ETHYLENE-VINYL ALCOHOL COPOLYMER-RESIN Particle COMPOSITION, ETHYLENE-VINYL ALCOHOL COPOLYMER FILM MADE FROM THEREBY AND MULTI-LAYER STRUCTURE

Description

BACKGROUND OF THE INVENTION 1. Technical Field

[0001] The present disclosure relates to an ethylene-vinyl alcohol copolymer (EVOH) composition, and more particularly to an ethylene-vinyl alcohol copolymer (EVOH) resin particle composition, a film and multilayer structure formed from the EVOH resin particle composition.2. Description of Related Art

[0002] EVOH resin is widely applied to multilayer substances to preserve perishable goods. For instance, EVOH resin and multilayer substances made therefrom are commonly used in the food packaging industry, medical equipment and consumables industry, pharmaceutical manufacturing industry, electronics industry and agricultural chemical industry. In general, EVOH resin is incorporated into multilayer substances to function as a unique layer, i.e., an oxygen blocking layer.

[0003] Existing thin film formed from EVOH resin particles is susceptible to gas discharge and thus has drawbacks, such as thickness unevenness, overly high oxygen exchange rate, and poor stretchability. Although attempts were made to improve the workability of EVOH, there is still room for improvement in thin film formed from EVOH resin particles.

[0004]

[0009] However, the prior art has never disclosed a concept or means of effectively meeting the aforesaid requirements.

[0005] JP H11 294947 A discloses a method for drying a saponified pellet of ethylene-vinyl acetate copolymer for obtaining moldings of a film or a sheet and the like with less fine fish eyes and excellent fusion moldability, and the method comprises that when forming alcohol solution or alcohol / water mixed solution of a saponified substance of ethylene vinyl acetate copolymer into a strand and drying a pellet obtained by cutting the strand, at least two stages of drying are performed wherein the speed of the heating gas passing the pellet surface is 1.0 to 10 m / sec for a primary drying thereof and the speed of heating gas passing the pellet surface is 1.0 m / sec or less for a secondary drying thereof.

[0006] JP H11 291244 A discloses a method for drying saponified ethylene / vinyl acetate copolymer pellets reduced in the fluctuations of torque or change in injection amt. at a time of melt molding and capable of obtaining a molded article such as a film or a sheet excellent in thickness uniformity, and the method comprises that an alcohol soln. of a saponified ethylene / vinyl acetate copolymer or an alcohol / water mixed soln. thereof is molded into a strand and this strand is cut to obtain pellets and, when these pellets are dried, static drying and fluidizing drying are combined to be used.

[0007] CN 113 024 936 A discloses an ethylene-vinyl alcohol copolymer resin composition and a multilayer structure comprising the same, and the ethylene-vinyl alcohol copolymer resin composition typically comprises at least two melting point temperatures and a boron compound, wherein the boron content of the ethylene-vinyl alcohol copolymer resin composition is from about 25 to about 300 ppm; and the ethylene-vinyl alcohol copolymer resin composition has an iodine-dyed region of 0.1 mm 2< or less after dropping 0.01 mL of an iodine solution onto the surface of the ethylene-vinyl alcohol copolymer resin composition, immersing the ethylene-vinyl alcohol copolymer resin composition in water for 5 seconds, and drying at a temperature of 120 °C for 2 hours.

[0008] CN 111 944 262 A discloses an ethylene-vinyl alcohol copolymer resin particle, a forming method thereof, a film formed by the ethylene-vinyl alcohol copolymer resin particle and a multilayer structure, and the ethylene-vinyl alcohol copolymer resin particle have at least two melting point temperatures and have a transmittance of greater than 8% for visible wavelengths. The haze of the particles can be lower than 99.8%, and the method for preparing the EVOH particles comprises the following steps: obtaining a first solution containing first ethylene vinyl acetate having a first ethylene content; obtaining a second solution comprising a second ethylene vinyl acetate, the second ethylene vinyl acetate having a second ethylene content, the second ethylene content being different from the first ethylene content; mixing the solutions; saponifying; granulating using the mixed solution to form particles; contacting the particles with a boron solution and drying the particles.BRIEF SUMMARY OF THE INVENTION

[0009] It is an object of the present invention to provide an ethylene-vinyl alcohol copolymer (EVOH) resin particle composition that can form a film with satisfactory film thickness uniformity, oxygen exchange rate and stretchability.

[0010] This problem is solved by an ethylene-vinyl alcohol copolymer (EVOH) resin particle composition as claimed in claim 1. Further advantageous embodiments are the subject-matter of the dependent claims.

[0011] The inventor of the disclosure conducted research on the aforesaid technical issue and discovered that thin film formed from an EVOH resin particle composition comprising two EVOH resin particles each having a specific range of surface valley void volume (Vvv) values exhibits satisfactory film thickness uniformity, oxygen exchange rate and stretchability.

[0012] Therefore, the disclosure in one aspect provides an ethylene-vinyl alcohol copolymer (EVOH) resin particle composition, comprising: a first EVOH resin particle having a surface valley void volume (Vvv) of 0.00003 to 2 µm 3< / µm 2< ; and a second EVOH resin particle having a surface valley void volume (Vvv) of 0.00005 to 10 µm 3< / µm 2< , wherein the surface valley void volume (Vvv) of the second EVOH resin particle is greater than the surface valley void volume (Vvv) of the first EVOH resin particle, and the surface valley void volume (Vvv) is measured as outlined in the description hereinafter in more detail..

[0013] According to some embodiments of the disclosure, the first EVOH resin particle has a melting point of 135 to 179 °C, and the second EVOH resin particle has a melting point of 180 to 198 °C.

[0014] According to some embodiments of the disclosure, the first EVOH resin particle has an ethylene content of 36 to 50 mole%.

[0015] According to some embodiments of the disclosure, the second EVOH resin particle has an ethylene content of 20 to 35 mole%.

[0016] According to some embodiments of the disclosure, the EVOH resin particle is cylindrical, elliptic cylindrical, prismoidal, spherical, ellipsoidal or biconvex-disk-shaped and has a major axis or height of 1 to 5 mm and a minor axis of 1 to 5 mm.

[0017] According to some embodiments of the disclosure, the EVOH resin particle composition has a ratio of the first EVOH resin particle to the second EVOH resin particle by weight percentage ranges from 5 : 95 to 75 : 25.

[0018] According to some embodiments of the disclosure, the EVOH resin particle composition has a boron content of 5 to 550 ppm.

[0019] According to some embodiments of the disclosure, the EVOH resin particle composition has an alkali metal content of 10 to 550 ppm.

[0020] According to some embodiments of the disclosure, the first EVOH resin particle has a maximum trough depth (Sv) of 0.0005 to 25 µm 2< , and the second EVOH resin particle has a maximum trough depth (Sv) of 0.001 to 75 µm 2<

[0021] According to some embodiments of the disclosure, the first EVOH resin particle has a root-mean-square slope (Sdq) surface parameter of 0.0001 to 15, and the second EVOH resin particle has a root-mean-square slope (Sdq) surface parameter of 0.0002 to 50.

[0022] According to some embodiments of the disclosure, the first EVOH resin particle has an interface expansion area ratio (Sdr) surface parameter of 0.001 to 60 %, and the second EVOH resin particle has an interface expansion area ratio (Sdr) surface parameter of 0.02 to 150 %.

[0023] According to some embodiments of the disclosure, the first EVOH resin particle has an arithmetic mean height (Sa) surface parameter of 0.0003 to 25 µm, and the second EVOH resin particle has an arithmetic mean height (Sa) surface parameter of 0.0005 to 55 µm.

[0024] According to some embodiments of the disclosure, the first EVOH resin particle has a linear arithmetic mean height (Ra) surface parameter of 0.001 to 0.990 µm, and the second EVOH resin particle has a linear arithmetic mean height (Ra) surface parameter of 0.001 to 0.990 µm.

[0025] According to some embodiments of the disclosure, the first EVOH resin particle has a linear maximum height (Rz) surface parameter of 0.001 to 9.900 µm, and the second EVOH resin particle has a linear maximum height (Rz) surface parameter of 0.001 to 9.900 µm.

[0026] The disclosure in another aspect provides an ethylene-vinyl alcohol copolymer film formed from the EVOH resin particle composition.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0027] The disclosure is illustrated by embodiments and depicted with an accompanying diagram briefly described as follows: FIG. 1 is a schematic view of the disclosure according to an applicable surface valley void volume.DETAILED DESCRIPTION OF THE INVENTION

[0028] The disclosure in one aspect provides an ethylene-vinyl alcohol copolymer (EVOH) resin particle composition, comprising a first EVOH resin particle having a surface valley void volume (Vvv) of 0.00003 µm 3< / µm 2< to 2 µm 3< / µm 2< and a second EVOH resin particle having a surface valley void volume (Vvv) of 0.00005 µm 3< / µm 2< to 10 µm 3< / µm 2< .

