JP5660136B2 - Drying shrinkage reducing agent for ceramic molding and method for reducing drying shrinkage of ceramic molded body - Google Patents

Description

  The present invention relates to a drying shrinkage reducing agent for ceramic molding which is effective for reducing shrinkage in a drying process particularly in water-based ceramic molding and obtaining a highly accurate molded body with good reproducibility, and a method for drying a ceramic molded body using the same. About.

As a general molding method of ceramic, there are various methods such as extrusion molding, injection molding, and casting molding. For example, with regard to extrusion molding, it is a method of molding by applying pressure to a kneaded composition (hereinafter also referred to as a kneaded material) kneaded with ceramic powder, a binder, water, etc., and having a constant cross section. It is suitable for efficiently producing a product having a shape such as a rod or pipe. Filters, catalyst carriers, etc. are also manufactured by this extrusion molding method, but in recent years, high-precision extrusion molding has been strongly demanded to improve these performances, and the dimensional stability and processing of the molded body The demand for shape retention at the time is also increasing.
As a general method for producing a ceramic, a molding process for obtaining a molded body by extrusion or the like, a drying process for irradiating the molded product with hot air or microwaves, and a firing process for firing organic substances such as a binder are performed. The method of obtaining a ceramic product is mentioned. As a means for improving the molding accuracy described above, there is a method of improving the fluidity of the clay by increasing the moisture content of the binder phase. In this case, the molding is performed because a large amount of water evaporates in the drying process. The degree of shrinkage of the body increases, causing problems such as deviating from the size of the molded body suitable for the production line.

  A method for effectively reducing the shrinkage at the time of drying the ceramic compact has not been proposed. In order to reduce the shrinkage, it is effective to reduce the amount of water used for kneading as much as possible. However, in this case, the viscosity of the kneaded material becomes high, causing a problem in operability. On the other hand, Patent Document 1 discloses a method of adding a dispersant composed of a specific fatty acid salt to reduce the viscosity of the clay, but the moldability is insufficient and it is difficult to obtain a smooth molded body. There was a problem. In addition, Patent Document 2 discloses a polyoxyalkylene unit-containing dispersant having excellent lubricity of a molded product, but a large amount of dispersant is necessary to sufficiently reduce the viscosity of the clay, and this is a binder. In order to inhibit the interaction between molecules, the shape retention and the strength of the molded body may be greatly reduced.

JP 2002-293645 A JP 2009-46385 A

  An object of the present invention is to obtain a highly accurate molded product with good reproducibility, which is effective in suppressing shrinkage due to drying of a molded product obtained by extrusion molding and the like, and also has good shape retention. It is to provide a reducing agent and a method for reducing drying shrinkage of a ceramic molded body using the same.

  As a result of intensive studies in view of the above problems, the present inventors have found that the average particle diameter in the state of saturated swelling with ion-exchanged water is more than 10 μm and not more than 100 μm, and the water absorption amount of ion-exchanged water at normal pressure is 0.1. It was found that it is effective to use polymer fine particles of ˜60 mL / g at the time of ceramic molding, and the present invention was completed.

The present invention is as follows.
1. Polymer fine particles produced by a reverse-phase suspension polymerization method using an oil-soluble oxidant and a water-soluble reducing agent as a polymerization initiator, and the average particle diameter in a state of saturated swelling with ion-exchanged water exceeds 10 μm and is 100 μm A drying shrinkage reducing agent for ceramic molding, comprising polymer fine particles having a water absorption of from 0.1 to 60 mL / g at normal pressure, which is below.
2. 2. The drying shrinkage reducing agent according to 1 above, wherein the reverse phase suspension polymerization is carried out using one or more of (meth) acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid.
3. 3. A method for reducing drying shrinkage of a ceramic molded body using the drying shrinkage reducing agent according to 1 or 2 above.

  By using the drying shrinkage reducing agent for ceramic molding containing the polymer fine particles of the present invention at the time of ceramic molding, the fluidity of the kneaded material is increased, so that extrusion molding or the like is possible even with a small amount of water. For this reason, drying shrinkage in the drying step after molding is suppressed, and good shape retention is obtained, so that a highly accurate molded body can be obtained with good reproducibility.

It is a figure which shows the apparatus used for the measurement of the water absorption amount of a polymer microparticle.

TECHNICAL FIELD The present invention relates to a drying shrinkage reducing agent for ceramic molding. Specifically, the average particle diameter in a state of saturated swelling with ion exchange water is more than 10 μm and not more than 100 μm, and water absorption of ion exchange water at normal pressure. The present invention relates to a drying shrinkage reducing agent for a ceramic molded body containing polymer fine particles having an amount of 0.1 to 60 mL / g, and a method for reducing the drying shrinkage of a ceramic molded body using the same.
The drying shrinkage reducing agent of the present invention is kneaded with ceramic powder, a binder, water and the like and used in ceramic molding such as extrusion molding.
Hereinafter, the drying shrinkage reducing agent for a ceramic molded body of the present invention and the method for reducing the drying shrinkage of a ceramic molded body using the dry shrinkage reducing agent of the present invention will be described in detail. In the present specification, acrylic acid or methacrylic acid is represented as (meth) acrylic acid.

  The polymer fine particles used in the present invention are required to have an average particle size of more than 10 μm and not more than 100 μm, preferably 15 to 80 μm, in a state of saturated swelling with ion exchange water. It is a range. If the average particle diameter exceeds 100 μm, a ceramic molded body having a smooth surface cannot be obtained. On the other hand, in the case of 10 μm or less, the lubricity becomes insufficient.

