Discussion on the key aspects of rubber roller manufacturing and processing

Rubber rollers and aprons are important drafting devices for spinning. The rubber roller and the roller, the apron and the upper and lower pins form two pairs of elastic grip jaws to complete the holding and drawing of the fibers.

 

When many rubber roller manufacturers sell their own products, they often say that their rubber rollers are manufactured with advanced technology formula, which can improve the yarn level, anti-winding, anti-static performance and so on. Exaggerated the formulation of the rubber roller and the apron. In fact, the production process of the rubber roller is the same as the spinning process. The five elements of “man, machine, material, method and ring” are indispensable. The rubber roller formula is only ranked fourth. People are the primary factor in completing production and technology, ranking first, and equipment and raw materials are ranked second and third. Without good equipment and good equipment status, high-quality rubber raw materials, and advanced formulating technology, it is impossible to produce good rubber roller and apron products.

 

1 Classification of textile rubber

 

Nitrile rubber is the main raw material for the manufacture of textile rubber rolls, referred to as “NBR”. The content of acrylonitrile (%) in nitrile rubber is 42~46, 36~41, 31~35, 25~30, 18~24. The higher the acrylonitrile content, the better the oil resistance of the rubber. This feature is very suitable for textile drafting equipment with oil resistance requirements, especially textiles containing colored oils and chemical oils. High acrylonitrile content is used to develop chemical fiber, color spinning, wool spinning and spandex core yarn. Roller.

 

 

 

 

Carboxyl nitrile rubber: Carboxy nitrile rubber is a ternary copolymer of butadiene, acrylonitrile and organic acids (acrylic acid, methacrylic acid, etc.). Referred to as XNBR, the relative density is 0.98-0.99. The introduction of carboxyl groups into the nitrile rubber increases the polarity, increases the compatibility of NBR with PVC and phenolic resin, imparts high strength, has good adhesion and aging resistance, improves wear resistance and tear strength, and further improves Oil resistance. The tensile strength is generally 25.5-26.5 MPa, the elongation at break is 310 to 380%, and the tear strength is 51.0 to 55.9 kN/m.

 

2 main process of textile rubber roller and rubber ring

 

The production and processing of textile butadiene nitrile rolls generally goes through: plasticating → mixing → rolling → extrusion → injection → die casting → vulcanization → cutting → chamfering → rough grinding → inspection → packaging process.

 

Vulcanization has a critical impact on product quality throughout the butadiene nitrile roll production process. Vulcanization refers to the cross-linking of rubber molecular chains, giving the rubber various good physical properties. Because the rubber lacks good mechanical properties (tensile strength, tensile strength, elongation, elasticity, etc.) before it is vulcanized, the practical performance is not large. Therefore, it is necessary to accurately calculate the amount of sulfur used in the vulcanization reaction in the rubber roller formulation, and reduce the generation of free sulfur (excess unreacted sulfur) during the vulcanization reaction, so that the hardness of the rubber roller is more stable, and the hardness after one year of use. The rise control is within 2 degrees. TMTD, TMTM rapid vulcanization accelerator is used in the selection of accelerator to improve the crosslink density of rubber and improve the elasticity and deformation resistance of rubber roller. Special attention should be paid to the precise control of key process parameters such as extrusion process pressure and vulcanization temperature and vulcanization time.

 

3 key process control in the manufacturing process of rubber roller and its influence on yarn quality

 

3.1 The comprehensive dispersion of rubber roller compound

 

The comprehensive dispersion of the rubber roller rubber is an important indicator for assessing the internal quality of the rubber roller. The higher the dispersion, the more uniform the distribution of the components (including antistatic agent and reinforcing filler) in the rubber compound formulation, and the corresponding various The function is fully utilized, so the strength, abrasion, elasticity and antistatic properties of the rubber compound can be improved. The rubber roller with high dispersion forms an electron channel in the rubber compound, which is often called tunneling effect, which can reduce the volume resistivity and improve the electrical conductivity (antistatic property); on the contrary, the rubber roller with low dispersion and the dispersion of antistatic agent are not Evenly, the volume resistivity is increased, the electrical conductivity is lowered, and because the rubber contains small pores and no dispersed blocks, the rubber material in the area is unevenly distributed, which may cause unevenness of the rubber roller and cause the rubber roller to operate during operation. The periodic grip force fluctuates, directly affecting the sliver. Therefore, in order to ensure the quality of the rubber roller, the high-quality rubber roller should adopt the method of small batch and multiple mixing to achieve the proper dispersion of the rubber compound.

