KR20220087161A - Highly insulating vulcanized rubber composition, footwear article thereof and manufacturing mehtod thereof - Google Patents

Abstract

The highly insulating vulcanized rubber composition of the present invention, a shoe part using the same, and a manufacturing method thereof can improve work efficiency and work stability by using carbon fiber to improve both electrical insulation and lightness.
In addition, the highly insulating vulcanized rubber composition of the present invention, a shoe part using the same, and a method for manufacturing the same can improve the electrical concentration by improving the dispersibility of the composition and at the same time have excellent mechanical strength even at a high voltage.

Description

Highly insulating vulcanized rubber composition, shoe parts using same, and manufacturing method thereof

The present invention relates to a highly insulating vulcanized rubber composition, a shoe part using the same, and a method for manufacturing the same, and more particularly, by using carbon fiber to improve electrical insulation to improve lightness and at the same time improve dispersibility of the composition. It relates to a highly insulating vulcanized rubber composition with improved electrical concentration, a shoe component using the same, and a method for manufacturing the same.

Insulation, a type of safety boots, has been established with the basic 14,000V withstand voltage characteristics as the standard, but as the industry advances, the demand for insulation that requires a non-standardized 30,000V withstand voltage is increasing in Korea. Current insulation protects workers from electricity, but it weighs more than 1.2 kg (based on 265 mm). As a result, work fatigue increases and there is a risk of falling or falling while working.

Specifically, the weight of the outsole in direct contact with electricity is increased to increase the weight of the outsole in direct contact with electricity to secure high-voltage insulation characteristics, so the weight of the outsole is 25% higher than that of general safety shoes. As a result, the fatigue level of workers due to the weight of insulation is higher than that of the general work group by more than 30%.

That is, the existing rubber composition and shoe parts using the same have a limitation in that it is difficult to achieve electrical insulation and lightness at the same time. In addition, mechanical properties such as durability are deteriorated at high voltage, and the dispersibility of the composition is lowered, and there is a limit in that an electric concentration phenomenon occurs.

Republic of Korea Patent Registration 10-1662007

The first object to be solved by the present invention is to provide a highly insulating vulcanized rubber composition in which both electrical insulation and lightness are improved using carbon fiber, a shoe part using the same, and a manufacturing method thereof.

A second object to be solved by the present invention is to provide a highly insulating vulcanized rubber composition that has excellent mechanical properties even at high voltage and has improved electrical concentration by improving the dispersibility of the composition, a shoe component using the same, and a manufacturing method thereof.

In order to solve the above problems, the present invention provides a rubber composition comprising 5 to 15 parts by weight of carbon fibers with respect to 100 parts by weight of raw rubber, and wherein the carbon fibers have an average length of 0.3 to 6 mm.

According to a preferred embodiment of the present invention, the raw rubber is natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber ( It may be any one or more selected from the group consisting of rubbers such as nitrile-butadiene rubber, NBR) and ethylene propylene monomer rubber (EPDM).

According to a preferred embodiment of the present invention, 10 to 50 parts by weight of a filler is further included based on 100 parts by weight of the raw rubber, and the filler is silica, carbon black, clay, magnesium carbonate, and calcium carbonate. It may be any one or more selected from.

In addition, the present invention provides a highly insulating vulcanized rubber composition comprising the step of kneading the raw rubber after inputting and mixing 5 to 15 parts by weight of carbon fiber and 10 to 50 parts by weight of a filler with respect to 100 parts by weight of the raw rubber A manufacturing method is provided.

According to a preferred embodiment of the present invention, an additive, a vulcanization accelerator and a vulcanizing agent are further added in the mixing step.

According to a preferred embodiment of the present invention, the kneading step may be performed at a temperature of 80 ~ 160 ℃ at 20 ~ 40rpm.

Furthermore, the present invention provides a shoe component manufactured using any one of the above compositions.

The highly insulating vulcanized rubber composition of the present invention, a shoe part using the same, and a method for manufacturing the same can improve work efficiency and work stability of workers who are wearing boots by improving both electrical insulation and lightness by using carbon fiber.

