JP2011148892A - Butyl-based rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a butyl-based rubber composition including butyl-based rubber as a principal component that simultaneously satisfies air permeability resistance, flexural fatigue resistance, and low-temperature embrittlement properties, thus being suitably used as a molding material for an inner liner of a pneumatic tire. <P>SOLUTION: The butyl-based rubber composition comprises (A) 95-99 pts.wt. of diene-based rubber containing 50 pts.wt. or more of butyl-based rubber and (B) 5-1 pts.wt. of a hydrogen-bondable thermoplastic elastomer having a main chain comprising diene-based rubber and a carbonyl-containing group and a nitrogen-containing heterocycle in a molecule, with a weight-average molecular weight Mw of 50,000 or less, wherein the total of both components (A) and (B) is 100 pts.wt. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a butyl rubber composition. More specifically, the present invention relates to a butyl rubber composition suitably used as a molding material for an inner liner of a pneumatic tire.

  Maintaining internal pressure in pneumatic tires is important from the viewpoint of suppressing compound air deterioration and reducing air pressure, and if this performance is low, the deterioration of tires over time or acceleration will occur, and the deflection of pneumatic tires will increase due to the decrease in air pressure. Will lead to failure.

  In order to suppress the air permeability that exerts these performances, it is also performed by blending a material having low air permeability compared to rubber, such as various fillers typically represented by carbon black, In this case, the bending fatigue resistance and the embrittlement temperature deteriorate, and there is a problem that cracks occur in the inner liner.

  Butyl rubber [IIR], a diene rubber obtained by copolymerizing a small amount (about 0.5 to 3% by weight) of isoprene with isobutylene, has steric hindrance because isobutylene, the main skeleton, has two methyl groups per monomer unit. This suppresses the molecular mobility of the polymer chain, and its gas permeability is very small compared to other diene polymers. Therefore, it is widely used as a molding material for rubber for inner liners of pneumatic tires due to these characteristics. .

  However, butyl rubber satisfies the air permeation resistance and the bending fatigue resistance among the various properties required as a rubber for an inner liner, but is not necessarily satisfied in terms of low temperature embrittlement.

Japanese Patent No. 3,998,690 Japanese Patent No. 4,011,057 Japanese Patent No. 4,037,016 EP 0 933 381 A1

  An object of the present invention is a butyl rubber composition containing butyl rubber as a main component, which simultaneously satisfies air permeation resistance, flex fatigue resistance and low temperature embrittlement, and is therefore used for an inner liner of a pneumatic tire. An object of the present invention is to provide a molding material that can be suitably used.

  The object of the present invention is to provide (A) 95 to 99 parts by weight of a diene rubber containing 50 parts by weight or more of a butyl rubber and (B) a main chain comprising a diene rubber, and a carbonyl-containing group and a nitrogen-containing heterocyclic ring. In a molecule, and consisting of 5 to 1 part by weight of a hydrogen-bonding thermoplastic elastomer having a weight average molecular weight Mw of 50,000 or less (however, the total of both components (A) and (B) is 100 parts by weight) Achieved by the composition.

  The butyl rubber composition according to the present invention satisfies the air permeation resistance, the bending fatigue resistance and the low temperature embrittlement at the same time, and therefore can be suitably used as a molding material for an inner liner of a pneumatic tire.

  The butyl rubber composition of the present invention comprises (A) 95 to 99 parts by weight of a diene rubber containing butyl rubber and (B) 5 to 1 part by weight of a hydrogen bonding thermoplastic elastomer (provided that (A) (B) The total of both components is 100 parts by weight).

  The diene rubber as component (A) is used in a ratio of 95 to 99 parts by weight in a total of 100 parts by weight of both components (A) and (B), and contains 50 parts by weight or more of butyl rubber. It becomes. As the butyl rubber, butyl rubber which is an isobutylene-isoprene copolymer, chlorobutyl, bromobutyl, etc. obtained by reacting it with a halogenated chlorine are used. When these butyl rubbers are blended with other diene rubbers, natural rubber, styrene butadiene rubber (SBR), and butadiene rubber are preferably used as the other diene rubbers. As SBR, either emulsion polymerization SBR (E-SBR) or solution polymerization SBR (S-SBR) can be used.

  As the component (A) component diene rubber, a butyl rubber is used at a ratio that occupies 50 parts by weight or more of 95 to 99 parts by weight as described above. That is, the component (A) diene rubber can be used by blending with other diene rubbers in such a ratio that butyl rubber alone or butyl rubber accounts for 50 parts by weight or more. When the proportion of the butyl rubber is used in a proportion of less than 50 parts by weight in 95 to 99 parts by weight of the component (A), the low temperature embrittlement point cannot be improved.

