Rubber Metal Bonding – Cobalt Salt Detail
Cobalt salts are substances consisting of cobalt ions and acid roots, which can also contain a certain percentage of other ions. There are many different kinds of cobalt salts. There are many types of cobalt salts, such as CoX2, CoF2, CoCl2, CoBr2, CoI2, CoOCo(OH)2, CoCO3, Co(NO3)2, CoSO4 and so on.
1 Introduction
Cobalt salt is a substance composed of cobalt ions and acid roots, which can also contain a certain proportion of other ions. There are many different kinds of cobalt salts. Cobalt salt has CoX2, CoF2, CoCl2, CoBr2, CoI2, CoOCo(OH)2, CoCO3, Co(NO3)2, CoSO4 and many other types.
English name: cobaltsalt
Appearance and properties: Rose red monoclinic crystal.
Melting point(℃): 96～98
Relative density (water=1): 1.948(25℃)
Boiling point(℃): 420(-7H2O)
Molecular formula: CoSO4-7H2O
Molecular weight: 281.15
Solubility: soluble in water, methanol, slightly soluble in ethanol. Cobalt salt
2 Varieties of cobalt salts
Organic acid cobalt salt is a special binder for rubber and brass-plated or galvanized steel wire cord, which can be used alone in the manufacture of high-performance steel wire radial tires and high-load steel wire hoses.
According to the understanding of Huacheng metal network, there are several types of cobalt salts widely used at home and abroad, such as cobalt naphthenate, cobalt stearate, cobalt neodecanoate and cobalt boronylated: commonly used are cobalt naphthenate (cobalt content: 10-11%), cobalt stearate (cobalt content: 9-10%), cobalt neodecanoate (cobalt content: 20-21%) and cobalt boron modified neodecanoate (cobalt content: 22-23%).
3 Cobalt salt dosage
Cobalt salt is used to improve the adhesion of rubber and metal, which has been widely recognized and used in radial tires and steel wire hoses. Cobalt salts can be added directly to rubber alone as a rubber-to-metal bonding enhancer. In addition to the direct use of cobalt salts as a bonding enhancer, many companies use cobalt salts in combination with methacrylate (white) resin bonding systems due to differences in products and bonding technologies of each company. However, whether used alone or in combination, the cobalt content of the adhesive must be controlled regardless of the type of cobalt salt. This is because from the bonding mechanism, if the cobalt ion content in the rubber is too high, it will not only promote the generation of a large number of inactive copper sulfide, but also catalyze the aging of rubber hydrocarbons; while the cobalt ion content is too low, the brass is difficult to generate active copper sulfide with sulfur, so that a good bond cannot be obtained. Considering the performance of the rubber formula itself, adding a small amount (moderate amount) of cobalt salt is beneficial to bonding, but the high ratio of cobalt salt is not only harmful to the adhesion after steam aging, but also has a negative impact on the strong and tensile properties of the rubber after thermal aging.
It is usually recommended that the amount of cobalt salt should not exceed 0.3% of the mass of the rubber hydrocarbon in the formulation, i.e. no more than 0.3 parts of cobalt metal in 100 parts of rubber hydrocarbon. Due to the differences in technology of each company, this dosage is for reference only.
Since the average molecular weight of various cobalt salt binders varies, it is necessary to convert the actual amount of cobalt metal required into the number of parts of cobalt salt binder in the formulation. For this purpose, the actual number of parts of the formulation can be calculated by the following formula.
Number of parts in the formula = number of parts of cobalt metal / percentage of cobalt in the product (the amount of cobalt metal in the formula should be between 0.15 and 0.35 parts)
Example: Calculate the number of parts of RC-B23 (cobalt content: 23%) binder with 0.25 parts of cobalt metal added to the formula.
Number of parts = 0.25/23% = 1.08 parts
Second, several common adhesive enhancer system and features ( y2 p N4 e. ?3 ]’ t7 {. B5 S2 u7 o( f, }
1. Cobalt bonding system 7 Q) B% i( V3 y- r
The organic cobalt salts: cobalt stearate, cobalt decanoate, cobalt naphthenate and cobalt borylate, etc. + B7 m, _, `( ? ?” ?
2. inter, a, white bonding system; k) ]9 l0 T) L+ i1 G
A common adhesive added to the rubber, its composition is resorcinol giving body, methylene giving body and white carbon black. It can bond rubber to fibers, metals, etc.
3. Kaimarock, lek sodium and other coated adhesives) S7 [9 t; c5 O6 v& j. t$ I2 Y5 o
The bonding system for bare steel and rubber bonding effect is more ideal, but the heat resistance is poor, the product due to constant contact with the hot environment and the product itself endogenous heat and loss of due effect. : i, |” O( z- U+ L! B
4. m, A, white – cobalt system2 e8 s! q8 B: D. `& b& Q
There are relevant literature, combined with years of practical evidence, between, a, white system and cobalt salt system combined, the bonding strength remains high after aging in moisture, so it is preferred.
