HIGH PENETRATION, LOW VISCOSITY PARAFFIN WAX AND PROCESS FOR ITS PRODUCTION

Abstract: The invention relates to a high penetration - minimum value 30 0.1 mm at 25 DEG C - and low viscosity - maximum value 10 m<2>/s - paraffin wax. The invention also relates to a process for producing said paraffin wax by redistilling a mixture of slack waxes and de-oiling the resulting individual fractions I, II, III and IV (the residue) to obtain foot oil I, foot oil II, foot oil III and foot oil IV. According to the invention at least two of the resulting foot oils are mixed with one another and optionally with up to 65 w/w % of a foot oil resulting from non-redistilled slack waxes to obtain a final mixture containing at least 15 w/w % of foot oil IV (petrolatum oil), and this mixture is de-oiled in a manner known per se in an apparatus used for de-oiling of slack waxes with a solvent mixture comprising ketones and aromatics with a ketone content of not less than 29 % by volume, wherein dissolution and mixing are performed at temperatures not higher than 125 DEG C and crystallization is performed at a final cooling temperature not less than -17 DEG C.

Description: HIGH PENETRATION, LOW VISCOSITY PARAFFIN WAX AND PROCESS FOR ITS PRODUCTION This invention relates to high penetration and low viscosity paraffin wax of especially advantageous characteristics, and to a process for its production. According to the general terminology of the oil industry, "paraffin waxes" are solid hydrocarbons, which are mainly composed of paraffins in the chemical sense of the word, corresponding to. the general formula C π H_. n+2 , but have some cycloalkane content as well . Additionally, in the large molecules of petroleum waxes (C 1B or above) normal- iso- and cycloparaffinic structures may occur within one single molecule. Thus, no uniform terminology has been accepted for the definition and classification of petroleum waxes. Hungarian authors have classified paraffins as liquid, macrocrystalline, intermediate and microcrystalline paraffins (Feund, M., Csikόs, R., Keszthelyi, S. Mόzes, Gy.; Paraffin Products, - Properties, Technologies, Application; Akademiai Kiadό, Budapest, 1982, p. 19) . Microcrystalline paraffins are divided to brittle and ductile ones, and the latter group is divided to elastic and plastic waxes . Macrocrystalline paraffin waxes can be classified on the basis of their pour point or refining grade. Those with pour points below 45 °C are soft paraffin waxes; hard paraffin waxes have pour points above 45 °C, Ubbelohde drop points between 50 and 58 °C and penetration values between 12 and 16 0.1 mm at 25 °C. According to H. Bennett, paraffin waxes are characterized by pour points between 27 and 68,9 °C and penetration values of 16 0.1 mm at 32 °F (Bennett, H., Industrial Waxes, Chem. Publ. Co. Inc., New York NY, 1975, p. 14) . Petroleum waxes are divided generally to paraffin waxes and microcrystalline waxes on the basis of their pour point and refractive index at 210 °F, while semi microcrystalline waxes are distinguished by their viscosity below 10 mmVsec at 210 °F ( ibid . p.101) . A great variety of production methods for petroleum waxes are known in the prior art. Feedstocks are mainly light or medium vacuum cuts of paraffinic, sometimes of intermediate crudes. Such distillates are used for the production of lubricants, and dewaxing is an important step of this process. Dewaxing used to be achieved by direct cooling followed by pressure filtering in more stages, giving first " +slack" and then "-slack" as by-products. These slack waxes were used as feedstocks for the production of paraffin waxes, mainly by the technology called " sweatening" . New technologies apply selective solvents before cooling to ease filtration and improve the processibility of viscous distillates and residual oils. Selective solvents leave paraffinic components and pour point increasing intermediate hydrocarbons - structurally between paraffins and oils - in the solid phase, and