JP2008260876A - Low-toxic, silicone rubber-based, heat-resistant insulating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To amend the lightweight insulating material for a cosmic rocket to a safe heat-resistant insulating material for general use. <P>SOLUTION: The polysiloxane polymer used in the reference patent 1 has achieved a highly heat-resistant (500°C) insulating material (0.1 w/mk) by making it a highly pure material. This is switched to a general-purpose silicone rubber to reduce the manufacturing cost sharply and to permit the product to be used generally. Next, the average particle size of the microballoons is changed to 95-150 μm to improve the heat conductivity to 0.06 w/mk. Further, by changing the flame retardant to a low-toxic material there is provided a silicone rubber-based heat-resistant insulating material that is high in safety and versatility and has low toxicity and flame retardancy. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a low-toxic and flame-retardant silicone rubber heat-resistant heat insulating material. More specifically, the present invention relates to a low-toxic and flame-retardant silicone rubber heat-resistant heat insulating material used for building materials, heat storage tanks and tanks, chemical plants, automobiles, food machinery, testing machines, electric furnaces, and the like.

  Conventionally, as a general-purpose heat insulating material, those made of various materials are known. Typical examples include glass wool and urethane foam. In glass wool, bundled or cotton-like fibers and an air layer contained therein function as a heat insulating layer. However, when water enters the air layer or gap of glass wool, it is difficult to scatter and evaporate the water, and the heat insulating performance of glass wool is greatly reduced. Glass wool insulation is used for heat insulation in general steam pipes, heat exchangers, ducts, etc., and exterior work (racking) is performed on the outside of the insulation to protect it with steel plates, stainless steel plates, etc. Protective exterior construction is very laborious and expensive. However, even if the protective exterior material is applied, the ingress of moisture cannot be completely prevented, and the protective exterior material may be corroded or the heat insulating function may be deteriorated due to the infiltrated moisture.

  Next, a heat insulating material made of urethane foam resin is widely used for building facilities due to its excellent heat insulating property. Foamed urethane resin insulation has improved moisture absorption compared to glass wool, but it is easy to burn, spreads fires in buildings and equipment due to fire, and generates a lot of black smoke, which may hinder fire fighting activities. is there.

  As a heat insulating material that solves the problems of hygroscopicity, heat resistance, and flame retardance as described above, a lightweight heat insulating rubber composition as described in Patent Document 1 has been proposed. The heat insulating material of Patent Document 1 has characteristics such as light weight, pressure resistance, heat insulating property, heat resistant temperature of 500 ° C. (general heat insulating material glass wool is 180 ° C.), and exhibited excellent performance. In order to exhibit this excellent function, a high-purity condensed diorganopolysiloxane polymer is used. However, in order to purify this polymer to high purity, it takes a lot of labor and energy and is expensive, and the thermal conductivity is 0.1 w / mk, compared with general-purpose insulation (0.05 w / mk). It has poor thermal insulation and is not widely used except for space rockets.

Furthermore, antimony oxide and bromine phosphate compounds are used to improve the heat resistance and flame retardancy of heat insulation materials. The flame retardancy and heat resistance due to the synergistic effect of these two types of compounds are described in the patent literature. It was an essential condition for 1 heat insulating material. However, antimony oxide and bromine phosphate compounds have been pointed out to be toxic and environmental pollution problems, and development of a heat insulating material containing a safe flame retardant containing no antimony or halogen compound is desired. Recent development of flame retardants has proposed many materials with high thermal conductivity that emphasize heat dissipation, but it was a conflicting goal with the heat-resistant insulation of the present invention that requires low thermal conductivity. . Also, aluminum hydroxide has been proposed as a low-smoke flame retardant, but this material also has high thermal conductivity and cannot be expected to have heat insulation. In the background as described above, it has not been easy to develop a combination of a silicone rubber, a glass balloon and a flame retardant, and a heat insulating material having safety and versatility.
Japanese Patent No. 2990534

The object of the present invention is to provide a heat-resistant heat insulating material (thermal conductivity 0.06 w / mk) as follows.
1. To provide heat-resistant insulation that is safe and versatile without harmful flame retardants.
2. To provide a heat-resistant heat insulating material in which an air layer is not significantly reduced when a load is applied and compressed, and the heat insulation performance is not deteriorated due to moisture absorption.
3. To provide heat-resistant insulation that does not require protective exterior construction (racking).

