Development and Use of Water-Based Ink for Printing Clothes (Part One)

Seventy-eight years ago, most T-shirt printers used plastic inks, but there were a few unsatisfactory ideals, the most prominent being that they were harder after being dried on clothing. Therefore, people have to turn to water-based inks, which have better feel and appearance after printing.

The main advantage of water-based inks is that they do not involve any organic solvents. They are cleaned and diluted with water and do not require any organic solvents in the press room. For manufacturers that are still using large amounts of organic solvents, this is indeed a big improvement, because exposure to too much organic solvent will make people feel dizzy.

The garments printed with the water-based inks have a good feel and a high definition. A few years ago, it was easy to print half-tone images of 65 to 75 lines/inch. The main problem was that the ink was easy to dry and was particularly prominent on the screen. Since the moisture in the ink is continuously evaporated, the ink is almost impossible to use in hot summer (above 27°C). Second, the hiding power of ink is not very good. As we all know, a few years ago, there was no water-based ink that could print in dark colors such as red, green, red blue, navy, and black. A few years later, these inks have fundamentally improved.

Manufacturers and suppliers responded quickly. They realized that people's requirements for improving the feel of printed clothing have become increasingly strong. Around the 80s, the market began to feel good plastic ink. At present, most plastic inks can be used for screen printing at 305, 350, and 390 mesh/inch, and their appearance and feel are comparable to those of water-based inks.

In general, plastic inks are capable of copying fine texts, and 85 line/inch halftone printing has become commonplace. Many screen printers have been involved in this area and the results are particularly satisfactory. Of course, Sol ink does not have a dry solid problem. Recently, water-based inks with strong hiding power have also been continuously developed. Therefore, in effect, the difference between the two types of ink is not very great, and is constantly shrinking. Therefore, it is difficult to say who can replace water-based inks and plastic inks, and they all have their own applications. As a screen printer, only two types of inks can be tested according to their own needs, and the better one is selected. The choice of ink is the same as choosing a squeegee or mesh, and the printer must choose according to the printing needs.

Current industry trends indicate that water-based inks have grown faster in the past few years. The history of water-based ink technology alone has been more than 30 years or even longer. It has been used in rotary screen printing in the textile industry for many years, and flat-screen printing and textile/clothing printing are now used. We have noticed that many countries and regions have made legal and regulatory restrictions on the solvents used in inks because the volatilization of solvents in the ink will cause air pollution. At present, the monitoring of volatile organic solvents is more stringent. In addition, workers are increasingly complaining about exposure to toxic and hazardous chemicals during the labor process. The current trend is to reduce toxic substances in the ink as much as possible to ensure production safety.

Energy is another important factor. In the traditional printing, to make the plastic ink and water-based ink fully cured, the temperature is usually required to reach 149 ~ 176 °C, at the same time, in order to achieve better wear resistance, curing takes 2 ~ 3min. In recent years, energy prices have risen at an alarming rate. The original curing system requires heating. A more concentrated ink drying/curing system should be pursued. Now, there are some curing systems that do not require heating.

Compared with previous years, the price of industrial alcohol has been increased by five times, and the increase in solvent prices has also increased the cost of ink production. The use of plastic ink requires the purchase of a considerable amount of organic solvents, while water-based inks do not require organic solvents, which in turn can reduce the cost.

The last point is that T-shirts have been a very popular commodity in recent years, and this momentum will not decline in the future. More and more people are entering this industry. Consumers’ awareness of consumption has increased. They are more discerning about products, and require higher levels of overlay accuracy, uniformity of ink distribution, and feel.

In the market, two-color printing and three-color printing are extremely common. At present, there are certain market demands for screen printing, of which 65% to 80% are four-tone screen printing, which means that consumers need And preferences are changing.

Now, it has been possible to print 5 to 7 colors of water-based ink on substrates such as navy blue or black. If you print plastic inks, you will find that the inks are particularly sticky and stiff. The development trend of ink is to have a good hiding power on dark fabrics, and at the same time wet and wet printing. In the past, it was difficult to print a 75-line/inch screen, but now it is easy, it is not blocked, and the effect is very good. It can be seen from this that water-based ink printing has many advantages, the most obvious being the print's good hand feel.

Using water-based inks, the poor stability of the screen is a serious problem, especially the use of screen printing screen image 230 ~ 300 mesh / inch, the operator should pay special attention, otherwise, a few minutes of delay will result in blocking Net, and then give up. Some manufacturers are developing an ink that has a wet process after dilution and can hold 5 to 10 on the screen.
The min or even 15 min does not dry, does not block the net, the operator may stop or leave for a short time. Even if the ink appears dry solid phenomenon, as long as the time is not too long, scraping back and forth with a spatula several times, the ink can be re-adjusted to eliminate plugging problems, which is a major technical breakthrough.

Water based inks do not require heat curing or low temperature curing after printing. Please note the difference between curing and drying. Drying of water-based inks completely eliminates water. Afterwards you can stack code. Curing refers to heating the printed article to a certain temperature and then maintaining the temperature to cure the ink. After this process, the ink becomes insoluble in water, has resistance to washing and firmness. At present, some inks have hardeners (and also no hardeners). After printing, the water may evaporate slightly or dry at a low temperature of 110-116°C. The printed garments can be stacked and packed when the last printing throne is down. After 2 to 4 days, the ink will completely dry and have good resistance to washing and stability.

Related to water-based inks is photosensitive adhesives. If an automatic printing device is used, it requires that the screens made of photosensitive adhesives can continuously print 300 or 400 dozens (1 dozen = 12 pieces) without problems, which is not easy.

Another major advantage of water-based inks is their ability to maintain a good working environment. The plastic ink will not dry out, but the water-based ink requires sealed storage, otherwise, the ink will appear dry solid phenomenon, which requires the staff to operate proficiently, in the boot before printing, to check whether the necessary items for printing Qi, do not find this in the printing process to find that, as long as you pay attention to these, will greatly improve the quality of printing and reduce defective products.

When using water-based inks and water-based emulsions, printers often encounter problems. Here are a few suggestions to help prevent the ink from drying on the screen or printing during the printing process to ensure a good printing effect. First of all, to use single-screen cloth, multi-screen cloth will make the ink easily infiltrated between the mesh, resulting in expansion, deformation of the mesh, increase the opportunity for the ink to dry on the mesh. Single screen fabrics used with the current photosensitive adhesives are generally not prone to problems such as dry or screen adhesion.

Stretchers are required to use a tension gauge. The screen should be tight and the tension should be uniform. In the printing process, the screen wears more and the stencil layer is more easily damaged. It is very important for the screen to properly remove the grease. After the screen is dry, it should be coated as soon as possible.

Generally, a layer of photoresist is scraped on the printing surface of the screen, and then scraped on the scraping surface. Afterwards, the stencil is printed with the printing surface facing down and dried. This placement is conducive to evenly leveling the photoresist on the screen. In addition, it is very important to raise the temperature of the plate making shop to 27 to 29°C. Otherwise, moisture in the photosensitive paste cannot be evaporated. If the surface of the photosensitive film is dry and moisture remains in the photosensitive layer, this will greatly shorten the service life of the screen printing plate. A dehumidifier should be placed in the darkroom to eliminate indoor moisture and reduce the humidity to less than 10% so that moisture in the stencil layer can evaporate quickly.