WO2017138932A1 - Process for producing blown film - Google Patents

Process for producing blown film Download PDF

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Publication number
WO2017138932A1
WO2017138932A1 PCT/US2016/017298 US2016017298W WO2017138932A1 WO 2017138932 A1 WO2017138932 A1 WO 2017138932A1 US 2016017298 W US2016017298 W US 2016017298W WO 2017138932 A1 WO2017138932 A1 WO 2017138932A1
Authority
WO
WIPO (PCT)
Prior art keywords
film
thermoplastic elastomer
elastomer composition
discharge port
annular
Prior art date
Application number
PCT/US2016/017298
Other languages
French (fr)
Inventor
Shusaku Tomoi
Shun Sato
Hari P. NADELLA
Original Assignee
The Yokohama Rubber Co., Ltd.
Exxonmobil Chemical Patents Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The Yokohama Rubber Co., Ltd., Exxonmobil Chemical Patents Inc. filed Critical The Yokohama Rubber Co., Ltd.
Priority to PCT/US2016/017298 priority Critical patent/WO2017138932A1/en
Publication of WO2017138932A1 publication Critical patent/WO2017138932A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D30/00—Producing pneumatic or solid tyres or parts thereof
    • B29D30/06—Pneumatic tyres or parts thereof (e.g. produced by casting, moulding, compression moulding, injection moulding, centrifugal casting)
    • B29D30/0681—Parts of pneumatic tyres; accessories, auxiliary operations
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    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/001—Combinations of extrusion moulding with other shaping operations
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    • B29C48/022—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the choice of material
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Definitions

  • the present invention relates to a process for producing a blown film. More specifically, the present invention relates to a process for producing a blown film having a reduced shrinkage with time from a
  • thermoplastic elastomer composition thermoplastic elastomer composition
  • thermoplastic elastomer composition comprising a
  • thermoplastic resin and rubber particles dispersed in the thermoplastic resin to inflation molding (referred to also as “blown film extrusion molding") is known in the art (see PTLs 1 to 3) .
  • inflation molding process such a thermoplastic elastomer
  • composition is extruded from an annular discharge port of an annular die as a tubular soft film (hereinafter, referred to also as a "bubble") and stretched in the circumferential direction and vertical direction
  • thermoplastic elastomer composition due to the rubber 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, 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 for producing a film, the conventional practice has 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
  • 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.
  • thermoplastic elastomer composition when a molten thermoplastic elastomer composition is subjected to inflation molding by extruding it as a bubble from an annular discharge port of an annular die of an inflation molding equipment, it is possible to restrain the resulting film after inflation molding from shrinking with time when the lip gap of the annular discharge port of the annular die, the blow-up ratio (BUR) , the flow rate of the cooling gas for cooling the bubble, and the thickness of the resulting blown film satisfy a specific relationship with respect to the discharge rate of the thermoplastic elastomer
  • the present invention includes following
  • Embodiment 1 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 inflation molding equipment comprises:
  • annular die for extruding the thermoplastic elastomer composition into a tubular film
  • the annular die is attached to a discharge port of the extruder, and an air ring device for blowing a cooling gas to the tubular film extruded from the annular die in order to cool the tubular film
  • the annular die has an annular discharge port having an inner diameter (Dl) (mm) and a lip gap (G) (mm) ; and wherein the process comprises:
  • t thickness of the blown film produced by the process is represented by "t" (mm) , G, Q, f, t, and the blow-up ratio (BUR) (i.e., D2/D1) satisfy a relationship of following formula (1) :
  • Embodiment 1 or 2 wherein Dl (mm) and G (mm) satisfy a relationship of following formula (3) :
  • Embodiment 4 The process according to any one of Embodiments 1 to 3 above, wherein the thickness t is 50 to 300 ⁇ , and the BUR is 1.2 to 5.0.
  • thermoplastic resin includes one or more nylons and the rubber particles dispersed in the thermoplastic resin comprise a brominated isobutylene-p-methylstyrene copolymer, maleic anhydride-modified ethylene-a-olefin copolymer, acid anhydride-modified styrene-isobutylene- styrene block copolymer, or a combination of two or more thereof .
  • thermoplastic elastomer composition does not comprise a higher alcohol-based plasticizer, aromatic sulfonamide-based plasticizer, or phenolic plasticizer.
  • Embodiment 9 A pneumatic tire comprising the gas permiation preventive film for the pneumatic tire according to Embodiment 8 above.
  • the tubular film obtained after inflation molding has a reduced shrinkage with time, and accordingly has reduced wrinkles or
  • the film produced by the process for producing a blown film of the present invention exhibits excellent gas barrier properties in addition to reduced wrinkles or deformation due to shrinkage with time.
  • FIG. 1 is a schematic view showing one example of the process for producing a blown film according to the present invention.
  • FIG. 2 is a graph plotting the
  • FIG. 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 elastomer composition is introduced into cylinder 12 set to a temperature capable of melt- extruding the thermoplastic elastomer composition from stock material feeder 11 of extruder 10, and the
  • thermoplastic elastomer composition is allowed to melt in cylinder 12 while extruding it by a rotating screw (not shown) to the discharge port side, and then the resulting molten thermoplastic elastomer composition is extruded from discharge port 13 to annular die 20.
  • Annular die 20 has annular discharge port 21 defined as a gap between an inner lip 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 annular discharge port has an inner diameter of Dl .
  • 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
  • Extruded bubble B is stretched in the circumferential direction by the air enclosed inside bubble B and is also stretched in the vertical direction (machine
  • Bubble B can be cooled by blowing a cooling gas to the outside of extruded bubble B with air ring device 30 provided above annular
  • Air ring device 30 has at least one cooling gas outlet port 31 which 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 more cooling gas outlet ports. 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 annularly formed and are arranged
  • 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 air ring device is shown by the cross-sectional view in the vertical direction along the center axis of the annular die .
  • 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 maximum diameter D2.
  • the term "the diameter of the bubble” refers herein to the outer diameter of the bubble
  • the term "the maximum diameter of the bubble” refers herein to the maximum value of the outer diameter of the bubble.
  • the blow-up ratio (BUR) is defined as "D2/D1".
  • a pair of stabilizing plates 40A, 40B facing each other are provided above air ring device 30. Bubble B expanded to have the maximum diameter is further cooled and is deformed into flat while being conveyed by the pair of stabilizing plates 40A, 40B facing each other.
  • 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.
  • a pair of pinch rolls 50A, 50B are arranged for folding bubble B deformed into flat by stabilizing plates 40A, 40B, into a sheet.
  • Tubular film F which is obtained by folding the bubble by the pair of pinch rolls 50A, 50B is wound up by windup roll 60 through guide rolls 51, 52A, 52B, 53. Before the tubular film is wound up by the windup roll or after it is wound up, one end of the tubular film may be cut open to obtain a wide film, as necessary.
  • 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 50A, 50B, but it is also
  • G, Q, f, t, and BUR satisfy a relationship of formula (2) :
  • Inner diameter Dl of the annular discharge port of the annular die is selected on the basis of the shape and size of the target final product.
  • Inner diameter Dl of the annular discharge port is preferably from 50 to 500 mm, and more preferably from 100 to 250 mm.
  • the lip gap G of annular die 20 is selected depending on the upper pressure limit and extrusion rate of the inflation molding equipment.
