JP2017165867A - Rubber composition for fender - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel rubber composition for fender capable of forming a high durability fender excellent in cushioning performance, having high reactive force even with downsizing and hardly generating reduction of the cushioning performance or crack even with maintaining to use especially under high temperature environment for long time.SOLUTION: A rubber composition for fender contains a rubber component containing at least natural rubber and SBR, and carbon black, the SBR has vinyl content of 30 to 45 mass% and styrene content of 25 to 40 mass% and blended percentage thereof of 10 to 40 pts.mass based on 100 pta.mass of the total amount of the rubber component.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition for a fender as a material for forming a fender that is installed on, for example, a quay and functions as a buffer when a ship is berthed or moored.

As a fender that is installed on a quay and functions as a cushioning material when docking or mooring a ship, etc., the entire structure is made of an elastic material, especially a rubber cross-linker, and the structure is simple. Widely popular because it is hard to break.
Such a fender is prepared from a rubber composition prepared by blending a crosslinkable rubber with a filler such as carbon black, a cross-linking component for cross-linking the rubber, and various additives. And is produced by crosslinking the rubber component (for example, Patent Document 1).

For the cross-linkable rubber component, it is necessary to give a good cushioning performance to the fender by appropriately balancing the rubber properties (rubber properties) such as rubber hardness, elongation at break, and tensile strength. From the viewpoint of availability, etc., natural rubber is preferably used.
Natural rubber may be used alone or in combination with other rubber such as styrene butadiene rubber.

Further, as a crosslinking component for crosslinking the rubber component including the natural rubber, a combination of sulfur (crosslinking agent) and a crosslinking accelerator having an action of promoting the crosslinking of the rubber component by the sulfur is suitably employed. The
The fender has a high reaction force even if it is miniaturized in order to exhibit good shock-absorbing performance without taking up space at the installation location, or to reduce the production cost by using less materials. Desired.

The fender is also required to be resistant to reduced buffering performance and cracking when repeated compression and expansion, even if it is used for a long period of time, especially in high temperature (severe heat) environments. It is done.
In other words, the fender is usually installed outdoors, and depending on the area or season of installation, the fender may continue to be used in a high temperature environment such as 40 ° C. or higher.

Further, for example, depending on the installation location, the surface temperature of the fender may even reach a high temperature of 80 ° C. or more due to direct sunlight.
In addition, once installed, the fender can be used in the same place for a long time in units of several years to several tens of years.
However, rubber fenders are good in a relatively short period of time, especially in the above-mentioned high temperature environment, for example, because the rubber hardness is increased or the elongation at the time of cutting is reduced and the balance of rubber properties is easily lost. There is a problem that it is difficult to maintain a sufficient cushioning performance or cracks are likely to occur.

In Patent Document 2, the maximum reaction force R ₂₃ at a temperature of 23 ° C. and the maximum reaction force at a temperature of 60 ° C. are exhibited in a rubber fender so as to exhibit a buffer performance that is not significantly different from that in a normal temperature environment even in a high temperature environment. the compression performance change rate expressed by the ratio _R 60 _{/ R 23} and R ₆₀ be greater than 0.90 has been proposed.
However, since the invention described in Patent Document 2 does not take into account the suppression of a decrease in buffer performance, the occurrence of cracks, etc., when such a fender is continuously used particularly in a high temperature environment, a short period of time is required. However, it is easy to cause these problems.

JP 2013-194155 A JP 2002-13120 A

  The object of the present invention is to provide a highly durable anti-shock material that is excellent in shock-absorbing performance, has a high reaction force even if it is downsized, and is unlikely to cause a decrease in shock-absorbing performance or cracks even when used for a long period of time in a high-temperature environment. It is an object of the present invention to provide a novel rubber composition for fenders that can form a fender.

  The present invention includes at least a rubber component including natural rubber and styrene butadiene rubber, and carbon black. The styrene butadiene rubber has a vinyl content of 30% by mass to 45% by mass, a styrene content of 25% by mass or more, 40%. The blending ratio of the styrene butadiene rubber is 10% by mass or more and 40% by mass or less in the total amount of the rubber content, and is a rubber composition for a fender.

  According to the present invention, it has excellent shock-absorbing performance, has a high reaction force even if it is downsized, and has a high durability that is unlikely to cause a decrease in shock-absorbing performance or cracks even when used continuously for a long period of time in a high-temperature environment. A novel rubber composition for fenders that can form a fender can be provided.

