Original title: Take you to know the common titanate coupling agent of calcium carbonate (CaCO3) I. Overview Titanate ester coupling agent has been developed into a new type of coupling agent system parallel to silicon coupling agent since it was first reported publicly by Ken Petrochemical Company (Richpetrocheoical Co.) in the United States at the end of 1984. As a molecular bridge connecting inorganic fillers and organic polymers, it has fully demonstrated its excellent performance and has been widely used in various fields of polymer synthetic materials, such as resins, coatings, rubbers and plastics. With the development of contemporary synthetic materials from single organic polymer to organic and inorganic polymer composite, people put forward endless requirements for coupling agents and other additives, but the renewal and innovation of coupling agents give new vitality to composite materials. In this paper, the preparation methods, functions and applications of coupling agents are briefly introduced. II. Preparation method of iron-based coupling agent In short, the titanium-based coupling agent is obtained by reacting a Titanic acid lower ester with a fatty acid having a higher carbon number or a fatty alcohol. In which that low ester of titanate may be tetraisopropyl titanate, tetra-n-butyl titanate, tetra-tert-butyl titanate and the like. They are made by the reaction of titanium chlorides with the corresponding monohydric alcohols; high-carbon-number fatty acids are generally referred to as Cg or more fatty acids, usually C12 to C18 fatty acids, such as lauric acid, tridecanoic acid, myristic acid, palmitic acid, pearlescent acid, stearic acid and other saturated monobasic acids and oleic acid, acrylic acid and other unsaturated monobasic acids, can also be mixed acids. At present, there are few data and patent reports on the preparation of titanium-based coupling agents, and only some preparation methods of Titanic acid lower esters have been preliminarily found. Therefore, this paper can only slightly mention the principle preparation method of titanium-based coupling agent after describing the preparation method of Titanic acid lower ester. 1. Preparation of Titanic acid lower ester : Titanate lower esters are formed by the reaction of titanium chlorides with the corresponding monohydric alcohols. (1) general preparation: A few examples are listed below and briefly explained. (A) Lenis method: When a monofunctional alcohol is reacted with TICI4 in an inert solvent, the reaction can only proceed to the extent of the following formula in the absence of an HCl gas absorbent: TICl4+3ROH(OR)2TICI3·ROH+3HCl↑ When anhydrous ammonia is introduced into the reaction process, the reaction can be completed: TICI4 + 4ROH + 4NH3Ti (OR) 4 + 4NH4CI ↓ (B) Herman's Law: This law is an improvement on the shortcomings of the Lenis Law. Before neutralization, half of the HCI gas released by the reaction is blown off by N: or dry air, and then the remaining half of the HCI is neutralized by ammonia, so as to achieve the purpose of using less ammonia. (C) Dupont Law: The characteristic of this method is that ammonia reacts with TICI4 in a solvent to form a complex of TICI4 · 8NH3. The ability of the complex to react with virtually any alcohol is then exploited to produce the corresponding alkoxytitanates which may be substituted. Reaction equation: TICI4.8 NH3 + 4 ROHTi (OR) 4 + 4 NH4Cl ↓ + 4 NH3 ↑ (D) Monsanto Act: Expand the full text TIS2 reacts with alcohol to generate alkoxy titanate and H2S, and the reaction equation is as follows: TiS2+4ROHTi(OR)4+2H2S↑ (E) Levrens method: At the beginning of the reaction, only less than the calculated amount of alcohol is added to react with TiC14 to facilitate the release of two molecules of HC1. Then, less than the calculated amount of the alcohol is added for the reaction. It is obvious that the above synthetic routes of titanate can be summarized into two ideas, resulting in two methods and obtaining the same result. J,G. Lenis laid down the idea of acid-binding agent. Ammonia is used to neutralize the hydrogen chloride generated in the reaction process to promote the smooth completion of the reaction; another idea is the intermediate complex proposed by DuPont. With the help of the strong reactivity of the complex, the reaction proceeds smoothly. No matter how other routes change, they are just using their ideas to seek better results. Therefore, the focus of research is how to effectively remove the reaction acid gas. However, if the acid gas treatment technology is solved, the industrialization of titanate is not without problems. According to the author's conjecture, the selection of reaction solvent and how to avoid the decomposition of products in the post-treatment process are also