KR20020066883A - Rubber Compound with Red Mud - Google Patents

Abstract

PURPOSE: Provided is a rubber composition containing a red mud generated as a byproduct of aluminum-producing process, which can overcome environmental problems and reduce a unit cost of rubber article. CONSTITUTION: The mixed rubber composition is produced by mixing 1-80 wt%(based on weight of rubber) of red mud generated in aluminum producing process into the rubber. The red mud is mixed, or pre-reacted, or coated with saturated or unsaturated fatty acid or fatty acid metal salt, fatty acid alcohol, fatty acid ester, fatty acid amide, high molecular resin, or silane coupling agent. The use of coupling agent can improve a dispersibility of red mud, and prevent the degradation of physical property of the red mud.

Description

Rubber compound with red mud {Rubber Compound with Red Mud}

The present invention relates to a rubber composition for reducing the unit cost of rubber and improving specific properties of the rubber composition while solving environmental problems by using red mud as an environmental by-product in the rubber composition. This rubber composition can be used for all rubber products as well as for tires, dustproof rubbers, building materials, and radio wave absorbers.

Red mud is an industrial waste that is inevitably generated during the extraction and production of aluminum hydroxide from bauxite. Its high content of sodium or iron causes problems such as cracking, shrinkage and warping when used as a building material. Therefore, it is impossible to use it as it is, and in the end, it is not economically recycled, and it is used to throw it in mining caves, inexpensive dams, and deep seabeds. Recycling is still being studied, but its utilization is very low. If you look at the patents on red mud, there are more than 100 US patents published, but most of them try to improve process efficiency, and there are very few patents on recycling. US Patent Publications US03886244 (1975.05) and US03886245 (1975.05), such as the case of manufacturing bricks using red mud, and other specific recycling methods are difficult to find. Regardless of the patent, there is an attempt to use it as a floor tile or a building agent, and there is an attempt to neutralize it by treating it with acid to stabilize the red mud, and then discard or recycle it, but there are problems such as secondary pollution, pigments and packaging materials Various attempts have been made to artificial soils, artificial soils, and so on, but specific economic methods have not been suggested. Recently, it has been reported to be effective in artificial reefs (Kim Jang-won, basic research on ceramic artificial reefs based on Red Mud, Master's Thesis, Chonnam National University, 2000.02), but there are still many problems to be solved. As a result, red mud has not yet found economic recycling. The inventors of the present invention, while investigating the economical application of red mud, invented the use of various reinforcing agents and fillers used in rubber products after testing in various ways, with many components similar to red mud. . So far no attempt has been made to use red mud in rubber.

The present invention focuses on the fact that they are relatively fine powders and that the constituents are compounds usable in the rubber industry in order to use red mud having the above-mentioned treatment problems without cost, but rather as a valuable material. By studying the method of using directly or pre-treated in the rubber to invent a method that can be used as an excellent material for rubber products.

All rubber products are designed with suitable properties according to their purpose. To achieve this, the materials contained in the rubber mixture must be well dispersed. Therefore, in order to use them in rubber products, they should be mixed well with rubber, and if possible, the physical benefits should be improved or the economic benefits obtained from addition should surpass the degree of decrease in physical properties. The task is to give rubber and appropriate affinity between them. It should also be subjected to low shear forces whenever possible during rubber processing. Only then will the processing energy be small and the pores become easier. In addition, the vulcanization characteristics are preferably shorter if possible because the time taken from the initial vulcanization start point and the completion time of vulcanization is reduced. Of course, even if these sacrifices are slightly sacrificed, they can be used if they are economical, but they are not desirable.

Hereinafter, the present invention will be described by showing that the red mud is used as it is on rubber or through a separate treatment process through theory and experiment.

[Table 1] Composition of domestic red mud

ingredient Content (wt%) SiO ₂ 15-20 Al ₂ O ₃ 20-25 Fe ₂ O ₃ 30-50 Na ₂ O 7-12 TiO ₂ 5-10 Other 5 ~ 8

