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Common coating materials PE, PP, PETP, PVC, etc PP), polyester (PETP), polyvinyl chloride (PVC), etc. The thickness of these films is generally between 15-20 μm. Commonly used width specifications are 450mm, 700mm, 1000mm and many other. Coating material is also divided into light and matt. At present, the most widely used is the new biaxially oriented polypropylene film (BOPP film). The BOPP film has the advantages of low price, excellent transparency, heat resistance, good barrier property, good water resistance, good mechanical properties, good rigidity, and no toxicity.
Common coating adhesive materials
Common coating adhesive materials include ester-soluble polyurethane adhesives, water-based polyurethane adhesives, and solvent-free polyurethane adhesives. At present, most ester-soluble polyurethane adhesives are made from polycondensation of adipic acid and ethylene glycol as the main raw materials. The curing agent is based on toluene diisocyanate (TDI) and trimethylolpropane as the main raw material. Made. Due to high temperature hydrolysis, it will turn into a carcinogenic substance, toluenediamine (TDA). Domestic and foreign countries, especially the United States, have a clear restriction on this matter. China's domestic requirements for TDA content must not exceed O. 004mg/L, so ester soluble polyurethane adhesive is not suitable for cooking packaging. Aqueous polyurethane adhesives are obtained by dispersing a polyurethane resin in water to form an emulsion or splicing a polyurethane resin in a hydrophilic group to dissolve in an aqueous solution. Waterborne polyurethane adhesives have the advantages of no pollution to the environment, non-flammability, non-toxicity, and wide adaptability. However, the composite strength of water-based adhesives is still lower than that of ester-soluble polyurethane adhesives. The technical development in cooking is still a problem at present, and the drying speed is slow, and the energy consumption and cost are high. In a real sense, solvent-free polyurethane adhesives are environmentally friendly adhesives, and solvent-free adhesives have been widely used abroad. The advantage is that there is no solvent pollution and the cost is relatively low; no solvent evaporation drying process is needed, and energy consumption is reduced; composite products are free from residual solvents, and fire and other risks are also reduced in the production process; applicable to various types of plastics Composite packaging and aluminum foil also has a good adhesive effect, high peel strength; chemical resistance and high temperature cooking performance can be comparable with ester-soluble polyurethane.
How to ensure the quality of the coating process is stable
1. The coating materials and adhesive glue should be checked for incoming materials to ensure the stability of quality.
2. When laminating, the tension of the film must be strictly controlled to prevent warpage after lamination.
3. To avoid problems such as blistering and poor adhesion, generally wait for the ink to dry before laminating.
4. When laminating, pay attention to the adjustment of the machine speed, drying temperature, and compound pressure. (Tier 3) Common Quality Problems and Improvement Measures (See Table 3) Table 3, Reasons for Common Problems in Laminating Process Analysis and Improvement Countermeasures Common Causes Analysis of Causes Improvement Measures Adhesion is poor. On the paper (Fig. 7) Abnormal quality of the coating material. Replace the new film. Try the film with impurities. Check if the film is clean. Replace the surface tension of the new film. Check whether the surface tension is greater than 36 or use a new one. Film coating process is not correct Check whether the solvent before drying film is dry, when the film pressure, heating roller temperature, the speed is normal and adjust accordingly Adhesive glue dilution excess Add the appropriate amount of original glue glue Poor viscosity Change for better viscosity The glue is poorly adhered and all the glue is left on the film when it is torn (Fig. 8) The surface of the print is abnormal. For example, UV ink or pasted oil has been changed to special properties. , The ink is not dried. Increase the amount of adhesive coating, increase the pressure and the composite temperature. The coating process is not correct. Check whether the solvent has been dried before lamination. Is the pressure, heating roller temperature, and the speed of the film normal? Should adjust the glue to open and dilute abnormally. Add original glue to the glue tank. Poor glue quality. Use better quality glue. Adhesion is poor. When the glue is torn, it stays on the film and remains on the