KR102576446B1 - POLYETHYLENE RESIN COMPOSITION AND blown film PREPARED BY USING THE SAME - Google Patents

Abstract

The present invention provides a polyethylene resin composition that minimizes the decrease in pH of contents when used as a liquid filling and packaging material, and a blown film manufactured using the same.

Description

Polyethylene resin composition and blown film manufactured using the same {POLYETHYLENE RESIN COMPOSITION AND blown film PREPARED BY USING THE SAME}

The present invention relates to a polyethylene resin composition that minimizes a decrease in pH of contents when used as a liquid filling and packaging material, and a blown film manufactured using the same.

Polyethylene resin is a type of thermoplastic synthetic resin, and is a resin having excellent properties such as hardness, mechanical strength, heat resistance, and cold resistance, and is used for extruded products such as various containers, insulating materials, packaging materials, hoses, pipes, and ropes.

In particular, low-density polyethylene resin is widely used in food and beverage containers and medical packaging containers. However, when a film and a container are made of low-density polyethylene resin to store the liquid, the pH of the liquid content decreases over time. This pH decrease phenomenon appears larger as the temperature increases.

The cause of the pH decrease of the liquid content is determined to be due to the case where external carbon dioxide permeates and dissolves into the content through the low-density polyethylene layer and the phenomenon in which a substance that causes acidity inside the low-density polyethylene is transferred to the content.

Accordingly, in manufacturing a liquid packaging container using a low-density polyethylene resin, there is a continuing demand for the development of a polyethylene resin composition capable of minimizing a drop in pH of liquid contents and a blown film technology manufactured using the same.

An object of the present invention is to provide a polyethylene resin composition that minimizes the drop in pH of contents when used as a liquid filling and packaging material, and a blown film manufactured using the same.

According to one embodiment of the present invention, a polyethylene resin composition comprising 100 parts by weight of a polyethylene resin, 0.07 to 0.18 parts by weight of hydrotalcite, and 0.001 to 0.035 parts by weight of polyalkylene glycol is provided. .

In addition, the present invention provides a blown film for liquid packaging, prepared from the polyethylene resin composition.

The present invention provides a polyethylene resin composition that minimizes a decrease in pH of contents when used as a liquid filling and packaging material, and a blown film manufactured using the same.

In the present invention, terms such as first and second are used to describe various components, and the terms are used only for the purpose of distinguishing one component from another.

In addition, terms used in this specification are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise", "comprise" or "having" are intended to indicate that there is an embodied feature, number, step, component, or combination thereof, but one or more other features or It should be understood that the presence or addition of numbers, steps, components, or combinations thereof is not precluded.

Since the present invention can have various changes and various forms, specific embodiments will be exemplified and described in detail below. However, it should be understood that this is not intended to limit the present invention to the specific disclosed form, and includes all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Hereinafter, the present invention will be described in more detail.

According to one embodiment of the present invention, when manufacturing a liquid packaging container with a blown film using a low density polyethylene resin, the pH drop of the liquid contents through the acid-base neutralization reaction and the ion exchange reaction on the liquid contact surface can be minimized. A polyethylene resin composition is provided.

The polyethylene resin composition may include 100 parts by weight of a polyethylene resin, 0.07 to 0.18 parts by weight of hydrotalcite, and 0.001 to 0.035 parts by weight of polyalkylene glycol.

The present invention can significantly improve the pH drop phenomenon of liquid contents, which is difficult to overcome with low-density polyethylene resin itself, by introducing hydrotalcite and polyalkylene glycol, known as functional additives, in a predetermined range by optimizing them. In particular, hydrotalcite-based compounds are ingredients that have been approved for use by the FDA and the European Pharmacopoeia and whose stability has been confirmed. may act as a contributing factor. In addition, polyalkylene glycol used as a compressor oil used in a high-temperature, high-pressure process for producing polyethylene resin is a component that serves as a lubricant, and when used in excess at a high temperature of 80 ° C. or higher, formic acid (formic acid), which lowers the pH of the liquid content. Accordingly, the present invention is to mix hydrotalcite and polyalkylene glycol in an optimal range at the same time in a polyethylene resin composition for use as a liquid filling and packaging material, thereby reducing the pH drop of the liquid content even when stored at a high temperature for a long time. can be significantly improved.

