JP2000034366A - Rubber composition for inner liner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for inner liner that is inexpensive, can develop well balanced mechanical properties and has excellent air- impermeability by formulating coal ash to diene rubber as a filler. SOLUTION: The objective rubber composition for inner liner comprises (A) 100 pts.wt. of at least one of diene rubber selected from natural rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber and butyl rubber, (B) 5-30 pts.wt. of coal ash with an average particle size of 3-7 μm. In a preferred embodiment, the component A comprises <=40 pts.wt. of natural rubber and >=60 pts.wt. of butyl rubber. The coal ash is given as a residue after coal is combusted, for example, in a power station or the like. The component B mainly contains silica, alumina, ferric oxide and calcium oxide and preferably the total of these main components amounts to >=90 wt.%. This composition is molded and vulcanized to provide inexpensive and high air-impermeable tires having the inner liner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition for an inner liner which is inexpensive and has excellent air impermeability.

[0002]

2. Description of the Related Art Tire inner liners are required to have excellent air impermeability. Therefore, a filler such as carbon black is usually blended in the rubber composition for the inner liner, and this filler also imparts appropriate mechanical properties (hardness, tensile properties, etc.) to the inner liner. However, if a large amount of filler is added for the purpose of increasing air impermeability, the hardness of the rubber is increased, but the tensile properties are reduced, and there is a problem that the inner liner is cracked during running. However, carbon black is expensive and a substitute for it has been sought.

[0003] When coal is burned in a thermal power plant or the like, about 20% of it is burned, that is, coal ash remains. At present, part of coal ash is effectively used in the cement field, but most of it is landfilled and dumped as waste. For this reason, it is feared that the coal ash will cause environmental degradation problems in the future, and it is an issue to consider how to effectively utilize it.

[0004]

An object of the present invention is to provide an inner liner which is inexpensive, has balanced mechanical properties, and is excellent in air impermeability by effectively utilizing coal ash. To provide a rubber composition for an inner liner.

[0005]

Means for Solving the Problems The present inventor considered that the coal ash was blended as a filler in order to make effective use of the above-mentioned coal ash. Use of coal ash as a filler
Not only utilization of coal ash, but also cost reduction of the rubber composition for the inner liner is enabled. However, since the average particle diameter of a commonly used filler such as carbon black, silica, and calcium carbonate is as fine as 0.01 to 3 μm, the mechanical properties such as hardness and tensile properties can be balanced. In contrast, normally obtained coal ash has an average particle size of 3
Large particles of about 10 to 10 μm. If this was used as it was, a decrease in tensile properties was expected, and the expected results were obtained in experiments. Therefore, as a result of further experiments in order to optimize the particle size of coal ash, it was found that mechanical properties were balanced and air non-permeability was excellent except for large particles, that is, large particles exceeding 7 μm. Was confirmed, and the present invention has been achieved.

That is, the rubber composition for an inner liner of the present invention has an average particle size of 100 parts by weight of at least one diene rubber selected from natural rubber, butadiene rubber, styrene / butadiene rubber, isoprene rubber and butyl rubber. It is a composition comprising 5 to 30 parts by weight of coal ash having a diameter of 3 to 7 μm.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION First, each component constituting the rubber composition for an inner liner of the present invention will be described in detail, and then this rubber composition will be described. (Diene rubber) Diene rubber used in the present invention,
It is a base component of the inner liner and is a main component constituting the rubber composition for the inner liner.

[0008] The diene rubber is not particularly limited.
For example, natural rubber (NR), butadiene rubber (B
R), styrene-butadiene rubber (SBR), isoprene rubber (IR) and butyl rubber (IIR). Among these, natural rubber and butyl rubber having excellent air impermeability are preferable, and the compounding ratio thereof is based on 100 parts by weight of the diene rubber.
Natural rubber may be 40 parts by weight or less, and butyl rubber may be 60 parts by weight or more. [Coal ash] Coal ash used in the present invention is a component that is inexpensive, enhances the air impermeability of the inner liner, and imparts balanced mechanical properties.

Coal ash is burnt coal remaining after burning coal, and is made of silica (SiO ₂ ), alumina (Al
₂ O ₃ ), ferric oxide (Fe ₂ O ₃ ), and calcium oxide (CaO) as main components, and the total of these is preferably 90% by weight or more, and silica is 50% by weight or more of the whole. Is more preferable. The coal ash has a composition further containing magnesium oxide (MgO), potassium oxide (K ₂ O), sodium oxide (Na ₂ O), sulfur trioxide, unburned carbon, and the like, in addition to the above main components. The composition and properties of the coal ash vary depending on the type of coal, the coal-producing area and the combustion method, but are generally glassy, spherical, and have a specific gravity smaller than that of sand and exhibit strong alkalinity. Table 1 shows specific examples of the chemical composition of coal ash obtained by burning domestic coal and foreign coal.

