JP4754163B2 - Vinyl acetal polymer and use thereof - Google Patents

Description

The present invention relates to a vinyl acetal polymer. More specifically, the present invention relates to a vinyl acetal polymer obtained by acetalizing a vinyl alcohol polymer containing an ionic group via a sulfide bond at a terminal and its use.

  It has long been known that a vinyl acetal polymer is obtained by acetalizing a vinyl alcohol polymer under acidic conditions using an aldehyde compound. Since a vinyl alcohol polymer usually has a vinyl alcohol unit and a vinyl ester unit, the vinyl acetal polymer obtained by acetalizing the vinyl alcohol polymer is one of these two types of monomer units. And at least three types of monomer units containing vinyl acetal units. In recent years, since many types of vinyl alcohol polymers have been proposed, many types of vinyl acetal polymers have become known by combining these with various aldehydes. Yes.

  Among them, a vinyl formal polymer produced from a vinyl alcohol polymer and formaldehyde, a vinyl acetal polymer produced from a vinyl alcohol polymer and acetaldehyde, and a vinyl alcohol polymer and butyraldehyde. The vinyl butyral polymer produced occupies a commercially important position.

In particular, vinyl butyral polymers are not only used as intermediate films for automobile and building window glass, but are also widely used in various industrial fields such as ceramic molding binders, photosensitive materials, and ink dispersants. It is used. Among these, the vinyl butyral polymer is used as a ceramic molding binder, for example, as a molding binder in the process of manufacturing a ceramic multilayer capacitor or a ceramic electronic circuit board. Widely used as a binder.
In particular, in recent years, it has been desired to reduce the size and weight of precision electrical devices such as mobile phones and notebook computers, and the electrical and electronic components used in these devices are also required to be reduced in size and performance. It has been.

  For example, in ceramic multilayer capacitors, small and large-capacity capacitors are desired, and attempts have been made to reduce the thickness of electrodes or ceramic parts or to increase the capacity. Thin film formation is an important issue. In order to make such a thin film, it is necessary to use a ceramic powder having a small particle size as a raw material. However, if the particle size of the ceramic powder is reduced, the surface area of the ceramic powder increases and is likely to aggregate. Therefore, irregularities are likely to occur on the surface of the ceramic green sheet, it becomes difficult to obtain a homogeneous ceramic green sheet, and the strength is lowered by reducing the thickness of the sheet.

  These problems have been highlighted in recent years as electric and electronic parts have been reduced in size and weight, and currently known vinyl acetal polymers cannot be satisfactorily solved. is there. For example, it has been proposed in the past to use an α-olefin-modified vinyl acetal polymer as a binder for ceramic molding (see Patent Document 1), but at the technical level at that time, the problems pointed out earlier were considered. The current situation is that the problem has not been solved.

Prior art document information related to the invention of this application includes the following.
JP-A 63-79752

  The object of the present invention is for ceramic molding that enables the production of ceramic green sheets that are homogeneous and have high sheet strength even when ceramic powder having a small particle size is used as a raw material, corresponding to the thinning of ceramic green sheets The object is to provide a vinyl acetal polymer suitable for a binder.

As a result of intensive studies to solve the above problems, the present inventors have found that when a vinyl acetal polymer made from a specific vinyl alcohol polymer is used as a ceramic molding binder, a ceramic powder having a small particle size is used. Even when a ceramic green sheet is produced using the body as a raw material, it has been found that a ceramic green sheet having a uniform and high sheet strength can be obtained, and the present invention has been completed.
That is, in the first aspect of the present invention, the degree of polymerization is 50 to 1000, the degree of saponification is 80.0 to 99.99 mol%, and the ionic group bonded to the terminal via a sulfide bond satisfies the following formula (1). It is a vinyl acetal polymer having an acetalization degree of 45 to 80 mol% obtained by acetalizing a vinyl alcohol polymer contained under the above conditions.
0.15 ≦ Content ≦ 218.3 × P ^−1.046 (1)
(In the formula, the content represents the content (mol%) of an ionic group bonded through a sulfide bond, and P represents the degree of polymerization of the vinyl alcohol polymer.)
A second aspect of the present invention is an acetalization of the vinyl acetal polymer (A) of the first invention and a vinyl alcohol polymer having a polymerization degree of 100 to 4000 and a saponification degree of 80.0 to 99.99 mol%. And a vinyl acetal polymer (B) having a degree of acetalization of 45 to 80 mol% obtained in a weight ratio of 5/95 ≦ (A) / (B) ≦ 100/0. It is a vinyl acetal polymer composition.
3rd of this invention is the binder for ceramic shaping | molding which has the vinyl acetal type polymer of 1st invention or the vinyl acetal type polymer composition of 2nd invention as a main component.

  The vinyl acetal polymer of the present invention obtained by acetalizing a vinyl alcohol polymer containing an ionic group through a sulfide bond at the terminal is used as a binder for ceramic molding, so that a conventional vinyl acetal is obtained. Compared with the case where a polymer is used as a binder for ceramic molding, a ceramic green sheet having a uniform surface state and high sheet strength and capable of coping with thinning can be produced. The ceramic green sheet thinning is particularly useful for downsizing and high performance of electrical and electronic components that have been desired in recent years. Therefore, the ceramic molding binder according to the present invention is a small and large capacity ceramic multilayer capacitor. It is particularly useful as a molding binder when manufacturing ceramic electronic circuit boards for IC chips and the like.

