Hu袁继伟Abstract: UV-curable material at home and abroad, the latest market development and application of UV curing technology to discuss several new trend. Key words: UV-curable; coating; Photoinitiators; Commentary; development trend of the new generation of environmentally friendly O foreword products - UV-curable material since the 70's commercialization in foreign countries has been to maintain 8% ~ 10% of high-speed growth. Its advantage lies in: (1) curing fast, automated production to meet modern needs.

 Currently, the fastest of its production lines up to 200 m / min; (2) non-polluting, adapted to the development direction of modern paint. In addition to spray a small amount of products containing volatile solvents, the leaching Tu, roller coating, painting methods, such as rejection Tu solid content of the products are up to 100%; (3) coating of high quality, high hardness, scratch resistance, corrosion resistance, etc. a new generation of UV-curable material is gradually overcome the coating of high crosslinking density resulting from the negative effects, such as brittleness, such as flexibility and low temperatures in the -20 ℃ resistance turns 30,000 times a UV-curable materials have been asked City. UV-curing system typically include Photoinitiators, functionalized oligomers, single or multi-functionality monomer functionality. (1) Photoinitiator photolysis generated through active groups such as free radicals or cations, directly affect the polymerization rate. (2) functionalized oligomers constitute the size of the mesh structure of compounds skeleton decided UV-curable materials physics, chemistry nature. (3) single-or multi-functionality functionality as a reactive diluent monomer, not only affects the ultimate material for the physical and chemical properties, but also affect the curing rate and the degree of polymerization. Over the past 10 years, UV curing system on the raw materials for the rapid development of technology and market expansion provide the necessary guarantees, for example, different varieties of Photoinitiators development and performance, so that is no longer limited to ultra-violet curing coating traditional varnish. Through Photoinitiators compound to containing titanium dioxide pigments, such as the depth of the UV curing system entirely possible. With the high Weatherability oligomer emergence has been proven weatherability certain system is not bad at Hyundai Motor coatings, there is no doubt that the future UV-curable material in any field of application will not expand and we are surprised.

  1 UV curing system of market conditions

  1.1 foreign market the North American market, its total capacity in 1995 from the 45000t growth in 2000 80000t, the average annual growth of about 10%, the U.S. market accounted for 90%, Canada 7%, Mexico 3%.

 The main application areas in Table 1. Table 1 2000 North American market, the distribution of UV-curable material and capacity of the market in 2000 the distribution of market capacity / t paint (wood, plastic, metal, etc.) 47,000 ink (offset, screen printing, Flexo,凸印etc.) 16000 electronic and high photosensitive 15000 molecular adhesive 2000 Table 2 for coating applications is further broken down, we can see that, although in the traditional field of application is still a larger proportion, but the new areas being infiltrated is an indisputable fact. For example, optical fiber coatings, in the 20th century, the beginning of the commercialization of 90's, and now the annual growth rate of 30% ~ 40%. Table 2 in North America in 2000 the distribution of UV curable coatings market and capacity of the scope of application in 2000 market capacity / t printing paper and paperboard, packaging 20000 wooden furniture, wood flooring, instrument panel, control panel plastic plate 14000 reflective film, PC, CD, credit cards, 8400 metal lights and other types of metal cans, metal pipes, such as 1100 1.2 domestic market since the 20th century, the early 90s UV-curable material in the realization of China's first commercial production, the annual growth rate has remained at 40% ~ 60%, This shows China's strong market-based UV curing system and huge market potential. In raw materials, Photoinitiators products in recent years, the rapid development of foreign products, not only shattered the levy price of China's market dominance, many manufacturers have sold products abroad, in the international market place. However, it must be seen in product development and applications, and power compared to Europe and the United States, is still a huge gap. Table 3 for 2002 of China's market distribution of UV-curable material and capacity. Table 3 2002 domestic UV-curable material distribution in major markets and demand for applications in 2002 market capacity / t sources 10000 wooden floor paint products to be imported a small number of high-grade paper, plastic and other types of varnish 6000 a small number of high-end products to be imported electronic and photosensitive polymer 5000 the vast majority of dependence on imported printing ink 3000 the vast majority of dependence on imports the vast majority of the automobile industry dependent on imports of 800 various types of adhesive 500 can be seen the vast majority of dependence on imports, China has the commercialization of products, mainly at the initial stage of technology . Currently, competition among manufacturers focused on the price of low-level warfare. On the one hand, the basis of the chemical industry as a result of China's relatively backward, thereby affecting raw materials, research and development, our country at this stage there is no large-scale production of oligomers, monomers and stable quality manufacturers; On the other hand, also reflects the application of a small number of products manufacturers psychological impatient for success.

