JP2022058232A - Paper packaging material for ice and/or frozen product - Google Patents

Abstract

To provide a paper packaging material which can be easily worked into a box, has waterproofness, and is used for applications for putting ice and/or a frozen product.SOLUTION: There is provided a paper packaging material for storing ice and/or a frozen product in which a waterproof resin layer is coated onto at least one surface of a paper base material having two or more paper layers.SELECTED DRAWING: Figure 2

Description

The present invention relates to paper packaging materials for ice and / or frozen products. In particular, the present invention relates to a paper packaging material for producing a box for containing ice and / or frozen products.

When transporting fresh fish and the like, it has been widely practiced to put ice and fresh fish inside a styrofoam container for transportation. When using a paper container from the viewpoint of environmental protection, an inner bag is usually provided inside a paper container such as corrugated cardboard, and ice and fresh fish are put in the inner bag for transportation. It is necessary to use a bag or the like (Patent Document 1 or the like).

Japanese Unexamined Patent Publication No. 9-240765

The subject of the present invention is not only waterproofness but also ice and / or frozen products having good hot-melt adhesiveness and recyclability without reducing the box compressive strength even when ice and / or frozen products are put. It is to develop paper packaging materials used for applications.

As a result of diligent studies on the above problems, the present inventors have obtained an excellent paper packaging material for accommodating ice and / or frozen products by applying a waterproof resin layer to at least one side of the paper substrate. I was able to realize it.

The present invention includes, but is not limited to, the following aspects.
[1] A paper packaging material for accommodating ice and / or frozen products, wherein a waterproof resin layer is coated on at least one side of a paper base material having two or more paper layers.
[2] The paper packaging material according to [1], wherein the coating amount of the waterproof resin layer is 1 to 20 g / m ² .
[3] The paper packaging material according to [1] or [2], wherein the waterproof resin layer contains at least one of a styrene resin, an acrylic resin, and a polyolefin resin, and a wax.
[4] The paper packaging material according to any one of [1] to [3], which can be adhered with a thermoplastic resin.
[5] The method for producing the paper packaging material according to any one of [1] to [4].
The above method comprising the step of applying a waterproof resin layer to at least one side of a paper substrate.
[6] A box containing the paper packaging material according to any one of [1] to [4].
[7] A corrugated cardboard sheet containing the paper packaging material according to any one of [1] to [4].
[8] A method for producing a paper package for containing ice and / or a frozen product, which is ice and / or frozen from the paper packaging material according to any one of [1] to [4]. The above method comprising the step of forming a paper package for accommodating the goods.

According to the present invention, an excellent paper packaging material for accommodating ice and / or frozen products is obtained.

It is a perspective view which shows one aspect of the box for accommodating ice and / or the frozen product. It is a photograph showing the state of the waterproofness test. It is a photograph which shows the state of the peelability test of a frozen product. It is a photograph which shows the state of the peelability test of a frozen product.

The present invention relates to a paper packaging material for accommodating ice and / or frozen products. The packaging material according to the present invention has waterproof property, and even if ice and / or a frozen product is stored, the water in which the ice melts does not easily permeate, and the frozen product that has been frozen after storage is applied when it is taken out from the contents. It refers to paper that has a function as a packaging material whose work layer does not adhere to frozen products and can be easily peeled off. Further, in a preferred embodiment of the present invention, the packaging material according to the present invention is less likely to seep out water even when ice is stored and left for a long time, and is applied when the frozen product that has been frozen after storage is taken out from the contents. The layer does not adhere to the frozen product and can be easily taken out, and the strength of the packaging material does not easily decrease. The paper packaging material according to the present invention is not particularly limited as long as it is used for packaging ice and / or frozen products, and for example, applications for storing meat, fish, vegetables, etc. together with ice as contents. It can be used for storing frozen products. The paper packaging material according to the present invention can also be used for applications such as directly accommodating meat, fish, vegetables, etc. as contents without adding ice and then freezing.

The basis weight of the paper packaging material according to the present invention is not particularly limited, but may be, for example, 30 to 800 g / m ² . When the paper substrate is a multi-layered paper having two or more layers, the basis weight of the packaging material is 75 to 750 g / m ² , 100 to 700 g / m ² , and further 200 to 600 g / m ² . can do.

In a preferred embodiment, the paper packaging material of the present invention has a surface water absorption of 3 g / m ² or less for 120 seconds, more preferably 2 g / m ² or less, and may be 1 g / m ² or less. In the case of paper having a water absorption of less than 1 g / m ² (including the case where it does not absorb water and is less than the measurement limit value) when the water absorption of the Cobb for 120 seconds is measured, in a preferred embodiment, the water absorption of the Cobb for 30 minutes on the surface is 25 g / m / 2. It is m ² or less, more preferably 20 g / m ² or less, and may be 10 g / m ² or less. In the present invention, the Cobb water absorption is measured by bringing 100 ml of distilled water into contact with the coating layer and measuring the weight per unit area of the absorbed water after a specified time in accordance with the Cobb method specified in JIS P8140. The smaller the value of the water absorption of the Cobb, the higher the waterproofness of the packaging material.

