Phosphorus-containing fluoromonomers and polymers thereof

Details Phosphorus-containing fluoromonomers and polymers thereof Phosphorus-containing fluoromonomers and polymers thereof

1999-02-23

2001-01-23

Zitomer, Fred (Department: 1713)

Stock material or miscellaneous articles

Composite

Of fluorinated addition polymer from unsaturated monomers

C428S421000, C428S447000, C428S450000, C428S451000, C428S457000, C428S461000, C428S500000

Reexamination Certificate

active

06177196

ABSTRACT:

FIELD OF THE INVENTION
This invention is in the field of fluorinated compounds useful as monomers in making fluoropolymers.
BACKGROUND OF THE INVENTION
There is an increasing demand for functionalized fluoromonomers and polymers to be applied in the areas of adhesion enhancement, cured coatings, interface compatibilizers for compounding/blending, and so on. Known cure site monomers such as CF
2
═CFOCF
2
CF(CF
3
)OCF
2
CF
2
—CN (U.S. Pat. 4,281,092) used in perfluoroelastomers require high temperature and the presence of catalysts to complete the curing. Hence, the direct utilization of such functional monomers in fluoroplastics is generally inconvenient to use and not practical.
Thus, there is an unfilled need for a convenient functional monomer for use in fluoropolymers.
SUMMARY OF THE INVENTION
This invention provides a compound having the formula
CF
2
═CF—R
f
—(CH
2
)
n
—OP(O)
p
—&PHgr;
2
  (I)
wherein n is 1-3, p is 0 or 1, R
f
is perfluoroalkyl or perfluoroalkoxy having 1-20 carbon atoms, &PHgr; is bromine, chlorine, or OM, and M is H, NH
4
or alkali metal.
Polymers comprising units derived from compound (I) are also provided. Preferred polymers contain units derived from at least one other fluoromonomer. The presence in such polymers of units derived from (I) can transform the normally chemically inert fluoropolymer into a reactive fluoropolymer to enhance its adhesion to other materials.
Aqueous dispersions, solutions in highly fluorinated solvents, and coatings of the phosphorus-containing fluoropolymers are further embodiments of the invention.
DETAILED DESCRIPTION
It has been discovered that compounds having the general formula
CF
2
═CF—R
f
—(CH
2
)
n
—OP(O)
p
—&PHgr;
2
  (I)
wherein n is 1-3, p is 0 or 1, R
f
is linear or branched perfluoroalkyl or perfluoroalkoxy having 1-20 carbon atoms, &PHgr; is bromine, chlorine or OM, and M is H, NH
4
or alkali metal, are useful as monomers in making fluoropolymers, and are particularly useful in minor amount to introduce highly reactive functional side groups into the fluoropolymer. Such fluoropolymers are useful materials in the areas of adhesion enhancement, coatings, thermosetting resins, grafting polymers, curable elastoplastics and elastomers, and the like.
In compound (I), preferably n=1. Preferred R
f
are perfluoroalkoxy having 2-20 carbon atoms, including [O—CF
2
CF(CF
3
)]
k
—O—CF
2
CF
2
wherein k=1-5, most preferably k=1, and O—(CF
2
)
m
wherein m=2-20, most preferably m=2-4. When R
f
is (CF
2
)
j
, j=2-12. Preferably, j=2-8. When &PHgr; is OM, a preferred M is H or NH
4
.
The phosphorus-containing compound (I) of this invention exhibits a desirable combination of properties. The functional group —OP(O)
p
—&PHgr;
2
has sufficient stability to survive polymerization processes, aqueous when &PHgr; is OM, non-aqueous when &PHgr; is chlorine or bromine. However, (I) is thermally active enough to provide rapid crosslinking at moderate temperatures, even without catalyst, making it useful, for example, as a crosslinking site in polymers. Additionally, the functionality of (I) can be used to provide fluoropolymers, which are normally non-adherent, with adhesive properties. In either case, the functional comonomer units in the copolymer may be changed from the original comonomer, but are nevertheless derived therefrom.
The unusual temperature response of (I) has several implications for utility, such as when used as a monomer incorporated into fluoropolymers. Because of its high thermal activity, (I) can be very useful in polymer resins that are fabricated without high temperature exposure before shaping, as in powder coating or in deposition from solution or aqueous dispersion, or in polymers that can be shaped by melt processing techniques at relatively low temperature and subsequently cured, such as for low-melting polymers or for elastomeric polymers.
