JP5052764B2 - Method for producing metallocene linear low density polyethylene resin composition containing nucleating agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyethylene resin composition having improved mechanical properties such as rigidity and transparency by homogeneously mixing and dispersing a nucleating agent in a low-density polyethylene resin and having improved molding cycle ability by increasing crystallization temperature, and to provide a method for producing the same. <P>SOLUTION: The polyethylene resin composition is obtained by mixing and dispersing 0.01-0.5 wt% of a nucleating agent in a polyethylene resin having a density of 0.900-0.925 g/cm<SP>3</SP>and a melt mass flow rate (MFR) of 1-100 g/10 min. The polyethylene composition has improved rigidity and transparency and a higher crystallization temperature by 3&deg;C or more by the addition of the nucleating agent. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a polyethylene resin composition obtained by uniformly mixing and dispersing a nucleating agent in a low-density polyethylene resin, wherein the mechanical properties and transparency are improved, and the crystallization temperature is increased. The present invention relates to a product and a manufacturing method thereof.

  Polyethylene resins include high-density polyethylene, low-density polyethylene, linear low-density polyethylene obtained by copolymerization of ethylene and α-olefin, and are molded into films, sheets, and various containers according to their properties. Widely used. However, the polyethylene resin has higher demands from the market, and various improvements have been made to meet these demands. As one of the improvement methods, there are an improvement in molding cycle property by adding a nucleating agent, an improvement in mechanical properties such as rigidity and impact resistance, and an improvement in appearance such as transparency and gloss.

  Among polyethylene resins, in general, a high-density polyethylene resin has a high crystallization temperature, so that it quickly solidifies when cooled and has a relatively good molding cycle property and a high rigidity, but its transparency is extremely poor. On the other hand, a low-density polyethylene resin has relatively good transparency but low rigidity and a low crystallization temperature, so that solidification during cooling is slow and molding cycle performance is poor.

  At present, a copolymer of ethylene and α-olefin produced using a metallocene catalyst, that is, a metallocene linear low density polyethylene is widely used. Since the metallocene catalyst can control the polymerization at the molecular level, it has a low molecular weight component and a uniform composition distribution compared to conventional ones. It is highly transparent, has a low melting point, has excellent impact resistance, and has a higher density. Small linear low density polyethylene can be produced. This metallocene linear low-density polyethylene has high transparency and good low-temperature sealability, so it is processed into a film and widely used in food containers and the like. However, since the crystallization temperature is low, the molding cycleability is poor. In particular, when the number of small containers is large, the molding cycle performance greatly affects the productivity, that is, the cost.

  As mentioned above, low-density polyethylene is often used after being formed into a film by taking advantage of its excellent transparency and low-temperature sealing properties. However, the addition of a nucleating agent improves the molding cycle performance. In other words, when trying to increase the crystallization temperature, it is difficult to use the nucleating agent because there is a risk of occurrence of defects due to poor dispersion of the nucleating agent and / or deterioration of the polyethylene resin. It was said.

  Patent Document 1 discloses that the phosphoric acid ester metal salt in polyolefin, particularly polypropylene, is pulverized by pulverizing the phosphoric acid ester metal salt nucleating agent to an average particle size of 10 μm or less, particularly preferably 0.5 μm or less. An example in which the dispersibility of the system nucleating agent is improved is disclosed.

In Patent Document 2, a nucleating agent is added to a high density polyethylene having a density of 0.940 g / cm ³ or more, and mixed and dispersed, thereby improving the molding cycle performance and excellent rigidity, impact strength and transparency. Although a polyethylene resin composition is disclosed, it is said that if the density is less than 0.940 g / cm ³ , the addition of a nucleating agent lowers the rigidity, so that it cannot be used. Thus, when trying to improve molding cycle performance by adding a nucleating agent, the effect is insufficient in a low-density polyethylene resin, and mechanical properties such as rigidity must be sacrificed. It was.

JP 2004-83852 A JP-A-6-248123

  When trying to improve molding cycleability by adding a nucleating agent to low-density polyethylene, there is a risk of generating defects due to poor dispersion of the nucleating agent and / or deterioration of the polyethylene resin, particularly in film molded products. So far, it has been virtually impossible to use nucleating agents.

  Further, as described in Patent Document 1, in order to reduce the nucleating agent particles to 0.5 μm or less in order to improve dispersibility, a large amount of energy is used over a long period of time using a special pulverizer. In addition, the effect of adding a nucleating agent has not been confirmed in the case of low density polyethylene.

  Further, as described in Patent Document 2, in a low-density polyethylene resin, the addition of a nucleating agent increases the crystallization temperature without impairing mechanical properties such as rigidity, that is, molding cycle properties. It was considered difficult to improve.

The present invention has been made in view of solving the above-mentioned problems, and is a metallocene linear low-density polyethylene resin obtained by uniformly mixing and dispersing a nucleating agent in a specific metallocene linear low-density polyethylene resin. A method for producing a composition comprising: a metallocene linear low density polyethylene resin composition having improved molding cycle performance by improving mechanical properties such as rigidity and transparency, and increasing a crystallization temperature . The object is to provide a manufacturing method .

