Pentaerythritol terephthalic acid alkyd resin and preparation method thereof

Abstract

The invention discloses pentaerythritol terephthalic acid alkyd resin, which is prepared from the following raw materials in parts by mass: 281 to 305 parts of soybean oil, 94 to 102 parts of pentaerythritol, 26 to 28 parts of glycerol, 57 to 63 parts of benzoic acid, 165 to 175 parts of terephthalic acid, 1.8 to 2.2 parts of hypophosphorous acid, 18 to 22 parts of reflux SA-1000 solvent oil and 373 to 382 parts of SA-1500 solvent oil. Various reaction raw material compositions and specific reaction steps are screened out through a large number of experiments, pentaerythritol and benzoic acid which are good in dryness are adopted to be matched, and a small amount of trihydric alcohol glycerin is adopted to reduce the functionality of polyhydric alcohol. A proper amount of hypophosphorous acid is used as an esterification catalyst to promote the esterification reaction of pentaerythritol and benzoic acid, and the esterification reaction of pentaerythritol and terephthalic acid is not obviously promoted by using the proper amount of hypophosphorous acid, so that the cleaning time of the resin is shortened, and meanwhile, the problem of sublimation of benzoic acid is solved. According to the technical means, the clear, transparent and stable pentaerythritol terephthalic acid alkyd resin is directly prepared without an alcoholysis step, the dryness of the resin is faster than that of all-glycerol terephthalic resin, the defects in the prior art can be overcome, and a very good technical effect is achieved.

Description

Technical Field

[0001] The present invention relates to a pentaerythritol terephthalate alkyd resin and a preparation method thereof. Background Art

[0002] Alkyd resin is the most widely used synthetic resin for coatings. Air-drying alkyd resin can be used alone as a paint-making resin, automatically oxidizing and drying in air to form a film that can be made into varnishes, blended paints, enamels, etc.

[0003] Phthalic anhydride is typically used as the polyacid for alkyd resins due to its plentiful raw material, low price, and low reaction temperature. In the past 20 years, industry professionals have begun using waste terephthalic acid or terephthalic acid to produce terephthalic alkyd resins, achieving some success in reducing the cost of alkyd resins. However, using waste terephthalic acid or terephthalic acid introduces new challenges. It is more difficult to react than phthalic anhydride and isophthalic acid, leading to the general use of the fatty acid method and the rarer alcoholysis method. Alkyd resins produced by the alcoholysis method are rarely clear, and therefore, the resulting resin is often unclear and turbid.

[0004] In patent CN118652413A, which I applied for in 2024, I used soybean oil, glycerin, terephthalic acid, and rosin to directly produce a clear, transparent, and stable terephthalic acid alkyd resin without the need for an alcoholysis step. The resin's performance is comparable to that of terephthalic acid alkyd resin produced by the fatty acid method, and it is also storage-stable and does not become turbid. This invention has been applied in actual production by our company and has been well-received by many customers. Because this invention uses glycerin as the polyol, the paint has a moderate drying time, with a surface drying time of approximately 4.5 hours and a through-drying time of 17 hours. This makes it unsuitable for applications with demanding drying requirements (surface drying within 2 hours and through-drying within 15 hours).

[0005] In summary, if soybean oil, terephthalic acid and pentaerythritol, a polyol with good drying properties, can be used to produce stable, clear and good drying alkyd resin, the application scope of terephthalic acid alkyd resin will definitely be expanded. Summary of the Invention

[0006] Purpose of the Invention: The present invention provides a pentaerythritol terephthalate alkyd resin and a preparation method thereof. Through extensive experimentation, the present invention screened various reaction raw material compositions and specific reaction steps. The present invention utilizes pentaerythritol and benzoic acid, both of which have good drying properties, and incorporates a small amount of triol glycerol to reduce the functionality of the polyol. An appropriate amount of hypophosphorous acid is used as an esterification catalyst to promote the esterification reaction between pentaerythritol and benzoic acid. While hypophosphorous acid does not significantly promote the esterification reaction between pentaerythritol and terephthalic acid, the present invention not only accelerates the resin's clearing time but also solves the problem of benzoic acid sublimation.