  Furthermore, the water absorption amount of the above polymer fine particles at normal pressure needs to be in the range of 0.1 to 60 mL / g, and preferably in the range of 0.1 to 20 mL / g. When the water absorption is less than 0.1 mL / g, the moisture content of the binder phase cannot be sufficiently reduced, and thus the drying shrinkage reduction effect is insufficient. On the other hand, when the amount of water absorption exceeds 60 mL / g, the amount of water absorption of the polymer fine particles becomes too large so that the water cannot be mixed without increasing the amount of water used for kneading the ceramic. In some cases, the shape-retaining property of the resin may deteriorate.

  When the drying shrinkage reducing agent according to the present invention is used, the dry shrinkage reducing agent itself has a function of increasing the fluidity of the clay because it has a fine particle shape. Therefore, it is presumed that extrusion molding or the like is possible even with a small amount of water, and shrinkage during drying is reduced.

  As a method for producing the polymer fine particles of the present invention, known polymerization methods such as aqueous solution polymerization, reverse phase suspension polymerization, dispersion polymerization and the like can be adopted, but micron-sized highly crosslinked spherical fine particles can be easily obtained. Therefore, reverse phase suspension polymerization is preferable.

Reverse phase suspension polymerization generally means reverse phase suspension polymerization in which an oil phase is a dispersion medium and an aqueous phase is a dispersoid. In the present invention, an oil phase (hydrophobic organic polymer) containing a dispersion stabilizer is used. Polymer fine particles are produced by water-in-oil type (W / O type) reversed-phase suspension polymerization in which the aqueous phase (aqueous solution of vinyl monomer mixture) is suspended in water droplets in a dispersion medium comprising a solvent. It is preferred that
Moreover, in reverse phase suspension polymerization, the particle diameter of the fine particles obtained can be adjusted by the type and amount of the dispersion stabilizer, the rotation speed of stirring, or the like.

  Examples of the hydrophobic organic solvent that forms the oil phase (dispersion medium) in the reversed-phase suspension polymerization of the present invention include, for example, aliphatic hydrocarbon solvents having 6 or more carbon atoms, and aromatic hydrocarbon solvents such as benzene, toluene, xylene, and ethylbenzene. In addition, silicone solvents such as octamethylcyclotetrasiloxane can be used. In particular, hexane, cyclohexane, and n-heptane have low solubility in vinyl monomers and water, and can be easily removed after polymerization. It is preferably used because of its existence.

As the initiator used for the reverse phase suspension polymerization, a known initiator such as a thermal decomposition type initiator or a redox type initiator can be used, but a redox type initiator is preferably used. The redox reaction can start polymerization at a low temperature, and the vinyl monomer concentration in the polymerization reaction solution can be increased and the polymerization rate can be increased. It becomes possible to increase the molecular weight.
In addition, the use of a redox initiator that uses an oil-soluble oxidant and a water-soluble reducing agent is particularly preferable because polymer fine particles having a narrow particle size distribution can be obtained without producing aggregated particles.

  As described above, since the hydrophobic organic solvent is used as the continuous phase (oil phase) in the reverse phase suspension polymerization, the oil-soluble oxidant means an oxidant that dissolves in these continuous phases. Further, a dispersion stabilizer may be dissolved or dispersed in the oil phase.

  As the oil-soluble oxidant in the present invention, those having an octanol / water partition coefficient (logPow) of -1.4 or more as defined in Japanese Industrial Standard Z7260-107 and OECDTEST Guideline 107 are preferred, and those having 0.0 or more are more preferred. 1.0 or more is particularly preferable.

  Specific examples include t-butyl hydroperoxide (log Pow = 1.3), di-t-butyl hydroperoxide, t-hexyl hydroperoxide, di-t-amyl peroxide, cumene hydroperoxide (log Pow = 2. 2) Organic peroxides such as dicumyl peroxide (logPow = 5.5), t-butylcumyl peroxide, t-butylperoxypivalate, benzoyl peroxide (logPow = 3.5), lauroyl peroxide Is mentioned. Among these, t-butyl hydroperoxide and cumene hydroperoxide are preferable, and cumene hydroperoxide is particularly preferable.

  As the water-soluble reducing agent, known reducing agents can be used as the reducing agent used in the redox polymerization initiator. Among these, sodium sulfite, sodium bisulfite, and sodium hydrosulfite are preferable, and hydrosulfite is particularly preferable. Sodium. In addition, since these water-soluble reducing agents are gradually deactivated by contact with air, it is preferable to dissolve and add to water several minutes before the desired polymerization start timing.

  When using an oil-soluble oxidant and a water-soluble reducing agent, the uniformity of the particle size of the produced particles becomes higher when the water-soluble reducing agent is supplied to the reactor first and then the oil-soluble oxidant is supplied to the reactor. Therefore, it is preferable. It is more preferable to polymerize by supplying an oil-soluble oxidant within 0.5 to 15 minutes after water-soluble reducing agent is made water-soluble and supply it to the reactor, and supply an oil-soluble oxidant within 1 to 5 minutes. More preferably.

