JPS6163564A - Manufacture of sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [I] Object of the Invention The present invention provides a method of kneading and molding a powdered metal and/or inorganic compound with a high melting point and a resin, followed by calcination (
The present invention relates to a method for producing a sintered product, which is characterized in that, in producing a sintered product by subsequent sintering (degreasing), the obtained molded product is heat-treated in a specific temperature range before calcination.

More specifically, (A) essentially has an average particle size of 0.1 to
500 microns of sinterable material consisting of metals and/or inorganic compounds, (B) consisting essentially of ethylene and vinyl acetate, alkyl acrylates, alkyl methacrylates,
A molded product obtained by molding a composition consisting of an ethylene copolymer with at least one organic compound having one double bond selected from the group consisting of acrylic acid and methacrylic acid and (C) an organic peroxide. When producing a sintered product by sintering, the molded product is held at a temperature 10°C or more higher than the temperature at which the half-life of the aerobic peroxide used is 10 minutes for 1 to 60 minutes. This relates to a method for manufacturing sintered products characterized by performing calcination and sintering, which not only has excellent formability and can significantly shorten the degreasing time, but also has no blisters or cracks. The purpose is to provide a sintered product.

[II] Background of the Invention (Prior Art) Recently, various sintered bodies using ceramics or metal powders have been widely used in fields such as electronic materials, electric materials, and automobile materials. However, the currently widely used methods of manufacturing powder for molding using a spray dryer and then manufacturing molded products for sintering using a rubber press are extremely complicated processes and have extremely low yields. Not only is there a problem, but molded products with complex shapes cannot be obtained! ,) has some drawbacks. In order to solve these problems, methods have been proposed in which a composition obtained by kneading ceramics or metal powder and various thermoplastic resins is formed into various shapes as an injection molding material (for example, Tokuko Showa 51-2917
No. 0, JP-A-55-113510, JP-A No. 55-1145
24 publications).

However, when such a thermoplastic resin is used as a matrix, it is necessary to slow down the temperature increase rate during degreasing (calcination), and it is extremely difficult to control the temperature increase pattern with precision. As a result, there was a problem that so-called "voids" and "spas" were generated in the molded product.In order to improve these problems, for example, Japanese Patent Application Laid-Open Nos. 55-1138713 and 55-1145
No. 24.

As seen in No. 57-174H, an attempt was made to solve the problem by making various improvements in the degreasing process, but solvent extraction did not require pretreatment such as debinding, and there was no void generation. Moreover, it was difficult to perform degreasing in a short time.Among the thermoplastic resins, ethylene copolymers are particularly useful as matrix (binder) because they have good activity properties and are easy to mold.1. X is desirable. However, when a composition of ethylene copolymer and ceramic or metal powder is degreased, the
(0 to 500°C), the decomposition rate becomes significantly faster. Therefore, unless the heating rate is extremely slow to 1 to 10° C. per hour, there is a problem that blisters and cracks occur in the molded product.

Based on these facts, the present inventors developed an ethylene copolymer and a metal and/or inorganic compound (ceramifukus).
By further adding (compounding) a peroxide to the resulting composition, even if the resulting composition is calcined (degreased) at a relatively fast temperature increase rate (1,0~b), it will not cause blisters or cracks. It was discovered that a molded product (sintered product) can be obtained and was previously proposed.

[III] Structure of the Invention In view of the above, the present inventors have conducted various searches to not only shorten the calcination process but also obtain a good sintered product using the previously filed composition. As a result, (A) a sinterable material consisting essentially of metals and/or inorganic compounds with an average particle size of 0.1 to 500 microns; (B) essentially ethylene and vinyl acetate, alkyl acrylates, alkyl methacrylates; , an ethylene copolymer with at least one type of organic compound having one double bond selected from the group consisting of acrylic acid and methacrylic acid, and CG) an organic peroxide; When producing a sintered product by sintering an object, the molded product must be heated to 10°C above the temperature at which the half-life of the organic peroxide used is 10 minutes.
In a method for producing a sintered product by holding the structure at a higher temperature for 1 to 60 minutes, followed by sintering, the total amount of sinterable material and ethylene copolymer in the structure is The composition ratio of the sinterable material is 50 to 85
The amount of nails is %, and the composition ratio of organic peroxide is 0.1 with respect to 100 parts by weight of the total amount of sinterable material and ethylene copolymer.
A method for producing a sintered product characterized in that the amount of sintered product is from 1 to 10 parts by weight not only has excellent shapeability by injection molding and the like, and can significantly shorten the sintering time, but also can be obtained. It was discovered that there was no occurrence of blistering φ cracks in the sintered product,
We have arrived at the present invention.

