JP2021154603A - Packaging material - Google Patents

Abstract

To provide a packaging material having such transparency as to allow a stored object to be confirmed.SOLUTION: A packaging material has base paper containing pulp and resin layers on both surfaces of the base paper, in which the base paper contains polyalkylene glycol.SELECTED DRAWING: None

Description

The present invention relates to a transparent packaging material whose contents can be confirmed.

In recent years, there has been a tendency to remove plastics to prevent environmental pollution. As for packaging materials, there is a tendency to change from synthetic resin film to paper. For example, wrapping paper or glassine paper used for wrapping paper or wrapping container used for food packaging or punch molding for cups such as cakes and chocolates is known (see, for example, Patent Document 1).

It contains at least pulp and wax having a melting point of 35 ° C. or higher under normal pressure, the pulp has a Canadian standard freshness of 300 ml or more and 600 ml or less, and at least one of the pulps is LBKP and the content of LBKP is the total amount of pulp. A transparent paper having excellent transparency and dimensional stability and strength against changes in humidity, which is 70% by mass or more of the above, is known (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 06-316899 Japanese Unexamined Patent Publication No. 2020-029626

Conventional packaging materials using glassine paper, resin-coated paper, resin-impregnated paper, and the like do not have sufficient transparency so that the contained matter can be confirmed.

An object of the present invention is to provide a transparent packaging material in which the contents can be confirmed.

As a result of diligent studies by the present inventors, the above-mentioned problems of the present invention can be solved by the following.

[1] A packaging material having a base paper containing pulp and resin layers on both sides of the base paper, and the base paper contains polyalkylene glycol.

[2] The packaging material according to the above [1], wherein the polyalkylene glycol is polyethylene glycol.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a packaging material having transparency so that the contained matter can be confirmed.

The present invention will be described in detail below.

The packaging material of the present invention has a base paper and resin layers on both sides of the base paper. The base paper contains pulp. In some embodiments, the base paper is made up of 70% by mass or more of pulp with respect to the components forming the base paper. The reason for this is that it may be discarded as paper.

The pulp is conventionally known in the field of papermaking. Examples of pulp include chemical pulps such as LBKP (Leaf Bleached Kraft Pulp) and NBKP (Needle Bleached Kraft Pulp), GP (Groundwood Pulp), PGW (Pressure GroundWood pulp), RMP (Refiner Mechanical Pulp), and TMP (ThermoMechanical Pulp). , CTMP (ChemiThermoMechanical Pulp), CMP (ChemiMechanical Pulp), CGP (ChemiGroundwood Pulp) and other mechanical pulps, and DIP (DeInked Pulp) and other used paper pulps. Pulp is at least one or more selected from the group consisting of these.

The base paper is a slurry in which pulp is dispersed in water, and if necessary, a filler, a sizing agent, a binder, a fixing agent, a yield agent, a cationizing agent, a paper strength agent, a dispersant, a thickener, a fluidity improving agent, and the like. Defoamer, antifoaming agent, mold release agent, foaming agent, penetrant, colorant, fluorescent whitening agent, ultraviolet absorber, antioxidant, preservative, antibacterial agent, water resistant agent, wet paper strength enhancer , A paper material containing one or more of a dry paper strength enhancer as appropriate is produced by using a paper machine conventionally known in the papermaking field. Further, the base paper includes a treated base paper that has been subjected to a calendar treatment, and a treated base paper that has been surface-sized or surface-treated with starch, polyvinyl alcohol, or the like. Further, the base paper includes a processed base paper that has been subjected to surface size treatment or surface treatment and then calendar-treated. In some embodiments, the base paper is not surface sized or surface treated. The reason for this is that the transparency is improved in combination with the following resin layer.

The papermaking may be acidic, neutral or alkaline. Examples of conventionally known paper machines include a long net paper machine, a twin wire paper machine, a combination paper machine, a circular net paper machine, and a Yankee paper machine.

The calendar process is a process of smoothing, smoothing, and averaging the thickness by passing paper between rolls. Examples of the calendar processing device include a machine calendar, a soft nip calendar, a super calendar, a multi-stage calendar, and a multi-nip calendar.

In some embodiments, the base paper does not contain a filler. The reason for this is that the filler has an effect on light scattering, so that the transparency is deteriorated.

