Title of invention METHOD FOR PRODUCING BLOWN FILM

Technical Field

[00011 The present invention relates to a process for producing a blown film. More speci ically, the present invention relates to a process for producing blown film having a reduced shrinkage with time from a thermoplastic elastomer coioposition.

Background Art

[0002] A process for producing a film by subjecting a thermoplastic elastomer .composition comprising a

thermoplastic .resin and rubber gartides dispersed in the thermoplastic .resi to: inflation molding .(referred to also as ^' "blown film, extrusion molding."} is known .in the art {see PTLs 1 to 3} According to the inflatio molding process, such a thermopl st c elastomer composition is extruded from :a.n annular discharge port of an. annular die as a tubular soft film (hereina er, referred to also as a ^bubble" } and stretched in. the circum erential

direction .and vertical direction (machine directio or conveyance direction): of the. bubble, However, due to the ru ber component contained in the thermoplastic elastomer composition, the tubular film which has been stretched during the inflation molding process may easily shrink after the release of the stretching force during the inflation molding process, and therefore has low

dimensional stability. Further, due to the shrinkage of the film, there was also a problem in terms of wrinkling of the film. Furthermore, in order to improve the moldability of a thermoplastic elastomer composition during inflation molding fo producing a film, the conventional practice lias been to add a plasticizer to the thermoplastic elastomer composition, when a

thermoplastic elastomer composition which does not contain a plasticizer is subjected to inflation molding, the resulting film exhibits remarkable shrinkage with time .

Citations List

Patent Literature

[00031

PTL 1: Japanese Unexamined Patent Publication No. 2014-- 117827A

PTL 2c Japanese Unexamined Patent Publication Eo, 2005- 1254.99A

PTL 3: Japanese nexamined Patent Publication No. H3-

4.9S3 OA

Summary of Invention

Technical Problem

[0004] In view of the above conventional problems, the present invention is directed to provide a process for producing a blown film, enabling restraint of the film after inflation, molding from shrinking with time, thereby enabling provision of a blown film ^' having high

dimensional stability,

[0005] The inventors have carried oat experiments in order to achieve the above object, and as a result found that, it is possible to restrain the resulting film after inflation molding from shrinking wioh time when the distance i the extruding direction of tubular film from an annular discharge port having an outer diameter I>1 (mm) of an -annular die to a position at which the tubular film has been expanded to have a maximum diameter D2 is represented by L2, and the distance in the

extruding direction of the tubular film from the annular discharge port of the annular die to a position at which the tubular film has been expanded to have an

intermediate diameter D3- (DI-D25. /2 is represented by L3., Dl, Ό2, L.2, and L3 satisfy both relationships of formulas (I) and {2} below,

[0006] 0.3 x 12 < 13≤ 0.7 x 12 (2;) ,

[0007J

resulting in a blown film having high dimensional

stability, and consequently completed the present invention.

Solution to Problem

0008] The present invention includes following

[Embodiment 1] to {Embodiment 9] .

[Embodiment i] A process for producing a blown film from a thermoplastic elastomer composition ^' comprising a, thermoplastic resin and rubber particles dispersed in the thermoplastic resin by inflation molding equipment , wherein the in lation molding equipment comprises: an annular die having _: an annular discharge port having an outer diameter DX (mm) , and

wherein the process ¹ comprises:

melting the thermoplas ic elastomer composition to form a molten thermoplastic elastomer composition;

extruding the molte thermopl stic elastomer composition from th annular discharge port of the

annular die as a. tubular film; and

expanding the tubular ilm extruded from the annular discharge port to have a maximum diameter Ό2 (mm; ;

and when the distance in the extruding direcrion of the tubular film from she annula discharge port of the annular die to a. position at which the tubular film, has been expanded to have the maximum diameter D2 is

represented by L2, and the distance in the extruding direction of the tubular film from the annular discharge port of the annular die to a position at which the tubular film has been expanded to have an intermediate diameter D3 {D1+D2 } ,/2 is represented by L3 , Dl, D2, L2, and L3 sa isfy both reiarionships of following formulas (1) and (2) :

100093 0,5 < 12/[D2 x™j≤ 1.0. (1)

0,3 x LZ≤ 13≤ 0,7 x L2 (2),

[00103 [Embodiment 21 The process according to

Embodiment 1, wherein the annular discharge port of the annular die has a lip ga G (mm) , and the outer diameter 01. {nun} and lip gap G (mm,) of the annular discharge port satisfy a relationship of following formula (3) ;

[0011]

80 < Dl K G < 300. (3),

[00121 [Embodiment 3] The process according to

E bo iment 1 or 2, wherein the resulting film has a thickness of from 50 to 300 pm and a ratio D2/D2 of 1.2 to 5.0.

