1. PVC wood plastic production process
PVC resin plus wood powder, calcium carbonate, additives are mixed with the high temperature mixer to the required temperature. According to the filling temperature, the temperature is generally 115 °C-125 °C, and then cold mixed to 50-40 degrees.
1. It is a one-step method to directly extrude the product with a mixed powder through a cone double extruder. The one-step production advantage is that no granulation is required, which saves the investment in granulating equipment and the maintenance cost of water, electricity, labor and equipment, and reduces material loss. However, the quality and appearance of the product is not as good as the two-step method. In particular, eco-wood is imitation of wood for indoor and outdoor decoration. It is difficult to have the same wood grain as wood. (One-step method can also produce wood grain, such as density of 1.0 or more, but increase the cost).
2. The cooled powder is produced by cone double granulation and then by single screw extrusion or two-step method. The advantages and disadvantages are the opposite of the above. Ecological wood is ideally produced by a two-step process.
Second, molding process and equipment
Good processing techniques and equipment should ensure that the material and foaming agent are evenly mixed, and maintain a sufficiently high and stable head pressure to make the die pressure large enough and the pressure drop fast enough to obtain well-formed cells.
1. Mixing and feeding
The production process of raw materials: wood fiber is a material with strong water absorption. Generally, the water content is about 15% or even higher, and the inorganic filler is also about 5%. The water content is high and low, which affects the stability and products of plastics, especially wood plastic production. Natural enemies of quality, such as affecting the expansion ratio, the water absorption of the product, the deformation of the product, the weather resistance of the product and other physical properties. Therefore, the moisture is preferably controlled within 1%. Control the fibers and fillers with reasonable moisture—–Add to the high-mixer—–mix to 100 degrees—–add the appropriate amount of coupling agent—-mix to 110-115 degrees– — Turn off the mixer cover when the motor is not turned off for 2-3 minutes —– Add PVC, stabilizer—–mix to 80 degrees—–add lubricants and other additives– —100 degrees plus processing aids, foaming agent ——120-125 unloading powder—–after the powder is discharged, the motor stops and then open the big cover for 2-3 minutes and then mix the next batch. (It is best to mix the five hand materials to clean the mixer once)—–The powder can be granulated or added to the twin-screw production in the cold mixing barrel to 40 degrees (the cold mixing barrel must have circulating cooling water). In the mixing, it is necessary to pay attention to observe the temperature and time. For example, the common cold pot is mixed for about 20-25 minutes, and the hot pot is about 12-15 minutes (the temperature is set to about 125 degrees). If there is a difference of 3 minutes or longer. That may be a problem with the temperature sensing line or the temperature control is not correct, or the mixer horn knife is seriously worn. This will affect the stability and color of the expansion ratio. When granulating, it is often necessary to pay attention to whether the temperature control temperature is accurate, whether the fan is in normal operation, the magnitude of the current, the particle size, the surface, the length of the material, whether the material is stable or not, and the material cannot be broken.
The mixing process affects the dispersion of the components by affecting the contact and reaction between the different components, thereby affecting the material properties. When mixing, you should choose the appropriate feeding sequence, feeding temperature, and feeding time. Due to the fluffy wood powder, it is prone to “bridge” and “pilling” during the feeding process. Instability of the feed will cause the extrusion to fluctuate, resulting in a decrease in the quality of the extrusion. Therefore, it is necessary to strictly control the feeding mode and the feeding amount, and generally adopt a forced feeding device or a hungry feeding to ensure the stability of the extrusion. PVC/wood flour composite extrusion foaming is generally divided into two steps: one step and one step. The two-step method is to form the pellet after the first step; the one-step method eliminates the granulation process and uses the surface modified wood. The powder and PVC powder are mixed at high speed and directly extruded. Studies have shown that the masterbatch method (two-step method) is beneficial to improve the mechanical properties of PVC/Wood.
Post time: Jun-25-2019