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Innovating In-Can Preservatives Depends on Finding and Testing the Perfect Blend

Finding a “golden ratio” of time-tested preservatives has wide-ranging benefits for formulators in the paints and coatings space, enabling customers to serve local markets and meet global standards.

By Judy Betancur, Americas Marketing Manager; and Beth Ann Browne, Ph.D., Industrial Preservation Specialist, IFF Microbial Control, Wilmington, DE

There’s no question that the advent of water-based paints and coatings brought its fair share of challenges. For formulators looking to offer new and innovative products for their customers, approximating the performance of solvent-based coatings in low-VOC, water-based alternatives can be a constantly moving target — there’s no shortage of microbial foes standing in the way, from bacteria and yeast, to mold and algae.

Global regulations add yet another layer of complexity. Waterborne solutions are now a permanent fixture in the paints and coatings industry, but many of the most effective preservatives in that arena — including formaldehyde releasers — face stringent dosage limitations for consumer markets, especially in Europe.

How can formulators meet the challenges of myriad microbes and regulatory guidelines that shift across borders? One might think the answer lies in a novel chemical preservative that’s yet to be discovered, but in reality, finding a perfect ratio of existing industry stalwarts — and adjusting that ratio to suit multiple regions and applications — is the clearest path toward preservative innovation.

Many additives exist today that can be blended to meet application needs and regulatory expectations across the board. After extensive research and testing, experts at IFF Microbial Control (MC) have found that the right combination of BIT and CMIT/MIT actives (see below) results in an ideal in-can preservative against bacteria and fungi. These findings led to the release of a BIT/CMIT/MIT blend, BIOBAN™ BTCM, which offers robust efficacy, formulation flexibility, preservative stability, and better logistics and ease-of-use.

BIOBAN BTCM is the latest in MC’s portfolio, which comprises a wide range of in-can and dry film solutions for the preservation of paints, latex emulsions and other paint formulation ingredients, as well as building and construction materials. The release comes shortly after the introduction of BIOBAN BZ Antimicrobial, which combines BIT with ZPT for optimal antibacterial and antifungal properties across a broad pH range (2-12) of products to be preserved.

Active Ingredients in Depth

Formulators have always found great success with 1,2-Benzisothiazolin-3-one (BIT) as an in-can preservative that defends against a broad spectrum of bacteria and some fungi in the wet state. It is highly stable across a wide range of temperatures and pH, offering long-term preservation to ensure a more stable shelf life. The consistency of this ingredient has made it a popular choice as a base when mixing with other additives with more specialized or acute modes of action.

Widely accepted as the gold-standard preservative for in-can preservation of water-based paints and binders with pH up to 8.5, chloromethylisothiazolone/methylisothiazolone (CMIT/MIT) is effective at low levels — 15 to 22.5 parts per million active ingredient in the finished product. CMIT/MIT preservatives provide broad-spectrum protection against microorganisms, such as bacteria, yeast and mold, which in turn enables robust preservation of water-based products, including paints, adhesives, latex emulsions, mineral slurries and tape joint compounds, among others. CMIT/MIT preservatives are compatible with water-based paints, and typically do not cause coagulation or changes in viscosity, color, gloss, film formation or other critical parameters of finished formulations. Most importantly, CMIT/MIT offers solid protection against Pseudomonas bacteria, which has become an all-too-common issue when preserving paints and coatings.

When looking for other in-can preservatives that are effective against a broad spectrum of both bacteria and fungi in the wet state, formulators should consider 1,2-Benzisothiazolin-3-one/Zinc 2-pyridinethiol-1-oxide (BIT/ZPT). BIT/ZPT combinations like BIOBAN BZ are water-based dispersions, which are proven to be compatible and effective in a range of latex emulsions, building materials and some paint and coating applications. Thanks to the inclusion of BIT and ZPT, this product variation also boasts stability across the temperature and pH spectrum.

Prized throughout the industry as a cost-effective preservative with nearly instantaneous antimicrobial activity, 2,2-dibromo-3-nitrilopropionamide (DBNPA) is widely used in paint and coating manufacturing plants for hygiene purposes. Many paint and coating producers typically use DBNPA to keep raw materials preserved, purify wash water and contaminated products, and as a quick-killing agent for plant equipment. Effective at low concentrations, DBNPA provides a broad-spectrum quick-kill of bacteria, mold and yeast. It is completely miscible with water, and effective microbial control is often achieved within minutes to a few hours.

DOWICIL™ QK-20 Antimicrobial is a fast-acting, broad-spectrum DBNPA-based technology that is ideal for treating production batches to mitigate microbial contamination and optimize the performance and dosage of long-term in-can preservation systems. It can be used to complement in-can preservative systems in aqueous paints and coatings, latex and resin emulsions, and many other products.

