JP7268683B2 - Polyethylene fiber and products using it - Google Patents

Description

TECHNICAL FIELD The present invention relates to polyethylene fibers with excellent cut resistance and products containing such fibers.

Traditionally, cotton, which is a natural fiber, and general organic fibers have been used as cut-resistant materials. In addition, gloves knitted from such fibers have been widely used in fields requiring cut resistance. Therefore, knitted fabrics and woven fabrics made of spun yarns of high-strength fibers such as aramid fibers have been devised to impart cut resistance. However, these were dissatisfied with hair loss and durability. On the other hand, as another means, attempts have been made to improve cut resistance by using metal fibers in combination with organic fibers or natural fibers. However, there is a problem that the combination of metal fibers makes the texture hard and impairs the flexibility.

In order to solve the above problems, there is known a technology for producing polyethylene fibers with excellent cut resistance, in which the weight-average molecular weight (Mw) and the ratio (Mw/Mn) of the weight-average molecular weight and the number-average molecular weight (Mn) are specified. (See Patent Document 1, for example).

Also, there is known a technique for ultra-high molecular weight polyethylene fibers that are excellent in cut resistance due to yarns containing hard fibers (see Patent Documents 2 and 3, for example).

Furthermore, a polyethylene fiber having a polygonal shape, an average particle size of 1.0 μm or less, and containing hard particles such as alumina and having excellent cut resistance has also been proposed (see Patent Document 4).

Japanese Patent Application Laid-Open No. 2004-019050 Japanese Patent Publication No. 2010-507026 Japanese translation of PCT publication No. 2015-518528 JP 2017-179684 A

However, when the techniques disclosed in Patent Documents 2 and 3 are used for melt spinning, there is a problem that the added hard fibers clog the filtration filter in the spinning process, resulting in a significant decrease in productivity.

Furthermore, according to a detailed study by the present inventors, the polyethylene fiber of Patent Document 4 has a problem that the cut resistance evaluation varies greatly and it is difficult to obtain a stable high evaluation (poor reproducibility). was newly discovered.

The present invention has been made to solve the above problems, and its object is to stably exhibit high cut resistance, suppress agglomeration of hard particles, and improve productivity. An object of the present invention is to provide a high-quality novel polyethylene fiber and a product using the fiber.

In order to solve the above problems, the inventors of the present invention conducted intensive studies. As a result, by appropriately controlling the shape (multi-angle) and specific surface area of the hard particles contained in polyethylene fibers, it is possible to obtain polyethylene fibers that have both stably high cut resistance and hard particle aggregation resistance. We found that and completed the present invention.

That is, the present invention consists of the following configurations.
1. A polyethylene fiber comprising hard particles having an aspect ratio of less than 3, a Hausner surface index represented by the following formula of 1.06 or more, and a specific surface area of 5.0 m ² /g or less.
Hausner's surface index = P ² /4πA
During the ceremony,
P is the perimeter of the projected particle image (μm),
A is the area (μm ² ) of the projected image of the particle.
2. 2. The polyethylene fiber according to 1 above, wherein the hard particles are silicon compounds.
3. 3. The polyethylene fiber according to 1 or 2 above, wherein the hard particles contain 20% by mass or more of _SiO2 in the hard particles.
4. 4. The polyethylene fiber according to any one of 1 to 3 above, wherein the hard particles have an average short diameter of 1.0 μm or more.
5. 5. The polyethylene fiber according to any one of 1 to 4 above, wherein the hard particles have a Mohs hardness of 4.5 or more.
6. 6. The polyethylene fiber according to any one of 1 to 5 above, wherein the intrinsic viscosity [η] of polyethylene is 0.8 dL/g or more and less than 4.9 dL/g.
7. 7. The polyethylene fiber according to any one of 1 to 6 above, which contains 2% by mass or more of the hard particles in the polyethylene fiber.
8. A product characterized by comprising the polyethylene fiber according to any one of 1 to 7 above.
9. 9. The product of claim 8, wherein said product is a cut resistant knitted fabric.
10. 10. A product according to claim 8 or 9, wherein said product is a glove.

ADVANTAGE OF THE INVENTION According to the present invention, a novel polyethylene fiber that can stably exhibit high cut resistance, suppresses agglomeration of hard particles, and has high productivity, and a product using the fiber are provided. can do.

First, the details of how the present invention was reached will be described.
After proposing the polyethylene fiber of Patent Literature 4, the present inventors have made repeated studies in order to further improve cut resistance. Specifically, the hard particles described in Patent Document 4; specifically, polyethylene containing hard particles having a polygonal shape, an average particle size of 1.0 μm or less, and a Mohs hardness of 4.5 or more When the cut resistance of the fiber was repeatedly evaluated, it was found that the measurement was inconsistent and a high evaluation could not be obtained stably, resulting in a lack of reproducibility.

