JP2010215883A - Rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition having a low glass transition temperature, a low elastic modulus even in a cold district and excellent low fuel consumption properties. <P>SOLUTION: The rubber composition for a fender includes a rubber (A) which can be vulcanized and a branched rubber (B) having a high cis-structure except (A). The branched rubber (B) having the high cis-structure has ≥80% 1,4-cis structure and a ratio (Tcp/ML<SB>1+4</SB>) of a 5% toluene solution viscosity (Tcp) to a Mooney viscosity (ML<SB>1+4</SB>) at 100°C of 0.5 to 2.0. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

By applying a binary rubber of a vulcanizable rubber and a branched rubber having a high cis structure other than that, the glass transition temperature is low, and a low elastic modulus is maintained even at a low temperature, In addition, the present invention relates to a rubber composition excellent in fuel efficiency.

In general, the characteristics of a synthetic rubber as an elastic body are one of excellent materials that can be applied in various fields as compared with other materials. In particular, its use extends to the tire industry, industrial products and daily necessities.
However, the use of general synthetic rubber in a low temperature environment is restricted due to its high glass transition temperature, and there is a problem in using it at a low temperature.

Despite these problems, various improvements have been made in recent years so that they can be used even in cold regions while taking advantage of the properties of synthetic rubber. Examples include tires for cold regions and fenders in the extremely cold ocean.

  In the pneumatic tire field where low temperature characteristics are important, studless tires are used, and a blend of natural rubber and polybutadiene is applied as the rubber component. In particular, in the tread portion of the tire, it is necessary to improve the low-temperature characteristics to provide flexibility and improve the characteristics on ice.

  In order to improve the characteristics on ice, it is necessary to increase the coefficient of friction with the road surface by increasing the flexibility of the rubber in the tread at a low temperature, particularly in the vicinity of −30 ° C. At low temperatures, the elastic modulus of the rubber increases, making it impossible to follow the unevenness of the road surface. Also, the frozen road surface has less surface unevenness than the normal road surface, so the energy dissipation that occurs between the rubber and the road surface (tanδ) Contributes to the performance on ice. It is necessary to increase the real contact area between the rubber and the road surface at a low temperature, and it is more important to lower the storage elastic modulus around −30 ° C. (lower elastic modulus). For example, the use of butadiene rubber or natural rubber, which is a polymer having a low glass transition temperature, and a large amount of a softening agent are added to the rubber composition to improve flexibility at low temperatures. In particular, high-cis butadiene rubber having a high cis content that lowers the glass transition temperature is used for butadiene rubber. However, the high-cis butadiene rubber has the property of crystallizing in a low temperature region around -10 to 0 ° C because the microstructure is more uniform. This crystallization remains after vulcanization and raises the storage elastic modulus around -30 ° C.

In order to solve the above problem, the low temperature characteristics are improved while maintaining the characteristics as a tire by applying natural rubber and a high cis butadiene rubber with a cis content suppressed to some extent (Reference 1).
Further, in Reference Document 2, low temperature characteristics and fracture characteristics are improved by appropriately blending brominated butyl rubber as a third component with natural rubber and polybutadiene.
Furthermore, in Reference Document 3, on-ice performance, wear resistance, and heat generation characteristics are achieved by using three rubber components obtained by adding natural rubber to a blend of polybutadiene that does not crystallize in a low temperature environment and polybutadiene that crystallizes. ing.

On the other hand, since the environment where the fender is used is always exposed to the sea surface, the performance of the rubber is significantly deteriorated due to salt damage. In addition, since the ship is large, not only the load resistance but also the large number and volume of the fenders are required as the required characteristics of the fenders. For this reason, material cost becomes very expensive and initial installation cost is large. In addition, the service life is often not as long as 10 years, leading to an increase in maintenance costs.

As the fender, various types of cushioning functions are known, but among them, a thick solid fender made of an elastic material such as rubber has a simple structure, Because of its buffer function, it is hard to break and is widely used.

As solid-type fenders, various efforts have been made to devise the form and structure (Patent Documents 4 and 5). As a result, it has become possible to create an effect that further enhances the buffer function.

  Furthermore, improvements and efforts have been made with regard to specifications in cold regions, and rubber elastic materials with less temperature dependence have been developed by using a mixture of natural rubber and other rubbers, focusing on the rubber composition (patents) Reference 6). However, even with these more severe cold specifications, it has become possible to provide fenders with better mechanical properties.