[0029] The term "surface valley void volume (Vvv)" used herein refers to the valley void volume of bearing area ratio p% and is defined by ISO 25178:2012. It is also feasible to quantify a center portion, a protruding peak portion, and the size of a protruding valley with volume parameters. As shown in FIG. 1, Vmp denotes the volume of the protruding peak portion, Vmc denotes the volume of the center portion, Vvc denotes the spatial capacity of the center portion, and Vvv denotes the spatial capacity of the protruding valley. In FIG. 1, for example, the range 10% to 80% is specified to be the interval of the center portion. The surface valley void volume Vvv of the first EVOH resin particle falls within the range of 0.00003 µm 3< / µm 2< to 2 µm 3< / µm 2< and is, for example, 0.00003, 0.00005, 0.00010, 0.00050, 0.00100, 0.00500, 0.01000, 0.05000, 0.10000, 0.50000, 1, 1.5000 or 2. The surface valley void volume Vvv of the second EVOH resin particle falls within the range of 0.00005 µm 3< / µm 2< to 10 µm 3< / µm 2< and is, for example, 0.00005, 0.00010, 0.00050, 0.00100, 0.00500, 0.01000, 0.05000, 0.10000, 0.50000, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 µm 3< / µm 2< . According to a preferred embodiment of the disclosure, the surface valley void volume Vvv of the second EVOH resin particle is greater than the surface valley void volume Vvv of the first EVOH resin particle.

[0030] According to some embodiments of the disclosure, the first EVOH resin particle has a melting point of 135 °Cto 179 °C, for example, 135, 140, 145, 150, 155, 160, 165, 170, 175 or 179 °C. In another aspect, the second EVOH resin particle has a melting point of 180 °Cto 198 °C, for example, 180, 182, 184, 186, 188, 190, 192, 194, 196 or 198 °C.

[0031] According to some embodiments of the disclosure, the first EVOH resin particle has an ethylene content of 36 mole% to 50 mole%, for example, 36, 38, 40, 42, 44, 46, 48 or 50 mole%. In another aspect, the second EVOH resin particle has an ethylene content of 20 mole%to 35 mole%, for example, 20, 21, 23, 25, 27, 29, 31, 33 or 35 mole%.

[0032] Furthermore / alternatively, the EVOH has a saponification degree of 90 mole% or higher, preferably 95 mole% or higher, preferably 97 mole% or higher, and preferably 99.5 mole% or higher.

[0033] The expression "the EVOH particle" used herein implies the form and / or shape of one or more particles formed when the EVOH resin undergoes pelletization; although the formation of one or more EVOH particles by pelletization is expressly described herein, the EVOH particle can be processed to take on the shape of e.g. a bead, a cube, a fragment, a shaving according to the disclosure. According to some embodiments of the disclosure, the EVOH resin particle is cylindrical, elliptic cylindrical, prismoidal, spherical, ellipsoidal or biconvex-disk-shaped (corresponding to go-shape) in shape and has a major axis or height of 1 mm to 5 mm, for example, 1, 2, 3, 4 or 5 mm, and a minor axis of 1 to 5 mm, for example, 1, 2, 3, 4 or 5 mm. The term "major axis or height" means the longest outer diameter of an object whose surface is defined by a closed curved surface. The term "minor axis" means the shortest diameter perpendicular to the major axis or height to thereby define a cross section with the maximum area. The aforesaid expression "an object whose surface is defined by a closed curved surface" can be regarded as an object whose surface is integrally formed of a curved surface, an object being defined by multiple mutually-crossing surfaces and thus having no corners, or an object having no rectangular cross sections wherever they are.

[0034] When the EVOH resin particle is cylindrical or elliptic cylindrical, its height falls within the range of 1 mm to 5 mm, for example, 1.5 mm to 5.0 mm, 1.7 mm to 5.0 mm, 2.2 mm to 5.0 mm, 2.4 mm to 5.0 mm, 2.6 mm to 5.0 mm, 2.8 mm to 5.0 mm, 3.0 mm to 5.0 mm, 3.2 mm to 5.0 mm, 3.4 mm to 5.0 mm, 3.6 mm to 5.0 mm, 3.8 mm to 5.0 mm, 4.0 mm to 5.0 mm, 1.7 mm to 4.5 mm, 1.7 mm to 4.4 mm, 1.7 mm to 4.2 mm, 1.7 mm to 4.0 mm, 1.7 mm to 3.8 mm, 1.7 mm to 3.6 mm, 1.7 mm to 3.4 mm, 1.7 mm to 3.2 mm, or 1.7 mm to 3.0 mm, and its minor axis falls within the range of 1 mm to 5 mm, for example, 1.5 mm to 5.0 mm, 1.7 mm to 5.0 mm, 2.2 mm to 5.0 mm, 2.4 mm to 5.0 mm, 2.6 mm to 5.0 mm, 2.8 mm to 5.0 mm, 3.0 mm to 5.0 mm, 3.2 mm to 5.0 mm, 3.4 mm to 5.0 mm, 3.6 mm to 5.0 mm, 3.8 mm to 5.0 mm, 4.0 mm to 5.0 mm, 1.7 mm to 4.5 mm, 1.7 mm to 4.4 mm, 1.7 mm to 4.2 mm, 1.7 mm to 4.0 mm, 1.7 mm to 3.8 mm, 1.7 mm to 3.6 mm, 1.7 mm to 3.4 mm, 1.7 mm to 3.2 mm, or 1.7 mm to 3.0 mm.

[0035] When the EVOH particle is spherical, ellipsoidal or biconvex-disk-shaped, its major axis falls within the range of 1 mm to 5 mm, for example, 1.5 mm to 5.0 mm, 2.2 mm to 5.0 mm, 2.4 mm to 5.0 mm, 2.6 mm to 5.0 mm, 2.8 mm to 5.0 mm, 3.0 mm to 5.0 mm, 3.2 mm to 5.0 mm, 3.4 mm to 5.0 mm, 3.6 mm to 5.0 mm, 3.8 mm to 5.0 mm, 4.0 mm to 5.0 mm, 2.0 mm to 4.5 mm, 2.0 mm to 4.4 mm, 2.0 mm to 4.2 mm, 2.0 mm to 4.0 mm, 2.0 mm to 3.8 mm, 2.0 mm to 3.6 mm, 2.0 mm to 3.4 mm, 2.0 mm to 3.2 mm, or 2.0 mm to 3.0 mm, and its minor axis falls within the range of 1 mm to 5 mm, for example, 1.5 mm to 5.0 mm, 1.8 mm to 4.6 mm, 2.4 mm to 4.6 mm, 2.6 mm to 4.6 mm, 2.8 mm to 4.6 mm, 3.0 mm to 4.6 mm, 3.2 mm to 4.6 mm, 3.4 mm to 4.6 mm, 3.6 mm to 4.6 mm, 3.8 mm to 4.6 mm, 4.0 mm to 4.6 mm, 1.6 mm to 4.5 mm, 1.6 mm to 4.4 mm, 1.6 mm to 4.2 mm, 1.6 mm to 4.0 mm, 1.6 mm to 3.8 mm, 1.6 mm to 3.6 mm, 1.6 mm to 3.4 mm, 1.6 mm to 3.2 mm, or 1.6 mm to 3.0 mm.

[0036] According to some embodiments of the disclosure, the ratio by weight percentage of the first EVOH resin particle to the second EVOH resin particle ranges from 5 : 95 to 75 : 25 and is, for example, 5 : 95, 15 : 85, 25 : 75, 35 : 65, 45 : 55, 55 : 45, 65 : 35 or 75 : 25.

[0037] According to some embodiments of the disclosure, in some situations the EVOH resin particle composition complies boron compound and / or boric acid and / or cinnamic acid and / or alkali metal and / or conjugated polyene and / or lubricant and / or alkaline earth metal. The aforementioned substances improve the properties of the EVOH resin particle composition.

