Effect of functional monomer on the leveling performance of polyester resin/TGIC thermal transfer powder coating

Abstract:
studied the effects of functional monomers on polyester resin, coating and coating properties by single-factor method, and focused on the leveling and transfer performance of powder coating coatings, and the results showed that 4-amino-1-butanol could improve both thermal transfer and leveling performance; 4-cyclohexane methamphetamine (CHDA) improves leveling performance but reduces thermal transfer performance;
keywords: functional monomer; polyester resin; powder coating; thermal transfer
leveling
0 introduction
thermal transfer is also known as thermal sublimation, is a variety of patterns using transfer ink printed on high-precision paper / film, and the use of thermal transfer equipment in a short period of time to heat it to set the temperature, so that the transfer paper / film on the pattern transfer to aluminum coating and other materials on a special process. The technology can provide bright colors, rich levels of transfer patterns, to achieve imitation wood grain, stone statues and other purposes, can save a large number of non-renewable natural resources, so since the emergence of widely praised, the market growth is fast . At the same time, with the rapid development of China's economy and the people's growing need for a better life, people put forward higher requirements for the quality and appearance of daily necessities, ecological and environmental protection concepts deeply rooted in the hearts of the people. "Aluminum wood" and "paint powder" and other markets, technology has more room for development.
At the beginning of the development of thermal transfer powder coating, supporting polyester resin is relatively small, in the field of TGIC curing, mainly using 93/7 (polyester resin and curing agent quality ratio) series polyester resin, in order to solve the thermal transfer ink Penetration, transfer of sticky paper and other issues, is usually to increase polyerymelic monomer in polyester resin and reaction activity, although it is conducive to improve transfer performance, but not conducive to the polyester resin curing when the full melt level, resulting in poor leveling performance.
With the development of technology, the development of TGIC type 92/8 series of polyester resins, the series of polyester resins in the transfer performance and leveling performance have been some improvements, mainly by increasing the acid value of the way to improve the crosslinking of the powder coating Density to solve the problem of paper in the thermal transfer process, at the same time, the series of polyester resins due to the degree of branching is not high, so the viscosity is not large, in the powder coating curing process has a relatively sufficient amount of time for leveling, so can not affect the transfer performance to improve the leveling performance.
However, with the improvement of people's aesthetic level, the appearance of powder coating leveling put forward higher requirements, we are also focusing on the development of TGIC type 90/10 series of polyester resins, although increasing the acid value, increase the cross-link density of powder coating is conducive to transfer, but the acid value increased polyester resin reaction activity will also increase, resulting in some decline in leveling. At the same time, after improving the level performance of the transfer performance requirements are higher, in the high level appearance of the transfer process residual oil printing is more prominent, so the need to further improve the transfer performance and level performance.
In order to better improve the leveling performance of polyester resins in TGIC curing systems, the solution in the powder coating industry is to lower the acid value and reaction activity of polyester resins appropriately so that polyester resins can be fully melted when cured, and in order to enable TGIC curing system polyester resins to have good transfer performance, the industry solution The method is still to improve the acid value, branching degree and reaction activity of polyester resin to solve the problems of paper and oil printing in the transfer process, but the improvement of acid value, branching degree and reaction activity leads to the decline of leveling performance. At present, conventional monomers such as new glycol, trihydroxymethyl propane, hexydiacid, benzoic acid and interbenzene and other synthetic polyester resins can obtain a certain comprehensive performance, but transfer performance and leveling performance has not been able to take into account, can not meet the needs of the market. In order to further improve the appearance effect and excellent transfer performance of thermal transfer powder coating, this paper adopts the unconventional functional monomer, through the study of the type and dosing of monomer in the process of 90/10 polyester resin synthesis, explores the effect of functional monomer on the performance of polyester resin leveling in thermal transfer powder coating.
1 Test part
1.1 Test raw materials
notyl glycol (NPG), parabens (PGAs), interphenyl xylene (IPA), 1,4-cyclohexane xylene (CHDA), diphenylate (PMDA), 2, 2-hydroxymethyl acid (DMPA), 4-amino-1-butanol, monobutyl tin oxide (F4100), tri-shrink glycerin isocyanate (TGIC), titanium white powder, sulphate, sabbath, leveling agent, lightener, are industrial grade.
