Isocyanate modified high-functionality alkyd resin as well as preparation method and application thereof

Abstract

The invention relates to isocyanate modified high-functionality alkyd resin as well as a preparation method and application thereof. The isocyanate modified high-functionality alkyd resin is prepared from the following raw materials in percentage by mass: 10%-20% of oleic acid or grease, 10%-15% of polyol, 20%-25% of polybasic acid or anhydride, 0.1%-0.2% of a catalyst, 1%-10% of isocyanate and the balance of a solvent. The isocyanate modified high-functionality alkyd resin provided by the invention has the characteristics of good leveling property, high hardness, damp heat resistance, salt mist resistance, corrosion resistance, high insulativity, quick drying, excellent adhesive force and the like, and can meet the requirements of different application scenes.

Description

Technical Field

[0001] The invention relates to the field of coatings, and in particular to an isocyanate-modified high-functionality alkyd resin and a preparation method and application thereof. Background Art

[0002] Alkyd resin coatings have the characteristics of high gloss, good fullness, low price, and easy access to raw materials. However, the coating film is soft, water-resistant, slow to dry, and poorly resistant to salt spray. In addition, it has poor adhesion to some materials and poor corrosion resistance. During construction, it is easy to produce sagging; this has led to a great degree of restrictions on the application of alkyd resin coatings. At present, many alkyd resin coatings adopt the method of adding corresponding additives or materials to achieve the desired performance. Although this method can improve the performance, it is easy to cause poor compatibility, easy separation, and affect the storage performance. Summary of the invention

[0003] In order to solve the problems existing in the existing alkyd resin coatings, the present invention provides an isocyanate-modified high-functionality alkyd resin and a preparation method and application thereof.

[0004] The technical solution provided by the present invention is as follows:

[0005] In a first aspect, the present invention provides an isocyanate-modified high-functionality alkyd resin, wherein the isocyanate-modified high-functionality alkyd resin is made of the following raw materials in percentage by weight:

[0006] 10% to 20% oleic acid or oil, 10% to 15% polyol, 20% to 25% polyacid or anhydride, 0.1% to 0.2% catalyst, 1% to 10% isocyanate, and the balance is solvent.

[0007] In combination with the first aspect of the present invention, in some embodiments, the polyol is one or more of ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, glycerol, pentaerythritol, butanethritol, xylitol, and sorbitol.

[0008] In combination with the first aspect of the present invention, in some embodiments, the polyacid is one or more of adipic acid, sebacic acid, phthalic anhydride, acetic anhydride, and maleic anhydride.

[0009] In combination with the first aspect of the present invention, in some embodiments, the solvent is one or more of propylene glycol methyl ether, propylene glycol propyl ether, propylene glycol butyl ether, ethyl acetate, butyl acetate, cyclohexane, and ethylcyclohexane.

[0010] In combination with the first aspect of the present invention, in some embodiments, the isocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dimethyl diphenyl diisocyanate, and aliphatic isocyanate.

[0011] In conjunction with the first aspect of the present invention, in some embodiments, the viscosity of the alkyd resin at 25° C. is 1000-3000 cps.

[0012] In conjunction with the first aspect of the present invention, in some embodiments, the acid value of the alkyd resin is 10 to 20 mgKOH / g.

[0013] In a second aspect, the present invention provides a method for preparing the above-mentioned isocyanate-modified high-functionality alkyd resin, comprising the following steps:

[0014] Add oleic acid or oil, polyol, polyacid or anhydride into the reaction kettle in sequence, and quickly heat it to 160-180°C under the protection of inert gas, start stirring and keep warm for 2-3 hours, then slowly heat it to 220-230°C and keep warm;

[0015] When the viscosity of the resin at 50°C is monitored to be 300-1000cps, the hydroxyl value is 120-160mgKOH / g, and the acid value is 10-20mgKOH / g, the temperature is lowered to 30-40°C, isocyanate and solvent are added, and the temperature is adjusted to 85-90°C and kept warm for 3-4 hours. When the acid value of the resin is monitored to be 5-10mgKOH / g, the reaction is stopped to obtain an isocyanate-modified high-functionality alkyd resin.

[0016] In conjunction with the second aspect of the present invention, in some embodiments, the solvent is propylene glycol propyl ether:butyl acetate in a mass ratio of 1:7.

