JP2011208162A - Polyolefin resin film and composition for manufacturing polyolefin resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin resin film with high modulus which hardly causes pores and breakage upon drawing, and to provide a composition for manufacturing the polyolefin resin film with high modulus.SOLUTION: The polyolefin resin film includes a polyolefin [A] having weight average molecular chain length of 2,850 nm or more and density of ρ1(g/cm) and a polyolefin wax [B] having weight average molecular weight of 700 to 6,000 and density of ρ2(g/cm) which are blended so as to be [A]/[B]=90/10 to 50/50 (wt.ratio), wherein ρ1 and ρ2 satisfy the following relations: 0.92≤ρ1≤0.94, 0.91≤ρ2≤0.93 and -0.01≤(ρ1-ρ2)≤0.03.

Description

  The present invention provides a high modulus polyolefin resin film and a composition for producing a high modulus polyolefin resin film.

  As one of high-strength and high-elasticity film materials, ultra-high molecular weight polyolefin is known. However, ultra-high molecular weight polyolefin has high melt viscosity due to its high molecular weight, and it is difficult to form a film such as thinning or stretching. Therefore, commercially available ultra-high molecular weight polyolefin films are generally produced by a method of slicing block-like resin.

  However, although a film can be obtained by slicing ultrahigh molecular weight polyolefin, its thickness accuracy is poor, and a portion with low strength and elastic modulus is locally generated, making it difficult to obtain a film with high strength and high elastic modulus. there were.

  An object of the present invention is to provide a polyolefin resin film having a high strength and a high elastic modulus and a composition for producing a polyolefin resin film having a high strength and a high elastic modulus.

  As a result of intensive studies to develop a polyolefin-based resin film having a high elastic modulus, the present inventors mixed a specific molecular chain length polyolefin having a specific density relationship and a polyolefin wax in a specific ratio. It has been found that the above problems can be solved by using it as a composition, and the present invention has been completed.

The above object can be achieved by the present invention as described below.
That is, the polyolefin resin film of the present invention is
[A] A polyolefin having a weight average molecular chain length of 2850 nm or more and a density ρ1 (g / cm ³ ), and [B] a polyolefin wax having a weight average molecular weight of 700 to 6000 and a density ρ2 (g / cm ³ ), ] / [B] = 90 / 10-50 / 50 (weight ratio), and ρ1 and ρ2 satisfy the following conditions.

0.92 ≦ ρ1 ≦ 0.94
0.91 ≦ ρ2 ≦ 0.93
−0.01 ≦ (ρ1−ρ2) ≦ 0.03

  When [A] / [B] exceeds 90/10 and the ratio of [A] polyolefin increases, processability decreases, the ratio of [B] polyolefin wax increases, and [A] / [B] is 50 If it is less than / 50, the physical properties of the resulting film will be reduced.

Moreover, the composition for polyolefin resin film production of the present invention is:
[A] A polyolefin having a weight average molecular chain length of 2850 nm or more and a density ρ1 (g / cm ³ ), and [B] a polyolefin wax having a weight average molecular weight of 700 to 6000 and a density ρ2 (g / cm ³ ), ] / [B] = 90 / 10-50 / 50 (weight ratio), and ρ1 and ρ2 satisfy the following conditions.

0.92 ≦ ρ1 ≦ 0.94
0.91 ≦ ρ2 ≦ 0.93
−0.01 ≦ (ρ1−ρ2) ≦ 0.03

Schematic diagram showing an example of polyolefin resin manufacturing process The figure which shows the detail of the screw of a screw kneading apparatus The figure which shows the structure of the full flight disk of the screw kneading machine The figure which shows the structure of the kneading disk of a screw kneading apparatus

  The [A] polyolefin in the present invention has a weight average molecular chain length of 2850 nm (28500 angstroms) or more. If the weight average molecular chain length is less than 2850 nm, entanglement of molecular chains in the polyolefin is insufficient, and it is difficult to obtain a film having high strength and high elastic modulus when a film is produced from the composition of the present invention. It is.

  [B] The polyolefin wax in the present invention has a weight average molecular weight of 700 to 6000. When a polyolefin wax having a weight average molecular weight of less than 700 is used, both are easily separated in a composition comprising [A] polyolefin and [B] polyolefin wax, and the polyolefin wax tends to bleed from the composition. When a polyolefin wax having a weight average molecular weight of more than 6000 was used, the melt viscosity at the time of mixing [A] polyolefin and [B] polyolefin wax was high, and it was difficult to obtain a uniform composition. When a film is produced from the composition, a portion having low strength and elasticity is locally generated, and it is difficult to obtain a film having high strength and high elastic modulus.

And the density of the polyolefin of the present invention [A] ρ1 (g / cm 3), the density of the polyolefin wax [B] ρ2 (g / cm 3) is characterized in that the following conditions are satisfied.

