KR20120069960A - Polypropylene resin composition for bottle cap - Google Patents

Abstract

PURPOSE: A polypropylene-based resin composition for bottle caps is provided to reduce manufacturing cost and to manufacture plastic bottle caps with high transparency and shock resistance without using metallocene ethylene-based resin. CONSTITUTION: A polypropylene-based resin composition for bottle caps comprises polypropylene-based resin mixed in single phase. The polypropylene- based resin mixed in single phase comprises 40-60 parts by weight of a first ethylene-propylene random copolymer which includes 0.5-3 weight% of ethylene and 40-60 parts by weight of a second ethylene propylene random copolymer which includes 6-15 weight% of ethylene based on 100.0 parts by weight of polypropylene based resin. A melt index of the polypropylene-based resin is 1-10g/10minute(230 deg. Celsius).

Description

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

The present invention relates to a polypropylene resin composition for bottle caps excellent in impact resistance and transparency.

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. High-density polyethylene, polypropylene, etc. are mainly used for plastic bottle cap materials, and bottle caps based on these materials are lighter and less corrosive than bottle caps made of aluminum, and have excellent moldability and molding of various designs. It has possible advantages.

In the plastic bottle cap material, the high density polyethylene has a flexible property compared to polypropylene, but has excellent impact resistance, but has a disadvantage of low transparency of the product. On the other hand, in the case of polypropylene, a nucleating agent may be added or it may be manufactured transparently using a copolymerization technique. However, the use of the nucleating agent may deteriorate impact resistance properties.

In order to supplement the weakness of the impact strength of the polypropylene, a method of blending a metallocene ethylene rubber with a polypropylene resin has been proposed. However, this method is expensive because the rubber is inexpensive, there is a problem that the transparency is lowered above a certain rubber content is limited in its use. In addition, a method using an ethylene-propylene random block copolymer has been proposed, but a bottle cap manufactured based on such a copolymer is not broken at about 70 to 90% in an impact test for measuring the degree of cracking when falling at a height of 1 m. Moderate impact resistance is shown.

Accordingly, there is a demand for development of a plastic material for bottle caps having low manufacturing cost and excellent impact resistance and transparency.

The present invention is to solve the problems of the prior art as described above, an object of the present invention is a polypropylene-based resin for a bottle cap that can manufacture a plastic bottle cap having an economical cost, excellent transparency and impact resistance It is to provide a composition.

Another object of the present invention is to provide a molded article made of the polypropylene resin composition.

Aspects of the present invention for achieving the above object,

For 100 parts by weight of polypropylene resin,

a) 40 to 60 parts by weight of the first ethylene-propylene random copolymer having an ethylene content of 0.5 to 3% by weight; And

b) 40 to 60 parts by weight of a second ethylene-propylene random copolymer having an ethylene content of 6 to 15% by weight relates to a polypropylene resin composition for a bottle cap including a polypropylene resin mixed in a single phase.

Melt index of the polypropylene resin may be 1 ~ 10 g / 10 minutes (230 ℃).

The polypropylene resin composition may further include 0.1 to 0.5 parts by weight of antioxidant based on 100 parts by weight of polypropylene resin. In addition, the polypropylene resin may further comprise 0.01 to 0.5 parts by weight of the nucleating agent with respect to 100 parts by weight of the polypropylene resin. In addition, the polypropylene resin may further comprise 0.05 to 2.0 parts by weight of the catalyst neutralizer relative to 100 parts by weight of the polypropylene resin.

According to another aspect of the present invention,

It relates to a molded article produced from the polypropylene resin composition.

The polypropylene resin composition according to the present invention is a plastic bottle cap having excellent transparency and impact resistance without using expensive metallocene ethylene rubber because it uses a single phase of a polypropylene resin having a different ethylene content. It can be provided at economic cost.

Hereinafter, the present invention will be described in detail so that those skilled in the art can easily practice.