In order to solve the above problems, the method for producing a metallocene linear low-density polyethylene resin composition of the present invention comprises a cavity serving as a container,
Density is 0. 9 0 to 0. A metallocene linear low density polyethylene resin having a melt mass flow rate (MFR) of 1 to 100 g / 10 min at 9 25 g / cm ³ ,
The concentration of at least one nucleating agent selected from a phosphate ester metal salt nucleating agent, a sorbitol nucleating agent and a carboxylic acid metal salt nucleating agent is 0.
0 1 to 0. 5% by weight of the added formulation
When mixing and stirring the metallocene linear low density polyethylene resin and the nucleating agent by a rotating mixing stirrer that rotates in the cavity,
Until the metallocene linear low density polyethylene resin and the nucleating agent are mixed and stirred in the cavity to form a uniformly dispersed state,
Below the softening temperature of the metallocene linear low density polyethylene resin,
The tip peripheral speed of the rotary mixing stirrer is controlled to be not less than 20 m / sec and not more than 20 m / sec;
By making the flow of material in the cavity laminar,
Rigidity and transparency are improved before addition of the nucleating agent, and the crystallization temperature is increased by 3 to 21C .

  The polyethylene resin composition of the present invention has improved mechanical properties such as rigidity and transparency even with a low-density polyethylene resin, and the crystallization temperature is increased, that is, the molding cycle property is remarkably improved. In this molding process, significant productivity improvement can be achieved.

  As an application, since transparency is improved and there is no irregularity even if it is in a film form, it is suitable for a field in which low density polyethylene is suitably used, for example, a food packaging material, a pharmaceutical packaging material, etc. after being processed into a film Used.

  The polyethylene resin composition according to the present embodiment and the production method thereof will be described. In addition, this embodiment is only one form for implementing this invention, and this invention is not limited by this embodiment.

As a result of intensive research, the inventors have found that a polyethylene resin having a density of 0.900 to 0.925 g / cm ³ and a melt mass flow rate (MFR) of 1 to 100 g / 10 min has a nucleating agent of 0. A polyethylene resin composition obtained by adding 01 to 0.5% by weight and mixing and dispersing, with improved mechanical properties and transparency, and a crystallization temperature of 3 ° C. or more higher than before the addition of the nucleating agent. And a method for producing the same.

The polyethylene resin used in the present invention is a polyethylene resin having a density of 0.900 to 0.925 g / cm ³ and an MFR of 1 to 100 g / 10 min. A polyethylene resin having a density in this range is suitable for film molding because of its low melting point and excellent low-temperature sealing properties, but its molding cycleability is poor because of its low crystallization temperature. Moreover, about MFR, if it is less than 1 g / 10min, fluidity | liquidity is bad, and it is inferior to a moldability, and when it exceeds 100g / 10min, mechanical characteristics are inferior.

  Examples of the polyethylene resin used in the present invention include low density polyethylene, linear low density polyethylene and metallocene linear low density polyethylene, which are copolymers of ethylene and α-olefin. In particular, metallocene linear low density polyethylene has a high effect of increasing the crystallization temperature by adding a nucleating agent.

  Examples of the α-olefin copolymerized with ethylene include propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene and 1-decene. Those having 3 to 18 carbon atoms can be mentioned.

  As the nucleating agent used in the present invention, a phosphoric acid ester metal salt nucleating agent, a sorbitol nucleating agent, a carboxylic acid metal salt nucleating agent, and a mixture thereof are commonly used as nucleating agents. What is being done is mentioned.

  Examples of the phosphoric acid ester metal salt nucleating agent include sodium bis (4-tert-butylphenyl) phosphate, sodium 2,2'-methylenebis (4,6-ditert-butylphenyl) phosphate, and the like.

  Examples of the sorbitol-based nucleating agent include dibenzylidene sorbitol, bis (4-methylbenzylidene) sorbitol, bis (3,4-dimethylbenzylidene) sorbitol, and the like.

  Examples of the carboxylic acid metal salt nucleating agent include lithium benzoate, sodium benzoate, 4-tert-butylbenzoic acid aluminum salt, sodium adipate and the like.

The addition amount of the nucleating agent is 0. 0 with respect to the polyethylene resin composition of the present invention . 0 1 to 0. 5% by weight, and may be added directly to the polyethylene resin, or may be added to the polyethylene resin after a nucleating agent master batch is produced in advance. The concentration of nucleating agent is 0
. If it is less than 0 1% by weight, the increase in the crystallization temperature is insufficient. If it exceeds 5% by weight, the increase in the crystallization temperature reaches its peak, resulting in an increase in cost.

  The polyethylene resin composition of the present invention may contain other additives as necessary. As these additives, hindered amine light stabilizers (HALS), ultraviolet absorbers, phosphorus antioxidants, phenolic antioxidants, sulfur antioxidants, aliphatic organic acid metal salts and the like are generally used. Additive.

  If necessary, the polyethylene resin composition of the present invention may further comprise an antistatic agent comprising a cationic surfactant, an anionic surfactant, a nonionic surfactant, an amphoteric surfactant, and the like; a halogen compound, phosphorus Flame retardants such as acid ester compounds, phosphoric acid amide compounds, melamine compounds, melamine salt compounds of polyphosphoric acid, fluororesins or metal oxides; hydrocarbons, fatty acids, aliphatic alcohols, aliphatic esters, Lubricants such as aliphatic amides and metal soaps; heavy metal deactivators; hydrotalcites; organic carboxylic acids; colorants such as dye pigments; processing aids such as polyolefin powders; fumed silica, fine particle silica, silica, Diatomaceous earth, clay, kaolin, silica gel, calcium silicate, sericite, kaolinite, flint, feldspar powder, meteorite, attapa It can be used an additive such as calcium carbonate; Jaito, talc, mica, minnesotaite, silicate-based additives such as pyrophyllite.

