Research on polyester resin synthesis catalysts for powder coatings

Pan Ziyi, Lin Xien, He Tao, Liu Liang, Gu Zhi Chang
(Guangzhou Dynasky Industrial Co., Ltd., Guangzhou 510860)
Abstract: Study of non-butyl tin catalysts and mono-butyl tin catalysts and their dosages on
powder coatings
The catalytic ester reaction activity of polyester resin, the influence of polyester resin relative to molecular mass and its distribution, the effect of non-butyl tin catalyst and its dosing on the heat resistance and aging properties of powder coating prepared with synthetic polyester resin were discussed, and the appropriate non-butyl tin catalyst varieties and their dosing were determined.
key words: non-butyl tin catalysts; Polyester resin; Powder
coating
; Performance
: TQ633 Document Identification Code: A Article No: 1007-9548 (2013) 01-0019-04
Currently used in powder coatings around the world Polyester resin manufacturers mainly choose butyl tin compounds as catalysts for polyester esterification reaction, catalysts involved in catalytic reactions, their own will be permanently left in the molecular structure of polyester resins, and gradually over time to the surface, the environment and biological mutation.
with the increase of environmental pressure in China, in the reaction of synthetic resin, the choice of catalysts without pollution or low pollution to the environment has become an urgent problem to be solved. At present, the main choice of titanium system has catalysts and non-butyl tin catalysts, of which titanium catalysts are prone to hydrolysing, poor stability, used to synthesize polyester resin reaction time is long, yellow color problems, there are still many technical problems to be solved, not large-scale promotion and use. Non-butyl tin catalysts mainly change the structure and type of hydrocarbon base, thus reducing environmental hazards. On the other hand, China's larger foreign trade market in the European Union in 2010 issued (EU) 276/2010 (REACH) regulations, the use of organo tin compounds put forward new restrictions, the use of no more than 0.1%. In order to adapt to this new change, the domestic powder polyester resin industry is currently studying the production of catalyst powder coating resins without butyl tin. Organo tin compounds are metal organic compounds formed by the direct binding of two elements of tin and carbon, the general form is RnSnX4-n, in the general form, n-3 organo tin compounds are the most toxic, n-1 and n-2 organo tin compounds are toxic, n-4 organo tin compounds are very toxic or non-toxic. The properties of R-based in the general form have a great influence on the toxicity of the compound, and when R is propyl or butyl, it has the strongest biological activity and the greatest influence. In this paper, the catalyst C-01 was the most toxic, C-02, C-03, C-04.
1. Test Part
1.1 Raw Materials
refined parabens, interbenzene, neo-glycol, solid butyl tin catalyst C-01, non-butyl tin catalyst C-02, C-03, C-04, TGIC,
titanium white powder
, vanadium sulfate, leveling agent, sabbath, are industrial products
1.2 main test equipment
test with 8L small stainless steel reactor; 30 twin screw extruders and other small powder-making equipment; Small electrostectrectrectrectrative spraying equipment; Coating performance detection equipment such as spectrographs.
synthesis process of 1.3 polyester resins
add polyols and polyic acids and catalysts to the 8L reactor according to the formulation amount and stir well. Under the protection of N2, gradually heated up to 180 to 250 degrees C reaction 12 to 16h, vacuum shrinking to get acid value, viscosity and other products in line with the requirements.
1.4 powder coating and coating preparation
according to the basic formula of Table 1 preparation powder coating, the process is: ingredients →mixed→ extruded →pressure→→sieve→ products, the resulting powder coating with electrostectrulation spray, and in certain curing conditions solidified coating, coating and coating performance testing.
Table 1 Powder Coatings Basic Formula
1.5 Performance Detection
1.5.1 Gel Permeability Chromatography (GPC)
GPC Test Conditions: Column Fillers are Style-divinylbenzenegels; The flow phase is THF; The column length is 300mm; Column diameter 8mm; The flow rate reaches 1.0mL/min; The column pressure is 0.5 to 0.6MPa; The IR detector is used to detect at 30 to 34 degrees C. The sample amount is 20 μL.
