KR20010088837A - Method for treatment of vulcanized rubber - Google Patents

Abstract

According to the invention,

Providing a sulfuric acid solution dissolved in a fatty acid or ester or salt thereof;

Mixing the solution with particulate vulcanized rubber; And

A vulcanized rubber treatment method is provided that comprises heating the mixture for a period of time substantially at a temperature and pressure sufficient to de-vulcanize the rubber.

Description

Processing method of vulcanized rubber {METHOD FOR TREATMENT OF VULCANIZED RUBBER}

Sulfur vulcanization of rubber polymers is a chemical process that forms three-dimensional networked structures by linking polymer chains, such as through sulfur atoms. Various other vulcanization systems may include processes where the crosslinking is a carbon-carbon bond, a divalent organic radical, or a polyvalent metal. The processes produce vulcanized rubber with increased elasticity and reduced plasticity. In this regard, the vulcanized rubber is usually forcibly shrunk to its original molding after being deformed by some form of mechanical force.

Fundamentally, due to the lack of natural raw rubber, the cost of natural raw rubber continues to increase, and the recycling or recycling of waste rubber has attracted economic interest for a long time. For example, some acid processes are known which utilize rubber to recycle. This process is generally applied to waste rubber treatment where the degree of vulcanization is relatively low and does not contain free sulfur. However, this process is generally not suitable for more highly vulcanized rubber such as hoses, belt materials and tire waste. Moreover, rubbers that have been recycled and used by the acid process usually contain traces of acid, which undesirably quickly deteriorates the rubber. The tensile strength and other physical properties of the rubber recycled by the acid process are usually poor.

Alkali processes that utilize rubber regeneration are also known and are generally believed to provide some advantages over the acid processes mentioned above. However, sulfur contained in the waste rubber is not removed by the alkali process, but rather the bond between the sulfur and the rubber is changed. Unfortunately, after the vulcanized rubber waste is recycled through an alkaline process, the rubber usually loses toughness and elasticity and is usually susceptible to plastic deformation.

The present invention relates to a process for treating vulcanized rubber, in particular waste rubber, and a chemical solution for use in such a process. In particular, the present invention relates to a method for reclaiming and utilizing waste rubber such as rubber scrap from used tires, tire tubing, housings or other waste by devulcanization.

The present invention aims to provide an alternative method for the treatment and regeneration use of vulcanized rubber and the solution used in such a method.

According to one embodiment of the invention,

Providing a treatment solution of sulfur in a fatty acid or ester or salt thereof;

Mixing the solution with the vulcanized particulate rubber; And

A vulcanized rubber treatment method is provided that includes heating the mixture to sufficiently devulcanize the rubber at a sufficient temperature and pressure for a period of time.

Preferably an oil-based softener is added to the mixture before heating the mixture to soften the rubber during processing. Softener addition is particularly preferred when the rubber to be treated is dry. On the other hand, the softener may not be required if the rubber is a relatively early waste. Suitable amount of softener may generally be determined empirically from the type of rubber.

While mixing the vulcanized rubber with the solution and optionally the softener, the mixing vessel is preferably cooled, for example by water cooling. Cooling of the mixture advantageously ensures that the mixture is not sticky and can be mixed thoroughly.

The mixture may for example be heated for a suitable time depending on the degree of vulcanization of the rubber to be treated and / or the particle size of the particulate rubber. However, the mixture is usually heated for about 1 hour to about 8 hours, preferably about 4 hours to about 8 hours.

The temperature at which the mixture is heated is preferably chosen so that the rubber to be treated is not burned. In view of the foregoing, the mixture is preferably heated at a temperature of about 180 ° C to about 200 ° C. Similarly, the pressure at which the treatment is performed may be determined based on the degree of vulcanization of the rubber and may be affected by the selected treatment time and temperature. In a preferred embodiment, the treatment is performed at about 18 kg / cm ² to about 20 kg / cm ² pressure.

The amount of components of the mixture will generally depend on the unique properties of the rubber to be treated. For example, the amount of sulfur and the solution of fatty acids or esters or salts thereof may vary depending on the degree of vulcanization of the rubber. In a preferred embodiment, the mixture comprises about 100 parts particulate rubber, 4 to 6 parts softener and about 2 to 4 parts treatment solution.

The particulate rubber may have any suitable particles. In general, the smaller the particle size, the more effective and more efficient the reaction. In a preferred embodiment, the rubber is a piece of rubber with particles less than 6 mm in size. Most preferably the rubber is a powdered rubber.

The solution of sulfur and fatty acids or esters or salts thereof preferably comprises sulfur and fatty acids or esters or salts thereof in 1: 4. However, the concentration of sulfur in the solution may vary depending on the degree of vulcanization of the rubber. In a preferred embodiment, the fatty acid or ester or salt thereof is an unsaturated fatty acid or ester or salt thereof. More preferably the fatty acid is oleic acid.

