Ink and Printing Relationships, Defects, and Remedies

I. Introduction

In normal inks, varnish and packaging printing or post-printing and finishing technology, some people always want to simply attribute the problem of defective products appearing on packaging printing to the quality of substrates, or inks or coating oils. (commonly known as paint) is of poor quality and fitness. The reason why printers justifiably shirk their responsibilities is to first look for causes from past incidents. The reason why they gave up their responsibility to others without any concealment was that some of them were unwilling to scientifically and systematically learn and master the technology of packaging and printing technology and finishing technology, and they were even less reluctant to let others judge their technical skills. .

After nearly 30 years of technical follow-up services for ink production and printing operations across the country, the author summarized the shortcomings of the recent 16 major technical phenomena, and theoretically summarized the remedial plans into pieces. The assertion is wrong. Some people often do not really see the packaging printing to dilute the ink or polish the ink for excessively low cost, resulting in poor color; in order to pursue high profits, use inferior substrates to shoddy, which is out of frustration. The phenomenon has created new problems and our operators have been poorly dealt with all day long. Because the times are changing, the environment is changing, the trend is changing, and the quality of printing inks or varnish is also changing. If it is the same today and tomorrow will not change, the problems in packaging and printing will become more and more serious and become a burden. Until the technical retrogression. This is like the symptomatic treatment program in the past, which lags behind today's solution, which should be attributed to the three main reasons for the performance of ink or coating, the nature of substrates, and the skills of operators. It has also contributed to this new doctrine in conjunction with historical trends, methods of printing, means of finishing, and personal skills.

The facts are enough to prove that pursuing first-class is not a quantifiable standard. It can only be divided into lower and middle ranks. Symptomatic treatment methods also mistakenly create one or another troubles along one line of thought and spend enormous economic power to reform and waste. How many precious time to deal with the technical problems like the ones discussed below will instead distract attention from a certain problem and often make it more difficult to implement the solution because of the problem—that is, “the water is hoisted according to the hoist”. However, it becomes more and more complicated. In order to realize this dream, I will briefly discuss my own opinions on eight issues in order to discuss the issue.

Second, the major defects of ink or coating oil products

2.1 Insufficiency:

1. Packaging printing inks and coating oils often appear during production and storage: sedimentation, precipitation, gelation, thickening, thickening, thickening, crusting, hair growth, color mixing, discoloration, fading, color, and filler precipitation. And caking.

Poor pigment dispersion, poor resin compatibility, poor solvent blending, pigment production, storage, swelling, gels. These defects severely hamper normal ink production, storage, and use.

2, packaging, printing and coating finishing process often appears: sag, ink film white, bleeding, floating color, graphic migration, deformation, ink film softening, cracking, orange peel, wrinkle, no flatness, Bite at the end, cross-color, shrink holes, shrink edges, pinholes, blisters, side rainbow, yellow, fade, and so on.

3, printing and post-printing often appear after finishing: discoloration, fading, chalking, cracking, peeling and peeling ink layer, blistering, spoilage, pinholes, blooming, fogging and so on.

Before and after the two are mainly related to the quality of packaging printing inks or coating oils, and the middle is mainly related to the quality of inks or coating oils, and the design of printing and finishing processes, quality management of finishings, printing, and finishing environmental conditions. Therefore, ink and varnish development and production personnel must understand the difference between packaging and finishing products, production process and environmental requirements are different, the choice of ink or coating oil is not the same. For example, different temperatures in spring, summer, autumn and winter, different humidity in coastal areas and highlands, differences in sunny weather and rainy season, differences in the speed of printing machinery or finishing and coating machines, and differences in drying (infrared, ultraviolet, etc.) conditions may produce The flaws will not be the same.

A, failure phenomenon:

For ink or varnish packaging of printed products (paper or plastic flexible packaging), special attention should be paid to:

1. The surface state of the printing medium (substrate), the flatness of the surface of different substrates, and the deformation, cracks, and adhesions caused by bubbles and internal stresses. On the one hand, the printing or finishing molding techniques should be improved. On the other hand, necessary surface treatment measures must be taken to implement treatments such as corona discharge treatment or chemical spray surface treatment.

2. The surface polarity of substrates, especially polyolefins, is generally surface polar, and substrates with low crystallinity have strong adhesion to packaging printing inks or coating oils. For example, the surface of flexible packaging printing carriers such as PE and PP must be special Pretreatment before printing or glazing.

3. The surface concentration of additives in the ink or varnish system, such as the plasticizer in the flexible packaging substrate carrier, tends to migrate to the surface, especially when the ink film with the low softening point migrates and deforms during compounding or cooking. There is also the presence of mold release agents such as silicones, paraffins, etc. after molding, which is not conducive to the normal display and adhesion of packaging printing inks or coating oils. Degreasing and cleaning should be performed, but excessive use of stearic acid or Where silicone oil is completely removed, it is very difficult. For example, the surface of a flexible packaging plastic product is in a charged state. However, as an insulator, the surface of the substrate, the ink, or the varnish is likely to be electrostatically generated by friction. Therefore, the surface is easily adsorbed with dust. Before the ink or varnish is produced, it is necessary to carry out a solution to eliminate static electricity.

B. Reasons:

In order to facilitate a careful analysis of the defects of the packaging printing and printing carrier, we will give a rough sub-classification of the reasons for this.

1. Factors related to the quality of inks or coating oils include: A. The surface tension of the ink or varnish after filming, the wetting and adhesion of the packaging printing and printing carrier, and the leveling of the ink film and the oil film surface; Are the solubility parameters of solvents and thinners used in packaging printing inks or coating systems similar? Surface tension and volatilization rate, especially whether the volatility gradient is balanced; C, ink or varnish viscosity, viscosity and rheological properties, with particular attention to the viscosity in the film formation process tends to follow the ink printing, Varnish coating method Method and the characterization and characteristics of the printing and coating environment change; D, inks or varnishes in the system of various additives in its rationality and compatibility and tolerance.

