Study on the formulation of powder coating for medium and low light transfer effect

Abstract: This paper introduces the polyester/TGIC plus detergent and polyester dual-part mixed lighting two transfer formula research, through polyester resin, anti-lighting agent comparison, the different manufacturers of raw materials screening, and resin DSC curing behavior discussion and analysis, combined with resin Tg changes, to solve the low-light transfer powder production oil printing and transfer pattern is not clear and so on.
1 foreword
In recent years, the state attaches great importance to environmental protection, environmental protection conditions are becoming more and more stringent, "paint powder" slowly in the major manufacturers quietly carried out, ushered in the development of powder opportunities. Thermal transfer powder coating as an important branch of powder coating, with the domestic several major polyester resin manufacturers in-depth research and development and powder tongren constantly updated, powder thermal transfer technology has achieved rapid development, and now the entire domestic thermal transfer technology industry chain has basically formed .
With the development of the economy, the shortage of timber resources gradually become concerned, thermal transfer technology is gradually deeply covered to the furniture industry, the concept of all-aluminum thermal transfer home is also constantly put forward, the use of aluminum alloy furniture cases are also being produced. Household aluminum products are mostly medium and low light effect, with its unique advantages and soft wood texture, by aluminum alloy furniture manufacturers focus on promotion and application.
low-light transfer powder coating preparation, in addition to expensive polyurethane body anti-light system, polyester / TGIC and polyester dual-part mixed lighting system, to the price of the people and beautiful and diverse appearance, has been widely used in thermal transfer, has developed more mature (including powder coating manufacturing, spraying process, heat transfer paper and equipment manufacturing process). However, in practice, there are still fog shadow, oil printing, paper tearing difficulties and other issues, need to be controlled from the formulation system, curing degree and transfer process.
2 Experimental part
2.1 Experimental materials
thermal transfer polyester resin: Guangzhou Dynasky and other factories of a number of polyester; curing agent: TGIC; pigments: Bayer, Jiangxi Tianguangqin, etc., fillers: sulphate, commercially available. Additives: leveling agent, sabbath, brightener, promoter, wax powder;
2.2 Experimental instrument
SLJ-30A twin screw extruder: Shandong Lingyu General Equipment Co., Ltd.; DFY-5 million-energy Chinese medicine shredder: Wenling City Linda Machinery; ACM-02 type grinding system: Yantai Dongyuan Chemical Equipment Co., Ltd.; AG-4442 gloss instrument: BIK, Germany; SURE COAT small electrostitectrectranscopic spray equipment: Nordsin electrostitive spray gun; GPH-30 high temperature oven: Espeke Environmental Instruments (Shanghai) Co., Ltd.; DSC differential scanning volume heat Shanghai and Exhibition Instrument Technology Co., Ltd.; thermal transfer machine hot painting machine: Feilong Technology Development Co., Ltd.
2.3 Preparation of powder coatings and their coatings
in accordance with the corresponding formulation design, resin 300g, curing agent TGIC according to formulation ratio, filler: 200g, leveling agent: 3.5g, brightener 1.6g, sabbath 1.8g, promoter: 1.2g, polyfluoroethylene wax: 2.6g, pigment suitable. Weighing raw materials, premixed, molten extruded into a pressure sheet (I. zone temperature: 80 to 105 degrees C; II. zone temperature: 100 to 120 degrees C). Crushed 180 mesh sieves to make powder. The powder is sprayed with a high-pressure electrostation spray gun to cure the resulting model at 200 degrees C/10min and to make a thermal transfer model (thermal transfer temperature 200 degrees C, time 180s).
3 Results and Discussion
3.1 Polyester/TGIC-anti-lighting agent formulation design discussion
3.1.1 Resin selection
medium-gloss polyester/TGIC thermal transfer powder coating gloss is generally 40% to 60%, the formulation design is designed with polyester/TGIC-anti-lighting agent design mode. Such as Table 1, the test selected 4 different manufacturers at home and abroad market more mature thermal transfer resin, resin manufacturers give the parameters of the indicator difference is small (mainly 93/7 and 92/8 two resin systems), in the selection of thermal transfer resin different ratios have advantages and disadvantages, but after making the formula performance is different, there are large differences.
according to the transfer characteristics requirements, to choose a high reaction activity (i.e., high acid value), low viscosity, good leveling, excellent anti-light effect of the resin. However, the resin crosslink density is fast, the curing degree is high and the resin good de-lighting in the reaction dynamics are contradictory, the general fast curing resin is more difficult to de-light. The experimental formula added about 2.0% of the anti-lighting agent, the performance of the anti-light is different, the transfer effect and leveling are also different. By contrast, the selection of transfer resin D, its performance takes into account the rapid reaction speed, good light-down effect, and in the transfer of paper tearing effect, oil printing and flow are very good.
3.1.2 The
polyester/TGIC-type de-lighting mechanism of the anti-light agent is used: by matching the reaction speed of the curing system formed by the anti-light agent in the melting and curing process with the powder itself, the cured surface forms a uneven coating surface, and when the light is applied to the coating surface, diffuse reflection occurs to achieve the goal of ablation. According to the data, such as Table 2, the commercially available anti-lighting agent is mainly divided into the following: wax and organic zinc salt de-lighting system, improve polypropylene resin-polyethylene wax de-lighting system and acrylic resin-sulfur particle de-lighting system, different types of anti-lighting agent, different synergies in resin curing, resin reaction in the coating residue is different, different detergents have a greater impact on the transfer effect.