[0007] The above technical means enable the direct preparation of a clear, transparent, and stable pentaerythritol terephthalate alkyd resin without the need for an alcoholysis step. The resin dries faster than a 100% glycerol-containing terephthalate resin, overcoming the shortcomings of existing technologies and achieving excellent technical results. This has important application value.

[0008] Technical solution: In order to achieve the above objectives, the technical solution adopted by the present invention is: A pentaerythritol terephthalate alkyd resin is prepared from the following raw materials in parts by mass: The invention is made from 281-305% soybean oil, 94-102% pentaerythritol, 26-28% glycerin, 57-63% benzoic acid, 165-175% terephthalic acid, 1.8-2.2% hypophosphorous acid, 18-22% reflux SA-1000 solvent oil and 373-382% SA-1500 solvent oil.

[0009] As a preferred embodiment, the above-mentioned pentaerythritol terephthalate alkyd resin is characterized in that the pentaerythritol is 95 grade industrial pentaerythritol.

[0010] As a preferred embodiment, in the above-mentioned pentaerythritol terephthalate alkyd resin, the glycerol content is greater than or equal to 95%, preferably greater than or equal to 98%.

[0011] As a preferred embodiment, the above-described pentaerythritol terephthalate alkyd resin, wherein the hypophosphorous acid is an industrial hypophosphorous acid having a content greater than or equal to 50%, preferably an industrial hypophosphorous acid having a content of 50 to 52%. As a preferred embodiment, in the above-mentioned pentaerythritol terephthalate alkyd resin, the SA-1000 solvent oil is a solvent having a distillation range of 155-175°C and a density between 0.862-0.875 (20°C).

[0012] As a preferred embodiment, in the above-mentioned pentaerythritol terephthalate alkyd resin, the SA-1500 solvent oil is a solvent with a distillation range of 180-210°C, a density between 0.890-0.930 (20°C), and a flash point between 62-70°C (closed cup).

[0013] A preparation method of pentaerythritol terephthalate alkyd resin comprises the following steps: 1) After introducing nitrogen or carbon dioxide protective gas into the reactor, start the reactor and stir. Add soybean oil, pentaerythritol, glycerol, benzoic acid, terephthalic acid, and hypophosphorous acid into the reactor according to mass parts. After heating, turn off the nitrogen or carbon dioxide protective gas, continue to heat, keep warm, and take samples until the resin is clear and transparent. 2) After the resin becomes transparent, continue to keep the temperature for a while, then cool it down and slowly add the reflux SA-1000 solvent oil into the reactor for reflux esterification; 3) After reflux esterification, start taking samples to measure the acid value and viscosity. When the acid value and viscosity are qualified, immediately cool down, then partially dilute the SA-1500 solvent oil and pour it into the dilution kettle. Add the remaining solvent into the dilution kettle, stir evenly, and cool down to obtain the resin.

[0014] As a preferred embodiment, the preparation method of the pentaerythritol terephthalate alkyd resin described in the present invention comprises the following steps: 1) After nitrogen or carbon dioxide protective gas is introduced into the reactor for 15 minutes, the reactor is opened and stirred. 281-305 parts by mass of soybean oil, 94-102 parts by mass of pentaerythritol, 26-28 parts by mass of glycerol, 57-63 parts by mass of benzoic acid, 165-175 parts by mass of terephthalic acid, and 1.8-2.2 parts by mass of hypophosphorous acid are added into the reactor. The temperature is raised to 200°C, the nitrogen or carbon dioxide protective gas is turned off, and the temperature is continued to rise to 240-250°C. After keeping the temperature for 2 hours, a sample is taken until the resin is clear and transparent.