a great problem. In the absence of foreign disclosure of the true location, the United States Ken Ruiqi Company solved this problem in the early 1970s and became the only foreign company monopolizing the production technology of titanate coupling agent. (2) preparation of tetra-n-butyl titanate: This article quotes the method proposed by Yoshino and Ichiro Kijima. Examples are as follows: TiCl4+-4C4H90HTi( OC4H9)4+4HC1↑ A 1000 ml four-necked flask was equipped with a sealed stirrer, a reflux condenser, and a dropping funnel. Add 4.8mol of n-butanol into the flask, place it in a water bath, and slowly add 0.3mol of TiCl 4 dropwise when the temperature in the flask does not exceed 80 ℃. After dropping, replace the dropping funnel with an ammonia inlet tube, and slowly introduce dry ammonia. When ammonia is introduced,titanium bar gr7, white smoke is produced in the reaction bottle, and the temperature in the bottle keeps rising. The reaction temperature is controlled not to exceed 100 deg C by adjusting the ammonia feeding speed. When the HC1 produced by the reaction is completely neutralized by ammonia, the introduction of ammonia is stopped. At this time, that wat bath was replaced with an oil bath, and the reaction was carry out at 110. degree. C. to 115. degree. C. for one hour. Then cooling to normal temperature, and carrying out suction filtration by using a dry filter in a moisture-free environment. Distilling the white NH4Cl4 filtrate under normal pressure after removing the filter cake, intercepting excessive n-butanol, distilling under reduced pressure, and collecting 172-3. /6 distillate, I. e., that product, is obtain in an amount of 80-85 G, with a yield of 80% for TiCI4. As an industrial production method, it is said that the ammonia method is preferred, and the production methods of other Titanic acid lower esters are not described in detail. 2. Preparation of titanium coupling agent : There is no formal report on the specific preparation method of titanium coupling agent at home and abroad. The author makes an inference only from the point of view of the given molecular structure. Isopropyl tri (acrylic acid) titanate of (I) alkoxy type It is the reaction between tetraisopropyl titanate and acrylic acid, and the end point of the reaction is determined by removing a certain amount of isopropanol. The reaction equation is: III. Functions and Types of Titanium Coupling Agents 1. Function It is well known that tetravalent carbon atoms form the basis of life. Chemists, inspired by the characteristics of tetravalent titanium,nickel titanium wire, have ingeniously designed multi-functional titanates with the general formula: (R1O) mTi- (OX-R2-Y) n, in an attempt to act as molecular bridges linking inorganic fillers to organic polymers. As shown in fig. 1, one end (R1O) m2 reacts with the surface water and free proton hydrogen (H +) of the inorganic substance to form a monomolecular layer surrounding the inorganic substance, thereby causing a new change in the surface energy between the inorganic filler and the organic polymer, and as a result, the viscosity of the system is greatly reduced. For example, when polystyrene is filled with 50% CaCO3, the melt flow is 0.36, and when titanate coupling agent is added, the melt flow is increased to 1.17. Due to the difference of the state and humidity of the water on the surface of inorganic fillers and the difference of the system, the corresponding (R, 0) and mechanism of action are also very different. See Table 1: Titanium coupling agent can improve the mechanical properties of composites, especially improve the flexibility and impact strength. For example, the impact strength of polypropylene filled with 70% CaCO _ 3 and added with titanium coupling agent (TTS) is increased by 7.5 times, and the melt flow is close to that of the unfilled system. The titanium-based coupling agent can promote bonding and obtain excellent bonding force. For example, when 1% of KR-44 is added to the natural rubber filler to bond with polyurethane, the bonding force is 27% higher than that of the best product. Can improve chemical activity and promote cure. If the amine azodicarboxylate blowing agent is treated with TTS, the gas evolution is increased from 182 m3/G to 298 m3/G at 190.d egree. C. The chemical corrosion resistance of the coating can be improved. A new coating of silica, treated with a superposed titanate pyrophosphate, failed after 370 hours. The phosphate ester-containing titanium coupling agent also has flame retardancy. But also can protect that performance stability of inorganic substance and prevent moisture absorption. In some systems where a low moisture content of the inorganic filler is required, such as in Hypalon rubber where water plays a disadvantageous catalytic role and moisture present in the iron oxide will cause premature cure. After treatment with titanium coupling agent, the iron oxide absorbed only 0.14% of moisture when exposed to 100% relative humidity for two days, while the untreated iron oxide absorbed 2-3% of moisture under the same conditions. 