KR102615820B1 - A rubber composition for a tire belt - Google Patents

Abstract

The present invention discloses a rubber composition for tire belts.
The rubber composition for tire belts according to the present invention is characterized in that it contains surface-modified zinc oxide represented by the formula (1) below, which improves the crosslink density and modulus of the rubber for tire belts and at the same time improves aging resistance. By securing performance, you can ultimately improve the durability of tires.
<Formula 1>

Description

Rubber composition for a tire belt {A rubber composition for a tire belt}

The present invention relates to a rubber composition for a tire belt, and more specifically, to a rubber composition for a tire belt that improves the crosslink density and modulus of the rubber for a tire belt and at the same time secures aging resistance, ultimately improving the durability of the tire. It relates to composition.

In general, tire belts serve to increase the rigidity of the tread section by overlapping layers of steel cord. Accordingly, the belt rubber must have good adhesion to the steel cord and durability to withstand long-term driving. To this end, it must have a high modulus and be resistant to aging. There is a need for a rubber composition to be used as a belt rubber with certain properties.

These rubber compositions for tire belts are generally composed of additives such as natural rubber, sulfur, crosslinking accelerator, carbon black, inorganic propellant, zinc oxide, stearic acid, process oil, and anti-aging agent.

Among them, zinc oxide is an activator that reacts with stearic acid to increase its activity and facilitates the accelerating action of the accelerator, thereby improving the cross-linking efficiency of the rubber and increasing the cross-linking density, resulting in a belt rubber with a high modulus.

Several technologies have been attempted to produce rubber compositions for belt toffees with high crosslink density and modulus, the most common techniques being the use of a high amount of carbon black or an increased amount of vulcanizing agent.

However, rubber compositions using an excessive amount of carbon black are undesirable because they are overloaded during the process and roll processability is disadvantageous, resulting in low productivity in terms of productivity.

Additionally, if an increased amount of vulcanizing agent is used, there is a risk of blooming phenomenon where the compounding agent seeps out onto the surface.

Existing zinc oxide has the disadvantage of low crosslinking efficiency due to low activity, and since zinc oxide is electrostatic, it is difficult to disperse within the composition when used in excessive amounts due to entanglement, and furthermore, the rubber properties may become uneven or localized. There is a risk that problems may arise due to excessive amounts.

Registered Patent Publication No. 1527860 (registration date: June 4, 2015)

Therefore, the technical problem to be solved by the present invention is to provide a rubber composition for a tire belt that improves the crosslink density and modulus of the rubber for a tire belt and at the same time secures aging resistance and ultimately improves the durability of the tire. .

In order to solve the above-mentioned technical problems, the present invention provides a rubber composition for a tire belt, which includes surface-modified zinc oxide represented by the formula (1) below.

<Formula 1>

(RO is an alkoxy group, R ₁ is a hydrocarbon group having 1 to 4 carbons (C), and R ₂ is hydrogen (H) or an alkyl group having 1 to 3 carbons)

According to another embodiment of the present invention, the zinc oxide may be pretreated with silane.

According to another embodiment of the present invention, the surface-modified zinc oxide may be used in an amount of 1 to 5 parts by weight based on 100 parts by weight of raw rubber.

According to the rubber composition for a tire belt according to the present invention, it is possible to improve the crosslink density and modulus of the rubber for a tire belt, and at the same time secure aging resistance, ultimately improving the durability of the tire.

It should be noted that the technical terms used in the present invention are only used to describe specific embodiments and are not intended to limit the present invention, and the technical terms used in the present invention are not specifically defined in any other way in the present invention. Unless otherwise stated, it should be interpreted in the sense generally understood by those skilled in the art to which the present invention pertains, and should not be interpreted in an excessively comprehensive sense or in an excessively reduced sense.

Additionally, if the technical term used in the present invention is an incorrect technical term that does not accurately express the idea of the present invention, it should be replaced with a technical term that can be correctly understood by a person skilled in the art. In addition, general terms used in the present invention should be interpreted according to the definition in the dictionary or according to the context, and should not be interpreted in an excessively reduced sense.