In addition, the highly insulating vulcanized rubber composition of the present invention, a shoe component using the same, and a method for manufacturing the same can improve the electric concentration by improving the dispersibility of the composition and at the same time have excellent mechanical properties even at a high voltage.

1 is a process flow diagram according to a preferred embodiment of the present invention.
2 is a process flow diagram according to a preferred embodiment of the present invention.
3 is a view showing a process for measuring the dielectric breakdown strength of a flat specimen according to a preferred embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily carry out the present invention.

As described above, the conventional vulcanized rubber composition and shoe parts using the same have a limitation in that it is difficult to achieve electrical insulation and lightness at the same time. In addition, mechanical properties such as durability are deteriorated at high voltage, and the dispersibility of the composition is lowered, and there is a limit in that an electric concentration phenomenon occurs.

Accordingly, the present invention provides a high-insulating rubber composition comprising carbon fibers in an amount of 5 to 15 parts by weight based on 100 parts by weight of the raw rubber, and wherein the carbon fibers are carbon fibers having an average length of 0.3 to 6 mm to solve the above-mentioned limitations. searched for.

Accordingly, the present invention can improve work efficiency and work stability by improving both electrical insulation and lightness by using carbon fiber. In addition, the present invention improves the electric concentration phenomenon by improving the dispersibility of the composition and at the same time has excellent insulation performance.

First, the raw material rubber will be described.

The raw rubber refers to a rubber used as a base material of the rubber composition of the present invention, and high-temperature/high-pressure vulcanized rubbers may be used.

According to a preferred embodiment of the present invention, the raw rubber is natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber ( It may be any one or more selected from the group consisting of rubbers such as nitrile-butadiene rubber, NBR) and ethylene propylene monomer rubber (EPDM).

In this case, 'any one or more' may mean any one, two or more, or a combination of two or more.

Next, carbon fiber, which is a conductive filler, will be described.

Carbon fiber means a carbon material having a fiber length of 90% by weight or more by mass content of carbon element. Carbon fiber is a material that combines the characteristics of carbon material and fiber form. Heat resistance, chemical stability, electrical and thermal conductivity, dimensional stability according to low thermal expansion, low density, friction and abrasion characteristics, X-ray permeability, electromagnetic wave shielding, bio-friendly It has excellent characteristics such as consistency and flexibility. In addition, it is possible to impart remarkably excellent adsorption properties depending on the activation conditions. The electrical conductivity of carbon fiber depends on crystallinity, and generally corresponds to a conductor having an electrical resistance value of 0.5 ~ 0.8 × 10 ^-3 Ω·cm.

The rubber composition of the present invention contains 5 to 15 parts by weight of carbon fiber based on 100 parts by weight of the raw rubber. Accordingly, the present invention has the effect of securing a desired level of hardness and insulation while maintaining high tensile strength.

If the carbon fiber is added to less than 5 parts by weight, the tensile strength and elongation can be maintained high, but there may be problems in that hardness and insulation properties are lowered. Strength and elongation are significantly lowered, density and hardness are increased more than necessary, and there may be problems in that electricity cannot be prevented through relatively well high voltage.

In addition, the average length of the carbon fiber is 0.3 ~ 6 mm. This means that carbon fibers are cut to an average length of 0.3 to 6 mm. Preferably, carbon fibers having an average length of 1 to 3 mm can be used, and through this, dispersibility can be improved, so that a uniform composition can be obtained.

Next, a filler is demonstrated.

According to a preferred embodiment of the present invention, it may further include a filler, and the filler may use a variety of materials commonly used in the art, and more preferably silica, carbon black, clay, carbonic acid. It may be any one selected from the group consisting of magnesium (MgCO ₃ ) and calcium carbonate (CaCO ₃ ). The filler has an effect of improving cutting properties, chipping properties, tear resistance and abrasion resistance, thereby improving the mechanical strength of the rubber composition.

