Cobalt salt adhesion promoter
1. Overview
Cobalt salt adhesion promoter (hereinafter referred to as cobalt salt adhesive) series products are direct additive adhesives for high-strength bonding of rubber and metal. They are mainly used for steel wire radial tires, steel wire reinforced conveyor belts, steel braided rubber hoses and rubber Roller and other rubber products industry. Cobalt salt-type adhesives are not used in large amounts in rubber products, but they have a huge effect. They are important additives for rubber products with metal skeleton materials, and are also one of the most expensive additives among all additives. Since the cobalt salt adhesive does not participate in the chemical reaction during the bonding reaction, but only plays the role of adhesion promotion, that is, catalysis, the correct name should be cobalt salt adhesion promoter. Cobalt salt adhesives are fine chemical products. Due to their importance in rubber products, the formula design, manufacturing process, quality control and inspection process of this type of product need to be particularly meticulous to ensure superior performance and stable quality of the product. , in order to ensure that we can provide users with high-quality cobalt salt adhesive products.
two. The development history and current situation of cobalt salt adhesives
As early as the early 1940s, cobalt resinate and cobalt stearate had been used in the production of radial tires by Dunlop and other companies. Later, liquid cobalt naphthenate, which was used as a paint drier, was also used as a cobalt salt adhesive. agent. By the mid-1960s, people noticed that one of the raw materials for liquid cobalt naphthenate was natural naphthenic acid, and the composition of natural naphthenic acid was particularly complex. The naphthenic acid content was generally 70% to 80%. After refinement, The naphthenic acid content of PVC can only reach about 90%, and the other components are neutral oil, butter, asphalt and a small amount of esters. Its low-boiling part contains neutral oils such as diesel, and its high-boiling part (above 320°C) contains asphalt impurities as high as 15% to 30%. These impurities will cause swelling and damage to the rubber, which is unacceptable for rubber products, so High-purity solid cobalt naphthenate gradually replaced liquid cobalt naphthenate. In the 1980s, the British company “Manchem” launched a new series of cobalt salt adhesives called “Manobond”, a series of cobalt borate adhesives. In addition to its excellent adhesive properties, it also has the properties of resistance to hot oxygen and It is resistant to heat and humidity, salt water and slows down metal corrosion. It is favored by the international rubber industry and is recognized as a revolution in adhesive technology. In the early 1990s, the French company VAS-SET and the British company Manchem successively launched a replacement product of solid cobalt naphthenate, “cobalt decanoate” (Manobond 740C). This adhesive has excellent adhesive properties and anti-aging properties. All have new improvements and breakthroughs compared with solid cobalt naphthenate. The above varieties constitute a large series of cobalt salt adhesives. Cobalt salt bonding system, m-methyl-white bonding system, m-methyl-white-cobalt bonding system constitute the three major bonding systems in the rubber industry,
It is widely used in the rubber products industry.
Before the late 1980s, our country could not produce such products and relied entirely on imports from abroad. Imported products are expensive. Manobond 680C (cobalt acylate 23) is as high as RMB 480,000/ton, and Manobond 740C (cobalt decanoate) is also as high as RMB 420,000/ton. In order to realize the localization of such raw materials, the former State Planning Commission and the Ministry of Chemical Industry organized the national “Seventh Five-Year Plan” and “Eighth Five-Year Plan” key scientific and technological research. I was fortunate to serve as the leader of the public relations team, leading the team to successfully complete public relations tasks, etc. Effectively adopting foreign standards, we successfully developed the Manobond series of products and achieved the goal of localization. Forcing similar imported products from abroad to significantly reduce their prices. At present, the domestic production capacity of such adhesives can fully meet the needs of the domestic market, and it is imperative to realize the localization of cobalt salt adhesive raw materials. However, although there are more than ten large and small manufacturers of cobalt salt adhesives in China, except for a few manufacturers, most of their products are specious, and their formulation technology and equipment level are extremely low. It is impossible to guarantee the quality and level of the products, and it is impossible to match them. compete with similar foreign products.
three. Manufacturing of cobalt salt adhesive products
Cobalt salt adhesives include cobalt stearate, solid cobalt naphthenate, cobalt decanoate and cobalt borate (23, 16) and other varieties and brands, among which cobalt stearate, solid cobalt naphthenate, cobalt decanoate It is a cobalt diphosphate product with the schematic molecular structure formula: R1-Co-R2
In the formula: R is an organic acid radical, which can be a single organic acid radical or a mixed organic acid radical composed of several organic acids. Cobalt borate has B as the central element.The spatial three-dimensional structure of ��, its structural schematic formula is:
At present, there are usually four methods for manufacturing organic cobalt salts.
1. Metal replacement method
The displacement reaction is carried out directly by active metal powder and organic acid. The reaction schematic formula is:
CO+2HR=COR2+H2↑
In the formula, HR is a monovalent organic acid (the same below).
2. Metal oxide neutralization method
The neutralization reaction is carried out directly from metal oxide powder and organic acid. The reaction schematic formula is:
COＯ＋2ＨＲ＝CORＲ＋Ｈ2Ｏ
3. Metal hydroxide neutralization method
The metal is first made into hydroxide CO (ＯＨ)2, and then neutralized with organic acid. The reaction diagram is:
CO (OH)2+2HR= CO R2+2H2O
4. Metal salt metathesis method
First, the organic acid is made into sodium soap, and then the metathesis reaction is carried out with the metal salt. The schematic reaction formula is:
2NaR+Co2+=CoR2+2Na+
At present, the metal hydroxide neutralization method is mainly used in China to produce a series of cobalt salt adhesive products.
