Polymer films

Abstract

There is provided a polymer film which includes a base film layer having an absolute weight average molecular weight of 50,000 to 1,000,000 and an adhesive layer, and a method for manufacturing the polymer film. This film for a tire inner liner can endow an excellent gas barrier property even to tires having a relatively thin thickness so that weight of the tire can be reduced and fuel efficiency of automobiles can be improved. Further, the present film facilitates molding in a tire manufacturing process, and exhibits excellent adhesion force to a carcass layer while having excellent mechanical properties such as high durability and fatigue resistance together with excellent moldability.

Claims

1. A polymer film which comprises: a base film layer comprising a polyamide-based resin; an olefinic polymer compound; and a copolymer containing a polyamide-based segment and a polyether-based segment; and an adhesive layer formed on at least one side of the base film layer and containing a resorcinol-formalin-latex (RFL)-based adhesive, wherein the content of the polyether-based segment of the copolymer is more than 2% by weight and less than 15% by weight with respect to the total weight of the base film layer, and wherein the base film layer has an absolute weight average molecular weight of 50,000 to 1,000,000, and the olefinic polymer compound includes a dicarboxylic acid or its acid anhydride-grafted olefinic polymer or copolymer, wherein the polyamide-based resin, the copolymer, and the olefinic polymer compound, respectively are included in a weight ratio of 2:2:1 to 2:3:1 in the base film layer.

2. The polymer film of claim 1, wherein a specific refraction increment (dn/dc) of the base film as measured at 40 C. using a 1:4 mixed solvent of m-cresol and chloroform containing tetramethylammonium chloride at a concentration of 0.02 M is 0.04 mL/g to 0.14 mL/g.

3. The polymer film of claim 1, wherein the polymer film is used for a tire inner liner film.

4. The polymer film of claim 1, wherein the grafted dicarboxylic acid or its acid anhydride is contained in an amount of 0.1% to 10% by weight.

5. The polymer film of claim 1, wherein the base film layer includes the olefinic polymer compound in an amount of 0.1% to 40% by weight.

6. The polymer film of claim 1, wherein the polyamide-based resin has a relative viscosity with respect to 96% sulfuric acid solution of 3.0 to 3.5.

7. The polymer film of claim 1, wherein the copolymer containing polyamide-based segments and polyether-based segments has an absolute weight average molecular weight of 50,000 to 1,000,000.

8. The polymer film of claim 1, wherein the copolymer includes the polyamide-based segments and the polyether-based segments in a weight ratio of 1:9 to 9:1.

9. The polymer film of claim 1, wherein the base film layer has a thickness of 30 m to 300 m, and the adhesive layer has a thickness of 0.1 m to 20 m.

10. The polymer film of claim 1, wherein the base film layer is an undrawn film.

11. The polymer film of claim 1, wherein the resorcinol-formalin-latex (RFL)-based adhesive includes 2% to 30% by weight of a condensate of resorcinol and formaldehyde and 68% to 98% by weight of a latex.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

DETAILED DESCRIPTION OF THE EMBODIMENTS

(2) Specific embodiments of the invention will be explained in detail in the following examples. However, these examples are only to illustrate specific embodiments of the invention, and the scope of the invention is not limited thereto.

EXAMPLE

Manufacture of a Film for a Tire Inner Liner

Example 1

(3) (1) Manufacturing of a Base Film

(4) A polyamide-based resin (nylon 6) having a relative viscosity (96% sulfuric acid solution) of 3.3, a copolymer resin having an absolute weight average molecular weight of 145,000 (including 55% by weight of a polyamide-based repeating unit and 45% by weight of a polyether-based repeating unit) and maleic anhydride-grafted (0.7 wt %) ethylene-propylene copolymer (density: 0.870 g/cm.sup.3) were mixed with a weight ratio of 4:4:2.

(5) At this time, the raw material feeder was adjusted to a temperature of 50 C. to 100 C. and then the above mixture was supplied to an extrusion die, while preventing the mixture from being fused in an extruder screw and thus causing a feeding failure.

(6) Then, the supplied mixture was extruded through a T-type die (die gap 1.0 mm) at a temperature of 260 C. while maintaining uniform flow of melted resin. The extruded melted resin was cooled and solidified into a film with a uniform thickness using an air knife on the surface of a cooling roll that was controlled to 25 C.

