DE3323135A1 - STABILIZED RED PHOSPHORUS AND METHOD FOR STABILIZING RED PHOSPHORUS - Google Patents

Description

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description

The invention relates to red phosphorus, which is anti-oxidation is stabilized.

It is known that red phosphorus undergoes a chemical reaction when stored in a humid atmosphere, with various Phosphoric acids, mainly phosphoric acid and phosphoric acid, as well as phosphine are formed. The formation of the highly toxic phosphine gives rise to dangerous working conditions and the formation of phosphoric acid and phosphoric acid is undesirable for the finite use of red phosphorus. Aluminum in the form of hydroxide has been used in large quantities Scope used to stabilize red phosphorus against such oxidation. However, it will be relative Large amounts of aluminum are required to achieve a significant degree of stabilization to reach.

An additional problem encountered with prior art treatment with aluminum is that the Product is difficult to process. A layer of aluminum oxide is placed on the particles of red phosphorus an aqueous dispersion of these particles is precipitated, and then the treated red phosphorus is filtered off and dried. Effective filtration of the treated red phosphorus is difficult to achieve due to gelation of the aluminum hydroxide and large amounts of water are retained by the aluminum hydroxide.

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Recently, US Pat. No. 4,115,522 proposed stabilization by using the salts of aluminum, To effect magnesium, calcium or zinc with orthophosphoric acid. The aluminum salt is most effective, but here too relatively large quantities are required.

According to an even more recent proposal of US Pat. No. 4,210,630, improved stabilization can be achieved by using lead hydroxide can be achieved in combination with aluminum hydroxide. According to a further suggestion in accordance with CA-PS 1097 152, anyone can Particles of red phosphorus are artificially covered with a thin film of cured melamine-formaldehyde resin.

It has now surprisingly been found that titanium dioxide and titanium phosphate are particularly effective stabilizers are of red phosphorus and can be used in lesser amounts than when treated with aluminum hydroxide be used. In addition, if the titanium dioxide and titanium phosphate can be applied by precipitation from an aqueous medium the treated red phosphorus can be filtered easily and quickly, in contrast to treatment with Aluminum hydroxide.

In contrast to the red phosphorus treated with aluminum hydroxide, the red phosphorus treated with titanium dioxide can be heated according to the invention to elevated temperatures up to 300 ° C without water is developed, whereby the Product is suitable to be added to plastics that are processed at high temperatures.

The red phosphorus which is treated by titanium dioxide or titanium phosphate according to the invention is present in particulate form a particle size of at most 2 mm and preferably about 0.01 to 0.15 mm. The particles are made of red phosphorus brought to a homogeneous mixture with titanium dioxide or titanium phosphate. The amount of the titanium compound can be from about 0.05 to

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about 2.0% by weight in terms of titanium.

The treatment of the red phosphorus with titanium dioxide can be carried out in the aqueous phase in order to prevent precipitation to effect hydrated titanium dioxide on the red phosphorus, after which it is dried and dehydrated. In this procedure For example, the red phosphorus particles can be suspended in water and the resulting slurry can on about 60 to 95 ° C, preferably about 80 to 90 ° C. The heated slurry will gradually increase with what is needed Amount of a water-soluble titanium salt mixed, e.g. B. with titanium sulfate or titanium tetrachloride to achieve the desired To achieve the degree of treatment at a slightly acidic pH. The pH of the slurry is then adjusted to a value of im Range from about 2 to about 6 adjusted to prevent precipitation of the hydrated titanium dioxide from the particles of red Effect phosphorus. The mixture is filtered and the treated red phosphorus is dried and dehydrated at a temperature of about 100 to about 130 C in a vacuum oven.

Treatment of the red phosphorus particles by titanium phosphate can in the aqueous phase in a manner analogous to the treatment with titanium dioxide in the aqueous phase, as just mentioned described, with the exception that orthophosphoric acid or a water-soluble salt of orthophosphoric acid, z. B. sodium dihydrogen phosphate, and titanium sulfate can be added to the slurry instead of titanium sulfate or titanium tetrachloride can be added as such.

