Evaluation of the Problem Associated with Application of Low Solvent Coating to Wood Furniture

United States Environmental Protection Agency
Research and Development
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711

Carl Uhrmacher

EPA/600/S2-87/007
May 1987

EPA Project Summary

The coatings manufacturing industry has advanced the state-of-the-art for producing low volatile organic compound (VOC) based finishes for wood furniture. These improved coatings have the potential to overcome earlier objections of the furniture industry to attempts to regulate lower VOC emissions in this industry. The objective of this project was to evaluate a low-VOC finishing system for the manufacture of wood furniture and to compare its performance in the manufacturing process to an equivalent conventional solvent based system. The production of furniture finished with a conventional solvent-based system and several days production of wood furniture finished with a low-VOC system were observed and evaluated. All furniture was produced under a single contract with the General Services Administration (GSA), and was to be similar in color and style. In the low-VOC system, a waterbased combined toner and washcoat, a ratelyzed sealer, and a catalyzed topcoat were used in place of part of the normal coatings used in the conventional finishing system. All problems, processing changes, personnel comments, and production figures were noted and analyzed. The reduction in VOC emissions was estimated from consumption data obtained during the observation period. The manufacturing economics, process changes, impacts on the environment, potential effects on worker health, and changes in energy requirements were evaluated for these low-VOC coatings.

This Project Summary was developed by EPA's Air and Energy Engineering Research Laboratory, Research Triangle Park, NC, to announce key findings of the research project that is fully documented in a rate report of the = me title (see Project Report Ordering Information at beck).

Introduction

In 1979, the U.S. Environmental Protection Agency (EPA) issued draft control technique guidelines for volatile organic emissions (VOCs) resulting from the application of coatings in the manufacture of wood furniture. The industry, as represented by several trade associations, and several individual companies objected to the suggested use of new furniture coating technology based on the use of waterborne coatings in lieu of the conventional solvent-borne coatings.

Since 1979, the coatings manufacturing industry has advanced the state-of-the-art for the production of low-VOC coatings. Their efforts have improved low-VOC coatings, including high solids, catalyzed high solids, and waterborne coatings. These improved coatings could help to overcome the earlier objections of the furniture industry to the use of low-VOC coatings.

The General Services Administration (GSA), in cooperation with EPA and the U.S. Army, awarded a contract to United Globe Corporation, a division of Turner Furniture Industries, for the manufacture of traditional style household wood furniture for use by Army personnel stationed overseas. A special clause in this contract required that 1000 buffets be finished with a low-polluting coating system, defined by GSA and EPA to be one that contains less than 100 lb VOC/1 1000 ft2 of surface area finished (45.4 kg/92.9 m2).

Objective

The objective of this project was to determine the off effects of using a low-VOC coating system in lieu of a conventional solvent system in the manufacture of comparable or equivalent wood furniture. The major elements in the manufacturing process to be evaluated in this study included:

This report does not present opinions about the aesthetic quality or commercial acceptability of the low-VOC finishes since the primary objective of this project was to determine the effect of low-VOC coatings on the manufacturing and finishing processes. The furniture produced during this program was required to meet minimum GSA standards for quality and color.

Materials and Procedures

Coating Material

All of the coating materials used in the low-VOC trials and in the conventional GSA finishes are listed, along with their density and VOC content, in Table 1.

The Furniture

The finishing of GSA contract furniture that was coated with conventional act vent-borne coatings was observed. This furniture was a mix of the bedroom and dining room suites produced with the same finish. Buffets were chosen by GSA to be used in the trials. One thousand buffets were produced with the new finish and were to blend in with the non-test dining room furniture.

Procedures

No air samples were collected for this project because of the plant configuration. It was assumed that all volatile material eventually was released to the atmosphere sphere, that total emissions could be calculated from density, and that VOC content data could be determined by laboratory analysis.

Results

Releases to the Atmosphere

The use of the low-VOC system in this study reduced the amount of VOCs released to the atmosphere. There was a 40% reduction based on the EPA laboratory analysis of the coating system. Of the 50.8 lb (23 kg) reduction: 59% was produced by using the waterborne coating in place of the washcoat and toner; 12%, by using the catalyzed sealer; and 23%, by using the catalyzed topcoat.

The goal of 100 lb VOC emitted/1000 ft2 Coated was met with this system. The total was estimated to be 75.7 lb/1000 ft2 (34.3 kg/93 M2), a reduction of 50.8 lb/1000 ft2(23 kg/93 M2).The use of the waterborne coating accounted for 29.9 lb (13.6 kg) of this reduction, the catalyzed sealer for 6.1 lb (2.8 kg), and the catalyst topcoat for 11.6 lb (5-2 kg).The rest are summarized in Table 2.

Solid Waste

There was an increase in the amount of solid waste generated as sludge trapped in the water pan booth after the spraying of the high solids catalyzed coatings. This was estimated by plant personnel to be a 30% increase over the normal conventional coatings. This is not a major environmental problem for this plant, because these sludges, which are metal free, can be burned in a state-approved incinerator.

