Difficultly flammable polyarylene ether resins containing phosphorus having the structure ##STR1## and methods for making the same.

The present invention relates to difficultly flammable polyarylene ethers 
having a very high decomposition temperature and a glass transition 
temperature ranging from 100.degree. C. to 300.degree. C., and to a 
process for making the same. 
Published German patent application No. 29 25 206 teaches polyester 
phosphonates having molecular weights ranging from 11,000 to 200,000 and 
comprising mixed polyesters of an aromatic diol, an aromatic dicarboxylic 
acid, and a phosphonic acid. They have a decomposition temperature of over 
300.degree. C. and range from difficultly flammable to nonflammable. They 
are partially hydrolyzed at high temperature by water or alkalis and are 
thus dissociated into oligomers. This sensitivity to hydrolysis limits the 
potential uses of these polymers. 
Phosphorus-containing aromatic polyethers prepared by the polycondensation 
of bis-(para-chlorophenyl)phenylphosphine oxide with aromatic diols in the 
presence of an alkali are known from an article by S. Hashimoto et al., 
Journal of Macromol. Sci. Chem. A 11 (12), 2167-2176 (1977). The 
polyethers there described have a relatively low molecular weight and a 
reduced viscosity, .eta..sub.sp /c, of 0.15 dl/g or less. They are formed 
partly of brown, viscous oils and partly of rubberlike masses or friable 
powders. Sintering of the solid reaction products results in bodies of low 
strength which have none of the properties of synthetic resins. 
The object of the present invention is to improve the resistance to 
hydrolysis and weathering of the prior art difficultly flammable 
polycondensates containing phosphorus and to increase their thermal 
stability. A feature of the invention are polyarylene ether polymers 
according to the invention which differ from the compounds described by 
Hashimoto et al. in that they have a larger reduced viscosity, i.e. a 
higher molecular weight. Surprisingly, they are materials possessing 
considerable strength and the typical properties of plastics. 
The new materials can be molded at high temperature or can be thermoformed 
in the thermoplastic state into shaped articles of all kinds. In 
particular, they are processed into foils and fibers. These can be further 
shaped into three dimensional articles while in the thermoplastic state. 
The new materials are suited for end uses requiring the typical properties 
of plastics, such as low weight, high impact strength, and high 
flexibility, and where at the same time complete or almost complete 
nonflammability and extremely high thermal stability are required. 
The new materials differ from prior art polyarylene ethers containing 
phosphorus in that they have the properties of true synthetic resins, 
which properties render them suitable for use as engineering materials. 
They possess higher resistance to hydrolysis and higher thermal stability 
than do prior art materials comprising polyester phosphonates. 
Thermogravimetric analyses and differential scanning calorimetry (DSC) 
measurements both show that the decomposition temperature is about 
500.degree. C. 
It has been found that the new polyarylene ethers containing phosphorus 
exhibit the desired properties of synthetic resins only when they have a 
reduced viscosity of at least 0.25 dl/g. Preferably, the reduced viscosity 
is greater than 0.3 dl/g and still more preferably is in the range from 
0.4 to 2 dl/g. These reduced viscosity ranges correspond to molecular 
weights of at least 10,000, and preferably from 15,000 to 500,000. 
These compounds are difficultly flammable or non-flammable if they have a 
phosphorus content of at least 2 weight percent. The phosphorus content 
preferably ranges from 4 to 11 percent. Their flammability is reduced 
further if the composition of the polyethers includes chlorinated or 
brominated aromatic hydrocarbon compounds. 
It has been found that polyarylene ethers containing phosphorus having the 
requisite minimum value of reduced viscosity can be prepared by the 
polycondensation of a difunctional phosphine or phosphine oxide of the 
following formula I with a difunctional aromatic compound of following 
formula II if half of the functional groups, X, are fluorine atoms and the 
other half are hydroxyl groups. Polycondensation probably proceeds such 
that the aromatic hydroxyl groups first react with an equivalent amount of 
alkali to give the corresponding alkali metal salt. These groups then 
react with the fluorinated compound with elimination of an alkali metal 
fluoride in according to the following schematized formulas. 
