Low-phosphorus dimer acid and preparation method thereof

Abstract

The invention discloses low-phosphorus dimer acid and a preparation method thereof. The invention provides a method for purifying phosphorus-containing crude dimer acid, which comprises the following steps: washing the phosphorus-containing crude dimer acid with water, and carrying out hot water treatment on the washed crude dimer acid at the temperature of 170 DEG C or above. According to the method disclosed by the invention, the phosphorus-containing crude dimer acid can be efficiently purified, and the obtained dimer acid product has extremely excellent purity and performance.

Description

Technical Field

[0001] This application belongs to the chemical industry field, and specifically relates to a dimer acid with low phosphorus content and a preparation method thereof. Background Art

[0002] Dimer acid refers to dimer fatty acid, which is usually prepared by the dimerization reaction of unsaturated (such as straight-chain) fatty acids (including monobasic fatty acids or polybasic fatty acids, such as oleic acid, linoleic acid, linolenic acid, etc.) containing at least one carbon-carbon double bond in the molecule. Dimer acid is a transparent light yellow or light brown viscous liquid at room temperature, has good thermal stability, does not coagulate at -20°C, has a certain fluidity and good transparency. It does not boil at 250°C, and no gel precipitation will occur in the system. When heated in air, the color will become significantly darker.

[0003] Dimer acid has a wide range of applications as a basic chemical raw material, such as synthesizing polyamide resins, synthesizing dimer acid polyester polyols, and additives in metalworking fluids. Especially high-viscosity dimer acid has excellent performance in the applications of synthesizing polyamide ink resins and as corrosion inhibitors, adhesives, and lubricants in metalworking fluids. There is a great demand for high-purity and high-quality dimer acid.

[0004] The existing dimer acid preparation processes usually start with raw materials containing various olefinic unsaturated fatty acids (such as vegetable oil fatty acids obtained from various vegetable oils, which are usually mixtures of various olefinic unsaturated fatty acids with different chain lengths), carry out catalytic dimerization reaction and acidification on them, and then carry out various subsequent separation, treatment, and purification operations on the obtained crude dimer acid. However, all these existing technology processes have many defects without exception, such as low conversion rate, low yield and insufficient content of dimer acid products, long production cycle, poor production efficiency, poor product color and quality, and being not environmentally friendly. And a very serious problem among them is that the dimer acid prepared by the existing technology processes often contains a relatively high content of impurities, especially a relatively high content of phosphorus impurities. For example, in order to achieve an ideal preparation of dimer acid in the existing technology processes, acidifying agents are often required. Compared with other acidifying agents, phosphoric acid has the advantages of mildness, non-volatility, moderate acidity, being friendly to equipment, easy filtration and separation of the acidification product phosphate, and good color of the product prepared using phosphoric acid, and has become the preferred acidifying agent. In addition, in this acidification step, phosphoric acid must be added in excess, otherwise the metal impurities cannot be completely removed, which will lead to defects such as deepening of the product color and poor subsequent filtration efficiency. All the above reasons result in the inevitable inclusion of a large amount of phosphorus (in the forms of phosphoric acid, phosphate radicals, etc.) impurities in the dimer acid. These phosphorus impurities will seriously affect the performance of the dimer acid, may make it completely unsuitable for some downstream uses, and may also cause serious negative impacts on the processing processes and equipment of downstream uses.

[0005] To overcome the above problems, researchers in this field have invested a great deal of funds and energy in research over the past few decades and made improvements from various different perspectives. For example, improving the catalyst and process conditions for the dimerization reaction, and treating the crude dimer acid obtained from the dimerization reaction with various separation and purification steps. However, these research results cannot truly and effectively solve the above problems. For example, while leading to increased complexity of the production process and significantly increased production costs, the removal effect of various impurities such as phosphorus is not satisfactory, and the obtained dimer acid product still has an unacceptable high impurity (such as phosphorus) content; it may further lead to further deterioration of the performance and industrial applicability of the dimer acid.

[0006] Therefore, there is a strong desire to develop a novel technology to purify phosphorus-containing crude dimer acid with a simple and low-cost process, especially to effectively remove the phosphorus impurities therein to obtain low-phosphorus dimer acid with excellent purity and performance. Summary of the Invention

[0007] Through extensive research, the inventors of the present application unexpectedly developed a novel process that can meet the above requirements and successfully solved the long-standing technical problems in the prior art. The first aspect of the present application provides a method for purifying phosphorus-containing crude dimer acid, and the method includes the following steps:

[0008] Step A: Washing the phosphorus-containing crude dimer acid with water;

[0009] Step B: Subjecting the washed crude dimer acid to hydrothermal treatment at a temperature above 170 °C;

[0010] Based on the total weight of the low-phosphorus dimer acid, the phosphorus content in the low-phosphorus dimer acid is less than 3 ppm.

