Aromatic carbamate modified alkyd resin as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of resin, and discloses aromatic carbamate modified alkyd resin as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing benzoic acid, oleic acid, polyol, anhydride and hypophosphorous acid, heating, and carrying out a first reaction to obtain a precursor; and mixing the precursor with an aromatic toluene diisocynate tripolymer and triphenyl phosphite, and carrying out a second reaction to obtain the aromatic carbamate modified alkyd resin. The aromatic carbamate modified alkyd resin is applied to a nitro coating to replace a nitrocotton component, so that the VOC emission of the nitro coating during construction is remarkably reduced, for example, the emission is lower than 650g / L, the environmental protection property is good, and a formed coating is excellent in performance, for example, the yellowing resistance, the adhesive force and the thermal cycling performance are excellent.

Description

Technical Field

[0001] The invention belongs to the technical field of resins, and particularly relates to an aromatic carbamate-modified alkyd resin and a preparation method and application thereof. Background Art

[0002] GB18581-2019 stipulates the limit value requirements for VOC (volatile organic compounds) content in solvent-based coatings: NC (nitro) coating (mixed according to the construction ratio under the construction conditions indicated on the product) has a VOC content of ≤700 g / L after testing.

[0003] After years of development, the most commonly used oil-based wood paints at this stage are NC (nitro) paint, PE (unsaturated polyester) paint and PU (polyurethane) paint.

[0004] NC (nitro) paint is a relatively common paint for wood and decoration. The main film-forming material of NC (nitro) paint is nitrocellulose, which is combined with soft and hard resins such as alkyd resin, modified rosin resin, acrylic resin, and amino resin. Generally, plasticizers such as dibutyl phthalate, dioctyl phthalate, and oxidized castor oil are also required. The solvents mainly include true solvents such as esters, ketones, and alcohol ethers, auxiliary solvents such as alcohols, and diluents such as benzene. NC (nitro) paint is mainly used for wood and furniture coating, home decoration, general decorative coating, metal coating, general cement coating, etc.

[0005] NC (nitro) paint is made of nitrocellulose, alkyd resin, pigment, plasticizer and organic solvent. NC (nitro) paint film dries quickly, is smooth and bright, has good weather resistance, and shortens the construction period. Among them, the high content of nitrocellulose leads to large VOC emissions and poor environmental protection.

[0006] Nitrocellulose is the nitrate ester of cellulose, called "nitrocellulose ester". In the early days, the raw material of cellulose was cotton or its scraps, so it was usually called "nitrocellulose". In addition to cotton, there are also wood cellulose and other cellulose raw materials. Nitrocellulose is obtained by the reaction of hydroxyl groups in cellulose and nitric acid in the presence of sulfuric acid, a water absorbent. According to the design of formulas and processes for different performance requirements, mononitrates, dinitrates and trinitrates with different nitrogen contents and properties can be obtained. The nitrogen contents are 6.76%, 11.11% and 14.14% respectively. The nitrogen content of nitrocellulose used for nitro paint is 10.5% to 12.2%. This kind of paint should be called nitrocellulose ester paint, referred to as "nitro paint" or "nitro paint" in the industry.

[0007] Nitrocellulose solution is often called "nitrocellulose solution" (abbreviated as cotton liquid). This liquid is obtained by adding a certain proportion of ester or alcohol solvents to nitrocellulose, and then dispersing and dissolving to obtain a liquid product with certain technical indicators such as viscosity, solid content, and color. After adding the solvent, the nitrocellulose is transformed from solid to liquid. Due to the change in form, the safety level has changed. Nitrocellulose belongs to Class 4.1 flammable solids, while nitrocellulose solution belongs to "Class III flammable liquids".

[0008] The industrial nitrocellulose standard is WJ 9028-2005. The classification method of industrial nitrocellulose is similar to the American method, which is to determine the viscosity by measuring the ball drop time. Nitrocellulose used in coatings is divided into L type with low nitrogen content (10.7% to 11.4%) and H type with high nitrogen content (11.5% to 12.2%).

[0009] Generally, the solid content of nitro paint shipped out of the factory is 36% at most, 18% at least, and about 28% on average. Although the national standard GB 18581-2019 stipulates that the solvent content of nitro paint is ≤72%, this is the standard for solvent-based paints for interior decoration. Furniture factories are not subject to this standard when painting, and their solid content will be lower. Using 1 ton of nitro paint will evaporate about 800 kg of solvent, which not only pollutes the environment but also wastes resources.