An alternative procedure for treating the red phosphorus with titanium dioxide is through formation of titanium dioxide in the vapor phase. Such a practice is beneficial when the source of the titanium is easy hydrolyzable organic titanate, e.g. B. those easily hydrolyzable organic titanates from DuPont,

which are sold under the names Tyzor TPT (tetraisopropyl titanate) and Tyzor TBT (tetrabutyl titanate). In this Process can transfer the liquid titanate through an atomizing nozzle into a stream of hot dry air at one temperature from about 150 to about 180 ° C are metered in, wherein this current is then brought into contact with the red phosphorus particles. Alternatively, a preheated Stream of nitrogen or other suitable gas can be passed through the liquid titanate, and the stream obtained be brought into contact with the red phosphorus. The contact between the vapors of the organic titanate emitted by the Gas flow are carried, and the particles of the red phosphorus causes adsorption of the organic titanate on the Particles of red phosphorus.

Similarly, some inorganic titanium compounds that readily hydrolyze, e.g. B. Titanium tetrachloride, for steam treatment can be used. The red phosphorus can be combined with titanium tetrachloride in a closed container Ambient temperature are mixed in order to adsorb the titanium tetrachloride with the particles of red phosphorus cause.

The red phosphorus particles that carry the titanium compound are then exposed to moisture to protect the Hydrolyze titanate and form a coating of titanium dioxide on the surface of the red phosphorus particles. The by-products of hydrolysis are removed by heating under vacuum to avoid odor formation during storage.

Treatment of the red phosphorus particles with titanium tetrachloride or another easily hydrolyzable titanium compound, e.g. B. hydrolyzable organic titanates, can be used to remove residual moisture from the red phosphorus. In this procedure the titanium tetrachloride with the particles of red phosphorus in

a closed container at ambient temperature for 1 to 2 hours long treated. The reaction occurs between the moisture in the particles of red: around phosphorus and the titanium tetrachloride, which the titanium dioxide biIdol.

The amount of titanium tetrachloride that is used depends on the moisture content of the red phosphorus particles. Anything Excess titanium tetrachloride can be used along with HCl as a by-product with dry air or dry nitrogen be driven out. Removing moisture from red phosphorus in this way not only stabilizes the red one Phosphorus, but also allows the red phosphorus to dry out without heating to excessively high temperatures.

Red phosphorus, that with titanium dioxide or titanium phosphate according to the invention has been treated is considerably more stable than one that has been treated with aluminum phosphate, aluminum hydroxide or a combination of aluminum and ßleihydruxid in the same amount treated by titanium and aluminum. Titanium dioxide is slightly better than titanium phosphate in stabilizing of red amorphous phosphorus.

Although it is known to improve the stability that becomes erruic: lil with aluminum hydroxide, by using a combination von B. '. Egg hydroxide (see. US Pat. No. 4,210,630) has been found that the combination of titanium dioxide with aluminum or Lead oxides show no greater stability than with titanium dioxide alone, so titanium dioxide is preferred according to the invention to use alone or the titanium phosphate alone.

Red phosphorus that has been treated in the manner according to the invention takes much less time to filter and shows a much lower retention force for water than red Phosphorus that has been treated with aluminum hydroxide, which significantly reduces the processing time causes, which is required according to the invention, compared to the

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State of the art.

The improved stability achieved according to the invention results in a significant reduction in acid and phosphine production when the treated red phosphorus is stored .

The invention is illustrated in more detail by the following examples. In the examples reference is made to the accompanying drawings, in which:

Fig. 1 is a graphical representation of the effect of titanium dioxide and of aluminum hydroxide on oxidation stability of red phosphorus represents

Figure 2 is a graphical illustration of the effect of titanium and aluminum compounds on the oxidation stability of red phosphorus;

Figure 3 is a graph showing the effect of titanium dioxide in combination with other hydroxides Metals on the oxidation stability of red phosphorus is, and

4 shows the graphic representation of the effect of the ρII- WerLa in the precipitation of TiLandioxid on the Oxidation stability, of red phosphorus is.

example 1

Red amorphous phosphorus in a particle size of usually 0.15 to 0.01 mm was dissolved in water to a concentration suspended by about 25 wt .-% red amorphous phosphorus and the resulting slurry heated to about 80 to 90 ° C.

