CA1036779A - Biaxially stretched film - Google Patents
Biaxially stretched filmInfo
- Publication number
- CA1036779A CA1036779A CA196,911A CA196911A CA1036779A CA 1036779 A CA1036779 A CA 1036779A CA 196911 A CA196911 A CA 196911A CA 1036779 A CA1036779 A CA 1036779A
- Authority
- CA
- Canada
- Prior art keywords
- polyester
- carboxyl group
- film
- group content
- biaxially stretched
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
- C08G63/16—Dicarboxylic acids and dihydroxy compounds
- C08G63/18—Dicarboxylic acids and dihydroxy compounds the acids or hydroxy compounds containing carbocyclic rings
- C08G63/181—Acids containing aromatic rings
- C08G63/185—Acids containing aromatic rings containing two or more aromatic rings
- C08G63/187—Acids containing aromatic rings containing two or more aromatic rings containing condensed aromatic rings
- C08G63/189—Acids containing aromatic rings containing two or more aromatic rings containing condensed aromatic rings containing a naphthalene ring
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
- H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
- H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
- H01B3/42—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes polyesters; polyethers; polyacetals
- H01B3/421—Polyesters
- H01B3/422—Linear saturated polyesters derived from dicarboxylic acids and dihydroxy compounds
- H01B3/423—Linear aromatic polyesters
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- Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
- Polyesters Or Polycarbonates (AREA)
- Organic Insulating Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A biaxially stretched film composed of a polyester at least 90 mol% of which recurring structural units consist of ethylene 2,6-naphthalate, said polyester having an intrinsice viscosity (7). as calculated from the value measured in o-chlorophenol at 35°C., of at least 0.40, and a carboxyl group content of not more than 30 equivalents/ton; and an electrically insulating material consisting essentially of aforesaid biaxially stretched film.
A biaxially stretched film composed of a polyester at least 90 mol% of which recurring structural units consist of ethylene 2,6-naphthalate, said polyester having an intrinsice viscosity (7). as calculated from the value measured in o-chlorophenol at 35°C., of at least 0.40, and a carboxyl group content of not more than 30 equivalents/ton; and an electrically insulating material consisting essentially of aforesaid biaxially stretched film.
Description
~036779 This invention relates to a biaxially stretched film consisting essentially of a l~ighly polymerized polyester at least 90 mol% of the re-curring units of which are composed of ethylene 2,6-naphtl~alate units, such polyester having a carboxyl group content of not more tl~an 30 cquivalents/
tOII, The invention also relates to a thermally sta~le material, especially an electrically insulatin~ material, consisting essentially of the above biaxially stretched film.
It has already been known that films composed of polyethylene
tOII, The invention also relates to a thermally sta~le material, especially an electrically insulatin~ material, consisting essentially of the above biaxially stretched film.
It has already been known that films composed of polyethylene
2,6-naphthalate (to be referred to as PEN) have superior heat-resistant pro-perties, and are suited, for example, for use as an electrically insulating material (see, for example, Belgian Patent No. 777,126).
We have now found that as compared with the known biaxiallyoriented films of ethylene 2,6-naphthalate polyester, biaxially oriented films composed of ethylene 2,6-naphthalate polyesters having a low carboxyl group content, especially a carboxyl group content not exceeding 30 equiva-lents/ton have very superior heat~resistant properties, for example, resis-tance to wet heat, resistance to dry heat, and resistance to oils or cooling media at an elevated temperature of, for example 80C. or above, and retain their superior properties even when allowed to stand for long periods of time in the wet state, in the dry state, or in oils or in an atmosphere of cooling media at an elevated temperatureO
The term "ethylene 2,6-naphthalate polyester", as used in the present specification and the appended claims, denotes not only a polyester 100 mol% of which recurring units are composed of ethylene 2,6-naphthalate ~i.e., polyethylene 2,6-naphthalate or PEN), but also a copolyester wherein not more than 10 mol%, preferably not more than 5 mol%, of the total recur-ring units are composed of a comonomer or modifier other than the ethylene 2,6-naphthalate, and a mixture of at least 90 mol%, preferabl~ at least 95 mol%, of PEN and not more than 10 mol%, preferably not more than 5 mol%, of - 1 - ~
another polyester. lV~9 In general, the polyethylene 2,6 naphthalate is prepared by reac-ting naphthalene-2,6^dicarboxylic acid or its functional derivative or deri-vatives ~ith ethylene glycol or its functional derivative or derivatives in the presence of a catalyst or catalysts. The reaction conditions and opera-ting procedures have been known in the art, and are disclosed, for example, in British Patent No. ~04,073 and United States Patent No. 3,161,710. When the copolyesters are to be prepared, one or more suitable comonomers or modifiers are added to the polymerization system before the completion of the reaction of forming the polyethylene 2,6-naphthalate, and then the polymeriz-ation is continued until the copolyestersare formed.
The comonomer or modifier may be a compound or compounds having a divalent ester-forming functional groupO Examples of this compound are dicarboxylic acids such as oxalic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-1,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, 4,4-diphenoxyethane dicarboxylic acid, succinic acid, diphenyl ether dicarboxylic acid and lower alkyl esters of these dicarboxylic acids; hydroxycarboxylic acids such as E~hydroxybenzoic acid and ~-hydroxyethoxybenzoic acid, and lower alkyl esters of these hydroxycarboxylic acids; and dihydric alcohols such as trimethylene glycol, tetramethylene glycol, hexamethylene glycol, or neopentyl glycol.
The polyethylene 2,6-naphthalate or its modified product may have terminal hydroxyl and/or carboxyl groups capped with a monofunctional compound or compounds such as benzoic acid, benzoyl benzoic acid, benzyloxybenzoic acid or methoxypolyalkylene glycols. There can also be used polyethylene 2,6-naphthalate polyesters modified with a very small amount of a polyfunctional compound or compounds such as glycerol and pentaerythritol to such an extent that the linearity of the polymer is not substantially lost.
The other polyesters used to form the PEN mixtures are, for ~3~77~
example, those derived from a dicarboxylic acid component selected from terephthalic acid, isophthalic acid, adipic acid, succinic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, 4,4-diphenoxyethane dicarboxylic acid, 4,4'-tetramethylene diphenyl dicarboxylic acid, and functional derivatives thereof and a glycol component selected from ethylene glycol, trimethylene ~lycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, and functional derivatives thereof. The functional deri-vatives may, for example, be lower alkyl esters of the carboxylic acids, as exemplified ~Yith respect to the polyethylene 2~6-naphthalate.
The ethylene 2~6-naphthalate polyester for making the biaxially stretched film of this invention should have (1) an intrinsic viscosity [n], calculated from the value measured in o-chlorophenol at 35C., of at least 0.40, preferably at least 0.45, (100 cc/g), and (2) a carboxyl group content of not more than 30 equivalents/ton, preferably not more than 25 equivalents/ton.
Those having a lower intrinsic viscosity than that specified above have too low degrees of polymerization, and reduced mechanical properties, and are naturally not preferred for use in the present invention.
So long as the polyester meets the above requirements (1) and (2), it may contain a delusterant such as titanium dioxide, a stabilizer or stabilizers such as phosphoric acid, phosphorous acid or an ester of any of these, a lubricant or lubricants such as finely divided silica or china clay, or other fillers.
