JP2018104572A - Dynamically crosslinked product, low air-permeable film, and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamically crosslinked product capable of improving processability by lowering melt viscosity while maintaining low air permeability.SOLUTION: The dynamically crosslinked product according to an embodiment contains a nylon resin forming a continuous phase, a crosslinked product of a rubber dispersed in the continuous phase, and a fatty acid amide lubricant. A low air-permeable film according to one embodiment comprises the dynamically crosslinked product. A pneumatic tire according to one embodiment includes the low air-permeable film. A method for producing a dynamically crosslinked product according to one embodiment comprises: kneading a nylon resin and a rubber together with a crosslinking agent to dynamically crosslink the rubber; and adding a fatty acid amide lubricant and mixing them after the crosslinking.SELECTED DRAWING: None

Description

  The present invention relates to a dynamic cross-linked product, a low air permeability film, and a pneumatic tire.

  Conventionally, for example, as a gas barrier layer (that is, an inner liner) of a pneumatic tire, a technique using a low air permeable film made of a dynamic cross-linked product of a thermoplastic resin as a continuous phase and rubber as a dispersed phase is known. ing.

  Such a dynamically cross-linked product increases in viscosity as the cross-linking of the rubber by the cross-linking agent proceeds. Further, when the fine dispersion of the crosslinked rubber dispersed phase proceeds, the surface areas of the resin and the crosslinked rubber increase, and the viscosity further increases. Therefore, when a film is formed using a dynamic cross-linked product, the melt viscosity is larger than that of a film formed using a normal thermoplastic resin, and a large load is applied when the film is processed.

  In order to reduce this load, it is conceivable to add a plasticizer. As a technique for adding a plasticizer, for example, in Patent Document 1, in order to improve processability and low-temperature characteristics, a sulfonamide plasticizer is added together with a nylon resin and a rubber component to dynamically crosslink. Proposed. However, when a plasticizer is added, the fluidity at the time of molding can be improved, but the air permeability becomes large and it may be difficult to use as a low air permeability film. In general, plasticizers emit a lot of smoke (outgas) and are not necessarily desirable from the viewpoint of environmental impact.

  On the other hand, Patent Document 2 discloses that an alkaline earth metal salt of a higher fatty acid is added to reduce the extrusion load during film molding. However, alkaline earth metal salts of higher fatty acids have poor external lubricity and are insufficient for improving film moldability.

Japanese Patent No. 4942253 JP 2011-231166 A

  An object of the embodiment of the present invention is to provide a dynamically cross-linked product capable of improving the workability by lowering the melt viscosity while maintaining low air permeability.

  The dynamically cross-linked product according to an embodiment of the present invention includes a nylon resin forming a continuous phase, a cross-linked product of rubber dispersed in the continuous phase, and a fatty acid amide-based lubricant.

  The low air permeability film according to one embodiment is composed of the dynamic cross-linked product. Moreover, the pneumatic tire which concerns on one Embodiment is equipped with this low air permeability film.

  The method for producing a dynamically cross-linked product according to an embodiment of the present invention includes kneading nylon resin and rubber together with a cross-linking agent to dynamically cross-link the rubber, and adding and mixing a fatty acid amide lubricant after cross-linking. is there.

  According to the present embodiment, by using a fatty acid amide-based lubricant, the melt viscosity of the dynamic cross-linked product can be reduced while maintaining low air permeability, for example, improving processability during film molding. Can do.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The dynamically cross-linked product according to this embodiment includes a nylon resin forming a continuous phase, a cross-linked product of rubber dispersed in the continuous phase, and a fatty acid amide-based lubricant. A dynamically cross-linked product is obtained by melt-kneading nylon resin and rubber to dynamically cross-link the rubber. The nylon resin is used as a continuous phase (matrix phase), and the cross-linked product of rubber is used as a dispersed phase (domain phase). It has a sea-island structure.

  Examples of the nylon resin include nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 610, nylon 612, nylon 6/66 copolymer, nylon 6/66/610 copolymer, nylon MXD6, nylon Examples thereof include aliphatic polyamide resins such as 6T and nylon 6 / 6T copolymers. These may be used alone or in combination of two or more.

