JPS6183669A - Binder for ceramic green 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 A. Field of Industrial Application The present invention relates to a binder for binder green bodies, and more specifically, binder for binder green bodies, and more specifically, binder for binder green bodies, which is characterized by being made of a specific polyvinyl alcohol having a reactive silicon group at the end. This relates to a binder for green bodies.

By firing the high-strength, high-density, and highly homogeneous solid green body obtained using the binder for solid green bodies of the present invention, high strength, high density,
A ceramic molded body with extremely homogeneous properties is obtained.

In recent years, ceramics have been used in a wide range of applications such as electronic materials, magnetic materials, optical materials, and high-temperature materials, taking advantage of their unique properties. Requests for ceramics from various aspects, for example,
Products with higher dVB homogeneity, products with complicated shapes, and even larger products may be stronger.

In order to realize these demands, extensive studies have been made from both the aspects of raw ceramic powder and molding binder, but when we look at Setsumitsuku green body, it is difficult to realize the above demands. Therefore, there is a need for a solid green body that has high strength, high processability, and has a low content of organic binder.

Conventionally, various polymers have been used as binders for set green bodies. For example, polyvinyl alcohol, cellulose derivatives such as hydroxyethylcellulose, polymers mainly based on (meth)acrylic acid esters,
The main ones are polyvinyl butylar and the like. However, when using these organic binders, always (
1) Problems in the binder removal operation, (2) Problems in the mixing of impurities, etc., and (3) Problems in dimensional accuracy. However, in order to obtain a solid green body with higher strength and better workability, the amount of organic binder used so far must be increased. This will have a great negative effect on the properties of the resulting ceramic molded body.
At present, there is a strong demand for a binder for solid green molding that provides a highly homogeneous solid green body.

C Problems to be Solved by the Invention The present invention provides a green material with higher strength, higher density, higher homogeneity, and a lower content of organic binder than the above-mentioned conventional green material using an organic binder. This is an attempt to provide a binder for the body that can be used as a binder.

D. Means to Solve Problem D As a result of intensive study on the above points, the inventors of the present invention found that from a polyvinyl mono-alcohol summer polymer having a reactive silicon group at one end (hereinafter abbreviated as PVA polymer polymer). The binder is used as a binder for green bodies with low f
? It was discovered that a solid green body with high strength, high density, and high homogeneity can be obtained by applying A and C, and the present invention was completed.

PVA having a reactive silicon group at the end used in the present invention
In the case of thread strand coalescence, I'V has a reactive silicon group at the end, which is obtained by hydrolyzing a silicate group represented by the following formula (1).
This includes all A-based polymers.

[However, R+ is a hydrocarbon group having 1 to 20 carbon atoms, more preferably a hydrocarbon group having 1 to 10 carbon atoms, and 2 is an alkoxy group, acyloxy group, phenoxy group, or alkylphenoxy group having 1 to 20 carbon atoms. group, (acyloxy group, acyloxy group, phenoxy group, and alkylphenoxy group may have an acid-containing substitution or substituent.) n is 1 to
It is an integer of 3. ] n is preferably 3 or 2, and 3 is particularly preferable because the reactivity of the silicon group is large.

By hydrolyzing the above-mentioned silyl group with only alkali, acid or water, alkoxy groups, acyloquine groups, phenoxy groups, and alkylphenoxy groups can be relatively easily converted into OH- groups, OM (af is an alkali metal group, ammonium group, etc.) This results in a reactive silicon group.

The bond between the PVA main chain and the reactive silicon group is not particularly limited, but it is preferably a group that is difficult to decompose by hydrolysis or heating.

The present invention includes PVA having reactive silicon groups at the ends. In the present invention, the aqueous injection includes not only those that completely dissolve in water but also those that contain some insoluble matter but are water-dispersible and can be dissolved in water. However, in order to more efficiently exhibit the effects of the present invention, the vinyl alcohol unit should be 50 mol% or more,
Preferably, the polymer containing 70 mol% or more is hazy.

There are no particular limitations on component units other than vinyl alcohol units as long as the polymer is water-soluble or water-dispersible. Examples include vinyl ester units, olefin units such as ethylene and propylene, and vinyl units such as acrylic acid, methacrylic/L/acid, or salts, amides, and esters thereof.

Various degrees of polymerization of the PVA polymer having a reactive silicon group at the end of the present invention can be used. However, the lower the viscosity of the inorganic slurry, the better; from this point of view, the degree of polymerization should be 2,000 or less. The relative viscosity of is ηrel, the degree of polymerization is P, and the viscosity of the measurement solution is C!
O//), (yl]=2483

The lower limit is preferably 50 or more.