In the present invention, the polyethylene resin may be an ethylene homopolymer that does not include a separate copolymer.

The polyethylene resin, for example, has a melt index (MI _2.16 ) of about 0.1 g/10min to about 10 g/10min, or about 0.2 g/10min to about It may be 0.5 g/10 min. This is characterized by high melt strength of the polyethylene resin in order to have high bubble stability capable of stably producing a blown film. Here, the melt index MI _2.16 of the polyethylene resin is a value measured under the condition of a load of 2.16 kg at a temperature _of 190 ° C by the method of ASTM D 1238, and is represented by the weight (g) of the resin melted for 10 minutes.

In addition, the polyethylene resin may be a low density polyethylene resin. For example, the low-density polyethylene resin may have a density of about 0.915 g/ ^{cm 3} to about 0.935 g/cm 3 , or about 0.92 g/cm ³ to about 0.93 g/cm ³ as measured by the ASTM D 792 method. . This is characterized by high density of the polyethylene resin, so that the inflow of external carbon dioxide is reduced, so that the pH drop phenomenon is small, and the heat resistance of the film product is high due to high crystallinity.

The polyethylene resin, for example, may have a weight average molecular weight of about 90000 g/mol to about 200000 g/mol, or about 100000 g/mol to about 190000 g/mol. In addition, the polyethylene resin, for example, may have a molecular weight distribution (MWD) of about 5.5 to about 10, or about 6.5 to about 8.

Here, the molecular weight distribution (MWD, polydispersity index) of the polyethylene resin is, for example, the weight average molecular weight (Mw) and number average molecular weight of the polyethylene resin using gel permeation chromatography (GPC, manufactured by Water). (Mn) can be measured and the molecular weight distribution (MWD) can be calculated by dividing the weight average molecular weight by the number average molecular weight.

Specifically, as a gel permeation chromatography (GPC) device, a Waters PL-GPC220 instrument can be used using a Polymer Laboratories PLgel MIX-B 300 mm long column, and a Polymer Laboratories PLgel MIX-B 300 mm long column can be used for measurement. there is. For example, the measurement temperature is 160 °C, 1,2,4-trichlorobenzene is used as a solvent, and the flow rate can be measured at 1 mL/min. Polyethylene resin samples were pretreated by melting them in trichlorobenzene (1,2,4-Trichlorobenzene) containing 0.0125% BHT at 160 ° C for 10 hours using a GPC analyzer (PL-GP220), respectively, and 10 mg/10mL After preparing to a concentration, it can be measured by supplying in an amount of 200 μL. At this time, the values of Mw and Mn may be derived using a calibration curve formed using a polystyrene standard specimen. The weight average molecular weight of the polystyrene standard specimen is 2000 g/mol, 10000 g/mol, 30000 g/mol, 70000 g/mol, 200000 g/mol, 700000 g/mol, 2000000 g/mol, 4000000 g/mol, 10000000 g 9 types of /mol can be used.

In addition, the polyethylene resin composition of the present invention includes about 0.07 part by weight to about 0.18 part by weight, or about 0.1 part by weight to about 0.15 part by weight of a hydrotalcite-based compound with respect to the polyethylene resin as described above.

Generally, a hydrotalcite-based compound has an acid acceptor and can serve as an acid scavenger or neutralizer. However, when the hydrotalcite-based compound is included as a neutralizing agent in an amount exceeding about 0.18 parts by weight based on 100 parts by weight of the polyethylene resin, it is saturated and there is no pH drop effect, but rather the content of inorganic substances different from the polyalkylene component is increased, so that the film It acts as a factor that causes my gel and deteriorates physical properties. In addition, when the hydrotalcite-based compound is included in an amount of less than about 0.07 parts by weight, the pH lowering effect is insignificant.

