JPH0730326B2 - Decolorization method of red phosphorus flame retardant - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for decolorizing a red phosphorus flame retardant, and more specifically, more effectively using a unique purple color of a red phosphorus flame retardant by using an inorganic pigment. It relates to a method of erasing.

(Background and problems of the invention) Red phosphorus flame retardants are widely used as flame retardants for synthetic resins, have a large flame retardant effect, have little effect on the physical properties of synthetic resins, and emit smoke or harmful gases during combustion. It is well known that it has advantages over other flame retardants, such as less occurrence of methane.

However, red phosphorus-based flame retardants have relatively poor stability,
It has been pointed out that there are drawbacks derived from red phosphorus itself, such as the range of use being limited because it exhibits a deep purple color. Red phosphorus has a low ignition point, is unstable against impact, and is not only dangerous to explode, but it also causes a disproportionation reaction in the presence of trace amounts of water and oxygen, and gradually decomposes and deteriorates. At that time, phosphine gas, which is harmful to the human body, is generated.Therefore, red phosphorus flame retardants pose a risk of storage, handling, and kneading with synthetic resins, and the decomposition products reduce the physical properties of the resin. is there. As a result of various methods tried to obtain a stable red phosphorus flame retardant by preventing the decomposition of such red phosphorus, a method of coating red phosphorus particles with an inorganic or organic stabilizer was developed, Although the stability is remarkably improved, a sufficient solution to the coloring problem has not been obtained.

Red phosphorus flame retardants are generally not used at a high concentration, so for products that are colored to a high concentration and for applications where the color tone is not emphasized, the red phosphorus coloration is not a problem and the co-tone may be considered. As the material, a decolorizing type red phosphorus flame retardant mixed with a masking agent is used. Further, conventionally, when the color tone is generally emphasized, it has been usual to use a flame retardant agent which has almost no effect on the color tone, such as a halogen-based flame retardant agent.

However, it has recently been pointed out that synthetic resins containing halogen-based flame retardants cause a large amount of smoke and harmful gas in the event of a fire, significantly increasing the damage caused by the fire. The use of flame retardants has been restricted, and red phosphorus flame retardants have been reviewed. However, red phosphorus-based flame retardants cannot be avoided because of their coloring, and their use is inevitable, especially for white and other highly saturated and saturated colors. The current situation is that it is not possible.

Conventionally, two methods have been known as a decoloring method for red phosphorus flame retardants. One is to mix red phosphorus with titanium oxide in a powder to dilute the color of red phosphorus, and the other is to coat red phosphorus particles with a radical-polymerizable polymer such as polyacrylate and titanium oxide ( JP-A-59-195512). In the case of powder mixing, even if the red phosphorus content is about 10%, the color of red phosphorus clearly remains, and in the latter method, there is a limit to the amount of titanium oxide that can be introduced into the coating layer, and thus decolorization is still unsuccessful. It cannot be used for materials that require sufficient white color or subtle color expression.

In the case of powder mixture, the decolorization rate increases to some extent with increasing dilution, but the red phosphorus content of at least 20% is necessary for the powder red phosphorus flame retardant to exert a sufficient effect as a flame retardant. The degree is necessary, and if the concentration is lower than that, the flame retarding effect is reduced even if the decoloring property is improved, so the required amount is increased, and the diluent mixed in a large amount is also introduced into the synthetic resin. . As a result, the physical properties of the synthetic resin are deteriorated and the original characteristics of the red phosphorus flame retardant are lost. Red phosphorus flame retardants are usually used in combination with metal hydroxides such as aluminum hydroxide and magnesium hydroxide, but the physical properties of synthetic resins are affected by the amount of kneaded inorganic substances. However, there is a limit to the amount that can be added. From this point as well, it is preferable that the red phosphorus flame retardant contains as few additives as possible and has a higher red phosphorus concentration.

As described above, the conventional method known as a red phosphorus decolorizing method is insufficient in decoloring, or when an attempt is made to enhance the decolorizing effect, the additive increases and the red phosphorus concentration decreases, None of these are effective erasing methods, and there is a demand for an effective erasing method having a higher red phosphorus concentration and a higher erasing degree.

(Method for Solving Problems) According to the inventors, a product obtained by coating red phosphorus with a thermosetting resin containing titanium oxide and further mixing titanium oxide with a powder contains red phosphorus simply containing titanium oxide. Compared to those coated with synthetic resin and powder mixture of titanium oxide and red phosphorus,
It was found that the whiteness was extremely high at the same red phosphorus concentration and the same titanium oxide concentration. Such a synergistic effect of the combined use of coating and mixing is particularly remarkable when the content of titanium oxide in the coating layer with respect to red phosphorus is within a certain range. It is essential that the coating resin is a thermosetting resin,
Such effects cannot be obtained with the radical-polymerizable polymer used in the conventional method.

