KR100550313B1 - Polypropylene Resin Composition Having Good Low Heat Sealing Property, Good Transparency and Good Tear Strength - Google Patents

Abstract

The polypropylene resin composition excellent in low temperature thermal adhesiveness, transparency and tear strength of the present invention is (a) crystalline containing 80 to 99.5 wt% propylene, 0.5 to 10 wt% ethylene and 0.5 to 10 wt% 1-butene 65 to 95% by weight of ethylene-propylene-1-butene terpolymer; And (b) 20 to 70% by weight of ethylene and 30 to 80% by weight propylene, with an absolute viscosity of 5 to 35% by weight of an elastic ethylene-propylene copolymer of 0.5 to 1.5 dl / g.

Polypropylene, low temperature thermal adhesiveness, transparency, tear strength, ethylene-propylene-1-butene terpolymer, block copolymer

Description

Polypropylene Resin Composition Having Good Low Heat Sealing Property, Good Transparency and Good Tear Strength

Field of invention

The present invention relates to a polypropylene resin composition excellent in low temperature thermal adhesiveness, transparency and tear strength. More specifically, the present invention relates to a polypropylene resin composition consisting of a crystalline ethylene-propylene-1-butene terpolymer and an elastic ethylene-propylene copolymer, and having excellent low temperature thermal adhesiveness, transparency and tear strength. .

Background of the Invention

Unstretched polypropylene films are widely used in food packaging because of their low cost and excellent thermal adhesiveness. In order to increase the production speed during packaging of the unstretched polypropylene film, the time required for thermal bonding should be reduced. Therefore, it is preferable to use a resin having a low thermal bonding temperature because it may be bonded at a high temperature or lower the thermal bonding temperature of the resin used in the thermal bonding layer. Conventionally, the unstretched polypropylene resin film used ethylene-propylene-1-butene terpolymer as an unstretched film, but the low-temperature thermal adhesiveness is insufficient and the tearability is poor.

In general, the thermal bonding temperature of the resin is related to the melting temperature of the resin, and the lower the melting temperature, the lower the thermal bonding temperature. As the content of ethylene and 1-butene increases in the ethylene-propylene-1-butene terpolymer, the melting temperature and the heat bonding temperature decrease, but the low polymer increases when the content of ethylene and 1-butene increases in the polymerization process. There is a problem in that the transparency is worse due to a lot of crawling to the surface.

Therefore, polybutene-1 or metallocene PE is blended in ethylene-propylene-1-butene terpolymer to improve thermal adhesion without degrading transparency. have. However, in the case of polybutene-1, the low temperature thermal adhesiveness is improved, but there is a limit in the improvement of transparency because there is a limit in the fine dispersion between polypropylene and polybutene-1. In addition, in the case of Metallocene PE, both low temperature heat adhesiveness and transparency are improved, but when the content of Metallocene PE is blended more than 10 wt%, there is a disadvantage in that workability is inferior due to the limitation of kneading of polypropylene and Metallocene PE.

In order to overcome these disadvantages, many studies have been conducted. In Japanese Patent Laid-Open No. 1-234447, low-density polyethylene alone or ethylene-based α having a density of 0.925 g / cm 3 or less in polypropylene having a melting point of 150 ° C. or lower to improve transparency and surface gloss. A composition containing 30 parts by weight of a mixture with an -olefin copolymer and 0.05-2.0 parts by weight of rosin ester was provided, but the low temperature heat sealability, processability and hot tack were not satisfactory.

JP-57-57740 discloses polypropylene having a melting point of 150 ° C. or lower, a low melt polyethylene index of low density polyethylene, and a high or two ethylene polypropylene having a density of 0.925 g to improve transparency, surface gloss and processability. Although a mixture with an α-olefin copolymer having a / cm 3 or less is provided, a satisfactory result is obtained in terms of heat sealability, but not satisfactory in view of workability.

In addition, Korean Patent No. 2001-0012600 discloses 0-20% by weight of a propylene-α-olefin copolymer containing 40-80% by weight of crystalline polypropylene and 20-80% by weight of propylene units in a polypropylene unoriented molded body. The molding material is applied to the film or sheet but has a disadvantage due to processing technology rather than the resin composition itself.