##STR2## 
wherein 
Ar is phenylene, naphthalene, or 
##STR3## 
R taken alone, is hydrogen; adjacent R's, taken pairwise, are an oxygen 
atom or are R"; 
R' is alkyl, chloromethyl, aryl, alkoxy, or aryloxy; 
R" is a covalent bond, a sulfur atom, or a sulfonyl, carbonyl, methylene, 
or isopropylidene bridging group; 
E are the same or different terminal groups which are hydrogen, halogen, 
alkyl, aryl, alkoxy, alkoyl, or oxyalkoyl; 
m has an average value from 0 to 10; 
q is 0 or 1; and 
n is a number corresponding to the degree of polycondensation of the 
polyarylene ether obtained, i.e. has an average value of at least 10. The 
product has a reduced viscosity, .eta..sub.sp /c equal to or greater than 
0.25 dl/g. 
A phosphine or phosphine oxide (I) wherein X is OH and a compound (II) 
wherein X is F may be reacted in analogous fashion. When a strictly 
alternating structure built up from units corresponding to (I) and (II) is 
desired, symmetrical compounds (I) and (II) are used in which the X groups 
are the same; in other words, a difluoride is reacted with a diol. 
Asymmetrical compounds (IV) and (V) below could be co-condensed 
statistically and, depending on the reactivity of the functional groups, 
in a more or less broad chemical distribution: 
##STR4## 
Product (III) wherein m is 0 is obtainable by polycondensation of (IV) 
alone or by reaction of (I) (X=F) with (I) (X=OH). 
The reaction is appropriately carried out at an elevated temperature in a 
suitable solvent. The solvent should preferably dissolve both of the 
starting materials and the corresponding polycondensate, whereas the 
alkali metal fluoride should remain undissolved. The latter can then be 
removed from the reaction solution by filtration or centrifugation. 
Examples of suitable solvents are chlorobenzene and N-methylpyrrolidone. 
The condensation can be carried out at a temperature from 100.degree. to 
300.degree. C., and preferably from 120.degree. to 200.degree. C. The 
condensation conditions are maintained until the requisite minimum reduced 
viscosity value is attained as condensation proceeds. This calls for a 
very high degree of conversion. As a rule, nearly complete conversion of 
the functional groups is desired. This requires reaction times from 2 to 
10 hours, and occasionally of over 10 hours. 
In order that the desired degree of polycondensation n may be attained, it 
is necessary that the fluorine atoms and the hydroxyl groups be present in 
the starting mixture in a stoichiometric ratio of exactly 1:1, while the 
alkali may be used in limited excess. Moreover, the difunctional starting 
materials should be of high purity. Secondary constituents which might 
enter into the condensation reaction but are not difunctional should be 
less than 0.1 weight percent, and preferably less than 0.01 weight 
percent, of the starting materials (I) and (II). 
When the starting materials (I) and (II) are symmetrical, they may be used 
in any desired mixing ratio, provided that the condition is satisfied that 
the functional fluorine atoms and hydroxyl groups are present in 
equivalent numbers. 
For example, the difluorine component may be formed of several compounds, 
some of which may have the structure (I) while others have the structure 
(II). The same applies to the dihydroxy component. When only components of 
structure (I) are used, then m will have the value 0 in the end product of 
formula (III). When the components of structure (I) predominate 
stoichiometrically, m has an average value between 0 and 1. If, on the 
other hand, the components of structure (II) predominate, the average 
value of m will be over 1 and may be as high as 10. With values over 10, 
the influence of the units having the structure (I) would be too slight 
and the desired advantageous properties would not be fully obtained. 
