Nylon's scientific name is polyamide resin (PA), which is a polymer with repeating amide groups on the macromolecule. It is formed by ring-opening polymerization of lactam or polycondensation of diamines and dibasic acids. There are many types of nylon. The nylon film currently used for composite flexible packaging is mainly nylon 6, which is formed by the ring-opening polymerization of caprolactam. Nylon 66 is formed by the condensation of hexamethylenediamine and adipic acid. Regardless of the type of nylon, their films share common features:
1, great strength and toughness, high tensile strength, elongation, tear strength and wear resistance.
2, excellent puncture resistance.
3, high resistance to low temperature performance, can be used normally in the range of 60 °C ~ 200 °C.
4, excellent chemical resistance, oil resistance, acid resistance, alkali resistance, solvent resistance, drug resistance.
5, printing performance is good.
Due to the above superior performance, nylon membranes are more widely used in composite flexible packaging, and there are two major types of more common applications. One is for making high-temperature cooking sterilization bags, which are to be sterilized by high temperature at 121° C., 40 minutes or more. Its structure can be: PA / CPP, PET / PA / CPP, PET / AL / PA / CPP, used to do this type of compound are using special high-temperature cooking adhesive, such as Sino-US joint venture Beijing Moike Technology Co., Ltd. The company's HS3135 and HS3121 belong to such products.
The other type of packaging is an ordinary vacuum bag. PA as the outer layer, color printing, inner composite PE or CPP. When using such a bag, it is generally only required to sterilize it at a temperature below 100°C. Such as packaging some aquatic products, wild vegetables, fresh mushrooms, etc., or just vacuum packaging, without heat treatment, there are some liquid packaging bags that do not require vacuum packaging, such as alcohol, beverages, detergents and so on. This type of packaging utilizes the performance advantages of nylon membranes: flexibility, puncture resistance, impact resistance, and high and low temperature resistance. Therefore, after the requirements for composite bag making, it is still necessary to maintain these advantages, that is, to achieve:
1. After vacuuming, no matter how complicated the shape of the contents is, it is required that the composite film should be smooth and fit tightly without any wrinkles. It will be easy to cause damage at the wrinkles.
2. After sterilization, the packaging bag will not wrinkle, shrink or harden.
3. When the packing line is on the bottling line, there is no crease in the folded bag, and the drop is not damaged after sealing.
4. The bag after low-temperature freezing is not hard and brittle, and storage stack pressure is not damaged.
In order to meet the above requirements, Moike developed a special composite adhesive for PA2070/GT30 nylon film. This product is specially designed for the PA film composite and has a polar group close to the acyl group of the nylon film in its molecular structure. Therefore, it can have excellent soaking and leveling on the nylon film, showing excellent initial tack and final peel strength, high transparency, good optical properties, and strong decorative properties. And in the molecular structure design, it has an excellent macromolecular flexibility. The cured adhesive layer is still soft as before, without any change in the softness characteristics of the original substrate, and folding folds do not occur. Compared with the composite products used by everyone in the industry today, there are several advantages:
1. PA2070/GT30 adhesive has better adhesion to PA film, and the initial and final peel force exceeds that of general-purpose adhesive.
2. In the process of packaging, the compound bag has stronger resistance to the mechanical operation of the equipment, which greatly reduces the damage caused by the creases left by the mechanical injury during storage and transportation.
3, have a better low temperature resistance, greatly improving the safety of low temperature storage.
4. With more outstanding flexibility, all kinds of special-shaped contents can ensure that the composite film will not be damaged after evacuation.
5. Comprehensive analysis of composite film quality problems 1. Insufficient adhesion of composite film 1. Ink transfer 1 Adhesive unbaked 2. Ink connection material problem 3. Electro-activation treatment of printing film 2. Transfer of aluminum layer 1 Quality problem of aluminum plating 2. Adhesive The elasticity is too small 3 The winding tension is too high 3. The glue turns to the ink 1 The inner film If it is an aluminum film, it means that the glue is not suitable for the complex aluminum film 2 The amount of glue is too small 3 The inner film corona treatment problem 4 The glue turns to the film: Ink Problem 5, intermediate separation 1 non-dry separation a, curing agent ratio is not enough b, excess water (solvent) C, air humidity is too high D, ink solvent contains alcohol E, (aluminum) film surface hydroxyl-containing substances are too much F, film additives (softeners, etc.)
2 dry separation a, too little glue b, glue quality problems 2, composite film surface quality problems 1, small white spots: (ink is too thin, reflection effect)
a, the ink is too rough; b, the poor wetting of the glue; C, too little glue or uneven glue; D, less pressure;
2, small gray point:
1 Insufficient or uneven ink hiding power; 2 The glue is too thin and the ink is dissolved;
3, small crystal point:
1 The use time of the glue is too long or the preparation method is wrong; 2 the crystal point on the film; 3 the problem of the ink (including many additives) [analysis]; 4 the problem of the color masterbatch of the intima; 5 the curing time of the glue is too fast;
4, black spots: after a period of time can appear. May be aluminum film corrosion by ink; glue impurities;
5, small bubbles: too much water (solvent); the weather is too wet.
6, small scars: the four points on the convex concave point, mainly due to uneven film activation caused;
7, wave pattern: easy to occur in the white film, mainly because the glue molecular weight is not neat, after heating, elastic shrinkage within the polymer chain, different molecular weight of the intramolecular contraction caused by inconsistencies;
8, cocoon: early adhesion is too small (aluminum film, aluminized film); too much tension; wrinkling phenomenon.