  The hydrogen-bonding thermoplastic elastomer of component (B) is composed of a diene rubber in the main chain, has a carbonyl-containing group and a nitrogen-containing heterocyclic ring in the molecule, and has a weight average molecular weight Mw (measured by GP method) of 50,000. Hereinafter, preferably 10,000 to 40,000 is used. Such hydrogen bondable thermoplastic elastomers are described in Patent Documents 1 to 3 and the like that describe patent inventions related to the applicant's application.

  As the hydrogen-bonding thermoplastic elastomer, a polymer main chain composed of a diene rubber is preferably reacted successively with a carbonyl group-containing unsaturated compound and a nitrogen-containing heterocyclic compound substituted with a functional group capable of reacting with the carbonyl group. The diene polymer obtained in this way is used.

  Natural rubber, isoprene rubber, butadiene rubber, chloroprene rubber, nitrile rubber, styrene butadiene rubber, etc. are used as the diene rubber molecule of the hydrogen bondable thermoplastic elastomer whose main chain is composed of a diene rubber molecule, preferably isoprene rubber. Is used.

  Examples of the carbonyl group-containing unsaturated compound that undergoes an addition reaction to the polymer main chain of these diene rubber molecules include maleic anhydride and maleic acid, and maleic anhydride is preferably used. The modification rate of maleic anhydride is generally set to about 0.1 to 10% by weight based on the weight of the polymer molecule to be modified.

  The addition reaction of maleic anhydride to the polymer main chain is preferably carried out by an ene reaction. As described in Patent Document 4, maleic anhydride is ring-opened in the usual addition reaction, and many are added as maleic acid. However, according to the ene reaction, maleic anhydride has almost no acid anhydride structure. It is added while holding

  As such a maleic anhydride-added diene rubber, a commercially available product can be used as it is. Examples of maleic anhydride-modified liquid polyisoprene rubber include Kuraray product LIR-410A.

  The maleic anhydride group thus added includes a nitrogen-containing heterocyclic compound in which the nitrogen-containing heterocyclic ring is a 5-membered ring or a 6-membered ring and is substituted with a functional group capable of reacting with maleic acid, for example. 4H-3-amino-1,2,4-triazole, 4-aminopyridine and the like in which the substituted functional group is an amino group, 4-hydroxypyridine in which the substituted functional group is a hydroxyl group, 4- The addition reaction is further carried out by heating at about 120 to 200 ° C. using a small excess of methylolpyridine and the like.

  Here, as a thermoplastic elastomer, an addition reaction of maleic anhydride to a diene rubber and further reaction with a functional group-substituted nitrogen-containing heterocyclic compound is a carbonyl group derived from a carbonyl group-containing unsaturated compound, and Self-crosslinking is possible by forming a hydrogen bond consisting of donor-H-acceptor as shown by OH… O, NH… O, OH… N, NH… N with the reacted nitrogen-containing heterocyclic compound. In addition, it dissociates during heating (120 ° C.) and re-forms hydrogen bonds near room temperature.

  A hydrogen-bonding thermoplastic elastomer obtained by sequentially reacting a carbonyl group-containing unsaturated compound and a nitrogen-containing heterocyclic compound substituted with a functional group capable of reacting with the polymer main chain obtained by such a series of reactions ( B) is used in a ratio of 5 to 1 part by weight in a total of 100 parts by weight of both components (A) and (B). When used at a lower ratio, there is no particular improvement in low temperature embrittlement, while when used at a higher ratio, the low temperature embrittlement is improved, but the air permeation resistance and resistance. Flexural fatigue is impaired.

  In the butyl rubber composition containing the above components as essential components, carbon black as a reinforcing filler, zinc oxide as a vulcanizing agent, sulfur and thiazole (MBT, MBTS, ZnMBT, etc.), sulfene Amides (CBS, DCBS, BBS, etc.), guanidines (DPG, DOTG, OTBG, etc.), thiurams (TMTD, TMTM, TBzTD, TETD, TBTD, etc.), dithiocarbamates (ZTC, NaBDC, etc.), xanthogenic acid Any one or more of vulcanization accelerators such as salt-based (ZnBX, etc.) are blended and used. As carbon black, carbon black having a larger particle diameter than FEF grade is preferred. Furthermore, other compounding agents generally used as rubber compounding agents, for example, reinforcing agents or fillers such as silica, talc, clay, graphite, calcium silicate, processing aids such as stearic acid, softeners, plasticizers. An agent, an anti-aging agent, and the like are appropriately mixed and used as necessary.

  Preparation of the composition is carried out by kneading by a general method using a kneader such as a kneader, a Banbury mixer or a mixer and an open roll, and the obtained composition is molded into a predetermined shape, The butyl rubber-containing diene rubber, vulcanizing agent, vulcanization accelerator is vulcanized at a vulcanization temperature according to the type and blending ratio thereof, and an inner liner of a pneumatic tire is formed.

  Next, the present invention will be described with reference to examples.

