Polyester resin with excellent adhesive force and leveling property for transparent powder coating as well as preparation method and application of polyester resin

Abstract

The invention provides polyester resin for a transparent powder coating with excellent adhesive force and leveling as well as a preparation method and application of the polyester resin, and belongs to the technical field of powder coatings. The polyester resin is mainly prepared by taking diethylenetriamine pentaacetic acid, triethyl chlorosilane, 1, 6-hexanediol, N, N-diisopropylethanolamine, 2, 2-dimethyl propanol, neopentyl glycol, 3, 3-tetramethylene glutaric anhydride, 1, 4-cyclohexanedimethanol and the like as raw materials through polymerization. The obtained polyester resin chain segment has many branched structures, the number of amino groups and ester groups in the branched structures is large, the softening point is low, the low-temperature melting fluidity is good, the transparency is high, the adhesive force with a base material is good, then high-functionality diethylenetriamine pentaacetic acid is adopted for carboxyl end capping, the terminal carboxyl functionality is high, the curing activity is high, and the curing effect is good. After being cured with E-12 epoxy resin at low temperature, a coating film is good in leveling property and high in transparency, and can be used in the fields of thermosensitive base materials which are not easy to adhere, such as thin glass materials and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of powder coatings, and particularly relates to a transparent polyester resin for powder coatings with excellent adhesion and leveling, and a preparation method and application thereof. BACKGROUND

[0002] Powder coatings are widely used in various decorative materials due to the advantages of no solvent pollution, 100% film formation, and low energy consumption. With the gradual expansion of application fields, powder coatings are increasingly used in the field of decoration, and the application in some heat-sensitive substrates, such as medium-density fiberboard, wood substrates, and thin-layer glass substrates, is also gradually increasing. In order to highlight the decorative effect, the transparency of the coating is also required to a certain extent. Therefore, powder coatings with low-temperature curing and high transparency are a new direction of industry demand. However, for materials that are difficult to adhere to the surface of the substrate, such as glass substrates, it is also a problem that the industry cannot solve how to achieve high transparency while achieving excellent adhesion on the surface. SUMMARY

[0003] In view of the above problems, the present application provides a transparent polyester resin for powder coatings with excellent adhesion and leveling. The branched structure in the polyester resin segment is more, and the number of amino groups and ester groups in the branched structure is more. The softening point of the polyester resin is low, and the low-temperature melt flowability is good. The transparency is high and the adhesion to the substrate is good. Finally, high-functionality diethylene triamine pentaacetic acid is used to cap the carboxyl group, the carboxyl group functionality is high, the curing activity is strong, and after low-temperature curing at 150 DEG C / 15 min with E-12 epoxy resin, the coating film has good leveling and high transparency, and can be used in heat-sensitive substrates such as thin glass materials. One of the purposes of the present application is to provide a transparent polyester resin for powder coatings with excellent adhesion and leveling.

[0004] The second purpose of the present application is to provide a preparation method of the polyester resin.

[0005] The third purpose of the present application is to provide an application of the polyester resin in transparent powder coatings.

[0006] In order to achieve the above purposes of the present application, the following technical solutions are adopted: In a first aspect, the present application provides a transparent polyester resin for powder coatings with excellent adhesion and leveling, which is prepared from raw materials including the following mole fractions: diethylene triamine pentaacetic acid 7-10 parts; triethylchlorosilane 12-16 parts; N,N-dimethylformamide 15-20 parts; N,N-diisopropyl ethanolamine 6-9 parts; 1,6-hexanediol 6-8 parts; neopentyl glycol 2-4 parts; 3,3-tetramethylene glutaric anhydride 3-5 parts; 1,4-cyclohexane dimethanol 2-3 parts.

[0007] The raw materials also include a catalyst and an antioxidant; the catalyst is tetrabutyl titanate, and the amount is 0.3-0.4% of the mass of diethylenetriamine pentaacetic acid; the antioxidant is antioxidant 1010, and the amount is 0.2-0.3% of the total mass of the raw materials.