[0010]

[Table 1]

The average particle size of the coal ash is 3 to 7 μm, preferably 4 to 6 μm. If the average particle size of the coal ash is less than 3 μm, it is difficult to work and productivity is reduced,
The compounding cost increases. On the other hand, if the average particle diameter exceeds 7 μm, the tensile properties are reduced, and the balance of the mechanical properties is lost. The maximum particle size of the coal ash is preferably less than 10 μm, more preferably less than 8 μm. If the maximum particle size of the coal ash is 10 μm or more, the tensile properties may be reduced, and the balance of the mechanical properties may be lost.

The specific gravity of the coal ash is not particularly limited, and is preferably 2.3 to 2.5, more preferably 2.
3 to 2.4. The specific gravity of coal ash is smaller than that of other fillers such as hard clay and heavy calcium carbonate, and the unit price per unit volume is low. The coal ash used in the present invention can be obtained at low cost by crushing and classifying the combustible remaining after burning coal in a thermal power plant or the like, so that the combustible industrial waste is effectively used. Become. [Rubber composition for inner liner] The amount of each component constituting the rubber composition for inner liner of the present invention will be described.

The mixing ratio of coal ash is 100% diene rubber.
The amount is 5 to 30 parts by weight, preferably 15 to 25 parts by weight, based on parts by weight. When the compounding ratio of the coal ash is less than 5 parts by weight based on 100 parts by weight of the diene rubber,
If the amount is too small, the air impermeability decreases. On the other hand, if the amount exceeds 30 parts by weight with respect to 100 parts by weight of the diene rubber, the tensile properties are reduced, the balance of the mechanical properties is lost, and cracks occur.

The rubber composition for an inner liner of the present invention may contain, if necessary, other reinforcing agents such as carbon black and silica; softeners such as naphthenic process oils; and additives such as sulfur, insoluble sulfur and sulfur compounds. Sulfuric acid; zinc oxide,
Vulcanization aids such as stearic acid; mercaptobenzothiazole (MBT), benzothiazyl disulfide (MBT)
S), N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2
-Vulcanization accelerators such as thiazole accelerators such as benzothiazylsulfenamide (CBS) and guanidine accelerators such as diphenylguanidine (DPG); organic fibers; foaming agents; aging inhibitors; An additive such as wax can be blended. The amounts of these additives in the rubber composition are not particularly limited, and can be appropriately used.

As a method for producing the rubber composition for an inner liner of the present invention, a known method can be applied. Each of the above components, for example, Banbury mixer,
It is obtained by kneading using a kneading machine such as a twin-screw roller or the like, and kneading, extruding or the like by a usual method such as extruding the obtained kneaded material using a calendar extruder or the like. By molding and vulcanizing using the rubber composition for an inner liner of the present invention, a tire having an inner liner which is inexpensive and has excellent air impermeability can be obtained.

[0016]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following Examples. Hereinafter, “parts” indicates “parts by weight” and “%” indicates “% by weight”. Example A1-70 parts of natural rubber (RSS # 3, manufactured by TECK BEE HANG), styrene-butadiene rubber (SBR150
2. Sumitomo Chemical Co., Ltd.) 30 parts, carbon black GPF
(Diablack N660, manufactured by Mitsubishi Chemical Corporation) 40 parts, coal ash A (FA10, manufactured by Techno Resources Co .; average particle diameter: 4.8 μm, maximum particle diameter: 10 μm, specific gravity: 2.
4) 20 parts, 2 parts of a tackifier (Heiretz G100X, manufactured by Mitsui Petrochemicals), stearic acid 2 as a vulcanization aid
Parts and 3 parts of zinc oxide, 5 parts of aromatic oil, 1.5 parts of sulfur as a vulcanizing agent and 1 part of a vulcanization accelerator (Sancellar NS, manufactured by Sanshin Chemical Co., Ltd.), and a 270 liter Banbury mixer ( Using Kobe Steel)
Kneaded at 0 ° C. for 5 minutes. Next, the obtained kneaded material was extruded using a calender extruder (manufactured by Nakata Engineering Co., Ltd.) to prepare a rubber composition (A1).

