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Synthesis of epoxy resin modified waterborne polyurethane

Waterborne polyurethane is a kind of polymer material with good physical properties, mechanical properties, weather resistance, environmental friendliness and other advantages. However, the performance of water-based polyurethane is still inferior to that of oil-based polyurethane in some aspects due to the limitation of synthetic methods. In order to improve the comprehensive properties of water-based polyurethane, more and more scientific researchers are devoted to the modification of water-based polyurethane resin. The current modification methods mainly include: 1. Improvement of monomer and synthesis process; 2. Additives; 3. Cross-linking; 4. Compounding. waterborne polyurethane The optimized compounding of waterborne polyurethane mainly includes epoxy resin modification, polysiloxane modification and acrylic compound modification. The following will briefly introduce epoxy resin modified waterborne polyurethane. Epoxy resin itself has the characteristics of high mechanical strength, good adhesion, good chemical stability and low cost, and has long been widely used in the industry. However, it also has some disadvantages, such as poor toughness, brittleness after curing, and low impact resistance, which limit its application field. Epoxy modified polyurethane with excellent performance can be obtained by combining polyurethane with high elasticity and high adhesive force with epoxy resin. There are three main methods for epoxy resin modified waterborne polyurethane: 1. Mechanical blending, that is, mixing epoxy resin and water-based polyurethane in a certain proportion; 2. Graft copolymerization of epoxy resin and polyurethane: After graft copolymerization of epoxy resin and polyurethane prepolymer, water emulsification is performed to obtain epoxy resin modified waterborne polyurethane; 3. Ring-opening of epoxy resin into polyurethane: the epoxy resin after ring-opening is introduced into the polyurethane prepolymer as a polyol component.

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11

2018-09

Analysis of Common Problems of Dry Coating in the Manufacturing Process of Waterborne Polyurethane Synthetic Leather

 Time of issue:2018-09--11

pinholes on the surface The reasons for the occurrence of pinholes on the surface are: the viscosity of the surface layer is too high, the coating is too thick, the temperature of the first oven is too high, the drying time of the surface layer is too short, there are too many bubbles in the prepared material, and there is air in the coating tank Join etc. The situation of the slurry during drying is shown in the figure below. Since the release liner is much thicker than the stock, this structure is formed before the heat of heating arrives. Analysis of Common Problems of Dry Coating in the Manufacturing Process of Waterborne Polyurethane Synthetic Leather When the viscosity of the surface layer is too high, the water vapor generated during drying is not easy to escape from the coating, resulting in small air pockets and pinholes. Reducing the viscosity of the top layer mixture can solve the pinholes caused by this reason. If the coating is too thick, the water vapor will not be easily discharged, which will also cause pinholes. Coating thickness should be reduced when this problem is encountered. If the temperature of the first oven is too high, a large amount of water vapor will be generated instantaneously, and these water vapors cannot be effectively discharged, resulting in pinholes. Therefore, the temperature of the first oven should not be too high. When the drying time of the surface layer is short and the surface layer is not completely dried, the slurry of the second layer will affect the discharge of water vapor from the surface layer, and will also cause pinholes. This requires the surface layer slurry to be completely dried before the second layer can be applied. There are many bubbles in the prepared material, which is also one of the reasons for the pinholes on the surface. The prepared slurry needs to be left to stand for defoaming before use. The addition of air into the coating tank will also cause surface pinholes. At this time, it is necessary to add a baffle to the coating to fill the material tank. jam The reasons for paper jams are: too small gap, residues on the paper, too thick paper joints or tape roll, improper operation, the edge of the first coating scraper is covered by the second coating to accumulate the jammed paper, there are tapes and other debris on the back of the paper Wait. When the knife gap is too small, the knife may come into contact with the release liner and cause paper jams. Therefore, it is necessary to operate according to the standard process gap. Residual debris on the paper will be caught between the paper and the knife, causing paper jams. In this case, the paper inspector should remove the debris on the paper in advance. Paper jams can also occur if the paper splices are too thick or if the tape is rolled up. Therefore, the paper joint must be straight, and the tape must be glued and flattened. Paper jams will also occur when there are debris such as tapes on the back of the paper. Before using the paper, in addition to checking the surface, pay attention to the back. If the edge of the first coating scraper is covered by the second coating material, the second coating should be used to cover the first coating, and the edge material should be removed at any time with a feeler gauge. Improper operation is also one of the causes of paper jams, so it is necessary to operate according to the operating procedures. scratches on the surface The reasons for the scratches on the surface are: the blade of the scraper is defective, there are debris in the material, the filter barrel is not clean, the coating equipment such as the scraper is not clean, the tools are not clean, the filter is not used properly, the mesh size is wrong, and people are careless. fall into debris, etc. The defective blade of the scraper will lead to uneven feeding, too much or too little local material, resulting in scraping lines. In this case, the scraper should be repaired or replaced. If there are debris in the material and the filter barrel is not clean, these debris will be stuck in the gap between the coating knives, affecting the feeding and causing scraping. Therefore, the filtration should be strengthened, and the clean barrels can be used. Similarly, the coating equipment such as scraper is not clean, and the tools used are not clean, which will also cause scratches. The equipment should be hygienic, and the necessary tools should be cleaned. If the filter is used improperly and the mesh size is wrong, the large particles in the material may be stuck in the gap between the coating knives, resulting in scratches. Therefore, when filtering, it is necessary to clarify the scope of use of the filter and pay attention to the number of meshes. Of course, the accidental drop of debris is also one of the reasons for scratching the line. In this case, the responsibility should be strengthened. As soon as there is a drag line, it should be handled

