JP7780250B2 - Dial lacing system laces - Google Patents

Description

The present invention relates to laces for use in dial-type lacing systems.

In recent years, dial-type lacing systems, such as the BOA (registered trademark) closure system, have been adopted for sports shoes such as golf shoes and snowboard shoes.

Dial lacing systems allow the laces to be evenly tightened and loosened using a dial, resulting in a natural fit. They also offer various advantages, such as the ability to easily tighten and loosen laces and instantly adjust the tightness. They are used in a variety of products, including sports shoes, protective gloves, hats, and medical prosthetics. However, due to the way they are used, the laces are held in place by high tension, which places a great deal of strain on them.

If the string breaks, it can be replaced, but repairs are expensive, and even if you do replace it yourself, it can be difficult to do so quickly unless you're used to it, so it's important that it can withstand repeated use over a longer period of time.

Therefore, in order to reduce the load on the string, there is technology that reduces the sharp angle of the string's direction changes at the guide section by adjusting the position and angle of the guide, and increases the radius of curvature of the string between the guides (Patent Document 1).

Examples of strings include unresin-coated twisted steel wire, resin-coated (e.g., polyamide-coated) twisted steel wire, monofilament (e.g., polyamide), and braided or twisted string made of Spectra (registered trademark), a high-density polyethylene.

JP 2015-198952 A

The string is repeatedly subjected to a variety of large loads, including tensile loads from tightening, bending loads at the guide sections that support the string path and at the bends inside the dial, and friction with the guide and between the strings themselves. Therefore, the string must have high tensile strength and excellent bending and abrasion resistance. Furthermore, when considering the intertwining of the strings and knots such as knots inside the dial, high knot strength and knot strength retention are also required.

Stranded steel wire is highly strong against tensile loads, but bending can cause kinking, a phenomenon in which the twist tightens or unwinds locally, resulting in a decrease in strength. Furthermore, even with a resin coating, kinking cannot be completely prevented. When monofilament is made thick enough to withstand high tensile loads, it becomes rigid and has poor bending resistance. Spectra (registered trademark) is also highly strong against tensile loads and does not kink, but due to the structure of the braided cord, the length of the fibers is oblique to the direction of movement when loosening or tightening. This makes it prone to fibrillation due to friction with the guide and between the cords, resulting in a decrease in strength. Twisted wire, while not as susceptible to fibrillation as braided cord, is also prone to fibrillation due to friction with the guide and between the cords, resulting in a decrease in strength. While fibrillation can be prevented by coating with a resin, Spectra (registered trademark) has a low heat resistance of 100°C, compared to the melting temperature of coating resins such as polyamide, which is 180-260°C. Therefore, its strength decreases depending on the melting temperature of the coating resin.

The position, angle, or material of the guides can reduce the bending and friction of the laces, but in dial-type lacing systems, even if the direction change between the guides is at an obtuse angle, the laces still bend at acute angles inside the dial, resulting in places with a small radius of curvature. Furthermore, since the laces are subject to friction not only with the guides, but also with the contact points between the laces and the gears inside the dial, laces that can withstand a variety of loads are required.

For these reasons, the laces exemplified in Patent Document 1 do not satisfy all of the requirements for tensile strength, knot strength, knot strength retention, flex resistance, and abrasion resistance when used repeatedly over long periods of time as laces for dial-type lacing systems.

Therefore, the object of the present invention is to provide a lace for a dial-type lacing system that has high tensile strength, knot strength, and knot strength retention, as well as excellent flex resistance and abrasion resistance, and can withstand repeated use over long periods of time.

After extensive investigations, the present inventors have found that by coating a core fiber made of a twisted multifilament yarn of wholly aromatic polyester fiber with polyamide 6 and setting the ratio of the core fiber to the coating resin within a specific range, a lace can be obtained that has high tensile strength, knot strength, and knot strength retention, as well as excellent flex resistance and abrasion resistance, all of which are required characteristics of a lace for a dial-type lacing system, and have completed the present invention. That is, the object of the present invention is achieved by a lace for a dial-type lacing system, comprising a core fiber made of a twisted multifilament yarn of wholly aromatic polyester fiber and resin-coated with polyamide 6, wherein the twisting factor of the twisting yarn is 30 , the total fineness of the core fiber is 840 to 1670 dtex, the diameter of the lace is 0.8 mm, and the ratio of the diameter of the core fiber to the diameter of the lace is 0.43 to 0.6.