paper (Figure 9). The glue is too thick. Appropriately reduce the thickness of the glue. Adhesion of the ink and paper is too good. Adjust the amount of glue to open. The proportion of the glue is unqualified. Replace with a new glue. Or equipment failure Dilution of glue in appropriate amount, check whether the equipment is faulty. The printing ink layer is too thick or not dry. After the ink is dry, it is covered and the drying temperature and compound pressure are adjusted. The surface of the film or paper is not clean, the dust or impurities are removed, and then the film is wrinkled or relaxed. The film is curled and replaced with a new film. The drying temperature is too high. The adhesive surface crust adjusts the temperature of the drying path. Adhesive strength and heat resistance of the crust adhesive are not sufficient. Change the wrinkle of the wrinkle film transfer roller after coating with better glue. If the film transfer roller is unbalanced, the elasticity of both ends of the film is inconsistent or wavy. Adjust the laminating machine's glue layer too thick and the solvent evaporates. Incompletely, it affects the viscosity. It is pressed by the pressure roller, and the sliding adjustment between the paper (printed matter) and the film occurs. The electric roller and the rubber roller are uneven at both ends, the pressure is not uniform, and the line speed is not adjusted. The main resins in the yellow plastic water, especially some of the tackifier resins or additives, are not resistant to aging. Under the influence of light, heat, and ultraviolet rays, chemical changes occur. The colored substances should be replaced with new glue.
Environmental and safety features
After the ester-soluble polyurethane adhesive is subjected to high-temperature cooking, it is hydrolyzed to form a potentially carcinogenic aromatic amine (TDA) and cannot be used for cooking and packaging. It uses industrial alcohol as a solvent and is flammable. Waterborne polyurethane adhesives have the advantages of no pollution to the environment, non-flammability, non-toxicity, and wide adaptability. Solvent-free polyurethane adhesives are truly environmentally friendly adhesives. Due to the high cost of recycling, coated paper products are not conducive to recycling, and countries with stringent environmental protection requirements in Europe and the United States generally do not allow the use of a film coating process.
Coating method inspection method
Appearance inspection: The coating surface is smooth, free of blisters, wrinkles, yellowing, etc. The gloss is consistent with the pattern or customer requirements. Performance test: Adhesion is firm and tearing will tear the surface of the print. In terms of weatherability, it was baked at 65°C for 15 minutes without foaming, and frozen at -15°C for 30 minutes without embrittlement.
Comparison of various coating processes
At present, there are many kinds of coating methods used in the printing and packaging industry, which are mainly manifested in the variety of machines, coating methods, drying and curing methods, and coating methods. (See Table 4 for details.) Table IV. Comparison of Different Coating Processes Process Name Machine Polishing Method Drying and Curing Method Coating Method Solvent-based Coating Process Stand-alone Oil Dispenser Offline Hot Air Drying and Curing Roller Direct Coating Offset Off-line Natural Oxidation Drying Blanket Indirect coating Water-based glazing process Free-standing oil-removal machine Off-line hot-air drying Curing roller Direct coating or offset coating Special glazing equipment connected to the printing press Hot air drying Curing blanket Indirect coating UV coating Process Stand-alone UV Machines Off-Line UV Curing Roller Coating or Offset Coating Special Glossing Equipment Connected to the Press Line Wiring UV Light Curing Blanket Indirect Coating Laminating Process Instant Coating Machine Off-line Hot Air Drying Roller Direct Coating The glue precoat laminator is not required to be dried offline without glue (Title 1) Characteristics of different coating methods (see Table 5 for details) Table V. Comparison of different glazing method characteristics Process name Gloss Wear resistance Scratch-resistance Water-resistance Smoothness Environmental-friendly Cost Solvent-based coating Polishing General low-water-borne coating General general general higher environmental protection Higher UV coating Good The highest environmental best best of the best high-covered high environmental protection is generally not high? Gloss finish is not the worst, the polished sheen than water. The wear resistance of ordinary polishing oil is the worst, and the wear resistance of light oil is more abrasion resistant than water.