The total amount of the oil-soluble oxidant is preferably supplied to the reactor over a period of 20 seconds to 120 seconds, particularly preferably 20 seconds to 60 seconds.
When the supply time of the oil-soluble oxidant is shorter than 20 seconds, the diffusion does not catch up with the supply of the oxidant, and there is a case where a problem such as occurrence of agglomerates occurs due to local generation of radicals. Yes, not preferred. If it is longer than 120 seconds, the reducing agent is decomposed and consumed by another mechanism, so that a part of the oxidizing agent may remain unreacted in the system. If the oxidizing agent remains unreacted, it is not preferable because it may cause problems such as generation of aggregates in a subsequent azeotropic dehydration step or drying step.
The supply time of the water-soluble reducing agent is not particularly limited, but in general, since the reducing agent is easily decomposed by contact with air or the like, it is preferably supplied within 15 minutes.

The oil-soluble oxidant is preferably supplied to the reactor from a supply port located below the liquid level of the reaction solution. In general, the polymerization catalyst inlet is attached to the upper part of the reactor, and the polymerization catalyst is supplied to the liquid level of the reaction liquid from this inlet in a batch or continuously. A method of supplying the reaction solution through a pipe connected to the catalyst is preferable from the viewpoint of uniform diffusion of the catalyst.
The position of the supply port is not limited as long as it is always immersed in the reaction solution, but it is preferably within ± 1 m from the top or bottom of the stirring blade in the vertical direction, and within ± 50 cm. More preferably.
Examples of the method for supplying the oil-soluble oxidant include a method for supplying the oil-soluble oxidant at a gas pressure of an inert gas such as a pump through a pipe leading to a supply port located below the surface of the reaction solution.

The amount of the polymerization initiator used can be adjusted according to the type of vinyl monomer used, the particle size and molecular weight of the resulting polymer fine particles, etc., but the total amount of vinyl monomers is 100 mol. On the other hand, the amount of the oil-soluble oxidant is preferably 0.001 to 0.15 mol, particularly preferably 0.003 to 0.07 mol.
The ratio of the oil-soluble oxidizing agent and the water-soluble reducing agent is not particularly limited, but the oil-soluble oxidizing agent: water-soluble reducing agent is preferably 1.0: 0.25 to 15.0 in terms of molar ratio, Preferably it is 1.0: 1.0-10.0.
If it is out of the above range, the reaction rate of the monomer is reduced, the chain length of the polymer constituting the particle is shortened, or the catalyst remains even after the completion of the polymerization. May occur.

In the reverse phase suspension polymerization of the present invention, a dispersion stabilizer can be used.
Specific examples of the dispersion stabilizer include macromonomer type dispersion stabilizers, sorbitan fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, sorbitol fatty acid esters, polyoxyethylene alkyl ethers and other nonionic surfactants.
Among these, it is preferable to use a macromonomer type dispersion stabilizer. The macromonomer type dispersion stabilizer has a radically polymerizable unsaturated group at the end of a polymer derived from a vinyl monomer.

  Further, it is preferable to use a macromonomer type dispersion stabilizer in combination with a relatively hydrophobic nonionic surfactant having an HLB of 3 to 8, such as sorbitan monooleate and sorbitan monopalmitate. Two or more species may be used in combination.

A preferred macromonomer as the macromonomer-type dispersion stabilizer is a compound derived from the formula (1); H _{2 at} the end of a polymer derived from a vinyl monomer obtained by radical polymerization of a vinyl monomer at 150 to 350 ° C. At the end of a polymer derived from a macromonomer and / or vinyl monomer having an α-substituted vinyl group represented by C = C (X)-(where X is a monovalent polar group) A macromonomer having an acryloyl group is suitable because of its excellent function as a dispersion stabilizer, and the weight average molecular weight of the macromonomer is preferably 1000 to 30000. The macromonomer is derived from a hydrophilic vinyl monomer. It is preferable to have both a structural unit and a structural unit derived from a hydrophobic vinyl monomer, and the structural unit derived from the hydrophobic vinyl monomer at that time is (meth) acrylic acid. Preferably the structural units derived from prime 8 or more alkyl esters, structural unit derived from a vinyl monomer having a carboxyl group is preferred as the structural unit derived from a hydrophilic vinyl-based monomer.

  In particular, when a hydrophilic polymer fine particle is produced by reverse-phase suspension polymerization of a hydrophilic vinyl monomer using a macromonomer type dispersion stabilizer, a polyfunctional vinyl monomer is used together with a monofunctional compound. It is preferable to use a monomer, whereby hydrophilic cross-linked polymer fine particles having improved strength and shape retention are obtained.

The dispersion stabilizer is preferably added to the polymerization system after being dissolved or uniformly dispersed in a hydrophobic organic solvent which is a dispersion medium (oil phase).
In order to obtain hydrophilic polymer fine particles having a uniform particle size while maintaining good dispersion stability, the amount of the dispersion stabilizer used is 0.1 with respect to a total of 100 parts by mass of the vinyl monomer. It is preferable that it is -50 mass parts, It is more preferable that it is 0.2-20 mass parts, It is still more preferable that it is 0.5-10 mass parts. If the amount of the dispersion stabilizer used is too small, the dispersion stability of the vinyl monomer in the polymerization system and the generated polymer particles will be poor, and the generated polymer particles will aggregate, settle, and the particle size will vary. Is likely to occur. On the other hand, if the amount of the dispersion stabilizer used is too large, the amount of by-product fine particles (1 μm or less) produced may increase.