The hydrotalcite-based compound may be a magnesium aluminum hydroxide carbonate hydrate-based compound. Such a hydrotalcite-based compound is also referred to as a magnesium aluminum hydroxycarbonate-based compound.

For example, the hydrotalcite-based compound may include one or more selected from the group consisting of compounds represented by Formula 1 below.

[Formula 1]

Mg _x Al ₂ (OH) _{2x +4} (CO ₃ )ㆍmH ₂ O

In Formula 1, 4.0 < x ≤ 6.5, and m is a rational number from 1 to 5.

Specifically, in Chemical Formula 1, x may be 4.2 < x ≤ 6.3 or 4.4 < x ≤ 6.

Specifically, in Chemical Formula 1, m is a rational number of 1.5 to 4.5 or 2 to 4.

More specifically, Formula 1 is Mg _{4 . 5} Al ₂ (OH) ₁₃ (CO ₃ )ㆍ3.5H ₂ O or Mg ₆ Al ₂ (CO ₃ )(OH) ₁₆ ㆍ4H ₂ O.

Meanwhile, the aforementioned hydrotalcite-based compound may have a magnesium (Mg) content of about 25% to about 45%, or about 30% to about 40%, and an aluminum (Al) content of about 10% to about 30%. %, or from about 15% to about 25%. In particular, it may be a carbonate-based compound containing a -CO ₃ (carbonic acid) substituent having the highest anion exchange capacity in order to maximize the effect of lowering the pH by increasing the anion exchange efficiency. In particular, the particle size of the hydrotalcite measured by the laser diffraction scattering method is preferably about 100 nm to about 3000 nm, or about 200 nm to about 2500 nm, or about 200 nm to about 2000 nm. When the particle size is less than about 100 nm, dispersibility problems may occur, and when the particle size exceeds about 3000 nm, commercial use may be limited due to reduced transparency.

In addition, the polyethylene resin composition of the present invention includes about 0.001 part by weight to about 0.035 part by weight, or about 0.001 part by weight to 0.03 part by weight of polyalkylene glycol together with the polyethylene resin and hydrotalcite as described above. can do.

In general, polyalkylene glycol can act as a lubricant in a high-temperature, high-pressure process as a compressor oil, and contains about 0.001 parts by weight or more based on 100 parts by weight of polyethylene resin for smooth process progress. However, when the polyalkylene glycol is included in an excessive amount of more than about 0.035 parts by weight based on 100 parts by weight of the polyethylene resin, it is changed to formic acid, thereby lowering the pH of the liquid contents.

The polyalkylene glycol has a number average molecular weight (g/mol) of about 5000 g/mol to about 70000 g/mol, or about 7000 g/mol to about 60000 g/mol, or about 10000 g/mol to about 50000 g/mol. This means that polyalkylene glycol has excellent viscosity characteristics and low friction characteristics at high temperatures, and it has characteristics capable of performing an excellent lubricant role as a compressor oil in a high-temperature and high-pressure process.

For example, the number average molecular weight (g / mol) of the polyalkylene glycol can be measured using gel permeation chromatography (GPC, gel permeation chromatography, manufactured by Water), specifically related to measuring the molecular weight of polyethylene resin Thus, the GPC device and method as described above can be applied.

The aforementioned polyalkylene glycol may be at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, and ethylene-propylene glycol copolymers. Among these, it is preferable to use polyethylene glycol in view of the application target being a polyethylene resin.

In addition, the polyethylene resin composition of the present invention is characterized in that it does not contain antioxidants such as phenol-based antioxidants or phosphorus-based antioxidants in addition to the above-described polyethylene resin, hydrotalcite, and polyalkylene glycol. . In particular, when such an antioxidant is further included, it is adsorbed to the hydrotalcite-based compound to inhibit anion exchange action, thereby increasing the pH drop range of the liquid content.

