JP7082898B2 - A method for manufacturing a thermoplastic resin composition for a tire inner liner, a tire inner liner, a pneumatic tire, a tire inner liner, and a method for manufacturing a pneumatic tire. - Google Patents

Description

The present invention relates to a thermoplastic resin composition for a tire inner liner, a tire inner liner, a pneumatic tire, a method for manufacturing a tire inner liner, and a method for manufacturing a pneumatic tire.

A thermoplastic resin composition containing an ethylene-vinyl alcohol copolymer and a polyamide is known to be used for a tire inner liner because it has excellent gas barrier properties and heat resistance during vulcanization (Patent Document 1).

Japanese Unexamined Patent Publication No. 2012-46622

The combination of ethylene-vinyl alcohol copolymer and polyamide is excellent in gas barrier property and heat resistance during vulcanization, but during melt molding (during film formation), the ethylene-vinyl alcohol copolymer and polyamide interact with each other to gel. Has the disadvantage that it is easy to occur.
An object of the present invention is to provide a thermoplastic resin composition for a tire inner liner, which has excellent gas barrier properties, has both heat resistance that does not break down in tire vulcanization and good film-forming properties.

In the present invention, a thermoplastic resin composition containing an ethylene-vinyl alcohol copolymer and a polyamide elastomer having a melting point of 170 ° C. or less interacts with the ethylene-vinyl alcohol copolymer and the polyamide elastomer in the thermal history of vulcanization. It was found that heat resistance can be exhibited, and at the same time, the temperature of melt molding can be significantly lowered compared to the conventional method due to the low melting point, so that gelation during film formation can be suppressed, that is, both heat resistance and moldability can be achieved. , The present invention has been completed.
The present invention is a thermoplastic resin composition for a tire inner liner containing an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer (A) and a polyamide elastomer (B) having a melting point of 170 ° C. or lower.

The present invention includes the following aspects.
[1] A thermoplastic resin composition for a tire inner liner containing an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer (A) and a polyamide elastomer (B) having a melting point of 170 ° C. or lower.
[2] The thermoplastic resin composition according to [1], which can be melt-molded at a discharge temperature of 180 ° C. or lower.
[3] The thermoplastic resin composition according to [1] or [2], wherein the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) has a melting point of 170 ° C. or lower.
[4] Further containing at least one elastomer component (C) selected from the group consisting of an acid-modified polyolefin-based elastomer, an acid-modified styrene-based elastomer, and a halogenated isomonoolefin-paraalkylstyrene copolymer [1] to The thermoplastic resin composition according to any one of [3].
[5] The ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) is a continuous phase, the polyamide elastomer (B) is a continuous phase or a dispersed phase, and the elastomer component (C) is a dispersed phase. The thermoplastic resin composition according to [4].
[6] The thermoplastic resin composition according to any one of [1] to [5], wherein the modified ethylene-vinyl alcohol copolymer is an aliphatic polyester-modified ethylene-vinyl alcohol copolymer.
[7] The thermoplastic resin composition according to any one of [1] to [6], wherein the polyamide elastomer (B) is a thermoplastic elastomer composed of a hard segment made of polyamide and a soft segment made of polyether.
[8] The content of the polyamide elastomer (B) is 5 to 100 parts by volume based on 100 parts by volume of the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A), [1] to The thermoplastic resin composition according to any one of [7].
[9] A tire inner liner made of the film of the thermoplastic resin composition according to any one of [1] to [8].
[10] A pneumatic tire including the tire inner liner according to [9].
[11] A thermoplastic resin composition containing an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer (A) and a polyamide elastomer (B) having a melting point of 170 ° C. or lower is melted at a discharge temperature of 180 ° C. or lower. A method for manufacturing a tire inner liner including a molding process.
[12] Prior to the melt molding step, the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) has a compound or a plasticizer (D) having two or more hydroxyl groups in one molecule. The method for producing a tire inner liner according to [11], further comprising a step of lowering the melting point of the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) to 170 ° C. or lower by mixing the above. ..
[13] Discharge a thermoplastic resin composition containing an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer (A) and a polyamide elastomer (B) having a melting point of 170 ° C. or less at a vulcanization temperature of _Tv or less. The process of producing a thermoplastic resin composition film by melt molding at temperature,
A method for manufacturing a pneumatic tire, comprising a step of manufacturing a green tire containing the thermoplastic resin composition film as an inner liner, and a step of vulcanizing the green tire at a vulcanization temperature _Tv to manufacture a pneumatic tire.

The thermoplastic resin composition of the present invention has both heat resistance and film-forming property.

The thermoplastic resin composition for a tire inner liner of the present invention contains an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer (A). The ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer is also hereinafter referred to as “component (A)”.

