JPH052612B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing calcium aluminate hydrate for use as an inexpensive inorganic flame-retardant filler that does not generate toxic gases, and more specifically, it relates to a method for producing calcium aluminate hydrate for use as an inexpensive inorganic flame-retardant filler that does not generate toxic gases. This invention relates to a method for producing calcium aluminate hydrate with high purity and uniform particle size distribution, which has excellent flammability and mechanical properties. [Conventional technology] Conventionally, calcium aluminate hydrate
3CaO・Al ₂ O ₃・6H ₂ O (hereinafter abbreviated as C ₃ AH ₆ ) belongs to the equiaxed crystal system, and the shape of its particles can be 6, 8, 12, 24, or 68-hedral depending on the synthesis conditions. It is generally known that it has a nearly spherical shape, so it is possible to mix it in a large amount when kneaded into a synthetic resin. It contains 6 molecules of bound water in its composition, and theoretically has the property of decomposing and releasing most of the bound water at 240 to 350°C, and has a particle size of 1 to 350°C.
It is said that particles of 3 μm, preferably finer, have a greater flame retardant effect, but on the other hand, fine particles have the disadvantage of extremely poor dispersibility in synthetic resins. Therefore, conventional calcium aluminate hydrate used as a filler for flame-retardant resins has been considered to have a uniform particle size of 1 to 3 μm, taking into account flame-retardant performance and mechanical properties. A method is being considered that focuses mainly on the production of such substances, and also minimizes the residual presence of metastable substances that have a low decomposition temperature of bound water. For example, JP-A No. 59-203727 discloses that calcium aluminate is advantageous for use not only in thermosetting resins but also in thermoplastic resins that require high molding temperatures by increasing the decomposition temperature of bound water. Attempts have been made to provide hydrate fine powders. This is because calcium aluminate hydrate, a metastable mineral with a low decomposition temperature of bound water that is partially generated and mixed crystallized during hydrothermal synthesis, such as C ₄ AH ₁₃ and C ₃ AH ₁₂ , is processed in the drying process. A fine powder having a particle size of 0.5 to 5 μm is obtained by air drying and heating at 150 to 200°C for high purity. In addition, JP-A-62-128919 provides a calcium aluminate hydrate that is uniform and has a particle size of 1 to 3 μm and has good dispersibility in resin for the purpose of improving flame retardant performance. Attempts are being made.
In this attempt, a mixed slurry of calcium hydroxide and aluminum hydroxide is pretreated at a temperature below 60°C to generate a large amount of crystal nuclei, and then raised to the hydrothermal synthesis temperature to complete the C ₃ AH ₆ reaction. Something,
A powder with a fine and uniform particle size is obtained by causing crystal growth using crystal nuclei. [Problems to be Solved by the Invention] However, among the above conventional methods, the former method cannot avoid secondary agglomeration of particles during drying, making it difficult to obtain products with uniform particle diameters, and It has the disadvantage of poor dispersibility. Therefore, although high purity can be achieved, there is a problem that flame retardancy and mechanical properties are inferior. Although the latter method has the advantage of simplifying the manufacturing process and reducing production costs, the amount of primary nuclei produced during general processing and the size of the nuclei ultimately affect the particle size distribution of C ₃ AH ₆ . Considering the quality of the raw materials calcium hydroxide and aluminum hydroxide, especially the variation in activity and reactivity, it is important to obtain the desired fine particles and uniform calcium aluminate hydrate in the batch method. It is still difficult to obtain calcium aluminate hydrate that can satisfy both flame retardancy and mechanical properties. It has been desired to be able to produce a calcium aluminate hydrate for filling synthetic resins that also has improved mechanical properties. The present invention was made in view of this point, and it is possible to freely obtain a desired particle size,
In addition, we provide a calcium aluminate hydrate that is uniform and highly pure, and by modifying the surface of the particles, we provide a calcium aluminate hydrate that has excellent dispersibility and affinity for synthetic resins. The purpose of this product is to provide a calcium aluminate hydrate that takes advantage of the characteristics of both Nito and Nito. [Means for Solving the Problem] As a result of various studies to achieve the above object, the present inventors have found that by adding a third substance, the desired particle size can be freely obtained, and that the particle size is uniform and highly pure. can be,
Furthermore, it has been possible to produce a calcium aluminate hydrate with excellent dispersibility and affinity for synthetic resins. That is, the method for producing calcium aluminate hydrate according to the present invention hydrothermally synthesizes calcium hydroxide and aluminum hydroxide to produce C ₃ AH ₆
To produce calcium aluminate hydrate whose main component is C ₃ AH ₆ , an organic acid is added before or during hydrothermal synthesis. To produce C ₃ AH ₆ , an aqueous alkali silicate solution is added before or during hydrothermal synthesis.
