Process for preparing aluminum salts of organic phosphoric...

Details Process for preparing aluminum salts of organic phosphoric... Process for preparing aluminum salts of organic phosphoric...

1999-05-03

2001-02-06

Ambrose, Michael G. (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Aluminum containing

Reexamination Certificate

active

06184405

ABSTRACT:

The invention relates to a process for the preparation of aluminum salts of organic acids of phosphorus. More specifically, these are phosphonic half-esters, phosphinic acids and phosphonous acids.
The aluminum salts of these organic phosphoric acids are valuable flame retardants.
Aluminum salts of phosphonic half-esters have hitherto been prepared by reacting aluminum chloride with phosphonic diesters (EP-A 245 207), by reacting elemental aluminum with phosphonic diesters (EP-A 299 922) and by reacting aluminum hydroxide with phosphonic diesters in the absence of water at 180° C. (EP-A 327 496). Aluminum salts of phosphinic acids and cyclic phosphinic acids (1-hydroxy-dihydrophosphole oxides and 1-hydroxy-phospholane oxides) have hitherto been prepared by reaction with aluminum hydroxide in water (EP-A2-0 699 708).
The reaction of phosphonic diesters with aluminum chloride, aluminum or aluminum hydroxide inevitably leads to undesired byproducts such as alkyl chlorides, alcohols, carbon monoxide, ethylene, ethane and low dialkyl ethers. The phosphonic diesters also have to be used in excess. The reaction of organic phosphoric acids in water with aluminum hydroxide is in itself technically simple. A disadvantage is the long reaction time which is required.
There was therefore a need to develop a process which avoids the aforementioned disadvantages, is industrially feasible without great expenditure and, moreover, makes the desired products available both in high yield and in high purity.
Surprisingly, this object was achieved by a process for the preparation of aluminum salts of organic phosphoric acids of the formula (I)
where
R
1
is a saturated or unsaturated or unbranched C
1
-C
8
, preferably C
1
-C
4
alkyl, or phenyl,
when n=0
R
2
is as defined for R
1
or is hydrogen, it also being possible for R
1
and R
2
to be joined to give a saturated or unsaturated ring,
when n=1
R
2
is a saturated C
1
-C
4
preferably C
1
, alkyl, which comprises reacting, in the absence or presence of water, organic phosphoric acids of the formula (II)
where R
1
, R
2
and n are as defined above, with aluminum hydroxide in the presence of polar solvents.
Surprisingly, it was found that the chemically largely inert aluminum hydroxide reacts more quickly in the presence of polar solvents.
Examples of organic phosphoric acids which may be mentioned are:
1. Phosphonic monoesters: monomethyl methanephosphonates, monomethyl propanephosphonates, monoethyl ethanephosphonates, mono-n-propyl phenylphosphonates.
2. Phosphinic acids: dimethylphosphinic acid, ethylmethylphosphinic acid, propylmethylphosphinic acid, methylphenylphosphinic acid.
3. Cyclic phosphinic acids: 1-hydroxy-3-methyl-2,5-dihydro-1H-phosphole 1-oxide, 1-hydroxy-2,3-dihydro-1H-phosphole 1-oxide, 1-hydroxy-2,5-dihydro-1H-phosphole 1-oxide, 1-hydroxy-1H-phospholane 1-oxide and 1-hydroxy-3-methyl-1H-phospholane 1-oxide.
4. Phosphonous acids: methanephosphonous acid, propanephosphonous acid, octanephosphonous acid, phenylphosphonous acid.
Polar solvents which may be mentioned in particular are: acetic acid, propionic acid, methanol, ethanol, propanol, butanol, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane and acetonitrile. Acetic acid and isopropanol are particularly preferred.
The solvents can also be used as mixtures. In particular, mixtures with water can be used advantageously.
The reaction temperatures are 50 to 200° C., preferably 70 to 100° C. The reaction is preferably carried out under reflux conditions. At higher temperatures, the reaction may be carried out under pressure.
The reaction components can be mixed with the solvents and are then usually stirred for several hours at the desired reaction temperature. It can also be advantageous to introduce the solvent or solvent mixture with aluminum hydroxide, and slowly meter in the organic phosphoric acid at the reaction temperature with continuous stirring. After the reaction has finished, the mixture is filtered off with suction and the aluminum salt produced is dried. In the process of the present invention, the aluminum salts which are produced are finely particulate with a mean particle size of from 2 to 25 &mgr;m. It is not therefore necessary to grind these salts after drying for plastics compounding.


REFERENCES:
patent: 3494949 (1970-02-01), Monroe et al.
patent: 4481026 (1984-11-01), Prisbylla
patent: 5174991 (1992-12-01), Omatsu et al.
patent: 5773556 (1998-06-01), Kleiner et al.
patent: 5891226 (1999-04-01), Kleiner et al.
patent: 700042 (1967-06-01), None
patent: 0 699 708 A2 (1996-03-01), None
Derwent World Patents Index, ©Derwent Information Ltd., Accession No. 1968-98748P (1968).

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