[0017] In a third aspect, the present invention provides the use of the above-mentioned isocyanate-modified high-functionality alkyd resin in the field of coatings.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] The isocyanate-modified high-functionality alkyd resin provided by the present invention has the characteristics of good leveling, high hardness, moisture and heat resistance, salt spray resistance, corrosion resistance, high insulation, quick drying, excellent adhesion, etc., and can meet the needs of different application scenarios.

[0020] The invention uses vegetable oil acid or fat to synthesize alkyd resin, does not need the step of alcoholysis, and directly synthesizes isocyanate-modified high-functionality alkyd resin in one step. The obtained product can meet the performance requirements of commercial products, greatly simplifies the alkyd resin production process, and greatly reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 This is a test diagram of the surface insulation resistance of the alkyd resin prepared in various embodiments of the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The isocyanate-modified high-functionality alkyd resin provided by the invention is prepared from the following raw materials in percentage by mass: 10% to 20% of oleic acid or fat, 10% to 15% of polyol, 20% to 25% of polyacid or anhydride, 0.1% to 0.2% of catalyst, 1% to 10% of isocyanate, and the balance is solvent.

[0025] The polyols selected from the isocyanate-modified high-functionality alkyd resin provided by the present invention include trimethylolpropane, glycerol, pentaerythritol, butanethritol, and sorbitol, wherein the functionality of pentaerythritol, butanethritol, and sorbitol is greater than four, and pentaerythritol and trimethylolpropane are all primary hydroxyl groups, which ensures high reactivity and high functionality of subsequent modification reactions, and the prepared alkyd resin has ultra-high crosslinking density. The alkyd resin prepared by the present invention has high hardness, fast surface drying speed, and good film-forming effect.

[0026] The isocyanate-modified high-functionality alkyd resin provided by the present invention adopts different polyacid / acid anhydride combinations, the polyacid / acid anhydride containing a benzene ring can increase the hardness and strength of the overall molecular chain segment, and the aliphatic polyacid / acid anhydride can improve the hydrolysis resistance and weather resistance of the alkyd resin. Through different ratio adjustment, the alkyd resin prepared by the present invention has high hardness and good water and salt spray resistance.

[0027] The present invention selects a variety of polyols with high functionality for compounding, improves the crosslinking density of the alkyd resin, and makes it have the characteristics of good adhesion, high hardness, moisture and heat resistance, etc. The drying speed of the alkyd resin is accelerated by compounding different types of plant oil acids, adjusting the oil content and adjusting the solvent. The prepared isocyanate-modified high-functionality alkyd resin has a stable structure and long-lasting performance.

[0028] The invention does not need to add anti-corrosion additives and anti-sagging agents, and the prepared isocyanate-modified high-functionality alkyd resin has good anti-corrosion performance and anti-sagging performance.

[0029] The method for preparing the above-mentioned isocyanate-modified high-functionality alkyd resin provided by the present invention comprises the following steps:

[0030] Add oleic acid or oil, polyol, polyacid or anhydride into the reaction kettle in sequence, and quickly heat it to 160-180°C under the protection of inert gas, start stirring and keep warm for 2-3 hours, then slowly heat it to 220-230°C and keep warm;

[0031] When the viscosity of the resin at 50°C is monitored to be 300-1000cps, the hydroxyl value is 120-160mgKOH / g, and the acid value is 10-20mgKOH / g, the temperature is lowered to 30-40°C, isocyanate and solvent are added, and the temperature is adjusted to 85-90°C and kept warm for 3-4 hours. When the acid value of the resin is monitored to be 5-10mgKOH / g, the reaction is stopped to obtain an isocyanate-modified high-functionality alkyd resin.

[0032] The alkyd resin of the present invention is prepared by a one-step method before being modified with isocyanate, which saves a large number of processes and improves the stability of the process. Different solvents are used for isocyanate modification, which reduces the risk of gelation of the reaction and improves the storage stability. No xylene is used, which can meet the environmental protection needs of customers and significantly improve the surface drying speed.

[0033] The technical solution of the present invention is described in detail below through specific embodiments:

[0034] Embodiment 1

[0035] The isocyanate-modified high-functionality alkyd resin provided in this embodiment is made of the following raw materials in percentage by mass: 22% oleic acid, 10% phthalic anhydride, 3% ethylene glycol, 6% pentaerythritol, 4% trimethylolpropane, 5% toluene diisocyanate, and 50% solvent (propylene glycol propyl ether: butyl acetate in a mass ratio of 1:7).

