What Is Solvent? What Is Its Contribution to Ozone Formation?

What is Solvent? Solvents, or chemical solvents, are organic liquids composed of numerous chemical substances generally used to dissolve or dilute other substances or materials. Solvents are one of the most comprehensively regulated chemical classes and are further regulated as volatile organic compounds (VOC) that contribute to lower-level ozone formation.

Production methods can be divided into two categories as follows.

a) Conventional methods b) Bio-based methods In the conventional method, solvents are obtained in secondary and tertiary stages through distillation of natural gas and/or petroleum, as we all know.   In the bio-based method, the need for greener sustainable chemicals is met through processing of renewable raw materials. Therefore, not only plant-based products but also various types of waste such as fruit peels and ashes from biomass combustion furnaces are utilized to produce bio-based chemicals. These plant-based products can be identified as bio-ethanol and its derivatives or vegetable oil products such as biodiesel and glycerol.  

Types of Solvents

Solvents are classified as oxygenated solvents, hydrocarbon solvents, halogenated solvents, and bio-based solvents. Alcohols, esters, glycol esters and acetates, and ketones are part of the oxygenated solvents group and are used in the paints sector to dissolve resins that are insoluble in hydrocarbons. Due to the presence of oxygen, the solvent gains polar properties and its solvent power increases. However, since oxygenated solvents are more expensive than hydrocarbons, their industrial use is less than hydrocarbons. Methanol, which has the highest solvent power among alcohols, is not widely used due to its toxic effects and rapid evaporation, and is not preferred due to its direct impact on human health. The use of ethanol in the paints industry is also not widespread. Glycol ethers and acetates are used in dissolving polymers such as oils, natural resins, alkyd acrylic, nitrocellulose, ethyl cellulose, polystyrene, and polyvinyl acetate. Interest in ethylene glycol products has declined in recent years due to their toxic nature, while interest in propylene glycol derivatives has increased.

Although acetone from the ketones group is an excellent solvent, it is not widely preferred due to its high evaporation rate. Methyl ethyl ketone is used as a primary solvent in lacquer paints.

Its solvent power is close to acetone and it evaporates more slowly than acetone, but it is not always preferred due to its higher cost. Hydrocarbon solvents are preferred both because of their low cost and because they dissolve oils, alkyds, varnishes, and other resins well. From the hydrocarbon solvents group, n-hexane, solvent naphtha, and white spirit from aliphatic hydrocarbons, and toluene and xylene from aromatic hydrocarbons are the most commonly preferred solvents. Toluene is used more than xylene because it is easier to obtain and more affordable. Aromatic solvents have much higher solvent power compared to aliphatic solvents. Examples of halogenated solvents include methylene chloride, perchloroethylene, and trichloroethylene. However, the use of these solvents has declined significantly today due to their effects on human health. Examples of bio-based solvents include bio alcohols, D-limonene, lactate esters, and methyl soyate. If they become more economical compared to today's conventional solvents, we will see their usage increase over time. Solvents have a very wide range of applications. The largest use is paints at 46%. Pharmaceuticals at 9%, adhesives, cosmetics, and inks at 6% follow paints. Other sectors can be described as cleaning, agriculture, separation, household care, and various other sectors.  

Applications of Solvents in Purification Processes

Solvents are used in processes such as crystallization and extraction. Depending on the application, solvents with low boiling points, non-toxic, dissolving only the desired substance, and carrying low flammability risk are selected.

As Auxiliary Materials

Solvents are used as degreasing and cleaning agents in the rubber, adhesive, leather, shoe, and floor polish industries. Solvents are also used to spray herbicides and insecticides.

In Applications Not Related to Solvent Power

They are also used as antifreeze (frost protection), fire extinguishing liquids, hydraulic fluids, and desiccating agents.