[0008] The typical but non-limiting mole fraction of diethylenetriamine pentaacetic acid is, for example, 7, 8, 9, 10, 11 parts; The typical but non-limiting mole fraction of triethylchlorosilane is, for example, 12, 13, 14, 15, 16 parts; The typical but non-limiting mole fraction of N,N-dimethylformamide is, for example, 15, 16, 17, 18, 19, 20 parts; The typical but non-limiting mole fraction of N,N-diisopropylethanolamine is, for example, 6, 7, 8, 9 parts; The typical but non-limiting mole fraction of 1,6-hexanediol is, for example, 6, 7, 8 parts; The typical but non-limiting mole fraction of neopentyl glycol is, for example, 2, 3, 4 parts; The typical but non-limiting mole fraction of 3,3-tetramethylene glutaric anhydride is, for example, 3, 4, 5 parts; The typical but non-limiting mole fraction of 1,4-cyclohexane dimethanol is, for example, 2, 2.5, 3 parts.

[0009] In a second aspect, the present application provides a preparation method of the above-mentioned transparent powder coating polyester resin with good adhesion and leveling, comprising the following steps: A. The formula amount of N,N-dimethylformamide, triethylchlorosilane and catalyst are added into a reaction kettle, and after being stirred uniformly, 85-90% of the formula amount of diethylenetriamine pentaacetic acid is added, and the temperature is raised while continuously blowing nitrogen and carrying out heat preservation reaction; B. When the content of triethylchlorosilane is lower than 0.5%, the formula amount of N,N-diisopropylethanolamine is added, and the temperature is raised to carry out esterification grafting reaction; C. When the content of N,N-diisopropylethanolamine is lower than 1%, the formula amount of 1,6-hexanediol and neopentyl glycol is added, and the temperature is gradually raised while removing N,N-dimethylformamide solvent; D. When the acid value of the polymer reaches 18-25 mgKOH / g, the formula amount of 3,3-tetramethylene glutaric anhydride and 1,4-cyclohexane dimethanol is added, and the temperature is raised to carry out secondary chain extension polymerization reaction; E, when the acid value of the polymer is 30-37 mgKOH / g, add the formula amount of antioxidant, stop blowing nitrogen, and start the vacuum system for vacuum polycondensation reaction; F, when the acid value of the polymer is reduced to 7-12 mgKOH / g, remove the vacuum system, continue to blow nitrogen at this time, then add the remaining formula amount of diethylene triamine pentaacetic acid, and heat for carboxyl end-capping reaction, stop the reaction when the acid value of the polymer is 46-53 mgKOH / g, hot high-temperature discharge, and then cool the polyester resin with a steel belt with condensed water, and then break and granulate to obtain the polyester resin.

[0010] In some embodiments, in step A, the temperature is raised to 110-115°C; In some embodiments, in step B, the temperature is raised to 135-138°C; In some embodiments, in step C, the temperature is raised at a rate of 15-18°C / h to 210-215°C; In some embodiments, in step D, the temperature is raised to 220-225°C; In some embodiments, in step E, the vacuum degree is maintained at -0.095 Mpa to -0.098 Mpa; In some embodiments, in step F, the temperature is raised to 230-235°C.

[0011] In a specific embodiment, the preparation method of the polyester resin for transparent powder coating with good adhesion and leveling comprises the following steps: A, add the formula amount of N,N-dimethylformamide, triethylchlorosilane, and catalyst to the reaction kettle, stir uniformly, then add 85-90% of the formula amount of diethylene triamine pentaacetic acid, heat to 110-115°C, continuously blow nitrogen, and heat for reaction; B, take a sample for gas chromatography detection, when the content of triethylchlorosilane is less than 0.5%, it indicates that the triethylchlorosilane has completed grafting reaction, then add the formula amount of N,N-diisopropylethanolamine, and heat to 135-138°C for esterification grafting reaction; C, take a sample for gas chromatography detection, when the content of N,N-diisopropylethanolamine is less than 1%, it indicates that the N,N-diisopropylethanolamine has completed esterification reaction, to obtain the intermediate of organosilicon and N,N-diisopropylethanolamine grafting reaction; at this time, add the formula amount of 1,6-hexanediol and neopentyl glycol, and gradually heat to 210-215°C at a heating rate of 15-18°C / h, and remove N,N-dimethylformamide solvent during the heating process; D, sample detection, when the acid value of the polymer reaches 18-25 mgKOH / g, add the formula amount of 3,3-tetramethylene glutaric anhydride and 1,4-cyclohexane dimethanol, and heat to 220-225 DEG C to carry out secondary chain extension polymerization reaction; E, sample detection of the acid value of the reaction polymer, when the acid value is 30-37 mgKOH / g, add the formula amount of antioxidant 1010, stop blowing nitrogen, and start the vacuum system to carry out vacuum polycondensation reaction, the vacuum degree is kept at-0.095 Mpa to-0.098 Mpa; F, when the acid value of the reaction polymer is reduced to 7-12 mgKOH / g, the vacuum system is removed, at this time continue to blow nitrogen, then add the remaining formula amount of diethylene triamine pentaacetic acid, and heat to 230-235 DEG C to carry out carboxyl end capping reaction, when the acid value of the polymer is 46-53 mgKOH / g, stop the reaction, hot high temperature discharge, and cool the polyester resin with a steel belt with condensed water, then break and granulate to obtain the polyester resin.