The vinyl acetal polymer of the present invention has a polymerization degree of 50 to 1000, a saponification degree of 80.0 to 99.99 mol%, and an ionic group bonded to the terminal via a sulfide bond is represented by the following formula (1). It is produced by acetalizing a vinyl alcohol polymer (hereinafter sometimes abbreviated as “PVA”) contained under satisfying conditions.
0.15 ≦ Content ≦ 218.3 × P ^−1.046 (1)
(In the formula, the content represents the content (mol%) of an ionic group bonded through a sulfide bond, and P represents the degree of polymerization of the vinyl alcohol polymer.)

The degree of polymerization of PVA used for producing the polyvinyl acetal of the present invention is 50-1000, preferably 50-850, 100-700 are more preferred. When the degree of polymerization of PVA is less than 30, it becomes difficult to industrially produce PVA, and when the degree of polymerization exceeds 1000, the homogeneity may deteriorate when a ceramic green sheet is produced. .

The degree of polymerization of PVA, which is a raw material for the vinyl acetal polymer of the present invention, means the viscosity average degree of polymerization, and is measured according to JIS-K6726. That is, after re-saponifying and purifying PVA to a saponification degree of 99.5 mol% or more, it can be obtained from the intrinsic viscosity [η] measured in water at 30 ° C. by the following equation.
P = ([η] × 1000 / 8.29) ^{(1 / 0.62)}

  In the present invention, the saponification degree of PVA used as a raw material for the vinyl acetal polymer is 80.0 to 99.99 mol%, preferably 85 to 99.5 mol%, more preferably 90 to 99 mol%, ˜98.5 mol% is particularly preferred. When the degree of saponification is less than 80 mol%, the homogeneity of the ceramic green sheet may deteriorate. When the saponification degree exceeds 99.99 mol%, it becomes difficult to produce PVA.

In the present invention, the PVA used as a raw material for the vinyl acetal polymer has a content of ionic groups bonded to the terminals via sulfide bonds of 0.15 mol% or more, and the polymerization degree of the vinyl alcohol polymer is P. (218.3 × P ^−1.046 ) mol% or less.

If the content of ionic groups is less than 0.15 mol%, the homogeneity of the ceramic green sheet deteriorates when a vinyl acetal polymer obtained by using such PVA is used as a binder for ceramic molding. There are things to do. On the other hand, when the content of ionic groups exceeds (218.3 × P ^−1.046 ) mol% when the degree of polymerization of the vinyl alcohol polymer is P, by using such PVA, When the obtained vinyl acetal polymer is used as a ceramic molding binder, the homogeneity of the ceramic green sheet may be deteriorated or the strength of the sheet may be reduced.

In the present invention, the PVA used as a raw material for the vinyl acetal polymer needs to contain an ionic group via a sulfide bond at the terminal. An ionic group refers to a cationic ionic group of a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof. Among these, carboxylic acid or sulfonic acid, or alkali metal salt or ammonium salt thereof is preferable.

The terminal structure of the PVA used in the present invention is shown by the following formula.
-S- _{(CH 2)} n -A
(In the above formula, n is an integer of 1 to 10, A is —COOX or —SO ₃ X, where X is a hydrogen atom, an alkali metal or NH ₄ )

  The content of the ionic group bonded to the end of PVA via a sulfide bond can be determined from the peak of proton NMR. That is, PVA was saponified until the saponification degree became 99.95 mol% or more, sufficiently washed with methanol, and then dried at 90 ° C. under reduced pressure for 2 days to prepare PVA for analysis as a solvent. Proton NMR measurement is performed using DMSO-d6, and the content of ionic groups is calculated from the peak (2.6 to 2.8 ppm) derived from methylene bonded to a sulfur atom.

  The content of the ionic group bonded to the end of PVA via a sulfide bond is not changed by acetalizing the PVA. Therefore, the polyvinyl acetal polymer of the present invention contains an ionic group bonded to the end of the same amount as the PVA used as the raw material via a sulfide bond.

The content of the ionic group bonded to the end of the polyvinyl acetal polymer of the present invention via a sulfide bond can also be determined from the peak of proton NMR. That is, a sample for analysis was prepared from a polyvinyl acetal polymer, proton NMR measurement was performed using DMSO-d6 or methanol-d4 as a solvent, and a peak derived from methylene bonded to a sulfur atom (2.6 to The content of ionic groups is calculated from 2.8 ppm).
Further, the vinyl acetal polymer is reacted with hydroxyamine hydrochloride in an alcohol solvent, and the resulting reaction product is sufficiently reprecipitated and purified with water / alcohol to obtain PVA. The resulting PVA has a saponification degree of 99.95. The ionic group content can also be calculated by preparing a sample for analysis by saponification until it is at least mol% and drying, and measuring proton NMR using DMSO-d6 as a solvent. .

In the vinyl acetal polymer of the present invention, it is preferable that PVA used as a raw material thereof contains 1,2-glycol bond in an amount of 1 to 2 mol% and satisfies the following formula (2).
0.15 ≦ content ≦ −0.0606 × Y + 2.3049 (2)
(In the formula, the content represents the content (mol%) of an ionic group bonded via a sulfide bond, and Y represents the content of 1,2-glycol bond in PVA.)

  When the content of 1,2-glycol bond is less than 1 mol% or exceeds 2 mol%, the vinyl acetal polymer obtained by using such PVA is used as a binder for ceramic molding. In such a case, the homogeneity of the ceramic green sheet may deteriorate or the strength of the sheet may decrease.

