NONWOVEN LOOP SHEET AND METHOD FOR MANU¬

FACTURING THE SAME Technical Field [1] The present invention relates to a nonwoven loop sheet which fastens on a hook tape of a Velcro fastener (a hook and loop fastening tape), and a method of producing the same. [2] Background Art [3] A hook and loop fastening tape, which is a bonding unit, like an adhesive tape, a zipper, or a button, comprises a hook tape and a loop sheet, and is used as a connection unit of disposable diapers, clothes, sundries, or miscellaneous goods. [4] In the present invention, a nonwoven loop sheet is used as a connection unit in a disposable diaper. In the present invention, a hook tape for fastening is a tape in which hook-shaped piles are densely formed. The nonwoven loop sheet is a loop sheet in which fiber loops are densely formed so as to fasten on hooks of the hook tape. In the present invention, the loop means fibers of a nonwoven fabric, which fasten on the hook tape to generate fastening strength. If a hook side of the hook tape, on which the hooks are densely formed, comes into close contact with a fastening side of the loop sheet, the hooks fasten to the fastening side, thus two structures are connected. If a pre¬ determined force is applied to the connected structure so as to separate the hook tape from the loop sheet, they are separated from each other with noise. [5] Conventionally, in miscellaneous goods including clothes, wearing apparel, and bags, and in disposable diapers for adults and infants, a fastening unit, including a hook tape and a loop sheet, is used for fastening parts of goods. The hook tape and the loop sheet of the conventional disposable diaper fasten in such a way that i) a fastening side of a woven loop tape fasten on a hook side of the hook tape, or ii) a fastening side of a nonwoven loop sheet fastens on the hook side of the hook tape. The woven loop tape is costly, thus it is unsuitable to apply to a disposable product. The nonwoven loop sheet is produced by embossing nonwoven fabrics and is low-priced. However, a lot of fluff is generated when it fastens on the hook tape and is separated from the hook tape. In the use of the hook and loop fastening tape, if fluff is formed on the nonwoven loop sheet, it is valuated as a low-grade nonwoven loop sheet. The fluff separated from the disposable diaper floats in the air in the form of dust, and may be mixed with food for infants. Thus, generation of fluff is an important item in the evaluation of quality of the nonwoven loop sheet. [6] With respect to fastening between the hook tape and the loop sheet of the disposable diaper, it is required that it be easy to conduct fastening and separation, repetition of fastening and separation be feasible, fastening performance be stable, they be low-priced, and little fluff be generated. However, if a surface of the unprocessed nonwoven fabric comes into contact with the hook side of the hook tape, the fastening is conducted with difficulty. The reason is as follows. 1) a fiber density of the nonwoven fabric is high and a surface thereof is smooth, thus it insufficiently fastens on the hook side. 2) a lot of fluff is generated during repetition of fastening and separation. 3) desirable fastening strength is not maintained during repetition of fastening and separation. In the present invention, the low-priced nonwoven fabric is processed at low cost so as to have loop protrusions, thereby suitable and stable fastening strength to the hook tape is assured. [7] Disclosure of Invention Technical Problem [8] In the present invention, it is observed that since a low-priced nonwoven fabric including a polypropylene nonwoven fabric has a high fiber density, it very weakly fastens on a hook tape. In order to produce a nonwoven loop sheet which readily fastens on the hook tape using the nonwoven fabric, the fiber density of a surface of the nonwoven fabric must be reduced. Additionally, it is observed that, if the nonwoven fabric fastens on the hook tape and is separated therefrom repeatedly a few times, a lot of fluff is generated. In a diaper made of the nonwoven fabric using the hook tape, it is required that desired fastening strength to the hook tape be maintained and that little fluff is generated while fastening is repeated a few times. Only when the nonwoven loop sheet can be produced at low cost, it can be commercialized. The present invention aims to provide a nonwoven loop sheet which readily fastens on a hook tape using a