JP2001226520A - Rubber composition using recovered carbon black - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a recovered carbon black which has been recovered from a rubber composition and has qualities equal or superior to those of a carbon black used as a raw material for preparing the rubber composition, and a rubber composition which contains the recovered carbon black and has good physical properties. SOLUTION: The recovered carbon black is obtained by subjecting a recovered solid obtained from a rubber composition at least containing a rubber and a carbon black to a heat treatment in a non-oxidative atmosphere at 400 deg.C-1,000 deg.C for 5 min-60 min, and the amount of organic components present at the surface of the recovered carbon black is equal to or smaller than that of organic components present at the surface of a carbon black used as a raw material. The rubber composition contains the recovered carbon black and a rubber and/or a resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recycled carbon black, and more particularly, to a recycled carbon black.
The present invention relates to a recovered carbon black having excellent physical properties obtained by subjecting a waste of a rubber composition to a predetermined treatment, and a rubber composition containing the recovered carbon black.

[0002]

2. Description of the Related Art In recent years, the problem of treating industrial waste has been an important social issue. In particular, tires have a large amount of waste, and not only are they incinerated as fuel, but also rubber as raw material. It is increasingly important to collect and effectively reuse secondary materials.

For this reason, a conventional method for recovering rubber materials such as rubber and carbon black from vulcanized rubber waste is to thermally decompose the vulcanized rubber waste and convert the rubber into gaseous or liquid hydrocarbon. And a method of recovering it. For example, a method of directly or indirectly heating at a high temperature of 500 ° C. or more, a method of thermally decomposing in the presence of a solvent, a catalyst and hydrogen (US Pat. No. 3,704,108)
), A method of pyrolysis in the presence of a molten salt (European Patent No. 7)
1789, U.S. Pat. No. 3,996,022) and the like.

However, carbon black recovered by a pyrolysis method at a high temperature of 500 ° C. or higher is generally
It is said that the carbon black used as a raw material is inferior in quality and difficult to reuse, and carbon black that can actually withstand reuse has not been obtained. On the other hand, substances recovered by a pyrolysis method in the presence of a solvent and a catalyst at a relatively low temperature of about 400 ° C. are oil, rubber,
Carbon black was a mixed substance, and it was difficult to separate each of these substances. In addition, such industrial waste treatment problems are not limited to vulcanized rubber products, but also in the treatment of unvulcanized waste rubber such as smelting waste and processing waste unavoidably generated when manufacturing vulcanized rubber products. It is becoming a problem, and collecting and effectively reusing the rubber sub-materials, which are these raw materials, has also become an important issue.

[0005] On the other hand, conventionally, as a rubber composition mainly used for tires, a rubber composition having a small rolling resistance and capable of reducing energy loss during running of an automobile has been developed. As such a rubber composition,
The value of the loss tangent (tan δ), which is one of the characteristics of rubber and governs rolling resistance, must be reduced at 50 ° C. to 70 ° C., and the demand for such a rubber composition has been greatly increased. ing. For this reason, it is possible to recover carbon black having a quality equal to or higher than that of carbon black used as a raw material, which is high in purity and can withstand reuse from rubber waste in general, and the recovered carbon can be recovered. If a rubber composition containing black shows specific properties required for a rubber composition with high demand, its industrial utility value is enormous.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and is a carbon black recoverable from a rubber composition, which is equivalent to carbon black used as a raw material. An object of the present invention is to provide a recovered carbon black having the above-mentioned quality and a rubber composition having good physical properties obtained by blending the recovered carbon black.

