JP2012111801A - Composition for packaging material - Google Patents

Abstract

Provided are a packaging material composition that does not require the use of an unnecessary resin in a desired container while maintaining multiple functions, and a packaging material and packaging container using the composition. thing.
A composition for a packaging material, a packaging material using the composition, and a packaging container include 90 to 60 wt% of high-density polyethylene obtained by using a metallocene catalyst, and an ethylene vinyl alcohol copolymer 10 to 10%. The high-density polyethylene has a density of 950 to 970 kg / m ³ , an MFR of 3.0 to 30 g / 10 min (190 ° C.), and a die swell of 1.2 to 1.6. The ethylene vinyl alcohol copolymer has an ethylene content of 35 to 50 mol, an MFR of 10 to 20 g / 10 min (210 ° C.), and the particle size of the ethylene vinyl alcohol copolymer in the kneaded product is 20 to 100 μm. It is.
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Description

The present invention relates to a composition, a packaging material, and a packaging container for packaging materials filled with milk, juice, alcoholic beverages, mineral water, green tea, dressing, soup and the like.

Packing and filling containers such as juice, milk, mineral water, green tea and other low-viscosity liquid foods, fluid foods, etc., for example, base materials (for example, fibers and plastics such as paper) / barrier layers such as aluminum foil / It is obtained from a packaging material such as a web-like packaging material in which an appearance design is printed on a laminate of heat seal layers.
For example, low density polyethylene (LDPE) / printing ink layer / paper substrate layer (fibrous carrier layer) / LDPE (extruded laminate layer for adhesion) / aluminum foil (gas barrier layer) / LDPE / LDPE, LDPE / printing ink layer / Laminated packaging of paper base layer / LDPE / LDPE, printing ink layer / LDPE / paper base layer / LDPE / LDPE, and LDPE / printing ink layer / paper base layer / LDPE / aluminum foil / polyester (PET) There are materials.

In general, a laminated packaging material is obtained by bringing a base paper roll of a paper base layer into a printing machine, printing on the surface of the base paper, winding the printed paper again into a roll, and then feeding it to an extrusion laminator. For example, when there is a gas barrier layer (aluminum foil or the like) in addition to the base paper, LDPE or the like is extruded on the surface of the base paper, and melted polyolefin is extruded between the gas barrier layers to produce a laminate coating. When laminating the gas barrier layer as described above or adding another functional layer, instead of laminating all the layers at once, a partial laminate is separately prepared and temporarily rolled. Then, these partial laminates are further laminated to obtain a final laminated packaging material.

Packaging filling containers obtained from the above laminated packaging materials, plastic materials, etc. include brick-type packaging containers, roof-type packaging containers, composite containers composed of a paper body and a plastic lid that is injection-molded at the end of the body, and paper There are composite containers made of a main body and a plastic top part joined to the end of the main body.

The plastics (thermoplastic resins) used in the packaging materials and packaging containers are mainly low density polyethylene (LDPE), linear low density polyethylene (LLDPE), metallocene catalyzed linear low density polyethylene (mLLDPE), and medium density polyethylene. , High density polyethylene, polypropylene, polyethylene naphthalate, ethylene vinyl alcohol, polyamide, condensation polymer of metaxylenediamine and adipic acid, polyvinyl alcohol, ethylene vinyl acetate copolymer, ethylene methacrylic acid copolymer, ethylene ethyl acrylate copolymer Examples thereof include one or more polymers selected from a polymer, an ethylene methyl acrylate copolymer, an ethylene acrylic acid copolymer, and a cyclic olefin copolymer.

Each layer of the laminated packaging material has its function and function. The fiber base material layer of the packaging container paper is provided with a plastic coating for liquid-tightness on both sides of the base material layer. Protect effectively. These laminated outer layers usually impart excellent heat sealability to the packaging material and, as mentioned above, are made of a heat adhesive plastic such as low density polyethylene.

