Need for Antimicrobials / Biocides
Need for Antimicrobials / Biocides
At every stage of their service lives, paints and coatings are susceptible to contamination and degradation by a variety of microorganisms. Further, the presence of water makes these paints very susceptible to microbial attack - both in the wet state and as dry film.
- Bacteria can spoil emulsions and paint in the storage container
- After the paint has been applied to a substrate and dried, it becomes vulnerable to attack by the fungi that cause mildew
To protect against the microorganisms that can cause problems, paint manufacturers must customarily use biocides.
What is biocide? Antimicrobial additives (also called Biocides) are used in formulations to keep bacteria from spoiling paint during storage, or to keep fungi, algae and other micro-organisms from growing on the applied paint.
What is biocide used for? The two main applications of biocides are:
Main Types of Biocides Used in Paints & Coatings
Main Types of Biocides Used in Paints & Coatings
In-Can Preservatives
All waterborne paints contain nutrients for bacteria, fungi and yeast. Microbial attack can therefore happen inside the can, which would affect the quality of the paint. When it happens, you can experience:
- Foul odor
- Loss of viscosity
- Gassing
- Phase separation
- Discoloration
- pH drop
To protect your coating from such issues & extend the storage life of your coating, you have to use In-can Preservatives. They are organic materials. They are used at low levels; < 0.1% by weight typically.
An efficient in-can biocide should have the following properties:
- A broad-spectrum antimicrobial efficacy
Measurement of Minimum Inhibitory Concentration (MIC) is a good way to test biocide efficacy. MIC is the lowest preservative concentration at which growth of a test organism is inhibited under laboratory conditions.
- Long-term protection
Paints may be kept in storage for long periods and exposed to wide temperature variations. Optimum preservation can only be achieved if the in-can preservative is compatible with coating ingredients and is stable over time.
Download Brochure: In-can preservatives to overcome regulatory challenges
Anti-Fouling Agents
This is specific for marine coatings or anti-fouling paints. The goal is to avoid marine organisms such as algae and molluscs to attach themselves to the ship. They would otherwise impact the ship performance (speed, maneuverability, fuel consumption).
Anti-Fouling Agents include both organic and inorganic chemistries. The use of some chemistries are restricted geographically for their effect on marine wildlife, so ensure to be compliant with regulatory guidelines for chemistry as well as use level.
Check out BactiBlock® antimicrobial additives for long-lasting and efficient protection of your coatings
Mildewcide/Anti-fungal
Mildewcides and antifungal materials are used in all exterior coatings where any moisture will promote the growth of organisms, such as mold, mildew and other fungi. Paints for interior applications where higher moisture levels are encountered, such as kitchens and especially bathrooms, also utilize mildewcides.
Since mold and mildew will grow even on glass in the presence of water, additives to prevent the microorganisms from establishing colonies are essential to keeping the coating looking pristine and free of discoloration due to mildew growth.
Zinc Oxide (ZnO) is by far the most common inorganic material used. There are several processes used to manufacture ZnO and it is important to adjust usage level based on type due to particle size distribution and therefore reactivity with the coating components.
Many organic materials work well alone or better in conjunction with ZnO, assuming the ZnO can be stabilized. The organics are highly-scrutinized and it is imperative that any used to formulate a coating are appropriate for the climate, but most importantly that they are approved geographically from the regulatory agency.
Other Types of Anti-microbial Additives
Nanomaterials are also used to prevent microbial growth - Silver (Ag) is used more often than others.
The effectiveness of such silver products is based on the slow and continuous leaching of superfine silver ions that interact with the metabolism of the microorganisms in various ways. For example, silver ions can inhibit enzyme activity, especially those containing sulfur. In doing so, they have a major influence on the energy metabolism of these microorganisms.
Products containing silver demonstrate a broad level of antimicrobial effectiveness, however, significantly less activity is observed for attack with fungus when compared to bacteria.
Most applications are where there is a concern for microbes (bacteria, viruses) developing resistance to an organic antimicrobial.
Classification by Chemical Family
Classification by Chemical Family
- Isothiazolinone based biocides are the most popular and this class contains multiple chemistries. Derivatives of isothiazolinone used as biocides include:
- BIT products have been used in a limited range of industrial applications requiring long-term
preservation for bacterial control.
