Cylindrical battery cell having heat-shrinkable tube comprising ultraviolet stabilizer

Abstract

Disclosed is a cylindrical battery cell in which a heat-shrinkable tube wraps an outer surface of a cylindrical case of the cylindrical battery cell except electrode terminals, the heat-shrinkable tube including: a base material, which is a polyester resin, capable of shrinking by heat; a supplement, which is a nylon resin, capable of increasing a tensile strength and operating temperature of the heat-shrinkable tube; and an ultraviolet stabilizer capable of inhibiting a chain reaction of free radicals generated by cleavage of polymer chains of the nylon resin or the polyester resin, when the heat-shrinkable tube is exposed to an ultraviolet ray irradiation.

Claims

1. A cylindrical battery cell in which a heat-shrinkable tube wraps an outer surface of a cylindrical case of the cylindrical battery cell except electrode terminals, the heat-shrinkable tube comprising: a base material, which is a polyester resin, capable of shrinking by heat; a supplement, which is a nylon resin for increasing tensile strength and operating temperature of the heat-shrinkable tube; and an ultraviolet stabilizer for inhibiting a chain reaction of free radicals generated by cleavage of polymer chains of the nylon resin or the polyester resin when the heat-shrinkable tube is exposed to an ultraviolet ray irradiation, wherein the ultraviolet stabilizer is butyl-4-hydroxybenzoate, wherein the ultraviolet stabilizer is included in an amount of 0.1 wt % to 5 wt %, based on a total weight of the heat-shrinkable tube, wherein the heat-shrinkable tube has no cracking when irradiated for 1,000 hours at an intensity of 61.5 W/m.sup.2 and at a wavelength of 300 nm to 400 nm, wherein the heat-shrinkable tube is 1 μm to 100 μm in thickness, and wherein the heat-shrinkable tube is one layer.

2. The cylindrical battery cell of claim 1, wherein the heat-shrinkable tube further comprises a coloration pigment.

3. The cylindrical battery cell of claim 1, wherein the polyester resin is a polyethylene terephthalate resin.

4. The cylindrical battery cell of claim 3, wherein the polyester resin is included in an amount of 70 wt % to 90 wt %, based on a total weight of the heat-shrinkable tube.

5. The cylindrical battery cell of claim 1, wherein the nylon resin is included in an amount of 3 wt % to 10 wt %, based on a total weight of the heat-shrinkable tube.

6. The cylindrical battery cell of claim 2, wherein the pigment is included in an amount of 10 wt % to 20 wt %, based on a total weight of the heat-shrinkable tube.

7. The cylindrical battery cell of claim 1, wherein the nylon resin is included in the polyester resin as a blended state.

8. The cylindrical battery cell of claim 1, wherein the heat-shrinkable tube further comprises an ultraviolet absorber that absorbs radiated ultraviolet rays and emits absorbed energy as heat energy.

9. The cylindrical battery cell of claim 8, wherein the ultraviolet absorber is a benzophenone-based compound.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a vertical cross-sectional perspective view showing a conventional cylindrical battery;

(2) FIG. 2 is a photograph showing an experimental procedure of Experimental Example 1 of the present invention;

(3) FIG. 3 is a schematic view showing a mechanism of a UV stabilizer included in a heat-shrinkable tube of the present invention;

(4) FIG. 4 depicts photographs showing a result of a heat-shrinkable tube according to Example 1 in Experimental Example 2;

(5) FIG. 5 depicts photographs showing a result of a heat-shrinkable tube according to Comparative Example 2 in Experimental Example 2;

(6) FIG. 6 is a graph showing stress-strain curves (S-S curves) of heat-shrinkable tubes according to Example 1 in Experimental Example 3; and

(7) FIG. 7 is a graph showing stress-strain curves (S-S curves) of heat-shrinkable tubes according to Comparative Example 3 in Experimental Example 3.

BEST MODE

(8) Hereinafter, the present invention will be described with reference to the following example. This example is provided only for illustration of the present invention and should not be construed as limiting the scope of the present invention.

Example 1

(9) 80 g of polyethylene terephthalate resin, 2 g of butyl-4-hydroxybenzoate, which is an UV stabilizer, 8 g of pigment, and 10 g of nylon 66 were mixed together based on a total weight of a composition and melt-blended to prepare a resin composition. The resin composition was prepared in a cooling equipment by quench hardening method to manufacture a cylindrical heat-shrinkable tube in which an upper portion and a lower portion thereof were open.

Comparative Example 1

(10) A heat-shrinkable tube was manufactured in the same manner as Example 1, except that a resin composition was prepared without using butyl-4-hydroxybenzoate, which is the UV stabilizer, and nylon 66.

Comparative Example 2

(11) A heat-shrinkable tube was manufactured in the same manner as Example 1, except that a resin composition was prepared without using butyl-4-hydroxybenzoate, which is the UV stabilizer.

Comparative Example 3

(12) A heat-shrinkable tube was manufactured in the same manner as Example 1, except that a resin composition was prepared without using nylon 66.

Experimental Example 1

(13) FIG. 2 of the present invention shows a photograph of an experimental procedure of Experimental Example 1. As shown in FIG. 2, heat-shrinkable tubes 110 according to Example 1 and Comparative Example 1 to Comparative Example 3 were disposed to be spaced apart from lamps of a UV irradiator 200 at a distance of 3 cm and were irradiated for 1,000 hours at an intensity of 61.5 W/m.sup.2, at a wavelength of 300 nm to 400 nm, and at a temperature of 50 celsius degrees. Then, it was confirmed whether or not cracking occured on surfaces of the tubes.