  As described above, the present invention includes at least a rubber component including natural rubber and styrene butadiene rubber (SBR), and carbon black, and the styrene butadiene rubber has a vinyl content of 30% by mass to 45% by mass, and a styrene content. Is 25 mass% or more and 40 mass% or less, and the blending ratio of the styrene butadiene rubber is 10 mass parts or more and 40 mass parts or less in the total amount of 100 mass parts of the rubber. It is a thing.

  According to the anti-mold rubber composition of the present invention, the SBR having the specific vinyl content and the styrene content is used together with natural rubber as a rubber component at the predetermined ratio, and the examples and comparative examples described later are used. As is clear from the results, the buffering performance is excellent, it has a high reaction force even if it is downsized, it has excellent heat resistance, and even if it continues to be used for a long time in a high temperature environment, the buffering performance is deteriorated or cracked. A highly durable fender that is unlikely to occur can be formed.

That is, natural rubber functions mainly to moderately balance rubber physical properties as described above and to impart good cushioning performance to the fender. SBR functions in combination with natural rubber to improve the heat resistance of the fender.
However, SBR with a vinyl content of less than 30% by mass has insufficient functions as described above, and particularly, as described above, the balance of the rubber physical properties of the fender is lost in a high temperature environment, resulting in reduced buffering performance and cracks. It is easy to occur.

Further, SBR having a vinyl content exceeding 45% by mass has a low dispersibility of carbon black as a filler, and the reinforcing effect of the carbon black cannot be sufficiently obtained, so that the strength and rigidity of the fender are easily insufficient. In addition, since the SBR has a low crosslinking rate, the productivity of the fender may be lowered.
In addition, SBR having a styrene content of less than 25% by mass has a low fracture energy, and thus the strength of the fender is likely to be insufficient. On the other hand, SBR having a styrene content exceeding 40% by mass is susceptible to brittle fracturing. There is a risk of reducing the wear resistance.

Moreover, when the blending ratio of SBR is less than 10 parts by weight in 100 parts by weight of the total amount of rubber, the effect of improving heat resistance by blending the SBR cannot be sufficiently obtained, and particularly in a high temperature environment as described above. Thus, the balance of the rubber physical properties of the fender is lost, and the buffer performance is likely to be lowered or cracks are likely to occur.
Natural rubber has a function of suppressing the growth of cracks generated in the fender by appropriately balancing the physical properties of the rubber, but the blending ratio of SBR exceeds 40 parts by mass in 100 parts by mass of the total amount of rubber. In some cases, since the proportion of natural rubber is relatively small, such a function cannot be obtained sufficiently and cracks are likely to grow. Further, the cushioning performance of the fender may be reduced, or a high reaction force may not be obtained when the fender is downsized.

Therefore, in any of the above cases, the manufactured fender can not obtain a high reaction force particularly when downsized, and has a buffering performance when used for a long period of time particularly in a high temperature environment. There exists a problem that it falls easily or a crack is easy to be produced.
On the other hand, by setting the SBR vinyl content, styrene content, and SBR blending ratio within the above ranges, it is possible to suppress the occurrence of the above-mentioned various problems, and as described above, the buffer performance is excellent, and the compact size. Even if it is made, a highly durable fender can be formed which has a high reaction force and is less likely to cause a decrease in buffer performance or crack even when used for a long period of time, particularly in a high temperature environment.

In consideration of further improving this effect, the vinyl content of SBR is preferably 35% by mass or more, and more preferably 42% by mass or less even in the above range.
In addition, the styrene content is preferably 29% by mass or more, and more preferably 34% by mass or less even in the above range.
<Rubber>
As the rubber component, as described above, at least SBR having a specific vinyl content and styrene content and natural rubber are used in combination.

(SBR)
Among these, as SBR, among various SBRs synthesized by copolymerizing styrene and 1,3-butadiene by various polymerization methods such as emulsion polymerization method and solution polymerization method, vinyl content is 30% by mass or more, Those having 45% by mass or less and having a styrene content of 25% by mass or more and 40% by mass or less are selected and used.

The SBR includes an oil-extended type in which flexibility is adjusted by adding an extending oil and a non-oil-extended type in which flexibility is not added. In the present invention, any type of SBR can be used.
As such SBR, for example, SE0372 manufactured by Sumitomo Chemical Co., Ltd. [vinyl content: 41% by mass, styrene content: 33% by mass, oil-extended SBR containing 20 parts by mass of extended oil per 100 parts by mass of SBR], SE6701 [vinyl content : 36% by mass, styrene content: 30% by mass, and oil-extended SBR containing 15 parts by mass of extended oil per 100 parts by mass of SBR].