low-priced nowoven fabric which generates little fluff and includes a polypropylene nonwoven fabric. In the present invention, protrusions which are formed when the nonwoven fabric is holed and have predetermined fastening strength to the hook tape are realized as loop protrusions. Holes are formed through the protrusions. [9] Technical Solution [10] In the present invention, a nonwoven fabric is pressed and holed simultaneously, or heated, pressed, and holed simultaneously so as to form loop protrusions having a low fiber density on a surface thereof. A loop sheet of the present invention, in which a loop fastening side is formed by fastening parts of the loop protrusions having the low fiber density and the holes at tops thereof, has fair fastening strength to a hook side of the hook tape for fastening and fastening stability. Even if it is repeatedly used for fastening, its fastening strength is desirably maintained. Nonwoven fabrics have different fiber densities, degrees of generation of fluff, and fastening strengths to the hook tape depending on their types. However, they almost all have suitable fastening strength to the hook tape after formation of holes for shaping the loop protrusions. [H] Advantageous Effects [12] The present invention provides a nonwoven loop sheet which has desirable fastening strength to a hook tape. The present invention provides a nonwoven loop sheet in which a loop fastening side is formed on a nonwoven fabric by arranging loop protrusion fastening parts on a surface of the nonwoven fabric. The present invention provides a nonwoven loop sheet which is used for fastening on a hook tape and in which a nonwoven fabric is pressed and holed simultaneously, or heated, pressed, and holed simultaneously so as to form loop protrusions having a low fiber density and holes. The present invention provides a nonwoven loop sheet which has fair fastening strength to a hook tape for fastening and fastening stability. The fastening strength is desirably maintained after fastening has been repeated a few times. [13] Brief Description of the Drawings [14] FIG. 1 is an expanded view of a loop sheet according to the present invention, in which fibers are conceptually shown; [15] FIG. 2 is a plane view of the loop sheet according to the present invention, in which the fibers are conceptually shown; [16] FIG. 3 is a plane view of another loop sheet according to the present invention, in which fibers are conceptually shown; [17] FIG. 4 is a partially enlarged view of a device according to the present invention; [18] FlG. 5 illustrates the formation of a nonwoven loop layer using the device according to the present invention; [19] FlG. 6 is a side view of a hard roll according to the present invention; [20] FlG. 7 is a front view of a wire brush soft roll as an example of a forming roll according to the present invention; and [21] FlG. 8 is a front view of an iron scrubber soft roll as another example of the forming roll according to the present invention. [22] Best Mode for Carrying Out the Invention [23] The present invention relates to a nonwoven loop sheet for fastening. The nonwoven loop sheet comprises nonwoven loop protrusions which protrude so as to be distributed over an entire nonwoven fabric to form a loop fastening side having fastening strength to a hook side of a hook tape, the nonwoven loop protrusions having holes formed at tops thereof; and hook tape connection parts which are formed around the nonwoven loop protrusions having the holes and which each have a fiber density that is lower than that of the bottom of the nonwoven fabric. In order to produce the loop sheet of the present invention, a nonwoven fabric, which is movably supported by a forming roll, is pressed, or heated and pressed using pin punches on a surface of a pin punch roll which is heated (or maintained at ambient temperature). In a pressing process, fibers of the nonwoven fabric are stretched, the loop protrusions are formed on a surface of the nonwoven fabric, the holes are formed through tops of the loop protrusions, and the fiber density of the nonwoven fabric is lowered around the loop protrusions having the holes. The connection parts, which have the low fiber density around the loop protrusions having the holes, form a fastening side on the surface of the nonwoven fabric. The fastening side provides excellent fastening strength to the hook tape. Furthermore, the loop protrusions make the smooth surface of the