JPS59102807A - Production of modified red phosphorus - Google Patents

Abstract

PURPOSE:To obtain red phosphorus valuable as a flame-retardant having a high ingition point, evolving a small amount of phosphine, not reducing physical properties of base material, by covering the surfaces of red phosphorus particles with methacrylic acid polymer having a crosslinking structure under specific conditions. CONSTITUTION:A methacrylic acid lower alkyl ester monomer are copolymerized in a water suspension of red phosphorus at 2-6 pH in the presence of 2,2'-azobis-(2-amidinopropane)dihydrochloride, a polymerization initiator, and a crosslinking agent. The surfaces of red phosphorus particles are thus convered with a polymer having a crosslinking structure. A polyfunctional monomer such as ethyl dimethacrylate, etc., forming a polymer having a crosslinking structure, having two or more double bonds in the molecule, may be cited as the crosslinking agent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing modified red phosphorus. More specifically, the present invention relates to a method for producing Kaiken Red Phosphorus, which has a high ignition point, produces a small amount of phosphino, and does not deteriorate the physical properties of the base material, and is particularly valuable as a flame retardant.

It is already known that red phosphorus has a high phosphorus content and exhibits effective flame retardancy even when added in small amounts. Moreover, unlike halogen flame retardants, red phosphorus generates less organic gas, and since it is a solid substance, it does not change the physical properties of the resin, so it can be added simply as an extender. This is one of the flame retardants that has been attracting particular attention recently.

However, if red phosphorus is added as it is, red phosphorus reacts with water and undergoes hydrolysis, becoming phosphine and volatilizing, so it has been desired to modify red phosphorus.

In addition, when red phosphorus is used as a flame retardant in a resin, the following three conditions must be satisfied in order to prevent the generation of phosphine.

(1) High ignition point: Depending on handling and storage stability, or depending on the resin, the temperature may be quite high during kneading, so safety in this respect is required.

(2) Low generation of phosphine Red phosphorus undergoes hydrolysis in the presence of moisture, and some of it becomes phosphine and scatters, which is an occupational health problem. Particularly when it is added to a resin at a high temperature, the generation of this phosphine is significant.

(3) Avoid degrading the physical properties of the base material (especially synthetic resin) Acidic substances produced when red phosphorus is oxidized or hydrolyzed cause deterioration of the physical and electrical properties of the synthetic resin. This is particularly noticeable when the resin is exposed to high temperatures for a long period of time.

Conventionally, various efforts have been made to improve the properties of red phosphorus in order to meet these conditions.

For example, red phosphorus can be replaced with aluminum hydroxide, red sea bream hydroxide, etc.
A method of treatment with an inorganic substance such as silium, a method of treatment with an organic substance such as paraffin, wax, caprolactam, thermosetting resin, etc. (U.S. Patent No. 2,635,953,
Special Publication No. 45-37125 and Special Publication No. 49-16354) were carried out.

However, both methods are difficult to form a uniform film industrially, and although they are effective to some extent on the ignition point, they are less effective in suppressing phosphine despite the large amount of coating, and the coating and red phosphorus are simply Since it is only bonded, there are problems such as weak mechanical and thermal strength and easy peeling.

In addition, Japanese Patent Publication No. 53-38171 describes a method of encapsulating red phosphorus using a thermoplastic polymer using a conventional general encapsulation method, but these methods have low coating efficiency and are difficult to integrate with red phosphorus. In addition, the encapsulation process requires a large amount of organic solvent as a nutrient, which is unfavorable industrially from the viewpoint of cost, safety, and hygiene. For example, when used in resins such as unsaturated polyester, they have some problems such as poor chemical resistance to styrene and the like.

There is a method of polycondensing phenol-formalin, urea-formalin, etc. in an aqueous suspension and coating it with a thermosetting resin (Japanese Patent Publication No. 54-39200), but this method In the suspension, polycondensation and curing are completed, but the polycondensation is completed during the drying process, and at that time, aggregation between red phosphorus particles, which is thought to be caused by the sticky initial condensate, occurs. There are problems that can easily occur.

