JP2008143922A - Modified polyvinyl acetal resin, coating paste, electroconductive paste and ceramic paste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a modified polyvinyl acetal resin excellent in thixotropy and thermal decomposition property, and coating paste containing the modified polyvinyl acetal resin, such as an electroconductive paste, ceramic paste, etc., excellent in printability, hardly developing thread formation, clogging or blurring on printing. <P>SOLUTION: This modified polyvinyl acetal resin synthesized by the acetalization reaction of a modified polyvinyl alcohol resin obtained by saponification of a modified polyvinyl ester resin, with an aldehyde is provided by having 1 to 20 mol% content of ethylene component, ≥80 mol% degree of saponification, 15 to 40 mol% content of hydroxy group bonding as a side chain, 0.01 to 10 mol% content of carboxy group bonding as the side chain and 40 to 80 mol% degree of acetalization. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a modified polyvinyl acetal resin and a coating paste such as a conductive paste and a ceramic paste containing the modified polyvinyl acetal resin.

  A multilayer electronic component, for example, a multilayer ceramic capacitor, is generally manufactured through the following steps. First, after adding a plasticizer, a dispersant, etc. to a solution in which a binder resin such as polyvinyl butyral resin is dissolved in an organic solvent, a ceramic raw material powder is added, mixed uniformly by a ball mill, and a ceramic slurry having a constant viscosity after defoaming A composition is obtained. This slurry composition is cast on a support surface such as a polyethylene terephthalate film or a SUS plate which has been subjected to a release treatment using a doctor blade, a reverse roll coater or the like. By heating this, the volatile matter of the organic solvent is distilled off, and then peeled off from the support to obtain a ceramic green sheet.

  Next, a plurality of screen-printed conductive pastes serving as internal electrode layers are alternately stacked on the obtained ceramic green sheet, and heat-pressed to obtain a laminate, and a binder resin component contained in the laminate is obtained. A multilayer ceramic capacitor is obtained through a process of performing thermal decomposition and so-called degreasing treatment, and then sintering an external electrode on the end face of the fired ceramic product obtained by firing.

  In recent years, ceramic green sheets have been made thinner and multilayered for the purpose of reducing the size and increasing the capacity of multilayer ceramic capacitors. However, as the ceramic green sheets become thinner and multi-layered, the level difference between the part where the conductive paste is printed and the part where the conductive paste is not printed increases, and delamination (delamination) occurs when the laminate is heat-pressed. ) Or the deformation of the ceramic green sheet and the internal electrode layer, resulting in a problem that the electrical characteristics and reliability of the multilayer ceramic capacitor deteriorate.

  Therefore, as described in Patent Document 1, after printing the conductive paste, the ceramic paste is printed on a portion of the ceramic green sheet where the conductive paste is not printed, and there is a step when the ceramic green sheets are stacked. There has also been proposed a method of manufacturing a multilayer ceramic capacitor so as not to occur.

  As the conductive paste used to form the internal electrode layer of the multilayer ceramic capacitor, a paste composed of a metal powder, a binder resin, and an organic solvent is used. For example, in Patent Document 2, metal palladium is used as a conductive metal. A conductive paste containing powder, ethyl cellulose as a binder resin, terpineol and kerosene as an organic solvent is disclosed. Patent Document 3 discloses metallic palladium powder as a conductive metal, ethyl cellulose as a binder resin, turpentine oil and ethyl as an organic solvent. A conductive paste containing cellosolve is disclosed.

  On the other hand, as the ceramic paste printed to make it difficult to generate a step when the ceramic green sheets are stacked, a ceramic powder, a binder resin and an organic solvent are used, and as the binder resin, Ethyl cellulose is used.

  However, coating pastes such as conductive pastes and ceramic pastes that use ethyl cellulose as a binder resin as described above are not formed with these coating pastes because they have insufficient adhesion to ceramic green sheets made of polyvinyl butyral resin. The internal electrode layer and ceramic paste layer peel off from the ceramic green sheet, and the thermal decomposition of ethyl cellulose is inferior, so carbon components remain on the ceramic green sheet even after degreasing and firing. There was a problem that the electrical characteristics of ceramic capacitors were impaired.

