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    Home > Coatings News > Paints and Coatings Market > Advances in water-based polyurethane plastic coatings

    Advances in water-based polyurethane plastic coatings

    • Last Update: 2020-12-28
    • Source: Internet
    • Author: User
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    China Coatings Online News Information
    Zhang Fan, Yang Jianjun, Wu Qingyun, Zhang Jian'an, Wu Mingyuan (Anhui Province, School of Chemical and Chemical Engineering, Anhui Province Green Polymer Materials Key Laboratory, Hefei 230601)
    Abstract: Plastics are a class of plastic synthetic polymer materials, compared with other materials, because of light weight, chemical stability and excellent electrical insulation properties and other characteristics have been widely used. However, the plastic itself is not ideal for environmental aging such as ultraviolet light resistance, and the surface often produces various defects during the process of processing and molding, so surface coating is required. This paper introduces the research progress of plastic water-based polyurethane coating and makes a prospect for its future development.

    keywords: plastic products, water-based polyurethane, paint
    0 Introduction
    With the rapid development of the plastics industry, plastic products are widely used in all walks of life, has become an indispensable national economy and national defense construction of one of the important materials. However, the plastic itself is not ideal for environmental aging, such as ultraviolet light resistance, in the processing and molding process surface also often produces a variety of defects, so the need for surface coating, to give the plastic a special color or a certain gloss, and cover the plastic surface defects, so that it has a more attractive appearance.

    plastic coatings include common plastic coatings and engineering plastic coatings. When used in polystyrene products, polyester film products, lysoglass products and other ordinary plastics, it can be given friction-resistant, not easy to scratch and other properties;

    1. Polyurethane coatings
    polyurethane coatings have good weather resistance, good light preservation, good color stability, corrosion resistance, acid rain resistance, low temperature construction, good coating re-coatability, easy repair, good coating flexibility and excellent stretch, impact resistance and shock resistance and other advantages of performance, so in plastic coatings have been widely used. In view of the environmental protection and resource requirements, promote the paint industry to water-based coatings, high solid sub-coatings, photo-cured coatings and powder coatings as the representative of the direction of low-toxic, environmentally friendly coatings, the most important of which is water-based coatings. Although plastic coatings are still solvent-based, the water-based coatings market will continue to rise with the increasingly stringent environmental regulations and their own technology. High-performance and low VOC content of plastic water-based polyurethane coating is an environmentally friendly coating material, with broad application prospects. This paper mainly introduces the traditional plastic water-based polyurethane coatings and modified and functional polyurethane coatings.

    a wide variety of plastic products, performance is different, because the molecular structure and surface polarity of different plastic substrates vary greatly, so different plastic substrates to choose different coating systems. Water-based polyurethane has many advantages, such as non-polluting, wear-resistant, corrosion-resistant, soft and hardness adjustable, and is cost-effective.

    1.1 Traditional single-group water-based polyurethane coatings
    Lin Xiaoqiong, etc., selected water-based polyurethanes that can give the coating a soft touch as film-forming substances, and studied defoulants, silane coupled agents, elastic powders, wax dispersants, etc. The type and dosage of additives such as nitrogen propylene crosslinkers and thickeners have an effect on the properties of coating film adhesion, water resistance and scratch resistance, and a water-based ABS plastic coating with soft feel, soft luster, good scratch resistance and excellent adhesion.

    , Jiang Shouxia, etc., explores the synthesis process of water-based polyurethane, synthesizes water-based polyurethane dispersions, and introduces epoxy resin E-20, inline agent trihydroxymethylene propane (T MP), using small molecule chaining agent BDO (1,4-butyl glycol) and other means, to achieve the cross-linking of water-based polyurethane structure, so as to arrive at a reasonable formula and appropriate reaction conditions. When the content of E-20 is 6.0% to 8.0% (mass fraction, the same between 2 and 2- dmPA), the addition of hydrothermic chaining agent 2,2-dehydroxymethyl acid (DMPA) is 7.0% to 8.0%, the amount of chain-expanding agent ethyldiamine (EDA) is 1.0%, and the mesothimlic degree is 90% to 100%, the emulsion performance is the best.