In addition, the singular expression used in the present invention includes plural expressions unless the context clearly indicates otherwise. For example, terms such as 'consists' or 'comprises' refer to various constituent elements described in the invention, or It should not be interpreted as necessarily including all of the steps, and some components or steps may not be included, or additional components or steps may be included.

Hereinafter, the present invention will be described in detail.

The rubber composition for a tire belt according to the present invention has the feature of containing surface-modified zinc oxide represented by Chemical Formula 1 below.

<Formula 1>

(RO is an alkoxy group, R ₁ is a hydrocarbon group having 1 to 4 carbons (C), and R ₂ is hydrogen (H) or an alkyl group having 1 to 3 carbons)

Here, the RO is an alkoxy group and includes methoxy and ethoxy, which have a small number of carbon atoms. Up to 4 carbon atoms can be used. If the number of carbon atoms exceeds 5, steric hindrance may occur, which may reduce the reaction efficiency during surface modification of zinc oxide.

In addition, R ₁ is a hydrocarbon group having 1 to 4 carbons (C), and R ₂ may be hydrogen (H) or an alkyl group having 1 to 3 carbons.

Meanwhile, looking at the reaction formula of Chemical Formula 1, zinc oxide can first be pretreated with silane. For example, as shown in Scheme 1 below, zinc oxide (ZnO) powder is dispersed in an ethanol (Absolute ethanol, 99.9%) solution and then CTS (Chloropropyltrimethoxysilane) can be added and reacted at 50°C for 24 hours.

The zinc oxide powder used here has a surface area of 60 to 90 m ² /g as measured by BET and an average particle diameter of 10 to 20 nm.

In order to ensure stability and aging resistance when mixing the rubber composition for a tire belt according to the present invention, it can be post-treated for further reaction with a compound having a thiol group (-SH). For example, pretreated zinc oxide can be used for further reaction. After washing and dispersing by impregnating again with an ethanol solution, MB (2-Mercapto-4(5)-Methylbenzimidazole) and NaOH can be added and reacted at 50°C for 24 hours, and the obtained zinc oxide is a rubber composition. It is easy to disperse within the tire and can improve the modulus and aging resistance of rubber, which can help strengthen the durability of tires.

<Scheme 1>

Meanwhile, the surface-modified zinc oxide can be used in an amount of 1 to 5 parts by weight based on 100 parts by weight of raw rubber. If it is less than 1 part by weight, the effect may be minimal, and if it exceeds 5 parts by weight, the increase in differential effect may be minimal. there is.

<Examples and Comparative Examples>

Tire belt rubber was manufactured by mixing and extruding the rubber mixture with the composition shown in Table 1 below.

item Comparative Example 1 Comparative example 2 Example 1 Example 2 Example 3 Example 4 Natural rubber (NR) 100 100 100 100 100 100 carbon black 80 80 80 80 80 80 zinc oxide 4 4 4 4 4 4 stearic acid One One One One One One anti-aging agent 1.5 1.5 1.5 1.5 1.5 1.5 Sulfur 6.2 6.2 6.2 6.2 6.2 6.2 vulcanization accelerator One One One One One One regular zinc oxide 5 nano zinc oxide 3 (no surface treatment) One 3 5 7

* General zinc oxide has a surface area of 3 to 6 m ² /g as measured by BET and an average particle diameter of 300 to 400 ㎚.

* Nano zinc oxide has a surface area of 60 to 90 m ² /g as measured by BET, and an average particle diameter of 10 to 20 ㎚.