Furthermore, it is preferable that the tensile strength of the string is 160N or more, and more preferably 220N or more.

It is also preferable that the knot strength retention rate of the string be 30% or more.

Furthermore, it is preferable that the retention rate of the tensile strength of the string after the following bending resistance test is 30% or more.
(Flexibility test)
A bending test is carried out under the following conditions using a bending tester (manufactured by Ichikawa Iron Works), and the tensile strength of the string is measured after the bending test. The tensile strength retention rate (%) after the bending test is calculated using the following formula.
Tensile strength retention rate after flex resistance test (%) = (tensile strength after flex resistance test (N) / tensile strength before flex resistance test (N)) × 100
Bending speed: 20 reciprocations/times Bending angle: 90° left and right
Number of bending times: 5,000

It is also preferable that the lace has a breakage count of 300 or more in the abrasion resistance test described below.
(Wear resistance test)
The test was conducted under the following conditions using an abrasion tester (manufactured by Ichikawa Iron Works) in which a string was moved back and forth on the surface of a rotating abrasion element, while the string itself was simultaneously rotated around its axis in the length direction to cause abrasion, and the number of times until the string broke was recorded as the number of times to break.
Wear element: metal disc with knurled diamond-shaped grooves Wear element rotation speed: 100 rpm
Number of string strokes: 50 times/min Number of string rotations: 16 rpm
String rotation direction: Counterclockwise

This invention makes it possible to obtain a lace that not only satisfies short-term performance requirements but also withstands repeated use over a long period of time when used as a lace for a dial-type lacing system, which is subjected to various loads such as tensile load, tensile load taking into account the knot, bending load, and friction.

The lace of the present invention is a lace for a dial-type lacing system, in which a core fiber made of twisted multifilament yarn of high-strength fibers is resin-coated. The resin-coating of the core fiber improves abrasion resistance, flex resistance, and knot tenacity retention.
The laces of the present invention can be used as laces for dial-type lacing systems adopted in various products, such as not only shoes but also protective gloves, hats, medical prostheses, etc., as long as the product adopts a dial-type lacing system.

The core fiber in this invention is a twisted multifilament yarn made of high-strength fibers.

The high-strength fibers used in the present invention preferably have a tensile strength of 160 N or more. A tensile strength of 160 N or more will ensure that the fibers can withstand repeated use over long periods of time when used as laces for dial-type lacing systems.

The high strength fiber in the present invention is preferably made of at least one type of fiber selected from wholly aromatic polyester fiber, aramid fiber, polyparaphenylene benzobisoxazole fiber, and polyphenylene sulfide fiber, and more preferably made of at least one type of fiber selected from wholly aromatic polyester fiber, aramid fiber, and polyparaphenylene benzobisoxazole fiber.
It is particularly preferable that the fiber is made of wholly aromatic polyester fiber.
Wholly aromatic polyester fibers have high tensile strength and can withstand tensile loads when used as strings. Furthermore, their high melting temperature of 300-360°C prevents deterioration of physical properties due to thermal decomposition when melt-coating with a coating resin. Furthermore, their low water content minimizes the generation of bubbles during resin coating. Excessive bubble generation leads to poor appearance, reduced physical properties, impaired smoothness of the coating resin, and increased susceptibility to localized loads.

Among the high-strength fibers, for example, fully aromatic polyester fibers are formed from fully aromatic polyester-based polymers.

Fully aromatic polyester polymers are composed of aromatic dicarboxylic acids, aromatic diols, and/or aromatic hydroxycarboxylic acids, or their derivatives, and in some cases also include copolymers of these with alicyclic dicarboxylic acids, alicyclic diols, aliphatic diols, or their derivatives. Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 4,4'-dicarboxydiphenyl, 2,6-dicarboxynaphthalene, 1,2-bis(4-carboxyphenoxy)ethane, etc., as well as their nucleus-substituted derivatives with alkyl, aryl, alkoxy, and halogen groups. Examples of aromatic diols include hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxybenzophenone, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenylethane, 2,2-bis(4-hydroxyphenyl)propane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, 2,6-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, etc., and their nucleus-substituted derivatives with alkyl, aryl, alkoxy, and halogen groups. Examples of aromatic hydroxycarboxylic acids include p-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxynaphthalene-6-carboxylic acid, 1-hydroxynaphthalene-5-carboxylic acid, etc., and their nucleus-substituted derivatives with alkyl, aryl, alkoxy, and halogen groups. Alicyclic dicarboxylic acids include trans-1,4-dicarboxycyclohexane, cis-1,4-dicarboxycyclohexane, and their alkyl, aryl, and halogen-substituted nuclei. Alicyclic and aliphatic diols include trans-1,4-dihydroxycyclohexane, cis-1,4-dihydroxycyclohexane, ethylene glycol, 1,4-butanediol, and xylylenediol.

