JP2008302702A - Method for manufacture of oriented thermoplastic elastomer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacture of an oriented thermoplastic elastomer film with low permeability and improved fatigue resistance. <P>SOLUTION: The oriented thermoplastic elastomer film contains a polymer blend in which (A) a halogenated isobutylene elastomer and (B) a polyamide are dynamically crosslinked, and has reduced permeability and improved fatigue resistance. The production method includes cast-molding or inflation-molding the polymer blend by adjusting the shear rate of die lips to control the molecular orientation of the film so that the planar birefringence (PBR) of the prepared film is equal to or greater than 0.002. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method for producing an oriented thermoplastic elastomer film having reduced permeability and improved fatigue resistance. More specifically, the present invention relates to a method for producing a thermoplastic elastomer film composition having a high surface orientation in order to reduce gas permeation, and a method for producing a pneumatic tire using the same.

  Patent Document 1 discloses a low-permeability thermoplastic elastomer composition excellent as a gas barrier layer of a pneumatic tire. The thermoplastic elastomer composition comprises a low-permeability thermoplastic matrix, such as polyamide or a blend of polyamides, in which a low-permeability rubber such as a bromide of isobutylene-p-methylstyrene copolymer (ie BIMS) is present. Is distributed. Subsequently, both patent documents 2 and 3 specify the viscosity ratio of the thermoplastic matrix and the rubber dispersion as a function of the volume fraction ratio in order to achieve phase continuity of the thermoplastic part and refinement of the rubber dispersion. And is being brought close to 1 independently. U.S. Patent No. 6,099,051 recognizes the importance of smaller rubber dispersions in these thermoplastic elastomers to provide acceptable durability, particularly for use as the innerliner of their pneumatic tires. ing.

Furthermore, the low transmission improvement of these low transmission thermoplastic elastomers is
This is achieved by paying attention to orientation. Patent Document 4 conceptually discloses introducing orientation into a thermoplastic elastomer film for enhancing physical properties and reducing permeation. This patent document does not describe any experimental data. Further, the method specified in this patent document is based on the assumption that the film has strain-hardening characteristics and moderate stretching dynamics, drafting, tentering, and Including biaxial orientation of the cast film through a heat set. In the present invention, the thermoplastic elastomer cast film is intended to improve the film properties simply by the film cast ratio and / or the film inflation process. This thermoplastic elastomer film does not have an elongational fluidity suitable for orientation by a subsequent biaxial orientation process.

European Patent No. 722850 European Patent Application No. 857761 European Patent Application No. 969039 WO0214410

An object of the present invention is to provide a method for producing an oriented thermoplastic elastomer film having reduced permeability and improved fatigue resistance.

According to the present invention, there is provided a method for producing an oriented thermoplastic elastomer film having reduced permeability and improved fatigue resistance by dynamic crosslinking of a blend of (A) a halogenated isobutylene elastomer and (B) a polyamide , comprising : Planar birefringence (PBR) of the film measured by the formula: PBR = [(n1 + n2) / 2] / 2-n3
(Where n1, n2 and n3 are the refractive indices along the machine direction, the transverse direction and the film normal direction, respectively)
Adjusting the shear rate of the die lip when making the film so as to control the molecular orientation of the film so that is equal to or greater than 0.002 and casting or blowing the polymer blend. A method for producing an oriented thermoplastic elastomer film is provided.

  In this specification and in the claims, the singular forms also include the plural unless the context clearly dictates otherwise.

The present invention relates to a method for producing an oriented thermoplastic elastomer film having reduced permeation and improved fatigue resistance.

  More particularly, the present invention relates to a film casting and inflation process for producing a thermoplastic elastomer film having an increased plane orientation and a process for producing a pneumatic tire using the same.

The preferred planar birefringence of the oriented thermoplastic elastomer film produced according to the present invention is equal to or greater than 0.002. This orientation can be achieved by increasing the winding speed during casting and inflation or by increasing blow-up during film inflation.

