CA1038545A - Process for the preparation of poly (haloaryloxyphosphazene) homopolymers - Google Patents

Abstract

A B S T R A C T
Poly(haloaryloxyphosphazenes) which consist of recurring units represented by the following general formula

Description

1038~i45 PROCESS FOR THE PREPARATION OF
POLY(HALOARYLOXYPHOSPHAZ~NE) HOMOPOLYMERS

Specific_tion This invention relates to a process for the preparation of soluble, high molecular weight poly~haloary~oxyphosphazene) homopolymers which are essentially free of P-Cl site~ and the polymers obtained thereby. The polymers of this invention are characterized by the repeating structure:

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wherein each of Rl, R2, and R3 is a monovalent radical selected from H, Cl, Br or alkyl (one to 5 carbon atoms), and one o~ the R ~roups must be halo~en, and n is ~rom 20 ~o S0,000.
The polymers of this invention are film formers, which often can be rendered into fibers. Many of these poly(aryloxy-phosphazenes) are particularly useful in flame-retardant applica-tions in the form o~ wire insulation, structural composites, carpet backing and ln wearing apparel. Because the homopolymers of this invention are free o~ P-Cl sites (l,e, less ~han 0.1%
chlorine at;P-Cl), the polymers may be safely utilized in moist environments. , `-2~

