KR101597802B1 - Film for tire inner-liner and preparation method thereof - Google Patents

Abstract

The present invention relates to a film for a tire innerliner comprising a base film having a relatively high surface energy and a specific copolymer or a mixture of specific polymers and an adhesive layer formed on the base film and a method for producing the same, Since the inner liner film can realize excellent airtightness even with a thin thickness, it is possible to reduce the weight of the tire and to improve the automobile fuel economy, and to form a uniform adhesive layer, the tire can exhibit excellent adhesion to the carcass portion, Excellent durability and endothelial property can be realized with respect to repeated deformations that occur.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a film for a tire innerliner,

The present invention relates to a film for a tire innerliner and a method of manufacturing the same, and more particularly to a tire for a tire innerliner which is capable of realizing excellent airtightness even with a thin thickness, A tinner inner liner film capable of exhibiting excellent adhesion to a tire carcass portion due to the formation of an adhesive layer and capable of realizing excellent durability and endothelial property against repeated deformation occurring during tire running and a method for manufacturing the tire innerliner .

The tire supports the load of the vehicle, mitigates the impact from the road surface, and transmits the driving force or braking force of the vehicle to the ground. Generally, a tire is a composite of a fiber / steel / rubber and has a structure as shown in Fig.

Tread (1): It is a part that comes into contact with the road surface, it should provide friction force necessary for braking and driving, good abrasion resistance, able to withstand external impact, and low heat generation.

Body Ply (or Carcass) (6): It is a coil layer inside the tire. It should support the load and resist the impact.

Belt (5): It is located between the body fly, and it is made of steel wire in most cases, it alleviates the external impact and keeps the ground surface of the tread wide to improve the running stability.

Side Wall (3): A rubber layer between the lower portion of the shoulder (2) and the bead (9), and protects the inner body ply (6).

Inner Liner (7): Located inside the tire instead of the tube, it prevents leakage of air to enable pneumatic tires.

BEAD (9): A square or hexagonal wire bundle with rubber coated wire to seat and fix the tire on the rim.

CAP PLY (4): It is a special cloth paper placed on the belt of the radial tires for some passenger cars, minimizing the movement of the belt when driving.

APEX (8): It is a triangular rubber filling material used to minimize the dispersion of beads, protect the beads by mitigating external impact, and prevent the inflow of air during molding.

In recent years, tube-less tires having high-pressure air of about 30 to 40 psi have been generally used without using a tube. In order to prevent the inner air from leaking to the outside during the operation of the vehicle An inner liner having high airtightness is disposed on the inner layer of the carcass.

Previously, a tire inner liner having rubber components such as butyl rubber or halobutyl rubber, which is relatively low in air permeability, was used. In this inner liner, the rubber content or the thickness of the inner liner had to be increased in order to obtain sufficient airtightness . As the content and the thickness of the rubber component increase, the total weight of the tire increases and the fuel consumption of the automobile decreases. Also, air pockets are formed between the inner rubber of the carcass layer and the inner liner in the process of vulcanizing the tire or running the vehicle, And the shape and physical properties of the material are changed.

Accordingly, various methods have been proposed to reduce the thickness and weight of the inner liner to reduce the fuel consumption, and to reduce changes in the shape and physical properties of the inner liner that occur in the vulcanization or running process of the tire.

However, any previously known method has had a limitation in maintaining excellent air permeability and moldability of the tire while sufficiently reducing the thickness and weight of the inner liner. In addition, the inner liner obtained by a previously known method often fails to have sufficient fatigue resistance, such as cracking due to repeated deformation during the manufacturing process or running process of the tire. Further, since the previous tire inner liner has poor adhesion to the carcass layer inside the tire, it is often separated or peeled off during the tire manufacturing process or automobile running process, so that the inner liner is damaged by friction to form cracks and fractures Respectively.

The present invention can realize excellent airtightness even with a thin thickness, thereby making it possible to reduce the weight of the tire and improve the fuel consumption of automobiles, and to exert an excellent adhesive force to the tire carcass portion due to the formation of a uniform adhesive layer, To provide a film for a tanner inner liner capable of realizing excellent durability and endothelial characteristic against repeated deformation.

The present invention also provides a method for producing the film for a tire innerliner.

The present invention relates to a process for the production of a copolymer comprising a polyamide-based segment and a poly-ether-based segment, or a polymer comprising a polyamide-based segment and a polymer comprising a poly- A substrate film; And an adhesive layer formed on at least one surface of the base film and including a resorcinol-formalin-latex (RFL) adhesive, wherein the surface energy of one surface of the base film measured by ASTM D 2578 is 40 dyne / cm or more , And a film for a tire inner liner.

The present invention also provides a process for producing a raw material for a substrate film comprising a copolymer containing a polyamide segment and a polyether segment or a mixture of a polymer containing a polyamide segment and a polymer containing a polyether segment At 230 to 300 占 폚 to form a base film; Treating at least one side of the base film with a plasma of oxygen, air, helium or argon; And forming an adhesive layer including a resorcinol-formalin-latex (RFL) -based adhesive on one surface of the plasma treated base film layer. The present invention also provides a method for manufacturing a film for a tire innerliner.

Hereinafter, a method for manufacturing a film for a tire innerliner and a film for a tire innerliner according to a specific embodiment of the present invention will be described in detail.

According to one embodiment of the invention, there is provided a composition comprising a copolymer comprising a polyamide-based segment and a poly-ether-based segment, or a polymer comprising a polyamide-based segment and a poly- A base film comprising a mixture of polymers; And an adhesive layer formed on at least one surface of the base film and including a resorcinol-formalin-latex (RFL) adhesive, wherein the surface energy of one surface of the base film measured by ASTM D 2578 is 40 dyne / cm or more , A film for a tire inner liner may be provided.

Accordingly, the present inventors proceeded with research on a tire inner liner film, and found that a copolymer containing a polyamide-based segment and a poly-ether-based segment, or a polymer containing a polyamide-based segment and a poly- ether group, and a resorcinol-formalin-latex (RFL) -based adhesive are used, and even in the case of a thin thickness, excellent airtightness, high air pressure holding performance and excellent mechanical properties And that the inner liner can be firmly and uniformly bonded to the inside of the tire even with a thin and lightweight adhesive layer.