[0013] [Embodiment 4] The process according to any one of Embodiments 1 to 3, wherein the inflation molding equipment further comprises an air ring devi e arranged at the circumference of the annular discharge port of the annular die, and the process further comprises cooling ^' the tubular film with a cooling gas blown from the air ring device,.

[0014] [Embodiment 5] The process according to any one of Embodiments 1 to 4, wherein the blown film is a mem er: for a tire.,

[0015] [Embodiment S] The process according to any one of Embodiments 1 to , wherein the blown film is an inner liner for a tire,

[0016] [Embodiment 7] The process according to any one of Embodiments l to 6 , wherein the thermoplast c resin comprises one or more nylons,

[00171 [Embodimen S] The process according to any one of Embodiments l to 7, wherein the rubber particles dispersed in the thermoplastic resin comprise a.

brominated isohutylene ^« p-methyIstyrene copolymer, aleic anhydride-modified ethylene~a~oiefin copolymer,, acid anhydride -modi £led styrene - isobatylene- styrene block copolymer, or a combination of two or more thereof.

O IS] [Embodiment 9] The process according to any one of Embodiments 1 to 8, writ rein the thermoplas ic elastomer composition does not comprise a higher alcohol- based plasticizer, aromatic sulfonamide-based

plastic! zer, or phenolic piasticiser.

Advantageous Effects of Invention

[0019] According to the process for producing a blown film of the present invention,, the tubular f lira, obtained after inflation mold ng has a reduced shrinkage with time, and accordingly has reduced wrinkles or deformation due to shrinkage,, thereby enabling the production of a. blown film having excellent dimensional stability.

Further, the film produced by the process for producing a blown film of the present invention exhibits excellent gas barrie properties in addition to reduced wrinkles, or deformation due to shrinkage with time.

Brief Description of Drawings

[0020] [FIG. .I] s' G., 1 is a schematic: view

illustrating one ^' example of the process for producing a blown film according to the present invention,

[FIG, 2] FIG. 2 is a schematic view illustrating a process of extruding a molten thermoplastic elastomer composition from an annular discharge port of an annular die as a bubble, and expanding the bubble,, in the process for producing a blown film according to the present invention.

[FIG , 31 FIG . 3 is a view schematically showing as a dot image a temperature distribution, image captured by infrared thermography for a bubble formed during the production, of a blown film of Comparative Example 1 by inflation molding..

[FIG. 41 FIG . 4 is a view schem tically showing as a dot Image a temperature distribution, image captured by infrared thermography for a bubble formed, during the production of a blown film of Example 2 by inflation, molding . [FIG, 5] FIG. 5 is a iew schematically showing as a dot image a temperature distribution image captured by infrared thermography for a bubble formed during the production of blown f ilm of Coit¾>arative Example 11 by inflation molding.

Description of Embodiments

[0021] Embodiments of the present invention will be explained below in detail along with referring to the attached drawings. WIG . 1 shows one embodiment of an inflation molding equipment used in the process of the present invention-. This inflation molding equipment 1 comprises extruder 10 comprising stock material feeder 11,- cylinder 12 and discharge port 13, and annular die 20 connected to discharge port 13 of extruder 10. A

thermoplastic elastome composi ion is introduced into cyli der 12 set to a temperature capable of rnelt- excr din the thermoplastic elastomer composition from s-toch material feeder 11 of extruder 10, and the

thermoplastic elastomer composition is allowed to melt in cylinder 12 while extruding in by a rotating screw (not shown) to the discharg port side, and then the molten thermoplastic elastomer composition is extruded from, discharge port 13 to annular die 20.

10Q22] Annular die 20 has annular discharge port 21 defined as a gap between an inner li and an outer lip (both not shown) . The molten thermoplastic elastomer resin composition is extruded upwardly from, annular discharge port 21 as a bubble. The width of the gap in the radial direction between the inner lip and outer lip of annular die 20 is a lip gap "G" of annular die 20. Annular die 20: further has an air passage {not shown) for blowing air inside bubble B. Bubble B can be expanded by the pressure of air enclosed inside bubble S. Extruded bubble B is stretched in the oircursferentiai direction by the air enclosed inside bubble B and is also stretched in the vertical direction {machine direction or conveyance direction) by drawing the bubble in the vertical direction., Bubble B can be cooled by blowing a cooling gas to t e outside of extruded bubble B with air ring device 30 provided above annular discharge port 21 and in proximity to the outer circumferential side of annular discharge port 21, in concentrically to annular discharge port 21, Examples of the cooling gas include air, inert gases {for example., nitrogen and argon) , etc. Air ring device 30 has at least one cooling gas outlet port 31 whic blows out the cooling gas. It is preferable that, in the air. ring device, the opening area of the cooling gas outlet port is adjustable. It is preferable that the air ring device has two or mo e cooling gas outlet ports. When the air ring device has two or more cooling gas outle ports, it is preferable that the two or more cooling .gas. outlet ports, .are annularly formed and are arranged concentrically with each other to have a common center axis. The direction of the. common center axis coincides with the direction of the ce ter axis of the annular die or the direction in which, the bubble is .extruded from the annular die.. When the air ring device has two ^: or more: cooling, gas outlet ports, it is