, the coating gloss increased with the addition of anti-light agent, the lower the gloss. Mid-light 40% to 60% gloss addition between 1.5 and 2.5. The addition of a light-absorbing agent to the experiment prolongs the geling time of the formula (i.e., the degree of curing of the resin), affects the curing degree of the powder, and affects the transfer effect, as shown in Figure 1. In the regulation of the formula, the appropriate amount of promoter to adjust the curing degree of the powder, the powder adhesion time is controlled at about 100 to 180s, flow control between 22 and 25 is appropriate.
3.1.3 Effect of anti-light agent on resin Tg transfer effect
As can be known from Table 4, the experiment selected resin D with high cross-link density and fast reaction speed, and when different anti-lighting agents were added to the formula, the effect on powder Tg was greater, but it had no effect on the coating Tg. When selected to choose the powder Tg high, transfer effect of good light-absorbing agent A, so that the powder can get good storage, at the same time will not put the powder for a period of time decay, affecting the effect of the powder coating in the transfer.
3.1.4 Resin Curing Behavior Analysis
Usually transfer powder curing time is l0min@200 degrees C When the coating tear paper has residue, transfer oil printing, powder manufacturers will recommend transfer customers Raise the furnace temperature by 10 to 15min@210 degrees C, so that the remaining unresponsive chemical molecules in the powder fully react, improve the cross-link density of the powder, to improve the effect of coating transfer, it can be seen that the cross-link density and reaction degree of the resin on the effect of the powder.
based on the experiment we selected resin D, through 200 degrees C iso-curing to further demonstrate the resin's re reactivity, compared with several other types. As shown in Table 3, it can be seen that the conversion rate of resin A, 120s is 84.75 percent, 180s conversion rate is 93.11 percent, 240s conversion rate is 96.82 percent, resin B's 120s conversion rate is 72.51 percent, 180s resin conversion rate is 83.56 percent, 240s conversion rate is 91.1 percent. 57%, resin C 120s conversion rate of 67.83%, 180s resin conversion rate of 80.56%, 240s conversion rate of 88.29%, resin D 120s conversion rate of 79.37%, 150s resin conversion rate of 88.18%, 240s conversion rate of 93,02%. By comparison, it can be found that the resin D curing process is slower than A curing, faster than B and C in the baking process. It can ensure that the coating is fully cured, de-lighted and leveled, while reducing the residual molecules inside the coating during the thermal transfer of the coating to the coating surface again, to achieve a good transfer effect.
3.2 Polyester two-part mixed anti-light formula design discussion
3.2.1 resin selection
aluminum powder coating, most of the two-part de-lighting, which can save costs, but also can achieve a lower gloss (20% to 30%). Ordinary two-part resin, transfer often has oil printing, and serious sticky paper. The powder manufacturer has achieved good transfer effect by adding an appropriate proportion of the fast-curing resin to the slow-reaction components and adjusting the curing degree of the coating. After nearly two years of transfer market promotion, dynasky double-component transfer resin quickly to the market, fully meet the flatness of customer coating, transfer of color fullness, appearance density and other requirements, become the preferred manufacturer of double-component transfer resin.
according to the experiment, it can be known that the two-part resin improved by Dynasky, in the polyester/TGIC dual-part light transfer, the ordinary formula can meet the transfer requirements (Figure 2). Not only to ensure the density of the product coating, and the transfer of the pattern clarity is good, no oil printing (and polyurethane low-light transfer effect also has a certain difference), but also excellent leveling performance.
3.2.2 Two-part resin curing behavior analysis
As shown in Table 6, according to the experimental data, the transfer effect is good dynamite double-part formula A and formula B, C, D for curing conversion rate comparison. It can be known that the conversion rate of the two-part resin in the same time is better than that of the other three products, that is, the curing degree and cross-link density of the resin under the same conditions is significantly better than that of other products. Under 200 degrees C/10min conditions can be fully cured, transfer can obtain excellent plumpness and brightness of the transfer coating film, and the coating film has a good leveling.
3.2.3 Tg's effect on thermal transfer effect
As can be known from Table 7, the Tg distribution of the curing coating of the four formulations is between 81 and 83 degrees C, there is no big difference, and it is inferred that the Tg of the resin cured coating has not had much effect on the transfer effect.
effects of 3.3 fillers
Fillers are essential components of powder coatings, commonly used in nirconium sulfate, calcium carbonate, and silicon micropowrines. Heat transfer effect with the increase of filler content, tearing paper easy, transfer paper is not easy to stick with the coating film. However, in the formulation design, the amount of filler addition should have a limit (usually the amount of filler accounted for 30% to 40% of the total), the amount of filler will lead to orange peel, spray area reduction and other construction problems. Depending on the customer's needs, adding fluffy fillers to the formula can help to spray powder or finely grind the powder particle size for better leveling when applied in practice.
4 Conclusion
When making low-light powder coatings for thermal transfer, the production process control, formulation design, baking conditions for powder, all aspects of the transfer process have certain requirements, the specific problems in the production are different, the manufacturer and spray manufacturers need to communicate the relevant formula process and transfer problems in a timely manner, promote the development of industrial technology, in order to heat transfer powder more reasonable promotion and application.