JPS61213331A - Production of improved molding - Google Patents

Abstract

PURPOSE:To improve workability and to prevent cracking in the stage of secondary calcination by compounding a binder and conjugate diolefin low polymer at a specific ratio with aggregate consisting of metallic powder and ceramic powder, mixing further steel fibers therewith and molding and calcining the mixture. CONSTITUTION:An additive D consisting of the binder C contg. an evaporating component and the conjugate diolefin low polymer (deriv.) is compounded with the aggregate consisting of ferrous metal or the metallic powder of >=1 kinds among Fe, Ni and Al. The compounding ratio is made 1-5:1-5:0.05-0.5 A:B:C:D by weight. The steel fibers E are mixed at 0-50vol% with such compd. The slurry thereof is molded in a mold and is subjected to natural drying or primary calcination. The molding is then calcined at 300-1,300 deg.C in an oxidizing atmosphere. The molding is porous and has a dense solidified shell layer on the surface. The green strength of the solidified molding is thus improved and the cracking in the stage of secondary molding is prevented.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a suction mold, particularly a fired body having a porous ventilation structure useful for suction molding or vacuum forming, and a method for manufacturing the same. More specifically, the molded body has a dense hardened shell layer in which metal oxide powder is dispersed and an internal unfired backing layer, and the entire mold has a porous structure with a porosity of 1 to 50%. The present invention relates to an improved method of manufacturing a durable mold, characterized in that:

Technical Background and Problems of the Invention When molding a composite fired body whose main aggregate is a ferrous metal or one or more metal powders selected from iron, nickel, and aluminum and ceramic powder, an aggregate mixture thereof is used. A caking agent containing components that evaporate during the curing process is mixed in a weight ratio of (1 to 5): (1 to 5) = 1 to form a slurry, and then poured into a mold to form a primary molded body, A method has been proposed in which, after air drying and/or primary firing, the material is removed from the mold and subjected to secondary firing at a high temperature of 300°C or higher (JP-A-60-6241@, JP-A-60-6242).
No. 60-6243). When using this method, a fired product with an excellent porous aeration structure can be obtained, but the strength of the solidified molded product before firing, that is, the green strength, is not necessarily sufficient, and it may be partially damaged when taken out of the mold, or when fired. There are drawbacks such as cracks that may occur, and it has been considered to improve the yield by improving these.

In addition, in order to particularly improve transferability, it is known that the smaller the particle size of the aggregate, the better, but the conventional technology has a limit of about 50μ due to the above-mentioned drawbacks, and it is desirable to improve this point as well. Mareta.

OBJECT OF THE INVENTION The object of the present invention is to dry naturally in a mold and/or to dry a primary molded product having improved green strength, especially a slurry-like material made by blending an aggregate mixture and a caking agent. The purpose of the present invention is to provide an improved manufacturing method that improves the strength of a fired green molded body, improves handling workability, and prevents cracking during secondary firing at high temperatures.

Summary of the Invention The present invention uses ferrous metals or one or more metal powders (A) selected from iron, nickel, and aluminum as aggregates and ceramic powders (B), and adds evaporated components to the aggregates during the curing process. A:B:
C: [) is the weight blending ratio (1-5): (1-5):1
:(0.05~0.5), and steel fiber (, E
) is poured and molded, the molded body is air-dried and/or primarily fired, and then fired at a firing temperature of 300-1300°C in an oxidizing atmosphere. , production of a porous composite molded body, which is characterized by having a porous and dense hardened shell layer on the surface, thereby increasing the green strength of the solidified molded body and preventing cracking during secondary firing. It is about law.

Furthermore, by using aggregate with a particle size of 50μ or less, which was limited in use due to the risk of cracks occurring in the conventional technology, it was possible to create an excellent molded product, that is, with improved surface roughness and good transferability. A molded body can be obtained.

Furthermore, as an unexpected effect, the use of the additive (D) improved the strength of the composite molded product after sintering, which means that the range of applications of the composite molded product will be expanded. This is a favorable result.

This is especially true when said additives are derivatives with unsaturated bonds or/and other suitable polar groups, which suggests that they are particularly effective when the additives are derivatives with unsaturated bonds or/and other suitable polar groups. It is thought that the viscosity of the slurry was improved due to improved surface wetting, and the packing density was improved, which is closely related to the mechanism of improving green strength, which is the intended purpose of the present invention. It is thought that it is related to.