- Blends of the above biocides are frequently used
- More recently, a new microemulsion technology was introduced using 4,5-dichloro-2-n-octyl-4-
isothiazolin-3-one (DCOIT)
| Chemical Family |
Characteristics |
| Formaldehyde/formalin and formaldehyde donors (e.g. Triazines) |
Environmental concerns but still used due to low cost |
|
Heavy metals (silver, mercury etc.) |
Some restrictions due to toxicity and environmental concerns |
| Organosulfur; isothiazoline-based |
Combination and separate use of 5-chloro-2-methyl4-isothiazolin-3-one (CIT) and 2-methyl-4-
isothiazolin-3-one (MIT) and 1,2-benzisothiazolin-3-
one (BIT) |
| Organosulfur; pyridine derivatives |
Zinc pyrithiones have low solubility in water |
| Others |
Organic acids and
salts, nitrogen and phenolics compounds, glutaraldehyde, cyanobutane |
| Blended
formulations of the above |
Allows custom
formulations for a specific product, processing range and microorganism |
Some Common Biocides Used in Emulsions
- BIT: 1,2-Benzisothiazolin-3-one (BIT) is an effective broad-spectrum microbiocide widely used in the
polymer dispersion industry. It is stable at temperatures up to 100°C. BIT provides biocide efficacy
at a wide range of pH (2-14).
- MIT: Methylisothiazolinone (MIT) is an industrial bactericide used in paints, adhesives and cosmetics
products. It is an effective bactericide with limited fungicidal efficacy.
- BIT/MIT: The combination of BIT and MIT provides a broad-spectrum bactericide.
- CMIT/MIT: The three-to-one blend of methylchloro-isothiazolinone (CMIT) and methylisothiazolinone (MIT) is commonly
used as a biocide in polymer dispersions. CMIT/MIT is a broad-spectrum biocide that works between
3-9 pH. Alkaline solutions degrade the CMIT molecule. CMIT has also been identified as a skin
sensitizer at levels above 64 ppm.
- FA-R: Formaldehyde-releasing biocides (FA-R) are mainly bactericides, but they have some
efficacy against fungal organisms at higher dosages.
Criteria to Consider for Good Biocide Selection
Criteria to Consider for Good Biocide Selection
In paints or coatings systems where antimicrobials are soluble and easily dispersed during paint processing, the surface is well-protected against biocidal growth.
While, in systems where the antimicrobial is immiscible or difficult to disperse, a much higher level of biocide may be required to provide the same protection versus an antimicrobial with excellent dispersibility.
| |
Organic Antimicrobials |
Inorganic Antimicrobials |
| Pros |
- Non-reactive in total paint systems
- Don't lead to gelation
|
- Inert to UV
- Do not leach from the film, thanks to their low water solubility
|
| Cons |
- Can leach out from a coating over time with repeated exposure to water (rain, humidity)
- May be sensitive to sunlight (U-V)
|
- Small particle size inorganic antimicrobials are reactive, especially w.r.t binders
- Can lead to increased viscosity or even gelation
|
Among several factors, 5 important points to consider while selecting an anti-microbial or biocide for your coating system are:
Will it be used for a Waterborne or Solventborne Coating?
When a paint is formulated, there are several aspects to be taken care of. First of course, is performance of the paint as formulated. The other is the stability of the paint, which includes maintaining viscosity as well as minimum or no phase-separation.
If an
antimicrobial is at least not miscible, it will separate and may form a thin layer at the surface of the paint in the container. Unless well-stirred, the paint applied to the substrate may not be uniform in the protection by the
antimicrobial. Resistance to mildew and fungus may be poor as a result.
- Antimicrobial suppliers aren’t always specific about applications, as they want customers to use their products in as many applications (and therefore greater volumes) as possible. Many TDS’ show
antimicrobial to be slightly miscible in water and only soluble or miscible in certain solvents.
- This becomes a key area for testing – compatibility. A good screening method is to make a very simple mixture of resin and solvent proportional to the coating and place in a small bottle or vial and shake vigorously. Incorporate the
antimicrobial to determine if it is:
- Compatible
- Can be dispersed
- Stays dispersed over time, or
- Incompatible and cannot be dispersed or/and forms seeds.
- Try adding and shaking in, and if that doesn’t work, use a table/bath sonicator for 10 minutes.