    Among the inks produced in China, the adhesion of water-based inks and plastics based on acrylic resin is poor, which is only suitable for paper trademarks and carton packaging, and there is little research on its process improvement to overcome the disadvantages of water-based inks, in order to meet the needs of plastic printing. Using polyester (PBA), small molecule alcohol, dihydroxymethylprolic acid (DMPA) and isoflavone diocyanate (IPDI) as raw materials, the anionic polyurethane water emulsion was made by means of synthesis of first emulsification and then chain expansion. The ratio of isocyanate to hydroxyl material, the percentage content of DMPA mass, etc., has an effect on the comprehensive properties of viscosity, hardness and oscide, and the results show that when isocyanate (-NCO)/hydroxyl (-OH) has a mass ratio of 1 .8, n (PBA)/n (small molecule alcohol) is 0.67 to 1.0, DMPA mass score is 4%, the choice of chaining agent is ethylene ddiamine (EDA), the chain spreader mass score is 0.8%, The synthetic adipose aquatic polyurethane has the characteristics of good adhesion, high transparency and low viscosity, and meets the requirements of plastic printing ink.

    1.2 two-component polyurethane coatings
    Wang Yuxiang, etc., synthesized cation-type hydroxyacrylate resin dispersion (component A), which is composed with polycyanate curing agent (component B) two-component water-based polyurethane coating can be used in ABS, PC/ABS, PC, PVC and other plastic parts of the surface coating. The dosage of methyl acrylates-N, N-dmethyl (DMAEMA), acrylic hydroxyethyl ethyl (HEA), hard monomethyl acrylates and soft monocepthyl acrylates (MMA/BA) were studied. The mass ratio and the effect of the quantity ratio of A and B parts (-NCO/-OH) on the performance of polyurethane coating film were indicated by FT-IR (infrared spectroscopy) and DSC (differential scanning heat method). The results showed that the DMAEMA dosing was 5%, the HEA dosing was 15%, m (MMA)/m (BA) was 2, n (-NCO)/n (-OH) was 1.2 to 1.4 to obtain an excellent coating film with excellent performance, water resistance and chemical resistance.

    Song Liang, etc. , with acrylic resin and high butyl content acetate cellulose (CAB) as film-forming substances, TDI-type polycyanate as a curing agent, prepared a fast-drying scratch-resistant two-part polyurethane coating. Studies have shown that the addition of acetate cellulose can help to increase the hard-drying rate of the coating system, adding 2% of the total amount of paint glass powder and 3% of the acetate cellulose can reduce the hard-drying time of the paint film to less than 5min. The performance tests show that the coating has the characteristics of low curing temperature, short hard drying time, good scratch resistance and excellent corrosion resistance, and is suitable for coating work parts containing plastic parts or hydraulic oil, and the work parts that need to be flipped manually.

    Jinqing, etc. , the use of trihydroxymethyl propane (TMP) for the chain expansion agent synthesis with cross-linked structure of water-based polyurethane dispersion polyols, and polycyanate curing agent to form a two-component water-based polyurethane coating. The study found that the mechanical properties and appearance of the two-component coating film were determined by the synthetic water-based polyurethane polyol chaining agent (TMP) content, neutrality, neutrality process and ratio of two-component coatings. When the content of the chain expander is 2% to 4%, the neutrality is 100%, n (-NCO):n (-OH) is 1.0 to 1.2, the resulting two-group water-based polyurethane coating film appearance is good, fast dry, high hardness, construction is convenient.

    2. modified polyurethane plastic coating
    polyurethane chain segment because it contains a strong polar group - NCO, OH and niacin, etc. , in addition to the molecular can form hydrogen bonds and van der Walli, has a high cohesion, so the polar plastic surface has a good adhesion. However, for non-polar PE, PP and other plastics with very little surface stress, polyurethane is difficult to attach to the substrate surface, the plastic needs to be surface modified or attached to polyurethane resin chemical properties, surface stress and solubility parameters and These non-polar resins are similar to the chain segments, or are used in a composite with other types of coatings, making them available on non-polar plastic surfaces such as polycarbonate, ABS, polypropylene, polystyrene, etc.
    2.1 Silicon-modified polyurethane coatings
    Xu Fei, etc.) introduce triacetone and polydymethylsilane into the main chain of water-based polyurethanes to create silicane-modified UV-cured water-based polyurethane emulsions, which are indicated by the FT-IR infrared spectrum. The emulsion is combined with the additive to make a water-based plastic coating, and the curing dynamics and surface properties of the coating are studied. Compared with unmodified coatings, sioxane modified UV-cured water-based coatings have good water resistance and solvent resistance, while retaining an excellent feel and can be used as water-based flexible plastic coatings.

    2.2 epoxy modified polyurethane coating
    Jiang Sheng male, etc. With adhesion as the main index, the optimal process conditions of epoxy modified polyurethane coatings were determined, and infrared spectroscopy, thermal weight analysis and other comprehensive performance tests were carried out. The experimental results show that the optimum process conditions are 8% epoxy resin addition, 5% DOP addition, reaction time of 35min and reaction temperature of 70 oC, and the developed epoxy modified polyurethane coating has high mechanical strength, good adhesion, low water absorption rate and good thermal stability for plastics.

