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Process for preparing aqueous fluoropolymer dispersions and the concentrated aqueous fluoropolymer dispersions produced by such process

Inactive Publication Date: 2006-04-06
AGC CHEM AMERICAS INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013] Accordingly, it is one object of the present invention to provide novel process for preparing concentrated aqueous dispersions of PTFE with reduced content of APFO.

Problems solved by technology

Thus, the presence of APFO in the PTFE dispersions raises concerns about its ability to accumulate in the environment and the unknown long-term effects.

Method used

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  • Process for preparing aqueous fluoropolymer dispersions and the concentrated aqueous fluoropolymer dispersions produced by such process

Examples

Experimental program
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example 1

[0070] Four samples of PTFE dispersions containing 19.3 wt. % of PTFE, 754 ppm of APFO (3907 ppm of APFO based on the weight of PTFE), and having a pH of 3.5 were processed as follows: [0071] 1. The raw latex was stabilized with 18 wt. % of Triton X-100. 0.1 wt. % of NH4OH (30 wt. % aqueous solution) was added to adjust the pH. [0072] 2. It was then transferred into a lab Thermal Concentrator, which was connected to a circulating temperature control bath with maximum temperature set at 83° C. [0073] 3. The dispersion was slowly heated up from room temperature with no agitation. [0074] 4. Heating continued until temperature reached about 75° C. [0075] 5. The temperature was maintained between 75 and 80° C. until phase separation was complete. [0076] 6. The concentrated latex contained 66.9 wt. % of PTFE, 2.6 wt. % Triton X-100 and 450 ppm of APFO (673 ppm of APFO based on the weight of PTFE). The APFO reduction from 3907 to 450 ppm (based on PTFE) was 83% after one cycle of thermal c...

example 2

[0083] An aqueous dispersion of PTFE with trace commoner PPVE containing 18.8 wt. % by weight of modified PTFE, 210 ppm of APFO (1117 ppm of APFO based on the weight of PTFE), and having a pH of 3.5 was processed as follows: [0084] 1. The raw latex was stabilized with 18 wt. % of Newcol 1308 FA(90). NH4OH (30 wt. % aqueous solution) was added to adjust the pH. [0085] 2. It was then transferred into a lab Thermal Concentrator, which was connected to a circulating temperature control bath with maximum temperature set at 54° C. [0086] 3. The dispersion was slowly heated up from room temperature with no agitation. [0087] 4. Heating continued until temperature reached about 50° C. [0088] 5. The temperature was maintained between 50 and 52° C. until phase separation was complete. [0089] 6. The concentrated latex contained 64.3 wt. % PTFE, 3.1 wt. % Newcol 1308 FA(90) and 188 ppm of APFO (292 ppm of APFO based on the weight of PTFE). [0090] 7. The supernatant was drained into a separate co...

example 3

[0093] An aqueous dispersion of PTFE with trace commoner PPVE containing 20.5 wt. % by weight of modified PTFE, 66 ppm of APFO (322 ppm of APFO based on the weight of PTFE), and having a pH of 3.5 was processed as follows: [0094] 1. The raw latex was stabilized with 18 wt. % of Triton X-100. 0.25 ml of NH4OH (30 wt. % aqueous solution) was added to adjust the pH. [0095] 2. It was then transferred into a lab Thermal Concentrator, which was connected to a circulating temperature control bath with maximum temperature set at 80° C. [0096] 3. The dispersion was slowly heated up from room temperature with no agitation. [0097] 4. Heating continued until temperature reached about 72° C. [0098] 5. The temperature was maintained between 70 and 75° C. until phase separation was complete. [0099] 6. The concentrated latex contained 71.8 wt. % PTFE, 4 wt. % Triton X-100 and 108 ppm of APFO (150 ppm of APFO by weight of PTFE). [0100] 7. The supematant was drained into a separate container for futu...

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Abstract

Fluorine-containing emulsifiers can be removed from fluoropolymer dispersions by multiple cycles of thermal concentration. After repeated cycles of dilution and extraction the fluorine-containing emulsifier can be reduced to a very low level. The resulting dispersion can be formulated into an aqueous dispersion that can be used for coating applications, such as seal, packing, fabric and metal coating.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a process for preparing an aqueous dispersion of polytetrafluoroethylene (PTFE). The present invention also relates to the resulting aqueous dispersions of PTFE produced by such a process. [0003] 2. Discussion of the Background [0004] PTFE dispersions can be produced by suspension or emulsion polymerization. A fluorinated emulsifier, ammonium perfluorooctanoate, C7F15CO2NH4 (APFO), is generally used to stabilize the particles as they grow in the autoclave during the polymerization process. Other fluorosurfactants such as straight chain or branched chain C4-C12-perfluorocarboxylic acid salts (including ammonium perfluorononanoate, APFN), straight chain or branched chain C4-C12-hydrofluorocarboxylic acid salts, straight chain or branched chain C4-C12-perfluoroalkane sulfonic acid salts, straight chain or branched chain C4-C12-hydrofluoroalkane sulfonic acid salts, straight chain or bra...

Claims

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Application Information

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IPC IPC(8): D06M15/277
CPCC08J3/05C08J2327/18D06M15/256
Inventor AUYEUNG, KIM F.CHRISTIANI, BRIAN R.
Owner AGC CHEM AMERICAS INC
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