Will it be used for Interior / Exterior Paints & Inks?
| Market |
SB / WB |
Antimicrobial Type |
Chemistry |
| In-Can |
Anti-fouling |
Mildewcide /antifungal |
Other |
Organic |
Inorganic |
Blend O |
Blend O/I |
| Paints |
SB - Interior |
|
|
|
X |
X |
|
|
|
| SB - Exterior |
|
X |
X |
X |
|
X |
|
X |
| WB - Interior |
X |
|
|
X |
X |
X |
X |
X |
| WB - Exterior |
X |
|
|
X |
X |
X |
X |
X |
| Inks |
SB |
|
|
|
X |
X |
|
|
|
| WB |
X |
|
|
X |
X |
|
X |
|
| Paper Coating |
|
X |
|
|
|
X |
|
|
|
Antimicrobials for Other Applications
|
Market
|
SB / WB |
Antimicrobial
Type |
Chemistry |
|
In-Can |
Anti-fouling |
Mildewcide
/antifungal
|
Other
|
Organic |
Inorganic
|
Blend O
|
Blend
O/I
|
|
Adhesives |
SB
|
|
|
|
X
|
X
|
|
|
|
|
WB
|
X
|
|
|
X
|
X
|
|
X
|
|
|
Construction Products
|
|
|
|
X |
|
X |
X |
|
X |
| Textiles |
Clothing
|
|
|
|
X |
X |
|
X |
|
|
Other
|
|
|
X |
X |
X |
X |
X |
|
|
Paper as raw material
|
|
X |
|
|
X |
X |
|
|
X |
The greatest application concerns are related to the regulatory environment and solubility. In the former, a paint using a specific level of an
antimicrobial in one geography of the world, may not be in compliance in another geography due to use level or local regulations.
It also has to be known how the
antimicrobial will be used. For example, there are FDA regulations that dictate use levels and chemistries with respect to indirect or direct food contact and others for adhesives, etc. In each case, the material has to be approved for use in that application, along with the maximum level of usage.
Solubility dictates toxicity which can affect humans on exposure to leachates present in water and plants due to solubility and runoff.
Effects of Environment
- Damp, humid, overcast environment /
weather will be harsher on an
antimicrobial
- Sunlight can dry out the surface on a regular basis
- UV can itself kill bacteria (think southern vs northern exposure; mold and mildew vs. nearly none)
What Range of Microorganisms are Present?
In general, you won’t know specifically what microorganisms are present, but the environment in which the coating is applied dictates this. In an institutional setting, such as a hospital, doctor’s office, veterinarian, etc., there will be bacteria and viruses.
- In an interior room with humidity >75% regularly, the conditions are prime for mold and mildew, although bacteria and viruses will also exist.
- Outside in humid climates and particularly on the northern exposure of a building, mold and mildew and algae will readily grow. Other microbials are not of interest.
In which Geographies will it be used?
There has been a move to deregulate some products, so ensure that you use the most current MSDS from the supplier’s website and not rely on a document that your company may have filed.
Let's find out more about European regulations as well as registration requirements in US in detail...
How to meet European Regulations?
How to meet European Regulations?
Today, the increased awareness of the potential toxic hazard of chemicals, and the evolution of the legislations towards very high standards of human, and environment protection, conducted to the implementation of more restrictive regulations for the control of chemicals.
Also nowadays 2 main piece of legislation have been adopted by the European Union:
- REACH regulation: Stands for Registration, Evaluation, Authorization and Restriction of Chemicals. It entered into force on 1 June 2007. Its objective is to improve the protection of human health and the environment from the risks that can be posed by chemicals, while enhancing the competitiveness of the EU chemicals industry. It also promotes alternative methods for the hazard assessment of substances in order to reduce the number of tests on animals.
- CLP Regulation:
Stands for Classification, Labelling and Packaging Regulation. It entered into force in January 2009. It introduces a method of classifying and labelling based on the United Nations' Globally Harmonised System (GHS).
Biocidal products are subject to the Biocidal Products Regulation (BPR) that was adopted in May 2012.
Although the new European regulations have changed the industry standard for active agents, the ability of fungal and algal to grow on both exterior and interior coatings makes the use of biocidal additives necessary. Several biocide active agents exist but only a small number of them respond totally to European regulations, industry needs, environmental and consumer demands.
Such demands represent a significant challenge for biocides manufacturers, but it is possible to meet these requirements in terms of performance and safety.
For food compliance, ensure you are using the most current MSDS. Secure a letter certifying compliance and level usage from the antimicrobial supplier if in doubt.
Registration Requirements in the US
Registration Requirements in the US
In the US, all states require registration of biocides. The major regulatory bodies include EPA, FIFRA, FDA and TSCA. Additionally, the states have individual bodies regulating these chemicals in their respective states. For instance, California conducts one of the most stringent reviews.
Procedural Steps for Registration
Before registering a new chemical or a formulation, internal testing is required to check for efficacy and safety (for users & the environment). Companies are required to submit exposure data to determine the lowest amount at which risks exist. The specific requirements vary depending on the type of application (for example: If the intended use is in food-contact applications, a lot more data is required). Also, if the formulation to be registered already contains a registered active, the data to be collected is significantly reduced since the data for the active already exists.
