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All you want to know about calcium stearate is here

All you want to know about calcium stearate is here

2022-09-16

Calcium stearate is a white powder that is insoluble in water, cold ethanol, soluble in organic solvents such as hot benzene, benzene and turpentine, and slightly soluble in hot ethanol. It decomposes slowly when heated to 400 ℃ and is flammable. It decomposes into stearic acid and corresponding calcium salt when encountering strong acid and is hygroscopic. It is mainly used as stabilizer,  lubricant , paint polish, lubricant for pencil lead, etc.

Calcium stearate will show some interesting effects when heated. It begins to soften at the temperature between 120 ° C and 130 ° C, and its viscosity will not change after reaching about 160 ° C. In DSC test, there is a crystallization peak indicating the separation of crystal water, indicating that calcium stearate is not a classic melt. It is flammable, decomposes into stearic acid and corresponding calcium salt when encountering strong acid, has water absorption in the air, and is not resistant to lipolytic microorganisms.

1. Production method

(1) Direct method

Add a certain amount of stearic acid and CaO into the reaction pot equipped with agitator and thermometer, raise the temperature to melt, slowly add catalyst H2O2 under constant stirring, vacuum, control the reaction temperature at 140~150, and react for 1.5~2.0h. After the reaction is completed, the material is discharged, cooled and crushed to obtain the product.

(2) Complex decomposition method

Dissolve stearic acid in hot water of 20 times the mass, add saturated caustic soda solution, conduct saponification reaction at 75 ℃, and generate dilute sodium stearate solution. Then add the calcium chloride solution with the content of 1074kg/m3 into the sodium stearate solution, perform the double decomposition reaction at 65 ℃, and the product calcium stearate is precipitated. The finished product is then filtered, washed and dried at 90 ℃.

2. Application

Calcium stearate is used as heat stabilizer of PVC and lubricant and release agent for various plastics processing. As a PVC lubricant, it is generally considered as an internal lubricant. Calcium stearate is the stearate of medium strong calcium base, with strong polarity. The chemical active point of PVC resin particles can form a more stable complex system with calcium stearate. However, the two long-chain alkyl groups of calcium stearate are less compatible with polar resins such as PVC, forming a local micro two-phase interface in PVC resin, that is, a lubricating film. The micro essence of its lubricating effect is that the force between the local lubricating interface formed by non-polar long chain alkyl and the polar resin chain segment is less than the force between the resin chain segments, and because there are many small pores between the resin chain segments, when the resin chain segment is displaced, the arbitrarily deformed alkyl is squeezed into other adjacent pores, thus reducing the resistance when the resin chain segment is displaced and playing the role of internal lubrication.

In practical application, calcium stearate, as a PVC lubricant, does not only play the role of internal lubrication, but also plays a complex role. In other cases where the proportion of internal lubrication is relatively high, it will play the role of external lubrication. Moreover, it has synergistic effect with many lubricants.

In the hard products, the gelling speed can be improved by combining with basic lead salt and lead soap. It is also used for food packaging, medical appliances and other non-toxic soft films and appliances. It can be used as halogen absorbent for PE and PP to eliminate the adverse effect of residual catalyst on color and stability. As a plasticizer in rubber processing, it can soften natural rubber and synthetic rubber, but has little effect on vulcanization. It is also used as a lubricant for polyolefin fibers and molding plastics, a thickener for lubricating grease, a waterproof agent for textiles, a matting agent for paints, a plasticizer for making plastic records, a lubricant and a release agent for thermosetting plastics such as phenolic and amino compounds, a lubricant for pencil lead, and a food grade calcium stearate as an anti bonding agent.

The use of calcium stearate alone in the formula can accelerate the plasticization, improve the melt viscosity, increase the torque, and have a certain demoulding effect. The use of paraffin alone shows delayed plasticization, reduced torque, and no demoulding effect. When calcium stearate and paraffin wax (polyethylene wax) are mixed in a certain proportion, it shows a good effect, and the torque value of the material can be reduced a lot. This is because paraffin penetrates into calcium stearate molecules, strengthens the lubrication, shows a strong synergistic effect, and changes the dispersion of the lubricant.

3. Function

The acid neutralizer in polyolefin has a direct contribution to the color stability and corrosion resistance of polyolefin; Lubrication/processing aids improve the processability of polyolefin, polyamide, styrene and rubber in extrusion (film, fiber, profiling, etc.) and compression molding. Demolding properties for thermoplastic, rubber and thermosetting products, such as polyurethane foam and unsaturated polyester.

Qingdao Sainuo Chemical Co.,Ltd. We are manufacturer for PE wax, PP wax,OPEwax,EVAwax, PEMA, EBS,Zinc/Calcium Stearate…. Our products have passed the REACH, ROHS, PAHS, FDA testing.

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