  When the content of ionic groups exceeds (-0.0606 × Y + 2.3049) mol% when the content of 1,2-glycol bond in PVA is Y, by using such PVA, When the obtained vinyl acetal polymer is used as a ceramic molding binder, the homogeneity of the ceramic green sheet may be deteriorated or the strength of the sheet may be reduced.

In the present invention, the content of 1,2-glycol bond of PVA can be determined from the NMR peak. That is, PVA is saponified until the saponification degree becomes 99.9 mol% or more, thoroughly washed with methanol, and then dried at 90 ° C. under reduced pressure for 2 days to prepare a sample for analysis. . A sample for analysis is dissolved in DMSO-D6, a few drops of trifluoroacetic acid are added, and then measured at 80 ° C. using 500 MHz proton NMR (JEOL GX-500). From the peak derived from methine of vinyl alcohol unit (3.2 to 4.0 ppm; integrated value A) and the peak derived from one methine of 1,2-glycol bond (3.25 ppm; integrated value B), The content of 1,2-glycol bond is calculated according to the formula.
1,2-glycol bond content (mol%) = 100 B / A

  The 1,2-glycol bond content of PVA can also be determined from a vinyl acetal polymer. In this case, the vinyl acetal polymer is reacted with hydroxyamine hydrochloride in an alcohol solvent, and the resulting reaction product is sufficiently reprecipitated with water / alcohol to obtain PVA, and the subsequent operations are the same as described above. To prepare a sample for analysis.

  In the present invention, as a method for introducing an ionic group to the end of PVA through a sulfide bond, a chain transfer polymerization method in which radical polymerization of a vinyl ester monomer is performed in the presence of a mercaptan having an ionic group is adopted. Can do. Production of modified PVA based on this method is described in detail in JP-A-57-28121, JP-A-57-105410, JP-A-1-26602 and the like.

  In the present invention, the 1,2-glycol bond content of PVA is determined based on the polymerization temperature at the time of radical polymerization of vinyl ester monomers or other monomers such as vinylene carbonate and vinyl ester monomers. It can adjust by copolymerization with.

  Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and vinyl versatate. Among these, vinyl acetate is preferable from the viewpoint of obtaining PVA.

  Examples of mercaptans having an ionic group include mercaptocarboxylic acids such as mercaptoacetic acid, 3-mercaptopropionic acid, 4-mercaptobutanoic acid, 5-mercaptopentanoic acid, 6-mercaptohexanoic acid and 8-mercaptooctanoic acid; mercaptomethanesulfonic acid Mercaptosulfonic acids such as 2-mercaptoethanesulfonic acid, 3-mercaptopropanesulfonic acid, 4-mercaptobutanesulfonic acid, 5-mercaptopentanesulfonic acid, 6-mercaptohexanesulfonic acid, 8-mercaptooctanesulfonic acid; Phosphonic acid, 2-mercaptoethanephosphonic acid, 3-mercaptopropanephosphonic acid, 4-mercaptobutanephosphonic acid, 5-mercaptopentanephosphonic acid, 6-mercaptohexanephosphonic acid, 8-mer Mercaptophosphonic acids such as ptooctanephosphonic acid; mercaptomethane monophosphate, 2-mercaptoethane monophosphate, 3-mercaptopropane monophosphate, 4-mercaptobutane monophosphate, 5-mercaptopentane monophosphate, 6- Mercaptoalkane monophosphates such as mercaptohexane monophosphate and 8-mercaptooctane monophosphate; mercaptomethanetrimethylammonium chloride, 2-mercaptoethanetrimethylammonium chloride, 3-mercaptopropanetrimethylammonium chloride, 4-mercaptobutanetrimethylammonium chloride 5-mercaptopentane trimethylammonium chloride, 6-mercaptohexane Emissions trimethyl ammonium chloride, 8-such dimercaptooctanoic trimethyl ammonium chloride mercaptoalkyl group-containing quaternary ammonium salts, such as chloride and the like, mercapto carboxylic acids and mercapto sulfonic acid Among these, preferred.

  As long as the effects of the present invention are not impaired, PVA may contain monomer units other than vinyl alcohol units and vinyl ester units. Examples of such units include α-olefins such as ethylene, propylene, and isobutene; monomers having a carboxyl group derived from fumaric acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, etc .; acrylic acid or Acrylates such as salts thereof, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate; methacrylic acid or a salt thereof, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, methacryl Methacrylic acid esters such as i-propyl acid; acrylamide derivatives such as acrylamide, N-methylacrylamide, N-ethylacrylamide; methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide; -N-vinylamides such as vinylacetamide, N-vinylpyrrolidone, N-vinylcaprolactam; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether; ethylene glycol vinyl ether, 1 Hydroxy group-containing vinyl ethers such as 1,3-propanediol vinyl ether and 1,4-butanediol vinyl ether; allyl ethers such as allyl acetate, propyl allyl ether, butyl allyl ether, and hexyl allyl ether; monomers having an oxyalkylene group Vinyl silanes such as vinyltrimethoxysilane, isopropenyl acetate, 3-buten-1-ol, 4-penten-1-ol, 5-hexene- Hydroxy group-containing α-olefins such as 1-ol, 7-octen-1-ol, 9-decene-1-ol, 3-methyl-3-buten-1-ol; ethylene sulfonic acid, allyl sulfonic acid, meta Monomers having a sulfonic acid group derived from allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, etc .; vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyldimethylamine, vinyloxymethyl Diethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine, allyltrimethylammonium chloride, methallyltrimethylammonium Umukuroraido, dimethylallylamine, monomer units can be given from a variety monomers such as monomers having cationic groups such as from allyl ethylamine. The unit content of these monomers is usually 20 mol% or less, preferably 10 mol% or less, more preferably 5 mol% or less.

