Polyolefin waxes

The properties of polylefin waxes derived from polypropylene, polybutene, and their copolymers are described, with particular references to those which are useful as coatings and barrier materials. These products can be applied with conventional melt- and curtain-coating machines on paper and other substrates to give coatings with properties comparable to those of extrusion-coated, plastic-grade polyolefins. Because of their low melt viscosity and consequent ease of application, they should find wide application in the packaging industry.     

Extractable waxes from Greek lignites

An investigation on the solvent-extraction yields of Greek lignites has shown that the yields are generally low compared with the yields from certain American and German lignites, and similar to the yields from Czechoslovakian lignites. The highest yields were obtained from lignites of the Psachna deposit. The only extract which resembled rather closely in its nature the Riebeck crude montan wax was obtained by benzene extraction from Ptolemais lignite. The most significant differences between benzene extracts from Greek lignites and Riebeck crude montan wax were the differences in melting points and the greater resin content of the Greek waxes. Extraction with benzene/methanol mixture instead of benzene gave higher yields and extracts characterized by higher melting points, and higher acid and ester values. The compatibility of the extracts with paraffin wax was low; only benzene extract from Ptolemais lignite was completely miscible. No relation was found between the wax yield and the ratio volatile matter/fixed carbon of the coal. We also conclude that extraction of waxes from Greek lignites is not commercially attractive.     

Crystallization of sunflower oil waxes

Activation free energies of nucleation (ΔG _c ) were calculated using induction times of crystallization measurements. Results showed that ΔG _c decreased exponentially as wax concentration increased at a constant crystallization temperature (T _c ). In contrast, for a constant supersaturation, ΔG _c increased from 12 to 22°C but decreased between 22 and 35°C. Melting behavior of purified waxes and solutions of purified waxes in sunflower oil were studied by DSC after crystallization at fast and slow cooling rates (20 and 1°C/min, respectively). Low supercooling temperatures (T _c >65°C) showed an increase in the onset temperature (T ₀ ) as T _c increased for both fast and slow cooling rates. Broader peaks were obtained for samples crystallized at a slow cooling rate at the same T _c . Regarding the solutions of waxes in sunflower oil, the wax concentration (supersaturation of the system) controlled crystallization as well as T _c . As T _c increased, the enthalpy (ΔH) decreased at a constant wax concentration. When wax concentration decreased, ΔH decreased at a constant T _c . For a low driving force, a small shoulder was obtained in the DSC diagrams owing to some type of fractionation. These results showed that wax crystallization is affected by different experimental parameters, such as T _c and cooling rate, depending on the wax concentration of the sample.     

Melting and crystallization of vegetable waxes

Summary A rapid but sufficiently accurate method is applied to the observation of phase changes in vegetable waxes and is suggested for adoption as a routine procedure. Five indications are obtained in about 20 minutes for each sample: odor, surface appearance, initial melting, melting and crystallization points. A hot stage is used, designed by the author, and made under his supervision at the Instituto de óleos. Data are discussed concerning carnuauba (Copernicia cerifera, Mart.) and licuri or ouricuri (Syagrus coronata, Mart., Becc.) waxes. Some results related to carandá (Copernicia australis, Becc.), cuban carnauba, sugar cane,Heliconia farinosa, Raddi.,Heliconia pendula, Wawra., candelilla, and caá-uassú (Calathea lutea, Mey.) waxes are also included.     

Structure and properties of microcrystalline waxes

The structure of three series of microcrystalline waxes has been studied using X-ray diffraction and i.r. techniques. Their relative methylene/methyl group ratios as well as solid state parameters like size and shape of the unit cell, crystallite size and total crystalline fraction have been calculated. An attempt has been made to correlate these structural data with gross physical properties like oil content and needle penetration point. These correlations are found to hold good within any given series but varies from one series to another.     

Microcrystalline waxes. 1. Investigations on the structure of waxes by proton nuclear magnetic resonance spectroscopy

Information on the degree and type of branching in ten different microcrystalline waxes, their saturated and aromatic fractions has been obtained by proton nuclear magnetic resonance. The branches present in these waxes are of the long-chain type with a terminal methyl group and an average of about 1.3 branches per molecule.     

Characterisation of waxes by differential scanning calorimetry

The characterisation of hydrocarbon and natural waxes by differential scanning calorimetry is described. It is shown that the determination of the melting, cooling and remelting curves of a wax, and comparison with the corresponding curves of authenticated waxes, affords a rapid and valuable method for the identification of many waxes. Heats of transition of many waxes are also given.     

Crystallization of waxes during sunflowerseed oil refining

Cooling conditions and wax content in oil determine the morphologies adopted by crystals. At high cooling rates (K) and low temperatures of the refrigerant (T_f), nucleation temperatures are low. This induces the formation of a great number of small nuclei. However, at low K and high T_f, nucleation temperatures are high, producing a few large nuclei. The wax/oil equilibrium curve was determined; it allows the evaluation of the wax remaining in the oil after a given treatment. In addition, experiments were performed to evaluate crystal separation from oil. The increase of temperature from 10 to 25 C and the presence of soaps in the oil facilitate wax separation. These results give additional information that can improve operating conditions and make the choice of technological alternatives in wax separation easier.     

聚烯烃蜡改性的研究进展

归纳了聚乙烯蜡的几种改性方法,其中接枝法得到产品接枝率高,相关研究较多;氧化法相对研究较少,具有较大研究价值。在此基础上对聚乙烯蜡氧化改性的研究前景进行了展望。     

聚烯烃蜡改性的研究进展

归纳了聚乙烯蜡的几种改性方法,其中接枝法得到产品接枝率高,相关研究较多;氧化法相对研究较少,具有较大研究价值。在此基础上对聚乙烯蜡氧化改性的研究前景进行了展望。     

The interaction of waxes with pour point depressants

Paraffin wax deposition from crude oils at low temperature is one of the serious and long-standing problems in petroleum industry. Addition of pour point depressants (PPD) has been proved to be an efficient way to inhibit wax deposition. The influence of PPD on wax precipitation at low temperature was investigated. The amount and composition of wax precipitated from paraffin solutions with and without PPD at different temperatures were studied by high speed centrifuge and gas chromatography (GC), respectively. The interactions between waxes and PPD were investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results showed that PPD do not completely prevent the wax from precipitating, but just shift the precipitation toward a lower temperature. This conclusion was identified from the analysis of the amount and composition of precipitated wax as well as the transition temperatures and energies of wax. It was shown that this effect is due to the structure of wax is partly transformed from orthorhombic into hexagonal form by PPD.     

Composition of waxes from crude rice bran oil

Hard and soft waxes were separated from the tank settling of crude rice bran oil by solvent extraction and analyzed for their composition by gas liquid chromatography (GLC). The results showed that the melting points of the hard wax and the soft wax were 79.5 C and 74 C, respectively, and that the hard wax was mainly composed of saturated fatty alcohols of C24, C26 and C30, saturated fatty acids of C22, C24 and C26, andn-alkanes of C29 and C31. The soft wax was mainly composed of saturated fatty alcohols of C24 and C30, saturated fatty acids of C16 and C26, andn-alkanes of C21 and C29. In the soft wax, lauric acid was also detected.