JPH058125B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to stabilized red phosphorus in which the surface of red phosphorus particles is coated with a composite film of a titanium-cobalt compound, and a method for producing the same. The stabilized red phosphorus according to the present invention is particularly useful as a flame retardant for synthetic resins, and can be used in the fields of resins, paints, and adhesives. [Prior Art] It is well known that red phosphorus imparts an excellent flame retardant effect to synthetic resins, and is actually used as a flame retardant. However, when red phosphorus is used as it is, it reacts with moisture and causes a hydrolysis reaction accompanied by the generation of phosphine gas. Many red phosphorus modifications have been proposed. For example, a method of depositing aluminum hydroxide on the surface of red phosphorus using aluminum sulfate and sodium hydrogen carbonate [Gmelin, Handbutzuf der Anorganisien Chemier, 8th edition (1964)]
“Phosphorus” Part B, p. 83 (Gmelin.
"Handbuchder anorganischenChemie" th
Edtion (1964), vol Phosphorus, Parts B.
Page 83)] has been reported. However, this red phosphorus modification method requires coating a large amount of aluminum hydroxide in order to completely stabilize red phosphorus, which not only reduces its effectiveness as a flame retardant, but also reduces the effectiveness of red phosphorus depending on the application. It may have a negative effect. Another example of a red phosphorus reforming method is a method of coating aluminum hydroxide with a composite of zinc or magnesium hydroxide (U.S. Pat. No. 2,635,953).
specification), modified red phosphorus coated with a thermosetting resin (Japanese Patent Application Laid-Open No. 105996/1983), modified red phosphorus coated with a thermosetting resin after converting the red phosphorus surface into a metal phosphide (Japanese Patent Laid-Open No. 105996/1983) modified red phosphorus (US Pat. No. 4,421,782) in which the surface of red phosphorus is coated with a hydrated oxide of titanium; or modified red phosphorus in which the surface of red phosphorus is coated with a hydrated oxide of titanium. In addition to the above, modified red phosphorus coated with a thermosetting resin has been proposed. [Problems to be Solved by the Invention] As mentioned above, many proposals have been made for stabilizing red phosphorus through modification, but all of them have advantages and disadvantages, and still have some important problems. In particular, red phosphorus is easily hydrolyzed in the presence of moisture and is accompanied by the generation of phosphine gas, which is odorous and toxic even in a very small amount, so it has been extremely difficult to completely suppress the generation of this gas. For this reason, proposals have been made to suppress the generated phosphine gas by coexisting metals that have a high affinity with phosphine gas, such as heavy metals such as copper and nickel. However, many heavy metals have the disadvantage of accelerating the hydrolysis of red phosphorus. This results in a decrease in moisture resistance and promotes the generation of phosphine gas. Furthermore, the modified red phosphorus disclosed in Japanese Patent Application Laid-open No. 52-125489 can be considered to be a type of plating film by the so-called galvanic method, but it is an extremely thin and incomplete metal phosphide film. The present invention has been achieved through extensive research and exploration of various stabilization methods in order to substantially completely suppress the generation of phosphine gas accompanying the decomposition of red phosphorus.