[0015] 2) After the resin becomes transparent, continue to keep the temperature for 30 minutes, then cool it down to 220℃. Slowly add 18-22 parts by weight of reflux SA-1000 solvent oil into the reactor and reflux esterification at 200℃-220℃.

[0016] 3) After 1 hour of reflux esterification, start sampling to measure the acid value and viscosity until the acid value reaches less than 6 mgKOH / g (solid). Viscosity: 50-70 seconds* format tube (SA-1500 to 60 solid content). After the acid value and viscosity are qualified, immediately cool down. When the kettle temperature drops to 200°C, dilute 373-382 parts by mass of SA-1500 solvent oil and pour it into the dilution kettle. Pour the remaining solvent into the dilution kettle, stir evenly, and then cool down to below 100°C to obtain a resin with a solid content of 59-61%.

[0017] The present invention mainly realizes the following points to directly prepare clear, transparent and stable terephthalic acid alkyd resin using soybean oil, pentaerythritol, benzoic acid and terephthalic acid without the need for an alcoholysis step: 1. During screening, the present inventors discovered that pentaerythritol is more difficult to prepare alkyd resin using whole soybean oil without alcoholysis than glycerol. This is because pentaerythritol has a higher functionality and is more likely to react with terephthalic acid to form insoluble matter. If pentaerythritol is the only polyol used, the resin is difficult to clear and requires incubation at 240-250°C for over 8 hours. During this time, the resin is very viscous and unsuitable for coatings. A small amount of glycerol resin with lower functionality must be added to achieve clarity within 3 hours, while minimizing the effect on the resin's drying properties.

[0018] 2. The present invention also found in the screening that the polyol mainly uses pentaerythritol. If it is matched with monoacid rosin, the resin will not be clear and will be gelled. Or because the functionality of pentaerythritol is large, some pentaerythritol molecules must be connected to two monoacids so that the resin will be easy to clear. Due to steric hindrance, the steric hindrance of large-molecule monoacid rosin is large, and it is difficult to connect two large-molecule monoacid rosins at the same time. A monoacid with a smaller molecular weight is needed to match. We began to screen isooctanoic acid and benzoic acid. Isooctanoic acid reacts well but has poor drying properties. Benzoic acid is easy to sublimate, which not only increases consumption but also blocks the condenser. In the patent CN118652413A applied by me in 2024, about 1‰ of hypophosphorous acid color reducer was added to the soybean oil, glycerol, terephthalic acid and rosin system, and the resin was difficult to clear. This is because hypophosphorous acid has the effect of catalyzing esterification reaction. Under hypophosphorous acid conditions, terephthalic acid and glycerol are more likely to react to form insoluble matter, resulting in the resin being difficult to clear and having high viscosity. However, in the present invention, it is found that an appropriate amount of hypophosphorous acid can promote the esterification reaction of pentaerythritol and benzoic acid, while an appropriate amount of hypophosphorous acid does not significantly promote the esterification reaction of pentaerythritol and terephthalic acid. In the present invention, an appropriate amount of hypophosphorous acid is used to promote the esterification reaction of pentaerythritol and benzoic acid, thereby solving the problem of benzoic acid sublimation.

[0019] 3. The present invention has also found in screening that, without hypophosphorous acid, not only benzoic acid can sublime, resin also is difficult to be limpid, or because monoprotic acid formic acid does not well connect with pentaerythritol molecule, the functionality of pentaerythritol does not decline, and easily generates insoluble matter with terephthalic acid, and resin is not easy to be clear.If use the esterification catalyst of organotin class, it promotes very obviously to the esterification reaction of pentaerythritol and terephthalic acid, easily generates insoluble matter, and resin is not clear.But the amount of hypophosphorous acid also will be controlled well, the present invention has also found in screening, the hypophosphorous acid amount is less than the present invention's amount, and catalytic effect is not obvious, if greater than the present invention's amount, hypophosphorous acid promotes obviously to the esterification reaction of pentaerythritol and terephthalic acid, and resin is difficult to be clear, arrives certain amount, and resin can not be limpid.

