Analysis of Current Development of Adhesive for Composite Membrane and Blister

Adhesives, also known as adhesives, adhesives, and adhesives, have many types of adhesives on the market. The adhesives described here are mainly used in the field of medicines or food packaging, such as the compounding of medicinal plastic films with metal aluminum and plastics. Medicinal aluminum foil and PVC hot pressed together.

1 Basic requirements for adhesives for pharmaceutical packaging

1.1 The safety and health performance is good, there should be no odor, odorless, non-toxic, if the direct contact with the drug adhesive, it should also be non-corrosive to the packaged drug. The products that are protected or packaged by the medicine packaging materials are direct entrances and are responsible for the health of the consumers. Not only do the substrates need to be odorless, odorless, and non-toxic, the adhesives used must also have the same properties. Therefore, raw materials, auxiliary materials, and solvents for adhesive production should be safe and hygienic.

1.2 excellent adhesive properties. Because the packaging materials are made of different materials, the adhesives are used to bond them. Therefore, the adhesive must have excellent adhesion to various materials. There are various types of substrates used in the pharmaceutical packaging composite materials, and the performance Various, such as paper, fabrics, aluminum foils, and plastics, and plastics have a variety of brands. Their surface properties are different in molecular structure. In the face of so many complex materials, adhesives must have two or more different materials at the same time. Performance.

1.3 good heat resistance. A variety of pharmaceutical packaging materials are subjected to high temperature during the manufacturing process. For example, aluminum foil blister packs must receive 150°C～220°C for hot-press sealing of aluminum foil and PVC, as well as steamed foods. Sterilize with high temperature cooking. This requires the adhesive to withstand the test of high temperatures.

1.4 Excellent chemical resistance and medium resistance. The drug itself is a very complex chemical substance. In the face of these complex components, it must undergo high-temperature treatment and long-term storage after packaging. It is necessary to maintain the perfect packaging material, in addition to the excellent chemical resistance of the substrate itself against the media. In addition to the erosion ability, the stability of the adhesive is also very important. It must be able to resist the erosion of various media and chemical components, otherwise it will cause the layered peeling of the compound and lose the function of packaging medicines to protect the drugs.

1.5 soft performance. Soft packaging composites are widely used in packaging medicines. The flexibility is very important for easy carrying. It is better to fold them. Therefore, the adhesive must have such properties. If the adhesive film is hard, brittle, and unfoldable, it will be lost if it does not match the substrate. The use of flexible packaging.

2 Medicinal Flexible Packaging Composite Films with Different Material Properties and Selected Adhesives

2.1 The composition of the composite film

The composition of the composite film is various, and as the outer layer material, there are mainly used materials such as paper, cellophane, aluminum foil and the like which have better heat resistance, dimensional stability, and printing performance. As an inner layer of a flexible packaging composite film, it is mainly a material having excellent heat-sealability and hygienic properties such as polyethylene, polypropylene, and soft polyvinyl chloride. In addition, a variety of stretch film such as: polyester, polypropylene, nylon, polycarbonate, cellulose acetate, hard polyvinyl chloride, etc. can also be used for the outer layer material. The general types of composite films currently used are the following types. Therefore, depending on the nature of the composite material, a suitable adhesive can be selected. (1) Cellulose paper is a composite outer layer: cellophane/polyethylene or polypropylene, cellophane/aluminum foil/polyethylene, cellophane/polyethylene/paper/polyethylene; (2) aluminum foil as the outer layer of the composite material: aluminum foil/polyethylene, Aluminum foil/paper/polyethylene; (3) Plastics as composite outer layers: polyester/polyethylene, polyester/aluminum foil/polyethylene, polypropylene/polyethylene, polypropylene/glassine/polyethylene, nylon/polyethylene , PVC / polyethylene, polypropylene / polyvinyl acetal / polyethylene.

2.2 According to the laminating method of flexible packaging composite film, laminating methods for selecting adhesive composite film are generally wet lamination, dry lamination, hot melt lamination, co-extrusion lamination, extrusion lamination, etc. According to these methods and Process characteristics, choose different types of adhesives.