In particular, as shown in the manufacturing method described later, the surface of the base film can be modified through plasma treatment in a specific method, and the surface of the base film thus modified can have high surface energy, i.e., high hydrophilicity. Accordingly, the resorcinol-formalin-latex (RFL) -based adhesive can be more uniformly applied to the base film layer and the amount to be applied can be greatly increased. Specifically, the surface energy of one surface of the base film may be 40 dyne / cm, preferably 40 to 70 dyne / cm. The measurement of the surface energy of such a base film can be carried out according to ASTM D 2578.

Typically, a tie gum or a certain adhesive is used to bond the inner liner film to the inside of the tire, but there is a certain limit in uniformly applying or laminating the adhesive on the surface of the inner liner film owing to the high surface tension of the adhesive in the aqueous solution . Further, in the case of the inner liner film of the previously known polymer resin type, there has been a problem that it is difficult for the applied adhesive to be uniformly formed on the surface of the inner liner film due to low wettability or low surface energy, There may be a problem that the adhesive is not bonded to a part of the surface of the liner film or the difference between the maximum thickness and the minimum thickness of the adhesive is from 5 mu m to 6 mu m.

In this way, when the adhesive layer is not uniformly formed on the inner liner film or does not have an appropriate adhesive force, the adhesive force of the adhesive layer is further lowered due to the expansion occurring during the tire molding. As a result, after the tire vulcanization, May be separate from other components, for example carcass. When these tires are used in the actual running process of the vehicle, due to deformation and high temperature, continuous friction may occur with other tire components such as inner liner film and carcass, and the deformation force generated in the running process is not dispersed to other parts of the tire The film itself may be broken or partial cracks may occur while concentrating on the inner liner film.

On the contrary, when the base film layer containing the specific copolymer or mixture of polymers is subjected to plasma treatment, the resorcinol-formalin-latex (RFL) adhesive can be applied more uniformly, and the inside of the tire and the base film It can be more firmly coupled. The uniformity of the adhesive layer may vary depending on the thickness of the adhesive layer itself and the characteristics of the adhesive to be applied. For example, the difference between the maximum thickness and the minimum thickness of the adhesive layer may be 2um or less, preferably 1um or less.

On the other hand, the base film may have a thickness of 30 to 300 占 퐉, preferably 40 to 250 占 퐉, more preferably 40 to 200 占 퐉. Accordingly, the film for a tire inner liner of an embodiment of the present invention has a low thickness and a low air permeability, for example, an oxygen permeability of 200 cc / (m < 2 > have.

The base film is preferably composed of a polyamide-based segment and a poly-ether-based segment in order to realize excellent airtightness even with a thin thickness, to lighten the tire, improve automobile fuel economy, and have excellent moldability and mechanical properties Copolymer; Or a mixture of a polymer comprising a polyamide-based segment and a polymer comprising a poly-ether-based segment.

More preferably, the content of the polyether segment of the copolymer or the content of the polymer containing the poly-ether segment may be 15 to 50 wt% of the total weight of the base film.

Since the base film contains the copolymer of the polyamide-based segment and the polyether-based segment, it can be distinguished from the film for the previous tire inner liner having the components of the rubber-based component or the thermoplastic resin as the main components of the base material , And may have characteristics that do not require additional vulcanizers.

The characteristics of the film for a tire inner liner appear to be due to the use of a base film obtained by using a polyether-based segment that gives elastomeric properties together with the polyamide-based segment in a specific amount range. The polyamide-based segment exhibits excellent airtightness due to its inherent molecular chain properties, for example, 10 to 20 times more airtightness than butyl rubber commonly used in tires at the same thickness, and has a modulus Lt; / RTI > Since the polyether-based segments together with the polyamide-based segments are used in an amount of 15 to 50% by weight based on the total weight of the base film, the film for the innerliner of the tire exhibits a low modulus characteristic or occurs under a specific stretching condition The physical properties of the film are not greatly changed even after a specific heat treatment process, and the structural change due to the crystallization of the polyamide component can be suppressed, so that the durability against tire deformation can be improved.

In addition, even when the base film contains a mixture of a polymer containing a polyamide segment and a polymer containing a poly-ether segment, the above-described characteristics such as airtightness and modulus can be exhibited.

Accordingly, the inner liner film can be stretched or deformed to fit the shape of the tire even when a force which is not so great when the tire is molded, which enables the expression of excellent moldability of the tire.

The polyamide-based segment means a repeating unit containing an amide group (-CONH-), and may be formed from a polyamide-based resin participating in the polymerization reaction or a precursor thereof.

Since the polyamide segment has sufficient heat resistance and chemical stability, it is possible to prevent deformation or denaturation of the inner liner film upon exposure to chemical substances such as high temperature conditions or additives applied in the tire manufacturing process. The polyamide-based segment may have a relatively high reactivity to an adhesive (for example, a resorcinol-formalin-latex (RFL) -based adhesive) as it is copolymerized with a polyether-based segment, The film can be easily adhered to the carcass portion.

Specifically, the polyamide segment may be a copolymer of nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 610, nylon 612, nylon 6/66, nylon 6/66/610 copolymer, nylon MXD6 , Nylon 6T, nylon 6 / 6T copolymer, nylon 66 / PP copolymer, nylon 66 / PPS copolymer, 6-nylon methoxymethylate, 6-610-nylon methoxymethylate and 612- And the main repeating unit contained in one type of polyamide resin selected from the group consisting of methacrylic acid, For example, to a main repeating unit of nylon 6, and the R ₁ in the formula (1) known to be an alkylene having 6, also known as the main repeating unit of another polyamide resin readily apparent to those skilled in the art.

The polyamide-based segment may include a repeating unit represented by the following formula (1) or (2).

[Chemical Formula 1]

In Formula 1, R ₁ may be a linear or branched alkylene group having 1 to 20 carbon atoms or a linear or branched alkylene group having 7 to 20 carbon atoms.

(2)

R ₂ is a linear or branched alkylene group having 1 to 20 carbon atoms and R ₃ is a linear or branched alkylene group having 1 to 20 carbon atoms or a linear or branched alkylaryl group having 7 to 20 carbon atoms It can be a ring.

In the present specification, 'alkylene group' means a divalent functional group derived from an alkyl group, and 'arylalkylene group' means a divalent functional group derived from an alkyl group into which an aryl group is introduced. ≪ / RTI & gt ;

On the other hand, the polyether-based segment means a repeating unit containing an alkyl oxide ('-Akyl-O-') group, and may be formed from a polyether resin or its precursor participating in the polymerization reaction.