When red phosphorus particles were coated with a titanium-cobalt composite hydrated oxide film, they found that surprisingly stable red phosphorus powder could be obtained, and the present invention was completed. [Means for Solving the Problems] and [Operations] That is, the present invention provides stabilized red phosphorus, characterized in that the surface of red phosphorus particles is coated with a titanium-cobalt composite hydrated oxide; Then, an alkali agent is added to an aqueous suspension of red phosphorus dispersed in an aqueous mixed salt solution of a titanium salt and a cobalt salt to neutralize it. The present invention relates to a method for producing stabilized red phosphorus, which is characterized in that it is separated and recovered after being deposited on the surface of phosphorus particles. The present invention will be explained in detail below. The red phosphorus particles in the present invention are at least as large as
100 μm or less, and the average particle size is 5
~30 μm, preferably 10-20 μm is suitable. Further, since fine powder increases the surface area of the particles and tends to become unstable, it is preferable to use particles with a particle size of about 1 μm or less that are cut as much as possible. Therefore, the red phosphorus particles in the present invention are
It is preferable that the particle size is substantially in the range of 1 to 100 μm, and even if particles with a particle size outside the above range are contained, the content of particles with a particle size of 1 μm or less and 100 μm or more is 5% by weight or less is desirable. Note that the particle size and average particle size are values measured by the Coulter counter method. The stabilized red phosphorus according to the present invention is formed by depositing a titanium-cobalt composite hydrated oxide, which is a hydrolysis product of a soluble salt of titanium and cobalt, on the surface of red phosphorus particles to form a coating. This deposit appears to be TiO ₂ .nH ₂ O and Co.nH ₂ O, but since it is a coprecipitate, it is presumed that it is not just a mixture of these. In addition, the amount of titanium-cobalt composite hydrated oxide deposited on the red phosphorus particles varies depending on the use of the stabilized red phosphorus, but in most cases it is 0.5 to 10% Ti+Co based on the total weight of the red phosphorus particles. %,
It is desirable that the amount is preferably in the range of 1 to 6% by weight. The reason for this is that if it is less than 0.5% by weight, the suppression of phosphine gas is incomplete, and if it exceeds 10% by weight, it is inappropriate from a practical standpoint. In addition, the weight ratio of titanium and cobalt in the titanium-cobalt composite hydrated oxide is Ti:Co=
1: preferably in the range of 0.1 to 0.5. The stabilized red phosphorus according to the present invention can be confirmed by microscopic observation to have a deposited coating formed on the particle surface, and can be easily identified in comparison with the original red phosphorus. The modified red phosphorus according to the present invention is a stabilized red phosphorus that almost completely suppresses the generation of phosphine gas, but the details of the suppression mechanism are unknown.
It is also not clear why the combination of titanium and cobalt shows good results.
This combination was discovered as a result of numerous experiments, some of which are shown in Comparative Examples 4 to 15.
Unique effects that cannot be achieved in combination with other elements can be obtained in the combination of titanium and cobalt. Next, a method for producing stabilized red phosphorus according to the present invention will be explained. First, red phosphorus is dispersed in a mixed salt aqueous solution of titanium salt and cobalt salt, and an alkali agent is added to the resulting red phosphorus suspension while stirring to neutralize the pH.
Adjust to 6.5-8.5. After neutralization, the fine precipitates of the titanium-cobalt complex hydrated oxide are deposited on the surface of the red phosphorus particles by heating with stirring, followed by separation and recovery, which makes it industrially advantageous and homogeneous. It is possible to produce stable stabilized red phosphorus. In the present invention, the aqueous suspension of red phosphorus is a mixed salt aqueous solution in which a predetermined amount of titanium salt and cobalt salt is dissolved in water in an amount of at least twice the amount of red phosphorus, preferably 5 to 10 times, by weight. It can be obtained by adding red phosphorus particles to the liquid under stirring. In this case, if the amount of water in the mixed salt aqueous solution is less than twice the amount of red phosphorus, the red phosphorus concentration becomes too high and stirring becomes impossible. In addition, as another method for preparing an aqueous suspension of red phosphorus, contrary to the above, a mixed salt aqueous solution of a titanium salt and a cobalt salt is added to a red phosphorus slurry prepared by dispersing red phosphorus in water in advance. mosquito,
Alternatively, an aqueous suspension can be obtained by adding and dissolving crystals of predetermined titanium salts and cobalt salts. However, if an aqueous solution or crystals of a mixed salt of titanium salt and cobalt salt is added to an alkaline slurry of red phosphorus, there is a risk that the red phosphorus will be hydrolyzed, so it is better to avoid this. In addition, the titanium salt and cobalt salt used in the preparation of the mixed salt aqueous solution can be used without particular limitation as long as they are salts of titanium and cobalt, but among them, sulfate, hydrochloride, or nitrate are particularly preferred. At least one selected from the following is preferred. The concentration of the mixed salt aqueous solution of titanium salt and cobalt salt is not particularly limited as long as it is below the solubility of each salt at room temperature, but it is usually 0.5 to 1.0 as Ti.
