KR101812890B1 - Radiation resistant polyethylene resin composition and molded article prepared therefrom - Google Patents

Abstract

Disclosed is a polyethylene resin composition capable of being applied to medical containers or food packing containers, which require sterilization, by causing only small changes of matter properties and colors even when irradiated because of excellent radiation-resistance. The polyethylene resin composition includes: 100 parts by weight of a polyethylene polymer (A) having a melting index (190C, 2.16kg) of 0.035-60g/10min and a density of 0.850-0.970g/cm^3; 0.01-0.1 parts by weight of amine antioxidant (B); and 0.03-0.12 parts by weight of phosphorus antioxidant (C).

Description

TECHNICAL FIELD [0001] The present invention relates to a radiation-resistant polyethylene resin composition and a molded article produced from the same. BACKGROUND ART [0002]

More particularly, the present invention relates to a polyethylene resin composition having excellent radiation resistance and low physical property change and color change before and after irradiation, and a molded article produced using the same.

Polyethylene is a highly crystalline polymer produced by the polymerization of ethylene and has good thermal and thermal properties, and has excellent physical and chemical properties and is widely known as a general purpose plastic. In addition, since transparency and strength can be easily improved according to the polymerization method during polymerization, they are used in various fields such as packaging materials, household products, and industrial products. In particular, polyethylene 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 has high permeability, sterilization is possible in a completely packaged state, and there is no possibility of secondary microbial infection.

On the other hand, irradiation with a general polymer material causes decomposition and crosslinking through ionization and excitation of the polymer main chain. Covalent bond dissociation or bond formation reaction occurs by the radical reaction generated by irradiation. In the case of polyolefin polymer, polypropylene shows decomposition by radiation. Therefore, the decomposition reaction is dominant rather than the crosslinking reaction in the irradiation, and the radicals remaining in the crystalline portion react with the oxygen in the air even after the irradiation, The deterioration of the material is continued and the mechanical properties are lowered. In addition, discoloration phenomenon occurs due to the deterioration of additives and polymers prescribed to solve this problem. For polypropylene polymers, studies on additives and irradiation conditions have been continuously carried out in order to resolve discoloration and deterioration of physical properties.

Among the polyolefin-based polymers, polyethylene generates cross-linking reaction when irradiated with other high energy such as gamma rays and electron beams. Therefore, a polyethylene material that forms a crosslinked structure by irradiation with radiation is widely used in industrial products such as electric, electronic, automobile industry, electric wire, and cable. When exposed to a certain level of gamma rays, for example, when exposed to gamma rays (25 kGy) for medical sterilization, the deterioration of physical properties of the polyethylene containing no additive is not generally large. However, when the product is to be molded into a product and stored for a long period of time, the polyethylene having no additive has a problem in that the physical properties are partially deteriorated. Therefore, in order to solve the problem, an additive must be formulated in polyethylene, and the materials used for this purpose are mostly used together with the pigment, so that the discoloration property is not required to be important.

BACKGROUND ART [0002] Recently, there is a demand for a market for medical plastic moldings and medical nonwoven fabrics which apply gamma-ray sterilization to polyethylene. However, when a general antioxidant is added to prevent product deterioration occurring in the process for molding a product or in long-term storage as described above, discoloration still occurs.

On the other hand, various prior arts have been developed for radiation sterilized polyethylene, and they have been used as radiation-resistant medical containers. However, they are produced from these materials because of the physical deterioration such as physical strength or yellowing after processing and irradiation with the existing polyethylene It is difficult to apply the radiation sterilization method to many medical products such as disposable packaging materials, medical nonwoven fabrics, and syringes. In particular, the rate of yield stress change increases after processing and irradiation. In this case, it is easily broken or problematic.

Korean Patent Laid-Open Publication No. 2014-0035616 discloses a polyolefin resin composition having a long life when exposed to radiation with a low-density polyolefin polymer, and includes an antioxidant, a crosslinking agent, a flame retardant and the like, The present invention has a disadvantage in that the applicable resins and applications are limited depending on the extrusion characteristics of the composition.

Korean Patent No. 0639269 is related to packaging of polyethylene and polyolefins by irradiation of gamma-irradiated polyethylene, and does not contain specific details related to physical properties that may be degraded when polyethylene exposed to gamma rays is used for the presented purposes.