2. Types of titanium-based coupling agents : Before the seventies, people only used silicon-based coupling agent, but because of its price and performance limitations, often can not achieve Degree of satisfaction. From 1976 to 1980, the consumption of titanium coupling agents in the United States increased from 25 tons to 1300 tons, and the varieties have developed into five major ones. Type, nearly 60 varieties. The representative varieties are listed in Table 2. IV. Application of iron-based coupling agent 1. Use Titanate lower esters are widely used in organic synthesis and polymer chemistry. For example, the coating made of tetra-n-butyl titanate, modified silicone, epoxy and alkyd resin as base materials and appropriate amount of aluminum powder pigment can be used for a long time at 600 ℃. When tetrabutyl titanate or tetraisopropyl titanate is used as the catalyst for esterification or alcoholysis, titanium filler rod ,ti6al4v eli, it can be used at a temperature higher than 200 ℃, and the side reaction of dehydration of alcohol can be avoided, and the after-treatment such as water washing can be avoided, but the color of the product obtained is light. This feature is not possessed by acidic catalysts. Titanate low ester is also widely used as crosslinking agent for epoxy resin, curing agent for epoxy resin, catalyst for polyurethane reaction, and curing accelerator for polyester and silicone. In summary, Titanic acid lower ester is not only an intermediate for preparing titanium coupling agent, but also a fine organic chemical worthy of attention. Titanate coupling agents suitable for different applications can be summarized as follows: (1) When improving the adhesion between polymer and metal, most polymers can be selected. KR-38 S-58, -138S; selected when polyester is bonded to wood TTS, KR-201, -138S, et al. (2) Metal primer for corrosion protection: KR-38S, -58, -46, etc. for solvent-based, and KR-38S, -58, -46, etc. for water-based. K · R-138, -158 + hydrotropic solvent. (3) for improve that pigmentation degree and the dispersibility of the pigment, for improving the pigmentation degree of TIO2, KR-12 is use when a solvent is used as a base, and KR-12 is used when water is use as a base. KR-1125，KR-212。 Polymers for pigment dispersion and most Titanic acid phenols when solvent based; optional when water based KR-212 4, -133 4, KR-55. (4) KR-95 and KR-12 can be selected for flame retardancy. (5) As a promoter: to promote the decomposition of azoformamide, TTS, KR-385, -95; catalytic function To lower the crosslinking temperature of melamine or the baking temperature of alkyd resin, KR-55 and KR-62 are used together, and as esterification transfer agent at room temperature. TTS, KR-95; 300-500F 'for most titanates; in Chelate titanate for use above 700 F '. KR-1355 can be used to avoid the curing gel of alkyd paint. 2. How to use As mentioned above, when the polymer and the coupling agent are determined, inorganic substances commonly used as fillers include calcium carbonate, calcium sulfite, talc, mica and glass fiber. Because of the difference between titanium and silicon coupling agents, the choice of fillers is also different. Silicon series Silica, glass and bauxite are effective; asbestos is ineffective Titanium dioxide, iron oxide, and completely ineffective are calcium carbonate, calcium sulfate, barium sulfate, and carbon black. Titanium series: the effect is remarkable: calcium carbonate. Barium sulfate , calcium sulfate, aluminum hydroxide, titanium oxide, zinc oxide, metasilicate, asbestos, etc.; those with certain effects include Mica, glass; poor effect Talc powder, carbon black and wood flour; graphite with no effect 。 (1) amount of coupling agent: The amount of coupling agent used is based on the protons that can be obtained from the contact of inorganic and organic materials in the organic phase, which is determined by the company. These protons react with the alkoxy groups of the titanate and completely replace the alkoxy groups during the reaction. Therefore, when an excessive amount of titanate is added, unreacted alkoxy groups remain, which is unfavorable to the reaction. The addition amount of the titanate is calculated according to the weight percent of the added filler and pigment. In general, an inorganic powder having a specific gravity of 2.7 and a particle size of 2.5 pieces is added with a titanate in an amount of 0.4% of its weight. In a polymerization system with a small amount of filler, the