Manufacturing method of polyethylene fiber and manufacturing method of cooling fabric

Abstract

To provide a method for producing a polyethylene fiber which includes a microcapsule enclosed with a phase transfer substance capable of increasing the dispersibility in polyethylene of the microcapsule enclosed with the phase transfer substance.SOLUTION: A method for producing a polyethylene fiber includes: a raw material mixing step of mixing a raw material including granular polyethylene and a microcapsule enclosed with a phase transfer substance; a melt blending step of melt-mixing the raw material mixed in the raw material mixing step with an extrusion machine to generate a resin mixture; a spinning step of introducing the mixture into a spinning machine without solidifying in a molten state so as to be spinning; and a drawing step of drawing the spun yarn.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing polyethylene fibers containing microcapsules in which a phase transition material is encapsulated, and a method for producing a cooling fabric. [Background technology]

[0002] Phase transition materials undergo an endothermic reaction when they transition from a solid state to a liquid state, for example. The endothermic effect of such phase transition materials is utilized to enhance the cool-to-the-touch sensation.

[0003] For example, US Pat. No. 5,399,633 discloses mixing microcapsules containing a phase transition material with a polymeric dispersion material to form a first blend, which is then processed to form a polymer composite. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-163886 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, a temperature regulating material (microcapsules containing a phase transition substance) is mixed with a molten polymeric material, but due to low compatibility between the temperature regulating material and the polymeric material, there is a problem that the temperature regulating material is not uniformly dispersed in the polymeric material. Thus, uneven distribution of the temperature regulating material in the polymer causes stress concentration, which leads to a problem that the strength of the polymer material decreases as the content of the temperature regulating material increases.

[0006] In addition, in Patent Document 1, a temperature regulating material is mixed with a dispersion polymer material to form a first blend, the first blend is mixed with a base polymer material to form a second blend (pellets of polymer composite) shaped into various shapes such as pellets, fibers, flakes, sheets, films, rods, etc., and this second blend is melt-spun to produce fibers. However, when the temperature regulating material is mixed with molten resin and the obtained pellets are melted and spun again as described above, there is a problem that the microcapsules, which are the temperature regulating material, are easily destroyed and the phase transition material is easily leaked out.

[0007] The present invention has been made in consideration of the above-mentioned points, and aims to provide a method for producing polyethylene fibers containing microcapsules encapsulating a phase transition substance, and a method for producing a cooling fabric, which increase the dispersibility of the microcapsules encapsulating a phase transition substance in polyethylene while suppressing the destruction of the microcapsules containing the phase transition substance. [Means for solving the problem]

[0008] In order to achieve the above object, the method for producing polyethylene fiber of the present invention is characterized by comprising a raw material mixing step of mixing raw materials including granular polyethylene and microcapsules in which a phase transition material is encapsulated; a melt mixing step of melt-mixing the raw materials mixed in the raw material mixing step in an extruder to produce a resin mixture; a spinning step of introducing the mixture in a molten state into a spinning machine without solidifying it and spinning it; and a drawing step of drawing the spun yarn.

[0009] According to the method for producing polyethylene fibers of the present invention, granular polyethylene and microcapsules containing a phase transition material are mixed before melting the polyethylene, and the mixture is fed to an extruder to be melted, so that the microcapsules can be uniformly dispersed in the polyethylene. Furthermore, the mixture melted and mixed in the extruder is introduced directly into a spinning machine for spinning without being solidified, so that the destruction of the microcapsules containing the phase transition material can be suppressed.

[0010] According to a preferred embodiment of the present invention, the melt mixing step is carried out under conditions of an extruder temperature of 160 to 270° C. and an extrusion pressure of 100 to 130 MPa, and the spinning step is carried out under conditions of a spinning pressure of 150 to 170 MPa.

[0011] According to the above embodiment, the melt mixing step is carried out under conditions of an extruder temperature of 160 to 270°C and an extrusion pressure of 100 to 130 MPa, thereby making it possible to further improve the dispersibility of the microcapsules in the polyethylene fibers. Furthermore, the spinning step is carried out under conditions of a spinning pressure of 130 to 170 MPa, thereby making it possible to efficiently produce polyethylene fibers containing microcapsules. The drawing step of drawing the spun yarn makes it possible to impart sufficient strength to the polyethylene fibers containing microcapsules.