[0011] According to a preferred embodiment of the first aspect of the present application, based on the total weight of the low-phosphorus dimer acid, the phosphorus content in the low-phosphorus dimer acid is less than 2 ppm. According to another preferred embodiment of the first aspect of the present application, based on the total weight of the low-phosphorus dimer acid, the phosphorus content in the low-phosphorus dimer acid is less than 1 ppm.

[0012] According to an embodiment of the first aspect of the present application, before the step A, the phosphorus-containing crude dimer acid is obtained through the following steps: causing an unsaturated fatty acid containing at least one carbon-carbon double bond to undergo a dimerization reaction in the presence of a catalyst and a cocatalyst, and then acidifying with an acidifying agent to obtain crude dimer acid; the acidifying agent includes phosphoric acid. According to an embodiment of the first aspect of the present application, the method of the present invention further includes performing solid-liquid separation on the material after the above dimerization reaction.

[0013] According to an embodiment of the first aspect of the present application, before performing step A, based on the total weight of the crude dimer acid, the phosphorus content in the crude dimer acid is 10 ppm or more. According to a preferred embodiment of the first aspect of the present application, before performing step A, based on the total weight of the crude dimer acid, the phosphorus content in the crude dimer acid is 50 ppm or more. According to a preferred embodiment of the first aspect of the present application, before performing step A, based on the total weight of the crude dimer acid, the phosphorus content in the crude dimer acid is 100 ppm or more.

[0014] According to an embodiment of the first aspect of the present application, in step B, the hot water treatment is carried out at a temperature of 180 - 300 °C. According to an embodiment of the first aspect of the present application, in step B, the weight ratio of the crude dimer acid to water is 10:1 or more, preferably 4:1 or more, and more preferably 1:1 or less. According to an embodiment of the first aspect of the present application, the duration of the hot water treatment is 1 hour or more.

[0015] According to an embodiment of the first aspect of the present application, the unsaturated fatty acid containing at least one carbon-carbon double bond is a straight-chain or branched-chain C3 - C22 aliphatic monocarboxylic to hexacarboxylic acid containing at least one carbon-carbon double bond.

[0016] According to an embodiment of the first aspect of the present application, the catalyst is selected from one or more of the following: clay, nano-calcium.

[0017] According to an embodiment of the first aspect of the present application, the cocatalyst is selected from one or more of the following: lithium carbonate, lithium hydroxide.

[0018] According to an embodiment of the first aspect of the present application, the acidifying agent is phosphoric acid.

[0019] According to an embodiment of the first aspect of the present application, the reaction temperature of the dimerization reaction is 180 - 260 °C. According to an embodiment of the first aspect of the present application, the reaction time of the dimerization reaction is 1 - 16 hours. According to an embodiment of the first aspect of the present application, based on 100 parts by weight of the unsaturated fatty acid containing at least one carbon-carbon double bond, the amount of the catalyst used is 0.1 - 16 parts by weight, the amount of the cocatalyst used is 0.01 - 0.5 parts by weight, and the amount of the acidifying agent used is 0.5 - 6 parts by weight.

[0020] According to an embodiment of the first aspect of the present application, the solid-liquid separation is carried out as follows: mixing the crude dimer acid and water at a weight ratio of 5:1 to 1:2, washing the crude dimer acid, and separating the crude dimer acid from water after washing.

[0021] According to an embodiment of the first aspect of the present application, the water washing is carried out at a temperature of 50 - 100°C, preferably 80 - 99°C, more preferably 85 - 95°C.

[0022] According to an embodiment of the first aspect of the present application, after step B, step C is further included: distilling the crude dimer acid that has undergone heated water treatment. According to a preferred embodiment of the first aspect of the present application, the crude dimer acid that has undergone heated water treatment is subjected to two distillation treatments. The first distillation treatment removes water and low-boiling fractions from the crude dimer acid, and the second distillation treatment removes monomeric acid from the crude dimer acid.

[0023] According to an embodiment of the first aspect of the present application, the first distillation treatment is carried out in a thin-film evaporator, and the second distillation treatment is carried out in a molecular evaporator.

[0024] According to an embodiment of the first aspect of the present application, in all steps of the method, inorganic acids other than phosphoric acid are not added.

[0025] The second aspect of the present application provides a low-phosphorus dimer acid obtained by the method of any one of the embodiments in the first aspect of the present invention.

[0026] According to an embodiment of the second aspect of the present application, based on the total weight of the low-phosphorus dimer acid, the phosphorus content in the low-phosphorus dimer acid is less than 3 ppm. According to a preferred embodiment of the second aspect of the present application, based on the total weight of the low-phosphorus dimer acid, the phosphorus content in the low-phosphorus dimer acid is less than 2 ppm. According to a more preferred embodiment of the second aspect of the present application, based on the total weight of the low-phosphorus dimer acid, the phosphorus content in the low-phosphorus dimer acid is less than 1 ppm.

