JPH0372567B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to modified red phosphorus coated with titanium oxide and polymer. More specifically, it has been stabilized to satisfy conditions such as a high ignition point, a small amount of phosphine generation, and no deterioration of the physical properties of the base material, and at the same time it has been decolored by concealing the dark red characteristic of red phosphorus. , relating to modified red phosphorus coated with titanium oxide and polymers, which is particularly valuable as a flame retardant. It is already known that red phosphorus has a high phosphorus content as a flame retardant for resins, and exhibits effective flame retardancy even when added in small amounts. Moreover, unlike halogen flame retardants, red phosphorus does not generate as much toxic gas, and since it is a solid substance, it does not change the physical properties of the resin, so it can be added from the perspective of being a mere filler. It is one of the flame retardants that has received particular attention recently because of its ability to When using red phosphorus as a flame retardant, there are risks of ignition during handling, storage, and kneading with resin, generation of harmful phosphine gas, or physical properties of resin due to acidic substances generated by oxidation or hydrolysis. Since there are problems such as deterioration of physical and electrical properties, various methods of stabilizing red phosphorus have been studied. For example, there are methods of treating red phosphorus with inorganic substances such as aluminum hydroxide and magnesium hydroxide, and methods of treating red phosphorus with organic substances such as paraffin, wax, caprolactam, thermoplastic resins, and thermosetting resins (US Pat. No. 2,635,953, Special Publication 1971-37125, Special Publication 49-16354, Special Publication 1973-
38171, Special Publication Showa 54-39200) is known. However, red phosphorus alone or red phosphorus stabilized by the above method exhibits a unique deep dark red color, so when used as a flame retardant for resins, if the amount added exceeds a certain level, the resin may become unsuitable. Because it is colored in a unique color, its use in resin parts where color tone is an issue is restricted. Currently, there are high expectations for a red phosphorus flame retardant that hides the deep dark red color inherent in red phosphorus and allows for more flexible coloring of resins. In view of the above, the present inventors conducted research on modified red phosphorus, which is excellent as a flame retardant and which hides, decolorizes, and stabilizes the dark red color inherent in red phosphorus.
The present invention was completed by discovering that the above object can be achieved by coating red phosphorus with titanium oxide and a polymer. That is, the present invention provides modified red phosphorus in which the particle surface is coated with at least titanium oxide and an organic polymer, in which the organic polymer has a double bond in the molecule and contains a monomer capable of radical polymerization and a polymerization initiator. It is a modified red phosphorus characterized by being polymerized using In the present invention, the red phosphorus before coating (hereinafter referred to as "red phosphorus" to distinguish from "modified red phosphorus") may be of course untreated after production, or red phosphorus stabilized with aluminum oxide, magnesium oxide, etc. A mixture of phosphorus allotropes other than yellow phosphorus, such as black phosphorus, may be used, and modified red phosphorus coated with titanium oxide and polymer obtained by using particles with a particle size in the range of 0.1 to 100μ can be used. It is preferable to mix it into a resin because it has good kneadability with the resin. Both rutile and anatase types of titanium oxide can be used in the present invention, but the rutile type is preferred from the viewpoint of its hiding degree. In addition, the particle size is 0.01~
A material within the range of 1μ is generally used, but there is no particular limitation. The amount of titanium oxide coated on red phosphorus is not particularly limited as long as the required degree of hiding can be obtained, but it is usually 30 to 150 parts by weight per 100 parts by weight of red phosphorus. The organic polymer used in the present invention is one that has a double bond in its molecule and is obtained by polymerizing a monomer obtained by radical polymerization (hereinafter referred to as a "radically polymerizable monomer") and a polymerization initiator. Here, the monomers that can be used are not particularly limited as long as they can undergo radical polymerization, but specific examples include methacrylic acid esters such as methyl methacrylate and ethyl methacrylate, methyl acrylate, and ethyl acrylate. Examples include one or more selected from acrylic esters such as methacrylic acid, acrylic acid, styrene, vinyl acetate, acrylonitrile, and the like. These monomers are used for homopolymerization or two or more types of monomers are used for copolymerization. In addition, when using modified red phosphorus as a flame retardant for unsaturated polyester, if the coating is required to have chemical resistance against styrene, etc., by copolymerizing a crosslinking agent, It is also possible to provide a polymer coating with a crosslinked structure. The crosslinking agent referred to here is a polyfunctional monomer having two or more polymerizable double bonds in one molecule, such as ethylene dimethacrylate, diethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, dimethacrylate, etc. acid 1,