The conjugated diolefin low polymer constituting the additive (D) used in the present invention usually has 4 to 8 carbon atoms, such as butadiene, isoprene, 1,3-pentadiene, cyclopentadiene, and 1,3-octadiene. A polymer of one type of conjugated diolefin, a copolymer of two or more of these, and one or more of these conjugated diolefins as the main component (40 wt% or more), styrene, vinyltoluene, acrylic acid and its esters, acrylonitrile, It refers to a low copolymer of vinyl monomers such as vinyl acetate, other phenols, rosin acid, etc.

The polymerization method of the conjugated diolefin low polymer is not particularly limited, and any polymerization method suitable for each monomer or their combination may be adopted, including anionic polymerization using an alkali metal or an organometallic compound thereof. Any of the following methods are possible: cationic polymerization using a Friedel-Crauch catalyst, coordination anionic polymerization using a transition metal catalyst such as nickel, telomerization using a radical initiator, or thermal polymerization.

In the present invention, derivatives of these polymers can also be suitably used. As derivatives, acid groups,
Those into which an epoxy group, a human O-oxyl group, an amine group, a mercapto group, etc. are introduced are used. Examples of these are:
These include products in which maleic anhydride is added to a polymer, or products in which the adduct is esterified with alcohols, products in which the polymer is epoxidized, and products in which amine, acid, mercaptan, etc. are further reacted after epoxidation. .

The molecular weight of the conjugated diolefin low polymer or its derivative constituting the additive (D) can be selected within a fairly wide range, but usually has a number average molecular weight of 11,300 to 60,000.
Preferably it is 500 to 20,000. If the molecular weight is too low, the desired strength cannot be obtained, and if the molecular weight is too high, the compatibility with the binder (C) may be poor, or there may be problems such as elution and separation from the slurry. arise.

Furthermore, in order to carry out the present invention smoothly, it is recommended to use an appropriate solvent, but in that case, if the molecular weight of the polymer is too high, the solution viscosity will increase and a good slurry-like product cannot be obtained. In such a case, the solvent is not particularly limited as long as it is a good solvent for the conjugated diolefin low polymer or its derivative, but aromatic solvents such as benzene, toluene, xylene, methylene chloride, etc. A halogen-containing solvent such as ethanol, alcohols such as isopropyl alcohol, cellosolves such as Putiluse O Tsuru 7, etc. can be arbitrarily selected. Particularly preferred solvents are alcohols and soaps.

Among the metal powders (A), iron powders such as cast iron powder, electrolytic powder, pure iron powder, copper powder, etc. are used as the iron-based powder. This inner cast iron powder has the advantage of promoting pore formation by burning free carbon during firing.

The ceramic powder (8) has a small deformation rate at high temperatures and is easily bonded to the metal powder (A), such as neutral materials such as mullite, calcined alumina, activated alumina, fused alumina, chromite, and sillimanite. Generally, acidic materials such as fused silica, zirconium, and fused zircon are suitable, but basic materials such as magnesia, talc, etc. can also be used.

As a binder (C) containing components that evaporate during the curing process,
Ortho methyl silicate, ethyl silicate, ortho n
- Silica sol, colloidal silica, etc., typified by butyl silicate or a condensate thereof, etc., are used. In this case, it is also possible to use a suitable catalyst, such as an organic or inorganic acid or base, which reacts with the binder to promote the curing reaction.

As the steel fiber H (E>), stainless steel is generally suitable, and free-cutting steel can also be used, but for example, one produced by the chatter vibration cutting method is suitable.

The blending ratio of the iron-based powder or one or more metal powders selected from iron, nickel, and aluminum (A), ceramic powder (B), and caking agent (C) is approximately (1) by weight.
~5): (1~5)=1 is preferable, and by this blending ratio, properties such as strength, air permeability, thermal conductivity, and surface texture can be obtained in a well-balanced manner. The lower limit of the mixing ratio was specified here because it is necessary to obtain the minimum strength that can be used as a mold, and the upper limit was specified because if there is too much aggregate, moldability will deteriorate. Reduces the coating ability of the binding agent,
This is because it causes a decrease in strength and a deterioration in the stability of the mold surface. The reason for setting the upper limit for metal powder is that even if the mixture of ceramic powder and binder is perfect, if metal powder is used in excess, sufficient strength cannot be obtained, and the surface may become more porous than necessary. This is because the properties deteriorate and the transferability is impaired. Caking agents are necessary for bonding aggregates and also for achieving air permeability.

