JPH01163235A - Polyethylene resin composition - Google Patents

Abstract

PURPOSE:To obtain the title composition, having improved rigidity and tear properties and optimum for producing large-sized and thin-walled injection molded products, by adding specific high-density PE in a constant amount based on a PE resin composition to specific straight-chainlike low-density PE. CONSTITUTION:The aimed composition obtained by adding high-density PE (HDPE) having 5-30g/10min melt index (MI) and 0.945-0.968g/cm<3> density in an amount of 10-50wt.% based on a PE resin composition to straight- chainlike low-density PE (LLDPE) having 5-50g/10min MI and 0.915-0.935g/cm<3> density. Furthermore, the HDPE is preferably blended in an amount of 15-30wt.% based on the total composition.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a polyethylene resin composition with improved tearability. In particular, the present invention relates to a polyethylene resin composition suitable for manufacturing large, thin-walled injection molded products.

(Prior Art) Conventionally, the polyethylene resins used to obtain large, thin-walled injection molded products include: (1) High-density polyethylene resin (hereinafter referred to as HDPE).

) A polyethylene resin composition to which low-density polyethylene (hereinafter referred to as LDPE) with a large K melt index (hereinafter referred to as MI) is added.

■ LDPE resin with large MI.

■Linear low-density polyethylene resin with large MI (hereinafter referred to as LLDPE).

etc. are known.

(Problems to be Solved by the Invention) The composition (2) above has the disadvantage that the molded product when molded using the composition has poor tearability. The disadvantage is that the resulting molded product has low rigidity and poor tearability. Furthermore, the above-mentioned resin (3) has the disadvantage that the rigidity of molded products obtained using the resin is low.

The present inventors have conducted extensive research in order to obtain a polyethylene resin composition that has higher rigidity than LDPE resin or LLDPE and can yield molded articles with excellent tearability. As a result, a polyethylene resin composition formed by adding HDPE having a specific MI and density to LLDPE having a specific MI and density has a high rigidity and tear resistance when the molded product is made from the composition. The present invention was completed based on the discovery that the properties can be improved.

As is clear from the above description, an object of the present invention is to provide a polyethylene resin composition from which large, thin-walled injection molded articles with improved rigidity and tearability can be obtained.

(Means for solving problems) The present invention has the following configuration.

(1) Melt index (hereinafter referred to as MI)
is 5 to 50y/10 minutes, and the density is 0.915 to 0.
93511crd linear low density polyethylene (hereinafter referred to as
It is called LLDPE. ), MI is 5 to 30 g/10 min, and density is 0.945 to 0.968. A polyethylene resin composition for injection molding with improved tearability, which is obtained by adding F/d high-density polyethylene (hereinafter referred to as HDPE) in an amount of 10 to 50% by weight to a polyethylene resin composition.

The LLDPE used in the present invention is a copolymer of ethylene and other α-olefins and is different from LDPE produced by conventional high pressure methods.

The LLDPE is a copolymer of ethylene and other α-olefins such as butene, hexene, octene, decane, and 4-methylpentene-1 in an amount of 4 to 15 g/wt, preferably 5 to 15 g/wt. Yes, conventional medium and low pressure HDP
It is produced using a Ziegler type catalyst or a Phillips type catalyst used in E production. Conventional HDP
It has a short branched structure like E, and the density can be appropriately lowered using this short chain branching to 0.910 to 0.950.
p/crA level, compared to conventional LDPE.
It is a polyethylene resin with a more linear structure and a more branched structure than HDPH.

The LLDPE used in the present invention is MI (JIS K
6760) is 5 to s o y71
°min and a density of 0.915 to 0.935 g/d, preferably 0.920 to 0.930 F/i.

If the MI of the LLDPE is as low as 5.9/10 minutes, the fluidity of the molten resin will deteriorate, and the MI of the LLDPE will be 50/10.
If it exceeds F/10 minutes, the tearability of the obtained molded article will decrease, which is not preferable.

Further, the density of the LLDPE is 0.915. If P/d is smaller, the rigidity of the obtained molded product will be reduced, and the LLDPE
If the density exceeds 0.93597 cd, it is not preferable because it reduces tearability.

The HDPE used in the present invention is a homopolymer of ethylene or a copolymer of ethylene and an olefin monomer such as propylene or butene-1.

The HDPE is obtained by homopolymerizing ethylene or copolymerizing ethylene with an α-olefin such as propylene, butene-1, etc. using a catalyst comprising a transition metal compound and an organometallic compound. Examples of the transition metal compound include one or more transition metal compounds such as titanium, vanadium, and chromium, or those supported on silica, alumina, magnesium compounds, etc., or reacted with them. In particular, a solid catalyst component in which a titanium compound such as titanium chloride, haloalcolade, or alcolade is supported on or reacted with a magnesium compound such as magnesium alcolade or magnesium chloride is preferably used.

The organometallic compound is represented by the general formula AlRn Examples include organoaluminum compounds. Specifically, triethylaluminum, tri-n-propylaluminum, triisobutylaluminum, dimethylaluminum monochloride, ethylaluminum sesquichloride and the like can be mentioned.

