JPS61176648A - Rubber composition for inner liner of tire - Google Patents

Abstract

PURPOSE:The titled composition having improved impermeability to air, adhesiveness, and thermal aging resistance, obtained by blending regenerated butyl rubber with an aromatic hydrocarbon resin having an average molecular weight, a softening point, and an iodine absorption amount in specific ranges in a specified ratio. CONSTITUTION:(A) >=30pts.wt., preferably 30-70pts.wt. calculated as polymer component of regenerated butyl rubber is blended with (B) 2-15pts.wt. aromatic hydrocarbon resin having 30-1,500 average molecular weight, 50-160 deg.C softening point, and >=20g/100g iodine absorption amount to give a composition. Improved adhesiveness can be maintained only by adding <=1.8pts.wt. sulfur as a vulcanizing agent, and curing during thermal aging and release of splice part can be prevented when the composition is used as an inner liner of tire.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a rubber composition made of recycled butyl rubber,
More specifically, the present invention relates to a rubber composition for tire inner liners that has excellent air impermeability, adhesive properties, and heat aging resistance.

[Prior art]

Conventionally, various ways to use recycled butyl rubber have been studied from the perspective of resource conservation, but its use in parts that come into direct contact with air, reach relatively high temperatures, and require bending resistance is difficult due to its heat aging resistance. It is limited due to its stiffness and poor adhesion to other parts. Therefore, at present, recycled butyl rubber is not used in the inner liners of high-load running tires such as truck and bus tires or tires used in high-temperature regions.

[Purpose of the invention]

An object of the present invention is to provide a rubber composition made of recycled butyl rubber, which can be used for the inner liner of any tire and has excellent air impermeability, adhesiveness, and heat aging resistance. shall be.

[Structure of the invention]

For this reason, the present invention uses recycled butyl rubber and an average molecular weight of 30.
0-1500, softening point 50-160℃, iodine adsorption amount 2
0g/100g or more of aromatic hydrocarbon resin, and the amount of recycled butyl rubber is 30% in terms of polymer content.
The amount of the aromatic hydrocarbon resin is 2 parts by weight or more.
The gist of the present invention is a rubber composition for an inner liner of a tire, characterized in that the amount is 15 parts by weight.

Hereinafter, the configuration of the present invention will be explained in detail.

The recycled butyl rubber used in the present invention is recycled butyl rubber after use, is a known rubber, and is not specified.

Further, the aromatic hydrocarbon resin used in the present invention has an average molecular weight of 300 to 1500, a softening point of 50 to 160°C, and an iodine adsorption amount of 20 g/100 g or more. Examples of this resin include Fukol resin (trade name, manufactured by Fuji Kosan Co., Ltd.).

The rubber composition of the present invention comprises the recycled butyl rubber described above and the aromatic hydrocarbon resin described above. The amount of recycled butyl rubber blended is 30 parts by weight or more, preferably 30 to 70 parts by weight in terms of polymer content. This is because if it is less than 30 parts by weight, the air permeability coefficient will not reach the initial target value. Further, the blending amount of the aromatic hydrocarbon resin is 2 to 15 parts by weight.

This is because if it is less than 2 parts by weight, no improvement in adhesion can be expected, while if it exceeds 15 parts by weight, heat generation will increase.

The amount of sulfur added as a vulcanizing agent may be 1.8 parts by weight or less. If the amount of sulfur is small as described above, adhesion tends to deteriorate, but in the present invention, since the aromatic hydrocarbon resin is used in an amount of 2 to 15 parts by weight, good adhesion can be maintained. Note that as the vulcanizing agent, other vulcanizing agents may be used in place of sulfur, or other vulcanizing agents may be used in combination with sulfur.

〔Effect of the invention〕

As explained above, since the rubber composition of the present invention is made by blending recycled butyl rubber and aromatic hydrocarbon resin in a specific ratio, it has excellent air impermeability, adhesiveness, and heat aging resistance. Therefore, when used in the inner liner of a tire, it is possible to prevent the inner liner from hardening during heat aging, and also to prevent peeling at the splice portion. Furthermore, it can be said that the present invention expands the possibility of effective use of recycled butyl rubber from the standpoint of resource conservation.

EXAMPLES The effects of the present invention will be specifically explained below with reference to Examples.

Example (a) Various rubber compositions with the blending contents (parts by weight) shown in Table 1 were prepared with various blending ratios of natural rubber and recycled butyl rubber, and after vulcanization, air impermeability was evaluated. . The results are shown in FIG.

Figure 1 shows the blending amounts of natural rubber and recycled butyl rubber and the gas permeability coefficient (ml-cm/ci-sec, ・cnHg)
(60° C.) is an explanatory diagram showing a graph of the relationship between the temperature and the temperature. The amount of recycled butyl rubber is calculated in terms of polymer content. The dashed line a in the figure is for comparison and represents the currently required upper limit of the gas permeability coefficient of the tire inner liner. The method for measuring the gas permeability coefficient in Figure 1 is as follows:
Each rubber composition was made into a sheet with a thickness of 0.4 mm±0 and 0.5 mm, and was determined by a volumetric method using a Warburg manometer.

From FIG. 1, it can be seen that the amount of recycled butyl rubber blended should be 30 parts by weight or more in terms of polymer content.