The biaxially stretched film of this invention is characterized by being composed of the ethylene 2,6-naphthalate polyester having a low carboxyl group content. The carboxyl group content of the polyester can be measured by the method of A. Conix disclosed in Die Makromolekulare Chemie, Vol. 26, pages 226 et seq. (1958). Briefly stated, this method comprises i779 f.
dissolving the polyester in hot benzyl alcohol in an inert gas atmosphere, and titrating it with sodium hydroxide using Phenol Red. Therefore, the equivalents/ton of the polyester represent the equivalents of sodium hydroxide required to titrate every 106 grams (one ton) of the polymer.
This sho~s the concentration of the free carboxyl group present in the polyester.
The biaxially stretched film of this invention can be produced by forming a film of an ethylene 2,6-naphthalate polyester having a high degree of polymerization and a low carboxyl group content which fully meets the requirements of intrinsic viscosity (l) and carboxyl group content (2) described above, biaxially stretching the resulting polyester film, and if desired, further heat-treating the stretched film.
The conventional method for producing polyesters as mentioned above is not preferred for forming polyesters having such a high degree of polymerization and a low carboxyl group content, because such a conventional method generally requires high temperatures and relatively long periods of time in order to obtain highly polymerized polyesters. The polymerization reaction at high temperatures for a long period of time can result in an increase in the degrees of polymerization of the resulting polyester, but on the other hand, tends to cause an increase in the amount of the carboxyl end groups of the polyester.
Accordingly, in order to produce ethylene 2,6-naphthalate polyes-ters having a high degree of polymerization and a low carboxyl group content which are suitable for use in preparing the biaxially stretched films of this invention, the followirg methods are recommended.
For example, the polyester used in this invention can be prepared by the melt-polymerization process disclosed, for example, in United States Patents Nos. 3,433,770, 3,637,910, 3,714,125 and 3,787,370 in which a com-pound such as diphenyl carbonate or diphenyl oxalate is added to the polyester-forming reaction system described above. Alternatively, polyesters having a high degrees of polymerization and a relatively low carboxyl group content, as used in the present invention,can be synthesized by forming PEN
having a medium degree of polymerization by the melt-polymerization process, and then polymerizing the PEN in the solid state.
In this case too, a compound such as diphenyl carbonate or di-phenyl oxalate is preferably added to the polyester-forming reaction system in the molten state or the solid state.
Furthermore, ethylene 2,6-naphthalate polyesters prepared by methods known per sie may be treated~ in the form of chips or films, with an epoxy compound such as epoxidized glycerol or vinyl cyclohexene dioxide, or diazomethane, thereby to reduce the carboxyl group content of the polyesters to the values specified in the present invention.
In short, so long as the intrinsic viscosity and carboxyl group content as defined in this invention are completely satisfied, any ethylene 2,6-naphthalate polyesters can be used irrespective of the method of preparation.
The polyesters can be fabricated into biaxially oriented films by any desired method, but some preferred embodiments are cited below.
For example, the biaxially stretched film of this invention can be obtained by first preparing an unstretched film by drying the polyester at a temperature of 140C. to 220C., and then melt-extruding the dried polyester at a temperature of 280C. to 330C., preferably 285C. to 315C. The resul-ting unstretched film is stretched in the longitudinal direction at a ratio of about 3 to 5, preferably 3 to 4 at a temperature of about 120C. to 160C., preferably 135C. to 160C., and then in the transverse direction at ratio of about 3 to 5, preferably about 3 to 4, at a temperature of about 115C. to 150C., preferably 120C. to 140C., and then if desired, heat-treating the stretched film at a temperature of about 170C. to 240C.
10367~9 Alternatively, an unstretched tubular film of the polyester is stretched at a temperature of 125C. to 160C., preferably 130C. to 150C.
both in the longitudinal direction at a ratio of about 2.5 to about 5 and in the direction of the diameter of the tube at a ratio of about 2.5 to about 5, and then, if desired, the stretched film is heat-treated at a temperature of 170C. to 240C., thereby to obtain the biaxially stretched film of this invention.
The biaxially stretched film of this invention can be a '`shrink-able~ film if in the above-described procedures, the film is not heat-set after the stretching, or it is heat-set at a temperature above the stretching temperature but below 170C. after the stretching.
Depending upon the conditions described above, the film of this invention can ei~her be a thermally stable film or a shrinkable film. How-ever, irrespective of whether it is shrinkable or not, the film of this invention retains the superior properties for prolonged periods of time when exposed to heat in the dry or wet state, or to elevated temperatures in the presence of a cooling medium or oil, as will be described below.
As stated above, it is important that in the preparation of the biaxially stretched f;l~ of this invention, the ethylene 2,6-naphthalate p`Dlyester should be used which has an intrinsic viscosity, as defined hereinabove, of at least 0.40, preferably at least 0.45, and a carboxyl group content of not more than 30 equivalents/ton, preferably not more than 25 equivalents/ton.
In order to prevent the intrinsic viscosity from decreasing and/or the carboxyl group content from increasing, during the preparation of the unstretched film and/or during the heat-treatment of the stretched film, it is preferred to employ one or more of the following conditions.
(a) The starting polyester should be dried as sufficiently as possible.
(b) In the preparation of an unstretched film of the polyester, the melting and extrudirg temperatures of the polyester should be kept as low as possible.
(c) The extrusion of the polymer shou~l be carried out in an inert gas atmosphere, for example, a nitrogen gas.
(d) The residence time of the polyester in the molten state should be sh~rtened as much as possible.
By employing these conditions, it is possible to prepare a biaxially stretched film composed of the polyester having the intrinsic viscosity and the carboxyl group content as specified above.
The biaxially stretched films of this invention which have the high degrees of polymerization and low carboxyl group content as defined above retain superior properties, for example, high tensile strength and high elongation at break, as compared with biaxially oriented films composed of ethylene 2, & naphthalate polyesters having a carboxyl group content exceeding the upper limit specified in the present invention, when the films are sub-jected to the following conditions.
(i) When maintained in an atmosphere having a high moisture content and held at an elevated temperature (a wet heat atmosphere).
(ii) When maintained in a dry atmosphere held at an elevated temperature (a dry heat atmosphere).
(iii) When maintained in an atmosphere held at an elevated temperature in which a cooling medium gas such as a fluorohydrocarbon or fluorochlorohydrocarbon is present (an atmosphere of a cooling medium held at an elevated temperature).
(iv) When maintained in an atmosphere held at an elevated temper-ature in which an oil such as a lubricating oil, machine oil, or insulating oil is present (an atmosphere of an oil held at a high temperature).
Accordingly, the biaxially stretched films of this invention are 1036~79 superior as thermally stable materials, and find utility as decorative and other industrial materials which are to be subjected to coating, metallizing or other treatments at high temperatures.
In addition to these superior properties, the biaxially stretched films of this invention have high dielectric strergth, and therefore, are suitab`1e as insulating materials for electric appliances which are likely to come into contact with a cooling medium of, for example, refrigerators, or lubricating oils, machine oils, or insulating oils.