preferable that the two or more cooling gas outlet ports are arranged spaced apart in the .extrusion direction of the bubble and the cooling gas outlet port provided farther from the center axis and at an outer

circumferential side has a distal end farther from the annular die. The temperatur of the cooling gas blown from the air ring devics to the bubble is preferably from 0 to 30 ^o e _. , and more preferably from 5 to 15°C. If the temperature of the cooling gas is lower than 0°C, the cooling rate of the bubble is excessively high. If the temperature of the cooling gas is above 3 °C, the cooling efficiency is decreased. In F1C3. i, the air ring devic is shown by the cros -sectional view in the vertical direction along the center axis of the annular die.

10023] In FIG. I, a pair of stabilizing plates OA, GB facing each other are provided above air ring device 30. Bubble 8 ex anded to have the maximum diameter is further cooled and is de ormed into fiat wh le being conveyed by the pair of stabilizing plates 4OA, 408 facing eac other. In place of the pair of stabilizing plates 4OA, 40.Β·, for exam le, a plurality of guide rollers arranged in parallel with each other in a direction perpendicular to the conveyance direction of bubble^ B may be used. Above stabilising plates 40A, 40B, a pair of pinch rolls 50A, SOB are arranged for folding bubble B deformed into flat by stabilizing plates 40A, 4QB, into a sheet. Tubular film ^' F which is obtained b folding the bubble by the pair of pinch rolls 5GA, SOB is wound u by windup roll .so. through guide rolls 51, S2.A, 52B, 53, Before the tubular .film is wound up by the w rta p roil or after it is wound up, one end of the tubular film, may foe out open to obtain a wide film, as. necessary.

[0024] in the embodiment shown in PIS. I, bubble B extruded upwardly from annular discharge port 21 is conveyed upward while being folded into a sheet form- by the pair of pinch rolls SOA, .5.0.8, but it is also possible to extrude the bubble downward from annular discharge port 2.1 and convey the bubble downward while folding it in a sheet form by a pair of pinch rolls.

C0025-] Next, an embodiment of the present invention will be- explained in more detail with referring to .PIG. 2. FIG. 2 schematically shows the process from when the bubble is extruded upward from annular discharge port 21 which is defined as the gap between the inner lip and outer lip of annular di 20 (not shown} to when it i expanded up to the maximum diameter D . Annular discharge port 21 has an outer diameter of Dl . The bubble extruded from annular discharge port 21 of annular die 20

gradually expands as it is conveyed upward, and the bubble expands- until the diameter thereof reaches the isa itmasB diameter D2. The terxn "the diameter of the bubble" refers herein, to the outer diameter of the bubble., and the term "maximum diameter of the bubble" refers herein to the max snutn value of the outer diameter of the bubble. In the process for producing a blown film according to the present ven ion, when the distance in the extruding direction of the bubble from annular discharge port 21 of annular die 20 to a position at which the bubble has been expanded to have the axim m diameter D2 is represented by L2, and. the distance in the extruding direction of the bubble from annular discharge port 21 of annular die 20 to a position at which th diameter of ^: the bubble ^' has been expanded to an

intermediate drameher D.3 which is an average value of Dl and D2 {i.e., .D ^' 3- f0l÷D2) J 2 ) is represented by 13, Dl, D2 , L . , and L3 satisfy both relationships of following ^' formulas (1) and (2) :

[0026]

0.5 <L2/tD2x™) 1.0 (1)