  2 UV-curable materials market and technology trends

  2.1 UV Powder Coatings traditional powder coatings in the 160 ~ 200 ℃ about curing, can not be used for heat-sensitive substrates, UV Curing Powder Coatings combination of traditional powder coatings and the advantages of UV curable coatings, has the following characteristics: (1) to overcome the traditional powder easy to paint "orange peel" defects. This is because when the UV powder melting heating system in the melting temperature of about 80 ~ 120 ℃, the system does not occur crosslinking curing, coating have enough time leveling.

  (2) comprehensive performance system is more liquid than UV advantage because of the oligomer molecular weight increased after taking into account the flexibility and hardness and adhesion to the substrate.

  (3) paint recycling easier, lower cost, reducing the construction of powder coatings occupied a lot of space and efficient.
   (4) to overcome the traditional powder coating can not be used for heat-sensitive material (such as wood, plastic) shortcomings, especially for some at the same time contain metal, plastic pieces of the coating composite construction, a more simple and convenient. A commercialization of the world's first UV powder coating production lines in 1998 in the United States Baldor electronics companies, the coating applied to the electronic motors. With the closure of the product and some pieces of plastic parts can not afford the high temperature 130 ℃, the previous method is to use different parts of the paint coating, respectively, after the assembly, and the application of UV powder coatings can be fabricated after the one-time coating greatly enhanced efficiency and reduce VOC emissions. The most active current study, the most widely used is UV powder system in the medium-density fibreboard (MDF) applications. With the reduction of natural timber resources, MDF is widely used in office and household furniture, such as MDF in Europe in 2000 production reached 8,000,000 m3, an annual growth rate of 11%. At present, in Europe and America have been built about 16 MDF UV coating powder coating production lines. Table 4 lists the main foreign supplier of UV powder coatings, can be seen, UV powder system, except in MDF has been widely used, the positive metal, plastic and other fields. Table 4 Main UV Powder Coatings foreign suppliers of goods were the commercialization of the company time applications Akzo Nobel Woodcote 2001 MDF years Du Pont UV-TEC 1999 MDF years Morton UltroVTM Lamener 1999 years MDF, metal density years Valspar 2000 plate, metal Protech NuvocoatTM 2001 years HBFuller DesignkoteTM 2001 MDF MDF years UV Curing Powder Coatings by oligomers, photoinitiators, pigments, such as composition, its key technologies focused on the study of oligomer , Moens reported, such as crystalline unsaturated polyester synthesis: Using 1,6 - F diol, trimethylolpropane, 1,4-cyclohexane b methanol as raw materials, first of all be the end for the hydroxyl or carboxyl polyester, and then with the reaction of glycidyl methacrylate, the introduction of photosensitive groups, the introduction of crystalline resin to make UV powder coating melt when heated substrate better wettability and liquidity, thereby improving the paint adhesion and the apparent effect of powder coatings to overcome the traditional shortcomings of easy to peel. Kempter, were reported by acrylate or methyl acrylate, styrene copolymerization as raw materials, product copolymerization with glycidyl methacrylate reaction can be used for UV powder coatings Photosensitivity unsaturated polyester . Mithiah reported double UV curing powder coating systems, UV systems have overcome the depth of the opaque coating curing and thermal curing bad easily peel powder system problems.

