POLYMER FILM AND POLYMER FILM MANUFACTURING METHOD

Abstract

The present invention relates to a polymer film comprising a base film comprising polyamide-based resin; and two or more kinds of copolymers comprising polyamide-based segments and polyether-based segments, and a method for preparing the polymer film.

Claims

1. A polymer film for an inner liner, comprising a base film comprising: polyamide-based resin; and two or more kinds of copolymers comprising polyamide-based segments and polyether-based segments.

2. The polymer film according to claim 1, wherein the two or more kinds of copolymers include copolymer comprising different polyether-based segments.

3. The polymer film according to claim 1, wherein at least one kind of copolymer comprises polyether-segments comprising repeat units of the following Chemical Formula 31 among the copolymers: ##STR00007##

4. The polymer film according to claim 3, wherein another kind of copolymer comprises polyether-based segments comprising repeat units of the following Chemical Formula 32 among the copolymers: ##STR00008##

5. The polymer film according to claim 4, wherein the weight ratio of one kind of copolymer comprising polyether-based segments comprising repeat units of the Chemical Formula 31 and polyamide-based segments and another kind of copolymer comprising polyether-based segments comprising repeat units of the Chemical Formula 32 and polyamide-based segments, is 1:1 to 1:5.

6. The polymer film according to claim 1, wherein the total content of the polyether-based segments included in the base film is 2 wt % to 40 wt %.

7. The polymer film according to claim 1, wherein the base film further comprises an olefin-based polymer compound.

8. The polymer film according to claim 7, wherein the olefin-based polymer compound comprises one or more compounds selected form the group consisting of olefin-based polymer, olefin-based copolymer and olefin-based polymer or copolymer grafted with dicarboxylic acid or acid anhydride thereof.

9. The polymer film according to claim 7, wherein the base film comprises 0.1 wt % to 30 wt % of the olefin-based polymer compound.

10. The polymer film according to claim 1, wherein the thickness of the base film is 30 to 300 μm, and oxygen permeability measured at 25° C. and 60RH % according to the method of ASTM D 1434 is 200 cm.sup.3/(m.sup.2×24 hr×atm) or less.

11. The polymer film according to claim 1, wherein heat-resistant impact strength toward the transverse direction (TD) of the base film, measured after heat treating the base film at 170° C. for 1 hour according to ISO 8256 Method A, is 800 to 4,000 kJ/m.sup.2.

12. The polymer film according to claim 11, wherein the ratio of heat-resistant impact strength toward the machine direction (MD) of the base film to heat-resistant impact strength toward the transverse direction (TD) of the base film, measured after heat treating the base film at 170° C. for 1 hour according to ISO 8256 Method A, is 1 to 3.

13. The polymer film according to claim 1, further comprising an adhesive layer with a thickness of 0.1 μm to 20 μm, formed on at least one side of the base film, and comprising resorcinol-formalin-latex (RFL)-based adhesive.

14. A method for preparing a polymer film for an inner liner, comprising the step of melting a mixture comprising polyamide-based resin; and two or more kinds of copolymers comprising polyamide-based segments and polyether-based segments at 200 to 300° C. and extruding it to form a base film.

15. The method for preparing a polymer film according to claim 14, wherein the two or more kinds of copolymers include different polyether-based segments.

16. The method for preparing a polymer film according to claim 14, wherein at least one kind of copolymer comprises polyether-segments comprising repeat units of the following Chemical Formula 31 among the copolymers: ##STR00009##

17. The method for preparing a polymer film according to claim 16, wherein another kind of copolymer comprises polyether-based segments comprising repeat units of the following Chemical Formula 32 among the copolymers: ##STR00010##

18. The method for preparing a polymer film according to claim 17, wherein the total content of the polyether-based segments included in the mixture is 2 wt % to 40 wt %.

19. The method for preparing a polymer film according to claim 14, wherein the mixture further comprises an olefin-based polymer compound.