In a preferred embodiment, the paper packaging material of the present invention is also excellent in moisture resistance, and the moisture permeability is preferably 100 g / m 2.24 h or less, and 75 g / ^m 2.24 h or less or 50 g / ^{m 2 .} It may be 24 hours or less. The moisture permeability of the paper packaging material can be measured from the coating layer side in accordance with JIS Z 0208, and the smaller the value, the higher the moisture resistance.

In a preferred embodiment, the paper packaging material of the present invention is also excellent in oil resistance, and the oil repellency on the coating layer side is preferably kit number 7 or higher, even if it is 8 or higher or 9 or higher. good. Here, the oil-repellent degree of the paper packaging material is measured from the coating layer side in accordance with "Paper and Paperboard-Paper Oil Degree Test Method-Kit Method" (JAPAN TAPPI Pulp and Paper Test Method No. 41). The larger the value of the kit number, the higher the oil resistance.

In the paper packaging material of the present invention, the smoothness of the coated surface is preferably 15 seconds or longer, more preferably 20 seconds or longer, still more preferably 25 seconds or longer. When the smoothness of the surface of the coated layer of the waterproof paper is within the above range, high gloss can be obtained on the surface of the coated layer, and a paper packaging material having more cosmetic properties can be obtained.

Paper Substrate The paper packaging material according to the present invention has at least a paper substrate and a waterproof resin layer coated on at least one surface of the paper substrate. In the present invention, the basis weight of the paper substrate is not particularly limited, and can be, for example, 50 to 800 g / m ² . The paper base material used in the present invention is preferably a multi-layered corrugated board having two or more layers of paper from the viewpoint of having sufficient strength as a paper box when processed into the form of a paper box. The amount can be appropriately set in the range of 70 to 800 g / m ² , and for example, in the case of a corrugated cardboard liner, the basis weight can be set in the range of 80 to 600 g / m ² .

In a preferred embodiment, the paper substrate used in the present invention has a 120-second hump water absorption of 40 g / m ² or less, more preferably 30 g / m ² or less, still more preferably 25 g / m on the surface on which the waterproof resin layer is provided. The range is ² or less, most preferably 20 g / m ² or less. Further, in a preferred embodiment, the paper substrate used in the present invention has a Cobb water absorption rate of 5 g / m ² or more for 120 seconds, more preferably 7 g / m ² or more, still more preferably 10 g / m ² or more. In the present invention, the hump water absorption of the packaging material can be adjusted by applying a waterproof resin layer or the like, but the 120-second hump water absorption of the paper substrate is within the above range, so that the waterproof paint is used. Prevents the paper strength from deteriorating due to excessive permeation of the water contained in the solvent, and the solid content in the waterproof paint stays on the surface of the paper layer to ensure a reliable coating, achieving both waterproof and moisture proof. It will be easier to make it.

The paper substrate used in the present invention is, in a preferred embodiment, the JAPAN TAPPI pulp and paper test method No. The water repellency measured in accordance with 68 "Paper and Paperboard-Water Repellent Test Method" is R4 or more, more preferably R6 or more, and even more preferably R8 or more. When the water repellency of the paper base material is R4 or higher, when the waterproofing agent is applied, the water contained in the coating liquid does not excessively permeate into the paper base material, and it is easy to suppress the decrease in the strength of the paper. Become.

In a preferred embodiment, the paper substrate used in the present invention has a drip oil absorption degree of 5 seconds or more, more preferably 7 seconds or more, still more preferably 10 seconds or more on the surface on which the waterproof resin layer is provided. The upper limit is not particularly limited, but is preferably 80 seconds or less, more preferably 75 seconds or less, and further preferably 70 seconds or less. When the degree of oil absorption is within the above range, the waterproof resin layer stays on the paper surface and is less likely to penetrate into the paper layer, so that it becomes easy to improve the waterproof property and the moisture proof property. The oil absorption of the paper substrate is the time until one drop of light oil No. 1 whose kinematic viscosity coefficient is adjusted to 3 cSt is dropped on the sample surface using a microsyringe equipped with an injection needle H5 until the surface becomes glossy. Can be evaluated by.

The physical properties of the paper base material are not particularly limited, and can be appropriately set according to the use of the paper packaging material. In the present invention, for example, the longitudinal elongation is 1.0 to 15.0%, the lateral elongation is 2.0 to 12.0%, the specific compressive strength is 100 to 350 Nm ² / g, and the specific burst strength is 2. It can be set to be 80 to 5.00 kPa · m ² / g.