nonwoven fabric uneven, thus increasing fastening strength to the hook tape. The fastening side of the nonwoven fabric according to the present invention is stably and suitably combined with the hook side of the hook tape, thereby stable fastening strength is assured. When the nonwoven loop sheet of the present invention is combined with the hook tape, desirable fastening is realized and little fluff is generated during separation after fastening. [24] A detailed description will be given of the present invention, referring to the ac¬ companying drawings. In a nonwoven loop sheet according to the present invention, one or more loop protrusions 20 are formed on a surface of a nonwoven fabric 10 to form a fastening side of the nonwoven fabric. The fastening side of the nonwoven fabric has fastening strength to a hook side of a hook tape, on which hooks 60 are densely formed. Holes 25 are formed through tops of the nonwoven loop protrusions. Fiber densities of parts around the loop protrusions 20 through which the holes 25 are formed are lower than those 14 of the bottom 11 of the nonwoven fabric 10, and thus connection parts 21 are formed around the loop protrusions 20 through which the holes 25 are formed. The low fiber density of the connection part positively affects connection to rakes 61 of the hooks 60. The connection parts 21 of the loop protrusions 20 form a fastening side of the nonwoven fabric. When the fastening side of the nonwoven fabric comes into close contact with the hook side of the hook tape, the rakes 61 of the hook side fasten on fibers of the connection parts 21 having low fiber density, which are positioned on a cylindrical wall of the loop protrusions 20, thereby the fastening side of the nonwoven fabric and the hook side of the hook tape desirably fasten to each other. When the loop protrusions 20 on the surface of the nonwoven fabric according to the present invention are formed, heating and pressing are conducted using pin punches 30 to form recesses 23 which correspond to the loop protrusions 20. The loop protrusions 20 of the present invention are arranged at intervals (x, y) of 0.2 35 mm, and each have a diameter (d) of 0.2 - 9 mm and a height (h) of 0.1 - 9 mm. [25] In the nonwoven loop sheet according to the present invention, the nonwoven fabric 10 is holed while it is heated and pressed to form the loop protrusions having the low fiber density on the surface of the nonwoven fabric. A punch roll 40, on a surface of which pin punches 30 are arranged, and a forming roll 50 which comes into close contact with the pin punch roll 40 for heating and pressing and movably supports the nonwoven fabric 10 to form the loop protrusions on the nonwoven fabric are provided in order to form the loop protrusions 20 of the present invention. Examples of the forming roll may include a hard forming roll or a soft forming roll. In FIGS. 4 to 6, shaping holes 51 corresponding to the pin punches 30 of the punch roll 40 are formed in the hard forming roll 50. The nonwoven fabric which is movably supported by the forming roll 50 is pressed by the pin punches 30 toward the center of the forming roll 50 in the shaping holes 51, thereby the loop protrusions of the nonwoven fabric are formed using the pin punches 30 and the forming roll 50, and fibers of the nonwoven fabric are stretched. The fibers of the nonwoven fabric are stretched by the pin punches 30 in the shaping holes 51 to form the loop protrusions and the holes 25 through the tops of the loop protrusions. The fibers around the protrusions through which the holes 25 are formed have low density and form the loop protrusion connection parts 21, and the fastening side of the nonwoven fabric which is formed by the loop protrusion connection parts 21 fastens well on the hook tape. Consequently, little fluff is formed on the fastening side of the nonwoven fabric. [26] The forming roll 50 may be exemplified by the soft forming roll instead of the hard forming roll. Examples of the soft forming roll are illustrated in FIGS. 7 and 8. One of the soft forming rolls is an elastic rubber roll, elastic rubber of which is pressed toward the center thereof by pin punches while a nonwoven fabric is movably supported to stretch fibers of the nonwoven fabric to form loop protrusions and holes through tops of the loop protrusions. Another soft forming roll is a woven textile roll for nonwoven fabrics, in which a woven textile constituting a surface layer of the roll is pressed toward the center of the roll by pin punches while the nonwoven fabric is movably supported to stretch fibers of the nonwoven fabric to form loop protrusions and holes through tops of the loop protrusions (a woven textile layer is formed on the roll so that the pin punches are temporarily inserted thereinto to form marks on a surface of the roll). Still another soft forming roll is a wire brush roll 50a, in which fibers of a nonwoven fabric are pressed between wires by pin punches while a nonwoven fabric is movably supported to stretch fibers of the nonwoven fabric to form loop protrusions and holes through tops of the loop protrusions (the wires are densely formed so that the pin punches are inserted into a surface layer of the roll in the wire brush roll). Yet another soft forming roll is an iron scrubber roll 50b, in which fibers of a nonwoven fabric are pressed toward a cushion layer of an iron scrubber by pin punches while a nonwoven fabric is movably supported to stretch fibers of the nonwoven fabric to form loop protrusions and holes through tops of the loop protrusions (the iron scrubber, in which metal wires are rolled to be flattened and curled to form bubbles, is provided on a surface of the roll so that the pin punches are inserted thereinto). As described above, various types of materials may be used to produce the soft forming roll, and softness of the roll contributes to partial modification of the nonwoven fabric using the pin punches 30. [27] The heating temperature of the pin punch roll according to the present invention is set depending on the intrinsic heat deflection temperature of the nonwoven fabric. The heating temperature range of the pin punch roll is from ambient temperature to 2000C. In the present invention, the forming roll 50 may be heated depending on charac¬ teristics of the nonwoven fabric. [28] Some patterns may be printed on the loop sheet for fastening according to the present invention. A predetermined color and pattern are printed on the loop sheet for fastening, or on a laminate of the loop sheet and a reinforcing material, so as to improve qualities of products. [29] The loop sheet for fastening according to the present invention may be laminated with a plastic film or a nonwoven fabric as a reinforcing material at a rear side thereof. In order to laminate the loop sheet for fastening with the reinforcing material, the loop sheet for fastening and the plastic film are subjected to an extrusion lamination process, adhered to each other using an adhesive agent, laminated by heat, or laminated through an embossing process. The loop sheet for fastening and the reinforcing material may be totally or partially laminated. If the loop sheet for fastening and the re¬ inforcing material are laminated in a process for producing a diaper, it is easy to combine the diaper with the loop sheet. [30] The nonwoven fabric which is used to produce the loop sheet for fastening according to the present invention has a weight of 10 102 g/m , and is any one of nonwoven fabrics selected from the group consisting of a polypropylene thermal-bond nonwoven fabric, a polypropylene spunbond nonwoven fabric, a polypropylene melt- blown nonwoven fabric, a bicomponent nonwoven fabric of polypropylene and polyethylene, a nonwoven fabric in which a polypropylene melt-blown nonwoven fabric and a polypropylene spunbond nonwoven fabric are combined by heat to form a structure having two or more layers, a polyethylene nonwoven fabric, a nylon nonwoven fabric, a polyester nonwoven fabric, a nonwoven fabric which is produced by mixing one or more selected from the group consisting of a bicomponent grey yarn of polypropylene and polyethylene mixed with each other, a polypropylene grey yarn, a polyethylene grey yarn, a viscose grey yarn, a polyester grey yarn, and a nylon grey yarn, an air-laid nonwoven fabric, an air-through nonwoven fabric, a spunlace nonwoven fabric, and a nonwoven fabric which is produced by needle-punching any one of the above-mentioned nonwoven fabrics. The above nonwoven fabrics have different fiber densities, degrees of generation of fluff, fastening strengths to the hook tape, and prices. The polypropylene-based nonwoven fabric which is cheapest and capable of being easily purchased is used in the examples of the present invention. [31] Mode for the Invention [32] [33] EXAMPLE 1 [34] [35] Pin punches which included rolls of FIGS. 4, 5, and 6 and had a diameter of 2 mm were arranged at