1.2 Polyester resin synthesis
will match alcohols, acids and other monomers and catalysts into the 30 L reactor, into nitrogen protection and gradually heat up to 240 degrees C insulation 4 h, detection of acid After the value is met with acid antidote and insulation of 3 h at 240 degrees C, the acid value is up to the standard and then starts vacuuming to a vacuum level of -0.095 MPa, reacting 1.5 to 3.0 h, the discharge obtains the target resin.
1.3 Preparation of powder coatings and coatings
powder coating formulations are listed in Table 1.
powder coating powdering process is: ingredients, premixed, extruded, pressed, crushed, screened, products. The resulting powder coating is electrostated, cured to 10 min at 200 degrees C, and then the properties of the coating are detected.
1.4 Performance characteristics
acid value, viscosity measurement method by reference to T/GDTL 004-2018; horizontal mobility by reference to GB 6554-1986; flow equal grade reference ACT Test Panels LLC orange plate standard; thermal transfer method by reference to industry-wide method; melting viscosity using Brookfield CAP2000 plus cone plate viscosity meter at 200 degrees C.
2 Results and discussion
thermal transfer process mainly occurs in the coating and transfer paper / film interface, after the transfer of paper / film and coating peeling, usually the transfer effect is divided into easy to tear paper oil-free printing, easy to tear paper slightly oil printing, easy to tear paper a small amount of oil printing, easy to tear paper heavy oil printing, hard-tearing paper with confetti residue, can not tear paper and other cases. During the study, the acid value of polyester resin was set at about 52 mgKOH/g, which is commonly used in the industry, to explore the effect of polyester resin monomer on polyester resin and powder coating properties.
2.1 4-amino-1-butanol dosing affects polyester resin and coating performance
4-amino-1-butanol is a fat family straight-chain compound containing both end hydroxyl and end-amino, whose end hydroxyl and end-amino can react with pyridine, compared to ester bonds, amide With stronger bond energy and the formation of hydrogen bond between the molecular chain segment, is conducive to improve the internal energy of polyester and powder coating, so as to better resist thermal denaturation in transfer to improve the transfer effect, new glycol is a common monomer in powder polyester, the following 4-amino-1-butanol instead of new glycol test, the results are listed in Table 2.
From Table 2, it can be seen that with the increase of 4-amino-1-butanol dosing, the acid value of polyester resin fluctuates slightly, viscosity is gradually decreasing, horizontal fluidity is gradually improved, transfer performance is also improving, in the first step of alcohol content score of 3.0%, plate satiety has significantly improved. 4-amino-1-butanol can improve thermal transfer performance may be due to the alamide key replacement ester bond increased intermoleculation energy, in the thermal transfer coating of the molecular chain is more inclined to internalum without excessive movement to the transfer paper / film ink layer, the viscosity decreased mainly because 4-amino-1-butanol contains 4 methylene, soft chain segment increased, so that the plate surface has a higher satiety and greater level of fluidity.
2.2 CHDA dosing effect on polyester resin and coating performance
1,4-cyclohexane methamphetamine (CHDA) is a lipid cyclic acid with secondary energy, usually more than aromatic acid Better reaction activity, better weather resistance and anti-yellowing properties, interphenyl xylene acid (IPA) is widely used as an acid antidote during powder polyester synthesis, so the CHDA replacement part of the IPA was tested, the results are listed in Table 3.
can be seen from Table 3, with the increase of CHDA dosing, acid value fluctuates, viscosity gradually decreases, horizontal flow gradually increases, transfer performance decreases. Structurally, CHDA belongs to the structural symmetry type, the fat ring structure of 6 carbon atoms is not in a plane, its flip can form a variety of compositions, with better smooth performance, in addition to the introduction of CHDA into the polyester molecular chain will reduce the average benzene on the molecular chain The number of rings, thus weakening the π-π between benzene rings, further reducing viscosity, improve the level of fluidity, it is precisely because of the molecular chain between the role of less force, cohesion can be reduced, resulting in a decrease in transfer performance, which is consistent with the previous results.