  In order to solve the above problems, it was considered to use a polyvinyl acetal resin as a binder resin of the coating paste, but this coating paste causes stringing and clogging when printing on a ceramic green sheet. The internal electrode layer and the ceramic paste layer cannot be printed with high accuracy, and the yield of the multilayer ceramic capacitor is reduced.

  As a polyvinyl acetal resin that eliminates such drawbacks, the inventors have proposed a binder resin for conductive paste containing a modified polyvinyl acetal resin as shown in Patent Document 4. However, in order to cope with further downsizing and higher capacity of multilayer ceramic capacitors in recent years, the printing performance required for coating pastes has become more severe, and stringing, clogging and blurring during screen printing have been reduced. There is a need for a polyvinyl acetal resin that can provide a coating paste that can be further reduced.

  Here, the stringing means that the coating paste does not leave cleanly from the screen plate used for screen printing, and the printing surface is in a state where the thread is pulled. The clogging is applied to the eyes of the screen plate. This refers to a phenomenon in which the working paste becomes clogged and cannot be printed, and these occur when the apparent viscosity of the coating paste is high at a high shear rate. On the other hand, the term “brightening” refers to a phenomenon in which a printed coating paste flows on a ceramic green sheet and is printed in a state where it is wider than the intended printing shape. Occurs when the apparent viscosity of the coating paste is low.

  Therefore, a coating paste having a low apparent viscosity when the shear rate is high and a high apparent viscosity when the shear rate is low and when the shear rate is not sheared, that is, a coating paste having excellent thixotropic properties. There is a need for a polyvinyl acetal resin that can be obtained.

Japanese Patent No. 3744368 Japanese Patent Publication No. 3-35762 Japanese Patent Publication No. 4-49766 JP 2005-298792 A

  The present invention comprises a modified polyvinyl acetal resin excellent in thixotropy and thermal decomposability, and this modified polyvinyl acetal resin, and is excellent in printability in which stringing, clogging and blurring are unlikely to occur during printing. Provide coating paste such as conductive paste and ceramic paste.

  The modified polyvinyl acetal resin of the present invention is a modified polyvinyl acetal resin synthesized by an acetalization reaction between a modified polyvinyl alcohol resin and an aldehyde, and has an ethylene component content of 1 to 20 mol% and a saponification degree of 80 mol. % Or more, the amount of hydroxyl groups bonded as side chains is 15 to 40 mol%, the amount of carboxy groups bonded as side chains is 0.01 to 10 mol%, and the degree of acetalization is 40 to 80 mol% It is characterized by being.

  The modified polyvinyl alcohol resin is not particularly limited as long as the content of the ethylene component of the modified polyvinyl acetal resin obtained by acetalizing the polyvinyl alcohol resin can be adjusted within the above range. Saponification of a resin mixture of a copolymer of a carboxylic acid or an unsaturated (di) carboxylic acid derivative and a vinyl ester, and a copolymer of ethylene and a vinyl ester before or after mixing; Examples thereof include those obtained by saponifying a copolymer of (di) carboxylic acid or unsaturated (di) carboxylic acid derivative and ethylene and vinyl ester. In addition, it is necessary to adjust so that content of the vinyl ester component in modified polyvinyl alcohol resin may exceed 50 mol%.

  The vinyl ester is not particularly limited, and examples thereof include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate and the like, and vinyl acetate is preferable from the viewpoint of economy.

  The unsaturated (di) carboxylic acid is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, crotonic acid, phthalic acid, maleic acid, and itaconic acid, and itaconic acid is preferable.

The unsaturated (di) carboxylic acid derivative refers to one having a carboxy group derivative, and the carboxy group derivative refers to a functional group that can be easily substituted with a carboxy group in the presence of an acid catalyst. , Ester group (—COOR), amide group (—CO—NH ₂ ), cyano group (—CN), acid anhydride group (—CO—O—CO—), carboxy group salt (—COOX) and the like. It is done. These carboxy group derivatives are substituted with a carboxy group by an acid catalyst used in the acetalization reaction. Examples of R in the ester group include alkyl groups such as a methyl group, an ethyl group, a propyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group, and a carboxy group. Examples of X in the salt include Na and the like.