[IV] Effects of the Invention The method for producing a sintered product of the present invention exhibits the following effects, including the properties of the molded product during molding of the composition used and after sintering.

(+) The composition has excellent kneading properties and no secondary aggregation occurs.

(2) Since the composition has good flow characteristics, it is easy to shape even molded products with complicated shapes.

(3) No voids or cracks occur in the molded product when the composition is degreased.

(4) During the production of the composition, there is very little contamination of impurities from the screw, barrel, nozzle, etc. of the molding machine during kneading, and therefore the sintered product is not colored by impurities after sintering.

When producing a sintered product by sintering the composition used in the present invention, the most remarkable effect is that the temperature increase rate during degreasing (calcination) can be increased, resulting in a reduction in the degreasing time. can be done. That is, in the conventional method of degreasing a molded product of a composition, the binder in the molded product was always removed slowly at a rate of temperature increase from room temperature of 1 to b. On the other hand, when degreasing the composition used in the present invention, it is also possible to increase the heating rate to 10 to 50°C/hour.

Therefore, in conventional methods, calcination (degreasing) requires 5 to 10
However, using the composition of the present invention,
One to two days is sufficient, and not only can productivity be greatly improved, but it is also advantageous in terms of fuel costs.

The method for manufacturing a sintered product according to the present invention exhibits more than one effect and can be used for manufacturing sintered products in various fields. Typical applications are shown below.

(1) Electronic and electrical parts such as various bearings, cores, casings, motor shafts, insulators, circuit boards, etc. (2) Industrial parts such as various plates, large industrial parts such as turbine blades (3) Cylinder liners, turbochargers, etc. Automotive parts (4) Precision equipment parts such as gears and shafts [V]
Detailed Description of the Invention (A) Sinterable Substance The sinterable substance of the present invention has a melting point 1 decomposition temperature or sublimation point of usually 800"C or higher, preferably 1,000"C or higher, particularly 1, A temperature of 400°C or higher is preferable.

The use of metals or inorganic compounds with melting points, decomposition temperatures or sublimation points below 600° C. as sinterable substances results in harmful deformation and blistering during degreasing (calcination). Moreover, the average particle size is 0.1 to 500 microns. This average particle size varies depending on the type of sinterable substance, but in the case of metals it is usually 1 to 500 microns, preferably 1 to 300 microns, most preferably 1 to 200 microns. When a metal with an average particle size of less than 1 micron is used, crosstalk is difficult. On the other hand, if a metal with a diameter exceeding 500 microns is used, the mechanical properties of the molded product obtained by sintering will deteriorate. In the case of inorganic compounds, generally o, l
N200 microns, preferably 0.1 to +5 (H'10), especially 0.1 to 100 microns. When using inorganic compounds with an average particle size of less than 0.1 microns, the composition can be prepared. In particular, it is difficult to uniformly disperse the inorganic compound during kneading.

On the other hand, if an inorganic compound with a diameter exceeding 200 microns is used, shape retention will deteriorate when sintering a molded product of one composition, the density after sintering will decrease, and the mechanical strength of the sintered body will decrease. descend.

Typical examples of metals used as sinterable substances in the present invention are aluminum, iron, and copper.

Titanium, molybdenum, zirconium, co/ruto, 22
-Metals such as Kel and chromium and alloys containing these metals as the main component (at least 50% by weight). Powders of these metals and alloys are widely used as bearing alloys, free-cutting steels, heat-resistant materials, wear-resistant materials, etc., and are commonly referred to as powder metallurgy materials.