The polypropylene resin composition according to the present invention includes a polypropylene resin composed of two or more kinds of ethylene-propylene random copolymers having different ethylene contents.

The ethylene-propylene random copolymers having different ethylene contents are excellent in compatibility between components, and unlike a mixture by a simple blending method, can provide a single-phase polypropylene resin without phase separation. Single-phase resins of ethylene-propylene random copolymers having different ethylene contents may provide a uniform composition to the polypropylene resin composition, and may provide an effect of improving impact resistance and transparency of injection molded articles.

In one embodiment of the present invention, the polypropylene resin may be a resin composed of two or more ethylene-propylene random copolymers having different ethylene contents in a single phase.

More specifically, the polypropylene resin may be 0.5 to 3 wt% of the first ethylene-propylene random copolymer and 6 to 6 ethylene of the second ethylene-propylene random copolymer, based on the first ethylene-propylene random copolymer. 15 wt% of a second ethylene-propylene random copolymer.

When the ethylene content of the first ethylene-propylene random copolymer is less than 0.5% by weight, the impact resistance of the resin composition may be lowered. If the content of the ethylene-propylene random copolymer is greater than 3% by weight, the rigidity may be lowered.

The first ethylene-propylene random copolymer may be included in an amount of 40 to 60 parts by weight based on 100 parts by weight of the polypropylene resin. When the first ethylene-propylene random copolymer deviates from 40 parts by weight and 60 parts by weight, it is difficult to obtain an effect of improving the impact resistance and transparency of the resin composition.

When the ethylene content of the second ethylene-propylene random copolymer is less than 6% by weight, the impact resistance may be lowered. When the second ethylene-propylene random copolymer is more than 15% by weight, the ethylene content is increased to cause agglomeration between ethylene-propylene random copolymers. It may be difficult to be mixed into a single phase resin due to poor compatibility, and phase separation may occur to reduce transparency of the resin composition.

The second ethylene-propylene random copolymer may be included in an amount of 40 to 60 parts by weight based on 100 parts by weight of the polypropylene resin. If the second ethylene-propylene random copolymer deviates from 40 parts by weight and 60 parts by weight, the effect of improving the impact resistance and transparency of the resin composition cannot be obtained.

The melt index of the polypropylene resin may be 1 to 10 g / 10 min ((ASTM D 1238, 230 ° C., 2.16 kg load). The melt index of the polypropylene resin may be less than 1 g / 10 min. The workability and product productivity of the polypropylene resin may be lowered, and if it exceeds 10 g / 10 minutes, the melt strength is lowered so that the cutting of the molding is not clean, and thus the defective rate may be increased in the extrusion process. Due to the deterioration of the impact resistance, it is difficult to apply the final product to the plastic bottle cap.

The polypropylene resin may be prepared by a gas phase polymerization method.

The gas phase polymerization method includes a first gas phase polymerization step and a second gas phase polymerization step.

The first gas phase polymerization step is a step of preparing a first ethylene-propylene random copolymer by gas phase polymerization by injecting ethylene and propylene in the presence of a catalyst. The first ethylene-propylene random copolymer prepared in the first gas phase polymerization step is polymerized into fine particles and simultaneously dispersed in the gas phase in the polymerization tank.

The second gas phase polymerization step is a step of preparing a second ethylene-propylene random copolymer by gas phase polymerization in the presence of a catalyst by injecting ethylene and propylene in the presence of the first ethylene-propylene random copolymer.

In the second gas phase polymerization step, the second ethylene-propylene random copolymer is polymerized in a state in which the first ethylene-propylene random copolymer is dispersed into fine particles in a gas phase, and as in the first ethylene-propylene random copolymer. Polymerized into fine particles and dispersed in the gas phase.

The first and second ethylene-propylene random copolymers have different ethylene contents from each other. The first gas phase polymerization step and the second gas phase polymerization step may be continuously repeated at regular intervals for the purpose of the invention, and may be carried out in the same or different polymerization baths.

