KR101812887B1 - Resin compositions of polyethylene used general purpose film and film manufactured by using the same - Google Patents

Abstract

The present invention relates to a resin composition for general industrial purposes including a linear low density polyethylene resin made with a Ziegler-Natta catalyst, a linear low density polyethylene resin made with a metallocene catalyst, and a low density polyethylene prepared in a tubular process. The resin composition has excellent mechanical properties such as excellent tensile strength, tear resistance, dart impact resistance, high transparency, and film formability. According to the present invention, the resin composition includes: (A) 45-93 wt% of the linear low density polyethylene resin made with a Ziegler-Natta catalyst while having the concentration rate of 0.910-0.930 g/cm^3 and a melt index (ASTM D1238, 190C, 2.16kg) of 0.2-3.0 gram per 10 minutes; 2-3 wt% of the linear low density polyethylene resin made with a metallocene catalyst while having the concentration rate of 0.910-0.930 g/cm^3 and a melt index (ASTM D1238, 190C, 2.16kg) of 0.2-3.0 gram per 10 minutes; and (C) 5-25 wt% of the low density polyethylene prepared in a tubular process while having the concentration rate of 0.915-0.930 g/cm^3 and a melt index (ASTM D1238, 190C, 2.16kg) of 0.2-3.0 gram per 10 minutes as well as single-pole molecular weight distribution.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene resin composition for general industrial use, and a film produced using the same. BACKGROUND OF THE INVENTION [0002]

TECHNICAL FIELD The present invention relates to a polyethylene resin composition for general industrial use and a film produced using the same. More particularly, the present invention relates to a linear low density polyethylene resin produced under a Ziegler-Natta catalyst and a linear low density polyethylene resin prepared under a metallocene catalyst A polyethylene resin composition for general industrial use, and a film produced using the same.

Polyethylene is a general purpose polymer widely used in various applications such as packaging films, pipes, bottles and containers. It is classified into high density polyethylene (HDPE), low density polyethylene (LDPE) and linear low density polyethylene (LLDPE).

Films used in general industrial products are used in garbage bags, shopping bags, food packaging films, and thus require excellent mechanical properties and transparency. Particularly, in linear low density polyethylene, films employing linear low density polyethylene (mLLDPE) made of a metallocene catalyst are used to increase the mechanical strength of the film.

However, when the linear low-density polyethylene produced by the metallocene catalyst is used singly, the load of the extruder and the melt fracture of the surface of the film are increased in the film forming process, so that the extrusion amount and film smoothness are lowered do.

Japanese Patent Application Laid-Open No. 1996-269257 discloses a polyethylene resin for laminated films produced by using a linear low density polyethylene (mLLDPE) produced by a linear low density polyethylene or a metallocene catalyst and a linear low density polyethylene or a mixed composition of high density polyethylene and low density polyethylene But there is a limit to improvement in film formability, stability, synthesis characteristics of a low temperature heat seal, and transparency of the film.

Korean Patent Publication No. 1019656 discloses a polyolefin resin composition for a film comprising an elastomer, a linear low density polyethylene made of a metallocene catalyst, a low density polyethylene, an ethylene copolymer prepared by a Ziegler-Natta catalyst, etc. However, And 40 to 60% by weight of linear low density polyethylene prepared by the use of a cobalt-based catalyst, which may cause problems in flowability and film smoothness.

 Korean Patent Publication No. 0203444 discloses a film made of a linear low density polyethylene and a low density polyethylene. However, the resin composition for a shrinkable film focuses on the production of a shrinkable film and does not mention the use as a general industrial film It is not.

Korean Patent Laid-Open Publication No. 2003-0019454 discloses a film made of a mixed composition and a composition of a linear low density polyethylene and an ultra-low density polyethylene made of a metallocene catalyst. However, there is a problem in improving film forming stability and transparency of the film have.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and it is therefore an object of the present invention to provide a low-density polyethylene resin, which is produced by a Ziegler-Natta catalyst in the production of a general industrial film, a linear low-density polyethylene resin produced by a metallocene- A resin composition comprising polyethylene is intended to provide a resin composition having excellent mechanical properties such as excellent tensile strength, tear strength and dart impact strength, high transparency and excellent film formability.