When oil-extended SBR is used as SBR, the total amount of rubber or the total amount of rubber is excluded based on the mass part of SBR itself as a solid, excluding the extension oil contained in the oil-extended SBR. The mass part of the SBR is set.
(Natural rubber)
Examples of the natural rubber include one or more of various grades of natural rubber such as TSR20 and RSS # 3, and various deproteinized natural rubbers.

The blending ratio of natural rubber is the remaining amount of SBR and other rubber described below. That is, SBR and, if necessary, other rubber components are blended at a predetermined ratio, and natural rubber may be blended so that the total amount of rubber components is 100 parts by mass.
(Other rubber)
As the rubber component, it is preferable to use only two kinds of SBR and natural rubber together in order to obtain a good effect while simplifying the structure. However, in order to adjust the characteristics of the fender, Other rubber components other than the two types may be used in combination.

  Examples of such other rubber components include SBR in which at least one of the vinyl content and the styrene content is outside the above-mentioned range, for example, isoprene rubber (IR), butadiene rubber (BR), butyl rubber (IIR), Examples thereof include one or more synthetic rubbers such as ethylene propylene diene rubber (EPDM), acrylonitrile butadiene rubber (NBR), and chloroprene rubber (CR).

However, considering that the effect of using the specific SBR and natural rubber in combination is well expressed, when the other rubber component is used in combination, the blending ratio is 100 parts by mass of the total rubber component. It is preferably 10 parts by mass or less, particularly 5 parts by mass or less.
<Carbon black>
As the carbon black, various carbon blacks that can function as a filler and a reinforcing agent for rubber can be used.

However, when considering the balance between the blending ratio and the reinforcing effect with respect to the total amount of rubber for carbon black, the rubber hardness is increased with a smaller amount of blending than the total amount of the rubber, and the cushioning performance of the fender is increased. In order to improve more efficiently, it is preferable to use a grade having a relatively small particle size and a developed structure and a large surface area.
In particular the nitrogen adsorption specific surface area of ^70m 2 / g or more, 120 m ² / g or less, DBP oil absorption of 90cm ^3/100 g or ^more, the carbon black is not more than 130 cm 3/100 g is preferably used.

Since the nitrogen adsorption specific surface area is less than 70m 2 / ^g carbon black particle size is too large, also carbon black DBP oil absorption amount is less than 90cm ^3/100 g is insufficient development of the structure, using either the Even in this case, the above-described reinforcing effect cannot be obtained sufficiently, and the rubber hardness cannot be increased sufficiently, so that there is a possibility that good cushioning performance cannot be imparted to the fender.

On the other hand, since carbon black nitrogen adsorption specific surface area exceeds 120 m ² / g particle size is too small, also carbon black DBP oil absorption exceeds 130 cm ^3/100 g is the development of structures is excessive, using either the Even in this case, the reinforcing effect described above becomes too strong, the rubber hardness becomes too large, or the elongation at the time of cutting becomes too small, so that there is a possibility that good cushioning performance cannot be imparted to the fender.

On the other hand, by selectively using carbon black whose nitrogen adsorption specific surface area and DBP oil absorption amount are both in the above-mentioned range, it is possible to secure an appropriate reinforcing effect and to impart good buffer performance to the fender. .
The carbon black satisfying the above characteristics, for example, by Tokai Carbon Co., Ltd. Seast 6 [ISAF, nitrogen adsorption specific surface ^area: 119m 2 / g, DBP oil ^absorption: 114 cm 3/100 g], SEAST 5H [IISAF, nitrogen adsorption specific surface ^area: 99m 2 / g, DBP oil ^absorption: 129 cm 3/100 g], Seast KH [N399, the nitrogen adsorption specific surface ^area: 93m 2 / g, DBP oil ^absorption: 119cm 3 / 100g], SEAST 3H [HAF-HS, nitrogen adsorption specific surface ^area: 82m 2 / g, DBP oil ^absorption: 126 cm 3/100 g], SEAST NH [N351, the nitrogen adsorption specific surface ^area: 74m 2 / g, DBP oil ^absorption: 127 cm 3/100 g], SEAST 3 [HAF, nitrogen adsorption specific surface ^area: 79m 2 / g, DBP oil ^absorption: 101 cm 3/100 g], the Strike N [LI-HAF, nitrogen adsorption specific surface ^area: 74m 2 / g, DBP oil ^absorption: 101 cm 3/100 g] one or more of the like.

