Polyhydric alcohol polyesters

Polyesters from polybasic acids and polyhydric alcohols. Alkyd resins. The condensation of polyhydric alcohols and polybasic acids or anhydrides leads to polj esters known as alkyd resins. The most common member of the group is a glycerol - phthahc acid polymer, and this has led to the term glyptal resins being frequently apphed to the whole group. 

Polyols. Several important polyhydric alcohols or polyols are made from formaldehyde. The principal ones include pentaerythritol, made from acetaldehyde and formaldehyde trimethylolpropane, made from -butyraldehyde and formaldehyde and neopentyl glycol, made from isobutyraldehyde and formaldehyde. These polyols find use in the alkyd resin (qv) and synthetic lubricants markets. Pentaerythritol [115-77-5] is also used to produce rosin/tall oil esters and explosives (pentaerythritol tetranitrate). Trimethylolpropane [77-99-6] is also used in urethane coatings, polyurethane foams, and multiftmctional monomers. Neopentyl glycol [126-30-7] finds use in plastics produced from unsaturated polyester resins and in coatings based on saturated polyesters. 

As a dibasic acid, malic acid forms the usual salts, esters, amides, and acyl chlorides. Monoesters can be prepared easily by refluxing malic acid, an alcohol, and boron trifluoride as a catalyst (9). With polyhydric alcohols and polycarboxyUc aromatic acids, malic acid yields alkyd polyester resins (10) (see Alcohols, polyhydric Alkyd resins). Complete esterification results from the reaction of the diester of maUc acid with an acid chloride, eg, acetyl or stearoyl chloride (11). 

Alkyds. Alkyd resins (qv) are polyesters formed by the reaction of polybasic acids, unsaturated fatty acids, and polyhydric alcohols (see Alcohols, POLYHYDRic). Modified alkyds are made when epoxy, sUicone, urethane, or vinyl resins take part in this reaction. The resins cross-link by reaction with oxygen in the air, and carboxylate salts of cobalt, chromium, manganese, zinc, or zirconium are included in the formulation to catalyze drying. 

Paraplex. A trademark for a group of alkyd type polymeric materials known as polyester resins. These resins are primarily long chain polybasic acids esterified with polyhydric alcohols such as glycol sebacate, glycerol, or ethylene glycol. Some are oil-modified while others are unmodified polyesters... 

The term alkyd is sometimes used to describe all polyesters produced from polybasic acids and a polyhydric alcohol. The terms saturated and unsaturated polyesters have been used to distinguish between those alkyd polyesters that are saturated from those that contain unsaturation. 

The term alkyd resins represents a broad class of compounds commonly used in coatings and is a particular type of polyester formed by the reaction of polyhydric alcohols and polybasic acids. 

Polyester. A condensation polymer formed by the reaction between a polyhydric alcohol and a polybasic acid, as the polymeric product resulting from the reaction of glycerol and phthallic acid or anhydride. 

Consider the simple alkyd recipe shown in Table 5-1, part (i). Alkyds are polyesters produced from polyhydric alcohols and polybasic and monobasic acids. They are used primarily in surface coatings. The ingredients of these polymers contain polyfunctional monomers and it is possible that such polymerizations could produce a thermoset material during the actual alkyd synthesis. This is of course an unwanted outcome, and calculations based on the Carothers equation can be used to adjust the polymerization recipe to produce a finite molecular weight polymer in good yield. The recipe can also be adjusted to provide other desirable characteristics of the product, such as an absence of free acid groups which may react adversely with some pigments. 

In step-growth polymerizations with unfavorable values of K, it is therefore standard practice to operate at high temperatures and reduced pressures to remove the condensation products. This is typical of the manufacture of linear polyesters where the final stages of the polymerization are at pressures near I mm Hg and temperatures near 280 C. Alkyds (Section 5.4.2) are branched polyesters produced by esterification reactions of mixtures of polyhydric alcohols and acids with varying functionalities. They are used primarily in surface coatings. Alkyd syntheses are completed at temperatures near 240°C. It is not necessary to reduce the pressure to pull residual water out of the reaction mixture, because the final products are relatively low-molecular-weight fluids that are diluted with organic solvents before further use. In one process variation, a small amount of a solvent like xylene is added to the reactants to facilitate water removal by azeotropic... 

Glycerol is a polyhydric alcohol that finds wide uses in several areas of applications. These include as solvent or drugs carrier in pharmaceutical products as humectants in cosmetics and tobacco as ingredients for the production of explosives as plasticizer/stabilizer for less polar polymers as antifreeze or heat transfer agent as hydraulic fluid for the production of polyesters that can be used in grease and/or lubricants and for polyols and polyurethanes and mono and diglycerides, which are useful food emulsifiers. 

Alkyd resins have been the workhorse for the coatings industry over the last half century. The term alkyd was coined to define the reaction product of polyhydric alcohols and polybasic acids, in other words, polyesters. However, its definition has been narrowed to include only those polyesters containing monobasic acids, usually long-chain fatty acids. Thus thermoplastic polyesters typified by polyethylene terephthalate (PET) used in synthetic fibers, films, and plastics and unsaturated polyesters typified by the condensation product of glycols and unsaturated dibasic acids (which are widely used in conjunction with vinylic monomers in making sheet molding compounds or other thermosetting molded plastics) are not considered as part of the alkyd family and are beyond the scope of the present discussion. 

The diisocyanates are used mainly in the manufacture of polyurethanes (PUR). These are produced by polyaddition of diisocyanates and dihydric alcohols, in particular the polyether alcohols (i.e., polyethylene glycols, polypropylene glycols, and the reaction products of propylene oxide with polyhydric alcohols). In addition, oligomeric esters from dicarboxylic acids and diols (polyester alcohols) are also used [91] ... 

Alkyd resins have been defined as the reaction product of a polybasic acid and a polyhydric alcohol. This definition Includes polyester resins of which alkyds are a particular type. The specific definition that has gained wide acceptance is that alkyds are polyesters modified with monobasic fatty acids. In recent years, the term nonoil or oil-free alkyd has come into use to describe polyesters formed by the reaction of polybasic acids with polyhydric alcohols in non-stoichlometric amounts. These products are best described as functional saturated polyesters containing unreacted OH and/or COOH groups, and they are finding rapidly increasing uses in organic coatings. 

The unsaturated polyester prepolymers are obtained from the condensation of polyhydric alcohols and dibasic acids. The dibasic acid consists of one or more saturated acid and/or unsaturated acid. The saturated acid may be phthalic anhydride, adipic acid, or isophthalic acid, while the unsaturated acid is usually maleic anhydride or fumaric acid. The polyhydric alcohols in common use include glycol (such as ethylene glycol, propylene glycol, diethylene glycol), glycerol, sorbitol, and pentaeiythritol (Equation 5.1). 

DIN 53183 defines an alkyd resin as follows Alkyd resins are synthetic polyester resins produced by esterifying polyhydric alcohols with polybasic carboxylic acids. At least one of the alcohols must be trihydric or higher. Alkyd resins are always modified with natural fatty acids or oils and/or synthetic fatty acids. In order to obtain particular application technology properties, alkyd resins may be additionally modified with compounds such as resin acids, benzoic acid, styrene, vinyltoluene, isocyanates, acrylic, epoxy, or silicone compounds. ... 

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