Alternating amounts of titanium sulfate, corresponding to 2,000, 3,000, and 5,000 ppm titanium, were added to samples of the slurry and the pH of the slurry adjusted to 3 µm then precipitate hydrated titanium dioxide. The suspension was stirred for a further hour, the mixture was filtered and the filter residue at about 100 ° C for about 16 h in a vacuum oven dried.

The samples of treated red phosphorus were tested for oxidative stability and the results compared to those for untreated red phosphorus and treated with aluminum hydride compared to red phosphorus. The treatment with aluminum hydroxide would be done with the use of aluminum oxide pH 9 was carried out for the precipitation of aluminum hydroxide on the red phosphorus in an amount corresponding to 2,000 ppm Al .

The oxidation stability of the red phosphorus was tested by storing samples at 70 ° C. under 100 % relative humidity and measuring the acidity, expressed as phosphoric acid, by titration. The results obtained are shown in FIG. 1.

As can be seen from Fig. 1, red amorphous phosphorus treated with titanium dioxide is extremely stable with amounts of titanium of 3,000 ppm and more. Treatment with titanium dioxide at the same level of concentration (2,000 ppm) produces a greater one Stability compared to red phosphorus treated with aluminum.

It has also been observed that the amount of PH ₃ evolved from the red phosphorus also decreases significantly upon treatment with titanium dioxide.

Example 2

Red phosphorus, with a typical particle size of 0.15 to 0.01 mm, was boiled with caustic soda for removal of unreacted yellow phosphorus treated with titanium and aluminum compounds using the procedures according to Example 1. Treatment with titanium phosphate was added to the slurry by adding sodium hydroxide and hydrogen phosphate along with titanium sulfate, and adjusting the pH to about 3.

The treated samples were tested for acid development under the conditions given in Example 1, and the Results are shown graphically in the drawing Fig. 2. As can be seen from Fig. 2, the red amorphous phosphorus, treated with titanium dioxide or titanium phosphate is considerably more stable than that treated with aluminum phosphate or a combination of aluminum and lead hydroxides has been treated with the same contents of titanium and aluminum (3,000 ppm). In the case of the aluminum phosphate treatment, the amorphous red phosphorus was considerably less stable when it was treated at pH 7 than when treated at pH 3.2.

The treated samples were also checked for development of phosphine and compared to untreated samples. Portions of 1 g were stored in glass containers (69 cm) with a partition, through which by means of a syringe directly Samples could be taken. After repeated stirring and standing at room temperature, the phosphine concentration became (expressed in ppm weight of red phosphorus) by gas chromatography with a flame photometry Detector checked. The results obtained are shown in Table I below.

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Tabel

Sample treatment test duration PH conc

No. (days) (ppm)

1 RAP ⁺⁾ + 3000 ppm Al as AlPO ₄ , 6 2.12 pH 7

2 as 1, but treatment at 6 0.27 pH 3.2

3 RAP + 3000 ppm Ti as TiO ₂ 6 0.33

4 RAP + 3000 ppm Ti as Ti phosphate 6 0.38

5 RAP + 30J0 ppm Al as Al (OH) ₃ 6 0.12 + 8500 ppm Pb as Pb (OH) ₂

6 untreated IiAP 6 2.23

7 usual RAP 10 8.06

+) RAP is red amorphous phosphorus

As can be seen from the results in Table 1, the Phosphine evolution greatly reduced by treating the red amorphous phosphorus with both aluminum and with Titanium compounds.

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Example 3

There were samples of red amorphous phosphorus with a typical particle size of 0.15 to 0.01 now with a combination of Titanium dioxide and other metal compounds treated, among Using the procedure of Example 1 with the appropriate Salts have been used to cause precipitation of the other metals in hydroxide form.

