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"Blow" and "casting" technology

2016-08-29 16:22:30 Leqi Intelligent Technology Co., Ltd. Read

In the field of film production, blow molding method "and" casting method "is more commonly used two techniques, the following the two film production in the production process of the most commonly used do a simple introduction and comparison.

1, multilayer coextrusion blow molding method: the production process is divided into cold blowing and blowing water cooling under two forms.

Blowing cold, mainly consisting of a plurality of extruder, the multi-layer die head, multi outlet wind ring, IBC inner cooling system, spica splint, rotating traction system, traction system and coiling system the main part. At present, the import unit in the original German battenfeid, German W& h, Canada Brampton, domestic units in Guangdong Jinming represented. Overall analysis, the core of the currentMechanicsCapacity is still controlled by foreign companies, such as the Guangdong gold group of the core components of the majority still need foreign manufacturers supply.

Blowing water, the basic component and blowing type is the same, the difference is in cooling, blowing in a cyclic Ling but water as the main form of cooling, to all parts of the design of the position and blowing vary, the production process in China's PE and PP film production in common. In the multi-layer high barrier film production, mainly still above blowing cooling unit. No matter which kind of form of unit, in appearance, is a tubular membrane as the main features, in the vacuum bag making, due to the reduction of the two heat sealing, in to protect the contents of the package than cast film has a very big advantage. In terms of tensile strength than cast film.

2, multi-layer co extruded cast: this process is mainly composed of multiple extruder, multi channel distributor (commonly known as "feeder"), T-type die, casting system, the horizontal traction system, oscillator, roll system.

The production process is characterized in that the surface gloss of the film produced is good, the flatness is high, the thickness tolerance is small, the mechanical extension performance is good, the flexibility is good, and the transparency is higher than the blow molding method. Currently imported units to the original German Baden Field, Germany W& H, Corinth, Italy, Austria Lenzing Co, the former Japanese MITSUBISHI heavy industries as the representative, domestic units to Foshan Shi Cheng as the representative. Similarly, domestic tape units of production and blow molding, core components mainly come from foreign suppliers. At present this production technology is mainly used in the industry of CPP, in seven layer coextrusion high barrier production also has a small number of applications.

In the imported production line mainly in Zhongshan, Guangdong Xiangfu of seven and eleven layer units and Changzhou Haiqi plastic nine layer units represented.

The two kinds of production technology in our country is the most common, due to a blow molding process in the flatness of the product as well as the transparency and the cast film compared, but its production efficiency, equipment investment is low, low material loss is unmatched by tape casting process.

Therefore, in the improvement of foreign enterprises on the inadequacies of blow molding process, in-depth research and development, mainly reflected in (1) die design improvement, using a unique multi parallel channel design concept; (2) the extrusion machines placed in position and angle; (3) Ling is improved in the wind ring and the inner cooling technology (4) material composition and structure design these four aspects. The practice proved that in the transparency of the film roughness, uniform thickness of each layer of material of have reached or close to the level of casting method. If the domestic enterprises in the high barrier film equipment investment, mainly basic to the film after 2010.

Production process comparison

1, casting compare blowing method is more suitable for multi-layer co extruded film production and processing, especially when using a variety of different materials Materials Co extrusion, production process parameters of casting method is easier to control, design of processing equipment of the key part -- die more effectively protect the product in a variety of materials distribution uniformity. The molding method of multilayer coextrusion die technology is more difficult, the structure is more complex and the technology is still not mature enough.

2, casting processing equipment and die to cold and (molding and shaping) distance is generally 10 ~ 20mm, melt film curtain is very short and the in vacuum suction hood, air knife and deckle help soon finalize the design, product quality good and stable. And blow molding method because the melt film has a blowing process, and rely on air or water to cool the stereotypes. Product setting time is too long and the change before the design is very big (general blow 7 ~ 4 times). It is easy to be affected by the external and internal factors, the difficulty of product quality control is very large and the stability is poor.

3, in the selection of raw materials, blow molding and casting method also have bigger difference, multilayer coextrusion blow molding requirements as far as possible to choose close to the flow of material to match each other, when there is a big difference in material flow, lack of corresponding measures to adjust, so when selected one kind of material, and co extrusion of other materials do not have much choice, this reflected in a in extent restricted the multi-layer coextrusion processing technology advantages in the quality of the products, and casting method of processing equipment by shunt regulator can easily solve the problem almost can not solve the blow moulding.

Comparison of product features

1, because of a blow molding process and lead to molecular product longitudinal and transverse tensile in different degrees. Products of high temperature properties and heat sealing performance will be affected greatly, when the product needs to be disinfected cooking (such as 121 DEG C vapor), molding is heated, the stretching of the molecular chain have obvious retraction phenomenon, leading to severe deformation of the product and greatly reduce the heat sealing connection strength and lead to leakage of bag phenomenon.

2, cast film production (also known as the unstretched films), the molecules are arranged in an orderly fashion, product cooling speed, to improve the transparency, gloss, and thickness uniformity and product texture is soft, rather tough; impact resistance, heat resistance and low temperature adaptability were better in blow molding method.

High production efficiency 3, casting method, good product quality and stability. In the production process of waste less, and easier to achieve online recycling, scrap, high utilization of materials.

4, casting method using a flat die, die head is arranged in special detention tank, so as to guarantee the uniformity of the material flow, and through the die of automatic regulation device can automatically control die lip gap uniformity, control accuracy is very high, thick film can be controlled below the + 3%. And blow moulding the annular die and multi-layer core and on machining precision and assembly precision requirement is very high and particularly difficult to control, if the processing and with the precision has little error, not through the regulator to make up for, so product thickness tolerances basic (+ 10%), for the 200 m thick film means 180 m and the thinnest and thickest at 220 m, in the welding sealing bag making, die gap and heat sealing temperature any are difficult to guarantee the thickest and thinnest can achieve the required sealing strength. Leakage phenomenon is inevitable, the finished product rate is very low.

5, the melt strength of the material, the need to use the lower blowing method, water cooling. The water is not thoroughly dried or corona layer unsuitable material will lead to poor treatment effect or corona corona attenuation. Impact printingprinting inkAdhesive fastness to bleaching. Steel casting piece roll by casting method (internal cooling water) setting on the film cooling water is not in direct contact with the film.

6, for the need of cooking (121 DEG C steam sterilization) films, whether casting or molding method must choose high cooking raw materials. After cooking, the film will become hard, brittle and the phenomenon of bleaching. The impact of the appearance of the film will lead to a bag of impact resistance and pressure drop, can not meet the testing standards and use requirements.

7 and in the plastic molding process, due to the thermal decomposition or low molecular rhythm of the accumulation of material easily in the die to generate residue. Casting method can be easily removed and the residue can only blow molding film inside the bubble down clear. Not timely removal is very easy to be entrained in the film, resulting in the content of impurities in the content or the film surface has obvious scratches. Due to the blow molding process itself is low production, driving a large waste, such as frequent driving, parking unit production costs increased significantly.


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