1.5.2 differential scanning volume heat (DSC)
using the United V1.717TAInstrumentsDSC2910 thermal analyzer, the heating rate is 20 degrees C/min, the test temperature range is -80 to 200 degrees C, the ambient atmosphere is N2.
1.5.3 boiling
using HH-S number of thermostat water bath pot, pot distilled water in a boiling state, will be model hanging in the water, to ensure that 4/5 of the board in water, do not touch the inner wall of the water bath pot; At the same time, there is a certain gap between the test plates to prevent the iron plates from touching each other to affect the test. After boiling water of 2h, remove the model and measure its chroma, L1, a1, b1 and gloss G1.
1.5.4 heat-resistant
using precision heating oven, set the temperature of 230 degrees C, to be reached, the test model into. Then, when the display temperature reaches 230 degrees C, after baking 60min, measure the model color difference of L1, a1, sb1 and gloss G1.
1.5.5 Aging
QuV-B fluorescent UV lamp exposure test on the test model, according to GB/T14522 "artificial climate acceleration test method for plastics, coatings, rubber materials for mechanical industrial products" (UVB313 lamp, irradiance 0.68W (m2.nm), light 60C/4h, condensation 50C/4h). The gloss is measured by GB/T9754 and the degree of color change is measured by GB/T1766.
2. Results and discussion
2.1 catalyst and esterification reaction time
4 additions of 4 catalysts were selected as the subject of investigation, and the reaction time of catalytic polyesterization in different proportions of each catalyst was shown in Figure 1.Figure
Figure 1 Reaction time of catalytic polyesterization in different catalysts
it can be seen that the esterification reaction stage, with the increase of the proportion of catalyst use, the reaction time of the whole process is shorter, the biool hydroxyl and polyic acid of the esterification dewatering reaction of the reaction can gradually decrease with the increase of catalyst dosing, the easier the reaction. By lateral comparison, C-03 has the best catalytic reaction effect of 4 catalysts, which have the shortest catalytic reaction time at different proportions, C-01 and C-03 are 0.10% and C-04 are 0 .15% of the reaction time to reach the same level of reaction is basically equivalent, it can be considered that its bioactive energy is basically the same, the corresponding catalytic efficiency is also basically equivalent, but because C-01 contains butyl tin, so in the actual synthesis can give priority to the use of non-butyl catalyst C-03.
, in the synthesis of polyester resins used in powder coatings, the amount of catalyst is most suitable at 0.10%, and the catalytic efficiency is obtained at the same time with less addition. When the addition ratio of non-butyl tin catalyst C-03 is about 0.10%, its catalytic reaction time and butyl tin catalyst C-01 are basically consistent, the esterification reaction is smooth, the process is controllable, because C-03 does not contain butyl tin, the environmental pollution is small, can become a substitute for C-01.
2.2 synthetic polyester resin relative molecular mass and distribution
the relative molecular mass and distribution of synthetic polyester resin results can be found in Table 2. It can be known that the number of synthetic polyester resins are relative to molecular weight Mn between 3100 to 4000, the weight is relative to molecular mass Mw between 7000 to 9000, the distribution of relative molecular mass D between 2.10 and 2.30 The relative molecular mass distribution tends to balance with the increase of catalyst dosing, and finally stabilizes at about 2.12, as can be seen from the distribution curve of relative molecular mass, the distribution of relative molecular mass is basically in line with the normal distribution, which shows that the synthetic polyester resin is evenly distributed relative to molecular mass, and the side reaction in the process of shrinking fusion reaction is less.
Figure 2 Synthetic Polyester Resin GPC Curve
Table 2 Partial Catalyst Synthesis Resin Sample GPC Analysis
Observation of Mn and Mw when non-butyl tin catalyst C-03 dosing 0.15%, compared to butyl tin catalyst C -01, it can be found that C-03 prepared Mn and non-butyl tin catalyst C-01 gap is not large, Mw is slightly smaller than C-01, but slightly narrower relative to molecular mass distribution, synthesis reaction results are more ideal, to achieve the desired goal, as detailed in Table 2.