Japanese Patent No. 2668567 and Japanese Patent Application Laid-Open No. 5-43745 disclose a polyethylene resin composition containing an antioxidant and a UV stabilizer as a polyolefin composition having improved radiation resistance of polyethylene. However, The properties such as the strength of polyethylene are maintained, but in some polyethylene products, there is a limit to products for medical use due to the occurrence of color degradation upon exposure to gamma rays.

On the other hand, in order to solve the problem of discoloration and deterioration of physical properties upon irradiation with radiation of the polypropylene type resin as described above, the present applicant has proposed in Korean Patent No. 1189004 a polypropylene resin composition containing a specified phosphorus antioxidant and an amine antioxidant . However, since the polypropylene resin and the polyethylene resin exhibit completely different physical properties according to the radiation irradiation, it is not expected that the discoloration and lowering of the physical properties due to irradiation of the polyethylene resin with the use of the antioxidant composition can be solved.

It is an object of the present invention to provide a polyethylene resin composition which can be applied to medical containers and 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 polyethylene resin composition.

(A) 100 parts by weight of a polyethylene polymer having a melt index (190 占 폚, 2.16 kg) of 0.035 to 60 g / 10 min and a density of 0.850 to 0.970 g / cm3; (B) 0.01 to 0.1 parts by weight of an amine antioxidant; And (C) 0.03 to 0.12 part by weight of a phosphorus-containing antioxidant.

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

The phosphorus-based antioxidant may be at least one selected from the group consisting of tris (2,4-di-t-butylphenyl) phosphite or [4- [4- bis (2,4- 4-ditert-butylphenol silane) phosphane. The present invention also provides an radiation-resistant polyethylene resin composition.

The polyethylene resin composition of the present invention is characterized in that the rate of change in yield point stress is 10% or less, the rate of change in yellowness is 20% or less, and the rate of change in total light transmittance is 3% or less before and after irradiation with radiation.

According to another aspect of the present invention, there is provided a molded article obtained by processing the polyethylene resin composition.

And the molded article is a sterilizing plastic article.

According to the present invention, it is possible to provide a polyethylene resin composition excellent in radiation resistance and high in strength by using an amine-based and phosphorus-based antioxidant, which are nonphenolic antioxidants, in combination with the highly crystalline polyethylene polymer.

In addition, the polyethylene 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 polyethylene polymer having a melt index (190 占 폚, 2.16 kg) of 0.035 to 60 g / 10 min and a density of 0.850 to 0.970 g / cm3; (B) 0.01 to 0.1 parts by weight of an amine antioxidant; And (C) 0.03 to 0.12 parts by weight of a phosphorus-containing antioxidant, and a molded article produced from the same.

The present invention relates to a conventional polyethylene polymer composition for solving the problems of decrease in physical properties and discoloration when applied to a medical container or a food container for radiation radiation, and it is an object of the present invention to effectively mix an amine-based antioxidant and a phosphorus- A polyethylene resin composition capable of retaining excellent radiation resistance even after irradiation and capable of minimizing physical property degradation and color change, and to provide a plastic molded article such as a food container or medical product manufactured therefrom.

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

(1) Polyethylene polymer

Highly crystalline polyethylene polymers can be used which are conventionally prepared by known processes. For example, it can be produced by adding an ethylene monomer to a polymerization reactor and injecting triethylaluminum, a Ziegler-Natta catalyst or a metallocene catalyst or an initiator, and conducting polymerization.

In the present invention, the polyethylene polymer preferably has a melt index of 0.035 to 60 g / 10 min, preferably 1 to 50 g / 10 min, more preferably 10 to 30 g / 10 min at 190 ° C. and 2.16 kg and a density of 0.850 to 0.970 g / , Preferably 0.920 to 0.960 g / cm < 3 > can be used according to an extruder for molding.

(2) Antioxidants

In the polyethylene resin composition according to the present invention, an amine-based antioxidant and a phosphorus-based antioxidant, which are nonphenolic antioxidants, should be simultaneously added to 100 parts by weight of the polyethylene polymer. 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 0.01 to 0.06 part by weight, more preferably 0.015 to 0.03 part by weight based on 100 parts by weight of the polyethylene homopolymer . If the content of the amine antioxidant is less than 0.01 part by weight, the physical properties, particularly the yield stress, of the polyethylene composition during processing may be affected. If the amount is more than 0.1 part by weight, the color change may be affected after irradiation.