[0010] Standards GB 18581 and GB 18582 are mandatory standards. Nitro paints are required to have VOC ≤ 720g / L, benzene ≤ 0.3g / L, and a total amount of (toluene + ethylbenzene + xylene) ≤ 30g / L. Limits are set for toxic and hazardous substances such as heavy metals and free formaldehyde. The new standard will be implemented in December 2020, with stricter restrictions on VOV content. The national standard GB 18581-2020 stipulates that the VOC content of nitro paints is limited to ≤ 700g / L, and it is also clearly stipulated that it is limited to factory use. In fact, furniture factories are convenient for construction during painting, and the solid content may be lower under construction. Using 1t of nitro paint will evaporate about 800kg of solvent, which not only pollutes the environment, but also wastes resources. If the industry can plan ahead according to the current situation and speed up the development of low-pollution nitro paint varieties, it can take the initiative in development.

[0011] Patent application number 202211246782.8 discloses a nitro high-hardness black topcoat and its preparation method. The raw materials include, by weight percentage: 20%-40% resin matrix, 10%-20% nitrocellulose, 1%-10% filler, 0.2%-1% additive, 0.2-0.4% defoamer, and the balance is solvent. The patent uses a combination of short-oil alkyd resin and 1 / 16s and 1 / 4s nitrocellulose with good compatibility, and adds polytetrafluoroethylene as a filler. The prepared nitro high-hardness black topcoat film has excellent adhesion and hardness performance.

[0012] Patent No. 202111335498.3 discloses a nitro varnish with dimer acid modified castor oil alkyd resin as internal plasticizer and a preparation method thereof, wherein the nitro varnish comprises the following components in weight percentage: dimer acid modified castor oil alkyd resin 22-45wt%, nitro cotton liquid 50%-70wt%, hard resin 2-7wt%, defoamer 0.05-0.2wt%, leveling agent 0.1-0.5wt%. It can meet the requirement of VOC limit less than 700g / L in the new national standard GB18581-2020.

[0013] The patent with application number 201710285765.8 discloses a nitrocellulose substitute for coatings and a preparation method thereof, and also discloses a nitrocellulose substitute for coatings and a preparation method thereof. The nitrocellulose substitute for coatings is composed of the following components by weight: 38-42 parts of acrylic monomer, 0.8-1.0 parts of organic peroxide, 2-3 parts of silicone resin, and 56-60 parts of organic solvent. After the provided nitrocellulose substitute replaces nitrocellulose in the coating, it not only avoids the defects of high risk coefficient of nitrocellulose coatings, high costs such as sewage discharge and tax payment, but also greatly reduces the content of volatile organic compounds (VOC) in the coatings, reduces pollution to the environment, and maintains or even improves the performance of the original NC (nitro) coatings.

[0014] The existing NC (nitro) coatings use alkyd resins or acrylate resins, which can replace a portion of nitrocellulose, but the replacement amount is small, or there are deficiencies in performance, especially in drying.

[0015] Therefore, there is an urgent need to provide a new resin for nitrocellulose coatings, which can replace a large amount of nitrocellulose and significantly reduce VOC emissions, and the product has the performance of conventional NC wood coatings. Summary of the invention

[0016] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides an aromatic carbamate-modified alkyd resin and a preparation method and application thereof. The aromatic carbamate-modified alkyd resin of the present invention can be applied to NC (nitro) coatings to replace the nitrocellulose component, thereby significantly reducing the VOC emission of NC (nitro) coatings during construction, for example, below 650 g / L, having good environmental protection, and the formed coating has excellent performance, for example, excellent yellowing resistance, adhesion and hot and cold cycle performance.

[0017] A first aspect of the present invention provides a method for preparing an aromatic urethane-modified alkyd resin.

[0018] Specifically, a method for preparing an aromatic carbamate-modified alkyd resin comprises the following steps:

[0019] Mix benzoic acid, oleic acid, polyol, acid anhydride and hypophosphorous acid, raise the temperature, and carry out a first reaction to obtain a precursor;

[0020] The precursor is mixed with aromatic toluene diisocyanate trimer and triphenyl phosphite, and a second reaction is carried out to obtain the aromatic urethane-modified alkyd resin.

[0021] Preferably, the polyol comprises trimethylolpropane.

[0022] Preferably, the acid anhydride includes maleic anhydride and phthalic anhydride.