The rubber composition (A1) is molded and vulcanized at 170 ° C. for 12 minutes. The hardness, tensile properties (rupture strength and elongation), crack growth and tire airness of the inner liner (A1) are obtained. The permeability was evaluated for performance by the following evaluation method. The compounding cost of the rubber composition (A1) was evaluated by the following evaluation method. Table 2 shows the results. <Evaluation method> Hardness was measured according to JIS-HS. Tensile properties A dumbbell No. 3 based on JIS K6251 was molded under the same conditions as the inner liner, and the breaking strength (unit: MP)
a) and elongation (unit:%) were measured. Crack growth was measured according to JIS K-6260. Example A
In Comparative Example A1 and Comparative Examples A1 to A6, Comparative Example A6 was 100, and in Example B1 and Comparative Examples B1 to B6, Comparative Example B6 was 10.
The measurement result was calculated with an index of 0. The higher the index, the better the cracks are less likely to occur. Comparative Example A6
The reason why B6 is set to 100 is that the hardness of Comparative Example A6 is the same as that of Example A1 and that of Comparative Example B6 is the same as that of Example B1, and the crack growth properties are easily compared. A rim-mounted tire (18) with a tire air-impermeable inner liner
Attach a Bourdon tube pressure gauge to 5/65 R14)
After measuring the initial pressure (P ₀ ), 9
It was left for 0 days, and the pressure (P ₉₀ ) after 90 days was measured. P
₀ and P _90, the air pressure loss rate per month (%)
Was calculated according to the following equation. The measurement results are indicated by indices. In Example A1 and Comparative Examples A1 to A6, Comparative Example A6 was used.
Was 100, and Comparative Example B6 was 100 in Example B1 and Comparative Examples B1 to B6. The smaller the index, the better the air is less likely to penetrate. It should be noted that the comparative examples A6 and B6 were 100 because the hardness of the comparative example A6 was the same as that of the example A1 and the comparative example B6 was the same as that of the example B1.
This is because it is easy to compare the air non-permeability.

Air pressure loss rate per month (%) =
[(P ₀ -P ₉₀ ) / P ₀ ] × 100 × (30/90) Compounding cost The unit price per liter of compounded rubber was calculated in each of Examples and Comparative Examples. Example A1 shows the calculation result as an index.
In Comparative Examples A1 to A6, Comparative Example A6 was 100, and in Example B1 and Comparative Examples B1 to B6, Comparative Example B6 was 100.
And The reason why the comparative examples A6 and B6 are set to 100 is that since inexpensive materials are not blended in these, the blending cost is highest and the comparison is easy.

Comparative Examples A1 to A4- Comparative rubber compositions (A1) to (A4) were prepared in the same manner as in Example A1, except that coal ash A was changed to the fillers shown in Table 2. ) Was prepared and evaluated in the same manner as in Example A1. Table 2 shows the results. In addition, as heavy calcium carbonate, Whiten SB (average particle diameter: 1.5 μm, specific gravity:
2.7); As the ultrafine surface-treated calcium carbonate, Hakuenka CC (average particle diameter: 0.
03 μm, specific gravity: 2.6); Hard clay manufactured by Shiraishi Calcium Co. (average particle diameter: 2.0)
μm, specific gravity: 2.6); As coal ash B, FA20 (average particle diameter: 10.4 μm, maximum particle diameter: 20 μm, specific gravity: 2.4) manufactured by Techno Resource Co., Ltd. was used.

Comparative Example A5- Carbon black GPF and coal ash A in Example A1
Example A1 except that the compounding amount of was changed to the amount shown in Table 2.
In the same manner as in Example 1, a comparative rubber composition (A5) was prepared and evaluated in the same manner as in Example A1. Table 2 shows the results. -Comparative Example A6- In Example A1, carbon black GPF and coal ash A
Example A1 except that the compounding amount of was changed to the amount shown in Table 2.
In the same manner as in Example 1, a comparative rubber composition (A6) was prepared and evaluated in the same manner as in Example A1. Table 2 shows the results.

Comparative Example A7 A comparative rubber composition (A7) was prepared in the same manner as in Example A1, except that the amount of coal ash A was changed to the amount shown in Table 2. Evaluation was performed in the same manner as in Example A1. Table 2 shows the results. -Comparative Example A8-A comparative rubber composition (A) was prepared in the same manner as in Example A1 except that the amount of coal ash A was changed to that shown in coal ash C in Example A1.
7) was prepared and evaluated in the same manner as in Example A1. Table 2 shows the results. As the coal ash C, a small particle (average particle diameter: 2.5 μm, maximum particle diameter: 6 μm, specific gravity: 2) obtained by further classifying FA10 (coal ash A) manufactured by Techno Resources Co., Ltd. .4) was used.

[0022]

[Table 2]

In Table 2 above, the amounts of the tackifier, vulcanization aid, aromatech oil, vulcanizing agent and vulcanization accelerator are not described, but all were blended in the same amounts as in Example A1. <Evaluation Results> Example A1 is less expensive, has balanced mechanical properties, and has excellent tire air impermeability than Comparative Example A6 having the same hardness.

