GB1579653A - Structurally regulated polyphosphazene copolymers - Google Patents

Description

(54) STRUCTURALLY REGULATED POLYPHOSPHAZENE COPOLYMERS (71) We, ARMSTRONG WORLD INDUSTRIES, INC., formerly The Armstrong Cork Company, a Corporation organized according to the laws of the Commonwealth of Pennsylvania, Lancaster, Pennsylvania 17604, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention provides polyphosphazenes which have an at least partially regulated structure corresponding to the formula: -[-N3P3(Cl)5(OR)-]n- (1) where n is greater than 2, and where R' is phenyl or substituted phenyl and copolymers, derived from the above polymers (I), which correspond to the formula: [N3P3(OR1)(OR2)5ln (tri) where R' is phenyl or substituted phenyl and where R2 is different from R' and is an alkyl or substituted alkyl radical or a phenyl or substituted phenyl radical.

This invention is based on the observation that cyclic polyphosphazenes of the formula: where R1 is

the R3s, when present, being located in the meta or para positions on the phenoxy ring, where x is 0 to 3; preferably 0 or l (where x is l, R3 preferably is in the para position); and where R3 is, independently, lower (e.g. C1-C10) linear or branched alkyl, for example, methyl, ethyl, n - butyl, sec.butyl or tert.butyl, 2 - ethyl hexyl and n - nonyl; lower (e.g., C1-C4) linear or branched alkoxy, for example, methoxy, ethoxy, butoxy, halo (e.g., chloro, bromo or fluoro), cyano, or nitro, or substituted alkyl or alkoxy (e.g., nitro, cyano, halo or lower alkoxy) can be polymerized to form polymers having repeating units corresponding to the formula: N3P3(Cl)s(OR1)n (I) where n is at least 2 and may be up to 600 or higher and where R1 is defined as above.

Throughout this specification, including the claims, the term "lower" when referring to an alkyl group refers to a group having from 1 to 10 carbon atoms and when referring to an alkoxy group refers to a group having from I to 4 carbon atoms.

The polymers (I) can be further reacted to form copolymers containing repeating units corresponding to the formula: lN3P3(OR1)(OR2)5]n (11) where n and R' are defined as above and where R2 is different from Rl and is lower linear or branched alkyl, lower alkaryl, substituted lower alkyl, for example lower alkoxy-, halo-, cyano- or nitro-substituted alkvl or

where R4s, when present, are substituted on any sterically permissible position on the phenoxy ring, preferably meta and para, where z is 0 to 3; preferably 0 or 1, (where z is 1, R4 preferably is in the para position) and where R4 is independently, lower linear or branched alkyl, lower linear or branched alkoxy, halo (e.g., chlorine, bromine or fluorine), nitro, cyano or substituted alkyl or alkoxyl (e.g., nitro, cyano, halo or lower alkoxy substituted).

Examples of OR2 include methoxy, ethoxy, propoxy, n - butoxy, sec.butoxy, tert.butoxy, octyloxy, phenoxy, tolyloxy, xylyloxy, benzyloxy, phenethyloxy, methoxyphenoxy, propoxyphenoxy, p - nitrophenoxy, OCH2CF3, OCH2C3F7, OCH2C3 F6CF2H, 2,2,3,3 - tetrafluoropropoxy, 3,4 - dichlorophenoxy, 4 bromophenoxy, 2 - chloroethylphenoxy, or 2 - chloroethoxyphenoxy.

It is to be understood that while it is preferred that all R's are the same and all R2s are the same the Rl can be mixed and the R2 can be mixed, in which case it is to be understood that the R' of some units of the polymer may be the same as the R2 of that unit, or of other units. The mixtures may be mixtures of different substituents or mixtures of different positional isomers. In preparing specific polymers steric hindrance must be considered. For example, one skilled in the art readily will recognize that steric hindrance will dictate the propriety of using relatively bulky groups in the ortho position on the phenoxy ring since as set forth hereinafter the R7 is provided by reacting a substituted metal phenoxide with a chlorine atom on a phosphorus atom. Desirably, groups which sterically inhibit such a substitution reaction should be avoided. Subject to the foregoing proviso, the selection of the various R2s will be apparent to anyone skilled in the art based upon this disclosure.

The repeating units of the polymer (II) can be represented by the formulae:

where the ratio of unit IV to unit V is 1:2, since the repeating unit is derived from ring opening of the triphosphazene (III). For example, typical polymer segments would be one or more of

The above described polymers (II), as well as those containing reactive sites designated as W below, may be crosslinked and/or cured at moderate temperatures (for example, 200--350"F) by the use of free radical initiators, for example, peroxides, using conventional amounts, techniques and processing equipment.

