Since the appearance of the true Banbury mixer in 1916, the power of the mixer has gradually been recognized. It shows a series of characteristics that are superior to those of the open mixer in the rubber mixing process. Such as: large mixing capacity, short time, and high production efficiency; better overcome dust flying, reduce the loss of compounding agents, improve product quality and working environment; safe and convenient operation, reduce labor intensity; beneficial to the realization of machinery and automated operations, etc. . Therefore, the emergence of the internal mixer is an important achievement of rubber machinery. It is still a typical important equipment in plasticizing and mixing, and it is still continuously developing and improving. Basic knowledge and basic structure of mixer
The mixer is generally composed of a mixing chamber, two relatively rotating rotors, an upper top bolt, a lower top bolt, a temperature measurement system, a heating and cooling system, an exhaust system, a safety device, a discharge device and a recording device. The surface of the rotor has helical ridges. The number of ridges is two, four, six, and so on. The section geometry of the rotor has three types: triangular, cylindrical, or oval. There are two types of tangential and meshing. . The temperature measurement system is composed of thermocouples, which is mainly used to measure the temperature change in the mixing chamber during the mixing process; the heating and cooling system is mainly used to control the temperature of the rotor and the cavity wall surface in the mixing chamber.
When the mixer is working, the two rotors rotate relative to each other, and the material from the feeding port is clamped and brought into the roll gap to be squeezed and cut by the rotor. After passing through the roll gap, the sharp edge of the lower bolt is divided into two parts, respectively. Along the gap between the front and rear chamber walls and the rotor, return to the nip above. During one week of flow around the rotor, the material is subjected to shear and friction everywhere, which causes the temperature of the rubber compound to rise sharply and the viscosity to decrease, which increases the wettability of the rubber on the surface of the compounding agent and makes the rubber and the surface of the compounding agent fully contact. Together with the rubber compound, the compound mass passes through the gap between the rotor and the rotor, between the rotor and the upper and lower top bolts, and the inner wall of the mixing chamber. It is broken by shearing, surrounded by stretch-deformed rubber, and stabilized in a broken state. At the same time, the convex edges on the rotor move the rubber material along the axial direction of the rotor, and play a role of stirring and mixing, so that the compounding agent is mixed uniformly in the rubber material. The compounding agent is repeatedly sheared and broken in this way, the rubber compound repeatedly deforms and recovers from deformation, and the rotor ribs are constantly stirred, so that the compounding agent is uniformly dispersed in the compound and reaches a certain degree of dispersion. Because the shearing effect of the rubber compound during mixing by the mixer is much larger than that of the mixer, and the temperature of the mixer is high, the efficiency of the mixer is much higher than that of the mixer.
The main parameters
Rotating speed and speed ratio of rotor; Rotor edge ratio and gap of inner wall of mixing room; Production capacity and filling factor; Unit pressure of upper pin on rubber; Power.
1. According to the capacity of the mixer and the appropriate filling factor (0.6 ～ 0.7), calculate the amount of rubber and the actual formula at one time;
2.According to the actual formula, accurately weigh the amount of various raw materials in the formula, raw rubber, small materials (ZnO, SA, accelerator, antioxidant, solid softener, etc.), reinforcement or filler, liquid softener , Sulfur are placed separately, arranged in order on the shelf;
3. Turn on the power switch and heating switch of the internal mixer, and preheat the internal mixer. At the same time, check whether the air pressure, water pressure, and voltage meet the process requirements. Check the temperature measurement system, timing device, and power system instructions and records.
4. After the mixer has been preheated, it is stable for a period of time and is ready to make rubber;
5. Lift the top plug, put the raw rubber that has been cut into small pieces into the mixer from the feeding port, drop the top plug, and mix the rubber for 1 min;
6. Lift the top plug, add small materials, drop the top plug and mix for 1.5min;
7. Lift the top plug, add carbon black or filler, drop the top plug and mix for 3min;
8. Lift the top plug, add liquid softener, drop the top plug and mix for 1.5min;
9. Debinding, use a thermocouple thermometer to measure the temperature of the rubber compound, record the initial temperature of the mixing chamber, the temperature of the mixing chamber and the debinding temperature at the end of mixing, high power, and the speed of the rotor;
10. Adjust the roll distance of the open mill to 3.8mm, turn on the power switch, make the open mill run, open the circulating water valve, and then throw the rubber discharged from the internal mixer into the upper roll of the open mill, wait for the rubber. The temperature drops below 110 ° C, sulfur is added, and the left and right cutting knives are each twice, until the sulfur is completely eaten, the surface of the rubber is smooth, and the rubber is cut off.