[0012] The polyester resin obtained by the application is light yellow transparent particles, the acid value is 46-53 mgKOH / g, and the softening point is 94-103 DEG C.

[0013] In a third aspect, the application provides a use of the polyester resin in transparent powder coating.

[0014] Advantages: The application mainly uses diethylene triamine pentaacetic acid, triethyl chlorosilane, 1,6-hexanediol, N,N-diisopropyl ethanolamine, 2,2-dimethylpropanol, neopentyl glycol, 3,3-tetramethylene glutaric anhydride, 1,4-cyclohexane dimethanol, etc. as raw materials to carry out polymerization. The diethylene triamine pentaacetic acid is first grafted and modified with triethyl chlorosilane and N,N-diisopropyl ethanolamine, and then chain extension polymerization is carried out with other raw materials. The branched structure in the chain segment of the finally obtained polyester resin is more, and the number of amino groups and ester groups in the branched structure is more, the softening point of the polyester resin is low, the low-temperature melt flowability is good, the transparency is high, and the adhesion to the substrate is good. Finally, high-functionality diethylene triamine pentaacetic acid is used for carboxyl end capping, the carboxyl end capping functionality is high, the curing activity is strong, and after low-temperature curing at 150 DEG C / 15 min with E-12 epoxy resin, the coating film has good leveling property and high transparency, and can be used in the fields of heat-sensitive substrates such as thin glass materials which are not easy to adhere.

[0015] The application has been described in detail in the foregoing, but the above-mentioned embodiments are only illustrative in nature and are not intended to limit the application. Furthermore, the present text is not limited by any theory described in the foregoing prior art or summary of the application or in the following examples. DETAILED DESCRIPTION

[0016] The application will be further described in connection with the following examples. It should be noted that the following examples are provided for illustration purposes only and do not constitute a limitation on the scope of the application.

[0017] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are conventional raw materials, reagents, methods in the art.

[0018] Determination of softening point: according to the method of GB / T 15332-1994 "Determination of softening point of hot melt adhesive - Ring and ball method"; Determination of acid value: according to the method in HG / T2708 "Determination of acid value in polyester polyol".

[0019] Example 1 A polyester resin for transparent powder coating with good adhesion and leveling, comprising the following raw materials in mole fraction: diethylene triamine pentaacetic acid 9 parts; triethyl chlorosilane 12 parts; N,N-dimethylformamide 20 parts; N,N-diisopropyl ethanolamine 9 parts; 1,6-hexanediol 7 parts; neopentyl glycol 4 parts; 3,3-tetramethylene glutaric anhydride 3 parts; 1,4-cyclohexane dimethanol 3 parts; titanium tetrabutoxide, used in an amount of 0.4% of the mass of diethylene triamine pentaacetic acid; antioxidant 1010, used in an amount of 0.3% of the total mass of raw materials.

