CN114058074A

CN114058074A - Waste polytetrafluoroethylene recovery method, application of recovered polytetrafluoroethylene and polytetrafluoroethylene regenerated product

Info

Publication number: CN114058074A
Application number: CN202111562142.3A
Authority: CN
Inventors: 郭强; 贾志军; 王迎娣
Original assignee: Hebei Zhongke Tongchuang Technology Development Co ltd
Current assignee: Hebei Zhongke Tongchuang Technology Development Co ltd
Priority date: 2021-12-17
Filing date: 2021-12-17
Publication date: 2022-02-18

Abstract

The invention provides a method for recovering waste polytetrafluoroethylene, application of the recovered polytetrafluoroethylene and a polytetrafluoroethylene regenerated product, and relates to the technical field of high polymer materials. The waste polytetrafluoroethylene is crushed, and the obtained waste polytetrafluoroethylene particles are subjected to microwave radiation. The recovery method provided by the invention destroys the stable crystalline state in the waste polytetrafluoroethylene, so that the waste polytetrafluoroethylene is converted into the transparent colloid with an amorphous structure, mutual diffusion of polytetrafluoroethylene molecular chains is realized, and the tensile strength and the elongation at break of the recovered polytetrafluoroethylene are not obviously reduced compared with those of pure polytetrafluoroethylene. Moreover, the method provided by the invention improves the reutilization rate of the waste polytetrafluoroethylene. As shown in the results of examples, the tensile strength and elongation at break of the regenerated polytetrafluoroethylene tube were reduced by 4.3% and 46.2% respectively, relative to the pure polytetrafluoroethylene tube, and the requirements of ZBG33001-1985 polytetrafluoroethylene tubes were satisfied.

Description

Waste polytetrafluoroethylene recovery method, application of recovered polytetrafluoroethylene and polytetrafluoroethylene regenerated product

Technical Field

The invention relates to the technical field of high polymer materials, in particular to a method for recovering waste polytetrafluoroethylene, application of the recovered polytetrafluoroethylene and a polytetrafluoroethylene regenerated product.

Background

Polytetrafluoroethylene (PTFE), commonly known as "plastic king", is a high molecular compound prepared by polymerizing tetrafluoroethylene, has excellent chemical stability, corrosion resistance, sealing property, high lubrication non-adhesiveness, electrical insulation and good aging resistance, and is widely applied in the fields of environmental protection, filtration, construction, aerospace and the like. The polytetrafluoroethylene has excellent performance, high price and high recovery value.

PTFE has a high melt viscosity and hardly flows when reaching the melting point, and is decomposed by heating, so that it cannot be recovered by extrusion or injection molding after melting. At present, the recovery method of waste PTFE mainly comprises a mechanical crushing method, a radiation cracking method and a high-temperature cracking method, wherein waste PTFE such as unqualified products in PTFE production, waste products of PTFE without filler in the production process and vehicle scraps generated in the mechanical processing process of PTFE finished products without filler are suitable for the radiation cracking method. The radiation cracking method has the basic principle that high-energy ray gamma rays or accelerated electron rays are utilized to overcome fluorine-carbon bonds with high bond energy under the condition that the radiation dose is not less than 100kGy, the shielding effect of fluorine atoms is removed, the molecular chains of the fluorine atoms are broken, the PTFE molecular chains are randomly broken to obtain PTFE with low molar mass (30-200 kg/mol), the tensile strength of an unirradiated PTFE film is 26.9MPa, the breaking elongation is 129%, the tensile strength of the PTFE film subjected to vacuum radiation with the radiation dose of 100kGy is 13.6MPa, and the breaking elongation is 10% (see: populus, Zhang Xiaoping, Dengyen, Yirong, the recovery method of waste polytetrafluoroethylene and the application [ J ] plastics industry, (2005 04): 47-49.). However, the tensile strength of the recovered PTFE obtained by the radiation cracking method is reduced by 49.4%, the elongation at break is reduced by 92.2%, and the mechanical properties are greatly reduced compared with those of pure PTFE.

Disclosure of Invention

In view of the above, the present invention aims to provide a method for recovering waste polytetrafluoroethylene, an application of the recovered polytetrafluoroethylene, and a polytetrafluoroethylene regenerated product. The regenerated polytetrafluoroethylene product prepared from the recovered polytetrafluoroethylene obtained by the recovery method provided by the invention has good mechanical properties.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a method for recovering waste polytetrafluoroethylene, which comprises the following steps:

crushing waste polytetrafluoroethylene to obtain waste polytetrafluoroethylene particles;

and carrying out microwave radiation on the waste polytetrafluoroethylene particles.

