JPS6086184A - Binder for powder - Google Patents

Abstract

PURPOSE:A binder for powder, consisting of a water-soluble diene based polymer, having improved binding power for the powder, capable of giving molded articles having improved flexibility, and useful for the molded articles produced from the powder, e.g. ceramic molded articles, etc. CONSTITUTION:A binder for resin obtained by using a modified diene based polymer prepared by preferably adding (B) preferably 10-30mol, based on 100 monomeric units of a component (A), maleic anhydride or a derivative thereof to (A) the diene based polymer (having preferably 10,000-50,000mol.wt. such as polyisoprene), and reacting (C) a basic compound, e.g. a monoamine, with the resultant addition product as a water-soluble diene based polymer. Ceramic particles, etc. are preferred as the powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-soluble binder for powders in moldings made of powders. More specifically, the present invention relates to a water-soluble powder binder used in the production of casting molds and ceramic molded bodies.

Traditionally, when manufacturing molds for casting or ceramic moldings, etc., it is necessary to give plasticity to the powder and bind the powder particles together (
In the case of a sintered body, the powder binder used for the purpose of firing the molded body and retaining its shape until sintering is a hydrophobic bond represented by polyvinyl plastic. Water-soluble binders such as agents, starch, molasses, casein, methylcellulose, carboxymethylcellulose, and polyvinyl alcohol are used. However, none of these binders can be said to have satisfactory performance.

In other words, for example, when using a hydrophobic binder such as polyvinyl gutilate P, it is necessary to dissolve it in an organic solvent, which makes the process complicated, and it is also prone to explosions and large fires. There is a problem in that there are major restrictions in terms of safety measures, sanitary measures for treatment against the absorption of solvent vapor, and measures for the installation of the solvent recovery device, etc.

Furthermore, when using the above-mentioned water-soluble binder, since it is dissolved in water and used, there is no problem when using an organic solvent, but a problem arises in its performance as a binder. That is, for example, when using starch or molasses,
The strength of the molded product obtained is not sufficient and the molded product collapses.
Easy to cause cracks, etc. Furthermore, when using methylcellulose, carboxymethylcellulose, polyvinyl alcohol, etc., the adhesiveness necessary for molding cannot be obtained, and the resulting molded product is not brittle because the dried film itself is hard, and it is prone to chipping and cracking. Indicates a defect that is easy to occur. For this reason, it is necessary to use a plasticizer to impart flexibility to the molded article, but the use of a plasticizer is accompanied by a decrease in adhesiveness as a binder and brings about various disadvantages.

Of the binders mentioned above, natural or semi-synthetic ones are biodegradable, so when they are stored in the form of an aqueous solution or in a molded product containing water, molecules Deterioration and rot occur due to cutting, and the performance as a binder decreases, causing problems in practical use.

Under these circumstances, there is a strong demand for binders that are water-soluble, have excellent bonding strength between powders, and provide molded products with excellent flexibility.

In consideration of this situation, the present inventors investigated various water-soluble binders for powder suitable for manufacturing molded articles made of powder, and as a result, they found that a water-soluble diene polymer was used as the binder. It was discovered that a molded body exhibiting excellent bonding strength to powder and having sufficient flexibility could be obtained by this method, and the present invention was completed.

That is, according to the present invention, maleic anhydride or a derivative thereof is added to a water-soluble diene polymer, particularly a diene polymer, in an amount of 95 per 100 monomer units of the diene polymer.
A powder binder made of a water-soluble modified diene polymer obtained by adding ~50 mol and then reacting with a basic compound provides excellent bonding strength to powder and prevents chips and cracks. To provide a molded article having flexibility that does not cause such problems.

Typical water-soluble diene polymers used in the present invention include a carboxyl group, that is, a group represented by the general formula -000°, in the monomer constituting the main chain, and an alkali ionically bonded to the carboxylado group. metal ions, alkaline earth metal ions, substituted or unsubstituted ammonium ions), and such modified diene polymers include unsaturated polymers containing carboxyl groups or groups derivable into carboxyl groups. A method (I
), or produced by method (n) in which a diene polymer is subjected to an addition reaction with an unsaturated compound having a carboxyl group or a group that can be induced into a refoxyl group, and then reacted with the basic compound. Ru.

The diene used herein means butadiene, isoprene, chloroprene, pentadiene, or the like. In addition, unsaturated compounds having a levoxyl group or a group derivable into a carboxyl group include (meth)acrylic acid, maleic acid, maleic anhydride, maleic acid (monomodi)ester,
It means an α, β-unsaturated (mono- or di)carboxylic acid such as maleic acid (mono- or di)amide, maleimide, itaconic acid, or a derivative thereof.

