Ｘ線回折による塗工紙の分析（第１報） 顔料配合比率定量法の試み

Abstract

X-ray diffraction method was applied to quantifying pigments weight or composition of coatings. This method has some advantages over the method by electron probe microanalyzer (EPMA) which is conventionally used at present. One is that it is capable of distinguishing the different crystal forms of certain materials. It also permits analysis of samples deeply.The quantification principle follows Alexander's theory which states that the X-ray diffraction intensity ratio is proportional to the components weight ratio.Measurements were made for coated paper samples containing solely clay and calcium carbonate, which were prepared using a laboratory blade coater or by manual bar coating.First, the X-ray diffraction intensity ratio is approximately linear to coating weight under a limited range. But, the diffraction intensity ratio of clay peak to calcium carbonate peak for the samples with coatings of constant composition. This finding proved to derive from diffraction of calcium carbonate contained in base papers as fillers. To separate calcium carbonate diffraction stemmed from only coatings, the diffraction of internally loaded filler was calculated in the following ways. That is, the diffraction intensity of filler was calculated compared to cellulose (101), (101) peak after diffraction measurement of only base paper. Then its amount was subtracted from the total diffraction intensity of calcium carbonate contained in coated papers. The diffraction intensity ratio thus corrected resulted in almost constant value independent of coating weight. Besides, the diffraction intensity ratio of a series of coated paper samples proved to be proportional to coatings' formulation of coated paper samples.In conclusion, quantification of pigments contained in coatings by X-ray diffraction method was established. But some problems still remains to be solved. Firstly, the measurement of only base paper must be made to apply this method to commercial coated papers. Secondly, calendering or double coating process probably affect diffraction patterns.