Fluorocyanate and fluorocarbamate monomers and polymers thereof

Details Fluorocyanate and fluorocarbamate monomers and polymers thereof Fluorocyanate and fluorocarbamate monomers and polymers thereof

1998-08-27

2001-10-09

Copenheaver, Blaine (Department: 1773)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C428S421000, C428S422000

Reexamination Certificate

active

06300445

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 cyano-containing cure site monomers such as CF
2
═CFOCF
2
CF(CF
3
)OCF
2
CF
2
—CN (8-CNVE, U.S. Pat. No. 4,281,092) used in perfluoroelastomers require high temperature and the presence of catalysts to complete the curing. Hence, the direct utilization of functional monomers such as 8-CNVE in fluoroplastics is generally inconvenient to use and not practical.
Thus, there is an unfilled need for convenient functional monomers for use in fluoropolymers.
SUMMARY OF THE INVENTION
This invention provides compounds having the formula
CF
2
═CF—R
f
—(CH
2
)
n
—X  (I)
wherein —X is —OCN (cyanate) or —O—(CO)—NH
2
(carbamate), n is 1-3, and Rf is perfluoroalkyl or perfluoroalkoxy having 1-20 carbon atoms.
Polymers comprising units derived from compound (I) are also provided. Preferred polymers contain units derived from at least one other fluoromonomer. Thus, this invention provides polymers having at side groups —R
f
—(CH
2
)
n
—X, wherein —X is at least one of —OCN and —O—(CO)—NH
2
. The presence of such groups can transform the normally chemically inert fluoropolymer into a reactive fluoropolymer to enhance its adhesion to other materials.
DETAILED DESCRIPTION
It has been discovered that compounds having the formula
CF
2
═CF—R
f
—(CH
2
)
n
—X  (I)
wherein —X is —OCN or —O—(CO)—NH
2
, n is 1-3, and R
f
is linear or branched perfluoroalkyl or perfluoroalkoxy having 1-20 carbon atoms 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.
The new functional fluorinated compounds (I) wherein —X is —OCN, i.e., cyanates, can be synthesized by reacting compounds of the general formula CF
2
═CF—R
f
—(CH
2
)
n
—OH with CNY, Y=Br or Cl, to obtain
CF
2
═CF—R
f
—(CH
2
)
n
—OCN  (II)
It has also been discovered that the cyanate can be hydrolyzed under acidic conditons to obtain the new functional fluorinated compounds (I) wherein —X is —O—(CO)—NH
2
, i.e., carbamates having the formula
CF
2
═CF—R
f
—(CH
2
)
n
—O—(CO)—NH
2
  (III)
In compounds (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=1-12. Preferably, j=2-8.
The cyanate compound CF
2
═CF—R
f
—(CH
2
)
n
—OCN (II) of this invention exhibits an unusual combination of properties. Hydrolytic stability of the cyanate is good under neutral conditions and even under acidic conditions at ambient temperature, thereby making it possible to use (I) wherein —X is —OCN in controlled aqueous polymerization processes, as well as in non-aqueous processes, to obtain polymers with side groups containing the cyanato group (—OCN). However, under acidic conditions at elevated temperature, the cyanate can be converted to the carbamate compound CF
2
═CF—R
f
—(CH
2
)
n
—O—(CO)—NH
2
(III). The carbamate compound can also be used in polymerization processes to obtain polymers with side groups containing the carbamate group (—OCONH
2
). Furthermore, the unique combination of conditions under which the cyanate hydrolyzes to the carbamate and the acidic nature and/or elevated temperature of aqueous polymerization of fluoromonomers makes it possible to introduce (II) into polymerization and to obtain polymer with side groups containing the carbamate group, i.e., to hydrolyze some of the —OCN to —O—(CO)—NH
2
during the polymerization process. This is illustrated by Example 12 below. Nevertheless, the compounds (I) are thermally active enough to provide rapid crosslinking at moderate temperatures, making them useful, for example, as crosslinking sites 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 as a monomer 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.
Cyanates (II) of this invention can be prepared in high yield by a one-step process in which compounds having the general formula
CF
2
═CF—R
f
—(CH
2
)
n
—OH  (IV)
wherein n and R
f
are as defined above, are reacted with cyanogen bromide (CNBr) or cyanogen chloride (CNCl) in the presence of base. Starting compounds (IV) are known, and are disclosed, for example, in U.S. Pat. Nos. 4,564,717 and 5,059,720. Bases that can be used are non-nucleophilic bases including tertiary amines such as trialkylamines, e.g., triethylamine; cyclic amines such as 1,8-bis(methylamino)naphthalene, morpholine, and N-methylmorpholine; 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU); 1,5-diazabicyclo[4.3.0]non-5-ene (DBN); and the like. In carrying out the reaction, it is preferred for the cyanogen halide and the base each to be present in an amount slightly in excess of the amount of (IV) on a molar basis. Large excesses of base and/or cyanogen halide can be used but are not necessary. The reaction can be carried out at atmospheric pressure under essentially anhydrous conditions in a convenient medium that is stable toward nonnucleophilic base such as acetone, tetrahydrofuran, or ethyl ether. Peaction temperature is not critical, but the reaction is exothermic and the heat of reaction is desirably removed by appropriate cooling means. Preferably, the reaction is carried out at temperature below room temperature, most preferably at about 0°-10° C. which is conveniently achieved with ice water.
Carbamates (III) of this invention can be prepared from the cyanates (II) by contacting the cyanate with acid at elevated temperature for time sufficient to complete conversion of cyanate to carbamate. Suitable acids include hydrochloric, nitric, sulfuric, and other common inorganic acids. Temperature is desirably at least 30° C. but less than 100° C., preferably in the range 40°-75° C.
The processes for making the cyanates (II) and the carbamates (III) are further aspects of the invention.
Polymers of this invention comprise units derived from compound (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 generally contain at least 35 wt % fluorine and 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 prefer

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