JP2007091325A - Corrugated board made of polyolefin-based resin and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corrugated board made of polyolefin-based resin which is excellent in conductivity, flame retardancy, and mechanical strength. <P>SOLUTION: The corrugated board made of the polyolefin-based resin includes two liners placed oppositely in parallel or approximately parallel to each other and a rib provided between both liners to couple the liners. At least one of the liners is a multilayered liner formed of two or more layers including an internal layer and a surface layer containing a conduction agent. In addition, the liner other than the surface layer and the rib in the corrugated board made of the polyolefin-based resin contains a flame retardant. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a polyolefin resin corrugated board structure plate having excellent conductivity and flame retardancy and excellent mechanical strength, and a method for producing the polyolefin resin cardboard structure board.

A polyolefin resin corrugated cardboard structural board, so-called plastic corrugated board, having two liner parts arranged in parallel or substantially parallel to each other and ribs provided between the liner parts so as to connect both liner parts Has been conventionally used as a returnable box, building material, and the like because of its excellent balance between lightness and strength. However, such a corrugated cardboard made of polyolefin resin is easily combusted and easily charged, and therefore cannot be used for applications such as building materials such as walls and electronic / electrical members.

On the other hand, as the flame retardant conductive resin composition, (B) polystyrene-based thermoplastic elastomer and / or polyolefin-based thermoplastic elastomer 10-80 parts by weight with respect to (A) polyethylene resin and / or polypropylene resin 100 parts by weight, And (C) dibutyl phthalate (hereinafter abbreviated as DBP) consisting of 30 to 100 parts by weight of carbon black having an oil absorption of 20 to 150 g / ml, and a total of 100 parts by weight of the above (A), (B) and (C) On the other hand, a flame-retardant conductive resin composition comprising (D) 30 to 50 parts by weight of a phosphorus-based flame retardant is known (see Patent Document 1).

JP 2003-96247 A

However, when an attempt is made to produce a resin corrugated board using the flame retardant conductive resin composition as described above, the molding itself is difficult because the flame retardant and the conductive agent are contained in a large amount relative to the resin. Even when it can be molded, there is a problem that the mechanical strength of the corrugated board obtained is insufficient.
An object of the present invention is to provide a polyolefin resin corrugated board structure plate having excellent electrical conductivity and flame retardancy and excellent mechanical strength, and a method for producing the polyolefin resin cardboard structure board.

That is, the present invention relates to a polyolefin resin corrugated cardboard having two liner portions arranged facing each other in parallel or substantially in parallel and a rib portion provided between the liner portions so as to connect both liner portions. In the structure board, at least one liner part is a multilayer liner part formed of two or more layers of a surface layer containing an inner layer and a conductive agent, and the liner other than the surface layer in the polyolefin resin corrugated cardboard structure board It is a corrugated board made of polyolefin resin in which a flame retardant is contained in the part and the rib part.
Further, the present invention is a method for integrally molding a polyolefin resin-made corrugated cardboard structure board by multilayer extrusion molding, and the conductive agent-containing resin composition constituting the surface layer has an MFR (MFRs) at 230 ° C. of 0.1 to 10 g / The MFR (MFRc) at 230 ° C. of the flame retardant-containing resin composition constituting the inner layer and the rib part is 0.1 to 10 g / min, and the MFRs / MFRc is 0.1 to 1.0. It is a manufacturing method of a certain corrugated board made of polyolefin resin.

The polyolefin resin cardboard structure board of the present invention is a polyolefin resin cardboard structure board having excellent electrical conductivity and flame retardancy and excellent mechanical strength. Further, the polyolefin resin corrugated board structure plate having excellent conductivity and flame retardancy and excellent mechanical strength can be produced by the method for producing a polyolefin resin cardboard structure board of the present invention.

The polyolefin-based resin corrugated board structure board of the present invention comprises two liner parts arranged facing each other in parallel or substantially in parallel, and a rib provided between the liner parts so as to connect both liner parts. Have. The shape of the rib portion is not particularly limited as long as the liner portions are connected to each other and have a reinforcing function. For example, as shown in FIG. A shape in which a plurality of rib portions are obliquely disposed between both liner portions as shown in FIG. 1C and one end of adjacent rib portions is in contact with one liner portion, as shown in FIG. In addition, a shape in which a plurality of rib portions are arranged in parallel or substantially in parallel between both liner portions can be mentioned. In particular, as shown in FIG. 1A, a shape in which a plurality of rib portions are arranged in parallel or substantially in parallel between both liner portions is preferable.

