A modified alkyd resin special for quick-drying ink and a preparation method thereof

Abstract

This invention provides a modified alkyd resin for fast-drying inks and its preparation method, comprising a dry resin and additives. The dry resin is prepared from the following raw materials: 48-58 parts of dehydrated castor oil fatty acid, 14-19 parts of tetrahydrophthalic anhydride, 8-12 parts of neopentyl glycol, 10-15 parts of trimethylolpropane, 3-7 parts of tall oil fatty acid, 2-4 parts of stearic acid, and 0.06-0.18 parts of esterification catalyst; wherein the total carboxyl equivalent provided by the dehydrated castor oil fatty acid, tetrahydrophthalic anhydride, tall oil fatty acid, and stearic acid is n. COOH The total hydroxyl equivalent provided by neopentyl glycol and trimethylolpropane is n. OH R = n OH / n COOH The values ​​are 1.10 to 1.14. This invention prepares dry resin by controlling the relationship between total hydroxyl equivalent and total carboxyl equivalent, the acid value and hydroxyl value of the dry resin; and uses Gardner bubble viscosity to determine the finished resin, so that the functional groups, molecular weight and viscosity of the dry resin are controlled simultaneously, taking into account both fast drying and storage stability.

Description

Technical Field

[0001] This invention relates to the field of resin synthesis technology for printing inks, and in particular to a modified alkyd resin for fast-drying inks and its preparation method. Background Technology

[0002] Alkyd resins are widely used as binders in offset and solvent-based printing inks due to their combination of the oxidative crosslinking activity of fatty acid side chains and the film-forming properties of polyester backbones. In ink applications, binders need to maintain good flowability and pigment wetting during printing, while also rapidly losing flowability after printing to prevent smudging and sticking during stacking.

[0003] To improve the fast-drying properties of alkyd resins, the art typically employs methods such as increasing the unsaturation of raw materials, increasing branching degree, or increasing molecular weight. Dehydrated castor oil fatty acids (DCOFA), due to their conjugated diene structure, exhibit significantly better oxidative crosslinking activity than ordinary unsaturated fatty acids, making them an important raw material for preparing fast-drying alkyd resins. However, while the high conjugated diene content of DCOFA brings the advantage of rapid oxidative film formation, it also presents significant technical challenges: on the one hand, excessively low resin molecular weight or excessively high hydroxyl value can lead to insufficient crosslinking density and poor abrasion resistance in the ink film; on the other hand, increasing branching degree or polycondensation degree to improve molecular weight and crosslinking density can easily result in excessively high system viscosity, decreased pigment wettability, and viscosity drift and surface skinning during storage due to continued reaction of residual active groups.

[0004] To address the aforementioned contradictions, existing technologies typically address them in the following ways: First, by controlling the excess amount of polyols to regulate molecular weight and end-group functionality. However, the excess ratio of polyols lacks precise constraints based on functional group equivalents, leading to significant fluctuations in acid value, hydroxyl value, and viscosity between different batches. Second, by introducing saturated monobasic fatty acids (such as stearic acid) as chain terminators to reduce system polarity and the tendency for increased storage viscosity. However, the addition of stearic acid dilutes the oxidative crosslinking network of unsaturated components, and improper dosage significantly slows down the drying rate. Existing technologies have not yet provided a clear solution for achieving a balance between rapid drying and storage stability. Third, by selecting different combinations of diols and triols to regulate the degree of branching. However, most of these methods rely solely on empirical adjustments based on mass ratios, without considering the actual acid value and functionality of each raw material, making it difficult to achieve precise control of the molecular structure.

[0005] Furthermore, existing technologies employ varying methods for determining the endpoint of polycondensation. Some literature uses the acid value of the reaction system as a single endpoint indicator, while others use Gardner bubble viscosity as the endpoint criterion. However, for highly conjugated diene fatty acid systems, using the viscosity of undiluted dry resin as the endpoint can lead to significant measurement errors due to the extremely high viscosity and temperature sensitivity of the dry resin, potentially resulting in insufficient or excessive polycondensation. Conversely, using only acid value as the endpoint cannot guarantee that the hydroxyl values ​​of the resin end groups will simultaneously fall within the target range, thus affecting the crosslinking density and abrasion resistance of the subsequent ink film. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a modified alkyd resin for fast-drying inks and its preparation method, which solves the problems in the prior art where the dosage is determined only by the mass parts of each raw material without constraining the relationship between the total hydroxyl equivalent and the total carboxyl equivalent, resulting in the inability to simultaneously achieve the target acid value, hydroxyl value and viscosity, and the incorrect determination of the polycondensation endpoint due to the unclear object of Gardner bubble viscosity measurement.

[0007] To achieve the above and other related objectives, the present invention provides the following technical solutions: In a first aspect, the present invention provides a modified alkyd resin for fast-drying inks, comprising a dry resin and additives; The dry resin, by weight, is prepared from the following raw materials: 48-58 parts of dehydrated castor oil fatty acid, 14-19 parts of tetrahydrophthalic anhydride, 8-12 parts of neopentyl glycol, 10-15 parts of trimethylolpropane, 3-7 parts of tall oil fatty acid, 2-4 parts of stearic acid, and 0.06-0.18 parts of esterification catalyst. The total carboxyl equivalent provided by the dehydrated castor oil fatty acids, tetrahydrophthalic anhydride, tall oil fatty acids, and stearic acid is n. COOH The total hydroxyl equivalent provided by the neopentyl glycol and trimethylolpropane is n. OH R = n OH / n COOH It ranges from 1.10 to 1.14.