[0038] According to some embodiments of the disclosure, the EVOH resin particle composition comprises a boron compound with a boron content of 5 ppm to 550 ppm. In some situations, the boron content of the EVOH resin particle composition depends on the total weight of the EVOH resin particle composition which falls within the range of 10 ppm to 450 ppm, 10 ppm to 400 ppm, 10 ppm to 350 ppm, 10 ppm to 300 ppm, 10 ppm to 275 ppm, 10 ppm to 250 ppm, 10 ppm to 225 ppm, 10 ppm to 200 ppm, 10 ppm to 175 ppm, 20 ppm to 450 ppm, 20 ppm to 400 ppm, 20 ppm to 350 ppm, 20 ppm to 300 ppm, 20 ppm to 275 ppm, 20 ppm to 250 ppm, 20 ppm to 225 ppm, 20 ppm to 200 ppm, 20 ppm to 175 ppm, 60 ppm to 450 ppm, 60 ppm to 400 ppm, 60 ppm to 350 ppm, 60 ppm to 300 ppm, 60 ppm to 275 ppm, 60 ppm to 250 ppm, 60 ppm to 225 ppm, 60 ppm to 200 ppm, 60 ppm to 175 ppm, 100 ppm to 450 ppm, 100 ppm to 400 ppm, 100 ppm to 350 ppm, 100 ppm to 300 ppm, 100 ppm to 275 ppm, 100 ppm to 250 ppm, 100 ppm to 225 ppm, 100 ppm to 200 ppm, 100 ppm to 175 ppm, 140 ppm to 450 ppm, 140 ppm to 400 ppm, 140 ppm to 350 ppm, 140 ppm to 300 ppm, 140 ppm to 275 ppm, 140 ppm to 250 ppm, 140 ppm to 225 ppm, 140 ppm to 200 ppm, 180 ppm to 450 ppm, 180 ppm to 400 ppm, 180 ppm to 350 ppm, 180 ppm to 300 ppm, 180 ppm to 275 ppm, 180 ppm to 250 ppm, 180 ppm to 225 ppm, 220 ppm to 450 ppm, 220 ppm to 400 ppm, 220 ppm to 350 ppm, 220 ppm to 300 ppm, or 220 ppm to 275 ppm. When the boron content of the EVOH resin particle composition falls within a specific range, it enhances the binding adhesiveness of the EVOH resin particle composition and reduces the chance that the EVOH resin particle composition will adhere to a screw, or removes the EVOH from the screw, to thereby attain the self-cleansing capability of materials, further improving film thickness uniformity. In a preferred embodiment of the disclosure, in addition to a boron compound, the EVOH resin particle composition further comprises cinnamic acid, alkali metal, conjugated polyene, alkaline earth metal, a salt thereof and / or a mixture thereof. The substances are commonly found in EVOH resin particle compositions to enhance the properties thereof. When the aforesaid compounds with a conjugated polyene structure each account for 1 ppm to 30000 ppm of the EVOH resin particle composition of a unit weight, they further inhibit after-heating coloring to thereby enhance thermal stability. If each unit weight of the EVOH resin composition comprises 10 ppm to 550 ppm (calculated by metal conversion) of the alkali metal compound or alkaline earth metal compound, operation can last longer to enhance the formation process. The aforesaid concentration / content falls within any one of the following ranges as needed: 10 ppm to 550 ppm, 10 ppm to 500 ppm, 10 ppm to 450 ppm, 10 ppm to 400 ppm, 10 ppm to 350 ppm, 10 ppm to 300 ppm, 10 ppm to 250 ppm, 10 ppm to 200 ppm, 10 ppm to 150 ppm, 10 ppm to 100 ppm, 10 ppm to 50 ppm, 50 ppm to 550 ppm, 50 ppm to 500 ppm, 50 ppm to 450 ppm, 50 ppm to 400 ppm, 50 ppm to 350 ppm, 50 ppm to 300 ppm, 50 ppm to 250 ppm, 50 ppm to 200 ppm, 50 ppm to 150 ppm, 50 ppm to 100 ppm, 100 ppm to 550 ppm, 100 ppm to 500 ppm, 100 ppm to 450 ppm, 100 ppm to 400 ppm, 100 ppm to 350 ppm, 100 ppm to 300 ppm, 100 ppm to 250 ppm, 100 ppm to 200 ppm, 100 ppm to 150 ppm, 200 ppm to 550 ppm, 200 ppm to 500 ppm, 200 ppm to 450 ppm, 200 ppm to 400 ppm, 200 ppm to 350 ppm, 200 ppm to 300 ppm, 200 ppm to 250 ppm, 300 ppm to 550 ppm, 300 ppm to 500 ppm, 300 ppm to 450 ppm, 300 ppm to 400 ppm, 300 ppm to 350 ppm, 400 ppm to 550 ppm, 400 ppm to 500 ppm, 400 ppm to 450 ppm, and 500 ppm to 550 ppm.

[0039] According to some embodiments of the disclosure, the boron compound includes boric acid or its metal salts. Examples of the metal salts include to calcium borate, cobalt borate, zinc borate (for example, zinc tetraborate, zinc metaborate), potassium aluminum borate, ammonium borate (for example, ammonium metaborate, ammonium tetraborate, ammonium pentaborate, ammonium octaborate), cadmium borate (for example, cadmium orthoborate, cadmium tetraborate), potassium borate (for example, potassium metaborate, potassium tetraborate, potassium pentaborate, potassium hexaborate, potassium octaborate), silver borate (for example, silver metaborate, silver tetraborate), copper borate (for example, copper(II) borate, copper metaborate, copper tetraborate), sodium borate (for example, sodium metaborate, sodium diborate, sodium tetraborate, sodium pentaborate, sodium hexaborate, sodium octaborate), lead borate (for example, lead metaborate, lead hexaborate), nickel borate (for example, nickel orthoborate, nickel diborate, nickel tetraborate, nickel octaborate borate), barium borate (for example, barium orthoborate, barium metaborate, barium diborate, barium tetraborate), bismuth borate, magnesium borate (for example, magnesium orthoborate, magnesium diborate, magnesium metaborate, trimagnesium tetraborate, pentamagnesium tetraborate), manganese borate (for example, manganese(I) borate, manganese metaborate, manganese tetraborate), lithium borate (for example, lithium metaborate, lithium tetraborate, lithium pentaborate), a salt thereof or a combination thereof. It includes borate minerals, such as borax, kainite, inyoite, kotoite, szaibelyite / suanite, and szaibelyite. Preferably, it includes borax, boric acid and sodium borate (for example, sodium metaborate, sodium diborate, sodium tetraborate, sodium pentaborate, sodium hexaborate and sodium octaborate).

[0040] According to some embodiments of the disclosure, the first EVOH resin particle has a maximum trough depth (Sv) surface parameter of 0.0005 µm to 25 µm, for example, 0.001 µm to 25 µm, 0.0100 µm to 25 µm, 0.1000 µm to 25 µm, 1 µm to 25 µm, 1 µm to 23.3000 µm, 1 µm to 20 µm, 1 µm to 15 µm, 5 µm to 15 µm or 7 µm to 10 µm. In another aspect, the second EVOH resin particle has a maximum trough depth (Sv) surface parameter of 0.001 µm to 75 µm, for example, 0.003 µm to 65 µm, 0.010 µm to 65 µm, 0.100 µm to 65 µm, 1 µm to 61.300 µm, 10 µm to 61.300 µm, 20 µm to 50 µm, 25 µm to 40 µm, 30 µm to 40 µm or 30 µm to 36 µm.

[0041] Please refer to ISO 25178:2012 for the definition of the term "maximum trough depth (Sv) surface parameter" which can be regarded as the absolute value of the height of the lowest point relative to a standard surface within a sampling range.

[0042] According to some embodiments of the disclosure, the first EVOH resin particle has a root-mean-square slope (Sdq) surface parameter of 0.0001 to 15, for example, 0.0005 to 15, 0.0050 to 15, 0.0500 to 15, 0.5000 to 15, 1 to 15, 5 to 15, 13 to 15, 4 to 9 or 7 to 10. In another aspect, the second EVOH resin particle has a root-mean-square slope (Sdq) surface parameter of 0.0002 to 50, for example, 0.0005 to 50, 0.0050 to 50, 0.0500 to 50, 0.5000 to 50, 1 to 50, 30 to 50, 35 to 50, 35 to 48 or 15 to 32.

[0043] Please refer to ISO 25178:2012 for the definition of the term "root-mean-square slope (Sdq) surface parameter" which can be regarded as a parameter obtained by calculating the slope root-mean-square of all the points within a sampling range and can indicate the average magnitude of a portion of the slope of the surface outline. The root-mean-square slope of a completely flat surface is 0.

[0044] According to some embodiments of the disclosure, the first EVOH resin particle has an interface expansion area ratio (Sdr) surface parameter of 0.001 % to 60%, for example, 0.010 % to 60%, 0.100 % to 60%, 1 % to 18%, 1 % to 34%, 1 % to 55%, 23 % to 43% or 37 % to 58%. In another aspect, the second EVOH resin particle has an interface expansion area ratio (Sdr) surface parameter of 0.02 % to 150%, for example, 0.05 % to 150%, 0.50 % to 150%, 5 % to 150%, 35 % to 150%, 60 % to 150%, 95 % to 150%, 100 % to 130%, 82 % to 120% or 73 % to 140%.

[0045] Please refer to ISO 25178:2012 for the definition of the term "interface expansion area ratio (Sdr) surface parameter" which can be regarded as the ratio of the expansion surface area to the defined range area increase within a sampling range.

[0046] According to some embodiments of the disclosure, the first EVOH resin particle has an arithmetic mean height (Sa) surface parameter of 0.0003 µm to 25 µm, for example, 0.0005 µm to 25 µm, 0.0050 µm to 25 µm, 0.0500 µm to 25 µm, 0.5000 µm to 25 µm, 5 µm to 25 µm, 15 µm to 25 µm or 10 µm to 20 µm.In another aspect, the second EVOH resin particle has an arithmetic mean height (Sa) surface parameter of 0.0005 µm to 55 µm, for example, 0.0050 µm to 55 µm, 0.0500 µm to 55 µm, 0.5000 µm to 55 µm, 5 µm to 55 µm, 25 µm to 55 µm, 35 µm to 45 µm, 10 µm to 25 µm, 1 µm to 18 µm or 20 µm to 43 µm.

[0047] Please refer to ISO 25178:2012 for the definition of the term "arithmetic mean height (Sa) surface parameter" which can be regarded as a parameter obtained by performing superficial expansion on Ra (linear arithmetic mean height), denoting the average of the absolute values of height differences at each point on the average surface relative to the surface.