  PVA containing an ionic group via a sulfide bond at the terminal used in the present invention uses the mercaptan having the ionic group described above and further uses a thiol compound such as 2-mercaptoethanol and n-dodecyl mercaptan. It can also be produced by polymerizing a vinyl ester monomer such as vinyl acetate and saponifying the resulting vinyl ester polymer.

  As a method for radical polymerization of a vinyl ester monomer in the presence of a mercaptan having an ionic group, known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method and an emulsion polymerization method are employed. Among them, a bulk polymerization method in which polymerization is performed without solvent or a solution polymerization method in which polymerization is performed in a solvent such as alcohol is usually employed. In order to efficiently introduce a mercaptan having an ionic group at the end of PVA, it is desirable to add the mercaptan according to the reaction rate of the vinyl ester monomer. As a specific method thereof, a method of adjusting the molar concentration of the vinyl ester monomer and the mercaptan in the polymerization system to be constant can be mentioned. Examples of the alcohol used as a solvent when the polymerization is performed using a solution polymerization method include lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol. Examples of the initiator used for the polymerization include α, α′-azobisisobutyronitrile, azo initiators such as 2,2′-azobis (2,4-dimethyl-valeronitrile), and benzoyl peroxide, Examples thereof include peroxide initiators such as n-propyl peroxycarbonate. Although there is no restriction | limiting in particular about superposition | polymerization temperature, 0 to 150 degreeC is preferable, 10 to 120 degreeC is more preferable, 30 to 100 degreeC is further more preferable, and 40 to 80 degreeC is more preferable.

  A vinyl ester polymer obtained by radical polymerization of a vinyl ester monomer in the presence of a mercaptan having an ionic group in accordance with the above-described method is saponified in an alcohol or dimethyl sulfoxide solution, and has a terminal sulfide. PVA containing ionic groups is obtained through the bond.

In saponifying the vinyl ester polymer, an alkaline substance such as potassium hydroxide or sodium hydroxide is used as a catalyst. The alkaline substance is preferably used in a molar ratio to the vinyl ester unit of 0.004 to 0.5, particularly preferably 0.005 to 0.05. The alkaline substance may be added all at once in the initial stage of the saponification reaction, or may be added in the middle of the saponification reaction.
Examples of the solvent used for the saponification reaction include methanol, methyl acetate, diethyl sulfoxide, dimethylformamide and the like. Among these solvents, methanol is preferable, and when using methanol, the water content is preferably adjusted to 0.001 to 1% by weight, more preferably 0.003 to 0.9% by weight, and 0.005 to 0.8%. Weight percent is particularly preferred.

  When saponifying the vinyl ester polymer, the concentration of the vinyl ester polymer is preferably 10 to 70% by weight, more preferably 20 to 65% by weight. The temperature of the saponification reaction is preferably 5 to 80 ° C, more preferably 20 to 70 ° C. The saponification reaction time is preferably 5 minutes to 10 hours, more preferably 10 minutes to 5 hours. As a method for saponifying a vinyl ester polymer, a known method such as a batch method or a continuous method can be applied.

The PVA containing an ionic group via a sulfide bond at the terminal obtained by saponifying the vinyl ester polymer is then subjected to washing.
Usable cleaning liquids include methanol, acetone, methyl acetate, hexane, water and the like. Among these, methanol, methyl acetate and water are preferably used alone or as a mixed liquid.
The washing liquid is preferably used in an amount of usually 2 to 10000 parts by weight, more preferably 3 to 3000 parts by weight with respect to 100 parts by weight of PVA. 5-80 degreeC is preferable and the temperature at the time of washing | cleaning has more preferable 20-70 degreeC. The washing time is preferably 20 minutes to 10 hours, and more preferably 1 hour to 6 hours. As a method for cleaning PVA, a known method such as a batch method or a countercurrent cleaning method can be applied.

  PVA containing an ionic group via a sulfide bond at the terminal produced by the above method is acetalized in a hydrous solvent under acidic conditions according to a known method to obtain a vinyl acetal polymer. The vinyl acetal polymer used in the present invention has an acetalization degree of 45 to 80 mol%, preferably 50 to 80 mol%, particularly preferably 60 to 80 mol%. When the degree of acetalization of the vinyl acetal polymer is less than 45 mol%, it is difficult to recover the powdered reaction product obtained by the acetalization reaction, or the homogeneity of the ceramic green sheet deteriorates There is. If the degree of acetalization of the vinyl acetal polymer exceeds 80 mol%, it may be difficult to produce the vinyl acetal polymer.

As a method for acetalizing PVA containing an ionic group via a sulfide bond at the terminal, for example, a) The PVA is heated and dissolved in water to prepare an aqueous solution having a concentration of 5 to 30%. A method of starting the acetalization reaction by adding a predetermined amount of aldehyde and cooling to -10 to 30 ° C. and then adding an acid to make the pH of the aqueous solution 1 or less, and b) 5-30% strength aqueous solution is prepared by heating and dissolving, and this is cooled to 5-50 ° C., the pH of the aqueous solution is reduced to 1 or less by adding acid, and then cooled to −10-30 ° C., Examples thereof include a method of starting acetalization reaction by adding a predetermined amount of aldehyde.
The time required for the acetalization reaction is usually about 1 to 10 hours, and the reaction is preferably carried out with stirring. Further, when the acetal reaction is performed by the above-described method, the reaction may be continued at a high temperature of about 50 to 80 ° C. when the degree of acetalization of the vinyl acetal polymer does not increase.
The powdery reaction product obtained after the acetalization reaction is filtered, neutralized with an aqueous alkali solution, washed with water and dried to obtain the intended vinyl acetal polymer.