[0008] Specifically, when each fatty acid is measured based on its acid value and tetrahydrophthalic anhydride is calculated based on the reaction equivalence of providing two carboxyl groups per mole, the equivalence relationship is determined according to the following formula: n OH =2m(NPG) / M(NPG)+3m(TMP) / M(TMP), n COOH =m(DCOFA)×AV(DCOFA) / 56100+m(TOFA)×AV(TOFA) / 56100+m(SA)×AV(SA) / 56100+2m(THPA) / M(THPA), In the formula, m represents the mass of the corresponding raw material, M represents the molar mass of the corresponding raw material, AV represents the measured acid value of the corresponding fatty acid; NPG represents neopentyl glycol, TMP represents trimethylolpropane, DCOFA represents dehydrated castor oil fatty acids, TOFA represents tall oil fatty acids, SA represents stearic acid, and THPA represents tetrahydrophthalic anhydride. Acid value is expressed in mgKOH / g, mass in g, and molar mass in g / mol. In the above formula, 56100 is the product of the molar mass of potassium hydroxide (56.1 g / mol) and the mass conversion factor 1000.

[0009] The above-mentioned weight range should be selected based on the measured acid value and molar mass of the raw materials to ensure that R meets the requirements of 1.10 to 1.14. This R value range is an operable window determined for the specific raw material system and endpoint indicators of this invention: samples with R=1.10 and R=1.14 can simultaneously meet the requirements for dry resin acid value, hydroxyl value, number-average molecular weight, and finished resin viscosity; when R is below 1.10, the excess margin of hydroxyl groups is insufficient, and continued polycondensation will result in higher molecular weight and viscosity; when R is above 1.14, the hydroxyl value is still too high when the acid value reaches the lower limit, and the molecular weight and finished resin viscosity are too low.

[0010] Meanwhile, the dry resin has an acid value of 8–12 mg KOH / g and a hydroxyl value of 35–45 mg KOH / g. The acid value was determined by titration with a potassium hydroxide ethanol standard solution, and the hydroxyl value was determined by back titration after acetylation.

[0011] This invention addresses highly conjugated dienoic acid resin systems with dehydrated castor oil fatty acids as the main unsaturated monomers, providing a method for precisely controlling the ratio of total hydroxyl equivalents to total carboxyl equivalents (R=n). OH / n COOH This technical solution, which limits the acid value and hydroxyl value of the dry resin as the polycondensation endpoint (range 1.10–1.14), addresses the problems in existing technologies where uncontrolled equivalence relationships lead to the inability to simultaneously meet acid value, hydroxyl value, and viscosity standards, and where unclear endpoint determination criteria result in poor batch stability. Furthermore, by limiting the dosage of stearic acid within a specific range as an end-adjusting component, viscosity growth and skinning during storage are suppressed without significantly sacrificing fast drying properties, thus achieving a comprehensive balance between fast drying, printability, and storage stability.

[0012] Furthermore, the iodine value of the dehydrated castor oil fatty acids is 140–153 gI₂ / 100g, the mass content of conjugated diene fatty acids is not less than 35%, and the acid value is 187–195 mgKOH / g. The fact that the mass content of conjugated diene fatty acids in the dehydrated castor oil fatty acids is not less than 35% ensures the content of conjugated unsaturated structures in the resin, thereby promoting the oxidative cross-linking of the ink film after printing, improving the initial curing speed and the ink film's abrasion resistance.

[0013] Furthermore, the APHA color of the tetrahydrophthalic anhydride is not greater than 30.

[0014] Furthermore, the abietic acid content in the tall oil fatty acids is no more than 2% by mass. A abietic acid content of no more than 2% in the tall oil fatty acids is beneficial for controlling the resin color and storage stability.

[0015] Furthermore, the mass ratio of neopentyl glycol to trimethylolpropane is 1:1.2 to 1:1.5. This ratio, constrained by the total equivalent ratio R, further limits the ratio between difunctional and trifunctional polyols, which is beneficial for achieving a balance between chain growth and controlled branching, resulting in a resin with suitable molecular weight and degree of branching.

[0016] Furthermore, the number-average molecular weight of the dry resin is 4000–6000, which was determined using gel permeation chromatography with tetrahydrofuran as the mobile phase and polystyrene as the calibration standard. A number-average molecular weight within the range of 4000–6000 is beneficial for the resin to form stable adsorption on the pigment surface, while maintaining suitable rheological properties, thus balancing pigment wettability and ink film strength.

[0017] Furthermore, the added components include an antioxidant and anti-skinning agent, a high-boiling-point low-aromatic hydrocarbon solvent, and soybean oil. Relative to the reactive raw materials used in the preparation of the dry resin, the amount of the antioxidant and anti-skinning agent is 0.05–0.15 parts by weight, the amount of the high-boiling-point low-aromatic hydrocarbon solvent is 12–18 parts by weight, and the amount of soybean oil is 5–9 parts by weight. The high-boiling-point low-aromatic hydrocarbon solvent has a boiling range of 240–280°C and an aromatic hydrocarbon content of no more than 0.5%.

[0018] Furthermore, the antioxidant and anti-skinning adjuvant is selected from 2,6-di-tert-butyl-p-cresol or other phenolic antioxidants.