(7) Subsequently, a undrawn base film having a thickness of 100 um was obtained without going through the drawing and heat treatment section at a speed of 15 m/min.

(8) (2) Coating of Adhesive

(9) Resorcinol and formaldehyde were mixed at a mole ratio of 1:2 and then subjected to a condensation reaction to obtain a condensate of resorcinol and formaldehyde.

(10) 12% by weight of the 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)-based adhesive with a concentration of 20%.

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

Example 2

(12) (1) Manufacturing of a Base Film

(13) The base film was manufactured in the same manner as in Example 1, except that a polyamide-based resin (nylon 6) having a relative viscosity (96% sulfuric acid solution) of 3.3, a copolymer resin having an absolute weight average molecular weight of 110,000 (including 40% by weight of a polyamide-based repeating unit and 60% by weight of a polyether-based repeating unit), and maleic anhydride-grafted (0.7 wt %) ethylene-propylene copolymer (density: 0.870 g/cm.sup.3) were mixed with a weight ratio of 4:6:2.

(14) (2) Coating of Adhesive

(15) The adhesive layer was formed on the above manufactured base film in the same manner as in Example 1.

COMPARATIVE EXAMPLE

Manufacture of a Film for a Tire Inner Liner

Comparative Example 1

(16) (1) Manufacturing of a Base Film

(17) The base film was manufactured in the same manner as in Example 1, except that 60% by weight of a polyamide-based resin (nylon 6) having a relative viscosity (96% sulfuric acid solution) of 3.3 and 40% by weight of a copolymer resin having an absolute weight average molecular weight of 120,000 (including 80% by weight of a polyamide-based repeating unit and 20% by weight of a polyether-based repeating unit) were mixed.

(18) (2) Coating of Adhesive

(19) The adhesive layer was formed on the manufactured base film in the same manner as in Example 1.

Comparative Example 2

(20) (1) Manufacturing of a Base Film

(21) The base film was manufactured in the same manner as in Example 1, except that 20% by weight of a polyamide-based resin (nylon 6) having a relative viscosity (96% sulfuric acid solution) of 3.3 and 80% by weight of a copolymer resin having an absolute weight average molecular weight of 100,000 (including 20% by weight of a polyamide-based repeating unit and 80% by weight of a polyether-based repeating unit) were mixed.

(22) (2) Coating of Adhesive

(23) The adhesive layer was formed on the above manufactured base film in the same manner as in Example 1.

EXPERIMENTAL EXAMPLE

Measurement of Physical Properties of a Film for a Tire Inner Liner

Experimental Example 1

Measurement of the Absolute Weight Average Molecular Weight

(24) In order to measure the absolute weight average molecular weight, 2.192 g of tetramethylammonium chloride was weighed and introduced in a 1 L volumetric flask to produce m-cresol/chloroform (1/4, V/V).

(25) 0.050 g of the base film obtained in the examples and comparative examples was completely dissolved by further adding 10 ml of 0.02 M-TMAC m-cresol/chloroform 1/4 (V/V).

(26) Then, the solution in a state where the base film was completely dissolved was filtered with a 0.45 um syringe filter, and then mounted on the MALS autosampler.

(27) In this case, specific measurement conditions were as follows.

(28) (1) Specific measurement conditions

(29) injection volume: 100 ul

(30) injector temperature: 40 C.

(31) flow rate: 1 ml/min

(32) Eluent: m-cresol/chloroform 1/4 (V/V) (containing 0.02 mol of tetramethyl ammonium chloride)

(33) (2) Measurement of dn/dc

(34) The specific method for measuring the specific refractive index increment (dn/dc) is as follows.

(35) To 1 L of the 1:4 mixed solvent of m-cresol and chloroform, 0.02 mol of tetramethylammonium chloride was added to prepare a solution.

(36) To 100 ml of this mixed solvent, 2 g of the base film obtained in Examples 1 to 4 and Comparative Example 1 was added and completely dissolved. Then, foreign materials were removed by using a 0.45 um syringe filter.

