Selection of high temperature resistant cooking gravure composite ink on formula

1 Foreword

China's flexible packaging technology has developed rapidly and its level has been continuously improved. The flexible packaging materials produced are of various styles, of which the composite flexible packaging material has become one of the more mature domestic main packaging materials. For example, PET, BOPP, VMPET, VMCPP, PE, CPP, and AL are used as film substrates. The trend toward flexible packaging will be toward high barrier properties and high-temperature cooking resistance. In particular, external flexible packaging materials such as foods and pharmaceuticals require high-temperature anti-virus, environmental protection, and other high performance. This requires a combination of printing inks suitable for high-temperature cooking resistance to meet such high-performance conditions. As a result, high-temperature cooking-intaglio plastic composite ink came into being.

2 high temperature resistant cooking gravure plastic composite ink and its characteristics

The high temperature resistant cooking gravure plastic compound ink uses the relevant chloroacetic resin and special polyurethane as the linking material, and adds a series of special auxiliaries and organic solvents, together with organic pigments with high temperature resistance, uniformly stirring, dispersing and grinding, and adhering. Paired with color. It is suitable for printing in low-speed to high-speed plastic films. The substrate is generally a composite plastic film such as PET, BOPP, NYLON (nylon) and aluminized films. The printed products can be used in ordinary composite processes, and are more suitable for high-temperature cooking compound processes. The ink film solvent residues are low, odorless, non-toxic, environmentally safe and can be used for the packaging of food and medicine, and meet the sanitary requirements.

High temperature resistant cooking gravure plastic composite ink has the following characteristics: 1 high attachment fastness, suitable for a variety of printing films; 2 low viscosity, good leveling, solid content, bright colors, high color concentration, dot reproducibility Good, suitable for chromatic printing of gradation printing; 3 Good printability, good ink transferability, suitable for different machine speeds and printing depths; 4 Printing products can be resistant to high temperature cooking, and generally can be boiled up when used in one-component use ( 90 ~ 100 ) °C, high-temperature cooking up to (100 ~ 120) °C; two-component printing by adding 3% ~ 4% curing agent can improve the ink printing high temperature performance, film properties, printability, composite fastness, etc. .

3 recipe design points

3.1 Selection of Binder

The properties of the ink such as viscosity, flowability, drying property, transferability, glossiness and fixing property are mainly determined by the linking material, and its characteristics such as acid and alkali resistance, high temperature resistance and retortability are closely related to the properties of the linking material. Therefore, the focus of the development of high-temperature cooking-resistant intaglio plastic compound ink formulations lies in the research and selection of related materials. At present, it can be applied to the high-temperature resistant intaglio plastic composite ink formulation of the linking material, and the ink body of the improved ink is only the chloroacetic resin and the polyurethane resin.

Chloro-acetic acid resin is a copolymer of vinyl chloride (VC) and vinyl acetate (VAC). It is essentially a dry paint base and forms a thin film after evaporation of the volatile organic solvent contained in the formulation. In the high temperature resistant cooking gravure plastic compound ink formula, generally used after the film has a high tenacity, durable softness, abrasion resistance, low water swell, low permeability, high temperature cooking and other characteristics of the vinegar vinegar Resin. Since gravure inks are used on a variety of plastic film substrates, these plastic films have a smooth surface. Therefore, when selecting this type of chloroacetic resin in the ink formulation, the carboxyl group (—COOH) should be considered in the vinyl acetate molecule. A class of chlorocyanic resins therefore exhibit excellent adhesion on smooth-surfaced substrates, especially for substrates such as aluminum foil. Therefore, the carboxyl-containing vinyl chloride and vinyl acetate as well as the dimer of dicarboxylic acid (ie, the ternary chloroacetic resin) are one of the indispensable linking materials in the high-temperature cooking-retarding plastic composite ink formulation. Ketones, esters, and chlorinated hydrocarbons are commonly used solvents for carboxyl-containing chloroacetic resins. The ternary chloro-acetate resins used in inks are generally formulated with a mixed solvent of butanone, isopropyl alcohol, ethyl acetate, and toluene. Chloro-acetate resin solution with a solid content of about 20% is stored in a barrel or storage tank for use.