[0048] According to some embodiments of the disclosure, the first EVOH resin particle has a linear arithmetic mean height (Ra) surface parameter of 0.001 µm to 0.990 µm, for example, 0.001 µm to 0.990 µm, 0.001 µm to 0.700 µm, 0.001 µm to 0.500 µm, 0.001 µm to 0.300 µm, 0.010 µm to 0.100 µm, 0.050 µm to 0.990 µm, 0.050 µm to 0.700 µm, 0.050 µm to 0.500 µm, 0.050 µm to 0.300 µm or 0.050 µm to 0.100 µm. In another aspect, the second EVOH resin particle has a linear arithmetic mean height (Ra) surface parameter of 0.001 µm to 0.990 µm, for example, 0.001 µm to 0.990 µm, 0.001 µm to 0.700 µm, 0.001 µm to 0.500 µm, 0.001 µm to 0.300 µm, 0.010 µm to 0.100 µm, 0.050 µm to 0.990 µm, 0.050 µm to 0.700 µm, 0.050 µm to 0.500 µm, 0.050 µm to 0.30 µm or 0.050 µm to 0.100 µm.

[0049] The term "linear arithmetic mean height (Ra) surface parameter" used herein is a parameter for defining surface roughness, and its definition is set forth in JIS B 0601. Specifically speaking, it can be regarded as an average absolute value of an outline on a standard length.

[0050] According to some embodiments of the disclosure, the first EVOH resin particle has a linear maximum height (Rz) surface parameter of 0.001 µm to 9.900 µm, for example, 0.001 µm to 9 µm, 0.001 µm to 7 µm, 0.001 µm to 5 µm, 0.001 µm to 3 µm, 0.050 µm to 5 µm, 0.050 µm to 3 µm, 0.050 µm to 1 µm or 0.050 µm to 0.080 µm. In another aspect, the second EVOH resin particle has a linear maximum height (Rz) surface parameter of 0.001 µm to 9.900 µm, for example, 0.080 µm to 9 µm, 0.100 µm to 9 µm, 0.150 µm to 9 µm, 0.150 µm to 7 µm, 0.500 µm to 5 µm, 0.500 µm to 2.500 µm or 1 µm to 2.500 µm.

[0051] The term "linear maximum height (Rz) surface parameter" is a parameter that defines surface roughness, and its definition is set forth in JIS B 0601. Specifically speaking, it can be regarded as the distance between the highest peak and the lowest trough of an outline relative to a standard length.

[0052] In another aspect, the disclosure provides an ethylene-vinyl alcohol copolymer film formed from the EVOH resin particle composition. Specifically speaking, the ethylene-vinyl alcohol copolymer film is a single-layer thin-film.

[0053] In yet another aspect, the disclosure provides a multilayer structure comprising: (a) at least one layer of the ethylene-vinyl alcohol copolymer film formed from the EVOH resin particle composition; (b) at least one layer of a polymer layer; and (c) at least one layer of a binding layer.

[0054] According to some embodiments of the disclosure, the polymer layer is one selected from the group consisting of a low-density polyethylene layer, polyethylene grafted maleic anhydride layer, polypropylene layer and nylon layer, and the binding layer is a tie layer exemplified by ARKEMA OREVAC 18729 provided by ARKEMA. Specifically speaking, the layers of the multilayer structure are arranged in the following order: a polymer layer, binding layer, ethylene-vinyl alcohol copolymer film, binding layer and polymer layer. According to some embodiments of the disclosure, the polymer layer has a thickness of 100 µm to 500 µm, preferably 200 µm to 400 µm, and more preferably 300 µm, the binding layer has a thickness of 10 µm to 40 µm, preferably 20 µm to 30 µm, and more preferably 25 µm, and the ethylene-vinyl alcohol copolymer film has a thickness of 20 µm to 80 µm, preferably 40 µm to 60 µm, and more preferably 50 µm.

[0055] In the absence of any limitations imposed by any theory, a core region with a valley void volume Vvv of 80% to 100%, i.e., a low-lying region of the surface, is the major factor that affects the gas charge performance of the EVOH resin particle in a screw and thus affects film thickness uniformity and oxygen transmission rate. The first EVOH resin particle has a low melting point and can be controlled to achieve a relatively small Vvv and thus is conducive to having a melting zone positioned backward. By contrast, the second EVOH resin particle with a high melting point can be controlled to achieve a relatively great Vvv so as to speed up gas discharge, and reduce the tiny bubbles otherwise generated from the EVOH resin particles traveling from one single screw to a measurement segment, thereby stabilizing its discharge. Thus, according to the disclosure, an EVOH composition comprising two different types of EVOH particles with controlled Vvv ranges exhibits close particle melting zones to stabilize the outfeeding and thus enhance the film thickness uniformity, oxygen transmission rate and stretchability of the EVOH composition.Embodiment

[0056] Nonrestrictive embodiments for all aspects of the disclosure are provided below to describe all the aspects of the disclosure and the advantages they achieve. The EVOH formula of each example and each comparative example comprises at least two ingredients. The two ingredients of the EVOH resin particle composition of each example and each comparative example are two types of EVOH resin particles.Preparation of EVOH Resin Particle Composition

[0057] A nonrestrictive preparation method for the EVOH resin particle composition is provided and described below. According to a method similar to the method disclosed below, five EVOH resin particle compositions of nonrestrictive embodiments (examples EVOH 1-5) and six EVOH resin particle compositions of comparative examples (comparative examples EVOH 1-6) are prepared. However, a specific method of preparing examples EVOH 1-5 and comparative examples EVOH 1-6 is usually different from the method disclosed below in one or more aspects.First EVOH resin particle in example 1

[0058] 500 kg of vinyl acetate, 100 kg of methanol, 0.0585 kg of acetyl peroxide, and 0.015 kg of citric acid are introduced into a polymerizer with cooling coils. Then, the polymerizer is temporarily filled with nitrogen gas. Next, ethylene is introduced and pressurized until the ethylene pressure reaches 45kg / cm 2< . In the ethylene-pressurized environment, the mixture in the polymerizer is stirred and heated up to 67 °C to start polymerization. After the polymerization has been occurring for six hours, 0.0525 kg of conjugated polyene sorbate functioning as a polymerization inhibitor is added into the polymerizer as soon as the polymerization rate reaches 60%. Thus, an ethylene-vinyl acetate copolymer with a content of 44 mole% of ethylene structural units is obtained. After that, a reaction solution that contains ethylene - vinyl acetate copolymer is supplied to a distillation column, and methanol vapor is introduced into the distillation column via the lower portion thereof to eliminate unreacted vinyl acetate, so as to obtain a methanol solution of ethylene - vinyl acetate copolymer. In this embodiment, ethylene-vinyl acetate copolymer (hereinafter referred to as "EVAC" polymer) formed by the polymerization of ethylene monomer and vinyl acetate monomer undergoes saponification at a saponification degree of 99.5% to form EVOH. Then, EVOH is dissolved in an aqueous solution of alcohol with a methanol-to-water ratio of 70:30. The solution of EVOH / methanol / water is left to stand still at 60 °C for 1 hour to promote the dissolution of EVOH in the solution of EVOH / methanol / water. The solution of EVOH / methanol / water has a solid content of 41 wt%.

[0059] Then, the solution of methanol, water and EVOH undergoes pelletization by strip cutting. Specifically speaking, with a pump, the solution of methanol, water and EVOH is delivered to a feeding pipe at a flow rate of 120 L / min and then introduced into an opening portion mold with a round shape and a diameter of 0.5 mm to squeeze the EVOH solution into a water / methanol mixture solution (with a water / methanol quality ratio of 9 / 1) having a temperature of 5 °C, being thread-shaped at a precipitation outlet and being severed by a rotating knife with a rotation speed of 500 rpm, so as to produce EVOH particles. EVOH particles are cooled down with circulating condensation water of a temperature of 5 °C. Then, the EVOH particles undergoes centrifugation to release EVOH particles. The released EVOH particles are rinsed with water. The centrifugation and rinsing steps are described below. The first instance of centrifugation and rinsing is carried out at a dehydrator rotation speed of 5000 rpm, at a water to wet particle ratio of 10 during delivery, with an open-style delivery-dedicated centrifugal pump, at a delivery pump rotation speed of 3000 rpm, at a water to wet particle weight ratio of 5 during rinsing, and at a water flow speed of 2 m / min during rinsing. The second instance of centrifugation and rinsing is carried out at a dehydrator rotation speed of 2000 rpm. Then, the EVOH particles are immersed in a boric acid / sodium acetate solution, followed by performing three phases of drying and adding calcium stearate to obtain the end product of the EVOH resin particles. The first phase of drying uses a belt dryer in carrying out drying at 80 °C for 2 hours. The second phase of drying uses a belt dryer in carrying out drying at 100 °C for 20 hours. The third phase of drying uses a fluid dryer in carrying out drying at 120 °C for 20 hours to obtain cylindrical EVOH particles each being 5 mm in height with a minor axis of 1 mm. Finally, the particles are delivered for storage.