In some embodiments, the basis weight of the base paper is 20 g / m ² or more and 50 g / m ² or less. The reason for this is that when the basis weight is 20 g / m ² or more and 50 g / m ² or less, the packaging material, in combination with the following resin layer, has better strength that can be used for the packaging material and transparency to the extent that the contents can be confirmed. It is compatible. The basis weight of the base paper is a value obtained according to ISO 536: 1995 "Paper and board-Determination of grammage".

The base paper contains polyalkylene glycol. Polyalkylene glycol is a polymer obtained by polymerization or copolymerization of alkylene oxides such as ethylene oxide and propylene oxide. The base paper can be made transparent by containing polyalkylene glycol. Polyalkylene glycol corresponds to a hydrophilic wax used as a lubricant or the like. Since the wax has hydrophilicity, it easily penetrates into the voids between the fibers so as to coat the fibers of pulp. As a result, the present inventors infer that the scattering of light is suppressed and the base paper is made satisfactorily transparent. In some embodiments, the polyalkylene glycol has a weight average molecular weight of 1000 or more and 20000 or less. The reason for this is that transparency is improved. The polyalkylene glycol is commercially available from, for example, Sanyo Chemical Industries, Ltd., NOF Corporation, Toho Chemical Industry Co., Ltd., Showa Chemical Industries, Ltd., and the like.
In at least one example, the polyalkylene glycol is preferably polyethylene glycol. The reason for this is that polyethylene glycol is easily available as a material.

The methods in which the base paper contains polyalkylene glycol are (a) a method of blending polyalkylene glycol with a paper material to make a paper, and (b) a conventionally known coating such as a size press on the base paper obtained by making a paper material. Examples thereof include a method of applying and drying an aqueous solution containing polyalkylene glycol by a working device and a drying device. In some embodiments, the production of the packaging material is the method (b) above. The reason for this is that it is easy to obtain transparency in the base paper with a relatively small content of polyalkylene glycol. In at least one embodiment, in the production of the packaging material by the method (b) above, coating and drying of an aqueous solution containing polyalkylene glycol is both sides of the base paper.

Examples of conventionally known coating devices include size presses, gate roll coaters, film transfer coaters, blade coaters, rod coaters, air knife coaters, comma coaters (registered trademarks), gravure coaters, bar coaters, E bar coaters, and curtain coaters. And so on.

Examples of size presses include inclined size presses, horizontal size presses, rod metering size presses, roll metering size presses and blade metering size presses as film transfer methods, and sim sizers and optimizers for rod metering size presses. Speed sizers and film presses, and roll metering size presses include gate roll coaters. Other examples include bill blade coaters, twin blade coaters, velva papa coaters, tab size presses, and calendar size presses. Preferred size presses are inclined size presses, horizontal size presses, gate roll coaters, sim sizers and film presses.

Examples of conventionally known drying devices include hot air dryers such as straight tunnel dryers, arch dryers, air loop dryers, and sine curve air float dryers, infrared heating dryers, and dryers using microwaves. can.

In some embodiments, the content of the polyalkylene glycol in the base paper is 5% by mass or more based on the mass of the base paper containing the polyalkylene glycol. The reason for this is that the transparency of the packaging material is improved. In some embodiments, the content of the polyalkylene glycol in the base paper is 25% by mass or less based on the mass of the base paper containing the polyalkylene glycol. The reason for this is that there is no further transparency effect above 25% by mass and the material cost increases. In at least one embodiment, the content of the polyalkylene glycol in the base paper is 5% by mass or more and 25% by mass or less with respect to the mass of the base paper containing the polyalkylene glycol.

As disclosed in Patent Document 2, it is effective to add wax to the base paper to make the base paper containing pulp transparent. The present invention aims at further transparency by providing the following resin layer on the base paper. However, in general, when the base paper contains wax as a clearing agent, wrinkles occur even if the resin layer is peeled off from the base paper or is not peeled off from the base paper. The present inventors have found that it is possible to provide a resin layer on the base paper if it is a polyalkylene glycol. That is, the present inventors have found a packaging material having transparency enough to confirm what is contained by containing polyalkylene glycol in the base paper to make it transparent to some extent and further providing a resin layer on the base paper.