In order to solve the above problem, the present inventors have made detailed studies on the shape (multiple angles) of the hard particles. As a result, it was found that when the multiple angle represented by the Hausner's surface index (details will be described later) is increased to 1.06 or more, high cut resistance can be stably obtained. According to Hausner's surface index, the more the shape deviates from the circle, the higher the number. However, it has also been found that if the surface index becomes too high, for example, 10 or more, the specific surface area increases, causing the hard particles to agglomerate and clog the spinning nozzle. Therefore, the present inventors made further studies to obtain a polyethylene fiber having both stably high cut resistance and resistance to hard particle agglomeration (no clogging of the spinning nozzle). As a result, the inventors have found that the above problems can be solved by appropriately controlling both the surface index and the specific surface area of the hard particles contained in the polyethylene fibers, and have completed the present invention.

The usefulness of the configuration of the present invention will be described in more detail based on the results shown in Table 1 below.

First, Comparative Examples 2 to 4 in Table 1 correspond to Examples 1 to 3 of Patent Document 4, respectively, and are examples in which alumina having an average short diameter of 0.5 μm was used as the hard particles. Although these are different in the content of alumina contained in the polyethylene fibers, they are all examples of large specific surface areas. The comparative examples were evaluated for cut resistance and cut resistance stability based on the evaluation method described later in Examples, and generally good results were obtained in terms of cut resistance. However, it was found that the stability of the cut resistance was remarkably lowered.
Furthermore, when the resistance to hard particle agglomeration of the comparative examples was evaluated based on the evaluation method described later in Examples, clogging of the spinning nozzle occurred in all cases.

Comparative Example 1 in Table 1 is an example in which silica having an average short diameter of 2.0 μm and a Hausner surface index of 1.01 is used as the hard particles. In Comparative Example 1, clogging of the spinning nozzle did not occur, but because substantially circular silica was used, the stability of the cut resistance was remarkably lowered as in Comparative Examples 2 to 4 above.

The results of the above comparative examples show that even with hard particles that are conventionally disclosed as having excellent cut resistance, there is variation in cut resistance, poor reproducibility, and stable cut resistance cannot be obtained. clearly shows that

The same results as in Comparative Example 1 were also observed when the material of the hard particles was changed.
That is, Comparative Example 6 in Table 1 is an example in which glass having an average short diameter of 5.0 μm and a Hausner surface index of 1.02 is used as the hard particles. In Comparative Example 6, clogging of the spinning nozzle did not occur, but the stability of the cut resistance was remarkably lowered, as in Comparative Examples 2 to 4, because the substantially circular glass was used.
Comparative Example 7 in Table 1 is an example in which glass having an average short diameter of 0.3 μm and a Hausner surface index of 1.32 is used as the hard particles. In Comparative Example 7, as in Comparative Examples 2 to 4, a material having a large specific surface area was used, so the stability of cut resistance and resistance to hard particle agglomeration were remarkably lowered, and clogging of the spinning nozzle occurred. .

On the other hand, Examples 1 to 7 in Table 1 are examples in which various glasses having different average short diameters are used as hard particles, and the surface index and specific surface area are controlled within the range of the present invention. Both stability and hard particle agglomeration resistance (no spinning nozzle clogging) are improved. Therefore, according to the present invention, it is possible to provide a polyethylene fiber that can stably exhibit high cut resistance with good reproducibility, and in which agglomeration of hard particles is suppressed.

The present invention will be described in detail below.

The polyethylene fiber of the present invention preferably has an intrinsic viscosity [η] of 0.8 dL/g or more and less than 4.9 dL/g, more preferably 1.0 dL/g or more and 4.0 dL/g or less. It is more preferably 1.2 dL/g or more and 2.5 dL/g or less.

By setting the intrinsic viscosity to less than 4.9 dL/g, spinning by a melt spinning method becomes easy, and spinning by so-called gel spinning or the like is unnecessary. Therefore, it is advantageous in terms of suppressing the manufacturing cost and simplifying the work process. Furthermore, since no solvent is used during manufacturing, the effect on workers and the environment is small. In addition, since there is no residual solvent in the product fiber, there is no adverse effect of the solvent on the user of the product. Further, by setting the intrinsic viscosity to 0.8 dL/g or more, the number of structural defects in the fiber can be reduced due to the reduction of molecular terminal groups of polyethylene. Therefore, it is possible to improve the mechanical physical properties of the fiber such as strength and elastic modulus, as well as the cut resistance performance.

