| 1. | A tarpaulin having HDPE twisted split yarns comprising: a HDPE woven cloth layer formed by twisting a few times a HDPE split yarn which is divided into a few strands and split; and LDPE coating layers formed by stacking a LDPE resin on both surfaces of the HDPE woven cloth layer. |
| 2. | The tarpaulin having HDPE twisted split yarns according to claim 1, wherein a molten LDPE resin is additionally stacked on the outer surfaces of the LDPE coating layers, thereby forming a second LDPE coating layer. |
| 3. | A method for manufacturing a tarpaulin having HDPE twisted split yarns comprising: a split step for forming a split yarn by dividing a high density polyethylene resin and polypropylene resin into a few strands and forming splits thereon; a drawing step for drawing the split yarn by using a drawing plate; a setting step for maintaining the split yarn in the drawing state by using a setting plate; a woven cloth layer formation step for forming a HDPE woven cloth layer by twisting the drawn split yarn a few times; and a coating layer formation step for forming a LDPE coating layer by stacking a molten LDPE resin on both surfaces of the HDPE woven cloth layer. |
| 4. | The method for manufacturing a tarpaulin having HDPE twisted split yarns according to claim 3, wherein the method further comprises a second coating layer forming step in which a molten LDPE resin is additionally stacked on the outer surfaces of the LDPE coating layers. |
Background of the Invention A tarpaulin used in various uses including a
waterproof cloth such as a waterproof tent is classified into a polyvinyl chloride (PVC) tarpaulin and a polyethylene (PE) tarpaulin according to the quality of a woven cloth. The PVC tarpaulin is produced by coating PVC on both surfaces of a PET woven cloth composed of multi- filament yarns, and the PE tarpaulin is produced by coating LDPE on both surfaces of an HDPE tape yarn.
Figure 1 is a process view illustrating sequential steps of a process for manufacturing the multi-filament yarn composing the PVC tarpaulin. In order to produce the PVC tarpaulin, a few strands of filaments 12 are extracted from a PET material 10, drawn by adding emulsion thereto 14, and twisted a few times to form a multi-filament yarn 16.
Thereafter, as shown in Figure 2, a PET woven cloth layer 16 is formed by using the multi- filament yarn, and PVC films 18 and 18'are fused on the both surfaces of the PET woven cloth layer 16 at a high temperature or sol-type PVC is coated thereon, to prepare the PVC tarpaulin. This manufacturing process has been disclosed in detail under USP. 4,298, 645.
However, the HDPE basically has an excessive melting tension in manufacturing, and thus is hardly manufactured by the aforementioned process.
A melting-state tension in the manufacturing is closely related to drawability. When the melting tension of the resin is appropriately maintained in a manufacturing range of the filament, drawability can be sufficiently obtained even in the melting state. In general, a diameter of a nozzle used in manufacturing facilities of the multi-filament is about 0.5mm (500pm), and a diameter of the filament after drawing is about lOpm. That is, the diameter is reduced by 50 times in the drawing.
Since the HDPE has the excessive melting tension, the HDPE obtains limited drawability in the melting state. In the case of a mono-filament produced by using the HDPE, a diameter ratio of the nozzle and filament is changed below 20 times. It is thus very difficult to manufacture the multi- filament yarn.
SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide a PE tarpaulin by producing a tape yarn by using a HDPE resin which is cheap, reproducible and easily manufactured and which requires a low equipment cost due to simple facilities, and forming vertical splits on the HDPE tape yarn to achieve the same effects as a multi-
filament yarn.
Another object of the present invention is to- provide a method for manufacturing a tarpaulin having HDPE twisted split yarns which can obtain a smooth and clean surface, increase intensity, and improve appearance like a multi-filament yarn, by performing a split process for dividing a high density polyethylene resin and polypropylene resin into a few strands and forming splits thereon, drawing the split yarn by 7 to 8 times by using a drawing plate, maintaining the split yarn in the drawing state by using a setting plate, forming a HDPE woven cloth layer by twisting the split yarn a few times, forming a LDPE coating layer by stacking a LDPE resin on both surfaces of the HDPE woven cloth layer, and forming a second LDPE coating layer by stacking a LDPE resin at the outer portion of the LDPE coating layer.
In order to achieve the above-described object of the invention, there is provided a tarpaulin having HDPE twisted split yarns including a HDPE woven cloth layer formed by twisting a few times a HDPE split yarn which is divided into a few strands and split, and LDPE coating layers formed by stacking a LDPE resin on both surfaces of the HDPE woven cloth layer.
In addition, a method for manufacturing a
tarpaulin having HDPE twisted split yarns includes: a split step for forming a split yarn by dividing a high density polyethylene resin and polypropylene resin into a few strands and forming splits thereon; a drawing step for drawing the split yarn by using a drawing plate; a setting step for maintaining the split yarn in the drawing state by using a setting plate; a woven cloth layer formation step for forming a HDPE woven cloth layer by twisting the drawn split yarn a few times; and a coating layer formation step for forming a LDPE coating layer by stacking a molten LDPE resin on both surfaces of the HDPE woven cloth layer.
BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not limitative of the present invention, wherein: Figure 1 is a process view illustrating a process for manufacturing a multi-filament yarn composing a conventional PVC tarpaulin; Figure 2 is a cross-sectional view illustrating a structure of the conventional PVC tarpaulin;
Figures 3a to 3e are process views illustrating sequential steps of a process for manufacturing a split yarn composing a PE tarpaulin in accordance with the present invention; Figure 4 is a cross-sectional view illustrating a structure of the PE tarpaulin in accordance with the present invention; and Figures 5a to 5c are process views illustrating sequential steps of a process for manufacturing the PE tarpaulin in accordance with the present invention.
BEST MODE FOR CARRYING THE INVENTION A PE tarpaulin having HDPE twisted split yarns and a manufacturing method therefor in accordance with a preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.
Figures 3a to 3e are process views illustrating sequential steps of a process for manufacturing a split yarn composing the PE tarpaulin in accordance with the present invention, and Figure 4 is a cross-sectional view illustrating a structure of the PE tarpaulin in accordance with the present invention. The process for manufacturing the HDPE split yarn will now be
explained with reference to Figure 3.
Referring to Figure 3a, a HDPE resin 20 is divided into a few strands 22 by using a cutter, and the surfaces of the respective divided tapes are split in a vertical direction, to produce a split yarn (Figure 3b). Thereafter, the split yarn 24 is drawn by about 7 to 8 times by using a drawing plate 26, and the drawn split yarn 24 is passed through a setting plate 28 to maintain a drawing state. Accordingly, the split yarn 24 maintains such a drawing state. A few strands of split yarn 24 is twisted a few times to produce a twisted split yarn 30 as shown in Figure 3e.
Thereafter, the PE split yarn 30 becomes a woven cloth according to a weaving process. The sectional structure of the tarpaulin manufactured by using the split yarn 30 is depicted in Figure 4.
In accordance with the present invention, the PE tarpaulin includes a HDPE woven cloth layer 30 formed by twisting a few times the HDPE split yarn 30 which is divided into a few strands and split, and LDPE coating layers 32 and 32'formed by stacking a LDPE resin on both surfaces of the HDPE woven cloth layer 30. For convenience, the split yarn and the HDPE woven cloth layer are represented by the same reference numeral.
Figures 5a to 5c are process views
illustrating sequential steps of a process for manufacturing the PE tarpaulin in accordance with the present invention. When the HDPE woven cloth formed by using the split yarn 40 is transferred by a conveyor (Figure 5a), the high temperature LDPE resin of a melting state is stacked on the top surface of the HDPE woven cloth. The LDPE resin supplied onto the HDPE woven cloth is fused through a pair of rollers including a cooling roller and a pressure roller, thereby forming the upper LDPE coating layer 42.
In addition, on the bottom surface of the HDPE woven cloth, the high temperature LDPE resin is stacked and fused through the pair. of rollers including the cooling roller and the pressure roller, thereby forming the lower LDPE coating layer 42'. Accordingly, the tarpaulin is manufactured as having the structure of Figure 5b.
The both ends of the coated tarpaulin is cut and wound around a bobbin, to complete finished or semi-finished goods.
In Figure 5c, when the LDPE layer is coated thick, a second coating layer is formed on the outer surface of the LDPE layer. In order to improve appearance and prevent intensity of the HDPE woven cloth layer from being reduced due to heat of the molten LDPE, a molten LDPE resin is
stacked on the top surface of the first LDPE coating layer 42, thereby forming a second LDPE coating layer 44. In addition, a molten LDPE resin is stacked on the bottom surface of the first LDPE coating layer 42', to form a second LDPE coating layer 44'. As a result, the tarpaulin has a double coating structure.
Industrial Applicability As discussed earlier, in accordance with the present invention, appearance can be improved and intensity can be enhanced due to high density by dividing the high density polyethylene resin into a few strands and forming splits thereon, drawing the split yarn by 7 to 8 times by using the drawing plate, maintaining the split yarn in the drawing state by using the setting plate, forming the HDPE woven cloth layer by twisting the split yarn a few times, and forming the LDPE coating layer by stacking the LDPE resin on both surfaces of the HDPE woven cloth layer.
Moreover, in the general PE tarpaulin, a ratio of HDPE to LDPE averaged 60 to 40. When the ratio of HDPE to LDPE is increased, intensity of the HDPE woven cloth layer is sharply reduced due to heat applied in the LDPE coating. Here, the LDPE layer
is formed thick by double coating, thereby preventing reduction of intensity.
Furthermore, the second LDPE coating layer is formed by stacking the LDPE resin at the outer portion of the LDPE coating layer, thereby obtaining the smooth and clean surface. In addition, the first LDPE coating layer stacked in the second coating layer serves as a heat barrier wall, to prevent intensity of the woven cloth layer from being reduced due to heat.
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