Stearate heat stabilizers

In addition to traces of metals due to catalyst remnants, metal containing processing chemicals and adventicious impurities, polymers might also contain higher concentrations of metals. Examples of this include metallic stearate heat stabilizers in PVC and fire retardant additives such as antimony trioxide in acrylics and polyolefins. Such elements can be determined by atomic absorption procedures such as that described in Method 71. 

Rigid Applications. The use of the lead stabilizers is very limited in the United States but, they are stiU used in several rigid PVC appHcations in Europe and Asia. The highest use of lead stabilizers in rigid PVC is for pipe and conduit appHcations. Tribasic lead sulfate is the primary heat stabilizer with lead stearates included to provide lubrication. The lead products are typically fully formulated, usually including lubricants and pigments for pipe extmsion appHcations. These lead one-packs, when used at about 1.8—2.5 phr, provide all of the stabilizer and lubrication needed to process the polymer. A lead one-pack contains tribasic lead sulfate, dibasic lead stearate calcium stearate, polyethylene wax, paraffin wax, ester wax, and pigments. 

Costabilizers. In most cases the alkyltin stabilizers are particularly efficient heat stabilizers for PVC without the addition of costabilizers. Many of the traditional coadditives, such as antioxidants, epoxy compounds, and phosphites, used with the mixed metal stabilizer systems, afford only minimal benefits when used with the alkyltin mercaptides. Mercaptans are quite effective costabilizers for some of the alkyltin mercaptides, particulady those based on mercaptoethyl ester technology (23). Combinations of mercaptan and alkyltin mercaptide are currently the most efficient stabilizers for PVC extrusion processes. The level of tin metal in the stabilizer composition can be reduced by up to 50% while maintaining equivalent performance. Figure 2 shows the two-roll mill performance of some methyltin stabilizers in a PVC pipe formulation as a function of the tin content and the mercaptide groups at 200°C. The test formulation contains 100 parts of PVC (Fikentscher K = 65), 1.2 parts of paraffin wax, 0.6 parts of calcium stearate, and 0.4 parts of methyltin-based stabilizers. 

By far the most common lead salt used for PVC stabilization is tribasic lead sulfate. It can be found either alone or combined with another lead salt in almost every lead-stabilized PVC formulation. Many of the combinations are actually coprecipitated hybrid products, ie, basic lead sulfophthalates. Dibasic lead stearate and lead stearate are generally used as costabilizers combined with other primary lead salts, particularly in rigid PVC formulations where they contribute lubrication properties dibasic lead stearate provides internal lubrication and lead stearate is a good external lubricant. Basic lead carbonate is slowly being replaced by tribasic lead sulfate in most applications due the relatively low heat stability of the carbonate salt which releases C02 at about 180°C during PVC processing. 

Lubricants are used in rigid PVC (PVC-U) in amounts 0.3-0.8% (metallic soaps acting primarily as heat stabilizers are used at levels up to 1.5 %). In polyolefins, calcium or zinc stearates used as antiacids provide the lubricating effect at 0.1 to 0.2%. Fluoropolymers are used specifically for L-LDPE. 

An additive system was developed for poly(vinyl chloride) for medical applications. The additives include primary stabilisers (Ca-Zn stearate and Zn stearate), secondary stabilisers (epoxides) and lubricants (ethylene bisamide and high density polyethylene), to improve melt processing and heat stability. The use of the stabilisers resulted in reduced equipment down-time, increased the level of recycled material which could be incorporated, and enhanced the product characteristics, including colour, clarity, blush, aqueous extractables and particle generation. 5 refs. 

The variety of substances used as additives in polymers is considerable. For example, the fillers may include china clay, various forms of calcium carbonate, talc, silicas (diatomaceous silica), silicates, carbon black, etc. The impact modifiers typically include other polymers. Plasticizers include certain polymers with low (oligomers), dialkyl phthalates, dialkyl sebacates, chlorinated paraffin waxes, liquid paraffinic fractions, oil extracts, etc. Heat stabilizers include heavy metals salts such as basic lead carbonate, basic lead sulfate, dibasic lead phosphite (also acting as a light stabilizer), dibasic lead phthalate, stearates, ricinoleates, palmitates and octanoates of cadmium and barium, epoxide resins and oils, amines, diphenylurea, 2-phenylindole, aminocrotonates. The antioxidants include tris-nonyl phenyl phosphite, 2,6-di-ferf-butyl-p-cresol (BHT), octadecyl-3,5-di-terf-butyl-4-hydroxyhydrocinnamate, etc. The UV stabilizers include modified benzophenones and benzotriazoles. Processing lubricants include calcium stearate, stearic acid, lead stearate, various wax derivatives, glyceryl esters and long-chain acids. Fire retardants include antimony oxide, some pyrophosphates, etc. 

When used in PVC organophosphites act as secondary heat stabilizers. In other resins such as PP, PS, HOPE and ABS plastics they function as antioxidants. p-Diketones are well-known co-stabilizers more particularly for zinc carboxylates. The synergistic action of epoxidized fatty acid esters like ESO or butylepoxy stearate as plasticizer, HCl scavenger and stabilizer for labile chlorine atoms in the catalytic presence of Zn and Cd salts is shown in Fig. 7 (see also 5.2.3)... 