Reference Example Maleic anhydride-modified liquid isoprene rubber (Kuraray product LIR-410A; Mw 25,000, maleic anhydride modification rate 3.9% by weight) 200.00 g (79.6 mmol in terms of maleic anhydride skeleton) was added 4H-3-amino-1, 6.97 g (82.9 mmol) of 2,4-triazole was added and stirred at 160 ° C. for 3 hours. After confirming that the solution was uniform, the solution was allowed to stand overnight to obtain 202.8 g of a gel-like hydrogen-bonding thermoplastic elastomer (yield 98%).

または

The gel-like hydrogen-bonding thermoplastic elastomer that is the reaction product is considered to have an amic acid bond [I], an imide bond [II], or both, and the main product is [II 〕it is conceivable that.

Or

Comparative example 1 (standard example)
Butyl rubber (LANXESS product BROMOBUTYL2030) 50 parts by weight Natural rubber (RSS # 3) 50 部
GPF grade carbon black (Mitsubishi Chemical Products Dia Black G) 50 〃
Vulcanization accelerator (Ouchi Emerging Chemical Industries Noxeller DM-PO) 1 1
Stearic acid (NOF product beads stearic acid) 1 〃
Zinc Hana (Zinc Oxide Industrial Products, 3 types of zinc oxide) 3
Sulfur (Akzo Nobel product Christex HS OT 20) 1 〃
The above components were kneaded using a 16 L Banbury mixer, and the kneaded product (butyl rubber composition) was subjected to press vulcanization at 160 ° C. for 20 minutes.

With respect to the vulcanized product of the butyl rubber composition, the following items were measured. All measurement results are indicated by an index with a standard example of 100.
Air permeation resistance: Compliant with JIS K7126-1987 A method
(The larger the index, the better the air permeation resistance)
Bending fatigue resistance: JIS K6260-1999 compliant
Measure the number of times until the measurement sample breaks under the condition of 40mm strain
(The larger the index, the better the bending fatigue resistance)
Low temperature embrittlement: JIS K6261 compliant
Measure 50% impact embrittlement temperature
(The higher the index, the better the low temperature embrittlement)

Comparative Example 2
In Comparative Example 1, the amount of GPF grade carbon black [CB] was changed to 60 parts by weight.

Comparative Example 3
In Comparative Example 1, natural rubber was not used, and the amount of butyl rubber [IIR] was changed to 100 parts by weight.

Example 1
In Comparative Example 1, the amount of natural rubber [NR] was changed to 49 parts by weight, and 1 part by weight of the hydrogen bonding thermoplastic elastomer [TPE] obtained in the above Reference Example was used.

Example 2
In Comparative Example 1, the amount of NR was changed to 47 parts by weight, and 3 parts by weight of TPE was used.

Example 3
In Comparative Example 1, the amount of NR was changed to 45 parts by weight, and 5 parts by weight of TPE was used.

Example 4
In Comparative Example 3, the amount of IIR was changed to 97 parts by weight and 3 parts by weight of TPE was used.

The results obtained in the above Examples and Comparative Examples are shown in the following table together with the blending amounts (parts by weight) of IIR, NR, TPE and GPF grade carbon black [CB] used.
table
Compounding component measurement results
Example IIR NR TPE CB Air permeation resistance Bending fatigue resistance Low temperature embrittlement
Comparative Example 1 50 50-50 100 100 100
〃 2 50 50 − 60 110 95 93
３ 3 100 − − 50 120 109 85
Example 1 50 49 1 50 103 103 105
〃 2 50 47 3 50 108 110 109
３ 3 50 45 5 50 103 101 107
97 4 97 − 3 50 116 104 101

Claims (5)

  (A) 95 to 99 parts by weight of a diene rubber containing 50 parts by weight or more of a butyl rubber and (B) the main chain is a diene rubber, and has a carbonyl-containing group and a nitrogen-containing heterocycle in the molecule. A butyl rubber composition comprising 5 to 1 part by weight of a hydrogen-bonding thermoplastic elastomer having a weight average molecular weight Mw of 50,000 or less (however, the total of both components (A) and (B) is 100 parts by weight).   (B) Component Hydrogen-bonding thermoplastic elastomer reacts sequentially with polymer main chain made of diene rubber with carbonyl group-containing unsaturated compound and nitrogen-containing heterocyclic compound substituted with functional group capable of reacting with this carbonyl group The butyl rubber composition according to claim 1, wherein the butyl rubber composition is a diene polymer obtained.   The butyl rubber composition according to claim 2, wherein the nitrogen-containing heterocyclic compound substituted with a functional group capable of reacting with a carbonyl group is an amino group-substituted or hydroxyl group-substituted nitrogen-containing heterocyclic compound.   The butyl rubber composition according to claim 1, 2 or 3, which is used as an inner liner molding material for a pneumatic tire.   A pneumatic tire having an inner liner molded and vulcanized from the butyl rubber composition according to claim 4.