KR20210066218A - Composition of polypropylene resin with excellent impact strength and heat sealability and film prepared by using the same - Google Patents

Abstract

The present invention relates to a polypropylene resin composition having excellent impact strength and heat sealability, and a film using the same. Particularly, the polypropylene resin composition includes, based on the total weight of the polypropylene resin composition: (a) 55-85 wt% of crystalline polypropylene; and (b) 15-45 wt% of amorphous ethylene-propylene copolymer including 30-45 wt% of ethylene and 55-70 wt% of propylene based on the weight of the amorphous ethylene-propylene copolymer. The film obtained by using the polypropylene composition according to the present invention shows excellent impact resistance and heat sealability, and thus can be applied to retort food container materials requiring such physical properties, or the like.

Description

A polypropylene resin composition with excellent impact strength and thermal adhesion and a film manufactured using the same {COMPOSITION OF POLYPROPYLENE RESIN WITH EXCELLENT IMPACT STRENGTH AND HEAT SEALABILITY AND FILM PREPARED BY USING THE SAME}

The present invention relates to a polypropylene resin composition capable of producing a film having improved impact strength and thermal adhesion at the same time, and a film provided using the same.

In general, polypropylene resin compositions are widely used as materials for injection-molded products or films because they are light and have excellent mechanical properties compared to price. In recent years, the use of products using polypropylene has been expanded from simple exterior finishing materials or packaging materials to various fields requiring durability according to the user's usage environment. In particular, as products using polypropylene become larger, the products are thinned in order to reduce the weight of the products. However, due to such a thin film, there is a problem that it is easily broken by an external impact, and in order to improve this, a polypropylene product having a higher level of impact resistance is required.

Meanwhile, with the recent increase in single-person households and dual-income couples, consumer demand for simple and delicious food is increasing. In line with this social trend, interest in ready-to-cook food is increasing in the food market. In particular, a variety of retort products, a type of ready-to-eat food, are being released. Retort products are easy to carry, and most of them have a long shelf life, so they can be stored for a long time.

Retort products can preserve food for a long period of time in a state where air and light are blocked by putting various cooked and processed foods in a pouch-like container, sealing them, and then putting them in a high-pressure sterilization pot (retort) to heat sterilize them at high temperature. Therefore, materials used for containers for retort products require heat resistance, and properties such as impact resistance and thermal adhesion are required to prevent breakage during food packaging and transportation. In addition, since the appearance of the package must be beautiful, it is necessary to suppress the occurrence of orange peel, which is a fine unevenness that occurs after sterilization.

Since general polypropylene homopolymer is weak to impact, a method of adding an impact modifier is used to increase impact resistance. However, the impact modifier is expensive, and when added, the composition between the amorphous ethylene propylene rubber and the impact modifier in the polypropylene homopolymer is different, resulting in poor dispersion, which may result in reduced impact resistance and surface defects such as orange peel. In addition, general polypropylene has low low-temperature impact resistance, so polyethylene with excellent low-temperature impact resistance is mainly used for frozen storage products. However, polyethylene has a lower melting point, that is, heat resistance, compared to polypropylene, so it is not suitable for retort products sterilized at high temperature. not. For example, Japanese Patent Publication No. 2003-183418 discloses a film comprising a propylene-ethylene block copolymer having a melting point of 150 to 168° C., the film having a surface roughness strain of -10 to 50%. However, although the film can improve the orange peel, there is a disadvantage in that the impact strength and peel strength are weak.

Therefore, it is possible to sterilize at a high temperature, so that it can be used for manufacturing retort food containers, etc., and the development of a polypropylene resin composition capable of manufacturing molded articles such as films with improved impact strength and thermal adhesion at the same time is still required. .

One aspect of the present invention is to provide a polypropylene resin composition capable of producing a molded article such as a film having improved impact strength and thermal adhesion at the same time.

Another aspect of the present invention is to provide a film having improved impact strength and thermal adhesion by using the polypropylene resin composition of the present invention.

According to one aspect of the present invention, based on the total weight of the polypropylene resin composition, (a) 55 to 85% by weight of crystalline polypropylene; and (b) 15 to 45% by weight of an amorphous ethylene-propylene copolymer consisting of 30 to 45% by weight of ethylene and 55 to 70% by weight of propylene, based on the weight of the amorphous ethylene-propylene copolymer. A resin composition is provided.

According to another aspect of the present invention, there is provided a film made of the polypropylene resin composition of the present invention.

