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
8 Cites 36 Cited by

AI-Extracted Technical Summary

Problems solved by technology

Thus, the presence of APFO in the PTFE dispersions raises concerns about its...
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Method used

[0052] In another preferred embodiment, after the addition of the non-fluorinated emulsifier, an electrolyte is added to the stabilized dispersion. In thermal concentration process which includes step (1a), a base is added to induce rapid phase separation. It has also been found that addition of an electrolyte can also facilitate phase separation.
[0056] When the temperature of the dispersion is higher than the cloud point of the non-fluorinated emulsifier, PTFE particles start to settle out to the bottom to form a dense layer of latex, while leaving a clear layer of supernatant ...
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Benefits of technology

[0013] Accordingly, it is one object of the present invention to provide novel proces...
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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.

Application Domain

Technology Topic

FluoropolymerFluorine containing +3

Image

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

Examples

  • Experimental program(13)

Example

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 concentration. [0077] 7. The supernatant was drained into a separate container for future recycling. [0078] 8. The concentrated latex was diluted to 33 wt. % PTFE with purified water and re-concentrated according to step 1 to 7 as shown above except that the total surfactant was reduced to 10 wt. %. NH4OH were added to adjust the pH. [0079] 9. The concentrated latex contained 63.5 wt. % PTFE, 3.1 wt. % Triton X-100 and 209 ppm (329 ppm by weight of PTFE). The APFO reduction from 673 to 329 ppm (based on PTFE) was 51 % on the second cycle of thermal concentration. [0080] 10. The latex was diluted to 33 wt. % PTFE with purified water and re-concentrated for the 3rd time as described above. [0081] 11. The concentrated latex contained 65.9 wt. % PTFE, 5.1 wt. % Triton X-100 and 127 ppm (193 ppm by weight of PTFE). The APFO reduction from 329 to 193 ppm was 41% on the 3rd cycle of thermal concentration. The overall APFO reduction from 3907 to 193 ppm (based on PTFE) was about 95%. [0082] 12. The concentrated latex was used for coating application.

Example

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 container for future recycling. [0091] 8. The reduction of APFO (1117 to 292 ppm on PTFE) was 74%. [0092] 9. The concentrated latex was used for metal coating application.

Example

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 future recycling. [0101] 8. The reduction of APFO (322 to 150 ppm on PTFE) was 53%. [0102] 9. The concentrated latex was used for metal coating application.
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PUM

PropertyMeasurementUnit
Temperature40.0 ~ 100.0°C
Fraction5.0E-5fraction
Fraction3.0E-4fraction
tensileMPa
Particle sizePa
strength10

Description & Claims & Application Information

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