Further, typical examples of inorganic compounds include alumina, silicon carbide, silicon nitride, zirconia, cordierite, tungsten carbide, aluminum nitride, and the like. Furthermore, as a sintering aid, a small amount of ceramic material such as boron, beryllium, carbon, yttrium oxide, cerium oxide, magnesium oxide, lithium oxide, etc. (generally at most 20 parts by weight per 100 parts by weight of the inorganic compound) is added as a sintering aid. ) may be added.

(B) Ethylene copolymer The ethylene copolymer used in the present invention is composed of ethylene and at least one double bond of at least one type selected from the group consisting of vinyl acetate, alkyl acrylate, alkyl methacrylate, acrylic acid, and methacrylic acid. It is a copolymer with an organic compound having Among these organic compounds, the alkyl groups of alkyl acrylate and alkyl methacrylate both have 1 to 1 carbon atoms.
Two pieces are common, and 1 to 10 pieces are preferable. Particularly suitable are alkyl acrylates and alkyl methacrylates in which the alkyl group has 1 to 8 carbon atoms, as well as vinyl acetate, acrylic acid and methacrylic acid. Representative examples of suitable organic compounds having double bonds include vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate. and hexyl methacrylate.

The copolymerization ratio of these "organic compounds having - double bonds" (hereinafter referred to as "comonomers") in the ethylene copolymer is usually 1 to 50 mol%, preferably 1 to 40 mol%, and particularly 2 to 35 mol% is suitable. If the copolymerization ratio of the comonomer exceeds 50 mol %, the strength of the molded product before degreasing decreases, and the molded product formed by injection molding or the like will be deformed when taken out from the mold, which is undesirable.

The melt index of these ethylene copolymers (JT
Measured according to S K-8780 at a temperature of 190°C and a load of 2.18 kg, hereinafter rM, 1. J) is generally 0.01 to 500/10 minutes, and 1
．． 0 to 400 g/10 min is preferable, especially lO to 30
0 g/10 minutes is suitable. , ■, is 0. O1
If an ethylene copolymer with a ratio of less than g/10 min is used, the resulting composition will have poor moldability and dispersibility. On the other hand, 5
If an ethylene copolymer exceeding 00 g/10 minutes is used, the green body physical properties of the resulting composition will not be satisfactory.

This ethylene copolymer is a radical initiator (e.g.
It is obtained by copolymerizing ethylene and the above comonomer using an organic peroxide.

This ethylene copolymer is industrially produced and used in a wide variety of fields, and its manufacturing method is well known.

(C) Organic peroxide Furthermore, the organic peroxide used in the present invention is generally used as an initiator in radical polymerization and a crosslinking agent for polymers. The decomposition temperature (temperature at which the half-life is 10 minutes) is generally 90 to 290°C, preferably 100 to 290°C.
In particular, a temperature of 120 to 250°C is optimal. It is not desirable to use an organic peroxide with a decomposition temperature of less than 90° C., since it is not only difficult to handle, but also the effects of its use are not very noticeable. On the other hand, if an organic peroxide with a temperature exceeding 290° C. is used, not only will the heat treatment described below take a long time, but also harmful deformation will occur in the molded product, which is not preferable. Representative examples of optimal organic peroxides include 1,1-bis-primary-butylperoxy-3,,1
Ketone peroxides such as 1,5-')limethylcyclohexane, alkyl peroxides such as dicumyl peroxide, 2,5-dimethyl-2,5-di(
tertiary-methylperoxy)-hexyne-38 and 2,
Hydroperoxides such as 5-dimethylhexane-2,5-hydroperoxide, diacyl peroxides such as benzoyl peroxide, and 2,
Examples include peroxy esters such as 5-dimethyl-2,5-dibenzoylperoxyhexane.

In the present invention, among these organic peroxides, liquid ones can also be used as they are. In addition, a solid substance can be used by dissolving it in a solvent, or by dispersing it in a synthetic oil such as mineral oil, animal or vegetable oil, or silicone oil, or making it into a paste. In this case, the amount of organic peroxide contained in the oil is usually 5 to 70% by weight.