In a preferred embodiment, the paper substrate used in the present invention has a Wangken-style smoothness of 10 seconds or more, more preferably 13 seconds or more, and further preferably 16 seconds or more on the surface on which the coating layer is provided. The upper limit is not particularly limited, but is preferably 100 seconds or less, more preferably 90 seconds or less, still more preferably 80 seconds or less, and most preferably 70 seconds or less. When the smoothness of the surface on which the waterproof resin layer is provided is within the above range, the waterproof resin layer makes it easy to uniformly cover the paper substrate, and an excellent packaging material can be obtained.

In a preferred embodiment, the paper substrate used in the present invention has a moisture permeability of 1500 g / ^m 2.24 h or more, more preferably 1750 g / ^m 2.24 h or more, still more preferably 1750 g / m 2.24 h or more, as measured from the side where the waterproof resin layer is provided. It is 2000 g / ^m 2.24 hours or more. The upper limit of the water permeation is not particularly limited, but in a preferred embodiment, it is 5000 g / ^m 2.24 h or less, more preferably 4500 g / ^m 2.24 h or less, and further preferably 4000 g / ^m 2.24 h or less. Since the moisture permeability of the surface on which the waterproof resin layer is provided is within the above range, the moisture in the coating agent is efficiently evaporated to the paper layer side in the drying process after coating. It becomes easy to cover the base material uniformly.

In a preferred embodiment, the paper substrate used in the present invention has a water contact angle of 70 degrees or more, more preferably 75 degrees or more on the surface on which the waterproof resin layer is provided. When the water contact angle is in the above range, it is possible to prevent the water contained in the coating liquid from excessively permeating into the paper base material and prevent the strength of the paper base material from being lowered.

As the raw material pulp for the paper base material, known materials can be used without particular limitation. Specifically, for example, coniferous bleached kraft pulp (NBKP), broadleaf bleached kraft pulp (LBKP), coniferous unbleached kraft pulp (NUKP), broadleaf bleached kraft pulp (LUKP), crushed wood pulp (GP), refiner ground pulp. Various wood-derived pulps such as (RGP), chemical pulp (CP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), and non-wood pulp obtained from Kenaf, Bagus, bamboo, hemp, straw, etc. Can be mentioned.

The paper base material may contain recycled paper pulp or may not contain recycled paper pulp. When the recycled paper pulp is contained, for example, when the paper base material is a single-layer paper, the blending ratio of the recycled paper pulp in the total pulp is preferably 10% by mass or more, more preferably 25% by mass or more, still more preferable. Can be 50% by mass or more, most preferably 70% by mass or more, and 100% by mass (consisting only of pulp derived from used paper). Further, kraft pulp may be blended as pulp other than used paper pulp, or the entire amount may be kraft pulp. Further, when the paper base material is a multi-layer paperboard having two or more layers of paper, the recycled paper pulp mixing ratio per layer can be as described above, and the used paper pulp mixing ratio in each layer is different. There may be.

As used paper pulp, used paper pulp, high-quality paper, high-quality coated paper, medium-quality paper, medium-quality coated paper, shavings, etc. Printed used paper, written used paper, paper such as discarded confidential documents, used magazine paper, used newspaper, and deinked pulp (DIP) can be used.

Further, in the paper-based papermaking, a sizing agent and a water-repellent agent can be added internally or externally, and further, a paper strength enhancing agent can be internally added in order to improve the strength. Examples of the sizing agent include rosin-based sizing agent, rosin emulsion-based sizing agent, α-carboxymethyl saturated fatty acid, neutral rosin-based sizing agent, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), and cationic polymer-based sizing agent. Examples include sizing agents. Examples of the water repellent include a fluorine-based resin, a polyamide-based resin, and a wax. In addition, examples of the paper strength enhancer include conventionally used paper strength enhancers such as polyacrylamide (PAM) and modified starch. In the present invention, it is preferable to include wax in the waterproof resin layer, and it is more preferable to include paraffin wax.

Further, a known filler can be added to the paper substrate as needed, and an inorganic filler or an organic filler can be used without limitation. Examples of the inorganic filler include kaolin, calcined kaolin, delaminated kaolin, clay, calcined clay, delaminated clay, erite, heavy calcium carbonate, light calcium carbonate, light calcium carbonate-silica complex, magnesium carbonate, and carbonic acid. Examples thereof include barium, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide and the like, and examples of the organic filler include urea-formalin resin and polystyrene resin. , Phenolic resin and the like.

Furthermore, even if a sulfate band, aluminum chloride, sodium aluminate, basic aluminum compound, water-soluble aluminum compound, polyvalent metal compound, silica sol, etc. are used internally as long as the quality of the paper substrate is not affected. good.

The paper substrate can be produced by a known papermaking method. For example, it can be performed using a long net paper machine, a gap former type paper machine, a hybrid former type paper machine, an on-top former type paper machine, a round net paper machine, and the like, but the present invention is not limited thereto.

