JP4072866B2 - Cold-resistant shoes - Google Patents

Description

  The present invention relates to a cold-resistant shoe used in a workplace that handles a cryogenic liquid typified by liquid nitrogen and liquefied natural gas.

  2. Description of the Related Art Conventionally, workers wear winter shoes in workplaces represented by liquid nitrogen and liquefied natural gas (LNG) and handling cryogenic liquids including liquefied propane gas, such as storage tanks and tank trucks. Most of the winter shoes used are made of leather or rubber and have a waterproof function.

  Cold protection shoes for cryogenic work have low temperature insulation performance, excellent heat retention, and handle cryogenic liquids so that workers will not suffer from frostbite even in a cryogenic environment below -100 ° C. It is necessary to be able to protect workers against unexpected accidents.

Conventionally used winter shoes having a waterproof function made of leather or rubber have the following problems.
(1) When cryogenic liquid flows out due to an accident caused by a large earthquake and the shoe sole is immersed in the cryogenic liquid, cracking occurs and the cryogenic liquid penetrates into the shoe, making it difficult to ensure safe walking. become.
(2) If an attempt is made to approach the outflow location of the cryogenic liquid, the shoe sole may be cracked, so that the outflow location cannot be repaired as soon as possible, making it difficult to prevent a major accident.
(3) Especially when the cryogenic liquid is flammable, such as liquefied propane gas or liquefied natural gas, it burns due to an accident and is exposed to the flame, but the heat resistance required for emergency evacuation It has no flame resistance.

  In other words, natural rubber-based or urethane-based elastomer materials are mainly used for the sole of cold protection shoes that have been distributed in the past, and are manufactured by pressure heating molding or injection molding using a mold. When these materials are manufactured as bottoms by these molding methods, residual stress is generated inside the bottoms material. When a shoe sole is immersed in a cryogenic liquid that flows out due to an accident or the like, residual stress increases due to thermal contraction at a low temperature, and a crack occurs in the shoe sole.

  Moreover, although the shoe sole of the shoes for cold work generally circulated has an airtight structure, the airtightness is maintained by the material used for the sole. For this reason, when the shoe is immersed in the cryogenic liquid that flows out due to an accident or the like, if the bottom of the shoe is cracked, the airtightness is lost instantly and the cryogenic liquid penetrates into the shoe.

  Further, natural leather, synthetic leather, rubber, or the like is used as a material for a general cold work shoe. These materials do not have heat resistance or flame resistance when a fire occurs in a flammable liquid due to an accident, etc., so it is possible to ensure the safety at the time of emergency evacuation etc. in a state exposed to flame. Can not.

  An object of the present invention is to provide a cold-resistant shoe that enhances the wearer's safety for various operations required when handling a cryogenic liquid, and allows the operator to perform sufficient activities.

  The present invention relates to a cold-resistant shoe used in a work place handling a cryogenic liquid typified by liquid nitrogen and liquefied natural gas, wherein the bottom is formed by laminating a rubber sheet with a woven fabric made of aramid fibers. This is a cold-resistant shoe.

  According to the present invention, the bottom of the cold-resistant shoe is formed by laminating a rubber sheet with a woven fabric made of aramid fibers, so that residual stress that may occur when molding the bottom is dispersed and molded. By reducing the shrinkage rate when the temperature drops from the temperature region to the cryogenic region, it is possible to suppress the occurrence of cracks in the bottom due to the low temperature heat shrinkage even when the cold-resistant shoes are immersed in the cryogenic liquid.

  In the present invention, a material in which a low temperature rubber or a polymer film is coated on a woven fabric made of a fiber having a small decrease in physical properties even at −100 ° C. or less represented by an aramid fiber between the bottom and the midsole. It is inserted.

  According to the present invention, a woven fabric of fibers typified by an aramid fiber with little deterioration in physical properties even at −100 ° C. or less is inserted between the bottom and insole of the cold-resistant shoes. Since this woven fabric is coated with the coldest rubber or polymer film, it has airtightness, and the airtightness can be secured even at extremely low temperatures by the aramid fiber. For this reason, even if it is immersed in a cryogenic liquid and cracks occur in the sole and the cryogenic liquid enters the cold-resistant shoe, it is inserted between the sole and the midsole, and the low-temperature resistant rubber or polymer film The woven fabric coated with can prevent the penetration of cryogenic liquid.

  In the present invention, the former is formed of a woven fabric made of a heat-resistant fiber represented by aromatic polyamide and aromatic polyimide, which has no self-combustibility even when exposed to a flame, and a felt base. It is characterized by that.