[0060] The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 152.4 mm, four bends, a pipeline length of 30 m, and a delivery speed of 40 m / min.Second EVOH resin particle of example 1

[0061] The second EVOH resin particle of example 1 is prepared with a method similar to the method described above. The differences of the method for preparing the second EVOH resin particle of example 1 are as follows: performing saponification at a saponification degree of 99.5% on an ethylene-vinyl acetate copolymer (hereinafter referred to as "EVAC") with an ethylene content of 32 mole% to prepare an EVOH polymer; producing cylindrical EVOH particles having a height of 2 mm and a minor axis of 3 mm each with a strip-cutting opening mold having a diameter of 2 mm and with a rotating knife with a rotation speed of 2000 rpm to obtain particles 2 mm in height each; and delivering the particles.

[0062] The aforesaid delivery occurs in the condition as follows: belt-based delivery, a pipeline diameter of 101.6 mm, a belt roughness (Rz) of 40 µm, five bends, a pipeline length of 15 m, and a delivery speed of 20 m / min.

[0063] For the purpose of carrying out a subsequent preparation process, the first EVOH resin particle and the second EVOH resin particle are further mixed at a ratio by weight percentage of 25:75 wt%, with a conical screw mixer (Model No.: CM-2, purchased from She Hui Machinery Co., Ltd.), at a rotation speed of 10 rpm for 5 minutes continuously, so as to prepare the EVOH resin particle composition of example 1.First and second EVOH resin particles of example 2

[0064] First and second EVOH methanol aqueous solutions for use in example 2 are prepared with a preparation process similar to that for preparing the EVOH resin particles of example 1. However, the preparation of the first EVOH methanol aqueous solution of example 2 has the differences as follows: an ethylene content of 48 mole%, and the pelletization step that entails performing pelletization on the solution of methanol, water and EVOH through underwater pelletization. Specifically speaking, with a pump, the solution of methanol, water and EVOH is delivered into a feeding pipe at a flow rate of 120 L / min and then delivered into an input pipe with a diameter of 1 mm before being severed by a rotating knife with a rotation speed of 1500 rpm to obtain EVOH particles. The EVOH particles are cooled down with circulating condensation water of a temperature of 5 °C. Then, the EVOH particles undergo centrifugation to release the EVOH particles. The released EVOH particles are rinsed with water. Next, the second instance of the centrifugation-based dehydration step is carried out. After that, the EVOH particles are immersed in a boric acid / sodium acetate solution, followed by performing a drying step and adding calcium stearate to obtain the end product of the EVOH resin particles. The drying step produces EVOH ellipsoidal particles each having a major axis of 3 mm and a minor axis of 2 mm. The aforesaid delivery occurs in the condition as follows: belt-based delivery, a pipeline diameter of 177.8 mm, a belt roughness (Rz) of 30 µm, six bends, a pipeline length of 15 m, and a delivery speed of 25 m / min. In another aspect, the preparation of the second EVOH methanol aqueous solution in example 2 has the differences as follows: an ethylene content of 27 mole%, a preparation process similar to that for preparing the first EVOH resin particle of example 2, and an input pipe with a diameter of 2 mm. The dried EVOH particles are spherical particles each having a minor axis of 3 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 127 mm, four bends, a pipeline length of 20 m, and a delivery speed of 30 m / min. Furthermore, the first EVOH resin particle and second EVOH resin particle are further mixed at a ratio by weight percentage of 10:90 wt% to prepare the EVOH resin particle composition of example 2.First and second EVOH resin particles of example 3

[0065] First and second EVOH methanol aqueous solutions for use in example 3 are prepared by a preparation process similar to that for preparing the EVOH resin particles of example 2. However, the preparation of the first EVOH methanol aqueous solution of example 3 has the differences as follows: an ethylene content of 38 mole%, and the pelletization step that entails performing pelletization on the solution of methanol, water and EVOH through underwater pelletization. Specifically speaking, with a pump, the solution of methanol, water and EVOH is delivered at a flow rate of 120 L / min to a feeding pipe and then delivered into an input pipe with a diameter of 0.5 mm before being severed by a rotating knife with a rotation speed of 3000 rpm to obtain EVOH particles. The EVOH particles are cooled down with circulating condensation water of a temperature of 5 °C. Then, the EVOH particles undergo centrifugation to release the EVOH particles. The released EVOH particles are rinsed with water. Next, the second instance of the centrifugation-based dehydration step is carried out. After that, the EVOH particles are immersed in a boric acid / sodium acetate solution, followed by performing a drying step and adding calcium stearate to obtain the end product of the EVOH resin particles. The drying step produces EVOH spherical particles each having a minor axis of 1 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 101.6 mm, three bends, a pipeline length of 30 m, and a delivery speed of 25 m / min. In another aspect, the preparation of the second EVOH methanol aqueous solution of example 3 has the differences as follows: an ethylene content of 29 mole%, a preparation process similar to that for preparing the EVOH resin particles of example 1, a strip-cutting opening mold with a diameter of 4 mm, and a rotating knife with a rotation speed of 3000 rpm. The drying step produces EVOH cylindrical particles each having a height of 1 mm and a minor axis of 5 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 76.2 mm, seven bends, a pipeline length of 20 m, and a delivery speed of 35 m / min. Furthermore, the first EVOH resin particle and second EVOH resin particle are further mixed at a ratio by weight percentage of 50:50 wt% to prepare the EVOH resin particle composition of example 3.First and second EVOH resin particles of example 4

[0066] First and second EVOH methanol aqueous solutions for use in example 4 are prepared with a preparation process similar to that for preparing the EVOH resin particles of example 2. The preparation of the first EVOH methanol aqueous solution of example 4 has the differences as follows: an ethylene content of 48 mole%, and the pelletization step that entails performing pelletization on the solution of methanol, water and EVOH through underwater pelletization. Specifically speaking, with a pump, the solution of methanol, water and EVOH is delivered at a flow rate of 120 L / min to a feeding pipe and then delivered into an input pipe with a diameter of 0.5 mm before being severed by a rotating knife with a rotation speed of 500 rpm to obtain EVOH particles. The EVOH particles are cooled down with circulating condensation water of a temperature of 5 °C. Then, the EVOH particles undergo centrifugation to release the EVOH particles. The released EVOH particles are rinsed with water. Next, the second instance of the centrifugation-based dehydration step is carried out. After that, the EVOH particles are immersed in a boric acid / sodium acetate solution, followed by performing a drying step and adding calcium stearate to obtain the end product of the EVOH resin particles. The drying step produces EVOH ellipsoidal particles each having a major axis of 5 mm and a minor axis of 1 mm. The aforesaid delivery occurs in the condition as follows: belt-based delivery, a pipeline diameter of 76.3 mm, a belt roughness (Rz) of 50 µm, three bends, a pipeline length of 20 m, and a delivery speed of 20 m / min. In another aspect, the preparation of the second EVOH methanol aqueous solution of example 4 has the differences as follows: an ethylene content of 32 mole%, a preparation process similar to that for preparing the first EVOH resin particle of example 1, a strip-cutting opening mold with a diameter of 2 mm, and a rotating knife with a rotation speed of 1500 rpm. The drying step produces EVOH cylindrical particles each having a height of 3 mm and a minor axis of 3 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 101.6 mm, two bends, a pipeline length of 15 m, and a delivery speed of 25 m / min. Furthermore, the first EVOH resin particle and second EVOH resin particle are further mixed at a ratio by weight percentage of 15:85 wt% to prepare the EVOH resin particle composition of example 4.First and second EVOH resin particles of example 5

[0067] First and second EVOH methanol aqueous solutions for use in example 5 are prepared with a preparation process similar to that for preparing the EVOH resin particles of example 2. However, the preparation of the first EVOH methanol aqueous solution of example 5 has the differences as follows: an ethylene content of 38 mole%, and the pelletization step that entails performing pelletization on the solution of methanol, water and EVOH through underwater pelletization. Specifically speaking, with a pump, the solution of methanol, water and EVOH is delivered at a flow rate of 120 L / min to a feeding pipe and then delivered into an input pipe with a diameter of 1 mm before being severed by a rotating knife with a rotation speed of 1000 rpm to obtain EVOH particles. The EVOH particles are cooled down with circulating condensation water of a temperature of 5°C. Then, the EVOH particles undergo centrifugation to release the EVOH particles. The released EVOH particles are rinsed with water. Next, the second instance of the centrifugation-based dehydration step is carried out. After that, the EVOH particles are immersed in a boric acid / sodium acetate solution, followed by performing a drying step and adding calcium stearate to obtain the end product of the EVOH resin particles. The drying step produces EVOH ellipsoidal particles each having a major axis of 4 mm and a minor axis of 2 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 127 mm, four bends, a pipeline length of 30 m, and a delivery speed of 20 m / min. In another aspect, the preparation of the second EVOH methanol aqueous solution of example 5 has the differences as follows: an ethylene content of 24 mole%, using an input pipe with a diameter of 0.5 mm to facilitate cutting, and using a rotating knife with a rotation speed of 1000 rpm to carry out cutting. The drying step produces EVOH ellipsoidal particles each having a major axis of 4 mm and a minor axis of 1 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 152.4 mm, five bends, a pipeline length of 20 m, and a delivery speed of 30 m / min. Furthermore, the first EVOH resin particle and second EVOH resin particle are further mixed at a ratio by weight percentage of 35:65 wt% to prepare the EVOH resin particle composition of example 5.First and second EVOH resin particles of comparative example 1

