WO2015159934A1

WO2015159934A1 - Rubber composition

Info

Publication number: WO2015159934A1
Application number: PCT/JP2015/061654
Authority: WO
Inventors: 達宮崎
Original assignee: 株式会社ブリヂストン
Priority date: 2014-04-16
Filing date: 2015-04-16
Publication date: 2015-10-22

Abstract

Provided is a rubber composition for retread tires, which is characterized by containing, as vulcanization accelerators, 0.1 to 3.0 parts by mass of a xanthate-type accelerator, 0.05 to 3.0 parts by mass of a thiuram-type accelerator and 0.1 to 4.0 parts by mass of an amine-type or aldehyde-amine-type accelerator relative to 100 parts by mass of a rubber component, wherein the total amount of the three types of accelerators is 0.5 part by mass or more. The rubber composition for retread tires is one which has both a vulcanization rate and scorch resistance, i.e., one which has a relatively slow vulcanization time (T0.1) and a rapid vulcanization time (T0.9).

Description

Rubber composition

The present invention relates to a rubber composition.

Retread tires are designed to be reused by attaching new tread rubber to the base tire after removing the worn-out tread part, and for tires for large vehicles such as trucks and buses, and aircraft tires. Many are used. Regarding the renewal of the tread part, the method of vulcanizing the mold while forming the tread pattern on the base tire with the unvulcanized tread rubber is called the hot method, and as the name of the method indicates, vulcanization at a relatively high temperature is required. Is what you do. On the other hand, the method of adhering precure tread, which is tread rubber vulcanized in advance, through cushion rubber is called cold method or precure method, and as the name of the method indicates, vulcanization at a relatively low temperature is performed. And bonding.

In any case, vulcanization is necessary for the unvulcanized rubber part, but the problem of overvulcanization where the tyre part and the newly attached tread are also affected by heating and the vulcanization proceeds newly. Occurs. The overvulcanization proceeds cumulatively every time the retread is performed, and damage is gradually accumulated in the base tire. In particular, in order to prevent overvulcanization and reduce damage to the base tire, the cold method has been developed in response to a demand for vulcanization at a low temperature in a short time. Naturally, improvement in productivity is also desired by shortening the entire vulcanization time.

When the cushion rubber is processed into a sheet shape, or when the cushion rubber is wound around the base tire by an extruder, a thermal history is added to the cushion rubber. In this case, so-called rubber burns are not preferable and must be avoided. From this point, scorch resistance is also required. In addition, it is necessary to consider the standing stability after the cushion rubber is prepared until it is actually used for tire retreading. In order to satisfy such vulcanization characteristics, it has been studied to control by selecting and combining the types of vulcanization accelerators. For example, Patent Document 1 refers to the fact that when a xanthate accelerator is used, the overall vulcanization speed is increased and the vulcanization time is shortened. However, further improvement is desired in the vulcanization characteristics over the entire process. In particular, since the vulcanization rate is fast, it is difficult to secure a sufficient induction period, so that it is also a vulcanization accelerator that is easily scorched and difficult to control.

JP2013-039818A

However, although xanthate accelerators are difficult to control, they are one of vulcanization accelerators with excellent potential that realize ideal vulcanization characteristics at low temperatures and in a short time. If the problem of initial vulcanization characteristics can be solved and controlled, it will be particularly suitable for tire retrending by the cold method, and productivity will also be improved.
In view of such circumstances, the present invention intends to provide a rubber composition that achieves both vulcanization speed and scorch resistance.

Therefore, the present inventor has realized a rubber composition having both vulcanization speed and scorch resistance by using a xanthate accelerator in combination with a thiuram accelerator and an amine or aldehyde-amine accelerator. It is a thing.

That is, the present invention contains 0.1 to 3.0 parts by mass of a xanthate accelerator as a vulcanization accelerator and 0.05 to 3.0 parts by mass of a thiuram accelerator with respect to 100 parts by mass of the rubber component. A rubber composition comprising 0.1 to 4.0 parts by mass of an amine or aldehyde-amine accelerator, and a total of the three types of accelerators of 0.5 parts by mass or more It is. Preferably, the xanthate accelerator is contained in an amount of 0.2 to 1.5 parts by mass. More preferably, it contains 0.2 to 1.0 parts by mass of a xanthate accelerator and 0.5 to 2.0 parts by mass of an amine or aldehyde-amine accelerator. When measuring the vulcanization torque curve using a rheometer based on JIS K6300-2, the torque value F reaches the minimum torque value Fmin + xx (maximum torque value Fmax−minimum torque value Fmin) at 120 ° C. The time T0.1 for reaching x = 0.1 is 0.9 minutes or longer, and the time T0.9 for reaching x = 0.9 is within 18 minutes. It is characterized by being.

According to the rubber composition having both vulcanization speed and scorch resistance according to the present invention, aging deterioration due to overvulcanization of the base tire is prevented by adhesion at low temperature and short time vulcanization. Long life can be achieved. In addition, an increase in production efficiency can also have an excellent effect of being economical overall and contributing to resource and energy savings.

The relationship between the vulcanization torque curve and the parameters related to the characteristics is schematically shown.

Hereinafter, the present invention will be described with reference to the accompanying drawings.
The vulcanization torque curve shown in FIG. 1 shows the change in torque with the progress of crosslinking from the start of heating of the vulcanized rubber with a rheometer. For a while after the start of heating, the torque value may once decrease due to the uniformity and temperature increase due to the diffusion of heat, and reaches the minimum torque value Fmin. Thereafter, the torque value often increases with the progress of crosslinking. However, depending on the vulcanization characteristics, the torque starts to increase immediately without decreasing, and the start of heating may become the minimum torque value Fmin. On the other hand, the behavior when the torque increases may reach the maximum torque value Fmax, reach equilibrium, indicate vulcanization returning to decrease, or continue to increase to a limit torque value that can be measured by the rheometer. . Here, it is assumed that it will not continue to rise. That is, when the maximum torque value Fmax is taken regardless of whether or not it starts to decrease, when the increase range ΔF of the torque value is the maximum torque value Fmax−the minimum torque value Fmin, the increase range ΔF is calculated from the minimum torque value Fmin. The time required to increase by 0.1 times is T0.1, and similarly the time required to increase by 0.9 times ΔF is T0.9. T0.1 is an initial time, and T0.9 is a time showing vulcanization characteristics at the end. In the case of the rubber composition as in the present application, the values of T0.1 and T0.9 are usually represented by a time scale in minutes when measured at 120 ° C.

Here, the slope of the vulcanization torque curve is the rate of increase in torque, but since the increase in torque correlates with the degree of progress of vulcanization, this correlates with the vulcanization rate. That is, the slope of the curve at a certain time represents the vulcanization speed, and a large slope represents a fast vulcanization speed, and a small slope represents a slow vulcanization speed. On the other hand, T0.1 and T0.9 described above are vulcanization times, and are expressed as early if the time is short and slow if the time is long.

Since the vulcanization speed usually changes continuously, when the vulcanization speed at a certain time is slow, the time to reach that time is relatively long, that is, slow. On the other hand, if the vulcanization speed is high at a certain time, the time until the time is reached is relatively short, that is, becomes faster.

In terms of vulcanization in a short time, it is preferable that the vulcanization time T0.9, which is an index of the time required for the entire vulcanization process, is shortened. In such a case, the vulcanization time T0.1 is generally shortened with the vulcanization time T0.9, but this is not preferable from the viewpoint of scorch resistance. According to the request from the scorch resistance, the relatively slow vulcanization time T0.1 indicates that the crosslinking does not proceed abruptly from the initial stage and the vulcanization speed is slow, and an appropriate induction time is ensured. This is preferable because it is possible. When the vulcanization time T0.1 is 0.9 minutes or longer, practical usefulness is recognized, further 0.9 to 5 minutes is preferable, and 1 to 5 minutes is particularly preferable. On the other hand, the vulcanization time T0.9 is ideally as early as possible, but if it is within 18 minutes, practical usefulness is recognized, more preferably within 15 minutes, and particularly within 8 minutes. preferable.

As described above, in order to change the vulcanization rate appropriately in the vulcanization process so that the vulcanization time T0.1 is relatively slow and T0.9 is fast, the vulcanization acceleration effect is large. , Xanthate-based accelerator, blended to shorten the overall vulcanization time while combining with other accelerators to suppress the initial vulcanization rate and ensure sufficient induction time It is conceivable to adjust.

Accelerators other than xanthate are mainly nitrogen-containing amine, aldehyde-amine, aldehyde-ammonia, guanidine, thiazole, sulfur-containing sulfenamide, thiourea, thiuram In addition to the xanthate accelerators as the main accelerators as described above, accelerators of various groups of compounds such as dithiocarbamates are known. The combination characterizing the present invention is to use a thiuram accelerator, an amine or an aldehyde-amine accelerator as the accelerator used in combination. Although there are many methods of combination, care must be taken because the characteristics may be impaired.

The xanthate accelerator refers to xanthate and derivatives thereof, mainly esters, having a structure of —OC (═S) —S— in the molecule. As a specific compound, at least one is selected from the compound group consisting of sodium isopropyl xanthate, zinc ethyl xanthate, zinc isopropyl xanthate, zinc butyl xanthate, and butyl xanthogen disulfide. From the viewpoint of the promoting effect and the storage stability of the accelerator, zinc butylxanthate, zinc isopropylxanthate, and the like are preferable, and zinc isopropylxanthate is particularly preferable.

The xanthate accelerator needs to be balanced with other accelerators, but is blended in the range of 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the rubber component. The acceleration effect is manifested at 0.1 parts by mass or more, and by setting it to 3.0 parts by mass or less, control can be performed with other accelerators so that the initial vulcanization time T0.1 does not become too early. .

Thiuram accelerators are a series of accelerators that have been used for a long time as vulcanization accelerators. In the present invention, in particular, thiuram compounds having a bulky hydrocarbon group having 4 to 10 carbon atoms are used. For example, tetra (2-ethylhexyl) thiuram disulfide, 1,6-bis (N, N'-dibenzylthiocarbamoyldithio) -hexane, 1,6-bis {N, N'-di (2-ethylhexyl) thiocarbamoyl And a compound group consisting of dithio} -hexane, and at least one is selected.

The thiuram accelerator needs to be balanced with other accelerators, but is blended in the range of 0.05 to 3.0 parts by mass with respect to 100 parts by mass of the rubber component. A promoting effect is exhibited at 0.05 parts by mass or more, and a sufficient effect is obtained at 3.0 parts by mass or less.

Aldehyde-amine accelerators are those obtained by reacting aldehydes with amines, such as n-butyraldehyde-aniline condensate, butyraldehyde-butylamine condensate, heptylaldehyde-aniline condensate, α-ethyl-β-propyl. Examples include compounds composed of acrolein-aniline condensate, butyraldehyde-butylidene aniline reactant, butyraldehyde-acetaldehyde-butylidene aniline reactant. At least one selected from the above group of amine compounds or group of aldehyde-amine compounds is used in combination with the xanthate compound and thiuram compound. From the viewpoint of the acceleration effect and the storage stability of the accelerator, it is preferable to use butyraldehyde-butylamine condensate, n-butyraldehyde-aniline condensate or heptylaldehyde-aniline condensate, and n-butyraldehyde-aniline. Condensates can be used particularly preferably. As mentioned above, the aldehyde-amine is aldimine because the main component is derived from imine, which is a condensate, in particular aldehyde, but it is an unreacted amine, aldehyde, or aldimine of condensate that is further reacted with amine. Some aminals and compounds obtained by further reacting aldehyde with the condensate aldimine are included, and these are used as aldehyde-amine accelerators. In addition, when an amine is used as an accelerator, it is referred to as an amine or aldehyde-amine accelerator as a vulcanization accelerator system in the present application.

The amine or aldehyde-amine accelerator needs to be balanced with other accelerators, but is added in the range of 0.1 to 4.0 parts by mass with respect to 100 parts by mass of the rubber component. An acceleration effect is manifested at 0.1 parts by mass or more, and a sufficient effect is obtained at 4.0 parts by mass or less. Depending on the balance with the xanthate accelerator, 0.1 to 2.0 parts by mass is a preferred range.

As indicated above, the xanthate accelerator is 0.1 to 3.0 parts by weight, the thiuram accelerator is 0.05 to 3.0 parts by weight, and the amine or aldehyde-amine accelerator is 0.1 to 3.0 parts by weight. The blending is carried out in the range of 4.0 parts by weight, and it is particularly necessary to blend 0.5 parts by weight or more as the lower limit of the total of the above three types of system promoters. The upper limit is preferably 6.0 parts by mass or less.

As the rubber component to be compounded in combination with the above three types of accelerators, various diene rubbers can be used, natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), styrene. -At least one rubber component selected from butadiene rubber (SBR), butyl rubber (IIR) and the like can be used. In particular, natural rubber is preferably used in an amount of 50 parts by mass or more based on 100 parts by mass of all rubber components, and when combining other rubber components, it is preferable to select SBR or IR.

