EA001545B1 - Process for modifying the surfaces of rubber crumbs - Google Patents

Abstract

A process for modifying the surfaces of rubber crumbs by ozonization, characterized in that ozonization of rubber particles 0,5-0,7 mm in size is carried out by ozone and oxygen mixture with volumetric concentration of ozone being from 1% to 5% during 10 to 40 minutes with continuous agitation, the ozone-containing mixture is removed through a rubber crumb layer to be ozonized.

Description

The invention relates to the rubber industry, namely, to the technology of modifying rubber crumb and can be used, for example, in the production of bitumen mastics in road construction, as well as in the production of various rubber products (RTI), such as tires, conveyor belts and t dd

Rubber crumb in the rubber industry, mainly obtained from waste recycled rubber mechanical grinding (Drozdovsky VF Obtaining crushed vulcanizates. Rubber and rubber, 1993, No. 5, p. 44-50). However, the resulting rubber crumb cracked in storage conditions, which then complicates the process of its processing into finished rubber and bitumen mastic, leads to deterioration of the technological properties of rubber crumb and, consequently, degrades the quality of the finished rubber and materials obtained from it. Therefore, in the rubber industry there is the problem of improving the technological properties of crumb rubber, including its caking.

The known method of surface modification of polymeric materials by a stream of neutral atomic oxygen, obtained by glow discharge (8I A, 877394, Ο01Ν 1/32, 1981). However, this method is not economical and can not be used for surface modification of large quantities of crumb rubber in industrial volume. Any information on caking rubber crumb in the named source is not given.

It is also known that when exposed to ozone, the surface of rubber is ozonized (Chemical Encyclopedia, M., scientific publishing house of the Great Russian Encyclopedia, 1992, p. 334-335). This process is used in some well-known methods of processing rubber (VI C1, 2111859, B 29B 17/00, 1998; CI C1, 2123425, B 29B 17/00, 1998). However, information on caking rubber crumb, obtained from the RTI according to the above-mentioned known methods, in one of the known sources is also not given.

The closest in technical essence to the present invention is a method of surface modification of crumb rubber by ozonating it for 1-6 hours (8A, 138034, 1962). The rubber crumb modified according to this method with oxygen-containing groups is used as an initiator in the polymerization process of polyesters. Data on the caking of the most modified rubber crumb in the description of this invention is not given.

The technical task that this invention is directed to is to reduce the caking of the rubber crumb to improve its processability into rubber products and materials while improving their quality.

This technical problem is solved by a method of modifying rubber crumb by ozonization, and according to the invention, ozonation is carried out for less than one hour.

In this case, if necessary, before ozonization, the rubber crumb is additionally subjected to mechanical grinding effect to the specified dimensions.

Ozonation of crumb rubber for one hour or more can lead to over-oxidation of its surface.

The invention is illustrated by the examples below, a table in which comparative figures are given characterizing the caking of the rubber crumb before and after its modification by the method according to the invention according to the examples given, and also FIG. 1, which schematically shows a batch device for modifying rubber crumb used in the examples.

The one shown in FIG. 1 to illustrate the method according to the invention, the device of periodic action consists of a working chamber 1, equipped with nozzles 2 and 3, intended, respectively, for supplying an ozone-containing gas mixture to the inside of the working chamber 1. The device also contains a device 4 for loading the initial rubber crumb inside the working chamber 1 and a device 5 for unloading the modified rubber crumb from the working chamber 1, for example, made in the form of an auger. Before the device 4 for loading the original rubber crumb, a known means for mechanical grinding of the original rubber crumb can be additionally installed.

Inside the working chamber 1 mounted paddle stirrer 6 for mixing rubber crumb in the process of ozonation. In the process of mixing during the rotation of the blades around the axis of the agitator, rubber crumb is poured from one blade to another.

The spent ozone-containing mixture passes through the layer of initial rubber crumb loaded by means of device 4, where its partial surface modification begins to occur, and ozone is also burned before it is removed from working chamber 1.

Below are examples of the method according to the invention.

Example 1

Rubber crumb 0.7 mm in size is loaded into the working chamber 1 of the device shown in FIG. 1, through the device 4. Through the pipe 2 inside the working chamber 1 serves ozone-air mixture with a volume concentration of 1% ozone in it.

Ozonation is carried out for 40 minutes while stirring the rubber crumb with a paddle stirrer 6, and during the mixing process the crumb rubber is poured from one blade to the other when the paddle stirrer rotates around an axis. At the end of the process of surface modification, the rubber crumb is discharged from the working chamber through the screw 5, and the spent ozone-containing gaseous mixture is discharged from the working chamber through the nozzle 3. At the same time, it first passes through the layer of initial rubber crumb loaded by means of adaptation 4, where the partial surface modification process begins crumb rubber and at the same time achieves ozone before removing it from the working chamber 1. The table below shows the comparative figures spruce, characterizing the caking of the original and modified crumb rubber.

Caking rubber crumb was evaluated by the angle of external friction before storage and after storage for 10 days.

Table

Original Modified Before storage After storage 0.5 mm 34 26 26 0.7 mm 36 27 27

Comparative indicators of the caking of the original and modified crumb rubber are presented in the table.

As can be seen from the tests presented in the data table, the rubber crumb modified by the method of the invention is characterized by good flowability, unlike the original rubber crumb.

Thus, the method according to the invention allows to reduce caking rubber crumb under conditions of storage, transportation and dispensing and thereby improve its processability into rubber products and materials while improving their quality.

Claims (1)

CLAIM The method of surface modification of rubber crumb by ozonization, characterized in that the ozonization of crumbs with a size of 0.5-0.7 mm is carried out by an ozone-oxygen mixture with a volume concentration of ozone in it from 1 to 5% for 10-40 minutes with constant stirring, while removal of ozone-containing mixture is carried out through a layer of crumb rubber to be ozonated. Example 2 The process of surface modification of rubber crumb 0.5 mm in size is carried out with an ozone-oxygen mixture with a volume concentration of 5% ozone in it for 10 minutes in the device shown in FIG. 1, the effect of which is described in detail in Example 1. Mechanical grinding effect, with the only difference is that before entering the working chamber 1 for ozonation, the original rubber crumb is subjected to grinding effect at the final stage of the process of the processing line of the RTI or on a specially installed grinding device.