  The vinyl monomer used for the reverse phase suspension polymerization of the present invention is not particularly limited as long as it is a radical polymerizable vinyl monomer. For example, a hydrophilic vinyl monomer having a hydrophilic group such as a carboxyl group, amino group, phosphoric acid group, sulfonic acid group, amide group, hydroxyl group, amino group or quaternary ammonium group can be used.

  Specific examples of the vinyl monomer used in the reverse phase suspension polymerization of the present invention include (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, monobutyl itaconate, monobutyl maleate, and cyclohexanedicarboxylic acid. Vinyl monomers having a carboxyl group such as those or neutralized products thereof (partially); N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethyl Vinyl monomers having an amino group such as aminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide or the like (partially) acid neutralized product or (partially) quaternized product; N- Vinylpyrrolidone, acryloylmorpholine; acid phosphooxyethyl methacrylate, reed Vinyl monomers having a phosphoric acid group such as dophosphooxypropyl methacrylate and 3-chloro-2-acid phosphooxypropyl methacrylate, or their (partially) alkali neutralized products; 2- (meth) acrylamide-2-methyl Sulfonic acid groups or phosphonic acid groups such as propanesulfonic acid, 2-sulfoethyl (meth) acrylate, 2- (meth) acryloylethanesulfonic acid, allylsulfonic acid, styrenesulfonic acid, vinylsulfonic acid, allylphosphonic acid, vinylphosphonic acid Or (part) alkali neutralized product thereof; (meth) acrylamide, N, N-dimethylacrylamide, N-isopropylacrylamide, N-methylol (meth) acrylamide, N-alkoxymethyl (meth) Acrylamide, Nonionic hydrophilic monomers such as (meth) acrylonitrile, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, methoxypolyethyleneglycol mono (meth) acrylate, and the like, one or two of these The above can be used.

Among these, (meth) acrylic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, N, N-dimethylaminoethyl (meth) acrylate, (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, and Methoxypolyethylene glycol mono (meth) acrylate is preferred because it has high hydrophilicity and is suitable for reverse phase suspension polymerization.
Furthermore, among these, it is excellent in polymerizability that the reverse phase suspension polymerization is performed using one or more of (meth) acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, and the obtained heavy weight. The coalesced fine particles are particularly preferable from the viewpoint that the polymer fine particles are excellent in water absorption performance and water retention performance.

Moreover, in this invention, the polyfunctional vinyl which has 2 or more of radical polymerizable unsaturated groups with 1 type or 2 types or more of the above-mentioned monofunctional hydrophilic vinyl monomer as a vinyl monomer. System monomers can be used.
Therefore, the “vinyl monomer” referred to in the present invention is a general term for monofunctional vinyl monomers and polyfunctional vinyl monomers.

  The polyfunctional vinyl monomer may be any vinyl monomer having at least two radically polymerizable groups with the hydrophilic vinyl monomer. Specific examples thereof include polyethylene glycol di (meta ) Acrylate, polypropylene glycol di (meth) acrylate, glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethylene oxide modified tri (meth) acrylate and other di- or tri- (meta) ) Bisamides such as acrylate and methylene bis (meth) acrylamide, divinylbenzene, allyl (meth) acrylate, and the like, and one or more of these may be used.

  Among these, as the polyfunctional vinyl monomer, polyethylene glycol di (meth) acrylate and methylenebis (meth) acrylamide are excellent in solubility in a mixed solution of the hydrophilic hydrophilic vinyl monomer and water, and have a high crosslinking density. It is advantageous and preferably used when increasing the amount used to obtain polyethylene glycol, and particularly preferred is polyethylene glycol di (meth) acrylate.

  The ratio of the polyfunctional vinyl monomer used may vary depending on the type of vinyl monomer used, the intended use of the resulting polymer fine particles, etc. The total monomer content is preferably 0.01 to 30 mol%, more preferably 0.05 to 10 mol%. If it is 0.01 mol% or more, the strength of the fine particles is secured, and if it is 30 mol% or less, sufficient water absorption performance can be obtained.

The polymer fine particles used in the present invention preferably contain 1.5 to 9.0 mmol / g of acidic functional groups neutralized with alkali, more preferably in the range of 3.0 to 9.0 mmol / g. is there. When the acidic functional group neutralized with an alkali is less than 1.5 mmol / g, a sufficient amount of water absorption cannot be obtained, and the shrinkage reduction effect during drying may be insufficient. On the other hand, if it exceeds 9.0 mmol / g, the amount of the eluted component increases, and a molded article having a smooth surface may not be obtained due to generation of coarse particles.
Here, the acidic functional group is introduced by using a vinyl monomer having an acidic group such as carboxylic acid (salt) or sulfonic acid (salt). Alternatively, a polymer can be obtained using an alkyl ester (meth) acrylate or the like and then saponified with an alkali.

  As described above, in the present invention, a vinyl monomer having an acidic group such as a carboxyl group or a sulfonic acid group can be neutralized with a suitable alkali. By making the vinyl monomer having the acidic group by neutralization into an ammonium salt, a volatile organic amine salt, or an alkali metal salt, an aqueous solution in which the vinyl monomer mixture is well dissolved can be prepared. it can.

Here, specific alkalis for obtaining the volatile organic amine salt include triethylamine, triethanolamine, N, N-dimethylpropylamine and the like.
Specific examples of the alkali for obtaining the alkali metal salt include sodium hydroxide and potassium hydroxide.

