Mechanism of action of lubricant
Lubricant is to be able to improve plastic processing flow properties of a kind of additive, its structure generally has a long chain of nonpolar and polar group two parts, in addition to improve the melt flow, it also has promotes molten, easy stripping, prevent electrostatic, prevent adhesion effect, according to the mechanism can be divided into external lubricant and lubricant in two.
(1) Mechanism of action of external lubricant
Improve the friction between the plastic melt and the metal surface of the forming equipment, reduce the friction between the two, so that the plastic parts easy demoulding. The external lubricant has poor compatibility with the plastic and is easy to migrate outward from the melt, thus forming a thin isolation film between the melt and the mold to avoid the plastic melt sticking to the barrel or the surface of the mold.
(2) Action mechanism of internal lubricant
Internal lubricant has good compatibility with plastics, it plays a role in reducing intermolecular cohesion in plastic melt, can reduce internal friction of plastic melt, increase melt rate and melt deformation, reduce melt viscosity and improve plasticizing properties.
Most lubricants are both inside and outside the function of the lubricant, but some lubrication, on some outside on lubrication, and the same kind of lubricant in different plastic or under different processing conditions will show different lubrication, it is commonly believed, has good compatibility with plastic, polar groups polarity of lubricants used as lubricant inside; Otherwise, it is used as an external lubricant.
Among them, if the fluidity of plastic has been able to meet the needs of the molding process, the main consideration is whether the external lubricant meets the process requirements, whether it is easy to demoulding, in order to ensure the balance between inside and outside. When selecting external lubricant, it should be noted that the melting point should be close to the forming temperature, but there should be a difference of 10~30℃, so as to form a complete isolation film on the plastic surface.
The properties of excellent lubricants
(1) It must have excellent and lasting lubrication performance.
(2) moderate compatibility with plastic, internal and external lubrication to balance, does not affect the transparency of plastic, not frost, not easy to scale, not with other additives reaction.
(3) Small viscosity, small surface tension, good expansion at the interface, easy to form an interface layer.
(4) Excellent thermal stability, in the process of processing molding does not decompose, does not volatilize, does not reduce the various excellent properties of plastic, does not affect the second processing performance of products.
(5) non-toxic, pollution-free, non-corrosive equipment, cheap price.
Introduction of the main types of lubricants
One, fatty acid amide lubricant
(1) Stearate amide: white or light yellow brown powder, relative density 0.96, molecular weight 283, melting point 98~103℃, insoluble in water, soluble in hot ethanol, chloroform, ether. With excellent external lubrication effect and film removal, transparency, dispersion, gloss, electrical insulation, non-toxic, PVC, PS, urea-formaldehyde resin processing lubricant, but also as polyolefin slippery agent and anti-adhesion agent. The general dosage is 0.1%~2.0%.
(2) ethylene distearate amide (EBS) : white or milky powder or granular. Relative density 0.98, molecular weight 593, melting point 142℃, insoluble in water, soluble in hot chlorinated hydrocarbons and aromatic solvents. Widely used in slippery agent, anti-adhesion agent, lubricant and antistatic agent. Non-toxic, suitable for PE, PP, PS, ABS resins and thermosetting plastics internal and external lubricants. The general dosage is 0.2%~2.0%.
(3) oleate amide: white powder, fragment or pellet. Relative density 0.90, molecular weight 281, melting point 68~79℃, insoluble in water, soluble in ethanol and many other solvents. Non-toxic, can be used as PE, PP, PA and other plastic slippery agent, anti-sticky agent, improve processing performance, but also has antistatic effect, can reduce the dust on the surface of the product adhesion, PVC processing molding in its is a good internal lubricant.
(4) erucic acid amide: shape, performance and use similar to oleate amide, better than oleate amide.
(5) N-butyl stearate (BS) : light yellow liquid, relative density 0.855~0.862, soluble in most organic solvents, slightly soluble in glycerol, ethylene glycol and some amines, and ethyl cellulose, and cellulose nitrate, acetate butyrate, chlorinated rubber and other parts of the compatible. BS is non-toxic, as an internal lubricant in resin processing, with water resistance and good thermal stability, can be used in coatings. Although incompatible with PVC, but can be used as PVC transparent sheet extrusion, injection molding, calendering lubricant, stripping agent. The general dosage is 0.5%~1.0%.
(6) Glycerol trihydroxystearate: powder, melting point 85~87℃, non-toxic, with excellent heat resistance and fluidity. Can be used as PVC, ABS, MBS lubricant and smooth agent and synthetic rubber stripping agent. The general dosage is 0.25%~1.5%.
Two, hydrocarbon lubricants
(1) Microcrystalline wax: white or yellowish flake or granular substance, solid relative density 0.89~0.94, liquid relative density 0.78~0.81, melting point 70~90℃, soluble in non-polar solvents, insoluble in polar solvents. Better thermal stability and lubricity than paraffin, but will reduce the gelation speed, so the dosage should not be too large. Non-toxic, often used with butyl stearate or higher fatty acids, used in plastic lubricants. The general dosage is 0.1%~0.2%.
