JPS6252164A - Ceramic composition for injection molding - 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 (Field of Industrial Application) The present invention relates to a ceramic composition for injection molding, which is used to manufacture ceramic products by injection molding.

′ (Prior art) Generally, when obtaining ceramic products by injection molding,
First of all, the ceramic powder and the organic binder as its caking agent are kneaded to uniformly disperse the ceramic powder in the organic binder, and then it is made into a suitable shape, such as a coarsely pulverized product or a pellet shape, and then molded into a shape for injection molding. Use as material (kneading process).

Next, using this material, an injection molding machine is used to obtain a molded product in the desired shape by a method similar to that normally used in plastic molding (molding process). After this, the organic binder is removed by a method such as thermal decomposition. By sintering the material at a certain temperature (sintering step), a product with the desired shape and characteristics of ceramics is manufactured.

Here, the organic binder is important for the uniformity of dispersion of ceramic powder in the injection molding material, the fluidity of the molten material during the molding process, the strength of the obtained molded product, and the removal of the organic binder in one debinding step. It is an important component related to ease of construction and debinding properties.

If the wettability between the organic binder component and the ceramic powder is poor or if the amount of organic binder used is incorrect, it will not only be difficult to uniformly disperse the ceramic powder in the organic binder, but also the ceramic powder and organic It is not possible to obtain a large number of uniform molded products due to separation of the binder component or lack of fluidity of the molten molding material. Also, if the type or blending ratio of the organic binder component is incorrect, the molding The strength of the product becomes significantly lower, making it difficult to remove the molded product from the mold and move it to the next process.
Damage may occur during storage, and molded products may crack, blister, or deform during the binder removal process. Furthermore, if the thermal stability of the organic binder component is poor, the organic binder component will deteriorate during injection molding, and not only will it not be possible to obtain a certain level of fluidity, but the materials such as spools and fillers may be reused as molding materials. Not available.

(Problems to be Solved by the Invention) Various organic substances have been conventionally used as organic binder components.

For example, Japanese Patent Publication No. 51-29170 discloses that when atactic polypropylene (hereinafter abbreviated as APP) is used, ceramic powder can be dispersed well, and a ceramic composition for molding having good fluidity, thermal stability, and appropriate strength can be obtained. It has been shown that it can be obtained. However, APP has the drawback that cracks, blisters, and deformations are likely to occur in the molded product in one step of removing the binder.

In addition, when using olefin wax, paraffin wax, etc., there are fewer problems in the single step of removing the binder, but the wettability with the ceramic powder is poor, making it difficult to uniformly disperse the ceramic powder in the binder. There are problems such as a certain level of fluidity cannot be obtained due to poor thermal stability, difficulty in reusing materials such as spools and lantenors, and the strength of the obtained molded products being extremely low.

Furthermore, acrylic polymers have good dispersibility and thermal stability of ceramic powder, and generate less heat during debinding.
Although it is characterized by being less prone to cracking, blistering, and deformation, it has the disadvantage that the injection molded product has a low strength of 1 and is easily damaged when handled.

(Means for solving the problem) As a result of intensive research in view of the above situation, the present inventors have found that
Acrylic copolymer and ethylene as organic binder
It was discovered that a well-balanced ceramic composition for injection molding without the above-mentioned drawbacks can be obtained by using the present invention in combination with an ethyl acrylate copolymer in a specific proportion, and the present invention was completed based on this finding.

That is, the present invention provides a composition comprising a ceramic powder (I), an acrylic polymer (n), and an ethylene-ethyl acrylate copolymer (III), and furthermore, the acrylic polymer (n) and ethylene-ethyl The weight ratio (II)/(III) of the acrylate copolymer (II[) is 1
The object of the present invention is to provide a ceramic composition for injection molding, characterized in that the ratio is from /4 to 20/1.

As the ceramic powder (I) used in the present invention, any known ceramic powder can be used, such as aluminum oxide,
Silicon oxide, magnesium oxide, calcium oxide, titanium oxide, zirconium oxide, mullite, cordierite, forsterite, steatite, kaolin, talc, synthetic mica, ferrite, barium titanate, silicon carbide, titanium carbide, tungsten carbide, boron carbide , silicon nitride, boron nitride, sialon, and the like, each of which may be used alone or in an appropriate mixture of two or more. The amount of ceramic powder (I) used is usually 40 to 70% by volume, preferably 4% by volume in the ceramic composition for injection molding.
The content is 5 to 67% by volume.

The acrylic polymer (II) used as one type of organic binder in the present invention includes (meth)acrylic acid ester (al) and, if necessary, other monomers copolymerizable therewith (b) ( However, examples include (co)polymers obtained from (excluding ethylene), which are used alone or in combination of two or more.Usually, from the viewpoint of fluidity, they are used alone or in combination.
The weight average molecular weight of the (co)polymer mixture of more than one species is 500
0 to 200,000 are used, but especially 800
0 to 100,000 is preferred.

