Claims
- 1. Polyphosphazenes having a degree of polymerization of 10 to 50,000 the skeletal chains of which comprise randomly repeating units represented by the general formulas ##EQU8## wherein each R is a monovalent radical selected from the group consisting of alkyl, substituted alkyl, fluoroalkyl, aryl, substituted aryl and arylalkyl and not every R in the polyphosphazene is required to be identical to every other R; and each R' is a monovalent group containing OH functionality and the ratio of R':R being between 0.5 to 99.5 and 35 to 65.
- 2. The polymers of claim 1 wherein R' is represented by the general formula ##EQU9## in which Q is selected from the group consisting of --(CH.sub.2 ).sub.n and --C.sub.6 H.sub.4 X(CH.sub.2).sub.m wherein the --X(CH.sub.2).sub.m group is meta or para, n is an integer from 1 to 6, m is an integer from 1 to 3, X is O or CH.sub.2, and R" is selected from the group consisting of H and alkyl with up to four carbon atoms.
- 3. A terpolymer according to claim 1 in which the randomly repeating units bonded to phosphorus comprise CF.sub.3 CH.sub.2 O--; C.sub.3 F.sub.7 CH.sub.2 O-- and ##EQU10##
- 4. The polymers of claim 1 as curable compositions which can be crosslinked at room temperature or above.
- 5. A cured polyphosphazene of claim 1, cured with a polyisocyanate.
- 6. A cured polyphosphazene of claim 1, cured with a polyanhydride.
- 7. The polyphosphazenes of claim 1 in which R is CF.sub.3 CH.sub.2 --.
- 8. The polyphosphazenes of claim 1 in which R is selected from the group which is comprised of --CH.sub.2 (CF.sub.2).sub. m F and --CH.sub.2 (CF.sub.2).sub. p H groups where m and p are integers from 1 to 8.
- 9. The polyphosphazenes of claim 1 in which up to 35 mole percent of the groups attached to the P atoms contain --OH functionality.
- 10. A process for the preparation of the polymers of claim 1 which comprises the reaction of poly(dichlorophosphazene) with the alkali salt or salts of ROH and the alkali salt of ##EQU11## R, Q, and R" being as defined in claims 1 and 2.
- 11. A process for the preparation of soluble polymers of claim 1 which comprises the reaction of a polymer which contains the units ##EQU12## where not every R is required to be identical to every other R with the alkali salt of ##EQU13## R, Q, and R" being as defined in claims 1 and 2.
Government Interests
The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section 395 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat 435; 42 U.S.C. 2457).
This is a continuation of application Ser. No. 303,159, filed Dec. 2, 1972, and now abandoned.
This invention relates to polymers containing repeating ##EQU3## units in the polymer chain. More particularly it relates to polyphosphazene copolymers and terpolymers which contain --OH functionality attached to an organic radical which is boned to phosphorus.
The invention is applicable to the polyphosphazene homopolymers described in U.S. Pat. No. 3,370,020 (Allcock et al) issued Feb. 20, 1968, and in Polymer, 11, 31 (1970), to the poly(fluoralkoxyphosphazene) elastomers described in U.S. Pat. No. 3,515,688 (Rose) issued June 2, 1970, to the polyphosphazene copolymers and terpolymers described in pending U.S. Pat. Nos. 3,702,833 and 3,700,629, and Polymer, 13, 253 (1972), and to other polymers characterized by a repeating sequence of ##EQU4## units in which various groups are attached to the P atoms, such groups including alkoxy, fluoroalkoxy, aryloxy, substituted aryloxy, and other groups. Suitable substituents on the phenoxy ring include halogen, nitro, cyano, phenyl, phenoxy and alkoxy. Other homopolymers and copolymers to which this invention is applicable are described in Chem. Rev., 72, 315 et seq. (1972).
The poly(fluoroalkoxyphosphazene) copolymers of U.S. Pat. 3,515,688 and the terpolymers of U.S. Pat. No. 3,702,833 have been crosslinked. However, cures which involved radical formation generally at elevated temperatures were employed. In contrast, the polymers of this invention can be crosslinked at room temperature without the necessity of a free radical source. By incorporation of a reactive --OH site as described herein, a controlled cure of these compositions is possible.
The polymers described in the prior art had structures of the type: ##EQU5## where R = R' for homopolymers but not for copolymers and R and R' are selected from alkoxy, substituted alkoxy, aryloxy, substituted aryloxy and arylalkoxy.
The polymers of this invention contain small amounts of randomly distributed repeating units in addition to the repeating units described above. The polymers of this invention have a degree of polymerization of 10 to 50,000. Examples of the additional repeating units are: ##EQU6## wherein R and R' are defined as described as above and R" represents an organic monovalent radical containing a group with --OH functionality which is capable of further reaction at relatively moderate temperature represented by the formula ##EQU7## where R.sub.1 is a divalent organic radical represented by --(CH.sub.2).sub.n or --C.sub.6 H.sub.4 X(CH.sub.2).sub.m, the --X(CH.sub.2).sub.m group being either meta or para, and R.sub.2 is H or a monovalent lower alkyl radical with up to four carbon atoms and n is an integer from 1 to 6, m is an integer from 1 to 3, and X is O or CH.sub.2.