(D) Composition ratio (composition ratio) In the easily sinterable composition used in the present invention, the composition ratio of the sinterable substance to the total amount of the sinterable substance and the ethylene copolymer is 50 to 95% by weight. and 60 to 95
% by weight is preferred, particularly 85-95% by weight. If the composition ratio of the sinterable material to the total amount of the sinterable material and the ethylene copolymer is less than 50% by weight, the physical properties of the green body (strength, shape retention) will deteriorate.

However, the density after removing the binder is low and it is difficult to sinter. On the other hand, if it exceeds 95% by weight, not only will the kneadability, moldability and dispersibility of the composition be poor, but it will also be difficult to produce a uniform composition, and even if a uniform composition is obtained, , a good green body cannot be obtained.

In addition, the addition ratio (composition ratio) of organic peroxide to 100 parts by weight of the total amount of sinterable material and ethylene copolymer is 0.
．． 1 to 8.0 parts by weight is desirable, especially 0.1 to 5.0 parts by weight.
0 parts by weight is preferred. If the addition ratio of organic peroxide to 100 parts by weight of the total amount of sinterable material and ethylene copolymer is less than 0.1 parts by weight, not only will degreasing take a long time, but the resulting sintered product may swell. , cracks, etc. occur. On the other hand, if it is added in excess of 10 parts by weight, the moldability of the composition decreases, making it difficult to produce a sintered product having a complicated shape.

(E) Production and molding method of composition In producing the composition of the present invention, a stabilizer against oxygen and heat, an IF agent for preventing metal deterioration, and a lubricant, which are commonly used in the field of olefin polymers, are further added. You may.

The composition used in the present invention can also be produced by drag blending using a mixer such as a Henschel mixer, which is commonly used in the field of olefin polymers;
It can also be obtained by melt-kneading using a mixer such as a roll mill or a single-screw extruder. At this time, a homogeneous M1 composition can be obtained by triblending in advance and melting and kneading the resulting mixture. In this case, the mixture is generally melt-kneaded and then molded into pellets, which are then subjected to the molding described later. The composition thus obtained is molded into a sheet or a molded product having various shapes by a molding method such as injection molding, extrusion molding, or press molding that is commonly practiced in the field of olefin polymers. be done.

In addition, in both melt-kneading and molding, the melting point must be higher than the melting point of the ethylene copolymer used, but it must be carried out within a range that essentially does not cause crosslinking. For these reasons, it may be carried out at a temperature range of 120 to 200°C.

(F) Heat treatment The molded article formed as described above is heat treated before being calcined and sintered. This heat treatment is important in order to shorten the time required for calcination and sintering of the resulting molded product.

This heat treatment can be achieved by maintaining the composition at a temperature 10°C or more higher than the temperature at which the half-life of the organic peroxide used to prepare the composition is 10 minutes for 1 to 60 minutes. The heat treatment temperature is at least 10°C higher than the temperature at which the half-life of the organic peroxide used is 10 minutes, preferably 10 to 200°C higher, particularly 20 to 200°C higher.
A temperature of 200°C higher is preferred. If the heat treatment is performed at a temperature lower than 10°C above the temperature at which the half-life of the organic peroxide used in the calcination is 10 minutes, the forming process will occur unless the heating rate is slowed down in the calcination described below, unless this heat treatment is carried out for a long time. Cracks occur on objects. Furthermore, if this heat treatment is performed at a temperature considerably higher than the half-life of the organic peroxide (200° C. or higher), which is 10 minutes, the molded product will flow and become deformed. Further, the treatment time is 1 to 60 minutes within the above temperature range, preferably 5 to 80 minutes, most preferably 10 to 60 minutes. By performing this heat treatment within the above temperature range for 60 minutes or less, a molded product without blisters or cracks during calcination can be obtained. However, if the treatment time is less than 1 minute in the above temperature range, the molded product will be deformed during calcination.

By heat-treating the molded product in this manner, the organic binder (ethylene copolymer) in the molded product is completely cured, and a molded product having an organic binder with a three-dimensional network structure can be obtained. If the ethylene polymer in the molded product is not completely cured, flaky cracks will occur in the molded product when the molded product is heated at a high rate as described below.

