JP2017155075A - Coupling agent for rubber-carbon black and rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coupling agent for rubber-carbon black that is suitable as raw materials for tires that exhibit excellent wear resistance and fuel economy, and also suitable as raw materials for vibration-insulating rubber that exhibits excellent compression set resistance and vibration-insulating performance, and a rubber composition comprising the same.SOLUTION: The present invention provides a rubber composition in which: a coupling agent for rubber-carbon black composed of an isocyanate compound represented by chemical formula (I) is blended, together with carbon black, to diene rubber (Rand Rindependently represent H or a C1-3 linear/branched alkyl group; n is an integer of 2-11).SELECTED DRAWING: None

Description

  The present invention relates to a coupling agent for rubber and carbon black and a rubber composition containing the same.

  In recent years, as the interest in the environment has increased, there has been an increasing demand for lower fuel consumption for automobiles. Since the tire characteristics have a great influence on the fuel consumption of automobiles, a tire rubber composition suitable for such purposes is strongly desired. In order to improve fuel consumption characteristics, it is necessary to reduce the rolling resistance of the tire. On the other hand, wear resistance is also emphasized in order to increase driving safety and tire life.

  In addition, vibration-proof rubber is used in vehicles such as automobiles in order to absorb vibrations of the engine and the vehicle body and improve riding comfort and prevent noise. As the anti-vibration rubber, a rubber having a small dynamic magnification which is a ratio (Kd / Ks) of a dynamic spring constant (Kd) of 100 Hz to a static spring constant (Ks) is desired. Furthermore, in the vibration-proof rubber, heat resistance is regarded as important, and it is required to have excellent compression set resistance at high temperatures.

  In order to realize tires with low rolling resistance and anti-vibration rubbers with low dynamic magnification, it is known that the use of rubber with a low loss factor tan δ is effective. A coupling agent for rubber and carbon black that improves the dispersibility of carbon black in the rubber composition and strengthens the chemical bond between the carbon black and the rubber molecules that are blended as a rubber reinforcing agent. Use is in progress.

  Many of the coupling agents for rubber and carbon black that have been developed so far are amino group-containing compounds, and the acid between the carbonyl group and carboxyl group present on the surface of carbon black and the amino group of the coupling agent. We expect the effect of binding by base interaction. In addition, a compound having sulfur or a double bond in the molecule is expected to have a bonding effect with a diene radical of rubber.

  For example, a dialkylamino group-containing sulfur compound (Patent Document 1), an organic sulfide compound having a quaternary ammonium salt structure (Patent Document 2), a thiosulfate metal salt having an aminopropyl group (Patent Document 3), an aminophenyl group Proposed metal salts of butenoic acid (Patent Document 4), organic sulfur compounds having a nitrogen-containing aromatic heterocycle (Patent Documents 5 and 6), and the like.

  However, in any case, although the loss factor tan δ of rubber obtained by vulcanization / molding is reduced, it is not yet a satisfactory level, and the wear resistance and compression set of rubber deteriorate. There was also a need for further improvement.

JP-A-9-278742 JP 2000-239446 A JP 2012-126923 A JP 2014-95014 A JP 2013-23610 A Japanese Patent Laying-Open No. 2015-21097

  The present invention is suitable as a raw material for tires exhibiting excellent wear resistance and low fuel consumption performance, and also suitable as a raw material for vibration-proof rubbers exhibiting excellent compression set properties and vibration-proof performance, An object of the present invention is to provide a coupling agent for rubber and carbon black and a rubber composition containing the same.

As a result of intensive studies in order to solve the above-mentioned problems, the present inventor achieved the intended purpose by using the isocyanate compound represented by the chemical formula (I) as a coupling agent for rubber and carbon black. As a result, the present invention has been completed.
That is, the first invention is a coupling agent for rubber and carbon black characterized by comprising an isocyanate compound represented by the chemical formula (I) as a component.
2nd invention mix | blends carbon black in the ratio of 10-100 weight part with respect to 100 weight part of diene rubbers, and for rubber | gum and carbon black of 1st invention with respect to 100 weight part of this carbon black A rubber composition characterized in that a coupling agent is blended at a ratio of 0.5 to 30 parts by weight.