[0020] The method for preparing the above-mentioned polyester resin for transparent powder coating with good adhesion and leveling comprises the following steps: A. The formula amount of N,N-dimethylformamide, triethyl chlorosilane and catalyst are added to the reaction kettle, stirred uniformly, then 85% of the formula amount of diethylene triamine pentaacetic acid is added, heated to 110°C, while continuously blowing nitrogen and carrying out heat preservation reaction; B. Take sample for gas chromatography detection. When the content of triethyl chlorosilane is less than 0.5%, it indicates that the triethyl chlorosilane has completed grafting reaction, then the formula amount of N,N-diisopropyl ethanolamine is added, and the temperature is raised to 135°C for esterification grafting reaction; C, sample by gas chromatography, when the content of N,N-diisopropyl ethanolamine is less than 1%, it indicates that the esterification reaction of N,N-diisopropyl ethanolamine is completed, and the intermediate of silicone and N,N-diisopropyl ethanolamine grafting reaction is obtained; at this time, the formula amount of 1,6-hexanediol and neopentyl glycol is added, and gradually heated to 210℃ at a heating rate of 15℃ / h, and the N,N-dimethylformamide solvent is removed during the heating process; D, sample detection, when the acid value of the polymer reaches 18-25 mgKOH / g, the formula amount of 3,3-tetramethylene glutaric anhydride and 1,4-cyclohexane dimethanol is added, and the temperature is raised to 225℃ for secondary chain extension polymerization reaction; E, sample detection of the acid value of the reaction polymer, when the acid value is 30-37 mgKOH / g, the formula amount of antioxidant 1010 is added, the nitrogen gas is stopped, and the vacuum system is started for vacuum polycondensation reaction, and the vacuum degree is kept at-0.095 Mpa; F, when the acid value of the reaction polymer is reduced to 7-12 mgKOH / g, the vacuum system is released, at this time, the nitrogen gas is continued to be blown in, then the remaining 15% formula amount of diethylenetriamine pentaacetic acid is added, and the temperature is raised to 235℃ for carboxyl end-capping reaction, when the acid value of the polymer is 46-53 mgKOH / g, the reaction is stopped, the high-temperature discharge is carried out, and the polyester resin is cooled by steel belt with condensed water, then broken and granulated, and the polyester resin is obtained.

[0021] The prepared polyester resin has an acid value of 49 mgKOH / g and a softening point of 101℃.

[0022] Example 2 A transparent powder coating polyester resin with good adhesion and leveling, comprising the following raw materials by mole fraction: Diethylenetriamine pentaacetic acid 7 parts; Triethylchlorosilane 13 parts; N,N-dimethylformamide 15 parts; N,N-diisopropyl ethanolamine 7 parts; 1,6-hexanediol 8 parts; Neopentyl glycol 2 parts; 3,3-tetramethylene glutaric anhydride 5 parts; 1,4-cyclohexane dimethanol 2 parts; Titanium tetrabutoxide, the amount is 0.3% of the mass of diethylenetriamine pentaacetic acid; Antioxidant 1010, the amount is 0.2% of the total mass of raw materials. The preparation method is the same as that of Example 1.

[0023] The prepared polyester resin has an acid value of 52 mgKOH / g and a softening point of 96℃.

[0024] Example 3 A polyester resin for transparent powder coating with good adhesion and leveling, comprising the following raw materials in mole fraction: diethylenetriamine pentaacetic acid 10 parts; triethylchlorosilane 16 parts; N,N-dimethylformamide 16 parts; N,N-diisopropylethanolamine 8 parts; 1,6-hexanediol 8 parts; neopentyl glycol 4 parts; 3,3-tetramethylene glutaric anhydride 3 parts; 1,4-cyclohexane dimethanol 2.5 parts; titanium tetrabutoxide, used in an amount of 0.35% of the mass of diethylenetriamine pentaacetic acid; antioxidant 1010, used in an amount of 0.2% of the total mass of raw materials. The preparation method is the same as that of Example 1.

[0025] The polyester resin prepared has an acid value of 50 mgKOH / g and a softening point of 102℃.

[0026] Example 4 A polyester resin for transparent powder coating with good adhesion and leveling, comprising the following raw materials in mole fraction: diethylenetriamine pentaacetic acid 8 parts; triethylchlorosilane 15 parts; N,N-dimethylformamide 18 parts; N,N-diisopropylethanolamine 6 parts; 1,6-hexanediol 6 parts; neopentyl glycol 3 parts; 3,3-tetramethylene glutaric anhydride 3.5 parts; 1,4-cyclohexane dimethanol 3 parts; titanium tetrabutoxide, used in an amount of 0.3% of the mass of diethylenetriamine pentaacetic acid; antioxidant 1010, used in an amount of 0.25% of the total mass of raw materials. The preparation method is the same as that of Example 1.

