Long-chain dibasic acid products and their refining processes

Abstract

The present invention discloses a long-chain dibasic acid product and a refining process thereof, wherein the refining process comprises: heating and melting a mixture containing a long-chain dibasic acid, and then performing a first distillation to obtain a first distillation product; mixing the first distillation product with an oxidant, reacting at a temperature not higher than 240° C., and further performing a second distillation, a third distillation, and other multiple distillation treatments to purify the long-chain dibasic acid. This process does not require the consumption of a large amount of acid, alkali, and solvent, and does not generate a large amount of waste liquid. Impurities are oxidized by oxidation treatment to change the boiling point or volatility of the impurities, and impurities that are difficult to remove by conventional evaporation technology are removed by combining multi-stage distillation. The long-chain dibasic acid product obtained by the present invention has good quality, high product yield, low ash content, and low impurity content. The long-chain dibasic acid product has broad application prospects, especially when applied to hot melt adhesives, the hot melt adhesive product obtained has good quality.

Description

Technical Field

[0001] The invention relates to a long-chain dibasic acid and a refining process thereof. Background Art

[0002] Long chain dicarboxylic acids (LCDA, DCn, n = 10-18) are important organic intermediates that are widely used in the fields of chemical industry, light industry, pesticides, medicine, new materials, etc. The extraction and purification technology of long chain dicarboxylic acids also affects the final industrial production cost of dicarboxylic acids. Therefore, the development of simple and efficient extraction and purification technology of dicarboxylic acids will promote the promotion and application of fermentation process technology.

[0003] In the existing scheme for extracting long-chain dibasic acids, a mixture containing long-chain dibasic acids is dissolved with alkali and then acidified to precipitate the long-chain dibasic acids. This often requires multiple alkali dissolution-acid precipitation, which consumes a large amount of alkali and acid. On the one hand, it has a great impact on the environment, and the mother liquor of crystallization is difficult to post-process due to its high salt content. On the other hand, this extraction method has a poor effect on removing pigments, and the obtained product has a dark color and a high impurity content.

[0004] And there is the method that uses multiple solvent recrystallization to extract long-chain dibasic acid, utilizes the difference of solubility to remove impurity, some impurities are similar to long-chain dibasic acid solubility, and the solubility gap is small between different long-chain dibasic acids, monoprotic acids, and unsaturated acids, therefore even if recrystallization is used repeatedly to purify long-chain dibasic acid, it is also difficult to fundamentally remove the impurities with similar solubility, and there are still some long-chain dibasic acids to dissolve in the solvent after recrystallization, bring the loss of yield, cause production cost height, and market is difficult to accept.And for the raw material with more impurities, crystallization is difficult to carry out, and such raw material is difficult to purify.In addition, organic solvent is flammable, volatile, poisonous, must have fireproof, explosion-proof, anti-toxic device during aftertreatment, organic solvent price is expensive, volatile and easy to lose, and cost is higher. Summary of the invention

[0005] One of the objects of the present invention is to provide a long-chain dibasic acid product.

[0006] The total acid content of the long-chain dibasic acid product is ≥97%, further ≥97.5%, such as 98.0% or more, 98.2% or more, or 98.5% or more.

[0007] The light transmittance of the long-chain dibasic acid product is ≥80%, further ≥85%, for example, 87% or more, 90% or more, 91% or more, or 94% or more.

[0008] The ash content of the long-chain dibasic acid product is ≤30 ppm, further ≤25 ppm, for example, below 20 ppm, below 17 ppm, below 15 ppm, below 13 ppm.

[0009] The nitrogen content of the long-chain dibasic acid product is ≤50 ppm, further ≤40 ppm, for example, below 35 ppm, below 30 ppm, below 28 ppm.

[0010] The unsaturated dibasic acid content of the long-chain dibasic acid product is ≤0.5%, further ≤0.35%, for example, below 0.3%, below 0.25%.

[0011] The saturated long-chain dibasic acid content of the long-chain dibasic acid product is ≥90%, further ≥91%, further ≥93%, further ≥94%, for example, above 95%, above 96%.

[0012] Furthermore, the long-chain dibasic acid product is used in hot melt adhesives.

[0013] Furthermore, the long-chain dibasic acid product is used to prepare hot melt adhesive.

[0014] Furthermore, the long-chain dibasic acid is prepared by any of the following methods.

[0015] The second object of the present invention is to provide a purification process for long-chain dibasic acids, which can extract and purify long carbon chain dibasic acids from a mixture containing long-chain dibasic acids.

[0016] The refining process comprises:

[0017] (1) heating and melting a mixture containing a long-chain dibasic acid, and then performing a first distillation, collecting a distillate, and obtaining a first distillation product;

[0018] (2) The first distillation product is mixed with an oxidant and reacted at a temperature not higher than 240° C. to obtain an oxidation product.

[0019] According to some embodiments of the present invention, the mixture containing long-chain dibasic acids includes but is not limited to: crude long-chain dibasic acids, the residue after most of the solvent is recovered from the recrystallization mother liquor of the crude long-chain dibasic acids, and long-chain dibasic acid precipitates accumulated in a long-chain dibasic acid wastewater treatment workshop.

[0020] According to some embodiments of the present invention, the long-chain dibasic acid is prepared by biological method. It is obtained by using alkanes, fatty acids and their derivatives as substrates and using microbial fermentation method. The microorganism can oxidize the terminal methyl groups of alkanes, fatty acids and fatty acid derivatives to carboxyl groups to generate long-chain dibasic acids.

[0021] According to some embodiments of the present invention, the long-chain dibasic acid is a saturated long-chain dibasic acid.

[0022] According to some embodiments of the present invention, the mixture comprising long-chain dibasic acids contains saturated long-chain dibasic acids.

[0023] Furthermore, the carbon number of the saturated long-chain dibasic acid is 10 to 18. Furthermore, both ends of the saturated long-chain dibasic acid have carboxyl groups. Furthermore, the molecular chain of the saturated long-chain dibasic acid is a straight chain, and its chemical formula is HOOC(CH2)mCOOH, where m is an integer selected from 8 to 16. It is abbreviated as DCn, where n is an integer selected from 10 to 18. For example, DC10 represents decacarbon dibasic acid, and DC18 represents octacarbon dibasic acid.

[0024] Furthermore, the saturated long-chain dicarboxylic acid is selected from one or a combination of the following: sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedicarboxylic acid, hexadecanedioic acid, heptadecanedioic acid, and octadecanedicarboxylic acid.

[0025] According to some embodiments of the present invention, the content of saturated long-chain dibasic acid in the mixture containing long-chain dibasic acid is 10 to 98 wt%, further 10 to 90 wt%, for example 20 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 70 wt%, 75 wt%, 80 wt%.

[0026] According to some embodiments of the present invention, the mixture containing long-chain dibasic acids contains unsaturated dibasic acids, and the content of unsaturated dibasic acids is 0.1-40wt%, further 1%-30%, for example 5%, 8%, 10%, 15%, 20%, 25%.

[0027] According to some embodiments of the present invention, the oxidant includes a neutral oxidant, an acidic oxidant, or a basic oxidant.

[0028] According to some embodiments of the present invention, the oxidant includes potassium permanganate, ozone, air, and more than 60 wt % nitric acid.

[0029] According to some embodiments of the present invention, the oxidation product is subjected to a second distillation, the distillate of the second distillation is collected to obtain a second distillation product, and then the second distillation product is subjected to a third distillation, the distillate of the third distillation is removed, and the remainder of the third distillation is collected to obtain a third distillation product.

[0030] According to some embodiments of the present invention, the oxidation product is directly subjected to a third distillation without undergoing a second distillation treatment, the distillate of the third distillation is removed, and the distillation residue is collected to obtain a third distillation product.

[0031] According to some embodiments of the present invention, the third distillation product is subjected to a fourth distillation, and the distillate is collected to obtain a fourth distillation product.

[0032] According to some embodiments of the present invention, in order to further purify the product, the fourth distillation product may be distilled N times. The N≥1. Specifically, the distillate after each distillation is used as the raw material for the next distillation until N distillations are completed, and the distillate after N distillations is collected to obtain the 4+Nth distillation product. In any distillation process, the vacuum degree is ≤100 Pa, and the temperature is 220-250° C., and further 180-280° C.

[0033] According to some embodiments of the present invention, the vacuum degree of the first distillation in step (1) is ≤100 Pa, further ≤80 Pa, such as 65 Pa or less, 50 Pa or less, 30 Pa or less, 15 Pa or less. The temperature of the first distillation is 180-280°C, further 180-260°C, such as 200°C, 210°C, 220°C, 230°C, 240°C, 250°C.

[0034] Furthermore, in step (2), the content of the oxidant is converted to 100 wt%, and the amount of 100 wt% of the oxidant used per 100 g of the first distillation product is 1 to 20 g, and can further be 1 to 10 g, for example, 3 g, 4 g, 5 g, 6 g, 7 g, 8 g, 9 g, 12 g, 15 g, 17 g.

[0035] When the oxidant is air, converting the content of the oxidant to 100% means converting the content of oxygen in the air to 100 wt %.

[0036] According to some embodiments of the present invention, the temperature of the (oxidation) reaction in step (2) is 140 to 240° C., further 160 to 220° C., for example 175° C., 180° C., 193° C., 195° C. The time for the (oxidation) reaction in step (2) is 0.5 to 6 h, further 0.5 to 3 h, for example 1 h, 1.5 h, 2 h, 2.5 h, 3.5 h, 4 h.

[0037] According to some embodiments of the present invention, the vacuum degree of the second distillation in step (2) is ≤100 Pa, further ≤80 Pa, such as 65 Pa or less, 50 Pa or less, 30 Pa or less, 15 Pa or less. The temperature of the second distillation is 180-280°C, further 180-260°C, such as 200°C, 220°C, 240°C.

[0038] According to some embodiments of the present invention, the vacuum degree of the third distillation is ≤100Pa, further ≤80Pa, such as 65Pa or less, 50Pa or less, 30Pa or less, 15Pa or less. The temperature of the third distillation is 150-240°C, further 150-220°C, such as 170°C, 180°C, 190°C, 200°C.

[0039] According to some embodiments of the present invention, the third distillation can be carried out by rectification, and its vacuum degree is ≤100Pa, further ≤80Pa, for example, 65Pa or less, 50Pa or less, 30Pa or less, 15Pa or less; its plate number is 2 to 24, further 3 to 12, for example, 4, 5, 6. The bottom temperature is 150 to 230°C, further 150 to 220°C, for example, 170°C, 180°C, 190°C, 200°C, 210°C. The top temperature is 120 to 195°C, further 120 to 190°C, for example, 140°C, 150°C, 160°C, 170°C, 175°C.

[0040] According to some embodiments of the present invention, the vacuum degree of the fourth distillation is ≤100 Pa, further ≤80 Pa, such as 65 Pa, 50 Pa or less, 30 Pa or less, 15 Pa or less. The temperature of the fourth distillation is 180-280°C, further 180-260°C, such as 200°C, 205°C, 215°C, 225°C, 240°C, 250°C.

[0041] According to some embodiments of the present invention, the fourth distillation can be carried out by rectification, and its vacuum degree is ≤100Pa, further ≤80Pa, for example, 65Pa or less, 50Pa or less, 30Pa or less, 15Pa or less. The number of plates is 3 to 24, further 3 to 12, for example, 4, 5, 6. The bottom temperature is 200 to 280°C, further 200 to 260°C, for example, 210°C, 220°C, 225°C, 230°C; the top temperature is 180 to 230°C, further 180 to 225°C, for example, 190°C, 195°C, 200°C, 205°C, 210°C.

[0042] According to some embodiments of the present invention, the remainder of the second distillation and the remainder of the fourth distillation are returned to the first distillation for recycling.

[0043] The distillate in the distillation or rectification process is the low boiling point substance, and the remainder of the distillation or rectification is the high boiling point substance.

[0044] The first distillation is used to remove most of the high-boiling-point substances and salts. The obtained fraction is mainly composed of saturated long-chain dibasic acids, and also contains a small amount of unsaturated acids, low-carbon chain acids, etc. Most of the high-boiling-point impurities such as inorganic salts, pigments, proteins, sugars, etc. remain in the distillation residue, but a small amount of impurities such as pigments may still exist in the distillate. At the same time, since the solubility of some impurities in the distillate is close to that of saturated long-chain dibasic acids, they cannot be removed by recrystallization or alkali dissolution followed by acidification and crystallization.

[0045] The introduction of an oxidant can oxidize easily oxidizable impurities, thereby changing their boiling point or volatility, while saturated long-chain dibasic acids are difficult to oxidize. For example, acids containing unsaturated bonds or non-acid impurities can be oxidized to break double bonds.

[0046] The second distillation is used to remove the residual oxidant after oxidation, and further remove high-boiling-point substances, including pigments, high-boiling-point substances generated after oxidation reaction, etc.

[0047] Furthermore, the third distillation can be used to remove low-boiling substances generated after the oxidation reaction, such as low-carbon chain compounds formed by molecular chain breakage after the oxidation reaction, as well as unsaturated acids and monobasic acid impurities. Further, the fourth distillation can be used to further remove high-boiling substances and purify the product.

[0048] According to some embodiments of the present invention, the refining process may further include a decolorization step, which may further improve product quality.

[0049] Specifically, any distillation product is contacted with a decolorant for decolorization. For example, the fourth distillation product is contacted with a decolorant for decolorization. The decolorization process may be, for example, passing the decolorized material through the decolorant and collecting the effluent as a decolorized product. For example, passing the decolorized material through the decolorant in a molten state. After the decolorization process, the decolorant is removed to obtain a decolorized material.

[0050] Decolorizing the vacuum distillation product in a molten state can reduce the energy consumption of heating and simplify the process.

[0051] According to some embodiments of the present invention, the amount of the decolorizing agent is 3-40wt%, further 5-30wt%, such as 7wt%, 20wt%, 25wt% of the material to be decolorized. The decolorizing temperature is 130-180°C, further 140-160°C, such as 170°C. The decolorizing time is 3-120min, further 5-60min, such as 10min, 15min, 20min, 45min, 75min, 100min.

[0052] According to some embodiments of the present invention, the decolorizing agent includes but is not limited to activated carbon, activated clay, diatomaceous earth, and bentonite.

[0053] The technical effects of the present invention are at least:

[0054] 1. This process is different from the traditional process of dissolving a long-chain dibasic acid with alkali and then acidifying and precipitating it, so it does not require the consumption of a large amount of acid and alkali. It is also different from the solvent recrystallization purification method that requires the consumption of solvent, so it does not produce a large amount of waste liquid.

[0055] 2. By adopting oxidation process combined with multi-stage distillation, impurities that are difficult to remove by conventional evaporation technology can be removed.

[0056] 3. The long-chain dibasic acid product has good quality, high product yield, low impurity content, and has broad application prospects, especially when used in hot melt adhesives, the hot melt adhesive products produced have good quality. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] The mixture containing long-chain dibasic acid includes but is not limited to: crude long-chain dibasic acid, the residue after recovering most of the solvent from the recrystallization mother liquor of crude long-chain dibasic acid, and long-chain dibasic acid precipitate accumulated in a long-chain dibasic acid wastewater treatment workshop.

[0059] For example: Extracting crude DCn from DCn fermentation broth:

[0060] Any fermentation broth of DC10 to DC18 is heated to 60 to 100° C., the bacteria are removed by centrifugation or membrane filtration, 0.05 to 5 wt % of activated carbon by volume of the obtained clear liquid is added for decolorization, the activated carbon is removed by filtration, the decolorized liquid is heated to 50 to 100° C., the pH is adjusted to 2 to 5 for acidification and crystallization, and solid-liquid separation is performed to obtain a crude product of DC10 to DC18.

[0061] Long-chain dibasic acid fermentation broth refers to a fermentation broth obtained by a method of fermenting alkanes, fatty acids and their derivatives using microorganisms as substrates. The microorganism can oxidize the terminal methyl groups of alkanes, fatty acids and fatty acid derivatives to carboxyl groups to generate long-chain dibasic acids. The microorganism can be, for example, Candida.

[0062] The recrystallization refining process of DC10-DC18 crude products includes:

[0063] The crude product of DC10-DC18 is recrystallized with an acetic acid solution of more than 90 wt%, and the crystals are filtered to obtain a DC10-DC18 crystal product and an acetic acid mother liquor. The acetic acid in the acetic acid mother liquor is recovered by a distillation tower and reused, and the bottom material (i.e., the residue after the acetic acid is recovered by distillation of the acetic acid mother liquor) is a mixture containing long-chain dibasic acids.

[0064] After recrystallization, most of the impurities (including pigments, sugars, inorganic salts, cell tissues of fermenting microorganisms, proteins, etc.) and most of the miscellaneous acids (including saturated long-chain dibasic acids, some short-chain saturated dibasic acids, and unsaturated dibasic acids produced as byproducts in the fermentation process and having carbon chain lengths different from those of the fermentation substrate) in the crude long-chain dibasic acid are dissolved in the solvent and separated from the main long-chain dibasic acid (i.e., the long-chain dibasic acid object refined during the recrystallization process, referred to as the target long-chain dibasic acid) in the crude long-chain dibasic acid. Since the recrystallization process adopts a method of first dissolving the crude long-chain dibasic acid in the solvent and then cooling (preferably controlling the temperature below 50°C but above 20°C) to precipitate, part of the target long-chain dibasic acid is also dissolved in the solvent mother liquor. After the crude long-chain dibasic acid is recrystallized in the solvent, the residue after filtering the crystals is the solvent mother liquor. The mixture containing long-chain dibasic acids described in the present invention can be, for example, a solvent mother liquor. It can also be the residue after recovering most of the solvent from the solvent mother liquor, such as the bottom material left after using a distillation tower to recover the solvent. The bottom material often appears brown due to the presence of pigments; in addition to pigments, it also contains impurities such as inorganic salts, cell tissues of fermented microorganisms, proteins, etc., resulting in its melting point often being lower than that of pure long-chain dibasic acids.

[0065] Detection method of long-chain dibasic acid product index in the embodiment:

[0066] 1. Ash content detection: Take the sample to be tested and burn it in a crucible, then burn it in a muffle furnace at 700-800℃ for 2 hours. After cooling to constant weight, measure the weight and calculate the percentage weight.

[0067] 2. Nitrogen content detection: Kjeldahl method.

[0068] 3. Transmittance detection: Use a spectrophotometer to detect the transmittance of a 25% dimethyl sulfoxide solution of the sample at 440 nm.

[0069] Example 1

[0070] 500 kg of the bottom material (of which the content of DC10-DC18 is 82 wt% and the content of unsaturated dibasic acid is 3 wt%) is heated to melt and then distilled at 250°C and a vacuum degree of 10 Pa until no fraction is produced. The distillate is collected to obtain 470 kg of the first distillation product.

[0071] The first distillation product was heated to 180°C, and reacted with 20 kg of potassium permanganate powder at 180°C for 2 h under stirring at normal pressure to obtain an oxidation product. The oxidation product was subjected to a second distillation at a vacuum degree of 10 Pa and a temperature of 250°C until no fraction was produced as the distillation end point, and the distillate was collected to obtain 435 kg of a second distillation product.

[0072] The second distillation product was subjected to a third distillation under the conditions of a vacuum degree of 10 Pa and 215° C., and the distillate was collected. The remainder was the third distillation product, and 422 kg of the third distillation product was obtained.

[0073] The third distillation product was subjected to a fourth distillation at 240° C. and a vacuum degree of 8 Pa until no fraction was produced, which was the distillation end point. The distillate was collected to obtain 380 kg of the fourth distillation product, which was the obtained product.

[0074] Among them, the residue of the second distillation and the residue of the fourth distillation are returned to the first distillation for recycling.

[0075] The product was tested and the test results are shown in Table 1.

[0076] Example 2

[0077] 500 kg of the bottom material (of which the content of DC10-DC18 is 82 wt% and the content of unsaturated dibasic acid is 3 wt%) is heated to melt and then distilled at 250°C and a vacuum degree of 10 Pa until no fraction is produced. The distillate is collected to obtain 470 kg of the first distillation product.

[0078] The first distillation product was heated to 150°C, and reacted with 51 kg of ozone at 150°C for 2 hours under normal pressure and stirring to obtain an oxidation product, wherein the rate of ozone introduction was 200 L / min. The oxidation product was subjected to a second distillation at a vacuum degree of 10 Pa and a temperature of 250°C until no fraction was produced as the distillation end point, and the distillate was collected to obtain 438 kg of a second distillation product.

[0079] The second distillation product was subjected to a third distillation under the conditions of a vacuum degree of 10 Pa and 215° C., and the distillate was collected. The remainder was the third distillation product, and 425 kg of the third distillation product was obtained.

[0080] The third distillation product was subjected to a fourth distillation at 240° C. and a vacuum degree of 8 Pa until no fraction was produced, which was the distillation end point. The distillate was collected to obtain 384 kg of the fourth distillation product, which was the obtained product.

[0081] Among them, the residue of the second distillation and the residue of the fourth distillation are returned to the first distillation for recycling.

[0082] The product was tested and the test results are shown in Table 1.

[0083] Example 3

[0084] 500 kg of the bottom material (of which the content of DC10-DC18 is 82 wt% and the content of unsaturated dibasic acid is 3 wt%) is heated to melt and then distilled at 250°C and a vacuum degree of 15 Pa until no fraction is produced. The distillate is collected to obtain 468 kg of the first distillation product.

[0085] The first distillation product was heated to 190°C, and reacted with 20 kg of 95% nitric acid at 190°C for 2 hours under stirring at normal pressure to obtain an oxidation product. The oxidation product was subjected to a second distillation at a vacuum degree of 10 Pa and a temperature of 250°C until no fraction was produced as the distillation end point, and the distillate was collected to obtain 445 kg of a second distillation product.

[0086] The second distillation product was subjected to a third distillation under the conditions of a vacuum degree of 10 Pa and 215° C., and the distillate was collected. The remainder was the third distillation product, and 425 kg of the third distillation product was obtained.

[0087] The third distillation product was subjected to a fourth distillation at 240° C. and a vacuum degree of 8 Pa until no fraction was produced, which was the distillation end point. The distillate was collected to obtain 382 kg of the fourth distillation product, which was the obtained product.

[0088] Among them, the residue of the second distillation and the residue of the fourth distillation are returned to the first distillation for recycling.

[0089] The product was tested and the test results are shown in Table 1.

[0090] Example 4

[0091] 500 kg of the bottom material (of which the content of DC10-DC18 is 82 wt% and the content of unsaturated dibasic acid is 3 wt%) is heated to melt and then distilled at 240°C and a vacuum degree of 8 Pa until no fraction is produced. The distillate is collected to obtain 466 kg of the first distillation product.

[0092] The first distillation product was heated to 180°C, and reacted with 77.58 kg of air at 180°C for 2 h under normal pressure and stirring to obtain an oxidation product, wherein the air introduction rate was 500 L / min. The oxidation product was subjected to a second distillation at a vacuum degree of 10 Pa and a temperature of 250°C until no fraction was produced as the distillation end point, and the distillate was collected to obtain 433 kg of a second distillation product.

[0093] The second distillation product was subjected to a third distillation under the conditions of a vacuum degree of 10 Pa and 216° C., and the distillate was collected. The remainder was the third distillation product, and 420 kg of the third distillation product was obtained.

[0094] The product of the third distillation was subjected to a fourth distillation at 240° C. and a vacuum degree of 8 Pa until no fraction was produced, which was the end point of the distillation. The distillate was collected to obtain 377 kg of the fourth distillation product, which was the obtained product.

[0095] Among them, the residue of the second distillation and the residue of the fourth distillation are returned to the first distillation for recycling.

[0096] The product was tested and the test results are shown in Table 1.

[0097] Example 5

[0098] 500 kg of the bottom material (of which the content of DC10-DC18 is 82 wt% and the content of unsaturated dibasic acid is 3 wt%) is heated to melt and then distilled at 240°C and a vacuum degree of 8 Pa until no fraction is produced. The distillate is collected to obtain 466 kg of the first distillation product.

[0099] The first distillation product was heated to 200°C, and reacted with 93.096 kg of air at 200°C for 2 h under normal pressure and stirring to obtain an oxidation product, with the air introduction rate being 600 L / min. The oxidation product was subjected to a second distillation at a vacuum degree of 8 Pa and a temperature of 240°C until no fraction was produced as the distillation end point, and the distillate was collected to obtain 437 kg of a second distillation product.

[0100] The second distillation product was subjected to a third distillation under the conditions of a vacuum degree of 8 Pa and 216° C., and the distillate was collected. The remainder was the third distillation product, and 420 kg of the third distillation product was obtained.

[0101] The third distillation product was subjected to a fourth distillation at 240°C and a vacuum degree of 5 Pa until no fraction was produced as the distillation end point, and the distillate was collected to obtain 378 kg of a fourth distillation product. The fourth distillation product was contacted with activated carbon for decolorization at a decolorization temperature of 150°C and a decolorization time of 30 min. The amount of activated carbon accounted for 8% of the weight of the fourth distillation product. The activated carbon was removed, and the decolorized product was collected to obtain 359 kg of the product.

[0102] Among them, the residue of the second distillation and the residue of the fourth distillation are returned to the first distillation for recycling.

[0103] The product was tested and the test results are shown in Table 1.

[0104] Example 6

[0105] 500 kg of the bottom material (of which the content of DC10-DC18 is 82 wt% and the content of unsaturated dibasic acid is 3 wt%) is heated to melt and then distilled at 250°C and a vacuum degree of 5 Pa until no fraction is produced. The distillate is collected to obtain 475 kg of the first distillation product.

[0106] The first distillation product was heated to 200°C, and reacted with 155.16 kg of air at 200°C for 2 hours under normal pressure and stirring to obtain an oxidation product, wherein the air introduction rate was 1000 L / min. The oxidation product was subjected to a second distillation at a vacuum degree of 5 Pa and a temperature of 250°C until no fraction was produced as the distillation end point, and the distillate was collected to obtain 442 kg of a second distillation product.

[0107] The second distillation product was subjected to a third distillation with a vacuum degree of 8 Pa, a bottom temperature of 216°C, a top temperature of 182°C, and 8 plates of the distillation tower. The distillate was collected and the remainder was the third distillation product, obtaining 427 kg of the third distillation product.

[0108] The third distillation product was subjected to a fourth distillation with a vacuum degree of 5 Pa, a bottom temperature of 240°C, a top temperature of 215°C, and 8 plates of the distillation tower. The distillation end point was when no fraction was produced. The distillate was collected to obtain 383 kg of a fourth distillation product, which was the obtained product.

[0109] The residue of the second distillation and the residue of the fourth distillation are returned to the first distillation for recycling.

[0110] The product was tested and the test results are shown in Table 1.

[0111] Example 7

[0112] 500 kg of the bottom material (of which the content of DC10-DC18 is 82 wt% and the content of unsaturated dibasic acid is 3 wt%) is heated to melt and then distilled at 250°C and a vacuum degree of 5 Pa until no fraction is produced. The distillate is collected to obtain 475 kg of the first distillation product.

[0113] The first distillation product was heated to 200°C, and reacted with 155.16 kg of air at 200°C for 2 hours under normal pressure and stirring to obtain an oxidation product, wherein the air introduction rate was 1000 L / min. The oxidation product was subjected to a second distillation at a vacuum degree of 5 Pa and a temperature of 250°C until no fraction was produced as the distillation end point, and the distillate was collected to obtain 442 kg of a second distillation product.

[0114] The second distillation product was subjected to a third distillation with a vacuum degree of 8 Pa, a bottom temperature of 216°C, a top temperature of 182°C, and 8 plates of the distillation tower. The distillate was collected and the remainder was the third distillation product, obtaining 427 kg of the third distillation product.

[0115] The third distillation product was subjected to a fourth distillation, with a vacuum degree of 5 Pa, a bottom temperature of 240°C, a top temperature of 215°C, and a number of plates of 8 in the distillation tower, until no fraction was produced as the distillation end point, and the distillate was collected to obtain 383 kg of a fourth distillation product, and the fourth distillation product was contacted with activated carbon for decolorization, the decolorization temperature was 150°C, the decolorization time was 30 min, and the amount of activated carbon accounted for 10% of the weight of the fourth distillation product. The activated carbon was removed, and the product was collected after decolorization to obtain 363 kg of the product.

[0116] The residue of the second distillation and the residue of the fourth distillation are returned to the first distillation for recycling.

[0117] The product was tested and the test results are shown in Table 1.

[0118] Example 8

[0119] 500 kg of the bottom material (of which the content of DC10-DC18 is 82 wt% and the content of unsaturated dibasic acid is 3 wt%) is heated to melt and then distilled at 235°C and a vacuum degree of 5 Pa until no fraction is produced. The distillate is collected to obtain 461 kg of the first distillation product.

[0120] The first distillation product was heated to 190°C, and reacted with 155.16 kg of air at 200°C for 2 hours under normal pressure and stirring to obtain an oxidation product, wherein the air introduction rate was 1000 L / min. The oxidation product was subjected to a second distillation at a vacuum degree of 8 Pa and a temperature of 255°C until no fraction was produced as the distillation end point, and the distillate was collected to obtain 426 kg of a second distillation product, which was a long-chain dibasic acid product.

[0121] Example 9

[0122] 500 kg of the bottom material (of which the content of DC10-DC18 is 82 wt% and the content of unsaturated dibasic acid is 3 wt%) is heated to melt and then distilled at 250°C and a vacuum degree of 5 Pa until no fraction is produced. The distillate is collected to obtain 475 kg of the first distillation product.

[0123] The first distillation product was heated to 200°C, and reacted with 155.16 kg of air at 200°C for 2 hours under normal pressure and stirring to obtain an oxidation product, wherein the air introduction rate was 1000 L / min.

[0124] The oxidation product was directly subjected to the third distillation with a vacuum degree of 8 Pa, a bottom temperature of 216°C, a top temperature of 182°C, and 8 plates of the distillation tower. The distillate was collected and the remainder was the third distillation product, obtaining 436 kg of the third distillation product.

[0125] The third distillation product was subjected to a fourth distillation at a vacuum degree of 8 Pa and a temperature of 240° C., and the distillation end point was when no fraction was produced. The distillate was collected to obtain 387 kg of a fourth distillation product, which was the obtained product.

[0126] The residue of the fourth distillation is returned to the first distillation for recycling.

[0127] The product was tested and the test results are shown in Table 1.

[0128] Example 10

[0129] 850 kg of the bottom material (of which the content of DC10-DC18 is 53 wt% and the content of unsaturated dibasic acid is 18 wt%) is heated to melt and then distilled at 250°C and a vacuum degree of 5 Pa until no fraction is produced. The distillate is collected to obtain 670 kg of the first distillation product.

[0130] The first distillation product was heated to 200°C, and reacted with 310.32 kg of air at 200°C for 2 h under normal pressure and stirring to obtain an oxidation product, wherein the air introduction rate was 2000 L / min. The oxidation product was subjected to a second distillation at a vacuum degree of 5 Pa and a temperature of 250°C until no fraction was produced as the distillation end point, and the distillate was collected to obtain 640 kg of a second distillation product.