（式中、Ｒ₁およびＲ_２は同一または異なって、水素原子または炭素数１〜３である直鎖状もしくは分岐状のアルキル基を表す。ｎは２〜１１の整数を表す。）

(In the formula, R ₁ and R ₂ are the same or different and each represents a hydrogen atom or a linear or branched alkyl group having 1 to 3 carbon atoms. N represents an integer of 2 to 11)

When the isocyanate compound of the present invention is blended with a diene rubber containing carbon black as a component of a coupling agent for rubber and carbon black, the isocyanate group of the isocyanate compound is present on the surface of the carbon black. Since it interacts with a carboxyl group or a hydroxyl group to form a bond, the affinity between the isocyanate compound and carbon black is increased.
In addition, since the carbon of the maleimide group of the isocyanate compound interacts with the carbon atom of the rubber to form a bond, the affinity between the isocyanate compound and the rubber is increased.
As a result, the dispersibility of the carbon black contained in the rubber is improved, and the rubber restrains the carbon black via the rubber / carbon black coupling agent of the present invention. Can be suppressed. When the rubber composition of the present invention is used for a tire, it is possible to obtain a tire with reduced loss coefficient tan δ, low rolling resistance, and improved fuel efficiency while maintaining excellent wear resistance. it can. Further, when the rubber composition of the present invention is used for a vibration-proof rubber, the loss factor tan δ is reduced while maintaining excellent compression set resistance characteristics, the dynamic magnification is small, and the vibration-proof performance is improved. It can be a vibration rubber.

Hereinafter, the present invention will be described in detail.
The component of the coupling agent for rubber and carbon black of the present invention is an isocyanate compound represented by the chemical formula (I), and has a structure in which a maleimide group and an isocyanate group are bonded via an alkylene group.

Examples of the isocyanate compound represented by the chemical formula (I) used in the practice of the present invention include
1- (2-isocyanatoethyl-1) -1H-pyrrole-2,5-dione,
1- (3-isocyanatopropyl-1) -1H-pyrrole-2,5-dione,
1- (4-isocyanatobutyl-1) -1H-pyrrole-2,5-dione,
1- (5-isocyanatopentyl-1) -1H-pyrrole-2,5-dione,
1- (6-isocyanatohexyl-1) -1H-pyrrole-2,5-dione,
1- (7-isocyanatoheptyl-1) -1H-pyrrole-2,5-dione,
1- (8-isocyanatooctyl-1) -1H-pyrrole-2,5-dione,
1- (9-isocyanatononyl-1) -1H-pyrrole-2,5-dione,
1- (10-isocyanatodecyl-1) -1H-pyrrole-2,5-dione,
1- (11-isocyanatoundecyl-1) -1H-pyrrole-2,5-dione,
1- (3-isocyanatopropyl-1) -3-methyl-1H-pyrrole-2,5-dione,
Examples include 1- (3-isocyanatopropyl-1) -3,4-dimethyl-1H-pyrrole-2,5-dione.
In addition, you may use the isocyanate compound shown by Chemical formula (I) as a component of the coupling agent for rubber | gum and carbon black combining 1 type (s) or 2 or more types from which a type differs.

  These isocyanate compounds can be synthesized in accordance with, for example, the methods described in “Chemical Communications, 49 (22), 2249-2251, 2013.” and Japanese Translation of PCT International Publication No. 2006-505627.

  In the rubber composition of the present invention, carbon black is preferably blended at a rate of 10 to 100 parts by weight, more preferably 30 to 80 parts by weight, with respect to 100 parts by weight of diene rubber. . If the blending ratio of the carbon black is less than 10 parts by weight, the abrasion resistance of the vulcanized and molded rubber is reduced. If it exceeds 100 parts by weight, the rubber composition at the time of kneading before vulcanization is thickened and processability is increased. Decreases.