  In the following, the present invention will be described for better understanding with reference to FIG. 1 which shows the correlation between the degree of plane orientation of the film and the transmission coefficient of the film.

  The thermoplastic elastomer composition is dynamically crosslinked with a blend of halogenated isobutylene elastomer and polyamide.

  Here, “dynamic crosslinking” refers to a crosslinking process in which an engineering resin and a crosslinkable elastomer are crosslinked under high shear conditions. As a result, the crosslinkable elastomer is simultaneously crosslinked and dispersed as fine particles of “microgel” in the engineering resin matrix.

  Dynamic cross-linking mixes the components at an elastomer cross-linking temperature or higher in an apparatus such as a roll mill, a Banbury ™ mixer, a continuous mixer, a kneader or a mixing extruder (eg, a twin screw extruder). Is done. The unique property of dynamically cross-linked compositions is that the composition is processed and reworked by general-purpose thermoplastic processing techniques such as extrusion, injection molding, compression molding, etc., even if the elastomer component is fully cross-linked be able to. Scrap and flushing can be used and reprocessed.

  In a preferred embodiment, the halogenated isobutylene elastomer component comprises a copolymer of isobutylene and p-alkylstyrene, as described, for example, in European Patent Application No. 0344402. This copolymer has a substantially homogeneous composition distribution. Preferred alkyl groups in the p-alkylstyrene moiety are alkyl groups having 1 to 5 carbon atoms, primary haloalkyl groups having 1 to 5 carbon atoms, secondary haloalkyl groups, and mixtures thereof. A preferred copolymer comprises isobutylene and p-methylstyrene.

  Suitable halogenated isobutylene elastomer components include copolymers (eg, brominated) having a number average molecular weight Mn of at least about 25,000, preferably at least about 50,000, preferably at least about 100,000, preferably at least about 150,000. Isobutylene-p-methylstyrene copolymer). These copolymers also have a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), ie Mw / Mn, of less than about 6, preferably less than about 4, more preferably less than about 2.5. Small, most preferably less than about 2.0. In another embodiment, a suitable halogenated isobutylene elastomer component has a Mooney viscosity (1 + 4) at 125 ° C (measured according to ASTM D 1646-99) of 25 or more, preferably 30 or more, more preferably 40. Or a further copolymer (for example, brominated isobutylene-p-methylstyrene copolymer).

  The preferred brominated isobutylene and p-methylstyrene copolymer is 5-12 wt% p-methylstyrene, 0.3-1.8 mol% brominated p-methylstyrene and Mooney viscosity (1 + 4) 30 at 125 ° C. Copolymers having ~ 65 (measured according to ASTM D 1646-99).

  The halogenated isobutylene elastomer component (A) according to the present invention comprises about 0.5 to 25% by weight, preferably about 2 to 20% by weight of p-alkylstyrene, preferably about 2 to 20% by weight, based on the total amount of isobutylene and comonomer. It can be prepared from p-methylstyrene and by halogenation. The content of halogen (eg Br and / or Cl, preferably Br) is preferably less than about 10% by weight, more preferably about 0.1 to 7% by weight, based on the total amount of copolymer.

  The copolymerization can be carried out in a known manner, for example as described in European Patent Application Publication No. 34402 (EP 34402A) published November 29, 1989, the halogenation being for example a US patent. It can be carried out by a known method as described in Japanese Patent No. 4548995.

  The halogenated isobutylene elastomer preferably has a number average molecular weight (Mn) of at least about 25,000, more preferably at least about 100,000, and is preferably a number average of less than about 10, more preferably less than about 8. It has the ratio of the weight average molecular weight (Mw) to the molecular weight (Mn), ie Mw / Mn.

