CH627630A5 - Smoking tobacco mixture and use thereof - Google Patents

Description

The object of the invention is to provide a smoking tobacco mixture which contains additives which reduce the content of polycyclic aromatic hydrocarbons in tobacco smoke without impairing the taste and smell of the smoke. This object is achieved by the invention.

The invention thus relates to the subject matter characterized in the claims.

According to the present invention, the concentration of the polycyclic aromatic hydrocarbons in tobacco smoke is greatly reduced by the addition of metallic palladium or a palladium salt and a nitrate of metals of the group IIa or IIb of the periodic table, without an adverse organoleptic effect on the tobacco smoke. In contrast to group Ia metal nitrates, group IIa and IIb metal nitrates do not accelerate tobacco combustion. In addition, under the conditions existing in the cigarette, they form more nitrogen oxide per mole and consequently bring about a more effective reduction in the concentration of polycyclic aromatic hydrocarbons in the smoke condensate.

The additional use of calcium, magnesium or zinc nitrate reduces the concentration of the polycyclic aromatic hydrocarbons more than when using palladium oxide alone. This effect already occurs at nitrate concentrations that are so low that they do not impair the organoleptic properties of tobacco smoke. Especially when using a nitrate amount of less than 0.8% nitrate nitrogen, based on the weight of the

Smoking tobacco, the concentration of polycyclic aromatic hydrocarbons is greatly reduced.

The palladium can be added to the smoking tobacco mixture in finely divided, metallic form, e.g. as palladium black, and / or in the form of a salt which can be decomposed into metallic palladium in situ, preferably under the action of heat. Water-soluble palladium salts are preferred because they can be more easily incorporated into the smoking tobacco mixture and distributed evenly therein. Examples of suitable palladium salts are simple salts, such as palladium nitrate, palladium halides, such as palladium chloride, diammine complexes, such as diammine-palladium (II) chloride (Pd (NH3) 2Cl2), and palladates, especially ammonium palladates, such as ammonium tetrachloropalladate and ammonium hexachloropalladate. The use of palladium in the form of ammonium hexachloropalladate, (NH4) 2PdCl6 (manufacturer: Research Organic-Inorganic Chemicals Corp .; purity: 99.5%) is particularly preferred.

The amount of palladium used in the smoking tobacco mixture is 0.001 to 1 percent by weight, based on the tobacco weight. When such amounts are used, the formation of the polycyclic aromatic hydrocarbons resulting from the pyrolysis is reduced. The best results are obtained when the palladium is preferably used in an amount of about 0.01 to 0.1 percent by weight based on the weight of the tobacco.

The nitrates used according to the invention are calcium, magnesium and zinc nitrate. A nitrate that is particularly effective for the smoking tobacco blend of the invention is ACS grade Mg (N03) 2 • 6H20 which is less than about 0.0005 weight percent chloride ions, 0.005 weight percent sulfate ions and 0.0004 weight percent heavy metals, calculated as lead , contains.

The proportion of the nitrate used in the smoking tobacco mixture according to the invention is less than 0.8%, namely 0.25 to 0.75%, calculated as nitrate nitrogen. A greater reduction in the formation of polycyclic aromatic hydrocarbons can be achieved by increasing the amount of nitrate, but the taste and aroma of the smoke then become increasingly unpleasant. In connection with palladium, nitrate nitrogen is preferably used in an amount of 0.25 to 0.60%.

The additives must be well distributed in the smoking tobacco, so that a uniform effect is guaranteed during the entire smoking process. It is also important to ensure that the dispersion effectively comes into contact with a maximum volume of smoke inhaled by the smoker. Since the catalytic activity of the palladium is presumably due to a surface reaction, the greatest likelihood of maximum contact between the smoke inhaled by the smoker and the zinc oxide is when the surface area to volume ratio of the zinc oxide particles is as large as possible. For this reason, the palladium, when used in the form of metallic palladium black, has a particle size of preferably less than about 0.15 mm. Water-soluble palladium salts, such as hexachloropalladates, tetrachloropalladates, nitrates, chlorides or diamine complexes, have the advantage that they can be used as dilute solutions, which makes it easier to achieve a good or uniform distribution over the entire smoking tobacco mixture.

The calcium, magnesium and zinc nitrates are readily soluble in water and can be used as a relatively concentrated solution. This prevents excessive moistening of the smoking tobacco and still ensures an even distribution in the smoking tobacco.