The following examples illustrate the present invention. It should be understood that these examples are only illustrative, and are not in any way intended to limit the present invention.
The various properties in the examples were measured by the follow-ing methods.
(a) Tensile Mechanical Properties Determined at 23C. in an atmosphere having a relative humidity of 65% using an Instron-type tensile tester under the following conditions.
Sample form: strip (15 cm x 1 cm) Chuck distance: 10 cm Pulling rate: 10 cm/min.
(b) Moisture Content of Polyester (1) A sample was taken out in an atmosphere of dry nitrogen.
(2) The sample was transferred to an oven of a moisture analyzer (Bell ~ Howell 26-321) placed in a dry box.
We have now found that as compared with the known biaxiallyoriented films of ethylene 2,6-naphthalate polyester, biaxially oriented films composed of ethylene 2,6-naphthalate polyesters having a low carboxyl group content, especially a carboxyl group content not exceeding 30 equiva-lents/ton have very superior heat~resistant properties, for example, resis-tance to wet heat, resistance to dry heat, and resistance to oils or cooling media at an elevated temperature of, for example 80C. or above, and retain their superior properties even when allowed to stand for long periods of time in the wet state, in the dry state, or in oils or in an atmosphere of cooling media at an elevated temperatureO
The term "ethylene 2,6-naphthalate polyester", as used in the present specification and the appended claims, denotes not only a polyester 100 mol% of which recurring units are composed of ethylene 2,6-naphthalate ~i.e., polyethylene 2,6-naphthalate or PEN), but also a copolyester wherein not more than 10 mol%, preferably not more than 5 mol%, of the total recur-ring units are composed of a comonomer or modifier other than the ethylene 2,6-naphthalate, and a mixture of at least 90 mol%, preferabl~ at least 95 mol%, of PEN and not more than 10 mol%, preferably not more than 5 mol%, of - 1 - ~
another polyester. lV~9 In general, the polyethylene 2,6 naphthalate is prepared by reac-ting naphthalene-2,6^dicarboxylic acid or its functional derivative or deri-vatives ~ith ethylene glycol or its functional derivative or derivatives in the presence of a catalyst or catalysts. The reaction conditions and opera-ting procedures have been known in the art, and are disclosed, for example, in British Patent No. ~04,073 and United States Patent No. 3,161,710. When the copolyesters are to be prepared, one or more suitable comonomers or modifiers are added to the polymerization system before the completion of the reaction of forming the polyethylene 2,6-naphthalate, and then the polymeriz-ation is continued until the copolyestersare formed.
The comonomer or modifier may be a compound or compounds having a divalent ester-forming functional groupO Examples of this compound are dicarboxylic acids such as oxalic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-1,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, 4,4-diphenoxyethane dicarboxylic acid, succinic acid, diphenyl ether dicarboxylic acid and lower alkyl esters of these dicarboxylic acids; hydroxycarboxylic acids such as E~hydroxybenzoic acid and ~-hydroxyethoxybenzoic acid, and lower alkyl esters of these hydroxycarboxylic acids; and dihydric alcohols such as trimethylene glycol, tetramethylene glycol, hexamethylene glycol, or neopentyl glycol.
The polyethylene 2,6-naphthalate or its modified product may have terminal hydroxyl and/or carboxyl groups capped with a monofunctional compound or compounds such as benzoic acid, benzoyl benzoic acid, benzyloxybenzoic acid or methoxypolyalkylene glycols. There can also be used polyethylene 2,6-naphthalate polyesters modified with a very small amount of a polyfunctional compound or compounds such as glycerol and pentaerythritol to such an extent that the linearity of the polymer is not substantially lost.
The other polyesters used to form the PEN mixtures are, for ~3~77~
example, those derived from a dicarboxylic acid component selected from terephthalic acid, isophthalic acid, adipic acid, succinic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, 4,4-diphenoxyethane dicarboxylic acid, 4,4'-tetramethylene diphenyl dicarboxylic acid, and functional derivatives thereof and a glycol component selected from ethylene glycol, trimethylene ~lycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, and functional derivatives thereof. The functional deri-vatives may, for example, be lower alkyl esters of the carboxylic acids, as exemplified ~Yith respect to the polyethylene 2~6-naphthalate.
The ethylene 2~6-naphthalate polyester for making the biaxially stretched film of this invention should have (1) an intrinsic viscosity [n], calculated from the value measured in o-chlorophenol at 35C., of at least 0.40, preferably at least 0.45, (100 cc/g), and (2) a carboxyl group content of not more than 30 equivalents/ton, preferably not more than 25 equivalents/ton.
Those having a lower intrinsic viscosity than that specified above have too low degrees of polymerization, and reduced mechanical properties, and are naturally not preferred for use in the present invention.
So long as the polyester meets the above requirements (1) and (2), it may contain a delusterant such as titanium dioxide, a stabilizer or stabilizers such as phosphoric acid, phosphorous acid or an ester of any of these, a lubricant or lubricants such as finely divided silica or china clay, or other fillers.
The biaxially stretched film of this invention is characterized by being composed of the ethylene 2,6-naphthalate polyester having a low carboxyl group content. The carboxyl group content of the polyester can be measured by the method of A. Conix disclosed in Die Makromolekulare Chemie, Vol. 26, pages 226 et seq. (1958). Briefly stated, this method comprises i779 f.
dissolving the polyester in hot benzyl alcohol in an inert gas atmosphere, and titrating it with sodium hydroxide using Phenol Red. Therefore, the equivalents/ton of the polyester represent the equivalents of sodium hydroxide required to titrate every 106 grams (one ton) of the polymer.
This sho~s the concentration of the free carboxyl group present in the polyester.
The biaxially stretched film of this invention can be produced by forming a film of an ethylene 2,6-naphthalate polyester having a high degree of polymerization and a low carboxyl group content which fully meets the requirements of intrinsic viscosity (l) and carboxyl group content (2) described above, biaxially stretching the resulting polyester film, and if desired, further heat-treating the stretched film.
The conventional method for producing polyesters as mentioned above is not preferred for forming polyesters having such a high degree of polymerization and a low carboxyl group content, because such a conventional method generally requires high temperatures and relatively long periods of time in order to obtain highly polymerized polyesters. The polymerization reaction at high temperatures for a long period of time can result in an increase in the degrees of polymerization of the resulting polyester, but on the other hand, tends to cause an increase in the amount of the carboxyl end groups of the polyester.
Accordingly, in order to produce ethylene 2,6-naphthalate polyes-ters having a high degree of polymerization and a low carboxyl group content which are suitable for use in preparing the biaxially stretched films of this invention, the followirg methods are recommended.
For example, the polyester used in this invention can be prepared by the melt-polymerization process disclosed, for example, in United States Patents Nos. 3,433,770, 3,637,910, 3,714,125 and 3,787,370 in which a com-pound such as diphenyl carbonate or diphenyl oxalate is added to the polyester-forming reaction system described above. Alternatively, polyesters having a high degrees of polymerization and a relatively low carboxyl group content, as used in the present invention,can be synthesized by forming PEN
having a medium degree of polymerization by the melt-polymerization process, and then polymerizing the PEN in the solid state.
In this case too, a compound such as diphenyl carbonate or di-phenyl oxalate is preferably added to the polyester-forming reaction system in the molten state or the solid state.
