First, the requirements for the use of poplar plywood
The national standard stipulates that the diameter of the small head of plywood must be greater than or equal to 26 cm and the length is more than 2 meters. At present, the diameter of the poplar logs used by most enterprises in production is 18 cm, and the length is more than 1 m, 2 m, 1.3 m. And 2.6 meters, in order to meet this requirement, each plywood factory has developed the standard for the acquisition of poplar according to actual needs, and the price difference is relatively large. The grade standard for the acquisition of poplar is: first-class material: no material, no holes, no cracking, no warp in length, no thrift, and full dry; second grade: no decay, no cracking, bending The degree does not exceed 1%-2%, the number of joints does not exceed 2-3, and the maximum diameter does not exceed 4-10 cm. Secondary material: The second grade is the second grade for the bonded sheet.
Second, the standard of poplar pulp and its wood material requirements
Poplar papermaking is an important aspect of the use of poplar. The scale and development speed of poplar paper utilization depends on the size and management level of poplar forest. The size and level of poplar forests depend on the existing forestry techniques and depend on the improved varieties of poplars and their coordinated allocation. In other words, the level of poplar trees and their forests required by the poplar paper industry depends to a large extent on the corresponding varieties of poplar and their allocation.
At present, China's poplar paper industry is entering a new stage. The progress and level of poplar forest has become a bottleneck restricting the development of the poplar paper industry. The key to restricting the development of poplar paper and poplar forests depends on the corresponding poplar varieties.
(A), Poplar pulpwood at home and abroad and its adaptability in thoroughbred history <br> <br> Poplar paper is part of the development of the wood and paper industry, mainly the product of 20th century industrial development.
European countries such as Britain, France, Germany, Italy, Netherlands, Belgium, Yugoslavia, Hungary, Romania, Russia, and Czech Republic, and the United States and Canada are the main countries of poplar paper. In the early stage of development, natural poplar forests and existing poplar plantations were the main ones. That is to find the material on the spot, how to use it. In the United States, Russia, and Canada, the natural forest poplars have more poplars, so the aspens become the main raw material for paper-making poplar. If the poplar, black poplar or other existing poplar, black poplar hybrids and other plantations are available, then these poplars are used interchangeably or in combination. Including Italian I-214, Jian Yang, newborn Yang, late flowering Yang and other European and American poplars, American black poplar and its hybrids with Qingyang. In short, as long as it is not seriously affected by pests and diseases, which affects the quality of paper and increases the cost of poplar, no matter what kind of variety can be used.
The above-mentioned basis for determining the improved varieties of poplar paper is: all the natural species, varieties and their variants of poplar, and all varieties and strains artificially selected, although there are many differences in genetic and physiological traits, but the quality of poplar papermaking They are all at the same level. All kinds of poplars belong to short fibers, and the physical and chemical properties are similar. There is no need to classify the grades. In other words, according to the current papermaking process, various poplars can meet the needs of papermaking.
The scientific standards for the approval of papermaking varieties are mainly based on the forestry standards such as fast-growing, trunk straightness, fullness, and sharpness, and related forestry standards such as pest resistance and cold resistance. Among them, the indicators may be coordinated and balanced to achieve advantages and fill the gap.
According to the long-term multi-species test of Chinese forestry science experts Sun Chengzhi and Chai Xiuwu, Shalan Yang, Xiaoheiyang, Zhonglin 46, Zhongzhan, Zhonghan and other American black poplar series and European and American pop series are all good papermaking varieties. In view of the close proximity of various papermaking performance indicators, it is considered that pulping and papermaking can be mixed.
(II) On the scientific standards of Yangshuo papermaking and its mutual constraints and advantages
In summary, the objective criteria for poplar papermaking include:
(1) Fast-growing high-quality forestry index A. Fast-growing poplar can achieve high volume growth under local conditions. According to the high-yield level at home and abroad, the general growth indicators of fast-growing varieties are shown in Table 4-24.
B. Shape index: It has the advantage of the top, the trunk is straight and straight, the sharpness is small, the branches are well-proportioned, and the branch angle is less than 70-80°.
C, material index
Wood properties require white or light wood, less resin, easy to bleach, wood pulp yield, strength and bleaching. The fiber length is high, the ratio is high, the cell wall thickness of the fiber is small, the cellulose content is high, and the lignin, pentose, resin and ash content are low.
The fiber should have a certain flexibility, elasticity, and a large length and width (interlacing is better than 35 to 45, and the strength is large).
D. Cold resistance: The winter is safe in the local area, the trunk is not frozen, and the seedlings are not frozen.
E, insect resistance: no devastating pests, high resistance to pests that damage the trunk.
F, disease resistance: no devastating disease, high resistance to diseases that endanger the trunk; at the same time, it must be highly resistant to various leaf diseases.
(2) "One-vote veto" and advantages to fill the relevant indicators
Among the above indicators, the variables are small, the traits are stable, and the various poplars generally meet the papermaking requirements.
The five indicators, A, B, D, E, and F, have a wide range of variations. Any one of them fails to negate the selection of a variety. It can be called a "one-vote veto system."
When a variety meets the basic standards for improved varieties, and the first two indicators are particularly excellent, which can bring high benefits to local production, the variety can be selected as a good variety. For example, the variety is generally resistant to pests and diseases, and there is a slight frostbite in winter, but it is particularly fast-growing. When the growth volume still has a large benefit after offsetting the economic loss caused by its shortcomings, the variety is selected as a good variety. Need to know, there is no, it is difficult to have a perfect variety of poplar.
(III) Prospects for the application of improved varieties of poplar paper
The situation of poplar paper is very good, which is a rare opportunity and challenge. At present, the main problems are: breaking the one-sidedness and narrow local protectionism and one-sided empiricism; excluding the interference and obstacles of pseudo-fertilization, inferiority, and fraud in the poplar seedling market, and the basis of research and experimental data for many years at home and abroad. On the basis of identifying the authenticity, removing the obstacles, reviewing the situation, determining the fast-growing high-quality and suitable varieties from the high standards and strict requirements, making the healthy development of the Yangshu papermaking materials and contributing to the papermaking.
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