[0020] 4. The present invention also finds in screening that if 95 grades of industrial pentaerythritols are substituted for the present invention's use with 98 grades of industrial pentaerythritols, the resin is easily clear under the same conditions. This is because 95 grades of industrial pentaerythritols contain a small amount of dipentaerythritol with higher functionality, which is more likely to react with terephthalic acid to generate insoluble matter. If the present invention uses 98 grades of industrial pentaerythritols, even without adding hypophosphorous acid, the resin also will be clear and transparent, but the time to become clear will increase, and benzoic acid will sublime, blocking the condenser, causing the reaction to be unable to proceed. Considering comprehensive cost, the present invention selects 95 grades of industrial pentaerythritols for use.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following advantages: The present invention screens out various reaction raw material compositions and specific reaction steps through a large number of experiments, adopts pentaerythritol and benzoic acid with good drying properties, and adopts a small amount of triol glycerol to reduce the functionality of the polyol. An appropriate amount of hypophosphorous acid is used as an esterification catalyst to promote the esterification reaction of pentaerythritol and benzoic acid, while the use of an appropriate amount of hypophosphorous acid to promote the esterification reaction of pentaerythritol and terephthalic acid is not obvious, not only accelerating the clearing time of the resin, but also solving the problem of benzoic acid sublimation. The above technical means are achieved without the need for an alcoholysis step, and a clear, transparent and stable pentaerythritol terephthalic acid alkyd resin is directly prepared. The drying property of the resin is faster than that of a terephthalic acid resin containing all glycerol. Specific embodiments

[0022] The embodiments of the present invention are described in detail below with reference to the examples. In the examples, if the specific conditions are not specified, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be obtained commercially.

[0023] In the following examples of the present invention, the pentaerythritol is 95-grade industrial pentaerythritol, the glycerol is glycerol with a content of greater than or equal to 95%, and the hypophosphorous acid is industrial hypophosphorous acid with a content of greater than or equal to 50%.

[0024] The SA-1000 solvent oil is a solvent with a distillation range of 155-175° C. and a density between 0.862-0.875 (20° C.).

[0025] The SA-1500 solvent oil is a solvent with a distillation range of 180-210° C., a density between 0.890-0.930 (20° C.), and a flash point between 62-70° C. (closed cup).

[0026] The raw material compositions of the following examples are shown in Table 1: Table 1 Raw material composition of each example

[0027] The method for preparing the quick-drying high-performance alkyd resin of the present invention comprises the following steps: 1) After nitrogen or carbon dioxide protective gas was introduced into the flask for 15 minutes, stirring was started. Soybean oil, pentaerythritol, glycerol, benzoic acid, terephthalic acid, and hypophosphorous acid were added to the flask in the amounts by mass according to Examples 1 to 5. The temperature was raised to 200°C, the nitrogen or carbon dioxide protective gas was turned off, and the temperature was further raised to 240-250°C. After holding for 2 hours, a sample was taken. In Examples 1 to 5, the resin was generally clear and transparent after about 2 hours.

[0028] 2) After the resin becomes transparent, continue to keep the temperature for 30 minutes, then cool it down to 220°C. Slowly add 1 to 5 parts by weight of reflux SA-1000 solvent oil into the flask according to the above example, and reflux at 200°C-220°C for esterification.

[0029] 3) After reflux esterification for 1 hour, begin sampling and measuring the acid value and viscosity until the acid value reaches less than 6 mgKOH / g (solid). Viscosity: 50-70 seconds* (format tube (SA-1500 to 60% solid content). After the acid value and viscosity meet the requirements, immediately cool the flask. When the flask temperature drops to 200°C, add all of the SA-1500 solvent oil in the amounts of 1 to 5 parts by weight according to the above example to the flask. After stirring evenly, cool the flask to below 100°C to obtain a resin with a solid content of 59 to 61%.