(Margins below this page) note): (1) NRR5S#4.

(2) The polymer content is 55% (JIS).

(3) N 660 (Dia Black G).

(4) Kaolin clay (Suprex C1ay).

(5) Aromatic hydrocarbon resin manufactured by Fuji Kosan Co., Ltd. (average molecular weight 4
00~800, softening point 70~150℃, iodine value 20~
40g/100g, specific gravity 1.12-1 at 25℃
．． 14, fixed carbon 20-35%).

(No. 3 Zinc White manufactured by Seido Chemical.

(7) N-cyclohexyl-2-benzothiazylsulfenamide.

(b) Compounding contents (parts by weight) shown in Table 2 with various blending ratios of chlorobutyl rubber and recycled butyl rubber
Various rubber compositions were prepared, and after vulcanization, the elastic modulus E'' (MP^) after aging was evaluated (the degree of curing was small because the amount of sulfur compounded was suppressed). The results are shown in FIG.

FIG. 2 is an explanatory diagram showing the relationship between the compounding amounts of chlorobutyl rubber and recycled butyl rubber and the elastic modulus E" (MPA) after aging. The amount of recycled butyl rubber is calculated in terms of polymer content. Among them, b is the case where each rubber composition was aged in a gear oven at 120°C for 72 hours, and C is the case where each rubber composition was aged at 120°C for 48 hours.
This is the case when aging is performed with the time gear open, and d is
This is a case of alienation. In addition, the elastic modulus in FIG. 2 is calculated using a viscoelasticity spectrometer (VH5-R3'' manufactured by Iwamoto Manufacturing Co., Ltd.) at 20°C for 20 hours.
z, measured at 10±2% amplitude.

From FIG. 2, it can be seen that the elastic modulus increases more when recycled butyl rubber is used than when chlorobutyl rubber is used.

(Margins below this page) (Various rubber compositions with the compounding contents (parts by weight) shown in Table 3 in which the compounding ratio of C1 sulfur was varied were prepared, and after vulcanization, the elastic modulus after aging EwI (MPA ) was evaluated.The results are shown in Figure 3.

Figure 3 shows the amount of sulfur blended and the elastic modulus after aging Ell (MP
It is an explanatory diagram showing a relationship with A) in a graph. In the figure,
e is the case when each rubber composition was aged in a gear open for 72 hours at 120°C, f is the case when each rubber composition was aged in a gear oven at 120°C for 48 hours, and g is the case when each rubber composition was aged in a gear oven for 48 hours at 120°C This is the case when the patient is not aged. The method of measuring the elastic modulus in FIG. 3 is to measure each rubber composition using a viscoelastic spectrometer (VHS-H manufactured by Iwamoto
S ) at 20° C., 20 Hz, and 10±2% amplitude.

From FIG. 3, it can be seen that if the amount of sulfur added is 1.8 parts by weight or less, changes in the elastic modulus can be kept relatively small.

(Margins below this page) (d) Various rubber compositions with the blending contents (parts by weight) shown in Table 4 were prepared in which the blending ratio of aromatic hydrocarbon resin (Funcor resin) was varied, and natural rubber was mixed. After laminating with a rubber composition having the formulation shown in Table 5 as a raw material and vulcanizing it, the peel force (kg/cII+) was measured. The results are shown in FIG.

Figure 4 shows the blending amount of aromatic hydrocarbon resin and peeling force (kg
/cm) is an explanatory diagram showing a graph of the relationship between In addition, the method of measuring the peel force in FIG. 4 was performed based on JIS K 6301 for each rubber composition, and the dimensions were 25.0 ± 0.51 I to I in width and 150 n + m in length.
A strip-shaped test piece with a thickness of 6 mm with reinforcing material laminated on both sides was 180 mm using an autograph at a tensile speed of 50 mm/win.
° A peel test was conducted.

From FIG. 4, it can be seen that the peeling force increases significantly when the amount of fluorocarbon resin blended is 2 to 15 parts by weight.

(Margins below this page) Table 5 Natural rubber (R5S #4) 100 parts by weight Zinc oxide 10 parts by weight Carbon blank (HAP) 55 parts by weight Aroma oil
3 parts by weight Vulcanization accelerator (OBS) 0.
8 parts by weight Sulfur 2 parts by weight

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the blending amounts of natural rubber and recycled butyl rubber and the gas permeability coefficient, and Figure 2 is a graph showing the relationship between the blending amounts of chlorobutyl rubber and recycled butyl rubber and the elastic modulus after aging. Figure 3 is an explanatory diagram showing the relationship between the amount of sulfur blended and the elastic modulus after aging.
FIG. 4 is an explanatory diagram showing the relationship between the blending amount of aromatic hydrocarbon resin and peeling force in a graph.

Claims (1)

[Claims] It consists of recycled butyl rubber and an aromatic hydrocarbon resin with an average molecular weight of 300 to 1500, a softening point of 50 to 160°C, and an iodine adsorption amount of 20 g/100 g or more, and the amount of the recycled butyl rubber blended is 30 parts by weight or more in terms of polymer content, A rubber composition for an inner liner of a tire, characterized in that the aromatic hydrocarbon resin is blended in an amount of 2 to 15 parts by weight.