[0027] In the following specific implementation part, the technical solution of the present application will be described in conjunction with the accompanying drawings. Description of the Drawings

[0028] Figure 1 Shows a flow chart of a purification method according to an embodiment of the present application;

[0029] Figures 2A to 2C Shows the water washing step of the method of the present invention;

[0030] Figure 3 Shows the heated water treatment step of the method of the present invention. Specific Embodiments

[0031] The "ranges" disclosed herein are in the form of a lower limit and an upper limit. There can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges that can be defined in this way are inclusive and combinable, that is, any lower limit can be combined with any upper limit to form a range. For example, ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, and ranges of 60 - 110 and 80 - 120 are understood to be contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5.

[0032] In the present invention, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations.

[0033] In the present invention, if there is no special instruction, all the embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution.

[0034] In the present invention, if there is no special instruction, all the technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0035] In the present invention, if there is no special instruction, all the steps mentioned herein can be carried out sequentially or randomly, but preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0036] In the present invention, if there is no special instruction, the "including" mentioned herein means open-ended, and can also be closed-ended. For example, the "including" can mean that other components not listed can also be included, or can only include the listed components.

[0037] In the present invention, when describing the spatial relationship of a specific component or object relative to other components or objects, the terms "inside", "outside", "above", "below", etc. are used to indicate that the former is located inside, outside, above, or below the latter, and the two can be in direct contact, or separated by a certain distance or separated by a third component or object.

[0038] Figure 1 Shows a flowchart according to an embodiment of the present application.

[0039] According to an embodiment of the present application, the raw material for synthesizing dimer acid is a C3-C22 aliphatic mono- to hexacarboxylic acid containing at least one carbon-carbon double bond. For example, the raw material unsaturated carboxylic acid may contain 1-4 carbon-carbon unsaturated double bonds, preferably 1-2 carbon-carbon unsaturated double bonds; the number of carbon atoms in the raw material unsaturated carboxylic acid molecule may be C4-C20, such as C6-C18, or C12-C18; the raw material unsaturated carboxylic acid may be a mono-, di-, tri-, or tetra-carboxylic acid, preferably a mono- or di-carboxylic acid. Examples of the raw material unsaturated carboxylic acid may include oleic acid, linoleic acid, linolenic acid, etc. The raw material used in the present invention may be a mixture containing a variety of the above unsaturated carboxylic acids, such as vegetable oil acids derived from various vegetable oils (for example, vegetable oil acids obtained by hydrolysis or transesterification of vegetable oils), such as cottonseed oil acid, soybean oil acid, tall oil acid, palmitoleic acid, castor oil acid, peanut oil acid, sunflower seed oil acid, etc.

[0040] According to an embodiment of the present application, the "phosphorus-containing crude dimer acid" which is the object of purification in the present invention is obtained by subjecting the above raw materials to a dimerization reaction in the presence of a catalyst and a cocatalyst. The catalyst is selected from clay and nano-calcium; preferably clay. The nano-calcium refers to calcium carbonate and the like with particles in the nano-scale or close to the nano-scale. The cocatalyst is selected from lithium carbonate and lithium hydroxide, preferably lithium carbonate.

[0041] According to an exemplary embodiment of the present application, the reaction temperature of the dimerization reaction is 180-260 °C, preferably 200-250 °C, more preferably 220-240 °C. The dimerization reaction can be carried out in a closed high-pressure reactor. The reaction duration of the dimerization reaction is 1-16 hours, preferably 2-6 hours, more preferably 3-5 hours.

[0042] According to an exemplary embodiment of the present application, based on 100 parts by weight of the unsaturated fatty acid containing at least one carbon-carbon double bond, the dosage of the catalyst is 0.1-16 parts by weight, preferably 1-12 parts by weight, more preferably 4-8 parts by weight. Based on 100 parts by weight of the unsaturated fatty acid containing at least one carbon-carbon double bond, the dosage of the cocatalyst is 0.01-0.5 parts by weight, preferably 0.1-0.4 parts by weight, more preferably 0.2-0.3 parts by weight.

[0043] According to an embodiment of the present application, as Figure 1 shown, after the dimerization reaction is completed, an acidifying agent (preferably excessive phosphoric acid) is added to the reaction-generated material, and after the acidification reaction, crude dimer acid is obtained. According to an exemplary embodiment of the present application, the acidifying agent includes phosphoric acid, and its concentration can be 10-90% by weight, such as 40-88% by weight, or 60-85% by weight. According to an exemplary embodiment of the present application, based on 100 parts by weight of the alkane fatty acid containing at least one carbon-carbon double bond, the dosage of the acidifying agent is 0.5-6 parts by weight, such as 0.8-5 parts by weight, or 1-4 parts by weight, or 2-3 parts by weight. According to another embodiment of the present application, the temperature of the acidification reaction is 50-200 °C, preferably 70-150 °C, more preferably 80-100 °C. According to another embodiment of the present application, the duration of the acidification reaction is 20 minutes to 12 hours, or 30 minutes to 8 hours, or 40 minutes to 2 hours.

