Requirements and types of packaging adhesives for

2022-07-23
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Requirements and types of pharmaceutical packaging adhesives

adhesives are also called adhesives. There are many kinds of adhesives sold in the market. The adhesives described in this paper are mainly used in the field of pharmaceutical or food packaging, such as the adhesives used for medical plastic film compounding with metal aluminum, compounding with plastic, and hot pressing of medical aluminum foil and PVC

(I) basic requirements for adhesives in drug packaging

good safety and health performance. It shall be free of odor and non-toxic. If the drug directly contacts the adhesive, the packaged drug shall also be free of corrosion. Since the products protected or packaged by the drug packaging materials are imported directly, not only the base materials should be tasteless, odorless and non-toxic, but also the adhesives used should have the same performance. Therefore, the raw materials, auxiliary materials and solvents for the production of adhesives should be safe and hygienic

excellent adhesion. Due to the different materials of packaging materials, adhesives are used to bond them. The adhesives must have excellent adhesion to different materials. There are many kinds of base materials with different properties used in pharmaceutical packaging composites, such as paper, fabric, aluminum foil, plastic, etc. plastics have many brands, and their surface properties and molecular structures are different. In the face of so many and complex materials, the adhesive must have the performance of sticking to more than two different materials at the same time

excellent chemical resistance and medium resistance. The chemical composition of the drug itself is very complex. After packaging, it has to undergo high-temperature treatment and long-term storage. To maintain the integrity of the packaging materials, in addition to the excellent chemical resistance and medium corrosion resistance of the substrate itself, the stability of the adhesive is also very important. It must be able to resist the corrosion of various media and chemical components, otherwise the composite will be stripped and lose its function

good softness. When using flexible packaging composite materials to package drugs, it is very important that the packaging is soft and easy to carry. It should be foldable, and the adhesive should also have this property. If the adhesive film is hard, brittle and not foldable, it will lose the performance of flexible packaging if it does not match with the substrate

(II) types and properties of adhesives for drug packaging

pressure sensitive adhesive

pressure sensitive adhesive is suitable for paper and plastic film, such as PVC, polyethylene, polypropylene, polyester, polytetrafluoroethylene, polyimide, cellulose acetate, etc. Metals such as aluminum foil, copper foil, lead foil, etc

the main components of pressure-sensitive adhesive include synthetic resin adhesive (including natural rubber, synthetic rubber, cellulose, polyacrylate), adhesive (rosin, rosin ester, various petroleum resins, epoxy resin or phenolic resin when their own laboratories introduce standard methods into their own testing work), plasticizer (chlorinated paraffin, benzoic acid), antioxidant, stabilizer, cross-linking agent Colorants and fillers, etc

the early pressure-sensitive adhesives were all made of natural rubber as the main component. The formula was a mixture of 100 parts of natural rubber, 75 parts of polypinene resin (melting point 70 ℃), 5 parts of petroleum resin and 2 parts of trimethyl dichloroquinoline. The other formula is composed of 100 parts of plasticized cigarette rubber, 50 parts of zinc oxide, 75 parts of hydrogenated rosin and a small amount of tackifier and plasticizer. Later, synthetic rubber and synthetic resin were used to replace natural rubber, among which acrylate and its copolymers were most widely used, such as acrylic acid copolymer lotion high-strength pressure-sensitive adhesive, The proportioning manufacturing method is to mix 100 parts of butyl acrylate 2-ethylhexyl acrylate vinyl acetate copolymer lotion (composition ratio: 50:17:33) with 43% solid content and 30 parts of ethylene vinyl acetate vinyl chloride copolymer lotion (composition ratio: 19:36:45) with 50% solid content, apply it to the polypropylene film treated by corona discharge, and dry it at 110 ℃ for 1 minute to prepare pressure-sensitive adhesive tape. The peel strength of this tape to stainless steel is 600g/25mm

with the increasing requirements for the hygienic performance of drug packaging materials, the additives added to the natural rubber adhesive have peculiar smell and some are toxic, which have not been used in the composite packaging of drugs and foods. However, acrylate pressure-sensitive adhesive still has certain advantages. For example, because it is a single component, it will not be cross-linked and cured, it does not need to be mixed, it is easy to use, and the unused glue solution will not be recycled overnight or for a longer time. It can be stored as long as it is sealed without air leakage. Moreover, the surface condition of the adherend is good. Many non-polar materials, such as plastic and metal materials, can stick firmly even with small surface tension. However, due to the wide variety of materials in composite drug packaging, enterprises have turned to two-component polyurethane adhesive for the composite of polar plastic materials and non-polar materials

