JPS6158853A - 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 [T] Object of the Invention The present invention is directed to a material having a high melting point, which is obtained by mixing and molding a powdered metal and/or inorganic compound with a resin, followed by degreasing (
Calcination) This relates to a method for producing a sintered product in a short time by sintering it. More specifically, (A) a sinterable material consisting essentially of a metal and/or an inorganic compound having an average particle size of 0.1 to 500 microns, (B) syndiotactic 1,2-polybutadiene, and (C) When producing a sintered product by molding a composition made of an organic peroxide and sintering the resulting molded product, the molded product is heated in advance to a temperature 50°C to 200°C higher than the weight loss starting temperature at 50°C per hour. Raise the temperature at a rate of ~100°C, then raise the temperature at a rate of 10~50°C per hour to a temperature 10"C to 150°C higher than the decomposition end temperature of syndiotactic 1,2-polybutadiene. This method relates to a method for manufacturing sintered products characterized by calcination (degreasing), which not only has excellent formability and can significantly shorten the degreasing time, but also eliminates blisters and cracks. The purpose is to provide a sintered product free of

[II] Background of the invention (prior art) Recently, various sintered bodies using ceramics or metal powder have been used as electronic materials,
It has been widely used in fields such as electrical 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 this problematic, but it also has the disadvantage that a molded product with a complicated shape cannot be obtained. In order to solve these problems, methods have been proposed in which a composition obtained by kneading ceramic or metal powder and various thermoplastic resins is formed into various shapes as an injection molding material (for example, Publication No. 51-29170, JP-A No. 55-119510, JP-A No. 55-114524
(issues of each publication).

However, when such a thermoplastic resin is used as a matrix, it is necessary to slow down the temperature increase rate for degreasing (calcination), and it is extremely difficult to control the temperature increase pattern due to accuracy. There has been a problem in that so-called "voids" and "holes" occur in the resulting molded product.In order to improve these problems, for example, Japanese Patent Laid-Open Nos. 55-113876 and 55-11452 have been proposed.
As seen in No. 4 and No. 57-17468, attempts to solve the problem by making various improvements in the degreasing process were proposed, but there was no pretreatment such as debinding by solvent extraction, and voids were generated. Syndiotactic 1,2-polybutadiene has good fluidity and is easy to mold, making it difficult to perform degreasing in a short time. ) is desirable.

However, when a composition of syndiotactic 1,2-polybutadiene and ceramic or metal powder is degreased, at around a certain temperature (950 to 500°C), - air melting and decomposition proceed; Temperature speed 1
Unless the heating rate is extremely slow at 1 to 10° C. per hour, syndiotactic 1,2-polybutadiene and/or decomposed products start to bump, causing blisters and cracks in the molded product.

Based on these facts, the inventors of the present invention developed a composition obtained by further adding (blending) an organic peroxide to syndiotactic 1,2-polybutadiene and metals and/or inorganic compounds (ceramics). Even if the object is heated at a relatively fast rate (10 to 50°C/hour) and calcined (degreased), the molded object will be free from blisters and cracks (
We have previously proposed that a sintered product can be obtained.