The ratio of (R and R') groups to R" groups is between 99.5/0.5 and 65/35. Lower molecular weight polymers require higher concentrations of R" groups for subsequent crosslinking; whereas higher molecular weight polymers require much smaller concentrations of R".
Optimization of physical and chemical properties of polymers can generally be accomplished by crosslinking reactions. When crosslinked, the polymers of this invention are useful as solvent- and chemical-resistant coatings, sealants, potting compounds, elastomers and plastics. They are particularly suited to applications where flame retardancy is desirable. The polymers of this invention contain hydroxyl sites and can be crosslinked by a variety of chemical agents, including those that contain at least two isocyanate or anhydride sites per molecule. The presence of a catalyst to achieve a cure is often desirable.
In one process for the preparation of the polymers of this invention poly(dichlorophosphazene) is dissolved in a suitable solvent such as benzene, toluene, xylene, chlorobenzene, o-dichlorobenzene, tetrahydrofuran or mixtures thereof. This polymer solution is gradually added to a well stirred solution or suspension of alkoxide salt(s), e.g. as described in U.S. Pat. No. 3,515,688. If preferred, the salt(s) may be added to the solution of poly(dichlorophosphazene). Sodium alkoxides are normally employed but lithium or potassium salts are also suitable. The salts should be present in excess. The total mole percent of salts is preferably in the range 105 to 200 percent based on equivalents of chlorine originally present in the poly(dichlorophosphazene). The alkali salts derived from such alcohols or diols as trifluoroethanol, 2,2,3,3,3-pentafluoropropanol, 2,2,3,3,4,4,4-heptafluorobutanol, 2,2,3,3,-tetrafluoropropanol, 2,2,3,3,4,4,5,5-octafluoropentanol, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptanol, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanol, 1,2-propanediol, 1,3-butanediol, 1,5-hexanediol, 1,2-hexanediol, 2-(m-hydroxyphenoxy)ethanol, ethylene glycol, 1,3-propanediol, and 1,4-butanediol, methanol, n-butanol, n-octanol, 2-methoxyethanol, 2-(n-butoxy)ethanol, phenol, 3- or 4-chlorophenol, 4-bromophenol, 4-methoxyphenol, 4-(n-butoxy)phenol, 4-phenylphenol, 4-phenoxyphenol, and benzyl alcohol may be employed. Other alcohols that can be used will be obvious to those skilled in the art.
Reaction temperatures in the range of 0.degree. to 200.degree.C. are useful, but the range of 20.degree. to 150.degree.C is preferred. The reaction is essentially complete when there is no change in the concentration of alkoxide reactant with reaction time.
Another method by which the above polymers may be prepared is as follows: a poly(phosphazene)homopolymer or copolymer is reacted with the alkali salt of glycol. The hydroxyalkoxy moiety is introduced onto the phosphazene polymer in amounts from 0.5 up to 35 mole percent.
Polymers prepared by either of the two aforementioned processes may be isolated by known procedures. They may be formulated into crosslinkable systems with isocyanate or anhydride reagents by physical or by solution techniques. Catalysts may also be present to accelerate the curing reaction. Tertiary amines such as trialkylamines, triethylenediamine N-alkylated derivatives of piperidine, morpholine or piperazine, and 2,4,6-tris(N,N-dimethylaminomethyl)phenol, metal salts, and metal alkylhalides are representative of suitable catalysts. The amount of catalyst used is generally 0.1 to 5% by weight on polyphosphazene.
The following curing agents are representative of those found suitable for the curing of the polymers of this invention:
The above list is for purposes of illustration only and is not intended to be all inclusive. Other polyisocyanate or anhydride crosslinking reagents may be used as curing agents.
The amount of curing agent will generally vary from 2-50% by weight on polyphosphazene and is determined by the functionality and molecular weight of both the polyphosphazene and the curing agent itself. The preferred ratio of reactive group of curing agent to hydroxyl group of the polyphosphazene is 1.0 to 1.1.
The crosslinking reaction may be performed at ambient or elevated temperatures. For example, a polyphosphazene derived from trifluoroethanol (45 mole percent), 2,2,3,3,4,4,5,5, octafluoropentanol (45 mole percent) and 1,3-butanediol (10 mole percent) when dissolved in tetrahydrofuran can be crosslinked at room temperature in the presence of 2,4-toluene diisocyanate and dibutyltin diacetate catalyst. The same polymer can be crosslinked with dianhydrides but longer times and/or higher temperatures are required. Systems which crosslink slowly are particularly useful for solvent based coatings and solventless sealant and potting compositions.
In these instances, the formulated polymer is applied to the desired substrate or form and subsequently crosslinked in situ upon standing and/or upon application of heat. These crosslinking reactions are often run in the presence of inert, reinforcing or other fillers and the presence of these additives should in no way be construed as falling outside the scope of this invention.
US Referenced Citations (5)
Continuations (1)
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303159 |
Nov 1972 |
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Patent Grant
3948820