The polyolefin resin corrugated board structure board of the present invention is a multilayer liner part in which at least one liner part is formed of two or more layers of an inner layer and a surface layer containing a conductive agent. As a combination of the liner portions of the corrugated board made of polyolefin resin of the present invention, one liner portion is a single layer, and the other liner portion is formed of two or more layers of an inner layer and a surface layer containing a conductive agent. When it is a multilayer liner part, when both liner parts are multilayer liner parts formed from two or more layers of an inner layer and a surface layer containing a conductive agent, both liner parts are multilayer liner parts, A case where the surface layer of the multilayer liner portion contains a conductive agent and the surface layer of the other multilayer liner portion does not contain a conductive agent can be mentioned. The multilayer liner portion may have another layer between the surface layer and the inner layer. In addition, as shown in FIG. 2, the surface layer of the multilayer liner part in this invention is a liner part surface which is not opposite to the other liner part. The inner layer of the multilayer liner portion is a liner portion surface that faces the other liner portion and contacts the rib.

FIG. 2 is a schematic cross-sectional view of one embodiment of the polyolefin resin corrugated board structure plate of the present invention shown in FIG. In the polyolefin resin-made corrugated board structure board of the present invention shown in FIG. 2, each of the two liner portions 2 is formed of two layers of a surface layer 21 and an inner layer 22, and the inner layer 22 and the rib portion 3 are made of the same material. Is formed integrally.

The corrugated cardboard structure board made of polyolefin resin according to the present invention is a corrugated cardboard in which at least one of the liner layers contains a conductive agent and the liner and rib portions other than the surface layer containing the conductive agent contain a flame retardant. It is a structural board. By using the corrugated board structure plate having such a structure, the flame retardancy and the conductive property can be reduced with a smaller amount of the flame retardant and the conductive agent than the production of the corrugated board structure board using the resin composition as described in Patent Document 1. It is possible to obtain a corrugated board having excellent properties and mechanical strength.

Examples of polyolefin resins used in the present invention include polyethylene resins and polypropylene resins, and these may be used in combination. Examples of the polyethylene resin include low density polyethylene, medium density polyethylene, high density polyethylene, and linear low density polyethylene. Examples of the polypropylene resin include a propylene homopolymer, a copolymer of propylene and a small amount of a comonomer such as ethylene and / or α-olefin, or an amorphous ethylene / α-olefin copolymer. Examples thereof include dispersed polymers. In particular, a polypropylene resin is preferable from the viewpoint of rigidity and heat resistance.

The polyolefin resin constituting the surface layer and the inner layer of the liner portion and the rib portion need not be the same, but preferably contains the same resin in order to increase the bonding strength.

Examples of the conductive agent include carbon black, carbon fibrils represented by carbon nanotubes, carbon nanofibers, and graphite. Among these, carbon black, carbon nanotube, and carbon nanofiber are preferable, and carbon black can be used more preferably from the viewpoint of cost.

The carbon black preferably has a dibutyl phthalate (DBP) oil absorption of 250 ml / 100 g or more, more preferably a carbon black having a DBP oil absorption of 300 ml / 100 g or more, more preferably 350 ml / 100 g or more. The DBP oil absorption referred to here is a value measured by a method defined in ASTM D2414. Carbon black preferably has a BET surface area of 200 cm2 / g or more, and more preferably 400 cm2 / g or more. Examples of commercially available products include Ketjen Black International's Ketjen Black EC and Ketjen Black EC-600JD.

The carbon nanotubes are US Pat. No. 4,663,230, US Pat. No. 4,663,230, US Pat. No. 5,165,909, US Pat. No. 5,171,560, US Pat. No. 5,578,543, US Pat. No. 5,589,152, US Pat. No. 6, U.S. Pat. No. 6,235,674, etc., and the fiber diameter is less than 75 nm. Moreover, the thing of the coil shape which a helix makes a round with the pitch of 1 micrometer or less is also contained. Examples of commercially available products include Hyperion manufactured by Hyperion Catalyst.