[III] Structure of the Invention Based on 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 a metal and/or inorganic compound having an average particle size of 0.1 to 500 microns and a melting point of 600° C. or higher; (B) 1.2-bonds; containing at least 85% of melt index (J
Measured according to IS K-7210 at a temperature of 150°C and a load of 2.16 kg, hereinafter referred to as r MFrJ) is 0.1 to 30 g/10 minutes, and the crystallinity is 10 to 45%. When producing a sintered product by molding a composition consisting of a certain syndiotactic 1,2-polybutadiene and (C) organic peroxide and sintering the resulting molded product, the molded product is heated in advance to a temperature below the weight loss start temperature. The temperature is raised at a rate of 50 to 100°C per hour to a temperature 50°C to 200°C higher than the decomposition temperature of syndiotactic 1,2-polybutadiene for 1 hour. 1 hit
After performing calcination by increasing the temperature at a temperature increase rate of 0 to 50°C,
In a method for producing a sintered product by sintering, the sinterable substance in the composition and syndiotactic 1.2-
The composition ratio of the sinterable material to the total amount of polybutadiene is 50 to 85% by weight, and the total amount of the sinterable material and syndiotactic 1,2-polybutadiene is 50 to 85% by weight. ILio
A method for producing a sintered product characterized by a composition ratio of organic peroxide of 0.1 to 10 parts by weight based on 0.0 parts by weight, which has excellent shapeability by injection molding, etc., and greatly reduces the sintering time. The present invention has been achieved based on the discovery that not only is it possible to shorten the length of the sintered product, but also that the resulting sintered product is free from blisters and cracks.

Cr7] Effects of the Invention According to the method for producing a sintered product of the present invention, the following effects are exhibited, including the properties of the molded product during molding of the composition used and after sintering.

(1) The composition has excellent kneading properties and does not cause secondary aggregation.

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

(3) No voids or cranks 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 wire cross-talk, 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.1. As a result, the degreasing time can be shortened. In other words, in the conventional method of degreasing molded products of compositions, the heating rate is 1 to 10' from room temperature.
The binder in the molding was removed very slowly at C/hour. On the other hand, when degreasing the composition used in the present invention, the heating rate is increased to 10 to 100°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 producing a sintered product according to the present invention can be used to produce sintered parts in various fields in order to exhibit the above-mentioned effects. Typical applications are shown below.

(1) Electronic and electrical parts such as various bearings, core rods, 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. Auto parts (4) The essence of gears, shafts, etc. E equipment parts [
V]) Specific explanation of A Ming (A) Sinterable material The sinterable material of the present invention has a melting point, decomposition temperature, or sublimation point of usually 600°C or higher, and a temperature of 1,000°C or higher. Preferably, temperatures above t, aoo°C are particularly suitable.

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. If 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 addition, in the case of inorganic compounds, generally 0
．． 1 to 200 microns, preferably 0.1 to 150 microns, particularly preferably 0.1 to 100 microns. When an inorganic compound having an average particle size of less than 0.1 micron is used, it is difficult to uniformly disperse the inorganic compound during kneading during production of the composition.

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 the composition, the density after sintering will decrease, and the mechanical strength of the sintered body will decrease. do.

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 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. Furthermore, typical examples of inorganic compounds include ceramic materials such as alumina, silicon carbide, silicon nitride, zirconia, cordierite, tungsten carbide, and aluminum nitride. Additionally, as a sintering aid.

Boron, beryllium, carbon, yttrium oxide.

Cerium oxide, magnesium oxide, lithium oxide, etc. may be added in an appropriate small amount (generally, at most 20 parts by weight per 100 parts by weight of the inorganic compound).

(B) Syndiotactic 1.2-polybutadiene Also used in the present invention is syndiotactic 1.2-polybutadiene.
2-Polybutadiene is obtained by polymerizing butadiene. This syndiotactic 1.
MFI of 2-polybutadiene is 0.1-3.0g/10
minutes, preferably from 0.2 to 30 g/10 minutes, particularly preferably from 0.5 to 20 g/10 minutes.

Syndiotactic 1 with MFI less than 0.1 g/LQ min
．． When 2-polybutadiene is used, it not only has poor dispersibility with the sinterable substance when producing the composition, but also
The moldability is also not good. On the other hand, if syndiotactic 1,2-polybutadiene exceeding 30 g/10 minutes is used,
Syndiotactic 1 of the present invention, in which the green body physical properties of the obtained composition are not satisfactory, and the degree of crystallinity is preferably 10 to 45%, particularly preferably 15 to 40%. .2-The characteristics of polybutadiene are 1.2
It is different from cis-1,4-polybutadiene and trans-1,4-polybutadiene in that it contains at least 85% (particularly 80% or more) of - bonds. That is, the syndiotactic 1,2-polybutadiene used in the present invention is 1,4-polybutadiene, which is used as a normal rubber.
- It is a polymer that is different in substance from polybutadiene and has the characteristics of plastic and rubber, and is generally widely used as a stretch film.