[0030] Comparative Example 1 (full pentaerythritol, glycerol-free) 1) After nitrogen protective gas is introduced into the flask for 15 minutes, the reactor is opened for stirring and 293 parts by mass of soybean oil, 130 parts of pentaerythritol, 60 parts of benzoic acid, 168 parts of terephthalic acid and 2.0 parts of hypophosphorous acid are added into the reactor. The temperature is raised to 200°C and the nitrogen protective gas is turned off. The temperature is further raised to 240-250°C and kept warm for 8.5 hours until the resin begins to become clear. The temperature is kept warm for 30 minutes and then lowered to 220°C. 20 parts by mass of reflux SA-1000 solvent oil is slowly added into the reactor and refluxed at 200-220°C for esterification.

[0031] 3) After 1 hour of reflux esterification, samples were taken to measure the acid value and viscosity. The acid value was 12.3 mgKOH / g (solid), and the viscosity was 264 seconds per square tube (SA-1500 to 60 solid content), which was close to gelation. The experiment failed.

[0032] Comparative Example 2 (using monobutyltin oxide instead of hypophosphorous acid as catalyst) Table 2 Raw material composition of each embodiment 2

[0033] After nitrogen was introduced into the flask for 15 minutes, stirring was started. Soybean oil, pentaerythritol, glycerol, benzoic acid, terephthalic acid, and monobutyltin oxide were added to the flask in the same proportions as described above for Examples 2A to 2D. The temperature was raised to 200°C, the nitrogen or carbon dioxide gas was turned off, and the temperature was further raised to 240-250°C and kept for 8 hours. Samples were taken after the resin was still turbid, with a colloidal suspension in the flask. The turbidity gradually worsened with increasing amounts of monobutyltin oxide, and the experiment failed.

[0034] Comparative Example 3 (using rosin instead of benzoic acid)

[0035]

[0036] After nitrogen or carbon dioxide protective gas was introduced into the flask for 15 minutes and stirring was started, soybean oil, pentaerythritol, glycerin, rosin, terephthalic acid, monobutyltin oxide, and hypophosphorous acid were added to the flask in the same proportions by weight as described above for Examples 3A-D. The temperature was raised to 200°C, the nitrogen or carbon dioxide protective gas was turned off, and the temperature was further raised to 240-250°C and maintained for 1-1.5 hours. The resins all began to gel and stratify, becoming turbid. The four comparative examples 3A-3D showed similar results, and the experiment failed.

[0037] Comparative Example 4 (Based on Example 4, the amount of hypophosphorous acid was adjusted)

[0038]

[0039] 1) After nitrogen or carbon dioxide blanketing gas was introduced into the flask for 15 minutes, stirring was initiated. Soybean oil, pentaerythritol, glycerol, benzoic acid, terephthalic acid, and hypophosphorous acid were added to the flask in the same proportions as described above for Examples 4A-D. The temperature was raised to 200°C, the nitrogen or carbon dioxide blanketing gas was turned off, and the temperature was continued to 240-250°C and held for 2 hours before sampling. The resins in Comparative Examples 4A and 4D remained turbid after 9 hours of holding, indicating failure in these two experiments. Too little hypophosphorous acid does not significantly catalyze the esterification reaction between pentaerythritol and benzoic acid, while too much hypophosphorous acid can catalyze the esterification reaction between pentaerythritol and terephthalic acid.

[0040] 2) After 4 hours of incubation in Comparative Example 4B and 5 hours of incubation in Comparative Example 4C, the resin began to become clear. The temperature was continued to be maintained for 30 minutes, and then the temperature was lowered to 220°C. 18% by weight of reflux SA-1000 solvent oil was slowly added to the flask, and esterification was refluxed between 200°C and 220°C.

[0041] 3) After reflux esterification for 1 hour, begin sampling to measure the acid value and viscosity until the acid value reaches less than 6 mgKOH / g (solid). Measure the viscosity of the flask (SA-1500 to 60% solid content) and cool the flask. When the flask temperature drops to 200°C, add all of the 382% by mass SA-1500 solvent oil to the flask, stir evenly, and cool to below 100°C to obtain a resin with a solid content of 59-61%.

