Heat-treating method of a thermoplastic resin film

Abstract: A thermoplastic resin film (17) is preheated as the temperature T is changed to at a temperature of Tg < T < m.p.-10 °C, and absolutely contacted with a belt (14) by being pressed at a linear pressure of 9.8N/cm -980.0N/cm (Tg: a glass transition temperature of the thermoplastic resin film, m.p.: a melting point of the thermoplastic resin film). Next, the thermoplastic resin film is heated as the temperature T is changed to at a temperature of m.p.-20 °C < T < m.p.+20 °C while being absolutely contacted with the belt, and successively, the thermoplastic resin film is cooled while being absolutely contacted with the belt, and then the thermoplastic resin film is peeled from the belt.

Description: This invention relates to a heat-treating method of a thermoplastic resin film, in which a produced film can be used for structural materials, materials for electronic components and so on. After a thermoplastic resin film is conducted with, for example, simultaneous biaxial orientation, the oriented film is removed with residual stress caused by deformation of the orientation by being heat-treated. In a conventionally typical heat-treating method, the film is moved while both ends of the film in a direction transverse to the longitudinal direction are fixed in a heating-atmosphere. According to the aforementioned heat-treating method, however, a stress easily concentrates in parts, especially, the stress concentrates in a part where a fish eye, a gel or the like is produced on the film, so that the film is ripped sometimes. Provided that the film is heat-treated at an approximate melting point, the film has a thermal deformation, resulting in a disadvantage that the heat-treatment at an approximate melting point cannot be carried out. Japanese Patent Application Laid-open No. Sho59-178223 proposes a method, in which an oriented thermoplastic film, having an adherent layer on the surface thereof, undergoes annealing while being attached through the adherent layer on a support plate made by stainless steel. According to the aforementioned heat-treating method, the film is attached on the support plate by way of the adherent layer, so that the film is prevented from rip caused by the concentrated stress, however, another disadvantage is produced. That is to say, in order to attach the film on the support plate, the film should be formed with the adherent layer, resulting in necessity of a forming process for the adherent layer. The film should be forcibly peeled from the support plate after the heat-treatment, resulting in difficulty in carrying out processes successively. And further, some types of the films are fused to the support plate made of stainless steel, resulting in impossibility of the successive processes. Accordingly, in a first aspect, the present invention consists in a heat-treating method of a thermoplastic resin film, comprising the steps of: preheating the thermoplastic resin film as the temperature T is changed to a temperature of Tg<T<m.p.-10°C and contacting and pressing the thermoplastic resin film with an endless belt at a linear pressure of between 9.8N/cm and 980.0N/cm (Tg: a glass transition temperature of the thermoplastic resin film, m.p.: a melting point of the thermoplastic resin film); heating the thermoplastic resin film as the temperature T is changed to a temperature of m.p.-20°C<T<m.p.+20°C while the thermoplastic resin film is in contact with the belt; cooling the thermoplastic resin film while in contact with the belt; and peeling the thermoplastic resin film from the belt. When the temperature T for preheating the thermoplastic resin film is lower than Tg, the contact of the film with the belt is inferior, with the result that the heat-treating temperature of the film becomes uneven. When the temperature T is higher than m.p.-10°C, the film contacted with the belt is easily deformed, with the result that the accuracy of the thickness of the film is inferior, and furthermore, the film is easily cut or ripped by heating. The preferred temperature is Tg+10°C<T<m.p.-20°C. When the thermoplastic resin film is pressed at a linear pressure of less than 9.8N/cm, it is possible to gulp air between the belt and the film. Further, when the linear pressure is more than 980.0N/cm, it is possible that the film might be deformed or cut. The preferred linear pressure is defined as from 98-0N/cm to 490.0N/cm. When the temperature T for heating the thermoplastic resin film is lower than m.p.-20°C, effects of the heat-treatment according to the present invention cannot be sufficiently obtained. When the temperature T is higher than m.p.