[0007]

Means for Solving the Problems The present inventors have found that the poor quality of conventional recovered carbon black recovered by heat treatment of a vulcanized rubber composition can be solved by heat treatment under specific conditions. Was. That is, these conventional recovery methods have been performed on an industrial scale or method, that is, a large amount of the vulcanized rubber composition has been heat-treated at once, resulting in insufficient heat treatment. When the vulcanized rubber composition is subjected to a heat treatment, the amount of the organic component adhered to the surface of the carbon black may be reduced to the surface of the carbon black used as a raw material. It is possible to perform a sufficient heat treatment so as to be equal to or less than the amount of the organic component having, and, surprisingly, the rubber composition containing the recovered carbon black obtained in this manner is the same as the ordinary carbon used as a raw material. Compared to a rubber composition containing black, there is a possibility that a resin having a higher tensile stress (modulus) and a smaller loss tangent (tan δ) can be obtained. In addition, the recovered carbon black having such excellent properties can be obtained not only from the vulcanized rubber composition but also from unvulcanized waste rubber and the like which are inevitably generated in the process of manufacturing vulcanized rubber products. The present inventors have found that a recovered solid obtained by decomposing a vulcanized rubber composition or an unvulcanized rubber composition itself can be obtained by heat treatment in the same manner, thereby completing the present invention.

That is, the recovered carbon black of the present invention is:
A recovered solid obtained from a rubber composition containing at least rubber and carbon black is treated in a non-oxidizing atmosphere with 4
The amount of the organic component on the surface obtained by heat treatment at a temperature of 00 ° C. to 1000 ° C. for 5 to 60 minutes is equal to or less than the amount of the organic component on the surface of the carbon black used as the raw material It is characterized by the following.

Here, the method for obtaining the recovered solid is as follows: the rubber composition is added to an organic solvent containing 0.01% by weight to 50% by weight of a peroxide; It is preferable that the immersion or immersion stirring is performed so that the (ml) ratio becomes 30 or less, and the peroxide is benzoyl peroxide and the organic solvent is toluene.

[0010] The rubber composition of the present invention is characterized by containing any one of the above-mentioned recovered carbon blacks, and a rubber and / or a resin.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The recovered carbon black of the present invention is obtained by collecting a recovered solid obtained from a rubber composition containing at least rubber and carbon black in a non-oxidizing atmosphere at 400 ° C to 1000 ° C.
At a temperature of 5 minutes to 60 minutes to make the amount of the organic component on the surface equal to or less than the amount of the organic component on the surface of the raw carbon black.

In the present invention, the rubber composition used as a raw material for obtaining a recovered solid is all rubber compositions having carbon black. That is, the rubber composition may be vulcanized or unvulcanized (unvulcanized), and includes a partially vulcanized rubber and a vulcanized rubber having an insufficient degree of vulcanization. Examples of the vulcanized rubber composition include various rubber products such as tires for automobiles, cables, sheets, packing, molded waste rubber, hoses and belts.
These may include other components, for example, steel materials such as brass-plated steel cords, and resins such as organic fibers such as polyester carcass cords. Further, as the unvulcanized rubber composition, the degree of vulcanization is not particularly limited as long as it is a rubber composition having at least a portion that does not reach the degree of vulcanization of the vulcanized rubber product. And unvulcanized waste rubber discharged at a vulcanized rubber product factory. Specifically, during the kneading process or the forming process, the rubber vulcanized material discharged due to early vulcanization or uneven vulcanization (burning, scorch), and the so-called dripping during the vulcanization process, is discharged. Defective products and the like. Similarly, these may include other constituent members such as the above-described steel materials and organic fibers. In addition, these rubber compositions may include a rubber, a filler, and the like contained in the rubber composition of the present invention described below.

The above-mentioned rubber composition is subjected to a predetermined heat treatment as described later.
It is preferable that the carbon black component and the rubber component are substantially separated, and the recovered solid obtained thereby is subjected to a heat treatment. The reason is that the rubber component is removed from the carbon black component by separation, so that in the heat treatment of the recovered solid in a non-oxidizing atmosphere, the organic matter on the surface of the carbon black is efficiently removed and emits a bad smell. This is because there is almost no generation of liquid organic components.

In the present invention, the recovered solid obtained from the rubber composition contains carbon black,
The rubber composition itself may be used, or a recovered material mainly composed of carbon black obtained by decomposing the rubber composition may be used. Further, a liquid such as water or a solvent may be contained.

