JP2019142002A - Resin pellets - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin pellet having excellent film strength, optical property and foreign matter removing property when molded into a film. SOLUTION: The polyethylene having a viscosity average molecular weight or the viscosity average molecular weight of the resin pellet contained in the resin pellet is 200,000 or more, and the resin pellet is folded, separable, or laminated. It is a form that has been done. [Selection diagram] Fig. 1

Description

  The present invention relates to a resin pellet and a method for producing a resin composition or film using the same, and more specifically, a product excellent in various physical properties such as strength, film quality, and optical properties can be obtained in molding processing of a film or the like. Polyolefin-based resin pellets, and resin composition or film manufacturing method using the same, and in particular, relatively low molecular weight high density polyethylene (HDPE) having a molecular weight of 150,000 or less, especially low density polyethylene (LDPE) and / or linear The present invention relates to a polyolefin resin pellet that can be mixed with a small amount of low density polyethylene (LLDPE) to improve physical properties.

  Polyolefin resins such as polyethylene and polypropylene have a good balance of molded product properties, molding processability, weather resistance, etc., production of industrial films such as packaging films and agricultural films, blow molding applications such as bottle containers, or structural materials It is widely used for injection molding applications such as large containers, fiber applications such as monofilaments, and recently separators for lithium ion batteries. In particular, molded products such as films have been made thinner from the viewpoint of saving raw materials used, but it has been necessary to prevent a decrease in mechanical strength due to the thinner film. In order to improve the film strength, conventionally, a technique using a high molecular weight component as a resin raw material has been proposed.

  For example, Patent Document 1 describes a polyethylene resin composition having a very high molecular weight. However, since the viscosity of the polyethylene resin composition is too high by itself, in extrusion molding such as a general inflation method, the resin pressure of a molding machine is described. Alternatively, the load current becomes too high to form a film. Also, a method of mixing such a polymer powder of a polyethylene resin composition having a very high molecular weight with conventional linear low density polyethylene (LLDPE) or low density polyethylene (LDPE) resin pellets and kneading them in an extruder. Then, the kneading is insufficient, the strength does not increase, and the poor phenomenon presumed to be caused by the poor dispersion of the high molecular weight component that the high molecular weight component becomes an unmelted gel is likely to occur. These phenomena occur remarkably in high molecular weight polyethylene compositions, generally in polyethylene compositions having a viscosity average molecular weight higher than about 200,000, which is caused by the molecular chains of such high molecular weight polyethylene being very It is presumed that the energy that can be imparted for unraveling the crystal inside a general extruder is insufficient because it is long, and the molecular chain remains in an undissolved state.

  In Patent Document 2, when polymerizing high-density polyethylene, two components having different molecular weights are formed in a double-structured form (hereinafter referred to as “ It is proposed to have “two-stage polymerization” or “multi-stage polymerization”. The introduction of a high molecular weight component by the method described in Patent Document 2 has been put into practical use for high-density polyethylene having very little branched structure of the polyethylene main chain, but it is branched into the main chain like LLDPE, high-pressure method LDPE resin, In many polyethylene resins, it is difficult to increase the molecular weight due to the influence of a branched portion, and it has not been put into practical use.

  As a method for obtaining a pellet of the polyolefin resin composition, generally, a method described in Patent Document 2, that is, a method in which polymerized polyethylene powder is heated and kneaded with an extruder to be pelletized is used. For example, a polyolefin resin can be extruded into a strand having a diameter of 10 mm or less, generally about 1 to 5 mm, and the extruded product can be cut into lengths of about 2 to 5 mm to obtain pellets. Patent Document 3 describes a method of re-pelletizing a resin composition once molded into a film or the like for recycling. This method is a method in which a resin film is compressed without heating and then cut into a desired length.

JP 2007-23171 A JP-A-10-101854 JP 2006-21519 A

  In the technique described in Patent Document 1 or 2, even if a high molecular weight component having a molecular weight of about 200,000 or more is dispersed in a polyethylene resin composed of a low molecular weight component having a molecular weight of about 150,000 or less, dispersion is not achieved. It was enough. These dispersions are generally made by heating and melting pellets composed of low molecular weight components and powders having polymerized high molecular weight components in an extruder, but the high molecular weight components are not sufficiently dispersed in the extruder and remain in a lump. It remained and caused a poor dispersion called so-called fish eye or unmelted gel, which deteriorated the film quality or optical properties. Furthermore, since the high molecular weight component is not sufficiently dispersed in the film having such poor dispersion, the film strength is not improved. The poor dispersion of the high molecular weight component is presumed to be because the low molecular weight component is first softened in the extruder, but sufficient shear stress required for dispersion is not transmitted to the slow softening high molecular weight component. In addition, powders of high molecular weight components generally have a large particle size and take a long time to melt, which is a cause of poor dispersion in the extruder.

  In general, fisheye occurs in a film-like or sheet-like product as defined in “Polymer Dictionary” (Taiseisha, 2000, 6th edition, page 337) by the Polymer Editorial Board. The name is given because it is a small spherical mass, and many of them show transparency like fish eyes. Fisheye is distinguished from its production factors, with unmelted lumps resulting from insufficient kneading of molding materials, lumps due to part of the raw material gelling, lumps due to partial deterioration of the material being molded, and foreign matter as the core. Like things, there are a wide variety. In this specification, the fish eye originates from the material used as the raw material of the microporous membrane, and excludes those having foreign matter as the core. Examples of the foreign material include cellulose, dust, metal pieces, resin carbide, plastics of different types, lint, and pieces of paper. In this specification, unmelted gel is also used synonymously with fish eye.

