JPH05305605A - Manufacture of premolded body containing whisker - Google Patents

Abstract

PURPOSE:To provide a manufacture of a premolded body containing whiskers which are scattered evenly, connected strongly with each other and possess sufficient shape retention and strength. CONSTITUTION:At the time of manufacturing of a premolded body containing whiskers for impregnation of a metal of aqueous slurry containing the whiskers and an inorganic binder, cationic starch is added to the aqueous slurry which is prior to dehydration molding and the inorganic binder is fixed to the surface of the whisker.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a preform containing whiskers for obtaining a whisker reinforced metal composite material by impregnating a metal.

[0002]

2. Description of the Related Art Recently, whiskers such as potassium titanate type whiskers and aluminum borate type whiskers are dispersed in a metal matrix such as aluminum and magnesium, and have high strength, high elasticity and abrasion resistance. Excellent whisker reinforced metal composite (WRM: Whisker Re
Inforced Metal) is attracting attention in various fields.

The above-mentioned whisker-reinforced metal composite material is mainly produced by a high-pressure casting method in which a whisker-containing preform is preheated and a molten metal of a matrix metal is press-fitted and impregnated. The above-mentioned whisker-containing preform is produced by mixing whiskers, a binder, inorganic fibers, and water to prepare an aqueous slurry, which is then dehydrated, dried, and fired (JP-A-53-12446). Gazette, ibid. 54-
40209).

[0004]

In the above-described preform containing whiskers, the distribution of whiskers is likely to be nonuniform in the preform, resulting in insufficient and nonuniform shape retention and strength, and impregnation with the molten matrix metal. The shape and the cracks are apt to occur due to the pressure and thermal shock at the time of making. In particular, the preform having a low whisker content has a remarkably low shape retention property. For example, in a preformed body having a whisker content of less than 20%, in addition to the non-uniform distribution of whiskers,
Since the contact area between the whiskers is reduced, the whiskers hardly function as a reinforcing material, and the shape and shape of the whiskers may be deformed or cracked by a slight external force, or by the metal intrusion pressure or thermal shock during metal impregnation, making handling difficult. There is also a cause of reducing the productivity of the product.

Therefore, in order to improve the shape retention of the preform, it has been attempted to use an inorganic binder such as alumina sol or silica sol. However, the inorganic binder is largely used when the aqueous slurry is dehydrated and formed. It was very difficult to add the optimum inorganic binder, because part of it would flow out. Therefore, if a large amount of inorganic binder is added in anticipation of the amount that flows out, the distribution of whiskers in the preformed body becomes more uneven, and excess inorganic binder remains on the surface of the preformed body. ,
It also causes a decrease in the strength of the preformed body.

On the other hand, the higher the porosity of the whisker-containing preform, the higher the efficiency in impregnating the matrix metal, but at present, the preform having a porosity of 60% by volume or more has a good shape retention property. However, since the strength is significantly reduced, it has not yet been put to practical use. The present invention has been made in view of the above circumstances, and has sufficient shape retention even if the content of whiskers is lower than 20% by volume or the porosity is higher than 60% by volume. It is an object of the present invention to provide a manufacturing method for manufacturing a preformed body containing whiskers.

[0007]

Means and Actions for Solving the Problems In order to solve the above-mentioned problems, a method for producing a preformed body containing whiskers of the present invention comprises a water-based slurry containing whiskers and an inorganic binder, which is dehydrated and dried, and impregnated with a metal. In producing a whisker-containing preformed product for use in a whisker, a cationized starch is added to the above aqueous slurry to fix an inorganic binder on the surface of the whisker.

According to the manufacturing method of the present invention having the above-mentioned structure, since the aqueous slurry is dehydrated and molded with the inorganic binder fixed on the surface of the whiskers, most of the excess inorganic binder flows out during the dehydration. However, an almost optimum amount of inorganic binder can be added. Further, the whiskers and the inorganic binder are uniformly dispersed, and the contact area between the whiskers can be secured. Therefore, the whisker-containing preform obtained by the production method of the present invention has sufficient shape retention even if the content of whiskers is lower than 20% by volume or the porosity is higher than 60% by volume. It has high strength and does not vary in shape retention. Further, according to the present invention, the dehydration property of the aqueous slurry can be improved.