  2.2 UV water-based paint UV oily water-based paint made up for some of the shortcomings of UV system: viscosity control system over-dependent on the activity of diluted monomer; monomer itself has a lot of skin irritation, volatile after (although rarely) causes environmental pollution. Especially for spray paint, water-based system to meet its requirements低黏度, in addition, water-based system so that equipment is easy to clean, non-toxic, non-irritant, non-combustion, in recent years has developed into a new light-curing system

 . 2.2.1 UV-curable waterborne paint the field of classification and application of light-curing water-based coating is mainly divided into water-soluble, water dispersion (mainly dispersed emulsion system can be divided into outside the emulsion-type, self-emulsifying type), soluble colloidal dispersion (base resin material with a small amount of ionic or non-ionic hydrophilic group) three. Compared to water-soluble light-cured coating, emulsion paint curing light-curing membranes are highly water-resistant, better application prospects. Waterborne UV-curing paint a broader range of applications, can be used for plastic varnish, Clear varnish, light polymer print, screen printing ink, intaglio and lithography, such as printing ink. Many high-quality printing ink used multicolor overprint technology, low solid content of water-based light-cured coating to meet that request. And water-based paint in the light-cured wood, wood finishing is also a higher application value.

  2.2.2 UV-curable waterborne coating composition and the progress of water-based light-cured coating composition in general include: base material resin, surfactant, or other decentralized stabilizer, Photoinitiators, reactive monomer, wetting agent, leveling agent , fillers, pigments and so on.

  (A) final curing resin coating film performance of the major decisions by the base material resin. Water-based paint curing resin-based material more commonly used unsaturated resin derived functionalized. Resin-based material commonly used in the following categories: (1) waterborne epoxy acrylic resin to epoxy acrylic resin (EA) with anhydride (maleic anhydride, phthalic anhydride, trimellitic anhydride, etc.) was modified, the introduction of carboxyl, and then in and agent (such as triethanolamine, N-methyl diethanolamine, methyl acrylate, N, N-dimethylamino-ethyl, ammonia, etc.) and into a carboxylic acid salt, can be synthesized with photosensitive properties of water-soluble epoxy acrylic resin. Experiments show that: the water-soluble resin with carboxyl content increased, with the improvement of solid content increased, and by the impact of the type of neutralizer; resin curing rate and with the improvement in the level of increase, not pre-drying Resin drying faster than the resin, and with the increase of the content of acid anhydride, curing at a slower rate.
  (2) waterborne polyurethane acrylate such products is currently the most studied system, and research directions include the following: a. light-cured polyurethane acrylate integrated performance is better, and more by non-ionic monomer hydrophilic poly diol synthesis, although the polymer can be avoided Polyelectrolyte effect, but one of Asia need to reach a higher water content ethoxy before they can get enough water dispersion, so the water dispersion of the poor. PHStenson (ZENECA Resin Company) using dimethylolpropionic acid (DMPA) instead of polyethylene glycol, and then react with the isocyanate, and then use the ammonia or organic amines and salt, to balance the polyurethane synthesized water dispersion stability curing membrane and water resistance of light-cured waterborne polyurethane, the introduction of two light-cured acrylic waterborne polyurethane wood coatings: Neo Rad 3709 and Neo Rad 440. Tsinghua University, Fang Yu, who studied in detail the molecular weight of polyethylene glycol and polyethylene Ethylbenzene alcohol, 2,2 - dimethylolpropionic acid molar ratio on the Synthesis and film properties, results show that the coating has a curing excellent hardness, impact strength, adhesion and anti-fog performance. b. Austin Hansen, Kim Yang-chi and others of polyester polyurethane acrylate had an in-depth studies: to toluene diisocyanate, polyethylene adipate butanediol, dimethylolpropionic acid, HEMA as raw materials Synthesis of photosensitive resin, by triethylamine and stability after the self-emulsifying system. The results showed that: with the hydrophilic group (-COOH) and an increase in content and degree of the improvement of emulsion dispersion and stability of enhanced emulsion viscosity, curing membrane of water absorption with the-COOH content increases; curing Tg membrane with DMAP / PBA proportion increases; curing membrane has excellent oil resistance, solvent resistance, adhesion. c. polyurethane acrylic resin composite raise light-cured water-based paint and / price method: Stenson will be simple polyurethane and acrylic resin blends, the dispersed emulsion after a light-cured coating, but the two types of resin compatibility bad, derived from a comprehensive system of poor performance. Application of hybrid technology can be effectively two types of resin composite Nucleation - shell structure, decentralized systems of stability and greatly enhanced coating performance, but the process of preparation by the hybrid UV-curing water-based resins still greater difficulty. d. grafting method is the use of polyurethane and acrylic resin to enhance the compatibility of an effective way, it combines the advantages of comprehensive performance polyurethane and acrylic resin price advantage, has a high conversion rate of photopolymerization. The main synthetic thinking: the main chain of polyurethane graft acrylic resin and acrylic resin side chain chain polyurethane graft side chain. Yang Jianwen and others by polyurethane (PUA) grafted to the methyl methacrylate, glycidyl methacrylate (MMA / GMA) copolymer, with the amine and post-production from acrylic emulsion access Chi polyurethane system (g-PUA), increased sexual / price.