Among these combinations, preferred wholly aromatic polyester polymers in the present invention include, for example, (a) copolyesters consisting of 40 to 70 mol% of p-hydroxybenzoic acid residues, 15 to 30 mol% of the above-mentioned aromatic dicarboxylic acid residues, and 15 to 30 mol% of aromatic diol residues; (b) copolyesters consisting of terephthalic acid and/or isophthalic acid and chlorohydroquinone, phenylhydroquinone, and/or hydroquinone; and (c) copolyesters consisting of 20 to 80 mol% of p-hydroxybenzoic acid residues and 20 to 80 mol% of 2-hydroxynaphthalene-6-carboxylic acid residues.

To obtain the wholly aromatic polyester polymer used in the present invention using the above starting materials, a polycondensation reaction is carried out either directly or via esterification with an aliphatic or aromatic monocarboxylic acid or a derivative thereof, an aliphatic alcohol, a phenol, or a derivative thereof. Known methods such as bulk polymerization, solution polymerization, and suspension polymerization can be used for the polycondensation reaction. The resulting polymer can be used directly or in powder form by heat treatment in an inert gas or under reduced pressure to prepare a sample for spinning. Alternatively, the polymer may be granulated in an extruder before use.

The ingredients may contain other polymers or additives (pigments, carbon, heat stabilizers, UV absorbers, lubricants, fluorescent whitening agents, etc.) as long as the strength is not substantially reduced.

The wholly aromatic polyester polymers of the present invention have a molecular weight range suitable for spinning. The "flow onset temperature" is used as the physical property value corresponding to the molecular weight suitable for these melt spinning conditions. The "flow onset temperature" is defined as the temperature at which an aromatic polyester sample flows through a nozzle with a diameter of 1 mm, a length of 10 mm, and a pressure of 100 kg/cm2 when heated at a rate of 4°C/min using a Flow Tester CFT-500 (Shimadzu Corporation). The sample flows through the nozzle and exhibits an apparent viscosity of 4,800 Pascal-seconds.

In the present invention, the "flow initiation temperature" of aromatic polyester suitable for melt spinning is preferably 305 to 325°C.

The wholly aromatic polyester fiber of the present invention may be produced by a known melt extrusion method.

The total fineness of the multifilament high-strength fiber of the present invention must be thick enough to accommodate laces for dial-type lacing systems, for example, 500 to 10,000 dtex.

The twist factor of the multifilament twisted yarn of high strength fiber in the present invention is preferably 5 to 80. The twist factor is calculated by the following formula.
K = T × √D ÷ 100
(Twist coefficient: K, twist number: T (turns/m), fineness: D (dtex))

The coating resin in the present invention is preferably at least one polymer selected from polyamide, fluororesin, polyurethane, polyethylene, polyvinyl alcohol, etc., and is more preferably polyamide because it has high abrasion resistance, moderate firmness, and loosens moderately when tightened. Furthermore, the polyamide is at least one polymer selected from polyamide 6, polyamide 11, polyamide 12, polyamide 66, etc., with polyamide 6 being particularly preferred.

The ratio of the diameter of the core fiber to the diameter of the cord of the present invention (hereinafter sometimes referred to as the core-sheath ratio) is 0.4 to 0.7. A diameter ratio within this range can satisfactorily improve knot strength, knot strength retention, flex resistance, and abrasion resistance without compromising tensile strength.

The thickness of the coating resin in the present invention is preferably 0.15 mm or more, and more preferably 0.2 mm or more. A coating resin thickness of 0.15 mm or more prevents wear of the core fibers due to their surface exposure. Furthermore, since the irregularities of the core fibers do not appear on the surface, the appearance is smooth and the localized load on the coating resin is reduced. The appearance of the string is also excellent.

The string of the present invention may be used with a known diameter. While not limited to the range described below, for example, a string with a diameter of 0.5 to 5 mm is suitable.