Meanwhile, as disclosed in Korean Patent Laid-Open No. 2001-006497, a method of controlling the melt flow rate ratio and the viscosity ratio of the ethylene copolymer and the olefin copolymer has been proposed, and the composition obtained by this method does not have sufficient transparency improvement. The thick film of the film does not have sufficient transparency.

In contrast, the present inventors kneaded together an crystalline ethylene-propylene-1-butene terpolymer containing a proportion of ethylene and 1-butene with an elastic copolymer having optical and thermodynamic compatibility to overcome the above problems. by doing, It is to develop a resin composition having excellent low temperature thermal adhesiveness, transparency and tear strength.

An object of the present invention is to provide a polypropylene resin composition excellent in low temperature thermal adhesiveness.

Another object of the present invention is to provide a polypropylene resin composition having excellent transparency.

Still another object of the present invention is to provide a polypropylene resin composition having excellent tear strength.

Still another object of the present invention is to provide a polypropylene resin composition particularly suitable for film applications requiring heat adhesiveness, transparency, and tear strength, such as retort food packaging films and frozen food packaging films.

The above and other objects of the present invention can be achieved by the present invention described below. Hereinafter, the content of the present invention will be described in detail.

The polypropylene resin composition of the present invention comprises (a) crystalline ethylene-propylene-1-butene terpolymer 65 to 80 to 99.5 wt% propylene, 0.5 to 10 wt% ethylene and 0.5 to 10 wt% 1-butene 95 wt%; And (b) from 20 to 70% by weight of ethylene and from 30 to 80% by weight of propylene and having from 5 to 35% by weight of an elastic ethylene-propylene copolymer having an absolute viscosity of 0.5 to 1.5 dl / g.

(a) Crystalline Ethylene-propylene-1-butene Terpolymer

The ethylene-propylene-1-butene terpolymer (a) used in the present invention is a random copolymer prepared by simultaneously adding ethylene, propylene, and 1-butene to the polymerization reactor, and the content of the propylene component in the copolymer is 80 to 99.5% by weight, the content of the ethylene component is 0.5 to 10% by weight and the content of the 1-butene component is preferably 0.5 to 10% by weight.

The role of the ethylene-propylene-1-butene terpolymer (a) in the present invention imparts an appropriate degree of heat resistance while maintaining the heat sealability and transparency of the preparation. In addition, it has proper optical and thermodynamic compatibility with the elastic ethylene-propylene copolymer (b) to maintain transparency and to lower the thermal bonding temperature due to the low melting temperature of the elastic block copolymer to increase the thermal bonding strength.

If the content of ethylene or 1-butene component of the terpolymer (a) is less than 0.5% by weight, the degree of crystallinity of the copolymer becomes higher than necessary, thereby lowering the transparency of the resulting composition. It falls rapidly, rigidity falls, heat resistance falls, and it becomes unsuitable as the material of the film used in daily life.

The difference in the physical properties of the composition containing ethylene and 1-butene is that ethylene shows better physical properties than 1-butene with transparency and heat adhesiveness, but the low polymer content of 1-butene is higher than that of 1-butene. Sticky) may be the cause.

(b) elastomeric ethylene-propylene copolymers

The elastic ethylene-propylene copolymer is prepared in a series of reactors following the preparation of the ethylene-propylene random copolymer.

The role of the elastic ethylene-propylene copolymer in the present invention is to give the random block copolymer composition impact resistance properties, low temperature heat adhesive properties and excellent tear strength. In addition, it has an optical and thermodynamic compatibility of the terpolymer (a) with an appropriate degree, it is possible to finely disperse micrometers at the time of manufacturing the composition, and has the characteristics of simultaneously giving transparency, heat adhesion characteristics and excellent tear strength.

The ethylene content in the elastic ethylene-propylene copolymer (b) is preferably 20 to 70% by weight. If the ethylene content is less than 20% by weight or more than 70% by weight, the melting temperature of the ethylene-propylene copolymer is increased to lower the heat adhesiveness.

