阅读说明：本技术 半芳香族聚酰胺膜及其制造方法 (Semi-aromatic polyamide film and method for producing same ) 是由 冈部贵史 山本真史 木原澄人 于 2020-05-13 设计创作，主要内容包括：一种半芳香族聚酰胺膜,其特征在于,在250℃×5分钟条件下测定的膜的长边方向的热收缩率S-(MD)和宽度方向的热收缩率S-(TD)分别为－1.0～1.5％,长边方向和宽度方向的拉伸断裂伸长率分别为70％以上,雾度为14％以下。(A semi-aromatic polyamide film characterized by having a thermal shrinkage S in the longitudinal direction of the film measured at 250 ℃ for 5 minutes MD And heat shrinkage rate S in the width direction TD The values of-1.0 to 1.5% respectively, the tensile elongation at break in the longitudinal direction and the tensile elongation at break in the width direction of 70% or more, and the haze of 14% or less.)

1. A semi-aromatic polyamide film characterized by having a thermal shrinkage S in the longitudinal direction of the film measured at 250 ℃ for 5 minutes_MDAnd heat shrinkage rate S in the width direction_TDRespectively account for-1.0 to 1.5 percent,

the tensile elongation at break in the longitudinal direction and the width direction is 70% or more,

the haze is 14% or less.

2. The semi-aromatic polyamide film according to claim 1, wherein S is_MDAnd S_TDAbsolute value of the difference, i.e. | S_MD－S_TDLess than 1.2.

3. A method for producing a semi-aromatic polyamide film according to claim 1, wherein the semi-aromatic polyamide film is produced by a method comprising the steps of,

comprising a step of biaxially stretching an unstretched film of a semi-aromatic polyamide, wherein the step of biaxially stretching uses an unstretched film having a heat of crystallization of 20J/g or more.

4. The method for producing a semi-aromatic polyamide film according to claim 3, wherein in the step of biaxially stretching, the film is stretched at a ratio of 2.0 to 3.5 times in the longitudinal direction and at a ratio of 2.0 to 4.0 times in the width direction.

5. The method for producing a semi-aromatic polyamide film according to claim 3 or 4, wherein the biaxially stretched film is subjected to a heat-setting treatment at 260 to 280 ℃ and subjected to a relaxation treatment at a relaxation rate of 1.0 to 10.0% in the longitudinal direction and 1.0 to 12.0% in the width direction.

6. An electronic material using the semi-aromatic polyamide film according to claim 1 or 2.

7. An optical part using the semi-aromatic polyamide film according to claim 1 or 2.

Technical Field

The present invention relates to a semi-aromatic polyamide film in which thermal shrinkage is suppressed.

Background

Semi-aromatic polyamide films stretched in the longitudinal direction (longitudinal direction) and the width direction (transverse direction) of the film are used in various fields because of their excellent heat resistance and mechanical properties. Among the semi-aromatic polyamides constituting the semi-aromatic polyamide film, polyamide 9T containing an aliphatic diamine having 9 carbon atoms and terephthalic acid as constituent elements and polyamide 10T containing an aliphatic diamine having 10 carbon atoms and terephthalic acid as constituent elements are excellent in mechanical properties and thermal properties.

For example, patent document 1 discloses a biaxially stretched film made of a semi-aromatic polyamide resin, which is obtained by subjecting the film to biaxial stretching, heat-setting treatment, and further relaxation treatment in the film width direction.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2012/067172

Disclosure of Invention

In recent years, optical films such as display members are strictly required to be free from strain during transportation and processing.

The film disclosed in patent document 1 has a sufficiently reduced heat shrinkage rate under 200 ℃ for 15 minutes. However, if the temperature reaches 250 ℃, the heat shrinkage rate in the longitudinal direction of the film may increase significantly even under the condition of 5 minutes, and depending on the temperature condition during processing, deformation may not be avoided due to strain accompanying heat shrinkage.

In addition, the film disclosed in patent document 1 may have a high tensile elongation at break in the longitudinal direction but a low tensile elongation at break in the width direction, and may fail to follow external stress, thereby causing a break in the film.

The present invention addresses the problem of providing a semi-aromatic polyamide film in which the thermal shrinkage in the longitudinal direction of the film is sufficiently reduced and the tensile elongation at break in the width direction of the film is sufficiently improved.

As a result of intensive studies, the present inventors have found that a semi-aromatic polyamide film obtained by controlling the crystal state of the film before stretching, stretching conditions, heat-setting conditions, and relaxation conditions can achieve the above object, and have completed the present invention.

The semi-aromatic polyamide film of the present invention is characterized in that,

thermal shrinkage S in the longitudinal direction of the film measured at 250 ℃ for 5 minutes_MDAnd heat shrinkage rate S in the width direction_TDRespectively account for-1.0 to 1.5 percent,

the tensile elongation at break in the longitudinal direction and the width direction is 70% or more,

the haze is 14% or less.

According to the semi-aromatic polyamide film of the present invention, S is preferable_MDAnd S_TDAbsolute value of the difference (| S)_MD－S _TD|) less than 1.2.

The method for producing a semi-aromatic polyamide film of the present invention is characterized in that,

comprising a step of biaxially stretching an unstretched film of a semi-aromatic polyamide, wherein the step of biaxially stretching uses an unstretched film having a heat of crystallization of 20J/g or more.

According to the method for producing a semi-aromatic polyamide film of the present invention, in the step of biaxial stretching, the film is preferably stretched at a ratio of 2.0 to 3.5 times in the longitudinal direction and at a ratio of 2.0 to 4.0 times in the width direction.

According to the method for producing a semi-aromatic polyamide film of the present invention, the biaxially stretched film is preferably subjected to a heat-setting treatment at 260 to 280 ℃ and then subjected to a relaxation treatment at a relaxation rate of 1.0 to 10.0% in the longitudinal direction and 1.0 to 12.0% in the width direction.

The electronic material of the present invention uses the above-described semi-aromatic polyamide film.

The optical component of the present invention uses the above-described semi-aromatic polyamide film.

According to the present invention, a semi-aromatic polyamide film having a small heat shrinkage rate in the width direction and a small heat shrinkage rate in the longitudinal direction under conditions of 250 ℃ for 5 minutes, excellent dimensional stability, and sufficiently improved tensile elongation at break in the longitudinal direction and tensile elongation at break in the width direction can be provided.

Further, the semi-aromatic polyamide film of the present invention can suppress the increase in haze even when a lubricant is contained for improving the sliding property, and is excellent in transparency.

The semi-aromatic polyamide film of the present invention can be suitably used as an electronic material film such as a substrate film and a coverlay film for FPC, an optical film used as a substrate for display material, a heat-resistant tape, and the like.

Detailed Description

The heat shrinkage rate S in the longitudinal direction of the semi-aromatic polyamide film of the present invention measured at 250 ℃ for 5 minutes_MDAnd heat shrinkage rate S in the width direction_TDRespectively-1.0 to 1.5%, a tensile elongation at break of 70% or more, and a haze of 14% or less.

< semi-aromatic polyamide >

The semiaromatic polyamide constituting the semiaromatic polyamide film of the present invention is composed of an aromatic dicarboxylic acid component and an aliphatic diamine component.

