KR20150037675A - Polymer film - Google Patents

Abstract

The present invention relates to a polymer film for an inner liner, comprising: a polyamide-based resin; a copolymer including a polyamide-based segment and a poly-ether-based segment; and a base film including a compound comprising an oxazoline functional group.

Description

POLYMER FILM

The present invention relates to a polymer film and a pneumatic tire. More particularly, the present invention relates to a polymer film and a pneumatic tire which are excellent in airtightness even with a thin thickness, And a pneumatic tire including the polymer film for inner liner having physical properties and the polymer film for inner liner.

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 . However, when the content of the rubber component and the tire thickness are increased, the total weight of the tire is increased and the fuel economy of the automobile is lowered.

In addition, the rubber components have relatively low heat resistance, and air pockets are formed between the inner rubber of the carcass layer and the inner liner during the vulcanization process of the tire or the running of the vehicle in which repeated deformation occurs at high temperature, There is a problem that the shape and physical properties are changed. In order to bond the rubber components to the curl layer of the tire, a vulcanizing agent or a vulcanization process has to be applied.

Accordingly, various methods have been proposed to reduce the thickness and weight of the inner liner to reduce fuel consumption, and to reduce changes in the form and physical properties of the inner liner that occur during the molding or running 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 the previously known method has a problem in that the properties of the inner liner itself deteriorate in the manufacturing process of the tire in which the high temperature repetitive molding is performed or the repeated process of deformation, This phenomenon appeared.

An object of the present invention is to provide a polymer film for an inner liner which realizes excellent airtightness even with a thin thickness, can reduce the weight of a tire, improve automobile fuel economy, and has mechanical properties such as high durability and fatigue resistance with excellent moldability.

The present invention also provides a pneumatic tire including the polymer film for an inner liner.

In the present specification, a polyamide based resin; A copolymer comprising a polyamide-based segment and a poly-ether-based segment; And a compound containing an oxazoline functional group, wherein the polymer film for inner liner having a strength of 10 MPa to 30 MPa when stretched by 25% in one direction of the base film is provided.

Further, in the present specification, a pneumatic tire including the polymer film for inner liner is provided.

The polymer film for an inner liner and the pneumatic tire according to a specific embodiment of the present invention will be described in more detail below.

According to one embodiment of the invention, a polyamide-based resin; A copolymer comprising a polyamide-based segment and a poly-ether-based segment; And a compound containing an oxazoline functional group. The polymer film for an inner liner having a strength of 10 MPa to 30 MPa when the base film is stretched at 25% in one direction may be provided.

As a result of research conducted by the present inventors, it has been found that the use of a base film containing a polyamide resin, a copolymer containing the specific segments and a compound containing an oxazoline functional group as described above realizes excellent airtightness even with a thin thickness, It has been confirmed that a polymer film for an inner liner can be provided which can improve the fuel consumption of an automobile and exhibits high moldability and mechanical properties such as high durability and fatigue resistance while having high heat resistance characteristics.

In particular, as the base film contains a compound containing an oxazoline functional group, the polymer film for inner liner can have a sufficient modulus and low modulus, and the polymer film for inner liner can have low modulus, The modulus of elasticity or the elasticity recovery rate and the like are not significantly lowered and the excellent formability can be ensured.

The use of the compound containing an oxazoline functional group can lower the crystallinity of the base film itself or the tendency of crystallization at high temperature. Specifically, by using a compound containing an oxazoline functional group, a polymer used or synthesized in the production process of the base film, for example, a polyamide resin (a) and a poly-amide-based segment A cross-linking reaction may occur between each of the copolymers (b) containing a poly-ether group segment or each other, and thus the crystallinity of the base film may be lowered.

Accordingly, the polymer film for inner liner can have high durability against external impact or self-deformation, and can prevent the film itself from breaking or tearing during the storage process of the film or the tire manufacturing process, The orientation of the base film is lowered and the modulus is also optimized so that the inner liner film having high elasticity and durability can be provided. Further, the use of the compound containing an oxazoline functional group enables the physicochemical properties of the base film to be optimized for the inner liner film.

Specifically, the strength of the base film at 25% stretching in one direction may be 10 Mpa to 30 Mpa. Further, the strength at 100% stretching of the base film in one direction may be 10 Mpa to 30 Mpa. The strength refers to a critical stress at which elastic deformation occurs, and specifically refers to a stress occurring in a predetermined elongation period.

