WO2014161115A1

WO2014161115A1 - METHOD FOR PREPARING PTFE SUPERFINE POWDER BY COMBINING γ RAYS WITH OZONE AND HYDROGEN PEROXIDE

Info

Publication number: WO2014161115A1
Application number: PCT/CN2013/000801
Authority: WO
Inventors: 顾建忠; 吴明红; 蔡建球
Original assignee: 太仓金凯特种线缆有限公司
Priority date: 2013-04-03
Filing date: 2013-06-28
Publication date: 2014-10-09
Also published as: CN103183835A; CN103183835B

Abstract

Disclosed is a method for preparing a PTFE superfine powder by combining γ rays with ozone and hydrogen peroxide. The method comprises: quenching a dry polytetrafluoroethylene raw material in liquid nitrogen; crushing same into a polytetrafluoroethylene powder having a grain size of 100-1000 μm with a pulverizer; then placing same into a container on an automatic production line of a cobalt 60 device; first spraying hydrogen peroxide and ozone on the automatic production line, and then irradiating when passing through the cobalt 60 device, wherein the irradiation dose is 40-60 KGy, and the radiation time is determined according to the radioactivity of the cobalt 60 device; conveying the radiated polytetrafluoroethylene powder out of the radiation chamber via the automatic production line; and placing same into an airflow crushing system for sufficient crushing, so as to obtain a polytetrafluoroethylene superfine powder with a grain size of 0.2-5 μm. According to the method provided by the present invention, using the automatic production line can further improve the production efficiency while the degradation rate of polytetrafluoroethylene can be increased.

Description

TECHNICAL FIELD The present invention relates to the field of chemical engineering, and in particular to a method for preparing PTFE ultrafine powder by combining γ-ray with ozone and hydrogen peroxide. BACKGROUND OF THE INVENTION Polytetrafluoroethylene (PTFE), commonly known as plastic king, is a polymer obtained by polymerizing tetrafluoroethylene monomers. It has strong cohesiveness and is easily attached and difficult to disperse. PTFE ultrafine powder (micronized powder) is a low molecular weight polytetrafluoroethylene with a molecular weight of less than 10,000 and a particle size of 0.5-15μηι. The PTFE ultrafine powder not only maintains all the excellent properties of polytetrafluoroethylene, but also Has many unique properties: such as no self-cohesiveness, no static effect, good compatibility, low molecular weight, good dispersibility, high self-lubricity, reduced friction coefficient, no agglomeration, easy to mix with oil or organic liquid, and Other solid particles may also be uniformly mixed and the like. The average particle size of PTFE ultrafine powder is less than 5μηι, the specific surface is larger than 10m ² /g, the friction coefficient is 0.06~0.07, the lubricity is good, and it can be well dispersed in many materials. It can be used as anti-sticking, anti-friction and flame retardant additives for plastics, rubber, inks, coatings and lubricating greases. It can also be used as a dry lubricant to make aerosols. PTFE ultrafine powder can be used as a solid lubricant alone or as an additive for plastics, rubber, paints, inks, lubricants, greases, etc. Various typical powder processing methods can be used to mix with plastic or rubber, such as blending. Adding PTFE ultrafine powder to oils and greases can reduce the coefficient of friction. By adding a few percent, the life of the lubricant can be increased. The organic solvent dispersion can also be used as a release agent.

Ozone is an allotrope of oxygen. It is a blue gas with a special odor at room temperature and is insoluble in carbon tetrachloride. Ozone is highly oxidizing and easily decomposed, and the hydroxyl radical (.OH) produced during decomposition has a strong oxidizing power.

Hydrogen peroxide, commonly known as hydrogen peroxide, molecular formula H202, is another hydrogen oxygen other than water. Compound. Viscosity is slightly higher than water, chemically unstable, and is generally stored as a 30% or 60% aqueous solution. Hydrogen peroxide is highly oxidizing and weakly acidic.

The method of preparing PTFE ultrafine powder determines the structural properties, molecular weight and distribution of the PTFE ultrafine powder. There are two main preparation methods for PTFE ultrafine powder: 1. The polymerization is directly adjusted with tetrafluoroethylene. After a certain period of time, the polymerization reaction is terminated, and the product is further processed; 2. The high molecular weight PTFE is used for cracking and then pulverized. The cleavage reaction to prepare PTFE ultrafine powder mainly involves thermal cracking and irradiation cracking. During the irradiation cracking process, the cracking of PTFE is affected by the irradiation conditions. The irradiation dose, the energy source used for the irradiation and the oxidation conditions have a great influence on the physical properties and chemical properties of the PTFE ultrafine powder. Therefore, the equipment and process conditions in the PTFE irradiation cracking process need to be optimized and strictly controlled. SUMMARY OF THE INVENTION In view of the problems in the prior art described above, it is an object of the present invention to provide a method of preparing PTFE ultrafine powder by combining Y radiation with ozone and hydrogen peroxide.