The aromatic dicarboxylic acid component preferably contains terephthalic acid at 60 mol% or more, more preferably 70 mol% or more, and still more preferably 85 mol% or more. When the content of terephthalic acid is less than 60 mol%, the heat resistance and low water absorption of the resulting film may be lowered.

Examples of the aromatic dicarboxylic acid component other than terephthalic acid include isophthalic acid and naphthalenedicarboxylic acid (1, 2-, 1, 3-, 1, 4-, 1, 5-, 1, 6-, 1, 7-, 1, 8-, 2, 3-, 2, 6-, and 2, 7-forms).

The semi-aromatic polyamide may contain a dicarboxylic acid component other than the aromatic dicarboxylic acid component as the dicarboxylic acid component within a range not to impair the effects of the present invention. Examples of the other dicarboxylic acid include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, and octadecanedioic acid.

The aliphatic diamine component preferably contains an aliphatic diamine having 6 to 12 carbon atoms as a main component, more preferably contains an aliphatic diamine having 9 to 12 carbon atoms as a main component, and further preferably contains an aliphatic diamine having 9 or 10 carbon atoms as a main component.

The content of the aliphatic diamine having 6 to 12 carbon atoms in the aliphatic diamine component is preferably 60 mol% or more, more preferably 75 mol% or more, and still more preferably 90 mol% or more. When the content of the aliphatic diamine having 6 to 12 carbon atoms is 60 mol% or more, the film obtained can achieve both heat resistance and productivity. The aliphatic diamine having 6 to 12 carbon atoms may be used alone in 1 kind or in combination with 2 or more kinds. When 2 or more kinds are used in combination, the content is the total of them.

Examples of the aliphatic diamine having 6 to 12 carbon atoms include straight-chain aliphatic diamines such as 1, 6-hexamethylenediamine, 1, 7-heptamethylenediamine, 1, 8-octamethylenediamine, 1, 9-nonanediamine, 1, 10-decanediamine, 1, 11-undecanediamine, 1, 12-dodecanediamine, 2-methyl-1, 8-octamethylenediamine, 4-methyl-1, 8-octamethylenediamine, 5-methyl-1, 9-nonanediamine, 2, 4-/2, 4, 4-trimethyl-1, 6-hexanediamine, 2-methyl-1, 5-pentanediamine, 2-methyl-1, 6-hexanediamine, and 2-methyl-1, 7-heptamethylenediamine.

Examples of the aliphatic diamine other than the aliphatic diamine having 6 to 12 carbon atoms include straight-chain aliphatic diamines such as 1, 4-butanediamine and 1, 5-pentanediamine.

The semi-aromatic polyamide may contain a diamine component other than the aliphatic diamine component as the diamine component within a range not impairing the effects of the present invention. Examples of the other diamine include alicyclic diamines such as isophorone diamine, norbornanediamine and tricyclodecane dimethylamine, and aromatic diamines such as m-xylylenediamine, p-xylylenediamine, m-phenylenediamine and p-phenylenediamine.

The semi-aromatic polyamide may be copolymerized with a lactam such as epsilon-caprolactam, zeta-enantholactam, eta-octalactam, omega-laurolactam, or the like, as long as the effects of the present invention are not impaired.

The type and copolymerization ratio of the monomers constituting the semi-aromatic polyamide are preferably selected so that the melting point (Tm) of the obtained semi-aromatic polyamide is in the range of 270 to 350 ℃. When Tm is in the above range, the semi-aromatic polyamide can effectively suppress thermal decomposition during processing of the film. If the Tm is less than 270 ℃, the heat resistance of the resulting film may be insufficient. On the other hand, if Tm exceeds 350 ℃, thermal decomposition sometimes occurs at the time of film production.

The intrinsic viscosity of the semi-aromatic polyamide is preferably 0.8 to 2.0dL/g, more preferably 0.9 to 1.8 dL/g. If the intrinsic viscosity of the semi-aromatic polyamide is 0.8dL/g or more, a film having excellent mechanical strength can be produced, but if it exceeds 2.0dL/g, it may be difficult to produce the film.

The semi-aromatic polyamide may contain a polymerization catalyst and an end-capping agent. Examples of the blocking agent include acetic acid, lauric acid, benzoic acid, octylamine, cyclohexylamine, and aniline. Examples of the polymerization catalyst include phosphoric acid, phosphorous acid, hypophosphorous acid, and salts thereof.

< semi-aromatic polyamide film >

The semi-aromatic polyamide film of the present invention requires a heat shrinkage rate S in the longitudinal direction of the film measured at 250 ℃ for 5 minutes_MDAnd heat shrinkage rate S in the width direction_TDRespectively-1.0-1.5%, preferably-0.8-1.3%, more preferably-0.6-1.0%. When the heat shrinkage ratio of the semi-aromatic polyamide film is 1.5% or less, the dimensional stability is improved and the heat resistance is excellent. On the other hand, if the heat shrinkage rate of the semi-aromatic polyamide film exceeds 1.5%, the dimensional change increases when the film is processed at a high temperature, and thus processing failure occurs, which is a problem.

The semi-aromatic polyamide film of the present invention preferably has a thermal shrinkage S in the longitudinal direction measured at 250 ℃ for 5 minutes_MDHeat shrinkage ratio with width direction S_TDAbsolute value of the difference (| S)_MD－S_TDI) is less than 1.2, more preferably less than 1.1, and still more preferably less than 1.0. If | S of the semi-aromatic polyamide film_MD－S_TDIf | is less than 1.2, the thermal shrinkage rates in the longitudinal direction and the width direction become equal, and the anisotropy is relaxed even when the thermal shrinkage rate is equal to or lower than 1When heat is applied to the film by flow welding, bonding processing of other materials, or the like, the generation of strain or bending can be suppressed.

The semi-aromatic polyamide film of the present invention is required to have a tensile elongation at break in the longitudinal direction and the width direction, measured according to JIS K7127, of 70% or more, preferably 70 to 150%, and more preferably 80 to 140%. When the tensile elongation at break of the semi-aromatic polyamide film is 70% or more, the film is excellent in deformation following property, and therefore, the film is deformable without breaking by external stress. On the other hand, if the tensile elongation at break of the semi-aromatic polyamide film is less than 70%, the film cannot be broken following the stress from the outside. In the semi-aromatic polyamide film of the present invention, the tensile elongation at break in the longitudinal direction and the width direction do not need to be necessarily uniform, and for example, the tensile elongation at break in the longitudinal direction is 140%, the tensile elongation at break in the width direction is 80%, or the tensile elongation at break in the longitudinal direction is 80%, the tensile elongation at break in the width direction is 140%, and the like, and the relationship of imbalance is acceptable as long as the preferable numerical range of the tensile elongation at break is satisfied.

Further, the haze of the semi-aromatic polyamide film of the present invention measured according to JIS K7105 needs to be 14% or less, preferably 12% or less, and more preferably 10% or less. Further, the haze of the semi-aromatic polyamide film having a thickness of 25 μm or less is preferably 7% or less, more preferably 6% or less, and further preferably 5% or less. The semi-aromatic polyamide film has a haze of 14% or less, and thus has excellent visibility. On the other hand, the semi-aromatic polyamide film having a haze of more than 14% is poor in visibility.