(37) The resulting high-concentration samples were diluted to prepare samples having concentrations of 0.02 g/ml, 0.010 g/ml, 0.005 g/ml, and 0.002 g/ml. The refractive index of these samples in response to the concentrations was measured by using 0.45 m syringe filter.

(38) (3) Analysis Method of dn/dc Sample injection volume: 0.9 ml injector temperature: 40 C. flow rate: 0.3 ml/min eluent: m-Cresol+Chloroform (1:4) solvent (containing 0.02 mol of tetramethyl ammonium chloride)

(39) TABLE-US-00001 TABLE 1 Results of Experimental Example 1 Base Film Absolute weight average Classification molecular weight dn/dc [mL/g] Example 1 296,700 0.0842 Example 2 762,400 0.0638 Comparative Example 1 102,100 0.1410 Comparative Example 2 1,102,100 0.0589

Experimental Example 2

Oxygen Permeability Test

(40) The oxygen permeability of each film for a tire inner liner obtained in the examples and comparative examples was measured.

(41) Specific measurement method thereof is as follows.

(42) (1) Oxygen permeability: measured at 25 C. under a 60 RH % atmosphere using an Oxygen Permeation Analyzer (Model 8000, Illinois Instruments product) according to ASTM D 3895.

Experimental Example 3

Measurement of Internal Pressure Retention

(43) The tire was manufactured using the tire inner liner films of the examples and comparative examples according to the standard 205R/65R16.

(44) Then, 90-day internal pressure retention according to the following Equation 2 was measured at a temperature of 21 C. under a pressure of 101.3 kPa in accordance with ASTM F1112-06.
Internal Pressure Retention (%)={1(Tire inflation pressure upon initial testingTire inflation pressure after having been left for 90 days)/(Tire inflation pressure upon initial testing)}100[Equation 2]

Experimental Example 4

Measurement of Modulus at Room Temperature

(45) The room temperature modulus of the film for inner liner obtained in examples and comparative examples was measured without elongation of the film.

(46) Then, the film for inner liner was subjected to 100% elongation at room temperature based on the MD (machine direction) thereof to measure the modulus.

(47) Specific measurement method is as follows.

(48) (1) InstrumentUniversal Material Tester (Model 4204, Instron Co., Ltd.)

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

(50) (3) Each of measurements was conducted five times, respectively, and the average value thereof was obtained.

Experimental Example 5

Determination of the Ease of Molding

(51) The tire was manufactured using the tire inner liner film of the examples and comparative examples according to the standard of 205R/65R16.

(52) In a manufacturing process of a tire, a green tire was manufactured and then the manufacturing ease and appearance were evaluated. Then, after vulcanization, the final appearance of the tire was observed.

(53) In this case, when there was no distortion in a green tire or a tire after vulcanization and a standard deviation of diameter was within 5%, it was evaluated as good.

(54) Also, when distortion was generated in a green tire or a tire after vulcanization and thus the tire was not properly made or the inner liner in the inside of the tire was melted or torn and broken or when a standard deviation of the diameter was greater than 5%, it was evaluated as poor form.

(55) TABLE-US-00002 TABLE 2 Results of Experimental Examples 4 and 5 90-day Load at 100% elongation at Oxygen internal room temperature (kgf)/Load per Manufacturing permeability pressure unit thickness at 100% elongation state of a green cc/(m.sup.2 .Math. 24 h .Math. retention at room temperature (gf/um) tire atm) (%) Example 1 1.26/16.4 Good/good 83 95.2 Example 2 1.12/14.2 Good/good 95 93.4 Comparative 4.12/42 Bad form 30.2 Example 1 Comparative 1.02/11.2 Good/good 625 87 Example 2

(56) As shown in Table 2 above, in the case of the examples, the base film layer having uniform physical prosperities in the entire area of the film can be formed. Further, the film for a tire inner liner of the examples using the base film layer has excellent moldability as well as a high gas barrier property and internal pressure retention performance.

DESCRIPTION OF REFERENCE NUMERALS

(57) 1: Tread

(58) 2: Shoulder

(59) 3: Sidewall

(60) 4: Cap ply

(61) 5: Belt

(62) 6: Body ply

(63) 7: Inner liner

(64) 8: Apex

(65) 9: Bead