Therefore, the molded product of the composition of the present invention is prepared under the above-mentioned conditions [i.e., at a temperature higher than the temperature at which the half-life of the organic peroxide used is 10 minutes (preferably at 10°C or higher).
It is necessary to carry out a heat treatment at a temperature of 0° C. to 200° C. higher for 1 to 60 minutes.

(G) Calcining/Sintering As mentioned above, the heat-treated molded product has a three-dimensional network structure due to the organic binder (ethylene copolymer) in the molded product being completely hardened. Even if the temperature of the object is raised at a high rate of 55 to 100"C per hour, it is possible to obtain a molded object without blisters or cracks. In order to calcinate a molded product without blisters or cracks,
It is necessary to raise the temperature at a slow rate of 10 to 50° C. per hour. On the other hand, even if the heat-treated molded product obtained by the present invention is heated at a high rate as described above, no blistering or cracking will occur. This is thought to be because they do not.

This calcination may be carried out in an inert gas (eg, argon, helium, nitrogen) atmosphere using a degreasing (calcination) furnace such as an electric furnace or a gas furnace. This calcination is a process in which the organic binder (mainly a cured product of ethylene copolymer) in the molded product is completely decomposed and volatilized. The end of calcination is when the organic binder in the molded product is completely removed, and as a guideline, a thermobalance [゛Basic Chemistry Sensho 7 "Instrumental Analysis"°' (Shokabo, August 20, 1976)
The objective is to determine the decomposition end temperature of the thermal decomposition curve obtained by the following method (see pages 308 to 317).

In the commonly performed calcination, the polymer does not harden because the molded product does not contain a hardening agent such as an organic peroxide, and does not have a three-dimensional network structure.

Therefore, if calcination is carried out too quickly, many problems such as harmful deformation of the molded product such as blisters and cracks, and the generation of voids inside the molded product occur. For this reason, these problems are prevented by slowing down the temperature increase rate during calcination (usually a temperature increase rate of 0.1'C to 10C per hour). On the other hand, the calcination of the present invention is extremely advantageous in terms of fuel cost and productivity, as the above-mentioned harmful deformation and internal voids do not occur in the molded product even if the temperature is raised rapidly as described above. .

The molded product calcined in this way (molded product that does not substantially contain an organic binder) can be left as it is or once cooled (
to produce the sintered product, which is the final object of the present invention, by raising the temperature under the same atmosphere or reduced pressure as in the case of calcination using the same type of furnace used for calcination. I can do it. In this case, the temperature can be raised faster than during calcination because the molded product does not contain an organic binder. Generally, the heating rate is 150°C per hour.
The temperature is raised to a temperature slightly lower than the melting point of the sinterable material used. In carrying out this sintering, in the case of ceramic materials, a so-called normal pressure sintering method can be mainly used, but it is also possible to apply a reaction sintering method, a hot press method, etc.

[VT] Examples and Comparative Examples The present invention will be explained in more detail with reference to Examples below.

In addition, in the examples and comparative examples, the density is JTS K
-13758.

The heat treatment was performed using a hot air dryer. Furthermore, degreasing was carried out using an electric furnace (inner volume 2000 cc) under a nitrogen atmosphere at a heating rate of 75°C/hour for approximately 12 hours to 900°C.
The temperature was raised to ℃. In addition, sintering is performed using the same electric furnace as above, under an atmosphere of inert gas (argon) or under vacuum (
The temperature was increased to the sintering temperature at 90° C./hour at a temperature of 10” (below 3 torr).

The types and physical properties of the ethylene copolymer, sinterable substance, and organic peroxide used in Examples and Comparative Examples are shown below.