The semi-aromatic polyamide film of the present invention preferably has a moisture absorption elongation N in the longitudinal direction of the film measured under the conditions of 20 ℃x90% RH_MDAnd the wet elongation N in the width direction_TDEach of the amounts is 1% or less, more preferably 0.8% or less, and still more preferably 0.5% or less.

Further, the wet elongation N in the longitudinal direction measured under the conditions of 20 ℃ X90% RH_MDMoisture absorption elongation N in the width direction_TDAbsolute value of the difference (| N)_MD－N_TDI) is preferably less than 0.3, more preferably less than 0.2, and further preferably less than 0.1. If | N of the semi-aromatic polyamide film_MD－N_TDIf | is less than 0.3, the elongation in the longitudinal direction and the width direction under the moisture absorption condition becomes uniform, and the occurrence of strain and bending can be suppressed.

Thermal shrinkage S in the longitudinal direction of the semi-aromatic polyamide film of the present invention measured at 250 ℃x5 minutes_MDAnd heat shrinkage rate S in the width direction_TDWithin the predetermined range, the dimensional stability upon receiving heat during film processing or the like can be improved. In addition, when the semi-aromatic polyamide film of the present invention has a moisture absorption elongation within the above range, dimensional change due to humidity during film processing or the like can be suppressed. That is, the film can improve dimensional stability when absorbing moisture, not only improve positioning when laminating other materials and dimensional accuracy when punching, but also reduce the risk of curling or strain after laminating other materials.

Method for producing semi-aromatic polyamide film

The semi-aromatic polyamide film of the present invention can be produced by: in the step of biaxially stretching an unstretched film of a semi-aromatic polyamide, an unstretched film having a heat of crystallization of 20J/g or more is stretched at a rate of 2.0 to 3.5 times in the longitudinal direction and at a rate of 2.0 to 4.0 times in the width direction, for example, and the biaxially stretched film is subjected to a heat-setting treatment at 260 to 280 ℃ to relax at a relaxation rate of 1.0 to 10.0% in the longitudinal direction and 1.0 to 12.0% in the width direction.

(semi-aromatic polyamide)

Commercially available semi-aromatic polyamides can be preferably used for producing the semi-aromatic polyamide film. Examples of such commercially available products include KURARAY co, Genestar (registered trademark) manufactured by ltd, XecoT (registered trademark) manufactured by engineco, reniki engineering plastic corporation, Reny (registered trademark), Arlen (registered trademark) manufactured by mitsubishi engineering plastic corporation, and Ultramid (registered trademark) manufactured by BASF.

The semi-aromatic polyamide can be produced by a method known as a method for producing a crystalline polyamide. For example, there are a solution polymerization method or an interfacial polymerization method (a method) in which an acid chloride and a diamine component are used as raw materials, a method (B method) in which an oligomer is produced from a dicarboxylic acid component and a diamine component, and the oligomer is polymerized to a high molecular weight by melt polymerization or solid phase polymerization, a method (C method) in which a pulverized mixture of a salt and an oligomer is produced from a dicarboxylic acid component and a diamine component, and a method (D method) in which a salt is produced from a dicarboxylic acid component and a diamine component, and the solid phase polymerization is carried out. Among them, the C method and the D method are preferable, and the D method is more preferable. Compared with the method B, the method C and the method D can produce a pulverized mixture of the salt and the oligomer and the salt at a low temperature, and do not need a large amount of water when producing the pulverized mixture of the salt and the oligomer and the salt. Therefore, the generation of gel can be reduced, and fish eyes can be reduced.

In the method B, for example, a diamine component, a dicarboxylic acid component, and a polymerization catalyst are mixed together to prepare a nylon salt, and the nylon salt is heated and polymerized at a temperature of 200 to 250 ℃. The oligomer preferably has an intrinsic viscosity of 0.1 to 0.6 dL/g. By setting the intrinsic viscosity of the oligomer within this range, the following advantages are obtained: in the subsequent solid-phase polymerization or melt polymerization, the molar balance between the carboxyl group in the dicarboxylic acid component and the amino group in the diamine component is not lost, and the polymerization rate can be increased. If the intrinsic viscosity of the oligomer is less than 0.1dL/g, the polymerization time may be prolonged, resulting in poor productivity. On the other hand, if it exceeds 0.6dL/g, the obtained semi-aromatic polyamide may be colored.

The solid-phase polymerization of the oligomer is preferably carried out under reduced pressure or under inert gas flow. The temperature of the solid phase polymerization is preferably 200 to 280 ℃. When the temperature of the solid-phase polymerization is in this range, the obtained semi-aromatic polyamide can be inhibited from coloring and gelling. If the temperature of the solid-phase polymerization is less than 200 ℃, the polymerization time may be prolonged, resulting in poor productivity. On the other hand, if the temperature exceeds 280 ℃, coloration or gelation may occur in the obtained semi-aromatic polyamide.

The melt polymerization of the oligomer is preferably carried out at a temperature of 350 ℃ or lower. If the polymerization temperature exceeds 350 ℃, decomposition and thermal deterioration of the semi-aromatic polyamide may be promoted. Therefore, the film obtained from such a semi-aromatic polyamide may have poor strength and appearance. The melt polymerization also includes melt polymerization using a melt extruder.

In the method C, for example, a suspension of a molten aliphatic diamine and a solid aromatic dicarboxylic acid is stirred and mixed to obtain a mixed solution. Then, in the mixed solution, a salt-forming reaction by a reaction between the aromatic dicarboxylic acid and the aliphatic diamine and an oligomer-forming reaction by polymerization of the formed salt are carried out at a temperature lower than the melting point of the finally formed semi-aromatic polyamide to obtain a mixture of the salt and the oligomer. In this case, the reaction may be carried out while pulverizing, or the reaction product may be taken out once after the reaction and pulverized. Then, the obtained reaction product is solid-phase polymerized at a temperature lower than the melting point of the finally produced semi-aromatic polyamide to have a high molecular weight to a predetermined molecular weight, thereby obtaining the semi-aromatic polyamide. The solid-phase polymerization is preferably carried out in an inert gas stream such as nitrogen at a polymerization temperature of 180 to 270 ℃ for a reaction time of 0.5 to 10 hours.

In the method D, for example, an aromatic dicarboxylic acid powder is heated in advance to a temperature equal to or higher than the melting point of the aliphatic diamine and equal to or lower than the melting point of the aromatic dicarboxylic acid, and the aliphatic diamine is added to the aromatic dicarboxylic acid powder at that temperature to maintain the powder state of the aromatic dicarboxylic acid, thereby producing a salt. Then, the obtained salt is solid-phase polymerized at a temperature lower than the melting point of the finally produced semi-aromatic polyamide to have a high molecular weight to a predetermined molecular weight, thereby obtaining the semi-aromatic polyamide. The solid-phase polymerization is preferably carried out in an inert gas stream such as nitrogen at a polymerization temperature of 180 to 270 ℃ for a reaction time of 0.5 to 10 hours.

