JPH04191303A - Compound for compacting powder and manufacture of sintered body - Google Patents

Abstract

PURPOSE:To obtain a compound for compacting powder efficiently shortening degreasing time by incorporating the specific quantity of vaporizing component reacted with water at the temp. of the fluidized point or below in the mixture having the specific composition composed of organic compound and sinterable powder. CONSTITUTION:In the mixed material composed of 40-50vol.% the organic compound and the balance substantially sinterable powder of metal, ceramic, cermet, etc., the organic compound generating gaseous compound by reacting the water or steam at the time of fluidized point or below of this mixed material or capable of steam- distillation, is incorporated at 2.5-25vol.% to volume partial ratio of the whole organic compound. As this reactive organic compound, e.g. acetophenon oxime, etc., is used. This mixed material is used as the compound for compacting powder, and this green compact is heated at <=150 deg.C in steam-containing atmosphere. By this method, the component reaction with the water or the steam in the organic compound is removed. Thereafter, the residual organic compound is heated and removed and successively, the green compact is heated to the sintering temp. and sintered to obtain good sintered body for a short time.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to mixing and molding a sinterable powder material with an organic material, efficiently removing the organic material, and then sintering the resulting metal, The present invention relates to a powder molding compound used in the production of ceramics and cermet sintered bodies, and a method for producing sintered bodies using the compound.

[Prior Art] A method of obtaining a sintered body of a desired shape by sintering powder materials such as metals, ceramics, and cermets has been known since ancient times as a technique for producing ceramics such as porcelain and pottery, and for powder metallurgy.

In recent years, as this technology has progressed, a technology has been developed that mixes thermoplastic organic materials and sinterable powders to form products with fluidity at high temperatures and complex shapes similar to plastics. The most difficult part of this technique is the molding purpose.
~50vo 1% of the added organic material is removed (degreased) without deforming the molded body to produce a sintered body. Prior art related to this includes: ■ A method of extracting and removing a soluble binder with an organic solvent (Japanese Patent Publication No. 57-40111) ■ A method of thermally decomposing it by heating (Japanese Patent Publication No. 57-26105) ■ Heating above the pour point A typical method is a method in which the binder is absorbed into a porous absorbent body from which the binder flows out (Japanese Patent Publication No. 33282/1982).

[Problem to be solved by the invention 1 Compound (composite material) made by sufficiently mixing organic material and powder
After producing this compound, a molded article of a desired shape is produced using a molding technique such as injection molding or extrusion molding. At this time, the properties required for the compound are fluidity and shape retention. Furthermore, in order to produce the final sintered body, unless the resin component in the molded body is removed, carbide may be generated, making it impossible to obtain a product with desired characteristics.

For this reason, conventionally the binder was removed by evaporation by slowly heating the molded body (Japanese Patent Publication No. 48-2280
Publication No. 4). Rapid removal of the binder would cause cracks and breakage in the molded body, so the binder had to be removed gradually over several days, leaving much room for improvement in productivity. Various methods have been developed to solve this problem, and representative methods include: (1) A method in which a portion of the binder is dissolved and removed in a solvent, and then the remaining binder is removed by heating (Japanese Patent Publication No. 57-40111).
1) There is a method (Japanese Patent Publication No. 62-33282) in which a part of the binder is heated to a temperature higher than its melting point so that it flows out and is absorbed into a porous absorbent body.

Although these methods reduce the degreasing time considerably compared to the simple heating method described above, they still have the following problems.

That is, in the method of dissolving and removing the binder with a solvent, there is a problem in processing the solvent after removing the binder, and the quality of the product varies due to deterioration of the solvent and is unstable. Furthermore, when an organic solvent is used, solvent treatment equipment is required for environmental protection, which increases equipment costs and increases the cost of the product.

The method of draining the binder and absorbing it into the absorbent body to shorten the degreasing time has major drawbacks in terms of product characteristics. Particularly, when the binder flows out, some of the powder components also flow out, and when the porous body contracts during sintering, the powder in the porous body becomes an anchor and does not shrink uniformly.

The present invention aims to overcome the drawbacks of the above-mentioned techniques and efficiently shorten the degreasing time without impairing the product properties, and provides a method for producing a powder molding compound and sintered body that satisfies these requirements. The purpose is to provide.

"Means for Solving the Problems" The present invention provides a mixture containing 40 to 50 vol% of an organic compound and the remainder substantially sinterable powder. Organic compounds that react with gas to form gaseous compounds or that can be steam distilled in a volume fraction of 2.5 to 25% of the total organic compounds.
This is a powder molding compound characterized by containing 1% of vo.