The same synergistic effect is also observed with inorganic pigments other than titanium oxide, and the effect is remarkable especially in colors that are easily affected by the coloring of red phosphorus. In the following, titanium oxide will be mainly described as a typical example.

First, the raw material of the thermosetting resin is dissolved in an aqueous suspension of red phosphorus, and an emulsion of titanium oxide and a curing agent which are separately prepared while stirring are added to the red phosphorus coated with a resin layer containing titanium oxide. Phosphorus is obtained. This is filtered off and dried by heating to complete the curing reaction of the coating layer. The amount of titanium oxide added is preferably 20 to 100 parts by weight with respect to 100 parts by weight of red phosphorus. If the amount of titanium oxide is 20 parts by weight or less, no synergistic effect is observed, and addition of 100 parts by weight or more does not improve the synergistic effect.

The thermosetting resin imparts sufficient stability to red phosphorus, and it is necessary to be able to introduce a pigment into the coating layer, but in the case of the present invention, it is not particularly necessary to increase the resin amount for introducing the pigment, The amount used for normal stabilization is sufficient,
Generally, 1 to 20 parts by weight is preferable to 100 parts by weight of red phosphorus. The coated red phosphorus thus obtained has a red phosphorus content of 50-
35 to 15 in coating layer at 80% (weight percent, and so on)
% Titanium oxide, and the color tone is a reddish gray with a shade depending on the red phosphorus content. This coated red phosphorus powder-mixed with titanium oxide shows a significantly higher whiteness than the one treated by the resin coating method or the powder mixing method alone at the same red phosphorus content. The table shows the degree of decolorization of the decolorized red phosphorus by the method of the present invention, the resin coating method and the powder mixing method. It is apparent that the decolorization degree of the flame retardant of the present invention at the same red phosphorus content is significantly higher than that by any other method, and as a method of adding a pigment, resin coating with a thermosetting resin and powder mixing method are used. When used in combination, the concealing effect is synergistically exhibited, and a decoloring effect exceeding the expectation that cannot be achieved by a single method can be obtained. As an example, when compared at a level of red phosphorus content of 30%, the sample of Comparative Example 1 having only resin coating had red phosphorus of 32.8% and titanium oxide of 63.5.
%, Whiteness 73.2, red phosphorus 30% in case of powder mixture,
Titanium oxide 70%, whiteness 71.4, while the method of the present invention provides titanium oxide 67-68%, whiteness 81-84, which has a little more pigment than the resin coating alone, but Chromaticity has shown a marked effect far beyond what would be expected from an increase in pigments, and it is surprising that the decolorization is conversely high in comparison with the powder mixture despite the low pigments. That is, the excellent decoloring effect of the present invention is exhibited.

Therefore, according to the method of the present invention, the inclusion of inorganic substances due to the addition of the red phosphorus flame retardant is relatively small, and the influence on the physical properties of the synthetic resin is reduced, and an extremely advantageous effect can be obtained in this respect as well. Although the conventional coating method using a radical-polymerizable polymer is slightly better in decolorization than the powder mixing method,
There is a limit to the amount of introduction because it is necessary to adsorb titanium oxide to red phosphorus in advance, and since the stabilizing effect of the radically polymerizable polymer is smaller than that of the thermosetting resin, a large amount of resin is required, resulting in Only low levels of titanium oxide content and red phosphorus content are obtained, and this method cannot improve the decoloring effect by increasing the amount of pigment introduced while maintaining the content of red phosphorus.

On the other hand, the method of the present invention uses a thermosetting resin having a large stabilizing effect, and it is not necessary to adsorb the pigment to red phosphorus in advance during the coating treatment, and the pigment is added to the suspension containing red phosphorus and the resin raw material. The coating polymerization can be carried out while adding a curing agent. Not only does the thermosetting resin originally require a small coating amount for stabilization, but it is not necessary to increase the resin coating amount in order to introduce a pigment. Significantly higher than Therefore, the coated red phosphorus thus obtained can maintain a sufficiently high red phosphorus content even if the pigment is powder-mixed, and the pigment introduced into the coating layer has already decolored the powder. The decoloring effected by the compound acts more effectively, and the decolorizing effect is remarkably enhanced.

This synergistic effect increases or decreases depending on the ratio of red phosphorus and the pigment introduced into the resin coating layer, and the maximum effect is obtained when the weight ratio of red phosphorus and the pigment is approximately 2: 1. The effect decreases with more or less pigment. This is because if the coating pigment is small, the exposed surface of the red phosphorus particles is large and it cannot be sufficiently covered by powder mixing.If the coating pigment is large, the red phosphorus content is reduced. This is because the addition amount by mixing is reduced and the synergistic effect of the present invention cannot be sufficiently exhibited. As a result, in the present invention, the ratio of red phosphorus to the coated pigment is 100 parts by weight of red phosphorus to 2% of the coated pigment.
A range of 0 to 100 parts by weight is preferred.

