CN115819650A - Method for preparing polytetrafluoroethylene from waste polytetrafluoroethylene - Google Patents
Method for preparing polytetrafluoroethylene from waste polytetrafluoroethylene Download PDFInfo
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- CN115819650A CN115819650A CN202211702759.5A CN202211702759A CN115819650A CN 115819650 A CN115819650 A CN 115819650A CN 202211702759 A CN202211702759 A CN 202211702759A CN 115819650 A CN115819650 A CN 115819650A
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- polytetrafluoroethylene
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- deionized water
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
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Abstract
The invention discloses a method for preparing polytetrafluoroethylene from waste polytetrafluoroethylene, which adopts an oxygen-free cracking mode to realize the complete cracking of the waste polytetrafluoroethylene so that the waste polytetrafluoroethylene is cracked into tetrafluoroethylene gas basically, adopts special absorption liquid to absorb, polymerizes the absorption liquid after absorption saturation under the catalysis of a fixed bed, filters and dries to obtain a polytetrafluoroethylene product. The method really realizes the regeneration of the waste polytetrafluoroethylene, and has good product quality and wide application prospect.
Description
Technical Field
The invention belongs to the field of high polymer materials, and particularly relates to a method for preparing polytetrafluoroethylene from waste polytetrafluoroethylene.
Background
Polytetrafluoroethylene (PTFE) is the main representative of fluoroplastics, has high chemical and thermal stability, high lubricity and excellent insulating properties and is commonly referred to as "plastic king". The polytetrafluoroethylene is formed by polymerizing Tetrafluoroethylene (TFE), the amount of waste polytetrafluoroethylene formed after the polytetrafluoroethylene is used is increased along with the increase of the yield of the polytetrafluoroethylene, and the preparation of the tetrafluoroethylene monomer by cracking the waste polytetrafluoroethylene by a technical means has great significance.
At present, most of the recovery of waste polytetrafluoroethylene stays in the rough recovery stage, and the waste polytetrafluoroethylene is mostly cleaned → dried → crushed → molded in the recovery process. CN104175421A discloses a method for recycling polytetrafluoroethylene waste, which recycles polytetrafluoroethylene particles by cleaning → drying → crushing → three-stage temperature control molding, and the method has the advantages of low quality of recycled polytetrafluoroethylene and limited use scene. Patent CN114058074A discloses a method for recovering waste polytetrafluoroethylene, an application of the recovered polytetrafluoroethylene, and a method for recovering polytetrafluoroethylene regenerated products, which adopts a microwave radiation technology to regenerate the waste polytetrafluoroethylene, and the main principle is to destroy the stable crystalline state of the polytetrafluoroethylene to convert the polytetrafluoroethylene into amorphous colloid, and then prepare the polytetrafluoroethylene products with different forms.
The following problems in the prior art are found through comparative analysis and practical production experience in the recycling of waste polytetrafluoroethylene: the waste polytetrafluoroethylene is recycled only by a simple physical mode, the recycling is not thorough, the product quality is poor, and the application scene is limited; the waste polytetrafluoroethylene is recovered by adopting radiation modes such as microwave and the like, so that the energy consumption is high, and the industrialization difficulty is high.
Disclosure of Invention
The invention aims to provide a method for preparing polytetrafluoroethylene from waste polytetrafluoroethylene.
In one embodiment, the present invention provides a method for preparing polytetrafluoroethylene from waste polytetrafluoroethylene, comprising the following steps:
1) Pretreatment: crushing and sieving waste polytetrafluoroethylene to obtain fine particles with proper size;
2) Cracking to prepare gas: cracking the screened fine particles under the protection of nitrogen, and carrying out quenching and dust removal on the cracked gas to obtain cracked gas;
3) Absorption of cracked gas: absorbing the pyrolysis gas by adopting an absorption solvent system until the absorption is saturated to obtain absorption liquid;
4) Polymerizing to obtain a product: enabling the saturated absorption liquid to enter a fixed catalyst bed, and carrying out catalytic polymerization to obtain polytetrafluoroethylene;
5) Filtering and separating the polytetrafluoroethylene, and drying the solid to obtain the polytetrafluoroethylene product.