11. Adjust the roller distance of the open mill to 0.5mm, put the rubber material through, pass the triangle bag, and pass 5 times, adjust the roller distance to about 2.4mm, put the rubber bag roller, and wait until the surface is smooth and free of bubbles. Tablets, weigh the total mass of the compound, place it on a flat, clean metal surface and cool to room temperature, label it with the compound number and date of mixing, and park it for future use.
The mixing process test report of each batch of the internal mixer should record: the temperature at the beginning of mixing, the mixing time, the rotor speed, the pressure of the top pin, the discharge temperature, the power consumption, the difference between the quality of the mixing rubber and the total mass of raw materials And mixer type.
Note: When starting the mixing experiment, you can first mix a compound with the same formula as the test compound to adjust the working state of the mixer, and then formally mix; for the same batch of compound, the control conditions of the mixer and The mixing time should remain the same.
2 influencing factors
The quality of the rubber compounded by the mixer is mainly determined by the mixing temperature, charging capacity, rotor speed, mixing time, top bolt pressure, and the type of rotor, in addition to the feeding order.
That is, the mixing capacity. Insufficient capacity will reduce the shearing and kneading effects on the rubber, and even the phenomenon of rubber slipping and rotor idling will result in poor mixing effect. On the contrary, the capacity is too large, the rubber material is difficult to flip, the position of the top pin is improper, and a part of the rubber material stays at the neck of the feeding mouth, so that the rubber material is unevenly mixed, the mixing time is long, and the equipment is easily overloaded. Large energy consumption. Therefore, the mixing capacity should be appropriate, usually 60% to 70% of the total effective volume of the closed chamber is appropriate. The capacity of the mixer to mix the materials can be calculated by the following empirical formula:
Q——loading capacity, Kg;
K——filling factor, usually 0.6 ～ 07;
V——total effective volume of the closed room, L;
ρ——density of rubber material, g / cm3.
The selection and determination of the filling factor K should be determined according to the type of rubber and the characteristics of the formula, the characteristics of the equipment and the degree of wear, and the pressure of the top bolt. For NR and formula with high rubber content, K should be appropriately increased; for synthetic rubber and formula with low rubber content, K should be appropriately reduced; for old equipment with large abrasion, K should be increased; for new equipment, smaller; K of the rotor type internal mixer should be smaller than that of the shear type rotor internal mixer; the pressure of the top bolt increases, and K should increase accordingly. In addition, the K of the inverse mixing method must be as large as possible.
In the mixer mixing, the order and mixing time of the raw rubber, carbon black and liquid softener are particularly important. Generally, the raw rubber is added first, and then the carbon black is added. After dispersing, add a liquid softener, which is conducive to mixing, improves the mixing effect, and shortens the mixing time. Adding the liquid softener too early or too late is not good for mixing, it is easy to cause uneven dispersion, prolong the mixing time, and increase energy consumption. The addition time of the liquid softener can be determined by the distribution coefficient K. Sulfur and overspeed accelerators are usually added at the end of the mixing or discharged to the tablet press to reduce the risk of scorch. Small medicines (solid softeners, activators, accelerators, antioxidants, scorch retarders, etc.) are usually added after the raw rubber and before the carbon black.
Top bolt pressure
When mixing in an internal mixer, the rubber compound must be subjected to a certain pressure from the upper plug. It is generally considered that the pressure of the upper plug is 0.6-0.8MPa. When the rotor speed is constant, the effect of further increasing the pressure is not great. When the mixing capacity is insufficient, the pressure of the upper plug cannot fully function. Increasing the pressure of the top plug can reduce the non-filled space in the enclosed room, and increase its filling degree by about 10%. With the increase of capacity and speed, the pressure of the upper plug must be increased.
