(fineness, temperature, color saturation)
I. Basic equipment in the production of coatings:
In the process of paint production, pigments and paints are usually pre-mixed before dispersed grinding. During the process, pigments and paints are combined into one. First, the pigments are pre-mixed through our mixer, so that the foreign substances such as gas and water held on the surface of the pigments can be replaced initially to achieve the purpose of initial wetting. So we can get the second-order particles.
Because it is impossible to break secondary particles into primary particles by initial wetting, it is necessary to grind and disperse them again. The equipment used is usually three-roll machine and vertical and horizontal grinder. The function of grinder is to disperse the original pigment particles by mechanical shearing, so that the original pigment particles can be permanently dispersed.
The particle size of the primary particles formed by the crystallization and crystalline conjoints of the pigments themselves is usually about 0.01~2 um, but after mixing, the primary particles become aggregates, which increase the particle size to about 100 um. Therefore, the mixer and grinder become the most basic equipment in the production of coatings, and filter and gas impurities in the products at the same time. Bubble pressure out of such equipment is also indispensable.
2. Structure and principle of grinding machine:
Sand mill, as a fine grinding and dispersing equipment, has been accepted by various manufacturers. It has been widely used in fine dispersion of paint, ink, dyes, pesticides, chemicals, pharmaceuticals, magnetic powder, paper and other non-metallic mineral industries, and its application field is still expanding.
As far as grinding machine itself is concerned, it can be divided into vertical and horizontal types according to the design method of dispersed spindle, while vertical type can be divided into open type and closed type. Horizontal grinding machine is closed type because dispersed spindle is horizontally arranged. (The advantages and disadvantages of open grinding machine and its application range are well known, so its use is affected. According to the dispersed components, it can be divided into disc type, rod type and other mixing type. Usually, disc type is used to process medium and low viscosity materials, and rod type is used to process high viscosity materials.
From the hydrodynamic analysis, the flow of liquid in any shape of the channel presents-ldquo; motion gradient-rdquo; which is caused by the internal friction force (viscosity) on the unit surface, which is the main driving force for the dispersion of pigments. When the internal friction force is greater than the cohesion force of pigments, the secondary cohesion begins to disperse because of the fact that the internal friction force is greater than the cohesion force of pigments. This suitable viscosity is conducive to the dispersion of secondary particles, and the grinder is through this basic principle, the use of dispersed components to transfer mechanical energy to the grinding medium, so that the grinding medium to mix, collision, shear movement, in order to disperse secondary particles, so that the pigment to achieve the required fineness, which is what we propose. The first degree is ldquo; that is, the fineness of pigment particles - rdquo;.
3. Characteristics of closed grinder:
The former describes two types of closed grinder, discrete type and horizontal type. According to the effective volume of the cylinder, from 0.5 to 3000L, the basic action is feeding and dispersed grinding. Sealing, cooling and separating material are necessary auxiliary devices.
At present, when energy saving and environmental protection are becoming more and more loud, the closed sand mill plays an active role. As the name implies, it can disperse and grind the products under certain pressure in the sealed cylinder, which greatly reduces the volatilization of solvents and pollution to the atmosphere, especially the horizontal sand mill, because the spindle becomes water. Horizontal design, which consumes less power than vertical grinder in start-up and normal operation, has been widely used, and more efficient models are still being introduced.
The sand mill we are talking about at present is actually an energy conversion mechanism. In order to make the secondary particles disperse permanently and distribute independently in the paint, it relies entirely on the impact, mixing, shearing of the grinding media to make the “ pigment suspension ” produce strong internal friction, therefore, narrow grinding. Regional and reasonable energy conversion curves are the ideal values for our design and manufacture, because only in narrow channels can we produce enough energy for secondary particle depolymerization.
Because of the energy conversion, the strong contact between the disperser and the abrasive medium leads to friction heating. A large amount of heat is taken away partly by cooling circulating water and partly stored in the product material, which has a negative effect on the volatilization of some heat-sensitive products and solvents. This is the second degree we have proposed, that is, & l Dquo; grinding dispersion temperature & rdquo;.
Because too high grinding temperature will lead to the development of product color image towards carbonization, we should check and find a balance point for the number, size and viscosity of the grinding media used in the grinding machine to ensure the best grinding effect, so as to control the appropriate grinding temperature. It is impossible to fit every kind of material with different specifications, and it is impossible for all kinds of materials to be processed in one type of machine.
4. The unavoidable phenomena in grinding and dispersing:
At present, the main body of domestic and foreign models is metal material, and only the grinding chamber and dispersing parts are treated accordingly in the manufacture. Therefore, the wear and tear of metal material and the consumption of medium are unavoidable, which pollutes the products and materials under allowable conditions, together with the addition of various additives, which greatly improves the quality of products and materials. It reduces the original saturation of pigments, which is the third degree we proposed, namely, & ldquo; color saturation & rdquo;.
According to this phenomenon, many experts have put forward various schemes, some of which have played a positive role, such as the use of electropolishing, high wear-resistant alloy steel, ceramics and polyurethane as dispersive components, the purpose of which is to reduce or avoid the pollution of materials. We believe that different products can be adopted. Different dispersions should be used, but due consideration should also be given to the current manufacturing process and the feasibility of wide promotion. If the process is too difficult, the manufacturing cost is too high, and the user can not accept it, it will not be promoted eventually. Therefore, & ldquo; color saturation & rdquo; will become a relative value.
Expanding the grinding area, reducing the residence area, increasing the energy density, increasing the gradient of dispersion and medium motion, choosing the suitable grinding medium and material viscosity, completing the dispersion of secondary particles in unit time as far as possible, reducing the temperature and improving the color saturation become our system.Manufacturers and coatings industry are the focus of common concern, but also our power and direction.
Fifth, the company's models and characteristics:
The company has independently developed a series of horizontal grinders with its own characteristics. Its specifications range from 5L to 3000L, which basically meet the choice of users. Especially the recently developed high-wear-resistant grinder model of our company has more extensive applicability. It also plays a positive role in the color saturation of materials and improves the sealing original parts. In order to overcome the contamination of user's products caused by accidental leakage of machine seals, the traditional single-end machine seals are changed to double-end machine seals.
Faced with the rapid development of the paint industry and the fierce competition in the paint machine market, we will continue to introduce new products to meet the needs of the paint industry, such as & ldquo; gear-disc Grinder & rdquo; and & ldquo; wheel-pin Grinder & rdquo; and so on. We hope that the new models will be welcomed and approved by all users in the paint industry.
I would like to take this opportunity to express my deep respect to all users and thank you for your generous acceptance of our products. At the same time, I urge all users to give us valuable comments and suggestions to help us do better in the future.