Polymer film

Abstract

This disclosure relates to a polymer film including: a base film including polyamide-based resin including two or more different kinds of repeat units; and a copolymer including polyamide-based segments and polyether-based segments.

Claims

1. A polymer film comprising: a base film comprising a polyamide-based resin comprising two or more different kinds of repeat units; and a copolymer comprising polyamide-based segments and polyether-based segments, wherein the polyamide-based resin includes a repeat unit of the following Chemical Formula 1 and 0.5 wt % to 20 wt % of a repeat units of the following Chemical Formula 2: ##STR00006## ##STR00007## wherein, in Chemical Formula 2, R.sub.1 is a linear or branched alkylene group having 2 to 4 carbon atoms.

2. The polymer film according to claim 1, wherein the polymer film is used as a tire inner liner.

3. The polymer film according to claim 1, wherein the polyamide-based resin further comprises a repeat unit of the following Chemical Formula 3: ##STR00008## wherein, in Chemical Formula 3, R.sub.2 is a linear or branched alkylene group having 1 to 20 carbon atoms, and R.sub.3 is a linear or branched alkylene group having 1 to 20 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a linear or branched arylalkylene group having 7 to 20 carbon atoms.

4. The polymer film according to claim 3, wherein the polyamide-based resin comprises 0.5 wt % to 20 wt % of the repeat units of Chemical Formula 3.

5. The polymer film according to claim 1, wherein the polyamide-based copolymer has a relative viscosity (96% sulfuric acid solution) of 3.0 to 4.0.

6. The polymer film according to claim 1, wherein the copolymer comprising polyamide-based segments, polyether-based segments, and polyamide-based resin form a crosslink.

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

8. The polymer film according to claim 1, wherein the content of the polyether-based segments in the base film is 4 wt % to 20 wt %.

9. The polymer film according to claim 1, wherein the copolymer comprising polyamide-based segments and polyether-based segments has a weight average molecular weight of 50,000 to 300,000.

10. The polymer film according to claim 1, wherein the basic unit of the polyether-based segment has a weight average molecular weight of 500 to 10,000.

11. The polymer film according to claim 1, wherein the base film has a thickness of 30 m to 300 m.

12. The polymer film according to claim 1, wherein the base film further comprises a nylon 6 resin.

13. The polymer film according to claim 1, further comprising an adhesive layer that is formed at at least one side of the base film and that comprises a resorcinol-formalin-latex (RFL)-based adhesive.

14. The polymer film according to claim 13, wherein the adhesive layer has a thickness of 0.1 m to 20 m.

15. A pneumatic tire comprising the polymer film of claim 1 as an inner liner.

Description

BRIEF DESCRIPTION OF FIGURES

(1) FIG. 1 schematically shows the structure of a pneumatic tire.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(2) Hereinafter, the embodiment of 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.

EXAMPLES AND COMPARATIVE EXAMPLES: MANUFACTURE OF A POLYMER FILM FOR AN INNER LINER

Example 1

(1) Preparation of a Base Film

(3) 50 wt % of a polyamide-based copolymer resin having relative viscosity (96% sulfuric acid solution) of 3.8 [synthesized using -caprolactam and -valerolactam at a weight ratio of 92:8] and 50 wt % of a copolymer resin having a weight average molecular weight of 145,000 [synthesized using 45 wt % or polyether-based segments having an amine end group and a polypropylene oxide main chain and 55 wt % of polyamide-based segments of caprolactam] were mixed.

(4) Herein, the mixture was fed to an extrusion die while controlling the temperature of a part for supplying raw material to prevent fusion of the mixture to the screw of the extruder and resulting faulty feeding. The fed mixture was melted at a temperature of 260 C. and extruded through a T-type die (die gap1.0 mm) while maintaining uniform flow of molten resin, and the molten resin was cooled and solidified to a film with a uniform thickness using an air knife on the surface of a cooling roll that is controlled to 25 C., thus obtaining an unstretched based film (E1) having a thickness of 100 um at a speed of 15 m/min.

(2) Coating of Adhesive

(5) 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 were mixed to obtain resorcinol-formalin-latex (RFL)-based adhesive at a concentration of 20%.

(6) The resorcinol-formalin-latex (RFL)-based adhesive was coated on the base film to a thickness of 1 um using a gravure coater, dried at 150 C. for 1 min, and reacted to form an adhesive layer.

Example 2

(1) Preparation of a Base Film

(7) 50 wt % of a polyamide-based copolymer resin having relative viscosity (96% sulfuric acid solution) of 3.3 [synthesized using -caprolactam and 2-azacyclononanone at a weight ratio of 85:15] and 50 wt % of a copolymer resin having a weight average molecular weight of 105,000 [synthesized using 20 wt % of polyether-based segments having an amine end group and a polypropylene oxide main chain and 80 wt % of polyamide-based segments of caprolactam] were mixed to obtain an unstretched base film (E2) having a thickness of 100 um by the same method as Example 1.