In addition to the above components, the resin composition of the present invention may further include an antistatic agent, a surfactant, an anti-dropping agent, a surface lubricant, an ultraviolet (UV) blocker, and the like commonly used in the art to which the present invention pertains.

On the other hand, according to another embodiment of the present invention, a blown film for liquid packaging prepared using the polyethylene resin composition as described above is provided.

Except for using the polyethylene resin composition of the present invention, the above-described blown film may be obtained by a polyethylene processing method generally used in the technical field to which the present invention belongs, and, for example, the resin composition of the present invention It may include a process of extruding by a cylindrical tube structure and stretching using internal air pressure inside the molten resin composition tube to expand the dimensions. More specifically, it is prepared according to a method of inflation molding by introducing pellets of the polyethylene resin composition into an extruder to have a thickness of about 10 μm to about 100 μm, preferably about 50 μm to about 60 μm, but limited thereto It doesn't work.

The blown film according to the present invention may include other additives as necessary in addition to the polyethylene resin composition. Specifically, such additives include heat stabilizers, antioxidants, UV absorbers, light stabilizers, metal deactivators, fillers, reinforcing agents, plasticizers, lubricants, emulsifiers, pigments, optical brighteners, flame retardants, antistatic agents, foaming agents, and the like. The type of the additive is not particularly limited, and general additives known in the art to which the present invention pertains may be used.

In particular, the above-described blown film is prepared using a polyethylene resin composition in which a predetermined amount of hydrotalcite and polyalkylene glycol are added to a polyethylene resin as described above, so that even when stored at a high temperature for a long time, The pH drop can be minimized to within about 0.3 or from about 0 to about 0.3, or within about 0.26 or from about 0 to about 0.26.

For example, in a container made of the blown film, put an evaluation solution in the range of pH 5 to 7 at a concentration of 3 g of sodium chloride in 1 L of purified water, leave it in an oven at about 109 ° C. for about 1 hour, and then the pH value ( pH-1) was measured, and the pH value (pH-2) was measured after leaving it in the oven at about 85 ° C. for about 7 days to calculate the range of pH change from the pH-1 to the pH-2, The range of pH change may be about 0.3, about 0 to about 0.3, or about 0.26, about 0 to about 0.26, or about 2 to about 0.26.

Hereinafter, a preferred embodiment is presented to aid understanding of the present invention. However, the following examples are only provided to more easily understand the present invention, and the content of the present invention is not limited thereby.

Example One

With the composition shown in Table 1 below, a magnesium aluminum hydroxide carbonate hydrate-based compound (Mg _4.5 Al ₂ (OH) ₁₃ (CO ₃ )·3.5H ₂ O, trade name: DHT-4A, as a hydrotalcite-based compound) Manufacturer: Nippon Kyohwa), and polyethylene glycol having a number average molecular weight of 35,000 g / mol with polyalkylene glycol (product name: PEG-35000, manufacturer: Clariant). A concentrated mixture was prepared in a kneader at 160 ° C., Polyethylene resin composition pellets were prepared by mixing with a low density polyethylene resin having a density of 0.925 g/cm ³ and a melt index (MI _2.16 , 190 °C, 2.16 kg) of 0.3 g/10min in an extruder at 190 °C.