[0068] First and second EVOH methanol aqueous solutions for use in comparative example 1 are prepared with a preparation process similar to that for preparing the EVOH resin particles of example 2. However, the preparation of the first EVOH methanol aqueous solution of comparative example 1 has the differences as follows: an ethylene content of 44 mole%, and the pelletization step that entails performing pelletization on the solution of methanol, water and EVOH through underwater pelletization. Specifically speaking, with a pump, the solution of methanol, water and EVOH is delivered at a flow rate of 120 L / min to a feeding pipe and then delivered into an input pipe with a diameter of 2.5 mm before being severed by a rotating knife with a rotation speed of 1200 rpm to obtain EVOH particles. The EVOH particles are cooled down with circulating condensation water of a temperature of 5°C. Then, the EVOH particles undergo centrifugation to release the EVOH particles. The released EVOH particles are rinsed with water. Next, the second instance of the centrifugation-based dehydration step is carried out. After that, the EVOH particles are immersed in a boric acid / sodium acetate solution, followed by performing a drying step and adding calcium stearate to obtain the end product of the EVOH resin particles. The drying step produces EVOH spherical particles each having a minor axis of 3.5 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 177.8 mm, no bends, a pipeline length of 5 m, and a delivery speed of 5 m / min. In another aspect, the preparation of the second EVOH methanol aqueous solution of comparative example 1 has the differences as follows: an ethylene content of 29 mole%, a preparation process similar to that for preparing the EVOH resin particles of example 1, a strip-cutting opening mold with a diameter of 3.5 mm, and a rotating knife with a rotation speed of 500 rpm. The drying step produces EVOH cylindrical particles each having a height of 5 mm and a minor axis of 4.5 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 203.2 mm, one bend, a pipeline length of 10 m, and a delivery speed of 15 m / min. Furthermore, the first EVOH resin particle and second EVOH resin particle are further mixed at a ratio by weight percentage of 5:95 wt% to prepare the EVOH resin particle composition of comparative example 1.First and second EVOH resin particles of comparative example 2

[0069] First and second EVOH methanol aqueous solutions for use in comparative example 2 are prepared with a preparation process similar to that for preparing the EVOH resin particles of example 2. However, the preparation of the first EVOH methanol aqueous solution of comparative example 2 has the differences as follows: an ethylene content of 35 mole%, and the pelletization step that entails performing pelletization on the solution of methanol, water and EVOH through underwater pelletization. Specifically speaking, with a pump, the solution of methanol, water and EVOH is delivered at a flow rate of 120 L / min to a feeding pipe and then delivered into an input pipe with a diameter of 1 mm before being severed by a rotating knife with a rotation speed of 1500 rpm to obtain EVOH particles. The EVOH particles are cooled down with circulating condensation water of a temperature of 5°C. Then, the EVOH particles undergo centrifugation to release the EVOH particles. The released EVOH particles are rinsed with water. Next, the second instance of the centrifugation-based dehydration step is carried out. After that, the EVOH particles are immersed in a boric acid / sodium acetate solution, followed by performing a drying step and adding calcium stearate to obtain the end product of the EVOH resin particles. The drying step produces EVOH ellipsoidal particles each having a major axis of 3 mm and a minor axis of 2 mm. The aforesaid delivery occurs in the condition as follows: belt-based delivery, a pipeline diameter of 152.4 mm, a belt roughness (Rz) of 10 µm, two bends, a pipeline length of 10 m, and a delivery speed of 10 m / min. In another aspect, the preparation of the second EVOH methanol aqueous solution of comparative example 2 has the differences as follows: an ethylene content of 24 mole%, a preparation process similar to that for preparing the EVOH resin particles of example 1, a strip-cutting opening mold with a diameter of 1 mm, and a rotating knife with a rotation speed of 1000 rpm. The drying step produces EVOH cylindrical particles each having a height of 4 mm and a minor axis of 2 mm. The aforesaid delivery occurs in the condition as follows: belt-based delivery, a pipeline diameter of 12.7 mm, a belt roughness (Rz) of 100 µm, nine bends, a pipeline length of 70 m, and a delivery speed of 50 m / min. Furthermore, the first EVOH resin particle and second EVOH resin particle are further mixed at a ratio by weight percentage of 75:25 wt% to prepare the EVOH resin particle composition of comparative example 2.First and second EVOH resin particles of comparative example 3

[0070] First and second EVOH methanol aqueous solutions for use in comparative example 3 are prepared with a preparation process similar to that for preparing the EVOH resin particles of example 1. However, the preparation of the first EVOH methanol aqueous solution of comparative example 3 has the differences as follows: an ethylene content of 48 mole%, a strip-cutting opening mold with a diameter of 3 mm, and a rotating knife with a rotation speed of 1700 rpm. The drying step produces EVOH cylindrical particles each having a height of 2.5 mm and a minor axis of 4 mm. The aforesaid delivery occurs in the condition as follows: belt-based delivery, a pipeline diameter of 25.4 mm, a belt roughness (Rz) of 150 µm, 10 bends, a pipeline length of 100 m, and a delivery speed of 30 m / min. In another aspect, the preparation of the second EVOH methanol aqueous solution of comparative example 3 has the differences as follows: an ethylene content of 32 mole%, a preparation process similar to that for preparing the EVOH resin particles of example 1, a strip-cutting opening mold with a diameter of 2 mm, and a rotating knife with a rotation speed of 1200 rpm. The drying step produces EVOH cylindrical particles each having a height of 3.5 mm and a minor axis of 3 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 50.8 mm, eight bends, a pipeline length of 90 m, and a delivery speed of 50 m / min. Furthermore, the first EVOH resin particle and second EVOH resin particle are further mixed at a ratio by weight percentage of 15:85 wt% to prepare the EVOH resin particle composition of comparative example 3.First and second EVOH resin particle of comparative example 4

[0071] First and second EVOH methanol aqueous solutions for use in comparative example 4 are prepared with a preparation process similar to that for preparing the EVOH resin particles of example 2. The preparation of the first EVOH methanol aqueous solution of comparative example 4 has the differences as follows: an ethylene content of 38 mole%, and the pelletization step that entails performing pelletization on the solution of methanol, water and EVOH through underwater pelletization. Specifically speaking, with a pump, the solution of methanol, water and EVOH is delivered at a flow rate of 120 L / min to a feeding pipe and then delivered into an input pipe with a diameter of 0.5 mm before being severed by a rotating knife with a rotation speed of 3000 rpm to obtain EVOH particles. The EVOH particles are cooled down with circulating condensation water of a temperature of 5 °C. Then, the EVOH particles undergo centrifugation to release the EVOH particles. The released EVOH particles are rinsed with water. Next, the second instance of the centrifugation-based dehydration step is carried out. After that, the EVOH particles are immersed in a boric acid / sodium acetate solution, followed by performing a drying step and adding calcium stearate to obtain the end product of the EVOH resin particles. The drying step produces EVOH spherical particles each having a minor axis of 1 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 101.6 mm, five bends, a pipeline length of 20 m, and a delivery speed of 20 m / min. In another aspect, the preparation of the second EVOH methanol aqueous solution in comparative example 4 has the differences as follows: an ethylene content of 27 mole%, using a preparation process similar to that for preparing the first EVOH resin particle of example 2, using an input pipe with a diameter of 3 mm to facilitate cutting, and using a rotating knife with a rotation speed of 1000 rpm to carry out cutting. The drying step produces EVOH spherical particles each having a minor axis of 4 mm. The aforesaid delivery occurs in the condition as follows: belt-based delivery, a pipeline diameter of 25.4 mm, a belt roughness (Rz) of 10 µm, eight bends, a pipeline length of 80 m, and a delivery speed of 10 m / min. Furthermore, the first EVOH resin particle and second EVOH resin particle are further mixed at a ratio by weight percentage of 10:90 wt% to prepare the EVOH resin particle composition of comparative example 4.First and second EVOH resin particle of comparative example 5

[0072] First and second EVOH methanol aqueous solutions for use in comparative example 5 are prepared with a preparation process similar to that for preparing the EVOH resin particles of example 2. The preparation of the first EVOH methanol aqueous solution of comparative example 5 has the differences as follows: an ethylene content of 44 mole%, and the pelletization step that entails performing pelletization on the solution of methanol, water and EVOH through underwater pelletization. Specifically speaking, with a pump, the solution of methanol, water and EVOH is delivered at a flow rate of 120 L / min to a feeding pipe and then delivered into an input pipe with a diameter of 2.5 mm before being severed by a rotating knife with a rotation speed of 1000 rpm to obtain EVOH particles. The EVOH particles are cooled down with circulating condensation water of a temperature of 5 °C. Then, the EVOH particles undergo centrifugation to release the EVOH particles. The released EVOH particles are rinsed with water. Next, the second instance of the centrifugation-based dehydration step is carried out. After that, the EVOH particles are immersed in a boric acid / sodium acetate solution, followed by performing a drying step and adding calcium stearate to obtain the end product of the EVOH resin particles. The drying step produces EVOH ellipsoidal particles each having a major axis of 4 mm and a minor axis of 3.5 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 203.2 mm, no bends, a pipeline length of 5 m, and a delivery speed of 60 m / min. In another aspect, the preparation of the second EVOH methanol aqueous solution of comparative example 5 has the differences as follows: an ethylene content of 29 mole%, using a preparation process similar to that for preparing the first EVOH resin particle of example 2, using an input pipe with a diameter of 0.5 mm to facilitate cutting, and using a rotating knife with a rotation speed of 1700 rpm to carry out cutting. The drying step produces EVOH ellipsoidal particles each having a major axis of 2.5 mm and a minor axis of 1 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 76.2 mm, three bends, a pipeline length of 20 m, and a delivery speed of 25 m / min. Furthermore, the first EVOH resin particle and second EVOH resin particle are further mixed at a ratio by weight percentage of 20:80 wt% to prepare the EVOH resin particle composition of comparative example 5.First and second EVOH resin particle of comparative example 6

