The tannin-rich wood, cortex, leaves, pod shells, etc. used for the industrial production of tannins are commonly called vegetable tanning materials. There are hundreds of kinds of vegetable tanning materials, but only 20 to 30 kinds can be used as raw materials for tannins, such as larch, spruce, casuarina, tangerine, bayberry, black wattle, cork oak, large scale oak, and chestnut. and 159129 Wood et al. Their conditions are: the tannin content of bark is not less than 15% and that of wood is not less than 10%; resources are concentrated and easy to harvest, dry and store; and the processed products have good tanning properties.
Classification
Classified by plant family: such as larch and spruce of the Pinaceae family; tangerines of the Euphorbiaceae family; black wattle trees of the Mimosa family; 159129 of the Anacardiaceae family. Wood; cork oak, large scale oak, chestnut of Fagaceae; Casuarina of Casuarinaceae, etc. Classified according to the parts used: such as bark-type larch, spruce, black wattle, casuarina, etc.; wood-type wood, chestnut, etc.; shell-type oak bowls and myrobalan; leaves-type lacquer leaves; Roots such as red root, sorrel root, etc. Classification according to tannin structure: such as condensed black wattle, larch, bayberry, spruce, 159129, etc.; hydrolyzed oak bowl, chestnut, myrobalan, etc. (Table 1).
Collection
Different raw materials use different collection methods. ①Leather raw materials: peeled manually or mechanically. The manual peeling method varies depending on the tree species. For example, black wattle bark has long fibers and thin bark, and is peeled in strips. Larch bark has short fibers and many corks, so it can only be peeled off with tools. Mechanical peeling is divided into cutting method and friction method. The former method has low production capacity, and the cut bark is about 10% woody. The bark quality is poor and should not be used. The latter method is better, and two types of peeling machines, chain type and cam type, can be used. The chain peeling machine consists of a frame, a peeler rotating tray and a feeder. Driven by a motor, it can peel logs with a diameter of 6 to 25 cm. The machine is equipped with an annular chain, fixed on the lever, and the rotating joint is installed on the end face of the flat plate. The chain is close to the log, and the bark is peeled off by friction. The cam peeling machine uses a cam to replace the easily worn chain. The cam is made of alloy material and has a triangular cross-section. It is fixed on a roller that rotates around the log. It uses a spring to make it close to the log and peel off the bark. ②Wood raw materials: manual or mechanical logging is used. After the trees are felled, the branches and bark are removed, cut into specified lengths, and concentrated on forest roads for transportation. ③Nutshell raw materials: such as oak bowl. The large scale oak trees in Turkey are short trees and are mainly picked manually. The new oak bowls picked are laid flat on the ground, dried and transported to the factory. China mainly picks up floor-standing oak bowls. It starts collecting in August and September every year. It is operated by the purchasing station and then resold to the factory. The former method produces oak bowls with a light color, few impurities, and high tannin content. The oak bowls harvested by the latter method are dark in color, have many impurities, and are of low quality. ④Rhizome raw materials: harvested manually. Shallow roots such as dioscorea and red roots can be pulled out by hand or dug with tools with hooks. Deeply buried roots such as tower soil and sorrel roots can be dug with an iron rake. If it is artificial planting, use a harvester to dig a 40 cm deep trench before harvesting.
Italy, France, brown-yellow color, good penetration and bonding, 10?14 hydrolyzed wood used in about 50 years, Fagaceae chestnut, Paraguay, used as woodworking adhesive, Argentina, fast penetration, good bonding, light brown color, can be large Arbor, 16-25 condensation of heartwood was used in about 200 years. Heartwood of Anacardiaceae is good in Kenya and Brazil. It can also be used as woodworking adhesive. It was used in the Commonwealth of South Africa in about 200 years. Color is light yellowish brown, fast penetration, tanning tree, fast-growing, artificial planting, 636-45 condensation. Bark Mimosaaceae black wattle Turkish color light brown to yellow, good tanning properties 25-35 hydrolyzed bowl shell Fagaceae Quercus squamata good filling performance 8 to 50 years using China color brown to yellow brown, convergence, combination with trees, Wild or artificially planted, 18?33 hydrolyzed bark of Fagaceae, cork oak (Emblica emblica), Chinese color, light brown, fast penetration, good tanning properties, shrubs, small trees, wild 21?33 condensed bark, Euphorbiaceae, tangerine (Terraceae) Bayberry) Chinese color is light brown, penetrates quickly, and has good tanning properties. Shrubs, small trees, and wild 15-18 condensed bark Myricaceae have good heat resistance. China and the Soviet Union have brown-red color. They are used for tanning inner bottom leather and large leather. Trees, about 100 years old, using 12 to 18 condensed bark, pinaceae, larch, main origin, specialty products, tree species, tannin content (%), tannin category, utilization, some family tree species
Table 1 Post-harvest Bark, wood, and fruit shells contain about 60% moisture, and fresh roots contain more than 60% moisture. It must be dried as quickly as possible to prevent the raw materials from deteriorating. Generally, natural air drying is used to reduce the moisture in the raw materials to less than 16%.
