There are a large amount of agricultural and forestry waste and waste plastics in our country every year that are not fully utilized. Among them, forestry waste is about 600 million tons every year, and agricultural waste alone amounts to about 800 million tons, but the current comprehensive utilization rate is less than 10%; my country's total annual output of plastic products has reached 40 million tons, currently producing 40 million tons per year. China's waste plastics amounted to 14 million tons (statistics in 2008), but the domestic recycling rate of waste plastics is less than 30%. The insufficient utilization of a large amount of agricultural and forestry waste has not only caused huge waste, but also caused excessive deforestation; insufficient recycling of waste plastics has led to serious "white pollution" and a series of environmental and ecological problems.
Wood-plastic composite materials are boards, profiles, etc. made from agricultural and forestry waste and waste plastics as the main raw materials, adding a small amount of additives, and using extrusion (or injection molding, pressing) molding methods. They are mainly used as a substitute for wood. Therefore, the development of wood-plastic composite materials is conducive to the comprehensive utilization of agricultural and forestry waste and the reduction of deforestation. It is conducive to the full utilization of waste plastics and the control of "white pollution", and is conducive to alleviating the increasing pressure on wood.
However, the traditional wood-plastic composite material has a single color, and the color is not bright enough. It is easy to fade in the sun and rain for a long time, and the aesthetic level of the surface is greatly reduced, which makes it very difficult for wood-plastic composite materials to replace high-end solid wood products. Co-extrusion technology is used to extrude two-color wood-plastic composite materials at one time. The surface of the product is covered with a layer of super weather-resistant polymer. At the same time, flow pattern masterbatch is added to greatly enrich the color of the surface.
The two-color co-extrusion technology of plastic-wood composite materials is provided with a molded body and a covering body. The covering body includes a covering body one and a covering body two.And the first covering body surrounds the periphery of the upper part of the molding cavity, and the second covering body surrounds the periphery of the lower part of the molding cavity.A feed hole 1 and a feed hole 2 are provided on the co-extrusion feed plate, and a first flow channel for connecting the two is provided between the feed hole 1 and the cladding body 1,A second flow channel is provided between the second feed hole and the second covering body for connecting the two.By setting up co-extrusion flow channels, the color materials in the co-extrusion material are evenly dispersed and flow into the mold cavity to ensure the flow pattern effect.
The mixing process design of two-color co-extruded wood composite materials is to first dry the wood powder and control the moisture content of the wood powder at 0.5% to 0.8%; add 60% high-density polyethylene to the mixer.Then add a heat stabilizer; after high-speed stirring, it melts into a liquid in a flowing state, and then add 3% of the dyeing agent;Then add 25% wood powder filler at a temperature of 100°C and high speed, and finally add 12% plastic powder and mix thoroughly for 18 minutes.Then the uniformly mixed materials are sent to the cold mixer, cooled to below 45°C and discharged.