0.92 ≦ ρ1 ≦ 0.94
0.91 ≦ ρ2 ≦ 0.93
−0.01 ≦ (ρ1−ρ2) ≦ 0.03
When the density ρ1 and ρ2 do not satisfy the above conditions, the compatibility of the polyolefin [A] and the polyolefin wax [B] is poor, and when the film is produced from the composition of the present invention, the portion having low strength and elasticity is locally localized. This is undesirable because it is difficult to obtain a film having a high strength and a high elastic modulus.

  Examples of the olefin constituting the [A] polyolefin used in the present invention include known olefins such as ethylene, propylene, butene and hexene. In particular, it is preferable to use ultra high molecular weight polyethylene or ultra high molecular weight polypropylene.

  Specific examples of the polyolefin wax [B] include polyethylene resins such as low density polyethylene, linear polyethylene (ethylene-α-olefin copolymer) and high density polyethylene, and polypropylene resins such as polypropylene and ethylene-propylene copolymer. Examples thereof include resin, poly (4-methylpentene-1), poly (butene-1) and ethylene-vinyl acetate copolymer wax.

  The molecular chain length, weight average molecular chain length, molecular weight and weight average molecular weight of polyolefin are measured by GPC (gel permeation chromatography), and the mixing ratio (% by weight) of polyolefin in the specific molecular chain length range or specific molecular weight range is GPC. It can be obtained by integration of a molecular weight distribution curve obtained by measurement.

  The polyolefin resin film production composition of the present invention can contain various additives and fillers as necessary. Examples of such additives include antioxidants, ultraviolet absorbers, pigments, dyes, inorganic fillers, organic fillers such as resin fine powders, and the like.

  The polyolefin resin film and the polyolefin resin film composition of the present invention preferably contain 10% by weight or more of a polyolefin resin having a molecular chain length of 2850 nm or more. Since the polyolefin resin having a molecular chain length of 2850 nm or more is particularly excellent in strength, when such a resin is contained in an amount of 10% by weight or more, more preferably 20% by weight or more, a polyolefin resin film having a remarkable strength is obtained. Obtainable.

  The composition for producing a polyolefin-based resin film of the present invention can be obtained by kneading the raw materials [A] polyolefin and [B] polyolefin wax with a kneading apparatus having high shearing force. Specifically, a Banbury mixer, a kneader, a kneading roll used for rubber kneading, a screw kneading apparatus used for kneading a thermoplastic resin, and the like are exemplified.

  When using a screw kneading device, the L / D having at least a full flight screw and a kneading block has a screw of 30 or more, the kneading block has an Ln / D of 5 or more, and the full flight screw Lf / D is It is preferable to use one that is 3 or more and satisfies the following conditional expression.

(Condition) 35 ≦ α ≦ 60
0.15 ≦ (M / D) ≦ 0.25
Where α is the flight angle of the full flight screw (°), M is the depth of the screw groove of the full flight screw (mm), L is the total screw length (mm), D is the barrel diameter (mm), and Ln is kneading The element length of the block (mm) (however, if the screw contains two or more kneading blocks, the total length of those elements), Lf is the element length of the full flight screw (mm) (however, the screw In the case where two or more full flight screws are included, the total element length).

  When using a screw kneading device, unlike the case of using a Banbury mixer or kneader, it is also possible to provide processing steps necessary for film production after kneading, for example, a calendar processing step, a stretching step, etc., continuously. ,preferable.

  Embodiments of the present invention will be described with reference to the drawings, taking as an example the case where a screw kneading device is used as the kneading device.

<Film production process>
FIG. 1 is a schematic view showing a production line for producing a polyolefin-based resin film. This production line is composed of a kneading step 1, a rolling step 2, a first slit step 3, a stretching step 4, and a second slit step 5 in the order of steps.

  In the kneading step 1, a screw kneading apparatus 10 is used, and this kneading apparatus includes a first hopper 11 for supplying polyolefin PE1 and polyolefin wax PE2 having an average molecular chain length of 2850 nm or more. Further, the kneading apparatus may be provided with a second hopper for supplying a desired additive, for example. The screw kneading device 10 includes a biaxial screw 13 and strongly kneads the mixed resin supplied from the hopper 11 and pushes it forward. The polyolefin resin film production composition obtained by kneading is pelletized.

  In the rolling step 2, a screw extruder 20 is used. The apparatus 20 includes a hopper 21 for charging the resin composition pellets obtained in the kneading step 1 and a screw 22. By this apparatus 20, the resin composition is extruded forward, discharged as a rod-like or sheet-like molten resin by a die 23, and a film rolled by a rolling roll mechanism 24 is obtained.

  In the first slitting process 3, the film obtained in the rolling process 2 is cut into two in the width direction, and for example, two 300 mm wide films are obtained from a 600 mm wide film.