  • the lip gap G is preferably from 0.50 to 4.00 mm, and more preferably from 0.50 to 2.00 mm. If the lip gap G is less than 0.50 mm, then the pressure required for extruding the
  • thermoplastic elastomer composition through the annular discharge port of annular die 20 is too high. If the lip gap G is more than 4.00 mm, when a film having a
  • thermoplastic elastomer composition and the drawing speed by the pinch rolls is large, thereby making it difficult to stabilize the bubble.
  • discharge port of the annular die is selected on the basis of the temperature of the thermoplastic elastomer composition excluded from the annular discharge port of the annular die and the total residence time in the extruder and annular die.
  • the discharge rate Q of the thermoplastic elastomer composition is preferably 20 to 100 kg/h, and more preferably 30 to 90 kg/h. If the discharge rate Q of the thermoplastic elastomer
  • composition is less than 20 kg/h, then the total
  • thermoplastic elastomer residence time of the thermoplastic elastomer in the extruder and annular die may be prolonged, thereby promoting the thermal degrdation of the thermoplastic elastomer composition. If the discharge rate Q of the thermoplastic elastomer composition is more than 100 kg/h, then the temperature of the thermoplastic
  • thermoplastic elastomer composition is increased excessively, thereby promoting the thermal degradation of the thermoplastic elastomer composition.
  • the blow-up ratio is selected on the basis of the shape of the target final product.
  • the "BUR is preferably from 1.1 to 6.0, and more preferably from 1.2 to 5.0.
  • the bubble has a maximum diameter D2 of from 55 to 3000 mm, and preferably a maximum diameter D2 of from 60 to 2500 mm.
  • the flow rate "f" of the cooling gas which is blown from the air ring device to the bubble is selected on the basis of the stability and target shape of the bubble.
  • the flow rate "f" of the cooling gas is
  • the temperature of the cooling gas which is blown from the air ring device to the bubble is preferably from 0 to 30°C, and more preferably from 5 to 15°C. If the temperature of the cooling gas is less than 0°C, the cooling of the film is rapid. If the temperature of the cooling gas is above 30°C, the cooling efficiency is decreased.
  • a blown film of the present invention it is possible to produce a blown film having a thickness "t" of 40 to 400 ⁇ from a thermoplastic elastomer composition.
  • the thickness "t" of the blown film produced by the process of the present invention is preferably 50 to 300 ⁇ .
  • shrinkage with time of the film after inflation molding can be restrained due to the restriction of the rapid and excessive stretching of the film by satisfying the relationship of the above formula (1) to optimize the cooling strength per unit discharge rate and the blow-up ratio per unit lip gap and unit film thickness. If the relationship of the above formula (1) is not satisfied, rapid and excessive stretching action is applied to the film, and as a result, it is difficult to produce a blown film and even if a film is produced by the inflation molding, the resulting film has a high shrinkage factor and accordingly has poor dimensional stability.
  • the inner diameter Dl (mm) and lip gap G (mm) of the annular discharge port of the annular die preferably satisfy formula (3) :
  • Dl (mm) xG (mm) is an index of the magnitude of the opening area of the annular discharge port of the annular die. The smaller the value of Dl
  • thermoplastic elastomer composition and the drawing speed of the pinch roll is large, and as a result, it is difficult to stabilize the bubble.
  • the thermoplastic elastomer composition may include at least one thermoplastic resin.
  • polyamide-based resins examples include
  • Nylon 6 N6) , Nylon 66 (N66) , Nylon 46 (N46), Nylon 11 (Nil), Nylon 12 (N12), Nylon 69 (N69) , Nylon 610 (N610), Nylon 612 (N612), Nylon 6/66 (N6/66), Nylon 6/66/610 (N6/66/610) ; semi-aromatic and all-aromatic nylons such as Nylon MXD6 (MXD6) , Nylon 6T, Nylon 6/6T, and Nylon 9T; Nylon 66/PP copolymer, Nylon 66/PPS copolymer, etc.
  • polyester-based resins include aromatic polyesters such as polybutylene terephthalate (PBT) , polyethylene terephthalate (PET) , polyethylene
  • PET/PEI copolymer PET/PEI copolymer
  • PAR polyarylate
  • PBN polybutylene naphthalate
  • polyesters polyoxyalkylenediimidic acid/polybutylate terephthalate copolymers, etc.
  • polynitrile- based resins include polyacrylonitrile (PAN) ,
  • polymethacrylate-based resins examples include
  • polyvinyl-based resins examples include vinyl acetate (PVAc) , poly(vinyl alcohol) (PVA) , ethylene-vinyl alcohol copolymer (EVOH) , poly (vinylidene chloride) (PVDC) , poly (vinyl chloride) (PVC) , vinyl chloride/vinylidene chloride copolymer, vinylidene chloride/methyl acrylate copolymer, etc.
  • PVDC poly (vinylidene chloride)
  • PVVC poly (vinyl chloride)
  • vinyl chloride/vinylidene chloride copolymer vinylidene chloride/methyl acrylate copolymer
  • cellulosic resins examples include cellulose acetate, cellulose acetate butylate, etc.
  • fluororesins include poly (vinylidene fluoride) (PVDF) , poly (vinyl fluoride) (PVF) , polychlorofluoroethylene (PCT
  • imide-based resins include aromatic, terephthalate, terephthalate, terephthalate, terephthalate, terephthalate, terephthalate, terephthalate, phthalate, phthalate, phthalate, phthalate, phthalate, phthalate, phthalate, phthalate, phthalate, phthalate, phthalate, phthalate, phthalate, phthalate, phthalate, terephthalate (PS) terpolyrenethacrylate, etc.
  • imide-based resins include aromatic
  • polyimides PI
  • polystyrenic resins include polystyrene (PS), etc.
  • polyolefinic resins include polyethylene (PE) , polypropylene (PP) , etc.
  • PE polyethylene
  • PP polypropylene
  • Nylon 6 Nylon 6
  • semi-aromatic and all-aromatic nylons such as Nylon MXD6, Nylon 6T, Nylon 9T, and Nylon 6/6T are preferred, in view of gas barrier properties and processability .
  • processing aids may optionally be added at a common amount to the
  • thermoplastic resin which constitutes the thermoplastic elastomer composition used in the process for producing an inflation film according to the present invention.
  • thermoplastic elastomer composition it is preferred to not add a plasticizer to the thermoplastic resin or thermoplastic elastomer composition.
  • An inflation film having a reduced shrinkage with time after inflation molding can be produced even if a plasticizer such as, for example, higher alcohol-based plasticizers, aromatic sulfoneamide-based plasticizers, phenolic plasticizers, etc., conventionally used in the inflation molding of a thermoplastic elastomer composition, is not incorporated into the thermoplastic elastomer composition, and
  • thermoplastic elastomer composition therefore it is possible to prevent the decrease in the gas barrier properties and heat resistance which may be caused when a plasticizer is added to the thermoplastic elastomer composition.
  • thermoplastic elastomer composition [0043] The thermoplastic elastomer composition
  • thermoplastic resin comprises at least one rubber dispersed in at least one thermoplastic resin, wherein the at least one thermoplastic resin constitutes a matrix phase (or a continuous phase) and the rubber constitutes a disperse phase (or a discontinuous phase) .
  • the rubber is
  • thermoplastic elastomer composition examples include diene-based rubbers and hydrogenated products thereof, olefin-based rubbers, halogen-containing rubbers, silicone rubbers, sulfur-containing rubbers, fluoro rubbers, etc.
  • diene-based rubbers and hydrogenated products thereof include natural rubbers (NR.), isoprene rubbers (IR), epoxidized natural rubbers, styrene-butadiene rubbers (SBR) , butadiene rubbers (BR) (high-cis BR and low-cis BR) , acrylonitrile butadiene rubbers (NBR) , hydrogenated NBR, hydrogenated SBR, etc.