Increasing the pressure of the upper plug will accelerate the heat generation of the rubber compound and increase the power consumption during mixing.
Rotor structure and type
The geometry and size of the rotor's working surface largely determine the throughput and mixing quality of the mixer. There are two basic types of internal mixer rotors: shear rotors and meshing rotors. Generally speaking, the production efficiency of the shear-type rotor internal mixer is relatively high, and it can quickly feed, mix and discharge quickly. The meshing rotor mixer has the characteristics of high dispersion efficiency and low heat generation rate, which is suitable for manufacturing hard rubber and one-stage mixing. The dispersion and homogenization effect of the meshing rotor mixer is better than that of the shearing rotor mixer, and the mixing time can be shortened by 30-50%.
Increasing the speed of the mixer rotor is one of the effective measures to strengthen the mixing process. When the speed is doubled, the mixing cycle is shortened by about 30% to 50%. Increasing the speed will accelerate heat generation, resulting in a decrease in the viscosity of the rubber compound and a reduction in the mechanical shear effect, which is not conducive to dispersion.
The high mixing temperature is conducive to the plastic flow and deformation of the raw rubber and the rubber compound, and it is good for the rubber to wet the surface of the solid compound particles and to mix the powder. Disperse and mix. Excessive mixing temperature will also accelerate the thermal oxygen aging of the rubber, which will reduce the physical and mechanical properties of the vulcanizate, that is, over-refining will occur; it will also cause scorching of the rubber, so it is necessary to take effective Cooling measures; but the temperature should not be too low, otherwise rubber dispersion will occur.
Under the same conditions, the mixing time required to mix the rubber compound with the internal mixer is much shorter than that of the open mixer. When the mixing quality requirement is constant, the required mixing time is shortened with the increase of the mixer speed and the pressure of the upper plug. Improper feeding sequence and unreasonable mixing operation will extend the mixing time.
Prolonging the mixing time can increase the dispersion of the compounding agent in the rubber compound, but it will also reduce the production efficiency. If the mixing time is too long, it is easy to cause the rubber to be over-refined, which will damage the physical and mechanical properties of the vulcanizate. It will also cause the "thermal history" of the rubber to increase and prone to scorch. Refining time.
3 common faults
Leakage treatment of the mixer surface
During the long-term operation of the internal mixer, due to the effects of vibration, wear, pressure, temperature, and repeated disassembly, the static sealing parts of the joint surfaces are prone to leakage, which not only causes a large amount of oil waste, but also affects the site of the enterprise. management. The traditional method of controlling the leakage of the internal mixer is to disassemble and open the internal mixer, and then replace the gasket or apply sealant, but it is time-consuming and laborious, and it is difficult to ensure the sealing effect. Leaks will occur again during operation. New modern repair methods mostly use polymer composite materials,
4 acceptance requirements
One: Preparations before the dry running test of the internal mixer
1: The dry running test of the internal mixer must be performed after the foundation is completely dry.
2: Check whether there is foreign matter in each part of the internal mixer, and whether there is slackness in each joint and fastener.
3: Check the lubrication circuit of the internal mixer, whether the hydraulic circuit is connected correctly, whether the amount of lubrication and hydraulic oil is appropriate, whether the oil level is appropriate, and whether the lubrication part is properly lubricated.
4: The internal equipment of the mixer needs to be inspected separately before running to verify whether its performance meets the requirements.
5: Check whether the cooperation between the electrical equipment of the internal mixer and the hydraulic system and air control system is accurate.
6: Before connecting the coupling to the mixer, first idle the main motor for 20 minutes. After there is no abnormality, install the coupling and install the protective cover.
7: At the high speed shaft end of the main reducer of the internal mixer or at the coupling, manually drive the transmission system to rotate the rotor for two cycles to confirm that there are no abnormalities.
2: No-load test run
1: First start the lubricating oil pump and hydraulic station of the internal mixer, and check whether the oil supply is normal in each part. After the oil pump and hydraulic station work normally for 15 minutes, start the main motor, and see if the rotor turns correctly from the water outlet end of the mixing room. Usually, the internal mixer is idled for more than 2h after leaving the factory, and is idled for more than 4h at the user.