The water-soluble diene polymer preferably used in the present invention is as described in (II) above, which is subjected to an addition reaction with an α,β-unsaturated carboxylic acid or a derivative thereof, and then a basic Those obtained by reacting compounds are preferred.

In particular, it is preferable to use maleic anhydride or a derivative thereof as the α,β-unsaturated carboxylic acid or its derivative, and this will be explained below.

That is, the diene polymer that is the base of the water-soluble diene polymer produced by the method (n) above is as follows:
polybutadiene, polyisoprene, polypentadiene,
Examples include butadiene-isoprene copolymer, butadiene-styrene copolymer, isoprene-styrene copolymer, butadiene-acrylonitrile copolymer, isoprene-acrylonitrile copolymer, and the like. Among these polymers, those with sufficient binding strength when used as binders,
Polybutadiene, polyisoprene, and butadiene-isoprene copolymers are preferably used because they provide flexible molded products. Among these, isoprene-based polymers such as polyisoprene and butadiene-isoprene copolymers are preferred from the viewpoint of ease of reaction when maleic anhydride or its derivatives are added.

These diene polymers may be used alone or in combination of two or more.

If the molecular weight of the diene polymer is too small, the binding force will not be sufficient when used as a binder, and the strength of the molded product will not be sufficiently high.
If it is too large, there will be problems such as the viscosity of the reaction system being too high when maleic anhydride or its derivatives are added, and it becoming difficult to dissolve in water.
5,000~100,000, 10,000~
It is desirable that the molecular weight is in the low molecular weight range of so, o o o. Note that the molecular weight here refers to the viscosity average molecular weight (Mv)
In the case of the isoprene-based polymer that is most preferably used in the present invention, [η] =
1. '21X 10 My.

In the diene polymer, if the amount of vinyl bonds is too high, flexibility cannot be imparted to the resulting molded product, so the amount of vinyl bonds is preferably 40% or less, specifically 25% or less. In addition, when the above-mentioned diene-based polymer is a copolymer, its form may be block copolymerization or random copolymerization, as long as the above conditions are satisfied.
There is also no problem with graft copolymerization. Here, the amount of vinyl bonding is measured by infrared absorption.

Such diene polymers are produced, for example, by anionic polymerization, Ziegler polymerization, etc. using an alkali metal such as lithium metal or a lithium compound as a catalyst. It can also be produced by depolymerizing natural rubber or synthetic rubber.

Maleic anhydride or its derivatives are added to the diene polymer, but examples of maleic anhydride derivatives include maleic acid, monoalkyl maleate/I/(methyl, ethyl, propyl), dialkyl maleate, etc. Maleic acid ester, monoalkyl maleate (methyl and ethyl 110 p/I/) amide, dialkyl maleate amide, maleimide, and the like. During this addition reaction, maleic anhydride is used because of the ease of reaction, or
By reacting with lecol or amines and esterifying or amidating it, it is essentially the same as adding a maleic acid derivative from the beginning. This can be carried out by various known methods including heating in the presence or absence.

The amount of maleic anhydride or its derivatives added to the diene polymer is one of the important factors in the present invention in order to make the diene polymer water-soluble; if the amount added is too small, basicity may occur. When treated with a compound and dissolved in water, it becomes extremely difficult to dissolve in water.On the other hand, if the amount added is too large, the viscosity of the reaction system increases significantly during the addition reaction, and the basic compound When dissolved in treated water, the viscosity of the aqueous solution is too high and a molded product with high flexibility cannot be obtained. Therefore, the addition amount is preferably 5 to 50 mol, preferably 10 to 60 mol, per 100 monomer units of the diene polymer.

The diene polymer is made into a water-soluble diene polymer by adding maleic anhydride or a derivative thereof, and then reacting a basic compound with a group based on the added maleic anhydride or a derivative thereof. used in

Examples of the basic compound include hydroxides or carbonates of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, sodium suboxide, and potassium suboxide, ammonia,
Organic amines such as trimethylamine and triethylamine may be used alone or in combination of two or more. Among these, when it is necessary to sinter the molded product obtained by the present invention, ammonia and monoamine, which do not leave any residue on the sintered body, may be preferably used.