In the present invention, the method for decomposing the rubber composition is described in Japanese Patent Application No. 11-13 / 1999 filed by the present applicant.
The processing method described in Japanese Patent No. 2744 can be employed. For example, as a decomposition treatment method for a rubber composition employed in the present invention, a peroxide is used in an amount of 0.01% by weight to 50% by weight.
A method of immersing or immersing the rubber composition in an organic solvent containing by weight so that the ratio of rubber composition (mg) / organic solvent (ml) is 30 or less can be adopted.

Here, when the above-described method is employed as a method for decomposing the rubber composition, a known organic peroxide can be widely used as the peroxide.
Specifically, benzoyl peroxide, diisopropylbenzene hydroperoxide (trade name, Parkmill P (manufactured by NOF Corporation), etc.), t-butyl hydroperoxide (80% di-t-butyl peroxide solution, etc.), p-
Mentane hydroperoxide (trade name: Permenta H
(Manufactured by NOF Corporation), cumene hydroperoxide (trade name: Parkmill H-80 (manufactured by NOF Corporation), etc.)
And the like, and also a radical generator such as azobisisobutyronitrile and the like. These peroxides may contain water or the like to prevent explosion. Of these, benzoyl peroxide is particularly preferred.

As the organic solvent, known organic solvents can be widely used as long as they are liquid at normal pressure and normal temperature and can dissolve peroxide. Specific examples include hydrocarbons and alcohols, and the hydrocarbons may be saturated or unsaturated, and are not particularly limited to aromatics, aliphatics, alicyclics, and the like. Such organic solvents include, for example, benzene, toluene, xylene, hexane, decalin (decahydronaphthalene), methanol,
Ethanol, tetralin (tetrahydronaphthalene),
Examples thereof include cyclohexane, and particularly preferred are toluene, benzene, and xylene.

The treating solution for decomposing the rubber composition may contain peroxide in the above organic solvent in an amount of 0.01 to 50% by weight, preferably 0.1 to 10% by weight, more preferably 0.1 to 10% by weight.
What is contained at a concentration of 5% by weight to 2% by weight is used. This is because, if it is in this range, there is an advantage that the reaction proceeds efficiently. This treatment liquid may contain two or more kinds of organic solvents and / or peroxides.

In the above method, a toluene solution containing 0.01% by weight to 50% by weight of benzoyl peroxide can be preferably used as the treatment liquid.

In the above method, the rubber composition is immersed or immersed in the above-mentioned organic solvent containing a peroxide.
At this time, the ratio of the rubber composition to the organic solvent, the rubber composition (m
g) / Organic solvent (ml) is preferably 30 or less, more preferably 15 or less, and most preferably 5 or less. When the above ratio is within this range,
This is because the rubber component can be efficiently separated.
In the case where the rubber composition includes other components such as steel and resin, the ratio is preferably in the above range except for the weight portion of the other components. In addition, the processing temperature of the above method does not need to be particularly high, and is preferably 0 ° C to 40 ° C, more preferably 10 ° C to 30 ° C,
Particularly preferred is the ambient temperature.

In the present invention, the rubber composition is decomposed by an appropriate decomposition method, and when the rubber composition includes other components such as steel and resin, these components are removed and the solid composition of the rubber composition is removed. Collect minutes. Here, as a method for recovering the solid product of the decomposed rubber composition, centrifugation, membrane separation,
Normal separation means such as decantation and filtration can be used. Further, the collected solid product is sufficiently washed with toluene or the like, and if necessary, a drying process such as natural drying at room temperature or vacuum drying is performed to remove a liquid component, and then subjected to a heat treatment described below. Is preferred.

The rubber composition as a raw material may be directly subjected to a heat treatment described later. In this case, it is preferable to make the rubber composition finer so that the average particle diameter is 1.8 mm or less, and it is more preferable that the average particle diameter be 0.3 mm to 0.8 mm. Further, it is preferable to reduce the amount of the rubber composition to be subjected to the heat treatment described below. For example, when a heat-resistant tube is used for the heat treatment, the rubber composition is 7 mg to 13 m per 1 cm ^{3 of} the tube volume.
g is preferable.

