KR20240114318A - Biodegradable packaging material for low temperature food and manufacturing method therof - Google Patents

Abstract

The present invention relates to a biodegradable packaging material for low-temperature food and a manufacturing method thereof. Specifically, the present invention relates to a biodegradable packaging material for low-temperature food that contains ultra-low-density polyethylene and low-content polylactic acid and has a high storage modulus and low-temperature impact strength while simultaneously having high biodegradability. It relates to biodegradable packaging materials and their manufacturing methods.

Description

Biodegradable packaging material for low-temperature food and manufacturing method thereof {BIODEGRADABLE PACKAGING MATERIAL FOR LOW TEMPERATURE FOOD AND MANUFACTURING METHOD THEROF}

The present invention relates to a biodegradable packaging material for low-temperature food and a manufacturing method thereof. Specifically, the present invention relates to a biodegradable packaging material for low-temperature food that contains ultra-low-density polyethylene and low-content polylactic acid and has a high storage modulus and low-temperature impact strength while maintaining high biodegradability. It relates to biodegradable packaging materials and their manufacturing methods.

As the demand for home convenience foods has increased significantly due to the impact of the COVID-19 pandemic, the demand for frozen (low-temperature) foods that can be easily cooked is increasing, and various frozen (low-temperature) food products are being released.

Plastic is generally used as food packaging material, but it can take hundreds of years for plastic to decompose, causing the problem of plastic pollution to increase.

Packaging materials, which account for the largest share of total plastic production (26%), are reused/recycled, 14% are incinerated, and the remainder is lost in landfills or unmanageable forms. In the case of landfill, it is not easy to secure a sufficient landfill site, and due to the nature of plastic that exists semi-permanently in the natural world after landfill, there are difficulties in ensuring that plastic waste remains without rotting. When plastic is incinerated, harmful gases such as dioxin and carbon monoxide are generated, causing additional pollution, and disposal of the residue remaining after incineration is also problematic.

As awareness of environmental pollution becomes a global concern, the demand for eco-friendly, biodegradable packaging materials is increasing. Biodegradable materials are made from renewable natural resources and can break down into natural components when disposed of in the environment.

Types of biodegradable resins (or polymers) include starch, cellulose, chitin, polylactic acid (PLA), polyhydroxy alkanoate (PHA), polycaprolactone (PCL, poly ε-caprolactone), etc. It exists in a variety of ways and is used alone or mixed with other resins (or polymers). The biodegradable resin most commonly used in food utensils, containers, and packaging is polylactic acid (PLA). However, polylactic acid (PLA) has physical properties such as insufficient flexibility and heat resistance, so it has limitations as a packaging material for low-temperature food.

In addition, most polymer films rapidly harden as temperatures deviate from room temperature and reach lower temperatures, deteriorating their mechanical properties.

Accordingly, as a packaging material for low-temperature food, there was a need to develop a composition that could have a storage modulus and low-temperature impact strength above a certain level and at the same time have high biodegradability.

The technical problem to be achieved by the present invention is to provide a low-temperature biodegradable packaging material for food containing ultra-low-density polyethylene and low-content polylactic acid, which has a high storage modulus and low-temperature impact strength while also having high biodegradability, and a method for manufacturing the same. .

However, the problem to be solved by the present invention is not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

One embodiment of the present invention for achieving the above-described object includes: a base layer; A biodegradable resin layer containing very low density polyethylene (VLDPE), biodegradable filler, oxidative biodegrader, and low content polylactic acid (PLA); and a bonding layer that joins the base layer and the biodegradable resin layer. It relates to a biodegradable packaging material for low-temperature food, including a.

The biodegradable resin layer may further include one or more selected from the group consisting of a binder, a commercial catalyst, a plasticizer, a radical initiator, and an oxidative biodegradation accelerator.

The biodegradable resin layer may have a storage modulus (E') of 0.3 x 10 ⁹ Pa or more to 4.0 x 10 ⁹ Pa or less in a temperature range of -20 ℃ or more to 5 ℃ or less.

The ultra-low density polyethylene may have a density of 0.890 g/cm3 or more and 0.914 g/cm3 or less.

