The present invention provides polyvinyl acetal fine particles for an aqueous dispersion which exhibit excellent dispersion stability in a water-containing dispersion medium, and allow for formation of a film having sufficient mechanical strength and flexibility without voids and non-uniform structures such as irregularities, and an aqueous dispersion of the polyvinyl acetal fine particles for an aqueous dispersion.

The polyvinyl acetal fine particles for an aqueous dispersion, adapted for use as dispersoids in an aqueous dispersion, the polyvinyl acetal fine particles including a polyvinyl acetal resin with an ionic functional group, and having a volume average particle size of 10 nm to 100 m, and a CV value of a volume-based particle size distribution of at most 40%.

The present invention provides a vinyl alcohol-amino acid ester copolymer that is excellent in properties such as cell culture properties, biocompatibility, antibacterial properties, and solubility in organic solvents, and is applicable to the medical field, the biomaterial field, and the agricultural field (medical and life science fields). Provided is a vinyl alcohol-amino acid ester copolymer including a unit represented by the following formula (1) and a unit represented by the following formula (2): ##STR00001## where, in the formula (2), R.sup.1 represents a hydrocarbon group that may optionally have a substituent, R.sup.2 and R.sup.3 each independently represent a hydrogen atom or a hydrocarbon group, and R.sup.1 and R.sup.2, or R.sup.2 and R.sup.3, may optionally be bonded together to form a cyclic structure.

The present invention provides a vinyl alcohol-amino acid ester copolymer that is excellent in properties such as cell culture properties, biocompatibility, antibacterial properties, and solubility in organic solvents, and is applicable to the medical field, the biomaterial field, and the agricultural field (medical and life science fields). Provided is a vinyl alcohol-amino acid ester copolymer including a unit represented by the following formula (1) and a unit represented by the following formula (2): ##STR00001## where, in the formula (2), R.sup.1 represents a hydrocarbon group that may optionally have a substituent, R.sup.2 and R.sup.3 each independently represent a hydrogen atom or a hydrocarbon group, and R.sup.1 and R.sup.2, or R.sup.2 and R.sup.3, may optionally be bonded together to form a cyclic structure.

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):
[(3,470A)/Hydroxy group content]5.5(1)
(3,470A)185(2)
wherein A is a wavenumber which is lower than 3,470 cm.sup.1 and at which a transmittance a (%) satisfying [100(100X)/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):
[(3,470A)/Hydroxy group content]5.5(1)
(3,470A)185(2)
wherein A is a wavenumber which is lower than 3,470 cm.sup.1 and at which a transmittance a (%) satisfying [100(100X)/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 that has an excellent dispersing property and enables the production of a formed article having high mechanical strength. Provided is a polyvinyl acetal resin having a water absorption per unit area of 2 mg/cm.sup.2 or greater and 50 mg/cm.sup.2 or less when formed into a film having a thickness of 10 m.

The present invention provides a polyvinyl acetal resin that has an excellent dispersing property and enables the production of a formed article having high mechanical strength. Provided is a polyvinyl acetal resin having a water absorption per unit area of 2 mg/cm.sup.2 or greater and 50 mg/cm.sup.2 or less when formed into a film having a thickness of 10 m.