In Example A1, the compounding cost is lower and lower than in Comparative Examples A1 to A3 in which the type of filler is different. In Example A1, cracks are less likely to occur and tensile properties are higher than in Comparative Example A4 using coal ash B having an average particle diameter of more than 7 μm or Comparative Example A5 in which the blending amount of coal ash A is large, and the balance is high. Mechanical properties.

In Example A1, a comparative example using coal ash C, which is less expensive, has higher tire air impermeability and has an average particle diameter of less than 3 μm, is lower than Comparative Example A7 in which the blending amount of coal ash A is small. It is cheaper than A8. -Example B1-A rubber composition (B1) was prepared in the same manner as in Example A1, except that the styrene-butadiene rubber was changed to butyl rubber (chlorobutyl HT1068, manufactured by Sumitomo Chemical Co., Ltd.).
Was prepared and evaluated in the same manner as in Example A1. Table 3 shows the results.

Comparative Examples B1 to B4 Comparative rubber compositions (B1) to (B4) were prepared in the same manner as in Example B1, except that coal ash A was changed to the fillers shown in Table 3. ) Was prepared and evaluated in the same manner as in Example B1. Table 3 shows the results. The heavy calcium carbonate was Whiten SB (average particle diameter: 1.5 μm, specific gravity: 2.7) manufactured by Shiraishi Calcium Co., Ltd.
The ultra-fine surface-treated calcium carbonate is Hakuenka CC (average particle size: 0.03 μm, specific gravity:
2.6), the hard clay is a hard clay manufactured by Shiraishi Calcium Co. (average particle diameter: 2.0 μm, specific gravity: 2.6), and the coal ash B is FA20 manufactured by Techno Resource Co. (average particle diameter: 10.4 μm) , Maximum particle diameter: 20 μm, specific gravity: 2.
4) was used.

Comparative Example B5- Carbon black GPF and coal ash A in Example B1
Example B1 except that the blending amount of was changed to the amount shown in Table 3.
In the same manner as in Example 1, a comparative rubber composition (B5) was prepared and evaluated in the same manner as in Example B1. Table 3 shows the results. -Comparative Example B6- Carbon black GPF and coal ash A in Example B1
Example B1 except that the blending amount of was changed to the amount shown in Table 3.
In the same manner as in Example B1, a comparative rubber composition (B6) was prepared and evaluated in the same manner as in Example B1. Table 3 shows the results.

Comparative Example B7 A comparative rubber composition (B7) was prepared in the same manner as in Example B1, except that the amount of coal ash A was changed to the amount shown in Table 3 in Example B1. Evaluation was performed in the same manner as in Example B1. Table 3 shows the results. -Comparative Example B8- A comparative rubber composition (B) was prepared in the same manner as in Example B1 except that the amount of coal ash A was changed to that shown in coal ash C in Example B1.
7) was prepared and evaluated in the same manner as in Example A1. Table 3 shows the results.

[0029]

[Table 3]

In Table 3 above, the amounts of tackifier, vulcanization aid, aromatech oil, vulcanizing agent and vulcanization accelerator are not described, but all were mixed in the same amounts as in Example B1. <Evaluation Results> Example B1 is less expensive, has balanced mechanical properties, and is excellent in tire air impermeability than Comparative Example B6 having the same hardness.

In Example B1, the compounding cost is lower and lower than in Comparative Examples B1 to B3 in which the type of filler is different. In Example B1, cracks are less likely to occur, and the tensile properties are higher and more balanced than Comparative Example B4 using coal ash B having an average particle diameter of more than 7 μm or Comparative Example B5 having a large amount of coal ash A. Mechanical properties.

In Example B1, a comparative example using coal ash C, which is less expensive, has higher tire air impermeability, and has an average particle diameter of less than 3 μm, is lower than Comparative Example B7 in which the amount of coal ash A is small. It is cheaper than B8.

[0033]

The rubber composition for an inner liner according to the present invention is inexpensive by effectively utilizing coal ash,
Moreover, it can be used for producing an inner liner having balanced mechanical properties and excellent air impermeability. When this inner liner is used, the inner liner gauge can be reduced, and the cost of tire production can be reduced. At present, most of coal ash is landfilled and discarded as industrial waste, but it will be effectively used as a component of this rubber composition.

Claims (1)

[Claims] 1 to 5 parts by weight of coal ash having an average particle diameter of 3 to 7 μm per 100 parts by weight of at least one diene rubber selected from natural rubber, butadiene rubber, styrene / butadiene rubber, isoprene rubber and butyl rubber. A rubber composition for an inner liner, wherein the rubber composition comprises parts.