Based on 100 parts by weight of the very low density polyethylene (VLDPE), 5 to 80 parts by weight of the biodegradable filler, 0.05 to 5 parts by weight of the oxidative biodegrader, and 1 to 30 parts by weight of the low content polylactic acid (PLA). It can be included as a part.

The base layer may include paper.

The bonding layer may include polyvinyl alcohol (PVA).

One embodiment of the present invention includes a method of manufacturing the biodegradable packaging material for low-temperature food.

The biodegradable packaging material for low-temperature food according to the present invention has high storage modulus and low-temperature impact strength while maintaining high biodegradability.

The method for manufacturing biodegradable packaging material for low-temperature food according to the present invention can produce biodegradable packaging material for low-temperature food that has high storage modulus and low-temperature impact strength while maintaining high biodegradability.

In this specification, when a part “includes” a certain component, this means that it may further include other components rather than excluding other components, unless specifically stated to the contrary.

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

According to one embodiment of the present invention, a biodegradable packaging material for low-temperature food includes a base layer; A biodegradable resin layer containing very low density polyethylene (VLDPE), biodegradable filler, oxidative biodegrader, and low content polylactic acid (PLA); and a bonding layer that bonds the base layer and the biodegradable resin layer.

In general, polyethylene (PE, polyethylene) has good moisture barrier properties, chemical resistance, low price, and high gas permeability. In addition, because it is easy to process and economical, it is widely used in food packaging in the form of a transparent or translucent film.

The polyethylene (PE) is an ethylene polymer and is the first commercialized polyolefin-based material. Depending on the density, it is classified into very low density polyethylene (VLDPE, very low density polyethylene), linear low density polyethylene (LLDPE), and low density polyethylene (LDPE, low density polyethylene). density polyethylene), medium density polyethylene (MDLE), and high density polyethylene (HDPE).

In the present invention, the very low density polyethylene (VLDPE) has high cold resistance and good heat adhesion to frozen food packaging, so it is widely used as a heat adhesive packaging material when laminating with other packaging materials. In addition, it has excellent impact resistance, very high oxygen permeability, and low moisture permeability, making it suitable for low-temperature food packaging.

In the present invention, it is not necessary to include only one type of resin, the very low density polyethylene (VLDPE), and may be a mixture of two or more types of resin.

The very low density polyethylene (VLDPE) can be combined with the biodegradable filler to form a biodegradable polyethylene-based composition. When combining the very low density polyethylene (VLDPE) and the biodegradable filler, it is important to prevent a decrease in the physical properties of polyethylene (PE) as well as the physical bonding force.

In the present invention, the biodegradable filler may be selected from the group consisting of regular starch, acid-treated starch, ester starch, ether starch, amphoteric starch, and mixtures thereof, for example, corn starch, acetic acid starch, and phosphoric acid. It may be starch or amphoteric starch, and corn starch is preferably used. This can be made biodegradable by combining it with the very low density polyethylene (VLDPE).

In the present invention, the content of the biodegradable filler may be 5 to 80 parts by weight, preferably 5 to 50 parts by weight, 5 to 30 parts by weight, more preferably, based on 100 parts by weight of very low density polyethylene (VLDPE). It may be 5 to 15 parts by weight. When the above content is satisfied, when combined with the very low density polyethylene (VLDPE), not only the physical bonding force but also the physical properties of polyethylene (PE) can be prevented from decreasing and it can be biodegradable.

In the present invention, the biodegradable resin layer may further include one or more selected from the group consisting of a binder, a commercial catalyst, a plasticizer, a radical initiator, and an oxidative biodegradation accelerator.

In the present invention, the binder may be maleic anhydride, methacrylic anhydride, or maleimide. Preferably, maleic anhydride can be used. In order to increase the compatibility of starch and polymer in conventional starch-added polymers, a biodegradable film could be manufactured by surface treating starch with a silane-based coupling agent and modifying it to be lipophilic, but only the physical bonding force between the polymer and starch was used. It was difficult to solve the decrease in the physical properties of the film due to starch filling by slightly increasing the amount.

Accordingly, the present invention completely broke away from the attempt to overcome the decrease in physical properties of the film due to starch filling by only increasing the physical bonding force between the polymer and starch, and overcome the decrease in physical properties by connecting the polymer and starch through a chemical bond using a binder. Of course, manufacturing costs can be significantly reduced through simplification of the manufacturing process.