  • natural rubbers NR.
  • IR isoprene rubbers
  • SBR styrene-butadiene rubbers
  • BR butadiene rubbers
  • NBR acrylonitrile butadiene rubbers
  • hydrogenated NBR hydrogenated SBR, etc.
  • olefin-based rubbers examples include ethylene propylene rubbers (EPM) , ethylene propylene diene rubbers (EPDM) , maleic acid- modified ethylene propylene rubbers (M-EPM) , maleic anhydride-modified ethylene-a-olefin copolymers, ethylene-glycidyl methacrylate copolymers, maleic anhydride-modified ethylene-ethyl acrylate copolymers (modified EEA) , butyl rubbers (IIR), copolymers of isobutylene and an aromatic vinyl or diene monomer (for example, styrene-isobutylene-styrene block copolymers, acid anhydride-modified styrene-isobutylene-styrene block copolymers), polyisobutylene succinic acid
  • EPM ethylene propylene rubbers
  • EPDM ethylene propylene diene rubbers
  • halogen-containing rubbers examples include
  • halogenated butyl rubbers such as brominated butyl rubbers (Br-IIR) , chlorinated butyl rubber (Cl-IIR) , etc., brominated isobutylene-p-methyl styrene copolymer (Br-IPMS), halogenated isobutylene-isoprene copolymer rubbers, chloroprene rubbers (CR) , hydrin rubbers (CHR) , chlorosulfonated polyethylenes (CSM) , chlorinated polyethylenes (CM) , maleic acid-modified chlorinated polyethylenes (M-CM) , etc.
  • silicone rubbers include methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber, etc.
  • sulfur-containing rubbers examples include
  • fluoro rubbers examples include vinylidene fluoride rubbers, fluorine-containing vinyl ether rubbers, tetrafluoroethylene-propylene rubbers, fluorine-containing silicone rubbers, fluorine- containing phosphazene rubbers, etc.
  • fluoro rubbers include vinylidene fluoride rubbers, fluorine-containing vinyl ether rubbers, tetrafluoroethylene-propylene rubbers, fluorine-containing silicone rubbers, fluorine- containing phosphazene rubbers, etc.
  • brominated isobutylene-p-methylstyrene copolymers, maleic anhydride-modified ethylene-a-olefin copolymers, acid anhydride-modified styrene-isobutylene-styrene block copolymers are preferred in view of gas barrier properties, durability and processability .
  • 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 isobutylene-p-methylstyrene copolymer rubber; a combination of a polyamide-based resin and a maleic anhydride-modified ethylene-a-olefin copolymer; a combination of a polyamide-based resin and an acid anhydride-modified styrene-isobutylene-styrene block copolymer; a combination of a polyamide-based resin, a brominated isobutylene-p-methylstyrene
  • polyamide-based resin brominated isobutylene-p- methylstyrene copolymer rubber, and polyisobutylene succinic anhydride; etc.
  • a combination of butyl rubber having excellent gas barrier properties and a polyamide- based resin is preferred.
  • a combination of a brominated isobutylene-p-methylstyrene copolymer rubber, which is a modified butyl rubber, and one or more polyamide-based resins (for example Nylon 6, Nylon 6/66, Nylon 612, etc.) is specifically preferred in view of achieving both fatigue resistance and gas barrier properties .
  • thermoplastic elastomer composition may contain carbon black, silica, or other reinforcing agents (fillers), cross-linking agent, antioxidant, processing aid, or other compounding agents that are commonly blended into a rubber composition to the extent that the effects of the present invention are not impaired.
  • thermoplastic elastomer composition Before the thermoplastic elastomer composition is introduced into extruder 10, the thermoplastic elastomer composition is introduced into extruder 10, the thermoplastic
  • elastomer composition can be prepared in advance by melt-kneading at least one thermoplastic resin, at least one rubber, and optionally additives by, for example, a single-screw or twin-screw kneading extruder, to
  • 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.
  • thermoplastic resin the rubber is preferably
  • thermoplastic resin and rubber thermoplastic resin and rubber.
  • dynamic cross- linking refers herein to cross-linking simultaneous with melt-kneading.
  • the melt-kneading temperature may be equal to or higher than the melting point of the
  • thermoplastic resin and is preferably a temperature which is higher than the melting point of the
  • thermoplastic resin by 20°C, for example, is from 200 to 250°C.
  • the total time of the kneading operation is not particularly limited, but is usually from 1 minute to 10 minutes.
  • the thermoplastic elastomer composition which is obtained after melt-kneading the thermoplastic resin and the rubber can be extruded into, for example, a strand form, and then pelletized with a resin pelletizer.
  • the cross-linking agent can be suitably selected depending on the type of the rubber and is not particularly limited.
  • the cross-linking agent include zinc oxide, stearic acid, zinc stearate, magnesium oxide, m-phenylene bismaleimide, alkylphenol resin and halogenates thereof, secondary amines (for example, N- ( 1 , 3-dimethylbutyl ) -N' -phenyl-p- phenylenediamine (6PPD), a polymerized 2 , 2 , 4-trimethyl- 1 , 2-dihydroquinoline ) , etc.
  • these cross-linking agents zinc oxide, stearic acid, and N-(l,3- dimethylbutyl ) -N' -phenyl-p-phenylenediamine are examples of these cross-linking agents.
  • the amount of the cross-linking agent is preferably 0.1 to 12 parts by weight, and more
  • thermoplastic elastomer composition used in accordance with the process of the present invention can be formed in-situ by introducing the thermoplastic resin, rubber, and optionally additives from stock material feeder 11 of extruder 10 which is a single-screw or twin-screw kneading extruder, to the inside of cylinder 12, and melt-kneading them by means of rotating single or double screws.
  • stock material feeder 11 of extruder 10 which is a single-screw or twin-screw kneading extruder
  • thermoplastic elastomer composition can be extruded as a tubular film without being pelletized, from the annular die attached to the discharge port of the extruder.
  • the film produced by the process of the present invention is useful as, for example, a member for a pneumatic tire due to excellent gas barrier properties thereof.
  • the film produced by the process of the present invention is particularly useful as a gas barrier film, for example, an inner liner, for producing a pneumatic tire .
  • any conventional process may be used as the process for producing a pneumatic tire.
  • a pneumatic tire when using the film produced by the process of the present invention as an inner liner in the production of a pneumatic tire, a pneumatic tire can be produced by laminating the film produced by the process of the present invention onto a tire molding drum in
  • the film produced by the process of the present invention has a reduced shrinkage with time as described above, and accordingly has fewer wrinkles and is excellent in dimensional stability. Therefore, the film produced by the process of the present
  • Br-IPMS was processed into pellets in advance by a rubber pelletizer (manufactured by Moriyama Works) .
  • the resulting rubber pellets, nylons as thermoplastic resins, the acid-modified elastomer, acid-modified elastomer, and additives i.e., zinc oxide, stearic acid, and 6PPD
  • additives i.e., zinc oxide, stearic acid, and 6PPD
  • thermoplastic elastomer compositions 1 and 2 in the form of pellets.
  • Br-IPMS Brominated isobutylene-p-methylstyrene copolymer rubber (Exxpro® MDX89-4 from ExxonMobil
  • PIBSA Polyisobutylene succinic anhydride
  • M-EPM Maleic anhydride-modified ethylene-propylene copolymer rubber (Exxelor® VA1803 from ExxonMobil
  • Zinc oxide Zinc White No. 3 from Seido Chemical Industry Co., Ltd.