The polyether-based segment can inhibit the growth of large crystals in the tire inner liner film during the manufacturing process of the tire or the running of the vehicle, or prevent the film from breaking easily. In addition, the polyether-based segment can further lower the load generated during the modulus or elongation of the film for a tire innerliner, so that even when a relatively small force is applied to the tire, the tire can be stretched or deformed So that the tire can be easily molded. The polyether segment can prevent the rigidity of the film from rising at a low temperature and can prevent crystallization at a high temperature and can prevent damage or tear of the inner liner film due to repeated deformation or the like, The durability of the tire or inner liner can be improved by suppressing the occurrence of wrinkles of the film due to the permanent deformation by improving the resilience against deformation of the liner.

The polyether segment may be a main repeating unit that may be contained in a polyalkylene glycol resin or a derivative thereof. In the polyalkylene glycol derivative, the terminal of the polyalkylene glycol resin may be an amine group, a carboxyl group or an isocyanate group , Preferably an amine group-substituted derivative. Preferably, the polyether-based segment is at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyethylenediamine, polyoxypropylenediamine, polyoxytetramethylenediamine, and copolymers thereof And may be a main repeating unit contained in the polyether-based resin.

Specifically, the polyether-based segment may include a repeating unit represented by the following formula (5).

[Chemical Formula 5]

In the general formula (5), R ₅ may be a linear or branched alkylene group having 1 to 10 carbon atoms, and n may be an integer of 1 to 100. R ₆ and R ₇ may be the same or different from each other and may be a direct bond, -O-, -NH-, -COO- or -CONH-.

Meanwhile, in order to improve the mechanical properties or airtightness of the base film, the above-mentioned copolymer has a polyamide segment and a poly-ether segment at a weight ratio of 6: 4 to 3: 7 .

Further, in order to improve mechanical properties or airtightness of the base film, the mixing weight ratio of the polymer including the polyamide segment and the polymer including the polyether segment is from 6: 4 to 3: 7 .

On the other hand, the base film of the film for a tire innerliner may further include a polyamide resin in order to improve mechanical properties or airtightness. Such a polyamide-based resin may be present on the film in a mixed state or in a copolymerized state with the copolymer of the polyamide-based segment and the polyether-based segment described above. As shown in the manufacturing method described later, the polyamide based resin may be mixed with a copolymer of a polyamide-based segment and a polyether-based segment, and then may be contained in the film for a tire inner liner by being melted and extruded.

The polyamide resin which may be further included may be used to improve the mechanical properties such as heat resistance or chemical stability and airtightness of the film for a tire innerliner, but if the amount used is too large, the tire innerliner The characteristics of the film for use can be deteriorated. Particularly, even when the polyamide resin is further used, the content of the polyether segment in the film should be maintained at 15 to 50 wt%, so that the polyamide based resin, the polyamide based segment And other additives to be added should be 50 to 85% by weight.

The polyamide resin which can be further used is not particularly limited and it is preferable to use a polyamide resin containing the same or similar repeating unit as the polyamide segment in order to improve the compatibility with the copolymer .

The polyamide based resin may have a relative viscosity (96% sulfuric acid solution) of 3.0 to 3.5, preferably 3.2 to 3.4. If the viscosity of the polyamide resin is less than 3.0, a sufficient elongation can not be secured due to a reduction in toughness, which may cause breakage during tire manufacturing or automobile operation, and the airtightness or airtightness of the base film layer It may be difficult to ensure physical properties such as moldability. When the viscosity of the polyamide resin exceeds 3.5, the modulus or viscosity of the base film layer to be produced may become unnecessarily high, and the innerliner of the tire may not have adequate moldability or elasticity.

Examples of the polyamide based resin include polyamide based resins such as copolymers of nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 610, nylon 612, nylon 6/66, nylon 6/66 / 610 copolymers, nylon MXD6, nylon 6T, nylon 6 / 6T copolymers, nylon 66 / PP copolymers and nylon 66 / PPS copolymers; Or N-alkoxyalkylates thereof, such as methoxymethylated 6-nylon, methoxymethylated 6,610-nylon or methoxymethylated 612-nylon, and nylon 6, nylon 66, nylon 66, 46, nylon 11, nylon 12, nylon 610 or nylon 612 is preferably used.

The base film may contain a mixture of the polyamide based resin and the copolymer or the polymers at a weight ratio of 6: 4 to 3: 7.

Meanwhile, the film for a tire innerliner may include an adhesive layer formed on at least one side of the base film and including a resorcinol-formalin-latex (RFL) -based adhesive. The adhesive layer containing the resorcinol-formalin-latex (RFL) adhesive has excellent adhesion and adhesive holding performance to the base film layer and the tire carcass layer, and accordingly, It is possible to prevent the inner liner film and the carcass layer interface from being broken due to heat or repetitive deformation, so that the inner liner film has sufficient fatigue resistance.

The main characteristic of the adhesive layer described above appears to be due to the inclusion of certain resorcinol-formalin-latex (RFL) based adhesives having a particular composition. Previously, as the adhesive for the inner liner of a tire, a rubber type tie gum or the like was used, and accordingly, an additional vulcanization process was required.

On the contrary, the adhesive layer contains a resorcinol-formalin-latex (RFL) -based adhesive having a specific composition and has high reactivity and adhesion to the base film, and is also pressed under high temperature heating conditions without increasing the thickness The base film and the tire carcass layer can be firmly bonded. This makes it possible to reduce the weight of the tire and to improve the fuel consumption of the automobile and to prevent the separation of the carcass layer and the inner liner layer or the base film and the adhesive layer even in the tire manufacturing process or the repeated deformation in the automobile running process .

Also, since the adhesive layer can exhibit high endothelial characteristics against physical / chemical deformation that can be applied in the tire manufacturing process or automobile operation process, the adhesive layer can exhibit high endothelial property even during the manufacturing process of the high temperature condition or the long- And deterioration of other physical properties can be minimized.

In addition, the above-mentioned resorcinol-formalin-latex (RFL) -based adhesive is capable of crosslinking between latex and rubber to exhibit adhesive performance, and since it is a latex polymeric material physically, Chemical bonding between the methylol end group of the resorcinol-formalin polymer and the substrate film is possible. Accordingly, when the above-mentioned resorcinol-formalin-latex (RFL) -based adhesive is applied to a base film, a film for a tire innerliner having a sufficient adhesive property and high elastic properties can be provided.

