JPS60257218A - Orientated article of polyester family resin and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain the transparent molded product of polyester resin having no surface unevenness or inner microvoid and high strength and toughness by orientating the resin so as to obtain specified melting property and birefringence index. CONSTITUTION:The melting curve obtained at the temperature elevating speed of 8 deg.C/min, using a differential scanning calorimeter, must have its crystal melting point at higher temperature side, by at least 7 deg.C or more, than the crystal melting point in the melting curve in which the temperature is lowered from said molten state at the temperature lowering speed of 8 deg.C/min, and again the temperature is elevated at the same temperature elevating speed. Further, the birefringence index must be equal to or higher than 35X10<-3>. Such polyester family resin orientated article is produced by following method. That is to say, polyester family resin is fusion-extruded without melt fracture at the temperature equal to or lower than the decomposition temperature of said resin, and the resin is cooled, while drafting it at the draft ratio equal to 50% or more from said fusion-extruded condition.

Description

DETAILED DESCRIPTION OF THE INVENTION 11 Mottling 1 The present invention relates to an oriented polyether resin molded product that has no internal microvoids, has an excellent surface smoothness, and is transparent, and a method for producing the same.

11. Traditionally, polyether resins, especially polyoxymethylene resins, have been used as engineering plastics due to their properties such as hardness and abrasion resistance due to their crystallinity. It is used to manufacture parts materials and associated gears. All of these polyether resin molded products are white and opaque due to the development of spherulites associated with high crystallinity.

Furthermore, even when these polyether resins are extruded into a film or thread, the resulting film or thread remains white and opaque and is extremely brittle due to the development of spherulites. Furthermore, if such a white opaque film or thread is heated and stretched at a temperature below its melting point, a -axis-oriented film or thread can be obtained, but since these are obtained by the destruction of spherulites. The surface of the film or thread thus obtained has significant irregularities, and often contains microvoids inside.

Such surface or internal defects are an important obstacle to the use of oriented polyether resin products in various applications, particularly in electrical applications. For example, when attempting to use it as a film for electronic materials, microdischarge may occur under an electric field. Furthermore, when used in a capacitor film, it is clear that microvoids inside the film cause microdischarge inside the voids, leading to film destruction, and such a film could never be a reliable capacitor film. In addition, filamentous polyether resins have the same drawbacks as the above-mentioned films, and have not yet been produced with sufficient strength and toughness for use in various applications.

The object of the present invention is to provide a polyether resin molded product that is free from such surface irregularities and internal microvoids, has high strength and toughness, and is transparent, and a method for producing the same. Our goal is to provide the following.

4岨L11 As a result of research for the purpose described above, the present inventors have found that oriented polyether resins that are oriented to have specific melting characteristics and birefringence have good strength, few surface and internal defects, and It has been found that a molded product having toughness and transparency can be obtained.

The oriented polyether resin material of the present invention is based on such knowledge, and more specifically, it is characterized by having the following characteristics (a) and (b).

(B) The melting curve obtained using a differential scanning calorimeter at a heating rate of 8°C/min was obtained by cooling from the molten state at a cooling rate of 8°C/min, and then raising the temperature again at the above temperature rate A. and (b) have a birefringence of 35 X I O-1 or more.

It has also been found that such an oriented product can be obtained by cooling a melt extruded product of polyether resin while drafting it at a draft rate of at least a certain level. That is, the method for producing an oriented polyether resin material of the present invention is as follows:
This method is characterized by melt-extruding a polyether resin at a temperature below the decomposition temperature of the resin without causing melt fracture, and cooling the melt-extruded state while drafting at a draft ratio of 50 or more.

・ = 1 In this invention, the polyether resin is a linear molecule containing an ether bond in the main chain, and is a polyether containing a homopolymer or copolymer consisting of a single unit having such an ether bond. In addition to this, the composition includes a composition containing at least one of these polyethers in an amount of 70% by weight or more and other resins that can be mixed and molded. Typically, polyoxymethylene, polyacetaldehyde, polyethylene oxide, polypropylene oxide, polycyclooxabutane, 3,3-dichloromethyloxacyclobutane, etc. are used.

The oriented polyether resin of the present invention has a melting curve determined by a differential scanning calorimeter (DSC) at a temperature increase rate of 8°C/min, which changes from its molten state at a cooling rate of 8°C/min. It is characterized by having a crystal melting point that is at least 7° C. higher than the crystal melting point in the melting curve when it is cooled and then heated again at the above temperature increase rate. Here, the crystal melting point refers to the temperature at which a melting endothermic peak occurs.

Taking polyoxymethylene as an example, conventionally known polyoxymethylene has a crystalline melting point of 159°C. A molded article having such properties of polyoxymethylene itself cannot satisfy the requirements for strength and transparency targeted by the present invention. On the other hand, the oriented polyoxymethylene that achieves the object of the present invention is, for example, 16
It has another crystalline melting point around 9°C. This crystal melting point is based on a unique structure caused by an orientation that is not observed when the temperature is raised again after melting and cooling under the conditions described above (that is, the original melting curve of the resin). This crystal melting point varies depending on the type of main resin that makes up the polyether resin, but it must be 7°C or more higher than the crystal melting point that is observed even when the temperature is raised again after melting and cooling under the conditions described in 2. is necessary.

Another feature of the oriented polyether resin of the present invention is that it has a birefringence of 35 X I O-'' or more. X 10-3"-1 or more preferably 60
It is formed in a state of 10-3 or more. As described above, one of the main characteristics of the oriented polyether resin of the present invention is that it is highly oriented, but its shape is not limited to films and threads, but is highly uniaxial, such as tube-shaped objects. It may be a general oriented molded body.

