| 摘要 |
<p>Unburnt coloured pencils and chalks consist of pigments kaolin or similar silicaceous materials, binders, opt. lubricants and/or other additives. The binders comprise salts of a lignin sulphonic acid contg. a dispersing acid. The coloured pencils and chalks have optimal writing props. with high resistance to breaking, and may be finished in automatically operating drying means without undergoing change in shape and distortion.</p> |
