1 Introduction
Polyurethane coating because of its unique structure and gives processing products to highlight the strength, flexibility, wear-resistant, breathable, low temperature resistance performance; and is widely used in the coatings industry, leather industry, textile industry, construction industry and other fields; but PU coating is solvent-based. With the awareness of environmental protection continue to strengthen, the labor protection, safety, fire control, environmental protection and other laws and regulations become more and more perfect, and the organic solvent prices soaring, and the water of PU replace solvent-based PU become inevitable; and because of pure PU emulsion in stability, self thickening, solid content, scope of application, film gloss aspect is insufficient, and the PUA composite emulsion cheap, safe, Noncombustible, non-toxic; not only strong toughness, wear resistance, water resistance, chemical resistance and good stability; and, since the thickening, solid content, scope of application, film and good light. Therefore, PA latex and PU emulsion in the nature have certain complementary function, so the PUA composite emulsion has become inevitable trend.
The emergence and development of 2.PU coatings
In foreign countries, Germany does obeisance to ear ( OttoBayer ) in 1948, the development of isocyanate chemical basis, by the reaction of diisocyanate and ethylene glycol and two amine reaction, were prepared linear polyurethane and polyurea. In 1955 made the toluene diisocyanate ( TDI ) and three methyl propane ( TMP ) adduct ( DESMODURL ). In 1961 made the hold the diisocyanate (HDI ) shrink two urea, on this basis can be prepared with excellent properties of PU coatings. In recent years at home and abroad PU coating can be widely applied, is because the PU coating performance character and development of coatings industry "three conditions" ( resources, energy, no pollution ) and" the four principles of E ( ECONOMY EFFICIENCY" economy, efficiency, ecological energy ECOLOGY, ENERGY ) and increasingly aggrandizement adapted to the requirements of the times. An estimated 90 abroad in the polyurethane coating will get further progress, obtained a lot of achievements.
China's PU coating development of Dalian dye factory began in 1956 the first successful form of toluene diisocyanate ( TDI ), was carried out the experimental study of PU coating, and in 1958 the PU coating trial production, but it was not until 1956 in Tianjin, Shanghai and other places have a small amount of commercial paint production. To 80 time, after the reform and opening up, technical exchanges at home and abroad is growing, PU coating production technology and construction technology progress increasingly, ushered in our country in the 90 PU coating to flourish in new period. However, because PU coating in stability, self thickening, solid content, film gloss is relatively poor, its development has certain limitation.
The emergence and development of 3.PA coatings
In 1927, Germany Rohm&Hass company began acrylate production. After 1931, the British, the United States and countries develop methacrylate industrialized production, made of organic glass. The early 50's, the United States of America DoPont company started to research the polyacrylate coating and used in automotive coatings, after several years of application and development, in 50 time later period, excellent performance, acrylate coatings gradually importance for the people.
China's acrylic coatings research and later, in the 50's by the Ministry of Chemical Industry Institute of industrial coatings and Beijing, Tianjin, household of individual units started to develop, mainly for aircraft coating. In 60, 70 time of acrylic resin coatings have the further development, have successfully developed acrylic modified several conventional resin coating, such as acrylic modified vinyl chloride resin, nitrocellulose, alkyd resin and paint are up to the industrialized application. 80 time up to now since the Beijing Dongfang Chemical Plant with an annual output of 38000 tons, Jilin chemical industry company with an annual output of 40000 tons of acrylic monomers have been put into production, greatly promoting the development of acrylic coating industry speed. However, because PA coating in toughness, wear resistance, water resistance, chemical resistance is relatively poor, its development also has certain limitation.
4.1 water PU coating production and development
Waterborne PU paint was invented in 1943, the first industrialization in 1967, 1972 the German Bayer company pioneered the development of the imprainil series used in leather coating agent PU water emulsion.
For decades, Europe and the United States, Japan on the water of the PU research and development seriously very much, now has many types of water-borne PU products, successfully used in textile, printing and dyeing, leather processing, textile coating, paint, adhesives, wood processing building, papermaking, rubber and elastic fibers, elastomers and other fields. Especially in recent years, global environmental protection requirements of increasingly high, at the same time, considering the economic savings, traditional solvent based PU system receives serious challenge, its application has a trend of decreasing. Water based PU replace solvent-based PU will become a 4 third generation water-based PU-PUA coating production and the development, compared with foreign countries, the domestic water of PU research and development is relatively backward, still in the prototype and small batch production phase. According to incomplete statistics, our country waterborne PU research, production unit only has more than 40, which is about more than 20 production units to total annual production of 10000 tons and above. Most of the production of leather finishing agent. The domestic production of water-based PU small product range, performance of poor quality, and similar foreign products compared to the gap between the large, many industry long-term dependence on imports, therefore, according to the national condition, research and development of high quality of PU products, to replace imported products, to meet the urgent demand of domestic relevant industry has very important significance.
