DE2341928C3 - Process for the production of metal-containing azodicarbonamides - Google Patents

Description

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Azodicarbonamide has so far been largely used as marriage-δο mixed blowing agents have been used for plastics and rubbers; it is used as an excellent blowing agent regarded as immediately after heating it supplies gaseous nitrogen and its thermal decomposition products are not flammable and it is not itself toxic.

However, this compound has too high a thermal decomposition temperature, and the purified itself Product decomposes at 230 C; therefore, in US Pat. No. 28 04 435, the addition of I to 5 Weight percent hydrazodicarbonamide has been suggested to reduce the decomposition temperature to 205 ° C Reduce. The reduced decomposition temperature is also still too high when using the Mixture as a blowing agent. If azodicarbonamide z. B. as a blowing agent for rubber, polyethylene, ethylene / Vinyl acetate copolymers, polyvinyl chloride and similar high molecular weight materials with low If you use softening points, it is difficult to find a compatibility between your level Achieve softening of the high molecular weight material and the amount of gas formed by the blowing agent, therefore decomposition, scorching or aging of the high molecular weight material occurs, which is disadvantageous Limitations of the field of application of the compound as a blowing agent leads.

Recently, there has been a problem of the high decomposition temperature of the azodicarbonamide blowing agent by using a biurea, urea, metal stearate, dibutyltin maleate or the like Connection as a blowing aid or by application a chromium salt on the crystal surfaces of the azodicarbonamide to adjust the decomposition temperature encountered. However, the decomposition temperature can only be up to due to this expansion aid can be adjusted to a certain extent. Furthermore, the effect is through the entire mass of the high molecular weight Material into which it is incorporated is insufficient and uniform enough as blowing agents and Bulking agents both are diluted by the high molecular weight material. It's hard to expand one Body with a uniform, fine cell or pore structure by increasing the amount of expansion aid to achieve, since the increased amount of expansion aid makes the cell or pore structure brittle and has adverse effects on the properties of the expanded body so formed.

It was already known to produce azodicarbonamide by oxidation of hydrazodicarbonamide, and the current industrial processes are generally a bichromate oxidation process and a chlorine oxidation process been classified. Of these two methods, the former is versus the latter superior because the azodicarbonamide so produced has better properties for use as a blowing agent for low-softening materials compared to that formed by the latter method Material has. Unfortunately, the first-mentioned process also provides chromium sulfate as an undesirable by-product a substantial amount of sulfuric acid and therefore requires extensive equipment and treating agent to treat the waste water, which makes the bichromate oxidation process more expensive. The Chloroxidation process is more advantageous in terms of cost, but it provides an azodicarbonamide, that for use as a blowing agent for high molecular weight materials with low softening points Unsuitable because of its high decomposition temperature.

The aim of the present invention is to provide a method for producing metal-containing Azodicarbonamide with reduced decomposition temperature and improved properties.

A method has been developed for the production of metal-containing azodicarbonamide crystals by oxidation of hydrazodicarbonamide in aqueous suspension

found with hydrogen peroxide and in the presence of a bromine compound that is characterized is that the oxidation with hydrogen peroxide in the presence of bromine or a bromine compound, which releases bromine ions in the aqueous reaction solution, in an amount of 0.1 to 5 parts by weight per 100 parts by weight of hydrazodicarbonamide, 5 to 45 percent by weight of a water-soluble acid and 0.1 to 50 percent by weight, based on the reaction mixture, of a sulfate, nitrate, chloride or oxide of at least one metal from the group of zinc, aluminum, tin, chromium, tungsten, manganese, cobalt and nickel at a temperature of 30 to 85 ° C.

So it is possible to use an azodicarbonamide with the necessary properties as a chemical blowing agent for high molecular weight materials with a low softening point without the discharge of harmful substances To obtain wastewater and the use of a treatment plant for the same.

It is not known in what form the metal compound contained in the azodicarbonamide crystals is. It is only known that this cannot be washed out of the crystals, which leads to it indicates that it is not only deposited on the surface, but is in the crystal. Whether you randomly located in the crystal or in the form of a chemical bond is not known.