In the present invention, the recovered solid obtained as described above is subjected to a predetermined heat treatment. The predetermined heat treatment means that the collected solid is heated to 400 ° C. to 1000 ° C. in a non-oxidizing atmosphere such as a nitrogen atmosphere using a heat-resistant tube.
The heating is performed at a temperature of 5 ° C. for 5 to 60 minutes. The amount of recovered solids subjected to heat treatment is 1 cm ³
It is preferable to be 9 mg to 15 mg. In addition, as the heat resistant tube, a quartz glass tube,
A metal tube such as stainless steel can be used.

In the present invention, the heat treatment temperature is 400 ° C.
The temperature is 1000C, preferably 500C to 800C. When the content is within this range, the rubber component can be sufficiently decomposed and removed, and the carbon black to be recovered is not recovered as graphite.

In the present invention, the heat treatment time is from 5 minutes to 60 minutes, and when the material subjected to the heat treatment is a solid product after the rubber composition decomposition treatment, it is from 7 minutes to 60 minutes. When the rubber composition itself is subjected to a heat treatment, the heating time is preferably 15 minutes to 60 minutes. When the content is within the above range, as described later, the amount of the organic component on the surface of the carbon black falls within a predetermined range, whereby the physical properties of the carbon black to be recovered are used as a raw material. This is because the physical properties are equal to or higher than the physical properties of the carbon black.

In the present invention, since the carbon black recovered after the heat treatment has been sufficiently subjected to the heat treatment, the amount of the organic component such as the rubber component on the surface depends on the surface of the carbon black used as the raw material. It is equal to or less than the amount of the organic component.

Here, the amount of an organic component such as a rubber component on the surface of carbon black is determined by a thermal analysis method of thermogravimetry (TGA) based on a change in weight between 20 ° C. and 700 ° C. in a non-oxidizing atmosphere. I do. The equivalent of the amount of the organic component on the surface of the carbon black used as the raw material is 20%.
20 ° C to 700 ° C, where the weight of the sample at 100 ° C is 100%
Means that the weight loss of the sample is 1.5% to 2.5%. The recovered carbon black of the present invention has a temperature of 20 ° C to 7 ° C.
The weight loss of the sample at 00 ° C. is 2.5% or less, preferably 1% to 2%.

The recovered carbon black of the present invention can sufficiently withstand reuse. If this recovered carbon black is used, as described later, the tensile stress and loss of a rubber composition containing ordinary carbon black can be reduced. A material having a loss tangent equal to the tangent or having a large tensile stress and a small loss tangent can be obtained. Although the reason for this is not clear at present, the inventors believe that the organic component does not adhere to the surface of the carbon black, or even if it adheres, the amount is very small.

Next, the rubber composition of the present invention will be described. The rubber composition of the present invention is a rubber composition produced using the above-described recovered carbon black of the present invention as a filler.

The rubber forming the rubber composition of the present invention includes natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), and butadiene rubber (B
R), butyl rubber (IIR), chloroprene rubber (C
R) and the like, and blends thereof.

The rubber composition of the present invention may contain known vulcanizing agents, for example, non-elemental sulfur vulcanizing agents such as sulfur, tetramethylthiuram disulfide, tetraethylthiuram disulfide, bismorpholine disulfide, dipentamethylenethiuram. Tetrasulfide, organic peroxide, quinone dioxime, phenol formaldehyde resin, nitroso compound and diisocyanate mixture,
Zinc oxide, magnesium oxide, zinc peroxide, triethylenetetramine, methylenedianiline, diphenylguanidine, hexamethylenediaminecarbamate, ethylenediaminecarbamate, bis-p-aminocyclohexylmethanecarbamate, and the like can be used.

The rubber composition of the present invention contains the above-described carbon black of the present invention as a filler.
At this time, the rubber composition is decomposed, and the recovered carbon black obtained by heat-treating the collected solid product may be used alone, or may be obtained by heat-treating the rubber composition itself. The recovered carbon black may be used alone or both may be used. In the present invention, the amount of the carbon black is preferably 1 part by weight or more, more preferably 10 parts by weight to 130 parts by weight, based on 100 parts by weight of the rubber component.