  Examples of the aldehyde compound used in the acetalization reaction include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, hexylaldehyde, benzaldehyde, and the like, and these can be used alone or in admixture of two or more. Examples of preferred aldehyde compounds are alkyl aldehydes having 4 or less carbon atoms, and benzaldehyde, with butyraldehyde being particularly preferred.

  Examples of acids used in the acetalization reaction include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as p-toluenesulfonic acid. These may be used alone or in combination of two or more. Can be used. Alkali compounds used to neutralize the powdered reaction product obtained after the acetalization reaction include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, as well as ammonia, triethylamine, and pyridine. And amine compounds such as

The vinyl acetal polymer composition of the present invention has a polymerization degree of 50 to 1000, a saponification degree of 80.0 to 99.99 mol%, and an ionic group bonded to the terminal via a sulfide bond is represented by the above formula 1. A vinyl acetal polymer (A) having a degree of acetalization of 45 to 80 mol%, obtained by acetalizing a vinyl alcohol polymer contained under satisfactory conditions, a degree of polymerization of 100 to 4000, and a degree of saponification of 80.000. A vinyl acetal polymer (B) having an acetalization degree of 45 to 80 mol% obtained by acetalizing 0 to 99.99 mol% of a vinyl alcohol polymer is 5/95 ≦ ( A) / (B) ≦ 100/0.

  When the degree of polymerization of the vinyl acetal polymer (B) used in combination with the vinyl acetal polymer (A) is less than 100, it is difficult to industrially produce PVA, and the degree of polymerization is 4000. If it exceeds 1, the homogeneity of the green sheet may deteriorate when used as a ceramic molding binder. Moreover, when the degree of saponification of the vinyl acetal polymer (B) is less than 80 mol%, the homogeneity of the green sheet may be deteriorated when used as a ceramic binder. Moreover, when the degree of saponification exceeds 99.99 mol%, it becomes difficult to produce PVA.

As a method for producing the vinyl acetal polymer composition of the present invention, (A) and (B) may be separately produced, and both may be mixed, or (A) and A method may be used in which an aqueous solution in which (B) is mixed is prepared and subjected to the acetalization reaction described above to obtain a vinyl acetal polymer in which (A) and (B) are mixed. .

  Average of ionic groups bonded via sulfide bonds contained in PVA used as a raw material for vinyl acetal polymer (A) when two types of vinyl acetal polymers (A) and (B) are used in combination Content is 0.15 mol% or more with respect to the total monomer units of the total of PVA used for the raw material of the vinyl acetal polymer (A) and PVA used for the raw material of the vinyl acetal polymer (B). It is preferable that The average content of ionic groups bonded via sulfide bonds contained in the PVA used for the raw material of the vinyl acetal polymer (A) is PVA used for the raw material of the vinyl acetal polymer (A) and the vinyl acetal type. Two types of vinyl acetal polymers (A) and (B) are used so that the total monomer unit of PVA used as a raw material for the polymer (B) is 0.15 mol% or more. When used in combination as a binder for ceramic molding, as shown in Examples 18, 19, 23 and 24, which will be described later, a ceramic green sheet that is remarkably superior in terms of surface condition and sheet strength. Can be manufactured.

  Using the vinyl acetal polymer or vinyl acetal polymer composition of the present invention as a binder for ceramic powder, the method for molding ceramic powder includes sheet molding, press molding, extrusion molding, injection molding, etc. Is mentioned.

  The vinyl acetal polymer or vinyl acetal polymer composition of the present invention is used as a binder for a ceramic powder, and an organic solvent is usually used when the ceramic powder is molded, and a plasticizer is also used at that time. May be. Examples of organic solvents include alcohols such as methanol, ethanol, isopropanol, n-propanol and butanol; cellsolves such as methyl cellsolve and butylcellsolve; ketones such as acetone and methylethylketone; aromatics such as toluene and xylene Hydrocarbons: Halogen-based hydrocarbons such as dichloromethane and chloroform can be used, and these can be used alone or in combination of two or more.

  Examples of plasticizers include triethylene glycol-di-2-ethylhexanoate, tetraethylene glycol-di-2-ethylhexanoate, triethylene glycol-di-n-heptanoate, tetraethylene glycol-di- -Dicarboxylic acid diesters of tri- or tetraethylene glycol such as n-heptanoate; diesters of dicarboxylic acids such as dioctyl adipate, dibutyl adipate, dioctyl phthalate, dibutyl phthalate, etc., which are used alone or in combination of two or more Can be used.

Applicable ceramic powders include metal or non-metal oxide or non-oxide powders used in the manufacture of ceramics. Specifically, Li, K, Mg, B, Al, Si, Cu, Ca, Sr, Ba, Zn, Cd, Ga, In, Y, lanthanoid, actinoid, Ti, Zr, Hf, Bi, V, Nb , Ta, W, Mn, Fe, Co, Ni, and other oxides, carbides, nitrides, borides, sulfides, and the like. Moreover, usually when classified concrete things a crystal structure of an oxide powder containing a plurality of metal elements referred to as double _{oxides, NaNbO 3, SrZrO 3, PbZrO} 3, SrTiO 3 as taking a perovskite structure, BaZrO ₃ , PbTiO ₃ , BaTiO _3, etc. take a spinel structure, and MgAl ₂ O ₄ , ZnAl ₂ O ₄ , CoAl ₂ O ₄ , NiAl ₂ O ₄ , MgFe ₂ O _4, etc. take an ilmenite type structure. Examples thereof include MgTiO ₃ , MnTiO ₃ , FeTiO _{3 and the} like, and examples of those having a garnet type structure include GdGa ₅ O ₁₂ and Y ₆ Fe ₅ O ₁₂ . These ceramic powders may be used alone or as a mixture of two or more.