Further, telechelic liquid polybutadiene having an allyl type cylindrical hydroxyl group is different from the syndiotactic 1,2-polybutadiene of the present invention, and even if it is used, a good composition cannot be obtained.

(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.

Its decomposition temperature (the temperature at which the half-life is 1 minute) is 110
~300℃ is common, 110~250℃
Organic peroxides with a zero decomposition temperature of less than 110°C are not only difficult to handle, but also have little effect. On the other hand, if an organic peroxide with a temperature exceeding 300°C is used, not only will the heat treatment described below take a long time, but it will also cause harmful deformation of the molded product, which is undesirable. Representative examples include ketone peroxides such as 1,1-bis-tertiary-butylperoxy-3,3,5-trimethylcyclohexane, alkyl peroxides such as dicumyl peroxide, and 2,5-dimethyl-2. ，
Hydroperoxides such as 5-di(tertiary-methylperoxy)-hexyne-3 and 2,5-dimethylhexane-2,5-hydroperoxide, diacyl peroxides such as benzoyl peroxide, and 2,5- Examples include peroxy esters such as dimethyl-2,5-dibenzoyl peroxyhexane.

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 composition used in the present invention, the composition ratio of the sinterable material to the total amount of the sinterable material and syndiotactic 1,2-polybutadiene is 50 to 85% by weight. It is preferably 60 to 85% by weight, particularly preferably 65 to 85% by weight. Sinterable substances and syndiotactic 1.
If the composition ratio of the sinterable material to the total amount of 2-polybutadiene is less than 50% by weight, the physical properties of the green body (strength,
Shape retention) is good, but the density after removing the binder is low and sintering is difficult.On the other hand, if it exceeds 95% by weight, the composition not only has poor wire cross-talk, moldability, and dispersibility, but also has poor uniformity. It is difficult to produce the composition, and even if a uniform composition is obtained, a good green body cannot be obtained.

Further, the addition ratio of the organic peroxide to the total amount of sinterable material and syndiotactic 1,2-polybutadiene (100 parts by weight) is preferably 0.1 to 8.0 parts by weight, particularly 0.1 to 8.0 parts by weight. 1 to 5.0 parts by weight is suitable. If the ratio of organic peroxide added to the total amount of sinterable material and syndiotactic 1,2-polybutadiene (1004]i parts is less than Q,li parts), not only will degreasing take a long time; Blisters, cracks, etc. occur in the resulting sintered product. On the other hand, if more than 10 parts by weight is added, the moldability of the composition will decrease, making it difficult to produce a sintered product with a complicated shape.

(E) Production and molding method of composition In producing the composition of the present invention, stabilizers against oxygen and heat, metal deterioration inhibitors, and lubricants commonly used in the field of syndiotactic 1,2-polybutadiene are used. may be further added.

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 syndiotactic 1,2-polybutadiene, or by dry blending using a mixer such as a Henschel mixer, which is commonly used in the field of syndiotactic 1,2-polybutadiene. It can also be obtained by melt-kneading using a mixer such as , Nigu, roll mill, or single-screw extruder. At this time, a homogeneous 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 formed into a sheet or various shapes by molding methods such as injection molding, extrusion molding and press molding which are commonly practiced in the field of syndiotactic 1,2-polybutadiene. Molded into a molded object.

Note that even in the case of melt-kneading as described above, there is no place for molding.

The melting point of syndiotactic 1,2-polybutadiene, which is also used in the polymerization process, is higher than the melting point of the syndiotactic 1,2-polybutadiene, but it must be carried out within a range that essentially does not cause crosslinking. From these things, 100~
It may be carried out within a temperature range of 160°C.