Furthermore, ethylene 2,6-naphthalate polyesters prepared by methods known per sie may be treated~ in the form of chips or films, with an epoxy compound such as epoxidized glycerol or vinyl cyclohexene dioxide, or diazomethane, thereby to reduce the carboxyl group content of the polyesters to the values specified in the present invention.
In short, so long as the intrinsic viscosity and carboxyl group content as defined in this invention are completely satisfied, any ethylene 2,6-naphthalate polyesters can be used irrespective of the method of preparation.
The polyesters can be fabricated into biaxially oriented films by any desired method, but some preferred embodiments are cited below.
For example, the biaxially stretched film of this invention can be obtained by first preparing an unstretched film by drying the polyester at a temperature of 140C. to 220C., and then melt-extruding the dried polyester at a temperature of 280C. to 330C., preferably 285C. to 315C. The resul-ting unstretched film is stretched in the longitudinal direction at a ratio of about 3 to 5, preferably 3 to 4 at a temperature of about 120C. to 160C., preferably 135C. to 160C., and then in the transverse direction at ratio of about 3 to 5, preferably about 3 to 4, at a temperature of about 115C. to 150C., preferably 120C. to 140C., and then if desired, heat-treating the stretched film at a temperature of about 170C. to 240C.
10367~9 Alternatively, an unstretched tubular film of the polyester is stretched at a temperature of 125C. to 160C., preferably 130C. to 150C.
both in the longitudinal direction at a ratio of about 2.5 to about 5 and in the direction of the diameter of the tube at a ratio of about 2.5 to about 5, and then, if desired, the stretched film is heat-treated at a temperature of 170C. to 240C., thereby to obtain the biaxially stretched film of this invention.
The biaxially stretched film of this invention can be a '`shrink-able~ film if in the above-described procedures, the film is not heat-set after the stretching, or it is heat-set at a temperature above the stretching temperature but below 170C. after the stretching.
Depending upon the conditions described above, the film of this invention can ei~her be a thermally stable film or a shrinkable film. How-ever, irrespective of whether it is shrinkable or not, the film of this invention retains the superior properties for prolonged periods of time when exposed to heat in the dry or wet state, or to elevated temperatures in the presence of a cooling medium or oil, as will be described below.
As stated above, it is important that in the preparation of the biaxially stretched f;l~ of this invention, the ethylene 2,6-naphthalate p`Dlyester should be used which has an intrinsic viscosity, as defined hereinabove, of at least 0.40, preferably at least 0.45, and a carboxyl group content of not more than 30 equivalents/ton, preferably not more than 25 equivalents/ton.
In order to prevent the intrinsic viscosity from decreasing and/or the carboxyl group content from increasing, during the preparation of the unstretched film and/or during the heat-treatment of the stretched film, it is preferred to employ one or more of the following conditions.
(a) The starting polyester should be dried as sufficiently as possible.
(b) In the preparation of an unstretched film of the polyester, the melting and extrudirg temperatures of the polyester should be kept as low as possible.
(c) The extrusion of the polymer shou~l be carried out in an inert gas atmosphere, for example, a nitrogen gas.
(d) The residence time of the polyester in the molten state should be sh~rtened as much as possible.
By employing these conditions, it is possible to prepare a biaxially stretched film composed of the polyester having the intrinsic viscosity and the carboxyl group content as specified above.
The biaxially stretched films of this invention which have the high degrees of polymerization and low carboxyl group content as defined above retain superior properties, for example, high tensile strength and high elongation at break, as compared with biaxially oriented films composed of ethylene 2, & naphthalate polyesters having a carboxyl group content exceeding the upper limit specified in the present invention, when the films are sub-jected to the following conditions.
(i) When maintained in an atmosphere having a high moisture content and held at an elevated temperature (a wet heat atmosphere).
(ii) When maintained in a dry atmosphere held at an elevated temperature (a dry heat atmosphere).
(iii) When maintained in an atmosphere held at an elevated temperature in which a cooling medium gas such as a fluorohydrocarbon or fluorochlorohydrocarbon is present (an atmosphere of a cooling medium held at an elevated temperature).
(iv) When maintained in an atmosphere held at an elevated temper-ature in which an oil such as a lubricating oil, machine oil, or insulating oil is present (an atmosphere of an oil held at a high temperature).
Accordingly, the biaxially stretched films of this invention are 1036~79 superior as thermally stable materials, and find utility as decorative and other industrial materials which are to be subjected to coating, metallizing or other treatments at high temperatures.
In addition to these superior properties, the biaxially stretched films of this invention have high dielectric strergth, and therefore, are suitab`1e as insulating materials for electric appliances which are likely to come into contact with a cooling medium of, for example, refrigerators, or lubricating oils, machine oils, or insulating oils.
The following examples illustrate the present invention. It should be understood that these examples are only illustrative, and are not in any way intended to limit the present invention.
The various properties in the examples were measured by the follow-ing methods.
(a) Tensile Mechanical Properties Determined at 23C. in an atmosphere having a relative humidity of 65% using an Instron-type tensile tester under the following conditions.
Sample form: strip (15 cm x 1 cm) Chuck distance: 10 cm Pulling rate: 10 cm/min.
(b) Moisture Content of Polyester (1) A sample was taken out in an atmosphere of dry nitrogen.
(2) The sample was transferred to an oven of a moisture analyzer (Bell ~ Howell 26-321) placed in a dry box.
(3) The temperature of the oven was raised to 200C., and measure-ment was continued until there was no moisture.
(4) The sample was taken out of the oven, and was weighed by a balance. The moisture content is defined by the following equation.
Weight of moisture Moisture content= x 100 Welght of sample (c) Carboxyl group content Measured in accordance with the A. Conix's method disclosed in "Die Makromolekulare Chemie", Vol. 26, P 226 et seq. (1918). About 100 mg (W) of the polymer was added to 10 ml. of benzyl alcohol and dissolved at 215C. in 2.5 min. The solution was cooled to room temperature by adding 10 n~. of chloroform, and then titrated with a 0.1N benzyl alcohol solution of sodium hydroxide. The amount titrated is designated A ml. Then, 10 ml.
of benzyl alcohol alone was taken, and titrated with a 0.1N benzyl alcohol solution of sodium hydroxide. The amount titrated at this time is desig-nated B ml. Then, the carboxyl group content of the sample polymer is calculated in accordance with the following equation.
CarboXyl group =0.1 (A-B)F/W
content (F=factor of a O.lN benzyl alcohol solution of sodium hydroxide) (d) A test to determine the resistance to cooling medium was performed in the following manner.
(1) A film sample was wrapped with a stairless steel net, and dried in vacuo at 110C. for 5 hours.
(2) The film ~as placed in a 800 ml. shakirg-type autoclave in an atmosphere of nitrogen gas.
(3) 250 g of CHClF2 as a cooling medium (Daiflon R-22, the product of Daikin Kogyo Kabushiki Kaisha, dried by being passed through a molecular sieve) and 250 g of Suniso 3&S (an insulating oil of Sun Oil Company, dried for 1 hour at 100C) were added.
(4) The temperature of the autoclave was elevated to 155C., and the autoclave was maintained at this temperature for 18 days.