According to the present invention, there is provided a polypropylene resin composition capable of manufacturing a molded article such as a film capable of exhibiting excellent impact resistance and thermal adhesion properties, so that it can be applied as a material for manufacturing retort food containers requiring such physical properties. can

Hereinafter, preferred embodiments will be described. However, the embodiment of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

The polypropylene resin composition of the present invention comprises, based on the total weight of the polypropylene resin composition, (a) 55 to 85% by weight of crystalline polypropylene; and (b) 15 to 45% by weight of an amorphous ethylene-propylene copolymer composed of 30 to 45% by weight of ethylene and 55 to 70% by weight of propylene, based on the weight of the amorphous ethylene-propylene copolymer.

Hereinafter, each component will be described in more detail.

(a) crystalline polypropylene

The component (a) is a propylene homopolymer, and may be polymerized by adding propylene alone to a polymerization reactor. The polymerization method of the propylene homopolymer is by a conventional method known in the art, and is not particularly limited in the present invention.

Component (a) is included in an amount of 55 to 85% by weight based on the total weight of the resin composition, for example, it may be included in an amount of 70 to 85% by weight. If the content of the component (a) is less than 55% by weight, the crystallinity is lowered, the heat resistance is lowered, and the heat bonding strength is lowered. In addition, when the content of component (a) exceeds 85% by weight, impact resistance is lowered, and orange peel occurs after sterilization, which is not preferable.

(b) amorphous ethylene-propylene copolymer

The component (b) is a polymer of ethylene and propylene, and may be polymerized by putting ethylene and propylene together in a polymerization reactor. For example, after polymerizing the component (a), it may be continuously polymerized in the presence of the component (a) in a subsequent polymerization reactor. The polymerization method of the ethylene-propylene copolymer is by a conventional method known in the art, and is not particularly limited in the present invention.

Since both components (a) and (b) contain propylene chains, and further, component (b) can be continuously polymerized in the reactor after polymerization of component (a), the affinity of the two phases is improved and uniform dispersion can be obtained, and as a result, it is possible to minimize the deterioration of the thermal adhesive properties, improve the impact strength, and further suppress the occurrence of fish eyes and orange peel due to aggregation of component (b).

In this case, the component (b) is included in an amount of 15 to 45% by weight based on the total weight of the polypropylene resin composition. When the content of component (b) is less than 15% by weight, the content of component (a) exceeds 85% by weight, so that impact resistance is reduced, orange peel occurs after sterilization, and the content of component (b) is 45% by weight %, the content of component (a) becomes less than 55% by weight, which is not preferable because the degree of crystallinity is lowered, heat resistance is lowered, and heat bonding strength is lowered.

On the other hand, (b) may be composed of 30 to 45% by weight of ethylene and 55 to 70% by weight of propylene based on the weight of the amorphous ethylene-propylene copolymer, preferably 30 to 35% by weight of ethylene and 65 to 70% by weight of propylene. When the ethylene content in the amorphous ethylene-propylene copolymer is less than 30% by weight, the amorphous copolymer portion in the copolymer decreases and the elasticity decreases to decrease the impact resistance properties, and when it exceeds 45% by weight, the component (a) and the component The compatibility of (b) is lowered, and fish eyes are generated due to excessive polymerization of the crystalline polyethylene component, which may result in poor appearance or reduced impact resistance.

It is preferable that the intrinsic viscosity (xylene solvent) of the solvent extract in the component (b) is 0.5 to 2.5 dl/g. When the intrinsic viscosity is less than 0.5 dl/g, the size and molecular weight of the amorphous ethylene-propylene copolymer corresponding to the rubber component are reduced, and the impact properties are deteriorated. When the intrinsic viscosity exceeds 2.5 dl/g, the size of the rubber component increases and agglomeration occurs, thereby reducing dispersibility, resulting in fish eyes. In addition, due to such agglomeration phenomenon, a drop in impact resistance in the fish-eye portion may occur. Furthermore, when such local aggregation occurs, partial breakage may occur after sterilization when applied to a pouch film, which is a container for a retort product.

On the other hand, since the dispersion of the rubber component (b) is affected by the difference in viscosity between the component (a) and the component (b), (b) the intrinsic viscosity of the amorphous ethylene-propylene copolymer and the intrinsic viscosity ratio of the solvent extract ( The intrinsic viscosity ratio, dl/g) is preferably 0.8 to 2.5, and this value can be calculated as (intrinsic viscosity of solvent extract)/(intrinsic viscosity of ethylene propylene rubber). When the intrinsic viscosity ratio is less than 0.8, the molecular weight of the component (b) ethylene-propylene copolymer rubber is relatively lower than that of the continuous phase component (a) crystalline propylene homopolymer, so it is difficult to absorb shock, and the intrinsic viscosity ratio exceeds 2.5 In this case, the size of the dispersed phase of the component (b) increases after molding to generate fish eyes, and thus the appearance characteristics may be deteriorated.