0.3 XL2≤L3≤ 0.7 x L2 (2).

[0027] The relationship in formula (2} shows that L3 has a value ^' in the range of ±0.2xL2 ^: centered at .half the distance L2- (i .e . , 0.. SxL2) , meaning that the bubble i gradually expanded up to the maximum diameter D2 after being extruded from the annular discharge port of the annular die. While not being bound by an specific theory, it is believed that, by satisfying the

relationships of formulas (1) and {2}; the bubble formed by extruding the molten thermoplastic elastomer

composition from the annular discharge port of the annular die is gradually cooled and thereby gradually stretched until reaching the maximum diameter of the bubble. Due to the gradual stretching of the bubble extruded from the annular discharge port, of the annular die until reaching the maximum diameter, it is believed that the shrinkage of the film after inflation molding ^' can be restrained. If DO,, D2 _» L2, and L3 do not satisfy both of the relationships of the above formulas (1) and (2) , then the bubble pulsates, and accordingly does not stabilize, and as a result, it is difficult to produce a blown film, or even if a film can be obtained, by

inflation molding, the resulting film has a high

shrinkage factor and is poor in dimensional stability.

[0028] In the process for producing a blown film according to the present invention , the outer diameter Dl ivrni) and G (mml of annular dischaxge port 21 preferably satisfy the relationship of following formula (3} :

[0Q2S]

80<»l G<30e (33.

[0030] If Dl (mm,) x: G .(·ϊρη) is less than SG inrrrt then the pressure required for extruding the thermoplastic ■elastomer composition through the annular discharge port of annula die 20 is too high. If Dl <∑mn) x G (ma) is above 300 mm ² ., the difference between the discharge rate of the thermoplas ic elastomer composition and the drawing .speed by the pinch rolls is large, thereby making it difficult to stabilise the bubble.

£003X1 In the process for producing a blows film according to the present invention, the ..blow-up ratio

(BUR) , i.e...,. B2/B1, is. preferably in the range of .from 1. _.. 2 to 5 _. ..0. If the blow-up ratio is _. less, than 1.2, the. resulting, blown film has stretching degree in the e trusion direction which is higher than the _: stretching degree in the transverse direction perpendicular to the extrusion direction, as with monoaxially stretched film. For this reason, the resulting blown film has a problem in that physical properties, such as tensile stress, elongation at break, breaking strength, etc., differ between the extrusion direction and the transverse direction perpendicular to the extrusion direction. If the blow-up ratio is above 5.0, then the bubble is excessively stretched in the circumferential direction, thereby the resulting blown film has a relatively large shrinkage factor. The blown film, produced by the process 1.1 - according to the present invention preferably has a thickness ^!! t ^!i of from 50 to 300 μκκ When a blown film having a thickness "t" of less than SO urn is to be produced, it is generally necessary to increase the stretching degree in t e: extrusion, direction and

circumferential direction of the bubble, causing a problem that the resulting blown film has a relatively large shrinkage factor. When a blown film having a thickness "t" of more than 300 um is to be produced, then the discharge rate, drawing speed, and cooling strengt are unbalanced, resulting in th destabilization of the bubbl ,

10032] In order to satisf both o the relationships of the above formulas {1} and (2} to form a desired bubble, shape, the discharge rate, .of the thermoplastic elastomer composition is se to 30 to 100 kg/h, the drawing speed of the film is set to 2 to 25 /min, the cooling gas flow rate is set to 10 to 50.m*/miii, and the temperature of the cooling gas is set to 0 to 30°C. For exampl , when the values of L2 and L3 are set to

relatively large values within the scope _: ©.£ the present invention, the discharge rate of the thermoplastic, elastomer composifion is increased, the drawing speed of the film is increased, the cooling air flow rate is decreased, the temperature of th cooling air i raised, etc., for exam le.

108333 Examples of the thermoplastic resin which can form the thermoplastic elastomer composition, used in she process for producing a blown film according to the present invention, include poly mide-based resins,

polyester-based resins, pclynitriie-based resins, polymethacryiate-based resins, polyvinyl -based resins, celluiosic resins, fiuororesins ,« imide-based resins, polystyrenic resins, polyolefinic resins, etc. The thermoplastic elastomer composition may include at least one thermoplastic resin. C0034] Examples of polyamids resins include Nylon 6 t ) , Nylon 66 {MS) , Nylon 46 (N46) , ylon 11 (Nil}, Nylon 12 -(N12) , Nylon €9 (N69) , Nylon 510 (N610) , Nylon 612 (N612), Nylon 6/66 (N6/66), Nylon 6/66/610

ίΝδ/δδ/610) ; semi-aromatic and all -aromatic nylons such as Nylon MXDS ( XD6) _r Nylon 6T, Nylon 6/6T, and Nylon 9T _f - Nylon S ^' 6/PF copolymer, Nylo 6S/PPS copoiyriier, etc.

