SE461332B - COMPOSITION CONTAINING STABILIZED RED PHOSPHORUS AND PROCEDURES FOR PREPARING THEREOF - Google Patents

Description

46% by weight of the red phosphorus and there is a general indication that metal oxides or salts in amounts up to 100% by weight of the coated particles may also be present in the composition.

It has also been proposed in U.S. Patent 4,315,897 to stabilize red phosphorus against oxidation by simultaneously treating the red phosphorus particles with aluminum hydroxide and cured epoxy resin.

According to the present invention, it has now surprisingly been found that a combination of particular amounts of titanium in the form of titanium dioxide or titanium phosphate and particular organic resins is particularly effective as a stabilizer for red phosphorus. This invention achieves both retardation of red phosphorus oxidation and inhibition of phosphine formation.

According to one aspect of the present invention there is provided a composition containing red phosphorus having a particle size of at most about 2 mm, characterized in that it additionally contains from 0.05 to 1.0% by weight (expressed as weight). titanium) titanium dioxide or titanium phosphate and from 0.1 to 5.0% by weight of an organic resin.

When the combination of TiO 2 with epoxy resin is used in this invention, the improvement achieved in oxidation stability is significantly greater than that obtained using the combination of aluminum hydroxide and epoxy resin of the prior art.

The present invention also encompasses a novel process for treating red phosphorus particles to achieve stabilization. Thus, according to another aspect of the present invention, there is provided a process for producing treated red phosphorus, characterized in that a titanium compound is added to a slurry of red phosphorus particles having a particle size of at most about Z mm, the pH of the slurry is adjusted to a value of Z to 4 to cause precipitation of titanium dioxide or titanium phosphate on the particles of red phosphorus in an amount of about 0.05 to about 1.0% by weight as Ti, a water-soluble or water-emulsifiable resin is added to the slurry and resin in a an amount of about 0.1 to about 5.0% by weight is precipitated on the red phosphorus particles, and the treated red phosphorus particles are separated from the slurry. The organic resin used to treat red phosphorus according to this invention is either water soluble or water emulsifiable. One type of organic resin used in this invention is an epoxy resin. Epoxy resins are thermosetting resins based on the reactivity of the epoxy group. A common type of such resins is prepared from epichlorohydrin and aromatic and aliphatic polyols, such as 2,2-bis- (4-hydroxyphenyl) -propane (bisphenol A), and has glycidyl ether end structures, contains many hydroxy groups and cures easily with water-soluble, internally modified polyamines. Curing is usually carried out in the aqueous phase at a temperature of about 100 DEG to about 900 DEG C. while maintaining the pH of the aqueous phase at about 5 to 9 ° C.

The epoxy resins that can be used in this invention typically have an epoxy equivalent weight of about 170 to 5000.

An additional type of organic resin used in this invention is a melamine-formaldehyde resin. Melamine-formaldehyde resins are amino resins made from melamine and formaldehyde.

The first step in the formation of these resins is the formation of trimethylol melamine, whose molecules contain a ring with three carbon and three nitrogen atoms. This molecule or polymer thereof is reacted with formaldehyde. Lower molecular weight uncured melamine resins are water-soluble types and are preferred for use in this invention. The curing is carried out with heat and in an acidic environment.

Another type of organic resin used in this invention is a urea-formaldehyde resin. Urea-formaldehyde resins are an additional class of amino resins and are formed in a two-step process involving the initial formation of methylol ureas, which are then heat cured with controlled heating and pressure in the presence of heavy catalysts.

The red phosphorus, which is treated in accordance with this invention, is in particulate form with a size of at most 2 mm and preferably about 0.01 to 0.15 mm. The particles of the red phosphorus are treated with titanium dioxide or titanium phosphate and an organic resin. The amount of the titanium compound used varies from about 0.05 to about 1.0% by weight expressed as Ti, and the amount of the organic resin used varies from 0.1 to 5% by weight, preferably 0.5 to 3%. 0%. In view of the prior art, it is surprising that such small amounts of titanium and organic resin provide effective stabilization of red phosphorus for both oxidation and phosphine formation.