On an average, it takes 3 years to collect all the required data to support the registration of a new active ingredient (AI). This is followed by the submission of the full data set to EPA for evaluation. The review period for a new AI can last as long as two years if the product might contact food and during this time, some observations may be made, or questions asked. Further, 6-8 months might be required to get registered in other states (California, New York, etc.). States like California may also require the review of additional data on efficacy, which may not be mandatory for EPA.
Overall, the expected investment is around 5 years and 3 million dollars!
To assist the registration process for their products, smaller companies either reach out to bigger companies or work with regulatory consultants / contractors. They may also partner with registrants of existing products for a supplemental registration.
Registration Review Cycle & Data Call-In (DCI)
Since regulations change and science improves over time, a re-evaluation of each registered product is conducted every 15 years. New data is usually required and a fresh assessment is made to ensure that the product complies with the current regulations. Multiple companies often join hands to create Task Forces to generate the required new data, where each member contributes. There is often a 3rd party like American Chemistry Council or TSG Consulting that manages the Task Force to ensure that the responses to the DCI are uniform and to ensure that fair competition laws are not violated in the process. Such a combined task force helps minimize costs and animal testing.
When should you Consider Blends?
When should you Consider Blends?
There is no universal biocide system that is compatible with all formulations and meets the requirements of the coatings manufacturer.
Among the various actives used for in-can preservation, there are:
- Fast-acting biocides, e.g., O-formals, N-formals and 5-chloro-N-methylisothiazolin-3-one (CIT)
- Slow-acting biocides, e.g., benzisothiazoline (BIT) and chloroallyl-3,5,7-azoniaadamantane chloride (adamantane)
- Biocides with deficiencies in their activity spectra, such as BIT and N-methylisothiazolone (MIT), which have limited antifungal activity
- Some biocides (e.g., isothiazolones) are known to be skin irritants and sensitizers, and
- Others they may release formaldehyde. These include O-formals, N-formals, triazines and adamantanes.
Bioactives suitable for dry-film preservation differ in water solubility. Two of the more water-soluble are 2-n-octyl-4-isothiazolin-3-one (OIT) and 3-iodo-2-propylbutyl carbamate (IPBC). Some, such as the fungicide carbendazim, have deficiencies in antifungal spectra. Carbendazim does not inhibit the common fungal isolates, Alternaria sp.
While the use of single active ingredients may be sufficient to prevent in-can microbial spoilage or dry film defacement, however, in many cases blends of actives may be used to optimize biocide performance. Depending on the blend, the advantages of using blends of actives may include:
- Lower use levels
- Fast-acting/longer term protection
- Broader antimicrobial spectrum
- Improved compatibility profile
- Increased cost effectiveness, and
- Environmentally friendly end products
In addition, with varying regulations globally limiting the use levels of A-M, a blend or a blended material may meet the performance requirements as well as the regulatory requirements.
Find Suitable Biocide Grade
View a wide range of biocides available in the market today, analyze technical data of each product, get technical assistance or request samples.
Get inspired: Microbiological protection for sustainable paints by LANXESS
About Marc Hirsch
Mr. Hirsch is a Senior Development Scientist and Principal Consultant at M&M Hirsch & Associates.
In his career, he has formulated architectural, industrial, military and specialty coatings. Developed applications and methodologies for sol gel coatings, earned his Green Belt in MAIC Six Sigma and trained for MAIC Black Belt, applied MAIC methodology to the CTR for several laboratory and manufacturing processes in Coatings resulting in substantial savings, successfully facilitated numerous ideation teams within his expertise as well as outside his core competencies. These included cross-functional and cross-business groups.
Prior to his current position, he worked at GE Energy (2008-2011) in the Simulation group; writing proposals to published specifications for training simulators for both fossil and nuclear power plants. At Luna Innovations (2004-2008) he was a Developmental Scientist in the Advanced Materials group. At Dow Chemical (1995-2004) he was the applications and development manager in Core R&D in the Coatings & Functional Polymers Group. He managed the TS&D group for coatings while at Dow (1995-99), and held positions at Rhodia (Laboratory Manager, Latex & Specialty Polymers (1989-95) and Development Chemist, exterior latex paints at Benjamin Moore &Co. (1979-82).
Mr. Hirsch consults to organizations to provide mentoring, coaching and leadership training, as well as the facilitation of problem solving teams.