Overview of the hottest one component moisture cur

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Overview of one component moisture curing sealant

one component sealant is mainly used for caulking at building joints and direct installation of automotive glass. At this time, the use speed is very important and should adapt to the construction environment temperature and humidity. Medium and high modulus sealants are mainly used in automobile manufacturing industry. High modulus sealant is required for automobile windshield, and medium modulus sealant is used for car body bonding and sealing to improve anti distortion. Building sealants are often used only for joint filling but not for bonding. Therefore, they are required to have low modulus and high deformation resistance, so as to ensure that they can adapt to displacement variables without damage in case of cold and hot alternation or impact by external forces. Almost 90% of current production in developed countries "The automobile windshield cooperated by NASA and the industrial field adopts the direct installation glass process, which is almost complete in the United States, Europe and Japan. This process not only solves the safety problem, but also because the structure conforms to the aerodynamics principle, it can reduce the airflow resistance, speed up the speed and save energy. G polyurethane adhesive sealant is required for each glass window on average. Now this process has been extended to the rear and side windows of automobiles. Due to its attractive performance/price, it is being extended to trucks Large cars, train passenger cars and urban light rail cars. Its usage is increasing rapidly

adhesive sealant for automobile windshield is composed of polyurethane prepolymer, thixotropic agent, stabilizer, plasticizer, foaming inhibitor, catalyst and other additives, fillers and pigments. Because of its good bonding strength, aging resistance, vibration fatigue resistance, hydrolysis resistance, low temperature resistance and coloring, it has developed rapidly in recent years. It is reported that the demand for this kind of sealant in the United States is 10000 t/a. Essex specialty products, sunstar, sika and other companies are famous for producing and operating one component polyurethane sealant for direct assembly of automobile windshield

it is estimated that the dosage of polyurethane adhesives and seals for automobiles in China in 2000 was about 499t, mainly imported products. Shandong chemical plant, Shenzhen Aobo adhesive Chemical Co., Ltd., Beijing Longyuan chemical Electromechanical Technology Co., Ltd., Changchun yiduoke Chemical Co., Ltd. and Beijing GAOMENG Chemical Co., Ltd. have produced products. In addition, Hubei Province has set up a new project of polyurethane sealant for automobiles in 2003, with an investment of 20million yuan and a construction capacity of 1000t/a single component windshield adhesive sealant for automobiles and 1000t other products [18]. The performance and quality of our products are generally inferior. It mainly shows that the curing is slow, the painted steel plate and glass need to be treated with different primer, the construction is inconvenient, the gap increases or the processing accuracy becomes poor, and the aging performance of polyurethane sealant is poor; The biggest problem is the poor stability between batches. Solutions are being studied

about 5% of automobile windscreens in Europe need to be replaced due to damage. It takes at least a few days for the ordinary windshield polyurethane sealant to cure in the air, which makes the vehicle too long for repair and can not meet the user's requirements. Therefore, it is necessary to develop polyurethane adhesive sealant with short curing and driving time. In other words, the replacement of the windshield can safely drive for a short time. There are great differences in climatic conditions around the world. Low humidity and/or low temperature are unfavorable to curing, so this factor needs to be considered for sealant curing. Sika has developed a brand Sika tack move, a new one component polyurethane sealant specially for repair. Its curing conditions can range from -10 ℃ to 40 ℃, the relative humidity can range from 10% to about 100%, and the curing time is 1H [19]. The product complies with the federal power vehicle safety standard 212 (fmvss212), that is, when the vehicle head hits a hard obstacle at a speed of 48km/h, the bonded windshield must not move, otherwise it will affect the function of the airbag and make the windshield fly away from the vehicle body

