JPS62220565A - Coating material composition for heat control - Google Patents

Abstract

PURPOSE:The titled composition, containing a condensate of a specific organosilicon compound having no silanol group, titanium oxide and mica in a specific proportion, capable of reducing absorptivity of sunlight and ensuring high heat radiation property of antennas, towers, etc. CONSTITUTION:A coating material, containing (B) 100-300pts.wt. mica having <=40mum particle diameter and (C) 50-200pts.wt. titanium oxide having <=1mum particle diameter in (A) 100pts.wt. film-forming component consisting of a high condensate which is one compound, consisting of an organosilicon compound expressed by the formula (R is H, 1-8C hydrocarbon or phenyl) and a condensate thereof without containing silanol group, capable of improving the heat- resistant cycle and having excellent heat control performance even in the form of a thin film by optimizing the particle diameter and amount to be added of the titanium oxide and mica.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention is applied to the surfaces of antennas, towers, etc. used in artificial satellites, space bases, etc., and controls heat input and output to the antennas, towers, etc. The present invention relates to a heat control coating composition that can maintain the temperature within a predetermined temperature range.

BACKGROUND OF THE INVENTION Since equipment used in artificial satellites and the like is generally placed under harsh conditions, they are required to withstand harsh environmental conditions, be lightweight, and have high reliability. For example, satellite antennas are exposed to extremely large temperature differences between sunlight and shade.
In order for the antenna to work properly, the antenna must be
It is necessary to maintain the temperature below 0°C. The temperature of this antenna is determined by the balance between thermal energy absorbed by sunlight and heat dissipated by the antenna's own radiation, so either increase the radiant thermal energy of the antenna at high temperatures or reduce the absorption rate of sunlight. It is necessary to devise some kind of device to reduce the amount.

Therefore, in order to keep the temperature of the antenna below 100 degrees Celsius, heat control paints have been used that have the function of suppressing the absorption of solar energy incident on the antenna and radiating heat into space. .

The performance of this heat control paint is determined by the solar absorption rate (α,), which indicates the degree to which sunlight is absorbed, and the thermal emissivity (ε), which indicates the degree to which the absorbed heat is radiated. That is, the antenna temperature is 1o.

In order to maintain the temperature below °C, a heat control paint with a small αS and a large ε is required.

In addition, satellite antennas are exposed to radiation such as electron beams and gamma rays, and the temperature is close to -180℃ in the shade, so it is important to note that the paint will deteriorate due to radiation and αS will not increase. It is necessary that abnormalities such as cracks and peeling do not occur in the coating film within the temperature range of .

BACKGROUND ART As conventional heat control paints, those in which a silicone alkyd resin or a silicone resin is used as a film-forming component and titanium oxide and/or zinc oxide are added are known.

All of these paints have excellent radiation resistance, but silicone alkyd resin paints can be heated from -180°C to 10°C.
It has the disadvantage that a temperature change of 0°C will cause cracks in the coating film.On the other hand, silicone resin paints have α of 0.
In order to make it 3 or less, it is necessary to use a thick coating film of 80 to 100 μm, which poses a problem in terms of weight reduction.

On the other hand, many paints that use silicate as a film-forming component have been proposed for various applications that require corrosion resistance and heat resistance.For example, alkyl silicate-based zinc-rich paints are well known. . The curing reaction of this alkyl silicate-based zinc rich paint is based on the reaction between the zinc dust added as a pigment and the film-forming component. It was not possible to form a coating film with a thickness of

Problems to be Solved by the Invention As mentioned above, antennas used in artificial satellites, space bases, etc. are subject to harsh conditions.
If the temperature exceeds 100° C. at 1.11°, the function will not be fully exhibited. Therefore, various heat control coating compositions have been used for the purpose of reducing the sunlight absorption rate of the antenna and ensuring high heat dissipation. However, as mentioned above, conventionally proposed methods tend to crack due to thermal distortion caused by large temperature differences, and are difficult to maintain in order to ensure the necessary physical properties (sunlight absorption rate, etc.). Another important characteristic in the above field, which is weight reduction, is sacrificed.

Under these circumstances, developing a paint composition for thermal control that is advantageous in terms of weight reduction as well as improving the thermal characteristics of antennas is important for the future progress of space development and satellite communication technology. This is extremely important, and this is also the purpose of the present invention.

That is, the purpose of the present invention is to improve the thermal characteristics of equipment used under harsh environmental conditions, such as antennas and towers in space bases, artificial satellites, etc., and to develop a new thermal technology that can enable them to function normally. An object of the present invention is to provide a control coating composition.

That is, the purpose of the present invention is to improve the crack resistance due to heat cycles, which is a drawback of conventional heat control paints, to have excellent radiation resistance and heat cycle resistance, and to absorb sunlight with a thin coating that is lightweight. When the thermal emissivity (α,) is 0.3 or less, the thermal emissivity (ε
) is to provide a heat control coating material having a heat control performance of 0.8 or more.

Means for Solving the Problems In view of the above-mentioned current state of paint compositions for heat control, the inventors have conducted various studies and studies to solve the various drawbacks thereof, and as a result, they have developed a paint composition that does not contain silanol groups. The inventors have discovered that combining a condensate of a specific organosilicon compound with titanium oxide and mica in a specific ratio is extremely effective in achieving the above object, leading to the present invention.

That is, the heat control coating composition of the present invention has the following general formula [
[Engine]: ■ R-0-3i-0-R [I] 1 In the general formula [I], R may be the same or different σ), a hydrogen atom, a carbon atom number of 1 to 8 An organosilicon compound represented by and a lower condensate thereof, which represents a hydrocarbon group or a phenyl group.

a film-forming component consisting of a high condensate containing no silal group of at least one compound selected from the group consisting of;
Mica below μm and 50 to 200 parts by weight of particle size 1 μm
It is characterized by containing the following titanium oxide.

That is, according to the present invention, a high condensate of inorganic silicone that does not contain silanol groups and whose molecular chain consists of only 5i-0 bonds, which is suitable for obtaining excellent radiation resistance, has been discovered, and it has been found that it is suitable for obtaining excellent radiation resistance. In addition to titanium oxide, which is one of the white pigments in the market, by adding mica to the inorganic silicone high condensate, we have improved heat cycle resistance, and by optimizing the particle size and amount of titanium oxide and mica, A thin film coating composition for heat control with excellent heat control performance has been realized.

This invention will be explained in more detail below.

R in the organosilicon compound represented by the general formula [I] used as a raw material in the present invention may be the same or different, and may be a hydrogen atom, a phenyl group, or a carbon atom number of 1
~8 hydrocarbon group, preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Specific compounds include tetramethoxysilane, tetraethoxysilane,
Examples include tetraphenoxysilane. Moreover, the low condensate means an oligomer having a degree of polymerization of IO or less.

Organosilicon compound or (and) represented by the general formula [■]
When condensing the low condensate, the compound or (and) the low condensate is added to a water-soluble solvent, and R Water is added at a ratio of 0.2 to 2 moles per mole of the group, and the mixture is allowed to react at about 20 to 100°C with stirring for about 30 minutes to IO hours. An amine or the like is added to increase the pl+ of the system to 7 or more to allow the condensation reaction to proceed. After the reaction is completed, the desired high condensate can be easily obtained by removing remaining water by distillation, azeotropy, or the like.

In the production of high condensates useful in the compositions of the present invention, during the condensation of the compound of formula [I] and/or its low condensates, by-products such as alcohol, water, etc. are formed. Therefore, by using a combination of raw materials such that the by-product has a high vapor pressure at the condensation temperature, a high condensate containing no silanol groups can be advantageously obtained.

