Why is soft water necessary for washing?

According to the interview, only 20% of operators do not know that the water used to wash clothes needs to be treated. Some people think that only the main washing water needs to be treated. Many people know that water needs to be treated, but they don't know why; in terms of treatment methods, more people use the method recommended by chemical material suppliers-softeners.

This is the necessity of water treatment.

Generally speaking, suspended matter, colloids, dissolved oxygen, or free carbon dioxide in water will not have a great impact on washing. Of course, if the suspended matter is turbid, that's another matter.

The quality of water washing is greatly affected by ionic impurities in water. It is well known that water rich in carbon dioxide will come into contact with calcium carbonate or magnesium carbonate in rocks and produce magnesium bicarbonate or calcium carbonate. When inorganic salts dissolve in water, ionized impurities are produced, mainly composed of sodium, calcium, magnesium, potassium plasma, and a small amount of iron ions, all of which are positive ions. Of course, it does not mean that all impurities in water are positive, but there are also anions, such as chloride ions. These impurities are heated during the washing process, and after washing the cloth, the ironing machine will form a scale after a high temperature of 140-160℃.

The reason why the raw water cannot be used is that the water quality is not pure, especially the high content of multivalent calcium and magnesium ions in the water. Generally speaking, the sum of calcium and magnesium ions in the water is called the total hardness of the water. After removing calcium and magnesium ions in the water by certain methods, the water that will not cause secondary pollution to the linen is called soft water. This process is the process of softening water!

When the water temperature is high, there will be some white precipitates-calcium carbonate and magnesium carbonate. After precipitation, the calcium and magnesium ions in the water are reduced, and the water becomes soft. This kind of water hardness is called temporary hardness. Because the precipitated carbonate is also called carbonate hardness. But at this time, it is only slightly softened. There are calcium and magnesium ions in the water, and there is hardness in the water. This hardness is called permanent hardness, also known as non-carbonate hardness.

It is estimated that people are not interested in reading these boring words. I talked about impurities in the water. In short, no matter what the composition of the scales, the cloth will be contaminated because scales can be produced. Impurities in the water will affect washing. It can even be said that no matter how hard you try, it is difficult to wash the sheets and quilts well, not to mention towels.

Detergents and hard water

Practitioners in the washing industry should understand the basic principles of washing and the main components of chemical materials. Let's not talk about the washing principle . There is usually a saponification phenomenon in the washing process. Saponification is the fatty acid salt generated by the reaction of oil and alkali, which is the soap in our home. In addition, the detergent contains sodium alkylbenzene sulfonate, and calcium and magnesium ions react with it to produce very difficult-to-dissolve calcium soap and magnesium soap. They are not only difficult to dissolve but also have no washing effect. What's worse is that they will adhere to the inner and outer tanks of the washing machine, and also to the linens. Over time, there will be more accumulation, and the linens will also become dark and dull, which is hateful!

Detergents usually contain silicates, carbonates, and phosphates. Calcium and magnesium ions are also easy to form insoluble salts when they encounter these substances. Due to the formation of insoluble salts, they will exist in the water as non-ions after precipitation. If it cannot resist deposition well, it will bring undesirable results.

Calcium and magnesium ions in water are usually multivalent cations with positive charges, which are easily adsorbed on fabric fibers or dirt. This will offset the negative charge on the surface and weaken the electrostatic repulsion of the cloth fibers and dirt. At this point, purification and anti-reposition will be weakened. Of course, during the neutralization process, impurities will form calcium oxalate with some neutralizing acids containing oxalic acid.

Let me give you a simple example to illustrate: calcium bicarbonate, carbon dioxide, and water will be produced when calcium bicarbonate is heated. Similarly, magnesium bicarbonate also produces magnesium carbonate, water, and carbon dioxide when heated.

Iron ions are turned into iron hydroxide precipitation by heating and oxidation (mainly washing), and then turned into brown precipitation iron oxide by further heating. The reaction of copper with alkali will produce blue copper hydroxide, and the heating and oxidation of manganese will also produce substances that make the fabric black.

These oxides tend to have strong adhesion, and coupled with alkaline action, they will actually rust and have a strong decomposition ability under the catalysis of chlorine bleaching or color bleaching.

You can do an experiment: wet the cotton yarn with water, and then hang it on a rusty iron nail. After a few days, bleach it with chlorine bleach, and the rusted place will definitely break. Therefore, if there is rust on the cloth, after repeated use of bleach, over time, this place may basically be a hole. Of course, the hole in the cloth is not entirely caused by this reason.

It is not difficult to see from the above examples that these insoluble salts will be deposited on the fabric, the fabric will become unclean, not soft, and not beautiful, the washing effect will naturally be poor, and the service life of the fabric will be reduced in the long run.