Ptfe powder and method of producing ptfe powder for molding

a technology of polytetrafluoroethylene and ptfe powder, which is applied in the field of polytetrafluoroethylene powder, can solve the problems of reducing the tensile strength of the cylinder, the inability to mold the resin, and the inability to meet the requirements of the mold or cylinder, so as to/or tensile elongation, improve the surface roughness ra, and improve the tensile strength

Inactive Publication Date: 2005-01-13
DAIKIN IND LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

In view of the state of the art as discussed above, it is an object of the present invention to provide a polytetrafluoroethylene powder capable of giving moldings which are improved in surface roughness Ra, tensile strength and/or tensile elongation as

Problems solved by technology

However, it is very high in melt viscosity, so that it has been regarded as impossible to mold the resin by applying ordinary plastics molding processes used in molding general thermoplastic resins low in melt viscosity, such as conventional extrusion molding and injection molding techniques.
On the other hand, the PTFE powder ground just after polymerization is generally inferior in such powder characteristics as apparent density and powder flowability and, therefore, the molding powder tends to aggregate in the hopper or small-diameter cylinder of the molding machine, causing bridging or uneven filling in the mold or cylinder, hence the handleability tends to become unsatisfactory.
Further, the PTFE powder ground just after polymerization is low in apparent density and bulky per unit weight, so that it is not easy to reduce the size of the mold or cylinder.
It is thus difficult to increase the productivity per mold or cylinder; th

Method used

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  • Ptfe powder and method of producing ptfe powder for molding
  • Ptfe powder and method of producing ptfe powder for molding
  • Ptfe powder and method of producing ptfe powder for molding

Examples

Experimental program
Comparison scheme
Effect test

production example 1

Production of PTFE Powder (I) not Reduced in Size

A 2,000-liter stainless steel autoclave equipped with a stirrer was charged with 1,600 liters of deoxygenated pure water, and the air in the autoclave was purged with nitrogen, which was in turn substituted with tetrafluoroethylene. Then, while maintaining the inside temperature at 30° C., tetrafluoroethylene was pressed into the autoclave until an internal pressure of 4 atmospheres, (NH4)2S2O8 was added as a polymerization initiator, and the polymerization of tetrafluoroethylene was carried out with stirring. As the polymerization progresses, the pressure lowered. Therefore, tetrafluoroethylene was added continuously so that the internal pressure might be maintained at 4 atmospheres. After 5 hours, stirring was discontinued, the unreacted tetrafluoroethylene was recovered, and the autoclave contents were taken out. The product polymer, namely the virgin polymer of a PTFE-based polymer with an average particle diameter of 5 to 7 mm,...

production example 2

Production of PTFE Powder (III) not Reduced in Size

A 170-liter autoclave was charged with a solution of 3.3 g of ammonium carbonate in 54.8 liters of pure water, and the solution was stirred using an anchor impeller at 110 rpm. After deaeration, tetrafluoroethylene was charged into the autoclave until a gauge pressure of 0.5 kgf / cm2G. After three repetitions of this procedure, perfluoro(propyl vinyl ether) was pressed into the autoclave using tetrafluoroethylene and, after raising the reaction system temperature to 50° C., tetrafluoroethylene was fed to the autoclave under pressure until a reaction system internal pressure of 8 kgf / cm2 G. Thereto was added ammonium persulfate to initiate the polymerization. While continuously feeding tetrafluoroethylene under pressure to maintain the reaction system internal pressure at 8 kgf / cm2 G, the polymerization was carried out until the tetrafluoroethylene consumption amounted to 30% by weight relative to the weight of the aqueous medium. T...

production example 3

Production of PTFE Powder (II) not Reduced in Size

A 170-liter autoclave was charged with a solution of 3.3 g of ammonium carbonate in 54.8 liters of pure water, and the solution was stirred using an anchor impeller at 110 rpm. After deaeration, tetrafluoroethylene was charged into the autoclave until a gauge pressure of 0.5 kgf / cm2 G. After three repetitions of this procedure, perfluoro(propyl vinyl ether) was pressed into the autoclave using tetrafluoroethylene and, after raising the reaction system temperature to 70° C., tetrafluoroethylene was fed to the autoclave under pressure until a reaction system internal pressure of 8 kgf / cm2 G. Thereto was added ammonium persulfate to initiate the polymerization. While continuously feeding tetrafluoroethylene under pressure to maintain the reaction system internal pressure at 8 kgf / cm2 G, the polymerization was carried out until the tetrafluoroethylene consumption amounted to 22.5% by weight relative to the weight of the aqueous medium....

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Abstract

This invention provides a polytetrafluoroethylene powder capable of giving moldings which are improved in surface roughness Ra, tensile strength and/or tensile elongation as compared with the prior art ones and can be excellent in dielectric breakdown strength and, further, can be excellent, if desired, in apparent density and/or powder flowability as well, and a method of producing a polytetrafluoroethylene molding powder. The present invention is a PTFE powder wherein a surface roughness Ra of molded articles a1 for measurement is less than 0.92 μm.

Description

TECHNICAL FIELD The present invention relates to a polytetrafluoroethylene powder capable of giving moldings which are improved in surface smoothness, tensile strength and / or tensile elongation as compared with the prior art ones and can be excellent in dielectric breakdown strength and, further, can be excellent, if desired, in apparent density and / or powder flowability as well, and to a method of producing polytetrafluoroethylene (PTFE) molding powders. BACKGROUND ART Polytetrafluoroethylene (PTFE) is a thermoplastic resin excellent in heat resistance, chemical resistance, weather resistance, electrical insulation properties and nontackiness, among others, and is useful in a wide range of fields of application. However, it is very high in melt viscosity, so that it has been regarded as impossible to mold the resin by applying ordinary plastics molding processes used in molding general thermoplastic resins low in melt viscosity, such as conventional extrusion molding and injectio...

Claims

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Application Information

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IPC IPC(8): C08J3/12C08L27/18
CPCC08J3/12C08J3/122C08J2327/18Y10T428/2982C08L2205/02C08L27/18C08L2666/04
Inventor TSUJI, MASSAYUKIASANO, MICHIOSUKEGAWA, MASAMICHI
Owner DAIKIN IND LTD
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