  In order to solve the dispersion failure, Patent Document 2 describes that a resin composition is obtained by combining low molecular weight and high molecular weight in a polymerization stage by two-stage polymerization of polyethylene. However, the dispersion was still insufficient to the extent that dispersion of 100 μm units was already achieved at the stage where the high molecular weight component and the low molecular weight component took a double structure in one powder.

  In view of the above circumstances, the present invention provides a resin pellet excellent in strength and optical properties, and excellent in the removal of foreign matter such as fish eye and unmelted gel, and a resin composition and film using the same. Objective.

The present inventors have found that the above problems can be solved by specifying the resin composition, shape, component, bulk density, etc. of the resin pellets, and have completed the present invention. That is, the present invention is as follows.
[1]
A resin pellet containing polyethylene as a main component,
Resin pellets in which the polyethylene or the resin pellets contained in the resin pellets have a viscosity average molecular weight of 200,000 or more and are folded, separable, or laminated.
[2]
A resin pellet containing polyethylene as a main component,
A resin pellet having a viscosity-average molecular weight of 200,000 or more of the polyethylene or the resin pellet contained in the resin pellet and having a planar, fibrous, hollow fiber, or non-woven fabric component.
[3]
A resin pellet containing polyethylene as a main component,
The polyethylene or the resin pellets contained in the resin pellets have a viscosity average molecular weight of 200,000 or more, and a bulk density measured according to Japan Powder Industry Technical Association Standard SAP01-79 is 0.1 to 0.4 g. / Cm ³ resin pellet.
[4]
The resin pellet according to any one of [1] to [3], which is a recycled resin pellet.
[5]
Polyolefin pellets were prepared by dry blending 5-60 mass% of the resin pellets with linear low density polyethylene (LLDPE) having a melt index (MI) of 2 and a density of 0.940 g / cm ^3. Then, using a lab plast mill manufactured by Toyo Seiki Co., Ltd., the polyolefin pellets were kneaded at 200 ° C. and 50 rpm for 10 minutes to obtain a molten resin, and after molding the molten resin on a press plate at 10 MPa, [1] to [4], in which when a film is formed by stretching 5 times by 5 times by a biaxial stretching machine, 5 or less unmelted gels exist per 100 cm ^{2 of the} film. The resin pellet of any one of Claims.
[6]
The resin pellet according to any one of [1] to [5], which is a laminate in which films having a thickness of 500 μm or less are laminated.
[7]
The resin pellet according to [6], wherein the laminate includes two or more resin films having different resin compositions.
[8]
The method to manufacture a resin composition using the resin pellet of any one of [1]-[7].
[9]
The method according to [8], wherein the resin composition includes the resin pellets and a low-density polyethylene polymer.
[10]
A method for producing a packaging film or an agricultural film using the resin composition produced by the method according to [8] or [9].

  According to the present invention, a resin molded product excellent in high strength and optical properties and having very little unmelted gel can be obtained particularly when used for a film.

Fig.1 (a) is a typical perspective view of the resin pellet which has a planar component part, FIG.1 (b) is a typical pellet sectional drawing in case a component part has an individual plane. And FIG.1 (c) is typical pellet sectional drawing in the case where a component part is the state which folded the single film | membrane. FIG. 2A is a schematic perspective view of an embossed resin pellet having a planar constituent part, and FIG. 2B is a case where the constituent part has an individual plane. It is typical pellet sectional drawing. FIG. 3 is a schematic view showing an example of a resin pellet production line.

Hereinafter, modes for carrying out the present invention (hereinafter abbreviated as “embodiments”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.
The physical property values or evaluation values described in this specification are measured or calculated according to the methods described in the examples unless otherwise specified.
Moreover, in this specification, including a specific component as a main component means including in a ratio exceeding 50 mass% on the basis of the total mass of all the components.

<Resin pellets>
One embodiment of the present invention is a resin pellet containing polyethylene as a main component.
In the present specification, the resin pellet is a resinous particle lump having a size suitable for serving as a raw material for conventional extrusion processing. Extrusion molding is, for example, film molding such as inflation molding, microporous membrane molding, blow molding, injection molding, pipe molding, monofilament molding, and the like.
As for the size of the pellet, the maximum length of the pellet is preferably 10 mm or less from the viewpoint of being easily transported without clogging during pneumatic transportation on an idle running line or the like, and further improving the transportability in the extruder. From a viewpoint of making it, it is more preferable that it is 6 mm or less. The maximum length of the pellet is preferably 1 mm or more, particularly in a large extruder having a large clearance between the screw and the cylinder, so that the pellet is transported satisfactorily. Moreover, like the conventional resin pellet described in background art, the diameter of a pellet has preferable 10 mm or less, More preferably, it is about 1-5 mm in diameter, and is 2 mm or more and 5 mm or less in a longitudinal direction.

  In the present specification, “comprising polyethylene as a main component” means that, in addition to polyethylene, polypropylene, other polyolefin resins, and further polyethylene terephthalate ( PET) and non-polyolefin resin such as nylon may be included. In mixing with a resin other than polyethylene, the ratio of the resin other than polyethylene in the pellet is preferably less than 30% by mass from the viewpoint of dispersibility and / or strength retention, and more preferably 20% by mass from the viewpoint of dispersibility. Less than, more preferably less than 10% by mass.

