Chlorinated polyvinyl chloride DN400 conduction through pipe fitting once injection moulding technique and device thereof

Abstract

The invention relates to a manufacturing technique of a wood-gum tubular element, in particular to a disposable injection molding technique and the devices of a CPVC straight-through tubular element. The technique comprises technical processes of charge mixture, drying, injection molding, pressure maintaining and model opening, wherein a heating portion of a charging barrel of an injection machine is divided into seven segments in the process of injection, the temperature ranges of the segments are respectively 150-155 DEG C, 168-173 DEG C, 162-167 DEG C, 160-165 DEG C, 155-160 DEG C, 150-155DEG C, and 145-150DEG C, and the temperature of a mould is controlled between 60 and 70 DEG C. When injected, pressures of an ejection is divided into three segments which are respectively 55 MPa, 60MPa and 75 MPa. The screw pitch of a screw rod of the injection machine used by the method is equal to the diameter of the screw rod, a feeding segment takes up 25 percent of the total length, a compression segment takes up 50 percent of the total length, and a homogenizing segment takes up 25 percent of the total length. The invention achieves the disposable injection molding of a DN400 large-scale straight-through tubular element via the improvement of the technique and the device.

Description

technical field [0001] The invention relates to a production process of resin pipe fittings, in particular to a one-time injection molding process and equipment for chlorinated polyvinyl chloride straight-through pipe fittings. Background technique [0002] PVC-C (chlorinated polyvinyl chloride) is produced by the chlorination of PVC free radicals. The general chlorine content is 63% to 69%. Different chlorination methods, states and chlorine reactions, the resulting PVC-C has Big difference. Its chlorination reaction process is as follows: [0003] start up: [0004] Derivation: RH+Cl→R+HCl [0005] R+Cl 2 →RCl+Cl [0006] Termination: R+Cl→RCl [0007] Cl+Cl→Cl 2 [0008] R+R→R 2 [0009] (RH stands for PVC, → stands for heating) [0010] PVC-C is produced according to the chlorination reaction mechanism of PVC free radicals mentioned above, controlling a certain percentage of chlorine content, controlling start-up temperature and other process factors. Its ch...

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Problems solved by technology

[0011] DN400 straight-through pipe fittings refer to large-scale straight-through pipe fittings with a nominal diameter of 400. When the existing process is used for one-time injection molding of DN400 straight-through series pipe fittings, the following problems often exist: (1) due to PVC-C (chlorinated polyvinyl chloride) The proportion of resin raw materials is large, and the torque generated by the screw of the injection molding machine in the premolding exceeds the design requirements of the standard screw; (2) PVC-C (chlorinated polyvinyl chloride) resin has a high chlorine content, and the deviation of the temperature control range is small. The frictional heat generated during premolding is difficult to control, so the premolding time required for DN400 straight-through pipe fittings is long, and the material is easily burnt in the barrel; (3) PVC-C (chlorinated polyvinyl chloride) resin has good toughness and impact High strength, large cut, injection molding machine oil motor rotation speed is unstable during pre-molding during processing

Due to the above reasons, according to the existing technology and process, it is impossible to solve the problem of one-time injection molding of DN400 straight-through series pipe fittings

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