Third, odor problems 1, the glue contains high-boiling substances and unreacted residual monomer 2, the drying tunnel temperature is too low 3, the film of certain local substances (such as additives, PE oxidation odor, inhalation of air smell Wait)
4, ink penetration through the adhesive layer
1, great strength and toughness, high tensile strength, elongation, tear strength and wear resistance.
2, excellent puncture resistance.
3, high resistance to low temperature performance, can be used normally in the range of 60 °C ~ 200 °C.
4, excellent chemical resistance, oil resistance, acid resistance, alkali resistance, solvent resistance, drug resistance.
5, printing performance is good.
Due to the above superior performance, nylon membranes are more widely used in composite flexible packaging, and there are two major types of more common applications. One is for making high-temperature cooking sterilization bags, which are to be sterilized by high temperature at 121° C., 40 minutes or more. Its structure can be: PA / CPP, PET / PA / CPP, PET / AL / PA / CPP, used to do this type of compound are using special high-temperature cooking adhesive, such as Sino-US joint venture Beijing Moike Technology Co., Ltd. The company's HS3135 and HS3121 belong to such products.
The other type of packaging is an ordinary vacuum bag. PA as the outer layer, color printing, inner composite PE or CPP. When using such a bag, it is generally only required to sterilize it at a temperature below 100°C. Such as packaging some aquatic products, wild vegetables, fresh mushrooms, etc., or just vacuum packaging, without heat treatment, there are some liquid packaging bags that do not require vacuum packaging, such as alcohol, beverages, detergents and so on. This type of packaging utilizes the performance advantages of nylon membranes: flexibility, puncture resistance, impact resistance, and high and low temperature resistance. Therefore, after the requirements for composite bag making, it is still necessary to maintain these advantages, that is, to achieve:
1. After vacuuming, no matter how complicated the shape of the contents is, it is required that the composite film should be smooth and fit tightly without any wrinkles. It will be easy to cause damage at the wrinkles.
2. After sterilization, the packaging bag will not wrinkle, shrink or harden.
3. When the packing line is on the bottling line, there is no crease in the folded bag, and the drop is not damaged after sealing.
4. The bag after low-temperature freezing is not hard and brittle, and storage stack pressure is not damaged.
In order to meet the above requirements, Moike developed a special composite adhesive for PA2070/GT30 nylon film. This product is specially designed for the PA film composite and has a polar group close to the acyl group of the nylon film in its molecular structure. Therefore, it can have excellent soaking and leveling on the nylon film, showing excellent initial tack and final peel strength, high transparency, good optical properties, and strong decorative properties. And in the molecular structure design, it has an excellent macromolecular flexibility. The cured adhesive layer is still soft as before, without any change in the softness characteristics of the original substrate, and folding folds do not occur. Compared with the composite products used by everyone in the industry today, there are several advantages:
1. PA2070/GT30 adhesive has better adhesion to PA film, and the initial and final peel force exceeds that of general-purpose adhesive.
2. In the process of packaging, the compound bag has stronger resistance to the mechanical operation of the equipment, which greatly reduces the damage caused by the creases left by the mechanical injury during storage and transportation.
3, have a better low temperature resistance, greatly improving the safety of low temperature storage.
4. With more outstanding flexibility, all kinds of special-shaped contents can ensure that the composite film will not be damaged after evacuation.
5. Comprehensive analysis of composite film quality problems 1. Insufficient adhesion of composite film 1. Ink transfer 1 Adhesive unbaked 2. Ink connection material problem 3. Electro-activation treatment of printing film 2. Transfer of aluminum layer 1 Quality problem of aluminum plating 2. Adhesive The elasticity is too small 3 The winding tension is too high 3. The glue turns to the ink 1 The inner film If it is an aluminum film, it means that the glue is not suitable for the complex aluminum film 2 The amount of glue is too small 3 The inner film corona treatment problem 4 The glue turns to the film: Ink Problem 5, intermediate separation 1 non-dry separation a, curing agent ratio is not enough b, excess water (solvent) C, air humidity is too high D, ink solvent contains alcohol E, (aluminum) film surface hydroxyl-containing substances are too much F, film additives (softeners, etc.)
2 dry separation a, too little glue b, glue quality problems 2, composite film surface quality problems 1, small white spots: (ink is too thin, reflection effect)
a, the ink is too rough; b, the poor wetting of the glue; C, too little glue or uneven glue; D, less pressure;
2, small gray point:
1 Insufficient or uneven ink hiding power; 2 The glue is too thin and the ink is dissolved;
3, small crystal point:
1 The use time of the glue is too long or the preparation method is wrong; 2 the crystal point on the film; 3 the problem of the ink (including many additives) [analysis]; 4 the problem of the color masterbatch of the intima; 5 the curing time of the glue is too fast;
4, black spots: after a period of time can appear. May be aluminum film corrosion by ink; glue impurities;
5, small bubbles: too much water (solvent); the weather is too wet.
6, small scars: the four points on the convex concave point, mainly due to uneven film activation caused;
7, wave pattern: easy to occur in the white film, mainly because the glue molecular weight is not neat, after heating, elastic shrinkage within the polymer chain, different molecular weight of the intramolecular contraction caused by inconsistencies;
8, cocoon: early adhesion is too small (aluminum film, aluminized film); too much tension; wrinkling phenomenon.
Third, odor problems 1, the glue contains high-boiling substances and unreacted residual monomer 2, the drying tunnel temperature is too low 3, the film of certain local substances (such as additives, PE oxidation odor, inhalation of air smell Wait)
4, ink penetration through the adhesive layer
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