In Paints, Varnishes, and Paint Strippers

This is the largest application area for solvents. Solvents are one of the basic materials used in production. The primary function of solvents is to act as a carrier for non-volatile components in paint. It has the power to dissolve binders and additives. Here, the volatility rate of the solvent and the viscosity it provides are important. It gives paint fluidity and homogeneous mixing properties, viscosity drops rapidly, and paint becomes fluid. This fluidity enables even spraying of pigments and binders, spreading them on the surface, and achieving appropriate thickness. In the second stage, it makes the paint in the packaging applicable with a brush or roller during application. In paint strippers, solvents swell and dissolve the paint film. The paint is thus separated from where it adheres and can be easily scraped off. The volatile substance content in solvent-based paints approaches 80%, while the volatile substance content in water-based paints is around 10%. Although solvent-containing thinners are not used in water-based paints, they contain approximately 10% solvent because the pigments are solvent-based.

Global Market

The global solvent market, measured at USD 26.80 billion in 2016, is expected to reach USD 33.0 billion by 2022, and is projected to grow at a CAGR (compound annual growth rate) of 4.0% between 2017 and 2022. In terms of volume, global solvents were measured at 31,239.5 kilotons in 2016. The global solvent market is developing based on increasing demand from end-use applications such as paints, agricultural chemicals, printing inks, adhesives, rubber and polymers, personal care, metal cleaning, pharmaceuticals, and others. Consumption in paints and related sectors constitutes the largest share of the global solvent market at 46% of solvent usage. Despite the trend in the paints and related sectors towards technologies containing less solvent (such as powder coatings, high solids, and water-based coatings) over the past thirty years, the fact remains that significant amounts of solvent are still being used. Alcohol-based solvents have emerged as the leading product segment and held a 29.7% share in the global market in 2011. Besides being the market leader, it is also expected to be among the fastest-growing markets. Hydrocarbon-based solvents follow alcohol-based solvents and are expected to grow at a moderate pace in the coming period. Traditional solvents hold the largest share in the source segment. The traditional solvents market is expected to experience significant growth due to increasing use in various applications due to lower costs and better performance compared to bio and green solvents. Potential demand for bio-based solvents, particularly those derived from soy, is growing rapidly in millions of metric tons due to their preference in terms of VOC, including glycols and soya oils.

Regional Status

Asia-Pacific has dominated the solvent market and accounts for 40.1% of global consumption. The Asia-Pacific region is the largest market for solvents in both value and volume terms. With increasing demand in automobiles and construction, population growth in key countries such as China and India, and rapid urbanization contribute to the growth of the solvent market in this region. While overall consumption of solvents in China is expected to grow at an average rate of 5-6% per year in the coming years, demand is expected to remain flat or decline as a result of environmental regulations in the United States and the European Union. Rising economic growth rates, heavy investments in chemical-containing industries, and the absence of strict regulations naturally increase demand for solvents in Asia. Europe made the second-largest contribution to the solvent market in 2016. Acceleration of restructuring activities and industrialization in the region has contributed to market growth. Development of the automotive sector in Europe also supports increased demand for solvents. Rapid urbanization, increasing disposable incomes, and changing lifestyle trends are also expected to contribute to the growth of the solvent market in the region, but it is reasonable to limit this with expected growth of approximately 3-4%. North America shows similar characteristics to Europe and is expected to have moderate growth rates. Awareness in the United States of the negative effects of solvent exposure on human health and the environment is supported by government regulations that have governed the production and application of solvents since the 1960s. Latin America is expected to achieve moderate growth in the solvent market. The largest factor in the growth of the solvent market is the support of construction activities in the region with tourism activities. The Middle East and Africa solvent markets are also expected to witness good growth. However, with infrastructure and restructuring activities in the Gulf countries and the influence of changing lifestyles, it is expected to be a developing market. The growth of the middle-class population is expected to increase demand for solvents.

