CN113999378A - Low-cost polyester resin with excellent heat transfer printing effect for powder coating and preparation method thereof - Google Patents
Low-cost polyester resin with excellent heat transfer printing effect for powder coating and preparation method thereof Download PDFInfo
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- CN113999378A CN113999378A CN202111559629.6A CN202111559629A CN113999378A CN 113999378 A CN113999378 A CN 113999378A CN 202111559629 A CN202111559629 A CN 202111559629A CN 113999378 A CN113999378 A CN 113999378A
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- 238000000576 coating method Methods 0.000 title claims abstract description 64
- 229920001225 polyester resin Polymers 0.000 title claims abstract description 61
- 239000004645 polyester resin Substances 0.000 title claims abstract description 61
- 239000011248 coating agent Substances 0.000 title claims abstract description 55
- 238000002360 preparation method Methods 0.000 title claims abstract description 9
- 239000000843 powder Substances 0.000 title claims description 44
- 230000000694 effects Effects 0.000 title abstract description 17
- 238000010023 transfer printing Methods 0.000 title abstract description 10
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 32
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 claims abstract description 27
- 229920005552 sodium lignosulfonate Polymers 0.000 claims abstract description 24
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 claims abstract description 18
- VERAMNDAEAQRGS-UHFFFAOYSA-N butane-1,4-disulfonic acid Chemical compound OS(=O)(=O)CCCCS(O)(=O)=O VERAMNDAEAQRGS-UHFFFAOYSA-N 0.000 claims abstract description 11
- ZJCCRDAZUWHFQH-UHFFFAOYSA-N Trimethylolpropane Chemical compound CCC(CO)(CO)CO ZJCCRDAZUWHFQH-UHFFFAOYSA-N 0.000 claims abstract description 9
- SLCVBVWXLSEKPL-UHFFFAOYSA-N neopentyl glycol Chemical compound OCC(C)(C)CO SLCVBVWXLSEKPL-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000006227 byproduct Substances 0.000 claims abstract description 7
- 238000006243 chemical reaction Methods 0.000 claims description 44
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 34
- 239000002253 acid Substances 0.000 claims description 34
- FOGYNLXERPKEGN-UHFFFAOYSA-N 3-(2-hydroxy-3-methoxyphenyl)-2-[2-methoxy-4-(3-sulfopropyl)phenoxy]propane-1-sulfonic acid Chemical compound COC1=CC=CC(CC(CS(O)(=O)=O)OC=2C(=CC(CCCS(O)(=O)=O)=CC=2)OC)=C1O FOGYNLXERPKEGN-UHFFFAOYSA-N 0.000 claims description 25
- 229920000642 polymer Polymers 0.000 claims description 24
- 239000002994 raw material Substances 0.000 claims description 22
- 238000010438 heat treatment Methods 0.000 claims description 20
- 239000011780 sodium chloride Substances 0.000 claims description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 17
- 230000020477 pH reduction Effects 0.000 claims description 15
- 239000007787 solid Substances 0.000 claims description 15
- 238000004821 distillation Methods 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 13
- 238000012544 monitoring process Methods 0.000 claims description 12
- 238000007599 discharging Methods 0.000 claims description 9
- 238000004321 preservation Methods 0.000 claims description 9
- LCFVJGUPQDGYKZ-UHFFFAOYSA-N Bisphenol A diglycidyl ether Chemical compound C=1C=C(OCC2OC2)C=CC=1C(C)(C)C(C=C1)=CC=C1OCC1CO1 LCFVJGUPQDGYKZ-UHFFFAOYSA-N 0.000 claims description 8
- 239000003963 antioxidant agent Substances 0.000 claims description 8
- 230000003078 antioxidant effect Effects 0.000 claims description 8
- 239000003054 catalyst Substances 0.000 claims description 8
- 238000001816 cooling Methods 0.000 claims description 8
- BVFSYZFXJYAPQJ-UHFFFAOYSA-N butyl(oxo)tin Chemical group CCCC[Sn]=O BVFSYZFXJYAPQJ-UHFFFAOYSA-N 0.000 claims description 6
- 239000003795 chemical substances by application Substances 0.000 claims description 6
- 238000005886 esterification reaction Methods 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 6
- 238000006068 polycondensation reaction Methods 0.000 claims description 6
- 229920000728 polyester Polymers 0.000 claims description 6
- 238000005070 sampling Methods 0.000 claims description 6
- 238000000926 separation method Methods 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 238000011085 pressure filtration Methods 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- 230000015572 biosynthetic process Effects 0.000 abstract description 3
- 239000011812 mixed powder Substances 0.000 abstract description 3