Examples of the (meth)acrylic acid ester (a) used here include n-alkyl (meth)acrylate whose alkyl group has 1 to 8 carbon atoms, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (
meth)acrylate, 2-ethylhexyl(meth)acrylate, cyclohexyl(meth)acrylate, 2-
Hydroxy (meth)acrylate, 2-hydroxypropyl (meth)acrylate, diethylene glycol (meth)acrylate, glycidyl (meth)acrylate,
Examples include aminoalkyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl methacrylate, and aryl (meth)acrylate, each of which may be used alone or in a mixture of two or more.

Among them, n-alkyl whose alkyl group has 1 to 4 carbon atoms (
Useful are meth)acrylate, isobutyl(meth)acrylate, isopropyl(meth)acrylate, and t-butyl(meth)acrylate.

Other monomers (b) copolymerizable with (meth)acrylic acid ester (al) include, for example, vinyl acetate, vinyl chloride, vinylitine chloride, butadiene, vinyl ether, styrene, methylstyrene, acrylonitrile, methacrylonitrile, Examples include (meth)acrylic acid, itaconic acid, methaconic acid, citraconic acid, among others, styrene,
Methylstyrene and (meth)acrylic acid are useful.

In addition, the usage ratio of (meth)acrylic acid ester fal and other monomers (bl) copolymerizable with this is t in weight ratio.
a+/(bl is usually 10010 to 40/60, preferably 10010 to 60/40.

Another type of organic binder component, ethylene-ethyl acrylate copolymer (hereinafter abbreviated as EEA) (■), includes a copolymer obtained from ethylene and ethyl acrylate, and usually has an ethyl acrylate content of 1
~50% heavy view is used, but especially 10~40%
Preferably, the weight is %. Regarding the molecular weight of ERA, those with a weight average molecular weight of 00,000 or less are usually used, but in particular, those with a weight average molecular weight of 10,000 to 10,000 are used in terms of strength and fluidity.
70,000 is preferred.

The weight ratio of acrylic polymer (H) and EEA (II) is 1/(II)/(II[).
The ratio is 4 to 20/1, especially the molded product strength,
1/4 to 10/1 in terms of excellent balance of binder removal properties
1 is preferred. The weight ratio of (■)/(III) is 1 part 4
If the ratio is less than 20/1, the binder removal property will deteriorate and cracks, blisters, and deformations will easily occur, and if it exceeds 20/1, the strength will decrease, so these are not preferred.

The composition of the present invention may further include additives such as a surface treatment agent for ceramic powder, a sintering aid, a reinforcing material, an acrylic polymer (n), and an EEA to the extent that the effects of the present invention are not impaired. Synthetic resins other than (II[) can be added.

Examples of surface modifiers include silane camping agents such as vinyl silane, amino silane, epoxy silane, and methacryl silane, monoalkoxy titanium,
Titanium coupling agents such as tetraalkoxytitanium, titanium acylate, and titanium chelate; metal soaps such as stearate metal salts and laurate metal salts; nonionic, anionic, cationic, and amphoteric surfactants. etc., and the amount added is 100% of the ceramic powder.
It is usually 0.01 to 5 parts by weight.

Examples of reinforcing materials include inorganic or metal fibers, whiskers, etc., and are usually included in the ceramic composition for injection molding.
It is used in an amount of up to 50% by volume.

To give specific examples, inorganic fibers include asbestos, rock wool, slag wool, kaolin, bauxite, kyanite, glass, fused silica, alumina/silica, magnesia, potassium titanate, alumina, zirconia, silicon carbide, silicon nitride. Inorganic whiskers include whiskers made of sapphire, boron nitride, silicon nitride, aluminum nitride, beryllia, boron carbide, silicon carbide, graphite, etc., and metal fibers. Examples of metal whiskers include fibers and whiskers made of steel, stainless steel, aluminum, bronze, brass, copper, magnesium, nickel, titanium, beryllium, tungsten, molybdenum, boron, and the like.

Examples of the synthetic resin include polyethylene, polypropylene, polyacrylonitrile, acrylonitrile-styrene copolymer, ethylene-vinyl acetate copolymer, and the like.

To obtain the composition of the present invention, ceramic powder (I), acrylic polymer (n), ERA (II[), and additives, reinforcing materials, etc., which may be added as necessary, are mixed in a predetermined manner. It is sufficient to melt and mix the ceramic powder ( In T), it is preferable to add and mix a surface treatment agent and a sintering aid in advance.