  Such an unsaturated (di) carboxylic acid derivative is not particularly limited, and examples thereof include unsaturated (di) carboxylic acid salts, unsaturated (di) carboxylic acid alkyl esters, unsaturated (di) carboxylic acid anhydrides, and the like. Is mentioned. Specifically, phthalic anhydride, maleic anhydride, itaconic anhydride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, trimethyl- (3-acrylamido-3-dimethylpropyl) -ammonium chloride, and the aforementioned unsaturated (Di) Sodium salt of carboxylic acid and the like. These may be used alone or in combination of two or more, and may be used in combination with the unsaturated (di) carboxylic acid described above.

  In addition, if the degree of saponification of the modified polyvinyl alcohol resin is low, the solubility in water decreases and the acetalization reaction becomes difficult, or the degree of acetalization of the resulting modified polyvinyl acetal resin decreases, or Since the solubility of the modified polyvinyl acetal resin in an organic solvent is reduced, the production of a coating paste such as a conductive paste or a ceramic paste is hindered, and the viscosity stability with time is reduced, 80 mol% or more is preferable. In addition, when the modified polyvinyl alcohol resin is a mixture of a plurality of types of modified polyvinyl alcohol resins, the saponification degree of the entire mixture of modified polyvinyl alcohol resins is preferably 80 mol% or more.

The degree of saponification of the modified polyvinyl alcohol resin refers to the ratio of the number of hydroxyl groups B to the total number of hydroxyl groups A and B esterified in the modified polyvinyl alcohol resin, according to the following formula (1). Can be calculated.
Degree of saponification (mol%) = 100 × B / (A + B) (1)

  Further, if the number average polymerization degree of the modified polyvinyl alcohol resin is low, the coating strength when the coating paste is printed on the ceramic green sheet is lowered, and cracks (cracks) are formed in the formed internal electrode layer and ceramic paste layer. On the other hand, if it is high, the solubility in water is lowered, or the viscosity of the aqueous solution becomes too high, and acetalization may be difficult. In addition, the number average degree of polymerization of the resin in the present invention refers to the average degree of polymerization obtained according to the section “5.4 Average degree of polymerization” of JIS K6726 “Polyvinyl alcohol”. Moreover, when mixing and using 2 or more types of polyvinyl alcohol resin as a polyvinyl alcohol resin, the apparent number average degree of polymerization of the whole polyvinyl alcohol resin after mixing is said.

  The aldehyde used to acetalize the modified polyvinyl alcohol resin is not particularly limited. For example, formaldehyde (including paraformaldehyde), acetaldehyde (including paraacetaldehyde), propionaldehyde, butyraldehyde, amylaldehyde , Hexyl aldehyde, heptyl aldehyde, 2-ethylhexyl aldehyde, cyclohexyl aldehyde, furfural, benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, β-phenylpropiyl Examples include onaldehyde, and acetaldehyde and butyraldehyde are preferable. These aldehydes may be used alone or in combination of two or more.

  The point of the acetalization reaction between the modified polyvinyl alcohol resin and the aldehyde is not particularly limited, and a conventionally known method can be used. For example, the modification can be performed in the presence of an acid catalyst such as hydrochloric acid, nitric acid, and sulfuric acid. A method of adding an amount of aldehyde necessary for imparting a predetermined degree of acetalization to an aqueous solution of a polyvinyl alcohol resin to cause an acetalization reaction, neutralizing with an alkali such as sodium hydroxide, washing with water, and drying. Can be mentioned.

  If the content of the ethylene component in the modified polyvinyl acetal resin is small, the dispersibility of the metal powder or ceramic powder in the coating paste is reduced, or the apparent viscosity is high in a state where the shear rate of the coating paste is high. It becomes too much, and during screen printing, it tends to cause stringing and clogging, while when it is large, the solubility of the modified polyvinyl acetal resin in the organic solvent is lowered, and the production of the coating paste may be hindered, Since the viscosity stability with time of the coating paste decreases, it is limited to 1 to 20 mol%, and preferably 1 to 10 mol%.

