The invention is a polyoxymethylene film and a preparation method. The polyoxymethylene film comprises: 96 to 98 parts by weight of polyoxymethylene resin, 0.5 to 2 parts by weight of nucleating agent, 0.5 to 1 parts by weight of antioxidant, and 0.5 to 1 parts by weight of formaldehyde absorbent. In view of the high crystallinity and fast crystallization rate of polyoxymethylene, blown film process is used to directly blowing the molten mass extruded through a die of a screw extruder to form a blown film bubble. It is easy to form thin neck and easy to break when stretching, so the method is beneficial to form polyoxymethylene film, and has high processing efficiency, and is suitable for industrialization. Copolymerization unit CH.sub.2CH.sub.2O is introduced into the molecular chain of polyoxymethylene and its ratio is increased, thereby effectively reducing the crystallization rate of the materials and making it easier to form a film.

The invention is a polyoxymethylene film and a preparation method. The polyoxymethylene film comprises: 96 to 98 parts by weight of polyoxymethylene resin, 0.5 to 2 parts by weight of nucleating agent, 0.5 to 1 parts by weight of antioxidant, and 0.5 to 1 parts by weight of formaldehyde absorbent. In view of the high crystallinity and fast crystallization rate of polyoxymethylene, blown film process is used to directly blowing the molten mass extruded through a die of a screw extruder to form a blown film bubble. It is easy to form thin neck and easy to break when stretching, so the method is beneficial to form polyoxymethylene film, and has high processing efficiency, and is suitable for industrialization. Copolymerization unit CH.sub.2CH.sub.2O is introduced into the molecular chain of polyoxymethylene and its ratio is increased, thereby effectively reducing the crystallization rate of the materials and making it easier to form a film.

An apparatus includes an upper lip positioned with respect to an air flow passage. The upper lip is to direct air flow from the air flow passage around a bubble of blown film. The apparatus further includes a Venturi ring movably mounted with respect to the upper lip and adjustable in position with respect to the upper lip. The Venturi ring is to adjustably lock the bubble of blown film.

The continuity of a functional layer of a web (32, 60, 78) is assessed by forwarding the web, detecting (42, 63) the presence of the functional layer and a discontinuity and/or a thin region in the functional layer, and generating a signal in response to the discontinuity and/or thin region. The functional layer comprises a detectable component (360) in a thermoplastic composition. The detecting is carried out by a machine vision system capable of detecting the detectable component (360) in the functional layer. The detectable component (360) can be active or passive. Also included are systems for carrying out the process.

Polymeric multilayer film comprising a layer exhibiting a random network of strands and connective regions that is separable from the remaining polymeric multilayer film. The polymeric multilayer films are useful, for example, for tape and graphic articles.

Polymeric multilayer film comprising a layer exhibiting a random network of strands and connective regions that is separable from the remaining polymeric multilayer film. The polymeric multilayer films are useful, for example, for tape and graphic articles.

The invention describes a process for starting up a film production in a film manufacturing machine, in particular a blown film machine, by means of a control device, comprising the following steps: detecting a start-up request setting start-up parameters providing film material commencing the film production setting film production parameters.

The invention describes a process for starting up a film production in a film manufacturing machine, in particular a blown film machine, by means of a control device, comprising the following steps: detecting a start-up request setting start-up parameters providing film material commencing the film production setting film production parameters.

The present invention relates to an external cooling system for a molten film tube produced by a blown film tubular extrusion process, comprised of a divergent cooling element with a divergent cooling interface containing a cooling gas deflector spaced adjacent to the molten film tube and providing an expelled cooling gas (i) in a path opposing the flow of the molten film tube toward a first exit gap and (ii) in a path with the flow of the molten film tube toward a second exit gap. A minimum gap between the divergent cooling interface and the molten film tube occurs at the first exit gap and/or the second exit gap. Advantageously, the divergent cooling interface is provided with one or more compound angles to maximize stability and cooling efficiency. Additionally, multiple cooling elements can preferably be arranged in a stackable configuration to achieve higher throughput rates. Operation is characterized by improved film holding forces without the presence of high noise levels or detrimental vibration, flutter, and drag. Additionally, employing simplified single air delivery channels, and a stackable design, significantly reduces complexity and manufacturing costs.

The present invention relates to an external cooling system for a molten film tube produced by a blown film tubular extrusion process, comprised of one or more enclosures with one or more respective cavities that directly receive a portion of cooling gas emanating from one or more associated cooling elements. Each enclosure includes a port containing a variable exhaust device and optional flow buffer, acting to maintain a pressure differential between the cavity and an adjacent inside volume of the molten film tube, adjustable to optimize molten film tube stability cooling element efficiency and spaced apart dimension between cooling elements. Significant increases in production speeds are achieved with improved film quality over an increased range of tubular film sizes, down to a minimum size which occurs when operating at zero internal to molten film tube pressure.