JP7640970B2 - Manufacturing method of polyethylene fiber and manufacturing method of cooling fabric - Google Patents

Description

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.

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

For example, Patent Document 1 discloses that microcapsules containing a phase transition material are mixed with a polymeric material for dispersion to form a first blend, and that the first blend is processed to form a polymer composite.

JP 2013-163886 A

However, in Patent Document 1, a temperature regulating material (microcapsules containing a phase transition substance) is mixed with a molten polymeric material, but since the compatibility between the temperature regulating material and the polymeric material is low, 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.

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, and rods, and this second blend is melt-spun to produce fibers. However, as described above, when the temperature regulating material is mixed with molten resin and the resulting pellets are melted and spun again, there is a problem that the microcapsules of the temperature regulating material are easily destroyed and the phase transition material is easily leaked out.

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 improve the dispersibility of the microcapsules encapsulating a phase transition substance in polyethylene and suppress the destruction of the microcapsules containing the phase transition substance.

To achieve the above object, the method for producing polyethylene fiber of the present invention is characterized by comprising a raw material mixing process for mixing raw materials including granular polyethylene and microcapsules containing a phase transition material, a melt mixing process for melt mixing the raw materials mixed in the raw material mixing process in an extruder to produce a resin mixture, a spinning process for introducing the mixture in a molten state into a spinning machine without solidifying it and spinning it, and a drawing process for drawing the spun yarn.

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

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

According to the above aspect, the melt mixing process 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. In addition, the spinning process is carried out under conditions of a spinning machine pressure of 130 to 170 MPa, thereby making it possible to efficiently produce polyethylene fibers containing microcapsules. By carrying out a drawing process in which the spun yarn is drawn, it is possible to impart sufficient strength to the polyethylene fibers containing microcapsules.

In the method for producing polyethylene fibers of the present invention, it is preferable that the raw material mixing step is carried out so that the content of the microcapsules is 2 to 50 mass% relative to the total amount of the granular polyethylene and the microcapsules.

This embodiment allows for a sufficient cooling effect while maintaining the strength of the polyethylene fibers and not compromising manufacturing stability.

In the method for producing polyethylene fibers of the present invention, it is preferable that, before the drawing step, a cooling step is performed in which the yarn that has undergone the spinning step is exposed to cooling air at 15 to 40°C and a humidity of 60 to 90%, and an oil application step is performed in which 0.5 to 3.5% oil is applied to the polyethylene fibers that have undergone the cooling step.

In this manner, the solidification of the polyethylene fibers is promoted by applying cooling air, and the adhesion of adjacent fibers to each other is suppressed by applying oil and grease, and the stretching process is carried out in this state, thereby enhancing the stretching effect.

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

According to this embodiment, the strength of the polyethylene fiber containing the microcapsules can be increased without breaking.

The polyethylene fibers described above can maintain the strength of the polyethylene fibers while exerting a heat absorbing effect due to the microcapsules containing a phase transition material.

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.

The cooling fabric of the present invention makes it possible to enhance the cooling effect while maintaining a good feel to the touch, etc.

The present invention makes it possible to provide a cooling mat that has excellent cooling performance and high breathability.

FIG. 1 is a flow diagram showing a process for producing a polyethylene fiber according to the present invention.

Below, we will explain one embodiment of the cooling mat of the present invention with reference to the drawings.

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

In this embodiment, as shown in FIG. 1, after the spinning process (step S03), a cooling process (step S04) is performed, followed by an oil application process (step S05). The drawing process (step S06) is performed after the oil application process (step S05).

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

The melting point of the polyethylene used as the raw material should be 100 to 145°C, preferably 105 to 138°C, and more preferably 115 to 135°C.

The phase-change 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 preferably of 10 to 39°C, and more preferably 25 to 32°C. Phase-change materials absorb heat when they change from a solid to a liquid. Therefore, the surroundings of the phase-change material are affected by this endothermic effect.

The phase transition material is used in the form of a solid or emulsion and enclosed in a microcapsule. For example, melamine resin, phenolic resin, polystyrene, acrylic resin, etc. are used as the wall material of the microcapsule. However, acrylic resin such as polymethyl methacrylate resin is preferably used because it has a high effect of suppressing the seepage of the phase transition material and there is no risk of generating formaldehyde, etc.

In addition, it is recommended that the moisture content of the microcapsules containing the phase transition material be 30 ppm or less.

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.

In the raw material mixing process, the amounts of granular polyethylene and microcapsules should be precisely measured using a weighing device, and then these should be mixed in their solid state. Mixing should be carried out thoroughly so that the granular polyethylene and microcapsules are both uniformly dispersed.