they can thus be separated from oils by filtration. Both slack wax and oil contain solvent, which must be evaporated. Slack waxes obtained as by-products are feedstocks for the production of paraffin waxes. In this process, the application of solvent technologies for the separation of paraffins with low oil content, similarly to dewaxing, has increased capacities and plants can be operated continuously. Slack waxes are diluted with a solvent. Most often, solvents of ketone-aromatic type are used, the ketone component of which can be acetone, methyl-ethyl ketone or methyl-isobutyl ketone, and the aromatic component is benzene, toluene or their mixture (nowadays, benzene is less frequently used because of its hazardous nature) . This solvent dissolves slack by warming. The solution is then cooled, whereupon paraffin wax crystallizes and can be separated by filtration. Quality requirements prescribe low oil contents; maximum values are 2 % by weight (further on: w/w%) for technical grade products, 1 w/w% for fine products and 0.5 w/w% for food grade products. To meet requirements, filtration is performed in more stages, and paraffinic filter cake is washed with the solvent. The product of this process is paraffin wax, the by-product is "foot oil", which is used basically as fuel oil, but sometimes it is added to FCC feedstocks as it can be cracked easily. Macro or macrocrystalline paraffin waxes are widely used for various applications. In the United States, more than 60 % of them is used for the production of laminated foils and papers for the food industry, and about 18 % for manufacturing of candles . On the contrary, in Europe 43-55 % of paraffin waxes are used for candle production and 25-26 % for other industrial purposes. As it is clear from the publications referred, paraffin waxes are hard, have low penetration values, thus they are brittle and only scarcely suitable as such e.g. for coating purposes. Their flexibility is improved by microwaxes and plastics. The authors of the USSR patent 1121284 (" Process for the production of plastic, ductile paraffins" ) have recognized that plasticity of paraffins is sometimes an important feature, and describe a method for producing plastic paraffin waxes having pour points as low as 37 - 45 °C and containing crystallizable hydrocarbons with an iso- and cycloparaffin content of 20 to 35 w/w% . This plastic paraffin wax is then mixed with hard paraffin wax in a weight ratio of (10:90) to (90:1) . Their method differs from the general practice. The feed is not slack wax, but a cut boiling between 280 - 470 °C that has been de- oiled in a ketone-aromatic type selective solvent, giving paraffin wax with a pour point of 50-55 °C and an oil content of 0.5-2.3 % by weight. The filtrate of the first filtration stage is then dewaxed by crystallization at (- 20) - (-30) °C followed by filtration, according to the general practice in the oil industry. A slack wax with low pour point is obtained as by-product; it is de-oiled again, and the resulting plastic paraffin wax, that shows the characteristics mentioned above, is mixed with hard paraffin wax. The characteristics of the plastic component given in the examples of the cited Soviet patent are as listed in Table 1. Table 1 Characteristics of the plastic paraffin wax according to USSR 1121284 Pour point, U C 38.3 - 50.5 Oil content % by weight 1 - 3 n-Alkane content, w/w% 64.5 - 91.3 Viscosity at 100 °C, 2.80 - 3.08 mm'/sec Penetration (cone) at 20 13 - 49 °C The procedure has some disadvantages : following the separation of hard paraffin waxes, the feedstock for the next stages, "low pour point slack wax", can be obtained by a dewaxing step with extremely high energy consumption; and, since the raw material for the first step is a vacuum fraction with low viscosity and not a finished product, the oil product of the dewaxing is a low value "distillate oil" . In addition, the isoalkane content of the plasticity-enhancing end product is relatively low. The