DSC signation of 2.3 synthetic polyester
Tg is the conversion temperature of non-stereotyped polymer from glass state to high bullet state (or the other way), is an important index of heat resistance of polymer in use, thus affecting the stability of powder coating storage, Tg of polyester resin is one of the important parameters of resin. The test measured the Tg of some synthetic polyester resins by the method shown in 1.5.2, with the results listed in Table 3. It can be seen that several proportions of the catalyst's Tg variation area is very close, Tg is near 68 degrees C. Polyester resins for powder coatings generally require Tg>50 degrees C, while Tg > 65 degrees C. Therefore, the test synthetic sample polyester resin Tg can meet the requirements of use. And different proportions of C-01, C-032 catalyst synthesis resin Tg is not much different, to meet the needs of use.
Table 3 Partial Catalyst Synthetic Resin Sample DSC Analysis
2.4 Catalyst's Effect on Water-resistant Cooking Performance
the standard test model was used as listed in 1.5.3 to determine the water-resistant cooking performance, after the test gloss and color difference changes can be seen in Figures 3 and 4.
Figure 3 Change in loss of light after boiling
Figure 4 Color difference and yellow change after boiling 2H
From Figure 3, it can be seen that after cooking 2h in distilled water, the gloss of the test model is greatly reduced, the loss rate is larger. As can be seen from Figure 4, after the test, the color difference of the model color difference E in addition to C-04 in the dosing of 0.15% deviated from the larger, there is a very slight color change≤, the color difference of the other models of the color difference before and after boiling, non-butyl catalyst and butyl catalyst catalytic synthesis resin performance before and after boiling is not much difference, the impact is small. It can be seen from the test data that when the deviation of the color difference is large, the color difference of the color difference of the color E becomes larger, so it can be thought that the change of the color difference of the color difference of the color E in the boiling test is mainly caused by the change of the yellow edge of the color e.
effect of 2.5 catalyst dosing on heat resistance
The heat resistance of the test model was determined according to the method listed at 1.5.4, and the results were shown in Figures 5 and 6 after continuous roasting of 60min at 230 degrees C.
Figure 5 Glossy Change
Figure 6 The relationship between heat-resistant chroma and yellow change
As can be seen from Figure 5, the coating surface of part of the test sample begins to decompose after continuous baking at 230 degrees C, resulting in a higher gloss. From the test results, for polyester resins synthesized with butyl tin or non-butyl tin catalysts, the preservation rate after heat-resistant test is ideal, it can be said that the model is basically free of light loss. And as the proportion of catalyst increases, the color difference will increase. As the heat resistance time increases, the color difference and yellowing of the coating become more pronounced. As can be seen from Figure 6, the larger the sb, the greater the color difference, i.e. the color difference change is mainly caused by yellow change, that is, the heat resistance performance mainly investigates the yellowing performance of polyester powder coating.
2.6 Effect of catalyst dosing on aging performance
Test the anti-aging performance of the test model according to the method listed in 1.5.5, and conduct QUV-B aging tests of 96h and 240h for the test sample, with gloss changes and chroma variation results as shown in Figures 7 to 10.
7
8
Figure 9
Figure 10
after quLV-B aging test 96h, found that the gloss of the model slightly decreased, all samples are in a level 2 loss of light, that is, a very slight loss of light. And the color difference basically did not change, in the level 1 color difference. Butyl tin catalyst C-01 and non-butyl tin catalyst C-02, C-03, C-04 gloss hold rate is high, the effect is very ideal. The longer the aging time, the greater the change in gloss and color difference. The loss rate of the coating film will be in the 2 to 3 levels, and the color difference is basically unchanged. There is no significant difference in aging properties between polyester resins synthesized from non-butyl tin catalysts.
3. Conclusion
Through the study of the catalytic effect of catalysts and their key properties on polyester resins and powder coatings, it is found that the effect of C-03 is basically equivalent to that of butyl tin catalysts currently in use, and they are not subject to THECH regulations in the European Union. In the range, in the current stage of titanium catalyst application is not mature, can be used as an effective substitute for butyl tin catalyst as a powder coating polyester resin synthesis catalyst, its high catalytic reaction activity, can effectively shorten the time of ester reaction, to improve the production efficiency of polyester resin enterprises has an important significance.
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