  Since the polyethylene resin composition of the present invention has almost no blisters and good low-temperature sealing properties and molding cycle properties, it is mainly molded into a film and used for food packaging materials and the like.

  The polyethylene resin composition of the present invention is produced by adding a nucleating agent and, if necessary, the additive to a polyethylene resin, and mixing and dispersing it. In addition, a nucleating agent and, if necessary, the above-mentioned additives are added to a polyethylene resin in advance and mixed and dispersed to produce a high concentration nucleating agent master batch, which is then added to the polyethylene resin and mixed and dispersed. it can.

  The average particle size of the polyethylene resin used in the present invention is preferably 10 μm or more, and more preferably 100 μm or more. When the particle size is less than 10 μm, the polyethylene resin is not subjected to sufficient centrifugal force, so that it takes a long time for mixing and dispersing. As a result, the properties of the polyethylene resin composition are deteriorated. The particle size can be measured using a micrograph or the like in addition to using a measuring device such as a laser diffraction particle size distribution measuring device.

  In order to produce the polyethylene resin composition of the present invention, when the nucleating agent is mixed and dispersed in the polyethylene resin, the polyethylene resin composition is mixed and stirred below the softening temperature of the polyethylene resin until a uniform dispersion state is formed. It is utilized that the chemical bond of at least a part of the resin is cleaved and recombined after the molecular weight is lowered.

  When mixing and dispersing a nucleating agent in a polyethylene resin, the inventors have made a state in which at least a part of the chemical bond of the polyethylene resin is cut and reduced in molecular weight, and then recombined, thereby making the polyethylene resin more than conventional. It has been found that the nucleating agent can be more uniformly dispersed therein and is effective in suppressing characteristic deterioration.

  In order to obtain a uniformly dispersed state in a short time at a low temperature below the softening temperature, it is utilized to temporarily lower the molecular weight of the polyethylene resin. When the polyethylene resin and the nucleating agent are mixed and stirred in the cavity, the physical impact force exerted on the polyethylene resin by the rotating mixing stirrer rotating in one direction and the laminar flow created by the rotating mixing stirrer make it to the polyethylene resin. Due to the applied centrifugal force or the like, a part of the chemical bond of the polyethylene resin is broken, so that at least a part of the polyethylene resin is temporarily reduced to a lower molecular weight than before stirring. This low molecular weight substance makes it easier to diffuse the polyethylene resin and the nucleating agent than the polyethylene resin alone before being temporarily reduced in molecular weight, and contributes to bringing the mixed agitation into a uniformly dispersed state in a short time. be able to. Since a uniformly dispersed state can be obtained in a short time, it is possible to prevent deterioration of characteristics due to impact force and / or frictional heat accompanying long-time stirring.

  In order to determine the low molecular weight of polyethylene resin and the recombination of polyethylene resin after the low molecular weight, for example, detection of presence / absence of radical species such as ESR spectrum, infrared absorption spectrum and nuclear magnetic resonance Each determination means such as determination of structural identity by spectrum, determination that the change in molecular weight is within a predetermined value can be used, and also the relaxation time of the polymer.

  Further, in order to determine that the molecular weight of the polyethylene resin of the polyethylene resin composition obtained in the present invention is within a desired change amount, for example, within 20%, gel permeation chromatography for measuring the molecular weight, light Examples include a scattering method, a centrifugal separation method, and a viscosity measurement method.

  In the present invention, the structure of the polyethylene resin of the obtained polyethylene resin composition, particularly the primary structure, is compared with that of the polyethylene resin before mixing, in order to determine that there is no change, an infrared absorption spectrum or nuclear magnetic field is used. A resonance spectrum or the like is used.

  By using each of the above criteria, those skilled in the art can design a production method, such as forming a state in which at least a part of the chemical bond of the polyethylene resin is cleaved and reduced in molecular weight and then recombined. .

  In addition, if the peripheral speed of the tip of the rotary mixing stirrer is controlled to 20 m / sec or more and 200 m / sec or less and the flow of the mixed stirrer in the cavity is laminar, at least a part of the chemical bond of the polyethylene resin is broken. It was found that it was easy to obtain a recombined state after the molecular weight was lowered. Note that laminar flow is a concept including powder agitation, and when a cylindrical internal space is used as the cavity, the mixed substance moves concentrically and is defined in a state where it hardly moves in the radial direction. The state can be confirmed visually.

  In addition, when the internal space of a cylindrical container is used as the cavity, it is found that it is easy to obtain a state in which at least a part of the chemical bond of the polyethylene resin is broken and recombined after the molecular weight is lowered. I was able to.

  It has also been found that when the rotary mixing stirrer has a blade-like shape, it is easy to obtain a state where at least a part of chemical bonds of the polyethylene resin is cut and recombined after the molecular weight is lowered. The more these conditions are combined, the easier it is to obtain a state where all of the conditions are desirably combined, and at least a part of the chemical bonds of the polyethylene resin is cut and the molecular weight is lowered.

