KR100633789B1 - Polypropylene Resin Composition for Plastic Bottle Cap - Google Patents

Abstract

The present invention relates to a polypropylene resin composition for plastic bottle caps, and more particularly, comprising a high-stereoregular polypropylene resin having a wide molecular weight distribution and an organic nucleating agent, and having excellent dominance, impact resistance and productivity. It relates to a polypropylene resin composition for bottle caps.

Plastic, Bottle Cap, Polypropylene, Resin, Composition

Description

Polypropylene resin composition for plastic bottle caps {POLYPROPYLENE RESIN COMPOSITION FOR PLASTIC BOTTLE CAP}

The present invention relates to a polypropylene resin composition for plastic bottle caps, and more particularly, comprising a high-stereoregular polypropylene resin having a wide molecular weight distribution and an organic nucleating agent, and having excellent dominance, impact resistance and productivity. It relates to a polypropylene resin composition for bottle caps.

Recently, due to the diversification of packaging containers and the expansion of the separate collection in an environmentally friendly aspect, plasticization of bottle cap materials used for beverage containers such as glass bottles and polyethylene terephthalate (PET) bottles is increasing. Existing iron or aluminum metal bottle caps are likely to cause injury to hands when the lid is opened, and additional sorting equipment is required for recycling, as users do not separate the containers and lids well. There is such a problem.

Therefore, the development of bottle cap material that can replace metal is being actively made. Especially, the bottle cap is made by using resin such as polyethylene, polypropylene, etc., which is excellent in processability, mechanical properties, appearance, durability and economic efficiency, and is suitable for recycling. Techniques for preparing the polymer are actively being developed. In these technologies, high density polyethylene resins or ethylene propylene copolymer resins are mainly used. For example, Korean Patent Laid-Open Publication No. 2004-89205 discloses a resin composition for bottle caps based on polyethylene, 211855 discloses a polypropylene copolymer as a substrate for forming a container for non-acidic beverages.

However, the resin compositions used in the prior art as described above are all suitable for use in the manufacture of containers for non-acidic beverages such as drinking spring water and tea, and when molded into bottle caps of carbonated beverage containers, Due to the low domming property, there is a problem in that the amount of carbonic acid remaining in the beverage is reduced when left for a long time. Therefore, there is a demand for the development of a resin composition which is excellent in processability, mechanical properties, appearance, durability and economy, is suitable for recycling, and has excellent domming properties and can be suitably applied to the bottle cap of a carbonated beverage container. .

The present invention is to solve the problems of the prior art as described above, the object of the present invention is excellent in processability, mechanical properties, appearance, durability and economics, and is suitable for recycling, and at the same time excellent in carbonate drink It is to provide a polypropylene resin composition that can be suitably applied to the bottle cap of the container.

According to the present invention, the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by the gel permeation chromatography (GPC) method is in the range of 7 to 12, and the nuclear magnetic resonance pen Provided is a polypropylene resin composition for plastic bottle caps comprising 100 parts by weight of a high stereoregular propylene-alphaolefin copolymer resin having a stereoregularity index of 96% or more on the TARD method and 0.05 to 0.3 parts by weight of an organic nucleating agent.

In the high stereoregular propylene-alpha olefin copolymer resin contained in the resin composition of the present invention, the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) method. (Mw / Mn) represents a molecular weight distribution, the value of which must be within the range of 7-12. When the value of Mw / Mn is less than 7, the flowability of the resin composition may be deteriorated, which may cause molding defects during molding of the product. When the Mw / Mn value exceeds 12, extrusion stability may be worse during melt extrusion.

In addition, in the high stereoregular propylene-alpha olefin copolymer resin, the stereoregularity index on the nuclear magnetic resonance pentad method should be high stereo regularity of 96% or more. When the stereoregularity index is less than 96% based on the nuclear magnetic resonance pentad method, there is a disadvantage in that the heat resistance and strength of the resin are lowered.

The high-stereoregular propylene-alpha olefin copolymer resin included in the resin composition of the present invention is a resin prepared by copolymerizing propylene with alpha olefins such as ethylene and butylene, and the alpha olefin content in the resin is 5 to 15 mol%. Is preferably. When the alpha olefin content is less than 5 mol%, impact resistance and the like of the resin composition are lowered, and when it exceeds 15 mol%, hardness, heat resistance and the like are lowered.