The viscosity average molecular weight (Mv) of the polyethylene contained in the resin pellet of the present invention or the resin pellet itself of the present invention is 200,000 or more.
When the Mv of the polyethylene contained in the resin pellet or the resin pellet itself is 200,000 or more, when the resin pellet is mixed with a resin containing a low molecular weight component of less than Mv200,000 as a main component, a molded product of the mixture Alternatively, the tear strength or tensile strength of the film is significantly improved.
The Mv of polyethylene contained in the resin pellets is preferably more than 200,000, more preferably more than 300,000 (or more), even more preferably more than 500,000 (or more) from the viewpoint of the tensile strength of the molded product. It is. From the same viewpoint, the Mv of the resin pellet is preferably 300,000 or more, more preferably 500,000 or more.

  Further, the polyethylene in the resin pellet may be one containing a plurality of components having different molecular weights, for example, a mixture. For example, a mixture of polyethylene of Mv 100,000 and polyethylene of Mv 700,000 may have Mv of 200,000 or more as a whole.

Examples of the polyethylene include high density polyethylene (HDPE), ultra high molecular weight polyethylene (UHMWPE), linear low density polyethylene (LLDPE), high pressure method low density polyethylene, and mixtures thereof. Further, polyethylene having a narrow molecular weight distribution obtained using a metallocene catalyst and HDPE obtained by multistage polymerization may be used.
The proportion of polyethylene in the resin pellets is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and still more preferably 80 to 100% by mass.
In this specification, ultra high molecular weight polyethylene (UHMWPE) refers to polyethylene having a viscosity average molecular weight (Mv) of 350,000 or more. The proportion of UHMWPE in the total polyethylene is preferably 5 to 50% by mass from the viewpoint of optical properties, strength, and foreign matter removability of a molded product obtained using resin pellets, and from the viewpoint of dispersibility, Preferably it is 9-40 mass%.

  The resin pellets according to the first embodiment of the present invention are folded, separable, or laminated. In the first embodiment, the resin pellets having excellent strength and optical properties at the time of film formation and excellent removal of foreign matters such as fish eyes and unmelted gels are folded, separated, or laminated. Identified.

  FIG. 1A shows a schematic perspective view of a resin pellet according to the first embodiment. The cross section of the laminated resin pellet can have, for example, individual planes (FIG. 1B). As for the cross section of the resin pellet in the folded form, for example, one ends of a plurality of planar components can be bound to each other (FIG. 1C). Since Fig.1 (a)-(c) is typical, the resin pellet of this embodiment is not restricted to what has the uniform lamination | stacking state shown to Fig.1 (a)-(c).

  About the resin pellet of the separable form, it is sufficient that at least a part of the pellet is separable. The resin pellet in the separable form may specifically have a non-binding portion, and more specifically may have a non-crimped portion, a non-adhesive portion, or a non-fused portion. For example, as shown in FIG. 2A, a resin pellet having both a binding part and a non-binding part by embossing a pellet having a folded form or a laminated form (FIG. 2B) Is obtained. Since FIGS. 2A and 2B are schematic, the resin pellets of this embodiment are limited to those having the uniform laminated state and the embossed portion shown in FIGS. 2A and 2B. I can't.

  The resin pellet according to the first embodiment is to uniformly stretch the molecular chains of polyethylene contained in the pellet, and to ensure strength and foreign matter removability when forming a film from the pellet and other materials, It is preferable to include at least one film having a thickness of 500 μm or less, at least one fiber having a diameter of 100 μm or less, or at least one particle having a particle diameter of less than 100 μm, and a laminate in which a plurality of films having a thickness of 500 μm or less are stacked. More preferably, the plurality of films having a thickness of 500 μm or less preferably have different resin compositions. In the case of a film, a more preferable range of the film thickness is 100 μm or less, and if it is within this range, it is not necessary to reduce the extrusion amount in order to reduce unmelted gel. The film thickness is still more preferably 50 μm or less, and if it is within this range, the components having a high molecular weight are already dispersed to 50 μm or less, so that unmelted gel is not visually observed.

The resin pellet according to the second embodiment of the present invention has a constituent part (S), and the constituent part (S) has a planar shape, a fibrous shape, a hollow fiber shape, or a non-woven fabric shape.
In this specification, a component part (S) means the lump which comprises one piece of pellet, The shape is planar shape, a fiber shape, a hollow fiber shape, or a nonwoven fabric shape. In the second embodiment, the resin pellets having excellent strength and optical properties at the time of film formation and excellent removal of foreign matters such as fish eyes and unmelted gel are planar, fibrous, hollow fiber, or nonwoven fabric. It is specified by the component part (S) which is a shape.

  The perspective view of the resin pellet which has a planar structural part (S) is shown by Fig.1 (a) or FIG.2 (b). In FIG. 1, the component (S) having a substantially uniform film thickness is shown, whereas in FIG. 2, the component (S) is embossed.

  In the second embodiment, the molecular chain of polyethylene contained in the pellet is uniformly stretched, and from the viewpoint of ensuring strength and foreign matter removability when forming a film from the pellet and other materials, The constituent part (S) is preferably formed from a film having a film thickness of 500 μm or less or a fiber having a diameter of 100 μm or less, and the resin pellet is more preferably a laminate in which a plurality of films having a film thickness of 500 μm or less are laminated. Preferably, it is more preferable that the plurality of films have different resin compositions.