  When the tip peripheral speed of the rotary mixing stirrer exceeds 200 m / sec, heat generation due to friction becomes intense, which may cause thermal degradation of the polyethylene resin. Thermal degradation temporarily reduces the recombination ability of the cleavage site when the chemical bond of the polyethylene resin is broken to lower the molecular weight. Normally, a polyethylene resin that has been cut recombines with a decrease in stirring energy, but thermal degradation tends to hinder the binding of this low molecular weight polyethylene resin. In many cases, the polyethylene resin reduced in molecular weight that cannot be bonded attacks the polyethylene resin and / or the formed polyethylene resin composition, and deteriorates the properties of the formed polyethylene resin composition. There is a case. If the tip peripheral speed of the rotating mixing stirrer is less than 20 m / sec, laminar flow stirring cannot be obtained, sufficient impact force and centrifugal force cannot be transmitted to the polyethylene resin, and the molecular weight is not temporarily reduced. In some cases, the material may not be uniformly dispersed, resulting in poor dispersion.

  The mixed stirring state is performed under a laminar flow state. Compared to turbulent flow, laminar flow enables efficient use of centrifugal force and shearing force due to impact force with rotating blades, etc., and is advantageous for producing a low molecular weight polyethylene resin temporarily. It is. Since centrifugal force and shearing force can be used efficiently, the peripheral speed of the blade can be minimized, and characteristic deterioration due to frictional heat or the like can be prevented. A person skilled in the art can visually determine the laminar flow that is concentric stirring.

  In order to suppress characteristic deterioration due to frictional heat or the like, it is also effective to cool the inside of the container and / or the inside of the stirring blade through a coolant such as water.

  An example of a mixing and dispersing apparatus capable of forming a state in which a chemical bond of at least a part of a polyethylene resin is cut and reduced in molecular weight and then recombined will be described below with reference to the drawings. 1A and 1B are sectional views of a mixing and dispersing apparatus 100 according to the present embodiment. FIG. 1A is a longitudinal sectional view taken along a gravity direction plane with the rotation axis direction perpendicular to the gravity direction of the rotation shaft body 14 to be described later as a vertical direction, and FIG. 1B is a vertical plane with respect to the rotation axis direction. FIG. 1B is a lateral cross-sectional view taken along the line XX ′ of FIG.

  The mixing and dispersing apparatus 100 includes an inner wall member 32 that surrounds and forms a cavity 10 that serves as a container, and a cavity 10 that is formed therein, and powder resin particles and additives are mixed into the cavity 10 inside the mixing / dispersing device 100. And a mixing and stirring chamber 12 for mixing and stirring.

  In the mixing and stirring chamber 12, the inner wall member 32 has a cylindrical shape, and the cavity 10 surrounded by the inner wall member 32 also forms a cylindrical internal space.

  The cavity 10 is a cylindrical internal space having a perfect circular shape in the cross section in the lateral direction, and is a cylindrical internal space having a bottom surface diameter of 198 mm and a height of 162 mm.

  Similar to the cavity 10, the inner wall member 32 has a perfect circular cross section in the lateral direction and a radius of 99 mm. The thickness of the inner wall surface member 32 is 5 mm. The inner wall member 32 uses “DUSA-RESIST” as a material, and the surface on the cavity 10 side is a smooth surface.

  The mixing and stirring chamber 12 is provided with a rotating shaft body 14 penetrating the central axis in the lateral direction. The rotating shaft body 14 has a cylindrical shape, and the rotating shaft body 14 inside the cavity 10 has a thick shape with respect to the outside of the cavity 10, but each of the outside and inside of the cavity 10 has a uniform thickness. . The rotating shaft body 14 is a rotating mechanism that is rotated counterclockwise with respect to the horizontal direction by a rotating shaft driving unit that drives a rotating shaft (not shown). The rotating shaft 14 has a lateral diameter of 123 mm and a longitudinal length in the mixing and stirring chamber 12 of 162 mm. The material is SUS316.

  Rotating blades 18 a, 18 b, 18 c, and 18 d that mix and agitate powder resin particles and additives mixed in the cavity 10 as the rotating shaft 14 rotates as the rotating shaft 14. It is attached to the place.

  The rotary blades 18 a, 18 b, 18 c, and 18 d each have a fan-shaped shape on the surface 30 that narrows toward the rotary shaft body 14. This sector shape is the surface 30, and more specifically, is a quadrangular shape that simulates a shape in which two isosceles triangles are merged from the side surface direction.

The fan-shaped surface 30 has almost no area at the portion attached to the rotating shaft body 14. On the other hand, the side surface 28 has a thickness, and the rotating blades have the same thickness. Therefore, the rotating blades 18 a, 18 b, 18 c, 18 d are linear only of the thickness of the rotating shaft 14 and the side surface 28. It is attached at the contact surface. The area of the surface 30 and the surface opposite to the surface is 500 mm ² , and the thickness of the side surface 28 is 10 mm on the shaft side and the tip is inclined 2 mm.