Examples of polyester-based resins include aromatic polyesters such as poiybutyiene terephthalate (ΡΒΤϊ , polyethylene terephthalate (PET) , polyethylene

isopnthalate i El) , PET/PBI copolymer, poiyarylste (PAR).,, polybutylene riaphthalate (PBN) , liquid crystal polyester poly©xyalky1enedii idic cid/polyb tyIate t rephtha1ate copolymers,, etc. E m les of polynitrile-based resins inoio.de p lyaorylonitrile (PAN) , polyT«ethaerylo itrile ,. acr ionitrile/styrene copolymer (AS) ,

meth cry1onxtri1e/s _: t rene co olymer,,

methacrylonitrile/styrene/butadiene copolymer,, etc .

Examples of polymethacrylate-based resins includ

poly (methyl methaeryiace.} (PHMA} , poly (ethyl

me haorylate) , etc . Examples ^' - of polyvinyl-based resins include vinyl acetate {PVAc}. , poly (vinyl alcohol) (PVA ⁾ , ethylen -vinyl alcohol copolymer (BVOFi) , poly (vinylidene chloride) (FvDC) , poly (vinyl chloride} (PVG) , vinyl chloride/vinyl idene chloride: copolymer, vinylidene chloride/methyl acryiaos copolymer, etc. ^' Bx -sspies- of cellulosic resins include cellulose acetate, cellulose acetate butyiate, etc. Examples of fluororesins include poly vinylidene fluoride} (PVDP) , poly (vinyl fluoride}

(PVF) , poiychlorofluoroeohyiene PCTFE) ,

tetrafluoroethyiene/etbylene copolymer (ETFB) , etc.

Examples of iraide-based resins include aromatic

polyimides (PI) , etc. Examples of polystyrenic resins include polystyrene (PS), etc. Examples of poiyolefinic resins includ polyethylene (PS), po-lypropy1ene CPP). , et Among these thermoplastic resins. Nylon 6, Nylon 66, Nylon 46, Nylon 11, Nylon 12, Nylon 63, Nylon 610, Nylon 6:12, Nylon S S-S, Nylon 6/66/12, Nylon 6/6S/610, and semi- aromatic and all-aromatic nylons, suc as Nylon MXDS , Nylon 6T, Nylon 9T, and Nylon 6/6T are preferred, in view of gas barrier properties and proesssability ,

S [0035] Common ingredients for common thermoplas ic resin compositions, such as fillers, reinforcing agents , processing aids, stabilisers, antioxidants., etc ma optionally be added at a common amount to the

thermoplastic resin, which constitutes the thermoplastic0 elastomer composition used in the process for producing an inflation film according to the present invention. In view of the gas barrier properties and heat resistance of the film obtained by inflation molding of -the

thermoplastic elastomer composition, it is preferred to5 not add plastieizer to the thermoplastic resin or

thermoplastic elastomer composition. An inflatio film having a reduced shrinkage with time after inflation molding can be produced even if a. plasticise such as, tor example, higher alcohol -based plasticizetfs., aromatic.0 sulfon atttide -based plasbicizers, phenolic la _. stieizers, etc. _f conventionally used in the inflation mold ng of a thermoplastic elastomer composition, is not incorporated into the thermoplastic elastomer .composition, and ^:

therefore it is possible to prevent the decrease in the5 g s barrie properties and ^' heat resistance -hic may be caused when a piasticizer is added to the thermoplastic elastomer composition.

£0036-3 The thermoplastic elastomer composition

comprises at least one rubber dispersed in at least one-D thermoplastic resin, wherein the at least one

thermoplastic resin constitutes a matrix phase (or a continuous phase) and the rubber constitute a disperse phase (or a discontinuous phase) . The rubber is dispersed in the form of particles in the thermoplastic resin,5 Examples of the rubber which can constitute the

thermoplastic elastome composition include diene-based rubbers and hydrog-enated products thereof, olefin-based rubbers, halogen-containing rubbers, silicone rubbers, sulfur- containing rubbers, fiuoro rubbers, etc. Examples of diene-based rubbers and hydrogenated products thereof include natural rubber {NR.}, isoprene robbers (IE) ,.

epoxi&lzed natural rubbers, styrene-butadiene rubbers (SBR? , butadiene rubbers (BR) (high-cis BR and iow-cis BR) , acrylonitrile butadiene rubbers (MB ) , hydrogenated NBR, hydrogenated SBR, etc. Examples of clefin-based rubbers include ethylene propylene rubbers (BPM) , ethylene propylene diene rubbers (BPBM) , irtaieie acid- modified ethylene propylene rubbers (M~EP¾) , jnaleic aiihydri.d -modified ethylene- ole in copolymers,

ethylene-glycidyl ethacrylats copolymers, malei _. c anhydride-modifled ethylene- thyl aerylate co ol m rs ^' (modi ied .SEA) , butyl rubbers (IIS) , copolymers: of.