Specifically, for example, (1) A method for producing a polypropylene resin using a gas phase reactor having a single polymerization tank: The polymerization tank is divided into a first zone and a second zone. Ethylene and propylene are injected into the first zone, and a first ethylene-propylene random copolymer is prepared by gas phase polymerization in the presence of a catalyst. The prepared first ethylene-propylene random copolymer is transferred to the second zone, ethylene and propylene are injected in the presence of the first ethylene-propylene random copolymer, and the second ethylene-propylene is produced by vapor phase polymerization using a catalyst. Prepare a propylene random copolymer. The prepared first and second ethylene-propylene random copolymers are transferred back to the first zone and the first ethylene-propylene in the same manner in the presence of the first and second ethylene-propylene random copolymers in the first zone. Prepare a random copolymer. The gas phase polymerization of such first and second ethylene-propylene random copolymers can be carried out continuously and repeatedly according to the above method.

In another method, (2) a method for producing a polypropylene resin using a gas phase reactor in which a first and a second polymerization tank are connected in series: ethylene and propylene are injected into a first polymerization tank, and a gas phase is present in the presence of a catalyst. A first ethylene-propylene random copolymer is prepared by the polymerization method. The first ethylene-propylene random copolymer prepared above is transferred to a second polymerization tank. Ethylene and propylene are injected in the presence of the first ethylene-propylene random copolymer in the second polymerization tank, and a second ethylene-propylene random copolymer is prepared by gas phase polymerization using a catalyst. The gas phase polymerization of such first and second ethylene-propylene random copolymers can be carried out continuously and repeatedly according to the above method.

The first ethylene-propylene random copolymer and the second ethylene-propylene random copolymer prepared by the above method are uniformly mixed during the polymerization process so that a single phase having no phase separation compared to the resin mixture by a simple blending method between the resins during melt kneading is obtained. The resin of the phase can be provided.

The polypropylene resin composition may further include an antioxidant.

The antioxidant may be included in an amount of 0.1 to 0.5 parts by weight based on 100 parts by weight of the polypropylene resin. If the content of the antioxidant is less than 0.1 parts by weight, it is difficult to ensure long-term heat stability of the resin composition, if the content of more than 0.5 parts by weight does not improve the heat stability of the product any more, the problem of economic efficiency of the product by using excessive antioxidant May occur.

The antioxidants are tetrakis (methylene (3,5-di-t-butyl-4-hydroxy) hydrosilylate), and 1,3,5-trimethyl-tris (3,5-di-t-butyl- Phenol-based antioxidants such as 4-hydroxy benzene) and the like, and phosphite-based antioxidants such as tris (2,4-di-t-butylphenol) phosphite, and the like, but are not limited thereto. It is not.

The polypropylene resin composition may further include a nucleating agent.

The nucleating agent may be included in an amount of 0.01 to 0.5 parts by weight based on 100 parts by weight of the polypropylene resin. If the content of the nucleating agent is less than 0.01 parts by weight, it is difficult to ensure long-term heat stability, and if it exceeds 0.5 parts by weight, the heat stability of the injection molded article may not be increased, and manufacturing costs may increase.

The nucleating agent is a sorbitol-based nucleating agent such as benzylidene sorbitol, methylbenzylidene sorbitol, ethylbenzylidene sorbitol and 3,4-dimethylbenzylidene sorbitol, aluminum-based nucleating agent such as aluminum hydroxy-di-t-butylbenzoate, sodium 2 It may be at least one selected from the group consisting of sodium-based nucleating agents such as, 2-methylenebis (4,6-di-t-butylphenyl) phosphate and magnesium oxide silicate (talk: MgO? SiO ₂ ), but is not limited thereto. no.

The polypropylene resin composition may further include a catalyst neutralizing agent.