  And it is preferable to mix | blend the coupling agent for rubber | gum and carbon black of this invention in the ratio of 0.5-30 weight part with respect to 100 weight part of carbon black, and mix | blend in the ratio of 1-10 weight part. Is more preferable. If the blending ratio of the coupling agent for rubber and carbon black is less than 0.5 parts by weight, the effect of reducing the loss factor tanδ of the rubber obtained by vulcanization and molding is small, and the rolling resistance of the tire and the dynamic ratio of the vibration-proof rubber The effect of reducing is not sufficiently obtained. Further, even if the blending ratio exceeds 30 parts by weight, the effect of the reduction is almost flat, and the use amount of the coupling agent for rubber / carbon black is increased, which is not economical.

  As the diene rubber, those conventionally used in the field of rubber industry can be used without particular limitation. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR). Styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), chloroprene rubber (CR) and the like can be preferably used. These diene rubbers can be used alone or in combination of two or more.

About said carbon black, it is preferable that the nitrogen adsorption specific surface area (BET method) is 20-250 m < ² > / g.
About carbon black mix | blended with the rubber composition for tire uses, it is more preferable that it is 70-200 m < ² > / g. If the nitrogen adsorption specific surface area is less than 70 m ² / g, the abrasion resistance of the vulcanized and molded rubber is reduced. If it exceeds 200 m ² / g, the rubber composition during kneading before vulcanization is thickened and processed. Sex is reduced.
About carbon black mix | blended with the rubber composition for a vibration-proof rubber use, it is more preferable that it is 20-100 m < ² > / g. When the nitrogen adsorption specific surface area is less than 20 m ² / g, the elastic modulus of the vulcanized / molded rubber decreases, and when it exceeds 100 m ² / g, the loss factor tan δ of the vulcanized / molded rubber increases, and the dynamic magnification becomes It becomes high and the vibration proof performance decreases.

The type of carbon black is not particularly limited. For example, furnace black, acetylene black, thermal black, channel black, and the like can be used, but furnace black can be preferably used.
As furnace black, commercially available products such as SEAST 3G, SEAST SO and SEAST V manufactured by Tokai Carbon Co., Ltd. can be used.

  Soluble sulfur and insoluble sulfur can be mix | blended with the rubber composition of this invention as a vulcanizing agent. These blending ratios are preferably blended with 0.5 to 10 parts by weight of soluble sulfur or insoluble sulfur with respect to 100 parts by weight of the diene rubber, more preferably 2 to 5 parts by weight. preferable.

  The rubber composition of the present invention can be blended with reinforcing agents and fillers such as silica, clay, talc and the like conventionally used for rubber. Although these compounding ratios can be made into a general ratio, it is preferable to mix | blend in the ratio of 40-120 weight part with respect to 100 weight part of diene rubbers.

  Further, the rubber composition of the present invention includes a vulcanization accelerator such as sulfenamide, thiuram, or thiazole, a vulcanization accelerator such as zinc oxide (zinc white), magnesium oxide, naphthene oil, aroma oil. In addition to process oils such as stearic acid, dispersants (waxes) such as stearic acid, antioxidants, antioxidants, ozone cracking inhibitors, peptizers, adhesive resins, vulcanization retarders, etc. It can mix | blend in the range which is not.

  The rubber composition of the present invention can be obtained by kneading the above-described raw materials using a Banbury mixer or a kneader such as an open roll. For example, in tire use, it is vulcanized and molded as a member such as carcass, belt, bead, tread, etc., and in anti-vibration rubber use, it is vulcanized and molded as a vibration-proof rubber member.

  Hereinafter, the present invention will be specifically described with reference to control tests, examples and comparative examples, but the present invention is not limited thereto. The main raw materials used in these are as follows.