amount of titanate added is 0.5% of the amount of filler or 0.25% of the weight of the organic matter, in short, the larger amount is selected. (2) Filler dosage and dispersibility a. Dosage When the coupling agent is added to the filler, the critical volume concentration of the filler will change greatly. The chemical wettability dominates the variation of the chemical critical volume concentration of the filler, while the physical mechanical dispersibility It dominates the change of the physical critical volume concentration of the filler. Fig. 2 shows the filler volume concentration change curve of the mineral oil filled with CaCO3 It can be seen from the figure that the viscosity of CaCO3 increases sharply when it is filled to 40% without surface treatment, so it is usually impossible to fill the polymer with 40% CaCO3. However, after treatment with 0.5% by weight of titanate, the critical point of the volume concentration curve of the filler reaches 65-70. Accordingly, that amount of the fill in the thermoplastic resin after treatment with the couple agent can be as high as 60 to 70%. b. Dispersibility The filler is uniformly dispersed in the resin, which has a direct effect on the strength of the composite. Especially when the filler forms a local "stiff block" in the composite material, the composite material will lose its use value. For a single-screw extruder, the impact strength of the material is 8.9 kg-cm/m2 due to the poor dispersion of the filler in the resin if it is mixed and plasticized once, and it is 8.9 kg-cm/m2 if it is mixed and plasticized twice It reaches 13.4 kg/cm/cm2, which is 50% higher than that of plasticizing once. Not only that, the dispersion of the filler is good or bad, but also directly affects the processing and molding. For example, if 15% of the filler is directly injected without refining, the nozzle will be blocked because the filler does not melt. 90% of the filler and 10% of the polypropylene, after being fully plasticized, can still smoothly pass through the nozzle and fill the mold cavity during the processing. 3. Filling process : In the process of filling modification, the mixing degree of filler and resin determines the key of the modification system. Enhancing the surface affinity of filler and polymer Ensuring the complete action of the titanate cheese is also the key to affect the performance of the complex. The use of titanate coupling agent is generally divided into direct method and pretreatment method. a. Direct method Titanate is added directly to the system and mixed with all the components. The method is relatively simple, and that addition amount of the titanate can be arbitrarily Chan. However, attention should be paid to two problems: one is the feeding sequence, because the titanate and the inorganic filler have a proton abstraction reaction, so in order to use successfully, attention must be paid to the moisture content in the filler and the pH value of the system. If stearic acid is used as a lubricant and then TTS is added to CaCO 3 filled polypropylene, it will fail because of the interaction between TTS and stearic acid. In order to uniformly mix the coupling agent to form a monomolecular film, a diluent may be added and sprayed into a high-speed mixer. The diluent must be a substance inert to the titanate, such as white oil, petroleum ether, methanol, ethanol, and isopropanol. And must wait until the solvent is completely volatilized before use. Another problem is that the processing temperature of the system should be below the decomposition temperature of the titanate. If the processing temperature is higher than the decomposition temperature of the titanate, the titanate will fail due to decomposition. For example, the decomposition temperature of TTS is 210 ℃, while the processing temperature of polypropylene is 1 ~ 210 ℃, so the coupling agent can be decomposed prematurely. At this time, it is necessary to adopt the pretreatment method or fully knead below 210 ℃ until the reaction is complete, and then re-pelletize. After the reaction of the titanate and the filler, the decomposition point is obviously improved. For example,ti6al4v eli, the decomposition temperature of the combination of TTS and filler is 335 ℃, and the processing is not a problem in general. b. Pretreatment method : The advantage of the pretreatment is that the efficiency of the filler and the titanate coupling agent is high. The filler is changed from hydrophilic to hydrophobic and lipophilic through pretreatment. Prevent moisture invasion And that performance of the fill is kept stable. At present, several foreign companies have sold fillers pretreated by titanate. Return to Sohu to see more Responsible Editor:. yunchtitanium.com
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