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Final Report Summary - DRYFOAM (Super-Stabilised Opaque Foam Coatings for Architectural Applications)

Executive Summary:
DRYFOAM – Super-stabilised opaque foam coatings for architectural applications

Titanium dioxide (TiO2) is an engineered pigment commonly used to create whiteness and opacity in architectural paints and coatings. The high refractive index of this pigment (ƞ ≈ 2.8) relative to the refractive index of a polymer matrix (ƞ ≈ 1.5) results in a high light scattering efficiency, which is desirable for high performance coatings products. The TiO2 content of architectural coatings is typically in the range of 5-15% by weight and accounts for about 20-40% of the total raw material cost. Recent shortages in the supply of TiO2 have led to challenges in pigment availability and increasing costs. Alongside these pressures, there has been a growing awareness that TiO2 is a significant contributor to the carbon footprint of coatings. These concerns have driven coatings developers to consider alternative strategies for product formulation.

DRYFOAM was a two year research project funded through the Seventh Framework Programme (FP7) of the European Commission. The primary objective of the research was to develop opaque paints that were completely free of titanium dioxide without sacrificing coating performance. This was to be accomplished using an innovative stabilized foam structure, leveraging developments in polymerization, surface modification, and formulation. The foam structure was stabilized to create air voids (refractive index ƞ = 1.0) in the dried paint film, thereby serving as the source of light scattering. The partners in this development project were:
• Lankem Ltd. (UK)
• Resiquímica - Resinas Químicas, S.A. (Portugal)
• Danske Malermestre (Denmark)
• Le Comptoir de Minéraux et Matières Premières (France)
• Ronseal Ltd. (UK)
• SP Sveriges Tekniska Forskningsinstitut (Sweden)
• PRA Trading Ltd. (UK)

Initial work focused on preparing polymer latices and surface modified inorganic particles that were evaluated for the stabilization of aqueous foam structures. Styrene acrylate, vinyl acetate, and core/shell latices were prepared by emulsion polymerization having varying monomer compositions, surfactant stabilization systems, particle sizes, morphologies, and surface polarities. Submicron inorganic particles (e.g. silica, clay, mica) were also prepared having differing hydrophilic-lipophilic balance (HLB) surface modification, particle sizes, and either film-forming or non-film forming character. The latex particles and inorganic particles were screened as prepared and/or in surfactant solutions for their ability to stabilize foam. Strongly adsorbing particles at the air bubble / water interface were expected to create a steric barrier to inhibit foam collapse.

Paint formulations free of titanium dioxide were prepared. Several methods to introduce air into the waterbased paints were evaluated, including chemical blowing and gas expansion. Paints were dried and characterized for film appearance, opacity, and wet scrub resistance (durability). Although the ideal model of foam structure having a bubble size of 700 nm diameter was not achieved, promising systems were found that demonstrated excellent whiteness (> 75 units per ASTM E313) and scrub resistance. Two prototype formulations were optimized and successfully scaled up to 10 L to complete professional user application and performance validation trials. DRYFOAM paints were applied to pre-painted and non-primed plasterboard and were visually rated. The opacity of the coatings looked good and was comparable to a standard TiO2-based paint.

Three notable accomplishments resulted from this project. A novel Lankem emulsifier system (Kemsurf ESD and Lanspec HSR) was identified which helped to improve the durability of latex films by remaining within the polymer matrix. Two new Resiquimica vinyl acetate based emulsion polymers were synthesized using the novel emulsifier system, which offered up to 150% increase in scrub resistance relative to standard emulsifier systems. Finally, a paint formulation and method of application was developed that maintained air voids in the matrix during film formation and drying, resulting in a coating that demonstrated comparable performance to a conventional architectural coating.

Project Context and Objectives:
The objectives for the DRYFOAM project were to develop opaque paints that are completely free of TiO2 and comprise an innovative stabilised foam structure, using recent developments in the polymerisation and surface modification fields. Finally, to develop and scale up a TiO2 free coating with a stable foam structure or ambient sintered coating. The resultant coating should have the following characteristics:

1. A white opaque coating with a contrast ratio of at least 95% (0.95) when applied at a nominal spreading rate of at least 6 m2/L, according to BS EN ISO 2814:2006;
2. The coating needs to have good whiteness, greater than 75 units (measured according to ASTM E 313);
3. The coating needs to be non-yellowing, i.e. on leaving the coating in the dark for 6 weeks and separately 1000 hrs in a UV weatherometer, the change in the yellowness index (measured according to ASTM E 313) should be less than 2 units, and the opacity should not change by more than 5 units;
4. The coating needs to be low odour and meet the appropriate VOC content, 30 g/l, for interior walls and ceilings according to the VOC in Paint Directive 2004/42/EC (and amended article 13 of the Paints Directive);
5. For an interior wall coating, the coating needs to meet Class 1 (according to EN 13300: 2001) for wet scrub resistance (ISO 11998: 2006 for toughness and washability), ie less than 5 μm film thickness loss after 200 double rubs (ceiling paints do not necessarily need such good scrub resistance). The change in opacity after 200 double rubs should be less than 5 units;
6. The coating would be commercially competitive at €7-10/L relative to other interior wall and ceiling paints, and may be higher by up to 50%

The scientific objectives were:

• To develop organic and inorganic particles that will provide 16 hours stabilisation of the foams (generated by various means), long enough to allow most thermoplastic coatings to fully dry, and to formulate the particles into robust stable coatings suited to architectural applications (see particularly the wet scrub resistance test below).
• To quantify the light scattering capability of different foam morphologies with a target contrast ratio of 95%.
• To investigate the film formation characteristics of ‘paint foams’ including rates of water loss relative to property development. It is important that water escapes from the coating (less than 16 hours) before the particle coalescence process is complete. If water is trapped in the coating, it may penetrate the air voids and negate the opacifying effect).
• To investigate and optimise the rheology of foamed paints in relation to their flow and levelling characteristics.

Project Results:
Significant Results in Work Package WP1:

An extensive survey was carried out to identify suitable inorganic extender materials, which selected SiO2, Al2O3, CaCO3, Mica, Talc and Clays. It was found that surface-modified particles with a certain contact angle were suitable for stabilization of aqueous foams. More than 12 surface modified inorganic particulate materials were prepared and supplied to WP3. The as-received sample of Finntalc P05 performed better than the milled or silanized and milled sample. This was likely to be due to the combination of favourable surface energy as well as its flaky nature. The Micasoft, when milled and silanized showed some promise. Lav 8 performed well without any modification and created stable foams in the form of kugelshaum. Hydrophobic pyrogenic silica HDK-H18 and HDK-H30 (in surfactant solution or Bindzil CC302) reduced drainage of the liquid film between the air bubbles.

The most promising system for the amphiphilic-stabilised inorganic particles for ambient sintering was Opacilite/L81, Opacilite/Lansurf DPE808 and Calopake/Lansurf DPE808.

Inorganic/polymer hybrid particles were synthesized and characterised. However, only low solids contents were achieved (typically 10%) with samples yielding agglomeration and quickly sedimenting products. Only solvent dispersed silica particles showed stable products with inorganic particles encapsulated in polymer, but these could not be used for further work due to the low solids content.

Following significant work, heteroflocculated particles with Opacilite/PEI/Latex were recommended for ambient sintering coatings.

Significant Results in Work Package WP2:

A total of 22 samples from Task 2.1 were sent to PRA for investigation with a size of 80 to 150nm for further investigation in WP3. For Task 2.2, the core/shell latices (CS) where prepared by means of seeded emulsion polymerization. 18 batches of two-phase particles were synthesized and 17 of these were sent to PRA for evaluation. Analysis of the produced particles show that CS013, CS014 and CS016 (all acrylic/styrene seed and acylic shell) were the most successful batches in relation to the formation of a core/shell structure. Preliminary foam-stabilization studies however suggested that CS002, CS006 (acrylic/styrene seed and acrylic shell), CS009 (acrylic seed and shell), CS011 (pure acrylic seed and acrylic shell) and CS018 (acrylic/styrene seed and acrylic shell) were most suited to stabilize a foam.

Significant Results in Work Package WP3:

It was shown in WP3 work that, unfortunately, none of the inorganic particles developed in WP1 were suitable for the ambient sintering methodology as they did not form durable films to overcome the low scrub resistance typical of dry-hiding formulations.

It was found that as-received Opacilite can provide good opacity and whiteness, and with the right amount of Polidisp 7241, good wet scrub resistance in ambient sintering formulations. The two best formulations, described in Table 15 in D3.1 (Best 1 and Best 2) gave similar performance to a benchmark product, Ronseal white-wash, in terms of whiteness and opacity and a much improved wet scrub resistance.