The high condensate thus obtained is a three-dimensional condensate with a degree of condensation of at least 20 or more and a molecular weight of about 3,000 or more, and has sufficient performance as an inorganic film-forming component of paints, for example, it can be used as a clear coating as it is. However, a coating film with a thickness of about 20 μm can be formed.

The titanium oxide used as the white pigment in the present invention has an average particle size of 1 μm or less, preferably 0.1 to 0.4 μm.
It is m. Titanium oxide is the above-mentioned inorganic film-forming component 100
50 to 200 parts by weight, preferably 100 to 200 parts by weight
It is used in a proportion of 150 parts by weight.

Furthermore, the mica used in the present invention has an average particle diameter of 40 μm or less, preferably 15 μm or less. Mica is contained in an amount of 10 parts per 100 parts by weight of the above inorganic film-forming component.
It is used in a proportion of 0 to 300 parts by weight, preferably 150 to 250 parts by weight.

When applying the composition of the present invention to antennas etc., the above-mentioned titanium oxide and mica are added to the above-mentioned inorganic film-forming component,
A solvent such as thinner or toluene is added, and the additives are dispersed in the film-forming components using a high-speed stirrer. After being coated by various known coating methods, it is cured by moisture in the air in about 10 minutes to 10 hours.

The coating composition according to the present invention has superior coating performance compared to conventional silicate-based coatings, and can be made thinner than conventional heat control coatings, with a coating thickness of 30 μm and sunlight exposure. It has excellent thermal control performance with an absorption rate (α5) of 0.3 or less and a thermal emissivity (ε) of 0.8 or more.

As mentioned above, the heat control coating compositions that have been proposed so far and are useful for antennas used in artificial satellites, space bases, etc. are particularly effective in terms of heat cycle resistance, radiation resistance, and light weight. However, by using the coating composition of the present invention, these conventional problems can almost be solved.

This is a film-forming component that uses a novel inorganic silicone condensate with a molecular chain consisting only of Si-〇 bonds and does not contain silanol groups, and has a specific particle size in a specific ratio. This is the result of using titanium and mica as additives.

That is, in order to ensure heat cycle resistance and weight reduction between large temperature differences and excellent heat control properties, the sunlight absorption rate of the coating composition should be 0.3 or less, and the thermal emissivity should be 0. .8 or more, and for that purpose, the amount of titanium oxide must be 50 to 100 parts by weight per 100 parts by weight of the above-mentioned high condensate.
200 parts by weight, and the amount of mica should also be from 100 to 300 parts by weight per 100 parts by weight of the high condensate. The lower limit of each additive cannot prevent the occurrence of cracks, etc. when subjected to thermal cycles, which has been a problem in conventional coating compositions for heat control. On the other hand, the upper limit is not particularly limited in terms of physical properties (αs1ε), but since problems arise in terms of workability, ie, coatability, and mechanical strength, the upper limit is 200 parts by weight (titanium oxide) and 3 parts by weight, respectively.
00 parts by weight (mica). Furthermore, the amounts used of these are 100 to 150 parts by weight and 150 to 2 parts by weight, respectively.
By setting the amount to 50 parts by weight, a heat control coating composition having various desired properties can be advantageously obtained.

In addition, it is important to adjust the particle size of titanium oxide and mica as additives in order to satisfy the above characteristics and weight reduction requirements, and the average particle size of each is 1 μm or less, preferably 0.1 to 1 μm. 0.4 μm and 40 μm or less, preferably 1
It is necessary that the thickness be 5 μm or less.

Thus, according to the present invention, a high condensate of inorganic silicone with excellent radiation resistance is used as a film-forming component of a coating composition for heat control, and titanium oxide and mica are further used with controlled particle size and addition profile. , an excellent heat control coating composition is obtained,
This is an environment under radiation exposure and
It provides a long life, low solar absorption rate (αs), and high thermal emissivity (ε) in a temperature environment of 100 mL, with a coating thickness less than half that of conventional products. Therefore, when applied to the surfaces of antennas and towers in space bases, artificial satellites, etc., these original functions can be fully demonstrated.

