GB1561146A

GB1561146A - Process for the preparation of hydrazines

Info

Publication number: GB1561146A
Application number: GB4230676A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-10-12
Filing date: 1976-10-12
Publication date: 1980-02-13
Also published as: BE846469A; AU2206677A; FR2370035A1; AU505827B2

Description

(54) PROCESS FOR THE PREPARATION OF HYDRAZINES (71) I HANS OSBORG, of 80 Longview Road, Port Washington, N.Y. 11050, United States of America, a citizen of the United States of America; do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a process for the preparation of hydrazines, more particularly, it relates to a process for the preparation of hydrazine, phenyl-substituted and alkylsubstituted hydrazines.

Hydrazine, phenyl-substituted and alkyl-substituted hydrazines, particularly asymmetrical dimethyl hydrazine, have become important commercially useful compounds for a wide variety of applications, for example, for use as intermediates in the manufacture of blowing agents, pharmaceuticals, fuels and agricultural products.

Numerous processes are known for the preparation of hydrazine and its alkyl-substituted derivatives. One such process is, for example, the Raschig process in which hydrazine is obtained from ammonia and sodium hypochlorite in two stages. In the first stage, chloramine is formed with sodium hydroxide as by-product. The choramine is then reacted with an excess of ammonia to form hydrazine. Chloramine is rapidly formed in the first stage. In the second stage, however, the reaction velocity of the chloramine with ammonia is slow and requires the application of heat in order to complete the reaction. The rate at which the required hydrazine is formed increases with increasing temperature. A secondary reaction occurs in which hydrazine reacts with the chloramine initially formed to form ammonium chloride and nitrogen. This is. of course. undesirable. In order to avoid a high rate of hydrazine decomposition, the process has to be carried out at elevated temperature (about 1300C) using a large excess of ammonia (from 20:1 to 30:1) in order to minimise reaction of the hydrazine obtained with the chloramine.

The Olin process (Kobe et al, Advances In Petroleum Chemistry And Refining, Vol. 2, Interscience Pub. Inc., New York, New York. 1959, Chapter 9) is a modification of the Raschig process in which anhydrous ammonia is used. The anhvdrous ammonia is injected under pressure into an aqueous chloramine solution. which procedure has the advantage that, on account of the heat of solution, the reaction temperature is immediately increased to about 1300C, i.e. to the ideal redaction temperature for the reaction of ammonia with chloramine. However, heat has to be supplied from external heat sources in order to complete the reaction and to remove the large quantities of ammonia during the subsequent distillation steps. In addition, energy is required for removing sodium chloride and sodium hydroxide as secondary product and for recovering the hydrazine. The hydrazine recovered is the monohydrate. In order to obtain the (anhydrous) pure product, considerable additional energy is required for removing the chemically bound water.

The Schestakoff process is based on the degradation of urea by hypochlorite to form hydrazine. The reaction resembles Hoffmann's degradation of primary amides to amines.

In this process, a cold aqueous solution of urea and sodium hydroxide is added to a cold solution of sodium hypochlorite. The heat of reaction increases the temperature to 100"C at which temperature the reaction takes place rapidly. In this process, large quantities of steam are required for preparing the urea solution (43who solution) in order to counteract the high endotherm of solution. As in the Raschig process, the product is the monohydrate in low concentration (approximately 3CSc). Additional energy is required for the concentration stage and for converting the hydrate and for fractionating the hydrazine end product.

Excess quantities of alkali or alkali salts are also formed as valueless by-products (the ratio, by weight, of the secondary products to N2H4 is about 12:1).

The Bergbau or Bayer process is not a commercially used process although the heat requirements are not as great as in the commercially worked processes described above. In the Bergbau or Bayer process, ammonia is reacted with chlorine in the presence of a ketone to form diazocyclopropane or ketazine as intermediate compound. The intermediate compound is hydrolysed to form hydrazine hydrate which is then converted into the required anhydrous product. Recovery of the hydrazine involves the same energy requirements as in the processes described above.

The prior art also acknowledges the difficulty of isolating anhydrous hydrazine from a variety of reaction mixtures, cf. in this connection US Patent Nos. 2,735,752 and 2,899,364.

By virtue of the process according to the present invention, it is possible to obtain anhydrous hydrazine in high concentrations within the reaction mixture. The pure product is readily separated off by conventional distillation techniques.

