KR20200139029A - Composition for ceramic fiber and ceramic fiber manufactured therefrom - Google Patents

Abstract

The present invention relates to: a ceramic fiber composition containing 35 to 65 parts by weight of SiO_2, 1 to 5 parts by weight of CaO, 35 to 60 parts by weight of MgO, and 1 to 20 parts by weight of Al_2O_3, wherein a weight ratio of MgO/CaO is 10 to 35; and a ceramic fiber for salt-soluble high-temperature insulation manufactured from the ceramic fiber composition. The present invention has excellent salt solubility and thus has low human toxicity.

Description

Ceramic fiber composition and ceramic fiber manufactured therefrom TECHNICAL FIELD

The present invention relates to a ceramic fiber composition and a salt-soluble ceramic fiber for a high temperature insulating material prepared therefrom.

Ceramic fiber is a representative inorganic insulating material, and is divided into amorphous, semi-crystalline and crystalline. In addition, amorphous ceramic fibers having excellent physical properties at high temperatures include Al ₂ O ₃ -SiO ₂ (RCF-AS) and Al ₂ O ₃ -SiO ₂ -ZrO ₂ (RCF-ASZ) fibers. These ceramic fibers have excellent heat resistance and water resistance and have low thermal conductivity, so they are being applied to various products such as high-temperature insulation and fire protection in various fields such as architecture, industrial plants, and ships.

As such, ceramic fibers applied to various fields may cause harm to the human body when crushed fine fibers are inhaled and accumulated in the lungs due to low salt solubility, and thus, there is a controversy about its harmfulness. Therefore, in order to improve construction convenience and harmlessness to the human body, there is a need for a study on a salt-soluble ceramic fiber composition for minimizing harmfulness by increasing the dissolution rate in the collection solution and satisfying high temperature properties at the same time.

In this regard, Korean Laid-Open Patent No. 2017-0026704 (Patent Document 1) discloses silicon dioxide (SiO ₂ ) 30 to 60 wt%, aluminum oxide (Al ₂ O ₃ ) 7 to 28 wt%, iron dioxide (Fe ₂ O ₃ ) 0.1 to 7% by weight, and 15 to 50% by weight of alkaline earth metal oxide, and the alkaline earth metal oxide contains calcium oxide (CaO) and magnesium oxide (MgO) in a weight ratio of 1:0.1 to 1 Is disclosed. However, the mineral fiber of Patent Document 1 has a high impurity content, low heat resistance, and has a problem of melting at a high temperature of 1,000°C or higher.

Accordingly, there is a need for research and development on a ceramic fiber composition capable of manufacturing fibers having excellent salt solubility, low toxicity to the human body, and excellent physical properties at high temperatures.

Korean Patent Application Publication No. 2017-0026704 (Publication date: 2017.3.9.)

Accordingly, an object of the present invention is to provide a ceramic fiber composition capable of manufacturing fibers having excellent thermal durability, excellent salt solubility, and excellent fiber resilience, and ceramic fibers manufactured therefrom.

The present invention includes 35 to 65 parts by weight of SiO ₂ , 1 to 5 parts by weight of CaO, 35 to 60 parts by weight of MgO and 1 to 20 parts by weight of Al ₂ O ₃ , and the weight ratio of MgO/CaO is 10 to 35 It provides a fiber composition.

In addition, the present invention provides a ceramic fiber prepared from the ceramic fiber composition.

The ceramic fiber prepared from the ceramic fiber composition according to the present invention has excellent fiber resilience, and even after heat treatment at a high temperature of 1,400°C for 24 hours, the hot pre-contraction rate is 5% or less, and the dissolution rate constant for artificial body fluid is 500 ng. It is remarkably larger than /㎠·hr, so it has excellent salt solubility and has low human toxicity.

Hereinafter, the present invention will be described in detail.

Ceramic fiber composition

The ceramic fiber composition according to the present invention includes SiO ₂ , CaO, MgO and Al ₂ O ₃ .

The ceramic fiber composition of the present invention as described above has a large dissolution rate constant for artificial bodily fluids, the fiber produced therefrom has low harm to the human body, and it is possible to manufacture ceramic fibers for high-temperature insulation materials having salt solubility using existing equipment. .

Hereinafter, each component of the ceramic fiber composition of the present invention will be described in detail.

SiO ₂

SiO ₂ is a network former oxide that serves to form the basic skeleton of glass.