[0027] The polyester resin prepared has an acid value of 47 mgKOH / g and a softening point of 98℃.

[0028] Comparative Example 1 A commercially available polyester resin for high-gloss, high-leveling powder coating, with an acid value of 54 mgKOH / g and a softening point of 115℃, model SJ6200, purchased from Anhui Shenjian New Material Co., Ltd.

[0029] Comparative Example 2 Other than Comparative Example 1, only the curing condition is adjusted from 150℃ / 15min to 200℃ / 15min.

[0030] Performance tests The mixed powder coating formulation is generally as follows, in parts by weight: Example and Comparative Example Polyester Resin 400 parts; High Flow E-12 Epoxy Resin 200 parts; Leveling Agent 10 parts; Gloss Enhancer 5 parts; Benzoine 2 parts.

[0031] The high flow E-12 epoxy resin is HT-242GHF, purchased from Anhui Hengtai New Material Science and Technology Co., Ltd.; the leveling agent is a transparent powder special leveling agent, GLP100, and the gloss enhancer is BLC701, both purchased from Ningbo Nanhai Chemical Co., Ltd.

[0032] Coating Layer Preparation: According to the above mixed powder coating formulation, the materials are uniformly mixed, extruded, tabletted, broken, and then the tablet is crushed and sieved to prepare the powder coating. The powder coating is sprayed on the surface treated tinplate substrate and glass plate substrate using an electrostatic spray gun, with a film thickness of about 80μm. After curing at 150℃ / 15min, the coating layer is obtained.

[0033] Coating Index Detection Basis: GB / T 21776-2008 “Guidelines for Testing Standards of Powder Coatings and Their Coatings”. The leveling performance is tested using PCI leveling grade, with a scale of 1-10, and the larger the number, the better the leveling. The adhesion test is carried out according to GB / T9286-2021 “Cross-hatch Test for Pigmented and Clear Coatings”.

[0034] Transmittance Test: The powder coating is sprayed on a clean transparent standard glass plate preheated at 120℃ / 5min, and then cured at 150℃ / 15min to obtain a transparent powder coating film. The transmittance of the standard glass plate after spraying the transparent powder coating and curing is tested, and the transmittance of the standard glass plate after spraying the transparent powder coating and curing is compared with the transmittance of the pure standard glass plate. The transmittance of the transparent powder coating film = test plate transmittance / standard glass plate transmittance x 100%.

[0035] The polyester resins prepared in the above examples and comparative examples are tested for their coating performance after being prepared into coatings according to the coating formulation, and the results are shown in Tables 1 and 2.

[0036] Table 1 Coating Film Performance of Powder Coating (Tinplate Substrate)

[0037] Table 2 Film performance of powder coating (glass plate substrate)

[0038] Note: The light transmittance of the standard glass plate without sprayed sample for experiment is 90.6%.

[0039] As shown in Table 1, the powder coating prepared from the polyester resin of the present application and the high leveling E-12 epoxy resin, after low temperature curing at 150℃ / 15min, has a smooth and flat film appearance, and the 50cm positive and negative impact on the tinplate substrate is passed, the film gloss is basically above 94%, the adhesion reaches 0 level, the leveling grade is above 6, and the boiling water boiling performance is good. As shown in Table 2, the powder coating prepared from the polyester resin of the present application is electrostatically sprayed on the glass plate substrate with a smoother surface and is not easy to adhere, and after low temperature curing at 150℃ / 15min, the adhesion can still reach above 1 level, the leveling grade and boiling water boiling performance are good, and the light transmittance can reach above 88%. The product of the present application uses a specific raw material formula and process, realizes low temperature curing, high leveling and high light transmittance, and also realizes high adhesion on the glass substrate.