[0019] Furthermore, the dry resin is vacuum treated, then the additives are added, and the mixture is filtered to obtain the finished resin. The Gardner bubble viscosity of the finished resin measured at 25±0.5℃ is Z4~Z6.

[0020] A second aspect of the present invention provides a method for preparing the above-mentioned modified alkyd resin for fast-drying inks, comprising the following steps: S1. Dehydrated castor oil fatty acids, tall oil fatty acids and stearic acid are added to a reaction vessel, and trimethylolpropane is added in batches under inert gas protection for pre-esterification to obtain fatty acid ester intermediates containing residual hydroxyl groups. S2. Add tetrahydrophthalic anhydride, neopentyl glycol and esterification catalyst to the fatty acid ester intermediate, and carry out polycondensation under inert gas protection. The polycondensation endpoint is obtained when the acid value of the dry resin sample obtained during the polycondensation process and after vacuum removal of volatiles is 8-12 mgKOH / g and the hydroxyl value is 35-45 mgKOH / g. S3. The polycondensation product is subjected to vacuum treatment, and then the additive components are added for formulation. The mixture is then filtered to obtain the modified alkyd resin for quick-drying ink.

[0021] This method involves S1, where three fatty acids are first pre-esterified with trimethylolpropane in a controlled manner to form fatty acid ester intermediates that still retain reactive hydroxyl groups, which is beneficial for uniform chain growth in the subsequent polycondensation stage; S2, using both acid value and hydroxyl value of the dry resin sample as the polycondensation endpoint, rather than relying on the Gardner bubble viscosity of the unmixed dry resin, thus avoiding misjudgment of the endpoint due to unclear viscosity measurement targets; and S3, adding diluents at a lower temperature, which reduces the degree to which soybean oil participates in further transesterification reactions, thus facilitating batch-to-batch consistency control of the viscosity and storage stability of the finished resin.

[0022] Further, in step S1, the pre-esterification includes: heating three fatty acids to 150-165°C, adding trimethylolpropane in batches over 20-40 minutes, then heating to 170-185°C for pre-esterification reaction, taking samples, cooling and measuring the acid value, and ending the pre-esterification when the acid value of the pre-esterification system is 25-35 mgKOH / g to obtain a fatty acid ester intermediate containing the remaining hydroxyl groups.

[0023] Furthermore, in step S1, the inert gas is nitrogen. During the addition of trimethylolpropane to the fatty acids in batches after heating to 150–165°C, esterification water is continuously discharged. Nitrogen protection effectively prevents the oxidation of the conjugated unsaturated structures in the fatty acids of dehydrated castor oil at high temperatures, and continuous drainage helps shift the esterification equilibrium towards ester formation, improving pre-esterification efficiency.

[0024] Further, in step S2, the polycondensation includes: cooling the reaction system to 150-170°C, adding tetrahydrophthalic anhydride, neopentyl glycol, and an esterification catalyst to the fatty acid ester intermediate obtained in step S1, and carrying out the polycondensation reaction by increasing the temperature to 225-235°C at a rate of 6-10°C every 30 minutes under inert gas protection. The endpoint of the polycondensation is defined as an acid value of 8-12 mgKOH / g and a hydroxyl value of 35-45 mgKOH / g for the dry resin sample obtained during the polycondensation process and after the volatiles have been removed by vacuum in the laboratory, thereby obtaining the polycondensation product.

[0025] Furthermore, in step S2, the esterification catalyst is an organotin catalyst, used in an amount of 0.06–0.18 parts by weight. Organotin catalysts exhibit good catalytic activity for esterification reactions.

[0026] Furthermore, the organotin catalyst is selected from monobutyltin oxide or dibutyltin oxide. Alternatively, the esterification catalyst is selected from commonly used esterification catalysts in the art, such as tetrabutyl titanate and p-toluenesulfonic acid.

[0027] Furthermore, the polycondensation endpoint is not determined by the Gardner bubble viscosity of the undiluted dry resin, but solely by the acid value of the dry resin sample (8–12 mg KOH / g) and the hydroxyl value (35–45 mg KOH / g) as the bifunctional endpoint. Clearly defining the endpoint using both acid value and hydroxyl value ensures that the end-group composition of the dry resin is within the target range, avoiding over- or under-reactions caused by viscosity measurement errors.

[0028] Furthermore, in step S3, the added components include an antioxidant and anti-skinning agent, a high-boiling-point low-aromatic hydrocarbon solvent, and soybean oil.

[0029] Further, in step S3, the vacuum treatment includes: cooling the polycondensation product obtained in step S2 to 190-205°C, maintaining it under an absolute pressure of 8-15 kPa for 15-30 minutes for vacuum treatment; after the vacuum treatment, restoring inert gas protection and cooling to 140-160°C, sequentially adding an antioxidant and anti-skinning agent, a high-boiling-point low-aromatic hydrocarbon solvent preheated to 80-120°C, and soybean oil, stirring for 20-40 minutes, and then filtering to obtain the modified alkyd resin for quick-drying ink.

[0030] Furthermore, the antioxidant and anti-skinning agent is 2,6-di-tert-butyl-p-cresol. Adding 2,6-di-tert-butyl-p-cresol at a lower temperature and mixing thoroughly before adding the solvent and soybean oil can provide effective antioxidant protection to the resin system, reducing the risk of oxidative thickening and skinning during storage.

[0031] Furthermore, a 300-mesh filter is used for filtration.