The copolymers of this invention may contain small amounts of substituents W, which randomly replace a portion of the -OR2 groups, resulting in the presence of, for example, the following units:

where W represents a group capable of a crosslinking chemical reaction, for example, an olefinically unsaturated, preferably ethylenically unsaturated, monovalent radical containing a group capable of further reaction at relatively moderate temperatures, the ratio of W:R'+R2 being less than 1:5. Examples of W are -OCH=CH2; -OR5CH=CH1;

-OR5CF=CF2 and similar groups which contain unsaturation, where R5 and Rs are aliphatic or aromatic radicals, preferably R5 is -CH2-. These groups are capable of further reaction at moderate temperatures (for example, 203500F) in the presence of free radical initiators, conventional sulfur curing or vulcanizing additives known in the rubber art or other reagents, often even in the absence of accelerators, using conventional techniques and processing equipment. Examples of free radical initiators include benzoyl peroxide, bis(2,4 - dichlorobenzoyl peroxide), di - tert - butyl peroxide, dicumyl peroxide, 2,5 - dimethyl(2,5 - di tert - butylperoxy)hexane, t - butyl perbenzoate, 2,5 - dimethyl - 2,5 - di(tert butylperoxy)hepyne - 3, and 1,1 - bis(tert - butylperoxy) - 3,3,5 trimethylcyclohexane. Thus, the general peroxide classes which may be used for crosslinking include diacyl peroxides, peroxyesters, and dialkyl peroxides.

Examples of sulfur-type curing materials include vulcanizing agents, for example, sulfur, sulfur monochloride, selenium, tellurium, thiuram disulfides, p quinone dioximes, polysulfide polymers, and alkyl phenol sulfides. The above vulcanizing agents may be used in conjunction with accelerators, such for example, as aldehyde amines, thio carbamates, thiuram sulfides, guanidines, and thiazols, and accelerator activators, for example, zinc oxide or fatty acids, e.g., stearic acid.

It is also possible to use as W in the above formulae, monovalent radicals represented by the formulae (1) -OSi(OR7)2R8 and other similar radicals which contain one or more reactive groups attached to silicon; (2)OR9NR9H and other radicals which contain reactive -NH linkages. In these radicals, R7, R8 and R9 each represent aliphatic aromatic and acyl radicals. Like the groups above, these groups are capable of further reaction at moderate temperatures in the presence of compounds which effect crosslinking. The presence of a catalyst to achieve a cure is often desirable. The introduction of the groups W into polyphosphazene polymers is shown in U.S. Patents 3,888,799; 3,702,833 and 3,844,983.

The amount of W present in the copolymer affects the processability, smoke production, glass transition temperature and a number of other properties of the copolymers. These ratios also affect the copolymer's ability to be foamed and the properties, such as the rigidity, of the resulting foams.

The cyclic polyphosphazenes (III) can be prepared, for example, by following the general reaction scheme taught by Dell et al, "Phosphorus Nitrogen Compounds Part XIII Phenoxy and p - B romophenoxy - Chlorocyclotriphosphazatrienes", J. Chem. Soc. (1965) 40704073.

Generally, the procedure comprises forming the sodium salt of the desired phenolic compound (HOR', where R1 is defined as above) in a suitable solvent such as tetrahydrofuran or dioxane. This phenoxide is then slowly added to the trimer, hexachlorocyclotriphosphazene in a suitable solvent, as above, the reaction being conducted at low temperatures to retard side reactions. The use of significant amounts of solvent also promotes a uniform product. The product is then isolated.

In a preferred isolation technique, a water immiscible solvent is substituted for the reaction solvent and the solution is washed seriatim with dilute acid, dilute base and water to remove unreacted starting materials and by-products. The organic layer is then vacuum distilled.

There follow several examples showing the preparation of cyclic phosphazenes (III).

EXAMPLE 1 N2P3Cl5(OC6H5) Sodium phenoxide was formed by reacting 8.0 parts of sodium with 44.0 parts of phenol in 1800 parts of tetrahydrofuran.

120.0 parts of hexachlorocyclotriphosphazene was charged into a reactor together with 1000 parts of tetrahydrofuran and the mixture cooled to -780C. To the stirred reactor, there was then added dropwise, over a three hour period, the previouslv prepared sodium phenoxide solution, while maintaining the temperature at -78 C until the addition was complete. The reaction mixture was then allowed to warm to room temperature.

The reaction mixture was then worked up in the following manner: The solvent was evaporated and the resultant oil was dissolved in petroleum ether. The ether solution was washed with 5% aqueous hydrochloric acid, then 5% aqueous sodium bicarbonate, followed by several washings with water. The petroleum ether was then evaporated and the resultant oil was vacuum distilled to obtain phenoxypentachlorocyclotriphosphazene (b.p. 740C at .07 Torr).

Elemental Analysis: Theoretical-C 17.78, H 1.24, N 10.37, P 22.93; Found- C 17.65, H 1.24, N 10.44, P 22.88.

EXAMPLE 2 N3P3CIs(OC6H4-P-F) Sodium p - fluorophenoxide was formed by reacting 4 parts of sodium with 26.9 parts of p - fluorophenol in 900 parts of tetrahydrofuran.

60 parts of hexachlorocyclotriphosphazene were charged into a reactor together with 500 parts of tetrahydrofuran and the mixture cooled at -78 C. The previously prepared sodium p - fluorophenoxide solution was added dropwise and reacted as in Example 1. The resultant product was worked up as in Example 1 to yield p - fluorophenoxypentachlorocyclotriphosphazene (b.p. 1070C at .02 Torr).

Elemental Analysis: Theoretical-C 17.02, H 0.95, N 9.93, P 21.94; Found-C 17.36, H 1.00, N 9.86, P 21.85.

EXAMPLE 3 N3P3Cls(OC6Hs-p-CI) Using sodium p - chlorophenoxide, p - chlorophenoxy pentachlorocyclotriphosphazene was prepared following the procedure of Example 1 (b.p. 1260C at 0.25 Torr).