The content of the binder may be 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, and 0.1 to 1 part by weight, based on 100 parts by weight of very low density polyethylene (VLDPE). When the above content is satisfied, it is possible to prevent a decrease in physical properties as well as physical bonding force with very low density polyethylene (VLDPE).

In the present invention, the commercial catalyst may be acrylic acid and/or methacrylic acid, preferably acrylic acid. The commercial catalyst can serve as both a catalyst and a compatibilizer in the combination of very low density polyethylene (VLDPE) and biodegradable filler.

The content of the commercial catalyst may be 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, 0.1 to 1 part by weight, or 0.1 to 0.5 parts by weight, based on 100 parts by weight of very low density polyethylene (VLDPE). When the above content is satisfied, it can more appropriately serve as a catalyst and compatibilizer in the combination of very low density polyethylene (VLDPE) and biodegradable filler.

In the present invention, the plasticizer may be oleamide, viton, or erucamide, and is preferably oleamide. The plasticizer can improve the physical properties of the polymer and increase compatibility with the polymer in the combination of very low density polyethylene (VLDPE) and biodegradable filler.

The content of the plasticizer may be 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, and 0.5 to 5 parts by weight, based on 100 parts by weight of very low density polyethylene (VLDPE). When the above content is satisfied, the physical properties of the polymer can be improved when combining very low density polyethylene (VLDPE) with a biodegradable filler, while compatibility with the polymer can be further improved.

In the present invention, the radical initiator is benzoyl peroxide, di-tributyl peroxide, azobisisobutyl nitrile, tributyl hydroperoxide, dicumyl peroxide, Lupersol 101 (produced by Pennwalt), or percadox. -14 (manufactured by AKZO) may be used, and benzoyl peroxide is preferred.

The content of the radical initiator may be 0.01 to 1 part by weight, preferably 0.05 to 0.5 parts by weight, based on 100 parts by weight of very low density polyethylene (VLDPE).

In the present invention, polylactic acid (PLA) is a biodegradable resin (polymer) that is made from lactic acid made by fermenting glucose extracted from corn and sugarcane and turns lactic acid into ring-shaped lactide. After conversion, it can be manufactured through a polymer polymerization process. The glass transition temperature (Tg) of polylactic acid (PLA) is 60°C, the melting temperature is 180°C, and it has mechanical properties similar to those of general non-degradable polymers. However, due to the short repeat unit length of the polylactic acid (PLA) chain, it has a semi-rigid main chain and slow chain mobility, resulting in a slow crystallization rate, low melt strength and thermal stability, and high brittleness and hygroscopicity. As a result, polylactic acid (PLA) may have limited processing and applications.

In addition to combining the biodegradable filler with the very low density polyethylene (VLDPE), a biodegradable polyolefin-based composition can be made by additionally including polylactic acid (PLA). However, since there are limitations in the physical properties of polylactic acid (PLA), which lacks flexibility and heat resistance, it is necessary to develop a composition that can naturally decompose after a certain period of use while maintaining the necessary physical properties.

To this end, the polylactic acid (PLA) may further include an oxidative biodegradation agent that causes decomposition by inducing oxidation of the very low density polyethylene (VLDPE) while using a low content, and promotes the reaction of the oxidative biodegradation agent. It may further contain an oxidative biodegradation accelerator.

The content of polylactic acid (PLA) is 1 to 30 parts by weight, preferably 1 to 25 parts by weight, 1 to 20 parts by weight, 1 to 15 parts by weight, 1 to 10 parts by weight, based on 100 parts by weight of very low density polyethylene (VLDPE). Parts by weight, 1 to 5 parts by weight, 5 to 30 parts by weight, 5 to 25 parts by weight, 5 to 20 parts by weight, 5 to 15 parts by weight, 5 to 10 parts by weight, 10 to 30 parts by weight, 10 to 25 parts by weight , 10 to 20 parts by weight, 10 to 15 parts by weight, 15 to 30 parts by weight, 15 to 25 parts by weight, and 15 to 20 parts by weight. The above content can be suitable as a packaging material for low-temperature food by adding a lower content compared to very low density polyethylene (VLDPE). If it is less than 1 part by weight, there is a problem that the biodegradability of packaging materials for low-temperature foods is lowered, and if it is more than 30 parts by weight, it may not be suitable for packaging materials for low-temperature foods due to the physical properties of polylactic acid (PLA), which lacks flexibility and heat resistance. You can.