Such an oriented polyether resin product is preferably produced according to the method of the present invention as follows.

If the melt viscosity of the raw polyether resin is too high, melt fracture will occur and uniform molding will not be possible, but if the melt viscosity is too low, orientation relaxation will occur after drafting, making it difficult to obtain the desired product. If the melt viscosity is low to some extent, it is possible to use a material with a relatively low melt viscosity if the material is rapidly cooled to such an extent that orientation relaxation is difficult to occur after drafting, but there is a limit to cooling unless it is a thin material such as a thread or film. From this point of view, it is preferable to use a polyether resin having a mel index in the range of 0.02 g/min to 5 g/min, more preferably 0.05 g/min to 3 g/min.

The upper limit of the resin temperature when melt-extruding the polyether resin is the decomposition temperature of the resin. The decomposition temperature mainly depends on the type of resin,
It cannot be determined uniformly because it varies depending on polymerization conditions, compounding recipe, molding residence time, etc. Further, the lower limit of the resin temperature is determined by the degree of sliding that does not cause melt fracture. As is well known, melt fracture is affected by the melt viscosity and flow rate of the resin, and therefore the lower limit of the resin temperature is not strictly defined.

- For example, in the case of polyoxymethylene, generally:
A temperature range of 170°C to 260°C, particularly 200 to 240''C, is preferably used.

For such melt extrusion, known methods such as the T-Guy method and the inflation method are adopted. As mentioned above, the main feature is cooling while drafting.

Here, the trough i ratio refers to the ratio S 2 /S 1 of the drawing line speed (S2) to the extrusion line speed (Sl). The higher the draft rate, the better it is, preferably 100 or more.
”-1, preferably 300 or more, particularly preferably 50
0 or more is used.

Furthermore, when the obtained oriented material is a film or thread, the thickness (thickness or thickness) is 50 gm or less, preferably 1 to 20 gm.
It is desirable to select the draft rate so that it becomes km, more preferably 2 to lopLm.

Immediately after extrusion, a molded product, particularly a film or thread, with excellent transparency can be obtained by cooling as quickly as possible, preferably by forced air cooling, while applying a draft.

The oriented polyether of the present invention thus obtained has a thickness of, for example, 311 mm. When formed as a film having a wavelength of 500 mK, the film has a transparency of 70% or more, more preferably 75% or more.

As mentioned above, according to the present invention, an oriented molded product of polyether resin having high strength and toughness without surface irregularities or internal microvoids can be obtained. Further, the oriented polyether resin of the present invention has excellent transparency, with no spherulites observed when observed with an optical microscope or an electron microscope. Because it has such characteristics, it can be widely used as an industrial material, and is particularly suitable for use as a film for capacitors with improved voltage resistance characteristics.

Round lid 1 Polyoxymethylene (melt index Ig/min) is extruded in three directions from a 35φ extruder equipped with an inflation tie (diameter 30mmφ, lip clearance 2mm) at a stick temperature of 230°C and an extrusion speed of 60g/min. did. While drafting this extruded tube at a draft rate of 800, cold air was blown through an air ring attached at a position 5 cm from the second part of the die to cool and solidify it. The tube diameter of the tubular film at this time is approximately 30 mm.
φ, the film thickness was 2 to 3 pm, it was largely oriented in the -axis direction, and the birefringence was 64×10 −3 .

The melting curve of this film determined by DSC at a heating rate of 8° C./min is shown in FIG. 1(a), and the remelting curve after crystallization at the same heating rate is shown in FIG. 1(b). Note that the intermediate crystallization was performed at a cooling rate of 8° C./min. The stress-strain curve of this film is shown as curve A in FIG. According to this, the tensile strength at break in the orientation direction is 15 kg/mm2. The elongation at break (strain) is 45%, and the Young's modulus is 530 kg/
m m 26 [111 constant conditions are test length Loom
m, tensile speed 100 mm/min, and room temperature.

Furthermore, no microvoids were observed by small-angle X-ray scattering.
Under a microscope, the surface of the film was found to be extremely smooth, and the light transmittance was 80% at a wavelength of 500 m.

Comparison 1 When extruded under the same conditions as in Example and drafted at a draft rate of about 20, a film with a thickness of about 100 gm was obtained. This film was white and opaque.

The stress-strain curve of this film was as shown by curve B in FIG.

Comparing curves A and B in Figure 2, the film according to the present invention has significantly improved not only the breaking strength but also the toughness (i.e., the product of stress and strain up to breakage) compared to the conventional film. I know that there is.

[Brief explanation of the drawing]

FIG. 1(a) is a DSC melting curve of the example, and FIG. 1(b) is a remelting curve after crystallization. Also, fiS
Figure 2 shows the stress-strain characteristic measurement results of various films, and curves A and B are stress-strain curves for the films of Examples and Comparative Examples, respectively.

Claims (1)

[Claims] 1. An oriented polyether resin material having the following properties (a), 8 and (b). (b) The melting curve obtained using a differential scanning calorimeter at a temperature rate of 8°C/min shows that the temperature is cooled from the molten state at a cooling rate of 8°C/min, and then raised again at a temperature rate of 8°C/min. The crystal melting point must be at least 7°C higher than the crystal melting point in the melting curve when heated, and (b) the birefringence must be 35 x 10-'' or higher. 2. Polyether-based A method for producing an oriented polyether resin product, which comprises melt-extruding a resin at a temperature below the decomposition temperature of the resin without causing melt fracture, and cooling the melt-extruded state while drafting at a draft rate of 50 or more. .