And a general industrial film produced using the resin composition.

And to provide an optimum method for producing the resin composition having the above excellent properties.

(A) a linear low density manufactured by a Ziegler-Natta catalyst having a density of 0.910 to 0.930 g / cm 3 and a melt index (ASTM D 1238, 190 ° C, 2.16 kg) of 0.2 to 3.0 g / 45 to 93% by weight of a polyethylene resin; (B) 2 to 30% by weight of a linear low density polyethylene resin made from a metallocene catalyst having a density of 0.910 to 0.930 g / cm 3 and a melt index (ASTM D 1238, 190 캜, 2.16 kg) of 0.2 to 3.0 g / 10 min; And (C) a low density polyethylene resin having a density of 0.915 to 0.930 g / cm 3, a melt index (ASTM D 1238, 190 캜, 2.16 kg) of 0.5 to 5.0 g / 10 min, 25% by weight based on the total weight of the composition.

The polyethylene resin composition for general industrial use has a density of 0.915 to 0.930 g / cm 3 and a melt index (190 ° C, 2.16 kg) of 0.2 to 2.0 g / 10 minutes.

The polyethylene resin composition for general industrial use is capable of forming a wide film having a thickness of 1.0 m or more at the time of forming an inflation film and has a haze of 15% or less and a tensile strength of Elmendorf of 220 And a transverse direction (TD) of 800 g or more, and a dart impact strength of 130 g or more.

In order to solve the above-mentioned problems, the present invention provides a general industrial polyethylene film produced from the composition.

According to another aspect of the present invention, there is provided a method for producing a thermoplastic resin composition, comprising the steps of: (A) injecting a linear low density polyethylene resin into an extruder; Introducing the linear low density polyethylene resin (B) and the low density polyethylene resin (C) using a side feeder of the extruder; And mixing in a molten state at a temperature of 150 to 230 ° C in the extruder to produce a general industrial polyethylene resin composition in the form of a pellet. The general industrial polyethylene resin composition is capable of forming a wide film of 1.0 m or more in the inflation film molding And a film having a thickness of 40 占 퐉 has a haze of 15% or less and an Elmendorf tear strength of 220 g or more in the machine direction (MD), 800 g or more in the transverse direction (TD) and a dart impact strength of 130 g or more There is provided a method for producing a polyethylene resin composition for general industrial use.

INDUSTRIAL APPLICABILITY According to the present invention, by combining linear low density polyethylene resin, a linear low density polyethylene resin produced under a metallocene catalyst and a low density polyethylene resin in an optimum composition when applied to a general industrial film, the tensile strength, tear strength, Dart It is possible to manufacture a film having excellent film formability while having mechanical properties such as impact strength and high transparency.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. It is to be understood that various equivalents and modifications may be substituted for those at the time of the present application.

The present inventors have found that, in the prior arts which provide a resin composition having excellent mechanical properties and transparency and excellent film formability in the production of a general industrial film using a linear low density polyethylene resin, As a result of extensive research, it has been found that a general industrial polyethylene resin comprising a linear low density polyethylene resin produced under a Ziegler-Natta catalyst having a specific physical property and a content and a linear low density polyethylene resin produced under a metallocene catalyst and a low density polyethylene resin It has been found that the composition has dramatic improvement in film formability while having mechanical properties such as excellent tensile strength, tear strength, dart impact strength, and high transparency, and has led to the present invention.

Therefore, according to one aspect of the present invention, there is provided a linear low density (A) catalyst prepared by a Ziegler-Natta catalyst having a density of 0.910 to 0.930 g / cm 3 and a melt index (ASTM D1238, 190 캜, 2.16 kg) of 0.2 to 3.0 g / 45 to 93% by weight of a polyethylene resin; (B) 2 to 30% by weight of a linear low density polyethylene resin made from a metallocene catalyst having a density of 0.910 to 0.930 g / cm 3 and a melt index (ASTM D 1238, 190 캜, 2.16 kg) of 0.2 to 3.0 g / 10 min; And (C) a low density polyethylene resin having a density of 0.915 to 0.930 g / cm 3, a melt index (ASTM D 1238, 190 캜, 2.16 kg) of 0.5 to 5.0 g / 10 min, Based on the total weight of the composition.

