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    Home > Coatings News > Paints and Coatings Market > An analysis of the powder coating thermal transfer "tear paper" factors

    An analysis of the powder coating thermal transfer "tear paper" factors

    • Last Update: 2020-11-10
    • Source: Internet
    • Author: User
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    Abstract:
    This paper discusses the effects of each on the effect of thermal transfer powder coating tearing paper from the aspects of transfer paper, coating curing degree, coating film crosslink density, filler content and additives.
    introduction isIn recent years, with the rapid development of aluminum profiles, anti-theft doors, curtain walls and home appliances and other industries and more stringent environmental requirements, "paint change powder" and "oil to water" has become imminent.
    powder coatings are recognized as 4E (energy, resources, low pollution, high efficiency) environmentally friendly coatings, and are increasingly used in various industries of surface coating treatment

    .
    At the same time, thermal transfer technology in recent years, especially after the localization of transfer paper technology has also made rapid development, thermal transfer products with its realistic wood grain, marble decorative effect has been widely welcomed, soon in the anti-theft door, aluminum profiles, office furniture and other industries widely used.
    thermal transfer wood-printed metal materials have both the inherent characteristics of metal and reflect the high-grade decorative effect of wood-printed. Thermal transfer treatment does not change the original materialization performance of the powder coating.
    Compared with other wood-print decorative materials, with anti-corrosion, fire, anti-mold, high hardness, light weight, no deformation, non-toxic environmental protection, pattern does not fall off, do not crack, durable and safe recovery and so on.
    , especially in the environmental protection, energy-saving modern decoration market, has been a popular and trend. At present, the domestic monthly wood transfer paper and transfer film market about 25 million square meters.thermal transfer powder coating as a large branch of powder coating, has a long history, the earlier use of polyester / isocyanate powder coating has many advantages, but due to the high price, marketing and use is limited.
    In recent years, polyester/TGIC and polyester/epoxy powder coatings have been widely used in thermal transfer, and the price of people has stimulated market demand, but sometimes there are problems in actual production that the transfer effect is not ideal.
    the clarity and permeable brightness of the transfer ink can be adjusted by masking the pigment filler. After the transfer of torn paper has paper hair and ink printing, or even can not tear down the paper and other more troublesome, need to be from the curing process, formulation system and transfer process to control.the most intolerable thing for the construction staff at the site is the difficulty of tearing the paper. This not only seriously affects their work efficiency occasionally, increases the workload, but also reduces the finished grade.
    Whether it is vacuum thermal transfer or brush glue transfer, later may encounter difficult to tear paper or tear paper after the surface there is fog shadow, paper printing, paper wool, oil printing, offset printing and other issues, which is related to transfer paper, with the transfer of vacuum negative pressure high and low, but also related to the degree of solidification of the base powder, but also related to the bottom powder formula system.This paper focuses on five factors, such as transfer paper, powder coating curing degree, curing cross-link density, filler content and additives, and discusses and analyzes the effect of various factors on the performance of transfer torn paper.
    1, the experimental part
    1.1 experimental principle heat sublimation transfer technology initially appeared in the transfer printing of polyester textile. In thermal sublimation transfer technology, the substrate must be made of polyester with a fixed area or a product with a surface similar to polyester material.
    a small gap of about 1-100 E exists in the a fixed region of the united States. When the thermal transfer is made around 200 degrees C, the amorphic zone is subjected to heat and violent vibration, when the gap size will change significantly and present a melting state, the so-called "liquid layer".
    time, the ink on the transfer paper is also sublimation by heat, gaseous ink movement to the polyester surface, further diffusion motion to the melting amorphous area. Sometimes pressure and vacuuming are performed to ensure ink transfer rates and vertical transfers. After a certain period of time, the temperature decreases and the ink molecules condense.
    is wrapped in a fixed area of polyester, which transfers the ink pattern to the substrate surface for satisfactory surface results.transfer tearing effect is difficult to quantify the comparison directly, there is no clear evaluation level. In this paper, a single-variable experimental method is used to analyze the influence factors of the effect of transfer tearing paper from five aspects, such as transfer paper, coating curing degree, cross-link density filling content and additives.In order to compare the effect is obvious, in the analysis of the "curing degree, cross-link density, filling content and additives" these four factors, the transfer of two inks used heavier, transfer paper is easier to stick to the transfer paper.vacuum transfer, there is a vacuum negative pressure, than brush glue transfer is more prone to paper tearing difficulties, transfer ink residue and so on. In this paper, vacuum transfer as an example to discuss the actual situation, the actual results in the brush glue transfer is also universal.