(F) Calcining (degreasing) method, sintering method The molded product obtained as described above is heated to 50°C or 2°C below the weight loss starting temperature.
The temperature is raised at a rate of 50 to 100°C per hour to a temperature 00°C higher than the decomposition end temperature (hereinafter referred to as "first calcination"), and then the temperature is increased to a temperature 10°C to 150°C higher than the decomposition end temperature.
Time r! The calcination can be completed by raising the temperature at a rate of 10 to 50° C. (hereinafter referred to as "second calcination").

Here, the weight loss start temperature and the decomposition end temperature can be determined by continuously measuring the temperature-sample weight change curve using a thermal decomposition weight loss curve. For details on the measurement method, please refer to “Basic Chemistry Volume 7 “Instrumental Analysis”
′°(Shokabou.

Published September 20, 1975) ftS pages 308 to 3
It is described on page 17. This IJfC amount starting temperature (hereinafter referred to as rT1) and decomposition end temperature (hereinafter referred to as ``T2'')
) represent the temperature at which weight loss starts and the temperature at which weight loss ends, respectively, which were measured on a 70a+H sample under a nitrogen atmosphere at a heating rate of 3° C./min.

In the first calcination, if the temperature increase rate is less than 50° C./hour, it takes a long time to increase the temperature. on the other hand, ! If the temperature exceeds 00°C/hour, harmful deformations such as blisters and cracks will occur in the molded product during calcination.

The primary calcination end temperature (hereinafter referred to as "ta") satisfies Tl+50≦ta≦TI+200 ("C").

If the first calcination is completed at a temperature lower than T1+50°C, a long time is required for the second calcination, and a long time is required for the entire calcination.

On the other hand, if the primary calcination is continued until T1 + 200°C is exceeded, the entire calcination can be completed in a relatively short time, but even if the temperature increase rate is slowed down, blisters, cracks, etc. will occur in the molded product. do.

Further, in the second calcination, if the temperature increase rate is less than 10° C./hour, it takes a long time to increase the temperature. On the other hand, if it exceeds 50°C/hour, harmful deformations such as blisters and cracks will occur in the molded product during calcination. Moreover, this second calcination end temperature (hereinafter referred to as r tbJ) is T2+lO≦tb≦T2+
150 ('O).

If the secondary calcination is completed at a temperature lower than T2+10°C, deformations such as sag and cracks will occur in the molded product during the subsequent sintering process. On the other hand, if the second calcination is continued until the temperature exceeds T2 + 150°C, it is not preferable because the second calcination takes a long time.

The above primary calcination and secondary calcination are continuously carried out in an atmosphere of an inert gas (for example, nitrogen, argon, helium) using a degreasing furnace such as an electric furnace or a gas furnace. The molded product obtained by calcination (degreasing) in this manner may be continuously sintered at a higher temperature using the same furnace used for degreasing.

The molded product degreased (calcined) as described above is heated to a temperature slightly below the melting point of the sinterable material used in the inert gas or hydrogen atmosphere or under vacuum at 10°C/hour to 150°C/hour. A sintered final product can be produced by increasing the temperature at a rate of increase in time. When performing this sintering, in the case of ceramic materials,
Mainly, so-called pressureless sintering method can be used, but 1
It is also possible to apply the reaction-sintering method, hot press method, etc.

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

In addition, in Examples and Comparative Examples, T1 (reduction start temperature) and T2 (decomposition end temperature) are TG/DTA
It was determined from a thermal decomposition loss curve measured using a measuring device (manufactured by Shinku Riko Co., Ltd., model PGD-3000) using 70 mg of a measurement sample under a nitrogen atmosphere at a heating rate of 3° C./min.

An electric furnace (inner volume: 2000 cc) was used for calcination (degreasing). Sintering was performed using the same electric furnace as above, under an atmosphere of inert gas (argon) or under vacuum (10-3)-
The temperature was raised to the sintering temperature at a rate of 80°C/hour.