Further, in order to adjust the smoothness of the paper substrate of the present invention, a smoothing treatment may be performed if necessary. For the smoothing process, a smoothing process device such as a normal calendar, a super calendar, a gloss calendar, a soft calendar, a thermal calendar, or a shoe calendar can be used. The smoothing processing device may appropriately adjust the form of the pressurizing device, the number of pressurizing nips, heating, linear pressure, and the like.

Waterproof resin layer The paper packaging material according to the present invention has a waterproof resin layer on at least one side of a paper base material. The waterproof resin layer according to the present invention contains a synthetic resin and wax. The synthetic resin preferably contains at least one of a styrene resin, an acrylic resin, and a polyolefin resin. In particular, it is preferable that the synthetic resin is a styrene resin and / or an acrylic resin.

As the styrene resin that can be contained in the waterproof resin layer, the copolymerization ratio of the styrene monomer having a styrene skeleton in the structure is preferably 50% by mass or more, and the weight of the styrene monomer is heavy. It may consist only of coalescence.

Examples of the styrene-based monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α-methylstyrene, and α. -Methyl-p-methylstyrene and the like can be mentioned.

Examples of the monomer copolymerizable with the styrene monomer include alkyl methacrylates such as methyl methacrylate, cyclohexyl methacrylate and methyl phenyl methacrylate, alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate and cyclohexyl acrylate, and methacrylic acid. , Unsaturated carboxylic acids such as acrylic acid, unsaturated dicarboxylic acid anhydrides such as maleic acid and itaconic acid, unsaturated nitriles such as acrylonitrile and methacrylonitrile, 1,3-butadiene, 2-methyl-1. , Conjugate diene such as 3-butadiene and the like. These can be used alone or in combination of two or more.

The acrylic resin that can be contained in the waterproof resin according to the present invention is a resin in which the copolymerization ratio of acrylic acid, methacrylic acid and the acrylic monomer which is a derivative thereof is 50% by mass or more. It may consist only of a polymer of an acrylic monomer.

Examples of the acrylic monomer include methacrylic acid esters such as cyclohexyl methacrylate, t-butyl cyclohexyl methacrylate and methyl methacrylate, and acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate and isopropyl acrylate. And the like, the acrylic resin may be one obtained by polymerizing one or more kinds of monomers selected from these acrylic monomers.

Examples of the monomer copolymerizable with the acrylic monomer include styrene, o-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, and α-methyl. Aromatic vinyl compounds such as styrene, α-methyl-p-methylstyrene, unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide, and unsaturated dicarboxylic acids such as maleic anhydride. Examples thereof include unsaturated carboxylic acids such as anhydrides, methacrylic acid and acrylic acid. These can be used alone or in combination of two or more.

The waterproof resin layer according to the present invention preferably has a melting point of 65 ° C. or higher, more preferably 70 ° C. or higher, and even more preferably 75 ° C. or higher. The upper limit of the melting point of the waterproof resin layer is not particularly limited, but is preferably 200 ° C. or lower, more preferably 190 ° C. or lower, and even more preferably 180 ° C. or lower. When the melting point of the waterproof resin layer is within these ranges, the waterproof resin melts when hot melt bonding is performed, so that the bonding effect of the hot melt adhesive can be improved, and thus it is strong. Adhesion can be done.

The waterproof resin layer according to the present invention preferably has a glass transition point of 55 ° C. or lower, more preferably 50 ° C. or lower, and even more preferably 45 ° C. or lower. Since the glass transition point of the waterproof resin layer is the above value, it is waterproof not only in a refrigerated (0 to 10 ° C) environment but also in a household refrigerator or a frozen (-20 to 0 ° C) environment during transportation. The resin layer does not crack, and waterproofness can be maintained.

The waterproof resin layer according to the present invention contains wax. Examples of the wax contained in the waterproof resin layer include polyethylene wax, Fishertroph wax, oil-based synthetic wax (fatty acid ester-based, fatty acid amide, ketone / amines), synthetic wax such as hydrogen hardening oil, beeswax, and wood wax. , Paraffin wax, natural wax such as microcrystallin wax and the like. These waxes can be used alone or in combination of two or more, and a hydrocarbon wax containing paraffin is particularly suitable.

In the present invention, the pigment may be contained in the waterproof resin layer for the purpose of improving the whiteness. In this case, it is preferable that the whiteness of the surface is increased by 1% or more as compared with the whiteness of the paper substrate by containing the pigment. Such pigments include calcium carbonate, titanium oxide, kaolin, clay, engineered kaolin, delaminated clay, talc, barium sulphate, calcium sulphate, zinc oxide, silicic acid, silicate, colloidal silica, satin white, mica, etc. Examples thereof include inorganic pigments such as montmorillonite, and these pigments can be used alone or in combination of two or more. Among these pigments, kaolin, calcium carbonate or mica, which have flat particles, is particularly suitable because it does not easily impair waterproofness. Such a flat-shaped inorganic pigment preferably has an aspect ratio of 10 or more. The content of the pigment in the waterproof resin layer is preferably 5 to 40% by mass, more preferably 10 to 35% by mass. When the content of the pigment is 5 to 40% by mass, it is easy to effectively improve the whiteness without significantly impairing the waterproof property.