  • Nylon 6/66 copolymer UBE Nylon® 5023B from Ube Industries, Ltd.
  • Nylon 6 UBE Nylon® 1013B from Ube Industries, Ltd.
  • Nylon 6/12 copolymer UBE Nylon® 7024B from Ube Industries, Ltd. [ 0055 ] (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 cp75 mm single-screw extruder
  • the annular discharge port of the annular die was directed upward in the vertical direction (i.e., the direction opposite to the gravity direction) .
  • a pair of guides and a pair of pinch rolls were arranged in order upward in the vertical direction of the annular discharge port.
  • Each of the thermoplastic elastomer compositions 1 and 2 was extruded from the annular discharge port of the annular die, then the bubble extruded from the annular discharge port was folded by the pair of pinch rolls, and subsequently was wound up by the windup roll through a plurality of guide rolls to produce a blown film.
  • the cylinder temperature of the extruder was 230°C, and the temperature of the annular die for inflation molding was 240°C.
  • the molten thermoplastic elastomer composition was extruded from the annular die at a discharge rate in the range from 48 to 88 kg/h.
  • the drawing speed of the film was set to a value in the range of from 5.9 to 15.7 m/min.
  • a film was obtained by inflation molding under the conditions shown in Table 2.
  • An air ring device for bubble cooling was provided above the annular discharge port and in
  • 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 rate was in the range of from 13.3 to 40 m 2 /min, and the temperature of the blowing air was 10°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) .
  • the measurement of the width W of the film was carried out within 5 to 10 minutes from the formation of the film.
  • the width W of the film is the arithmetic mean (arithmetic average) of the widths measured at three locations 25 cm intervals in the windup direction of the film for a sample having a length of more than 75 cm in the windup direction of the film.
  • the thickness (t) of each film obtained by inflation molding was determined by unwinding each film
  • the measurement of the thickness "t" of the film was carried out within 5 to 10 minutes from formation of the film.
  • the thickness "t” of the film is the arithmetic mean of the thicknesses measured at 64 locations on the
  • each film obtained by inflation molding the film immediately after being inflation molded and wound up in a roll form was unwound, a sample in the form of belt having a width of 10 cm was cut out from the film at right angles to the windup direction of the film, and the sample was measured for the width (Wl) in the longitudinal direction within 5 to 10 minutes from formation of the film. Further, each film thus cut was allowed to stand in a room at an air temperature of about 25°C for 1 week, and then was again measured for the width (W2) in the longitudinal direction.
  • shrinkage factor (%) was determined by entering the measured Wl and W2 into the formula:
  • Shrinkage factor ( % ) 100* (W1-W2 ) /Wl .
  • the bubble stability was determined by visually evaluating the bubble according to the following
  • the blown film obtained by the process of the present invention can be suitably used as an air barrier layer for a pneumatic tire etc.

Abstract

A process for producing a blown film from a thermoplastic elastomer composition comprising a thermoplastic resin and rubber particles dispersed therein by inflation molding equipment is disclosed. In the process, a lip gap (G) (mm) of an annular discharge port of an annular die from which the thermoplastic elastomer composition is melt-extruded as a tubular film, & discharge rate (Q) (kg/h) of the thermoplastic elastomer composition from the annular discharge port, a cooling gas flow rate (f) (m3/min), a thickness (t) (mm) of the blown film, and a blow-up: ratio (BUR) satisfy a relationship- of following formula (1) :

Description

DESCRIPTION
Title of Invention: Process for Producing Blown Film Technical Field
[0001] The present invention relates to a process for producing a blown film. More specifically, the present invention relates to a process for producing a blown film having a reduced shrinkage with time from a
thermoplastic elastomer composition.
Background Art
[0002] A process for producing a film by subjecting a thermoplastic elastomer composition comprising a
thermoplastic resin and rubber particles dispersed in the thermoplastic resin to inflation molding (referred to also as "blown film extrusion molding") is known in the art (see PTLs 1 to 3) . According to the inflation molding process, such a thermoplastic elastomer
composition is extruded from an annular discharge port of an annular die as a tubular soft film (hereinafter, referred to also as a "bubble") and stretched in the circumferential direction and vertical direction
(machine direction or conveyance direction) of the bubble. However, due to the rubber 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, 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 for producing a film, the conventional practice has 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.
Citation List
Patent Literature
[0003]
PTL 1: Japanese Unexamined Patent Publication No. 2014- 117827 A
PTL 2: Japanese Unexamined Patent Publication No. 2005- 125499 A
PTL 3: Japanese Unexamined Patent Publication No. H3- 49930 A
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 out experiments in order to achieve the above object, and as a result found that, when a molten thermoplastic elastomer composition is subjected to inflation molding by extruding it as a bubble from an annular discharge port of an annular die of an inflation molding equipment, it is possible to restrain the resulting film after inflation molding from shrinking with time when the lip gap of the annular discharge port of the annular die, the blow-up ratio (BUR) , the flow rate of the cooling gas for cooling the bubble, and the thickness of the resulting blown film satisfy a specific relationship with respect to the discharge rate of the thermoplastic elastomer
composition from the annular discharge port, resulting in a blown film having high dimensional stability, and consequently completed the present invention. Solution to Problem
[ 0006 ] The present invention includes following
[Embodiment 1] to [Embodiment 9] .
[Embodiment 1] 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 inflation molding equipment comprises:
an extruder,
an annular die for extruding the thermoplastic elastomer composition into a tubular film, the annular die is attached to a discharge port of the extruder, and an air ring device for blowing a cooling gas to the tubular film extruded from the annular die in order to cool the tubular film,
the annular die has an annular discharge port having an inner diameter (Dl) (mm) and a lip gap (G) (mm) ; and wherein the process comprises:
melt-extruding the thermoplastic elastomer
composition from the annular discharge port of the annular die as a tubular film at a discharge rate (Q) ( kg/h) ; and
expanding the tubular film to have a maximum
diamater (D2) (mm) while blowing the cooling gas from the air ring device at a flow rate (f) (m3/min) to the tubular film melt-extruded from the annular discharge port ;
and when D2/D1 is represented by BUR, and a
thickness of the blown film produced by the process is represented by "t" (mm) , G, Q, f, t, and the blow-up ratio (BUR) (i.e., D2/D1) satisfy a relationship of following formula (1) :
[ 0007 ]
Figure imgf000005_0001
[ 0008 ] [Embodiment 2] The process according to Embodiment 1, wherein G, Q, f, t, and BUR satisfy a relationship of following formula (2) :
[0009]
Figure imgf000006_0001
[0010] [Embodiment 3] The process according to
Embodiment 1 or 2, wherein Dl (mm) and G (mm) satisfy a relationship of following formula (3) :
[0011]
Figure imgf000006_0002
[0012] [Embodiment 4] The process according to any one of Embodiments 1 to 3 above, wherein the thickness t is 50 to 300 μπι, and the BUR is 1.2 to 5.0.
[0013] [Embodiment 5] The process according to any one of Embodiments 1 to 4 above, wherein the blown film is a member for a tire.
[0014] [Embodiment 6] The process according to any one of Embodiments 1 to 5 above, wherein the
thermoplastic resin includes one or more nylons and the rubber particles dispersed in the thermoplastic resin comprise a brominated isobutylene-p-methylstyrene copolymer, maleic anhydride-modified ethylene-a-olefin copolymer, acid anhydride-modified styrene-isobutylene- styrene block copolymer, or a combination of two or more thereof .