[0012] In the method for producing polyethylene fibers of the present invention, the raw material mixing step is preferably carried out so that the content of the microcapsules is 2 to 50 mass % based on the total amount of the granular polyethylene and the microcapsules.

[0013] According to such an embodiment, it is possible to impart a sufficient cooling sensation while maintaining the strength of the polyethylene fibers and preventing a loss of production stability.

[0014] In the method for producing a polyethylene fiber of the present invention, it is preferable that, before the drawing step, a cooling step of applying cooling air having a temperature of 15 to 40°C and a humidity of 60 to 90% to the yarn that has been subjected to the spinning step and an oil application step of applying 0.5 to 3.5% of an oil to the polyethylene fiber that has been subjected to the cooling step are performed.

[0015] According to such an embodiment, the solidification of the polyethylene fibers is promoted by applying cooling air, and adhesion between adjacent fibers is suppressed by applying oil or grease, and the drawing step is performed in this state, thereby enhancing the drawing effect.

[0016] In the method for producing polyethylene fibers of the present invention, it is preferable that the drawing step is performed in a drawing device including a first stretching roller and a second stretching roller for performing the first drawing, and the second stretching roller and a third stretching roller for performing the second drawing, and that the first stretching roller has a temperature of 50 to 80°C and is rotated at a speed of 600 to 1000 m / min, the second stretching roller has a temperature of 50 to 80°C and is rotated at a speed of 1800 to 2500 m / min, and the third stretching roller has a temperature of 60 to 130°C and is rotated at a speed of 1800 to 3600 m / min.

[0017] According to such an embodiment, the strength of the polyethylene fiber containing the microcapsules can be increased without breaking.

[0018] The polyethylene fibers can exhibit a heat absorbing effect due to the microcapsules containing a phase transition material while maintaining the strength of the polyethylene fibers.

[0019] The method for producing a cooling fabric of the present invention is characterized in that the fabric is produced using the above-mentioned polyethylene fiber and at least one type of fiber selected from nylon, polyester, cotton, rayon, and acrylic.

[0020] According to the cooling fabric of the present invention, it is possible to enhance the effect of cooling sensation to the touch while maintaining a good feel to the touch, etc. Effect of the Invention

[0021] According to the present invention, it is possible to provide a cooling mat having excellent cooling performance and high breathability. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a flow diagram showing a process for producing a polyethylene fiber according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of a cooling mat according to the present invention will be described with reference to the drawings.

[0024] As shown in FIG. 1, the method for producing polyethylene fibers of the present invention includes a raw material mixing process (step S01) of mixing raw materials including granular polyethylene and microcapsules in which a phase transition material is encapsulated, a melt mixing process (step S02) of melt-mixing the raw materials mixed in the raw material mixing process in an extruder to produce a resin mixture, a spinning process (step S03) of introducing the mixture in a molten state into a spinning machine without solidifying it and spinning it, and a drawing process (step S06) of drawing the spun yarn.

[0025] In this embodiment, as shown in Fig. 1, after the spinning step (step S03), a cooling step (step S04) is performed, and then a grease application step (step S05) is performed. The drawing step (step S06) is performed after the grease application step (step S05).

[0026] The granular polyethylene used as a raw material in the raw material mixing process may be any of low density polyethylene (LDPE), linear short chain branched polyethylene (LLDPE), high density polyethylene (HDPE), and metallocene-catalyzed linear short chain branched polyethylene (LLDPE).

[0027] The melting point of the polyethylene used as the raw material is preferably 100 to 145°C, more preferably 105 to 138°C, and even more preferably 115 to 135°C.

[0028] The phase-transition material used as the raw material is, for example, a mixture of alkanes such as n-heptadecane, n-octadecane, nonadecane, and n-eicosane, and has a melting point of preferably 10 to 39° C., more preferably 25 to 32° C. The phase-transition material absorbs heat when changing from a solid to a liquid. Therefore, the surroundings of the phase-transition material are affected by the endothermic effect.