  As long as the effects of the present embodiment are not impaired, the nylon resin forming the continuous phase may contain additives such as a plasticizer, a softener, a filler, a reinforcing agent, a processing aid, a stabilizer, and an antioxidant as necessary. May be blended as appropriate.

  As the rubber forming the dispersed phase, various rubber polymers generally used after being crosslinked (vulcanized) (that is, capable of crosslinking) are used, for example, natural rubber (NR), epoxidized natural rubber (ENR). , Diene rubbers such as isoprene rubber (IR), styrene butadiene rubber (SBR), butadiene rubber (BR), nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), hydrogenated styrene butadiene rubber and hydrogenation thereof Rubber; Ethylene-propylene rubber (EPDM), maleic acid-modified ethylene propylene rubber, maleic acid-modified ethylene butylene rubber, butyl rubber (IIR), acrylic rubber (ACM) and other olefin rubbers; halogenated butyl rubber (for example, brominated butyl rubber (Br) -IIR), chlorinated butyl rubber (Cl-IIR)), chloropre Halogen-containing rubbers such as rubber (CR) and chlorosulfonated polyethylene; other examples include silicon rubber, fluorine rubber, polysulfide rubber and the like. These may be used alone or in combination of two or more. As one embodiment, at least one selected from butadiene rubber (BR), butyl rubber (IIR), halogenated butyl rubber, nitrile rubber (NBR), and hydrogenated nitrile rubber (H-NBR) may be used.

  The rubber forming the dispersed phase may be blended with a crosslinking agent for dynamically crosslinking the rubber polymer, or the rubber and the crosslinking agent may be mixed in advance to form a master batch. Examples of the crosslinking agent include vulcanizing agents such as sulfur and sulfur-containing compounds, vulcanization accelerators, and phenol resins. Preferably, a phenol resin is used from the viewpoint of heat resistance and the like. Examples of the phenol resin include a resin obtained by a condensation reaction of phenols and formaldehyde, and examples thereof include alkylphenol-formaldehyde resins. Moreover, you may use halogenated phenol resin, such as brominated alkylphenol-formaldehyde resin, from the point which can make a vulcanization | cure speed | rate fast. The amount of the crosslinking agent is not particularly limited as long as the rubber can be appropriately crosslinked, but may be 0.1 to 10 parts by mass or 0.5 to 5 parts by mass with respect to 100 parts by mass of the rubber. .

  The rubber forming the dispersed phase may be blended with various additives generally blended in the rubber composition, such as a filler, a softening agent, an anti-aging agent, and a processing aid.

  In the dynamically cross-linked product according to the present embodiment, the blending ratio of the nylon resin and the rubber (ratio as a polymer excluding the additive) is not particularly limited. For example, the mass ratio (nylon resin / rubber) is 90 / 10-30 / 70, 70 / 30-40 / 60, 60 / 40-40 / 60 may be sufficient.

  The dynamic cross-linked product according to the present embodiment is mixed with a fatty acid amide lubricant. Various fatty acid amides can be used as the fatty acid amide lubricant. For example, monoamides such as lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, hydroxy stearic acid amide, ethylene bis lauric acid amide, ethylene bis stearic acid amide, ethylene bis hydroxy Examples thereof include bisamides such as stearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, ethylene bisoleic acid amide, and hexamethylene bisoleic acid amide.

  As the fatty acid amide lubricant, a polycondensate of alkylene diamine, higher fatty acid and dicarboxylic acid may be used as belonging to the above bisamides because it has an alkylene bisamide structure. Examples of the alkylene diamine include ethylene diamine and hexamethylene diamine. Examples of the higher fatty acid include various higher fatty acids such as palmitic acid and stearic acid. Examples of the dicarboxylic acid include sebacic acid and azelaic acid. The fatty acid amide lubricant according to a preferred embodiment is a polycondensate of ethylenediamine, stearic acid, and sebacic acid. Specific examples of such a polycondensate include “Light Amide WH-215” and “Light Amide WH-255” manufactured by Kyoeisha Chemical Co., Ltd.