[0015] [Embodiment 7] The process of production of a blown film according to any one of Embodiments 1 to 6 above, wherein the thermoplastic elastomer composition does not comprise a higher alcohol-based plasticizer, aromatic sulfonamide-based plasticizer, or phenolic plasticizer.
[0016] [Embodiment 8] A gas permiation preventive film for a pneumatic tire, comprising a blown film produced by the process according to any one of
Embodiments 1 to 7 above. [0017] [Embodiment 9] A pneumatic tire comprising the gas permiation preventive film for the pneumatic tire according to Embodiment 8 above.
Advantageous Effects of Invention
[0018] According to the process for producing a blown film of the present invention, the tubular film obtained after inflation molding 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 barrier properties in addition to reduced wrinkles or deformation due to shrinkage with time.
Brief Description of Drawings
[0019] [FIG. 1] FIG. 1 is a schematic view showing one example of the process for producing a blown film according to the present invention.
[0020] [FIG. 2] FIG. 2 is a graph plotting the
shrinkage factor of a blown film produced by the process according to the present invention with respect to the value
Figure imgf000007_0001
Description of Embodiments
[0021] Embodiments of the present invention will be explained below in detail along referring to the
attached drawings. FIG. 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 elastomer composition is introduced into cylinder 12 set to a temperature capable of melt- extruding the thermoplastic elastomer composition from stock material feeder 11 of extruder 10, and the
thermoplastic elastomer composition is allowed to melt in cylinder 12 while extruding it by a rotating screw (not shown) to the discharge port side, and then the resulting molten thermoplastic elastomer composition is extruded from discharge port 13 to annular die 20.
[ 0022 ] Annular die 20 has annular discharge port 21 defined as a gap between an inner lip 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 annular discharge port has an inner diameter of Dl . 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 B. Extruded bubble B is stretched in the circumferential 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 the 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 which 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 more cooling gas outlet ports. 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 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 center 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. In FIG. 1, the air ring device is shown by the cross-sectional view in the vertical direction along the center axis of the annular die .
[ 0023 ] 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 maximum diameter D2. The term "the diameter of the bubble" refers herein to the outer diameter of the bubble, and the term "the maximum diameter of the bubble" refers herein to the maximum value of the outer diameter of the bubble. In the present invention, the blow-up ratio (BUR) is defined as "D2/D1". In FIG. 1, a pair of stabilizing plates 40A, 40B facing each other are provided above air ring device 30. Bubble B expanded to have the maximum diameter is further cooled and is deformed into flat while being conveyed by the pair of stabilizing plates 40A, 40B facing each other. In place of the pair of stabilizing plates 40A, 40B, for example, 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 stabilizing plates 40A, 40B, a pair of pinch rolls 50A, 50B are arranged for folding bubble B deformed into flat by stabilizing plates 40A, 40B, into a sheet. Tubular film F which is obtained by folding the bubble by the pair of pinch rolls 50A, 50B is wound up by windup roll 60 through guide rolls 51, 52A, 52B, 53. Before the tubular film is wound up by the windup roll or after it is wound up, one end of the tubular film may be cut open to obtain a wide film, as necessary.
[ 0024 ] In the embodiment shown in FIG. 1, 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 50A, 50B, but it is also
possible to extrude the bubble downward from annular discharge port 21 and convey the bubble downward while folding it in a sheet form by a pair of pinch rolls.
[ 0025 ] In the process for producing a blown film of the present invention, G, Q, f, t, and BUR satisfy a relationship of formula (1) :
[ 0026 ]
Figure imgf000010_0001
[ 0027 ] Preferably, G, Q, f, t, and BUR satisfy a relationship of formula (2) :
[ 0028 ]
Figure imgf000010_0002
[ 0029 ] When the value of fxBUR/QxGxt is more than 15.0, even if inflation molding is used to produce the film, the resulting film has an unacceptably high shrinkage factor, and accordingly has a poor dimensional stability. If the value of fxBUR/QxGx t is less than 7.0, the bubble is unstable.
[ 0030 ] Inner diameter Dl of the annular discharge port of the annular die is selected on the basis of the shape and size of the target final product. Inner diameter Dl of the annular discharge port is preferably from 50 to 500 mm, and more preferably from 100 to 250 mm.
[ 0031 ] The lip gap G of annular die 20 is selected depending on the upper pressure limit and extrusion rate of the inflation molding equipment. The lip gap G is preferably from 0.50 to 4.00 mm, and more preferably from 0.50 to 2.00 mm. If the lip gap G is less than 0.50 mm, then the pressure required for extruding the
thermoplastic elastomer composition through the annular discharge port of annular die 20 is too high. If the lip gap G is more than 4.00 mm, when a film having a
thicknes as described below is to be obtained, the difference between the discharge rate of the
thermoplastic elastomer composition and the drawing speed by the pinch rolls is large, thereby making it difficult to stabilize the bubble.
[0032] The discharge rate Q of the thermoplastic elastomer composition extruded from the annular
discharge port of the annular die is selected on the basis of the temperature of the thermoplastic elastomer composition excluded from the annular discharge port of the annular die and the total residence time in the extruder and annular die. The discharge rate Q of the thermoplastic elastomer composition is preferably 20 to 100 kg/h, and more preferably 30 to 90 kg/h. If the discharge rate Q of the thermoplastic elastomer
composition is less than 20 kg/h, then the total
residence time of the thermoplastic elastomer in the extruder and annular die may be prolonged, thereby promoting the thermal degrdation of the thermoplastic elastomer composition. If the discharge rate Q of the thermoplastic elastomer composition is more than 100 kg/h, then the temperature of the thermoplastic
elastomer composition is increased excessively, thereby promoting the thermal degradation of the thermoplastic elastomer composition.
[0033] The blow-up ratio (BUR) is selected on the basis of the shape of the target final product. The "BUR is preferably from 1.1 to 6.0, and more preferably from 1.2 to 5.0. Accordingly, in the process of the present invention, the bubble has a maximum diameter D2 of from 55 to 3000 mm, and preferably a maximum diameter D2 of from 60 to 2500 mm. The maximum diameter D2 of the bubble is determined by unwinding a film immediately after being inflation molded and wound up in a roll form, measuring the width W of the unwound film, and using the relation n<D2=2W between W and D2 when the circular constant is represented as n.
[0034] The flow rate "f" of the cooling gas which is blown from the air ring device to the bubble is selected on the basis of the stability and target shape of the bubble. The flow rate "f" of the cooling gas is
preferably from 5 to 100 m3/min, and more preferably from 10 to 50 m3/min. If the flow rate "f" of the
cooling gas is less than 5 m3/min, it is difficult to stabilize the bubble. If the flow rate "f" of the
cooling gas is more than 100 m3/min, it is difficult to obtain a bubble having a desired shape. The temperature of the cooling gas which is blown from the air ring device to the bubble is preferably from 0 to 30°C, and more preferably from 5 to 15°C. If the temperature of the cooling gas is less than 0°C, the cooling of the film is rapid. If the temperature of the cooling gas is above 30°C, the cooling efficiency is decreased.
[0035] According to the process for producing a blown film of the present invention, it is possible to produce a blown film having a thickness "t" of 40 to 400 μπι from a thermoplastic elastomer composition. The thickness "t" of the blown film produced by the process of the present invention is preferably 50 to 300 μπι.