Sulfur used for vulcanization can be appropriately selected from ordinary sulfur, insoluble sulfur, sulfur white, deoxidized sulfur, powdered sulfur, precipitated sulfur, colloidal sulfur, rubbery sulfur and the like. Usually, sulfur or insoluble sulfur is used, and it can be used at 0.5 to 12 parts by weight, preferably 1 to 8 parts by weight, and more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the rubber component.

As the reinforcing filler for securing the strength as a cushion rubber, a filler usually used in a rubber composition can be used. However, as described above, three types of vulcanization accelerators are used, and in balancing the blending, it becomes difficult to adjust when using a filler that will adsorb components. From such a point, the use of carbon black is preferable. It can be used in an amount of 20 to 60 parts by weight, preferably 25 to 45 parts by weight, particularly preferably 25 to 40 parts by weight with respect to 100 parts by weight of the rubber component.

The carbon black can be appropriately selected according to the purpose, but it is preferable that the specific surface area is small and adsorption is suppressed. As a standard, a nitrogen adsorption specific surface area N ₂ SA is preferably about 20 to 100 m ² / g, and grades include HAF, FEF and GPF, and HAF and FEF are preferred.

When inorganic fillers are used as other reinforcing materials, for example, silica, aluminum hydroxide, clay, alumina, talc, mica, kaolin, glass balloon, glass beads, calcium carbonate, magnesium carbonate, magnesium hydroxide, carbonate At least one can be selected from calcium, magnesium oxide, titanium oxide, potassium titanate, barium sulfate, and the like. However, as mentioned above, problems such as adsorption of components are likely to occur. Therefore, using silane coupling agents as appropriate, not only improving affinity with rubber components, but also controlling surface activity to adsorb It is necessary to devise measures to control the above.

In addition, the effects of the present invention include aroma oils, zinc oxide, vulcanization aids, anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, etc., usually blended in the rubber composition as necessary. It can mix | blend in the range which is not impaired. Amine-based compounds are often used as anti-aging agents, and the effects of some of the three types of vulcanization accelerators of the present invention are similar to those of amine-based or aldehyde-amine-based accelerators. Consideration of balance is necessary. In particular, in the present invention, when used as a cushion rubber, a tackifier can be blended in order to improve adhesion between layers.

The above-mentioned zinc oxide particularly works with a sulfur-based vulcanization accelerator and has a function of controlling vulcanization, so that it relates to vulcanization characteristics. Therefore, the blending needs to be performed based on the balance with the vulcanization accelerator. For example, it is necessary to adjust appropriately when using a zinc salt as a xanthate type | system | group accelerator which is the characteristics of this invention. 1 to 10 parts by mass can be blended with 100 parts by mass of the rubber component, and 2 to 5 parts by mass is preferable.

A retreaded tire can be obtained by performing retreading using the rubber composition of the present invention. That is, the tire tires that have reached the end of their service life and have the tread portion shaved are covered with the rubber composition of the present invention as a cushion rubber and further covered with a vulcanized or semi-vulcanized tread rubber. Then, they are placed in a vulcanizing can and vulcanized at a temperature of 80 to 130 ° C. Compared to conventional cushion rubber using a vulcanization system, the vulcanization speed is high and vulcanization is possible for a short time and low temperature vulcanization. The ability to suppress the deterioration of the base tire and improve the durability is also advantageous in that the number of rehabilitation can be increased.

Hereinafter, the present invention will be described using examples and comparative examples, but the configuration of the present invention is not limited to the following examples.

In addition to the blending components common to all Examples / Comparative Examples shown in Table 1, individual blending was carried out in each Example / Comparative Example according to Table 2 to obtain an unvulcanized rubber composition. Each rubber composition was measured for a vulcanization torque curve using a rheometer based on JIS K6300-2 under the condition of 120 ° C., and vulcanization times T0.1 and T0.9 were determined. Furthermore, the breaking elastic modulus Tb was measured according to JIS K 6301, the value of Example 1 was set to 100, and the value of each Example and Comparative Example was indexed. A larger value indicates better fracture resistance. The evaluation results are shown together with the formulation specific to each Example / Comparative Example in Table 2.