Also, the weight average molecular weight (Mw) of the polyethylene fiber according to the present invention is preferably 50,000 to 600,000. By setting Mw to 50,000 or more, the number of structural defects in the fiber can be reduced due to the reduction of molecular end groups of polyethylene. Therefore, the mechanical physical properties of the fiber such as strength and elastic modulus and cut resistance are improved. On the other hand, by setting Mw to 600,000 or less, spinning by melt spinning becomes easy, and spinning by so-called gel spinning or the like is unnecessary. Therefore, it is advantageous in terms of suppressing the manufacturing cost and simplifying the work process. Furthermore, since no solvent is used during manufacturing, the effect on workers and the environment is small. In addition, since there is no residual solvent in the product fiber, there is no adverse effect of the solvent on the user of the product.

In addition, the polyethylene in the present invention may have a repeating unit that is substantially ethylene, and the ethylene and a small amount of other monomers; It may be a copolymer with a derivative or the like. Alternatively, it may be a blend of these copolymers, a copolymer of ethylene homopolymer and the above copolymer, or a blend of ethylene homopolymer and other homopolymer such as α-olefin. In particular, the use of a copolymer with an α-olefin such as propylene or butene-1 to contain a certain amount of short-chain or long-chain branches is particularly useful in producing the polyethylene fiber of the present invention, particularly in spinning and drawing. It is more preferred because it provides the above stability. However, if the content of components other than ethylene is excessively increased, it becomes a hindrance to stretching. The unit is preferably 0.2 mol % or less, more preferably 0.1 mol % or less. Of course, polyethylene in the present invention may consist of ethylene alone.

The polyethylene fibers of the present invention contain a plurality of hard particles. The hard particles in the present invention include at least hard particles having an aspect ratio of less than 3, a Hausner surface index represented by the following formula of 1.06 or more, and a specific surface area of 5.0 m ² /g or less.
Hausner's surface index = P ² /4πA
During the ceremony,
P is the perimeter of the projected particle image (μm),
A is the area (μm ² ) of the projected image of the particle.

In particular, the hard particles used in the present invention are characterized by satisfying both the Hausner surface index represented by the above formula of 1.06 or more and the specific surface area of 5.0 m ² /g or less. , the desired effect is exhibited.

First, the hard particles used in the present invention satisfy a Hausner surface index of 1.06 or more. Here, the Hausner surface index is an index representing multiple angles of particles, and was first adopted by the present inventors as an index for evaluating the stability of cut resistance. According to Hausner's surface index, circle = 1, regular octagon ≈ 1.055, regular hexagon ≈ 1.103, square ≈ 1.273, equilateral triangle ≈ 1.654. becomes higher.

When the Hausner surface index is less than 1.06, the effect of improving the stability of cut resistance is not effectively exhibited. On the other hand, when the Hausner surface index exceeds 10, the specific surface area becomes large, causing a new problem that the hard particles tend to aggregate. Agglomeration of hard particles leads to filter clogging of spinning nozzles, making it impossible to obtain undrawn yarn. The Hausner surface index is preferably 1.25 or higher, more preferably 1.30 or higher, and even more preferably 1.40 or higher. If the Hausner surface index is too large, the specific surface area increases as described above, which may cause clogging of the spinning nozzle.

Furthermore, the specific surface area of the hard particles used in the present invention satisfies 5.0 m ² /g or less. The above specific surface area range is used as an index for suppressing agglomeration of hard particles. If the specific surface area exceeds 5.0 m ² /g, the hard particles tend to agglomerate, causing clogging during spinning. The specific surface area is preferably 4.5 m ² /g or less, more preferably 3.0 m ² /g or less, still more preferably 2.0 m ² /g or less. On the other hand, if the specific surface area is too small, the size of the filler becomes too large, causing the problem of thread breakage. The specific surface area is preferably 0.02 m ² /g or more, more preferably 0.6 m ² /g or more.

Further, the aspect ratio of the hard particles used in the present invention is less than 3. If the aspect ratio of the hard particles is 3 or more, the filtration filter will clog during spinning, which is not preferable because there is a concern that the productivity of the fiber will be significantly reduced. The aspect ratio is preferably 1 or more and 2 or less. Here, the aspect ratio of hard particles is a value calculated based on JIS8900-1 (that is, in a microscopic image of particles, the shape of the particles defined by (maximum diameter/width perpendicular to the maximum diameter). index). A method for measuring the aspect ratio of the hard particles will be described in detail in the Examples section below.