[0023] Preferably, in the process of preparing the precursor, a phenolic substance is also added, and the phenolic substance includes 2,6-di-tert-butyl-4-methylphenol.

[0024] Preferably, after the first reaction is completed, n-butyl acetate is added to obtain a precursor with a specific solid content and viscosity, which can improve the compatibility of the precursor with the subsequent reaction raw materials and facilitate the second reaction.

[0025] Preferably, the temperature of the first reaction is 151-156° C., and the reaction time is 2-4 hours; further preferably, the temperature of the first reaction is 152-156° C., and the reaction time is 3-4 hours.

[0026] Preferably, after the first reaction is completed, the temperature is continued to be raised to 200-215° C., and when the acid value is esterified to ≤15 mgKOH / g, the temperature is lowered to below 180° C., and then n-butyl acetate is added.

[0027] Preferably, xylene is added before the first reaction.

[0028] Preferably, the weight ratio of benzoic acid, oleic acid, polyol, anhydride and hypophosphorous acid is 4.0-6.5:(16-19):(20-25):26.7:(0.1-0.5), and more preferably 4.5-5.5:(17-18):(21.5-23.5):26.7:(0.1-0.2).

[0029] Preferably, during the preparation of the precursor, the weight ratio of benzoic acid, oleic acid, polyol, acid anhydride, hypophosphorous acid, phenolic substances, xylene, and n-butyl acetate is 4.5-5.5: (17-18): (21.5-23.5): 26.7: (0.1-0.2): (0.1-0.2): (1-3): (26-28).

[0030] Preferably, the solid content of the precursor is 68-69.2%, and the viscosity at 25° C. is 650-1000 mPa·S.

[0031] Preferably, the acid value of the precursor is 12-15 mgKOH / g, and the hydroxyl value is 58-73 mgKOH / g.

[0032] Preferably, the weight ratio of the precursor, aromatic toluene diisocyanate trimer and triphenyl phosphite is 88.33-98.3:(1.58-11.56):(0.11-0.25).

[0033] Preferably, the temperature of the second reaction is 110-130° C., and the time is 1-6 hours.

[0034] The molar ratio of the hydroxyl group of the precursor to the -NCO of the aromatic toluene diisocyanate trimer can be 1:1 to 100:1, preferably 2.5-25:1.

[0035] A second aspect of the present invention provides an aromatic urethane-modified alkyd resin.

[0036] Specifically, an aromatic carbamate-modified alkyd resin is prepared by the above preparation method.

[0037] Preferably, the aromatic urethane-modified alkyd resin has a solid content of 68.8-69.6% and a hydroxyl value of 35-60 mgKOH / g.

[0038] Preferably, the aromatic urethane-modified alkyd resin has a viscosity of 2000-4000 mPa·S at 25°C.

[0039] The aromatic urethane-modified alkyd resin is a yellow or light yellow transparent liquid.

[0040] The aromatic urethane-modified alkyd resin has a very low Bolife rotation viscosity under a high solid content condition.

[0041] The third aspect of the present invention provides an application of a method for preparing an aromatic urethane-modified alkyd resin.

[0042] A nitro paint comprises an aromatic carbamate-modified alkyd resin prepared by the above preparation method, a maleic anhydride resin, an auxiliary agent and a solvent.

[0043] Preferably, the nitrocellulose coating further comprises nitrocellulose or does not comprise nitrocellulose.

[0044] Preferably, in the nitro paint, the weight ratio of the aromatic carbamate-modified alkyd resin to the nitrocellulose is 58.2-60.2:(0-18), and more preferably 58.2-60.2:(0-16).

[0045] Preferably, the auxiliary agent includes at least one of a defoamer and a leveling agent. The auxiliary agent is a conventional substance in the art.

[0046] Preferably, the nitro paint further comprises polyamide wax slurry, talcum powder and zinc stearate.

[0047] Preferably, the solvent comprises sec-butyl acetate and dimethyl carbonate.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0049] The present invention adopts specific raw materials and preparation steps to prepare an aromatic carbamate-modified alkyd resin. The aromatic carbamate-modified alkyd resin is applied to NC (nitro) coatings to replace nitrocellulose components, thereby significantly reducing the VOC emission during the construction of the NC (nitro) coatings, for example, to less than 650 g / L, and has good environmental protection. In addition, the formed coating has excellent performance, for example, excellent yellowing resistance, adhesion and hot and cold cycle performance. DETAILED DESCRIPTION

[0050] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0051] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0052] The aromatic toluene diisocyanate trimer used in the following examples was provided by Shandong Yantai Wanhua Company, product model: TT-350B.