The phosphorus antioxidant may be added in an amount of 0.03 to 0.12 parts by weight, preferably 0.03 to 0.08 part by weight, more preferably 0.04 to 0.06 parts by weight based on 100 parts by weight of the polyethylene polymer. 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, the amine antioxidant is preferably an alkylamine antioxidant, and the phosphorus antioxidant is preferably tris (2,4-di-t-butylphenyl) phosphite or Bis (2,4-ditert-butylphenylphosphinophenyl) phenyl] -bis (2,4-ditert-butylphenolyl) phosphane is preferable, and [4- [4- (2,4-ditert-butylphenylphosphinophenyl) phenyl] -bis (2,4-ditert-butylphenol) phosphane is more preferable.

As described above, the polyethylene resin composition according to the present invention can effectively mix the phosphorus-based antioxidant and the amine-based antioxidant, which are biphenol-based antioxidants, with the crystalline polyethylene polymer, thereby securing a polyethylene resin composition having excellent radiation resistance , When a phosphorus-based antioxidant or an amine-based antioxidant is used alone in a polyethylene polymer, sufficient physical properties and color can not be secured as a material for radiation resistance.

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 polyethylene resin composition of the present invention.

On the other hand, the present invention provides a molded article produced from the polyethylene resin composition. The polyethylene resin composition according to the present invention has a yield point change rate of 10% or less, a yellowness degree change rate of 20% or less, and an optical property change rate (rate of change in total light transmittance) Preferably not more than 3%, a rate of change in yellowness of not more than 18%, an optical property change rate of not more than 2%, and an optical characteristic change rate of not more than 2%, depending on the combination of the optimal contents of the polyethylene polymer, amine antioxidant and phosphorus- Can have a physical property of not more than 2%, more preferably not more than 2% of the yield point stress, not more than 18% of the yellowness degree change, and not more than 1% of the optical characteristic change rate.

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

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 method for measuring the physical properties of the polyethylene resin composition prepared according to the following Examples and Comparative Examples is 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) Optical Characteristics (Total Luminous Transmission (T.T)): Measured using an injection specimen of 2 mm thickness (T) according to ASTM D1003 evaluation method.

4) Thermal Stability: The degree of discoloration (dYI) was measured according to the ASTM D1925 evaluation method by setting the temperature of the forced circulation hot air dryer at 190 캜 for 48 hours.

Example  One

0.05 part by weight of calcium stearate (A1), 0.02 part by weight of an alkylamine compound (A2) and 0.02 part by weight of tris (2,4-di-t-butylphenyl) phosphite were added to 100 parts by weight of an ethylene polymer, And 0.05 part by weight of Fate (A3) were mixed and mixed in a Henschel mixer for 1 minute and then extruded by a twin-screw extruder at 170 to 220 DEG C to obtain a pelletized polyethylene resin composition. The obtained resin composition on the pellet was injected with a 150-ton injection molding machine to prepare specimens for measuring tensile strength, yellowness and optical properties.

Example  2

Bis (2,4-ditert-butylphenylphosphinophenyl) phenyl] -bis (2, 3-di-tert-butylphenyl) phosphite (A3) was obtained in the same manner as in Example 1, , 4-ditert-butylphenolylsilane) Phospene (A6) was used in place of the phospene (A6).

Comparative Example 1

Except that 0.07 part by weight of tris (2,4-di-t-butylphenyl) phosphite (A3) was used instead of the alkylamine compound (A2) in Example 1 Specimens were prepared.

Comparative Example 2

Except that tris (2,4-di-t-butylphenyl) phosphite (A3) was not used and 0.07 part by weight of alkylamine compound (A2) was used in Example 1 Specimens were prepared.

Comparative Example 3

Except that 0.07 part by weight of the phenol-based antioxidant (A4) was used without using the alkylamine-based compound (A2) and tris (2,4-di-t-butylphenyl) phosphite (A3) Was prepared in the same manner as in Example 1.

Comparative Example 4

A specimen was prepared in the same manner as in Example 1, except that phenol-based antioxidant (A4) was used instead of alkylamine-based compound (A2) in Example 1.

Comparative Example 5

A specimen was prepared in the same manner as in Example 1 except that 0.05 parts by weight of a HALS-based UV stabilizer (A5) was further added in Example 1.

Comparative Example  6

(2,4-di-t-butylphenyl) phosphite (A3) instead of the alkylamine compound (A2) in Example 1, Phenylphosphinophenyl] phenyl] -bis (2,4-ditert-butylphenol) phosphine (A6) was used in an amount of 0.07 part by weight.

[Irradiation condition]

The irradiated specimens (Co-60 250, 959Ci) were irradiated with gamma rays with a total irradiation dose of 25 kGy for 10 hours on 2 mmT thickness specimens for tensile strength specimen, yellowness degree and optical properties. 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 Table 2, according to the present invention, a polyethylene resin composition comprising an amine-based antioxidant, which is a biphenol-based antioxidant and a phosphorus-based antioxidant, and an amine-based antioxidant and an phosphorus- (Examples 1 and 2) show that the yield point stress change ratio is 1% or less, the yellowness degree change ratio is 18% or less, and the total light transmittance change rate is 1% or less, whereby the mechanical property, color and transparency change degree are remarkably low.

On the other hand, when only one type of antioxidant was used for the ethylene polymer (Comparative Examples 1 and 2) or when a generally used phenolic antioxidant was used (Comparative Examples 3 and 4), the change in the yield point stress Is remarkably large. This leads to deterioration of the physical properties of radiation sterilized molded articles, which may be difficult to use as a result.

When the phosphorus antioxidant was used alone (Comparative Example 1), it was found that the factors causing discoloration were not included and the degree of change in yellowness was somewhat low, but the change in physical properties occurred at a higher level than in the Examples. It is also seen that the use of a general phenol antioxidant and an amine antioxidant (Comparative Example 4) significantly change the physical properties and the yellowness as compared with the Examples. When the HALS-based UV stabilizer was additionally used (Comparative Example 5), the difference in the degree of change in physical properties was low, but the degree of change in yellowness was remarkably large.

On the other hand, when a phenol antioxidant or a UV stabilizer is used (Comparative Examples 3 to 5), the thermal stability is excellent, but it is difficult to apply because of high physical properties and color change after irradiation. On the other hand, the present invention can be applied to a resin composition in which an amine-based antioxidant and a phosphorus-based antioxidant (Examples 1 and 2) are effectively mixed with radiation-resistant materials, but when thermal stability and long- Bis (2,4-ditert-butylphenylphosphinophenyl) phenyl] -bis (2,4-ditert-butylphenol) phosphine (Example 2) (DYI) of not more than 2, preferably not more than 1, more preferably not more than 0.5, as measured by a differential scanning calorimeter.

As described above, it was confirmed that the resin which effectively mixed the amine-based antioxidant, the biphenol-based antioxidant and the phosphorus-based antioxidant, into the ethylene polymer was remarkably low in physical properties and color change after irradiation. And the results are shown in Fig.

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 (6)

(A) 100 parts by weight of a polyethylene polymer having a melt index (190 占 폚, 2.16 kg) of 0.035 to 60 g / 10 min and a density of 0.850 to 0.970 g / cm3;
(B) 0.01 to 0.1 parts by weight of an amine antioxidant; And
(C) 0.03 to 0.08 part by weight of a phosphorus-containing antioxidant;
Wherein the radiation-resistant polyethylene resin composition comprises:
Wherein the rate of change in yield point stress is 10% or less, the rate of change in yellowness is 20% or less, and the rate of change in total light transmittance is 3% 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,
The phosphorus-based antioxidant may be at least one selected from the group consisting of tris (2,4-di-t-butylphenyl) phosphite or [4- [4-bis (2,4-ditert-butylphenylphosphinophenyl) phenyl] -Deter-butylphenol-silane) phosphane. delete A molded article obtained by processing the radiation-resistant polyethylene resin composition according to any one of claims 1 to 3. 6. The method of claim 5,
Wherein the molded article is a sterilizing plastic article.