EXAMPLES The thermal control coating composition of the present invention will be explained in more detail with the following examples, but the scope of the present invention is not limited to the following examples.

Example 1 In a reaction vessel, 62 g of tetraethoxysilane, 125 g of methyltriethoxysilane, and 1 portion of ethyl alcohol were added.
Add 87g and heat to 80℃ while stirring the contents.
After that, 30g of 0.2N hydrochloric acid was added and the mixture was heated to 1 at 80°C.
The reaction was allowed to proceed for 0 hours. Next, 30 g of triethylamine was added to this reaction product to raise the pH to 7 or higher and the temperature was raised to 80°C.
Linearization reaction was carried out for 2 hours, and then 100 g of benzene was added and the solvent was removed until the nonvolatile content became 40% by weight.

The reaction product thus obtained was transparent, had a viscosity of 5.8 centipoise, and did not change at all even after being stored at 30° C. for 2 months, exhibiting excellent storage stability. Hereinafter, this product will be referred to as "reaction product A."

Next, for the reaction product Al00 heavy part, rutile titanium oxide with an average particle size of 0.3 μm (particle size distribution 0.05 to 0.5 μm) and rutile titanium oxide with an average particle size of 4 μm (particle size distribution 0.5 μm) were added.
A total of 200 parts by weight of muscovite (05 to 12 μm) was added and diluted with thinner to form heat control coating compositions with four different compositions.
thickness, αs: 0.916, ε: 0.79) and film thickness 30μ
After applying it to m and setting it at room temperature for 30 minutes,
It was cured by heat treatment at ℃ for 20 minutes.

Regarding αs and ε of the heat control paint obtained by the above method, the irradiation amount (corresponding to 300 eV, to16e /cffl electron beam irradiation (fluence rate 6.25XIO” e /enf, see
, temperature 15°C, degree of vacuum 5 Xl0-'Torr) L
The values after , are shown in Table 1 together with the initial values.

・The heat control paint shown in this example has an electron beam of 1016e.
/cr1. The increase in αs upon irradiation was only 0. It was old. In addition, α5 is Beckman
Using a V5240 device, ε was measured using a Gier Dunkel refractometer model/L/ (Gier Dunke
lReflectometerModel)DB 1
Measured using 00. The measurements in the following examples are also similar.
Fifty cycles of thermal cycle tests were conducted at -180 to 100°C, which corresponds to temperature changes in outer space (geostationary orbit), using a 4D thermal cycle test device. Paints containing 100 parts by weight or more of mica performed well, but paints containing no mica caused cracks in the coating film.

From the above results, it was found that the heat control paint shown in this example has excellent electron beam resistance, and that the heat cycle resistance can be improved by adding mica.

Example 2 Based on 100 parts by weight of the reaction product A obtained in Example 1,
100% of rutile titanium oxide with an average particle size of 0.3 μm
50 to 300 parts by weight of muscovite having an average particle diameter of 4 μm were added to obtain seven types of coating compositions for heat control. These coating compositions were applied to a CFRP board with a film thickness of 30 mm in the same manner as in Example 1.
It was coated in micrometers and cured.

Initial thermal control characteristics (αs
1ε) is shown in FIG.

All paints had αS of 0.27 or less and ε of 0.85 or more, achieving the targets. In addition, the above paint was subjected to a thermal cycle test in the same manner as in Example 1.

As a result, cracks occurred in paints containing 50 and 75 parts by weight of mica. From the results of heat cycle resistance, it is necessary to add mica in an amount of 100 parts by weight or more.

Furthermore, in terms of heat control performance, especially regarding αS, it is preferable to add mica in an amount of about 200 parts by weight in order to lower α5.