  All the volumes of the rotary blades 18a, 18b, 18c, and 18d are the same. Further, the side surface shape and the side surface area, the surface shape and the surface area are all the same. Examples of the material constituting the rotary blades 18a, 18b, 18c, and 18d include stainless steel (stellite spraying). The surface shape of the surface 30 and the opposite surface and side surface of the surface is a smooth surface.

  Any two or more rotary blades of the rotary blades 18a, 18b, 18c, and 18d are not provided at positions that coincide with each other in the vertical direction, and are in a shifted positional relationship. The distance by which the rotary blades 18a, 18b, 18c, and 18d are displaced is 65 mm at regular intervals to the adjacent blade.

  The rotary blades 18a, 18b, 18c, and 18d are attached to the rotary shaft body 14, and the relative positional relationships with respect to the vertical direction are all shifted. Of the rotary blades 18a, 18b, 18c, and 18d, Any two or more rotating blades are not provided at positions that coincide with the vertical direction. The distance by which the rotary blades 18a, 18b, 18c, and 18d are shifted is equal to the adjacent blade.

  The relative positional relationship of the rotary blades 18a, 18b, 18c, and 18d relative to the lateral direction attached to the rotary shaft body 14 is the opposite positional relationship in which the angle is shifted by 180 °. The rotary blades 18a and 18b are in the same direction, and the rotary blades 18c and 18d are in a positional relationship opposite to the rotary blades 18a and 18b. The rotary blades in the same direction are arranged at substantially the same position.

  The rotary blades 18 a, 18 b, 18 c, and 18 d are provided at oblique positions where the angle at which the rotary blades 18 are attached to the rotary shaft body 14 is shifted from the vertical direction and the horizontal direction with respect to the rotary shaft body 14. The rotating blades 18a and 18b and the rotating blades 18c and 18d, which are in the same direction with respect to the lateral direction, have the same angle of attachment with the rotating shaft body 14, and the blades in the opposite positional relationship are shifted by 90 °. Attached.

  The rotary blades 18 a, 18 b, 18 c, and 18 d have a gap between the tip end portion 26 closest to the inner wall surface member 32 and the inner wall surface member 32. The size of the gap is 1 mm in all of the rotary blades 18a, 18b, 18c, and 18d. The size of the gap is uniform during rotation. In FIG. 1A, the scraping blade 36 is disposed along the bottom surface of the cavity 10. The scraping blade 36 is a part of the rotating blade and scrapes the material existing at the end in the cavity inward.

  As the rotary shaft 14 rotates, the polyethylene resin and the nucleating agent 34 mixed in the cavity by the rotary blades 18a, 18b, 18c, and 18d are vertically stirred in the direction of gravity (FIG. 1A). This vertical stirring is performed in a laminar flow state that is a concentric stirring of a laminar flow (FIG. 1B). In FIG. 1B, the polyethylene resin and the nucleating agent 34 are laminar stirred so as to form a perfect circle along the circumference.

  The mixing and stirring chamber 12 is attached to a side wall perpendicular to the rotation axis direction of the rotation shaft body 14 and has a hopper portion 16 through which polyethylene resin and / or a nucleating agent are mixed into the cavity 10. .

  The hopper portion 16 includes a hopper wall surface member 24 made of a conical wall surface member and a hopper through hole 22 formed by the hopper wall surface member 24.

  The hopper through-hole 22 has a through-hole shape that narrows into a conical shape from the hopper port 24 into which the polyethylene resin and / or the nucleating agent is introduced toward the wall surface through-hole 20.

  The wall surface through-hole 20 is a wall surface through-hole 20 that is a side wall of the mixing and stirring chamber 12 and penetrates a wall in the direction opposite to the gravitational direction. The hopper portion 16 is attached to the mixing and stirring chamber 12 by joining the hopper wall surface member 24 to the wall surface through hole 20.

  The polyethylene resin and / or the nucleating agent is put into the hopper port 24 from the outside. The introduced polyethylene resin and / or nucleating agent is mixed into the cavity 10 through the hopper through hole 22 and finally through the wall surface through hole 20.

  In the above description, the mixing / dispersing device has been described as a horizontal type in which the stirring direction in the cavity is the gravity direction, but a vertical type in which the stirring direction is perpendicular to the gravity direction can also be used.

  Next, a method for forming a polyethylene resin composition by mixing and stirring a polyethylene resin and a nucleating agent using the mixing and dispersing apparatus will be described.

  A polyethylene resin and a nucleating agent 34 are introduced from the hopper port 24 and mixed into the cavity 10. After mixing, the rotating shaft body 14 is rotated by setting it below the softening temperature of the polyethylene resin. The rotational peripheral speed of the rotating shaft body 14 is controlled so that the peripheral speed at the tip of the rotary blades 18a, 18b, 18c, 18d is 20 m / sec to 200 m / sec, and the laminar agitation shown in FIG. After forming the desired dispersion, the polyethylene resin composition is removed.

  The nucleating agent can be mixed and dispersed in the polyethylene resin as a high concentration nucleating agent master batch, but the nucleating agent master batch can also be suitably manufactured by using the above-described manufacturing method and manufacturing apparatus. .

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these specific examples.

