| 摘要 |
PURPOSE:To obtain high density polyethylene film whose haze value is 10% or less and being high density and highly transparent by passing a raw film having been prepared by inflation molding of high density polyethylene between three heating rolls under a specified temp. condition to heat-treat it at the condition where the draw ratio is below five and by cooling the film thereafter. CONSTITUTION:A raw film having been prepared by inflation molding of high density polyethylene whose density is 0.935g/cm<3> or higher under the condition where the blow ratio is 3 or less is passed through between three heating rolls under the following temp. conditions, thereby heat-treated at the condition where the draw ratio is five or less thereafter cooled. The temp. conditions of three rolls are in such conditions that the temp. of R2 is higher than those of R1 and R3 and below the m.p. of the film and above 105 deg.C. The temp. of R1 should be below 90 deg.C as neck-in of the film becomes larger when the temp. exceeds 90 deg.C. The temp. of R3 should be below 120 deg.C and above 80 deg.C and good transparency can not be obtained when the temp. exceeds 120 deg.C. When the temp. is below 80 deg.C, the film tightly adheres to R3 and sufficient transparency can not be obtained, too. |