The hard particles used in the present invention preferably have an average short diameter of 1.0 μm or more. If the average short diameter is less than 1.0 μm, the specific surface area increases and the hard particles agglomerate as aggregates, causing clogging during spinning. On the other hand, when the average short diameter of the hard particles becomes large, the filtration filter is clogged during spinning, and the productivity of the fiber is remarkably reduced, especially the stretchability is greatly reduced. The average particle size of the hard particles is preferably 2 μm or more, still more preferably 3 μm or more, and more preferably 10 μm or less.
The average minor axis of the hard particles was calculated by measuring the minor axis (maximum minor axis) of each of 10 hard particles by the same method as the aspect ratio of the hard particles described later, and calculating the average value.

The hard particles used in the present invention are preferably silicon compounds. The silicon compound is not particularly limited as long as it is a compound containing silicon, and examples thereof include silica, glass, silicon carbide, and the like. More preferably, hard particles containing 20% by mass or more of SiO ₂ are used, such as silica and glass. Glass is more preferable. Silica and glass are distinguished mainly by the content of SiO ₂ . Silica is substantially composed only of SiO ₂ , and the SiO ₂ content of silica is generally 95% by mass or more. On the other hand, the main component of glass is generally SiO ₂ , and alumina, B ₂ O ₃ , P ₂ O ₅ in general, etc. may be included. The SiO ₂ content in the glass is approximately 50% by mass or more.

The shape of the glass used in the present invention is not particularly limited as long as it satisfies the above requirements, and either glass fiber or glass frit can be used. Here, the glass fiber has an average short diameter of approximately 4 to 12 μm, and both glass fiber (long glass fiber) and glass wool (short glass fiber) can be used in the present invention. The glass frit is in the form of flakes or powder having an average short diameter of approximately 1.0 to 5.0 μm.

The hard particles used in the present invention preferably have a Mohs hardness of 4.5 or more. If the Mohs hardness is less than 4.5, the hard particles do not interfere with the blade during cutting, making it difficult to obtain the effect of improving cutting resistance. However, if the Mohs hardness becomes too high, there is a risk that the machine base of the extruder or the like may be damaged, so it is preferably 8.0 or less.
Examples of hard particles that satisfy the above preferable range include glass (when the SiO ₂ content is about 50%, the Mohs hardness is about 4.5 to 5.5, although it varies depending on the SiO ₂ content), silica (Mohs hardness of about 6), titanium alone (Mohs hardness of about 6), and the like.
Titanate has a Mohs hardness of about 4, and alumina has a Mohs hardness of about 9, which do not satisfy the above preferred range.
Regarding the method for measuring the Mohs hardness of hard particles, it is generally difficult to measure the Mohs hardness of fillers, but in the present invention, the fibers are ashed, the composition is confirmed by elemental analysis, and the The Mohs hardness was estimated by matching and rubbing against a standard sample on a Mohs hardness scale to see if the standard sample was scratched.

The plurality of hard particles contained in the polyethylene fiber of the present invention may be used as they are, or may be used after surface modification. A dimethyl group, an epoxy group, a hexyl group, a phenyl group, a methacryl group, a vinyl group, an isocyanate group, or the like can be applied as the surface modification.

The content of the plurality of hard particles contained in the entire polyethylene fiber of the present invention is preferably 2% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, preferably 30% by mass or more. % by mass or less. If the content of the hard particles is less than 2% by mass, the frequency of contact between the hard particles present in the fiber and the blade is low, making it difficult to obtain the effect of improving cut resistance. However, if the content of the hard particles is too high, problems such as yarn breakage may occur during spinning and drawing, so the upper limit is preferably 30% by mass or less, for example.

When spinning the polyethylene fiber of the present invention, the hard particles may be used as a masterbatch that has been kneaded with polyethylene in advance, or may be used alone.

The polyethylene fiber of the present invention preferably has a fiber diameter per single yarn of 45 μm or less, more preferably 37 μm or less. If the fiber diameter per single yarn is larger than 45 μm, the woven fabric or knitted fabric (woven or knitted fabric) will have a hard texture and will lose flexibility. The fiber diameter per single yarn can be determined by, for example, a method of determining from dtex and the specific gravity of the fiber, or a method of determining using a microscope. Although the upper limit is not particularly limited from the above viewpoint, it is preferably about 10 μm or more in consideration of productivity and the like.

The polyethylene fiber of the present invention preferably has an average strength of 4 cN/dtex or more, preferably 6 cN/dtex or more. If the average strength is less than 4 cN/dtex, there is a possibility that the strength will be insufficient when an applied product is produced. Although the upper limit is not particularly limited from the above viewpoint, considering productivity such as spinnability, it is preferably about 50 cN/dtex or less.

The polyethylene fiber of the present invention may have a core-sheath structure, or may have an irregular shape such as a star shape, a triangle shape, or a hollow shape.