20. The method for preparing a polymer film according to claim 14, comprising the step of forming an adhesive layer comprising resorcinol-formalin-latex (RFL)-based adhesive on at least one side of the base film.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0136] FIG. 1 schematically shows the structure of a tire.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0137] Hereinafter, the present invention will be explained in detail with reference to the following examples. However, these examples are only to illustrate the invention and the scope of the invention is not limited thereto.

Example: Preparation of Polymer Film

Example 1

[0138] (1) Preparation of a Base Film

[0139] Polyamide-based resin (nylon 6) with a relative viscosity (sulfuric acid 96% solution) of 3.3 prepared from ε-caprolactam, copolymer resin with a weight average molecular weight of about 105,000 (comprising 25 wt % of polyether-based segments including a polytetramethylene oxide main chain and 75 wt % of polyamide-based segments derived from ε-caprolactam), and copolymer resin with a weight average molecular weight of about 115,000 (synthesized using 25 wt % of polyether-based segments including a poly(iso-propylene) oxide main chain with an amine end group, and 75 wt % of polyamide-based segments derived from ε-caprolactam) were mixed at a weight ratio of 5:2.5:2.5, and a cross linking agent styrene 2-isopropenyl-2-oxazoline copolymer and a heat resistant agent [a mixture of copper iodide and potassium iodide—the content of Cu in the mixture 7 wt %] were added thereto, thus preparing a mixture for preparing a base film. The content of the cross linking agent in the mixture was 0.5 wt %, and 0.3 wt % of the heat resistant agent was included.

[0140] And, the mixture was extruded at a temperature of 260° C. through a T type die (Die Gap—1.0 mm) while maintaining uniform flow of molten resin, and the molten resin was cooled and solidified in the shape of a film with uniform thickness using an air knife on the surface of a cooling roll that is controlled to 25° C. And, an undrawn base film having a thickness of 100 um was obtained at a speed of 15 m/min without passing drawing and heating sections.

[0141] (2) Coating of Adhesive

[0142] Resorcinol and formaldehyde were mixed at a mole ratio of 1:2, and then, condensed to obtain a condensate of resorcinol and formaldehyde. 12 wt % of the condensate of resorcinol and formaldehyde and 88 wt % of styrene/butadiene-1,3/vinylpyridine latex were mixed to obtain resorcinol-formalin-latex (RFL)-based adhesive of concentration of 20%.

[0143] And, the resorcinol-formalin-latex (RFL)-based adhesive was coated on both sides of the undrawn base film using a gravure coater, dried at 150° C. for 1 minute, and reacted to form adhesive layers of 2 μm thickness, respectively, on both sides.

Example 2

[0144] Polyamide-based resin with a relative viscosity (sulfuric acid 96% solution) of 3.8 [synthesized using ε-caprolactam, and hexamethylene diamine and adipic acid at a weight ratio of 94:6], copolymer resin with a weight average molecular weight of about 130,000 (comprising 40 wt % of polyether-based segments including a polytetramethylene oxide main chain and 60 wt % of polyamide-based segments derived from ε-caprolactam), and copolymer resin with a weight average molecular weight of about 85,000 (comprising 20 wt % of polyether-based segments including a poly(iso-propylene) oxide main chain with an amine end group, and 80 wt % of polyamide-based segments derived from ε-caprolactam) were mixed at a weight ratio of 4:4:2, and a heat resistant agent [a mixture of copper iodide and potassium iodide—the content of Cu in the mixture 7 wt %] was added thereto, thus preparing a mixture for preparing a base film. The content of the heat resistant agent in the mixture was 0.8 wt %.

[0145] And, the mixture was extruded at a temperature of 250° C. through a T type die (Die Gap—0.8 mm) while maintaining uniform flow of molten resin, and the molten resin was cooled and solidified in the shape of a film with uniform thickness using an air knife on the surface of a cooling roll that is controlled to 20° C. And, an undrawn base film having a thickness of 90 um was obtained at a speed of 10 m/min without passing drawing and heating sections.