  In addition, if the saponification degree of the modified polyvinyl acetal resin is low, the degree of acetalization of the modified polyvinyl acetal resin is lowered. Therefore, it is limited to 80 mol% or more, and preferably 80 to 99.9 mol%.

The saponification degree of the modified polyvinyl acetal resin refers to the acetalization reaction relative to the total number of hydroxyl groups C esterified, hydroxyl groups D lost by the acetalization reaction, and hydroxyl groups E in the modified polyvinyl acetal resin. The ratio of the total number of the hydroxyl group number D and the hydroxyl group number E disappeared by the above formula (2) can be calculated.
Degree of saponification (mol%) = 100 × (D + E) / (C + D + E) (2)

  If the amount of hydroxyl groups bonded as side chains to the main chain of the modified polyvinyl acetal resin is small, the strength of the modified polyvinyl acetal resin is impaired, and the coating paste when the coating paste is printed on the ceramic green sheet is used. While the film strength is reduced and cracks are likely to occur in the formed internal electrode layer and ceramic paste layer, the solubility of the modified polyvinyl acetal resin in an organic solvent is reduced, and the coating paste is produced. Therefore, it is limited to 15 to 40 mol%, and 18 to 35 mol% is preferable.

  In addition, when the amount of the carboxy group bonded as a side chain to the main chain of the modified polyvinyl acetal resin is small, the apparent viscosity of the coating paste is insufficient in a state where the shear rate is low and in a state where the shear rate is not sheared, On the other hand, blurring tends to occur when screen printing is performed. On the other hand, the solubility of the modified polyvinyl acetal resin in an organic solvent is reduced, and the production of the coating paste is hindered. 0.1 to 5 mol% is preferable.

  The amount of hydroxyl groups and carboxy groups bonded as side chains to the main chain of the modified polyvinyl acetal resin refers to the ratio (mol%) of the number of hydroxyl groups or the number of carboxy groups to the total number of side chains of the modified polyvinyl acetal resin. . Here, as the number of side chains of the acetalized portion in the modified polyvinyl acetal resin, the number of hydroxyl groups lost by the acetalization reaction is adopted.

The amount of hydroxyl group and carboxy group bonded as side chains to the main chain of the modified polyvinyl acetal resin is determined by dissolving the modified polyvinyl acetal resin in DMSO-d ₆ (dimethyl sulfoxide), and ¹³ C-NMR. The spectrum is measured and can be calculated by the peak area derived from the esterified hydroxyl group, the methine group to which the hydroxyl group and the carboxy group are bonded, and the peak area derived from the methine group of the acetalized portion. .

  On the other hand, if the degree of acetalization of the modified polyvinyl acetal resin is small, the solubility of the modified polyvinyl acetal resin in an organic solvent is reduced, which may hinder the preparation of a coating paste. The number of hydroxyl groups bonded as side chains to the chain is reduced, the strength of the modified polyvinyl acetal resin is impaired, the coating strength when the coating paste is printed on the ceramic green sheet is reduced, and the formed interior Since cracks (cracks) are likely to occur in the electrode layer and the ceramic paste layer, it is limited to 40 to 80 mol%, and preferably 65 to 78 mol%.

  Here, the degree of acetalization of the modified polyvinyl acetal resin refers to the ratio (mol%) of the number of hydroxyl groups lost during the acetalization reaction with respect to the total number of side chains of the modified polyvinyl acetal resin. The total number of side chains of the modified polyvinyl acetal resin is calculated as the number of side chains of the acetalized portion in the modified polyvinyl acetal resin as the number of hydroxyl groups lost by the acetalization reaction.