* Surface treatment of nano zinc oxide in Examples 1 to 4 (Silane is pretreated with CTS (Chloropropyltriethoxysilane), and the post-treatment thiol compound is Formula 2 using MB (2-Mercapto-4(5)-Methylbenzimidazole))

<Formula 2>

<Experimental example>

Prepare each belt rubber manufactured in Table 1 above, and for this specimen Mooney viscosity (250±5g), tensile properties (Tensile, specimen type: Type1A), dynamic viscoelasticity (DMA, specimen according to ASTM D2231-87), and adhesive properties were measured according to ASTM-related regulations and the results are presented below. It is shown in Table 2.

item Comparative Example 1 Comparative example 2 Example 1 Example 2 Example 3 Example 4 Mooney viscosity MV@100℃ 85.2 84.1 78.4 88.5 89.1 89.5 T05 (min) 4.5 4.5 4.2 4.3 4.6 4.6 Tensile properties
(Early) Hardness(%) 100 101 102 105 105 106 300% Modulus (%) 100 99 103 107 106 107 T.S. (%) 100 102 104 108 108 109 E.B. (%) 100 100 97 95 96 95 Tensile properties
(Aging) Hardness(%) +15 +13 +12 +8 +9 +9 300% Modulus (%) +12 +13 +10 +7 +8 +8 T.S. (%) -28 -28 -25 -20 -18 -19 E.B. (%) -34 -30 -28 -25 -23 -23 DMA tanδ@60℃ (%) 100 101 102 107 107 108 Adhesion properties Adhesion force (%) 100 102 105 110 110 111 Coverage(%) 100 95 100 100 100 100

* Mooney viscosity: The minimum torque value for viscosity measured at 125°C Mooney viscosity was measured according to ASTM D1646.

* Tensile properties (initial): To evaluate the mechanical properties of rubber, tensile properties of a dumbbell-shaped specimen (ASTM D-412-89C type) were tested before and after aging. (Aging: left at 80℃ for 7 days)

* DMA: Measures the response (viscoelasticity) of rubber when repeated stress is applied to the rubber. Evaluated according to ASTM D-2231-87.

* Adhesion properties The adhesion between rubber and steel cord was evaluated according to ASTM D2229-80. The steel cord was evaluated based on the force and rubber coverage when it was pulled out from the rubber (T-test).

* Tensile properties, DMA, heat generation, and adhesive properties are expressed as relative percentages, with higher values indicating superior properties.

As can be seen from the experimental results in Table 2, the examples of the rubber composition for a tire belt according to the present invention are effective even if a small amount of nano-silane-treated zinc oxide is used compared to the case of using 5 parts by weight of conventional zinc oxide (Example 2 ) It can be seen that it is excellent in hardness, modulus, T.S., and characteristics, and is excellent in terms of aging.

In addition, even when used in small quantities as in Example 1, the surface area is large due to the even dispersion of nano-zinc oxide, so it can be seen that the effect is slightly better than the comparative example.

In Examples 3 and 4, it can be seen that although the amount of zinc oxide is increased, the effect due to the activity of zinc oxide converges to the maximum value, and the increase in the differential effect is minimal.

In addition, it can be seen that the DMA characteristics and the adhesion force of the steel cord are also excellent.

item Comparative Example 1 Comparative example 2 Example 1 Example 2 Example 3 ECE-R30 hour(%) 100 101 88 104 105 100 102 87 105 103 DOT-139(E) hour(%) 100 98 94 103 104 100 99 95 105 105 DOT-139(H) hour(%) 100 97 90 107 108 100 98 91 106 108

Table 3 above shows the results of the finished product durability test. The examples were comparatively evaluated by applying them to the P225/45 R17 TA71 PCR standard in a conventional manner, and it can be seen that the durability performance of Example 2 was improved compared to the comparative examples.

In Examples 1 and 3, it can be seen that the durability performance is also excellent as the rubber properties are improved compared to the comparative example.

Claims (3)

Contains surface-modified zinc oxide represented by Formula 2 below,
A rubber composition for a tire belt, characterized in that the zinc oxide has a surface area of 60 to 90 m ² /g as measured by BET and an average particle diameter of 10 to 20 nm.
<Formula 2>

delete According to claim 1,
A rubber composition for a tire belt, characterized in that the surface-modified zinc oxide is used in an amount of 1 to 5 parts by weight based on 100 parts by weight of the raw rubber.