[0032] As described above, the modified alkyd resin for fast-drying inks and its preparation method of the present invention have the following beneficial effects: 1. This invention calculates the R value by measuring the acid value of fatty acids, the functionality of acid anhydrides, and the functionality of polyols, and sets R=n. OH / n COOHThe range of R is limited to 1.10–1.14, ensuring that the acid value, hydroxyl value, and molecular weight of the dry resin are correlated within a repeatable reaction window. Endpoint tests at R=1.10 and R=1.14, and out-of-range comparative tests at R=1.080 and R=1.150, demonstrate the feasibility and critical effects of this range: when R is below 1.10, continued polycondensation results in a molecular weight exceeding 6000, a finished product viscosity exceeding Z6, and increased filter residue; when R is above 1.14, even when the acid value reaches the lower limit, the hydroxyl value still exceeds 45 mg KOH / g, and the molecular weight and finished product viscosity are below the target. Only by controlling R within the range of 1.10–1.14 can all the indicators of functional groups, molecular weight, and finished resin viscosity be stably and simultaneously met.

[0033] 2. This invention clearly distinguishes between the test objects of "dry resin" and "finished resin." The Gardner bubble viscosity Z4-Z6 test object is defined as the original finished resin sample after dilution, preparation, and filtration. The endpoint of polycondensation is no longer determined using the Gardner viscosity of undiluted dry resin. Because the viscosity of dry resin changes significantly after the addition of high-boiling-point solvents and soybean oil, using the viscosity of undiluted dry resin as the endpoint would lead to a systematic deviation in the degree of polycondensation. Using both the acid value and hydroxyl value of the dry resin as the endpoint allows for accurate control of the resin end-group composition, ensuring that the viscosity of the finished resin falls within the Z4-Z6 target window and improving batch consistency.

[0034] 3. This invention uses 2-4 parts by weight of stearic acid as a small amount of saturated end-capping regulator. It is clarified that stearic acid does not act as an active monomer to promote rapid oxidative drying, but rather reduces viscosity drift, surface skinning, and microgel growth during storage by adjusting the end-capping composition and oxidation sensitivity of the highly unsaturated fatty acid resin. Comparative experiments show that completely eliminating stearic acid (replacing it with an equal mass of dehydrated castor oil fatty acids) slightly accelerates initial solidification and surface drying, but the viscosity of the finished resin increases by 28.5% and surface skinning occurs after 14 days of accelerated storage at 50°C. Increasing stearic acid to 6 parts extends the initial solidification time to 41 seconds, the surface drying time to 86 minutes, and the frictional weight loss rate to 2.5%. The amount of 2-4 parts stearic acid, under the premise that unsaturated fatty acids dominate oxidative film formation, simultaneously achieves an initial solidification time of 22-29 seconds, a surface drying time of 36-50 minutes, and an accelerated storage viscosity change rate not exceeding 9.6%, thus achieving a comprehensive balance between rapid drying, rheological properties, and storage stability. Detailed Implementation

[0035] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. It should be noted that, unless otherwise specified, the following embodiments and features described herein can be combined with each other.

[0036] The term "dry resin" as used in this specification refers to the resin product after vacuum treatment of the condensation polymerization product, before the addition of other components. Dry resin is used for the determination of acid value, hydroxyl value, and number-average molecular weight.

[0037] The term "finished resin" as used in this instruction manual refers to the resin binder obtained by adding additives to the above-mentioned dry resin, followed by blending and filtration.

[0038] Gardner bubble viscosity Z4~Z6 was measured only after the finished resin sample was sealed and kept at a constant temperature of 25±0.5℃ for 24 hours, without further dilution.

[0039] All embodiments and comparative examples used the same batch of raw materials: Dehydrated castor oil has an acid value of 191 mg KOH / g and an iodine value of 146 g I2 / 100g, with a conjugated linoleic acid mass fraction of 36.8%. The tall oil fatty acid (TOFA) has an acid value of 195 mg KOH / g and a rosin acid mass fraction of 1.5%. Stearic acid (SA) has an acid value of 197 mgKOH / g and is classified as a superior industrial grade. Tetrahydrophthalic anhydride (THPA), purity 99.0%, melt color 20 APHA; molar mass 152.15 g / mol; Neopentyl glycol (NPG), purity ≥ 99%; molar mass 104.15 g / mol; Trimethylolpropane (TMP), purity ≥99%; molar mass 134.17 g / mol; High-boiling-point, low-aromatic hydrocarbon solvent, distillation range 240–280℃; aromatic hydrocarbon content ≤0.5% (by mass). 2,6-Di-tert-butyl-p-cresol (BHT for short).

[0040] Acid value was determined by titration with potassium hydroxide ethanol standard solution; hydroxyl value was determined by back titration after acetylation; number-average molecular weight was determined by gel permeation chromatography, using tetrahydrofuran as the mobile phase and polystyrene as the calibration standard. All three measurements were performed on dry resin.

[0041] Gardner bubble viscosity was measured using the original finished resin sample, after being sealed and kept at a constant temperature of 25±0.5℃ for 24 hours.

[0042] Accelerated storage tests and Gardner bubble viscosity tests were conducted separately. In the accelerated storage test, the finished resin was placed in a sealed container with 10% vapor space and stored at 50±2℃ for 14 days. After being restored to 25℃, the viscosity was measured using a cone-plate viscometer at a shear rate of 100 s⁻¹. -1The dynamic viscosity was measured, the rate of change relative to the initial value was calculated, and the crust formation and delamination were observed.