The solution is preferably prepared by adding oxygen supplied powdered sulfur to oleic acid heated to about 160 ° C. while stirring the solution. After sulfur is added, usually sulfur: oleic acid 1: 4, the temperature of the solution is raised until the sulfur is completely dissolved in oleic acid. In general, it was found that a temperature of 180 ° C. was sufficient to dissolve sulfur in oleic acid. Alternatively, the sulfur may be added to cold oleic acid followed by heating the solution to dissolve the sulfur.

Thus, the invention also provides a solution for the treatment of vulcanized rubber, the solution comprising:

Fatty acids or esters or salts thereof; And

Contains sulfur

The oil-based softener may comprise any suitable softener. However, in a preferred embodiment the emollient is an aromatic oil. For example, in some embodiments filtered sump oil may be used as an oil-based softener.

The process of heating the mixture may be accomplished by any suitable means. In a preferred embodiment the heating process is achieved in an autoclave, most preferably in a rotating autoclave. For example, "Mexiterm" autoclaves are known to be suitable for this purpose. On the one hand, it is contemplated that the entire process or at least a substantial part of the process may be achieved using a continuous process. In this regard, the treatment process may also include conveying the material to be treated through a number of treatment steps, each of which performs a step in the process of the present invention.

When the heating process is carried out in an autoclave, the mixture is preferably placed in a dish about 10 cm deep. The mixture is preferably evenly spread on the dish to about 5 cm deep.

The mixture is heated or left to cool. For example, cooling may be accomplished with the use of a water cooling system. Once the mixture is cooled, it is transferred to a grinding site where the mixture can be milled, preferably water cooled again. Most preferably the treated rubber is ground several times, for example three times.

Thereafter, the ground rubber is preferably heated to about 130 ° C., for example in an oven. After heating, the rubber is once again cooled and regrind. The regrind rubber is substantially 100% recycled rubber, which may then be made into commercial pellets.

Preferably, the waste rubber treated by the process according to the present invention produces recycled rubber, which may be similar to raw rubber and thus can be used for the production of rubber workpieces. In addition, the regenerated rubber may be revulcanized in the usual way or may be mixed with synthetic or natural rubber as desired.

Preferred embodiments of the present invention will be described in more detail with reference to the following examples, which should not be considered as limiting the invention in any way.

Preparation of Sulfur Solution

1000 g of oleic acid was placed in a cold reaction vessel and 250 g of oxygenated powdered sulfur was added thereto with stirring. The solution continued to mix as the reaction vessel was closed. The solution was then heated between 160 ° C. and 180 ° C. to completely dissolve the sulfur in the oleic acid. The solution is then allowed to cool.

Throughout the heating process, the solution was periodically checked to see if the sulfur was dissolved. Generally, the solution was checked by placing the liquid drop on a glass plate at about 150 ° C., 160 ° C. and 170 ° C. If the droplet was not clear, the sulfur was not completely dissolved. The heating process continued until the liquid droplets on the glass plate became clear and transparent.

When preparing the sulfur solution, care must be taken to discharge or remove all sulfur dioxide gas produced. This may be accomplished through a blower or using a caustic vapour trap.

Waste rubber disposal

1. Rubber devulcanization process

Rubber particles and chemical additives in the car tire piece were appropriately added or subtracted to a specific specification. The components were mixed well in a rotary mixer. The mixed compound was then placed in layers in a device and heated. The result was then ground in a mill with two rolls.

The same procedure was followed for the rubber particles of the truck tire pieces.

2. Preparation of Rubber Samples

The treated rubber was mixed with curatives in the next three steps.

Car tire samples:

(a) 50% devulcanized rubber and 50% unused tire tread (mainly natural rubber).

(b) 60% devulcanized rubber and 40% unused tire tread.

(c) 30% devulcanized rubber and 70% unused tire tread.

Truck tire sample:

(a) 50% rubber treated and 50% unused tire tread (mainly natural rubber).

(b) 60% rubber treated and 40% unused tire tread.

(c) 30% rubber treated and 70% unused tire tread.

The car and truck tire samples were processed in a mill with two rolls and there were no processing difficulties. The treated rubber was mixed with the unused tire stock without difficulty.

The sample was cured under normal curing conditions for truck tires in a compression press.

3. Sample evaluation

3.1 Sample Preparation and Conditions

Test specimens were cut from the cured samples with ASTM D412 Die C and placed at 23 ° C., 50% humidity for 24 hours.

3.2 Test Conditions

Test machine: Lloyd 2000R with computer interface

Testing speed: 500mm / min

Temperature: 23 ℃

Humidity: 50%

Samples tested: 3 for each sample

3.3 Test Results

Average results are summarized in the following table.