Elemental Analysis: Theoretical-C 16.39, H 0.90, N 9.56, P 21.13; Found- C'16.34, H 0.82, N. 9.42, P 21.05.

EXAMPLE 4 N3P3Cls(OC6H4-p-CH3) Using sodium p - methylphenoxide, p - methylphenoxypentachlorocyclotriphosphazene is prepared following the procedure of Example 1 (b.p. 1300C at .05 Torr).

Elemental Analysis: Theoretical-C 20.05, H 1.68 N 10.02, P 22.16; Found- C 20.18, H 1.69, N 10.08, P 22.09.

EXAMPLE 5 N3P3Cls(OC6H4-p-OCH3) Using sodium p - methoxyphenoxide, p - methoxyphenoxypentachlorocyclotriphosphazene was prepared following the procedure of Example 1 (b.p. 121 C at .025 Torr).

Elemental Analysis: Theoretical-C 19.31, H 1.62, N 9.65, P 21.34; Found- C 19.58, H 1.79, N 9.67, P 21.43.

In a manner similar to the above teachings or using variants obvious to those skilled in the art, other cyclic trimers (III) can be prepared.

The polymers (I) are prepared by thermally polymerizing the cyclic triphosphazenes by heating them at a temperature and for a length of time ranging from 200 C for 72 hours to 300 C for 30 minutes. That is to say the compounds are heated to a temperature ranging from 2000C to 3000C for from 30 minutes to 72 hours, the higher temperatures necessitating shorter contact times and the lower temperatures necessitating longer contact times. The compounds must be heated for such a length of time that only a minor amount of unreacted charge material remains and a major amount of high polymer has been produced. Such a result is generally achieved by following the conditions of temperature and contact time specified above.

It is preferred that the thermal polymerization be carried out in the presence of an inert gas for example, such as nitrogen, neon, argon or a vacuum, for example, about 10-2 Torr, inasmuch as the reaction proceeds very slowly in the presence of air. The use of such a gas, however, is not critical. The presence of moisture is also preferably avoided.

The polymerization process follows that taught for the polymerization of -(-NPCl2-)3-, as described in U.S. 3,370,020.

The polymers resulting from the thermal polymerization process are in the form of a polymeric mixture of different polymers of different chain lengths. That is to say, the product of the thermal polymerization is a mixture of polymers having the formula (I) [N3P3(Cl)s(OR1)]n where n ranges from 2 to 600 or higher. For example, the recovered media may contain minor amounts of a polymer where n is 2 and major amounts of polymer where n is 600 or higher. The media may also contain polymers composed of from 3-599 or higher recurring units, the complete mixture of polymers may constitute the starting material for forming the polymer (II).

The polymers (I) exhibit excellent elastomeric properties but display instability to atmospheric moisture.

There follow several examples of the preparation of polymers (I). These examples, as is true of all the examples herein, are exemplary and are not to be construed as limiting.

EXAMPLE 6 -(-N3P3Cl5(OC6H5] n- A quantity of the trimer of Example 1 was deoxygenated with inert gas and sealed in a suitable, thick-walled reaction vessel at 10-2 Torr and heated at 2500C for 15 hours. Polymerization was terminated at this time since a glass ball, one-half inch in diameter, ceased to flow due to the increased viscosity of the molten mass, when the vessel was inverted; termination was effected by cooling the vessel to room temperature. The resultant polymer had a Tg of -49.1"C.

Elemental Analysis: Found ( /nAC 17.62, H 1.20, N 10.28, P 23.12.

EXAMPLE 7 -[-N2P3Cl5(OC6H4-p-Fl- In the same manner as Example 6, the trimer of Example 2 was thermally polymerized at 2500C for 8 hours. The resultant polymer had a Tg of -47.6 C.

EXAMPLE 8 -{-N3P3Cl5(OC6H4-p-Cli- In the same manner as Example 6, the trimer of Example 3 was thermally polymerized at 2500C for 10 hours. The resultant polymer had a Tg of -39.3"C.

Elemental Analysis: Found-C 16.29, H 0.82, N 9.49, P 21.05.

EXAMPLE 9 -[-N3P3Cl5(OC6H4-p-CH)-l- In the same manner as Example 6, the trimer of Example 4 was thermally polymerized at 250 C for 18 hours. The resultant polymer had a Tg of-44.2 C.

EXAMPLE 10 -[-N3PCl5(OC6H4-p-OCII3)-l- In the same manner as Example 6, the trimer of Example 5 was thermally polymerized at 2500C for 6 hours. The resultant polymer had a Tg of -43.7"C.

The polymers (II) are formed in a process which comprises treating the polymer mixture (I) resulting from the thermal polymerization step with a mixture of compounds having the formulae M(OR2)V and if desired, M(W)V wherein M is lithium, sodium, potassium, magnesium or calcium, v is equal to the valence of metal M, and -OR2 and W are as specified above.

The polymer mixture is reacted with the mixture of metal compounds at a temperature and a length of time ranging from about 25"C for 7 days to about 200"C for 3 hours.