All strongly basic alkali compounds which bind the hydrogen fluoride which 
is split off during the condensation in the form of an alkali metal 
fluoride are suitable condensing agents. For example, alkali metal oxides, 
hydroxides, or carbonates are suitable. Sodium or potassium compounds, and 
especially their carbonates, are preferred. This component should be used 
in as finely divided form as is possible. 
During the condensation, solid alkali metal fluoride is precipitated. This 
is removed from the solution of the polyether by filtration. The 
polycondensate can then be recovered in pure form by distilling off the 
solvent. 
Symmetrical compounds (I) and (II) are preferably used in a stoichiometric 
ratio of exactly 1:1, and in particular compounds (I) wherein X is F and 
compounds (II) wherein X is OH. Strictly alternating products (III) are 
thus obtained wherein m as a rule has a value of 1. However, m may also 
have a uniform or average value greater than 1 if an appropriate starting 
compound such as an oligomeric polyphenylene oxide is used. It is possible 
to deviate from this composition as desired and to prepare condensation 
products (III) wherein units of structure (I) or units of structure (II) 
predominate. This can be accomplished by the co-condensation of 
unsymmetrical starting materials (IV) and (V) for example, in the desired 
mixing ratio. 
Among the starting materials (I) containing phosphorus, derivatives of 
methyl diphenyl phosphine, and particularly of triphenyl phosphine, are 
preferred, in other words compounds wherein R' is methyl or phenyl. 
Compounds (I) wherein R' is alkyl other than methyl or aryl other than 
phenyl, or is alkoxy (and in particular one having from 1 to 4 carbon 
atoms), or aryloxy (and in particular phenyloxy), or chloromethyl, may be 
used but are less readily obtainable industrially. The phenyl groups in 
the main chain may be linked in the ortho positions by a bridge which is 
symbolized by R------R in formula (I). The R------R bridge may be formed 
by any of the members named under R", including a single bond between the 
two ortho carbon atoms of the phenyl groups. If R------R is a single bond, 
the phosphorus atom is located in a five-membered ring between the phenyl 
groups. In all other cases in which R------R has one of the meanings given 
under R", the ortho carbon atoms are connected through a single-membered 
bridge which, together with the phenyl groups and the phosphorus atom, 
forms a six-membered ring. A single bond or an oxygen atom is the 
preferred R------R bridge, but the latter may also be a sulfonyl 
(.dbd.SO.sub.2), carbonyl, methylene, or isopropylidene group. Starting 
compounds (I) in which there is no bridge and R is a hydrogen atom are 
particularly preferred. 
Phosphine oxides wherein q is 1 are generally preferred to phosphines 
wherein q is 0. The latter may be prepared from the correponding phosphine 
oxides by reduction. This is true particularly of compounds wherein R' is 
methyl or phenyl and R is hydrogen. 
The X groups, and particularly the F atoms, are preferably in a position 
para to the carbon atoms which is attached to the phosphorus atom. The 
preferred representatives of compound (I) are 
di(4-fluorophenyl)-phenylphosphine oxide and 
di(4-fluorophenyl)-methylphosphine oxide. 
In the difunctional aromatic compound represented by the formula 
X--(Ar-O).sub.m-1 --Ar--X (II), Ar may be a divalent arylene group, for 
example a para-phenylene, meta-phenylene, 1,4-naphthalene, or 
1,5-naphthalene group. In compounds wherein m is greater than 1, Ar may be 
a para-phenylene group in particular, X being OH. (II) then is an 
oligomeric polyphenyl oxide or a corresponding mixture of oligomers. In 
the latter case, m represents the average value of the degree of 
oligomerization. Di(para-hydroxyphenyl) ether is particularly preferred. 
Ar may also be a structure of the formula 
##STR5## 
In that case, suitable compounds (II) are primarily those wherein m is 1, 
the free valences preferably being in a position para to R". In the 
simplest case, R" represents a covalent single bond between the phenyl 
groups. Other possible meanings of R" are, for example, sulfide and 
sulfonyl, and especially carbonyl, methylene, and isopropylidene. 