[0044] According to a preferred embodiment of the present application, in the above dimerization reaction, only the raw materials and reagents described above are used, and no other components that may introduce impurities are added, such as saturated organic carboxylic acids (such as formic acid, oxalic acid, acetic acid, oxalic acid, etc.), metal cations other than the catalyst (such as aluminum salts, calcium salts, iron salts, magnesium salts, etc.).

[0045] According to an embodiment of the present application, after the dimerization / acidification reaction, the crude dimer acid obtained from the dimerization / acidification reaction is subjected to solid-liquid separation to remove the mixed solid components therein. The solid-liquid separation can be carried out by, for example, conventional filtration, suction filtration, pressure filtration, etc. The solid-liquid separation step is an "optional" step, that is to say, when there are indeed solid impurities in the crude dimer acid obtained from the dimerization reaction that need to be removed, this step can be carried out; and when there are no solid impurities in the crude dimer acid obtained from the dimerization reaction, this step can be omitted. According to a preferred embodiment of the present application, a positive pressure filter is used for solid-liquid separation.

[0046] According to an embodiment of the present application, as Figure 1As shown, step A is carried out after the above operations. Specifically, in step A, the crude dimer acid is washed with water. For example, the crude dimer acid can be fully mixed with water, and after washing, the crude dimer acid and the aqueous phase are separated by an oil / water phase separation device (such as a separating funnel, etc.). Figures 2A to 2C shows the water washing process carried out in the laboratory, where Figure 2A shows adding deionized water to the crude dimer acid, Figure 2B shows the full mixing of the crude dimer acid and deionized water, and Figure C shows the oil / water phase stratification after water washing, and then the aqueous phase is removed with a separating funnel.

[0047] For another example, after mixing the crude dimer acid with water (preferably deionized water), centrifugation can also be carried out to promote oil / water phase separation.

[0048] According to an exemplary embodiment of the present application, in step A, the crude dimer acid and water are mixed at a weight ratio of 5:1 to 1:2, preferably at a weight ratio of 3:1 to 1:1, and more preferably at a weight ratio of 2:1. According to another exemplary embodiment of the present application, in step A, mixing, water washing and liquid separation are carried out under a temperature condition of 50 - 100 °C, preferably 80 - 99 °C, and more preferably 85 - 95 °C.

[0049] According to one embodiment of the present application, as Figure 1 shown in the flowchart, the heat treatment with water of the crude dimer acid after water washing is carried out in step B. For example, the heat treatment with water may include mixing the crude dimer acid after water washing with water (such as deionized water), and then carrying out the treatment at a temperature above 170 °C, preferably 170 - 300 °C, and more preferably 170 - 220 °C. According to an exemplary embodiment of the present application, the duration of the heat treatment with water can be 1 hour or more, preferably 1 - 24 hours, preferably 2 - 16 hours, and more preferably 2 - 3 hours. According to an exemplary embodiment of the present application, in the heat treatment with water, the weight ratio of the crude dimer acid to water is 10:1 or more, preferably 4:1 or more, and from the perspective of cost, preferably 1:2 or less, and more preferably 1:1 or less; most preferably 10:3 to 10:7. According to another exemplary embodiment of the present application, the heat treatment with water is carried out in a closed high-pressure reaction kettle. For example, the Figure 3 shown high-pressure reaction kettle can be used.

[0050] According to one embodiment of the present application, after the above heat treatment with water, the temperature can be lowered (such as to room temperature), the mixture of the crude dimer acid and water is allowed to stand and stratify, and then the lower aqueous phase is removed.

[0051] According to one embodiment of the present application, as Figure 1As shown in the flowchart, in step C, the crude dimer acid after being processed in step B is distilled one or more times, preferably twice. According to an exemplary embodiment of the present application, the crude dimer acid after being processed in step B is first subjected to thin-film evaporation in a thin-film evaporator to remove the light fractions therein. Most of the light fractions are water, and in addition, it may also contain some light organic compounds, such as 2-nonene, 3-nonene, 4-nonene, 5-decene, undecene, dodecene, etc. Then it is distilled in a molecular evaporator to be separated into monomer fractions and dimer acid fractions. The monomer fractions are mainly monomer unsaturated fatty acids that have not undergone dimerization reaction, such as monomer phytic acid.

[0052] According to an embodiment of the present application, the temperature of the thin-film evaporator is 100 - 200 °C, preferably 170 - 190 °C, and the pressure is 30 - 200 mbar, preferably 100 - 160 mbar. According to another embodiment of the present application, the temperature of the molecular evaporator is 230 - 250 °C, preferably 230 - 235 °C, and the pressure is 1 - 100 Pa, preferably 30 - 80 Pa.