Hereinafter, each constitution of the polyethylene resin composition for general industrial use according to the present invention will be described in detail.

(A) a linear low density polyethylene resin produced under a Ziegler-Natta catalyst

In the present invention, the linear low density polyethylene can be obtained by copolymerizing ethylene with homopolymerization of ethylene, alpha-olefin such as propylene, butene-1, hexene-1 or octene-1 using a Ziegler-Natta catalyst. The polymerization method is not particularly limited, and any method such as a gas phase method, a solution method, or a slurry method can be used.

The linear low density polyethylene may have a melt index (ASTM D1238, temperature 190 ° C, load 2.16 kg) of 0.2 to 3.0 g / 10 min, preferably 0.5 to 1.5 g / 10 min. If the melt index of the linear low density polyethylene is less than 0.2 g / 10 min, the moldability may be deteriorated. If the melt index exceeds 3.0 g / 10 min, the mechanical properties after the film formation may be deteriorated.

The density of the linear low density polyethylene may be 0.910 to 0.930 g / cm3, preferably 0.915 to 0.925 g / cm3. If the density of the linear low density polyethylene is less than 0.910 g / cm 3, the film tends to stick to each other after the film is formed due to the sticky property of the product, so that the friction property and the transparency may be lowered and the density may exceed 0.930 g / The dart impact strength of the film may be lowered.

In the present invention, the content of the linear low density polyethylene is 45 to 93% by weight, and preferably 70 to 87% by weight based on the total weight of the entire polyethylene resin composition. When the content of the linear low density polyethylene is low, the dart impact strength of the polyethylene film may be lowered, and if the content ratio is excessively high, the transparency of the polyethylene film may be deteriorated.

(B) a linear low density polyethylene resin prepared under a metallocene catalyst

In the present invention, the linear low density polyethylene resin produced under the metallocene catalyst may have a melt index (ASTM D1238, temperature 190 ° C, load 2.16 kg) of 0.2 to 3.0 g / 10 min, preferably 0.5 to 1.5 g / 10 min . When the melt index of the linear low density polyethylene produced by the metallocene catalyst is less than 0.2 g / 10 min, the extrusion load of the film forming machine may become large. When the melt index exceeds 3.0 g / 10 min, The mechanical strength may be lowered.

The density of the linear low density polyethylene produced from the metallocene catalyst may be 0.910 to 0.930 g / cm3, preferably 0.915 to 0.925 g / cm3. If the density is less than 0.910 g / cm 3, there may be stickiness of the film. If the density exceeds 0.930 g / cm 3, the dart impact strength may be lowered.

The linear low density polyethylene produced by the metallocene catalyst is obtained by copolymerizing ethylene with homopolymerization of ethylene and alpha-olefin such as propylene, butene-1, hexene-1, octene-1 . The polymerization method is not particularly limited, but can be produced by a vapor phase method, a solution method, or the like.

In the present invention, the content of the linear low density polyethylene made of the metallocene catalyst based on the total weight of the entire polyethylene resin composition may be 2 to 30 wt%, preferably 3 to 20 wt%. If the content ratio is low, transparency and mechanical strength may be lowered, and if the content ratio is excessively high, bubble instability may occur during film forming.

(C) Low-density polyethylene resin produced by tubular process

In the present invention, the low density polyethylene resin may have a melt index (ASTM D1238, temperature 190 캜, load 2.16 kg) of 0.5 to 5.0 g / 10 min, preferably 1.0 to 4.0 g / 10 min. If the melt index of the low-density polyethylene is less than 0.5 g / 10 min, the extrusion load of the film-forming machine may become large. If the melt index exceeds 5.0 g / 10 min, the bubble stability and mechanical strength of the low- .

The density of the low-density polyethylene may be 0.915 to 0.930 g / cm3, preferably 0.920 to 0.925 g / cm3. When the density of the low density polyethylene is less than 0.915 g / cm 3, the friction characteristics may be deteriorated due to excessive stickiness of the product, and when the density is higher than 0.930 g / cm 3, transparency of the film may be lowered.