Passenger car tires

Sample Inner Diameter (Devulcanized Rubber / Tire Tread Raw Material) Tensile Strength (Mpa) Modulus at 300% Elongation (Mpa) Elongation at break (%) Shore A (a) (50/50) 4.29 2.57 463.6 56.8 (b) (60/40) 4.74 2.76 489.7 56.4 (c) (30/70) 7.23 2.61 702.4 58.0

Truck tires

Sample Inner Diameter (Devulcanized Rubber / Tire Tread Raw Material) Tensile Strength (Mpa) Modulus at 300% Elongation (Mpa) Elongation at break (%) Shore A (d) (50/50) 6.5 3.0 559.4 59 (e) (60/40) 7.2 3.3 586.1 58 (f) (30/70) 9.8 2.7 803.3 61

conclusion

The rubber devulcanization process can produce a product that is compatible with the rubber compound. The performance for these compounds can be optimized taking into account the curing system, polymer form, degree of additive content, degree of sulfur content, and degree of addition of the devulcanized material.

The tests conducted show that 30% of the devulcanized material exiting the airliner tires is included in the tread formulation to be a material having useful properties, ie, significant tensile strength, modulus, elongation and hardness.

These values can be further improved by adjusting the blending. The product properties may vary depending on the actual composition to be cured and the curing conditions.

Unless otherwise stated in the context of this specification and the claims below, the words "comprise or comprise" or "comprising" may include not only the specified members, but also the others. Means.

Those skilled in the art will appreciate that there is room for change and modifications other than those specifically described herein. It is to be understood that the present invention includes all changes and modifications included within the spirit and scope of the present invention. The invention also encompasses any and all steps, properties, compositions and compounds and any combination of any two or more steps or properties mentioned or indicated individually or collectively herein. do.

Included in the above.

Claims (30)

Provided according to the invention: Providing a sulfuric acid solution dissolved in a fatty acid or ester or salt thereof; Mixing the solution with particulate vulcanized rubber; And And heating said mixture for a period of time substantially at a temperature and pressure sufficient to de-vulcanize said rubber. The method of claim 1, The vulcanized rubber processing method wherein an oil-based softener is added to the mixture before heating the mixture to soften the rubber during the treatment. The method of claim 2, The softener is a vulcanized rubber treatment method is an aromatic oil. The method of claim 1, Wherein the mixture is cooled while mixing the vulcanized rubber with the solution. The method of claim 4, wherein And the mixture is cooled by water cooling the mixing vessel in which the vulcanized rubber and the solution are mixed. The method of claim 1, And the mixture is heated for about 1 hour to about 8 hours. The method of claim 6, And the mixture is heated for about 4 hours to about 8 hours. The method of claim 1, And the mixture is heated at a temperature of about 180 ° C to about 200 ° C. The method of claim 1, Wherein said treating is carried out at a pressure of about 18 kg / cm ² to about 20 kg / cm ² . The method of claim 1, And the mixture comprises about 100 parts particulate rubber, 4 to 6 parts softener and 2 to 4 parts treatment solution. The method of claim 1, Wherein the particulate rubber is a rubber piece having a particle size of less than 6 mm. The method of claim 1, The particulate rubber is a vulcanized rubber processing method that is a powder rubber. The method of claim 1, Wherein said solution of sulfur and fatty acid or ester or salt thereof comprises a solution of sulfur and fatty acid or ester or salt thereof in a ratio of 1: 4. The method of claim 1, The said fatty acid or ester or its salt is unsaturated fatty acid or ester or its salt. The method of claim 14, Vulcanized rubber processing method wherein the fatty acid is oleic acid. The method of claim 1, The treating solution is prepared by adding oxygen supplied powdered sulfur to oleic acid heated to about 160 ° C. while stirring the solution and increasing the temperature of the solution until the sulfur is completely dissolved in the oleic acid. Way. The method of claim 16, Wherein the temperature of the solution is increased to about 180 ° C. such that sulfur is dissolved in the oleic acid. The method of claim 1, Wherein the heating step of the mixture is carried out in an autoclave. The method of claim 18, Wherein said autoclave is a rotary autoclave. The method of claim 1, Wherein said method is carried out in a continuous process comprising a number of processing steps. The method of claim 1, After the heating process, the mixture is cooled or left to cool and then the cooled mixture is optionally water cooled and sent to a pulverization site that is pulverized one or more times. The method of claim 21, Wherein the cooled mixture is ground at least three times. The method of claim 21, Wherein the ground rubber is cooled and then heated to about 130 ° C., recooled and regrind. Fatty acids or esters or salts thereof; And A solution for treating vulcanized rubber containing sulfur. The method of claim 24, Vulcanized rubber solution further comprising an oil-based softener. The method of claim 25, The softener is a solution for treating vulcanized rubber, which is an aromatic oil. The method of claim 25, A solution for treating vulcanized rubber comprising about 100 parts of particulate rubber, 4 to 6 parts softener and 2 to 4 parts treatment solution. The method of claim 24, Vulcanized rubber treatment solution containing the sulfur and fatty acids or esters or salts thereof in a ratio of 1: 4. The method of claim 24, The said fatty acid or ester or its salt is unsaturated fatty acid or ester or its salt, The solution for vulcanized rubber processing. The method of claim 29, The fatty acid is oleic acid solution for the vulcanized rubber treatment.