Again, as in the polymerization step mentioned above, the polymer mixture is reacted with the alkali or alkaline earth metal compounds at a temperature ranging from 25"C to 2000C for from 3 hours to 7 days, the lower temperatures necessitating the longer reaction times and the higher temperatures allowing shorter reaction times. These conditions are, of course, utilized in order to obtain the most complete reaction possible, i.e., in order to insure the complete conversion of the chlorine atoms in the polymer mixture to the corresponding ester of the alkali or alkaline earth starting materials.

The above esterification step is carried out in the presence of a solvent. The solvent employed in the esterification step must have a relatively high boiling point (e.g., about 1 150C or higher) and should be a solvent for both the polymer and the alkali or alkaline earth metal compounds. In addition, the solvent must be substantially anhydrous, i.e., there must be no more water in the solvent or metal compounds than will result in more than 1%, by weight, of water in the reaction mixture. The prevention of water in the mixture is necessary in order to inhibit the reaction of the available chlorine atoms in the polymer therewith. Examples of suitable solvents include diglyme, triglyme, tetraglyme, toluene and xylene. The amount of solvent employed is not critical and any amount sufficient to solubilize the chloride polymer mixture can be employed. Either the polymer mixture or the alkaline earth (or alkali) metal compounds may be used as a solvent solution thereof in an inert, organic solvent. It is preferred, however, that at least one of the charge materials be used as a solution in a compound which is a solvent for the polymeric mixture.

The amount of alkali metal or alkaline earth metal compound or compounds employed should be at least stoichiometrically equivalent to the number of availahle chlorine atoms in the polymer mixture. However, it is preferred that an excess of the metal compound be employed in order to assure complete reaction of all the available chlorine atoms. Where a mixture of metal compounds is employed, generally, the ratio of the individual alkali metal or alkaline earth metal compounds in the combined mixture governs the ratio of the groups attached to the polymer backbone. However, those skilled in the art readily will appreciate that the nature and, more particularly, the steric configuration of the metal compounds employed may effect their relative reactivity. Accordingly, the ratio mixed R2s in the esterified product, if necessary may be controlled by employing a stoichiometric excess of the slower reacting metal compound.

Examples of alkali or alkaline earth metal compounds which are useful in the process of the present invention include: sodium phenoxide potassium phenoxide sodium p-methoxyphenoxide sodium o-methoxyphenoxide sodium m-methoxyphenoxide lithium p-methoxyphenoxide lithium o-methoxyphenoxide lithium m-methoxyphenoxide potassium p-methoxyphenoxide potassium o-methoxyphenoxide potassium m-methoxyphenoxide magnesium p-methoxyphenoxide magnesium o-methoxyphenoxide magnesium m-methoxyphenoxide calcium p-methoxyphenoxide calcium o-methoxyphenoxide calcium m-methoxyphenoxide sodium p-ethoxyphenoxide sodium o-ethoxyphenoxide sodium m-ethoxyphenoxide potassium p-ethoxyphenoxide potassium o-ethoxyphenoxide potassium m-ethoxyphenoxide sodium p-n-butoxyphenoxide sodium m-n-butoxyphenoxide lithium p-n-butoxyphenoxide lithium m-n-butoxyphenoxide potassium p-n-butoxyphenoxide potassium m-n-butoxyphenoxide magnesium p-n-butoxyphenoxide magnesium m-n-butoxyphenoxide calcium p-n-butoxyphenoxide calcium m-n-butoxyphenoxide sodium p-n-propoxyphenoxide sodium o-n-propoxyphenoxide sodium m-n-propoxyphenoxide potassium p-n-propoxyphenoxide potassium o-n-propoxyphenoxide potassium m-n-propoxyphenoxide sodium p-methylphenoxide sodium o-methylphenoxide sodium m-methylphenoxide lithium p-methylphenoxide lithium o-methylphenoxide lithium m-methylphenoxide sodium p-ethylphenoxide sodium o-ethylphenoxide sodium m-ethylphenoxide potassium p-n-propylphenoxide potassium o-n-propylphenoxide potassium m-n-propylphenoxide magnesium p-n-propylphenoxide sodium p-isopropylphenoxide sodium o-isopropylphenoxide sodium m-isopropylphenoxide calcium p-isopropylphenoxide calcium o-isopropylphenoxide calcium m-isopropylphenoxide sodium p-sec butylphenoxide sodium m-sec butylphenoxide lithium p-sec butylphenoxide lithium m-sec butylphenoxide lithium p-tert. butylphenoxide lithium m-tert. butylphenoxide potassium p-tert. butylphenoxide potassium m-tert. butylphenoxide sodium p-tert. butylphenoxide sodium m-tert. butylphenoxide sodium propeneoxide sodium p-nonylphenoxide sodium m-nonylphenoxide sodium o-nonylphenoxide sodium 2-methyl-2-propeneoxide and potassium buteneoxide.

This process results in the production of a polymer mixture having the formula (it).

The polymeric reaction mixture resulting from this reaction or esterification step is then treated to remove the salt which results upon reaction of the chlorine atoms of the starting polymer mixture with the metal of the alkali or alkaline earth metal compounds. The salt can be removed by merely precipitating it out and filtering, or it may be removed by any other applicable method, such as by washing the reaction mixture with water after neutralization thereof with, for example, an acid such as hydrochloric acid.