The method for producing the PVA-based polymer having a reactive silicon group at the end of the present invention is a method in which a 1'VA-based polymer in which a reactive silicon group is introduced at the end of the molecule by hydrolyzing a silyl group is produced. There are no restrictions. For example, by radical/L/polymerizing a vinyl ester such as FK vinyl acetate coexisting with a thiol compound containing a silyl group that provides the reactive silicon group of the present invention by hydrolysis, the silyl/L/group is added to the terminal end. Do you have rt? I) Saponifying polyvinyl esters such as vinyl acetate, and simultaneously saponifying vinyl ester units
A method of hydrolyzing the V group, radical polymerization of vinyl esters such as acetic acid, vinyl, etc. in the coexistence of b or thioacetic acid,
Polyvinyl esters such as polyvinyl acetate obtained by saponifying PVA-based polymers having IiS groups at the terminals and vinyl esters having nitrogenyl groups, such as vinyl trimethoxysilane, γ-methacryloxypropylene ! It can also be produced by an addition reaction of retrimethoxysilane (methoxysilane) and hydrolyzing the group to form a silicon group.

The former manufacturing method is particularly preferred because it is simple, but
/IJ in the polymerization system in order to efficiently introduce the IJ group.
It is desirable to keep the concentration of the thiol compound having a / group relative to the vinyl ester monomer as constant as possible. Since the chain transfer constant of the thiolated metal is large, for example, if the thiol compound and vinyl ester monomer are mixed and batch polymerized without adding the thiol compound afterwards, the thiol compound will be rapidly consumed and run out. , as the polymerization progresses, a
A large amount of polyviniflester containing no J/ groups is produced as a by-product. Therefore, even if the saponified PvA threads are combined, only a PVA-based polymer containing a large amount of PVA-based polymer that does not have a reactive silicon group at the end can be obtained, which is not preferable. Therefore, PVA with silicon groups efficiently introduced into the terminal
In order to obtain a system polymer, IJ is consumed during polymerization.)
It is preferred to replenish the group-containing thiol compound by post-addition to keep g& relative to the vinyl ester monomer constant.

In addition, a method in which vinyl ester with a certain amount of the thiol compound and continuous extraction of the direct reaction solution can also maintain the total concentration of the thiol in the polymerization system at a constant value.
) is preferable because the group can be efficiently introduced.

The thiol compound having an IJ) group at the terminal has 18 groups and (R')3-n-si-(2)τ1 [1 is a hydrocarbon group having 1 to 20 carbon atoms, more preferably a carbon Hydrocarbon group of number 1 to 10, R2 is an alkoxy group of carbon a1 to carbon a20, alkoxy group, pheno-? 6- or 7-p-kylphenoxy group (here, alecoxynyl group, acyloxyl group, phenoxy group, and alkylphenoxy group may have an oxygen-containing substituent group), n is an integer of 1 to 3 . ] is used.

For example, 3-(1-limethoxysilyl)-propyl mercaptan, 3-(1-limethoxysilyl/L/)proyl mercaptan, 2-(rimethoxysilyl)-ethyl mercaptan-methyl mercaptan-propyl mercaptan, 3-(monomethoxysilyl)-propyl mercaptan, Examples include dimethyl mercaptan (I/)-propyl mercaptan.

Polymerization of vinylifle esters is carried out using conventional radical/l/metal initiators. During the polymerization, an appropriate solvent may be used for the purpose of lowering the viscosity of the straight wire.

Polymerization temperature and time can be selected as appropriate.

After the polymerization is completed, the unpolymerized residual vinyl ester monomer is separated and removed, and the obtained polyvinyl ester having a silyl group at the end is saponified by a conventional method. Usually, it is preferable to saponify the mixture by adding a basic filter or an acidic catalyst to an alcohol such as methanol. The degree of saponification of the vinyl ester unit can be determined by appropriately adjusting the saponification conditions such as catalyst amount, saponification time, and 1M degree to obtain a PVA-based polymer having silicon groups.

The rate of this decomposition increases as the amount of alkali increases.

2. During the polymerization of Vinyleste P, copolymerizable unsaturated monomers are copolymerized and saponified to obtain a PVA thread copolymer having reactive silicon groups at the terminals. For example, ethylene, propylene, gtylene, α-
Olefins such as hexene, (meth)acrylic acid, unsaturated acids such as crotonic acid, (anhydrous) maleic acid, tuma/'d, itaconic acid, and their alkali esters, alkali salts, (meth)acrylamide, N, Sulfonic acid-containing monomers such as N-dimethylacrylamide, alkyl vinyl ether, 2-acrylamido-2-methylpropanesulfonic acid and their alkali salts, trimethyl-2-(1
-(meth)acrylamide-1,1-dimethylethyl)
Examples include cationic monomers such as ammonium chloride.
Ru.

