LIFE CYCLE ASSESSMENT OF WATER BASE COATING SYSTEMS IN THAILAND - ISO 14040 "GREEN PRODUCTS"

By MM, published on Asia Pacific Coating Journal (APCJ)

Sustainable Development: “… is a form of development that meets the needs of the present without compromising the ability of future generations to meet their own needs”

Sustainability is a concept of growing international importance “that recognizes the interconnected impacts of industrial activity on environmental, economical, health, safety, energy efficiency, societal needs and security”.

 

For many years, the concepts of sustainable development and sustainability have been the exclusive territory of the Western richest countries, such as Europe and USA. Only those so-called developed countries were able to develop business under a new spot light, "the green light".

Although the vast majority of directives, restrictions, standards and regulations concerning the use of solvents, of biocides and other substances considered harmful to humans and the environment are mainly European and American based, nonetheless they are having a significant impact on Southeast Asia.

In Asia, several countries are moving towards greater environmental awareness. Among those, there is certainly Thailand. Three years ago in fact, Thailand has started an important journey to promote in the Kingdom new products and new technologies which are more environmental friendly for their entire life cycle. For this reason, the BOI (Board of Investments) have issued a special Announcement 2/2553 - Sustainable Development  ‘to enhance the domestic industrial growth and upgrade the industry to knowledge-based industry that uses higher technology’, and specifically, ‘manufacturing of eco friendly chemicals and eco friendly products which must have less overall impact on the environment throughout their life cycle,’. In virtue of this act, the BOI, with the technological support of the NIA (National Innovation Agency), offers remarkable benefits and incentives to projects that are about environmentally friendly technologies brought and developed in the Kingdom. This awareness about the importance of environmental protection, and the possible impacts associated with products, both manufactured and consumed, necessitates the use of methods to better understand and address these impacts and assess each project. BOI and NIA have specifically indicated in the ISO 14040 ‘Life Cycle Assessment’ (LCA) the preferred method.

This memory specifically report, in short, the results of a specific LCA carried out by Associate Prof. Prasert Pavasant and his Team (Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University) and Dr. Mauro Montalbetti (Asiantech Enterprise), about a pilot sized project regarding manufacturing of eco friendly chemicals for environmentally friendly wood coating systems, in particularly the family of water borne polyurethane dispersions. With current technological advancement, new polymers grades are available, which are water base and exempt of hazard classification and thus allow chemists to formulate new low VOC and ‘zero’ VOC environmentally friendly coatings for woods. Typical applications where it is possible to formulate modern water base wood coating systems with good success, which are also environmentally friendly, are: wood stains, wood protection for exterior, wooden windows and doors, medium density fibreboards, eco-furniture, wooden toys, highly pigmented formulation, DIY’s.

New generation of water borne polyurethane resin are based on preparation of an NCO-terminated pre-polymer and then incorporation of carboxylic acid functionality on the backbone, at low temperature, with very small quantity of solvent. The use of DMPA reduces particles size and increase viscosity at desired levels. Then neutralization of the carboxyl group with a tertiary amine which introduces ionic centres enables dispersion in water and total distillation of solvent to be accomplished. New production process has not only eliminated the VOC residues, but also the use of NMP (N-methylpyrrolidone), traditionally used in polyurethane and acrylic resins, which is considered toxic also in concentration of 5% .

These water borne polyurethane dispersions can be used by expert formulators in production of new environmentally friendly wood coating systems. Low VOC or zero VOC water borne polyurethane is  mixed with some parts of low VOC or zero VOC acrylic resins, some parts of VOC free water base synthetic waxes, water, pigments, fillers, antifoaming agents and thickeners, to get final desired results. This type of formulations  has not only eliminated the VOC’s, but also the use of alkylphenol ethoxylates (APEO),  nonylphenol compounds (NPEO), which are considered to be very toxic for aquatic life and the environment.

 

Due to longer life time in application for exterior, and due to limited use of solvent throughout the life cycle of these product compared with the solvent base, the assessment reveals that the water base polyurethane coatings provide a significantly better environmental performance, during the entire life cycle: from raw material acquisition through production, use, end-of-life treatment, final disposal.

This study (presented here in its final outcomes) reveals the results from quantitative examination of the environmental impacts of both water base and solvent base polyurethanes in one equivalent application (exterior).

 

Description of LCA study for polyurethane coatings

This evaluation was set out to compare life cycle impacts of the proposed water based polyurethane coating (WBPUC) and a typical solvent based polyurethane coating (SBPUC). It was assumed that the product is used for exterior coating and the solvents in the products are totally evaporated during the application of such products. As the water based polyurethane products typically inherits high UV resistant properties as proven with standard test methods as indicated in [1] and 2. For the application of exterior wood protection, the water based product with proper formulation can last 10 years whilst the solvent based (also with proper formulation) can last 5 years. Based on this knowledge, it is assumed a case scenario here that the WBPUC is used in actual outdoor along with the lower UV resistance SBPUC, and the life time of WBPUC is 10 years whereas the life time of SBPUC is 5 years.

 

Boundary of the evaluation

To ensure that the comparison was reliable, it was recommended that the boundary of the evaluation was clearly stated. Figure 1 demonstrates the flow of materials and energy throughout the life cycle of polyurethane coatings which adequately sets out the boundary of this evaluation.

 

Figure 1 Boundary of the system to be evaluated in the work

 

As mentioned, the production of WBPUC examined in this study follows a three main step process. Polyurethane is first made with solvent, typically acetone, and other ingredients where the mixture undergoes reaction at certain temperature for a certain period of time. The solvent is thereafter removed for recycle where water is mixed to make final WBPUC product.

The production requires the use of energy to heat the mixture to the required temperature and to distillate the solvent out of the reaction product.

Simplification  was made that SBPUC is being manufactured with an almost equivalent process, with the main difference at the later stage as the solvent, e.g. toluene, is mixed with the PU to make the final solvent based PU product.

Based on this consideration, inventory data for WBPUC and SBPUC can be constructed as shown in Table 1.

Life cycle impacts of WBPUC and SBPUC

In this work, the impacts of the polyurethane products are estimated based on the direct effect on environment and this is carried out according to the standard set out in CML 2001. These indicators include:

  1. Global warming potential (GWP) (g CO2e)

  2. Acidification potential (AP) (g SO2e)

  3. Eutrophication potential (EP) (g PO4e)

  4. Photo chemical oxidation potential (PCOP) (g C2H4e)

  5. Ozone layer depletion (ODP) (g CFC11e)

  6. Human toxicity (g 1,4 DCBe)

  7. Ecotoxicity (g 1,4 DCBe)

 

Figure 1 illustrates clearly that all selected impacts from the life cycle of SBPUC are about two times higher than those of WBPUC. This is mainly due to the fact that the life time of SBPUC is only half of that of WBPUC which renders it necessary to be used at the amount two times that of WBPUC. Table 1 correspondingly shows that the raw materials and energy flows into the boundary of WBPUC are mostly less than half of those required for SBPUC, and as a result, this proportionally cuts down the environmental impacts associated with WBPUC when compared with those of SBPUC.

One of the major advantages of using WBPUC is reduction of solvent usage which also lowers the chance of fugitive emission particularly during the application of the coatings, and this is demonstrated in Figure 3. The reduction in VOCs emission would mean that there is less chance of human being exposed to VOCs that could otherwise be evaporated from the finished coatings.

Figure 1 Comparison between impacts from CML 2001 methodology

Figure 2 VOC emissions

 

By MM, published on Asia Pacific Coating Journal (APCJ)