[raw materials]
・ NR (natural rubber): Product name “SMR-CV60” manufactured by Chong Hutton
SBR (styrene-butadiene rubber): manufactured by Nippon Zeon Co., Ltd., trade name “Nipol 1723”
・ Carbon black 1: manufactured by Tokai Carbon Co., Ltd., trade name “SEAST 3G”, nitrogen adsorption specific surface area 79 m ² / g
Carbon black 2: manufactured by Tokai Carbon Co., Ltd., trade name “SEAST SO”, nitrogen adsorption specific surface area 42 m ² / g
・ Carbon black 3: manufactured by Tokai Carbon Co., Ltd., trade name “SEAST V”, nitrogen adsorption specific surface area 27 m ² / g
・ Process oil: Made by Idemitsu Kosan Co., Ltd.
・ Stearic acid: manufactured by Miyoshi Oil & Fats Co., Ltd., trade name “MXST”
・ Zinc flower: Made by Shodo Chemical Industry Co., Ltd., trade name "Zinc oxide 2 types"
・ Vulcanizing agent: Shikoku Kasei Kogyo Co., Ltd., insoluble sulfur, trade name "Muclon OT20"
・ Vulcanization accelerator: Ouchi Shinsei Chemical Industry Co., Ltd., trade name “Noxeller NS”
・ Anti-aging agent: Product name “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.

The coupling agents for rubber and carbon black used in the examples are as follows.
1- (2-isocyanatoethyl-1) -1H-pyrrole-2,5-dione (synthesized according to the method described in “Chemical Communications, 49 (22), 2249-2251, 2013.” above) (Abbreviated as “MIC2”, see chemical formula (I-1)).
1- (3-isocyanatopropyl-1) -1H-pyrrole-2,5-dione (synthesized according to the method described in the above-mentioned Special Table 2006-505627. It is abbreviated as “MIC3”. (See chemical formula (I-2))
1- (5-isocyanatopentyl-1) -1H-pyrrole-2,5-dione (same as “MIC5”, see chemical formula (I-3))
1- (11-isocyanatoundecyl-1) -1H-pyrrole-2,5-dione (same as “MIC11”; see chemical formula (I-4))

The coupling agents for rubber and carbon black used in the comparative examples are as follows.
Bis (dimethylaminoethyl) tetrasulfide (synthesized according to the method described in Patent Document 1. Abbreviated as “DME”.)
Bis (dimethylaminopyridinium hexyl chloride) tetrasulfide (synthesized according to the method described in Patent Document 2. Abbreviated as “DPH”.)
-Sodium salt of S- (3-aminopropyl) thiosulfuric acid (synthesized according to the method described in Patent Document 3. Abbreviated as “ATS”.)
(2Z) -4-[(4-Aminophenyl) amino] -4-oxo-2-butenoate sodium (Synthesis example is shown in Reference Example 1. It is abbreviated as “AOB-Na”.)
2,2′-bis (benzimidazolyl-2) ethyl disulfide (synthesized according to the method described in Patent Document 5. Abbreviated as “2EBZ”.)

[Reference Example 1]
<Synthesis of AOB-Na>
After dissolving 10.81 g (0.1 mol) of p-phenylenediamine in 100 g of THF, a THF solution of 9.81 g (0.1 mol) of maleic anhydride was added dropwise at 5 to 10 ° C. over 3 hours. Stir overnight at room temperature. The THF suspension was cooled, and 19.3 g (0.1 mol) of 28% sodium methoxide in methanol was added so as not to exceed 20 ° C., and the mixture was stirred as it was for 1 hour. The obtained crystals were collected by filtration and dried to obtain 20.1 g (yield 88%) of the target AOB-Na.