2. There are relevant factors in the process of dilution and stirring and dispersion of packaging printing inks or coating oils: A. The mixing of dust and impurities; B. Filtration; C. Dilution is suitable for the ink or coating oil; D. Ink printing, The viscosity of the varnish finish is adjusted and kept stable.

3. Factors related to the packaging, printing and coating environment of factories, especially workshops, are: A. Temperature, humidity, indoor wind direction during production, air volume, and wind speed; B. Printing ink splash, aerosol pollution; C. Dust and impurities prevention.

4. Environmental factors for open-air production and printing and coating include: A. Selection of ink printing and gloss coating time—temperature and humidity; B. Wind direction, air volume and wind speed; C. Weather conditions, such as cloudy and sunny , morning and evening etc.

5, substrate carrier related factors are: A, whether it is full version of ink printing or full version of the coating finishing base oil, especially the middle of the overprint version of the version and the distance between the printing speed, ink layer, the thickness of the light oil layer B, surface treatment, dust blowing and corona treatment; C, solvents, chemical reagents, surfactant treatment, cross-linking agents and coupling agents to promote; D, drying principle, in addition to static devices, methods.
6. The packaging and printing of ink and coating and finishing processes of coating oil include: A. Printing and coating methods (such as manual or mechanical, high-speed or low-speed/offset printing, gravure printing, flexo printing, silk screen printing or transfer printing Transfer coating); B, in addition to the quality of the ink, varnish, substrate, the operator's technical (experience and skill) level; C, printing, coating angle, speed, distance, ink film and film thickness, packaging One-color printing or multi-version printing and coating channels, thickness and type of primer, varnish, etc.; D, air pressure, air volume, light energy, light intensity, curing method and degree of drying and curing; E, The cycle speed, make-up volume, and interval time in the replenishing system for packaging printing ink or varnish, and the viscosity of the diluent.

7, drying methods and placement time factors are: A, drying (drying, air dry, infrared, ultraviolet, etc.) and open time; B, temperature and heating rate and the length of the temperature range; C, environmental ventilation and change The speed of gas.

8. Factors related to film formation conditions of inks or coating oils include: A. Temperature and distribution of drying tunnel (chain drying bed), heating rate and constant temperature time; B. Length of drying time; C. Ventilation speed and air Pollution degree.

We can analyze one by one in the above-mentioned exchanges: The printing defects caused by ink printing and varnish coating are various. Some are one cause, one is a result of several causes, and there is a result. As long as we are open-minded and clear-cut, and then propose solutions for ourselves, we will not apply the traditional methods of symptomatic treatment in summing up lessons and accumulating experience.

Although some of the theoretical analysis involved is ideal, the actual situation tends to be much more complicated than analysis. The combination of theory and practice can just narrow this gap.
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2.2 Sinks:

A, failure phenomenon:

When the ink is packaged and printed on the vertical surface and the varnish coating and finishing production process flow, the ink or the coating oil tends to flow down due to gravity during the film formation (A. When the ink or oil contacts the substrate and spreads out B. When a certain amount of gravitational force is reached at the last minute; C. Contact with the substrate is gradually spread.) This flow is maintained after the film is formed, resulting in uneven surface flow (spreading), uneven thickness of the upper and lower film, and thickening of the bottom edge. From the above three conditions A, B, and C, we hope to see that the status of C is encouraging. Because from the observed fluidity, the spreading task was completed within the prescribed time, but A often produces water marks, and B often produces cracks. This is based on the above-mentioned shape of the flow mark is divided into the following types: (1) sag: ink and coating oil can not go up (front) flow and gradually thickening, or stranded on the bottom edge, dry curing Afterwards, they are often retained as they are; (2) Rogue: When ink or varnish is mechanically printed on the surface of the substrate, it hangs on a large area and is often called a watermark. (3) Dropping: This is the state of B in this article. Local sagging occurs during printing, painting, or temperature-increasing drying, forming wave-shaped (called watermarks), semi-circular (stripes) or stripe-like secondary waste products.

B. Reasons:

In essence, ink or varnish sag is associated with the fluidity or rheological characteristics of the ink or varnish during printing and coating. Sometimes it is related to the processing quality of the substrate. For example, when the pressure of printing or coating is still on a smooth surface with poor adhesion, the sag situation may easily occur.

When we adjusted the rheological properties of packaging printing inks or coating oils, it greatly promoted the low viscosity of inks or coating oils at high shearing speeds, which in turn facilitates the inks or coating oils. Leveling. At the same time, when we have a high viscosity at a low shear rate (ink or varnish film), it prevents sagging, which is a very difficult task. Most manufacturers use appropriate low-viscosity, high-content resin binders. Choosing a pigment, filler, and adjuvant with a moderate pH, the inks or varnish made to make it thixotropy for general printing. It pursues the unifying purpose of preventing conflicts between sag and leveling.

The viscosity of packaging printing inks and coating oils has a great relationship with the solvent volatilization rate and volatilization gradient in the printing and coating processes. The volatilization of the solvent is fast and the viscosity of the ink is fast, which helps to prevent sagging, but it is not easy to level out. The drying and curing speed of thermosetting or light-curing packaging printing inks or coating oils is directly related to viscosity changes. Slow response, low viscosity, and easy sagging are tasks that we should take seriously.

We know that the temperature and light intensity have a great influence on the viscosity. In the packaging printing ink or varnish system with volatilization and drying properties, oxidative permeation and drying properties, photocurable properties and thermosetting properties, the viscosity of the wet film of the amino ink is high-temperature baking. Falling, often causing sag is a headache