[0036] The preparation method of the isocyanate-modified high-functionality alkyd resin provided in this embodiment comprises the following steps: oleic acid, phthalic anhydride, sorbitol, pentaerythritol, and trimethylolpropane are sequentially added into a reaction kettle according to the above mass percentages, nitrogen is introduced and the temperature is raised to 180°C, stirring is started, and after keeping the temperature for 2 hours, the temperature is raised to 220°C at a rate of 5°C / 15min, and the temperature is kept. When the resin viscosity is

[0037] When the temperature is 300-1000cps / 50℃, the resin hydroxyl value is 120-160mgKOH / g, and the acid value is 10-20mgKOH / g, cool down to 30-40℃, add toluene diisocyanate and solvent according to the formula, stir quickly to mix, adjust the temperature to 85-90℃ after 30 minutes, keep warm for 3-4 hours, terminate the reaction when the acid value is 5-10mgKOH / g, and obtain alkyd resin.

[0038] Embodiment 2

[0039] The isocyanate-modified high-functionality alkyd resin provided in this embodiment is made of the following raw materials in percentage by mass: 22% oleic acid, 10% phthalic anhydride, 3% neopentyl glycol, 6% pentaerythritol, 4% trimethylolpropane, 5% toluene diisocyanate, and 50% solvent (propylene glycol propyl ether: butyl acetate in a mass ratio of 1:7).

[0040] The preparation method of the isocyanate-modified high-functionality alkyd resin provided in this embodiment comprises the following steps: oleic acid, phthalic anhydride, sorbitol, pentaerythritol, and trimethylolpropane are sequentially added into a reaction kettle according to the above mass percentages, nitrogen is introduced and the temperature is raised to 180°C, stirring is started, and after keeping the temperature for 2 hours, the temperature is raised to 220°C at a rate of 5°C / 15min, and the temperature is kept. When the resin viscosity is

[0041] When the temperature is 300-1000cps / 50℃, the resin hydroxyl value is 120-160mgKOH / g, and the acid value is 10-20mgKOH / g, cool down to 30-40℃, add toluene diisocyanate and solvent according to the formula, stir quickly to mix, adjust the temperature to 85-90℃ after 30 minutes, keep warm for 3-4 hours, terminate the reaction when the acid value is 5-10mgKOH / g, and obtain alkyd resin.

[0042] Embodiment 3

[0043] The isocyanate-modified high-functionality alkyd resin provided in this embodiment is made of the following raw materials in percentage by mass: 22% oleic acid, 10% phthalic anhydride, 3% butanediol, 6% pentaerythritol, 4% trimethylolpropane, 5% toluene diisocyanate, and 50% solvent (propylene glycol propyl ether: butyl acetate in a mass ratio of 1:7).

[0044] The preparation method of the isocyanate-modified high-functionality alkyd resin provided in this embodiment comprises the following steps: oleic acid, phthalic anhydride, sorbitol, pentaerythritol, and trimethylolpropane are sequentially added into a reaction kettle according to the above mass percentages, nitrogen is introduced and the temperature is raised to 180°C, stirring is started, and after keeping the temperature for 2 hours, the temperature is raised to 220°C at a rate of 5°C / 15min, and the temperature is kept. When the resin viscosity is

[0045] When the temperature is 300-1000cps / 50℃, the resin hydroxyl value is 120-160mgKOH / g, and the acid value is 10-20mgKOH / g, cool down to 30-40℃, add toluene diisocyanate and solvent according to the formula, stir quickly to mix, adjust the temperature to 85-90℃ after 30 minutes, keep warm for 3-4 hours, terminate the reaction when the acid value is 5-10mgKOH / g, and obtain alkyd resin.

[0046] Embodiment 4

[0047] The isocyanate-modified high-functionality alkyd resin provided in this embodiment is made of the following raw materials in percentage by mass: 22% oleic acid, 10% phthalic anhydride, 3% sorbitol, 4% pentaerythritol, 6% trimethylolpropane, 5% toluene diisocyanate, and 50% solvent (propylene glycol propyl ether: butyl acetate in a mass ratio of 1:7).