The evaluation tests employed in the control test, examples and comparative examples are as follows.
[Loss factor measurement test]
The unvulcanized rubber composition processed into a sheet shape is heated in a 200 × 200 × 2 mm mold at 160 ° C. for 15 minutes to produce a vulcanized rubber sheet, and from this vulcanized rubber sheet, 5 × 20 × A 2 mm strip test piece was cut out. This test piece was set on a viscoelastic spectrometer (Model Rheosol-G5000, manufactured by UBM) with a gripping tool spacing of 15 mm, and subjected to a torsional deformation at an ambient temperature of 60 ° C., a frequency of 10 Hz, and a dynamic strain of 5 °. The loss factor tan δ of the piece was measured.
The loss coefficient tan δ at 60 ° C. is an index of rolling resistance, and the smaller the value, the smaller the rolling resistance of the tire and the better the fuel efficiency performance. Further, it is determined that the smaller the numerical value is, the smaller the dynamic ratio of the vibration-proof rubber is and the better the vibration-proof performance is.

  The results of the loss factor measurement test are shown in Table 1 as relative values when the value of the loss factor tan δ in the control test 1 is 100, and in Table 2, the value of the loss factor tan δ in the control test 2 is shown. In Table 3, the relative value when the value of the loss coefficient tan δ in the control test 3 is set to 100 is shown.

[Abrasion resistance test]
The unvulcanized rubber composition processed into a sheet shape was heated in a mold having a diameter of 63 mm and a thickness of 12.7 mm at 160 ° C. for 25 minutes to prepare a disk-shaped vulcanized rubber test piece. The specimen was allowed to cool in a room at a set temperature of 25 ° C. for 24 hours, and then set in an Akron abrasion tester (manufactured by Ueshima Seisakusho) under the conditions of a contact angle of 15 ° to the polishing plate and a load of 44.1 N The running-in operation was performed up to 1000 times. The test piece after the break-in operation is taken out from the test machine, and the weight of the test piece is measured with an accuracy of 0.1 mg. Then, the test piece is set on the wear tester again, and the accumulated number of revolutions of the polishing plate is 1000 times. This test was conducted. The test piece weight after this test was measured with an accuracy of 0.1 mg. The weight loss after wear-in was calculated by subtracting the weight after this test from the weight after running-in.

The results of the abrasion resistance test are shown in Table 1 as relative values when the value of wear loss in the control test 1 is 100, and in Table 2, the value of wear loss in the control test 2 is 100. In Table 3, relative values are shown when the wear loss value in the control test 3 is 100.
It is determined that the smaller the value, the better the wear resistance.

[Compression set test]
The unvulcanized rubber composition processed into a sheet shape was heated at 160 ° C. for 25 minutes in a mold having a diameter of 29 mm and a thickness of 12.5 mm to prepare a disk-shaped vulcanized rubber test piece. After measuring the thickness of this test piece with a rubber thickness meter, the test piece was put into a compression apparatus having a spacer thickness of 9.3 mm and compressed at a compression rate of 25%. The compression device in a state where the test piece was compressed was placed in a heating oven and heated at 70 ° C. for 24 hours. After heating, the test piece was taken out from the compression apparatus, placed on a wooden table, and the thickness of the test piece was allowed to cool in a room at a set temperature of 25 ° C. for 30 minutes. Based on JIS K6262, compression set CS (%) was measured from the thickness of the test piece before putting into a compression apparatus and the thickness of the test piece after compressing and allowing to cool.

In Table 1, the result of the compression set test is shown as a relative value when the compression set CS value in the control test 1 is 100. In Table 2, the compression set CS value in the control test 2 is shown. In Table 3, relative values are shown, with the compression set CS value in the control test 3 being 100.
The smaller this value is, the better the compression set resistance is.

[Control study 1]
NR, carbon black 1, process oil, and stearic acid were weighed so as to have the composition shown in Table 1, and kneaded using a Banbury mixer to prepare a master batch. To this, zinc white, vulcanizing agent, vulcanization accelerator and anti-aging agent are blended so as to have the composition shown in Table 1, kneaded using a two-roll mixer with a surface temperature of 70 ° C., and processed into a sheet form. An unvulcanized rubber composition was prepared.
When an evaluation test was performed using a test piece prepared by vulcanization molding of the obtained unvulcanized rubber composition, the test result obtained was as shown in Table 1.