The ethylene-vinyl alcohol copolymer (hereinafter, also referred to as "EVOH") is a copolymer composed of an ethylene unit (-CH ₂ CH _2- ) and a vinyl alcohol unit (-CH ₂ -CH (OH)-). However, in addition to the ethylene unit and the vinyl alcohol unit, other constituent units may be contained as long as the effects of the present invention are not impaired. As the ethylene-vinyl alcohol copolymer used in the present invention, one having an ethylene unit content, that is, an ethylene composition ratio of preferably 32 to 48 mol%, more preferably 38 to 48 mol% is used. If the ethylene composition ratio of the ethylene-vinyl alcohol copolymer is too small, the flexibility of the ethylene-vinyl alcohol copolymer is reduced and the durability is lowered. On the contrary, if the ethylene composition ratio is too large, the gas barrier property is lowered. The ethylene-vinyl alcohol copolymer is a saponified product of the ethylene-vinyl acetate copolymer, and the degree of saponification is preferably 90% or more, more preferably 98% or more. If the saponification degree of the ethylene-vinyl alcohol copolymer is too small, the gas barrier property is lowered and the thermal stability is also lowered. Ethylene-vinyl alcohol copolymers are commercially available, for example, under the trade name of "EVAL" (registered trademark) from Kuraray Co., Ltd. and under the trade name of "Soanol" (registered trademark) from Nippon Synthetic Chemical Industry Co., Ltd. You can get it.

The modified ethylene-vinyl alcohol copolymer (hereinafter, also referred to as "modified EVOH") has an ethylene unit (-CH ₂ CH _2- ) and a vinyl alcohol unit (-CH ₂ -CH (OH)-) as main repeating units. However, it refers to a copolymer containing a repeating unit other than these repeating units. An aliphatic polyester-modified ethylene-vinyl alcohol copolymer is preferable.

The aliphatic polyester-modified ethylene-vinyl alcohol copolymer is a thermoplastic resin obtained by grafting an aliphatic polyester on the hydroxyl group of the ethylene-vinyl alcohol copolymer.
Ratio of the content of EVOH units forming the trunk of the aliphatic polyester-modified ethylene-vinyl alcohol copolymer to the content of the aliphatic polyester units grafted on this trunk (content of EVOH units / content of aliphatic polyester units) The content) is usually 40/60 to 99/1, preferably 60/40 to 95/5, and particularly preferably 80/20 to 90/10 in terms of mass ratio. If the content of EVOH units is too low, the gas barrier property tends to decrease. The ratio of the content of the EVOH unit to the content of the aliphatic polyester unit can be controlled by the charging ratio of EVOH and the aliphatic polyester at the time of the graft reaction.

As a method for producing an aliphatic polyester-modified ethylene-vinyl alcohol copolymer, a known method of grafting an aliphatic polyester to EVOH forming a trunk can be used, and in particular, lactones are opened in the presence of EVOH. A method of ring-opening polymerization is preferably used.

The lactones used are not particularly limited as long as they have 3 to 10 carbon atoms. Such lactones are represented by the following formula (1) when they do not have a substituent. Here, n is an integer of 2 to 9, and preferably n is 4 to 5.

Specific examples thereof include β-propion lactone, γ-butyrolactone, ε-caprolactone, δ-valerolactone, and ε-caprolactone and δ-valerolactone are preferable, and ε is inexpensive and easily available. -Caprolactone is more preferred.
These lactones can be used in combination of two or more.

Further, in the ring-opening polymerization reaction, it is preferable to add a conventionally known ring-opening polymerization catalyst, and examples thereof include titanium-based compounds and tin-based compounds. Specific examples thereof include titanium alkoxides such as tetra-n-butoxytitanium, tetraisobutoxytitanium and tetraisopropoxytitanium, tin alkoxides such as dibutyldibutoxystin, and tin ester compounds such as dibutyltin diacetate. Among them, tetra-n-butoxytitanium is preferable because it is inexpensive and easily available.

Examples of the method of ring-opening polymerization of lactones on EVOH to graft them include a method of melt-kneading both in a kneader, and the kneader at that time includes a single-screw and twin-screw extruder and a Banbury mixer. , Kneader, brabender, etc.
The time and temperature of melt-kneading are not particularly limited, and the temperature at which both substances melt and the time at which grafting is completed may be appropriately selected, but are usually 50 to 250 ° C. for 10 seconds to 24 hours, particularly 150 to 230. The range of 5 minutes to 10 hours at ° C is preferably used.

The ethylene composition ratio of EVOH used as a raw material is not particularly limited, but is usually 20 to 60 mol%, preferably 25 to 50 mol%, and more preferably 30 to 45 mol%. If the ethylene composition ratio is too large, the gas barrier property tends to decrease, and conversely, if it is too small, the reactivity of ring-opening polymerization with lactones tends to decrease.