The next step in the process comprises fractionally precipitating the polymeric material to separate out the high polymer from the low polymer and any unreacted trimer. The fractional precipitation is achieved by the, preferably dropwise, addition of the esterified polymer mixture to a material which is a non-solvent for the high polymer and a solvent for the low polymer and unreacted trimer. That is to say, any material which is a non-solvent for the polymers wherein n is higher than 350 and a solvent for the remaining low polymers may be used for fractional precipitation of the desired polymers. Examples of materials which can be used for this purpose include hexane, diethyl ether, carbon tetrachloride, chlororform, dioxane methanol and water. The fractional precipitation of the esterified polymeric mixture generally should be carried out at least twice and preferably at least four times in order to remove as much of the low polymer from the polymer mixture as possible. The precipitation may be conducted at any temperature, however, it is preferred that room temperature be employed. The novel high molecular weight copolymer mixture may then be recovered, for example, by filtration, centrifigation or decantation or the like.

There follow several examples of the preparation of polymers (II). In Examples 11 and 12, R' and R2 are identical, resulting in homopolymers; these are not claimed but the Examples illustrate reaction processes suitable for preparing the polymers (II) of the invention.

EXAMPLE 11 1NP(OC,Hs)2]n An anhydrous toluene solution of the polymer formed in Example 6, containing 31.2 parts of the polymer, was added to an anhydrous diglyme-benzene solution of 53.9 parts of sodium phenoxide at a temperature of 95"C with constant stirring. After the addition, benzene was distilled from the reaction mixture until a temperature of 115-1 160C was attained. The reaction was then heated to reflux for 6065 hours. At the end of this time, the resultant polymer was precipitated by pouring the reaction mixture into an excess of methyl alcohol. The polymer was stirred in the methyl alcohol for 24 hours. Next, the polymer was added to a large quantity of water and stirred an additional 24 hours. The -polymer was then separated and dried. The resultant homopolymer was a semicrystalline solid having a glass transition temperature (Tg) of -4.76"C. The polymer was soluble in benzene, tetrahydrofuran (THF) and dimethylformamide (DMF). Films cast from THF were tough and opaque. The films did not burn and were water repellent.

Elemental Analysis: Theoretical-C 62.34, H 4.36, N 6.06, P 13.40; Found-C 62.10, H 4.36, N 5.97, P 13.69.

EXAMPLE 12 -[-NP(OC6H4-p-Cl)2-l n- The procedure of Example 11 was followed, except that 15.0 parts of the polymer of Example 8 were reacted with 30.8 parts of sodium p - chlorophenoxide.

The resultant homopolymer (79 /" yield) was a semicrystalline solid having a Tg of -1.54"C. The polymer was soluble in benzene, THF, DMF and chloroform. Films cast from the THF were tough and opaque. The films did not burn and were water repellent.

Elemental Analysis: Theoretical-C 48.18, H 2.70, N 4.68, P 10.36; Found-C 47.90, H 2.63, N 4.49, P 10.28.

EXAMPLE 13 -1-N2P3(OC6H5)(OC6H4-p-Cl)5-1 The procedure of Example 11 was followed, except that 16.5 parts of the polymer of Example 6 were reacted with 37.1 parts of sodium p - chlorophenoxide.

The resultant copolymer (56% yield) was a solid soluble in benzene, THF and DMF. Films cast from THF were tough and opaque. The films did not burn and were water repellent.

Elemental Analysis: Theoretical-C 64.48, H 5.28, N 5.50, P 12.17; Found-C 64.34, H 5.22, N 5.42, P 12.30.

EXAMPLE 14 -[-N2P3(OC6H)(OC6H4-p-CH3)-i n- The procedure of Example 11 was followed, except that 14.1 parts of the polymer of Example 6 were reacted with 27.3 parts of sodium p methylphenoxide.The resultant polymer (40% yield) was a solid, soluble in benzene, THF and DMF. Films cast from THF were tough and transparent. The films did not burn and were water repellent.

Elemental Analysis: Theoretical-C 64.48, H 5.28, N 5.50, P 12.17; Found-C 64.34, H 5.22, N, 5.42, P 12.30.

EXAMPLE 15 -[-N3P3(OC6H4-p-F)(OC6H4-p-CH3)5-ln- The procedure of Example 11 was followed, except that 18.9 parts of the polymer of Example 7 were reacted with 35.3 parts of sodium p - methylphenoxide.

The resultant polymer (70 /^ yield) was a solid with a Tg of +0.08 C, soluble in benzene, THF and DMF. Films, cast from THF, were tough and transparent, did not burn, and were water repellent.

Elemental Analysis: Theoretical-C 63.00, H 5.03, N 5.37, P 11.89; Found-C 62.91, H 5.18, N 5.26, P 12.01.

EXAMPLE 16 -[-N3P3(OC6H4-p-Cl)(OC6H4-p-CH3)5-]n- n- The procedure of Example 11 was followed, except that 15.0 parts of the polymer of Example 8 were reacted with 26.6 parts of sodium p - methylphenoxide.

The resultant polymer (72 /n yield) was a solid with a Tg of -3.65 C, soluble in benzene, THF and DMF. Films, cast from THF, were tough and transparent, did not burn and were water repellent.

Elemental Analysis: Theoretical-C 61.93, H 4.56, N 5.28, P 11.69; Found-C 61.83, H 4.72, N 5.18, P 11.52.