The raw material of the semi-aromatic polyamide film may be a raw material obtained by mixing the above-mentioned raw materials, or may be a raw material prepared by adding the raw material to a waste mixture of a film produced in the production of the semi-aromatic polyamide film and a waste mixture produced as a scrap. Their mixing can be carried out as follows: a known method such as a method of dry blending with a known apparatus, or a mixing method of melt-kneading and mixing with a single-screw or twin-screw extruder.

(additives)

The semi-aromatic polyamide film of the present invention is composed of the above semi-aromatic polyamide, and may contain additives such as a lubricant, a pigment such as titanium, a colorant such as a dye, an anti-coloring agent, a heat stabilizer, an antioxidant such as hindered phenol, phosphate ester, phosphite ester, a weather resistance improver such as a benzotriazole compound, a bromine-based or phosphorus-based flame retardant, a plasticizer, a release agent, a reinforcing agent such as talc, a modifier, an antistatic agent, an ultraviolet absorber, an antifogging agent, various polymer resins, and the like, as necessary, within the range that the properties of the film are not sacrificed.

Examples of the lubricant having good sliding properties include inorganic particles such as silica, alumina, titania, calcium carbonate, kaolin, and barium sulfate. Examples of the organic fine particles include acrylic resin particles, melamine resin particles, silicone resin particles, crosslinked polystyrene particles, and the like. The average particle diameter of the lubricant is preferably 0.05 to 5.0 μm. The content of the lubricant is preferably 0.2% by mass or less, and may be selected according to friction characteristics, optical characteristics, and other characteristics required for the film.

As a method of incorporating the above-described additive into the semi-aromatic polyamide film, various methods can be used. Typical examples of the method include the following methods.

(A) A method of adding the semi-aromatic polyamide during polymerization.

(B) A masterbatch method in which the compound is directly added to a semi-aromatic polyamide to prepare a melt-kneaded pellet.

(C) And a method in which the compound is directly added to the semi-aromatic polyamide at the time of film formation and melt-kneaded by an extruder.

(D) And a method in which the mixture is directly added to an extruder for melt kneading in film formation.

(extrusion)

In the method for producing a semi-aromatic polyamide film of the present invention, the heat of crystallization of the unstretched film of the semi-aromatic polyamide used in the biaxial stretching step needs to be 20J/g or more, preferably 25J/g or more. If the heat of crystallization of the unstretched film is less than 20J/g, the semi-aromatic polyamide film obtained by biaxial stretching is crystallized, and therefore, the tensile elongation at break is low, and if a lubricant such as silica is contained, the haze is high. Further, an unstretched film having a heat of crystallization of less than 20J/g may not be stretched stably or may not be stretched because of frequent cutting, and a higher stretching force is required at the start of stretching, and therefore it is difficult to obtain a stretched film having a uniform thickness.

An unstretched film of a semi-aromatic polyamide having a heat of crystallization of 20J/g or more can be produced by: the semi-aromatic polyamide is melted and mixed for 3-15 minutes at the temperature of 280-340 ℃ in an extruder, and then extruded into a sheet shape through a T-shaped die head, and the sheet shape is closely adhered to a cooling roller with the temperature adjusted to be 30-40 ℃ for cooling. If the temperature of the cooling roll exceeds 40 ℃, the heat of crystallization of the obtained unstretched sheet is less than 20J/g, and the above-mentioned problem occurs after stretching.

(stretching)

In the method for producing a semi-aromatic polyamide film of the present invention, the unstretched film is biaxially stretched, and the semi-aromatic polyamide is oriented and crystallized by the stretching.

The stretching method is not particularly limited, but a sequential biaxial stretching method of a planar type, a simultaneous biaxial stretching method of a planar type, a tube film method, or the like can be used. Among them, the planar simultaneous biaxial stretching method is preferable from the viewpoint of good film thickness accuracy and uniform physical properties in the film width direction. Examples of stretching apparatuses used in the planar simultaneous biaxial stretching method include a screw type tenter, a pantograph type tenter, and a linear motor-driven clip type tenter.

The stretch ratio is preferably 2.0 to 3.5 times in the longitudinal direction, 2.0 to 4.0 times in the width direction, more preferably 2.0 to 3.0 times in the longitudinal direction, and 2.0 to 3.5 times in the width direction.

In the case of sequential biaxial stretching, if the stretching ratio in the longitudinal direction exceeds 3.5 times, the obtained stretched film may excessively crystallize, and the stretchability in the width direction may decrease. Even when stretching in the width direction is possible, the resulting stretched film is likely to suffer stretching unevenness, and thus the thickness accuracy is lowered, the tensile elongation at break in the longitudinal direction is lowered, and the transparency is lowered in some cases.

In the sequential biaxial stretching method, the stretching magnification is more preferably 2.3 to 2.5 times in the longitudinal direction and 3.3 to 3.5 times in the width direction.

In the case of simultaneous biaxial stretching, if the stretching ratio in the longitudinal direction exceeds 3.5 times, the heat shrinkage ratio of the resulting stretched film may be high, and the dimensional stability may be low. On the other hand, if the draw ratio in the width direction exceeds 4.0 times, the thermal shrinkage rate becomes high, the dimensional stability is lowered, and the tensile elongation at break is lowered in some cases.

In the simultaneous biaxial stretching method, when a biaxially stretched film having a thickness of 1 to 25 μm is obtained, the stretching ratio is preferably 2.5 to 3.0 times in the longitudinal direction and 2.5 to 3.3 times in the width direction, and when a biaxially stretched film having a thickness of 26 to 50 μm is obtained, the stretching ratio is preferably 3.0 to 3.5 times in the longitudinal direction and 2.8 to 3.3 times in the width direction.

If the stretching ratio in the longitudinal direction and the width direction is less than 2.0 times, the resulting stretched film tends to be stretched unevenly, resulting in uneven thickness and reduced planarity.

The stretching rate is preferably a rate exceeding 400%/min in both the longitudinal direction and the transverse direction, more preferably 800 to 12000%/min, and still more preferably 1200 to 6000%/min. If the strain rate is 400%/min or less, crystal growth may occur during stretching, and the film may break, whereas if the strain rate is too high, the unstretched sheet may fail to follow the deformation and break.

The stretching temperature is preferably not lower than the glass transition temperature (Tg) of the semi-aromatic polyamide, more preferably not higher than Tg but not higher than (Tg +50 ℃). If the stretching temperature is less than Tg, the film is likely to break and stable production cannot be achieved, whereas if it exceeds (Tg +50 ℃ C.), stretching unevenness may occur in the film.

(Heat fixation)

After the above stretching, the semi-aromatic polyamide film is preferably subjected to a heat-fixing treatment in a state where the film is sandwiched by a jig used in the stretching. By performing the heat-fixing treatment, the heat shrinkage rate of the obtained film can be reduced without generating unevenness in heating. The heat-fixing treatment temperature is preferably 260-280 ℃, more preferably 263-278 ℃, and further preferably 265-275 ℃. If the heat-setting treatment temperature is less than 260 deg.C, the heat shrinkage of the resulting film becomes high. If the heat-setting treatment temperature exceeds 280 ℃, the tensile elongation at break of the obtained film is reduced, appearance defects due to thermal wrinkles are likely to occur, and in some cases, the film is broken during the heat-setting treatment, and it is difficult to obtain a biaxially stretched film.