  (4) unsaturated polyester (WB-UPE) MJDvorehak and others reported that a non-use of styrene monomer, such as cross-linked non-ionic self-emulsifying unsaturated polyester Waterborne (WB-UPE), its light-cured base The Corps is Allyl ether: Polyester A: TMPdiallylether-[maleic acid-diol-maleic acid] - TMPdiallyl ether polyester B: TMPdiallyl ether-[maleic acid-polyglyol-maleic acid]-TMPdiallyl ether TMPdiallyl ether: CH3CH2 - C (CH20CH2-CH) 2 - CH20H polyester A, B do not have to, respectively, synthesis, can be used simultaneously diol and polyethylene glycol and maleic anhydride reaction, obtained after acid and polyester Trimethylolpropane Diallyl ether for esterification. The resin can be directly adding water emulsion, the coating can be used by the pre-dry Photoinitiators common, such as Darocur 1173 \ Darour 4265 such as UV-curable and can be used with paint and varnish (such as titanium dioxide) system. In the above-mentioned system, B polyester polymer used as a reactive emulsifier, can be overcome in addition to light-curing agent Films. Of course, polyester B can also be used alone, but its poor water resistance. Polyester A role is to improve the crosslinking density and improve the performance of curing membrane. By regulating the polyester A, B ratio can be both a certain dispersion stability as well as the good performance of the UV light curing system. This system can be one-step synthesis: first 2 mol of glycol and polyethylene Diols reaction mixture, and then with 2 mol of trimethylolpropane esterification, and finally with 4 mol of allyl chloride reaction.

   (4) water-based acrylic polyester M. Philips, such as reported in different alcohols and diversified multi-acid synthesis of polyester acrylate. The results show that: molecular weight in the 640 ~ 3000 about molecules contain at least 6% to 7% of the hydrophilic group can only be a good water-soluble, curing the product has good solvent resistance and water resistance, but the most a small quantity of water to obtain a suitable coating viscosity is still a pending problem.
   (5) water-based acrylic esterification Polyacrylate with inexpensive, easy preparation, coating fullness, the advantages of a good gloss. Most of the introduction of hydrophilic acrylic acid copolymer of carboxyl, with (meth) HEMA or (methyl) glycidyl epoxy copolymerization or the introduction of hydroxyl groups in order to further the introduction of propylene acyl Mission.