- 238000003786 synthesis reaction Methods 0.000 abstract description 3
- 230000000379 polymerizing effect Effects 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 19
- 238000012546 transfer Methods 0.000 description 9
- 238000003825 pressing Methods 0.000 description 7
- 239000007788 liquid Substances 0.000 description 6
- 229910000831 Steel Inorganic materials 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 239000010959 steel Substances 0.000 description 5
- BGYHLZZASRKEJE-UHFFFAOYSA-N [3-[3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoyloxy]-2,2-bis[3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoyloxymethyl]propyl] 3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoate Chemical compound CC(C)(C)C1=C(O)C(C(C)(C)C)=CC(CCC(=O)OCC(COC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)(COC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)COC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)=C1 BGYHLZZASRKEJE-UHFFFAOYSA-N 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000003973 paint Substances 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 229920001732 Lignosulfonate Polymers 0.000 description 2
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000002023 wood Substances 0.000 description 2
- -1 [ methyl-beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] pentaerythritol ester Chemical class 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000002981 blocking agent Substances 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000008199 coating composition Substances 0.000 description 1
- 239000013065 commercial product Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 125000000542 sulfonic acid group Chemical group 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 239000005028 tinplate Substances 0.000 description 1
- 239000002966 varnish Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/68—Polyesters containing atoms other than carbon, hydrogen and oxygen
- C08G63/688—Polyesters containing atoms other than carbon, hydrogen and oxygen containing sulfur
- C08G63/6884—Polyesters containing atoms other than carbon, hydrogen and oxygen containing sulfur derived from polycarboxylic acids and polyhydroxy compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/82—Preparation processes characterised by the catalyst used
- C08G63/85—Germanium, tin, lead, arsenic, antimony, bismuth, titanium, zirconium, hafnium, vanadium, niobium, tantalum, or compounds thereof
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
- C09D5/03—Powdery paints
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Wood Science & Technology (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Paints Or Removers (AREA)
- Polyesters Or Polycarbonates (AREA)
Abstract
Provides a polyester resin for 60/40 mixed powder coating with low cost and excellent heat transfer printing effect and a preparation method thereof. The polyester resin is mainly obtained by polymerizing sodium lignosulfonate, hydrochloric acid, neopentyl glycol, diethylene glycol, trimethylolpropane, terephthalic acid and 1, 4-butanedisulfonic acid. In the synthesis of the polyester resin, a large amount of sodium lignosulfonate serving as a papermaking byproduct is used, the hardness of the polyester resin is improved, the cost is reduced, the activity of the polyester resin is obviously improved by using the 1, 4-butanedisulfonic acid for end capping, full curing is realized under the curing condition of 160 ℃/12min, and the transfer printing effect is clear.
Description
Technical Field
The invention relates to the field of powder coatings, in particular to a polyester resin for a powder coating with low cost and excellent heat transfer printing effect and a preparation method thereof.
Background
As a 100% solid powdery paint, the powder paint has the characteristics of no solvent, no pollution, recoverability, environmental protection, labor intensity reduction, high mechanical strength of a coating film and the like, and is widely applied to the field of the current surface coating.
The common 60/40 mixed type powder coating polyester resin has wide application in powder coating, especially in thermal transfer powder coating, but because the common 60/40 mixed type polyester resin has soft segment and general carboxyl end activity, the paper sticking phenomenon caused by insufficient curing often occurs when the common 60/40 mixed type polyester resin is used in thermal transfer powder coating, and the customer complaints are more.