2: Turn on the cooling water system of the internal mixer and check for leaks.
3: In the manual and automatic operation state, the press, feeding door and discharge door are opened multiple times, and the action should be flexible and reliable.
4: Check the following items during the dry running test of the internal mixer:
a: The lubrication points of the reducer transmission gear and bearing are fully lubricated, and the sealing parts are well sealed.
b: There must be no large vibration and periodic noise during operation.
c: During dry running, the main motor is single speed, and its power consumption should be less than 15% of the rated power.
d: There should be no sudden rise in the bearing temperature of each part of the internal mixer. The temperature rise of the rotor bearing and the reducer bearing is ≤20 ℃.
Three: Load test run
1: The load trial run can only be performed after the mixer has passed the no-load trial run. During load trial operation, each device needs to run continuously with no less than 20 trucks.
2: During the trial run of the mixer, the rotation speed should be performed from low speed to high speed, and the soft material and the hard material should be tested first.
3: During the trial run of the mixer, the amount of glue is gradually increased from 50% and 75% of the working volume to full load.
4: The internal mixer should have an interlock device that can start the main motor after starting the lubricating oil pump at the same time, and at the same time, it can be put into load trial operation after running for 10-15 minutes.
5: After the next car is finished mixing, stop after 15-20 minutes of dry running. During dry running, the face seal lubrication system continues to inject oil into the seal face to achieve cleaning and lubrication of the seal face.
6: The following items should be checked during the trial run of the mixer:
A: Whether the basic technical parameters meet the requirements of the mixer.
B: The temperature rise of the rotor bearing should be ≤40 ° C.
C: The temperature rise of the reducer bearing should be ≤40 ° C.
D: Rotor, reducer bearing high temperature≤80 ℃.
E: The oil temperature in the oil tank of the hydraulic system is ≤60 ° C.
F: The high temperature of the fixed end of the rotor end face sealing device is ≤85 ° C.
G: The discharge temperature (actual measurement) should be consistent with the temperature value displayed by the sensor (thermocouple), and the difference is 3-5 ° C.
7: There is no glue leakage or powder leakage at the seal on the end face of the mixer. The glue, oil and powder mixture paste is allowed to leak out.
8: The discharge door should be well sealed without leaking.
9: The electric, hydraulic and other control systems of the internal mixer should be flexible, safe and reliable.
10: The temperature control effect of the temperature control system of the internal mixer can meet the requirements of the rubber mixing process, and the temperature of the rubber discharge should be within the allowable range of the process conditions.
After confirming that there are no abnormalities in the mixer after the test run of the load, it can be transferred to production with the consent of the relevant parties. ?
5 development direction
The mixer is abbreviated as "Lina", and the full name is "closed rubber mixer", which was developed on the basis of the open mixer. After the invention of the mill in 1820, the rubber industry has undergone a fundamental change. However, because of the many disadvantages of the mill, such as high labor intensity, low efficiency, and large dust, it seriously affects people's health, so people began to consider If this processing equipment is covered with a cover, it will gradually develop into an internal mixer. Because it works inside the mixing chamber, it is called closed. Because the open mill work is open, it is called an open rubber mill. Generally speaking, it is believed that the internal mixer was invented by Banbury in 1916. It was actually designed by a commercial engineer (British) in West Germany based on the company's prototype machine. Due to its rapid development, the output is also widely used. Wider, so people have always thought that the Banbury mixer was introduced early.
Since the appearance of the internal mixer, it has shown a series of advantages over the open mixer in the mixing process, such as short mixing time, high production efficiency, easy operation, better overcome dust flying, and reduce the loss of compounding agents. Improve labor conditions and reduce labor intensity. Because it has been developed to a large extent through experience, there have been statements in the early development that plasticization is not efficient and cannot be used for plasticization, but it has been denied by production practice. Therefore, the emergence of the internal mixer is an important achievement of the rubber mixing machine, and it still has become a typical equipment in plasticizing and mixing, and is constantly developing and improving. According to statistics from foreign countries, 88% of rubber compounds in the rubber industry are manufactured by internal mixers, and plastic and resin industries are also widely used in internal mixers. Now-due to the continuous improvement of the metal powder industry, part of it can also be mixed with an internal mixer.