Example 3 To 00 parts by weight of the reaction product Al obtained in Example 1, 200 parts by weight of muscovite with an average particle size of 4 μm and 0 parts by weight of muscovite with an average particle size of 0
．． 50 to 200 parts by weight of 3 μm rutile titanium oxide were added to six types of heat control coating compositions. These coating compositions were coated on a CFRP board with a film thickness of 30 mm in the same manner as in Example 1.
It was coated in micrometers and cured.

Figure 2 shows αS and ε of the six types of paints obtained by the above method. For all paints, α is 0.27 or less, and ε is 0.
．． The score was 85 or higher and the goal was reached. In addition, the larger the amount of titanium oxide added, the lower αS is possible, but the amount of addition of 10
It was found that αS does not change much at 0 parts by weight or more.

Comparative example Silicone resin paint for thermal control 313G-L○■ [IIT Research Institute] (IIT
[manufactured by Re5search Institute] and silicone alkyd resin paint for thermal control APA-2
474 (manufactured by Whittaker) was coated on a CFRP board with a film thickness of 40.80.13 in the same manner as in Example 1.
It was applied to a thickness of 0 μm and cured at room temperature for 48 hours. α5 and ε of these paints are shown in Table 2. In the case of 313G-LO, in order to achieve the target of α5 of 0.3 or less, a film thickness of 80 μm or more is required, but the product of the present invention has a film thickness of 30 μm.
The αS achieved 0.23, which is far below the target value.

Furthermore, as a result of conducting a thermal cycle test on these paints in the same manner as in Example 1, cracks occurred in APA-2474 within 50 cycles regardless of the film thickness, and the durability was lower than that of the present invention. It can be seen that crack resistance is inferior.

Table 2 ■ τ As explained above, the heat control paint according to the present invention has a coating thickness of 40 μm, which is about 1/3 of that of conventional products, has a small solar absorption rate (α,), and has a low thermal radiation It has heat control performance with a large rate (ε), and has good radiation resistance and heat cycle resistance, so if it is applied to the surface of an artificial satellite antenna, for example, it can maintain the antenna temperature below a certain temperature for a long period of time. Moreover, it has the excellent advantage of being able to reduce the weight of the paint by reducing the thickness of the coating.

[Brief explanation of drawings]

Figures 1 and 2 show the solar absorption rate (α,) and thermal emissivity (ε) as a result of changes in the amount of mica added and the amount of titanium oxide added, respectively, in the coating composition for heat control according to the present invention. It is a graph showing changes in.

Claims (6)

[Claims] (1) The following general formula [I]: ▲There are mathematical formulas, chemical formulas, tables, etc.▼[I] However, in the general formula [I], R may be the same or different, and the number of hydrogen atoms, carbon atoms, etc. A film-forming component consisting of a high condensate containing no silal group of at least one compound selected from the group consisting of organosilicon compounds and low condensates thereof representing 1 to 8 hydrocarbon groups or phenyl groups. and the film-forming component 1
1. A coating composition for heat control, comprising 100 to 300 parts by weight of mica with a particle size of 40 μm or less and 50 to 200 parts by weight of titanium oxide with a particle size of 1 μm or less. (2) The heat control coating composition according to claim 1, wherein R in the general formula [I] is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. (3) The heat control coating composition according to claim 1 or 2, wherein the degree of condensation of the low condensate is 10 or less. (4) The film-forming component hydrolyzes at least one compound selected from the compounds of the general formula [I] and low condensates thereof in the presence or absence of an acid catalyst, and then adjusts the pH to 7.
The heat control coating composition according to any one of claims 1 to 3, which is obtained by condensation with the above adjustment. (5) The particle size of the mica is 15 μm or less, and the amount added is within the range of 150 to 250 parts by weight. The thermal control coating composition described. (6) The particle size of the titanium oxide is within the range of 0.1 to 0.4 μm, and the amount added is within the range of 100 to 150 parts by weight. Fifth
The heat control coating composition according to any one of the above items.