2.3 EFFECT of DMPA dosing on polyester resin and coating performance
2,2-dehydroxymethylate (DMPA) molecular structure has 2 hydroxy and 1 xenon, also belongs to the triornial energy monomer, can improve polyester and coating branching, but different from conventional tricetamumatic monomers such as trihydroxymethylane and benzodialycerides, conventional monomers contain only the same type of body. Table 4 shows changes in polyester and coating properties under different dosing levels of DMPA.
can be seen from Table 4, with the increase in DMPA dosing, acid values show a fluctuating state, viscosity is gradually increasing, horizontal flow is gradually decreasing, transfer performance will also be improved. DMPA belongs to the three-function energy monomer, with the increase of the added amount, the branching degree of polyester resin increases, resulting in the increase of molecular weight and then the increase of viscosity, and the increase of viscosity will hinder the flow of polyester resin melting, so it can be seen that the flow of fluid energy; The amount of addition gradually increases, the transfer effect gradually becomes better, this is because increasing the amount of DMPA added also increases the intersection point of polyester resin, when curing the film crosslink density is increased, the coating is not easy to soften when heat transfer, so the smaller the plate oil printing residue, the better the transfer effect.
2.4 PMDA dosage on polyester resin and coating performance
the diabenzene tyrenylate (PMDA) belongs to the symmetrical four-function monomer, can greatly improve the degree of polyester and coating branching, from the previous research, improve the branching degree is conducive to improving thermal transfer performance, in the powder polyester synthesis process, PMDA is usually used as an antidote, table 5 is pmDA different amount of polyester and coating performance changes.
from Table 5, it can be seen that with the increase of PMDA dosing, acid value is also in a state of fluctuation, viscosity gradually increased, horizontal fluidity gradually decreased, transfer performance has improved. With the previous research results are basically consistent, increase the degree of polyester branching, thereby increasing cross-link density, and because it contains four-member groups, high reaction activity, it can improve the reaction activity of polyester resin, thereby improving the curing reaction degree of polyester resin, there is a use to improve thermal transfer performance, but will increase the viscosity of polyester and reduce the level of fluidity, so in the synthesis process needs to choose the appropriate amount according to the actual situation.
2.5 Effect of functional monomer on coating level fluidity
Level mobility energy is one of the indicators used to evaluate the leveling performance of powder coatings, and Figure 1 is a comparison of the horizontal mobility energy of powder coatings made from different polyester resins.
As can be seen from Figure 1, with the increase of acid value, the horizontal flow of thermal transfer powder coating increases and then decreases, mainly due to the small acid value of the 93/7 series of products, its cross-link density is low, to achieve a certain thermal transfer performance needs to improve the branching of polyester itself Degree and reaction activity, resulting in a small horizontal flow, and 92/8 series acid value is relatively high, the production of powder coating through the increase of acid value can obtain a certain cross-link density to promote transfer performance, so the polyester resin itself does not need a high degree of branching can obtain a certain transfer performance. Polyester resin itself is less branched, with the increase of 90/10 series acid value, resulting in increased reaction activity, so the horizontal mobility can be reduced compared to the 92/8 series, and the use of functional monomer in this study on the basis of the 90/10 series can obtain a better level of mobility, greatly promoting the leveling performance of powder coating.
2 is a model powder coating made of different polyester resins compared to the flow level of the ACT standard model.
From Figure 2, it can be seen that the flow equality level of powder coating using functional monosome 90/10 is about 6 levels, the flow equality level of conventional monosome 90/10 is about 5 levels, 92/8 flow equality level is about 5 levels, and the flow equality level of 93/7 is about 3 levels, using the functional monos in this paper can obtain better leveling performance, consistent with the horizontal flow law.
3 Conclusion
Thermal transfer powder coating needs to take into account thermal transfer performance and leveling performance, which requires coordination of performance and improve the comprehensive performance of polyester resin, this paper uses functional monomer synthetic polyester, using the same formula to prepare it into powder coating, the results show that: the use of functional unit can obtain a powder with better level performance Coatings; 4-amino-1-butanol can improve both thermal transfer performance and leveling performance; CHDA can improve leveling performance but reduce thermal transfer performance; DMPA and PMDA can improve thermal transfer performance but reduce level performance, so the use of individual units needs to be coordinated to meet comprehensive performance requirements.
(see Modern Coatings and Coatings 2020-2)
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