The resorcinol-formalin-latex (RFL) based adhesive comprises 2 to 32% by weight, preferably 10 to 20% by weight of a condensate of resorcinol and formaldehyde, and 68 to 98% by weight, 90% by weight.

The condensate of resorcinol and formaldehyde may be obtained by mixing resorcinol and formaldehyde in a molar ratio of 1: 0.3 to 1: 3.0, preferably 1: 0.5 to 1: 2.5, followed by condensation. In addition, the condensate of resorcinol and formaldehyde may be contained in an amount of 2% by weight or more based on the total amount of the adhesive layer in terms of chemical reaction for excellent adhesion, and may be contained in an amount of 32% by weight or less have.

The latex may be one or a mixture of two or more selected from natural rubber latex, styrene / butadiene rubber latex, acrylonitrile / butadiene rubber latex, chloroprene rubber latex and styrene / butadiene / vinylpyridine rubber latex. The latex may be contained in an amount of not less than 68% by weight based on the total amount of the adhesive layer for the flexibility of the material and an effective crosslinking reaction with the rubber, and not more than 98% by weight for the chemical reaction with the base film and the rigidity of the adhesive layer.

The adhesive layer may further include at least one additive such as a surface tension regulator, a heat resistant agent, a defoamer, and a filler together with a condensate of resorcinol and formaldehyde and a latex. At this time, the surface tension modifier of the additive is applied for uniform application of the adhesive layer, but it may cause a problem of decrease in the adhesive strength when an excessive amount of the additive is added. Therefore, the amount of the surface tension modifier is preferably 2% by weight or 0.0001 to 2% by weight, 1.0% by weight or less, or 0.0001% by weight to 0.5% by weight. At this time, the surface tension regulator may be at least one selected from the group consisting of a sulfonate anionic surfactant, a sulfuric acid ester salt anionic surfactant, a carboxylate anionic surfactant, a phosphoric acid ester salt anionic surfactant, a fluorinated surfactant, a silicone surfactant and a polysiloxane surfactant And at least one selected from the group consisting of

The adhesive layer may have a thickness of 10 占 퐉 or less, preferably 0.1 占 퐉 to 10 占 퐉, more preferably 0.2 占 퐉 to 8 占 퐉, still more preferably 0.5 占 퐉 to 6 占 퐉, Can be formed on both surfaces. If the thickness of the adhesive layer is too thin, the adhesive layer itself may become thinner when the tire is inflated, the crosslinking adhesive force between the carcass layer and the base film may be lowered, and the stress may concentrate on a part of the adhesive layer. In addition, if the adhesive layer is too thick, the interface separation in the adhesive layer may occur and the fatigue characteristics may be deteriorated. In order to adhere the inner liner film to the carcass layer of the tire, an adhesive layer is generally formed on one surface of the base film. However, in the case of applying the inner liner film of a multilayer or the tire laminating method It is preferable to form an adhesive layer on both sides of the base film when adhesion with rubber is required on both sides in accordance with the structural design.

On the other hand, when the base film is stretched at 100% at room temperature, the modulus may be 10 to 40 MPa, preferably 15 to 35 MPa. When the base film having such modulus characteristics is applied, the film for a tire innerliner not only has excellent moldability in the process of manufacturing a tire, but also can stably maintain its physical properties even in severe deformation during tire molding, Allowing the tire to be stretched or deformed to conform to the shape of the tire even when the force is applied. Further, the tire to which the tire innerliner film is applied may not significantly change its modulus or rigidity even when operated for a long period of time, and cracks in the internal structure of the tire, which may occur during operation, can be minimized.

The modulus refers to a modulus of elasticity that represents the ratio of stress to strain, and specifically refers to the slope of the stress-strain curve (S-S curve) measured at room temperature conditions and 100% elongation point.

Also, when the base film is stretched at 100% at room temperature, the stress at the yield point may be 35 MPa or less, preferably 25 MPa or less, or more preferably, there is no yield point. The yield point refers to a stretching point at which elastic deformation occurs, and a strength at a yield point means a maximum stress or a stress at a point at which such elastic deformation occurs. As described above, when the base film is stretched 100% at room temperature, the modulus difference between the rubber such as the tire inner liner film and the tire carcass layer may not be large due to the strength at the yield point being 35 MPa or less, It is possible to prevent the separation of the film and the rubber due to the expansion in the tire forming process, thereby obtaining a good green tire shape. In addition, when such a tire base film is used, the stress concentration phenomenon can be relieved in the shoulder portion of the tire where deformation is concentrated due to the modulus of the film increased due to the expansion even after tire production, And an effect of preventing bending can be exhibited.

On the other hand, the base film may be an unoriented film. When the base film is an unstretched film, it can be suitably applied to a tire forming process in which high expansion occurs due to low modulus and high strain. Further, since the crystallization phenomenon hardly occurs in the unstretched film, damage such as cracks can be prevented even by repeated deformation. In addition, since the unoriented film does not have a large deviation in orientation and physical properties in a specific direction, an inner liner having uniform physical properties can be obtained.

As shown in the method for producing a film for a tire innerliner to be described later, a method of suppressing the orientation of the base film to the maximum, for example, a method of adjusting the viscosity through optimization of the melt extrusion temperature, The base film may be produced as an unoriented or unstretched film.

When an unoriented film is applied to the base film, the inner liner film can be easily formed into a cylindrical shape or a sheet shape in a tire manufacturing process. In particular, when an unstretched sheet-like film is applied to the base film, it is not necessary to separately construct a film manufacturing facility for each tire size, and it is possible to minimize shocks and creases that are applied to the film during transportation and storage . In addition, when the base film is formed into a sheet shape, the step of adding an adhesive layer described below can be performed more easily, and damage or dents or the like occurring during the manufacturing process can be prevented due to the difference in specification from the forming drum.

On the other hand, the base film may further include additives such as heat resistant antioxidants, heat stabilizers, adhesion promoters, or a mixture thereof. Specific examples of the heat-resistant antioxidant include N, N'-hexamethylene-bis- (3,5-di- (t-butyl) -4-hydroxy-hydrocinnamamide (3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide, for example, Methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate)] methane such as Irganox 1010) or 4,4'-dicumyldiphenylamine (4,4 ' Specific examples of the heat stabilizer include benzoic acid, triacetonediamine, N, N'-bis (2-phenyl-amine) , 2,6,6-tetramethyl-4-piperidyl) -1, 3-benzenedicarboxamide (N, N'- , 3-benzenedicarboxamide), etc. However, the additive is not limited to the above-mentioned examples, and the additives can be used for a tire innerliner film It is known can be used without limitation.