A best formulation based on the mechanical entrapment methodology achieved a contrast ratio of greater than 95 at a wet film thickness of 400µm. The whiteness of this formulation was greater than 75 units (according to ASTM E313) and showed no yellowing in a UV weatherometer for 100hr (according to EN927-6). The theoretical VOC content of the formulation was 1.13 g/L. Although the Class 1 (according to EN 13300:2001, 5µm film thickness loss) for wet scrub resistance (SIO 11998:2006) was not achieved, the wet scrub resistance was sufficient for internal wall coatings. D3.2 showed that the foam structure significantly contributed to the opacity of the film.

Work within the project proved that the gas expansion method could not produce satisfactory films. Although fine bubbles could be achieved via this method, either the mechanical properties or the opacity of the resultant films were adversely effected. Paints produced via this method were not suitable for any of the target applications.

All routes to achieving a suitable film via the chemical blowing method produced large, uncontrollable and unstable bubbles. This method was found not to be suitable for producing a viable product.

D3.4 details a number of foam model structures. This report shows that although the theoretical ideal model of foam structure was not achieved, that the mechanical entrapment methodology gave the closest match. The desired bubble size was 700nm in diameter and presented in a closely packaged arrangement. The final result gave non-connected bubbles of between 30 and 100µm.

Significant Results in Work Package WP4:

Two vinyl acetate/VeoVa latex formulations were successfully scaled up to 10L, one of them twice to ensure suitable quantities of raw materials for the remainder of WP4. WP 3 work revealed that the inorganic and organic particles developed in WP1&2 were not required for the final paint and as a result were not scaled up. Reproducibility from batch to batch was obtained. Wet scrub was improved with these formulations with the best results from the formulation with less emulsifiers.

Two paint formulations were scaled up to 10L, a foaming formulation based on mechanical entrapment and an ambient sintering formulation. Both were scaled up successfully and posed no issues for manufacture.

After assessing a number of applicators, the sponge pads appeared to be the applicator of choice. One coat with the sponge pads gave the specified opacity and whiteness, with a second coat covering any small mud cracks. A short flocked pad was optimal for the ambient sintering formulation, whilst the flocked reticulated pad was best for the mechanical entrapment formulation.
The user validation trials showed good opacity, but commented that the application method was slow and should be optimised in the future. The visual finish of the paint was somewhat rustic.

Significant Results in Work Package WP5:

The project website was set up successfully.

Several patent searches were conducted in order to identify competitive patents that could inhibit progression of the DRYFOAM project, as well as, to seek opportunities for new intellectual property. The search was carried out in PatBase, a commercial patent database application by Minesoft, Ltd. that covers over 45 million patent families with historical records dating back to the early 1900s.1 PatBase is unique in that it allows users to gather data from all patent offices worldwide. It also allows users to manipulate output data by fields that are relevant to a patent examiner, such as assignee, title, inventor, kind codes, etc., helping to make post analysis easier.

All results were initially downloaded into separate spreadsheets, which were then collated into one master spreadsheet. This master spreadsheet, our competitive patents database, has been saved and placed securely on the DRYFOAM website for future use by the consortium partners. The search strategy included five key areas for diligence: (1) paint and coatings, (2) opacity or hide, (3) air or gas voids, (4) durable, and (5) creation and stabilization of foam.

Potential Impact:
It is the belief of the SME partners that the DRYFOAM technology has potentially wide ranging application; however, the immediate focus of the project was on the application of the technology for ceiling paints and paints for lower performance-demanding interior walls (e.g. for interior garage and utility rooms). This is not to say that we believe the technology to only deliver low performance coatings. On the contrary, we believe these DRYFOAM paints will actually be superior in performance to the paints currently used in this market, which are formulated at high pigment volume concentrations and have inferior mechanical properties (poor scrub resistance). The DRYFOAM coatings will be thicker than conventional paints and will have better crack-bridging and perhaps anti-condensation properties.
In the longer term, we believe the technology will be applicable to the more aesthetic interior wall paints and the higher durability exterior paints with more development using other pigments for giving pastel shades, etc. By focusing on this smaller market, it will also allow the SME companies time to build additional capacity to better service this market and maximise their direct sales of the DRYFOAM components. Nevertheless Resiquímica, CMMP and to a lesser extent Lankem will not be able to supply sufficient DRYFOAM components to satisfy even this smaller market immediately and it is envisaged that all three companies will seek to license the relevant technology to other companies, especially companies with complementary geographic market strengths.