Therefore, in view of the above, the present inventors conducted various studies on a method for producing modified red phosphorus that satisfies the three conditions mentioned above as a flame retardant, and as a result, under specific conditions, the particle surface of red phosphorus is converted into a polymer having a crosslinked structure. The present invention was completed by discovering that the above conditions can be achieved by coating.

That is, in the present invention, a lower alkyl methacrylate monomer, 2,2'-azobis-(
This method for producing modified red phosphorus is characterized in that the surface of red phosphorus particles is coated with a polymer having a crosslinked structure by adding and co-merging 2-amidinopropane (2-amidinopropane) dihydrochloride and a crosslinking agent.

The red phosphorus used in the present invention may not only be untreated after production, but also red phosphorus stabilized with aluminum oxide, magnesium oxide, etc., or a mixture of phosphorus allotropes other than yellow phosphorus such as black phosphorus, and the particle size is usually It is preferable that the value falls within the range of 01 to 100μ because it has good kneadability with the resin when the obtained modified red phosphorus is mixed into the resin.

As for the concentration of such an aqueous suspension of red phosphorus, a suspension of about 5 to 80 parts by weight of red phosphorus per 100 parts by weight of water provides good workability. In other words, the suspension having the above concentration range has good dispersibility and can uniformly coat the surface of the red phosphorus particles with the polymer. If it is less than 5 parts by weight, the yield of the target product will be poor and economical efficiency will be poor, and if it exceeds 80 parts by weight, the resulting polymer will become a binder and agglomeration of red phosphorus particles will easily occur, which is not preferable.

Next, the lower alkyl methacrylate monomer used in the present invention is a polymer having a crosslinked structure by copolymerizing with the crosslinking agent described below in the presence of 2,2'-azobis-(2-amidinopropane) dihydrochloride, which is a polymerization initiator. is a compound that forms on the surface of red phosphorus particles.Specifically, methyl methacrylate,
Examples include lower alkyl esters of methacrylic acid such as methacrylic acetate, isobutyl meccrylate, M-n-butyl methacrylate, and t-butyl methacrylate.

Vinyl yarn threads similar to lower alkyl methacrylate monomers, such as vinyl chloride 7mer 1 vinyl acetate 7mer
, methyl acrylate monomer, methacrylic acid monomer,
The use of acrylic acid monomers may also be considered; however, these monomers have a low boiling point, are easily hydrolyzed, have a low solubility in water, and have a high affinity for red phosphorus particles (wetting ) Contains one of the following problems, such as poor effectiveness or poor polymerizability. Therefore, lower alkyl methacrylate monomers which do not have the above-mentioned disadvantages are most suitable in combination with red phosphorus.

However, the lower alkyl methacrylate monomer of the present invention is not limited to being used 100% alone, and if the properties of the lower alkyl methacrylate monomer are dominant, other vinyl yarn threads such as It is also possible to partially copolymerize styrene and the like.

The appropriate amount of lower alkyl methacrylate monomer added to red phosphorus is 0.5 to 0.05 parts by weight per 100 parts by weight of red phosphorus.
It is 100 parts by weight. If the amount added is less than 0.5 parts by weight, a stable effect cannot be obtained in achieving the object of the present invention,
In addition, if a large amount exceeding 100 parts by volume is used, polymerization in the water 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 become a binder and cause the red phosphorus to polymerize considerably. This is not preferable as it may cause agglomeration. The presence of free polymers in this way unnecessarily contaminates the resin when kneading it with the resin.
Moreover, coarse particle size also impairs the dispersibility of the resin.

Further, the crosslinking agent of the present invention is a polyfunctional heptadmer having two or more two-bundle bonds in one molecule, which makes the produced polymer a crosslinking groove, such as ethylene dimethacrylate, diethylene glycol dimethacrylate, etc. , triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, dimethacryl lvl, 3-butylene, trimethylolpropane trimethacrylate, and the like.