It is preferably 0.05 to 0.2% by weight as Co. Any device can be used to prepare the aqueous suspension of red phosphorus as long as it can homogeneously disperse red phosphorus particles, but specifically, any desired means may be used as appropriate, such as normal stirring. It is desirable to prepare a suspension in a state of dispersion close to that of primary particles, with as much agglomerate of red phosphorus particles removed as possible, using high-speed stirring or a shear dispersion device such as a colloid mill or homogenizer. Further, when dispersing the red phosphorus particles, a small amount of a dispersant such as a surfactant or sodium hexametaphosphate can be used as necessary to the extent that the coating conditions are not impaired. There is no particular reason to limit the concentration of red phosphorus in an aqueous suspension of red phosphorus, but it is often 50 g/~
A range of 700 g/, preferably 100 g/ to 500 g/ is desirable; if it is less than 50 g//, the slurry concentration will be low and the deposited coating density will be reduced, making it uneconomical because the processing capacity will be large; and if it exceeds 700 g//, red This is not preferable because the dispersibility of the phosphorus particles becomes poor. In addition, in depositing and coating the red phosphorus particles in this aqueous suspension, the temperature is raised to effectively carry out the deposition process, but the temperature of the aqueous suspension is adjusted in advance before the deposition process. There is no problem in adding an alkaline agent and performing a deposition treatment after that. Alkaline agents include ammonia gas, aqueous ammonia, caustic soda, caustic potash, NaHCO ₃ ,
At least one selected from inorganic alkaline agents such as Na ₂ CO ₃ , K ₂ CO ₃ , KHCO ₃ , Ca(OH) ₂ , and organic alkaline agents such as ethanolamine is used, but by-products Ammonia gas and ammonia water are preferred because they can be easily removed by washing. The end point pH of neutralization needs to be set at a pH at which cobalt and titanium ions remain in the solution at the end of the deposition process. This PH varies depending on the combination of titanium salt and cobalt salt used, but the liquid property after the deposition process is 6 to 8, preferably 6 to 8.
It is desirable to fall within the range of 7.0±0.5 for complete coverage. In addition, heating lowers the PH by 1 to 1.5, so if you adjust the PH before heating, 6.5
Liquidity should be ~8.5, preferably 8.0±8.5. At this time, since red phosphorus is easily hydrolyzed in alkaline conditions, the pH should not exceed 9. When an alkali agent is added to an aqueous suspension of red phosphorus, a precipitation reaction begins immediately, but the addition rate as well as the liquid concentration directly affect the reaction;
These factors are significantly related to the physical properties of red phosphorus, especially its surface properties, so after fully considering these factors, the addition rate of the alkali agent should be set and controlled to prevent uneven deposited film. It is necessary to. In many cases it is better to add gradually and quantitatively. With such neutralization under stirring, fine precipitates of titanium-cobalt complex hydrated oxide are deposited on the red phosphorus particle surface, whether at room temperature or under heating, forming a uniform and strong deposited film. is being formed. At this time, the thickness of the deposited film changes depending on the amount of titanium salt and cobalt salt present in the liquid, so by adjusting this it is possible to set a coating suitable for various uses. Note that the slurry temperature during deposition is preferably 60°C or higher, more preferably in the range of 80 to 90°C. After the completion of the deposition process, the mother liquor is separated by a conventional method, and the red phosphorus coated with the titanium-cobalt composite hydrated oxide is filtered, and if necessary, washed with water, separated, and dried to be recovered. [Examples] Hereinafter, the present invention will be explained in more detail by showing examples. Examples 1 to 6 Titanium sulfate solution (as reagent Ti(SO ₄ ))
The amounts of cobalt sulfate (reagent, manufactured by Kanto Kagaku Co., Ltd.) and cobalt sulfate (reagent, manufactured by Kanto Kagaku Co., Ltd.) shown in Table 1 below were weighed and dissolved in 50 g of water. To this, particles with a particle size of 3 to 44 μm, which have been washed with water and dried in vacuum (100 ° C.), are added.