  According to the present invention, on the instep portion of the cold-resistant shoe, there is no self-combustion property even when exposed to a flame, and a woven fabric and a felt fabric made of heat-resistant fibers represented by aromatic polyamide and aromatic polyimide having a high heat-resistant temperature. Even if a fire occurs due to an accident, etc., the cryogenic liquid is flammable liquefied propane gas or liquefied natural gas. Can be protected.

  According to the present invention, the bottom of the cold-resistant shoe has a laminated structure, disperses residual stress during molding, reduces the low-temperature heat shrinkage rate, and prevents cracking when immersed in a cryogenic liquid. it can.

  In addition, according to the present invention, even if a crack occurs in the sole and the cryogenic liquid tries to penetrate into the cold-resistant shoe, the woven fabric is coated with a cryogenic rubber or a polymer film inserted between the sole and the midsole. The cloth can prevent the penetration of the cryogenic liquid and ensure safety.

  Further, according to the present invention, even if a flammable cryogenic liquid flows out and a fire or the like further occurs, it is possible to ensure the safety of an operator who performs emergency evacuation or fire fighting activities.

  FIG. 1 shows a schematic cross-sectional configuration of a cold-resistant shoe 1 according to an embodiment of the present invention. The structure itself of the cold-resistant shoes 1 of this embodiment is equivalent to the cross-sectional structure of a general rubber bottom waterproof shoe. In the cold-resistant shoes 1, the upper 2 is suspended from the bottom surface and fixed to the midsole 3 by sewing with an adhesive or a metal needle, and then the bottom 4 is attached and molded. Further, it is reinforced with a rubber rim winding tape 5. In a general rubber-bottom waterproof shoe, a compression molding material mainly made of paper is used for the insole 3. When such a material is used for the insole 3, the airtightness is lost when a crack penetrating the outsole 8 occurs. Even when a plastic material having airtightness is used for the insole 3, the liquid permeates through the gap between the suspended upper 2 and the insole 3 or the cut surface of the upper 2. End up.

  FIG. 2 shows a cross-sectional configuration of the bottom 4 of FIG. FIG. 2A shows an overall cross section, and FIG. 2B shows an enlarged part thereof. The bottom 4 of the present embodiment is a chopped strand obtained by cutting a typical aramid fiber filament 11 as a fiber that does not deteriorate in physical properties such as strength and flexibility even at −100 ° C. or less to the bottom rubber 10, that is, a fiber chop. The bottom rubber 10 is vulcanized by mixing in the form. When the aramid fiber chop is mixed, a slight space 12 is generated between the periphery of the aramid fiber filament 11 and the bottom rubber 10. It is considered that this small space 12 has a function of relaxing and absorbing stress concentration at the time of low-temperature heat shrinkage, and exhibits the effect of preventing the occurrence of cracks at extremely low temperatures. This space 12 can be efficiently generated when the aramid fiber filament 11 is not subjected to chemical treatment or the like for improving the adhesion to rubber.

  FIG. 3 shows a cross section of the bottom rubber 10 vulcanized and molded without mixing the chops of the aramid fiber filaments 11. The space 12 as shown in FIG. 1 is not formed at all.

  The chopping of the aramid fiber filament 11 related to the bottom 4 of the present embodiment is performed in a kneading process using a metal roll for the bottom rubber 10 before vulcanization. In general, when a fiber chop is kneaded with rubber, chemical processing is performed to provide adhesion to rubber, but in this embodiment, chemical processing is not performed for the reasons described above.

  In this embodiment, in order to determine the mixing ratio of the chops of the aramid fiber filaments 11, the bottom 4 having a changed fiber chop mixing ratio is formed, and a 20-minute liquid nitrogen immersion test is performed. The test results are shown in Table 1 below.

  In Table 1, o indicates no cracking, and x indicates cracking. In addition, as the shape of the bottom 4 formed by the chop mixing method, a block pattern often seen in mountain climbing shoes or the like is selected. Moreover, the shape of the bottom 4 by the multilayer structure mentioned later is made into the roll bottom, and it is testing simultaneously.