The catalyst neutralizing agent may be included in an amount of 0.05 to 2.0 parts by weight based on 100 parts by weight of the polypropylene resin. When the content of the catalyst neutralizing agent is less than 0.05 parts by weight, it may be difficult to neutralize the catalyst when it is included in the polypropylene resin composition in a small amount so that the catalyst used in the polymer synthesis remains in the polymer and remains as a catalyst residue. Exceeding the parts by weight may cause excessive use of the catalyst neutralizing agent, thereby reducing the economics of product production. The catalyst neutralizing agent may be calcium stearate or synthetic hydrotalcite, but is not limited thereto.

The polypropylene resin composition according to the present invention may be used for bottle caps such as reinforcing materials, fillers, heat stabilizers, weather stabilizers, lubricants, slip agents, antistatic agents, etc. Various additives conventionally added to the resin composition may be further included. The content of the component to be added can be appropriately adjusted by those skilled in the art within a range that does not impair the object of the present invention.

There is no particular limitation in the method for producing the polypropylene resin composition according to the present invention, and a conventionally known method for producing a polypropylene resin composition may be used as it is or as appropriately modified. You can freely select and mix in the order you want. That is, the resin composition of the present invention is specifically, for example, a kneader such as a kneader, a roll, a short-barrier mixer, or a single-screw / two-screw extruder in a necessary amount of the polypropylene-based resin and / or other additives as described above. It can be produced by a method of kneading the raw materials introduced using these devices after the addition.

The present invention can be understood in more detail by the following examples, the following examples are only examples for illustrating the present invention, and do not limit the protection scope of the present invention.

Example  One

Using a porous solid titanium catalyst prepared by reacting diethoxy magnesium with a titanium tetrachloride compound and an internal electron donor succinate compound in the presence of a hydrocarbon solvent, ethylene and Propylene is injected to vapor phase polymerization to prepare an ethylene-propylene random copolymer having an ethylene content of 2% by weight, and then the resulting copolymer is transferred to a second polymerization tank. Next, ethylene and propylene were added in the second polymerization tank to prepare an ethylene-propylene random copolymer having an ethylene content of 6% by weight as described above. The prepared ethylene-propylene random copolymers were pelletized by melt mixing through a twin screw extruder.

The prepared pellets were put into a Samsung Klucner FCM-110 (mold force 110 tons) injection machine and injected at a temperature gradient of 200/210/210/210 and an injection pressure of 70 to 120 bar at 60 ° C. (mould temperature), Each test piece for physical properties (ASTM Family No. 4) was produced. A bottle cap was prepared by using an injection molding machine with the prepared pellets.

Example  2

As shown in Table 1, ethylene-propylene random copolymers, pellets, injection specimens, and bottle caps were prepared in the same manner as in Example 1, except that there was a difference in ethylene content and additives.

Comparative example  1 to 3

As shown in Table 1, but the difference in the metallocene rubber was prepared by the gas phase polymerization of the ethylene-propylene random copolymer in the same manner as in Example 1, pellets, injection specimens and bottle caps were prepared.

(Unit: wt%) Configuration Example
One Example
2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Polypropylene resin A-1 100 A-2 100 Ethylene-propylene Random Copolymer B-1 100 90 B-2 100 Metallocene Rubber C 10

One) Polypropylene system  Suzy:

A-1 : A mixed resin having a polymerization ratio of 50:50 (% by weight) of an ethylene-propylene random copolymer having an ethylene content of 2% by weight and an ethylene-propylene random copolymer having an ethylene content of 5% by weight

A-2 : A mixed resin having a polymerization ratio of 50:50 (wt%) of an ethylene-propylene random copolymer having an ethylene content of 1% by weight and an ethylene-propylene random copolymer having an ethylene content of 7% by weight

2) ethylene-propylene random copolymer:

B-1 : Ethylene-propylene random copolymer having an ethylene content of 2% by weight

B-2 : Ethylene-propylene random copolymer having an ethylene content of 3% by weight

3) Metallocene  Rubber:

Metallocene C2-C4 rubber (Tafmer, Mitsui Chemicals)

Experimental Example

The melt index of the polypropylene resin pellets prepared in Examples and Comparative Examples and the physical properties of the injected specimen, that is, the cloudiness, impact strength and impact resistance, and impact test of the bottle cap was carried out by the following physical property measurement method, The results are shown in Table 2.