In the method of the present invention, a molded body made of such a compound is heated in an atmosphere containing water vapor at a temperature of 150°C or less to remove components that react with water or water vapor in the organic compound, and then the remaining organic compound is sintered. This method of producing a sintered body is characterized in that the sintered body is removed by heating at a temperature lower than the sintering temperature, and then heated to the sintering temperature for sintering.

The present invention uses a compound containing a binder that can be effectively degreased, and easily accomplishes degreasing to produce a sintered body. The basic constituent requirements are that it contains an organic compound that can be easily removed from the molded article as a gaseous compound by reacting with water or steam, or it must contain an organic compound that can be steam distilled. The object of the present invention is to efficiently degrease a compound of a binder and a sinterable powder below the pour point.

Furthermore, the most important features of the method of the present invention are that specific components in the binder can be efficiently removed by decomposition or distillation at a low temperature of around 100'C, and that degreasing in the post-process can be carried out in a short time. .

[Function] The present inventor investigated various methods for the purpose of shortening the degreasing time by improving the conventional technology.

As a result, if specific components are removed from the molded body to make it porous, the organic components can be efficiently removed through the pores, so the degreasing speed can be increased (even if it does not cause blistering, cracking, etc.). The present invention is based on this knowledge.

If the binder is simply evaporated by heating, a compound with a low boiling point is effective, but in order to give the compound fluidity during molding, when the compound is heated to around 150°C, the evaporated components cause defects such as pores in the molded product. Therefore, there is a limit to evaporation removal by heating. The present invention is characterized in that it contains components that can react and remove specific organic compounds in the binder in a gas phase reaction, and that these components can be effectively degreased below the pour point of the compound.

When organic substances are used as reactive gases, exhaust gas treatment equipment,
This is not an improvement, as it is no different from conventional extraction techniques using organic solvents in terms of equipment costs, etc. Therefore, we developed a method of decomposing with steam, which is the cheapest and easiest to process.

Components in the binder that react with water or steam to generate gaseous compounds and decompose, or components that can be steam distilled, must be components that cannot be easily removed at temperatures around 150°C during molding. It satisfies two conditions: it reacts with water or steam efficiently at the lowest possible temperature during degreasing, or it is distilled.

Compounds that satisfy these two requirements include acetophenone oxime, atrobic acid, P-anisaldehyde, anisic acid, aminoacetophenol, aminocinnamic acid, menyl aminonaphthole anthranilate, ethyl isocyanurate, isophthalaldehyde, indolizine itaconate, and ethyl Malonic acid, xanthine, coumarin, glyoxylic acid, diaminobenzoic acid, diaminophenol, dimethylbenzoic acid, detuxaric acid, tetramethylbenzene, dehydroastoic acid, trimethylphenol, toluleic acid, hydroxytoluic acid, biphenyl, phenylglyoxal, phenylnaphthalene, Examples include furocarboxylic acid, fluoroamic acid, ethyl heptanoate, methacroleic acid, methacroylene 4,2-ethylhexanol, and the like.

These easily reactive organic substances react with water or steam at low temperatures and are removed from the molded body, creating vents, so that the volume fraction of pores in all organic compounds is 2.5.
The amount is preferably 2.5 vol% to 25 vol%.
If it is less than 25 vol %, the effect will be small (if it is more than 25 vol %, problems will occur during compound molding in terms of fluidity and shape retention).

Other components of the binder include acrylic resin, which is essential for adhesion between particles and maintaining the shape retention of the molded product.
Typical ingredients include vinyl acetate polystyrene, polyethylene, polypropylene, and polybutyl methacrylate, and if it is necessary to easily enter a complex-shaped mold during molding, it is necessary to improve fluidity. Therefore, wax, stearic acid, oleic acid, etc. are used.

As a plasticizer for imparting elasticity to the molded article, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, butyl stearate, etc. may be added. Furthermore, coupling agents, surfactants, etc. are sometimes added as powder processing agents to improve compatibility with resins to improve fluidity.

Usually, the component ratio of adhesive, lubricant, and plasticizer is adjusted depending on the particle shape of the powder. Adhesives and lubricants are usually required.

The volume fraction of the organic compound is usually 40 to 50%. Another requirement is that when the degreasing accelerator is reacted with water or steam, it must contain a component that does not react with water or steam at a temperature below the pour point of the compound in terms of shape retention.

The degreasing accelerator is not preferable at temperatures above the pour point because it flows out and comes out with powder. Therefore, it is necessary to remove it by heating at a temperature below the pour point. With ordinary binders, as the temperature increases, the viscosity of the molded product decreases, causing problems in shape retention such as sagging. Therefore, it is preferable to use a material that can be removed at a temperature as low as 150'C or less.