(14) TABLE-US-00001 TABLE 1 Cracking occurred (◯ or X) Example 1 X Comparative Example 1 ◯ Comparative Example 2 X Comparative Example 3 X

(15) Referring to Table 1, cracking occurred in the heat-shrinkable tube according to Comparative Example 1, which was lacking nylon and an UV stabilizer. On the other hand, in the heat-shrinkable tubes according to Example 1, Comparative Example 2, and Comparative Example 3, cracking did not occur after ultraviolet irradiation for 1,000 hours. That is, when a nylon resin is added to a base material for tubes, which is a polyester resin, as in Comparative Example 2, cracking on the heat-shrinkable tube can be prevented due to the inherent elasticity of nylon. In addition, when an UV stabilizer is added to the base material for tubes, which is a polyester resin, as in Comparative Example 3, the UV stabilizer inhibits a chain reaction of free radicals generated by cleavage of polymer chains of the nylon resin and the polyester resin whereby it is possible to prevent cracking.

(16) Furthermore, when a nylon resin and an UV stabilizer are added to the base material for tubes, which is a polyester resin, as in Example 1, it is possible to further prevent the formation of cracks in the heat-shrinkable tube due to the synergistic effect thereof.

(17) Meanwhile, FIG. 3 shows a schematic view of a mechanism of the UV stabilizer included in the heat-shrinkable tube of the present invention. Referring to FIG. 3, a free radical 120 reacts with a UV stabilizer 130 whereby a chain reaction of the free radical 120 can be suppressed, the free radical 120 generated by cleavage of polymer chains of the nylon resin and the polyester resin in which the polymer chains are cut by an ultraviolet ray radiated from the UV irradiator 200 to the heat-shrinkable tube 110.

Experimental Example 2

(18) The heat-shrinkable tube according to Example 1 and the heat-shrinkable tube according to Comparative Example 2 were prepared and surfaces of the tubes were printed with black writing. The heat-shrinkable tubes were irradiated for 500 hours by the UV irradiator at an intensity of 61.5 W/m.sup.2 and at a wavelength of 300 nm to 400 nm. Then, color changes of the black writing were confirmed, and the results are shown in FIGS. 4 and 5.

(19) FIG. 4 shows color changes of the heat-shrinkable tube according to Example 1 and FIG. 5 shows color changes according to Comparative Example 2.

(20) Referring to FIGS. 4 and 5, color of the writing on the heat-shrinkable tube according to Example 1 rarely changed after irradiation with an ultraviolet ray. On the other hand, color of the writing on the heat-shrinkable tube according to Comparative Example 2 changed from black to grey, which was blurred. Therefore, it was confirmed that when the heat-shrinkable tube contains the UV stabilizer, color of the tube does not change, but when the tube does not contain the UV stabilizer, color of the tube changes remarkably.

Experimental Example 3

(21) Three heat-shrinkable tubes according to Example 1 and three heat-shrinkable tubes according to Comparative Example 3 were prepared and a universal test machine was used to measure tensile strengths and percentage strains thereof.

(22) Specimens of the tubes, which are insulating exteriors, were placed in the universal test machine and strained at a constant speed to measure tensile strengths and percentage strains of the specimens whereby stress-strain curves (S-S curves) were obtained. The results of the tubes according to Example 1 are shown in FIG. 6, the result of the tubes according to Comparative Example 3 are shown in FIG. 7, and the detail values are shown in below Table 2.

(23) TABLE-US-00002 TABLE 2 Example 1 Comparative Example 3 Tensile strength (Kgf/cm.sup.2) 636 (average) 569 (average) Percentage strain (%) 750 (average) 683 (average)

(24) Referring to Table 2, FIGS. 6 and 7, the tensile strength and the percentage strain of the heat-shrinkable tube according to Example 1 show remarkably improved values compared with the heat-shrinkable tube according to Comparative Example 3. Therefore, it was confirmed that the heat-shrinkable tube containing the UV stabilizer and the nylon has improved mechanical strength compared to the heat-shrinkable tube without nylon. It is considered that this is because the heat-shrinkable tube according to Example 1 includes of nylon, which has high tensile strength and elasticity.

(25) As shown above, the base material for the heat-shrinkable tube of the present invention contains the nylon resin and the UV stabilizer, and cracking is inhibited in the heat-shrinkable tube containing any one of the nylon resin and the UV stabilizer. In addition, it was confirmed that when the heat-shrinkable tube contains the nylon resin but not the UV stabilizer, the tensile strength and the percentage strain thereof can be improved, but color thereof remarkably changes upon irradiation by ultraviolet rays.

(26) That is, the present invention generates synergy by containing the nylon resin and the UV stabilizer together, whereby cracking on the tube and color change by ultraviolet rays can be prevented.

(27) Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

INDUSTRIAL APPLICABILITY

(28) As described above, the heat-shrinkable tube of the cylindrical battery cell according to the present invention includes the UV stabilizer that inhibits a chain reaction of free radicals generated by cleavage of polymer chains of the nylon resin and the polyester resin in which the polymer chains are cut by an ultraviolet ray irradiated to the heat-shrinkable tube such that the tube is not damaged or discolored even when the heat-shrinkable tube is exposed to ultraviolet rays for a long time, which means that the inherent insulating function can be maintained and the exterior of the battery can be protected.

(29) In addition, the heat-shrinkable tube of the cylindrical battery cell according to the present invention includes a supplement, which is the nylon resin, that increases the tensile strength and operating temperature of the heat-shrinkable tube whereby when exposed to a high temperature or external impact, deformation of the tube can be prevented.