 

In the past, the quality standard of rubber roller was mainly to evaluate hardness, resilience, constant compression set rate and geometric size. At present, the dispersity of rubber roller is more and more important. The national standard GB 6030-85 "carbon black dispersion in vulcanized rubber" The determination of the dispersion is divided into 10 grades, the grade 5 is the difference, the grade 5-6 is better, the grade 7-8 is good, the grade 9-10 is excellent, the dispersion of the textile rubber roller should be Level 8 or above.

 

3.2 Surface roughness of the rubber roller

 

The surface roughness of the rubber roller can be expressed by the arithmetic mean deviation Ra of the profile, and Ra can be tested by a roughness instrument.

 

3.2.1 Relationship between dispersion and surface roughness

 

The hardness, molecular density and microstructure of the rubber roller with high dispersion are stable, so the surface roughness is uniform and uniform after the honing process, and the yarn quality is consistent.

 

3.2.2 Sets

 

The set difference is an important process for the production of rubber rollers. If the difference is large, the internal stress of the rubber roller is large, so that the rubber molecules are always in tension. The rubber roller is prone to cracking and aging, and the spinning performance is degraded, thus affecting the rubber roller. The uniformity of the layer hardness and the excessive difference in the circumferential hardness of the rubber roller have an influence on the uniformity of the surface roughness of the rubber roller. Therefore, we want to use high-quality yarns. We recommend the use of aluminum-lined rubber rollers. The aluminum-lined rubber rollers use the elasticity of metal aluminum to insert the rubber rollers into the rubber roller bearings, eliminating the internal stress of the rubber sleeves. Generally, we call aluminum. The rubber-lined roller is 'zero set difference' and should actually be a micro-set. Because it can reduce the production process and improve the quality of yarn, it is currently the mainstream product.

 

3.2.3 Number of grinding times

 

The surface roughness of the rubber roller has a close relationship with the number of honing; the number of rubber roller honing is not as good as possible, because the friction between the rubber roller and the grinding wheel causes the rubber roller and the grinding wheel to heat up, causing damage to the surface roughness of the rubber roller, especially When the temperature rises above 120 degrees, it will also burn the rubber molecules on the surface of the rubber roller, resulting in an increase in roughness unevenness. The number of rubber roller grinding times is three to four reciprocating, 40-60mm atmospheric hole wide grinding wheel grinding machines for ordinary 802 grinding machines. It is advisable to use two reciprocations, which can improve the surface roughness uniformity after the rubber roller is honed, and also take into account the production efficiency of the grinding machine. Table 1 shows the measured roughness values ​​of LXC-966A rubber roller under different grinding parameters of FM-1 grinding machine.

 

Table 1 Effect of different grinding parameters on the surface roughness of rubber roller

 

3.2.4 Grinding amount

 

The size of the rubber roller grinding directly affects the Ra value of the surface roughness of the rubber roller. The grinding amount of the grinding roller should be controlled between 0.15-0.20mm. The excessive friction between the rubber roller and the grinding wheel is too large. The surface temperature will rise rapidly, even up to 200 ° C. Burning the surface of the rubber roller will cause the roughness uniformity of the rubber roller surface to decrease, and it will easily lead to the overflow of the antistatic agent on the surface of the rubber roller. Especially in the case of improper operation of the hand plate too fast, too much grinding, etc., it may also cause wear marks on the surface of the rubber roller. As long as the precision of the grinding machine is allowed, we recommend to adopt the method of “hard grinding and less grinding”, which can not only improve the quality of the yarn but also the consumption of the rubber roller, and achieve the purpose of energy saving and efficiency improvement.

