Abstract : At this stage, the high-temperature resistant retort pouch in China's flexible packaging printing industry is one of the products with high added value, but it requires relatively high printing and post-processing technologies, in which the gravure compound heat-resistant cooking bag ink used for printing is The key printing materials, this type of gravure ink in the research and development and production process requires a relatively complete set of procedures for the selection and detection of ink raw materials, its formula selection and printing performance requires our ink manufacturing staff constantly groping, continuous testing , continuous improvement.

Keywords: plastic flexible bags, composite high-temperature cooking bag ink, formula selection, high chlorine content of ternary chlorine resin, high temperature polyurethane, gravure printing requirements.

prologue

Nowadays, in the current ink industry and printing industry in China, many people concerned about ink and printing industry are interested in discussing the current situation and development prospects of China's alcohol-soluble and water-based gravure printing inks. This is a great good for the development of our country's current ink and printing industry. It also indicates that China's ink and printing technology will leap forward. However, on the soft packaging market in China, some flexible packaging materials with special functions and special purposes are alcohol-soluble and water-based gravure inks, and even ordinary plastic gravure printing inks cannot print these special features. Therefore, some flexible packaging materials that require special applications need special inks for printing. The compound high-temperature retort pouch that we have heard from time to time is one of the flexible packaging materials that have special applications. Therefore, in China's ink market, gravure plastic compound high-temperature cooking bag ink is quietly rising, its special printing function is being recognized by the printing ink market, and gradually accepted and promoted by the printing industry, in some special printing area There is also a certain market within. The formulation of the special gravure printing ink needs some skills in design, and it also requires ink technicians to constantly research and explore and boldly innovate. This article gives a brief introduction to this type of ink formulation design and usage requirements. I hope readers can learn some ideas from them and resonate with them. I also hope that all of my peers can discuss and discuss together, and work together for our ink and printing industry. Some contributions.

Gravure compound high-temperature cooking bag ink formula selection principles

With the continuous and steady development of China's ink and printing industry, China's flexible packaging technology has also developed rapidly, and its level has been continuously improved. The flexible packaging materials produced are of various styles and are emerging in an endless stream. Among them, composite flexible packaging materials have become one of the more mature domestic main packaging materials. . In China's current flexible packaging printing industry, there are NY, PET, BOPP, CPP, RCPP, PE, and AL film substrates used in flexible packaging plastic bags. The future trend of film materials used in flexible packaging printing in China may be toward High barrier property, high temperature cooking resistance direction. In particular, external flexible packaging materials such as foods and pharmaceuticals require high-temperature anti-virus, environmental protection and sanitation performance due to the special requirements of the contents. Since there are so many varieties of flexible packaging materials with different properties on the market, it is essential to have inks compatible with such high-performance conditions suitable for high-temperature cooking-resistant composite printing. Therefore, a solvent-based gravure printing composite high-temperature cooking bag ink came into being. The following is a brief introduction of the factors that should be taken into consideration when formulating designs for this type of gravure printing ink.

1, the choice of cooking bag ink connection material

Solvent type ink connecting material commonly known as resin, is a dispersion medium in the gravure ink, so that the ink toner or other compatible substances are evenly dispersed in the ink system, forming a protective shell around them, so as not to agglomerate Block precipitation phenomenon, so that the ink has a good printability. When the ink is transferred to the surface of the plastic film substrate by the action of a printing press, the organic solvent in the ink quickly evaporates, and the binder resin is immediately fixed on the surface of the film and forms a firm high-temperature cooking ink layer, uniformly spreading the color Powder and pigment granules make the printed product colorful and dazzling. The properties of gravure ink such as viscosity, fluidity, drying property, transferability, ink film gloss and fixing property are mainly determined by the main body connection material. The characteristics of gravure ink film, such as acid and alkali resistance, and high-temperature cooking resistance, are also inseparable from the properties of the main body connection material. Therefore, in the consciousness of ink engineering technicians, the development of the formula design of the gravure compounded high-temperature retort pouch ink is focused on the test selection and production research of the heat-resistant cooking material binder.

According to our development of ink contact with new materials and ink manufacturing processes, we can now qualify the main body resin binder in the formulation of gravure plastic compound high-temperature retort pouch ink, improve ink body bone, improve ink fluid properties, and apply to gravure printing on the machine. Ink resins are nothing more than these two types: high temperature resistant polyurethane resins for gravure inks and trivalent chlorine vinegar resins with high chlorine content and medium viscosity.