(2) Coating of Adhesive

(8) By the same method as Example 1, the resorcinol-formalin-latex (RFL)-based adhesive was coated on the base film (E2) to a thickness of 1 um using a gravure coater, dried at 150 C. for 1 min, and reacted to form an adhesive layer.

Example 3

(1) Preparation of Base Film

(9) 50 wt % of a polyamide-based copolymer resin having relative viscosity (96% sulfuric acid solution) of 3.6 [synthesized using -caprolactam and 2-pyrrolidone at a weight ratio of 94:6] and 50 wt % of a copolymer resin having a weight average molecular weight of 85,000 [synthesized using 20 wt % of polyether-based segments having a polytetramethylene oxide main chain and 80 wt % of polyamide-based segments of caprolactam] were mixed to obtain an unstretched base film (E3) having a thickness of 100 um by the same method as Example 1.

(2) Coating of Adhesive

(10) By the same method as Example 1, the resorcinol-formalin-latex (RFL)-based adhesive was coated on the base film (E3) to a thickness of 1 um using a gravure coater, dried at 150 C. for 1 min, and reacted to form an adhesive layer.

Example 4

(1) Preparation of Base Film

(11) 40 wt % of a polyamide-based copolymer resin having relative viscosity (96% sulfuric acid solution) of 3.6 [synthesized using -caprolactam and 2-pyrrolidone at a weight ratio of 94:6] and 60 wt % of a copolymer resin having a weight average molecular weight of 65,000 [synthesized using 60 wt % of polyether-based segments having a polytetramethylene oxide main chain and 40 wt % of polyamide-based segments of caprolactam] were mixed to obtain an unstretched base film (E4) having a thickness of 100 um by the same method as Example 1.

(2) Coating of Adhesive

(12) By the same method as Example 1, the resorcinol-formalin-latex (RFL)-based adhesive was coated on the base film (E4) to a thickness of 1 um using a gravure coater, dried at 150 C. for 1 min, and reacted to form an adhesive layer.

Example 5

(1) Preparation of Base Film

(13) An unstretched base film (E5) having a thickness of 100 um was obtained by the same method as Example 1, except mixing 70 wt % of the polyamide-based copolymer resin of Example 2, 20 wt % of a copolymer resin including polyether-based segments and polyamide-based segments, and 10 wt % of nylon 6 resin having relative viscosity of 3.6.

(2) Coating of Adhesive

(14) By the same method as Example 1, resorcinol-formalin-latex (RFL)-based adhesive was coated on the base film (E5) to a thickness of 1 um using a gravure coater, dried at 150 C. for 1 min, and reacted to form an adhesive layer.

Example 6

(1) Preparation of Base Film

(15) 40 wt % of a polyamide-based copolymer resin having relative viscosity (96% sulfuric acid solution) of 3.6 [synthesized using -caprolactam and compounds of hexamethylene diamine and adipic acid at a weight ratio of 95:5] and 60 wt % of a copolymer resin having a weight average molecular weight of 125,000 [synthesized using 60 wt % of polyether-based segments having a polytetramethylene oxide main chain and 40 wt % of polyamide-based segments of caprolactam] were mixed to obtain an unstretched base film (E6) having a thickness of 100 um by the same method as Example 1.

(2) Coating of Adhesive

(16) By the same method as Example 1, resorcinol-formalin-latex (RFL)-based adhesive was coated on the base film (E5) to a thickness of 1 um using a gravure coater, dried at 150 C. for 1 min, and reacted to form an adhesive layer.

COMPARATIVE EXAMPLE

(1) Preparation of Base Film

(17) 85 wt % of nylon 6 resin having relative viscosity (96% sulfuric acid solution) of 3.3 and 15 wt % of a copolymer resin having a weight average molecular weight of 45,000 [synthesized using 10 wt % of polyether-based segments having a polytetramethylene oxide main chain and 90 wt % of polyamide-based segments of caprolactam] were mixed to obtain an unstretched base film (CE1) having a thickness of 100 um by the same method as Example 1.

(2) Coating of Adhesive

(18) By the same method as Example 1, the resorcinol-formalin-latex (RFL)-based adhesive was coated on the base film (CE1) to a thickness of 1 um using a gravure coater, dried at 150 C. for 1 min, and reacted to form an adhesive layer.

EXPERIMENTAL EXAMPLE

Experimental Example 1: Oxygen Permeability Test

(19) For the tire inner line films obtained in the examples and comparative examples, oxygen permeability was measured under 25 C. and 60 RH % using a gas transmission rate tester (Model BR-1/BT-2, manufactured by Toyoseiki Seisaku-Sho Company) according to ASTM D 1434.

Experimental Example 2: Evaluation of the Properties of Film

(20) The base film was allowed to stand at 23 C., relative humidity of 50% for 24 h, and then, with a sample length of 30 mm, a sample width of 30 mm, and tension speed of 300 mm/min, breaking strength, elongation at break, and strength at 2 5% elongation in the machine direction (MD) and the transverse direction (TD) of the base film were respectively measured 10 times using a tensile test machine (Instron Company), and the mean value of 8 values except the maximum value and minimum value was calculated.