In producing a calcium aluminate hydrate containing as a main component, an organic acid and an aqueous alkali silicate solution are added before or during hydrothermal synthesis. In the present invention, calcium hydroxide includes:
Quicklime, slaked lime, and carbide slag can be used, but those with fine particles, high activity, high reactivity, and high purity are desirable.Aluminum hydroxide can also be commercially available, but it is desirable to have high purity. The standard blending ratio of calcium hydroxide and aluminum hydroxide is a molar ratio of CaO/Al ₂ O ₃ of 3/1, but it can be used in the range of 2.9/1 to 3.2/1, and should not exceed 2.9/1. In the case of
This is not preferable because the residual amount of CaO increases. In addition, there are no particular restrictions on the concentrations of calcium hydroxide and aluminum hydroxide, but for industrial production, the solid concentration [Ca(OH) ₂ + Al(OH) ₃ ] is required.
A range of 100 to 500 g/ is preferable, and if it is less than 100 g/, the produced particles will be as large as 4 to 10 μm, and the uniformity will be poor, which is also unfavorable from the economic point of view. If the amount is more than 500 g/min, the viscosity of the slurry during hydrothermal synthesis becomes 16,000 cp or more, making uniform stirring and mixing impossible, resulting in a large amount of metastable minerals other than C ₃ AH ₆ being produced, which is not preferable. There are no particular restrictions on the timing of using the organic acid and aqueous alkali silicate solution, but preferably before or during hydrothermal synthesis, and when used together, the organic acid should be added first. Most preferably, the alkali silicate aqueous solution is added after thorough stirring. When only the above-mentioned organic acid is used, a calcium aluminate hydrate having the desired uniform particle size and a high decomposition temperature of bound water can be obtained. However, although the flame retardant performance and mechanical properties are improved over conventional products, they are not superior. When only the above aqueous alkali silicate solution is used, excellent flame retardant performance and mechanical properties can be obtained. However, although the decomposition temperature of bound water is improved over conventional products, it is not superior. In the case of using the above-mentioned organic acid and aqueous alkali silicate solution in combination, it is possible to achieve the desired uniform particle size, which can exhibit the effects shown above and in combination, with a high decomposition temperature of bound water, flame retardant performance, and mechanical properties. High purity calcium aluminate hydrate with particularly excellent properties can be easily produced at low cost. Examples of the organic acids used in the present invention include formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, and tartaric acid, which may be used singly or in combination of two or more. The amount used is based on the calcium aluminate hydrate produced.
The amount is 0.1 to 12% by weight, and within this range, as the amount used increases, the particle size of the generated C ₃ AH ₆ becomes smaller and the uniformity effect becomes more pronounced. and more preferably 1 to 10
% by weight is good; if it is less than 1%, it is advantageous in terms of the fineness effect, but the uniformity effect is low; if it is more than 10% by weight, the effect of fineness and uniformity is inferior to the increase in the amount used. As a result, product yield,
This range is advantageous in terms of economy and industrial production. Examples of the aqueous alkali silicate solution used in the present invention include sodium silicate and potassium silicate, which may be used alone or in combination of two or more. The amount used is 0.2 in terms of SiO ₂ for the calcium aluminate hydrate produced.