If the strength of the base film stretched to some extent is too small, it is difficult to maintain the shape or mechanical properties of the base film in a tire manufacturing process or an automobile running process, or the inner film film of the embodiment may easily break have. In addition, when the base film is stretched to some extent and the strength is too large, the polymer film for inner liner of the embodiment can be sufficiently stretched even when the elasticity of the base film is low or the expansion pressure is applied in the tire manufacturing process Or may not be deformed, and the rigidity or crystallinity may be greatly increased in a high temperature molding process.

In addition, the base film may include a compound containing the oxazoline functional group together with the polyamide based resin and the above-mentioned copolymer, and may have higher elasticity, and the polymer chain may be cut or the structure of the polymer may easily change The rigidity or crystallinity of the polymer film for inner liner of the embodiment can be prevented from increasing.

For example, the base film may be combined with a carcass rubber layer having a thickness of 0.50 mm to 1.0 mm so as to have an elasticity of 80 % Stress generated when stretching can be 3 MPa or less, or 1.0 to 3.0 MPa. That is, since the difference in elastic force between the tire and the component used as the carcass rubber is not so large, the stress generated when the tire is stretched 80% in one direction in combination with the carcass rubber layer as described above may not be very high.

The residual stress measured after stretching the base film combined with the carcass rubber layer having the thickness of 0.50 mm to 1.0 mm in the one direction by 80% and heat treatment at 160 캜 for 20 minutes is 0.3 MPa or less, or 0.10 MPa to 0.30 Lt; / RTI >

Due to the high elasticity of the base film, the polymer structure is deformed in the course of 80% elongation in the state of being bonded to the carcass rubber layer as described above, and the physical properties and shape of the film are largely changed as the polymer chain is cut I never do that. Accordingly, since the stress remaining on the base film after stretching by 80% is insignificant, the stress measured in the state of being thermally fixed after stretching may also be considerably low. Accordingly, the polymer film for an inner liner according to an embodiment including the base film can prevent stress from concentrating on a part of the tire during a tire manufacturing process or an automobile running process, so that it can have uniform physical properties as a whole, Can be prevented.

When the polymeric film for inner liner is produced by using the above-mentioned polyamide resin alone, it can not be sufficiently expanded during the elongation process applied in tire manufacturing due to its high modulus characteristic, The inner liner may be cracked or broken.

In addition, when a polymer film for an inner liner is produced by using a copolymer containing the polyamide-based segment and a poly-ether-based segment alone, the resulting inner liner may fail to secure sufficient heat resistance And it is easy to be thermally decomposed at a low temperature or to be cut in a polymer chain and the elasticity of the inner liner film produced by cutting the polymer chain may be lowered or the crystallinity due to heat may be greatly increased, Cracks or fractures can be more prominent in the process or in the course of running a car.

On the contrary, the polymer film for inner liner of the embodiment includes the polyamide resin and the copolymer including the polyamide segment and the polyether segment, It can have a low modulus. Specifically, due to the inherent molecular chain characteristics of the polyamide based resin contained in the base film, the polymer film for inner liner of the embodiment has an airtightness of about 10 to 20 times the same thickness as the butyl rubber commonly used in a tire, And the copolymer is present in a state of being bonded or dispersed among the polyamide based resins to further lower the modulus of the base film and suppress the increase in the rigidity of the base film It is possible to prevent crystallization at a high temperature.

Further, in the polymer film for inner liner according to one embodiment, the base film is a copolymer comprising the polyamide-based resin and the polyamide-based segment and a poly-ether-based segment, May have the above-mentioned characteristics as including a compound containing a functional group.

The polyamide-based resin and the copolymer comprising the polyamide-based segment and the polyether-based segment may be bonded via a compound containing the oxazoline-based functional group.

The oxazoline functional group-containing compound is oxazoline, which is at least one substituted with hydrogen, an alkyl group having 1 to 5 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms; A (meth) acrylate-based polymer having one or more oxazolines substituted; And styrenic polymers in which one or more oxazolines are substituted.

The (meth) acrylate-based polymer or the styrene-based polymer having one or more oxazolines substituted therein may have a weight average molecular weight of 1,000 to 300,000.