(e) Dielectric stren~th Determined in accordance wi*n the method of JIS C 2318. An _g_ alternate current was applied using a disc electrode with a diameter of 25 mm, and the voltage was elevated at a rate of 1 KV/sec.
(f) Retention of each of the properties Let the value of a property of a sample before being subjected to each of the tests mentioned above (e.g. cooling medium resistance test) be A, and the value of the property of the sample after the test be B, then the retention (%) can be expressed by Retention (%)-- A 11 x 100 (g) Treatment with Diazomethane In accordance with the method disclosed in '`Organic Synthesis"
(John Wiley ~ Sons, New York, Champman and Hall, London, edited by A. H.
Blatt), Collective Vol.2, page 165, diazomethane was produced and sufficient-ly dissolved in ethyl ether. A sample film was immersed in the solution at room temperature, and allowed to stand for a certain period of time, after which the film was taken out.
Examples 1 to 3 and Controls 1 and 2 Polyethylene 2,6-naphthalate having a carboxyl group content of 35.3 equivalents/ton and an intrinsic viscosity of 0.62 and containing 0.065 mol % of trimethyl phosphite as a stabilizer was dried for 3 hours in hot air held at 175C At this time, the polymer had a moisture content of 0.002%.
The dried polymer was melt-extruded at a temperature of 300C.. The result-ing unstretched film was stretched at 135C. in the longitudinal direction at a ratio of 3.5, and then at 127C. in the transverse direction at a ratio of 3.8, and then heat-set at 230C. for 12 second to form a 27~ thick stretched film. The film was immersed in ethyl ether with diazomethane at room temp-erature for varying periods of time thereby to form films having different carboxyl group content.
103~
~ he c~rboxyl group content, tensile strength, elong~tion ~t bre~k, ~nd dielectric strength of e~ch film ~re shown in ~ble 1.
= ~
. ..
~ ~ o ~ ~ o U) ~. ~ ~ ~ ~ ~ ~ ~
C~
~1 OGD~`3u)~
ao ~1 o E~l ~ U~
C`l C`~ C~ C`l C`J
..
U~ o ~ ~ ~ .
o ~ ,o, C, o ~ ~ ' I X
~*
I! ~ ~
~036~9 It is seen from Table 1 that the films were not affected in their tensile strength, elongation at break and dielectric strength by the diazo-methane treatment alone.
Each of the films was then subjected to the cooling medium resis-tance test as described hereinabove. The values and retentions of each property after the test are shown in Table 2.
Table 2 .
Runs Tensile Elongation Dielectric strength(Kg/cm2)at break(%) strength (retention in (retension (K~/mm) %) in %) (retention _ .
Example 1 2340 78 311 (85) (98) (115) Example 2 2320 80 304 (83) (103) (110) Example 3 2380 73 254 (86) (89) (93) Control 2120 57 232 1 (78) (76) (83) Control 1860 54 234 2 (68) (70) (85) (The values in the parentheses show the retention.) The measurements of the tensile strength and elongation at break were performed both in the longitudinal direction and in the transverse direction of the films. But the above tables show the values obtained by the measurement in the longitudinal direction, because the values in the transverse direction were substantially the same as, or greater than, those in the longitudinal direction.
Examples 4 to 6 and Controls 3 and 4 Polyethylene 2~6-naphthalate having a carboxyl group content of 103~779 12.1 equivalents/ton and an intrinsic viscosity of 0.62 and containing 0.1 mol% of trimethyl phosphite as a stabilizer was dried, and then melt-extruded in a dry air atmosphere to form an unstretched film. The drying temperature and time, and the extruding temperature were changed as shown in Table 3.
Table 3 ~uns ~ DryingDrying Moisture Extruding COOH content temper-time content temper- of the ature(minutes) of dried ature unstretched (C) polymer C) film (%) (equivalents/
Example 160300 0.0019 388 24.0 175180 0.0016 298 18.5 Example 220 60 O.OQ23 295 27.3 Control 1001800 0.0078 295 57.2 G~otrcl O. O
Each of the unstretched films was stretched first in the longi-tudinal direction at a ratio of 3.5 at 135C., and then in the transverse direction at a ratio of 3.8 at 127C., and then the stretched film was heat-set at 230C. for 15 seconds to form a 2.7,u thick film. The carboxyl group content of each of the stretched films coincided with that of the unstretched film within the range of experimental errors.
Each of the stretched films was subjected to the cooling medium resistance test, and the retentions of the various properties of the film were determined. The results are shown in Table 4. The retentions of the --1~
properties were those of the properties measured in the longitudinal direc-tion of the films.
Table 4 . ., Runs Retention of Retention of Retention of tensile elongation dielectric strength ~) at break(%) resistance (%) _ E~cample 4 83 103 110 Example 5 85 98 115 Example 6 86 89 93 Control 3 58 68 83 Control 4 Not measureable because of marked deterioration E~camPles 7 and 8 and Control 5 A copolyester consisting of 96.5 mol% of ethylene naphthalate units and 3.5 mol% of ethylene terephthalate units which had a carboxyl group content of 37.1 equivalents/ton and an intrinsic viscosity of 0.63 and contained 0.08 mol% of phosphorous acid was fabricated into an unstretched 10 ~` film and stretched and heat-set under the same conditions as in Example 1 to form a 23~ thick film. Each of the stretched films was then treated with diazomethane to form stretched films of varying carboxyl group content.
Each of the films was then subjected to the cooling medium resis-tance test, and the retention of the properties of each of the films were determined. The results are shown in Table 5.
1036~
Table 5 -Runs COOH Retention Retention Retention of content of tensile of elon- dielectric (equivalents/ strength gation at resistance ton) break (%) (%) (%) _ .. __ Example 7 17.1 88 102 109 Example 8 26.3 85 97 111 Control 5 38.? 73 74 83 .
ExamPles ~ and 10 Two polymers were prepared in accordance with the method disclosed in United States Patent No. 3,433,770 in the following manner.
An autoclave equipped with a rectifying column was charged with 5,000 parts of 2~6-dimethyl naphthalate~
2,600 parts of ethylene glycol, 3.50 parts of calcium acetate monohydrate and 1.80 parts of antimony trioxide, and heated at 165 to 230C for 4 hours. After releasing methanol formed, 0.840 parts of phosphorous acid was added.
The reaction mixture was then transferred to a polymerization vessel, and the temperature was gradually raised, after which the reaction mixtùre was reacted for 10 minutes at 260C. and at atmospheric pressure, and for 40 minutes at 275C. and at 20 mmHg. The polymerization was further continued at 290C. at a reduced pressure of less than J~
i7'~9 0.5 mmHg, and diphenyl oxalate was added in an amount of 0.8 mol%
(Example 9), and 1.2 mol% (Example 10) respectively based on the total acid component. After the addition of the diphenyl oxalate, the reaction was carried out for several minutes at atmospheric pressure, and the pressure of the reaction system was gradually reduced. Finally, the reaction was performed for 15 minutes at a pressure of less than 0.5 mmHg to form two polymers, one having an intrinsic viscosity of 0.69 and a carboxyl group content of 11.2 equivalents/ton (Example 9) and the other having an intrin-sic viscosity of 0.66 and a carboxyl group content of 6.3 equivalents/ton. (Example 10).