The types and physical properties of syndiotactic 1,2-polybutadiene, sinterable substances, and organic peroxides used in Examples and Comparative Examples are shown below.

[(A) Syndiotactic 1,2-polybutadiene] As syndiotactic 1,2-polybutadiene, M
, 1. 1,2-polybutadiene [density 0.901 g/cm', microstructure: 1.2-bond amount 80%, hereinafter referred to as FRB(1)J] and M, 1. is 20g/lo min.
Polybutadiene [density 0, 8 O8g/cm'
, as a microstructure 1.2-binding amount 82%, hereinafter rR
B(2)J] was used.

[(B) Sinterable substance]

As a sinterable substance, alumina (manufactured by Showa Light Metal Co., Ltd., trade name AL-45-A,
Silicon carbide (manufactured by Showa Denko K.K., trade name: DU A-2S, boron 0.5% by weight,
Carbon (containing 3.0% by weight) and pure iron having an average particle size of 40 microns (manufactured by Showa Denko K.K., trade name: Atomilon Fine Powder 44MR) were used.

[(C) Organic peroxide]

As an organic peroxide, 2,5-dimethyl-2,5-di(
Tertiary-butylperoxy)hexyne-3 (decomposition temperature 183°C) was used.

Examples 1-7. Comparative Examples 1 to 7 The above syndiotactic 1,2-polybutadiene, sinterable substance (types are shown in Table 1), and organic peroxide were mixed in advance in the amounts shown in Table 1 using a Henschel mixer. Tri-blending was performed for 2 minutes each. Each of the obtained mixtures was transferred to a vented twin-screw extruder (diameter 95 m).
Pellets were produced using m) with kneading at a temperature of 150°C. Place each pellet into an injection molding machine (
A bending test measurement sample and a sintering disk (thickness: 3 mm, diameter: 22.5 mm) were manufactured using a resin temperature of 180°C.

The thus produced sintering disks were degreased (first calcination and second calcination) using a degreasing furnace under the conditions shown in Table 2. After degreasing, sintering may be carried out immediately, but in order to observe the appearance of the degreased product obtained, it was left to cool. The resulting degreased products were sintered under the conditions described above (in Example 2, under an argon cloud atmosphere; in other Examples and Comparative Examples, in vacuum) (sintering completion temperatures are shown in Table 2). ) Each sintered product was manufactured. Table 2 shows the appearance of the sintered product.

(The following is a blank space) In Comparative Example 6, an attempt was made to melt and knead the mixture obtained by dry pelleting, but cross-mixing was not possible. Furthermore, the calcined products obtained in Comparative Examples 1, 2.3, and 5 were not sintered because blisters occurred.

From the results of the above Examples and Comparative Examples, it is clear that the sintered product obtained by the method of the present invention has 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) containing at least 85% 1,2-bonds; Syndiotactic 1,2 having a melt index of 0.1 to 30 g/10 min and a crystallinity of 10 to 45%
- When producing a sintered product by molding a composition consisting of polybutadiene and (C) organic peroxide and sintering the resulting molded product, the temperature of the molded product is 50°C to 200°C higher than the weight loss start temperature. temperature at a heating rate of 50 to 100°C per hour, and then 10°C to 150°C per hour above the decomposition end temperature of syndiotactic 1,2-polybutadiene.
In a method for producing a sintered product by performing calcination by increasing the temperature at a temperature increase rate of 0 to 50°C, and then sintering, the sinterable substance in the composition and the syndiotactic 1,2- The composition ratio of the sinterable material to the total amount of polybutadiene is 50 to 95% by weight, and the composition ratio of the organic peroxide to 100 parts by weight of the total amount of the sinterable material and syndiotactic 1,2-polybutadiene. is 0.1 to 10
A method for producing a sintered product, characterized in that parts by weight.