Polyurethane plastic (PU), whose chemical name is polyurethane foam, is a foam plastic obtained by reacting a polyurethane monomer resin solution with a polyether polyol or a polyester polyol through a catalyst and other additives, according to raw materials. The components are different, divided into two kinds of polyether and polyester, and there are soft and hard points. The polyurethane resin solution used in the ink formulation is only the monomer component of the above-mentioned polyurethane plastic (PU), which is modified and blended with organic solvents such as ketones and esters. The solid content is generally about 30%, and it is colorless or light. Yellow transparent viscous liquid. As a binder for inks, the polyurethane resin liquid molecules generally contain -NCO groups, and the degree of polymerization of the molecules is small, but the molecular structure is complex and there are many kinds of them. Among them, simple monomers have toluene diisocyanate (TDI), two. Phenyl methane diisocyanate (MDI), polyphenyl polymethylene polyisocyanate (PAPI), trihydroxy polyether (glycerol polyether). Polyurethane adhesives for inks sold in the market are modified polyurethane monomer resin liquids, and some important molecular functional groups are introduced to provide various excellent properties after film formation. Especially with some curing agents (the main component is polyether or polyester polyol compound) can produce ink film with different properties, such as having soft, high tensile strength, good oil and solvent resistance , Excellent insulation and barrier properties; especially high temperature resistance, when designing high-temperature cooking-resistant intaglio plastic compound ink formulations, consideration should be given to the selection of such polyurethane resin solution as the main linking agent.

When choosing a polyurethane resin liquid for inks, the required ink has excellent adhesion with the plastic film, the ink film has good resistance to heat and boiling resistance, good solvent release, and a small amount of residual, and the pigment is 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 % to 35%; The amount added in the ink formulation is usually 35% to 45%.

3.2 The choice of pigment

High temperature resistant cooking gravure plastic composite ink has a series of special requirements for pigments: 1 color should be bright; 2 gloss is better; 3 high coloring power, which is a measure of the use of pigment and the economic value of the conditions; 4 transparency and hiding power is better Depending on the application of the ink, the transparency and hiding power of the pigment have different requirements; 5 The amount of oil absorption should be small, so that the ink concentration can be easily increased, the ink property can be easily adjusted; 6 the wetting and dispersing property is better, and the pigment is connected in the ink The dispersion ability in the material directly affects the success or failure of the preparation of the ink; 7 other physical and chemical properties, such as light resistance, heat resistance, solvent resistance, acid and alkali resistance, resistance to migration, and other pigments with few properties, only according to the application The special requirements, choose the right variety.

The pigments used in high-temperature cooking-intaglio plastic composite inks must first be solvent-resistant, followed by high-temperature cooking, and can withstand temperatures above 160 °C without discoloration. According to the standard, the black pigments used in the ink are all carbon black; most of the white pigments are rutile titanium dioxide; the pigment inks are tested conditionally, such as the pigmented condensed azo and benzimidazolone azos. Ingredients, indigo blue, and indigo green, etc., they can not change color after 200 °C high temperature.

3.3 Selection of Wetting and Dispersing Agents

The wetting and dispersing of pigments is an important part of the manufacturing technology of high temperature resistant intaglio plastic composite inks. The pigments are crushed into fine particles and evenly distributed in the ink binder to obtain a stable suspension mixed system. The dispersion of pigments in the ink is quite complex and is generally considered to be related to wetting, smashing, and stabilization. Wetting refers to replacing the adsorbent on the surface of the pigment such as air, moisture, etc. with a resin liquid, an organic solvent, or an additive, that is, a process of changing from a solid/gas interface to a solid/liquid interface; smashing refers to using a mechanical force to agglomerate The secondary particles disperse into fine particles close to the primary particles to form a suspension dispersion; the stability means that the suspension dispersion formed can still be in a dispersed suspension state without external force. Wetting and dispersing agent is a kind of special surfactant, which has two functions of wetting and dispersing. Its wetting and dispersing action is to reduce the surface tension of the substance, so that the molecules of the surfactant are adsorbed on the surface of the pigment, thereby generating charge repulsion or steric hindrance, preventing the pigment from producing harmful flocculation and leaving the dispersion system in a stable state of suspension. . The dispersant for high temperature resistant cooking gravure plastic compound inks is generally anionic surfactant. Its main component is carbonic acid ester or special metal aluminum chromium complex, light yellow or yellow brown liquid, it is an oil-soluble dispersant, improving Dispersion of pigments in the ink prevents flooding and discoloration of pigments in the ink, improves color concentration and color development, and enhances adhesion and composite fastness of the ink film to the plastic film.