[0131] The second distillation product was subjected to a third distillation with a vacuum degree of 8 Pa, a bottom temperature of 216°C, a top temperature of 182°C, and 8 plates of the distillation tower. The distillate was collected and the remainder was the third distillation product, obtaining 438 kg of the third distillation product.

[0132] The third distillation product was subjected to a fourth distillation with a vacuum degree of 5 Pa, a bottom temperature of 240°C, a top temperature of 215°C, and 8 plates of the distillation tower. The distillation end point was when no fraction was produced. The distillate was collected to obtain 395 kg of a fourth distillation product, which was the obtained product.

[0133] The residue of the second distillation and the residue of the fourth distillation are returned to the first distillation for recycling.

[0134] The product was tested and the test results are shown in Table 1.

[0135] Comparative Example 1

[0136] 500 kg of the bottom material (of which the content of DC10-DC18 is 82 wt% and the content of unsaturated dibasic acid is 3 wt%) is heated to melt and then distilled at 250°C and a vacuum degree of 10 Pa until no fraction is produced. The distillate is collected to obtain 470 kg of the first distillation product.

[0137] The first distillation product was subjected to a second distillation at a vacuum degree of 10 Pa and a temperature of 250° C. until no fraction was produced as the distillation end point, and the distillate was collected to obtain 435 kg of a second distillation product.

[0138] The second distillation product was subjected to a third distillation under the conditions of a vacuum degree of 10 Pa and 215° C., and the distillate was collected. The remaining high boiling substances were the third distillation product, and 422 kg of the third distillation product was obtained.

[0139] The third distillation product was subjected to a fourth distillation at 240° C. and a vacuum degree of 8 Pa until no fraction was produced, which was the distillation end point. The distillate was collected to obtain 380 kg of the fourth distillation product, which was the obtained product.

[0140] Among them, the residue of the second distillation and the residue of the fourth distillation are returned to the first distillation for recycling.

[0141] Comparative Example 2

[0142] Take 500kg of the bottom material of the tower (of which the content of DC10-DC18 is 82% and the content of unsaturated dibasic acid is 3wt%) and add it into the melting tank, melt it at 180℃ for 1 hour, and after melting, use a pump to pump the material into the scraped film evaporator. The material temperature during scraped film evaporation is 176℃ and the vacuum degree is 500pa.

[0143] The material after light components were removed was subjected to short-path distillation, the hot and cold surface temperatures of the short-path distillation device were 222-230°C and 134-143°C respectively, the vacuum degree was 15-19 Pa, the feed temperature was 180°C, and the time was 1 hour. 415 kg of long-chain dibasic acid product was obtained.

[0144] Comparative Example 3

[0145] Take 850kg of the bottom material (of which the content of DC10-DC18 is 53% and the content of unsaturated dibasic acid is 18wt%), add 1700kg of 95% acetic acid solution, dissolve it at 95℃, add 50kg of activated carbon, stir for 30min, and then filter to remove the activated carbon. Cool the obtained clarified liquid at a cooling rate of no more than 3℃ / h, keep it warm for 1h after cooling to the appearance of crystals, and then cool it to the terminal temperature of 25℃, filter it, wash the filter cake with 70kg of 95% acetic acid solution, then wash it with 700kg of water, and then dry it at 80℃.

[0146] It was found that the filtration was difficult due to the viscosity of the material. The product obtained by drying was yellow, and the yield of the long-chain dibasic acid product was 41%.

[0147] Table 1: Long-chain dibasic acid product test results

[0148]

[0149] Application Examples

[0150] The above-mentioned long-chain dibasic acid product is used to prepare hot melt adhesive, and the preparation process is as follows:

[0151] (1) Under a nitrogen atmosphere, 260 g of pentamethylenediamine, 200 g of adipic acid, 322 g of a long-chain dibasic acid, 65 g of isophthalic acid, 250 g of caprolactam and water were uniformly mixed to prepare an 80 wt.% polyamide salt solution. The pH value of the polyamide salt solution was 7.89 when the concentration was 10 wt.%.

[0152] (2) The salt solution of polyamide obtained in step (1) is filtered and heated, the pressure in the reaction system is raised to 1.7 MPa, the air is exhausted, and the pressure is maintained. At the end of the pressure maintenance, the temperature of the reaction system is 244° C., and the pressure is then reduced to reduce the pressure in the reaction system to 0.01 MPa (gauge pressure), and maintained for 20 min. After the pressure reduction, the temperature of the reaction system is 264° C., and the pressure is maintained at -0.09 MPa. The vacuum time is maintained for 22 min. The temperature after vacuum is 269° C., and a polyamide hot melt adhesive melt is obtained.

[0153] (3) Melting and discharging the material, and pelletizing it underwater; the temperature of the cooling water is 20° C., and the cooling time is 35 min to obtain polyamide hot melt adhesive resin chips.

[0154] The hot melt adhesive resin slices were tested for melting point, peel strength and yellow index. The test results are shown in Table 2.

[0155] The test method is as follows:

[0156] 1. Melting point test: Differential scanning calorimetry was used.

[0157] 2. Peel strength test method: refer to the adhesive lining peel strength test standard FZ / T 80007.1-2006.

[0158] 3. Yellowness index (YI value) test: refer to ASTM D6290.

[0159] Table 2: Hot melt adhesive performance test results

[0160]

[0161] When hot melt adhesive is used in the textile field, the lower the melting point of the hot melt adhesive, the more convenient the operation. The lower the application temperature, the easier it is to use with a hot melt adhesive gun or hot melt adhesive machine. By adding long-chain dibasic acid products to the hot melt adhesive, the density of amide bonds and the number of hydrogen bonds are reduced, the crystallinity decreases, and the melting point decreases.