polyurethane adhesive

polyurethane adhesive has high elasticity. Compared with other flexible adhesives, it has better heat resistance, solvent resistance, cold resistance, chemical resistance, oxidation resistance and ozone resistance. It has good affinity for metal, plastic, wood, rubber and fabric, so it is widely used, especially in the field of medicine and food packaging. The most widely used are plastic and plastic composite, metal and plastic composite, hot pressing of blister packaging, etc

polyurethane adhesives were first used in the 1960s, when food composite packaging was just launched. When they were used as adhesives, they were mainly divided into polyisocyanate, urethane prepolymer and isocyanate modified polymer according to their composition

polyisocyanate

triphenylmethane p-triisocyanate, hexamethylene diisocyanate, diphenylmethane-4, 4-diisocyanate or toluene diisocyanate are usually used. These polyisocyanates are rarely used alone, and are mainly used as a crosslinking agent for rubber adhesives, or as a curing agent for polyester and polyether polyhydroxy compounds. The polymers used with it include polyacrylate, epoxy resin, xylene resin, polyphenylamine resin, etc

carbamate prepolymer

it is the product of partial reaction of polyisocyanate and polyhydroxy compound. Because the end group of this polymer has NCO group, it can be cured in the presence of appropriate curing agent or through the moisture of air to make a one component adhesive

isocyanate modified polymer

is a linear polymer with hydroxyl groups at the end groups, which is also called thermoplastic polymer, by the reaction of diisocyanate with polyester or polyether with more than two functions. According to the dosage form, polyurethane adhesive can be divided into single component and two-component, and the latter is better than the former in terms of bonding strength. Two component component A is mainly isocyanate modified polymer, and component B is also the introduced urethane prepolymer. The polyols are mainly castor oil or polyethylene glycol. The single component can be divided into two categories. One category directly uses component a of the two components, i.e. isourethane modified polymer; The other is the carbamate formed by the reaction of diisocyanate and ethylene glycol, which has the inherent good adhesion of ethylene glycol, a short chain compound

development trend of adhesives for drug packaging

at present, the pressure-sensitive adhesive for drug composite packaging materials has been replaced by polyurethane adhesive, mainly ester soluble polyurethane adhesive. This kind of adhesive is a two-component ester soluble polyurethane adhesive. Its main agent is polyether or polyester polyol modified by aromatic isocyanate, which contains hydroxyl polyurethane polyol. The curing agent is a composite of aromatic isocyanate and trimethylolpropane. This kind of adhesive has excellent performance, mature process and many varieties, but it is toxic and costly. A large number of solvents emitted by it pollute the environment. The composite material may be hydrolyzed for a long time, releasing a carcinogen TDA (aminoethanesulfonic acid diacetic acid), which seriously endangers the health of operators. With the increasing awareness of environmental protection, the use of this adhesive is declining. At present, the use of such adhesives in packaging in developed countries in Europe and the United States has dropped sharply from 80% 10 years ago to 30% today. Alcohol soluble polyurethane adhesive has the advantages of using industrial alcohol as solvent, low production cost, good sanitary performance, no harm to workers and no pollution to the environment. Its disadvantage is that it can not withstand 100 ℃ high temperature and can not package highly corrosive products. The glue prepared in the production process can only be used up on the same day. If the remaining glue can only be diluted and stored, it can be used as a diluent in the next day's production. Do not use if the glue has turned white or thickened

adhesives based on water-soluble or water dispersible solvents are called waterborne polyurethane adhesives. Their advantages are that water replaces organic solvents, there is no potential danger of combustion and explosion, and the cost is low. However, the performance of this adhesive is poor, and the wettability of the adhesive liquid to the substrate bonded by the adhesive is poor, because the surface tension of water is 72Mn/m, while the surface tension of the substrate is only 40Mn/m, which is quite different, incompatible, and the adhesive force is not high. In addition, the heat capacity of the external water is large and needs to be dried, so more energy is consumed, the cost is increased, the production speed is low, and some properties are worse than those of the solvent based adhesive

the adhesive for pharmaceutical composite materials is developing towards the solvent-free type. The solvent-free adhesive is basically composed of two-component polyurethane adhesive. Its main agent and curing agent have high viscosity and fluidity at room temperature. When compounding, the main agent and curing agent are mixed in proportion and rolled onto the substrate after heating. Because no organic solvent is used, the cost is reduced, and there is no environmental pollution caused by the volatilization of organic solvent. The huge drying, heating and blowing devices and waste gas emission devices of the equipment are omitted, and the energy consumption is reduced. The product has no residual solvent damage, improved production speed, low maintenance cost, obvious benefits, and also consumes a lot of natural resources. It has a promising application prospect in the field of pharmaceutical packaging

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