The present invention aims to provide a rubber composition in a cold region specification, which is considered to be a particularly harsh environment, and further exhibits a superior low temperature elastic property and low fuel consumption effect that could not be achieved by the prior art. To provide things.

JP2003-292676 JP2007-211180 JP2007-314605 JP2000-303431 JP 10-176321 A JP2002-13121

By applying vulcanizable rubber and other branched rubbers with a high cis structure, it has a low glass transition temperature, low elasticity even at low temperatures, and low fuel consumption. A rubber composition having excellent properties is provided.

The present invention relates to a rubber composition characterized in that it is a vulcanizable rubber (A) and a branched rubber (B) having a high cis structure other than (A).

  The present invention also relates to the rubber composition, wherein the vulcanizable rubber (A) is natural rubber.

Further, according to the present invention, the branched rubber (B) having a high cis structure has a 1,4-cis structure of 80% or more, a 5% toluene solution viscosity (Tcp), a Mooney viscosity (ML _{1 + 4} ) at 100 ° C. The ratio (Tcp / ML _{1 + 4} ) is 0.5 to 2.0.

  A rubber composition having a low glass transition temperature, a low elastic modulus even in a cold region, and excellent fuel efficiency can be provided.

(A) Vulcanizable rubber As vulcanizable rubber, natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), nitrile rubber (NBR), ethylene propylene Examples thereof include rubber (EPM), chloroprene rubber (CR), butyl rubber, urethane rubber, acrylic rubber, and silicon rubber.

  Of these, natural rubber (NR) is particularly desirable.

  The amount of (A) to be blended is 20 to 90 parts by weight, more preferably 30 to 80 parts by weight, particularly preferably 40 to 70 parts by weight of vulcanizable rubber in 100 parts by weight of the total rubber. What to mix | blend is preferable. When blended, various physical properties (tensile strength, elongation, tear strength, compression set, etc.) necessary for compression characteristics are obtained, and sufficient rubber elastic material is obtained at a low temperature characteristic of the present invention. Can do.

(B) Branched rubber having a high cis structure The branched rubber having a high cis structure is selected from rubbers other than those selected from the above-mentioned (A) vulcanizable rubber. The types include natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), nitrile rubber (NBR), ethylene propylene rubber (EPM), chloroprene rubber (CR), Examples include butyl rubber, urethane rubber, acrylic rubber, and silicon rubber.

  Of these, butadiene rubber (BR) is particularly desirable.

Furthermore, the following two structures must be defined quantitatively as necessary conditions for a branched rubber having a high cis structure.
(1) High cis structure In other words, the rubber microstructure contains a cis structure, and the ratio is generally preferably 80% or more, more preferably 88.0% to 99.8%, and 96.0 to 99.0%. More preferably, 95.0 to 98.9% is particularly preferable.
(2) The ratio (Tcp / ML _{1 + 4} ) of 5% toluene solution viscosity (Tcp) and Mooney viscosity (ML _{1 + 4} ), which is an index indicating the degree of branching of the branched structure molecule, is preferably 0.5 to 2.0, More preferably, it is 0.7-1.8, Most preferably, it is 0.8-1.5.
Tcp indicates the degree of molecular entanglement in the concentrated solution. In the case of high cis rubber having the same molecular weight distribution, the degree of branching is the same if the molecular weight is the same (ie, ML _{1 + 4} is the same). (The larger Tcp, the smaller the branching degree). Moreover, (the larger Tcp / _{ML 1 + 4,} degree of branching is small) index when Tcp / _{ML 1 + 4} is for comparing the degree of branching of different height Shisugomu of _{ML 1 + 4} is used as a.
In other words, the smaller the value of Tcp / ML _{1 + 4} , the more branched.

If Tcp / ML _{1 + 4} is larger than the above range, the problem of low-temperature crystallization is likely to occur. Conversely, if Tcp / ML _{1 + 4} is smaller than the above range, the problem of deterioration in fracture characteristics is likely to occur.

  Further, the molecular weight distribution (Mw / Mn) is preferably 1.5 to 9.0, more preferably 2.0 to 5.0, and particularly preferably 2.5 to 4.0.

