Hyperbranched polyesters used in powder coatings-Iota

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Service > Hyperbranched polyesters used in powder coatings

Hyperbranched polyesters used in powder coatings

3. Hyperbranched polyesters used in powder coatings
Hyperbranched polyester is ideal for coating resins promising, its unique charm lies in its highly branched three-dimensional spherical structure and a large number of end groups and low viscosity without winding between molecules, the nature of high chemical reactivity, etc. that when the linear polyester blends and allows mobility, viscosity, thermal stability and mechanical properties of the blend to produce a greater change. A large number of terminal functional groups makes hyperbranched polyester can be modified with a strong ability, capable of producing a variety of resins for powder coating applications. Here are a few examples of hyperbranched polyester powder coating applications.
3.1 hyperbranched polyester used in polyurethane powder coatings
3.1.1 Preparation of hyperbranched polyester
Distillation head equipped with a short neck, a stirrer, a thermometer and a nitrogen-protected round-bottomed flask was added dimethylolpropionic acid (DMPA) 200 g, 200 g methane sulfonic acid (MSA) 0.46 克 and deionized water, The flask was then placed in a silicone oil bath and heated to 160 ℃, oil bath temperature reached 140 ℃ when water starts distillate. The initial nitrogen gas flow rate of 0.5 standard cubic feet / hour (SCFH), with the reaction temperature reached 160 ℃, flow rate increased to about 1.5SCFH. Nitrogen was stopped when the amount of water evaporated to about 220 ml. The polymer was poured in aluminum foil, cooled at room temperature overnight to give 175 g of transparent white solid.
GDC molecular weight = 2558, polydispersity = 1.2, 0.42% residual monomer. Thermal gravimetric analysis (TGA): Thermal dispersion temperature (Td) 365 ℃, differential scanning calorimetry (DSC): The glass transition temperature (Tg) 60 ℃.
3.1.2 Preparation of powder paint coating
In Table 1 formulation with powder coatings, premixed with ZSK-30 twin screw extruder, tablet, and then pulverized in a hammer mill in decline.
Nordson electrostatic powder coating spray gun to 3 inches × 6 × 0.02 英寸英寸 clean cold rolled sheet and bake at 193 ℃ 17 minutes. Table 2 lists the physical properties of the cured coating film of the powder coating.
3.2 hyperbranched polyester-modified UV-curable powder coatings
3.2.1 hyperbranched synthetic resin (HBP) is
3.2.1.1 Synthesis of monomer N, N- bis-hydroxyethyl ester of acrylic-3-amine
After a nitrogen blanket and condenser connected with mechanical stirring in a four-necked flask, methanol was added and quantitative diethanolamine, open stirring at room temperature was added dropwise methyl acrylate, nitrogen protection, the reaction 0.5h, slowly warmed to the set temperature After the reaction 4h evacuated 1h, cooling the material.
3.2.1.2 hyperbranched polyester synthetic
In connection with the protection of a nitrogen trap, condenser, mechanical agitation of four bottles, the core component was added trimethylol propane, heated to 110-120 ℃, 3-fold molar solution of monomer (including the catalyst), The reaction was evacuated after 3h 1h, then add 6-fold molar monomer, reaction above, 4h after cooling the material.
3.2.2 TDI / HEA modified
Equipped with a condenser, a dropping funnel, a mechanical stirrer necked flask, hang out with the right amount of TDI February dibutyl tin catalyst, stirring at 30-50 ℃ solution containing the polymerization inhibitor HEA, the reaction every 30min sampling, measuring the value of a isocyanate to isocyanate is half of the initial value, adding the one-step synthesis of polyester, while warming-induced reaction was continued at 60-70 ℃ isocyanate value is less than 1%, heated to 80-90 ℃, when the isocyanate value can not be measured, cooling the material.
Powder Coating 3.2.3 photocurable
Weigh 93g resin Uvecoat3000, added 7g modified HPB and the same photoinitiator Irgacure651 and Irgacur2959 and additives, cooling the molten mixed pulverized into a fine powder, applied to the substrate at 120 ℃ melt stream at full level, then 1KW high pressure mercury lamp illumination 80w.cm ultraviolet light cured.
3.3 hyperbranched polyester with polyester powder coating to improve the apparent performance