[0053] According to a preferred embodiment of the present application, in all steps of the present invention, only the raw materials and reagents described above are used, without adding other components that may introduce impurities, such as saturated organic carboxylic acids (such as formic acid, oxalic acid, acetic acid, oxalic acid, etc.), metal cations other than catalysts (such as aluminum salts, calcium salts, iron salts, magnesium salts, etc.).

[0054] According to an embodiment of the present application, the crude dimer acid with a large amount of phosphorus impurities can be very effectively purified by the method of the present invention, so that the purified dimer acid product has a very low phosphorus content, for example, reducing the phosphorus content in the crude dimer acid by one order of magnitude, or two orders of magnitude, or more. For example, the phosphorus content in the dimer acid purified by the method of the present invention can be < 3 ppm, preferably < 2 ppm, preferably < 1 ppm, preferably < 0.5 ppm, more preferably < 0.3 ppm, and most preferably lower than the detection limit of the detection instrument / detection method.

[0055] In the present invention, the phosphorus content in the dimer acid product can be detected by known standard methods. The national standard method GB / T 5537 - 2008 can be adopted. In this method, first, the sample is burned to generate phosphorus pentoxide from the phosphorus therein, which is converted into phosphoric acid with hot hydrochloric acid, then converted into sodium phosphomolybdate with sodium molybdate, and then reduced to molybdenum blue with hydrazine sulfate, and finally, the absorbance of molybdenum blue is detected at a wavelength of 650 nm with a spectrophotometer, and the phosphorus content can be determined by comparing with the standard curve.

[0056] The method of the present invention solves the problems existing in the prior art through delicate design of each step. For example, it realizes the efficient synthesis of dimer acid, achieves a very high yield of dimer acid, has a short process time, simple process steps and low cost. There is no need to additionally add high-cost impurity removal reagents, but high-temperature water treatment is used to achieve efficient impurity removal, avoiding the content of other impurities caused by the additionally added impurity removal reagents. The phosphorus content in the dimer acid product can be significantly reduced, the quality of the dimer acid product is significantly improved, and the downstream applicability and economic benefits are greatly improved.

[0057] It should be emphasized here that only some specific embodiments of the present invention are described below, and the protection scope of the present invention is not limited to these specific embodiments. The protection scope of the present invention is defined by the claims of the present invention, and may include any technical solutions within the scope of the claims, including but not limited to further improvements and substitutions of these specific embodiments.

[0058] Examples

[0059] In the following examples, the preferred embodiments of the present invention are specifically listed, but it should be understood that the protection scope of the present application is not limited thereto. Any equivalent transformation or modification made according to the essence of the present application should be covered within the protection scope of the present application.

[0060] The raw material vegetable oil acid used in the following examples is soybean oil acid purchased from Wilmar Renewable Resources (Tianjin) Co., Ltd., and its main components are palmitic acid: 2.3% by weight, stearic acid: 4.5% by weight, oleic acid: 30.4% by weight, linoleic acid: 55.8% by weight, linolenic acid: 2.4% by weight, arachidic acid: 0.4% by weight; the clay used in the following examples is Sun's clay purchased from Anji Sun's Bentonite Factory; the rest of the reagents are commercially available analytical pure reagents; the water used is deionized water.

[0061] The thin-film evaporator used in the following examples is the BWG-7 type thin-film evaporator produced by Nanjing Zhibote Technology Co., Ltd.;

[0062] The molecular distillation apparatus used is the BOG-15 type molecular distillation apparatus produced by Nanjing Zhibote Technology Co., Ltd.;

[0063] The composition of the product is characterized by using an Agilent 1260 Infinity high-performance liquid chromatograph produced by Agilent Technologies;

[0064] The viscosity of the product is measured at 25 °C using a DVNXRV type rotational viscometer produced by Brookfield Engineering Laboratories, Inc., and the unit is mPa·S;

[0065] The dimerization reaction in the following examples was carried out in an HT500KJ type quick-opening mechanical reaction kettle manufactured by Shanghai Huotong Experimental Instrument Co., Ltd.; the solid-liquid separation of the crude dimer acid was carried out using a KN-100-500mL stainless steel jacketed positive pressure filter produced by Haining Kenuo Filtration Equipment Co., Ltd.

[0066] Example 1

[0067] Add 5000 grams of soybean oleic acid, 400 grams of clay, 10.0 grams of lithium carbonate and 50 grams of deionized water to a 10L high-pressure reaction kettle, start the stirring device to make the materials in the reaction kettle evenly mixed, then seal the high-pressure reaction kettle, heat the reaction kettle to 240°C and maintain at this temperature for 3 hours. After the reaction is completed, cool the reaction kettle to 90°C, add 150 grams of phosphoric acid with a concentration of 85% by weight to the reaction materials and mix well, and acidify the reaction materials at 90°C for 1h. Then use a stainless steel jacketed positive pressure filter to filter the reaction materials.