2.2.1 Wet lamination process for composite flexible packaging

The water-based adhesive is applied to the first surface to be bonded. When the surface is wetted, the other surface is closed, pressed by a pressure roller, and then dried by heating. Select the type of adhesive, mainly starch, tyrosin, polyvinyl alcohol, sodium silicate and other aqueous solutions, and polyvinyl acetate, ethylene-vinyl acetate copolymer, polyacrylate and other emulsions, natural rubber, butyl rubber, polyisobutylene And other rubber latex. In wet laminating, since the adhesives are all water-containing, the adhesive film is dried, and at least one of the adherends is a water-permeable material such as paper, fabric or cellophane, for example for paper/glass paper, paper/aluminum foil, Paper / plastic, cloth / aluminum foil and other composite film manufacturing. The adhesive used for wet laminating is less expensive, but the bonded material is subject to certain restrictions, and in particular, it cannot be adhered with a plastic film, and therefore has great limitations.

2.2.2 Dry lamination of composite flexible packaging

Dry lamination is an important method for lamination of paper, aluminum foil, plastic film, etc., especially suitable for lamination of same or dissimilar plastic films, such as polyester/polyethylene, nylon/polyethylene, polypropylene/polyethylene , polyester / poly foil / polyethylene, glass paper / aluminum foil / polyethylene composite film. Its process method is to apply the adhesive solution on the first block, dry it by opening it, close the second block, and pressurize it under heating to obtain the finished product. The application of the adhesive can take the form of a squeeze roll, a counter roll, a photographic roller, an air knife, and the like. When open and dry, in order to prevent curling, a horizontal arch tunnel dryer can be used. Hot air can be used as a heat source or a far-infrared heater can be used. When laminating, the steam heating roller and the rubber roller are used for uniform pressurization. As the binder for dry lamination, rubbers and thermoplastic resins (vinyl acetate resins, vinyl chloride-vinyl acetate copolymer resins) have been used in the past. Since the softening point is low, the film peels at the time of shrinkage and the shortcomings such as local peeling occur at the time of heat sealing (150° C. to 200° C.), so later two-component thermosetting resins such as acrylic resin and epoxy resin are frequently used. , polyurethane and so on. However, the heat resistance of the acrylate is not ideal; the epoxy resin is too brittle to use, the polyurethane has good heat resistance, and the peel strength is high, especially the polyester polyurethane is most commonly used. Polyurethane-bonded composite film with good elasticity, excellent aging resistance, long-term application without peeling over a wide range of temperature and humidity, good heat resistance and chemical resistance, boiled, pasteurized, thermoformed and heated The seals are excellently tolerated.

2.2.3 Hot Melt Laminating of Composite Flexible Packaging Materials

This method has been developed with the advent of hot-melt adhesives and is suitable for the lamination of aluminum foil/paper, cellophane/glassine paper, and aluminum foil/glassine paper. The most original application of hot-melt adhesives is waxes, in addition to modified wax hot melt adhesives such as ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers, polyisobutylene, polybutadiene, and petroleum resins. . The method is that the adhesive in the molten state is coated on the first surface and is directly faced to the second one, and the bonding is facilitated by the cooling roller. The adhesive is generally applied using a gravure roll or impregnation method. South does not require thermal drying, so it has the advantages of simple equipment and simple operation.

2.2.4 Coextrusion lamination of composites

This method is only applicable to the lamination between plastic films, mainly by using the porous head of a plastic extruder (film blowing machine), and by co-extrusion, the different base materials in the molten state are laminated into one body. Thus no adhesive is required. Coextrusion lamination is based on the principle of molecular compatibility. Only the plastics with the same (or at least similar) molecular structure can achieve fusion, such as high-density polyethylene/low-density polyethylene, high-density polyethylene, and medium-density polycondensation. Ethylene/low density polyethylene composite or ethylene propylene copolymer/polyethylene composite and so on. For plastics with completely different molecular structures, it is necessary to add a third substance that can be used as a medium to achieve fusion. When nylon/polyethylene compound, ionic resin can be mixed in the resin. Graft copolymerization with acrylic resin and maleic anhydride can also achieve good results.

