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Research progress of new silane coupling agents
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- Time of issue:2020-12-25
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(Summary description)Coupling agent is a composite system of inorganic materials and polymer materials that can combine the two through physical and/or chemical action, or through physical and/or chemical reactions,
Research progress of new silane coupling agents
(Summary description)Coupling agent is a composite system of inorganic materials and polymer materials that can combine the two through physical and/or chemical action, or through physical and/or chemical reactions,
- Categories:Company news
- Author:
- Origin:
- Time of issue:2020-12-25
- Views:0
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Coupling agent is a composite system of inorganic materials and polymer materials that can combine the two through physical and/or chemical action, or through physical and/or chemical reactions, the affinity of the two can be obtained A substance that improves, thereby enhancing the overall performance of composite materials. The coupling agent can be divided into silane coupling agent, titanate coupling agent, zirconate coupling agent, aluminate coupling agent, bimetallic coupling agent (aluminum-zirconate, aluminum titanium Compound coupling agent), rare earth coupling agent, phosphorus-containing coupling agent, boron-containing coupling agent, etc. Currently, silane coupling and titanate coupling agents are widely used [1] [2].
Silane coupling agent is an organosilicon compound with a special structure. In its molecule, there are both reactive groups that can be combined with inorganic materials (such as glass, cement, metals, etc.) and reactive groups that can be combined with organic materials (such as synthetic resins, etc.). Therefore, the interface of two materials with very different properties can be coupled by the silane coupling agent to improve the performance of the composite material and increase the bonding strength, so as to obtain a new composite material with excellent performance and reliability [3]. Silane coupling agents play an increasingly important role in the silicone industry and have become an indispensable supporting chemical additive in the modern silicone industry, organic polymer industry, composite material industry and related technical fields. The application of silane coupling agent is very extensive, mainly in the following aspects:
(1) Used as a surface treatment agent to improve the bonding performance of room temperature curing silicone rubber and metal;
(2) When used in inorganic materials to fill plastics, it can improve its dispersibility and adhesion;
(3) Used as a tackifier to improve the adhesion of cement and epoxy resin in hydropower projects;
(4) Used as a sealant, it has the properties of water resistance, high temperature resistance, weather resistance, etc., used for the bonding and sealing of chloro rubber and metal;
(5) used as a crosslinking agent for single-component silicone rubber;
(6) Used as an adhesion promoter for difficult-to-bond materials such as polyolefin (such as PE, PP) and special rubber (such as silicone rubber, EPR, CR, chloro rubber).
The three major application areas of silane coupling agents at present are as crosslinking curing agents for non-crosslinked polymer systems.
Make it solidify at room temperature and pressure: the second is the material surface modifier, which gives anti-static, anti-corrosion, deodorization, anti-coagulation and physiological inertness properties; the third is the elastic bridging agent between dissimilar substrates, that is, to improve two different chemistry The anvil connection between performance materials achieves the purpose of improving the comprehensive properties of the product such as mechanical, electrical insulation, anti-aging and water repellency.
2. Structure and coupling mechanism of silane reagent
2.1 Structure of silane reagent
Silane coupling agent is a kind of low molecular weight organosilicon compound with special structure. Its general formula is RSiX3, where R represents amino, mercapto, vinyl, epoxy, cyano and methyl propionyloxy. These groups and different base resins have strong reactivity. X represents a hydrolyzable group, such as halogen, alkoxy, acyloxy, etc. Therefore, the silane coupling agent can not only interact with the hydroxyl in the inorganic substance but also with the long molecular chain in the organic polymer, so that two materials with different properties can be coupled, thereby improving the various properties of biological materials[4] . Table 1 lists the varieties and structural formulas of common silane coupling agents.
2.2 Coupling mechanism of silane reagent
Silane coupling agent has a significant effect in improving the performance of composite materials. But so far, no one theory can explain all the facts. Commonly used theories include chemical bond theory, surface wettability theory, deformation layer theory, restraint layer theory and so on. The first two theories are mainly introduced here [2].