Thermosetting resins that can be used for the resin coating of the present invention include phenol-formalin type, urea-formalin type, melamine-formalin type, furfuryl alcohol-formalin type, acetone-formalin type, aniline-formalin type, polyhydric alcohol-polyhydric type. Polymerization reaction of the raw material such as basic acid system easily proceeds in red phosphorus-water suspension, or the initial condensate can be emulsified and dispersed in water to form a uniform coating on the surface of red phosphorus particles by the condensation reaction. Anything may be used as long as it is one.
When an initial condensate having a relatively high viscosity is used, a solvent or an emulsifying dispersant can be used to improve dispersibility.
Generally, 20 to 100 parts by weight of red phosphorus is suspended in 100 parts by weight of water, and 1 to 20 parts by weight of a synthetic raw material or an initial condensate of a thermosetting resin is dissolved in 100 parts by weight of red phosphorus. 40-100
Heat to ℃. While stirring this, an aqueous emulsion of a pigment prepared separately and a curing agent are added. The concentration of the pigment emulsion is not particularly limited, but a pigment emulsion consisting of 10 parts by weight of pigment and 100 parts by weight of water is conveniently used. The curing agent is an acidic or alkaline curing agent depending on the resin raw material, and phosphoric acid, hydrochloric acid-ammonium chloride, sodium carbonate or caustic soda is typically used. After treatment at a heating temperature for 1 to 3 hours, filtration, washing with water, heating at 90 to 150 ° C and drying. Upon heating, the polycondensation reaction is completed and a highly stabilized coating is obtained.

The conventional method of coating with a radical-polymerizable polymer requires complicated apparatus and steps because the radical polymerization reaction itself has many restrictions on reaction conditions and the like, but it is inevitable that it will be technically complicated. The method of the present invention does not require any special device, and can be easily carried out using a conventional resin coating device for stabilization.

In the method of the present invention, 30 parts by weight per 100 parts by weight of red phosphorus is used.
~ 100 parts by weight of titanium oxide is coated with a resin, and the resulting product having a red phosphorus content of 70 to 50% is powder-mixed with titanium oxide to adjust the red phosphorus content to 20 to 40%. A white red phosphorus flame retardant that has a significantly higher degree of whiteness than other materials and does not need to consider the effect of coloring due to red phosphorus even when added to materials that require white or subtle color tone expression. Obtainable.

The decoloring material that can be used in the present invention may be any other thermally stable inorganic pigment, for example, an oxide type such as nickel titanium yellow, a sulfide type such as cadmium yellow, or a chrome yellow type. Chromate type is typical.

Since the red phosphorus flame retardant obtained by the present invention is coated with a thermosetting resin having an excellent stabilizing effect, the stability is naturally extremely good, and there is no problem at the time of storage, handling or working. However, it is extremely useful and has a high degree of stability and decolorization. In addition to powder, it can be kneaded with various thermoplastic resins according to a conventional method to prepare pellets having an arbitrary red phosphorus content, which can be used for more convenient use. The present invention will be specifically described below with reference to examples.

(Example 1.) 2.2 g of phenol in a suspension consisting of 50 g of red phosphorus and 100 ml of water,
Add 3.5 g of 37% formalin and heat to 80 ° C. While stirring, an emulsion containing separately prepared 25 g of titanium oxide and 200 ml of water and 1.4 g of 85% phosphoric acid as a curing agent are added.
Continue heating and stirring at the same temperature for 1 hour, then allow to cool, filter and wash with water.
Dry at 140 ° C for 2 hours. Titanium oxide and phenol-
78.7 g of red phosphorus coated with formalin resin was obtained.

This coated red phosphorus contains 63.3% of red phosphorus and 31.2% of titanium oxide. Titanium oxide is mixed with this powder to adjust the red phosphorus content to 30%, 40% and 50%, respectively. It was measured.

(Example 2) 1.3 g of urea and 2.5 g of 37% formalin are dissolved in a suspension of 50 g of red phosphorus and 85 ml of water, and the mixture is stirred and heated to 90 ° C.
An emulsion consisting of 50 g of titanium oxide and 400 ml of water and 85
% G of phosphoric acid is added, and heating and stirring are continued at the same temperature for 2 hours. Allow to cool, filter, wash with water and dry at 140 ° C for 2 hours. Red phosphorus coated with titanium oxide and urea-formalin resin 10
1.9 g was obtained. This coated red phosphorus contains 48.3% red phosphorus and 49.2% titanium oxide. Titanium oxide is mixed with this powder to adjust the red phosphorus content to 20%, 30% and 40%, and the whiteness of each is adjusted. It was measured.