  To achieve the above object, in the present invention, 100 to 100 parts by weight of a room temperature curable silicone rubber, 70 to 100 parts by weight of a glass balloon having an average particle size of 95 to 150 μm, an Mg compound, a Ca compound, and a silica compound A low-toxic and flame-retardant silicone rubber-based heat-resistant heat insulating material comprising 2 to 20 parts by weight of one or two selected from 5 and 10 parts by weight of a curing agent To do.

The present invention is as described in detail below, and has the following particularly excellent effects.
1. Since the heat-resistant heat insulating material according to the present invention does not contain halogen, antimony, etc., there are few problems of environmental pollution, low toxicity, high safety, and no special raw materials are used, so it is highly versatile.
2. The heat-resistant heat insulating material according to the present invention has good interfacial adhesion between the silicone rubber and the glass balloon, and does not have a large air layer like the heat insulating material made of glass wool. There is no decrease in the number of layers, and there is little deterioration in the heat insulation performance due to the ingress of moisture from outside air.
3. Since the heat-resistant heat insulating material according to the present invention has a dense structure with pressure resistance, it is difficult for moisture from outside air to enter and does not require protective exterior construction (racking).
4). The heat-resistant heat insulating material according to the present invention comprises a composition of a heat-resistant 200 ° C. silicone rubber having an inorganic siloxane bond and a glass balloon having heat resistance and heat insulating properties, and exhibits excellent heat resistance and heat insulating properties.

Hereinafter, the present invention will be described in detail.
The heat insulating material according to the present invention is a silicone rubber composition comprising a general-purpose silicone rubber and a glass balloon as main components and a flame retardant and a curing agent as auxiliary agents. All the components are made of low-toxic and highly safe raw materials, and the silicone rubber and glass balloon of the components have a close structure with good interfacial adhesion, so the volume is greatly reduced by external pressure. It is difficult to be affected by (bending) and moisture, and can provide stable heat insulation performance for a long time.

  The silicone rubber in the present invention refers to a polymer material having a main chain having an inorganic siloxane bond (—Si—O—) and a side chain having a methyl group. The siloxane bond in the main chain of silicone rubber has many characteristics such as heat resistance, weather resistance, and flexibility that are not found in the C—C bond of organic polymers. This characteristic can be attributed to the fact that the Si—O bond energy (444 KJ / mol) is more stable than the C—C bond energy (356 KJ / mol), and the three-dimensional helical structure (helix structure). The silicone rubber used in the heat insulating material of the present invention consists of a polymer of several thousand siloxane bond units, and the physical properties of the product vary depending on the group bonded to Si. In order to improve heat resistance, a phenyl group may be introduced. The terminal has an alkoxy group or an acetoxy group and can be cured by reacting with moisture in the air or a polyfunctional group such as a hydroxyl group, an alkyl group or an alkoxysilane group is condensed with a catalyst such as tin or platinum. Although there is a thing etc., it is not limited to these. Silicone rubber includes products that cure at room temperature, those that cure by heating, those that add a curing agent separately, and products that are pre-loaded with the necessary curing agent.

  The function of silicone rubber is to join with a large amount (8 to 10 times by volume) of glass balloons, heat resistance, flexibility and shape maintenance of the heat insulating material, and further to adhere to the workpiece. To work. Silicone rubber has a siloxane bond and a terminal silanol group (Si-OH), and chemically bonds with the silanol group on the surface of the glass balloon to exhibit excellent adhesion and weather resistance. The three-dimensional helical structure of silicone rubber imparts flexibility to the heat-resistant heat insulating material of the present invention, and functions to protect a glass balloon that is weak against impact by a load.

  Next, the glass balloon is made of a highly versatile and safe raw material mainly composed of borosilicate, and is composed of granular material in the form of a hollow vacuum, with low heat loss, excellent heat resistance, heat insulation, and shape. Demonstrate retention.

  Glass balloons form a vacuum hollow granule, exhibit a heat insulating function, and constitute a major component of a heat insulating material due to a dense structure chemically bonded to an intimate silicone rubber. Almost no moisture can enter this structure. If the particle size of the glass balloon is small, the thermal conductivity increases and the heat insulating performance decreases. On the contrary, when the particle size is large, the thermal conductivity is improved, but the pressure strength is lowered. The average particle size of the glass balloon used in the present invention is in the range of 95 μm to 150 μm. When the average particle size of the glass balloon is 95 μm or less, the thermal conductivity exceeds 0.06 w / mk, and when it is 150 μm or more, the insulation of the glass balloon is caused by spraying the heat insulating material with a spray gun and stirring during production. The rate of destruction is increased, and the heat insulation is reduced.

