The so-called structural ratio refers to the ratio of the weight of the fiber layer to the weight of the bottom mesh layer. Generally, the ratio of the two to the total weight of the felt is taken as the ratio. For example, if the fiber layer accounts for 54% of the total weight of the felt and the bottom mesh layer accounts for 46% of the total weight of the felt, the structure ratio of the felt is 54:46, or the structure ratio is 1.17. The structural ratio is closely related to the water permeability of the paper-making felt, and it is also related to the wear resistance, self-cleaning ability and compression resistance of the felt. The larger the structure ratio, the smaller the water permeability of the felt, the wear resistance and compression resistance are improved, and the self-cleaning ability is reduced. The size of the structural ratio should be controlled according to factors such as the paper grade produced, the state of the pulp, the press type of the paper machine, the size of the line pressure, the setting state of the washing, the setting state of the vacuum system, etc. Generally, the grade of the paper produced is higher and the washing effect In the case of good, high line pressure, high vacuum, etc., the structure ratio can be adjusted higher, so that the blanket is more durable.

4. Acupuncture state [5] [6]

     Whether the needle-punched flocking process is reasonable will directly determine the tightness (density) of the finished blanket, the smoothness and smoothness of the surface, and the degree of damage to the fiber and the bottom net, which is related to the water permeability of the blanket, the state of hair removal and hair removal, and the surface silkiness. The state, the state of uniform density and the state of strong loss of fiber bottom net and so on. Therefore, the selection of the puncture needle, the condition of the needle hole of the needle plate, the depth of the needle puncture, the number of needle punctures, the speed of the cloth feed, the control of the needle breakage rate, and the state of the laying of the net, etc. Add control.

1. The needle density of the needle board is an important parameter to measure the quality of a needle punching machine. It is related to the processing accuracy of the needle hole on the needle board and the strength of the needle board. It is about 3000 pieces / m.

2. The arrangement of the needles is very critical to the smoothness of the surface of the processed papermaking felt. Poor arrangement will inevitably lead to regular and obvious needle marks (needle points) on the surface of the felt. The distribution of the needle points is related to the arrangement of the needles, the longitudinal length of the needle plate, the speed of the web advancement and other parameters. Now, the arrangement of the lancets has been mostly random and disorderly arranged by computer.

3. Selection of flocking needles: When producing BOM paper felts, the needles not only have to pass through a certain thickness of the felt, but also overcome the resistance formed by the multi-layer bottom net, so the rigidity, toughness, elasticity and wear resistance of the needle body are required It should be good, with good straightness, smooth surface, smooth barbs, no burrs, precise geometric dimensions, and consistent needle shape. The equilateral triangle needle is the most widely used in the production of paper felts, and there are three barbs on each of the three edges. Although this type of needle has a large amount of fiber, it is easy to cause damage to the fiber and the bottom mesh. In recent years, many needle factories are actively developing and promoting trigonal single-sided toothed flocking needles. From the perspective of theory and trial use, the needle has the effect of improving the needle punching quality of papermaking blankets, reducing the needle punching of fibers and the bottom net Silk is very helpful.

    4. Acupuncture frequency: The acupuncture frequency should be moderate. If the frequency is too low, it will affect the production efficiency, but if the frequency is too high, it will produce large mechanical vibrations. , Causing excessive needle breakage or fiber breakage. The frequency of acupuncture is generally 300 ～ 800 times / min.

    5. Number of acupuncture areas: Acupuncture machine with single acupuncture area, obvious needle marks will appear after needle breakage, while acupuncture area of acupuncture machine with multiple acupuncture areas will pass through other acupuncture areas even if there are broken needles The acupuncture will also make some compensation, which is very beneficial to the flatness of the blanket surface. Generally speaking, the single-needle needle punching machine is used for the pre-punching of the fiber web, and the double-needle needle punching machine and the three-needle needle punching machine are generally used in the lamination of papermaking felts.

    6. Network delivery speed: The network delivery speed must be reasonable. If the network delivery speed is too fast, the needle will be pulled by the fiber web and deviate from the pinhole of the pallet, causing the needle to break. At the same time, the damage to the carpet skeleton material and fiber will also increase accordingly. The wire feeding speed is generally 0.6 ～ 10m / min.