As for the absolute viscosity of the elastic ethylene-propylene copolymer (b) of this invention, 0.5-1.5 dl / g is preferable. If the absolute viscosity is greater than 1.5 dl / g, the dispersibility of the elastomeric copolymer component during molding of the composition is lowered, leading to a decrease in transparency and tear strength. If the absolute viscosity is less than 0.5 dl / g, the dispersibility is good immediately after molding during processing of the block copolymer composition, but as the crystallinity of the ethylene-propylene random copolymer progresses, a phenomenon occurs that comes to the surface of the product, resulting in transparency and phosphorus. The thermal strength is lowered and greatly deteriorates the appearance of the product.

In the present invention, the weight ratio of the ethylene-propylene-1-butene terpolymer (a) and the elastic ethylene-propylene copolymer (b) is 65 to 95% by weight of ethylene-propylene-1-butene terpolymer (a), It is preferable that the elastic ethylene-propylene copolymer (b) is 5 to 35% by weight. (b) If the component is less than 5% by weight can not increase the low temperature thermal adhesive strength, if more than 35% by weight can increase the low temperature thermal adhesive strength, but the transparency is worsened and may cause the stickiness of the film (Sticky).

In addition to the above components, the resin composition of the present invention may be added to various additives, such as antioxidants, neutralizing agents, antiblocking agents, slip agents, etc., within the range that does not deviate from the characteristics of the present invention, depending on the respective uses.

In the resin composition of the present invention, propylene, ethylene and 1-butene are simultaneously charged and polymerized to prepare terpolymer (a), and ethylene and propylene are added to a series of subsequent reactors, followed by a separate polymerization reaction. (b) is prepared to prepare a block copolymer composition in which (a) and (b) are kneaded.

The present invention may be understood in more detail by the following examples, which are intended to illustrate the present invention and are not intended to limit the scope of the invention.

Example 1

(1) Step 1: Preparation of ethylene-propylene-1 butene terpolymer (a)

Propylene, ethylene, and 1-butene were simultaneously injected into the reactor to react. When the content ratio of propylene, ethylene and 1-butene in the produced copolymer was 94% by weight of propylene, 3% by weight of ethylene and 1-butene 3 The terpolymer (a) was prepared by copolymerization so as to be a weight% ratio.

(2) Step 2: Preparation of Ethylene-Propylene Elastomer Copolymer (b) and Preparation of Copolymer

After the first stage of polymerization, the reaction is carried out in a series of reaction apparatuses, and when the ratio of propylene and ethylene in the elastic copolymer produced in the second stage is 75% by weight of propylene, 25% by weight of ethylene is obtained. An elastomeric copolymer (b) was prepared so as to have a viscosity of 0.88 dl / g to obtain a composition in which (a) and (b) were kneaded. The absolute viscosity is the intrinsic viscosity measured in 135 ° C decalin solvent.

The ratio of the content of terpolymer (a) and the elastic copolymer (b) in the copolymer after completing steps 1 and 2 is 10% by weight of the elastic copolymer (b) when the terpolymer (a) is 90% by weight. The polymerization amount of was adjusted to obtain a block copolymer composition.

(3) step 3: pellet preparation and test specimen preparation

0.2 parts by weight of the antioxidant and 0.2 parts by weight of the antiblocking agent were kneaded into the composition obtained above, which was extruded in a twin screw extruder to produce pellets, and then extruded at a melting temperature of 240 ° C. using an extruder having a diameter of 45 mm and a T-die. Then, it quenched with the cooling roll of surface temperature 20 degreeC, the film was shape | molded, and the roll shape film of 30 micrometers of winding thickness, and width 40cm was obtained.

Examples 2-4

As shown in Table 1, it was carried out in the same manner as in Example 1 except that the composition and content ratio of the terpolymer (a) and the elastic copolymer (b) were modified.

Comparative Example 1

The same procedure as in Example was carried out except that the elastic copolymer (b) was not used.

