RU2099362C1 - Method of preparing rubber compound - Google Patents

Abstract

FIELD: rubber industry. SUBSTANCE: uncured rubber is mixed, in rubber mixer, with carbon black, sulfur-containing curing group, target additive, and rubber waste. The latter constitutes crushed wastes of polyamide and viscose rubber-covered uncured cords which are preliminarily crushed on rotor tyre-cutter-type crusher with rotation speed 600 rpm using double passage of waste through 6-8-mm clearance between mobile and stationary knives. Further, waste is crushed on muller with 2 rolls, clearance 0.35-0.65 mm, friction 1: 3.08 - 3-4 passages are recommended. The operation is repeated on muller wherein one roll is smooth and the other wavy (3-4 passages). Resultant sheet 3.5-6.5 mm thick is disintegrated on noodle-cutter-type crusher with rotation speed 375 rpm and 0.2-0.3 mm clearance between mobile inclined knives and stationary knife. Disintegration is performed across threads oriented by "calender effect" when treated on mullers. Material is once again treated on mullers and noodle-cutter-type crusher. 2 to 10 weight parts of thus treated waste is mixed with 100 weight parts of uncured rubber. Characteristics of resultant rubber: apparent tensile strength 165-173 kg/sq.cm; elongation 483-510%; hardness 63-66 conditional units, frame run 4700-4850 rm. EFFECT: improved performance characteristics. 1 dwg , 1 tbl

Description

 The invention relates to methods for producing a rubber compound.

 In the production of tires and other products using rubberized cord, waste is inevitably generated, especially when cutting the cord fabric, waste that is not used for its intended purpose, but is processed into products such as mats, livestock mats, roofing, rail linings.

 However, such uses of rubberized cord waste are economically inefficient due to the low cost per unit weight of the products obtained.

It is also known the use of crushed rubberized cords as a reinforcing material for tire rubbers [1]
The disadvantages of this method, developed at the Department of Rubber Technology of the Yaroslavl Polytechnic Institute, are the unreliability of the grinding equipment, based on the principle of quick cutting, and its low productivity, insufficient for industrial use.

A known method of producing a rubber mixture by mixing general-purpose unsaturated rubber with a vulcanizing group, target additives and crushed rubber from worn cooking chambers (in the amount of 4-20 wt. Parts per 100 wt. Rubber), sequential processing of this rubber on a rotary grinding machine or on parallel circular knives to pieces with a maximum size of 200-300 mm and further on crushing and grinding rollers [2]
The aim of the invention is to obtain a rubber mixture using unvulcanized rubber cord waste with a simultaneous increase in the operational quality of products, for example, a pneumatic tire due to the additional reinforcement of lining rubbers and increase the elastic-stiffness characteristics of the tire.

 This goal is achieved by the fact that as rubber waste use waste polyamide and viscose rubberized unvulcanized cords, which are sequentially crushed on a rotary grinder of the type "tire cutter" with a rotor speed of 600 rpm by double passing through the gap of 6-8 mm between movable and fixed knives, then crushed on crushing rollers with two rolls with a gap of 0.35-0.65 mm, friction 1: 3.08 by three or four passes through the gap, processed on the second crushing rollers, in which one the in roll is smooth, the other is grooved with a gap of 0.35-0.65 mm, a friction of 1: 3.08 by three to four passes through the gap, and a sheet thus prepared with a thickness of 3.5-6.5 mm is crushed using a drum grinder of the type "noodle cutter" with the number of drum rotations 375 rpm, with a gap between movable knives mounted on the drum 0.2-0.3 mm, and the sheet is crushed across the threads oriented by the "calender" effect when processing on crushing rollers.

 Simultaneous longitudinal cutting of the blade is allowed by installing a set of circular knives immediately before the transverse cut.

 To ensure reliable grinding, the resulting mass is re-processed and ground on crushing rollers and a rotary grinder of the "noodle cutter" type and packaged in plastic bags, and when mixing the components to obtain a rubber mixture, the prepared rubber cord waste is introduced in an amount of 2-10 wt. hours per 100 wt. including rubber.

To enhance the effect of orientation of the cord along the direction of movement of the web, removed from the rollers, the so-called "calender effect", on the second crushing rollers one of the rolls is made corrugated and the other smooth
(combined rollers).

 During the subsequent grinding of the sheet taken from the combination rollers on a rotary grinder of the “noodle cutter” type, it is directed along the oriented threads to ensure a transverse cut of the threads.

 The choice of the number of passes of rubber-cord waste through a splitter (double) is justified by the fact that with a single pass, insufficient crushing of the waste is ensured, which reduces the efficiency of subsequent processing on crushing rollers.

 Repeated skipping (3 or more times) at the tire cutter reduces the productivity of the equipment and leads to unjustified losses of electricity.

 The choice of the gap on the "cutter" between movable and fixed knives 6-8 mm is optimal for this type of equipment and provides maximum efficiency for grinding rubber cord waste into individual pieces of an indefinite shape, the number of rotor revolutions 600 rpm is also associated with optimal equipment performance and the quality of the milled masses.

 Three-four-fold pass of the crushed mass of rubber-cord waste on two crushing rollers with a gap between the rollers of 0.35-0.65 mm and a friction of 1: 3.08 also provides optimal material preparation for subsequent grinding on a noodle cutter. A smaller number of passes does not provide sufficient sheet preparation and orientation of the threads, a larger number of passes increases the cost of electricity.

