Polyester resin for low-temperature curing excellent-leveling 70 / 30 mixed powder coating and preparation method of polyester resin

Abstract

The invention relates to a low-temperature curing excellent-leveling polyester resin for a 70 / 30 mixed powder coating. The low-temperature curing excellent-leveling polyester resin is prepared by copolymerizing recycled frying waste oil, 2-ethylhexyl acrylate, acrylic acid, xylene, neopentyl glycol, E-51 liquid epoxy resin, terephthalic acid, glutaric anhydride and the like. A glyceride chain segment is introduced into a polyester resin chain segment, so that the product is relatively low in softening point and good in leveling property; due to the introduction of the E-51 liquid epoxy resin, the adhesive force of the polyester resin and a base material is improved, the final product is good in low-temperature fluidity and high in terminal carboxyl activity, the 70 / 30 polyester resin and the E-12 epoxy resin can be subjected to low-temperature curing (145 DEG C / 15min), and the leveling grade is high; and the recycling of the recycled frying waste oil is fully realized, and the method has better environmental protection and economic values.

Description

Technical Field

[0001] The invention relates to the technical field of powder coatings, and in particular to a polyester resin for a 70 / 30 mixed powder coating with low-temperature curing and excellent leveling, and a preparation method thereof. Background Art

[0002] At present, with the improvement of environmental protection requirements, the emission requirements for VOC in the field of coatings are getting higher and higher. Solvent-based coatings are facing serious environmental emission problems and are restricted in development. Powder coatings have the advantages of no VOC emissions and high powder utilization rate and are developing rapidly. Among indoor powder coatings, 70 / 30 powder coatings are a very important variety. Compared with 50 / 50 mixed powder coatings, it uses a relatively large amount of polyester resin and relatively less E-12 epoxy resin, so its leveling performance is lower than that of 50 / 50 mixed varieties, and its leveling grade is lower than that of 50 / 50 mixed varieties. Moreover, with the requirements of energy conservation and environmental protection and the expansion of the application range of substrates, the coating of low-temperature substrates such as plastics is more sensitive to temperature. Low-temperature curing that can meet energy conservation and low-temperature substrate coating is also the direction pursued by the industry.

[0003] At the same time, with the improvement of people's living standards, fried foods can be seen almost everywhere in outdoor snacks, such as fried skewers, fried chicken and other fried foods, which also leads to a large amount of frying waste oil. Since soybean oil is relatively cheap, it accounts for a large proportion of frying oil. Because the frying process is a high-temperature process, the frying oil becomes darker due to high-temperature oxidation after frying for more than 6 times. The fried food is not only ugly in color, but also the frying oil will generate carcinogens when it is too high for a long time, which leads to the need to replace the frying oil, which produces a large amount of frying waste oil, which not only pollutes the environment, but also is difficult to use. How to make comprehensive use of these frying waste oils with high added value is a difficulty in the current frying industry. Summary of the invention

[0004] In view of the above-mentioned existing problems, the present invention develops a 70 / 30 hybrid powder coating polyester resin with low temperature curing and excellent leveling, which is prepared by copolymerization of recycled frying waste oil, isooctyl acrylate, acrylic acid, xylene, neopentyl glycol, E-51 liquid epoxy resin, terephthalic acid, and glutaric anhydride. First, the recycled frying waste oil is decolorized, and then copolymerized and grafted with isooctyl acrylate and acrylic acid in a xylene solution using olefin double bonds to obtain a carboxyl-containing prepolymer; then, it is subjected to chain extension and end-capping polymerization with neopentyl glycol, E-51 liquid epoxy resin, terephthalic acid, glutaric anhydride, etc. The final product has good low-temperature fluidity and high terminal carboxyl activity. As a 70 / 30 polyester resin, it can be cured at low temperature (145°C / 15min) with E-12 epoxy resin, and has a high leveling grade.

[0005] A low-temperature curing, excellent-leveling 70 / 30 mixed type polyester resin for powder coatings, comprising the following raw materials in parts by weight:

[0006]

[0007] The raw materials also include catalyst 1, catalyst 2, decolorizing agent and antioxidant.