(Example 3) 1.5 g of phenol in a suspension consisting of 50 g of red phosphorus and 100 ml of water,
Add 2.7 g of 37% formalin and heat to 80 ° C. While stirring this, an emulsion consisting of 15 g of titanium oxide and 150 ml of water and
Add 1 g of 85% phosphoric acid and continue heating and stirring for 2 hours. After left to cool, it is filtered, washed with water and dried at 140 ° C for 2 hours.
Obtained 6.3 g.

The coated red phosphorus contained 74.4% red phosphorus and 22.2% titanium oxide. Titanium oxide was mixed with this powder to give a red phosphorus content of 30%, 4
Whiteness was measured for each of 0%, 50% and 60%.

Example 4. Phenol 1.8 g in a suspension consisting of red phosphorus 50 g and water 100 ml,
Add 3.2 g of 37% formalin and heat to 80 ° C. While stirring this, an emulsion consisting of 25 g of chrome yellow and 200 ml of water and 1.3 g of 85% phosphoric acid were added, and heating and stirring were continued for 2 hours. This was allowed to cool, filtered, washed with water, and then dried at 140 ° C. for 2 hours to obtain 77.2 g of red phosphorus coated with chrome yellow and phenol-formalin resin. This coated red phosphorus contains 64.2% red phosphorus and 31.8% chrome yellow.

Chrome red powder was mixed with this to give a red phosphorus content of 30.
%, 40% and 50% were adjusted and the yellowness of each was measured.

Comparative Example 1. 3.8 g of phenol in a suspension composed of 30 g of red phosphorus and 100 ml of water,
Add 5.5 g of 37% formalin and heat to 80 ° C. With stirring, an emulsion consisting of 55 g of titanium oxide and 400 ml of water and 1.4 g of 85% phosphoric acid are added. After heating and stirring for 1 hour, the mixture is allowed to cool, filtered, washed with water and dried at 140 ° C for 2 hours.

90.1 g of red phosphorus coated with titanium oxide and phenol-formaldehyde resin was obtained. This coated red phosphorus is red phosphorus 3
Contains 2.8% and titanium oxide 63.5%.

(Comparative Example 2) A coated red phosphorus was prepared in exactly the same manner as in Comparative Example 1 except that 30 g of red phosphorus and 40 g of titanium oxide were used. The obtained coated red phosphorus contains 41.2% red phosphorus and 51.4% titanium oxide.

(Comparative Example 3) 30 g of red phosphorus was coated with 25 g of titanium oxide, 3 g of phenol and 5 g of 37% formalin in the same manner as in Comparative Example 1 to give red phosphorus 4.
60.2 g of red phosphorus containing 9.8% and titanium oxide 39.8% was obtained.

(Comparative Example 4) Comparative Example 1 using 57 g of chrome yellow against 30 g of red phosphorus.
Treated in the same manner as red phosphorus 31.5%, chrome yellow 63.2%
91.3 g of coated red phosphorus containing was obtained.

Comparative Example 5 30 g of red phosphorus and 25 g of chrome yellow were treated in the same manner as in Comparative Example 1 to obtain 59.4 g of coated red phosphorus containing 49.8% of red phosphorus and 43.1% of chrome yellow.

(Effects of the Invention) As described above, it is clear that a higher decoloring effect can be obtained with a smaller amount of the decoloring material without lowering the concentration of red phosphorus by the decoloring method for a red phosphorus flame retardant of the present invention. Therefore, the problem of color, which is a drawback of red phosphorus flame retardants, has been greatly improved, and free coloring is possible without giving much consideration to the unique purple-red color of red phosphorus. Is significantly improved. In addition, it does not require a special device for erasing and can be carried out at the same time as the stabilizing treatment, which is a simple and extremely efficient method.

Measurement method In order to compare the degree of decolorization at a practical concentration in synthetic resin, each sample was conveniently kneaded with a polyamide hot melt resin to prepare a sample with a red phosphorus content of 10%. Whiteness (L value) and yellowness (b value) CR-
Measured at 200.

Claims (2)

[Claims] 1. A red phosphorus flame retardant quenching agent, characterized in that 100 parts by weight of red phosphorus is coated with 20 to 100 parts by weight of an inorganic pigment and a thermosetting resin, and then mixed with a powdery inorganic pigment. Color method. 2. 100 parts by weight of red phosphorus is coated with 30 to 100 parts by weight of titanium oxide and a thermosetting resin, and then titanium oxide is mixed to obtain a red phosphorus content of 20 to 40%. A method for producing a white red phosphorus flame retardant.