  The case where the resin pellet has a film having a film thickness of 50 μm as the constituent part (S) will be described. Since the crystalline region of polyethylene is also extended to the level of the film thickness of 50 μm, the size is smaller than that of polyethylene powder. It is presumed that good dispersion was obtained even when melt-kneaded with conventional LLDPE. Since this dispersion becomes better as the film becomes thinner, the film thickness is preferably less than 30 μm, and preferably 3 μm or more from the viewpoint of the handling properties of the film.

The resin pellet according to the third embodiment of the present invention has a bulk density of 0.1 to 0.4 g / cm ³ measured according to Japan Powder Industry Technical Association Standard SAP01-79. In the third embodiment, the structure of the resin pellets having excellent strength and optical properties at the time of film formation and excellent removal of foreign matters such as fish eyes and unmelted gel is 0.1 to 0.4 g / cm. Specified by a bulk density in the range of ³ . The bulk density of the resin pellets is preferably less than 0.35 g / cm ³ , more preferably 0.30 g / cm 2 from the viewpoint of further improving the strength, optical property, or foreign matter removal property of the film obtained using the resin pellets. cm ³ or less, most preferably less than 0.28 g / cm ³ .

  The resin pellet according to the third embodiment is from the viewpoint of uniformly stretching the molecular chain of polyethylene contained in the pellet and ensuring strength and foreign matter removability when forming a film from the pellet and other materials. The plurality of constituent parts (S) are preferably a laminate in which a plurality of films having a film thickness of 500 μm or less are laminated, and more preferably a laminate comprising two or more resin films having different resin compositions. preferable.

The resin pellet according to the fourth embodiment has the following conditions (a) to (c):
(A) in a folded, separable or laminated form;
(B) having a planar, fibrous, hollow fiber, or non-woven fabric component; and (c) a bulk density measured according to Japan Powder Industry Technical Association Standard SAP01-79 is 0.1-0.5 g / cm ³ ;
Satisfying at least one of the following.
The configuration common to the resin pellets according to the first, second, third and fourth embodiments will be described in detail below.

As an index for removing foreign matter such as unmelted gel, resin pellets 5 to 60% by mass, linear low density polyethylene (LLDPE) having a melt index (MI) of 2 and a density of 0.940 g / cm ³ The polyolefin pellets were prepared by dry blending, and the resulting polyolefin pellets were kneaded at 200 ° C. and 50 rpm for 10 minutes using a lab plast mill manufactured by Toyo Seiki Co., Ltd. When a film having a thickness of 20 μm is formed by forming a sheet having a thickness of 500 μm at 10 MPa on a pressed plate with the obtained molten resin by stretching it 5 × 5 times by a biaxial stretching machine. has been 100 cm ² per film, it is preferred that there are 10 or fewer unmelted gels, more preferably 5 or less unmelted Le is present, more preferably there are more than one, unmelted gel, is even more preferably unmelted gel zero. In this case, the unmelted gel is caused by poor dispersion of the high molecular weight component, and means that the diameter exceeds 0.3 mm when observed with a magnifying glass or the like. Contaminants or foreign matters having a diameter smaller than 0.3 mm or other than that are not counted as unmelted gel.

  The main component of the resin pellet is preferably melt-kneaded polyethylene. In this technical field, it is known that the strength of a polymer molded product varies depending on the number of entanglement points between tie molecules. Although not wishing to be bound by theory, melt kneading reduces the polymer crystallite size and increases the entanglement points between tie molecules, thereby improving the strength of resin pellets and molded articles using the same. It is possible. The melting and kneading of polyethylene can be performed by a melting device (melter) and / or a kneader.

  The resin pellet preferably has a planar constituent part, more preferably the constituent part is a film, and still more preferably the film is a microporous film. When a resin pellet having a planar portion formed from a film or microporous film containing polyethylene as a main component is produced using a pellet compared to a resin pellet formed from polyethylene particles or powder. In addition, the strength of the produced molded product tends to be excellent.

The thickness of the microporous membrane is preferably 3 μm or more and 50 μm or less from the viewpoint of handling, and improves the strength of the polyethylene-based resin composition produced using resin pellets having planar components derived from the microporous membrane. From the viewpoint of making it, it is more preferably 10 μm or more and 20 μm or less, and further preferably 4 μm or more and 20 μm or less.
The porosity of the microporous film is preferably 10% or more and 80% or less, more preferably 20% or more and 60% or less, and still more preferably, from the viewpoint of balancing strength, optical properties, foreign matter removal property, and permeability. 30% or more and 50% or less.

  Even when a polyethylene microporous membrane is used in the resin pellet, the viscosity average molecular weight (Mv) of the polyethylene is preferably 200,000 or more (or more), more preferably from the viewpoint of the strength of the molded product using the resin pellet. It is 300,000 or more (or more), more preferably 500,000 or more (or more).

