Cylindrical battery cell having heat-shrinkable tube comprising ultraviolet absorber

Abstract

Disclosed is a cylindrical battery cell configured such that the outer surface of a cylindrical case excluding electrode terminals is wrapped by a heat-shrinkable tube, wherein the heat-shrinkable tube includes a tube substrate made of a polyester-based resin, the tube substrate being heat-shrinkable; a reinforcement agent, made of a nylon-based resin, for increasing the tensile stress and operating temperature of the heat-shrinkable tube; and an ultraviolet (UV) absorber for absorbing ultraviolet rays radiated to the heat-shrinkable tube and emitting the absorbed ultraviolet rays as thermal energy to prevent the scission of polymer chains of the nylon-based resin or the polyester-based resin as the result of reaction with oxygen.

Claims

1. A cylindrical battery cell configured such that an outer surface of a cylindrical case excluding electrode terminals is wrapped by a heat-shrinkable tube, wherein the heat-shrinkable tube comprises: a tube substrate made of a polyester-based resin, the tube substrate being heat-shrinkable; a reinforcement agent, made of a single nylon-based resin consisting of nylon 66, for increasing tensile stress and operating temperature of the heat-shrinkable tube, the nylon-based resin being included in an amount of 3 weight % to 10 weight % of a total weight of the heat-shrinkable tube; and an ultraviolet (UV) absorber for absorbing ultraviolet rays radiated to the heat-shrinkable tube and emitting absorbed ultraviolet rays as thermal energy to prevent scission of polymer chains of the nylon-based resin or the polyester-based resin as a result of reaction with oxygen wherein the ultraviolet absorber is a benzophenone-based compound, and wherein no cracks are formed in the heat-shrinkable tube even when the heat-shrinkable tube is exposed to ultraviolet rays having a light intensity of 61.5 W/m.sup.2 and a light wavelength of 300 nm to 400 nm for 1,000 hours in an atmospheric condition of 50° C.

2. The cylindrical battery cell according to claim 1, wherein the heat-shrinkable tube further comprises a pigment for realizing a color.

3. The cylindrical battery cell according to claim 1, wherein the polyester-based resin is polyethylene terephthalate.

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

5. The cylindrical battery cell according to claim 1, wherein the heat-shrinkable tube of the cylindrical battery cell has a thickness ranging from 1 μm to 100 μm.

6. The cylindrical battery cell according to claim 1, wherein the benzophenone-based compound is hydroxy benzophenone.

7. The cylindrical battery cell according to claim 1, wherein the ultraviolet absorber is included in an amount of 0.1 weight % to 5 weight % of the total weight of the heat-shrinkable tube.

8. The cylindrical battery cell according to claim 2, wherein the pigment is included in an amount of 10 weight % to 20 weight % of the total weight of the heat-shrinkable tube.

9. The cylindrical battery cell according to claim 1, wherein the nylon-based resin is contained in the polyester-based resin in a blended state.

Description

BRIEF DESCRIPTION OF DRAWINGS

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

(2) FIG. 2 is a photograph showing an experimentation process according to Experimental Example 1 of the present invention;

(3) FIG. 3 is a schematic view illustrating the mechanism of an ultraviolet absorber included in a heat-shrinkable tube according to the present invention;

(4) FIG. 4 is a photograph showing the results of Example 1 according to Experimental Example 2;

(5) FIG. 5 is a photograph showing the results of Comparative Example 2 according to Experimental Example 2;

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

(7) FIG. 7 is a graph showing stress-strain curves (S-S Curve) of Comparative Example 3 according to 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.

(9) <Example 1>

(10) Based on the total weight of a composition, 80 g of polyethylene terephthalate, 2 g of hydroxy benzophenone as an ultraviolet absorber, 8 g of pigment, and 10 g of nylon 66 were mixed, melted, and blended to manufacture a resin composition. The manufactured resin composition was hardened through rapid cooling performed by a cooling device to manufacture a heat-shrinkable cylindrical tube open at the upper and the lower parts thereof.

(11) <Comparative Example 1>

(12) A heat-shrinkable tube was manufactured in the same manner as in Example 1 except that a resin composition was manufactured without using hydroxy benzophenone as an ultraviolet absorber and without using nylon 66.

(13) <Comparative Example 2>

(14) A heat-shrinkable tube was manufactured in the same manner as in Example 1 except that a resin composition was manufactured without using hydroxy benzophenone as an ultraviolet absorber.

(15) <Comparative Example 3>

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

(17) <Experimental Example 1>

(18) FIG. 2 is a photograph showing an experimentation process according to Experimental Example 1 of the present invention. As shown in FIG. 2, each of the heat-shrinkable tubes 110 manufactured according to Example 1 and Comparative Examples 1 to 3 was disposed so as to be spaced 3 cm apart from a lamp of an ultraviolet radiator 200, and was exposed to ultraviolet rays having a light intensity of 61.5 W/m.sup.2 and a light wavelength of 300 nm to 400 nm for 1,000 hours in an atmospheric condition of 50° C. to check whether cracks were formed in the surface of each tube.