In the above embodiment, the process of the present invention, the moderately sized fine particles of step 1) are of 10 to 30 mesh size, and the absorption solvent system of step 3) is selected from the group consisting of: 1) a solvent consisting of deionized water, polyvinyl alcohol and ammonium bicarbonate, 2) a solvent consisting of deionized water, polyvinyl alcohol and triethanolamine, and 3) a solvent consisting of deionized water, polyvinyl alcohol, triethanolamine and paranonyl phenol, wherein the mass ratio of the deionized water to the polyvinyl alcohol to the triethanolamine is 95%, 4% or 1%; the mass percentages of the deionized water, the polyvinyl alcohol and the triethanolamine are 95 percent, 3 percent and 2 percent; 94.5 percent, 3 percent, 2 percent and 0.5 percent of deionized water, polyvinyl alcohol, triethanolamine and paranonyl phenol.
In the above embodiment, in the method of the present invention, the cracking temperature in step 2) is 550 to 600 ℃, the temperature of the absorption solvent system in step 3) is controlled to 65 ℃ or less, preferably 35 to 55 ℃, or the polymerization temperature in step 4) is 40 to 80 ℃, or the drying condition in step 5) is 80 ℃ or 5kpa under vacuum.
Wherein the absorption solvent system is selected from: 1) a solvent consisting of deionized water, polyvinyl alcohol and ammonium bicarbonate, 2) a solvent consisting of deionized water, polyvinyl alcohol and triethanolamine, and 3) a solvent consisting of deionized water, polyvinyl alcohol, triethanolamine and paranonyl phenol, wherein the mass ratio of the deionized water to the polyvinyl alcohol to the triethanolamine is 95%, 4% or 1%; the mass percentages of the deionized water, the polyvinyl alcohol and the triethanolamine are 95 percent, 3 percent and 2 percent; 94.5 percent, 3 percent, 2 percent and 0.5 percent of deionized water, polyvinyl alcohol, triethanolamine and paranonyl phenol.
In the above embodiment, the method of the present invention further comprises the step of pressing the solid residue after cracking in step 3) into a solid fuel product after water extraction, and further comprises the step of recycling the filtrate filtered in step 5) to step 3) for reuse as an absorption solvent.
In a specific embodiment, the method for preparing polytetrafluoroethylene from waste polytetrafluoroethylene comprises the following steps:
1) Crushing waste polytetrafluoroethylene, sieving to obtain fine particles with a predetermined granularity of 10-30 meshes, returning the coarse particles, and crushing again to obtain fine particles;
2) Feeding the fine particles screened in the step 1) into a rotary anaerobic cracking furnace, cracking under the protection of nitrogen at 550-600 ℃, and removing dust from the cracked gas after quenching to obtain cracked gas; pressing the residual solid residues into a solid fuel product after water extraction;
3) Absorbing the pyrolysis gas generated in the step 2) to a saturated solution by adopting a special solvent system, and continuously absorbing and continuously extracting;
4) And 3) allowing the saturated solution in the step 3) to enter a fixed catalyst bed, carrying out catalytic polymerization to form polytetrafluoroethylene at the temperature of 40-80 ℃, filtering, carrying out solid-liquid separation, drying the solid under the vacuum condition of 5kpa at the temperature of 80 ℃ to obtain a polytetrafluoroethylene product, and circulating the filtrate serving as an absorption solvent to the step 3) for reuse.
Wherein the absorption solvent system is selected from: 1) a solvent consisting of deionized water, polyvinyl alcohol and ammonium bicarbonate, 2) a solvent consisting of deionized water, polyvinyl alcohol and triethanolamine, and 3) a solvent consisting of deionized water, polyvinyl alcohol, triethanolamine and paranonyl phenol, wherein the mass ratio of the deionized water to the polyvinyl alcohol to the triethanolamine is 95%, 4% or 1%; the mass percentages of the deionized water, the polyvinyl alcohol and the triethanolamine are 95 percent, 3 percent and 2 percent; 94.5 percent, 3 percent, 2 percent and 0.5 percent of deionized water, polyvinyl alcohol, triethanolamine and paranonyl phenol. More preferably, the absorption solvent system consists of 94.5% by weight of deionized water, 3% by weight of polyvinyl alcohol, 2% by weight of triethanolamine and 0.5% by weight of paranonyl phenol.