[0043] The filter residue is the percentage of the dried mass of the residue on the filter screen after the finished resin has passed through a 300-mesh filter, relative to the sample mass.

[0044] The raw material formulations and equivalent ratios of Examples 1 to 5 are shown in Table 1. Examples 1 to 3 are representative formulations within the range. Examples 4 and 5 respectively verify the endpoints of R=1.10 and R=1.14. In Examples 4 and 5, the mass ratio of NPG to TMP is maintained at approximately 1:1.25. R is adjusted to 1.100 and 1.140 respectively by adjusting the total amount of polyol.

[0045] Table 1. Raw material formulations and equivalent ratios (parts by weight) for Examples 1-5

[0046] Example 1 This embodiment provides a modified alkyd resin for quick-drying inks, the formulation of which is shown in Table 1.

[0047] The preparation method of this modified alkyd resin for fast-drying inks includes the following steps: S1. Add 53 parts by weight of DCOFA, 5 parts by weight of TOFA, and 3 parts by weight of SA to a reactor equipped with a mechanical stirrer, thermometer, nitrogen inlet, condenser, and oil-water separation receiving device. Purge with nitrogen and stir to raise the temperature to 160°C. Add 12.40 parts by weight of TMP in batches over 30 minutes. Then raise the temperature to 178°C and continuously drain the esterification water. Take a sample, cool it, and determine the acid value. When the acid value of the pre-esterification system is 30 mg KOH / g, the pre-esterification is terminated, and a fatty acid metaester intermediate containing the remaining active hydroxyl groups is obtained.

[0048] S2. Cool the system to 160°C, add 16 parts by weight of THPA, 10 parts by weight of NPG, and 0.12 parts by weight of monobutyltin oxide. Under nitrogen protection, increase the temperature to 230°C at a rate of 8°C every 30 minutes and continue the reaction. Take a sample, remove volatiles, and determine the acid value and hydroxyl value of the dry resin. Polycondensation ends when the acid value is 10.0 mg KOH / g and the hydroxyl value is 40.8 mg KOH / g; at this stage, the Gardner bubble viscosity of the dry resin is not measured or is used as the endpoint of polycondensation.

[0049] S3. Cool the polycondensation product obtained in step S2 to 195°C and perform vacuum treatment under an absolute pressure of 10 kPa for 20 min. Remove the vacuum and restore nitrogen protection, cool to 150°C, add 0.08 parts by weight of BHT and stir for 10 min; then add 15 parts by weight of a high-boiling-point low-aromatic hydrocarbon solvent preheated to 100°C and 7 parts by weight of soybean oil, stir for 30 min, and filter through a 300-mesh filter to obtain the finished resin, namely the modified alkyd resin for fast-drying inks.

[0050] The filtered finished resin was sealed and kept at a constant temperature for 24 hours. The Gardner bubble viscosity Z5 was measured at 25±0.5℃ as is.

[0051] Example 2 This embodiment follows the formulation shown in Table 1. The preparation method is the same as that in Example 1, except that the pre-esterification temperature in step S1 is adjusted to 175°C and the polycondensation temperature in step S2 is adjusted to 228°C. The rest of the operation process is the same as in Example 1.

[0052] In this embodiment, the amount of DCOFA is increased to 58 parts by weight, TOFA is reduced to 3 parts by weight, SA is reduced to 2 parts by weight, R=1.119, and the proportion of dehydrated castor oil fatty acids in the three fatty acids is higher, which is beneficial to increase the content of conjugated unsaturated structure in the resin and promote the oxidative crosslinking of the ink film after printing.

[0053] Example 3 This embodiment follows the formulation shown in Table 1. The preparation method is the same as that in Example 1, except that the pre-esterification temperature in step S1 is adjusted to 182°C and the polycondensation temperature in step S2 is adjusted to 232°C. The rest of the operation process is the same as in Example 1.

[0054] In this embodiment, the amount of THPA was increased to 18 parts by weight, TMP was increased to 13.00 parts by weight, DCOFA was reduced to 48 parts by weight, R=1.101, the ratio of tetrahydrophthalic anhydride and trimethylolpropane was increased, and the resulting resin had a relatively high content of alicyclic structure and degree of branching.

[0055] Example 4 This embodiment uses the formulation shown in Table 1. The preparation method is the same as that in Example 1, except that step S1 is pre-esterified at 178°C and step S2 is polycondensed at 230°C. The rest of the operation process is the same as in Example 1.

[0056] In this embodiment, the amount of NPG was adjusted to 9.77 parts by weight and the amount of TMP was adjusted to 12.21 parts by weight. The mass ratio of NPG to TMP was approximately 1:1.25, and R=1.100. This is the verification sample at the lower end of the R value range.

[0057] Example 5 This embodiment uses the formulation shown in Table 1. The preparation method is the same as that in Example 1, except that step S1 is pre-esterified at 178°C and step S2 is polycondensed at 230°C. The rest of the operation process is the same as in Example 1.

[0058] In this embodiment, the amount of NPG was adjusted to 10.12 parts by weight and the amount of TMP was adjusted to 12.65 parts by weight. The mass ratio of NPG to TMP was approximately 1:1.25, and R=1.140. This is a verification sample at the upper end of the R value range.

[0059] It is understood that the esterification catalyst is not limited to monobutyltin oxide, but can also be dibutyltin oxide, tetrabutyl titanate, p-toluenesulfonic acid and other commonly used esterification catalysts in the art. Under the premise of meeting the stoichiometric relationship and reaction endpoint requirements, the substitution of catalyst type is a conventional choice for those skilled in the art.

