Fluoropolymers and processes therefor and therewith

Details Fluoropolymers and processes therefor and therewith Fluoropolymers and processes therefor and therewith

2002-01-29

2003-07-22

Wu, David W. (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S253000, C526S206000, C526S247000, C526S255000

Reexamination Certificate

active

06596829

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a class of fluorotelomers end-capped with secondary alcohols or their ethers or esters, to a process for producing the polymer, and to a process for using the polymer as insoluble, chemically and thermally stable lubricants, mold release agents, polishes, and coatings.
BACKGROUND OF THE INVENTION
Wax-like fluorotelomers are disclosed in U.S. Pat. No. 3,067,262. Such fluorotelomers were based predominately on a fluorotelomer backbone of polytetrafluoroethylene (PTFE) formed by telomerization of tetrafluoroethylene (TFE) in 1,1,2,-trichloro-1,2,2-trifluoroethane (TCTFE) in the presence of a peroxide free-radical initiator wherein the TCTFE served both as a solvent and as a telogen. Telomerization can be defined as a reaction between two substances in which one substance provides the terminal groups (telogen) and the other provides the internal linkages of the telomer.
U.S. Pat. No. 5,552,500 and U.S. Pat. No. 5,665,838 disclose a process for producing a fluorotelomer in which a hydrochlorofluorocarbon is used both as telogen and solvent. The fluorotelomers, dispersed in 1,1-dichloro-1-fluoroethane (HCFC-141b), have been used commercially as dry film lubricants, and sold by E. I. du Pont de Nemours & Co. under the trademarks DryFilm DF and DryFilm 1000.
An international agreement in the 1980's banned most uses for chlorofluorocarbons such as TCTFE and minimized over time the uses of hydrochlorofluorocarbons (HCFC) such as HCFC-141b, because of their threat to the ozone layer in the upper atmosphere and their involvement in global warming. U.S. Pat. No. 5,310,870 discloses a process for producing a fluorotelomer by reacting TFE or hexafluoropropylene with a hydrofluorocarbon telogen in solution, in the presence of a free radical initiator. This hydrofluorocarbon telogen consists essentially of an acyclic organic compound having a boiling point at atmospheric pressure between 25° C. and 150° C.
Many industrial operations require the use of release agents to reduce the tendency of a molded product to stick to the mold, or that of a tool to stick to the object on which it is working. In some cases, where a typical lubricant would be unsatisfactory or unsightly, e.g., a window frame, a release agent may also be used as a dry film lubricant to make it easier for a movable part to slide on a stationary piece of equipment. Release agents may be a solution, dispersion or solid, and typically form a thin, generally invisible film on one or both of the above touching objects.
For example, Japanese Kokai JP6-157614A discloses a polymerization process using 2,3-dihydro-decafluoropentane as polymerization medium; JP10-158335A discloses a fluoropolymer containing a hydroxyl group having a fluorine content of 20 weight % or more and a molecular weight of 500-1,000; U.S. Pat. No. 5,789,504 discloses a process for producing a low molecular weight polytetrafluoroethylene having a melting point of 250° C.-325° C.; and EP 0723979A1 discloses a comparable process wherein the solvent is selected from a group that also includes hydrofluorocarbons. However, these patents and applications do not disclose a process or composition for use as release agents or lubricants.
WO 98/51649 discloses a fluorinated saturated hydrocarbon containing 10%-95% of a trihydrofluorocarbon and useful as a solvent or forming a polymer coating to promote cleaning, lubrication or repellency on surfaces. Also U.S. Pat. No. 5,476,603 discloses a composition which is liquefied under pressure, and comprises certain non-polymeric hydrofluorocarbons and an agent having a releasing action selected from the group of certain waxy esters having 34 to 50 carbon atoms, a paraffin wax, a polyethylene wax and a metal soap.
There is a constant need for providing an improved release agents and lubricants that are environmentally friendly, i.e., not based on chlorine-containing fluorocarbons.