On the other hand, according to another embodiment of the present invention, there is provided a polymer composition comprising a mixture of a polymer containing a polyamide-based segment and a polyether-based segment, or a polymer containing a polyamide-based segment and a polymer containing a polyether- Melting and extruding the raw material for a base film at 230 to 300 캜 to form a base film; Treating at least one side of the base film with a plasma of oxygen, air, helium or argon; And forming an adhesive layer including a resorcinol-formalin-latex (RFL) adhesive on one surface of the plasma treated base film layer.

A mixture comprising the polyamide-based segment and a polymer comprising a poly-ether segment, or a polymer comprising a polyamide-based segment and a polymer comprising a poly-ether segment, The film for a tire innerliner formed by forming a film and applying the resorcinol-formalin-latex (RFL) -based adhesive on the base film has excellent airtightness, high air pressure holding performance and excellent mechanical properties And that the inner liner can be firmly and uniformly bonded to the inside of the tire even with a thin and lightweight adhesive layer.

In particular, by treating at least one side of the substrate film with a plasma of oxygen, air, helium or argon, the surface of the substrate film can be modified to have high surface energy, i.e. high hydrophilicity, Can be applied more uniformly in greater amounts on the layer and can exhibit a higher bond strength to the tire interior structure, for example the tire carcass layer. Specifically, the surface energy of one surface of the substrate film may be 40 dyne / cm, preferably 40 to 70 dyne / cm. The measurement of the surface energy of such a base film can be carried out according to ASTM D 2578.

Previously, in order to increase coating uniformity and coating amount, a wetting agent was added to the adhesive, a coating speed of the adhesive was lowered, a method of lowering the concentration of the adhesive, and the like. However, Deterioration, decrease in coating amount, and the like, which may reduce the efficiency of the production process or deteriorate the quality of the final product. In contrast, according to the method for manufacturing a tire innerliner according to the embodiment of the present invention, an inner liner having a uniform thickness and physical properties and having an adhesive layer having a high adhesive force is formed only by performing a simple plasma treatment on a base film of a specific composition .

In the plasma treatment step, the surface of the base film can be treated with a plasma power of 100 to 500 W, preferably 240 to 360 W. If the power of the plasma treatment process is excessively low, the surface modification effect of the plasma treatment process may be hardly exhibited. Therefore, adhesion between the base film treated with the RFL adhesive and the carcass rubber layer may not be sufficient. On the other hand, if the plasma power is excessively high, there is little additional surface modification effect or adhesive force improving effect, and the energy of the plasma applied to the surface of the base film becomes too high to damage the surface texture of the polymer constituting the base film . The damaged portion of the base film acts as a weak point in the tire forming process, and if the force is concentrated, breakage and breakage are likely to occur at the portion, and the tire may be easily broken by repeated deformation in the course of driving the vehicle.

The step of treating with the plasma may be performed for less than 500 seconds, preferably for 5 to 300 seconds, more preferably for 100 to 200 seconds. If the plasma treatment time is too short, the effect of surface modification by the plasma treatment and the effect of improving adhesion between the inner liner film and the carcass rubber layer may not be sufficient. On the other hand, if the plasma treatment time is excessively long, there is little additional surface modification effect or adhesive force improving effect, and the plasma energy applied to the surface of the base film becomes high, and the surface texture thereof may be damaged. As described above, the damaged portion of the base film acts as a weak point in the tire building process, and if the force is concentrated, breakage or breakage of the portion may easily occur, and the tire may be easily broken by repeated deformation in the course of driving the vehicle.

In the method of manufacturing the inner liner film, the plasma of oxygen, air, helium, or argon applied to the surface treatment of the base film may be atmospheric plasma of these gases. Such a plasma is a state in which the gas particles constituting the plasma are ionized and maintain electrical neutrality as a whole, and the ionization degree is relatively low (for example, about 10 ^-5 ) and the average temperature becomes a low temperature plasma near room temperature. Generally, such a low-temperature plasma treatment process proceeds in a reactor having a low pressure close to a vacuum. However, according to the experimental results of the present inventors, it has been found that even when the above-mentioned atmospheric plasma is applied, lost. Accordingly, the plasma can be applied at atmospheric pressure during the unwinding process during the coating process, thereby contributing to the mass productivity and practicality of the manufacturing process

Meanwhile, the step of forming an adhesive layer containing a resorcinol-formalin-latex (RFL) -based adhesive on one side of the plasma treated base film layer may be carried out within 6 hours, preferably within 2 hours after the plasma treatment step And it is more preferable that the plasma treatment step and the RFL adhesive treatment step proceed to a continuous process. If an excessively long time has elapsed after the plasma treatment step, the surface modification effect due to the plasma treatment may deteriorate, and the inner liner film having excellent adhesion and uniform coating layer may not be produced properly.

On the other hand, in order to realize excellent air-tightness even with a thin thickness of the tire innerliner film to be manufactured, the base film can be made of a polyamide-based segment and a poly Copolymers comprising poly-ether based segments; Or a mixture of a polymer comprising a polyamide-based segment and a polymer comprising a poly-ether-based segment. More preferably, the content of the polyether segment of the copolymer or the content of the polymer containing the poly-ether segment may be 15 to 50 wt% of the total weight of the base film.

Specifically, the step of forming the base film comprises melting and extruding a raw material for a base film including a mixture of the above-mentioned copolymer and polymers at 230 to 300 캜 to form a film having a thickness of 30 to 300 탆 . ≪ / RTI >

The extrusion die for pouring and extruding the raw material for the base film can be used without any limitations as long as it can be used for extrusion of the polymer resin. However, the thickness of the base film can be made more uniform, It is preferable to use a T-die for uniformizing the viscous characteristics through the die.

In the step of forming the base film layer, the base film material may be melted and extruded to form a base film having a thickness of 30 to 300 mu m. The thickness of the base film may be controlled by adjusting extrusion conditions such as the extruder discharge rate or the speed of a casting roll.

