Ink appeared with the revision of writing tools, such as the use of pens. According to the chemical properties of its raw materials, it can be divided into blue-black ink and color ink.
(1) blue and black ink
Also known as iron tannate ink, it consists of blackening component, pigment component, stabilizer, corrosion inhibitor, wetting agent and preservative.
1. Black persistent ingredient:
Mainly tannic acid (C4H 10O9) and gallic acid (C7H6O5? H2O) and ferrous sulfate (FeSO4) combine with each other to form ferrous tannic acid and ferrous gallate, which are insoluble high-valent iron after oxidation, namely ferric tannic acid and ferric gallate. The former enhances water resistance, while the latter enhances blackening, thus making the ink water-resistant, blackening and durable.
2. Pigment composition:
At present, acid ink blue and direct lake blue dyes are commonly used. Black water blue is the main color of ink, and the aqueous solution does not deteriorate in acid, but turns brown in alkali. Direct lake blue plays an auxiliary role in ink, because it contains more impurities, so it is not suitable for multi-use, and it is easy to grow mildew in wet environment.
3. Stabilizer:
The main purpose of adding stabilizer to ink is to eliminate the precipitation of ink and avoid the phenomenon of water shortage when writing. Commonly used stabilizers are sulfuric acid (HSO4), oxalic acid (COOH)2 and formaldehyde (HCHO) solution. These stabilizers have certain acidity, which lays a hidden danger for paper acidification and should not be used more.
4. boycott:
Because the stabilizer added in ink has strong acidity, in order to prevent corrosion, a corrosion inhibitor is often added to form a film with iron to reduce the corrosion effect of sulfuric acid by 90%. The iron content in the ink will not increase due to the corrosion of the pen tip, thus increasing the stability of the ink.
5. Wetting agent:
In order to prevent the water in the ink from evaporating, which makes writing inconvenient, glycerol [C3H5 (OH) 3] which is non-volatile and absorbent is added to the ink to keep the nib moist and facilitate writing.
6. Preservatives:
Organic substances and other substances contained in ink raw materials are easy to rot and mold in humid environment. In order to prevent decay, chemicals such as phenol or sodium pentachlorophenol are often added as preservatives.
Why does the blue-black ink appear reddish-brown insoluble after adding lime water?
Because there are divalent and trivalent iron ions in blue-black ink, when iron ions meet hydroxide ions in limewater, iron hydroxide precipitate will be generated, and the color of iron hydroxide precipitate is reddish brown.
Printing ink consists of ink base and colorant.
First of all, ink base is mainly divided into the following categories:
1, water-based type
According to its characteristics, it can be divided into solution ink, diffusion ink and microemulsion ink;
2, non-aqueous type
According to its characteristics, it can be divided into oil-based ink and solvent-based ink;
3. Type of phase transition
According to its characteristics, it can be divided into liquid to colloid and liquid to solid.
4. Reactive type
Mainly ultraviolet curing type and so on. , generally used for printing on glass, rubber and other accessories.
Secondly, colorants are mainly composed of the following two types:
dyestuff
Completely dissolved at the molecular level, the ink formed is a complete composite solution, which is not easy to block; The main users paint internally, which is not waterproof and has weak anti-ultraviolet ability.
pigment
It is a small solid particle, which is ground into several tiny particles and dissolved in a special aqueous solvent (containing polyol) to form a colloidal suspension solution or semi-solution, called pigment ink or pigment ink, which is waterproof and anti-ultraviolet. Equipped with outdoor anti-ultraviolet consumables.
1. Waterborne ink mainly consists of the following components:
Component functional concentration%
Deionized water carrier medium 60-90
Water-soluble solvent wetting agent with viscosity of 5-30.
Dyes or pigments provide the color of 1- 10.
Surfactant wetting, penetration 0. 1- 10.
Biocide prevents biological growth by 0.05- 1.
Buffer controls the PH value of the ink at 0. 1-0.5.
Other additives: chelating agent, defoaming agent, dissolving agent 1.
Note: The three main factors that affect ink quality are:
1. Purity of solvent in water
2. Moisturizing cream
Because the nozzle is in the idle state of printing, the volatile components and moisture in the nozzle will evaporate, so moisturizing is necessary.
Step 3 eliminate bubbles
If there are a lot of bubbles in the ink cartridge during printing, it may cause printing interruption or damage to the print head due to empty burning.
The quality of ink can be judged from the following aspects:
1, purity and salt content of raw materials
High-purity raw materials will better restore the saturation of the image and fully show the bright part of the image; If the salt content is too high, the ink will produce a certain amount of alkali in the process of high-temperature inkjet, resulting in nozzle hole blockage.
Step 2 be sticky
The ink viscosity is too high, which will interrupt the ink supply during printing; If the viscosity is too small, the ink head will flow when printing.
1, optical density
2. La and B values of color
3. Drying speed
Drying speed affects the winding speed of drawings and the overall efficiency of inkjet printing.
4. Measuring point test
5, silt permeability test
6. Siltation test
7. Anti-smear performance
10, light resistance
1 1, waterproof
12, pH control
The pH value of ink is directly related to the service time of the ink supply part of the machine; As well as the printing effect and the storage time length after the image is combined with the ink-jet medium.
13, conductivity control
14, metal ion content
15, particle distribution (pigment type)
The distribution of particles directly affects the effects of anti-ultraviolet, waterproof and image saturation.
16, bacterial content
17, heat resistance
18, weather resistance
Ink is generally divided into 1 to 8 levels of weather resistance, and the higher the level, the longer the weather resistance. Including anti-ultraviolet, anti-acid rain, anti-humidity, anti-sand and so on.
