Foam plastics extrusion molding equipment
DATE：2022/4/14 9:04:13 / READ： / SOURCE：This station
Foam plastics extrusion molding equipment
1、 Extruder1. Twin screw extruder twin screw extruder has the function of forced feeding. The residence time of foamed plastic at the injection point in the twin screw extruder is short and the mixing uniformity is good. Moreover, the heating of 11-10 plastic in the twin screw extruder is also small, so the extrusion temperature of the twin screw extruder is easy to control. Therefore, twin screw extruder is a promising foam extruder. A typical foaming agent intermediate injection twin-screw foaming extruder is shown in Figure 5-11. Its screw 9- injection point
The whole length is divided into plasticizing section, blocking section, cross-section section of mixing injection point and cooling section. Foaming agent coalesces in the choke section
Beam, inject people at the decompression point at the beginning of the mixing section. Fig. 5-11 the forced feeding performance of twin screw will cause 1 a transmission system of twin screw foaming extruder; 2. A feeder; 3. One feeding level: the feeding is overloaded, so there is a 4-plasticizing section under the hopper; 5 - choke zone; 6 - mud section; 7 a cooling section; One die 8; 9 - feeder with accurate metering of the check circumference. There are 10 metering pumps in the form of twin-screw; 11. Two kinds of foaming agent: parallel and conical. L / D is generally 16 kinds of double, especially suitable for eating powder 157
2. Single screw extruder type UPVC material. At present, it is mainly used in the production of rigid PVC foam pipe. Due to the high cost of twin-screw extruder, the control requirements are strict. At present, screw extruders and two-stage series single screw extruders are still widely used. It's a single screw extruder. There are two types of single screw extruder for foaming. The single-stage single (1) agent feeding type is divided into two types: intermediate injection type and imported mixed type. The foaming agent of the inter type extruder can be injected into the decompression section in the middle of the screw. Generally, it is required to add people when the material has been basically plasticized, so the extrusion screw is divided into 6 sections: feeding section, first compression section, first metering section, decompression section, second compression section and second metering section. The total length diameter ratio is about 30. The barrel at the decompression section is provided with an orifice, and the liquid chemical foaming agent or physical foaming agent can be injected into the screw decompression section with a series plunger pump.
The added foaming agent consists of a mixture of 50% butane and 50% trichlorofluoromethane (Freon). Before injecting this foaming agent, the material in the decompression section is required to form a viscous flow state. The injection rate of foaming agent is controlled according to the requirement that the mass ratio of foaming agent to material remains about 10%. There are two typical forms of this extruder. One is extrusion 1- transmission system with barrier section and cooling section; 2 - hopper; 3 - plasticizing area; 4. Mixing in the plasticizing area to reach the basic plasticizing area; 5 - cooling zone; 6. One die; 7 - foaming agent storage tank; 8 - metering pump; 9. A check valve; 10 after the first barrier section, the flow is intercepted through the barrier section to ensure that the large particles with poor plasticization will not enter the mixing section. The junction between the mixing zone and the barrier section creates a decompression zone, where the foaming agent is injected. See Fig. 5-14 for the principle of the check valve at the place where the foaming agent is injected. When the pressure of the foaming agent pumped out by the metering pump is greater than the material pressure in the pressure reducing area of the extruder, the foaming agent pushes the check ball 3 into the extruder barrel. If the material pressure of the extruder is higher than the foaming agent pressure, a foaming agent injection port; 2 - guide chute; 3-check ball: it can prevent the plastic melt from flowing back and blocking the foaming agent channel. There are three key points in the design of this check net: one is to feel the pressure change of foaming agent; Second, it can effectively prevent backflow; Third, it is easy to clean up. The other is to use static mixers to replace the cooling section just now. These static mixers play the role of mixing and cooling materials. This form is more suitable for small foam extruders. The length of static mixer is about 6 ~ 8 times of screw diameter. However, because the amount of materials required to cool the injection point is proportional to the square of screw diameter, this form is not suitable for large foam extruders. According to some data, the length of static mixer required by large foaming extruder is about 12 ~ 18 times of screw diameter. Fig. 5-15 single stage intermediate injection foaming machine obviously has a long transmission system for a long static mixer; 2. A hopper; 3. Plasticizing area; 4 - choke zone; 5. A check valve; The 6-chenghe area is inappropriate. Therefore, later there was 7 a static mixer; One die 8; Many can replace the axial static mixing 9- foaming agent storage tank; The structure of a metering pump came out. As shown in Figure 5-16, one is the radial shunt mixer, which can achieve the same mixing and cooling effect as the axial static mixer, but the length is greatly shortened, which is more suitable for large foam extruders.
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