[0060] It is understood that the antioxidant and anti-skinning adjuvant is not limited to 2,6-di-tert-butyl-p-cresol, but may also be other phenolic antioxidants.

[0061] It is understood that the soybean oil can also be partially replaced with refined vegetable oils such as refined flaxseed oil or refined sunflower oil.

[0062] It is understood that, provided that the total equivalence relationship, reaction endpoint and final resin structure parameters of this invention are satisfied, those skilled in the art can make conventional adjustments to the heating time, stirring speed and nitrogen flow rate according to the scale of the reactor.

[0063] The raw material formulations and equivalent ratios of Comparative Examples 1–4 are shown in Table 2. Comparative Examples 1 and 2 were used to verify the effect of exceeding the R-value limit; the acid component, NPG to TMP mass ratio, catalyst, dilution components, and process were the same as in Examples 4 and 5, only the total amount of polyol was changed. Comparative Examples 3 and 4 were used to verify the effect of stearic acid dosage, keeping the total fatty acid content, R-value, and NPG to TMP mass ratio essentially unchanged.

[0064] Table 2. Raw material formulations and equivalent ratios (parts by weight) for Comparative Examples 1-4

[0065] Comparative Example 1 In this comparative example, R = 1.080, which is lower than the 1.10–1.14 range specified in this invention. The remaining acid components, catalyst, diluent components, and process were the same as in Example 4. When the reaction reached an operable acid value, the dry resin acid value was 13.2 mg KOH / g and the hydroxyl value was only 33.8 mg KOH / g, indicating insufficient hydroxyl excess margin. While continued polycondensation could lower the acid value, it resulted in a number-average molecular weight exceeding 6000, a Gardner viscosity increase to Z7 in the finished resin, and increased viscosity due to filtration residue and accelerated storage.

[0066] Comparative Example 2 In this comparative example, R=1.150, which is higher than the 1.10-1.14 range defined in this invention. The remaining acid components, catalyst, diluent components, and processes are the same as in Example 5. When the dry resin acid value reaches 8.0 mg KOH / g, the hydroxyl value is still 46.0 mg KOH / g, significantly higher than the upper limit of the target range; the number-average molecular weight decreases to 3800, and the viscosity of the finished Gardner resin decreases to Z3, with both molecular weight and viscosity below the target range.

[0067] Comparative Example 3 In this comparative example, the 3 parts by weight of stearic acid in Example 1 were replaced with an equal mass of DCOFA, increasing the total amount of DCOFA to 56 parts by weight. The amount of SA was 0, R=1.120, and the total amount of fatty acids, R value, and NPG to TMP mass ratio remained essentially unchanged. The remaining procedures were the same as in Example 1.

[0068] The comparative example dry resin had an acid value of 10.1 mg KOH / g, a hydroxyl value of 40.5 mg KOH / g, and a number-average molecular weight (Mn) of 5180, which was close to that of Example 1. However, after accelerated storage at 50°C for 14 days, the viscosity of the finished resin increased by 28.5%, and a significant surface skin appeared, indicating that although the complete removal of stearic acid increased the unsaturation of the system, it sacrificed storage stability.

[0069] Comparative Example 4 In this comparative example, stearic acid was increased to 6 parts by weight, and DCOFA was correspondingly reduced to 50 parts by weight. TOFA was kept at 5 parts by weight, R=1.120, and the total amount of fatty acids, R value, and NPG to TMP mass ratio remained essentially unchanged. The remaining procedures were the same as in Example 1.

[0070] The comparative example resin had an acid value of 10.3 mg KOH / g, a hydroxyl value of 40.7 mg KOH / g, and a number-average molecular weight (Mn) of 5220. The resin structural parameters were similar to those in Example 1. However, due to the excessive amount of stearic acid, the saturated fatty acids significantly diluted the unsaturated segments, resulting in an extended initial curing time of 41 seconds, a surface drying time of 86 minutes, and an increase in the abrasion resistance weight loss rate to 2.5%, significantly reducing the fast-drying performance.

[0071] Test 1 The functional groups and molecular weight of the dry resins obtained in Examples 1-5 and Comparative Examples 1-4 were determined, and the results are shown in Table 3; the viscosity and storage stability of the finished resins are shown in Table 4.

[0072] Table 3. Results of Functional Groups and Molecular Weight Tests of Dry Resin

[0073] Table 4. Test results of viscosity and storage stability of finished resin

[0074] As can be seen from Tables 3-4, the dry resins obtained in Examples 1-5 have an acid value of 8.5-11.8 mgKOH / g, a hydroxyl value of 35.6-44.2 mgKOH / g, and a number-average molecular weight of 4600-5350, all of which fall within the range of structural parameters defined in this invention; the viscosity of the finished Gardner resin is Z4-Z5, the viscosity change rate after 14 days of accelerated storage is no higher than 9.6%, the filter residue is no higher than 0.11%, and there is no skinning or stratification during storage.