In the present invention, the polylactic acid (PLA) may have a weight average molecular weight (MW) of 200,000 g/mol to 21,000 g/mol and a density of 1.20 g/cm ³ to 1.30 g/cm ³ .

In the present invention, the oxidative biodegradation agent is not particularly limited as long as it causes decomposition by inducing oxidation of very low density polyethylene (VLDPE) by light. Likewise, the wavelength of light that induces decomposition is not particularly limited. For example, the oxidative biodegradation agent may be a fatty acid salt. These fatty acid salts can be used regardless of whether they are saturated or unsaturated fatty acid salts. For example, it may be one or more selected from the group consisting of stearate, oleate, maleate, erucate, linolenate, and succinate. Preferably, it may be manganese/iron-oleate (Mn/Fe oleate).

The content of the oxidative biodegradation agent may be 0.05 to 5 parts by weight, preferably 0.1 to 4 parts by weight, and more preferably 0.1 to 3 parts by weight, based on 100 parts by weight of very low density polyethylene (VLDPE). If it is included in less than 0.05 parts by weight, the polyolefin-based resin is not sufficiently oxidized to the degree desired by the present invention, and the environmentally friendly material properties targeted by the present invention cannot be achieved. On the other hand, if it exceeds 5.0 parts by weight, the manufacturing cost of the composition increases, it becomes unstable to the extent that it is unsuitable for use in industrial fields and daily life, and further abrasion of the manufactured article is accelerated or durability is weakened. There is a risk that it will happen.

The oxidative biodegradation accelerator promotes the reaction of the oxidative biodegradation agent and helps the oxidative biodegradation agent induce oxidation of very low density polyethylene (VLDPE). Therefore, even if only a small amount of the oxidative biodegradation agent is added, biodegradability can be achieved. In the case of the present invention, by adding a small amount of the oxidative biodegradation accelerator instead of reducing the content of the oxidative biodegradation agent, biodegradability is achieved while maintaining good physical properties of very low density polyethylene (VLDPE).

The oxidative biodegradation accelerator is, for example, one selected from the group consisting of α, β-unsaturated carboxylates, unsaturated carboxylates with an aromatic substituent, cycloalkyl carboxylates, cycloalkenyl carboxylates, and isomers thereof. It could be more than that.

Among the unsaturated carboxylic acid salts, the most preferred examples are 3-phenyl-2-propenoate and 3-cyclohexyl-2-propenoate. It may be one or more selected from the group consisting of.

The content of the oxidative biodegradation accelerator may be 0.05 to 2 parts by weight, preferably 0.1 to 1.5 parts by weight, and more preferably 0.1 to 1 part by weight, based on 100 parts by weight of very low density polyethylene (VLDPE).

Most polymer films rapidly harden as temperatures go beyond room temperature and their mechanical properties deteriorate. Therefore, cold resistance is directly related to flexibility, and flexibility is directly related to the storage modulus that viscoelastic polymers can have.

In the present invention, the biodegradable resin layer may have ^a storage modulus (E') of ^0.3 It may be 10 ⁹ Pa or more to 3.8 x 10 ⁹ Pa or less, 1.0 x 10 ⁹ Pa or more to 3.5 x 10 ⁹ Pa or less, and 2.0 x 10 ⁹ Pa or more to 3.5 x 10 ⁹ Pa or less. When the above range is satisfied, it has excellent flexibility, cold resistance, and impact resistance, and can be usefully used as a packaging material for low-temperature food.

In the present invention, the very low density polyethylene (VLDPE) may have a density of 0.890 g/cm3 or more to 0.914 g/cm3, preferably 0.890 g/cm3 or more to 0.910 g/cm3, or 0.890 g/cm3 or more to 0.905 g/cm3. It may be g/cm3 or less, 0.890 g/cm3 or more to 0.900 g/cm3 or less, or 0.890 g/cm3 or more to 0.895 g/cm3 or less.