Although the manufacturing method in particular of a microporous film is not ask | required, you may use the film | membrane manufactured by the method of international publication 2005/103127 or international publication 2006/38532, for example. Specifically, from the viewpoint of dispersing polyethylene having an Mv of 200,000 or more, a plasticizer is mixed into a raw material polyethylene, melt-extruded, and phase-separated when cooled by a casting apparatus or the like, then stretched, Furthermore, a microporous film can be produced by a method of extracting and removing the plasticizer using a solvent to open the holes, a so-called wet method. According to the wet method, polyethylene plastics having an Mv of 200,000 or more are swollen by the plasticizer, so that the high molecular weight component is easily dispersed, and a film with good film quality can be obtained when the resin pellet is mixed with conventional LLDPE. It is done.
The microporous membrane here has a porosity of preferably 10% to 80%, more preferably 20% to 65%, and an air permeability of preferably 10 sec / 100 cc to 5000 sec / 100 cc, more preferably 50 sec /. 100 cc or more and 1000 sec / 100 cc or less.
As for the wet method, for example, the microporous membrane manufactured by the method described in International Publication No. 2006/38532 has a pore diameter of about 0.05 μm and the thickness of the resin trunk around the pore is about 0.1 μm. Therefore, the high molecular weight component of polyethylene constituting the trunk is already dispersed to 0.1 μm, and polyolefin resin pellets are manufactured using this microporous membrane, and the manufactured resin pellets are melted with general LLDPE. When kneaded, a film having a very high molecular weight component and excellent strength and film quality can be obtained. The thickness of the trunk can be confirmed by observing with a scanning electron microscope or the like.
Examples of the strength herein include tensile strength and tear strength for the film, and the puncture strength of the film may be used as an evaluation standard in this specification.
The film quality means that there is no fish eye or unmelted gel generated on the film surface. The film quality may be judged by observing the number of fish eyes or unmelted gel in a film cut out in a 100 mm square with a loupe or visually.

  As a method for producing resin pellets, for example, a method described in JP-A-2006-21519 (Patent Document 3) can be used. Specifically, a polyethylene raw material prepared in advance, for example, a polyethylene film or a microporous membrane, is individually focused, overlapped, cut, or mixed with another resin raw material, and then pressure, etc. The resin pellets can be manufactured by binding to the desired size and then cutting to a desired size.

In the conventional manufacturing method of resin pellets, for example, in the case of high-density polyethylene (HDPE), the resin powder polymerized in a polyethylene manufacturing plant is melt-kneaded with an extruder, and the molten resin extruded into a string shape is cut and the maximum size is obtained. In the case of obtaining pellets of about 2 to 5 mm, in the first, second, third or fourth embodiment, a film formed in advance, a molded fiber or the like can be used. For this, a laminate (F) in which a plurality of films, more preferably several hundred layers, are laminated can be used.
Each layer constituting the laminate (F) may have a thickness of 500 μm or less. It is preferable that a laminated body (F) contains two or more types of resin films from which resin composition mutually differs from viewpoints of productivity, handling property, versatility, etc.

  As a manufacturing method of a laminated body (F), when using a film, it compresses in a thickness direction with a roll etc., and cuts out to the size of about 6 mm in length and width, with several layers of the film previously wound around the paper tube etc. piled up. And a known method such as a method of compressing a film formed by the method described in JP 2006-21519 A (Patent Document 3) with a roll while converging in the width direction, and then cutting out in the length direction. May be used.

  When the resin pellet has a fibrous component, an ultrahigh molecular weight polyethylene fiber described in Japanese Patent Publication No. 6-15721 or a fiber produced by the method described in Japanese Patent No. 4623780 can be used. The fiber used for forming the fibrous component also has a fiber diameter of preferably 500 μm or less, more preferably 50 μm or less, as with the film thickness.

  When the resin pellet has a particulate constituent part, the particle diameter of the constituent part is preferably 500 μm or less, more preferably 50 μm or less. Porous particles can be used, and in that case, the thinner the trunk portion, the better, as in the case of the microporous membrane.

  The films, microporous membranes, fibers and particles described above can be used alone or in combination to form the constituent parts of the resin pellets. For example, a microporous film containing polyethylene as a main component and a nonporous film containing polypropylene as a main component may be combined.

The resin pellets may contain a known antioxidant such as a phenol-based antioxidant, a phosphorus-based antioxidant, and a sulfur-based antioxidant. The amount of the antioxidant added to the resin pellet can be adjusted according to the use of the pellet, and is generally in the range of 100 PPM to 1% by mass.
The resin pellet may contain an additive for modifying the pellet as long as the problem of the present invention can be solved. Additives include, for example, antifogging materials such as glycerin esters; slip materials typified by fatty acid amides such as erucic acid, stearic acid, and oleic acid; antistatic agents; inorganic fillers such as silica and alumina; liquid paraffin; and lubrication Oil or calcium stearate as an internal lubricant.

  The resin pellets may be recycled resin pellets from the viewpoints of productivity, environmental considerations, and the like.

<Resin composition>
Another aspect of the present invention is a resin composition manufactured using the resin pellets according to the first, second, third or fourth embodiment, and a method for manufacturing the same.
Dry mixing of resin pellets according to the first, second, third or fourth embodiment into a mixture such as pellets, powder, particles, slurry, paint, etc. containing HDPE, LDPE, LLDPE, etc. as main components The polyethylene resin composition can be obtained by mixing and / or adding by a method or a wet mixing method. As a dry mixing method here, the method of melt-mixing with a normal single screw or a twin screw extruder, or the method of Unexamined-Japanese-Patent No. 2006-21519 (patent document 3) can be used.
When the obtained polyethylene resin composition is made into a film by extrusion molding such as inflation molding, generation of unmelted gel during extrusion can be suppressed or eliminated, and the strength of the obtained film is greatly improved. Can be made.
As the mixture, LDPE or LLDPE, in particular LLDPE using a metallocene catalyst as a raw material, is preferable from the viewpoint of the strength, optical properties, or foreign matter removability of the molded product of the resin composition.
As an example, when a polyolefin resin pellet of the present invention is dry blended with a conventional low molecular weight polyethylene such as LDPE or LLDPE to form a film, the strength dramatically increases and the optical properties are impaired. A film in which no unmelted gel is generated is obtained.

When the mixture contains LLDPE, the density of LLDPE is preferably in the range of 900 to 945 kg / m ³ , more preferably 910 to 940 kg / m ³ , and still more preferably 915 to 940 kg / m ³ . The melt flow rate (MFR) of LLDPE is preferably in the range of 0.1 to 50, more preferably in the range of 0.1 to 10, and still more preferably in the range of 0.3 to 4.0.

  In order to improve the film strength by using the resin composition for film production, the mixture is preferably LLDPE polymerized by using a metallocene catalyst and hexene or octene as a comonomer component, and its molecular weight. The distribution is preferably 3 or more and less than 15, more preferably 5 or more and less than 10.

  The amount of resin pellets according to the first, second, third or fourth embodiment added to low molecular weight high-density polyethylene such as LLDPE or LDPE is determined depending on the strength of the resin composition or its molded product and its unmelted state. From the viewpoint of gel removability, it is preferably 5% by mass or more and 60% by mass or less, and more preferably 10% by mass or more and 40% by mass or less, considering the optical properties of the molded product. In consideration of the properties, the content is more preferably 10% by mass or more and 30% by mass or less.

  In order to improve the heat resistance of the molded film, polypropylene can be mixed with the polyethylene resin composition. In that case, from the viewpoint of removing fish eyes, the viscosity average molecular weight (Mv) of polypropylene is preferably 1,3,000,000 or less, more preferably 700,000 or less, and even more preferably 600,000 or less. From the viewpoint of the strength of the resin composition containing polyethylene and polypropylene and the strength of the molded product, the Mv of polypropylene is preferably 100,000 or more, more preferably 200,000 or more. From the same point of view, the use of polypropylene having reduced stereoregularity using a metallocene catalyst or the like as a mixture, or block polypropylene (BPP) or random polypropylene (RPP) with respect to isotactic polypropylene (IPP) It is preferable to use a resin composition blended with 0.5 to 30% by mass as a mixture.

  In addition to polypropylene and polyethylene, other resin components; or inorganic fillers, organic fillers, antioxidants, dispersion aids, antistatic agents, processing stabilizers, crystal nucleating agents, internal lubricants, etc. Additives can be mixed. The proportion of any of these components in the resin composition is preferably 5% by mass or less, more preferably 2% by mass or less, and may be substantially 0% by mass.

Examples of the resin component include engineering plastic resins such as polyphenylene ether; polyamide resins such as nylon 6, nylon 6-12 and aramid resin; polyimide resins; polyester resins such as PET and PBT; polycarbonate resins; polyvinylidene fluoride (PVDF) A copolymer of ethylene and vinyl alcohol, a copolymer of C _{2 to} C ₁₂ α-olefin and carbon monoxide and hydrogenated product thereof; a hydrogenated product of styrenic polymer; and styrene. Copolymer of α-olefin and hydrogenated product thereof; Copolymer of styrene and aliphatic monounsaturated fatty acid; Polymer of acrylic acid and / or its derivative; Styrene and conjugated diene unsaturated monomer Copolymers, thermoplastic resins selected from these hydrogenated products, polyketones, and the like, as well as polybutene-1, polymethylpentene- It may be 1 etc.

  Examples of the inorganic filler include oxide ceramics such as alumina (eg, α-alumina), silica, titania, zirconia, magnesia, ceria, yttria, zinc oxide, iron oxide; silicon nitride, titanium nitride, boron nitride, etc. Nitride ceramics: silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin clay, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amicite, bentonite, asbestos Ceramics such as zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand; glass fibers and the like may be mentioned, and these may be used alone or in combination.

Examples of the antioxidant include phenolic antioxidants such as “Irganox 1010”, “Irganox 1076”, “BHT” (both are trademarks, manufactured by Ciba Specialty Chemicals), phosphorus-based or sulfur-based two-component antioxidants. Examples thereof include secondary antioxidants, hindered amine-based weathering agents, and the like, which can be used alone or in combination.
From the viewpoint of strength, optical properties and foreign matter removability of a molded product obtained from the resin composition, a combination of a phenolic antioxidant and a phosphorus antioxidant is preferable. Specifically, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butylhydroxyphenyl) propionate 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butylhydroxybenzyl) benzene, tris (2,4-di-t-butylphenyl) phosphite, tetrakis (2 , 4-Di-tert-butylphenyl) -4,4′-biphenylene phosphite, 6- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8, 10-tetra-t-butyldibenzo [d, f] [1,3,2] dioxyphosphate pins and the like.
The blending amount of the antioxidant is preferably 100 ppm to 10,000 ppm with respect to the total resin solid content of the microporous film formed using the resin composition. When a phenolic antioxidant and a phosphorus antioxidant are used in combination, the ratio of phenolic / phosphorous is preferably 1/3 to 3/1.

  As a dispersion aid for polypropylene and polyethylene, for example, a hydrogenated styrene-butadiene elastomer, an elastomer copolymerized with ethylene and propylene, or the like can be used. The blending amount of the dispersion aid is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the total amount of polypropylene and polyethylene.