intervals of 2 mm in every direction. A polypropylene spun-bond nonwoven fabric of 30 g/m was provided between a pin punch roll, which was heated to 100°C, and a forming roll, in which shaping holes were arranged so as to engage with pins, to produce a nonwoven loop sheet. In the nonwoven loop sheet, loop protrusions having fastening sides were formed on the nonwoven fabric, holes were formed through tops of the protrusions, and parts around the protrusions having the holes had a low fiber density so as to form connection parts. [36] [37] EXAMPLE 2 [38] [39] A flower pattern was printed on the loop sheet of example 1, and a film of 20 g/m which included 70 parts by weight of polyethylene and 30 parts by weight of polypropylene mixed therein was extrusion laminated on a rear side of the loop sheet. [40] [41] EXAMPLE 3 [42] [43] An embossed nonwoven loop (L) was removed from a disposable infant diaper manufactured by a Y company, and the loop sheet for fastening (A) of example 1 was attached to the area from which the loop (L) was removed. Next, a fastening side of a hook tape (H) of the diaper was brought into close contact with a fastening side of the loop sheet for fastening (A). The hook tape (H) stably and firmly fastened to the nonwoven loop sheet (A). Fastening and separation between the loop sheet (A) and the hook tape (H) were repeated five times. Little fluff was formed on the nonwoven fabric, and stable fastening strength was maintained during repeated fastening operations. [44] Fastening and separation between the conventional loop (L) and the hook tape (H) were repeated five times, and fastening and separation between the loop sheet (A) and the hook tape (H) were repeated five times. Next, the fluff which was formed on the loop sheet (A) and the loop (L) were compared using the naked eye. It was observed that the amount of fluff on the loop sheet (A) was less than that on the loop (L). The loop sheet of example 1 was produced by processing the low-priced nonwoven fabric using a simple device. [45] [46] EXAMPLE 4 [47] [48] An embossed nonwoven loop (L) was removed from a disposable infant diaper manufactured by Y company, and the loop sheet (B) of example 2 was attached thereto. Next, a hook tape (H) of the diaper was brought into close contact with the loop sheet (B). The hook tape (H) stably and firmly fastened to the nonwoven loop sheet (B). Fastening and separation between the loop sheet (B) and the hook tape (H) were repeated five times. Little fluff was formed on the nonwoven fabric, and stable fastening strength was maintained during repeated fastening operations. [49] Fastening and separation between the conventional nonwoven loop (L) and the hook tape (H) were repeated five times, and fastening and separation between the loop sheet (B) and the hook tape (H) were repeated five times. Next, the fluff which was formed on the loop sheet (B) and the loop (L) were compared using the naked eye. It was observed that the amount of fluff on the loop sheet (B) was less than that on the loop (L). The loop sheet (B) had an appearance that was better than that of the loop sheet (A) because the loop sheet (B) was printed, and was easily attached to the diaper because a film was laminated on the loop sheet (B). [50] Industrial Applicability [51] A polypropylene-based nonwoven fabric that is cheapest among the above- mentioned nonwoven fabrics is recommended as a nonwoven fabric to be used to produce a loop sheet of the present invention. Some patterns may be printed on one side of the above-mentioned nonwoven loop sheet according to the present invention to be used for disposable diapers and miscellaneous goods or improve the quality thereof, and a plastic film or a nonwoven fabric as a reinforcing material may be laminated on a rear side of the nonwoven sheet so that the sheet may be easily attached to other products. Alternatively, the sheet may be used without the reinforcing material. The nonwoven loop sheet of the present invention may be partially laminated with the plastic film, the nonwoven fabric, or a textile as the reinforcing material, or subjected to an embossing process to form embossments on a surface of the loop sheet. The em¬ bossments on the surface of the loop sheet increase the fastening strength to the hook tape. The loop sheet of the present invention may be used as a fastening part for nonwoven products, such as infant diapers, nonwoven panties, nonwoven clothes, and adult diapers. [52] [53]