[0042] Comparative Example 5 (Using 98-grade industrial pentaerythritol without adding hypophosphorous acid) 1) After nitrogen or carbon dioxide protective gas is introduced into the flask for 15 minutes, start the reactor and stir. Add 293 parts by mass of soybean oil, 98 parts of industrial pentaerythritol, 27 parts of glycerol, 60 parts of benzoic acid, and 168 parts of terephthalic acid into the flask. Raise the temperature to 200°C, turn off the nitrogen or carbon dioxide protective gas, and continue to raise the temperature to 240-250°C and keep it warm for 4 hours. The resin begins to become clear and benzoic acid condenses on the upper part of the flask and on the condenser.

[0043] 2) After the resin becomes transparent, continue to keep the temperature for 30 minutes, then cool it down to 220℃, slowly add 20 parts by mass of reflux SA-1000 solvent oil into the reactor, and reflux esterification at 200℃-220℃.

[0044] 3) After reflux esterification for 1 hour, sampling was started to measure the acid value and viscosity until the acid value reached 3.5 mgKOH / g (solid). Viscosity: 145 seconds * format tube (SA-1500 to 60 solid content). After the acid value and viscosity were qualified, the temperature was immediately lowered. When the kettle temperature dropped to 200°C, 380 parts by weight of SA-1500 solvent oil was partially diluted and transferred to the dilution kettle. The remaining solvent was added to the dilution kettle. After stirring evenly, the temperature was lowered to below 100°C to obtain the resin of Comparative Example 5.

[0045] Comparative Example 6 (using 2-ethylhexanoic acid instead of benzoic acid) 1) After nitrogen or carbon dioxide protective gas is introduced into the flask for 15 minutes, start the reactor and stir. Add 293 parts by mass of soybean oil, pentaerythritol, 27 parts of glycerol, 60 parts of isooctanoic acid, 168 parts of terephthalic acid and 2.0 parts of hypophosphorous acid into the flask. Heat the flask to 200°C, turn off the nitrogen or carbon dioxide protective gas, and continue to heat the flask to 240-250°C. Keep warm for 2 hours until the resin begins to become clear.

[0046] 2) After the resin becomes transparent, continue to keep the temperature for 30 minutes, then cool it down to 220℃, slowly add 20 parts by mass of reflux SA-1000 solvent oil into the reactor, and reflux esterification at 200℃-220℃.

[0047] 3) After reflux esterification for 1 hour, sampling was started to measure the acid value and viscosity. The acid value was 2.9 mgKOH / g (solid), and the viscosity was 32 seconds * format tube (SA-1500 to 60 solid content). After the acid value and viscosity were qualified, the temperature was immediately lowered. When the kettle temperature dropped to 200°C, 380 parts by mass of SA-1500 solvent oil was partially diluted and poured into the dilution kettle. The remaining solvent was poured into the dilution kettle. After stirring evenly, the temperature was lowered to below 100°C to obtain the resin of Comparative Example 6.

[0048] Application Example 1 1. Take the alkyd resins obtained in Examples 1 to 5 and Comparative Examples 4B, 4C, 5, and 6 above and prepare colored paints according to the paint formula in Table 5 below: Table 5 Paint formula raw material Ratio (number of servings) Resin (Examples 1 to 5 and Comparative Examples 4B, 4C, 5, and 6) 50 Titanium dioxide 22 Heavy Calcium 17 Wetting and dispersing agents 1 Bentonite 0.1 wax paste 0.5 Anti-skinning agent 0.2 Drier 0.5 SA-1500 solvent oil 8.7

[0049] The paints prepared in Examples 1 to 5 and Comparative Examples 1-2 were tested as follows: Among them, flexibility is in accordance with the GB / T1731-2020 standard method.

[0050] Impact strength is in accordance with GB / T1732-2020 standard method.