  As the chop of the aramid fiber filament 11 used for the test, two kinds of materials having chop lengths of 3 mm and 6 mm are used. The impact test is performed by dropping the concrete floor from a height of 1 mm, and the load test is performed by applying a load of 100 kg. From the test results in Table 1, it is clear that if the aramid fiber filament 11 having a chop length of 3 mm is mixed in an amount of 12% or more, cracks do not occur in the bottom 4 in normal use. The mixing ratio described here is expressed as wt% with respect to the weight, and is a value relative to the total amount of rubber obtained by adding a compounding agent such as carbon to pure rubber. If the mixing rate exceeds 20%, the kneading operation becomes difficult and the production becomes impossible. Therefore, the mixing ratio of the aramid fiber filament 11 as a chop is appropriately 12 to 20%.

  The chop of the aramid filament 11 is loosened to a substantially filament state during the kneading process and is dispersed in the bottom rubber 10. That is, the bottom rubber 10 is divided into innumerable cells by the aramid fiber filaments 11 and can be captured as an aggregate of cells. In the contraction process when cooling from the vulcanization temperature to the extremely low temperature range, the generated stress is dispersed in the fine cells and is not concentrated locally. In particular, in a block pattern typified by a shoe sole of a mountain climbing shoe, stress tends to concentrate on the corner of the lower part of the block, but it is possible to prevent the occurrence of cracking as shown in Table 1.

  FIG. 4 shows a cross-sectional structure of the outsole 14 according to another embodiment of the present invention. The bottom 14 of the present embodiment has a multilayer structure of an aramid fiber woven fabric 15 and a rubber sheet 16, and the stress and strain generated in the rubber sheet 16 from the vulcanization temperature to the extremely low temperature are caused by the aramid fiber woven fabric. 15 is dispersed and relaxed and absorbed. Thereby, even if the rubber sheet 16 shrinks at a low temperature, the aramid fiber woven fabric 15 can suppress the occurrence of cracks.

  FIG. 5 shows a schematic cross-sectional structure of a cold-resistant shoe 21 as still another embodiment of the present invention. In this embodiment, parts corresponding to those in the embodiment of FIG. 1 are denoted by the same reference numerals, and redundant description is omitted. In this embodiment, a laminate material 22 as shown in FIG. 6 is inserted between the bottom 4 and the midsole 3. For example, the laminate 22 has a three-layer structure in which a mixed rubber sheet of natural rubber and butadiene rubber having a thickness of 1 mm is attached to both sides of an aramid fiber woven fabric 23 having a thickness of 0.8 mm and a coating 24. Further, a multilayer structure can be formed. The roll bottom shown in Table 1 is formed in such a multilayer structure.

The cold-resistant shoes 21 as shown in FIG. 5 can be manufactured by the steps (1) to (4) as shown in FIG.
(1) Cut the upper 2 and fix it to the insole 3.
(2) Next, a laminate material 22 as shown in FIG. 6 is bonded with a rubber adhesive.
(3) The rubber-made wrapping tape 5 is bonded and reinforced from the upper 2 to the laminate 22.
(4) The bottom 4 is attached to a rubber adhesive.

  FIG. 8 shows a schematic configuration of an apparatus for the purpose of testing the airtightness of the test body 29 before the main base 4 is pasted in the embodiment of FIG. The test body 29 is installed in a metal pad 30, and liquid nitrogen 31 is supplied from the supply nozzle 32 into the metal pad 30. The change over time in the temperature inside the shoe sole is measured by a thermocouple 33.

  FIG. 9 shows an example of the measurement result. In FIG. 9, the temperature of the upper part rises after about 600 seconds, because the liquid nitrogen 31 of the metal pad 30 is full, so that the supply of the liquid nitrogen 31 from the supply nozzle 32 is stopped. This is because it was suspended. The upper part directly hits the liquid nitrogen 31 supplied from the supply nozzle 32 and is easily affected by this. Considering the configuration of the test apparatus as shown in FIG. 8, although a temperature rise is seen, it is not a problem. Since the shoe sole remains immersed in the liquid nitrogen 31, the temperature continues to decrease thereafter. However, even after about 25 minutes, the temperature inside the shoe is -160 ° C and does not reach -196 ° C, which is the temperature of the liquid nitrogen 31. Therefore, the liquid nitrogen 31 does not permeate the inside of the test body 29 and proves that the airtightness is maintained by the laminate 22. Since the test body 29 does not have the bottom 4 attached thereto, the temperature drop is expected to be further reduced if the bottom 4 is attached. Even if a cryogenic liquid invades when the bottom 4 is cracked, airtightness can be secured. Therefore, even if immersed in a cryogenic liquid as in the bottom 4 of each of the embodiments described above, the crack is not generated. If the bottom 4 that does not occur is used, safety can be further enhanced.

