KR102906830B1 - A composition for spokes of a non-pneumatic tire, a method for manufacturing the same, and a non-pneumatic tire prepared from the composition - Google Patents

Abstract

The present invention relates to a composition for a spoke of a non-pneumatic tire, a method for manufacturing the same, and a non-pneumatic tire manufactured with the composition, and more particularly, to a composition for a spoke of a non-pneumatic tire having improved mechanical properties and heat resistance, a method for manufacturing the same, and a non-pneumatic tire manufactured with the composition. In order to achieve the above-described object, one embodiment of the present invention provides a composition for a spoke of a non-pneumatic tire, comprising SBR (Styrene Butadiene Rubber), a silica reinforcing material, a silane coupling agent, and an isocyanate additive, a method for manufacturing the same, and a non-pneumatic tire using the same, thereby solving the above-described problem.

Description

Composition for spokes of a non-pneumatic tire, a method for manufacturing the same, and a non-pneumatic tire prepared from the composition

The present invention relates to a composition for a spoke of a non-pneumatic tire, a method for producing the same, and a non-pneumatic tire produced using the composition, and more particularly, to a composition for a spoke of a non-pneumatic tire having improved mechanical properties and heat resistance, a method for producing the same, and a non-pneumatic tire produced using the composition.

Pneumatic tires support the vehicle's weight, transmit power to the ground, and absorb vibration and shock generated during driving by the air injected into them. However, pneumatic tires are highly susceptible to punctures and have a very short lifespan. Consequently, approximately 1 billion tires are discarded annually, resulting in enormous environmental and economic losses. Furthermore, if pneumatic tires are damaged by external impacts while driving, the air pressure inside the tire decreases, making it difficult to control the vehicle, potentially leading to a major accident and impairing performance. Therefore, frequent pressure checks are inconvenient.

In fact, according to data released by Hyundai Marine & Fire Insurance's Transportation Climate and Environment Research Institute, which analyzed 230,000 traffic accidents that occurred nationwide between June and August 2020, the rate of tire puncture accidents increased by 66% when the temperature exceeded 30 degrees Celsius, the fatality rate was 12.3 times higher than that of general traffic accidents, and the rate of serious injury was 3.4 times higher. To solve this problem, active research is being conducted on non-pneumatic tires that can fundamentally solve the problem of tire punctures by designing spokes that utilize elastic supports instead of air tubes.

The spokes of airless tires must support the heavy weight of the vehicle body solely through deformation of the elastic support, so the materials used as spokes require extremely high strength and Young's modulus. Polyurethane is the most commonly used material for airless tire spokes, but due to the long processing time and high rolling resistance of polyurethane, research into other materials is currently underway. According to Michelin's patent US20210362548A1, a composite material of styrene-co-butadiene copolymer and polyether exhibited excellent physical properties. Therefore, improving the physical properties of SBR material itself can be expected to improve the physical properties of airless tire spoke materials accordingly.

Styrene butadiene rubber (SBR) is a rubber material obtained through a compounding and vulcanization process based on the poly(styrene-co-butadiene) polymer obtained by polymerizing styrene and butadiene monomers. When compounding SBR, silica particles and a silane coupling agent can be mixed in addition to the SBR copolymer to obtain a silica-reinforced SBR rubber material, which has superior physical properties to general SBR rubber material.

Silica has a large number of silanol groups on its surface, which makes it highly polar. However, it has low affinity with the SBR polymer, which has low polarity, making it difficult to disperse silica within rubber. Therefore, a common method is to use a silane coupling agent to induce a chemical bond between silica and rubber, thereby increasing the affinity between silica and the SBR polymer and improving dispersibility. Bis(triethoxysilylpropyl) tetrasulfide (TESPT) has been commonly used as a silane coupling agent.

Republic of Korea Patent No. 10-0437688 (registration date: June 26, 2004) US20210362548A1 (publication date: November 25, 2021)

However, according to a recent analysis by A. Blume et al., when Bis(triethoxysilylpropyl) tetrasulfide (TESPT) was applied as a silane coupling agent, only about 25% of the silane coupling agent reacted with silica, which reduced the efficiency of the coupling agent, and in the process of forming a bond, additional substances such as ethanol and water were generated, which caused bubbles in the rubber material and resulted in a decrease in physical properties.

Accordingly, the present invention aims to improve tensile properties by utilizing an isocyanate-based additive to increase the efficiency of the coupling agent and suppress bubble generation due to the additive, while also securing heat resistance.