The molecular weight distribution curve of the low-density polyethylene has a single-rod distribution. The single-pole molecular weight distribution means that for the purposes of the present invention, the molecular weight distribution has no inflection point other than the maximum. If the molecular weight distribution of the low density polyethylene has a distribution having a large number of inflection points such as a double rod or a triple rod other than a single rod, the transparency may be lowered when blended with the linear low density polyethylene.

The low-density polyethylene is produced by a high-pressure tubular process. Low density polyethylene produced by the high pressure autoclave process may be less transparent when blended with linear low density polyethylene.

In the present invention, the content of the low density polyethylene is 5 to 25% by weight, and preferably 10 to 20% by weight based on the total weight of the entire polyethylene resin composition. When the content of the low density polyethylene is low, the transparency of the polyethylene film lowers, bubble instability may occur during molding of the inflation film, and when the content ratio is excessively high, the dart impact strength and tensile strength of the polyethylene film may be lowered have.

The polyethylene resin composition for general industrial use according to the present invention is a linear low density polyethylene resin produced under (A) a Ziegler-Natta catalyst having the above specific properties and content, (B) a linear low density polyethylene resin prepared under a metallocene catalyst, and C) Low density polyethylene resin prepared in tubular process can be produced using an extruder.

That is, the linear low density polyethylene resin produced under the (A) Ziegler-Natta catalyst was introduced into an extruder, and (B) the linear low density polyethylene resin produced by the metallocene catalyst (B) using a side feeder of the extruder and C) a low-density polyethylene resin produced in a tubular process, and mixing in a molten state in an extruder to prepare a polyethylene resin composition on a pellet. Here, the temperature at the time of melt-mixing the polyethylene resin composition is set to 150 to 230 캜. When the film is produced by simple dry blending of the polyethylene resin composition, transparency and dart impact strength may be lowered due to the poor dispersibility of the polyethylene resin composition.

The polyethylene resin composition thus prepared has a density of 0.915 to 0.930 g / cm 3 and a melt index (190 ° C, 2.16 kg) of 0.2 to 2 g / 10 min, which is suitable for general industrial use. (B) a linear low density polyethylene resin prepared under a metallocene catalyst; and (C) a low density polyethylene resin produced by a tubular process, wherein the linear low density polyethylene resin When a low-density polyethylene resin is used, a polyethylene resin composition having a density of 0.918 to 0.925 g / cm 3 and a melt index (190 ° C, 2.16 kg) of 0.5 to 1.2 g / 10 minutes and having more desirable physical properties for general industrial use can be produced .

The polyethylene resin composition for general industrial use according to the present invention may contain various additives such as a pigment master batch, an antioxidant, a heat and light stabilizer, an antistatic agent, a lubricant, an antiblocking agent, a preservative, An antistatic agent, a pigment, a flame retardant, a foaming agent, and the like. The amount of these additives to be used can be adjusted to the optimum range in consideration of the total production amount and the manufacturing process within a range known to be usable for the production of the polyethylene resin composition according to the present invention. (A) a linear low density polyethylene resin prepared under the above (A) Ziegler-Natta catalyst, (B) a linear low density polyethylene resin prepared under a metallocene catalyst, and (C) a low density polyethylene resin May be added in the step of adding the catalyst and may be added by kneading in a separate additional step.

The polyethylene resin composition for general industrial use according to the present invention can be produced by the air-cooled inflation method to produce a general industrial polyethylene resin film having excellent mechanical properties and high transparency while having excellent film formability.

Accordingly, the polyethylene resin composition for general industrial use according to the present invention is capable of forming a wide film having a thickness of 1.0 m or more when forming an inflation film, and has a haze of 15% or less and a Elmendorf tear strength in a machine direction MD) and a transverse direction (TD) of 800 g or more and a dart impact strength of 130 g or more can be provided, and it is possible to form a wide-angle film of 1.0 m or more in the inflation film molding, The molded film having a thickness of 40 탆 has a haze of 12% or less and Elmendorf tear strength of 240 g or more in the machine direction (MD), 830 g or more in the transverse direction (TD), and a dart impact strength of 140 g or more A polyethylene film can be provided.