[0073] First and second EVOH methanol aqueous solutions for use in comparative example 6 are prepared with a preparation process similar to that for preparing the EVOH resin particles of example 2. The preparation of the first EVOH methanol aqueous solution of comparative example 6 has the differences as follows: an ethylene content of 38 mole%, and the pelletization step that entails performing pelletization on the solution of methanol, water and EVOH through underwater pelletization. Specifically speaking, with a pump, the solution of methanol, water and EVOH is delivered at a flow rate of 120 L / min to a feeding pipe and then delivered into an input pipe with a diameter of 1.5 mm before being severed by a rotating knife with a rotation speed of 1700 rpm to obtain EVOH particles. The EVOH particles are cooled down with circulating condensation water of a temperature of 5 °C. Then, the EVOH particles undergo centrifugation to release the EVOH particles. The released EVOH particles are rinsed with water. Next, the second instance of the centrifugation-based dehydration step is carried out. After that, the EVOH particles are immersed in a boric acid / sodium acetate solution, followed by performing a drying step and adding calcium stearate to obtain the end product of the EVOH resin particles. The drying step produces EVOH spherical particles each having a minor axis of 2.5 mm. The aforesaid delivery occurs in the condition as follows: air delivery, a pipeline diameter of 50.8 mm, 10 bends, a pipeline length of 70 m, and a delivery speed of 40 m / min. In another aspect, the preparation of the second EVOH methanol aqueous solution of comparative example 6 has the differences as follows: an ethylene content of 32 mole%, a preparation process similar to that for preparing the first EVOH resin particle of example 2, an input pipe with a diameter of 0.5 mm, and a rotating knife with a rotation speed of 1000 rpm. The drying step produces EVOH ellipsoidal particles each having a major axis of 4 mm and a minor axis of 1 mm. The aforesaid delivery occurs in the condition as follows: belt-based delivery, a pipeline diameter of 152.4, a belt roughness (Rz) of 20 µm, five bends, a pipeline length of 20 m, and a delivery speed of 20 m / min. Furthermore, the first EVOH resin particle and second EVOH resin particle are further mixed at a ratio by weight percentage of 35:65 wt% to prepare the EVOH resin particle composition of comparative example 6.Parameters Related to EVOH Resin Particles

[0074] Parameters related to the EVOH resin particles of the disclosure and techniques for assessing / analyzing the parameters are described below.Particle surface roughness

[0075] To assess / analyze the surface roughness of the EVOH resin particles in the aforesaid embodiments, it is desirable to place the EVOH resin particles flatly on a board to undergo measurement of the particle surface roughness. The measurement process entails eliminating whatever data associated with a tilting angle greater than 0.5 to ensure the scanning planes relatively horizontal (tilting angle = surface maximum height Sz / border length 129 µm of the analysis range). The required laser microscope is LEXT OLS5000-SAF manufactured by Olympus, carrying out imaging at an air temperature of 24 ± 3 °C and a relative humidity of 63 ± 3%. The filter in use is configured to operate in the "no filtering" state. The required light source has a wavelength of 405 nm. The objective lens is capable of 100x magnification (MPLAPON-100xLEXT). The optical zoom is set to 1.0x. The image area is set to be 129 µm x 129 µm (The measurement of Rz is performed by focusing on the central axis in the image area.) The resolution is set to be 1024 pixels x 1024 pixels. The numerical values of 100 particles are measured, and then the average is calculated. The parameters Sdq, Sdr, Sa and Sv are measured with the techniques set forth in SO 25178:2012, whereas the parameters Ra and Rz are measured with the techniques set forth in JIS B 0601 (2001).Ethylene Content Analysis

[0076] To assess / analyze the ethylene content of the EVOH resin particles in the aforesaid embodiments, the disclosure entails using a Raman spectrometer (manufactured by UniDRON) to measure the ethylene content of each EVOH resin particle at five points thereof randomly with a laser source having a wavelength of 473nm and calculate the average, using the average as the ethylene content value of the EVOH resin particle samples.Melting Point Analysis

[0077] The melting point of the EVOH resin particles is measured by the DSC Q200 device (TZERO TECHNOLOGIES, INC., with the lid (Tzero lid) being TA instrument T 170607, and the pan (Tzero pan) being TA instrument T 170620) with the techniques set forth in ISO 11357-3-2011.

[0078] In practice, in the absence of any limitations imposed by a specific theory, in case of a large number of EVOH resin particles, only 100 EVOH resin particles may be selected to obtain individual ethylene content with a related technique of analysis of ethylene contents. Then, those EVOH resin particles which have an ethylene content of 35 mole% to 48 mole% are allocated to the category of EVOH resin particles with a low melting point of 135 °C to 179 °C, whereas those EVOH resin particles which have an ethylene content of 24 mole% to 34 mole% are allocated to the category of EVOH resin particles with a high melting point of 180 °C to 198 °C. Furthermore, 10 EVOH resin particles are randomly selected from each of the category of EVOH resin particles with a low melting point and the category of EVOH resin particles with a high melting point to calculate their surface roughness with a surface parameter assay technique and then determine their melting points with a melting point assay technique.Preparation and Analysis of Single-Layer EVOH Film

[0079] With the technique described below, films are formed from EVOH resin particle compositions of examples 1 to 5 and comparative examples 1 to 6, respectively. The EVOH resin particle compositions of examples 1 to 5 and comparative examples 1 to 6 are fed to a single screw extruder (Model No.: ME25 / 5800V4; brand: OCS) to undergo extrusion in order to prepare single-layer thin-films. The films formed from the EVOH resin particle compositions of examples 1 to 5 and comparative examples 1 to 6 have a thickness of 20 µm each. The temperature of the extruder is set to 220 °C, and the rotation frequency of the screw is set to 7 rpm (rotations per minute).

[0080] Furthermore, the film thickness uniformity of the single-layer thin-films of the examples 1 to 5 and comparative examples 1 to 6 is analyzed with a thickness gauge (Model No.: SM-114; manufactured by UniDRON) by measuring the film thickness at five points of each thin-film randomly and then calculating their standard deviations. Finally, the findings are displayed by marking the sign "O" to indicate a standard deviation less than 0.3, the sign "△" to indicate a standard deviation equal to 0.3 to 0.5, and the sign "X" to indicate a standard deviation greater than 0.5.

[0081] Furthermore, the film stretching rate of the single-layer thin-films of the examples 1 to 5 and comparative examples 1 to 6 is analyzed as described below. A thin-film with a thickness of 180 µm is formed from EVOH with a single screw extruder. The thin-film thus formed is cut to acquire the required properties of MD 30* TD 90 mm (TD (transverse direction) is also known as "width direction"; MD (machine direction) is also known as "machine direction" or "longitudinal lengthwise direction") and then left to stand still at 130 °C for 30 minutes. Next, the thin-film undergoes a tensile force test with ASTM D882 at a tensile force speed of 1000 mm / min along the directions MD and TD. The term "stretching rate (%)" used herein is defined as [(after-stretch length - before-stretch length) / before-stretch length]*100%. The findings are displayed by marking the sign "O" to indicate a stretching rate greater than 1000 %, the sign "△" to indicate a stretching rate equal to 800 to 1000 %, and the sign "X" to indicate a stretching rate less than 800 %.

[0082] According to the disclosure, gas barrier properties of a thin-film are evaluated by measuring the oxygen transmission rate (OTR) of the thin-film as described below. The OTR of the single-layer thin-films of the examples 1 to 5 and comparative examples 1 to 6 is measured with OX-TRAN Model 2 / 22oxygen transmission rate tester (Mocon), using a related technique set forth in ISO 14663-2. The OTR test is carried out at a relative humidity of 65% and a temperature of 20°C, using the unit as follows: cm 3< *20 µm / m 2< *24Hrs*atm. The findings are displayed by marking the sign "O" to indicate an OTR less than 0.7cm 3< *20 µm / m 2< *24Hrs*atm, the sign "△" to indicate an OTR equal to 0.7 to 1cm 3< *20 µm / m 2< *24Hrs*atm, and the sign "X" to indicate an OTR greater than 1cm 3< *20 µm / m 2< *24Hrs*atm. Then, their standard deviations are calculated. The findings are displayed by marking the sign "O" to indicate a standard deviation less than 0.1, the sign "△" to indicate a standard deviation equal to 0.1 to 1, and the sign "X" to indicate a standard deviation greater than 1.Preparation of Multilayer Structure

[0083] Tie layers (for example, OREVAC ®< 18729, Arkema), polypropylene, and the EVOH resin particle compositions of examples 1 to 5 and comparative examples 1 to 6 undergo coextrusion to form multilayer films of examples 1 to 5 and comparative examples 1 to 6, respectively. The multilayer films each have five layers. Specifically speaking, EVOH particles (I), polypropylene(II) and binding resin (III) are each fed to a five-layer coextrusion film-forming machine to prepare multilayer sheets (II) / (III) / (I) / (III) / (II) with the structures described below and with thickness of 300 / 25 / 50 / 25 / 300 µm, respectively.Analysis of Findings in Embodiments and Comparative Examples

[0084] The EVOH resin particle compositions of examples 1 to 5 and comparative examples 1 to 6 are compared in terms of resultant thin-film thickness uniformity, resultant thin-film oxygen transmission rate (OTR), and resultant thin-film stretchability. The findings are shown in Table 1 and Table 2.

