JPH02204355A - Production of sinterable mixture - Google Patents

Abstract

PURPOSE:To prevent mutual sticking of granular composition and deformation at a time for degreasing and sintering and to obtain granular material ungiving adverse effect to performance of a sintered body by uniformly sticking sublimable substance on the surface of granular composition consisting of sinterable substance, a binder and a liquid plasticizer and specifying the composition. CONSTITUTION:Sublimable substance having >=15 deg.C sublimation temp. is uniformly stuck on the surface of granular composition consisting of sinterable substance, a binder and a plasticizer being liquid at 200 deg.C. The mixing rate of sublimable substance is regulated to 1.0-30 pts.wt. for 100 pts.wt. granular composition. The rate of the platicizer occupied in total amounts of the binder and the plasticizer is regulated to 5.0-50%. The rate of sinterable substance occupied in the granular composition is regulated to 60-95%. In this case, when m.p. of sublimable substance is less than 150 deg.C, such a trouble is caused that a void is generated to the inside at times of kneading and injection molding. As the preferable sublimable substance, melamine, cyanuric acid and melamine cyanurate, etc., are shown.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to the production of a sinterable mixture by uniformly adhering a sublimable substance to the surface of a granular composition consisting of a sinterable substance, a binder, and a plasticizer. Regarding the method.

More specifically, after mixing and kneading with various thermoplastic resins, a sublimable substance is attached to the surface of the granular composition to prevent the sinterable substance, binder, and plasticizer from adhering to each other. A method of forming a compact into a complex shaped body by pelletizing and injection molding, and obtaining a compacted body through a degreasing and sintering process has been widely used in various industrial fields.

Conventionally, for such a method, although it is necessary to have good fluidity during injection molding, attempts have been made to improve fluidity by changing the type and molecular weight of various binders. However, there is a limit to the improvement in fluidity simply by examining the binder, and attempts have been made to improve fluidity by adding a liquid plasticizer.

When a liquid plasticizer is added to form a sinterable material-containing composition into a cross wire pellet in this way, the resulting composition pellet (
(granules) easily stuck to each other, making it difficult to measure accurately during injection molding. In order to solve these problems, attempts have been made to mix finely powdered inorganic substances such as talc and calcium carbonate into the resulting pellets, but if such inorganic substances are mixed into the sinterable material, This becomes a problem because it not only hinders sintering but also adversely affects the performance after sintering. In addition, attempts have been made to similarly mix various resin powders with kneaded pellets, but although it is possible to prevent the pellets from sticking together, when degreasing and sintering the injection molded product, the molded product is deformed and has a complicated shape. It was difficult to obtain concretions.

[Problem to be solved by the invention]

From the above, the sinterable substance, binder and liquid 1L
The object of the present invention is to provide a granular material that prevents granular compositions consisting of ilJ plasticizer from adhering to each other, prevents deformation during degreasing and sintering, and does not adversely affect the performance of the sintered body. .

[Means and operations for solving the problems] According to the present invention, these problems are solved by the following: (A) a sinterable material, (B) a binder, and (C) a plasticizer that is liquid at a temperature of 20°C. (D) The sublimation temperature is 1 on the surface of the granular composition.
This is a method for producing a sinterable mixture in which a sublimable substance having a temperature of 50°C or higher is uniformly deposited, and the mixing ratio of the sublimable substance to 100 parts by weight of the granular composition is 1. σ〜
The composition ratio of the plasticizer in the total amount of the inder and the plasticizer is 5.0 to 50% by weight, and the composition ratio of the sinterable material in the granular composition is 60 to 30 parts by weight. This can be solved by a method for producing a sinterable mixture characterized in that the content of the sinterable mixture is 95% by weight. The present invention will be specifically explained below.

The granular composition of the invention consists essentially of the following sinterable material, a binder and a plasticizer which is liquid at a temperature of 20°C.