For the reaction between a diene polymer to which maleic anhydride or its derivative has been added and a basic compound, the basic compound is dissolved in water, and the diene polymer to which maleic anhydride or its derivative has been added is added to this. Alternatively, a method may be adopted in which a diene polymer to which maleic anhydride or a derivative thereof is added is reacted with a basic compound in bulk, in a molten state, or in a state dissolved in an organic solvent. Incidentally, maleic anhydride or a derivative-added diene polymer thereof which has been reacted with a basic compound in advance can be easily made into an aqueous solution by adding water. The amount of the basic compound used in this reaction is preferably in the range of 0.65 to 1 equivalent relative to the carboxyl group derived from maleic anhydride or its derivative.

The powder binder of the present invention, which is made of a water-soluble diene polymer, is usually used as it is when the powder is used in the form of an aqueous dispersion, or in the form of an aqueous solution, so that the concentration of the aqueous solution in the powder-containing slurry is 5 to 50% by weight, at a ratio of 0.01 to 50 parts by weight per 100 parts by weight of powder, for forming casting molds, granulating or forming pulverized charcoal (charcoal, old method), cement. It is used in the production of molded products made of powder, such as granulation or molding of raw material ferrite for magnets, granulation and molding of refractory particles, molding or granulation of ceramic powder, etc. It can also be used to prevent the powder from scattering by spreading it thinly over the surface of a large amount of powder to bond only the surface layer. Among these, it is useful for forming ceramic particles, and so-called ceramics have high heat resistance, hardness,
Since it has excellent insulation properties and is of great importance in various fields as a heat-resistant material, a superhard material, an insulating material, a shielding material, and a structural material, it will be explained below.

In other words, ceramic moldings are made of silica sand, silica stone,
Natural ceramics such as pyrolite, montmorillonite, selinite, kaolinite ζ column dam, pottery stone, feldspar, magnesite, alumina, magnesia, zirconia,
Consisting of ceramic particles such as spinel, silicon ash, boron ash, silicon nitride, boron nitride, artificial ceramics such as graphite, or ceramic particles dispersed in water, and the water-soluble diene polymer of the present invention. This is carried out by mixing the binder or its aqueous solution in a conventional manner using a mixer such as a ball mill, and molding the resulting molding composition in a conventional manner. Examples of the gearing method include slurry casting, a doctor blade method, an extrusion method, an injection molding method, and a pressure molding method. In such a molding method, the composition may be used as it is, but the composition may also be granulated and then subjected to molding.

Alternatively, a method may be adopted in which the material is formed into a sheet or film and then punched into a desired shape. In order to obtain high quality products in the production of ceramic sintered bodies,
The quality of the powder molding stage plays an important role, and in order to produce a product with the desired properties at a high yield, it is necessary to produce a molded product with a uniform structure and shrinkage. It's out of nowhere.

In such molding, the concentration of the water-soluble diene polymer used in the aqueous solution can be determined arbitrarily, but considering the workability when dissolving the water-soluble diene polymer or the workability when making a molded article. , preferably in the range of 5 to 50% by weight. In addition, the amount of water-soluble diene polymer used for ceramic particles depends on the type of ceramic particles,
Although it is determined by the molding method, the shape of the molded product, and the plasticity of the molded product, it is generally 25 parts by weight per 100 parts by weight of the ceramic powder, preferably 11. <Hao, 2~20
A range of 1i11:m is desirable.

In addition, when producing a molded article made of powder using the binder for powder of the present invention, a dispersant, lubricant, surfactant, mold release agent, etc. may be added as necessary. . Also,
There is no problem in adding a plasticizer such as dioctyl phthalate or polyethylene glycol to an extent that does not impair the spirit of the present invention.

It is also possible to use a conventionally used binder such as carbon fiber, carboxymethyl cellulone, or polyvinyl alcohol.

The binder for powder of the present invention imparts plasticity to the powder, binds the powder particles to each other, and provides a molded article that is uniform, has little shrinkage, and has excellent flexibility. Therefore, it is useful for molding powder molded products used in various fields. The above-mentioned molded product may be used as it is or dried, such as a casting mold or a molded product of pulverized coal (fuel), or may be sintered, such as a ceramic molded product. Advantageously, the binder of the present invention does not adversely affect such processing, nor does it cause problems of deterioration or spoilage.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 and Comparative Example 1 A molecule obtained by polymerizing isoprene monomer using n-butyllithium as a catalyst. Low molecular weight polyisoprene 10 with a JJi of 15,000 and a cis'+4 bond content of 81%.
Add 30i parts of maleic anhydride to 0 parts by weight and heat at 180°C.
The addition reaction of maleic anhydride was carried out by heating at . The obtained reactant contains polyisoprene monomer units j
It was a modified polyisoprene to which 19 moles of maleic anhydride had been added at OD. The modified polyisoprene was added to 600 parts by weight of water in which 25 parts by weight of sodium hydroxide was dissolved to obtain an aqueous solution of water-soluble polyisoprene.