In order to achieve the above object, the technical solution adopted by the present invention is as follows:

A method for preparing PTFE ultrafine powder by combining Y-ray with ozone and hydrogen peroxide, comprising the following steps:

(1) quenching the dried polytetrafluoroethylene raw material with liquid nitrogen; pulverizing the quenched polytetrafluoroethylene raw material into a powder having a particle diameter of 100-1000 μm;

(2) placing the polytetrafluoroethylene powder into a holder, the holder being sealed and located on an automatic assembly line running through the cobalt 60 irradiation chamber, and having at least one shower device interface disposed therein and At least one release device interface, the cobalt 60 irradiation chamber includes at least one cobalt 60 irradiation device in the middle of the irradiation chamber, an automatic assembly line through the cobalt 60 irradiation device, at least one ozone release device, and at least one hydrogen peroxide spray Leaching device, radiation barrier wall and control room;

(3) The PTFE powder enters the irradiation chamber at a constant speed with the open automatic line. When the PTFE powder passes through at least one cobalt 60 irradiation device, the at least one ozone release device is directed to the polytetrafluoroethylene powder. The fluoroethylene powder is sprayed with ozone, and at least one hydrogen peroxide spray device sprays hydrogen peroxide onto the PTFE powder, and the weight ratio of the sprayed ozone to the PTFE powder is 0.1%-0.5%, the weight ratio of sprayed hydrogen peroxide to polytetrafluoroethylene powder is 3%-8%;

(4) When passing through the at least one cobalt 60 irradiation device, the gamma ray generated by at least one cobalt 60 irradiation device irradiates the polytetrafluoroethylene powder, and the irradiation dose is 40-60 KGy _;

(5) The ware containing the irradiated PTFE powder is transported out of the irradiation and chamber by an automatic assembly line;

(6) The irradiated polytetrafluoroethylene powder is repulverized and classified by a jet mill, and the polytetrafluoroethylene fine powder is dispersed into a polytetrafluoroethylene ultrafine powder having an average particle diameter of 5 μm or less.

Further, the at least one hydrogen peroxide spray device and the at least one ozone release device respectively spray hydrogen peroxide and ozone to the polytetrafluoroethylene powder, and the weight ratio of the sprayed hydrogen peroxide to the polytetrafluoroethylene powder is 5 %, the weight ratio of sprayed ozone to polytetrafluoroethylene powder is 0.3%.

Further, the at least one cobalt 60 irradiation device is a single grid cobalt source.

Further, the at least one cobalt 60 irradiation device is a double grid cobalt source.

Further, the step (4) further includes the automatic assembly being joined to the holder containing the Teflon powder, and the irradiated Teflon powder is poured at the outlet end of the automatic assembly line. Enter the feed port of the jet mill described in step (5).

Further, the jet mill comprises a gas flow nozzle and a pulverizing chamber, and the compressed air is jetted into the pulverizing chamber at a high speed through the nozzle, so that the irradiated polytetrafluoroethylene fine powder particles repeatedly collide at the intersection of the plurality of high-pressure air streams, Rub, shear and smash.

Further, the jet mill further includes a cyclone separator, a dust remover and an induced draft fan; the jet mill includes a classification zone, and the polytetrafluoroethylene pulverized in the crushing chamber is moved to the classification zone by the induced draft fan. Under the action of the classifying wheel, the fine particles of polytetrafluoroethylene are separated according to the particle size, and the fine particles satisfying the particle size requirement are collected by the classification wheel into the cyclone or the dust collector, and the cyclone collects the coarse particles in the fine particles. A small part of the ultrafine particles are collected by the dust collector, and the coarse particles that do not meet the particle size requirements are lowered to the pulverizing chamber to continue pulverization.

Further, the airflow nozzle of the jet mill is a Laval nozzle.

Further, the jet mill has a dry filter device, and the dry filter device is located Before the nozzle.

Further, the automatic line is a bucket conveyor or a suspended chain conveyor system that can achieve automatic reversing.