EXAMPLE 17 -[-N3P3(OC6H4-p-CH3)(OC6H4-p-Cl)5-]n The p p - chlorophenoxide at 90"C. The sodium aryloxide solution was prepared by the reaction of 31.6 g (0.246 mole) of p - chlorophenol with 5.6 g (0.241 mole) of sodium in 300 ml of anhydrous bis - (2 - methoxyethyl)ether and 100 ml of dry benzene. After the addition, benzene was distilled until a temperature of 115 116"C was attained. The reaction mixture was then heated at 115---1160C for 60 70 hours with constant stirring. The polymer was precipitated into a large excess of methanol and washed in methanol for 24 hours. It was removed from the methanol, exhaustively washed with distilled water, and dried. The product is a colorless, fibrous material.

Following similar procedures, other homopolymers and copolymers, such as described above, can be prepared.

The novel polymers (II) of this invention, as mentioned above, are very thermally stable. The mixtures are soluble in specific organic solvents, for example, tetrahydrofuran. benzene. xylene, toluene and dimethylformamide and can be formed into films from solutions of the copolymers by evaporation of the solvent.

The polymers are water resistant at room temperature and do not undergo hydrolysis at high temperatures. The polymers may, for example, be used to prepare films, fibers, coatings, and molding compositions. They may be blended with such additives as, for example, antioxidants, ultraviolet light absorbers, lubricants, plasticizers, dyes, and pigments, fillers, for example litharge, magnesia, calcium carbonate, furnace black, alumina trihydrate and hydrated silicas, and other resins, without departing from the scope of the present invention.

The polymers may be used to prepare foamed products which exhibit excellent fire retardance and in some cases produce low smoke levels, or essentially no smoke when heated in an open flame. The foamed products may be prepared from filled or unfilled formulations using conventional foam techniques with chemical blowing agents. i.e. chemical compounds stable at original room temperature which decompose or interact at elevated temperatures to provide a cellular foam.

Suitable chemical blowing agents include: Effective Temperature Blowing Agent Range OC Azobisisobutyronitrile 105-120 Azo dicarbonamide(l,l - azobisformamide) 100200 Benzenesulfonyl hydrazide 95-100 N,N' - dinitroso - N,N' - dimethyl terephthalamide Dinitrosopentamethylenetetramine 130150 Ammonium carbonate 58 p,p' - oxybis - (benzenesulfonylhydrazide) 100200 Diazoaminobenzene 84 Urea - biuret mixture 90-140 2,2' - azo - isobutyronitrile 9140 Azohexahydrohenzonitrile 90140 Diisobutylene 103 4,4' - diphenyl disulfonylazide 110--130 Typical foamable formulations include: Phosphazene copolymer (e.g., [N4P3(OC6Hs)(OC6H4 - p OCH3)sln 100 parts Filler (e.g., alumina trihydrate) 0--100 phr Stabilizer (e.g magnesium oxide) 2.5-10 phr Processing aid (e.g., zinc stearate) 2.5 10 phr Plasticizer resin (e.g., Cumar P-10 coumarone indene resin) 0--50 phr Blowing agent (e.g., 1,1' - azobisformamide) 1-50 phr Activator (e.g., oil-treated urea) 1-40 phr Peroxide curing agent (e.g., 2,5 - dimethyl - 2,5 - di(t butylperoxy)hexane) 2.5-10 phr Peroxide curing agent (e.g., benzoyl peroxide 2.5-10 phr While the above are preferred formulation guidelines, obviously some or all of the adjuvants map be omitted, replaced by other functionally equivalent materials, or the proportions varied, within the skill of the art of the foam formulator.

In one suitable process, the foamable ingredients are blended together to form a homogeneous mass: for example, a homogeneous film or sheet can be formed on a 2-roller mill, preferably with one roll at ambient temperature and the other at moderately elevated temperature, for example, 100--120"F. The homogeneous foamable mass can then be heated, to provide a foamed structure; for example, by using a mixture of a curing agent having a relatively low initiating temperature, for example, benzoyl peroxide, and a curing agent having a relatively high initiating temperature, for example, 2,5 - dimethyl - 2,5 - di(t - butylperoxy)hexane, and partially pre-curing in a closed mold for about 6-30 minutes at 202500F, followed by free expansion for 30--60 minutes at 300--3500F. In the alternative, the foaming may be accomplished by heating the foamable mass for 3060 minutes at 300--3500F using a high temperature or low temperature curing agent, either singly or in combination. One benefit of utilizing the "partial pre-cure" foaming technique is that an increase in the molecular weight of the foamable polymer prior to the foaming step enables better control of pore size and pore uniformity in the foaming step. The extent of "pre-cure" desired is dependent upon the ultimate foam characteristics desired. The desired foaming temperature is dependent on the nature of the blowing agent and the crosslinkers present. The time of heating is dependent on the size and shape of the mass being foamed. The resultant foams are generally light tan to yellowish in appearance, and vary from flexible to semirigid, depending upon the glass transition temperature of the copolymer employed in the foam formulation, that is to say, the lower the glass transition of the polymer the more flexible will be the foam produced therefrom.

As indicated, inert, reinforcing or other fillers, for example, alumina trihydrate, hydrated silicas or calcium carbonate can be added to the polymer foams and the presence of these and other conventional additives should in no way be construed as falling outside the scope of this invention.