11

2018-09

What is the difference between water-based acrylic resin and water-based polyurethane resin

 Time of issue:2018-09--11

Water-based acrylic resin: including acrylic resin emulsion, acrylic resin aqueous dispersion (also known as water-dilutable acrylic) and acrylic resin aqueous solution. Emulsions are mainly synthesized by emulsification of oily vinyl monomers in water under the initiation of aqueous free radical initiators, while resin aqueous dispersions are synthesized by different processes such as free radical solution polymerization or stepwise solution polymerization. Acrylic emulsion is mainly used as the base material of latex paint, and occupies an important application in the architectural coatings market, and its application is still expanding; in recent years, the development and application of acrylic resin water dispersion have attracted more and more attention, and it is widely used in industrial coatings, civil Applications in the field of coatings continue to expand. According to the monomer composition, it is usually divided into pure acrylic emulsion, styrene acrylic emulsion, vinyl acrylic emulsion, silicone acrylic emulsion, tertiary vinegar (tertiary carbonate-vinyl acetate) emulsion, tertiary acrylic (tertiary carbonate-acrylate) emulsion, etc. Waterborne polyurethane resin: It is a very fine aliphatic polyurethane dispersion. Mainly used to improve the adhesion of finishing, with ultra-fine and stretched film, excellent cold resistance, but will not overfill the grain. Specifically designed for substrate bonding. Waterborne polyurethane resin is often used in the adhesive layer, and can be added to 20-30% of the resin amount to adjust the hardness of the coating film with other resins.

11

2018-09

Waterborne polyurethane applied to wallpaper composite

 Time of issue:2018-09--11

Water-based polyurethane, also known as WPU, is more and more used in people's daily life, such as: dyeing, finishing, printing, etc. of various textile materials; coating of slow-release fertilizer, seed coating, etc.; building inner and outer walls of houses Latex paint, furniture paint for solid wood furniture, leather and synthetic leather on sofas, etc.; interior adhesives for buses, high-speed railways, private cars, car paint, etc....Wallpapers are widely used in the interior decoration of residences, offices, hotels and hotels It is widely used in developed countries and regions because it has the characteristics of various colors, rich patterns, luxurious style, safety and environmental protection, convenient construction, and reasonable price that other interior decoration materials cannot match. In the Chinese market, more and more young people now have an explosive growth in the choice of wallpaper when decorating. At present, the wallpaper composite glue on the market is mainly solvent-based glue, water-based styrene-acrylic glue, and bio-based glue. Solvent-based glue contains a lot of VOC and other unenvironmental factors, which are harmful to human health and will eventually be eliminated; water-based styrene-acrylic glue Due to the poor aging resistance of the benzene ring structure in the glue, it is not conducive to the long-term use of the product, and the characteristics of acrylic acid are hot, sticky, cold and brittle, which will cause inconvenience in transportation and construction in winter and summer; bio-based glue is prone to mold and bacteria, especially in Meiyu in Jiangnan Seasons have an immeasurable impact on the entire family environment and human health. The use of aliphatic water-based polyurethane as the main material of the wallpaper composite adhesive, supplemented by various environmental protection additives, has achieved good results. The specific process is as follows: Material: thick paper, thin paper Product: Waterborne Polyurethane Resin Apparatus: 30 micron wire rod, oven, heat press

