1. Field of the Invention
The invention pertains to the field of solvent systems. More particularly, the invention pertains to a solvent system including at least one terpene.
2. Description of Related Art
The U.S. federal government has assigned to the Environmental Protection Agency (EPA) the responsibility of regulating man-made volatile emissions, which may pollute the air and atmosphere. The EPA has listed a group of VOCs as “Exempt VOCs”, which is published in the Federal Register under 40 CFR 51.100(s), which is hereby incorporated by reference herein, and addendums. All other VOCs are restricted for use and weight-limited for emission discharge into the atmosphere and environment. Formulators and compounders of products using VOCs are challenged to use and obtain the required VOC combinations for use in their products, to comply with toxic emissions, and to provide for safety in manufacturing, shipping, storage, and ultimate use. VOCs are further sub-classified based upon their vapor pressures, boiling points, and flash points. The flash point of the VOC becomes a critical factor for emission discharge and safety, because it is critical because it is the point at which the liquid becomes a volatile vapor, mixes with oxygen, and thereby acquires its most combustible or flammable state. Flash point, as used herein, refers to the lowest temperature at which a volatile liquid can vaporize to form an ignitable mixture in air. In the United States, the Environmental Protection Agency (EPA) and the Department of Transportation (DOT) have classified such compounds based on their volatilities or “flash points”.
The current EPA and DOT Volatile Organic Compound (“VOC”) classifications are as follows:
Class I liquids (flammable)flash point at or below 100° F.Class II liquids (combustible)flash point from 100° F. to below 140° F.Class III liquids (combustible)flash point above 140° F. to below 200° F.
International standards are generally stricter, with 43° C. (109.4° F.) generally being the separation point between flammable and combustible liquids.
There are currently six commonly used exempt VOCs on the U.S. federal list of acceptable VOCs. Of the six, four have flash points below 10° C./50° F. and they are therefore classified as “flammable and hazardous”, thus rendering their respective use to safe and unpopulated areas. P-Chlorobenzotrifluoride (PCBTF) has a “combustible” flash point rating of 43° C./109° F., and propylene carbonate lists as “combustible” with a flash point of 107.8° C./226° F.
Organic solvents, such as acetone, xylene, ketones, esters, ethers, aliphatic hydrocarbons, and aromatic hydrocarbons such as benzene, are widely used as additives for industrial and commercial purposes. Due to the high volatility of these compounds, their uses are regulated by many countries' governmental agencies. Obviously, the more flammable a solvent, the more restrictions exist on its use. Further, manufacturers that utilize solvents must handle the more flammable liquids more carefully and have to address issues involving atmospheric volatility and worker health concerns due to excessive exposure to these chemicals. If these solvents can be modified so that their flash points can be increased, this would result in significantly more uses for these compounds as well as increasing their shelf lives. It is desirable therefore to increase the flash point of a variety of solvents without substantially increasing the cost of the solvent while maintaining the solvent and its utility and effectiveness for its purpose.
“Green” solvents are regarded as such because of their sources of origin (non-petroleum based) and the fact that they biodegrade readily after use without environmental damage. Green solvents include, but are not limited to, certain alcohols such as methanol, ethanol, benzyl alcohol, certain acetates, certain esters, and turpentine. The problem with these solvents, however, is that due to their high volatility, they are considered hazardous air pollutants which violate Federal and State emissions regulations. Ethyl lactate, one example of a green solvent, has a flash point of about 115° F., which despite not being considered a Class I VOC, is still combustible, which limits its potential uses. Green esters, such as N-butyl propionate, ethyl lactate, and methyl soyate, are also considered combustible, with flash points ranging from 115° F. up to 250° F. However, they are slow to evaporate and exhibit good solvating characteristics when used in blended compositions. Nevertheless, this group of solvents is considered environmentally clean and could be utilized more extensively if their volatilities could be reduced.
The growing environmental concerns over the use of petroleum lubricants for industrial and transportation needs has expanded the uses of oleochemicals, vegetable oils, and recyclables for use as alternative lubricants. Environmental concerns and efforts toward resource renewability, biodegradability, and utility have led to the introduction and use of vegetable oils and synthetic esters. Of the major candidates considered, coconut oil, hydro-processed mineral oil, rapeseed (canola) oil, soy methyl esters, palm oil, and recyclable vegetable oils have been found to offer the best overall performance.
The art of selecting and using various oils for lubricants is routinely practiced. However, environmental regulations now restrict the use of volatile organic compounds (VOCs), which affects the lubricating oil selection and/or the method of application. U.S. federal and state regulations governing the composition and emissions content of lubricants conforms and limits choices.
Terpenes are a large and varied class of hydrocarbons with the molecular formula (C5H8)n and are produced by a wide variety of plants and trees, such as conifers and pines. Terpenes are derived biosynthetically from units of isoprene, which has the molecular formula C5H8. The term “terpene” is sometimes used broadly to also include the terpenoids which are terpenes that have been chemically changed or modified, such as through oxidation. A terpene, as used herein, may be any hydrocarbon, natural or synthetic, formed from isoprene units. Terpenes as well as terpenoids, are the primary ingredients of the essential oils of many types of trees, plants, and flowers, including citrus fruits. Terpenes are the major components of rosin (resin) as well as turpentine produced from gum rosin (resin).
The terpenes are generally classified sequentially by the number of isoprene units they contain as hemiterpenes (one isoprene unit), monoterpenes (two isoprene units), sesquiterpenes (three isoprene units), diterpenes (four isoprene units), sesterterpenes (five isoprene units), triterpenes (six isoprene units), and tetraterpenes (eight isoprene units).