In the method for producing a film for a tire innerliner, the thickness of the base film produced by the above-described step is continuously measured, and the result of the measurement is fed back to the portion of the extrusion die corresponding to the position where the non- And adjusting the lip gap adjusting bolt of the T-die to reduce the deviation of the base film to obtain a film having a more uniform thickness. In addition, automated process steps can be configured by using an automated system, such as an Auto Die system, to control the thickness of the film-feedback-extrusion die.

In the step of forming the base film, the extrusion processing conditions of a film commonly used in the production of a polymer film, for example, a screw diameter, a screw rotation speed, or a line speed Can be appropriately selected and used.

The temperature for melting the base film raw material may be 230 to 300 캜, preferably 240 to 280 캜. The melting temperature should be higher than the melting point of the polyamide-based compound. However, when the melting point is too high, carbonization or decomposition may occur to deteriorate the physical properties of the film, and bonding between the polyether- Which may be disadvantageous for producing a film.

Meanwhile, the method for producing a film for a tire innerliner is characterized in that the base film formed by melting and extrusion is solidified in a cooling part casting roll maintained at a temperature of 5 to 40 캜, preferably 10 to 30 캜 Step < / RTI >

The base film layer formed by melting and extruding is solidified in a cooling part casting roll which is maintained at the temperature of 5 to 40 캜 and can be provided as a film having a more uniform thickness. The base film layer obtained by melting and extruding can be grounded or brought into close contact with a cooling part casting roll maintained at the above-mentioned appropriate temperature to uniformize the physical properties of the base film by substantially uniform cooling, Uniform stretching is possible.

Specifically, the solidifying step may be performed by cooling the base film layer, which is formed by melting and extruding, using a knife, an air nozzle, an electrostatic application device (pinning device), or a combination thereof, And uniformly adhering the sheet to a casting roll.

The base film layer formed by melting and extruding is adhered to the cooling part casting roll by using an air knife, an air nozzle, an electrostatic application device (pinning device) or a combination thereof in the solidification step, It is possible to prevent the phenomenon that the film layer is blown out in the air or partially unevenly cooled in the air after the extrusion and thus a film having a more uniform thickness can be formed and the film can be formed relatively thick Or a thin region may not be substantially formed.

The raw material for the base film may further comprise a polyamide based resin. Preferably, the raw material for the base film comprises a mixture of the polyamide based resin and the copolymer or the polymer in a ratio of 6: 4 to 3: 7 Weight ratio.

As described above, the copolymer may include a poly-amide-based segment and a poly-ether-based segment at a weight ratio of 6: 4 to 3: 7. The mixing weight ratio between the polymer comprising the polyamide segment and the polymer comprising a poly-ether segment may be from 6: 4 to 3: 7.

The polyamide resin and the copolymer comprising the polyamide segment and the polyether segment or the polymer containing the polyamide segment and the polymer containing the polyether segment The details of the compounding are as described above.

On the other hand, the base film of the film for a tire innerliner can be obtained by producing an unstretched film having a thickness of 30 to 200 mu m as a result of the melt extrusion step. The thickness of the extrudate can be adjusted according to the specifications of the apparatus such as the extruder used. In order to form an unstretched film, it is necessary to optimize the melt extrusion temperature to adjust the viscosity of the melt, adjust the discharge amount of the melt, adjust the distance between the die outlet and the device for cooling the melt, A method of adjusting the winding speed of the film, or the like can be used.

For example, the Lip Opening of the retaining die can be set to around 1 mm, and the too narrowing of the Lip Opening may be undesirable because the pressure applied to the die shear may be too high. In addition, it is desirable that the winding speed of the film is maintained at a proper speed in order to prevent problems of poor cooling and increase in orientation. For example, it is preferable to set the speed at 100 m / min or less, preferably 50 m / min or less Can be applied.

On the other hand, the method for producing a film for a tire innerliner includes an adhesive layer forming step of applying a resorcinol-formalin-latex (RFL) based adhesive on at least one surface of the base film layer to a thickness of 0.1 to 20 μm .

It is preferable to treat the resorcinol-formalin-latex (RFL) -based adhesive within 6 hours, preferably within 2 hours, of the plasma treatment when the base film is treated using the above plasma treatment conditions, It is preferable to proceed as in the treatment process. For example, after the substrate film is unwound from the adhesive treatment facility, the plasma treatment is performed and then the adhesive treatment process is started.

The step of forming the adhesive layer may be carried out by coating a resorcinol-formalin-latex (RFL) -based adhesive on one surface or both surfaces of the substrate film formed above and then drying the adhesive layer. , Preferably 0.1 占 퐉 to 10 占 퐉, more preferably 0.2 占 퐉 to 8 占 퐉, still more preferably 0.5 占 퐉 to 6 占 퐉. The resorcinol-formalin-latex (RFL) based adhesive may comprise 2 to 32% by weight of a condensate of resorcinol and formaldehyde and 68 to 98% by weight, preferably 80 to 90% by weight of latex.

More specific details regarding the resorcinol-formalin-latex (RFL) -based adhesive of the above specific composition are as described above.

The application of the adhesive may be carried out by any conventional coating or coating method or apparatus without limitation, but it may be applied by a knife coating method, a bar coating method, a gravure coating method, a spraying method, Can be used. However, it is preferable to use a knife coating method, a gravure coating method or a bar coating method in terms of uniform application and coating of the adhesive.

After the adhesive layer is formed on one surface or both surfaces of the base film, the drying and the adhesive reaction may be simultaneously performed. However, the reaction may be divided into a drying step and a heat treatment reaction step in consideration of the reactivity of the adhesive, In order to apply the thickness of the adhesive layer or the multi-stage adhesive, the adhesive layer formation, the drying and the reaction step may be applied several times. Further, the heat treatment reaction may be performed by applying an adhesive to the base film, and then solidifying and reacting at 100 to 150 ° C for about 30 seconds to 3 minutes under heat treatment conditions.

On the other hand, in the step of forming the copolymer or the mixture, or in the step of melting and extruding the copolymer, an additive such as a heat-resistant antioxidant or a heat stabilizer may be further added. The specific contents of the additive are as described above.

According to the present invention, it is possible to realize excellent airtightness even with a thin thickness, thereby making it possible to reduce the weight of the tire and to improve the automobile fuel economy and to exert an excellent adhesive force to the tire carcass portion owing to the formation of the uniform adhesive layer, It is possible to provide a tanner inner liner film capable of realizing excellent durability and endothelial characteristics against repeated deformations occurring.

