Method for preparing rosin methyl ester by adopting composite catalyst, product and application

Abstract

The invention relates to the technical field of deep processing of rosin, in particular to a method for preparing rosin methyl ester by adopting a composite catalyst, a product and application. The composite catalyst is selected from p-benzene methanesulfonic acid and two or more of calcium citrate, calcium acetate and calcium oxalate. Compared with rosin, the methanol used in the method disclosed by the invention is less in mass, a washing process is not needed, and the method has the advantages of energy conservation, environmental protection, reduction of production cost and improvement of efficiency. The viscosity of the rosin methyl ester prepared by the method is 240-280 cps at 50 DEG C, the acid value is 5-10 mgKOH / g, and the color is less than or equal to Ghana color No. 2.

Description

Technical Field

[0001] The invention relates to the technical field of rosin deep processing, and in particular to a method for preparing rosin methyl ester by using a composite catalyst, a product and an application thereof. Background Art

[0002] Methyl rosin is an organic compound with a wide range of uses. Methyl rosin has important applications in the field of inks. Due to its good solubility and stability, methyl rosin is often used as the main solvent and diluent for inks. In the production process of inks, methyl rosin can be fully mixed with pigments to make the ink bright in color, high in gloss, and have good printing properties. In addition, methyl rosin can also improve the fluidity and drying speed of the ink, making the printing effect more ideal.

[0003] Rosin methyl ester is also widely used in the coating industry. Coating is a substance that is applied to the surface of an object to protect and decorate it. Rosin methyl ester can be used as a thickener and diluent for coatings. By controlling the amount of rosin methyl ester added, the viscosity and drying speed of the coating can be adjusted, and the adhesion and durability of the coating can be improved. In addition, rosin methyl ester can also increase the glossiness and anti-yellowing properties of the coating, making the coating more decorative.

[0004] Methyl rosin is also widely used in the production of rubber products. Rubber products are an important industrial raw material, widely used in automobile tires, rubber pipes, rubber seals and other fields. Methyl rosin can be used as a plasticizer and tackifier for rubber, which can improve the softness and ductility of rubber, making rubber products more durable.

[0005] The traditional preparation method of rosin methyl ester is often carried out under high temperature and high pressure, with high energy consumption and strict requirements on equipment. With solid acid ZnO and tungstate as catalysts, rosin and methanol are reacted under pressure, with an alcohol-acid ratio of 25:1, a catalyst dosage of 1%, a reaction temperature of 220°C, a reaction pressure of 5.5MPa, and a reaction time of 5h; for example, Chinese patent CN103013343 uses 100 parts of rosin and no less than 400 parts of methanol, and no less than 20 parts of ≥98% sulfuric acid as catalysts, reacts at 80-95°C for 12-15h, washes with water to neutrality, and vacuumizes at 280-300°C for 30min to obtain rosin methyl ester products. This method increases the reaction speed by more than 3-5 times by increasing the amount of methanol and catalyst, and can react at a lower temperature, making the reaction stable, mild, and easy to control, but requires a large amount of methanol, which makes the production efficiency too low, and the use of concentrated sulfuric acid requires a water washing process to remove it, which easily produces a large amount of acid-containing wastewater, which is not conducive to environmental protection.

[0006] Another example is Chinese patent CN107573851, which uses a composite catalyst composed of aluminum oxide, dibutyltin dilaurate and neodymium oxide, with a methanol to rosin mass ratio of 1:0.8, and esterification is carried out at 250-270°C for 2.5 hours, followed by reduced pressure and vacuum for 30 minutes to obtain rosin methyl ester. Although this method greatly reduces the amount of methanol used and improves production efficiency, the esterification reaction temperature is 250-270°C, which is far higher than the boiling point of methanol, which is 64.5°C. At such a high temperature, the reaction pressure will reach 5-10MPa.

[0007] Another example is Chinese patent CN 107674591A, which discloses a method for preparing hydrogenated rosin methyl ester. The catalyst used in the esterification reaction stage of the patent is a mixture of chromium oxide and titanium dioxide. The esterification reaction is carried out at 205°C-220°C for 1-2 hours, and the temperature is further raised to 230°C-265°C for 0.5-1 hour. In the process of preparing hydrogenated rosin in the invention, the temperature is gradually lowered, the reaction is moderate, and the purity of hydrogenated rosin is high; and the catalyst is a mixture of chromium oxide and titanium dioxide, and its catalytic activity is far greater than that of pure chromium oxide or pure titanium dioxide, and the reaction is more stable. However, chromium oxide and titanium dioxide are relatively expensive, especially high-purity raw materials, which will increase production costs. Moreover, chromium oxide is a known carcinogen, which poses certain risks to human health and the environment. Therefore, special attention should be paid to safety protection and waste disposal during use. Moreover, the mass ratio of chromium oxide and titanium dioxide in this patent is 1:3-5, which means that the ratio of the two needs to be precisely controlled to ensure the best catalytic effect, which increases the complexity of process control.