While all of these active ingredients are excellent choices, BIT and CMIT/MIT have risen to the top as primary workhorses for the preservation of industrial products such as paints and building materials, each bringing complimentary properties to the table. What BIT offers in terms of staying power, CMIT/MIT compliments by adding a swifter speed of kill. And by combining them into one carefully blended pre-mixed additive, formulators can capitalize on the strengths of both without compromise.

Regulations and Ratios

The convenience of combining BIT and CMIT/MIT in one can is no doubt advantageous for operations of all sizes, and several attempts at similar combinations have already been offered to the market. However, when choosing an in-can blend, formulators should take care to partner with a preservatives supplier that can offer rigorous lab testing to confirm efficacy in unique formulations against robust microorganisms that may be present in a manufacturing environment.

The implications for decisions on preservative packages are wide reaching, given the complexity of the global regulatory climate. As regulations become more stringent, the toolbox of preservative active ingredients available to formulators shrinks at a commensurate rate. And MIT, one of the three active ingredients in BIOBAN BTCM, is one of the most in-demand preservative options facing dosage limitations for consumer markets, especially in Europe.

In the United States, antimicrobials must be registered under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) and by each U.S. state in which they are used. Conventional chemicals are subject to regulation under the Toxic Substances Control Act (TSCA), and paint and coating products used in the food and personal care markets are subject to regulations under the Federal Food Drug and Cosmetics Act.

European products must meet the requirements of the European Union’s Biocidal Products Regulation (BPR) — (EU) No 528/2012, along with the ongoing requirement to register products at the national level. In addition, there are requirements under REACH, the EU’s regulation for the Registration, Evaluation, Authorization and Restriction of Chemicals.

As for the rest of the world, countries typically have their own regulations governing the use of antimicrobials, although in some instances they rely on products that have EU BPR or U.S. EPA approval. Preservative suppliers to the paint and coatings industry should have a working knowledge of these regulations. In the case of BIOBAN BTCM, formulators have the unique flexibility to avoid H317 labeling at typical dose levels by ensuring that CMIT/MIT concentration remains below 15 ppm. The active substances in this product are supported under the EU BPR for in-can preservation purposes (PT-6) by MC, so corresponding treated articles are compliant for both import and placing on the European market.

European formulators — and those in the U.S. who simply wish to export their products to Europe — must overcome these challenges with the help of innovative suppliers that can provide robust options that don’t create conflict with regulators. It is advisable that formulators looking for shelter from the regulatory storm should partner with manufacturers that are equipped with the expertise and lab infrastructure to offer products that are globally compliant. In the case of BIOBAN BTCM, the blend offers the most BIT possible while maintaining a level of CMIT/MIT that is effective and acceptable for Europe.

From Implications to Applications

Meeting regulatory guidelines around the world is essential, but achieving an ideal BIT/CMIT/MIT ratio has smaller-scale implications, too. For many small- to medium-sized businesses, a two-in-one product offers a level of convenience they can’t afford to pass up.

Preservation is an industry-wide concern for companies of all sizes, but smaller formulators may lack the time and resources to dedicate to it. Formulators of this size depend on antimicrobial suppliers to deliver solutions that work without fail. By offering a combination preservative made from common ingredients, taking one source of stress off the to-do list of formulators is that much easier. The idea of offering peace of mind in a one-drum solution takes on a new level of importance amid a pandemic, when only workers deemed essential have been able to be present in the lab, and resources are unavoidably scarce.

Testing for real-world applications is just as important. Before choosing a supplier, determine if they have the necessary lab infrastructure to evaluate products in customers’ requested formulations and applications. The right company will be able to make changes on the fly and offer experimental design processes. For example, IFF ushered one of its customers through an experimental design phase that focused on control of specific microorganisms over a 100-day period.

In terms of product testing, the case of tape joint compounds (TJCs) provides an ideal case study. TJCs need to have a specific consistency while maintaining protection against microbes. Not only will an ideal BIT/CMIT/MIT combo offer great bacterial protection, but it will also protect the viscosity of the TJC product. Previously, many formaldehyde donors were popular for this use, but many actually led to a decrease in viscosity of the compound. Optimal blends will defend against microorganisms while ensuring that the product functions as it should.

A Final Word on Preservative Suppliers

Regardless of the preservative blend a formulator chooses, it is essential to partner with suppliers who can demonstrate a deep understanding of process preservation chemistries, water treatment chemistries and microbiology. Suppliers should also be capable of providing formulators with plant hygiene audits to identify and remedy all points of microbial contamination, as well as lab capabilities to help optimize product development. There is no substitution for the rigorous testing that a world-class laboratory infrastructure can provide, enabling experimental design and real-world application troubleshooting.

Despite a shrinking preservative toolbox, there is still a robust range of options available to formulators. The good news is that, with the help of an experienced preservatives supplier, formulators can identify compatible, approved preservative solutions to navigate the shifting trends of marketplace demands and regulatory mandates. As we’ve discovered, the perfect blend of workhorse ingredients can extend a formulator’s reach in the global market and help companies of all sizes serve their local markets with ease and consistency.