One particular advantage of the process according to the present invention is that it is particularly suitable for the production of alkyl-substituted hydrazines, especially asymmetrical dimethyl hydrazine.

The advantages of the process according to the present invention are two-fold in regard to the production of asymmetrical dimethyl hydrazine, occasionally referred to hereinafter as UDMH. The first advantage is that it satisfies fully the thermodynamic requirements in the sense of a very large reduction of these requirements. In particular there is a saving of energy in the preparation of the starting materials which have to be included in the overall analysis of effectiveness of the process. The commercially worked process for the production of UDMH comprises nitrosation of dimethylamine by way of its sulphuric acid salt and by means of sodium nitrite to obtain dimethyl nitrosoamine which is then reduced to form UDMH. The disadvantage of this process lies in the considerable amount of energy required for preparing the starting materials and in the separation of the required product.

The second and probably the more important advantage concerns the dangers to which personnel are exposed in handling the dangerous nitrosoamine intermediate products in the production of UDMH. Dimethyl nitrosoamine is a highly active carcinogen. The process normally used for the production of UDMH is attended by the following problems: (1.) The process results in the production as a waste product of large quantities of sodium sulphate, which sodium sulphate is contaminated with nitroso compounds which cannot be isolated or recovered in a way which complies satisfactorily with safety regulations.

(2.) It is difficult to handle the nitroso compound produced without personnel being exposed to it.

(3.) The incomplete conversion of the nitroso compound into the other hydrazineforming nitroso compound residues constitutes a hazard and gives rise to difficulties so far as treatment, conversion or disposal are concerned.

(4.) Furthermore, the hydrazine produced has to be fractionated or distilled in order to bring it to the required purity level. In addition, a nitroso compound containing residue is formed in this final stage which presents problems.

Accordingly, it is not surprising that a general review of the literature reveals numerous disclosures as to how the nitroso compound may be converted into hydrazine and UDMH.

The advantage of the process according to the present invention is that high yields of hydrazine and alkyl-substituted hydrazine are obtained under conditions which represent only a minor hazard, if any, to the personnel involved and also to the environment.

The present invention provides a process for the preparation of a hydrazine corresponding to the following general formula:

wherein R and R', which may be the same or different, each represents hydrogen, phenyl or C1-C6 alkyl, with the proviso that, when one of R and R' represents phenyl then the other represents hydrogen; which comprises: (a) reacting substantially equimolar quantities of an amine corresponding to the following general formula:

wherein R and R' are as defined above; and X represents chlorine or bromine; with an alkali metal and/or alkaline earth metal amide at a temperature of from 0 to -500C in the presence of a liquid non-aqueous inert carrier, which carrier is liquid anywhere in the temperature range of from -110 to +200"C and (b) separating the thus-obtained hydrazine from the reaction mixture.

Examples of alkyl radicals such as may be represented by R and R' include methyl, ethyl, propyl, butyl, pentyl and hexyl, including isomeric forms thereof.

As alkali metals are to be mentioned lithium, sodium, potassium, rubidium and caesium, and as alkaline earth metals magnesium, calcium, barium and strontium.

As used herein, a non-aqueous inert carrier is a liquid solvent or a carrier for the reactants used. This carrier does not take any part in the reaction nor does it adversely affect the reaction and is substantially anhydrous. The expression "substantially anhydrous" means that the water content is less than 1%, by weight, preferably less than 0.1% by weight. Examples of such carriers include dried kerosene (preferably of low sulphur content and freshly distilled) anhydrous liquid ammonia, dialkylamines, such as dimethylamine, trialkylamines, such as tripropylamine and tributylamine, also tetraalkyl diamines, such as N, N, N', N'-tetramethyl-1, 3-butane diamine, and mixtures thereof. One particularly suitable carrier for the preparation of asymmetrical dimethyl hydrazine is dimethylamine.