The preparation method of the polytetrafluoroethylene ultrafine powder provided by the invention can increase the degradation rate of the polytetrafluoroethylene under the same irradiation condition, or can achieve the same degradation rate under the condition of reducing the irradiation time. The production efficiency can be greatly improved, the production cost can be saved, and the product quality can be ensured, and the average particle diameter of the low molecular weight polytetrafluoroethylene obtained can be ensured to be less than 5 μm, and the entire manufacturing process is strictly controllable. BEST MODE FOR CARRYING OUT THE INVENTION In order to make the objects, technical solutions and advantages of the present invention more comprehensible, the present invention will be described in detail below with reference to the embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

PTFE has poor radiation resistance (1000Gy) and is degraded by high-energy radiation. The present invention utilizes the characteristic of polytetrafluoroethylene to irradiate PTFE with a cobalt 60 device, and then uses a jet mill. Dispersion treatment can be carried out to obtain a polytetrafluoroethylene ultrafine powder material.

Cobalt-60 (Co) is one of the radioisotopes of metallic cobalt and has a half-life of 5.27 years. It emits high-speed electrons with energy up to 315 keV into nickel-60 through beta decay, and emits two gamma rays with energies of 1.17 and 1.33 MeV, respectively. The gamma ray, also known as the Υ particle stream, is an electromagnetic wave having a wavelength shorter than 0.2 angstrom and has a strong penetrating power.

After the radiation degradation, the polytetrafluoroethylene changes from a polymer to a low molecule, but the low molecular weight polytetrafluoroethylene remains agglomerated without ultrafine powder dispersed into small molecules. In order to obtain ultrafine powder, the low molecular weight polytetrafluoroethylene after irradiation degradation must be pulverized and pulverized by air flow.

The jet mill used in the following embodiments of the present invention comprises a gas flow nozzle and a pulverizing chamber, and the compressed air is jetted into the pulverizing chamber at a high speed through the nozzle, and at the intersection of the plurality of high-pressure air streams, the irradiated PTFE fine The powder particles are repeatedly crushed, rubbed, sheared and pulverized. Wherein, the airflow nozzle of the jet mill is a Laval nozzle, and a dry filter device is arranged in front of the airflow nozzle. The jet mill also includes a cyclone, a precipitator and an induced draft fan. Jet mill also includes grading Zone, the PTFE pulverized in the crushing chamber is moved to the classification zone under the action of the induced draft fan. Under the centrifugal force generated by the high-speed rotating classification turbine, the polytetrafluoroethylene particles are separated according to the particle size, and the fine particles satisfying the particle size requirement Collecting through a grading wheel into a cyclone or a dust collector, the cyclone collects coarser particles in the fine particles, and a small portion of the ultrafine particles are collected by the dust collector. The coarse particles that do not meet the particle size requirements are lowered to the pulverizing chamber to continue pulverization. Embodiment 1

A preparation method of a polytetrafluoroethylene ultrafine powder, comprising the following steps:

(1) The dried polytetrafluoroethylene raw material is subjected to low-temperature cold treatment with liquid nitrogen; the low-temperature treated polytetrafluoroethylene raw material is pulverized into a powder having a particle diameter of 100-1000 μm;

(2) The PTFE powder is placed in a holder, the container is a bucket on a bucket conveyor that runs through the cobalt 60 irradiation chamber, and the cobalt 60 irradiation chamber includes a single sheet in the middle of the irradiation chamber. Cobalt source of cobalt, a bucket conveyor through a single grid of cobalt source, located on the automatic assembly line and adjacent to an ozone release device of the cobalt 60 irradiation device and a hydrogen peroxide spray device, radiation barrier and control

(3) The PTFE powder enters the irradiation room at a constant speed with the open bucket conveyor, and the ozone release device and the hydrogen peroxide spray device spray ozone and hydrogen peroxide to the PTFE powder as it passes, spraying The weight ratio of ozone to polytetrafluoroethylene powder is 0.5%, and the weight ratio of sprayed hydrogen peroxide to polytetrafluoroethylene powder is 3%;

(4) When passing through a single grid cobalt source, the gamma ray generated by the single grid cobalt source irradiates the PTFE powder at an irradiation dose of 40 KGy, and the speed of the bucket conveyor is determined by a single grid cobalt. The source (201) is determined by the size of the radioactivity and is controlled by the control room;

(5) The cargo bucket containing the irradiated Teflon powder is transported out of the irradiation chamber by the bucket conveyor, and the irradiated PTFE powder is discharged into the airflow pulverizing raw material zone;