The heat-setting temperature is preferably 260 to 275 ℃ in the sequential biaxial stretching method, and is preferably 260 to 280 ℃ in the case of obtaining a biaxially stretched film having a thickness of 1 to 25 μm in the simultaneous biaxial stretching method, and is preferably 260 to 275 ℃ in the case of obtaining a biaxially stretched film having a thickness of 26 to 50 μm.

Examples of the heat-fixing treatment method include a known method such as a method of blowing hot air, a method of irradiating infrared rays, and a method of irradiating microwaves. Among them, a method of blowing hot air is preferable from the viewpoint of enabling uniform and accurate heating.

(relaxation)

The film after the heat-fixing treatment is subjected to a relaxation treatment at a relaxation rate of 1.0 to 10.0% in the longitudinal direction and 1.0 to 12.0% in the width direction at the same temperature as the heat-fixing treatment temperature while being held by a jig. If the relaxation rates in the longitudinal direction and the width direction are less than 1.0%, a film having a sufficiently reduced heat shrinkage rate cannot be obtained. If the relaxation rate in the longitudinal direction exceeds 10.0%, the film may be relaxed. A film having a reduced heat shrinkage rate and improved dimensional stability can be obtained by performing a relaxation treatment at a relaxation rate of 1.0 to 10.0% in the longitudinal direction and 1.0 to 12.0% in the width direction.

In the sequential biaxial stretching method, when a biaxially stretched film having a thickness of 1 to 50 μm is obtained, the relaxation rate is preferably 1.0 to 6.0% in the longitudinal direction and 1.0 to 12.0% in the width direction, and when a biaxially stretched film having a thickness of 51 to 150 μm is obtained, the relaxation rate is preferably 1.0 to 3.0% in the longitudinal direction and 6.0 to 12.0% in the width direction.

In the simultaneous biaxial stretching method, the relaxation rate is preferably 1.0 to 6.0% in the longitudinal direction and 1.0 to 12.0% in the width direction.

The relaxation treatment in the longitudinal direction and/or the width direction of the film is independently controlled in the production of the film, but in both the simultaneous biaxial stretching method and the sequential biaxial stretching method, it is preferable that the absolute value of the difference between the relaxation rate in the longitudinal direction and the relaxation rate in the width direction is 2 or less. In this case, the resulting biaxially stretched film had a reduced moisture absorption elongation and a long-side moisture absorption elongation N_MDMoisture absorption elongation N in the width direction_TDAbsolute value of the difference (| N)_MD－N_TD|) is reduced, and generation of curl when moisture is absorbed in a laminate obtained by laminating other materials is suppressed.

In the simultaneous biaxial stretching method, the relaxation treatment may be performed simultaneously or separately in the longitudinal direction and the width direction on line. In the case of separate execution, there may be mentioned: a method of performing the longitudinal direction relaxation and then the width direction relaxation, and a method of performing the transverse direction relaxation and then the longitudinal direction relaxation.

On the other hand, in the sequential biaxial stretching method, the above-mentioned relaxation treatment (i) may be performed simultaneously in the longitudinal direction and the width direction on line after the longitudinal stretching and the transverse stretching are performed and the thermosetting treatment is performed, or (ii) may be performed after the longitudinal stretching, the relaxation treatment in the longitudinal direction, the transverse stretching, the heat setting treatment, and the relaxation treatment in the transverse direction. In addition, in (ii), if the heat-fixing treatment is performed after the longitudinal stretching and the longitudinal relaxation treatment, the resulting film is not easily stretched in the transverse direction, and therefore, it is not preferable to perform the heat-fixing treatment at a stage before the transverse stretching. In the sequential biaxial stretching method (i) and (ii), the stretching in the longitudinal direction is performed first and then the stretching in the transverse direction is performed, but the sequential biaxial stretching method may be performed first and then the stretching in the transverse direction is performed.

Alternatively, the relaxation treatment may be performed in the longitudinal direction by performing the relaxation treatment in the width direction on a wire after biaxial stretching, then winding the wire once, and passing the wire under a low tension in a drying furnace set to a predetermined temperature while being off-line.

The thickness of the semi-aromatic polyamide film of the present invention is suitably changed depending on the application and purpose, but is preferably 1 to 150 μm, more preferably 10 to 100 μm, and further preferably 20 to 80 μm.

Since the crystallinity of the semi-aromatic polyamide resin constituting the semi-aromatic polyamide film of the present invention is very high, if the sequential biaxial stretching method is applied, oriented crystallization is likely to occur when the film in an unstretched state is stretched in the longitudinal direction or the width direction, and the oriented crystallized film is sometimes difficult to be stretched in the next orthogonal direction, so that the simultaneous biaxial stretching method is preferably applied. On the other hand, in the semi-aromatic polyamide film of the present invention, when the thickness exceeds 50 μm, the stretching force at the time of stretching is excessively high by the simultaneous biaxial stretching method, and thus the difficulty of stretching is remarkably improved. Therefore, in the biaxial stretching of such a film having a high stretching force, it is preferable to apply the sequential biaxial stretching method as compared with the simultaneous biaxial stretching method.

In the apparatus for producing the semi-aromatic polyamide membrane of the present invention, it is preferable to perform a treatment of reducing the roughness of the surface of the cylinder, the melting section of the cylinder, the metering section, the single tube, the filter, the T-die, and the like, in order to prevent the resin from staying therein. As a method for reducing the surface roughness, for example, a method of modifying with a substance having a low polarity can be cited. Alternatively, a method of depositing silicon nitride or diamond-like carbon on the surface thereof may be mentioned.

The obtained semi-aromatic polyamide film may be formed into a single sheet or may be wound around a winding roll to form a film roll. From the viewpoint of productivity when used for various applications, it is preferable to form the film in the form of a roll. In the case of a roll of film, it may be cut to the desired width.

The semi-aromatic polyamide film may be a single-layer film composed of 1 layer or a multilayer structure in which 2 or more layers are stacked. In the case of forming a multilayer structure, for example, in a film of a two-layer structure, any one of the two layers may contain a lubricant, and in a film of a three-layer structure, the layers located on both surfaces of the three layers may contain a lubricant, respectively. The type and content of the lubricant contained therein may be independently designed. By forming such a multilayer structure, the surface roughness of each surface of the semi-aromatic polyamide film can be independently controlled.

The surface of the semi-aromatic polyamide film may be subjected to corona treatment, plasma treatment, acid treatment, flame treatment, or the like in order to improve adhesion to other materials.

The semi-aromatic polyamide film of the present invention may be laminated with inorganic substances such as metals and oxides thereof, other polymers, paper, woven cloth, nonwoven fabric, wood, and the like.

< use >)

The semi-aromatic polyamide film of the present invention has heat resistance and excellent dimensional stability, and therefore, can be used for various electronic materials, optical components, and other applications.