One embodiment of the present invention for achieving the above-described object provides a composition for a spoke of a non-pneumatic tire, comprising SBR (Styrene Butadiene Rubber), a silica reinforcing material, a silane coupling agent and an isocyanate additive, a method for producing the same, and a non-pneumatic tire using the same, thereby solving the above-described problem.

According to one embodiment of the present invention described above, when an isocyanate additive is applied, the interaction between silica and a coupling agent is increased to a urethane bond, and this can be confirmed as an increase in physical properties through a tensile test. In addition, it can be seen through FT-IR data that the added isocyanate forms a urethane bond.

In addition, the thermal stability of the SBR of the present invention to which the isocyanate additive was applied was confirmed through DSC analysis.

Therefore, when the isocyanate of the present invention is added, the physical properties of the SBR composition are dramatically improved, and this can be expected to have the effect of improving the performance of non-pneumatic tires in the future.

The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the composition of the invention described in the claims.

Figure 1 is the structural formula of the above TESPT.
Figure 2 a) is a structural diagram of hexamethylene diisocyanate (HDI), and b) is a structural formula of 4,4'-methylene diphenyl diisocyanate (MDI).
Figure 3 is a side view of the non-pneumatic tire of the present invention.
Fig. 4 is an explanatory drawing illustrating a method for manufacturing a sample of a composition for a spoke of a non-pneumatic tire of the present invention.
Figure 5 is a graph showing the tensile properties of the basic sample E45 and the sample with added HDI (E45-H20~160).
Figure 6 is a graph showing the tensile properties of the basic sample E45 and the sample with added MDI (E45-M20~160).
Figure 7 is a graph of the FT-IR analysis results for each specimen.
Figure 8 is a graph of the DSC measurement results for each specimen.
Figure 9 is an explanatory diagram of the silica-silane reinforced molecular structure after addition of an isocyanate substance.
Figure 10 is a schematic diagram of the microstructure of a SBR-silica-coupling agent-diisocyanate system sample.
Figure 11 is a photograph of the change in film condition depending on whether HDI is added.

In describing the present invention below, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

Since embodiments according to the concept of the present invention can be modified in various ways and take on various forms, specific embodiments are illustrated in the drawings and described in detail in this specification or application. However, this is not intended to limit embodiments according to the concept of the present invention to a specific disclosed form, and it should be understood that the present invention includes all modifications, equivalents, and alternatives included within the spirit and technical scope of the present invention.

When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components in between. Conversely, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between. Other expressions that describe the relationship between components, such as "between" and "directly between" or "adjacent to" and "directly adjacent to", should be interpreted similarly.

The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. The singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, it should be understood that the terms "comprises" or "has" indicate the presence of a described feature, number, step, operation, component, part, or combination thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings showing embodiments of the present invention.

As described above, when compounding SBR, silica particles and a silane coupling agent can be mixed together in addition to the SBR copolymer to obtain a silica-reinforced SBR rubber material, which has superior physical properties to general SBR rubber materials. A silane coupling agent has been used to induce a chemical bond between silica and rubber, thereby increasing the affinity between silica and SBR polymer and improving dispersibility. In the past, Bis(triethoxysilylpropyl) tetrasulfide (TESPT), which has somewhat lower efficiency, has been generally used as a silane coupling agent. Figure 1 is a structural formula of the TESPT.

Accordingly, the present invention provides a technology for applying an isocyanate additive to improve the efficiency of TESPT, which is a silane coupling agent. Figure 2 a) is a structural diagram of hexamethylene diisocyanate (HDI), and b) is a structural formula of 4,4'-methylene diphenyl diisocyanate (MDI). That is, the present invention provides a composition for a spoke of a non-pneumatic tire, comprising SBR (Styrene Butadiene Rubber), a silica reinforcing material, a silane coupling agent, and an isocyanate additive.

The above SBR (Styrene Butadiene Rubber) may be added at 100 phr, the silica reinforcing material at 10 to 90 phr, the silane coupling agent at 2 to 5 phr, and the isocyanate additive at 2 to 5 phr. It is preferable that the isocyanate additive be at least one selected from the group consisting of 4,4'-methylene diphenyl diisocyanate (MDI) and hexamethylene diisocyanate (HDI).

In addition, the present invention relates to a method for manufacturing a composition for a spoke of a non-pneumatic tire,

Step of preparing a silica solution (s100);

Step of adding SBR, silane coupling agent, and isocyanate additive (s200);

Heating and forming step (s300);

A method for producing a composition for a spoke of a non-pneumatic tire including:

In the step (s200) of adding the SBR, silane coupling agent, and isocyanate additive, it is preferable that the isocyanate additive is at least one selected from the group consisting of 4,4'-methylene diphenyl diisocyanate (MDI) and hexamethylene diisocyanate (HDI), as described above.