~15% by weight, flame retardant performance within this range,
The improvement in mechanical properties and decomposition temperature of bound water is remarkable, but it is more preferably 1 to 12% by weight; below 1%, there is no significant effect on improving flame retardant performance, and above 12%, water The viscosity of the slurry during thermal synthesis increases, making it impossible to stir uniformly, resulting in increased C ₃
This causes uneven surface modification of AH ₆ and causes variations in the effect of imparting mechanical properties to the synthetic resin. The hydrothermal synthesis method of calcium aluminate hydrate in the present invention may be either a normal pressure method or a pressurization method. There are no particular restrictions on the hydrothermal synthesis temperature, but for industrial manufacturing purposes, a range of 90 to 160 degrees Celsius is suitable for productivity, energy saving, and maintenance management.
If the temperature is below 160°C, the time required for synthesis will be long and it is not suitable for industrial use, and if it is above 160°C, special expenses will be required to maintain and manage the synthesis equipment (boilers, piping, etc.), which is not favorable from an economic standpoint. The hydrothermal synthesis time required is 4 hours at 95°C and 2 hours at 160°C. The calcium aluminate hydrate slurry obtained in the present invention may be surface-treated with various fatty acid soda salts, resin acid (including synthetic products) soda salts, other various surfactants, or various coupling agents. This can be dehydrated using a centrifuge, filter press, etc., and dried at 100-200°C using a ventilation dryer, spray dryer, flush dryer, paddle dryer, etc., and used as various resin fillers. I can do it. [Function] In the above-mentioned invention, the organic acid mainly reacts with the raw material calcium hydroxide to form a calcium salt of the organic acid with high solubility, which is used to refine the C ₃ AH ₆ particles produced under hydrothermal synthesis. , which promotes uniformity. In the above invention, an aqueous alkali silicate solution reacts with aluminum acid under hydrothermal synthesis to generate highly reactive SiO ₂ , which is converted into C ₃
Coating the particle surface of AH ₆ and modifying the particle surface to increase affinity for synthetic resins, improve dispersibility, and impart mechanical properties.
It improves flame retardancy. In the above-mentioned invention, both of the above effects are achieved. [Examples] The present invention will be explained in more detail below using Examples and Comparative Examples. Example 1 430g of aluminum hydroxide with quality characteristics of 99.7% purity and average particle size of 52μm, and effective lime content of 97.5
%, 625 g of calcium hydroxide with an average particle size of 6.2 μm
Mix and add water to make 4, add 55g of industrial acetic acid with 90% purity, and then add 250g of No. 3 sodium silicate.
After diluting to 1 and adding and stirring, the effective volume is 7.
Hydrothermal synthesis was carried out at 95°C for 4 hours in a stainless steel container. 0.5% of solids in the produced calcium aluminate hydrate slurry
The surface was treated by adding sodium stearate.
Next, filter and dehydrate with a filter, then add water 3
After washing with water and dehydration, dry in an electric dryer at 110±5℃.
and crushed using a 200 mesh wire mesh sieve to obtain a sample. The obtained sample is a uniform particle of 0.8 to 1 μm,
Fig. 1 shows a scanning electron micrograph (5000x) showing the particle structure. Figure 2 shows an X-ray diffraction chart of this product, which is mostly C ₃ AH ₆ .
Figure 3 shows differential thermogravimetric analysis (TGA/
The temperature at which bound water starts to decompose, indicating the DTA) chart, was 260°C. Also, from the chemical analysis results, T-
SiO ₂ = 6.21%, Na = 0.014%, F-CaO = 0.22%
It was hot. The method for evaluating flame retardant performance and mechanical properties is shown below, and the results are shown in Table 1.
The obtained sample was mixed with 125 PHR and calcium stearate 1 PHR in polyethylene resin DFDA-1137 (trade name of Nippon Unicar Co., Ltd.) and heated at 160±5℃ for 2 hours.
Knead with this roll, then press cure at 170±5℃ for 20 minutes to form 2mm and 3mm thick.