[0068] The viscosity of the obtained crude dimer acid at 25°C was measured to be 1047 mPa·S, and the phosphorus content was 125 ppm. This crude dimer acid was not only used in the heating water treatment step of Example 1, but also used in the subsequent purification experiments of Examples 2-5 and Comparative Examples 2-4.

[0069] Weigh 100 grams of the crude dimer acid prepared in the above steps, and as Figures 2A to 2C shown, mix it well with 50 grams of deionized water heated to 90°C in a 250ml separating funnel, keep it warm at 90°C and let it stand for 10 min, then separate and drain the lower aqueous phase. Pour the upper oil phase into the Figure 3 shown reaction kettle, add another 30 grams of deionized water and mix, treat the mixture at a temperature of 180°C for 3 hours, then cool the mixture to 90°C, transfer the oil-water mixture to a separating funnel, keep it warm at 90°C and let it stand for 10 min, and separate and drain the lower aqueous phase after separation. The crude dimer acid treated by the above heating water treatment is fed into a thin-film evaporator at a flow rate of 3 mL / min, and the light-boiling substances are removed under the conditions of a temperature of 180°C and a pressure of 110 mbar, and finally fed into a molecular evaporator at a flow rate of 5 mL / min, and most of the monomeric acids are removed under the conditions of a temperature of 235°C and a pressure of 30 - 80 Pa.

[0070] The obtained dimer acid product is a yellowish-brown liquid, with a viscosity of 8030 mPa·S at 25°C, and the phosphorus content therein is 0.24 ppm.

[0071] Example 2

[0072] Weigh 100 g of the crude dimer acid prepared in Example 1 above, mix it thoroughly with 50 g of deionized water heated to 90 °C in a 250 ml separatory funnel, keep it warm at 90 °C and let it stand for 10 min, then separate the lower aqueous phase and drain it off. Pour the upper oil phase into a reaction kettle, add another 70 g of deionized water and mix. Treat the mixture at a temperature of 180 °C for 3 hours, then cool the mixture to 90 °C, transfer the oil-water mixture to a separatory funnel, keep it warm at 90 °C and let it stand for 10 min, and separate the lower aqueous phase and drain it off after separation. The crude dimer acid treated by the above heating and water treatment is fed into a thin-film evaporator at a flow rate of 3 mL / min, and the light-boiling components are removed under the conditions of a temperature of 180 °C and a pressure of 100 mbar. Finally, it is fed into a molecular distillation apparatus at a flow rate of 5 mL / min, and most of the monomeric acids are removed under the conditions of a temperature of 235 °C and a pressure of 30 - 80 Pa.

[0073] The dimer acid product obtained thereby is a yellowish-brown liquid with a viscosity of 8027 mPa·S at 25 °C, and the phosphorus content therein is 0.13 ppm.

[0074] Example 3

[0075] Weigh 100 g of the crude dimer acid prepared in Example 1 above, mix it thoroughly with 50 g of deionized water heated to 90 °C in a 250 ml separatory funnel, keep it warm at 90 °C and let it stand for 10 min, then separate the lower aqueous phase and drain it off. Pour the upper oil phase into a reaction kettle, add another 70 g of deionized water and mix. Treat the mixture at a temperature of 200 °C for 3 hours, then cool the mixture to 90 °C, transfer the oil-water mixture to a separatory funnel, keep it warm at 90 °C and let it stand for 10 min, and separate the lower aqueous phase and drain it off after separation. The crude dimer acid treated by the above heating and water treatment is fed into a thin-film evaporator at a flow rate of 3 mL / min, and the light-boiling components are removed under the conditions of a temperature of 180 °C and a pressure of 120 mbar. Finally, it is fed into a molecular distillation apparatus at a flow rate of 5 mL / min, and most of the monomeric acids are removed under the conditions of a temperature of 235 °C and a pressure of 30 - 80 Pa.

[0076] The dimer acid product obtained thereby is a yellowish-brown liquid with a viscosity of 8022 mPa·S at 25 °C, and the phosphorus content therein is not detected.

[0077] Example 4

[0078] Weigh 100 g of the crude dimer acid obtained in Example 1 above. Mix it thoroughly with 50 g of deionized water heated to 90 °C in a 250 ml separatory funnel. Keep it warm at 90 °C and let it stand for 10 min, then separate the lower aqueous phase and drain it off. Pour the upper oil phase into a reaction kettle, add another 20 g of deionized water and mix. Treat the mixture at a temperature of 180 °C for 3 hours, then cool the mixture to 90 °C. Transfer the oil-water mixture to a separatory funnel, keep it warm at 90 °C and let it stand for 10 min, then separate the lower aqueous phase and drain it off. The crude dimer acid treated by the above heat treatment with water is fed into a thin-film evaporator at a flow rate of 3 mL / min. Under the conditions of a temperature of 180 °C and a pressure of 120 mbar, the light-boiling substances in it are removed. Finally, it is fed into a molecular evaporator at a flow rate of 5 mL / min. Under the conditions of a temperature of 235 °C and a pressure of 30 - 80 Pa, most of the monomeric acids are removed.