  (B) plus surfactant surfactants for waterborne paint photocuring, select the appropriate surfactant is important. Surfactants can be divided into non-ionic, anionic, cationic and amphoteric ion type. In addition to zwitterionic surfactant rarely used for water-based light-cured coating, the principles of the three can be selected immediately. Anionic surfactants, especially of long-chain fat and acid and long-chain hydrocarbons of ammonium acid is more commonly used. Studies have shown that ionic surfactant because of their compatibility with the curing membrane problem, easy to enrichment in the membrane surface, and easy to infiltrate and easy extraction, and detrimental to coating performance, but also easily lead to health problems. Better solution is the use of polymerizable surfactants, is involved in the process of optical cross-linked and fixed at curing membrane, or the introduction of resin in the main vulnerable group of water-based (such as hydroxyl, quaternary ammonium groups, etc.), so resin with self-emulsifying properties.

  (C) Photoinitiator traditional solvent-based light-curing coatings used in Photoinitiators can be free radical type, can also be cationic. However, the general water-based light-cured coating can only be used free radical type photoinitiators. Cationic Photoinitiator can also be used for water-based light-cured coating, but the bad effects. For water-based UV-curing coatings, Photoinitiators Apart from solvent-based system used in the absorption of Photoinitiators nature, the nature of anti-yellowing outside requirements, but also have the following characteristics: ① water-based photosensitive resin with a high degree of compatibility, dispersibility well, not only in the wetland system to be compatible, but also key in the curing of the former dry evenly dispersed. ② the water vapor with a low volatility (which, together with the evaporation of volatile extent). This request is in order to pre-paint drying (typically 60 ~ 80 ℃, depending on the coating thickness, the activity of the substrate and air humidity, etc.) can still maintain the required concentration (including ion substrate Photoinitiators better). Of water-soluble light-curing system, it is necessary to use water-soluble Photoinitiator (WSP). Commonly used water-soluble monomer acrylamide (AM), (meth) acrylic acid (AA), (methyl) HEMA (HEMA). By chemical structure to points, the current water-soluble Photoinitiator can be divided into aryl ketones, PAHs category polysilane category, aroyl bisphosphonates, Azo and metal organic complexes. Aryl ketones in which most varieties can be divided into thia ketone derivatives, benzophenone derivatives, benzil derivatives and alkyl aryl ketone derivatives, and now feel insecure thia ketone, diphenyl ketone and α-hydroxy benzene reported a maximum of one study. For price and compatibility considerations, the current formula has been widely used in water-soluble Photoinitiator not many still-fang WSP ketones and α-hydroxy benzene ketone (such as Darocur 2959) accounted for the vast majority of . At present, water-based light-cured coating used in the Photoinitiators not all water-soluble, can be through the use of surfactant (Irgacure 651) dispersed in the water the way to achieve the purpose of compatibility with the resin, which is particularly suitable for emulsifying dispersion or suspension system . And with the polyhydroxy thia unhappy one has a certain hydrophilicity, suitable for coloring the light-curing water-based system.
   2.3 Technology 2.3.1 double double curing type curing mechanism (1) free radicals - free radicals free radical reactions are usually the first step for UV curing reaction, and the second step not only for the UV free radical reactions curing, but also for the thermal curing reaction, such as dual-curing mechanism through the UV system to enable access to low-gloss coating. The first step, paint with low-intensity ultraviolet light, at this time due to oxygen inhibition, surface coatings have not been completely solidified, will enable the agents of extinction, as far as possible to move to the surface, and the second step by high UV coating so that it eventually Curing (especially the surface). UV intensity control by regulating the production line conveyor belt speed to get, it is clear that such dual-curing mechanism in the curing characteristics of energy, rather than curing chemistry. Miller reported that another radical - radical double curing system. The first step in the use of UV radiation curing, and the second step by thermal curing, formulas as shown in table 5. Table 5 UV-curing and air curing formula of combining the formula 1 formula 2 formula 3 PEAa 7 UA1b 4 UA2c 4 Mon-did 3 5 Mon-trie 2.5 TMPTA 2.5 Darocur1173 0.2 0.2 Iragcure 651 0.2 benzophenone 0.5 0.5 0.5 Co2 + 0.25 0.25 0.25 PEAa - a mixture of acrylic polyester products, including air-drying of functional groups. UA1b-a mixture of acrylic polyurethane acrylate, including air-drying of functional groups. UA2c-a functional group that contains air-drying polyurethane acrylate. Mon-did-containing two acrylic functional groups and an air-drying functional group of TMP derivatives. Mon-trie-a TMP derivatives, including fully air-drying of functional groups.