[0051] Surface drying and through drying are in accordance with the GB / T1728-2020 standard method.

[0052] Gloss is in accordance with GB / T9754-2007 standard method.

[0053] Hardness is in accordance with GB / T6739-2022 standard method.

[0054] The specific paint test results are shown in Table 6: Table 6 Paint test results Detection indicators Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 4B Comparative Example 4C Comparative Example 5 Comparative Example 6 Surface drying time (h) 1.5 1.5 1.5 1.5 1.5 2.5 4.5 2.5 4.5 Work hard (h) 15 15 15 15 15 18 24 18 30 Gloss (60°) 95-99 95-99 95-99 95-99 95-99 95-99 95-99 95-99 95-99 flexibility 1mm 1mm 1mm 1mm 1mm 1mm 1mm 1mm 1mm Impact strength (kg.cm) 50 positive and negative 50 positive and negative 50 positive and negative 50 positive and negative 50 positive and negative 50 positive and negative 50 positive and negative 50 positive and negative 50 positive and negative hardness HB HB HB HB HB B B B 2B The above experimental results show that the present invention has screened out various reaction raw materials and reaction specific steps through a large number of experiments, adopts pentaerythritol and benzoic acid with good dryness to match, and adopts a small amount of trivalent alcohol glycerol to reduce the functionality of polyol. The appropriate amount of hypophosphorous acid adopted is used as an esterification catalyst to promote the esterification reaction of pentaerythritol and benzoic acid, and the esterification reaction of pentaerythritol and terephthalic acid promoted by an appropriate amount of hypophosphorous acid is not obvious, not only accelerates the clearing time of resin, but also solves the problem of benzoic acid sublimation. By the above technical means, it is realized that no alcoholysis step is required, and clear and transparent stable pentaerythritol terephthalic acid alkyd resin is directly prepared, and the dryness of resin is faster than that of phenyl resin with full glycerol, which can overcome the deficiencies in the prior art and obtain good technical effect.

[0055] Examples 1-5: Within the scope of the present invention, good results were achieved.

[0056] For Example 4B, Example 4C, and Comparative Example 5: Since the resin was kept warm for a long time, the molecular weight distribution of the resin was wide, and an etherification side reaction occurred, resulting in a decrease in the dryness and hardness of the resin.

[0057] Comparative Example 6: The glass transition temperature of 2-ethylhexanoic acid is low, and the drying property and hardness of the resin are poor.

Claims

1. A pentaerythritol terephthalate alkyd resin, characterized in that: It is made from soybean oil, pentaerythritol, glycerin, benzoic acid, terephthalic acid, hypophosphorous acid, refluxed SA-1000 solvent oil and SA-1500 solvent oil.

2. A pentaerythritol terephthalate alkyd resin according to claim 1, characterized in that: It is prepared from the following raw materials in parts by weight: 281-305 parts of soybean oil, 94-102 parts of pentaerythritol, 26-28 parts of glycerin, 57-63 parts of benzoic acid, 165-175 parts of terephthalic acid, 1.8-2.2 parts of hypophosphorous acid, 18-22 parts of reflux SA-1000 solvent oil and 373-382 parts of SA-1500 solvent oil.

3. A pentaerythritol terephthalate alkyd resin according to claim 1, characterized in that: The pentaerythritol is 95 grade industrial pentaerythritol.

4. A pentaerythritol terephthalate alkyd resin according to claim 1, characterized in that The glycerol content is greater than or equal to 95%.

5. The pentaerythritol terephthalate alkyd resin according to claim 1, characterized in that: The hypophosphorous acid is industrial hypophosphorous acid with a content of greater than or equal to 50%.

6. The pentaerythritol terephthalate alkyd resin according to claim 1, characterized in that: The SA-1000 solvent oil is a solvent with a distillation range of 155-175° C. and a density of 0.862-0.875 at 20° C.

7. The pentaerythritol terephthalate alkyd resin according to claim 1, characterized in that: The SA-1500 solvent oil has a distillation range of 180-210° C., a density of 0.890-0.930 at 20° C., and a closed-cup flash point of 62-70° C.