  The vinyl acetal polymer or vinyl acetal polymer composition of the present invention is used as a binder for ceramic powder, and a method suitable for molding the ceramic powder includes an organic solvent, a ceramic powder, and a vinyl acetal heavy polymer. A so-called sheet molding is obtained by applying a slurry containing a coalescence or vinyl acetal polymer composition as a main component onto a carrier film using a blade coater and the like, drying, and then releasing from the carrier film to obtain a ceramic green sheet. Is the law. In this sheet molding method, the slurry applied on the carrier film is added with a peptizer, plasticizer, lubricant, etc., if necessary, in addition to the organic solvent, ceramic powder, and vinyl acetal polymer. May be.

  In adopting the above-mentioned sheet forming method, the amount of vinyl acetal polymer used varies depending on the purpose of use of the obtained ceramic green sheet, and thus cannot be uniformly defined. The amount is 3 to 20 parts by weight, preferably 5 to 15 parts by weight per part.

  In adopting the above-described sheet forming method, there is no particular limitation on the method of dispersing the ceramic powder in the slurry, a method using a medium type dispersing machine such as a bead mill, a ball mill, an attritor, a paint shaker, a sand mill, a kneading method, Various dispersion methods such as a method using three rolls can be used. In this case, as the dispersant, an anionic dispersant having a carboxylic acid group, a maleic acid group, a sulfonic acid group, a phosphoric acid group or the like in the molecule may be used in combination. The use of agents is preferred.

  The thickness of the ceramic green sheet varies depending on the purpose of use, and thus cannot be defined unconditionally. Moreover, since the drying temperature at the time of drying the coating film formed on the carrier film changes with thickness of a ceramic green sheet etc., it cannot unconditionally define, but it is the range of 60-200 degreeC in general.

  A ceramic green sheet obtained by molding a ceramic powder using the vinyl acetal polymer or vinyl acetal polymer composition of the present invention as a ceramic molding binder is used as an electrode on various electronic components, particularly ceramic green sheets. Can be suitably used for a chip-type multilayer capacitor, an IC chip circuit board, and the like produced by a process in which the electrodes and the ceramic are fired at the same time.

  The vinyl acetal polymer of the present invention can be used as a component for an interlayer film for laminated glass, a primer for metal, a lacquer, etc. in addition to a binder for ceramic molding and a binder for ink or paint, or a urea resin It can be suitably used for a crosslinking reaction with melamine resin, epoxy resin and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this. In the following Examples and Comparative Examples, “parts” and “%” mean weight basis unless otherwise specified.

[Analysis method of PVA]
Analysis of PVA was performed according to the method described in JIS-K6726 unless otherwise specified. The amount of ionic groups bonded to the end of PVA via a sulfide bond and the content of 1,2-glycol bond were determined using a 500 MHz proton NMR measurement apparatus (JEOL GX-500) according to the method described above. .

[Analytical method of vinyl acetal polymer]
The degree of acetalization of the vinyl acetal polymer was determined by dissolving the vinyl acetal polymer in DMSO-d6 and using a 500 MHz proton NMR measurement apparatus (JEOL GX-500).

Synthesis example (synthesis of PVA)
A 6 L separable flask equipped with a stirrer, a reflux tube, and an addition port for a delay solution was charged with 2800 g of vinyl acetate and 680 g of methanol, heated to 60 ° C., and then bubbled with nitrogen gas for 30 minutes to nitrogen the system. Replaced. A 5 wt% methanol solution of 3-mercaptopropionic acid was prepared as a chain transfer agent, and this was bubbled with nitrogen gas to substitute with nitrogen. 5.4 g of this solution was added into the flask. After adjusting the internal temperature of the flask to 60 ° C., 2.2 g of 2,2′-azobisisobutyronitrile as an initiator was dissolved in 20 g of methanol and added to the flask to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 60 ° C., and a 5 wt% methanol solution of 3-mercaptopropionic acid was continuously added to carry out the polymerization. After 5 hours, when the polymerization rate reached 70%, the flask was cooled to stop the polymerization. The amount of 5-mercaptopropionic acid in a 5% by weight methanol solution added continuously during the polymerization was 129.3 g. Next, methanol vapor was introduced into the reaction solution obtained by polymerization to drive off unreacted vinyl acetate monomer, and a methanol solution containing 50% of a vinyl ester polymer was obtained.
A methanol solution containing 50% of a vinyl ester polymer was used, and an appropriate amount of methanol and a methanol solution containing 10% by weight of sodium hydroxide were added in this order, and a saponification reaction was started at 40 ° C. The solid content concentration of the vinyl ester polymer at the start of saponification was 35% by weight. The methanol solution containing sodium hydroxide was added with stirring, and the amount of sodium hydroxide added was 0.015 in terms of a molar ratio of the vinyl ester polymer to the vinyl acetate unit. After about 2 minutes from the start of the addition of the methanol solution containing sodium hydroxide, the gelled product obtained was pulverized with a pulverizer and allowed to stand at 40 ° C. for 1 hour to proceed saponification, and then methyl acetate was added. The remaining alkali was neutralized. After confirming the completion of neutralization using a phenolphthalein indicator, a white PVA solid was filtered off. The PVA solid was washed by an operation of adding 5 times the amount of methanol to the obtained PVA solid and allowing it to stand at room temperature for 3 hours. After the above washing operation was repeated three times, the PVA that had been drained by centrifugation was placed in a dryer and allowed to stand at 70 ° C. for 2 days for drying. Table 2 shows analytical values of the PVA (PVA-1a) thus obtained.
Separately, the above vinyl ester polymer was saponified to a saponification degree of 99.95 mol% or more, extracted with methanol Soxhlet for 3 days, thoroughly washed, and then dried at 90 ° C. under reduced pressure for 2 days. To prepare a PVA for analysis. Proton NMR measurement was performed using DMSO-d6 as a solvent, and the content of ionic groups was calculated from a peak derived from methylene bonded to a sulfur atom (2.6 ppm). As a result, it was 0.28 mol%. Similarly, as a result of calculating the 1,2-glycol bond content, it was 1.52 mol%.
Various PVA (PVA-2a to PVA-17a and PVA-1b to PVA-10b) was synthesized in the same manner as PVA-1a except that the reaction conditions were changed to those shown in Tables 1 and 3. The analysis values for each PVA are shown in Tables 2 and 4. In addition, when superposition | polymerization temperature exceeded 60 degreeC, superposition | polymerization reaction was performed using the autoclave which has the same incidental equipment.