In the laminated packaging material which consists only of the paper base material layer and the thermoplastic outer layer, it is difficult to maintain the quality of the contents product.
In order to maintain the quality of the contents product, it is necessary to prevent the fragrance and flavor of the contents product from passing through the packaging material and scattering to the outside, or to use the packaging material that contacts the fragrance and flavor with the contents product. Perfumes to prevent absorption or odors from oozing out of the packaging material into the contents product, and to inhibit the fragrance, flavor, etc., and gases (oxygen gas etc.) that impair the quality of the contents product However, the packaging material needs a gas barrier property that permeates the laminated container wall of the packaging container and protects the contents product, and a packaging material that has sufficient aroma retaining property and gas barrier property is preferable.

Examples of gas barrier materials that impart gas barrier properties to packaging materials include aluminum foil, EVOH (ethylene vinyl alcohol, that is, saponified ethylene-vinyl acetate random copolymer), PVOH (polyvinyl alcohol), polyamide (nylon MXD6, etc.) In addition, materials having excellent oxygen gas barrier properties such as inorganic oxide vapor deposition layers are known.

Among gas barrier materials, EVOH has a strong polarity because the portion with high electron density and the portion with low electron density are clearly separated in the molecule, so it has affinity with non-polar gas such as oxygen gas such as water and oil. In addition, the hydroxyl groups (OH) in the polymer are strongly attracted to each other, so that there is almost no gap between the polymer molecules and is crystalline, so that the gas cannot easily pass through the EVOH. (See Patent Document 1)

Plastics (thermoplastic resins) used in packaging containers include antioxidants, UV absorbers, antistatic agents, lubricants, antiblocking agents, flame retardants, inorganic and organic fillers, paints, depending on the application. Various additives such as pigments are appropriately added. Examples of white pigments include zinc white, lead white, lithopone, titanium dioxide, precipitated barium sulfate and barite powder. However, in food applications, it is limited to food additives.
As a white pigment titanium dioxide which is a food additive compliant with the Food Sanitation Law, there is 99% or more of high-purity titanium oxide. This white pigment of titanium dioxide has significance in food applications in terms of hygiene, hygiene management, and food impression. (See Patent Document 2)

JP-A-63-312143 JP 2007-090876 A

As described above, the packaging material must have various functions and functions, that is, multi-functionality. For that purpose, in addition to the water-resistant outermost layer for liquid tightness and the innermost layer of sealant for heat sealing, an aroma / gas barrier barrier layer for maintaining the quality of the contents product is laminated to form a multilayer structure. Has been taken.
However, in order to make a multilayer structure, a laminating / joining facility for manufacturing the laminate is required, which is complicated, and an adhesive layer for joining them between a functional layer and another functional layer is provided. It becomes necessary, and it will spur further multilayering.
The present invention provides a composition for a packaging material that does not require the use of an unnecessary resin in a desired container while maintaining multiple functions while suppressing the multilayering, and a packaging material and a packaging container using the composition The purpose is to do.

The packaging material composition of the present invention, the packaging material and packaging container using the composition are high density polyethylene (mHDPE) 90 wt% to 60 wt% obtained using a metallocene catalyst, and ethylene vinyl alcohol co-polymer A composition comprising a kneaded product (blend) of 10 wt% to 40 wt% of combined (EVOH), a packaging material and a packaging container using the composition,
The high density polyethylene has a density of 950-970 kg / m ³ , an MFR of 3.0-30 g / 10 min (190 ° C.), a die swell of 1.2-1.6,
The ethylene vinyl alcohol copolymer has an ethylene content of 35 to 50 mol, an MFR of 10 to 20 g / 10 min (210 ° C.), preferably an MFR of 7 to 20 g / 10 min, and the ethylene vinyl alcohol copolymer in the kneaded product. The particle size of the polymer is 20-100 μm,
It is characterized by that.

In a preferred embodiment of the present invention, the composition comprising the kneaded product contains substantially no additive.

In a preferred embodiment of the present invention, the kneaded product is kneaded by a twin screw extruder.

According to the present invention having the above configuration, the following functions are exhibited and advantageous effects can be obtained.
The packaging material composition of the present invention, the packaging material and packaging container using the composition are high density polyethylene (mHDPE) 90 wt% to 60 wt% obtained using a metallocene catalyst, and ethylene vinyl alcohol co-polymer It consists of a kneaded product (blend product) of 10 wt% to 40 wt% of combined (EVOH).
In this kneaded product, high-density polyethylene (mHDPE) as a main component is defined as polyethylene having a density of 0.942 or more. In this invention, high density polyethylene is a polymer obtained using a metallocene catalyst. The catalyst used for the polymerization is a metallocene catalyst having a very high activity as a catalyst, and has a feature that the molecular weight distribution of the polymerized polymer is extremely narrow. Bimodal metallocene catalysts having active sites that generate different molecular weights can also be used.
The above-mentioned high-density polyethylene can fulfill various functions and functions in the packaging material, such as water resistance for liquid-tightness and sealant property for heat-sealing.