The waterproof resin layer according to the present invention is characterized by containing an antifoaming agent. By containing the defoaming agent, the generation of fine swelling and bubbles (hereinafter, also referred to as "blister") that are likely to occur on the surface of the coating layer when the coating agent is applied and dried is suppressed. The paper base material can be reliably covered with the waterproof resin layer, and the waterproof property can be further improved. The type of defoaming agent can be appropriately selected according to the components of the waterproof resin, but mineral oil is used as a defoaming agent when applying a waterproof resin containing a styrene / acrylic resin as a main component. , Polyether, and silica are more preferably contained. As the amount of the defoaming agent added, it is preferable to add 0.05 to 6.0 parts by weight, more preferably 0.1 to 5.0 parts by weight, and 0.15 parts by weight with respect to 100 parts by weight of the waterproof resin. It is more preferable to add ~ 4.0 parts by weight.

The waterproof resin layer according to the present invention may contain, for example, a binder, a stabilizer, a viscosity improver, a water retention agent, a preservative, a colorant and the like. The waterproof resin layer according to the present invention can be formed by applying a paint on a paper substrate and drying it. The coating amount of the waterproof resin layer is preferably 1 to 20 g / m ² , and more preferably 4 to 15 g / m ² . If it exceeds 20 g / m ² , further improvement in waterproofness cannot be expected, but the manufacturing cost may increase.

In a preferred embodiment, the waterproof resin layer provided on the paper packaging material of the present invention has an average thickness of 5.5 to 20 μm, more preferably 5.6 to 15 μm, and more preferably 5.7 to 12.5 μm. More preferred. Here, the average thickness of the coating layer is an average value of the thickness of the waterproof resin layer measured by cutting the sample into strips and observing the cross section at arbitrary 10 points using an electron microscope.

In the paper packaging material according to the present invention, the moisture permeability per unit thickness of the waterproof resin layer is preferably 15 (g / m ^2.24h ) / μm or less, and 10 (g / m ^2.24h ) / μm or less. Is more preferable, and 7 (g / m ^2.24h ) / μm or less is further preferable. Here, the moisture permeability per unit thickness of the waterproof resin layer is calculated by dividing the moisture permeability measured according to JIS Z 0208 from the coating layer side of the waterproof paper by the average coating layer thickness.

The paper packaging material of the present invention can be produced by applying a waterproof resin to at least one surface of a paper base material and drying it. The waterproof resin layer can be formed by applying a coating agent using a known coating method, for example, air knife coating, curtain coating, blade coating, gate roll coating, and die. A coating method such as coating can be used. Further, the coating layer may be a single layer or a plurality of layers, a plurality of coating layers may be sequentially coated, or two or more layers may be simultaneously coated by curtain coating or the like. good. When the coating layer is dried, the temperature of the coating layer at the outlet of the drying step is preferably adjusted to be less than 120 ° C. The coating speed at the time of coating the coating agent can be appropriately set in consideration of the viscosity of the coating agent and the target coating amount.

As a preferred embodiment, the waterproof resin layer is coated on the paper substrate by a contour coating method such as air knife coating or curtain coating, so that the amount of the coating agent applied to the surface of the paper substrate is uniform. Therefore, the thickness of the coating film becomes uniform, and the generation of blister in the coating layer can be suppressed in the drying step which is a subsequent step. In addition, the amount of the coating agent used can be reduced as compared with the contact coating method, and the manufacturing cost can be suppressed.

The waterproof resin layer coated on the paper substrate is dried. In this drying step, the temperature of the coating layer at the outlet is preferably less than 120 ° C, and even if the temperature is adjusted to 100 ° C or less. good. If the temperature of the coating layer at the outlet is 120 ° C. or higher, the incidence of blisters in the coating layer may be high, and blocking occurs in the paper wound after the coating layer is formed. Sometimes. On the other hand, the temperature of the coating layer at the outlet is preferably 60 ° C. or higher, more preferably 70 ° C. or higher, and may be 80 ° C. or higher. If the coating layer temperature at the outlet is less than 60 ° C., in some cases, not only blocking may occur in the rolled paper after the coating layer is formed, but also the coating layer is not dried. Since it is sufficient, it may not be possible to fully exhibit the waterproof performance.