Carbon nanofibers are carbon-based fibers having a fiber diameter of 75 nm or more, a hollow structure, and many branched structures. Commercially available products include VGCF, VGNF, etc. from Showa Denko Co., Ltd.

Examples of graphite include those obtained by heating anthracite / pitch at a high temperature in an arc furnace, and graphite produced in nature.

The amount of these conductive agents used varies depending on the type and performance, and is not particularly limited. For example, in the case of carbon black, the weight of the surface layer containing the conductive agent is usually 1 to 30% by weight, Preferably it is 5-25 weight%, More preferably, it is 10-25 weight%.

Examples of the flame retardant include phosphorus-based flame retardants, halogen-based flame retardants, and inorganic flame retardants. In particular, inorganic flame retardants can be preferably used.

Phosphorus flame retardants are known to accelerate the carbonization of the resin by the dehydrating action of polyphosphoric acid generated by thermal decomposition during combustion, and to form a non-volatile protective film on the resin surface to achieve flame retardancy. ing. For example, trimethyl phosphate (TMP), triethyl phosphate (TEP), tributyl phosphate (TBP), trioctyl phosphate (TOP), tributoxyethyl phosphate (TBXP), octyl diphenyl phosphate, triphenyl phosphate (TPP), tricresyl phosphate (TCP), cresyl diphenyl phosphate (CPP), trixylenyl phosphate, xylenyl diphenyl phosphate, cresyl bis (di2,6 xylenyl) phosphate, 2-ethylhexyl diphenyl phosphate, dimethyl methyl phosphate, resorcinol bis (diphenyl) phosphate, Bisphenol A bis (diphenyl) phosphate, bisphenol A bis (dicresyl) phosphate, resorcino Phosphate compounds such as bis (di2,6xylenyl) phosphate, diethyl-N, N-bis (2-hydroxyethyl) aminomethylphosphonate, triphenylphosphine, triphenylphosphine oxide, tetrakis (hydroxymethyl) phosphonium chloride And organic phosphines / phosphine oxides such as tetrakis (hydroxymethyl) sulfate, polyphosphate esters, and ammonium polyphosphate.

The halogen-based flame retardant generates a large amount of a non-combustible halogen-based gas or the like at the time of combustion, and blocks the oxygen around the combustible material by the halogen-based gas to prevent combustion. For example, decabromodiphenyl oxide, octabromodiphenyl oxide, tetrabromodiphenyl oxide, tetrabromobisphenol A, brominated polystyrene, hexabromocyclododecane, tribromophenol, tetrabromophthalic anhydride, bis (tribromophenoxy) ethane, hexabromo Benzene, polydibromophenylene oxide, polypentabromobenzyl acrylate, ethylenebistetrabromophthalimide, TBA epoxyphenoxy oligomer, TBA polycarbonate oligomer, chlorinated paraffin, perchlorocyclopentadecane (dechlorane plus), chlorendic acid, halogen-containing phosphate ester And the like. However, although it exhibits high flame retardancy, harmful gases such as hydrogen chloride and dioxin are likely to be generated.

Therefore, in recent years, inorganic flame retardants such as metal hydroxides such as aluminum hydroxide and magnesium hydroxide, basic magnesium carbonate, basic zinc carbonate, zinc carbonate, zinc borate, and calcium aluminate have been used instead of halogen flame retardants. Flame retardants are attracting attention.
Among these, metal hydroxides control combustion by the endothermic action of the hydroxide releasing crystal water during combustion, and can be preferably used with very little smoke, toxicity and corrosivity. In particular, magnesium hydroxide is more preferable.

The amount of these flame retardants used varies depending on the type and performance and is not particularly limited. For example, in the case of magnesium hydroxide, the weight of the liner portion and the rib portion other than the surface layer containing the conductive agent is usually 10%. -60% by weight, preferably 20-50% by weight, more preferably 30-50% by weight.

The polyolefin resin used in the present invention includes molding processability when a corrugated board is molded using the polyolefin resin, and the conductivity, flame retardancy and mechanical properties of the resulting corrugated board made of polyolefin resin. As long as the strength is not impaired, fillers such as silica, mica and talc, reinforcing materials such as glass fibers, aramid fibers and ultrahigh molecular weight polyethylene fibers, heat stabilizers, UV absorbers, UV stabilizers and colorants Various additives such as these may be included.
In addition, a flame retardant may be added to the surface layer containing the conductive agent, or a conductive agent may be added to the liner portion and the rib portion other than the surface layer to such an extent that the moldability and mechanical strength are not impaired. .