In addition, it is also possible to copolymerize silyl group-functionalized unsaturated monoelectric materials such as vinyltrimethoxysilane and allyltriethoxysilane. However, in this case, it is preferable that the amount of copolymerization is such that the water solubility of the resulting PVA-based polymer is not inhibited and there is no problem with the viscosity of the aqueous solution.

When the PVA-based polymer having reactive silicon groups at the terminals of the present invention (hereinafter abbreviated as silicon terminals or modified PVA) is applied as a binder for a set green body, the molding method that exhibits its binder properties is as follows: Examples of forming methods include press molding, extrusion molding, tape molding, slurry casting, and the like, which involve aqueous kneading as a molding step. The aqueous kneaded material referred to here consists of an inorganic raw material powder, water, and a binder for a set green body consisting of the silicon-terminated L'VA, and if necessary, a deflocculant, plasticizer, lubricant, etc. This is an added system. Also, terminal silicon paternity P, VA
There may be a considerable degree of organic bath contamination as well as dissolution rc problems.

When the silicon-terminated PVA used in the present invention is used in ceramic powder, the appropriate addition amount will vary depending on the type of ceramic powder, molding method, shape of the molded product, etc. On the other hand, the effect can be exerted by using the binder for a set green body made of silicon-terminated PVA of the present invention in an amount of 0.1 to 20 parts by weight, preferably 0.2 to 15 parts by weight.

The present invention is characterized in that the above-mentioned silicon-terminated PVA has binder properties for a set green body. It is also possible to use it in combination with a known binder. Especially normal Pv
When used in combination with A, terminal silicon paternity P with a low degree of 200 or less
The effect is strong in VA.゛Again. In this case, as a molding method, it is of course effective to blend terminal silicon paternal P■λ and normal 1'VA and apply it to the ceramic powder at the same time, but first add silicon terminal modified tJVA. , (so-called pre-treatment) followed by the usual method of adding t'VA, a very small amount of γ of silicon-terminated paternal biVA,
1S/J! Get a great effect with +.

It can also be used in conjunction with a plasticizing agent, plasticizer, and lubricant. Examples of deflocculants, transportability agents, sealing agents, and binders are listed below.

For example, inorganic peptization? Examples of l11 include zendan soda, caustic soda, sodium citrate, and linau tvn-da, and examples of organic deflocculants include amines, pyridine, piperidine, metal chloride or ammonium salts of polyacrylic acid, and polyoxyethylene. Nonylphenol ether, etc.

On the other hand, as the binder, for example, glyco-A/grain, polyethylene glycol, glycerin, Trio-/I/ etc. are used.

In addition, lubricants that are commonly used include natural waxes such as beeswax and Japanese wax, paraffin wax,
Synthetic waxes such as microcrystalline wax, low-molecular polyethylene and its derivatives, fatty acids such as stearic acid and lauric acid, metal salts of fatty acids such as magnesium stearate and calcium stearate, fatty acid amides such as oleic acid amide and stearic acid amide, polyethylene glycol, etc. Even if it is an aqueous dispersion, it doesn't matter.

Examples of common binders include powders, saccharides and their derivatives, rubbers, soluble protein derivatives, cellulose derivatives, synthetic water-soluble polymers, PvA, polyvinylpyrrolidone, polyacrylvamide, isobutylene.
Maleic anhydride copolymer, acrylic acid, methacrylic db
- and esterified products of these alone or in co-conjunctions, as aqueous dispersions such as olefins such as ethylene and propylene, diolefins such as butadiene and isoprene, vinyl esters such as vinyl acetate, vinyl ethers such as lauryl vinyl ether, and acrylic acid. An aqueous dispersion of a polymer consisting of one layer or two or more of esters such as methacrylic acid and esters, and a styrene equivalence lid can be used.

Ceramic powders to which the binder for fixed green bodies made of silicon-terminated PVA of the present invention is applied include powders of metal or nonmetal oxides or nonoxides that can be used in ceramic production. Further, these powders may have a single composition, or may be used in the form of a compound alone or as a mixture. Note that the constituent elements of metal oxides or non-oxides may be composed of a single element or multiple elements for both cations and anions, and are additives added to improve the properties of the oxide or non-oxide. A thread containing the following can also be used in the present invention.

Specifically, Li, L%Be, Mg, B, A
I, Si, Ou.