3.3.1 stearic acid modified Blotorn H2O
Blotorn H2O by the Swedish Perstorp AB, is a second-generation hyperbranched polyester.
Weigh 8.4g of Blotorn H2O (1747g / mol), 22.7g of stearic acid in the four-necked flask, with a small amount of N, N- dimethylformamide (DMF) was dissolved, was added 0.5% of acid at 130 ℃ reaction 3h, the reaction was continued for 12h vacuum terminated to give yellow-brown liquid, neutralized with sodium hydroxide and an excess of stearic acid, ethanol precipitation, and dried under vacuum to give acid terminated hyperbranched polyester Blotorn H2O ( SA-HBP), after crushing speed as a slightly yellow powder.
Blotorn H2O no glass transition, SA-HBP glass transition temperature increased to 70 ℃.
Preparation 3.3.2 HAA powder coating paint
The introduction of capped BlotornH2O hyperbranched polyester powder coating formulations, the melt viscosity is reduced to 20% -50%, the surface contact angle decreased from 1000 to 800, it can greatly improve their leveling, reduce defects and surface coating insufficient, without compromising performance powder coating adhesion, pencil hardness, impact resistance, flexibility and gloss and other aspects.
3.4 hyperbranched polyester as powder coating curing agent
3.4.1 Synthesis of hyperbranched polyester
Acid anhydride was slowly added to an excess of the amine (diisopropanolamine), and to prevent undesired side reactions, such as diisopropanolamine molecules bis acylated. In the absence of a catalyst, and further increasing the reaction temperature to 140-180 ℃, condensation quickly, the desired amount of water evaporated (finally under vacuum), about 2-6 hours to generate body heat polymer solution (reaction time depends on the acid anhydride
The types). Synthesis of the final acid number close to zero (usually less than 0.02 meq acid / g resin). Calculated degree of branching of 0.3 to 0.45.
Suitable for this reaction of hydroxyl acid anhydride ring are: cis-1,2-cyclohexane dicarboxylic acid anhydride (HHPA), cis-1,2-cyclohexane-4-ene - dicarboxylic acid anhydride (THPA), phthalic anhydride (PA), succinic anhydride (SA), glutaric anhydride (GA).
HHPA and THPA synthetic hyperbranched polyester glass transition temperature of 45-70 ℃, PA is 70-100 ℃, SA and GA was 20-40 ℃.
3.4.2 Preparation of powder paint coating
In Table 5 formulation with powder coating by mixing and extrusion (Prism extruder, 120 ℃) crushing, screening. Electrostatic spraying on the aluminum plate, as shown in circulating oven conditions for curing. Film properties shown in Table 5.
Uralac P5040, Uralac P5261 is a carboxyl group of the polyester resin, the former is an acid value of 55mgKOH / g, which was 47mgKOH / g. Branched polyester amide 1a and 1b is diisopropanolamine and phthalic anhydride (PA) synthesis, 2a, 2b, 2c is cis-1,2 - cyclohexane dicarboxylic acid anhydride (HHPA) synthesis. 1a, 2a having a number average molecular weight of about 1500 (1.20 molar ratio) and the number average functionality 8.1b, 2b having a number average molecular weight of about 900 (1.33 molar ratio) and the number average functionality 6.2c number average molecular weight of about 2000 ( The molar ratio of 1.14) and the number average functionality of 10. Gel time was measured at 200 ℃.
Crosslinking the coating during curing, and so if there is water or ethanol volatiles in thicker coatings (> 100μm) formed in the bubble, often affect the surface properties of the coating. The polyester powder coating to add more functionality (functionality greater than 4) hyperbranched polyester amide curing agent obtained excellent film properties and effectively improve the bubble threshold (120-140μm), and in this process does not extend gel time. Therefore hyperbranched polyester curing agents suitable for obtaining a thick coating of powder coatings.
4. Conclusion
Hyperbranched polyesters used in powder coatings is a new topic, but also our common concern, and further efforts to do more, produce more new polyester, reduce costs, to meet the needs of application development. Hyperbranched polyester modified to give more performance hyperbranched polyester. I believe that in the near future, hyperbranched polyesters used in powder coatings to achieve market-oriented, large-scale.

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