WO1999031163A1

WO1999031163A1 - Preparation of high-solids, low voc polyester resins based on empd for use in coil coating applications

Info

Publication number: WO1999031163A1
Application number: PCT/US1998/027312
Authority: WO
Inventors: James Thomas Tanner, Iii; Keith Matthew Moody
Original assignee: Eastman Chemical Company
Priority date: 1998-12-22
Filing date: 1998-12-22
Publication date: 1999-06-24

Abstract

Disclosed are high-solids, low VOC resins based on EMPD for use in coil coating applications. EMPD based resins result in compositions that require less solvent for viscosity reduction.

Description

PREPARATION OF HIGH-SOLIDS, LOW VOC POLYESTER RESINS BASED ON EMPD FOR USE IN COIL COATING APPLICATIONS

Background of the Invention

Coil coatings are formulated to be applied from a rolling operation of a coil of metal being unwound and run through a coil line where the coating is applied. The coating is then exposed to high temperature to cause curing needed to produce the final performance properties in the film. The coating system is usually reacted during this heating to react the polyester with a corresponding cross-linking agent, i.e., a melamine, isocyanate, epoxy or other material. The solvent from the coating is often incinerated in the process. Many coil operations are limited to how much solvent can be incinerated due either to legislation in the corresponding state or the capacity of the incineration equipment.

One of the drivers in the coil coating operation is to obtain coatings with less volatile organic content (VOC). One way to get lower VOC, is to produce resins that give lower viscosity and therefore require less solvent to reduce the coating to application viscosity.

2,2,4-Trimethyl-1 ,3-pentanediol (TMPD) has been used successfully to produce such resins. To be effective, the glycol must be reacted with other glycols and diacids to form a high molecular weight slightly branched or linear polyester. The reaction rate, called esterification rate, is a critical measure of a glycols' utility in coil resins. The TMPD is difficult to react to the molecular weights needed to obtain excellent flexibility and performance properties with very low amount of crosslinking. Brief Description of the Invention

The present invention describes a method to process resins using EMPD based on data generated from TMPD glycol based work. Detailed Description of the Invention

The present invention relates to the use of EMPD (CAS registry number 149-31-9) to prepare low VOC, high-solids resins suitable for coil coating applications, as compared to TMPD. It has been found that TMPD consistently gives low VOC in high-solids lower molecular weight resins. TMPD, and thus EMPD, should also result in low VOC, high-solids resins.

1-Ethyl-2-methyl-1 ,3-propanediol (EMPD) is a high molecular weight glycol that could be used to produce low-viscosity high-solids resins that could be formulated into coatings that are coil applied. The reaction rate or esterification rate of EMPD should be faster than that of TMPD.

Additionally, the EMPD should give low viscosity in a high molecular weight resin, similar to TMPD, which results in resins that require less solvents for viscosity reduction and can be formulated into a high-solids, low VOC, coil coating. It is important that EMPD allow for excellent flexibility and the EMPD should outperform the corresponding TMPD resin. One of the deficiencies with TMPD, is that it tends to make the films more brittle.

EMPD may be used as a glycol and reacted with diacids such as isophthalic acid, orthophthalic acid and anhydride, terephthalic acid, adipic acid, glutaric acid, succinic acid, 1 ,4-cyclohexanedicarboxylic acid (1 ,4-

CHDA), sebacic acid, dodecanedioc acid, etc. Instead of diacids, diesters can be used such as the dimethyl esters of adipic, glutaric and succinic acids, dimethyl 1 ,4-cyclohexanedicarboxylic acid (DMCD), etc. Other ingredients would be branching agents used in low amounts including triols such as trimethyol propane (TMP), trimethylol ethane (TME), glycerine, etc., and triacids, such as Amoco t melletic anhydride, etc. Additionally, this technology can incorporate oils and fatty acids to produce alkyd type systems. Other glycols that are typically used include 2,2-dimethyl-1 ,3- propanediol (NPG), hydroxypivalyl hydroxypivalate (HPHP), 1 ,4-cyclohexanedimethanol (CHDM), 2-butyl-2-ethyl-1 ,3-propanediol (BEPD), 1 ,4-butanediol, 1 ,6-hexanediol (1 ,6-HD), etc. Unique, acid diols such as dimethyloipropionic acid can also be used.

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

Examples 1 and 2:

Coil resins with TMPD were made with the same components and the same weights of ingredients. The only differences is that they processed to different molecular weights, acid numbers and hydoxyl numbers.

The materials above are staged and heated in a standard resin reactor till a low acid number (less than 10) is obtained. In both cases, a small amount (between .01 and .05% by weight) of butyl stannoic acid (Elf Atochem Fascat 4100 catalyst) was used as an esterification catalyst. The first stage consists of the TMPD, one half of the TMP and all of the isophthalic acid with half of the catalyst. The materials are heated to a maximum temperature of 215°C until no more distillate is being generated during the esterification reaction.

The second stage consists of all of the adipic acid, the remaining half of TMP, and the remaining half of the catalyst. The material is charged at 150°C, and the reactor is heated again slowly to 215°C, with the removal of water of esterification. The endpoint is reached upon reacting till the acid number is below 10. The resin is cooled and diluted with xylene.

Example 1 demonstrates how TMPD was used to make a high molecular weight resin that was reduced in solids and viscosity by adding 10% by weight of xylene resulting in a very high solids coil resin at 90% solids.

Examples 2 demonstrates how TMPD was used to make a higher molecular weight resin for coil application. This resin was reduced in solids and viscosity by adding 20% by weight of xylene resulting in a high solids coil resin at 80% solids. Because of the higher molecular weight, less cross-linking (therefore lower hydroxyl number resin) is required to get performance in a coil application.

Compared with TMPD, EMPD should give faster reactivity than TMPD. This decreases the reactor time for making the resin and will decrease the overall cost of the resin. Also, faster reactivity may translate to lower resin processing temperature, which could give lower resin color. Compared with TMPD, EMPD should give a more flexible coating, which is a critical performance parameter in coil applied coatings. As the glycol component of a coil resin, EMPD could be used at levels from 0 to 100%. The final molecular weights could vary from Mn of 2000 to 5000. The Mw could range from 4000 to 100,000. The amount of branching agent could vary from 0 to 15 weight percent. The amount of hydroxyl content remaining unreacted can result in a hydroxyl number between 20 and 150.

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 resin comprising 1-ethyl-2-methyl-1 ,3- propanediol reacted with at least one component selected from the group consisting of diacids, diesters, triols, oils, fatty acids, other glycols and acid diols.

2. A coil coating composition comprising the high-solids, low VOC resin of claim 1.