The hottest cationic latent curing agent

2022-08-01
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Cationic latent curing agent

cationic latent curing agent

when it comes to latent curing agents, people usually think of the names of Japanese companies such as Ajinomoto and ADK. The imidazole adducts of Ajinomoto are really unique. The technical content of polyamide adducts of ADK is also quite good. Their products basically cover the Chinese latent curing agent market. If an engineer who makes one component epoxy adhesive has not heard of the names of these two companies, I am afraid he will be laughed at by others

generally speaking, their curing agents basically belong to the ring opening catalyzed by tertiary amine, and they are cured according to the anionic polymerization mechanism. Generally speaking, when used as a dicy accelerator, the addition amount is 3-5 parts. When used alone, the addition amount is about 25 parts. According to the most ideal condition, it can be stored for one month at 40 ℃. Hehe, this is only in theory. In practice, it is very difficult to do this. Because in the formula, diluents, low viscosity epoxy resins, or additives will reduce the storage stability. These curing agents are dispersive. They are heat initiated, swelled or dissolved in epoxy resin, and the active point contacts with epoxy group for curing. To apply the latent curing agent well, we must first understand the latent mechanism, and everything becomes simple

generally speaking, this kind of latent curing agent has many advantages, but also many disadvantages. According to my own experience, I mainly focus on the following points:

1 In order to achieve rapid reaction, the viscosity of the system increases greatly with the addition of a large amount

2. Short storage time at normal temperature

3. It is a dispersive curing agent. Due to the influence of dissolution kinetics, a small amount of it must be dissolved in the epoxy resin during storage, changing from dispersed phase to continuous phase. If the system requires high convective denaturation, the impact is very large, and the storage stability cannot be guaranteed. It is necessary to find other methods

4. The use of diluent is limited

5. Some latent curing agents have strong carbon nitrogen triple bonds, which have a great impact on some metals. If functional metals are added to the system, their functionality will be reduced. (for those who are interested, please refer to relevant data)

in conclusion, engineers naturally think of finding a curing agent that can dissolve epoxy resin. The addition amount is required to be relatively small, and the initiation speed of medium and high temperatures should be fast. This is also some consulting I often receive. There are also higher requirements. A customer hopes to operate at 70 ℃ for one hour, but requires curing within 150 ℃ and 150 seconds, etc

according to these requirements, we naturally think of cationic curing agents. The first thing we think of must be boron trifluoride series, boron trifluoride amine latent curing agents. From the point of view of curing, although the curing time is not very fast, at least it can meet the requirement of dissolving in epoxy resin. However, this series of curing agents has a very big disadvantage, which many engineers do not want to choose. It is very easy to hydrolyze and is not very popular

in foreign countries, there are many kinds of heat initiated cationic latent curing agents, but each has its own characteristics. Only by mastering its reaction process can it be used freely. I have asked for several cationic latent curing agents in some companies in Japan. They are closed hexafluoroantimonic acid series. The curing speed and storage stability are very good. However, there is a drawback. During heat initiated curing, a gas will be released (the Japanese say it is a monomer). This monomer has a great impact on the growth of the curing chain. For example, each part has its own effect. When cured in a closed system, this monomer cannot volatilize, It will inhibit the growth of chains and cannot form polymers, which is what many people call non solidification. Later, a friend of mine got some samples of cationic curing agent in Germany, which is Lewis acid containing arsenic. Hehe, this thing has good curing speed and storage stability, and there will be no gas emission. However, I am useless when it comes to arsenic

according to the market demand, the start-up application materials have introduced several types of heat initiated latent curing agents, of which icam-8409 and icam-8416 are the most characteristic and representative. Icam-8409 is also a closed Hexafluoroantimonate. Hehe, this latent curing agent has no volatile during the curing process, so there is no need to be careful about the chain growth. At the same time, the addition amount is small, and it can cause curing at 80 degrees. In addition, the cured product has good toughness, low curing shrinkage and fast curing speed (it can be done in a few seconds). These characteristics are unmatched by Traditional Anionic latent curing agents. Low metal content, non corrosive solidification, specially designed for electronics and microelectronics, so engineers should not worry about the so-called electrical performance and corrosion performance of components and parts, and storage stability should hardly be considered (I made a product, which was put at 40 ℃ for a month, and the viscosity did not change)

