Forming
Rubber roller molding is mainly to paste coating rubber on the metal core, including wrapping method, extrusion method, molding method, injection pressure method and injection method. At present, the main domestic products are 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, continuous pasting molding by extruded film or continuous winding molding by extruding tape. At the same time, in the molding process, the specifications, dimensions and appearance shape are automatically controlled by a microcomputer, and some can also be molded by the method of right-angle extruder and special-shaped extrusion.
The above-mentioned molding method can not only reduce labor intensity, but also eliminate possible bubbles. In order to prevent the rubber roller from deforming during vulcanization and to prevent the generation of bubbles and sponges, especially for the rubber roller molded by the wrapping method, a flexible pressurization method must be used outside. Usually, the outer surface of the rubber roller is wrapped and wound with several layers of cotton cloth or nylon cloth, and then fixed and pressurized with steel wire or fiber rope. Although this process has already been mechanized, the dressing must be removed after vulcanization to form a "cecal" process, which complicates the manufacturing process. Moreover, the use of dressing cloth and winding rope is extremely limited and the consumption is large. waste.
For small and micro rubber rollers, a variety of production processes can be used, such as manual patching, extrusion nesting, injection pressure, injection and pouring. In order to improve production efficiency, most of the molding methods are now used, and the accuracy is much higher than that of the non-molding method. Injection pressure, injection of solid rubber and pouring of liquid rubber have become the most important production methods.
Vulcanization
At present, the vulcanization method of large and medium-sized rubber rollers is still vulcanization tank vulcanization. Although the flexible pressurization mode has been changed, it still does not break away from the heavy labor burden of transportation, lifting and unloading. The vulcanization heat source has three heating methods: steam, hot air and hot water, and the mainstream is still steam. The rubber rollers with special requirements due to the contact of the metal core with water vapor adopt indirect steam vulcanization, and the time will be prolonged by 1 to 2 times. It is generally used for rubber rollers with hollow iron cores. For special rubber rollers that cannot be vulcanized with a vulcanizing tank, hot water is sometimes used for vulcanization, but the treatment of water pollution needs to be solved.
In order to prevent the rubber and the metal core from being delaminated due to the different shrinkage of the heat conduction difference between the rubber roller and the rubber core, the vulcanization usually adopts a slow heating and pressure increase method, 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 the metal core and rubber similar, the large rubber roller stays in the tank for 24 to 48 hours, which is about 30 to 50 times the normal rubber vulcanization time.
Small and micro rubber rollers are now mostly converted to plate vulcanizing press molding vulcanization, completely changing the traditional vulcanization method of rubber rollers. In recent years, injection molding machines have been used to install molds and vacuum vulcanization, and molds can be opened and closed automatically. 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 a rubber injection molding vulcanizing machine, the two processes of molding and vulcanization are combined into one, and the time can be shortened to 2 to 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 pouring form to get rid of complex molding operations and bulky vulcanization equipment, greatly simplifying the production process of rubber rollers. However, the biggest problem is that molds must be used. 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, a new process of PUR rubber roller without mold manufacturing has appeared in recent years. It uses polyoxypropylene ether polyol (TDIOL), polytetrahydrofuran ether polyol (PIMG) and diphenylmethane diisocyanate (MDl) as raw materials. It reacts quickly after mixing and stirring, and is quantitatively poured onto the slowly rotating rubber roller metal core. , It is realized step by step while pouring and curing, and finally the rubber roller is formed. This process is not only short in process, high in mechanization and automation, but also eliminates the need for bulky molds. It can produce rubber rollers of various specifications and sizes at will, which greatly reduces the cost. It has become the main development direction of PUR rubber rollers.
In addition, the micro-fine rubber rollers used in the manufacture of office automation equipment with liquid silicone rubber are also developing rapidly all over the world. They are divided into two categories: heating curing (LTV) and room temperature curing (RTV). 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 rubber compound so that it can maintain a certain pressure and extrusion speed.
Post time: Jul-07-2021