(c) polyethylene, ethylene-alpha-olefin copolymers or mixtures thereof

In the polypropylene resin composition of the present invention, an ethylene-alpha-olefin copolymer, polyethylene, or a mixture thereof having a density of 850 to 940 kg / ㎥ and a melt index of 1 to 10 g / 10 min (230 ° C.) for reinforcing impact resistance in the polypropylene resin composition of the present invention. can

Preferably, the polyethylene, ethylene-alpha-olefin copolymer, or a mixture thereof may be further included in an amount of 5 to 30% by weight based on the total weight of the polypropylene resin composition. When the content of the component (c) is less than 5% by weight, the synergistic effect of impact resistance may be insignificant, and when it exceeds 30% by weight, the dispersibility with polypropylene may deteriorate, thereby reducing processability.

On the other hand, when the density of the ethylene-alpha-olefin copolymer in the component (c) exceeds 940 kg/m 3 , the amorphous portion that improves the impact may decrease, and the impact resistance may decrease, and the density of polyethylene is 850 kg/m3 In the case of less than m 3 , the low molecular weight increases and the processability may be deteriorated due to the occurrence of blocking during the manufacture of a shape such as a film. When the density of the ethylene-alpha-olefin copolymer is less than 850 kg/m3 or the density of polyethylene exceeds 940 kg/m3, the crystalline polyethylene component increases and fish eyes occur, which results in poor appearance or Impact resistance properties may be reduced.

The ethylene-alpha-olefin copolymer rubber is a copolymer of ethylene and alpha-olefin, and the alpha-olefin includes propylene, butene, pentene, hexene, propene, and octene. may use one or a mixture of two or more selected from ethylene-propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM), and ethylene-octene rubber (EOR), but in the case of ethylene-octene rubber, octene as a comonomer It can be used more preferably in that the length of the side chain is long and the impact property at low temperature is very excellent. The ethylene-alpha-olefin fin copolymer rubber has an alpha-olefin content of 10 to 30% by weight, and when the alpha-olefin content is less than 10% by weight, the melt strength is lowered, and when it exceeds 30% by weight, the impact strength is lowered. Problems may arise.

The melt index of the polypropylene resin composition of the present invention is preferably 1 to 30 g/1 min (ASTMD1238, 230° C./2.16 kg, Melt Index, M). When the melt index is less than 1 g/10 min, the flowability of the molten resin is lowered, and productivity in the extrusion process is lowered. When the melt index exceeds 30 g/10 min, the viscosity of the molten resin discharged from the die is lowered, so that the thickness is uniform during film molding. It is undesirable because the mechanical strength and impact resistance properties of the final product are deteriorated due to the reduced properties and low molecular weight.

The polypropylene resin composition according to the present invention may further include additives and solvents known in the art within a range that does not impair the object of the present invention. Specifically, for example, an antioxidant, a nucleating agent, a heat-resistant stabilizer, a weathering stabilizer, an antistatic agent, a lubricant, a slip agent, a flame retardant, a pigment, a dye, etc. may be used, and preferably, an antioxidant and ultraviolet rays to impart heat resistance and weathering stability An absorbent or the like may be added. The content of the additive may be appropriately adjusted by those skilled in the art within a range that does not impair the purpose of the present invention.

There is no particular limitation in the method for preparing the polypropylene resin composition of the present invention, and a conventionally known method for preparing a polypropylene resin composition may be used or a part may be modified to achieve the object of the present invention.

In addition, the components constituting the polypropylene resin composition may be selected and mixed in a desired order without particular order restrictions, and specifically, for example, each component and other additives as described above may be kneaded in a required amount. ), a roll, a Banbury mixer, etc., or a single screw/two screw extruder, etc., and then it can be prepared by a method of kneading the input materials using the above equipment, but limited to this it is not

According to another aspect of the present invention, there is provided a molded article prepared from the polypropylene resin composition of the present invention, and the molded article may be a film, for example, a protective film, a decorative sheet or a film for a retort pouch. More specifically, the film may be applied to a protective film, a decor sheet, a retort pouch, etc. of electronic products requiring high precision, such as a liquid crystal display, and in particular, may be preferably applied to a retort pouch.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are merely examples to help the understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

Example One

(a) Preparation of crystalline propylene homopolymer

A crystalline propylene homopolymer (a) was prepared by injecting propylene into the reactor for bulk polymerization.