High temperature resistant polyurethane resin for gravure printing ink, chemical name polyurethane plastic resin. Abbreviation code in English is PU. It is a liquid resin obtained by reacting a polyurethane monomer resin liquid with a polyether polyol or a polyester polyol through a catalyst and other auxiliary agents. According to the composition of these liquid resin raw materials, it is divided into a polyether type and a polyester type. Kind and soft and hard. The polyurethane resin solution used in our intaglio high-temperature compound ink formulations is only the monomer component of the above-mentioned polyurethane plastic (PU), which is modified and compounded with organic solvents such as ketones and esters or alcohols, and the solid content is generally About 25-35%, colorless or light yellow transparent viscous liquid. As the main binder resin of the gravure high temperature resistant composite ink, it functions as a film to increase the adhesion and dispersion of the pigment to enhance color development. The polyurethane resin liquid molecules generally contain NCO groups, the degree of polymerization of the molecules is less, but the molecular structure is complex and there are many kinds, among which the simple monomer has toluene diisocyanate (TDI) and diphenylmethane diisocyanate. (MDI), polyphenyl polymethyl polyisocyanate (PAPI), trihydroxy polyether (glycerol polyether). Polyurethane adhesives for printing inks sold in the market are modified polyurethane monomer resin liquids, which generally introduce some important molecular functional groups in the molecules, making them excellent performances after being printed into an ink film. . In particular, it reacts with certain curing agents (mainly composed of isocyanate prepolymers or polyether or polyester polyol compounds) to produce unique ink films with unique functions and properties, such as soft, lightweight and high stretch. Strength, better oil and solvent resistance, excellent insulation and barrier properties, and more. In particular, its high-temperature retortability is the reason that when designing and manufacturing high-temperature retort pouch inks for gravure printing and compounding, we must not consider the use of this type of inks as the main binder material for high-temperature polyurethane resin.

When choosing a polyurethane resin liquid for inks, we require that the resulting ink has excellent adhesion to the plastic film, the ink film has good resistance to heat and boiling, good solvent release, less residue, and pigment Good wetness, high gloss properties. Polyurethane resin solutions for inks currently on the market are mainly composed of polyurethane compounds, isopropyl alcohol, butanone, toluene, and the like. The appearance is colorless or light yellow transparent viscous liquid, and the solid content is generally 25 -35%, usually 35-45% in ink formulation.

The high-chlorine content chloroacetic resin used for high-temperature inks is actually a copolymer of vinyl chloride (VC) and vinyl acetate (VAC), which is essentially a dry paint base. After the ink is printed on the surface of the plastic film, the volatile organic solvent contained in the ink system rapidly evaporates away, and the high chlorine content ternary chloroacetic resin is combined with other system compatible resins to form an ultra-thin ink film. In the gravure compounded high temperature retort pouch ink formula, we generally choose the film has a high toughness, durable flexibility, wear resistance, low water swell, low permeability, high temperature cooking characteristics Chloro-acetate resin. Since gravure inks are used on various plastic film substrates, such as BOPP, RCPP, PE, PET, NY, etc., these plastic films have smooth surfaces, and some even have a low surface finish. Therefore, when selecting this type of chloroacetic resin in the gravure compound high-temperature retort pouch ink formulation, it is necessary to consider a class with carboxyl groups (—COOH) in the chloroacetic resin molecule, because according to our ink test, it is known that The carboxyl chloride vinegar resin shows good adhesion on a smooth surface substrate, especially for metallic substrates such as aluminum foil. Therefore, carboxyl-containing vinyl chloride and vinyl acetate and dicarboxylic acid trimers (ie, ternary chloroacetate resins) are one of the indispensable binders in the gravure compound high-temperature retort pouch ink formulations. Among them, we also know that ketones, esters, and chlorinated hydrocarbons are commonly used solvents for carboxyl-containing chloroacetic resins. The ternary chloro-acetate resins used in gravure composite high-temperature retort pouch inks generally require acetone or methyl ethyl ketone, and ethyl acetate. Ester or butyl ester, toluene or xylene and other organic mixed solvents, and then dissolved the resin to make a solid content of about 25% of the vinegar resin solution, do a good job of identification, use iron barrels or storage tanks to be used .

2. Selection of high-temperature compound resistant cooking powder and pigment

The first characteristic of toners and pigments as ink coloring substances is to be bright, bright, and saturated. This is the primary condition for selecting pigments when making inks. The composite high-temperature cooking bag ink for gravure printing has a series of special requirements for its toners and pigments: the color should be bright, the gloss should be better, and the colorful world should have dazzling colors to decorate; the coloring power should be high, which is a measure The use of pigments and economic value conditions; transparency and hiding power is better, according to the different uses of ink, the transparency of the pigment and the hiding power have different requirements; the amount of oil absorption should be small, so that the ink concentration can be easily improved, ink Easy to adjust; better wetting and dispersing; the ability of the pigment to disperse in the ink binder directly affects the success or failure of the ink. Other physical and chemical properties, such as light resistance, heat resistance, solvent resistance, acid and alkali resistance, resistance to migration and other properties combined with few pigments, only according to the special requirements of the application, select the appropriate species.

The pigments used in gravure printing for composite high-temperature retort pouch inks must first be solvent-resistant, followed by high-temperature cooking, and can withstand temperatures above 120°C without discoloration. According to the retort pouch ink standard, the black pigments used in the ink should all be channel black; most of the white pigments are silica-modified rutile titanium dioxide, which is also modified with alumina, but its temperature resistance is yellow. Slightly worse; color ink should be conditionally used to ink selection test, such as indigo blue and indocyanine green, benzimidazolone azo, condensation azo, etc., after resin particle surface treatment, according to the test They can withstand high temperatures above 180°C without discoloration.