    vacuum transfer temperature, pressure and transfer glue formula composition will also affect the transfer tearing paper performance, space limits, not discussed here.polyurethane powder, polyester powder, mixed powder and purified oxygen powder can be used as transfer powder, the experiment in this paper mainly uses the more commonly used polyester TGIC powder system, the experimental results and analysis in other systems can also be analogy.in the process of powdering by adding incompatible additives, such as special wax materials, the incompatible material in the curing process to the surface of the coating film, forming a thin layer of incompatible.
    also reduces the tightness between the thermal transfer paper and the powder coating, making it easier to tear the paper. This method is more selective of incompatible materials, ordinary wax materials will affect the transfer of thermal transfer paper pigments, so that the pattern after thermal transfer is blurred, the actual production also found this phenomenon, so this method is not discussed.
    1.2 Experimental materialsPolyester resin: Dixing (DSM), Anhui Shenjian, Hangzhou, China and France and other manufacturers of a number of polyester
    curing agents: TGIC (Huangshan Huahui), B1530 (Bayer)
    additives: 588,701, Sabbath and other chemical products for the South China Sea
    Pigments: Bayer, Jiangxi Tianguang Titanium Industry, etc.
    Fillers: 44HB (Head)
    Transfer Paper: Foshan Na crowd Decorative Materials Co., Ltd., Omar Paper and other paper mills transfer paper
    substrate: cold plate (180mm x 180mm x 0.8mm), aluminum plate (180mm x 150mm)
    1mm)
    1.3 Main equipmentvacuum transfer machine, twin screw extruder (SLJ-30A) high-speed shredder, high-voltage electrostature spray gun, electric thermostat blow drying box.
    1.4 powdering, film preparation and transferWeighing the raw materials according to the respective formulations, each mixed by the twin screw extruder melt extrusion press into a thin sheet, set the temperature of zone I is: 85-105 degrees C;
    after cooling with a high-speed powder machine crushed, sieve by the standard, respectively, to make powder. The resulting powder is sprayed with a high-pressure electrostature spray gun, which is placed in a thermostat blowing drying box 200 degrees C/15min cured and removed and cooled to room temperature for testing. Transfers are made by vacuum transfer, at 180 degrees C/4min.
    2, results and discussion
    2.1 transfer paper quality, ink depth experiment selected a total of two manufacturers a total of 6 kinds of paper of different depths were tested. As can be seen from Table 1, the transfer effect is greatly affected by the transfer paper.
    Different transfer paper in the curing of the same coating film performance is not the same, and on the coating film 1 transfer effect of good transfer paper, in other film transfer effect also has a trend of number, which is related to the ink concentration of transfer paper and the production of transfer paper used additives.
    performance, the lighter the ink concentration, the easier it is to tear the paper, and the transfer effect is clear, the ink concentration is too deep there is a tendency to tear the paper. The quality of the transfer paper and the quality and concentration of the ink directly affect the final transfer effect. ink: heat transfer depends on the heat sublimation of the ink. Ink is a mixture consisting of dyes that display color, connecting materials for bonding, solvents, and a small amount of additives.
    to meet the requirements of thermal sublimation transfer, dyes need to have a better sublimation, sublimation temperature control at 180-240 degrees C.
    connection material in the role at the same time to try to maintain a small affinity with the dye, so that when heat, the dye is easy to release, with better thermal transfer adaptability.
    of thermal sublimation ink directly affects the quality of the printed image, which in turn affects the transfer quality and the print quality of the final product. Therefore, high-quality inks are a key factor in ensuring good print quality. heat sublimation transfer paper: heat sublimation transfer paper quality on the product printing quality plays a direct role. the uniform type of ink absorption of
    paper, the degree of absorption of ink determines the printing quality of hot sublimation printing paper, good printing quality is the basis to ensure the quality of product printing;
    At the same time, thermal sublimation transfer paper should also have better paper stability, otherwise the heat deformation, or there will be paper or paper printing residue will lead to the transfer layer on the ghost blurring or paper hair, paper printing residue.
    paper should also have good heat resistance, in the heat does not allow the phenomenon of carbonization, not to allow the phenomenon of paper breaking, affecting the continuous production of thermal transfer, reduce production efficiency.