When the filler does not satisfy the specific surface area range, there may occur a problem in that the reproducibility of mechanical strength such as tear resistance and abrasion resistance of the rubber composition is deteriorated.

Preferably, the filler may be included in an amount of 20 to 40 parts by weight based on 100 parts by weight of the raw rubber, and more preferably, it may be included in an amount of 25 to 35 parts by weight based on 100 parts by weight of the raw rubber. When the filler is included in this way, the dispersibility of the composition is improved, thereby improving the mechanical strength of the rubber composition, such as tear resistance and abrasion resistance. If carbon fibers are used alone without including fillers, there may be a problem in that the dispersion of carbon fibers becomes non-uniform.

The present invention may further include an additive. In addition, the additive may be any one or more selected from the group consisting of zinc oxide, stearic acid, and polyethylene glycol.

Zinc oxide can improve heat resistance and vulcanization rate, stearic acid can improve dispersibility and processability of additives, and polyethylene glycol is coated on silica added as a filler. It is possible to prevent the vulcanization time from being prolonged due to unnecessary combination of the filler and the vulcanization accelerator.

Specifically, since numerous silanol groups exist on the silica surface, the interaction between the filler aggregates is very strong, and thus may not be easily dispersed in non-polar rubber. In addition, the silanol groups on the surface of the filler adsorb them by hydrogen bonding with the polar organic substances present in the rubber composite material. It forms strong hydrogen bonds and is well adsorbed to the surface. Accordingly, the vulcanization time is extended due to unnecessary bonding of the filler and the vulcanization accelerator, and there is an effect that can be suppressed by adding polyethylene glycol.

According to a preferred embodiment of the present invention, the additive may be included in an amount of 5 to 10 parts by weight based on 100 parts by weight of the raw rubber. More preferably, it may contain 2 to 8 parts by weight of zinc oxide, 0.1 to 2 parts by weight of stearic acid, and 0.5 to 3 parts by weight of polyethylene glycol based on 100 parts by weight of the raw rubber. More preferably, it may contain 4 to 6 parts by weight of zinc oxide, 0.5 to 1.5 parts by weight of stearic acid, and 1 to 2 parts by weight of polyethylene glycol based on 100 parts by weight of the raw rubber.

In this case, the crosslinking reaction can be maintained at an appropriate rate, thereby improving productivity. If the additive is included below the above range, a problem in that the crosslinking reaction is excessively slow may occur. This may cause a problem in which a blooming phenomenon occurs.

The present invention may further include a vulcanization accelerator. In addition, the vulcanization accelerator is a thiazole type such as 2-mercapto benzo thiazole, dibenzothiazyl disulfide, tetramethylthiuram disulfide, tetramethyl Thiuram such as thiuram monosulfide (Tetramethylthiuram monosulfide), zinc dibutyldithiocarbamate (Zinc dibutyldithiocarbamate), zinc diethyldithiocarbamate (Zinc diethyldithiocarbamate), such as dithiocarbamate (Zinc diethyldithiocarbamate) may be any one or more selected from the group consisting of have.

The vulcanization accelerator has the effect of reducing the crosslinking time by increasing the vulcanization rate when manufacturing the rubber composition, and at the same time lowering the crosslinking temperature and reducing the amount of the vulcanizing agent used. In addition, there is an effect that can improve the quality of the rubber product using the rubber composition.

According to a preferred embodiment of the present invention, the vulcanization accelerator may be included in an amount of 1 to 3 parts by weight based on 100 parts by weight of the raw rubber. More preferably, 0.45 to 1.4 parts by weight of 2-mercaptobenzothiazole, 0.45 to 1.4 parts by weight of dibenzothiazyl disulfide, and 0.1 to 0.2 parts by weight of tetramethylthiuram dicuffide based on 100 parts by weight of the raw rubber can

In this case, there is an effect of uniformly improving mechanical strength such as abrasion resistance and strength. If the vulcanization accelerator is included in less than the above range, the vulcanization time is delayed and the productivity is lowered. This increasing problem may occur.