The total thickness of the polyolefin-based resin corrugated board structure board of the present invention, the thickness of the rib portion and the liner portion, and the basis weight are not particularly limited, but the total thickness is usually 1 to 30 mm.

The thickness of the surface layer containing the conductive agent is preferably 20 to 100 μm, more preferably 20 to 60 μm, and further preferably 30 to 50 μm from the viewpoint of the balance between conductivity and flame retardancy.

Examples of the method for producing a polyolefin resin corrugated cardboard structure board of the present invention include, for example, a method of integrally molding the entire polyolefin resin cardboard board by multilayer extrusion molding, and a method of joining a liner part and a rib part that have been molded in advance. Is mentioned. In the latter method, it is preferable that the liner part and the rib resin plate are joined by heat fusion. Also, by extrusion molding, a polyolefin-based resin having two liner portions arranged so as to face each other in parallel or substantially parallel and a rib portion provided between the liner portions so as to connect both liner portions. After producing the corrugated board, a sheet containing a conductive agent may be laminated on at least one liner part. From the viewpoint of productivity, the entire polyolefin-based corrugated board made of polyolefin resin is formed by multilayer extrusion molding in which the surface layer of at least one liner portion contains a conductive agent and the liner portion and rib portion other than the surface layer contain a flame retardant. A method of integrally molding is particularly preferable. As the multilayer extrusion molding method, a known method such as a feed block method or a multi-manifold method may be used.

When producing a polyolefin resin corrugated cardboard structure board having a multilayer liner part formed of two layers of a surface layer containing a conductive agent and an inner layer containing a flame retardant, the surface layer is constituted. Fluidity of a conductive agent-containing polyolefin resin used as a material to be used, that is, MFRs of 0.1 to 10 g / 10 min, fluidity of a flame retardant-containing polyolefin resin used as a material constituting an inner layer and a rib part, that is, It is preferable to use a material having an MFRc of 0.1 to 10 g / 10 min and an MFRs / MFRc ratio of 0.1 to 1.0. Here, MFR is a value measured according to JIS K7210 at a temperature of 230 ° C. and a load of 2.16 kgf. The subscript s for MFRs and MFRc MFR indicates the surface layer, and c indicates the inner layer and the rib portion. By using the above-mentioned materials, it is easy to stack a surface layer having excellent multilayer extrusion moldability and productivity, and is excellent in uniformity of thickness, and can express good conductivity. Especially, the smoothness of the liner surface is 100 μm. The following can be improved.

When MFRs and MFRc are less than 0.1 g / 10 min and fluidity is low, there is a concern that the resin pressure becomes high and the extrusion amount is lowered. Further, when the fluidity is high exceeding 10 g / min, it may be difficult to form a corrugated board structure. MFRs and MFRc are preferably 0.3 to 6 g / min.

In the case of a multi-layer corrugated cardboard structure board made of ordinary polyolefin resin, not the polyolefin resin corrugated cardboard structure board of the present invention containing a conductive agent or a flame retardant, the uniformity of the surface layer thickness and the smoothness of the surface of the corrugated cardboard structure board From the viewpoint, the ratio of MFRs / MFRc is about 1.0, that is, the fluidity of the material constituting the surface layer and the material constituting the inner layer and the rib portion is preferably equal. However, when the polyolefin resin-made corrugated board structure containing the conductive agent and flame retardant of the present invention was examined, the ratio of MFRs / MFRc was 0.1 to 1.0, that is, the surface layer was It has been found that the fluidity of the constituting material is preferably the same or lower than the fluidity of the material constituting the inner layer and the rib portion. By selecting such a material, the surface of the obtained corrugated cardboard structure board made of polyolefin resin becomes hard and the corrugated cardboard structure is easily held, and defects such as undulation are unlikely to occur. Further, the higher the fluidity of the material constituting the inner layer and the rib portion, the lower the resin pressure, and the easier it is to improve the extrusion amount. Moreover, it became clear that it was excellent also in the uniformity of the thickness of surface layer, and surface smoothness. When manufacturing the polyolefin resin-made corrugated board structure board of this invention, it is more preferable that ratio of MFRs / MFRc is 0.2-0.7, and it is further more preferable that it is 0.3-0.5.