The method can thoroughly recycle the waste polytetrafluoroethylene and form a polytetrafluoroethylene product which is not different from a primary product.
The method can realize the recovery of all the substances of the waste polytetrafluoroethylene, and the polytetrafluoroethylene obtained by the recovery polymerization has good quality, excellent performance and wide application; the method adopts the process route of liquid phase absorption and liquid phase polymerization, avoids the high pressure process of the traditional gas phase compression, and effectively reduces the danger of the device; the process has the advantages of cyclic utilization of absorption liquid, high efficiency and environmental protection.
Detailed Description
The following examples are merely representative for further illustration and understanding of the nature of the invention, and are not intended to limit the scope of the invention in any way.
Example 1 Recycling and polymerization of waste Polytetrafluoroethylene to New Polytetrafluoroethylene
The waste polytetrafluoroethylene is crushed, then is sieved to reach fine particles with the preset granularity of 10-30 meshes, and the coarse particles are returned and crushed into fine particles again. The screened fine particles enter a rotary anaerobic cracking furnace M1, the temperature is raised to 550-600 ℃ under the protection of nitrogen for cracking, and cracking gas enters the next procedure after quenching and dust removal; and extruding the residual solid residue into a solid fuel product after water extraction. The pyrolysis gas is continuously absorbed to saturated solution in an absorption tower by adopting a special solvent system, the special solvent system consists of deionized water, polyvinyl alcohol, triethanolamine and paranonyl phenol, and a circulating system adopts an external heat exchanger to cool circulating liquid, so that the temperature of the absorption system is ensured to be less than or equal to 65 ℃. Absorbing the saturated absorption liquid (saturated solution) into a fixed catalyst bed, catalytically polymerizing the absorption liquid to form a polytetrafluoroethylene product at the temperature of 40-80 ℃, filtering, performing solid-liquid separation to obtain polytetrafluoroethylene, drying the polytetrafluoroethylene product at the temperature of 80 ℃ under the vacuum condition of 5kpa to obtain a product, taking the filtrate as an absorption solvent, and circulating the product to an absorption tower for use after separation.
Example 2
The procedure is as in example 1, except that the absorption solvent system and the absorption temperature are varied.
(1) The absorption solvent system consists of 95 percent of deionized water, 4 percent of hydroxypropyl methylcellulose and 1 percent of ammonium bicarbonate by weight, the absorption temperature is controlled between 35 and 45 ℃, and the absorption rate is about 87 percent.
(2) The absorption solvent system consists of 95 percent of deionized water, 4 percent of polyvinyl alcohol and 1 percent of ammonium bicarbonate by weight, the absorption temperature is controlled between 35 and 45 ℃, and the absorption rate is about 93 percent.
Example 3
The procedure is as in example 1, except that the absorption solvent system and the absorption temperature are varied.
(1) The absorption solvent system consists of 95 percent of deionized water, 3 percent of hydroxypropyl methylcellulose and 2 percent of triethanolamine by weight percentage, the absorption temperature is controlled between 35 and 45 ℃, and the absorption rate is about 90 percent.
(2) The absorption solvent system consists of 95 percent of deionized water, 3 percent of polyvinyl alcohol and 2 percent of triethanolamine by weight percentage, the absorption temperature is controlled to be 35 to 45 percent by weight percentage, and the absorption rate is about 95 percent.
Example 4
The procedure is as in example 1, except that the absorption solvent system and the absorption temperature are varied.
(1) The absorption solvent system consists of deionized water 94.5 wt%, hydroxypropyl methyl cellulose 3 wt%, triethanolamine 2 wt% and p-nonyl phenol 0.5 wt%, and has absorption temperature of 35-55 deg.c and absorption rate of 91 wt%.
(2) The absorption solvent system consists of deionized water 94.5 wt%, PVA 3 wt%, triethanolamine 2 wt% and p-nonyl phenol 0.5 wt%, and has absorption temperature controlled at 35-55 deg.c and absorption rate of 97%.
As described in (1) in the above examples, absorption rates of absorption liquids of hydroxypropylmethylcellulose series are generally inferior to those of polyvinyl alcohol series; the absorption effect of the same series of absorption liquid adopting triethanolamine as a buffering agent is superior to that of the ammonium bicarbonate series; after the p-nonyl phenol is added as a polymerization inhibitor, the absorption efficiency of the absorption liquid can be effectively improved.