The ethylene vinyl alcohol copolymer (EVOH) itself functions as a gas barrier property, and can also exhibit a gas barrier property function by being dispersed in a metallocene high-density polyethylene (mHDPE) in this kneaded product. .
Blending is carried out at a kneading ratio of 90-60 wt% of metallocene high-density polyethylene and 10-40 wt% of ethylene vinyl alcohol copolymer. Within the above kneading ratio range, in the kneaded material, EVOH is dispersed in a sea-island structure corresponding to islands and mHDPE is equivalent to the sea, and it is difficult to obtain a desired sea-island structure outside the above range. Become.

In the features of this invention, the high density polyethylene has a density of 950-970 kg / m ³ , an MFR of 3.0-30 g / 10 min (190 ° C.), and a die swell of 1.2-1.6.
In general, die swell is a phenomenon in which the diameter of a melt becomes larger than the diameter of a die in extrusion molding, and a die swell or a resin having a higher melt tension can mold a product having a larger internal volume.
In this invention, the die swell or the die swell ratio is a capillary viscometer, and the piston speed is set to 200 mm and 500 mm / min under the measurement conditions of a die diameter of 1.0 mm, a length of 10 mm, and a temperature of 190 ° C. This is a value (ratio) obtained by laser measuring the strand diameter and dividing by the die diameter of 1.0 mm.
In addition, the ethylene vinyl alcohol copolymer has an ethylene content of 35 to 50 mol, an MFR of 10 to 20 g / 10 min (210 ° C.), preferably an MFR of 7 to 20 g / 10 min, and the ethylene vinyl in the kneaded product. The particle size of the alcohol copolymer is 20 to 100 μm.
Under the above conditions and conditions, the kneaded product can be used without impairing the functions of the high-density polyethylene and the ethylene vinyl alcohol copolymer.

In a preferred embodiment of the present invention, the composition comprising the kneaded material does not substantially contain additives such as a compatibilizer and a dispersant.
It can be used as a packaging material or packaging container without any additives.
In a preferred embodiment, the kneaded product is kneaded by a twin screw extruder.
This is because Bundred of high-density polyethylene and ethylene vinyl alcohol copolymer can be performed by a twin-screw extruder from the management and productivity of the manufacturing process.

As described above, while maintaining multiple functions, suppressing multilayering, unnecessary resin in a desired container, composition for packaging material that does not need to use additives, packaging material using the composition, and A packaging container can be provided.

Hereinafter, embodiments of the present invention will be described in detail.
A packaging material composition of this form, a packaging material using the composition, and a packaging container are made of 90-60 wt% high-density polyethylene (mHDPE) obtained using a metallocene catalyst, and an ethylene vinyl alcohol copolymer (EVOH) It consists of a kneaded product (blend) with 10 to 40 wt%.
In this form, the high density polyethylene obtained using the metallocene-based catalyst performs various functions in the packaging material, such as water resistance for liquid tightness, sealant property for heat sealing, packaging material. It functions as a support material that imparts mechanical strength to the material.
In the form according to the invention, the composition is blended with EVOH, which minimizes the loss of the function of the high density polyethylene. For example, the strength reduction can be suppressed to within 30%, and the deterioration can be further reduced by optimization of the blend.

On the other hand, the gas barrier ethylene vinyl alcohol copolymer is dispersed in metallocene high-density polyethylene (mHDPE) even in this kneaded product, so that the gas barrier function can be obtained, that is, the blending ratio (10 to 40 wt%). Exhibits gas barrier properties suitable for
Within the range of the kneading ratio of the above form, in the kneaded material, EVOH is dispersed in a sea-island structure corresponding to islands and mHDPE is corresponded to the sea, and when outside the above range, a desired sea-island structure can be obtained. It becomes difficult.