  Any of the above fatty acid amide-based lubricants may be used alone or in combination of two or more. As the fatty acid amide-based lubricant, those having an alkylene bisamide such as ethylene bis stearic acid amide and alkylene bis amide structures such as “light amide WH-215” and “light amide WH-255” are preferably used.

  The number of carbon atoms of the fatty acid constituting the fatty acid amide lubricant is preferably 12 or more, more preferably 12 to 30, and 14 to 28. In addition, carbon number here is carbon number of each fatty acid in the case of bisamides.

  The compounding amount of the fatty acid amide lubricant is not particularly limited, but is preferably 0.5 to 10 parts by mass, more preferably 0.6 to 6 parts by mass with respect to 100 parts by mass of the nylon resin. .

  The fatty acid amide lubricant is preferably contained in a nylon resin forming a continuous phase. That is, the fatty acid amide-based lubricant is not contained in the rubber forming the dispersed phase but in the nylon resin forming the continuous phase. Thus, the melt viscosity of the dynamically cross-linked product can be effectively lowered by being mixed in the nylon resin forming the continuous phase.

  You may mix | blend a compatibilizing agent with a dynamic crosslinked material with nylon resin, rubber | gum, a crosslinking agent, and a fatty-acid-amide type | system | group lubricant. The compatibilizing agent lowers the interfacial tension between the nylon resin and the rubber and makes them compatible. Although it does not specifically limit as a compatibilizing agent, As one embodiment, ethylene-glycidyl (meth) acrylate copolymer (namely, ethylene-glycidyl methacrylate copolymer and / or ethylene-glycidyl acrylate copolymer) is used. It may be used. The amount of the compatibilizing agent is not particularly limited, and may be 0.5 to 20 parts by mass with respect to 100 parts by mass of the total amount of nylon resin and rubber (amount as a polymer excluding additives). A mass part may be sufficient.

  In this embodiment, when producing a dynamically crosslinked product, a nylon resin and rubber (that is, uncrosslinked rubber) are melt-kneaded together with a crosslinking agent, and the rubber is dynamically crosslinked (that is, kneaded while being crosslinked). The rubber polymer is crosslinked). The fatty acid amide-based lubricant may be added before crosslinking, but is preferably added to the kneaded material and kneaded after crosslinking of the rubber. By adding after the crosslinking, the fatty acid amide lubricant is not easily taken into the crosslinked rubber and can be effectively contained in the nylon resin. Here, after crosslinking, that is, whether the crosslinking has been completed or not can be determined by the gelation rate of the rubber in the kneaded product, and the gelation rate is 70% or more, more preferably 90% or more. If present, it is in the post-crosslinking stage. The method for measuring the gelation rate is as follows.

The kneaded product is extracted with acetone, then immersed in toluene for 3 days, and then dried. The value obtained by subtracting the mass after immersion from the mass before immersion in toluene is defined as the mass of uncrosslinked rubber (that is, the mass of uncrosslinked rubber = the mass before immersion−the mass after immersion), and the gelation rate is calculated by the following formula. .
Gelation rate (%) = {(Rubber mass in kneaded product−Uncrosslinked rubber mass) / Rubber mass in kneaded product} × 100
In addition, what is necessary is just to extract | collect the kneaded material used as the measuring object of a gelation rate from the biaxial opening part which will introduce | transduce a lubricant, for example, when kneading using a biaxial extruder.

  For additives other than fatty acid amide-based lubricants (including compatibilizers and crosslinking agents), the timing of addition to the nylon resin and rubber may be added and mixed in advance, for example, before kneading the nylon resin and rubber. It may be added during kneading.

  As one embodiment, a rubber composition (masterbatch) pellets are prepared by adding a crosslinking agent or the like to rubber, and the pellets are put into a kneader together with a nylon resin and a compatibilizer, and melt-kneaded to dynamically crosslink. Then, a pellet of a dynamically crosslinked product may be obtained by adding and kneading a fatty acid amide lubricant after crosslinking.

