JP2003128843A - Method for making reclaimed rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for making reclaimed rubber to recycle to a tire that has superior fracture property, wear resistance, crack growth resistance and exothermic property by pulverizing waste rubber with a little energy. SOLUTION: This method for making reclaimed rubber comprises blending 100 pts.wt. of raw reclaimed rubber of 100-300 mesh with 3-50 pts.wt. of diene rubber and shearing them at a maximum shear rate of 300/s or more. The period of time of shearing is decided such that the product of the maximum shear rate and the period of time of shearing is 15,000 or more. Then, the raw reclaimed rubber may be desulfurized after pulverization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing recycled rubber for tires for reusing vulcanized rubber such as waste tires.

[0002]

2. Description of the Related Art Conventionally, waste rubber products such as waste tires have been reused. Since these rubber products are made of vulcanized rubber, when reusing them, the vulcanized rubber of the waste rubber product was crushed and then used by blending it with the unvulcanized rubber of the new material or the roughly crushed waste rubber. After that, the vulcanized rubber is generally subjected to a desulfurization treatment to obtain a regenerated desulfurized rubber, and the desulfurized rubber is vulcanized again and used. In these methods, there is a problem of how much the desulfurization of the vulcanized rubber to be reused proceeds, and to what extent the rubber to be reused is finely pulverized.

Recycled rubber has poorer properties as a rubber than new rubber. In particular, the degree of desulfurization of waste rubber affects the fracture properties (strength and elongation) and elastic modulus of recycled rubber products. In addition, when crushed waste rubber is blended with new material rubber, if the particle size of the waste rubber after crushing is large, the recycled rubber becomes a fracture nucleus, reducing the breaking strength of rubber products that use recycled rubber. Affects rubber physical properties. As a crushing method, a method in which waste rubber is freeze-crushed to have a particle size of 10 μm or less has little adverse effect on physical properties as a fracture nucleus, but the energy cost of freezing is high, and it has not been put to practical use.
In addition, the method of pulverizing by applying a large shearing force with an extruder or the like also increases the energy cost. Therefore, the issue is how much fine powder can be made with a small amount of energy, and using extruders, stone mills, rolls, etc., is used to make fine powder with less energy than before, but it is still insufficient. There is no such method, and further improvement is required.

[0004]

DISCLOSURE OF THE INVENTION In the present invention, when waste rubber is crushed to be a vulcanized rubber or desulfurized and blended with a new material rubber to be reused in a tire, it is crushed with a small amount of energy. It is an object of the present invention to provide a method for producing a reclaimed rubber for obtaining a tire having excellent wear resistance, crack growth resistance and heat generation characteristics as compared with the use of the crushed rubber.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to solve the above-mentioned problems, and as a result, pulverized waste rubber to a particle size within a specific range and added a specific amount of a new material, diene. The inventors have found that the above object can be achieved by subjecting a mixture obtained by mixing a system rubber to shearing depending on the combination of rubber species used and the state of rubber to be recycled, and have completed the present invention. That is, the present invention comprises the following (1) to (4). (1) Mix 100 parts by weight of raw powder rubber of 10 to 300 mesh and 3 to 50 parts by weight of diene rubber,
A method for producing a recycled rubber for tire, which comprises applying shearing at a maximum speed of 300 / sec or more. (2) The product of the maximum shearing speed and the shearing time is 15,000 or more, (1)
The method for producing a recycled rubber for tires according to. (3) The method for producing a recycled rubber for tire according to (1) above, wherein the raw material powder rubber is pulverized and then desulfurized. (4) Any one of (1) to (3) above, wherein the diene rubber is at least one selected from natural rubber, synthetic isoprene rubber, styrene-butadiene copolymer rubber, butadiene rubber, and butyl rubber. Item 6. A method for producing a recycled rubber for tire according to the item. In the above manufacturing method, the temperature at which shearing is applied is appropriately set according to the state of the rubber to be recycled. further,
Desulfurization may be performed by a known method such as a method called the PAN method.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below. In the present invention, the waste vulcanized rubber to be regenerated is obtained by mixing sulfur or a sulfur compound with a polymer to form various sulfur cross-linking bonds such as a monosulfide bond, a disulfide bond and a polysulfide bond between carbon main chains. , Is a substance that exhibits rubber elasticity.

As the polymer component, natural rubber, butadiene rubber, isoprene rubber, butyl rubber, ethylene-propylene rubber, styrene-butadiene rubber, EPD
Examples thereof include M (ethylene propylene diene terpolymer), acrylic rubber, and acrylonitrile-butadiene rubber.

Such waste vulcanized rubber is obtained from used waste materials, unnecessary end materials generated during molding, defective molding products, and the like. In the present invention, powdered rubber having a particle size of 10 mesh to 300 mesh obtained by crushing and classifying such waste rubber is used. As such powdered rubber, for example, commercially available # 30T
B (manufactured by Muraoka Rubber Industry Co., Ltd.) can be used.

As the diene rubber to be blended with the powdered rubber, natural rubber (NR) and synthetic isoprene rubber (I
R), styrene-butadiene copolymer rubber (SBR),
Butyl rubber (BR) and the like can be mentioned.