06

2018-09

Comparison of water-based paint and oil-based paint

 Time of issue:2018-09--06

Water-based paint is a paint that uses water as a thinner and does not contain organic solvents. It does not contain toxic heavy metals such as benzene, toluene, xylene, formaldehyde, and free TDI. It is non-toxic and non-irritating. , crystal clear, good flexibility and has the characteristics of water resistance, wear resistance, aging resistance, yellowing resistance, fast drying, easy to use and so on. Can be used on: wood, metal, plastic, glass, building surfaces and other materials. The oil-based paint refers to the paint made of organic solvents, containing volatile organic compounds (VOC), which are not only toxic to the human body and pollute the environment, but also flammable and explosive; some varieties also contain a large amount of formaldehyde, benzene, Toxic substances such as lead are "invisible killers" that pollute the environment and damage consumers' health. In addition, due to the composition of oil-based paint, its transportation conditions are quite harsh, but it is undeniable that the contribution made by oil-based paint in water-based paint is undeniable. Advantages of water-based paint: 1. Water-based coatings use water as a solvent, which saves a lot of resources; water-based coatings eliminate the risk of fire during construction; reduce air pollution; water-based coatings only use a small amount of low-toxic alcohol ether organic solvents, which improves the operating environment conditions. 2. Water-based coatings can be directly applied on wet surfaces and in humid environments; water-based coatings have good adaptability to material surfaces and strong coating adhesion. 3. The water-based paint coating tools can be cleaned with water, which greatly reduces the consumption of cleaning solvents. 4. The electrophoretic coating of water-based paint is uniform and smooth. Good flattening; inner cavity, welds, edges and corners can be coated with a certain thickness of coating, which has good protection; electrophoretic coating has the best corrosion resistance, thick-film cathodic electrophoretic coating The salt spray resistance can reach up to 1200h. Advantages of oil-based paint: 1. Anti-corrosion, waterproof, oil-proof, chemical resistance, light resistance, temperature resistance, etc. Objects are exposed to the atmosphere and are eroded by oxygen, moisture, etc., causing damage such as metal corrosion, wood decay, and cement weathering. The surface of the object is coated with oil-based paint to form a protective film, which can prevent or delay the occurrence and development of these damage phenomena and prolong the service life of various materials. . 2. Color, gloss, pattern and flatness, etc. Objects of different materials are coated with oil-based paint to obtain a colorful and colorful appearance. 3. Low price and easy to produce. Good brushing effect Disadvantages of water-based paint: 1. Water-based coatings have high requirements on the cleanliness of the construction process and the surface of the material. Due to the large surface tension of water, the dirt is likely to cause shrinkage holes in the coating film. 2. The water-based paint is highly corrosive to the coating equipment. It needs to use anti-corrosion lining or stainless steel material, and the equipment cost is high. 3. Baking water-based coatings have stricter requirements on construction environmental conditions (temperature, humidity), which increases the investment in temperature and humidity control equipment, and also increases energy consumption. 4. The latent heat of evaporation of water is large, and the baking energy consumption is large. Cathodic electrophoretic coatings need to be baked at 180°C; latex coatings take a long time to dry completely. 5. Organic co-solvents with high boiling point will produce a lot of oil fumes during baking, which will drop on the surface of the coating film after condensation to affect the appearance. 6. The water-based paint has the problem of poor water resistance, which makes the stability of the paint and the bath liquid poor, and the water resistance of the coating film is poor. Disadvantages of oil-based paint: 1. Slow drying and poor physical and chemical properties of the coating film 2. The harmful substances are high to the human body, and the harmful substances are continuously released and long-term volatilized. 3. It is easy to yellow, and the quality of the paint film is not good. Most of the paint films have been replaced by synthetic resin paints with excellent performance. 4. The paint film is harder and more brittle, and it is not easy to repair after damage. 5. Extremely flammable, must be stored separately in accordance with fire protection requirements Both oil-based paint and water-based paint have their own shortcomings. In decoration, it is necessary to consider where they can be used. The advantages and disadvantages must be clearly understood, so as to avoid the trouble of repainting.

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