Demand and Interactions

The use of inks and cleaning products, particularly in the semiconductor industry, appears to have a positive impact in the coming years. The increase in demand for adhesives in various end-use applications is similarly expected to be one of the factors that will increase market demand in the coming years. Growth in solvents is being witnessed due to demand for end-use industries such as paints and pharmaceuticals. Growing construction and automobile industries, particularly in developing regions such as Asia-Pacific, are increasing demand for solvents. With growth in the automobile industry, the increase in residential and commercial infrastructure supports growth in paint consumption.

Opportunities

Agricultural chemicals are expected to be one of the rapidly growing areas for solvents. Rapidly increasing demand for food products and increasing yields are driving the growth of the traditional solvent market in agricultural chemical applications and are expected to drive the solvent market over the next 5-10 years. Another factor affecting demand is the transfer of industrial processes that consume large amounts of solvents, such as wood furniture paints and shoe assembly using solvent-based adhesives, to China. However, due to restrictive measures being taken in China, water-based paints are expected to grow at 16% annually, while traditional solvent-based paints are expected to grow at a maximum of 2% annually. However, when more restrictive regulations are implemented in the United States and the European Union over the next five years, consumption percentages are likely to continue to decline. Moderate growth in demand is expected. However, solvent production and mixing will continue to change dramatically under environmental and regulatory impacts designed to reduce emissions of ODS (ozone-depleting substances), VOC (volatile organic compounds), and HAP (hazardous air pollutants). Production of low-VOC-value solvents less harmful to people and the environment is part of the "green chemistry" movement, including supercritical CO2 that can be used for extraction. Other promising green solvents currently being studied are essentially ionic liquids with no vapor pressure and are environmentally harmless, with limited use, and production will continue to increase. Unfortunately, low oil prices also support continued traditional solvent consumption. Consumer pressure may indirectly influence solvent selection, depending on the sector and how much value is placed on "greenness." Additionally, we should note that there may be institutional resistance to change. This is not mostly due to stubbornness alone; because if the solvent is changed, some processes will directly affect the purity profile of the final product.

Limitations

Solvent market growth has been overshadowed by several limitations; first is usage regulations in developed regions. The other is the evolution of technologies using less (or no) solvent, such as water-based paints. Green and bio-based solvents are helping revive the global solvent market. Europe, with the implementation of the Registration, Evaluation, and Authorization of Chemicals (REACH) regulation in Europe, has imposed stricter restrictions on solvents. Bio-based solvents, particularly those derived from soy, have limited potential in the cosmetics, pharmaceutical, food, and electronics sectors. Similarly, there is no potential for soy in antifreeze, aircraft de-icing fluids, and dry cleaning sectors. Developments in regulations have begun to prevent the complete use of certain solvents due to environmental, health, and safety concerns.

Conclusion

The competitiveness of the solvents market is continuously increasing with expansion and new product launches. Strategic developments are mostly undertaken by large players. In this scenario, it is extremely important for players operating in the market to remain competitive by adopting the best growth strategies. This includes a focus on capacity expansion and reducing additional burdens to increase profitability. Companies are increasingly expanding their capacity in the Asia-Pacific region to meet high solvent demand in the region. Other reasons justifying this growth strategy are the easy availability of raw material stocks, low levels of regulation, and cheap labor. Bio-based products have a limited market due to unwanted features/issues such as supply, purity, price, or high viscosity. Neoteric bio-based solvents are viable products, but they need to demonstrate their performance characteristics to be supported and develop market share. A wide variety of bio-based materials exist and have achieved commercial success in niche markets. The opportunity to develop and market solvents with low ecological and toxicological profiles appears possible, particularly with the strong global green movement and increasing regulatory oversight of the solvent industry. There is no perfect solvent, so manufacturers must strike a balance between efficiency, cost, and environmental impact. The perfect opportunity to develop and market solvents with low ecological and toxicological profiles is particularly positive with the strong "green" movement. Tezel Kökdemir - General Director / Arkem Kimya San ve Tic A.Ş.