| 摘要 |
<p>The reflective, transparent grains, are made by preforming and rolling a sheet of uniformly thick, transparent thermoplastic material to give a flat semi-finished product, comprising a large number of grains all interconnected by a thin film. This interconnecting film is then broken away to give the separate particles. Pref. the semi-finished prod. is formed by passing the sheet between opposed rolls having hemispherical depression in their surfaces. The starting material is pref. preheated, whereas the rolls are cooled. Subsequently the separated grains are mechanically treated to remove any projecting rough edges resulting from the interconnecting film. One face of the semi-finished sheet may be coated with transparent microspheres attached by a polymer adhesive. Rapid, economic mass production of particles of various shapes is possible. In particular, shapes other than spherical can be produced.</p> |