[0162] When the purity of the long-chain dibasic acid product decreases, the peel strength of the hot melt adhesive decreases significantly. At the same time, due to the influence of impurities and unsaturated acids in the system, its yellow index also increases significantly. The different impurity contents in the product also affect the composition of the final hot melt adhesive polymer, which in turn causes differences in the melting point of the hot melt adhesive.

[0163] In addition, the hot melt adhesive to which the long-chain dibasic acid product of the present invention is added is colorless and transparent, and is suitable for bonding in high-end markets, such as plastics, toys, electronics, furniture, leather, handicrafts, shoe materials, coatings, ceramics, etc., and in transparent adhesive fields visible from the outside. At the same time, by adding the long-chain dibasic acid product of the present invention to the hot melt adhesive, the hydrophobicity of the hot melt adhesive is improved, and the solubility in organic solvents is reduced, thereby improving the water washing resistance and dry cleaning resistance.

[0164] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A long-chain dibasic acid refining process comprising: (1) heating and melting a mixture containing a long-chain dibasic acid, and then performing a first distillation, collecting a distillate of the first distillation, and obtaining a first distillation product; (2) mixing the first distillation product with an oxidant and reacting the mixture at a temperature not higher than 240° C. to obtain an oxidation product; subjecting the oxidation product to a second distillation treatment, collecting a distillate of the second distillation to obtain a second distillation product, and then subjecting the second distillation product to a third distillation, collecting a distillation residue to obtain a third distillation product; and subjecting the third distillation product to a fourth distillation, and collecting the distillate of the fourth distillation to obtain a fourth distillation product; The mixture containing long-chain dibasic acid includes: crude long-chain dibasic acid, the residue after most of the solvent is recovered from the recrystallization mother liquor of the crude long-chain dibasic acid, and the long-chain dibasic acid precipitate accumulated in the long-chain dibasic acid wastewater treatment workshop for a long time; the oxidant is selected from one or more of potassium permanganate, ozone, and air; The vacuum degree of the first distillation is ≤100 Pa, and the temperature of the first distillation is 180~280°C; the vacuum degree of the second distillation is ≤100 Pa, and the temperature of the second distillation is 180~280°C; the vacuum degree of the third distillation is ≤100 Pa, and the temperature of the third distillation is 150~240°C; the vacuum degree of the fourth distillation is ≤100 Pa, and the temperature of the fourth distillation is 180~280°C.

2. The process according to claim 1, characterized in that The following steps are involved: The fourth distillation product is distilled N times, and the distillate after each distillation is used as the raw material for the next distillation, until N distillations are completed, and the distillates after N distillations are collected to obtain the 4+Nth distillation product; during any distillation process, the vacuum degree is ≤100 Pa and the temperature is 220~250° C.; the N≥1.

3. The process according to claim 2, characterized in that The following steps are involved: Decolorization treatment: The product of any distillation is brought into contact with a decolorizing agent for decolorization treatment.

4. The process according to claim 3, characterized in that The dosage of the decolorizing agent is 3-40wt% of the material to be decolorized, and / or the decolorizing temperature is 130-180°C, and / or the decolorizing time is 3-120min.

5. The process according to claim 1, characterized in that: The mixture containing long-chain dibasic acids contains saturated long-chain dibasic acids, and the number of carbon atoms of the saturated long-chain dibasic acids is 10 to 18; and / or, the content of saturated long-chain dibasic acid in the mixture comprising long-chain dibasic acid is 10-98 wt %; and / or, in step (2), the content of the oxidant is converted to 100 wt%, and the amount of 100 wt% of the oxidant used per 100 g of the first distillation product is 1 to 20 g; wherein, when the oxidant is air, converting the content of the oxidant to 100% means converting the content of oxygen in the air to 100 wt%; And / or, the reaction temperature in step (2) is 140-240°C; And / or, the reaction time of step (2) is 0.5~6h.

6. The process according to claim 5, characterized in that: The saturated long-chain dibasic acid is selected from one or a combination of the following: sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedicarboxylic acid, hexadecanedioic acid, heptadecanedioic acid, and octadecanedicarboxylic acid; And / or, the amount of 100 wt% of the oxidant used is 1-10 g per 100 g of the first distillation product.

7. The process according to claim 1, characterized in that The third distillation is rectification, the vacuum degree is ≤100pa, the bottom temperature is 150-230°C, and the top temperature is 120-195°C.

8. The process according to claim 1, characterized in that The fourth distillation is rectification, the vacuum degree is ≤100pa, the bottom temperature is 200-280°C, and the top temperature is 180-230°C.

9. The process according to claim 1, characterized in that The total acid content of the long-chain dibasic acid product is ≥97%, the saturated long-chain dibasic acid content is ≥90%, the ash content is ≤30ppm, the nitrogen content is ≤50ppm, the unsaturated dibasic acid content is ≤0.5%, and the light transmittance is ≥80%.

10. The process according to claim 1, characterized in that The ash content of the long-chain dibasic acid product is ≤25ppm, and / or the nitrogen content is ≤40ppm, and / or the unsaturated dibasic acid content is ≤0.35%, and / or the light transmittance is ≥85%.

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