[0029] The phase transition material is, for example, a material enclosed in a microcapsule in the form of a solid or emulsion. As the wall material of the microcapsule, for example, a melamine resin, a phenolic resin, a polystyrene, an acrylic resin, etc. are used, but an acrylic resin such as a polymethyl methacrylate resin is preferably used because it has a high effect of suppressing the exudation of the phase transition material and is free from the risk of generating formaldehyde, etc.

[0030] It is advisable that the microcapsules in which the phase transition material is encapsulated have a moisture content of 30 ppm or less.

[0031] The phase transition enthalpy of the phase transition material is preferably 50 to 300 KJ / Kg, more preferably 70 to 250 KJ / Kg, and even more preferably 100 to 200 KJ / Kg.

[0032] In the raw material mixing step, the amounts of the granular polyethylene and the microcapsules are precisely measured using a weighing device, and these are mixed in a solid state. The mixing should be carried out sufficiently so that the granular polyethylene and the microcapsules are uniformly dispersed.

[0033] The melt mixing step is carried out using an extruder (not shown). The extruder may be, for example, a screw extruder. The melt mixing step is carried out under the conditions of a temperature of 160 to 270°C and an extrusion pressure of 100 to 130 MPa.

[0034] The polyethylene and the microcapsules are preferably mixed together before being introduced into the extruder.

[0035] The temperature of the extruder is more preferably 180 to 250° C., and even more preferably 190 to 240° C. If the temperature of the extruder is below 160° C., the viscosity of the molten polyethylene increases, tending to make mixing difficult. On the other hand, if the temperature exceeds 270° C., deterioration of the polyethylene tends to be accelerated.

[0036] The extrusion pressure of the extruder is preferably 105 to 125 MPa, more preferably 110 to 120 MPa. If the extrusion pressure of the extruder is less than 100 MPa, the microcapsules and polyethylene may not be mixed properly. If the extrusion pressure of the extruder is more than 130 MPa, the microcapsules may be damaged.

[0037] The melt mixing step is preferably carried out at a blending ratio such that the content of microcapsules in the polyethylene fibers is 2 to 50% by mass, preferably 5 to 40% by mass, and more preferably 10 to 30% by mass.

[0038] The spinning process is carried out by continuously introducing the melt-mixed mixture into a spinning machine without solidifying it. That is, the mixture is discharged from the nozzle of the spinning machine under pressure. The spinning temperature is preferably, for example, 210 to 260°C, and the number of holes in the nozzle is preferably 12 to 192.

[0039] In the spinning process, the pressure of the spinning machine is preferably 130 to 170 MPa, more preferably 140 to 165 MPa, and even more preferably 150 to 160 MPa. If the pressure of the spinning machine is less than 130 MPa, the distribution of the microcapsules tends to be non-uniform. If the pressure of the spinning machine is more than 170 MPa, the microcapsules may burst.

[0040] The cooling process is carried out by applying cooling air having a temperature of 15 to 40°C and a humidity of 60 to 90% to the yarn that has been through the spinning process. If the temperature of the cooling air is below 15°C, the cooling of the inside and outside tends to become uneven. If the temperature of the cooling air exceeds 40°C, the cooling efficiency tends to deteriorate. If the humidity of the cooling air is below 60%, the thickness of the fibers tends to become uneven. If the humidity of the cooling air exceeds 90%, it tends to damage the equipment.

[0041] The oil application step is preferably carried out when multiple polyethylene yarns are processed at the same time. The oil application step is carried out by applying oil to the polyethylene fibers that have been subjected to the cooling step in an amount of 0.5 to 3.5 mass% of the weight of the polyethylene fibers. If the amount of oil applied is less than 0.5%, adjacent fibers tend to be attracted to each other due to static electricity (Coulomb force). If the amount of oil applied is more than 3.5%, the polyethylene fibers after production tend to be sticky.

[0042] The oil used in the oil application step is preferably liquid at room temperature, and for example, low viscosity mineral oil can be used. For example, white oil saturated cycloalkane and alkane mixture can be used.