One of the hallmarks of the development of modern mixers is high speed, high pressure, and functional machines. Generally, a rotor speed of 20 rpm is referred to as a low-speed internal mixer, a speed of 30 to 40 rpm is referred to as a medium-speed internal mixer, and a speed of 60 rpm or higher is referred to as a high-speed internal mixer.
There have been internal mixers with a rotation speed of 80 rpm or higher. There are also two-speed, three-speed, variable-speed internal mixers that have a wide range of adaptability to processing and efficiency, and also internal mixers with adjustable rotor speed ratios. Its operating time is greatly shortened, from 8 to 15 minutes of the slow machine in the past to 1.5 to 3.5 minutes, and even up to 1 to 1.5 minutes (including the process using the mixing method and supplementary mixing method, etc.).
The structure of the mixer is also constantly developing. The working process of the internal mixer and the mechanization and automation level of the entire unit are also continuously improved, and program control is adopted. Nowadays, computer control is adopted in large-scale imported machines.
In short, this development is to greatly strengthen the mixing process, improve machine efficiency, reduce physical labor and improve the working environment.
In this intense mixing process, of course, many new problems will be brought. Therefore, for the mechanical research and design, from the kneading system, cooling system, sealing system, feeding and pressing system, unloading system of the machine The technical decisions and theories of transmission systems, control systems, main components, materials, and various parameters need to be developed accordingly to make the machine perform well and provide possible adaptability and adjustment for the production process.
The development status of China's internal mixers is that before the liberation, there was a blank, and after the liberation, domestic domestic mixers gradually developed. The domestic manufacturer of mixers in China is Dalian Rubber & Plastic Machinery Factory. First, PC-2 140 / 20L mixers were produced in imitation of Soviet Union, and now they are being changed to 250L, 75 / 40L mixers. Then Shanghai and other places gradually produced these machines, such as 250/20/40, 75/30/60, 75/35/70, and 50L mixers. Recently, F080, F160, F270 have been exported after imitating the F series mixer. In addition, it also produced flip type 50L and 70L mixers for Japan. Yiyang Rubber Machinery Plant also introduced GK series technology from West Germany to produce GK series internal mixer. F series and GK series are the world's two most advanced series of internal mixers. Large domestic rubber factories have been introduced. Our institute has been researching internal mixers, pin rotors, and pin mixing chamber internal mixers.
The development direction of the mixer: "two big", "two high", "one low", that is, large specifications (large capacity), high power, high speed, high pressure, low unit energy consumption, the main problem: end seal ?
First, the purpose
The purpose of standardized equipment operation and equipment maintenance is to ensure the normal operation and extended life of the equipment, reduce maintenance costs and improve production efficiency.
Working instructions for rubber and plastic mixer equipment
Third, special duties
The special equipment operators and maintenance personnel designated by the user shall not violate the rules and operate the equipment skillfully. Supervised unrelated personnel shall not approach or disturb the duties of the equipment.
Fourth, the operating rules
1. Turn on the power one by one. If you need to warm up, set the temperature and observe whether the heating is normal. If the water is cooled, open the inlet and outlet valves for normal water flow.
2. Clean up the mixing room. Do not use hard objects such as iron wire to check the oil level and lubrication status of each gear oil, oil and butter. Pay special attention to the oil level of the triple oil cup not less than half, and regularly Observe the oil level change of the triplet. It is not normal for the fuel to be consumed or the fuel consumption is too fast (the knob of the triplet must be adjusted). The gear oil of the new machine is replaced half a year later. Lubricant is added at least once a week at the active part. Do not exceed half of the oil mirror, otherwise oil leakage will occur.
3. Prepare the materials and turn on the power and air pressure, raise the pressure cap to the upper limit position, then start the main motor motor, put in the prepared materials half a minute after the main motor starts, and then press the pressure cap to carry out the material Smelting.
4. If you need to change the color, please pour in the cleaning material or raw material cleaning agent, and then clean the old materials in the rotor shaft gap in the mixing chamber with a broom or iron wire.
5. According to the physical properties of the materials, the mixing can be adjusted automatically or manually. The hard materials should not be too large or too large, otherwise it will crash or burn out the main motor.