In addition, the present invention further provides, as shown in FIG. 3, a non-pneumatic tire including a tread portion 100), a rim (300) coupled to a wheel, and a spoke portion (200) supporting between the tread portion (100) and the rim (300).

The above spoke part (200) provides a non-pneumatic tire formed with a composition for spokes of a non-pneumatic tire selected from one of claims 1 to 3.

Example

1. Psalm production

Figure 4 is a schematic diagram illustrating a method for manufacturing a sample of a composition for spokes of a non-pneumatic tire of the present invention. Silica is dissolved in a solvent to form a colloidal suspension, into which a coupling agent, SBR copolymer, and isocyanate additive are added and dispersed. A film is then formed using solution casting, and heat is applied using a hot press process to produce the final film.

When the above sample manufacturing method is applied to the manufacturing process of an actual product, the required organic substances are drastically reduced from about 10 to 3 compared to the conventional mixing process, and the amount of substances is also drastically reduced to about 1/50, so cost reduction can be expected.

2. Test results

Table 1 shows the material composition and process conditions for each sample.

SBR copolymer Silica TESPT HDI MDI Hot press a. Bare 3 g 240 mg - - - O b. E45 3 g 240 mg 45 mg - - O c. E45-H20 3 g 240 mg 45 mg 20 mg O d. E45-H80 3 g 240 mg 45 mg 80 mg O e. E45-H160 3 g 240 mg 45 mg 160 mg - O f. E45-M20 3 g 240 mg 45 mg - 20 mg O g. E45-M80 3 g 240 mg 45 mg - 80 mg O h. E45-M160 3 g 240 mg 45 mg - 160 mg O i. E45-M160, No HP 3 g 240 mg 45 mg - 160 mg X

In Table 1 above, a and b are control groups, where a is a control group to which neither TESPT nor isocyanate additives were applied, and b is a control group to which only TESPT was added. c to g are experimental groups, which have variables depending on the type of isocyanate, the amount added, and whether or not hot pressing was performed.

Fig. 5 is a graph showing the tensile properties of the basic sample E45 and the samples with added HDI (E45-H20~160). The graph of Fig. 5 shows the results of analyzing the tensile properties of the samples with and without added HDI, and it was confirmed that the 10% and 50% modulus of E45-H20 with added HDI increased by about 2 times compared to E45 (0.051, 0.149) to 0.09 and 0.356, respectively. As can be seen in the graph of Fig. 5, the properties of the E45-H20 sample were the best, and the properties actually decreased as the excess HDI was added thereafter. This is expected to be because the excess HDI acted as an impurity and interfered with the interaction between polymers or polymers and fillers.

Fig. 6 is a graph showing the tensile properties of the basic sample E45 and the sample with added MDI (E45-M20~160). The graph of Fig. 6 is the result of analyzing the tensile properties of the specimen with added MDI and the E45 sample without added MDI, and it was confirmed that the 10% and 50% modulus of the E45-M160 sample with added MDI were 0.192 and 0.762, respectively, which was about 5 times that of the E45 sample (0.051, 0.149). The graph of Fig. 6 shows that as the amount of added MDI increased, the overall strength increased, but the elongation decreased, and it was confirmed that the samples with added MDI (E45-M20~160) both showed improvements in strength and elongation compared to E45.

Figure 7 is a graph of the FT-IR analysis results for each specimen. As shown in the graph in Figure 7, the FT-IR results from 1200 cm-1 to 1700 cm-1 for various specimens were analyzed to confirm the presence or absence of urethane bonds. No peaks corresponding to urethane bonds were observed in the bare sample, while a minimal peak was observed in the E45-H160 sample.

For the E45-M160 and E45-M160, No HP samples, the peak corresponding to the urethane bond was strongly observed. Therefore, it was confirmed that MDI has a much higher reactivity than HDI and readily forms urethane bonds even at room temperature without high-temperature pressing.

Figure 8 is a graph of the DSC measurement results for each specimen. DSC analysis was performed to confirm the heat resistance of samples with added isocyanate. For the bare and E45 samples made only of silica-SBR, an exothermic peak appeared at a temperature of 87 to 92°C, which could be inferred that oxidation of the polymer chain occurred due to heat. For the samples with added isocyanate, oxidation did not occur because the radicals formed during the oxidation reaction were effectively consumed by the isocyanate or urethane bonds. Only the E45-M160-NoHP sample, which was not heat-treated, underwent a silane coupling agent-silica condensation reaction at a temperature of 180°C.

