High acid number

Acidic contaminants are poisonous to the alcoholysis catalysts and must be avoided. If the oil has a high acid number, or there are high acidity residues left in the reactor from the previous batch, such as sublimed phthaUc anhydride condensed under the dome of the reactor, the reaction can be severely retarded. A longer batch time or additional amount of catalyst is then required. Both are undesirable. 

For rosins and rosin esters, the produets having high aeid numbers are the most susceptible to oxidation and have inferior viscosity stability and colour stability in adhesive formulations. Thus, when stability properties are essential in adhesives, rosin esters rather than high aeid number rosins are used. However, the high acid number resins are polar and display better adhesion to polar elastomers and polymeric surfaces. 

Hillshafer et al. reported that aromatic polyester urethanes based on orthoph-thalic anhydride had better hydrolysis resistance than polycaprolactone urethanes, despite high acid numbers [91]. 

Water-Based Inks. Approximately 50% of all flexographic inks use water as their primary solvent and diluent. They contain vehicles based on either acrylic emulsions, or hydrosols or an alkali-soluble rosin ester having a high acid number such as partially esterified fiimurated rosin and shellac. Carboxylated acrylic polymers, usually containing some styrene, have largely replaced natural resins because they provide better abrasion and water resistance. Ammonia or other volatile amines are used to solubilize these carboxylated resins and form resin salts. The volatile alkali evaporates from the ink film, rendering the printed matter water resistant. 

Oils with high acid numbers emulsify with caustic, some spontaneously. 

Kawahara and Ono (90) reviewed methods of pre-esterifying oils with high acid numbers and found that these methods often produced poor quality esters. They attributed the low quality to impurities that were readily extracted by washing the esters with alcohol immediately after pre-esterification. 

An oil s natural soap amount cannot be determined just by nonaqueous phase titration. Oils with high acid number by nonaqueous phase titration usually have high soap content however, this is not always true (Liu, 2007). Because those acids that cannot generate soap will not be detected by the potentiometric titration, the acid numbers obtained by the soap extraction are less than the acid numbers determined by nonaqueous phase titration, as expected. There is no general ratio between those two acid numbers. Figure 10.10 compares the acid numbers measured from the two methods. The data in this figure show that the acid number from the soap extraction was about one half of the value from the nonaqueous phase titration. 

A. (2.0) Ratio Polymers. 1. High Acid Number Polyester Glycol Effects Figure 2 shows the polymerization viscosity-time-temperature relations for three (2.0) ratio thermoplastic poly(ester-urethane) elastomers. Numbers 1 and 2 were both made from the same reactant lots (I, II, and IX - Table I) at about the same reaction temperatures. 

High acid number (2.4) polyester was used in these runs. Number 3 was made from reactant lots IV, XVI and X. The polyester used also had high acid number (2.00) and the polymerization temperature was 200°C. None of these polymerizations was deliberately shortstopped. 

Apparently, higher acid number of a given crude, either by nature or due to the addition of known acid, would lower its interfacial tension. However, Cooke, Williams, and Keledzne (4) found that although in-situ oxidation with air further increases the acid number of a given crude, this artificially-made high acid number crude could not be successfully flooded with alkaline water. 

The stability improvement of Ti02 suspensions is important not only for water-based paints, but also for paints based on non-polar or low-polar solvents. It is shown in [208] that Ti02 powders modified with an anionic surfactant, e.g. sodium dodecyl sulphate, are dispersed to smaller sizes, and their sedimentation stability increases. The production of water-alkyd emulsions is inhibited due to low mechanical stability. These emulsions can easily break when exposed to shear forces such as those produced by pumps, and when intensively agitated during dispersion. [209] demonstrates that most stable emulsions can be obtained with alkyds showing high acid numbers, as well as with highly polymerised alkyds of low viscosities. 

Alkyd resins with high acid numbers (> 50) are neutralized with amines (normal air-drying resins have an acid number < 10, oven-drying resins 20-35) solubility in water is due to salt formation... 

Reactive resins n. (1) Resins of phenol-formaldehyde type which are beheved to react with drying oils on heating, more particularly those of conjugated types. (2) Resins capable of cross-hnking with themselves or other resins. (3) Resins with a high acid number. 

Some crude oils are known for their high acid number which corresponds to a low API degree ... 

There is the added possibility of reaction between any carboxylic groups which the polyester may contain and the isocyanate to give amide and acylurea links. Indeed, the earliest foams were made from polyesters with high acid numbers, the isocyanate-carboxy acid reaction being used as the gas-generating reaction. 

The industry standard for this test is based on ASTM D 664. Normally expressed as Neutralization Number, this test predicts the acidity of an oil/distillate fraction. The sample normally dissolved in Toluene/IPAAVater is titrated with potassium hydroxide and the results are expressed as mg KOH per gram of sample. Crude Oils having high acid numbers are purchased cautiously due to possible corrosion problems in the refineries. Crudes typically have TAN values form 0.05-6.0 mg KOH/gm of sample. While whole crudes are outside the scope of this titration method, it is the only recognized method in the industry. 

Pruthtikul and co-workers demonstrated the in situ reactive functionalisation of PP in a twin-screw extruder. Dicumyl peroxide was used as the precursor during functionalisation. It was found that the sample acid number significantly changed as a function of the precursor/MA ratio. Their results showed that PP-g-MA, which has a high acid number, had a greater effect on improving the compatibility of the PP/... 

PA-6 polymer blend. Basically, both the tensile strength and impact strength of the composites were better in the presence of PP-g-MA, which had a high acid number, than in samples without the addition of the compatibiliser. Based on the surface analysis, better adhesion was also demonstrated using scanning electron microscopy (SEM) micrographs [70]. 

Resins capable of crosslinking with themselves or other resins. (3) Resins with a high acid number. 

It also reduces adsorption of the (mostly anionic) surfactant on the reservoir rock, essentially by enhancing the negative surface charge. In some cases (alkaline-polymer floods), where there are high levels of saponifiable crude oil acids present in the crude oil (high acid number) added surfactant is not even required. The polymer is present to assist in mobility control and to ensure that the injected chemical slug remains intact and promotes the formation of an oil bank ahead of it. 

---