| 摘要 |
PROBLEM TO BE SOLVED: To obtain a polyvinyl acetal resin having excellent adhesive strength, heat resistance, the dispersibility of an inorganic matter therein, or the like, and being satisfactory both in solution properties and in coating film properties, which resin has a specified number-average molecular weight and a weight- average molecular weight/number-average molecular weight ratio. SOLUTION: This resin has a number-average molecular weight (Mn) of 5,000-30,000 and an Mn/Mn ratio of above 4 to 50 (wherein Mw is the weight- average molecular weight). The resin contains vinyl alcohol units and may contain in addition to vinyl alcohol units, units derived from a monomer such as a vinyl ester or a vinyl ether. The resin is not limited on its production process, its production conditions, or the like. For example, the acetalization reaction can be performed in a medium being an organic solvent, water, or a mixture thereof and can be performed by a process such as a dissolution process, a precipitation process, a homogeneous process, or a combination thereof. The acetalization reaction is performed in the presence of an acid catalyst.
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