+20°C, the resin becomes flowable in the heat-treatment, resulting in inferior accuracy ofthe thickness of the film. Preferably, the belt may be coated with a polyimide resin. The thickness of the polyimide resin coated on the belt is selective, and more preferably 1µm-1000µm. When the thickness is less than 1µm, durability of the coated polyimide resin is inferior. When the thickness is greater than 1000µm, the expensive polyimide resin causes the high cost. The peeling properties of the thermoplastic resin film from the belt are improved by the polyimide resin. In the present invention, it is advisable that the processing steps for contacting the thermoplastic resin film with the belt by preheating, heating the thermoplastic resin film, and peeling the thermoplastic resin film from the belt are carried out at different locations from one another but are successively carried out by way of the belt. That is to say, places where the aforementioned three processes are carried out are defined as three places, the belt on which the thermoplastic resin film is contacted is circulated among the three places, thereby the successive heat-treatment according to the present invention is allowed. In a second aspect, the invention consists in apparatus for heat-treating a thermoplastic resin film comprising: a first roller for preheating the film, a second roller for heating the film, a third roller for cooling the film, a metallic endless belt coated with a polyimide resin being wound around the first, second and third rollers, and a fourth roller located to urge the thermoplastic resin film to the first roller through the endless belt, so that the thermoplastic resin film is guided between the endless belt and the fourth roller to be preheated while the temperature T is maintained at Tg<T<m.p.-10°C while in contact with the belt by being pressed by the fourth roller at a linear pressure of between 9.8N/cm and 980-0N/cm, the thermoplastic resin film being moved to and heated by the second roller as the temperature T is maintained at m.p.-20°C<T<m.p.+20°C while in contact with the belt, and the thermoplastic resin film then moved to and cooled by the third roller while in contact with the belt and subsequently peeled from the belt. The material of the aforementioned metallic endless belt can be, for example, stainless steel, titanium alloy or the like. The thickness of the endless belt is selective, but 0.3mm - 1.5mm is preferable, more preferably 0.5mm - 0.8 mm. If the belt is thinner than 0.3mm, durability ofthe belt becomes inferior by decreasing the strength of the belt. If the belt is thicker than 1.5mm, the efficiency of heating and cooling becomes inferior, with the result that cost for producing is increased, furthermore, the size of the apparatus is larger by increasing the diameters of the rollers around which the belt is wound. The conditions of the thickness of the polyimide resin coated on the metallic endless belt has been described above. It is advisable that the material of at least the surface of the fourth roller is heat-resistant resin, for example, silicone rubber, in order to prevent gulping air between the endless belt and the thermoplastic resin film. As a thermoplastic resin of the aforementioned film, for example, the following can be used: polyethylene, polypropylene, polyvinyl chloride, polyvinyl alcohol, polyethylene terephthalate, polyarylate, polyethylene-2,6-naphthalate, polyethylene-α,β bis (2-clorophenoxy-4,4'-dicarboxylate), polyphenylene oxide, polyester, polyphenylene sulfide, polyether etherketone, aromatic polyamides, polyarylate, polyimide, polyamideimide, polyetherimide, syndiolactic polystyrene, biphenyl etherketone and so on. Incidentally, the apparatus may have at least three rollers (the first roller to the third roller), but can have, for example, a fourth roller as necessary. In the present invention, the thermoplastic resin film is used, but things called as a sheet can be conceptually included because the sheet differs in only relative thickness from the film. In the accompanying drawings: Fig. 1 is a diagrammatic view of a heat-treating apparatus used in a heat-treating method of a thermoplastic resin film according to a preferred embodiment of the present invention. A heat-treating method of a thermoplastic resin film according to the preferred embodiment of the present invention will be explained below with reference to Fig. 1. First, a structure of a heat-treating apparatus used in the embodiment will be described. The heat-treating apparatus is composed of first, second and third rollers 11, 12 and 13, a metallic endless belt 14 wound around the three rollers 11 to 13, a fourth roller 15 abutting through the endless belt 14 to the first roller 11, and a fifth roller 16 abutting through the endless belt 14 to the third roller 13. In turn, the first roller 11 is for preheating the thermoplastic resin film 17, which has a heating means (not shown) for controlling the temperature of the first roller 11 at the range of 100°C-400°C. The second roller 12 is for heating the thermoplastic resin film 17, which has a heating means (not shown) for controlling the temperature of the second roller 12 at the range of 100°C-400°C. The third roller 13 is for cooling the thermoplastic resin film 17, which has a cooling means (not