The saponification degree of EVOH is not particularly limited, but is usually 80 mol% or more, preferably 90 to 99.99 mol%, and particularly preferably 99 to 99.9 mol%. If the degree of saponification is too low, the gas barrier property tends to decrease.

The melt flow rate (MFR) used as an index of molecular weight in EVOH is usually 0.1 to 100 g / 10 minutes, preferably 0.5 to 50 g / 10 minutes under the conditions of 210 ° C. and a load of 2160 g. Particularly preferably, it is 1 to 25 g / 10 minutes. If the MFR value is too low, the reactivity of ring-opening polymerization with lactones tends to decrease.

As the EVOH, if the average value is a combination of EVOH satisfying the above requirements, two or more kinds of EVOH having different ethylene composition ratios, saponification degree, and MFR may be mixed and used.

In the thermoplastic resin composition of the present invention, an ethylene-vinyl alcohol copolymer and a modified ethylene-vinyl alcohol copolymer may be used in combination.

The ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) preferably has a melting point of 170 ° C. or lower. By using an ethylene-vinyl alcohol copolymer and a modified ethylene-vinyl alcohol copolymer having a melting point of 170 ° C. or lower, the temperature of melt molding can be significantly lowered compared to the conventional method, and gelation during film formation is suppressed. Can be done.

If the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer has a melting point higher than 170 ° C., the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer has a hydroxyl group in one molecule. A polymer having two or more compounds or a plasticizer may be mixed and the melting point lowered to 170 ° C. or lower may be used. A compound or plasticizer having two or more hydroxyl groups in one molecule is hereinafter also referred to as “component (D)”.

Compounds having two or more hydroxyl groups in one molecule include tris (2-hydroxyethyl) isocyanurate, diols such as ethylene glycol and propylene glycol, triols such as glycerin, and sugar alcohols such as xylitol and sorbitol. Although mentioned, preferred are tris (2-hydroxyethyl) isocyanurate and glycerin.

Examples of the plasticizer include aromatic esters, aliphatic esters, phosphoric acid esters, phthalates and the like.

Aromatic esters include dibutyl phthalate, dioctyl phthalate, diheptyl phthalate, bis (2-ethylhexyl) phthalate, dicyclohexyl phthalate, butyl lauryl phthalate, diisooctyl phthalate, butyl coconut alkyl phthalate, ditridecyl phthalate, dilauryl phthalate, diisodecyl. Phthalate, Butylbenzyl Phthalate, Octyldecanoyl Phthalate, Dimethylglycolphthalate, Ethylphthalylethylene Glycolate, MethylphthalylethyleneGlycolate, Butylphthalylbutylene Glycolate, Dinonylphthalate, Diheptylphthalate, Octyldecylphthalate, Ditridecyl Examples thereof include phthalate, dicaprylphthalate, bis (3,5,5-trimethylhexyl) phthalate, isooctylisodecylphthalate, bis (diethyleneglycolmonomethyl ether) phthalate, and henzophenol.

Aliphatic esters include monoesters, diesters, or monoesters of polyhydric alcohols (dihydric, trihydric or higher polyhydric alcohols) and higher fatty acids (higher fatty acids with 8 or more carbon atoms, preferably 8 to 30 carbon atoms). More polyvalent esters are preferred. For example, stearic acid esters include glycerin monostearate, glycerin mono12-hydroxystearate, glycerin disstearate, diglycerin monostearate, tetraglycerin monostearate; lauric acid esters include glycerin monolaurate and diglycerin monostearate. Examples include rates, tetraglycerin monolaurates and the like. Other aliphatic esters include polypropylene adipate, diisodecyl adipate, bis (2-methylhexyl) adipate, dicapryl adipate, diisooctyl adipate, octyldecyl adipate, isooctylisodecyl adipate, dibutylfumarate, dioctyl fumarate, and triethyl. Examples thereof include citrate, acetyltriethylcitrate, tributylcitrate, and acetyltributylcitrate.

Phosphate esters include tricresyl phosphate, phenyldic cresyl phosphate, xylenyl dicledyl phosphate, cresyl dicylenyl phosphate, triphenyl phosphate, tributyl phosphate, trichloroethyl phosphate, and trioctyl. Examples thereof include phosphate, tributyl phosphate, trichloroethyl phosphate, trioctyl phosphate, triethyl phosphate, arylalkyl phosphate and the like.

Examples of the phthalate include dimethylphthalate, diethylphthalate, dibutylphthalate, bis (2-ethylhexyl) phthalate, diisodecylphthalate, diisononylphthalate, ethylphthalylethylglycolate and the like, and dimethylphthalate, dimethylphthalate, etc. are preferable. It is diethyl phthalate, dibutyl phthalate, and bis (2-ethylhexyl) phthalate.