8. The method for preparing a pentaerythritol terephthalate alkyd resin according to claim 1, wherein: The following steps are involved: 1) After introducing nitrogen or carbon dioxide protective gas into the reactor, start the reactor and stir. Add soybean oil, pentaerythritol, glycerol, benzoic acid, terephthalic acid, and hypophosphorous acid into the reactor according to mass parts. After heating, turn off the nitrogen or carbon dioxide protective gas, continue to heat, keep warm, and take samples until the resin is clear and transparent. 2) After the resin becomes transparent, continue to keep the temperature for a while, then cool it down and slowly add the reflux SA-1000 solvent oil into the reactor for reflux esterification; 3) After reflux esterification, start taking samples to measure the acid value and viscosity. When the acid value and viscosity are qualified, immediately cool down, then partially dilute the SA-1500 solvent oil and pour it into the dilution kettle. Add the remaining solvent into the dilution kettle, stir evenly, and cool down to obtain the resin.

9. The method for preparing a pentaerythritol terephthalate alkyd resin according to claim 8, wherein: The following steps are involved: 1) After nitrogen or carbon dioxide protective gas is introduced into the reactor for 15-30 minutes, the reactor is opened and stirred. 281-305 parts by weight of soybean oil, 94-102 parts of pentaerythritol, 26-28 parts of glycerol, 57-63 parts of benzoic acid, 165-175 parts of terephthalic acid, and 1.8-2.2 parts of hypophosphorous acid are added into the reactor. The temperature is raised to 200°C, the nitrogen or carbon dioxide protective gas is turned off, and the temperature is continued to rise to 240-250°C. Keep warm for 1-3 hours and take samples until the resin is clear and transparent. 2) After the resin becomes transparent, continue to keep the temperature for 20-40 minutes, then cool it down to 220°C. Slowly add 18-22 parts by weight of reflux SA-1000 solvent oil into the reactor and reflux at 200-220°C for esterification. 3) After reflux esterification for 1-2 hours, start taking samples to measure the acid value and viscosity. When the acid value and viscosity are qualified, immediately cool down. When the kettle temperature drops to 200°C, dilute 373-382 parts by mass of SA-1500 solvent oil and pour it into the dilution kettle. Pour the remaining solvent into the dilution kettle, stir evenly, and then cool down to below 100°C to obtain the resin.

10. The method for preparing a pentaerythritol terephthalate alkyd resin according to claim 9, wherein: The following steps are involved: 1) After nitrogen or carbon dioxide protective gas is introduced into the reactor for 15 minutes, the reactor is opened and stirred. 281-305 parts by weight of soybean oil, 94-102 parts of pentaerythritol, 26-28 parts of glycerol, 57-63 parts of benzoic acid, 165-175 parts of terephthalic acid, and 1.8-2.2 parts of hypophosphorous acid are added into the reactor. The temperature is raised to 200°C, the nitrogen or carbon dioxide protective gas is turned off, and the temperature is continued to rise to 240-250°C. Keep warm for 2 hours and take samples until the resin is clear and transparent. 2) After the resin becomes transparent, continue to keep the temperature for 30 minutes, then cool it down to 220°C. Slowly add 18-22 parts by weight of reflux SA-1000 solvent oil into the reactor and reflux at 200-220°C for esterification. 3) After 1 hour of reflux esterification, start sampling to measure the acid value and viscosity until the acid value reaches less than 6 mgKOH / g solid. Viscosity: 50-70 seconds* format tube, SA-1500 with 60% solid content. After the acid value and viscosity are qualified, cool down immediately. When the kettle temperature drops to 200℃, dilute 373-382 parts of SA-1500 solvent oil by mass and pour it into the dilution kettle. Pour the remaining solvent into the dilution kettle, stir evenly, and then cool to below 100℃ to obtain a resin with a solid content of 59~61%.

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