Third, the main varieties of cobalt salt-based adhesive enhancers, the market situation 1 i& n$ s ]” u3 ?0 ?4 Z) `) J” G5 ], G) h# X6 \
Cobalt salt type bonding enhancer includes cobalt stearate, cobalt decanoate, cobalt naphthenate and cobalt borylate four types. Most manufacturers choose cobalt decanoate and cobalt borylate, when using different varieties of cobalt content to calculate the amount of this product added.
1. Cobalt decanoate ( ~* ? & ~5 ~/ M/ e- ]: @’ E: U
Cobalt decanoate is a carboxylic acid type cobalt salt bonding enhancer, cobalt content (mass fraction %, the same below) is 20.5 ± 0.5, softening point 85 ~ 110 ℃. }; V( ?” e4 {‘ }+ j
2. cobalt boride& z4 m+ L* |+ @4 M, S
The cobalt borylate is a borylated carboxylic acid line cobalt salt bonding enhancer with a cobalt content of 22.5±0.5. It contains boron and has good corrosion resistance and flame retardancy. 7 D( c+ d+ ~/ h
3. cobalt stearate cobalt stearate is a single carboxylic acid type cobalt salt, cobalt content of 9.5 ± 0.5, softening point 80 ~ 100 ℃. D( w2 F1 O! `& f$ S
4. cobalt naphthenate2 g3 o&B’. ~0 _- l9 U/ O8 a1
Z cobalt naphthenate for high acid value naphthenic acid and cobalt synthesis products, cobalt content ≥ 10.0, softening point 80 ~ 100 ℃. China’s radial tire industry started late, most of the raw and auxiliary materials required for the production of radial tires also rely on imports to solve, especially cobalt salt bonding enhancer all rely on foreign imports. In order to achieve the goal of localization of radial tires raw materials, the former State Planning Commission and the Ministry of Chemical Industry has organized a series of national “seventh five-year plan”, “eight five-year plan” key scientific and technological research, the initial realization of this series of products localization of this goal. In recent years, with the rapid development of China’s radial tire industry, the market demand for cobalt salt adhesion enhancers has increased year by year, and the total domestic market demand reached 2,500-3,000 tons in 2006. The pace of localization of cobalt salt is also accelerating year by year, but the current imports still account for 60% of the market demand. Fourth, the cobalt salt bonding enhancer bonding mechanism of all the cobalt salt bonding enhancer in the rubber and metal bonding process are not directly involved in the reaction, only to promote the bonding role. Cobalt salt bonding enhancer for rubber and plated brass, galvanized steel wire bonding to promote the mechanism: rubber before vulcanization, with cobalt salt bonding enhancer rubber and plating is simply contact, without any interpenetrating connection; after vulcanization, rubber and plating between the formation of a new material layer, that is, the newly formed metal sulfide layer, neither the chemical measurement of copper sulfide layer and zinc sulfide layer. Since they have the activity to continue the reaction, they can diffuse to the interface layer through the vulcanization bridge with the rubber vulcanization to generate the chemical bonding of the copper sulfide – rubber vulcanization, i.e., the bonding reaction between the rubber and the plating layer is produced. The divalent cobalt ion in the cobalt salt bonding enhancer can promote the growth of copper sulfide on the surface of copper-plated steel wire, which helps to fix the vulcanized rubber on the copper-plated steel wire. % I% f/ J% ^% r7 o) ^
V. Tire retreading process methods Currently, tire retreading methods usually use the traditional hot fluidization method and pre-cure retreading process. The overall technical level of China’s retreading industry is low, still dominated by the traditional thermal retreading method, retreading enterprises, the scale is relatively small. The cost of retreading tires using the traditional retreading method is much lower than that of the pre-curing retreading process. Pre-vulcanization retreading process due to the production of pre-vulcanized tread rubber pressure is much greater than the pressure of hot retreading, so the production of retreaded tires beautiful, tread especially resistant to puncture, good wear resistance, high mileage, and because the tire is vulcanized at low temperature, the degree of damage to the tire body is small, can greatly increase the number of tire retreading, with significant economic benefits. At present, foreign tire retreading has basically completed the transfer from hot curing to cold curing, due to advanced technology, the service life of retreaded tires is close to 100% of the new tires.