The appropriate amount of this crosslinking agent to be added to the lower alkyl methacrylate monomer is 1 part of the lower alkyl methacrylate monomer.
The amount is 1 to 20 parts by weight per 00 parts by weight. Addition amount is 1
If it is less than 20 parts by weight, the produced polymer will have poor chemical resistance, and if it exceeds 20 parts by weight, the yield of the produced polymer will be low.

The produced polymer having a crosslinked structure firmly adheres to the surface of the red phosphorus particles as a coating, and is not exposed to organic solvents such as styrene, etc.
This is confirmed by the fact that it is not destroyed or extracted by methyl ether ketone, etc.

The amount of 2,2'-azobis-(2-amidinopropane) dihydrochloride, which is a polymerization initiator, is related to Togane conditions such as monomer concentration, polymerization temperature, and atmosphere during polymerization at pH 1 of the suspension. Usually O, OOO1-0 per 1 ton of water
In the present invention, modified red phosphorus is produced using the above-mentioned raw materials, but to describe an embodiment of the invention, a predetermined amount of red phosphorus is sufficiently added to water to make it cloudy. A suspension of red phosphorus in water having a pH of 2 to 6 is prepared, and a lower alkyl methacrylate monomer, 2,2'-azobis-(2-amidinopropane) dihydrochloride, and a crosslinking agent are added thereto for co-polymerization.

Here, the pH of the red phosphorus suspension is within the above range.
When the undercarriage reaction is carried out, red phosphorus can be coated efficiently. For example, when using red phosphorus stabilized with aqueous magui-sium as red phosphorus, if the reaction is carried out under conditions where the pH is higher than 6, such as in an aqueous suspension, the polymer yield will be low and red phosphorus will be formed. If the pH is higher than 6, hydrochloric acid, sulfuric acid,
The reaction is carried out by adjusting the pH to 2 to 6 using a common mineral acid such as phosphoric acid. On the other hand, in the case of unstabilized untreated red phosphorus, the surface of the phosphorus particles is often slightly oxidized, and its aqueous suspension falls within the above pH range, so it can be used as is for the polymerization reaction. It will be done.

Regarding raw materials and the order of addition, while stirring the aqueous suspension of red phosphorus, add the lower alkyl methacrylate monomer in which cross-linked finish 1j has been dissolved, bring the red phosphorus particles into sufficient contact with the monomer liquid, and then add It is advantageous to carry out the polymerization reaction by adding the polymerization initiator 2,2'-azobis-(2-amidinopropane) dihydrochloride. However, it is not necessarily necessary to do it in the above order, for example, red phosphorus water? @' A method in which 2,2'-azobis-(2-amidinopropane) dihydrochloride is first added to the suspension, and then a monomer is added to carry out the polymerization reaction, or a method in which the polymerization reaction of the monomer is first carried out in water. It is also possible to add red phosphorus in the middle of the reaction to cover it with red phosphorus.

In any case, it is sufficient for the polymerization reaction to be carried out preferably under an inert gas atmosphere such as nitrogen gas at a temperature of 30 to 90°C for 1 to 7 hours. After the polymerization reaction is completed, the product is filtered, washed with water and dried using conventional methods.

Thus, according to the present invention, the surface of red phosphorus particles can be firmly coated with a polymer having a crosslinked structure, and as is clear from the test examples described later, the ignition point is high, phosphine generation is small, and the base material Modified red phosphorus is obtained which is excellent as a flame retardant because it does not significantly reduce the physical properties of the substance used as a flame retardant.

Hereinafter, the present invention will be specifically explained with reference to Examples, Comparative Examples, and Test Examples. 450 ml of water and unstabilized untreated red phosphorus (average particle size 18 μm) 5002 were charged into a reaction vessel and stirred to uniformly disperse the mixture.

