Quality control of the hottest printing raw materi

The quality control of printing raw materials

product quality is related to the survival and development of each enterprise. The quality of products depends on the five production factors in the production process: personnel (man), equipment (machine), materials (material), method (method), environment (environment), that is, we often say 4mie rule. Due to the great differences in the scale and grade of domestic plastic color printing manufacturers, the importance and actual implementation of 4mie law are also different. Due to the limitation of financial strength, it is highly operable for most small and medium-sized plastic color printing plants to control the printing raw materials and reduce the factors of quality accidents from the source. In the process of plastic color printing, the raw materials are mainly film, ink and solvent. Overall quality control principle: determine the appropriate film and structure according to the specific requirements of customers, the requirements of tensile testing machine for fixture materials, or the characteristics and post-processing of packaging contents; After selecting the material structure, the appropriate ink is determined according to different films, and the corresponding solvent is matched; Avoid over packaging or shoddy

there are many kinds of films on the market, but the most commonly used printing films are BOPP, NY, pet, PE. In terms of printing, the most important thing is, of course, the surface treatment effect of the film and whether the NY film is affected by moisture. When printing, the process requirements of measuring the surface tension of the film in one roll should be formulated. The corona effect is time-dependent, and if it is placed for a long time, the corona effect may decline too much, which cannot meet the requirements of printing; It can also avoid the hidden trouble of inadvertently reversing the film printing. PE film is the focus of our attention: when blowing film, corona treatment may be omitted from the film roll; Excessive or uneven film thickness causes insufficient corona effect; Film blowing is to add too much smooth agent or the proportion of high smooth granular material is too large, resulting in a significant decline in corona effect. When the corona effect of 12~15um PET film on both sides is not different, it is easy to cause the back adhesion failure of the printing film roll. Corona requirements of printing film: BOPP, PE ≥ 38 dyne, pet ≥ 50 dyne, NY ≥ 52 dyne. After the NY film absorbs water, it will not have a great impact on the corona effect. Judge whether the NY film absorbs water to see whether the film has shrinkage and tendency. Cut a film and put it into the oven for a few hours to see whether it feels hard. If there is tendency and rigidity, the NY film absorbs too much water. When purchasing film, you must explain the purpose and requirements of the film to the supplier. Now the variety of film is refined. Just say the names of pet, NY and BOPP, the supplier may have several varieties, but not all of them are suitable

when choosing gravure printing ink, we should first consider several factors: on what substrate should we print? What kind of machine is used for printing? What kind of effect do you want? What are the conditions for post printing processing and end products? Now ink manufacturers are in fierce competition and have a large choice of products, which may also dazzle our color printing factory. Before printing, confirm the above points, not only choose the ink with the best performance price ratio, but also reduce or avoid printing failures. Ink suppliers should not be too many, not more than three is appropriate, different brands of ink can not be blended, resulting in a great waste of residual ink; Perhaps some color printing manufacturers hold the mentality of occupying the funds of ink suppliers, but running enterprises should be based on honesty. Anyway, they have to pay sooner or later, so there is no need

there are three common types of inks in the market: polyamide surface printing inks, chlorinated polypropylene composite inks, and polyurethane inks. Choose the corresponding matching ink for different substrates. Chlorinated polypropylene composite ink is used for printing BOPP. If composite is not required, polyamide surface printing ink is used. If general polyurethane ink is used for printing BOPP, not only the cost is high, but also the adhesion fastness cannot meet the requirements. NY and PET films must be printed with polyurethane ink. If they are printed with chlorinated polypropylene ink, they are prone to low peel strength, high temperature delamination and other faults. Polyamide ink has a particularly good adhesion to PE film, but it can only be used in general dry packaging. When making high-temperature, grease resistant and water-resistant packaging, such as milk film and bottle label, polyurethane ink should be preferred

there are several basic indicators of ink that our color printing enterprises should test to promote the democratic process in Hong Kong to take a historic step: viscosity, fineness, hue and adhesion fastness. The required test tools include scraper (contrast hue, test adhesion fastness), 3 × chaenhuai (viscosity), and fineness plate (fineness). During viscosity detection, it is best to dilute the matching mixed solvent to a specific viscosity (such as 18 seconds/25 ℃), and calculate the amount of solvent added, so as to eliminate the phenomenon of "false viscosity" that may be caused by some inks (the ink looks very thick, but the solvent cannot be added). The national standard (gb/t 13217.) can be selected for the detection of adhesion fastness, However, for some surface printing inks, it may not be enough. It is best to simulate the specific requirements of product packaging and post-processing conditions for testing

the good quality of solvent directly affects the quality of ink printing, but for general small and medium-sized enterprises, the solvent quality is related to the regular application of 2 molybdenum sulfide grease: it is the most difficult to grasp. The main indicators to distinguish between good and bad solvents are purity and moisture content. The quantitative and qualitative detection of solvents is best through chromatography, but the required instruments are expensive and the technical requirements are high. If only for printing, without considering the dry composite process, here are a few simple and practical methods. Look at the appearance of the solvent, at least it should be clear and transparent. If there is turbidity and floating debris, this batch of solvent should be used with caution. Smell the smell of the solvent. After contacting the commonly used solvent for a long time, the operator has a general impression of the smell of a specific solvent. If the smell of this batch of solvent is found to be impure, it can be sure that the purity of this batch of solvent is not high and there are many impurities. Use the principle of different dissolution effects to roughly determine the water content in the solvent: use a 100ml glass measuring cylinder to take more than half a cup of transparent toluene solvent, take a small amount of esters or ketones and other solvents to be measured, and evenly pour them into toluene. When the solvent is just poured into toluene, observe whether there is turbidity (milky white) phenomenon. If there is, the water content in the solvent seriously exceeds the standard. Experience shows that this phenomenon is obvious when the water content exceeds 0.5%. The moisture test of benzene solvents can be determined by extracting the solvent through a long glass tube and observing whether there is stratification

there are many factors that affect the quality of printing. How can we better grasp the quality of printing with an ordinary tensile testing machine? Each color printing enterprise has its own management methods. The quality control of raw materials is the most basic and critical process requirement in the process of color printing. It is difficult to imagine that unqualified or inappropriate raw materials can ensure the production of printing products with quality. Therefore, our color printing enterprises must constantly and effectively control the quality of raw materials

(text/Yu Yongyue)

source: Zhejiang New Oriental ink Group Co., Ltd