How many purposes of white corundum /fused alumina sand should be used for rubber roller filling
Definition of rubber roller:
rubber roller is a roller-shaped product made of metal or other materials as the core and vulcanized rubber.
Classification of rubber rollers:
According to the purpose, it can be divided into: papermaking rubber rollers, printing and dyeing rubber rollers, printing rubber rollers, hulling rubber rollers, metallurgical rubber rollers and mimeograph rubber rollers, etc.; according to the surface shape can be divided into:
flat rollers and pattern rubber rollers ;
According to the material, it can be divided into: butyl rubber roller, nitrile rubber roller, polyurethane rubber roller and silicone rubber roller, etc.
The rubber roller is generally composed of outer rubber, hard rubber layer, metal core, roll neck and vent holes. Its processing includes roller core sandblasting, bonding treatment, glue molding, wrapping, wire winding, vulcanization tank vulcanization and surface processing. Waiting for the process. Cots are mainly used in papermaking, printing and dyeing, printing, food processing, metallurgy, plastic processing, etc.
Cots are often filled with fused alumina, white corundum 150 mesh 180 mesh 220 mesh 240 mesh 280 mesh 360 mesh 400 mesh 600 mesh 800 mesh 1000 mesh 1200 mesh 1500 mesh 2000 mesh 2500 mesh 3000 mesh 4000 mesh
Rubber roller production process and technical explanation:
In recent years, technologies such as injection, extrusion and winding have been continuously developed, and rubber roller forming vulcanization equipment has gradually mechanized and automated the production of rubber rollers. The performance of the rubber roller has a huge impact on the whole machine, the process operation and production quality are extremely strict, and many types of products have been listed as fine products, of which the selection of rubber and plastic materials and the control of product dimensional accuracy are the key. The rubber surface of the rubber roller is not allowed to have any impurities, sand holes and bubbles, and there can be no scars, defects, grooves, cracks and local sponges and soft and hard phenomena.
To this end, the rubber roller must be kept absolutely clean and meticulous in the entire production process to achieve unified operation and technical standardization. The bonding of rubber and plastic with metal core, pasting, injection molding, vulcanization grinding and other processes have become high-tech processes.
Over the years, due to the unfixed nature of products and the diversity of size specifications, the mechanization and automation of process equipment have become difficult, and so far, most of them are still manual intermittent unit operation production lines. Recently, some large professional manufacturers have begun to realize continuous production from rubber materials to molding and vulcanization processes, which has doubled production efficiency and greatly improved the working environment and labor intensity.
1. Preparation of rubber materials
For rubber rollers, the mixing of rubber is the most critical link. There are more than 10 kinds of rubber materials for rubber rollers from natural rubber, synthetic rubber to special materials, with a rubber content rate of 25%~85% and a hardness of soil (0~90) degrees, spanning a large range. Therefore, how to make these compounds evenly mixed has become a major problem. The conventional method is to use a mill to mix and process in the form of a variety of master compounds. In recent years, companies have increasingly switched to meshing mixers to produce rubber in segmented mixtures.
After the rubber material reaches uniform mixing, the glue filter machine is used to filter the glue to eliminate the impurities in the rubber material. Then use calender, extruder, and laminating mechanism to form film or rubber strips without bubbles and impurities for rubber roller forming. Before molding, these films and strips are also subject to strict visual inspection, limiting the parking period, maintaining a fresh surface and preventing adhesion and extrusion deformation. Because most of the rubber rollers are non-molded products, once there are impurities and bubbles on the surface rubber, there may be trachoma when grinding the surface after vulcanization, which will lead to excessive repair of the entire rubber roller or even scrap.
2. Molding
Rubber roller forming is mainly pasted and coated rubber on the metal core, including coating method, extrusion method, molding method, injection pressure method and injection method. At present, the domestic is mainly based on mechanical or manual pasting and molding, and most foreign countries have realized mechanical automation. Large and medium-sized rubber rollers are basically produced by profiling extrusion, which is produced by pressing out the film continuously pasted and forming or extruded rubber strips continuously winding and forming. At the same time, in the molding process, the microcomputer automatically controls its specifications, sizes and appearance shapes, and some can also be molded by pressing out machine right angle and special-shaped extrusion.
The above molding method can not only reduce labor intensity, but also eliminate the bubbles that may be generated. In order to prevent the deformation of the rubber roller in vulcanization and prevent the generation of bubbles and sponges, especially for the rubber roller formed by the coating method, the external method of flexible pressure should also be adopted. Usually several layers of cotton or nylon cloth are wrapped on the outer surface of the rubber roller, and then fixed and pressurized with steel wire or fiber rope. Although this process has long been mechanized, the manufacturing process is complicated by the removal of the wrapping after vulcanization, forming a “cecum” process, and causing waste due to the extremely limited number of uses of bandaging cloth and winding rope.
For small and micro rollers, a variety of production processes such as manual mounting, extrusion insertion, pressure injection, injection and pouring can be used. In order to improve production efficiency, most of the molding method is now used, and the accuracy is much higher than that of the non-molded method. Solid rubber injection, injection and liquid rubber pouring have become the most important production methods.
Third, vulcanization
At present, the vulcanization method of large and medium-sized rubber rollers is still vulcanization of vulcanization tanks, although the flexible pressurization mode has changed, but it has not been separated from the heavy labor burden of round-trip transportation and lifting. There are three heating methods for vulcanization heat sources: steam, hot air and hot water, and the mainstream is still steam. Due to the metal core contact with water vapor and have special requirements of the rubber roller, the use of indirect steam vulcanization, the time to be extended by 1~2 times, generally used for hollow iron core rubber roller. For special rubber rollers that cannot be vulcanized with vulcanization tanks, hot water is sometimes vulcanized, but the treatment of water pollution needs to be solved.