  Polyamides that can be used in the present invention are thermoplastic polyamides (nylons) containing crystallized or resinous, high molecular weight solid polymers such as copolymers and terpolymers having amide repeat units in the polymer chain. Polyamides can be prepared by polymerization of one or more of ε-laclams such as caprolactam, pyrrolidione, lauryl lactam and aminoundecan lactam, or by polymerization of amino acids, or by condensation of dibasic acids with diamines. it can. Both fiber-forming and molded great nylon are suitable. Examples of such polyamides are polycaprolactam (nylon 6), polylauryl lactam (nylon 12), polyhexamethylene adipamide (nylon 66), polyhexamethylene azelamide (nylon 69), polyhexamethylene sebacamide ( Nylon 610), polyhexamethylene isophthalamide (nylon 6IP), and a condensation product of 11-amino-undecanoic acid (nylon 11). Nylon 6 (N6), nylon 11 (N11), nylon 12 (N12), nylon 6/66 copolymer (N6 / 66), nylon 610 (N610), nylon 46, nylon MXD6, nylon 69 and nylon 612 (N612) It can also be used. These copolymers, any blends thereof, can also be used. Additional examples of satisfactory polyamides (especially those with softening points below 275 ° C.) can be found in Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 10, page 919 and Encyclopedia of Polymer pages, 10 and 19 ing. Commercially available thermoplastic polyamides can be advantageously used in the practice of the present invention, with linear crystalline polyamides having a softening or melting point of 160-230 ° C. being preferred.

  The amounts of the elastomer (A) and polyamide that can be used in the present invention are preferably 95 to 25 parts by weight and 5 to 75 parts by weight, more preferably 90 to 25 parts by weight and 10 to 75 parts by weight, respectively (component ( The total amount of A) and (B) is 100 parts by weight).

The oriented thermoplastic elastomer film produced in the present invention includes, in addition to the essential components described above, a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator, various oils, an anti-aging agent, a reinforcing agent, a plasticizer, and a softening agent. Alternatively, various additives mixed in other general rubbers can be included. These additives can be mixed and vulcanized by a general method to obtain a composition used for vulcanization or crosslinking. The amount of these additives to be added can be the amount generally used so far as long as the object of the present invention is not violated.

  EXAMPLES Hereinafter, although this invention is further demonstrated according to an Example, it cannot be overemphasized that this invention is not what is limited to these Examples.

The following commercial products were used as the components used in the following examples.
1. Resin component Nylon 1: Blend of N11 (Rilsan BESN O TL) and N6 / 66 (Ube 5033B) Nylon 2: N6 / 66 (CM6001FS)
Additive 1: Plasticizer: N-butylbenzenesulfonamide
Compatibilizer: AR-201
Additive 2: Stabilizer: Irganox 1098, Tinuvin (Tin)
uvin) 622LD and CuI

2. Rubber component BIMS: isobutylene having a Mooney viscosity of about 45, p-methylstyrene of about 5 wt% and bromine of about 0.75 mol%, commercially available from ExxonMobil Chemical Company under the trade name EXXPRO 89-4 Brominated copolymer of p-methylstyrene DM16D: Hexadecyldimethylamine (Akzo Nobel)
6PPD: N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine ZnO: Zinc oxide (crosslinking agent)
St-acid: stearic acid (crosslinking agent)
ZnSt: Zinc stearate (crosslinking agent)
MBTS: benzothiazyl disulfide

3. Anti-adhesive agent Talc: Magnesium silicate hydrate (Ciba)
ZnO: Zinc oxide IGAFOS: Igafos 168 anti-aging agent (Ciba)

The test methods used for evaluating the examples and comparative examples are as follows.
A) Measurement of volume average equivalent dispersion diameter and number average equivalent dispersion diameter Dispersion diameter and diameter distribution were evaluated by applying the tapping method AFM to these films. All film samples were freeze cut at −150 ° C. with a diamond knife using a Reichert cryogenic microtome. The surfaced sample was warmed to ambient temperature without moisture in a dentator flushed with dry nitrogen gas. Samples were tested for 24 hours after freeze cutting in tapping mode with a square 225-μm silicon cantilever using an AFM (DI-3000 Digital Instrument). All tapping phase AFM micrographs were converted to TIFF format and processed using PHOTOOSHOP (Adobe Systems) for image enhancement. All image measurements were performed using a commercially available image process tool kit (Reindeer Games) as an attachment to PHOTOSHOP. The image measurement results were written to a text file for data processing by the next Microsoft. The number average dispersion diameter Dn was calculated as follows.