The carrier must be a liquid at some temperature within the cited range, but it need not be a liquid over the whole range. Those skilled in the art will appreciate that, by varying pressure conditions, many gaseous materials, e.g. ammonia suitable for use as carriers may be liquefied and so the selection of a particular liquid carrier should not be limited because it may be a gas under certain other conditions within the temperature range. The liquid should not become viscous or freeze at the lowest temperature of the reaction. After the reaction has been initiated and the hydrazine is being or has been formed, the temperature has to be raised so that the hydrazine may be distilled off with the carrier liquid and the sodium chloride remaining. For this purpose, the boiling point of the carrier liquid should be at a comfortably high temperature so that its simultaneous distillation with the hydrazine or its entrainment in the hydrazine distilled is avoided under all circumstances.

The process according to the present invention is carried out by reacting substantially equimolar quantities of the compounds (II) and the amide of an alkali metal of an alkaline earth metal. The reaction may be illustrated by the following schematic equation:

wherein X, R and R' are as defined above; and the sodium amide (III) represents the amide of an alkali or alkaline earth metal.

As used herein, the expression "substantially equimolar" means that the quantities in which the haloamine reactant (II) and the amide of an alkali or alkaline earth metal are used may differ from one another by + 5%. These quantities should, of course, be as near equimolar as possible.

The reaction illustrated in the above scheme is preferably carried out under atmospheric pressure. However, it is also possible to apply super-atmospheric pressures in cases where it is desired to accelerate the reaction, to obtain higher yields or to use carriers which are normally not liquid at the temperature used for carrying out the reaction.

In the process according to the present invention, the reactants are first combined with one another at a temperature of from 0 to -500C, preferably from -20 to -50 C. If the carrier is anhydrous ammonia, temperatures of from -2 to -35 C are preferred because at these temperatures the desired product may be quickly obtained and considerable secondary reactions are avoided. At temperatures in the ranges indicated above, the reaction generally takes place immediately or at least in a matter of minutes. The reaction is generally slower when the carrier used is solely ammonia. The progress of the reaction may be followed by means of conventional analytical apparatus suitable for determining the gradual disappearance of the reactants and the formation of the desired product.

Once a partial conversion has been obtained (generally after the yield has reached about 20%), the reaction mixture may be heated to accelerate the further reaction. It is surprising that, after the reaction has started, brief heating of the reaction mixture to reflux temperatures (over a period of from 10 minutes to a few hours) results in a very rapid completion of the reaction.

The haloamine reactant (II) and the amide reactant may be combined with one another by conventional means and in either order of addition, provided that the addition is rapid.

For example, one or two haloamine reactants (II) or the amide reactant may first be taken up in the carrier and then combined. However, it is preferred initially to dissolve or suspend the amide reactant in the carrier and then to add the halo gamine reactant (II). The reaction is exothermic. The reaction mixture has to be cooled to maintain the required temperature.

If the reactants are combined slowly, the temperature of the reaction mixture is prevented from increasing rapidly and may be maintained below the prescribed limits. It is advantageous to cool the reactants to a predetermined temperature before they are combined.

In general, the reaction on which the process according to the present invention is based begins almost immediately after the reactants have been combined. The desired hydrazine product (I) may be separated off from the reaction mixture as it forms by means of conventional apparatus. However, the reaction may also be completed without separation of the hydrazine product (I). If it is desired to complete the reaction more quickly, the reaction mixture may be left to heat slowly to room temperature after the reaction has progressed to a state of partial completion. It is important to ensure that, during heating, the reaction mixture does not undergo any drastic increase in temperature. If there were such a drastic increase in temperature, this would be a sign that the reaction is not progessing in the required manner so that the reaction mixture should immediately be cooled to below 0 C. After a brief cooling period, gradual heating may be allowed to take place. The increase in temperature should be as uniform as possible. The appearance of sudden increases in temperature during the heating is an indication of an irregular reaction.

When the gradient of the temperature curve is shallow or uniform, the reaction mixture may be heated slightly more quickly to 0 C. Once the reaction mixture has reached a temperature of approximately 0 C without any sudden increases or steep rises, it may be quickly heated to room temperature. If it is desired to complete the reaction quickly, the reaction mixture may be rapidly heated to reflux temperature. However, the reflux temperature should only be maintained briefly. In general, the reaction mixture need not be heated to reflux temperature for more than from 5 to 15 minutes in order to ensure favourable yields without undue expenditure of energy. In cases where ammonia is used as carrier, it may be evaporated off during heating and recovered in the conventional way. The residue, which contains hydrazine and chloride secondary products, may be worked-up in the conventional way, for example by filtration, crystallisation and distillation.