In features of this form, the high density polyethylene has a density of 950-970 kg / m ³ , an MFR of 3.0-30 g / 10 min (190 ° C.), and a die swell of 1.2-1.6.
Die swell refers to a phenomenon in which the diameter of a melt becomes larger than the diameter of a die in plastic extrusion. In this embodiment, the die swell or the die swell ratio (DS) is a capillary viscometer having a die diameter of 1.0 mm and a length of 10 mm, and is set at a temperature of 190 ° C., a piston speed of 200 mm, and 500 mm / min. It is a ratio obtained by measuring the strand diameter with a laser and dividing by a die diameter of 1.0 mm.
In this form, the ethylene vinyl alcohol copolymer has an ethylene content of 35-50 moles, an MFR of 10-20 g / 10 min (210 ° C.), preferably an MFR of 7-20 g / 10 min.
The particle size of the ethylene vinyl alcohol copolymer in the kneaded product is 20 to 100 μm. When blending (primary blending), it can be obtained by using a material having low elasticity during flow.
In such a form, the high density polyethylene and the ethylene vinyl alcohol copolymer do not impair each function.

In a preferred embodiment, the composition comprising the kneaded material does not substantially contain additives such as a compatibilizer and a dispersant. It can be used as a packaging material or packaging container without any additives.
Furthermore, in a preferred embodiment, the kneaded product is kneaded by a twin-screw extruder from the viewpoint of management of the manufacturing process and productivity.

A composition for a packaging material using the kneaded material of this form or obtained by further adding a polymer, a packaging material laminated using the composition, and a packaging container molded from the packaging material are produced.
The packaging container to be manufactured includes a brick-type packaging container, a roof-type packaging container, a composite container composed of a paper body and a plastic lid injection-molded at the body end, and a plastic joined to the paper body and the body end. There is a composite container with a top.
Furthermore, a lid for a container, a straw or the like can be formed using the above composition.

A high density polyethylene (mHDPE) obtained by using a metallocene catalyst having an MFR of 12 g / 10 min and a density of 966 kg / m ³ was prepared, while an ethylene vinyl alcohol copolymer having an ethylene content of 44 mol% and an MFR of 12 g / 10 min ( EVOH) was prepared.
mHDPE and EVOH were loaded and kneaded in a different-direction, intermeshing type twin screw extruder at a ratio of 70 wt% and EVOH 30 wt%, respectively.

The resin of the obtained kneaded product was molded into a 0.6 mm flat plate and the oxygen permeability was measured.
For comparison, a high density polyethylene (HDPE) resin produced with a conventional (Ziglar-Natta) catalyst was molded into a 0.6 mm flat plate and the oxygen permeability was measured.
The oxygen permeability of the resin of the example was approximately half of the oxygen permeability of the resin of the comparative example, and the oxygen barrier property was approximately doubled.
Regarding the mechanical strength, the strength of the resin of the example was only 30% or less of the strength of the resin of the comparative example.
As demonstrated above, the packaging material does not require the use of unnecessary resins and additives in the desired container, while maintaining the functions such as barrier properties and suppressing the multilayering due to the addition of an adhesive layer, etc. The composition for use could be provided.

The present invention is not limited to the embodiments, and various modifications can be made based on the gist of the present invention, and they are not excluded from the scope of the present invention.

The present invention can be applied to the manufacture of liquid food packaging.

Claims (3)

A composition for packaging materials and packaging containers comprising a kneaded product of 90 wt% to 60 wt% of high density polyethylene obtained using a metallocene catalyst and 10 wt% to 40 wt% of an ethylene vinyl alcohol copolymer, ,
The high density polyethylene has a density of 950-970 kg / m ³ , an MFR of 3.0-30 g / 10 min (190 ° C.), a die swell of 1.2-1.6,
The ethylene vinyl alcohol copolymer has an ethylene content of 35 to 50 mol, an MFR of 10 to 20 g / 10 min (210 ° C.), and the particle size of the ethylene vinyl alcohol copolymer in the kneaded product is 20 ~ 100 μm,
The composition for packaging materials characterized by the above-mentioned. The composition for packaging materials according to claim 1, wherein the composition comprising the kneaded material contains substantially no additive. The composition for packaging materials according to claim 1, wherein the kneaded product is kneaded by a twin-screw extruder.