JP2546329B2 - Method for producing aromatic polyester tape - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a heat-resistant polyester tape having high strength and high elastic modulus, and in particular, it has a uniform thickness and isotropically high strength. The present invention relates to a method for producing a polyester tape exhibiting a high elastic modulus.

[Prior Art] An aromatic polyamide film as disclosed in, for example, JP-A-56-109224 is known as a film having high strength and high elastic modulus and excellent heat resistance. However, the dry film forming method is adopted as a means for manufacturing this film, and as a result, the film forming process becomes complicated and the manufacturing cost is high. Further, although the film has a certain high strength and high elastic modulus, its value is not sufficient because it contains a meta-orientation copolymerization component, and further improvement in strength and elastic modulus is required. .

[PROBLEMS TO BE SOLVED BY THE INVENTION] The present invention aims to provide a heat-resistant polyester tape (including a film, the same applies hereinafter) having excellent strength and elastic modulus as well as good processability, focusing on these circumstances. To do. In particular, a wide polyester tape is required to have isotropic high strength and high elastic modulus because it is subjected to tension from various directions during manufacturing and use. Further, if the tape thickness has a slight non-uniformity, the non-uniformity is further amplified by the tensions from the multiple directions, so that there is a drawback that a polyester tape having a uniform property cannot be obtained. Therefore, the present inventors have conducted various studies for the purpose of providing a polyester tape having isotropically excellent strength and elastic modulus in addition to the required characteristics described above and having a uniform thickness.

[Means for Solving the Problems] The present invention, which has achieved the above object, provides a method for producing a tape comprising a liquid crystal-forming aromatic polyester.
The gist of the present invention is that the polyester filaments are processed into a sheet, and the polyester filaments are heat-sealed to each other in a temperature environment of melting point −50 ° C. or higher and melting point + 20 ° C. or lower, and further solid-phase polymerized.

[Operation] In order to obtain a tape having high strength and high elastic modulus, it is necessary to orient the polymer chains of the tape material in the longitudinal direction. Therefore, conventionally, it has been devised to subject the polymer chain of the tape material to flow deformation by increasing the degree of orientation by appropriately subjecting the tape formed by discharge molding using a rectangular die to extensional deformation. However, when molten polyester is discharged from the rectangular die and formed into a tape, the surface of the polyester material that is being solidified is still in a slight fluid state, so there is surface tension, and the tape shape during ejection cannot be maintained. Inevitably, a thickness distribution occurs in the tape width direction.

On the other hand, in the present invention, after the liquid crystal molded polyester in a fluid state is extrusion molded into a filament shape, the filament is subjected to sufficient extensional deformation to be a filament having a high strength and a high elastic modulus, and then the filament is appropriately treated. It is prepared in the form of a web by the method, and if necessary, a plurality of webs are superposed and heat-sealed to each other to form a tape shape, and finally the final stage of the production is made into a tape shape. That is, when manufacturing a filament having a substantially circular cross section, the surface tension acts in the direction of maintaining a circular shape, and thus it is relatively easy to obtain a filament having a uniform cross section and improved strength and elastic modulus. In the present invention, since filaments having high uniformity are aligned and processed into a tape shape, the uniformity of the tape is extremely high. Then, for the purpose of further stabilizing this homogeneous state, a solid phase polymerization step is added after the tape shape is adjusted. By the way, solid phase polymerization is carried out, for example, by heat treatment in an N ₂ atmosphere, which further increases the degree of polymerization of the material polyester and contributes to higher strength and higher elastic modulus. In the present invention, it is possible to employ a method completely different from the conventional method for producing a long tape because a liquid crystal-forming aromatic polyester is used as a material,
Since the aromatic polyester has a remarkably long orientation relaxation bending of the polymer chain as compared with a polyester having a general flexible polymer chain, after the polymer chain is oriented in the longitudinal direction in the filament state in advance as described above, Even if these are made into a web state and heat-sealed, the orientation is maintained and high strength and high elastic modulus are not lost. Thus, it is possible to obtain a heat-resistant wide polyester tape having isotropically improved strength and elastic modulus, having a substantially small heat shrinkage, and having a non-uniform thickness distribution, that is, a small thickness unevenness.