The mixing amount of the component (D) is not limited as long as the melting point of the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer can be lowered to 170 ° C. or lower, but the ethylene-vinyl alcohol copolymer weight is not limited. Based on 100 parts by mass of the combined or modified ethylene-vinyl alcohol copolymer, it is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 8 parts by mass, and further preferably 0.5 to 6 parts by mass. It is a mass part. If the mixing amount of the component (D) is too small, the melting point of the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer may not be lowered to 170 ° C. or lower, and the mixing of the component (D) may not be possible. If the amount is too large, the gas barrier property may be insufficient.

The thermoplastic resin composition of the present invention contains a polyamide elastomer (B) having a melting point of 170 ° C. or lower. A polyamide elastomer having a melting point of 170 ° C. or lower is also hereinafter referred to as “component (B)”.

Examples of the polyamide elastomer include thermoplastic elastomers composed of a hard segment made of polyamide and a soft segment made of polyether. Examples of the polyamide constituting the hard segment include nylon 6, nylon 66, nylon 11, nylon 12, and the like, and nylon 12 is preferable. Examples of the polyether constituting the soft segment include polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like. Commercially available products can be used as the polyamide elastomer. Commercially available products of polyamide elastomer include "UBESTA" (registered trademark) XPA manufactured by Ube Kosan Co., Ltd. and "Pebax" (registered trademark) 33 series, 53 series, MV series, MH series, HD series, MP series manufactured by Arkema Co., Ltd. And so on.

The polyamide elastomer needs to have a melting point of 170 ° C. or lower. The melting point of the polyamide elastomer is preferably 120 to 165 ° C, more preferably 125 to 160 ° C. If the melting point is too high, the temperature of melt molding must be raised, and gelation during film formation cannot be suppressed.

The content of the polyamide elastomer in the thermoplastic resin composition of the present invention is preferably 5 to 100 parts by volume based on 100 parts by volume of the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer. It is more preferably 10 to 80 parts by volume, and even more preferably 15 to 60 parts by volume. If the content of the polyamide elastomer is too small, the heat resistance developed by the interaction between the ethylene-vinyl alcohol copolymer and the polyamide elastomer in the vulcanization step cannot be sufficiently obtained, and a vulcanization failure may occur. If the content of the polyamide elastomer is too large, the gas barrier property of the thermoplastic resin composition may be deteriorated.

The thermoplastic resin composition of the present invention preferably further contains at least one elastomer component (C) selected from an acid-modified polyolefin-based elastomer, an acid-modified styrene-based elastomer, and a halogenated isomonoolefin-paraalkylstyrene copolymer. )including. At least one elastomer component selected from an acid-modified polyolefin-based elastomer, an acid-modified styrene-based elastomer, and a halogenated isomonoolefin-paraalkylstyrene copolymer is hereinafter simply referred to as "elastomer component (C)" or "(C). Also called "ingredient". By containing the elastomer component (C), flexibility, durability and cold resistance are imparted when the tire is arranged as an inner liner.

Examples of the acid-modified polyolefin-based elastomer include an ethylene-α-olefin copolymer modified with an unsaturated carboxylic acid or an unsaturated carboxylic acid anhydride, an ethylene-unsaturated carboxylic acid copolymer or a derivative thereof.
Examples of the ethylene-α-olefin copolymer modified with unsaturated carboxylic acid or unsaturated carboxylic acid anhydride include maleic anhydride graft-modified ethylene-propylene copolymer, maleic anhydride graft-modified ethylene-butene copolymer, and the like. Maleic anhydride graft-modified ethylene-hexene copolymer, maleic anhydride graft-modified ethylene-octene copolymer and the like can be mentioned.
Examples of the ethylene-unsaturated carboxylic acid copolymer or a derivative thereof include an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, an ethylene-methyl acrylate copolymer, and an ethylene-methyl methacrylate copolymer. Can be mentioned.
Among them, the preferred acid-modified polyolefin-based elastomers are maleic anhydride-grafted ethylene-propylene copolymer and maleic anhydride-grafted ethylene-butene copolymer.
Commercially available products can be used as the acid-modified polyolefin-based elastomer. Examples of commercially available acid-modified polyolefin-based elastomers include "Toughmer" (registered trademark) MH7010, MP7020, and MP0610 manufactured by Mitsui Chemicals, Inc.

Examples of the acid-modified styrene-based elastomer include maleic anhydride-modified styrene-ethylene-butylene-styrene copolymer, maleic anhydride-modified styrene-ethylenepropylene-styrene copolymer, and maleic anhydride-modified styrene-butadiene-styrene copolymer. Examples thereof include maleic anhydride-modified styrene-isoprene-styrene copolymer, and preferred are maleic anhydride-modified styrene-ethylene-butylene-styrene copolymer. Commercially available products can be used as the acid-modified styrene-based elastomer. Commercial products of maleic anhydride-modified styrene-ethylene-butylene-styrene copolymer include "Tough Tech" (registered trademark) M1943, M1913, M1911 manufactured by Asahi Kasei Co., Ltd., and "Kraton" (registered trademark) manufactured by Kraton Polymer Japan Co., Ltd. FG1924 and the like can be mentioned.