[0048] The preparation method of the isocyanate-modified high-functionality alkyd resin provided in this embodiment comprises the following steps: oleic acid, phthalic anhydride, sorbitol, pentaerythritol, and trimethylolpropane are sequentially added into a reaction kettle according to the above mass percentages, nitrogen is introduced and the temperature is raised to 180°C, stirring is started, and after keeping the temperature for 2 hours, the temperature is raised to 220°C at a rate of 5°C / 15min, and the temperature is kept. When the resin viscosity is

[0049] When the temperature is 300-1000cps / 50℃, the resin hydroxyl value is 120-160mgKOH / g, and the acid value is 10-20mgKOH / g, cool down to 30-40℃, add toluene diisocyanate and solvent according to the formula, stir quickly to mix, adjust the temperature to 85-90℃ after 30 minutes, keep warm for 3-4 hours, terminate the reaction when the acid value is 5-10mgKOH / g, and obtain alkyd resin.

[0050] Embodiment 5

[0051] The isocyanate-modified high-functionality alkyd resin provided in this embodiment is made of the following raw materials in percentage by mass: 20% soybean oil fatty acid, 10% phthalic anhydride, 5% sorbitol, 4% pentaerythritol, 6% butanethrol, 5% toluene diisocyanate, and 50% solvent (propylene glycol propyl ether: ethyl cyclohexane in a mass ratio of 1:7).

[0052] The preparation method of the isocyanate-modified high-functionality alkyd resin provided in the present embodiment comprises the following steps: adding soybean oil fatty acid, phthalic anhydride, sorbitol, pentaerythritol and butanethrol into a reaction kettle in order according to the above mass percentages, introducing nitrogen and heating to 180° C., starting stirring, keeping warm for 2 hours, heating to 220° C. at a rate of 5° C. / 15 min, keeping warm, when the resin viscosity is 300-1000 cps / 50° C., the resin hydroxyl value is 120-160 mgKOH / g, and the acid value is 10-20 mgKOH / g, cooling to 30-40° C., adding toluene diisocyanate and solvent according to the formula amount, stirring and mixing quickly, adjusting the temperature to 85-90° C. after 30 minutes, keeping warm for 3-4 hours, and terminating the reaction when the acid value is detected to be 5-10 mgKOH / g, to obtain an alkyd resin.

[0053] Embodiment 6

[0054] The isocyanate-modified high-functionality alkyd resin provided in this embodiment is made of the following raw materials in percentage by mass: 20% oleic acid, 7% phthalic anhydride, 3% sebacic acid, 5% sorbitol, 4% pentaerythritol, 6% butanetetraol, 5% toluene diisocyanate, and 50% solvent (propylene glycol propyl ether: ethyl cyclohexane in a mass ratio of 1:7).

[0055] The preparation method of the isocyanate-modified high-functionality alkyd resin provided in the present embodiment comprises the following steps: oleic acid, phthalic anhydride, sebacic acid, sorbitol, pentaerythritol and butanethrol are sequentially added into a reaction kettle according to the above mass percentages, nitrogen is introduced and the temperature is raised to 180° C., stirring is started, and after keeping the temperature for 2 hours, the temperature is raised to 220° C. at a rate of 5° C. / 15 min, and the temperature is kept, and when the resin viscosity is 300-1000 cps / 50° C., the resin hydroxyl value is 120-160 mgKOH / g, and the acid value is 10-20 mgKOH / g, the temperature is lowered to 30-40° C., toluene diisocyanate and solvent are added according to the formula amount, and the mixture is quickly stirred and mixed, and the temperature is adjusted to 85-90° C. after 30 minutes, and the temperature is kept for 3-4 hours. When the acid value is detected to be 5-10 mgKOH / g, the reaction is terminated to obtain an alkyd resin.

[0056] Embodiment 7

[0057] The isocyanate-modified high-functionality alkyd resin provided in this embodiment is made of the following raw materials in percentage by mass: 20% soybean oil fatty acid, 8% phthalic anhydride, 5% sorbitol, 4% pentaerythritol, 6% butanethrol, 7% toluene diisocyanate, and 50% solvent (propylene glycol propyl ether: ethyl cyclohexane in a mass ratio of 1:7).

[0058] The preparation method of the isocyanate-modified high-functionality alkyd resin provided in the present embodiment comprises the following steps: adding soybean oil fatty acid, phthalic anhydride, sorbitol, pentaerythritol and butanethrol into a reaction kettle in order according to the above mass percentages, introducing nitrogen and heating to 180° C., starting stirring, keeping warm for 2 hours, heating to 220° C. at a rate of 5° C. / 15 min, keeping warm, when the resin viscosity is 300-1000 cps / 50° C., the resin hydroxyl value is 120-160 mgKOH / g, and the acid value is 10-20 mgKOH / g, cooling to 30-40° C., adding diphenylmethane diisocyanate and solvent according to the formula amount, stirring and mixing quickly, adjusting the temperature to 85-90° C. after 30 minutes, keeping warm for 3-4 hours, and terminating the reaction when the acid value is detected to be 5-10 mgKOH / g, to obtain an alkyd resin.