Add 5g of red phosphorus powder with an average particle size of 20μm, add 5wt% ammonia aqueous solution while stirring,
The pH was adjusted to 7.5. Next, the mixture was heated with stirring to bring the temperature to 85°C, and heating and stirring was continued for 2 hours. Final PH at this time
was 6.8. After cooling, it was separated. The slag was washed with deionized water until the electrical conductivity of the liquid was 10 μs/cm or less, and dried in a vacuum dryer at 120° C. for 3 hours to obtain stabilized red phosphorus.

[Table] The results of measuring the amount of phosphine produced in the stabilized red phosphorus obtained were as shown in Table 2 below.

[Table] Measurement of the amount of Γphosphine generated.
Take 0.5g of the sample stored for a period of time and heat it in _N2 gas (150°C, 3 hours). The amount of PH ₃ generated was measured using a gas chromatograph, and the amount of PH ₃ generated per 1 g of sample (μg) was determined.
It was converted into Comparative Examples 1 to 3 In Examples 2 to 4, red phosphorus particles were coated using only a titanium sulfate solution without using cobalt sulfate. Other conditions were the same as in Examples 2-4. The test results for the amount of titanium sulfate added and the amount of phosphine generated are shown in Table 3 below.

[Table] Comparative Examples 4 to 15 Red phosphorus coating was carried out in the same manner as in Example 6, using various metal salts shown in Table 4 below in place of cobalt sulfate in Example 6. The test results for the type and amount of metal salt added and the amount of phosphine generated from the obtained metal salt-coated red phosphorus are shown in Table 4 below.

[Table] Example 7 Titanium tetrachloride solution (8.5wt% as Ti) 2.94g
(5 wt% as Ti relative to red phosphorus) and 0.12 g of cobalt sulfate (CoSO ₄ .7H ₂ O) (0.5 wt% as Co relative to red phosphorus) were dissolved in 50 g of water. To this was added 5 g of red phosphorus (particle size 3 to 44 μm, average particle size 15 μm) that had been previously washed with water and vacuum dried (100° C.), and a 5 wt % NaOH solution was added while stirring to adjust the pH to 8.0. Next, the mixture was heated to a temperature of 85° C., and heating and stirring were continued for 2 hours. The final pH at this time was 7.0.