Each of the polymers was dried for 3 hours at 175C., and then melt-extruded at 293C. in a dry nitrogen atmosphere.
The resulting unstretched film was stretched both in the longi-tudinal direction and in the transverse direction and heat-set under the same conditions as in Example 1 to form a 25~u thick film having a low carboxyl group content.
Each of the biaxially stretched films was subjected to the cooling medium resistance test, and the results are shown in Table 6.
103~;77~
Table 6 Runs COOH Retention Retention I ~etention .
content of of tensile of elo~ga- o~ dielect-the film strength tion at ric (equivalents/ break strength ton) (~) (~ (%) __ _ _ ._ .
Example 9 23.1 85 99 106 Examplc 10 19.2 87 I101 108 L
Exam~les 11 and 12 and Control 6 Each of polymers having different carboxyl group content was dried at 170C. for 5 hours, and melt-extruded at 295C. in a dry nltrogen atmosphere to form an unstretched film. me unstretched film was stretched at 130C. simultaneously in the longitudinal direction at a ratio of 3.6 and in the transverse direction at a ratio of 3.6, and then heat-set under tension at 240C. for 30 scconds.
The intrinsic viscosities and carboxyl group contents of the films are shown in T-able 7 below, Inciden-tally, each of these films contained 0.1 mol% of trimethyl phosphite.
/~
_,~ _ ~ 0 ~ 7 7 Table 7 Runs Intrinsic Carboxyl viscosity group con-(~quivalents/ton) , _ _ ~ .
Example 11 0.56 20,4 Example 12 0,58 28,0 Control 6 0,61 43,1 Each of the films was sub~ected to the following tests, (1) The film was wrapped with a stainless steel net, and dried at 110C. at reduced pressure for 5 hours, men the film was placed in a dry nitrogen atmosphere in a 800 ml. shaking-type autoclave, Furthermore, 250g of CHClF2 gas was added, and after sealing the autoclave, the temperature was raised to 185C., and the film was maintained at this temperature ~or 20 hours, me properties of the films before and after treatment with CHClF2 gas, and the retentions of these properties are shown in Table 8 below.
_ ~_ 10367~9 Table 8 . .
~Before tr~ atment ~ reatment Tensile Elongation Tensile Elongation Runs strength at break strength at break (K~/cm2) (S) tKg/cm2) (%) . __ . .
~xample 11 2860 68 1(70) 13 ¦ Examp e 12 ¦ 2730 ¦ 65 ¦ 10 0 ¦ (9 ) Control 6 2790 71 ~921) j7 * The values in the parentheses show the retentions.
(2) Each of the films shown in Table 7 was immersed in a refrigerator oil (Suniso 3GS) in an autocla~e, and after elevating the temperature to 185C, was maintained at this temperature for 48 hours. The properties of the films after this treatment, and the retentions of the properties are shown in Table 9 below.
o2~
~o367~9 Table 9 ~ . ~
Properties after treatment .
Runs Tensile strength Elongation at (Kg/cm ) break (%) .. .. . ~ .
Example 11 2020 (71) 52 (76) Example 12 1770 (65) 42 (65) Control 6 1760 (63) ~ 27 (38) * The values in the parentheses show the retentions (3) Each of the films shown in Table 7 was wrapped with a stainless steel net and suspended in a l-liter autoclave. 100 cc of water was added to the autoclave so that the water did not come into direct contact with the film. After sealing the autoclave, the temperature was raised to 150C., and the film was maintained at this tempera-ture for 40 hours. The properties of the films after treatment and the retentions of these properties are shown in Table 10, ~/
103~>779 T~ble 10 .
Properties after treatment ._ _ .
Runs Tsnsile strength Elongation at (Kg/cm ) break t%) . _ _ ._ .
Example 11 1720 (60) 35 (51) Example 12 1210 (44) 16 (24) Control 6 590 (21) 3 (4) ' - _ _ _ * The values in the parentheses show the retentions.
.`
.
(4) Each of the films shown in Table 7 was placed in a Gear oven held at 235C., and maintalned at this temperature for 45 hours. The properties of the films after the treatment, and the retentions of the properties are shown in Table 11.
103~.77g Table 11 Properties a~ter treatment Runs _ j _ . ~ .
Tensile strength Elongation at break (I~g/cm ) (%) - - ~_ _, . , Example 11 1290 (45) 82 (120) Example 12 1230 (45) 37 (57) Control 6 1060 (38) 5 (7) _ *The values in the parentheses show the retentions.
,~_
Weight of moisture Moisture content= x 100 Welght of sample (c) Carboxyl group content Measured in accordance with the A. Conix's method disclosed in "Die Makromolekulare Chemie", Vol. 26, P 226 et seq. (1918). About 100 mg (W) of the polymer was added to 10 ml. of benzyl alcohol and dissolved at 215C. in 2.5 min. The solution was cooled to room temperature by adding 10 n~. of chloroform, and then titrated with a 0.1N benzyl alcohol solution of sodium hydroxide. The amount titrated is designated A ml. Then, 10 ml.
of benzyl alcohol alone was taken, and titrated with a 0.1N benzyl alcohol solution of sodium hydroxide. The amount titrated at this time is desig-nated B ml. Then, the carboxyl group content of the sample polymer is calculated in accordance with the following equation.
CarboXyl group =0.1 (A-B)F/W
content (F=factor of a O.lN benzyl alcohol solution of sodium hydroxide) (d) A test to determine the resistance to cooling medium was performed in the following manner.
(1) A film sample was wrapped with a stairless steel net, and dried in vacuo at 110C. for 5 hours.
(2) The film ~as placed in a 800 ml. shakirg-type autoclave in an atmosphere of nitrogen gas.
(3) 250 g of CHClF2 as a cooling medium (Daiflon R-22, the product of Daikin Kogyo Kabushiki Kaisha, dried by being passed through a molecular sieve) and 250 g of Suniso 3&S (an insulating oil of Sun Oil Company, dried for 1 hour at 100C) were added.
(4) The temperature of the autoclave was elevated to 155C., and the autoclave was maintained at this temperature for 18 days.
(e) Dielectric stren~th Determined in accordance wi*n the method of JIS C 2318. An _g_ alternate current was applied using a disc electrode with a diameter of 25 mm, and the voltage was elevated at a rate of 1 KV/sec.
(f) Retention of each of the properties Let the value of a property of a sample before being subjected to each of the tests mentioned above (e.g. cooling medium resistance test) be A, and the value of the property of the sample after the test be B, then the retention (%) can be expressed by Retention (%)-- A 11 x 100 (g) Treatment with Diazomethane In accordance with the method disclosed in '`Organic Synthesis"
(John Wiley ~ Sons, New York, Champman and Hall, London, edited by A. H.
Blatt), Collective Vol.2, page 165, diazomethane was produced and sufficient-ly dissolved in ethyl ether. A sample film was immersed in the solution at room temperature, and allowed to stand for a certain period of time, after which the film was taken out.
