PREPARATION of UNSATURATED POLYESTER RESINS BASED on EMPD Background of the Invention EMPD (1-ethyl-2-methyl-1,3-propanediol) is a glycol intermediate that can impart unique performance when used in unsaturated polyester resins. Its chemical structure brings the following properties to polyester resins and composites made from these resins: better resin processability, improved resin solubility, lower resin viscosity, improved chemical, water & stain resistance, better fiberglass wetting, lower styrene content, low profile surfaces, higher filler content and better mold filling.

WO 97/16401 describes reaction mixtures containing substituted hydrocarbon diols and their preparation and using in coatings. The disclosure includes preparation of 2,2-disubstituted hydrocarbon diols and more specifically 2-ethyl-2-methyl-1,3-propanediol. The application further described the polyesters derived from such diols and their utility in coatings, ink, sealant and adhesive composition.

WO 97/16473 describes polyesters and processes for preparing same. The polyester are prepared from a diacids such as terephthalic acid or isophthalic acid and a diol, preferably, from 2,2-disubstituted 1,3- propanediol and more specifically 2-ethyl-2-methyl-1,3-propanediol. The application further described curable coating, ink, sealant and adhesive compositions based on such polyesters.

Brief Description of the Invention The present invention relates to the use of EMPD to create unsaturated polyester resins similar to those based on propylene glycol (PG) and other commonly used glycols in unsaturated polyester resins without the processing and performance deficiencies normally associated with PG.

Detailed Description of the Invention 1-Ethyl-2-methyl-1, 3-propanediol (EMPD), CAS registry number 149- 31-9, may be used as a glycol and reacted with diacids such as isophthalic acid (PIA), phthalic anhydride (PA), terephthalic acid, adipic acid, maleic anhydride (MA), etc. Other glycols that are typically used include neopentyl glycol, propylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, 2-methyl-1, 3-propanediol, 3-hydroxy-2,2-dimethylpropyl-3-hydroxy- 2,2-dimethylpropanoate, cyclohexanedimethanol, 2-butyl-2-ethyl-1,3- propanediol, 1,6-hexanediol, etc.

This invention can be further illustrated by the following examples of preferred embodiments thereof, although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated.

EXAM PLES EMPD resins made with isophthalic acid (PIA), phthalic anhydride (PA) and maleic anhydride (MA) are described below (Table 1).

Table 1: Reactor Charge EMPD/PIA/MA EMPD/PA/MA Reactants Moles Grams Moles Grams Stage 1 EMPD 8.4 996 7.1 835 PIA 3.2 534 PA 2. 7 393 MA 4.0 391 | Stage 2 MA 4.8 473 Total Charge 2003 1619 Distillate 203 107 Yield 1800 1512

The reactants were processed under a nitrogen blanket. The first stage reactants were charged into two liter resin kettles equipped with heating mantle, agitator, nitrogen purge, temperature probe, packed distillation column, and total condenser.

For the EMPD/PIA/MA resin, the first stage contents of the kettle was heated to 210°C and held until an acid number of 13-17 was reached. This completed the first stage reaction and the kettle contents were cooled to 120°C. For the second stage, the MA was added to the kettle and the temperature brought slowly to 210°C. The resins were held at 210°C until a neat resin ICI viscosity of 4.8-5.2 poise at 175°C. The resin was poured out hot into aluminum boats and allowed to harden.

For the EMPD/PA/MA resin, all of the reactants were added to the kettle and slowly heated to 200°C and held at 200°C until an ICI viscosity of 0.9-1.1 poise at 175°C. The resin was poured out hot into aluminum boats and allowed to harden.

Resin physical property data are given in Table 2.

Table 2: Resin Property Comparison Property EMPD/PIAIMA EMPD/PA/MA Molecular weight Mw 6922 3435 Mn 2433 1489 Neat resin ICI 4.9P 1.1P viscosity @175°C The EMPD/PIA/MA resin was made into a 55% solids solution in styrene and 1/8 inch castings were prepared. The following physical data was obtained from these castings (Table 3).

Table 3: 1/8 inch Casting Physical Testing Results for EMPD/PIA/MA Pro ert Value Standard Deviation Heat Deflection 111 2.6 Temperature, °C Flexural Modulus, Mpa 3199 144 Flexural Break Stress, 100 9.2 Mpa Flexural Break Strain, % 3.8 0. 5 Tensile Modulus, Mpa 3099 66 Tensile Break Stress, Mpa 34 15 Tensile Break Strain, % 1.2 0. 7

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.