Production process and technical progress of rubber rollers

In recent years, technologies such as injection, extrusion and winding have continued to develop, and rubber roller forming and 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, and it is extremely strict on the process operation and production quality. Many of its products have been classified as fine products. Among them, the selection of rubber and plastic materials and the control of product dimensional accuracy are the keys. The rubber surface of the rubber roller is not allowed to have any impurities, blisters and air bubbles, let alone scars, defects, grooves, cracks and local sponges and different soft and hard phenomena. For this reason, it is required that the rubber rollers must be kept absolutely clean and meticulous in the entire production process, so as to achieve unified operation and standardization of technology. The combination of rubber plastic and metal core, pasting and injection molding, vulcanization grinding and other processes have therefore become high-tech processes.

Over the years, due to the indeterminacy of products and the variety of sizes and specifications, the production of cots has made the mechanization and automation of process equipment difficult. So far, most chrome-plated roller manufacturers are still manual-based intermittent unit production lines. Recently, some large professional manufacturers have begun to realize continuous production from rubber compound to molding and vulcanization process, which has doubled the production efficiency and greatly improved the working environment and labor intensity.

1. Preparation of glue

For the rubber roller, the mixing of the rubber compound is the key link. There are more than 10 kinds of rubber materials for rubber rollers, ranging from natural rubber, synthetic rubber to special materials, with a rubber content of 25% to 85%, and a hardness of soil (0 to 90) degrees, spanning a wide range. Therefore, how to make these rubber materials evenly mixed has become a big problem. The conventional method is to use an open mill for mixing and processing in the form of a variety of masterbatches. In recent years, enterprises have switched to intermeshing mixers to produce rubber compound by segmented mixing.

After the rubber material is uniformly mixed, it is necessary to use a rubber filter machine to filter the rubber to eliminate impurities in the rubber material. Then, the calender, extruder and laminating machine are used to form films or strips without air bubbles and impurities for rubber roller forming. Before forming, these films and adhesive strips are also subject to strict visual inspection to limit the storage period to keep the fresh surface and prevent sticking and extrusion deformation. Because most of the rubber rollers are non-molded products, once there are impurities and bubbles in the surface rubber, the chrome-plated roller manufacturers may have blisters when they grind the surface after vulcanization, which will cause the entire rubber roller to be repaired or even scrapped.

2. Forming

Rubber roll forming is mainly to paste and cover the rubber on the metal core. There are wrapping method, extrusion method, molding method, injection method and injection method. At present, it is mainly based on mechanical or manual pasting and molding in China, and most foreign countries have realized mechanical automation. Large and medium-sized rubber rollers are basically produced by profiling extrusion, which is produced by continuous pasting of extruded film or continuous winding of extruded rubber strips. At the same time, during the molding process, the microcomputer automatically controls its size and appearance, and some can also be formed by the method of extruder right angle and special-shaped extrusion.

The above-mentioned molding method can not only reduce labor intensity, but also eliminate possible air bubbles. In order to prevent the deformation of the rubber roller during vulcanization and prevent the generation of air bubbles and sponges, especially for the rubber roller formed by the wrapping method, a flexible pressure method should be adopted on the outside. Usually, several layers of cotton or nylon cloth are wrapped around the outer surface of the rubber roller, and then fixed and pressed with steel wire or fiber rope. Although this process has been mechanized for a long time, because the dressing has to be removed after vulcanization, a "cecum" process is formed, which complicates the manufacturing process, and is caused by the extremely limited use of the dressing cloth and the winding rope and the large consumption. waste.

For small and micro rubber rollers, various production processes such as manual lamination, extrusion, injection, injection and pouring can be used. In order to improve production efficiency, the molding method is now mostly used, and the precision of the polyurethane roller is much higher than that of the non-molding method. Injection pressing, injection of solid rubber and pouring of liquid rubber have become the main production methods.