The above-mentioned water-soluble polyisoprene aqueous solution was poured onto No. 6 silica sand for molding, and the amount of water-soluble polyisoprene was 0.5.1% each.
and 5% by weight, and after thorough mixing, the resulting mixture f 50m771 x 25mm x 17mm
A molded product was produced by pressing into a rectangular parallelepiped shape.

For comparison, a molded product was similarly produced using polyvinyl alcohol (Kurare Bobber 7+z217) instead of water-soluble polyisoprene.

The bending strength of the obtained footwear molded product was measured at a span width of 18 mm. Furthermore, the compressive strength of the molded product was measured after drying it at 200° C. for 2 hours.

The results are shown in Table 1.

Table 1'/1,0 2.1853.1/15. D 3.0157. Q Comparative example None 0. 0.04 Example 2 and Comparative Example 2 By polymerizing isoprene monomer as n-butyllithium, the obtained molecular weight was 54,000;
c-1.4 Low molecular weight polyisoprene 10 with 84% bond content
Add 40]i parts of maleic anhydride to 0 parts by weight, 180°C
The addition reaction was carried out by heating at .

The resulting reactant was a modified polyisoprene to which 923 mol of maleic anhydride was added per 100 monomer units of polyisoprene. Next, the modified polyisoprene was added to 450 parts by weight of water in which 15 parts by weight of sodium hydroxide was dissolved to prepare a water-soluble polyisoprene aqueous solution.

The above water-soluble polyisoprene aqueous solution was added to the coal powder passed through a 1 mm sieve so that the solid content was 0.5.1% and 5% by weight to produce a cylindrical molded product with a diameter of 50 mm and a height of 48 mm. .

The compressive strength of this molded product and a molded product prepared in the same manner as above except that polyvinyl alcohol was used instead of water-soluble polyisoprene were measured for compressive strength. In addition, these molded products were dried at 150°C for 2 hours,
It was used to measure dry compressive strength. The results are shown in Table 2, and it can be seen that when water-soluble polyisoprene is used, sufficient bonding strength is exhibited and the molded product also has sufficient strength.

Below is the margin Table 2/l l 1.0 18.0145.6/l I 5.
[] 29. '9872.1 Comparative example None -1,0
92,1 〃 Polyviny/I/ 1.0 12. Oj 24.8 Alcohol Example 3 and Comparative Example 6 Anhydrous maleic acid was added to 100 parts of low molecular weight polyisoprene with a molecular weight of 29,000 obtained by polymerizing isoprene monomer using n-butyllithium as a catalyst. acid 25
A modified low molecular weight polyisoprene in which 16 moles of maleic anhydride was added per 100 isoprene monomer units was produced by adding the heavy background and heating at 180°C. The modified low molecular weight polyisoprene was added to 300 parts by weight of water containing 8 parts by weight of ammonia to prepare an aqueous solution of water-soluble polyisoprene.

Zirconium silicate (content 88% or more, 6
~100 mesh), and 10 parts by weight of the water-soluble polyisoprene described above was added as a binder to 100 parts by weight of the powder to prepare a blend. Further, a formulation was prepared in the same manner except that polyvinyl alcohol was used as the binder. These formulations were then used to create a 50 mm
A rectangular parallelepiped of 25 mm x 17 mm was press-molded, and its bending strength and compressive strength were measured in the same manner as in Example 1. Also, 100 m from the above formulation
A rectangular parallelepiped specimen of m×20η1771×2 mlH was press-molded, and the flexibility was evaluated by a curve test. The flexibility was evaluated based on the radius of curvature when cracks appeared in the molded product. These results are shown in Table 6, and it can be seen that when water-soluble polyisoprene is used, sufficient bonding strength is exhibited, and the resulting molded articles have sufficient strength and at the same time sufficient flexibility.

Table 6 with blank space below Alcohol Example 4 and Comparative Example 4 - 100 parts by weight of a low molecular weight polybutadiene with a molecular weight of 15,000 obtained by polymerizing a butadiene monomer using n-butiflerithium as a catalyst and 3 parts by weight of maleic anhydride.
By adding 0 H to the base and heating at 180°C, an addition reaction of maleic anhydride to polybutadiene was carried out.

The amount of maleic anhydride added was 914 mol per 100 monomer units of polybutadiene. Next, the obtained reaction product was added to 650 parts by weight of an aqueous solution containing 8 parts by weight of ammonia while stirring to prepare an aqueous solution of water-soluble polybutadiene.