6. After the material is compacted, first raise the air pressure cover, then turn over the mixing tank, pour out the material after it is in place, and then return the mixing tank to the next batch.
7. When stopping production, first turn off the power of each function in turn, then turn off the power of the host, and then quickly clean up the mixing room and clean up the dust.
Five, matters needing attention
1. Regularly check the insulation effect of each line, and always pay attention to the warning content on the machine warning sign.
2. When the moving parts and the mixing chamber are blocked, do not reach inside with your hands or iron rods, but use plastic sticks to handle them carefully.
3. When touching hot parts, be careful not to get burned.
4. When there is powder leakage or the scream of the seal ring, first loosen the four screw caps evenly and screw them in, then add some material oil or oil to the rotor gap in the mixing chamber, and then idling 3— At the same time, use a hammer to gently tap the periphery of the seal ring gland around the spring for 5 minutes. If the powder leaks, adjust the tightness of the individual spring. When it is very close, it means that the seal ring inside is worn and needs to be replaced again. For the method of replacing the seal ring, see the instruction manual.
5. Special attention: Check the gear oil, oil and butter oil level and lubrication status before turning on the machine every day. Pay attention to the oil level of the triple oil cup not less than half every day.
6. When the machine fails, stop the movement of the machine within a time period. Unrelated personnel must not perform any actions without authorization, and notify and wait for your company's machine maintenance personnel to inspect and maintain.
The open mill is a two-roller, which uses two rollers that move at different speeds to generate shear force to plasticize. During the operation, it is necessary to continuously perform triangle wrapping or curling operations on the rubber material.
The internal mixer uses the regular contraction of the space generated by the internally designed paddles to generate the shear force without manual operation, saving labor.
The open mill has a simple structure and low cost, but it is labor-intensive, polluting, and causing great harm to workers.
The internal mixer is more expensive, but it can be heated, and a pressure internal mixer can be used to handle materials that are difficult to plasticize. Low labor intensity and strong adaptability.
The internal mixer is a high-strength interstitial mixing device developed on the basis of an open mixer. Therefore, the emergence of the internal mixer is an important achievement of rubber machinery, and it is still a typical important equipment for plasticizing and mixing seeds, and it is still being continuously developed and improved.
The kneader is a device that cooperates with a pair of mutually rotating and rotating blades (usually in the shape of a Z) to make the semi-dry or rubbery viscous plastic material react quickly to obtain uniform mixing and stirring. It is an ideal equipment for mixing, kneading, crushing, dispersing and re-polymerizing various high-viscosity elastoplastic materials. It has the advantages of uniform stirring, no dead corners and high kneading efficiency. It is widely used in high-viscosity sealants, Silicone rubber, neutral acid glass glue, chewing gum, bubble gum, pulp, cellulose, also used in batteries, inks, pigments, dyes, medicine, resins, plastics, rubber, cosmetics and other industries.
7 operating procedures
1. Machine operators must take safety education and technical training and be familiar with the operating rules of the equipment before they can take up their posts.
2. Before going on the machine, the operator should wear the specified labor protection supplies.
3. Before turning on the machine, you must check and clean the debris around the machine that hinders the operation of the equipment.
4. Keep the working area around the machine clean and the road clear. Turn on the ventilation equipment (exhaust fan) to keep the workshop air flowing.
5. Open the water, gas and oil supply valves and check whether the water pressure gauge, water gas gauge and oil pressure gauge are normal.
6. Turn on the machine for trial operation and immediately stop it if you notice abnormal sounds or other faults.
7. Check whether the material door, top bolt and hopper can be opened normally.
8. Whenever the upper bolt is raised, the upper bolt control knob must be turned to the raised position.
9. During the kneading process, it is found that there is a jam phenomenon. Use jacking rods or other tools to operate. It is forbidden to dig directly by hand.
10. When the hopper is overturned and unloaded, pedestrians are prohibited from approaching around the hopper and the elevator. Be careful.
11. The top bolt must be raised before the shutdown, and the hopper should be turned back to the position. Close the material door to stop power failure.
12. After work is completed, turn off all power, water, gas, and oil sources.
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