Application analysis of the hottest aluminum foil

2022-08-05
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Application analysis of aluminum foil gravure printing materials

blister packaging of drugs is also known as "blister eye" packaging. It is one of the main flexible packaging forms of solid dosage forms such as tablets, capsules and pills. Because this packaging form has many advantages, it is deeply valued by pharmaceutical enterprises and welcomed by drug users, and its application is becoming more and more common. Blister packaging is to place the drug in the pit (called blister or blister eye) of the plastic hard sheet formed by suction molding, and then use a printed aluminum foil coated with protective agent and adhesive to bond and seal with the plastic hard sheet, so as to protect the drug. Drug blister packaging materials include: materials coated with protective layer and adhesive layer, called protective agent and adhesive; Medical aluminum foil printing materials; PVC (polyvinyl chloride) is the most widely used plastic hardening material in China, which can print words and patterns on aluminum foil. Pharmaceutical blister packaging was developed in Europe in the 1930s. The blister packaging materials used in China in the early 1970s were mainly imported. In the 1980s, Guangzhou, Lianyungang, Jinzhou and other places in China successively introduced Japanese pharmaceutical aluminum foil gravure coating equipment and its application technology, but the main materials such as substrate aluminum foil need to be imported. By the 1990s, China has been able to manufacture monochrome or multi-color aluminum foil printing and coating equipment, and can print gold series of aluminum-plastic products for external packaging of drugs, while the pharmaceutical aluminum foil materials, printing inks for aluminum foil, protective agents for aluminum foil and adhesives used in blister packaging have been localized and can meet domestic needs

1 application status of aluminum foil printing materials

printing material aluminum foil is a sealing material sealed on the hard medical plastic sheet, also known as capping material. Its surface can be printed with words or patterns, and the electronic universal testing machine for both front and back insulation materials has good printing performance. Aluminum foil material is made of 99% electrolytic aluminum by means of post-processing. It is non-toxic and tasteless, with high-quality conductivity, shading, high moisture resistance and gas resistance. Because aluminum foil has a highly dense metal crystal structure, it can completely block any gas. In modern packaging, almost all composite flexible packaging materials requiring shading or high barrier use aluminum foil as barrier material. The aluminum foil used in the pharmaceutical blister packaging and printing is made by using industrial pure aluminum foil as the base material, printing patterns on the pharmaceutical aluminum foil printing and coating machine, and coating adhesive on one of the surfaces. The thickness of aluminum foil used is 0.02mm. Its adaptability to printing and quality indicators mainly include: the number of pinholes in aluminum foil, the heat sealing strength of adhesive layer, and the abnormal toxicity of one-component polyurethane waterproof coating (and one-component polyurethane paint) due to its convenient construction and simple operation, the adhesion, heat resistance, rupture strength, volatile matter, easy oxide and heavy metal content. These indexes can ensure that the aluminum foil has good barrier, sanitation, heat sealing and good mechanical strength after printing. At present, there is still a gap in the application of aluminum foil in China compared with imported products in terms of quality, which is mainly reflected in the following aspects:

1. The number of pinholes of medicinal aluminum foil can not meet the use requirements. The number of pinholes in aluminum foil is a penetrating defect, which seriously affects the barrier property of aluminum foil. Especially when applied to the outer packaging of drugs, it is easy to let oxygen, water vapor and light penetrate and reduce the efficacy. The national standard for medicinal aluminum foil requires that aluminum foil shall not have pinholes with a diameter greater than 0.3mm, and there shall be no more than one pinhole with a diameter of 0.1mm ~ 0.3mm per square meter. At present, domestic aluminum foil rarely meets this standard

2. Domestic medicinal aluminum foil has uneven thickness and low tensile strength. Different thickness will affect the uniformity of the coating amount of the adhesive, and then affect the thermal bonding strength of the aluminum foil and the plastic hard sheet. The low tensile strength will cause the aluminum foil to break after the tension is applied during the unwinding and winding of the aluminum foil during the printing process, and the continuous printing operation cannot be carried out

3. Residual oil stains on the surface of aluminum foil. As the aluminum foil is cooled and shaped by oil in the process of calendering and drawing, there are often oil stains in the finished aluminum foil. This kind of oil stain on the surface will affect the adhesion between aluminum foil printing ink and protective agent and aluminum foil material, resulting in a series of quality problems, such as unclear handwriting, peeling of protective agent and aluminum foil, etc. Especially when the aluminum foil surface is coated with gold or printed with color patterns, due to the existence of oil stains on the aluminum foil surface, the words and patterns have almost no adhesion with the aluminum foil, resulting in color fading and word dropping, which seriously affects the product quality. At present, the consumption of medicinal aluminum foil is increasing year by year. It is expected that the consumption will exceed 5000 tons in 2002. It is used not only for the solid packaging of Chinese and Western tablets, capsules and pills, but also for the packaging of health products, and a large number of them are used for the outer packaging of injection boxes