Since the content of SiO ₂ affects the fiber resilience and salt solubility of the fabricated fibers, it is necessary to properly control the fiber resilience and salt solubility of the fabricated fibers. Specifically, the SiO ₂ may be included in the composition in an amount of 35 to 65 parts by weight. For example, the SiO ₂ may be included in the composition in an amount of 40 to 58 parts by weight. When the content of SiO ₂ is within the above range, the problem that the diameter of the fiber prepared from the composition containing the same is too large is prevented, and the heat resistance of the fiber is improved.

CaO

CaO acts as a fluxing agent as a modifier oxide, and improves durability such as brittleness of fibers prepared from a composition containing the same.

The CaO may be included in the composition in an amount of 1 to 5 parts by weight. For example, the CaO may be included in the composition in an amount of 2 to 3 parts by weight. When the content of CaO is within the above range, it is possible to prevent the problem of deteriorating elasticity due to excessively improved brittleness of the fiber prepared from the composition containing the same, a problem of lowering heat resistance, and a problem of insufficient melt viscosity.

MgO

MgO acts as a fluxing agent as a modifier oxide, and serves to increase the elasticity of fibers prepared from a composition containing the same. In particular, MgO controls the heat resistance, compressive strength, and compression resilience of the manufactured fibers at high temperatures, and controls the solubility of fibers in artificial body fluids.

The MgO may be included in the composition in an amount of 35 to 60 parts by weight. For example, the MgO may be included in the composition in an amount of 40 to 55 parts by weight. When the content of MgO is within the above range, the elasticity of the produced fiber is increased, so that the fiber resilience is excellent, and a problem of insufficient melt viscosity can be prevented.

Al ₂ O ₃

Al ₂ O ₃ is an intermediate oxide that serves to improve the biodegradability and thermal properties of the composition containing the same, and the elasticity of the fibers produced therefrom. In addition, depending on the coordination number of Al ³⁺ , some may replace the role of SiO ₂ or serve as a modifier oxide, which may vary depending on the content of other modified oxides.

The Al ₂ O ₃ may be included in the composition in an amount of 1 to 20 parts by weight. For example, the Al ₂ O ₃ may be included in the composition in an amount of 1 to 10 parts by weight. When the content of Al ₂ O ₃ is within the above range, there is an effect of improving the elasticity and thermal properties of the fiber prepared from a composition containing the same.

Other ingredients

The composition may additionally contain components such as K ₂ O, Na ₂ O, Fe ₂ O ₃ , TiO _2, etc., depending on the raw material used, so that the above components do not affect the thermal properties or physical properties of the fiber. , The total content of the components may be included in 1 part by weight or less.

The ceramic fiber composition has a weight ratio of MgO/CaO of 10 to 35. When the weight ratio of MgO/CaO is within the above range, heat resistance is increased, so that the hot pre-contraction rate decreases and the dissolution rate constant is increased.

Ceramic fiber

Further, the ceramic fiber according to the present invention is prepared from the ceramic fiber composition as described above.

The ceramic fiber has excellent fiber resilience, has an excellent hot pre-contraction rate of 5.0% or less even after 24 hours heat treatment at a high temperature of 1,400°C, and has excellent salt solubility due to a large dissolution rate constant for artificial bodily fluids, and thus has low toxicity to the human body.

For example, the ceramic fiber may have a height of 500 ml or more when the ceramic fiber is mixed with 20 g of fiber and 1 liter of water and then left standing in a 1 liter measuring cylinder. After mixing the ceramic fiber with water, the fiber recovery degree (elasticity) can be evaluated at the height at which the fiber rises when standing.

In addition, the ceramic fiber may have a dissolution rate constant of 500 ng/cm 2·hr or more, or 700 ng/cm 2·hr or more for the artificial body fluid. When the dissolution rate constant for the artificial body fluid of the ceramic fiber is 500 ng/cm 2·hr or more, there is an effect of having excellent salt solubility.

Further, the ceramic fiber may have an average particle diameter of 5 μm or less, or 4 to 5 μm. When the average particle diameter of the ceramic fiber is within the above range, there is an effect of increasing heat resistance due to an increase in fiber strength.

In addition, the ceramic fiber may have a fine fiber content of 50% by weight or less measured according to ASTM C892. When the content of the microfibrous material is 50% by weight or less, there is an effect of increasing thermal insulation due to an increase in fiber density.

