POLYCYANOARYL ETHER FILMS

Abstract: Polycyanoaryl ether stretched films and fibers prepared from polycyanoaryl ethers containing specific repeating units and number-average molecular weights or reduced viscosities by stretching molded films or melt-spinned fibers, said films and fibers having superior heat resistance and mechanical strength.

Description: This invention relates to a polycyanoaryl ether stretched or oriented film having superior heat resistance and mechanical strength. For electrical and electronic equipment, there have been widely employed films of those resins having superior heat resistance, mechanical strength or electric properties. Recently, as such equipment has been much more miniaturized and lightened, there is a need for more superior heat resistance and mechanical strength on the film materials to be applied. In order to meet such a need, stretched films of, e.g., aromatic polyesters have been hitherto employed in the art. However, such aromatic polyester oriented films would not be said to fully satisfy the above-depicted need as industrial films. Therefore, there is a need for a film with far higher heat resistance and mechanical strength. On the other hand, as application of various plastic materials has been recently broadened, there has become more serve a demand for properties of such materials, e.g., heat resistance or mechanical strength. Thus, it has been generally done to add a reinforcing fiber into plastic materials for providing a higher mechanical strength. As the reinforcing fiber, there have been employed a wide variety of fibers composed of, e.g., any inorganic material or synthetic resin. However, those inorganic fibers are difficult to be produced in a large scale and at a low cost owing to many steps required for the manufacture thereof, while those synthetic resin fibers present the problem that heat resistance and mechanical strength of the fiber itself are not necessarily satisfactory, though manufactured readily. Therefore, there is also a need for a reinforcing fiber composed of a synthetic resin with far higher heat resistance and mechanical strength. EP-A-0 121 257 describes a crystalline polyarylnitrile polymer having repeating units of the following formula: wherein A is independently selected from hydrogen, alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 4 carbon atoms and halogen, a is an integer of 1 or 2 and b is an integer of 1 to 3 and wherein the polyarylnitrile polymer has a reduced viscosity of at least 0.3 dl/g as measured in p-chlorophenol at 50°C. For meeting the aforesaid need in the art, this invention provides a stretched film with superior heat resistance and mechanical strength, which can be made of a polycyanoaryl ether having specific chemical structure and properties. Therefore, it is an object of this invention to provide an oriented film of a polycyanoaryl ether having specific structure and properties, which is superior in heat resistance and mechanical strength. According to the present invention there is provided a polycyanoaryl ether stretched film which is characterized by comprising a molded film being composed of a polycyanoaryl ether containing not less than 50 molar % of a repeating unit represented by the formula and having a reduced viscosity of 0.60 - 1.10 dl/g at 60 °C in a solution of a concentration of 0.2 g/dl in p-chlorophenol, and having been stretched at a drawing ratio of not less than 1.5 times. The polycyanoaryl ether used according to the present invention is a copolymer containing the repeating unit (I' ) and further less than 50 molar % of at least one of the repeating units represented by the formula wherein Ar' is a divalent aryl group other than As examples of the Ar', there may be mentioned, for instance, This polycyanoaryl ether has a molecular weight corresponding to a reduced viscosity [η sp/c] of 0.60 - 1.10 dl/g as measured at 60 o C when the ether is dissolved in p-chlorophenol at a concentration of 0.2 g/dl. If the reduced viscosity is less than 0.60 dl/g, both heat resistance and mechanical strength are insufficient, while such a polymer is melt-molded to a film to produce a brittle molded film, which is difficult to be stretched as disclosed below. If the reduced viscosity is more than 1.10 dl/g, film-forming becomes difficult and a uniform film could not be prepared. Modification of a molecular weight or reduced viscosity may be conducted by setting reaction parameters including temperature and period in the polymerization reaction to given figures or by adding a given amount of a molecular weight modifier. As the molecular weight modifiers which may be employed in the latter case, there may be desirably employed wherein R and X are as defined above. In the above polycyanoaryl ether, the repeating units (I') may be located straight or the both repeating units (I') and (II') may be located randomly or regularly straight in combination therewith and a terminal group thereof is blocked by, e.g., -H, -X, wherein R and X are as defined above. The above polycyanoaryl ether may be readily prepared according to a conventional method, for instance, by reacting a dihalogenobenzonitrile with an alkali metal salt of a dihydroxynaphthalene having the formula wherein M is an alkali metal and, where necessary, an alkali metal salt of any other dihydric phenol in the presence of a suitable solvent and then treating with water or an alcohol. As examples of the compound (IV), there may be mentioned, e.g., an alkali metal salt of 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene or 2,7-dihydroxynaphthalene and one or more of the compounds (IV) may be optionally applied to the reaction. The polycyanoaryl ether stretched film of this invention is prepared by orientation of a molded film made of the above polycyanoaryl ether. More specifically, the polycyanoaryl ether is first molded to a film form. This step may be carried out according to a conventional method, e.g., hot press or melt extrusion. A molding temperature is not critical, but usually 360 - 420 o C, preferably 380 - 410 o C. Then, the resultant molded film is subjected to orientation. In this step, there may be applied any of monoaxial orientation, simultaneous biaxial orientation and biaxial orientation after monoaxial orientation. In this invention, it is essential in any of the above orientations that a drawing ratio should be not less than 1.5 