3. Vulcanization

At present, the vulcanization method of large and medium-sized rubber rollers is still vulcanization tank vulcanization. Although the flexible pressurization mode has changed, it is still not free from the heavy labor burden of round-trip transportation and unloading. The vulcanization heat source has three heating methods: steam, hot air and hot water, and the mainstream is still steam. For rubber rollers with special requirements due to the contact of the metal core with water vapor, indirect steam vulcanization is adopted, and the time is extended by 1 to 2 times. Generally, it is commonly used for rubber rollers with hollow iron cores. For special rubber rollers that cannot be vulcanized in a vulcanization tank, hot water vulcanization is sometimes used, but the treatment of water pollution needs to be solved.

In order to prevent delamination between the rubber roller and the rubber core caused by the different shrinkage of the rubber and the metal core due to the difference in thermal conductivity, the general vulcanization usually adopts the method of slowly heating up and increasing the pressure, 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 the large rubber roller and make the thermal conductivity of the metal core and the rubber similar, the time spent in the tank is often as long as 24~48h, which is about 30~50 times the normal vulcanization time of the rubber.

Most of the small and micro rubber rollers have been changed to flat vulcanizing machines for molding vulcanization, which has completely changed the traditional vulcanization method of rubber rollers. In recent years, injection molding machine installation, vacuum vulcanization, and automatic opening and closing of molds are also implemented. The degree of mechanization and automation is greatly improved, and the vulcanization time is short, production efficiency is high, and product quality is good. Especially when using a rubber injection molding vulcanizer, the two processes of molding and vulcanization are combined into one, and the time can be shortened to 2~4 minutes, 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 has opened up a new way of material and process revolution for it. It adopts the casting form, and the polyurethane roller removes the complicated molding operation and the cumbersome vulcanization equipment, which greatly simplifies the production process of the rubber roller. However, the biggest problem is that the mold must be used. For large rubber rollers, especially for a single product, the production cost is greatly increased, which brings great difficulties to the promotion and use.

In order to solve this problem, a new process of moldless manufacturing of PUR rubber rollers has begun to appear in recent years. It uses polyoxypropylene ether polyol (TDIOL), polytetrahydrofuran ether polyol (PIMG) and diphenylmethane diisocyanate (MDl) as raw materials. After mixing and stirring, it reacts rapidly and is quantitatively poured onto the metal core of the slowly rotating rubber roller. , step by step to achieve curing while pouring, and then form a rubber roller. This process not only has a short process, high degree of mechanization and automation, but also eliminates the need for cumbersome molds. It can produce rubber rollers of various specifications and sizes according to requirements, which greatly reduces the cost and has become the main development direction of PUR rubber rollers. .

In addition, micro-fine rubber rollers used in the manufacture of office automation equipment from liquid silicone rubber around the world have also developed rapidly. They are divided into two categories: heat curing (LTV) and room temperature curing (RTV), and the equipment used is also different from the above PUR, forming another type of casting form. Here, the most critical issue is how to control and reduce the viscosity of the compound so that it can maintain a certain pressure and extrusion speed.

4. Surface treatment

Surface treatment is the most critical process after the production of the rubber roller. The surface grinding state directly affects the performance of the rubber roller. At present, there are various grinding methods, but the main ones are mechanical turning and polishing. For this reason, the grinding methods, grinding tools and abrasives used are very important. Many companies regard them as technical know-how and maintain an attitude of keeping it secret. Among them, the biggest problem is how to solve the heat generation phenomenon of rubber during grinding and maintain the best deflection of the surface after grinding.

In addition to grinding the surface of the rubber roller, it should also be thoroughly cleaned to remove the rubber powder attached to the surface. For higher requirements, the surface should be further polished, and some are coated with resin paint, latex paint, magnetic powder on the surface. , electrostatic powder, etc. At the same time, a desired coating can also be electroplated, or chemical oxidation treatment can be performed to achieve the functions of light sensitivity, corrosion resistance, magnetization and conduction.