Example 1
(Synthesis of vinyl acetal polymer)
540 g of PVA (PVA-1a) was put into 6600 ml of water, heated to 90 ° C. with stirring and dissolved, then cooled to 30 ° C., 290 g of butyraldehyde was added and dispersed, and then 0 ° C. The reaction was started by adding 1090 ml of 20% strength hydrochloric acid solution. After the addition of the hydrochloric acid solution was complete, the reaction solution was warmed to 30 ° C. over 3 hours and maintained at this temperature for an additional 2 hours. In order to filter off the precipitated particulates, wash them thoroughly with water and neutralize them, 350 ml of 10% sodium hydroxide solution is added to the suspension of the particulates, which is gently warmed again. did. Furthermore, after removing excess alkali by washing with water, the granular material was dried. The results of analyzing the vinyl acetal polymer (VAP-1a) thus obtained are shown in Table 9. After the vinyl acetal polymer was dried at 90 ° C. under reduced pressure for 2 days, proton NMR was measured using DMSO-d6 as a solvent, and a peak derived from methylene bonded to a sulfur atom (2.6 ppm) As a result of calculating the content of ionic groups from the results, it was the same as that of PVA-1a used as a raw material.
(Creation of ceramic green sheets)
100 parts of barium titanate powder with an average particle size of 0.2 μm as ceramic powder, 10 parts of vinyl acetal polymer (VAP-1a), 3 parts of dioctyl phthalate as plasticizer, 60 parts of toluene, 60 parts of isopropanol Was mixed and pulverized with 500 parts of zirconia balls (diameter 2 mm) for 16 hours by a ball mill, and then defoamed under reduced pressure to prepare a ceramic slurry. The ceramic slurry was applied on a polyethylene terephthalate film (PET film) for release by a doctor blade method, dried at 105 ° C. for 5 minutes, and then released from the PET film to obtain a ceramic green sheet having a thickness of 5 μm. .
(Observation of ceramic green sheet surface)
The surface of the ceramic green sheet was observed using an optical microscope and evaluated according to the following criteria. The evaluation results are shown in Table 2.
A: There is no unevenness due to voids or aggregated particles, and it is homogeneous.
B: Although there are no voids, irregularities due to aggregated particles are observed.
C: Both voids and irregularities due to aggregated particles are observed.
(Strength of ceramic green sheet)
A ceramic green sheet was punched into 40 mm × 100 mm, and the toughness of the green sheet was measured with an autograph DCS-100 manufactured by Shimadzu (chuck interval: 30 mm, tensile speed: 10 mm / min., Measurement temperature 20 ° C.). In addition, the ratio (times) when the average value which measured 5 times about one sample was made into the toughness value, and the toughness value obtained in the comparative example 1 was set to 1.0 was calculated | required. Table 5 shows the measurement results.

Examples 2-15
A vinyl acetal polymer was synthesized in the same manner as in Example 1 using PVA (PVA-1a and PVA-5a to PVA-16a) having a polymerization degree of 500 shown in Table 2. Next, a ceramic green sheet was prepared in the same manner as in Example 1, the surface of the ceramic green sheet was observed, and the strength of the sheet was further determined. The evaluation results and measurement results are shown in Table 5.

Comparative Examples 1-7
A vinyl acetal polymer was synthesized in the same manner as in Example 1 using PVA (PVA-1a, PVA-1b and PVA-7b to PVA-9b) having a polymerization degree of 500 shown in Tables 2 and 4. Next, a ceramic green sheet was prepared in the same manner as in Example 1, the surface of the ceramic green sheet was observed, and the strength of the sheet was further determined. The evaluation results and measurement results are shown in Table 5.

Example 16 and Comparative Examples 8 and 9
A vinyl acetal polymer was synthesized in the same manner as in Example 1 using PVA (PVA-2a, PVA-2b and PVA-10b) having a polymerization degree of 850 shown in Tables 2 and 4. Next, a ceramic green sheet was prepared in the same manner as in Example 1, the surface of the ceramic green sheet was observed, and the strength of the sheet was further determined. Table 6 shows the evaluation results and the measurement results.