 

3.2.5 Rubber roller surface treatment

 

If the surface of the rubber roller is improperly treated, it will inevitably increase the unevenness of the surface roughness of the rubber roller. There are usually three methods for surface treatment of the rubber roller: surface acid treatment (due to the great harm to the human body, and the operator is required to have a high risk, after treatment) The rubber roller is easy to age and crack early, and now it is basically not used), surface illumination treatment, surface chemical coating treatment, under the same grinding process conditions, the surface roughness of the three treatment rubber rollers are different, see Table 2.

 

Table 2 Roller re-relevance Ra value under different treatment modes

It can be seen that after the chemical coating treatment, the surface roughness of the rubber roller cannot be improved. The original method of processing the rubber roller by chemical coating can achieve the method of “cutting and filling low” and improving the roughness of the rubber roller. The method is not accurate. It is only on the surface of the rubber roller. A coating layer has been added. The method of treating the rubber roller by ultraviolet light changes the molecular structure of the rubber roller by ultraviolet gamma ray, and the roughness of the rubber roller is improved. Sometimes the coating treatment is better than the UV treatment, and the workshop life is good, but this is not the reason for reducing the roughness of the rubber roller after the coating treatment. The spinnability of the rubber roller and the roughness of the rubber roller are two different. the concept of.

 

The relationship between the Ra value of the surface roughness of the rubber roller and the quality of the yarn

 

The internal quality of the rubber roller is different. Under the same grinding process, the surface roughness Ra is not the same. The Ra value determines the holding force and friction of the rubber roller. The friction of the rubber roller directly affects the yarn. Dry quality; the recommended roughness of the yarn in the general spinning cotton is about 0.8 microns. Generally, the high-precision wide grinding wheel grinding machine can reciprocate; the spinning high-yarn yarn is generally recommended to be about 0.6 micron, and the high-precision wide grinding wheel is two. A reciprocating can also be satisfied. When spinning chemical fiber and special varieties (such as 0.8 denier ultrafine fiber), in order to improve the holding power, the surface roughness Ra of the rubber roller should not be too small, and it should be determined according to the processing method and process conditions of the rubber roller.

 

 

 

 

 The drawing ratio and the Ra value of the surface roughness of the rubber roller also have an influence on the yarn quality. In the spinning production, the requirement of the surface roughness Ra value of the rubber roller increases with the increase of the spinning drafting ratio. The draw ratio is reduced and reduced, the draw ratio is large, and the fiber dispersion is high. Only the large rubber roller dynamic friction can ensure the fiber cohesion and reduce the floating fiber. The spinning drafting ratio is small, and the surface roughness of the rubber roller is adapted to a wide range. For example, if the roughness Ra value is too high, the strip is not ideal, and the details are increased. In the spinning drafting, the surface of the rubber roller is rough. The degree should be increased to 0.8-1.0μm in the blended variety, and can be appropriately increased to 0.5-0.7μm in the spun cotton varieties, and the rubber roller roughness should be increased as much as possible in the production of fine denier varieties. Up to 1.0 μm or more. However, the roughness is too large to bring about static electricity accumulation, and it is easy to produce winding flowers. However, since the antistatic property of the rubber roller is not treated at present, the roughness is appropriately increased, and the electrostatic winding is not generated, and the roughness is stabilized for the drafting. Sex is good. However, excessive roughness will cause entanglement, and the anti-winding property must be improved by coating treatment.

 

The uneven surface roughness of the rubber roller is easy to cause the dynamic friction coefficient to fluctuate, the frictional force is not uniform, affecting the grip force of the whisker, and then the coarse detail is generated, and the surface roughness of the rubber roller is uniform, so that the dynamic holding force of the rubber roller is relatively uniform. It is beneficial to improve the drying of the yarn.

 

Since the roughness of the rubber roller directly affects the drafting holding force, when the spinning mill produces fibers of different fineness, length and different properties under different temperature and humidity and different processes, the roughness of the rubber roller processing will be There are different.

 

For example, when a well-known enterprise in Nantong, Jiangsu Province, produces 0.88 G100 Tencel and Lenzing Modal mixed 11.8tex spinning, when the imported Beck grinding machine is used to grind the rubber roller, the smoothness of the yarn is deteriorated due to the small roughness of the surface of the rubber roller. The detail increase is more obvious, and after adjusting the grinding parameters, the roughness of the rubber roller is improved, and the yarn forming details are significantly decreased, as shown in Table 3.