  The kneader used for kneading is not particularly limited, and examples thereof include a twin screw extruder, a screw extruder, a kneader, and a Banbury mixer. The kneading temperature may be at least the temperature at which the nylon resin melts and the crosslinking agent undergoes a crosslinking reaction.

  By forming the dynamic cross-linked product thus obtained into a film, a low air permeability film can be obtained. That is, the low air permeability film can be produced by molding a film using the pellets of the dynamically crosslinked product obtained by the above method. The method for forming the dynamically crosslinked pellets into a film is not particularly limited. For example, a method of forming a normal thermoplastic resin into a film, such as extrusion molding or calendar molding, can be used.

The air permeability of the low air permeability film is not particularly limited, but the air permeability coefficient at 80 ° C. is preferably 5 × 10 ¹³ fm ² / Pa · s or less, and the weight of the tire is reduced by thinning the inner liner. Can be achieved. The air permeability coefficient may be 0.1 × 10 ¹³ to 4 × 10 ¹³ fm ² / Pa · s, or may be 0.1 × 10 ^{13 to} 1.0 × 10 ¹³ fm ² / Pa · s. Here, the air permeability coefficient is measured in accordance with JIS K7126-1 “Plastics—Films and Sheets—Gas Permeability Test Method—Part 1: Differential Pressure Method” at test gas: air, test temperature: 80 ° C. Value.

  The thickness of the low air permeability film is not particularly limited, and may be, for example, 0.02 to 1.0 mm, 0.05 to 0.5 mm, or 0.1 to 0.3 mm.

  The low air permeability film according to this embodiment is applied to various pneumatic tires such as tires for passenger cars, various automobile tires including heavy load tires such as trucks and buses, and motorcycle tires including bicycles. can do. Preferably, it is used as a gas barrier layer of a pneumatic tire, and is preferably used as an inner liner provided over the entire inner surface of the tire. However, when it is used as a gas barrier layer, it is not limited to the inner liner provided on the inner surface of the tire, and it is possible to maintain air pressure of the tire by preventing permeation of air from inside the tire, that is, air permeation for maintaining internal pressure. As long as it is provided as a suppression layer, it can be provided at various positions such as the outer surface side of the carcass ply, and is not particularly limited.

  The production method of such a pneumatic tire is not particularly limited, and a green tire is produced by a known method using the low air permeability film, and the produced green tire is vulcanized and molded in a mold. A pneumatic tire according to the embodiment is obtained.

  Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to these examples.

  A dynamic cross-linked product was prepared according to the formulation (parts by mass) shown in Table 1 below. Specifically, rubber and a crosslinking agent were premixed under conditions that do not crosslink to produce rubber master batch pellets, and the obtained pellets, nylon resin, and compatibilizer were set at a temperature of 230 ° C. and a rotation speed of 200 rpm. The mixture was put into a twin-screw extruder (manufactured by Plastic Engineering Laboratory Co., Ltd.) and melt-kneaded to prepare dynamic cross-linked pellets. At that time, the lubricant and the plasticizer were added at the remaining 1/3 position in the kneading process of the twin-screw extruder (that is, the position 2/3 from the upstream side of the heating cylinder). The addition of the lubricant and the plasticizer was performed with a liquid feeder for liquids and with a side feeder for powders.

  The remaining 1/3 of the kneading step is at the stage where the rubber has been cross-linked. This was found to be 91.4% as a result of measuring the gelation rate at this position for the formulation of Comparative Example 1.

  The details of each component in Table 1 are as follows.