The blending ratio of carbon black is preferably 30 parts by mass or more, particularly preferably 40 parts by mass or more, more preferably 85 parts by mass or less, and particularly preferably 80 parts by mass or less, per 100 parts by mass of the total amount of rubber.
If the blending ratio of the carbon black is less than this range, a sufficient reinforcing effect cannot be obtained, and the rubber hardness cannot be increased sufficiently, so that there is a possibility that good cushioning performance cannot be imparted to the fender.

On the other hand, when the blending ratio of the carbon black exceeds the above range, the distance between the adjacent carbon blacks is too close, so that when the fender is repeatedly deformed, the carbon black is likely to wear, and due to changes over time. There is a risk that the cushioning performance of the fender will be lowered, cracks, etc. likely to occur.
On the other hand, by setting the blending ratio of carbon black within the above range, the reinforcing effect of the carbon black can be adjusted to an appropriate range, and good cushioning performance can be imparted to the fender. Further, even if the fender is continuously used over a long period of time particularly in a high temperature environment, it is possible to prevent the buffer performance from being lowered and cracks are hardly generated.

<Crosslinking component>
In the rubber composition for fenders of the present invention, a crosslinking component can be blended as in the prior art.
As the cross-linking component, it is preferable to use sulfur as a cross-linking agent and a cross-linking accelerator having a function of accelerating the cross-linking of rubber by the sulfur as described above.
(sulfur)
Among these, various sulfur which can function as a crosslinking agent for rubber can be used as sulfur.

The blending ratio of sulfur is preferably 0.5 parts by weight or more per 100 parts by weight of the total amount of rubber, and preferably 3 parts by weight or less. If the blending ratio of sulfur is less than this range, the rubber for fenders There is a possibility that the cross-linking speed of the composition as a whole becomes slow, the time required for cross-linking becomes long, and the productivity of the fender is lowered.
Moreover, when the compounding ratio of sulfur exceeds the above range, the compression set after crosslinking may increase, or excess sulfur may bloom on the surface of the fender.

On the other hand, by setting the mixing ratio of sulfur within the above range, the crosslink density can be adjusted to an appropriate range, and good buffer performance can be imparted to the fender. Further, even if the fender is continuously used over a long period of time particularly in a high temperature environment, it is possible to prevent the buffer performance from being lowered and cracks are hardly generated.
For example, when oil-containing powdered sulfur, dispersible sulfur, or the like is used as sulfur, the blending ratio is the ratio of sulfur itself as an active ingredient contained therein.

(Crosslinking accelerator)
Examples of the crosslinking accelerator include inorganic accelerators such as slaked lime, magnesia (MgO) and risurge (PbO), guanidine accelerators, thiazole accelerators, sulfenamide accelerators, thiuram accelerators, dithiocarbamates. 1 type, or 2 or more types of organic promoters, such as a system accelerator and a thiourea type accelerator, are mentioned. In particular, it is preferable to select and use a slow-acting crosslinking accelerator.

In general, the fender is formed into a three-dimensional shape of the fender by filling the mold with a rubber composition for the fender, for example, at a temperature of 130 to 160 ° C. for about 3 to 20 hours. It is manufactured by crosslinking by applying.
Therefore, by selecting and using a slow-acting crosslinking accelerator, it is possible to satisfactorily suppress the scorch during the molding.

As such a slow-acting crosslinking accelerator, a sulfenamide accelerator is particularly preferable.
Examples of the sulfenamide accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (NS), N-cyclohexyl-2-benzothiazolylsulfenamide (CZ), N-oxydiethylene- One type or two or more types such as 2-benzothiazolylsulfenamide (MSA) can be mentioned.

The sulfenamide accelerator may be used alone (including the case where two or more sulfenamide accelerators are used in combination; the same applies hereinafter), or may be used in combination with other crosslinking accelerators.
Other cross-linking accelerators used in combination with sulfenamide accelerators include preventing the occurrence of the above scorch and activating the sulfenamide accelerators to increase the cross-linking speed and shortening the cross-linking time to prevent this. Examples thereof include a crosslinking accelerator that can improve the productivity of the straw material.