The most effective way of applying the palladium and the nitrate compound to the tobacco is with a conventional method

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627 630

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Chen Casing solution of glycerol and propylene glycol, which is mixed with a hexachloropalladate solution, and in which the required amount of nitrate compound is dissolved by adding a sufficient amount of water. Such a solution can be suitably sprayed onto tobacco strips which have not yet been cut using a conventional casing device.

When using palladium black, another way of applying the additives to the smoking tobacco is to dry mix the palladium black, the ground tobacco, a fibrous material and a binder. By dry mixing, e.g. in a conventional double cone mixer, there is an effective distribution of the palladium over the surface of the tobacco into the pores, which are large enough to accommodate the palladium particles.

If necessary, the dry blending is followed by a wet blending with water and casing substances in amounts sufficient to provide the blend with a consistency suitable for conventional methods of making reconstituted tobacco slabs. The plates are then cut into strips. A solution of the nitrate compound in water is applied to the strips. If the tobacco moisture needs to be corrected, drying follows. The plates are used in this form in cigarette manufacturing either directly or mixed with ordinary tobacco.

The fibrous material which is a constituent of the dry mixture can be, for example, a-cellulose or fibrous material of tobacco stems. The proportion of binder in the dry mixture can e.g. Sodium carboxymethyl cellulose or a natural vegetable gum e.g. Guar gum. The casing substances used during wet mixing are generally glycerol and / or propylene glycol. Of course, other known fibrous materials, binders or auxiliaries, the use of which in combination with tobacco mixtures makes sense, can also be used in addition to or instead of the aforementioned substances.

The amounts of the aforementioned additives or auxiliaries for use in reconstituted tobacco plates are generally within the weight ranges given below. The amounts indicated are within the usual amounts required to obtain useful tobacco products.

Table I

Material weight percent

Fibrous material 4-8

Containing binders 1-20 casing substances about 3-9

(a) Glycerin 4-6

(b) Propylene glycol 0.5-2 tobacco balance 100%

The tobacco blends can be processed or packaged to any desired shape. Examples of suitable types of packaging are cigars, cigarettes or pipe tobacco.

The examples illustrate the invention.

example 1

0.35 kg of ammonium hexachloipalladate are dissolved in as little water as possible and added to a mixture of a glycerine propylene glycol casing solution and water. 8.59 kg of magnesium nitrate hexahydrate are dissolved in this mixture and sprayed onto 100.69 kg of an uncut tobacco mixture in a conventional casing applicator. The treated tobacco is mixed with 28.58 kg reconstituted tobacco slabs and 6.80 kg tobacco stems. The tobacco mixture obtained is cut with 32 cuts per 25.4 mm (sample 1). Tobacco blends that contain only the palladium (Sample 2) or only the magnesium nitrate (Sample 3) and a control blend that does not contain any of the additives are made in the same way.

All four samples are pyrolyzed in a pyrolysis reactor, which consists of a steel cylinder with a diameter of 10 cm and a length of 12.7 cm with an annular space, which is covered with a corrosion-resistant steel sieve. The cut tobacco is packed into this reactor in a similar manner to that of cigarettes and lit on the circumference. The burning tobacco itself generates the heat necessary for pyrolysis, and the reactor comes very close to the conditions in a burning cigarette. The combustion and pyrolysis products are sucked off through a small pipe, which is attached concentrically to the cylinder, and the dry solids in the smoke are analyzed for their content of polycyclic aromatic hydrocarbons. The concentration of the polycyclic aromatic hydrocarbons contained in the test tobacco is given in Table II as a percentage of the PCAH concentrations contained in the control tobacco.

Table II

sample

Additive,% by weight

PCAH concentration,

(NH4) PdCI6 * Mg (N03) 2 **

related to the PCAH

Concentration in

Control tobacco

Weight

IR

Base

Analysis***

1

0.06 0.55

50

50

2nd

0.06

60

59

3rd

0.55

78

78

Control

sample

-

100

100

* as palladium ** as nitrate nitrogen *** calculated from the absorption in the range of aromatic C-H bond vibrations (11.9 to 14.0 ß).

Example 2

0.64 g of ammonium tetrachloropalladate are dissolved in 100 ml of water and added to 56.6 g of a glycerol-propylene glycol casing solution. 27.5 g of magnesium nitrate hexahydrate are dissolved in the casing solution and the mixture is sprayed onto 400 g of a cut tobacco mixture (32 cuts per 25.4 mm) (sample 4). A tobacco blend containing only the (NH4) 2PdCl4 is made in the same way (Sample 5). The samples are tested as in Example 1; for comparison purposes, the values for sample 3 and the control sample from example 1 are also given.