The conductivity of the corrugated board made of polyolefin resin of the present invention is evaluated by the surface resistivity of the surface layer. The test piece is 90 mm × 90 mm, the apparatus is an insulation meter manufactured by Kessley, and the measurement is performed at 23 ° C. and 50% relative humidity at an applied voltage of 100V. The surface resistivity of the corrugated board made of polyolefin resin of the present invention is 10 ⁸ Ω / □ or less, preferably 10 ⁷ Ω / □ or less, more preferably 10 ⁶ Ω / □ or less.

The method for evaluating the flame retardancy of the polyolefin resin corrugated board structure board of the present invention is not particularly limited, but can be carried out by a combustion test of a test piece. There are various methods and standards in the combustion test, but according to UL94HBF (horizontal combustion test of foamed material), which has a relatively low flame retardance level, a test piece of 50 mm (MD direction) × 150 mm (TD direction) Perform the test at The flame retardancy of the corrugated board made of polyolefin resin of the present invention is not less than a level compatible with UL94HBF.

The application of the corrugated board made of polyolefin resin of the present invention is not particularly limited, but it is excellent in conductivity, flame retardancy and mechanical strength. It can be used for materials such as floor materials and wall materials for semiconductor manufacturing factories, anechoic chamber wall materials used for testing electronic devices and the like. Moreover, it can also be used as a molded product formed by thermoforming such as vacuum forming into a desired shape. A known method can be used as the thermoforming method, and examples thereof include vacuum forming and heat ruled line processing.

Hereinafter, although an example and a comparative example explain the present invention further, the present invention is not limited at all by this.

(1) MFR
According to JIS K7210, measurement was performed at a temperature of 230 ° C. and a load of 2.16 kgf. The unit is g / 10 minutes.

(2) The surface resistivity test piece was 90 mm × 90 mm, the apparatus was an insulation meter manufactured by Kessley, and measured at 23 ° C. and 50% relative humidity at an applied voltage of 100V.

(3) Combustion test According to UL94HBF (horizontal combustion test of foamed material), 50 mm (TD direction) × 150 mm (MD direction) as the test piece in the MD direction and 50 mm (MD direction) as the test direction in the TD direction. Direction) × 150 mm (TD direction). Those that did not burn at a rate of more than 40 mm per minute in the 100 mm section, or that ended burning before the flammable or flameless combustion reached the 125 mm mark, were judged as acceptable.

(4) Bending test Using a test apparatus shown in JIS K7203, 50 mm (TD direction) × 150 mm (MD direction) as a test piece in MD direction, and 50 mm (MD direction) × 150 mm (TD) as a test piece in TD direction. Direction) was used at a bending speed of 10 mm / min and a span distance of 100 mm.

(5) DuPont impact test In accordance with the standard of JIS K7211, a test piece of 70 mm x 70 mm and a ½ inch phi strikeer were used, and the test was performed at a temperature of 23 ° C.

(6) A smooth surface roughness measuring device surfcom200C (manufactured by Tokyo Seimitsu Co., Ltd.) was used, and the tip of the stylus was made of 5 μmR diamond. A test piece of 100 mm (TD direction) × 50 mm (MD direction) was extracted from an arbitrary part of the structural plate, 50 mm was measured in the TD direction at once, and the obtained maximum height was used as an index of smoothness.