Table 1 shows the general composition of red mud produced in Korea. They are made up of a variety of compounds, but first you need to see if they can be used in rubber. First, sodium oxide is a substance that contains about 5 to 6 percent in industrial aluminum silicate, which is commonly used as a rubber compound. In addition, by reacting with fatty acids such as stearic acid present in the rubber to produce a sodium salt has the advantage that the vulcanization rate can be faster. Sodium salts often vulcanize faster than zinc salts produced by reaction with zinc oxide and stearic acid used in rubber. Aluminum oxide, silicon oxide and the like are the main components of fillers for rubber such as kaolin clay and the like. Calcium oxide generally increases the hardness and modulus in styrene-butadiene rubber or butyl rubber, as well as toughens unvulcanized rubber in various rubber formulations, thereby preventing cold flow and improving dimensional retention. Also used to prevent. It also acts as an activator, which is larger than magnesium oxide. Also contained titanium oxide is a representative material used as a white filler of rubber. Ferrous oxide has both high light resistance and heat resistance and is chemically stable, and has a high thermal conductivity, so that a large amount of the ferric oxide is vulcanized to shorten the vulcanization time. In particular, ferrite is used to impart magnetism. However, the presence of other iron oxides that generate oxygen may accelerate the aging of the rubber, so be careful. The materials that make up the red mud are all materials that can be used for rubber. They do not meet the reinforcement of carbon black used as rubber reinforcing agents, but they are generally used as fillers to increase volume or increase unit cost. In order for inorganic reinforcing agents or fillers to be mixed with rubber for good physical properties, the particles must be small and well dispersed. The particle size of red mud is less than 44 µm (325 mesh truncated flour) and 95% or more, and the fraction passed through this is never larger than the average particle size of general fillers. It is possible to produce products with a particle size distribution that is readily available.

In other words, red mud can be used as it is if a slight drop in mechanical properties by itself is not a problem for the finished product. When used as it is, the physical properties are slightly reduced, but the vulcanization time is shortened due to the properties of the above-mentioned compositions and the influence of residual sodium hydroxide, and it is possible to manufacture rubber products having the same hardness and low modulus, and thermal conductivity. It has many advantages, such as the improvement of the resilience and the low elastic resilience, the excellent dust-proofing performance, and the improvement of the electromagnetic wave absorption performance when the magnetic is added. Of course, by using waste, the unit cost of the product is significantly lowered. When vulcanized, the product is almost neutral after the product is completed by a chemical reaction.

Red mud for rubber compounding can be used as it is, but it is better to separate it first and use it sufficiently dry. Most preferably, it is finely separated to 325 mesh or more and the residual moisture is not more than 1%. The amount of red mud can be varied from 1 to 100% of the weight of the rubber to suit the user's purpose. However, in order to maintain proper physical properties of rubber, 5 to 80% is appropriate, and when used for shortening the vulcanization time rather than physical properties, 1 to 10% is appropriate. If the amount of red mud is increased, it is preferable to neutralize it to an appropriate level because it will greatly affect the problem of increasing the residual alkali component in the rubber product and the vulcanization rate due to too much alkali component. As a neutralization method, the reaction with fatty acids is best, but it is also possible to neutralize with other acidic substances. The reaction with fatty acids will be explained later.

However, more preferably, they may be well dispersed in the rubber so that the mechanical properties of the red mud may be pretreated or mixed with the rubber at the same time.

Pretreatment is a method of reacting fatty acids, such as stearic acid, with red mud, which is used as an active agent for rubber and used in the preparation of process aids to aid rubber dispersion, to allow some of the red mud to react with them to form metal salts. .

At this time, the residual sodium hydroxide also reacts with the fatty acid, so red mud is neutral. The red mud, which has been converted to fatty acid metal salt form in part by reacting with fat, is greatly improved in dispersibility during mixing, processability is improved, and mechanical properties are also significantly improved than before treatment. Since the mixing ratio of red mud and fatty acid is about 4 to 1 in weight ratio of stearic acid, the remaining amount of stearic acid reacts without remaining, so about 25% of the weight of reamer mud is generally used, but since stearic acid is added to rubber, This can be added or subtracted. Suitably it is preferred to use at least 20% stearic acid.

However, when the amount of red mud used is high, the concentration of fatty acids remaining without reacting with the red mud should not be high, so it is necessary to use more than 30% stearic acid.

Another method is to pretreat the surface to be coated with a coupling agent to increase the molecular affinity between the inorganic material and the rubber. Various coupling agents can be used here. Such coupling agents include polysulphidic organo silanes having two functional groups, vinyl trichloro silanes having vinyl functional groups, amino silanes such as gamma aminopropyltriethoxy silane, and epoxy such as gamma-glycidoxypropyltrimethoxysilane. Silane, methoxy silane having a methacrynooxy functional group, and the like can be used. In particular, sulfideic silanes may be the easiest to use, such as gamma-mercaptopropyltrimethoxy silane, proprytari polysulfide silane, bis- (3- {triethoxysil} propyl tetrasulfane, proprietari disulfide silane The back belongs to this.