3.4 The choice of wax powder

High temperature resistant cooking gravure plastic compound ink formula usually add some special wax powder, it can provide excellent anti-abrasion and scratch resistance for printing ink film, anti-adhesion and increase ink fluidity, improve printability and improve Processing performance. Since the wax particle diameter is about 5 mm, which is larger than the diameter of the pigment particle and the thickness of the ink film, the wax particle can protrude the ink film and make the ink film surface rough. When the plastic film is printed on the ink for a long period of time, the rough ink film is advantageous in preventing the back side from sticking, and it is also advantageous for the uniform coating of the post-processed glue to enhance the composite fastness. Adding wax powder to the ink can also eliminate the drawback that the ink can easily fall off the roller during high-speed printing.

Most of the high temperature resistant cooking gravure plastic compound ink formulas should use molecular straight chain synthetic polyethylene wax with high melting point and strong hardness. There are two methods before and after adding. The general added amount is 1% to 2% of the total weight of the ink. Under normal circumstances, it is added before the ink is grinded, which is favorable for dispersing and improving the fluidity. Note that the grinding temperature should not be too high, so as to avoid deformation and aggregation of the wax particles and affect the performance. There is also a paste made of resin and organic solvent, which is added during the tack-adjustment and color-matching stage of the ink. However, in order to do so, it is necessary to prevent some organic solvents with strong penetrating power from dissolving the wax particles, resulting in recrystallization and coarsening. Some performance.

3.5 Selection of Antistatic Agents

When the gravure plastic ink is printed at a high speed, due to accumulation of static electricity, it may cause problems such as offset, blur, spots, beards, and edge repulsion. In serious cases, fire or explosion may occur. Therefore, adding an antistatic agent to the ink is to reduce the surface resistance of the plastic film during the printing process and eliminate the static electricity to solve the above-mentioned 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, which are soluble in water, ketones, and alcohols. Organic solvents such as benzenes and benzenes are sold as aqueous solutions of organic solvents containing 30% to 60% of actives. High temperature resistant cooking gravure plastic composite ink is mainly used as the antistatic agent of ethyl phosphonate isopropanol solution, and the added amount accounts for 0.1% to 0.3% of the total amount of ink without any adverse effect on the ink property.

3.6 Adhesion Promoting Resin and Fumed Silica Powder Selection

In the ink system of polyurethane and chloroacetic resin, since the flexibility of the chloroacetic resin itself is not enough, it is necessary to use an adhesion promoting resin to improve its flexibility. High temperature resistant cooking gravure plastic composite ink formula will need to add some modified chlorinated polypropylene resin solution, its solid content is generally about 20%, increase the adhesion of polyurethane ink on the plastic film, enhance the dispersion effect and fluidity.

Fumed silica powder, also called matt powder, is generally easy to disperse after it is organically surface-treated. Its role in high temperature resistant cooking gravure plastic composite ink is: 1 Prevent pigment from settling, keep the long-term rheological properties and fineness of the ink; 2 Improve the sag performance of the ink film when the ink is printed on the machine, and prevent water mark from being produced. ;3 can also be like wax powder, which is conducive to the uniform coating of adhesive and improve the composite fastness.

3.7 Selection of Organic Solvents

The plastic gravure ink is mainly formed by the solvent evaporation and drying. When the ink is printed on the surface of the substrate, the ink film thickness decreases and shrinks due to the volatilization of the solvent. Ink solvent volatilization is mainly divided into two stages