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Table III

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Sample additive, wt .-% PCAH concentration,

(NH4) PdCl4 * Mg (N03) 2 ** based on the PCAH

Concentration in control tobacco Weight-IR-based analysis ***

4 0.06

0.55

57

59

5 0.06

-

80

78

3rd

0.55

78

78

Control

sample -

-

100

100

* as palladium ** as nitrate nitrogen

*** calculated from the absorption in the range of the aromatic C — H bond vibrations (11.9 to 14.0 ß).

In sample (4) the concentration of the polycyclic aromatic hydrocarbons is significantly lower than when using palladium or magnesium nitrate alone. Comparison of the values for samples (1) and (4) shows that the concentration of polycyclic aromatic hydrocarbons is lower when using ammonium hexachloropalladate than when using the corresponding tetrachloropalladate.

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Claims (7)

627 630 2nd PATENT CLAIMS 1. Smoking tobacco mixture containing: a) tobacco; b) finely divided palladium or palladium salt in an amount of 0.001 to 1 percent by weight, calculated as palladium, based on the weight of the tobacco; and c) calcium, magnesium or zinc nitrate in an amount of 0.25 to 0.75 percent by weight, calculated as nitrate nitrogen, based on the weight of the tobacco. 2. Smoking tobacco mixture according to claim 1, characterized in that, based on the weight of the tobacco, the amount of palladium is 0.01 to 0.1 percent by weight and the amount of nitrate, calculated as nitrate nitrogen, is 0.25 to 0.6 percent by weight . 3. smoking tobacco mixture according to claim 1 or 2, characterized in that it contains metallic palladium, palladium black or a thermally decomposable to metallic palladium palladium salt. 4. Smoking tobacco mixture according to claim 1, characterized in that it contains a water-soluble palladium salt. 5. smoking tobacco mixture according to claim 5, characterized in that the water-soluble palladium salt is a nitrate, a halide, a diamine complex or a palladate. 6. smoking tobacco mixture according to claim 5, characterized in that the palladium salt is ammonium hexachloro-palladate. 7. Use of the smoking tobacco mixture according to claim 1 for cigarettes, cigars or as pipe tobacco. Observations of the combustion mechanism in smoking tobacco mixtures, for example in cigarette tobacco mixtures, have shown that the components responsible for the biological effect of the smoke arise in the pyrolysis zone of the cigarette. It is generally assumed that a large part of the biological effects observed with smoke condensate can be found in the neutral smoke fraction, especially in the sub-fraction containing polycyclic aromatic hydrocarbons (PCAH). Numerous attempts have been made to reduce the proportion of PCAH compounds in tobacco smoke. It is believed that the tobacco components are converted into polycyclic aromatic hydrocarbons in various ways. One of these ways is the thermal degradation of various organic substances, such as cellulose, into unsaturated radical fragments that contain two, four or five carbon atoms and, in the case of longer fragments, conjugated double bonds. The radical compounds participate in the pyrogenesis of aromatic ring structures, the fragments with two and four carbon atoms providing unsubstituted polycyclic aromatic hydrocarbons and the branched fragment with five carbon atoms with a methyl group substituted polycyclic aromatic hydrocarbons. Another way of forming the polycyclic aromatic hydrocarbons is via the basic structures that still exist in smoking tobacco, such as steroids. In this case, even small, thermally induced changes are sufficient to form polycyclic aromatic hydrocarbons. In addition, there are other ways that lead, for example, to ring closure reactions of side chains. Since the individual routes for the formation of polycyclic aromatic hydrocarbons are very different, it is very unlikely that a single catalyst or other additive will block all these different routes for the formation of PCAH. For example, a smoking tobacco blend has been proposed that contains tobacco in conjunction with finely divided metallic palladium or a palladium salt. In this tobacco mixture, the proportion of polycyclic, aromatic hydrocarbons, which result from the pyrolysis taking place in smoking tobacco, is said to be significantly reduced in comparison with a control cigarette. However, it has been found that the use of a palladium catalyst alone, despite its effectiveness in reducing the polycyclic aromatic hydrocarbons produced by pyrosynthesis, is limited and cannot affect all routes to the production of