The base film may contain 0.5 to 25% by weight of the compound containing the oxazoline functional group. If the content of the oxazoline functional group-containing compound is too small, the degree of cross-linking between the polymers contained in the base film is insufficient, and the crystallinity can not be sufficiently lowered. If the content of the oxazoline functional group-containing compound is too high, compatibility with other components contained in the base film is lowered, and the physical properties of the inner liner film are deteriorated or crosslinking is unnecessarily generated in the base film, Can be degraded.

The polyamide resin may have a relative viscosity (96% solution of sulfuric acid) of 3.0 to 4.0, preferably 3.2 to 3.6. If the viscosity of such a polyamide resin is less than 3.0, a sufficient elongation can not be secured due to a reduction in toughness, which may lead to breakage during tire production or automobile operation, and the airtightness or moldability of the base film for the inner liner polymer film It may be difficult to secure physical properties such as gender. When the viscosity of the polyamide resin exceeds 4.0, the modulus or viscosity of the substrate film to be produced may become unnecessarily high, and the innerliner of the tire may not have adequate moldability or elasticity.

The relative viscosity of the polyamide resin refers to the relative viscosity measured using a 96% solution of sulfuric acid at room temperature. Specifically, after dissolving a sample of a certain polyamide resin (for example, 0.025 g of a test piece) in 96% sulfuric acid solution at different concentrations to prepare two or more measuring solutions (for example, a polyamide based resin sample The solution was dissolved in 96% sulfuric acid so as to have a concentration of 0.25 g / dL, 0.10 g / dL and 0.05 g / dL to prepare three measurement solutions), and the relative viscosity of the solution for measurement , The ratio of the average passage time of the measuring solution to the viscosity tube passing time of the 96% solution of sulfuric acid).

Examples of polyamide based resins usable in the base film 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 polyamide-based resin may be included in the base film by preparing a base film using the monomer of the polyamide-based resin or the precursor of the polyamide-based resin as well as the method of using the resin itself.

On the other hand, the weight average molecular weight of the copolymer comprising the polyamide segment and the polyether segment may be 50,000 to 500,000, or 70,000 to 300,000. If the weight average molecular weight of the copolymer is less than 50,000, the prepared base film may not have sufficient mechanical properties to be used for the polymer film for inner liner, and the inner polymer film for inner liner has sufficient gas barrier It can be difficult. When the absolute weight average molecular weight of the copolymer exceeds 500,000, the modulus or degree of crystallization of the base film excessively increases during heating at a high temperature, and it may be difficult to ensure the elasticity or elastic recovery rate to be provided as the polymer film for inner liner.

The content of the polyether segment in the base film may be 2 wt% to 40 wt%, 3 wt% to 35 wt%, or 4 wt% to 30 wt%.

If the content of the polyether segment is less than 2% by weight based on the total weight of the base film, the modulus of the base film or the polymer film for inner liner becomes high, so that the moldability of the tire is deteriorated, have. If the content of the polyether segment exceeds 40 wt% of the entire film, the gas barrier property required for the tire inner liner is poor, and the tire performance may be deteriorated. The reactivity to the adhesive is lowered so that it is difficult for the inner liner to easily adhere to the carcass layer and the elasticity of the base film is increased, so that it may not be easy to produce a uniform film.

The polyether-based segment may be bonded to the polyamide-based segment or may be dispersed among the polyamide-based resins, and it is preferable that the polyether-based segment inhibits growth of large crystals in the base film Or the base film can be prevented from breaking easily.

In addition, the polyether segment can lower the modulus of the polymer film for inner liner. Thus, even when a relatively small force is applied to the tire, the tire can be stretched or deformed according to the shape of the tire, So that it can be 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 polyamide segment may serve to prevent the modulus of the copolymer from significantly increasing while allowing the copolymer to have mechanical properties above a certain level. In addition, as the polyamide-based segment is applied, the base film can have a low thickness and a low air permeability, and sufficient heat resistance and chemical stability can be ensured.

The polyamide-based segment of the copolymer may comprise repeating units of the following formula (1) or (2).

[Chemical Formula 1]

In the above formula (1), 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.

In addition, the polyether segment of the copolymer may include a repeating unit represented by the following formula (3).

(3)

Wherein 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-.

