Lubricants in plastics processing are an important plastic auxiliaries that impart lubricity to plastics to reduce harmful friction and prevent adhesion at the interface of the product. For PVC and other thermoplastic resins, lubricants as plastic auxiliaries can be classified into internal lubricants and external lubricants according to their functions. Currently, the products on the market are mostly single-performance lubricants, and their functions are limited. Products that have both internal and external lubricity are undoubtedly meaningful.
1. Formulation design The internal and external lubricity of plastic lubricants has no obvious limits in the strict sense. However, it is difficult to meet the external lubricity and internal lubricity of plastics in a single component. We choose fat. As an external lubricating component, amide has a high melting point and special interfacial lubrication. The amide compound has a certain surface activity, which can improve the dispersibility of fillers and pigments, and has antistatic function. The use of fatty acid esters as internal lubricating components, due to the presence of ester groups and unesterified hydroxyl groups of fatty acid esters, makes them more polar, has good compatibility with PVC polar resins, and has strong affinity. Sex. Ethylene bis-stearamide (EBS) was selected as the external lubricating component, and stearic acid monoglyceride (GMS) was used as the internal lubricating component.
2, the synthesis of ethylene double stearic amine (EBS) EBS is usually synthesized by: (1) stearic acid and amine compounds; (2) stearate and amine compounds; (3) hard The fatty acid chloride reacts with the amine; (4) the nitrile compound is hydrolyzed. The above four synthetic methods are the simplest in the first type, the reaction conditions are not harsh, and the preparation process is non-polluting. Therefore, stearic acid is reacted with an amine compound. The amines are made of ethylenediamine and the EBS is synthesized in one step. The EBS is synthesized by one-step method. The actual process is that the two processes are further heated to decompose the amine salt and remove the two molecules of water to obtain EBS. The reaction formula is: salt formation. The process is an exothermic reaction, and the reaction temperature should be controlled. If the temperature is too high, it will lead to an amine hydrolysis reaction, which will deepen the color of the amine salt, which will eventually affect the color of the product. The suitable temperature is 100~120*Q and cannot be higher than 120*C. The decomposition of the amine salt is a reversible process. When the temperature of the material is raised and the decomposition temperature is reached, the water should be quickly removed from the reaction system, so that the amine hydrolysis process can be carried out to the end. The temperature is controlled at 150~230C. In the stage, although the process is easy to carry out, the process is an exothermic reaction. Ethylenediamine is easily volatilized and the feed ratio is inaccurate, affecting the reaction, so an appropriate excess of ethylenediamine should be made.
3. Synthesis of glyceryl monostearate (GMS) The synthesis methods of glyceryl monostearate include glyceride esterification, transesterification, glycidylation, chemical gene protection, and oil hydrolysis. Compared with other methods, the glyceride esterification process is mature and simple. It is characterized by a monoester content of 60% to 70%, a 30% to 40% double fat, and a small amount of tristea and stearic acid. glycerin. If the content of monoester is to be increased, it needs to be treated by fractional distillation, the cost will be greatly increased and the process is complicated. The required vacuum is 1~1.5Pa, and the equipment conditions are difficult to meet the requirements. GMS as a plastic lubricant will have a reduced lubricity in the presence of a di-fat, but from the economic cost, it is acceptable to use glycerol esterification.
The reaction formula is: CH2OC - RCH2OH ratio: n (Stearic acid): n (glycerol) = 1: 1.5, the catalyst is an alkaline solid catalyst (such as NaOH), the amount is 0.1% of stearic acid, the reaction temperature is 180 ~ 200 time is 3 ~ 4h.
4. Preparation of composite plastic lubricant Ethyl bis-stearamide and glyceryl monostearate are separately pulverized, and uniformly mixed in an appropriate ratio, and extruded through a granulator to obtain plastic inner lubricity and outer lubricity. a package of lubricant.
5, the impact of composite lubrication system on the processing of PVC plastics
5.1. Extrusion test equipment: Y20 single screw extruder. Extrusion conditions: temperature C; rotation speed, 40 r / min. Extrusion test results are listed in Table 1. Table 1 extrusion test results number stearic acid / paraffin extrusion, GMS / EBS lubrication system than stearic acid / paraffin lubrication The extrusion amount of the system is high, especially when the GMS and EBS are 50% each, the extrusion amount is 25.13% higher than that of the stearic acid/paraffin lubrication system, but the extrusion is in the case of 8 dishes 3 accounting for 30% and the tile 83 accounting for 70%. The surface finish is lowered and the appearance is poor.
5.2. Impact test The test method is based on GB1043-93; test equipment: SK-160B, twin-roller simple plasticizer; XCT*500, impact tester; lubricant dosage: 1 is stearic acid/paraffin (1:1), 1 part; 2 is GMS/EBS (1:1), GMS/EBS lubrication system has better impact performance than stearic acid/paraffin lubrication system.
5.3. Electrical performance test test results, with GMS/EBS as the composite lubrication system, the volume resistivity is increased, which is more favorable for PVC cable materials. GMS/EBS system composite plastic lubricant is used in PVC plastics, the lubrication effect is better, and the physical properties of the products are also improved, but the optimum dosage needs further research.