[0008] Furthermore, catalyst 1 is dibenzoyl peroxide, and its dosage is 2-3% of the mass of acrylic acid; catalyst 2 is tetrabutyl titanate, and its dosage is 0.8-1.3% of the mass of recovered waste frying oil; the decolorizing agent is activated white clay, and its dosage is 0.8-1% of the mass of recovered waste frying oil; the antioxidant is antioxidant 1076, i.e. β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate octadecyl ester, and its dosage is 0.7-0.9% of the mass of recovered waste frying oil.

[0009] Furthermore, the recovered frying waste oil is a light brown viscous liquid, the main component of which is glyceride, and the iodine value is 130-150g / 100g, for example, it can be purchased from Anhui Changfa Qixiang Environmental Protection Technology Co., Ltd.

[0010] The method for preparing a 70 / 30 mixed type polyester resin for powder coatings with low temperature curing and excellent leveling as described above comprises the following steps:

[0011] A. Add the formula amount of recycled frying waste oil and xylene into the reactor, start stirring, mix thoroughly and evenly, heat to 70-80°C, then add the formula amount of decolorant, continue to keep warm and stir to perform thermal decolorization treatment, and then perform filter press treatment to obtain filtrate and filter cake;

[0012] B. Pump the filtrate into the reactor, start stirring, raise the temperature to 120-125°C and keep warm, then start dripping the mixed solution of isooctyl acrylate, acrylic acid and catalyst 1 in the formula amount, and continue to keep warm and react after the dripping is completed;

[0013] C. Take samples to test the iodine value of the polymer. When the iodine value of the polymer reaches 5-10g / 100g, it means that the copolymerization grafting reaction is basically completed. At this time, add the formula amount of neopentyl glycol, E-51 liquid epoxy resin, terephthalic acid and catalyst 2, and gradually raise the temperature to 210-215℃ for esterification and chain extension polymerization. During the heating reaction, the solvent and small molecules are removed at the same time;

[0014] D. Detect the acid value of the polymer in the system. When the acid value of the polymer reaches 20-25 mgKOH / g, add the formulated amount of antioxidant, raise the temperature to 230-235°C, and start the vacuum system for vacuum polycondensation reaction;

[0015] E. Take samples for testing. When the acid value of the polymer reaches 8-14 mgKOH / g, release the vacuum, add the formulated amount of glutaric anhydride as a capping agent and continue the capping reaction at 230-235°C. When the acid value of the polymer reaches 28-37 mgKOH / g, stop the reaction, discharge the material while hot, cool the polyester resin, and then crush and granulate it to obtain the polyester resin.

[0016] Furthermore, in step A, the thermal decolorization treatment time is 1-1.5h; in step B, the dropping time is controlled at 1.5-2h; in step C, the temperature is gradually increased at a heating rate of 12-15°C / h; in step D, the vacuum degree is controlled at -0.096Mpa to -0.099Mpa; in step E, the polyester resin is cooled with a steel belt with condensed water.

[0017] The obtained product has the appearance of light yellow transparent particles, an acid value of 28-37 mgKOH / g, and a softening point of 96-105°C.

[0018] For example, a method for preparing a 70 / 30 hybrid polyester resin for powder coatings with low temperature curing and excellent leveling comprises the following steps:

[0019] A. Add the formula amount of recycled frying waste oil and xylene into the reactor, start stirring, mix thoroughly and evenly, heat to 70-80°C, then add the formula amount of decolorant, continue to keep warm and stir to perform thermal decolorization treatment for 1-1.5h, and then perform filter press treatment to obtain filtrate and filter cake;

[0020] B. Pump the filtrate into the reactor, start stirring, raise the temperature to 120-125°C and keep warm, then start dripping the mixed solution of isooctyl acrylate, acrylic acid and catalyst 1 in the formula amount, and control the dripping time to 1.5-2h. After the dripping is completed, continue to keep warm for reaction;

[0021] C. Sampling and testing the iodine value of the polymer. When the iodine value of the polymer reaches 5-10g / 100g, it indicates that the graft polymerization reaction of the recovered frying waste oil after decolorization treatment and the acrylic acid mixed monomer is basically completed. At this time, the formula amount of neopentyl glycol, E-51 liquid epoxy resin, terephthalic acid and catalyst 2 are added, and the temperature is gradually increased to 210-215°C at a heating rate of 12-15°C / h for esterification and chain extension polymerization reaction. During the heating reaction, the solvent xylene and small molecular water are removed at the same time;