Examples of such other crosslinking accelerators include one or more of the organic accelerators described above, such as thiuram accelerators, guanidine accelerators, thiazole accelerators, dithiocarbamic acid accelerators, and the like.
When the sulfenamide-based accelerator is used alone, the blending ratio is preferably 0.5 parts by mass or more and preferably 2 parts by mass or less per 100 parts by mass of the total amount of rubber.

If the blending ratio of the sulfenamide accelerator is less than this range, the effect of promoting the cross-linking reaction between sulfur and the rubber component by blending the sulfenamide accelerator is not sufficiently obtained. There is a possibility that good cushioning performance cannot be imparted to the fender.
On the other hand, when the blending ratio of the sulfenamide accelerator exceeds the above range, the crosslinking density becomes too high, so that the buffer performance may be deteriorated particularly when used for a long period of time in a high temperature environment. There is a risk that cracks are likely to occur.

On the other hand, by setting the blending ratio of the sulfenamide-based accelerator within the above range, the crosslinking density can be adjusted to an appropriate range, and good buffer performance can be imparted to the fender. Further, even if the fender is continuously used over a long period of time particularly in a high temperature environment, it is possible to prevent the buffer performance from being lowered and cracks are hardly generated.
<Other ingredients>
The rubber composition for an antifungal material of the present invention may further contain a plasticizer, an anti-aging agent, a crosslinking aid, a wax, a tackifier, and the like as required.

(Plasticizer)
The plasticizer improves the processability when preparing a rubber composition for a fender or forms it into the shape of a fender, or a fender made of a crosslinked product of the rubber composition for a fender. It works to improve flexibility.
Examples of the plasticizer include oil and liquid rubber.

Of these, examples of the oil include one or more of various grades of oil such as Diana (registered trademark) process oil PW, NP, NS, NR, NM, AC, AH manufactured by Idemitsu Kosan Co., Ltd. .
Examples of the liquid rubber include one or more of liquid isoprene rubber, hydrogenated liquid isoprene rubber, liquid butadiene rubber, liquid styrene butadiene rubber, and terminal modified products thereof. In particular, liquid isoprene rubber having excellent compatibility with natural rubber is preferred.

Examples of the liquid isoprene rubber include Kuraray (trademark) LIR-30 (number average molecular weight: 28000), LIR-50 (number average molecular weight: 54000) manufactured by Kuraray Co., Ltd., and the like.
The blending ratio of the plasticizer is preferably 10 parts by mass or more, preferably 30 parts by mass or less, per 100 parts by mass of the total amount of rubber.

If the blending ratio of the plasticizer is less than this range, the above-described effects of improving the processability of the rubber composition for fenders and improving the flexibility of the fenders may not be sufficiently obtained.
On the other hand, when the blending ratio of the plasticizer exceeds the above range, the tensile strength itself of the cross-linked product is lowered, and the buffer performance is lowered particularly when the plasticizer is used for a long time in a high temperature environment. There is a risk that cracks are likely to occur.

On the other hand, by setting the blending ratio of the plasticizer within the above range, the above-mentioned anti-mold material is particularly high-temperature environment while maintaining the processability of the anti-mold rubber composition and the flexibility of the anti-mold material. Even if it continues to be used for a long period of time, it is possible to make it difficult to cause a decrease in buffer performance and cracks.
When oil-extended SBR is used as SBR, the total blending ratio of plasticizers including the extender oil (functioning as a plasticizer) contained in the oil-extended SBR may be set within the above range. .

(Anti-aging agent)
As an anti-aging agent, in particular, it is difficult to volatilize even when used in such a high temperature environment in consideration of satisfactorily suppressing a decrease in buffer performance or cracks due to a change over time in a high temperature environment. 4-Trimethyl-1,2-dihydroquinoline polymer (224) is preferably used.
The blending ratio of the 2,2,4-trimethyl-1,2-dihydroquinoline polymer is preferably 1 part by mass or more and preferably 3 parts by mass or less per 100 parts by mass of the total amount of rubber.

In addition, as an anti-aging agent, for example, N-phenyl-N′- excellent in the effect of preventing sunlight cracking, ozone cracking, bending cracking and the like together with the 2,2,4-trimethyl-1,2-dihydroquinoline polymer. Secondary anti-aging agents such as (1,3-dimethylbutyl) -p-phenylenediamine (6C) and 2-mercaptobenzimidazole (MB) may be used in combination.
The blending ratio of the secondary antiaging agent is preferably 1 part by mass or more and preferably 5 parts by mass or less per 100 parts by mass of the total amount of rubber.