Comparative Examples 2-4

The same procedure was followed as the terpolymer (a) except that ethylene or 1-butene was not included.

Comparative Examples 5-6

The ethylene content of the elastic copolymer (b) was carried out in the same manner as in the above example, except that the ethylene content was less than 20 wt% and more than 70 wt%, respectively.

Comparative Examples 7-8

The same procedure was carried out in the same manner as in the above example except that the absolute viscosity of the elastic copolymer (b) was greater than 1.5 dl / g and less than 0.5 dl / g, respectively.

Comparative Example 9

The same procedure as in Example 1 was carried out except that the content of the elastic copolymer (b) in the block copolymer composition was 51 wt%.

Comparative Example 10

Ethylene content of the elastomeric copolymer (b) 12% by weight, the absolute viscosity of 0.33 dl / g, the same as in the above embodiment except that the content of the elastic copolymer (b) in the total composition was 65% by weight Was performed.

The physical properties of the resins prepared in Examples 1-4 and Comparative Examples 1-10 were measured by the following method.

(1) Melt Index (g / 10min): Based on ASTM D1238, measured at 230 ° C. under 2.16 Kg load.

(2) Thermal bonding temperature (℃): The film is bonded at a constant temperature using a heat bonder for 2 seconds at a load of 2 kgf for 1.5 seconds, sampled at a width of 1.5 cm, and then bonded at 300 mm / min in a tensile tester. The strength was measured and measured at a temperature at which the thermal bond strength value was 0.6 kg. The lower the thermal bonding temperature, the better the thermal adhesiveness.

(3) Transparency (%): The haze value was measured according to ASTM D1004. Specimens were measured with a 30 μm thick film specimen.

(4) Tear Strength (N / mm): Elemendorf tear strength was measured in the MD and TD directions according to ASTMD1922.

Compositions and physical properties of the resins prepared in Examples 1-3 and Comparative Examples 1-3 are shown in Table 1 below.

As shown in Table 1, it can be seen that Example 1 has improved the low temperature thermal adhesiveness and tear strength compared to Comparative Example 1 does not include an elastomeric copolymer (b). In Comparative Example 2-4 in which the terpolymer (a) does not contain ethylene or 1-butene, it can be seen that low-temperature heat adhesiveness, transparency, and tear strength are reduced. In Comparative Example 4-5 in which the ethylene content of the elastomer was less than 20 wt% or more than 70 wt%, the low temperature thermal adhesiveness, transparency, and tear strength were greatly reduced. Also in Comparative Example 6-7 in which the absolute viscosity of the elastomer is smaller than 0.5 dl / g or larger than 1.5 dl / g, it was confirmed that the low temperature thermal adhesiveness, transparency and tear strength were remarkably decreased. In Comparative Example 9-10 in which the content of the elastic copolymer (b) in the total resin composition exceeds the range of the present invention, it was found that the low temperature thermal adhesiveness was excellent, but the transparency was largely inferior.

Since the present invention has excellent low temperature thermal adhesiveness and transparency and excellent tear strength, the present invention is particularly suitable for film applications requiring heat adhesiveness, transparency, and tear strength, such as retort food packaging films and frozen food packaging films. It has the effect of providing a polypropylene resin composition.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (2)

(a) 65 to 95 weight percent crystalline ethylene-propylene-1-butene terpolymer containing 80 to 99.5 weight percent propylene, 0.5 to 10 weight percent ethylene and 0.5 to 10 weight percent 1-butene; And (b) 5 to 35 weight percent of an elastic ethylene-propylene copolymer containing 20 to 70 weight percent ethylene and 30 to 80 weight percent propylene and having an absolute viscosity of 0.5 to 1.5 dl / g; Polypropylene resin composition, characterized in that consisting of. Propylene, ethylene and 1-butene were simultaneously charged and polymerized to prepare terpolymer (a), and ethylene and propylene were charged and polymerized in a subsequent series of reactors to prepare elastomer (b) to knead them. A method for producing a polypropylene resin composition, wherein the block copolymer composition according to claim 1 in which (a) and (b) is kneaded is obtained.