Preferably, the power of the microwave radiation is 220-360W, the temperature is 327-350 ℃, and the time is 30-60 min.

Preferably, the waste polytetrafluoroethylene is waste polytetrafluoroethylene without filler.

Preferably, the particle size of the waste polytetrafluoroethylene particles is 500-520 μm.

The invention provides an application of the recovered polytetrafluoroethylene obtained by the recovery method in the technical scheme in the preparation of a polytetrafluoroethylene regenerated product, wherein the polytetrafluoroethylene regenerated product comprises a polytetrafluoroethylene tube, a polytetrafluoroethylene rod, a polytetrafluoroethylene belt, a polytetrafluoroethylene plate or a polytetrafluoroethylene film.

Preferably, the thickness of the polytetrafluoroethylene tube, the diameter of the polytetrafluoroethylene rod, the thickness of the polytetrafluoroethylene tape, the thickness of the polytetrafluoroethylene plate and the thickness of the polytetrafluoroethylene film are 0.1-0.5 mm independently.

The invention provides a polytetrafluoroethylene regenerated product, which comprises a polytetrafluoroethylene tube, a polytetrafluoroethylene rod, a polytetrafluoroethylene belt, a polytetrafluoroethylene plate or a polytetrafluoroethylene film, and the recovered polytetrafluoroethylene obtained by the recovery method in the technical scheme is obtained by sintering after hot press molding.

Preferably, the hot-press forming temperature is 327-350 ℃, the pressure is 10-12 MPa, and the time is 1-2 min.

Preferably, the sintering temperature is 370-400 ℃, and the time is 2-4 h.

The invention provides a method for recovering waste polytetrafluoroethylene, which comprises the following steps: crushing waste polytetrafluoroethylene to obtain waste polytetrafluoroethylene particles; and carrying out microwave radiation on the waste polytetrafluoroethylene particles. The recovered polytetrafluoroethylene obtained by the recovery method provided by the invention is crushed and then treated into powder form, and after the microwave radiation energy effect, the stable crystalline state in the waste polytetrafluoroethylene is destroyed and begins to be converted into transparent polytetrafluoroethylene colloid with an amorphous structure, so that the mutual diffusion crosslinking of polytetrafluoroethylene molecular chains is realized, and polytetrafluoroethylene particles are bonded with each other again. Moreover, the recovery method provided by the invention solves the problem that part of waste materials are difficult to treat in the production process of the polytetrafluoroethylene, and improves the reutilization rate of the waste polytetrafluoroethylene.

The invention provides the recovered polytetrafluoroethylene obtained by the recovery method in the technical scheme. The recycled polytetrafluoroethylene provided by the invention has the advantages that the tensile strength and the elongation at break are not obviously reduced compared with those of pure polytetrafluoroethylene, the mechanical property is good, and the recycled polytetrafluoroethylene can be used as a raw material for preparing polytetrafluoroethylene tubes, polytetrafluoroethylene rods, polytetrafluoroethylene tapes, polytetrafluoroethylene plates or polytetrafluoroethylene films.

The invention provides a polytetrafluoroethylene regenerated product, which is obtained by sintering the recovered polytetrafluoroethylene after hot press molding. The tensile strength and the elongation at break of the polytetrafluoroethylene regenerated product provided by the invention are not obviously reduced compared with pure polytetrafluoroethylene, and the mechanical property is good. As shown in the results of examples, the tensile strength of the regenerated polytetrafluoroethylene tube obtained by hot pressing and sintering the recovered polytetrafluoroethylene prepared by the invention as a raw material was 26.4MPa, which is reduced by only 4.3% compared with the pure polytetrafluoroethylene tube; the elongation at break is 128.11 percent, which is only reduced by 46.2 percent compared with a pure polytetrafluoroethylene tube, and the tensile strength and the elongation at break meet the requirements of ZBG33001-1985 polytetrafluoroethylene tube on the tensile strength and the elongation at break.

Drawings

FIG. 1 is a cross-sectional SEM image of the PTFE regenerator tube prepared in example 1 at 10kX magnification;

FIG. 2 is a cross-sectional SEM image of the waste polytetrafluoroethylene particles prepared in example 1 at 10kX magnification;

FIG. 3 is a cross-sectional SEM image of a pure PTFE tube with a wall thickness of 1mm at 10kX magnification;

FIG. 4 is a cross-sectional SEM image of a pure polytetrafluoroethylene tube having a thickness of 1mm at 5kX magnification.

