Propylene glycol polyester resin

There is evidence in the literature that long-term, high-temperature production procedures bring about branching of the propylene glycol-MA resins. Other side reactions have also been detected and studied.The branching of polyester resins has been attributed to addition of the glycol to... 

Used as fibres, particularly in textiles and film. Many other polyester polymers are of importance, e.g. unsaturated polyester resins from phthalic anhydride, propylene glycol and maleic anhydride used with reinforcement in boats, cars, etc. (alkyd resins). U.S. production 1983 1-7 megatonnes. 

A polyester-type fluorescent resin matrix (22) is made by heating trimellitic anhydride, propylene glycol, and phthaUc anhydride with catalytic amounts of sulfuric acid. Addition of Rhodamine BDC gives a bright bluish red fluorescent pigment soluble in DME and methanol. It has a softening point of 118°C. Exceptional heat resistance and color brilliance are claimed for products of this type, which are useful for coloring plastics. 

Uses. About 35% of the isophthahc acid is used to prepare unsaturated polyester resins. These are condensation products of isophthahc acid, an unsaturated dibasic acid, most likely maleic anhydride, and a glycol such as propylene glycol. The polymer is dissolved in an inhibited vinyl monomer, usually styrene with a quinone inhibitor. When this viscous hquid is treated with a catalyst, heat or free-radical initiation causes cross-linking and sohdification. A range of properties is possible depending on the reactants used and their ratios (97). 

Polyester resins can also be rapidly formed by the reaction of propylene oxide (5) with phthaUc and maleic anhydride. The reaction is initiated with a small fraction of glycol initiator containing a basic catalyst such as lithium carbonate. Molecular weight development is controlled by the concentration of initiator, and the highly exothermic reaction proceeds without the evolution of any condensate water. Although this technique provides many process benefits, the low extent of maleate isomerization achieved during the rapid formation of the polymer limits the reactivity and ultimate performance of these resins. 

The basic patent (US Patent 3256219) indicates that the system is viable with conventional resins although special grades have been developed that are said to be particularly suitable. One example in the patent recommends the use of a polyester prepared using a maleic acid, phthalic acid and propylene glycol ratio of 2 1 33 and with an acid value of 40. To 500g of such a resin are added 10g of benzoyl peroxide and 167 g of styrene. Water 600 g is then stirred in at 5-10°C until a white creamy water-in-oil emulsion is obtained. A solution of 0.8 g of dimethyl-p-toluidine in lOOg of styrene is stirred into the emulsion and the resin is cast between plates and cured at 50°C. 

The only other glycol that is fairly common is propylene glycol which has a molecular formula of C3H (OH)2. It is a combustible liquid with a flash point of 210°F, and its major use is in organic synthesis, particularly of polyester resins and cellophane. 

Higher alcohols have more than three carbon atoms. Examples are the dihydric alcohol, ethylene glycol used for antifreeze, brake fluids and as derivatives in resins, paints " " osives, and polyester fibers. Reactions with propylene make propylene glycol, a moistening ag foods and tobacco. 

RECYCLING OF UNSATURATED POLYESTER RESIN USING PROPYLENE GLYCOL... 

About 60% of the propylene oxide made is polymerized to polypropylene glycol and other polyethers for use in polyurethane foams and adhesives. Propylene glycol is also widely used in polyester resins based on maleic anhydride. 

Propylene glycol, i.e., 1,2-propanediol (1,2-PDO), is an important commodity chemical. It is used as biodegradable functional fluids and as precursors for the syntheses of unsaturated polyester resins and pharmaceuticals (9-10). Propylene glycol is currently produced from petroleum-derived propylene via oxidation to propylene oxide and subsequent hydrolysis (9, 11). However, the rising cost of propylene provides an incentive to find a substitute to propylene for this... 

As is often said, the simplest unsaturated polyester resin (UPR) is the condensation product of maleic anhydride and propylene glycol dissolved in styrene. 

Unsaturated polyesters are generally very brittle materials. The tensile elongation for most UPRs is in the range of 1 % for dicyclopentadiene (DCPD)-based polyester resin to about 2.5 % for isophthalic acid and propylene glycol resins. This 1 % elongation posts a problem for using DCPD resin in making a... 

Uses. Polyester resins use up about 60% of the propylene glycol (and most of the dipropylene glycol) manufactured. The remainder is used as a tobacco and cosmetic humectant. (a chemical that keeps moisture around), automotive antifreeze and brake fluid ingredients, food additive, and plasticizers for various resins, and making nonionic detergents and coatings. Propylene glycol is an excellent solvent. 

Table 10.3 summarizes the uses of propylene oxide. Propylene glycol is made by hydrolysis of propylene oxide. The student should develop the mechanism for this reaction, which is similar to the ethylene oxide to ethylene glycol conversion (Chapter 9, Section 8). Propylene glycol is a monomer in the manufacture of unsaturated polyester resins, which are used for boat and automobile bodies, bowling balls, and playground equipment. 

Unsaturated polyester resins account for the majority of the commercial use of propylene glycol (40%). Other uses include liquid and laundry detergent (15%), cosmetics and pharmaceuticals (12%), antifreeze and deicers (10%), pet food (6%), functional fluids (6%), paint and coatings (4%), and tobacco humectants (3%). 

An unsaturated polyester resin consists of a linear polyester whose chain contains double bonds and an unsaturated monomer such as styrene that copolymerizes with the polyester to provide a cross-linked product. The most common unsaturated polyester is made by step growth polymerization of propylene glycol with phthalic and maleic anhydrides. Subsequent treatment with styrene and a peroxide catalyst leads to a solid, infusible thermoset. 

Polyesters from propylene glycol and dicarboxylic acids, especially adipic and sebacic acid, are commercial products suggested for PVC as well as for cellulose esters. The well known Paraplex resins of Rohm Haas, which are compatible with nitrile and GRS rubber, belong to this group. Other products are the Ultramolls of Farbenfabriken Bayer. Some polyesters of this type have a tendency to exude on storage, especially if esterification is not complete. 

In the manufacture of unsaturated polyester resins the polyester is synthesized and then diluted with a vinyl reactive monomer such as styrene (see POLYESTERS, UNSATURATED). A portion of the dibasic acid of the polyester is maleic or some other vinyl reactive diacid that can be polymerized with the styrene to yield a highly cross-linked, high performance polymer system. Other esters made with propylene glycol, dipropylene glycol, and tripropylene glycol are used as emulsifiers in foods, as plasticizers in polymer systems, and as part of acrylate resin systems. 

Maleic and phthalic anhydrides and fumaric acid are mainly used for polyester resin synthesis. However, dihydric alcohols such as ethylene and propylene glycols, diethylene, dipropylene, triethylene and neopentyl glycols, and hydrided or oxypropylened diphenylolpropane are also used.5 7 Different combinations of dibasic acids with diols allow us to vary the composition and properties of the resulting polyester resins over a wide range. 

Unsaturated polyester resins account for the majority of the commercial use of propylene glycol. Other uses include food, cosmetics, pharmaceuticals, pet food, and tobacco humectants. 

Manufacture of propylene glycol (CH3-CHOH-CH2OH) consumes about 30 percent of the propylene oxide produced. Like ethylene oxide, propylene oxide undergoes hydrolysis to yield the corresponding glycol. Propylene glycol is mainly used to make polyester resins, but it is also used in foods, pharmaceuticals, and cosmetics. 

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