(6) The irradiated polytetrafluoroethylene fine powder is repulverized and classified by a jet mill, and the polytetrafluoroethylene fine powder is dispersed into a polytetrafluoroethylene ultrafine powder having an average particle diameter of 5 μηη or less. Embodiment 2:

(1) Step (1) is the same as in the first embodiment;

(2) Put the PTFE powder into the ware, the ware is located in the cobalt 60 irradiation room The bucket on the bucket conveyor, the cobalt 60 irradiation chamber comprises two single-grid cobalt sources in the middle of the irradiation chamber, and the bucket conveyor passing through the single-grid cobalt source is located on the automatic assembly line and adjacent to the cobalt 60-spoke 1 hydrogen peroxide spray device and 2 ozone release devices, radiation barrier and control

(3) The PTFE powder enters the irradiation room at a uniform speed with the open bucket conveyor, and the hydrogen peroxide spray device and the ozone release device spray the hydrogen peroxide and ozone to the PTFE powder as it passes, spraying The weight ratio of hydrogen peroxide to polytetrafluoroethylene powder is 3%, and the weight ratio of sprayed ozone to polytetrafluoroethylene powder is 0.5%;

(4) After spraying hydrogen peroxide and ozone, the PTFE powder continues to move with the bucket conveyor. When passing through the single grid cobalt source, the gamma ray generated by the single grid cobalt source is PTFE. The powder is irradiated at an irradiation dose of 60 KGy, and the speed of the bucket conveyor is determined by the radioactivity of the cobalt source of the single grid and controlled by the control room;

Steps (5) to (6) are the same as in the first embodiment. Embodiment 3:

(1) Step (1) is the same as in the first embodiment;

(2) The PTFE powder is placed in a holder, the container is a cargo hopper on a suspension chain conveyor system running through the cobalt 60 irradiation chamber, and the cobalt 60 irradiation chamber includes a 1 in the middle of the irradiation room. Double grid cobalt source, suspension chain conveyor system through double grid cobalt source, 2 hydrogen peroxide spray devices and 1 ozone release device in the chain conveyor system adjacent to the double grid cobalt source, radiation barrier And control room;

(3) The PTFE powder enters the irradiation room at a constant speed with the open suspension chain conveyor system, and two hydrogen peroxide spray devices and one ozone release device spray the hydrogen peroxide water to the Teflon powder as it passes. And ozone, sprayed hydrogen peroxide and polytetrafluoroethylene powder weight ratio of 8%, sprayed ozone and polytetrafluoroethylene powder weight ratio of 0.1%;

(4) The PTFE powder continues to move with the hanging chain conveyor system. When passing through the double grid cobalt source, the gamma rays generated by the double grid cobalt source irradiate the PTFE powder, irradiating The dose is 50KGy, the speed of the hanging chain conveyor system is determined by the radioactivity of the double grid cobalt source, and is controlled by the control room; Steps (5) to (6) are the same as in the first embodiment. Embodiment 4:

(1) Step (1) is the same as in the first embodiment;

(2) The PTFE powder is placed in a holder, the container is a cargo hopper on a suspension chain conveyor system running through the cobalt 60 irradiation chamber, and the cobalt 60 irradiation chamber includes 3 in the middle of the irradiation room. A single grid cobalt source, a single chain grid cobalt source suspension chain conveyor system, two hydrogen peroxide spray devices located above the suspension chain conveyor system and adjacent to the single grid cobalt source, and two ozone release devices, radiation isolation Wall and control room;

(3) The PTFE powder enters the irradiation room at a constant speed with the open hanging chain conveyor system, and two hydrogen peroxide spray devices and two ozone release devices spray hydrogen peroxide to the PTFE powder as it passes by. And ozone, sprayed hydrogen peroxide and polytetrafluoroethylene powder weight ratio of 8%, sprayed ozone and polytetrafluoroethylene powder weight ratio of 0.3%;

(4) The PTFE powder continues to move with the hanging chain conveyor system. When passing through the single grid cobalt source, the gamma ray generated by the single grid cobalt source irradiates the PTFE powder. At a dose of 60 KGy, the speed of the hanging chain conveyor system is determined by the radioactivity of the single grid cobalt source and is controlled by the control room;

Steps (5) to (6) are the same as in the first embodiment. Embodiment 5:

(1) Step (1) is the same as in the first embodiment;

(2) The PTFE powder is placed in a holder, the container is a cargo hopper on a suspension chain conveyor system running through the cobalt 60 irradiation chamber, and the cobalt 60 irradiation chamber includes 2 in the middle of the irradiation room. Double grid cobalt source, suspension chain conveyor system through double grid cobalt source, 2 hydrogen peroxide spray devices and 3 ozone release devices in the automatic assembly line adjacent to the double grid cobalt source, radiation barrier wall and control room ;