The names of the ingredients and the manufacturers / suppliers shown in Tables 1 and 2 are as shown below.
* 1: Natural rubber (RSS # 3)
* 2: Carbon black N550 (Tokai Carbon, Seast F)
* 3: Process oil (Idemitsu Kosan Co., Ltd., Diana Process NH-70S)
* 4: Zinc flower (Hakusuitec Co., Ltd., 2 types of zinc oxide)
* 5: Stearic acid (Miyoshi Oil Co., Ltd., MXST)
* 6: Anti-aging agent (Sumitomo Chemical Co., Ltd. Antigen 6C)
* 7: Insoluble sulfur (Shikoku Kasei Kogyo Co., Ltd., Mucron OT-20-SO)
* 8: Zinc isopropyl xanthate (Ouchi Emerging Chemicals, Noxeller ZIX)
* 9: Tetra (2-ethylhexyl) thiuram disulfide (TOT, Ouchi Shinsei Chemical, Noxeller TOT-N (TOT: 67%, silica: 33% supported product) is used. The compounding amount in Table 2 excludes silica. (Depends on net weight.)
* 10: Butyraldehyde-aniline condensate (Ouchi Shinsei Chemical, Noxeller 8)
* 11: 2-Mercaptobenzothiazole (Ouchi Emerging Chemicals, Noxeller MP)
* 12: 1,3-Diphenylguanidine (Ouchi Shinsei Chemical, Noxeller D)

The vulcanization time T0.1, which is an index of scorch resistance, is 0.9 minutes or more, the vulcanization time T0.9 is an index of the time required for the entire vulcanization process, within 18 minutes, and the fracture resistance Tb index is If it is 80 or more, it can be said that the balance between vulcanization characteristics and fracture resistance is excellent. In Examples 1 to 3, in which the blending amounts of the three vulcanization accelerators are not so different, the balance between the vulcanization characteristics and the fracture resistance is very excellent. When comparing Comparative Examples 1 and 2 and Example 4 in which one component is reduced from Example 2 in which all three components are 1 part by mass with respect to 100 parts by mass of the rubber component in particular, Only when the thiuram system is reduced, the vulcanization time does not break the balance and stays at an appropriate time. On the contrary, when Example 5 and Comparative Examples 3 and 4 in which any one component is increased are observed, only Example 5 in which the amount of amine or aldehyde-amine accelerator is increased does not accelerate the vulcanization time T0.1. In addition to scorch, the fracture resistance is also kept good. In Comparative Examples 5 to 7 in which one component is reduced from Example 1 in which the amount of all three components is small, the fracture resistance is excellent, but both the vulcanization times T0.1 and T0.9 are too slow. In Comparative Examples 8 to 11 using thiazole type or guanidine type instead of thiuram type or amine or aldehyde-amine type accelerator, the vulcanization time T0.9 was too slow.

The rubber composition having both vulcanization speed and scorch resistance according to the present invention can be used as a cushion rubber that can withstand the repeated retreading and has excellent puncture resistance and can be produced with high productivity.

Claims

As a vulcanization accelerator, 0.1 to 3.0 parts by mass of a xanthate accelerator and 0.05 to 3.0 parts by mass of a thiuram accelerator as a vulcanization accelerator, and an amine or A rubber composition comprising 0.1 to 4.0 parts by mass of an aldehyde-amine accelerator, and the total of the three types of accelerators is 0.5 parts by mass or more.
When a vulcanization torque curve is measured using a rheometer at 120 ° C. according to JIS K6300-2, the torque value F reaches the minimum torque value Fmin + 0.1 × (maximum torque value Fmax−minimum torque value Fmin). The rubber composition according to claim 1, wherein T0.1 which is time (minutes) is 0.9 minutes or more.
When the vulcanization torque curve is measured using a rheometer at 120 ° C. according to JIS K6300-2, the torque value F reaches the minimum torque value Fmin + 0.9 × (maximum torque value Fmax−minimum torque value Fmin). The rubber composition according to claim 1 or 2, wherein T0.9 which is time (minutes) is 18 minutes or less.
The rubber composition according to any one of claims 1 to 3, comprising 0.2 to 1.5 parts by mass of a xanthate accelerator.
The xanthate accelerator is contained in an amount of 0.2 to 1.0 parts by mass, and the amine or aldehyde-amine accelerator is contained in an amount of 0.5 to 2.0 parts by mass. The rubber composition as described.
A retread tire characterized by using the rubber composition according to any one of claims 1 to 5 as a cushion rubber.