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

It is advisable to mix the polyethylene and microcapsules before feeding them into the extruder.

The extruder temperature is preferably 180 to 250°C, and more preferably 190 to 240°C. If the extruder temperature falls below 160°C, the viscosity of the molten polyethylene increases, making mixing difficult. If the temperature exceeds 270°C, degradation of the polyethylene tends to be accelerated.

The extrusion pressure of the extruder is preferably 105 to 125 MPa, and more preferably 110 to 120 MPa. If the extrusion pressure of the extruder is below 100 MPa, there is a risk that the microcapsules and polyethylene will not be mixed properly. Also, if the extrusion pressure of the extruder exceeds 130 MPa, there is a risk that the microcapsules will be damaged.

The melt mixing process 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.

The spinning process is carried out by continuously introducing the molten mixture into a spinning machine without solidifying it. In other words, it is carried out by applying pressure and discharging the mixture from the nozzle of the spinning machine. The spinning temperature is preferably, for example, 210 to 260°C, and the number of holes in the nozzle is preferably 12 to 192.

In the spinning process, the pressure of the spinning machine should be 130 to 170 MPa, preferably 140 to 165 MPa, and more preferably 150 to 160 MPa. If the pressure of the spinning machine is below 130 MPa, the distribution of the microcapsules tends to be non-uniform. If the pressure of the spinning machine exceeds 170 MPa, the microcapsules may burst.

The cooling process is carried out by applying cooling air at 15-40°C and humidity of 60-90% to the yarn that has gone through the spinning process. If the temperature of the cooling air falls 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 falls 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.

The oil application process is preferably carried out when multiple polyethylene threads are processed simultaneously. The oil application process is carried out by applying oil to the polyethylene fibers that have been subjected to the cooling process 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 exceeds 3.5%, the polyethylene fibers tend to be sticky after production.

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

The number of times the yarn is stretched in the stretching process is not limited, but it is preferable that the process be performed two or more times. The stretching process can be performed using a stretching device equipped with multiple stretching rollers capable of applying tension to the yarn. The stretching rollers can be appropriately set depending on the number of times the yarn is stretched.

In this embodiment, an example is described in which the yarn is drawn twice in the drawing process. In this embodiment, the first drawing is referred to as the first drawing, and the second drawing is referred to as the second drawing.

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.

At this time, the first stretching roller should have a temperature of 50-80°C and rotate at a speed of 600-1000 m/min, the second stretching roller should have a temperature of 50-80°C and rotate at a speed of 1800-2500 m/min, and the third stretching roller should have a temperature of 60-130°C and rotate at a speed of 1800-3600 m/min.

By performing the drawing process in this way, the molecular orientation of the polyethylene can be increased, and as a result, the strength of the polyethylene fiber can be increased.

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

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 only of polyethylene fibers containing microcapsules, or may be composed of the polyethylene and at least one type of 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.

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 improving 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 enabling efficient production of polyethylene fibers containing microcapsules. The drawing step of drawing the spun yarn allows sufficient strength to be imparted to the polyethylene fibers containing microcapsules.

(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.

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

The granular polyethylene and the microcapsules were mixed uniformly using a weighing mixer so that the microcapsules accounted for 5% by mass of the total amount of polyethylene and microcapsules, and this 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.

(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.

(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%.

(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 2.0% by mass of the spun yarn weight (polyethylene fiber).

(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.

(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.

(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.

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

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

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

As shown in Table 1, it was found that the maximum, minimum, and average temperature values 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 immediately after the start of the experiment than the knitted fabric of Comparative Example 1.

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

As shown in Table 2, it was found that the maximum, minimum, and average temperature values 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 maintained a longer cooling sensation than the knitted fabric of Comparative Example 1.

(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.

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

Granular polyethylene was melted in a screw extruder. Microcapsules containing a phase change material were added to the molten polyethylene in the screw extruder. 20% of the microcapsules were added. The mixture was created with the pressure of the screw extruder set to 120 MPa.

(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.

(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%.

(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).

(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.

(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. A woven fabric having a basis weight of 230 gsm was produced using the polyethylene fiber.

(Preparation of Comparative Example 2)
A 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. A knitted fabric having a basis weight of 230 gsm was produced using the polyethylene fiber of Comparative Example 2.

The knitted fabrics of Example 2 and Comparative Example 2 were each measured for coolness to the touch (QMAX) based on the JIS L 1927:2020 standard. 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 (6)

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: 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. 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. 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 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, 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. A method for producing a cooling fabric, comprising producing a fabric using the polyethylene fiber obtained by the method for producing the 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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