In addition, sodium lignosulfonate is a byproduct of papermaking waste liquid, has high yield, is generally only used in the field of low-end dispersants, has low additional value, and is a difficult problem on how to improve the additional value of lignosulfonate and realize comprehensive utilization of lignosulfonate.
Therefore, there is a need to develop a polyester resin for powder coating with low cost and excellent thermal transfer effect and a preparation method thereof to solve the above technical problems.
Disclosure of Invention
Therefore, the invention provides the polyester resin for the powder coating, which has low cost and excellent heat transfer printing effect, and the polyester resin mainly comprises the following raw materials in parts by mole:
wherein, besides the raw materials, the polyester resin is added with a catalyst and an antioxidant in the preparation process,
wherein the catalyst is monobutyl tin oxide, and the dosage of the catalyst is 0.1-0.15% of the total mass of the raw materials;
wherein the antioxidant is 1010, namely tetra [ methyl-beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] pentaerythritol ester, and the dosage of the antioxidant is 0.2-0.5% of the total mass of the raw materials.
The sodium lignosulfonate is a papermaking byproduct, is a common commercial product, and can be purchased from feihuang chemical industry limited company in New Yili city.
Wherein the polyester resin is light yellow transparent particles, the acid value is 48-54mgKOH/g, and the softening point is 112-120 ℃.
The invention also provides a preparation method of the polyester resin for the powder coating, which comprises the following steps:
(1) adding 20-30 molar parts of sodium lignosulfonate into a first reaction container, adding a proper amount of water, stirring, heating to completely dissolve the sodium lignosulfonate, and then adjusting the pH value of the solution to 3-4 to perform a sufficient acidification reaction;
(2) monitoring the pH value of the solution, stopping acidification reaction when the pH value is still between 3 and 4, then carrying out reduced pressure distillation to remove water and excessive hydrochloric acid, controlling the vacuum degree to be between-0.095 and-0.098 Mpa, simultaneously sampling and monitoring the content of sodium chloride in the solution, stopping distillation when the mass fraction of the sodium chloride in the solution reaches 18 to 21 percent, and realizing the separation of solid lignosulfonic acid and the solution through pressure filtration to obtain solid lignosulfonic acid for later use;
(3) adding the lignosulfonic acid obtained in the step (2), 15-25 molar parts of neopentyl glycol, 5-12 molar parts of diethylene glycol, 10-15 molar parts of terephthalic acid and a catalyst with the amount of 0.1-0.15% of the total mass of the raw materials into a second reaction container, heating to 185-190 ℃ and preserving heat for a period of time to perform esterification reaction;
(4) when the acid value of the system polymer reaches 50-65mgKOH/g, 8-15 molar parts of bisphenol A diglycidyl ether and 3-6 molar parts of trimethylolpropane are added, then the temperature is raised to 220-225 ℃, and the reaction is carried out for a period of time under the condition of heat preservation;
(5) when the acid value of the system polymer is reduced to 25-35mgKOH/g, adding antioxidant with the amount of 0.2-0.5% of the total mass of the raw materials, and starting a vacuum system to perform vacuum polycondensation;
(6) when the acid value of the system polymer is reduced to 12-18mgKOH/g, releasing the vacuum, adding 10-17 molar parts of 1, 4-butanedisulfonic acid as a polyester end-capping agent, and continuing to perform a heat-preservation end-capping reaction at 220-225 ℃;
(7) and stopping the reaction when the acid value of the system polymer reaches 48-54mgKOH/g, discharging, cooling, crushing and granulating to obtain the polyester resin.
Wherein, in the step (1) or (3), the reaction vessel is a reaction kettle.
Wherein in the step (1), the temperature is raised to 80-85 ℃.
In the step (1), a proper amount of hydrochloric acid solution is gradually dripped into the solution to adjust the pH value of the solution to be between 3 and 4.
Wherein, in the step (1), the hydrochloric acid is industrial hydrochloric acid with the mass concentration of 31%.
Wherein in the step (1), the acidification reaction time is 2-3 h.
In the step (2), the filter pressing is to separate solid lignosulfonic acid from a liquid sodium chloride solution through plate-and-frame filter pressing.