The degree of acetalization of the modified polyvinyl acetal resin is determined by dissolving the modified polyvinyl acetal resin in DMSO-d ₆ (dimethyl sulfoxide), measuring the ¹³ C-NMR spectrum, and esterifying the modified polyvinyl acetal resin. Peak area S ₁ derived from a methine group to which a hydroxyl group is bonded, peak area S ₂ derived from a methine group to which a hydroxyl group is bonded, peak area S derived from a methine group to which a carboxy group is bonded ₃ and the peak area S ₄ derived from the methine group of the acetalized portion can be calculated by substituting into the following formula (3).
Degree of acetalization (mol%) = 100 × S ₄ / (S ₁ + S ₂ + S ₃ + S ₄ ) (3)

  Further, if the number average polymerization degree of the modified polyvinyl acetal resin is low, the coating strength when the coating paste is printed on the ceramic green sheet is low, and the formed internal electrode layer and ceramic paste layer are cracked (cracked). On the other hand, if it is high, the apparent viscosity at a high shear rate of the coating paste becomes too high, and stringing or clogging may occur during screen printing. Is preferred.

  When the modified polyvinyl acetal resin is a mixture of two or more resins, the content of the ethylene component in the modified polyvinyl acetal resin, the saponification degree of the modified polyvinyl acetal resin, the main chain of the modified polyvinyl acetal resin The amount of hydroxyl groups and carboxy groups bonded as side chains, and the degree of acetalization and number average polymerization of the modified polyvinyl acetal resin are the apparent values of the entire mixed resin.

  The modified polyvinyl acetal resin of the present invention becomes a binder resin solution (vehicle) by dissolving it in an organic solvent as a binder resin, and a desired inorganic powder is mixed into the binder resin solution, thereby allowing yarns during screen printing. Thus, it is possible to obtain a coating paste such as a conductive paste and a ceramic paste that is less likely to be pulled, clogged, and smeared, and that is quickly decomposed during the degreasing process and does not easily leave a carbon component on the ceramic green sheet.

  The said electrically conductive paste is comprised from a modified polyvinyl acetal resin, a metal powder, and an organic solvent, and is obtained by mixing these using various mixers, such as a blender mill and 3 rolls.

  Examples of the metal powder used in the conductive paste include powders made of nickel, palladium, platinum, gold, silver, copper and alloys thereof, and these may be used alone or in combination of two or more. You may use together.

  If the content of the metal powder in the conductive paste is small, the conductivity of the obtained internal electrode layer may be low. On the other hand, if the content is high, the apparent viscosity at a high shear rate of the conductive paste is high. Thus, stringing or clogging may occur during screen printing, so 30 to 69% by weight is preferable, and 40 to 60% by weight is more preferable.

  The organic solvent used in the conductive paste is not particularly limited as long as it can dissolve the polyvinyl acetal resin of the present invention. For example, ketones such as acetone, methyl ethyl ketone, dipropyl ketone, and diisobutyl ketone, methanol , Alcohols such as ethanol, isopropanol and butanol, aromatic hydrocarbons such as toluene and xylene, methyl propionate, ethyl propionate, butyl propionate, methyl butanoate, ethyl butanoate, butyl butanoate, methyl pentanoate, Esters such as ethyl pentanoate, butyl pentanoate, methyl hexanoate, ethyl hexanoate, butyl hexanoate, 2-ethylhexyl acetate, 2-ethylhexyl butyrate, methyl cellosolve, ethyl cellosolve, butyl cellosolve, terpi Ol, dihydro terpineol, butyl cellosolve acetate, butyl carbitol acetate, terpinyl acetate, dihydro terpinyl acetate.

  And if there is little content of the organic solvent in the said electrically conductive paste, the apparent viscosity in the state where the shear rate of an electrically conductive paste is high will become high too much, and stringing and clogging may arise in screen printing. On the other hand, if the amount is too large, the viscosity of the conductive paste becomes too low and the handleability may be lowered, so 30 to 69% by weight is preferable, and 35 to 55% by weight is more preferable.

  The ceramic paste is composed of the modified polyvinyl acetal resin, ceramic powder, and an organic solvent, and can be obtained by mixing them using various mixers such as a blender mill and a three roll.

  The ceramic powder is not particularly limited, and examples thereof include alumina, zirconia, aluminum silicate, titanium oxide, zinc oxide, barium titanate, magnesia, sialon, spinemulite, silicon carbide, silicon nitride, aluminum nitride, and the like. These may be used alone or in combination of two or more.