Analysis

Waterborne Toner/Washcoat

The major problem with the waterborne coating was grain raising caused by the water in the formulation. This caused the surface to be rough and required extra sanding. This also opened the grain and allowed the wipe stain (filler) to operate too deeply and produce too dark a color. Extra retarder had to be added to the filler, and the furniture had to be wiped.

Table 1 Density and VOC Content of Coatings
Coating Manufacturer's Lab
EPA Lab

[(See document source for table.)]

Based on laboratory analysis of freshly catalyzed material. Same coating used in both systems.

Table 2 VOC Reduction

[(See document source for table.)]

Metric conversion: I lb/1000 ft2 0.0049 kg/m2. b Costing used by both systems, with naphtha to remove the excess Stain. The resultant problem with the filler could be solved, but the grain-raising problem remained throughout the trial, and procedural changes during the manufacturing process did not mitigate the problem.

Catalyzed Sealer

Three problems occurred with this coating:

  1. "Setting-up ...
  2. ..orange peel
  3. Worker complaints about eye irritation and smell

Setting-up refers to thickening of the catalyzed material when stored.

The coating used had a 1-day pot life, and usage, the attempt to extend its pot life failed during the evaluation.

Total VOC used VOC Reduction

Economic Analysis

Coating Cost

The low-VOC coating system was less expensive in material costs than conventional systems. Using proprietary pricing information, the cost of the low-VOC/ 1000 ft2 coated was estimated to be $101.03, or $4.59/buffet; the cost of the conventional finish was $129.26/1000 ft2 coated, or $5.98/buffet. The resulting material savings for 1000 buffets were reestimated to be $1280 in reduced coating.

Catalyzed Topcoat

Two major problems were observed with the catalyzed topcoat:

  1. "Bridging" (i.e., the topcoat along the molding edge remained wet or tacky after drying in the oven).
  2. Worker complaints about blowdown that made working conditions sticky.

Concern was voiced about "printing" (i.e., the soft surface imprinting with by 6% packing material), although there was no evidence that this occurred. Concern was also voiced about the ability to strip the topcoat if reworking of the finish was required. This could not be determined during this evaluation because no pieces required refinishing.

Personnel and Personnel Assignments

No additional workers were assigned to the finishing room floor for the low-VOC coating trials. However, floor inspectors were used during the test for wiping or sanding. If this system were to be permanently introduced, additional workers would be necessary. The labor requirements were estimated to increase.

Production Rates

Production rates for the low-VOC were not changed from the conventional system. Line speed was maintained once the initial adjustments were made for introduction of the new coatings.

Equipment

There was no increase in costs due to new equipment requirements. All low-VOC coatings were applied with in-house equipment. The waterborne coating was pumped from a local pressure pot and not supplied from the pump house as a precaution against possible corrosion.

Energy

There was no increase in the oven temperature during the low-VOC trial. The oven was maintained at approximately 1100F (430C), and the heat boosters were not used. There were no increases in energy costs from using the low-VOC coatings.

Based on estimates of costs given by plant management, there would be no overall net increase in cost to the manufacturer for this system because the increase in labor would be offset by the decrease in material costs.

Health and Worker Safety

The more toxic or hazardous system cannot be determined on the basis of information in the Material Safety Data Sheets alone because there is no estimation of worker exposure. However, the low-VOC system releases less solvents to the workplace because they are, by definition, lower in VOC. Despite this, there were worker complaints about eye and throat irritation when the catalyzed coatings were being used. The catalysts were p-toluenesulfonic acids, which are known to be mucous membrane irritants. No heavy metals are listed in either system.

Conclusions and Recommendations

Summary Conclusions

The waterborne and catalyzed coatings system used in this evaluation resulted in a 40% reduction of VOC content from the conventional coatings system. The low-VOC system used approximately 34 kg/93 M2 of surface area coated (76 lb/1000 ft2), compared to approximately 57 kg VOC/93 M2 for the conventional coatings system (127 lb/1000 ft2). The contract goal of 100 lb VOC emitted,/1000 ft2 covered (45.4 kg/93 M2) was met.

Catalyzed coatings can be used successfully in the furniture manufacturing process The problems noted during the trial can be eliminated by providing additional worker training, improving ventilation, making minor adjustments to materials, and using properly adjusted spray equipment. Catalyzed coatings did reduce VOCs by 35% of this total reduction, but their use alone would not have been sufficient to meet the goal specified in the GSA contract, less than 100 lb VOC emitted/1000 ft2 covered (45.4 kg/92.9 M2).

The major factor in achieving the contract reduction goals for VOC usage was the use of the waterborne toner/washcoat which accounted for 59% of the total reduction.

Some process modifications from conventional operations may be required to eliminate the problem of grain raising, seeding, and bridging. These problems were successfully addressed during this project to meet GSA specifications.

Carl Uhrmacher is with Carltech Associates, Inc., Columbia, MD 21045.

Charles Darvin is the EPA Project Officer (see below). The complete report, entitled "Evaluation of the Problems Associated with Application of Low Solvent Coatings to Wood Furniture", (Order No. PB 87-168 746/AS, Cost $18.95, subject to change) will be available only from:

National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650

The EPA Project Officer can be contacted at:

Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711


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Last Updated: January 17, 1996