  The drying shrinkage reducing agent of the present invention is kneaded in a clay together with ceramic powder, a binder, water and the like. A preferred use amount is 0.1 to 10% by mass, more preferably 0.1 to 5% by mass as a proportion of polymer fine particles in the clay. If it is 0.1 mass% or more, a drying shrinkage reduction effect can be shown, and if it is 10 mass% or less, generation | occurrence | production of the crack resulting from the drying nonuniformity at the time of drying, etc. can be suppressed.

  In general, in ceramic molding, a molded body is obtained by various molding methods, and then dehydration is performed by irradiating with hot air or microwaves in a drying process. When the drying reducing shrinkage agent of the present invention is used, shrinkage of the molded product due to the evaporation of moisture in the drying step is reduced.

  The ceramic in the present invention is not particularly limited as long as it can be molded in an aqueous system. Specific examples include oxide ceramics such as alumina, cordierite, mullite, silica, zirconia, and titania, and non-oxides such as silicon carbide, silicon nitride, aluminum nitride, boron nitride, titanium nitride, and titanium carbide. Mention may be made of ceramics.

  In addition, the binder contained in the ceramic kneaded composition is not particularly limited as long as it is applicable in an aqueous system. Examples include cellulose derivatives such as methylcellulose, hydroxypropylmethylcellulose, and hydroxypropylethylcellulose; synthetic polymer compounds such as polyacrylic acid, polyacrylamide, and polyvinyl alcohol. Among the above, cellulose derivatives are widely used for extrusion molding.

  In addition, the average particle diameter in the saturation swelling state by the ion-exchange water of the polymer fine particle in this specification, and the amount of water absorption say the value measured or calculated | required by the method as described in the term of an Example below.

Hereinafter, the present invention will be specifically described based on examples. In the following description, “part” means part by mass, and “%” means mass%.

Production Example 0: Production of Macromonomer Composition UM-1 The temperature of the oil jacket of a 1000 ml capacity pressurized stirred tank reactor equipped with an oil jacket was kept at 240 ° C.
75.0 parts of lauryl methacrylate (hereinafter referred to as “LMA”) as a monomer, 25.0 parts of acrylic acid (hereinafter referred to as “AA”), 10.0 parts of methyl ethyl ketone (hereinafter referred to as “MEK”) as a polymerization solvent As a polymerization initiator, a monomer mixed liquid adjusted at a ratio of 0.45 part of ditertiary butyl peroxide was charged into a raw material tank.
Start supplying the monomer mixture from the raw material tank to the reactor, and supply the monomer mixture and remove the reaction mixture so that the weight in the reactor is 580 g and the average residence time is 12 minutes. went. The reactor internal temperature was adjusted to 235 ° C., and the reactor internal pressure was adjusted to 1.1 MPa. The reaction mixture extracted from the reactor is decompressed to 20 kPa, continuously supplied to a thin film evaporator maintained at 250 ° C., and discharged as a macromonomer composition from which monomers and solvents are distilled off. . Distilled out monomers and solvents were cooled with a condenser and recovered as a distillate. After the start of the monomer mixture supply, 60 minutes after the reactor internal temperature was stabilized at 235 ° C., the recovery start point was set, and the reaction was continued for 48 minutes to recover the macromonomer composition UM-1. During this time, 2.34 kg of the monomer mixture was supplied to the reactor, and 1.92 kg of the macromonomer composition was recovered from the thin film evaporator. In addition, 0.39 kg of distillate was recovered in the distillate tank.
When the distillate was analyzed by gas chromatography, LMA 31.1 parts, AA 16.4 parts, other solvents, etc. were 52.5 parts with respect to 100 parts of distillate.
From the amount and composition of the monomer mixture, the recovered amount of the macromonomer composition, the recovered amount and composition of the distillate, the monomer reaction rate is 90.2%, and the composition of the macromonomer composition UM-1 The monomer composition ratio was calculated as LMA: AA = 76.0 / 24.0 (mass ratio).

Further, when the molecular weight of the macromonomer composition UM-1 was measured by gel permeation chromatograph (hereinafter referred to as “GPC”) using tetrahydrofuran as an eluent, the weight average molecular weight (hereinafter referred to as “Mw”) in terms of polystyrene was measured. And number average molecular weight (hereinafter referred to as “Mn”) were 3800 and 1800, respectively. Moreover, the density | concentration of the terminal ethylenically unsaturated bond in a macromonomer composition was measured from 1H-NMR measurement of a macromonomer composition. As a result of calculating the terminal ethylenically unsaturated bond introduction rate of the macromonomer composition UM-1 from the concentration of terminal ethylenically unsaturated bonds by 1H-NMR measurement, Mn by GPC, and the constituent monomer composition ratio, 97% Met. The solid content of the heating residue after heating at 150 ° C. for 60 minutes was 98.3%.
In addition, about each raw material, such as a monomer, a polymerization solvent, and a polymerization initiator, the commercially available industrial product was used as it was, without performing processes, such as refinement | purification.

