Coated paper and printability (2)

Three, then the agent

The agent is then divided into natural products and complexes. The natural products are starch, cheese, soy protein and so on.

Synthetic compounds include various synthetic latexes, polyvinyl alcohols, and the like. The most widely used is a mixture of starch-synthetic latex. The proportion of synthetic latex is increasing, and recently all-latex adhesives have also been developed. This is consistent with the development of high-concentration coatings. The following requirements apply to any adhesive:

(a) Strong adhesion to pigments.

(b) It has good adaptability and stability to pigments but does not react chemically with pigments.

(C) have the appropriate viscosity and film formation.

(d) Appropriate fluidity for coating operations and improved coating uniformity.

(e) The color should be light, free from foreign matter, and has good paint handling.

Because of the general adhesives, whether natural or synthetic, there are still some properties that cannot be improved, so in recent years there has been the emergence of so-called co-Binders to compensate for the lack of water retention and fluidity of adhesives. The dosage is only about 10-30% of the total subsequent dose. Now there are factories that are trying to use this to reduce the total continuation dose. Because of the small amount, it can sometimes be regarded as an additive. The commonly used auxiliary adhesives are soybean protein and rheoloe mdifier.

Fourth, additives

There are dispersants, lubricants, antiseptics, fluorescent agents, water-repellent agents, and dyes, inks, absorption and modifiers, etc., whose main role is to compensate for insufficient pigments and adhesives, and to reduce operating problems. In the use of good varieties and the amount of use should be selected, due to the opposite of more things, the need for prior research to prepare the most suitable coating.

Fifth, surface modification

(A) calendering

To produce a glossy coated paper, it is necessary to use a calender wheel for glossing. The equipment that was used more often in the past was a combination of an elastic wheel made of cotton or wool and a chilled roll. Super calender. Recently, starting from Europe and the United States, Japan now also uses soft calenders that contain a plastic material coated with a polymer product.

The soft calender has the following features compared to the plain paper machine and the super calender:

1. Give the paper higher twist, stiffness, opacity and strength, further improving the two sides of the paper.

2. The tightness of the paper web after calendering is consistent, the printability is good, and the ink penetration is uniform.

3. Allows slightly higher sheet moisture, less paper breakage, less black spots, and good running performance.

4. Moderately reduce the wood pulp ratio or reduce the basis weight of coated paper and newsprint paper without affecting the product print quality.

5. It can be installed on the machine, or it can be used after the machine can also be used as a semi-wet calender. All jaws can be individually driven and can be interchanged for a wide range of applications.

6. Compared with the super calender, there are advantages such as less investment, less occupied workshops, convenient operation and maintenance, less nip, and low power consumption.

However, when the soft calender has too few kneading numbers, it cannot place high-gloss art coated paper, and the super calender rotates at a too slow speed, which limits the output and has disadvantages. The Janus Concept calender with advantages of machine and soft calender came into being in 1995. Its characteristics are:

1. According to the need to select the number of nips, the 8 pinching of Janus Concept calender and the traditional 12 squeeze super calender calendering effect is equivalent.

2. The application of hot calendering, and the energy consumption is lower than the ordinary soft calender.