shown) for controlling the temperature of the third roller 13 at the range of 30°C-200°C. At least one of the aforementioned first to third rollers 11 to 13 is connected to a driving means for rotating the roller. The fourth roller 15 is covered with a silicone rubber 18 along the outer circumerefential face thereof. The fourth roller 15 is located to urge the thermoplastic resin film 17 to the first roller 11 through the endless belt 14. The pressing force is a linear pressure of 9.8N/cm - 980.0N/cm. The endless belt 14 is made of stainless steel. The thickness of the endless belt 14 is 0.3mm - 1.5mm. A polyimide resin is coated in strata on the surface of the metallic endless belt 14, on which the layer of the polyimide resin is 1µm - 100µm. The polyimide resin can be coated by selective means. For example, after the polyimide acid solution is coated on the endless belt 14, the solvent is removed with heating and drying and the inversion of imids is carried out. In the coating process, in order to avoid forming void caused by vaporizing water, emitted by a ring closure reaction, and the like, it is advisable to dry in stages, in which the inversion of imids is carried out by heating at 250 °C - 400 °C for 20 minutes - 60 minutes after the solvent is removed with heating at 80 °C - 180 °C for 20 minutes - 60 minutes to be dried. Next, the heat-treating method of the thermoplastic resin film 17 used in the heat-treating apparatus will be described below. As shown in Fig. 1, with guiding the thermoplastic resin film 17 into between the endless belt 14 and the fourth roller 15, the thermoplastic resin film 17 is preheated by the first roller 11 as the temperature T becomes a temperature of Tg < T < m.p.-10 °C, and absolutely contacted with the endless belt 14 by being pressed by the fourth roller 15 at a linear pressure of 9.8N/cm - 980.0N/cm. Here, Tg is a glass transition temperature of the thermoplastic resin film 17 and m.p. is a melting point of the thermoplastic resin film 17. And further, the thermoplastic resin film 17 is moved to the second roller 12 with moving the endless belt 14 while being absolutely contacted with the endless belt 14, and the thermoplastic resin film 17 is heated by the second roller 12 as the temperature T is changed to at a temperature of m.p.-20 °C < T < m.p.+20°C. Successively, the thermoplastic resin film 17 is moved to the third roller 13 with moving the endless belt 14 while being absolutely contacted with the endless belt 14, and the thermoplastic resin film 17 is cooled by the third roller 13. After that, the thermoplastic resin film 17 absolutely contacted with the endless belt 14 is peeled from the endless belt 14, and the heat-treated thermoplastic resin film 17 is obtained. [EXPERIMENT 1] In the aforementioned embodiment, the thermoplastic resin film 17 is heat-treated under the following concrete conditions. The thermoplastic resin film ...... syndiotactic polystyrene (SPS) film of a homo-type. Thickness : 100µum, Tg : 100 °C, m.p. : 270 °C. Diameter of the first roller 600mm Diameter of the second roller...... 600mm Diameter of the third roller 600mm Diameter of the fourth roller...... 150mm Temperature of the first roller 180 °C Temperature of the second roller 270 °C Temperature of the third roller ..... 100 °C Thickness of the endless belt ......0.5mm Width of the endless belt ......500mm Thickness of the polyimide resin on the endless belt 30µm Linear pressure by the fourth roller ..... 200N/cm Moving speed of the endless belt .....2m/min. [EXPERIMENT 2] In Experiment 1, the thermoplastic resin film 17 is heat-treated under the conditions of which a part of the conditions are changed as the following and the rest of the conditions are the same. The thermoplastic resin film polyether etherketone (PEEK) film. Thickness : 100µm, Tg: 143 °C, m.p. 334 °C. Temperature of the first roller 200 °C Temperature of the second roller 330 °C [EXPERIMENT 3] In Experiment 1, the thermoplastic resin film 17 is heat-treated under the conditions of which a part of the conditions are changed as the following and the rest of the conditions are the same. The thermoplastic resin film ...... polyarylate (PAR) film. Thickness : 100µm, Tg : 143 °C, m.p. 280 °C. Temperature of the first roller 180 °C Temperature of the second roller 280 °C [EXPERIMENT 4] In Experiment 1, the thermoplastic resin film 17 is heat-treated under the conditions of which a part of the conditions are changed as the following and the rest of the conditions are the same. The thermoplastic resin film ...... polyarylate (PAR) film. Thickness : 100µm, Tg : 143 °C, m.p. : 280 °C. Temperature of the first roller...... 