Further, in the base film, the polyamide based resin and the above-mentioned copolymer may be contained in a weight ratio of 9: 1 to 2: 8, or 3: 7: to 7: 3. If the content of the polyamide resin is too small, the density or airtightness of the base film may be lowered. If the content of the polyamide resin is too large, the modulus of the base film may be excessively high or the moldability of the tire may be deteriorated. In a high temperature environment occurring in a tire manufacturing process or an automobile running process, And a crack can be generated by repeated deformation.

The base film may have a thickness of 30 to 300 mu m, preferably 40 to 250 mu m, more preferably 40 to 200 mu m. Accordingly, the polymer film for an inner liner according to 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 24 hr 揃 atm) or less have.

Previously known inner liner used a butyl rubber or rubber copolymer, so it was relatively thick inside the carcass layer to ensure a certain level of airtightness. Accordingly, the previously known inner liner film has a weight of about 10% of the total weight of the tire, thereby hindering the improvement of automobile fuel economy.

On the other hand, the polymer film for inner liner of the embodiment can achieve airtightness improved by 20% or more while having a weight of 30% or less of that of the inner liner using the butyl rubber or the rubber component copolymer.

On the other hand, the base film may further include a heat resistant agent. As the base film further includes a heat resistant agent, the degree of crystallization of the polymer can be greatly lowered, and accordingly, even when the base film is allowed to stand for a long time in a high temperature environment or exposed, the physical properties thereof are not significantly deteriorated. That is, as the heat resistant agent is added to the base film, the phenomenon that the base film is crystallized or hardened to a high level can be remarkably reduced in the molding process of the tire, repeatedly deformed, It is possible to prevent the occurrence of cracks or breakage in the liner.

The base film may contain 50 to 5,000 ppmw of a heat resistant agent. If the content of the heat resistant agent is too small, the effect of improving heat resistance may be insignificant. If the content of the heat resisting agent is too large, the physical properties of the base film may be deteriorated, and the effect of improving the heat resistance depending on the content of the base film may be substantially lowered, thereby unnecessarily raising the price of the final product.

Specific examples of such heat resisting agents include aromatic amine compounds, hindered phenol compounds, phosphorus compounds, inorganic compounds, polyamide compounds, polyether compounds, or a mixture of two or more thereof. Such a heat resisting agent may be applied in the form of a powder or a liquid in the manufacturing method described later.

Specific examples of the hindered phenol compound include N, N'-hexamethylenebis (3,5-ditertiary-4-hydroxy-hydrosinamide) or pentaerythritol tetrakis 3- (3,5- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate as a commercially available product, and Irganox 1010 as a commercially available product. Examples of possible hindered phenol compounds are not limited thereto.

Specific examples of the aromatic amine compound include 2,2,4-trimethyl-1,2-dihydroquinoline or a polymer thereof, phenyl? -Naphthylamine, phenyl-? -Naphthylamine, aldol-? -Naphthylamine N, N'-bis (1-ethyl-3-methylphenyl) -p-phenylenediamine, p-iso-propoxyldi Phenylamine, 6-ethoxy-2,2,4-trimethyl 1,2-dihydroquinoline, N-phenyl-N'-isopropyl-para-phenylenediamine, di-beta-naphthyl- (3, 3, 5-di-tert-butyl) -4- (4-methylphenyl) Hydroxyphenyl-propionamide) or a mixture of two or more thereof. However, examples of the aromatic amine compound usable as the heat resisting agent are not limited thereto.

Specific examples of the phosphorus compound include triphenyl phosphate (PPP), triaryl phosphate, aromatic phosphate ester, 2-ethylhexyldiphenyl phosphate, triethylene phosphate, tricresyl phosphate (TCP), cresylphenyl phosphate, chlorethyl phosphate , Tris-β-chloropropyl phosphate, tris-dichloropropyl phosphate, halogen-containing condensed phosphate esters, aromatic condensed phosphoric acid esters, polyphosphates, red phosphorus or a mixture of two or more thereof. Examples of the phosphorus compounds usable as the heat resisting agent But is not limited thereto.

Specific examples of the inorganic compound include iodinated compounds such as Mg (OH) ₂ , Al (OH) ₂ , Sb ₂ O ₃ , Sodium salt, Sb ₂ O ₅ , Zinc borate, Molybdenum compound, Zinc tartrate, CuI or KI And mixtures of two or more thereof.

Even when a mixture of CuI and KI is used as the heat resisting agent, the heat resistance of the base film can be greatly improved, and even when exposed to a high temperature for a long time or exposed, the physical properties of the base film itself are not greatly changed.