The resin layer is a water-insoluble layer formed by a water-insoluble resin.
A type of water-insoluble resin that forms a resin layer is a resin that uses a solvent other than water as a medium. Examples of the resin using a solvent other than water as a medium include solvent-based resins. A type of water-insoluble resin that forms a resin layer is a solvent-free type resin. A type of water-insoluble resin that forms a resin layer is an emulsion-type resin. The water-insoluble resin is, for example, a polyolefin resin, a vinyl resin, a resin that is cured by an electron beam, or the like. Examples of water-insoluble resins include various polyethylenes such as high density polyethylene, low density polyethylene, medium density polyethylene and linear low density polyethylene; isotactics, syndiotactics, atactics, mixtures thereof, random with ethylene. Various polypropylenes such as copolymers and block copolymers; in addition, polybutylene succinate, polymethylpentene, polyethylene glycol terephthalate, polyvinyl chloride, polyvinylidene chloride, ethylene vinyl alcohol copolymer, ethylene vinyl acetate copolymer And so on. As the water-insoluble resin, one kind or two or more kinds selected from the group consisting of these can be used.
In some embodiments, the water-insoluble resin is various polyethylenes or various polypropylenes. The reason for this is that it is chemically stable against various chemicals. In at least one embodiment, the water-insoluble resin is various polyethylenes, wherein the various polyethylenes are a blend of low density polyethylene and high density polyethylene. The reason for this is that it is possible to achieve both the strength of the resin layer and the transparency of the resin layer.
In some embodiments, the resin layer has heat seal suitability.

The method of providing the resin layer on the base paper is not particularly limited. If it is a solvent-free type resin, for example, a method using a conventionally known laminator device such as a general melt extrusion die, a T die, or a multi-layer simultaneous extrusion die, and if it is a solvent type resin, for example, a solvent is not used as a medium. A method of applying and drying a resin layer coating liquid in which a water-soluble resin is dissolved, and in the case of an emulsion-type resin, for example, a resin layer coating liquid containing an emulsion of a water-insoluble resin is applied using water as a medium. And a method of drying. The method of applying and drying the resin layer coating liquid is not particularly limited. Examples of the method include a method of coating and drying using a coating device and a drying device conventionally known in the field of coated paper. Examples of conventionally known coating devices include size presses, gate roll coaters, film transfer coaters, blade coaters, rod coaters, air knife coaters, comma coaters, gravure coaters, bar coaters, E bar coaters, curtain coaters, and the like. Can be done. Examples of conventionally known drying devices include hot air dryers such as straight tunnel dryers, arch dryers, air loop dryers, and sine curve air float dryers, infrared heating dryers, and dryers using microwaves. can.

In some embodiments, in the production of packaging materials, the resin layer is heat-pressurized. The reason for this is that transparency is improved. Examples of the heat and pressure treatment method include a calendar treatment conventionally known in the papermaking field or a lithographic heat press machine. In at least one embodiment, in the production of the packaging material, the heating temperature of the heat-pressurizing treatment is equal to or higher than the softening point of the resin.

In some embodiments, the resin layer has a resin coating amount of 5 g / m ² or more in terms of dry solid content per side of the base paper. The reason for this is that transparency is improved. The upper limit of the amount of resin applied is not particularly limited. In some embodiments, the resin layer has a resin coating amount of 15 g / m ² or less in terms of dry solid content per side of the base paper. The reason for this is that there is no further transparency effect above ^{15 g / m 2 and the material cost increases.} In at least one embodiment, the amount of resin applied to the resin layer is 5 g / m ² or more and 15 g / m ² or less in terms of the amount of dry solids per side of the base paper.

The present inventors presume that the reason for making the resin transparent is as follows. When a resin layer is provided on the base paper, the water-insoluble resin partially fills the fine voids existing on the surface layer of the base paper. As a result, the packaging material has excellent transparency with further suppressed light scattering.

Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not limited to these examples. Here, "mass%" represents "mass%" of each of the dry solid content and the substantial component amount. The coating amount of the coating layer represents the amount of dry solid content.

<Example 1>
The NBKP pulp slurry was beaten using a refiner. The obtained pulp had a CSF drainage degree of 200 ml, which was determined according to ISO 5627-2: 2001 "Pulps-Determination of drainability-Part 2 Canadian Standard freedoms method". The beaten pulp was made with a long net paper machine, and then subjected to calendar processing with a machine calendar device to obtain a base paper ^{having a basis weight of 30 g / m 2.}
Next, a polyethylene glycol aqueous solution having a weight average molecular weight of 1540 was applied to both sides of the base paper using a size press device. The amount of polyethylene glycol applied was 0.5 g / m ^{2 in} terms of dry solid content per side.
A base paper containing polyethylene glycol was coated and dried with a melt-extruded die so that low-density polyethylene was ^{coated and dried at 10 g / m 2 on each side.} Then, the base paper having the resin layers of low-density polyethylene on both sides was subjected to heat and pressure treatment with a lithographic heat press machine set at 130 ° C. to obtain the packaging material of Example 1. Here, in the heat and pressure treatment, both sides of the base paper having the resin layer of low-density polyethylene on both sides were protected with a polyimide release film.