Examples of symmetrical compounds of the (II) type wherein X is OH are 
hydroquinone, resorcinol, 1,4-dihydroxynaphthalene, 
1,5-dihydroxynaphthalene, 4,4'-dioxydiphenyl, phenolphthalein, and the 
compounds known as bisphenol A and F. Examples of compounds wherein X is F 
are 4,4'-difluorobenzophenone, bis(4-fluorophenyl)sulfone, and 
4,4'-difluorodiphenyl ether. 
The terminal groups may be unreacted fluorine atoms or hydroxyl groups. The 
latter have an adverse effect on the properties of the polyarylene ethers 
and therefore are preferably etherified with methyl chloride. In lieu 
thereof, other alkylating, arylating, or acylating agents may be used.

The following examples illustrate preferred methods for making polyarylene 
ethers containing phosphorus in accordance with the invention. 
EXAMPLES 1 TO 6 
0.1 mol of the appropriate arylene diol, 0.1 mol of 
di(para-fluorophenyl)phenylphosphine oxide, and 0.105 mol of anhydrous 
potassium carbonate were dissolved in 150 g of N-methylpyrrolidone and 50 
g of chlorobenzene. The solution was heated to 180.degree. C. under an 
argon atmosphere and an azeotropic mixture of water of reaction and 
chlorobenzene was removed. At the same time, carbon dioxide escaped. 
Toward the end of the elimination of water after about 2 hours at reaction 
temperature, another 50 g of chlorobenzene were added dropwise within an 
hour for removal of the residual water. Final condensation then took place 
over a period from 5 to 10 hours at 180.degree. to 200.degree. C. under an 
argon atmosphere. Condensation was terminated by the introduction of 
methyl chloride for 30 minutes at 160.degree. C. to 180.degree. C. After 
cooling, the viscous reaction mixtures were diluted with tetrahydrofuran, 
the inorganic precipitate was filtered off, and the polyether in the 
filtrate was precipitated with a methanol/water mixture. Ultimate analysis 
of the polycondensates dried at 100.degree. C. to constant weight yielded 
data which were in good agreement with the calculated theoretical values. 
TABLE 
__________________________________________________________________________ 
Reduced 
viscosity 
T.sub.g by DSC.sup.1 
T.sub.d TGA.sup.2 
CR Value.sup.3 
P content 
.eta..sub.sp /c.sup.4 
Example 
Arylene Diol (.degree.C.) 
(.degree.C.) 
(%) (% of theory) 
(dl/g) 
__________________________________________________________________________ 
1 Hydroquinone 185 &gt;450 31.7 8.07 0.28 
2 4,4'-Dioxydiphenyl 
155 &gt;450 37.9 6.74 0.41 
3 1,5-Dioxynaphthalene &gt;450 36.2 7.14 0.33 
4 4,4'-Dioxydiphenyl ether 
170 490 32.8 6.51 0.32 
5 Bisphenol A 180 &gt;450 24.9 6.18 0.37 
6 4,4'-Dioxytriphenylphosphine oxide 
215 &gt;450 40.8 10.62 0.31 
__________________________________________________________________________ 
.sup.1 Glass transition temperature as determined by differential scannin 
calorimetry 
.sup.2 Onset of decomposition as determined by thermogravimetric analysis 
(N.sub.2) 
.sup.3 Pyrolysis residue after 30 min. at 800.degree. C. under 
.sup.4 c = 0.5 g/100 ml metacresol at 30.degree. C. 
EXAMPLE 7 
0.05 mol of di(para-hydroxyphenyl)phenylphosphine oxide was reacted with 
0.05 mol of 4,4'-difluorobenzophenone in the presence of 0.0525 mol of 
potassium carbonate under the preparation conditions used in Examples 1 to 
6 (10 hours reaction time at 180.degree. C. to 200.degree. C.). The 
polyether so obtained gave solid, flexible, transparent cast sheets (from 
chloroform) and compression molded chips. It had a reduced viscosity of 
0.47 dl/g. 