 

Table 3 Effect of the roughness of the rubber roller on the quality of the yarn

 

When a well-known enterprise in Shandong produces pure cotton high-count yarn (compact spinning JC11.7tex), it also uses Baker automatic grinding machine, ordinary grinding machine and high-precision grinding machine to grind rubber roller, measure the roughness of the rubber roller, and carry out the rubber roller. A comparative test of the influence of roughness on yarn quality is shown in Table 4.

 

Table 4 Comparative test of the influence of the roughness of the rubber roller on the quality of the yarn

 

5 production of different varieties of rubber roller with different properties

 

When producing color spinning yarns and spandex core-spun yarns, due to the presence of pigments and oils in the fibers, it is prone to drumming. The same rubber roller has different oil-resistant properties due to different oleophilic molecules and additives in the rubber molecule. The main performance is that the oil resistance of the rubber roller is different from that of the oil resistant agent. LXC-766 and LXC-766a are anti-oil rubber rollers, which can effectively solve the phenomenon of spinning and spinning of spandex yarns.

 

In some enterprises, the temperature and humidity in the workshop are poorly controlled, especially when producing chemical fiber varieties, the phenomenon of winding, winding and damage of the rubber roller is prominent. D-85/90 graphite selenium rubber roller with good anti-winding performance can be selected. The rubber roller has good performance even under the high temperature and high humidity condition of Huangmeitian.

 

Production of vortex spinning yarn, V-73, V-78 rubber roller can be selected, its performance can be comparable with imported rubber roller, life cycle and yarn 9 grade yarn defect level is not worse than imported rubber roller, but the price Far less than imported rubber rollers.

 

Production of products with high requirements on rubber roller wear resistance (such as compact spinning), JA-65, JA-75 polyurethane rubber roller can be used. The rubber roller has good wear resistance and long grinding cycle, which can effectively save the rubber roller housing. .

 

Enterprises that use spun yarns often suffer from problems such as under-ring ring breaks and bad circles when the cycle is not replaced. The LXA-2010K super-abrasive apron can effectively solve this problem. The apron adopts a special acid treatment process (acid liquid microcomputer metering pump replenishing process), the apron acid treatment has good consistency and high wear resistance, and can completely replace the imported apron in the high-configuration spinning equipment.

 

6 different processes, different fibers and different drafting types have different performance requirements for rubber rollers

 

6.1 Re-understanding of the traditional craft concept of “tight gauge, heavy pressurization and strong control”

 

The essence of the drafting process is the process of relative displacement between fibers, and the adoption of "tight gauge, heavy pressurization, and strong control" essentially restricts the shifting and displacement of the fiber. The draw ratio of the conventional spinning frame is generally small. “Close distance, heavy pressure, strong control” should be said to be feasible, but in the case of large drafting process or production of fine fibers, “tight distance, heavy pressure, strong control” will inevitably lead to excessive drafting force. On the contrary, it will cause the deterioration of yarn quality. This is like saying that "the faster the vehicle, the less secure it is," the sentence itself seems to make sense! But is the high-speed rail faster than the car? Is the plane faster than the high-speed rail? But from a security point of view, the actual situation is the faster the security performance, the premise is to look at your carrier.

 

6.2 Rethinking on "The softer the hardness of the rubber roller is, the better the yarn quality is"

 

According to the plastic roller apron technology textbook, the hardness of the rubber roller is in the range of 63-85 degrees. The softer the hardness, the better the yarn quality. This has become the consensus of the majority of technicians. However, in the production practice, it is often the case that the rubber roller having a high hardness has a better quality than the rubber roller having a small hardness. Why does this happen? Cotton spinning drafting theory believes that during the drawing process, the holding force must be greater than the drafting force. This pair of force mismatches will result in coarse details that affect the drying of the yarn. Under normal conditions, the good quality of the low-hardness and high-elastic rubber rolls is mainly due to the enhanced stability of the gripping force. In general, the harder the hardness of the rubber roller, the smaller the gap of the rubber molecules, and the lower the elasticity of the rubber roller.