  The compounding ratio of the silicone rubber and the glass balloon is selected from 70 to 100 parts by weight of the glass balloon with respect to 100 parts by weight of the silicone rubber. When the glass balloon is 70 parts by weight or less, the target thermal conductivity of 0.06 w / mk cannot be obtained, and when the glass balloon is 100 parts by weight or more, the strength of the heat insulating material cannot be maintained. In accordance with the requirements, determine the formulation while balancing strength and heat insulation. In addition, the pressure resistance strength of the heat insulating material of this invention is higher than the glass wool currently used as a general purpose heat insulating material.

  Mg compounds and Ca compounds are flame retardants of diatomaceous particles having silanol groups and crystal water. Silica compounds (white carbon) are flame retardants that have silanol groups and free water to form particles of around 50 microns. These flame retardants have a silanol group and crystal water, and have a complicated structure such as a diatom.

  The function of the flame retardant has the function of imparting flame retardancy when added to flammable plastics, resins, rubbers and the like. The halogen and antimony flame retardants used in the past have the function of imparting flame retardancy by the endothermic reaction when the material itself burns. However, the halogen and antimony compounds produced by combustion are toxic and environmental pollutants. Problems have been pointed out. In response to this problem solving requirement, the flame retardant used in the heat insulating material of the present invention has a feature that it is highly safe and does not cause environmental pollution. The flame retardant function has a function of imparting flame retardancy by having crystal water in these compounds and generating an endothermic reaction from around 300 ° C. when heated. Further, this compound has a diatom-like complex structure and has a feature that heat is not easily transmitted.

  Examples of the flame retardant include, but are not limited to, Mg compounds (for example, MOS), Ca compounds (for example, zonotlite), silica compounds (for example, white carbon), and the like. When 2 to 20 parts by weight of one or two of these flame retardants are dispensed with respect to 100 parts by weight of silicone rubber, flame retardancy and strength can be ensured, but flame retardancy is maintained at 2 parts by weight or less. If it exceeds 20 parts by weight, the strength is insufficient. In addition, the flame retardancy is a glass balloon used in the heat insulating material of the present invention melted from around 600 ° C. to become a glass film, and has a function of blocking the supply of oxygen, and is formed by a synergistic effect with the above flame retardant. ing. The blending ratio of the flame retardant is shown in Table 1, and the heat insulation performance test results are shown in Sample Examples (1), (2) and (3) in Table 2.

  As other flame retardants, oxides such as MgO and CaO, aluminum hydroxide, mica (sample comparison example 5), talc, etc. are flame retardant, but when used as heat insulation, the thermal conductivity is 0.06w / Beyond mk, there is a problem with heat insulation. A shirasu balloon produced by firing volcanic ash (shirasu) at 1000 ° C. is shown in sample comparison example (4).

  The curing agent is a silicone rubber curing regulator composed of an organic metal salt and an organic peroxide.

  The function of the curing agent has the function of reacting with a functional group contained in the silicone rubber or acting as a catalyst to make the soft silicone rubber a hard structure. As other curing methods, there are an addition type in which a heat insulating material is heated and cured after application, and a type in which it is cured by reacting with moisture in the air. The curing agent used in the heat insulating material of the present invention is used in an amount of 5 to 10 parts by weight with respect to 100 parts by weight of the silicone rubber. It becomes useless use.

  The sample is prepared by putting 100 parts by weight of silicone rubber into a stainless steel container, diluting with 300 to 400 parts by weight of solvent and stirring. A solvent such as methyl ethyl ketone, acetone or cyclohexane is used as the solvent. In addition, if the work environment is sufficiently safe, toluene, xylene or the like can be used. Next, 100 parts by weight of a glass balloon and 10 parts by weight of a flame retardant are added and stirred with respect to 100 parts by weight of silicone rubber, and finally 5 parts by weight of a curing agent is added and stirred. Add solvent to adjust viscosity to around 15 cp. Stirring is performed at a low speed because the glass balloon is broken when it is performed at a high speed. Be careful when handling the solvent as it will scatter and evaporate during adjustment and construction.

  In the construction of the heat-resistant heat insulating material, first, the base of the workpiece is processed to remove oil and dust. The heat-resistant heat insulating material has good adhesion to steel plates, aluminum, ceramics, epoxy resins, etc., but nylon, polyethylene, polypropylene, etc. have poor adhesion. In order to improve adhesiveness, a silicone-based paint or a ceramic-based (silicon-containing) paint is used as a base treatment. Next, the spray gun is sprayed after adjusting the viscosity to 13 to 14 cp with a B-type viscometer or the like. For the spray gun, use an M100 machine F100 type or Anest Iwata lysine gun, and perform the construction at a pressure of 0.2 to 0.3 MPa. The coating thickness for one application can be up to about 2 mm, and the next construction can be performed after drying for 2 hours. Further, the heat-resistant heat insulating material can be cast into a non-woven fabric or an aluminum plate to form a plate-like product.