Some special gloss coating solutions
Low-gloss paper glazing process generally for glazing process, the weight of paper less than 150g/m2 is called low gram paper, low gram-weight paper stiffness is less than the varnish paper adhesion, with traditional The roller type glazing process easily causes the paper to roll into the roller and cannot be applied. Therefore, for low grammage paper, guillotine greasers or printing machines are generally used for coating, and they can also be separately coated with offset presses. Some manufacturers also install an air knife device on drum type oil skimmers for low grammage papers. Heavy paper glazing. The guillotine oil machine or printing machine coating machine is the ideal glazing method for low-weight paper, the efficiency is very high, the coating quality is good, but the equipment is expensive, and small manufacturers often cannot. Because the offset printing machine alone is glazing, it is naturally dry. After the glazing, it takes at least 12 hours for the drying time. This can cause great problems for product delivery. The roll coater and air knife device is generally limited to UV coating, water-based gloss coating and solvent-based gloss coating are also likely to cause the paper to roll into the roll, and its role is very limited.
On the wear-resistant requirements of the coating process is very high, some large color box, because the machine directly after the installation of the export, if there is no very good wear resistance, it will often cause the surface of the color box to wipe flowers. If the lamination process can be used, then wear resistance is not a problem. However, for export products that only accept the coating process, the use of UV varnish or special wear-resistant solvent-based varnish should be the ideal way. Also need to pay attention to UV glazing must prevent the curing is not complete, otherwise there will be rubbing flowers
The glazing coating process with a very high degree of folding resistance is required for some heavy-duty corrugated color boxes, and if the folding-resistance is not good, the indentation line bursts when the die-cutting process is performed. Generally, the film coating can fundamentally solve the problem of bursting of the indentation line, but it must be weighed against the characteristics of non-environmental protection when the film coating process is adopted. If the glazing process is required, the UV glazing is slightly better than solvent-based glazing and water-based glazing.
Partial glazing process For the local glazing process, it is common to use a rake-type oiler and use an offset plate for glazing. For the UV box, since it is difficult to bond after UV polishing, the UV box is preferably applied with a local glazing technique, that is, the sticking part does not apply light when it is applied.
Common coating adhesive materials
Common coating adhesive materials include ester-soluble polyurethane adhesives, water-based polyurethane adhesives, and solvent-free polyurethane adhesives. At present, most ester-soluble polyurethane adhesives are made from polycondensation of adipic acid and ethylene glycol as the main raw materials. The curing agent is based on toluene diisocyanate (TDI) and trimethylolpropane as the main raw material. Made. Due to high temperature hydrolysis, it will turn into a carcinogenic substance, toluenediamine (TDA). Domestic and foreign countries, especially the United States, have a clear restriction on this matter. China's domestic requirements for TDA content must not exceed O. 004mg/L, so ester soluble polyurethane adhesive is not suitable for cooking packaging. Aqueous polyurethane adhesives are obtained by dispersing a polyurethane resin in water to form an emulsion or splicing a polyurethane resin in a hydrophilic group to dissolve in an aqueous solution. Waterborne polyurethane adhesives have the advantages of no pollution to the environment, non-flammability, non-toxicity, and wide adaptability. However, the composite strength of water-based adhesives is still lower than that of ester-soluble polyurethane adhesives. The technical development in cooking is still a problem at present, and the drying speed is slow, and the energy consumption and cost are high. In a real sense, solvent-free polyurethane adhesives are environmentally friendly adhesives, and solvent-free adhesives have been widely used abroad. The advantage is that there is no solvent pollution and the cost is relatively low; no solvent evaporation drying process is needed, and energy consumption is reduced; composite products are free from residual solvents, and fire and other risks are also reduced in the production process; applicable to various types of plastics Composite packaging and aluminum foil also has a good adhesive effect, high peel strength; chemical resistance and high temperature cooking performance can be comparable with ester-soluble polyurethane.
