Organic compounds -- part of the class 532-570 series – Organic compounds – Phosphorus acids or salts thereof
Reexamination Certificate
2000-03-06
2001-10-23
Vollano, Jean F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Phosphorus acids or salts thereof
C556S174000
Reexamination Certificate
active
06307097
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for the preparation of aluminum salts of cyclic saturated or unsaturated phosphinic acids, in particular aluminum salts of 1-hydroxydihydrophosphole oxides and 1-hydroxyphospholane oxides.
2. Description of the Prior Art
Salts of phosphinic acids have already been known per se for some time and are recommended in particular as flame-inhibiting additives for thermoplastics such as polyesters or polyamides. Thus, DE-A1-2252258 describes alkali metal salts of phosphinic acids. They must, however, be added in relatively large amounts and some have an unfavorable corrosion-promoting influence on the processing machinery.
EP-A3-0699708 discloses polyester molding compositions which contain calcium salts or aluminum salts of phosphinic acids of the following formulae:
wherein
R
1
and R
2
are C
1
-C
6
-alkyl, linear or branched; phenyl;
R
3
is C
1
-C
10
-alkylene, linear or branched; arylene; alkylarylene; or arylalkylene;
M is a calcium ion or aluminum ion;
m is 2 or 3;
n is 1 or 3; and
x is 1or 2.
The preparation of the aluminum salts, described in this European patent application, of the phosphinic acids mentioned therein requires a relatively long reaction time, namely 24, or even 65, hours.
Although a large number of phosphinic acid compounds and preparation processes for these compounds are already known, there is still a need for improved processes for the preparation of suitable phosphinic acid salts which may be used as agents for improving the flame resistance of plastics.
The object of the invention is thus to provide a process in which it is possible to prepare desirable phosphinic acid salts which may be used as flameproofing agents; the object of the invention is also to provide a process which is economical and which leads to high yields in short reaction times. The object of the invention is also to provide a process which is environmentally friendly and which produces no or only small amounts of substances which must be removed during isolation of the final product and be disposed of.
SUMMARY OF THE INVENTION
This object is achieved by a process for the preparation of aluminum salts of cyclic phosphinic acids, which comprises reacting cyclic phosphinic acids with aluminum hydroxide in the presence of water and in the absence of polar solvents at elevated temperature for a reaction time of from 1 to 20 hours. The reaction is preferably carried out for a period of from 1 to 10, in particular from 3 to 7, hours. Particularly advantageous reaction temperatures are from 50 to 200° C., in particular from 80 to 100° C. It is advantageous to react 1 mole of acid with ⅓ of a mole of aluminum hydroxide in the presence of from 0.5 to 3 ml of water, calculated per gram of acid; from 1 to 2 ml of water are preferably used per gram of acid.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The cyclic phosphinic acids used to react with aluminum hydroxide are preferably 1-hydroxydihydrophosphole oxides of the formula Ia or Ib and 1-hydroxyphospholane oxides of the formula Ic or mixtures thereof,
in which R
1
, R
2
, R
3
, R
4
are hydrogen or alkyl, preferably C
1
-C
12
-alkyl, in particular C
1
-C
4
-alkyl, preferably methyl or ethyl.
The reaction may be carried out under pressure, and is preferably carried out in an autoclave under autogenous pressure.
The cyclic phosphinic acids used according to the invention can be obtained by hydrolysis of the corresponding cyclic chlorine compounds. Thus, the preparation of 1-chlorodihydrophosphole oxide and hydrolysis of this compound to 1-hydroxydihydrophosphole oxide is described by Kurt Moedritzer in SYN. REACT. INORG. METAL-ORG. CHEM., 5(1), 45-58 (1975). Another synthesis for preparing such chlorine compounds can be found in EP-A1-0452755. The saturated cyclic phosphinic acids can be obtained by hydrogenating the corresponding unsaturated cyclic phosphinic acids.
