Preparation Of Neoprene Epoxy |PU| Adhesive

1 Preface

The preparation of neoprene epoxy |PU| adhesive has been in our country for several decades. There are nearly 1000 manufacturers of chloroprene rubber epoxy |PU| adhesives, with an annual output of nearly 200kt.

Making the quality of neoprene epoxy |PU| adhesive better and lower cost is the goal pursued by every neoprene epoxy |PU| adhesive manufacturer in these decades.

The preparation method and process of neoprene epoxy |PU| adhesive have great influence on its performance and production cost. It is one of the key technologies for the production of neoprene epoxy |PU| adhesive.

Preparation of 2 chloroprene rubber epoxy |PU| adhesive

2.1 mixing process

Mixing method is the most commonly used method of preparation.

The method is to make chloroprene rubber in cold start-up and degrade the polymer chain through shear force.

According to the three phase characteristics of chloroprene rubber, when the elastic state (temperature >93 degrees), the compound is mixed into the raw rubber in the rubber mixing machine.

The order of feeding is Magnesium Oxide, then antioxidant, and Zinc Oxide.

In order to increase the sol speed, the rubber compound often needs to be cut into small pieces and added into the sol kettle.

The agitator of the sol kettle is stirred by frame or anchor. When the rotational speed is between 60 and 80rpm, the 16 - 20h mixture is dissolved in the solvent, that is, the epoxy |PU| adhesive is made.

According to the technological requirements, Magnesium Oxide can also be chelated with 2402 resin for pre reaction and then mixed with glue to dissolve it.

According to the seasonal variation, the sol kettle can be heated or cooled.

2.2 direct sol method

Direct sol method is also adopted by many manufacturers.

The method is to directly mix and mix small chloroprene rubber raw materials and compounding agents directly in the sol kettle (stirrer for frame or anchor stirring, rotating speed is 60 - 80rpm) and mix and stir 24 - 32H.

Compared with mixing method, this method does not require mixing equipment investment and operation cost and manual operation of mixing equipment.

However, the dry compounding agent directly added to the solvent or glue solution will cause some of the fillers not to be wetted by solvents and not well dispersed.

On the one hand, small particles of filler particles will appear in epoxy |PU| binder; on the other hand, precipitation stratification will occur in the short period of storage of epoxy |PU| adhesive.

At this point, the dry complexes and solvents should be dispersed in a specific device, such as ball mill, and then added to the glue solution, so this method is also called "slurry method".

Magnesium Oxide and resin can also be chelated and then mixed.

2.3 high shear direct sol method

High shear direct sol method has been applied in some coastal areas such as Guangzhou, but it has not been understood, recognized and popularized in other areas.

The characteristics of the equipment are as follows: the ratio of height to diameter is 1.5 - 2: 1, the diameter of the kettle and the diameter of the agitator are 1: 0.6 - 0.9, the rotational speed of the agitator is about 1000rpm, and the agitators are different technical parameters of the conventional colloidal kettle, such as propeller or disc turbine.

The characteristic of this method is that the shear force of the high-speed mixer makes the polymer chain degradation reach the plasticizing effect of neoprene on the plasticator. The heat released during the high-speed stirring process accelerates the dissolution of neoprene, and the Magnesium Oxide and other agents can disperse well under the action of high-speed stirring.

The whole process is only 3 to 5h, and the product is uniform and stable, and the viscosity is between the mixing method and the direct sol method.

Since there is no investment in mixing equipment and operation cost and manual operation cost of mixing equipment, plus the short running time, high production efficiency, low running cost and labor cost, the mixer is more economical.

Magnesium Oxide and resin can also be chelated and then mixed.

In the case of adhesive type high crystalline chloroprene rubber, due to various reasons of production process, some branching and crosslinking phenomena occurred in polymer, that is, the gel part increased, resulting in higher Mooney value (such as some CR244 CR244 and some processed products).

Mixing method can not be used as raw materials for such products. One is that the time of rubber refining is not good enough to master the easy burning, and the two epoxy |PU| adhesive has a deep color.

Direct sol-gel process can not be used as raw materials for such products. Otherwise, the insoluble gels will seriously affect the quality of products.

However, the heat generated by the high shear direct sol method makes the crystallization of polymer clear. The high shear force degrades and dissolves the polymer, and the viscosity of the epoxy |PU| adhesive can be controlled by stirring time, so that the product quality reaches a predetermined value.

The raw materials which can not be directly sol method can be used by high shear sol method.

The excess heat generated during the operation of high shear sol method should be treated by cooling.

3 the necessity of generalized direct sol method with high shear rate.

According to the national standard of "epoxy resin |PU| adhesive for indoor decoration and finishing materials" (GB18583 2001), the content of benzene, toluene or xylene in chloroprene rubber epoxy |PU| adhesive is less than 20%.

The dissolution of neoprene with toluene and ethyl acetate or acetone, gasoline, cyclohexane, hexane and other two or more than two yuan mixture is much different than that of the original two or two yuan solvent mixed with benzene or benzene.

The specific differences are:

1. toluene as an excellent solvent dosage of chloroprene rubber is less than 20%, and the sol time is longer.

2. the viscosity of the epoxy |PU| adhesive decreases.

3. the stability of epoxy |PU| adhesive is poor.

4. increase in production cost.

Combined with table 1, it is known that the preparation of neoprene epoxy |PU| adhesive with high shear direct sol method is the best process.

4 concluding remarks

The high shear direct sol method not only maintains the fluidity of the neoprene epoxy |PU| adhesive, the smooth surface of the coating, the good dispersing of the dispersant, and the good storage stability, but also maintains the appearance of the chloroprene rubber epoxy |PU| adhesive with lighter appearance, higher viscosity of the product solution and more economical production cost. It also brings high production efficiency, lower running cost and lower labor cost, and it can digest the cheap and cheap raw materials which can not be used by mixing method and direct sol method (such as some of the CR244 III and CR244 processing products of some Mooney) to produce high quality products, and the economic benefits are more remarkable.

Therefore, it is worthy of attention and adoption by all neoprene manufacturers.