[Examples 1 to 6]
An unvulcanized rubber composition having the composition shown in Table 1 was prepared in the same manner as in Control Test 1 except that a coupling agent for rubber and carbon black was used, and this was vulcanized and molded to give a test piece. Were prepared and evaluated.
The test results obtained were as shown in Table 1.

[Comparative Examples 1-5]
In the same manner as in Examples 1 to 6, an unvulcanized rubber composition having the composition shown in Table 1 was prepared, and this was vulcanized to produce a test piece and subjected to an evaluation test.
The test results obtained were as shown in Table 1.

[Control study 2]
Table 2 shows the composition shown in Table 2, except that carbon black 2 is used in place of carbon black 1 and 60 parts by weight of carbon black 2 is blended with respect to 100 parts by weight of NR rubber. An unvulcanized rubber composition was prepared, vulcanized and molded to prepare a test piece, and an evaluation test was performed.
The test results obtained were as shown in Table 2.

[Examples 7 to 12]
An unvulcanized rubber composition having the composition shown in Table 2 was prepared in the same manner as in Control Test 2 except that a rubber / carbon black coupling agent was used, and this was vulcanized and molded to give a test piece. Were prepared and evaluated.
The test results obtained were as shown in Table 2.

[Comparative Examples 6 to 10]
In the same manner as in Examples 7 to 12, an unvulcanized rubber composition having the composition shown in Table 2 was prepared, and this was vulcanized to produce a test piece and subjected to an evaluation test.
The test results obtained were as shown in Table 2.

[Control study 3]
An unvulcanized rubber composition having the composition shown in Table 3 was prepared in the same manner as in Control Test 1, except that SBR was used instead of NR and carbon black 3 was used instead of carbon black 1. This was vulcanized to produce a test piece, and an evaluation test was conducted.
The test results obtained were as shown in Table 3.

[Examples 13 to 18]
An unvulcanized rubber composition having the composition shown in Table 3 was prepared in the same manner as in Control Test 3 except that a rubber / carbon black coupling agent was used. Were prepared and evaluated.
The test results obtained were as shown in Table 3.

[Comparative Examples 11-15]
In the same manner as in Examples 13 to 18, an unvulcanized rubber composition having the composition shown in Table 3 was prepared, and this was vulcanized to produce a test piece and subjected to an evaluation test.
The test results obtained were as shown in Table 3.

  According to the test results shown in Table 1, Table 2 and Table 3, the rubber composition containing the rubber / carbon black coupling agent of the present invention was blended with the conventional rubber / carbon black coupling agent. Compared to the rubber composition, it is possible to suppress a decrease in wear resistance and compression set resistance, and to reduce the loss coefficient tan δ that serves as a guide for tire rolling resistance and vibration damping rubber dynamic ratio.

  As described above, according to the present invention, the realization of a low fuel consumption type tire having excellent wear resistance and reduced rolling resistance, and the vibration-proof rubber having excellent compression set resistance and reduced dynamic magnification. Since the realization is expected, the industrial applicability of the present invention is great.

Claims (2)

A coupling agent for rubber and carbon black, comprising an isocyanate compound represented by the chemical formula (I) as a component.

(In the formula, R ₁ and R ₂ are the same or different and each represents a hydrogen atom or a linear or branched alkyl group having 1 to 3 carbon atoms. N represents an integer of 2 to 11)   Carbon black is blended at a ratio of 10 to 100 parts by weight with respect to 100 parts by weight of the diene rubber, and the coupling agent for rubber / carbon black according to claim 1 is added to 0.1 parts by weight with respect to 100 parts by weight of the carbon black. A rubber composition characterized by being blended at a ratio of 5 to 30 parts by weight.