[0036] While not being bound by any specific theory, it is believed that shrinkage with time of the film after inflation molding can be restrained due to the restriction of the rapid and excessive stretching of the film by satisfying the relationship of the above formula (1) to optimize the cooling strength per unit discharge rate and the blow-up ratio per unit lip gap and unit film thickness. If the relationship of the above formula (1) is not satisfied, rapid and excessive stretching action is applied to the film, and as a result, it is difficult to produce a blown film and even if a film is produced by the inflation molding, the resulting film has a high shrinkage factor and accordingly has poor dimensional stability.
[0037] In the process for producing a blown film according to the present invention, the inner diameter Dl (mm) and lip gap G (mm) of the annular discharge port of the annular die preferably satisfy formula (3) :
[0038]
Figure imgf000013_0001
[0039] The value of Dl (mm) xG (mm) is an index of the magnitude of the opening area of the annular discharge port of the annular die. The smaller the value of Dl
(mm) xG (mm) , the smaller the opening area of the annular discharge port of the annular die is, and the larger the value of Dl (mm) xG (mm) , the larger the opening area of the annular discharge port of the annular die is. If the value of Dl (mm) xG (mm) is less than 80 mm2, the opening area of the annular discharge port of the annular die is small, and as a result, the pressure needed to extrude the thermoplastic elastomer composition through the annular discharge port of annular die 20 is too high. If a film having the above thickness is to be obtained when the value of Dl (mm) xG (mm) is more than 300 mm2, the difference between the discharge rate of the
thermoplastic elastomer composition and the drawing speed of the pinch roll is large, and as a result, it is difficult to stabilize the bubble.
[0040] Examples of the thermoplastic resin which can form the thermoplastic elastomer composition used in the process for producing a blown film according to the present invention, include polyamide-based resins, polyester-based resins, polynitrile-based resins, polymethacrylate-based resins, polyvinyl-based resins, cellulosic resins, fluororesins , imide-based resins, polystyrenic resins, polyolefinic resins, etc. The thermoplastic elastomer composition may include at least one thermoplastic resin.
[ 0041 ] Examples of polyamide-based resins include
Nylon 6 (N6) , Nylon 66 (N66) , Nylon 46 (N46), Nylon 11 (Nil), Nylon 12 (N12), Nylon 69 (N69) , Nylon 610 (N610), Nylon 612 (N612), Nylon 6/66 (N6/66), Nylon 6/66/610 (N6/66/610) ; semi-aromatic and all-aromatic nylons such as Nylon MXD6 (MXD6) , Nylon 6T, Nylon 6/6T, and Nylon 9T; Nylon 66/PP copolymer, Nylon 66/PPS copolymer, etc. Examples of polyester-based resins include aromatic polyesters such as polybutylene terephthalate (PBT) , polyethylene terephthalate (PET) , polyethylene
isophthalate (PEI), PET/PEI copolymer, polyarylate (PAR), polybutylene naphthalate (PBN) , liquid crystal
polyesters, polyoxyalkylenediimidic acid/polybutylate terephthalate copolymers, etc. Examples of polynitrile- based resins include polyacrylonitrile (PAN) ,
polymethacrylonitrile, acrylonitrile/styrene copolymer (AS), methacrylonitrile/styrene copolymer,
methacrylonitrile/styrene/butadiene copolymer, etc.
Examples of polymethacrylate-based resins include
poly (methyl methacrylate ) (PMMA) , poly (ethyl
methacrylate) , etc. Examples of polyvinyl-based resins include vinyl acetate (PVAc) , poly(vinyl alcohol) (PVA) , ethylene-vinyl alcohol copolymer (EVOH) , poly (vinylidene chloride) (PVDC) , poly (vinyl chloride) (PVC) , vinyl chloride/vinylidene chloride copolymer, vinylidene chloride/methyl acrylate copolymer, etc. Examples of cellulosic resins include cellulose acetate, cellulose acetate butylate, etc. Examples of fluororesins include poly (vinylidene fluoride) (PVDF) , poly (vinyl fluoride) (PVF) , polychlorofluoroethylene (PCTFE) ,
tetrafluoroethylene/ethylene copolymer (ETFE) , etc. Examples of imide-based resins include aromatic
polyimides (PI), etc. Examples of polystyrenic resins include polystyrene (PS), etc. Examples of polyolefinic resins include polyethylene (PE) , polypropylene (PP) , etc. Among these thermoplastic resins, Nylon 6, Nylon 66, Nylon 46, Nylon 11, Nylon 12, Nylon 69, Nylon 610, Nylon 612, Nylon 6/66, Nylon 6/66/12, Nylon 6/66/610, and semi-aromatic and all-aromatic nylons such as Nylon MXD6, Nylon 6T, Nylon 9T, and Nylon 6/6T are preferred, in view of gas barrier properties and processability .
[0042] Common ingredients for common thermoplastic resin compositions, such as fillers, reinforcing agents,
processing aids, stabilizers, antioxidants, etc., may optionally be added at a common amount to the
thermoplastic resin which constitutes the thermoplastic 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 to not add a plasticizer to the thermoplastic resin or thermoplastic elastomer composition. An inflation film having a reduced shrinkage with time after inflation molding can be produced even if a plasticizer such as, for example, higher alcohol-based plasticizers, aromatic sulfoneamide-based plasticizers, phenolic plasticizers, etc., conventionally used in the inflation molding of a thermoplastic elastomer composition, is not incorporated into the thermoplastic elastomer composition, and
therefore it is possible to prevent the decrease in the gas barrier properties and heat resistance which may be caused when a plasticizer is added to the thermoplastic elastomer composition.
[0043] The thermoplastic elastomer composition
comprises at least one rubber dispersed in at least one thermoplastic resin, wherein the at least one thermoplastic resin constitutes a matrix phase (or a continuous phase) and the rubber constitutes a disperse phase (or a discontinuous phase) . The rubber is
dispersed in the form of particles in the thermoplastic resin. Examples of the rubber which can constitute the thermoplastic elastomer composition include diene-based rubbers and hydrogenated products thereof, olefin-based rubbers, halogen-containing rubbers, silicone rubbers, sulfur-containing rubbers, fluoro rubbers, etc. Examples of diene-based rubbers and hydrogenated products thereof include natural rubbers (NR.), isoprene rubbers (IR), epoxidized natural rubbers, styrene-butadiene rubbers (SBR) , butadiene rubbers (BR) (high-cis BR and low-cis BR) , acrylonitrile butadiene rubbers (NBR) , hydrogenated NBR, hydrogenated SBR, etc. Examples of olefin-based rubbers include ethylene propylene rubbers (EPM) , ethylene propylene diene rubbers (EPDM) , maleic acid- modified ethylene propylene rubbers (M-EPM) , maleic anhydride-modified ethylene-a-olefin copolymers, ethylene-glycidyl methacrylate copolymers, maleic anhydride-modified ethylene-ethyl acrylate copolymers (modified EEA) , butyl rubbers (IIR), copolymers of isobutylene and an aromatic vinyl or diene monomer (for example, styrene-isobutylene-styrene block copolymers, acid anhydride-modified styrene-isobutylene-styrene block copolymers), polyisobutylene succinic acid
anhydride, acrylic rubbers (ACM), ionomers, etc.
