Patent DE-10128711-A1 (DE)
Title: Label film useful as a top layer for PS, PP, PE, PVC, metal, and tin plate containers, has improved adhesion and subsequent application
Inventor: HOLZER SUSANNE
IPC: B32B27/32
Filed: 2001-06-13
Abstract: The biaxially oriented multi-layer coextruded polyolefin film comprising a base layer and at least one inner layer, which are simultaneously extruded through a multilayer nozzle and biaxially stretched together. The inner top layer comprises at least 70 wt.% of co- or terpolymer, which is obtained from an olefin and an unsaturated carboxylic acid or their esters or anhydrides, and contains at most 30 wt.% of additive.  Independent claims are included for: (1) a label film applied to a container in an in-mold or thermo labeling process, and the inner top layer is moved towards the container and forms the adjacent surface of the visible side; (2) a label container; (3) a multi-layer laminate in which the label film is laminated to a second film of thermoplastic polymer or a paper, wood, or metal substrate; (4) a biaxially oriented multi-layer polyolefin film as described above which can be applied by thermo labeling as a removeable protective film to tin plate, wood, glass, or metal, preferably aluminum; (5) preparation of a polyolefin film by coextrusion, in which the individual layers of the film are melted and coextruded through a flat nozzle, the film obtained is strengthened by drawing with one or more rollers, and the multi-layer film is stretched, and heat fixed. The top layer of the film comprises at least 70 wt.% of a co- or terpolymer etc. as described above. The film is stretched longitudinally on heated rollers at 10 deg C above or below the melting point of the Co-or terpolymer. The inner top layer contains 70-99.5 wt.% of co- or terpolymer. The copolymer contains more than 65 wt.% olefin units, preferably ethylene units and at most 35 wt.% unsaturated monocarboxylic acid units or their esters, preferably (meth)acrylic acid or their esters. The terpolymer comprises (wt.%): (a) olefin, preferably ethylene (65-96), (b) unsaturated carboxylic acids or their esters, preferably acrylic acid ester, preferably acrylic acid methyl-, ethyl-, n-propyl-, i-propyl-, n-butyl-, i-butyl-, sec-butyl-, or t-butyl ester (3-34), (c) various unsaturated mono- or dicarboxylic acid acids or their esters or anhydrides, preferably maleic acid anhydride or glycidyl methacrylate, in quantity 1-10 wt.% relative to (b). The inner top layer contains an antiblock agent (1-5), a lubricant, preferably erucic acid amide and/or a polydimethylsiloxane. The inner top layer contains a mixture of two or more additives, preferably wax (1-10) and HDPE (1-20), and is corona, plasma, or flame treated. The film on the side opposite the inner top layer of the base layer has an extra outer top layer which comprises a co- and/or terpolymer. The surface of the outer top layer is corona, plasma, or flame treated. The antiblock agent is silicon dioxide. The top layer film thickness is 15-150, preferably 25-90, and the base layer 40-60% of the total thickness of the label film. The base layer comprises propylene polymers, preferably propylene homopolymers, is opache, and contains vacuole initiated filler (-.5-30) and optionally pigment (1-10), contains lubricant and/or antistatic, preferably tertiary aliphatic amine.