Specifically, it can be used as a packaging material for pharmaceuticals; packaging materials for Food such as Retort Food (Retort Food); packaging materials for electronic parts such as semiconductor packages; electrical insulation materials for motors, transformers, cables, etc.; dielectric materials for capacitor applications and the like; magnetic tape materials such as magnetic tape cassettes, magnetic tapes for data storage for digital data storage, and video tapes; protective sheets for solar cell substrates, liquid crystal panels, conductive films, display devices, and the like; an electronic substrate material such as an LED mounting substrate, a substrate for flexible printed wiring, a flexible flat cable, or the like; heat-resistant tapes such as coverlay films for flexible printed wiring, heat-resistant masking tapes, and industrial process tapes; a heat resistant bar code label; a heat-resistant reflector; an insulating tape; various release films; a heat-resistant base film; a photo film; a molding material; agricultural materials; a medical material; materials for civil engineering and construction; filtration membranes, and the like, membranes for domestic use, industrial materials.

Further, the semi-aromatic polyamide film of the present invention is excellent in the above-described properties, that is, heat resistance, dimensional stability and transparency, and therefore can be used for applications such as display materials and display devices in mobile devices and the like. Specifically, the film can be used as a base material film for various functional materials such as an optical substrate for various displays such as liquid crystals and organic EL, a polarizing plate, and a retardation plate, and as a protective or sealing film for a light-emitting element and a display device.

Examples

The present invention will be specifically described below with reference to examples.

1. Evaluation method

(1) Intrinsic viscosity of semi-aromatic polyamide

The inherent viscosity (. eta.) of the resin at 30 ℃ at each concentration of 0.05, 0.1, 0.2, 0.4g/dL in concentrated sulfuric acid was determined by the following equation_inh) Extrapolating the concentration to 0 to obtain a value, and using the value as the intrinsic viscosity [. eta. ]]。

η_inh＝[ln(t₁/t₀)]/c

[ in the formula, [. eta. ]_inhDenotes the intrinsic viscosity (dL/g), t₀Represents the flow-down time (sec) of the solvent, t₁The flow-down time (sec) of the resin solution is shown, and c represents the concentration (g/dL) of the resin in the solution. Angle (c)

(2) Melting point and glass transition temperature of semi-aromatic polyamide

The semi-aromatic polyamide was heated from 20 ℃ to 350 ℃ at 10 ℃/min under a nitrogen atmosphere using a differential scanning calorimeter apparatus (DSC-7 manufactured by Perkinelmer Co., Ltd.) and held for 5 minutes (first scanning), and then cooled from 350 ℃ to 20 ℃ at 100 ℃/min and held for 5 minutes. The glass transition temperature in the further process of increasing the temperature from 20 ℃ to 350 ℃ at 10 ℃/min (second scan) was set as Tg of the semi-aromatic polyamide. Similarly, the peak temperature of the crystal melting peak observed in the second scan is taken as Tm.

(3) Heat of crystallization of unstretched film

The heat quantity of the obtained exothermic peak was determined by heating an unstretched sheet of a semi-aromatic polyamide (10 mg) at 20 ℃ per minute in a nitrogen atmosphere from 40 ℃ to 350 ℃ using a differential scanning calorimeter (DSC-7 manufactured by Perkinelmer).

(4) Heat shrinkage of semi-aromatic polyamide film

Test pieces (width 10 mm. times. length 100mm) in the form of strips were cut out in the longitudinal direction and the width direction of the semi-aromatic polyamide film, respectively. The resulting test pieces were subjected to a treatment at 250 ℃ for 5 minutes, and then to a standing at 23 ℃ and 50% RH for 2 hours, respectively, to measure the dimensions in the longitudinal direction, and the thermal shrinkage S of the test pieces in the longitudinal direction was determined from the following equation_MDAnd the thermal shrinkage rate S of the test piece in the width direction_TD。

Heat shrinkage (%) [ { original length-treated length }/original length ] × 100

In addition to the measurement of the thermal shrinkage rate after 5 minutes of treatment at 250 ℃ as described above, the thermal shrinkage rates after 15 minutes of treatment at 200 ℃ were also measured for comparative examples 1 to 4.

In addition, the thermal shrinkage rate S in the longitudinal direction was also calculated_MDHeat shrinkage ratio with width direction S_TDAbsolute value of the difference (| S)_MD－S_TDI) the anisotropy of the heat shrinkage rate was evaluated by the following criteria.

◎：|S_MD－S_TDLess than 0.4 |

○：|S_MD－S_TD| is 0.4 or more and less than 0.8

△：|S_MD－S_TD| is 0.8 or more and less than 1.2

×：|S_MD－S_TD| is 1.2 or more

(5) Tensile elongation at break of semi-aromatic polyamide film

The tensile elongation at break in the longitudinal direction and the width direction of the semi-aromatic polyamide film was measured according to JIS K7127.

(6) Haze of semi-aromatic polyamide film

The haze of the semi-aromatic polyamide film was measured according to JIS K7105 using a haze meter (NDH 2000) manufactured by japan electrochrome corporation.

(7) Moisture absorption elongation of semi-aromatic polyamide film

After the semi-aromatic polyamide film was left to stand at 20 ℃ and 40% RH for 2 days, test pieces (200 mm in width. times. 300mm in length) were cut out and marked with a dot pitch of 100mm in the longitudinal direction and the width direction, respectively. After the moisture absorption treatment was performed for 2 days at a temperature of 20 ℃ and a humidity of 90% RH, the distances between the respective dots in the longitudinal direction and the width direction were measured, and the moisture absorption elongations of the test pieces in the longitudinal direction and the width direction were determined from the following equation.

Moisture absorption elongation (%) [ { length-original length after moisture absorption treatment ]/original length ] × 100

In addition, the wet elongation N in the longitudinal direction was also calculated_MDMoisture absorption elongation N in the width direction_TDAbsolute value of the difference (| N)_MD－N_TD| for the evaluation of anisotropy of moisture absorption elongation, the following criteria were used.

◎：|N_MD－N_TDLess than 0.20 |

○：|N_MD－N_TD| is 0.20 or more and less than 0.30

△：|N_MD－N_TD| is 0.30 or more

(8) Deformation of a laminate

An aqueous dimer acid-based polyamide resin dispersion (20 mass% solid content, manufactured by Youngko Co., Ltd.) and a polyester resin composition containing the sameAn oxazoline-based polymer aqueous solution (EPOCROS WS-700 manufactured by Nippon catalyst Co., Ltd., solid content concentration: 25% by mass) was mixed so that the solid contents became 100 parts by mass and 10 parts by mass, and the mixture was stirred at room temperature for 5 minutes to obtain a coating agent.

A film cut piece (width 200 mm. times. length 300mm) was cut out from the semi-aromatic polyamide film in an oven-dried state immediately after production, the coating agent was applied thereto at a thickness of 3 μm after drying, and drying was performed at 150 ℃ for 30 seconds to form an adhesive layer on the film cut piece. Further, an electrolytic copper foil (surface CTS treated, thickness 18 μm, manufactured by Kogaku K.K.) having the same size as the film cut piece was laminated to the film cut piece through the adhesive layer to obtain a laminate. The bonding was performed using a hot stamping machine under conditions of 180 ℃ for 15 minutes and 2 MPa.

Test pieces (width 100 mm. times. length 100mm) were cut out from the obtained laminate, heat-treated in a reflow furnace set at a temperature of 260 ℃ for 15 seconds, taken out of the furnace, and left at room temperature (23 ℃) for 1 hour. The deformation of the laminate after the heat treatment was visually confirmed and evaluated according to the following criteria.

Very good: and is not deformed at all.