[0022] D. Detect the acid value of the polymer in the system. When the acid value of the polymer reaches 20-25 mgKOH / g, add the formulated amount of antioxidant, raise the temperature to 230-235°C, and start the vacuum system for vacuum polycondensation reaction. The vacuum degree is controlled at -0.096Mpa to -0.099Mpa;

[0023] E. Take samples for testing. When the acid value of the polymer reaches 8-14 mgKOH / g, release the vacuum, add the formulated amount of glutaric anhydride as a capping agent and continue the capping reaction at 230-235°C. When the acid value of the polymer reaches 28-37 mgKOH / g, stop the reaction, discharge the material while hot, cool the polyester resin with a steel belt with condensed water, and then crush and granulate it to obtain the polyester resin.

[0024] The use of the polyester resin for 70 / 30 hybrid powder coatings with low temperature curing and excellent leveling as described above or the polyester resin for 70 / 30 hybrid powder coatings with low temperature curing and excellent leveling obtained by the preparation method in low temperature curing hybrid powder coatings.

[0025] For example, a general-purpose 70 / 30 mixed powder coating formulation is usually formulated as follows in parts by weight:

[0026]

[0027]

[0028] According to the above powder coating formula, the materials are mixed evenly, extruded, tableted and crushed by a twin-screw extruder, and then the tablets are crushed and sieved to form powder coating. The powder coating is sprayed on the tinplate substrate after surface treatment by an electrostatic spray gun, and after curing, the coating coating is obtained.

[0029] Beneficial effects:

[0030] The product of the invention is prepared by copolymerizing recycled frying waste oil, isooctyl acrylate, acrylic acid, xylene, neopentyl glycol, E-51 liquid epoxy resin, terephthalic acid and glutaric anhydride. First, the recycled frying waste oil is decolorized, and then copolymerized and grafted with isooctyl acrylate and acrylic acid in a xylene solution by using olefin double bonds to obtain a carboxyl-containing prepolymer; and then chain-extending and end-capping polymerization is performed with neopentyl glycol, E-51 liquid epoxy resin, terephthalic acid, glutaric anhydride and the like to obtain the prepolymer. Glycerol ester segments and isooctyl acrylate segments are introduced into the polyester resin segment. The product has a low softening point and good leveling properties. The introduction of E-51 liquid epoxy resin improves the adhesion between the polyester resin and the substrate. The final product has good low-temperature fluidity and high terminal carboxyl activity. As a 70 / 30 polyester resin and E-12 epoxy resin, it can be cured at low temperature (for example, 145°C / 15min) and has a high leveling grade. In addition, it fully realizes the reuse of recycled frying oil, which has better environmental protection and economic value. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with embodiments. It should be noted that, in the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those generally understood by those of ordinary skill in the art to which this application belongs. The words "including" or "comprising" and the like used in the disclosure of the present invention mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0032] The raw materials of the present invention are all commercially available. For example, the recycled frying waste oil is a light brown viscous liquid, the main component of which is glyceride, with an iodine value of 130-150g / 100g, purchased from Anhui Changfa Qixiang Environmental Protection Technology Co., Ltd.

[0033] Preparation Example 1

[0034] A low-temperature curing, excellent-leveling 70 / 30 mixed type polyester resin for powder coatings, comprising the following raw materials in parts by weight:

[0035]

[0036] Catalyst 1 is dibenzoyl peroxide, and the dosage is 2% of the mass of acrylic acid;

[0037] Catalyst 2 is tetrabutyl titanate, and the amount used is 1.3% of the mass of the recovered frying waste oil;

[0038] The decolorizing agent is activated white clay, and the dosage is 1% of the mass of the recovered frying waste oil;

[0039] The antioxidant is antioxidant 1076, and the dosage is 0.9% of the mass of the recovered waste frying oil.