The polyethylene resin film for general industrial use according to the present invention is preferably used in a thickness range of 20 to 100 mu m.

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples.

Example 1

(A) 87 parts by weight of a linear low density polyethylene resin (melt index (190 DEG C, 2.16 kg) 1.0 g / 10 min., Density 0.920 g / cm3) produced under a Ziegler-Natta catalyst and (B1) 3 parts by weight of a linear low density polyethylene resin (melt index (190 占 폚, 2.16 kg) of 1.0 g / 10 min and a density of 0.918 g / cm3) and (C) a low density polyethylene resin , 2.16 kg) 3.0 g / 10 min., Density 0.922 g / cm 3, single-pole molecular weight distribution) 10 parts by weight were mixed by a tumble mixer for 10 minutes and extruded and cooled at 210 캜 with a 40 mm twin screw extruder to obtain a pellet-shaped composition. This composition was molded by the air-cooling inflation method in the following manner to produce a film.

[Production method of polyethylene film]

The polyethylene resin composition was formed into a film having a thickness of 40 占 퐉 by using a 60 mm blown film extruder having a length to diameter ratio (L / D) of 30. The die diameter is 300 mm, the die gap is 2 mm, the BUR (blow-up ratio) is 3, and the freezing line height is 30 cm.

Example  2

The same procedure as in Example 1 was carried out except that 85 parts by weight of a linear low density polyethylene resin (A) prepared in Example 1 under a Ziegler-Natta catalyst and 5 parts by weight of a linear low density polyethylene resin (B1) To prepare a composition and a film on a pellet.

Example 3

(B1) 15 parts by weight of a linear low density polyethylene resin prepared under metallocene catalyst, and (C) 10 parts by weight of a low-density polyethylene resin produced in a high-pressure tubular process, in the same manner as in Example 1, except that 70 parts by weight of a linear low density polyethylene resin And 15 parts by weight of the obtained low-density polyethylene resin was used in place of the low-density polyethylene resin.

Example 4

(B1) 5 parts by weight of a linear low density polyethylene resin prepared under metallocene-based catalyst, and (C) 100 parts by weight of a low-density polyethylene produced in a high-pressure tubular process And 20 parts by weight of the obtained low-density polyethylene resin was used in place of the low-density polyethylene resin.

Comparative Example 1

(A) 90 parts by weight of a linear low density polyethylene resin prepared under (A) a Ziegler-Natta catalyst, and (C) in a high-pressure tubular process in the same manner as in Example 1, except that the linear low- density polyethylene resin produced under the metallocene- A composition and a film in the form of a pellet were prepared in the same manner as in Example 1, except that 10 parts by weight of the low-density polyethylene resin thus prepared was used.

Comparative Example 2

A linear low density polyethylene resin (melt index (190 占 폚, 2.16 kg) of 3.7 g / 10 min, manufactured by metallocene catalyst (B2) instead of the linear low density polyethylene resin prepared under metallocene catalyst (B1) 0.915 g / cm < 3 >) was used in place of the pellet-like composition and the film.

Comparative Example 3

In Comparative Example 2, 82 parts by weight of a linear low density polyethylene resin (A) prepared under a Ziegler-Natta catalyst, (B2) 15 parts by weight of a linear low density polyethylene resin prepared under a metallocene catalyst, and (C) Was prepared in the same manner as in Comparative Example 2, except that 3 parts by weight of the obtained low-density polyethylene resin was used.

Comparative Example 4

(B1) 5 parts by weight of a linear low-density polyethylene resin produced under a metallocene-based catalyst, and (C) 10 parts by weight of a low-density polyethylene resin produced in a high-pressure tubular process And 35 parts by weight of the obtained low-density polyethylene resin were used in place of the low-density polyethylene resin.

Experimental Example

The polyethylene resin compositions and films prepared according to the above Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Table 1 below.

[Assessment Methods]

(1) Melt index: Measured according to ASTM evaluation method D1238 at a temperature of 190 占 폚 and a load of 2.16 kg.

(2) Density: Measured according to ASTM Evaluation Method D792.