The treatment of the red phosphorus particles with titanium dioxide or titanium phosphate and organic resin can be carried out in two steps, first by precipitating titanium dioxide or titanium phosphate on the particle and then depositing the organic resin on the red phosphorus particles.

The treatment of red phosphorus with titanium dioxide can be carried out in the aqueous phase to effect the precipitation of hydrogenated titanium dioxide on the red phosphorus. In this process, the particles of red phosphorus can be suspended in water and the resulting slurry heated to about 600 to about 900 ° C, preferably about 800 to about 900 ° C. The heated slurry is gradually mixed with the required amount of an aqueous solution. titanium salt, e.g. titanium sulfate, to achieve the desired level of treatment at a slightly acidic pH. The pH of the slurry is then adjusted to a value of the order of about 2 to about 4 to effect precipitation of hydrogenated titanium dioxide on the particles of red phosphorus.

The slurry is then treated with the organic resin material. The method and condition of treatment with organic resin depends on the shape and nature of the resin used to treat the particles of red phosphorus. The resin is usually added to the slurry in an uncured or partially cured form and cured on the surface of the red phosphorus particles.

When the organic resin is an epoxy resin, an aqueous dispersion of uncured epoxy resin is mixed with the slurry of titanium compound-treated particles of red phosphorus in an amount sufficient to achieve the desired level of treatment, and then an aqueous solution of an epoxy resin is mixed. hardener for epoxy to the slurry. The pH of the slurry is raised to about 4 to about 6 and the slurry is stirred for such a time that crosslinking occurs at a temperature of about 400 to about 800, preferably about 500 to about 650 ° C, usually below about 0.5 to about 6 ° C. about 2 hours.

Thereafter, the pH of the slurry is raised again to about 7 to 8 and the crosslinking is completed within about 10 to about 30 minutes.

When the organic resin is a melamine-formaldehyde resin, an aqueous solution of a heat-curable uncured melamine-formaldehyde resin is added to the slurry of the titanium compound-treated particles of red phosphorus and the pH of the slurry is adjusted to about 2 .5 to about 4. The slurry is then heated to about 800 to about 100 ° C to carry out the heat curing of the resin for about 0.5 to about Z hours.

When the organic resin is a urea-formaldehyde resin, an aqueous solution of uncured urea-formaldehyde resin is added to the slurry of titanium compound-treated red phosphorus particles. The pH of the slurry is adjusted to about 2.5 to about 4.0, the slurry is heated to about 800 to about 1000 ° C to effect curing of the resin for about 0.5 to about 2 hours.

The treatment of the particles of red phosphorus with titanium phosphate can be carried out in aqueous phase in an analogous manner with treatment in aqueous phase to precipitate titanium dioxide as described above except for orthophosphoric acid or a water-soluble salt of orthophosphoric acid, e.g. sodium dihydrogen phosphate, and titanium sulphate is added to the slurry, rather than titanium sulphate alone. After precipitation of the titanium phosphate, the slurry is then treated with the organic resin, as described above for titanium dioxide treatment.

After completion of the resin precipitation step, the treated red phosphorus is separated, e.g. by filtration, the treated red phosphorus is washed with water, dried and dehydrated at a temperature of about 100 to about 130 DEG C. in a vacuum oven.

Red phosphorus treated with particular amounts of titanium dioxide or titanium phosphate and particular amounts of particular organic resins of the present invention exhibit improved properties over the prior art. Red phosphorus treated with titanium dioxide and an epoxy resin has greater stability against degradation to form oxidation products and phosphine than red phosphorus treated with titanium at the same concentration level and the same stability can be achieved by using smaller amounts of titanium dioxide in combination with hart- set. Improved stability results in a reduction in acid formation and a reduction in phosphine formation during storage of the treated red phosphorus. The presence of the titanium dioxide or titanium phosphate on the red phosphorus seems to contribute most to the low acid formation, while the presence of the organic resin on the red phosphorus seems to contribute most to low phosphine formation.

Red phosphorus treated with titanium dioxide and a melamine resin, while having a lower stability than red phosphorus treated with titanium dioxide and epoxy resin, exhibits good dispersibility in water, which is advantageous in certain end uses of the red phosphorus, such as in the match industry.