[0146] (2) Coating of Adhesive

[0147] An adhesive layer identical to that of Example 1 was formed, except that the adhesive layer was dried and reacted at 140° C. for 2 minutes to form adhesive layers with each thickness of 5 μm on both sides.

Example 3

[0148] (1) Preparation of Base Film

[0149] Polyamide-based resin (nylon 6) with a relative viscosity (sulfuric acid 96% solution) of 3.5 prepared from ε-caprolactam, copolymer resin with a weight average molecular weight of about 75,000 (comprising 20 wt % of polyether-based segments including a polytetramethylene oxide main chain and 80 wt % of polyamide-based segments derived from ε-caprolactam), and copolymer resin with a weight average molecular weight of about 105,000 (comprising 25 wt % of polyether-based segments including a poly(iso-propylene) oxide main chain with an amine end group, and 75 wt % of polyamide-based segments derived from ε-caprolactam) were mixed at a weight ratio of 2:5:3, and a heat resistant agent [a mixture of copper iodide and potassium iodide—the content of Cu in the mixture 7 wt %] and ethylene-propylene copolymer (density 0.87 g/cm.sup.3) grafted with maleic anhydride (1.0 wt %) were added thereto, thus preparing a mixture for preparing a base film. In the mixture, the content of the heat resistant agent was 0.5 wt %, and the content of olefin-based copolymer was 15 wt %.

[0150] And, the mixture was extruded at a temperature of 250° C. through a T type die (Die Gap—0.8 mm) while maintaining uniform flow of molten resin, and the molten resin was cooled and solidified in the shape of a film with uniform thickness using an air knife on the surface of a cooling roll that is controlled to 18° C. And, an undrawn base film having a thickness of 150 um was obtained at a speed of 15 m/min without passing drawing and heating sections.

[0151] (2) Coating of Adhesive

[0152] Adhesive layers were formed on both sides of the base film, by the same method as Example 1.

Example 4

[0153] Polyamide-based resin with a relative viscosity (sulfuric acid 96% solution) of 3.8 [synthesized using ε-caprolactam, and hexamethylene diamine and adipic acid at a weight ratio of 94:6], copolymer resin with a weight average molecular weight of about 120,000 (comprising 50 wt % of polyether-based segments including a polytetramethylene oxide main chain and 50 wt % of polyamide-based segments derived from ε-caprolactam), and copolymer resin with a weight average molecular weight of about 95,000 (comprising 50 wt % of polyether-based segments including a poly(iso-propylene) oxide main chain with an amine end group, and 50 wt % of polyamide-based segments derived from ε-caprolactam) were mixed at a weight ratio of 8:1.5:0.5, and a heat resistant agent [a mixture of copper iodide and potassium iodide—the content of Cu in the mixture 7 wt %] was added thereto, thus preparing a mixture for preparing a base film. In the mixture, the content of the heat resistant agent was 0.3 wt %.

[0154] And, the mixture was extruded at a temperature of 260° C. through a T type die (Die Gap—0.8 mm) while maintaining uniform flow of molten resin, and the molten resin was cooled and solidified in the shape of a film with uniform thickness using an air knife on the surface of a cooling roll that is controlled to 18° C. And, an undrawn base film having a thickness of 70 um was obtained at a speed of 15 m/min without passing drawing and heating sections.

[0155] (2) Coating of Adhesive

[0156] Adhesive layers were formed by the same method as Example 1, except that adhesive layers with each thickness of 1 μm were formed on both sides of the base film.

Example 5

[0157] (1) Preparation of Base Film

[0158] Polyamide-based resin (nylon 6) with a relative viscosity (sulfuric acid 96% solution) of 3.3 prepared from ε-caprolactam, copolymer resin with a weight average molecular weight of about 85,000 (comprising 15 wt % of polyether-based segments including a polytetramethylene oxide main chain and 85 wt % of polyamide-based segments derived from ε-caprolactam), and copolymer resin with a weight average molecular weight of about 125,000 (comprising 35 wt % of polyether-based segments including a poly(iso-propylene) oxide main chain with an amine end group, and 65 wt % of polyamide-based segments derived from ε-caprolactam) were mixed at a weight ratio of 2.5:2.5:5, and a heat resistant agent [a mixture of copper iodide and potassium iodide—the content of Cu in the mixture 7 wt %] was added thereto, thus preparing a mixture for preparing a base film. The content of the heat resistant agent in the mixture was 0.2 wt %.

