cellulosic materials in the manner described in the aforementioned copending applications'to effect one or more additional processing steps, such as reduc tion with a borohydride to convert residual nitro groups to amino groups and/ or conversion of residual quinone,

ketone, aldehyde and unsaturate groups, and/ or to introduce one or more agents, such as mineralizing agents in the form of calcium oxalate and the like, smoke generating agents, neutralizing agents such as ammonium or amine salts, glow supporting agents and burning agents such as salts of potassium, cesium or rubidium, coloring agents and the like, all as described in the aforementioned copending applications.

It will be apparent from the foregoing that we have provided a process for producing a material suitable for use in the preparation of a smoking product by selective oxidation of a cellulosic material with liquid nitrogen dioxide including pre-treatments and/or post-treatments with anhydrous liquid nitrogen dioxide to remove undesirable components and impurities which otherwise remain to impart undesirable odors and taste to the smoking product that is formed, or to effect degradation and weakening.

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 process for preparation of a smoking product from cellulosic material, the steps of subjecting the cellulosic material to a selective oxidation with liquid nitrogen dioxide, subjecting the cellulosic material before and/or after the oxidation treatment to a treatment with anhydrous liquid nitrogen dioxide for removal of undesirable impurities, and separating the anhydrous liquid nitrogen dioxide from the cellulosic material.

2. The process as claimed in claim 1 in which, when the cellulosic material is subjected to pre-treatment with anhydrous liquid nitrogen dioxide, the materials are proc essed in the ratio of 1 part by weight of cellulosic material to 5 to parts by weight of anhydrous liquid nitrogen dioxide.

3. The process as claimed in claim 1 in which, when the cellulosic material is subjected to pre-treatment with anhydrous liquid nitrogen dioxide, the materials are processed in the ratio of 1 part by weight of cellulosic material to 10 to 25 parts by weight of anhydrous liquid nitrogen dioxide.

4. The process as claimed in claim 1 in which, when the cellulosic material is subjected to post-treatment after selective oxidation with anhydrous liquid nitrogen dioxide, the materials are processed in the ratio of 1 part by weight of liquid nitrogen dioxide to 0.5 to 5 parts by weight of oxidized cellulosic material.

5. The process as claimed in claim 1 which includes the step of adding water to the separated anhydrous liquid nitrogen dioxide in an amount within the range of 0.5% to 10% by Weight of the anhydrous liquid nitrogen dioxide to precipitate out dissolved impurities.

6. The process as claimed in claim 5 which includes the step of cooling the liquids after addition of water to separate an acid liquor from a supernatant nitrogen dioxide. 7. The process as claimed in claim 1 which includes the step of adding water to the separated anhydrous liquid nitrogen dioxide in an amount within the range of 2% to 5% by weight of the anhydrous liquid nitrogen dioxide to precipitate out dissolved impurities.

8. The process as claimed in claim 7 which includes the step of cooling the liquids after addition of Water to separate an acid liquor from a supernatant nitrogen dioxide.

9. An oxidized cellulose derivative for use in the preparation of a smoking product and prepared by the process of claim 1.

References Cited UNITED STATES PATENTS 3,364,200 l/l968 Ashton et al 2602l2 FOREIGN PATENTS 702,918 2/1965 Canada.

MELVIN D. REIN, Primary Examiner US. 01. X.R.