When a terpene is modified chemically, such as by oxidation or rearrangement of the carbon skeleton, the resulting compound is generally referred to as a terpenoid. Terpenes and terpenoids are typically derived from plants, trees, flowers, and other vegetation. They come in the form of liquids, solids, waxes, oils, and alcohols. Terpenes and terpenoids may be formed as acyclic, monocyclic, or polycyclic structures. Sometimes alternatively referred to as “isoprenoids”, terpenoids are derived from five-carbon isoprene units and can be classified as “modified terpenes”, where methyl groups have been moved or removed, or oxygen atoms added. Some researchers use the term terpene to include all terpenoids.
Terpenes and terpenoids in various forms have been used for centuries in fragrances due to their compatibility with other compounds and their minimal negative environmental impact. Terpineol, a terpene alcohol, has the chemical formula: C10H18O and is found in three isomeric forms, alpha, beta, and gamma, with beta-terpineol being non-naturally occurring. Terpenes and terpenoids have been used for other purposes, such as disinfectants, cleaning compounds, soaps, cosmetics, and colognes. They are also known to add, enhance, or mask the odor of products which might be offensive to humans or animals.
The term “terpene” is derived from the word “turpentine”. Turpentine is a volatile fluid which is distilled and refined for further commercial uses. The most common terpenes obtained from rosin (resin) distillation are the bicyclic terpenes alpha-pinene (α-pinene), beta-pinene (β-pinene), delta-3 carene (δ-3 carene), and sabinene, the monocyclic terpenes limonene and terpinolene, and smaller amounts of tricyclic sesquiterpenes longifolene, caryophyllene, and delta-cadinene. Rubber, which is a polyterpene, is one of the most widely known terpenes.
As with other plant essential oils, terpenes are major constituents of the essential oils of citrus fruits. However, they are removed before the essential oil is used for flavoring beverages and foods because they tend to produce undesirable tastes when permitted to oxidize and polymerize.
Terpene hydrocarbons are liquid distillates separated from rosin pitch or sap from conifers, pine trees, citrus, and varied vegetation. The volatile terpene hydrocarbons, Chemical Abstracts Service Number (CAS#) 8006-64-2, are non-oxygenated with the molecular formula C10H16. Common names include terpenes, diterpenes, pure gum turpentine (PGT), oil of turpentine (OT), and limonene. Commercial areas of use include in paint thinners, paint strippers, cleaners, disinfectants, and pharmaceuticals.
Pure gum turpentine is a complex formulation made of α-pinene (CAS#80-56-8) 40%-55% weight, β-pinene (CAS#127-91-3) 25%-35% weight, and the balance mixed trace terpenes. Pure gum turpentine is 99.5%-100% volatile, evaporating slightly less (0.9) than the reference standard (butyl acetate (1.0)) and has a flash point of 35° C./95° F., a boiling point of 155-180° C., and a Kauri-butanol (Kb) value greater than 50 and is generally soluble in organic solvents.
U.S. Pat. No. 7,273,839, issued Sep. 25, 2007 to Koetzle and hereby incorporated by reference herein, discloses the use of terpene alcohols with organic solvents and blends of solvents to increase the flash points of these solvents. Koetzle also discloses a method to decrease the flammability of normally flammable solvents using terpene alcohols, by blending the terpene alcohol into the flammable solvent. Koetzle discloses increasing the flash points of acetone, methanol, ethyl acetate, ethanol, and xylene by 50 to 60° C., by addition of 12-14% terpineol. Koetzle also discloses solvents blended with other organic solvents to produce performance solvents, such as paint strippers with flash points greater than 140° F.
Turpentine, which is also known as spirit turpentine, oil of turpentine, and wood turpentine, is obtained by the distillation of resin from trees, usually pine trees. Turpentine prepared in this manner includes mostly alpha-pinene and beta-pinene, two terpene isomers. The exact composition of turpentine may vary from batch to batch depending on the distillation conditions and the resin source. As a solvent, turpentine has been used in varnishes and for thinning oil-based paints.
Terpene alcohols generally have the structure of terpenes except that they include at least one hydroxyl group. A terpene alcohol, as used herein, may be any compound, natural or synthetic, formed from isoprene units and having at least one hydroxyl group. Terpene alcohols are also derived from plants, trees, flowers, and other vegetation which allows their classification as “green compounds”. Terpene alcohols are also divided into groups determined by the number of carbon atoms and repeating isoprene units. Terpene alcohols may be formed as acyclic, monocyclic, or polycyclic structures. Terpineol, a terpene alcohol, has the chemical formula: C10H18O and is found in three isomeric forms, alpha (α), beta (β), and gamma (γ), with β-terpineol being non-naturally occurring. Terpene alcohols have been used for many purposes, including, but not limited to, disinfectants, cleaning compounds, soaps, cosmetics, and colognes. They are also known to add to, enhance, or mask the odor of products which might be otherwise offensive to humans or animals.
Latex paints are currently being used almost exclusively today, because they are water based and nonflammable and they do not emit any harmful vapors into the atmosphere. Latex paints, however, do have drawbacks in comparison to oil-based paints, which are currently banned in many places for their flammability and vapor emissions. Oil-based coatings, such as vinyl coatings and oil-based paints, are more durable than latex paints. Lines on streets and roads made with latex paints must be repainted much more frequently than lines made with oil-based paints. Oil-based coatings are also easier to spread, easier to touch up, and can be made more resistant to fungus and molds than latex paints. There is a need in the art for an oil-based coating with reduced flammability, which meets stricter government regulations.