aim of our experiments was to develop a process for the production plastic paraffin waxes having low viscosity and high isoalkane content. Raw materials were light, medium and heavy vacuum cuts of paraffinic and intermediate crudes (originally manufactured as raw materials for lube production) and/or their raffinates after treatment with a selective solvent, preferably N-methyl-2-pyrrolidone . They were dewaxed with a ketone-aromatic solvent, preferably with a 30 - 70 : 70 - 30 v/v mixture of methyl ethyl ketone and toluene; slack wax by-products were then mixed in the proportion of their yields and redistilled in vacuo . This was a reasonable operation, as narrow cuts show advantageous properties in the de-oiling step of paraffin production due to their more uniform crystalline structure; additionally, the about 30 % macrocrystalline paraffin content of the heavy cut or its raffinate, with a pour point between 60 - 62 C C, can be recovered (third vacuum distillation cut) . The residue is a suitable feedstock for the production of paraffin waxes preferably with 62 - 66 °C pour points. The method provided three vacuum distillates and a residue, and in the following sections they are designated as slack I, slack II, slack III and slack IV (the residue) materials. Their properties are shown in Table 2. Table 2 Main characteristics of de-oiling feedstocks Property Slack-I Slack Slack Slack II III IV Density at 70 0.76 - 0.77 - 0.79 - 0.79 - °C 0.80 0.81 0.82 0.83 Pour point, 44 - 50 50 - 54 55 - 60 59 - 65 °C Viscosity at 2.0 - 3.1 - 4.4 - 5.5 - 100 °C mm 2 /sec 3.0 4.3 6.2 7.9 De-oiling was performed by known methods, and resulted in four different quality paraffin waxes, that have no further significance concerning our invention; and four foot oils. They are designed as foot oil I, foot oil II, foot oil III and foot oil IV (petrolatum oil), and their properties are shown in Table 3. Table 3 Properties of foot oils Property Foot Foot Foot Foot oil I oil II oil III oil IV Density at 70 0.76 • 0.77 - 0.79 0.80 °C 0.81 0.82 0.84 0.85 Viscosity at 2.0 ■ 3.2 - 4.0 6.2 100 °C mm 2 /:sec 3.1 4.4 6.2 8.8 Flash point 140 150 160 170 (M) , °C, min. Pour point, 10 - 35 12 - 38 15 - 40 20 - 45 °C Further investigations have surprisingly shown, that foot oils and especially their mixtures, used in the prior art as fuel oils or FCC feedstocks, are excellent raw materials for the production of high penetration and low viscosity soft paraffin waxes under properly controlled conditions. The invention relates to a process for the production of high penetration - minimum value 30 0.1 mm at 25 °C - and low viscosity maximum value 10 m /s - paraffin waxes by redistilling a mixture of slack waxes and de- oiling the resulting individual fractions I, II, III and IV (the residue) to obtain foot oil I, foot oil II, foot oil III and foot oil IV. According to the invention at least two of the resulting foot oils are mixed with one another and optionally with up to 65 w/w % of a foot oil resulting from non-redistilled slack waxes to obtain a final mixture containing at least 15 w/w % of foot oil IV (petrolatum oil), and this mixture is de-oiled in a manner known per se in an apparatus used for de-oiling of slack waxes with a solvent mixture comprising ketones and aromatics with a ketone content of not less than 29 % by volume, wherein dissolution and mixing are performed at temperatures not higher than 125 °C and crystallization is performed at a final cooling temperature not less than -17 °C. Two mixtures of foot oils were made for test purposes with the following compositions (in w/w %) : "A" "B" foot oil I 0 10-25 foot oil II 70-30 20-45 foot oil III 15-35 15-35 foot oil IV (petrolatum oil) 15-55 15-35 The mixtures were de-oiled by a method similar to that used in the production of paraffin waxes, but under different conditions. Either a (30-70) : (0-10) : (70-30) v/v mixture of acetone, methyl ethyl ketone and toluene or a (30-70) : (0-10) - (70-30) v/v mixture of methyl