4.2. The water of the emergence and development of PUA coatings [ 7-8 ]
Polyurethane ( PU ) emulsion and polyacrylate emulsion ( PA) with its solvent-based products compared with cheap, safe, nontoxic, nonflammable,, no environmental pollution and other advantages, and in the coating, adhesive, leather, fabric coating is widely used. But pure PA emulsion problem is: the toughness, wear resistance, water resistance, chemical resistance; and a single PU emulsion problems are: stability, self thickening, solid content, scope of application, film gloss difference. PU and PA in nature have a complementary role, PUA composite emulsion can overcome the shortcomings of PU and PA emulsion disadvantages, produce respective advantage, make the emulsion and film properties are improved obviously.
Be above suspicion doubt, PU coating has obvious advantages, but its price is higher, applications are restricted. So at home and abroad dedicated to water-based PU-PA modified resin research, to reduce the cost, has obtained the result, and the foreign countries have been commercially available. PU-PA modified resin two for optimum performance of the material integration in one, to overcome the disadvantages of PU, PA, coated soft, folding, resistance to cracking, printing effect is good, good weather resistance, hydrolysis resistance. PU-PA composite aqueous dispersion technology is the international material new research results, also represents a new trend in the development of PU.
Come nearly ten years, foreign to the PUA composite emulsion were studied, such as the United States, Germany, Japan and other reported for paint, fabric finishing agent and other aspects of the PUA composite emulsion, it is only in recent years that it has relatively few researchers conducted the preparation of PUA composite emulsion of exploratory experiments, such as dawn Chemical Research Institute, Anhui University, Jiangsu Chemical Industry Research Institute, Yantai Research Institute of chemical industry, Henan Chemical Research Institute, University of Shanghai for Science and Technology, but PUA composite emulsion commercialization, at present domestic has not been reported, PUA composite emulsion due to its excellent properties, known as the third generation of water-based PU.
4.3. The water of PUA characteristics of the coating and synthetic method
PUA composite milk promotes both PU, the advantages of PA, has the advantages of wear resistance, corrosion resistance, light, soft and flexible, water resistance, good mechanical properties, good weather resistance and other characteristics, the PUA composite emulsion has become the development trend of coating. PUA composite emulsion preparation method are the following: 1. PU latex and PA emulsion co-mixture crosslinking; II synthesis with double bond of unsaturated urethane monomers and acrylic ester copolymerization; the PU emulsion as seed emulsion polymerization method.
Wherein, a first composite emulsion polymerization preparation containing hydrophilic group PU, dispersing in water as a seed, and then the same acrylic emulsion composite polymerization, preparation of core / shell type PUA latex, or join a diene monomer interpenetrating polymer network ( IPN ) latex. The method can be divided into: solvent method for PU seed; direct acrylic monomer as solvent for PU; no solvent water chain extension for PU; the prepared PU contains hydrophilic, since milk to seed further with acrylate monomer emulsion polymerization. It is currently a very popular method.
4.4.IPN technology in the application of PUA coatings
Acrylic polyurethane coating agent coating on the surface of objects, the hydroxyl acrylic component and multi isocyanate resin component isocyanate resin reaction film, is a conversion coating, which both acrylic and polyurethane finishing agent has the advantages of two kinds, corrosion resistance, good wear resistance, strong adhesion, with aliphatic isocyanate resin is prepared with the raw material of the coating agent has excellent resistance to weathering, but at present the aliphatic polyisocyanate all rely on imports, expensive, using homemade aromatic polyisocyanate resin coating prepared with poor weatherability, coating detonation sun yellow, in order to reduce the external acrylic polyurethane finishing agent cost, we using IPN technology to coating is introduced in the part of aromatic polyisocyanate resin to replace the aliphatic isocyanate resin finishing agent, in ensuring the premise reduce the weatherability of.
IPN ( IPN ) is composed of two or more than two kinds of interpenetrating crosslinked polymer compositions of the mixed system, as the main means of polymer blends and composites, can be seen as using chemical methods to realize polymer blending method, using synchronous synthesis of similar chemical structure to a two network, plus the two network each other throughout the force to total capacity of action, can be expected that the system compatibility will be improved greatly, in the form of performance for the continuous phase structure, thus the introduction of Aromatic isocyanates caused by weathering problems can also be addressed.
With caprolactone as chain extender prepared crosslinked acrylic acid poly cyanide fat and has braces two isocyanate resin curing acrylic resin as raw material, the prepared PU / PAIPN, has excellent weather resistance, solvent resistance and adhesion, used as automobile paint and furniture coatings, has a good decorative effect.
The 5 ending
Sum up, polyurethane coating from the solvent to the development of waterborne PU, and then to the third generation of water-based PU-PUA composite emulsion, fully shows the PU coating exuberant vitality; now aqueous PU throughout the coating industry, leather industry, printing industry, building industry, textile industry and other fields, there is reason to believe that, with the society development, environment and the requirements of industrial production, water-based PU products will in the chemical industry of our country occupies a space for one person.