  And, if the content of the ceramic powder in the ceramic paste is small, cracks may occur in the ceramic paste layer in the drying or sintering process, while if it is large, the shear rate of the ceramic paste is high. The apparent viscosity of the ink is too high, and stringing or clogging may occur during screen printing, so 30 to 69% by weight is preferable, and 40 to 60% by weight is more preferable.

  In addition, the organic solvent used in the ceramic paste is not particularly limited as long as it can dissolve the polyvinyl acetal resin of the present invention, and examples thereof include the same organic solvents used in the above-described conductive paste.

  If the content of the organic solvent in the ceramic paste is small, the apparent viscosity at a high shear rate of the ceramic paste becomes too high, and stringing or clogging may occur during screen printing. On the other hand, when the amount is too large, the viscosity of the ceramic paste becomes too low and the handleability may be lowered. Therefore, 30 to 69% by weight is preferable, and 35 to 55% by weight is more preferable.

  In addition, as the binder resin of the coating paste such as the conductive paste and the ceramic paste, it is preferable to use the modified polyvinyl acetal resin of the present invention alone, but a resin such as an acrylic resin, a cellulose resin, or a polyvinyl acetal resin. And a resin mixture of the modified polyvinyl acetal resin of the present invention.

  And when using the mixture of the modified polyvinyl acetal resin of the present invention and other resins as the binder resin of the coating paste, if the content of the modified polyvinyl acetal resin of the present invention in this mixture is small, it is obtained. When screen printing is performed using the applied paste, stringing or clogging is likely to occur, or the adhesiveness to the ceramic green sheet is reduced. Therefore, 30% by weight or more is preferable, and 50% by weight or more is preferable. More preferred.

  Further, if the content of the binder resin in the coating paste is small, the adhesiveness between the coating paste and the ceramic green sheet becomes insufficient, and the formed internal electrode layer, ceramic paste layer, and ceramic green sheet are formed. While delamination may occur between the conductive paste and the ceramic paste, the apparent viscosity at a high shear rate of the conductive paste and ceramic paste becomes too high, and stringing and meshing may occur during screen printing. Since clogging may occur, 1 to 10% by weight is preferable, and 2 to 5% by weight is more preferable.

  In addition, you may add additives, such as a plasticizer, a lubricant, a dispersing agent, an antistatic agent, to the said coating paste, if it is in the range which does not impair the effect of this invention.

  Since the modified polyvinyl acetal resin of the present invention has the above-described configuration, the conductive paste or ceramic paste using the modified polyvinyl acetal resin as a binder resin has a low apparent viscosity in a state where the shear rate is high, In addition, in the state where the shear rate is low and the state where it is not sheared, the property that the apparent viscosity becomes high, that is, the thixotropic property is excellent. Therefore, by using the modified polyvinyl acetal resin of the present invention as a binder resin, a coating paste such as a conductive paste or a ceramic paste having excellent printability that is less likely to cause stringing, clogging, and blemishes during screen printing. Obtainable.

  Moreover, since the modified polyvinyl acetal resin is excellent in adhesion to a ceramic green sheet made of polyvinyl butyral resin, it can be suitably used as a binder resin for coating paste.

  Furthermore, the modified polyvinyl acetal resin of the present invention is excellent in thermal decomposability. Therefore, according to the coating paste using the modified polyvinyl acetal resin of the present invention as a binder resin, the internal electrode layer and the ceramic paste layer can be formed with almost no carbon component remaining in the ceramic green sheet. In addition, it is possible to manufacture a multilayer electronic component having excellent reliability.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Example 1)
130 g of ethylene-modified polyvinyl alcohol resin (ethylene component content: 8 mol%, saponification degree: 98 mol%) obtained by saponifying ethylene-vinyl acetate copolymer and saponifying itaconic acid-vinyl acetate copolymer 130 g of itaconic acid-modified polyvinyl alcohol resin (itaconic acid component content: 2 mol%, saponification degree: 88 mol%) is added to 2900 g of pure water and stirred at 90 ° C. for about 2 hours to obtain a modified polyvinyl alcohol resin aqueous solution. It was. In addition, the saponification degree of the whole modified polyvinyl alcohol resin was 93.4 mol%.