Examples include 3-butylene and trimethylolpropane trimethacrylate. The appropriate amount of this crosslinking agent added to the monomer used for coating is 1 to 20 parts by weight per 100 parts by weight of the monomer.
Parts by weight. If the amount added is less than 1 part by weight, the resulting polymer will have poor chemical resistance, and if it exceeds 20 parts by weight, the yield of the resulting polymer will be low. Regarding polymerization initiators, benzoyl peroxide, potassium persulfate, ammonium persulfate, organic or inorganic peroxide initiators such as hydrogen peroxide, azobisisobutyronitrile, 2,2'-azobis-
(2-amidinopropane) dihydrochloride and other azo compound-based initiators, and hydrogen sulfite ion-forming compound initiators such as sulfite water, sodium bisulfite, ammonium sulfite, sulfur dioxide gas, etc., or a combination of two or more thereof. and use it. The amount of organic polymer covering red phosphorus is
The amount is 5 to 100 parts by weight per 100 parts by weight. If the coating amount is less than 5 parts by weight, a sufficient coating effect cannot be obtained in terms of fixation of titanium oxide electrically coagulated and deposited on the surface of red phosphorus particles and stabilization of red phosphorus. Moreover, if the amount exceeds 100 parts by weight, the organic polymer may act as a binder, causing significant agglomeration of red phosphorus and coarsening the particle size, which is not preferable. In the present invention, titanium oxide polymer-coated red phosphorus is produced using the above-mentioned raw materials.In one embodiment, a predetermined amount of red phosphorus and titanium oxide are sufficiently suspended in water, and the PH2 ~6
A suspension is prepared, and the above-mentioned radically polymerizable monomer, polymerization initiator, and optionally a crosslinking agent are added thereto and polymerized. The concentration of such an aqueous suspension of red phosphorus is 5 to 5 parts by weight of red phosphorus per 100 parts by weight of water.
A suspension of 80 parts by weight has good workability.
In other words, the suspension having the above concentration range has good dispersibility, and the surfaces of the red phosphorus particles can be uniformly coated with titanium oxide and polymer. If it is less than 5 parts by weight, the yield of the target product is poor and economical efficiency is poor, and if it exceeds 80 parts by weight, the resulting polymer becomes a binder and the agglomeration between red phosphorus particles becomes severe, which is not preferable.
Red phosphorus particles are normally negatively charged in such an aqueous suspension. When the pH of the suspension is adjusted to a range of 2 to 6, the surface of the red phosphorus particles becomes negatively charged, while the surface of the titanium oxide particles becomes positively charged, so that both electrically attract each other and the monomer The polymerization reaction is carried out, and red phosphorus can be efficiently and firmly coated with titanium oxide and organic monomer. For example, when red phosphorus stabilized with magnesium hydroxide is used as red phosphorus, when the pH is higher than 6, such as in an aqueous suspension of red phosphorus and titanium oxide, titanium oxide becomes negatively charged or has an isoelectric point. This often results in problems such as incomplete integration of red phosphorus, titanium oxide, and the resulting polymer without agglomeration and deposition on the surface of red phosphorus particles, and low polymer yield. Therefore, when the pH of the liquid is higher than 6, the reaction is carried out by adjusting the pH to 2 to 6 with ordinary mineral acids such as hydrochloric acid, sulfuric acid, or phosphoric acid. On the other hand, in the case of untreated red phosphorus that has not been stabilized, the surface of the red phosphorus particles is often slightly acidic, and its aqueous suspension falls within the above pH range, so it can be used as is in the polymerization reaction. . The amount of titanium oxide added is not particularly limited, but the required degree of hiding can usually be obtained by adding 30 to 150 parts by weight per 100 parts by weight of red phosphorus. The amount of the radically polymerizable monomer added is 5 to 100 parts by weight per 100 parts by weight of red phosphorus. If the amount added is less than 5 parts by weight, a sufficient coating effect cannot be obtained in terms of fixation of titanium oxide electrically coagulated and deposited on the surface of red phosphorus particles and stabilization of red phosphorus. In addition, if it is used in a large amount exceeding 100 parts by weight, polymerization in the aqueous medium will occur considerably, resulting in the formation of a large amount of polymer that does not coagulate on the surface of the red phosphorus particles, or the formed polymer may act as a binder, causing red phosphorus to be significantly degraded. This is not preferable as it may aggregate and coarsen the particle size. Furthermore, the presence of such free polymers unnecessarily contaminates the resin when the modified red phosphorus is kneaded with the resin, and the coarse particle size also impairs the dispersibility in the resin. Regarding the order of addition of raw materials, it is advantageous to adjust the pH of the aqueous suspension of red phosphorus and titanium oxide as necessary, and then add monomers capable of radical polymerization, polymerization initiators, etc. while stirring to perform the polymerization reaction. It is.