In the present invention, in order to obtain a rubber composition having a large tensile stress (modulus) and a small loss tangent (tan δ), the recovered carbon black according to the present invention is used alone as a filler. However, other fillers, for example, known silica used as a raw material can be used without departing from the above-mentioned purpose.

In the present invention, in order to enhance the wear characteristics of the rubber composition, the filler used is a recovered carbon black according to the present invention and another filler, for example, a known abrasion resistant material used as a raw material. High carbon black can be used in combination. This makes it possible to obtain a rubber composition having a large tensile stress (modulus), a small loss tangent (tan δ), and excellent wear characteristics.

Here, the other fillers include known fillers, for example, generally known carbon black, silica and the like.

The rubber composition of the present invention comprises the raw material rubber described above,
In addition to fillers such as carbon black, other known resins,
Elastomers, other compounding agents, and rubber auxiliary materials may be widely contained. For example, vulcanization (curing) accelerators, vulcanization accelerators, activators, vulcanization retarders, softeners, plasticizers, adhesives, tackifiers, curing agents, foaming agents, foaming aids, reinforcing agents, aging An inhibitor, a colorant, a pigment, a flame retardant, a release agent and the like may be blended. These may be blended in any step such as kneading, vulcanizing, and reinforcing filling.

The method for producing the rubber composition of the present invention includes:
Although not particularly limited, for example, using a twin-screw extruder, a Banbury mixer, a kneader, and the like, a rubber raw material, recovered carbon black, and other additives as necessary,
A method of producing by kneading under heating to about 180 ° C. can be used.

[0038]

The present invention will be described in more detail with reference to the following examples. <Preparation of rubber composition as raw material> A rubber composition was prepared by compounding and kneading with the component compositions shown in Table 1, heating at 148 ° C for 10 minutes, and vulcanizing. In addition, carbon black whose ASTM code is N339 is used as carbon black, and N-phenyl-
N '-(1,3-dimethylbutyl) -p-phenylenediamine is used, and Nt-butyl-2-benzothiazylsulfenamide is used as a vulcanization accelerator.

[0039]

<Preparation of Recovered Carbon Black> 70 g of the above rubber composition was immersed in 7 L of a toluene solution having a benzoyl peroxide (hereinafter abbreviated as BPO) concentration of 1% by weight, and the mixture was stirred. (Suspension). The suspension was centrifuged to separate a clear solution phase and a solid product. The solid product was washed with toluene, and the collected product was naturally dried and vacuum dried to obtain carbon black 0. The solid product was washed with toluene, recovered, dried, and then heat-treated at 800 ° C. for 60 minutes in a nitrogen atmosphere to obtain carbon black 1.

The rubber composition described above has an average shape of about 1.5
mm × 1.5 mm × 1.5 mm, and heat-treated directly under the same conditions as for carbon black 1 to collect carbon black and carbon black 2
And The above-mentioned N339 is heat-treated under the same conditions as for carbon black 1 to collect carbon black,
Carbon black 3 was obtained.

(Examples 1 and 2, Comparative Examples 1 to 3) <Preparation of Rubber Composition> A rubber composition compounded and kneaded with the component compositions shown in Table 2 was heated at 148 ° C. for 10 minutes. And vulcanized to obtain Examples 1-2 and Comparative Examples 1-3. In addition, N339 is carbon black whose ASTM code is N339, and the used antioxidant and vulcanization accelerator are the same as those used in the above rubber composition.

[0043]

<Hysteresis curve> Example 1, Comparative Example 1
And 10 mm in width, 150 mm in length,
Cut out into a 1 mm thick strip-shaped test piece, JIS K6
According to a method based on H.254, tension was applied five times until the elongation reached 100%, and the tensile stress was measured. Figure 1 shows the results
Shown in (A) is Example 1, (b) is Comparative Example 1,
(C) shows the result of Comparative Example 3, and one scale on the vertical axis in the figure corresponds to 9.8N.