The metal compound used in the process according to the invention includes the sulfates, nitrates, chlorides and oxides of chromium, manganese, zinc, cobalt, nickel, tungsten, aluminum and tin, the Compounds of chromium, manganese, cobalt, zinc, nickel and tungsten and especially those of Chromium, manganese and zinc are particularly effective. The concentration of the metal compound in the oxidation system is a key factor; it is 0.1 to 50 percent by weight, in particular 0.1 to 5 percent by weight for a water insoluble compound, and 15 to 50 percent by weight for intrinsically water soluble Connection. The concentration of the metal compound is largely determined by adjusting the acid concentration influenced in the oxidation system. The amount contained in the crystals of azodicarbonamide the metal compound can be adjusted by adjusting the appropriate concentrations of Metal compound and acid, which regulates the decomposition temperature of the product. In the The following Tables I and II are changes in the decomposition temperature and ash content with the changed Concentration of chromium sulfate as a metal compound and sulfuric acid as an acid. The effect on the obtained containing a very small amount of metal compound in the crystal Azodicarbonamide, and its decomposition temperature, varies depending on the nature of the contained metal compound and its amount. It is therefore necessary to have the desired properties of the modified azodicarbonamide according to the resin and the other starting materials, as well as the Working conditions.

As a bromine compound you can use any bromine-containing compound that is in water in a Oxidation system with the release of bromine ions dissolves, such as bromine; Hydrogen bromide; Sodium bromide, Potassium bromide and lithium bromide, ammonium bromide and quaternary ammonium bromide, and the like quaternary organic ammonium bromides such as tetramethylammonium bromide and tetraethylammonium bromide. The bromine compound is used in an amount of 0.1 to 5, preferably 0.5 to 2 parts by weight per 100 parts by weight of hydrazodicarbonamide used, since an amount of 0.1% by weight is not sufficient to achieve a noticeable effect, while an amount above 5 percent by weight does not add any additional results in a positive effect.

As hydrogen peroxide, one can buy one

ίο available aqueous hydrogen peroxide from 35 to Use 60 percent by weight per se, or adjust its concentration accordingly if necessary. The hydrogen peroxide is used in an amount of usually 1.0 to 2.0 mol, preferably 1.05 to 1.5 moles per mole of hydrazodicarbonamide used. In the process according to the invention, as a by-product only water formed during the oxidation. In the reaction system is due to the use of Hydrogen peroxide as the only oxidizing agent none

* o other pollution present. Therefore, the Reaction mixture after separation of the azodicarbonamide crystals obtained and after adjustment of the Concentration of the constituents can be reused. It is thus in the method according to the invention

=> 5 not necessary to treat the wastewater like in the case of the bichromate oxidation process.

Egg is necessary in the method according to the invention, in addition to the bromine compound, an acid as a catalyst

3c to use. Suitable acids include strong ones Mineral acids such as hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and water-soluble organic acids of at least the same strength as acetic acid, e.g. B. formic acid, acetic acid, Propionic acid and maleic acid. The acid is used in a concentration of 5 to 45 percent by weight, preferably 5 to 15 percent by weight, in the case of hydrochloric acid, hydrobromic acid and phosphoric acid and nitric acid, from 10 to 40 percent by weight, in the case of sulfuric acid and from 5 to 20 percent by weight used in the case of water-soluble organic acids. Since hydrogen bromide also acts as an acid, it is not necessary to use another oxidation system as a bromine compound Add acid.

The concentration of the hydrazodicarbonamide is not critical as long as a stirrable slurry is used is formed; nevertheless, the concentration is preferably between 5 to 45 percent by weight, in particular 15 to 30 percent by weight.

The reaction temperature is an important factor in the production of the metal-containing azodicarbonamide crystals, d. H. in the formation of crystal structures from metal compounds and azodicarbonamide; she lies usually between 30 to 85 ° C., preferably between 30 to 60 ° C. In the following Table III the change in decomposition temperature and ash content with the change in reaction temperature in a system with chromium sulphate and sulfuric acid

⁶ <> posed. The reaction time is usually between 10 minutes and 10 hours, preferably between 30 minutes and 4 hours. The amount of metal compound contained in the azodicarbonamide crystals, namely ash content and decomposition temperature of the modified azodicarbonamide, is largely influenced by the concentration of metal compound and acid in the reaction system and by the reaction conditions (cf. Tables I to III).