Those having a methacrynoxyl substituent include gamma-methacryoxy propyl trimethoxy silane, gamma-methacryoxy propyl methyl dimethoxy silane, gamma-methacryoxy propyl methyl diethoxy silane or gamma-methacrine Cipropyl trioxy silane and the like. They may vary slightly depending on their functionality and molecular size, but they can usually be treated by wet or dry mixing a weight of 0.5 to 10 percent of the amount of red mud. Preferably, a wet surface treatment of 2 to 8 percent and complete drying are best used. If unavoidable, these coupling agents are mixed with rubber at the same time, but they have some effect, but they are difficult to be dispersed evenly, and the effect is reduced by the influence of carbon black mixed together. Increasing the amount is less effective than the pretreatment method.

Another method of use is to improve the dispersion by simultaneously mixing and mixing the above-mentioned fatty acid, a metal salt derived from a fatty acid, a fatty acid ester, an alcohol, an amine or the like, and a rubber formulation process aid when mixing with rubber. Can be. At this time, the added fatty acid is an amount added to the amount of fatty acids originally required by the rubber product may vary depending on the amount of red mud used. It is recommended that the amount used is 0.5 or more with respect to 100 of the rubber weight, and the maximum amount should not exceed 30% of the weight of the red mud. For the other rubber processing aids except fatty acids, it is recommended to use 0.5 to 10 based on the weight of rubber 100. Most preferably, about 1 to 5 percent of the weight of rubber is optimal in most cases.

The following describes the contents of the invention by showing some usage examples.

Table 2 Example of Rubber Using Red Mud (phr)

Mixing step Material used Synthetic rubber basic formulation Example 1 Example 2 Example 3 Example 4 Stage 1 Synthetic Rubber (SBR) 100 100 100 100 100 Zinc oxide 3 3 3 3 3 Stearic acid One One 0 One One Carbon black 50 50 50 50 50 Red mud 0 8 8 Red mud salt 10 Process 2 Red Mud + Coupling Agent 8.4 2 steps 1st mixture 154 162 163 164 162.4 brimstone 1.75 1.75 1.75 1.75 1.75 Accelerator (TBBS) One One One One One

Table 2 is a case of mixing various types of red mud based on the basic formulation of styrene-butadiene rubber which is often used for rubber testing. Example 1 is a case where only the red mud is mixed, Example 2 was neutralized by heating and mixing the red mud with stearic acid to 4 | 1 to form a salt and then mixed, Example 3 was prepared a process aid for the amide rubber Example 4 is a case where the red mud and 5% of bis- (3- {triethoxysilyl} propyl tetrasulfane are dry mixed and surface treated prior to mixing.

[Table 3] Vulcanization Rate and Physical Properties of Compound Rubber

division Basic blend Example 1 Example 2 Example 3 Example 4 Vulcanization Rate 10% Vulcanization Time 6.85 minutes 5.85 minutes 5.65 minutes 5.45 minutes 5.63 minutes 160 ℃ 90% Vulcanization Time 16.3 minutes 14.67 minutes 14.06 minutes 12.5 minutes 14.22 minutes Mooney viscosity (100 ℃) 81.4 88.9 82.6 80.3 102.1 Mooney Scotch t5 (minutes) 32 26.7 26.6 25.8 25.9 125 ℃ t35 (minutes) 41.6 31.6 34.3 32.1 34 Mechanical properties Hardness (Shore A) 65 65 65 66 68 160 ℃ 20 minutes Tensile Strength (kg / cm ² ) 280 260 265 260 290 cure Elongation (%) 400 380 380 360 390

Table 3 shows the vulcanization rates and physical properties of these rubbers, but the results showed that all of them showed that the vulcanization speed could be increased to increase the productivity of vulcanized rubber. Demonstrates a good rubber material. In particular, Example 4 treated with a coupling agent was more preferable because the physical properties of the rubber were improved. In addition, thermal conductivity has been improved by more than 15%, and the material cost per weight of rubber is reduced by more than 5%. There are various ways to use this, but all of them can be used according to the method described above.

By using red mud, which is difficult to treat as industrial waste, as a useful material for rubber, it can solve environmental problems and lower the cost of rubber products to make competitive rubber products. The rubber product thus made has a particularly low vulcanization time, low rebound elasticity, suitable for dustproofing, and the like, and has a low modulus at the same viscosity. In addition, its excellent electromagnetic wave absorption ability and high thermal conductivity can be used for various purposes.

In addition, all can be applied to the rubber, it can be utilized to lower the unit cost of the rubber without significantly lowering the mechanical properties.

Claims (2)

Mixed rubber composition characterized in that the red mud produced in the aluminum manufacturing process is prepared by mixing 1 to 80% by weight of the rubber. In using the red mud according to claim 1, a method of mixing with saturated or unsaturated fatty acids, fatty acid metal salts, fatty alcohols, fatty acid esters, fatty acid amides, polymer resins, silane coupling agents, or the like, or reacting or coating them with red mud in advance. Mixed rubber composition, characterized in that pre-treatment and mixing.