The present invention mixes 3 to 50 parts of the new diene rubber with 100 parts by weight of the powdered rubber as described above and applies shearing at a maximum shearing rate of 300 / sec or more to recycle the regenerated rubber with a small amount of energy. Is a way to get.

In the present invention, waste rubber powder and a new diene rubber are blended and the mixture is sheared by an extruder or the like. The powdered rubber does not need to be extremely fine, and preferably has 10 mesh to 300 mesh. If the particle size is smaller than 300 mesh, the particles are less likely to become smaller even if sheared, which is not desirable in terms of cost. On the other hand, if the particle size is larger than 10 mesh,
Even if it is sheared, there is little change in rubber properties, and the effect of shearing is small.

The amount of the new diene rubber mixed with the powdered rubber is preferably 3 to 50 parts by weight, more preferably 10 to 50 parts by weight, per 100 parts by weight of the powdered rubber. If the amount is less than 3 parts by weight, the powder rubber may not be sufficiently further refined, and if the amount is more than 50 parts by weight, the effect of chain breaking of the new diene rubber may not be negligible.

The maximum shear rate applied to the rubber mixture is 30.
It is important that it is 0 / second or more. If the maximum shear rate is low, the recycled rubber particles do not become fine, and the recycled rubber becomes a fracture nucleus, reducing the breaking strength of the tire using this, and if the shear rate is too high, the cutting reaction of the diene rubber occurs. , The physical properties deteriorate. The maximum shear rate varies depending on the condition of the rubber to be reused and the combination with the diene rubber.

The shearing time depends on the shear rate, but it is not effective if it is too short. In the method of the present invention, it is desirable to select the product of the maximum shear rate and the shearing time to be 15,000, preferably 20,000 or more. That is, at the maximum shear rate of 300 / sec, it is desirable that it is 50 seconds or more.

If the temperature at which the shearing is applied is too high, the polymer chains are broken and the rubber has a low molecular weight, which is not desirable. The temperature should be appropriately set depending on the state of the raw rubber.

As a device for applying shear, a uniaxial extruder,
A twin screw extruder or the like can be used. The raw material powder rubber and the diene rubber mixture thus sheared form a composite in which the raw material powder rubber is finely and highly dispersed, and can be used as a recycled rubber.

In the production of the recycled rubber of the present invention, the waste vulcanized rubber after pulverization may be desulfurized and used. As a method for desulfurizing the waste vulcanized rubber, a conventionally known method such as a pan method of treating with high-pressure steam and a reclamometer method using a single-screw extruder can be used, and there is no particular limitation. The desulfurization treatment is to cut off the vulcanization point of the vulcanized rubber to destroy the three-dimensional structure of the vulcanized rubber. In the desulfurization treatment, it is presumed that not only the desulfurization itself but also the breaking of the polymer chain actually occurs at the same time.

[0018]

EXAMPLES Next, the present invention will be explained based on examples and comparative examples, but the present invention is not limited to the following examples.

1. Production of Recycled Rubber 1) Raw Powder Rubber As a waste rubber to be reused, commercially available powder rubber # 30TB (manufactured by Muraoka Rubber Industry Co., Ltd.) was used. The particle size of the raw rubber powder is larger than 5 mesh (5 mesh <), smaller than 5 mesh and larger than 24 mesh (24 mesh <), similarly larger than 80 mesh (80 mesh <), 300 mesh Four types of larger ones (300 mesh <) were prepared by sieving. 2) Diene rubber Diene rubber is a styrene-butadiene rubber (SBR: JSR) when recycled rubber is used for a tire tread.
When SBR1500 manufactured by Co., Ltd. is used for tire sidewalls, isoprene rubber (IR: IR2 manufactured by JSR Co., Ltd.)
200) was used.

Examples 1 to 12 and Comparative Examples 1 to 10 Raw powder rubbers shown in Table 1 (for tread) and Table 2 (for side wall) and rubber components in the ratio of SBR1500 or IR2200 were used, screw diameter 20 mm, and tip clearance. Using a 0.15 mm same-direction twin-screw extruder (two-thread complete meshing screw), raw material powder rubber and diene rubber were simultaneously charged from a hopper and kneaded at a barrel temperature of 80 ° C. to obtain a reclaimed rubber. Further, the shear rate is controlled as shown in Tables 1 and 2 by changing the rotation speed, and the L / D (screw diameter (D) and extrusion length (L)) is changed by changing the popper position. Then, the time required for shearing was controlled together with the change in the rotation speed.