Hereinafter, test examples of the low toxicity silicone rubber heat resistant heat insulating material of the present invention will be described in detail.
Using the raw materials of the blending ratio (parts by weight) shown in Table 1, thermal insulation material examples (1), (2) and (3) and comparative examples (4) and (5) were prepared. Table 2 shows the results of the simple heat insulation test, the durometer A hardness, and the simple thermal conductivity of the same heat insulating material examples (1) to (5). Table 3 shows the detailed measurement results of the thermal conductivity of the heat insulating material example (1).

  In the embodiment, 300 to 400 parts by weight of a solvent is added to 100 parts by weight of silicone rubber, and dissolved in a stainless steel container. Next, 100 parts by weight of glass balloon and 10 parts by weight of flame retardant are added to 100 parts by weight of silicone rubber and stirred. The glass balloon and the flame retardant may be mixed in advance. Stirring here is sufficiently performed because it affects the performance of the heat insulating material. Finally, 5 parts by weight of the curing agent is added with respect to 100 parts by weight of the silicone rubber, sufficiently stirred, and adjusted to a viscosity of 13 to 14 cp with a solvent.

  The work is performed on the work to be grounded, such as removing dust and oil, using a Meiji machine F100 spray gun with a caliber of 1.5 mm under a discharge pressure of 0.2 to 0.3 MPa. In the case of a spray gun, the adjustment of the pressure and the distance from the workpiece are important. When the pressure is high, the amount of adhesion decreases, and when the pressure is low, sagging and lumps occur, resulting in poor adhesion. The distance from the workpiece is preferably around 20 cm, although it is related to pressure. In addition, an application test using an MG-2D type lysine gun manufactured by Anest Iwata was conducted, but although it is somewhat difficult to adjust, it is judged to be effective for large-scale construction. As described above, when applying with a spray gun, it is preferable to adjust the viscosity to about 13 to 14 cp with a B-type viscometer, but when casting or troweling, the viscosity is adjusted to be slightly higher. If the workpiece is a steel plate, aluminum, ceramic, etc., oil or dust on the coated surface is removed, and a silicone or ceramic coating is applied to the base treatment. The unevenness immediately after application of the heat insulating material can be adjusted with a trowel or the like, but cannot be adjusted because curing proceeds when the diameter exceeds 1 hour after the addition of the curing agent. For the top coat, a silicone or ceramic paint is selected.

  The simple thermal insulation test is a test method for quickly judging the performance, quantity or combination of many materials, and the test was advanced while comparing with the measured value of thermal conductivity. An external perspective view of the testing machine is as shown in FIG. 1, and includes a test steel plate 11 (15 cm × 15 cm) coated with a heat-resistant rust-proof paint, a testing machine body 12 and a heater bulb 13. A test steel plate coated with a heat-resistant heat insulating material to a thickness of 3 mm was dried at room temperature for 24 hours, then placed on a testing machine, heated from below with a 100 W electric heating bulb 13, and the surface temperature was measured with an infrared thermometer. The measurement results of the surface temperature of the heat insulating material were as shown in Table 2. In the blank test, as a result of heating in the same manner with a test steel plate without applying a heat insulating material, the temperature became 200 ° C. after 60 minutes. On the other hand, since the heat insulating material application surface of the sample examples (1) to (3) was 98 to 105 ° C., the surface temperature was lowered to 95 ° C. to 102 ° C., and the heat insulating performance was confirmed. did it. Comparative Example (4) was a test in which shirasu balloons and glass balloons were mixed, and Sample Comparative Example (5) was tested on mica having high heat resistance, but both of them were inferior in thermal insulation performance to Sample Example (1) Mg compound. It was. In addition, although the temperature of the lower part of the test steel plate under test was 210 degreeC, the surface of the heat insulating material did not show changes such as yellowing and cracks due to heating.

  The heat conductivity test results were 0.06 to 0.08 w / mk as shown in Table 2 when the heat-resistant insulation samples (2) to (5) were measured at the Saitama Industrial Center. Table 3 shows that the thermal conductivity of Sample Example (1) was measured in detail by a public institution, and it was 0.056 w / mk at 27 degrees and 0.063 w / mk at 76 ° C.

