Material selection of the most popular high temper

2022-08-02
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The material selection of high temperature cooking resistant gravure composite ink in the formulation

1 preface

China's flexible packaging technology has developed rapidly, the level has been continuously improved, and the flexible packaging materials are made in a variety of styles, among which the composite flexible packaging materials have become one of the more mature main packaging materials in China. For example, the film substrates used include pet, BOPP, VMPET, VMCPP, PE, CPP and al. In the future, the trend of flexible packaging will be towards high barrier and high temperature cooking resistance. In particular, the external flexible packaging materials for food, drugs, etc. require high-temperature anti-virus, environmental protection, sanitation and other high-performance, so it is required to have composite printing inks that meet such high-performance conditions and are suitable for high-temperature cooking. As a result, high temperature cooking resistant Gravure plastic composite ink came into being

2 high temperature cooking resistant Gravure plastic composite ink and its characteristics high temperature cooking resistant Gravure plastic composite ink is made by evenly stirring, dispersing and grinding, adjusting viscosity and color by using relevant chloroacetic resin and special polyurethane as binder, adding a series of special additives and organic solvents, and matching with organic pigments with high temperature resistance. It is suitable for printing in low-speed to high-speed plastic films. The base materials are generally composite plastic films such as pet, BOPP, nylon and aluminized film. The products after printing can be used in both common composite process and high-temperature cooking composite process. The ink film solvent residue is low, odorless, non-toxic, environmentally safe, and can be used in the packaging of food and drugs, which meets the health requirements

high temperature cooking resistant Gravure plastic composite ink has the following characteristics:

① high adhesion fastness, suitable for a variety of printing films; ② Low viscosity, good leveling, high solid content, bright color, high color concentration, good point reproducibility, suitable for chromatic printing of layered edition; ③ Good printability, good ink transfer, suitable for different machine speeds and plate depths; ④ Prints can withstand high-temperature cooking. Generally, when a single component is used, it can be boiled in water to (90 ~ 100) ℃ and boiled in high temperature to (100 ~ 120) ℃; The addition of 3% ~ 4% curing agent during two-component printing can improve the high temperature resistance, film-forming performance, printability, composite fastness and so on

3 key points for formulation design

3.1 selection of binders

experience the viscosity, fluidity, dryness, transfer, gloss and fixation of inks are mainly determined by binders, and their acid-base resistance, high-temperature cooking resistance and other characteristics are also closely related to the properties of binders. Therefore, the research and selection of binders are the key points in the development of high temperature cooking resistant Gravure plastic composite ink formulation. At present, it can be used as a binder for the formulation of high-temperature cooking resistant Gravure plastic composite ink. The only resins that can improve the ink body are chloroacetic acid resin and polyurethane resin. The real name of chloroacetic acid resin is the copolymer of vinyl chloride (VC) and vinyl acetate (VAC). In essence, it is a dry paint base. After the volatile organic solvent contained in the formula evaporates, a film is formed. In the formulation of high-temperature cooking resistant Gravure plastic composite ink, the chloroacetic resin with high toughness, long-lasting flexibility, wear resistance, low water swelling, low permeability and high-temperature cooking resistance after film formation is generally selected. As gravure inks are applied to various plastic film substrates, the surface of these plastic films is smooth. Therefore, when selecting this type of chloroacetic resin in the ink formula, the type with carboxyl (- COOH) in the chloroacetic resin molecules should be considered. Therefore, this kind of chloroacetic resin has good adhesion on the substrate with smooth surface, especially on the substrate such as aluminum foil. Therefore, the trimer of vinyl chloride and vinyl acetate containing carboxyl group and dicarboxylic acid (i.e. ternary vinyl chloride acetate resin) is one of the essential binders in the formulation of high temperature cooking resistant Gravure plastic composite ink. Ketones, esters and chlorinated hydrocarbons are common solvents for chloroacetic acid resins containing carboxyl groups. The ternary chloroacetic acid resin used for printing ink is generally mixed with butanone, isopropanol, ethyl acetate, toluene, etc. to prepare chloroacetic acid resin solution with a solid content of about 20% from the binding solvent on the impacted surface 1 of 10 samples, which is stored in Karen barrels or oil storage tanks for use. Polyurethane plastic (PU), with the chemical name of polyurethane foam, is a foam obtained by the reaction of polyurethane monomer resin liquid with polyether polyol or polyester polyol through catalyst and other additives. According to the composition of raw materials, it can be divided into polyether type and polyester type, with soft and hard parts. The polyurethane resin used in the ink formula is only the monomer component of the above-mentioned polyurethane plastic (PU). It is modified and mixed with ketones, esters and other organic solvents. The solid content is generally about 30%, colorless or light yellow transparent viscous liquid. As the binder of ink, the molecules of this kind of polyurethane resin liquid generally contain - NCO group, and the degree of polymerization of the molecules is less, but the molecular structure is complex and there are many kinds. Among them, the simple monomers are toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polyphenyl polymethyl polyisocyanate (Papi) and trihydroxypolyether (glycerol polyether). The polyurethane binder for printing ink sold on the market is the modified polyurethane monomer resin liquid, which introduces some important molecular functional groups, so that it can measure the progress of the development of new materials through a series of data. After the film is formed, it has various excellent properties. In particular, after reacting with some curing agents (mainly polyether or polyester polyol compounds), it can produce ink films with different properties, such as soft, high tensile strength, good oil and solvent resistance, excellent heat insulation and barrier properties, etc; In particular, the CIRA property of high-temperature cooking resistance is the main factor to consider when designing the formula of high-temperature cooking resistance gravure plastic composite ink. When selecting the polyurethane resin solution for ink, it is required that the ink has excellent adhesion with the plastic film, the ink film has good heat and water resistance, good solvent release, less residue, good wettability to the pigment, and high gloss. The polyurethane resin liquid for printing ink sold on the market is mostly composed of polyurethane compound, isopropanol, butanone, toluene, etc. the appearance is colorless or light yellow transparent viscous liquid, and the solid content is generally 25% ~ 35%; The addition amount in the ink formula is usually 35% ~ 45%