Therefore, the whisker-containing preform manufactured according to the present invention is not only fragile and easy to handle, but also when used in the above high pressure casting method, for example.
The whiskers are evenly distributed, and it becomes possible to manufacture a molded product of a whisker-reinforced metal composite material having excellent properties such as strength, elasticity, and wear resistance. It is also easy to improve the efficiency of impregnating the matrix metal by increasing the porosity as described above.

The kind of whiskers used in the present invention is not particularly limited, and examples thereof include potassium titanate type whiskers,
Aluminum borate whiskers, silicon carbide (SiC)
From among various conventionally known whiskers such as a whisker, a silicon nitride (SiN) whisker, and a zinc whisker, the whisker-containing preform can be appropriately selected and used according to the application and the like, Further, they can be used alone or in admixture of two or more. The fiber diameter and fiber length of the whiskers are not particularly limited and can be appropriately selected, but usually the fiber diameter is about 0.1 to 20 μm,
The fiber length may be about 5 to 300 μm.

As the inorganic binder, conventionally known ones such as colloidal binders such as silica sol, synthetic clay binders such as Kunipia and Wenger, and natural binders such as ceviolite can be used.
They can be used alone or in admixture of two or more. Further, as the inorganic binder, those having a spherical shape or a large surface area are preferably used, and the spherical shape is not particularly limited, but dispersibility in an aqueous slurry, fixability to whiskers, and mechanical strength of a fired product. Considering the characteristics such as the above, a particle diameter of 0.1 μm or less is preferable.

Although the amount of the inorganic binder used is not particularly limited, it is preferably about 1 to 20 parts by weight per 100 parts by weight of the whiskers. When the amount of the inorganic binder used is less than 1 part by weight, the shape retention and strength of the whisker-containing preform may be insufficient. Further, if the amount of the inorganic binder used exceeds 20 parts by weight, dehydration becomes difficult, and further, dehydration becomes difficult. Therefore, excess inorganic binder naturally remains and the porosity in the whisker-containing preform is reduced. It may decrease.

The aqueous slurry used in the present invention is produced by mixing the above whiskers and an inorganic binder with water, but inorganic fibers may be further added together with the whiskers as a reinforcing material. Examples of the inorganic fibers include alumina fibers, alumina-silica fibers, zirconia fibers, quartz fibers and the like. In the present invention, they may be used alone or in combination of two or more. The inorganic fiber has a fiber diameter of about 1 to 250 μm and a fiber length of 200 μm to 1
It may be about 0 mm.

The amount of the above-mentioned inorganic fibers used is not particularly limited, but it is preferably not more than 100 parts by weight with respect to 100 parts by weight of whiskers. The amount of inorganic fiber used is 100
If the amount exceeds the weight part, the content of the whiskers in the whisker-containing preform becomes too low, the airtightness is lost, and the fiber content per unit area is reduced. Further, a fibrous void material may be added to the aqueous slurry of the present invention. The fibrous void material has a function of further improving the dispersibility of the whiskers in the aqueous slurry and a function of further increasing the contact area between the whiskers.

As the fibrous void material, at least one of organic fiber and carbon fiber is used. As the organic fiber, various conventionally known natural fibers or artificial fibers can be used. As the natural fibers, both plant fibers and animal fibers can be used. Examples of the former include seed hair fibers such as cotton; bast fibers such as flax and ramie; stem stem fibers such as Manila hemp; Leaf fiber; wood fiber such as natural pulp and the like. Examples of the latter include
Examples include wool fibers such as wool; silk fibers such as silkworm silk.

As artificial fibers, synthetic fibers, regenerated fibers,
Any of the semi-synthetic fibers can be used. Examples of synthetic fibers include polyamide-based, polyester-based, polyvinylidene chloride-based, polyacrylonitrile-based, polyvinyl alcohol-based, polyurethane-based, polyethylene-based, polystyrene-based, polyfluorinated ethylene-based, phenol-based, etc. Fiber. Examples of the recycled fibers include fibrin-based fibers such as viscose human silk and viscose staple; protein-based fibers such as soybean casein fiber and milk casein fiber. Examples of the semi-synthetic fibers include artificial fibers of acetic acid.