In addition, the ceramic fiber may have a hot shrinkage of 5.0% or less calculated by Equation 1 below after maintaining at 1,400°C for 24 hours. When the hot pre-contraction ratio of the ceramic fiber is 5.0% or less, there is an effect of increasing the maximum use temperature of the fiber.

In Equation 1, l ₀ is a minimum distance (mm) between two points before heat treatment, and l ₁ is a minimum distance (mm) between two points after heat treatment.

Furthermore, the ceramic fiber may have a fiber recovery degree of 50% or more. At this time, the degree of fiber restoration is determined by mixing 20g of fiber and 1L of water, pulverizing with a grinder, pulverizing to an average length of 5mm, putting the pulverized product in a 1L measuring cylinder and allowing it to stand for 15 minutes to determine the maximum height of the fibers accumulated from the bottom of the measuring cylinder The degree of fiber restoration was evaluated by measuring the ratio of the maximum height of the fibers to the total height of water.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are only intended to aid understanding of the present invention, and the scope of the present invention is not limited to these examples in any sense.

[Example]

Examples 1 to 8 and Comparative Examples 1 to 12. Preparation of ceramic fibers

A ceramic fiber composition was prepared by mixing the components so as to have the composition shown in Table 1 below by a melting method of an electric current method using an electric furnace equipped with a three-phase electrode. Thereafter, the ceramic fiber composition was introduced into a conventional spinning process for producing ceramic fibers (a method in which the melt was dropped on the surface of a spinner in the form of a disk that rotates centrifugally to stretch the fibers, and at the same time, the fibers were turned into fibers by spraying high-pressure air from the rear side). Ceramic fibers were prepared.

Classification (part by weight) SiO ₂ Al ₂ O ₃ MgO CaO K ₂ O Na ₂ O Fe ₂ O ₃ TiO ₂ ZrO ₂ MgO/CaO Sum Example 1 52.72 1.9 42.56 2.25 0.13 0.01 0.41 0.02 - 18.92 100 Example 2 49.99 1.88 45.24 2.29 0.1 0.02 0.47 0.01 - 19.76 100 Example 3 47.96 1.82 47.23 2.31 0.11 0.04 0.5 0.03 - 20.45 100 Example 4 44.85 1.86 50.13 2.52 0.09 0.03 0.51 0.01 - 19.89 100 Example 5 40.5 1.25 55.4 2.1 0.14 0.05 0.52 0.04 - 26.38 100 Example 6 60.2 1.51 36.5 1.1 0.1 0.03 0.55 0.01 - 33.18 100 Example 7 42.3 18.8 37.2 1.25 0.13 0.05 0.23 0.04 - 29.76 100 Example 8 41.9 7.1 46.2 4.51 0.1 0.03 0.12 0.04 - 10.24 100 Comparative Example 1 50.1 49.9 - - - - - - - - 100 Comparative Example 2 75.9 0.4 9.4 12.5 0.2 0.1 0.2 - 1.3 0.75 100 Comparative Example 3 33.5 10.2 50.8 4.92 0.07 0.05 0.42 0.04 - 10.33 100 Comparative Example 4 37.28 24.2 36 1.91 0.11 0.08 0.37 0.05 - 18.85 100 Comparative Example 5 60.5 4.74 30.9 3.25 0.08 0.02 0.49 0.02 - 9.51 100 Comparative Example 6 36.2 1.1 61.2 1.1 0.1 0.08 0.18 0.04 - 55.64 100 Comparative Example 7 46.41 1.82 50.45 0.5 0.15 0.07 0.57 0.03 - 100.9 100 Comparative Example 8 41.84 1.52 47.93 8.1 0.14 0.05 0.39 0.03 - 5.92 100 Comparative Example 9 50.54 0.05 47.21 1.5 0.16 0.08 0.41 0.05 - 31.47 100 Comparative Example 10 59.5 4.7 29.9 5.15 0.11 0.05 0.52 0.07 - 5.81 100 Comparative Example 11 56.2 1.9 36.5 4.8 0.12 0.04 0.41 0.03 - 7.60 100 Comparative Example 12 50.2 1.7 46.2 1.2 0.16 0.05 0.47 0.02 - 38.5 100

Test example. Evaluation of physical properties of ceramic fiber

The physical properties of the ceramic fibers of Examples 1 to 8 and Comparative Examples 1 to 12 were measured in the following manner, and the results are shown in Table 3.