[0040] The polyester resin used in Comparative Example 1 cannot be effectively cured at 150℃ / 15min, not only the film surface is rough, but also the impact resistance, boiling water boiling, adhesion and leveling performance are poor; Comparative Example 2 increases the curing condition to 200℃ / 15min, and full curing can be achieved on the tinplate substrate and the glass substrate, but the film gloss, adhesion and leveling grade are still significantly lower than those of the product of the present application, especially on the glass substrate, the light transmittance is low, only about 78%, which is much lower than the performance of the polyester resin product of the present application.

[0041] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the foregoing examples, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing examples can be modified or some or all of the technical features can be replaced by equivalents without departing from the spirit and essence defined by the claims of the present application; and these modifications or replacements are still within the scope defined by the claims of the present application.

Claims

1. A polyester resin for transparent powder coatings with excellent adhesion and leveling properties, characterized in that, Prepared from raw materials including the following molar fractions: Diethylenetriamine pentaacetic acid 7-10 parts; Triethylchlorosilane 12-16 parts; N,N-dimethylformamide 15-20 parts; N,N-diisopropylethanolamine 6-9 parts; 1,6-hexanediol 6-8 parts; Neopentyl glycol 2-4 parts; 3,3-tetramethylene glutaric anhydride 3-5 parts; 1,4-cyclohexane dimethanol 2-3 parts.

2. The transparent polyester resin for powder coating with adhesion and leveling properties according to claim 1, characterized in that, The raw materials also include a catalyst and an antioxidant; the catalyst is tetrabutyl titanate, used in an amount of 0.3-0.4% of the mass of diethylenetriamine pentaacetic acid; the antioxidant is antioxidant 1010, used in an amount of 0.2-0.3% of the total mass of the raw materials.

3. A process for producing the polyester resin for transparent powder coating having high adhesion and leveling property according to claim 1 or 2, characterized in that, Including the following steps: A. The formula amount of N,N-dimethylformamide, triethylchlorosilane, and catalyst are added to a reaction kettle, stirred uniformly, then 85-90% of the formula amount of diethylenetriamine pentaacetic acid is added, heated, while continuously bubbling nitrogen and conducting a heat preservation reaction; B. When the triethylchlorosilane content is less than 0.5%, the formula amount of N,N-diisopropylethanolamine is added, heated, and esterification grafting reaction is conducted; C. When the N,N-diisopropylethanolamine content is less than 1%, the formula amount of 1,6-hexanediol and neopentyl glycol is added, gradually heated, while removing the N,N-dimethylformamide solvent; D. When the acid value of the polymer reaches 18-25 mgKOH / g, the formula amount of 3,3-tetramethylene glutaric anhydride and 1,4-cyclohexane dimethanol is added, heated, and secondary chain extension polymerization reaction is conducted; E. When the acid value of the polymer is 30-37 mgKOH / g, the formula amount of antioxidant is added, nitrogen bubbling is stopped, and a vacuum system is started to conduct vacuum polycondensation reaction; F. When the acid value of the polymer is reduced to 7-12 mgKOH / g, the vacuum system is removed, at this time nitrogen bubbling is continued, then the remaining formula amount of diethylenetriamine pentaacetic acid is added, heated, and carboxyl end capping reaction is conducted, the reaction is stopped when the acid value of the polymer is 46-53 mgKOH / g, hot high temperature discharge is conducted, the polyester resin is cooled with a steel belt with condensed water, then broken and granulated, and the polyester resin is obtained.

4. The production method according to claim 3, characterized by, In step A, the temperature is raised to 110-115°C.

5. The preparation method according to claim 3, characterized in that, In step B, the temperature is raised to 135-138°C.

6. The preparation method according to claim 3, characterized in that, In step C, the temperature is raised at a rate of 15-18°C / h to 210-215°C.

7. The preparation method according to claim 3, characterized in that, In step D, the temperature is raised to 220-225°C.

8. The preparation method according to claim 3, characterized in that, In step E, the vacuum degree is maintained at -0.095 Mpa to -0.098 Mpa.

9. The preparation method according to claim 3, characterized in that, In step F, the temperature is raised to 230-235°C.

10. Use of the polyester resin of claim 1 or 2 or the polyester resin prepared by the preparation method of any one of claims 3-9 in transparent powder coatings.

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