With the increasing awareness of environmental protection, people pay more and more attention to their living environment. Traditional solvent-based polyurethane adhesives are toxic, flammable, odorous, and easily cause air pollution. Water-based paints are non-toxic, non-flammable, and non-toxic. Water-based polyurethane resin has the advantages of high hardness, strong adhesion, corrosion resistance, good solvent resistance, low VOC content, etc. It is a binary colloidal system with water as the dispersion medium, which meets the requirements of current chemical environmental protection. Therefore, it has received increasing attention.
The modified polyurethane has outstanding comprehensive effects in the following applications: waterborne polyurethane wood coating, waterborne polyurethane fabric coating, building waterproof coating, waterborne polyurethane anticorrosive coating, waterborne polyurethane automotive coating, functional waterborne polyurethane coating.
Polyurethane synthesis process
1. Main raw material preparation and refining
Isophorone diisocyanate, industrial product; polyether polyol, industrial product; castor oil, analytical grade; 1,4-butanediol, industrial product; trimethylolpropane, reagent grade; epoxy resin E- 20 , industrial products; dimethylolpropionic acid, industrial products; methyl methacrylate, industrial products; N-methylpyrrolidone, industrial products; triethylamine, ethylenediamine, acetone, analytically pure, 4a molecular sieve before use Drying treatment; azobisisobutyronitrile, chemically pure; dibutyltin dilaurate, analytically pure; filming aid, leveling agent, thickener, all industrial products.
2, photoinitiator
As an important component of the photocurable material, the photoinitiator acts to absorb a certain wavelength of light energy to generate active radicals or cations, and initiate or catalyze the polymerization of the corresponding monomer or prepolymer.
In an ultraviolet curing system, a photoinitiator undergoes a photophysical process to an excited state after absorbing appropriate light energy. If the energy at this time is greater than the energy required for the bond to break, a primary active species such as a free radical can be produced. Or an ion to initiate the polymerization.
The free radical initiators include benzoin, benzoin, acetophenone, thioxanthone, etc., which are affected by the inhibition of oxygen in the air and affect the curing speed.
Another hydrogen abstraction initiator utilizes a tertiary amine photosensitizer to form an initiator/photosensitizer composite initiation system, which can inhibit the inhibition of oxygen and increase the curing speed.
In addition, macromolecular photoinitiators are classified into a side chain hydrogen abstraction type and a main chain split type. Photoactive aromatic ketones such as benzophenone and thioxanthone can be used as side groups to form macromolecular chains to obtain hydrogen scavenging macromolecular photoinitiators; main chain cleavage type is rare, with benzoin ether Polycarbonate is representative, and such a photoinitiator can be used to synthesize a block copolymer to obtain a polymer material having more balanced or excellent properties. The introduction of a polymerizable group on a conventional small molecule photoinitiator results in a polymerizable photoinitiator which is macromated in photocuring, and such an initiator is used only in some special cases. Titanocene photoinitiators are one of the few metal organic photoinitiators that meet various requirements and have good photoactivity, thermal stability and toxicological properties. Not only good absorption in the visible light region, but also strong absorption in the UV light region, but the extinction coefficient is too large, only suitable for thin coatings. The cationic photoinitiators are mainly iodonium salts and sulfonium salts, and ferrocene salts. The cationic photoinitiator has high efficiency, oxygen can not be inhibited, and the curing reaction is not easy to terminate, and is suitable for curing of color paint and thick film.
Other additives
The additives for UV curable materials mainly include stabilizers, leveling agents, defoamers, wetting agents, thickeners, dispersants, fillers and pigments. Its main functions are: improving the production process of the coating, improving the storage stability of the coating, improving the coating performance and improving the coating performance.
Synthesis process of waterborne polyurethane resin
1. Prepolymerization Under the protection of dry nitrogen, the dehydrated polyether diol, castor oil, IPDI and DBTDL were added to a 1000 mL four-necked flask equipped with a thermometer, a stirring device and a reflux condenser, using di-n-butylamine. The NCO value was determined by titration, and the reaction was carried out until the NCO was close to the theoretical value, then BDO was added dropwise and kept for 1 h. After the NCO reached the theoretical value, dimethylolpropionic acid (DMPa), epoxy resin and trimethylolpropane were added, and the reaction was carried out until the NCO reached the specified value, and then the temperature was added to MMA to obtain a PU/MMa prepolymer.
2, emulsified
(1) The room temperature emulsified prepolymer is neutralized with triethylamine and then emulsified in normal temperature water, and ethylenediamine is chain-extended to obtain PU/MMa emulsion a.
(2) Water emulsification at 45 °C The prepolymer was neutralized with triethylamine, emulsified in water at 45 ° C, and ethylenediamine was chain extended to obtain PU/MMa emulsion B.
3, free radical emulsion polymerization
The above emulsion a or emulsion B is heated to 70-75 ° C, and the initiator solution is uniformly added within 3 h, and the conversion rate of MMA is tested for 1~2 h until the conversion rate remains unchanged, and the temperature is discharged, with 200 The mesh is filtered, and the filtrate is a modified aqueous polyurethane (PUa) emulsion.
4, with paint
The quantitative self-made modified PUa emulsion is stirred at a certain rotation speed, and then a film-forming auxiliary agent, a leveling agent, and the like are sequentially added, and a thickener is added to adjust the viscosity to an appropriate value, and the mixture is uniformly stirred to obtain a varnish.
Lathe And Milling Processing Parts
Lathe and milling processing parts refer to precision metal parts that are manufactured using lathe and milling machines. These machines use computer numerical control (CNC) to produce parts to exacting specifications with high accuracy and precision.
Lathe machines are used to produce parts that have a cylindrical shape, while milling machines are used to produce parts with complex shapes and irregular surfaces. The combination of these two machining processes allows for the creation of parts with different shapes, sizes, and complexities.
Lathe and milling processing parts are used in a wide range of industries, including aerospace, automotive, electronics, and medical. These parts are typically produced from a variety of metals, including steel, aluminum, brass, and copper.
The advantages of lathe and milling processing parts are their high accuracy and precision. The CNC machines used in their production are programmed to make precise cuts and movements, resulting in parts that are consistent and accurate. This is especially beneficial in industries where quality control is essential for safety and reliability.
Another benefit of lathe and milling processing parts is their versatility. The combination of the two machining processes allows for the creation of a wide range of parts with complex shapes and irregular surfaces. These parts can also be produced in large quantities, allowing for efficient mass production.
Lathe and milling processing parts provide a cost-effective solution for many manufacturing needs. The precision of these machines means that parts can be manufactured to exact specifications, minimizing the need for additional processing or finishing. This can result in significant cost savings for manufacturers and ultimately lower prices for consumers.
In conclusion, lathe and milling processing parts are essential components in the manufacturing industry. These precision parts provide accuracy, versatility, and cost-effectiveness for a wide range of applications. With the ability to produce parts with high accuracy and precision, lathe and milling processing parts offer a powerful solution for many manufacturing needs.
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