WO1999031162A1

WO1999031162A1 - Preparation of high-solids, low voc solventborne polyester resins using empd

Info

Publication number: WO1999031162A1
Application number: PCT/US1998/027284
Authority: WO
Inventors: Stacey James Marsh; Travis Eugene Jones
Original assignee: Eastman Chemical Company
Priority date: 1998-12-22
Filing date: 1998-12-22
Publication date: 1999-06-24

Abstract

This invention relates to the use of 1-ethyl-2-methyl-1,3-propanediol (EMPD) to create low VOC, high-solids resins similar in VOC to those based on TMPD glycol without the handling and processing difficulties normally associated with TMPD glycol.

Description

PREPARATION OF HIGH-SOLIDS, LOW VOC SOLVENTBORNE POLYESTER RESINS USING EMPD

Background of the Invention

High solids coatings are typically used in industrial baking applications such as metal office furniture, appliance topcoats, spray primers, automotive basecoats, metal deco, exterior aluminum extrusions, and other general industrial finishing applications. These coatings are largely based on polyester resins crosslinked with amino resins.

High-solids coatings continue to be an effective method to meet government volatile organic compound (VOC) regulations. High-solids coatings are defined as having 75 to 80 wt.% solids or VOC approaching 2.8 Ibs./gal. of coating. To achieve high-soiids coatings at a usable application viscosity, low molecular weight resins must be employed. Such low molecular weight resins typically contain a certain percentage of unreacted glycol monomer as well as dimer and trimer materials that contribute to VOC.

TMPD glycol (2,2,4-trimethyl-1 ,3-pentanediol) has long been the standard in the production of high-solids resins for the metal office furniture coatings market. Its high molecular weight reduces its volatility during the baking of high-solids coatings. Also, its bulky, asymmetrical structure contributes to low resin viscosity. A new monomer, EMPD (1-ethyl-2- methyl-propanediol or 2-methyl-1,3-pentanediol) has structural similarities to TMPD glycol that make it a viable option for the production of high-solids polyester resins.

TMPD glycol inherently has several shortcomings in its handling and processing into polyester resins. Specifically, TMPD glycol is a cold-flowing solid at room temperature. This makes it difficult to store and charge into reaction kettles. It also decomposes during resin processing producing organic distillate that must be properly disposed of. Finally, its highly sterically hindered secondary hydroxyl contributes to long reaction times. As will be discussed below, these difficulties are not exhibited by EMPD or are greatly reduced in comparison. Brief Description of the Invention

This invention relates to the use of 1-ethyl-2-methyl-1 ,3-propanediol (EMPD) to create low VOC, high-solids resins similar in VOC to those based on TMPD glycol without the handling and processing difficulties normally associated with TMPD glycol. Detailed Description of the Invention

EMPD (CAS Registry Number 149-31-9) may be used as a glycol and reacted with diacids such as isophthalic acid, phthalic anhydride, terephthalic acid, adipic acid, glutaric acid, dodecanedioic acid, 1 ,4- cyclohexanedicarboxylic acid, hexahydrophthalic anhydride, etc. Other ingredients may include branching agents used in low amounts including glycerol, trimethyolpropane, trimethylolethane, pentaerythritol, trimellitic anhydride etc. Additionally, this technology can incorporate oils and/or fatty acids to produce alkyd type systems. 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, cydohexanedimethanol, 2-butyl-2-ethyl-1 ,3-propanediol, 1 ,6-hexanediol, 2,2,4-trimethyl-l ,3- pentanediol, etc. EMPD-based high-solids polyester resins may also be modified after polymerization with reagents such as t-butyl acetoacetate, ethyl acetoacetate, etc. for the purpose of further lowering resin viscosity or enabling the use of alternative crosslinking technologies.

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.

EXAMPLES Example 1

Resins based on TMPD glycol and EMPD were synthesized holding molar ratios constant (Table 1 ). Table 1 : Reactor Charge

The reactants were processed using 0.1% Fascat 4100 tin catalyst under a nitrogen blanket. Each glycol, TMPD or EMPD, was charged into two liter resin kettles equipped with heating mantle, agitator, nitrogen purge, temperature probe, packed distillation column, and total condenser. In addition to the glycol, isophthalic acid, adipic acid, and half of the total requirement of trimethylolpropane were also charged into the kettles. For the first stage, the temperature of the contents of the kettles was increased to 200°C and held for three hours. For the second stage, the remaining trimethylolpropane was added to each kettle and the temperature brought slowly to 215°C. The resins were held at 215°C until each reached a final acid number of six plus or minus two. After removal from heat, the resins were cut to 85% theoretical solids in xylene. Organic distillate data were gathered from the TMPD glycol-based resin and compared to data from the EMPD-based resin (Table 2). There was much less organic mass in the EMPD-based resin's distillate. Also, no separate organic phase was observed for the EMPD-based resin whereas an organic phase typical of TMPD glycol-based resins was evident for the TMPD-based resin cook.

Table 2: Distillate Analysis

Distillate EMPD-based resin TMPD glycol-based resin

Aqueous phase (wt.%) 100 96.5 Organic phase (wt.%) 0 3.5

Water (wt.%) 98.5 94.2 Organics (wt.%) 1.5 5.8

Cook time was shorter for the EMPD-based resin.

Resin physical property data are given in Table 3. When processed to approximately the same acid number and molecular weight, the neat and solution viscosities of the EMPD-based resin are significantly lower than with the TMPD-based resin.

When the resins are formulated to about the same application viscosity (40 sec. #4 Ford Cup), determined VOC was almost exactly the same (Table 4). Table 4: Enamel Pro ert Com arison

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.

Claims

CLAIMSWhat is claimed is:

1. A high-solids, low VOC solventborne coating comprising a resin formed by the reaction of 1-ethyl-2-methyl-1,3-propanediol reacted with at least one compound selected from the group consisting of diacids, branching agents, oils, fatty acids, and other glycols; a reagent selected from the group consisting of t-butyl acetoacetate and ethyl acetoacetate; and a crosslinker.