The adhesive of the composite aluminum foil was carried out on a paste machine, which was equipped with a roll of aluminum foil and paper (or plastic film) and a take-up shaft of a composite aluminum foil, a plate containing a binder, a roll of adhesive, Including a guide roller, a flattening roller, a nip roller, a heating roller, a cooling roller, and a regulating device for temperature and tension.
There are three kinds of methods: wet method, dry method and thermosetting method.
Wet bonding is a water-soluble or water-dispersible binder, in the wet state of the aluminum foil and composite layer paste together, and then dry, the method of evaporation of water, so the composite layer requires a certain permeability and porosity The
Wet bonding is often used for Biaozhi. Binders should be soluble in water or can be diluted with water, they can be glue, animal glue and cheese Nguyen and other protein-type binder, it can be starch, dextrin and cellulose and other carbohydrate type of binder ; Organic or inorganic binders such as water glass, acrylic acid, denatured vinyl acetate and ethylene-vinyl acetate copolymer may also be used. Adhesives are often neutral, but can also be slightly alkaline, slightly corroded aluminum foil to paste firmly.
Adhesive use of more water glass (sodium silicate, bubble alkali) and vinyl acetate. Water glass is cheap, but after the brittle and long-term put after the reset after the yellow; vinyl acetate bond strong, soft, water, but the price is higher.
Dry bonding is used for the adhesion of airtight plastic film. Adhesive is divided into three types: vinyl acetate, vinyl chloride and other solvent-based; nitrocellulose, acetaldehyde cellulose, formaldehyde cellulose and other fiber type; synthetic rubber and propylene resin copolymer and other types.
Dry bonding first dissolve the binder in volatile solvents, such as acetone and ethanol, coated on aluminum foil, dried, and then with a certain pressure and film together. Considering the drying temperature (around 240-250 ° C) exceeds the ability of the plastic film to withstand the temperature and the physical and chemical effects of the solvent on the plastic film, the binder is usually coated on the aluminum foil. In order to improve the paste fastness, plastic film in the paste before the first corona treatment.
In the wet and dry paste, the binder varieties, concentration, viscosity, solid content (kg / m3), operating temperature and coating volume and so on affect the paste fastness and operating speed, should be based on composite material Characteristics to determine.
Thermosetting Bonding Adhesive Wax Bonding and Coated Polyethylene Bonding.
Waxing is the use of molten paraffin as a paste, the paper attached to the aluminum foil. According to the melting temperature of wax during processing, can be divided into low melting point (66 - 99 ℃), the melting point (100 - 149 ℃) and high melting point (150 - 230 ℃) adhesive. To prevent surface agglomeration, can be added to the paraffin about 5% of polyethylene, this time the use of temperature than its cloud point 8 ℃ higher. Paraffin Biaozhi Aluminum foil has good elasticity and flexibility, can be used for packaging candy, snacks, butter, bread and other cooked food, can also be packaged with small metal products, instruments, instruments and photographic equipment.
Coated with polyethylene paste, because the melting point of polyethylene than wax high, can not be used roller coating, the use of extrusion coating: the granular polyethylene continuously added to the screw extruder, heating softening, Extruded from the gap of the mold, coated between paper and aluminum foil, and pasted them together. Polyethylene is divided into low density, medium and high grade 3. Adhesive use of low-density polyethylene, melting temperature of 260-280 ℃, preheating temperature of 310 ℃, while the paste site temperature of 205 ℃, paste the temperature should be controlled. Paste fastness and coating thickness, generally 0.01 - 0.07mm, thick paste fastness. In addition, this method is preferably a degreased soft aluminum foil. As the paste temperature is high, can also be used without oil hard aluminum foil directly paste, then should grasp the temperature and speed, in addition to ensuring a solid paste, but also to maximize the productivity.