 A gap between the rolls of the crushing rollers less than 0.35 mm reduces the productivity of the crushing rollers, and a gap of more than 0.65 mm reduces the efficiency of grinding and processing rubber cord waste on the crushing rollers.

 The choice of the caliber of the sheet with a thickness of 3.5-6.5 mm is justified by the fact that within these limits the maximum cutting efficiency is achieved on a drum grinder of the "noodle cutter" type.

 With a sheet thickness of less than 3.5 mm, the maximum productivity of the equipment is not ensured, with a thickness of more than 6.5 mm, cutting of the sheet is difficult.

 The gap between the inclined knives mounted on the drum and the fixed knife 0.2-0.3 mm is selected taking into account the fact that it is technically difficult to make a gap of less than 0.2 mm, and it is difficult to cut through a gap of more than 0.3 mm.

 The choice of the number of revolutions of the drum within 375 rpm provides high cutting efficiency and does not contribute to the formation of unacceptably high temperatures of the ground mass.

 The choice of the content of recycled rubber cord waste when mixing components to obtain a rubber mixture in an amount of 2-10 wt.h. per 100 wt. including rubber justified by the fact that with less than 2 wt. hours per 100 parts by weight not ensured the use of a significant part of the generated waste, and when the content of the additive is more than 10 wt. hours per 100 parts by weight there are certain difficulties in the technological properties of the mixture and especially when processing on rollers due to complications in the operation when cutting the sheet.

 To enhance the effect of orientation of the threads and fibers along the direction of movement of the web, one roll on two-crusher rollers is made smooth.

 To ensure effective grinding on a drum grinder of the “noodle cutter” type, the web is fed into the gap so that a transverse cut of the threads oriented by the “calendered effect” when processing the crushed mass on crushing rollers is performed.

 Wastes of rubberized polyamide or viscose cord are formed when rubberizing the cord fabric on the calender (specific and other defects), when closing the rubber cord fabric on diagonal cutting machines, as well as in the manufacture of "bracelets" and tire assembly.

 The most common brands of cord used in tire production: nylon: 23KNTS, 232KNTS, 123KNTS-O, 25KNTS, 252KNTS, 35KNTS-O, 352KNTS-O (GOST 24221-80 nylon cord fabric); viscose: 17В, 172ВР, 233ВР (GOST 24338-80 viscose cord fabric).

 The technological process of rubberizing and subsequent processing of the cord fabric is regulated by the technological regulation N 229Sh-93 for impregnation, heat treatment and rubberizing of the cord.

 The proposed method for producing a rubber compound is implemented as follows.

 The mixture is produced in a rubber mixer RS-270-40 by sequential loading of rubber, target additives, carbon black, recycled rubber cord waste.

Mixing with the upper press down is carried out for 120 s, the temperature of the discharged mixture is 135-145 ^o C, then the mixture enters the granulator and the cooling drum.

The temperature of the granules when fed to the second stage of mixing 40-65 ^o C; the second mixing stage is carried out in a rubber mixer RS-250-24 in order to introduce a sulfur-containing vulcanizing group.

The temperature of the mixture discharged from the rubber mixer RS-250-24 100-105 ^o C; then the finished mixture is processed on an aggregate of three rollers and fed to the calender for rubberizing the cord fabric.

 The introduction of recycled rubber cord waste in the second stage of rubber mixing is allowed.

Characteristics of equipment used for grinding and processing rubber cord waste:
1. Shinorez
The number of revolutions of the rotor 600 rpm
Electric motor LOZ-400 10U2
Electric motor power 132 kW.

2. Crushing rollers Dr 800 550/550
Roll diameter 500 mm; length of the working part of the roll 800 mm; friction 1: 3.08; peripheral speed of rolls:
front 13 m / min;
rear 40 m / min;
electric motor power 160 kW.

3. Machine for grinding rubber cord waste / "noodle cutter" /
Electric motor 4A 160M UZ
The number of revolutions 750 rpm; electric motor power 11 kW; the number of revolutions of the drum 375 rpm

 The scheme of grinding and processing of rubber cord waste is shown in the drawing.

 The principal compositions of the recipes, the test results of the vulcanizates and the results of the operational tests of tires with rubbers made by the proposed method are shown in the table.

Claims (1)

A method for producing a rubber mixture, in which unsaturated rubber is mixed in a rubber mixer with carbon black, a sulfur-containing vulcanizing group, target additives and rubber waste, crushed by pre-treatment, characterized in that polyamide and viscose rubberized rubberized crushed unvulcanized cords are used as rubber waste, which are sequentially crushed rotary grinder type "shinorez" at a speed of 600 ^min-1 by a double pass through gap 6 between 8 mm under with fixed and fixed knives, then they are crushed on crushing rollers with two rolls with a gap of 0.35 0.65 mm with a friction of 1 3.08 by passing 3 to 4 times through the gap, they are processed on the second crushing rollers, in which one roll is smooth, the other is grooved , with a gap of 0.35 0.65 mm, fraction 1 of 3.08, by passing 3 to 4 times through the gap, and thus prepared a sheet of thickness 3.5 to 6.5 mm, is crushed on a noodle cutter with a rotation speed of 375 min ^{- 1} with a gap between the movable inclined knives mounted on the drum and the fixed knife 0.2 0.3 mm, moreover, the sheet is crushed across the threads oriented by the "calender effect" when processing on crushing rollers, and after repeated processing and grinding on crushing rollers and a noodle cutter, the crushed mass is mixed into components to obtain a rubber mixture the amount of 2 to 10 parts by weight per 100 parts by weight rubber.

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