"Means for determining the state in which at least a part of chemical bonds of polyethylene resin is cleaved and reduced in molecular weight and then recombined"
The following ESR (Electron Spin Resonance) analysis, GPC (gel permeation chromatograph) is used to design a device in which at least a part of chemical bonds of the polyethylene resin is cleaved and reduced in molecular weight to be recombined. Analysis and IR (infrared absorption spectrum) analysis were used to determine whether the designed device can form a desired state, and the device according to the above embodiment was designed.

<Radical detection by ESR>
During stirring and immediately after stopping stirring, two points were put into liquid nitrogen at once, and after sufficiently cooled, sealed in a sample tube, using ESR, FA200 manufactured by JEOL Ltd., temperature 77K, sweep magnetic field 320 ± 7.5 mT, Measurement was performed at a magnetic field modulation frequency of 100 kHz, a magnetic field modulation width of 0.2 mT, a time constant of 0.1, and a microwave output of 1 mW, and two spectra were compared during stirring and immediately after stopping stirring.

<Detection of molecular weight change by GPC>
Senshu Co., Ltd. was prepared by preparing a TOSOH column, model TSK-GEL GMHHR-H (S) H, and RI detector before and after stirring. The measurement was performed at a flow rate of 1 mL / min and a temperature of 140 ° C. using a scientific GPC apparatus, model SSC-7100. The obtained chromatogram was converted into standard polystyrene, and the number average molecular weight (Mn) and the weight average molecular weight (Mw) were determined and compared before and after stirring for the molecular weight of the polyethylene resin.

<Detection of structural change by infrared absorption spectrum>
Two points of the resin polymer before stirring and the resin polymer after stirring were measured by the Spectrum One method using a FT-IR spectrophotometer manufactured by Perkin Elmer, and two spectra were observed during stirring and immediately after stopping stirring. Compared.

"Evaluation of uniform dispersibility and mechanical properties"
<Transparency>
A sample having a thickness of 1 mm of the manufactured polyethylene resin composition was measured according to JIS-K-7136-1 using a direct reading haze meter manufactured by Toyo Seiki Seisakusho Co., Ltd., and evaluated based on the Haze value.

<Uniform dispersibility>
An inflation film having a thickness of 50 μm is prepared from the manufactured polyethylene resin composition, and the number of bumps of 0.1 mm ² or more present in a film having an area of 100 cm ² is measured. In the polyethylene resin composition, this is due to poor dispersion of the nucleating agent and / or deterioration of the polyethylene resin. The results were evaluated for uniform dispersibility according to the following criteria.

  A: Less than 10 and uniform dispersibility is sufficient.

  Δ: 10 to less than 30 and uniform dispersibility is slightly inferior, which may be inappropriate for thin materials such as films.

  X: It is 30 or more and it cannot be said that uniform dispersibility is favorable.

<Young's modulus>
Measurement was performed according to JIS 7721 at a tensile speed of 50 mm / min using a 201B type tensile tester manufactured by Intesco.

"Evaluation of moldability"
<Crystalization temperature>
Using a differential scanning calorimeter DSC-7 manufactured by PerkinElmer, 1 mg of material was heated from 30 ° C. to 180 ° C. at 20 ° C./minute, held at that temperature for 1 minute, and then cooled at 20 ° C./minute. The temperature at the start of heat generation when this was taken was used as the crystallization temperature, and this was used as an index for evaluating the molding cycle property.

" Reference Example 1"
<Manufacturing method>
MFR value (melt mass flow rate) at a density of 0.922 g / cm ³ : 5 g / 10 min (conforming to JIS K-7210), softening temperature 100.2 ° C. (JIS
99.9% by weight of low density polyethylene (based on K-7206, manufactured by Ube Polyethylene Co., Ltd .: F522N, 3 mm diameter pellet), sodium 2,2′-methylenebis (4,6-ditert-butylphenyl) phosphate (Asahi Denka) Kogyo Co., Ltd .: ADK STAB NA-11) 0.1% by weight was stirred at room temperature for 34 seconds at a tip peripheral speed of 27 m / sec using the mixing and dispersing apparatus according to the above embodiment as a mixing apparatus, and a low density polyethylene resin composition I got a thing.

<Observation of a state in which at least a part of chemical bonds of the polyethylene resin is cut and the molecular weight is reduced and then recombined>
From the ESR spectrum shown in FIG. 1, it was confirmed that the main chain of the polyethylene resin was cleaved and recombined depending on the presence or absence of radical species during stirring and immediately after stopping. That is, since the absorption spectrum based on radical species was confirmed during stirring, it can be seen that the main chain of the polyethylene resin was cut and the molecular weight was temporarily reduced. Since the absorption spectrum based on the radical species disappears immediately after stopping, it can be seen that the polyethylene resin whose molecular weight has been reduced temporarily is recombined.

  Table 1 shows the change in molecular weight of the resin polymer (number average molecular weight: Mn, weight average molecular weight: Mw) by GPC analysis before and after stirring of the present stirred product. From this, it was found that the molecular weight change was within 20% in this stirring, and the molecular weight was hardly changed. This shows that the polyethylene resin whose molecular weight has been reduced almost temporarily is recombined.

  In the infrared absorption spectrum shown in FIG. 2, the absorption peaks were almost the same before and after stirring, and it was confirmed that there was no structural change in the resin polymer before and after stirring.