Wherein, in the step (3), the temperature is raised to 185-190 ℃ at a temperature raising rate of 25-30 ℃/h.
Wherein, in the step (4), the temperature is raised to 220-225 ℃ at a temperature raising rate of 6-8 ℃/h.
Wherein in the step (5), the vacuum degree is controlled to be between-0.096 and-0.098 MPa.
In the step (7), the discharging is discharging at a high temperature while the discharging is hot, and the cooling is performed by using a steel strip with condensed water.
The invention also provides a powder coating which contains the polyester resin for the powder coating.
Wherein the powder coating is 60/40 mixed powder coating.
The invention also provides a powder coating prepared from the powder coating.
The invention has the following beneficial technical effects:
1. the polyester resin suitable for 60/40 mixed powder coating is prepared by polymerizing sodium lignosulfonate, hydrochloric acid, neopentyl glycol, diethylene glycol, trimethylolpropane, terephthalic acid and 1, 4-butanedisulfonic acid. The acid value of the obtained polyester resin is 48-54mgKOH/g, and the softening point is 112-120 ℃.
2. According to the invention, a large amount of sodium lignosulfonate is used in the synthesis of the polyester resin, the sodium lignosulfonate is firstly subjected to acidification treatment to obtain lignosulfonic acid, and the lignosulfonic acid is used as a functional component and is matched with neopentyl glycol, diethylene glycol, terephthalic acid, bisphenol A diglycidyl ether, trimethylolpropane, 1, 4-butanedisulfonic acid and the like to synthesize the novel 60/40 polyester resin, so that the hardness of the polyester resin is improved, the cost is reduced, and a novel method is provided for the high added value reutilization of the sodium lignosulfonate. Specifically, sodium lignosulfonate and hydrochloric acid are adjusted to be acidic to obtain lignosulfonic acid, then solid lignosulfonic acid is obtained through reduced pressure distillation concentration and plate-frame filter pressing, and then the lignosulfonic acid, dihydric alcohol, dibasic acid and trihydric alcohol are polymerized to obtain the polyester resin, wherein the obtained polyester resin has the characteristics of high rigidity and high curing speed, and is suitable for indoor thermal transfer powder coating.
3. In the synthesis of the polyester resin, 1, 4-butanedisulfonic acid is used as a blocking agent, and sulfonic acid groups are used as blocking groups, so that the activity of the polyester resin is obviously improved, the polyester resin and E-12 epoxy resin are fully cured under the curing condition of low temperature of 160 ℃/12min, and the transfer printing effect is clear.
4. The chain segment of the polyester resin contains a large amount of rigid raw materials of lignosulfonic acid and bisphenol A diglycidyl ether, so that the rigidity and the adhesion with a base material part of the polyester resin are improved.
5. The coating obtained by curing the polyester resin at low temperature has high hardness, the pencil hardness is 2H, the coating does not stick to transfer paper, the transfer printing is clear, the adhesive force with tinplate is excellent, other properties of the coating can completely meet various requirements of powder coating, simultaneously, the raw material cost of the polyester resin is obviously reduced, and a novel method is provided for the comprehensive utilization of a paper-making byproduct sodium lignosulfonate.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
A method for preparing a polyester resin for powder coating, comprising:
(1) adding 21 molar parts of sodium lignosulfonate into a first reaction kettle, adding a proper amount of water, stirring, heating to 84 ℃ to completely dissolve the sodium lignosulfonate, gradually dropwise adding a proper amount of hydrochloric acid solution to adjust the pH value of the solution to 3, and carrying out full acidification reaction for 2.5 hours;
(2) monitoring the pH value of the solution, stopping acidification reaction when the pH value is still 3, then carrying out reduced pressure distillation to remove water and excessive hydrochloric acid, controlling the vacuum degree to be-0.095 Mpa, simultaneously sampling and monitoring the content of sodium chloride in the solution, stopping distillation when the mass fraction of the sodium chloride in the solution reaches 19%, and realizing separation of solid lignosulfonic acid and liquid sodium chloride solution through plate-and-frame filter pressing to obtain solid lignosulfonic acid for later use;