Ca, Sr, Ha, Zn, Cd, Ga,
In, lanthanide, actinide, Ti, Zr, R
f%Bi%”1%Nb, Ta%W, Mn, Fe,
Examples include oxides, carbides, nitrides, borides, sulfides, etc. of Co, Ni, etc. Furthermore, if we classify specific oxide powders containing multiple metal elements, which are usually referred to as dd oxides, based on their crystal structures, we find that NaN+O03, 8rZrOg, PbZr have a perovskite structure.
05.8rTi05; &ZrO3, PbTiO3,
bfgAJ t Us, ZnAl2O4, Co
Al2O, NiA12tJ4.31gFe2U4 etc. have an ilmenite structure, &1gTi
0. , MnTi0. , Fe'l'i05, etc., but Gd3Ga5O12, Y
Examples include 5Fe50,2.

The binder for green bodies made of silicon-terminated PvA used in the present invention has a shearing effect depending on the particle size and shape of the ceramic powder. Is the issue important? Especially 2.
Its effectiveness is further demonstrated for powders having an average particle diameter of att or less.

Among these ceramic powders, we manufacture oxide powders, especially electronic materials, magnetic materials, optical materials, Zhao Wen materials, etc.
For the gold MM compound powder, the binder for green body consisting of silicon-terminated t'VA used in the present invention is preferably used.

Reactive silicon group at the end of the present invention? When a ceramic molded body is manufactured using a binder for a set green body made of L'VA gelatin, the special effect described above can be seen compared to when a conventional binder is used.

(1) A green body with high strength and excellent workability can be obtained with a small amount of binder.

(2) A high-strength green body can be obtained using l'VA-based polymers that have a lower degree of polymerization than conventional PVA.

(3) Therefore, since the slurry has a low viscosity and can be highly concentrated, drying time can be shortened and costs can be reduced.

+4) PVA-based polymers having reactive silicon groups at the terminals are of course effective even when used alone, but when used in combination with other binders, especially regular PVA, the wood-end silicon-modified PVA-based polymers have a low degree of polymerization. When polymers are used in the form of pretreatment, a great effect can be obtained with very small amounts.

The reason why these unique effects occur is not fully understood.
However, it is thought that this is due to the unique reactivity of PVA-based polymers having silicon groups at the ends. That is, (1
) The terminal reactive silicon group interacts with many inorganic substances containing elements such as 81 and AI, and (2)
The reactive silicon groups at the ends dissociate in water and do not react much, but as water is removed by drying etc., they react with the hydroxyl groups of PvA, or reactions between silicon groups occur, resulting in polymerization and crosslinking. My thoughts spread. Due to this unique reactivity, as a result of the interaction between the PVA-based polymer having a reactive silicon group at the end and the inorganic powder, the dispersibility of the powder improves, and furthermore, the polymer crosslinking after drying improves the green body. It is expected that the strength will increase.

Incidentally, the reactive silicon groups present in the PvA molecule can be expected to have similar effects, not only the terminal reactive silicon groups, but for example, if reactive silicon groups exist randomly within the molecule, Compared to the terminal reactive silicon group of the present invention, the water solubility of the PVA polymer decreases or the viscosity of the water bath solution increases significantly, and furthermore, the viscosity of the slurry becomes too high.

Phenomena such as easy gelation are observed, making it impossible to achieve the effects obtained by the present invention. That is, the excellent effects described above can only be obtained by using a PVA-based polymer having a reactive silicon group at the end, as in the case of the invention.

By firing the solid green body thus obtained under normal conditions, a ceramic molded body such as porcelain having excellent strength can be obtained.

The present invention will be described below with reference to practical examples, but the present invention is not limited thereto. Note that parts and % mean all parts by weight and % by weight unless otherwise specified.

After charging 2,400 parts of vinyl acetate and 1,500 parts of methanol/L into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser, and a thiol compound addition device, the system was replaced with nitrogen while stirring. , the internal temperature was raised to 60°C. To this thread was added 2.48 t of 3-(1-IJ methoxysilyl)propyl mecaptan (hereinafter referred to as the initial addition of 1,000 ol), and an additional 0.87 t of 2.2'-agebisisobutyronitrile. A solution prepared by dissolving 100 parts of Meknol was added to initiate polymerization. 3 after starting polymerization
80 parts of a methanol solution containing 27 parts of 3-(rimethoxysilyl)propyl mercaptan (referred to as thiol post-addition) were added continuously over time. After continuing the polymerization for 3 hours, the polymerization was stopped. At this point, the solid content concentration in the system at 2 was 40.9% (polymerization rate 5
1.0%).

After expelling the unreacted vinyl acetate monomer by introducing methanol/L/vapor, a 40% methanol solution of polyvinyl acetate having a silyl group at the end was obtained.