Antistatic agents include amines such as alkyldiethanolamine and hydroxyalkylethanolamine; amine esters such as stearyl diethanolamine monofatty acid ester; alkyloamides such as lauric acid diethanolamide and stearic acid diethanolamide; glycerin, diglycerin and the like Mono-fatty acid esters; anionic antistatic agents such as alkylbenzene sulfonic acids; polyoxyethylene alkyl ethers and the like. These may be used alone or in combination. The blending amount of the antistatic agent is preferably 500 ppm to 10,000 ppm with respect to the total resin solid content of the microporous film formed using the resin composition.
Further, the resin composition may contain calcium stearate, magnesium stearate or a hydrate thereof, for example, sodium 12-hydroxystearate as an internal lubricant. In this case, the preferable content of the internal lubricant is 50 ppm or more and 5000 ppm.

  The resin composition of this invention can be used for manufacture of a molded article. For example, various types of molding such as extrusion molding, injection molding, blow molding, and molding can be performed. The manufactured molded article is preferably a packaging film or an agricultural film because it is excellent in optical properties, strength, and foreign matter removability.

[Measurement method of physical properties]
(I) The thickness of each layer and the total thickness (μm)
The thickness of the layer was measured by cross-sectional observation with a general scanning electron microscope (S4100, manufactured by Hitachi, Ltd.).

(II) Viscosity average molecular weight Mv
Based on ASTM-D4020, the intrinsic viscosity [η] at 135 ° C. in a decalin solvent was determined. Mv of polyethylene was calculated by the following formula.
[Η] = 6.77 × 10 ⁻⁴ Mv ^0.67

(III) Porosity of microporous membrane (%)
The basis weight W (g / cm ² ) and the average density ρ (g / cm ³ ) of the components (resin and additive) constituting the microporous membrane are calculated from the mass of the 100 mm square microporous membrane sample, and the microporous membrane is calculated. The following formula was calculated from the thickness d (cm).
Total layer porosity (%) = (100−W / (d × ρ)) × 100

(IV) Air permeability of microporous membrane (second / 100cc)
Based on JIS P-8117, it was measured with a Gurley type air permeability meter “G-B2” (trademark, manufactured by Toyo Seiki Seisakusho Co., Ltd.).
The values in Table 1 are air permeability in terms of 20 μm calculated by proportional calculation based on the total thickness.

(V) Puncture strength (g)
Using a handy compression tester “KES-G5” (trade name, manufactured by Kato Tech Co., Ltd.), the puncture test was performed under the conditions of a radius of curvature of the needle tip of 0.5 mm and a puncture speed of 2 mm / sec.
The values in Table 3 are puncture strengths in terms of 20 μm calculated by proportional calculation based on the total thickness.

(VI) Pore diameter of microporous membrane It judged from the surface photograph image | photographed by the surface observation by the general scanning electron microscope (Hitachi Ltd. S4100).

(VII) Bulk density The bulk density of the sample was measured in accordance with Japan Powder Industrial Technology Association standard SAP01-79.

(1) Manufacture of polyolefin resin pellet (1-1) Manufacture of member (1-1-1) Manufacturing method of microporous membrane 1 (S1) The manufacturing method of microporous membrane 1 (S1) is as follows. This is an example of using a microporous membrane mainly containing high molecular weight polyethylene.
90% by mass of polyethylene having a powdery viscosity average molecular weight of 400,000 and 10% by mass of polypropylene having a viscosity average molecular weight of 700,000 are used as a raw resin, and tetrakis- [methylene- ( 3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] 0.3 parts by mass of methane was mixed. These raw materials were stirred with a Henschel mixer to prepare the raw materials.
Next, this raw material was put into a twin screw extruder (caliber 404 mm, L / D = 49). In the middle of the cylinder of the extruder, 150 parts by mass of liquid paraffin (kinematic viscosity at 38 ° C .: 75.9 cSt, density: 868 kg / m ³ ) was injected. A 150 mesh screen and a metering gear pump were disposed between the extruder and the die. The die and extruder were set at 200 ° C. A T die was used as the die. The melted film original material coming out of the die was cooled and solidified with a cast roll to form a sheet having a thickness of 1.5 mm. This sheet was stretched at an area magnification of 45 times under a condition of 120 ° C. with a biaxial stretching machine, immersed in methylene chloride to extract and remove liquid paraffin, and then dried. Furthermore, heat treatment was performed in a heating furnace at 130 ° C., thereby obtaining a microporous film having a thickness of 20 μm. This microporous membrane was slit to a width of 30 cm and wound around a paper tube. The length of the microporous membrane was 300 m. The surface state of this microporous membrane was good, and no unmelted gel or the like having a high molecular weight component was observed. The average pore diameter of this microporous membrane was 0.05 μm, and the pores were uniformly opened over the entire surface. This microporous membrane was used as the microporous membrane 1 (component S1).
(1-1-2) Manufacturing method of S2 film It is the same method as the above (1-1-1) except that polyethylene having a viscosity average molecular weight of 300,000 is used and 20 parts by mass of liquid paraffin is added to the extruder. Film 1 was molded and used as component 2. This film had almost no pores.
(1-1-3) Method for Producing S3 Fine Particles S3 fine particles are powdery polyethylene having an average molecular weight of 400,000 used during production of the microporous membrane 1 (S1).

