Development of steel barrel sealant

Development of steel barrel sealant

Cong Lihua

【Abstract】The steel barrel sealant developed from latex as the main material is described. The reaction mechanism and process flow were introduced, and the effects of pH value, solid content and viscosity on the performance of the sealant were discussed.

Key words: steel drum; sealing; sealant; latex

1 Introduction

Steel drum sealant is an essential filler to prevent steel drum leakage. At present, the production level of the steel drum manufacturing industry has been quite high. The use of high-quality sealant to improve the sealing effect is a good way to further improve the quality of steel drum storage and transportation. China has only begun to develop steel barrel sealing sealant since the 1980s. Although it has developed greatly, there are still many problems. With the development of import and export trade, China's packaging industry has introduced foreign barrel production lines, and the requirements for sealants are getting higher and higher. In order to meet the needs of the market and further improve the quality of China's steel drum packaging, our hospital should develop according to the requirements of the majority of manufacturers. The development of steel drum sealant resistant to various solvents.

2 Experimental part

2.1 Reaction mechanism

(1) The accelerator reacts with zinc oxide to form a zinc salt

2R3C-SH+ZnO→(R3CS)2Zn+H2O

(2) The reaction between zinc salt and sulfur to form disulfide

(R3CS) 2Zn+S→(R3C)2S2+ZnS

(3) decomposition of disulfide to form active sulfur

(R3C)2S2→(R3C)2S+S [activity]

(4) Sulfuration reaction

The above steps are carried out in a latex state and are a solid-solid phase reaction. So this is a more complicated reaction process. In order to make the above steps proceed smoothly, it is necessary to fully grind and disperse various additives, and then through the diffusion of the liquid phase, the particles of the auxiliary agent are adsorbed on the surface of the latex particles, and further penetrate into the interior of the latex particles. The vulcanization reaction may occur at a temperature. Therefore, the surface properties of the latex, the particle size and its distribution, the performance and dispersion of the auxiliary agent, the speed of the particle adsorption aid and the diffusion rate of the auxiliary agent have an important influence on the vulcanization process.

Although the factors affecting the vulcanization process are many, the factors affecting the contact speed of the solid-solid phase are the key factors, namely the fineness of the auxiliary, the necessary agitation, the appropriate vulcanization temperature and time.

The solid builder is ground prior to compounding and made into an aqueous dispersion. The fineness of the grinding is measured by the sedimentation speed, and it is generally qualified that there is no obvious delamination within 8 to 24 hours. The grinding time is generally 8 to 100 hours.

Stirring is necessary to ensure uniform diffusion speed and reaction temperature. The stirring speed is too fast, and it is easy to produce a gel and break the milk. If it is too slow, the above purpose is not achieved. Generally, it is preferably 10 to 70 r/min.

The vulcanization temperature interacts with time. The higher the vulcanization temperature, the faster the vulcanization rate and the shorter the vulcanization time. Generally, the temperature is controlled at 40 to 80 ° C for 4 to 10 hours.

2.2 Process

The process flow is as follows:

We use this process to produce, the product meets the quality standards, and the process is reasonable and feasible.

3 Results and discussion

3.1 pH

The sealant uses latex as the main material. When the pH value is less than 9, the latex is unstable, and it is easy to produce particles or even demulsification during the vulcanization process. To ensure latex stability, the pH must be adjusted to greater than 9. However, the pH is too high, and the use of ammonia is high, which is irritating to the user. Therefore, the pH is controlled within the range of 10 ± 0.5.

3.2 degree of vulcanization

The degree of vulcanization has a great influence on the solvent resistance of the sealant. As the degree of vulcanization increases, the solvent resistance of the sealant increases. The solvent resistance is best when the degree of vulcanization of the sealant reaches the end.

3.3 Solid content

Solid content is an important indicator of sealant. The solid content is low, the film shrinkage is large, the filling is not full, affecting the sealing effect, and the drying speed of the sealant is also slow, which affects the production efficiency. Therefore, the higher the solid content, the better. Considering the price factor and the impact on other performance indicators, the sealant should have a solids content greater than 40%.

3.4 Viscosity

In sealants, viscosity is affected by many factors, but the most important is the thickener. Different thickeners have different effects on the viscosity, but the viscosity gradually increases with the increase of the amount of the thickener. See Table 1.

Table 1 Effect of the amount of thickener on viscosity

In the user's use, the viscosity generally has certain requirements, the viscosity is too small, easy to splash, runny; the viscosity is too large, the fluidity is not good, affecting the production speed, the dosage is also increased. Therefore, in order to ensure that the sealant has both a suitable viscosity and good fluidity, the viscosity is controlled between 60 and 360 mPa·s.

3.5 Solvent resistance

The sealant test piece was immersed in various solvents for 120 days, and the dissolution of the test piece was observed. It can be seen that the sealant is basically used in various solvents (benzene, 80# gasoline, dichloroethane, acetone, ethanol, ether, ethyl acetate, glycerin, ammonia, 30% NaOH solution, 36% acetic acid, glacial acetic acid, etc.). insoluble.

The sealant does not dissolve in the solvent, but has a certain degree of expansion, and the plugging property is good. Even if the steel drum is slightly deformed by the collision, it will not leak, thereby improving the quality of the steel drum package. The data is shown in Table 2.

Table 2 The degree of expansion of the sealant in the solvent

3.6 physical properties of dry film

For the sealant, the stronger the strength of the dry film, the stronger the bond strength, the stronger the bond, the higher the elongation and the better the elasticity. The better the sealant's ability to adapt to the deformation, the better the sealing effect on the steel drum. .

3.7 Storage period

The storage period of the sealant is 3 to 6 months. During the storage period, the viscosity increases slightly with the increase of storage time, but it is still within the requirements of the index and can meet the requirements for use.

3.8 Toxicity test

The acute oral LD50 of sealant mice is >1000mg/kg. According to the acute toxicity classification standard of chemical substances, the sealant is an actual non-toxic substance and can be used for sealing food packaging drums.

3.9 Comprehensive performance and application test

Table 3 lists the various performance indicators of this sealant. And compared with a sealant produced by a latex factory. The sealant products have been tested in airtight, water pressure, solvent resistance, etc. in Jinan, Linyi, Yantai and other barrel factories, which can fully meet the production requirements, and the users are satisfied with the quality and performance of the products.

Table 3 Sealant performance indicators

4 Conclusion

(1) The production process of sealant is simple, the product quality is stable, and there is no pollution of three wastes in the production process.

(2) The sealant does not contain organic solvents, has a high solid content, and has a small shrinkage after dry film, full filling, and good solvent resistance.

(3) The sealant is non-toxic and can be used for sealing food packaging drums.

(4) The sealant is tested by the manufacturer, the effect is good, and the user is satisfied.

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