(Crosslinking aid)
Examples of the crosslinking aid include metal compounds such as zinc oxide; fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid, and one or more conventionally known crosslinking aids.
The blending ratio of the crosslinking aid is preferably individually 0.5 parts by mass or more and preferably 7 parts by mass or less per 100 parts by mass of the total amount of rubber.

(wax)
The wax functions to form a film on the surface of the fender and prevent sun cracks and ozone cracks when used together with the anti-aging agent.
Examples of such wax include petroleum waxes such as paraffin wax.

As the paraffin wax, for example, Sannoc (registered trademark), Sannock N, Sannock P, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., Ozoace (registered trademark) 0355 manufactured by Nippon Seiki Co., Ltd., OK5258H manufactured by Paramelt Co., Ltd. 1 type, or 2 or more types, etc. are mentioned.
The blending ratio of the wax is preferably 0.5 parts by mass or more and preferably 2 parts by mass or less per 100 parts by mass of the total amount of rubber.

The rubber composition for fenders of the present invention can be prepared, for example, by first kneading each component other than the cross-linking component among the above components using a Banbury mixer or the like and then kneading by adding the cross-linking component.
The process of manufacturing a fender using the prepared rubber composition for fenders may be the same as before. That is, the fender can be produced by combining arbitrary processes such as molding, sheet molding, assembly, and crosslinking according to the size and shape of the fender to be produced.

<Example 1>
As rubber, 70 parts by weight of natural rubber (TSR20) and oil-extended SBR [SE6701, manufactured by Sumitomo Chemical Co., Ltd., vinyl content: 36% by weight, styrene content: 30% by weight, 15 parts by weight per 100 parts by weight of SBR 34.5 parts by mass were used in combination.
Both rubbers were kneaded together with components other than the crosslinking component among the components shown in Table 1 below at 150 ° C. for 5 minutes using a Banbury mixer, and then further added with a crosslinking component, and 5 ° C. at 70 ° C. using a biaxial open roll. A sheet-shaped rubber composition for fenders was prepared by kneading for a minute.

Each component in Table 1 is as follows. Moreover, the mass part in a table | surface shows the mass part per 100 mass parts of total amounts of rubber | gum content.
Carbon black: HAF, supra Tokai Carbon Co., Ltd. of SEAST 3, nitrogen adsorption specific surface ^area: 79m 2 / g, DBP oil ^absorption: 101cm 3 / 100g
Oil: Diana Process Oil NR26 made by Idemitsu Kosan Co., Ltd.
NOCRACK (registered trademark) 224: 2,2,4-trimethyl-1,2-dihydroquinoline polymer, manufactured by Ouchi Shinsei Chemical Co., Ltd. NOCRACK 6C: N-phenyl-N '-(1,3-dimethylbutyl) ) -P-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd. Wax: Ozoace 0355 manufactured by Nippon Seiki Co., Ltd.
2 types of zinc oxide: Cross-linking aid, manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Cross-linking aid, product name Tsubaki manufactured by NOF Corporation Sulfur: Cross-linking agent, 5% oil from Tsurumi Chemical Co., Ltd. Sulfur content in powdered sulfur Sulfenamide accelerator: N-tert-butyl-2-benzothiazolylsulfenamide, Sunseller (registered trademark) NS-G manufactured by Sanshin Chemical Industry Co., Ltd.
The blending ratio of SBR was 30 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 60 parts by weight per 100 parts by weight of the total amount of rubber.

<Example 2>
As SBR, oil-extended SBR having a vinyl content of 41% by mass and a styrene content of 33% by mass (including the above-mentioned SE0372 manufactured by Sumitomo Chemical Co., Ltd., including 20 parts by mass of extended oil per 100 parts by mass of SBR) 36 parts by mass And a sheet-like rubber composition for fenders was prepared in the same manner as in Example 1 except that the amount of oil was 14 parts by mass.

The blending ratio of SBR was 30 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 60 parts by weight per 100 parts by weight of the total amount of rubber.
<Example 3>
A sheet-shaped rubber for fenders in the same manner as in Example 1 except that the amount of natural rubber was 90 parts by mass, the amount of oil-extended SBR was 11.5 parts by mass, and the amount of oil was 18.5 parts by mass. A composition was prepared.

The blending ratio of SBR was 10 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 60 parts by weight per 100 parts by weight of the total amount of rubber.
<Example 4>
A rubber sheet for fenders in the same manner as in Example 1 except that the amount of natural rubber is 75 parts by mass, the amount of oil-extended SBR is 28.8 parts by mass, and the amount of oil is 16.2 parts by mass. A composition was prepared.