ethyl ketone, acetone and toluene was used as solvent. Solvents may also contain water or other impurities in an amount of up to 5 % by volume. The solvent was applied in a five- to twelwefold amount for the foot oil mixture, and final crystallization temperature was set to (-15) -(+1) °C. Filtration was also performed at this temperature. Rotary vacuum filters were used for filtration. Depending on the quality reqiurements set forth for the end product, the filter cake was diluted with the solvent once or twice again, and washed with the solvent after each of the filtration steps. Upon removing the solvent from the crystalline phase a soft paraffin wax according to the invention was obtained, and removal of the solvent from the filtrate gave a secondary foot oil. The characteristics of the soft paraffin wax are listed in Table 4. Table 4 Characteristics of high penetration, low viscosity soft paraffin wax Viscosity at 100 , 3.20 - 10.0 mmVsec Pour point, °C 42 - 59 Penetration at 25 °C, 0.1 30 - 170 mm Oil content, w/w% 0.6 - 42 Minimum amount of not normal alkanes, w/w % (by 37 gas chromatography) Filtration of soft paraffin waxes can sometimes be assisted by crystallizing aids. Thus, the essence of our invention is as follows : At least two of the foot oils obtained as by-products upon redistilling slack waxes to narrow boiling fractions and de-oilmg these fractions are mixed in a definite ratio. The resulting mixture is processed again in an apparatus for the production of paraffin waxes by the solvent technology, to yield soft paraffin wax and a secondary foot oil . Our invention can also be applied to mixtures of foot oils as base materials for the production of soft paraffin waxes, when one type of the components of the said mixture is foot oil produced by the de-oiling of redistilled slack waxes as described above and the other type of components is foot oil produced by the de- oiling of slack waxes made from light and/or medium vacuum cuts or their raffinates . Our invention is illustrated by the following examples: Example 1 23 w/w% of foot oil II, 29 w/w% of foot oil III and 48 w/w% of foot oil IV were mixed. The characteristics of the mixture are shown in Table 5. Table 5 Main characteristics of the foot oil mixture according to Example 1 Density at 70"C 0.814 Pour point, °C 39 Viscosity at 100°C, mmVs 5.62 Oil content, w/w% 21.7 Flash point, °C 238 Boiling points at vacuum distillation, °C (recalculated for atmo¬ spheric pressure) initial 351 end 532 4.5 Colour 1.4520 Refractive index at 70"C This starting mixture was diluted with a 8.5fold amount of solvent containing 51 % by volume of acetone, 4 % by volume of methyl ethyl ketone, 44 % by volume of toluene and 1 % by volume of water. Final crystallization temperature in the de-oiling process was -7 °C, and this was also the -temperature of filtration. The filter cake on the rotary vacuum filter was washed with an equal (onefold) amount of the cold solvent, then it was suspended in a twofold amount of the solvent, filtered again and then washed with a 1.5-fold amount of the solvent. Solvent present in the soft paraffin wax and in the filtrate was removed by distillation according to the usual practice. Soft paraffin wax was obtained with a yield of 44% (based on the weight of the starting mixture) , its characteristics are shown in Table 6. Table 6 Characteristics of soft paraffin wax according to Example 1 Pour point, U C 46.2 Oil content, w/w% 3.9 Viscosity at 100 °C, 5.12 mm /sec Penetration at 25 °C, 0.1 168 mm n-Alkanes, w/w% 43.6 Nonnormal alkanes, w/w% 56.4 Mean molecular weight 433 Example 2 28 w/w% of foot oil II, 18 w/w% of foot oil III and 54 w/w% of foot oil IV )petrolatum oil) were mixed to obtain a mixture with the characteristics shown in Table 7. The warm starting mixture was diluted with a 6.5-fold amount of a solvent containing 55 % by volume of methyl ethyl ketone, 4 % by volume of acetone, 39 % by volume of toluene and 2 % by volume of water. The solution was