Red phosphorus treated according to this invention requires much less time to filter and exhibits a much lower water retention than aluminum hydroxide-treated red phosphorus, resulting in a significant reduction in the required production time, compared to aluminum hydroxide treatment.

The invention is further illustrated by the following examples. In the examples, consideration is given to the accompanying drawings, in which: Fig. 1 is a graphical representation of the effect of titanium dioxide and an epoxy resin on the oxidation stability of red phosphorus; Fig. 2 is a graphical representation of the effect of titanium dioxide and an epoxy resin on the oxidation stability of wet red phosphorus; Fig. 3 is a graphical representation of the effect of titanium dioxide, titanium phosphate and a melamine-formaldehyde resin on the oxidation stability of red phosphorus; and Fig. 4 is a graphical representation of the effect of titanium dioxide and urea-formaldehyde resin on the oxidation stability of red phosphorus.

Example 1 This example illustrates stabilization of red phosphorus by a combination of titanium dioxide and epoxy resin.

Typical particle size red amorphous phosphorus (RAP) of 0.15 to 0.01 mm was suspended in water to a concentration of 25 g in 100 ml of water and heated to 60 DEG C. with stirring.

Various amounts of titanium sulfate were added to samples of the slurry and the pH of the slurry was adjusted to a value of 3 to effect precipitation of hydrogenated titanium dioxide thereon. The amount of Ti2 O deposited in these examples is expressed as ppm titanium thereof.

An aqueous dispersion of an uncured epoxy resin was then mixed with the suspension of the red phosphorus particles and a solution of epoxy resin and hardener was added. The epoxy resin used was that sold under the trademark D.E.R. 324 av á »10 15 20 25. 30 35 7 461 352 Chemroy Chemicals Ltd. This resin is a mixture of D.E.R. 331 epoxy resin and an aliphatic reactive diluent consisting of C12 to C14 aliphatic glycidyl ether. D.E.R. 324 has an epoxy equivalent weight of 197 to 206 and a viscosity at 250 DEG C. of 0 DEG to 800 cP. D.E.R. 331 is a product of the reaction of bisphenol A with epichlorohydrin, has an epoxy equivalent weight of 182 to 190 and a viscosity at 250 DEG C. of 11,000 to 14,000 cP. The resin was used in the form of an emulsion in water (3 g of resin in 50 ml of water) with the addition of 1% of the surfactant Tween 20 (sorbitol monostearate). The hardener was designated TSXll-548 by Henkel & Co. The hardener TSX11-548 is a water-reducible fatty amide amine with an amine value from 385 to 410 and is used in the form of an aqueous dispersion (3 g of amine in 50 ml of water).

A pH of 5 was then achieved by the addition of 5% by weight NaOH and the suspension was stirred for 1 hour at 600 DEG C. The pH was then raised to 7 by the addition of 5% by weight NaOH and the mixture was stirred for a further 15 minutes to crosslink the resin to form a coating on the RAP particles. The mixture was then filtered and the filter residue was washed with water and dried at about 1000 ° C for about 16 hours in a vacuum oven.

The samples with treated red phosphorus were stability tested and the results were compared with those for untreated red phosphorus, red phosphorus treated only with resin, red phosphorus treated with aluminum hydroxide and epoxy resin, and red phosphorus treated with titanium dioxide only. The Stability against oxidation of the red phosphorus was tested by holding the samples in the oven at 700 ° C under 100% relative humidity and measuring the acidity, expressed as HSPO4, by pH titration. The results obtained are shown in the curve in Fig. 1.

The reference numerals correspond to the samples listed in Table 1 below.

The results in Fig. 1 show that red phosphorus treated with 1000 ppm Ti and small amounts of resin has approximately the same stability against oxidation as 3000 ppm Ti, and is more stable than when treated with resin alone or with aluminum and resin.