SUMMARY OF THE INVENTION
A composition, which can be used as, for example, mold release agent or lubricant, comprises a fluorotelomer comprising repeat units derived from a fluoroalkene, and optionally a comonomer, having an end group derived from a secondary alcohol or derivative thereof.
A process comprises contacting a fluoroalkene, and optionally a comonomer, in a hydrofluorocarbon, with a free radical initiator and at least one secondary alcohol or derivative thereof.
DETAILS OF THE INVENTION
The composition comprising a fluorotelomer can be used as mold release agent. For example, a dispersion of the fluorotelomer in a solvent or water, when applied to a mold and solvent allowed to evaporate, provides a coating that affords multiple releases of an article from the mold. The coating can be used at temperatures ranging from ambient to over 300° C.
The composition can also be used as lubricant. For example, a coating of the fluorotelomer applied to a surface will provide a very lubricious coating with a low coefficient of friction. The surface can be a mold or other object made of wood, metal, plastic, rubber, stone, cement, glass, or fiber. These surfaces are well known to one skilled in the art.
Any fluoroalkene that can produce a fluorotelomer having the property disclosed herein can be used. The preferred fluoroalkene monomer contains 2 to about 10, preferably 2 to 3, carbon atoms. Examples of suitable fluoroalkenes include, but are not limited to, 1,1 -difluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene (TFE), 3,3,3-trifluoropropene, hexafluoropropylene (HFP), and combinations of two or more thereof. The most preferred fluoroalkene is TFE.
The preferred fluorotelomers are homotelomers, but a cotelomer (copolymer) containing repeat unit derived from a comonomer can also be produced. The comonomer is generally an ethylenically unsaturated compound, which can be fluorinated or perfluorinated. The amount of repeat units derived from a comonomer can be in the range of from about 0.1 to about 10, preferably 0.3 to 3.0 weight % of the copolymer.
Suitable comonomers include, but are not limited to, ethylene, propylene, butylene, decene, 1,1-difluoroethylene, 1,2-difluoroethylene, TFE, 3,3,3-trifluoropropene, HFP, and combinations of two or more thereof. The preferred comonomers are perfluorinated comonomers. The most preferred comonomer is TFE, HFP, or combinations thereof.
As disclosed below, a hydrofluorocarbon is used in a process for producing the fluorotelomer of the composition, a hydrofluorocarbon can also be incorporated into the fluorotelomer as an end group. The suitable hydrofluorocarbons include, but are not limited to, any of those disclosed in U.S. Pat. No. 5,310,870, the disclosure of which is incorporated herein by reference. Examples of suitable hydrofluorcarbons include, but are not limited to, 2,3-dihydrodecafluoropentane, perfluorobutyl methyl ether, perfluorobutyl ethyl ether, 2,4-dihydrooctafluorobutane, 1,1,2,3,3,3-hexafluoropropyl methy ether, 2-trifluoromethyl-2,3-dihydrononafluoropentane, 1,1,1,3,3-pentafluorobutane, or combinations thereof. These hydrofluorocarbons can be obtained commercially. For example, 2,3-dihydrodecafluoropentane is available from E. I. DuPont de Nemours & Co., Wilmington, Del. and perfluorobutyl methyl ether and perfluorobutyl ethyl ether are available from 3M Co., Minneapolis, Minn.
Generally, majority of the end group of the fluorotelomer can be derived from any secondary alcohol or derivative thereof. A suitable secondary alcohol or derivative thereof is the one that is substantially soluble in a hydrofluorocarbon disclosed herein. The most preferred secondary alcohols are those having at least 4 to about 12 carbon atoms and an &agr;-hydrogen. The end group can also be derived from a derivative of a secondary alcohol. The derivative of suitable secondary alcohol can include an ether or ester of a secondary alcohol or combinations thereof. Also suitable is the combinations of a secondary alcohol, ether thereof, and/or ester thereof. Examples of suitable secondary alcohols include, but are not limited to, 2-propanol, 2-butanol, 2-pentanol, 2-h

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