Societal and Ethical Issues of Exploitation:

We carried out a social assessment as an explorative analysis of the potential social risks associated with the eventual up-scaling of the formulations developed in the DRYFOAM project as market-available architectural coatings. The goal of this analysis was to identify the potential social risks and so provide valuable input for the project consortium for decisions regarding further developments of the DRYFOAM Technology.
The first steps towards identifying potential social risks associated with the up-scaling of the DRYFOAM coatings was to identify key components from a social risk perspective. The analysis was carried out for the mechanical entrainment formulation and the ambient sintering formulation. A benchmark reference system with titanium dioxide was also analysed, so eventual reduction of the associated social risks could be observed.

Social hotspot analysis methodology:

The final step in the analysis was to identify the associated social risks of manufacturing or raw material extraction in the countries and industrial sectors identified previously. These social risks were assessed using the Social Hotspots Database (SHDB), a tool designed to be used in social life cycle assessments (SLCA) (SHDB, 2013a). The SHDB is a directory of social risks in 227 countries and 57 sectors, given in 23 social themes divided into 5 social categories.
For each social theme, there were one or several quantitative or qualitative indicators. For each country and sector, a risk rating of 0 (low risk), 1 (medium risk), 2 (high risk) or 3 (very high risk) was given to each indicator, based on indicator-specific characterisation rules. Then a risk rating between 1 and 4 was generated for each theme, by averaging over all indicators and giving extra weight to particularly important indicators. The risk ratings for all themes within a category were then summed, divided by the highest sum possible for that sector, and multiplied with 100 to generate a value between 0 and 100, which is the social hotspot index for a particular social category in a particular sector and country. The indices for the five social categories may then be further summed into a total social hotspot index for a particular sector in a particular country. The social hotspot index can be seen as “a total number of weighted risks to be aware of when working in that particular country and sector” (SHDB 2013b, p. 4).


In order to identify the coating components which could generate social issues in eventual up-scaling, each of the formulations were broken down component by component. Each of the components was analysed from a supply-chain perspective, except for those components which had a concentration below the cut-off criteria set for the formulations analysed.
Looking at the information in Table 1 in D6.2 it suggests that there were several raw materials which might play a key role in the supply chain of an eventual product formulation due to their high relative contribution to the final product. The first of these was the mined mineral that was used to produce Pigment 2 and Pigment 4, as these raw materials are in high concentrations in the coatings. However, since these pigments can be produced from any mined or quarried source, the possibilities of sourcing such raw materials are numerous, which means the risk associated with sourcing them from industrial sectors in countries with high social risk can be avoided by choosing appropriate supplies. Moreover, this mineral-based pigment is present in the benchmark formulation as well, which means it would not be a differentiating factor in the assessment. Pigment5 has a high concentration in the product, but its abundance and the high number of alternative countries that produce it suggests that the associated social risks might be lower and difficult to capture.
There are some raw materials such as the binders which are fossil-based. Fossil fuels are a constrained resource, but the broad span of potential producers makes it difficult to make a realistic assumption regarding the sourcing of raw materials. Furthermore, two of the relevant binders are manufactured by companies that have most of their production plants in Europe. This means that it is most probable for these components to be sourced from European manufacturers, making their associated social risks lower than other components in the formulation. Substances such as water and ammonia are sourced and supplied all around the world under different circumstances, which makes it very difficult to estimate the risk of social hotspots in their sourcing.
On the other hand, Pigment6 (titanium dioxide) has been identified as the sole main source of social risks for the benchmark formulation. Mining and production of this pigment has a high risk of social issues because it is mainly produced by USA and China, making it highly probable that it is sourced from a country with high risk of social hot-spots.
Keeping in mind all of these facts, the main potential sources for social risks are Pigment1, the proprietary Binder, and Pigment6 used in the benchmark formulation.