    2.2 curing degree is Curing degree is another key factor affecting the transfer effect, in order to obviously compare the effect of curing degree, we chose a slow curing formula, only by adding a small amount of promoter to adjust the collation time, the specific experimental results are seen in Table 2.
    results show that if the coating film curing time is not enough, the transfer will seriously affect the performance of tearing paper. Because if the curing is not complete, in 180 degrees C to 210 degrees C transfer, the coating film is very mucous, and will stick to the transfer paper together again curing, in severe cases, the entire transfer paper will be strong embedded in the coating film.
    and with the longer curing time, the transfer tearing performance will be significantly improved. In addition, it is also found that the adhesion time is longer 3, in the curing process adjusted to 200 degrees C/20min, after tearing the paper there is still a certain amount of paper hair, transfer effect is not clear, surface blackening, which also shows that the extension of curing time can not solve all the paper tearing problems, but also need to consider from other factors.
    table 3 of
    2.3 cross-link density, formulas 1, 2 and 3 compare the tearing effect of the formulation system with the addition of different T105 curing agents, and formula 1 has the best substantive effect.
    Because T105 is a 4-degree curing agent, and TGIC is a 3-degree-of-energy curing agent, choose the same polyester, increase the amount of T105 can improve cross-link density, the result of transfer tearing paper performance also improved significantly, and add the appropriate amount of T105 to help powder.
    T105 curing system also has its disadvantages, such as, poor yellowing resistance, thick coating easy pinholes, wet environment spray easy to drop powder, etc. , the actual production should be used as needed or part of the use.
    the acid value of polyester resin determines the ratio of resin to curing agent, which ultimately affects the crosslink density of powder coating, in general, the higher the acid value of the resin cured, the higher the crosslink density of the coating film.
    table 3, 4 and 5 compared the different acid formula system tearing effect, after the transfer of formula 5 transfer board tearing paper effect is the best.
    Open the transfer machine after the transfer paper automatically out of the coating film, coating film smooth and bright paperless hair and other residues, formula 4 coating film can also easily tear paper, coating surface effect is good, there are a small number of not obvious paper hair, formula 3 tear paper is relatively difficult, the surface obviously exists part of the paper hair and black phenomenon.
    2.4 filler content In actual production, we also found that with the increase in pigment content, the resulting coating film transfer is significantly easier to tear paper, Table 4 formulas 6, 7 and 8 further verified this result.
    Our analysis may be in the transfer temperature near, the amount of filler increased, the volume of the coating film will be significantly increased, so that under the same pressure (vacuum negative pressure) transfer, the film's thermal variables will be reduced, the transfer paper is not easy to bond with the coating film, after the transfer is relatively easy to tear the paper.
    but the amount of pigment addition has a limit, too much pigment will lead to level difference, powder difference and so on.
    2.5 Additives In Table 4, Formulas 3, 9 and 10 compare the tearing effect of different B1530 additions to the formula system, formula 10 is slightly better than Formula 9, Formula 10 and 9 are significantly better than Formula 3.
    Because pyrethroide also has a certain (generally about 5) hydroxy value, in the reaction between pyrethroide and TGIC, nicosium retained, adding a certain amount of isocyanate (B1530) can react with some residual hydroxyl, improve the degree of reaction, in the actual experiment can significantly improve the effect of tearing paper (formula 10, formula 9 and formula 3).
    other practical experiments, it is found that the B1530 added to the hybrid formula system transfer tearing effect improved more obviously.
    3, Conclusion (1) transfer paper quality and ink quality and concentration directly affect the final transfer tearing effect, the shallower the general ink concentration is easier to tear the paper, and the transfer effect is bright and clear, and the ink concentration is too deep is difficult to tear paper trend; (2) curing is not completely will seriously affect the effect of tearing paper; (3) improving the cross-link density of the coating film can significantly improve the effect of transfer tearing paper, such as the selection of a higher official energy curing agent , or the selection of higher acid polyester ;
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