[0079] The dimer acid product obtained thereby is a yellowish-brown liquid with a viscosity of 8018 mPa·S at 25 °C, and the phosphorus content therein is 2.03 ppm.

[0080] Example 5

[0081] Weigh 100 g of the crude dimer acid obtained in Example 1 above. Mix it thoroughly with 50 g of deionized water heated to 90 °C in a 250 ml separatory funnel. Keep it warm at 90 °C and let it stand for 10 min, then separate the lower aqueous phase and drain it off. Pour the upper oil phase into a reaction kettle, add another 30 g of deionized water and mix. Treat the mixture at a temperature of 180 °C for 2 hours, then cool the mixture to 90 °C. Transfer the oil-water mixture to a separatory funnel, keep it warm at 90 °C and let it stand for 10 min, then separate the lower aqueous phase and drain it off. The crude dimer acid treated by the above heat treatment with water is fed into a thin-film evaporator at a flow rate of 3 mL / min. Under the conditions of a temperature of 180 °C and a pressure of 110 mbar, the light-boiling substances in it are removed. Finally, it is fed into a molecular evaporator at a flow rate of 5 mL / min. Under the conditions of a temperature of 235 °C and a pressure of 30 - 80 Pa, most of the monomeric acids are removed.

[0082] The dimer acid product obtained thereby is a yellowish-brown liquid with a viscosity of 8024 mPa·S at 25 °C, and the phosphorus content therein is 0.86 ppm.

[0083] Comparative Example 1

[0084] Weigh 100 g of the crude dimer acid obtained in Example 1 above, mix it thoroughly with 50 g of deionized water heated to 90 °C in a 250 ml separatory funnel, keep it warm at 90 °C and let it stand for 10 min, then separate and drain the lower aqueous phase. Feed the above-mentioned crude dimer acid into a thin-film evaporator at a flow rate of 3 mL / min, and remove the light-boiling components therein under the conditions of a temperature of 180 °C and a pressure of 130 mbar. Finally, feed it into a molecular distillation apparatus at a flow rate of 5 mL / min, and remove most of the monomeric acids under the conditions of a temperature of 235 °C and a pressure of 30 - 80 Pa.

[0085] The dimer acid product obtained thereby is a yellowish-brown liquid, with a viscosity of 8029 mPa·S at 25 °C, and the phosphorus content therein is 13.62 ppm.

[0086] Comparative Example 2

[0087] Weigh 100 g of the crude dimer acid obtained in Example 1 above, mix it thoroughly with 120 g of deionized water heated to 90 °C in a 250 ml separatory funnel, keep it warm at 90 °C and let it stand for 10 min, then separate and drain the lower aqueous phase. Feed the above-mentioned crude dimer acid into a thin-film evaporator at a flow rate of 3 mL / min, and remove the light-boiling components therein under the conditions of a temperature of 180 °C and a pressure of 120 mbar. Finally, feed it into a molecular distillation apparatus at a flow rate of 5 mL / min, and remove most of the monomeric acids under the conditions of a temperature of 235 °C and a pressure of 30 - 80 Pa.

[0088] The dimer acid product obtained thereby is a yellowish-brown liquid, with a viscosity of 8027 mPa·S at 25 °C, and the phosphorus content therein is 5.27 ppm.

[0089] Comparative Example 3

[0090] Weigh 100 g of the crude dimer acid obtained in Example 1 above, mix it thoroughly with 50 g of deionized water heated to 90 °C in a 250 ml separatory funnel, keep it warm at 90 °C and let it stand for 10 min, then separate and drain the lower aqueous phase. Then mix it thoroughly with another 50 g of deionized water heated to 90 °C in a 250 ml separatory funnel, keep it warm at 90 °C and let it stand for 10 min, then separate and drain the lower aqueous phase again. Feed the crude dimer acid washed twice as above into a thin-film evaporator at a flow rate of 3 mL / min, and remove the light-boiling components therein under the conditions of a temperature of 180 °C and a pressure of 110 mbar. Finally, feed it into a molecular distillation apparatus at a flow rate of 5 mL / min, and remove most of the monomeric acids under the conditions of a temperature of 235 °C and a pressure of 30 - 80 Pa.

[0091] The dimer acid product obtained thereby is a yellowish-brown liquid, with a viscosity of 8036 mPa·S at 25 °C, and the phosphorus content therein is 3.44 ppm.