(Effects of the Invention) The ceramic composition for injection molding of the present invention has ceramic powder that can be easily dispersed, has high fluidity, and can be easily molded into injection molded products that have excellent strength and are easy to handle. Moreover, it has excellent binder removal properties, so even if the binder is removed in a relatively short time, there will be no cracks or cracks.
It has the advantage of not causing blisters or deformation.

(Example) The present invention will be specifically described below with reference to Examples and Comparative Examples. Note that parts in the examples are parts by weight.

Example 1 100 parts of aluminum oxide, 9.3 parts of an acrylic polymer (consisting of 36 parts of methyl methacrylate, 54 parts of butyl methacrylate, 7 parts of ethyl acrylate, and 3 parts of acrylic acid, weight average molecular weight 25,000), EEA ( Ethyl acrylate content 18% by weight, weight average molecular weight 58,000
), 8.8 parts of polystyrene, 1.2 parts of dibutyl phthalate, and 1.0 part of stearic acid were added and kneaded at 130°C for 30 minutes using a pressure type double-arm kneader, and after cooling,
A ceramic composition for injection molding containing 55% by volume of aluminum oxide was obtained by pelletizing to about fi. When this composition was observed under a 100x optical microscope, no agglomerated particles were observed, and the ceramic powder was well dispersed.

This was injection molded under the conditions of a heating cylinder temperature of 150°C and an injection pressure of 600 kg/- to form a plate-shaped molded product (width: 50 kg/-) as shown in Figure 1.
Crane, length 90 cranes, thickness 3.6 days and 2 cranes) and Figure-2
A rod-shaped molded body (4 x 4 x 60 cranes) shown in Fig. 1 was obtained.

When a three-point bending test (span interval 30 m, loading speed 1 fi/min) was conducted using the molded article shown in Figure 2, the bending strength was 155 kg/cd.

Next, these molded bodies were heated to 500°C at a rate of 20°C/hr to remove the binder, and then held at 1700°C for 1 hour to sinter to obtain a good aluminum oxide sintered body. .

Example 2 Acrylic polymer (
Consisting of 40 parts of butyl methacrylate, 20 parts of butyl acrylate and 40 parts of styrene, weight average molecular weight 9000
0) 8 parts, EEA (ethyl acrylate content 25% by weight, weight average molecular weight 29000) 3 parts, dioctyl adipate 1.5 parts, stearic acid 1.0 parts, polyethylene wax 1.0 parts. In the same manner as in Example 1, a ceramic composition for injection molding containing 65% by volume of aluminum oxide was obtained. Similar to the composition of Example 1, this composition had good ceramic dispersion.

The heating cylinder temperature is 160℃ and the injection pressure is 800kg/a+.
The bending strength of the molded product shown in Figure 2, which was injection molded under the conditions of 1 and obtained the molded product in the shape shown in Figures 1 and 2, was 140.
kg/aj Next, these molded bodies were heated to 500°C at a rate of 25°C/hr to completely remove the binder, and then held at 1700°C for 1 hour to sinter and give a good result. A sintered aluminum oxide body was obtained.

Example 3 The molded product obtained in Example 1 and its molding waste (spool, runner, etc.) were coarsely ground to obtain a ceramic composition for injection molding. A good aluminum oxide sintered body was obtained in the same manner as in Example 1 except that this was used. Further, during injection molding, the molding ceramic composition was allowed to stay in a heating cylinder at 170° C. for 8 hours, but the moldability remained unchanged and a good molded product was obtained.

Example 4 A good aluminum oxide sintered body was obtained in the same manner as in Example 3 except that the molded product obtained in Example 2 and its molding product were used.

Example 5 100 parts of aluminum oxide, 9 parts of acrylic polymer (consisting of 50 parts of methyl methacrylate and 50 parts of butyl methacrylate, weight average molecular weight 8500), EEA (ethyl acrylate content 35% by weight, weight average molecular weight 156)
000), 4.5 parts of styrene, 2 parts of dioctyl phthalate, and 1 part of aluminum stearate were added, and the mixture was heated at 130°C for 30 minutes using a pressurized double-arm Nigu, and after cooling, it was pelletized and 51 volumes of aluminum oxide was added. A ceramic composition for injection molding was obtained. Similar to the composition of Example 1, this composition had good ceramic dispersion.

The heating cylinder temperature is 140℃ and the injection pressure cuff is 00kg/c1.
! The bending strength of the molded product shown in Figure 2 is 160.
kg/aJ.

Next, these molded bodies were heated to 500°C at a rate of 15°C/hr to remove the binder, and then held at 1650'C for 1 hour and sintered to obtain a good aluminum oxide sintered body. .