[0040] The method for preparing a 70 / 30 mixed type polyester resin for powder coatings with low temperature curing and excellent leveling comprises the following steps:

[0041] A. Add the formula amount of recycled frying waste oil and xylene into the reactor, start stirring, mix thoroughly and evenly, heat to 80°C, then add the formula amount of decolorant, continue to keep warm and stir to perform thermal decolorization for 1.5 hours, and then perform filter press treatment to obtain filtrate and filter cake;

[0042] B. Pump the filtrate into the reactor, start stirring, heat to 125°C and keep warm, then start dripping the mixed solution of isooctyl acrylate, acrylic acid and catalyst 1 in the formula amount, the dripping time is controlled within 2h, and after the dripping is completed, continue to keep warm for reaction;

[0043] C. Sampling and testing the iodine value of the polymer. When the iodine value of the polymer reaches 5-10g / 100g, it indicates that the graft polymerization reaction of the recovered frying waste oil after decolorization treatment and the acrylic acid mixed monomer is basically completed. At this time, the formula amount of neopentyl glycol, E-51 liquid epoxy resin, terephthalic acid and catalyst 2 are added, and the temperature is gradually increased to 215°C at a heating rate of 15°C / h for esterification and chain extension polymerization reaction. During the heating reaction, the solvent xylene and small molecular water are removed at the same time;

[0044] D. Detect the acid value of the polymer in the system. When the acid value of the polymer reaches 20-25 mgKOH / g, add the formulated amount of antioxidant, raise the temperature to 235°C, and start the vacuum system for vacuum polycondensation reaction. The vacuum degree is controlled to -0.099Mpa;

[0045] E. Take samples for testing. When the acid value of the polymer reaches 8-14 mgKOH / g, release the vacuum, add the formulated amount of glutaric anhydride as a capping agent and continue the capping reaction at 235°C. When the acid value of the polymer reaches the expected value, stop the reaction, discharge the material while hot, cool the polyester resin with a steel belt with condensed water, and then crush and granulate it to obtain the polyester resin.

[0046] The obtained product has the appearance of light yellow transparent particles, an acid value of 29 mgKOH / g, and a softening point of 97°C.

[0047] Preparation Example 2

[0048] A low-temperature curing, excellent-leveling 70 / 30 mixed type polyester resin for powder coatings, comprising the following raw materials in parts by weight:

[0049]

[0050]

[0051] Catalyst 1 is dibenzoyl peroxide, and the dosage is 3% of the mass of acrylic acid;

[0052] Catalyst 2 is tetrabutyl titanate, and the amount used is 1.3% of the mass of the recovered frying waste oil;

[0053] The decolorizing agent is activated white clay, and the dosage is 1% of the mass of the recovered frying waste oil;

[0054] The antioxidant is antioxidant 1076, and the dosage is 0.9% of the mass of the recovered waste frying oil.

[0055] The preparation method is the same as that of Preparation Example 1.

[0056] The obtained product has the appearance of light yellow transparent particles, an acid value of 36 mgKOH / g, and a softening point of 103°C.

[0057] Preparation Example 3

[0058] A low-temperature curing, excellent-leveling 70 / 30 mixed type polyester resin for powder coatings, comprising the following raw materials in parts by weight:

[0059]

[0060] Catalyst 1 is dibenzoyl peroxide, and the dosage is 3% of the mass of acrylic acid;

[0061] Catalyst 2 is tetrabutyl titanate, and the amount used is 1.3% of the mass of the recovered frying waste oil;

[0062] The decolorizing agent is activated white clay, and the dosage is 1% of the mass of the recovered frying waste oil;

[0063] The antioxidant is antioxidant 1076, and the dosage is 0.7% of the mass of the recovered frying waste oil.

[0064] The preparation method is the same as that of Preparation Example 1.

[0065] The obtained product has the appearance of light yellow transparent particles, an acid value of 32 mgKOH / g, and a softening point of 102°C.

[0066] Preparation Example 4

[0067] A low-temperature curing, excellent-leveling 70 / 30 mixed type polyester resin for powder coatings, comprising the following raw materials in parts by weight:

[0068]

[0069] Catalyst 1 is dibenzoyl peroxide, and the dosage is 2% of the mass of acrylic acid;

[0070] Catalyst 2 is tetrabutyl titanate, and the amount used is 0.8% of the mass of the recovered frying waste oil;

[0071] The decolorizing agent is activated white clay, and the dosage is 1% of the mass of the recovered frying waste oil;

[0072] The antioxidant is antioxidant 1076, and the dosage is 0.9% of the mass of the recovered waste frying oil.

