Natural rubber has high mechanical strength, good elasticity and high price, and the price of reclaimed rubber is low. Therefore, many rubber sheet manufacturers use natural rubber and reclaimed rubber in a certain proportion to produce rubber sheets; but natural rubber and reclaimed rubber are used together to produce rubber sheets. A problem may arise when the tablet has air bubbles. So what is the cause of this problem? Is it related to the use of reclaimed rubber? In what ways should we solve the problem of bubbles when the rubber sheet is pressed?
Generally, when natural rubber and reclaimed rubber are used together to produce rubber sheets, manufacturers will use recycled rubber as the main raw material and a small amount of natural rubber to reduce the production cost. Sulfur vulcanization system is the most commonly used, together with carbon black and aromatic oil, Anti-aging agents, etc.; there are two main reasons for the occurrence of bubbles in natural rubber/recycled rubber sheets in actual production. One is the formulation problem and the other is the process problem. The rubber product manufacturer can cut the rubber sheet to determine whether it is raw material or process. problem.
1. Adjust the natural rubber / reclaimed rubber sheet formula
The main reason for bubbles in the compression of rubber sheets is excessive moisture or volatile content. Excessive moisture content of reclaimed rubber or compounding agent or excessive moisture and other volatile substances produced during production will lead to reclaimed rubber sheet pressure. When the film appears bubbles, zinc oxide, accelerator and other compounding agents will absorb moisture; if the reclaimed rubber or the compounding agent itself has too much moisture content, it will be treated in advance before use, such as drying; if it is produced during the production process, it will be mixed with water. The absorption of the agent, the addition of an appropriate amount of desiccant such as calcium oxide in the formulation can alleviate bubble generation.
2. Improve the production process conditions of natural rubber / reclaimed rubber sheet
The use of reclaimed rubber as the main raw material and the rubber sheet used with natural rubber may cause bubbles in the filming process. Generally, the calendering temperature is too high, and bubbles are easily formed. Theoretically, the calendering temperature can reduce the shrinkage rate of the semi-finished product of the rubber sheet. The surface of the pressed film is smooth; however, in actual production, the calendering temperature needs to be strictly controlled, and the calendering temperature should not be too high, so as to avoid bubbles generated in the reclaimed rubber sheet.
Many people will attribute the bubble on the rubber sheet to the reclaimed rubber, or the quality of the reclaimed rubber is problematic, or the amount of reclaimed rubber is too high. If it is a quality problem, Xiaobian can only persuade you to cooperate with the formal reclaimed rubber factory. The quality of the reclaimed rubber is also guaranteed; from the point of view of the amount of reclaimed rubber, the amount of reclaimed rubber is generally too high, and the gelatinization rate of the rubber sheet is lower, and the gelatinization rate of the formulation can be lowered to some extent to improve the fluidity and plasticity of the rubber compound. Thereby reducing the chance of bubble generation.
When reclaimed rubber and natural rubber are used together to produce rubber sheets, selecting the right type of reclaimed rubber, adjusting the reclaimed rubber/natural rubber and using the rubber sheet formula can reduce the production cost and avoid bubble generation. I almost forgot, I heard that the three-roll calender uses the same speed of the middle and lower rolls when pressing the sheet. The upper and middle rolls of the glue are combined with the appropriate speed ratio. The speed ratio between the rolls helps to eliminate air bubbles. I don't know which calender you are using. If it is just a three-roll calender, how is the roll speed controlled?