In the present invention, the filament is prepared in a web shape and then heat-bonded, but immediately after the spinning step, that is, the filament just spun may be prepared in a web-shape and heat-bonded, or spun separately. The formed filament may be unwound from the bobbin, subjected to a web-like preparation step, and then heat-sealed. The temperature condition during heat fusion is melting point -50 ° C to melting point + 20 ° C, more preferably melting point -20 ° C to melting point + 10 ° C.
If the melting point is lower than −50 ° C., heat fusion cannot be sufficiently performed and a tape-shaped material cannot be formed. On the other hand, if the melting point exceeds + 20 ° C, the filament will melt and the shape retention will deteriorate, and the thickness of the filament will be uneven and the temperature will be too high, and the orientation of the molecular chains in the tape will loosen, preserving high strength and high elastic modulus. I can't. It is desirable that the gap between each filament of a web prepared from filaments is as small as possible, but it is 1/10 of the filament diameter.
Even if there is a gap of about 0 to 1/10, there is no particular problem.

In addition, when preparing a web, there is an official method of cutting filaments into appropriate lengths, dropping and stacking them, and then fusing them, as is commonly used in the manufacture of nonwoven fabrics. A method of forming the web by forming it can also be adopted.

The means for forming the tape shape by heat-sealing is not particularly limited, but it is preferable to use a web shape and preliminarily heated filaments to form a tape shape by sandwiching them with a heating roll. Is desirable.

Further, as the liquid crystal-forming aromatic polyester applied to the present invention, a molten liquid crystal-forming aromatic polyester which maintains liquid crystallinity in a molten state is preferable, and such an aromatic polyester is, for example, 2,5-diacetoxy. Biphenyl and terephthalic acid copolymer, p-acetoxybenzoic acid and 6
Examples thereof include acetoxy-2-naphthoic acid copolymers.

[Example 1] Example 1 2,5-diacetoxybiphenyl (1.01 mol) and terephthalic acid (1.0 mol) were charged into a polymerization tank, and a wholly aromatic polyester having melt anisotropy obtained by polymerization was melt-spun. .
The filament was shaken off from the spinneret using an interlacer to obtain a non-woven fabric having a width of 50 cm. This non-woven fabric was partially fused using 10 pairs of heated pair rolls (330 ° C.) in an N ₂ atmosphere, and processed into a sheet-like material having a thickness of 50 μm and a width of 50 cm. The obtained sheet-like material was further heat-treated (solid-state polymerization) for 3 hours in a N ₂ atmosphere at 325 ° C. Then, the lengthwise test piece and the widthwise test piece were cut out from the sheet-like material, and various characteristics were measured. The results shown in Table 1 were obtained.

Comparative Example 1 When various properties of the sheet-like material before solid-state polymerization were measured in the examples, the results shown in Table 2 were obtained.

Comparative Example 2 In the example, when the fusion temperature of the heated pair roll was 250 ° C., the thickness unevenness of the length direction test piece and the width direction test piece were 45% and 63%, respectively.

Comparative Example 3 Various sheets of a sheet obtained by casting a polymer having the same constitution as in the example from a rectangular die in an unoriented state, and a sheet obtained by heat-treating the same for 3 hours in a N ₂ atmosphere at 325 ° C. (solid-state polymerization) When the characteristics were examined, the results shown in Table 3 were obtained.

[Advantages of the Invention] The present invention is configured as described above and has excellent heat resistance,
It was possible to provide a wide polyester tape having isotropically improved remarkably improved strength and elastic modulus and having a uniform thickness distribution.

Claims (1)

(57) [Claims] 1. A method for producing a tape composed of a liquid crystal-forming aromatic polyester, wherein filaments of the polyester are processed into a sheet, and the melting point is -50 ° C. or higher, the melting point + 20 ° C.
A method for producing an aromatic polyester tape having a uniform thickness, a high strength and a high elastic modulus, which is characterized in that they are heat-fused to each other in the following temperature environment and further solid-phase polymerized.