 

Under the same cradle pressure, draw ratio and spinning condition, the higher the elastic contact area of ​​the rubber roller and the sliver, the less the thick knot and details in the spinning process, and the more stable the strip level. The higher the elasticity of the rubber roller, the smaller the energy loss caused by the elastic recovery hysteresis during the operation, and the slower the temperature rise, which is more advantageous for prolonging the service life of the rubber roller. The better the elasticity of the rubber roller, the smaller the difference between the strands. However, the hardness of the rubber roller should not be too low, otherwise the elastic recovery performance is low, which affects the stability of the grip force, which may cause the strip to deteriorate. If the elastic recovery of the rubber roller is not good, the extension of the reverse surrounding arc will also aggravate the breakage and separation of the fiber, the strip will be greatly deteriorated, the detail will increase, and the spindle difference will increase. At the same time, the skin roller is easy to be concave due to excessive pressurization, and it is prematurely damaged. If it is not timely returned or replaced, the strip will also deteriorate.

 

6.3 Rethinking the requirements of “light, slip, dry and cool” for rubber roller

 

The traditional rubber roller apron technical book requires the production of rubber roller to be “light, slippery, dry and cool”. With the improvement of the automation degree of the grinding equipment, the surface roughness of the rubber roller is also higher and higher. However, we found that when producing pure cotton varieties, the surface roughness of the rubber roller is generally required to be lower, and when producing chemical fiber varieties such as viscose, the surface roughness of the rubber roller is suitably higher. The reason is that the friction coefficient between the cotton fibers is small, and the fiber length of the chemical fiber is long, the friction coefficient between the fibers is large, and the roughness of the surface of the rubber roller is small, which is disadvantageous for the stability of the drafting.

 

 Generally, when the cotton varieties are spun, the roughness of the rubber roller should be controlled between 0.5 and 0.7 μm. When spinning and blending and chemical fiber varieties, the surface roughness of the rubber roller should be controlled between 0.7 and 1.0 μm.

 

6.4 Discussion on the proportion of coatings during surface treatment of rubber roller coating

 

According to the traditional theory, the lighter the coating ratio of the rubber roller coating (preferably not treated), the better the yarn quality. However, in recent years, with the emergence of large-quantity and high-efficiency processes, the proportion of the coating is often thicker. Good phenomenon, and different varieties. For example, Henan Yongan Textile uses high-staple cotton to produce high-yarn yarns, and it is optimal to determine the best ratio of paint to paint with a ratio of 1:15. The quality of the yarn produced by Fujian Changle Huayuan produces 50 viscose compact spinning. 8 is best. The role of the coating is not only to increase the antistatic properties of the rubber roller, but also to change the friction coefficient of the rubber roller surface. The different proportions of the paint directly affect the grip of the rubber roller on the fiber. Table 5 shows the comparative test of the CV% value of the strips when the different coating ratios are produced when the LXC-966A rubber roller of Henan Yongan Textile produces the compact spinning JC11.7tex yarn.

 

Table 5 Comparison test of strip dry CV% values ​​for different coating ratios

 

 

 

Tables 6 and 7 show the comparison between LXC-866A and LXC-963 in the production of carded C14.7tex yarns at the Yulun spinning mill in Nanding, Vietnam, and B2 (hemp) C14.8tex yarns at the Huafu plant in Long'an. Test situation.

 

After in-depth research and experimentation, it is not difficult to find that all phenomena follow the principle of drafting. The key is the balance between holding power and drafting force. When the paint ratio in the surface treatment of the rubber roller can achieve the best matching of the holding force and the drawing force, the product quality will be relatively stable.

 

7 Conclusion

 

Since the spinning variety, spinning process and spinning type of the textile mill have become more diversified, there are different requirements for the performance of the rubber roller, which requires the rubber roller, the apron technician and the rubber roller apron manufacturer to keep on The grinding parameters and the coating ratio are optimized. The application, manufacturing and surface treatment techniques of the rubber roller and the apron are studied in depth. The relationship between the main performance parameters of the rubber roller and the apron and the quality index of the yarn is discussed to ensure that the rubber roller and the rubber ring are played out. Its best process efficiency.