Property measurement method

The physical properties of the polypropylene resin composition shown in Table 2 were measured as follows:

1) Melt Index

The melt index of the polypropylene resin was measured under a load of 2.16 kg at 230 ° C. by the ASTM D1238 method.

2)% haze

The cloudiness was measured by the ASTM D1003 method (thickness: 1 mm).

3) Flexural modulus

Flexural modulus was measured by ASTM D638 method.

4) impact strength

Impact strength was measured by ASTM D256 method using Notched Izod specimens.

5) Impact test

The sorting test compared the number of broken bottle caps when the bottle cap was manufactured by injection and then dropped from a height of 1.5m with a Coca-Cola 500ml PET bottle filled with Coca-Cola. The specimens were marked as good if they were not> 90% broken, medium if they were not broken within 70 to 90%, and bad if they were broken> 70%.

Configuration Example 1 Example 2 Comparative Example 1 Comparative Example
2 Comparative Example
3 Melt Index (g / 10min) 5 2 2 2 2 Cloudiness (%) 7.6 7.8 9.9 7.5 8.5 Flexural Modulus (kgf / cm ² ) 10,600 8,500 13,300 10,700 10,500 Izod impact strength 23 ℃ (kgfcm / cm) 12 18 6 8 10 Izod impact strength 0 ℃ (kgfcm / cm) 6 8 4 5 5 Shock test Great Great weak usually usually

As shown in Table 2, the polypropylene-based bottle lids prepared from the polypropylene-based resin compositions according to Examples 1 and 2 are Comparative Examples 1 and 2, in which ethyl-propylene random copolymers are used alone. Compared with the low cloudiness or impact resistance can be confirmed. In addition, Comparative Example 3 relates to a metallocene-based rubber generally used in the production of polypropylene-based bottle caps, and compared with Example 1, it can be seen that the impact strength is low and the cloudiness is high.

The polypropylene resin composition according to the present invention may provide a bottle cap having excellent impact resistance and transparency to use a polypropylene resin in which phase separation between ethylene-propylene random copolymers having different ethylene contents does not occur. . In addition, the polypropylene-based resin composition according to the present invention can simplify the manufacturing process, reduce the use of expensive petarocene ethylene-based rubber can lower the manufacturing cost of the bottle cap.

Claims (6)

For 100 parts by weight of polypropylene resin,
a) 40 to 60 parts by weight of the first ethylene-propylene random copolymer having an ethylene content of 0.5 to 3% by weight; And
b) 40 to 60 parts by weight of a second ethylene-propylene random copolymer having an ethylene content of 6 to 15% by weight of a polypropylene resin mixed in a single phase
Polypropylene-based resin composition for a bottle cap comprising a. The method of claim 1,
The polypropylene resin composition for bottle caps, characterized in that the melt index of the polypropylene resin is 1 ~ 10 g / 10 minutes (230 ℃). The method of claim 1,
The polypropylene-based resin composition for a bottle cap, characterized in that it further comprises 0.1 to 0.5 parts by weight of antioxidant based on 100 parts by weight of the polypropylene resin. The method of claim 1,
Polypropylene-based resin composition for a bottle cap, characterized in that it further comprises 0.01 to 0.5 parts by weight of nucleating agent with respect to 100 parts by weight of the polypropylene resin. The method of claim 1,
The polypropylene-based resin composition for a bottle cap, characterized in that it further comprises 0.05 to 2.0 parts by weight of catalyst neutralizing agent with respect to 100 parts by weight of the polypropylene resin. A molded article made of the polypropylene resin composition according to any one of claims 1 to 5.