Next, while stirring, a monomer solution in which triethylene glycol dimethacrylate 05g as a crosslinking agent was dissolved in methyl methacrylate 957 was added, and the red phosphorus particles were brought into sufficient contact with the monomer. temperature of 60~
The temperature was adjusted to 65°C, and 0.05 i7 of 2,2'-azobis-(2-amidinopropane) dihydrochloride (5- as a 1% aqueous solution by volume) was cooled and polymerized for 2 hours in a nitrogen atmosphere. Ta. The pH of the suspension at this time was 3.

After the reaction was completed, almost no free polymer was observed in the red phosphorus suspension.

After cooling, this suspension was suction filtered and thoroughly washed with water, and the filter residue was dried under reduced pressure at 70 to 80°C for 4 hours to obtain 581 pieces of red phosphorus coated with a polymer. Therefore, when calculating the polymer yield from the weight increase of red phosphorus after the reaction, it is 8
It will be 1%.

Example 2 In an apparatus similar to Example 1, 450 g of water, a 7mer solution prepared by dissolving 05 g of trimethylolpropane trimethacrylate as a crosslinking agent in 95 g of methyl methacrylate, and 2,2'-azobis-(2-amidino) were added. 0.03 P of dihydrochloride (propane) (3 times as a 1% by weight aqueous solution) was added, the pH was adjusted to 5.0 with hydrochloric acid, and the mixture was mixed at 60 to 65° C. for 30 minutes in a nitrogen atmosphere. after that,
Untreated Akasu 75002.2.2'-Azobis-(2-amidinopropane) dihydrochloride 0.03 P (3- as a 1% aqueous solution) was cooled, and polymerization was further carried out for 2 hours. Polymer-coated red phosphorus 5 was prepared in the same manner as in Example 1.
I got 852. Polymer expropriation is 85%.

Example 3 Using the same equipment and operation as in Example 1, Motsumar was prepared by dissolving 0.5 g of triethylene glycol dimethacrylate as a crosslinking agent in 400 ml of water, 100.09 ml of untreated red phosphorus, 852 ml of methyl methacrylate, and 10 g of styrene. and 2,2'-azobis-(2-amidinopropane) dihydrochloride 0.05 F (1 wt% aqueous solution 5-) were charged in order and polymerized to obtain polymer-coated red sand 108.49. . The yield of polymer is 84%.

Example 4 Using the same equipment and operation as in Example 1, 0.3 g of 1,3-butylene dimethacrylate was dissolved as a crosslinking agent in 400 g of water, 200.0 g of untreated red phosphorus, and 97 g of ethyl methacrylate. Seventhmer solution, and 2,2'-azobis-(2
-amidinopropane) dihydrochloride 0.109 (1 car weight%)
10 aqueous solutions were sequentially charged and polymerized to obtain polymer-coated red phosphorus 208°17. The yield of polymer is 81
%.

Example 5 Using the same equipment and operation as in Example 1, a 7-mer solution prepared by dissolving 10 g of atophethylene glycol dimethacrylate in 500-1 water, 4002 untreated red phosphorus, and 9.07 g of ethyl methacrylate, and 2. 2'-azobis-(2-amidinopropane) dihydrochloride o10 F! (10 volumes of 1% by weight aqueous solution) were sequentially charged and polymerized to obtain polymerized red phosphorus 4769. The yield of polymer is 76%.

Comparative Example 1 A vehicle chassis was manufactured using the same equipment and operation as in Example 1, replacing untreated red phosphorus with red phosphorus stabilized with magnesium hydroxide, which is generally available on the market.

The pH of the suspension at this time was 8. After the reaction was completed, considerable white turbidity of free polymer was observed in the red phosphorus suspension, indicating that the red phosphorus particles and the produced polymer were not sufficiently integrated. The filter cake was dried to give a yield of 565 grams.

Therefore, the yield of the polymer is calculated to be 65X.

Comparative Example 2 Polymerization was carried out using the same equipment and operation as in Example 1, but without adding a crosslinking agent and adding 10.09 g of methyl methacrylate monomer. The filter cake was dried to give a yield of 583 grams. Therefore, the yield of the polymer is 83%.The polymer obtained in Example 1 and the polymer obtained in Comparative Example 2 were each converted into nutylene for 3 hours &? When dried after drying, the former did not change in appearance, but the latter's polymer coating became dull and turned into lumps.