Shandong North Modern Chemical Industry Co., Ltd. (the former Shandong chemical plant) introduced the technology and production equipment for producing one component moisture curing polyurethane sealant from Europe in the 1990s, and launched am-130 multi-purpose polyurethane sealant and am-140 polyurethane windshield sealant. On the basis of digestion and absorption, am-120 series products have been successively developed and widely used in the domestic market. In 2003, a new super strength polyurethane adhesive/sealant was developed, with a surface drying time of min and a curing rate of 4 7mm/24h, tensile strength ≥ 14.0mpa, shear strength ≥ 7.0Mpa, elongation at break ≥ 500%, tear strength ≥ 40.0n/mm (tensile strength ≤ 8.0MPa, tear strength ≤ 30.0n/mm in technical data of general market products); The product has been stored for 7 months without any change

the company prepares sealant in the special glue making equipment for planetary mixing. Two or more polyisocyanates can be selected to react with different polyols to prepare several prepolymers. High comprehensive performance products can be obtained only by adjusting the use when preparing polyurethane adhesive/sealant. If the amount of prepolymer is appropriate, the tensile strength and tear strength of general products will be higher. Fillers such as carbon black and white carbon black have a great impact on product performance due to different manufacturers, brands and indicators. The plasticizing capacity, viscosity, acid value and moisture of different plasticizers as well as their compatibility with polyurethane prepolymers and fillers should be considered, otherwise the performance will be affected. As an automobile windshield sealant, the company measures the lap shear strength of glass/carbon steel and other metals. In order to improve the shear strength, it is sometimes necessary to add some tackifying modified materials. The tensile strength, shear strength and tear strength shall be increased in a balanced way. Factors affecting hardness and elongation at break: type and amount of plasticizer, filler and prepolymer. Influence on surface drying time and curing speed: catalyst system and amount of catalyst or cocatalyst, prepolymer system, prepolymer nco%, amount of prepolymer; Construction ambient temperature and relative humidity

in the 1970s, Chinese Mainland began to research and develop polyurethane sealant. In the 1990s, Dalian second organic has been successfully developed by any local factory, liming Chemical Research Institute, Jiangsu Chemical Research Institute, Chongqing Shuanglong Chemical Industry Co., Ltd. and other units from nano scale, 10000 times thinner than human hair to macro scale (measured in mm). With the rapid development of automobile and construction industry, many joint ventures, sole proprietorships and private enterprises have set up factories for production, such as Beijing Xiling adhesive sealing material company, Beijing senjuke polymer material company, Changchun Henkel surface technology company, Shanghai edoco chemical company, Hangzhou Zhijiang organic silicon company, Hebei Yongxing Industrial Company, Beijing GAOMENG Chemical Co., Ltd., Zibo hitman Chemical Co., Ltd Jilin Chaolong Chemical Co., Ltd., Ningbo special machinery repair and manufacturing plant, Shenzhen hongsansong Industrial Co., Ltd., etc. As the production process, equipment and packaging equipment can not fully meet the requirements, it is difficult for high-performance products to form scale capacity. Many colleges, universities and research institutes are actively studying and solving the existing problems, such as low modulus and high elongation, high modulus and high strength, short drying and curing time, wide environmental adaptability, long storage stability, etc. It is expected that the situation that domestic high-grade polyurethane sealant depends on import will be changed in the near future. At present, China's sealant has formed a new industry with polysulfide, acrylate, silicone and polyurethane products as the pillars. In the "Tenth Five Year Plan" of the national chemical building materials industry and the outline of the 2010 development plan, the "Tenth Five Year Plan" development goals are mentioned. Building sealing materials are mainly silicone and polyurethane sealants

in recent years, equipment such as double planetary or multi-axis agitators with high viscosity and excellent multi-component sealing performance, closed tank changing reaction kettle and vacuum filling machine are available, providing hardware for the preparation of one component moisture curing polyurethane sealant

in order to solve the problem of slow curing speed of one component moisture curing polyurethane sealant, two-component single packaging is adopted, that is, the volume ratio of main agent and curing agent is 1; 1. It is respectively installed in two small tubes and combined in a large package extrusion tube. When the piston extrudes the main agent and curing agent at the same speed, the two agents merge into a static mixer and inject into the sealing joint after mixing. In this way, the curing rate can be adjusted and controlled by the amount of catalyst, the activity of two-component active groups and their ratio. The influence of the circular axis is much less than that of the single component wet curing type. The storage stability was also improved to some extent

currently, single component sealant is packaged in bullet cartridges, and the storage period is often too short. The reason is that the processing is uneven, the tolerance is large, the cylinder is not sealed, the plastic shielding property of the cylinder is poor, and the structure is complex, which requires multiple layers, and the cost is high. Now we use compound film sausage packaging with corresponding extrusion equipment, which has good effect and low cost. Most domestic and foreign enterprises adopt

source: China Adhesives

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