  If the value of the molecular weight distribution is less than 1.5, the processability deteriorates, which is not preferable. On the other hand, if it is larger than 9.0, it is not preferable because the destructive property is deteriorated.

Furthermore, ML _{1 + 4} at 100 ° C. is preferably 30 to 60, more preferably 35 to 55, and particularly preferably 37 to 50. If the value is smaller than this value, the physical properties of rubber such as fracture characteristics tend to be lowered. Furthermore, it is a requirement that the gel content is not substantially contained.

  As the amount of (B) to be blended, in 100 parts by weight of the total rubber, (B) a branched rubber having a high cis structure is 3-90 parts by weight, more preferably 5-80 parts by weight, particularly preferably 7 to 70 parts by weight are preferable. When blended, various physical properties (tensile strength, elongation, tear strength, compression set, etc.) necessary for compression characteristics are obtained, and sufficient rubber elastic material is obtained at a low temperature characteristic of the present invention. Can do.

  (A) A vulcanizable rubber and a branched rubber (B) having a high cis structure other than (A) can be obtained by using a kneader such as an open kneader such as a roll or a closed kneader such as a Banbury mixer. It can be obtained by kneading and vulcanizing after molding and can be applied to various rubber products.

As long as the object of the present invention is not impaired, various chemicals usually used in the rubber industry, for example, vulcanizing agents, vulcanization accelerators, process oils, anti-aging agents, anti-scorching agents, zinc white, stearin are used as desired. An acid etc. can be contained.

From Table 1, the example of the present invention is compared with Comparative Example 1 which is a binary rubber configuration of (A) a vulcanizable rubber and a branched rubber having a high cis structure other than (A), It can be seen that the elastic modulus at −30 ° C. is lowered. Furthermore, it can be seen that the crystallization temperatures are all lower than in the comparative example.
Therefore, in the binary rubber structure of the present invention, improvement in rubber elasticity at low temperatures is observed.

  Furthermore, from Table 1, the examples of the present invention are compared with the comparative example, which is a binary rubber configuration of (A) a vulcanizable rubber and a linear rubber having a high cis structure other than (A). It can be seen that the value of tan δ at 70 ° C. is low. That is, it suggests that there is an improvement effect on the low fuel consumption.

(Tensile modulus)
The tensile modulus M100 was measured according to JIS K6251. The index was calculated with a comparative example of 100. The larger the value, the higher the tensile stress.

(Molecular weight measurement)
The molecular weight and molecular weight distribution were calculated using a standard polystyrene calibration curve using two columns in series using HLC-8220 GPC manufactured by Tosoh Corporation. The column used was Shodex GPC KF-805L column, which was measured by measuring a column temperature of 40 ° C. in THF.

(Differential calorimeter (DSC)
The measurement was performed under a nitrogen atmosphere using a differential calorimeter (DSC). The temperature was raised from 30 ° C to 100 ° C at 10 ° C / min, held at 100 ° C for 10 minutes, and then immediately measured for crystallization from 100 ° C to -70 ° C at a rate of 5 ° C / min. did.

(Mooney viscosity measurement)
The Mooney viscosity (ML _{1 + 4} , 100 ° C.) measurement was performed in accordance with JIS K-6300 standard.

(Vulcanization speed)
The vulcanization speed was measured in accordance with JIS K-6300 standard, and the time required to reach 90% vulcanization degree was measured using JSR Clastometer 2F type.

[Vulcanized physical properties]
(hardness)
The hardness was measured according to a measurement method defined in JIS-K6253.

(Tensile stress)
Tensile stress measured 100% tensile stress according to JIS-K6251. The larger the value, the higher the tensile stress.

(Tensile strength)
For the tensile strength, the tensile strength at break was measured according to JIS-K6251. It shows that it is so favorable that a numerical value is large.

(Elongation at break)
The elongation at break was determined by measuring the elongation at break according to JIS-K6251. It shows that it is so favorable that a numerical value is large.

(Rebound resilience)
The rebound resilience was measured at 23 ° C. according to JIS-K6255. The larger the value, the better the resilience.

(Low fuel consumption (heat generation))
It measured according to the measuring method prescribed | regulated to JISK6265. PS (%) was shown as compression set at the time of dynamic change, and the temperature rise after 25 minutes at a start temperature of 100 ° C. was shown as ΔT. The index was calculated using a comparative example of 100. A larger index indicates better physical properties.