(Production Example 1: Production of polymer fine particles A-1)
For the polymerization, a reactor having a capacity of 2 L, having a stirring mechanism comprising a pitched paddle type stirring blade and two vertical baffles, and further equipped with a thermometer, a reflux condenser with a distillate separator, and a nitrogen introduction tube was used. . The nitrogen introduction pipe is branched into two outside the reactor, and nitrogen can be supplied from one side and a polymerization catalyst can be supplied from the other side using a pump. Further, the nitrogen introduction tube is connected to the reactor wall surface which is almost the same height as the upper end of the stirring blade.
In the reactor, 1.5 parts of UM-1 as a dispersion stabilizer, 10.0 parts of sorbitan monooleate (trade name “Leodol AO-10” manufactured by Kao Corporation), and n-heptane 400. 3 parts were charged and the oil phase was adjusted by stirring and mixing while maintaining the temperature of the solution at 40 ° C. The oil phase was stirred at 40 ° C. for 30 minutes and then cooled to 20 ° C.
On the other hand, 30.0 parts of AA in a separate container, 175.0 parts of an aqueous acrylamide solution (hereinafter referred to as “40% AMD”) 175.0 parts, polyethylene glycol diacrylate (manufactured by Toagosei Co., Ltd., trade name “Aronix M-243”) 8.7 parts of an average molecular weight of 425) and 30.0 parts of ion-exchanged water were charged, stirred and uniformly dissolved. Further, 21.3 parts of 25% aqueous ammonia was slowly added and neutralized while cooling so that the temperature of the mixed solution was kept at 40 ° C. or lower to obtain a monomer mixed solution.

  After setting the rotation speed of the stirrer to 870 rpm, the prepared monomer mixture was charged into the reactor to prepare a dispersion in which the monomer mixture was dispersed in the oil phase. At this time, the internal temperature of the reactor was kept at 20 ° C. Further, oxygen in the reactor was removed by blowing nitrogen into the dispersion. When 1 hour and 30 minutes passed from the preparation of the monomer mixture, an aqueous solution of 0.18 part of hydrosulfite Na and 2.9 parts of ion-exchanged water was added from the inlet provided in the upper part of the reactor. Three minutes later, a solution obtained by diluting 0.039 parts of an 80% solution of cumene hydroperoxide (trade name “Park Mill H80” manufactured by NOF Corporation) with 3.1 parts of n-heptane was pumped through a nitrogen introduction tube. Supplied. The supply was performed for 30 seconds. It was confirmed that the temperature inside the reactor immediately rose from the start of the supply, and the polymerization started. The rise in internal temperature reached a peak in about 30 seconds, and the temperature was 66.0 ° C.

After cooling the reaction liquid to a temperature of 20 ° C., an aqueous solution of 0.05 part of hydrosulfite Na and 1.8 parts of ion-exchanged water was added from the inlet provided at the top of the reactor while stirring. Three minutes later, a solution obtained by diluting 0.016 part of a 69% aqueous solution of t-butyl hydroperoxide (trade name “Perbutyl H”, manufactured by NOF Corporation) with 1.6 parts of ion-exchanged water was added from the same inlet. Added. It was confirmed that the internal temperature rose to 23.6 ° C. and the remaining monomer was polymerized.
Next, the temperature of the oil bath was raised to 130 ° C. to heat the reaction liquid, and water contained in the particles and n-heptane were azeotroped to dehydrate to a dehydration rate of 98%. The obtained dewatered slurry was suction filtered, and the fine particles separated by filtration were washed repeatedly with n-heptane to remove the dispersion stabilizer, and then the solvent was completely volatilized with a dryer to dry the polymer fine particles A-1. A powder was obtained.

(Production Example 2: Production of polymer fine particles A-2)
The monomer aqueous solution composition was changed to 50 parts of AA, 125 parts of 40% AMD, 4.8 parts of Aronix M-243, 35.4 parts of 25% ammonia water, and the production speed was the same as in Production Example 1 except that the stirring speed was 640 rpm. Produced in the same manner, a dry powder of polymer fine particles A-2 was obtained.

(Production Example 3: Production of polymer fine particles A-3)
Manufactured in the same manner as in Production Example 2 except that the stirring speed was changed to 420 rpm, and a dry powder of polymer fine particles A-3 was obtained.

(Production Example 4: Production of polymer fine particles A-4)
As monomers, 50.0 parts of AA, 125.0 parts of 40% AMD, 4.8 parts of Aronix M-243, and 30.0 parts of ion-exchanged water were charged, stirred, and uniformly dissolved. Further, while cooling so that the temperature of the mixed solution was kept at 40 ° C. or lower, 35.4 parts of 25% ammonia water was slowly added to neutralize to obtain a monomer mixture. As a polymerization initiator, 0.01 part of 2,2-dimethoxy-2-phenylacetophenone and 0.10 part of ammonium persulfate were added and charged into a cylindrical glass container having an inner diameter of 146 mm, while maintaining the temperature of the aqueous solution at 20 ° C. Nitrogen bubbling was performed for a minute. Thereafter, ultraviolet rays were irradiated from above the reactor using a 100 W black light at an irradiation intensity of 5.0 mW / cm ² for 3 minutes to prepare a sheet-like water-containing crosslinked polymer gel. This gel was dried, crushed, and further finely pulverized with a roll mill and an electric stone mill to obtain a dry powder of polymer fine particles A-4.

(Production Example 5: Production of polymer fine particles B-1)
The composition of the continuous phase was 1.5 parts of UM-1, 5.0 parts of rhodol AO-10V, and 160.0 parts of n-heptane, and Aronix M-243 was changed to 11.0 parts as the monomer aqueous solution composition and stirred. Manufactured in the same manner as in Production Example 2 except that the number of revolutions was increased to 1600 rpm, to obtain a dry powder of polymer fine particles B-1.

(Production Example 6: Production of polymer fine particles B-2)
Manufactured in the same manner as in Production Example 2 except that the stirring speed was lowered to 300 rpm, to obtain a dry powder of polymer fine particles B-2.

