The present invention provides a polyvinyl acetal resin which leaves less fine undissolved matter when dissolved in an organic solvent and thus can improve productivity particularly when used as a binder for a ceramic green sheet, and which can also provide a ceramic green sheet having excellent toughness and enables production of a highly reliable multilayer ceramic capacitor. Provided is a polyvinyl acetal resin having: a wavenumber A (cm.sup.−1) of a peak within a range of 3,100 to 3,700 cm.sup.−1 in an IR absorption spectrum measured using an infrared spectrophotometer; and a hydroxy group content (mol %), the wavenumber A of the peak and the hydroxy group content satisfying relations of the following formulas (1) and (2):

[(3,470−A)/Hydroxy group content]≤5.5  (1)

(3,470−A)≤185  (2)

wherein A is a wavenumber which is lower than 3,470 cm.sup.−1 and at which a transmittance a (%) satisfying [100−(100−X)/2] is exhibited, where X (%) is a minimum transmittance of the peak within the wavenumber range of 3,100 to 3,700 cm.sup.−1.

The present invention provides a polyvinyl acetal resin which leaves less fine undissolved matter when dissolved in an organic solvent and thus can improve productivity particularly when used as a binder for a ceramic green sheet, and which can also provide a ceramic green sheet having excellent toughness and enables production of a highly reliable multilayer ceramic capacitor. Provided is a polyvinyl acetal resin having: a wavenumber A (cm.sup.−1) of a peak within a range of 3,100 to 3,700 cm.sup.−1 in an IR absorption spectrum measured using an infrared spectrophotometer; and a hydroxy group content (mol %), the wavenumber A of the peak and the hydroxy group content satisfying relations of the following formulas (1) and (2):

[(3,470−A)/Hydroxy group content]≤5.5  (1)

(3,470−A)≤185  (2)

wherein A is a wavenumber which is lower than 3,470 cm.sup.−1 and at which a transmittance a (%) satisfying [100−(100−X)/2] is exhibited, where X (%) is a minimum transmittance of the peak within the wavenumber range of 3,100 to 3,700 cm.sup.−1.

A resin composition for a solar cell encapsulant that is used for forming a solar cell encapsulant, the resin composition including at least one kind of ethylene-polar monomer copolymer (A1) selected from an ethylene-vinyl ester copolymer and an ethylene-unsaturated carboxylic acid ester copolymer, an epoxy group-containing ethylene-based copolymer (A2) (excluding the ethylene-polar monomer copolymer (A1)), an ethylene-α-olefin copolymer (B), and a metal inactivating agent (C).

A resin composition for a solar cell encapsulant that is used for forming a solar cell encapsulant, the resin composition including at least one kind of ethylene-polar monomer copolymer (A1) selected from an ethylene-vinyl ester copolymer and an ethylene-unsaturated carboxylic acid ester copolymer, an epoxy group-containing ethylene-based copolymer (A2) (excluding the ethylene-polar monomer copolymer (A1)), an ethylene-α-olefin copolymer (B), and a metal inactivating agent (C).

A method for producing a polyvinyl alcohol resin having an absorbance of not less than 0.2 at 280 nm, which includes: melt-kneading a polyvinyl alcohol resin material; extruding the resulting melt-kneaded polyvinyl alcohol resin into a sheet; cooling the resulting polyvinyl alcohol resin sheet; and pulverizing the cooled polyvinyl alcohol resin sheet. The method ensures a higher productivity and an excellent long-run property.

A method for producing a polyvinyl alcohol resin having an absorbance of not less than 0.2 at 280 nm, which includes: melt-kneading a polyvinyl alcohol resin material; extruding the resulting melt-kneaded polyvinyl alcohol resin into a sheet; cooling the resulting polyvinyl alcohol resin sheet; and pulverizing the cooled polyvinyl alcohol resin sheet. The method ensures a higher productivity and an excellent long-run property.

Disclosed is a support material for a fused deposition modeling. The support material has excellent adhesion to a variety of model materials and is easily dissolved and removed by washing with water. Also, the waste liquid (PVA-based aqueous solution) generated after the washing operation may be allowed to be drained as it is, in compliance with environmental regulations. The support material comprises (A) PVA-based resin having a group containing sulfonic acid or a salt thereof and (B) biodegradable polyester. The (A) PVA-based resin having a group containing sulfonic acid or a salt thereof and (B) biodegradable polyester have a sea-island structure in which one is dispersed in the other as a matrix.

Disclosed is a support material for a fused deposition modeling. The support material has excellent adhesion to a variety of model materials and is easily dissolved and removed by washing with water. Also, the waste liquid (PVA-based aqueous solution) generated after the washing operation may be allowed to be drained as it is, in compliance with environmental regulations. The support material comprises (A) PVA-based resin having a group containing sulfonic acid or a salt thereof and (B) biodegradable polyester. The (A) PVA-based resin having a group containing sulfonic acid or a salt thereof and (B) biodegradable polyester have a sea-island structure in which one is dispersed in the other as a matrix.

Regarding the oxyalkylene group-containing PVA-based resin, a package which is almost free from a problem associated with viscosity increase during melt-kneading even if the package is stored for a long time period, and a method for manufacturing the package are disclosed. The package comprises a bag having an oxygen permeability of 1000 cc/m.sup.2.Math.day.Math.atm or less as an amount of oxygen permeated in 24 hours per 1 m.sup.2 of its constituent film under an condition of 25° C. and 65% RH, and an oxyalkylene group-containing PVA-based resin in the bag. The package can suppress the oxidation of the oxyalkylene group-containing PVA and the generation of the carboxyl group-containing compound which may cause to increase viscosity during melt kneading.

Regarding the oxyalkylene group-containing PVA-based resin, a package which is almost free from a problem associated with viscosity increase during melt-kneading even if the package is stored for a long time period, and a method for manufacturing the package are disclosed. The package comprises a bag having an oxygen permeability of 1000 cc/m.sup.2.Math.day.Math.atm or less as an amount of oxygen permeated in 24 hours per 1 m.sup.2 of its constituent film under an condition of 25° C. and 65% RH, and an oxyalkylene group-containing PVA-based resin in the bag. The package can suppress the oxidation of the oxyalkylene group-containing PVA and the generation of the carboxyl group-containing compound which may cause to increase viscosity during melt kneading.