(3) adding the lignosulfonic acid obtained in the step (2), 17 molar parts of neopentyl glycol, 11 molar parts of diethylene glycol, 12 molar parts of terephthalic acid and 0.12% of monobutyl tin oxide of which the amount is equal to the total mass of the raw materials into a second reaction kettle, gradually heating to 189 ℃ at a heating rate of 29 ℃/h, and preserving heat for a period of time to perform esterification reaction;
(4) when the acid value of the system polymer reaches 52mgKOH/g, 9 molar parts of bisphenol A diglycidyl ether and 5 molar parts of trimethylolpropane are added, then the temperature is raised to 223 ℃ at the heating rate of 7 ℃/h, and the temperature is kept for reaction for a period of time;
(5) when the acid value of the system polymer is reduced to 29mgKOH/g, adding antioxidant 1010 with the dosage of 0.3 percent of the total mass of the raw materials, starting a vacuum system to carry out vacuum polycondensation reaction, and controlling the vacuum degree to be-0.097 Mpa;
(6) when the acid value of the system polymer is reduced to 17mgKOH/g, releasing the vacuum, adding 12 molar parts of 1, 4-butanedisulfonic acid as a polyester end-capping agent, and continuing to perform heat preservation end-capping reaction at 223 ℃;
(7) and stopping the reaction when the acid value of the system polymer reaches 52mgKOH/g, discharging at high temperature, cooling by using a steel belt with condensed water, and crushing and granulating to obtain the polyester resin.
The polyester resin obtained was a pale yellow transparent particle having an acid value of 52mgKOH/g and a softening point of 115 ℃.
Example 2
A method for preparing a polyester resin for powder coating, comprising:
(1) adding 28 molar parts of sodium lignosulfonate into a first reaction kettle, adding a proper amount of water, stirring, heating to 81 ℃ to completely dissolve the sodium lignosulfonate, gradually dropwise adding a proper amount of hydrochloric acid solution to adjust the pH value of the solution to 4, and carrying out full acidification reaction for 2.8 hours;
(2) monitoring the pH value of the solution, stopping acidification reaction when the pH value is still 4, then carrying out reduced pressure distillation to remove water and excessive hydrochloric acid, controlling the vacuum degree to be-0.095 Mpa, simultaneously sampling and monitoring the content of sodium chloride in the solution, stopping distillation when the mass fraction of the sodium chloride in the solution reaches 20%, and realizing separation of solid lignosulfonic acid and liquid sodium chloride solution through plate-and-frame filter pressing to obtain solid lignosulfonic acid for later use;
(3) adding the lignosulfonic acid obtained in the step (2), 20 mol parts of neopentyl glycol, 10 mol parts of diethylene glycol, 13 mol parts of terephthalic acid and 0.14% of monobutyl tin oxide of which the amount is based on the total mass of the raw materials into a second reaction kettle, gradually heating to 188 ℃ at a heating rate of 29 ℃/h, and preserving heat for a period of time to perform esterification reaction;
(4) when the acid value of the system polymer reaches 64mgKOH/g, 13 molar parts of bisphenol A diglycidyl ether and 4 molar parts of trimethylolpropane are added, then the temperature is raised to 221 ℃ at the heating rate of 8 ℃/h, and the temperature is preserved for reaction for a period of time;
(5) when the acid value of the system polymer is reduced to 26mgKOH/g, adding antioxidant 1010 with the dosage of 0.4 percent of the total mass of the raw materials, starting a vacuum system to carry out vacuum polycondensation reaction, and controlling the vacuum degree to be-0.098 Mpa;
(6) when the acid value of the system polymer is reduced to 17mgKOH/g, releasing the vacuum, adding 13 molar parts of 1, 4-butanedisulfonic acid as a polyester end-capping agent, and continuing to perform heat preservation end-capping reaction at 221 ℃;
(7) and stopping the reaction when the acid value of the system polymer reaches 53mgKOH/g, discharging at high temperature, cooling by using a steel belt with condensed water, and crushing and granulating to obtain the polyester resin.