[0073] The preparation method is the same as that of Preparation Example 1.

[0074] The obtained product has the appearance of light yellow transparent particles, an acid value of 34 mgKOH / g, and a softening point of 99°C.

[0075] Examples 1-4 (obtained using the polyester resins described in Preparation Examples 1-4 above, respectively)

[0076] The general 70 / 30 mixed powder coating formula is as follows in parts by weight:

[0077]

[0078]

[0079] Preparation of coating: Mix all materials according to the above powder coating formula, extrude, tablet and crush with a twin-screw extruder, and then crush the tablets and sieve (160-180 mesh) to make powder coating. The powder coating is sprayed on the surface treated tinplate substrate with an electrostatic spray gun, with a film thickness of about 80μm, and cured at 145℃ / 15min to obtain the coating.

[0080] Comparative Example 1: A commercially available ordinary 70 / 30 polyester resin is used as Comparative Example 1, and the coating formula and preparation method are the same as those of Examples 1-4; acid value 34 mgKOH / g, softening point 109°C, model SJ7411, Anhui Shenjian New Materials Co., Ltd.

[0081] Comparative Example 2: The polyester resin is the same as that of Comparative Example 1, and the coating formulation and preparation method are the same as those of Examples 1-4; except that the curing conditions are adjusted from 145°C / 15min to 180°C / 15min.

[0082] Performance comparison

[0083] Coating index testing is based on: GB / T 21776-2008 "Guide to Testing Standards for Powder Coatings and Their Coatings". The leveling grade is carried out using the PCI grading method, 0-10, and the larger the number, the better the leveling.

[0084] The polyester resins prepared in the above examples and comparative examples were used to prepare coatings according to the coating formulations provided by the present invention, and the coating properties were tested as shown in Table 1 below.

[0085] Table 1 Properties of powder coating films

[0086]

[0087] As can be seen from Table 1, the product prepared by the formula and process of the present invention contains more frying waste oil glyceride functional groups and isooctyl acrylate functional groups that help leveling, resulting in extremely low softening point of polyester resin, which is basically between 96-105°C, good low-temperature fluidity, and the final product and E-12 epoxy resin achieve full low-temperature curing at 145°C / 15min, and the coating appearance and impact resistance are both good. At the same time, due to the introduction of glyceride and isooctyl methacrylate segments in the formula, the lubricity and compatibility of the film-forming resin segments are increased, and then under the condition of 145°C low-temperature curing, the leveling grade also reaches level 6, and the leveling performance is good.

[0088] The conventional 70 / 30 polyester resin used in Comparative Example 1 cannot be fully cured at 145°C / 15min due to insufficient segment lubricity, softening point and activity, and cracks due to recoil. Comparative Example 2 increases its curing conditions to 185°C / 15min, achieves full curing, and passes both positive and negative impacts, but its segment lubricity and compatibility with other components are insufficient, resulting in its leveling grade only reaching Grade 5, which is slightly lower than the product of the present invention.

[0089] The product of the invention not only obtains a 70 / 30 polyester resin product with excellent performance for low-temperature curing and high-leveling powder coating, but also realizes the recycling and reuse of waste frying oil, and has good economic and environmental protection value.

[0090] The above only describes some exemplary embodiments of the present invention by way of illustration. It is undoubted that, for those skilled in the art, the described embodiments can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the above description is illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A 70 / 30 hybrid polyester resin for powder coatings with low temperature curing and excellent leveling. It is characterized in that The invention comprises the following raw materials in parts by weight: The raw materials also include catalyst 1, catalyst 2, decolorizing agent and antioxidant.

2. A low temperature curing, excellent leveling 70 / 30 hybrid type polyester resin for powder coatings as claimed in claim 1, It is characterized in that Catalyst 1 is dibenzoyl peroxide, and its dosage is 2-3% of the mass of acrylic acid; catalyst 2 is tetrabutyl titanate, and its dosage is 0.8-1.3% of the mass of recovered waste frying oil.