However, it is not always necessary to carry out the procedure in the above order; for example, start polymerization by adding a monomer capable of radical polymerization, a polymerization initiator, etc. to an aqueous suspension of red phosphorus, add titanium oxide halfway through the polymerization, and then add titanium oxide as needed. The method is to adjust the pH depending on the situation and complete the polymerization, or to start the polymerization by adding a monomer capable of radical polymerization, a polymerization initiator, etc. to an aqueous suspension of titanium oxide.
It is also possible to add red phosphorus in the middle of polymerization, adjust the pH as necessary, and complete the polymerization. The polymerization reaction is preferably carried out under an inert gas atmosphere such as nitrogen gas at a temperature of 30 DEG to 90 DEG C. for 1 to 7 hours. After the polymerization reaction is completed, the product is thoroughly filtered, washed with water, and dried according to a conventional method. The thus obtained modified red phosphorus of the present invention can hide, decolorize, and stabilize the deep dark red color inherent in red phosphorus. The state in which red phosphorus or titanium oxide did not aggregate alone and red phosphorus was uniformly coated with titanium oxide and polymer was confirmed by electron micrographs, and as is clear from the test examples described below.
Titanium oxide and polymer-coated red phosphorus are excellent as flame retardants, with high whiteness, enabling more free coloring of resin, high ignition point, and low amount of phosphine generation. Hereinafter, the present invention will be specifically explained with reference to Examples, Comparative Examples, Reference Examples, and Test Examples. Example 1 In a 200 ml glass reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, 100 ml of water and 15.0 g of unstabilized untreated red phosphorus were added.
and stir to disperse the red phosphorus in the water. Next, while stirring continuously, 13.0 g of rutile titanium oxide treated with a hydrous oxide of Al (manufactured by Ishihara Sangyo Co., Ltd., trade name: TYPEQ R-630) is added to coagulate and deposit on the red phosphorus. The pH of the suspension at this time is 3
It was hot. Further, while stirring, a monomer solution prepared by dissolving 0.3 g of triethylene glycol dimethacrylate as a crosslinking agent in 10.0 g of methyl methacrylate was added to ensure sufficient contact with the red titanium phosphate aggregate particles. Then the temperature of this suspension is 60~
The temperature was adjusted to 65°C, and 0.1 g (10 ml as a 1% by weight aqueous solution) of 2,2'azobis(2-amidinopropane) dihydrochloride was added as a polymerization initiator, followed by a polymerization reaction for 2 hours in a nitrogen atmosphere. After the reaction is completed, the suspension is cooled, filtered with suction, washed thoroughly with water, and the filter cake is dried under reduced pressure at 60 to 70°C until it reaches a constant weight. 36.8 g of quality red phosphorus was obtained. Example 2 Using the same equipment and operation as in Example 1, 100 ml of water,
25.0 g of untreated red phosphorus, 17.5 g of rutile-type titanium oxide (manufactured by Ishihara Sangyo Co., Ltd., trade name: TYPEQ R-820) treated to make the main component a hydrous oxide of Al,
was added. The pH at this time was 3. Next, 10.0 g of vinyl acetate and 0.4 g of potassium persulfate as a polymerization initiator (40 ml as a 1% by weight aqueous solution) were sequentially added, and a polymerization reaction was carried out to hide and erase the deep dark red characteristic of red phosphorus, producing grayish-white titanium oxide and polymer. 49.3 g of modified red phosphorus coated with Example 3 Using the same equipment and operation as in Example 1, 100 ml of water,
25.0 g of untreated red phosphorus and 15.0 g of titanium oxide (same as in Example 1) were added. The pH at this time was 3. Next, add styrene to 10.0g of methyl methacrylate.
After sequentially adding 3.0 g of monomer solution and 2.0 g of sodium hydrogen sulfate (40 ml as a 5% by weight aqueous solution) as a polymerization initiator, a polymerization reaction was carried out to produce modified red phosphorus coated with pale gray-white titanium oxide and polymer. I got g. Reference Example Table 1 shows the measurement results of the charge (indicated by + or -) and zeta potential (mV) at each PH of red phosphorus and titanium oxide used as raw materials in each Example or Comparative Example in water. In addition, PH was adjusted using HCl and NaOH.