Examples 1 to 3 and Controls 1 and 2 Polyethylene 2,6-naphthalate having a carboxyl group content of 35.3 equivalents/ton and an intrinsic viscosity of 0.62 and containing 0.065 mol % of trimethyl phosphite as a stabilizer was dried for 3 hours in hot air held at 175C At this time, the polymer had a moisture content of 0.002%.
The dried polymer was melt-extruded at a temperature of 300C.. The result-ing unstretched film was stretched at 135C. in the longitudinal direction at a ratio of 3.5, and then at 127C. in the transverse direction at a ratio of 3.8, and then heat-set at 230C. for 12 second to form a 27~ thick stretched film. The film was immersed in ethyl ether with diazomethane at room temp-erature for varying periods of time thereby to form films having different carboxyl group content.
103~
~ he c~rboxyl group content, tensile strength, elong~tion ~t bre~k, ~nd dielectric strength of e~ch film ~re shown in ~ble 1.
= ~
. ..
~ ~ o ~ ~ o U) ~. ~ ~ ~ ~ ~ ~ ~
C~
~1 OGD~`3u)~
ao ~1 o E~l ~ U~
C`l C`~ C~ C`l C`J
..
U~ o ~ ~ ~ .
o ~ ,o, C, o ~ ~ ' I X
~*
I! ~ ~
~036~9 It is seen from Table 1 that the films were not affected in their tensile strength, elongation at break and dielectric strength by the diazo-methane treatment alone.
Each of the films was then subjected to the cooling medium resis-tance test as described hereinabove. The values and retentions of each property after the test are shown in Table 2.
Table 2 .
Runs Tensile Elongation Dielectric strength(Kg/cm2)at break(%) strength (retention in (retension (K~/mm) %) in %) (retention _ .
Example 1 2340 78 311 (85) (98) (115) Example 2 2320 80 304 (83) (103) (110) Example 3 2380 73 254 (86) (89) (93) Control 2120 57 232 1 (78) (76) (83) Control 1860 54 234 2 (68) (70) (85) (The values in the parentheses show the retention.) The measurements of the tensile strength and elongation at break were performed both in the longitudinal direction and in the transverse direction of the films. But the above tables show the values obtained by the measurement in the longitudinal direction, because the values in the transverse direction were substantially the same as, or greater than, those in the longitudinal direction.
Examples 4 to 6 and Controls 3 and 4 Polyethylene 2~6-naphthalate having a carboxyl group content of 103~779 12.1 equivalents/ton and an intrinsic viscosity of 0.62 and containing 0.1 mol% of trimethyl phosphite as a stabilizer was dried, and then melt-extruded in a dry air atmosphere to form an unstretched film. The drying temperature and time, and the extruding temperature were changed as shown in Table 3.
Table 3 ~uns ~ DryingDrying Moisture Extruding COOH content temper-time content temper- of the ature(minutes) of dried ature unstretched (C) polymer C) film (%) (equivalents/
Example 160300 0.0019 388 24.0 175180 0.0016 298 18.5 Example 220 60 O.OQ23 295 27.3 Control 1001800 0.0078 295 57.2 G~otrcl O. O
Each of the unstretched films was stretched first in the longi-tudinal direction at a ratio of 3.5 at 135C., and then in the transverse direction at a ratio of 3.8 at 127C., and then the stretched film was heat-set at 230C. for 15 seconds to form a 2.7,u thick film. The carboxyl group content of each of the stretched films coincided with that of the unstretched film within the range of experimental errors.
Each of the stretched films was subjected to the cooling medium resistance test, and the retentions of the various properties of the film were determined. The results are shown in Table 4. The retentions of the --1~
properties were those of the properties measured in the longitudinal direc-tion of the films.
Table 4 . ., Runs Retention of Retention of Retention of tensile elongation dielectric strength ~) at break(%) resistance (%) _ E~cample 4 83 103 110 Example 5 85 98 115 Example 6 86 89 93 Control 3 58 68 83 Control 4 Not measureable because of marked deterioration E~camPles 7 and 8 and Control 5 A copolyester consisting of 96.5 mol% of ethylene naphthalate units and 3.5 mol% of ethylene terephthalate units which had a carboxyl group content of 37.1 equivalents/ton and an intrinsic viscosity of 0.63 and contained 0.08 mol% of phosphorous acid was fabricated into an unstretched 10 ~` film and stretched and heat-set under the same conditions as in Example 1 to form a 23~ thick film. Each of the stretched films was then treated with diazomethane to form stretched films of varying carboxyl group content.
Each of the films was then subjected to the cooling medium resis-tance test, and the retention of the properties of each of the films were determined. The results are shown in Table 5.
1036~
Table 5 -Runs COOH Retention Retention Retention of content of tensile of elon- dielectric (equivalents/ strength gation at resistance ton) break (%) (%) (%) _ .. __ Example 7 17.1 88 102 109 Example 8 26.3 85 97 111 Control 5 38.? 73 74 83 .
ExamPles ~ and 10 Two polymers were prepared in accordance with the method disclosed in United States Patent No. 3,433,770 in the following manner.
An autoclave equipped with a rectifying column was charged with 5,000 parts of 2~6-dimethyl naphthalate~
2,600 parts of ethylene glycol, 3.50 parts of calcium acetate monohydrate and 1.80 parts of antimony trioxide, and heated at 165 to 230C for 4 hours. After releasing methanol formed, 0.840 parts of phosphorous acid was added.
The reaction mixture was then transferred to a polymerization vessel, and the temperature was gradually raised, after which the reaction mixtùre was reacted for 10 minutes at 260C. and at atmospheric pressure, and for 40 minutes at 275C. and at 20 mmHg. The polymerization was further continued at 290C. at a reduced pressure of less than J~
i7'~9 0.5 mmHg, and diphenyl oxalate was added in an amount of 0.8 mol%
(Example 9), and 1.2 mol% (Example 10) respectively based on the total acid component. After the addition of the diphenyl oxalate, the reaction was carried out for several minutes at atmospheric pressure, and the pressure of the reaction system was gradually reduced. Finally, the reaction was performed for 15 minutes at a pressure of less than 0.5 mmHg to form two polymers, one having an intrinsic viscosity of 0.69 and a carboxyl group content of 11.2 equivalents/ton (Example 9) and the other having an intrin-sic viscosity of 0.66 and a carboxyl group content of 6.3 equivalents/ton. (Example 10).
Each of the polymers was dried for 3 hours at 175C., and then melt-extruded at 293C. in a dry nitrogen atmosphere.
The resulting unstretched film was stretched both in the longi-tudinal direction and in the transverse direction and heat-set under the same conditions as in Example 1 to form a 25~u thick film having a low carboxyl group content.
Each of the biaxially stretched films was subjected to the cooling medium resistance test, and the results are shown in Table 6.
103~;77~
Table 6 Runs COOH Retention Retention I ~etention .
content of of tensile of elo~ga- o~ dielect-the film strength tion at ric (equivalents/ break strength ton) (~) (~ (%) __ _ _ ._ .
Example 9 23.1 85 99 106 Examplc 10 19.2 87 I101 108 L
Exam~les 11 and 12 and Control 6 Each of polymers having different carboxyl group content was dried at 170C. for 5 hours, and melt-extruded at 295C. in a dry nltrogen atmosphere to form an unstretched film. me unstretched film was stretched at 130C. simultaneously in the longitudinal direction at a ratio of 3.6 and in the transverse direction at a ratio of 3.6, and then heat-set under tension at 240C. for 30 scconds.
