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Core-shell fluoropolymer dispersions

A dispersion, polymer technology, used in transportation and packaging, coatings, latex paints, etc., to solve problems such as low molecular weight non-fibrillating polymers

Inactive Publication Date: 2005-05-04
EI DU PONT DE NEMOURS & CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] While advantageous for use in powder blends of the above resins with other materials, the presence of very low molecular weight, non-fibrillating polymers in the shell creates problems in dispersion coating applications

Method used

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  • Core-shell fluoropolymer dispersions
  • Core-shell fluoropolymer dispersions

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0100] This example illustrates the polymerization of TFE to produce fluoropolymer particles of the present invention having a core of high molecular weight PTFE and a shell of low molecular weight PTFE. A polymerization tank having a horizontal stirrer and a water capacity of 240 parts by weight was charged with 123.5 parts of demineralized water and 5.82 parts of paraffin wax supplied by Exxon. To the evacuated polymerization kettle was added 3.24 parts of a solution containing .0616 parts of ammonium perfluorooctanoate. The contents of the polymerization kettle were stirred at 50 rpm. The temperature was raised to 90°C. TFE was then added until the pressure was 2.72 MPa. Then, 1.29 parts of fresh initiator solution consisting of .01 parts of disuccinyl peroxide (DSP) and .00005 parts of ammonium persulfate (APS) per part of water was added at a rate of 0.129 parts / minute The solution. Once the pressure drops by .1 MPa, the batch is considered to have started. TFE was a...

Embodiment 2

[0102] Using the same procedure and essentially the same amounts of ingredients as in Example 1, except that the concentration of ammonium perfluorooctanoate initially added was increased to .1 parts per part of water, and the concentration of ammonium perfluorooctanoate solution pumped was reduced to 1% by weight . The solids content of the stock dispersion was 45.5% and the RDPS was 268 nm. Manual measurement of 328 particles from the SEM image showed globules and rod-shaped particles with an average length of 325 and a diameter of 195. Particles that are longer than 5 times the diameter have an average length of 770 nm and a diameter of 78 nm. The fraction of rod-shaped particles accounted for 4.9%, and on a weight basis, accounted for 1.9% of cylindrical geometry. The obtained PTFE resin had an SSG of 2.2217. Dried resin is a free-flowing powder. The resin was extruded as a paste at a shrinkage ratio of 1600:1, giving a continuous extrudate and an extrusion pressure of...

Embodiment 3

[0104] The same procedure and essentially the same amounts of ingredients were used as in Example 2, except that the concentration of ammonium perfluorooctanoate initially added was reduced to .08 parts per part of water, and the concentration of ammonium perfluorooctanoate pumped was increased to 2% by weight. The solids content of the stock dispersion was 45.3% and the RDPS was 283 nm. The obtained PTFE resin had an SSG of 2.209. A concentrated dispersion containing 6% by weight Triton(R) had a CCT of 22.9 microns and a gel time greater than 1800 seconds. At 8 wt% Triton(R), the GCT increased to 34.5 microns.

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Abstract

A dispersion of non-melt-processible fluoropolymer particles having an SSG of less than about 2.225 in aqueous medium. The fluoropolymer particles comprise a core of high molecular weight polytetrafluoroethylene having an average melt creep viscosity greater than about 1.5x10<10 >Pa.s and a shell of lower molecular weight polytetrafluoroethylene or modified polytetrafluoroethylene. The shell has an average melt creep viscosity greater than about 9x10<9 >Pa.s and comprises about 5 to about 30% by weight of the particles. The fluoropolymer in the dispersion of the invention is fibrillating.

Description

technical field [0001] This invention relates to dispersions of non-melt processible fluoropolymers and coatings formed from the dispersions. Background technique [0002] Fluoropolymers are used in a wide variety of substrates to provide properties such as release, chemical and heat resistance, corrosion protection, ease of decontamination, non-flammability and weatherability. Coatings of polytetrafluoroethylene (PTFE) homopolymers and modified PTFEs offer the highest thermal stability among fluoropolymers, but unlike tetrafluoroethylene (TFE) copolymers, they cannot be melt processed to form thin films and coating. Accordingly, other methods for coating PTFE homopolymers and modified PTFEs have been developed. One such method is dispersion coating, which applies the fluoropolymer in dispersion form. Dispersion coating methods typically use dispersions of such fluoropolymers, which are in a more concentrated form compared to dispersions obtained by polymerization. These...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08J3/16C08F259/08C08L51/00C09D5/02C09D127/18C09D127/22C09D151/00
CPCC08F259/08C09D151/003C08L51/003Y10T428/2982Y10T428/3154C08L2666/02
Inventor C·W·琼斯W·克拉科维亚克
Owner EI DU PONT DE NEMOURS & CO
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