As for the production method for obtaining the polyethylene fiber of the present invention, for example, a melt spinning method can be used. Here, for example, if a gel spinning method, which is one of the methods for producing ultra-high molecular weight polyethylene fibers using a solvent, is used, although high-strength polyethylene fibers can be obtained, the productivity is not only low, but also due to the use of solvents. The impact on the health and environment of manufacturing workers and the impact on the health of product users due to residual solvents in the fibers are significant.

Therefore, it is preferable to use the melt spinning method for the polyethylene fiber of the present invention. The method for producing the polyethylene fiber of the present invention using the melt spinning method will be specifically described below. In addition, the method for producing the polyethylene fiber of the present invention is not limited to the following steps and numerical values.

The above-mentioned polyethylene resin and hard particles in powder form are blended and melt extruded using an extruder or the like at a temperature higher than the melting point of the polyethylene resin by, for example, 10°C or higher, preferably 50°C or higher, more preferably 80°C or higher. and supplied to a spinning nozzle (spinneret) at a temperature higher than the melting point of the polyethylene resin by, for example, 80° C., preferably 100° C. or more, using a metering supply device. At this time, the pressure of the inert gas supplied into the extruder is preferably 0.001 MPa or more and 0.8 MPa or less, more preferably 0.05 MPa or more and 0.7 MPa or less, and still more preferably 0.1 MPa or more. , 0.5 MPa or less. Thereafter, it is discharged at a discharge rate of 0.1 g/min or more from a spinning nozzle having a diameter of, for example, 0.3 mm or more and 2.5 mm or less, preferably 0.5 mm or more and 1.5 mm or less. The linear velocity of ejection of the molten resin from the spinning nozzle is preferably 10 cm/min or more and 120 cm/min or less. The ejection linear velocity is more preferably 20 cm/min or more and 110 cm/min or less, and more preferably 30 cm/min or more and 100 cm/min or less.

Next, after cooling the extruded yarn to 5 to 40° C., it is wound up at 50 m/min or more, and the obtained undrawn yarn is heated at a temperature below the melting point of the undrawn yarn at least once or more. Stretch 1.2 times or more. Specifically, the stretching process is preferably performed in two or more stages. The temperature at the initial stage of drawing is preferably lower than the crystal dispersion temperature of the undrawn yarn, more preferably 80° C. or lower, and still more preferably 75° C. or lower. Next, the yarn is drawn at a temperature not lower than the crystal dispersion temperature of the undrawn yarn and not higher than the melting point, preferably not lower than 90° C. and lower than the melting point.

Here, the crystal dispersion temperature is a temperature measured by the following method.
First, the solid viscoelastic modulus is measured using a solid viscoelasticity measuring device (manufactured by TA Instruments, "DMA Q800"). "TA Universal Analysis" (manufactured by TA Instruments) is used for the analysis of the measured solid viscoelastic modulus. Here, the measurement start temperature is −140° C., the measurement end temperature is 140° C., and the temperature increase rate is 1.0° C./min. The strain amount is 0.04%, and the initial load at the start of measurement is 0.05 cN/dtex. Also, the measurement frequency is assumed to be 11 Hz. Next, the loss modulus is calculated based on the obtained solid viscoelastic modulus, the temperature distribution is obtained from the low temperature side, and the logarithm of the loss modulus is plotted on the vertical axis and the temperature on the horizontal axis. , the peak value of the loss modulus appearing on the highest temperature side is defined as the crystal dispersion temperature.

The total draw ratio is preferably 6 times or more, more preferably 8 times or more, and still more preferably 10 times or more. The total draw ratio is preferably 30 times or less, more preferably 25 times or less, and still more preferably 20 times or less. In the case of adopting multi-stage stretching, for example, when performing two-stage stretching, the stretching ratio in the first stage is preferably 1.05 times or more and 4.00 times or less, and the stretching in the second stage The magnification is preferably 2.5 times or more and 15 times or less.

Products using the polyethylene fiber of the present invention, such as woven and knitted fabrics, are suitably used as cut-resistant woven and knitted fabrics, gloves, vests, and the like. For example, gloves are obtained by knitting the polyethylene fibers of the present invention. Alternatively, the polyethylene fiber of the present invention may be woven on a loom to obtain a cloth, which may be cut and sewn into gloves.

The glove thus obtained can be used, for example, as a glove as it is, or can be coated with a resin to impart anti-slip properties, if necessary. Examples of resins used here include urethane-based and ethylene-based resins, but are not particularly limited.

The polyethylene fiber of the present invention has excellent cut resistance, as can be seen from the examples described later.
Therefore, the products using the polyethylene fiber of the present invention include tapes, ropes, nets, fishing lines, material protection covers, sheets, strings for kites, bow strings, sail cloths, etc., in addition to woven and knitted fabrics such as gloves and vests. It is suitably used as a curtain material. Of course, products using the polyethylene fibers of the present invention are not limited to these.