Dn = Σ (n ₁ D ₁ ) / Σ (n ₁ )
D ₁ is the equivalent diameter of the individual dispersions and n ₁ is the number of dispersions with an equivalent diameter of D ₁ . The volume average dispersion diameter Dv is expressed as follows.
Dv = Σ (n ₁ D ₁ ⁴ ) / Σ (n ₁ D ₁ ³ )
Where n ₁ is the number of dispersions having an equivalent diameter of D ₁ .

B) Durability (low temperature fatigue)
The film and carcass compound were laminated together with an adhesive and crosslinked at 190 ° C. for 10 minutes. Next, it was punched into a JIS-2 dumbbell shape and used for a life test at −20 ° C. with 6.67 Hg and 40% strain.

C) Oxygen permeability coefficient by Mocon The oxygen permeability coefficient was carried out at 60 ° C. using a Mocon OX-TRAN 2/61 permeability tester.

D) Main refractive index operation by Metricon Three main refractive indices were measured using Metricon at a wavelength of 632.8 nm. Planar birefringence, PBR and average refractive index, n are calculated in the following equation.

PBR = (n1 + n2) / 2-n3 (3)
n = (n1 + n2 + n3) / 3 (4)
Here, n1, n2, and n3 are refractive indexes along the machine direction, the transverse direction, and the film normal direction, respectively.

Examples 1-8
BIMS was pre-blended with a cross-linking agent in a closed Banbury mixer and pelletized with an anti-adhesive before mixing with nylon. Mixing of nylon and BIMS and dynamic crosslinking were performed at about 230 ° C. using a twin screw extruder. After mixing these, a film was formed by casting or inflation. 2 "diameter discs were cut from these films and conditioned in a vacuum oven overnight at 60 ° C prior to transmission measurements. The oxygen transmission coefficient of these films at 60 ° C was the Mocon OX-TRAN 2/61 permeability test. The principal refractive indices along the three major directions of these films were determined using a Metricon prism coupling device, and the operating wavelength was 632.8 nm generated by a low power He-Ne laser. Using these three main reflectivities, the average refractive index can be calculated as follows.

<N> = (n1 + n2 + n3) / 3
In the formula, <n> is an average refractive index, and 1, 2, and 3 indicate a machine direction, a transverse direction, and a normal direction (normal direction with respect to the film surface), respectively. Relative plane orientation can be expressed by the following formula using plane birefringence or PBR (see US Pat. No. 5,385,704).
PBR = (n1 + n2) / 2-n3

  In Examples 1 to 8, as shown in Table 1, a nylon 1 matrix was used with a plasticizer and a compatibilizer added thereto. Nylon 1 matrix with plasticizer has a viscosity close to that of BIMS. MBTS is a crosslinking retarder and DM16D is a viscosity increasing agent. Both of these can react with the benzylated bromine of BIMS and affect its reaction compatibility with nylon. Due to the modification of the interface bond between BIMS and nylon by MBTS and DM16D, the orientation of nylon during film casting or inflation is affected. As shown in Table 1, the degree of plane orientation increases due to a decrease in cast film thickness due to an increase in winding speed using the same cast die, and the transmittance decreases accordingly. Although the permeability of the blown film cannot be measured because of the adhesive on the film surface, decreasing the film thickness by increasing the winding speed without changing the die or blow-up leads to an increase in the plane orientation. Addition of MBTS and DM16D leads to a decrease in the degree of orientation. Overall, there is a strong correlation between PBR and transparency. As shown in Table 1, since the inventors use the same nylon matrix for all films, the average refractive index indicating the density or crystallinity of nylon is kept constant. The results are plotted in FIG. 1, and Examples 4, 7 and 8 (ie see plots # 4, # 7 and # 8) were not within the scope of the present invention.