In addition, it is preferable that the melt index based on ASTMD1238 of the said high-stereoregular propylene-alpha olefin copolymer resin is 5-15 g / 10min at 230 degreeC and 2.16 kg. If the melt index is less than 5 g / 10 minutes, the resin composition processability and product productivity worsens, and if the melt index is more than 15 g / 10 minutes, the melt strength is lowered and the cutting is not cleaned, thereby increasing the defective rate in the extrusion process.

The organic-based nucleating agent included in the resin composition of the present invention is added to impart heat resistance and high-speed crystallinity to the resin composition, and the organic nucleating agent is not particularly limited in kind, and includes sorbitol-based compounds such as heptane-bicyclodicarboxylic acid, Aluminum salt compounds such as aluminum para-t-butylbenzoic acid, calcium salt compounds such as calcium benzoic acid, sodium salt compounds such as sodium benzoic acid, sodium lithium phosphate, and the like may be preferably used. In the resin composition of the present invention, the organic-based nucleating agent is used by adding 0.05 to 0.3 parts by weight per 100 parts by weight of the high-stereoregular propylene-alpha olefin copolymer resin, if the content is less than 0.05 parts by weight sufficient heat resistance and high speed It is difficult to obtain crystallinity, and even if it exceeds 0.3 parts by weight, no further physical property improvement effect is expressed.

In addition to the above components, the resin composition of the present invention, within the range that can achieve the object of the present invention, resin compositions for bottle caps such as reinforcing materials, fillers, heat stabilizers, weather stabilizers, antistatic agents, lubricants, slip agents, etc. Various additives conventionally added to may be further included.

There is no restriction | limiting in particular in the manufacturing method of the resin composition of this invention, A conventionally well-known polypropylene resin composition can be used as it is or a suitable modification, and each said component is a desired order, without restriction | limiting in a special order. You can freely choose and mix according to your needs. That is, the resin composition of this invention is specifically, for example, injecting each component and the other additives as mentioned above by a necessary amount into a kneader such as a kneader, a roll, a short-barrier mixer, or a single screw twin screw extruder. Next, it can be produced by a method of kneading the raw materials introduced using these devices.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited by these Examples and Comparative Examples.

Examples 1-2 and Comparative Examples 1-3

For Examples 1 to 2 and Comparative Examples 1 to 3, all the components as shown in Table 1 below were added to the biaxial kneading extruder (manufactured by Korea EM) at once in each content as shown in Table 1 and kneaded. To produce a polypropylene resin composition. Melt index of each of the prepared resin compositions was measured and shown in Table 1 below.

For Examples 1 to 2 and Comparative Examples 1 to 3, the polypropylene resin composition prepared as described above was injected into and injected into Samsung Kleckerner FCM-110 (110 tons of clamping force), and required specimens for measuring the physical properties, respectively. Flexural modulus, impact strength, heat deflection temperature, hardness, crystallization temperature, and isothermal cryatallization half-time (ICHT) were measured for the fabricated specimens, and the measured results are shown in Table 1 below. It was.

In addition, using the polypropylene resin composition prepared as described above, the bottle cap was molded by a melt extruder manufactured by Nippon Crown Co., Ltd., and the production rate was measured in order to evaluate the productivity.

In addition, the bottle caps formed as described above were mounted on a beverage container filled with a carbonated beverage, and then evaluated for doming and carbonic acid gas remaining amount, and are shown in Table 1 below.

Property measurement / evaluation item and test method

1) Melt Index

It measured at 230 degreeC with a 2.16 kg load based on ASTMD1238.

2) flexural modulus

It was measured at room temperature in accordance with ASTM D770.

3) impact strength

In accordance with ASTM D256 was measured with a notched specimen at room temperature.

4) Heat deflection temperature

It measured at low weight (4.6kg) based on ASTMD648.

5) hardness

In accordance with ASTM D785 it was measured by R-SCALE at room temperature.

6) Crystallization Temperature

It was measured under the temperature condition of 10 ℃ / min using DSC equipment.

7) Isothermal semicrystallization time (ICHT)

Using the DSC equipment, the time taken for the crystallization to proceed 1/2 in the isothermal state of 140 ℃ was measured.

8) Doming

The bottle cap was placed in a beverage container filled with a carbonated beverage, left in a 42 ° C. thermostatic chamber for 2 weeks, and the domeability was evaluated by measuring the height of the upper portion of the bottle cap. The lower the inflated height, the better the dominance.

9) Residual Gas Volume

The bottle cap was placed in a beverage container filled with a carbonated beverage, and left in a 42 ° C. thermostatic chamber for two weeks. After all the gases in the container were released, the pressure formed in the container was measured by shaking the container.