The kneading conditions are as follows. Condition 1: 100 rpm, L / D = 30, residence time in the extruder at this time was 65 seconds, shear rate: 698 / s,
Product: 45370 Condition 2: Rotation speed 60 rpm, L / D = 30 Residence time in the extruder at this time is 80 seconds, shear rate: 419 / s, product:
33520 Condition 3: Rotation speed 30 rpm, L / D = 30 Residence time in the extruder at this time was 99 seconds, shear rate: 209 / s, product:
20690 If the shear rate is low, a sufficient effect cannot be obtained even if the time is lengthened. Condition 4: 100 rpm rotation speed, L / D = 15, residence time in the extruder at this time was 31 seconds, shear rate: 698 / s,
Product: 21640 Condition 5: Rotation speed 60 rpm, L / D = 15 Residence time in the extruder at this time was 45 seconds, shear rate: 419 / s, product:
18850 Condition 6: Rotation speed 30 rpm, L / D = 15 Residence time in extruder at this time was 58 seconds, shear rate: 209 / s, product:
12120

[0022]

[Table 1]

[0023]

[Table 2]

2. Evaluation of Reclaimed Rubber Using the reclaimed rubber produced in each of the above Examples and Comparative Examples, a rubber component was prepared by further mixing a new rubber with the reclaimed rubber, and a rubber compounding agent was added to the obtained rubber component. A rubber composition for tread and sidewall was obtained. With respect to this composition, abrasion resistance, fracture property, heat generation property, and crack growth property were measured to evaluate the recycled rubber.

1) Preparation of rubber component As a rubber component, a regenerated rubber obtained by kneading under the above kneading conditions is used. For a tread, the regenerated rubber (raw powder rubber + SBR1500) is mixed with SBR1712 (JSR Corporation).
And BR01 (manufactured by JSR Co., Ltd.) for sidewalls, natural rubber (RSS # 3) and BR01 are appropriately mixed with recycled rubber (raw powder rubber + IR2200),
It was prepared so that the blending ratio of the final rubber component would be a desired value (listed in the table). That is, for example, Examples 1 to 3 and
In Comparative Examples 2 and 5, 10 parts by weight of recycled rubber (9.09 parts by weight of raw material rubber + SBR1500: 0.91 parts by weight) is mixed with SBR1712: 63.7 parts by weight and BR27.3 parts by weight.

2) Blending of rubber composition In the case of the rubber composition for tread with respect to 100 parts by weight of each rubber component having the above blending ratio, in Table 3, in the case of the rubber composition for sidewalls. Was mixed with a rubber compounding agent so as to have the composition shown in Table 4 to obtain a rubber composition.

[0027]

[Table 3]

[0028]

[Table 4]

3) Measuring method With the above composition, abrasion resistance, fracture characteristics, low heat buildup,
The crack growth resistance was measured by the following method to evaluate the recycled rubber. In each evaluation, the value of Comparative Example 1 was 100 for the tread, and the value of Comparative Example 6 was 100 for the sidewall. The larger the index, the better the characteristics.

Breaking property The breaking strength (T _B ) was measured according to JIS K6301-1995, and expressed as an index with the control being 100. The larger the value, the better the fracture characteristics.

Bending crack growth property Tested in the same manner as JIS K6301-1995,
The number of times of bending when the length of the crack was 10 mm was measured and expressed as an index with the control being 100. The larger the value, the better the flex crack growth resistance.

Abrasion resistance It was measured by the Lambourn abrasion method. The measurement conditions are a load of 4.5 kg, a surface speed of the grindstone of 100 m / sec, a test speed of 130 m / sec, a slip ratio of 30%, and a falling sand amount of 2.
0 g / min, the measurement temperature was room temperature. In the table, the value of the control is set to 100 and is indexed. The larger the value, the better the wear resistance.

Exothermic characteristics Using a viscoelasticity tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), a test piece having a length of 20 × width of 4.7 × thickness of 2 mm was applied at an excitation frequency of 5
The loss component (tan δ) when 2% cyclic strain was applied at 2 Hz was measured and expressed as an index with the control being 100. The larger the value, the better the low heat buildup.

[0034]

As described above, by mixing the raw material powder rubber with the rubber component in advance and making it into a masterbatch, the regenerated rubber obtained becomes finer particles and the dispersion becomes better. As a result, the physical properties at the time of vulcanization of the rubber composition are improved as compared with the case where the raw material powder rubber is simply added as usual.

Continued front page    F-term (reference) 4F301 AA04 AA06 BF32 CA09 CA34                       CA71                 4J002 AC011 AC012 AC022 AC031                       AC032 AC041 AC042 AC061                       AC062 AC071 AC141 BB101                       BG041 GN01

Claims (4)

[Claims] 1. Raw rubber powder 10 of 10 to 300 mesh
A method for producing a recycled rubber for tires, characterized in that 0 part by weight and 3 parts by weight to 50 parts by weight of a diene rubber are mixed and subjected to shearing at a maximum shearing rate of 300 / sec or more. 2. The method for producing a reclaimed rubber for a tire according to claim 1, wherein the product of the maximum shearing rate of the shearing and the time (unit: second) for applying the shearing is 15,000 or more. 3. The method for producing a reclaimed rubber for a tire according to claim 1, wherein the raw material powder rubber is pulverized and then desulfurized. 4. The diene rubber is at least one selected from natural rubber, synthetic isoprene rubber, styrene-butadiene copolymer rubber, butadiene rubber, and butyl rubber, according to any one of claims 1 to 3. The method for producing a recycled rubber for tires according to.