[0159] And, the mixture was extruded at a temperature of 245° C. through a T type die (Die Gap—1.2 mm) while maintaining uniform flow of molten resin, and the molten resin was cooled and solidified in the shape of a film with uniform thickness using an air knife on the surface of a cooling roll that is controlled to 22° C. And, an undrawn base film having a thickness of 100 um was obtained at a speed of 15 m/min without passing drawing and heating sections.

[0160] (2) Coating of Adhesive

[0161] Adhesive layers were formed by the same method as Example 1, except that adhesive layers with each thickness of 7 μm were formed on both sides of the base film.

Comparative Example: Preparation of Polymer Film

Comparative Example 1

[0162] (1) Preparation of Base Film

[0163] 85 wt % of nylon 6 resin with a relative viscosity (sulfuric acid 96% solution) of 3.3, and 15 wt % of copolymer resin with a weight average molecular weight of about 45,000 (comprising 10 wt % of polyether-based segments including a polytetramethylene oxide main chain and 90 wt % of polyamide-based segments derived from ε-caprolactam) were mixed to obtain an undrawn base film with a thickness of 100 um by the same method as Example 1.

[0164] (2) Coating of Adhesive

[0165] Adhesive layers were formed on both sides of the base film by the same method as Example 1.

Experimental Example: Measurement of Properties of Polymer Film

Experimental Example

Experimental Example 1: Heat Resistant Impact Strength and Heat Resistant Impact Strength Ratio (MD/TD)

[0166] Heat resistant impact strength and heat resistant impact strength ratio of the base films obtained in Examples and Comparative Examples were measured as follows.

[0167] Heat resistant impact strength was measured using ISO 8256 Method A, and for the MD (Machine Direction) and TD (Transverse Direction) of the base film, each 10 specimens for evaluation were taken using a cutting device ISO 8256 Type 4.

[0168] Here, the specimen was cut such that the shape of the specimen for evaluation (specimen length×shoulder width×parallel specimen length×specimen width) became 60 mm×10 mm×25 mm×3 mm according to ISO 8256 type4, and the specimen for evaluation cut according to the standard was left under temperature of 23° C. and relative humidity of 50% for 24 hours, and then, heat treated in a hot air oven of 170° C. for 1 hour, and immediately after that, heat resistant impact strengths of the MD (Machine Direction) and TD (Transverse Direction) of the heat treated base film were measured each 10 times under temperature of 23° C. and relative humidity of 50% using a Pendulum Impact Tester, Zwick/Roell Company, Model HIT 5.5P according to ISO 8256 Method A, and the mean values of 8 values excluding the maximum and minimum were calculated.

[0169] When measuring the heat resistant impact strength, in order to minimize a deviation due to external environment, the specimens for evaluation were cut to a size required for measurement before heat treatment, and in order to minimize property change, measurement was completed within 15 minutes after heat treatment.

[0170] The heat resistant impact strengths for the MD (Machine Direction) and TD (Transverse Direction) of the base film were calculated according to the following Equation 1.

Heat resistant impact strength (kJ/m.sup.2)=impact energy(kJ)/[film thickness(m)×specimen width(0.003 m)]<Equation 1>

[0171] (wherein, the width of the specimen for evaluation was fixed to 3 mm)

[0172] And, the ratio of heat resistant impact strengths was calculated according to the following Equation 2.

Ratio of heat resistant impact strengths=(heat resistant impact strength of MD of film)/(heat resistant impact strength of TD of film)  <Equation 2>

Experimental Example 2: Oxygen Permeability Test

[0173] For the base films obtained in Examples and Comparative Examples, oxygen permeability was measured under 25° C. and 60RH % using a Gas Transmission Rate Tester (Model BR-1/BT-2, manufactured by Toyoseiki Seisaku-Sho Company) according to ASTM D 1434.