The halogenated isomonoolefin-paraalkylstyrene copolymer can be produced by halogenating a copolymer of isomonoolefin and paraalkylstyrene, and the mixing ratio and polymerization rate of isomonoolefin and paraalkylstyrene can be produced. , Average molecular weight, polymerization form (block copolymer, random copolymer, etc.), viscosity, halogen atom, etc. are not particularly limited and may be arbitrarily selected according to the physical properties required for the thermoplastic resin composition. Can be done. Examples of the isomonoolefin constituting the halogenated isomonoolefin-paraalkylstyrene copolymer include isobutylene, isopentene, and isohexene, but isobutylene is preferable. Examples of the paraalkyl styrene constituting the halogenated isomonoolefin-paraalkyl styrene copolymer include paramethyl styrene, paraethyl styrene, parapropyl styrene, parabutyl styrene and the like, but paramethyl styrene is preferable. Examples of the halogen constituting the halogenated isomonoolefin-paraalkylstyrene copolymer include fluorine, chlorine, bromine and iodine, but bromine is preferable. A particularly preferred halogenated isomonoolefin-paraalkylstyrene copolymer is a brominated isobutylene-paramethylstyrene copolymer (hereinafter also referred to as “Br-IPMS”).
The brominated isobutylene-paramethylstyrene copolymer is represented by the formula (2).

It is a bromine of an isobutylene-paramethylstyrene copolymer having a repeating unit represented by the formula (3).

It has a repeating unit represented by. The brominated isobutylene-paramethylstyrene copolymer is available from ExxonMobil Chemical Company under the trade name EXXPRO®.

The content of the elastomer component (C) in the thermoplastic resin composition of the present invention is preferably 0 to 0 to 100 parts by volume based on 100 parts by volume of the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A). It is 260 parts by volume, more preferably 20 to 230 parts by volume, and even more preferably 30 to 210 parts by volume. If the content of the elastomer component (C) is too large, the gas barrier property of the thermoplastic resin composition may decrease.

The thermoplastic resin composition of the present invention may have a sea-island structure.
When the thermoplastic resin composition of the present invention does not contain the elastomer component (C), the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) constitutes a continuous phase, and the polyamide elastomer (B) Preferably constitutes a dispersed phase.
When the thermoplastic resin composition of the present invention contains an elastomer component (C), the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) constitutes a continuous phase, and the elastomer component (C) forms a continuous phase. It is preferable to form a dispersed phase. The polyamide elastomer (B) may form a continuous phase, may form a dispersed phase, or may be present in both the continuous phase and the dispersed phase.
Since the thermoplastic resin composition of the present invention has a sea-island structure, it satisfies film-forming property, heat resistance, flexibility, durability, etc. while maintaining the excellent gas barrier property of the ethylene-vinyl alcohol copolymer. be able to.

The thermoplastic resin composition of the present invention is preferably melt-moldable at a discharge temperature of 180 ° C. or lower, more preferably melt-molded at a discharge temperature of 175 ° C. or lower, and at a discharge temperature of 170 ° C. or lower. It is more preferable that it can be melt-molded. Gel formation can be prevented by melt molding at a relatively low temperature of 180 ° C. or lower.

The thermoplastic resin composition of the present invention may contain various additives in addition to the components (A) to (D) as long as the effects of the present invention are not impaired. Additives include cross-linking agents, anti-aging agents, plasticizers, processing aids, cross-linking accelerators, cross-linking accelerators, reinforcing agents (fillers), scorch inhibitors, kneading accelerators, organic modifiers, softeners. , Adhesives and the like.

The tire inner liner of the present invention is a tire inner liner made of a film of the thermoplastic resin composition. The thermoplastic resin composition can be made into a film by an extruder with a T-shaped die, an inflation molding machine, or the like. Since the film has low air permeability, it can be suitably used as an inner liner for pneumatic tires. The thickness of the film is not limited as long as it functions as an inner liner, but is preferably 1 to 250 μm, more preferably 3 to 200 μm, and even more preferably 5 to 180 μm. If the thickness of the film is too thin, it becomes difficult to form a film, the handling property is poor when the film is applied to a tire, and the gas barrier property as an inner liner may be insufficient. If the thickness of the film is too thick, when the film is applied to the tire as an inner liner, the followability with the adjacent rubber sheet deteriorates, which may make it difficult to form the tire.

The pneumatic tire of the present invention is a pneumatic tire including the tire inner liner. As a method for manufacturing a pneumatic tire, a conventional method can be used. For example, the thermoplastic resin composition is extruded into a film having a predetermined width and thickness in advance, and the thermoplastic resin composition is attached to a cylinder on a tire molding drum. Members used in normal tire manufacturing such as a carcass layer made of unvulcanized rubber, a belt layer, and a tread layer are sequentially laminated on the tire, and the drum is removed to obtain a green tire. Then, by heating and vulcanizing this green tire according to a conventional method, a desired pneumatic tire can be manufactured.

The method for producing a tire inner liner of the present invention comprises a thermoplastic resin composition containing an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer (A) and a polyamide elastomer (B) having a melting point of 170 ° C. or lower. It includes a step of melt molding at a discharge temperature of 180 ° C. or lower. Gel formation can be prevented by melt molding at a discharge temperature of 180 ° C. or lower.
The method of melt molding is not limited, and examples thereof include a method of melt extrusion using an extruder equipped with a T-shaped die, an inflatation method using an inflation molding machine, and the like. By melt-molding the thermoplastic resin composition, a film of the thermoplastic resin composition can be produced.

In the method for producing a tire inner liner of the present invention, two hydroxyl groups are contained in 100 parts by mass of an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer (A) before the melt molding step. 0.1 to 10 parts by mass of the compound or plasticizer (D) having two or more is mixed to lower the melting point of the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) to 170 ° C. or lower. Further steps may be included.
The ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) used in the present invention preferably has a melting point of 170 ° C. or lower, but has a melting point higher than 170 ° C. for both ethylene-vinyl alcohol. Polymers or modified ethylene-vinyl alcohol polymers can be used. When an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer having a melting point higher than 170 ° C. is used, ethylene having a melting point higher than 170 ° C. is previously mixed with the polyamide elastomer (B). -Vinyl alcohol copolymer or modified ethylene-Vinyl alcohol copolymer mixed with a compound or plastic agent (D) having two or more hydroxyl groups in one molecule, ethylene-vinyl alcohol copolymer or modified ethylene- It is preferable to lower the melting point of the vinyl alcohol copolymer to 170 ° C. or lower.

The method for manufacturing a pneumatic tire of the present invention is
A thermoplastic resin composition containing an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer (A) and a polyamide elastomer (B) having a melting point of 170 ° C. or less is melted at a discharge temperature of vulcanization temperature _Tv or less. The process of molding to produce a thermoplastic resin composition film,
It includes a step of producing a green tire containing the thermoplastic resin composition film as an inner liner, and a step of vulcanizing the green tire at a vulcanization temperature _Tv to produce a pneumatic tire.
In the method for producing a pneumatic tire of the present invention, the temperature of melt molding when the thermoplastic resin composition is melt-molded to prepare a thermoplastic resin composition film is lower than the temperature at which the green tire is vulcanized. It is characterized by that.
The vulcanization temperature _Tv for producing a pneumatic tire is usually 165 to 200 ° C, typically 175 to 195 ° C.
If a film of a thermoplastic resin composition having a melting point that melts at the vulcanization temperature is used as the inner liner, it is expected that the inner liner will flow during tire vulcanization and the film shape cannot be maintained. It has been a common practice to use at least one thermoplastic resin having a melting point higher than the vulcanization temperature as a constituent component of the resin composition. For example, in a thermoplastic resin composition containing an ethylene-vinyl alcohol copolymer and a polyamide, the melting point of the ethylene-vinyl alcohol copolymer is lower than the vulcanization temperature, but the melting point of the polyamide is higher than the vulcanization temperature. It is believed that polyamide suppresses the fluidization of the ethylene-vinyl alcohol copolymer during vulcanization.
In the thermoplastic resin composition of the present invention, both the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) and the polyamide elastomer (B), which are the constituents thereof, are lower than the vulcanization temperature. Despite having a melting point, the film made of the thermoplastic resin composition of the present invention can, contrary to expectations, maintain its film shape during vulcanization. Although the reason is not clear, heat resistance is developed by the interaction between the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) and the polyamide elastomer (B) in the thermal history of vulcanization. It is presumed to be due.

(1) Raw materials The raw materials used in the following examples and comparative examples are as follows.

