Drawing for Package Material Elongation

Manufacturing method for heat shrinkable films that ensures uniform shrinkage in one direction. The method involves a specific stretching sequence. First, stretch the film 1.1-4x in the longitudinal direction. Then stretch crosswise 6x or more. Finally, stretch again longitudinally 3x or less. The ratios of the longitudinal and crosswise stretches should fill certain types of equations. This sequence ensures uniform shrinkage in the longitudinal direction when heated. The film can be made from any thermoplastic like polyester, polyethylene, polypropylene, etc.

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A method to manufacture synthetic paper with a texture similar to natural paper by laminating paper onto a stretched polymer film and then melt-extruding the composite. The steps involve: stretching the polymer film, cooling it below the glass transition temperature, stretching again in the transverse direction, heat treating, laminating paper, and melt-extruding the composite. This process allows the paper texture to be expressed on the surface of the synthetic paper. The adhesion between the paper and polymer is enhanced during the lamination and melt-extrusion steps.

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Stretching a film of a thermoplastic resin like polypropylene to obtain a stretched film with high thickness and thinness accuracy. The technique involves controlling the starting point of stretching during biaxial stretching to improve thickness uniformity. The key is to create localized high temperature spots on the film before stretching. This can be done by sequentially heating specific areas, using infrared lasers, or pulsed heating. By heating these spots before stretching, it forces the stretching to start from those areas instead of random spots. This allows more controlled and uniform stretching.

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A method to manufacture and store stretched plastic sheets that allows for improved packaging and dispensing of the sheets. The method involves stretching the plastic sheet beyond its elastic limit, then trimming the thickened edge areas to create a sheet with uniform thickness. This prevents issues like soft center, clogging, and tearing when winding and unrolling the stretched sheet. The stretched sheet is stored with some elasticity retained, allowing it to better conform to loads and avoid tearing when packaged or dispensed.

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A method to manufacture stretched plastic film with improved stretch ratio and reduced breakage compared to existing techniques. The method involves a two-step stretching process with higher stretch in the first step followed by relaxation. The first stretch ratio is higher than the second stretch ratio. This allows the film to be stretched more without breaking during the first step, followed by relaxation to release elastic deformation. The total stretch ratio can be adjusted by the two-step stretches.

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Stretching films like polypropylene to improve properties like thickness uniformity and strength by using specific stretching profiles. The profiles involve stretching simultaneously in both directions, but with lower ratios in one direction compared to natural stretch ratios. This prevents necking and maintains uniformity. The method involves first stretching at high ratios in both directions, then reducing only the first direction ratio. This allows uniform stretching even at lower ratios. The films have improved properties like thickness uniformity, tensile strength, and elongation at break compared to conventionally stretched films.

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Automated process and apparatus for producing biaxially stretched plastic wrap with improved compression properties. The process involves angling the plastic material across and partially around two stretching devices oriented at opposite angles. This biaxially stretches the material in both length and width directions. The resulting wrapped object has a pattern of periodic regions with impeded neck-down from the angle intersections. This prevents rupturing while maintaining compression in both directions.

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