After cooling, it was separated. Wash the slag with deionized water until the electrical conductivity of the liquid shows 10 μs/cm or less, and
Stabilized red phosphorus was obtained by drying in a vacuum dryer at .degree. C. for 3 hours. The result of the phosphine generation amount test of the obtained stabilized red phosphorus was undetectable. Example 8 Titanium tetrachloride solution (8.5wt% as Ti) 1.76g
(3wt% as Ti relative to red phosphorus) and 0.06 g of cobalt chloride (Cocl ₂ 6H ₂ O) (as Co relative to red phosphorus)
0.3wt%) was dissolved in 50g of water. To this was added 5 g of red phosphorus (particle size 3 to 44 μm, average particle size 15 μm) that had been previously washed with water and vacuum dried (100°C), and 5 wt% NH ₄ OH solution was added while stirring to adjust the pH to 7.5. . Next, the mixture was heated to a temperature of 85°C, and heating and stirring were continued for 2 hours. The final pH at this time was 6.8. After cooling, it was separated. The slag was washed with deionized water until the electrical conductivity of the liquid was 10 μs/cm or less, and dried in a vacuum dryer at 120° C. for 3 hours to obtain stabilized red phosphorus. The result of the phosphine generation amount test of the obtained stabilized red phosphorus was undetectable. Comparative example 16 Red phosphorus 100 with particle size 3 to 44 μm, average particle size 15 μm
g was suspended in 250 g of water to prepare a slurry of red phosphorus. Next, 120 g of an aqueous solution of 8 wt % aluminum sulfate as Al ₂ O ₃ was added, the temperature was raised to 80° C., and a 10 wt % NaOH solution was added dropwise over 2 hours with stirring to adjust the pH to 6.6. Further, heating and stirring were continued for 1 hour to deposit aluminum hydroxide on the surface of the red phosphorus particles. After cooling and separating, the electrical conductivity of the liquid is
After washing until the temperature decreased to 20 μs/cm or less, it was dried in a vacuum dryer at 100° C. for 5 hours to obtain stabilized red phosphorus. The result of the phosphine generation amount test of the obtained stabilized red phosphorus was 12.2 μg/g. Hot water resistance test of Γ-stabilized red phosphorus coating In an Erlenmeyer flask equipped with a reflux condenser,
1 g of the stabilized red phosphorus sample obtained in each of the Examples and Comparative Examples shown in the table and 180 ml of water were added and heated at a boiling state for 8 hours. The PH and electrical conductivity of the supernatant were measured before and after heating. The results are shown in Table 5.

[Table] [Effects of the Invention] As explained above, it has been found that the stabilized red phosphorus of the present invention exhibits heat decomposition resistance and hydrolysis resistance that were hitherto unimaginable. This titanium-cobalt composite coating almost completely suppresses the hydrolysis reaction of red phosphorus in the presence of moisture and at high temperatures, making it extremely useful as a flame retardant for various synthetic resins.

Claims (1)

[Scope of Claims] 1. Stabilized red phosphorus, characterized in that the surface of red phosphorus particles is coated with a titanium-cobalt composite hydrated oxide. 2. The stabilized red phosphorus according to claim 1, wherein the titanium-cobalt composite hydrated oxide is present in an amount of 0.5 to 10% by weight as Ti+Co based on the total weight of the red phosphorus particles. 3. The stabilized red phosphorus according to claim 1 or 2, wherein the titanium-cobalt-based composite hydrated oxide has a weight ratio of titanium and cobalt in the range of Ti:Co=1:0.1 to 0.5. 4. The stabilized red phosphorus according to claim 1, wherein the red phosphorus has an average particle size of 5 to 30 μm, and the content of particles with particle sizes of 1 μm or less and 100 μm or more is 5% by weight or less. 5 Add an alkaline agent to an aqueous suspension of red phosphorus dispersed in an aqueous mixed salt solution of a titanium salt and a cobalt salt to neutralize it, and remove the fine precipitates of the titanium-cobalt complex hydrated oxide. A method for producing stabilized red phosphorus, which comprises depositing it on the surface of phosphorus particles and then separating and recovering it. 6. The method for producing stabilized red phosphorus according to claim 5, wherein the aqueous suspension of red phosphorus is prepared by adding red phosphorus powder to an aqueous mixed salt solution of a titanium salt and a cobalt salt. 7. The method for producing stabilized red phosphorus according to claim 5 or 6, wherein the titanium salt and cobalt salt are at least one selected from sulfates, hydrochlorides, and nitrates. 8. The method for producing stabilized red phosphorus according to claim 5, wherein the alkaline agent is at least one selected from ammonia gas, aqueous ammonia, caustic soda, and caustic potassium. 9. The method for producing stabilized red phosphorus according to claim 5, wherein the deposition treatment of red phosphorus on the particle surface is carried out at a final pH of 6 to 8 in the reaction system and at a temperature of 60°C or higher.