Example 2

It was prepared in the same manner as in Example 1, but by mixing 0.15 parts by weight of a magnesium aluminum hydroxide carbonate hydrate-based compound and 0.03 parts by weight of polyethylene glycol with respect to 100 parts by weight of the low density polyethylene resin, polyethylene resin composition pellets were prepared.

comparative example One

It was prepared in the same manner as in Example 1, but by mixing 0.05 parts by weight of a magnesium aluminum hydroxide carbonate hydrate-based compound and 0.02 parts by weight of polyethylene glycol with respect to 100 parts by weight of the low-density polyethylene resin, to prepare polyethylene resin composition pellets.

comparative example 2

Octadecyl 3-(3',5'-di-t-butyl-4'-hydroxy, a phenolic antioxidant, prepared in the same manner as in Example 1, but without adding a magnesium aluminum hydroxide carbonate hydrate-based compound Mixing hydroxyphenyl) propionate [Octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)-propionate] in an amount of 0.05 parts by weight based on 100 parts by weight of the low-density polyethylene resin, Polyethylene resin composition pellets were prepared.

comparative example 3 and 4

It was prepared in the same manner as in Comparative Example 2, but the content of the phenolic antioxidant was changed to 0.1 part by weight and 0.15 part by weight, respectively, to prepare polyethylene resin composition pellets.

comparative example 5

Polyethylene resin composition pellets were prepared in the same manner as in Example 1, but without adding a magnesium aluminum hydroxide carbonate hydrate-based compound.

comparative example 6

It was prepared in the same manner as in Example 1, but the magnesium aluminum hydroxide carbonate hydrate-based compound and polyethylene glycol were not added, and polyethylene resin composition pellets were prepared.

comparative example 7

It was prepared in the same manner as in Example 1, but by mixing 0.2 parts by weight of a magnesium aluminum hydroxide carbonate hydrate-based compound and 0.02 parts by weight of polyethylene glycol with respect to 100 parts by weight of the low-density polyethylene resin, polyethylene resin composition pellets were prepared.

comparative example 8

It was prepared in the same manner as in Example 1, but by mixing 0.1 part by weight of a magnesium aluminum hydroxide carbonate hydrate-based compound and 0.04 part by weight of polyethylene glycol with respect to 100 parts by weight of the low-density polyethylene resin, polyethylene resin composition pellets were prepared.

comparative example 9

It was prepared in the same manner as in Example 1, but by mixing 0.15 parts by weight of a magnesium aluminum hydroxide carbonate hydrate-based compound and 0.05 parts by weight of polyethylene glycol with respect to 100 parts by weight of the low density polyethylene resin, to prepare polyethylene resin composition pellets.

Specific compositions of the polyethylene resin compositions of Examples 1 to 2 and Comparative Examples 1 to 9 are shown in Table 1 below.

Low density polyethylene resin (parts by weight) hydrotalcite
(parts by weight) polyethylene glycol
(parts by weight) antioxidant
(parts by weight) Example 1 100 0.1 0.02 - Example 2 100 0.15 0.03 - Comparative Example 1 100 0.05 0.02 - Comparative Example 2 100 - 0.02 0.05 Comparative Example 3 100 - 0.02 0.1 Comparative Example 4 100 - 0.02 0.15 Comparative Example 5 100 - 0.02 - Comparative Example 6 100 - - - Comparative Example 7 100 0.2 0.02 - Comparative Example 8 100 0.1 0.04 - Comparative Example 9 100 0.15 0.05 -

In Table 1, the contents of hydrotalcite, polyethylene glycol, and antioxidant are values based on 100 parts by weight of low density polyethylene resin.

manufacturing example 1 to 2 and Comparative Manufacturing Example 1 to 9

Blown films for liquid packaging were prepared using the polyethylene resin composition pellets of Examples 1 to 2 and Comparative Examples 1 to 9, and physical properties were evaluated for pH drop in the following manner. The physical property evaluation results measured in this way are shown in Table 2 below.

First, using the polyethylene resin composition pellets of Examples 1 to 1 and Comparative Examples 1 to 9, extrusion using a single screw extruder (Shinhwa Industrial Single Screw Extruder, Blown Film M/C, 50 pi, L/D = 20) A blown film for liquid packaging was prepared by inflation molding at a temperature of 130° C. to 170° C. to a thickness of 0.06 mm. At this time, the die gap was 2.0 mm and the blown-up ratio was 2.3.