The treated samples were tested for acid development under the conditions mentioned in Example 1 for comparison with untreated samples, and the results are shown in the drawing in FIG. As can be seen from the results of Fig. 3 for comparison of Figs. 1 and 2 shows a treatment of the red amorphous phosphor with a Combination of TiO “and lead or aluminum hydroxide none better stability than treatment with TiO ,, alone. In the case of copper hydroxide, the acid evolution was very high observed even more quickly than by the red phosphorus itself.

The treated samples were also checked for phosphine development, according to the procedure of Example 2 and for comparison with untreated samples. The results are in the reproduced in Table II below.

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Table II

Sample treatment test duration PH ^ conc

No. (days) (ppm)

3000 ppm Ti as TiO ₂ +

4000 ppm Pb as Pb (OlI) ₂ at 6 1.84

pH 9

3000 ppm Ti as ¹ Vi-O ₂ +

8000 ppm Pb as Pb (OH) at 6 0.32

pH 9

3000 ppn. Ti as TiO ₂ +

2000 ppn Cu as Cu (OH) ₂ at 6 0.015

pH 9

3000 ppn Ti as TiO ₂ + 6th 2.21 2000 ppr Al as Al (OH) ₃ at pH 9 6th 0.33 3000 ppm Ti as TiO ₂ 6th 2.23 untreated RAP

The results in Table II show that there is no improvement in achieving reduced phosphine production in the presence of lead, and indeed more phosphine is evolved than with titanium dioxide alone. Treatment with a combination of ¹ ^ ¹ IO ₂ and copper hydroxide Cu (OH) ₂ produced a considerable decrease in the formation of phospline, but, as mentioned above, leads to a considerable increase in the formation of acid.

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Example 4

The filtering properties of untreated red amorphous phosphorus, red phosphorus _{treated with Al (OH) 3} , and red phosphorus _{treated with TiO 2} were compared, in each case the particles were slurry for 1 hour at 80-85 Stirred ° C, cooled to 60 ° and filtered on a laboratory vacuum filter. The time required for filtration and the water content of the filter cake were determined. The results are given in Table III below.

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III

sample
No. treatment as Filtration
duration (see) Water return
attitude
(% By weight of
Cake) 1 3000 ppm Al pH 9 280 24.7 Al (OH) ₃ at

3000 ppm Ti than at pH 3

3000 ppm Ti than at pH 4

untreated RAP

149

143

126

18.6 19.3 13.7

As can be seen from the results in Table III, the untreated red amorphous phosphorus has the best filtering properties, but the red phosphorus treated with TiO 2 at pH 3 or 4 took significantly less time to filter and retained a smaller amount of water when red phosphorus had been treated with with Al (OH) _3.

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Example5

There were samples of red amorphous phosphorus in a typical Particle size from 0.15 to 0.01 mm and a moisture content of about 0.20% carefully with titanium tetrachloride mixed in a closed container at room temperature for 2 h. The titanium tetrachloride was in hydrolyzed red phosphorus, with the formation of titanium dioxide on the phosphorus. Excess titanium tetrachloride and the by-product HCl was removed by purging with dry air. The treated samples were determined to be acidic tested under the conditions of Example 1 and with the applied T; .tan content of 2400 ppm and 3100 ppm, the acid development was, as found comparable to that of samples dia containing 3000 ppm titanium by the solution method of Example I.

The moisture content of the treated particles of red Phosphorus worc .; also determined, and the results are reproduced in Table IV below.

Table IV

Sample treatment moisture content

No. (wt .-%)

1 3100 ppm Ti 0.08

2 2550 ppm Ti 0.05

3 2400 ppm Ti 0.05

The lower content of moisture in the samples is comparable to the moisture level of samples of red phosphorus, which ^{had been dried in a vacuum oven at 100 °} C. for three days.

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Example 6

The effect of the pH of the precipitation of TiO according to FIG The procedure of Example 1 for the stability of treated red amorphous phosphorus was tested. The oxidation stability obtained according to the experimental method of Example 1 are shown graphically in the drawing, FIG.