EVOH-1: Ethylene-vinyl alcohol copolymer "Soanol" manufactured by Nippon Synthetic Chemical Industry Co., Ltd. (registered trademark) H4815B (ethylene composition ratio 48 mol%, melting point 158 ° C)
EVOH-2: Ethylene-vinyl alcohol copolymer "Soanol" manufactured by Nippon Synthetic Chemical Industry Co., Ltd. (registered trademark) E3808 (ethylene composition ratio 38 mol%, melting point 173 ° C)
Modified EVOH: Aliphatic polyester modified ethylene-vinyl alcohol copolymer "Soanol" manufactured by Nippon Synthetic Chemical Industry Co., Ltd. (registered trademark) SG743 (melting point 110 ° C)

Polyamide Elastomer-1: "UBESTA" (registered trademark) XPA 9040X1 manufactured by Ube Kosan Co., Ltd. (hard segment = polyamide 12, soft segment = polyether, melting point 135 ° C)
Polyamide Elastomer-2: "UBESTA" (registered trademark) XPA 9048X1 manufactured by Ube Kosan Co., Ltd. (hard segment = polyamide 12, soft segment = polyether, melting point 153 ° C)
Polyamide Elastomer-3: "Pebax Rnew" (registered trademark) 55R53SP01 manufactured by Arkema Co., Ltd. (hard segment = polyamide 11, soft segment = polyether, melting point 167 ° C)
Nylon 6: "UBE Nylon" (registered trademark) 1013B (melting point 225 ° C) manufactured by Ube Kosan Co., Ltd.

Mah-PO: Maleic anhydride-modified polyolefin-based elastomer "Toughmer" (registered trademark) manufactured by Mitsui Chemicals, Inc. MH7010
Mah-SEBS: Maleic anhydride-modified styrene-ethylene-butylene-styrene copolymer "Tough Tech" (registered trademark) manufactured by Asahi Kasei Corporation M1943
Br-IPMS: ExxonMobil Chemical's brominated isobutylene-paramethylstyrene copolymer "EXXPRO" (registered trademark) 3745

The following two types were used as compounds having two or more hydroxyl groups in one molecule.
Tris (2-hydroxyethyl) isocyanurate: Shikoku Kasei Kogyo Co., Ltd. THEIC A
Glycerin: Glycerin DG manufactured by NOF CORPORATION

The following two types of plasticizers were used.
Triacetin: manufactured by Daihachi Chemical Industry Co., Ltd. Dimethyl phthalate: manufactured by Daihachi Chemical Industry Co., Ltd.

(2) Melting point depression treatment of EVOH EVOH-3: 100 parts by mass of EVOH-1 and 5 parts by mass of tris (2-hydroxyethyl) isocyanurate are introduced into a twin-screw kneading extruder set at a cylinder temperature of 180 ° C. and melted. After kneading, it was extruded into a strand and pelletized to prepare EVOH-3 having a lowered melting point. The melting point of EVOH-3 was 148 ° C.
EVOH-4: 100 parts by mass of EVOH-1 and 5 parts by mass of triacetin are introduced into a twin-screw kneading extruder set at a cylinder temperature of 180 ° C., melt-kneaded, extruded into strands, pelletized, and the melting point is lowered. EVOH-4 was prepared. The melting point of EVOH-4 was 150 ° C.
EVOH-5: 100 parts by mass of EVOH-1 and 5 parts by mass of dimethylphthalate are introduced into a twin-screw kneading extruder set at a cylinder temperature of 180 ° C., melt-kneaded, extruded into strands, pelletized, and the melting point is lowered. EVOH-5 was prepared. The melting point of EVOH-5 was 152 ° C.
EVOH-6: 100 parts by mass of EVOH-2 and 5 parts by mass of glycerin are introduced into a twin-screw kneading extruder set at a cylinder temperature of 180 ° C., melt-kneaded, extruded into strands, pelletized, and the melting point is lowered. EVOH-6 was prepared. The melting point of EVOH-6 was 167 ° C.

(3) Preparation of Thermoplastic Resin Composition An ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol (A), a polyamide elastomer (B) or a polyamide, and an elastomer component (C) are blended in the formulation shown in Table 1. It was introduced into a twin-screw kneading extruder (manufactured by Japan Steel Works, Ltd.) set to a cylinder temperature 20 ° C higher than the melting point of the raw material having the highest melting point among the components A), (B) or polyamide, and the residence time was about 3 to. It was conveyed to a kneading zone set for 4 minutes for melt-kneading, and the melt-kneaded product was extruded into a strand shape from a die attached to a discharge port. The obtained strand-shaped extruded product was pelletized with a resin pelletizer to obtain a pellet-shaped thermoplastic resin composition.

(4) Performance evaluation The prepared thermoplastic resin composition was subjected to viscosity measurement, and film film forming property and vulcanization failure were evaluated. The evaluation results are shown in Table 1. The evaluation method is as follows.