The polyester resin was a pale yellow transparent particle having an acid value of 53mgKOH/g and a softening point of 113 ℃.
Example 3
A method for preparing a polyester resin for powder coating, comprising:
(1) adding 27 molar parts of sodium lignosulfonate into a first reaction kettle, adding a proper amount of water, stirring, heating to 83 ℃ to completely dissolve the sodium lignosulfonate, gradually dropwise adding a proper amount of hydrochloric acid solution to adjust the pH value of the solution to 3, and carrying out full acidification reaction for 2.2 hours;
(2) monitoring the pH value of the solution, stopping acidification reaction when the pH value is still 3, then carrying out reduced pressure distillation to remove water and excessive hydrochloric acid, controlling the vacuum degree to be-0.096 Mpa, simultaneously sampling and monitoring the content of sodium chloride in the solution, stopping distillation when the mass fraction of the sodium chloride in the solution reaches 21%, and realizing separation of solid lignosulfonic acid and liquid sodium chloride solution through plate-and-frame filter pressing to obtain solid lignosulfonic acid for later use;
(3) adding the lignosulfonic acid obtained in the step (2), 22 molar parts of neopentyl glycol, 6 molar parts of diethylene glycol, 11 molar parts of terephthalic acid and 0.14% of monobutyl tin oxide of which the amount is based on the total mass of the raw materials into a second reaction kettle, gradually heating to 189 ℃ at a heating rate of 27 ℃/h, and preserving heat for a period of time to perform esterification reaction;
(4) when the acid value of the system polymer reaches 63mgKOH/g, 12 molar parts of bisphenol A diglycidyl ether and 5 molar parts of trimethylolpropane are added, then the temperature is raised to 222 ℃ at the temperature rise rate of 6 ℃/h, and the temperature is preserved for reaction for a period of time;
(5) when the acid value of the system polymer is reduced to 32mgKOH/g, adding antioxidant 1010 with the dosage of 0.4 percent of the total mass of the raw materials, starting a vacuum system to carry out vacuum polycondensation reaction, and controlling the vacuum degree to be-0.096 Mpa;
(6) when the acid value of the system polymer is reduced to 15mgKOH/g, releasing the vacuum, adding 11 molar parts of 1, 4-butanedisulfonic acid as a polyester end-capping agent, and continuing to perform heat preservation end-capping reaction at 222 ℃;
(7) and stopping the reaction when the acid value of the system polymer reaches 49mgKOH/g, discharging at high temperature, cooling by using a steel belt with condensed water, and crushing and granulating to obtain the polyester resin.
The appearance of the prepared polyester resin is light yellow transparent particles, the acid value is 49mgKOH/g, and the softening point is 114 ℃.
Example 4
A method for preparing a polyester resin for powder coating, comprising:
(1) adding 24 molar parts of sodium lignosulfonate into a first reaction kettle, adding a proper amount of water, stirring, heating to 81 ℃ to completely dissolve the sodium lignosulfonate, gradually dropwise adding a proper amount of hydrochloric acid solution to adjust the pH value of the solution to 4, and carrying out full acidification reaction for 3 hours;
(2) monitoring the pH value of the solution, stopping acidification reaction when the pH value is still 4, then carrying out reduced pressure distillation to remove water and excessive hydrochloric acid, controlling the vacuum degree to be-0.097 Mpa, simultaneously sampling and monitoring the content of sodium chloride in the solution, stopping distillation when the mass fraction of the sodium chloride in the solution reaches 18%, and realizing separation of solid lignosulfonic acid and liquid sodium chloride solution through plate-and-frame filter pressing to obtain solid lignosulfonic acid for later use;
(3) adding the lignosulfonic acid obtained in the step (2), 19 molar parts of neopentyl glycol, 11 molar parts of diethylene glycol, 13 molar parts of terephthalic acid and 0.11% of monobutyl tin oxide of which the amount is equal to the total mass of the raw materials into a second reaction kettle, gradually heating to 185 ℃ at a heating rate of 29 ℃/h, and preserving heat for a period of time to perform esterification reaction;
(4) when the acid value of the system polymer reaches 60mgKOH/g, adding 10 molar parts of bisphenol A diglycidyl ether and 4 molar parts of trimethylolpropane, heating to 225 ℃ at the heating rate of 8 ℃/h, and carrying out heat preservation reaction for a period of time;
(5) when the acid value of the system polymer is reduced to 31mgKOH/g, adding antioxidant 1010 with the dosage of 0.5 percent of the total mass of the raw materials, starting a vacuum system to carry out vacuum polycondensation reaction, and controlling the vacuum degree to be-0.097 Mpa;
(6) when the acid value of the system polymer is reduced to 17mgKOH/g, releasing the vacuum, adding 16 molar parts of 1, 4-butanedisulfonic acid as a polyester end-capping agent, and continuing to perform heat preservation end-capping reaction at 225 ℃;
(7) and stopping the reaction when the acid value of the system polymer reaches 51mgKOH/g, discharging at high temperature, cooling by using a steel belt with condensed water, and crushing and granulating to obtain the polyester resin.