2 varieties of aluminum foil gravure printing inks

at present, there are many kinds of printing inks in the market, with different brands. However, considering the special requirements of the printing process and drug packaging of medical aluminum foil, the ink for aluminum foil must meet the following requirements: good adhesion to aluminum foil, clear and firm printed words and patterns, fast solvent release, good heat resistance, excellent friction resistance, good gloss, and non-toxic pigments, The chemical components in the ink will not migrate and pollute the packaged drugs, and the viscosity meets the requirements of aluminum foil printing process. Based on these factors, the inks suitable for aluminum foil printing are mainly divided into two categories: the first is alcohol soluble polyamide inks. Because polyamide resin has good adhesion to various substrates, it is especially suitable for printing polyolefin plastic films. In addition, it has good dispersion, high gloss, softness, good wear resistance, good solvent release and printing performance, so it is widely used for surface printing of LDPE, CPP and OPP films. This kind of ink is also used for aluminum foil printing because of its anti adhesion, easy drying and heat resistance. However, since this kind of ink is not a special ink for aluminum foil printing, peeling may occur during large-area aluminum foil printing. At present, domestic manufacturers have produced polyamide inks for aluminum foil gravure printing. In the high temperature heat sealing experiment at 200 ℃, the printed words and patterns are still clear and do not change color. The second type is the special ink for aluminum foil with vinyl chloride, vinyl acetate copolymer resin and acrylic resin as the main components. This intaglio printing ink is characterized by bright color, high concentration, especially strong adhesion to aluminum foil, good transparency, and excellent metal luster reproducibility of aluminum foil. However, due to its high solvent volatility, it is easy to cause the intaglio printing ink to dry in the ink hole when it is used for printing on the surface of aluminum foil, resulting in paste phenomenon. At the same time, it is easy to form skin in the ink tank, resulting in color patches on the surface of aluminum foil Color line and other quality problems need to be further improved

3 aluminum can solve the problem of insufficient self owned funds of the company. Protective agent for foil printing adhesive application

the industrial production of medicinal aluminum foil is to apply ink protective agent on the words or patterns printed on the surface of aluminum foil. Apply adhesive to the other side of the aluminum foil. The purpose of coating protective agent on the surface of aluminum foil is to prevent the abrasion of the printing ink layer on the surface of aluminum foil, and also to prevent the pollution of drugs during packaging due to the contact between the outer ink and the inner adhesive layer in the winding process of mechanical operation. The function of the adhesive layer is to make the aluminum foil and the plastic hard sheet bond together after heat sealing, so that the medicine can be sealed. Most of the protective agents used now are solvent-based, and their main chemical components are: nitrocellulose synthetic resin, plasticizer, true solvent, cosolvent, diluent, etc. These ingredients are mixed in a certain proportion, stirred with the reactor to form a solvent, and then coated on the aluminum foil by the printing machine to produce a protective film. The specific requirements for the protective agent are that it has good film adhesion and flexibility with aluminum foil, good transparent gloss, good heat resistance, no residual odor, protects the printing ink layer from falling off, and has high wear resistance. At present, the adhesive used is mainly one component sol or two-component sol. The main component of one component sol is natural rubber or synthetic rubber, which can also be prepared by adding nitrocellulose, acrylic acid and solvent. As the main agent is polymer elastomer, and the tackifier is used as auxiliary agent, the lotion can be prepared by stirring the organic solvent in the reactor. This lotion is non drying and heat soluble. After aluminum foil coating, it has a certain bonding strength. After dry coating, it is thermally bonded with PVC. It has good heat sealing performance. This adhesive has been widely used in production. However, with the improvement of the requirements for the hygiene and sealing performance of drug packaging materials, the trend of using two-component adhesives is becoming more and more obvious. Two component adhesives are polyurethane adhesives, which are mainly composed of main agent and ammonia curing agent. The main agent generally contains many active hydrogen substances such as hydroxybenzene and aminobenzene. The curing agent is composed of polyisocyanate compounds. When the isocyanide in the curing agent contacts with the active hydrogen in the main agent molecule, the addition reaction will be carried out automatically to generate the structure of aminopropyl ester, so that the molecular weight will be doubled after the main agent and the curing agent are combined with each other, and even the cross-linking product with branched chain structure will be generated. It has good high and low temperature resistance, medium erosion resistance and high adhesion. Because polyurethane molecules contain a large number of polar groups, large dipole moment, and have great affinity for bonded materials, it plays an important role in aluminum foil, plastic and other packaging materials. In addition, isocyanate in the curing agent is a very active reactive group, which can react with the active hydrogen in the main agent molecule, and also with the active hydrogen in the surface substance molecules of the bonded material to form chemical bonds, so that the adhesive molecules can act as a bridge with the bonded material to produce a stronger adhesive force. Because of its high adhesive strength, this kind of adhesive is widely used in aluminum-plastic composite packaging and various plastic film composite flexible packaging products. In the future, the application of adhesive for aluminum foil coating will gradually develop in the solvent-free direction. Its composition is also a two-component polyurethane adhesive type. The difference is that the main agent and curing agent have high viscosity at room temperature, but they still have rolling properties and are semi-solid substances. When used, the main agent and curing agent are mixed in proportion in a container with heating and insulation function, and the viscosity is reduced after heating, Then the gravure roller with heat preservation function is applied to the printed aluminum foil substrate. After gluing, the adhesive can be directly thermally dried without drying channel. Because the adhesive itself has no solvent, it can be directly bonded with another kind of aluminum foil material, so there is no waste gas emission problem, which is conducive to environmental protection. In addition, the printing and coating equipment does not need to be equipped with a huge drying channel heating dryer and air blowing and exhaust device, which can also save equipment investment costs

4 current situation of application of blister hard sheet, which is heat sealed with aluminum foil

at present, PVC (polyvinyl chloride) is the most widely used blister plastic hard sheet in China, with a general thickness of 0.25mm. PVC hard sheet has good processing formability, heat sealing, transparency, barrier and mechanical strength. As the drugs are sensitive to moisture and light transmission, they are also required to have good barrier to moisture, light and odor for hard plastic films. However, the performance of PVC hard sheet in blocking water vapor transmission is not ideal, so it is not suitable for drug packaging with high moisture-proof requirements. In the near future, polyvinylidene chloride (PVDC) composites as pharmaceutical packaging materials will have greater development space. Due to PVDC

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