isobutyiene and an aromatic vinyl or diene monomer (fo example, styrene-'isobutyiene- styrene block copolymers, acid ariiiydride-modified, styrene- isobutyiene-styrene. block copolymers), polyisobutyiene succinic acid anhydride, acrylic rubbers (ACM) , ionomars, etc. Examples of halogen-containing rubbers include halogenated butyl rubbers such as brominsted butyl rubbers; .{Br-1IS) , chlorinated butyl rubber (Cl-II ) , etc., brorsinated isobutyiene- -methyl styrene copolymer (Br-IPi4S) , halogenated isobutyien -isoprene copolymer rubbers, chloroprene rubbers (CE) , hyd in rubbers (CHR) ,

chlorosulfonated poiyethyienes (CSM , chlorinated poiyethyienes (CM) , maleic acid-modified chlorinated poiyethyienes _, (M~CM) , etc . Examples of silicone rubbers include methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber, etc.

Examples of sulfur-containing rubbers include polysulfide rubbers, etc. Examples of fiuoro rubbers include

vinylidene fluoride rubbers, fluorine-containing vinyl ether rubbers, tetrafiuoroethyiene-propylene rubbers, fluorine-containing silicone rubbers, fluorine-containing phosphazene rubbers, etc. Among these rubbers , brorainated isobut lene-p-methylstyren copolymers., maleic anhydride-- modified ethylene-tf-olefin copolymers, acid anhydride- jsodified styrene-is tau.tylens-styrene block copolymers are preferred in view of gas barrier properties, durability and. processabilit ,

[0037] Examples of the combination of the

thermoplastic resin and rubber, capable of forming the thermoplastic elastomer composition of the present

invention, include a combination of a polyamide-based resin and a. brominated isobucylene-p-mechyistyrens

copolymer rubber; a combinatio of a polyamide-based resi and a maleic -anhydride-modified ethylene-a-olefin copolymer; a combination: o.£ a poiyamid -based resin and an acid anhydride-modi ied styrene-isobutylene-styrens block copolymer; a combination, of a polyamide-based resin, a brominated isobiityiene-p-rRethylstyrene copolymer rubber, and a aleic anhydrid -modifled ethylene--a-oiefin

copolymer _? a combination of a polyaiTiide-based resin, brominated isobutylene-p- ethylstyrene copolymer rubber, and polyisobutyiene succinic anhydride etc. A

combination of butyl rubber having excellent gas barrier properties and a polyamide-based resin is preferred.

Among these, a combination of a. brominated isobutyiene-p- methylstyrene copolymer rubber, which is a. modified butyl rubber, and one or more polyamide-b sed resins (for example K ion 6, Nylon S 66, Nylon 612, etc.} is

specifically preferred in iew of achieving both fatigue resistance and gas barrier properties.

[0038] The rubber particles included in the

thermoplastic elastomer composition may contain carbon black., silica, or other reinforcing agents (fillers) , cross--linking agent, antioxidant, processing aid, o othe compounding agents that are commonly blended into a rubber composition to the extent that the effects of the present invention are not impaired -

[0039] The thermoplastic elastomer composition can be prepared in advance by meIt-kneading at least one hermoplastic resin, at least on rubber, and optionall additives by, for example, a single-screw or twin- screw kneading extruder, to disperse the rubber particles as a disperse phase in the thermoplastic resin which forms a matrix phase. The weight ratio of the thermoplastic resin, to the rubber is preferably from 10/90 to 90/10, and more preferably from 15/85 to 90/10, but is not limited thereto.. In order to fi the dispersed state of the rubber in the thermoplastic resin, the rubber is

preferably -dynamically cross-linked while melt ---Kneading the thermoplastic resin and rubber. The term "dynamic cross- linking'' refers herein to cross- linking

simultaneous with meIt--kneading . The melt-kneading temperature may be equal to or higher than the melting point of the thermoplastic resin, and. is referabl a _. temperature which is higher than the ^' melting point of the thermoplastic resin b 20°C, for example, is from 200 to 2,50*C. The total time of the kneading operation, is not particularly limited, but is usually from X minute to 10 minutes.

