Introduction to planing and dyeing technology of i

2022-06-23
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Introduction to planing and dyeing process of imitation black walnut veneer

it is widely used in helicopter hub and various aircraft structures targeted by aluminum matrix composite research and Development Institute. Since the 1960s, Japan's Okawa Yong, Kitamura Yoko and Yasuda maoshu have studied wood dyeing technology, and other countries have also reported on veneer dyeing technology patents and products

China has been exploring and practicing wood dyeing since the 1990s. The imitation black walnut veneer, which is widely used in the market, is one of its achievements. The dyeing technology of imitation black walnut is a processing technology that cuts the wood of fast-growing species such as Paulownia and poplar, or imported ordinary tropical wood into thin wood with a thickness of 0.13 ~ 0.15 mm, and after dyeing treatment, it is dyed into a color close to that of precious wood such as natural black walnut. During the dyeing process, the veneer is not broken, and the dyeing solution can be recycled without pollution. The Dyed Veneer has uniform color, water and sun resistance. The veneer technology of wood-based panel imitating black walnut is to stick the dyed veneer glue on the surface of wood-based panel to increase the decorative effect of wood-based panel and increase its added value

ordinary wood-based panel veneer technology can be divided into dry veneer and wet veneer. At present, wet veneer is mainly used in industrial production. Processing methods include mechanical veneering and manual veneering. The mechanical veneer is mainly made of thick plates over 0.5mm. At present, the veneer in China is made by hand

dyeing and veneering technology of imitation black walnut veneer is mainly composed of veneer planing, dyeing of imitation black walnut veneer and veneering of wood-based panel veneer. Its processing process is briefly described as follows:

I. veneer planing process

process flow: Log - cutting - Cooking - planing - planing - stacking - cutting

(1) logs: white Wutong (commonly known as aegis), Paulownia, Fraxinus mandshurica, etc. After the logs arrive at the factory, they shall be peeled and cut off

(2) section: determine the sawing drawing according to the requirements of the product. At present, because the straight grain veneer has a good market, it generally adopts the four side sawing method. If more shadows are required, the number of radial cutting plates shall be ensured as much as possible; If mountain pattern is required, the number of chord cutting plates shall be ensured as much as possible

(3) cooking: it is the key process of wood planing. The temperature is controlled at 60 ~ 100 ℃, and the temperature is increased at 10 ℃/hour for 30 ~ 60 hours. If the temperature is too high, the temperature rises too fast, and the energy consumption is large, it is easy to cause log cracking and color difference; The temperature is too low and the cooking time is too long; The cooking time is too short, the softening degree inside and outside is different, and the color is inconsistent; The most important thing is that due to the different internal and external moisture content, the timbers are bent before planing, making the thin timbers degraded or scrapped

(4) planing: remove the pollution caused by cooking on the wood surface, especially the iron pollution

(5) planing: the thickness of thin wood is 0.13 ~ 0.15 mm, depending on the wood variety and production process requirements. The veneer is too thin, fragile and transparent, which makes the veneering process more difficult; If the thin wood is too thick, it will increase the cost and bring difficulties to dyeing

(6) stacking: count and stack the veneers orderly. In this process, unqualified thin wood with uneven thickness, knotting, skin clipping, decay, discoloration and other defects shall be removed

(7) cutting: cut into 5 ~ 16cm wide thin wood strips, 6 ~ 10cm thin wood is especially easy to glue, and the excellent grade rate of finished boards is high. In addition, defects are further removed in this process

II. Dyeing process of imitation black walnut veneer

process flow: veneer - dyeing solution - dyeing - washing - fixation - stacking

(1) veneer: after strict selection, unqualified veneers are removed and caged

(2) dye solution: A. dyes and proportion: dyes suitable for wood dyeing include acid dyes, weak acid dyes, direct dyes, etc., which depend on the wood variety, color depth and customer requirements. The basic ratio of dye is 80:15:5 for bright red, dark blue and orange. B. Auxiliaries: NaCl, Na2CO3, penetrant, acetic acid, color fixing agent and leveling agent, etc., depending on production demand

(3) dyeing: A. dyeing process parameters: dye concentration 1%, appropriate amount of additives, dyeing temperature 60 ~ 90 ℃, dyeing time 2 ~ 4 hours. B. Process: prepare the dyeing solution with warm water, put the caged veneer into the dyeing cylinder, compact it, heat it to the required temperature at the rate of 2 ℃/min, keep it warm for 2 ~ 4h, and keep the dyeing solution flowing during this period. C. Quality standard: the interior and exterior color of the veneer shall be uniform, without obvious color difference, and flat. D. Economic and technical indicators: the added value of ordinary thin wood can be greatly increased by dyeing, so that the price of thin wood with a thickness of 0.13 ~ 0.15mm can be increased from 0.5 ~ 1 yuan/m2 to 4.5 yuan/m2, and the dyeing cost is 0.5 yuan/m2

(4) water washing, fixation, etc.: the purpose is to remove floating color and increase the binding force between dye and wood

(5) stacking: count and stack in order to remove the veneers with dyeing defects

the dyeing cylinder can be divided into vertical type and horizontal type, both of which have their own advantages and disadvantages. The vertical equipment can be cut before dyeing, which is convenient for loading and unloading. The production capacity is large, but it is easy to cause uneven dyeing and uneven board surface. The horizontal equipment has a small production capacity, which is inconvenient for loading and unloading, but the thin wood is easy to be dyed evenly and thoroughly. Mainly dyeing before cutting, or cutting before dyeing. Stainless steel plate should be used as the material for manufacturing the dyeing cylinder, because the heating device, dye liquid flow device, filtering device, liquid inlet and discharge device, etc. should be considered; At the same time, it is also necessary to consider appropriate plate cages, hoisting facilities, etc. The most important thing in dyeing process is dye selection and color matching. The dyestuff shall be selected according to the wood material, product type and customer requirements. On the premise of meeting the target color, the less dyestuff varieties used, the better. First, check whether the installation of the pressure testing machine is horizontal, and level the host with a frame level in two directions perpendicular to each other on the outer ring of the working cylinder Adjust the front and rear levelness of the dynamometer on the front of the swing rod, align and fix the edge of the swing rod with the inner scribed line, and adjust the left and right levelness of the body with a level ruler against the side of the swing rod Drain and clean the internal parts of the oil cylinder and change the oil with appropriate viscosity The friction force of the driven needle of the dynamometer instigates the device to be too large, the gear tooth rod is too dirty, the pressing screw and the upper limit plate of the tooth rod can be cleaned and adjusted with gasoline, and the belt on the dynamometer piston can be replaced, which can achieve the purpose of eliminating errors and make the pressure testing machine reach the qualified use state

in the dyeing industry, in order to meet the color requirements of customers, it is often necessary to mix dyes of different colors. This work is called color matching, also known as color matching. Color matching is based on the "subtraction" color mixing principle. In practical application, red, yellow and blue are often used instead of the ideal three primary colors. Before production, color matching must be carried out. After small-scale color matching in the laboratory, and then large-scale color matching, batch production can be carried out only after the requirements are met. Color matching is a complex and meticulous work. In addition to having keen color discrimination ability and rich practical experience, the personnel in charge of color matching need to use a large number of reaction kettles that can be opened in production, and must also master the necessary color knowledge, preferably with the participation of color matching engineers. (end)

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