Table I.
Influence of the chromium sulfate concentration

Chromium sulfate concentration
Weight percent

Decomposition temperature
⁰ C

Ash content percent by weight

15.7 200.5 0.07 23.5 199 0.08 3}, 3 196 0.11 39.1 195 0.14

IO

H ₂ SO ₄ concentration 20.6 percent by weight; Reaction temperature 40 ± 1.5 ^{J C}

Table II
Influence of the H ₂ SO ₄ concentration

H ₁ SO, Kon Decomposition Ashes centering temperature salary Weight percent ⁰ C Weight percent 13.1 201 0.07 20.6 196 0.11 28.9 193 0.18 33.3 192.5 0.25

Cr sulfate concentration 31.3 percent by weight; Reaction temperature 40 ± 1.5 C

Table III Influence of the reaction temperature

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Reaction Decomposition Ashes temperature temperature salary ⁰ C ° C Weight percent 3O ± 1.5 194 0.21 40 ± l, 5 196 0.11 50 ± 1.5 198 0.10 60 ± 1.5 199 0.08

Cr sulfate concentration 31.3 percent by weight; H ₂ SO ₄ concentration 20.6 percent by weight

Although with the other suitable metal compounds there are certain differences in the numerical ^ A similar trend is observed.

Since in the process according to the invention for the production of azodicarbonamide by oxidation of hydrazodicarbonamide the only by-product formed is water and no other impurity is formed is, the reaction mixture can after separation of the product after a simple adjustment of the Components, e.g. B. by concentration, can be reused. Hence a plant for treatment of the waste water, as it is required in the bichromate oxidation process, is not necessary. Still receives azodicarbonamide crystals containing a metal compound due to the presence of the metal compound in the reaction system. Hence deliver the crystals of the metal-containing azodicarbonamide produced by the process according to the invention Expanded bodies with a smooth surface and a uniform microporous or -cellular structure, if you use them as a chemical blowing agent for rubbers, polyethylene, ethylene / vinyl acetate copolymers, Polyvinyl chloride and similar high molecular substances with low softening points used.

The following examples illustrate the present invention. All parts and percentages are unless otherwise indicated, parts by weight and percent by weight.

example 1

236 g of hydrazodicarbonamide were suspended in a mixture (sp. G. 1.4585) of 705 g of a 40% strength aqueous chromium sulfate solution and 196 g of 95% strength sulfuric acid to form a slurry. Then 1.6 g of bromine was added. To the resulting slurry, 136 g of 60% strength aqueous hydrogen peroxide were then added dropwise with stirring over the course of 30 minutes. The reaction temperature was kept at 40 ± 1.5 ° C. When the addition of the aqueous hydrogen peroxide had ended, the mixture was stirred for a further 1.5 hours. Then the reaction mixture was filtered, washed with water and dried; 229 g (98.5 mol percent of the theoretical yield) of azodicarbonamide with a decomposition temperature of 196 ° C., an ash content of 0.11% and a gas yield of 225 cm ³ / g (1 atm and 20 ° C.) were obtained in this way.

Example 2

The filtrate of the reaction mixture from Example 1 was on a spec. Weight d ³⁰ = 1.4585 concentrated; then 236 g of hydrazodicarbonamide was suspended therein to form a slurry. 9 g of 40% strength hydrogen bromide were added to the suspension, then 136 g of 60% strength aqueous hydrogen peroxide were added dropwise over the course of 30 minutes with stirring. The reaction mixture was kept at 40 ± 1.5 ° C. Thereafter, the mixture was further stirred for 1.5 hours, filtered to collect the crystals, which were washed with water and dried. 228 g (98.5 mol percent of the theoretical yield) of crystals of azodicarbonamide with a decomposition temperature of 96 ° C., an ash content of 0.11% and a yield of 225 cm ³ / g (STP) were obtained; ie the quality was the same as that of Example 1.

Example 3

In a mixture of 705 g of a 40% strength aqueous nickel nitrate solution and 196 g of 95% strength sulfuric acid, 236 g of hydrazodicarbonamide were suspended to form a slurry, to which 4.5 g of sodium bromide were added. To this end, 136 g of 60% strength aqueous hydrogen peroxide were added dropwise with stirring over the course of 30 minutes. The reaction temperature was maintained at 35 ± 2.0 ° C. The mixture was stirred for a further 2.5 hours, then the reaction mixture was filtered and the crystals thus obtained were washed with water and dried. 228 g (98.5 mol percent of the theoretical yield) of a crystallized azodicarbonamide with a decomposition temperature of 20PC, an ash content of 0.15% and a gas yield of 195 cm ³ / g (STP) were thus obtained.