(A) Sinterable substance The melting point, decomposition temperature, or sublimation point of the sinterable substance of the present invention is usually 600°C or higher, preferably 1000°C or higher, and particularly preferably 1400°C or higher. If a metal or inorganic compound with a melting point, decomposition temperature or sublimation point of less than 000° C. is used as a sinterable material, harmful deformation and blistering will occur during degreasing. Moreover, the average particle diameter is 0.1 to 500-. This average particle size varies depending on the type of sinterable substance, but in the case of metals, it is usually 1 to 500 ρ, preferably 1 to 300 ρ, and most preferably 1 to 200 ρ. If a metal with an average particle size of less than one grain is used, crosstalk will be difficult. On the other hand, if a metal with a sintering time exceeding 500 μs is used, the mechanical strength of the sintered body obtained by sintering will decrease. In the case of inorganic compounds, it is generally 0.1 to 200-, and 0.
1 to 150 km is preferable, and 0.1 to 10 km is particularly preferable. If an inorganic compound having an average particle size of less than 0.1 mm is used, it is difficult to uniformly disperse the inorganic compound during crosstalk during production of the composition. On the other hand, 200! If an inorganic compound exceeding s is used, the shape retention during sintering of the molded body of the composition will deteriorate, the density after sintering will decrease, and the mechanical strength of the sintered body will decrease.

Representative examples of metals used as sinterable materials in the present invention include metals such as aluminum, iron, copper, titanium, molybdenum, zirconium, cobalt, nickel, and chromium, and metals containing these metals as a main component (at least 6
50% by weight). Powders of these metals and alloys are widely used as bearing alloys, free-cutting steel, heat-resistant materials, wear-resistant materials, etc. Furthermore, typical examples of inorganic compounds include ceramic materials such as alumina, silicon carbide, silicon nitride, zirconia, cordierite, tungsten carbide, and aluminum nitride. In addition, boron, beryllium,
A small amount of carbon, ivtrium oxide, cerium oxide, magnesium oxide, lithium oxide, etc. (generally 100%
(at most 20 parts by weight based on fffffi parts of the inorganic compound).

(B) Binder Resins that can be used as binders include ethylene polymers, styrene polymers, propylene polymers, ethylene-vinyl acetate copolymers, and alkyl (generally having 6 or less carbon atoms) methane. The main component is acrylate (50
ffi amount% or more) (for example, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate) and polymers whose main component (50% by weight or more) is alkyl (usually 6 or less carbon atoms) acrylate (for example, , polymethyl acrylate, polyethyl acrylate, polybutyl acrylate). In the above, the term "system polymer" refers to a homopolymer of the monomer and a homopolymer containing the monomer as a main component (at least 50% by weight) and other monomers. The number average molecular weight of these binders [vapor pressure osmosis method (vap
or pressureO811010tOr method] is usually 200 to 500,000, and 400
It is preferably 0 or more. These binders are widely used in the field of manufacturing sintered materials by mixing with ceramic materials.

(C) Plasticizer Furthermore, the plasticizer is liquid at a temperature of 20°C. The plasticizer may be any one commonly used in the resin industry, and includes phthalic acid, adipic acid derivatives, azelaic acid derivatives, sebacic acid derivatives, maleic acid derivatives, fumaric acid derivatives, and the like.

Representative examples of phthalic acid derivatives used as plasticizers include dimethyl phthalate, dibutyl phthalate, and dioctyl phthalate; representative examples of adipic acid derivatives include diisobutyl adipate and benzyl octyl adipate. As representative azelaic acid derivatives such as
Typical sebacic acid derivatives include ethylhexyl-4-thioazelate and diisobutyl azelate, and typical maleic acid derivatives include dimethyl sebacate and dibutyl sebacate. Typical fumaric acid derivatives such as malate and dimethyl-malate include
Mention may be made of dibutyl fumarate and di(2-ethylhexyl) fumarate.

(D) Sublimable substance The melting point of the sublimable substance used in the present invention is 1
The temperature is 50°C or higher, preferably 180°C or higher, and particularly preferably 170°C or higher. If a sublimable substance with a sublimation temperature of less than 150° C. is used, there are problems such as voids occurring inside the material when it is kneaded with a sinterable substance or during injection molding as described later. Additionally, the upper limit of sublimation temperature is generally 800℃.
It is.

It is not preferable to use a sublimable substance whose sublimation temperature exceeds 800° C. because sintering becomes impossible. Suitable sublimable substances include melamine, cyanuric acid, melamine cyanurate, and the like.

The average particle size of the sublimable substance is usually 0.5 to 100 ts
and 0.5 to 80- is preferable. Average particle size is 0.5
If a sublimable substance with a value less than ρ is used, kneading is difficult.

On the other hand, if a sublimable substance exceeding 100 is used, the shape retention during degreasing and sintering will deteriorate and the density of the sintered body will decrease, which is not preferable.

(E) Composition ratio In the granular composition of the present invention, the composition ratio of the plasticizer in the total amount of the binder and plasticizer is 5.0 to 50.
% by weight, preferably 5.0 to 45% by weight, and 10 to 45% by weight.
45% by weight is preferred. If the composition ratio of the plasticizer is less than 5.0% by weight, the fluidity of the composition will be insufficient. On the other hand, 50
If it exceeds the weight percentage, the shape retention of the injection-molded green body will be poor and it will be deformed when ejected from the mold.