Examples of halogen-containing rubbers include
halogenated butyl rubbers such as brominated butyl rubbers (Br-IIR) , chlorinated butyl rubber (Cl-IIR) , etc., brominated isobutylene-p-methyl styrene copolymer (Br-IPMS), halogenated isobutylene-isoprene copolymer rubbers, chloroprene rubbers (CR) , hydrin rubbers (CHR) , chlorosulfonated polyethylenes (CSM) , chlorinated polyethylenes (CM) , maleic acid-modified chlorinated polyethylenes (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 fluoro rubbers include vinylidene fluoride rubbers, fluorine-containing vinyl ether rubbers, tetrafluoroethylene-propylene rubbers, fluorine-containing silicone rubbers, fluorine- containing phosphazene rubbers, etc. Among these rubbers, brominated isobutylene-p-methylstyrene copolymers, maleic anhydride-modified ethylene-a-olefin copolymers, acid anhydride-modified styrene-isobutylene-styrene block copolymers are preferred in view of gas barrier properties, durability and processability .
[ 0044 ] 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 isobutylene-p-methylstyrene copolymer rubber; a combination of a polyamide-based resin and a maleic anhydride-modified ethylene-a-olefin copolymer; a combination of a polyamide-based resin and an acid anhydride-modified styrene-isobutylene-styrene block copolymer; a combination of a polyamide-based resin, a brominated isobutylene-p-methylstyrene
copolymer rubber, and a maleic anhydride-modified
ethylene-a-olefin copolymer; a combination of a
polyamide-based resin, brominated isobutylene-p- methylstyrene copolymer rubber, and polyisobutylene 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 isobutylene-p-methylstyrene copolymer rubber, which is a modified butyl rubber, and one or more polyamide-based resins (for example Nylon 6, Nylon 6/66, Nylon 612, etc.) is specifically preferred in view of achieving both fatigue resistance and gas barrier properties .
[0045] 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, or other compounding agents that are commonly blended into a rubber composition to the extent that the effects of the present invention are not impaired.
[0046] Before the thermoplastic elastomer composition is introduced into extruder 10, the thermoplastic
elastomer composition can be prepared in advance by melt-kneading at least one thermoplastic resin, at least one rubber, and optionally 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 fix 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 melt-kneading. The melt-kneading temperature may be equal to or higher than the melting point of the
thermoplastic resin, and is preferably a temperature which is higher than the melting point of the
thermoplastic resin by 20°C, for example, is from 200 to 250°C. The total time of the kneading operation is not particularly limited, but is usually from 1 minute to 10 minutes. The thermoplastic elastomer composition which is obtained after melt-kneading the thermoplastic resin and the rubber can be extruded into, for example, a strand form, and then pelletized with a resin pelletizer.
[0047] The cross-linking agent can be suitably selected depending on the type of the rubber and is not particularly limited. Examples of the cross-linking agent include zinc oxide, stearic acid, zinc stearate, magnesium oxide, m-phenylene bismaleimide, alkylphenol resin and halogenates thereof, secondary amines (for example, N- ( 1 , 3-dimethylbutyl ) -N' -phenyl-p- phenylenediamine (6PPD), a polymerized 2 , 2 , 4-trimethyl- 1 , 2-dihydroquinoline ) , etc. Among these cross-linking agents, zinc oxide, stearic acid, and N-(l,3- dimethylbutyl ) -N' -phenyl-p-phenylenediamine are
preferred. The amount of the cross-linking agent is preferably 0.1 to 12 parts by weight, and more
preferably 1 to 9 parts by weight, with respect to 100 parts by weight of the rubber.
[0048] The thermoplastic elastomer composition used in accordance with the process of the present invention can be formed in-situ by introducing the thermoplastic resin, rubber, and optionally additives from stock material feeder 11 of extruder 10 which is a single-screw or twin-screw kneading extruder, to the inside of cylinder 12, and melt-kneading them by means of rotating single or double screws. In this case, the resulting
thermoplastic elastomer composition can be extruded as a tubular film without being pelletized, from the annular die attached to the discharge port of the extruder.
[0049] The film produced by the process of the present invention is useful as, for example, a member for a pneumatic tire due to excellent gas barrier properties thereof. The film produced by the process of the present invention is particularly useful as a gas barrier film, for example, an inner liner, for producing a pneumatic tire .
[0050] Any conventional process may be used as the process for producing a pneumatic tire. For example, when using the film produced by the process of the present invention as an inner liner in the production of a pneumatic tire, a pneumatic tire can be produced by laminating the film produced by the process of the present invention onto a tire molding drum in
cylindrical form; sequentially laminating thereon tire members such as a carcass layer, a belt layer, a tread layer, etc., to form a green tire; removing the
resulting green tire from the tire molding drum, 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 accordingly has fewer wrinkles and is excellent in dimensional stability. Therefore, the film produced by the process of the present
invention can suppress defects due to the wrinkles and delamination of the film, thereby reducing the failure rate of the tire after vulcanization.
Examples
[0051] 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 examples.
[0052] (1) Preparation of Thermoplastic Elastomer
Composition
Among the stock materials shown in Table 1 below, Br-IPMS was processed into pellets in advance by a rubber pelletizer (manufactured by Moriyama Works) . The resulting rubber pellets, nylons as thermoplastic resins, the acid-modified elastomer, acid-modified elastomer, and additives (i.e., zinc oxide, stearic acid, and 6PPD) were charged into a twin-screw kneading extruder
(manufactured by The Japan Steel WorksN Ltd.) at the compounding ratio shown in Table 1 and were kneaded at 250°C for 3 minutes. The resulting kneaded mass was continuously extruded into a strand form from the
extruder, cooled with water, and subsequently cut by a cutter to obtain thermoplastic elastomer compositions 1 and 2 in the form of pellets.
[0053] Table 1
Figure imgf000021_0001
[0054] Footnote of Table 1:
Br-IPMS: Brominated isobutylene-p-methylstyrene copolymer rubber (Exxpro® MDX89-4 from ExxonMobil
Chemical Company)
PIBSA: Polyisobutylene succinic anhydride
(DOVERMULSE H1000 from Dover Chemical Corporation)
M-EPM: Maleic anhydride-modified ethylene-propylene copolymer rubber (Exxelor® VA1803 from ExxonMobil
Chemical Company)
Zinc oxide: Zinc White No. 3 from Seido Chemical Industry Co., Ltd.
Stearic acid: Beads Stearic Acid from NOF
Corporation
6PPD : N- ( 1 , 3-dimethylbutyl ) -N' -phenyl-p- phenylenediamine (Santoflex 6PPD from Flexsys)
Nylon 6/66 copolymer: UBE Nylon® 5023B from Ube Industries, Ltd.
Nylon 6: UBE Nylon® 1013B from Ube Industries, Ltd.
Nylon 6/12 copolymer: UBE Nylon® 7024B from Ube Industries, Ltd. [ 0055 ] (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 cp75 mm single-screw extruder
(manufactured by GM Engineering Co., Ltd.) to form inflation molding equipment. The annular discharge port of the annular die was directed upward in the vertical direction (i.e., the direction opposite to the gravity direction) . A pair of guides and a pair of pinch rolls were arranged in order upward in the vertical direction of the annular discharge port. Each of the thermoplastic elastomer compositions 1 and 2 was extruded from the annular discharge port of the annular die, then the bubble extruded from the annular discharge port was folded by the pair of pinch rolls, and subsequently was wound up by the windup roll through a plurality of guide rolls to produce a blown film. The cylinder temperature of the extruder was 230°C, and the temperature of the annular die for inflation molding was 240°C. The molten thermoplastic elastomer composition was extruded from the annular die at a discharge rate in the range from 48 to 88 kg/h. The drawing speed of the film was set to a value in the range of from 5.9 to 15.7 m/min. A film was obtained by inflation molding under the conditions shown in Table 2. An 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 rate was in the range of from 13.3 to 40 m2/min, and the temperature of the blowing air was 10°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) . The maximum diameter D2 of the bubble was determined by unwinding the film immediately after being inflation molded and wound up in a roll form, measuring the width W of the unwound film, and using the relation nxD2=2W between W and D2 when the circular constant is represented as n. The measurement of the width W of the film was carried out within 5 to 10 minutes from the formation of the film. The width W of the film is the arithmetic mean (arithmetic average) of the widths measured at three locations 25 cm intervals in the windup direction of the film for a sample having a length of more than 75 cm in the windup direction of the film.