10) Productivity

The production rate of the bottle cap was measured by using a melt extruder manufactured by Nippon Crown Co., Ltd.

TABLE 1

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3  Resin composition (parts by weight) PL-EL Copolymer 1 100 100 - - 100 PL-EL copolymer 2 - - 100 - - PL homopolymer - - - 100 - Organic nucleating agent 0.1 0.2 0.1 0.1 -    Measurement / evaluation result Melt Index (g / 10min) 7.8 8.1 7.9 10.4 8.0 Flexural modulus (kg / ㎠) 16500 16500 16000 18500 14500 Impact Strength (kg cm / cm) 9.0 9.0 9.1 2.2 8.0 Heat Deflection Temperature (℃) 124 126 114 124 115 Longitude (R-SCALE) 96 95 84 106 90 Crystallization temperature (℃) 134 135 108 119 119 ICHT (minutes) 0.56 0.51 25 9.73 22 Doming property (mm) 3.4 3.4 4.8 3.1 3.6 Residual gas (psi) 34.3 34.3 33.6 37.1 34.1 Productivity (minutes / minute) 685 680 620 651 663

week)

1) PL-EL copolymer 1: Molecular weight distribution (Mw / Mn) by gel permeation chromatography (GPC) method is 8.0, the stereoregularity index is 96%, nuclear ethylene content 8 mol% by nuclear magnetic resonance pentad method, And a high stereoregular propylene-ethylene copolymer resin having a melt index of 8 g / min.

2) PL-EL copolymer 2: Molecular weight distribution (Mw / Mn) by gel permeation chromatography (GPC) method of 5.5, stereoregularity index of nuclear magnetic resonance pentad method of 92%, ethylene content of 8 mol%, And a high stereoregular propylene-ethylene copolymer resin having a melt index of 8 g / min.

3) PL homopolymer: High solids rule with molecular weight distribution (Mw / Mn) of 8.0 by gel permeation chromatography (GPC), 96% stereoregularity index by nuclear magnetic resonance pentad method, and 10g / min by melt index Propylene homopolymer resin.

4) Organic Nucleating Agent: Heptane-bicyclodicarboxylic acid

As shown in Table 1, the resin composition prepared in Examples 1 and 2, the thermal deformation temperature, hardness, crystallization temperature, ICHT, etc. were superior to the resin composition of Comparative Example 1, and thus the bottle prepared using the same The lid was superior to the comparative example 1, and was suitable as a bottle cap material for carbonated beverages, such as having a better dopeability and a large amount of residual gas. In addition, the resin compositions prepared in Examples 1 and 2 exhibited very high crystallization temperature and very short isothermal semi-crystallization time (ICHT), and as a result, productivity was increased by about 10% compared to Comparative Example 1.

On the other hand, the resin composition of Comparative Example 2 is a resin composition prepared using a high-stereoregular propylene homopolymer, has excellent flexural modulus, heat deformation temperature, hardness, and the like. Although it could be used as a bottle cap, the impact strength was low, and the product had a disadvantage in that the product could be broken even by a small impact, which is frequently generated due to the distribution characteristics of carbonated beverage products, and the productivity was high due to the low crystallization temperature and high ICHT. Poor compared to 2. In addition, the resin composition of Comparative Example 3 was a resin composition containing no organic nucleating agent, and had a low flexural modulus, a heat deformation temperature, a crystallization temperature, a high ICHT, and poor dominance compared with Examples 1 to 2.

As described above, by using the resin composition according to the present invention, it is possible to economically produce a plastic bottle cap product for carbonated beverages excellent in the dope properties, impact resistance and productivity.

Claims (4)

The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by the gel permeation chromatography method is in the range of 7 to 12, and the stereoregularity index in the nuclear magnetic resonance pentad method is 96 %, And the melt index according to ASTM D1238 is a plastic comprising 100 parts by weight of a high-stereoregular propylene-alpha olefin copolymer resin of 5 to 15 g / 10 minutes at 230 ° C. and 2.16 kg and 0.05 to 0.3 parts by weight of an organic nucleating agent. Polypropylene resin composition for bottle caps. The polypropylene resin composition for plastic bottle caps according to claim 1, wherein an alpha olefin content in the high stereoregular propylene-alpha olefin copolymer resin is 5 to 15 mol%. delete The plastic bottle cap according to claim 1, wherein the organic nucleating agent is selected from the group consisting of heptane-bicyclodicarboxylic acid, aluminum para-t-butylbenzoic acid, calcium benzoic acid, sodium benzoic acid and sodium lithium phosphate. Polypropylene resin composition.