The additive (D) of the present invention helps the bonding of the aggregates by the caking agent to make it stronger, and also increases the viscosity of the slurry made of the aggregates (A), (B) and the caking agent (C). It is used to obtain molded bodies with improved surface roughness and excellent green strength.

The appropriate amount to use is (0.05 to 0.5 degrees) based on the basic formulation. If the amount of additive (D) is too small, the desired strength cannot be obtained, and if it is too large, the composition of the slurry will become non-uniform, resulting in a decrease in strength or poor reproducibility.

When steel fibers are used in combination, the amount added is not particularly limited, but good results can be obtained with an amount of approximately 0 to 30% by volume, preferably 0 to 20% by volume. Addition of too much steel fiber tends to cause fiber balls, which may reduce moldability.

The particle size of the metal powder is generally 5 to 500 .mu.m in maximum dimension, while the particle size of ceramic powder is preferably 5 to 300 .mu.m in maximum dimension. The use of the additives of the present invention makes it possible to densely fill the aggregate, making it possible to use aggregate with a smaller particle size, which is effective in improving transferability, but using aggregate of 5μ or less may cause cracks. It becomes difficult to avoid the occurrence of The upper limits for each are determined from the viewpoint of strength and because excessive porosity would deteriorate the surface properties of the mold.

tj4tJAN has a length of 1 depending on the size of the mold etc.
A material having a thickness of 20 to 400 μm and a thickness of 20 to 400 μm may be appropriately selected.

Each of the constituent components (A) and (B) selected as described above
, (C), (D), and if necessary (E) are added, mixed well, poured into a specified mold, and if necessary, vibrated with a vibrator etc. to sufficiently fill the mixture. After being allowed to stand for a few minutes, the mold is removed, and then air-dried and/or primary firing is performed. This is to prevent the occurrence of cracks and distortion in the next secondary firing process, as well as to make it porous by evaporating the alcohol content contained in the binder and additives. Natural drying time is selected from a range of 1 to 48 hours. The latter primary firing may be performed by directly igniting the demolded molded body with a torch lamp or the like.

The molded body after this natural drying and/or primary firing process has air permeability throughout and can be used as it is for pressureless casting. However, the mechanical strength is still low and durability is undeniable, so the present invention
After the natural drying and/or primary firing, the molded body is subjected to secondary firing under oxidizing atmosphere conditions. The oxidizing atmosphere may be air, or may be oxygen-enriched air in consideration of oxygen supply. Although the firing conditions depend on the blending ratio of each component, the mold dimensions, the desired porosity, etc., it is generally preferred that the firing temperature is 300 to 1300°C and the firing time is 81 hours or more.

The lower limit of the firing temperature is 300°C and the lower limit of the firing time is 1 hour because if the firing temperature is lower than that, the firing will be insufficient and the dense hardened shell layer, which is a feature of the present invention, will not be formed.
This is because the strength necessary for a durable type cannot be obtained. The reason why the upper limit of the firing temperature was set at 1300° C. is that although a hardened shell layer is formed, the surface becomes rough and transferability is impaired.

The longer the firing time, the greater the strength that can be obtained, but the hardened shell layer does not grow beyond a certain limit, resulting in surface roughness and reduced productivity. Although it depends on the mold dimensions etc., the maximum length is 4
A maximum of 8 hours is preferred.

In the present invention, in order to adjust the air permeability (porosity), the types of metal powder (A) and ceramic powder (B), particle size mixture ratio, vibration and squeezing conditions during pour molding, etc. are adjusted depending on the purpose. It may be set arbitrarily, taking into consideration the required strength of the molded body. The porosity usually obtained is in the range of 1 to 50%, and the compressive strength is about 300 to 2000 ko/cs2
However, it is not impossible to obtain a strength of 2000kMcg+2 or more.

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

Stop wheel [Cast iron powder (particle size under 100μ) as metal powder (A)
, synthetic mullite powder (particle size 1
00 μ under), ethyl silicate was used as the binder (C), and the blending ratio (multilayering) was 25:2.
5:10, mix uniformly, pour into the specified mold, harden, leave as it is for 30 minutes, remove from the mold, length 20111111 diameter 10mm (hereinafter referred to as 20mm)
A cylindrical molded body (denoted as x 10 mmφ) (denoted as a >) was obtained.The obtained molded body was directly ignited to perform primary firing for 30 minutes, and then placed in an electric furnace and heated at 900°C under atmospheric conditions.
Firing was performed for 5 hours to obtain a composite molded product (b).