In addition, since the polyethylene fiber of the present invention has high cut resistance, it is assumed that materials that make use of the cut resistance, such as fiber reinforced resin reinforcing materials, cement reinforcing materials, fiber reinforced rubber reinforcing materials, or environmental changes are expected. protective materials, bulletproof materials, medical sutures, artificial tendons, artificial muscles, fiber-reinforced resin reinforcing materials, cement reinforcing materials, fiber-reinforced rubber reinforcing materials, machine tool parts, battery separators, and chemical filters. Of course, the polyethylene fiber of the present invention is not limited to these materials, and can be used as various materials.

EXAMPLES The present invention will be specifically described below by way of examples. However, the present invention is not limited to the following examples, and it is of course possible to make appropriate modifications within the scope that can be adapted to the gist of the preceding and following descriptions. included in the scope of

First, the measurement and evaluation of characteristic values performed on fibers (fiber samples) and tubular knitted fabrics (knitted fabric samples) using the fibers produced in Examples and Comparative Examples to be described later will be described.

(1) Intrinsic viscosity [η]
The intrinsic viscosity was measured using decalin heated to 135° C. as a solvent and using an Ubbelohde-type capillary viscosity tube. Specifically, the specific viscosities of various dilute solutions were measured, and the intrinsic viscosity was determined from the point of extrapolation to the origin of a straight line obtained by least-squares approximation of the plot of the viscosity versus concentration. When measuring the specific viscosity, the fiber sample was divided or cut into pieces of about 5 mm in length, 1% by mass of an antioxidant (Yoshinox BHT (registered trademark), manufactured by Yoshitomi Pharmaceutical Co., Ltd.) was added to the polymer, and the temperature was maintained at 135 ° C. for 4 hours. A measurement solution was prepared by stirring and dissolving.

(2) Multiple angles of hard particles (Hausner surface index)
The multiple angles of the hard particles were calculated based on the aforementioned Hausner surface index. Specifically, P (perimeter of projected particle image, μm) and A (area of projected particle image, μm ² ) of each hard particle were measured and calculated as follows.

First, each fiber sample prepared by the method described later is placed in a crucible and burned until it becomes ash and carbonaceous material, then placed in an electric furnace and heated at a temperature higher than the decomposition temperature of polyethylene (specifically 480 ° C.). bottom. When the carbonaceous material was completely ash, it was allowed to cool to room temperature in a desiccator to obtain ash. The hard particles contained in the ash thus obtained were observed at 500 to 1500 magnifications using an industrial microscope (Olympus, BX53M). Among these, 20 hard particles are randomly extracted, and using the analysis software (STREAM) attached to the industrial microscope, the area A and the perimeter P of each hard particle are measured, and the above formula is obtained. The Hausner surface index was calculated based on In this example, the average value of the 20 surface indices was determined and used as the surface index of each fiber sample.

(3) Specific Surface Area of Hard Particles About 10 g of the ash obtained by the above method (2) was sampled, vacuum-dried at 300° C. for 10 hours, and then weighed. Using an automatic specific surface area device of Micromeritics ASAP2020, the adsorption amount of nitrogen gas at the boiling point of liquid nitrogen (-195.8 ° C.) is gradually increased in the range of 0.05 to 0.3 relative pressure. While measuring at 40 points, an adsorption isotherm was prepared. Using the analysis software attached to the specific surface area device (GEMINI-PCW version 1.01), under BET conditions, the surface area analysis range is set to 0.01 to 0.15, and the BET specific surface area [m ² /g] is calculated. asked.

(4) Aspect Ratio of Hard Particles The aspect ratio of hard particles was obtained by using SEM photographs. Specifically, each fiber sample prepared by the method described later was placed in a crucible and burned until ash and carbonaceous substances were formed, then placed in an electric furnace and heated to a temperature equal to or higher than the decomposition temperature of polyethylene. Once the carbonaceous material was completely ash, it was allowed to cool in a desiccator to obtain ash to room temperature. An SEM photograph of the ash thus obtained was taken, and for each of 10 randomly selected hard particles, the major axis (maximum major axis) and the width perpendicular to the maximum major axis were measured, and the maximum major axis was The aspect ratio was calculated by dividing by the width orthogonal to the major axis and obtaining the average value. In addition, since the hard particles have high hardness, it is considered that the shape does not change even when heated.

(5) Average minor axis of hard particles The average minor axis of hard particles is obtained by taking SEM photographs in the same manner as the above aspect ratio, and measuring the minor axis (maximum minor axis) of 10 randomly selected hard particles. , was calculated by obtaining the average value.