2.2.5 Extrusion laminating of composite flexible packaging materials

Extrusion lamination, also known as extrusion coating, is a lamination process without adhesives. The basic condition for this method is that one of the two adhesive surfaces must be a plastic film, such as aluminum foil/plastic. Fabrics/Plastics, Paper/Plastics, Plastics/Plastics. The so-called extrusion lamination is to coat the heated molten resin on another already shaped film-like object through an extruder and laminate it into one body.

2.3 Current adhesives for pharmaceutical flexible packaging films

2.3.1 Polyurethane adhesives

Polyurethane is a kind of block compound whose oligomeric polyol is soft segment, isocyanate and hard segment. Its chemical structure contains various polar bonds such as urethane bond and urea bond, which gives it excellent adhesion. Connection performance and film formation performance. Polyurethane adhesives are used in applications such as ester-soluble polyurethane adhesives, alcohol-soluble polyurethane adhesives, water-based polyurethane adhesives, and solvent-free polyurethane adhesives. The respective performance and characteristics are discussed separately:

(1) Ester-soluble polyurethane adhesives, mostly two-component ester-soluble polyurethane adhesives. The main agent is a hydroxyl group-containing polyurethane polyol modified with an aromatic or isocyanate based polyether or polyester polyol, and the curing agent is a combination of aromatic isocyanate and trimethylolpropane. Its application performance is excellent, the technology is mature, and the variety is also more, but there are still drawbacks, such as high cost, high toxicity, and the large amount of solvent it emits pollutes the environment. The hydrolysis of the composite material may occur over time, releasing a carcinogenic substance TDA ( Aminoethane sulfonic acid diacetic acid) greatly jeopardizes the health of operators. Therefore, as China's environmental awareness has increased, the use of this type of adhesive has been declining. Nowadays, the packaging of such adhesives used in developed countries in Europe and America is from 10 The previous year's 80% dropped to 30%.

(2) alcohol-soluble polyurethane adhesive: It is a low-cost industrial alcohol as a solvent, low production costs, good health performance, harmless to workers, no pollution to the environment, it is suitable for domestic production of flexible packaging for export commodities. Its biggest drawback is that it can only be used up in the day when it is dispensed. If it can only be diluted several times, it can be stored. When it is produced the next day, it will be used as a thinner. If the glue is white or thickened, it cannot be used. use.

(3) Water-soluble polyurethane adhesive: At present, the polyurethane adhesive is mainly based on a solvent type, and the advantage of the aqueous adhesive is that the viscosity does not change significantly with the change of the molecular weight of the polymer, and thus the polymer can be quantified to increase its cohesive strength. Viscosity is generally lower than that of solvent type, easy to mix with other resins or pigments to improve performance, reduce costs, non-flammable, non-toxic, suitable for the substrate easily eroded by organic solvents, easy to formulate formula, easy to clean. The disadvantages are: the drying process is slow, the energy consumption is large, the initial viscosity is lower than the solvent type, the cost is high, and some properties are still inferior to the solvent type.

(4) Solventless Polyurethane Adhesives: The solventless composite process for producing composite film packaging materials has become a mature application technology. In addition to the advantages of using solvent-based adhesives for dry compounding, there are also the following features: no organic solvents are used, the cost is reduced, there is no environmental pollution caused by the volatilization of organic solvents, no solvent evaporation drying process is needed, and energy consumption is reduced; composite products have no residue Solvent problem, and eliminate the solvent erosion of the printing ink; does not contain organic solvents, eliminating the composite substrate vulnerable to solvent and high temperature drying damage, so that the composite membrane structure is dimensionally stable, simple equipment, floor space Small, saving investment.

2.3.2 Thermoplastic Elastomer Adhesives

The main raw material of this thermoplastic elastomer is: SBS (Styrene-Butadiene-Styrene Block Copolymer) The product is a one-component package, easy to use, characterized by: long service life, after bonding in 100` °C boiled in water for 1h without peeling, no hardening in 0cc environment, no deinking, no effect on printing ink; good drying performance, when the composite film is not heated, 24h can completely dry, transparent, and suitable for All kinds of film; non-toxic, no odor, no pollution, in line with the food and drug hygienic requirements, the production process does not produce harmful substances that pollute the environment.

3 Drugs Blister Packaging Adhesive Types and Performance

Adhesives used in pharmaceutical blister packs