Fig. 1 schematically shows the structure of a tire.
Fig. 2 is a SEM photograph of the surface of the tire inner liner film of Example 1. Fig.
3 is a SEM photograph of a surface of a tire inner liner film of a comparative example.

The invention will be described in more detail in the following examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

< Example  And Comparative Example : tire For inner liner  Production of Film>

 (1) Production of base film

50% by weight of a nylon 6 resin having a relative viscosity (96% solution of sulfuric acid) of 3.3 and 50% by weight of an elastomer copolymer (containing 50% by weight of a polyamide repeating unit and 50% by weight of a polyether repeating unit) The mixture was extruded at 260 &lt; 0 &gt; C temperature through a T-die (Die Gap - 1.0 mm) while maintaining a uniform molten resin flow. An unstretched base film having a thickness of 80 mu m was obtained without passing through the stretching and heat treatment sections at a speed of 30 m / min. The thickness of the base film was measured using a gauge tester.

(2) Plasma treatment

The surface of the base film was treated with an atmospheric plasma of oxygen or air while changing the processing conditions of the plasma. At this time, the processing conditions of the plasma are as shown in Table 1 below

(3) Application of adhesive

Resorcinol and formaldehyde were mixed at a molar ratio of 1: 2, followed by condensation reaction to obtain a condensate of resorcinol and formaldehyde. 12% by weight of a condensate of resorcinol and formaldehyde and 88% by weight of styrene / butadiene-1,3 / vinylpyridine latex were mixed to obtain a resorcinol-formalin-latex (RFL) adhesive having a concentration of 20%.

The resorcinol-formalin-latex (RFL) -based adhesive was coated on the substrate film to a thickness of 1 mu m using a gravure coater and dried and reacted at 150 DEG C for 30 seconds to form an adhesive layer.

Plasma treatment conditions of Examples and Comparative Examples Treatment conditions of the substrate film Example 1 Plasma treatment (air, 350 W, 180 sec) Example 2 Plasma treatment (air, 350 W, 240 sec) Example 3 Plasma treatment (air, 500 W, 120 sec) Example 4 Plasma treatment (air, 500 W, 180 sec) Example 5 Plasma treatment (oxygen, 350 W, 180 sec) Example 6 Plasma treatment (oxygen, 350W, 240 sec) Example 7 Plasma treatment (oxygen, 500 W, 120 sec) Example 8 Plasma treatment (oxygen, 500 W, 180 sec) Comparative Example Untreated

< Experimental Example : tire Inner Liner  Measurement of physical properties>

Experimental Example 1 : Example  And Comparative example  Measurement of surface energy of base film

The surface energy of the plasma-treated base film and the base film of the comparative example in the above examples were measured in the following manner.

(1) Measurement standard: ASTM D-2578

(2) Measurement reagent: Accu Dyne TEST reagent, Bottle Type (Maker = Diversified Enterprises) - 30 to 70 dynes / cm reagent use

(3) Measurement method

1) Put the measuring reagent on one end of the swab and draw a straight line of 10CM on the surface of the film to be evaluated.

2) After 2 seconds after drawing the above straight line, the reagent straightly formed on the film surface was rated as being wettable when the shape remained unchanged. When the shape of the reagent was changed, it was evaluated as not wettability. In this case, the meaning of "the shape of the reagent is changed" includes a change in the shape of the initially formed straight line, a change in the dotted line, and a phenomenon in which the reagent accumulates a certain portion.

3) If there is no wettability, select a reagent of Dynes / cm level higher than the measurement reagent. If wettability exists, select a reagent of Dynes / cm level lower than that of the measurement reagent and repeat steps 1) and 2) And repeated.

4) Repeat the above steps 1), 2) and 3) to select the minimum Dynes / cm level that will be the final wetting.

The measurement results of Experimental Example 1 are shown in Table 2 below. As shown in the following Table 2, it was confirmed that the surface treatment of the base film had a higher surface energy than the base film of the comparative example, and specifically, it was confirmed to have a surface energy of 45 dynes / cm or more.

The measurement result of Experimental Example 1 Surface energy
(dynes / cm) Example 1 62 Example 2 62 Example 3 55 Example 4 58 Example 5 59 Example 6 45 Example 7 52 Example 8 51 Comparative Example 35

Experimental Example 2 : tire For inner liner  Measure coating layer thickness of film

The thickness of the coating layer of the inner liner film obtained in the above Examples and Comparative Examples was measured under the following conditions.

(1) Measuring instrument: Electron microscope (SEM)

(2) Measurement conditions: Measure the center of the substrate film, and measure the maximum and minimum thickness in the measured photograph (100um length).

Results of coating layer thickness measurement Minimum thickness (um) Maximum thickness (um) Example 1 0.8 1.1 Example 2 0.8 1.1 Example 3 0.7 1.2 Example 4 0.6 1.5 Example 5 0.7 1.1 Example 6 0.6 1.5 Example 7 0.7 1.3 Example 8 0.5 1.4 Comparative Example 0 5.3

As shown in FIG. 2 and Table 3, it was confirmed that the difference between the maximum thickness and the minimum thickness of the adhesive layer was relatively small in the case of the surface treatment of the base film, as compared with the base film of the comparative example. Specifically, The difference between the maximum thickness and the minimum thickness was less than 0.9 μm.

That is, the surface of the base film of the embodiment is plasma-treated to have high hydrophilicity, and the thickness of the resorcinol-formalin-latex (RFL) adhesive applied to the base film layer can be more uniform.

On the other hand, as shown in FIG. 3 and Table 3, it was confirmed that a portion where the adhesive was not formed appeared on the surface of the substrate film of the comparative example, and a relatively thicker portion was observed in the applied adhesive as compared with the peripheral portion .

Experimental Example 3 : Measurement of maximum adhesion of adhesive layer

Adhesion of the tire innerliner films obtained in the above Examples and Comparative Examples to the tire carcass layer was measured according to the method of ASTM D 4393 of the American Society for Testing and Materials.

Specifically, a rubber sheet of 1.6 mm, a cord paper, a film for the innerliner of the tire, a rubber sheet of 1.6 mm, a cord paper, and a rubber sheet of 1.6 mm were laminated in this order. And vulcanized for 30 minutes. Thereafter, the vulcanized sample was cut and cut to a width of 1 inch.

