Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Extrusion molding
Reexamination Certificate
1999-03-09
2001-04-24
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Extrusion molding
C264S210500, C264S210700, C264S216000, C264S235600, C264S235800, C264S288400, C264S290200, C264S484000, C425S066000, C425S174400, C425S17480R, C425S17480E, C425S224000, C425S447000
Reexamination Certificate
active
06221301
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for producing a thermoplastic resin film, and an apparatus for producing a thermoplastic resin film suitable for executing said method.
BACKGROUND ART
In the conventional methods for producing a thermoplastic resin film, a thermoplastic resin film melt-extruded from a die is brought into contact with a cooling drum, to be quickly cooled to lower than the glass transition temperature of the resin, for forming a cast film low in crystallinity, good in clarity and smooth on the surface. It is, as required, in succession stretched monoaxially or biaxially.
However, these methods have the following problem.
The maximum speed at which a film low in crystallinity, good in clarity and smooth on the surface can be obtained by bringing a molten thermoplastic resin film into contact with a cooling drum is about 40~60 m/min at the highest, since it cannot be prevented that the air is caught in the clearance between the cast film and the cooling drum irrespective of whether any casting means effective for high speed casting such as electrostatic charging, vacuum suction or pressing is used. So, the productivity is inevitably low.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a method for producing a thermoplastic resin film excellent in both productivity and quality, by overcoming the above mentioned disadvantage, and also an apparatus for producing a thermoplastic resin film suitable for executing said production method.
The method for producing a thermoplastic resin film of the present invention to achieve the above object is a method for producing a thermoplastic resin film, in which a molten thermoplastic resin film is brought into contact with a cooling medium, to be cooled and solidified, for producing a cast film, characterized in that the surface temperature of the cooling medium in the region immediately before the melt reaching position is kept at not lower than the glass transition temperature Tg and not higher than the melting point Tm of the thermoplastic resin.
The method for producing a thermoplastic resin film of the present invention to achieve the above object as another version is a method for producing a thermoplastic resin film, in which a molten thermoplastic resin film is brought into contact with a cooling medium, to be cooled and solidified, for producing a cast film, characterized in that the surface temperature of the cooling medium in the region immediately before the melt reaching position is kept at not lower than the glass transition temperature Tg and not higher than the melting point Tm of the thermoplastic resin, and that the surface temperature of the cooling medium in the region immediately before the melt leaving position is kept at lower than the glass transition temperature Tg of the thermoplastic resin.
The apparatus for producing a thermoplastic resin film of the present invention is an apparatus for producing a thermoplastic resin film, characterized in that a cooling medium has a heater and a cooler, to ensure the surface temperature of said cooling medium in the region immediately before the melt reaching position may be kept at not lower than the glass transition temperature Tg and not higher than the melting point Tm of the thermoplastic resin, and that the surface temperature in the region immediately before the melt leaving position may be kept at lower than the glass transition temperature Tg of the thermoplastic resin.
According to the method and apparatus for producing a thermoplastic resin film of the present invention, the surface temperature of the cooling medium such as a casting drum with which the melt is kept in contact is kept at not lower than the Tg of the polymer and subsequently the surface temperature of the casting drum in the region corresponding to the melt leaving position is kept at lower than the Tg of the resin, or the melt leaves from the cooling medium after it has been crystallized on the cooling medium. Therefore, the following excellent productivity and excellent film properties can be obtained.
(1) In general, casting at a high speed of 80 m/min or more can be effected, and since stretching can be effected at a speed corresponding to the casting speed, a film can be formed at a high speed of 400 m/min or more, to greatly reduce the production cost.
(2) A film with very excellent properties as a film for general industrial use, packaging use, etc. can be provided.
(3) The method of the present invention is effective for less crystalline or amorphous thermoplastic resins and highly crystalline resins, and is high in productivity. So, it is very significant industrially in film production.
REFERENCES:
patent: 2405977 (1946-08-01), Peters
patent: 4-255322 (1992-09-01), None
patent: 5-16210 (1993-01-01), None
patent: 6-305013 (1994-11-01), None
patent: 8-197612 (1996-08-01), None
patent: 9-239812 (1997-09-01), None
Chigira Nobutsugu
Miyakawa Katsutoshi
Osada Shunichi
Toyama Masaharu
Tsunashima Kenji
Birch & Stewart Kolasch & Birch, LLP
Tentoni Leo B.
Toray Industries Inc.
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