(21) After being allowed to stand at 23 C., relative humidity of 50% for 24 h, the base film was allowed to stand in a 170 C. hot-air oven for 1 h, and immediately afterward, under the same conditions as the tension measuring condition, breaking strength, elongation at break, and strength at 25% elongation in the MD and TD of the heat treated base film were respectively measured 10 times, and the mean value of 8 values except the maximum value and minimum value was calculated.

(22) Brittleness of the base film was indicated by the modulus at 25% elongation obtained from the tensile evaluation. Durability of the base film was calculated from the toughness maintenance rate of the base film before and after heat treatment.

(1) Evaluation of Brittleness

(23) Brittleness change due to heat treatment was indicated by change in strength at 25% elongation, when the base film was elongated before/after heat treatment, and brittleness in MD and TD of the base film was calculated by the following Equation 1.
Brittleness (%)=[strength at 25% elongation after heat treatment (MPa)/strength at 25% elongation before heat treatment (MPa)]*100(%)<Equation 1>

(2) Evaluation of Durability

(24) Using the breaking strength and elongation at break of the base film before/after heat treatment, toughness of MD and TD of the base film was calculated by the following Equation 2, and durability of MD and TD of the base film before/after heat treatment was calculated by the following Equation 3.
Toughness of base film (MPa)=breaking strength (MPa)SQRT [elongation at break (%)]<Equation 2>

(25) (wherein SQRT denotes square root.)
Durability of base film (%)=[toughness of base film after heat treatment/toughness of base film before heat treatment]*100(%)<Equation 3>

Experimental Example 3: Measurement of Formability

(26) Using the tire inner liner films of the examples and comparative examples, 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.

(27) Herein, 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. Further, when the green tire or the vulcanized tire was crushed, and thus a tire was not properly manufactured, the inner liner inside the tire was melted or torn and thus damaged, or when the standard deviation of the diameter was greater than 5%, it was evaluated as faulty.

(28) For the 100 tires manufactured using the tire inner liner films of the examples and comparative examples, the number of tires having good appearance was confirmed to evaluate formability, wherein formability was calculated by the following Equation 4.
Formability (%)=[The number of tires evaluated as good/100 (the number of manufactured tires)]*100(%)<Equation 4>

Experimental Example 4: Measurement of Tire Durability

(29) The durability of a tire was tested and evaluated while increasing a load, according to the FMVSS139 tire durability measuring method. The measurement of durability was conducted by two methods of an endurance test which increases load by step loading, and a high speed test which increases speed, and it was confirmed whether or not a crack was generated inside a tire, wherein it was indicated as good when there was no crack, and as faulty when a crack was generated.

(30) The final appearance of tires was evaluated by the method of Experimental Example 3, 20 tires with good appearance were selected, and an endurance test and a high speed test were progressed for 10 tires to confirm whether or not a crack was generated. After measuring durability for 10 tires, the durability of tires according to the endurance test and high speed test was calculated by the following Equation 5, 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 5>

(31) The results of Experimental Examples 1 to 4 are shown in the following Table 1.

(32) TABLE-US-00001 TABLE 1 Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example Oxygen permeability 86 67 35 110 56 71 12 [cc/(m.sup.2 .Math. 24 h .Math. atm)] Brittleness Machine 180 192 215 165 207 185 450 (%) direction (MD) Transverse 176 190 216 161 205 178 397 direction (TD) Base film Machine 93 86 78 89 87 91 18 Durability direction (%) (MD) Transverse 89 79 69 85 71 85 15 direction (TD) Formability (%) 100 100 99 100 98 100 11 Durability Endurance 100 100 90 90 100 100 0 of tires (%) Test High 100 100 100 100 100 100 10 Speed Test

(33) As shown in the Table 1, it was confirmed that the polymer films for an inner liner obtained in Examples 1 to 6 have low oxygen permeability, and yet do not exhibit significant change in brittleness or durability of the film before and after heat treatment at a high temperature. Further, the polymer films for an inner liner obtained in Examples 1 to 6 may secure high formability of tires, and afford high durability to practical pneumatic tires even in an automobile running process during which rotations and deformations are repeatedly applied.

(34) That is, the polymer films for an inner liner obtained in Examples 1 to 6 exhibit a low modulus and low crystallinity, thus preventing crystallization of the film itself or damage such as cracks inside the films even in a tire manufacturing process during which significant deformation occurs under a high temperature condition or in an automobile running process during which deformations are repeatedly applied.

(35) On the other hand, it was confirmed that although the polymer film of a comparative example that uses high contents of nylon 6 and includes low contents of polyether-based segments in the base film exhibits lower oxygen permeability compared to the examples, brittleness of the film significantly increases and durability is lowered after heat treatment at high temperature. It was also confirmed that using the polymer film of the comparative example, it is not easy to form into a green tire or a pneumatic tire, and that a pneumatic tire including the polymer film of the comparative example cannot secure sufficient durability to withstand high speed high pressure deformation applied in a practical automobile running process.