As the carbon fiber, various conventionally known carbon fibers such as PAN type, pitch type (petroleum type), pitch type (coal type) and the like can be used. These organic fibers and carbon fibers may be used alone or in admixture of two or more. Of the various fibers described above, natural pulp and thermosetting polymer-based synthetic fibers (for example, phenol-based synthetic fibers) are preferably used as the fibrous void material.
Since these fibers do not melt or deform due to heat during drying or firing, there is no risk of disturbing the dimensional accuracy of the whisker-containing preform or distorting its shape.
It is cheap and easy to handle and obtain. As the above-mentioned natural pulp, ashless pulp in which ash does not remain after firing is more preferable.

The fiber diameter of the fibrous void material is usually 0.5 to
It is preferable that the fiber length is about 20 μm and the fiber length is about 0.05 to 10 mm. Also, the amount of the fibrous void material used is 100
The amount may not exceed 100 parts by weight with respect to parts by weight. Further, the above aqueous slurry contains a dispersant, a stabilizer,
Various conventionally known additives such as a coagulant, a paper strength enhancer, and a yield improver may be appropriately blended. By blending these additives, the fixing of the inorganic binder to the whiskers becomes even stronger.

In the present invention, in order to fix the inorganic binder on the surface of the whiskers in the aqueous slurry, cationized starch is added to the above aqueous slurry. The addition amount of the cationized starch is not particularly limited, and may be added in an appropriate amount according to the type of the inorganic binder and the like, but is usually about 5 to 150 parts by weight with respect to 100 parts by weight of the inorganic binder. The preform of the present invention can be produced according to the same method except that the cationized starch is added,
For example, it is manufactured as follows.

First, whiskers (or whiskers and inorganic fibers), an inorganic binder, cationized starch and water are uniformly mixed to obtain an aqueous slurry. In preparing the slurry, whiskers (or whiskers and inorganic fibers) may be dispersed in water by a conventional method, and cationized starch and an inorganic binder may be added. The amount of the cationized starch used is not particularly limited and may be appropriately selected depending on the type of the inorganic binder used, but it is usually about 5 to 150 parts by weight per 100 parts by weight of the inorganic binder.

Further, a polymer flocculant may be added to the above aqueous slurry in order to further accelerate the fixing. Examples of the polymer aggregating agent include polymer aggregating agents such as polyacrylonitrile, polyamide, polyamide epichlorohydrin, polyethyleneimine, and polythiourea, and polyacrylamide having a molecular weight of about 300,000 to 1,000,000 is preferably used. It

The polymer flocculant may be added in an amount of about 0.05 to 3.0 parts by weight per 100 parts by weight of whiskers. Although the solid content concentration of the aqueous slurry is not particularly limited, it is preferably within the range of 0.5 to 4% by weight in consideration of the ease of handling and the efficiency of dehydration molding. The aqueous slurry after the fixing process is poured into a dehydration molding die having a predetermined shape, and dehydration molding is performed according to a conventional method. For example, suction molding may be performed while preliminarily dehydrating the aqueous slurry under reduced pressure. Next, the obtained molded product is dried under the same conditions as before until the water is completely removed,
Further, if necessary, firing is performed to obtain a whisker-containing preform having a paper-like structure. The molded product before drying may be pressed to adjust the density and the porosity of the whisker-containing preformed product.

The firing temperature depends on the inorganic binder used,
The heat-resistant temperature of the whiskers (or the whiskers and the inorganic fibers) is preferably below the heat-resistant temperature. The inorganic binder fixed on the surface of the whiskers is crystallized by setting the firing temperature to the crystallization temperature of the binder. In this way, a preform having a papermaking structure can be obtained. For impregnating the preformed body with a metal, a usual method such as a molten metal forging method can be adopted.

Thus, according to the present invention, for example, the porosity is about 65 to 92% by volume and the whisker content is 8 to 35.
A preform having a volume% of about 10 can be obtained.