Acid acceptors are used when acids may be involved in the degradation of the polymer. Calcium stearate is often used with polypropylene to neutralize any mineral acids, such as hydrochloric acid, that might result from the reaction of water with catalyst residues. Various mixed metal laurates are used as stabilizers in polyvinyl chloride. Efforts are underway to replace the cadmium in some of these mixtures (see Chap. 4). Epoxidized soybean oil has been used as the acid acceptor, along with dioctyltinbis(thiogly-colate), to improve the heat stability of polyvinyl chloride.27... 

Metal Soaps—Barium and cadmium stabilizers are less toxic than lead and have lower cost on the basis of use levels, better sulfide stain resistance, and good clarity. They are a major class of heat stabilizers. Calcium and zinc soaps are also included in this classification because of their similar performance. The soaps used are based on a wide variety of anions such as octoates (2-ethyIhexanoic acid derived), benzoates, laurates, stearates, and substituted phenolates. 

Synpron . [Syn. Prods.] Antimtmy mercaptide, dibutyltin dilaurate, or metallic stearates PVC heat stabilizer, lubricant, i ocess aid. 

The most common mixed metal stabilizers are octoates, naphthenates and benzoates of barium and zinc metals which are liquids. Barium, cadmium and zinc stabilizers contain solid salts of fatty acids including stearates and laureates. Barium and cadmium provide the most effective thermal stability followed by barium and zinc and then calcium and zinc. However, cadmium is currently considered undesirable from environmental and health standpoints and is being replaced in heat stabilizers, particularly those for polymers used with food. 

Lead heat stabilizers are used for wire and cable applications as primary additives. They may be based on organic compounds including stearates and phthalates or inorganic salts such as sulphates, phosphates and carbonates. Although knowledge of the toxicity of lead has initiated the search for its replacement, no suitable, cost-effective material has yet been identified. 

Flame retardants and heat stabilizers contain halogens, particularly bromine or phosphorus, or metal soaps such as stearates, pahnitates and octoates of... 

Chem. Descrip. Zinc stearate CAS 557-05-1 EINECS/ELINCS 209-151-9 Uses Partitioning agent in dry form where thick uniform coatings are required promotes mold release internal lubricant Features Superior heat stability controlled particle size and high bulk dens, improves dispersion, provides faster, more uniform mixing Regulatory FDA accepted Properties Powd. 

Synonyms 9,10-Octyl epoxy stearate Uses Heat stabilizer and plasticizer for plasticized and paste PVC formulations, food pkg. 

Lead stearate, dibasic Empirical CseHroOePbs Formula [CH3(CH2)i6COO]2Pb 2PbO Uses Heat stabilizer for PVC lubricant Manuf./Distrib. ChemService http //www. chemservice. com Trade Name Synonyms Akstab BLS 51 [Akdeniz Kimya] Hal-Lub-D [Halstab... 

Heat stabilizers Protect pol3Tners during thermal processing Metallic salts, especially of weak fatty acids (e.g., zinc stearate)... 

Dibasic lead stearate n. 2PbO Pb(OOCCi7 H35)2. a good heat stabilizer with lubricating properties. 

Metallic stearates. Metallic stearates are the most widely used lubricants. They are utilized predominantly in PVC, but also find use in polyolefins, ABS, polyesters, and phenolics. The primary disadvantage of metallic stearates is their lack of clarity. Calcium stearate, the most common metallic stearate, is primarily used as an internal lubricant, but in PVC applications, it provides external lubricant and metal release characteristics while also acting as a heat stabilizer. 

Compounds of adipates, palmitates. sebacates. and stearates are used as lubricants and plasticizers for many types of plastics, including PVC and engineering plastics. Cetyl palmitate can be used in place of natural wax and can act as a lubricant for engineering plastics. Octyl and iso-octyl palmitate are clear oily liquids with anti-blocking properties and additional heat stability that are also used as plasticizers for PVC and as a viscosity modifier for plastisols. The stearates are used, broadly, as viscosity stabilizers in PVC and lubricant/flow promoters in PS and ABS, particularly where low-temperature properties are required. Cetyl stearate is used as a lubricant for engineering plastics. 

Metal stearates, including predominately calcium stearate as well as zinc stearate, are the most widely used lubricants. In PVC calendering and extrusion, the stearates provide heat stabilizing effects as well as act as an internal Inbri-cant. In polyolefins, stearates act as external lubricants as well as deactivators of catalyst residues. Ferro (Synpro, Petrac), Baerlocher (Hydense), and Crompton (Witco) are the major producers of metal stearates in North America. 

The majority of the commercial metal stearates (besides special grades) are produced by a reaction of certain metal hydroxides or oxides with hydrogenated tallow fatty acids (HTFA) or mixtures of stearic and palmitic acids. Dependent on the production process applied (direct fusion in molten fatty acid or precipitation in an excess of water) a broad range of qualities (from neutral to high base excess) is available in various commercial forms. Concerning polymer apphcations, a nearly neutral grade of high purity and heat stability, i.e. with low acid content and low amount of water soluble salts (basicity), should be preferred. 

Pationlc 909 is a distilled (95%, minimum monoester) glycerol mono stearate derived from fully hydrogenated vegetable oil and produced to polymer additive heat stability requirements. Designed Uses ... 

Barium Stearate Ba(Ci8H3502)2 White crystalline solid insoluble in water or alcohol mp of 160°C, and sp gr of 1.145. Used as a light and heat stabilizer in plastics. As a heat stabilizer, it is used particularly when sulfur staining is to be avoided. Also used as a lubricant where high temperatures are to be encountered. 

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