JPH0316380B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyethylene composition, and more particularly to an improved polyethylene composition comprising a specific copolymer of ethylene and α-olefin and a specific calcium carbonate. As polyethylene, conventionally, low-density polyethylene obtained by radical polymerization under high pressure (also called "high-pressure polyethylene") and high-density polyethylene obtained by ionic polymerization using a Ziegler catalyst under low pressure ("low-pressure polyethylene") are used.
), each of which is used in large quantities to take advantage of its characteristics. In addition, in recent years, ethylene copolymers have been developed that are copolymerized with α-olefin as a comonomer using Ziegler catalysts under low pressure or high pressure, and are called medium-density polyethylene or linear low-density polyethylene, and have solidified their position as general-purpose resins. There is. Furthermore, compositions made by blending inorganic fillers with low-density polyethylene or high-density polyethylene can be used to create films, sheets,
Used in fields such as blow molded products and injection molded products. However, these compositions have the disadvantage that their range of use is limited because their impact strength, tear resistance, etc. are greatly reduced as a result of the inorganic filler being blended. Recently, a composition has been proposed in which an inorganic filler is blended with the above-mentioned copolymer of ethylene and α-olefin. (Special Publication No. 57-26534). Therefore, the present inventors, in accordance with the description in the publication,
After conducting various studies on systems using calcium carbonate as a filler, as described therein, it was found that compositions with superior properties such as impact resistance were obtained compared to systems using conventional high-density polyethylene or low-density polyethylene. However, as suggested therein, under normal conditions, physical properties such as impact resistance were unavoidable when compared with the base resin. However, as a result of further in-depth studies by the present inventors on such systems, it has been found that when a specific range of ethylene copolymer and a specific range of calcium carbonate are used, the impact resistance is higher than that of the base resin before adding calcium carbonate. It has been found that a composition with extremely excellent properties can be obtained, exceeding the physical property values of . The first objective of the present invention is to obtain a composition with extremely excellent physical properties such as impact resistance by blending a filler into an ethylene copolymer. By blending a specific calcium carbonate, it is possible to obtain a composition with improved physical properties such as impact resistance than the ethylene copolymer before blending. A second object of the present invention is to provide a polyethylene composition with low calorific value and excellent properties such as easy incineration, printability, writability, opacity, and dimensional accuracy of molded products. A third object of the present invention is to provide a composition suitable for extrusion molded products such as films, sheets, blow molded products, etc., or injection molded products such as cups, containers, industrial parts, etc. The object of the present invention is to provide a polyethylene composition comprising an ethylene-α-olefin copolymer and calcium carbonate with a density of 0.870 to 0.935 g/
cm ³ , a melt index of 0.01 to 7 g/10 min, and an N value of 90 to 25% by weight of an ethylene-α-olefin copolymer, and 10 to 75% of calcium carbonate having an average particle size of 4 μm or less. % by weight of a polyethylene composition. It has long been common knowledge among those skilled in the art that when a granular filler with a relatively large particle size, such as calcium carbonate, is added to polyethylene, the impact resistance, etc. is greatly reduced. It was not known in the past that impact resistance, etc., could actually be improved by adding an agent, and this was completely unexpected even by the inventors of the present invention.This is a breakthrough that breaks the conventional concept. It can be said that it is a typical composition. Next, terms used in the present invention will be explained. "Melt index" (hereinafter referred to as "MI") It is roughly correlated to the molecular weight of polyethylene and serves as a measure of moldability.
Use the values measured according to 1238. "N value" (non-Newtonian fluidity value) This is approximately correlated to the molecular weight distribution of polyethylene and serves as a measure of fluidity. Die: 2 mm × 40 mm, measured at 170°C with a load of 150 kg and 20 kg, and calculated according to the following formula. N value = log(γ150/γ20)/log(τ150/τ20) where, γ: Shear rate (Sec ^-1 ) τ: Shear stress (dgn/ ^cm2 ) "Average particle size" What is the average particle size?
The specific surface area of particles is measured using a Mizuto type specific surface area measuring device manufactured by Shimadzu Corporation, and is determined by the following formula. Average particle size = 6/specific gravity x specific surface area x 10 ⁴ (μ) “Density” What is the density of the ethylene copolymer in the present invention?
Values measured in accordance with ASTM D-1505. (Ethylene copolymer) The ethylene copolymer used in the present invention is a Ziegler catalyst (basically composed of a combination of a transition metal compound such as Ti, V, Cr, or Zr and an organometallic compound such as alkyl aluminum). Ethylene and α-olefin are copolymerized under a pressure of several kg/cm ² or several thousand kg/cm ² . The above α-olefins include propylene, butene-1, pentene-1, hexane-1, heptene-1,
There are straight chain olefins such as 1, octene-1, 4-methyl, and pentene-1, and isomers thereof having a double bond at the terminal, and are preferably appropriately selected within the range of _C4 to _C10 . α- in ethylene copolymer
The amount of olefin introduced is closely related to the density of the obtained copolymer, and this relationship is known from a paper by JP Hogan et al. (Paper to 23rd Int.
Congress of Pure and Applied Chemistry
Boston, July 1971). In the present invention, since the density of the ethylene copolymer is regulated, the amount of α-olefin introduced is regulated according to the above relationship depending on the type of α-olefin used. For example, in the case of butene-1, this is in the range of about 30% by weight. The ethylene copolymer used in the present invention must meet certain conditions such as a relatively low density, a relatively large molecular weight, and a relatively narrow molecular weight distribution. If this condition is not met, a composition with better physical properties than the base ethylene copolymer resin cannot be obtained even if it is combined with calcium carbonate having a preferred particle size as described below. That is, the density of the ethylene copolymer of the present invention is
It needs to be in the range of 0.87 to 0.935 (g/cc).
Currently, it is extremely difficult to industrially produce ethylene copolymers with a density of less than 0.87 (g/cc), resulting in high costs;
If the above ethylene copolymers (cc) are used, a composition with good impact resistance etc. cannot be obtained. Also, the molecular weight is almost correlated with the molecular weight.
It is defined in the range of MI, and in the present invention, it is 0.01 to
7 (g/10 minutes). M.I.
If it is less than 0.01 (g/10 min), the processability is extremely poor and almost impossible to mold. MI is 7 (g/10 min)
If it exceeds, a composition with good impact resistance etc. cannot be obtained. The molecular weight distribution is defined by a range of N values that approximately correlates with the molecular weight distribution, and in the present invention,
Must be in the range 1.3 to 2.1. Ethylene copolymers with an N value of less than 1.3 are very difficult to produce industrially, and their poor fluidity makes them difficult to mold. If the N value exceeds 2.1, a composition with good impact resistance etc. cannot be obtained. In the present invention, the object of the present invention can be achieved only by using an ethylene copolymer having a relatively small density, MI, and N value in a specific range as described above, and blending calcium carbonate in a specific range as described below. This results in improvements in impact resistance, etc. In the present invention, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents,
A slip agent or the like may be added, and low density polyethylene, ethylene-vinyl acetate copolymer, etc. may be used in combination to improve moldability when the composition is used for film molding. The calcium carbonate used in the present invention may be so-called heavy calcium carbonate obtained by mechanically crushing coalstone, or so-called precipitated calcium carbonate obtained by a carbonation method. However, the average particle size must be 4μ or less. If calcium carbonate with a particle size of 4μ or more is used, a composition with excellent impact resistance etc. cannot be obtained. Further, when calcium carbonate having an average powder diameter of 3 microns or less, preferably 0.5 to 3 microns, is used, a composition with better impact resistance etc. can be obtained than an ethylene copolymer without calcium carbonate. In the present invention, the above calcium carbonate may be used as it is, but the dispersibility of calcium carbonate in the composition is further improved (therefore, impact resistance etc. are also improved).
In order to improve moldability, it is preferable to use a surface treatment with a fatty acid or a derivative thereof, or a titanate coupling agent. Examples of fatty acids or their derivatives include stearic acid, oleic acid, palmitic acid, linoleic acid,
There are derivatives such as lauric acid, sebacic acid, adipic acid, and their metal salts, esters, and amide compounds. Titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris(dioctylpyrophosphate) titanate, tetraisopropyl bis(dioctylphosphite) titanate, bis(dioctylpyrophosphate) oxyacetate titanate. , bis(dioctylpyrophosphate) ethylene titanate, etc. When surface treating with the above compounds, the amount of surface treatment is generally 0.2 to 2% by weight relative to calcium carbonate.
degree is preferred. If it is less than 0.2% by weight, dispersibility or processability may not be improved;
Even if the surface is treated by more than % by weight, no further improvement in properties can be expected and it is not economical. In the present invention, it is important that the blending ratio of calcium carbonate to the ethylene copolymer is 10 to 75% by weight. Within the above range, a composition with better impact resistance etc. than the ethylene copolymer before blending can be obtained. In carrying out the present invention, it is also possible to mix ethylene copolymer powder or pellets with calcium carbonate powder and directly mold the mixture into a film or injection mold, but this is not possible with a general-purpose molding machine. Dispersion cannot be obtained, resulting in inferior physical properties, appearance, etc. Therefore, it is generally preferable to knead the composition in advance using a machine with an excellent kneading effect and form it into pellets before molding. In the kneading, it is preferable to mix the ethylene copolymer and calcium carbonate using a mixer such as a Henschel mixer or a ribbon blender. There are two ways to make pellets: extrude and cut strands using a single-screw extruder or twin-screw extruder with a kneading section, or pre-knead them using a roll, kneader, Banbury mixer, etc. and turn them into sheets. There are methods such as forming it into a shape and then cutting it. The pelletized composition as described above is sent to an extruder or injection molding machine to form films, sheets, etc.
Formed into yarn, bottles, containers, etc. The present invention will be explained in more detail with reference to Examples below, but these Examples are not intended to limit the scope of the present invention. Further, the physical property values shown in this example were measured by the following methods. Tensile impact strength (hereinafter referred to as "TIS": ASTM D
1822 compliant 1.5mm sheet using S-shaped danzel Tear strength: ASTM D 1922 compliant Dard impact strength: ASTM D 1709 compliant Tensile strength, elongation: ASTM D 882 compliant Examples 1 to 7 and Comparative Examples 1 to 2 MI as an ethylene copolymer Approximately 1.0 (g/10
copolymers of ethylene and butene-1 with a uniform N value of 1.5 and various densities (2,6-di-tert-butyl-p-cresol and n-octadecyl as antioxidants). -3-(4'-Hydroxy-3',5'-di-t-butylphenyl)propionate was added in an amount of 0.1% by weight in all polyethylene and ethylene copolymers used in the Examples and Comparative Examples below. Average particle size surface treated with 60% by weight (including this additive) and 0.5% stearic acid
After kneading with 40% by weight of 1.5μ heavy calcium carbonate in a kneader, it is mixed with a 1.5mm thick press sheet.
TIS was measured and the results are shown in Table 1 and Figure 1 (in the figure, the solid line indicates the present invention,
The broken line indicates the base resin without calcium carbonate added. ) Examples 8 to 12 and Comparative Example 3 Ethylene-butene-1 copolymers with a density of about 0.927, an N value of about 1.5, and various MIs
40% by weight of the same calcium carbonate as in Example 1 was added to 60% by weight, and the TIS was measured in the same manner as in Example 1, and the results are shown in Table 2 and Figure 2. Examples 13 to 15 and Comparative Examples 4 to 5 60% by weight of ethylene-butene-1 copolymer having a density of 0.921, MI of approximately 0.7, and various N values, and 40% by weight of the same calcium carbonate as in the example. % was added and the TIS was measured in the same manner as in Example 1, and the results are shown in Table 3 and Figure 3. Examples 16-20 and Comparative Examples 6-7 40% by weight of calcium carbonate with different particle sizes was added to 60% by weight of an ethylene-butene-1 copolymer with a density of 0.921, an MI of 0.92, and an N value of 1.5, TIS was measured in the same manner as in Example 1, and the results are shown in Table 4. Examples 21-27 25% by weight of ethylene-butene-1 copolymer (MI = 1.0, density = 0.922, N value = 1.5) and stearic acid
75% by weight of calcium carbonate having an average particle size of 1.5 μm and surface-treated with 0.5% by weight was premixed in a Henschel mixer, kneaded in a Banbury mixer, formed into a sheet with a roll, and further finely cut into pellets. The above pellets were molded into a film under the following conditions using an inflation film molding machine (manufactured by Modern Machinery Co., Ltd.) consisting of a 50 mm extruder, a 100 mm die, and an air-cooled air ring. Molding conditions: Cylinder temperature: 200℃ Die temperature: 200℃ Extrusion rate: 20-50Kg/HR Blow-up: 1.9 times Film thickness: Approximately 30μ Also, fill the pellets containing 75% by weight of calcium carbonate with the above-mentioned ethylene-butene-1 copolymer to a predetermined filling amount. Dilute it and form it into a film in the same way.
The tear strength and Durd impact strength of the obtained film were measured and the results are shown in Table 5. Comparative Example 8 Only the ethylene-butene-1 coweight used in Example 21 was formed into a film in the same manner as in Example 21, and the physical properties of the obtained film were measured. The results are shown in Table 5. Example 28 60% by weight of the ethylene copolymer used in Example 5,
Then, 40% by weight of calcium carbonate with an average particle diameter of 1.5μ and surface-treated with 0.5% by weight of stearic acid were kneaded and extruded into pellets using an extruder with a screw diameter of 50 mm and a kneading mechanism (manufactured by Nakatani Kikai Co., Ltd.). A film was formed in the same manner, and the physical properties of the film were measured, and the results are shown in Table 6. Example 29 60% by weight of the ethylene copolymer used in Example 5,
The pellets were pelletized in the same manner as the composition containing 40% by weight of calcium carbonate with an average particle size of 1.5 μ without surface treatment, and formed into a film in the same manner as in Example 21. The characteristic values of the film were measured. are shown in Table 6. Comparative Example 9 Average particle size of 60% by weight of the ethylene copolymer used in Example 5 surface treated with 0.5% by weight of stearic acid
A composition to which 40% by weight of calcium carbonate of 4.4 μm was added was pelletized in the same manner as in Example 28, formed into a film in the same manner as in Example 21, and the physical properties of this film were measured. The results are shown in Table 6. Indicated. Comparative Example 10 A film was formed using only the ethylene copolymer used in Example 5 in the same manner as in Example 21, and the film properties were measured. The results are shown in Table 6. Examples 30 to 33 Adding a predetermined amount of calcium carbonate with an average particle size of 1.5μ surface-treated with 0.5% by weight of stearic acid to an ethylene-butene-1 copolymer having a density of 0.922, an MI of 1.1, and an N value of 1.5, TIS was measured in the same manner as in Example 1, and the results are shown in Table 7. Example 34 As an ethylene copolymer, density = 0.924, MI1.3,
Ethylene-hexane-1 copolymer with N value = 1.5 60
Calcium carbonate 40% by weight and same as Example 30
The TIS of the composition to which the compound was added was measured in the same manner as in Example 30, and the results are shown in Table 7. Comparative Examples 11-12 Instead of ethylene copolymer, commercially available high-density polyethylene (manufactured by Nisseki Chemical Co., Ltd., product name "Stafrene")
E807(F)'', density = 0.950, MI = 0.6) and commercially available low-density polyethylene (manufactured by Nisseki Chemical Co., Ltd., trade name ``Lexron F22'', density = 0.923, MI = 1.0).
A composition in which 40% by weight of the same calcium carbonate as in Example 30 was added to 60% by weight was subjected to TIS in the same manner as in Example 30.
was measured and the results are shown in Table 7. Examples 35-38 Surface treatment was performed when adding 40% by weight of calcium carbonate with an average particle size of 1.5μ to 60% by weight of ethylene-butene-1 copolymer with density = 0.927, MI = 1.1, and N value = 1.45. The TIS was measured in the same manner as in Example 1 by adding unfiltered materials and those surface-treated with stearic acid and a titanate coupling agent, and the results are shown in Table 8. The results showed that in all cases the TIS was superior to that of the single ethylene copolymer, and the TIS was further improved by using calcium carbonate surface-treated with stearic acid or titanate coupling agents. This was recognized.

【table】

【table】

【table】

【table】

【table】

【table】

[Table] *1 This is the only product without stearic acid treatment.
All others are treated with 0.5% stearic acid.

【table】

[Table] Example 39 As ethylene copolymer, density = 0.925, MI = 4.7
(g/10 min), nv = 1.45, 60% by weight of a copolymer of ethylene and butene-1 and 40% by weight of the calcium carbonate used in Example 5 were pelletized in the same manner as in Example 28. Next, the pellets were molded to a thickness of 2 mm using an injection molding machine (manufactured by Toshiba Machine Co., Ltd., IS90) under the following conditions.
A flat plate was formed. TLS in MD direction of this molding
was 190 (Kg・cm/cm ² ). Injection conditions: Temperature: 230°C Pressure: 1000Kg Mold temperature: 50°C Comparative Example 13 The ethylene copolymer itself used in Example 37 was injected in the same manner as in Example 37. This molded product
The TIS in the MD direction was 145 (Kg·cm/cm ² ).

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between density and tensile impact strength, Figure 2 is a diagram showing the relationship between melt index and tensile impact strength, and Figure 3 is a diagram showing the relationship between N value and tensile impact strength. FIG. Solid line: composition of ethylene copolymer and calcium carbonate, dotted line: ethylene copolymer.

Claims (1)

[Claims] 1. A polyethylene composition consisting of an ethylene-α-olefin copolymer and calcium carbonate, which has a density of 0.870 to 0.935 g/cm ³ , a melt index of 0.01 to 7 g/10 min, and an N value of 1.3 to 2.1.
Ethylene-α-olefin copolymer 90-25
% by weight and 10 to 75% by weight of calcium carbonate having an average particle size of 4 μm or less.