The strengthening of national environmental awareness. On the one hand, the whole society advocates clean production, requiring that the entire life cycle of products should achieve energy saving, consumption reduction, pollution reduction, and efficiency enhancement measures; on the other hand, in order to meet the needs of green packaging, packaging is required The product is safe and hygienic, has good adaptability to environmental protection, and can save resources. The production and use of paper cups are in line with the national environmental protection policy. Replacing disposable plastic cups with paper cups reduces "white pollution". The convenience, hygiene and low price of paper cups are the key to replacing other utensils and occupying the market widely. Paper cups are divided into cold drink cups and hot drink cups according to their uses. In addition to meeting the needs of packaging and processing performance, the materials of paper cups must also meet their printing adaptability. Among the many factors in printing technology, the conditions for heat sealing of paper cup processing must also be met. The following is a discussion on the material composition and printability of paper cups.
1 Composition of paper cup material
The production process of the cold drink cup is directly printed, die-cut, formed, and double-sided over-laminated from the paper cup base paper. The process of making hot drink cups is to make paper cup paper from paper base paper by laminating, printing, die cutting and forming.
1.1 Composition of paper base paper
The paper cup base paper is composed of plant fibers. The manufacturing process is generally to use conifer wood, broad-leaved wood and other plant fibers through pulping pulp board to disperse, grind, add chemical auxiliary materials, screening, paper machine making, etc.
1.2 Composition of paper cup paper
The paper cup paper is composed of paper cup base paper and plastic resin particles extruded and compounded. The plastic resin generally uses polyethylene resin (PE). The paper cup base paper is coated with single-sided PE film or double-sided PE film to become single PE cup paper or double PE cup paper . PE has its own non-toxic, odorless and tasteless; reliable hygienic performance; stable chemical performance; balanced physical and mechanical properties, good cold resistance; water resistance, moisture resistance and certain oxygen resistance, oil resistance; excellent molding performance and very good The heat sealing performance and other advantages. The production volume of PE is large, the source is convenient, and the price is low, but it is not suitable for high-temperature cooking. If the paper cup has special performance requirements, plastic resin with corresponding performance is used when laminating.
2 Printability of paper cups
2.1 Requirements for the base material of paper cups
2.1.1 Surface requirements of paper cup base paper
Directly printed paper cup base paper should have a certain surface strength (wax stick value ≥ 14A) to prevent fluffing and powdering during printing; at the same time, it must have a good surface fineness to meet the uniformity of the ink on the printed matter.
2.1.2 Surface treatment before printing
The surface of the base paper or base film to be printed must be clean, dry, smooth, dust-free, and oil-free. For non-polar, dense and smooth PE materials, the surface tension is low, only 29 ～ 31mN? M-1, corona treatment must be carried out in advance to change the surface state, the surface tension is increased to 40mN? M-1, at least 38mN? M-1, so that the printing ink can reach a certain fastness degree.
2.2 Requirements for printing ink on paper cups
Printing inks used in paper cups require good printing fastness. The printed matter has good acid resistance, alkali resistance, water resistance, temperature resistance, and light resistance. It will not fade, change color, or fall off due to these factors; in addition, the printed matter must have good Scratch and gloss, semi-matting and matting.
3 Paper cup printing technology (supplements other than general printing technology)
3.1 Ink components: The components of the ink must comply with the Food Sanitation Law and the corresponding food packaging hygiene standards.
3.2 Residual solvent: Control the amount of residual solvent to be small to prevent the printed product from generating odor. The back of the printed product is dirty. When the solvent adheres to the base material or base film of the seal, it will cause poor heat seal and form a seal. Poor adhesion or bulging caused by poor adhesion.
3.3 Drying temperature: The drying temperature of the ink should not be too high. When the temperature is too high, the surface of the base film will be over-oxidized, resulting in poor heat sealing. However, it is also necessary to prevent poor printing ink drying to avoid odor.
3.4 Selection of ink and ink solvent: the selected ink solvent should not swell the PE film or contain water in the solvent as much as possible to prevent the printed matter from curling; as far as possible, the ink containing plasticized free carrier should be selected to prevent the ink film and PE film from being affected by temperature The shrinkage caused by the change is different, resulting in curling of the printed matter. The curled printed matter will be warped after being die-cut into a fan-shaped piece, which makes it difficult for the paper cup to convey and form the curl when forming the cup.
3.5 Ambient temperature and humidity: too high humidity in the workshop will cause curling of the printed matter. If the temperature of the roll film after printing is too high, adhesion between the upper and lower two layers of film will occur, which will also affect the subsequent processing of the paper cup.
4 Paper cup processing performance
According to the processing performance and use performance of the paper cup, the paper cup base paper must have the following technical requirements:
4.1 Strong water resistance: no water leakage or leakage in the paper cup.
4.2 Ease of processing and formability: In order to avoid paper jams and wrinkles during the production process and the paper cups are not easily deformed after forming, the paper base paper is required to have high stiffness, good flatness, proper bulkiness, and easy processing and forming .
4.3 Fineness of paper surface: It is required to control the surface roughness value of the printing surface of the base paper to be printed or the film PE to meet the surface fineness of the paper cup surface printing requirements.
4.4 High whiteness: Under the premise that no fluorescent agent is used, the base paper should maintain the corresponding whiteness of the paper to ensure that the printed patterns are clear and beautiful.
4.5 High safety and hygiene: Paper cup base paper and paper cup products are regularly sent to the local national health and epidemic prevention system for sanitary safety testing to ensure the safety of users. The paper cup base paper meets the "Hygienic Standards for Food Packaging Base Paper" (GB 1 1680) The paper cups and papers comply with the "Hygienic Standards for Polyethylene Molded Products for Food Packaging" (GB / T 9687). At the same time, products (including special plastic particles) must also be sent to relevant institutions for lZDA quality testing to ensure that they meet the national regulations in terms of health and safety. Hygienic standards and meet the requirements of foreign users.
4 Conclusion
Paper cups are food packaging materials that are in direct contact with the population and must meet hygiene standards in terms of hygiene. The continuous sealing process of paper cups and the heat sealing performance and printing on the PE film surface require that the printing technology must be mixed with the paper cup performance. Suitable factors such as ink composition, residual solvent amount, and moderate drying conditions.
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