[0053] Example 1: Preparation of Precursor A

[0054] Preparation of Precursor A:

[0055] The weight parts of the raw materials used in the process of preparing precursor A are as follows:

[0056] 5.50 parts of benzoic acid, 17.00 parts of oleic acid, 23.50 parts of trimethylolpropane, 0.20 parts of maleic anhydride, 24.50 parts of phthalic anhydride, 0.20 parts of hypophosphorous acid, 3.00 parts of xylene, 26.00 parts of n-butyl acetate, 0.10 parts of 2,6-di-tert-butyl-4-methylphenol;

[0057] Benzoic acid, oleic acid, trimethylolpropane, maleic anhydride, phthalic anhydride, hypophosphorous acid and xylene were added to a reactor equipped with a fractionating column, a condenser and a water separator. Nitrogen was introduced and the temperature was raised to reflux at about 152°C. After reflux, the reaction was carried out for 4 hours, and then the temperature was slowly raised to 215°C. When the acid value was esterified to ≤15 mgKOH / g, the temperature was lowered to below 180°C, and n-butyl acetate and 2,6-di-tert-butyl-4-methylphenol were added to obtain precursor A.

[0058] The viscosity of the precursor A is 1000 mPa·S / 25° C., the acid value is 12 mgKOH / g, the solid content is 69.2%, the hydroxyl value is 73 mgKOH / g, and it is a light yellow viscous liquid.

[0059] Example 2: Preparation of Precursor B

[0060] Preparation of Precursor B:

[0061] The weight parts of the raw materials used in the process of preparing precursor B are as follows:

[0062] 4.50 parts of benzoic acid, 18.00 parts of oleic acid, 21.50 parts of trimethylolpropane, 0.40 parts of maleic anhydride, 26.30 parts of phthalic anhydride, 0.10 parts of hypophosphorous acid, 1.00 parts of xylene, 28.00 parts of n-butyl acetate, 0.20 parts of 2,6-di-tert-butyl-4-methylphenol;

[0063] Benzoic acid, oleic acid, trimethylolpropane, maleic anhydride, phthalic anhydride, hypophosphorous acid and xylene were added to a reactor equipped with a fractionating column, a condenser and a water separator. Nitrogen was introduced and the temperature was raised to reflux at about 156°C. After reflux, the reaction was carried out for 4 hours, and then the temperature was slowly raised to 215°C. When the acid value was esterified to ≤15 mgKOH / g, the temperature was lowered to below 180°C, and n-butyl acetate and 2,6-di-tert-butyl-4-methylphenol were added to obtain precursor B.

[0064] The viscosity of the precursor B is 650 mPa·S / 25° C., the acid value is 15 mgKOH / g, the solid content is 69.0%, the hydroxyl value is 58 mgKOH / g, and it is a light yellow viscous liquid.

[0065] Example 3

[0066] A method for preparing an aromatic carbamate-modified alkyd resin comprises the following steps:

[0067] Take 93.83 parts by weight of precursor A, the molar number of hydroxyl group is 0.0855, and the aromatic type toluene diisocyanate trimer TT-350B 6.06 parts by weight, its NCO mole number is 0.0115, triphenyl phosphite 0.11 parts by weight, the molar ratio of precursor hydroxyl -OH to aromatic isocyanate -NCO is 7.4.:1.

[0068] Put precursor A and aromatic toluene diisocyanate trimer into a reactor with a condenser and a water separator. TT-350B and triphenyl phosphite were reacted at 120°C for 1.5 hours under nitrogen gas flow until the NCO group was basically reacted to obtain an aromatic carbamate-modified alkyd resin.

[0069] The aromatic urethane-modified alkyd resin has a solid content of 68.8%, a viscosity of 2000 mPa·S / 25° C., a solid hydroxyl value of 60 mgKOH / g, and is a yellow viscous transparent liquid.

[0070] Example 4

[0071] A method for preparing an aromatic carbamate-modified alkyd resin comprises the following steps:

[0072] Take 88.33 parts by weight of precursor A, the molar number of hydroxyl group is 0.0804, and the aromatic type toluene diisocyanate trimer TT-350B 11.45 parts by weight, with an NCO molar number of 0.0218, triphenyl phosphite 0.22 parts by weight, and a molar ratio of precursor hydroxyl -OH to aromatic isocyanate -NCO of 3.5:1.