In a container made of the blown film, put an evaluation solution in the range of pH 5 to 7 at a concentration of 3 g of sodium chloride in 1 L of purified water, and leave it in the oven at about 109 ° C for about 1 hour, and then the pH value (pH-1) was measured, and the pH value (pH-2) was measured after leaving it in an oven at about 85° C. for about 7 days. The pH change range from the pH-1 to the pH-2 was calculated by subtracting the measured value of pH-2 from the measured value of pH-1, and the degree to which the pH was lowered was expressed as the pH change range.

Initial pH (pH-1) Final pH (pH-2) range of pH change Preparation Example 1 5.68 5.48 0.2 Preparation Example 2 5.83 5.57 0.26 Comparative Preparation Example 1 5.61 4.48 1.13 Comparative Preparation Example 2 4.15 3.32 0.83 Comparative Preparation Example 3 4.55 3.36 1.19 Comparative Preparation Example 4 5.32 3.38 1.94 Comparative Preparation Example 5 5.68 3.77 1.91 Comparative Preparation Example 6 4.88 4.53 0.35 Comparative Preparation Example 7 5.85 5.50 0.35 Comparative Preparation Example 8 5.51 5.09 0.42 Comparative Preparation Example 9 5.2 4.7 0.5

As shown in Table 2, in contrast to the comparative example, in the examples, the hydrotalcite-based compound and the polyethylene glycol are optimized and mixed with the low-density polyethylene resin, so that the pH drop of the liquid content is reduced even when stored at high temperature for a long time. 0.2 to 0.26, it can be seen that very few appear.

Claims (12)

100 parts by weight of polyethylene resin;
0.1 part by weight to 0.15 part by weight of a hydrotalcite-based compound, and
0.001 part by weight to 0.03 part by weight of polyalkylene glycol;
The hydrotalcite-based compound is a magnesium aluminum hydroxide carbonate hydrate-based compound,
The polyalkylene glycol has a number average molecular weight of 10000 g / mol to 50000 g / mol,
A polyethylene resin composition.
According to claim 1,
Characterized in that the polyethylene resin is an ethylene homopolymer,
A polyethylene resin composition.
According to claim 1,
The polyethylene resin has a melt index (MI _2.16 ) of 0.1 g / 10 min to 10 g / 10 min, measured under 190 ° C. and 2.16 kg load condition according to ASTM D 1238,
A polyethylene resin composition.
According to claim 1,
The polyethylene resin has a density of 0.915 g / cm ³ to 0.935 g / cm ³ as measured by the method of ASTM D 792,
A polyethylene resin composition.
According to claim 1,
Characterized in that the polyethylene resin has a weight average molecular weight of 90000 g / mol to 200000 g / mol,
A polyethylene resin composition.
According to claim 1,
The polyethylene resin is characterized in that the molecular weight distribution (MWD, Mw / Mn) is 5.5 to 10,
A polyethylene resin composition.
According to claim 1,
The hydrotalcite-based compound is characterized in that the particle size is 100 nm to 3000 nm,
A polyethylene resin composition.
According to claim 1,
Characterized in that the hydrotalcite-based compound includes at least one selected from the group consisting of compounds represented by the following formula (1),
Polyethylene resin composition:
[Formula 1]
Mg _x Al ₂ (OH) _{2x +4} (CO ₃ )ㆍmH ₂ O
In Formula 1,
4.0 < x ≤ 6.5;
m is a rational number from 1 to 5;
delete According to claim 1,
Characterized in that the polyalkylene glycol includes at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, and ethylene-propylene glycol copolymers,
A polyethylene resin composition.
According to claim 1,
Characterized in that the resin composition does not contain a phenol-based antioxidant and a phosphorus-based antioxidant,
A polyethylene resin composition.
Claims 1 to 8, 10, and produced from the polyethylene resin composition according to any one of claims 11, a blown film for liquid packaging.