The present invention can vulcanize the rubber composition by further including sulfur as a vulcanizing agent. Through this, it is possible to improve heat resistance and crosslinking density by reducing the spacing between rubber molecular chains.

According to a preferred embodiment of the present invention, the vulcanizing agent may be further included in an amount of 0.5 to 2 parts by weight based on 100 parts by weight of the raw rubber. More preferably, 1 to 1.5 parts by weight of the vulcanizing agent may be further included with respect to 100 parts by weight of the raw rubber. In this case, crosslinking density and mechanical strength can be improved, and heat resistance can be improved.

On the other hand, the present invention may further include additives, vulcanization accelerators, vulcanizing agents, etc. used in the conventional rubber industry in some cases.

In addition, the present invention provides a highly insulating vulcanized rubber composition comprising the step of kneading the raw rubber after inputting and mixing 5 to 15 parts by weight of carbon fiber and 10 to 50 parts by weight of silica with respect to 100 parts by weight of the raw rubber A manufacturing method is provided.

Hereinafter, it will be described in detail except for the content overlapping with the above-mentioned content.

1 is a process flow diagram according to a preferred embodiment of the present invention. Referring to Figure 1, the vulcanized rubber composition manufacturing method of the present invention includes the step of kneading the raw rubber after inputting (S1) and 5 to 15 parts by weight of carbon fiber and 10 to 50 parts by weight of silica based on 100 parts by weight of the raw rubber. It includes the step of adding and mixing (S2).

First, the step (S1) of kneading the raw rubber after input will be described.

Step S1 may be performed by pre-injecting raw rubber and mixing it evenly using heat and machines for a certain period of time to win. In the case of pre-kneading the raw rubber as described above, there is an advantage in that it is possible to more easily disperse and mix the additives added thereafter.

Meanwhile, step S1 may be performed in a kneader, and preferably may be performed at a temperature of 80 to 160° C. at 20 to 40 rpm. More preferably, it may be carried out at a temperature condition of 70 ~ 140 ℃. In addition, the kneading may be performed for 0.1 to 3 minutes.

Specifically, the rubber can be softened by pre-injecting the raw rubber into a kneader maintaining the above temperature range and kneading at 20 to 40 rpm for 0.1 to 3 minutes.

Next, the step (S2) of adding and mixing 5 to 15 parts by weight of carbon fiber and 10 to 50 parts by weight of a filler with respect to 100 parts by weight of the raw rubber will be described.

Step S2 may be performed by adding carbon fibers and silica satisfying the above content ranges to the raw rubber kneaded through step S1, and then dispersing and mixing. In addition, step S2 may be performed for 5 to 20 minutes.

The step S2 may be performed by further adding an additive, a vulcanization accelerator and a vulcanizing agent in addition to carbon fiber and silica. Thereafter, the rubber composition can be obtained by removing moisture.

In this regard, Figure 2 is a process flow diagram according to a preferred embodiment of the present invention. Referring to FIG. 2 , the method for preparing a vulcanized rubber composition of the present invention includes the step of kneading the raw rubber after input (S1) and 5 to 15 parts by weight of carbon fiber and 10 to 50 parts by weight of the filler based on 100 parts by weight of the raw rubber. , it can be seen that 5 to 10 parts by weight of an additive, 1 to 3 parts by weight of a vulcanization accelerator, and 0.5 to 2 parts by weight of a vulcanizing agent are added and mixed and mixed (S2) can be included.

On the other hand, in some cases, preferably, the steps S1 and S2 may be performed in a kneader, but the addition and mixing of the vulcanizing agent may be performed in a twin-screw roll mill. That is, after performing the mixing process in the kneader, the mixed composition is lowered into a sheet form using a twin-screw mill, and then a vulcanizing agent is added to enable dispersion and mixing in the twin-screw roll mill.