Example 6 100 parts of aluminum oxide, 15 parts of acrylic polymer (consisting of 50 parts of methyl methacrylate, 20 parts of glycidyl methacrylate, 10 parts of isobutyl acrylate and 20 parts of styrene, weight average molecular weight 20,000), EEA
(Ethyl acrylate content 18ii weight%, weight average molecular weight 62000) 1.5 parts, dioctyl phthalate 1.5
and 1.0 parts of stearic acid were added thereto and kneaded using a pressurized double-arm type Ni-Goo to obtain a pellet-shaped ceramic composition for injection molding material containing 60% by volume of aluminum oxide.

This was heated at a heating cylinder temperature of 160°C and an injection pressure of 600 kg/c.
Injection molding was carried out under the conditions of d to obtain a molded article having the shape shown in FIG. The bending strength of this molded body was 140 kg/cd. Next, this molded body was heated to 500° C. at a rate of 25° C./hr to remove the binder, and then held at 1700° C. for 1 hour and sintered to obtain a good aluminum oxide sintered body.

Example Example 1 except that 100 parts of Fittria solid solution zirconium oxide, 9 parts of the same acrylic polymer as in Example 1, EEAs part, 3 parts of dibutyl slate, and 3 parts of stearic acid were used.
In the same manner as above, a ceramic composition for injection molding containing 51% by volume of ceramic powder was obtained. As for the dispersibility of this composition, as in Example 1, the ceramics were well dispersed.

The heating cylinder temperature is 160℃ and the injection pressure is 800kg/cd.
Injection molding was carried out under the following conditions to obtain a molded article having the shape shown in Figure 2. The bending strength of this molded body was 140 kg/cd.

This molded body was heated to 500° C. at a rate of 15° C./hr to remove the binder, and then held at 1500° C. for 1 hour and sintered to obtain a good aluminum oxide sintered body.

Comparative Example I The use of EEA was omitted and the amount of acrylic polymer used was 1
Figure 2 was prepared in the same manner as in Example 6 except that the number was changed to 6.5 parts.
A molded body shown in was obtained, and the bending strength of this molded body was 115
It was as small as kg/-.

Next, when the plate-shaped molded body shown in FIG. 1 was injection molded in the same manner, the strength of the molded body was low, so cracks occurred during ejection for release from the mold, and a good molded body could not be obtained.

Comparative Example 2 Omitting the use of acrylic polymer and reducing the amount of EEA used to 1
Figure 1 was prepared in the same manner as in Example 6 except that the number was changed to 6.5 parts.
and 25°C to 500°C.
When the binder was removed by increasing the temperature at a rate of /hr,
Cracks and blisters occurred in all molded products, and no satisfactory binder-free product could be obtained.

Comparative Example 3 Omitting the use of acrylic polymer and reducing the amount of EEA to 1
A ceramic composition for injection molding containing 65% by volume of aluminum oxide was obtained in the same manner as in Example 2 except that the amount was changed to 1 part. When this composition was observed under an optical microscope with a magnification of 100 times, many aggregated particles were observed, indicating that the ceramic powder was poorly dispersed. The molded product shown in FIG. 1 was injection molded in the same manner as in Example 1, but the fluidity was poor and only a short shot molded product was obtained.

Comparative Example 4 60% by volume of aluminum oxide was prepared in the same manner as in Example 5 except that 14 parts of paraffin wax (melting point 135°F), 1 part of dibutyl butare and 2 parts of stearic acid were used for 100 parts of aluminum oxide. A ceramic composition for injection molding was obtained. When this composition was observed under an optical microscope with a magnification of 100 times, many aggregated particles were observed, and the dispersion of the ceramic powder was poor.

This was heated at a heating cylinder temperature of 140°C and an injection pressure of 800 kg/C.
When the plate-shaped molded body shown in Figure 1 was injection molded under the conditions of d, the strength of the molded body was low, so it broke during ejection for release from the mold, and a good molded body could not be obtained.

Further, when this ceramic composition for molding was retained in a heating cylinder at 170° C. for 8 hours and then injection molded, the fluidity decreased and only a short shot molded product was obtained.

Comparative Example 5 A molded article shown in Figure 1 was obtained in the same manner as in Example 1, except that 15 parts of APP, 1.0 part of dioctyl adipate, and 1.0 part of stearic acid were used for 100 parts of aluminum oxide, and then desorbed. When binder was applied, cracks and blisters occurred in all the samples, and satisfactory debinding products could not be obtained.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are perspective views of a molded article formed by injection molding a ceramic composition for injection molding.

Claims (1)

[Claims] Ceramic powder (I) and acrylic polymer (II)
and an ethylene-ethyl acrylate copolymer (III), further comprising an acrylic polymer (II).
and ethylene-ethyl acrylate copolymer (III) in a weight ratio (II)/(III) of 1/4 to 20/1.