JPH053421B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an inorganic material reinforced with magnesia whiskers, and more specifically to materials that require bending strength, impact resistance, etc., such as interior and exterior materials for buildings, interior materials for ships, and heat insulation materials. This invention relates to an inorganic material reinforced with magnesia whiskers, which is extremely useful as a magnet. [Conventional technology] Conventionally, interior and exterior materials for buildings, interior materials for ships,
Inorganic materials such as Portland cement, calcined gypsum, and calcium silicate produced by hydrothermal synthesis of calcareous and silicic acid materials are commonly used as the matrix of heat-retaining materials. Further, in order to improve the properties such as bending strength and impact resistance of such inorganic materials, reinforcing fibers are composited. Asbestos is a typical reinforcing fiber. Asbestos is compatible with Portland cement and is widely used in various building materials and heat-insulating materials, such as asbestos slate boards. However, the view that asbestos is harmful to the human body and carcinogenic has been raised particularly in Europe and the United States, and there are plans to ban its use in the future. For this reason, as an alternative fiber to asbestos,
Alkali-resistant glass fibers, carbon fibers, and other chemical fibers are being put into practical use. [Problems to be solved by the invention] Among these reinforcing fibers, alkali-resistant glass fibers are made by adding and mixing 10% zirconium oxide to give alkali resistance to the general E glass composition. However, even though it is alkali resistant, there is a limit to its properties; for example, if the matrix is ordinary Portland cement, the alkali resistant glass fiber will no longer be expected to be effective as a reinforcing fiber after a few years. In addition, when the matrix is a hardened calcium silicate obtained by hydrothermal synthesis, if the matrix and alkali-resistant fibers are mixed and molded and then cured at high temperature and high pressure, rapid alkali precipitation and high temperature and high pressure steam may occur. The alkali-resistant glass fibers deteriorate completely and show no reinforcing hardening. Carbon fiber does not have the same problems as glass fiber and has been used as a reinforcing material for plastics, but its high price makes it unsuitable for materials that require low cost, such as building materials. In addition, various chemical fibers do not have sufficient properties in terms of heat resistance and the like, and are therefore unsuitable for use as building materials. [Means for Solving the Problems] The present inventors have conducted research on methods for modifying and strengthening various inorganic materials to solve the above-mentioned conventional problems, and have also conducted research and development on inexpensive inorganic filler materials. As a result, we succeeded in synthesizing magnesia whiskers, which are extremely effective as reinforcing fillers for inorganic materials. The present inventors have further conducted research to apply this magnesia whisker as a filling material for hydraulic substances and inorganic hardened bodies such as hydrothermally synthesized calcium silicate hydrate, and have completed the present invention. . The present invention improves the mechanical properties such as bending strength and impact strength of the resin by filling and compounding the novel synthetic magnesia whiskers into an inorganic material. It is characterized by containing a matrix formed by hydrothermal synthesis of carbon dioxide and synthesized acicular magnesia whiskers. The present invention will be explained in more detail below. First, magnesia whiskers as a filling material in the present invention will be explained in detail. Magnesia has been used as a refractory material and an electrically insulating material, but it has been pointed out that the biggest drawback of fused magnesia is that it is hydrated. The present inventors conducted intensive research on improving this hydration property, and as a result, succeeded in synthesizing single-crystal magnesia whiskers. The present inventors investigated various conditions for synthesizing magnesia whiskers as a reinforcing filler material for thermoplastic resins.
We succeeded in synthesizing a large amount of magnesia whiskers as shown in 500)). Single-crystal magnesia whiskers as shown in Figure 1 can be easily precipitated at a relatively low temperature and in a short time by heating a molten salt of a mixture of halides and magnesium salts to 650 to 900°C in a steam atmosphere. I can do it. The fiber length and fiber diameter of the precipitated magnesia whiskers vary depending on the heating conditions, etc., but generally, the fiber length is 30 μm to 6 mm, the fiber diameter is 1 to 5 μm, and the aspect ratio is about 30 to 3000. When such magnesia whiskers are used as a reinforcing filling material for a matrix such as a hydraulic substance or hydrothermally synthesized calcium silicate hydrate, the shape of the whiskers depends on the method of filling the matrix and the method of molding, e.g. Since there may be restrictions due to the roll kneading method, extrusion molding method, mold molding method, injection molding method, paper making method, etc., the synthesis conditions must be adjusted appropriately to obtain magnesia whiskers with a shape that is suitable for the filling method and molding method. You need to choose. It is also effective to surface-treat magnesia whiskers with a fatty acid such as stearic acid or a salt thereof, or a silane coupling agent, etc., in order to improve dispersibility in a matrix or processability. In particular, excellent mechanical effects can be obtained by treatment with a silane coupling agent. In the present invention, such magnesia whiskers are used in an amount of 2 to 30 parts by weight per 100 parts by weight of the matrix.
It is preferable to fill parts by weight. When the content of magnesia whiskers is less than 2 parts by weight per 100 parts by weight of the matrix, it is difficult to obtain a sufficient improvement effect according to the present invention; If the amount exceeds 1 part by weight, the moldability of the matrix may deteriorate. By the way, the inorganic material reinforced with magnesia whiskers of the present invention can be obtained by filling and kneading a predetermined amount of magnesia whiskers into a matrix material in accordance with a conventional method, and then forming it by extrusion molding, molding, paper forming, etc. Although easily obtained, it is also a preferable embodiment to fill with various auxiliary materials for the purpose of improving moldability and reducing weight. Auxiliary materials include pulp, inorganic fibers,
Chemical fibers, lightweight materials, and other various filler materials can be mentioned, and one or more of these can be used. ``Operation'' Whiskers are thin fibrous crystals and are also called whisker crystals. A characteristic of whiskers is that the thinner they are, the fewer crystal defects (such as dislocations) there are, and in the presence of screw dislocations, the integrity of the crystal can be detected by the occurrence of kinks and a low elastic limit.
Therefore, magnesia whiskers have high strength and are useful as fiber reinforcing materials in composite materials. In the present invention, the reason why magnesia whiskers are particularly effective as a reinforcing filler material for inorganic materials is that they have an acicular shape and a large aspect ratio. In addition to being effective, it also has good compatibility with the matrix. Moreover, since magnesia whiskers are also excellent in water resistance, alkali resistance, heat resistance, etc., the effect of improving these properties of the composite material is extremely large. [Examples] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. Example 1 Slaked lime and siliceous earth were adjusted and mixed so that the molar ratio of CaO/SiO was 0.85, and 3, 7, 11, and 10% of magnesia whisker were added to 100 parts by weight of the dry matter of the mixed raw materials, respectively. 13 and 15 parts by weight and an additional 3 parts by weight of pulp were added and mixed, and then water was added to form a slurry, which was then molded into a green board using a molding method. The molded green board was cured in an autoclave at 183°C for 8 hours, cooled naturally, and then dried at 80°C for 24 hours to obtain a test piece. Various properties of the obtained test pieces were investigated, and the results are summarized in Table 1.