In order to perform a rubber sheet using the composition of the present invention, after the mixed composition is lowered into a sheet form using a twin-screw mill, it is necessary to undergo a stabilization process for 24 hours. In this case, by allowing the stabilization to proceed sufficiently, it is possible to prevent the vulcanizing agent from reacting with the substrate when the vulcanizing agent is added later due to residual heat remaining inside, and it is possible to prevent distortion or damage to the appearance. As described above, after lowering into a sheet form, a vulcanizing agent is added, dispersion and mixing are performed in a twin-screw roll mill, the sheet is cut to a predetermined size and shape, and then the forming process can be performed by pressing with a high-temperature press. .

Furthermore, the present invention provides a shoe component manufactured by the above composition. In this case, the shoe part may refer to various parts constituting the shoe, such as an outsole and a midsole, in various ways without limitation.

Accordingly, the present invention can provide a shoe part excellent in both electrical insulation and light weight, and in particular, the outsole using the composition of the present invention is excellent in both electrical insulation and light weight to significantly reduce work fatigue of workers wearing shoes. By lowering it, work efficiency can be improved, and work stability can also be improved by securing high-voltage insulation properties.

Hereinafter, the present invention will be described in more detail based on examples.

Example 1

The raw rubber base material according to Table 1 below was put into a kneader preheated to 100 ~ 140° C., and kneaded at a speed of 30 rpm for 1 minute. Thereafter, carbon fibers having an average length of 3 mm, silica, zinc oxide, stearic acid, polyethylene glycol, and a vulcanization accelerator were added as shown in Table 1 below, and dispersion and mixing processes were performed for about 13 minutes. Next, the vulcanizing agent was added, dispersed and mixed for 3 minutes, and then lowered into a sheet form through a twin-screw roll mill, and a stabilization process was performed for 24 hours. Thereafter, sulfur was added, dispersed and mixed for 5 minutes in a twin roll mill, and a sheet with a thickness of 3 to 3.5 mm was prepared. This was molded at a pressure of 130 kg/cm ² by a press at 155° C. to prepare a plate-shaped specimen of 22 cm×22 cm×0.3 cm (width×length×thickness).

Examples 2 to 6

It was carried out in the same manner as in Example 1 except that the components and contents according to Table 1 were added.

Comparative Examples 1 to 3

It was carried out in the same manner as in Example 1 except that the components and contents according to Table 2 were added.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 raw rubber
(parts by weight) NR 0 100 0 0 0 0 NBR 100 0 100 0 100 100 EPDM 0 0 0 100 0 0 conductive filler carbon fiber ¹⁾
(3mm) 7.5 7.5 10 10 12.5 15 filler Silica ²⁾ 30 30 30 30 30 30 additive
(parts by weight) zinc oxide 5 5 5 5 5 5 stearic acid One One One One One One polyethylene glycol 1.5 1.5 1.5 1.5 1.5 1.5 vulcanization accelerator
(parts by weight) M ³⁾ One One One One One One DM ⁴⁾ One One One One One One TT ⁵⁾ 0.1 0.1 0.1 0.1 0.1 0.1 vulcanizing agent
(parts by weight) sulfur 1.2 1.2 1.2 1.2 1.2 1.2

1) Carbon fiber: Manufactured by Dongbo Chain Industry Co., Ltd.

2) Zeosil-175, specific surface area 160 ~ 190m ² /g

3) 2-Mercaptobenzothiazole

4) Dibenzothiazyl dicurphide

5) Tetramethylthiuram dicurphide

Comparative Example 1 Comparative Example 2 raw rubber
(parts by weight) NBR 100 100 conductive filler Carbon fiber ¹⁾ (3mm) 0 20 filler Silica ²⁾ 30 30 additive
(parts by weight) zinc oxide 5 5 stearic acid One One polyethylene glycol 1.5 1.5 vulcanization accelerator
(parts by weight) M ³⁾ One One DM ⁴⁾ One One TT ⁵⁾ 0.1 0.1 vulcanizing agent
(parts by weight) sulfur 1.2 1.2

1) Carbon fiber: Manufactured by Dongbo Chain Industry Co., Ltd.