i l(~38545 It has now been found that high molecular weight, soluble poly(aryloxyphosphazene) polymers which are essentially free of P-Cl sites and possess properties useful for the applications cited above, can be prepared successfully by the use of reaction conditions which are critical, namely reaction temperatures of about 115 to 160C from 5 to lO0 h~urs.
In the process of this invention, for the preparation of the poly(aryloxyphosphazene) polymers,poly(dichlorophosphazene) is dissolved in a suitable solvent such as benzene, toluene, xylene, chlorobenzene, 1,2-dichlorobenzene, tetrahydrofuran or mixtures thereof. The resulting polymer solution is gradually added to a well stirred solution or suspension o~ a suitable aryloxide salt. Sodium salts are preferred but both the lithium and potassium salts are also suitable. The salt is preferably present in excess amounts from 105 to 150 mole percent based on equivalents of chlorine present in the poly(dichlorophosphazene), The alkali metal salts of phenols substituted in at least one of the 3,4 and 5 positions with Cl or Br are suitable. For example, alkali metal salts derived from 3-chlorophenol, 4-chlorophenol, 3-bromophenol, and 4-bromophenol, 3-chloro-4-methylphenol, 4-chloro-3-methylphenol, 4-bromo-3-methylphenol, ~-chloro-3,5-dimethylphenol, and 4-bromo-3,5-dimethylphenol, and their non-ortho substiltuted isomers have been found suitable. The reaction temperature is in the range of 115 to 160C, and is preferably in the range of 120 to 145C. The resulting phosphazene homo-polymers are isolated by known methods famlliar to those skilled in the art.
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.. . . . . . . . . . . . . ,. . ' . : l 1 ~038~ii45 ¦ The process conditions of this invention are critical.
¦Temperatures which are too low or times which are too short will ¦lead to incomplete substitution and result in polymers which are ¦unstable. Temperatures which are too high and to a lesser extent I times which are too long give complete substitution but lead to ¦reduction in molecular weight which affects polymer properties ¦ This method for the preparation o~ the polymers of this ¦ invention derived from 3- and/or 4-substituted halophenols con-¦sistently affords soluble materials that are free of P-Cl sites ¦ and were of high molecular weight (i.e., had intrinsic viscosi-¦ ties of at least 0.5 dl/g). By comparison~ the poly(aryloxyphos-¦ pha~enes) derived ~rom 2-substituted phenols such as 2-chloro-¦ phenol, 2-bromophenol, 4~chloro-2-methylphsnol, 2,6-dimethyl-4-¦ chlorophenol do not afford complete substitution of P-Cl sites ¦ when practicing the process of this invention, ¦ Related prior art has been disclosed in United States ¦ Patent 3,370,020, Inorg. Chem., 5, 1709 (1966), and Polymer, 11, ¦ 44 (1970). This invention teaches a process which produces ¦ halogenated poly(aryloxyphosphazenes) which are free of P-Cl ¦ sites and retain high molecular weights which improve physical ¦ and mechanical properties. Low molecular weight liquids which I contain some o~ the substituents of this inv~ tion are claimed ¦ in U~ited States Patent 3,505,087.
Preparation of the poly(aryloxyphosphazene~ polymers of as ¦ this invention is illustrated by the following examples which are ¦ not intended to limit the scope of the invention~
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--~ 3S45 Example 1 Preparation of ~(4-ClC6H40)2PN~n The [Cl2PN]n polymer (100 g, 1"72 ~ivs.) was dissolved in 600 ml of benzene/toluene (3~/2v) and added to a solution (123C) of sodium 4-c~lorophenoxide which had been prepared ~rom 4-chloro-ph~nol (267 g, 2.08 moles) and sodium (42.7 g, 1.85 moles) in 1.3 liters of bis(2-ethoxyethyl)ether/dioxane (3v/lv). The mixtur~
was maintained at 126C ~or 26 hours, a~ter which polymer was pre-cipitated by addition o~ 1.3 liters o~ methanol. The polymer was slurried repeatedly with methanol/water (lv/lv) and was dissolved in 2 liters o~ tetrahydro~uran and reprecipitated by addition o~
4 liters o~ water. The product (140 g, 54% yield) was a tough, l white plastic and had an intrinsic viscosity in tetrahydro~uran f o~ 1.8 dl/g at 30C. ~-~
¦ 15 The weight average molecular weight (light scattering) was ~ound to be 2,500,000 and the number average molecular weight I (osmometry) was 200,000. Films cast ~rom tetrahydro~uran were strong and ~lexible and oriented upon drawing. The product did not contain P-Cl sites and was una~ected by moisture at elevated temperatures. A so~tening point o~ 145C was obtained. Anal.
Calcd. ~or [(ClC6H~0)2PN¦n: C, 48.0; H, 2.7; N, 4.7; Cl, 23.7, Found: C, 48.2; H, 2.9; N, 4.8; Cl, 23.5.
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Example 2 ~(4-ClC6H40)2PN]n (Comparative) This preparation employed an aliquot of the same [Cl~PN~n polymer used in ~xample 1 and the reaction was conducted at 165C
for 16 hours. The solvent mixture was the same as in Example 1 except that suf~icient benzene was removed to achieve temperature.
The product was a white solid with an intrinsic viscosity of 0.6 dl/g in tetrahydrofuran at 30C. Films cast from tetrahydro~uran ;~;
were somewhat brittle and weak and did not orient upon drawing.
The polymer did not contain P-Cl sites. Anal. Calcd. for [(ClC6H~0)2PN~: C, 48.0; H, 2.7; N, 4.7; Cl, 23.7. Found:
C, 48.2; H, 2.8; N, 4.4; Cl, 23.6. Film properties and [y] values indicated molecular weight was reduced below acceptable values as compared to the polymer of Example 1. ,~
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Example 3 [(4-C1C6H~0)2PN]n (Comparative) This preparation employed an aliquot o~ the same [Cl2PN~n polymer used~in Example 1 and the reaction was conducted at 180-185C for 3 hours. The solvent mixture was the same as in Example 1 except that suf~icient benzene was removed to achleve temperatur The product was a light tan solid with an intrinsic viscosity in benzene of 0.4 dl/g at 30C. Films cast from tetrahydrofuran were very weak, very brittle, and did not orient upon drawing. The ~-~
~ polymer did not contain P-Cl sites. Anal. Calcd. for [(ClC6H40)2P ~]
C, 48.0; H, 2.7; N9 4.7; Cl, 23.7. Found: ~ C, 43.5; H, 2,9;
N, 4.9; Cl, 23.5. Film properties and [~] values indicated molecu lar weight was reduced below acceptable values as compared to the polymer ~ Example 1.
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; s.~ as Example 4 Preparation o~ [(4-ClC6H40)2PN]n (Comparative) A solution of sodium 4-chlorophenoxide, prepared by ~
addition of sodium (92 g, 4.0 moles) to 4-chlorophenol (514 g, ~ ~ ;
4,0 moles) in 2.2 liters of tetrahydrofuran, was added dropwise over 3 hours to a stirred solution of polymerized (Gl2PN) (200 g, 1.72 moles) in 1.5 liters of dry benzene. The reaction was stirred ~or 72 hours at re~lux (about 70C). Tetrahydro~uran was distilled and the mixture was diluted with dry benzene to maintain ~luidity. The reaction mixture was cooled to room tem-perature, and care~ully neutralized with aqueous hydrochloric ; acid. Separation o~ high polymer ~rom cyclic species and oligo-mers was ef~ected by fractional precipitation. The polymer was I ~ purified by exhaustive washes with methanol-water (lv~lv), dis-- 15~ solved in tetrahydrofuran, reprecipitated into methanol, and dried. The intrinsic viscosity in tetrahydrofuran was 1,0 dl/g at 30C. Anal. Calcd. ~or [(ClC6H40)2PN]n: C, 48.0; H~ 2-7;
N, 4.7; Cl, 23,7, Found: C, 46.3; H, 2.7; N, 4.6; Cl, 24.6, The polymer contained residual P-Cl sites and was degraded by moisture at elevated temperatures.
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Example 5 ~(4-ClC6H40)2PN]n (Comparative) When the above experiment was repeated at 80C ~or 50 hours, a po m0r havi~g t-e ollowlnl analysis wa~ obtained:

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C, 47.0; H, 2.8; N, 4,8; Cl, 24.5. Similar results were obtained when tetrahydroIuran was used as solvent :eor the aryloxide salt and when the aryloxide salt was added to the [Cl2PN]n polymer.
I In all cases the intrinsic viscosities Oe the produets were de-¦ creased rapidly upon exposure to moistu:re at 100C~. .
A summary o~ Examples 1-5 demonstrating the aIfect of the temperature range and reaction times is gi~ven in Table 1. It will be seen that higher temperatures lead to poor Inilm proper-l ties while lower temperatures give incomplete substitution, ¦ TABLE 1 ~.
,I Attempted Preparations o:L [(4-ClC6H~0)2PN]n I ~,eaction Analysis (%)a Conclitions O:e Product b P-Cl Hydro. Film I Ex. (C) (hrs) C H N C1 [r~ Present Stab. Properties 1 126 26 48.2 2.9 4.8 23.5 1.8 no yes Ilexible, strong, orients upon . drawing

2 165 16 48.2 2.8 4.4 23.6 0.6 no yes brittle, wea

3 180- .
20 185 3 48.S 2.9 4,9 23.5 0.4 no yes very brittle weak

4 70 72 46.3 2.7 4.6 24.6 1,0 yes rlo very :~lexibl strong, ' moderate l:
orien ta tion , 25 '.. ':
50 47.0 2.8 4.8 24.5 1.6 yes no very ~lexibl , ' strong, moderate '":
orientation ~ ;
a Caloulated lQor [ (ClC6H40)zPN]n C, 48.0; H, 2.7; N, 4.7; Cl, 2 .7.
¦~ b Intrir. visLosity (dl/g) in tetrahydro:~uran at 30C.

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-8- l :103~545 Example 6 PreparatiOn O:e [ (4-Brc6H4o)2PN~n The proce~ure o~ Example 1 was ~ollowed except that bis(2-methoxyethyl)ether was used as the solvent for the prepara-tion o~ sodium 4-bromophenoxide, and anhydrous sodium methoxide was used instead of metallic sodium. The methanol produced by ~
the interchange was completely removed by codistillation with -benzene prior to addition o~ ECl2PN]n polymer solution. m e reaction mixture was heated subsequently for 30 hours at 130C to ~`
afford a 63% yield o~ a white, fibrous plastic which had an in-trinsic viscosity of 1.0 d~/g in tetrahydro~uran at 30C. The polymer was immediately sel~-extinguishing upon removal ~rom a gas/oxygen flame. Anal. Calcd. ~or ~(4-BrC6H~0)2PN]n: C, 37.0;
H, 2.1; N~ 3.6; Br, 41.1; Cl, 0Ø Found: C, 36.9; H, 2.1;
N, 3.7; Br, 40.9; Cl, 0.03. ~ ;~
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Example 7 Preparation of [(4-BrC6H40)2PN]n (Comparative) The procedure of Example 6 was employed except the reac-tion temperature was held at 80C ~or 50 hours. The product was ~ound to contain 2. l~/o chlorine and was si~ni~icantly less hydro-Iytlcallv able than the product of ~xampl- ô.

' ' ' : . ,' ,` _9_ i 10:1'545 Examples 3-~2 ¦ The procedures Oe Examples 1 and 6 were ~ollowed and the ¦ appropriate sodium aryloxides and reaction times of 50 to 100 ¦ hours at temperatures of 115 to 135C were employed ~or the ¦ preparation of the homopolymers of Examples 8-11. All polymers ;
¦ were soluble in tetrahydro~uran at 25C and were self-extinguishi when withdrawn ~rom gas/oxygen flame. The analyses ~or these polymers are shown in Table 2.