[004-0] The cross- linking agent can be suitably

selected depending on the type of th rubber and is not particularly limited. Examples of the cross -linking agent include zinc oxide, stearic acid, zinc stearace,

magnesium oxide, m-phenylene bi.sm.a.lei lde _: , alkylphenol resin and haiogenates thereof, secondary amines (for example, & ^r - (l, 3-dime hyibutyi} ~_Y ^< -phenyl--p- phenyienediamine {6.ΡΡΌ} , a polymerized 2 , 2 , -trimethyl- 1, 2 -dihydroguinoline) , etc. Among these cross-linking agents, zinc oxide, stearic acid, and - (1, 3~

dimethyIbutyl) are

preferred. The amount of the cross- linking agent is preferably G.l to .12 parts by weight, and more preferably 1 to 3 parts by weight, with respect to 100 parts by weight of the rubber .

[0041] The thermoplastic elastomer composition which is used in the process according to the present invention may foe extruded into, far- example, a strand form, and then palletized with a. resin- pellet! zer after raelt- kneading of t e ^: thermoplastic resin and the rubber.

[004 _. 2J The film produced by the process of the present invention is useful as, for example, a tnemfeer for a pneumatic tire, preferably an inner liner for a. pneumatic tire, due to excellent gas barrier properties thereof. 00431 Any conventional process may be used as the process for producing a pneumatic tire. For example , w n using the film produced by the process of the present invention as an inner liner in the production of a pneumatic tire, _: a pneuma ic tir can. be produced .by laminating the film produced by the process o the:

present invention onto tire melding drum in eylindrioad ^' form; sequentially laminating thereon tire members such as _. a carcass layer, .a belt layer, a tread layer, etc., to form a green t-ire; removing the resulting green tire from the tire molding d um, and subsequently vulcanizing the green tire according to a. conventional method.. The film produced by the process of the present invention has a reduced shrinkage with time as described above, and accordingl has fewer wrinkles and is excellent in

dimensional stability.. Therefore, the filte produced by the process of the present invention can suppress defects due to the wrinkles and dslaraination of the film, thereby reducing the failure rate of the tire .after

vulcanization.

Examples

[00443 The present invention will be further explained with reference to the following examples, and it should be understood that the scope of the present invention is not limited .by these exam les.

[0045] (!) Preparation of Thermoplas ic Elastomer Composi ion

Among the stock materials shown in Table I below, Br- IPMS w s processed into pellets in advance by rubber pellet! cer (manu actured by Moriyama works) . The resulting rubber pellets, thermo l s ic resins (nylons), the acid-modifled elascoiaer, acid-modified elastomer, and additives (i.e., zinc oxide, stearic acid, and SPPD) we e charged into a twin- screw kneading extruder {manuf ctured, by The Japan Steel Works„ Ltd. } at the compounding ratio shown in Table I and were kneaded at 250 °C fox 3 minutes. The resulting kneaded mass was continuously extruded into a strand form from the extruder, cooled with water, and subsequently cut b a cutter to obt in thermoplastic elastomer compositions 1 and 2 in the form of pellets.

[0045] Table 1

Stock materials Thermoplastic Thermoplastic

elastomer elastomer

composition i composition 2

(parts- by (parts, by

weight) weight)

Rubber Br--JPMS :S0:..D 80.0

component

Acid-isodified P-SSk lo..ϋ - elastomer ^' M-SPM - 29.0

Gross-linking Sine oxide 5.0 5.0

agent Stearic acid 1.0 1.0

.Anioxida 6PFD - 3..S

Thermopiastic Kylon 6/66 δο,ΰ

xesin copolymer

Nylon 6 10.0 45.0

Nylon 6/12 10.0

CQ047] Footnote of Table 1:

Br-IPMS: Brominated isobntylene~p~msthyIscyrene copolymer rubber (Exxpro® DXS9-4 from ExxonMobil

Chemical Company}

PIBSA: Poiyisobutyiene succinic anhydride

(DOVBR^IJLSB ΗΓΟδΟ from Dover Chemical Corporation)

M--EPM: Maleic anhydride -modified ethylene - ropylene copolymer rubber (Exxelor® V&18Q3 from ExxonMobil

Chemical Company)

Zinc oxide; Zinc White No, 3 from Seido Chemical Industry Co., Ltd.

Stearic acid- Beads Stearic Acid from JJOF Corporation

6 ^' ΡΡΌ : N- {%, 3 -dimefchyltoutyl) -N ^< -phenyl-p- phenylenediamine (Santo lex 6 PD from Flexsys)

Nylon S/66 copolymer; UBS Nylon ^® 502.3 ^' B from Ube Industries, Ltd.

Nylon 6; UBE Nylon ^®' 1Q13B from Ube Industries, Ltd.