(5) Viscosity measurement Using the pellet-shaped thermoplastic resin composition prepared in (3), it was pre-dried at 100 ° C. for 4 hours at 100 ° C. at 100 ° C. and at temperatures 170 ° C., 190 ° C. and 240 ° C. The melt viscosity (Pa · S) was measured by detecting the load under the conditions of a piston speed of 5 mm / min, a capillary length of 10 mm, and a capillary inner diameter of 1 mm. When the melt viscosity at 200 seconds from the start of extrusion was η ₁ and the melt viscosity at 800 seconds was η ₂ , and η ₂ <1.2 η ₁ was satisfied, it was determined that there was no increase in viscosity.
By the way, when melt molding is performed at a temperature at which the viscosity does not increase, gelation does not occur and a good film can be formed. On the contrary, when melt molding is performed at a temperature at which the viscosity increases, gelation occurs and film formation failure occurs. If the viscosity increases at 190 ° C., the thermoplastic resin composition thickens in the thermal history during vulcanization, and foaming failure does not occur. When the product whose viscosity increases at 240 ° C. is molded at the conventional molding temperature (about 240 ° C.), gelation occurs and film formation failure occurs.

(6) Film-forming property The pellet-shaped thermoplastic resin composition prepared in (3) is extruded at an extrusion temperature of Cl / C2 / using a 40 mmφ single-screw extruder (Plastic Giken Co., Ltd.) with a 550 mm wide T-shaped die. The film was formed into a film having an average thickness of 0.05 mm under extrusion conditions of C3 / C4 / die = 230/230/230/230/230 ° C., a cooling roll temperature of 50 ° C., and a take-up speed of 4 m / min. Visually observe the film 90 minutes after the start of extrusion, and if there are 5 or more gels of 2 mm x 2 mm or more in a 100 cm long film, the film forming property is poor, and if less than 5 are made of film. It was judged that the film property was good.

(7) Vulcanization failure The film of the thermoplastic resin composition obtained in (6) is placed on the innermost surface of the tire, a green tire is manufactured, and then inserted into a mold set at 190 ° C. by a conventional method. Vulcanization was performed to prepare a radial tire 195 / 65R15. After vulcanization, the inner surface of the tire was observed to confirm that the film of the thermoplastic resin composition had no foaming failure. If bubbles are observed inside the film of the thermoplastic resin composition or at the interface between the film of the thermoplastic resin composition and the rubber layer, it is judged that there is a vulcanization failure, and if no bubbles are observed, it is judged that there is no vulcanization failure. did.

The thermoplastic resin composition of the present invention can be suitably used for an inner liner of a pneumatic tire.

Claims (12)

A thermoplastic resin composition for a tire inner liner containing an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer (A) and a polyamide elastomer (B) having a melting point of 170 ° C. or lower, wherein the thermoplastic resin composition is 180 ° C. or lower. A thermoplastic resin composition that can be melt-molded at the discharge temperature . The thermoplastic resin composition according to claim 1 , wherein the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) has a melting point of 170 ° C. or lower. The invention according to claim 1 or 2 , further comprising at least one elastomer component (C) selected from the group consisting of an acid-modified polyolefin-based elastomer, an acid-modified styrene-based elastomer, and a halogenated isomonoolefin-paraalkylstyrene copolymer. Elastomer resin composition. The ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) is a continuous phase, the polyamide elastomer (B) is a continuous phase or a dispersed phase, and the elastomer component (C) is a dispersed phase. The thermoplastic resin composition according to claim 3 . The thermoplastic resin composition according to any one of claims 1 to 4 , wherein the modified ethylene-vinyl alcohol copolymer is an aliphatic polyester-modified ethylene-vinyl alcohol copolymer. The thermoplastic resin composition according to any one of claims 1 to 5 , wherein the polyamide elastomer (B) is a thermoplastic elastomer composed of a hard segment made of polyamide and a soft segment made of polyether. Any of claims 1 to 6 , wherein the content of the polyamide elastomer (B) is 5 to 100 parts by volume based on 100 parts by volume of the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A). The thermoplastic resin composition according to item 1. A tire inner liner made of the film of the thermoplastic resin composition according to any one of claims 1 to 7 . A pneumatic tire comprising the tire inner liner according to claim 8 . A step of melt-molding a thermoplastic resin composition containing an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer (A) and a polyamide elastomer (B) having a melting point of 170 ° C. or lower at a discharge temperature of 180 ° C. or lower. Manufacturing method of tire inner liner including. Prior to the melt molding step, the ethylene-vinyl alcohol copolymer or the modified ethylene-vinyl alcohol copolymer (A) is mixed with a compound having two or more hydroxyl groups in one molecule or a thermoplastic agent (D). The method for manufacturing a tire inner liner according to claim 10 , further comprising a step. A thermoplastic resin composition containing an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer (A) and a polyamide elastomer (B) having a melting point of 170 ° C. or less is melted at a discharge temperature of vulcanization temperature _Tv or less. The process of molding to produce a thermoplastic resin composition film,
A method for manufacturing a pneumatic tire, comprising a step of manufacturing a green tire containing the thermoplastic resin composition film as an inner liner, and a step of vulcanizing the green tire at a vulcanization temperature _Tv to manufacture a pneumatic tire.