(6) Content of Hard Particles The content of hard particles was obtained by measuring the ash content based on JIS-2272. Specifically, 1.0 g of each fiber sample prepared by the method described later was placed in a crucible and burned until ash and carbonaceous substances were formed, then placed in an electric furnace and heated to a temperature equal to or higher than the decomposition temperature of polyethylene. After the carbonaceous material completely turned to ash, it was allowed to cool to room temperature in a desiccator, and the mass was measured to determine the ash content. The content of hard particles was determined based on the mass ratio of the ash content to the sum of the obtained ash content and the fiber sample content.

(7) Cut resistance The cut resistance was measured using a Couptester (manufactured by SODEMAT) based on the EN388 method, which is a European standard. Specifically, using each polyethylene fiber produced by the method described below, a tubular knitted fabric having a basis weight of 350 g/m ² ±35 g/m ² was produced using a circular knitting machine manufactured by Shima Seiki Seisakusho. The cut resistance of the tubular knitted fabric obtained was evaluated by calculating the index value of the coup tester as follows.

Here, an aluminum foil was provided on the sample stage of the above apparatus, and a knitted fabric sample was placed thereon. Next, a circular blade provided in the device was run over the sample while rotating in a direction opposite to the running direction. When the knitted sample was cut, it was detected that the cut resistance test was completed by contacting the circular blade with the aluminum foil and energizing it. A counter attached to the device counted while the circular blade was in motion and the number was recorded.

In this test, a plain weave cotton cloth with a basis weight of about 380 g/m ² was used as a blank to evaluate the cut level of knitted samples. A set of tests was completed starting with a blank, alternating between testing the blank and testing the knitted sample, testing the knitted sample 5 times, and finally testing the blank 6 times. Ten sets of the above tests were performed, and the average index value (index value) of the ten sets was used as a substitute evaluation of cut resistance. A higher index value means better cut resistance.

The index value is calculated by the following formula.
K = (count value of cotton fabric before sample test + count value of cotton fabric after sample test) / 2
Index value = (Sample count value + K)/K

The cutter used for the evaluation of cut resistance is φ45 mm for rotary cutter L type manufactured by OLFA Corporation. The material was SKS-7 tungsten steel, and the blade thickness was 0.3 mm. Moreover, the load applied at the time of the test was set to 5N, and the evaluation was performed.

In this example, the index value obtained in Comparative Example 1 is defined as 100 for cut resistance, and this is used as a reference value, and the other examples shown in Table 1 express the cut resistance as a relative ratio to Comparative Example 11. bottom. For example, the cut resistance of Example 1 is 110, which means that a high cut resistance of 110% (1.1 times) was obtained when the cut resistance of Comparative Example 1 was 100%. means.

(8) Stability of Cut Resistance The coefficient of variation CV value (=standard deviation/average value) was determined in 10 sets of tests performed in the evaluation of cut resistance in (7) above, and evaluated according to the following criteria.
CV value 25% or less: excellent stability of cut resistance (○)
CV value over 25%: Poor stability of cut resistance (×)

(9) Hard Particle Aggregation Resistance Hard particle aggregation resistance was evaluated based on the presence or absence of clogging in the spinning nozzle.

(10) Average Strength of Fiber The average strength of each fiber sample produced by the method described below was calculated as follows.
Using "Tensilon" manufactured by Orientic Co., Ltd., the strain-stress curve was measured under the conditions of a sample length of 200 mm (length between chucks), an elongation rate of 100% / min, an ambient temperature of 20 ° C., and a relative humidity of 65%. The strength (cN/dtex) was calculated from the stress at the breaking point of the curve obtained, and the elastic modulus (cN/dtex) was calculated from the tangent line giving the maximum gradient near the origin of the curve. The same operation was performed 10 times, and the average value was taken as the average strength of each fiber sample.

(Example 1)
78% by mass of polyethylene pellets having an intrinsic viscosity of 1.9 dL / g, and glass fibers (E glass; main component 3.0% by mass containing 53% by mass of SiO ₂ and 15% by mass of Al ₂ O ₃ were mixed to prepare a blend polymer. The aspect ratio of the hard particles was the average of 10 particles as described above, and the range was from 1.05 to 6.0. This blended polymer was supplied to an extruder, melted at 280° C., and extruded from a spinneret having an orifice diameter of φ0.8 mm and 30H at a nozzle surface temperature of 288° C. at a single hole ejection rate of 0.32 g/min.