  FIG. 10 shows a cross-sectional structure suitable for the upper 2 in each of the embodiments described above, and FIG. 11 shows an overall cross-sectional structure when used as the upper 2 of the embodiment of FIG. As the upper 2, a woven fabric 40 made of an aromatic polyamide fiber is disposed on the outermost side. On the surface of the woven fabric 40, a coating 41 made of silicon resin for maintaining airtightness is formed. Two felt fabrics 42 having a thickness of 5 mm made of aromatic polyamide fibers are arranged inside the woven fabric 40 provided with the coating 41. Furthermore, the quilting material | dough 43 is arrange | positioned inside. The quilting fabric 43 is formed by stitching together two felt fabrics 44 having a thickness of 2 mm made of aromatic polyamide fibers and a woven fabric 45 made of aromatic polyamide fibers. By inserting such a quilting material 43, the heat insulation can be improved.

  As shown in FIG. 11, even in the structure of the shoe sole, one felt fabric 42 having a thickness of 5 mm made of an aromatic polyamide fiber is arranged inside the bottom sole 4, the laminate material 22, and the midsole 3, The quilting fabric 43 is sewn together. Furthermore, in order to improve the protection against cooling from the foot, a 7 mm-thick felt fabric 46 made of aromatic polyamide fiber is arranged. FIG. 12 shows changes in the temperature of the skin surface of the foot when the cold-resistant shoes 21 by such use are attached to the thermal mannequin and liquid nitrogen is continuously applied for 25 minutes.

  As in FIG. 8, the measurement is performed by placing the cold-resistant shoes 21 in the metal pad 30 and pouring the toe portion, the heel portion, and the liquid nitrogen. In this test, since the metal pad 30 having a depth greater than that of the heel is used, the upper part is always immersed in liquid nitrogen. The liquid nitrogen 31 and the metal pad 30 start to accumulate about 240 seconds after the start of the test. Before this, the temperature of the cold-resistant shoes 21 is higher than that of the liquid nitrogen 31, and the liquid nitrogen evaporates to cool the cold-resistant shoes 21, so that it does not remain much in the metal pad 30.

  At the end of the test, the skin surface temperature of the toes and upper part is about 13 ° C., and the buttocks are 18 ° C. The cold-resistant shoes 21 of the present embodiment are not evacuated from sudden leakage due to a cryogenic liquid accident or the like, without lowering to −3 to −4 ° C., which is a temperature at which people suffer from frostbite. Or it is clear that it can sufficiently withstand the emergency repair work of the leaked part.

Next, assuming an accident when a flammable cryogenic liquid such as leaked liquefied propane gas or liquefied natural gas burned, a flame protection test by ISO DIS 9151 of the upper of the cold-resistant shoe 21 was performed. As a result of the test, it was found that the 12 ° C. temperature rise time was 58 seconds and the 24 ° C. temperature rise time was 95 seconds. This test measures the temperature rise on the back side of the fabric when a heat amount of 80 kW / m ^{2 is} applied to the surface of the fabric, and evaluates the protection against flame. A public fire engine evaluates fire fighting clothes using a 24 ° C temperature rise time of 15 seconds as a guide. Considering this guideline, it can be said that the cold-resistant shoes 21 of the present embodiment have sufficient protection against flames by having about six times the performance.

  In the cold-resistant shoes 1 and 21 of each embodiment described above, a rubber mixed with 12 to 20 wt% of aramid fiber chop is adopted as the material of the bottom 4, and the cryogenic temperature typified by liquid nitrogen or liquefied natural gas is used. Even when the feet are immersed in the cryogenic liquid due to the outflow of the cryogenic liquid due to a sudden accident or the like in the operation of handling the liquid, it is possible to prevent the bottom 4 from being cracked due to the low temperature thermal contraction. Further, in the cold-resistant shoes 21 having an airtight structure by the laminate material 22, a large force is locally applied, and even if the bottom 4 is cracked by any chance, it is possible to prevent the cryogenic liquid from penetrating into the shoes. It has a safety function. In addition, by using heat-resistant fiber represented by aromatic polyamide or aromatic polyimide for the upper 2, it can be used against flames when burning flammable gases such as liquefied propane gas and liquefied natural gas. It has sufficient protection. Therefore, in the workplace that handles cryogenic liquids such as liquid nitrogen and liquefied natural gas, if you wear cold-resistant shoes 1 and 21, emergency evacuation is possible even if the cryogenic liquid leaks due to an accident such as an earthquake. It is possible to secure walking necessary for work such as emergency repair of leaked parts.