In addition to conducting a tensile test according to the method specified in JISK6760, a 3 mm thick plate was cut into 127 mm length and 13 mm width, and a UL94 horizontal combustion test was conducted using this as a test piece, and the burning rate (mm /
The flame retardant performance was evaluated from (min). Example 2 Calcium hydroxide, aluminum hydroxide and water of the same quality and the same amount as in Example 1 were used, 33 g of acetic acid and 150 g of No. 3 sodium silicate of the same quality as in Example 1 were added, and the following operations were carried out. It was carried out in the same manner as in Example 1. The particle size and bound water decomposition onset temperature were measured for the obtained sample. The results are shown in Table 2. Furthermore, the results of flame retardant performance and mechanical properties are shown in Table 1. Example 3 Calcium hydroxide, aluminum hydroxide and water of the same quality and the same amount as in Example 1 were used, 11 g of acetic acid and 50 g of No. 3 sodium silicate of the same quality as in Example 1 were added, and the following operations were carried out. It was carried out in the same manner as in Example 1. The obtained sample was a uniform particle with a size of 1.5 to 2 μm, and FIG. 4 shows a scanning electron micrograph (magnified at 5000 times) as a substitute for a drawing showing the particle structure. Table 2 shows the starting temperature for decomposition of bound water. Furthermore, the results of flame retardant performance and mechanical properties are shown in Table 1. Example 4 Aluminum hydroxide and calcium hydroxide of the same quality and amount as Example 1 were mixed, water was added, and 4
11 g of acetic acid of the same quality as in Example 1 was added, and after mixing, the mixture was placed in a stainless steel container with an effective volume of 7.95 g.
Hydrothermally synthesized at ℃. After 1.5 hours, Example 1
Dilute 50g of No. 3 sodium silicate of the same quality to 1 and add. After the addition was completed, hydrothermal synthesis was continued at 95°C for 3 hours. The following operations were performed in the same manner as in the examples. The obtained sample is a 2-2.5 μm particle whose surface is covered with ultrafine needle-like crystals.
FIG. 5 shows a transmission electron micrograph (10,000 times magnification) as a substitute for a drawing showing the particle structure. FIG. 6 shows an X-ray diffraction chart of this product. Figure 7 shows a differential thermogravimetric analysis (TGA/DTA) chart of this material. The starting temperature for decomposition of bound water was 255°C. The results of flame retardant performance and mechanical properties are shown in Table 1. Example 5 Aluminum hydroxide and calcium hydroxide of the same quality and amount as in Example 1 were mixed, water was added, and 4
30g of lactic acid (1st grade reagent) was added, and then 150g of No. 3 sodium silicate of the same quality as in Example 1 was added.
The following operations were performed in the same manner as in Example 1. The obtained sample is 0.8 ~
They are uniform particles of 1 μm in size, and FIG. 8 shows a scanning electron micrograph (5000x) showing the particle structure. Table 2 shows the decomposition start temperature of bound water, and Table 1 shows the results of flame retardant performance and mechanical properties. Example 6 Aluminum hydroxide and calcium hydroxide of the same quality and amount as in Example 1 were mixed, water was added, and 4
Then, 250 g of No. 3 sodium silicate was diluted to 1, added, stirred and mixed, and the following operations were carried out in the same manner as in Example 1. The obtained sample had particles of 2 to 3 μm in size, and FIG. 9 shows a scanning electron micrograph (magnified at 5000 times) as a substitute for a drawing showing the particle structure. Figure 10 shows a differential thermogravimetric analysis (TGA/DTA) chart of this product, and the temperature at which decomposition of bound water began was 240°C. Also, from the chemical analysis results, T-SiO ₂ = 6.27
%, Na=0.010%, and F-CaO=0.27%.
The results of flame retardant performance and mechanical properties are shown in Table 1. Example 7 Aluminum hydroxide and calcium hydroxide of the same quality and amount as in Example 1 were mixed, water was added, and 5
Then, 33 g of acetic acid of the same quality as in Example 1 was added and mixed with stirring, and the following operations were performed in the same manner as in Example 1. The obtained sample was a uniform particle with a size of 1 to 1.4 μm, and FIG. 11 shows a scanning electron micrograph (5000x) showing the particle structure. Table 2 shows the decomposition start temperature of bound water, and Table 1 shows the results of flame retardant performance and mechanical properties. Comparative example 1 Aluminum hydroxide and calcium hydroxide of the same quality and amount as in Example 1 were mixed, water was added, and 5
After stirring and mixing, the mixture was placed in a stainless steel container with an effective volume of 7 and subjected to hydrothermal synthesis at 95° C. for 5 hours. Samples were obtained in the same manner as in Example 1. The obtained sample had particles of 1 to 3 μm in size, and FIG. 12 shows a scanning electron micrograph (magnified at 5000 times) as a substitute for a drawing showing the particle structure. FIG. 13 shows an X-ray diffraction chart of this product. Figure 14 shows a differential thermogravimetric analysis (TGA/DTA) chart of this product. The decomposition temperature of bound water was 130°C. Furthermore, the chemical analysis results showed that F-CaO was 0.34%. The results of flame retardant performance and mechanical properties are shown in Table 1.