(Low fuel consumption of vulcanizate (tan δ))
Using an EPLEXOR 100N manufactured by GABO, measurement was performed under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of 0.3%. The larger the index, the better.

(Crystallization temperature)
The crystallization temperature was measured using an EPLEXOR 100N manufactured by GABO under the conditions of a temperature of −30 ° C., a frequency of 10 Hz, and a dynamic strain of 0.3%, and the rise in elastic modulus was obtained from the tangent line between two points. Using temperature, the lower the temperature, the better.

(Low temperature storage modulus)
The low temperature storage modulus (E '@-30 ° C) is measured using an EPLEXOR 100N manufactured by GABO under the conditions of a temperature of -30 ° C, a frequency of 10 Hz, and a dynamic strain of 0.3%. 100, and the larger the value, the lower the elastic modulus at −30 ° C. and the better.

(Rambourn wear evaluation)
Abrasion resistance: 4.5 kg load using a Lambourn Abrasion Tester, sand fall rate of about 15 g / min. The following slip ratio was tested. Slip rate: 20%, sample rotation speed 60 m / min. , Drum rotation speed 48 m / min. Slip rate: 60%, sample rotation speed 60 m / min, drum rotation speed 24 m / min. The amount of wear (cc / min) measured in (1) was obtained and evaluated as an index with a comparative example of 100. The higher the index, the better the wear resistance.

Examples are shown below.
Patent range branching lower limit manufacturing method

(Example)
Manufacturing method of BR150B equivalent product Dehydration treatment using molecular sieves in advance in a stainless steel reaction tank with a stirrer (stirring blade diameter 0.06m) with an internal volume of 1.5L (tank diameter 0.08m) replaced with nitrogen gas 1.0 L of the polymerized solution (1.3-butadiene: 30.0 wt%, cyclohexane: 70.0 wt%) was added. Next, under stirring at 400 rpm, water 1.4 mmol, diethylaluminum chloride 4.2 mmol, cyclooctadiene 11.5 mmol, and cobalt octoate 0.0087 mmol were added, and cis-1,4 polymerization was performed at 50 ° C. for 30 minutes. .
Ethanol containing 4,6-bis (octylthioethyl) -o-cresol was added thereto to terminate the polymerization, and then unreacted butadiene and 2-butenes were removed by evaporation to obtain 86 g of polybutadiene rubber.
This polymer had a Mooney viscosity (ML1 + 4) at 100 ° C. of 40.1 and a 5 wt% toluene solution viscosity (Tcp) at 25 ° C. of 55.2. The weight average molecular weight (Mw) was 450,000, the 1,4-cis structure content was 97.3%, and the intrinsic viscosity ([η]) was 1.9.

Using the polybutadiene of Table 1 and mixing the natural rubber, branched polybutadiene, metallocene BR, carbon black, etc. using a 250 cc closed kneading machine according to the formulation shown in Table 2, open the vulcanization accelerator and sulfur. Mixed by roll. Then press vulcanize,
The physical properties were evaluated by the obtained vulcanized test pieces. The results are shown in Table 1.

(Comparative example)
According to the formulation shown in Table 2, a natural rubber, linear polybutadiene, carbon black and the like were kneaded using a 250 cc closed kneading apparatus, and then the vulcanization accelerator and sulfur were mixed with an open roll. Next, press vulcanization was performed, and the physical properties were evaluated by the obtained vulcanized test pieces.

The use of the rubber composition obtained in the present invention is a tire field, in particular, a cold region tire. Further, as a tire member, it is a base tread, a sidewall, a chafer, a beat, a rim strip and the like. Furthermore, the present invention can be applied to fenders, industrial rubber, belts, rubber crawlers, rubber hoses, rubber gloves, OA equipment, footwear members, medical members, and the like.

Claims (3)

A rubber composition characterized by being a vulcanizable rubber (A) and a branched rubber (B) having a high cis structure other than (A).   2. The rubber composition according to claim 1, wherein the vulcanizable rubber (A) is natural rubber. The branched rubber (B) having a high cis structure has a 1,4-cis structure of 80% or more, a ratio of 5% toluene solution viscosity (Tcp) to Mooney viscosity (ML _{1 + 4} ) at 100 ° C. (Tcp / The rubber composition according to claim 1, wherein ML _{1 + 4} ) is 0.5 to 2.0.