Phosphorus-containing compounds (I) of this invention can be prepared in high yield by a process in which compounds having the general formula
CF
2
═CF—R
f
—(CH
2
)
n
—OH  (II)
are reacted with P(O)
p
Cl
3
or P(O)
p
Br
3
wherein n, p and R
f
are as defined above, either neat or in aprotic solvent, to obtain the chloride or bromide, e.g.,
CF
2
═CF—R
f
—(CH
2
)
n
—OP(O)
p
(Cl
2
)  (III)
followed by hydrolysis to obtain the acid
CF
2
═CF—R
f
—(CH
2
)
n
—OP(O)
p
—(OH)
2
  (IV)
The acid can be further reacted with ammonium or alkali metal base to obtain the corresponding salt. Starting compounds (II) are known, and are disclosed, for example, in U.S. Pat. Nos. 4,564,717 and 5,059,720. Aprotic solvents that can be used include, for example, tetrahydrofuran and methylene chloride. Preferably, the reaction is carried out neat, i.e., without solvent. In carrying out the reaction of (II) with phosphoryl chloride to obtain (III), it is preferred for the phosphoryl chloride to be present in an amount in excess of the amount of (II) on a molar basis. Large excesses of phosphoryl chloride, e.g. 2× or 5×, can be used and are preferred, but are not necessary. The reaction can be carried out at atmospheric pressure under essentially anhydrous conditions. The reaction is faster at elevated temperature, and reaction temperature in the range 50°-150° C. is desirable, with temperature of 90°-130° C. preferred. The presence of a small amount of anhydrous metal salt in the reaction mass is beneficial, but is not required. The excess phosphoryl chloride can be recovered by distillation at atmospheric pressure, and the higher-boiling product (III) can then be recovered by distillation at reduced pressure.
Hydrolysis of the bromide or chloride product (III) to obtain the acid (IV) can be carried out simply by contacting (III) with water for a period of time sufficient to complete the hydrolysis. Agitation of the hydrolyzing mixture is desirable to promote good contact of (III) with the water. The hydrolysis reaction can conveniently be carried out at ambient temperature, or can be accelerated by moderate heating. After completion of hydrolysis, HCl resulting from hydrolysis along with any residual water can be removed under heat and vacuum.
Polymers of this invention comprise units derived from the phosphorus-containing monomer (I) of this invention. Preferred polymers of this invention contain units derived from at least one other fluorinated monomer, though such polymers can also contain units derived from fluorine-free monomers.
Fluorinated monomers that can be used include fluoroolefins having 2-10 carbon atoms, fluorinated dioxoles, and fluorinated vinyl ethers of the formula CY
2
═CYOR or CY
2
═CYOR′OR wherein Y is H or F, and —R, and —R′— are independently completely-fluorinated or partially-fluorinated alkyl and alkylene groups containing 1-8 carbon atoms. Preferred —R groups contain 1-4 carbon atoms and are preferably perfluorinated. Preferred —R′— groups contain 2-4 carbon atoms and are preferably perfluorinated.
Preferred fluoroolefins have 2-6 carbon atoms and include TFE, HFP, CTFE, vinyl fluoride, vinylidene fluoride, trifluoroethylene, hexafluoroisobutylene, and perfluorobutyl ethylene. Preferrec, cyclic fluorinated monomers include perfluoro-2,2-dimethyl-1,3-dioxole (PDD) and perfluoro-2-methylene-4-methyl-1,3-dioxolane (PMD). Preferred fluoropolymers include the group of tetrafluoroethylene (TFE) polymers. Preferred TFE polymers include perfluoropolymers, particularly copolymers of TFE and one or more of perfluoroolefins having 3-8 carbon atoms, especially hexafluoropropylene (HFP), and perfluoro(alkyl vinyl ethers) having alkyl groups containing 1-5 carbon atoms, especially 1-3 carbon atoms. Preferred fluoropolymers also include melt-fabricable copolymers of ethylene and TFE or chlorotrifluoroethylene, which copolymers can also contain up to 10 mol % of one or more additional monomers.
Copolymerizable fluorine-free monomers that can be used in conjunction with the phosphorus-containing monome

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