[Table] From Table 1, it is clear that the alkali-resistant glass fibers have a poor reinforcing effect, whereas the magnesia whiskers according to the present invention have a significantly high reinforcing effect. Example 2 6 parts by weight of magnesia whiskers or alkali-resistant glass fibers were added to 94 parts by weight of ordinary Portland cement, mixed, kneaded at a cement water ratio of 40%, and molded. The physical properties of the obtained molded product after natural curing and autoclave curing (183° C., 8 hours) after 3 days of age were measured, and the results are shown in Table 2.

[Table] From Table 2, the strength of alkali-resistant glass fibers is significantly reduced by autoclave curing, whereas the magnesia whisker according to the present invention has excellent strength even after autoclave curing. It is clear that good results can be obtained. [Effects of the Invention] As detailed above, the inorganic material of the present invention is formed by filling a matrix with synthetic acicular magnesia whiskers, and due to the excellent improving effects of the magnesia whiskers, the inorganic material has improved bending resistance and impact resistance. The mechanical properties such as these are significantly improved, and excellent improvement effects are also obtained in water resistance, alkali resistance, and heat resistance. Furthermore, since magnesia whiskers do not deteriorate at all even after autoclave treatment, autoclave curing can be incorporated into the composite material manufacturing process, making it possible to manufacture high-strength materials in a short manufacturing time.

[Brief explanation of the drawing]

FIG. 1 is a micrograph showing the fiber shape of magnesia whiskers.

Claims (1)

[Scope of Claims] 1. An inorganic material reinforced with magnesia whiskers, characterized by containing a matrix obtained by a hydraulic substance or hydrothermal synthesis, and synthesized acicular magnesia whiskers. 2 Auxiliary materials selected from the group consisting of pulp, inorganic fibers, chemical fibers, lightweight materials, and fillers 1
The inorganic material reinforced with magnesia whiskers according to claim 1, characterized in that it contains one or more kinds of magnesia whiskers. 3. The inorganic material reinforced with magnesia whiskers according to claim 1 or 2, wherein the content of magnesia whiskers is 2 to 30 parts by weight based on 100 parts by weight of the matrix.