Nylon 6/12 copolymer : UBS Nylon ^® 70-24-B from Ube Industries , Ltd .

[0048] (2) Production of Blown Film

An annular die for inflation molding (manufactured by Macro Engineering & Technology Inc..) was attached to a discharge port of a o75 mm, single-screw extruder

(manufactured by G Engineering ¹ Co., Ltd.) to form, inflation molding equipment. The annular discharge port of. the annular die- was directe upward in. the vertleal direction {i.e. _f the direction opposite to the gravity direction) . A pair of guides and a pair of pinch rolls ¾ere arranged in order upward in. the vertical direction of the annular discharge port. Each of the thermoplastic elastomer compositions .1. and ¾ was extruded from the annular discharge port of the annular die, then the bubble extruded from the annular discharge port was folded by th pair of pinch rolls, and subsequently was wound up by th windup roll through a plurality of guide rolls to produce a blown film. The cylinder temperature of the: extruder was 23G*C i and the temperature of the annular di for inflation molding ^' was 240 °C, The raclten therraoplastic elastomer composition was introduced to the inside o the cylinder of the extruder through a stock material feeder, and the resting molten thermoplastic elastomer was extruded from the annular die at a

discharge rate in the range, of from 40 to 80 kg/h. The drawing speed of the film was set to a value in the range of from 3,6 to 14.7 m/min, calculated on th basis of the discharge rate, the aximum diameter of the film, and. the thickness of the film. A film was obtained by inflation molding under the conditions shown in Table 2. ftn air ring device for bubble cooling was provided above ^' the annular discharge port and in proximity to the outer circumferential side of the annular discharge port.

Cooling of the bubble was carried out by an air-cooling method in which air is blown as a cooling gas to the bubble from the air ring device. The blowing air flow rats was in the range of from 13 to 40 ^/min, and the temperature of the blowing air was 1G°C. The direction of blowing of air from the air ring device was parallel to the direction of conveyance of the bubble (or upward in vertical direction} ,

[0049] (3) Evaluation of Shrinkage Factor

For each resulting film, a sample In the form of belt having a width of 10 cm. was cu out f om the film at right angles to the- windup direction of ^: the film, and the sample was immediately measured for the width (Wl) in the longitudinal direction. Fur her, each sample w s allowed to stand in. a room for 1 week, and then was again measured for the width in the longitudinal

direction. The- .shrinkage factor {%} was determined by entering the measured Wl said W2 into the formula;

Shrinkage factor (%} -lOQx (WI--W2 } /Wl . The obtained shrinkage factors (%) will be shown in Table 2 below, When the shrinkage factor was 2% or more, the shrinkage factor was rated as "high" . When the .shrinkage factor was 1% to less than .2%, the shrinkage factor was rated as "moderate" . When the shrinkage faccor was less than 1%, the shrinkage factor was rated as "low". The ratings will be shown in Table 2 below along with the values of the shrinkage factor {%) . Note that, in

Comparative Example 3, the bubble pulsated, and therefore it was not possible to orm the thermoplastic elastomer composition into film. [0051] Table 2 shows that the blown films of Examples

1 to 12 produced in accordance with the process of the present invention have more superior dimensional

stability with a lower shrinkage factor compared with the blown films of Comparative Examples I to 3.

[0052] {4} Evaluation by Infrared Thermography

When producing the blown, films of Comparative Example 1, Example 2, and Example 11 by inflation molding, the temperature distribution of the outer surf ce of the bubble extruded from the discharge port of the annular his was captured by an ixrfrared thermography (FlIS ESQ anufactured. by FLIR Systems) . FIGS. 3 to .5 schematically Show as tenip.s at.ure ^' distribution images of Comparative Example 1, Example 2, and Example 11 measured by infrared thermography as dot images , As shown in FIG . 3 , in the image of temperature distribution image of Comparative Example !, the intervals etween isotherms are narrow. Accordingly, FIG. 3 shows that the bubble of Comparative Example I was rapidly cooled. In contrast, as shown in FIGS. 4 and 5, in the temperature distribution images of Examples 2 and 11, the intervals between isotherm are large, accordingly, FIGS.. 4 and 5 show that the bubbles of Examples 2 and II were gradually stretched while being gradually cooled,

industrial Applicability

[0053] The blown film obtained by the process

according to the present invention can toe suitably used as an air barrier layer for pneumatic tire, etc.

Reference Signs List

[0054] I. Inflation molding equipment

10 , Extruder

20 , Annular die

21. Annular discharge port

30. Air ring device

40A, 40B. Stabilising plates

S0A, SOB. Pinch rolls

60.. Windu rol 1