[0059] Embodiment 8

[0060] The isocyanate-modified high-functionality alkyd resin provided in this embodiment is made of the following raw materials in percentage by mass: 20% soybean oil fatty acid, 8% phthalic anhydride, 5% sorbitol, 4% pentaerythritol, 6% butanethrol, 7% diphenylmethane diisocyanate, and 50% solvent (propylene glycol propyl ether: ethyl cyclohexane in a mass ratio of 1:7).

[0061] The preparation method of the isocyanate-modified high-functionality alkyd resin provided in the present embodiment comprises the following steps: adding soybean oil fatty acid, phthalic anhydride, sorbitol, pentaerythritol and butanethrol into a reaction kettle in order according to the above mass percentages, introducing nitrogen and heating to 180° C., starting stirring, keeping warm for 2 hours, heating to 220° C. at a rate of 5° C. / 15 min, keeping warm, when the resin viscosity is 300-1000 cps / 50° C., the resin hydroxyl value is 120-160 mgKOH / g, and the acid value is 10-20 mgKOH / g, cooling to 30-40° C., adding diphenylmethane diisocyanate and solvent according to the formula amount, stirring and mixing quickly, adjusting the temperature to 85-90° C. after 30 minutes, keeping warm for 3-4 hours, and terminating the reaction when the acid value is detected to be 5-10 mgKOH / g, to obtain an alkyd resin.

[0062] Embodiment 9

[0063] The isocyanate-modified high-functionality alkyd resin provided in this embodiment is made of the following raw materials in percentage by mass: 20% soybean oil fatty acid, 8% phthalic anhydride, 5% sorbitol, 4% pentaerythritol, 6% butanethrol, 7% hexamethylene diisocyanate, and 50% solvent (propylene glycol propyl ether: ethyl cyclohexane in a mass ratio of 1:7).

[0064] The preparation method of the isocyanate-modified high-functionality alkyd resin provided in the present embodiment comprises the following steps: adding soybean oil fatty acid, phthalic anhydride, sorbitol, pentaerythritol and butanethrol into a reaction kettle in order according to the above mass percentages, introducing nitrogen and heating to 180° C., starting stirring, keeping warm for 2 hours, heating to 220° C. at a rate of 5° C. / 15 min, keeping warm, when the resin viscosity is 300-1000 cps / 50° C., the resin hydroxyl value is 120-160 mgKOH / g, and the acid value is 10-20 mgKOH / g, cooling to 30-40° C., adding diphenylmethane diisocyanate and solvent according to the formula amount, stirring and mixing quickly, adjusting the temperature to 85-90° C. after 30 minutes, keeping warm for 3-4 hours, and terminating the reaction when the acid value is detected to be 5-10 mgKOH / g, to obtain an alkyd resin.

[0065] Embodiment 10

[0066] The isocyanate-modified high-functionality alkyd resin provided in this embodiment is made of the following raw materials in percentage by mass: 20% soybean oil fatty acid, 8% phthalic anhydride, 5% sorbitol, 4% pentaerythritol, 6% butanethrol, 7% dimethyl diphenyl diisocyanate, and 50% solvent (propylene glycol propyl ether: ethyl cyclohexane in a mass ratio of 1:7).

[0067] The preparation method of the isocyanate-modified high-functionality alkyd resin provided in the present embodiment comprises the following steps: adding soybean oil fatty acid, phthalic anhydride, sorbitol, pentaerythritol and butanethrol into a reaction kettle in order according to the above mass percentages, introducing nitrogen and heating to 180° C., starting stirring, keeping warm for 2 hours, heating to 220° C. at a rate of 5° C. / 15 min, keeping warm, when the resin viscosity is 300-1000 cps / 50° C., the resin hydroxyl value is 120-160 mgKOH / g, and the acid value is 10-20 mgKOH / g, cooling to 30-40° C., adding diphenylmethane diisocyanate and solvent according to the formula amount, stirring and mixing quickly, adjusting the temperature to 85-90° C. after 30 minutes, keeping warm for 3-4 hours, and terminating the reaction when the acid value is detected to be 5-10 mgKOH / g, to obtain an alkyd resin.