cooled to a final crystallization temperature of-11 °C and filtered. The filter cake on the rotary vacuum filter was washed with a 1.5-fold amount of cold solvent, then suspended in a 2.5-fold amount of solvent having the same temperature, filtered again and washed with a twofold amount of solvent having the same temperature. Solvent present in the soft paraffin wax and in the filtrate was removed by distillation according to the usual practice. The characteristics of the soft paraffin wax obtained according to Example 2 are shown in Table 8. The product was obtained with a yield of 42 % based on the weight of the starting mixture. Table 7 Characteristics of the starting substance used in Example 2 Density at 70 C 0.810 Pour point, °C 38 Viscosity at 100°C, mm /s 5.76 Oil content, w/w% 22.7 Flash point (M) , °C 235 Boiling points at vacuum distillation (recalculat¬ ed for atmospheric pressure) , initial, °C 335 end, °C 526 Colour 3.5 Refractive index, 70 °C 1.4481 Table 8 Characteristics of soft paraffin wax according to Example 2 Pour point, U C 45.8 Oil content, w/w% 4.1 Viscosity at 100°C, mm 2 /s 5.10 Penetration at 25 °C, 0.1 137 mm n-Alkanes, w/w% 47.5 Nonnormal alkanes, w/w% 52.5 Mean molecular weight 419 Example 3 28 w/w% of foot oil II, 22 w/w% of foot oil III and 50 w/w% of petrolatum oil were mixed. The characteristics of the mixture are shown in Table 9. Table 9 Characteristics of the starting mixture used in Example 9 Density at 70 C 0 . 821 Pour point , °C 44 . 5 Viscosity at 100°C, mm 2 /s 5.93 Oil content, w/w% 25.9 Flash point, °C 238 Boiling points at vacuum distillation (recalculat¬ ed for atmospheric pressure) , initial °C 333 end, °C 567 Colour 3 Refractive index, 70 °C 1.4529 The starting mixture was diluted with a 11-fold amount of warm solvent containing 44 % by volume of acetone, 6 % by volume of methyl ethyl ketone, 48 % by volume of toluene and 2 % by volume of water. The solution was cooled to -4 °C, and filtered. The filter cake was washed with a threefold amount of solvent, suspended in a 3.5-fold amount of solvent at -4 °C, filtered again and washed with an equal amount of solvent. Solvent was removed then as described in Examples 1 and 2. The plastic paraffin wax was obtained with a yield of 57% calculated for the amount of the starting substance. Its characteristics are shown in Table 10. Table 10 Characteristics of product according to Example 3 Pour point, U C 48.1 Oil content, w/w% 2.1 Viscosity at 10 °C, mm /s 5.72 Penetration at 25 °C, 0.1 110 mm n-w/wlkanes, w/w% 43.2 Nonnormal alkanes, w/w% 56.8 Example 4 Four foot oils were mixed: 12 w/w% of foot oil I, 41 w/w% of foot oil II, 31 w/w% of foot oil III and 48 w/w% of petrolatum oil. The characteristics of the mixture are shown in Table 11. Table 11 Characteristics of base material according to Example 4 Density at 70 U C 0.801 Pour point, °C 36 Viscosity at 100°C, mm /s 4.83 Oil content, w/w% 24.8 Flash point, °C 217 Boiling point at vacuum distillation (recalculat¬ ed for atmospheric pressure) , initial, °C 302 end, °C 518 Colour 3.5 Refractive index, 70 °C 1.4416 The warm starting mixture was diluted with a 5.8-fold amount of a solvent containing 29 % by volume of methyl ethyl ketone, 4 % by volume of acetone, 65 % by volume of toluene and 2 % by volume of water. Mixing was made at 121 ' ' C in a closed apparatus, then the solution was cooled to a final crystallization temperature of -17 °C and filtered. The filter cake on the rotary vacuum filter was washed with a 1.5-fold amount of cold solvent, suspended in a twofold amount of solvent at -17 ^ C , filtered again and washed with a 2.5-fold amount of solvent. - l\ - Solvent was removed from the soft paraffin wax and from the filtrate by distillation according to the usual practice. The characteristics of the soft paraffin wax are shown in Table 12. Table 12 Characteristics of product according to Example 4 Pour point, "C 42.1 oil content, w/w% 1.7 Viscosity at 100°C, mm 2 /s 5.03 Penetration at 25 °C, 