Because different inks have different chemical reagents and different solutions, there are certain differences in chemical composition and color composition. We put forward some basic opinions for your reference in use:
1, indoor and outdoor ink conversion, especially outdoor to indoor conversion, please empty the original ink first, and then clean the pipeline with cleaning solution or pure water, otherwise the chemicals in the ink may react chemically to block the nozzle.
2. Users who use HP, NovaJet and other thermal foaming machines must vent air when filling ink, otherwise it will cause the ink head to burn out, reduce the nozzle life, or may cause the ink head to be damaged or the ink cannot be printed.
3. Users who use miniature piezoelectric machines such as Epson, Mimaki, Mutoh and Roland. After using new ink, it is normal for the test paper to break within a few hours, because the ink head and ink need a melting time;
Such as monochrome or no ink, or ink is broken after long-term use, it may be that the ink in the ink bag is insufficient (less than two-thirds) or too much (full), or there is air in the pipeline, too much mud in the scraper, and the ink pad is wasted; It is best to manually empty the air in the pipeline, handle the ink bag and clean the unclean part.
4. It is best for piezoelectric machines to print test charts every day to keep the nozzles moist; When it is turned off for a long time, it should be turned on once a week to ensure that the ink path is smooth and the ink head is wet.
Ink plugging rate
Because ink can only be neutral ink and does not react with any material, ink must be attached to the coating. In order to prolong outdoor weather resistance time and improve waterproof performance, water-based pigment ink adds UV (anti-ultraviolet) component to the ink, and the UV component is directly proportional to the blocking rate, so when the UV component is too high, blocking will occur. Therefore, water-based pigment ink must also be covered with anti-ultraviolet film to ensure outdoor weather resistance time, and the ultraviolet component in the ink must have a certain proportion, otherwise it will be blocked. After the ink is waterproof, there is no protective measure, and the outdoor weather resistance is less than eight months, so it is not easy to block, otherwise it must be coated with UV glue. Therefore, the blocking rate can only be reduced by reducing the UV component of solvent-based ink, and the weathering period of solvent-based ink will not exceed 2 months.
Weathering resistance
Whether it is ink or ink, except for the different types of solvents, the use of dyes and pigments is different. Generally speaking, the weatherability of dyes is far less than that of pigments, and the weatherability of dyes varies with colors. Magenta is the worst, and cyan (cyan), yellow (yellow) and black (black) are far better than magenta. The weather resistance of pigments is very good in each color, and the average weather resistance level is six to eight.
In fact, in addition to pigment factors, the composition of ink formula is the key to the weatherability of ink. In addition to using mild and non-corrosive solvents, adding heat-resistant agents, ultraviolet absorbers, antioxidants and free radical scavengers can enhance the weatherability of ink dyes.
In addition, the choice of protective film on coating material is also one of the important factors affecting weather resistance;
In addition, its weather resistance will change with the weather resistance time in the external environment, the humidity in the area, the length of sunlight exposure, the orientation of picture layout and the climate of the place.
Therefore, the waiting time is not absolutely guaranteed. In fact, it is impossible to make the same guarantee with professional technology and evaluation from different angles. This is the absolute guarantee that distinguishes it from ordinary commodities.
1. How does viscosity affect printing?
Viscosity is absolutely important for inkjet printing. In order to obtain the best performance of inkjet printer, the viscosity of ink must be kept within a specific range. If the viscosity is too high, the ink will block the nozzle. If the viscosity is too low, air will flow back to the nozzle, causing ink leakage. By keeping the viscosity within the specified range, the maximum density can be obtained without ink flow or ink leakage.
2. What is the relationship between temperature and viscosity?
The increase of ink viscosity is usually mainly due to the operation of inkjet printers in cold environments. When ink gets cold, it becomes thick. The simple solution is to raise the temperature to keep the environment of the studio above 20 degrees Celsius. . Lower temperature will also lead to the weakening of the adhesion of ink on the medium, resulting in dot.
3. What is the relationship between the viscosity is too high or too low and painting?
If the viscosity is too high, you will start to see the density drop because there are fewer ink drops. If the ink is really too thick, the ink drops will never come out of the nozzle and printing will stop.
If the viscosity is too low, the ink will flow out of the print head, which will also cause air to flow back to the ink chamber.
4. What is the relationship between surface tension and inkjet printing?
Surface tension is the attractive force between molecules on the liquid surface. For example, if you look at the raindrops on the window, the beginning of the circle is caused by surface tension. Water molecules gather closely to form a hemisphere. The tension of pure water is very high, about 75 (up to trapped square centimeter). Most organic solvents are very low, about 25 dynes square centimeters. This is also the reason why oily solvents are better.
But since the plane tension of water is so great, why can water-based ink be used? This is the beginning of chemistry. Due to the phenomenon of hydrogen combination in pure water, water molecules are bound together, so the surface tension is improved. A chemical element called "wet base" is added to water-based ink. One end of this wet-based molecule is in contact with water to break the hydrogen bond, and the other end is in contact with the substrate. Wet base reduces the surface tension of ink. Wetting the substrate, another solution similar to alcohol, can also reduce the surface tension of water-based ink.
5. What is added to the water-based protective film?
Waterborne protective film is a kind of water-borne protective film containing alcohol. Sprinkling essence has three functions; Reduce the surface tension, make the water-based protective film dry compatible with the oily protective film, and make the water-based protective film dry faster.