Social hotspots analysis:

As explained in the experimental section, the result for the index can be interpreted as a total for the associated social risks for products or materials from a specific country and sector.
Figure 2 in D6.2 showed a relatively high possibility of sourcing the raw materials for Pigments2 & 4 from suppliers with high associated social risks, as the two countries with the biggest share of this pigment’s output in the world, China and India, have quite high index results for mineral products. In the case of China, the category with the highest index result was labour rights and decent work, where the themes with the highest contribution to the result were freedom of association, child labour and working time. Meanwhile, for India governance, health and safety and labour rights and decent work were the categories of most concern. A closer look shows that among the themes with highest contribution were working time, wage assessment, occupational injuries and deaths, and corruption. As for the remaining countries, even as their index results are relatively low, the health and safety category stands out in all of them, specifically for the occupational injuries and deaths theme.
The social hotspot index results for the raw materials required to produce chemicals such as the binder and Pigment6 are displayed in figure 3 in D6.2. From the countries assessed for the chemical products sector, China stands out as the one with higher associated social risks. Again, the labour rights and decent work categories have the highest contribution to the index score, being working time and migrant workers the main themes of concern. There were also themes in other categories which should be considered as hot-spots such as high conflict zones and gender equality in the human rights category and occupational toxics and hazards in health and safety. On the other hand, the index result for Japan, Holland and USA were lower, but for those the theme occupational toxics and hazards stood out as a social hotspot in the health and safety category.
Finally, the associated social risks for the raw materials for Pigment6 (metals extraction sector) can be found in figure 4 in D6.2. There, China stood out again as a supplier with high associated social risks. Labour rights and decent job was again the category with the highest result, being working time and freedom of association the most notable hotspots. Other themes that can be highlighted as hotspots were high conflict zones and gender equality in the human rights category, occupational toxics and hazards in health and safety and legal system in governance. As for Japan and USA, health and safety was again the category with the highest index result. In the case of Japan occupational injuries and deaths was the main hotspot, while for USA the theme with the highest contribution was occupational toxics and hazards.


The two countries with the highest output in the world of certain mined minerals, China and India, presented very high social hotspot index results, meaning that global sourcing comes with a high risk of social impacts. As for the benchmark material containing titanium dioxide, it showed a high risk for social impact sourcing as the country with the highest output (China) have a high social hotspot index result. However, the global output of the raw materials for Pigments2 & 4 was more evenly spread all over the world, as this material had a higher natural occurrence than titanium dioxide. This means that while the raw materials for Pigments2 & 4 can be easily sourced from several different countries with relatively lower social risks such as Finland, USA and Japan, there are fewer alternatives available for titanium dioxide for sourcing with lower social impacts. Therefore, in general, Pigments2 & 4 seemed to be a material with lower associated risks than pigment6 (the benchmark with titanium dioxide).
The case of the raw material for proprietary binders was different, as its global output was highly concentrated in one single supplier due to its long-time ownership of the patent for its production. This supplier had its own production concentrated in a few countries. However, this was also the case for titanium dioxide, as its global total output was concentrated in these very same countries. Seen from the perspective of sectorial and regional risks, it seems as if both the binder and Pigment6 have comparable associated social risks. However, the fact that one single company dominates the market for one of the largest binder’s raw material should be a matter for concern, as no alternative suppliers would be available and thus the social impact from the coating would be strongly dependent on a single supply chain. This means that any bad practice from coatings suppliers or their suppliers would unavoidably affect negatively the social impact from the coating product.


Even as some of the sectors and countries evaluated in this assessment gave high social hotspot index results, it seems like most of the risks of high social impact in the supply chain of the coating can be easily controlled. Certain mined minerals are among the identified critical raw materials that are both highly abundant and can be easily sourced from countries with low social associated risk such as Finland, Japan and USA. Nevertheless, in case the product is up-scaled, special attention should be paid to the supplier of Binder1, as the concentration of the global output in a single company with production in two countries might exacerbate the associated risks. It is recommended that specific requirements are set for this. If a comparison with a benchmark product is to be made, the associated social risks of the coating systems evaluated are very similar to that of a titanium dioxide benchmark.


Sean Hodgkinson Lankem +44 (0)161 343 3355
Elizabeth Bardsley Lankem +44 (0)161 342 1456
Jorge Moniz Resiquim +351 (21) 926 98 88
Joelle Briot CMMP +33 (1) 43 87 71 50
Niels Håkonsen Danske +45 (32) 63 03 70
Craig Reaney Ronseal +44 (0)114 2409307
Ian Wetherell Ronseal
Morgan Sibbald Ronseal
Bob A. Martuch Ronseal
Anders Larsson SP +46 (10) 516 60 60
Karin Persson SP
Jens Sommertune SP
Angie Miller PRAT +44 (0)208 487 0800
Wendy Williams PRAT +44 (0)208 487 0811
Decheng Meng PRAT +44 (0)208 487 0838

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United Kingdom