In the present invention, the base layer may include paper. The paper may be implemented using various types of paper, such as manila paper, CCP (cast coated paper) paper, white paper, thin leaf paper, roe paper, Korean paper, kraft paper, and white cardboard, but is not limited thereto. For example, paper may be implemented using roe paper or kraft paper, but is not limited thereto. Noruji is widely used as a food packaging material and has a smooth surface. It is a type of relatively thin wrapping paper made with glossy paper on one side.

In one embodiment, the base layer may be composed of high barrier paper coated with an aqueous coating solution containing a barrier material on the base material to increase barrier properties against moisture and air. Specifically, the base layer is made of various types of barrier materials, such as styrene-butadiene-based, styrene-acrylic-based, polyvinyl alcohol (PVA), vinylidene chloride polymer, acrylonitrile polymer, vinyl chloride polymer, and ethylene vinyl alcohol. It can be formed using high-barrier paper in which a barrier layer is formed by coating a paper substrate with an aqueous coating solution containing one or more polymers or copolymers thereof selected from polymers one or more times.

In this way, the base layer formed of high barrier paper may have excellent barrier properties against moisture and air. According to one embodiment, the base layer may have an oxygen permeability of 4 cc/(㎡·day·atm) or less at 23°C and 0% relative humidity, and may have an oxygen permeability of 11 g/(㎡·atm) at 38°C and 90% relative humidity. day) or less. However, this is an example and the physical properties of the base layer are not limited to the above values.

In particular, according to the present invention, by implementing a biodegradable packaging material for low-temperature food using a base layer with excellent barrier properties, the amount of metal materials such as plastic and aluminum used can be reduced by about 45%, and as a result, carbon emissions are reduced by about 45%. It can be reduced by about 48% compared to barrier film packaging.

According to the present invention, the bonding layer may include polyvinyl alcohol (PVA). Because of its biodegradability, biocompatibility, chemical resistance, and excellent physical properties, it is used in a variety of ways, including transparent packaging films, paper coatings, and reinforcements. In the present invention, the polyvinyl alcohol (PVA) serves to bond the biodegradable resin layer and the base layer.

The content of polyvinyl alcohol (PVA) is 1 to 9.2 parts by weight, preferably 3 to 7 parts by weight, and more preferably 5 to 6 parts by weight, based on 100 parts by weight of very low density polyethylene (VLDPE). If the content of polyvinyl alcohol (PVA) is less than 1 part by weight, the shock absorption strength and adhesive strength of the final product, the cushioning material, are lowered. If the amount exceeds 9.2 parts by weight, the effect of improving the above physical properties is minimal, which has the disadvantage of being uneconomical. However, it is not necessarily limited to this, and those skilled in the art can select the polyvinyl alcohol (PVA) content according to the required physical properties and use.

Since the base layer is also coated with polyvinyl alcohol (PVA), a barrier layer can be formed, and it can also be effective as an adhesive in joining the biodegradable resin layer and the base layer.

In the present invention, a method for manufacturing the biodegradable packaging material for low-temperature food is provided. The above manufacturing method can be used as long as it is a conventional method and is not limited to a specific method.

Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those skilled in the art.

[Example]

In this example, very low density polyethylene (VLDPE) was coated using parts by weight according to Table 1 below and the composition below.

In an extruder maintained at an extrusion temperature of 170°C and a screw speed of 250 rpm, 10 parts by weight of corn starch is reactively extruded based on the coated pellet and very low density polyethylene (VLDPE), so that the starch is converted into very low density polyethylene (VLDPE). ) Produce biodegradable master batch pellets chemically bonded to the chain.

The base layer was manufactured using kraft paper, and the pellet containing the very low density polyethylene (VLDPE) and the base layer were bonded using polyvinyl alcohol (PVA) to finally produce a biodegradable packaging material for low-temperature food.