EXAMPLE 20 Preparation of Foamed -[-N3P3(OC6lH5)(OC6H4-p-OCH3)-l- To 100 parts of the copolymer -[-N2P2(OC6H5)(OC6-H4 - p - OCH3)ln prepared in accordance with Example 20, there were added 100 parts of alumina trihydrate, 5 parts of magnesium oxide, 5 parts of zinc stearate, 3 parts of Cumar P10 (a coumarone-indene resin), 30 parts of Celogen AZ* (1,1' - azobisformamide), 23 parts of BIK-OT (an oil-treated urea), 5 parts of 2,5 - dimethyl - 2,5 - di(tert. butylperoxy)hexane, and 5 parts of benzoyl peroxide (78 /n active, wet with water).

The above ingredients were milled to insure homogeneous mixing of all materials.

This mix was then free blown at 325-3500F for 10 minutes. The resultant flexible foam was light tan in color with a uniform small cellular structure. There was no evidence of delamination or side splits. A piece of the foamed material when heated in a Bunsen burner flame evolved only a very slight trace of smoke. The sample did not burn when removed from the burner flame. Thus, it would not support combustion and was rated as non-burning.

Also, as mentioned above, the polymers of this invention can be crosslinked at moderate temperatures by conventional free radical and/or sulfur curing techniques when minor amounts of unsaturated groups W are present in the polymer backbone. The ability of these polymers to be cured at temperatures below about 3500F makes them particularly useful as potting and encapsulation compounds, sealants, and coatings. These polymers are also useful for preparing crosslinked foams which exhibit significantly increased tensile strengths over uncured foams.

These polymers are often crosslinked in the presence of inert, reinforcing or other fillers and the presence of these and other conventional additives are deemed to be within the scope of this invention.

WHAT WE CLAIM IS: 1. A polyphosphazene having the repeating unit: [-NaP3(Cl5)(OR )-] fl- where n is greater than 2 and where R' is

*Celogen AZ is a Trademark.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (23)

**WARNING** start of CLMS field may overlap end of DESC **. a 2-roller mill, preferably with one roll at ambient temperature and the other at moderately elevated temperature, for example, 100--120"F. The homogeneous foamable mass can then be heated, to provide a foamed structure; for example, by using a mixture of a curing agent having a relatively low initiating temperature, for example, benzoyl peroxide, and a curing agent having a relatively high initiating temperature, for example, 2,5 - dimethyl - 2,5 - di(t - butylperoxy)hexane, and partially pre-curing in a closed mold for about 6-30 minutes at 202500F, followed by free expansion for 30--60 minutes at 300--3500F. In the alternative, the foaming may be accomplished by heating the foamable mass for 3060 minutes at 300--3500F using a high temperature or low temperature curing agent, either singly or in combination. One benefit of utilizing the "partial pre-cure" foaming technique is that an increase in the molecular weight of the foamable polymer prior to the foaming step enables better control of pore size and pore uniformity in the foaming step. The extent of "pre-cure" desired is dependent upon the ultimate foam characteristics desired. The desired foaming temperature is dependent on the nature of the blowing agent and the crosslinkers present. The time of heating is dependent on the size and shape of the mass being foamed. The resultant foams are generally light tan to yellowish in appearance, and vary from flexible to semirigid, depending upon the glass transition temperature of the copolymer employed in the foam formulation, that is to say, the lower the glass transition of the polymer the more flexible will be the foam produced therefrom. As indicated, inert, reinforcing or other fillers, for example, alumina trihydrate, hydrated silicas or calcium carbonate can be added to the polymer foams and the presence of these and other conventional additives should in no way be construed as falling outside the scope of this invention. EXAMPLE 20 Preparation of Foamed -[-N3P3(OC6lH5)(OC6H4-p-OCH3)-l- To 100 parts of the copolymer -[-N2P2(OC6H5)(OC6-H4 - p - OCH3)ln prepared in accordance with Example 20, there were added 100 parts of alumina trihydrate, 5 parts of magnesium oxide, 5 parts of zinc stearate, 3 parts of Cumar P10 (a coumarone-indene resin), 30 parts of Celogen AZ* (1,1' - azobisformamide), 23 parts of BIK-OT (an oil-treated urea), 5 parts of 2,5 - dimethyl - 2,5 - di(tert. butylperoxy)hexane, and 5 parts of benzoyl peroxide (78 /n active, wet with water). The above ingredients were milled to insure homogeneous mixing of all materials. This mix was then free blown at 325-3500F for 10 minutes. The resultant flexible foam was light tan in color with a uniform small cellular structure. There was no evidence of delamination or side splits. A piece of the foamed material when heated in a Bunsen burner flame evolved only a very slight trace of smoke. The sample did not burn when removed from the burner flame. Thus, it would not support combustion and was rated as non-burning. Also, as mentioned above, the polymers of this invention can be crosslinked at moderate temperatures by conventional free radical and/or sulfur curing techniques when minor amounts of unsaturated groups W are present in the polymer backbone. The ability of these polymers to be cured at temperatures below about 3500F makes them particularly useful as potting and encapsulation compounds, sealants, and coatings. These polymers are also useful for preparing crosslinked foams which exhibit significantly increased tensile strengths over uncured foams. These polymers are often crosslinked in the presence of inert, reinforcing or other fillers and the presence of these and other conventional additives are deemed to be within the scope of this invention. WHAT WE CLAIM IS:

1. A polyphosphazene having the repeating unit: [-NaP3(Cl5)(OR )-] fl- where n is greater than 2 and where R' is

*Celogen AZ is a Trademark.

where x is 0 to 3, R3 substituents, where present, being located in the meta or para

positions on the phenoxy ring, and where R2 is independently lower alkyl, lower alkoxy, halo, cyano, nitro, substituted lower alkyl or substituted lower alkoxy.

