China's Dairy Industry Has Been Rapid Development and Growth

With Economy Development and improvement of living standard, China's dairy industry has been rapid development and growth, people's lifestyles and dietary patterns also changed significantly, the Milk on the table of ordinary people has become essential goods, which, using Plastic film flexible Packaging of milk accounts for a significant proportion of this packaged milk is usually carried out using automatic filling machine filling, we must first carry out sterilization of milk and packaging films, followed by aseptic filling into the milk then Plastic Packaging Bag.In this paper, this milk packaging film Print Process analysis and discussion. Milk Plastic Packaging 1.Types of thin film materials Milk packaging film materials used in the film mainly Polyethylene (PE) Co-extruded film, according to the basic can be divided into three layers: Simple milk packaging film, usually single-layer film, it is by a variety of Polyethylene (PE) Add a proportion of white material Color Masterbatch Material, formed by the blown film equipment.This milk, non-barrier packaging film structure, use of pasteurization (85 / 30min) for hot-fill, Shelf life is shorter, only 3 days. Three layers of black and white co-extruded packaging films, heat sealing the inner layer to add in the black Color Masterbatch Materials play a role in blocking light.The packaging film with ultra high temperature sterilization (UItraHighTemperatureSterilization, abbreviated UHT) and hydrogen peroxide (H2O2) sterilization method, room temperature shelf life of up to 30 days. Five-story structure of white co-extruded packaging film, blown film of the middle barrier layer increased (from EVA , EVA L and other high barrier resin composition), so that aseptic packaging films are high barrier packaging films, have a longer shelf life, stored at normal temperature is about 90 days. 2.Film performance requirements Be noted that, in order to meet the high-speed filling requirements of automatic filling machine, milk packaging, polyethylene film must meet the performance requirements of the following aspects: Good smoothness Film should have good internal and external surface smoothness to ensure high-speed automatic filling machine filling can be carried out smoothly, so the static friction coefficient of film surface should be relatively low, generally require 0.2 to between 0.4.Film smoothness is mainly achieved by adding the slippery agent, in the film after molding, slippery agent within the migration from film to the surface, accumulate into a uniform thin layer, can significantly reduce the friction coefficient of film to make film with good smoothness results.Slippery agent is usually oleic acid amide, or erucic acid amide, it is only a mechanical polymer mixture of polyethylene and can not very well compatible with the molecular thermal motion so that it gradually to the low free energy of the interface migration, forming a layer of weak interface layer, so if slippery agent content is too high, it will affect the film's printability, which is extremely unfavorable for printing. Strong tensile strength As plastic film in the filling process to be automatic filling machine from the role of mechanical tension, therefore, requested film must have sufficient tensile strength to prevent the automatic filling machine was under the influence of tension pull off.Used in the blown film process melt index (MI) or lower LDPE HDPE Particles, for improving the tensile strength of polyethylene film is very beneficial. Wetting surface tension values to meet the requirements To make printing ink to the smooth surface of the polyethylene plastic film spreading, wetting and adhesion, the surface tension of film should be required to achieve a certain standard, otherwise it will affect the adhesion of ink on the surface and solidity to affect the printing quality.General requirements for the surface tension of polyethylene film to achieve the best 38dyne (dyne) above, if we can reach more than 40dyne better. Since polyethylene is a typical non-polar polymers, the molecular structure of non-polar groups, and high crystallinity, surface free energy is low, highly inert, high crystallinity, chemical stability Therefore, poor printability of the film material, the adhesion of the ink is not ideal.In addition, the films of auxiliaries (slippery agent, Plasticizer Etc.) continue to migrate to the surface precipitation of a weak surface layer, will also affect the fastness of printing ink, therefore, must be printed on the plastic film before the general conduct Surface Treatment Change the chemical structure of films and improve film surface tension so as to enhance and improve the polyethylene film Printability purpose of improving the adhesion of the ink to ensure smooth production. Excellent sealing performance Films have a good seal bag, there has been a good sealed off, meaning that it is necessary to ensure the sealing, but also a smooth cut, so that molten resin will not stick knives.In the film blowing process of adding a certain percentage of LLDPE Milk film can be significantly improved low temperature sealing performance and sealing performance of inclusions, but the addition of LLDPE not too large, otherwise it would be too high viscosity of polyethylene Milk film, stick easily when knife seal failure. Source:Hicow.Com