The blending ratio of SBR was 25 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 60 parts by weight per 100 parts by weight of the total amount of rubber.
<Example 5>
A sheet-shaped rubber composition for fenders was prepared in the same manner as in Example 1 except that the amount of natural rubber was 60 parts by mass, the amount of oil-extended SBR was 46 parts by mass, and the amount of oil was 14 parts by mass. did.

The blending ratio of SBR was 40 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 60 parts by weight per 100 parts by weight of the total amount of rubber.
<Example 6>
A sheet-shaped rubber composition for fenders was prepared in the same manner as in Example 1 except that the amount of carbon black was 30 parts by mass.

The blending ratio of SBR was 30 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 30 parts by weight per 100 parts by weight of the total amount of rubber.
<Example 7>
A sheet-shaped rubber composition for fenders was prepared in the same manner as in Example 1 except that the amount of carbon black was 40 parts by mass.

The blending ratio of SBR was 30 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 40 parts by weight per 100 parts by weight of the total amount of rubber.
<Example 8>
A sheet-shaped rubber composition for fenders was prepared in the same manner as in Example 1 except that the amount of carbon black was 80 parts by mass.

The blending ratio of SBR was 30 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 80 parts by weight per 100 parts by weight of the total amount of rubber.
<Example 9>
A sheet-shaped rubber composition for fenders was prepared in the same manner as in Example 1 except that the amount of carbon black was 85 parts by mass.

The blending ratio of SBR was 30 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 85 parts by weight per 100 parts by weight of the total amount of rubber.
<Comparative example 1>
As SBR, 30 parts by mass of non-oil-extended SBR (Sumitomo SBR1502 manufactured by Sumitomo Chemical Co., Ltd.) having a vinyl content of 20% by mass and a styrene content of 23.5% by mass, and the amount of oil is 20 parts by mass. A sheet-like rubber composition for fenders was prepared in the same manner as in Example 1 except that.

The blending ratio of SBR was 30 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 60 parts by weight per 100 parts by weight of the total amount of rubber.
<Comparative example 2>
As SBR, 30 parts by mass of non-oil-extended SBR [Nipol NS612 manufactured by Nippon Zeon Co., Ltd.] having a vinyl content of 31% by mass and a styrene content of 15% by mass, and the amount of oil was 20 parts by mass. Except that, a sheet-like rubber composition for fenders was prepared in the same manner as in Example 1.

The blending ratio of SBR was 30 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 60 parts by weight per 100 parts by weight of the total amount of rubber.
<Comparative Example 3>
As SBR, 30 parts by mass of non-oil-extended SBR (N207 manufactured by Asahi Kasei Chemicals Co., Ltd.) having a vinyl content of 61% by mass and a styrene content of 30% by mass, and the amount of oil was 20 parts by mass. Except for the above, a sheet-shaped rubber composition for fenders was prepared in the same manner as in Example 1.

The blending ratio of SBR was 30 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 60 parts by weight per 100 parts by weight of the total amount of rubber.
<Comparative example 4>
As SBR, 30 parts by mass of non-oil-extended SBR [Nipol NS616 manufactured by Nippon Zeon Co., Ltd.] having a vinyl content of 67% by mass and a styrene content of 21% by mass, and the amount of oil was 20 parts by mass. Except that, a sheet-like rubber composition for fenders was prepared in the same manner as in Example 1.

The blending ratio of SBR was 30 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 60 parts by weight per 100 parts by weight of the total amount of rubber.
<Comparative Example 5>
A sheet-shaped rubber for fenders in the same manner as in Example 1 except that the amount of natural rubber was 95 parts by mass, the amount of oil-extended SBR was 5.8 parts by mass, and the amount of oil was 19.2 parts by mass. A composition was prepared.

The blending ratio of SBR was 5 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 60 parts by weight per 100 parts by weight of the total amount of rubber.
<Comparative Example 6>
A sheet-shaped rubber for fenders in the same manner as in Example 1 except that the amount of natural rubber was 55 parts by mass, the amount of oil-extended SBR was 51.8 parts by mass, and the amount of oil was 13.2 parts by mass. A composition was prepared.

The blending ratio of SBR was 45 parts by weight in 100 parts by weight of the total amount of rubber, and the blending ratio of carbon black was 60 parts by weight per 100 parts by weight of the total amount of rubber.
<Sample preparation>
The sheet-shaped rubber composition for fenders prepared in each of the above Examples and Comparative Examples was press-molded at 140 ° C. for 50 minutes to prepare a crosslinked sheet-shaped sample.