Detailed Description

In the present invention, all the raw material components are commercially available products well known to those skilled in the art unless otherwise specified.

The waste polytetrafluoroethylene is crushed to obtain waste polytetrafluoroethylene particles.

In the invention, the waste polytetrafluoroethylene is preferably waste polytetrafluoroethylene without filler, and more preferably comprises one or more of unqualified products in the production of the polytetrafluoroethylene without filler, waste products in the production process of the polytetrafluoroethylene without filler and vehicle scraps generated in the machining process of finished polytetrafluoroethylene products without filler; in the embodiment of the invention, the waste polytetrafluoroethylene is preferably polytetrafluoroethylene defective products generated in the process of preparing pure polytetrafluoroethylene materials in a laboratory; the thickness of the polytetrafluoroethylene defective product is preferably 0.1-0.12 mm, and more preferably 0.11 mm.

In the invention, the waste polytetrafluoroethylene is preferably subjected to rough treatment and then crushed; the roughening treatment is preferably performed by sanding, the sanding is preferably performed by using sand paper, and the sand grain size of the sand paper is 60-100 meshes, and more preferably 70-80 meshes; the sand paper is preferably water sand paper; the roughness of the waste polytetrafluoroethylene is not particularly limited, and the surface of the waste polytetrafluoroethylene has obvious friction marks. The crushing is not particularly limited, and the waste polytetrafluoroethylene particles are crushed until the particle size of the waste polytetrafluoroethylene particles is 500-520 mu m. In the invention, the surface area of the waste polytetrafluoroethylene can be increased through rough treatment, and the heating uniformity of the polytetrafluoroethylene in the microwave radiation process is ensured.

After the crushing, the invention preferably further comprises the step of washing the crushed particles with water to obtain the waste polytetrafluoroethylene particles. In the invention, the washing time is preferably 3-5 times, and more preferably 4 times; the purpose of the water wash is to remove impurities introduced during the course of the roughening treatment and the crushing.

After the waste polytetrafluoroethylene particles are obtained, the waste polytetrafluoroethylene particles are subjected to microwave radiation.

In the invention, the power of the microwave radiation is preferably 220-360W, more preferably 250-350W, and further preferably 300W; the temperature of the microwave radiation is preferably 327-350 ℃, more preferably 330-345 ℃, and further preferably 335-340 ℃; the time of the microwave radiation is preferably 30-60 min, more preferably 35-55 min, and further preferably 40-50 min. Based on the poor radiation resistance of PTFE, PTFE is the material which is the least resistant to radiation in all high polymer materials, and the mechanical property of PTFE can be completely lost by the dosage of thousands of gray (kGy), however, the radiation temperature is below the melting point of PTFE, and the tensile strength and the elongation at break are both reduced along with the increase of the temperature; however, when the irradiation temperature is close to 340 ℃ (i.e. the temperature is slightly higher than the melting point of PTFE), the two parameters are rapidly increased, the elongation at break reaches 600%, and the tensile strength is close to the level of normal temperature irradiation. When the temperature is higher than 350 ℃, the tensile strength and the elongation at break are reduced sharply. Under a specific high-temperature environment, the PTFE is subjected to radiation cracking and radiation crosslinking reaction along with PTFE molecular chains under the radiation action, so that the tensile strength and the elongation at break are not obviously reduced, and the mechanical property is good; the cross-linked PTFE molecules are connected by chemical bonds after specific microwave radiation, can slide to a certain extent in the friction process, but are not easy to separate and fall off, and the wear resistance is good. In the invention, in the microwave radiation process, the acting force among the molecules of the polytetrafluoroethylene molecules is increased along with the increase of the crosslinking degree, so that the polytetrafluoroethylene particles are not easy to deform greatly in the stretching process, but the stable crystalline state is damaged along with the increase of the crosslinking degree, and the polytetrafluoroethylene molecules begin to be converted into the transparent colloid with the amorphous structure, so that the proportion of the amorphous part is increased, and the possibility of greatly reducing the tensile strength and the elongation at break exists.

After the microwave radiation, the invention preferably further comprises cooling the material obtained by the microwave radiation to room temperature to obtain the recycled polytetrafluoroethylene. The cooling method of the present invention is not particularly limited, and a cooling method known to those skilled in the art may be used.