O: planarity is not compromised but is slightly strained.

And (delta): has strain, but has no practical problem.

X: serious strain and no practicability.

(9) Moisture absorption crimp of laminate

A test piece (width 100 mm. times. length 100mm) was cut out from the laminate obtained in (8) above, and the laminate was placed on a horizontal table with the film surface facing downward, and allowed to stand for 2 days in an atmosphere of 20 ℃ temperature and 40% RH humidity for humidity control. Then, the mixture was left for 2 days at 20 ℃ and 90% RH. The moisture absorption property of the film was evaluated from the degree of curling of the test piece, that is, the height at which the copper foil was not affected by moisture absorption but only the semi-aromatic polyamide film absorbed moisture and stretched and the test piece curled, and the end portion of the test piece lifted from the table portion.

Very good: no curling.

O: slightly curled in the longitudinal or width direction. There is no practical problem.

And (delta): curling in the long side direction or the width direction. Has a practical problem.

2. Raw material

(1) Semi-aromatic polyamides

The semi-aromatic polyamide A, B obtained in production examples 1 and 2 was used.

Production example 1

3289 parts by mass of Terephthalic Acid (TA), 2533 parts by mass of 1, 9-Nonanediamine (NDA), 633 parts by mass of 2-methyl-1, 8-octanediamine (MODA), 48.9 parts by mass of Benzoic Acid (BA), 6.5 parts by mass of sodium hypophosphite monohydrate (0.1 mass% with respect to the total of the above four polyamide raw materials), and 2200 parts by mass of distilled water were placed in a reaction vessel and subjected to nitrogen substitution. The molar ratio of these starting materials (TA/BA/NDA/MODA) was 99/2/80/20.

After stirring the contents of the reaction kettle at 100 ℃ for 30 minutes, the internal temperature was raised to 210 ℃ over 2 hours. At this time, the pressure inside the reactor was increased to 2.12MPa (22 kg/cm)²). After maintaining this state and continuing the reaction for 1 hour, the temperature was raised to 230 ℃ and then maintained at 230 ℃ for 2 hours, and water vapor was gradually discharged to maintain the pressure at 2.12MPa (22 kg/cm)²) While proceeding simultaneously. Next, the pressure was reduced to 0.98MPa (10 kg/cm) over 30 minutes²) And further reacted for 1 hour to obtain a prepolymer. The resultant was dried at 100 ℃ under reduced pressure for 12 hours, and then pulverized into a size of 2mm or less.

Next, the pulverized prepolymer was subjected to solid-phase polymerization at 230 ℃ under a pressure of 13.3Pa (0.1mmHg) for 10 hours to obtain a polymer. The resulting mixture was fed to a twin screw extruder (TEX 44C, manufactured by japan steelworks corporation), melt-kneaded at a cylinder temperature of 320 ℃, extruded, cooled, and cut to produce pellets of the semi-aromatic polyamide a.

Production example 2

Terephthalic Acid (TA)489 parts by mass, 1, 10-decamethylenediamine (DDA)507 parts by mass, Benzoic Acid (BA)2.8 parts by mass, sodium hypophosphite monohydrate 1.0 parts by mass (0.1% by mass relative to the total of the three polyamide raw materials), and distilled water 1000 parts by mass were placed in a reaction vessel and subjected to nitrogen substitution. The molar ratio of these feedstocks (TA/BA/DDA) was 99/2/100.

The contents of the autoclave were stirred at 80 ℃ for 0.5 hour with 28 revolutions per minute and then warmed to 230 ℃. Then, it was heated at 230 ℃ for 3 hours. Then, the reaction product was cooled and taken out.

After the reaction product was pulverized, the resultant was heated at 220 ℃ for 5 hours in a dryer under a nitrogen stream, and solid-phase polymerization was carried out to obtain a polymer. The resulting mixture was fed to a twin screw extruder (TEX 44C, manufactured by japan steelworks corporation), melt-kneaded at a cylinder temperature of 320 ℃, extruded, cooled, and cut to produce pellets of the semi-aromatic polyamide B.

The melting point, glass transition temperature, and intrinsic viscosity of the produced semi-aromatic polyamide are shown in table 1.

[ Table 1]

(2) Silicon dioxide

The master batches (M1) to (M3) containing 2 mass% of silica obtained in production examples 3 to 5 below were used.

Production example 3

98 parts by mass of a semi-aromatic polyamide a and 2 parts by mass of silica (SYLYSIA 310P, manufactured by ltd., average particle diameter 2.7 μ M) were melt-kneaded to prepare a master batch (M1) containing 2 mass% of silica.

Production example 4

98 parts by mass of the semi-aromatic polyamide B and 2 parts by mass of silica (SYLYSIA 310P, manufactured by ltd., average particle diameter 2.7 μ M) were melt-kneaded to prepare a master batch (M2) containing 2 mass% of silica.

Production example 5

98 parts by mass of a semi-aromatic polyamide A and 2 parts by mass of silica (NIPGEL AZ-200 manufactured by TOSOHSICA CORPORATION, average particle diameter 2.0 μ M) were melt-kneaded to prepare a master batch (M3) containing 2% by mass of silica.

(3) Hindered phenol heat stabilizer

GA: 3, 9-bis [ 2- { 3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy } -1, 1-dimethylethyl ] -2, 4,8, 10-tetraoxaspiro [5.5] undecane (Sumilyzer GA-80, Sumitomo chemical Co., Ltd., pyrolysis temperature 392 ℃ C.)

Example 1

Semi-aromatic polyamide A, GA and a base particle (M1) were mixed so that GA was 0.2 parts by mass and silica was 0.1 parts by mass, respectively, with respect to 100 parts by mass of semi-aromatic polyamide a.

This mixture was put into a 65mm single-screw extruder having cylinder temperatures of 295 ℃ (front stage), 320 ℃ (middle stage) and 320 ℃ (rear stage), melted, extruded from a T-die set at 320 ℃ into a sheet, and cooled while being electrostatically adhered to a cooling roll set at a surface temperature of 40 ℃ to obtain a substantially non-oriented unstretched sheet having a thickness of 250 μm.

The cooling roll was coated with ceramic (Al) to a thickness of 0.15mm on the surface₂O₃) And the obtained cooling roller. Two carbon brushes are arranged in parallel and contacted with the cooling roller at the upstream side of the contact point of the roller surface and the film, and the support of the carbon brush is grounded, thereby removing electricity on the surface of the ceramic coating layer. A tungsten wire having a diameter of 0.2mm was used as an electrode, and a voltage of 6.5kV was applied by a 300W (15 kV. times.20 mA) DC high voltage generator.

The obtained unstretched sheet was cut into 12X 12cm square, set on a batch biaxial stretcher (ICM-18 BE, manufactured by KANTO CORPORATION), and subjected to simultaneous biaxial stretching. The stretching conditions were preheating and stretching temperature of 115 ℃, tensile strain rate in the longitudinal direction and the width direction of 3200%/min, and stretching ratio in the longitudinal direction and the width direction of 3.0 times and 3.3 times, respectively.