[Example 1]
(Manufacture of corrugated board made of polyolefin resin) Material for the first extruder (50 mmΦ single screw extruder) for extruding the material for the surface layer of the liner part, and the intermediate part (that is, the inner layer and rib part of the liner part) In combination with a second extruder (115 mmΦ single-screw extruder) for extruding the material, for multi-layer extrusion using a feed block type multi-layer T-die (extrusion width 1500 mm, cross-sectional shape is the type shown in FIG. 1A) Thus, a corrugated board made of polyolefin resin containing a conductive agent in each surface layer of the two multilayer liner parts and a flame retardant in the middle part was prepared.
The surface layer material is composed of 22% by weight of carbon black (Ketjen Black International Ketjen Black EC) and 78% by weight of a polypropylene resin (Nobrene AS171L manufactured by Sumitomo Chemical Co., Ltd.) with an MFRs of 1.2 g / 10 min. A material was used. The material for the intermediate part is composed of 40% by weight of magnesium hydroxide (MGZ-1 manufactured by Sakai Chemical Industry Co., Ltd.), 60% by weight of polypropylene resin (Nobrene AS171L manufactured by Sumitomo Chemical Co., Ltd.), and MFRc is 2.9 g. A material that was / 10 min was used. The MFRs / MFRc was 0.41.
As conditions for the multilayer extrusion molding, the temperature of the extruder and multilayer T-die is 200 to 230 ° C., the extrusion amounts of the first extruder and the second extruder are 218 kg / h and 18 kg / h, respectively, and the take-up speed is 4.0 m / min.
The obtained polyolefin resin corrugated cardboard structural plates were evaluated, and the results are summarized in Tables 1 and 2.

[Example 2]
The intermediate portion material was processed in the same manner as in Example 1 except that the magnesium hydroxide content was 50% by weight, and the results are summarized in Tables 1 and 2.

[Comparative Example 1]
The same procedure as in Example 1 was carried out except that only the second extruder was used and a material consisting of 22% by weight of carbon black, 50% by weight of magnesium hydroxide and 28% by weight of polypropylene resin was used. Due to the small amount, the moldability was poor and a corrugated board structure board could not be obtained.

[Reference example]
As surface layer material and intermediate portion material, a surface layer material having a MFRs of 1.1, 2.0, and 2.6 g / 10 min (100% by weight) containing no conductive agent or flame retardant (Sumitomo, respectively) Example 1 with the exception of using Noblene AS171L, FS2011D, and AH161C manufactured by Chemical Co., Ltd., and using an intermediate material (Nobrene AS171L manufactured by Sumitomo Chemical Co., Ltd.) having an MFRc of 1.1 g / 10 min. The same was done. Here, the ratios of MFRs / MFRc were 1.00, 1.82 and 2.36, respectively. When the smoothness was measured, they were 62, 259, and 327 μm, respectively, and the smoothness was good when MFRs and MFRc were equivalent.

It is a schematic perspective view of the polyolefin resin-made corrugated board structure board of this invention. It is a schematic sectional drawing of the polyolefin resin-made corrugated board structure board of this invention shown by Fig.1 (a).

Explanation of symbols

1: Corrugated board made of polyolefin-based resin 2: Multi-layer liner part 21: Surface layer 22: Inner layer 3: Rib part

Claims (6)

In a polyolefin-based resin corrugated board structure board having two liner portions arranged facing each other in parallel or substantially parallel to each other, and a rib portion provided between the liner portions so as to connect both liner portions, One liner portion is a multilayer liner portion formed of two or more layers of an inner layer and a surface layer containing a conductive agent, and the liner portion other than the surface layer and the rib portion in the polyolefin resin corrugated cardboard structure plate A corrugated board made of polyolefin resin containing a flame retardant.   The polyolefin resin corrugated board structure board according to claim 1, wherein the conductive agent is carbon black, and the content of the carbon black is 1 to 30% by weight when the weight of the surface layer of the multilayer liner portion is 100%.   The flame retardant is magnesium hydroxide, and the content of the magnesium hydroxide is 10 to 60% by weight when the weight of the liner part and the rib part other than the surface layer in the polyolefin resin corrugated board is 100%. Item 3. The corrugated board made of polyolefin resin according to Item 1 or 2.   The polyolefin resin corrugated board according to any one of claims 1 to 3, wherein the thickness of the surface layer of the multilayer liner portion is 20 to 100 µm.   The polyolefin resin corrugated board structure board according to any one of claims 1 to 4, wherein the multilayer liner part is formed of two layers of a surface layer containing a conductive agent and an inner layer containing a flame retardant. A method for integrally molding the polyolefin resin corrugated board structure board according to claim 5 by multilayer extrusion molding, wherein the conductive agent-containing resin composition constituting the surface layer has an MFR (MFRs) at 230 ° C of 0.1 to 10 g. MFR (MFRc) at 230 ° C. of the flame retardant-containing resin composition constituting the inner layer and the rib part is 0.1 to 10 g / min, and MFRs / MFRc is 0.1 to 1.0. A method for producing a corrugated board made of polyolefin resin.

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