(3) The PTFE powder enters the irradiation room at a constant speed with the open suspension chain conveyor system, two hydrogen peroxide spray devices and three ozone release devices pass through the Teflon powder Spraying hydrogen peroxide and ozone to it, the weight ratio of sprayed hydrogen peroxide to polytetrafluoroethylene powder is

5%, the weight ratio of sprayed ozone to polytetrafluoroethylene powder is 0.5%;

(4) The PTFE powder continues with the hanging chain conveyor system. When passing through the double grid cobalt source, the gamma rays generated by the double grid cobalt source irradiate the PTFE powder. The irradiation dose is 60KGy, and the speed of the suspension chain conveyor system is determined by the radioactivity of the double grid cobalt source and controlled by the control room;

Steps (5) to (6) are the same as in the first embodiment.

The above-mentioned embodiments are merely illustrative of the embodiments of the present invention, and are not to be construed as limiting the scope of the invention. It should be noted that a number of variations and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be determined by the appended claims.

Claims

Claim

A method for preparing a PTFE ultrafine powder by combining Y-ray with ozone and hydrogen peroxide, and the method comprises the following steps:

(2) placing the polytetrafluoroethylene powder into a holder, the holder being sealed and located on an automatic assembly line running through the cobalt 60 irradiation chamber, having at least one shower device interface and at least one release therein Device interface, the cobalt 60 irradiation chamber comprises at least one cobalt 60 irradiation device in the middle of the irradiation chamber, an automatic assembly line through the cobalt 60 irradiation device, at least one ozone release device and at least one hydrogen peroxide spray device, radiation The wall and the control room;

(3) The PTFE powder enters the irradiation chamber at a constant speed with the open automatic line. When the PTFE powder passes through at least one cobalt 60 irradiation device, the at least one ozone release device is directed to the polytetrafluoroethylene powder. The fluoroethylene powder sprays ozone, at least one hydrogen peroxide spray device sprays hydrogen peroxide onto the PTFE powder, and the weight ratio of the sprayed ozone to the polytetrafluoroethylene powder is 0.1%-0.5%, sprayed The weight ratio of hydrogen peroxide to polytetrafluoroethylene powder is 3%-8%;

2. The method according to claim 1, wherein the at least one hydrogen peroxide spray device and the at least one ozone release device respectively spray hydrogen peroxide and ozone to the polytetrafluoroethylene powder, and spray the hydrogen peroxide with The weight ratio of the polytetrafluoroethylene powder was 5%, and the weight ratio of the sprayed ozone to the polytetrafluoroethylene powder was 0.3%.

3. The method of claim 1 wherein said at least one cobalt 60 irradiation device is a single grid cobalt source.

4. The method of claim 1 wherein said at least one cobalt 60 radiation device is a dual grid cobalt source.

5. The method according to claim 1, wherein the step (4) further comprises the automatic assembly being joined to the holder containing the Teflon powder and being disposed at the outlet end of the automatic assembly line. The irradiated polytetrafluoroethylene powder is poured into the feed port of the jet mill described in step (5).

6. The method according to claim 5, wherein the jet mill comprises an air flow nozzle and a pulverizing chamber, and the compressed air is jetted into the pulverizing chamber at a high speed through the nozzle to irradiate the irradiated polytetrafluoroethylene fine powder particles. Colliding, rubbing, shearing and pulverizing at the intersection of multiple high-pressure air streams.

7. The method according to claim 6, wherein the jet mill further comprises a cyclone, a dust remover and an induced draft fan; the jet mill comprises a classification zone, and the polytetrafluorocarbon after the crushing chamber is pulverized The ethylene moves to the classification zone under the action of the induced draft fan. Under the action of the classification wheel, the fine particles of polytetrafluoroethylene are separated according to the particle size. The fine particles that meet the particle size requirements are collected into the cyclone or the dust collector through the classification wheel. The coarse particles meeting the particle size requirements are lowered to the pulverizing chamber to continue pulverization.

8. The method of claim 7 wherein the airflow nozzle of the jet mill is a Laval nozzle.

9. The method of claim 8 wherein said jet mill has a dry filter device and said dry filter device is located in front of the nozzle.

The method according to any one of claims 1-9, wherein the automatic pipeline is a bucket conveyor or a hanging chain conveyor system that can be automatically reversed.