(Production Example 7: Production of polymer fine particles B-3)
The monomer aqueous solution composition was manufactured in the same manner as in Production Example 2 except that Aronix M-243 was changed to 0.95 parts and the stirring rotation speed was 830 rpm, to obtain a dry powder of polymer fine particles B-3.

(Production Example 8: Production of polymer fine particles B-4)
For the polymerization, a reactor having a stirring mechanism composed of a pitched paddle type stirring blade and two vertical baffles, and further equipped with a thermometer, a reflux condenser, and a nitrogen introduction tube was used. The reactor was installed in a bathtub equipped with a heater with a temperature controller.
In the reactor, 26.7 parts of polyvinyl alcohol (trade name “PVA-420” manufactured by Kuraray Co., Ltd.) and 1200.0 parts of ion-exchanged water as dispersion stabilizers were charged and stirred until they were uniformly dissolved. On the other hand, in a separate container, 100.0 parts of styrene (hereinafter referred to as “St”), 33.3 parts of divinylbenzene having a purity of 55% (hereinafter referred to as “55% DVB”) and benzoyl peroxide having a purity of 75% 3. A monomer mixture consisting of 0 parts was prepared, and the whole amount was charged into the reactor.
While stirring at 800 rpm in a nitrogen stream, the internal temperature was raised to 80 ° C., and stirring was continued for 8 hours. The total amount of the dispersion was filtered through a 200-mesh polynet, and the sedimented portion was collected by centrifugation and then dried for 1.5 hours with a ventilator set at 90 ° C. to obtain polymer fine particles B-4. The average particle diameter of the resin fine particles B-4 in a dry state was 32.5 μm.

Example 1
A dry shrinkage test of the ceramic extrusion was carried out according to the standard formulation shown in Table 1.
The amounts of talc, kaolin, alumina, aluminum hydroxide, and silica shown in Table 1 were weighed as ceramic raw material powders. To this, 4.6 parts of methylcellulose as a binder was added and dry blended. Furthermore, 0.4 parts of polymer fine particles A-1 were added and further dry blended.
While the above powder mixture was kneaded with a kneader, ion-exchanged water was added little by little and the kneading was continued. As the kneading, methylcellulose was dissolved and the current value of the kneader increased, and when it became constant, the kneading was judged to be completed and the kneaded product was taken out. The kneaded product was pushed into a piston and extruded into a columnar shape to obtain a cordierite-type ceramic extruded product having a general dimension of φ15 mm × 50 mm.

<< Evaluation of degree of drying shrinkage >>
The length and diameter of the obtained ceramic extrudate were measured with a vernier caliper and dried by heating in a draft dryer at 110 ° C. for 120 minutes. The size of the molded body after drying was measured in the same manner, and the volume of the molded body before and after drying was calculated. From these values, the dimensional ratio was calculated according to the equation (1) (the closer the dimensional ratio is to 1, the smaller the degree of drying shrinkage of the molded body). The test results are shown in Table 2.

<< Evaluation of shape retention >>
The appearance of the molded body obtained by the extrusion molding was visually confirmed before and after drying, and evaluated according to the following criteria. The results are shown in Table 2.
○: Maintaining good cylindrical shape △: Slightly deformed cylindrical shape ×: Largely deformed cylindrical shape

<< Evaluation of surface condition of molded body >>
Moreover, after heating up the obtained molded object dried material to 1000 degreeC, it heated up to 1400 degreeC with the temperature increase rate of 50 degreeC / hour. Further, when the temperature reached 1420 ° C., the temperature was maintained, and firing was performed for 4 hours. The surface state of the fired body was visually observed, and smoothness was evaluated according to the following criteria. The results are shown in Table 2.
A: The surface is smooth.
○: Fine irregularities are observed on a part of the surface.
Δ: Fine irregularities and cracks are observed on a part of the surface.
X: Fine irregularities and cracks are observed on the entire surface.
XX: The smoothness of the surface is extremely poor, and cracks are seen throughout.

(Examples 2 to 3 and Comparative Example 6 )
Except that A-2 to A-4 were used for the polymer fine particles, the degree of drying shrinkage and the surface state of the fired body were evaluated by the same operation as in Example 1. The test results are shown in Table 2.

(Comparative Examples 1-4)
Except for using B-1 to B-4 as polymer fine particles, the degree of drying shrinkage and the surface state of the fired product were evaluated by the same operations as in Example 1. In addition, about B-1, even if 33.4 parts of the total amount of water was added, a portion of the kneaded material was still crumpled, so 5.2 parts of water was further added and kneaded. Similarly, for B-3, 14.0 parts of water was added and kneaded. The test results are shown in Table 3.

(Comparative Example 5)
Except that the polymer fine particles were not used, the degree of drying shrinkage and the surface state of the fired product were evaluated by the same operations as in Example 1. However, it was necessary to add 8.0 parts of water during kneading. The test results are shown in Table 3.