3.2 selection of pigments high temperature cooking resistant Gravure plastic composite ink has a series of special requirements for pigments:

① bright colors; ② Good gloss; ③ Coloring power should be high, which is the condition to measure the use significance and economic value of pigments; ④ Transparency and hiding power are good. According to the different uses of the ink, there are different requirements for the transparency and hiding power of the pigment; ⑤ The oil absorption should be small, so that the ink concentration can be easily improved and the ink property can be easily adjusted; ⑥ The dispersibility of pigment in ink binder directly affects the success or failure of ink preparation; ⑦ There are few pigments with other physical and chemical properties, such as light resistance, heat resistance, solvent resistance, acid and alkali resistance, migration resistance and so on. Only according to the special requirements of application, select the appropriate varieties. The pigments used for high temperature cooking resistant Gravure plastic composite inks should first be solvent resistant, and then have high temperature cooking resistance. They can withstand high temperatures above 160 ℃ without decomposition and discoloration. According to the standard, all the black pigments used in the ink are carbon black; Most of the white pigments are rutile titanium dioxide; Color inks should be tested and selected conditionally, such as condensed azo, benzimidazolone azo, phthalocyanine blue and phthalocyanine green after pigmentation, which can withstand high temperature of 200 ℃ without discoloration

3.3 selection of wetting and dispersing agent

the wetting and dispersing of pigments is an important link in the manufacturing technology of high-temperature cooking resistant Gravure plastic composite ink. The pigments are crushed into fine particles, which are evenly distributed in the ink binder, in order to obtain a stable suspension mixing system. The dispersion of pigments in ink is very complex. It is generally considered that there are three related processes: wetting, crushing and stabilization. Wetting refers to the process that resin liquid, organic solvent or additive are used to replace the adsorbed substances on the pigment surface, such as air and moisture, that is, from solid/gas interface to solid/liquid interface; Comminution refers to the use of mechanical force to disperse the agglomerated secondary particles into fine particles close to primary particles, forming a suspended dispersion; Stability refers to that the formed suspended dispersion can still be in a dispersed suspension state when it is knocked and abnormal without external force. Wetting and dispersing agent is a special surfactant, which has two functions of wetting and dispersing pigments. Its wetting and dispersing function is to reduce the surface tension of substances, make the molecules of surfactants adsorb on the surface of pigments, so as to generate charge repulsion or steric hindrance, prevent harmful flocculation of pigments, and keep the dispersion system in a stable suspension state. The dispersant used for high temperature cooking resistant Gravure plastic composite ink is generally an anionic surfactant. Its main component is carbonate or special metal aluminum chromium compound, light yellow or yellowish brown liquid. It is an oil soluble dispersant, which can improve the dispersion of pigments in the ink, prevent the overflow and discoloration of pigments in the ink, improve the color concentration and color development, and enhance the adhesion and composite fastness between the ink film and the plastic film

3.4 selection of wax powder some special wax powder is usually added to the formula of high temperature cooking resistant Gravure plastic composite ink, which can provide excellent abrasion resistance and scratch resistance for the printing ink film, prevent sticking, increase the fluidity of the ink, improve the printability and improve the post-processing performance. Because the diameter of the wax powder particles is about 5m, which is larger than the diameter of the pigment particles and the thickness of the ink film, the wax powder particles can protrude the ink film and make the surface of the ink film rough. When the ink on the plastic film printing is rolled up and placed for a long time, the rough ink film is conducive to preventing the back adhesion, and is also conducive to the uniform coating of the post-processing glue to enhance the composite fastness. Adding wax powder to the ink can also eliminate the defect that the ink is easy to fall off on the roller in the process of high-speed printing. High temperature cooking resistant Gravure plastic composite ink formulations mostly use the molecular straight chain synthetic polyethylene wax with high melting point and strong hardness. There are two ways of pre addition and post addition, and the general addition amount is 1% ~ 2% of the total weight of the ink. Normally, it is added before ink grinding, which is conducive to dispersion and improve fluidity. Pay attention to the grinding temperature not to be too high, so as to avoid deformation and condensation of wax particles, which will affect the performance. It is also made into paste with resin and organic solvent, which is added in the viscosity adjustment and color matching stage of ink making. However, in this way, it is necessary to prevent some organic solvents with strong permeability from dissolving wax particles, resulting in recrystallization and coarsening, thus losing due performance

3.5 selection of antistatic agents during high-speed printing, the accumulation of static electricity in Gravure plastic ink will cause offset, blur, spots, beard, edge rejection and other problems, and even fire, explosion and other malignant events. Therefore, the purpose of adding antistatic agent to the ink is to reduce the surface resistance of plastic film in the printing process and eliminate static electricity to solve the above problems in printing. Anionic antistatic agents are generally used in plastics and inks, including higher fatty acid salts, alkyl phosphate salts, alkyl sulfate salts and sulfonate salts. These compounds can be dissolved in water, ketones, alcohols, benzene and other organic solvents. The products are

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