| 摘要 |
PURPOSE:To obtain a linear low density polyethylene packaging bag having excellent heat sealing strength by blowing specified linear low density polyethylene film under a specified condition. CONSTITUTION:Polyethylene composed mainly of linear low density polyethylene has a melt index 1.5g/10min or less and if the melt index is larger than this, no shrinkage occurs by thermal relaxation in case of heat seal and a good heat seal part can not be obtained. Film blowing is conducted at blowup ratios 0.9-2, draft ratios 10-40, a cooling speed index 30sec max. If the blowup ratio exceeds 2.0 shrinkage occurs in the lengthwise direction of heat seal in case of heat seal and the strength of the heat seal edge of the package is reduced. If the draft ratio does not reach 10, good shrinkage does not occur in case of heat seal and if it exceeds 40 the molecular orientation of the package barrel itself becomes excessively large in one direction. If the cooling speed index exceeds 30sec, the molecular orientation that occurred in the film is slackened by thermal relaxation and no sufficient strength is obtained. |