<Example 2>
In Example 1, the packaging material of Example 2 was obtained in the same manner as in Example 1 except that the amount of polyethylene glycol applied was 0.8 g / m ^{2 in terms of dry solid content per side.}

<Example 3>
In Example 1, the packaging material of Example 3 was obtained in the same manner as in Example 1 except that the amount of polyethylene glycol applied was 1.5 g / m ^{2 in terms of dry solid content per side.}

<Example 4>
In Example 1, the packaging material of Example 4 was obtained in the same manner as in Example 1 except that the amount of polyethylene glycol applied was 3 g / m ^{2 in terms of dry solid content per side.}

<Example 5>
In Example 1, the packaging material of Example 5 was obtained in the same manner as in Example 1 except that the amount of polyethylene glycol applied was 5 g / m ^{2 in terms of dry solid content per side.}

<Example 6>
In Example 1, the packaging material of Example 6 was obtained in the same manner as in Example 1 except that the amount of polyethylene glycol applied was 6 g / m ^{2 in terms of dry solid content per side.}

<Example 7>
In Example 3, the packaging material of Example 7 was obtained in the same manner as in Example 3 except that the polyethylene glycol was polypropylene glycol having a weight average molecular weight of 8000.

<Example 8>
In Example 3, the packaging material of Example 8 was obtained in the same manner as in Example 3 except that the low-density polyethylene was made of polypropylene.

<Example 9>
In Example 3, Example 9 was prepared in the same manner as in Example 3 except that low-density polyethylene was used as polybutylene succinate.

<Comparative example 1>
In Example 1, the packaging material of Comparative Example 1 was obtained in the same manner as in Example 1 except that the coating amount of polyalkylene glycol was set to 0 g / m ^2.

<Comparative example 2>
In Example 4, the packaging material of Comparative Example 2 was obtained in the same manner as in Example 4 except that polyethylene glycol was changed to paraffin wax as a clearing agent.

<Comparative example 3>
The NBKP pulp slurry was beaten using a refiner. The obtained pulp had a CSF drainage degree of 200 ml, which was determined according to ISO 5627-2: 2001 "Pulps-Determination of drainability-Part 2 Canadian Standard freedoms method". The beaten pulp was made with a long net paper machine, and then subjected to calendar processing with a machine calendar device to obtain a base paper ^{having a basis weight of 30 g / m 2.}
Next, a polyethylene glycol aqueous solution having a weight average molecular weight of 1540 was applied to both sides of the base paper using a size press device. The amount of polyethylene glycol applied was 3 g / m ^{2 in} terms of dry solid content per side.
The base paper containing polyethylene glycol was used as it was as the packaging material of Comparative Example 3.

The following were evaluated for the packaging materials of each Example and each Comparative Example.

<Transparency>
The total light transmittance and haze were measured using a haze meter NDH7000 manufactured by Nippon Denshoku Kogyo Co., Ltd. The evaluation was performed based on the following criteria based on the measurement results. In the present invention, the packaging material shall have transparency so that the contents can be confirmed by the evaluation of A and B.
A: The total light transmittance is 70% or more and the haze is 45% or less.
B: The total light transmittance is 70% or more and the haze is more than 45% and 60% or less.
C: The total light transmittance is 70% or more and the haze is more than 60% and 70% or less.
D: The total light transmittance is 70% or less and / or the haze is more than 70%.

The results are shown in Table 1. In Comparative Example 2, the resin layer partially floated or peeled off.

From Table 1, it can be seen that Examples 1 to 9 satisfying the configuration of the present invention are transparent packaging materials in which the stored items can be confirmed. On the other hand, Comparative Examples 1 to 3 that do not satisfy the constitution of the present invention can be found to be packaging materials that do not satisfy the effects according to the present invention.

Claims (2)

A packaging material having a base paper containing pulp and resin layers on both sides of the base paper, and the base paper contains polyalkylene glycol. The packaging material according to claim 1, wherein the polyalkylene glycol is polyethylene glycol.