[0073] Put precursor A and aromatic toluene diisocyanate trimer into a reactor with a condenser and a water separator. TT-350B and triphenyl phosphite were reacted at 130°C for 6 hours under nitrogen gas, and the reaction was completed after the NCO group was basically reacted to obtain an aromatic carbamate-modified alkyd resin.

[0074] The aromatic urethane-modified alkyd resin has a solid content of 68.0%, a viscosity of 3500 mPa·S / 25° C., a solid hydroxyl value of 49 mgKOH / g, and is a yellow viscous transparent liquid.

[0075] Example 5

[0076] A method for preparing an aromatic carbamate-modified alkyd resin comprises the following steps:

[0077] Take 98.3 parts by weight of precursor B, the molar number of hydroxyl group is 0.007, and the aromatic type toluene diisocyanate trimer TT-350B 1.58 parts by weight, its NCO mole number is 0.0030, triphenyl phosphite 0.12 parts by weight, the molar ratio of precursor hydroxyl -OH to aromatic isocyanate -NCO is 23:1.

[0078] Put precursor B and aromatic toluene diisocyanate trimer into the reactor with condenser and water separator. TT-350B and triphenyl phosphite were reacted at 110°C for 1 hour under nitrogen gas flow until the NCO group was basically reacted to obtain an aromatic carbamate-modified alkyd resin.

[0079] The aromatic urethane-modified alkyd resin has a solid content of 69.6%, a viscosity of 2200 mPa·S / 25° C., a solid hydroxyl value of 54 mgKOH / g, and is a yellow viscous transparent liquid.

[0080] Example 6

[0081] A method for preparing an aromatic carbamate-modified alkyd resin comprises the following steps:

[0082] Take 88.73 parts by weight of precursor B, the molar number of hydroxyl group is 0.0632, and the aromatic type toluene diisocyanate trimer TT-350B 11.02 parts by weight, with an NCO mole of 0.0210, triphenyl phosphite 0.25 parts by weight, and a molar ratio of precursor hydroxyl -OH to aromatic isocyanate -NCO of 4:1.

[0083] Put precursor B and aromatic toluene diisocyanate trimer into the reactor with condenser and water separator. TT-350B and triphenyl phosphite were reacted at 110°C for 1 hour under nitrogen gas flow until the NCO group was basically reacted to obtain an aromatic carbamate-modified alkyd resin.

[0084] The aromatic urethane-modified alkyd resin has a solid content of 67.6%, a viscosity of 4000 mPa·S / 25° C., a solid hydroxyl value of 35 mgKOH / g, and is a yellow viscous transparent liquid.

[0085] Comparative Example 1

[0086] The preparation method of 62% solid content 36 oil degree glycerol type oleic acid modified alkyd resin (not modified with aromatic carbamate) comprises the following steps:

[0087] 20.827 parts of oleic acid, 0.489 parts of maleic anhydride, 24.834 parts of phthalic anhydride, 17.076 parts of 99.5% glycerol, 0.088 parts of hypophosphorous acid, 1.701 parts of reflux xylene, 27.582 parts of diluted xylene, 7.308 parts of diluted n-butyl acetate, 0.095 parts of 2,6-di-tert-butyl-4-methylphenol;

[0088] Oleic acid, maleic anhydride, phthalic anhydride, 99.5% glycerol, hypophosphorous acid and xylene were put into a reactor equipped with a fractionating column, a condenser and a water separator, and nitrogen was passed through. The temperature was raised to reflux and dilution at about 152°C. After reflux, the reaction was carried out for 5 hours, and then the temperature was slowly raised to 215°C. When the acid value was esterified to ≤15 mgKOH / g, the temperature was lowered to below 180°C, and n-butyl acetate and 2,6-di-tert-butyl-4-methylphenol were added to obtain a 62% solid content 36 oil degree glycerol-type oleic acid modified alkyd resin.

[0089] The viscosity of the 62% solid content 36 oil degree glycerol type oleic acid modified alkyd resin is 17500mPa·S / 25℃, and the hydroxyl value is 125mgKOH / g.