(b) amorphous ethylene-propylene copolymer rubber ( EPR, Ethylene Manufacture of propylene rubber)

After the polymerization of the crystalline propylene homopolymer (a) is performed, a gas phase reaction is performed in the presence of the crystalline propylene homopolymer (a) in a series of reaction apparatuses that follow, but the ethylene content in the polyethylene-propylene copolymer rubber (EPR) is 45 After preparation so as to be % by weight, based on the total weight of the polypropylene resin composition (a), (b) and (c), component (a) is 85% by weight, component (b) has a content of 10% by weight, and , an ethylene-propylene copolymer rubber was prepared by adjusting the polymerization amount in each step so that the intrinsic viscosity ratio of (a) and (b) was 1.1. A final mixed resin composition was prepared by melt-mixing 95 wt% of the thus-obtained ethylene-propylene block copolymer with ^{5 wt% of (c) polyethylene having a density of 920 g/cm 3 through a single screw extruder.}

Example 2 to 4

A polypropylene resin composition was prepared in the same manner as in Example 1, except that the content was adjusted as shown in Table 1.

comparative example 1 to 5

A polypropylene resin composition was prepared in the same manner as in Example 1, except that the content was adjusted as shown in Table 2.

manufacturing example : Preparation of specimen using polypropylene resin composition

0.1 parts by weight of a phenolic antioxidant, 0.1 parts by weight of a phosphate-based antioxidant, and 0.05 parts by weight of calcium stearate as a catalyst neutralizing agent based on 100 parts by weight of the polypropylene resin composition to the polypropylene resin composition obtained by Examples and Comparative Examples By melt-mixing through a single screw extruder at 230 ° C. to form pellets, a polypropylene resin composition in the form of pellets was prepared. Further, a test specimen in the form of a film was prepared using the prepared pellets and the physical properties were evaluated, and the results are shown in Tables 1 and 2, respectively.

Experimental example : Characterization of resin composition and specimen

Component and physical properties analysis of the polypropylene resin compositions of Examples and Comparative Examples were performed in the following manner.

(1) Ethylene content: Using infrared absorption spectrum (FT-IR), ethylene content was measured using ^{720 cm -1} and 740 cm ^{-1 characteristic peaks.}

(2) Melting point (Tm): Using a differential scanning calorimeter (trade name: DSC, manufactured by Perkin-Elmer Co.) under a nitrogen gas atmosphere at 220° C. for 5 minutes, 10 mg of a specimen was pre-melted. Thereafter, the temperature is lowered to 40° C. at a temperature reduction rate of 5° C./min. Thereafter, the temperature was raised at a temperature increase rate of 5° C./min, and the peak temperature of the maximum peak of the obtained melting endothermic curve was defined as the melting point (Tm). In addition, the melting point of indium (In) measured by using the above-described measuring apparatus at a temperature increase rate of 5°C/min was 156.6°C.

(3) Intrinsic Viscosity Ratio: The solvent extract of the ethylene-propylene copolymer (b) represents a component soluble at 150° C. in 200 mL of a xylene solvent with respect to 4 g of the polypropylene block copolymer, and the crystalline polypropylene (a) is xyl Represents components that are not soluble in Len solvents. The intrinsic viscosity of each component was measured using a viscometer at 135 ° C. under decalin solution for the solvent extract obtained using the xylene solvent. The intrinsic viscosity ratio was calculated as follows.

* Intrinsic viscosity ratio = Intrinsic viscosity of ethylene-propylene copolymer (b) ÷ Intrinsic viscosity of crystalline polypropylene (a)

Component and physical properties analysis of specimens prepared using the polypropylene resin compositions of Examples and Comparative Examples were performed in the following manner.

(4) Melt index: measured under ASTM D1238 at 230°C under a load of 2.16 kg.

(5) Cloudiness: In accordance with ASTM D1003, the cloudiness of a 40 μm film was measured.

(6) Flexural modulus: measured according to ASTM D790 method.

(7) Izod and Dupont impact strength: It was measured at room temperature (23°C) and low temperature (-10°C) according to ASTM D256 method.

(8) Heat deflection temperature: It was measured according to ASTM D648 method.

(9) Falling dart impact strength: 60㎛ film was measured according to ASTM D1709 method.

(10) Thermal adhesion strength: After laminating polypropylene film (100㎛), Nylon (15㎛), aluminum foil (9㎛), PET (12㎛), 3kgf / cm ² After bonding under a pressure of 2 sec. make a sample The molded film was cut to a width of 15 mm, and peel strength was measured at a peel angle of 180° at a peel rate of 200 mm/min at 23°C.