When a mixture of CuI and KI is used as the heat resisting agent, it may be used in an amount of 50 ppm to 1,000 ppw based on the above-mentioned ground film layer. And, the content of copper (Cu) in the mixture of CuI and KI may be 5 to 10 wt%.

Even when a mixture of CuI and KI is used, the content of the heat resistant agent to be used is greatly reduced (for example, 50 ppm to 1,000 ppw in the base film), and the long term heat resistance is greatly increased Can be improved.

On the other hand, the base film may be an unoriented film. When the base film is in the form of 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. A method of suppressing the orientation of the base film as much as possible, for example, a method of adjusting the viscosity through optimization of the melt extrusion temperature, a change of the die die size, or a control of the winding speed The base film may be produced as an unoriented or unstretched film.

When the unstretched film is applied to the base film, the polymer film for inner liner 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.

Meanwhile, the polymer film for inner liner of the embodiment may further include an adhesive layer formed on at least one side of the base film and including a resorcinol-formalin-latex (RFL) adhesive.

The adhesive layer containing the resorcinol-formalin-latex (RFL) adhesive has excellent adhesion and adhesive holding performance to the base film and the tire carcass layer, and accordingly, the heat generated in the process of manufacturing or running the tire Or intermittent interface between the inner liner film and the carcass layer caused by repeated deformation is prevented, so that the inner liner polymer film can have 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. As the former adhesive for the inner liner, a rubber type tie gum or the like was used, and thus, an additional vulcanization step 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 the base film, sufficient adhesion performance can be realized.

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 have a thickness of 0.1 to 20 占 퐉, preferably 0.1 to 10 占 퐉, more preferably 0.2 to 7 占 퐉, still more preferably 0.3 to 5 占 퐉, and one surface of the polymer film for inner liner or 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.

According to another embodiment of the present invention, a pneumatic tire including the polymer film for inner liner may be provided.

As described above, since the polymer film for inner liner of the embodiment can realize excellent airtightness even with a thin thickness, the pneumatic tire can be lightened as compared with the pneumatic tire of the prior art, so that the fuel economy of the automobile can be improved . In addition, the polymer film for inner liner of the embodiment exhibits a low modulus and a low crystallinity, so that even in a tire manufacturing process in which a large deformation is performed under a high temperature condition, or in a car running process in which repetitive deformation is continuously applied, It is possible to prevent the occurrence of damage such as cracks in the inside.

The pneumatic tire may have the structure of a conventional pneumatic tire except that it includes the polymer film for the specific inner liner described above. For example, the pneumatic tire may comprise a tread portion; A pair of shoulder portions which are respectively continuous on both sides around the tread portion; A pair of side wall portions continuous with each of the shoulder portions; A pair of bead portions continuous to each of the side wall portions; A body fly portion formed on the inner side of the tread portion, the shoulder portion, the side wall portion and the bead portion; A belt portion and a cap ply portion sequentially stacked between the inner side surface of the tread portion and the body ply portion; And an inner liner film coupled to the inside of the body ply portion.

According to the present invention, it is possible to realize an airtightness and a gas barrier property (low oxygen permeability) even with a thin thickness to lighten the tire and to improve automobile fuel economy, and to have excellent mechanical properties such as durability and fatigue resistance A polymer film for an inner liner having a small crack occurrence and a pneumatic tire including the polymer film for an inner liner can be provided.

In addition, the provided polymeric film for inner liner can have a sufficient modulus and a low modulus, and the degree of crystallization of the base film does not become so large even through a molding process or a stretching process at a high temperature of 100 ° C or higher, The recovery rate and the like are not largely lowered, and excellent formability can be secured.

Fig. 1 schematically shows the structure of a tire.
FIG. 2 is a graph showing the results of stress and residual stress measurement performed in Experimental Example 4. FIG.

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 : For inner liner  Preparation of polymer film]

< Example 1 >

(1) Production of base film

(Nylon 6) having a relative viscosity (96% solution of sulfuric acid) of 3.3 and a copolymer resin having a weight average molecular weight of about 105,000 (25% by weight of a polyether segment based on polytetramethylene oxide having an amine terminus as a main chain and (Synthesized using 75% by weight of a polyamide segment of caprolactam) was mixed in a weight ratio of 5: 5, and an oxazoline compound and a heat resistant agent [copper (Cu) in a mixture of copper iodide and potassium iodide- 7 wt%] was added to prepare a mixture for producing a base film. The content of the oxazoline compound in the mixture was 1% by weight, and 100 ppmw of the heat resistant agent was contained.