[0090] Comparative Example 2

[0091] The preparation method of 65% solid content 33 oil pentaerythritol type oleic acid modified alkyd resin (not modified with aromatic carbamate) comprises the following steps:

[0092] 20.328 parts of oleic acid, 4.709 parts of diethylene glycol, 0.496 parts of maleic anhydride, 22.931 parts of phthalic anhydride, 4.338 parts of neopentyl glycol, 13.013 parts of pentaerythritol, 0.175 parts of hypophosphorous acid, 1.003 parts of reflux xylene, 26.092 parts of diluted xylene, 6.794 parts of diluted n-butyl acetate, 0.121 parts of 2,6-di-tert-butyl-4-methylphenol;

[0093] Oleic acid, diethylene glycol, maleic anhydride, phthalic anhydride, neopentyl glycol, pentaerythritol, hypophosphorous acid and reflux xylene were put into a reaction kettle equipped with a fractionating column, a condenser and a water separator, and nitrogen was introduced. The temperature was raised to 180°C and kept for 2 hours, and then the temperature was slowly raised to 215°C. When the acid value was esterified to ≤15 mgKOH / g, diluted xylene, diluted n-butyl acetate and 2,6-di-tert-butyl-4-methylphenol were added to obtain a 62% solid content and 33 oil degree pentaerythritol type oleic acid modified alkyd resin.

[0094] The viscosity of the 65% solid content 33 oil pentaerythritol type oleic acid modified alkyd resin is 12000mPa·S / 25℃, the solid content is 65%, and the hydroxyl value is 134mgKOH / g.

[0095] Comparative Example 3

[0096] The preparation method of 70% solid content 33 oil degree quaternary tetraol type lauric modified alkyd resin (not modified with aromatic urethane) comprises the following steps:

[0097] 4.900 parts of benzoic acid, 21.970 parts of lauric acid, 22.642 parts of phthalic anhydride, 21.695 parts of pentaerythritol, 0.125 parts of hypophosphorous acid, 2.250 parts of reflux xylene, 19.245 parts of diluted xylene, 7.173 parts of diluted n-butyl acetate;

[0098] In a reaction kettle equipped with a fractionating column, a condenser and a water separator, lauric acid, reflux xylene, benzoic acid, phthalic anhydride, pentaerythritol and hypophosphorous acid are added, the temperature is raised to 180°C and kept for 2 hours, then the temperature is slowly raised to 225°C, and when the acid value is esterified to ≤15 mgKOH / g, diluted xylene and diluted n-butyl acetate are added to obtain a 70% solid content and 33 oil degree quaternary tetraol type laurel modified alkyd resin.

[0099] The viscosity of the 70% solid content 33 oil degree quaternary tetraol type laurel modified alkyd resin is 85000mPa·S / 25℃, the solid content is 69.5%, and the hydroxyl value is 133mgKOH / g.

[0100] The resins prepared in the above examples and comparative examples were used to prepare nitro paint (also known as nitro special clear primer).

[0101] The composition of the nitro paint is shown in Table 1 (the numerical units in Table 1 are parts by weight, and "-" in Table 1 means no addition). The resin prepared in Example 3 was used to prepare the implementation example 3, the resin prepared in Example 4 was used to prepare the implementation example 4, the resin prepared in Example 5 was used to prepare the implementation example 5, the resin prepared in Example 6 was used to prepare the implementation example 6, the resin prepared in Comparative Example 1 was used to prepare the comparative application example 1, the resin prepared in Comparative Example 2 was used to prepare the comparative application example 2, and the resin prepared in Comparative Example 3 was used to prepare the comparative application example 3.

[0102] "20 seconds 30% nitrocellulose solution" is a nitrocellulose with high nitrogen content, i.e. H type, and a falling ball viscosity of 20S. The supply method is a 30% mass solid nitrocellulose solution diluted with butyl acetate + ethyl acetate. The supplier of nitrocellulose is: Guangdong Enping Wandafu Chemical Co., Ltd.

[0103] Table 1

[0104]

[0105]

[0106] The 60% in the 60% maleic anhydride resin in Table 1 refers to the solid fraction, that is, 60% is maleic anhydride resin and the remaining 40% is solvent. The values ​​in 30% defoamer, 30% leveling agent and 6% polyamide wax slurry have similar meanings.

[0107] The preparation of nitro paint includes the following steps:

[0108] The digested cotton liquid, the resin of the embodiment or the comparative example, the maleic anhydride resin, the defoamer, the leveling agent, the polyamide wax slurry and the sec-butyl acetate were mixed and stirred for 10 minutes at a stirring speed of 500 rpm, and then zinc stearate and talcum powder were added and stirred at high speed for 15 minutes at a high speed stirring rate of 2000 rpm, and then dimethyl carbonate was added and stirred at a stirring speed of 500 rpm for 3 minutes to prepare a nitro paint.