How to ensure the quality of the coating process is stable
1. The coating materials and adhesive glue should be checked for incoming materials to ensure the stability of quality.
2. When laminating, the tension of the film must be strictly controlled to prevent warpage after lamination.
3. To avoid problems such as blistering and poor adhesion, generally wait for the ink to dry before laminating.
4. When laminating, pay attention to the adjustment of the machine speed, drying temperature, and compound pressure. (Tier 3) Common Quality Problems and Improvement Measures (See Table 3) Table 3, Reasons for Common Problems in Laminating Process Analysis and Improvement Countermeasures Common Causes Analysis of Causes Improvement Measures Adhesion is poor. On the paper (Fig. 7) Abnormal quality of the coating material. Replace the new film. Try the film with impurities. Check if the film is clean. Replace the surface tension of the new film. Check whether the surface tension is greater than 36 or use a new one. Film coating process is not correct Check whether the solvent before drying film is dry, when the film pressure, heating roller temperature, the speed is normal and adjust accordingly Adhesive glue dilution excess Add the appropriate amount of original glue glue Poor viscosity Change for better viscosity The glue is poorly adhered and all the glue is left on the film when it is torn (Fig. 8) The surface of the print is abnormal. For example, UV ink or pasted oil has been changed to special properties. , The ink is not dried. Increase the amount of adhesive coating, increase the pressure and the composite temperature. The coating process is not correct. Check whether the solvent has been dried before lamination. Is the pressure, heating roller temperature, and the speed of the film normal? Should adjust the glue to open and dilute abnormally. Add original glue to the glue tank. Poor glue quality. Use better quality glue. Adhesion is poor. When the glue is torn, it stays on the film and remains on the paper (Figure 9). The glue is too thick. Appropriately reduce the thickness of the glue. Adhesion of the ink and paper is too good. Adjust the amount of glue to open. The proportion of the glue is unqualified. Replace with a new glue. Or equipment failure Dilution of glue in appropriate amount, check whether the equipment is faulty. The printing ink layer is too thick or not dry. After the ink is dry, it is covered and the drying temperature and compound pressure are adjusted. The surface of the film or paper is not clean, the dust or impurities are removed, and then the film is wrinkled or relaxed. The film is curled and replaced with a new film. The drying temperature is too high. The adhesive surface crust adjusts the temperature of the drying path. Adhesive strength and heat resistance of the crust adhesive are not sufficient. Change the wrinkle of the wrinkle film transfer roller after coating with better glue. If the film transfer roller is unbalanced, the elasticity of both ends of the film is inconsistent or wavy. Adjust the laminating machine's glue layer too thick and the solvent evaporates. Incompletely, it affects the viscosity. It is pressed by the pressure roller, and the sliding adjustment between the paper (printed matter) and the film occurs. The electric roller and the rubber roller are uneven at both ends, the pressure is not uniform, and the line speed is not adjusted. The main resins in the yellow plastic water, especially some of the tackifier resins or additives, are not resistant to aging. Under the influence of light, heat, and ultraviolet rays, chemical changes occur. The colored substances should be replaced with new glue.
Environmental and safety features
After the ester-soluble polyurethane adhesive is subjected to high-temperature cooking, it is hydrolyzed to form a potentially carcinogenic aromatic amine (TDA) and cannot be used for cooking and packaging. It uses industrial alcohol as a solvent and is flammable. Waterborne polyurethane adhesives have the advantages of no pollution to the environment, non-flammability, non-toxicity, and wide adaptability. Solvent-free polyurethane adhesives are truly environmentally friendly adhesives. Due to the high cost of recycling, coated paper products are not conducive to recycling, and countries with stringent environmental protection requirements in Europe and the United States generally do not allow the use of a film coating process.
Coating method inspection method
Appearance inspection: The coating surface is smooth, free of blisters, wrinkles, yellowing, etc. The gloss is consistent with the pattern or customer requirements. Performance test: Adhesion is firm and tearing will tear the surface of the print. In terms of weatherability, it was baked at 65°C for 15 minutes without foaming, and frozen at -15°C for 30 minutes without embrittlement.