Low soda high alumina (containing TT 98.9%) with a particle diameter of 1 to 3 μm is used as the ceramic raw material particles, and the above water-soluble polybutadiene aqueous solution is applied to the particles as a binder, so that the water-soluble polybutadiene is di- and triple-polymerized, respectively. %, ball milled, and dried in a desk type Nupre dryer to produce a granulated composition for a ceramic molded body.

By pressurizing the composition with a hydraulic press 40
A plate-shaped molded body with a size of mm x 20 mm x 5 mm was produced.

The obtained molded body and the molded body dried at 100°C for 2 hours were subjected to measurement of bending strength.
The results shown in Table 4 were obtained. For comparison,
Instead of water-soluble polydiene, polyvinyl alcohol) V (
A molded article was produced in the same manner except that Kuraray Bobber (Kuraray Bobber) v217) was used, and the bending strength was measured. The above-mentioned bending strength was determined by supporting the molded product at two points with a span width of 25 mtn, pushing up the middle part, and measuring the strength when the molded product breaks using an autograph.

Table 4 with blank spaces below tt 3.0 45.7 87.3 Comparative Example Polyvinyl 2.0 17.4 32.4 Alcohol Example 5 and Comparative Example 5 Using n-butyllithium as a catalyst, isoprene as a monomer, By adding butadiene and isoprene in this order and performing living polymerization, a block copolymer of polyisoprene-polybutadiene-polyisoprene (weight ratio of polyisoprene-polybutadiene-polyisoprene 60/40/30) with a molecular weight of 31,000 is produced. Obtained. By heating this low molecular weight block copolymer and maleic anhydride to perform an addition reaction, and then further adding methanol,
A modified low molecular weight block copolymer to which 921 mol of monomethyl maleate was added per 100 monomer units of the block copolymer was obtained. Next, 100 parts by weight of this copolymer was added to 6
．． The mixture was added to 600 parts by weight of water containing ammonia to obtain a water-soluble block copolymer aqueous solution.

High purity alumina (content 99.9% by weight, average particle size 0,
8 mm) and the water-soluble block copolymer aqueous solution were sufficiently mixed in a ball mill, and then pressed into a diameter of 50 m.
m. A disc-shaped molded body with a height of 17 nrm was produced.

This molded body was divided into semicircles, and one half was used to measure the bending strength at a span width of 18 mm, and the other half was used to measure the bending strength at a span width of 18 mm.
After drying at 00°C for 2 hours, the compressive strength was measured using an Amsler tester. The results are shown in Table 5. For comparison, the results for a molded article produced using polyvinyl alcohol/L/ (Kuraray Bovar 217) as a binder are also shown.

Table 5 below is a blank space A low molecular weight polyisoprene 100 with a molecular weight of 26,000 and a cis-1,4 bond content of 84% was obtained by polymerization as
Addition reaction of maleic anhydride to polyisoprene was carried out by adding 25 parts of maleic anhydride to the mi part and heating at 180°C. In the obtained modified polyisoprene, the amount of added maleic anhydride was 17 mol per 100 polyisoprene monomer units. This modified polyisoprene was added to 350 ii parts of water containing 9 parts by weight of ammonia to obtain a water-soluble polyisoprene aqueous solution.

The above water-soluble polyisoprene aqueous solution was added to low soda high alumina with a particle size of 1 to 3 μm in an amount of 15% by weight based on the alumina, and after thorough mixing in a ball mill, the resulting mixture was spread on a polyethylene film to a thickness of 15% by weight. The coating film was spread to a thickness of 2 mm, left at room temperature for 15 minutes, and then heated and dried in a hot air dryer at 70° C. for 5 hours. The plate-shaped molded product thus obtained had a bulk specific gravity of 2.59 and a size of 25 mm
When punching was performed using a 25 mm square punching blade and a 35 mm diameter circular punching blade, a molded article could be obtained without deformation.

Patent applicant RiRashi Co., Ltd. Representative Patent Attorney Ken Honda

Claims (4)

[Claims] (1) A binder for powder used in molded products made from powder, which is made of a water-soluble diene polymer. (2) A water-soluble diene polymer is prepared by adding 95 to 50 moles of maleic anhydride or a derivative thereof per 100 monomer units of the diene polymer, and then reacting with a basic compound. The binder for powder according to claim 1, which is a modified diene-based polymer obtained thereby. (3) The molecular weight of the diene polymer before modification is 5,000
The binder for powder according to claim 2, wherein the binder has a molecular weight of 100,000. (4) The binder for powder according to any one of claims 1 to 5, wherein the powder is a ceramic particle.