[0109] The nitro paint and the thinner were mixed and stirred in a weight ratio of 1:0.1, and then sprayed on the medium-density fiberboard (the ambient temperature during spraying was 26°C, the relative humidity was 60%, and a No. 4 gun was used for spraying). After curing, a paint film was formed. The construction process and the performance of the paint film were tested. The construction process was carried out with reference to GB25271-2010 "Nitro Paint". The results are shown in Table 2, and the index test was carried out with reference to GB-T 25271-2010 Nitro Paint.

[0110] Table 2

[0111]

[0112]

[0113] It can be seen from Table 2 that the resin prepared in the embodiment of the present invention can significantly reduce the use of chemical cotton liquid in the preparation of nitro paint, thereby greatly reducing the emission of VOCs during the construction process of the prepared nitro paint, and the environmental protection is significantly better than the comparative example.

[0114] GB18581-2019 "Limits of Hazardous Substances in Wood Coatings" and the upcoming GB30981.2 "Limits of Hazardous Substances in Coatings Part 2: Industrial Coatings" have made relevant restrictions on volatile organic compounds in nitrocellulose lacquers. Nitrocellulose lacquers (limited to factory coatings) have a volatile organic compound (VOC) content of ≤700g / L. The resin prepared in the embodiment of the present invention is applied to nitrocellulose coatings, so that the VOC emission does not exceed 527g / L. It can be seen that the resin prepared in the present invention has obvious improvements.

[0115] Under the trend of environmental protection, the standards for volatile organic compounds in nitrocellulose lacquers will become increasingly stringent.

[0116] The resin prepared by the present invention is a substitute product for nitro paint. The resin prepared by the present invention is used to replace all or part of the nitrocellulose in the nitro paint formula, which can not only maintain the excellent properties of nitro paint such as quick drying and odor removal, but also significantly reduce VOC emissions.

Claims

1. A method for preparing an aromatic carbamate-modified alkyd resin, characterized in that: The following steps are involved: Mix benzoic acid, oleic acid, polyol, acid anhydride and hypophosphorous acid, raise the temperature, and carry out a first reaction to obtain a precursor; The precursor is mixed with aromatic toluene diisocyanate trimer and triphenyl phosphite, and a second reaction is carried out to obtain the aromatic urethane-modified alkyd resin.

2. The preparation method according to claim 1, characterized in that: The polyol includes trimethylolpropane; and / or, the acid anhydride includes maleic anhydride and phthalic anhydride.

3. The preparation method according to claim 1, characterized in that: In the process of preparing the precursor, phenolic substances are also added, and the phenolic substances include 2,6-di-tert-butyl-4-methylphenol.

4. The preparation method according to claim 1, characterized in that: The temperature of the first reaction is 151-156° C., and the reaction time is 2-4 hours.

5. The preparation method according to claim 1, characterized in that: The weight ratio of the benzoic acid, oleic acid, polyol, acid anhydride and hypophosphorous acid is 4.0-6.5:(16-19):(20-25):26.7:(0.1-0.5).

6. The preparation method according to claim 1, characterized in that: The weight ratio of the precursor, aromatic toluene diisocyanate trimer and triphenyl phosphite is 88.33-98.3:(1.58-11.56):(0.11-0.25).

7. An aromatic carbamate-modified alkyd resin, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 6.

8. The aromatic urethane-modified alkyd resin according to claim 7, characterized in that: The aromatic urethane modified alkyd resin has a solid content of 68.8-69.6% and a hydroxyl value of 35-60 mgKOH / g; and / or the aromatic urethane modified alkyd resin has a viscosity of 2000-4000 mPa·S at 25°C.

9. A nitro paint, characterized in that: The invention comprises an aromatic carbamate-modified alkyd resin prepared by the preparation method according to any one of claims 1 to 6 or an aromatic carbamate-modified alkyd resin according to any one of claims 7 to 8, a maleic anhydride resin, an auxiliary agent and a solvent.

10. The nitro paint according to claim 9, characterized in that: The nitro paint may also include or not include nitrocellulose. In the nitro paint, the weight ratio of the aromatic carbamate-modified alkyd resin to the nitrocellulose is 58.2-60.2:(0-18).

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