180 °C Temperature of the second roller 270 °C [COMPARISON 1] In Experiment 1, the thermoplastic resin film is heat-treated under the same conditions except the use of a belt, which is not coated with a polyimide resin (PI), as the metallic endless belt. [COMPARISON 2] The thermoplastic resin film is heat-treated by using a conventional heat-treating method, which is carried out by moving the film in a heating-atmosphere (280 °C) while both ends of the film in a direction transverse of the longitudinal direction are fixed. [COMPARISON 3] In Experiment 1, the thermoplastic resin film is heat-treated under the same conditions except 90 °C of the temperature of the first roller. [COMPARISON 4] In Experiment 1, the thermoplastic resin film is heat-treated under the same conditions except 270 °C of the temperature of the first roller. [COMPARISON 5] In Experiment 1, the thermoplastic resin film is heat-treated under the same conditions except 240 °C of the temperature of the second roller. [COMPARISON 6] In Experiment 1, the thermoplastic resin film is heat-treated under the same conditions except 300 °C of the temperature of the second roller. [COMPARISON 7] In Experiment 1, the thermoplastic resin film is heat-treated under the same conditions except 270 °C of the temperature of the second roller, and the linear pressure of 5.0N/cm when the thermoplastic resin film is pressed by the fourth roller. [COMPARISON 8] In Experiment 1, the thermoplastic resin film is heat-treated under the same conditions except 270 °C of the temperature of the second roller, and the linear pressure of 1000.0N/cm when the thermoplastic resin film is pressed by the fourth roller. [COMPARISON 9] In Experiment 3, the thermoplastic resin film is heat-treated under the same conditions except 240 °C of the temperature of the second roller. As to the films heat-treated and obtained in the aforementioned experiments and comparisons, the following items of 1 ○to 6 ○ are evaluated. The results are shown in Tables 1 and 2. The following is the description of each item of the evaluation and the criterion of evaluation. As to the films obtained in Experiment 3 and Comparison 9, the surface peeling properties is evaluated. The results are shown in Table 3. 1 ○ the film is cut or not in the heat-treatment. O .... not cut. × .... cut. 2 ○ the film has a thermal deformation in the heat-treatment. O .... non-appearance of the thermal deformation. × .... impracticality of the heat-treatment because of the thermal deformation. 3 ○ the film is absolutely contacted with the endless belt or not after the heat-treatment. ○ .... non absolute contact. × .... the film is hardly peeled from the endless belt by being absolutely contacted. 4 ○ the film is ripped or not after the heat-treatment. O ... non-rip. × .... rip. 5 ○ the accuracy of the thickness of the film after the heat-treatment. O .... within ±8 %. × .... more than ±8 %. 6 ○the change of the physical properties of the film after the heat-treatment. O .... the physical properties are changed and the effects of the heat-treatment are produced. × .... the physical properties are not changed and the effects of the heat-treatment are not produced or the physical properties are changed but the effects of the heat-treatment are unevenly produced. The aforementioned surface peeling properties is evaluated by determining whether the surface peeling is produced or not by way of lightly rubbing the surface of the film with sandpaper. 1 ○ 2 ○ 3 ○ 4 ○ 5 ○ 6 ○ Experiment 1 the invention SPS 180°C 270°C ○ ○ ○ ○ ○ ○ Experiment 2 the invention PEEK 200°C 330°C ○ ○ ○ ○ ○ ○ Experiment 3 the invention PAR 180°C 280°C ○ ○ ○ ○ ○ ○ Experiment 4 the invention SPS 180°C 270°C ○ ○ ○ ○ ○ ○ 1 ○ 2 ○ 3 ○ 4 ○ 5 ○ 6 ○ Comparison 1 non-PI SPS 180 °C 270 °C × O × × O O Comparison 2 a conventional method SPS 180 °C 270 °C - × - - - - Comparison 3 the invention SPS 90°C 270°C O O O O O × Comparison 4 the invention SPS 270 °C 270 °C × ○ ○ × × ○ Comparison 5 the invention SPS 180°C 240°C ○ ○ ○ ○ ○ × Comparison 6 the invention SPS 180 °C 300 °C ○ ○ ○ ○ × ○ Comparison 7 the invention SPS 180 °C 270 °C ○ ○ ○ ○ × ○ Comparison 8 the invention SPS 180 °C 270 °C ○ ○ ○ × × ○ the surface peeling Experiment 3 No Comparison 9 Yes From Table 1, according to the heat-treating method of the thermoplastic resin of each experiment, with the use of the metallic endless belt 14 coated with the polyimide resin, the thermoplastic resin film 17 is preheated by the first roller 11 as the temperature T becomes a temperature of Tg < T < m.p.-10 °C, the thermoplastic resin film 17 is absolutely contacted with the endless belt 14 by being pressed by the fourth roller 15 at a linear pressure of 9.8N/cm - 980.0N/cm, and then the thermoplastic resin film 17 is heated by the second roller 12 as the temperature T is changed to at a temperature of m.p.-20 °C < T < m.p.