2.2.1 Chemical bond theory
In the coupling mechanism of silane coupling agents, the chemical bond theory is the main theory. The theory believes that silane coupling agents contain reactive groups, one end of which can form covalent bonds or hydrogen bonds with hydroxyl groups on the surface of inorganic materials or oxides on metal surfaces, and the other end can form hydrogen bonds or covalent bonds with organic materials. Valence bond; thus organically connect the interface of inorganic materials and organic materials to improve the performance of composite materials.
2.2.2 Surface Wetting Theory
Silane coupling agent has low surface energy and high wetting ability. It can be evenly distributed on the surface to be treated, thereby improving the compatibility and dispersibility between dissimilar materials. The function of the silane coupling agent is to improve the wetting ability of the organic material to the reinforced material [5].
In fact, the coupling process of silane coupling agent at the interface of different materials is a complex liquid-solid surface physical and chemical process. First of all, the viscosity and surface tension of the silane coupling agent are low, and the wetting ability is high. The contact angle to the glass, ceramic and metal surfaces is very small, and it can spread out quickly on the surface, so that the surface of the inorganic material is wetted by the silane coupling agent. ; Secondly, once the silane coupling agent spreads out on its surface and the surface of the material is infiltrated, the two groups on the silane coupling agent molecule will diffuse to the surface of similar polarity, because the surface of the material in the atmosphere always adsorbs thin In a thin water layer, the alkoxy group at one end is hydrolyzed to form silanol groups, which are oriented on the surface of inorganic materials, and at the same time undergo hydrolysis and condensation reaction with the hydroxyl groups on the surface of the material; the organic groups are oriented on the surface of the organic material. A chemical reaction occurs in the person, thereby completing the coupling process between dissimilar materials. The brief equation of the chemical reaction is as follows:
3. Introduction of new silane coupling agent
With the continuous development of composite materials research, higher requirements are put forward on the performance of silane coupling agents, which prompts people to research and develop new products with different functions and different requirements. Some new silane coupling agents developed in recent years have some special properties.
3.1 Organosilicon peroxide coupling agent
As early as more than 30 years ago, Union Carbide in the United States occasionally discovered that organic silicon peroxide has extraordinary bonding ability, which led to the vigorous development and utilization of this material. Organosilicon peroxide coupling agent has not appeared for a long time in my country, but many researches have been carried out around it, especially in the bonding of special composite materials. Its unique molecular structure makes it have unique applications. Fields, such as the bonding of silicone rubber, fluorine rubber, ethylene-propylene rubber and various metals, and its products have been widely used in the defense industry, medical and health services, aerospace and civil applications. The organic silicon peroxide coupling agent realizes the coupling effect by generating free radicals by thermal decomposition reaction. It can not only couple organics with inorganics, metals, etc., but also couple two identical or different organics; it can not only couple with organics with polar groups, but also with non-polar groups. Silicone rubber, polyethylene, etc. can also be coupled well. Due to heat, the peroxygen bond is cracked to generate active free radicals. Therefore, it reacts quickly and has strong adhesion. It is also called a universal adhesive [6].
Du Xizeng [7] used VTPS on a composite precision rubber roller consisting of a steel core, a silicone rubber sponge and a polyurethane skin, and it was very successful.
3.2 Epoxy-based silane coupling agent
Traditional silane coupling agents are prone to pre-crosslinking reactions in water-based systems, which limits their application. Epoxy silane coupling agents exhibit long-term storage stability in water-based systems and maintain good adhesion after storage at room temperature for more than 1 year. And physical properties. This type of silane coupling agent is suitable for a variety of polyester materials, especially for epoxy resin. Can improve the adhesion of two-component epoxy sealants. Improve the adhesion of acrylic latex, sealant, polyurethane and epoxy coatings. This type of product is represented by 3-(2,3-glycidoxy) propyltrimethoxysilane (A-187) [8].
Xi Liping and Wang Shaoming [9] introduced hydrolyzable siloxy groups through the reaction of the carboxyl groups in the resin and the epoxy groups in the silane, and then hydrolyzed and condensed the siloxane groups to form crosslinked Si—O—S i bond crosslinking. Since the bond energy of Si—O—S i is very high, the silane cross-linking system using this as the cross-linking point will significantly improve the gloss stability, water resistance, weather resistance and corrosion resistance of the coating film. The joint membrane has good mechanical strength, hardness, solvent resistance, water resistance and abrasion resistance. In addition, the surface energy of silane is low, and the stain resistance of its coating is also good. And used it in the modification of styrene-acrylic emulsion.