In cases where the carrier used is not ammonia, the reaction mixture may be heated to room temperature as described above and thereafter be heated rapidly to reflux temperature and maintained there at for from 5 to 15 minutes. Although longer periods at reflux temperature may lead to further increased yields, it is important to remember that any advantage gained in regard to yield must be weighed against the increase in expenditure of energy. At the end of the reflux period, the reaction mixture may be cooled rapidly to precipitate the chloride secondary product. The cooled reaction mixture is then filtered to remove the chloride deposit. The filtrate is distilled to separate off the hydrazine product (I). Alternatively, the hydrazine compound (I) may be directly distilled off from the reaction mixture in high yields at the end of the reflux period. In one preferred embodiment of the process according to the present invention, the reactants, amide and haloamine (II), are introduced together into the reaction zone and the hydrazine reaction product (l) is then immediately removed from the reaction zone before admixture with additional starting materials occurs. In this way, undesirable secondary reactions are avoided and the yields are considerably increased. Where this procedure is adopted, it is important to ensure that input of the halo gamine reactant (II) and the amide reactant is regulated in such a way that equimolar quantities are introduced and undesirable secondary reactions are also avoided in this way. When the product (I) is hydrazine, a molar excess of the sodium amide reactant (III) reacts with the hydrazine product and forms sodium hydrazide and ammonia. If, on the other hand, a molar excess of the haloamine reactant is present, disproportionation into sodium salt, nitrogen and ammonium salt occurs. Secondary reactions which result in poorer yields are avoided if the reaction product (I) in the equation is removed from the reaction zone immediately after its formation, thereby depriving it of the opportunity to react with the starting materials.

In the process according to the present invention, the ratio of main product to secondary products is extremely favourable, being of the order of 4:5. This is surprising in view of the theoretical ratio of 1:1.

The process according to the present invention may be carried out continuously or in batches in known apparatus. The haloamine compounds (II) and the preparation thereof are known. They include: chloramine, chloromethylamine, chlorodimethylamine, chlorethylamine, chlordiethylamine, chloropropylamine, butyl chloramine, chlorodibutylamine, amyl chloramine and chlorodihexylamine.

The amides of the alkali and alkaline earth metals which are used for the process according to the present invention when R and R' in the product (I) represent hydrogen or alkyl are known, as is the preparation thereof. Representatives of these compounds are sodium, lithium and potassium amide. Although higher yields may be obtained using potassium amide, it is preferred to use sodium amide for reasons of cost and easier availability. Calcium amide and barium amide are mentioned as examples of alkaline earth metal amides. When one of the radicals R and R' in the product (I) represents phenyl, the amide reactant may be an alkali metal anilide, for example sodium anilide.

In the production of phenyl hydrazine, the preferred carrier is xylene or dimethyl aniline.

The carrier which is particularly preferred for the process according to the present invention is a non-aqueous inert solvent for the amide reactant and is liquid at temperatures of form - 95 to +180"C, preferably form - 40 to +160"C. Examples of such inert organic solvents include dimethylamine, tripropylamine, kerosene, N, N, N', N'-tetramethyl-1,3butane diamine and liquid anhydrous ammonia.

The quantity in which the carrier is used is not critical. The carrier is advantageously used in a quantity of from 50 to 1000%, by weight, based on the amide reactant.

The following Examples illustrate the present invention.

EXAMPLE I A 5-litre three-necked spherical flask (ground ball-and-socket joint) equipped with a stirrer, thermometer, condenser, dropping funnel and means for cooling and heating is purged with nitrogen and filled with 1750 g of anhydrous liquid ammonia. 126 g of sodium amide are added with stirring at a temperature of from - 30 to - 35"C. 165 g of chloramine dissolved in 500 g of tripropylamine are then added to the mixture obtained, followed by chilling to a temperature of - 20"C. The addition is made dropwise over a period of 40 minutes at atmospheric pressure, the temperature being maintained below - 20"C. The reaction mixture is then stirred for another 20 minutes. The reaction mixture is then allowed to heat to room temperature over a period of 20 minutes. Vigorous refluxing occurs for the first 10 minutes, whilst ammonia evaporates during the last 10 minutes and is distilled off. The residue is heated for 10 minutes to from 100 to 1200C and fractionated at a temperature of from 110 to 1200C, giving 47 g (50% of the theoretical yield) of hydrazine.