[0085] The findings shown in Table 1 and Table 2 are explained below. Regarding the EVOH resin particle compositions of examples 1 to 5, the surface valley void volume (Vvv) of all the first EVOH resin particles falls within the range of 0.00003 µm 3< / µm 2< to 2 µm 3< / µm 2< , and the surface valley void volume (Vvv) of all the second EVOH resin particles falls within the range of 0.00005 µm 3< / µm 2< to 10 µm 3< / µm 2< , allowing the thin-films thus formed to exhibit satisfactory film thickness uniformity, oxygen exchange rate and stretchability. By contrast, regarding the EVOH resin particle compositions of comparative examples 1 to 6, the surface valley void volume (Vvv) of the first and second EVOH resin particles does not fall within the required numerical value range, causing the thin-films thus formed to exhibit poor film thickness uniformity, oxygen exchange rate and stretchability. Preferably, the second EVOH resin particle has a greater Vvv than the first EVOH resin particle. Preferably, the first EVOH resin particle has a melting point of 135 °Cto 179 °C, and the second EVOH resin particle has a melting point of 180 °C to 198 °C. Preferably, the first EVOH resin particle has an ethylene content of 36 mole% to 50 mole%, and the second EVOH resin particle has an ethylene content of 20 mole% to 35 mole%.

[0086] A further comparison of Table 1 and Table 2 reveals additional findings described below. Although the first EVOH resin particle of the EVOH resin particle composition of comparative example 4, the second EVOH resin particle of the EVOH resin particle composition of comparative example 5, and the second EVOH resin particle of the EVOH resin particle composition of comparative example 6 fall within the ranges of Vvv values of the first / second EVOH resin particles defined by the disclosure, respectively, none of the other EVOH resin particles of the EVOH resin particle compositions falls within the ranges of Vvv values. Thus, it is only when both of the two types of EVOH resin particles of an EVOH resin particle composition fall within the Vvv value range defined by the disclosure that the two EVOH resins can exhibit satisfactory miscibility and thereby enable thin-films thus formed to exhibit satisfactory film thickness uniformity, oxygen exchange rate and stretchability.

[0087] Yet another comparison of Table 1 and Table 2 reveals additional findings described below. By adjusting the delivery of EVOH particles, it is feasible to attain the surface roughness anticipated by the disclosure and thus achieve advantageous technical features as follows: appropriate pipeline dimensions (preferably controlling pipeline dimensions to fall within the range of 76.2 mm to 177.8 mmin air delivery and belt-based delivery); appropriate roughness of the belt in belt-based delivery (preferably controlling Rz to fall within the range of 30 µm to 50 µm); an appropriate number of bends (preferably controlling the number of bends to fall within the range of 3 to 7 in air delivery, and preferably controlling the number of bends to fall within the range of 3 to 6 in belt-based delivery); appropriate pipeline length (preferably controlling pipeline length to fall within the range of 15 m to 30 m in air delivery, and preferably controlling pipeline length to fall within the range of 15 m to 20 m in belt-based delivery); and appropriate delivery speed (preferably controlling delivery speed to fall within the range of 20 m / min to 40 m / min in air delivery, and preferably controlling delivery speed to fall within the range of 20 m / min to 25 m / min in belt-based delivery). Being above the upper limit of the range can cause collisions between the particles during delivery and thereby an increase in the roughness of the EVOH particles. Conversely, being below the lower limit of the range can cause the roughness of the EVOH particles to decrease and fall outside the roughness range anticipated by the disclosure.

[0088] In conclusion, the disclosure provides an EVOH resin composition comprising a first EVOH resin particle with a surface valley void volume (Vvv) of 0.00003 µm 3< / µm 2< to 2 µm 3< / µm 2< and a second EVOH resin particle with a surface valley void volume (Vvv) of 0.00005 µm 3< / µm 2< to 10 µm 3< / µm 2< . The control over the surface roughness of the EVOH resin composition is attained by controlling the factors in the delivery stage of the EVOH preparation process. The EVOH resin composition is for use in preparing a film or a multilayer structure. The inventor found that, the disclosure is effective in improving the thickness uniformity and stretchability of the film prepared and reducing the oxygen transmission rate by controlling the range of the surface valley void volume of the EVOH particles.

[0089] All the ranges set forth herein are intended to include every specific range that lies within a given range and include a combination of sub-ranges lying within the given range. Unlesss otherwise specified, every range set forth herein includes the endpoints of the range. Therefore, for example, "a range 1-5" means 1, 2, 3, 4 and 5 and includes sub-ranges, such as 2-5, 3-5, 2-3, 2-4, and 1-4.

Claims

1. An ethylene-vinyl alcohol copolymer (EVOH) resin particle composition, comprising: a first EVOH resin particle having a surface valley void volume (Vvv) of 0.00003 to 2 µm3 / µm2; and a second EVOH resin particle having a surface valley void volume (Vvv) of 0.00005 to 10 µm3 / µm2; wherein the surface valley void volume (Vvv) of the second EVOH resin particle is greater than the surface valley void volume (Vvv) of the first EVOH resin particle, and the surface valley void volume (Vvv) is measured according to the description.

2. The EVOH resin particle composition of claim 1, wherein the first EVOH resin particle has a melting point of 135 to 179 °C, and the second EVOH resin particle has a melting point of 180 to 198 °C.

3. The EVOH resin particle composition of claim 1 or 2, wherein the first EVOH resin particle has an ethylene content of 36 to 50 mole% and / or the second EVOH resin particle has an ethylene content of 20 to 35 mole%; wherein the ethylene contents of the first EVOH resin particle and the second EVOH resin particle are measured according to the description.

4. The EVOH resin particle composition of claim 1 or 2, wherein the EVOH resin particle is cylindrical, elliptic cylindrical, prismoidal, spherical, ellipsoidal or biconvex-disk-shaped and has a major axis or height of 1 to 5 mm and a minor axis of 1 to 5 mm, wherein the major axis or height corresponds to the longest outer diameter of the surface of the EVOH resin particle and the minor axis corresponds to the shortest diameter of the EVOH resin particle perpendicular to the major axis or height.

5. The EVOH resin particle composition of claim 1 or 2 which has a ratio of the first EVOH resin particle to the second EVOH resin particle by weight percentage ranges from 5 : 95 to 75 : 25.

6. The EVOH resin particle composition of claim 1 or 2, further comprising a boron content of 5 to 550 ppm.

7. The EVOH resin particle composition of claim 1 or 2, further comprising an alkali metal content of 10 to 550 ppm.

8. The EVOH resin particle composition of claim 1 or 2, wherein the first EVOH resin particle has a maximum trough depth (Sv) of 0.0005 to 25 µm, and the second EVOH resin particle has a maximum trough depth (Sv) of 0.001 to 75 µm; and / or wherein the first EVOH resin particle has a root-mean-square slope (Sdq) surface parameter of 0.0001 to 15, and the second EVOH resin particle has a root-mean-square slope (Sdq) surface parameter of 0.0002 to 50, wherein the maximum trough depth (Sv) and the root-mean-square slope (Sdq) surface parameter are measured according to the description.

9. The EVOH resin particle composition of claim 1 or 2, wherein the first EVOH resin particle has an interface expansion area ratio (Sdr) surface parameter of 0.001 to 60 %, and the second EVOH resin particle has an interface expansion area ratio (Sdr) surface parameter of 0.02 to 150 %; and / or wherein the first EVOH resin particle has an arithmetic mean height (Sa) surface parameter of 0.0003 to 25 µm, and the second EVOH resin particle has an arithmetic mean height (Sa) surface parameter of 0.0005 to 55 µm, wherein the interface expansion area ratio (Sdr) surface parameter and the arithmetic mean height (Sa) surface parameter are measured according to the description.

10. The EVOH resin particle composition of claim 1 or 2, wherein the first EVOH resin particle has a linear arithmetic mean height (Ra) surface parameter of 0.001 to 0.990 µm, and the second EVOH resin particle has a linear arithmetic mean height (Ra) surface parameter of 0.001 to 0.990 µm; and / or wherein the first EVOH resin particle has a linear maximum height (Rz) surface parameter of 0.001 to 9.900 µm, and the second EVOH resin particle has a linear maximum height (Rz) surface parameter of 0.001 to 9.900 µm, wherein the linear arithmetic mean height (Ra) surface parameter and the linear maximum height (Rz) surface parameter are measured according to the description.