At 2000 ppm Ti and 3000 ppm Ti in combination with resin, the stability was further increased and was greater than TiO2 alone or a combination of Al (OH) 3 with epoxy resin. 10 15 20 25 30 35 461 332 8 The treated samples were also tested for phosphine evolution and compared with untreated samples. 1 g portions were stirred with water in ampoules (69 cm 3) equipped with a septum to provide immediate access by syringe. After repeatedly stirring and allowing to stand at room temperature, the phosphine concentration was determined by gas chromatography with a flame photometry detector. The results obtained are given in the following table 1; ~ Table I sample exposure time PH3 conc. no sample treatment (days) (PPm) 1 0.7s 5 children (1) 6 0.20 2 0.64 1 parts (Z) 6 0.16 3 3000 ppm ri + 0.70 in resin (13 6 0.25 4 2000 ppm ri + 0.28 2 harn5 (13 6 0.30 5 3000 ppm A1 + 0.78 0 har: s (1) 6 0.2: 6 1000 ppm ri + 0.36 5 nar: s (23 4 0.44 7 1000 ppm ri + 0.50 z harps (z) 4 0.24 s 2000 ppm ri + 0.36 6 harns (2) 4 0.50 9 2000 ppm ri + 0.50 6 harcs (Z ) 4 0.28 10 3000 ppm ri + 0.20 6 har: s (2) 4 0.65 11 3000 ppm ri. 6 0.03 12 (3) 2000 ppm ri + 0.50 z har: s (2 ) 9 0.25 15 untreated RAP 5 5.80 Note: 1. Ratio of resin to harder 1: 1 2. Ratio of resin to harder 1: 0.6 3. In this experiment the titanium was deposited as the phosphate.

As can be seen from the results in Table I, phosphine evolution was greatly reduced by treating the red amorphous phosphorus with resin alone or in combination with Ti or Al. Phosphine development was less for the resin-treated samples than for treatment with Ti alone.

Example 2 This example illustrates stabilization of red amorphous phosphorus when stored wet.

The procedure of Example 1 was repeated except that the red phosphorus was not dried after treatment. Oxidation stability and phosphine evolution were determined as described in Example 1.

The oxidation stability determinations were plotted graphically and are shown in Fig. 2, while the determinations of phosphine evolution are set forth below in Table II: Table II Test Exposure Time PH3 Conc. no sample treatment (days) (ppm) l untreated RAP 6 20.8 2 3000 ppm Ti 6 5.9 3 2000 ppm Ti + 0.6% epoxy resin 6 l.14 2000 ppm Ti + 0.9% epoxy resin 6 2, 1 5 0.9% epoxy resin 6 2.1 6 5000 ppm Ti 6 6.1 Of the results in fig. 2 it can be seen that the use of the combination of titanium dioxide and epoxy resin leads to increased oxidation stability. The results in Table II show a significantly reduced phosphine evolution for wet samples treated with the combination of titanium dioxide and epoxy resin.

Example 3 This example illustrates stabilization of red phosphorus with a combination of titanium dioxide and melamine resin.

Red amorphous phosphorus with typical particle size of 0.15 to 0.01 mm suspended in water to a concentration of 20 g in 100 ml of water and stirred and mixed with 3.4 ml of a 10% aqueous solution of TiOSO4-H2SO4-8H2O. NaOH (1.0 N) was then added to achieve a pH of 3. A 10% aqueous solution of a melamine resin was added to the mixture in an amount sufficient to achieve the desired treatment and the pH was readjusted to a value of about 3 by the addition of 5% HSPO4. The suspension was heated with stirring to 95 DEG C., allowed to react for 1 hour and filtered. The pH was controlled during this curing period for the resin to about pH 3. The filter residue was washed with water and dried at about 100 ° C for about 16 hours in a vacuum oven.

The melamine resin used was a methylated melamine-formaldehyde resin sold by Monsanto under the trademark Scripset 10l.