The invention provides the recovered polytetrafluoroethylene obtained by the recovery method in the technical scheme.

The invention provides an application of the recovered polytetrafluoroethylene obtained by the recovery method in the technical scheme in the preparation of a polytetrafluoroethylene regenerated product, wherein the polytetrafluoroethylene regenerated product comprises a polytetrafluoroethylene tube, a polytetrafluoroethylene rod, a polytetrafluoroethylene belt, a polytetrafluoroethylene plate or a polytetrafluoroethylene film. In the present invention, the thickness of the polytetrafluoroethylene tube, the diameter of the polytetrafluoroethylene rod, the thickness of the polytetrafluoroethylene tape, the thickness of the polytetrafluoroethylene sheet, and the thickness of the polytetrafluoroethylene film are preferably 0.1 to 0.5mm, more preferably 0.2 to 0.4mm, and even more preferably 0.3mm, independently.

In the present invention, the kind and thickness of the polytetrafluoroethylene recycled product are the same as those of the polytetrafluoroethylene recycled product, and are not described herein again. In the invention, the hot-press forming temperature is preferably 327-350 ℃, more preferably 330-345 ℃, and further preferably 335-340 ℃; the hot-press forming pressure is preferably 10-12 MPa, more preferably 10.5-11.5 MPa, and further preferably 112 MPa; the time for hot press forming is preferably 1-2 min 1.2-1.8 min, more preferably 1.2-1.8 min, and even more preferably 1.5 min. In the embodiment of the invention, the recovered polytetrafluoroethylene obtained by microwave radiation is preferably directly subjected to hot press forming without cooling, and the utilization rate of a heat source can be improved and the energy consumption and the production cost are reduced by directly performing hot press forming on the recovered polytetrafluoroethylene obtained by microwave radiation.

In the invention, the sintering temperature is preferably 370-400 ℃, more preferably 375-395 ℃, and further preferably 380-390 ℃; the heating rate of the temperature from room temperature to the sintering temperature is preferably 80-120 ℃/h, and more preferably 90-100 ℃/h; starting timing when the temperature is increased to the sintering temperature, wherein the sintering time is preferably 2-4 h, more preferably 2.5-3.5 h, and further preferably 3 h; the sintering atmosphere is preferably air; the sintering is preferably carried out in a muffle furnace.

After the sintering, the invention preferably further comprises cooling the material obtained by the sintering to room temperature to obtain a polytetrafluoroethylene regenerated product. The cooling method of the present invention is not particularly limited, and a cooling method known to those skilled in the art may be used.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Sanding the two sides of the waste polytetrafluoroethylene by using 60-100 meshes of waterproof abrasive paper until obvious friction marks exist, then placing the sand in a crusher to be crushed until the particle size is 500-520 mu m, washing the sand for 5 times, and drying the sand at 105 ℃ until the weight is constant to obtain waste polytetrafluoroethylene particles; wherein the waste polytetrafluoroethylene is a polytetrafluoroethylene tube defective product produced in the process of preparing a pure polytetrafluoroethylene film in a laboratory, and the wall thickness is 0.1 mm.

And (2) placing the waste polytetrafluoroethylene particles into a mold, then placing the mold into a microwave reactor, and performing microwave radiation for 30min at 220W and 350 ℃ to obtain the recovered waste polytetrafluoroethylene particles.

And hot-press molding the recovered waste polytetrafluoroethylene particles for 1min under the condition of 12MPa, demolding, placing in a muffle furnace, heating to 380 ℃ at the heating rate of 90 ℃/h in the air atmosphere, then carrying out heat preservation sintering for 2h, and cooling to room temperature to obtain the polytetrafluoroethylene regenerative tube with the thickness of 0.1 mm.

FIG. 1 is a sectional SEM photograph of the polytetrafluoroethylene regenerated tube prepared in this example at 10kX magnification, FIG. 2 is a sectional SEM photograph of the waste polytetrafluoroethylene particles prepared in this example at 10kX magnification, FIG. 3 is a sectional SEM photograph of the pure polytetrafluoroethylene tube with a wall thickness of 1mm at 10kX magnification, and FIG. 4 is a sectional SEM photograph of the pure polytetrafluoroethylene tube with a thickness of 1mm at 5kX magnification. As can be seen from FIGS. 1 to 4, the microscopic morphology of the cross section of the polytetrafluoroethylene regenerative tube is similar to that of the pure polytetrafluoroethylene tube, and both the cross section and the microscopic morphology are fluffy; the section of the waste polytetrafluoroethylene tube is in a compact layer shape after sintering.