The coating layer temperature at the outlet of the drying process can be set in consideration of the basis weight and the thickness of the paper substrate. For example, when the paper base material is a multi-layer paperboard and the liner of corrugated board with a large basis weight and paper thickness, the coating layer is compared with the kraft paper which is a single layer paper and has a relatively small basis weight and paper thickness. Blister tends to occur on the surface of the corrugated cardboard. The reason is not limited, but in the case of corrugated cardboard liners, the basis weight and paper thickness are often larger and the air permeability is lower than that of kraft paper, and even if the moisture content in the paper is the same as that of kraft paper, in the drying process. It is considered that blister is likely to be generated on the surface of the coating layer because a large amount of water vaporized inside the paper substrate cannot sufficiently escape. Therefore, it is preferable to adjust the coating layer temperature at the outlet of the drying step to a lower value within the above range as the basis weight and the thickness of the paper base material become larger. Here, the outlet of the drying step is the outlet of the drying zone when there is one drying zone in the drying step, and the outlet of the most downstream drying zone when there are a plurality of drying zones in the drying step. ..

The temperature of the coating layer at the outlet of the drying step can be adjusted by adjusting the drying time and the temperature of the drying zone. The drying time is determined by the feeding speed of the paper substrate, the number of drying zones, the length, the equipment capacity of the drying zones (air volume, infrared output), and the like. Further, as the drying method, a known drying method can be used, and examples thereof include a steam cylinder heating drying method, a hot air drying method, a gas type infrared drying method, an electric infrared drying method, and any of these. It can be used alone or in combination of two or more.

Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited to the following specific examples. In the present specification, unless otherwise specified, the concentration and the like are based on weight, and the numerical range includes the end points thereof.

■ Manufacture of paper packaging materials (1) Sample 1
Back layer made of 100% recycled paper pulp, middle layer made of 100% recycled paper pulp, surface layer made of 70% unbleached kraft pulp and 30% recycled paper pulp, with a weight ratio of back layer: middle layer: surface layer = 25:60:15. After making and drying with a dryer, a water repellent containing paraffin wax and rosin is applied to the surface layer on one side, dried again with a dryer, and smoothed using a calender to make the paper substrate. Manufactured (basis weight: about 280 g / m ² ).

Next, a silica-based defoaming agent (SN deformer 777) was added to 100 parts by weight of a waterproofing agent (VaporCoat2200, Michaelman, glass transition point: 39 ° C.) containing a styrene / acrylic resin and wax on the surface layer side of the paper substrate. , San Nopco) Apply 10.0 g / m ² of the coating liquid to which 0.5 parts by weight is added using an air knife, and dry with hot air so that the temperature of the coating layer at the outlet of the drying process becomes 80 ° C. Obtained (basis weight: 290 g / m ² ).
(2) Sample 2
The back layer made of 100% recycled paper pulp, the middle layer made of 100% used paper pulp, the surface layer made of 25% unbleached kraft pulp and 75% recycled paper pulp are back layer: middle layer: surface layer = 25:65:10. After the pulping and drying with a dryer, a smoothing treatment was performed using a calender to produce a paper substrate (basis weight: about 280 g / m ² ).

Next, a silica-based defoaming agent (SN Deformer 777, San Nopco) Apply 0.5 parts by weight of the coating liquid to 8.9 g / m ² using an air knife, and dry with hot air so that the temperature of the coating layer at the outlet of the drying process becomes 80 ° C. to obtain a liner. (Basis weight: 288.9 g / m ² ).
(3) Sample 3 (Comparative example)
Using the same paper base material as in Sample 2, defoaming on the surface layer side of the paper base material with respect to 100 parts by weight of a styrene-butadiene copolymer (HOJ4072, ZEON CORPORATION, glass transition point: 21 ° C.) Average particle size 3 μm, Capim NP, RCC) 65 parts by weight, heavy calcium carbonate (average particle size 8 μm, BF300, Bikita Powder Industry Co., Ltd.) 15 parts by weight, silica-based defoamer (SN deformer 777, San Nopco) ) Apply 10.0 g / m ² of the waterproof coating liquid to which 0.9 parts by weight has been added using an air knife, and dry with hot air so that the temperature of the coating layer at the outlet of the drying process becomes 80 ° C. to obtain a liner. (Basis weight: 290 g / m ² ).
(4) Sample 4 (Comparative example)
Using the same paper base material (basis weight: about 280 g / m ² ) as in sample 2, a polyethylene film with a thickness of 20 μm is laminated on one side of the paper base material, and then bonded using a roller heated to a temperature of 80 ° C. A laminated liner was obtained (basis weight: 289 g / m ² ).
(5) Sample 5 (Comparative example)
A liner was produced in the same manner as in Sample 1 except that a paint containing a waterproofing agent was not applied (basis weight: about 280 g / m ² ).
(6) Sample 6 (Comparative example)
A liner was produced in the same manner as in Sample 2 except that a paint containing a waterproofing agent was not applied (basis weight: about 280 g / m ² ).