Similarly, those obtained in Example 1 and Comparative Example 2 were each 5.
0y with methyl ether ketone using a Soxhlet extractor
Time extracted. As a result, the extraction loss of the product obtained in Example 1 was 0092, so the amount of unextractable polymer was 871%.
The extraction loss of the polymer obtained in Comparative Example 2 was 0552, and therefore the amount of polymer that could not be extracted was 225X.

Test Next, the ignition point and amount of phosphine generated were measured for the Examples and are shown in Table 1 along with the Comparative Examples.

2 The ignition point measurement method device has a bottom area of 200 crZ with the outside covered with a heat insulating material,
A cylindrical electric furnace with a height of 25 cm was used. A 10-sized crucible can be held at a position approximately 1Qcm from the center of the bottom.

For measurement, 37 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 33-C. When 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 Examples and Comparative Examples are obtained by averaging three similar measurements. Values below 1 are rounded off.

Method for measuring the amount of phosphine generated (1) At 25'C, put sample F4109 into a 1000-℃ flask and seal it.
It was left in a constant temperature bath at 25"C±05 for a time.

After standing, quantify the phosphine concentration in the gas inside the flask,
This value was converted into the amount of phosphine generated per 1 g of red phosphorus.

When the temperature is +2 + 80℃, 10g of the sample is immersed in an oil bath at SO'C ± 0.5℃ in advance and placed in a 1000fni flask and sealed.
It was left for 0 minutes. After standing, the phosphine concentration in the gas in the flask was determined, and this value was converted into the amount of phosphine generated per 1 g of red phosphorus.

13) When the temperature was 150°C, sample 12 was immersed in an oil bath at 150°C±0.5°C, placed in a 1000° flask, sealed, and left for 30 minutes. After standing, the phosphine concentration in the gas in the flask was determined, and this value was converted into the amount of phosphine generated per 15' of red phosphorus.

In addition, each value was measured three times and is the average value thereof.

As described above, it can be seen that the polymer-coated red phosphorus obtained according to the present invention has a polymer coating that is stable in use, also from the test results of ignition point and amount of phosphine generated.

Incidentally, when the polymer-coated red phosphorus according to the present invention was added to a resin, the flame retardance was significantly the same as above, and there was no deterioration in the mechanical properties and electrical properties of the resin.

Patent applicant Yutaka Yutaka, representative of Nihon Kagaku Kogyo Co., Ltd. 1) Yoshio 31
−

Claims (1)

[Claims] 1) Copolymerization by adding a lower alkyl methacrylate monomer, 2,2'-azobis-(2-amidinopropane) dihydrochloride, and a crosslinking agent to an aqueous suspension of red phosphorus at pH 2 to 6. A method for producing modified red phosphorus, which comprises coating the surface of red phosphorus particles with a polymer having a crosslinked structure. 2) The method for producing modified red phosphorus according to claim 1, wherein the aqueous suspension of red phosphorus is a suspension of 5 to 80 parts by weight of red phosphorus in 100 parts by weight of water. 3) The method for producing modified red phosphorus according to claim 1 or 2, wherein the red phosphorus has a particle size of 01 to 100μ. 4) Red phosphorus 100% lower alkyl methacrylate monomer
The method for producing modified red phosphorus according to any one of claims 1 to 3, wherein the amount is 05 to 100 parts by weight. 5) Lower alkyl methacrylate monomer 100% as a crosslinking agent
The method for producing modified red phosphorus according to any one of claims 1 to 4, wherein the amount is 1 to 20 parts by weight. 6) The crosslinking agent was selected from ethylene dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene dimethacrylate, and trimethylolpropane trimethacrylate. The method for producing Kaibao red phosphorus according to any one of claims 1 to 5, using one or more types.