EXAMPLE 8 
0.1 mol of di(para-fluorophenyl)phenylphosphine oxide was reacted with 0.1 
mol of 4,4'-dihydroxy-diphenylsulfone in the presence of 0.105 mol of 
potassium carbonate under the preparation conditions used in Examples 1 to 
6 (10 hours reaction time at 180.degree. C. to 200.degree. C.). The 
polyether so obtained showed the following properties: 
T.sub.g &gt;150.degree. C.; T.sub.d &gt;450.degree. C.; CR-Value=34%.eta..sub.sp 
/C=0.4 dl/g 
and gave solid, flexible, transparent cast sheets. 
EXAMPLE 9 
0.04 mol of 4-fluoro-4'-hydroxybenzophenone and 0.02 mol of 
di(para-hydroxyphenyl)phenylphosphine oxide were reacted with 0.02 mol of 
di(para-fluorophenyl)phenylphosphine oxide in the presence of 0.042 mol of 
potassium carbonate under the preparation conditions used in Examples 1 to 
6 (180.degree. C. to 200.degree. C.). The polyether so obtained was 
crystalline (melting point T.sub.m =200.degree. C.) and had .eta..sub.sp 
/C=0.32 dl/g, T.sub.d &gt;400.degree. C., CR-Value=38% and a molecular weight 
of 18,000. The random distribution of benzophenone units within the 
polyether main-chain was verified by IR-spectroscopic data, showing 
typical absorption peaks at 1650 cm.sup.-1 and 920 cm.sup.-1 and by 
elemental analysis: 
______________________________________ 
C[%] H[%] P[%] 
______________________________________ 
calculated 75.4 4.4 7.9 
found 74.9 4.6 6.9 
______________________________________ 
EXAMPLE 10 
0.02 mol of 3,7-difluoro-10-phenylphenoxaphosphine-10-oxide was reacted 
with 0.02 mol of 4,4'-dihydroxy-diphenylether in the presence of 0.021 mol 
of potassium carbonate under the preparation conditions used in Examples 1 
to 6 (180.degree. C. to 200.degree. C.). The polyether so obtained had a 
reduced viscosity .eta..sub.sp /C=0.33 dl/g and a phosphorus content of 
5.9% (calculated value: 6.4%). 
EXAMPLES 11 TO 12 
0.1 mol of 4,4'-difluoro-benzophenone was reacted with 0.1 mol each of two 
phosphorus compounds shown in the table below, respectively, in the 
presence of 0.11 mol of potassium carbonate under the preparation 
conditions used in Examples 1 to 6 (180.degree. C. to 200.degree. C.). The 
resulting polyethers were isolated from the reaction mixture by 
precipitation with ethanol or with light petroleum. 
______________________________________ 
Ex- Pcontent intrinsic 
am- of the viscosity 
ple phosphorus polyether [%] 
.eta..sub.sp /C 
No. compound calc. found [dl/g] 
______________________________________ 
11 
##STR6## 7.28 6.8 0.45 
12 
##STR7## 6.38 5.8 0.36 
______________________________________ 
EXAMPLE 13 
0.05 mol of di(para-fluorophenyl)phenylphosphine oxide was reacted with 
0.05 mol of phenolphthalein in the presence of 0.053 mol of potassium 
carbonate under the reaction conditions described in Examples 1 to 6 (5 
hours; 180.degree. C. to 190.degree. C.). The isolated polyether had the 
following properties: 
T.sub.g =260.degree. C.; T.sub.d &gt;450.degree. C.; CR-Value=55%; 
.eta..sub.sp /C=0.56 dl/g 
and gave clear, transparent cast sheets.