7. Acupuncture density: The acupuncture density directly affects the flocking tightness and air permeability of papermaking felt. In the operation of the paper machine, the requirements for the permeability, water drainage and strength of the felt are very high, and the vacuum water absorption device, the carpet beater, the washing device (especially the high-pressure flush pipe) of the paper machine, and the inflexible drum etc. The friction effect is also very large, so it is necessary to adopt an appropriate needling density. Excessive needling density makes the felt lack elasticity, the structure is too rigid, and even affects the strength of the felt; if the needling density is too small, the felt produced is too loose, the wear resistance is insufficient, and the fibers are easy to loosen during use.

8. Needle punching depth: Needle punching depth is an important parameter in the needle punching process. In the process of combining the wool net layer and the bottom net (base cloth) layer of the papermaking felt, sufficient needle punch depth must be obtained to make the fiber There is sufficient entanglement and effective cohesion between the fiber and the bottom net (base fabric). However, the needling depth should be moderate. If the needling depth is too deep, the broken fibers of the punctured web will increase, which will reduce the strength of the felt; increase the needling force and equipment load and excessive needle breakage; at the same time, it will also cause the felting needle to be taken out of the blanket surface Of fibers increased. The depth of acupuncture is too shallow, the web is not tightly entangled, the strength is low, the blanket texture is soft, and it is easy to produce hair loss during use.

The determination of the needling depth depends on the type of papermaking felt, the square meter weight, the state of the barb hooks and the state of the raw materials. Generally, the needling depth ranges from 3 to 17 mm, and the depth of the needle punching is different for different net layers. Different. Table 4 lists the needle punching process of 950gsm single layer BOM paper felt.

9. Control of needle breakage rate: The needle breakage rate is an important indicator for controlling the uniformity of the needle marks during the needle punching process. When the needle breakage rate or local needle breakage reaches a certain level, it will inevitably affect the smoothness of the surface of the papermaking blanket. The state, that is, the state of the paper surface is particularly rough and the smoothness is uneven due to the needle marks on the surface of the papermaking felt. Generally, the needle breakage rate is strictly controlled in the range of 5 to 10% during the production of paper felts.

10. Laying method: BOM paper making blanket laying method generally adopts the method of laying thick wool on the front and laying thin wool on the back. The wool layer on the reverse side mainly protects the skeleton material of the carpet; the thick wool layer on the front side mainly meets the flatness of the paper surface The degree of sophistication reduces or eliminates the base mesh marks in the paper sheet, improves the wear resistance of the front of the blanket, and adjusts the air permeability of the blanket.

V. Sorting state [7]

     The post-order finishing of the BOM blanket includes washing, chemical treatment, heat setting, spraying of the logo and quality inspection of the blanket. The washing and chemical treatment of papermaking blankets have great benefits in improving their initial adaptability, removing floating hair on the surface of papermaking blankets, and giving them special properties such as stain resistance and corrosion resistance. Heat setting is to make the size (length extension, width shrinkage and thickness change) of the papermaking felt more stable, the air permeability more suitable for the needs of the paper machine, the surface is more flat and dense, and at the same time, the wear resistance of the papermaking felt can be improved. BOM blankets can only achieve the performance to meet the needs of high-grade paper grades produced by wide-width and high-speed paper machines only through a complete post-finishing process.

1. Washing the BOM blanket

     The washing of BOM blanket is mainly to wash off the floating hair on the surface of the blanket, improve the flatness of the surface of the blanket, improve the density of the fiber layer of the blanket, soften the fiber, and facilitate the purpose of chemical treatment and shaping in the next step. At the same time, it is also to improve the initial adaptability of the felt on the machine, reduce the idling time after loading the paper machine, and make the paper felt adapt to the requirements of high speed as soon as possible to improve the production efficiency of the paper machine.

2. Chemical treatment of BOM blanket

     The chemical treatment of BOM blankets is the special treatment and processing of papermaking blankets with chemicals with special properties, so that the papermaking blankets can obtain some special properties other than this performance.

At present, there are many types of chemical treatments on paper blankets in the world, including anti-staining chemical treatment, anti-hair removal chemical treatment, wear-resistant treatment, corrosion-resistant treatment, softening, hardening treatment, etc.