    2.3 Styrene modified polyurethane coatings
    Dng Sanjun, etc.) by introducing dual-functional group monomer methyl acrylic-β-hydroxyethyl ethyl (HEMA), the two-bonds into the polyurethane (PU) chain, and then polymerized with styrene (St) monomer emulsion, the synthesis of cross-linked polyurethane-polystyrene (PUS) composite emulsion. The effects of nuclear shell mass ratio and HEMA dosing on emulsion and film properties were studied, and polymer structure and particle morphology were indicated by FT-IR and TEM (transmission mirror). The research shows that with the increase of nuclear shell ratio, the average particle size and minimum film temperature (MFT) of emulsion increase and then decrease, and the adhesion of coating film to high impact-resistant polystyrene (HIPS) plastic substrate increases; When the nuclear shell mass ratio is 4/5 and HEMA/PU is 6%, the coating film adheres well to the HIPS plastic substrate.

    2.4 Acrylic modified polyurethane coatings
    Sun Fang, etc. prepared a water-based polyurethane (WPUA) composite emulsion with a nuclear shell structure with acrylic modified water-based polyurethane, etc. The water-based polyurethane (PU) content, n (-NCO)/n(-OH) (the ratio of the initial substance), the amount of hydro-hydroxymethyl acid (DMPA) and the soft and hard monomer mass ratio affected the performance of WPUA emulsion and its membrane. The results show that the WPUA emulsion particles are nuclear shell structure, polyacrylate (PA) and PU chain segment have good compatible, when the PU mass score is 80%, n (-NCO)/n (-OH) is 5:1, m (MMA)/m (2-EHA) is 1:4, DMPA mass score is 5.8%, the resulting WPUA composite emulsion and its coating performance is better.

    3. Functional polyurethane plastic coatings
    With the wider application of plastic products, the surface performance and weather resistance of plastic products are becoming more and more demanding, while plastic products with special functions are becoming more and more popular.
    3.1 Conductive polyurethane coatings
    Jiang Hongmei has studied conductive coatings based on epoxy-polyurethane interpassional polymer networks (EP-PUIPN) and silver-plated copper powder as conductive fillers. The two-phase compatible of different ratio EP-PUIPNs was observed by scanning mirror (SEM), the glass temperature of inter-wearing polymer network (IPN) was measured by differential scanning heat method (DSC), and the structure and selection of EP-PUIPN were discussed, and the particle size and content of silver-plated copper powder were discussed on the resistivity and performance of conductive coatings. The test shows that with 90/10EP-PUIPN as the base, the content of silver-plated copper powder is 80%, the particle size is 400 eyes, the resistivity of coating film is low, and the use performance is good.

    , Guo Ziqing, etc., has experimented with the preparation of a fire-resistant coating for plastics. In the experiment, the optimal ratio of two monomer toluene isocyanates (TDI) and polyethyl glycol was determined, and the best process conditions for the preparation of polyurethane fireproof coatings were obtained. Finally, infrared spectroscopy, thermal weight analysis and other comprehensive performance tests were carried out. The experimental results show that the optimal ratio of TDI and polyethyl glycol n (-NCO)/n(-OH) is 1.6:1; the best process conditions are ammonium polyphosphate content of 12%, melamine content of 5%, even agent content of 2%, reaction time of 40min, reaction temperature of 80 degrees C;

    3.2 Radiation-cured polyurethane plastic coatings
    Wang Bangqing
    using isofron diocyanate (IPDI), hydroxypropylate new glycol (ED204), polyester binary Alcohol 1000, polyether binary alcohol PPG2000, acrylic hydroxyl ethyl (HEA) as raw materials, through the body poly-legal, 2-step reaction synthesis of polyurethane acrylic low-polypolymer (PUA), for each step of the The effects of catalyst dosage, reaction temperature, reaction time and blocker dosage on synthetic PUA lymers are discussed in detail, and the FT-IR structure of synthetic PUA polymers is indicated, and the synthetic products are determined to be designed according to molecular structure and PU obtained. The best conditions for A lysum synthesis: the first step reaction temperature is controlled at 50 degrees C, the catalyst dosing is 0.1%, the reaction time is 1h, the second step reaction temperature is 70 degrees C, the catalyst dosing is 0.15%, the reaction time is 5h, The amount of phenol used by the blocker was 0.3%. Under the optimal synthesis conditions, the self-made PUA polymer was applied as a base resin in the UV curing coating, and the properties of lymer, active monomer and trigger on the coating film were examined in detail, including adhesion, hardness, impact strength, wear resistance, flexibility,
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