The following embodiments are possible for the present invention.
(1) In cold-resistant shoes used in workplaces handling cryogenic liquids typified by liquid nitrogen and liquefied natural gas, chopped strands of fibers with little deterioration in physical properties even at temperatures of −100 ° C. or lower typified by aramid fibers A cold-resistant shoe characterized by being formed of mixed rubber.

  The outsole of the cold-resistant shoes is formed of rubber mixed with chopped strands of fibers with little deterioration in physical properties even at −100 ° C. or lower. Since chopped strands of such fibers typified by aramid fibers are mixed with rubber, the residual stress when molding as the bottom is dispersed with aramid fibers, and from the molding temperature range to the cryogenic range By reducing the shrinkage rate up to this point, even if the shoe sole is immersed in a cryogenic liquid, it is possible to suppress the occurrence of cracks in the sole due to the low-temperature heat shrinkage.

  Even in the workplace where cryogenic liquids such as liquid nitrogen and liquefied natural gas are handled, there is an outflow of cryogenic liquid due to a sudden accident, etc., even when the feet are immersed in the cryogenic liquid, It is possible to prevent the occurrence of cracks at the bottom due to low temperature heat shrinkage.

  (2) In cold-resistant shoes used in workplaces handling cryogenic liquids typified by liquid nitrogen and liquefied natural gas, the woven fabric is made of fibers with little deterioration in physical properties even at temperatures of −100 ° C. or lower, typified by aramid fibers. A cold-resistant shoe, wherein a rubber sheet is laminated in multiple layers.

  The bottom of the cold-resistant shoe is formed by laminating multiple layers of woven fabric consisting of fibers with little deterioration in physical properties even at -100 ° C or lower, and a rubber sheet, so the residual stress that can occur when molding the bottom is dispersed In addition, by reducing the shrinkage rate when the temperature drops from the molding temperature region to the cryogenic region, even if the cold-resistant shoes are immersed in the cryogenic liquid, it is possible to suppress the occurrence of cracks in the bottom due to the low temperature heat shrinkage .

1 is a front sectional view showing a schematic structure of a cold-resistant shoe 1 according to an embodiment of the present invention. FIG. 2 is an overall cross-sectional view and a partially enlarged cross-sectional view of the bottom 4 of FIG. 1. FIG. 2 is a cross-sectional view when the aramid fiber filament 11 is not mixed in the bottom 4 in the cold resistant shoe 1 of FIG. 1. It is sectional drawing which shows the structure of the bottom 4 of other form of implementation of this invention. It is front sectional drawing of the cold-resistant shoes 21 as another form of implementation of this invention. It is sectional drawing of the laminate material 22 of FIG. It is the simplified perspective view which shows the manufacturing process of the cold-resistant shoes 21 of FIG. FIG. 6 is a simplified side cross-sectional view showing a configuration of an apparatus for performing a test for the purpose of investigating airtightness of a test body 29 in a state in which the bottom 4 is not attached to the cold-resistant shoes 21 of FIG. 5. It is a graph which shows the result of the airtight test with respect to the test body 29 of FIG. It is sectional drawing which shows the structure of the upper 2 with the cold-resistant shoes 1 and 21 of FIG. 1 or FIG. FIG. 6 is a partial cross-sectional view showing a detailed cross-sectional structure of the cold-resistant shoe 21 of FIG. 5. It is a graph which shows the test result about the protective function of the cold-resistant shoes 21 shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,21 Cold-resistant shoes 2 Upper material 3 Middle bottom 4,14 Bottom bottom 10 Bottom rubber 11 Aramid fiber filament 12 Space 15,23 Aramid fiber woven fabric 16 Rubber sheet 22 Laminating material 24 Coating 29 Specimen 31 Liquid nitrogen 33 Thermocouple 40 Woven cloth 41 Coating

Claims (3)

  In a cold-resistant shoe used in a workplace that handles a cryogenic liquid typified by liquid nitrogen and liquefied natural gas, the sole is formed by laminating a rubber sheet with a woven fabric made of aramid fibers. Cold resistant shoes.   A material coated with a low temperature resistant rubber or polymer film is inserted between the main bottom and the midsole with respect to a woven fabric composed of fibers having little physical property deterioration even at −100 ° C. or less represented by an aramid fiber. The cold-resistant shoe according to claim 1.   The upper is formed of a woven fabric and a felt fabric made of a heat-resistant fiber represented by aromatic polyamide and aromatic polyimide which are not self-combustible even when exposed to a flame and have a high heat-resistant temperature. The cold-resistant shoes according to 1 or 2.

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