【table】

〔effect〕

The present invention is a method for producing calcium aluminate hydrate containing C ₃ AH ₆ as a main component, and the above-mentioned calcium aluminate hydrate has a uniform particle size distribution of 0.8 to 0.8 to Calcium aluminate hydrate with a particle size of 2.5μm can be easily produced, and the decomposition temperature of bound water is 260℃.
By adding an aqueous alkali silicate solution, the particle surface can be easily modified to improve flame retardancy and mechanical properties. Calcium aluminate hydrate, which has both properties, can be easily obtained at low cost. Therefore, unlike conventional methods, it is not necessary to use high-temperature hot air in the drying process, nor is it necessary to change the crystal nucleus particles or the temperature conditions in two stages during production.・
Aluminate hydrate can be easily produced,
It is a simple process, highly economical, and has the advantage of reducing production costs.

[Brief explanation of drawings]

Figure 1 is a scanning electron micrograph (5000x) showing the particle structure of the sample obtained in Example 1, Figure 2 is an X-ray diffraction chart of the sample obtained in Example 1, and Figure 3 is an X-ray diffraction chart of the sample obtained in Example 1.
The figure is a differential thermogravimetric analysis chart of the sample obtained in Example 1, Figure 4 is a scanning electron micrograph (5000x) showing the particle structure of the sample obtained in Example 3, and Figure 5
The figure is a transmission electron micrograph (10,000x) showing the particle structure of the sample obtained in Example 4, Figure 6 is an X-ray diffraction chart of the sample obtained in Example 4, and Figure 7 is a graph of the sample obtained in Example 4. A differential thermogravimetric analysis chart of the obtained sample, Fig. 8 is a scanning electron micrograph (5000x) showing the particle structure of the sample obtained in Example 5, and Fig. 9 shows the particles of the sample obtained in Example 6. A scanning electron micrograph (5000x) showing the structure as a substitute for a drawing, Figure 10 is Example 6
Figure 11 is a scanning electron micrograph (5000x) showing the particle structure of the sample obtained in Example 7, and Figure 12 is a differential thermogravimetric analysis chart of the sample obtained in Comparative Example 1. A scanning electron micrograph (5000x) showing the particle structure, Figure 13 is an X-ray diffraction chart of the sample obtained in Comparative Example 1, and Figure 14 is a differential thermogravimetric analysis chart of the sample obtained in Comparative Example 1. be. In FIG. 3, FIG. 7, FIG. 10, and FIG. 14, TGA indicates a heating loss curve, and DTA indicates a differential thermal analysis curve.

Claims (1)

[Claims] 1 Hydrothermal synthesis of calcium hydroxide and aluminum hydroxide to produce calcium aluminate hydrate whose main components are 3CaO・Al ₂ O ₃・6H ₂ O Calcium, which is characterized by adding an organic acid before the start or during the hydrothermal synthesis.
A method for producing aluminate hydrate. 2. When hydrothermally synthesizing calcium hydroxide and aluminum hydroxide to produce calcium aluminate hydrate whose main components are 3CaO・Al ₂ O ₃・6H ₂ O, before the start of hydrothermal synthesis or A method for producing calcium aluminate hydrate, which comprises adding an aqueous alkali silicate solution during the synthesis. 3. When hydrothermally synthesizing calcium hydroxide and aluminum hydroxide to produce calcium aluminate hydrate whose main components are 3CaO・Al ₂ O ₃・6H ₂ O, before the start of hydrothermal synthesis or A method for producing calcium aluminate hydrate characterized by adding an organic acid and an aqueous alkali silicate solution during the synthesis.