In conclusion, the experimental data above showed that adding an isocyanate group increased the interaction between silica and coupling agent into a urethane bond, thereby increasing the physical properties through tensile tests. FT-IR data also showed that the added isocyanate formed a urethane bond. Furthermore, DSC analysis confirmed thermal stability.

Figure 9 is a schematic diagram of the silica-silane reinforced molecular structure after the addition of an isocyanate material. The experimental results above show that isocyanate groups (-NCO groups) readily form urethane bonds by reacting with hydroxyl groups (-OH groups). As shown in Figure 5, adding HDI or MDI to the silica-SBR system increases the reaction efficiency of the silane coupling agent and improves the physical properties by bonding the silanol of the silica with the silanol (Si-OH) of the unreacted silane coupling agent.

Figure 10 is a schematic diagram illustrating the microstructure of a SBR-silica-coupling agent-diisocyanate system sample. Figure 10 illustrates the microstructure of a SBR-silica-coupling agent-diisocyanate system sample when diisocyanate is added. As shown in Figure 10, the unreacted silanol groups between silica and silane react to form urethane bonds, thereby increasing the reaction efficiency. When the hot press process is performed, the sulfur present in the silane coupling agent reacts with the SBR due to the applied heat, forming a crosslinked network centered on silica particles, as shown in Figure 6.

Figure 11 is a photograph of the change in film condition depending on the addition of HDI. The residual isocyanate can suppress bubble formation and prevent deterioration of physical properties by consuming water and ethanol. Figure 11 compares the presence of bubbles in the absence and presence of HDI, respectively. In the absence of diisocyanate additive, many bubbles were generated around the outside of the sample, but when the additive was added, the bubbles were reduced to the point where they were difficult to observe with the naked eye.

While the technical concepts of the present invention described above have been specifically described in preferred embodiments, it should be noted that the above embodiments are intended for illustrative purposes only and are not intended to be limiting. Furthermore, those skilled in the art will appreciate that various embodiments are possible within the scope of the technical concepts of the present invention. Therefore, the true scope of technical protection of the present invention should be determined by the technical concepts of the appended claims.

100: Tread
200: Spoke department
300: Rim

Claims (6)

In a composition for spokes of a non-pneumatic tire,
Contains SBR (Styrene Butadiene Rubber), silica reinforcing material, silane coupling agent and isocyanate additive,
The isocyanate group (-NCO) included in the above isocyanate additive reacts with the silanol group (Si-OH) between the silica reinforcing material and the silane coupling agent to form a urethane bond,
A composition for spokes of a non-pneumatic tire, characterized in that the interaction between the silica reinforcing material and the silane coupling agent is increased by combining the silanol of the silica reinforcing material with the silanol (Si-OH) of the unreacted silane coupling agent. In the first paragraph,
A composition for spokes of a non-pneumatic tire, characterized in that the SBR (Styrene Butadiene Rubber) is added in an amount of 100 phr, the silica reinforcing material is added in an amount of 10 to 90 phr, the silane coupling agent is added in an amount of 2 to 5 phr, and the isocyanate additive is added in an amount of 2 to 5 phr.
In the first paragraph,
A composition for spokes of a non-pneumatic tire, characterized in that the isocyanate additive is at least one selected from the group consisting of 4,4'-methylene diphenyl diisocyanate (MDI) and hexamethylene diisocyanate (HDI).
In a method for manufacturing a composition for a spoke of a non-pneumatic tire,
Step of preparing a silica reinforcing material solution (s100);
Step (s200) of adding SBR, silane coupling agent, and isocyanate additive; and
Including a heating and forming step (s300);
Through the above heating and forming step (s300),
The isocyanate group (-NCO) included in the above isocyanate additive reacts with the silanol group (Si-OH) between the silica reinforcing material and the silane coupling agent to form a urethane bond,
A method for producing a composition for spokes of a non-pneumatic tire, characterized in that the interaction between the silica reinforcing material and the silane coupling agent is increased by combining the silanol of the silica reinforcing material with the silanol (Si-OH) of the unreacted silane coupling agent. In paragraph 4,
In the step (s200) of adding the above SBR, silane coupling agent, and isocyanate additive,
A method for producing a composition for a spoke of a non-pneumatic tire, characterized in that the isocyanate additive is at least one selected from the group consisting of 4,4'-methylene diphenyl diisocyanate (MDI) and hexamethylene diisocyanate (HDI). In a non-pneumatic tire including a tread portion (100), a rim (300) coupled to a wheel, and a spoke portion (200) supporting between the tread portion (100) and the rim (300),
A non-pneumatic tire, characterized in that the spoke portion (200) is formed of a composition for spokes of a non-pneumatic tire selected from one of claims 1 to 3.