Slip agents migrating

To decrease the friction of films in contact with processing and conversion equipment, a lubricating agent known as a slip agent is added. Slip agents migrate to the surface and reduce the coefficient of friction, allowing for faster line speeds (lubrication). Primary amides, secondary amides, and ethylene... 

Films are subjected to winding pressures during production and storage. The effect of pressure on slip agent migration is an essential element of the mechanism of its action.The results of studies are not conclusive yet. It was observed that... 

Some additives can interfere with the effects of others—like titanium dioxide diminishing the usefulness of slip agents—and many of them influence the efficiency of corona discharge treatment. The results vary with the additives concerned and with their concentration.19 The presence of additives on the surface will screen the film against the effects of the discharge, while difficulties may be caused after treatment when additives migrate to the surface (it is intended that they should so do) and impair in consequence the keying of ink. 

Three properties that contribute the most to migration are (1) incompatibility with the resin, (2) low melt point, and (3) low molecular weight. Examples of noncolorant additives that are prone to migrate are (1) lubricants/dispersants such as metal stearates and bis-stearamides, (2) mold release and slip agents, and (3) antistatic agents. All of these ingredients serve useful purposes in color formulations. If you exceed their solubility limit in the end-use resin, however, you risk blooming and its consequences. 

A special additive used to provide surface lubrication during and immediately following processing of the plastic material. Slip agents act as an internal lubricant which will eventually migrate to the surface. 

Reactivity with other additives Amine (EA) and amide (EDA) antistats can react with halogenated flame retardants and other acidic additives. They also compete for space at the surface of the polymer with other migrating additives, such as slip agents [6-27]. 

If the film requires a low CoF surface immediately, such as in bag conversion, slip agents based on unsaturated molecules are useful, such as unsaturated emcamide or oleamide. At high concentrations, these migrate within minutes to the polymer surface (where their effect then dissipates over several days or weeks). 

Ideally a slip agent should also fit the timing of printing or corona treatments on the film, which are affected negatively by migrated slip agents on the film surface. 

A slip agent can be specifically chosen for how it migrates through different POs in a multilayer film for example, a secondary amide such as stearyl erucamide will migrate through a PP copolymer layer but not through a homopolymer layer. 

Other additives may slow the expected migration rate of slip agents. And surface-acting agents such as anti-stats or anti-fogging agents may also interfere with the effects of slip agents (or be interfered with by them), since they all require exposed surface area to function [12-1, 12-2],... 

Chem. Descrip. Oleamide CAS 301-02-0 EINECS/ELINCS 206-103-9 Uses Lubricant, slip, antiblock, and mold release agent for plastics, rubber, crayons, petrol, prods., asphalts, inks, metals, textiles mold release agent for thermoplastic resins in inj. molding defoamer/water repellent in industrial/household applic. release agent migrating from food pkg. food pkg. adhesives, coatings in surf, lubricants for mfg. of food-contact metallic articles... 

It is known that additives such as slip agents and antioxidants can adversely affect the treatment if this is done out of line, that is, if the additives migrate before the treatment is carried out, then inferior adhesion may result. Another problem is that the effectiveness of the treatment can deteriorate over a period of a few weeks. 

A number of other companies such as Dover Chemical and Akzo Nobel have developed improved slip and antiblock additives. Ampacet markets a non-migrating slip agent for use in multilayer films where different coefficients of friction are needed in different directions. Antistat performance is provided on the irmer layer, and slip or antiblock performance on the outer one. 

Slip agents such as saturated and unsaturated fatty acid amides can overcome film surface friction. These agents migrate to the film surface dining processing and upon aging at elevated temperatures (see Release Agents). 

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