The polyester resin prepared was a pale yellow transparent particle with an acid value of 51mgKOH/g and a softening point of 118 ℃.
Comparative example 1
A commercially available polyester resin for 60/40 type powder coating was used as comparative example 1, model SJ5B, acid value 49mgKOH/g, available from New Material Ltd of Anhui Shenjian.
Comparative example 2
A commercially available polyester resin for 60/40 type powder coating was used as comparative example 2, model SJ5B, acid value 49mgKOH/g, available from New Material Ltd of Anhui Shenjian. Comparative example 2 differs from comparative example 1 in that the curing conditions for comparative example 1 were 160 deg.C/12 min and for comparative example 2 180 deg.C/15 min in the preparation of the powder coating.
Preparing a powder coating:
the powder coatings of examples 1-4 and comparative examples 1-2 were prepared using the polyester resins of examples 1-4 and comparative examples 1-2, respectively, according to the following powder coating formulations, wherein the component contents are in parts by weight:
preparing a powder coating:
the powder coatings of examples 1-4 and comparative examples 1-2 were prepared by mixing the materials, extruding the mixture through a twin-screw extruder, tabletting the mixture, crushing the crushed mixture, and pulverizing and sieving the crushed mixture. Then, the powder coatings of examples 1-4 and comparative examples 1-2 were respectively sprayed onto the aluminum substrate after surface treatment by an electrostatic spray gun to a film thickness of 70-80 μm, and cured at 160 ℃/12min (except that the curing conditions of comparative example 2 were changed to 180 ℃/15min), thus obtaining the coating coatings of examples 1-4 and comparative examples 1-2. After the aluminum plate and the coating are cooled, uniformly coating glue for thermal transfer printing on the surface of the coating, and then covering and wiping the wood grain transfer printing paper to be flat; placing the treated aluminum plate into a baking condition of 160 ℃ for baking for 10 min; after cooling, the transfer paper was torn off to obtain coating films of the wood grain powder coatings of examples 1 to 4 and comparative examples 1 to 2.
And (3) testing the performance of the coating:
and (3) detection of coating indexes: according to GB/T21776 & 2008 & ltStandard guidelines for testing powder coatings and coatings thereof';
and (3) hardness detection: the hardness of the paint film is tested according to GB/T6379-2006 Pencil method for color paint and varnish.
The results of the coating property tests are shown in table 1.
TABLE 1 test results of coating properties of powder coatings of examples and comparative examples
As can be seen from Table 1, the products of examples 1-4 of the present invention have good comprehensive properties, the cured coating film is flat and smooth, the gloss and impact resistance can meet the application requirements, the hardness and thermal transfer effect are significantly improved compared with the common products on the market, the pencil hardness is 2H, the transfer effect is clear, and no paper is adhered.
The common 60/40 polyester resin sold in the market in the comparative example 1 has poor curing effect after curing at 160 ℃/12min due to low carboxyl end group activity, and the appearance, the impact resistance, the gloss and the like of the cured coating film can not meet the requirements;
comparative example 2 is the product of the present invention in which the curing conditions of comparative example 1 were adjusted to 180 ℃/15min, and the appearance and impact properties of the coating film were good after the full curing was achieved at high temperature for a long period of time, but the hardness and thermal transfer effect were slightly inferior to those of the product of the present invention.