[0043] In the drawing process, the number of times the yarn is drawn is not limited, but it is preferable that the drawing process is performed two or more times. In the drawing process, a drawing device equipped with multiple drawing rollers capable of applying tension to the yarn can be used. The drawing rollers can be appropriately installed depending on the number of times the yarn is drawn.

[0044] In this embodiment, an example in which the yarn is drawn twice in the drawing step will be described. In addition, in this embodiment, the first drawing will be referred to as the first drawing, and the second drawing will be referred to as the second drawing.

[0045] For example, in this embodiment, the stretching process can be performed in a stretching device equipped with a first stretching roller and a second stretching roller for performing the first stretching, and the second stretching roller and a third stretching roller for performing the second stretching.

[0046] In this case, the first stretching roller should have a temperature of 50 to 80°C and be rotated at a speed of 600 to 1000 m / min, the second stretching roller should have a temperature of 50 to 80°C and be rotated at a speed of 1800 to 2500 m / min, and the third stretching roller should have a temperature of 60 to 130°C and be rotated at a speed of 1800 to 3600 m / min.

[0047] By carrying out the drawing step in this manner, it is possible to enhance the molecular orientation of the polyethylene, and as a result, it is possible to enhance the strength of the polyethylene fiber.

[0048] The polyethylene fiber containing microcapsules encapsulating a phase transition material produced through these processes has a melting point of 105 to 138°C, a tensile strength of 1.2 to 4.5 cN / dtex, a tensile elongation at break of 20 to 250%, a melting enthalpy of 2 to 60 J / g observed within a temperature range of 15°C or higher and lower than 45°C by differential scanning calorimetry, and a diameter of 20 to 1000 d.

[0049] Moreover, the polyethylene fibers containing microcapsules in which a phase transition material is encapsulated, which are manufactured through these processes, can be used as a cooling fabric. The cooling fabric may be composed of only the polyethylene fibers containing microcapsules, or may be composed of the polyethylene and at least one fiber selected from nylon, polyester, cotton, rayon, and acrylic. The fibers used together with the polyethylene fibers should preferably have high thermal conductivity, such as nylon long fibers or rayon long fibers.

[0050] As described above, according to the method for producing polyethylene fibers of the present invention, the melt mixing step is carried out under conditions of an extruder temperature of 160 to 270°C and an extrusion pressure of 100 to 130 MPa, thereby making it possible to enhance the dispersibility of the microcapsules in the polyethylene fibers. Furthermore, the spinning step is carried out under conditions of a spinning pressure of 150 to 170 MPa, thereby making it possible to efficiently produce polyethylene fibers containing microcapsules. The drawing step of drawing the spun yarn makes it possible to impart sufficient strength to the polyethylene fibers containing microcapsules. EXAMPLES

[0051] (Cooling sensation duration test) A knitted fabric made using polyethylene fibers containing a phase transition substance was prepared as Example 1, and a knitted fabric made using polyethylene fibers not containing a phase transition substance was prepared as Comparative Example 1, and the cool sensation sustaining effect of both was tested.

[0052] (Preparation of Example 1) The knitted fabric of Example 1 was produced in the following manner. (Melting and mixing process) Microcapsules were prepared that contained granular polyethylene (melting point: 130°C) and a phase transition material (paraffin name: normal octadecane) with a water content of 15 ppm.

[0053] Granular polyethylene and microcapsules were mixed uniformly using a weight-measuring mixer so that the microcapsules accounted for 5% by mass relative to the total amount of polyethylene and microcapsules, and the mixture was fed to a screw extruder, melt-mixed, and extruded. The pressure of the screw extruder was set to 110 MPa to prepare the mixture.

[0054] (Spinning process) The molten mixture of polyethylene and microcapsules extruded from the screw extruder was introduced into a spinning machine while controlling the volume of the melt with a pump, and spun. The spinning temperature of the spinning machine was 242°C, and the number of holes in the nozzle was 36. The pressure of the spinning machine was 160 MPa.

[0055] (cooling process) After the spinning process, each yarn is cooled by being exposed to cooling air at a temperature of 20°C and a humidity of 80%.