2. A polyphosphazene, as in Claim 1, where R' is phenyl.

3. A polyphosphazene, as in Claim 1, where R3 is lower alkyl or lower alkoxy and where x is 1.

4. A polyphosphazene, as in Claim 3, where R3 is located in the para position on the phenoxy ring.

5. A method of forming a polyphosphazene having the repeating unit: [N3P3(Cl)5(OR1)In where n is greater than 2 which method comprises polymerizing a triphosphazene corresponding to the formula where R' is

where x is 0 to 3, R3 substituents, where present, being located in the meta or para positions on the phenoxy ring, and where R2 is independently lower alkyl, lower alkoxy, halo, cyano, nitro, substituted lower alkyl or substituted lower alkoxy.

6. A method, as in Claim 5, where the triphosphazene is thermally polymerized in an inert atmosphere.

7. A method, as in Claim 6, where x is 0 or I and OR' is phenoxy, lower alkyl phenoxy or lower alkoxyphenoxy.

8. A polyphosphazene copolymer having the repeating unit: lN3P3(OR1)(OR2)5ln where n is greater than 2, where R' is

where x is 0 to 3, R3 substituents, where present, being located in the meta or para positions on the phenoxy ring, and where R3 is independently lower alkyl, lower alkoxy, halo, cyano, nitro, substituted lower alkyl or substituted lower alkoxy, and where R2 is different from R' and is lower alkyl, lower alkaryl, substituted lower alkyl or

where z is 0 to 3 and where R4 is independently lower alkyl, lower alkoxy, nitro, cyano, halo, substituted lower alkyl or substituted lower alkoxy.

9. A copolymer, as in Claim 8, where both OR' and OR2 are phenoxy or substituted phenoxy groups.

10. A copolymer, as in Claim 9, where the substituted phenoxy is an alkyl or alkoxy substituted phenoxy group.

II. A copolymer, as in Claim 8, where a portion of the OR2 groups are replaced by a group (W) capable of a crosslinking chemical reaction, the ratio of W:R'+R2 being less than 1:5.

12. A copolymer, as in Claim 11, where W is an ethylenically unsaturated monovalent radical.

13. A method of forming a polyphosphazene copolymer which comprises reacting a polymer having the repeating unit: [N3P2(Cl5)(OR1)ln with at least about a stoichiometric equivalent of one alkali or alkaline earth metal compound of the formula M(OR2)V where M is lithium, sodium, potassium, magnesium or calcium, v is the valence of the metal M, where n is greater than 2, where R' is

where x is 0 to 3, R3 substituents, where present, being located in the meta or para positions on the phenoxy ring, and where R3 is independently lower alkyl, lower alkoxy, halo, cyano, nitro, substituted lower alkyl or substituted lower alkoxy, and where R2 is different from R' and is lower alkyl, lower alkaryl, substituted lower alkyl, or

where z is 0 to 3 and where R4 is independently lower alkyl, lower alkoxy, nitro, cyano, halo, substituted lower alkyl or substituted lower alkoxy.

14. A method, as in Claim 13, where both OR' and OR2 are phenoxy or substituted phenoxy groups.

15. A method, as in Claim 14, where the substituted phenoxy is an alkyl or alkoxy substituted phenoxy group.

16. A foamed cellular article comprising a polyphosphazene polymer where the polyphosphazene polymer foamed has the repeating unit: [N3P3(0R')(OR2)s]n where n is greater than 2, where R' is

where x is 0 to 3, R3 substituents, where present, being located in the meta or para positions on the phenoxy ring, and where R3 is independently lower alkyl, lower alkoxy, halo cyano, nitro, substituted lower alkyl or substituted lower alkoxy, and where R2 is different from R' and is lower alkyl, lower alkaryl, substituted lower alkyl, or

where z is 0 to 3 and where R4 is independently lower alkyl, lower alkoxy, nitro, cyano, halo, substituted lower alkyl or substituted lower alkoxy.

17. A cellular article, as in Claim 16, where both OR' and OR2 are phenoxy or substituted phenoxy groups.

18. A cellular article, as in Claim 16, where the substituted phenoxy is an alkyl or alkoxy substituted group.

19. A cellular article, as in Claim 16, where the polyphosphazene foamed contains groups (W) capable of a crosslinking chemical reaction, the ratio of W:R'+R2 being less than 1:5.

20. A polyphosphazene as claimed in Claim 1 substantially as described in any one of Examples 6 to 10.

21. A polyphosphazene as claimed in Claim 8, substantially as described in any one of Examples 13 to 19.

22. Foamed and/or crosslinked polyphosphazenes produced from the polyphosphazenes of Claim 20 or Claim 21.

23. A process for making a polyphosphazene as claimed in any one of Claims I, 8, 11, 20, 21 or 22 substantially as described herein.