The resin was purchased in the form of a 75% aqueous solution. The resin was a polycondensation product of melamine and formaldehyde. The samples were tested for oxidation stability and phosphine evolution in the manner described in Examples 1 and 10 The results were compared with those for resin alone and for untreated red phosphorus. The oxidation stability results for Scripset 101-treated RAP were plotted graphically and shown in Fig. 3, while phosphine evolution data for Scripsct 101-treated RAP are presented in Table III below: Table III sample exposure time PH3-conc. no sample treatment (days) (ppm) l 2000 ppm Ti + 1% resin 6 0.54 2 2000 ppm Ti + 0.5% resin 6 0.57 3 3000 ppm Ti + 0.5% resin 6 0.45 4 1 % resin 6 0.91 5 2% resin 6 0.84 6 2000 ppm Ti + 0.5% epoxy 16 0.61 7 untreated RAP 6 7 23 As can be seen from the results in Fig. 3, RAP is stabilized with both TiO7 and melamine resin is stable against oxidation but the resin alone is infe particularly effective. Phosphine evolution was reduced by treatment with both TiO 2 and melamine resin compared to untreated RAP and treatment with resin alone.

Example 4 This example illustrates stabilization of red phosphorus by combining titanium dioxide and urea-formaldehyde resin.

The treatment method of Example 3 was repeated using two urea-formaldehyde resins, except that the pH was checked during the curing of the resin and adjusted to 2.9 to 3.0 using phosphoric acid, if necessary. The resins used were those sold by Monsanto under the brand name Resimene LTX-31-61 and LTX-31-62. LTX ~ 31-161 is a modified urea-formaldehyde resin with a minimum solids content of 98%, a viscosity at zs ° c of isoo CP and a density at zs ° c of 1.14 g / ml.

LTX-31-62 is a modified urea-formaldehyde resin with a solids content between 93 and 97%, a density at 25 ° C of 1.09 g / ml and a viscosity at 25 ° C of 600 cP.

The samples were tested for oxidation stability and phosphine evolution in the manner described in Example 1 and the results were compared with those for resin alone and for untreated red phosphorus. The oxidation stability results are plotted graphically and shown in Fig. 4 while phosphine evolution data are shown in Table f) 0 10 15 20 n 461 352 IV below: Table IV sample exposure time PH3 conc. no sample treatment (days) (ppm) 1 0.5 1 Lrx 31-61 12 0.8 Z 1.0% LTX 31-61 12 0.9 3 2000 ppm Ti + 0.5 0 Lrx 31-01 12 1, 7 4 2000 ppm Ti + 1.0% LTX 31-61 12 2.2 5 2000 ppm ri (1) + 1.0 1 LTX 31-01 12 2.7 6 2000 ppm Ti + 0.5 1 Lrx 31- 02 5 0.5 7 2000 ppm Ti + 1.0 0 LTX 31-02 5 0.5 Note: (1) Ti precipitated as titanium phosphate.

As can be seen from the graphical results in FIG. 4 The combination of TiO2 or titanium phosphate with the urea-formaldehyde resins increased the stability, with the LTX 31-62 resin it is even more effective.

Example 5 This example contains a compilation of data from the previous examples with some additional experimental results for the sake of comparison and conclusions drawn from these data.

Selected data from the previous example are repeated in Table V below: 10 15 Z0 25 30 35 461 532 12 Table V Sample treatment time acid-expone PH3 example in tet (mg ring time conc. (Sample) oven H3PO4 / g (days) (ppm ) (t) RAP) 3000 ppm Ti 168 4 6 0.9 l (ll) 3000 ppm A1 such as Al (oH) 3 120 ss (X) - - - 0.78% by weight epoxy resin 168 19.5 6 0.2 1 (1) 3000 ppm Ti + 0.78% epoxy 168 1.5 6 0.25 1 (3) 3000 ppm Al + 0.75% epoxy 168 12.5 6 0.2 l (S] zooo ppm ri 144 11.0 (“) - ~ - 2000 ppm Ti + _ zooo ppm A1 144 1o, o“ X) - - - 2000 ppm Ti + 0.5% epoxy 168 2.1 6 0.3 S (6 ) 2000 ppm Ti + 0.5% melamine 168 11.7 6 0.6 3 (2) o, s 1 meiamine ißs 9o, 2 (X) 5, - 0.5% urea-formaldehyde 122 114.0 12 0 , 8 4 (l) 2000 ppm Ti + 0.5% urea-formaldehyde 122 39.0 12 1.7 4 (3) zooo ppm ri + 0.5% urea-formaldehyde 144 17.0 s 0.5 4 ( 6) (x) Data obtained from additional experiments.