[0056] (Oil application process) Oil was applied to each of the yarns that had been through the cooling process. The oil used was a low-viscosity mineral oil. The amount of oil applied was 2.0% by mass of the spun yarn weight (polyethylene fiber).

[0057] (Stretching process) The stretching was carried out using a stretching device equipped with a first stretching roller, a second stretching roller, and a third stretching roller capable of applying tension to the yarn. The first stretching roller had a rotation speed of 800 m / min and a temperature of 60°C. The second stretching roller had a rotation speed of 2320 m / min and a temperature of 70°C. The third stretching roller had a rotation speed of 3200 m / min and a temperature of 75°C. Finally, the yarn was wound by fully automatic winding at a rotation speed of 3165 m / min.

[0058] (Physical Properties) The polyethylene fiber obtained by the above process had a thickness of 200D, a folding strength of 2.0 cN / dtex, a breaking elongation of 90%, and an enthalpy of 10 J / g. A knitted fabric having a basis weight of 200 gsm was produced using the polyethylene fiber.

[0059] (Preparation of Comparative Example 1) A polyethylene fiber of Comparative Example 1 was produced in the same manner as in Example 1, except for the microcapsules containing a phase transition material. The polyethylene fiber had the same thickness as the polyethylene fiber of Example 1, a latent heat value of 0, and a breaking strength and breaking elongation similar to those of the polyethylene fiber of Example 1. A knitted fabric having a basis weight of 200 gsm was produced using the polyethylene fiber of Comparative Example 1.

[0060] (Cooling sensation duration test) The specimen pieces (10 x 7 cm) were arranged on a sample stage inclined at 45 degrees, and a 90°C hot plate was set 15 cm in front of them parallel to the sample. The surface temperatures of the specimens were measured using a thermograph after 1 minute, 2 minutes, 4 minutes, 6 minutes, 8 minutes, and 10 minutes.

[0061] The test environment was as follows: Room temperature: 20℃±2℃ Humidity: 65±4%RH Measurement surface: surface Equipment used: Far-infrared 45-degree parallel re-radiation measuring device, thermography device

[0062] The surface temperatures of both samples were measured one minute after the measurement, and the results are shown in Table 1 below.

[0063] [Table 1]

[0064] As shown in Table 1, it was found that the maximum, minimum, and average temperatures of the knitted fabric of Example 1 were all lower than those of Comparative Example 1. From the above, it was found that the knitted fabric of Example 1 had a better cooling sensation than the knitted fabric of Comparative Example 1 immediately after the start of the experiment.

[0065] The surface temperatures of both samples were measured 10 minutes after the measurement, and the results are shown in Table 2 below.

[0066] [Table 2]

[0067] As shown in Table 2, it was found that the maximum, minimum, and average temperatures of the knitted fabric of Example 1 were all lower than those of Comparative Example 1. From the above, it was found that the knitted fabric of Example 1 also had a longer duration of cool sensation than the knitted fabric of Comparative Example 1. EXAMPLES

[0068] (Cool touch test) A woven fabric made using polyethylene fibers containing a phase transition material was prepared as Example 2, and a woven fabric made using polyethylene fibers not containing a phase transition material was prepared as Comparative Example 2, and the cool sensation sustaining effect of both was tested.

[0069] The fabric of Example 2 was made in the following manner. (Melting and mixing process) Microcapsules were prepared that contained granular polyethylene (melting point: 132°C) and a phase transition material (paraffin name: normal octadecane) with a water content of 20 ppm.

[0070] Granular polyethylene was melted in a screw extruder. Microcapsules containing a phase transition material were added to the molten polyethylene in the screw extruder. The microcapsules were added at 20% of the total amount. The pressure of the screw extruder was set to 120 MPa to create the mixture.

[0071] (Spinning process) The liquid mixture of polyethylene and microcapsules was spun in a spinning machine while controlling the volume of the melt with a pump. The spinning temperature of the spinning machine was 242°C, the number of holes in the nozzle was 96, and the pressure of the spinning machine was 150 MPa.