Example 4

23.6 g of manganese dioxide were added to a mixture of 718 g of water and 196 g of 95% strength sulfuric acid solved. Then 236 g of hydrazodicarbonamide were suspended therein to form a slurry. The slurry was mixed with 5 g of ammonium bromide

mixed, then 136 g of 60% strength aqueous hydrogen peroxide were added dropwise with stirring over the course of 1.5 h. The reaction temperature was maintained at 35 ± 5 ° C. After stirring for an additional 1.5 hours, the mixture was filtered and the crystals obtained were washed with water and dried. 228 g (98.5 mol percent of the theoretical yield) of a crystallized azodicarbonamide with a decomposition temperature of 2OTC, an ash content of 0.2% and a gas yield of 225 cm ³ / g (STP) were thus obtained.

Example 5

236 g of hydrazodicarbonamide were suspended in a mixture of 500 g of 40% strength aqueous cobalt chloride and 300 g of 35% strength hydrochloric acid to form a slurry. 1.6 g of bromine were added to this. 136 g of 60% strength aqueous hydrogen peroxide were added dropwise to the resulting slurry with stirring over the course of 1.5 hours. The reaction temperature was kept at 30 ° C. After the addition of hydrogen peroxide had ended, the reaction temperature was increased to 60 ° C. and the mixture was stirred for a further 1.5 h. The mixture was then filtered, and the crystals obtained were washed with water and dried, thus obtaining 222.8 g (96 mol% of the theoretical yield) of a crystallized azodicarbonamide having a decomposition temperature of 203 ° C., an ash content of 0.10% and a gas yield of 194cm ³ / g (STP).

For comparison purposes, the procedure was repeated without using a transition metal compound; 228 g (98.5 mol percent of the theoretical yield) of azodicarbonamide with the high decomposition temperature of 210 ° C., an ash content of 0.03% and a gas yield of 190 cm ³ / g (STP) were obtained in this way.

Example 6

The filtrate of the reaction mixture from Example 1 was on a spec. Weight d ³⁰ = 1.4585 concentrated, then 236 g of hydrazodicarbonamide were suspended therein to form a slurry. To this, 9 g of 40% strength hydrobromic acid were added and then 136 g of 60% strength aqueous hydrogen peroxide were added dropwise over the course of 30 minutes with stirring. With the addition of hydrogen peroxide, the temperature of the reaction mixture was brought from 35 to 60 ° C. by heating. The stirring was continued for 1.5 hours , then the reaction mixture was filtered to collect the crystals, which were washed with water and dried. 228 g of crystallized azodicarbonamide (98.5 mol percent of the theoretical yield) with a decomposition temperature of 198 ° C., an ash content of 0.10% and a gas yield of 220 cm ³ / g (STP) were obtained in this way.

Example 7

236 g of hydrazodicarbonamide were suspended in a mixture of 705 g of 50% strength aqueous zinc chloride solution and 196 g of 95% strength sulfuric acid to form a slurry. To this, 6 g of E'om were added, whereupon 136 g of 60% strength aqueous hydrogen peroxide were added dropwise over the course of 1.5 hours while stirring, the temperature nsf 50 ± 2 ° C. being maintained. The stirring was then continued for 1.5 hours, the reaction mixture was filtered to collect the crystals, which were washed with water and dried. This gave 229 g (98.7 mol percent of the theoretical yield) of a crystallized azodicarbonamide with a decomposition temperature of 199 ° C., an ash content of 0.13% and a gas yield of 232 cm ³ / g (STP).

Examples 8 to 16

In a mixture of 705 g of an aqueous metal salt solution with the concentration given in Table IV and 196 g of 95% strength sulfuric acid, 236 g of hydrazodicarbonamide were suspended to form a slurry. 1.6 g of bromine were then added and then 136 g of 60% strength aqueous hydrogen peroxide were added dropwise over the course of 30 minutes with stirring. The reaction mixture was kept at 40 ± 1.5 ^r C. The mixture was then stirred for a further 1.5 hours, the reaction mixture was filtered to obtain the crystals and these were washed with water and dried.

