Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-04-05
2004-12-21
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...
C526S249000, C526S250000, C526S206000, C524S805000, C524S458000
Reexamination Certificate
active
06833418
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of preparing an aqueous dispersion of poly(perfluorovinyl ether)homopolymers. The present invention further relates to a method of making an aqueous fluoropolymer dispersion comprising bicomponent particles of poly(perfluorovinyl ether)homopolymers and a second fluoropolymer. The dispersions of the present invention may be used for rendering fibrous substrates oil repellent, water repellent and/or stain repellent. The invention further relates to fibrous substrates, in particular textiles, treated with the fluorochemical composition and to a method of treating the fibrous substrate with the fluorochemical dispersions.
BACKGROUND
Compositions for making substrates, in particular fibrous substrates, such as textiles, oil- and water repellent have been long known in the art. When treating fibrous substrates and in particular textile such as apparel, it is a requirement that the textile retains its look and feel as much as possible. Therefore, the amount of composition that can be applied in any treatment to provide repellency properties to the substrates is limited because large amounts would result in disturbing the look and feel of the substrate and would make them useless for many applications. As a result, the composition used for treating the substrates need to be effective at low application levels.
Fluorochemical compounds have been well known as being highly effective in providing oil and water repellency to substrates and in particular textile substrates. The commercially available fluorochemical compositions can be applied at low levels and are generally effective in providing the desired oil and water repellency properties at these low levels.
Fluorochemicals taught for treating textile include polymers based on vinyl ethers that have a perfluoroalkyl group. For example, U.S. Pat. No. 4,929,471 discloses the use of a copolymer of CH
2
═CH—OR wherein R may represent a fluorinated group for treating polyester fabric during its manufacturing process so as to produce a polyester fabric that has similar physical properties as silk or rayon.
U.S. Pat. No. 4,029,867 discloses to provide soil repellency and soil release properties to textile using a copolymer of maleic anhydride and a comonomer of the formula CH
2
═CH—CH
2
—O—R
f
wherein R
f
represents a perfluorinated group. A homopolymer of CH
2
═CH—O—R
f
is disclosed in DE 1720799 and is mentioned to be suitable for rendering textile oil and water repellent. The aforementioned fluorochemical compositions are all based on fluorine containing polymers that do not have a fluorinated backbone.
Fluoropolymers having a fluorinated backbone such as for example polytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene (TFE), have been known for coating substrates to provide various properties to the substrate including repellency properties. Fluoropolymers have for example been coated on cookware to provide desired release properties thereto. Fluoropolymers having a fluorinated backbone are disclosed in U.S. Pat. Nos. 4,546,157, 4,619,983, 4,766,190, 5,110,385, 5,969,066, 3,450,684, 4,035,565, 4,368,308, 4,418,186, 4,654,394, 4,840,998, 5,639,838 and 3,136,745. However, to be effective as a repellent coating, it has been taught to apply fluoropolymer coatings in high amounts. Such thick coatings are however unsuitable for treating textiles as they change the look and feel of the textile substrate substantially, i.e. to the extent such textiles are unsuitable for use in apparel. Sometimes, such coatings are subsequently subjected to a sintering step at high temperatures that would generally destroy many of the fibrous substrates desired for treatment.
EP 969 055 for example discloses an aqueous dispersion containing PTFE and a copolymer of TFE and a perfluorovinyl ether (PVE) for coating substrates such as ceramics or to impregnate textile. However, the amount of fluoropolymer in the treatment solution is at least 25% by weight resulting in a fairly thick coating. Moreover, the coating is subjected to a sintering step at a temperature of 420° C. which would destroy many fibrous materials used for apparel.
U.S. Pat. No. 4,670,328 discloses aqueous dispersions of certain copolymers of TFE and PVE for the impregnation of textiles. Again, the level of fluoropolymer applied in the impregnation is so large that the look and feel of the textile is substantially affected. Accordingly, the impregnated materials are generally only useful in specialized applications such as dust free clothes or chemical resistant clothes where the appearance of the clothes is of secondary consideration.
EP 186186 discloses a curable fluoroolefin polymer for making coatings that have high weatherability and good repellency properties such as water repellency, oil repellency and/or stain repellency. However, a thick coating is apparently required to achieve these properties.
Fluorochemical compositions for rendering fibrous substrates oil- and/or water repellent are described in Applicant's co-pending application U.S. Ser. No. 09/861,782 filed May 21, 2001. The compositions comprise up to 4% by weight of a fluoropolymer having a fully- or partially fluorinated backbone and comprise repeating units of the formula —CF
2
—CFR
f
—, where R
f
is a perfluorinated organic group having a chain length of at least two atoms and having at least one carbon atom.
Although perfluorovinyl ether homopolymers have been prepared, and copolymers of perfluorovinyl ethers have been used in textile treatments, the difficulty in preparing perfluorovinyl ether homopolymers have heretofore prohibited their use in textile treatments. It would thus be desirable to find alternative fluorochemical compositions that do not display many of the disadvantages of the fluorochemical compositions in the prior art. In particular, it would be desirable to find fluorochemical compositions comprising perfluorovinyl ether homopolymers that are effective in providing oil and water repellency to a fibrous substrate, in particular a textile substrate, without substantially adversely affecting the appearance of the textile, i.e. such that the fibrous substrate is suitable for use in apparel. Preferably, the fluorochemical compositions are also capable of providing soil repellency and soil release properties to the fibrous substrate. Desirably, the fluorochemical compositions will be more environmental friendly and sufficiently stable to substantially avoid formation of low molecular weight fluorinated substances. The fluorochemical compositions are preferably also compatible with commonly used textile treatments and are preferably easy to apply by a customer in a reproducible and reliable way. Finally, the desired fluorochemical compositions are preferably capable of providing durable repellency properties to a fibrous substrate.
SUMMARY OF THE INVENTION
The present invention provides a method of making a poly(perfluorovinyl ether) homopolymer dispersion comprising the steps of:
a) pre-emulsifying an aqueous mixture of a perfluorovinyl ether in the presence of a fluorochemical emulsifier to an average emulsion droplet size of 1 micron or less, and
b) polymerizing said perfluorovinyl ether in the presence of a free-radical initiator at temperature and for a time sufficient to produce particles of poly(perfluorovinyl ether).
The perfluorovinyl ether used in the present invention of claim
1
are of the formula: CF
2
═CF—R
f
, wherein R
f
represents a perfluorinated organic group having a chain length of at least 2 atoms and having at least one carbon atom and at least one oxygen atom. The R
f
group may be a perfluoroalkoxy group, a perfluoroether group or a perfluoropolyether group.
The present invention further provides a method of making a fluoropolymer dispersion comprising bicomponent particles comprising the steps of:
a. pre-emulsifying an aqueous mixture of a perfluorovinyl ether monomer in the presence of a fluorochemical emulsifier to an average emulsion droplet size of one micron or less, and
Buckanin Richard S.
McAlister E. Steven
Tan Lian S.
3M Innovative Properties Company
Hu Henry S.
Kokko Kent S.
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