・ Nylon resin: “CM6021XF” manufactured by Toray Industries, Inc.
・ Rubber: BR, “BR150L” manufactured by Ube Industries, Ltd.
・ Crosslinking agent: alkylphenol-formaldehyde resin, “Tactrol 201” manufactured by Taoka Chemical Co., Ltd.
-Compatibilizer: ethylene-glycidyl methacrylate copolymer, "Bond First BF-E" manufactured by Sumitomo Chemical Co., Ltd.
BM-4: Plasticizer, N-butylbenzenesulfonamide, “BM-4” manufactured by Daihachi Chemical Industry Co., Ltd.
TCP: Plasticizer, tricresyl phosphate, “TCP” manufactured by Daihachi Chemical Industry Co., Ltd.
D620: Plasticizer, adipic acid-based polyester, “D620” manufactured by J. Plus
・ Metal soap: Lubricant, “Calcium stearate” manufactured by NOF Corporation
WH-215: Fatty acid amide lubricant, “Light Amide WH-215” manufactured by Kyoeisha Chemical Co., Ltd.
WH-255: Fatty acid amide-based lubricant, “Light Amide WH-255” manufactured by Kyoeisha Chemical Co., Ltd.

  The melt crosslinked product thus obtained was measured for melt viscosity and evaluated for processability. The pellets of the dynamically crosslinked product were formed into a film having a thickness of 0.2 mm using a single-screw extruder for film formation, and the workability was evaluated by reading the film-forming current value at a rotation speed of 50 rpm at the time of forming. Moreover, the air permeability coefficient of the obtained film was measured. Each evaluation method is as follows.

  Melt viscosity: The melt viscosity at 230 ° C. and a shear rate of 800 (1 / s) was measured using a capillary rheometer manufactured by Yasuda Seiki Seisakusho and displayed as an index with the value of Comparative Example 1 being 100. did. A larger index indicates a higher melt viscosity and inferior processability.

  Filming current value: The temperature of a single-screw extruder for film molding was 220 ° C., the current value (mechanical load) at 50 rpm was read, and displayed as an index with the value of Comparative Example 1 being 100. The larger the index, the higher the current value and the lower the workability.

  -Air permeability coefficient: According to JIS K7126-1 "Plastics-Film and sheet-Gas permeability test method-Part 1: Differential pressure method" Test gas: Air, Test temperature: 80 ° C, Air permeability coefficient It was measured. Table 1 also shows the value of the index with the value of Comparative Example 1 being 100, along with the value of the air permeability coefficient. The larger the index, the higher the air permeability and the lower the low air permeability.

  As shown in Table 1, compared to Comparative Example 1 in which no lubricant and plasticizer were added, in Comparative Examples 2 to 6, the addition of the plasticizer lowered the melt viscosity, and the current value when forming into a film was also small. As a result, the workability was improved, but the air permeability coefficient increased and the low air permeability deteriorated. In Comparative Example 7 in which the fatty acid metal salt was added, the effect of improving processability was insufficient. In contrast, the addition of the fatty acid amide lubricant in Examples 1 to 5 not only maintains low air permeability, but rather improves the melt viscosity of the dynamically cross-linked product while reducing it. In addition, the current value when forming into a film was small, and the workability could be improved.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their omissions, replacements, changes, and the like are included in the inventions described in the claims and their equivalents as well as included in the scope and gist of the invention.

Claims (7)

  A dynamically crosslinked product comprising a nylon resin forming a continuous phase, a crosslinked product of rubber dispersed in the continuous phase, and a fatty acid amide-based lubricant.   The dynamically crosslinked product according to claim 1, wherein the fatty acid amide-based lubricant has 12 or more fatty acids.   The dynamically cross-linked product according to claim 1 or 2, comprising 0.5 to 10 parts by mass of the fatty acid amide-based lubricant with respect to 100 parts by mass of the nylon resin.   The dynamically crosslinked product according to any one of claims 1 to 3, wherein the fatty acid amide-based lubricant is contained in the nylon resin forming a continuous phase.   The low air permeability film which consists of a dynamic crosslinked material of any one of Claims 1-4.   A pneumatic tire provided with the low air permeability film according to claim 5.   A method for producing a dynamically cross-linked product, wherein a nylon resin and rubber are kneaded together with a cross-linking agent to dynamically cross-link the rubber, and after the cross-linking, a fatty acid amide lubricant is added and mixed.