At this time, the rubber sheet of 1.6 mm, the cord paper, and the rubber sheet of 1.6 mm formed a carcass layer, and the rubber sheet was produced using a rubber composition having the composition shown in Table 4 below .

Composition of rubber sheet ingredient Content (parts by weight) caoutchouc 100 Zinc oxide 3 Carbon black 29.8 Stearic acid 2.0 Pine Tar 7.0 Mercaptobenzothiazole 1.25 sulfur 3.0 Diphenylguanidine 0.15 Phenylbetanaphthalamine 1.0 Sum 147.2

The cut sample was peeled off at 25 ° C at a rate of 300 mm / min using an universal material tester (Instron) to measure the maximum adhesion force (kgf / 2.5 cm) of the inner liner film to the carcass layer.

Adhesion measurement result Maximum adhesion force (kgf / 2.5cm) Example 1 55 Example 2 53 Example 3 46 Example 4 41 Example 5 47 Example 6 42 Example 7 45 Example 8 38 Comparative Example 27

As shown in Table 5, it was confirmed that the film for tire inner liner of the Example had a relatively good adhesion to the carcass layer. Specifically, the tire inner liner film of the Example was 38 kgf / 2.5 cm Or more.

1. Tread
2. Shoulder
3. Side Wall
4. Cap fly (CAP PLY)
5. Belt
6. Body Ply
7. Inner Liner
8. APEX
9. Beads (BEAD)

Claims (24)

A substrate film comprising a mixture of a polyamide-based segment and a poly-ether-based copolymer, or a polymer comprising a polyamide-based segment and a polymer comprising a poly-ether-based segment ; And
An adhesive layer formed on at least one surface of the base film and including a resorcinol-formalin-latex (RFL) -based adhesive,
Wherein the thickness of the adhesive layer is 0.1 to 10 mu m, the difference between the maximum thickness and the minimum thickness of the adhesive layer is 1 mu m or less,
Wherein the surface energy of one surface of the base film measured by ASTM D 2578 is 40 to 70 dyne / cm.
The method according to claim 1,
Wherein the base film has a thickness of 30 to 300 占 퐉.
delete delete delete The method according to claim 1,
Wherein the polyamide-based segment comprises a repeating unit represented by the following formula (1) or (2):
[Chemical Formula 1]

Wherein R ₁ is a linear or branched alkylene group having 1 to 20 carbon atoms or a linear or branched alkylene group having 7 to 20 carbon atoms,
(2)

R ₂ is a linear or branched alkylene group having 1 to 20 carbon atoms and R ₃ is a linear or branched alkylene group having 1 to 20 carbon atoms or a linear or branched alkylaryl group having 7 to 20 carbon atoms It is a stove.
The method according to claim 1,
Wherein the polyether-based segment comprises a repeating unit represented by the following formula (3): &lt; EMI ID =
(3)

In Formula 3,
R ₅ is a straight or branched alkylene group having 1 to 10 carbon atoms, n is an integer of 1 to 100,
R ₆ and R ₇ may be the same or different and are each a direct bond, -O-, -NH-, -COO- or -CONH-.
The method according to claim 1,
Wherein the content of the polyether segment of the copolymer or the content of the polymer containing the polyether segment is 15 to 50 wt% of the total weight of the base film.
The method according to claim 1,
Wherein the copolymer comprises a polyamide segment and a polyether segment in a weight ratio of 6: 4 to 3: 7.
The method according to claim 1,
Wherein the blend weight ratio of the polymer comprising the polyamide segment to the polymer comprising a poly-ether segment is from 6: 4 to 3: 7.
The method according to claim 1,
Wherein the base film further comprises a polyamide resin having a relative viscosity (96% solution of sulfuric acid) of 3.0 to 3.5.
12. The method of claim 11,
Wherein the polyamide resin and a polymer comprising a polyamide-based segment and a polyamide-based segment containing a polyether-based segment and a polymer comprising a poly-ether-based segment, Wherein the weight ratio of the mixture is from 6: 4 to 3: 7.
The method according to claim 1,
And a modulus of 10 to 40 MPa when the base film is elongated at 100% at room temperature.
The method according to claim 1,
Wherein the base film has a tensile strength at yield point of not more than 35 MPa when the base film is elongated at 100% at room temperature.
A raw material for a base film comprising a mixture comprising a polyamide-based segment and a polyether-based segment, or a mixture of polymers including a polyamide-based segment and a polymer including a polyether-based segment, Melting and extruding the base film to form a base film;
Treating at least one side of the base film with a plasma of oxygen, air, helium or argon; And
Forming an adhesive layer containing a resorcinol-formalin-latex (RFL) -based adhesive on one side of the plasma-treated base film layer,
Wherein the step of treating with the plasma is performed within a period of 500 seconds or less by applying a plasma power of 240 to 360 W. The method for manufacturing a film for a tire innerliner according to claim 1,
delete delete 16. The method of claim 15,
Wherein the plasma is an atmospheric plasma.
16. The method of claim 15,
Wherein the forming of the base film comprises forming a film having a thickness of 30 to 300 mu m from the result of the melting and extrusion process.
16. The method of claim 15,
Wherein the step of forming the adhesive layer comprises the step of applying a resorcinol-formalin-latex (RFL) -based adhesive on at least one surface of the base film layer to a thickness of 0.1 to 20 탆 Gt;
16. The method of claim 15,
Wherein the raw material for the base film comprises 15 to 50 wt% of a copolymer containing a polyamide segment and a poly-ether segment, or a mixture 15 to 50 wt% of a polymer containing a polyamide segment and a polyether segment, By weight based on the total weight of the tire inner liner film.
16. The method of claim 15,
The copolymer comprises a poly-amide-based segment and a poly-ether-based segment in a weight ratio of 6: 4 to 3: 7,
Wherein the weight ratio of the polymer comprising the polyamide segment to the polymer including the polyether segment is from 6: 4 to 3: 7.
16. The method of claim 15,
Wherein the raw material for the base film further comprises a polyamide resin having a relative viscosity of 3.0 to 3.5 (sulfuric acid: 96% solution).
24. The method of claim 23,
The raw material for the base film may be a copolymer comprising the polyamide resin, the polyamide-based segment and a poly-ether-based segment, or a polymer containing the polyamide-based segment and a polyether- Based segments in a weight ratio of 6: 4 to 3: 7.

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