+20 °C, therefore any disadvantage as to items 1 ○ to 6 ○ of the evaluation is not produced, namely it is understood that the result of the items of the evaluation is fine. From Table 2, according to Comparison 1, by using the belt which is not coated with the polyimide resin, it is understood that disadvantages are produced in items 1 ○, 3 ○ and 4 ○ of the evaluation. According to Comparison 2, the film has the thermal deformation in the heat-treatment in consequence of the conventional heat-treating method, with the result that the heat-treated film cannot be obtained. According to Comparison 3, from the reason that the temperature T heated in the first roller is lower than Tg (100 °C), a disadvantage is produced in item 6 ○. According to Comparison 4, from the reason that the temperature T heated in the first roller is higher than m.p. -10 °C (260 °C ), disadvantages are produced in items 1 ○, 4 ○ and 5 ○. According to Comparison 5, from the reason that the temperature T heated in the second roller is lower than m.p. -20 °C (250 °C ), a disadvantage is produced in item 6 ○. According to Comparison 6, from the reason that the temperature T heated in the second roller is higher than m.p. +20 °C (290 °C ), a disadvantage is produced in item 5 ○. According to Comparison 7, from the reason that the linear pressure is less than 9.8N/cm when the thermoplastic resin film is pressed by the fourth roller, a disadvantage is produced in item 5 ○. According to Comparison 8, from the reason that the linear pressure is more than 980.0N/cm when the thermoplastic resin film is pressed by the fourth roller, disadvantages are produced in items 4 ○ and 5 ○. From Table 3, according to Experiment 3, resin of the thermoplastic resin film is, especially, mesomorphism polymer, so that it is understood that effect of preventing the film from peeling by the heat-treatment according to the present invention. But, according to Comparison 9, although resin of the thermoplastic resin film is mesomorphism polymer, the temperature T heated by the second roller is lower than m.p.-20°C (260°C), with the result the surface peeling is produced in the test for the surface peeling.

Claims: A heat-treating method of a thermoplastic resin film (17), comprising the steps of: preheating the thermoplastic resin film (17) as the temperature T is changed to a temperature of Tg<T<m.p.-10°C and contacting and pressing the thermoplastic resin film with an endless belt (14) at a linear pressure of between 9.8N/cm and 980.0N/cm (Tg: a glass transition temperature of the thermoplastic resin film, m.p.: a melting point of the thermoplastic resin film); heating the thermoplastic resin film (17) as the temperature T is changed to a temperature of m.p.-20°C<T<m.p.+20°C while the thermoplastic resin film is in contact with the belt (14); cooling the thermoplastic resin film while in contact with the belt (14); and peeling the thermoplastic resin film from the belt. The heat-treating method according to claim 1, wherein the thermoplastic resin film (17) is contacted with the belt (14) by being pressed at a linear pressure of between 98.0N/cm to 490.0N/cm. The heat-treating method according to claim 1 or claim 2, wherein the thermoplastic resin film (17) is preheated as the temperature T is maintained at a temperature of Tg+10°C<T<m.p.-20°C. The heat-treating method according to any one of the preceding claims, wherein the belt (14) is coated with a polyimide resin. The heat-treating method according to claim 4, wherein the thickness of the polyimide resin coating on the belt is between 1µm and 1000µm. The heat-treating method according to any one of the preceding claims, wherein said processing steps for contacting the thermoplastic resin film (17) with the belt (14) by preheating, heating the thermoplastic resin film, and peeling the thermoplastic resin film from the belt are carried out at different locations from one another but are successively carried out by way of the belt. Apparatus for heat-treating a thermoplastic resin film (17) comprising: a first roller (11) for preheating the film, a second roller (12) for heating the film, a third roller (13) for cooling the film, a metallic endless belt (14) coated with a polyimide resin being wound around the first, second and third rollers, and a fourth roller (15) located to urge the thermoplastic resin film (17) to the first roller (11) through the endless belt (14), so that the thermoplastic resin film is guided between the endless belt (14) and the fourth roller (15) to be preheated while the temperature T is maintained at Tg<T<m.p.-10°C while in contact with the belt (14) by being pressed by the fourth roller (15) at a linear pressure of between 9.8N/cm and 980.0N/cm, the thermoplastic resin film (17) being moved to and heated by the second roller (12) as the temperature T is maintained at m.p.-20°C<T<m.p.+20°C while in contact with the belt (14), and the thermoplastic resin film (17) then moved to and cooled by the third roller (13) while in contact with the belt (14) and subsequently peeled from the belt. Apparatus as claimed in claim 7, wherein the thickness of the endless belt (14) is between 0.3mm and 1.5mm.

Inventors: FUJII ATSUSHI, FUNAKI AKIRA, MORIWAKI RYUJI, FUJII, ATSUSHI, FUNAKI, AKIRA, MORIWAKI, RYUJI
Applicants: IDEMITSU PETROCHEMICAL CO, IDEMITSU PETROCHEMICAL CO., LTD.
Application year: 1996
Main classification: B29C71
IPC codes: B29C71, B29C55, B29L7, B29C47