[(A) Ethylene copolymer]

Ethylene copolymer and vinyl acetate copolymerization ratio is 9
．． A copolymer of ethylene and vinyl acetate that is 8 mol% (
N.1. 50 g/10 minutes (hereinafter referred to as rEV AJ), a copolymer of thealethylene and acrylic acid with a copolymerization ratio of acrylic acid of 6.4 mol% (Ll, 25 g
/10 minutes, hereinafter referred to as "rEAA"), a copolymer of ethylene and methacrylic acid with a copolymerization ratio of methacrylic acid of 7.5 mol% (M, 1.80 g/10 minutes, hereinafter referred to as rEM).
AJ), the copolymerization ratio of ethyl acrylate is 8
．． The copolymerization ratio of ethylene and ethyl acrylate copolymer (M, 1.20 g/10 min, hereinafter referred to as rEEAJ) which is 5 mol% and methyl methacrylate is 6.5
A copolymer of ethylene and methyl methacrylate (M, 1.40 g/10 min, hereinafter referred to as rEMMAJ) with a mol% was used.

[(B) Sinterable substance]

As the sinterable substance, alumina (manufactured by Showa Light Metal Co., Ltd., trade name AL-45-A, melting point 2050°C, 1.0% by weight of Mg0 added) with an average particle size of 0.0 μm was used. Silicon carbide (manufactured by Showa Denko K.K., trade name DU A-2S, containing 0.5% by weight of boron and 3.0% by weight of carbon) with an average particle size of 6 microns and pure iron (manufactured by Showa Denko K.K.) with an average particle size of 40 microns. , Product name Atomiron
[(C) Organic peroxide] As the organic peroxide, 2,5-dimethyl-2,5-di(
Tertiary-butylperoxy)hexyne-3 (decomposition temperature: 170°C) was used.

Examples 1 to 10, Comparative Examples 1 to 6 The above ethylene copolymers, sinterable substances (types are shown in Table 1), and organic peroxides were mixed in advance in a Henschel mixer in the amounts shown in Table 1. Tri-blending was performed for 2 minutes each using the following. Each of the obtained mixtures was heated using a vented twin-screw extruder (diameter 35 mm) for 15 minutes.
Pellets were produced while kneading at a temperature of 0°C (however, kneading was not possible in Comparative Example 3), and each pellet was molded into a sintering disk using an injection molding machine (resin temperature 180°C). (Thickness 1mm, diameter 22.5mm)
was manufactured.

Each of the sintering disks thus obtained was heat-treated under the conditions shown in Table 1 (with the exception of Comparative Example 4).
In this case, each heat-treated sintering disk obtained as described above was degreased (calcined) under the conditions described above. I did it. Although sintering may be performed immediately after the completion of degreasing, the degreased product was allowed to cool in order to observe the appearance of the obtained degreased product. Table 1 shows the appearance of the degreased product. Each of the degreased products thus obtained was sintered under the conditions described above (in Example 2, under an argon atmosphere; in other Examples and Comparative Examples, in vacuum) (the sintering temperature was set to the first Each sintered product (shown in the table) was manufactured. Table 1 shows the appearance of each of the obtained sintered products.

(Left below) From the results of the above Examples and Comparative Examples, it was found that when the heat-treated product of the present invention is calcined, it is possible to produce a good final product without voids or cracks in a relatively short period of time (20 hours). It is clear that the concretions have a good appearance.

Claims (1)

Scope of Claims: (A) a sinterable material consisting essentially of a metal and/or inorganic compound having an average particle size of 0.1 to 500 microns; (B) essentially ethylene and vinyl acetate, alkyl acrylate; , an ethylene copolymer with at least one type of organic compound having one double bond selected from the group consisting of alkyl methacrylate, acrylic acid and methacrylic acid, and (C) an organic peroxide. When producing a sintered product by sintering the resulting molded product, the temperature of the molded product must be 10°C above the temperature at which the half-life of the organic peroxide used is 10 minutes.
A method for producing a sintered product by holding the structure at a higher temperature for 1 to 60 minutes, followed by sintering, the total amount of the sinterable substance and ethylene copolymer in the structure. The composition ratio of the sinterable material therein is 50 to 95% by weight, and the total amount of the sinterable material and the ethylene copolymer is 1
A method for producing a sintered product, characterized in that the composition ratio of organic peroxide to 0.00 parts by weight is 0.1 to 10 parts by weight.