[0092] Comparative Example 4

[0093] Weigh 100 g of the crude dimer acid obtained in Example 1 above, mix it thoroughly with 50 g of deionized water heated to 90 °C in a 250 ml separating funnel, keep it warm at 90 °C and let it stand for 10 min, then separate and drain the lower aqueous phase. Pour the upper oil phase into a reaction kettle, add another 30 g of deionized water and mix. Treat the mixture at a temperature of 160 °C for 3 hours, then cool the mixture to 90 °C, transfer the oil-water mixture to a separating funnel, keep it warm at 90 °C and let it stand for 10 min, and separate and drain the lower aqueous phase after separation. The crude dimer acid treated by the above heat treatment with water is fed into a thin-film evaporator at a flow rate of 3 mL / min, and the light-boiling components are removed under the conditions of a temperature of 180 °C and a pressure of 110 mbar. Finally, it is fed into a molecular evaporator at a flow rate of 5 mL / min, and most of the monomeric acids are removed under the conditions of a temperature of 235 °C and a pressure of 30 - 80 Pa.

[0094] The dimer acid product obtained thereby is a yellowish-brown liquid with a viscosity of 8024 mPa·S at 25 °C, and the phosphorus content therein is 3.73 ppm.

[0095] From the comparison of Examples 1 - 5 and Comparative Examples 1 - 4 above, it can be seen that after omitting the heat treatment step with water from the method of the present invention in Comparative Examples 1 - 4, it is impossible to achieve excellent dimer acid quality and low P content as in Examples 1 - 4.

Claims

1. A method for purifying crude dimer acid containing phosphorus, the method comprising the following steps: Step A: washing the crude dimer acid containing phosphorus with water; Step B: performing hydrothermal treatment on the washed crude dimer acid, the hydrothermal treatment being carried out at a temperature above 170 °C; Based on the total weight of the low-phosphorus dimer acid, the phosphorus content in the low-phosphorus dimer acid is less than 3 ppm, preferably less than 2 ppm, more preferably less than 1 ppm.

2. The method according to claim 1, wherein Before the step A, the crude dimer acid containing phosphorus is obtained through the following steps: subjecting an unsaturated fatty acid containing at least one carbon-carbon double bond to a dimerization reaction in the presence of a catalyst and a cocatalyst, and then acidifying with an acidifying agent to obtain crude dimer acid; the acidifying agent includes phosphoric acid; and Optionally, performing solid-liquid separation on the material after the above dimerization reaction; preferably, before performing step A, based on the total weight of the crude dimer acid, the phosphorus content in the crude dimer acid is 10 ppm or more; preferably 50 ppm or more, more preferably 100 ppm or more.

3. The method according to claim 1, characterized in that In the step B: The hydrothermal treatment is carried out at a temperature of 180-300 °C; The weight ratio of the crude dimer acid to water is 10:1 or more, preferably 4:1 or more, preferably 1:1 or less; The duration of the hydrothermal treatment is 1 hour or more.

4. The method according to claim 2, wherein The unsaturated fatty acid containing at least one carbon-carbon double bond is a straight-chain or branched-chain C3-C22 aliphatic monocarboxylic acid to hexacarboxylic acid containing at least one carbon-carbon double bond; The catalyst is selected from one or more of the following: clay, nano-calcium; The cocatalyst is selected from one or more of the following: lithium carbonate, lithium hydroxide; The acidifying agent is phosphoric acid.

5. The method according to claim 2, characterized in that, The reaction temperature of the dimerization reaction is 180-260 °C; The reaction time of the dimerization reaction is 1-16 hours; Based on 100 parts by weight of the unsaturated fatty acid containing at least one carbon-carbon double bond, the amount of the catalyst used is 0.1-16 parts by weight, the amount of the cocatalyst used is 0.01-0.5 parts by weight, and the amount of the acidifying agent used is 0.5-6 parts by weight.

6. The method according to claim 2, wherein The solid-liquid separation is carried out by the following method: mixing the crude dimer acid and water at a weight ratio of 5:1 to 1:2, washing the crude dimer acid, and separating the crude dimer acid from water after washing; The washing is carried out at a temperature of 50-100 °C, preferably 80-99 °C, more preferably 85-95 °C.

7. The method according to claim 1, wherein After the step B, there is further included step C: performing distillation treatment on the crude dimer acid after hydrothermal treatment; preferably, performing two distillation treatments on the crude dimer acid after hydrothermal treatment, the first distillation treatment removing water and low-boiling fractions from the crude dimer acid, and the second distillation treatment removing monomeric acid from the crude dimer acid.

8. The method according to claim 7, wherein The first distillation treatment is carried out in a thin-film evaporator, and the second distillation treatment is carried out in a molecular evaporator.

9. The method according to any one of claims 1-8, characterized in that, In all steps of the method, no inorganic acid other than phosphoric acid is added.

10. A low-phosphorus dimer acid obtained by the method according to any one of claims 1-9, wherein, based on the total weight of the low-phosphorus dimer acid, the phosphorus content in the low-phosphorus dimer acid is less than 3 ppm, preferably less than 2 ppm, and more preferably less than 1 ppm.

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