[0025]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples. Example 1 70 parts by weight of potassium titanate whiskers (manufactured by Otsuka Chemical Co., Ltd., average fiber length 14.3 μm, average fiber diameter 0.39 μm) and alumina short fibers (manufactured by ICI, fiber length 0.3 to 3)
mm, fiber diameter 3 μm) and 5 parts by weight of silica sol (trade name “Snowtex 30” manufactured by Nissan Chemical Industries, Ltd.) in 5000 parts by weight of water, and then cationized starch ( 5 parts by weight of Abeno Flock (trade name, manufactured by Abebe Co.) and 0.08 parts by weight of polyacrylonitrile were added and uniformly stirred and mixed to obtain an aqueous slurry.

Next, using a dehydration molding die in which a large number of small suction holes are provided on the bottom surface of the die cavity having an inner diameter of 40 mm and a depth of 40 mm,
While sucking from the suction small holes, 32 ± 1 aqueous slurry was injected into the mold cavity for dehydration molding, and the wet outer diameter 4
A disk-formed product having a thickness of 0 mm and a thickness of 40 mm was obtained. Since this molded product could be sufficiently dehydrated in the mold during the above dehydration molding, it did not crumble even when taken out of the mold. Further, the dehydrated waste liquid produced during the dehydration molding was filtered and subjected to X-ray diffraction, and as a result, a very small amount of SiO ₂ was not found.

Next, the molded product was heated at 120 ° C. for 120 minutes and then fired at 800 ° C. for 6 hours to produce a whisker-containing preform. The completed preform containing whiskers has an outer diameter of 38 mm, a thickness of 38 mm, and a density of 0.33 g / cc.
The content of whiskers was 10% by volume. Also,
The hardness of the surface of the above-mentioned preform body containing whiskers and the internal hardness obtained by cutting the preform body containing whiskers in half were measured using a hardness meter (Asuka hardness meter type C). It was found that there was no variation in the hardness and the hardness was uniform.

Comparative Example 1 A whisker-containing preform was prepared in the same manner as in Example 1 except that the fixing treatment was not performed by adding the cationized starch and the polymer flocculant in Example 1 above. It collapsed during the drying and baking process. In addition, a qualitative analysis of the dehydrated waste liquid during dehydration molding using an aluminone reagent revealed that a bright red colloidal precipitate indicating the presence of Al ³⁺ ions was generated, which caused a large amount of alumina sol to flow out into the waste liquid. Was confirmed.

[0029]

EFFECTS OF THE INVENTION According to the present invention, a preform having a paper-like structure, in which whiskers are uniformly dispersed and whiskers are firmly bonded to each other, can be obtained. Moreover, since almost all the inorganic binder is fixed on the surface of the whiskers in this molded product, the remaining inorganic binder is hardly present on the surface. Therefore, the preform obtained by the production method of the present invention has a whisker content of 2 or less.
Even if it is 0% by volume or less, it has a high shape retention property, and there is no variation in the shape retention property.

Further, according to the present invention, a preform having a high porosity (about 65 to 92% by volume) can be obtained while maintaining excellent shape-retaining property. Therefore, this preform is used. The impregnation with the metal can be performed very efficiently. The preformed body of the present invention can be used in a wide range of industrial fields such as FRM, heat storage bodies for fuel cells, high temperature battery separators, and protectors for IC substrates.

Front Page Continuation (72) Inventor Hiroki Murata 463 Kagasuno Kawauchi-cho, Tokushima City Otsuka Chemical Co., Ltd. Tokushima Research Laboratories (72) Inventor Rio Matsumoto 3-2 27 Otedori, Chuo-ku, Osaka Otsuka Chemical Co., Ltd. (72) Inventor Kihachiro Nishiuchi 463 Kagasuno, Kawauchi-cho, Tokushima City Otsuka Chemical Co., Ltd. Tokushima Research Institute (72) Inventor Kenichi Wada 463, Kawauchi-cho, Tokushima City Kagasuno Otsuka Chemical Co., Ltd.

Claims (1)

[Claims] 1. A method for producing a whisker-containing preformed body for metal impregnation by dehydration molding and drying an aqueous slurry containing whiskers and an inorganic binder, wherein cationized starch is added to the aqueous slurry to form an inorganic binder. Is fixed on the surface of the whisker, and a method for producing a preformed body containing the whisker.