<Tensile test>
The produced sheet-like sample was punched out to produce a dumbbell-shaped No. 3 test piece defined in Japanese Industrial Standard JIS K6251 _{: 2010} “vulcanized rubber and thermoplastic rubber—how to obtain tensile properties”, and the standard test temperature Below, the tensile test prescribed | regulated to the same specification was done, and tensile strength TS (MPa) and elongation at break _Eb (%) were calculated | required.

The tensile strength TS was evaluated as “X” when less than 16 MPa, “◯” when less than 16 MPa, “◯” when less than 20 MPa, and “◎” when more than 20 MPa.
Further, the elongation _Eb at the time of cutting was evaluated as “x” when less than 350%, “◯” when less than 350%, “◯” when less than 400%, and “◎” when 400% or more.
<Rubber hardness measurement>
The type A durometer hardness of the prepared sheet-like sample was measured under the standard test temperature, Japanese Industrial Standard JIS K6253-3 _{: 2012} “How to Obtain Vulcanized Rubber and Thermoplastic Rubber Hardness—Part 3: Durometer Hardness The measurement was performed according to the measurement method defined in “1.

As for the type A durometer hardness, less than 65 and more than 80 were evaluated as “X”, 65 or more and 80 or less as “◯”, particularly 70 or more and 75 or less in the above range of “◯” as “」 ”.
<High temperature durability test>
The produced sheet-like sample is punched out to produce the same dumbbell-shaped No. 3 test piece as in the tensile test, and conforms to Japanese Industrial Standard JIS K6257 _{: 2003} "Vulcanized rubber and thermoplastic rubber-How to obtain heat aging characteristics" Was subjected to heat aging by heating at 100 ° C. for 360 hours using the forced circulation heat aging test machine.

Next, when the elongation test was repeated using a Dematcher bending tester under the conditions of a temperature of 80 ° C. and a test frequency of 5 Hz and an elongation rate of 50%, the number of repetitions of elongation until the test piece was broken was 10 ³ times. The unit was counted up to a maximum of 100 × 10 ³ times.
And "×" those broken by extension of less than 30 × 10 ³ times, 30 × 10 ³ times or more, "○" and those broken by extension of less than 100 × 10 ³ times, at 100 × 10 ³ times extension Those that did not break were evaluated as “◎”.

<Comprehensive evaluation>
All the above test results were “◎”, “◎”, “○” and “○” were “○”, and any one was “×” was “×”. evaluated.
The above results are shown in Tables 2-4.

  From the results of Examples 1 to 9 and Comparative Examples 1 to 4 in Tables 2 to 4, the vinyl content is 30% by mass or more and 45% by mass or less, and the styrene content is 25% by mass or more and 40% by mass or less. By selecting and using SBR, it has excellent buffering performance and has a high reaction force even if it is miniaturized. It has been found that a durable fender can be formed.

However, from the results of Examples 1, 3 to 5 and Comparative Examples 5 and 6, in order to obtain the above effect, the specific SBR blending ratio is 10 parts by mass in 100 parts by mass of the total amount of rubber. As mentioned above, it turned out that it is necessary to set it as 40 mass parts or less.
Further, from the results of Examples 1 and 2, in order to further improve the above effect, the SBR vinyl content was 35% by mass or more and 42% by mass or less in the above range, and the styrene content was 29 or more in the above range. It was found that the content is preferably not less than 34% by mass and not more than 34% by mass.

  Furthermore, from the results of Examples 1 and 6 to 9, in order to further improve the above effect, the blending ratio of carbon black is 30 parts by mass or more, particularly 40 parts by mass or more, per 100 parts by mass of the total amount of rubber. In addition, it was found that the content is preferably 85 parts by mass or less, particularly 80 parts by mass or less.

Claims (2)

  It contains at least a rubber component including natural rubber and styrene butadiene rubber, and carbon black. The styrene butadiene rubber has a vinyl content of 30% by mass to 45% by mass and a styrene content of 25% by mass to 40% by mass. In addition, the blending ratio of the styrene butadiene rubber is a rubber composition for a fender, which is 10 parts by mass or more and 40 parts by mass or less in 100 parts by mass of the total amount of the rubber.   The rubber composition for a fender according to claim 1, wherein the blending ratio of the carbon black is 40 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the total amount of the rubber.