While stirring the methanol solution of the polymer at 40'C, a methanol bath solution containing 5 mol% sodium hydroxide dissolved in vinyl acetate units was added to carry out a saponification reaction. The obtained white gel) was pulverized, thoroughly washed with methanol, and then dried to obtain a PVA-based polymer having a reactive silicon group at the end. The structure of the reactive silicon group at the end of the obtained PVA was converted into a nucleus 6! in heavy water. I gas resonance spectrometry analysis revealed that the methyl group of CjH3-1)-8i was changed to 81 or Na→81. The obtained PVA was a 1% aqueous solution of VO
The relative viscosity (ηrel) at °C was 1.26 (degree of polymerization 216 (calculated from the formula given later)), and the saponification degree of $=vinyl unit was 99.2 mo) V%. This polymer is referred to as polymer (g).

Thereafter, in the same manner as this method, polymers (77L) and (to) with various degrees of polymerization were synthesized by changing the amount of thiol added.

For comparison, PVA without a silicon group at the terminal was synthesized using 2-mercaptoethanol-I as a thiol to obtain polymers Φ) to (F). Table 1 shows the polymerization conditions and the properties of the obtained PVA-based polymer.

Table 1 Example 1 After pulverizing 100 parts of alumina (99.8 parts rope strength), 50 parts of water, 0 parts and 3 parts of ammonium polyacrylate salt peptizer in a ball mill for 90 hours, reactive silicon was added to the terminal as a binder. 2 parts of an aqueous solution of PVλ-based blood compound 4 having a group of 4.2% in terms of solid content were added and mixed uniformly with the powder.

From this slurry, adjust the granules (particle size 100±20.
The rectangular parallelepiped was pressed (1,2) n/·1) with a mold to form a green body. The evaluation results are shown in Table 2.

Comparative Example 1 Test was conducted in the same manner as in Example 1, except that the donor material p) was used instead of the polymer (e) as the binder.

The evaluation results are shown in Table 2.

(a) Mold releasability: The releasability of the molded product from the mold was evaluated in three stages.

(○); No problem at all (△) Ink or difficult to remove (×
); Difficult to remove (b) Strength of green molded body; Conduct three-point bending test,
The energy required for a green molded body to break is determined from the S-S curve and expressed as a relative value.

(c) Workability: Cutting with a knife and drilling with a drill were performed, and the ease of cutting was evaluated at 91.

(○) 9 Easy to process (△); Processing is difficult (×); Processing is extremely difficult Examples 2 and 3 Tests were conducted in the same manner as in Example 1 except that the binder was changed. The evaluation results are shown in Table 3.

Comparative Example 2 Example 1 except that polymer (F) is used as the binder
It was tested in the same way. The evaluation results are shown in Table 3.

Table 3) Slurry viscosity: Measured with a B-type viscometer at 20°C and shown as relative values.

(For mold releasability, green molded body strength, and processability, see Table 2.
Same as . ) Example 4 After pulverizing 100 parts of alumina (99.8% purity), 50 parts of water, 1.3 parts of ammonium polyacrylate ↓1 peptizer C in a Bo/Remill for 90 hours, a reactive The water-soluble surface of the silicon-based polymer (C) is 0.0% in terms of solid content.
1 part was added and mixed with the powder until thoroughly homogeneous. Subsequently, 1.9 parts of a water bath solution of PVA-205 (manufactured by Kanri Rare, polymerization degree 500, saponification degree 88 mol%) was added in terms of solid content, and the mixture was thoroughly mixed.

Granules (grain stripes 100±20μ) are prepared from this slurry, and a rectangular parallelepiped with a width of 20 cm, a length of 100 μm, and a thickness of 10 m is pressed (1,21 mm/i) with a mold to form a green body. Molded. The evaluation results are shown in Table 4.

Comparative Example 3 A test was conducted in the same manner as in Example 4, except that Polymer 0 was changed to Polymer 0. The evaluation results are shown in Table 4.

Claims (1)

[Scope of Claims] 1) A set-up green body characterized by being made of a polyvinyl alcohol-based polymer containing a reactive silicon group obtained by hydrolyzing a silyl group represented by the following formula [I] at the molecular end. binder. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [I] [However, R^1 is a hydrocarbon group with a shore prime number of 1 to 20, R^
2 is an alkoxy group, acyloxy group, phenoxy group, or alkylphenoxy group having 1 to 20 carbon atoms (here, the alkoxy group, acyloxy group, phenoxy group, or alkylphenoxy group may have an oxygen-containing substituent ), and n is an integer of 1 to 3. ]