Huo Yingpeng, Liu Hongbo [10] and others have successfully synthesized a new type of silane coupling agent-3- (trimethoxysilyl) glycidyl propionate using classic hydrosilylation reaction. And through experiments, it has been proved that it has good corrosion resistance, and GMAS has the application prospect as a surface treatment agent for aluminum plates.
3.3 Long-chain alkyl silane coupling agent
Long-chain alkyl alkoxy silane is a new type of organosilicon compound. Due to its hydrophobic long chain, it greatly reduces the surface energy of the filler and makes the solvent, resin, auxiliary agent, etc. in the organic phase uniform. It penetrates into the glass fiber or uniformly dispersed on the surface of the nano-filler, which improves the impact strength and heat resistance of the composite material. Its general structural formula is YRnSiX3-n, where n=0~3, X is usually —OCH3 and —OC2H5, etc., and Y is a long-chain alkyl group. The representative product is DH-10, the chemical name is methyldodecyldimethoxysilane, and the structural formula is C12H25CH3Si(OCH3)2. Long-chain alkyl silane coupling agents are widely used in foreign countries and are also produced in China, but the production volume is very small. There are generally high production costs and poor product quality. Therefore, the current domestic long-chain alkyl silane coupling The agent mainly relies on imports, which not only increases the production cost of printing and dyeing factories, but also is not conducive to the improvement of domestic textile quality. In order to develop the national industry and revitalize the national economy, Peng Zili [11] and others studied the use of methyldichlorohydrosilane, 1-dodecene and methanol as the main raw materials, anhydrous methanol and other compounds as raw materials, through the hydrosilylation reaction. , Alcoholysis reaction synthesizes DH-109, which is used as the raw material of fabric finishing agent.
Zhu Huaijun [12] et al. used 1-octene, 1-dodecene, and 1-octadecene as the main raw materials to synthesize long-chain alkyl methyl dimethoxysilane. The addition reaction requires no heating at room temperature, no induction period, no need to add raw materials, no need to add solvents, high catalyst activity, low dosage, and high product yield. In a closed system, n(1-dodecene): n(methyldichlorosilane)=1: 1.1, n(platinum catalyst): n(methyldichlorosilane)=6.5×l0-5: 1 , The yield of dodecylmethyldichlorosilane can reach 8%. The yield of the alcoholysis reaction is also higher. The equipment is simple and easy to operate, the technology is advanced and pollution-free, and it has great industrial value. It has broad application prospects and is of great significance for promoting the production and processing of domestic long-chain alkyl products.
Zhong Guiyun et al. [13] used methyldimethoxysilane and octene as the reactants, toluene as the solvent, and platinum complex as the catalyst. At a certain temperature, the methyl octyl bis The yield of methoxysilane was 74% (calculated as octene).
3.4 modified amino silane coupling agent
Starting from the A-1100 developed by UCC, bisaminosilane (A-1120) containing 1 primary amino group and 1 secondary amino group can be derived, and triaminosilane containing 1 primary amino group and 2 secondary amino groups ( A-5162), and polyaminosilane (Y-5691) containing one primary amino group and multiple secondary amino groups, etc. These free amino-containing silanes are more basic and have higher reactivity, and with the increase of amino groups, the flexural strength of plastic products also increases. The synthesis of amino silane coupling agent roughly requires three processes: synthesis of chlorohydrocarbyl chlorinated silane, alcoholysis reaction, and amination reaction. Shi Baochuan et al. used methyldichlorosilane, allyl chloride and cyclohexylamine as raw materials to synthesize γ-cyclohexylamine propyltriethoxysilane and methyl through hydrosilation, alcoholysis and amination reactions. , Γ-cyclohexylamine propyl dimethoxy silane, and used elemental analysis, IR and 1HNMR to characterize them, confirming that they are novel silicone coupling agents, which can be used to make softeners in the textile industry [14]
Huang Changgen [15] Improved synthesis of N-vinylbenzyl-N-aminoethyl-γaminopropyl polytrimethoxysilane hydrogenated acetate. (Polytrimethoxysilane polymerization degree n is 1-12) is a group of oligomers with good wettability and homogeneous surface. The lateral and longitudinal cross-coupling can form a uniform interface layer with a suitable thickness and a relatively small number on the surface of the inorganic substance. Excellent solubility. Quick and rapid hydrolysis. Increased storage stability. O/W type is formed during hydrolysis. When used for chemical treatment of E glass fiber cloth, the W/O type/emulsion micro-explosion is avoided during the drying process, which ensures the consistency of LOI value distribution in the micro area ( (Refers to the micro area range), the stability of the hydrolyzed solution increases, and it can be stabilized at a higher pH value. When pH=3~4, it can effectively degenerate within seven days.