[0008] In summary, there is an urgent need to develop a method for preparing rosin methyl ester that is energy-saving, environmentally friendly, low-cost, at low temperature and low pressure and with high production efficiency. Summary of the invention

[0009] Based on the deficiencies of the prior art, the present invention aims to provide a method for preparing rosin methyl ester which is more energy-saving, environmentally friendly and has a high yield, so as to reduce production costs and improve production efficiency.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] In one aspect, the present invention provides a method for preparing rosin methyl ester using a composite catalyst, comprising the following steps:

[0012] (1) weighing rosin or a rosin derivative, methanol and a composite catalyst to carry out an esterification reaction, and then separating and filtering to obtain crude rosin methyl ester;

[0013] (2) subjecting the crude rosin methyl ester obtained in step (1) to vacuum distillation, collecting the fractions to obtain refined rosin methyl ester, adding an antioxidant and stirring to obtain the rosin methyl ester;

[0014] The composite catalyst is selected from two or more of p-toluenesulfonic acid and calcium citrate, calcium acetate and calcium oxalate; the mass of the rosin is 50-66.7% of the mass of methanol.

[0015] Preferably, the mass of the composite catalyst in step (1) is 3-6% of the mass of the rosin.

[0016] More preferably, the mass of the rosin in step (1) is 50% of the mass of the methanol, and the mass of the composite catalyst is 3.75% of the mass of the rosin.

[0017] Preferably, the esterification reaction in step (1) is first heated to 100°C-120°C, reacted for 1-2 hours, and then continued to heat to 130°C-150°C, reacted for 15-20 hours.

[0018] More preferably, the esterification reaction in step (1) is first heated to 100° C., reacted for 2 h, and then further heated to 135° C., reacted for 19 h.

[0019] Preferably, the esterification reaction is carried out in a pressure reactor, and the reaction pressure of the pressure reactor is 0.7-1.2 MPa.

[0020] More preferably, the reaction pressure of the pressure reactor is 0.7-1 MPa.

[0021] Further preferably, the reaction pressure of the pressure reactor is 0.8 MPa.

[0022] Preferably, the temperature of the vacuum distillation in step (2) is 210-230° C.; and the antioxidant needs to be stirred for 15-20 minutes when added.

[0023] More preferably, the temperature of the vacuum distillation in step (2) is 220° C.; and the anti-stirring time is 18 min.

[0024] Preferably, the rosin is selected from one or more of ester rosin, tall oil rosin, hydrogenated rosin and disproportionated rosin.

[0025] More preferably, the rosin is selected from ester rosin.

[0026] Further preferably, the rosin is selected from Guangxi Masson pine rosin.

[0027] Preferably, the composite catalyst is a mixture of p-toluenesulfonic acid, calcium citrate, calcium acetate and calcium oxalate.

[0028] More preferably, the composite catalyst is a mixture of p-toluenesulfonic acid and calcium acetate, and the mass ratio of p-toluenesulfonic acid to calcium acetate is 1-2:1.

[0029] More preferably, the mass ratio of the toluenesulfonic acid to calcium acetate is 2:1.

[0030] Preferably, the weight of the antioxidant is 0.1-0.2% of the weight of the rosin or rosin derivative.

[0031] More preferably, the weight of the antioxidant is 0.2% of the weight of the rosin or rosin derivative.

[0032] Preferably, the antioxidant is selected from one or more of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), β-(4-hydroxyphenyl-3,5-di-tert-butyl)propionate and 2,2'-thiobis[ethyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; and one or more of tris(nonylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite and triphenyl phosphite.

[0033] More preferably, the antioxidant consists of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and tris(2,4-di-tert-butylphenyl)phosphite.

[0034] Preferably, the mass ratio of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate to tris(2,4-di-tert-butylphenyl)phosphite is 0.6-3:1.

[0035] More preferably, the mass ratio of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate to tris(2,4-di-tert-butylphenyl)phosphite is 3:1.

[0036] On the other hand, the present invention provides a rosin methyl ester product obtained by the above method, wherein the rosin methyl ester product has a viscosity of 240-280 cps, an acid value of 5-10 mgKOH / g, and a color less than Ghana color number 2.

[0037] If high-quality rosin methyl ester products are required, an antioxidant stabilizer can be added and stirred evenly to achieve better application effects. The stirring time is 20-30 minutes.

[0038] In another aspect, the present invention also provides the use of the rosin methyl ester obtained by the above method in the preparation of adhesives, coatings, paints or ink products.

[0039] Compared with the prior art, the present invention has the following advantages and effects:

[0040] (1) The present invention is to prepare rosin methyl ester at low temperature and low pressure, the mass ratio of methanol to rosin is ≤2, the reaction temperature is 150°C, no water washing process is required, and it has the advantages of energy saving and environmental protection, reducing production costs and improving efficiency.

[0041] (2) The rosin methyl ester prepared by the present invention has a viscosity of 240-280 cps at 50° C., an acid value of 5-10 mgKOH / g, and a color less than or equal to Ghana color No. 2. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below with reference to specific embodiments.

[0043] Example 1 A method for preparing rosin methyl ester using a composite catalyst

[0044] 120g of ester rosin (Guangxi Masson pine rosin) (softening point 78.6°C, acid value 175 (mgKOH / g), Ghana color is 6+) is added to a pressure reactor, 240g of methanol, 2.4g of toluenesulfonic acid and 1.2g of calcium acetate as catalysts are added, the temperature is raised to 100°C, the esterification reaction is carried out for 1h, and then the temperature is further raised to 130°C, the esterification reaction is carried out for 20h, the reaction pressure is 0.7MPa, and the temperature is lowered to below 50°C to separate and obtain crude rosin methyl ester with an acid value of 11.5mgKOH; the crude rosin methyl ester is subjected to reduced pressure vacuum distillation at 220°C, the fractions are collected to obtain refined rosin methyl ester, 0.06g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and 0.06g of tris(2,4-di-tert-butylphenyl) phosphite are added and stirred for 18min to obtain a rosin methyl ester product.

[0045] Example 2

[0046] 120g of Guangxi Masson pine rosin (softening point 78.6°C, acid value 175 (mgKOH / g), Ghana color is 6+) is added to a reactor, 228g of methanol, 1.8g of toluenesulfonic acid and 1.8g of calcium acetate as catalysts are added, the temperature is raised to 100°C, the esterification reaction is carried out for 1.5h, and then the temperature is further raised to 140°C, the esterification reaction is carried out for 18h, the reaction pressure is 0.78MPa, and the temperature is lowered to below 50°C to separate and obtain crude rosin methyl ester with an acid value of 9.8mgKOH; the crude rosin methyl ester is subjected to reduced pressure vacuum distillation at 210°C, the fractions are collected to obtain refined rosin methyl ester, 0.12g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.12g of tris(2,4-di-tert-butylphenyl)phosphite are added, and the mixture is stirred for 15min to obtain a rosin methyl ester product.

[0047] Example 3

[0048] 120g of Guangxi Masson pine rosin (softening point 78.6°C, acid value 175 (mgKOH / g), Ghana color is 6+) is added to a reactor, 222g of methanol, 2.7g of toluenesulfonic acid and 2.7g of calcium oxalate as catalysts are added, the temperature is raised to 100°C, the esterification reaction is carried out for 2h, and the temperature is further raised to 145°C, the esterification reaction is carried out for 15h, the reaction pressure is 0.9MPa, the temperature is lowered to below 50°C, and the crude rosin methyl ester with an acid value of 10.6mgKOH is obtained by separation and filtration; the crude rosin methyl ester is subjected to reduced pressure vacuum distillation at 230°C, the fraction is collected to obtain refined rosin methyl ester, 0.12g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.06g of tris(2,4-di-tert-butylphenyl)phosphite are added, and the mixture is stirred for 20min to obtain a rosin methyl ester product.

[0049] Example 4

[0050] 120g of Guangxi Masson pine rosin (softening point 78.6°C, acid value 175 (mgKOH / g), Ghana color is 6+) is added to a reactor, 240g of methanol, 3g of toluenesulfonic acid and 1.5g of calcium citrate as catalysts are added, the temperature is raised to 100°C, the esterification reaction is carried out for 2h, and the temperature is further raised to 135°C, the esterification reaction is carried out for 19h, the reaction pressure is 0.8MPa, the temperature is lowered to below 50°C, and the crude rosin methyl ester with an acid value of 10.3mgKOH is obtained by separation and filtration; the crude rosin methyl ester is subjected to reduced pressure vacuum distillation at 220°C, the fractions are collected to obtain refined rosin methyl ester, 0.18g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.06g of tris(2,4-di-tert-butylphenyl)phosphite are added, and the mixture is stirred for 18min to obtain a rosin methyl ester product.

[0051] Example 5

[0052] 120g of Guangdong Yangjiang wetland pine rosin (softening point 77°C, acid value 166 (mgKOH / g), Ghana color is 6+) is added to a reactor, 198g of methanol, 3g of toluenesulfonic acid and 2.4g of calcium oxalate as catalysts are added, the temperature is raised to 120°C, the esterification reaction is carried out for 1h, and then the temperature is further raised to 150°C, the esterification reaction is carried out for 18h, the reaction pressure is 1MPa, the temperature is lowered to below 50°C, and the crude rosin methyl ester with an acid value of 8.8mgKOH is obtained by separation and filtration; the crude rosin methyl ester is subjected to reduced pressure vacuum distillation at 220°C, the fractions are collected to obtain refined rosin methyl ester, 0.072g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.12g of tris(2,4-di-tert-butylphenyl)phosphite are added, and the mixture is stirred for 18min to obtain a rosin methyl ester product.

[0053] Example 6

[0054] 120g of hydrogenated rosin (softening point 76°C, acid value 163 (mgKOH / g), Gardner color is 4+) is added to a reactor, 216g of methanol, 3.6g of toluenesulfonic acid and 2.4g of calcium acetate as catalysts are added, the temperature is raised to 110°C, the esterification reaction is carried out for 2h, the temperature is further raised to 140°C, the esterification reaction is carried out for 19h, the reaction pressure is 0.92MPa, the temperature is lowered to below 50°C, and crude rosin methyl ester with an acid value of 11.2mgKOH is obtained by separation and filtration; the crude rosin methyl ester is subjected to reduced pressure vacuum distillation at 210-230°C, the fraction is collected to obtain refined rosin methyl ester, 0.18g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.06g of tris(2,4-di-tert-butylphenyl)phosphite are added, and the mixture is stirred for 18min to obtain a rosin methyl ester product.

[0055] Example 7

[0056] 120g of disproportionated rosin (softening point 76.5°C, acid value 158 (mgKOH / g), Ghana color is 5) is added to a reactor, 180g of methanol, 3.6g of toluenesulfonic acid and 3.6g of calcium acetate as catalysts are added, the temperature is raised to 120°C, the esterification reaction is carried out for 1h, and then the temperature is further raised to 150°C, the esterification reaction is carried out for 20h, the reaction pressure is 0.95MPa, the temperature is lowered to below 50°C, and the crude rosin methyl ester with an acid value of 11.8mgKOH is obtained by separation and filtration; the crude rosin methyl ester is subjected to reduced pressure vacuum distillation at 220°C, the fraction is collected to obtain refined rosin methyl ester, 0.12g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.04g of tris(2,4-di-tert-butylphenyl)phosphite are added, and the mixture is stirred for 18min to obtain a rosin methyl ester product.

[0057] Example 8

[0058] 120g of floating oil rosin (softening point 76.5℃, acid value 167 (mgKOH / g), Ghana color is 8) is added to a pressure reactor, 240g of methanol, 2.4g of toluenesulfonic acid and 1.2g of calcium citrate as catalysts are added, the temperature is raised to 100℃, the esterification reaction is carried out for 1h, and then the temperature is further raised to 130℃, the esterification reaction is carried out for 20h, the reaction pressure is 1.2MPa, and the temperature is lowered to below 50℃ to separate and obtain crude rosin methyl ester with an acid value of 11.5mgKOH; the crude rosin methyl ester is subjected to reduced pressure vacuum distillation at 220℃, and the fractions are collected to obtain refined rosin methyl ester, 0.1g of 2,6-di-tert-butyl-4-methylphenol, 0.08g of β-(4-hydroxyphenyl-3,5-di-tert-butyl) propionate and 0.06g of tris(nonylphenyl) phosphite are added and stirred for 18min to obtain a rosin methyl ester product.