The mixing ratio of resin and wax varies depending on the shape, size, density, etc. of the particles, and is determined by actually kneading them with powder. The cross-wire method is such that the binder component has fluidity.
Generally, a method of vigorously stirring while applying pressure at 50° C. is used. The degreasing accelerator is added to the well-kneaded compound and uniformly dispersed.

Powder can be made of metals, ceramics, etc. as long as it can be sintered.
Any material such as cermet is also possible.

Furthermore, the manufacturing process of baked crystals using the above-mentioned compound will be explained below.

The compound can be molded into a certain shape by conventional methods such as press molding, extrusion molding, and injection molding. The present invention does not limit the molding method.

Next, the process of removing the binder from the molded body, which is the core technology of the present invention, will be explained.

First, the molded body is gradually heated in an atmosphere containing water vapor from around room temperature. The partial pressure of water vapor at this time may be such that it is supplied in an amount that reacts with the organic compound (degreasing accelerator) that can be removed at the desired low temperature. As described above, heating in a steam atmosphere is preferably performed at a temperature below the pour point of the binder, and the powder must be kept in shape while remaining in a molded state.

Subsequently, after the degreasing accelerator is removed, the remaining binder is heated to a temperature below the sintering temperature to completely remove the binder. Usually, the resin component is removed by heating to a temperature of around 500° C., which is the temperature at which the resin component is removed. The heating speed at this time is such that the degreasing accelerator is removed and vent holes are formed, making it easier for the remaining binder to evaporate, but rapid heating will generate more gas and cause cracks, blisters, etc. Therefore, it is necessary to decide the conditions by considering the dimensions of the molded body, etc.

Next, sintering can be performed using known techniques, although conditions vary depending on the target powder. This step may be a separate step from the above steps or may be a continuous step.

Example C] Example 2 parts by weight of vinyl acetate (adhesive), 2 parts by weight of wax (sliding material), and phthalate per 100 parts by weight of 5US304 stainless steel powder with an average particle size of 10.2 um produced by the water atomization method. 2 parts by weight of dibutyl acid (plasticizer) and 4 parts by weight of butyl polymethawalylate (adhesive) were subjected to IH crosstalk at 120°C using a 3β pressure kneader. After mixing, cool to 100°C and knead again to add 1.2 parts by weight of diethylhexanol (volume fraction in all organic compounds is approximately 11.9 vol%).
) was added, causing crosstalk for 1 hour. After that, 3
A compound was produced by sizing into pellets of ~5 mm.

This compound was then heated to 150°C using an injection molding machine.
φ40×φ30 under the molding condition of “x1000kgf/cm”
It was made into a ring-shaped molded body of XIO mm. The molded body did not deform during handling and was in good condition with appropriate strength. This molded body was placed on an alumina plate, set in a ventilation type dryer, heated to 75° C., and treated for 4 hours by blowing water vapor into the molded body using air as a carrier gas. At this time, the weight reduction rate was 0.8%, and the degreasing accelerator was efficiently removed.

Furthermore, it was set in an atmosphere furnace and heated at a rate of 5°C/min in a N2 atmosphere, and after being held at 500°C for 1 hour, it was continuously heated at a rate of 5°C/min, and heated at a rate of 1300°C.
The temperature was maintained at 1 h for 1 hour, and the atmosphere at this time was a vacuum condition of 1 O-IPa. The density of the obtained sintered body is 97%, and the dimensional accuracy of the inner diameter is 2 to 2 depending on the difference between the maximum and minimum diameters.
It was at the 3 μm level. The amount of remaining coal at this time is also O, OO2
% by weight and good conditions.

COMPARATIVE EXAMPLE A sintered body was produced by molding, degreasing, and sintering a compound from the example except that the degreasing accelerator was removed under the same conditions. The sintered body was not in a normal state, with swelling and cracks observed on the surface.

[Effect of the invention 1] The compound of the present invention reacts with water vapor and contains an organic compound that can be distilled, so it is now possible to produce baked products that are good even when degreased in a short time. .

It has become possible to easily shorten the degreasing time without particularly requiring new equipment.

Claims (1)

[Scope of Claims] 1. A mixture containing 40 to 50 vol% of an organic compound and the remainder being substantially sinterable powder, which reacts with water or steam at a temperature below the pour point of the mixture to form a gaseous state. The organic compound that can produce a compound or can be steam distilled is 2.5 to 25 vol% in volume fraction of the total organic compounds.
A powder molding compound characterized by containing: 2. A molded article made of the compound according to claim 1.
After heating in a steam-containing atmosphere at a temperature of 50 ° C. or lower to remove components that react with water or steam in the organic compound,
A method for producing a sintered body, which comprises removing remaining organic compounds by heating at a temperature lower than a sintering temperature, and then heating and sintering to a sintering temperature.