11L Cast iron powder (particle size under 50μ) as metal powder (A),
Synthetic mullite powder (particle size 50
μunder), ethyl silicate was used as the binder (C), and the blending ratio of A:B:C was 25:2 by weight.
A slurry mixture is made by uniformly mixing and stirring at a ratio of 5:10, and this slurry is poured into a master model with a grain pattern and hardened. After the demolding model is air-dried for 48 hours, The mixture was treated in a firing furnace at 900° C. for 6 hours to obtain a suction mold (C). Also, by the same operation, 20
a+mx 10a+mφ cylindrical green molded body (d
) and a fired molded body (e') were prepared.

An isopropyl alcohol solution (50%) of dicyclopentadiene (DqPD) and allyl alcohol copolymer on Lii,
2 for 60 g of the slurry obtained according to Comparative Example 1.
Test piece (f) before firing after molding with g added, 900
A test piece 1o) was obtained after firing at 5°C. The compressive strength of each test piece was determined, and the test piece of Comparative Example 1, <a
> and (b) are shown in Table 1.

It is clear from Table 1 that by using the additive of the present invention, the green strength of the molded product is improved, and furthermore, the strength after firing is significantly improved.

Liquid polybutadiene with 11,800 molecules (abbreviated as LP8)
was epoxidized according to a conventional method, and the oxirane oxygen content was 6.5
% of epoxidized LPB was obtained. Dimethylamine was added to this to obtain LPB derivative-A. An ethyl cellosolve solution (50%) of this LPBN conductor-A was added to Comparative Example 2.
2 g was added to 60° of the slurry obtained according to the above procedure, molded, and after being left for about 30 minutes, the mold was removed and baked at 900° C. for 6 hours. The compressive strength values of the test pieces before and after firing are shown in Table 2 together with the results obtained in Comparative Example 2.

It is clear from Table 2 that the addition of LPB derivative-A improves both the green strength and the strength after firing of the molded product.

Generally, when the amount of caking agent is increased to increase the porosity of a molded product, the strength of the resulting molded product decreases, but by using the additives of the present invention, even with a high porosity, sufficient strength can be obtained. It is also clear from Table 2 that strength is obtained.

Using various low polymers and their derivatives synthesized by prescribed methods as additives (D), molded bodies were prepared before and after firing according to the method of Example 1, and the compressive strength of each was measured. At the same time, the surface condition of each was observed. The results are shown in Table 3.

It is clear from Table 3 that by using the additive of the present invention, the surface roughness of the molded body is improved, and the compressive strength before and after firing is significantly improved.

1m Nickel powder (under 125μ) as metal powder (A), activated alumina (under 150μ) as ceramic powder (B)
μ under), ethyl silicate as the binder (C), and epoxidized LPB (D-1) as the additive (D).
), phenol was added, Pa (D-2> was added, and stainless steel iim (length 100 μm, thickness 20 μm) was added.
The resulting slurry was poured into a master model with a grain pattern and cured to obtain a molded product. Similarly, a test piece of 201111×1011φ was prepared, and the compressive strength was measured. The results are shown in Table 4.

'm'': Liquid polybutadiene

Claims (1)

[Scope of Claims] [1] Ferrous metals or one or more metal powders selected from iron, nickel, and aluminum (A) and ceramic powders (B) are used as aggregates, and evaporated during the curing process. A binder (C) containing the component and a conjugated diolefin low polymer or/
and its derivative (D), A:B:C:
The weight mixing ratio of D is (1-5):(1-5):1:(0.
05 to 0.5), and add steel fiber (E) to 0 to 5
A porous and molded product characterized by pouring and molding a slurry containing 0% by volume, air drying and/or primary firing of the molded product, and then firing at a firing temperature of 300 to 1300°C in an oxidizing atmosphere. A method for producing an improved composite molded body having a dense hardened shell layer on its surface. [2] The method for producing a composite molded article according to claim 1, wherein the conjugated diolefin low polymer and its derivative have a number average molecular weight of 300 to 60,000. [3] The composite molded body has a dense hardened shell layer in which metal oxide powder is dispersed and an internal unfired backing layer, and the entire mold has a porous structure with a porosity of 1 to 50%. A method for manufacturing a composite molded body according to claims 1 and 2, characterized in that: