KR101738767B1

KR101738767B1 - Radiation resistant polypropylene resin composition and molded article prepared therefrom

Info

Publication number: KR101738767B1
Application number: KR1020150126019A
Authority: KR
Inventors: 노태경; 이현섭; 황성욱; 박혜진
Original assignee: 롯데케미칼 주식회사
Priority date: 2015-09-07
Filing date: 2015-09-07
Publication date: 2017-05-22
Also published as: KR20170029112A

Abstract

Disclosed is a polypropylene resin composition applicable to medical containers and food packaging containers requiring sterilization due to excellent radiation resistance and little change in physical properties and color change even upon irradiation with radiation. (A) 100 parts by weight of a crystalline polypropylene homopolymer having a melt index (230 DEG C, 2.16 kg) of 2 to 60 g / 10 min and a xylene solubles content of 3 to 5 wt%; (B) 0.01 to 0.1 parts by weight of an amine antioxidant; (C) 0.03 to 0.12 part by weight of a phosphorus antioxidant; And (D) 0.05 to 0.3 parts by weight of a nucleating agent.

Description

TECHNICAL FIELD [0001] The present invention relates to a radiation-resistant polypropylene resin composition and a molded article produced from the same. BACKGROUND ART < RTI ID = 0.0 >

More particularly, the present invention relates to a polypropylene resin composition which is excellent in radiation resistance and has a small change in physical properties and color tone before and after irradiation, and a molded article produced using the same will be.

BACKGROUND ART Polypropylene is a highly crystalline polymer produced by polymerization of propylene and has good physical properties and excellent physical and chemical properties and is widely known as a general-purpose plastic. In addition, when the comonomer is used in the polymerization process, the impact strength and transparency can be easily improved according to the kind of the comonomer and the polymerization method, and thus it is used in various fields such as storage containers, packaging materials, home products and industrial products. In particular, polypropylene is one of the most widely used materials for food packaging containers and medical supplies because it is not toxic to the resin itself. Certain products, such as medical containers, require sterilization. As the sterilization method, ethylene oxide gas sterilization, high pressure steam sterilization and irradiation sterilization are utilized.

Among these sterilization methods, the irradiation sterilization method is characterized not only by unit sterilization, but also by a continuous sterilization process, simple and reliable. The sterilization effect can be expressed as an inactivation factor. The radiation sterilization method is 10 ⁵⁰ to 10 ¹⁷⁵ , the high pressure steam sterilization method is 10 ¹⁵ to 10 ^20, and the ethylene oxide sterilization method is 10 ⁹ , showing that the radiation sterilization method is the most excellent. In addition, radiation is not highly probable for sterilization and secondary microbial infection in a highly permeable, fully packaged state.

The polypropylene used as medical supplies or food packaging containers is classified into propylene homopolymer and ethylene-propylene random copolymer. The propylene homopolymer made only of a propylene monomer has excellent rigidity as compared with the ethylene-propylene random copolymer, and is thus widely used in a molded article requiring rigidity.

Various prior art ethylene-propylene random copolymers which can be sterilized by radiation have been developed and used as radiation-resistant medical containers. However, conventional polypropylene homopolymers have a problem in that, due to the physical deterioration such as physical strength or yellowing, The radiation sterilization method can not be applied to many medical products such as a disposable syringe produced by the present invention. In particular, the rate of change of the yield point stress increases after irradiation, which is easily disrupted.

Several methods for solving the radiation resistance of such a polypropylene resin composition have been proposed.

Korean Patent Publication No. 1189004 has proposed a radiation-resistant polypropylene resin composition comprising an ethylene-propylene random copolymer and a phosphorus-based antioxidant and an amine-based antioxidant, which are biphenol-based antioxidants, but ethylene- The random copolymers have a disadvantage that they are difficult to apply to radiation-resistant molded articles requiring high rigidity.

Korean Patent Registration No. 1392090 discloses a polypropylene homopolymer, a propylene-ethylene random copolymer having an ethylene content of 5% by weight or less, or a resin mixture thereof, which contains a phosphorus-based antioxidant and a hindered amine- 0.5 to 10 g / 10 min. This composition is advantageous for discoloration using a non-phenolic antioxidant, but has a drawback in that it is applied only to a T-die extrusion method.

Therefore, it is necessary to study the development of a radiation-resistant polypropylene homopolymer resin composition which can be applied to medical containers and food packaging for radiation sterilization, and which has less physical property degradation and less color change.

The object of the present invention is to solve the above problems, and an object of the present invention is to provide a medical container and a polypropylene resin composition applicable to food packaging containers requiring sterilization due to excellent radiation resistance, .

Still another object of the present invention is to provide a plastic molded article for sterilization made of the polypropylene resin composition.

(A) 100 parts by weight of a crystalline polypropylene homopolymer having a melt index (230 DEG C, 2.16 kg) of 2 to 60 g / 10 min and a xylene solubles content of 3 to 5 wt%; (B) 0.01 to 0.1 parts by weight of an amine antioxidant; (C) 0.03 to 0.12 part by weight of a phosphorus antioxidant; And (D) 0.05 to 0.3 parts by weight of a nucleating agent.

Also, the radiation-resistant polypropylene resin composition is characterized in that the amine-based antioxidant is an alkylamine-based antioxidant.

And the phosphorus antioxidant is tris (2,4-di-t-butylphenyl) phosphite.

The present invention also provides an radiation resistant polypropylene resin composition, wherein the nucleating agent is a sorbitol compound.

Further, the polypropylene resin composition is characterized in that the radiation-resistant polypropylene resin composition is characterized in that the rate of change in yield point stress is 10% or less, the rate of change in yellowness is 5% or less and the rate of change in haze is 5% or less before and after irradiation with radiation .

In order to solve the above-mentioned problem, the present invention provides a molded article injected with the polypropylene resin composition.

And the molded article is a sterilizing plastic article.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a polypropylene resin composition having excellent radiation resistance and high strength by mixing an amine-based and phosphorus-based antioxidant, which is a biphenol-based antioxidant, with a nucleating agent in a highly crystalline polypropylene homopolymer.

In addition, the polypropylene resin composition according to the present invention can be effectively used for the production of medical plastic products which can be sterilized by radiation using an injection molding process or the like.

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 The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Accordingly, it is to be understood that the constituent features of the embodiments described herein are merely the most preferred embodiments of the present invention, and are not intended to represent all of the inventive concepts of the present invention, so that various equivalents, And the like.

(A) 100 parts by weight of a crystalline polypropylene homopolymer having a melt index (230 占 폚, 2.16 kg) of 2 to 60 g / 10 min and a xylene solubles content of 3 to 5% by weight as a highly crystalline polypropylene homopolymer ; 0.01 to 0.1 parts by weight of an amine-based antioxidant (B) relative to 100 parts by weight of the crystalline polypropylene homopolymer; (C) 0.03 to 0.12 part by weight of a phosphorus antioxidant; And 0.05 to 0.3 parts by weight of a nucleating agent (D), and a molded article produced from the same.

The present invention relates to a conventional polypropylene homopolymer composition for solving the problem of reduction in physical properties and discoloration when applied to a medical container or a food container for internal radiation, and is characterized in that the content of xylene solubles is in the range of 3 to 5 wt% A polypropylene resin composition which effectively mixes a propylene homopolymer, an amine antioxidant, a phosphorus antioxidant and a nucleating agent and has excellent radiation resistance after irradiation to minimize physical properties and color change, and a food container prepared therefrom, Medical products and the like.

Hereinafter, each constitution of the polypropylene resin composition according to the present invention will be described in detail.

(1) Highly crystalline polypropylene homopolymer

Highly crystalline polypropylene homopolymers can be used which have conventionally been prepared by known processes. For example, propylene monomer may be added to a polymerization reactor, triethylaluminum, diisocyanate and a silane-based electron donor may be introduced, and slurry bulk polymerization may be carried out at a reaction temperature of 65 to 75 ° C and a pressure of 32 to 34 atm. However, phthalate catalysts and succinate catalysts may be used as other usable catalysts in the production of the polypropylene homopolymer, and therefore, the catalysts are not limited to diisocyanate catalysts.

In the present invention, the polypropylene homopolymer composition preferably has a melt index of 2 to 60 g / 10 min at 230 ° C. and 2.16 kg, and preferably 10 to 35 g / 10 min depending on an injection molding machine for molding the product. If the melt index is less than 2 g / 10 min, the moldability and productivity during injection molding may be decreased. If the melt index exceeds 60 g / 10 min, the impact strength of the molded article may be lowered in the injection process.

The content of xylene solubles in the polypropylene homopolymer may be 3 to 5 wt%, preferably 3 to 4 wt%. The xylene solubles are polymeric moieties that are soluble in cold xylene. When the content of xylene solubles is less than 3% by weight, the stereoregularity is increased and the rigidity is increased. However, when the radiation is irradiated, the chain is broken and can be easily broken, and if it exceeds 5% by weight, the radiation resistance is excellent. And may be difficult to use as a molded article.

(2) Antioxidants

In the polypropylene composition according to the present invention, an amine-based antioxidant and a phosphorus-based antioxidant, which are biphenol-based antioxidants, should be added simultaneously as additives to 100 parts by weight of the crystalline polypropylene homopolymer. The non-phenolic antioxidant is included to prevent degradation of physical properties and color change due to irradiation with radiation. It is caused by decomposition of a phenolic antioxidant by simultaneously applying an amine antioxidant and a phosphorus antioxidant as a biphenol antioxidant The generation of yellow chromophore can be suppressed, thereby improving the yellowing phenomenon.

In the present invention, the amine antioxidant is added in an amount of 0.01 to 0.1 part by weight, preferably 0.02 to 0.06 part by weight based on 100 parts by weight of the polypropylene homopolymer. If the content of the amine antioxidant is less than 0.01 part by weight, the physical properties of the polypropylene composition, particularly the yield stress, may be adversely affected. If the amount is more than 0.1 part by weight, the color change may be affected.

The phosphorus antioxidant may be added in an amount of 0.03 to 0.12 parts by weight, preferably 0.04 to 0.08 parts by weight, based on 100 parts by weight of the polypropylene homopolymer. When the content of the phosphorus antioxidant is less than 0.03 parts by weight, deterioration may occur due to heat generated during processing and the physical properties may be reduced. If the content is more than 0.12 parts by weight, discoloration may occur after irradiation.

The amine-based antioxidant and the phosphorus-based antioxidant are not particularly limited, and they may be used alone or in combination of two or more thereof. However, it is preferable that the amine-based antioxidant is an alkylamine-based antioxidant and that the phosphorus-based antioxidant is tris (2,4-di-t-butylphenyl) phosphite in view of property deterioration and color change.

As described above, the polypropylene resin composition according to the present invention effectively mixes the crystalline polypropylene homopolymer with the phosphorus-based antioxidant, which is a biphenol-based antioxidant, and the amine-based antioxidant, When a phosphorus-based antioxidant or an amine-based antioxidant is used alone in the crystalline polypropylene homopolymer, sufficient physical properties and color can not be secured as a material for radiation resistance.

(3) Nucleating agent

The polypropylene resin composition according to the present invention includes a nucleating agent to improve the strength, heat resistance, transparency and crystallization speed of the polypropylene, and preferably an organic nucleating agent can be used.

As such a nucleating agent, at least one organic nucleating agent such as a sorbitol compound, a phosphoric acid ester compound and the like can be selected and used. More preferably, the sorbitol compound can be used to improve the transparency and the heat resistance and effectively reduce the crystallization rate.

The nucleating agent is added in an amount of 0.05 to 0.3 parts by weight, preferably 0.1 to 0.25 parts by weight, based on 100 parts by weight of the polypropylene homopolymer. If the content of the nucleating agent is less than 0.05 parts by weight, the strength, transparency and heat resistance may be reduced. If the amount of the nucleating agent is more than 0.3 parts by weight, additional physical properties may not be exhibited.

In addition, a neutralizing agent, an antistatic agent, a slip agent, a light stabilizer, a pigment or an inorganic additive which are conventionally used may be added to the polypropylene resin composition of the present invention.

On the other hand, the present invention provides a molded article produced from the polypropylene resin composition. The polypropylene resin composition according to the present invention is characterized in that when measured by the method described later on the basis of an injection specimen, the change rate of the yield point stress is 10% or less, the rate of change in yellowness is 5% or less and the rate of change in haze is 5% And preferably has a yield point change rate of not more than 3%, a yellowness change rate of not more than 2%, a haze change rate of not more than 2%, and a haze change rate of not more than 2%, depending on the combination of the optimal contents of the crystalline polypropylene homopolymer, amine- Of not more than 2%, more preferably not more than 1% of the yield point stress, not more than 1% of the yellow degree of change, and not more than 1% of the haze change.

As described above, the molded article made from the polypropylene resin composition according to the present invention is superior to conventional polypropylene homopolymer compositions in terms of radiation resistance, heat resistance and transparency, and can be effectively used for products requiring sterilization such as medical containers and food packaging containers have.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. However, the following examples are illustrative of the present invention, and the present invention is not limited to the examples described below.

First, the properties of the polypropylene composition prepared according to the following Examples and Comparative Examples are measured as follows. More specifically, in order to measure the physical properties of the specimen before irradiation and measure the degree of aging of the specimen after irradiation, the specimen after irradiation was stored at 23 ° C for 4 weeks, and physical properties were measured by the following methods.

1) Yield point stress: The injection specimen was measured at 23 ° C and 50% relative humidity (RH) according to ASTM D638 test method.

2) Yellow Index (YI, Yellow Index): Measured according to the ASTM D1925 evaluation method.

3) Turbidity (Haze): The haze value was measured using an injection specimen of 2 mm thickness (T) according to ASTM D1003 evaluation method.

Preparation Example 1: Preparation of crystalline propylene homopolymer

Propylenemonomer was added to the polymerization reactor, triethylaluminum, diisopropylether and silane-based electron donors were charged, and slurry bulk polymerization was carried out at a reaction temperature of 65 to 75 ° C and a pressure of 32 to 34 atm to give a xylene solubles content of 3.5 wt% A1), 1.0 wt% (A2), 6.0 wt% (A3), and the melt index was controlled by hydrogen.

Production Example 2: Preparation of crystalline ethylene-propylene random copolymer

The slurry bulk polymerization was carried out at a reaction temperature of 65 to 75 ° C and a pressure of 32 to 34 atm, to obtain an ethylene copolymer having an ethylene content of 3.5% by weight A4) was prepared and the melt index was controlled by hydrogen.

Example

0.05 parts by weight of calcium stearate (B1), 0.04 parts by weight of an alkylamine-based compound (B2), 0.5 parts by weight of tris (2,4-di- (B3) and 0.2 part by weight of a sorbitol compound (B5) were mixed together in a Henschel mixer for 1 minute and then extruded by a twin-screw extruder at 170 to 220 DEG C to prepare a pellet-shaped polypropylene resin composition . The obtained resin composition on the pellet was injected with a 180-ton injection molding machine to prepare tensile strength specimens, yellowness degree and haze measuring specimens.

Comparative Example 1

A specimen was prepared in the same manner as in the Example except that the crystalline propylene homopolymer (A2) was used in place of the crystalline propylene homopolymer (A1) in the above Examples.

Comparative Example 2

A specimen was prepared in the same manner as in Example except that the crystalline propylene homopolymer (A3) was used instead of the crystalline propylene homopolymer (A1).

Comparative Example 3

A specimen was prepared in the same manner as the example except that the crystalline ethylene-propylene random copolymer (A4) was used instead of the crystalline propylene homopolymer (A1).

Comparative Example 4

The same procedure as in Example 1 was carried out except that the alkylamine compound (B2) was not added and the tris (2,4-di-t-butylphenyl) phosphite (B3) Specimens were prepared.

Comparative Example 5

The same procedure as in Example 1 was carried out except that tris (2,4-di-t-butylphenyl) phosphite (B3) was not added and the alkylamine compound (B2) Specimens were prepared.

Comparative Example 6

A specimen was prepared in the same manner as in Example except for adding 0.06 parts by weight of phenol antioxidant (B4) instead of alkylamine compound (B2).

Comparative Example 7

A specimen was prepared in the same manner as in Example except that phenol-based antioxidant (B4) was added instead of tris (2,4-di-t-butylphenyl) phosphite (B3).

[Irradiation condition]

The irradiated specimens (Co-60 250, 959Ci) from Korea Atomic Energy Research Institute were irradiated with gamma rays with a total dose of 25 kGy for 10 hours in 2 mmT thickness specimens for tensile strength specimen, yellowness and haze measurement. The physical properties of each of the samples thus prepared were measured as described above, and the results of the measurement are shown in Table 2 below.

As shown in the above Table 2, the crystalline propylene homopolymer having an optimal level of xylene solubles in accordance with the present invention was blended with an amine-based antioxidant, a phenolic antioxidant, a phenol antioxidant, and a polypropylene It can be seen that the resin composition has a markedly lower change in mechanical properties, color and transparency with a yield rate change ratio of 0.8% or less, a yellow degree of change of 0.5% or less and a haze change rate of 0.7% or less.

On the other hand, the polypropylene resin composition of Comparative Example 1 using a crystalline propylene homopolymer having a xylene solubles content of 1.0 wt% shows a large change in yield point stress. When the change in the yield point stress is large after such irradiation, the physical properties of the final molded product may deteriorate, which may be difficult to be used as a medical container and food packaging material. On the other hand, in the case of Comparative Example 2 using a crystalline propylene homopolymer having a xylene solubles content of 6.0% by weight, good physical property change was observed even after 4 weeks of irradiation, but the yield point stress was similar to that of Comparative Example 3 . Since the yield point stress is similar to that of the crystalline ethylene-propylene random copolymer, the advantages of the high-strength crystalline propylene homopolymer disappear and it is more advantageous to use a crystalline ethylene-propylene random copolymer having excellent transparency in the same properties Do.

In the case of the polypropylene resin composition of Comparative Example 3 using the crystalline ethylene-propylene random copolymer, the yield point stress change was 2.3%, the yellowness degree was 3.1% and the haze change was 1.9%, and good physical properties But the yield point stress is significantly lower than that of the polypropylene resin composition according to the embodiment. In particular, when the yield point stress is low, it can not be applied to a product requiring high rigidity.

On the other hand, in the case of using only one kind of antioxidant in the crystalline propylene homopolymer having a xylene solubles content of 3.5% by weight or in Comparative Examples 4 to 7 in which a phenol antioxidant was additionally used, the yield point stress or the yellowness or haze Is significantly larger than that of the first embodiment. This leads to deterioration of the physical properties of radiation sterilized molded articles, which may be difficult to use as a result.

As described above, it was confirmed that the resin which effectively mixed the amine-based antioxidant, the biphenol-based antioxidant, the phosphorus-based antioxidant and the nucleating agent, in the crystalline propylene homopolymer was significantly lower in physical properties and color change after the irradiation with radiation. And it can be applied to a molded article of polypropylene for radiation.

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

(A) 100 parts by weight of a crystalline polypropylene homopolymer having a melt index (230 占 폚, 2.16 kg) of 2 to 60 g / 10 min and a xylene solubles content of 3 to 5% by weight;
(B) 0.01 to 0.1 parts by weight of an amine antioxidant;
(C) 0.03 to 0.12 part by weight of a phosphorus antioxidant; And
(D) 0.05-0.3 parts by weight of a nucleating agent;
Wherein the polypropylene resin composition is a polypropylene resin composition,
Wherein the polypropylene resin composition is characterized in that the rate of change in yield point stress is 3% or less, the rate of yellowing change is 2% or less, and the rate of change in haze is 2% or less before and after irradiation with radiation.

The method according to claim 1,
Wherein the amine-based antioxidant is an alkylamine-based antioxidant.

The method according to claim 1,
Wherein the phosphorus antioxidant is tris (2,4-di-t-butylphenyl) phosphite.

The method according to claim 1,
Wherein the nucleating agent is a sorbitol compound.

delete

A molded article injected with the polypropylene resin composition according to claim 1.

The method according to claim 6,
Wherein the molded article is a sterilizing plastic article.