(19) TABLE-US-00001 TABLE 1 Formation of cracks (Yes or No) Example 1 No Comparative Example 1 Yes Comparative Example 2 No Comparative Example 3 No

(20) Referring to Table 1 above, cracks were formed in Comparative Example 1, in which neither nylon nor an ultraviolet absorber were used; however, no cracks were formed in Example 1 and Comparative Examples 2 and 3 even after ultraviolet radiation for 1,000 hours. That is, in the case in which a nylon-based resin is added to a tube substrate material made of a polyester-based resin, as in Comparative Example 2, it is possible to prevent the formation of cracks in the heat-shrinkable tube due to the elasticity of nylon, which is an inherent physical property of nylon. In addition, in the case in which an ultraviolet absorber is included in a tube substrate material made of a polyester-based resin, as in Comparative Example 3, it is possible to prevent the formation of cracks in the heat-shrinkable tube, since the ultraviolet absorber prevents the scission of polymer chains of the nylon-based resin and the polyester-based resin.

(21) In addition, in the case in which a nylon-based resin and an ultraviolet absorber are included in a tube substrate material made of a polyester-based 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.

(22) Meanwhile, FIG. 3 is a schematic view illustrating the mechanism of the ultraviolet stabilizer included in the heat-shrinkable tube according to the present invention. Referring to FIG. 3, free radicals 120, generated as the result of the polymer chains of the nylon-based resin or the polyester-based resin being cut by ultraviolet rays radiated to the heat-shrinkable tube 110 from the ultraviolet radiator 200, react with an ultraviolet stabilizer 130, whereby it is possible to restrain the chain reaction of the free radicals 120.

(23) <Experimental Example 2>

(24) The heat-shrinkable tube manufactured according to Example 1 and the heat-shrinkable tube manufactured according to Comparative Example 2 were prepared, and black letters were printed on the surface of each tube. The heat-shrinkable tubes were exposed to light radiated by the ultraviolet radiator, having a light intensity of 61.5 W/m.sup.2 and a light wavelength of 300 nm to 400 nm, for 500 hours to check the discoloration of the black letters. The results are shown in FIGS. 4 and 5.

(25) FIG. 4 shows the discoloration of the heat-shrinkable tube manufactured according to Example 1, and FIG. 5 shows the discoloration of the heat-shrinkable tube manufactured according to Comparative Example 2.

(26) Referring to FIGS. 4 and 5, in the case of Example 1, it can be seen that the letters was hardly discolored after the radiation of ultraviolet rays; however, in the case of Comparative Example 2, it can be seen that the color of the letters was changed from black to gray. That is, it can be seen that the letters became very dim. In the case in which the ultraviolet absorber is included, therefore, it can be seen that the discoloration of the tube is not affected. In the case in which the ultraviolet absorber is not included, however, it can be seen that the discoloration of the tube is remarkable.

(27) <Experimental Example 3>

(28) The tensile stress and strain of three heat-shrinkable tubes manufactured according to Example 1 and three heat-shrinkable tubes manufactured according to Comparative Example 3 were measured using a universal test machine.

(29) In the state in which each of the insulative sheathing test samples was placed on the test machine, a stress-strain curve (S-S curve) of each sample was measured while each sample was stretched at a predetermined speed. The results of Example 1 are shown in FIG. 6, and the results of Comparative Example 3 are shown in FIG. 7. Concrete values of the results are shown in Table 2.

(30) TABLE-US-00002 TABLE 2 Example 1 Comparative Example 3 Tensile stress (Kgf/cm.sup.2) 636 (Average) 569 (Average) Strain (%) 750 (Average) 683 (Average)

(31) Referring to Table 2 above and FIGS. 6 and 7, the tensile stress and strain of the heat-shrinkable tubes manufactured according to Example 1 are higher than the tensile stress and strain of the heat-shrinkable tubes manufactured according to Comparative Example 3. Consequently, it can be seen that a heat-shrinkable tube including an ultraviolet absorber and nylon exhibits higher mechanical strength than a heat-shrinkable tube including no ultraviolet absorber and no nylon. The reason for this is that nylon exhibits high tensile stress and elasticity.

(32) As can be seen from the above, the heat-shrinkable tube according to the present invention includes a nylon-based resin and an ultraviolet absorber in a tube substrate material, and the formation of cracks in the heat-shrinkable tube is restrained as long as the heat-shrinkable tube includes any one of the nylon-based resin and the ultraviolet absorber. In addition, in the case in which the nylon-based resin is included but the ultraviolet absorber is not included, it can be seen that the tensile stress and strain of the heat-shrinkable tube are increased, but the heat-shrinkable tube is remarkably discolored as the result of the radiation of ultraviolet rays.

(33) That is, the present invention has the synergistic effect that can be obtained by including both the nylon-based resin and the ultraviolet absorber. Consequently, it is possible to prevent the formation of cracks in the tube and to prevent the discoloration of the tube due to the radiation of ultraviolet rays.

(34) Although the example of the present invention has been disclosed 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

(35) As is apparent from the above description, in the case in which the cylindrical battery cell according to the present invention includes an ultraviolet absorber that absorbs ultraviolet rays radiated to a heat-shrinkable tube and emits the absorbed ultraviolet rays as thermal energy to prevent the scission of polymer chains of a nylon-based resin or a polyester-based resin as the result of reaction with oxygen, the heat-shrinkable tube is not damaged or discolored even when the tube is exposed to ultraviolet rays for a long time, whereby the cylindrical battery cell may remain insulated, and the external appearance of the cylindrical battery cell may be effectively protected.

(36) In addition, in the cylindrical battery cell according to the present invention, a reinforcement agent, made of a nylon-based resin, for increasing the tensile stress and operating temperature of the heat-shrinkable tube is added to the heat-shrinkable tube, whereby it is possible to prevent the tube from being easily deformed due to exposure to high temperatures or external impacts.