3.5 Some other new silane coupling agents
Crompton Osi Company has developed a new type of silane coupling agent NXT. According to the company, this coupling agent has brought a major breakthrough in the mixing technology of silica tire compounds. The new generation of NXT silane coupling agent is a replacement product of the existing coupling agent. It can be used in the tread rubber filled with silica to reduce the viscosity of the rubber, reduce the number of mixing stages, improve the processing performance of the rubber, and promote the dispersion of the reinforcing agent , Improve the dynamic mechanical properties of the rubber compound. In addition, this coupling agent improves the aging resistance of silica tread rubber, prolongs the storage time of the rubber compound, and reduces the content of volatile organic compounds in the finished tire [16].
Zhou Xingping [17] synthesized thiocyanopropyltriethoxysilane (trade name Si-264 from Digotha, Germany) from potassium thiocyanide and γ-chloropropyltriethoxysilane, at a temperature of 120-130 Reflux for 3h at ℃, the yield is about 82%. The silane coupling agent is used to reinforce a variety of natural and synthetic rubbers, with good coupling effect, and its advantage is that it is not easy to scorch the rubber.
Isocyanate-containing silane coupling agent is a new type of coupling agent. It has very good effects in surface treatment of organic materials and electrodeless metals, especially in glass fiber reinforced composite materials, treatment of inorganic powder fillers and coatings. The tackifier has a significant effect. Our country mainly imports from Japan, which is expensive. Bo Zhengwu et al. [18] used solid phosgene instead of phosgene to react with γ-aminopropyltriethoxysilane to form a γ-isocyanatepropyltriethoxysilane coupling agent, avoiding potential safety hazards during production and use. . Bian Gaofeng et al. [19] used amino silane and carbonyl diimidazole as raw materials to fully react under the action of a catalyst to prepare isocyanate silane coupling agent, which completely solved the problem of phosgene.
Si69是系含双官能团的有机硅烷, 它的乙氧基能与二氧化硅表面的硅醇基发生反应, 反应后的产物是硅烷改性二氧化硅它能显着降低白碳黑和橡胶复合料的粘度, 赋予生料良好的加工性能, 并能提高橡胶的抗撕裂、耐磨耗、耐屈挠龟裂等性能, 特别是能避免天然胶胶料发生返原现象等。 因此它被认为是近年来开发的橡胶助剂中很有发展前途的一种新型硅烷偶联剂.
用氯铂酸作催化剂, 由烯丙基和甲基的豆寇醇醚和豆寇醇醋与油酸和亚油酸合成而得。获得的氯硅烷衍生物采用通常的步骤进一步转化为甲氧基甲硅烷基衍生物。一种甲氧基甲硅烷基多硫化物田四氢胺果酚(T H A ) 多硫化合物和三氯硅烷合成, 所获得的氯硅烷衍生物转化为烷氧基甲硅烷基衍生物。
4.展望
我国硅烷偶联剂的开发主要集中在传统硅烷偶联剂,而新型的硅烷偶联剂则鲜有报道;同时,其所用原料多为石油化工产品,利用天然产物作原料来合成的也不多见。我国虽有二、三十家有机硅烷偶联剂生产企业,但其技术,工艺和装备水平相对落后,大多数企业的年生产能力仅为几十吨或几百吨。为打破国外跨国公司长期统治国内外硅烷偶联剂市场的被动局面,开发新型硅烷偶联剂也势在必行。
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