(3) Bubble stability: The film bubble stability of the polyethylene composition film was evaluated by the following criteria.

- ○: Bubble does not shake and there is no molding problem.

- ×: Film thickness and width are not uniform due to fluctuation of bubble.

(4) Haze: Measured according to ASTM Evaluation Method D1003.

(5) Tensile strength: Measured according to ASTM Evaluation Method D882.

(6) Elmendorf tear strength: measured according to ASTM evaluation method D1922.

(7) Dart impact strength: Measured according to ASTM Evaluation Method D1709A.

(B) a linear low-density polyethylene resin produced under a metallocene catalyst, and (C) a tubular polypropylene resin (C) having a desired physical property of the present invention. (Examples 1 to 4) prepared by using a polyethylene resin composition having a desirable density and a melt index of the present invention and containing an appropriate amount of the low-density polyethylene resin produced in the process (Examples 1 to 4) Elmendorf tear strength is 220 g or more in the machine direction (MD) and 800 g or more in the transverse direction (TD), the dart impact strength is 136 g or more, and the haze is 12% or less. It can be seen that a film having excellent physical properties and transparency is provided.

On the other hand, when the linear low density polyethylene resin (B) was not contained in a proper amount (Comparative Example 1) or the linear low density polyethylene resin (B) produced under a metallocene catalyst having a melt index exceeding a certain range When using a polyethylene resin (Comparative Example 2), a linear low density polyethylene resin produced under metallocene catalyst (B) in which transparency, tear strength and dart impact strength were not satisfactory and melt index exceeded a certain range When the low density polyethylene resin prepared in the C) tubular process is not contained in an appropriate amount (Comparative Example 3), the bubble stability is deteriorated. (C) When the low density polyethylene resin produced in the tubular process is used excessively 4), tensile strength, tearing strength and dart impact strength are decreased.

While the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, Such modifications and changes are to be considered as falling within the scope of the following claims.

Claims (5)

(A) 45 to 93% by weight of a linear low density polyethylene resin made by a Ziegler-Natta catalyst having a density of 0.910 to 0.930 g / cm3 and a melt index (ASTM D1238, 190 DEG C, 2.16 kg) of 0.2 to 3.0 g / 10 min;
(B) 2 to 30% by weight of a linear low density polyethylene resin made from a metallocene catalyst having a density of 0.915 to 0.925 g / cm3 and a melt index (ASTM D1238, 190 캜, 2.16 kg) of 0.2 to 3.0 g / 10 minutes; And
(C) a low density polyethylene resin having a density of 0.915 to 0.930 g / cm 3, a melt index (ASTM D 1238, 190 캜, 2.16 kg) of 0.5 to 5.0 g / 10 min and a single- weight%;
Wherein the polyethylene resin composition is a polyethylene resin composition for general industrial use,
The polyethylene resin composition for general industrial use is capable of forming a wide film having a thickness of 1.0 m or more at the time of forming an inflation film, and has a haze of 15% or less and a tensile strength of Elmendorf of 220 g or more in the machine direction And a transverse direction (TD) of 800 g or more, and a dart impact strength of 130 g or more.
The method according to claim 1,
Wherein the polyethylene resin composition for general industrial use has a density of 0.915 to 0.930 g / cm 3 and a melt index (190 ° C, 2.16 kg) of 0.2 to 2.0 g / 10 minutes. delete A polyethylene film for general industrial use produced from the composition of claim 1 or 2. (A) introducing the linear low density polyethylene resin of claim 1 into an extruder;
(B) introducing the linear low-density polyethylene resin of (1) and the (C) low-density polyethylene resin of claim 1 using a side feeder of the extruder; And
Mixing in a molten state at a temperature of 150 to 230 ° C in the extruder to prepare a general industrial polyethylene resin composition in the form of pellets;
Including,
The polyethylene resin composition for general industrial use is capable of forming a wide film having a thickness of 1.0 m or more at the time of forming an inflation film, and has a haze of 15% or less and a tensile strength of Elmendorf of 220 g or more in the machine direction And a transverse direction (TD) of 800 g or more, and a dart impact strength of 130 g or more.