Monomethyl hydrazine and asymmetrical dibutyl hydrazine are similarly obtained by replacing the chloramine used here with the same quantity of chloromethylamine and chlorodibutylamine, respectively.

EXAMPLE 2 63 g (65% of the theoretical yield) of hydrazine are obtained in the same way as described in Example 1, except that the reaction mixture is heated for 10 hours rather than 10 minutes.

EXAMPLE 3 The procedure is as in Example 1, except that 500 g of tripropylamine are added to the filling of anhydrous ammonia. It was found that the filling undergoes refluxing at about 20"C and 58 g (60% of the theorectical yield) of hydrazine are obtained in this way. It was found that the mixture of inert carriers significantly improves the yield of hydrazine product.

EXAMPLE 4 The procedure was as in Example 3, except that the chloramine used there was replaced by an equimolar quantity of dimethyl chloramine. Asymmetrical dimethyl hydrazine was obtained in a yield of 108 g (60% of the theoretical yield).

EXAMPLE 5 The apparatus described in Example 1 was purged with ammonia and then filled with 1750 g of anhydrous liquid ammonia and 125 g of a suspension of sodium amide in 500 g of tributylamine and then maintained at a temperature of - 20"C. 280 g of dimethyl chloramine mixed with 500 g of tributylamine chilled to - 20"C were added dropwise with stirring over a period of 40 minutes during which the reaction mixture was maintained at a temperature of about - 20"C. On completion of the addition, the reaction mixture was stirred for 10 hours and then left to warm to room temperature. In the meantime, ammonia evaporated off and was removed by distillation. The residue was heated to reflux temperature (from 100 to 1200C), after which the thus-obtained mixture was subjected to fractional distillation at a temperature of from 63 to 640C, giving 135 g (75% of the theoretical yield) of asymmetrical dimethyl hydrazine.

EXAMPLE 6 The apparatus described in Example 1 is purged with nitrogen and then filled with approximately 1720 g of tripropylamine and 126 g of sodium amide. The suspension obtained is chilled to approxmately - 20"C and saturated with anhydrous liquid ammonia, followed by the dropwise addition, with stirring, of 280 g of dimethyl chloramine in 500 g of tripropylamine over a period of 40 minutes during which the temperature is maintained. On completion of the addition, the mixture is stirred for 20 minutes and then left standing for 20 minutes to come to room temperature. In the meantime, ammonia is distilled off. The residue is heated under reflux for 10 minutes, the mixture obtained subsequently distilled at from 55 to 700C and the distillate re-distilled at from 62 to 66"C, giving 126 g (70% of the theoretical yield) of asymmetrical dimethyl hydrazine.

EXAMPLE 7 The procedure is as in Example 6, except that the tripropylamine used there is replaced by N, N, N',N'-tetramethyl 1,3-butane diamine and the mixture is maintained at - 20"C for 10 hours, rather than 10 minutes, before heading under reflux. Asymmetrical dimethyl hydraze is obtained in a yield of 162 g (90% of the theoretical yield).

EXAMPLE 8 The apparatus described in Example 1 is filled with 2000 g of dimethylamine and 126 g of sodium amide, the suspension obtained is thoroughly stirred whilst the reaction vessel is purged with nitrogen. The suspension is then cooled to - 20"C and at the same time saturated with liquid ammonia. 280 g of dimethyl chloramine in 500 g of dimethylamine are added, with stirring, over a period of 40 minutes. On completion of the addition, the reaction mixture is heated under reflux for 50 minutes to a temperature of between 0 C and room temperature. The dimethylamine is then distilled off from the resulting mixture. The required hydrazine is distilled off from the resulting residue under reduced pressure. The yields comprise from 30 to 50%.

EXAMPLE 9 The apparatus described in Example 1 is purged with nitrogen and filled with 2000 g of white kerosene (distilled over sodium) and 126 g of sodium amide. The filling is saturated with ammonia and cooled to - 20"C. 280 g of dimethyl chloramine in 500 g of distilled kerosene (chilled to about - 20"C) are then slowly added (dropwise) over a period of 40 minutes to the cold mixture. The reaction mixture is then left standing for 20 minutes to come to room temperature. In the meantime, ammonia is distilled off. The thus-obtained residue is heated under reflux for 10 minutes, after which the asymmetrical dimethyl hydrazine is distilled off.