(11) Fish Eye (F/E) occurrence: The appearance of the CPP film (area 600 cm2) was checked and the fish eyes were classified by size (diameter less than or equal to 200 µm/more than 200 µm in diameter). The number of micrometers or more was described.

(12) Orange peel: Visually evaluated, good (◎) if non-occurrence or difficult to distinguish with the naked eye, normal (△) when orange peel occurs partially or partially, and poor if it occurs entirely or partially. (X) was evaluated.

Item unit Example One 2 3 4 (a) crystalline polypropylene Based on the total weight of the polypropylene resin composition, weight % 85 80 70 70 (b) amorphous ethylene-propylene copolymer Based on the total weight of the polypropylene resin composition, weight % 10 10 30 20 (b) propylene content based on total weight, % by weight 55 55 70 65 (b) ethylene content based on total weight, weight % 45 45 30 35 (c) polyethylene Based on the total weight of the polypropylene resin composition, wt% 5 10 - 10 Intrinsic Viscosity Ratio 1.1 1.1 1.1 1.1 Melting Point (Tm) ℃ 163 163 164 164 melt index g/10 min 3 3 3 3 blur % 35 35 30 35 Izod impact strength (23℃) kgcm/cm 15 37 73 72 Izod impact strength (-10℃) kgcm/cm 2.5 3.0 2 4 Dupont impact strength (23℃) kgcm over 200 over 200 over 200 over 200 Dopont impact strength (-10℃) kgcm 20 50 80 100 flexural modulus kg f/cm ² 12000 11000 8000 8500 heat deflection temperature ℃ 103 98 85 93 Falling dart impact strength g 500 600 1200 800 heat bonding strength kgf 5 5 7 6.5 F/E ea/600cm ² 3 3 2 4 orange peel Visual evaluation ◎ ◎ ◎ ◎

Item unit comparative example One 2 3 4 5 (a) crystalline polypropylene Based on the total weight of the polypropylene resin composition, wt% 90 88 85 93 90 (b) amorphous ethylene-propylene copolymer Based on the total weight of the polypropylene resin composition, wt% 10 12 15 7 10 (b) propylene content based on total weight, % by weight 40 20 15 60 55 (b) ethylene content based on total weight, weight % 60 80 85 40 45 (c) polyethylene Based on the total weight of the polypropylene resin composition, wt% - - - - - Intrinsic Viscosity Ratio 2.2 2.9 1.6 0.9 1.2 Melting Point (Tm) ℃ 163 164 163 164 164 melt index g/10 min 10 9 4 3 3 blur % 50 60 65 20 35 Izod impact strength (23℃) kgcm/cm 7 10 60 5 7 Izod impact strength (-10℃) kgcm/cm 2 2 4.5 2 2 Dupont impact strength (23℃) kgcm 70 190 over 200 30 80 Dopont impact strength (-10℃) kgcm 35 50 90 10 35 flexural modulus kg f/cm ² 14000 13000 14000 15000 12000 heat deflection temperature ℃ 115 114 105 115 100 Falling dart impact strength g 80 80 300 80 450 heat bonding strength kgf 4 3 2.5 5 6 F/E ea/600cm ² over 50 over 50 20 3 3 orange peel Visual evaluation X X △ ◎ ◎

As can be seen in Tables 1 and 2, the polypropylene resin composition of the present invention had excellent thermal adhesive strength of 5 kgf or more, and at the same time, Dupont impact strength at room temperature (23°C) exceeded 200 kgcm. It was confirmed to exhibit excellent impact strength. In particular, the polypropylene resin compositions of Examples 3 and 4 exhibited excellent impact strength even at low temperatures as the Dupont impact strength at low temperature (-10°C) exceeded 80 kgcm.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible within the scope without departing from the technical spirit of the present invention described in the claims. It will be apparent to those of ordinary skill in the art.

Claims (3)

Based on the total weight of the polypropylene resin composition,
(a) 55 to 85% by weight of crystalline polypropylene; and
(b) a polypropylene resin comprising from 15 to 45% by weight of an amorphous ethylene-propylene copolymer consisting of 30 to 45% by weight of ethylene and 55 to 70% by weight of propylene, based on the weight of the amorphous ethylene-propylene copolymer. composition.
The polypropylene resin composition according to claim 1, further comprising polyethylene, an ethylene-alpha-olefin copolymer, or a mixture thereof in an amount of 5 to 30% by weight based on the total weight of the polypropylene resin composition.
A film made of the polypropylene resin composition according to any one of claims 1 to 2.