In this process, cobalt ions are first precipitated into cobalt hydroxide or basic cobalt carbonate, and then excess alkali and the generated sodium salt are rinsed away, dried and powdered before use. Because divalent cobalt ions are stable under acidic conditions (ionic state), but quite unstable under alkaline conditions, they are easily oxidized to trivalent by oxygen or oxidants in the air, and trivalent cobalt cannot react with organic acids. , it will become impurities (insoluble matter) entering the product and affecting product quality. Therefore, keeping the valence state of cobalt stable during the powdering process is one of the key technologies. The DCS fully-automatic controlled rotary flash evaporation system can reduce the moisture content of the cobalt hydroxide filter cake from 75% to less than 5% in about 3 seconds, and collect it as cobalt powder of more than 200 mesh. As a raw material for the synthesis of cobalt salt adhesives, trivalent cobalt is effectively controlled to less than one thousandth to ensure the quality of adhesive products.
The prepared cobalt powder and various organic acids and borate ester intermediates given according to the formula are synthesized in the reactor to obtain the required cobalt salt adhesive product. During the entire synthesis process, the main parameters are such as: various liquid materials The amount of feed, temperature, pressure, vacuum, reaction time, etc. at each stage of the reaction are automatically controlled and recorded by the DCS control system to ensure the controllability and stability of the product quality of each kettle.
six. Product quality judgment methods
Due to the importance of cobalt salt adhesives in rubber products, it is very important to conduct detailed quality inspections on the cobalt salt adhesive products used. Only cobalt salt products that fully meet the standards can guarantee the physical and chemical properties of the rubber. . Although each company has similar corporate standards, and there are industry standards for cobalt boroacylate 23, products that meet the standard indicators are not necessarily good products. We suggest that in addition to testing according to conventional indicators, some simple internal control judgments can be added Method:
①Judge from appearance
The degree of borylation reaction of cobalt borylate is a key indicator of product quality. Whether the borylation reaction can be fully reflected from the color, cross-section condition and crispness of the product. For a good cobalt borate product, the color of the product is dark blue. If the color of the product is blue with red, it means that the product is not fully dehydrated and the boric acid reaction is definitely not good. The cross section of the product should be bright and smooth, like a mirror. If the cross section is hairy or dark, it indicates that the borylation reaction of the product is incomplete. If there are many pores in the cross section of the product, it means that the product is not fully desolvated; if there are obvious small particles in the cross section, it means that the early reaction of the product is incomplete, and the borylation reaction is certainly not good. The crispiness of a product reflects the degree to which the product reacts completely and how well the product disperses during use. Products with good crispness can be easily crushed into beautiful blue powder by hand, while products with poor crispness cannot easily become powder when crushed by hand. In severe cases, they will be crushed into small balls or strips. The product has a shape, is sticky, and is dark in color. Such a product must have poor usability and dispersion properties, and it is also prone to agglomeration during packaging, storage and transportation.
②Discrimination based on heptane solubility
A good cobalt borate product is easily soluble in n-heptane. The solution is beautiful blue-purple, clear and transparent, and no Tyndall phenomenon occurs when irradiated with beam light. Products with added heptane insoluble matter should also be like this after the insoluble matter is separated by a centrifuge. At the same time, the separated insoluble matter should be an off-white powdery substance after being washed with heptane and insoluble in dilute sulfuric acid and hydrochloric acid. Bad cobalt borate products dissolve very slowly in n-heptane, and the solution is turbid and opaque; after centrifugation, the insoluble matter turns pink or black-red, and the amount is large. Use dilute sulfuric acid or hydrochloric acid water bath to heat and dissolve, and the solution turns pink. Color, the precipitate is off-white or earthy yellow, which indicates that during the manufacturing process of the product, due to poor activity of cobalt powder or high trivalent cobalt, the reaction between cobalt and organic acid was not fully completed, and of course the boric acylation reaction was not completed. Not good, the performance of the product can be imagined.
③Distinguish from the melting point
Cobalt diphosphate products are amorphous substances, and their test indicators have a softening point. Cobalt borate is not an amorphous substance. It does not have a softening point, but it does not have a constant melting point like typical crystalline substances such as metals. Cobalt borate is a crystalline substance with a relatively concentrated melting point area. The melting point areas of good cobalt borate 23 and 16 products measured by a microscopic melting point instrument are around 120°C and 110°C respectively. . A product with a melting point that is too high reflects that the reaction of the product is not complete enough and the dispersibility is poor when used; a product with a melting point that is too low may indicate that the product is a mixture of cobalt diphosphate and other organic and inorganic cobalt salts. Not a uniform cobalt boroacylate product.
For cobalt diphosphate products, in addition to melting point inspection, also refer to the above method for inspection and judgment
�Cobalt products are amorphous substances, and their test indicators have a softening point indicator. Cobalt borate is not an amorphous substance. It does not have a softening point, but it does not have a constant melting point like typical crystalline substances such as metals. Cobalt borate is a crystalline substance with a relatively concentrated melting point area. The melting point areas of good cobalt borate 23 and 16 products measured by a microscopic melting point instrument are around 120°C and 110°C respectively. . A product with a melting point that is too high reflects that the reaction of the product is not complete enough and the dispersibility is poor when used; a product with a melting point that is too low may indicate that the product is a mixture of cobalt diphosphate and other organic and inorganic cobalt salts. Not a uniform cobalt boroacylate product.
For cobalt diphosphate products, in addition to melting point inspection, also refer to the above method for inspection and judgment