Example 17 and Comparative Example 10
A vinyl acetal polymer was synthesized in the same manner as in Example 1 using PVA (PVA-3a and PVA-3b) having a polymerization degree of 200 shown in Tables 2 and 4. Next, a ceramic green sheet was prepared in the same manner as in Example 1, the surface of the ceramic green sheet was observed, and the strength of the sheet was further determined. Table 7 shows the evaluation results and the measurement results.

Comparative Examples 11 and 12
A vinyl acetal polymer was synthesized in the same manner as in Example 1 using PVA (PVA-5b and PVA-6b) having a polymerization degree of 1200 shown in Table 4. Next, a ceramic green sheet was prepared in the same manner as in Example 1, the surface of the ceramic green sheet was observed, and the strength of the sheet was further determined. Table 8 shows the evaluation results and the measurement results.

Examples 18-22 and Comparative Example 13
Two kinds of PVA (PVA-2a, PVA-4a, PVA-17a, PVA-2b and PVA-4b) having a degree of polymerization of 80 and 850 shown in Table 2 and Table 4 are selected, and this has an average degree of polymerization of 500. A vinyl acetal polymer was synthesized in the same manner as in Example 1 except that the acetalization was performed by mixing at a ratio of Next, a ceramic green sheet was prepared in the same manner as in Example 1, the surface of the ceramic green sheet was observed, and the strength of the sheet was further determined. Table 9 shows the evaluation results and the measurement results.

Examples 23 to 25 and Comparative Example 14
Two types are selected from PVA (PVA-2a, PVA-3a, PVA-2b, and PVA-3b) having a polymerization degree of 200 and 850 shown in Table 2 and Table 4, and the average degree of polymerization is 500. A vinyl acetal polymer was synthesized in the same manner as in Example 1 except that the mixture was used. Next, a ceramic green sheet was prepared in the same manner as in Example 1, the surface of the sheet was observed, and the strength of the sheet was further determined. Table 14 shows the evaluation results and the measurement results.

From the results shown in Tables 5 to 10, the ceramic green sheets (Examples 1 to 25) obtained when the vinyl acetal polymer of the present invention is used as a ceramic molding binder are vinyls that are outside the scope of the present invention. Compared to the ceramic green sheets (Comparative Examples 1 to 14) obtained when the acetal polymer is used as a ceramic molding binder, the surface state of the ceramic green sheets is homogeneous and the strength (toughness) of the ceramic green sheets Can be seen to be large.
In particular, as a vinyl acetal polymer, the 1,2-glycol content is 1 to 2 mol%, the ionic group is a carboxyl group or a sulfonic acid group, and the content of these ionic groups is the above formula (2). When a vinyl butyral polymer having a butyralization degree of 60 to 80 mol% is used (Examples 1, 2, 5, 6, 7, 10, 11, 14, 16, 17), the surface state of the ceramic green sheet, and the strength of the ceramic green sheet are remarkably excellent.

Claims (7)

A vinyl alcohol-based polymer having a polymerization degree of 50 to 1000, a saponification degree of 80.0 to 99.99 mol%, and containing an ionic group bonded to the terminal via a sulfide bond under the condition satisfying the following formula (1) A vinyl acetal polymer having a degree of acetalization of 45 to 80 mol% obtained by acetalizing a polymer , wherein the ionic group is at least one group selected from carboxylic acid and sulfonic acid or salts thereof Vinyl acetal polymer .
0.15 ≦ Content ≦ 218.3 × P ^−1.046 (1)
(In the formula, the content represents the content (mol%) of an ionic group bonded through a sulfide bond, and P represents the degree of polymerization of the vinyl alcohol polymer.) The vinyl acetal polymer according to claim 1, wherein the degree of polymerization of the vinyl alcohol polymer is 100 to 1000. The vinyl acetal polymer according to claim 1 or 2, wherein the ionic group is a sulfonic acid group or a salt thereof. The vinyl acetal polymer according to any one of claims 1 to 3, wherein the vinyl acetal polymer is obtained by butyralizing a vinyl alcohol polymer, and the degree of butyralization is 60 to 80 mol%. Acetal polymer. A ceramic molding binder comprising the vinyl acetal polymer according to any one of claims 1 to 4 . A vinyl alcohol-based polymer having a polymerization degree of 50 to 1000, a saponification degree of 80.0 to 99.99 mol%, and containing an ionic group bonded to the terminal via a sulfide bond under the condition satisfying the following formula (1) A vinyl acetal polymer (A) having a degree of acetalization of 45 to 80 mol% obtained by acetalizing the polymer, and vinyl alcohol having a degree of polymerization of 100 to 4000 and a saponification degree of 80.0 to 99.99 mol% A vinyl acetal polymer (B) having an acetalization degree of 45 to 80 mol% obtained by acetalization of a polymer is obtained from 5/95 ≦ (A) / (B) ≦ 100/0. And a vinyl acetal polymer composition containing at least one group selected from a carboxylic acid and a sulfonic acid or a salt thereof. Nil acetal polymer .
0.15 ≦ Content ≦ 218.3 × P ^−1.046 (1)
(In the formula, the content represents the content (mol%) of an ionic group bonded through a sulfide bond, and P represents the degree of polymerization of the vinyl alcohol polymer.)   A ceramic molding binder comprising the vinyl acetal polymer composition according to claim 6.