(2) Liquid paraffin: colorless transparent liquid, relative density 0.89, freezing point -35~-15℃, soluble in benzene, ether, carbon disulfide, slightly soluble in alcohols, good thermal stability and lubricity. Used for PVC, PS and other resin processing, as internal lubricant, poor compatibility with resin. The amount of additive is generally 0.3%~0.5%, too much, but the processing performance deteriorates.
(3) Solid paraffin wax: white solid, relative density 0.9, melting point 57~60℃, insoluble in water, soluble in gasoline, chloroform, carbon disulfide, xylene, ether and other organic solvents, slightly soluble in alcohols. Belong to external lubricant, can improve the surface gloss of products, non-polar straight chain hydrocarbon, can not wet the metal surface, that is, can not prevent PVC sticking to the metal wall, only when used with calcium stearate, can play a synergistic effect, but its compatibility, dispersity and thermal stability are relatively poor. Non-toxic, used in PVC, PE, PP, PS, ABS, PBT, PET, cellulose and other plastics.
(4) Chlorinated paraffin: paraffin is prepared by chlorination. Odorless transparent liquid, chlorine content of 42%, 52%, 70% and other kinds of good compatibility with PVC, but also play the role of plasticizer, flame retardant, but poor transparency, dosage below 0.3%, and other plasticizer with better effect.
(5) Polyethylene wax: also known as low molecular weight polyethylene, white powder or flake, low degree polymerization of ethylene products. Relative density of 0.9~0.93, molecular weight of 1000~5000, softening point of 100~115℃, with good mid and late lubricity, can play the role of anti-adhesive, pigment dispersant in the processing of masterbatch, as a lubricant in PVC-U, in PVC, PE, PP, ABS, PET, PBT plastic molding for lubricant and release agent. The general dosage is 0.1%~0.5%.
(6) Oxide polyethylene wax: White powder or granular solid, low molecular weight polyethylene for containing carboxylic acid, and contain alcohol, ketone, and ester compounds due to oxidation of alkane chain to generate a certain number of carboxyl polar groups, such as so to improve its in the compatibility of PVC, make it have good internal and external lubrication performance at the same time, with good transparency and gloss, The derivatives obtained by partial esterification with higher fat or fatty acid or partial saponification with calcium hydroxide have excellent internal and external lubrication properties. Mainly used in PVC, PE, PP, ABS, PBT, PET and so on. The dosage was 0.1%~1.0%.
Three, siloxane lubricants
Siloxane series is widely used in the processing and molding of phenolic, epoxy, polyester and other plastics as a release agent, anti-adhesion agent and lubricant. Commonly used varieties are polysiloxane, synthetic wax, silicon oil, silicon dioxide and diatomite.
(1) methyl silicone oil: namely polydimethylsiloxane, colorless, tasteless, transparent, viscous liquid, molecular weight of 5000-10000, soluble in ether, benzene, toluene, partially soluble in acetone, ethanol, butanol, insoluble in methanol, cyclohexanol, paraffin oil, vegetable oil. It can be used in the range of -50~200℃. It has excellent high and low temperature resistance, good light transmittance, electrical property, water increase and chemical stability. Used as a release lubricant.
(2) phenyl silicone oil: that is, polymethyl phenyl siloxane, performance with methyl silicone oil.
(3) Ethyl silicone oil: that is, polydiethyl siloxane, colorless or light yellow transparent liquid, average molecular weight 300-10000. Soluble in ether, chloroform, toluene. Can be mixed with petroleum products, the use of temperature -70~150℃, with excellent lubricity and electrical insulation, small surface tension, waterproof, chemical corrosion resistance. It can be used as a release agent and lubricant in plastic and rubber processing.
Type of lubricants for common resins
(1) POLYvinyl chloride: liquid paraffin wax, solid paraffin wax, high melting point paraffin wax, polyethylene wax, ethylene distearamide, ester wax butyl stearate, glycerin monostearate, metal soap, stearic acid, stearic alcohol.
(2) polyethylene, polypropylene: ethylene distearamide, stearamide, oleate amide, calcium stearate, zinc stearate, high boiling point paraffin wax, microcrystalline wax, fatty acid.
(3) polystyrene: zinc stearate, ethylene double stearamide, high melting point paraffin, butyl stearate.
(4)ABS: zinc stearate and other metal soap, fatty amide, ethylene double stearate amide, high melting point paraffin wax.
(5) polyamide: oleic acid amide, stearic amide, ethylene double hard ester amide.
(6)PBT/PET: zinc stearate, calcium stearate, fatty amide, high melting point paraffin wax, polyethylene wax.
(7) Phenolic resin, amino resin: zinc stearate and other metal soap, fatty amide, ethylene double stearate stearamide, high melting point paraffin.