(1) Average particle diameter of fiber

The average particle diameter of the fiber was magnified at a high magnification of 1,000 times or more using an electron microscope, and the average particle diameter was measured by repeatedly measuring at least 500 times.

(2) Content of microfibrous material

The content of the microfibrous material was measured according to ASTM C892. Specifically, the ceramic fiber was heat-treated at 1,200° C. for 5 hours, and then 10 g of the fiber was accurately weighed (W ₀ ) to 0.0001 g. Thereafter, the fibers were put in a 30 mesh sieve and passed through the sieve by pressing them using a rubber rod. After passing the fiber through the sieve through a 50 mesh and a 70 mesh sieve, the weight (W ₁ ) of the particles remaining in each sieve was measured, and then the content of the microfiber material (Ws) was calculated using Equation 2 below. .

In Equation 2, Ws is the content of the microfiber material, W ₀ is the weight of the initial fiber, and W ₁ is the weight of the remaining fiber.

(3) Hot pre-contraction ratio

The physical properties of the fabricated fibers at high temperature were measured by the change in length at high temperature of a molded article composed of fibers. In order to measure the hot shrinkage of ceramic fibers, the fibers were prepared as a pad-shaped specimen and used in the experiment.

First, 250 g of fibers were sufficiently sponged in a 2.5% aqueous starch solution, then poured into a 300 mm×300 mm (width×length) mold, and drained through the bottom of the mold to prepare a pad. Thereafter, the pad was dried in an oven at 100° C. for 24 hours, and then cut into a size of 100 mm×100 mm×20 mm (width×length×thickness) to prepare a specimen. Thereafter, two measurement points were marked using a platinum pin on the specimen, and then the distance between the measurement points was measured using a vernier caliper, placed in a furnace, heated at 1,400°C for 24 hours, and then gradually cooled. . Thereafter, the distance between the measuring points of the cooled specimen was measured to compare the measurement results before and after heat treatment, and the hot pre-contraction rate was calculated using Equation 1 below.

[Equation 1]

In Equation 1, l ₀ is a minimum distance (mm) between two points before heat treatment, and l ₁ is a minimum distance (mm) between two points after heat treatment.

(4) Dissolution rate constant (K _dis )

In order to evaluate the biodegradability of the prepared fiber, the dissolution rate for the artificial body fluid was calculated as follows.

Specifically, the biodegradability of ceramic fibers in the body is evaluated based on the solubility of the fibers in the artificial body fluid. After comparing the residence time in the body based on the dissolution rate, the dissolution rate constant (K _dis ) Was calculated.

In Equation 3, d ₀ is the initial average fiber diameter (µm), ρ is the initial density (g/cm 3) of the fiber, M ₀ is the initial fiber mass (mg), and M is the mass of the remaining fiber after being dissolved. (Mg), and t is the experiment time (hr).

At this time, the dissolution rate is determined by placing the ceramic fibers prepared in Examples and Comparative Examples between thin layers between 0.2 μm polycarbonate membrane filters fixed with plastic filter supports and filtering artificial bodily fluids between these filters. Was measured. During the experiment, the temperature of the artificial body fluid was continuously adjusted to 37°C and the flow rate was adjusted to 135 ml/day, and the pH was maintained at 7.4±0.1 using a mixed gas of CO ₂ and N ₂ (5:95 volume ratio). .

)를 계산하였으며, 그 결과를 표 3에 나타내었다.In order to accurately measure the solubility of the fiber that occurs over a long period of time, the fiber is leached for 21 days, while inducing the filtered artificial body fluid at specific intervals (1 day, 4 days, 7 days, 11 days, 14 days, or 21 days) After analyzing the dissolved ions using an Inductively Coupled Plasma Spectrometer (ICP), the dissolution rate constant (

) Was calculated, and the results are shown in Table 3.

In addition, the content (g) of the component contained in 1L of the artificial body fluid used to measure the dissolution rate of the fiber is shown in Table 2.