lTABLE 2 1Analytical Data :~or Poly (haloaryloxyphosphazenes) _ Analysis (%) O:e Polymer Example Sodium Aryloxide o:e C H N Cl 8 3-chlorophenol 48,0 2.9 4.7 23,6 l (48.0) (2.7) t4.7)(23.7 ) 1 9 4-chloro-3-methylphenol51.0 3.8 4,3 21.4 (51.1) (3.9) (4.3)(21.6 ) 4-chloro-3,5-dimethylphenol 53.7 4.6 3.8 20.1 (53.9) (4.5) (3.9)(~0, ) 11 4-bromo-3-methylphenol40.3 2.8 3.6 0.
(40.3~ (2.9) (3.4) (0) 12 3 4-chlorophenol 38.9 1.5 3.7 38.9 ' (39.1) (1.6) (3.8)(38.g Calculated v~lues are shown in parentheses.
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Example 12 Attempted Preparation of [(2-ClC6H4O)2PN~n (Comparative) The [C12PN] polymer (79.0 g,1.36 equiv~) was dissolved in 1850 ml of chloroben~ene/benzene (3v/2v) ~nd added over 1/2 hour to ¦a solution o~ sodium 2-chlorophenoxide at 125C. The aryloxide ¦was prepared from 2-chlorophenol (219.0 jg, 1.70 moles) and sodium ¦(37.0 g, 1.61 moles) in 1.5 liters o~ bis(2-ethoxyethyl)ether/
~dioxane (3v/lv). The reaction mixture was heated 19 hours at ¦135C before polymer was precipitated by addition o~ 3 liters of ¦methanol and was washed exhaustively with methanol/water, redis-Isolved in 1 liter tetrahydrofuran and reprecipitated with 3 liters ¦of distilled water. The product (86.5 g, 42.5% yield~ was a soft ¦plastic with an intrinsic viscosity in tetrahydrofuran of 1.4 dl/g ,-~
¦at 30C. Anal. Calcd. ~or [(ClC6H40)2PN]n: C, 48.0; H, 2.7; .
¦Cl, 23.7. Found: C, 46.1; H, 2.8; Cl, 24.3.
¦This analysis con~irms incompletely substituted polymer.

¦ Example 13 I
¦ Attempted Preparation o~ [(2,4-C12C6E30)2PN~n (Comparative) l The [C12PN]n polymer (11.6 g, 0.20 equi~.) was dissovled in -¦ 170 ml of benzene and added over 20 minutes to a solution of sodiu~
2,4-dichlorophenoxide at 140C. The aryloxide was prepared ~rom 2,4-dichlorophenol (40.7 g, 0.25 mole) and sodium (5.3 g, 0.23 mole) in 150 ml o~ bis(2-ethoxyethyl)ether. Additional solvent l (chlorobenzene, 225 ml) was added to the mixture which was heated ¦ ~or 27 hours at 147C. Polymer was precipitated by addition of 1 liter o~ methanol and was washed exhaustively with methanoltwater.
The product~(39.3 g, 100~ yield) was fine white powder, which was l insoluble in all common solvents and melted at 255-270C. Anal.
¦ Calcd- for ~:(C12C6H30)2PN]n: C, 39.1; H, 1.6; Cl, 38.4. Found:
¦ C, 39.4; H,-1.7: Cl, 36.4.
Extraction of the product with warm N,N-dimethylformamide (DMF) afforded about 10% of lower melting (190C) powder with an lntrins.c visoosity in DMF of 0.02 dl/g at 30C. The elemental ' I - .
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~ l nalysis of this soluble material was essentially identical to the analysis of the original material.
This experiment was repeated and several experiments were :
conducted at 123C (46 hours). The products were very similar in :;
elting behavior, in solubility and poor elemental analysis to the aterials described above.

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Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a method of preparing poly(haloaryloxyphosphazene) polymers consisting of recurring units represented by the following general formula:

in which n is between 20 and 50,000 and R1, R2 and R3 are each monovalent radicals selected from the group consisting of H, Cl, Br, and alkyl (one to five carbon atoms) and at least one R of the group con-sisting of R1, R2 and R3 is halogen, the improvement which comprises the formation of the polymer by reaction of poly(dichlorophosphazene) with a stoichiometric excess of alkali metal salt of a phenol substituted in at least one of the meta or para positions at a temperature and length of time between about 115°C for 100 hours and about 160°C for about 5 hours, whereby a poly(haloaryloxyphosphazene) product free from P-Cl sites and soluble in tetrahydrofuran is obtained.

2. The process of claim 1 in which the reaction is carried out at a temperature in the range of 120°C to 145°C.

3. Poly(haloaryloxyphosphazene) homopolymers consisting of recurring units represented by the following general formula:

in which n is between 20 and 50,000 and R1, R2 and R3 are each monovalent radicals selected from the group consisting of H, Cl, Br, and alkyl (one to five carbon atoms) and at least one R of the group consisting of R1, R2 and R3 is halogen, said homopolymer being free from P-Cl sites and soluble in tetrahydrofuran.

4. The homopolymer of claim 3 wherein R1 and R3 are H and R2 is Cl.

5. The homopolymer of claim 3 wherein R1 and R3 are H and R2 is Br.

6. The homopolymer of claim 3 wherein R1 is CH3, R2 is Cl or Br and R3 is H.

7. The homopolymer of claim 3 wherein R1 and R3 are CH3 and R2 is Cl or Br.