If necessary, artificial drying can also be used and baked below 50°C. This method can shorten the time, but is more laborious and expensive than natural air drying.
Grading
Dried raw materials can be graded according to color depth, moisture content, tannin content, etc. For example, larch bark is divided into two levels based on the quality of the wood in the bark, appearance and inner surface color. The wood quality of Grade I and Grade II is ≤0.5 and 0.8 respectively; the color ranges from brown-red to dark gray. Chinese oak bowls are divided into three grades (Table 2).
Table 2 Shipping
Before shipment, the bark is packed manually or mechanically into bundles (90×60×50 cm), the weight is not more than 80 kg, and the bark is cut or cannot be bundled The bark can be packaged in sacks or other packaging (such as containers). Each bundle or bag should be marked to indicate the variety, bundle weight and grade. Various types of raw materials are transported according to local transportation conditions, transportation distance and other conditions.
Acceptance
Raw materials should be sampled and inspected for each batch of tannin extract raw materials according to the relevant national standards for raw material sampling and inspection methods. Check whether the raw materials have mildew, inclusions or adulteration, and whether the appearance and color are consistent to determine the grade of the raw materials entering the factory.
Storage
There are two types of raw material storage: indoor and outdoor. The indoor warehouses are mainly simple warehouses. The warehouse volume is determined according to the quantity of raw materials stored. Generally, it is appropriate to store 200 to 300 tons. The floor should be paved with wooden boards or bricks to keep it dry, and 1.5-meter passages should be set up every 6 meters. Maintain good ventilation conditions on and around the warehouse, and no water seepage can occur on the top and walls. Stacking forms are adopted outdoors, such as conical, pyramidal and rectangular stacking, and the stacking height can reach more than 10 meters. The bottom of the stack is lined with wood and cement strips, and is above 30 cm above the ground to keep it ventilated and free from moisture. Cover the top with waterproof material (such as oil felt) to prevent the raw materials from deteriorating. The air-dried raw materials should be stored indoors for about one year. Due to long-term storage, the quality of raw materials changes, which is manifested as a decrease in the total extractables in the raw materials and a darker color. For example, if an oak bowl is stored for one year, the total extractable content will be reduced by about 4%. The color of tangerine bark (red + yellow) is 5-6 before storage and 17 after 2-3 years of storage; the color of oak bowl is 14 before storage and 40 after storage. Raw materials stored in the open air are more likely to deteriorate due to exposure to wind, rain and sunlight and should not be used.
P.Peter Koch, 1920 ~ famous American wood scientist. Born on October 15, 1920. He graduated from the University of Washington in the United States in 1954 and received a doctorate in wood science. He served as project director of the Southern Forestry Experiment Station and the Intermountain Forestry Experiment Station of the U.S. Forest Service. From 1972 to 1973, he served as the chairman of the American Forest Products Research Society. In 1974, he was elected as an academician of the International Wood Academy. In 1985, he served as a part-time professor at Nanjing Forestry University in China. He has been engaged in research on the rational utilization of pine and broad-leaved trees for a long time, and has obtained a number of patents, such as lumber chipping blade device, glued pine veneer square lumber, and various equipment for whole-tree utilization. Won the USDA Outstanding Service Award twice in a row (1968, 1973). He has published more than 100 papers, and his main monographs include "The Utilization of Southern Pine" (1972) *** 2 volumes, and "The Utilization of Broad-leaved Trees in Southern Pine Forests" (1985) *** 3 volumes. (Wang Kai)
Kollmann, F.F.P. Franz Friedrich Paul Kollmann, 1906 ~ famous wood scientist in the Federal Republic of Germany. Born on October 15, 1906. In 1932, he received a doctorate in engineering from the Technical University of Berlin. From 1934 to 1939, he served as professor and director of the Prussian Wood Research Institute. From 1940 to 1945, he served as director of the National Timber Research Institute. From 1949 to 1954, he served as professor of wood technology at the University of Hamburg. From 1954 to 1982, he served as professor and director of the Wood Research Institute of the University of Munich. He retired in 1986 and became an honorary professor of the school. Coleman is also a foreign academician of the Royal Swedish Academy of Engineering Sciences, an honorary doctorate from Stockholm University of Technology, a consultant to the Swedish Wood Institute, and the first president of the International Academy of Wood Sciences. In 1970, he received the Grand Cross of the Federal Republic of Germany.
Coleman has published hundreds of papers on wood science and wood technology. His main monographs include "Principles of Wood Science and Wood Technology" (co-authored with American W.A.C?té, Jr., etc., 1975), 2 volumes, of which the second volume has been translated into Chinese.