The blending ratio of HDPE used in the present invention is 10 to 50 weight percent, preferably 15 to 30 weight percent, based on the total composition. If the blending ratio is less than 10% by weight, the rigidity of the molded product will be low when the resulting composition is made into a molded product, and if the blending ratio exceeds 50% by weight, the resulting composition will have a low rigidity. This is not preferable because the tearability of the molded product obtained by using the method decreases. In addition, MI (JI) of the HDPE
Value measured according to SK 6760) is 5 to 3 (1/
10 minutes, preferably 10-259710 minutes. The H
If the MI of the DPE is less than 5II/10 minutes, the fluidity of the resin during melting will deteriorate, and if it exceeds 30.9/10 minutes, the molded product will tear when molded using the resulting composition. This is not preferable because it reduces performance.

The polyethylene resin composition of the present invention has the above-mentioned LLDP.
After stirring and mixing a predetermined amount of E and HDPE using a stirring device such as a Hensel mixer (trade name), a ribbon blender, or a super mixer, the mixture is mixed using a conventional melt mixing method such as a Banbury mixer, continuous mixer, mixing roll, or extrusion. Depending on the machine, melt crosstalk temperature 130~2
It is obtained by melt-kneading at 50°C and pelletizing.

In addition, the polyethylene resin composition of the present invention may optionally contain an antioxidant such as butylated hydroxytoluene (
lubricants such as calcium stearate, UV absorbers such as 2-(2'-hydroxy-3
'-1-butyl-5'-methylphenyl)-5-chlorobenzotriazole, bis(2,2'6,6'-tetramethyl-4-piperidine sebacate), antistatic agents such as glycerin monostearate) , N,N-bis(2-hydroxyethyl)alkylamine), pigments such as carbon black, and various known additives commonly used in polyethylene can be added.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the Examples unless the gist thereof is exceeded.

In the Examples, measurements of flexural modulus, Izot impact strength, tearability, and tear strength as methods for evaluating rigidity were carried out by the following methods.

(1) Flexural modulus: Conforms to JIS K 6760.

(li) Izot impact strength... JIS K 6
760.

(fil) Tearability and tear strength... Vertical 400f
A flat plate with a width of 80*xs and a thickness of 2u was molded using an injection molding machine and used as a test piece. The exam is
100B from the center of the short piece of the test piece to the inside parallel to the long side
A cut was made, each of the cut portions was attached to the upper and lower chucks of a tensile testing machine, and the maximum tensile load was measured to determine the tear strength. As for evaluation of tearability, those that were torn in a straight line were rated as ○, and those that were torn in a sawtooth pattern were rated as x. The measurement conditions are as follows.

Measurement temperature: 23 times 2°C Temperature: 50 ± 5 R, H Tensile speed: 500 seams Distance between chucks: 100 times Examples 1 to 5 LLDPE (stabilizer, butylated hydroxytoluene 0
．． HDPE (LLD
The same amount of PE (containing the same stabilizer) was placed in a Hensel mixer (trade name) at the mixing ratio listed in Table 1 below.
After stirring and mixing for 3 minutes, the mixture was heated to a cylinder temperature of 1
The mixture was melt-kneaded using a single-screw extruder at 90°C to obtain extruded pellets. A predetermined test piece was prepared using the obtained pellet,
The flexural modulus, Izot impact strength, tear strength, and tearability were measured and evaluated using the above measurement methods. The results are shown in Table 1.

Comparative Example 1 LLDPE similar to that used in Examples 1 to 5 was melt-kneaded and extruded using a single-screw extruder with a cylinder temperature of 190°C to form pellets. Examples 1 to 5 using the obtained pellets
Flexural modulus, Izot impact strength, tear strength, and tearability were measured and evaluated in accordance with the following. The results are shown in Table 1.

Comparative Example 2 LLDPE and HDPE similar to those used in Examples 1 to 5 were added at the blending ratios listed in Table 1 below, and Example 1
- 5 to form pellets by stirring, mixing, melt-kneading, and extruding. Using the obtained pellets, the flexural modulus, Izot impact strength, tear strength, and tearability were measured and evaluated in accordance with Examples 1 to 5. The results are shown in Table 1.

Comparative Example 3 LLDPE similar to that used in Examples 1 to 5 was melted and mixed and extruded into pellets using a single screw extruder with a cylinder temperature of 190°C. Using the obtained pellets, flexural modulus, Izot impact strength, tear strength,
Tearability was measured and evaluated. The results are shown in Table 1.

Comparative Examples 4-6 LLDPE and HDP similar to those used in Examples 1-5
E was added in the proportions shown in Table 1 below, and pellets were prepared by stirring, mixing, melt mixing, and extruding according to Examples 1 to 5. Examples 1 to 5 using the obtained pellets
Flexural modulus, Izot impact strength, tear strength, and tearability were measured and evaluated in accordance with the following. The results are shown in Table 1.

(Effect of the invention) By using the composition of the invention, LDPE and LL
A molded article with higher rigidity and improved tearability can be obtained than a molded article obtained by using each DPE alone. Therefore, the polyethylene resin composition of the present invention can be suitably used for large-sized, thin-walled injection molded products.

Claims (1)

[Claims] (1) Melt index (hereinafter referred to as MI) is 5
~50g/10min and density 0.915~0.93
Linear low density polyethylene of 5 g/cm^3, MI of 5 to 30 g/10 min, and density of 0.945 to 0.9
A polyethylene resin composition for injection molding with improved tearability, which is obtained by adding 68 g/cm^3 high-density polyethylene in an amount of 10 to 50% by weight based on the polyethylene resin composition.