  (2) a free radical polymerization in this type, containing epoxy group or isocyanate group of unsaturated oligomers first step is in response to UV radiation, and the second step through the epoxy groups or different cyanate groups to carry out curing polymerization. For example, the adoption of bisphenol A epoxy resin with different amounts of acrylic acid reaction with epoxy functional group of acrylic modified epoxy resin, using free radical initiator, such as Iragacure 184 epoxy curing agent and 2 - methylimidazole. UV cured, at 120 ℃ for 30 min heat treatment. All recipes in the crosslinking density after heat treatment changed significantly. Epoxy-free number of the more stronger after the stem effect. Adjust the acrylic group and the ratio of epoxy groups can get a good metal adhesion, epoxy and more attached to the better, which is epoxy smaller contraction rate and the second phase of heating curing coatings at the time of relaxation effect of a combination of reasons. Traditional polyurethane coating with good adhesion, flexibility, and good weather resistance, wear resistance, corrosion resistance and so on. Obviously, with double-isocyanate curing system features not only retains the advantages of UV curing system, but also to make up for its shortcomings, can be produced that contains a mixture of isocyanate - acrylate prepolymer functional group (IAP). UV radiation treatment, through the moisture-curing or joined IAP in polyol of-OH and-NCO for thermal reaction. This system is particularly applicable to UV paint system or can be overcome constraints often encountered in the thickness of the problem, and for a variety of different shapes of objects (including the shadow zone) for coating and curing.

  (3) Siloxane Siloxane reaction curing mechanism available through dual-curing system other than the advantages of electronic packaging materials on the application of Siloxane use their influence on the thermal stability, good low temperature flexibility and excellent electrical properties such as the nature of conventional moisture-curable silicone materials completely curing need a longer period of time, the other two components of curing certain weaknesses exist, but the reaction rate siloxane acrylate fast, UV curing provide rapid access to under the Road process conditions. The first step is still light-induced free radical crosslinking reaction, and the second step is the solidification of heavy metal-catalyzed hydrosilylation.

  2.3.2 Application of the dual curing system outlook double curing system in the electronic sealing materials, adhesives, wood primer and certain metals, such as hard substrate attachment can be widely used. At present, containing isocyanate-based PUA has been commercial production, such as VPLS 2337, LPFWO 3768, LPFWO3786, UVAPLS 2308 and so on. Dual-curing wood primer for industrial applications has been, it has resolved a UV curing system in some oily wood attached bad, bad oil seal and so on. In addition, the dual-curing technology is expected to three-dimensional objects, painting a very broad prospects, such as car decoration, single-use UV curing, UV light to be carefully designed system to ensure that all regions at the same time be uniform curing, and the use of dual-curing technology , then not only can avoid this problem, but also in the process and the performance of a combination of UV system, the advantages of fast-curing polyurethane coating and excellent performance.

  3 Conclusion In recent years, UV radiation curing materials in the market demand for high-speed growth at the same time, UV radiation curing system is working with a variety of technology to overcome some deficiencies to meet the practical application. UV powder system, UV water-based system, the dual curing system, on behalf of its future technology trends.