Examples 9-13
In Examples 9-13, a nylon 1 matrix was used without the use of plasticizers and compatibilizers. 6PPD acts as a cross-linking agent to crosslink BIMS through benzylated bromine at a mixing temperature of 230 ° C. and therefore not from reaction compatibilization. DM16D is a viscosity increasing agent for BIMS and also reacts with benzylated bromine of BIMS. The modification of the interfacial bond by using DM16D and 6PPD significantly reduces the degree of plane orientation and increases the film transmission as shown in Table 2. The results are shown in FIG. Nevertheless, a good correlation could be observed between PBR and transmission. The high refractive index compared to the refractive index in Table 1 reflects that the nylon matrix does not contain a plasticizer. Therefore, higher density or higher refractive index is expected.

Examples 14-19
In Examples 14-19, Nylon 2 matrix was used without N11 and plasticizer. When blending with nylon 2, viscosity modifiers such as DM16D and 6PPD are necessary to obtain good viscosity consistency and fine BIMS rubber dispersibility. The concentration used for the anti-sticking agents listed in Table 3 is 0.5-1 phr. As shown in Table 3, when ZnO is used as an adhesion preventive agent, the orientation is significantly affected. Since this deposition inhibitor can act as a crosslinking agent, it removes benzyl bromine from BIMS for reaction miscibility with nylon. Significant removal of benzyl bromine from BIMS reduces the interfacial bond between nylon and BIMS dispersion and reduces the ability of the film manufacturing process to orient the nylon. However, the overall correlation between PBR and transparency is retained. A higher refractive index than the refractive index in Table 2 is the result when the N6 / 66 matrix is used. The results are shown in FIG.

FIG. 1 is a drawing showing the correlation between the degree of plane orientation of a film and the transmission coefficient.

Claims (5)

Permeability by dynamic crosslinking of blends of (A) a halogenated isobutylene elastomer and (B) the polyamide is reduced to a process for the preparation of oriented thermoplastic elastomer film fatigue resistance was improved was measured by the following formula Planar birefringence (PBR) of film: PBR = [(n1 + n2) / 2] / 2-n3
(Where n1, n2 and n3 are the refractive indices along the machine direction, the transverse direction and the film normal direction, respectively)
Adjusting the shear rate of the die lip when making the film so as to control the molecular orientation of the film so that is equal to or greater than 0.002 and casting or blowing the polymer blend. A method for producing an oriented thermoplastic elastomer film comprising : The amount of the halogenated isobutylene elastomer (A) is 95 to 25 parts by weight, and the amount of the polyamide (B) is 5 to 75 parts by weight (provided that the total amount of the components (A) and (B) is 100 parts by weight). Item 2. A method for producing an oriented thermoplastic elastomer film according to Item 1. The method for producing an oriented thermoplastic elastomer film according to claim 1 or 2, wherein the halogenated isobutylene elastomer is a brominated product of a copolymer of isobutylene and p-methylstyrene. The oriented thermoplastic elastomer film according to claim 1, 2 or 3, wherein the polyamide is at least one selected from a crystallized or resinous, high molecular weight solid copolymer and terpolymer having an amide repeating unit in a polymer chain. Manufacturing method . The polyamide is at least one selected from the group consisting of nylon 6, nylon 66, nylon 11, nylon 12, nylon 69, nylon 610, nylon 46, nylon MXD6, nylon 6/66 and copolymers thereof and blends thereof. The method for producing an oriented thermoplastic elastomer film according to claim 4.

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