The intrinsic viscosities and carboxyl group contents of the films are shown in T-able 7 below, Inciden-tally, each of these films contained 0.1 mol% of trimethyl phosphite.
/~
_,~ _ ~ 0 ~ 7 7 Table 7 Runs Intrinsic Carboxyl viscosity group con-(~quivalents/ton) , _ _ ~ .
Example 11 0.56 20,4 Example 12 0,58 28,0 Control 6 0,61 43,1 Each of the films was sub~ected to the following tests, (1) The film was wrapped with a stainless steel net, and dried at 110C. at reduced pressure for 5 hours, men the film was placed in a dry nitrogen atmosphere in a 800 ml. shaking-type autoclave, Furthermore, 250g of CHClF2 gas was added, and after sealing the autoclave, the temperature was raised to 185C., and the film was maintained at this temperature ~or 20 hours, me properties of the films before and after treatment with CHClF2 gas, and the retentions of these properties are shown in Table 8 below.
_ ~_ 10367~9 Table 8 . .
~Before tr~ atment ~ reatment Tensile Elongation Tensile Elongation Runs strength at break strength at break (K~/cm2) (S) tKg/cm2) (%) . __ . .
~xample 11 2860 68 1(70) 13 ¦ Examp e 12 ¦ 2730 ¦ 65 ¦ 10 0 ¦ (9 ) Control 6 2790 71 ~921) j7 * The values in the parentheses show the retentions.
(2) Each of the films shown in Table 7 was immersed in a refrigerator oil (Suniso 3GS) in an autocla~e, and after elevating the temperature to 185C, was maintained at this temperature for 48 hours. The properties of the films after this treatment, and the retentions of the properties are shown in Table 9 below.
o2~
~o367~9 Table 9 ~ . ~
Properties after treatment .
Runs Tensile strength Elongation at (Kg/cm ) break (%) .. .. . ~ .
Example 11 2020 (71) 52 (76) Example 12 1770 (65) 42 (65) Control 6 1760 (63) ~ 27 (38) * The values in the parentheses show the retentions (3) Each of the films shown in Table 7 was wrapped with a stainless steel net and suspended in a l-liter autoclave. 100 cc of water was added to the autoclave so that the water did not come into direct contact with the film. After sealing the autoclave, the temperature was raised to 150C., and the film was maintained at this tempera-ture for 40 hours. The properties of the films after treatment and the retentions of these properties are shown in Table 10, ~/
103~>779 T~ble 10 .
Properties after treatment ._ _ .
Runs Tsnsile strength Elongation at (Kg/cm ) break t%) . _ _ ._ .
Example 11 1720 (60) 35 (51) Example 12 1210 (44) 16 (24) Control 6 590 (21) 3 (4) ' - _ _ _ * The values in the parentheses show the retentions.
.`
.
(4) Each of the films shown in Table 7 was placed in a Gear oven held at 235C., and maintalned at this temperature for 45 hours. The properties of the films after the treatment, and the retentions of the properties are shown in Table 11.
103~.77g Table 11 Properties a~ter treatment Runs _ j _ . ~ .
Tensile strength Elongation at break (I~g/cm ) (%) - - ~_ _, . , Example 11 1290 (45) 82 (120) Example 12 1230 (45) 37 (57) Control 6 1060 (38) 5 (7) _ *The values in the parentheses show the retentions.
,~_
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A biaxially stretched film composed of a polyester at least 90 mol% of which recurring structural units consist of ethylene 2,6-naph-thalate, said polyester having an intrinsic viscosity [n], as calculated from the value measured in o-chlorophenol at 35°C., of at least 0.40, and a carboxyl group content of not more than 30 equivalents/ton.
2. The biaxially stretched film of claim 1 wherein said polyester has an intrinsic viscosity of at least 0.45.
3. The biaxially stretched film of claim 1 or 2 wherein said polyes-ter has a carboxyl group content of not more than 25 equivalents/ton.
4. The biaxially stretched film of claim 1 wherein 95 to 100 mol% of the recurring units consist of ethylene 2,6-naphthalate, and the polyester has an intrinsic viscosity of at least 0.45 and a carboxyl group content of not more than 30 equivalents/ton.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3878373A JPS49132600A (en) | 1973-04-06 | 1973-04-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1036779A true CA1036779A (en) | 1978-08-22 |
Family
ID=12534879
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA196,911A Expired CA1036779A (en) | 1973-04-06 | 1974-04-05 | Biaxially stretched film |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS49132600A (en) |
| CA (1) | CA1036779A (en) |
| DE (1) | DE2416712C3 (en) |
| FR (1) | FR2224505B1 (en) |
| GB (1) | GB1450491A (en) |
| NL (1) | NL7404692A (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5832489A (en) * | 1981-08-20 | 1983-02-25 | 日東電工株式会社 | Polyester film for printed circuit |
| JPH0762964B2 (en) * | 1985-11-13 | 1995-07-05 | ダイアホイルヘキスト株式会社 | Electrical insulation material |
| JPS62113529A (en) * | 1985-11-13 | 1987-05-25 | Diafoil Co Ltd | Polyethylene naphthalate film |
| JPS62136013A (en) * | 1985-12-09 | 1987-06-19 | ダイアホイルヘキスト株式会社 | Polyethylene-2,6-naphthalate film for capacitor |
| JPH05230349A (en) * | 1992-02-25 | 1993-09-07 | Teijin Ltd | Thermoplastic resin composition |
| EP0590159B1 (en) * | 1992-04-16 | 2003-03-26 | Teijin Limited | Biaxially oriented polyester film |
| US5731071A (en) * | 1992-04-16 | 1998-03-24 | Teijin Limited | Biaxially oriented polyester film |
| DE4320593A1 (en) * | 1993-06-22 | 1995-01-05 | Akzo Nobel Nv | Multifilament yarn made of polyethylene naphthalate and process for its manufacture |
| JP6390336B2 (en) * | 2014-10-16 | 2018-09-19 | 東レ株式会社 | Polyester film for use in contact with R32 |
-
1973
- 1973-04-06 JP JP3878373A patent/JPS49132600A/ja active Pending
-
1974
- 1974-04-05 CA CA196,911A patent/CA1036779A/en not_active Expired
- 1974-04-05 DE DE19742416712 patent/DE2416712C3/en not_active Expired
- 1974-04-05 NL NL7404692A patent/NL7404692A/xx unknown
- 1974-04-05 GB GB1528774A patent/GB1450491A/en not_active Expired
- 1974-04-05 FR FR7412137A patent/FR2224505B1/fr not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2416712B2 (en) | 1977-08-25 |
| DE2416712C3 (en) | 1978-04-20 |
| FR2224505A1 (en) | 1974-10-31 |
| JPS49132600A (en) | 1974-12-19 |
| GB1450491A (en) | 1976-09-22 |
| FR2224505B1 (en) | 1976-12-17 |
| DE2416712A1 (en) | 1974-10-24 |
| NL7404692A (en) | 1974-10-08 |
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