Kauri-Butanol test

Ka.un. This fossil resin, classified as a copal, is found in the South Pacific, primarily in New Zealand. It formerly was used in protective coatings. It is still used in the Kauri-butanol test (ASTM D1133) to determine the volume of thinner that can be added to a varnish formulation without causing turbidity. 

A particularly common test for ranking hydrocarbon solvent strength is the kauri-butanol test. The kauri-butanol value (KB) of a solvent represents the maximum amount of the solvent that can be added to a stock solution of kauri resin (a fossil copal) in butyl alcohol without causing cloudiness. Because kauri resin is readily soluble in butyl alcohol but not in hydrocarbon solvents, the resin solution will tolerate only a certain amount of dilution. Stronger solvents such as toluene can be added in a greater amount (and thus have a higher KB value) than weaker solvents like hexane. 

The results obtained by the kauri-butanol test (ASTM D-1133) depend on factors other than solvent power and are specific to the solute employed. For this reason, the aniline point is often preferred to the kauri-butanol number. 

While the Hildebrand solubility parameter is justified on theoretical concepts, the Kauri butanol test is an empirical method of testing based on the solubility of a natural gum in hydrocarbon solvents. It is a good guide to the solubility of resins in paraffinic, naphthenic and aromatic hydrocarbons and some chlorohydrocarbons. Many of the hydrocarbons used in industry are mixtures, such as special boiling point spirits and white spirit, and it is easier to measure their solvent performance rather than to try to calculate it (Table 13.5). 

The first attempts at predicting solubility were largely empirical. Paint technologists employed various approaches. In one approach kauri-butanol values were equal to the minimum volume of test solvent that produced turbidity when added to a standard solution of kauri-copal resin in 1-butanol. The aniline point is the lowest temperature where equal volumes of aniline and the test solvent are completely miscible. Both tests are measures of the relative aromaticity of the test solvent. 

The test method for the determination of aniline point and mixed aniline point of hydrocarbon solvents (ASTM D-611, IP 2) is a means for determining the solvent power of naphtha by estimating of the relative amounts of the various hydrocarbon constituents. It is a more precise technique than the method for kauri-butanol number (ASTM D-1133). 

Existing methods use physical measurements and require suitable standards. Tests such as aniline point (ASTM D-611) and kauri-butanol number (ASTM D-1133) are of a somewhat empirical nature and can serve a useful function as control tests. Naphtha composition, however, is monitored mainly by gas chromatography, and although most of the methods may have been developed for gasoline (ASTM D-2427, ASTM D-6296), the applicability of the methods to naphtha is sound. 

Standard test method for Kauri-Butanol value of hydrocarbon solvents, ASTM D1133-02, Book of Standards, Vol. 6.04. 

Two standard tests. Kauri butanol (KB) number and dilution ratio, involving simple laboratory equipment can be used and there is a fair correlation (Fig. 13.4) between the former and the Hildebrand solubility... 

Also the paint industry, formerly the main end-user of solvents, attempted to produce a quantitative solvent power data system [5]. This related solvency to certain standard solutes, used in their industry. These could either be a well-known natural (Kauri-resin) or later a synthetic (nitrocellulose) paint binder. The result was the introduction of the Kauri-Butanol number, which applies to hydrocarbon solvents only and the NC-dilution ratio which is used for oxygenated solvents. Another test, used in conjunction with hydrocarbon solvents, is based on the fact that aniline is hardly miscible with aliphatic hydrocarbons but mixes very well with aromatics. The Kauri-Butanol (KB) number as defined in ASTM D 1133 is a measure of the tolerance of a standard solution of Kauri resin in -butanol to hydrocarbon diluent. Standard hydrocarbon solvents used to calibrate the Kauri solution are toluene (KB-number 105) and a 75% v -heptane/25% v toluene blend (KB-number 40). The KB-value increases from approx. 20 to over 100 in the order ... 

Kauri-butanol value Volume in ml at 25°C (77°F) of a solvent, corrected to a defined standard, required to produce a defined degree of turbidity when added to 20 g of a standard solution of kauri resin in normal butyl alcohol. For kauri-butanol values of 69 and above, the standard is toluene and has an assigned value of 105. For kauri-butanol values below 60, the standard is a blend of 75% n-heptane and 25% toluene and has an assigned value of 40. Abbreviation is KB value. Paint pigment, drying oils, polymers, resins, naval stores, cellulosics esters, and ink vehicles, vol 3. American Society for Testing and Material, Conshohocken, PA, 2001. Fhck EW (1991) Industrial synthetic resins handbook. Williams Andrews Publishing/Noyes, New York. 

Standard Test Method for Kauri-Butanol Value of Hydrocarbon Solvents,... 

The Kauri-butanol value, used to rate solvency of hydrocarbon solvents, is defined in ASTM Method D 1133 as the volume in milliliters of the hydrocarbon solvent at 25 °C that is required to produce a defined degree of turbidity when titrated into a specified quantity of a standard clear solution of kauri resin in n-butyl alcohol. Kauri-butanol values range from approximately 20 for the weakest hydrocarbon solvents to more than 100 for stronger aromatic solvents. The test is limited to hydrocarbon solvents and is not applicable to oxygenated solvents. As Kauri resin (a natural resin) is no longer easily available, the test has not maintained its acceptance in the industry. Aniline point (or mixed aniline point), another measure of solvency of hydrocarbon solvents, is more accepted. The ani-... 

All these empirical test methods for arbitrary rating of solvency have the common limitation that they compare the ability of a solvent to keep in solution one solute, namely kauri resin, aniline and nitrocellulose for Kauri-butanol value, aniline point and toluene... 

B = heptane-toluene blend required to titrate 20 g of kauri-butanol solution (7.3), mL, and C = solvent under test required to titrate 20 g of kauri-butanol solution (Section 8), mL. 

Bias—Test bias can result if the kauri-butanol solution is not carefully standardized and adjusted (see 7.2 and 7.3). The test method has no definitive bias statement because the value of the test result is defined only in terms of the test method. 

Solvents. Perhaps the single most important property of a solvent is its ability to dissolve various resins, gum-like materials, oils, nitrocellulose lacquers, etc., and accordingly there are numerous solvency tests of which the aniline point and kauri butanol number are the best known. The kauri butanol number consists of ascertaining the volume of sample that will cause a standard solution of kauri gum in butyl alcohol to become so opaque that 10-point type is illegible when viewed through the solution. Similar tests employ nitrocellulose and butyl or ethyl acetate solvents. 

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