     The common chemical treatment method is: after washing the paper-making blanket, the prepared chemical liquid is evenly penetrated into the entire thickness of the blanket by spraying or dipping, the excess chemical liquid is sucked away by a vacuum box, and then used Heat curing by means of pressure, drying and heat setting.

In the process of spraying or dipping, the chemicals must be uniform in the longitudinal direction, transverse direction and thickness direction of the blanket, and there should be no uneven strips, unevenness of positive and negative.

     At present, anti-contamination chemical treatment is the most frequently carried out on paper felts in China. The treated blanket has good anti-staining performance and self-cleaning ability. Under the same washing conditions, it is easy to wash. At the same time, the wear resistance and anti-fluff performance of the blanket have also been improved.

3. The finalization of BOM blanket [4]

     At present, advanced production enterprises have eliminated outdated thermal radiation far-infrared sizing machines, and most of them adopt advanced hot oil (wind) sizing equipment. Thermal radiating far-infrared sizing will cause the fibrous gum on the surface of the carpet to form hard particles, which are in use. As a result, holes (holes) appear on the paper surface, and the hot oil (wind) setting equipment integrates water washing, chemical treatment, and heat setting. The setting is more uniform and the blanket surface is smoother.

Precautions for BOM blanket styling

1) Control of the setting temperature and speed: the heat setting temperature should not be too low, and high is better under possible conditions. The lower temperature will affect the setting effect. The relatively high temperature can make the fiber quickly reach the setting requirements. The far-infrared shaping has a poor heat penetration effect and needs to be adjusted in an appropriate manner; the hot-air shaping has a good heat penetration effect, but the blanket surface is poor; the oil heat setting has both good heat penetration effect and good Blanket surface. The setting temperature and speed are related to each other, and it is necessary to determine a suitable data through measurement.

2) The tension of the felt when setting it should be controlled close to the tension when the paper machine is used, otherwise the felt will have excessive elongation when used.

     With the continuous development of the technical equipment of the paper industry and people's requirements for the refinement of different paper functions, the demand for the performance of the paper blankets closely related to it is also more stringent and refined. Therefore, in the design and production of paper blankets, especially BOM paper When felting, each parameter must be designed reasonably, and each production process should be implemented around the performance of the felt, so as to obtain a more optimized and more detailed papermaking felt to meet the needs of the paper machine.

1. About the author: Han Bangchun (December 1969-), male, engineer. Earlier graduated from the Pulp and Paper Major of the First Light Industry School of Anhui Province. Now Xuzhou Golden Crown Industrial Co., Ltd. is engaged in the development, development and technical service of paper blankets. He has published many articles on the design, manufacture and maintenance of papermaking blankets. Contact number: 13605219603.

[1] Ni Zhengxing, "The Essentials of Papermaking Blanket Design and Manufacturing", see "Proceedings of the National Papermaking Textile Technology Exchange Seminar", Editor-in-Chief of the Papermaking Textile Branch of China Nonwovens and Industrial Textile Industry Association, Shanghai, 2001, P31 34

[2] Liu Hui et al., "Practical Handbook of New Technology and Performance Testing and Quality Control Standards for Nonwoven Fabric Production and Processing," Yinsheng Video Publishing House, Part One Chapter Four, P50-55, Part Two Third to Sixth Chapter, P281 ～ 373

[3] Edited by Guo Bingchen, "Performance and Testing of Nonwovens", Beijing, China Textile Press, 1998, P27 ～ 29, P307 ～ 310

[4] Yang Peisong, "Net, Blanket, Dryer Canvas for Paper Making", internal communication materials

[5] School of Textiles, Donghua University, Shanghai, Paper Machine Fabric Database, 2006.6, Chapter 4

[6] Shi Hanqiang, "Design and Production of Needle-punched Blankets (BOM)", see "Technical Exchange Information Compilation 1992", Chinese Paper Society Dewatering Equipment Professional Committee, Beijing Hualun Paper Dewatering Equipment Joint Company, Shanghai, 1992 , P46 ～ 51

[7] Shanghai Donghua University Textile College. "Paper Machine Fabric Database", 2006.6, Chapter 4