3. A low temperature curing, excellent leveling 70 / 30 hybrid type polyester resin for powder coatings as claimed in claim 1, It is characterized in that The decolorizing agent is activated white clay, and the dosage is 0.8-1% of the mass of the recovered frying waste oil.

4. A 70 / 30 mixed type polyester resin for powder coatings with low temperature curing and excellent leveling as claimed in claim 1, It is characterized in that The antioxidant is antioxidant 1076, and the dosage is 0.7-0.9% of the mass of the recovered frying waste oil.

5. A low temperature curing, excellent leveling 70 / 30 hybrid type polyester resin for powder coatings as claimed in claim 1, It is characterized in that The recovered frying waste oil is a light brown viscous liquid, the main component of which is glyceride, and the iodine value is 130-150g / 100g.

6. A method for preparing a low temperature curing, excellent leveling 70 / 30 hybrid type polyester resin for powder coatings according to any one of claims 1 to 5, It is characterized in that Firstly, the recycled waste frying oil is decolorized, then copolymerized and grafted with isooctyl acrylate and acrylic acid in a xylene solution using olefin double bonds to obtain a carboxyl-containing prepolymer; then, the prepolymer is chain-extended and terminated with neopentyl glycol, E-51 liquid epoxy resin, terephthalic acid, glutaric anhydride, etc.

7. A method for preparing a low temperature curing, excellent leveling 70 / 30 hybrid type polyester resin for powder coatings as claimed in claim 6, It is characterized in that The steps include: A. Add the formula amount of recycled frying waste oil and xylene into the reactor, start stirring, mix thoroughly and evenly, heat to 70-80°C, then add the formula amount of decolorant, continue to keep warm and stir to perform thermal decolorization treatment, and then perform filter press treatment to obtain filtrate and filter cake; B. Pump the filtrate into the reactor, start stirring, raise the temperature to 120-125°C and keep warm, then start dripping the mixed solution of isooctyl acrylate, acrylic acid and catalyst 1 in the formula amount, and continue to keep warm and react after the dripping is completed; C. Take samples to test the iodine value of the polymer. When the iodine value of the polymer reaches 5-10g / 100g, it indicates that the copolymerization grafting reaction is basically completed. At this time, add the formulated amount of neopentyl glycol, E-51 liquid epoxy resin, terephthalic acid and catalyst 2, and gradually raise the temperature to 210-215°C for esterification and chain extension polymerization reaction. During the heating reaction, remove the solvent at the same time; D. Detect the acid value of the polymer in the system. When the acid value of the polymer reaches 20-25 mgKOH / g, add the formulated amount of antioxidant, raise the temperature to 230-235°C, and start the vacuum system for vacuum polycondensation reaction; E. Take samples for testing. When the acid value of the polymer reaches 8-14 mgKOH / g, release the vacuum, add the formulated amount of glutaric anhydride as a capping agent and continue the capping reaction at 230-235°C. When the acid value of the polymer reaches 28-37 mgKOH / g, stop the reaction, discharge the material while hot, cool the polyester resin, and then crush and granulate it to obtain the polyester resin.

8. A method for preparing a low temperature curing, excellent leveling 70 / 30 hybrid type polyester resin for powder coatings as claimed in claim 7, It is characterized in that In step A, the thermal decolorization treatment time is 1-1.5 hours; in step B, the dropwise addition time is controlled at 1.5-2 hours; in step C, the temperature is gradually increased at a heating rate of 12-15° C. / h.

9. A method for preparing a low temperature curing, excellent leveling 70 / 30 hybrid type polyester resin for powder coatings as claimed in claim 7, It is characterized in that In step D, the vacuum degree is controlled at -0.096 MPa to -0.099 MPa; in step E, the polyester resin is cooled by a steel belt with condensed water.

10. Use of a low-temperature curing, excellent-leveling 70 / 30 hybrid powder coating polyester resin as claimed in any one of claims 1 to 6 or a low-temperature curing, excellent-leveling 70 / 30 hybrid powder coating polyester resin obtained by the preparation method according to any one of claims 6 to 9 in low-temperature curing hybrid powder coatings.

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