■ Evaluation of paper packaging materials (1) Measurement of paper quality For each liner sample, the paper quality was evaluated according to the following procedure.
(Basis weight) Measured according to JIS P 8124.
(Average coating layer thickness, moisture permeability per unit coating layer thickness) Cut the sample into strips, measure the thickness of the coating layer by observing the cross section at any 10 points using an electron microscope, and average. The value was calculated and used as the average coating layer thickness. In addition, the moisture permeability per unit coating layer was obtained by dividing the moisture permeability by the average coating layer thickness.
(Oken type smoothness) According to JIS P 8155, the Oken type smoothness was measured using a digital type Oken type air permeability smoothness tester (Asahi Seiko).
(Vertical elongation, lateral elongation) Measured according to JIS P 8113.
(Specific compressive strength) The compressive strength was measured according to JIS P 8126, and this was divided by the basis weight to calculate the specific compressive strength.
(Specific burst strength) The burst strength was measured according to JIS P 8131, and this was divided by the basis weight to calculate the specific burst strength.
(Cobb water absorption) The measurement was performed by the Cobb method in accordance with JIS P 8140. That is, 100 ml of distilled water was brought into contact with the coating layer, and the weight per unit area of the absorbed water was measured after a specified time. The measurement time was not only 120 seconds (2 minutes), which is a normal specified time, but also 30 minutes.
(Humidity permeability) Measured from the coating layer side (surface layer side) in accordance with JIS Z 0208.
(Water repellency) JAPAN TAPPI Paper pulp test method No. The coating layer side was measured in accordance with 68 "Paper and Paperboard-Water Repellent Test Method".
(Contact angle) The contact angle 1 second after dropping 1 drop (50 μl) of distilled water on the sample surface was measured by a contact angle measuring device (manufactured by DAT1100 FIBRO System AB).
(Housekiyu degree) JAPAN TAPPI Paper and pulp test method No. The coating layer side was measured in accordance with 41 "Paper and Paperboard-Housden Oil Degree Test Method-Kit Method".
(Drip oil absorption) Using a microsyringe equipped with an injection needle H5, one drop of light oil No. 1 whose kinematic viscosity coefficient was adjusted to 3 cSt was dropped on the sample surface, and the time until the surface became glossy was measured. ..

(2) Folding evaluation After cutting to 50 × 50 mm and adjusting the humidity at 23 ° C. and 50% for 1 day, 3 sets of each liner sample sealed in a transparent plastic bag with a zipper were prepared. After each sealed sample is left in an environment of -18 ° C, 4 ° C or 23 ° C for 24 hours, a press machine having a V shape is used so that the coating layer side is folded at 90 ° in the flow direction of the paper. Pressurized and creases 50 mm long (same as the length of the paper) were made. After painting the creases with a water-based pen, the creases were wiped off with tissue paper, the length of the parts dyed by the cracks in the coating layer was measured, and the cracking rate was calculated using the following formula.
"Crack rate" = total length of dyed area ÷ crease length (50 mm in this evaluation) x 100
(3) Dissociation test (recyclability)
Each of the obtained liner samples was cut into a size of 25 mm square, 30 g was weighed, 1.5 L of water at 45 ° C. was added, diluted to 2%, and then dissociated for 30 minutes using a Tappi-type dissociator. Then, a sheet was formed and pressed in accordance with JIS P 8222 to obtain a wet paper, and then dried on a plate heated to 50 ° C. for 2 hours to prepare a hand-made sheet (basis weight: about 50 g /). m ² ).

Then, the state of the surface of the hand-made sheet was visually evaluated based on the following criteria.
〇: There are no noticeable foreign substances on the paper surface, and there are no particular problems in recycling.
X: Foreign matter is conspicuous on the surface of the paper, which causes a problem in recycling.
(4) Hot-melt adhesiveness test A corrugated cardboard sheet for box making was prepared from each liner sample (A flute, thickness: 5 mm). Specifically, each sample is used as a front liner, and the same liner as sample 5 is used as a back liner. The liner was glued to produce a corrugated board sheet.

Next, a thermoplastic resin (hot melt) was applied to a test piece obtained by cutting a corrugated cardboard sheet sample into a size of 50 mm in width × 150 mm in length and bonded. Specifically, prepare two test pieces of the same size in pairs, and add 0.5 g of hot melt (softening point: about 80 ° C., made by Daikyo, Eye Melt A-30) of ethylene-vinyl acetate copolymer. After applying linearly to the surface side end of the box-making liner using a glue gun, the back layer of the box-making liner was bonded so that the adhesive did not protrude from the test piece.