  Subsequently, this modified polyvinyl alcohol resin aqueous solution was cooled to 28 ° C., and 500 g of hydrochloric acid having a concentration of 35% by weight and 178 g of n-butyraldehyde were added thereto, and this solution was further lowered to 10 ° C. for acetalization reaction. . Next, the temperature of the solution was raised to 30 ° C. and held at this temperature for 5 hours to complete the acetalization reaction, and neutralized, washed with water and dried by a conventional method to obtain a modified polyvinyl butyral resin.

Next, the modified polyvinyl butyral resin was dissolved in DMSO-d ₆ (dimethyl sulfoxide), and the ¹³ C-NMR spectrum was measured to calculate the composition and the degree of butyralization of the modified polyvinyl butyral resin. The ethylene component content is 4.3 mol%, the degree of saponification is 93.4 mol%, the amount of hydroxyl groups bonded as side chains is 19.6 mol%, and the amount of carboxy groups bonded as side chains is 0.9 mol% and the degree of butyralization were 73 mol%.

(Example 2)
130 g of ethylene-modified polyvinyl alcohol resin (ethylene component content: 10 mol%, saponification degree: 90 mol%) obtained by saponifying ethylene-vinyl acetate copolymer, and saponifying itaconic acid-vinyl acetate copolymer 130 g of itaconic acid-modified polyvinyl alcohol resin (itaconic acid component content: 6 mol%, saponification degree: 98 mol%) is added to 2900 g of pure water and stirred at 90 ° C. for about 2 hours to obtain a modified polyvinyl alcohol resin aqueous solution. It was. In addition, the saponification degree of the whole modified polyvinyl alcohol resin was 94 mol%.

  Subsequently, this modified polyvinyl alcohol resin aqueous solution is cooled to 28 ° C., 500 g of hydrochloric acid having a concentration of 35% by weight, 98 g of n-butyraldehyde and 46 g of acetaldehyde are added thereto, and this solution is further lowered to 10 ° C. to acetalize. Reacted. Next, the solution was heated to 30 ° C. and held at this temperature for 5 hours to complete the acetalization reaction, and neutralized, washed with water and dried by a conventional method to obtain a modified polyvinyl acetal resin.

Then, this modified polyvinyl acetal resin was dissolved in DMSO-d ₆ (dimethyl sulfoxide), measured for ¹³ C-NMR spectrum, and the composition and degree of acetalization of the modified polyvinyl acetal resin were calculated. The component content is 5 mol%, the degree of saponification is 94 mol%, the amount of hydroxyl groups bonded as side chains is 25.2 mol%, the amount of carboxy groups bonded as side chains is 3 mol%, The degree of acetalization was 66 mol%.

(Comparative Example 1)
260 g of a polyvinyl alcohol resin (degree of saponification: 88 mol%) was added to 2900 g of pure water and stirred at 90 ° C. for about 2 hours to obtain an aqueous polyvinyl alcohol resin solution. Next, this polyvinyl alcohol resin aqueous solution was used in place of the modified polyvinyl alcohol resin aqueous solution, and a polyvinyl butyral resin was obtained in the same manner as in Example 1 except that the amount of n-butyraldehyde was 170 g instead of 178 g. It was.

And when this polyvinyl butyral resin was dissolved in DMSO-d ₆ (dimethyl sulfoxide) and measured for ¹³ C-NMR spectrum, the composition of the polyvinyl butyral resin and the degree of butyralization were calculated. The content is 0 mol%, the degree of saponification is 88 mol%, the amount of hydroxyl groups bonded as side chains is 23 mol%, the amount of carboxy groups bonded as side chains is 0 mol%, and the degree of butyralization is It was 65 mol%.