The tensile strength of the lace of the present invention is preferably 160 N or more, and more preferably 220 N or more. If the lace has a tensile strength of 160 N or more, it can withstand the tensile load when used as a lace for a dial-type lacing system.

The knot strength retention rate of the lace of the present invention is preferably 30% or more. If the lace has a knot strength retention rate of 30% or more, it can withstand repeated use over a long period of time when used as a lace for a dial-type lacing system.

The lace of the present invention preferably has a flex resistance of 30% or more, as described below. If the result of the flex resistance test for the lace is 30% or more, the lace can withstand repeated use over a long period of time when used as a lace for a dial-type lacing system.

The lace of the present invention preferably passes the abrasion resistance test described below 300 times or more. If the lace passes the abrasion resistance test 300 times or more, it can withstand repeated use over a long period of time when used as a lace for a dial-type lacing system.

The resin coating method in the present invention is not particularly limited, and any known method may be applied, but according to the present invention, a method of coating the resin by extrusion molding is particularly preferred.
In order to improve the adhesiveness between the coating resin and the core fiber, the core fiber may be coated with an adhesive resin before being coated with the resin.

The present invention will be explained in detail below using examples, but the present invention is not limited to these examples. Furthermore, the evaluations in the examples were carried out as follows:

(Measurement of cord diameter)
The diameter of the string was measured in accordance with JIS C3005:2014, 4.3.2.

(Measurement of core fiber diameter)
The diameter of the core fiber was measured in accordance with JIS C3005:2014, 4.3.2.

(Tensile strength test)
The tensile strength of the string was measured in accordance with JIS L1013:2010 8.5.

(Knot strength test)
The knot strength of the string was measured in accordance with JIS L1013:2010 8.6.

(Nodule strength retention rate)
The knot strength retention rate was calculated using the following formula.
Knot strength retention rate (%) = {knot strength (N) / tensile strength (N)} × 100

(Flexibility test)
The bending resistance was evaluated by the bending resistance test described above. The test conditions and evaluation method were as described above.

(Wear resistance test)
The abrasion resistance was evaluated by the abrasion resistance test described above, under the same test conditions and evaluation method as described above.

(Unevenness evaluation)
When the diameter of the string was measured at 100 points at 1 m intervals, a variation rate of less than 3% was evaluated as ⊚, a variation rate of 3% or more but less than 5% was evaluated as ○, and a variation rate of 5% or more was evaluated as ×.

Example 1
A core fiber was prepared by twisting one fully aromatic polyester multifilament (manufactured by KB Seiren Co., Ltd.) having a total fineness of 1670 dtex to a twist factor of 30. The core fiber was melt-coated with polyamide 6 by extrusion molding to prepare a cord having a diameter of 0.8 mm.
The obtained string was subjected to measurement of various physical properties and evaluation of appearance.

Example 2
A string was produced in the same manner as in Example 1 except that the total fineness of the multifilament used as the core fiber was 1100 dtex, and various physical property measurements and appearance evaluations were carried out using the obtained string.

Example 3
A string was produced in the same manner as in Example 1 except that the total fineness of the multifilament used as the core fiber was 840 dtex, and various physical property measurements and appearance evaluations were carried out using the obtained string.

(Comparative Example 1)
A string was produced in the same manner as in Example 1, except that three wholly aromatic polyester multifilaments (manufactured by KB Seiren Co., Ltd.) having a total fineness of 1,100 dtex were twisted at a twist factor of 30 to form a core fiber, and various physical property measurements and appearance evaluations were carried out using the obtained string.

(Comparative Example 2)
A string was produced in the same manner as in Example 1 except that the total fineness of the multifilament used as the core fiber was 110 dtex, and various physical property measurements and appearance evaluations were carried out using the obtained string.

(Comparative Example 3)
A cord was produced in the same manner as in Example 1, except that a concentric strand cable (manufactured by Nikko Rope Manufacturing Co., Ltd.) consisting of seven strands twisted together, each of which was made of seven stainless steel (SUS) single wires with a diameter of 50 μm, was used as the core fiber, and various physical property measurements and appearance evaluations were carried out using the obtained cord.

(Comparative Example 4)
A concentric strand cable (manufactured by Nikko Rope Manufacturing Co., Ltd.) was manufactured by twisting together seven strands each made of seven SUS single wires with a diameter of 90 μm. Various physical properties were measured and the appearance was evaluated.