To prepare the corresponding aluminum salts, the phosphinic acids are dissolved in water and reacted with aluminum hydroxide. If it is not absolutely necessary to carry out the reaction in exactly stoichiometric proportions, it is advantageous to use ⅓ of a mole of aluminum hydroxide per mole of acid. The amount of water used in the reaction can also vary within wide limits. It is, however, advantageous to use from about 1 to 2 ml of water per gram of acid used.
The reaction is carried out at elevated temperature, the reaction mixture advantageously being stirred during the reaction. It is advantageous to maintain a temperature of at least 50° C. and a very suitable temperature range is from 80 to 100° C.
The reaction can also be carried out very successfully under pressure, pressures of from 2 to 10 bar being particularly advantageous.
The reaction can also be carried out at temperatures above 100° C., temperatures of up to 200° C. being particularly advantageous.
Cyclic phosphinic acids which are suitable for the novel process and have proven successful include the following compounds:
1-Hydroxy-3-methyl-2,5-dihydro-1H-phosphole 1-oxide, 1-hydroxy-3-methyl-1H-phospholane 1-oxide, 1-hydroxy-2,3-dihydro-1H-phosphole 1-oxide, 1-hydroxy-2,5-dihydro-1H-phosphole 1-oxide and 1-hydroxy-1H-phospholane 1-oxide.
The times for the reaction of the invention are generally at most 20 hours, but are in most cases considerably less than this; it is advantageous to carry out the reaction within a period of from 1 to 10 hours, in particular from 3 to 7 hours. It is also very advantageous to carry out the reaction in an autoclave under autogenous pressure, i.e. the reaction components cyclic phosphinic acid, aluminum hydroxide and water are introduced into an autoclave where they are reacted under autogenous pressure, i.e. the reaction mixture is heated in the autoclave in a closed system so that the reaction is carried out under the pressure which arises during heating.
The reaction is carried out without the addition of polar solvents such as acetic acid, propionic acid, methanol, ethanol, propanol, butanol, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, acetonitrile and the like.
It was particularly surprising that it is possible, using the novel process, to prepare the desirable aluminum salts of cyclic saturated and unsaturated phosphinic acids within short reaction times. In contrast to the long reaction times of 24 or 65 hours, as required for the preparation of aluminum salts of noncyclic salts of phosphinic acids, the reaction times of the invention are significantly shorter. In most cases, a reaction time of at most 7 hours is sufficient to obtain very high yields.
The process gives very desirable aluminum salts of cyclic phosphinic acids, which can be used in particular as flame retardants for plastics such as polyamides, in particular polyesters.
Since the reaction requires just 3 components, namely the phosphinic acid, aluminum hydroxide and water, the process is also very environmentally friendly; removal and disposal of byproducts or undesired substances, such as organic solvents, is not necessary.
REFERENCES:
patent: 3594347 (1971-07-01), Lazarus et al.
patent: 3892998 (1975-07-01), Tsui et al.
patent: 3900444 (1975-08-01), Racky et al.
patent: 3953539 (1976-04-01), Kawase et al.
patent: 4036811 (1977-07-01), Noetzel et al.
patent: 4049612 (1977-09-01), Sandler
patent: 4078016 (1978-03-01), Kramer
patent: 4180495 (1979-12-01), Sandler
patent: 4208321 (1980-06-01), Sandler
patent: 4208322 (1980-06-01), Sandler
patent: 5780534 (1998-07-01), Kleiner et al.
patent: 6087423 (2000-07-01), Kleiner et al.
patent: 700 042 (1967-07-01), None
patent: 2 102 841 (1971-08-01), None
patent: 2 252 258 (1974-05-01), None
patent: 2 252 256 (1974-05-01), None
patent: 2 447 727 (1976-04-01), None
patent: 2 915 116 (1979-10-01), None
patent: 2 827 867 (1980-01-01), None
patent: 006 568 (1980-01-01), None
patent: 452 755 (1991-10-01), None
patent: 458 067 (1991-11-01), None
patent: 699 708 (1996-03-01), None
patent: 794 191 (1997-09-01), None
patent: 0794191 (1997-09-01), None
patent: 2 204
Connolly Bove & Lodge & Hutz LLP
Ticona GmbH
Vollano Jean F.
LandOfFree
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