(Comparative Example 2)
193 g of polyvinyl alcohol resin (degree of saponification: 96 mol%) was added to 2900 g of pure water and stirred at a temperature of 90 ° C. for about 2 hours to obtain a polyvinyl alcohol resin aqueous solution. Next, the same procedure as in Example 1 was used except that this polyvinyl alcohol resin aqueous solution was used in place of the modified polyvinyl alcohol resin aqueous solution, and n-butyraldehyde 90 g and acetaldehyde 43 g were used instead of n-butyraldehyde 178 g. A polyvinyl acetal resin was obtained.

Then, the modified polyvinyl acetal resin was dissolved in DMSO-d ₆ (dimethyl sulfoxide), and the ¹³ C-NMR spectrum was measured to calculate the composition of the polyvinyl acetal resin and the degree of acetalization. Is 0 mol%, the degree of saponification is 96 mol%, the amount of hydroxyl groups bonded as side chains is 28 mol%, the amount of carboxy groups bonded as side chains is 0 mol%, the degree of acetalization Was 68 mol%.

(Preparation of conductive paste)
(Modified) polyvinyl acetal resin 4.2% by weight obtained in Examples and Comparative Examples, nickel powder (trade name “2020SS” manufactured by Mitsui Kinzoku Co., Ltd.) 50% by weight and α-terpineol 45.8% by weight were mixed, A conductive paste was obtained by kneading with three rolls. The (modified) polyvinyl acetal resin means a modified polyvinyl acetal resin or a polyvinyl acetal resin.

(Production of ceramic paste)
4.2% by weight of (modified) polyvinyl acetal resin obtained in Examples and Comparative Examples, 50% by weight of barium titanate (trade name “BT-03” manufactured by Sakai Chemical Industry Co., Ltd., average particle size: 0.3 μm) and α-Terpineol 45.8% by weight was mixed and kneaded for 48 hours using a ball mill to obtain a ceramic paste.

Next, the viscosity and screen printability of the coating paste obtained as described above were evaluated in the following manner, and the results are shown in Table 1. In Table 1, “when 1 (s ⁻¹ )” indicates the viscosity of the coating paste when the shear rate is 1 (s ⁻¹ ), and when “100 (s ⁻¹ )” The viscosity of the coating paste when the shear rate is 100 (s ⁻¹ ) is shown.

(Viscosity of coating paste)
Using the rotary rheometer (trade name “Gemini 150” manufactured by Bolin), the viscosity at the time when the shear rate in the obtained conductive paste and ceramic paste was 1 (s ⁻¹ ) and 100 (s ⁻¹ ) was used. Measured. The viscosity is measured by using a cone plate with a diameter of 40 mm and an angle of 1 °, and increasing the shear rate from 0.1 (s ⁻¹ ) to 100 (s ⁻¹ ) at 25 ° C. It was done.

(Screen printability of coating paste)
Using a screen printing machine (trade name “Minomat Y-3540” manufactured by Mino Group) and an SX screen plate (trade name “SX300B” manufactured by Mino Group), the resulting conductive paste and ceramic paste are placed on a ceramic green sheet. The printed surface was observed visually and with a magnifying microscope, and screen printability was evaluated according to the following criteria.
○: No thread-like paste or blemishes were observed on the printed surface.
X: A thread-like paste or blemishes were observed on the printed surface.

Claims (5)

A modified polyvinyl acetal resin synthesized by an acetalization reaction between a modified polyvinyl alcohol resin and an aldehyde, wherein the ethylene component content is 1 to 20 mol%, the saponification degree is 80 mol% or more, and bonded as a side chain. The modified polyvinyl, characterized in that the amount of hydroxyl group is 15 to 40 mol%, the amount of carboxy group bonded as a side chain is 0.01 to 10 mol%, and the degree of acetalization is 40 to 80 mol% Acetal resin. The modified polyvinyl acetal resin according to claim 1, wherein the aldehyde is butyraldehyde and / or acetaldehyde. A coating paste comprising the modified polyvinyl acetal resin according to claim 1 or 2. A conductive paste comprising the modified polyvinyl acetal resin according to claim 1 or 2. A ceramic paste comprising the modified polyvinyl acetal resin according to claim 1 or 2.