Components of artificial body fluids Content (g/L) NaCl 7.120 MgCl ₂ 6H ₂ O 0.212 CaCl ₂ 2H ₂ O 0.029 Na ₂ SO ₄ 0.079 Na ₂ HPO ₄ 0.148 NaHCO ₃ 1.950 Na ₂ Tartrate 2H ₂ O 0.180 Na ₃ Citrate 2H ₂ O 0.152 90% Lactic Acid 0.156 C ₂ H ₃ NO ₂ Glycine 0.118 Na-Pyruvate 0.172 HCl (for pH adjustment) 0.750

(5) Fiber restoration degree

20 g of fibers of Examples 1 to 8 and Comparative Examples 1 to 12 were mixed with 1 L of water and pulverized for 30 seconds at 11,000 rpm using a grinder to obtain an average length of 5 mm. Thereafter, the pulverized material was put into a 1L measuring cylinder, mixed, and allowed to stand for 15 minutes to measure the maximum height of fibers accumulated from the inner bottom of the measuring cylinder. The degree of fiber restoration was evaluated as the ratio of the maximum height of the fibers to the total height of water, and the results are shown in Table 3.

division Average particle diameter (㎛) Content of fine fiber (% by weight) Hot pre-contraction rate (%) Dissolution rate constant (K _dis )(ng/㎠·hr) Maximum fiber height (ml) Fiber restoration degree Example 1 4.7 42 4.7 710 540 54% Example 2 4.8 40 4.4 740 610 61% Example 3 4.6 44 4.2 760 650 65% Example 4 4.8 46 4.1 780 680 68% Example 5 4.5 38 4.2 720 660 66% Example 6 4.8 42 4.5 760 620 62% Example 7 4.9 44 4.9 730 660 66% Example 8 4.9 43 4.8 710 630 63% Comparative Example 1 3.6 30 5.7 70 410 41% Comparative Example 2 4.1 30 6.1 330 470 47% Comparative Example 3 3.4 35 5.2 350 480 48% Comparative Example 4 3.6 38 6.4 310 450 45% Comparative Example 5 4.1 52 6.1 280 430 43% Comparative Example 6 3.8 45 7.8 250 400 40% Comparative Example 7 3.9 44 5.3 360 480 48% Comparative Example 8 3.4 51 9.2 220 250 25% Comparative Example 9 4.2 56 13.8 290 320 32% Comparative Example 10 4.3 58 19.7 320 310 31% Comparative Example 11 3.2 52 8.5 250 260 27% Comparative Example 12 4.4 53 15.4 240 280 29%

As shown in Table 3, the ceramic fibers of Examples 1 to 8 have an average particle diameter of 4.6 to 4.9 µm, and are judged to be of good quality because they are smaller than the average fiber particle diameter of 5 µm of commercial ceramic fibers. It is expected that the insulation effect of the fiber will be excellent. In addition, the ceramic fibers of Examples 1 to 8 have a fine fiber content of 50% by weight or less, a hot pre-contraction ratio of less than 5%, excellent thermal stability at high temperature, and excellent fiber resilience with a fiber recovery degree of 50% or more. Is expected to do. Further, it can be seen that the ceramic fibers of Examples 1 to 8 have a dissolution rate constant of 710 to 780 ng/cm 2·hr, which is remarkably excellent in dissolution rate in body fluid.

On the other hand, the ceramic fiber of Comparative Example 1, which is an Al ₂ O ₃ -SiO ₂ (RCF-AS)-based ceramic fiber, has a hot pre-contraction rate of 5.7%, which is insufficient in heat resistance, and the melting rate constant is 70 ng/cm 2·hr. Biodegradability is expected to be very low when inhaled into the human body. In addition, the ceramic fibers of Comparative Examples 1 to 12 had low thermal stability due to a hot precontraction ratio of more than 5.0%, and a dissolution rate constant for an artificial body fluid was less than 500 ng/cm 2 ·hr, and thus biodegradability was insufficient. Further, the ceramic fibers of Comparative Examples 1 to 12 had a fiber recovery degree of less than 50%, and the fiber recovery power was insufficient.

Claims (5)

35 to 65 parts by weight of SiO ₂ , 1 to 5 parts by weight of CaO, 35 to 60 parts by weight of MgO and 1 to 20 parts by weight of Al ₂ O ₃ , wherein the weight ratio of MgO/CaO is 10 to 35. Ceramic fiber prepared from the ceramic fiber composition of claim 1. The method according to claim 2,
The ceramic fiber has an average particle diameter of 5 μm or less, and a hot pre-contraction rate of 5.0% or less after maintaining at 1,400° C. for 24 hours. The method according to claim 2,
The ceramic fiber has a dissolution rate constant of 500 ng/cm 2·hr or more for an artificial body fluid. The method according to claim 2,
The ceramic fiber has a fiber restoration degree of 50% or more.