The bonded sample was left in an environment of −18 ° C., 4 ° C. or 23 ° C. for 24 hours, and then the sample was forcibly peeled off by human power, and the adhesive strength was evaluated from the appearance of the peeled surface. The evaluation criteria are as follows.
◎: Strongly adhered (when forced peeling, the entire bonded part is broken)
○: Well adhered (part of the bonded part is broken when forced peeling)
Δ: Adhesiveness is weak (the bonded part does not break even if it is forcibly peeled off)
(5) Waterproofness and ice resistance From the corrugated cardboard sheet manufactured in the adhesiveness test, the coated surface or the laminated layer side should be on the inside, and the corrugated cardboard box with a lid as shown in FIG. 22 cm wide x 13 cm deep, inner dimensions of the lid: 30 cm long x 24 cm wide x 13 cm deep) were prepared. Then, as shown in FIG. 2, 1 kg of ice was put in this cardboard box, covered with a lid, and then left to stand in an environment of a temperature of 5 ° C. for 24 hours.

The waterproof property was determined based on the following criteria by visually observing the state of water seepage after leaving and the shape of the box.
○: Water does not seep into the outer surface of the container or the inner surface of the container above the water surface, and the shape of the box can be maintained. ×: Water seeps out to the outer surface of the container, and the shape of the box cannot be maintained. The ice resistance was evaluated by measuring the compressive strength of the box both before and after leaving. The box compressive strength was measured according to JIS Z 0212 according to the following procedure.
(A) Set the box with the lid in the center of the compression tester.
(B) Start the compression tester and gradually apply downward force evenly to the entire upper surface of the box.
(C) The weight when the side surface of the box is deformed is read and used as the compressive strength of the box.
(D) After determining the rate of decrease in box strength before and after leaving (= box compressive strength after leaving / box compressive strength before leaving × 100), ice resistance was determined based on the following criteria.
◯: Box strength reduction rate is less than 50% ×: Box strength reduction rate is 50% or more (6) Peelability of frozen products Same as those used in the waterproof and ice resistance tests as shown in Fig. 1. A corrugated cardboard box with a lid was prepared, and the marine products were directly put into the box, and then frozen in a domestic freezer at -18 ° C for 24 hours.

In this experiment, the following were used as marine products.
(A) 1 slice of salmon fillet soaked in 3.4% saline solution (about 100 g, see Fig. 3)
(B) 40 horse mackerel (about 300 g) and 20 ml of 3.4% concentrated saline solution (see FIG. 4).
After the freezing treatment, the frozen seafood was taken out from the box and the peelability was judged based on the following criteria.
◯: The coating layer and the paper layer did not adhere to the frozen marine products and could be easily taken out.
X: A strong force was required to remove the marine products from the box when they were taken out, and a coating layer / paper layer was attached to the taken out marine products.

From the above results, it is clear that the paper packaging material (Samples 1 and 2) of the present invention has excellent foldability, recyclability, and waterproofness as compared with other samples. rice field. It was also clarified that the box compressive strength after ice was added and left for 2 hours also had sufficient strength, although a slight decrease was observed as compared with the blank product before the test. Furthermore, it was clarified that when the frozen product that had been stored in the box and then frozen was taken out, the packaging material did not adhere and the frozen product could be easily taken out. The ice-resistant liner of the present invention can be suitably used as a liner for manufacturing a box or the like for containing ice and / or a frozen product.

1 Box with lid 2 Box body 3 Lid body 4 Bottom 5 Folded line 6 Side part 7 Folded line 8 Side part 9, 10, 11 Folded line 12 Folded part 13a, 13b Projected piece part 14 Recessed part 15a, 15b Projected part 16 Folded line 17 Locking piece Parts 18a, 18b Fitting port 19 Connecting part 20 Notch 21 Top opening 22 Top plate part 23 Folded line 24 Side part 25 Folded line 26 Side part 27 Folded line 28 Folded piece 29 Folded line 30 Projection piece 31 Cutting line part 31a One of the cutting line parts Part 32 Notch 33 Opening end D Depth H Height

Claims (8)

A paper packaging material for accommodating ice and / or frozen products, wherein a waterproof resin layer is coated on at least one side of a paper substrate having two or more paper layers. The paper packaging material according to claim 1, wherein the coating amount of the waterproof resin layer is 1 to 20 g / m ² . The paper packaging material according to claim 1 or 2, wherein the waterproof resin layer contains at least one of a styrene resin, an acrylic resin, and a polyolefin resin, and a wax. The paper packaging material according to any one of claims 1 to 3, which can be adhered by a thermoplastic resin. The method for manufacturing the paper packaging material according to any one of claims 1 to 4.
The above method comprising the step of applying a waterproof resin layer to at least one side of a paper substrate. A box containing the paper packaging material according to any one of claims 1 to 4. A corrugated cardboard sheet comprising the paper packaging material according to any one of claims 1 to 4. A method of making a paper package for containing ice and / or frozen products.
The above method comprising the step of forming a paper wrapping body for accommodating ice and / or frozen products from the paper wrapping material according to any one of claims 1 to 4.

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