Experimental Example 3: Measurement of Formability

[0174] Using the polymer films of Examples and Comparative Examples as inner liners, each 100 tires were manufactured with a standard of 205R/65R16 During the tire manufacturing process, manufacturability and appearance were evaluated after preparing a green tire, and the final appearance of a tire was examined after vulcanization.

[0175] Here, when there was no crushing of the green tire or the vulcanized tire and the standard deviation of the diameter was within 5%, it was evaluated as ‘good’. And, when the green tire or the vulcanized tire was crushed, and thus a tire was not properly manufactured, or the inner liner inside the tire was molten or torn and damaged, or when the standard deviation of the diameter was greater than 5%, it was evaluated as ‘faulty’.

[0176] For the 100 tires manufactured using the polymer films of Examples and Comparative Examples as inner liners, the number of tires having good appearance was confirmed to evaluate formability, wherein the formability was calculated by the following Equation 3.

Formability(%)=The number of tires evaluated as ‘good’/100(the number of manufactured tires)×100(%)  <Equation 3>

Experimental Example 4: Measurement of Tire Durability

[0177] The durability of a tire was tested and evaluated while increasing load, according to FMVSS139 tire durability measuring method. The measurement of durability was conducted by two methods of Endurance Test which increases load by Step Loading, and High Speed Test which increases speed, and it was confirmed whether or not crack was generated inside a tire, and it was indicated as ‘good’ when there was no crack, and as ‘faulty’ when crack was generated.

[0178] The final appearance of tires was evaluated by the method of Experimental Example 3, and 20 tires with ‘good’ appearance were selected, and Endurance Test and High Speed Test were progressed for each 10 tires to confirm whether or not crack was generated. And, after measuring durability for 10 tires, the durability of tires according to Endurance Test and High Speed Test was calculated by the following Equation 4, using the number of ‘good’ tires without ‘crack’ generation.

The durability of tires(%)=The number of ‘good’tires/10(the number of evaluated tires)×100(%)  <Equation 4>

Experimental Example 5: Measurement of Internal Pressure Retention

[0179] For the tires manufactured in Experimental Example 3, 90 days internal pressure retention was measured at a temperature of 21° C. under pressure of 101.3 kPa according to ASTM F1112-06, as shown in the following Equation 5.

Internal pressure retention (%)={1−(internal pressure of tire at first evaluation-internal pressure of tire after 90 day standing)/(internal pressure of tire at first evaluation)}×100  <Equation 5>

[0180] The results of Experimental Examples 1 to 5 are shown in the following Table 5.

TABLE-US-00001 TABLE 1 Example Example Example Example Example Comparative 1 2 3 4 5 Example 1 Heat resistant impact 1,625 3,150 2,218 985 1,475 530 strength(kJ/m.sup.2; TD) Ratio of heat resistant impact 1.42 1.37 1.62 2.73 1.82 3.54 strengths(MD/TD) Oxygen permeability 66 89 112 45 119 18 [cm.sup.3/(m.sup.2 .Math. 24 hr*atm)] Formability(%) 99 100 100 97 100 35 Tire durability Endurance 100 100 100 90 100 10 (%) Test High Speed 100 100 100 100 100 60 Test Internal pressure retention(%) 97.8 97.3 96.9 98.1 95.8 98.3

[0181] As shown in Table 1, it was confirmed that the polymer films obtained in Examples have heat resistant impact strength of about 985 kJ/m.sup.2 or more and heat resistant impact strength ratio (MD/TD) of 2.8 or less, and thus, have a rigid bond at the copolymer interface and exhibit uniform properties to the direction of the film, and exhibit oxygen permeability of 120 cm.sup.3/(m.sup.2.Math.24 hr*atm) or less even at a thickness of 70 μm to 150 μm, and thus, can realize excellent gas barrier property even with a thin thickness, and can secure high durability when applied as a tire as well as excellent formability.