The following conclusions can be drawn from these data: (a) TiO 2 in combination with epoxy resin improved the stability of RAP treated with it by a factor of about 5 compared to resin alone, while A1 (OH) 3 in combination with the epoxy resin improved stability only by a factor of about 2; (b) TiO 2 in combination with melamine resin improved the stability of RAP treated with it by a factor of about 8 Ü).

F! (C) Cd) (e) (f) 15 461 352 in comparison with RAP treated with resin alone; TiO 2 in combination with urea-formaldehyde resin improved the stability of RAP treated with it by a factor of about 3 compared to resin-only treatment; treatment of RAP with TiO 3 and epoxy resins gave the best overall result expressed in best oxidation stability and lowest phosphine evolution; In general, treatment of RAP with resins, especially epoxy resin, increases the amount of phosphine evolved; while both TiO 2 and Al (OH) 3 are stabilizers for RAP against oxidation, the addition of Al (OH) 3 to RAP treated with TiO2 does not improve the stability of RAP.

In summary, this invention provides a novel red amorphous phosphorus which has improved stability against oxidation and phosphine formation by treatment with titanium dioxide or titanium phosphate and an organic resin. Modifications are possible within the scope of this invention.

Claims (12)

461 552 PATENT CLAIMS 1. 1. Composition containing stabilized red phosphorus having a particle size not exceeding 2 mm, characterized in that it contains from 0,05 to 1,0% by weight (expressed as weight of titanium) of titanium dioxide or titanium phosphate and from 0,1 to 5 .0% by weight of an organic resin: 2. A composition according to claim 1, characterized in that the organic resin is an epoxy resin, a melamine-formaldehyde resin or a urea-formaldehyde resin. 3. A composition according to any one of claims 1-2, characterized in that it contains from 0.5 to 3.0% by weight of the organic resin. Process for the production of stabilized red phosphorus, characterized in that a titanium compound is added to a slurry of particles of red phosphorus with a particle size of not more than about 2 mm, the pH of the slurry is adjusted to a value of from 2 to 4 for precipitating titanium dioxide or titanium phosphate on the particles of red phosphorus in an amount of from about 0.05 to about 1.0% by weight as Ti, a water-soluble or water-emulsifiable resin is added to the slurry and resin in an amount of from about 0.1 to about 5.0% by weight is precipitated on the red phosphorus particles, and the treated red phosphorus particles are separated from the slurry. 5. A process according to claim 4, characterized in that the organic resin is an epoxy resin, a melamine-formaldehyde resin or a urea-formaldehyde resin. 6. A method according to any one of claims 4-5, characterized in that the resin added to the slurry consists of an uncured resin and the resin which precipitates on the particles of red phosphorus consists of a cured resin. Process according to one of Claims 4 to 6, characterized in that the titanium compound consists of titanium sulphate. Process according to one of Claims 4 to 6, characterized in that the titanium compound is titanium sulphate and that orthophosphoric acid or a water-soluble salt thereof is also added to the slurry. Process according to one of Claims 4 to 8, characterized in that an uncured epoxy resin and a hardener for this resin are added to the slurry, and that the precipitation of cured resin is effected by adjusting the pH of the slurry to a value of from approx. 4 to 6 and its tam fi rann'pafrà140 ° to1180 ° C, the slurry is stirred for a period of from 0.5 to 2 hours, the pH of the slurry is raised to a value of from 7 to 8, and the slurry is stirred for from 10 to 30 minutes. 10. A method according to any one of claims 4-9, characterized in that an uncured melamine-formaldehyde resin or an uncured urea-formaldehyde resin is added to the slurry and that the precipitation of cured resin is effected by adjusting the slurry. pH of from 2.5 to 4 and its tamarind 'from 80 ° to 100 ° C and that the slurry is stirred for a period of from 0.5 to 2 hours. Process according to any one of claims 4-10, characterized in that the slurry is heated to a temperature of from 60 to 90 ° C before the addition of the titanium compound. Process according to one of Claims 4 to 11, characterized in that the separated particles of red phosphorus are washed and dried at a temperature of from 1000 to 1000 ° C.