The analysis conditions (1) to (3) of the polymer fine particles in the above examples are as described below.
(1) About 1 g of a solid content measurement sample was weighed (a), then the residue after drying for 60 minutes at 150 ° C. in an airless dryer was measured (b), and calculated from the following formula. A weighing bottle was used for the measurement. Other operations were in accordance with JIS K 0067-1992 (chemical product weight loss and residue test method).
Solid content (%) = (b / a) × 100

(2) Water-swelling particle diameter 20 ml of ion-exchanged water was added to 0.02 g of the measurement sample, and the sample was uniformly dispersed by shaking well. In order to make the particles into a water-saturated swelling state, the particle size distribution is measured after 1 minute of ultrasonic irradiation using a laser diffraction / scattering particle size distribution meter (manufactured by Nikkiso, MT-3000) for a dispersion dispersed for 30 minutes or more. Went. Ion exchange water was used as the circulating dispersion medium at the time of measurement, and the refractive index of the dispersion was 1.53. The median diameter (μm) was calculated from the particle size distribution on the basis of the volume obtained by the measurement, and was defined as the water-swelled particle diameter.

(3) Water absorption The water absorption was measured by the following method. A measuring apparatus is shown in FIG.
The measuring device is composed of <1> to <3> in FIG.
<1> Consists of a burette 1 with a branch pipe for venting air, a pinch cock 2, a silicon tube 3, and a polytetrafluoroethylene tube 4.
<2> A support cylinder 8 having a large number of holes in the bottom surface on the funnel 5, and a filter paper 10 for the apparatus is installed on the support cylinder 8.
<3> The sample 6 of polymer fine particles is sandwiched between two sample fixing filter papers 7, and the sample fixing filter papers are fixed by an adhesive tape 9. All filter papers used are ADVANTEC No. 2 The inner diameter is 55 mm.
<1> and <2> are connected by the silicon tube 3.
Further, the funnel 5 and the column cylinder 8 are fixed to the burette 1 at a fixed height, and the lower end of the polytetrafluoroethylene tube 4 installed inside the buret branch pipe and the bottom surface of the column cylinder 8 have the same height. (Dotted line in FIG. 1).

The measurement method will be described below.
The pinch cock 2 in <1> is removed, and ion exchange water is introduced from the upper part of the burette 1 through the silicon tube 3 so that the burette 1 to the apparatus filter paper 10 are filled with the ion exchange water 12. Next, the pinch cock 2 is closed, and air is removed from the polytetrafluoroethylene tube 4 connected to the buret branch pipe with a rubber stopper. In this way, the ion exchange water 12 is continuously supplied from the burette 1 to the filter paper 10 for the apparatus.
Next, after removing the excess ion-exchanged water 12 that oozes from the filter paper for apparatus 10, the reading (a) of the scale of the burette 1 is recorded.
Weigh 0.1 to 0.2 g of the dry powder of the measurement sample and place it uniformly on the center of the sample fixing filter paper 7 as shown in <3>. The sample is sandwiched with another filter paper, and the two filter papers are fastened with the adhesive tape 9 to fix the sample. The filter paper on which the sample is fixed is placed on the apparatus filter paper 10 shown in <2>.
Next, the reading (b) of the scale of the bullet 1 after 30 minutes from the time when the lid 11 is placed on the filter paper 10 for apparatus is recorded.
The sum (c) of the amount of water absorption of the measurement sample and the amount of water absorption of the two sample fixing filter papers 7 is obtained by (ab). By the same operation, the water absorption of only two filter papers 7 not including the polymer fine particle sample is measured (d).
The above operation was performed, and the water absorption was calculated from the following formula. In addition, the value measured by the method of (1) was used for solid content used for calculation.
Water absorption (mL / g) = (cd) / {measurement sample weight (g) × (solid content% ÷ 100)}

In comparison with Comparative Example 5 in which the polymer fine particles of the present invention are not used, each of Examples 1 to 3 can be molded with a small amount of water, the dimensional ratio before and after drying is small, and the degree of shrinkage due to drying is reduced. Can be confirmed. Among these, in addition to Comparative Example 6 in which the polymer fine particles were produced by bulk polymerization, Examples 1 to 3 in which the polymer fine particles were produced by reversed-phase suspension polymerization had a good surface state of the molded body. .
On the other hand, in Comparative Examples 1 and 2 in which the average particle diameter in the state of saturated swelling with ion-exchanged water is outside the range of the present invention, a molded article having a good surface state cannot be obtained, and the water absorption is outside the range of the present invention. In Comparative Examples 3 and 4, the drying shrinkage reduction effect was not recognized. Among these, Comparative Example 3 having a high water absorption amount required a large amount of water for kneading, and thus the shape retention of the molded product was insufficient.

  When the polymer fine particles of the present invention are used for ceramic molding, shrinkage of the molded body in the drying step after molding is reduced, and the molded body also exhibits good shape retention. For this reason, it becomes possible to obtain a highly accurate ceramic compact with good reproducibility.

1 Burette 2 Pinch cock 3 Silicone tube 4 Polytetrafluoroethylene tube 5 Funnel 6 Sample (polymer fine particles)
7 Sample (polymer fine particle) filter paper 8 Fixing column 9 Adhesive tape 10 Device filter paper 11 Lid 12 Ion exchange water

Claims (3)

Polymer fine particles produced by a reverse-phase suspension polymerization method using an oil-soluble oxidant and a water-soluble reducing agent as a polymerization initiator, and the average particle diameter in a state of saturated swelling with ion-exchanged water exceeds 10 μm and is 100 μm A drying shrinkage reducing agent for ceramic molding, comprising polymer fine particles having a water absorption of from 0.1 to 60 mL / g at normal pressure, which is below. The drying shrinkage reducing agent according to claim 1, wherein the reverse phase suspension polymerization is carried out using one or more of (meth) acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid. Drying shrinkage-reducing method of a ceramic molded body using the drying shrinkage-reducing agent according to claim 1 or 2.

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