[0059] Comparative Example 1

[0060] The only difference from Example 1 is that p-toluenesulfonic acid is replaced by 98% concentrated sulfuric acid. Specifically:

[0061] 120g of Guangxi Masson pine rosin (softening point 78.6°C, acid value 175 (mgKOH / g), Ghana color is 6+) is added to a reactor, 240g of methanol, 2.4g of 98% concentrated sulfuric acid as a catalyst and 1.2g of calcium acetate are added, the temperature is raised to 100°C, the esterification reaction is carried out for 1h, the temperature is further raised to 130°C, the esterification reaction is carried out for 20h, the reaction pressure is 0.7MPa, the temperature is lowered to below 50°C, and crude rosin methyl ester with an acid value of 11.5mgKOH is obtained by separation and filtration; the crude rosin methyl ester is subjected to reduced pressure vacuum distillation at 220°C, the fraction is collected to obtain refined rosin methyl ester, 0.06g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.06g of tris(2,4-di-tert-butylphenyl)phosphite are added, and the mixture is stirred for 18min to obtain a rosin methyl ester product.

[0062] Comparative Example 2

[0063] The only difference from Example 1 is that 1.2 g of calcium oxalate is replaced by 1.2 g of p-toluenesulfonic acid. Specifically:

[0064] 120g of Guangxi Masson pine rosin (softening point 78.6°C, acid value 175 (mgKOH / g), Ghana color is 6+) is added to a reactor, 240g of methanol and 3.6g of catalyst calcium oxalate are added, the temperature is raised to 100°C, the esterification reaction is carried out for 1h, and then the temperature is further raised to 130°C, the esterification reaction is carried out for 20h, the reaction pressure is 0.7MPa, the temperature is lowered to below 50°C, and the crude rosin methyl ester with an acid value of 11.5mgKOH is obtained by separation and filtration; the crude rosin methyl ester is subjected to reduced pressure vacuum distillation at 220°C, the fractions are collected to obtain refined rosin methyl ester, 0.06g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and 0.06g of tris(2,4-di-tert-butylphenyl) phosphite are added, and the mixture is stirred for 18min to obtain a rosin methyl ester product.

[0065] Comparative Example 3

[0066] The only difference from Example 1 is that 1.2 g of calcium oxalate is replaced by 1.2 g of calcium carbonate. Specifically:

[0067] 120g of Guangxi Masson pine rosin (softening point 78.6°C, acid value 175 (mgKOH / g), Ghana color is 6+) is added to a reactor, 240g of methanol, 2.4g of toluenesulfonic acid and 1.2g of calcium carbonate as catalysts are added, the temperature is raised to 100°C, the esterification reaction is carried out for 1h, and then the temperature is further raised to 130°C, the esterification reaction is carried out for 20h, the reaction pressure is 0.7MPa, the temperature is lowered to below 50°C, and the crude rosin methyl ester with an acid value of 11.5mgKOH is obtained by separation and filtration; the crude rosin methyl ester is subjected to reduced pressure vacuum distillation at 220°C, the fraction is collected to obtain refined rosin methyl ester, 0.06g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.06g of tris(2,4-di-tert-butylphenyl)phosphite are added, and the mixture is stirred for 18min to obtain a rosin methyl ester product.

[0068] Effect experiment

[0069] The acid value, color and viscosity of the rosin methyl ester product obtained by the preparation method described in the examples and comparative examples were measured.

[0070] Acid value measurement method: weigh 2g of sample into a 250mL conical flask, add 50mL of neutral ethanol, heat on a water bath if necessary, cool after the sample is completely dissolved, add a few drops of phenolphthalein indicator, and titrate with 0.5mol / L potassium hydroxide standard titration solution until the reddish color does not fade for 30s as the end point. The acid value is expressed as the mass number of potassium hydroxide, in milligrams per gram (mg / g).

[0071] Color measurement method: Weigh 5g of rosin methyl ester (accurate to 0.1g), add toluene to prepare a solution with a mass ratio of 1:1. Shake at room temperature until completely dissolved. If the sample solution is visibly turbid, it can be treated by filtration, centrifugation, ultrasound or other methods that do not cause color change until the sample is clear. Slowly inject the prepared sample solution into the colorimetric tube. Cover the stopper, place the colorimetric tube and the Ghana standard color scale in the Ghana colorimeter at the same time, and observe and compare.