The decomposition temperatures of the various modified azodicarbonamides in those thus obtained Crystals are listed in Table IV.

Table IV

example

Metal connection

Concentrate.

/O

Decomposition temperature ° C

8th Chromium chloride 12.8 198 9 Chromammonium alum 19.2 197 10 Manganese chloride 38.3 195 11th Manganese nitrate 51.1 195 12th Zinc sulfate 25.6 197 13th Tungsten oxide WO ₃ 1.3 203 14th Alumina 1.3 204 15th Aluminum chloride 38.3 202 16 Tin oxide SnO ₂ 1.3 204 By S pi el 17

Manufacture of a Polyäi ^ vlenschaumes

A mixture of 100 parts of high-pressure polyethylene with a melt index of 4 and a DicTite of 0.918 mk 1.0 part of dicumyl peroxide and 10.0 parts of that prepared in Example 1 «; Azodicarbonamids was thoroughly kneaded on a roller mill at 100 to 110 ° C and given a 5 mrr. thick film calendered. This was heated in a salt bath at 200 ^° C. for 2 minutes to achieve a cellular film with a density of 0.085 g / cm ³ with a uniform, fine cell structure and of white color.

The above method using an azodicarbonamide with a Zersetznngstemperatui of 210 ⁰ C and an ash content of 0.03%, prepared without using an MetaHverbindung was repeated, then one nril large cells Urd received a cellular foil small cells and slightly gel stained surfaces.

Example 18 Manufacture of a plasticized PVC foam

A partially expanded, plasticized polyvinyl chloride sheet 0.3 mm thick was made into conventional Way from a mixture of 1ΟΘ Teflon polyvinyl chloride, 80 parts of dioctyl phthalate, 3 parts of a Heat stabilizer (organic Ca-Zn complex and 3 parts of the Azodi prepared in Example 7

609 «53/29

652f

carbonamide manufactured. The film was applied to a fabric base and heated ^{to 200 ° C. in an oven for 90 seconds.} Thus, a cellular polyvinyl chloride leather with a thickness of 0.9 mm and a uniform fine cellular structure and of a white color was obtained.

When the above procedure was repeated using an azodicarbonamide, following a conventional Process was produced, then one obtained an artificial leather with more uniform, but coarser cellular Structure and completely light yellow in color.

Claims (8)

Patent claims: 1. A process for the production of metal-containing azodicarbonamide stones by oxidation of hydrazodicarbonamide in aqueous suspension with hydrogen peroxide and in the presence of a bromine compound, characterized in that the oxidation is carried out with hydrogen peroxide in the presence of bromine or a bromine compound which releases bromine ions in the aqueous reaction solution, in an amount of 0, 'to 5 parts by weight per 100 parts by weight of hydrazodicarbonamide, 5 to 45 parts by weight of a water-soluble acid and 0.1 to 50 percent by weight, based on the reaction mixture, of a sulfate, nitrate, chloride or oxide of at least one metal from the group of zinc, aluminum, tin, chromium, tungsten, manganese, cobalt and nickel at a temperature of 30 to 85 ° C. * ° 2. The method according to claim 1, characterized in that a water-soluble metal compound is used in a concentration of 15 to 50 percent by weight, based on the reaction mixture. * 5 3. The method according to claim 1, characterized in that there is a water-insoluble metal compound in a concentration of 0.1 to 5 percent by weight, based on the reaction mixture, begins. 4. The method according to claim 1 to 3, characterized in that hydrogen peroxide is in an amount of 1.0 to 2.0 mol per mol of hydrazodicarbonamide is used. 5. The method according to claim 1 to 4, characterized in that the acid is hydrochloric acid, Hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid or a water soluble one organic acid is used. 6. The method according to claim 5, characterized in that there is sulfuric acid as the acid in one Concentration of 10 to 40 percent by weight is used. 7. The method according to claim 1 to 6, characterized in that the hydrazodicarbonamide used in a concentration of 5 to 45 percent by weight. 8. Use of azodicarbonamide according to claim 1 to 7 as a blowing agent. 50