Then, the mixture was extruded at 260 DEG C while maintaining a uniform molten resin flow through a T-die (die gap - 1.0 mm), using an air knife on the surface of a cooling roll controlled at 25 DEG C, The resin was cooled and solidified on a film having a uniform thickness. Then, an unstretched base film having a thickness of 100 mu m was obtained without passing through the stretching and heat treatment sections at a speed of 15 m / min.

 (2) 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 base film with a thickness of 1 μm using a gravure coater and dried and reacted at 150 ° C. for 1 minute to form an adhesive layer.

< Example 2 >

The copolymer resin having a weight average molecular weight of about 100,000 was used instead of the copolymer resin having a weight average molecular weight of about 105,000 (25% by weight of a polyether segment based on an amine group-terminated polytetramethylene oxide as a main chain and a polyamide-based copolymer of caprolactam Segment: 75% by weight) A base film was produced in the same manner as in Example 1, except that the base film was used in a weight ratio of 6: 4, and the base film was coated on one surface of the base film in the same manner as in Example 1 An adhesive layer was formed.

< Example 3 >

A copolymer resin having a weight average molecular weight of about 92,000 (25% by weight of a polyether segment based on an amine group-terminated polytetramethylene oxide as a main chain and a polyamide-based copolymer of caprolactam as a main chain) was used in place of the copolymer resin having a weight average molecular weight of about 105,000 Segment 75 wt%) was used in a weight ratio of 7: 3 to prepare a base film in the same manner as in Example 1, and on one surface of the base film, An adhesive layer was formed.

< Example 4 >

A copolymer resin having a weight average molecular weight of about 85,000 (25% by weight of a polyether segment based on an amine group-terminated polytetramethylene oxide as a main chain and a polyamide-based copolymer of caprolactam as a main chain) was used instead of the copolymer resin having a weight average molecular weight of about 105,000 Segment 75% by weight) was mixed at a weight ratio of 2: 8 to prepare a base film. A base film was prepared in the same manner as in Example 1, and the same method as in Example 1 To form an adhesive layer.

[ Comparative Example : For inner liner  Preparation of polymer film]

< Comparative Example  1>

(1) Production of base film

85% by weight of a nylon 6 resin having a relative viscosity of 96% (sulfuric acid solution) 3.3 and a weight average molecular weight of 45,000 (10% by weight of a polyether segment based on polytetramethylene oxide as a main chain and a polyamide segment 90 of caprolactam 15 wt%) were mixed in the same manner as in Example 1 to obtain an unstretched substrate film (CE1) having a thickness of 100 mu m.

(2) Application of adhesive

An adhesive layer was formed on one side of the base film in the same manner as in Example 1.

< Comparative Example  2>

A release agent and a processing agent were added to the butyl rubber, and the mixture was refined to obtain a tire inner liner film having a thickness of 70 탆, and an adhesive rubber (tie gum) was formed on the inner liner film.

< Experimental Example : For inner liner  Measurement of physical properties of polymer film>

Experimental Example 1 : Durability measurement experiment

(One) Air mouth  Manufacture of tires

Tires of the 205R / 75R15 standard were manufactured and evaluated using the inner liner film of the above-described embodiment and comparative example. At this time, 1300De '/ 2ply HMLS tire cord was used as the cord included in the body fly, steel cord was used as the belt, and N66 840De' / 2ply product was used as the cap fly.

Specifically, the prepared inner liner film was wrapped on a tire building drum, and a length of 3 cm was overlapped to fix the inner liner film, and the overlapping area was fixed with a tie gauge having a thickness of 1 mm. Then, a 2 mm thick shower-reinforced rubber sheet was attached to one portion of the inner liner corresponding to the position where the crimp was to be formed, with a width of 5 cm from 9 cm to 14 cm from the center of the drum.

Then, a body fly rubber is laminated on the inner liner film, and a bead wire; A belt portion; Cap fly portion; And a rubber layer for forming a tread portion, a shoulder portion, and a side wall portion were sequentially formed to produce a green tire.

The green tire thus prepared was put into a mold and vulcanized for 160 minutes for 30 minutes to produce a tire.