In conclusion, the method can effectively utilize the papermaking by-product sodium lignosulfonate, and provides a method for the comprehensive utilization and development of the subsequent papermaking by-products.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (10)
1. A polyester resin for powder coating, which consists essentially of the following raw materials in parts by mole:
wherein, besides the raw materials, the polyester resin is added with a catalyst and an antioxidant in the preparation process.
2. The polyester resin according to claim 1, wherein the catalyst is monobutyl tin oxide, and the amount of the catalyst is 0.1-0.15% of the total mass of the raw materials; the antioxidant is 1010, and the dosage of the antioxidant is 0.2-0.5% of the total mass of the raw materials.
3. The polyester resin of claim 1, wherein the sodium lignosulfonate is a paper making byproduct.
4. The polyester resin according to claim 1, wherein the polyester resin has an acid value of 48 to 54mgKOH/g, a softening point of 112 ℃ to 120 ℃.
5. The method for preparing the polyester resin for powder coating according to claims 1 to 4, comprising:
(1) adding 20-30 molar parts of sodium lignosulfonate into a first reaction container, adding a proper amount of water, stirring, heating to completely dissolve the sodium lignosulfonate, and then adjusting the pH value of the solution to 3-4 to perform a sufficient acidification reaction;
(2) monitoring the pH value of the solution, stopping acidification reaction when the pH value is still between 3 and 4, then carrying out reduced pressure distillation to remove water and excessive hydrochloric acid, controlling the vacuum degree to be between-0.095 and-0.098 Mpa, simultaneously sampling and monitoring the content of sodium chloride in the solution, stopping distillation when the mass fraction of the sodium chloride in the solution reaches 18 to 21 percent, and realizing the separation of solid lignosulfonic acid and the solution through pressure filtration to obtain solid lignosulfonic acid for later use;
(3) adding the lignosulfonic acid obtained in the step (2), 15-25 molar parts of neopentyl glycol, 5-12 molar parts of diethylene glycol, 10-15 molar parts of terephthalic acid and a catalyst with the amount of 0.1-0.15% of the total mass of the raw materials into a second reaction container, heating to 185-190 ℃ and preserving heat for a period of time to perform esterification reaction;
(4) when the acid value of the system polymer reaches 50-65mgKOH/g, 8-15 molar parts of bisphenol A diglycidyl ether and 3-6 molar parts of trimethylolpropane are added, then the temperature is raised to 220-225 ℃, and the reaction is carried out for a period of time under the condition of heat preservation;
(5) when the acid value of the system polymer is reduced to 25-35mgKOH/g, adding antioxidant with the amount of 0.2-0.5% of the total mass of the raw materials, and starting a vacuum system to perform vacuum polycondensation;
(6) when the acid value of the system polymer is reduced to 12-18mgKOH/g, releasing the vacuum, adding 10-17 molar parts of 1, 4-butanedisulfonic acid as a polyester end-capping agent, and continuing to perform a heat-preservation end-capping reaction at 220-225 ℃;
(7) and stopping the reaction when the acid value of the system polymer reaches 48-54mgKOH/g, discharging, cooling, crushing and granulating to obtain the polyester resin.
6. The process for producing a polyester resin for powder coating according to claim 5, wherein the temperature is raised to 80 to 85 ℃ in the step (1).
7. The method for preparing polyester resin for powder coating according to claim 5, wherein the acidification reaction time in the step (1) is 2 to 3 hours.
8. The method for preparing polyester resin for powder coating according to claim 5, wherein in the step (3), the temperature is raised to 185-190 ℃ at a temperature raising rate of 25-30 ℃/h; in the step (4), the temperature is raised to 220-225 ℃ at a temperature-raising rate of 6-8 ℃/h.
9. A powder coating material comprising the polyester resin for powder coating material according to any one of claims 1 to 4.
10. A powder coating prepared from the powder coating of claim 9.
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