In order to prevent the rubber and metal core from shrinking differently due to the difference in thermal conductivity and causing delamination between the rubber roller and the rubber core, the general vulcanization is mostly used by slowly heating and pressurizing, and the vulcanization time is much longer than the vulcanization time required by the rubber itself. In order to achieve uniform vulcanization inside and outside and to make the thermal conductivity of metal core and rubber similar, the large rubber roller often stays in the tank for up to 24~48h, which is about 30~50 times the normal vulcanization time of rubber.
Most of the small and micro rubber rollers have now been molded and vulcanized by flat plate vulcanizing machines, completely changing the traditional vulcanization method of rubber rollers. In recent years, it has also implemented mold loading and vulcanization of injection press, and can automatically open and close the mold, and the degree of mechanization and automation has been greatly improved, and the vulcanization time is short, the production efficiency is high, and the product quality is good. Especially when using rubber injection molding vulcanizing machine, the two processes of molding and vulcanization are combined into one, and the time can be shortened to 2~4 min, which has become an important direction for the development of rubber roller production.
At present, liquid rubber represented by polyurethane elastomer (PUR) has developed rapidly in the production of rubber rollers and opened up a new way for material and process revolution. It adopts the pouring form, throwing off complex forming operations and bulky vulcanization equipment, greatly simplifying the rubber roller production process. However, the biggest problem is that due to the use of molds, for large rubber rollers, especially for individual products, the production cost is greatly increased, which brings great difficulties to the promotion and use.
In order to solve this problem, in recent years, a new process of PUR rubber roller manufacturing without mold has begun to appear. It uses polypropylene oxide ether polyol (TDIOL), polytetrahydrofuran ether polyol (PIMG) and diphenylmethane diisocyanate (MDl) as raw materials, mixes and stirs quickly reacts, quantitatively pours onto the slowly rotating rubber roller metal core, step by step to achieve solidification while pouring, and finally forms rubber roller. This process is not only short, mechanized, high degree of automation, but also eliminates the bulky mold, can be freely according to the requirements of the production of various specifications and sizes of rubber rollers, so that the cost is greatly reduced, has now become the main development direction of PUR rubber rollers.
In addition, the use of miniature fine rubber rollers in the manufacture of office automation equipment from liquid silicone rubber around the world is also developing rapidly. They are divided into two categories: heat curing (LTV) and room temperature curing (RTV), and the equipment used is also different from the PUR above, forming another type of pouring form. Here, the most critical question is how to control and reduce the viscosity of the compound so that it maintains a certain pressure and extrusion speed.
4. Surface treatment
Surface treatment is the last and most critical process in the production of rubber rollers, and the surface grinding state directly affects the performance of rubber rollers. At present, there are various grinding methods, but mainly mechanical turning and polishing, for this grinding method, grinding tools and abrasives used are very important, companies regard it as a technical know-how, maintain an unannounced attitude. One of the biggest problems is how to solve the heat generation phenomenon of rubber during grinding and maintain the optimal deflection of the surface after grinding.
In addition to grinding the surface of the rubber roller, it must be thoroughly cleaned to remove the rubber powder attached to the surface. For those with higher requirements, the surface should be further polished, and some resin coatings, latex paints, and magnetic powders should be coated on the surface. , electrostatic powder, etc. At the same time, a layer of required coating can also be electroplated, or chemical oxidation treatment can be performed to achieve the functions of light sensitivity, corrosion resistance, magnetization and conductivity.
With the continuous development of rubber rollers, the coating technology on the surface of rubber rollers has also been rapidly improved, and it has begun to change the traditional method that the performance of rubber rollers depends entirely on rubber coating. Specifically, it is to change and give new properties to the rubber roller by means of coating. For example, using equipment such as calenders and scraping machines to add oil shielding layers to achieve the purpose of improving oil resistance, etc. Although the shape and material of the rubber rollers are the same as before, their functions have undergone great changes, and some have become Functional rubber roller, this kind of surface treatment technology will have great development prospects in the future.
Main raw materials of rubber rollers: high molecular polymers such as rubber, vulcanizing agents, plasticizers, fillers, accelerators
Its main process flow and function: mixing–filtering–curing treatment–grinding–polishing
1. Mixing: Control the content of each component, heating temperature, etc., so that the hardness and composition are stable.
2. Filtration: Make the colloid uniform and free of impurities. This is especially important for high-speed printing machines: uniform force and uniform transmission of energy during high-speed operation. When expansion or contraction is caused by various factors, it can still remain uniform, so that adverse effects can be reduced or avoided only by adjustment.
3. Curing: through heat, pressure and vulcanization treatment, the accelerator is stabilized and the shrinkage of the rubber is minimized when it is subjected to external force. Change the soft and ductile compound into a solid and soft material, which is more suitable for the transfer and transfer of ink.
4. Grinding and polishing: the key to determine the dimensional accuracy and surface area of the rubber roller, especially the radian treatment of the alcohol water roller. The rubber surface looks smooth, but under a high-power magnifying glass, there are many small protrusions and depressions. These convex and concave parts increase the surface area of the rubber roller, making it have superior ink transfer and transfer performance.
To sum up, the rubber rollers used in production today have formed a product series with unique craftsmanship. Although traditional products are still the main products in China at present, the technical content is constantly improving, many products have entered the high-tech field, and the added value is gradually increasing, which is becoming another economic bright spot in industrial rubber products.