(2) Durability measurement experiment

The durability of the tire was evaluated using an FMVSS139 tire durability measurement method. This durability measurement was carried out by two methods; a step load endurance test which increases the load step by step and a high speed test which increases the speed step by step.

The tires will run about 60 million cycles under actual use conditions, and those 60 million cycles will be equivalent to about 12 million cycles under the FMVSS139 standard. That is, a tire capable of performing about 12 million cycles or more under the FMVSS139 test can be judged to have durability suitable for a practical use environment.

Results of Experimental Example 1 Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Step Load Endurance Test 105% 108% 107% 105% 60% 100% High Speed Endurance Test 110% 107% 107% 105% 90% 100% Crack or wrinkle occurrence X X X X O X

As shown in Table 1, it was confirmed that the tire to which the inner liner film of the example was applied had excellent durability as compared with the tire to which the polymer film for inner liner of the comparative example was applied.

These results show that the inner liner film of the embodiment can have a lower modulus characteristic and a higher elasticity or elastic recovery rate as the inner liner film has a relatively low crystallinity so that even in the running process of the vehicle in which continuous deformation and external pressure are applied, This is due to the prevention of breakage or tearing, thereby ensuring higher durability.

Experimental Example 2 : Tire Manufacturing Fairness

The tire inner liner film of each of the examples and the comparative examples was applied to produce 100 tires, and the inside of the manufactured tire was visually observed to measure the number of normal products having no film defects such as cracks or cracks The production yield of the normal product is expressed by the tire manufacturing processability.

At this time, when the green tire or the vulcanized tire had no distortion, and the standard deviation of the diameter was within 5%, it was evaluated as "good". And, when the tire was not made properly due to the occurrence of distortion in the green tire or the vulcanized tire, or when the inner liner inside the tire was melted or torn and broken, or when the standard deviation of the diameter exceeded 5%, it was evaluated as "poor".

Results of Experimental Example 2 Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Tire Manufacturing Fairness Good Good Good Good Bad Good

Experimental Example 3 : Measurement of Strength of Base Film

The intensities at 25% or 100% elongation in the MD and Machine Direction directions of the polymer film for inner liner obtained in the above Examples and Comparative Examples were respectively measured. The specific measurement method is as follows.

(1) Measuring instrument: universal material testing machine (Model 4204, Instron)

(2) Measurement conditions: 1) Head Speed 300mm / min, 2) Grip Distance 100mm, 3) Sample Width 10mm, 4) 25% and 100% elongation, 60RH% atmosphere

(3) 5 times each, and the average value was obtained.

And, in the stress-strain curves obtained from the data measured above, the strength was determined as the value of the stress at 25% and 100% elongation of the stress-strain curve.

Experimental Example 4 : Stress at 80% elongation and elongation at 160 ℃ after elongation For 20 minutes  Residual stress measurement after heat treatment

The polymer films for inner liner obtained in the above Examples and Comparative Examples were laminated in the same manner as in the case of general unvulcanized Carcass Standard rubber 0.7 mm.

Specifically, an inner liner film was placed on a carcass rubber layer, and a rubber-film laminate specimen was prepared by pushing a 10 kgf rubber roller 10 times. At this time, the inner liner film disposed the film TD in the longitudinal direction. In the tire manufacturing, the direction of MD is orientated by shear during film formation, and hard domain and soft domain are distributed in longitudinal direction. Therefore, TD film is placed in the circumferential direction of tire to improve durability. In order to simulate this, residual stress was evaluated in TD direction.

The prepared laminate specimens were cut through a sharp blade to have a 20 mm * 200 mm evaluation area, and then subjected to tensile evaluation through an Instron.

The C / H Speed progressed to 300 mm / min, and after 80% tensile, it was fixed, and the load value at that time was measured for 20 minutes. The residual stress of the tire was simulated by measuring the change of the load value for 20 minutes after placing the sample under the temperature of 160 ℃ by applying Movable Heater.

FIG. 2 is a graph showing the stresses occurring when the polymer films of Examples and Comparative Examples were stretched at 80% and the residual stress after heat treatment at 160 ° C. for 20 minutes after stretching.