[ 0056 ] (3) Evaluation of Film
(A) Thickness
The thickness (t) of each film obtained by inflation molding was determined by unwinding each film
immediately after being inflation molded and wound up in a roll form, and measuring the thickness of the unwound film with an off-line contact type thickness gauge TOF- 4R manufactured by Yamabun Electronics Co., Ltd. The measurement of the thickness "t" of the film was carried out within 5 to 10 minutes from formation of the film. The thickness "t" of the film is the arithmetic mean of the thicknesses measured at 64 locations on the
circumference of the film.
(B) Shrinkage Factor
For each film obtained by inflation molding, the film immediately after being inflation molded and wound up in a roll form was unwound, a sample in the form of belt having a width of 10 cm was cut out from the film at right angles to the windup direction of the film, and the sample was measured for the width (Wl) in the longitudinal direction within 5 to 10 minutes from formation of the film. Further, each film thus cut was allowed to stand in a room at an air temperature of about 25°C for 1 week, and then was again measured for the width (W2) in the longitudinal direction. The
shrinkage factor (%) was determined by entering the measured Wl and W2 into the formula:
Shrinkage factor ( % ) =100* (W1-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 factor was less than 1%, the shrinkage factor was rated as "low". The ratings wiil be shown in Table 2 below along with the values of the shrinkage factor (%) .
(C) Bubble Stability
The bubble stability was determined by visually evaluating the bubble according to the following
criteria. When a bubble stood up without pulsation or meandering, the bubble stability was evaluated as "good". When there were some pulsation or meandering of a bubble but was no obstacle to the film formation, the bubble stability was evaluated as "fair". When there was
remarkable pulsation or meandering of the bubble and a film having target dimensions could not be obtained, the bubble stability was evaluated as "unstable". The
results are shown in Table 2.
Figure imgf000025_0001
[0058] For Examples 1 to 20 and Comparative Examples 1 to 3, the shrinkage factors were plotted against the values of fxBUR/ (QxGxt) , whereby the curves shown in FIG. 2 were obtained. Table 2 and FIG. 2 show that the blown films of Examples 1 to 20 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 1 to 3. The blown films of Examples 1 to 20 exhibited bubble stability of "Fair" to "Good" in addition to a low shrinkage factor.
Industrial Applicability
[0059] The blown film obtained by the process of the present invention can be suitably used as an air barrier layer for a pneumatic tire etc.
Reference Signs List
[0060] 1. Inflation molding equipment
10. Extruder
20. Annular die
21. Annular discharge port
30. Air ring device
40A, 40B. Stabilizing plates
50A, 50B. Pinch rolls
60. Windup roll
B. Bubble
F. Folded tubular film

Claims

Claim 1. 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 inflation molding equipment comprises:
an extruder,
an annular die for extruding the thermoplastic elastomer composition into a tubular film, the annular die is attached to a discharge port of the extruder, and an air ring device for blowing a cooling gas to the tubular film extruded from the annular die in order to cool the tubular film,
the annular die has an annular discharge port having an inner diameter (Dl) (mm) and a lip gap (G) (mm) ; and wherein the process comprises:
melt-extruding the thermoplastic elastomer
composition from the annular discharge port of the
annular die as a tubular film at a discharge rate (Q) ( kg/h) ; and
expanding the tubular film to have a maximum diamater (D2) (mm) while blowing the cooling gas from the air ring device at a flow rate (f) (m3/min) to the tubular film melt-extruded from the annular discharge port;
and when D2/D1 is represented by BUR, and a thickness of the blown film produced by the process is represented by t (mm) , G, Q, f, t, and BUR satisfy a relationship of following formula (1) :
Figure imgf000027_0001
Claim 2. The process according to claim 1, wherein G, Q, f, t, and BUR satisfy a relationship of following formula ( 2 ) :
Figure imgf000027_0002
Claim 3. The process according to claim 1 or 2, wherein Dl (mm) and G (mm) satisfy a relationship of following formula (3) :
Figure imgf000028_0001
Claim 4. The process according to any one of claims 1 to 3, wherein the thickness t is 50 to 300 μπι, and the BUR is 1.2 to 5.0.
Claim 5. The process according to any one of claims 1 to 4, wherein the blown film is a member for a tire.
Claim 6. The process according to any one of claims 1 to 5, wherein the thermoplastic resin comprises one or more nylons and the rubber particles dispersed in the thermoplastic resin comprise a brominated isobutylene-p- methylstyrene copolymer, maleic anhydride-modified ethylene-a-olefin copolymer, acid anhydride-modified styrene-isobutylene-styrene block copolymer, or a combination of two or more thereof.
Claim 7. The process of production of a blown film according to any one of claims 1 to 6, wherein the thermoplastic elastomer composition does not comprise a higher alcohol-based plasticizer, aromatic sulfonamide- based plasticizer, or phenolic plasticizer.
Claim 8. A gas permiation preventive film for a pneumatic tire, comprising a blown film produced by the process according to any one of claims 1 to 7.
Claim 9. A pneumatic tire comprising the gas permiation preventive film for the pneumatic tire according to claim 8.
PCT/US2016/017298 2016-02-10 2016-02-10 Process for producing blown film WO2017138932A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3320340A (en) * 1964-07-20 1967-05-16 Minigrip Inc Controlled cooling of extruded plastic
US3819790A (en) * 1969-12-22 1974-06-25 Exxon Research Engineering Co Multi-step air ring for tubular film process
US20130269850A1 (en) * 2010-12-22 2013-10-17 The Yokohama Rubber Co., Ltd. Pneumatic tire
US20130333826A1 (en) * 2012-06-19 2013-12-19 Toyo Tire & Rubber Co., Ltd. Forming method of annular rubber member and forming equipment of annular rubber member
US20140150947A1 (en) * 2011-03-29 2014-06-05 Exxonmobil Chemical Patents Inc. Dynamically Vulcanized Thermoplastic Elastomer Laminates
WO2015183444A1 (en) * 2014-05-30 2015-12-03 Exxonmobil Chemical Patents Inc. Thermoplastic elastomeric films and the method of manufacturing same

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3320340A (en) * 1964-07-20 1967-05-16 Minigrip Inc Controlled cooling of extruded plastic
US3819790A (en) * 1969-12-22 1974-06-25 Exxon Research Engineering Co Multi-step air ring for tubular film process
US20130269850A1 (en) * 2010-12-22 2013-10-17 The Yokohama Rubber Co., Ltd. Pneumatic tire
US20140150947A1 (en) * 2011-03-29 2014-06-05 Exxonmobil Chemical Patents Inc. Dynamically Vulcanized Thermoplastic Elastomer Laminates
US20130333826A1 (en) * 2012-06-19 2013-12-19 Toyo Tire & Rubber Co., Ltd. Forming method of annular rubber member and forming equipment of annular rubber member
WO2015183444A1 (en) * 2014-05-30 2015-12-03 Exxonmobil Chemical Patents Inc. Thermoplastic elastomeric films and the method of manufacturing same

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