(1-2) Manufacture of polyolefin-based resin pellets POP1 to P3 The microporous film (component S1) wound around the paper tube manufactured in (1-1) above is once focused by the method shown in FIG. After performing point pressure contact with the embossing rollers (3, 3), the sheet was cut in the MD direction with a cutter (4) included in the apparatus to obtain a polyolefin resin pellet (POP1) as a pellet-shaped molded body. In this step, heating by an external heat source such as a heater was not performed. In FIG. 3, the component S1 is unwound from the two rolls (1, 2) and is subjected to point pressure contact by the embossing rollers (3, 3). However, a plurality of regions in one component S1 may be joined by unwinding the component S1 from only one roll (1) and compressing, folding, or converging (FIG. Not shown).
The pellet (POP1) is a laminate of a plurality of films. When each layer was peeled off with a finger, the outer edge portion was peeled off, but the center portion was partially peeled off, but most of the effect of the embossing roll It was firmly bonded. When the peeled portion was observed with an SEM, it exhibited a microporous structure, but the pores were blocked in the bonded portion. The long side of the pellet (POP1) was 7 mm, the short side was 4 mm, and the thickness was 1 mm. The bulk density of the pellet (POP1) was about 0.2.
POPs 2 to 4 were produced in the same manner as described above except that component 1 or 2 was changed as shown in Table 2. POP3 was obtained by the same method as described above using a mixture in which the constituent parts S1 and S2 were mixed by 50%, and POP4 was obtained by using polymerized powder as it was.

(2) Production of LLDPE film A commercially available LLDPE copolymer (main monomer: PE, comonomer: hexene, catalyst: metallocene catalyst, MI = 2, density: 940 kg / m ³ ) and polyolefin resin pellet POP are dry blended. Then, a polyethylene resin composition adjusted to the composition shown in Table 3 was obtained, and the polyethylene resin composition was kneaded for 10 minutes under the conditions of 200 ° C. and 50 rpm with a laboratory plastic mill manufactured by Toyo Seiki Co., Ltd. In Comparative Example 1, a film was formed using only the LLDPE copolymer, and in Comparative Example 2, the powder of component S3 (POP4) was directly blended with the LLDPE copolymer.
The molten resin was molded on a press plate at 10 mpa to a thickness of 500 μm, and then stretched with a biaxial stretching machine (stretcher) to form a film. The molding results of the formed film are also shown in Table 3, and the evaluation criteria for the film are shown in Table 4.

As shown in Table 3, in the film formation of the examples, good films were obtained with respect to the evaluation of tensile strength and unmelted gel.
In Comparative Example 2, although the polyethylene powder having a sufficiently high viscosity average molecular weight was mixed with the LLDPE copolymer as the constituent part S3, the strength did not increase and the unmelted gel evaluation was also deteriorated. This is presumed to be because the high molecular weight component of polyethylene that should help to improve the strength does not function sufficiently and exists as an agglomerated gel.

  The resin pellets according to the present embodiment are used for the production of products having excellent physical properties such as strength and optical properties in molding processing of films and the like, and more specifically, relatively low molecular weight polyethylene having a viscosity average molecular weight of 150,000 or less. In order to improve the physical properties, it is possible to mix with a low density polyethylene (LDPE) and / or a linear low density polyethylene (LLDPE).

1 Component 1
2 component 2
3 Embossed roller or compression roller 4 Cutter (included inside)
5 Polyolefin resin pellet (POP) container

Claims (10)

A resin pellet containing polyethylene as a main component,
Resin pellets in which the polyethylene or the resin pellets contained in the resin pellets have a viscosity average molecular weight of 200,000 or more and are folded, separable, or laminated. A resin pellet containing polyethylene as a main component,
A resin pellet having a viscosity-average molecular weight of 200,000 or more of the polyethylene or the resin pellet contained in the resin pellet and having a planar, fibrous, hollow fiber, or non-woven fabric component. A resin pellet containing polyethylene as a main component,
The polyethylene or the resin pellets contained in the resin pellets have a viscosity average molecular weight of 200,000 or more, and a bulk density measured according to Japan Powder Industry Technical Association Standard SAP01-79 is 0.1 to 0.4 g. / Cm ³ resin pellet.   The resin pellet according to any one of claims 1 to 3, which is a recycled resin pellet. Polyolefin pellets were prepared by dry blending 5-60 mass% of the resin pellets with linear low density polyethylene (LLDPE) having a melt index (MI) of 2 and a density of 0.940 g / cm ^3. Then, using a lab plast mill manufactured by Toyo Seiki Co., Ltd., the polyolefin pellets were kneaded at 200 ° C. and 50 rpm for 10 minutes to obtain a molten resin, and after molding the molten resin on a press plate at 10 MPa, The film according to any one of claims 1 to 4, wherein there are 5 or less unmelted gels per 100 cm ^{2 of the} film when the film is formed by stretching 5 times in length and 5 times in width with a biaxial stretching machine. 2. The resin pellet according to item 1.   The resin pellet according to any one of claims 1 to 5, which is a laminate in which films having a thickness of 500 µm or less are laminated.   The resin pellet according to claim 6, wherein the laminate includes two or more resin films having different resin compositions.   The method to manufacture a resin composition using the resin pellet of any one of Claims 1-7.   The method according to claim 8, wherein the resin composition comprises the resin pellets and a low density polyethylene polymer.   A method for producing a packaging film or an agricultural film using the resin composition produced by the method according to claim 8.

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