The extruded yarn was passed through a 10 cm heat-retaining section, cooled at 18° C. by quenching at 0.5 m/sec, and wound into a cheese shape at a spinning speed of 200 m/min to obtain an undrawn yarn. Then, the yarn was heated with hot air at 100° C. and wound up at the maximum draw ratio that allows stable drawing to obtain a drawn yarn. The drawn yarns were combined so as to have a total of 880 dtex±88 dtex to obtain the polyethylene fiber of Example 1. Using the obtained polyethylene fibers, a tubular knitted fabric was produced by the above method, and the cut resistance, the stability of the cut resistance, and the hard particle agglomeration resistance were evaluated. These results are shown in Table 1. In addition, in the following examples and comparative examples, including this example, the film was stretched 3 times at room temperature and stretched 2.3 times at 100°C.

(Examples 2 to 7, Comparative Examples 1 to 6)
Under the conditions of Example 1, the drawn yarn of the above example was obtained in the same manner as in Example 1 except that the material, average minor diameter, aspect ratio, and content of the hard particles were changed as shown in Table 1. properties were evaluated. These results are shown in Table 1.

Here, the details of the glasses used in Examples 2 to 7 are as follows.
Example 2: 18.0 mass of glass fiber (E glass; containing 53% by mass of SiO ₂ and 15% by mass of Al ₂ O ₃ as main components) having an average minor axis of 7.0 μm and an average major axis of 16.0 μm %
Example 3: Glass frit with an average short diameter of 1.3 μm (E glass; containing 53% by mass of SiO ₂ and 15% by mass of Al ₂ O ₃ as main components) 18.0% by mass
Example 4: Glass frit with an average minor axis of 3.5 μm (containing 53% by mass of SiO ₂ and 20% by mass of Al ₂ O ₃ as main components) 18.0% by mass
Example 5: Glass frit with an average short diameter of 3.5 μm (containing 60% by mass of SiO ₂ and 7% by mass of B ₂ O ₃ as main components) 6.0% by mass
Example 6: 3.0% by mass of glass fiber (glass wool, 60% by mass of _SiO2 as the main component) with an average minor axis of 4.0 μm and an average major axis of 8 μm
Example 7: 6.0 mass of glass fiber (E glass; containing 53% by mass of SiO ₂ and 15% by mass of Al ₂ O ₃ as main components) having an average minor axis of 10.0 μm and an average major axis of 25.0 μm %

Comparative Example 1 is an example simulating Example 1 (only the content is different) of Patent Document 4 described above.

As can be seen from Table 1, Examples 1 to 7 using polyethylene fibers that satisfy the requirements of the present invention are excellent not only in cut resistance but also in cut resistance stability and hard particle agglomeration resistance. . On the other hand, in Comparative Examples 1 to 7, which did not satisfy any of the requirements of the present invention, at least one of stability of cut resistance and resistance to hard particle agglomeration decreased.
Here, Comparative Example 5 is an example in which the average short diameter of the hard particles exceeded the preferable upper limit, and clogging occurred during spinning, so an undrawn yarn could not be obtained. Therefore, properties such as strength of the fiber sample could not be evaluated.

The polyethylene fiber of the present invention is excellent not only in high cut resistance but also in both stability of cut resistance and hard particle cohesion resistance. Best available. In addition, the polyethylene fiber alone can be used as tapes, ropes, nets, fishing lines, material protection covers, sheets, strings for kites, bow strings, sail cloths, curtain materials, protective materials, bulletproof materials, medical sutures, artificial tendons, artificial muscles. , fiber-reinforced resin reinforcing materials, cement reinforcing materials, fiber-reinforced rubber reinforcing materials, machine tool parts, battery separators, chemical filters, and other industrial materials. As described above, the polyethylene fiber of the present invention can exhibit excellent performance and can be widely applied, so that it can greatly contribute to the industrial world.

Claims (7)

Hard particles having an aspect ratio of less than 3, a Hausner surface index represented by the following formula of 1.06 or more, a specific surface area of 5.0 m ² /g or less, and containing 20% by mass or more of SiO ₂ in the particles ,
A polyethylene fiber characterized by having an intrinsic viscosity [η] of 0.8 dL/g or more and less than 4.9 dL/g .
Hausner's surface index = P ² /4πA
During the ceremony,
P is the perimeter of the projected particle image (μm),
A is the area of the projected particle image (μm ² )
is. The Hausner surface index is the average value of 20 randomly selected hard particles. 2. The polyethylene fiber according to claim 1, wherein said hard particles have an average short diameter of 1.0 [mu]m or more. 3. The polyethylene fiber according to claim 1, wherein the hard particles have a Mohs hardness of 4.5 or more. The polyethylene fiber according to any one of claims 1 to 3 , which contains 2% by mass or more of said hard particles. A product comprising polyethylene fibers according to any one of claims 1-4 . 6. The article of claim 5 , wherein said article is a cut resistant knitted fabric. 7. A product according to claim 5 or 6 , wherein said product is a glove.