[0068] Table 2 Product index test results of alkyd resin prepared in each embodiment

[0069]

[0070] Table 3 Product performance test results of alkyd resin prepared in each embodiment

[0071]

[0072]

[0073] As can be seen from Table 2, the alkyd resin prepared using low-functionality polyols has defects in water resistance, heat resistance, and salt spray resistance. The alkyd resin prepared using high-functionality polyols has good leveling, high hardness, moisture and heat resistance, salt spray resistance, quick drying, excellent adhesion, etc., which can meet the needs of different application scenarios.

[0074] Embodiment 11

[0075] The only difference from Example 1 is that the solvent in Example 1 is replaced by the solvent in Table 3 in this example.

[0076] Table 3 Effect of different solvents on the viscosity and storage stability of alkyd resin

[0077]

[0078]

[0079] In order to test the corrosion resistance and insulation of alkyd resin, the insulation resistance degradation evaluation system was used to monitor the resistance of alkyd resin under double 85 conditions, bias 50V, voltage 100V, 1000h. The results are as follows Figure 1 As shown, the initial resistance of low-functionality alkyd resin is 10 7 Ω, after 100h the resistance drops to 10 6 Ω, high functionality alkyd resin maintained at 10 for 200h 8 Ω, 1000h stable at 10 6 Ω, the initial resistance and the resistance after 1000h under double 85 condition of the alkyd resin with sebacic acid and dimethyl diphenyl diisocyanate as raw materials are better than those of the other examples, which shows that the high crosslinking density brought by high functionality, the addition of sebacic acid and dimethyl diphenyl diisocyanate can significantly improve the hydrolysis resistance, corrosion resistance, moisture and heat resistance and surface insulation of the alkyd resin.

[0080] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An isocyanate-modified high-functionality alkyd resin, characterized in that: The isocyanate-modified high-functionality alkyd resin is made from the following raw materials in percentage by mass: 10% to 20% oleic acid or oil, 10% to 15% polyol, 20% to 25% polyacid or anhydride, 0.1% to 0.2% catalyst, 1% to 10% isocyanate, and the balance is solvent.

2. The isocyanate-modified high-functionality alkyd resin according to claim 1, characterized in that: The polyol is one or more of ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, glycerol, pentaerythritol, butanethritol, xylitol, and sorbitol.

3. The isocyanate-modified high-functionality alkyd resin according to claim 1, characterized in that: The polyacid is one or more of adipic acid, sebacic acid, phthalic anhydride, acetic anhydride and maleic anhydride.

4. The isocyanate-modified high-functionality alkyd resin according to claim 1, characterized in that: The solvent is one or more of propylene glycol methyl ether, propylene glycol propyl ether, propylene glycol butyl ether, ethyl acetate, butyl acetate, cyclohexane, and ethylcyclohexane.

5. The isocyanate-modified high-functionality alkyd resin according to claim 1, characterized in that: The isocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dimethylbiphenyl diisocyanate, and aliphatic isocyanate.

6. The isocyanate-modified high-functionality alkyd resin according to any one of claims 1 to 5, characterized in that: The viscosity of the alkyd resin at 25° C. is 1000-3000 cps.

7. The isocyanate-modified high-functionality alkyd resin according to any one of claims 1 to 6, characterized in that: The acid value of the alkyd resin is 10 to 20 mgKOH / g.

8. A method for preparing the isocyanate-modified high-functionality alkyd resin according to any one of claims 1 to 7, characterized in that: The following steps are involved: Add oleic acid or oil, polyol, polyacid or anhydride into the reaction kettle in sequence, and quickly heat it to 160-180°C under the protection of inert gas, start stirring and keep warm for 2-3 hours, then slowly heat it to 220-230°C and keep warm; When the viscosity of the resin at 50°C is monitored to be 300-1000cps, the hydroxyl value is 120-160mgKOH / g, and the acid value is 10-20mgKOH / g, the temperature is lowered to 30-40°C, isocyanate and solvent are added, and the temperature is adjusted to 85-90°C and kept warm for 3-4 hours. When the acid value of the resin is monitored to be 5-10mgKOH / g, the reaction is stopped to obtain an isocyanate-modified high-functionality alkyd resin.

9. The method for preparing an isocyanate-modified high-functionality alkyd resin according to claim 8, characterized in that: The solvent is propylene glycol propyl ether: butyl acetate in a mass ratio of 1:

7.

10. Use of the isocyanate-modified high-functionality alkyd resin according to any one of claims 1 to 7 in the field of coatings.

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