EXAMPLE 10 The apparatus described in Example 1 is purged with nitrogen and then filled with 2000 g of xylene and 441 g of sodium anilide. Whilst the filling is maintained at a temperature of 20"C, it is saturated with liquid ammonia, followed by the dropwise addition to the resulting suspension, with constant stirring, over a period of 40 minutes, of 165 g of chloramine dissolved in 500 g of xylene chilled to a temperature of - 20"C. The reaction mixture is then stirred for another 20 minutes and left standing for about 20 minutes to return to room temperatures. In the meantime, ammonia distills off. On completion of refluxing, the residue is cooled to a temperature of 20"C and the precipitated deposit is filtered off. The filtrate and the deposit are then subjected to fractional distillation under reduced pressure, giving phenyl hydrazine.

Phenyl hydrazine may similarly be obtained by replacing the xylene used here with the same quantity of dimethyl aniline.

EXAMPLE 11 The procedures of Examples 6 to 10 are repeated with the difference that the filling is not saturated with liquid ammonia. Although the required hydrazine product (I) is obtained in every case, the yields are from 10 to 25%, by weight, lower than in cases where the carrier liquid is saturated with ammonia.

WHAT I CLAIM IS: 1. A process for the preparation of a hydrazine corresponding to the following formula:

wherein R and R' which may be the same or different, each represents hydrogen, phenyl, or C1-C6 alkyl, with the proviso that, when one of R and R' represents phenyl, then the other represents hydrogen; which comprises: (a) reacting substantially equimolar quantities of an amine corresponding to the following general formula:

wherein R and R' are as defined above; and X represents chlorine or bromine; with an alkali metal and/or alkaline earth metal amide at a temperature of from 0 to - 500C in the presence of a liquid non-aqueous inert carrier which carrier is liquid at some temperature in the range of from -110 to +2000C; and (b) separating the thus-obtained hydrazine from the reaction mixture.

2. A process as claimed in Claim 1 in which the amine (II) is selected from chloramine, chloromethylamine, chlorodimethylamine, chloroethylamine, chlorodiethylamine, chloropropylamine, butyl chloramine, chlorodibutylamine, amyl chloramine and chlorodihexylamine.

3. A process as claimed in Claim 1 or Claim 2 in which the reaction is carried out at a temperature of from -20 to -35 C.

4. A process as claimed in any of Claims 1 to 3 in which the liquid carrier is selected from kerosene, tripropylamine anhydrous liquid ammonia, N, N, N', N'-tetramethyl-1, 3-butane diamine and dimethylamine.

5. A process as claimed in any of Claims 1 to 4 in which the alkali metal amide is sodium amide.

6. A process as claimed in any of Claims 1 to 5 in which the hydrazine is separated off by distillation.

7. A process as claimed in Claim 1 substantially

Claims

**WARNING** start of CLMS field may overlap end of DESC **. dissolved in 500 g of xylene chilled to a temperature of - 20"C. The reaction mixture is then stirred for another 20 minutes and left standing for about 20 minutes to return to room temperatures. In the meantime, ammonia distills off. On completion of refluxing, the residue is cooled to a temperature of 20"C and the precipitated deposit is filtered off. The filtrate and the deposit are then subjected to fractional distillation under reduced pressure, giving phenyl hydrazine. Phenyl hydrazine may similarly be obtained by replacing the xylene used here with the same quantity of dimethyl aniline. EXAMPLE 11 The procedures of Examples 6 to 10 are repeated with the difference that the filling is not saturated with liquid ammonia. Although the required hydrazine product (I) is obtained in every case, the yields are from 10 to 25%, by weight, lower than in cases where the carrier liquid is saturated with ammonia. WHAT I CLAIM IS:

1. A process for the preparation of a hydrazine corresponding to the following formula:

7. A process as claimed in Claim 1 substantially as herein described.

8. A process as claimed in Claim 1 substantially as herein described with reference to

any one of the Examples.

9. A compound corresponding to general formula (I) as defined in Claim 1 when prepared by a process as claimed in any of Claims 1 to 8.