Results of Experimental Examples 3 and 4 Reference example
(0.7mm Carcass rubber layer) Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Rubber Laminate 80% Stress at elongation [Mpa] 0.359 2.31 1.82 1.68 1.41 3.02 The residual stress [Mpa] measured after heating at 160 [deg.] C for 20 minutes after elongation, 0.058 0.27 0.19 0.17 0.14 0.35 Strength at 25% elongation of base film
[Mpa] - 22 18 16 15 25 Strength at 100% elongation of base film
[Mpa] - 23 19 16 16 25

As shown in Table 3, it was confirmed that the base film in Examples 1 to 4 had a strength of 25 MPa in one direction or 15 MPa to 23 MPa in 100% elongation. Accordingly, the inner liner film containing the base film of each of Examples 1 to 4 has sufficient elasticity and moldability required in the tire manufacturing process while maintaining the shape and mechanical properties of the base film in a tire manufacturing process or an automobile running process .

Further, it was confirmed that the base film in Examples 1 to 4 exhibited a residual stress of not more than 2.31 MPa when the base film combined with the carcass rubber layer having a thickness of 0.7 mm was elongated at 80% in one direction, and the elongation at 80% It was confirmed that the residual stress measured after heat treatment for 20 minutes at &lt; RTI ID = 0.0 &gt; 0 C &lt; / RTI &gt; That is, it was confirmed that not only the base film in Examples 1 to 4 had a small residual stress even after elongation of 80%, but also the stress measured in the state of heat fixation after elongation was also considerably low.

Accordingly, the base film in Examples 1 to 4 exhibits a phenomenon that the polymer structure is deformed in the course of 80% elongation in the state of being bonded to the carcass rubber layer, or that the physical properties and shape of the film are largely changed Hardly occurs, and even after elongation conditions or high temperature conditions are applied, the elastic behavior can be substantially similar to that of carcass rubber.

Claims (18)

Polyamide based resin; A copolymer comprising a polyamide-based segment and a poly-ether-based segment; And a substrate film comprising a compound comprising an oxazoline functional group,
Wherein the base film has a strength at 25% stretching in one direction of 10 Mpa to 30 Mpa.
The method according to claim 1,
Wherein the base film has a strength at 100% stretching in one direction of 10 Mpa to 30 Mpa.
The method according to claim 1,
Wherein the base film is combined with a carcass rubber layer having a thickness of 0.50 mm to 1.0 mm to produce a stress of not more than 3 MPa when stretched 80% in one direction.
The method of claim 3,
Wherein the residual stress measured after stretching the base film combined with the carcass rubber layer having the thickness of 0.50 mm to 1.0 mm by 80% in one direction and heat-treated at 160 ° C for 20 minutes is 0.3 MPa or less.
The method according to claim 1,
Wherein the polyamide based resin and the copolymer comprising the polyamide based segment and the polyether based segment are bonded via a compound containing the oxazoline based functional group.
The method according to claim 1,
The oxazoline functional group-containing compound may be,
An oxazoline which is at least partially substituted with hydrogen, an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 6 carbon atoms; A (meth) acrylate-based polymer having one or more oxazolines substituted; And a styrenic polymer in which at least one oxazoline is substituted. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
The method according to claim 1,
Wherein the base film comprises 0.5 wt% to 25 wt% of the compound containing the oxazoline functional group.
The method according to claim 1,
And the relative viscosity (96% solution of sulfuric acid) of the polyamide based resin is 3.0 to 4.0.
The method according to claim 1,
Wherein the copolymer comprising the polyamide-based segment and the polyether-based segment has a weight average molecular weight of 50,000 to 500,000.
The method according to claim 1,
Wherein the content of the polyether segment in the base film is 2% by weight to 40% by weight.
The method according to claim 1,
Wherein the polyamide segment of the copolymer 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 segment of the copolymer comprises a repeating unit represented by the following formula (3):
(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 weight ratio between the polyamide resin and the copolymer in the base film is from 9: 1 to 2: 8.
The method according to claim 1,
Wherein the base film has a thickness of 30 to 300 占 퐉.
The method according to claim 1,
Wherein the base film further comprises 50 to 5,000 ppmw of a heat resistant agent.
The method according to claim 1,
Further comprising an adhesive layer formed on at least one side of the base film and including a resorcinol-formalin-latex (RFL) -based adhesive.
17. The method of claim 16,
Wherein the adhesive layer has a thickness of 0.1 占 퐉 to 20 占 퐉.
A pneumatic tire comprising the polymer film for an inner liner of claim 1.

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