(Comparative Example 5)
A polyamide 6 monofilament (manufactured by Unitika Ltd.) having a diameter of 0.81 mm was subjected to various physical property measurements and appearance evaluation.

(Comparative Example 6)
High density polyethylene (HDPE) multifilament (manufactured by Honeywell) with a total fineness of 220 dtex was used, and a 4-strand braided cord was prepared, and various physical property measurements and appearance evaluations were carried out.
These results are also shown in Table 1.

The lace of Example 1 had high tensile strength, knot strength, and knot strength retention, as well as excellent flex resistance and abrasion resistance. It also received a rating of ○ for unevenness, making it fully suitable as a lace for a dial-type lacing system.

The laces of Examples 2 and 3 had high tensile strength, knot strength, and knot strength retention, as well as excellent flex resistance and abrasion resistance. Furthermore, the unevenness evaluation was rated as Excellent, making them suitable for use in dial-type lacing systems.

The lace of Comparative Example 1 had high tensile strength and knot strength, and excellent abrasion resistance. However, it had low knot strength retention and poor flex resistance. It also received an x rating for unevenness. It was not suitable as a lace for a dial-type lacing system.

The lace of Comparative Example 2 also had a high knot strength retention rate and excellent flex resistance. It also received an excellent unevenness rating. However, it had low tensile strength and knot strength. It also had poor abrasion resistance. It was not suitable as a lace for a dial-type lacing system.

The strand cables of Comparative Examples 3 and 4 had high tensile strength, knot strength, and knot strength retention, and were excellent in abrasion resistance. However, they had poor flex resistance. Furthermore, although the unevenness rating was excellent, unevenness was visible to the naked eye. They were therefore unsuitable as laces for dial-type lacing systems.

The monofilament of Comparative Example 5 received a rating of ○ for unevenness. It also had high tensile strength, knot strength, and knot strength retention, but poor flex resistance and abrasion resistance. It was not suitable as a lace for a dial-type lacing system.

The lace of Comparative Example 6 had no irregularities. It also had high knot strength, knot strength retention, and flex resistance, but low tensile strength and abrasion resistance. It was not suitable as a lace for a dial-type lacing system.

The laces of the present invention can be used not only as laces for dial-type lacing systems used in shoes, but also as laces for dial-type lacing systems used in a variety of products such as protective gloves, hats, and medical prostheses, and can withstand repeated use over long periods of time.

Claims (5)

A lace for a dial-type lacing system, comprising a core fiber made of a twisted yarn of a multifilament of wholly aromatic polyester fiber, and the core fiber being resin-coated with polyamide 6, wherein the twisted yarn has a twist coefficient of 30 , the core fiber has a total fineness of 840 to 1670 dtex, the lace has a diameter of 0.8 mm, and the ratio of the diameter of the core fiber to the diameter of the lace is 0.43 to 0.6. The lace for a dial-type lacing system according to claim 1, having a tensile strength of 160 N or more. The lace for a dial-type lacing system according to claim 1 or 2, which has a knot strength retention rate of 30% or more. The lace for a dial-type lacing system according to any one of claims 1 to 3, which has a tensile strength retention rate of 30% or more after the following flex resistance test.
(Flexibility test)
A bending test is carried out under the following conditions using a bending tester (manufactured by Ichikawa Iron Works), and the tensile strength of the string is measured after the bending test. The tensile strength retention rate (%) after the bending test is calculated using the following formula.
Tensile strength retention rate after flex resistance test (%) = (tensile strength after flex resistance test (N) / tensile strength before flex resistance test (N)) × 100
Bending speed: 20 reciprocations/times Bending angle: 90° left and right
Number of bending times: 5,000 The lace for a dial-type lacing system according to any one of claims 1 to 4, which has a breakage count of 300 or more in the abrasion resistance test described below.
(Wear resistance test)
The test was conducted under the following conditions using an abrasion tester (manufactured by Ichikawa Iron Works) in which a string was moved back and forth on the surface of a rotating abrasion element, while the string itself was simultaneously rotated around its axis in the length direction to cause abrasion, and the number of times until the string broke was recorded as the number of times to break.
Wear element: metal disc with knurled diamond-shaped grooves Wear element rotation speed: 100 rpm
Number of string strokes: 50 times/minute Number of string rotations: 16 rpm Direction of string rotation: counterclockwise