  From the above test results of heat insulation performance, when the Mg compound (commonly known as MOS) of the example sample (1) is used, the result of the simple heat insulation test is the best value, and the thermal conductivity is also the target of 0.06 w / mk. Cleared. This Mg compound is a product that is highly safe and does not contain harmful substances, and exhibits excellent heat insulation performance.

  The flame retardancy test was conducted with reference to UL-94 (Plastic horizontal combustion test method). In the test method, a sample having a width of 5 cm, a length of 15 cm, and a thickness of 3 mm was placed horizontally, ignited with a gas burner, and the time to extinction and the distance of the burned sample were measured. The sample without flame retardant burned about 10 cm for 20 seconds, but the following sample examples (1) to (5) self-extinguished within 5 seconds, and the burned distance was in the range of about 5 to 8 cm. there were. This test method was based on the flame retardancy standard UL-94 and was used as a standard for judging the flame retardancy.

  The hardness test was measured by the durometer A method according to the test method of the silicone rubber manufacturer. The test result was hardness 50-52A. The manufacturer's standard hardness was 40A. It is thought that the hardness was improved by the chemical bond with the glass balloon used in the heat-resistant heat insulating material of the present invention.

  From the above examples, the heat insulation performance of the heat-resistant heat insulating material of the present invention is about 0.063 w / mk (at 76 ° C.), compared to the thermal conductivity 0.10 w / mk (at 80 ° C.) of the cited reference 1. ) And the heat insulation performance was excellent. Moreover, in the simple heat insulation test, although it heated at 200 degreeC for 1 hour, changes, such as yellowing of a heat insulating material and a crack, were not recognized. In the heat-resistant heat insulating material of the present invention, the chemical bonding between the glass balloon containing silica and the silicone rubber proceeds gradually, and the heat resistance and hardness are improved. As described above, the heat-resistant heat insulating material of the present invention can be provided as a general-purpose heat insulating material because of its high heat insulating properties, flame retardancy, heat resistance, safety, and low toxicity. Next, Table 1 describes the blending ratio of the heat-resistant heat insulating material of the present invention.

  In Example 2, the performance of the heat-resistant heat insulating material was measured using steam. A heat-resistant heat insulating material sample example (1) was sprayed to a thickness of about 3 mm with a spray gun on the entire 20L pail 15 shown in FIG. The pail can was covered and high-pressure steam 17 was put in, the steam was discharged from the exhaust port 18, and the inside of the can was maintained at 100 ° C. The temperature of the pail can outer wall 16 at this time was 57 ° C. Next, when the measurement temperature at the same place 16 was measured by peeling off 20 mm * 20 mm, it was 98 ° C., and the temperature difference before and after using the heat insulating material was 41 degrees. In the same manner as described above, a heat-resistant heat insulating material was sprayed to a thickness of 2 mm on another pail can. The temperature of the outer wall of the pail can was 67 ° C, and the temperature difference before and after using the heat insulating material was 31 ° C. In this way, heat insulation can be sprayed on equipment that uses steam to reduce heat dissipation.

The silicone rubber heat-resistant insulating material of the present invention can be used for the following equipment or machine.
1. 1. Insulation material that can be sprayed onto food manufacturing machines that frequently use cleaning water and steam. As a heat insulating material molded into a plate or cylinder for steam pipes and small heat exchangers, etc. 3. As a heat insulating material that can be sprayed onto the outer wall of an electric furnace, heating furnace, etc. 4. As a heat insulating material sprayed or molded on automobiles, various testing machines, cooling equipment, electrical appliances, etc. As a measure to keep heat or prevent condensation in various tanks, concrete heat storage tanks and air supply / exhaust ducts. As heat-resistant insulation building material applied to plywood, aluminum plate, non-woven fabric, etc.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an external perspective view of a simple heat insulation performance tester for measuring the performance of various heat insulating materials in Example 1 of the present invention. It is an external appearance perspective view of the heat insulation performance test in the steam use field of Example 2 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Test steel plate 12 of heat insulation material Simple heat insulation performance tester 13 100W light bulb 14 100V power supply 15 20L steel-made pail can 16 Outer wall temperature measuring point 17 High pressure steam 18 Steam outlet

Claims (1)

70 to 100 parts by weight of a glass balloon having an average particle size of 95 to 150 μm, 2 or 20 selected from Mg compound, Ca compound and silica compound to 100 parts by weight of room temperature curable silicone rubber. A low-toxic and flame-retardant heat-resistant silicone rubber heat-insulating material, comprising 5 parts by weight and 5 parts by weight of a curing agent.

Images