  As described above, it can be seen from FIGS. 1 and 2 and Table 1 that at least a part of chemical bonds of the polyethylene resin is cleaved and reduced in molecular weight to form a recombined state. Such a mixing and dispersing device could be determined to be a mixing and dispersing device capable of forming a state in which at least a part of chemical bonds of the polyethylene resin is cut and the molecular weight is lowered and then recombined.

<Evaluation of uniform dispersibility, improvement of mechanical properties and increase in crystallization temperature>
Table 2 shows the crystallization temperature, transparency, uniform dispersibility, and Young's modulus of the polyethylene resin composition obtained in Reference Example 1. Haze value of original low-density polyethylene: 92.6, Young's modulus: 110.6 MPa, crystallization temperature: 92.9 ° C. The obtained polyethylene resin composition has a smaller Haze value, and Young's modulus In addition, since the crystallization temperature is increased and almost no fuzz is observed, the nucleating agent is dispersed very uniformly in the polyethylene resin. As a result, mechanical properties such as rigidity and transparency are improved, and the crystallization temperature is increased. It turns out that it rose significantly. From the physical property data in Table 2, it can be seen that the production apparatus of this example is a production apparatus capable of improving the properties of the polyethylene resin by imparting uniform dispersibility to the produced polyethylene resin composition. In addition, as described above, it is known that the manufacturing apparatus of this example forms a state in which at least a part of the chemical bond of the polyethylene resin is cut and the molecular weight is lowered, and then recombined. It turns out that uniform dispersibility can be given to the manufactured polyethylene resin composition by forming.

" Reference Examples 2-9"
<Manufacturing method>
As shown in Table 2, the same low density polyethylene as in Reference Example 1 was used, and the type and concentration of the nucleating agent, the stirring time, and the peripheral speed were changed. Other than that, using the same mixing and dispersing apparatus as in Reference Example 1, a low density polyethylene resin composition was obtained by the same production method. The physical properties are shown in Table 2.

“Comparative Example 1”
The materials used are the same as in Reference Example 3, and all materials are charged using a Brabender mixer (Laboplast Mill manufactured by Toyo Seiki Seisakusho), and then melt-kneaded at 125 ° C. for 5 minutes at a rotation speed of 60 rpm. Got.

"Comparative Example 2"
The material used was the same as in Reference Example 5, and the production method was the same as in Comparative Example 1 to obtain a low density polyethylene resin composition.

<Evaluation of uniform dispersibility, improvement of mechanical properties and increase in crystallization temperature>
As shown in Table 2, the low density polyethylene resin compositions obtained in Reference Examples 2 to 9 have a higher Young's modulus and a smaller Haze value than the original low density polyethylene resin. From the fact that the crystallization temperature is increased, it can be seen that as a result of the nucleating agent being dispersed very uniformly, mechanical properties such as rigidity and transparency are improved, and the crystallization temperature is increased. It can also be seen that uniform dispersibility is ensured even if the amount of the nucleating agent, the stirring time, and the peripheral speed are changed within a predetermined range.

  On the other hand, in the low density polyethylene resin compositions obtained in Comparative Examples 1 and 2, although the crystallization temperature is somewhat increased, the Haze value is not greatly improved, and the Young's modulus is only slightly increased. From the fact that there are many, it is understood that the properties of the polyethylene resin used are deteriorated and the dispersibility is also poor.

<Manufacture of nucleating agent master batch>
Low density polyethylene (Mitsui Chemicals Co., Ltd .: Mirason 11P, 3 mm diameter pellet) with a density of 0.917 g / cm ³ and an MFR value of 5 g / 10 min and a softening temperature of 100.2 ° C. and sodium 2,2′-methylenebis (4,6-ditertiary butylphenyl) phosphate (Asahi Denka Kogyo Co., Ltd .: ADK STAB NA-11) 5% by weight was added, and the mixing and dispersing apparatus according to the above embodiment was used as a mixing apparatus. Then, the mixture was stirred at room temperature for 28 seconds to obtain a nucleating agent master batch of ADK STAB NA-11.

  By changing the type of nucleating agent in the same manner, bis (4-methylbenzylidene) sorbitol (manufactured by Shin Nippon Rika Co., Ltd .: Gelol MD) and 4-tert-butylbenzoic acid aluminum salt (manufactured by Dainippon Ink & Chemicals, Inc.) : AL-PTBBA) was produced.

Reference Example 10
<Manufacturing method>
2% by weight of the nucleating agent masterbatch of Adeka Stub NA-11 produced as described above is a linear low density polyethylene (Idemitsu Petrochemical Co., Ltd.) having a density of 0.919 g / cm3, MFR value: 2 g / 10 min, and softening temperature of 117 ° C (Product: IDEMITSU-LL 0234H, 3 mm diameter pellet) In addition to 98% by weight, the mixing and dispersing apparatus according to the above embodiment was used as a mixing apparatus, and the mixture was stirred at a tip peripheral speed of 27 m / sec for 44 seconds at room temperature. A density polyethylene resin composition was obtained. The physical properties are shown in Table 3.

"Reference Example 11 to 17"
<Manufacturing method>
As shown in Table 3, the same linear low density polyethylene resin as in Reference Example 10 was used, and the type and concentration of the nucleating agent master batch, the stirring time, and the peripheral speed were changed. Otherwise, a linear low density polyethylene resin composition was obtained by the same production method as in Reference Example 10. The physical properties are shown in Table 3.