The mechanical property test results of the teflon regeneration tube prepared in this example and the pure teflon membrane with the same wall thickness are shown in table 1:

table 1 mechanical property test results of the teflon rehabilitating pipe and the pure teflon pipe prepared in example 1

	Tensile strength/MPa	Elongation at break/%
			National standard reference value ZBG33001-1985 of polytetrafluoroethylene tube	≥25	≥100
Polytetrafluoroethylene regenerating pipe	26.4	128.11
			Pure polytetrafluoroethylene tube	27.6	238

As can be seen from Table 1, the tensile strength of the polytetrafluoroethylene regenerated pipe is only reduced by 4.3% and the elongation at break is only reduced by 46.2% relative to the tensile strength of the pure polytetrafluoroethylene pipe, and although the tensile strength and the elongation at break of the polytetrafluoroethylene regenerated pipe are reduced relative to the pure polytetrafluoroethylene pipe, the tensile strength and the elongation at break of the polytetrafluoroethylene regenerated pipe both meet the national standard reference value ZBG33001-1985 of the polytetrafluoroethylene pipe.

Example 2

Sanding the two sides of the waste polytetrafluoroethylene by using 60-100 meshes of waterproof abrasive paper until obvious friction marks exist, then placing the waste polytetrafluoroethylene into a crusher to be crushed until the particle size is 500-520 mu m, washing the waste polytetrafluoroethylene for 5 times, and drying the waste polytetrafluoroethylene at 105 ℃ until the weight is constant to obtain waste polytetrafluoroethylene particles; wherein the waste polytetrafluoroethylene is a polytetrafluoroethylene tube defective product produced in the process of preparing a pure polytetrafluoroethylene film in a laboratory, and the wall thickness is 0.1 mm.

And (2) placing the waste polytetrafluoroethylene particles in a mold, then placing the mold in a microwave reactor, and performing microwave radiation for 35min at the temperature of 280W and 345 ℃ to obtain the recovered waste polytetrafluoroethylene particles.

Table 2 mechanical property test results of the teflon rehabilitating pipe and the pure teflon pipe prepared in example 2

	Tensile strength/MPa	Elongation at break/%
			National standard reference value ZBG33001-1985 of polytetrafluoroethylene tube	≥25	≥100
Polytetrafluoroethylene regenerating pipe	25.8	119.51
			Pure polytetrafluoroethylene tube	27.6	238

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. The method for recovering waste polytetrafluoroethylene is characterized by comprising the following steps:

2. The recycling method according to claim 1, wherein the microwave radiation has a power of 220-360W, a temperature of 327-350 ℃ and a time of 30-60 min.

3. The recycling method according to claim 1, wherein the used polytetrafluoroethylene is a filler-free used polytetrafluoroethylene.

4. The recycling method according to claim 1 or 3, wherein the particle size of the waste polytetrafluoroethylene particles is 500-520 μm.

5. Use of the recycled polytetrafluoroethylene obtained by the recycling method according to any one of claims 1 to 4 for the preparation of a polytetrafluoroethylene recycled product comprising polytetrafluoroethylene tubes, polytetrafluoroethylene rods, polytetrafluoroethylene tapes, polytetrafluoroethylene sheets or polytetrafluoroethylene films.

6. The use according to claim 5, wherein the polytetrafluoroethylene tube has a wall thickness, a polytetrafluoroethylene rod diameter, a polytetrafluoroethylene tape thickness, a polytetrafluoroethylene sheet thickness, and a polytetrafluoroethylene film thickness independently of each other of 0.1 to 0.5 mm.

7. A polytetrafluoroethylene regenerated product comprises a polytetrafluoroethylene tube, a polytetrafluoroethylene rod, a polytetrafluoroethylene tape, a polytetrafluoroethylene plate or a polytetrafluoroethylene film, and is obtained by sintering a recovered polytetrafluoroethylene obtained by any one of the recovery methods 1-4 after hot press molding.

8. The recycled polytetrafluoroethylene product according to claim 7, wherein said hot press molding is carried out at a temperature of 327 ℃ to 350 ℃, under a pressure of 10 MPa to 12MPa, and for a period of 1min to 2 min.

9. The recycled polytetrafluoroethylene product according to claim 7, wherein said sintering is carried out at a temperature of 370-400 ℃ for 2-4 hours.