[0072] (cooling process) After the spinning process, each yarn is cooled by being exposed to cooling air at a temperature of 18°C ​​and a humidity of 75%.

[0073] (Oil application process) Oil was applied to each of the yarns that had been subjected to the cooling process. The oil used was a low-viscosity mineral oil. The amount of oil applied was 1.8% by mass of the spun yarn weight (polyethylene fiber).

[0074] (Stretching process) The stretching was carried out using a stretching device equipped with a first stretching roller, a second stretching roller, and a third stretching roller capable of applying tension to the yarn. The first stretching roller had a rotation speed of 700 m / min and a temperature of 65°C. The second stretching roller had a rotation speed of 1900 m / min and a temperature of 75°C. The third stretching roller had a rotation speed of 2600 m / min and a temperature of 80°C. Finally, the yarn was wound by fully automatic winding at a rotation speed of 2570 m / min.

[0075] (Physical Properties) The polyethylene fiber obtained by the above process had a thickness of 300D, a tensile strength of 2.5 cN / dtex, a breaking elongation of 140%, and an enthalpy of 20 J / g. The polyethylene fiber was used to prepare a woven fabric having a basis weight of 230 gsm.

[0076] (Preparation of Comparative Example 2) The polyethylene fiber of Comparative Example 1 was produced in the same manner as in Example 2, except that the microcapsules containing a phase transition material were excluded. The polyethylene fiber of Comparative Example 2 was used to produce a knitted fabric having a basis weight of 230 gsm.

[0077] The knitted fabrics of Example 2 and Comparative Example 2 were each measured for coolness to the touch (QMAX) based on the standard JIS L 1927:2020. As a result, the coolness to the touch (QMAX) of the knitted fabric of Example 2 was 0.401. In contrast, the coolness to the touch (QMAX) of the knitted fabric of Comparative Example 2 was 0.369. As described above, it was found that the coolness to the touch value of Example 2 was higher than that of Comparative Example 2.

Claims

1. A raw material mixing process for mixing raw materials including granular polyethylene and microcapsules containing a phase transition material; a melt mixing step in which the raw materials mixed in the raw material mixing step are melt mixed in an extruder to produce a resin mixture; a spinning step of introducing the mixture in a molten state into a spinning machine without solidifying it, and spinning the mixture; A drawing step of drawing the spun yarn; A method for producing polyethylene fibers, comprising the steps of:

2. The melt mixing step is carried out under the conditions of an extruder temperature of 160 to 270° C. and an extrusion pressure of 100 to 130 MPa, 2. The method for producing polyethylene fibers according to claim 1, wherein the spinning step is carried out under a condition where the pressure of the spinning machine is 130 to 170 MPa.

3. 3. The method for producing polyethylene fibers according to claim 1 or 2, wherein in the raw material mixing step, the raw material contains 5 to 50 mass% of the microcapsules relative to the total amount of the granular polyethylene and the microcapsules.

4. Before the stretching step is performed, a cooling step of applying cooling air having a temperature of 15 to 40° C. and a humidity of 60 to 90% to the yarn that has been subjected to the spinning step; an oil application step of applying an oil to the polyethylene fibers that have been subjected to the cooling step in an amount of 0.5 to 3.5% by mass of the polyethylene fibers; 3. The method for producing polyethylene fibers according to claim 1 or 2, wherein

5. The stretching step is performed in a stretching device including a first stretching roller and a second stretching roller for performing a first stretching, and a second stretching roller and a third stretching roller for performing a second stretching, The first stretching roller is rotated at a temperature of 50 to 80° C. and a speed of 600 to 1000 m / min. The second stretching roller is rotated at a temperature of 50 to 80° C. and a speed of 1800 to 2500 m / min.

3. The method for producing polyethylene fibers according to claim 1 or 2, wherein the third stretching roller is rotated at a temperature of 60 to 130° C. and at a speed of 1800 to 3600 m / min.

6. A method for producing a cooling fabric, comprising producing a fabric using the polyethylene fiber obtained by the method for producing a polyethylene fiber according to claim 1 or 2 and at least one type of fiber selected from nylon, polyester, cotton, rayon and acrylic.

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