Six, cobalt salt bonding enhancer in tire retreading the use of the scope and importance of ” R ‘ + H
1. The scope of use of this product bonding enhancers are widely used in the retreading of radial tires, to promote brass-plated steel wire and rubber bonding between. It is recommended to use cobalt decanoate according to the production of radial tires.0 w+ g( o” X$ X/ ]$ q8 I, O#
R- 2. The importance of this product in the product
The radial tires to be retreaded, according to its degree of damage, most of the carcass has exposed the metal cord, retreading treatment, must involve the bonding between the metal cord and the center pad rubber, which requires the addition of cobalt salt bonding enhancer. Otherwise, after the tire is vulcanized, only the bonding between the rubber is completed, and the bonding strength between the rubber and the metal cord is far from sufficient. The rubber products with skeleton material, skeleton material and rubber bonding is particularly important, especially radial tires, requiring good dynamics, rubber and metal cord bonding is not ideal, not only affect the service life of the retreaded tire, serious cases will cause the violent tire and other malignant consequences.
3. to choose a good quality cobalt salt type adhesive enhancer:
Now there are a number of domestic manufacturers, but the scale of production, technical level varies, due to the choice of raw material grade, production process control means, technical testing and processing methods and many other factors, so that the product of zinc, iron, copper, manganese and trivalent cobalt ions exceed the standard, the product bonding has a great negative impact.
Seven, the use of 7 b0 a” k* m0 p# f/ G! g4 e9 Z, M) y8 Y4 C
1. Preparation of slurry: i:
C will be made in a certain percentage of 120 # solvent oil in the pad film, while the cobalt salt bonding enhancer added to the film by dissolving the quality of 3-5%, and then soaked in the mixer together with swelling, about 24-48 hours, and then fully stirred to ensure that the bonding enhancer fully dispersed in the slurry. In order to improve the pulp efficiency and reduce the loss of solvent, you can add 50-70% of the solvent first, and then add the rest of the solvent after the film is swollen evenly, and stir quickly. The concentration of the glue paste: spraying can be adjusted to 10-15%, brushing can be adjusted to 25-30%. & ^7 ^/ y8 Y/ \ L( d! V+ k
2. Apply the mastic. c
The remaining glue paste should be stored at room temperature and sealed away from fire, and then stirred again for the next use. 2 b’ r2 q r$ G3
3. natural drying drying at room temperature for 30 to 45 minutes, so that the solvent evaporated completely. Residual solvent will cause the bonding place to produce porosity, thus affecting the bonding effect. Coating glue, drying, as soon as possible for vulcanization bonding, generally no more than 2 hours. , y7 c# 7 h4. Adhesive vulcanization + k
This product in the vulcanization stage of high-strength chemical bonding. If the traditional hot vulcanization retreading method is used, the vulcanization temperature is 145~150℃ and the vulcanization time is 45~60 minutes; if the pre-vulcanization retreading process is used, the vulcanization temperature is 100~115℃, the vulcanization time is 150~180 minutes, and the pressure of the vulcanization tank is 0.8Mpa, which completes the retreading process. X) S% V [5 h7 I! V. \ W9 s+ r- x% @9 d7 g; H1 |8 H2 @. The above method, based on my company over the past few years with the rubber industry colleagues service exchange, from the practice of accumulated, because of the impact of metal and rubber bonding many factors, and rubber formulation system, operation process, etc. are related, coupled with the late start of China’s tire retreading industry, we are engaged in this area of experience is insufficient to investigate how to make the process, what operating conditions and equipment conditions, in order to make it To achieve the best bonding effect, we still need to discuss and study together with our colleagues in the rubber industry.
Cobalt salt adhesion enhancer
First, an overview
Cobalt salt adhesion enhancers (hereinafter referred to as cobalt salt adhesives) are direct adhesives for high-strength bonding between rubber and metal, mainly used in rubber products such as steel wire radial tires, steel wire reinforced transportation belts, steel braided hoses and rubber rollers. Cobalt salt binders are used in small quantities in rubber products, but they are very important additives for rubber products with metal skeleton materials and are among the most expensive of all additives. Since cobalt salt binders do not participate in the chemical reaction, but only act as a bonding enhancer, i.e. catalyst, the exact name should be cobalt salt bonding enhancer. Due to the importance of cobalt salt binders in rubber products, the formulation design, manufacturing process, quality control and inspection process of these products need to be especially fine to ensure the superior performance and stable quality of the products and to ensure the provision of high quality cobalt salt binder products to customers.
II. History and status of development of cobalt salt binders
As early as the early 1940s, cobalt resinate and cobalt stearate were used in the production of radial tires of Dunlop and other companies, and later, liquid cobalt naphthenate, which was used as a paint drying agent, was also used as cobalt salt binder. In the mid-1960s, it was noticed that the liquid cobalt naphthenate was a natural naphthenic acid as one of its raw materials, and the components of natural naphthenic acid were particularly complex, with the naphthenic acid content generally ranging from 70% to 80%, and the refined naphthenic acid content only reaching about 90%, while the other components were neutral oil, butter, asphalt and a small amount of esters. Its low boiling part contains neutral oil such as diesel oil, and its high boiling part (above 320℃) has asphalt impurities as high as 15%~30%, these impurities will cause dissolution and destruction to rubber, which is unacceptable to rubber products, so high purity solid naphthenic acid