[0072] Viscosity measurement method: weigh 10g of sample into a measuring cylinder, install it on the measuring cylinder adjustment seat and fix it, rotate the lifting stand knob to slowly lower the viscometer, and the rotor is immersed in the measured liquid until the liquid level is exactly at the liquid level mark of the rotor. Adjust the viscometer and the measuring cylinder adjustment seat to be level, connect the screw to the center of the measuring cylinder, press the measurement key, and start measuring. After about 30 minutes, the viscosity value is stable and the sample viscosity can be measured in milligrams per gram (cps).

[0073] The measurement results are shown in Table 1 below.

[0074] Table 1

[0075] Serial number Acid value (mgKOH / g) color Viscosity (50℃)(cps) Yield % Example 1 7.3 1.5 269 98.2 Example 2 6.21 1 275 98.1 Example 3 6.8 1.5 280 98.4 Example 4 5.3 1.5 270 99 Example 5 5.0 1.5 252 98.8 Example 6 8.0 2 240 96.5 Example 7 8.0 1.5 255 97 Example 8 7.8 2 246 96.5 Comparative Example 1 23.6 2.5 375 89.4 Comparative Example 2 26.5 2 418 88.6 Comparative Example 3 20.8 2+ 343 90.3

[0076] As can be seen from the above table, the rosin methyl ester obtained within the scope of the present invention is superior to the comparative example in terms of acid value, color and yield. Therefore, replacement or lack of the catalyst of the present invention will deteriorate the quality of rosin methyl ester.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing rosin methyl ester using a composite catalyst, characterized in that: The steps include: (1) weighing rosin or a rosin derivative, methanol and a composite catalyst to carry out an esterification reaction, and then separating and filtering to obtain crude rosin methyl ester; (2) subjecting the crude rosin methyl ester obtained in step (1) to vacuum distillation, collecting the fractions to obtain refined rosin methyl ester, adding an antioxidant and stirring to obtain the rosin methyl ester; The composite catalyst is selected from two or more of p-toluenesulfonic acid and calcium citrate, calcium acetate and calcium oxalate; the mass of the rosin is 50-66.7% of the mass of methanol.

2. The method according to claim 1, characterized in that The mass of the composite catalyst described in step (1) is 3-6% of the mass of the rosin.

3. The method according to claim 1, characterized in that The reaction conditions of the esterification reaction described in step (1) are to first heat the temperature to 100°C-120°C, react for 1-2h, and then continue to heat the temperature to 130°C-150°C, and react for 15-20h.

4. The method according to claim 1, characterized in that: The esterification reaction in step (1) is carried out in a pressure reactor, and the reaction pressure of the pressure reactor is 0.7-1.2 MPa.

5. The method according to claim 1, characterized in that The temperature of the vacuum distillation in step (2) is 210-230°C.

6. The method according to claim 1, characterized in that The stirring time in step (2) is 15-20 min.

7. The method according to claim 1, characterized in that The rosin described in step (1) is one or more selected from the group consisting of gum rosin, tall oil rosin, hydrogenated rosin and disproportionated rosin.

8. The method according to claim 1, characterized in that The composite catalyst described in step (1) is a mixture of p-toluenesulfonic acid and calcium acetate, and the mass ratio of p-toluenesulfonic acid to calcium acetate is 1-2:

1.

9. The method according to claim 1, characterized in that: The mass of the antioxidant described in step (2) is 0.1-0.2% of the mass of rosin or rosin derivatives.

10. The method according to claim 1, characterized in that The antioxidant described in step (2) is one or more selected from 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), β-(4-hydroxyphenyl-3,5-di-tert-butyl)propionate and 2,2'-thiobis[ethyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; and one or more selected from tris(nonylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite and triphenyl phosphite.

11. The method according to claim 10, characterized in that The antioxidant consists of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and tris(2,4-di-tert-butylphenyl) phosphite; the mass ratio of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] to tris(2,4-di-tert-butylphenyl) phosphite is 0.6-3:

1.

12. A rosin methyl ester, characterized in that The rosin methyl ester product comprises rosin methyl ester obtained by the method according to any one of claims 1 to 11, wherein the rosin methyl ester has a viscosity of 240-280 cps at 50° C., an acid value of 5-10 mgKOH / g, and a color less than or equal to Ghana color number 2.

13. Use of rosin methyl ester obtained by the method according to any one of claims 1 to 11 in the preparation of adhesives, coatings, paints or ink products.