As can be seen from fig. 4, the red phosphorus treated at pH 3 is very stable to oxidation, but the stability decreases with increasing pH values during the precipitation of TiO ₂ .

In summary, the invention results in a new red one amorphous phosphorus with improved stability against oxidation by treatment with titanium in the form of titanium dioxide or Titanium phosphate. Modifications within the scope of the invention are possible.

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Claims (13)

Claims 1. Preparation consisting of a homogeneous mixture of red phosphorus and a stabilizer, characterized in that the red phosphorus has a particle size of at most 2 mm and an oxidation stabilizer in an amount effective for stabilization. ¹ made of titanium in the form of titanium dioxide or titanium phosphate. 2. Preparation according to claim 1, characterized in that the titanium is present in an amount of at least 0.05 weight percent. 3. Preparation according to claim 1 or 2, characterized in that titanium in an amount of 0.05 to 2.0 wt .-% is present. 4. Preparation according to Claim 1 to 3, characterized in that the particle size of the red phosphorus is 0.01 to 0.15 mm amounts to. 5. A process for the preparation of a stabilized against oxidation red phosphorus, characterized in that a homogeneous mixture of particulate red phosphorus and an amount effective to stabilize oxidation Titanium dioxide or titanium phosphate is formed. 6. The method according to claim 5, characterized in that the mixture is formed by (1) Forming a slurry of particles of red Phosphorus with a particle size of no more than about 2 mm, (2) heating the slurry to a temperature of about 60 to about 9 5 ° C, (3) adding a titanium compound in an amount sufficient to provide stabilization against oxidation, to the heated slurry of the particles of red phosphorus, the titanium compound being such that titanium dioxide is present in the slurry or titanium phosphate precipitates, (4) Adjust the pH of the slurry to one Value of about 2 to 6 for the precipitation of titanium dioxide or titanium phosphate on the particles of red phosphorus , (5) separating the treated red phosphorus particles from the slurry and (6) drying the separated treated particles. 7. The method according to claim 6, characterized in that the slurry is heated to a temperature of about 80 to 90 ° C, the treated particles of red phosphorus ^{are dried at about 100 to about 130 0} C and the titanium compound is added to the slurry in an amount sufficient to apply about 0.05 to about 2% by weight of titanium to the phosphor particles. 8. The method according to claim 6 or 7, characterized in that the titanium compound a) titanium sulfate or titanium tetrachloride is what titanium dioxide precipitates on the particles of red phosphorus, or b) titanium sulfate altogether with orthophosphoric acid or a water-soluble salt of orthophosphoric acid, the latter also being is added to the slurry, causing titanium phosphate to precipitate on the red phosphorus particles. Q 9 Q - "j ο ς 9. The method according to claim 5, characterized in that the mixture is formed by the following steps: (1) Contacting the vapors of a volatile, hydrolyzable Titanium compound with particles of red phosphorus about 2 mm or less in size and adsorption of the vapors on the surface of the particles, whereby the titanium compound is adsorbed in an amount sufficient to impart stability to oxidation to the red phosphorus particles, and then Hydrolysis of this compound and (2) Hydrolyze the adsorbed titanium compound to form a homogeneous mixture of red phosphorus and titanium dioxide. 10. The method according to claim 9, characterized in that the titanium compound is a volatile organic titanate or titanium tetrachloride and that contacting is by forming a stream of the titanium compound in one Carrier gas and flowing the stream in contact with a bed of particles of red phosphorus will. 11. The method according to claim 5, characterized in that the mixture is formed by the following stages: (1) Mixing particles of red phosphorus with a hydrolyzable titanium compound and (2) causing hydrolysis of the titanium compound in contact with the red phosphorus particles, under Formation of titanium dioxide on the surface of the red phosphorus particles. 12. The method according to claim 9, characterized in that the mixing stage is carried out in a closed container that the stage of hydrolysis by initiation caused by moisture in the container and that the unreacted titanium compound and by-products from the titanium dioxide treated particles of red phosphorus are removed. 13. The method according to claim 11 or 12, characterized in that that the titanium compound is titanium tetrachloride.