“Comparative Example 3”
Using the same material as in Reference Example 16 and stirring under the conditions shown in Table 3, a linear low density polyethylene resin composition was obtained.

“Comparative Example 4”
Stirring was performed under the conditions shown in Table 3 using the same material as in Reference Example 11 to obtain a linear low density polyethylene resin composition.

<Evaluation of uniform dispersibility, improvement of mechanical properties and increase in crystallization temperature>
As shown in Table 3, the linear low density polyethylene resin compositions obtained in Reference Examples 10 to 17 have a higher Young's modulus and a lower Haze value than the original linear low density polyethylene resin. However, when the peripheral speed is out of the predetermined range or the stirring temperature is higher than the predetermined temperature as in Comparative Examples 3 and 4, the polyethylene resin used deteriorates and the nucleating agent becomes uniform. It can be seen that as a result of the dispersibility being impaired, there are a lot of irregularities and there is little or no effect of improving the transparency and mechanical properties.

"Example 18"
<Manufacturing method>
Metallocene linear low density polyethylene (Mitsui Chemicals) having a density of 0.905 g / cm ³ , MFR value: 4 g / 10 min, and softening temperature of 83 ° C. was used. (Product: Evolue SP0540, 2.5 mm diameter pellet) In addition to 98% by weight, the mixing and dispersing apparatus according to the above embodiment was used as a mixing apparatus, and the mixture was stirred at a tip peripheral speed of 27 m / sec for 22 seconds at room temperature. A polyethylene resin composition was obtained. The physical properties are shown in Table 4.

"Examples 19 to 27"
<Manufacturing method>
As shown in Table 4, the same metallocene linear low-density polyethylene resin as in Example 18 was used, and the type and concentration of the nucleating agent master batch, the stirring time, and the peripheral speed were changed. Otherwise, a metallocene linear low density polyethylene resin composition was obtained by the same production method as in Example 18. The physical properties are shown in Table 4.

“Comparative Example 5”
Using the same material as in Example 20, the mixture was stirred under the conditions shown in Table 4 to obtain a metallocene linear low density polyethylene resin composition.

"Comparative Examples 6-8"
The materials shown in Table 4 were used, and all the materials were charged using a Brabender mixer (Laboplast Mill manufactured by Toyo Seiki Seisakusho), and then melt-kneaded at 125 ° C for 5 minutes at a rotation speed of 60 rpm to form a metallocene linear low density. A polyethylene resin composition was obtained.

<Evaluation of uniform dispersibility, effect of suppressing characteristic deterioration and increase in crystallization temperature>
As shown in Table 4, the metallocene linear low density polyethylene resin compositions obtained in Examples 18 to 27 have a higher Young's modulus and a lower Haze value than the original metallocene linear low density polyethylene resin. When the crystallization temperature is increased with almost no irregularities, but when the peripheral speed is outside the predetermined range as in Comparative Example 5, or when melt kneaded by a conventional method as in Comparative Examples 6-8 It can be seen that the uniform dispersibility and / or properties of the nucleating agent in the metallocene linear polyethylene resin used are impaired, and as a result, there are many irregularities and the effect of improving the transparency and mechanical properties is small or small.

  Since transparency is improved and there is no fluff even if it is in the form of a film, it can be suitably used in fields where low-density polyethylene is suitably used, for example, food wrapping materials and pharmaceutical wrapping materials after being processed into films.

It is an ESR spectrum concerning a present Example. It is sectional drawing of the mixing and dispersing apparatus which concerns on this embodiment. It is sectional drawing of the mixing and dispersing apparatus which concerns on this embodiment. It is an infrared absorption spectrum which concerns on a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cavity 12 Mixing and stirring chamber 14 Rotating shaft body 16 Hopper part 18a Rotary blade 18b Rotary blade 18c Rotary blade 18d Rotary blade 20 Wall surface through hole 22 Hopper through hole 24 Hopper port 26 Tip part 28 Side surface 30 Surface 32 Inner wall member 34 Polyethylene resin And nucleating agent 36 scraping blade 100 mixing and dispersing device

Claims (1)

In the cavity that becomes the container,
Density is 0. 9 0 to 0. A metallocene linear low density polyethylene resin having a melt mass flow rate (MFR) of 1 to 100 g / 10 min at 9 25 g / cm ³ ,
The concentration of at least one nucleating agent selected from a phosphate ester metal salt nucleating agent, a sorbitol nucleating agent and a carboxylic acid metal salt nucleating agent is 0.
0 1 to 0. 5% by weight of the added formulation
When mixing and stirring the metallocene linear low density polyethylene resin and the nucleating agent by a rotating mixing stirrer that rotates in the cavity,
Until the metallocene linear low density polyethylene resin and the nucleating agent are mixed and stirred in the cavity to form a uniformly dispersed state,
Below the softening temperature of the metallocene linear low density polyethylene resin,
The tip peripheral speed of the rotary mixing stirrer is controlled to be not less than 20 m / sec and not more than 20 m / sec;
By making the flow of material in the cavity laminar,
A method for producing a metallocene linear low-density polyethylene resin composition, wherein rigidity and transparency are improved before the nucleating agent is added, and a crystallization temperature is increased by 3 to 21 ° C.