[Table] Items without numerical values are due to agglomeration of the suspension and are quantitative.
It was impossible to measure.
Test Examples Next, the whiteness of each Example was measured using a photoelectric whiteness meter (Kett Science Institute Model C-1), and the ignition point and amount of phosphine generated were measured using the measurement methods described below. Shown in the table.

【table】

[Table] As described above, the modified red phosphorus coated with titanium oxide and polymer obtained based on the method of the present invention has a stable coating in terms of test results for ignition point and amount of phosphine generated. I know that I have it. Further, electron micrographs of the modified red phosphorus obtained in Example 1 of the present invention are shown in Figures 1 a to c, and electron micrographs of the red phosphorus obtained in Comparative Example 3 are shown in Figures 2 a to c.
Shown below. It can be seen from these photographs that the present invention is sufficiently coated. Ignition point measurement method The device used was a cylindrical electric furnace with a base area of 200 cm ² and a height of 25 cm, the outside of which was covered with a heat insulating material. It is designed to hold a 10ml crucible at a position approximately 10cm from the center of the bottom. For measurement, 3g of red phosphorus is placed in a crucible, a thermocouple is inserted into the center of the crucible, and the temperature is raised at a rate of 2.7°C/min. Once it reaches a certain point, the temperature rises rapidly and ignition begins. The ignition point was defined as the temperature just before the temperature suddenly rose. The ignition points in this example and comparative example were determined by averaging three similar measurements. Values below 1 were rounded off. Measuring method for the amount of phosphine generated (1) At 25℃ Place 10g of sample in a 1000ml flask and seal it.
Leave it in a constant temperature bath at 25℃±0.5℃ for 24 hours. After standing, the concentration of phosphine in the gas in the flask is determined using a detection tube, and this value is converted to the amount of phosphine generated per 1 g of red phosphorus. (2) At 80℃ Place 10g of the sample in a 1000ml flask that has been immersed in an oil bath at 80℃±0.5℃, seal it, and heat it for 30 minutes.
Leave for a minute. After standing, the concentration of phosphine in the gas in the flask is determined using a detection tube, and this value is converted to the amount of phosphine generated per 1 g of red phosphorus. (3) When the temperature is 150℃ Place 1g of the sample in a 1000ml flask that has been immersed in an oil bath at 150℃±0.5℃, seal it, and heat it for 30 minutes.
Leave for a minute. After standing, the phosphine concentration in the gas in the flask is measured with a detection tube, and this value is converted to the amount of phosphine generated per 1 g of red phosphorus. Note that each value was measured three times and is the average value thereof.

[Brief explanation of drawings]

Figures 1 a to c are electron micrographs of modified red phosphorus obtained in Example 1 of the present invention, and Figures 2 a to c
is an electron micrograph of red phosphorus obtained in Comparative Example 3.

Claims (1)

[Claims] 1 Modified red phosphorus whose particle surfaces are coated with at least titanium oxide and an organic polymer,
A modified red phosphorus characterized in that the organic polymer has a double bond in the molecule and is polymerized using a monomer capable of radical polymerization and a polymerization initiator.