  In the stretching step 4, the above 300 mm wide film is stretched 4 to 5 times in the width direction under a predetermined temperature condition. Thereby, the polyolefin resin film stretched in the width direction can be obtained.

  In the second slitting step 5, the polyolefin resin film obtained in the stretching step 4 is cut into a desired width dimension.

<Configuration of screw kneader>
Next, the detail of a structure of the screw 13 of the screw kneading apparatus 10 suitable for manufacture of the polyolefin resin film manufacturing method composition of this invention is demonstrated. FIG. 2 is a diagram showing details of the screw 13.

  The screw 13 is configured by fixing a component called an element on a shaft called a screw shaft.

  In FIG. 2, the element indicated by the symbol P is a full flight screw. A full flight screw is a screw segment in which a groove is spirally formed over its entire length. The element indicated by the symbol DP indicates a full flight screen in which a groove deeper than the full flight screw indicated by the symbol P is formed. By using such a deep groove full flight screw, the residence time of the resin can be lengthened. The full flight screw has a shape as shown in FIG. 3 and normally plays a role of feeding the kneaded material forward, that is, downstream of the kneading apparatus. In FIG. 3, D is the diameter (inner diameter) of the barrel (mm), Ds is the diameter of the screw (mm), M is the depth of the screw groove (mm), α is the flight angle (°) of the screw, and H is the inner surface of the barrel. Is the distance (mm) between the screw groove and the bottom of the screw groove, and δf is the distance (mm) between the screw crest and the barrel inner surface.

  Of the above parameters, α is related to the speed at which the resin is sent out, and as α decreases, the speed at which the resin is sent out becomes slower. As a result, the residence time of the resin becomes longer and the kneading degree of the resin improves. However, if α is too small, the production efficiency is deteriorated. The size of M is also a parameter related to the speed at which the resin is sent out and the strength of the kneading.

  An element indicated by a symbol ND is a kneading block. As shown in FIG. 4, a kneading block generally includes a plurality of kneading discs having the same cross-sectional shape, and the geometric centers of the discs are located on a common straight line. It has a shape that is overlapped with a predetermined angle deviation from each other in a certain direction. The thickness of each kneading disk may be the same or different.

  In the state in which the screw is loaded in the barrel, there is a distribution in the distance between the kneading disk and the barrel constituting the kneading block, and the shear stress acts on the mixed line material most strongly when the distance is the smallest.

  The element indicated by the reference symbol LND is a kneading block having a shape in which the kneading discs are stacked so as to twist in the direction opposite to the twisting of the stacking of the kneading discs in the kneading block of the reference symbol ND. By using a combination of two types of kneading blocks ND and LND, the residence time of the kneaded material can be made longer than in the case of one type of kneading block, and a stronger shear stress can be applied.

  The element indicated by the symbol SND is also a kneading block, but the feature is that when the adjacent kneading disks are compared, the kneading disk on the downstream side of the kneading apparatus is thinner than the kneading disk on the upstream side. is there. By using such a kneading block SND, the flow rate of the kneaded material to the downstream side can be adjusted. Strong compression / extension action can be given to the cross-line material.

  FIG. 4 is a view showing the kneading block loaded in the twin-screw extruder, but the screw shaft is not shown.

In the screw kneading apparatus suitable for the preparation of the polyolefin resin film production composition of the present invention, the L / D of the entire screw is 30 or more, the Ln / D of the kneading block is 5 or more, and the Lf / D of the full flight screw is Set to 3 or higher. Furthermore, in a full flight screw, parameters are designed so that 35 ≦ α ≦ 60 and 0.15 ≦ (M / D) ≦ 0.25. The larger the L / D, the longer the residence time. By selecting the parameters as described above, it is possible to obtain a polyolefin resin composition that can be molded into a film to give a film having a high elastic modulus.

Claims (2)

[A] A polyethylene having a weight average molecular chain length of 2850 nm or more and a density ρ1 (g / cm ³ ), and [B] a polyethylene wax having a weight average molecular weight of 700 to 6000 and a density ρ2 (g / cm ³ ). ] / [B] = 90/10 to 50/50 (weight ratio), and ρ1 and ρ2 satisfy the following conditions.
0.92 ≦ ρ1 ≦ 0.94
0.91 ≦ ρ2 ≦ 0.93
−0.01 ≦ (ρ1−ρ2) ≦ 0.03 [A] A polyethylene having a weight average molecular chain length of 2850 nm or more and a density ρ1 (g / cm ³ ), and [B] a polyethylene wax having a weight average molecular weight of 700 to 6000 and a density ρ2 (g / cm ³ ). ] / [B] = 90/10 to 50/50 (weight ratio), and ρ1 and ρ2 satisfy the following conditions.
0.92 ≦ ρ1 ≦ 0.94
0.91 ≦ ρ2 ≦ 0.93
−0.01 ≦ (ρ1−ρ2) ≦ 0.03

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