Further, the composition ratio of the sinterable substance in the composition is 60 to 95.
It is preferably 60 to 90% by weight, particularly preferably 70 to 90% by weight. If the proportion of the sinterable substance in the composition is less than 60% by weight, the density after degreasing will be low and sintering will be difficult. On the other hand, if it exceeds 95% by weight, not only the kneading properties and dispersibility of the composition are poor, but also it is difficult to produce a uniform composition.

(F) Production of composition To produce the granular composition of the present invention, the sinterable material,
Mix the binder and plasticizer uniformly.

As a mixing method, it can also be produced by triblending using a mixer such as a Henschel mixer, which is commonly used in the field of thermoplastic resins. It can also be obtained by melt-kneading using a mixer such as a Banbury mixer, kneader, roll mill, or screw extruder. At this time, a homogeneous granular composition can be obtained by triblending in advance and melt-kneading the resulting mixture.

Furthermore, fatty acid amide,
Processing aids such as fatty acids or esters thereof, fatty acid alcohols, fatty acid ethers, paraffin wax, etc. can be added.

(G) Production of mixture To produce the mixture of the present invention, the sublimable substance is uniformly deposited on the surface of the granular composition thus obtained.

The mixing ratio of the sublimable substance to 100 parts by weight of the granular composition is 1.0 to 30 parts by weight, preferably 1.0 to 20 parts by weight, and particularly preferably 2.0 to 20 parts by weight. If the mixing ratio of the sublimable substance to 100 parts by weight of the granular composition is less than 1.0 parts by weight, it is difficult to prevent mutual deterioration of the granules. On the other hand, if it exceeds 30 parts by weight, it becomes difficult to prevent deformation during debinding and sintering, and the density of the sintered body decreases, which is not preferable.

Further, as a method for adding and mixing the sublimable substance, when producing the granular composition, a predetermined amount may be continuously added and mixed from outside, or the pellets and the sublimable substance may be added and mixed in a tumbler.
Tri-blending may be performed using a mixer such as the following.

(H) Injection molding The thus obtained sublimable substance-containing mixture is shaped into molded bodies having various shapes by injection molding methods commonly practiced in the field of synthetic resins. In addition, both in the case of melt-kneading and in the case of molding, the temperature must be higher than the softening point of the binder used, but lower than the sublimation temperature of the sublimable substance.

From these reasons, melt mixing and injection molding are
What is necessary is just to carry out in the temperature range of 250 degreeC.

The thickness of the obtained molded body is generally 0.2 to 200 m1
1, preferably 0.5 to 150 mm, especially 1,
0 to 150 dragons are preferred. The thickness of this molded body is 200
If this is exceeded, blisters or cracks will occur on the surface of the molded product when degreasing and sintering as described below is performed. The shape of the molded body is not particularly limited, but typical examples include a plate, rod, box, vibrator, and cylinder, and other complex shapes may be used.

The molded body thus obtained is subjected to degreasing and sintering described later.

('') Degreasing The obtained molded body is degreased by raising the temperature of the atmosphere above room temperature until the binder and sublimable substances are essentially eliminated. At this time, the maximum temperature for degreasing is usually 200℃.
That's all. In general, the thicker the molded body, the more! & It is necessary to degrease to a high temperature. In addition, the temperature increase rate is usually 1 to 100°C per hour (preferably,
1-80°C). If the molded body is thin, the rising speed may be increased quickly, but if the molded body is thick, deformation such as blistering may occur in the molded body. This degreasing step may be performed under 1 atmosphere or reduced pressure.

Further, when an oxide such as alumina is used as a sinterable material, the sintering may be carried out in air, but it is preferable to carry out the sintering in an atmosphere of an inert gas such as silicon nitride or argon.

(K) Sintering The thus degreased molded body is sintered according to a commonly used method. If the sinterable substance is an oxide type,
It is sintered at a temperature ranging from 500 to 1,700°C, depending on the type. On the other hand, non-oxide materials are sintered in an inert gas atmosphere in a temperature range of 1,500 to 2,000° C., which also depends on the type of material.

[Examples and comparative examples]

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

In the Examples and Comparative Examples, degreasing was performed at 20°C in a nitrogen atmosphere using an electric furnace (inner volume 2000cc).
The temperature was raised to 500° C./hour over 45 hours. Further, the sintering was performed using the same electric furnace as above, and the temperature was raised at a rate of 90° C./hour in an atmosphere of inert gas (argon) or under atmospheric pressure.