After stretching, heat-setting treatment was carried out at 275 ℃ for 10 seconds to perform relaxation treatment at a relaxation rate of 1.0% in the longitudinal direction and 8.0% in the width direction, thereby obtaining a semi-aromatic polyamide film having a thickness of 25 μm. The stretching treatment of the unstretched sheet and the relaxation treatment of the stretched film were performed with the extrusion direction in the case of obtaining an unstretched sheet set to the longitudinal direction and the direction orthogonal to the extrusion direction set to the width direction.

Examples 2 to 16 and 18, and comparative examples 1 to 15

A semi-aromatic polyamide film was obtained in the same manner as in example 1 except that the type of semi-aromatic polyamide, the cooling roll surface temperature, the stretching ratio, the heat setting temperature, and the relaxation rate were changed as described in tables 2,3, 5, and 6. In example 18, a master batch (M2) was used instead of the master batch (M1). In comparative examples 1 and 3, a semi-aromatic polyamide film containing no silica was obtained without using the master batch (M1).

Example 17

The semi-aromatic polyamide a and the mother particles (M1) were mixed so that the content of silica became 0.1 part by mass. The mixture was charged into an extruder a, and melt-extruded (hereinafter referred to as resin X) while setting barrel temperatures at 295 ℃ (front stage), 320 ℃ (middle stage), and 320 ℃ (rear stage).

On the other hand, the semi-aromatic polyamide a was charged into the extruder B, and melt-extruded (hereinafter referred to as resin Y) while setting the cylinder temperatures at 295 ℃ (front stage), 320 ℃ (middle stage), and 320 ℃ (rear stage).

The resins X, Y melted in the extruders A, B were extruded from a T die set at 320 ℃ into a sheet form so as to have a three-layer structure of X/Y/X, and after being electrostatically bonded to and temporarily cooled by a cooling roll having a surface temperature of 40 ℃, the sheet was further cooled by a cooling roll having a surface temperature of 20 ℃ to obtain an unstretched film having a total thickness of 500 μm in which X/Y/X is 100/300/100 μm. The pattern of the cooling roll, the voltage application method, and the like are the same as those of example 1.

The obtained unstretched sheet was cut into 12X 12cm square, set on a batch biaxial stretcher (ICM-18 BE, manufactured by KANTO CORPORATION), and subjected to simultaneous biaxial stretching. The stretching conditions were preheating and stretching temperature of 115 ℃, tensile strain rate in the longitudinal direction and the width direction of 3200%/min, and stretching ratio in the longitudinal direction and the width direction of 3.0 times and 3.3 times, respectively.

After stretching, heat-setting treatment was performed at 275 ℃ for 10 seconds to perform relaxation treatment at a relaxation rate of 2.0% in the longitudinal direction and 8.0% in the width direction, thereby obtaining a 50 μm thick semi-aromatic polyamide film having a layer structure of X/Y/X of 10/30/10 μm.

Example 19

A semi-aromatic polyamide film was obtained in the same manner as in example 1, except that sequential biaxial stretching was performed with stretching ratios in the longitudinal direction and the width direction of 2.5 times and 3.3 times, respectively, and relaxation treatments were performed with relaxation rates in the longitudinal direction and the width direction of 2.0% and 4.0%, respectively.

Examples 20 to 38 and comparative examples 16 to 21

A semi-aromatic polyamide film was obtained in the same manner as in example 19 except that the type of semi-aromatic polyamide, the cooling roll surface temperature, the stretching ratio, the heat setting temperature, and the relaxation rate were changed as described in tables 3 to 6. In example 29, a master batch (M3) was used instead of the master batch (M1).

The structure of the semi-aromatic polyamide, the production conditions of the film, and the properties of the obtained semi-aromatic polyamide film are shown in tables 2 to 6.

The semi-aromatic polyamide films of examples 1 to 38 satisfied all the characteristic values specified in the present invention, and had a small heat shrinkage rate, a low haze, and a sufficiently large tensile elongation at break.

That is, in the production of the semi-aromatic polyamide film, the surface temperature of the cooling roll is lowered to obtain an unstretched film having an increased amount of crystallization heat, and the use of the unstretched film having an increased amount of crystallization heat as the semi-aromatic polyamide film can increase the tensile elongation at break and reduce the haze, and the relaxation treatment in the longitudinal direction and the width direction can reduce the thermal shrinkage in the longitudinal direction and the width direction and increase the tensile elongation at break.

In comparative example 1, an unstretched film was obtained using a semi-aromatic polyamide containing no silica and a cooling roll having a surface temperature of 50 ℃ in the same manner as in example 2 of patent document 1, and then stretched 3.0 times in the longitudinal direction and 3.3 times in the width direction, heat-set at 270 ℃, and then relaxed at a relaxation rate of 5.0% only in the width direction.

The heat of crystallization of the unstretched film obtained using a cooling roll having a surface temperature of 50 ℃ was 19J/g.

The heat shrinkage of the semi-aromatic polyamide film obtained from the unstretched film measured at 200 ℃x15 minutes was as low as 0.4% in the longitudinal direction and 0.1% in the width direction, but if measured at 250 ℃x5 minutes, the heat shrinkage in the longitudinal direction increased to 2.5%. The tensile elongation at break was 98% in the longitudinal direction, but 64% in the width direction, which was low.

In addition, in the semi-aromatic polyamide film of comparative example 2 obtained in the same manner as in comparative example 1 except that the semi-aromatic polyamide containing silica was used, an increase in haze was observed.

The semi-aromatic polyamide films of comparative examples 3 and 4 were obtained in the same manner as in comparative examples 1 and 2, except that the films were also relaxed at a relaxation rate of 2.0% in the longitudinal direction, and the heat shrinkage rate in the longitudinal direction was reduced to 1.3%, but the tensile elongation at break in the width direction was 67 to 69%, which was low.

In comparative examples 5 to 9, an unstretched film was obtained using a semi-aromatic polyamide containing silica and a cooling roll having a surface temperature of 50 ℃ or higher. The films of comparative examples 5 to 7 using the unstretched film had low tensile elongation at break in the width direction as in comparative examples 1 to 4. The film of comparative example 8 suppressed the decrease in tensile elongation at break, but had high haze. In comparative example 9, breakage occurred during film stretching, and a biaxially stretched film could not be obtained.

The films of comparative examples 10 to 11 had a direction in which relaxation treatment was not performed, and therefore had a direction in which the heat shrinkage rate was high, while the film of comparative example 12 had a low temperature in the heat-setting step, and therefore had a high heat shrinkage rate and poor dimensional stability.

In comparative example 13, breakage occurred during heat-setting treatment, and in comparative example 14, simultaneous biaxial stretching was attempted using a thick unstretched film, but none of them could obtain a biaxially stretched film.

The film of comparative example 15 has a high haze because of a large silica content.

In the film of comparative example 16 using the sequential biaxial stretching method, the heat shrinkage rate was high and the dimensional stability was poor because the temperature in the heat-setting step was low. The film of comparative example 17 has a stretch ratio exceeding the preferable range, and therefore has a tensile elongation at break of less than 70% and a high haze. The films of comparative examples 18 and 19 had a low heat of crystallization, and therefore had a tensile elongation at break of less than 70% and a high haze. In comparative example 20, breakage occurred during transverse stretching, and a biaxially stretched film could not be obtained. In addition, the film of comparative example 21 has a high haze because of a large silica content.