times. Namely, in the case of monoaxial orientation, a length ratio to oriented direction should be 1.5 times or higher, while an area ratio should be not less than 1.5 times in the case of biaxial orientation. If less than 1.5 times, a sufficient mechanical strength could not be undesirably provided in the resultant stretched film. The drawing ratio is preferably 3 - 6 times. A drawing temperature is usually approximately 220 - 280 o C, preferably 240 - 270 o C. Moreover, it is preferable that the resultant oriented film may be stabilized by thermal fixing. Thermal fixing may be desirably effected by keeping the stretched film under tension at a temperature higher than the stretching temperature applied and lower than a melting point of the film applied, e.g., 280 - 340 o C for 1 second to 10 minutes. This invention is further illustrated by way of the following Reference Example, Examples, Comparative Examples and Control Examples. Example 1 Into an autoclave having an inner volume of 5 liters and stirring means were placed 397 g (2.48 moles) of 2,7-dihydroxynaphthalene, 430 g (2.5 moles) of 2,6-dichlorobenzonitrile, 414 g (3.0 moles) of potassium carbonate, 2.5 liters of sulfolane, and 1.5 liters of toluene and reaction was carried out at 160 o C for 1.5 hours and then at 200 o C for further 1.5 hours under argon stream. After completion of the polymerization reaction, a large volume of water was added to the reaction mixture, thereby separating a granular polymer. the resultant polymer was recovered and washed three times with 3 liters of hot water and once with 3 liters of methanol to produce a polycyanoaryl ether having 100 % of a repeating unit of the formula 618 g (yield, 96 %) The resultant polymer was measured for its reduced viscosity [η sp/c] in a 0.2 g/dl solution in p-chlorophenol at 60 o C. The results are summarized in the following Table 1. Also, the polymer was confirmed to have thermal properties, namely, a glass transition temperature of 215 o C, a melting point of 345 o C and a thermal decomposition-starting temperature (in atmosphere) of 505 o C so that it possesses a practically acceptable heat resistance. Then, the polymer showed such solvent resistance as insolubility in solvents, i.e., acetone, ethanol, toluene, methylene chloride, and chloroform. The polymer was pelleted by melt extrusion and the resultant pellet after vacuum dried was press-molded to form a transparent film with 120 mm x 120 mm and a thickness of 0.3 mm. The resultant film was simultaneously subjected to biaxial orientation so that a drawing ratio was three times in both longitudinal and lateral directions. Subsequently, the stretched film was thermally fixed by keeping at 300 o C for 1 minute under tension. The resulting film was measured for mechanical properties, namely, breaking strength, elongation and modulus of elasticity. The results are also summarized in the following Table 1. Examples 2 - 4 and Comparative Example 1 Following the same procedured as in Example 1 except that various reaction times were employed at 200 o C, there were prepared polycyanoaryl ethers having reduced viscosity as indicated in the following Table 1. Then, stretched films were formed from the ethers in the same manner as in Example 1 except that drawing ratios were as indicated in the following Table 1. The resultant polymer showed good heat resistance, flame retardancy and solvent resistance as seen in Example 1. Comparative Example 2 Following the same procedures as in Example 1 except that a mixture of 238.3 kg (1.49 moles) of 1,5-dihydroxynaphthalene and 184.5 g (0.99 mole) of 4,4'-biphenol was used instead of the 2,7-dihydroxynaphthalene (397 g), there was prepared a polycyanoaryl ether. The resultant ether contained 60 molar % of a repeating unit having the formula and 40 molar % of a repeating unit having the formula The resultant copolymer was confirmed to show thermal properties, namely, a glass transition temperature of 221 o C, a melting point of 302 o C, a thermal decomposition-starting temperature (in atmosphere) of 519 o C and possess a practically acceptable heat resistance. Then, a stretched film was formed from the copolymer in the same manner as in Example 1 except that a drawing ratio was two times in both longitudinal and lateral directions. The resulting film was measured for properties in the same manner as in Example 1 and similar results to those of Example 1 could be obtained with regard to solvent resistance and flame retardancy. Comparative Example 3 A polycyanoaryl ether having a reduced viscosity of 0.34 dl/g was prepared by employing a shortened polymerization time at 200 o C in Example 1. The polymer was formed into a press film in the same manner as in Example 1. The resultant film was subjected to biaxial orientation in the same manner as in Example 1; however, the film was so brittle as not to be stretched. Comparative Example 4 A polycyanoaryl ether having a reduced viscosity of 2.10 dl/g was prepared in the same manner as in Example 1 except that a more prolonged ploymerization time at 200 o C was employed than that in Example 1. The resultant film was press-molded in the same manner as in Example 1; however, a homogeneous film could not be obtained. Biaxial orientation of the film could not provide a uniform elongation and thus a practically inferior film could only be obtained. Reference Example 1 The press film as produced in Example 1 (not stretched) was measured for mechanical properties. The results are also summarized in the following Table 1.

Claims: A polycyanoaryl ether stretched film characterized by comprising a molded film being composed of a polycyanoaryl ether containing not less than 50 molar % of a repeating unit represented by the formula and having a reduced viscosity of 0.60 - 1.10 dl/g at 60 °C in a solution of a concentration of 0.2 g/dl in p-chlorophenol, and having been stretched at a drawing ratio of not less than 1.5 times. A polycyanoaryl ether stretched film as claimed in claim 1 characterized in that said polycyanoaryl ether is a copolymer containing said repeating unit (I') and less than 50 molar % of at least one of repeating units represented by the formula wherein Ar' is a divalent aryl group other than

Inventors: MATSUO, SHIGERU, MURAKAMI, TOMOYOSHI
Applicants: IDEMITSU KOSAN COMPANY LIMITED
Application year: 1986
Main classification: C08G65
IPC codes: D01F6, C08J5, C08G65