The types and physical properties of the sinterable substances, sublimable substances, and binders used in Examples and Comparative Examples are shown below.

[(A) Sinterable substance]

As sinterable materials, alumina (melting point: 2050°C) with an average particle size of 0.4 m and silicon carbide (melting point: 2220°C) with an average particle size of 0.7 mm were used.

[(B) Binder]

In addition, as a binder, a binder prepared by adding 15 parts by weight of stearic acid to 100 parts by weight of butyl polymethacrylate having an average molecular weight of about 200,000 [hereinafter referred to as "binder (A)"] and the polybutyl methacrylate 50 parts by weight, 50 parts by weight of amorphous polypropylene having an average molecular weight of 20,000, and 15 ffif stearic acid.
1 part of a binder [hereinafter referred to as "binder (B)"]
] was used.

[(C) Liquid plasticizer]

Furthermore, dioctyl phthalate (hereinafter referred to as rDOPJ) and dibutyl phthalate (hereinafter referred to as rDBPJ) were used as liquid plasticizers.

[(D) Sublimable substance]

In addition, as a sublimable substance, the average particle size is 2.3-,
Melamine cyanurate with a sublimation temperature of 350°C [
hereinafter referred to as "compound (1)"] and an average particle size of 1.8
Melamine C, hereinafter referred to as "compound (2)", which has a sublimation temperature of 220° C. was used.

Example 1-7. Comparative Example 1-4 Liquid plasticizer whose type and proportion in the total amount of binder and plasticizer are shown in Table 1 and the total amount of sinterable substance, binder and plasticizer shown in Table 1 Each of the sinterable substances whose proportions are shown in the table was tri-blended for 2 minutes using a Henschel mixer.

Each of the obtained mixtures was passed through a vented twin-screw extruder (diameter 35 mm).
A pellet was produced while kneading at a temperature of 150°C. A sublimable substance whose mixing ratio is shown in Table 1 was added to the obtained pellet (granular powder) and tri-blended for 5 minutes using a tumbler.The resulting mixture pellet Pack 25kg each into bags, 4
They were stacked in tiers and left at a temperature of 40° C. and a humidity of 60% for 10 days. Thereafter, each pellet was molded using an injection molding machine (resin temperature 150°C) into a disc (2 mm thick, 50°
mm) was created. Each of the obtained discs was degreased using a degreasing furnace under the above conditions. Each of the degreased products thus obtained was sintered under the above conditions (in Example 2, it was sintered under an argon atmosphere, and in other Examples and Comparative Examples, it was sintered in a vacuum; the sintering temperatures are shown in Table 1). , each sintered product was manufactured. Table 1 shows the appearance and density of each sintered product thus obtained.

In Table 1, in Comparative Example 1, injection molding could not be performed because the pellets stuck to each other. In Comparative Example 3, the molded body fell apart during degreasing and sintering could not be performed. In Comparative Example 4, the molded body was deformed when ejected from the mold after injection molding, and it was difficult to degrease. - Sintering could not be performed.

(Hereinafter in the margin) [Effects of the invention] The composition obtained by the method of the present invention is a mixture thereof,
The properties of the molded body and sintered body, as well as the method for producing them, exhibit the following effects.

(1) When storing the pellets, the pellets do not stick to each other and have excellent long-term storage stability.

(2) Since the fluidity is good, it is easy to shape even molded products having complicated shapes.

(3) The sintered body has high density and excellent mechanical strength.

Since the sintered body obtained by the present invention exhibits the above-mentioned effects, it can be used in a wide variety of fields.

Typical uses are shown below.

(1) Automotive parts such as engine parts (2) Industrial parts such as gears and mechanical seals

Claims (1)

[Claims] (A) Sinterable substance, (B) binder and (C) 20
A method for producing a sinterable mixture, wherein (D) a sublimable substance having a sublimation temperature of 150°C or higher is uniformly adhered to the surface of a granular composition comprising a plasticizer that is liquid at a temperature of 150°C. The mixing ratio of the sublimable substance to 100 parts by weight of the granular composition is 1.0 to 30 parts by weight, and the composition ratio of the plasticizer to the total amount of the binder and plasticizer is 5.0 to 50 parts by weight. A method for producing a sinterable mixture, characterized in that the composition ratio of the sinterable substance in the granular composition is 60 to 95% by weight.