<Stress-Strain Curve> The rubber compositions of Examples 1 and 2 and Comparative Examples 1 to 3 were cut into dumbbell-shaped test pieces (JIS No. 3) having a thickness of 1 mm, and were subjected to a method in accordance with JIS K6251. The stress-strain characteristics were measured. The results are shown in FIG. In addition, an Example is shown with a solid line, a Comparative Example is shown with a dotted line, and Example 1 (solid triangle), Example 2 (x), Comparative Example 1 (solid diamond), Comparative Example 2 (O), Comparative Example 3 (Black square).

<Measurement of Loss Tangent (tan δ)>
, And the rubber compositions of Comparative Examples 1 to 3 were cut into strip-shaped test pieces having a width of 5 mm, a length of 100 mm, and a thickness of 1 mm.
Method based on JIS K 6394 (initial strain 10%,
The loss tangent (ta) is determined by the amplitude ± 2% and the frequency of 20 Hz.
nδ) was measured. The results are shown in FIG. The types and symbols of the lines are the same as those shown in FIG.

As is clear from FIGS. 1 and 2, a rubber composition containing carbon black 1, which is the rubber composition of the present invention (Example 1), and a rubber composition containing carbon black 2 (Example 2) ) Is the rubber composition of Comparative Example 1 containing the known carbon black N339, or the rubber composition of Comparative Example 2 containing carbon black 3, and the rubber composition of Comparative Example 3 containing carbon black 0, Although the stress-strain characteristics are equal or better, as is clear from FIG. 3, the loss tangent (tan δ)
Is low. In particular, 6 which is an index of rolling resistance
It can be seen that the rate of reduction of tan δ at 0 ° C. is large, indicating good rolling resistance.

[0048]

As described above, according to the present invention,
The carbon black can be easily recovered from the waste of the entire rubber composition regardless of the presence or absence of vulcanization, and the degree thereof, and the obtained recovered carbon black can sufficiently withstand reuse. Further, according to the rubber composition of the present invention, since the rubber composition has excellent tensile stress and extremely low loss tangent (tan δ), it has low rolling resistance, which is a characteristic necessary for a rubber composition for tires with particularly good fuel efficiency. Is sufficiently satisfied, and is particularly useful in a wide range of applications such as a tire tread and a tire undertread.

[Brief description of the drawings]

1A is a graph showing a hysteresis curve of Example 1, FIG. 1B is a graph showing a hysteresis curve of Comparative Example 1, and FIG. 1C is a graph showing a hysteresis curve of Comparative Example 3. is there.

FIG. 2 is a graph showing a relationship between strain and stress.

FIG. 3 is a graph showing a relationship between a temperature and a tangent loss (tan δ).

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D004 AA11 AA50 BA01 CA15 CA26 CA36 CA50 CC04 CC15 DA03 DA06 DA10 DA20 4J002 AC011 AC031 AC061 AC081 AC091 BB181 DA036 FD010 FD140 4J037 AA02 BB07 BB12 BB30 CC06 CC11 CC21 FF30

Claims (4)

[Claims] 1. A heat treatment of a recovered solid obtained from a rubber composition containing at least rubber and carbon black at a temperature of 400 to 1000 ° C. for 5 to 60 minutes in a non-oxidizing atmosphere. A recovered carbon black, wherein the amount of the organic component on the surface is equal to or less than the amount of the organic component on the surface of the carbon black used as the raw material. 2. A method for obtaining the recovered solid, wherein the rubber composition is added to an organic solvent containing 0.01% to 50% by weight of a peroxide, and the rubber composition (mg) / organic solvent ( m
1) The recovered carbon black according to claim 1, wherein the carbon black is immersed or immersed and stirred so that the ratio becomes 30 or less. 3. The method of claim 2, wherein said peroxide is benzoyl peroxide.
3. The recovered carbon black according to claim 2, wherein the organic solvent is toluene. 4. A rubber composition comprising the recovered carbon black according to claim 1 and a rubber and / or a resin.