polycyclic aromatic hydrocarbons. The use of nitrates and nitrites in smoking tobacco is known from numerous patents and other publications. From FR-PS 1 180 320 it is known to reduce the resulting polycyclic aromatic hydrocarbons by adding undefined quantities of nitrites to smoking tobacco and cigarette paper. US Pat. No. 3,121,433 describes the addition of potassium nitrate to reconstructed tobacco plates in order to improve their burning properties. The addition of 5.5 to 10% potassium and sodium nitrate to smoking tobacco is known from US Pat. No. 3,380,458 (NaN03: 0.91-1.65% nitrate nitrogen; KN03: 0.76-1.39% nitrate nitrogen) . According to the information in this patent, the increased taring rate of the cigarette reduces the amount of tar formed. Bentley and Burgan, Analyst, Vol. 85 (1960), pp. 727 to 730, have found that the addition of various nitrates to tobacco reduces the formation of 3,4-benzopyrene. According to this publication, a reduction is only achieved with copper and potassium nitrate; when using lead, silver and zinc nitrate, the formation of 3,4-benzopyrene increases. This finding that the formation of 3,4-benzopyrene is reduced when using copper nitrate is supported by Wyn-der and Hoffmann, Acta Pathol. Microbiol. Scand., Vol. 52 (1961), pp. 119 to 132 and Deutsche Medical Wochenschrift, Vol. 88 (1963), pp. 623 to 628, who found that cigarettes containing 5% copper nitrate (0.50% Nitrate nitrogen) were treated, deliver smaller amounts of 3,4-benzopyrene. According to Hoffmann and Wynder, Cancer Res., Vol. 27 (1967), pp. 172 to 174, the addition of 8.3% sodium nitrate (1.37% nitrate nitrogen) leads to a significant reduction in the formation of 3,4-benzopyrene and to a decrease in the biological effectiveness of the smoke condensate. On the other hand, from Pyriki et al., Ber. Inst. Tobacco research. Dresden, Vol. 12 (1965), pp. 37 to 55, found that the addition of 4% potassium nitrate (0.55% nitrate nitrogen) leads to a 40% increased formation of 3,4-benzopyrene in tobacco smoke. So far, almost all research results have been focused on the effect of the additive on the formation of 3,4-benzopyrene. In the meantime, however, it has been found that this compound plays at best a small role in relation to the biological effectiveness of the smoke condensate. The reduction in the formation of 3,4-benzopyrene, which is only a tiny component of the polycyclic aromatic hydrocarbon fraction, is not necessarily a reliable indicator of the effect of the additive on the amount of polycyclic aromatic hydrocarbons formed. It has been assumed that the effect of nitrates on the smoking tobacco mixture is based on two properties, namely a) their property as an oxidizing agent and 5 10th 15 20th 25th 30th 35 40 45 50 55 60 65 3rd 627 630 b) their ability to form the compound nitrogen oxide (NO) in the pyrolysis zone of the cigarette, which acts as a radical scavenger. If a sufficient amount of nitrates is used, all nitrates have the property of reducing the formation of polycyclic aromatic hydrocarbons to a certain extent, but depending on the cation, not necessarily their concentration in the smoke condensate. The ability of the nitrates to reduce the concentration of the polycyclic aromatic hydrocarbons is particularly dependent on the ability of the salt to form nitric oxide in the appropriate temperature section of the combustion zone. Many nitrates, especially the nitrates of Group Ia metals in the periodic table, accelerate combustion. When added to smoking tobacco, the cigarettes burn faster and the total amount of smoke produced decreases. However, the concentration of the polycyclic aromatic hydrocarbons in the smoke condensate is not necessarily reduced, but actually increases in some cases. Nitric oxide is formed from such nitrates in relatively small amounts. Therefore, nitrates of Group Ia metals of the periodic table must be added in relatively large amounts in order to reduce the concentration of polycyclic aromatic hydrocarbons in tobacco smoke. All added nitrates, especially those that accelerate combustion, give the smoke a bad taste and an unpleasant smell. For this reason, with regard to the taste and smell of a cigarette, additional amounts on the order of 5 to 10%, as claimed in the literature for producing a beneficial effect, are not acceptable. In summary, nitrates, like palladium, in spite of their ability to block some of the pathways for the formation of polycyclic aromatic hydrocarbons, cannot in any way completely suppress the formation of this compound, especially in the case of additions related to the taste and smell of tobacco smoke are still compatible.