Claims (10)
1. A method for preparing polytetrafluoroethylene from waste polytetrafluoroethylene comprises the following steps:
1) Pretreatment: crushing and sieving waste polytetrafluoroethylene to obtain fine particles with proper size;
2) Cracking to prepare gas: cracking the screened fine particles under the protection of nitrogen, and carrying out quenching and dust removal on the cracked gas to obtain cracked gas;
3) Absorption of cracked gas: absorbing the cracking gas by adopting an absorption solvent system until the absorption is saturated to obtain absorption liquid;
4) Polymerizing to obtain a product: introducing the saturated absorption liquid into a fixed catalyst bed, and catalytically polymerizing to obtain polytetrafluoroethylene;
5) Filtering the polytetrafluoroethylene, and drying the solid to obtain the polytetrafluoroethylene product.
2. The method of claim 1, comprising water extracting the cracked solid residue of step 3) and pressing the solid residue into a solid fuel product.
3. The method of claim 1, comprising recycling the filtrate filtered in step 5) as the absorption solvent to step 3) for reuse.
4. The method of claim 1 wherein the fine, moderately sized particles of step 1) are between about 10 and 30 mesh.
5. The process of claim 1, wherein the absorption solvent system of step 3) is selected from the group consisting of: 1) a solvent consisting of deionized water, polyvinyl alcohol and ammonium bicarbonate, 2) a solvent consisting of deionized water, polyvinyl alcohol and triethanolamine, and 3) a solvent consisting of deionized water, polyvinyl alcohol, triethanolamine and paranonyl phenol.
6. The method according to claim 5, wherein the mass ratio of the deionized water, the polyvinyl alcohol and the triethanolamine in the absorption solvent system is 95%:4%:1 percent.
7. The method according to claim 5, wherein the absorption solvent system comprises 95% of deionized water, 95% of polyvinyl alcohol and 95% of triethanolamine by weight: 3%:2 percent.
8. The method of claim 5, wherein the absorption solvent system comprises 94.5% by weight of deionized water, polyvinyl alcohol, triethanolamine and paranonyl phenol: 3%:2%:0.5 percent.
9. The process according to claim 1, wherein the temperature of the absorption solvent system of step 3) is controlled to 65 ℃ or less, preferably 35 to 55 ℃.
10. The process of claim 1, wherein the cracking temperature in step 2) is 550-600 ℃, or the polymerization temperature in step 4) is 40-80 ℃, or the drying condition in step 5) is 80 ℃ and 5kpa vacuum condition.
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| CN202211702759.5A CN115819650A (en) | 2022-12-28 | 2022-12-28 | Method for preparing polytetrafluoroethylene from waste polytetrafluoroethylene |
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| CN202211702759.5A CN115819650A (en) | 2022-12-28 | 2022-12-28 | Method for preparing polytetrafluoroethylene from waste polytetrafluoroethylene |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1048394A (en) * | 1989-06-30 | 1991-01-09 | 梁伦昊 | A kind of renovation process of tetrafluoroethylene |
| CN1164542A (en) * | 1996-05-07 | 1997-11-12 | 南京理工大学 | Method for preparation of hydrocarbon oil by using waste and old polyolefins |
| CN101341202A (en) * | 2005-11-30 | 2009-01-07 | 南非原子能股份有限公司 | Depolymerization of fluoropolymers |
| CN113453783A (en) * | 2018-10-18 | 2021-09-28 | 阿科玛法国公司 | Method for treating gaseous effluents resulting from the pyrolysis of polymers |
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- 2022-12-28 CN CN202211702759.5A patent/CN115819650A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1048394A (en) * | 1989-06-30 | 1991-01-09 | 梁伦昊 | A kind of renovation process of tetrafluoroethylene |
| CN1164542A (en) * | 1996-05-07 | 1997-11-12 | 南京理工大学 | Method for preparation of hydrocarbon oil by using waste and old polyolefins |
| CN101341202A (en) * | 2005-11-30 | 2009-01-07 | 南非原子能股份有限公司 | Depolymerization of fluoropolymers |
| CN113453783A (en) * | 2018-10-18 | 2021-09-28 | 阿科玛法国公司 | Method for treating gaseous effluents resulting from the pyrolysis of polymers |
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