Low cost rubber cold feed extruder for producing EPDM rubber sealing strips

EPDM sealing strip production introduction:

The production process of EPDM rubber sealing strips mainly includes the following steps:

1. Raw material preparation
- **EPDM rubber**: According to the use requirements of the sealing strip, select EPDM rubber with appropriate Mooney viscosity, ethylene and propylene content and third monomer type. For example, automobile door and window sealing strips often use EPDM rubber with a Mooney viscosity between 40-60.
- **Compounding agent**: Prepare compounding agents such as vulcanizers, accelerators, antioxidants, reinforcing agents, fillers, softeners, and colorants. For example, commonly used vulcanizers include sulfur and peroxides; reinforcing agents can be selected from carbon black and white carbon black; softeners include cyclohexane oil and paraffin oil.

2. Mixing
- **Equipment selection**: Mixing can be done using an internal mixer or an open mixer. Internal mixers have high mixing efficiency and good mixing uniformity; open mixers are convenient for observing the mixing situation and adding small doses of compounding agents.
- **Feeding order**: In the internal mixer, EPDM rubber is usually added first, followed by activator, antioxidant, accelerator, reinforcing agent, filler, softener, etc., and finally vulcanizer. In the open mixer, EPDM rubber is usually rolled first, and then compounding agents are added in the above order.
- **Process parameter control**: When mixing in the internal mixer, parameters such as rubber loading capacity, top bolt pressure, rotor speed, mixing time and temperature will affect the mixing effect. For example, the mixing temperature is generally controlled at 80-120℃; when mixing in the open mixer, the roller pitch, roller temperature, mixing time and roller speed need to be reasonably adjusted, and the roller temperature is usually between 40-60℃.

3. Extrusion molding
- **Extruder selection**: According to the cross-sectional size and output requirements of the sealing strip, select a suitable single-screw extruder or twin-screw extruder. For sealing strips with smaller cross-sectional sizes and low output requirements, a single-screw extruder can be selected.
- **Mold design**: Design an extrusion mold that matches the shape and size of the sealing strip to ensure that the extruded sealing strip has accurate size and smooth surface. The flow channel design of the mold should be reasonable to avoid problems such as uneven flow and retention of the rubber material.
- **Process parameter control**: The extrusion temperature is generally controlled at 60-130℃, the body temperature is low, and the head and die temperature are high. The extrusion speed should be moderate. Too fast will cause the surface of the sealing strip to be rough and the size to be unstable, while too slow will affect production efficiency.

4. Vulcanization
- **Vulcanization system selection**: Sulfur vulcanization system, peroxide vulcanization system or resin vulcanization system can be used. The sulfur vulcanization system has a fast vulcanization speed and low cost, and is widely used; the peroxide vulcanization system has good heat resistance and aging resistance, and is suitable for sealing strips with high heat resistance requirements.
- **Vulcanization equipment**: Commonly used vulcanization equipment includes vulcanization tanks and flat vulcanizers. Vulcanization tanks are suitable for large-scale production and can vulcanize multiple sealing strips at the same time; flat vulcanizers are suitable for small-batch production and sealing strips with complex shapes.
- **Process parameter control**: The vulcanization temperature is generally between 150-180℃, and the vulcanization time depends on the thickness of the sealing strip and the vulcanization system, usually ranging from a few minutes to tens of minutes. The vulcanization pressure is generally between 0.5-1.5MPa. Too low pressure will lead to incomplete vulcanization, and too high pressure may cause the sealing strip to deform.

5. Post-processing
- **Cooling and shaping**: The vulcanized sealing strip needs to be cooled and shaped, which can be done by natural cooling or water cooling. Water cooling has a fast cooling speed, but it is important to control the cooling speed to avoid internal stress in the sealing strip.
- **Cutting and finishing**: Cut the cooled and shaped sealing strip to the specified length, with high cutting accuracy to ensure that the length of the sealing strip is consistent. Then finish the cut sealing strip to remove defects such as burrs and flash.
- **Inspection and packaging**: Carry out a comprehensive inspection of the produced EPDM rubber sealing strips, including appearance quality, dimensional accuracy, physical properties and other aspects. The sealing strips that pass the inspection shall be packaged with appropriate packaging materials, such as plastic bags, paper boxes, etc., and shall be properly labeled with information such as product specifications, model, and production date.

Extrusion molding features:

1.Innovation in mold design:
Use computer simulation technology (such as CFD - computational fluid dynamics) to optimize the design of extrusion molds. By simulating the flow of rubber in the mold, adjust the shape, size and roughness of the mold flow channel to make the rubber flow more uniform and avoid excessive or low local pressure.
Adjustable molds can be quickly adjusted according to different sealing strip shape and size requirements to improve the versatility and adaptability of the mold. For example, for sealing strips with complex cross-sectional shapes, the mold can adjust the size of each part within a certain range to meet production needs.

2.Precise control of extrusion process parameters:
Install high-precision temperature sensors and speed sensors to monitor and accurately control the extrusion temperature and speed in real time. At the same time, a feedback control system is used to adjust the heating and motor speed in time according to the sensor data to ensure the stability of the extrusion process parameters.
Study the relationship between sealing strips of different formulations and sizes and extrusion process parameters, and establish a database. According to the specific type of sealing strip produced, call the best extrusion parameters from the database to improve extrusion quality and efficiency.
Vulcanization process improvement

3.Optimization of vulcanization system:
Develop new vulcanization systems, such as using environmentally friendly vulcanizers to replace traditional sulfur vulcanizers to meet increasingly stringent environmental protection requirements. At the same time, the new vulcanization system may bring better vulcanization effects, such as improving the heat resistance and aging resistance of vulcanized rubber.
Study the synergy between vulcanizers, accelerators and activators, and optimize the vulcanization system by adjusting their proportions and types, reduce the vulcanization temperature and time, and improve production efficiency.

4.Vulcanization equipment upgrade:
The use of energy-efficient vulcanization tanks, such as vulcanization tanks with thermal circulation systems, can make the temperature distribution in the tank more uniform and reduce the vulcanization time. At the same time, the thermal circulation system can recycle heat energy and reduce energy consumption.
For flat plate vulcanizers, install automatic pressure regulators and high-precision temperature controllers to ensure the accuracy and stability of vulcanization pressure and temperature. In addition, multi-layer flat plate vulcanizers can also be used to improve vulcanization efficiency and equipment utilization.

Product Parameters: