JPH0146534B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyethylene composition that has improved processability and provides molded articles with excellent surface conditions. Conventional polyethylene with a narrow molecular weight distribution has excellent spinnability, linear strength, knot strength, shrinkage rate, impact strength, drop strength, tear strength, and stress crack resistance, so it is used for monofilament, injection, blowing, It is used in various fields such as inflation film to take advantage of its characteristics. However, polyethylene with a narrow molecular weight distribution
On the other hand, due to its low non-Newtonian properties in the molten state, the degree of viscosity reduction in the high-speed shear region is small, and the moldability is extremely poor when the extrusion temperature is low or above a certain shear rate, and the surface of the molded product also becomes rough. The problem is that it is easy. The problems of the polyethylene with a narrow molecular weight distribution of the present invention, such as processability and surface condition, are solved without impairing other properties.
0.900 to 0.970g/cm ³ , melt index (MI ₂ ) at 2.16Kg load is less than 4g/10min, load
Polyethylene 100 with a ratio of melt index (MI ₂₀ ) to MI ₂ (MI ₂₀ / MI ₂ ) of 40 or less at 21.6 kg
parts by weight, and 0.01 to 2.0 parts by weight of at least one higher fatty acid metal salt selected from the group consisting of sodium stearate, lithium stearate, and lithium 12-hydroxystearate. be. In the present invention, polyethylene refers not only to ethylene homopolymers, but also to ethylene and other α-olefins, such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, It may also be a copolymer with 1-decene, 1-tetradecene, 1-octadecene, or a mixture thereof. Furthermore, if the melt index (ASTM D 1238: hereinafter referred to as MI ₂ ) at a load of 2.16 kg exceeds 4 g/10 min, the fluidity becomes too large and drawdown is likely to occur, making molding difficult. Also, load 21.6Kg
When the ratio of the melt index (hereinafter referred to as MI ₂₀ ) to MI ₂ (MI ₂₀ /MI ₂ ) exceeds 40, the molecular weight distribution becomes broader, and the effect of improving processability and surface condition is diminished. The other component used in the present invention, the metal salt of higher fatty acid, is sodium stearate,
At least one metal salt selected from lithium stearate and lithium 12-hydroxystearate is used. It is generally known that divalent metal salts of higher fatty acids are added to polyolefins as lubricants;
Even if divalent metal salts of higher fatty acids conventionally used in the polyethylene used in the present invention, such as calcium stearate, 12-hydroxycalcium stearate, zinc stearate, aluminum stearate, magnesium stearate, etc., are added, the molded product This is undesirable because the transparency of the film decreases, processability and surface condition are not significantly improved, and bleed-out occurs. The amount of the metal salt of higher fatty acid added to polyethylene is 0.01 to 2.0 parts by weight per 100 parts by weight of polyethylene. If the amount added is less than 0.01 part by weight, no effect on improving processability will be observed, and if it exceeds 2.0 parts by weight, processability will increase too much and slip phenomena and screen clogging will easily occur. Various known methods can be used to obtain the polyethylene composition of the present invention. For example, a method may be mentioned in which the components are mixed using a ribbon blender, tumbler blender, Henschel mixer, etc., and then melt-mixed using an extruder, Banbury mixer, two rolls, etc. Further, pigments, dyes, various stabilizers, antistatic agents, slip agents, antiblocking agents, hydrochloric acid absorbers, etc. may be added to the polyethylene composition of the present invention, if necessary. The polyethylene composition of the present invention has good processability, good surface condition, and good impact strength, drop strength, tear strength, and spinnability, so it can be widely used in the film field, monofilament field, etc. Example 1 MI ₂ 1.35g/10min, MI ₂₀ /MI ₂ 30, density 0.930
0.25 parts by weight of sodium stearate was added to 100 parts by weight of ethylene/4-methyl-1-pentene random copolymer (g/ ^cm3) , and the resin temperature was increased using a 40 mmφ extruder.
Granulation was carried out at 250°C. This pellet was molded into a 30 μm thick film using a 50 mmφ inflation molding machine at a die temperature of 170°C. The extrusion characteristics at this time are
Table 2 shows the performance of the film. Example 2 The same procedure as in Example 1 was carried out except that lithium stearate was used instead of sodium stearate. The results are shown in Tables 1 and 2. Example 3 The same procedure as in Example 1 was carried out except that lithium 12-hydroxystearate was used instead of sodium stearate. The results are shown in Tables 1 and 2. Comparative Example 1 A film was formed using the copolymer of Example 1 alone. The results are shown in Tables 1 and 2. Comparative Examples 2 to 4 The same procedure as in Example 1 was conducted except that calcium stearate (Comparative Example 2), zinc stearate (Comparative Example 3), and aluminum stearate (Comparative Example 4) were used instead of sodium stearate. The results are shown in Tables 1 and 2.

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Claims (1)

[Claims] 1 Density 0.900 to 0.970 g/cm ³ , melt index (MI ₂ ) at a load of 2.16 kg is 4 g/10 min or less, melt index (MI ₂₀ ) at a load of 21.6 kg
100 parts by weight of polyethylene having a ratio of MI ₂₀ / _{MI 2 of} 40 or less, and at least one higher fatty acid selected from the group consisting of sodium stearate, lithium stearate and lithium 12-hydroxystearate. A polyethylene composition comprising 0.01 to 2.0 parts by weight of a metal salt.