VLDPE biodegradable filling PLA binder commercial
catalyst plasticizer radical
initiator Oxidation
biodegradable Oxidation
biodegradable
accelerant Example 1 100 10 5 0.75 0.25 One 0.1 One One Example 2 100 10 10 0.75 0.25 One 0.1 One One Example 3 100 10 15 0.75 0.25 One 0.1 One One Example 4 100 10 25 0.75 0.25 One 0.1 One One Example 5 100 10 30 0.75 0.25 One 0.1 One One

(Unit: parts by weight)

- Very low density polyethylene (VLDPE): density 0.890 g/cm ³ to 0.895 g/cm ³

- Biodegradable filling: corn starch

- Polylactic acid (PLA): MW 207,000 g/mol, density 1.25 g/cm ³

- Binder: maleic anhydride

- Commercial catalyst: acrylic acid

- Plasticizer: oleamide

- Radical initiator: benzoyl peroxide

- Oxidative biodegrader: Manganese/Fe oleate (Mn/Fe oleate)

- Oxidative biodegradation accelerator: 3-phenyl-2-propenoate

- Base layer: Kraft paper

- Bonding layer: 5 parts by weight of polyvinyl alcohol (PVA)

[Experimental Example 1: Storage modulus]

For Examples 1 to 5, a sample film was obtained using a dynamic mechanical analyzer TA Instrument DMA SS6100 (Seiko) in stress mode at a frequency of 1 Hz and a temperature increase rate of 10°C/min. The elastic modulus was measured. At this time, the storage modulus (E') was determined in the temperature range of -20°C to 5°C.

Storage modulus (x 10 ⁹ Pa) Example 1 3.8 Example 2 3.3 Example 3 2.9 Example 4 2.1 Example 5 1.6

[Experimental Example 2: Low-temperature impact strength]

For Examples 1 to 5, the IZOD impact strength of 1/8" specimens was measured at -30°C according to ASTM D256 method.

Low-temperature impact strength (kgf·cm/cm) Example 1 48 Example 2 41 Example 3 36 Example 4 28 Example 5 21

[Experimental Example 3: Biodegradability]

For Examples 1 to 5, biodegradability was measured by cultivating for at least 21 days according to the ASTM G 21-70 method and dividing the degree to which the film was covered with mold as follows.

- When 0%: 0

- Below 10%: 1

- 10~30%: 2

- 30~60%: 3

- 60~100%: 4

Biodegradability (%) Example 1 2 Example 2 3 Example 3 4 Example 4 4 Example 5 4

According to Tables 2 to 4, it can be seen that as the content of polylactic acid (PLA) increases, the storage modulus and low-temperature impact strength decrease and biodegradability increases. Therefore, by adjusting the contents of very low density polyethylene (VLDPE) and polylactic acid (PLA), the storage modulus and low-temperature impact strength can be increased while maintaining high biodegradability.

Claims (8)

Base layer;
A biodegradable resin layer containing very low density polyethylene (VLDPE), biodegradable filler, oxidative biodegrader, and low content polylactic acid (PLA); and
A biodegradable packaging material for low-temperature food, comprising a bonding layer that joins the base layer and the biodegradable resin layer. According to paragraph 1,
The biodegradable resin layer further includes one or more selected from the group consisting of a binder, a commercial catalyst, a plasticizer, a radical initiator, and an oxidative biodegradation accelerator. According to paragraph 1,
The biodegradable resin layer has a storage modulus (E') of 0.3 x 10 ⁹ Pa or more to 4.0 x 10 ⁹ Pa or less in the temperature range of -20 ℃ or more to 5 ℃ or less. According to paragraph 1,
The ultra-low density polyethylene is a biodegradable packaging material for low-temperature food, having a density of 0.890 g/cm3 or more to 0.914 g/cm3 or less. According to paragraph 1,
Based on 100 parts by weight of the very low density polyethylene (VLDPE), 5 to 80 parts by weight of the biodegradable filler, 0.05 to 5 parts by weight of the oxidative biodegrader, and 1 to 30 parts by weight of the low content polylactic acid (PLA). Biodegradable packaging material for low-temperature food, which includes: According to paragraph 1,
A biodegradable packaging material for low-temperature food, wherein the base layer includes paper. According to paragraph 1,
A biodegradable packaging material for low-temperature food, wherein the bonding layer includes polyvinyl alcohol (PVA). A method for producing a biodegradable packaging material for low-temperature food according to any one of claims 1 to 7.