[0075] Examples 4 (R=1.100) and 5 (R=1.140) are located at the lower and upper ends of the R value range, respectively. Both simultaneously satisfy the following requirements: dry resin acid value of 8-12 mgKOH / g, hydroxyl value of 35-45 mgKOH / g, number-average molecular weight of 4000-6000, and Gardner viscosity of the finished resin of Z4-Z6, proving that the endpoints of this range are feasible. Comparative Example 1 (R=1.080) has insufficient excess hydroxyl margin, resulting in a high dry resin acid value (13.2 mgKOH / g) and a low hydroxyl value (33.8 mgKOH / g). Continued polycondensation leads to a molecular weight exceeding 6000, a finished product viscosity increasing to Z7, and a significant increase in viscosity growth in filter residue and during accelerated storage.

[0076] In Comparative Example 2 (R=1.150), when the acid value reached 8.0 mg KOH / g, the hydroxyl value was still 46.0 mg KOH / g, the number-average molecular weight was only 3800, and the viscosity of the finished product dropped to Z3, all exceeding the target range. This confirms that when R is below 1.10 or above 1.14, it is impossible to stably and simultaneously meet all the indicators of functional groups, molecular weight, and viscosity of the dry resin of this invention.

[0077] Test 2 Ink was prepared according to the following formula to test the above-mentioned finished resin: 45 parts by weight of finished resin, 18 parts by weight of phthalocyanine blue pigment, 18 parts by weight of high-boiling-point mineral oil, 6 parts by weight of soybean oil, 8 parts by weight of calcium carbonate, 1.5 parts by weight of polyethylene wax, 1 part by weight of dispersant, 1.5 parts by weight of manganese-zirconium composite drier, and 1 part by weight of anti-skinning agent. The finished resin, pigment, calcium carbonate, and part of the mineral oil were pre-dispersed, and then ground for 3.5 hours using the same three-roll mill. After grinding, the remaining components were added to adjust to the same printing viscosity to obtain the test ink.

[0078] Pigment fineness was measured using a scraper fineness meter. Initial curing time was determined using the impression transfer method: printing with the same ink layer quality on the same batch of substrate paper, covering with standard white paper at different time points and applying the same pressure, the initial curing time was the time when no visible ink transfer appeared on the covering paper. Surface drying time was the time it took for a 100μm wet film to show no fingerprints when lightly touched at 25±1℃ and 50%±5% relative humidity. 60° gloss and dot gain were measured under the same printing speed, pressure, screen ruling, and solid density. Abrasion resistance was tested by rubbing the printed sample 100 times after 24 hours, and the ink film weight loss was measured. The application performance test results for each ink are shown in Table 5.

[0079] Table 5. Ink Application Performance Test Results

[0080] As can be seen from Table 5, the inks prepared in Examples 1 to 5 have an initial curing time of 22 to 29 seconds, a surface drying time of 36 to 50 minutes, a fineness of no more than 9 μm, a dot gain of 6.8% to 8.2%, a 60° gloss of 77 to 80, and a weight loss rate of 1.1% to 1.5% after 100 rubs. All indicators are within a suitable range, taking into account fast drying, printability, and ink film abrasion resistance.

[0081] Comparative Example 1 (R=1.080) exhibited significantly deteriorated performance due to its higher molecular weight and viscosity, resulting in an extended initial curing time of 38 s, a surface drying time of 65 min, a fineness increase to 12 μm, a dot gain of 18.5%, and a friction loss rate of 2.1%. Comparative Example 2 (R=1.150), while having a relatively fine grinding, suffered from lower molecular weight and viscosity, leading to a dot gain of 21.5% and a friction loss rate of 3.8%, resulting in a marked decrease in ink printability and film strength.

[0082] Although the initial curing and surface drying of Comparative Example 3 (without stearic acid) were faster than those of Example 1, the viscosity of the finished resin increased by 28.5% and obvious surface skin formed after 14 days of accelerated storage at 50°C, indicating a significant deterioration in storage stability. This suggests that while completely eliminating stearic acid increased the degree of unsaturation, it sacrificed storage stability. Comparative Example 4 (stearic acid increased to 6 parts) showed an extended initial curing time of 41 seconds, an extended surface drying time of 86 minutes, and an increased abrasion resistance rate of 2.5%, indicating that excessive stearic acid hindered rapid drying by diluting the unsaturated segments.

[0083] In Examples 1-5, 2-4 parts by weight of stearic acid did not directly promote the oxidation reaction, but it simultaneously achieved initial solidification in 22-29 seconds, surface drying in 36-50 minutes, and accelerated storage viscosity change rate not exceeding 9.6%. This verifies the effect of this dosage range in balancing rapid drying and storage stability under the premise of unsaturated fatty acid-dominated oxidation film formation. In summary, the above results indicate that this invention, by using R=n... OH / nCOOH The viscosity was controlled at 1.10–1.14, and a segmented esterification process and a small amount of stearic acid were used for end-adjustment. This ensured that the functional groups and molecular weight of the resulting resin met the requirements, while the viscosity of the finished Gardner resin was stably within the Z4–Z6 target window, taking into account pigment wetting, fast drying, printability and storage stability.

[0084] In summary, this invention controls the relationship between total hydroxyl equivalent and total carboxyl equivalent (R=n). OH / n COOH Dry resins are prepared by controlling the functional groups, molecular weight, and viscosity of the dry resin (1.10–1.14), acid value (8–12 mg KOH / g), and hydroxyl value (35–45 mg KOH / g). The finished resin is then measured using Gardner bubble viscosity, ensuring simultaneous control over the dry resin's functional groups, molecular weight, and finished resin viscosity, thus balancing rapid drying and storage stability. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0085] The terms used in this specification, such as "upper," "lower," "left," "right," "front," "back," "middle," and "one," are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, shall also be considered within the scope of the invention.

[0086] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. All equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this invention should still be covered by the claims of this invention.

Claims

1. A modified alkyd resin for fast-drying inks, comprising a dry resin and additives, characterized in that, The dry resin, by weight, is prepared from the following raw materials: 48-58 parts of dehydrated castor oil fatty acid, 14-19 parts of tetrahydrophthalic anhydride, 8-12 parts of neopentyl glycol, 10-15 parts of trimethylolpropane, 3-7 parts of tall oil fatty acid, 2-4 parts of stearic acid, and 0.06-0.18 parts of esterification catalyst. The total carboxyl equivalent provided by the dehydrated castor oil fatty acids, tetrahydrophthalic anhydride, tall oil fatty acids, and stearic acid is n. COOH The total hydroxyl equivalent provided by the neopentyl glycol and trimethylolpropane is n. OH R = n OH / n COOH It ranges from 1.10 to 1.14; The dry resin has an acid value of 8-12 mgKOH / g and a hydroxyl value of 35-45 mgKOH / g.

2. The modified alkyd resin for fast-drying inks according to claim 1, characterized in that, The dehydrated castor oil fatty acids have an iodine value of 140-153 gI2 / 100g, wherein the mass content of conjugated diene fatty acids is not less than 35%, and the acid value is 187-195 mgKOH / g; the APHA color of the tetrahydrophthalic anhydride is not greater than 30; and the mass content of rosin acid in the tall oil fatty acids is not greater than 2%.

3. The modified alkyd resin for fast-drying inks according to claim 1, characterized in that, The mass ratio of neopentyl glycol to trimethylolpropane is 1:1.2 to 1:1.

5.

4. The modified alkyd resin for fast-drying inks according to claim 1, characterized in that, The added components include an antioxidant and anti-scabbing agent, a high-boiling-point low-aromatic hydrocarbon solvent, and soybean oil; relative to the reactive raw materials for preparing the dry resin, the amount of the antioxidant and anti-scabbing agent is 0.05 to 0.15 parts by weight, the amount of the high-boiling-point low-aromatic hydrocarbon solvent is 12 to 18 parts by weight, and the amount of soybean oil is 5 to 9 parts by weight.

5. The modified alkyd resin for fast-drying inks according to claim 4, characterized in that, The dry resin is vacuum treated, then the additives are added, and the mixture is filtered to obtain the finished resin. The Gardner bubble viscosity of the finished resin measured at 25±0.5℃ is Z4~Z6.

6. A method for preparing a modified alkyd resin for fast-drying inks, characterized in that, Includes the following steps: S1. Dehydrated castor oil fatty acids, tall oil fatty acids and stearic acid are added to a reaction vessel, and trimethylolpropane is added in batches under inert gas protection for pre-esterification to obtain fatty acid ester intermediates containing residual hydroxyl groups. S2. Add tetrahydrophthalic anhydride, neopentyl glycol and esterification catalyst to the fatty acid ester intermediate, and carry out polycondensation under inert gas protection. The polycondensation endpoint is obtained when the acid value of the dry resin sample obtained during the polycondensation process and after vacuum removal of volatiles is 8-12 mgKOH / g and the hydroxyl value is 35-45 mgKOH / g. S3. The polycondensation product is subjected to vacuum treatment, and then the additive components are added for formulation. The mixture is then filtered to obtain the modified alkyd resin for quick-drying ink.

7. The preparation method according to claim 6, characterized in that, In step S1, the pre-esterification includes: heating three fatty acids to 150-165°C, adding trimethylolpropane in batches over 20-40 minutes, then heating to 170-185°C for pre-esterification reaction, taking samples, cooling and measuring the acid value, and ending the pre-esterification when the acid value of the pre-esterification system is 25-35 mg KOH / g to obtain a fatty acid ester intermediate containing the remaining hydroxyl groups.

8. The preparation method according to claim 6, characterized in that, In step S2, the polycondensation includes: cooling the reaction system to 150–170°C, adding tetrahydrophthalic anhydride, neopentyl glycol, and an esterification catalyst to the fatty acid ester intermediate obtained in step S1, and carrying out the polycondensation reaction by increasing the temperature to 225–235°C at a rate of 6–10°C every 30 minutes under inert gas protection. The endpoint of the polycondensation is defined as an acid value of 8–12 mgKOH / g and a hydroxyl value of 35–45 mgKOH / g of the dry resin sample obtained during the polycondensation process and after the volatiles have been removed by vacuum in the laboratory, thereby obtaining the polycondensation product.

9. The preparation method according to claim 6, characterized in that, In step S3, the added components include an antioxidant and anti-skinning adjuvant, a high-boiling-point low-aromatic hydrocarbon solvent, and soybean oil; the antioxidant and anti-skinning adjuvant is selected from 2,6-di-tert-butyl-p-cresol.

10. The preparation method according to claim 9, characterized in that, In step S3, the vacuum treatment includes: cooling the polycondensation product obtained in step S2 to 190-205°C and maintaining it under an absolute pressure of 8-15 kPa for 15-30 minutes for vacuum treatment; after the vacuum treatment, restoring the inert gas protection and cooling it to 140-160°C, sequentially adding an antioxidant and anti-skinning agent, a high-boiling-point low-aromatic hydrocarbon solvent preheated to 80-120°C, and soybean oil, stirring for 20-40 minutes, and then filtering to obtain the modified alkyd resin for quick-drying ink.

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