2) Zeosil-175, specific surface area 160 ~ 190m ² /g

3) 2-Mercaptobenzothiazole

4) Dibenzothiazyl dicurphide

5) Tetramethylthiuram dicurphide

Experimental Example 1. Measurement of various characteristics

The specimens of Examples 1 to 6 and Comparative Examples 1 to 2 were cut using a specimen-shaped cutter that satisfies the respective measurement and test standards, and then measurements and tests were performed. The results are shown in Tables 3 and 4 below.

- Tensile strength and elongation

The measurement was carried out by cutting in the form of a dumbbell of the 'Die C' model specified in ASTM D 412. UTM was used, and the measurement speed was fixed at 500 mm/min. The measured value was rounded down from the range of 10% and expressed as an integer.

- Hardness measurement

According to ASTM D 2240 standard, the same specimen was overlapped up to a minimum of 0.6 cm, and then proceeded using a Shore A type hardness tester. During the measurement, the room temperature was adjusted to 24°C, and the result was recorded within 1 second after pressing the specimen with a hardness gauge.

- Insulation breakdown voltage and dielectric breakdown strength

In accordance with ASTM D 149 standard, connect electrodes to both sides of a 50×50 mm specimen in KS C 2301 Type 1 No. 2 insulating oil to 2,000 The voltage was increased at a rate of V/s, and the highest voltage to be destroyed was confirmed. A total of 5 times per specimen were performed and the average value was recorded. The dielectric breakdown strength measurement process is shown in FIG. 3 .

Evaluation items Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Hardness
Type A 72 73 75 74 76 78 The tensile strength
(kgf/cm ² ) 150 160 130 100 120 100 elongation
(%) 830 820 760 540 800 750 Insulation breakdown voltage (kV) 30 30 30 30 30 30 dielectric breakdown strength
(kV/mm) 10.5 10.5 11 10.5 12 10.5

Evaluation items Comparative Example 1 Comparative Example 2 Hardness
Type A 61 81 The tensile strength
(kgf/cm ² ) 120 90 elongation
(%) 870 640 Insulation breakdown voltage (kV) 27 28 dielectric breakdown strength
(kV/mm) 9 9

Referring to Tables 1 to 4, it can be seen that the present invention has excellent values for physical properties such as hardness, tensile strength, and elongation. In addition, at the same time, it can be seen that the dielectric breakdown voltage and dielectric breakdown strength also have excellent values. In particular, it can be seen from the comparative example that the existing rubber composition and the rubber product using the same had a rather high density and were heavy. On the other hand, it can be seen that the present invention has the advantage of being able to reduce the weight compared to the conventional insulating specimen because the thickness can be reduced by including the carbon fiber.

Claims (7)

A highly insulating vulcanized rubber composition comprising 5 to 15 parts by weight of carbon fiber based on 100 parts by weight of the raw rubber, wherein the carbon fiber has an average length of 0.3 to 6 mm.
According to claim 1,
The raw rubber is natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), ethylene propylene A highly insulating vulcanized rubber composition, characterized in that at least one selected from the group consisting of rubber (Ethylene propylene monomer rubber, EPDM).
According to claim 1,
It further comprises 10 to 50 parts by weight of a filler based on 100 parts by weight of the raw rubber, wherein the filler is at least one selected from the group consisting of silica, carbon black, clay, magnesium carbonate and calcium carbonate. A highly insulating vulcanized rubber composition.
A step of kneading after inputting the raw rubber; And
A method for producing a high insulating rubber composition comprising a; adding and mixing 5 to 15 parts by weight of carbon fiber and 10 to 50 parts by weight of a filler with respect to 100 parts by weight of the raw rubber.
5. The method of claim 4,
A method for producing a high insulating rubber composition, characterized in that further adding an additive, a vulcanization accelerator and a vulcanizing agent in the mixing step.
5. The method of claim 4,
The kneading step is a method for producing a highly insulating rubber composition, characterized in that it is carried out at a temperature of 100 ~ 200 rpm at 20 ~ 40 rpm.
A shoe component manufactured using the composition of any one of claims 1 to 3.

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