0.1 39 mm n-Alkanes, w/w% 60.2 Nonnormal alkanes, w/w% 39.8 Example 5 The starting mixture for the production of soft paraffin wax was composed of foot oils obtained from redistilled slacks and of foot oils obtained directly in the de-oiling of slacks from refined light and middle vacuum fractions. The composition was as follows: 27 w/w% of redistilled petrolatum oil, 11 w/w% of foot oil III, 6 w/w% of foot oil II, 21 w/w% of light foot oil and 35 w/w% of middle foot oil. The characteristics of the mixture are shown in Table 13. Table 13 Characteristics of foot oil mixture used in Example 5 Density at 70 U C 0.819 Pour point, °C 37 Viscosity at 100°C, mm /s 4.91 Oil content, w/w% 20.2 Flash point, °C 221 Boiling point at vacuum distillation (recalculat¬ ed for atmospheric pressure) , initial, °C 306 end, °C 522 Colour 4.0 Refractive index, 70 °C 1.4548 The starting mixture was diluted with a 7.5-fold amount of a solvent containing 52 % by volume of acetone, 4 % by volume of methyl ethyl ketone, 43 % by volume of toluene and 1 % by volume of water. Mixing was made at 116 °C in a closed apparatus, then the solution was cooled to the final crystallization temperature of -11 °C, which was also the temperature of filtration. The filter cake on the rotary vacuum filter was washed with an equal amount - 23 - of cold solvent, suspended in a twofold amount of solvent at -17 °C , filtered again and washed with a 1.5-fold amount of solvent. Solvent was removed from the soft paraffin wax and from the filtrate by distillation according to the usual practice. The soft paraffin wax was obtained with a yield of 49 % calculated for the weight of the starting mixture. Its characteristics are shown in Table 14. Table 14 Characteristics of product according to Example 5 Pour point, U C 43.7 Oil content, w/w% 3.7 Viscosity at 100°C, mm 2 /s 4.79 Penetration at 25 °C, 0.1 137 mm n-Alkanes, w/w% 58.1 Nonnormal alkanes, w/w% 41.9 Mean molecular weight 401

Claims: What we claim is: 1. A process for the production of a high penetration - minimum value 30 0.1 mm at 25 °C - and low viscosity - maximum value 10 m 2 /s - paraffin wax by redistilling a mixture of slack waxes and de-oiling the resulting individual fractions I, II, III and IV (the residue) to obtain foot oil I, foot oil II, foot oil III and foot oil IV, characterised in tha t at least two of the resulting foot oils are mixed with one another and optionally with up to 65 w/w % of a foot oil resulting from non-redistilled slack waxes to obtain a final mixture containing at least 15 w/w % of foot oil IV (petrolatum oil) , and this mixture is de-oiled in a manner known per se in an apparatus used for de-oiling of slack waxes with a solvent mixture comprising ketones and aromatics with a ketone content of not less than 29 % by volume, wherein dissolution and mixing are performed at temperatures not higher than 125 °C and crystallization is performed at a final cooling temperature not less than -17 °C. 2. A process as claimed in claim 1, character¬ ised in tha t the solvent-containing filter cake obtained at the de-oiling of foot oils is once or twice repeatedly resuspended in 5.5 to 23.5 parts by volume of cold solvent and/or filtrate, calculated for one part by volume of the filter cake, then the suspension is filtered, and the filter cake is washed. 3. A paraffin wax with a viscosity at 100°C of 3.2-10.0 mm /sec, a pour point of 42-59°C, a penetration at 25°C of 30-170 0.1 mm, an oil content of less than 4.2 w/w% and a nonnormal alkane content, as measured by gas chromatography, of at least 37 w/w%, characterised in tha t it is prepared according to the process of claim 1.

Inventors: BORSA GYOERGY, CZAGLER ISTVAN, FASI MATYAS, FODOR BARNABAS, LOVEY JOSZEF, TOTH ERNO, BORSA, GYOERGY, CZAGLER, ISTVAN, FASI, MATYAS, FODOR, BARNABAS, LOVEY, JOSZEF, TOTH, ERNO
Applicants: MOL MAGYAR OLAJ & GAZIPARI RT, MOL MAGYAR OLAJ- ES GAZIPARI RESZVENY-TARSASAG
Application year: 1996
Main classification: C10G73
IPC codes: C10G73