icam-8416 is even higher. The initiation temperature of this curing agent is 100 ℃, that is, the storage stability is longer than that of icam-8409. It does not contain metal. Of course, there must be no volatile during the curing process

special reminder: as a friend of UV curing, you can also choose these cationic curing agents in 1996, which can cooperate with photoinitiators to achieve dual curing

warm tips: the heat initiated cationic latent curing agent requires high professional knowledge in the use process, and there are relatively few domestic literature reports. You can refer to the mechanism of photoinitiated cationic curing

cationic latent curing agent (continued 1)

in the eyes of the older generation of R & D engineers, the cationic latent curing agent has many shortcomings, especially the water resistance, due to the manufacturer's investment in packaging machinery. Indeed, the familiar cationic latent curing agents in the market are all boron trifluoride amine cationic latent curing agents, needless to say, even Bian amine ones are not very popular, whether they are stored separately or the film performance after curing. A friend of mine once purchased a boron trifluoride curing agent. When the samples arrived at the factory, they were all deliquescent. If the latent curing agent is used to cure the epoxy resin, after the curing, after the water boiling test (only 1 hour), all the coatings will bubble, ha ha! With this performance alone, the application in electronic packaging materials is limited, and a PCT experiment will be made into a prototype. In addition, this kind of material is not designed for electronic materials, so its free acid content is not well controlled. Under the condition of heating, it has to be considered whether it will corrode metal components. Of course, for the comrades who only do the copycat market, everything is possible with the heart that as long as they can solidify. Therefore, the raw material technology has been supported for so long, and the most comrades are concerned about the curing speed and storage temperature. Few people will communicate about the curing kinetics, how to control the reaction kinetics, reaction kinetics and thermodynamics, such as how to control the reaction speed, how to initiate the chain, how to transfer, and why to terminate

cationic latent curing agent (continued 2)

according to the above two articles, it basically explains the unique advantages of ICAM series cationic latent curing agent (thermal initiation). As a research and development engineer, it is very important to understand why a certain raw material should be used. There are only three thousand weak water, and only one scoop should be taken. In many cases, the difference between high-level engineers and some engineers who need to improve their ability is here, Some engineers are very keen to find curing agents all over the world. As long as they are curing agents, they all want to find samples for experiments. Hehe, if the experimenters who follow such engineers are the most unlucky, they are tossing about every day. I have seen many excellent engineers. When they choose a raw material, they have to do a lot of preparatory work. At least in theory, they have to find out why to use it. Although they often fail, the probability of failure is much smaller. The experimenters who follow such engineers are very happy. They can not only learn some methods to analyze and solve problems, but also have a much smaller workload, Moreover, engineers will basically accompany you to do experiments because they care about the experimental results and hope to compare the experimental values with the theoretical values

I. reaction mechanism

understanding the reaction mechanism is a basic value for ordinary R & D engineers. The reaction of the cationic latent curing agent of ICAM series (see the above figure) can be seen from the reaction process that no volatile is released. Where m is an epoxy group and R is an alkyl group. According to the reaction mechanism in the above figure, it may be felt that cationic curing epoxy resin is indeed much more difficult than anionic system. At the same time, for experts, it is more conducive to the design of polymer structure. Hehe, everything has two sides. Of course, if you are an expert in the field, it is not enough to understand a certain reaction. You can control a certain reaction and react according to your own assumptions. That is the highest level

II. Mechanical properties after curing

generally speaking, especially for engineers who are deeply "toxic" to boron trifluoride cations, they are always careful that the cured epoxy resin is very brittle. The ICAM series of cationic curing agents have good toughness after curing, which is unmatched by the traditional cationic latent curing agents. In addition, it is also the biggest feature of cationic polymerization epoxy resin. The curing shrinkage is very low, which also explains why many systems that require dimensional stability before and after curing use cationic polymerization

III. cost budget

everything about business involves cost. Ha ha, if it is a national project, it can be ignored (our country is not poor in money). Generally speaking, at present, if the imidazole adduct or polyamide modifier is calculated at 500 yuan/kg (general), if 20phr is added per 100kg of resin, that is 10000 yuan; If it is a cationic latent curing agent, only about 1% needs to be added, that is, only 1kg is needed in 100kg, that is, as long as the unit price is lower than 10000 yuan, the cost is much lower.

in short, there are many temptations for cationic latent curing agents, but it is really difficult. Experts in the field welcome the use of ICAM series 360, which is a light-weight cationic latent curing agent. (end)

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