Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
1999-12-08
2001-05-08
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C524S783000, C524S786000, C524S789000, C528S275000, C528S286000, C528S287000, C528S293000, C528S295000, C528S308000, C428S328000, C428S329000, C428S330000, C428S331000, C428S480000, C428S690000, C428S910000
Reexamination Certificate
active
06228975
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a polyalkylene naphthalate, a composition and a film thereof, and production processes therefor. More specifically, it relates to a polyalkylene naphthalate containing an antimony compound and a specific quaternary phosphonium sulfonate compound in specific amounts, a film formed therefrom, and production processes therefor.
PRIOR ART
Of polyalkylene naphthalates comprising naphthalenedicarboxylic acid as a main dicarboxylic acid component and an aliphatic glycol as a main glycol component, polyethylene naphthalate is widely used in fibers, films, resins and the like due to its excellent physical and chemical properties. Of these, a polyethylene naphthalate film is used as a base film for a photo film and a magnetic tape, which reconciles cost and properties such as strength, heat resistance and chemical resistance.
The polyethylene naphthalate film is produced by the same method as that for a polyester film such as a polyethylene terephthalate film.
Polyester films are generally produced by quenching a film-form polyester melt extruded from an extrusion nozzle on the surface of a rotary cooling drum and stretching it in both longitudinal and transverse directions. To eliminate the surface defects of a film and improve thickness uniformity thereof, adhesion between the melt extruded film-form polyester and the surface of the rotary cooling drum must be improved. As means of improving the adhesion, there is known a method in which a wire metal electrode (to be referred to as “electrostatic wire” hereinafter) is provided between an extrusion nozzle and the surface of a rotary cooling drum to deposit static charge on the surface of a film-form melt (to be referred to as electrostatic casting method hereinafter).
Reducing production cost by increasing productivity in the formation of a film is as important a theme as improving the quality of a film. To this end, the improvement of film-forming speed by increasing the rotating speed of the rotary cooing drum is the most effective. However, when the rotating speed of the rotary cooling drum is increased in the above electrostatic casting method, the amount of unit area static charge on the surface of the film-form product decreases and adhesion between the rotary cooling drum and the film-form product lowers, thereby producing surface defects on the surface of the film or making film thickness non-uniform. To enhance this adhesion,there can be employed means of increasing the amount of static charge on the molten polyester by raising voltage to be applied to the electrode. If application voltage is raised excessively, arc discharge may occur between the electrode and the rotary cooling drum, the film-form product on the cooling drum may be broken, and the surface of the cooling drum may be damaged. Therefore, it is substantially impossible to increase voltage to be applied to the electrode to a level higher than a predetermined level.
To overcome the limitation of this electrostatic casting method and produce a polyester film efficiently by increasing a film-forming speed, there are proposed various methods of reducing the resistivity of a molten polyester.
The methods include, for example, one (JP-B 7-5765) in which a molten polyester film having an AC volume resistivity of 6.5×10
8
&OHgr;cm or less and containing in the polymer chain 0.1 to 45 mmol % of a quaternary phosphonium sulfonate having an ester-forming functional group based on a dicarboxylic acid component forming the polyester is used.
A catalyst is generally used for the production of a polyester. Particularly, an antimony compound is widely used because it has high polymerization speed and is excellent in various properties such as the thermal stability of the obtained polyester, the amount of a terminal carboxyl group and softening point. However, it is known that the antimony compound is often deposited in the production processes of a polymer and a film and the deposited particles form small protrusions on the surface of a film (JP-A 8-53541).
JP-A 8-104744 discloses a method of obtaining a film having excellent surface flatness by suppressing the formation of fine irregularities on the surface of the film caused by the deposition of a catalyst component such as an antimony compound and a film having excellent electrostatic adhesion at the time of film formation in the production of a polyethylene naphthalate film. In the method, a calcium compound, magnesium compound, phosphorus compound and antimony compound are added to polyethylene naphthalate in specific amounts and a specific ratio.
However, it has been found that it is difficult to fully prevent the formation of fine protrusions caused by the deposition of a catalyst component and troubles caused thereby, even by means of technologies for selecting one from the above proposed catalyst components and optimizing the amount of the catalyst component.
Especially in a film for a high-density magnetic recording medium typified by a metal-deposited video tape which requires surface flatness and uniformity, the existence of fine protrusions on the surface of the film causes an error disadvantageously.
It has also been found that when film formation speed is increased to improve productivity at the time of the formation of a polyalkylene naphthalate film, the deposition of an antimony compound used as a catalyst exerts an influence upon the maximum winding speed at the time of film formation.
Further, it has been found that the deposition of the antimony compound is also connected with film formation stability at the time of film formation.
That is, it has been discovered that the maximum winding speed can be increased and a homogeneous film can be produced stably and industrially advantageously by suppressing the formation of coarse particles caused by the deposition of the antimony compound and by controlling the size and number of the coarse particles if they are formed.
Problem To Be Solved by the Invention
The inventors of the present invention have found that, when a quaternary phosphonium sulfonate having an ester-forming functional group is added to produce a polyalkylene naphthalate film in the presence of an antimony compound as a catalyst, the number of finely deposited particles considered as reduced antimony in the film increases in proportion to the concentration of the quaternary phosphonium sulfonate.
It has been discovered that excellent adhesion to the rotary cooling drum is attained, high-speed winding speed is achieved and stable film productivity is obtained when a film is produced from a polyalkylene naphthalate obtained by optimizing the concentrations and ratio of the antimony compound and the quaternary phosphonium sulfonate having an ester-forming functional group in accordance with the electrostatic casting method. It has also been found that the obtained film has excellent surface flatness and uniformity and is suitable for use in high-density magnetic recording media.
Means for Solving the Problem
The present invention has been accomplished based on the above findings and is a polyalkylene naphthalate for a film, which comprises a naphthalenedicarboxylic acid component as a main dicarboxylic acid component and an aliphatic glycol component as a main glycol component and contains (a) an antimony compound and (b) a quaternary phosphonium sulfonate compound unit having an ester-forming functional group in such amounts which satisfy the following expressions (1) and (2):
0<Sb≦80 (1)
0<S/Sb≦0.4 (2)
wherein Sb and S are the molar ratios (mmol %) of the antimony compound and the quaternary phosphonium sulfonate compound unit having an ester-forming functional group to the total of all the dicarboxylic acid components forming the polyalkylene naphthalate, respectively.
The present invention will be described in detail hereunder.
The polyalkylene naphthalate of the present invention is a polyester which comprises a naphthalenedicarboxylic acid component as a main dicarboxylic acid component and an ali
Kosuge Masahiko
Kurihara Hideshi
Ura Tomokatsu
Sughrue Mion Zinn Macpeak & Seas, PLLC
Szekely Peter
Teijin Limited
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