Comparison of various coating processes
At present, there are many kinds of coating methods used in the printing and packaging industry, which are mainly manifested in the variety of machines, coating methods, drying and curing methods, and coating methods. (See Table 4 for details.) Table IV. Comparison of Different Coating Processes Process Name Machine Polishing Method Drying and Curing Method Coating Method Solvent-based Coating Process Stand-alone Oil Dispenser Offline Hot Air Drying and Curing Roller Direct Coating Offset Off-line Natural Oxidation Drying Blanket Indirect coating Water-based glazing process Free-standing oil-removal machine Off-line hot-air drying Curing roller Direct coating or offset coating Special glazing equipment connected to the printing press Hot air drying Curing blanket Indirect coating UV coating Process Stand-alone UV Machines Off-Line UV Curing Roller Coating or Offset Coating Special Glossing Equipment Connected to the Press Line Wiring UV Light Curing Blanket Indirect Coating Laminating Process Instant Coating Machine Off-line Hot Air Drying Roller Direct Coating The glue precoat laminator is not required to be dried offline without glue (Title 1) Characteristics of different coating methods (see Table 5 for details) Table V. Comparison of different glazing method characteristics Process name Gloss Wear resistance Scratch-resistance Water-resistance Smoothness Environmental-friendly Cost Solvent-based coating Polishing General low-water-borne coating General general general higher environmental protection Higher UV coating Good The highest environmental best best of the best high-covered high environmental protection is generally not high? Gloss finish is not the worst, the polished sheen than water. The wear resistance of ordinary polishing oil is the worst, and the wear resistance of light oil is more abrasion resistant than water.
Some special gloss coating solutions
Low-gloss paper glazing process generally for glazing process, the weight of paper less than 150g/m2 is called low gram paper, low gram-weight paper stiffness is less than the varnish paper adhesion, with traditional The roller type glazing process easily causes the paper to roll into the roller and cannot be applied. Therefore, for low grammage paper, guillotine greasers or printing machines are generally used for coating, and they can also be separately coated with offset presses. Some manufacturers also install an air knife device on drum type oil skimmers for low grammage papers. Heavy paper glazing. The guillotine oil machine or printing machine coating machine is the ideal glazing method for low-weight paper, the efficiency is very high, the coating quality is good, but the equipment is expensive, and small manufacturers often cannot. Because the offset printing machine alone is glazing, it is naturally dry. After the glazing, it takes at least 12 hours for the drying time. This can cause great problems for product delivery. The roll coater and air knife device is generally limited to UV coating, water-based gloss coating and solvent-based gloss coating are also likely to cause the paper to roll into the roll, and its role is very limited.
On the wear-resistant requirements of the coating process is very high, some large color box, because the machine directly after the installation of the export, if there is no very good wear resistance, it will often cause the surface of the color box to wipe flowers. If the lamination process can be used, then wear resistance is not a problem. However, for export products that only accept the coating process, the use of UV varnish or special wear-resistant solvent-based varnish should be the ideal way. Also need to pay attention to UV glazing must prevent the curing is not complete, otherwise there will be rubbing flowers
The glazing coating process with a very high degree of folding resistance is required for some heavy-duty corrugated color boxes, and if the folding-resistance is not good, the indentation line bursts when the die-cutting process is performed. Generally, the film coating can fundamentally solve the problem of bursting of the indentation line, but it must be weighed against the characteristics of non-environmental protection when the film coating process is adopted. If the glazing process is required, the UV glazing is slightly better than solvent-based glazing and water-based glazing.
Partial glazing process For the local glazing process, it is common to use a rake-type oiler and use an offset plate for glazing. For the UV box, since it is difficult to bond after UV polishing, the UV box is preferably applied with a local glazing technique, that is, the sticking part does not apply light when it is applied.
Smoking And Cooking Solutions
Helper have accumulated rich experience in the smoking(smoking chamber),dry maturing(dry maturing chamber) and cooking(cooking chamber) solutions through decades of years development. We know clearly the importance of the temperature, humidity and ventilation conrtrolling for sausage production, thus our machine can hold control all the key points and help our clients to avoid the risk of defective products. Not only the machine itself, we are always pleasure to give our suggestions on the auxiliary and some other supported devices and equipment.
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