JP2018100462A - Cold insulating liner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cold insulating liner which can be manufactured at a low cost and with a small environmental load.SOLUTION: A cold insulating liner comprises: a body paper 21; an anchor layer 22 containing both a polyurethane resin with an acid group and a polyamine compound; a heat insulating layer 23 containing both a resin component 23a and metal particles 23b; and a varnish layer 24 disposed on the heat insulating layer in a net shape or a dot shape so as to cover an area from 50% or more and 80% or less of the heat insulating layer. The content of the metal particles in the heat insulating layer is between 45% or higher and 65% or lower, and the water-vapor permeability of the cold insulating liner is 1000 g/mday or lower.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cold insulation liner suitable as a material for a cold insulation container for packaging refrigerated products and frozen products.

  Conventionally, when transporting refrigerated or frozen food such as cake and ice cream, containers made of expanded polystyrene have been used for the purpose of preventing the food from being melted or damaged.

  In addition, a cardboard box using a liner in which an aluminum foil or an aluminum vapor deposition film is laminated has been proposed. Patent Document 1 describes a liner having a moisture-proof coating layer containing a synthetic resin and a flat pigment as another configuration example of a liner having the same application.

JP 2004-52192 A

A container made of expanded polystyrene needs a thickness in order to obtain a desired cold-retaining property, so that the container tends to be large, and as a result, there is a problem that transportation efficiency is deteriorated.
A liner laminated with an aluminum foil or an aluminum vapor deposited film has a problem that it is difficult to separate an aluminum portion after use, and it is difficult to recycle and has a high environmental load.
The liner described in Patent Document 1 has a problem that it is necessary to provide a moisture-proof coating layer on both sides in order to exhibit sufficient cold insulation, and the manufacturing cost is high.

  In view of the above circumstances, an object of the present invention is to provide a cold insulation liner that can be manufactured at low cost and has a low environmental load.

The present invention includes a base paper, an anchor layer formed on the base paper and containing a polyurethane resin having an acid group and a polyamine compound, and a heat insulating layer formed on the anchor layer and containing a resin component and metal particles. A varnish layer disposed on the heat insulating layer in a net or dot shape and covering a range of 50% or more and 80% or less of the heat insulating layer, and the content of the metal particles in the heat insulating layer is 45% or more and 65%. This is a cold insulation liner having a moisture permeability of 1000 g / m ² · day or less.

  According to the cold insulation liner of the present invention, it can be manufactured at low cost and the environmental load can be reduced.

It is sectional drawing which shows typically the cold insulation liner which concerns on one Embodiment of this invention. It is sectional drawing which shows typically the corrugated cardboard using the same cool liner.

An embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 is a cross-sectional view schematically showing a cold insulation liner 20 of the present embodiment. The cold insulation liner 20 includes a base paper 21, an anchor layer 22 formed on the base paper 21, a heat insulating layer 23 formed on the anchor layer 22, and a varnish layer 24 formed on the heat insulating layer 23. .

FIG. 2 is a cross-sectional view schematically showing the cardboard 10 formed using the cold insulation liner 20. The cardboard 10 has a known basic structure in which the cold insulation liner 20 is a first liner, and a core 40 is disposed between a pair of liners of the first liner and the second liner 30.
When the cardboard 10 is used, a cold insulated cardboard box in which all inner surfaces are constituted by the cold insulated liner 20 can be manufactured.
In the following description, the cold insulating liner 20 may be referred to as the first liner 20.

As the base paper 21, a liner used for general cardboard can be used. In addition to the corrugated cardboard, white board such as manila ball or coat ball can be used according to the purpose of the box.
The anchor layer 22 has a function of improving the adhesion between the base paper 21 and the heat retaining layer 23. The material of the anchor layer 22 preferably includes an acid group-containing polyurethane resin and a polyamine resin, an acid group-containing polyurethane resin and an aqueous polyurethane resin containing a polyamine compound, a water-soluble polymer, an inorganic layered mineral, More preferably, it contains As the latter material, for example, an aqueous coating agent described in JP-A-2015-44944 can be exemplified. The anchor layer formed by this water-based coating agent has an effect of improving wettability, and adhesion with the heat retaining layer of this embodiment is preferably improved.

  The average molecular weight of the material of the anchor layer is preferably in the range of 800 to 10,000. When the average molecular weight is less than 800, it is difficult to obtain sufficient moisture permeability (details will be described later). When the average molecular weight is greater than 10,000, the solubility is lowered and it becomes difficult to prepare a coating ink for forming the anchor layer.

  The heat insulating layer 23 contains a resin component 23a and metal particles 23b. As the resin component 23a, for example, a copolymer resin of urethane and vinyl vinyl acetate (urethane-vinyl acetate resin), nitrified cotton resin, polyamide resin, acrylic resin, or the like can be used.

  For example, aluminum particles are suitable as the metal particles 23b. The particle size of the metal particles 23b is preferably in the range of 10 μm to 30 μm. When the particle size is smaller than 10 μm, the particles are likely to aggregate, and when larger than 30 μm, the particles are precipitated in the ink for forming the heat retaining layer and are difficult to process.

  The content of the metal particles 23b in the heat insulating layer 23 is preferably in the range of 45% to 65%. When the content is less than 45%, it is difficult to sufficiently secure the infrared emissivity, and when it is more than 65%, the heat retaining layer becomes brittle.

  The heat retaining layer 23 may contain a curing agent such as an isocyanate based agent that cures the resin component. As a result, the heat retaining layer 23 can be hardened to prevent the metal particles from falling off, and the adhesion to the base paper 21 can be enhanced.

The varnish layer 24 is formed so as to cover a part of the heat insulating layer 23. Examples of the varnish used for the varnish layer 24 include acrylic varnish, styrene-acrylic varnish, nitrocellulose varnish, and the like. Among them, acrylic varnish is preferable.
Since the varnish layer 24 has a function of preventing the heat insulating layer 23 from being worn, a region of the heat insulating layer 24 that is not covered with the varnish layer 24 does not continue in one direction for a predetermined length (for example, 0.1 mm) or more. Preferably it is formed. Examples of the shape of the varnish layer 24 that satisfies such conditions include a net-like or dot-like distribution, and can be formed by various printing methods.

The above-described cold insulated cardboard box can be manufactured by assembling the cardboard 10 by bending or bonding so that the surface of the first liner 20 on which the varnish layer 24 is formed constitutes all inner surfaces. Thereby, the internal space in which the contents are accommodated in the cold insulation cardboard box is covered with the heat insulation layer 23 partially covered with the varnish layer 24.
Since the heat retaining layer 23 contains metal particles, the emissivity of infrared rays is reduced to less than 0.6 on the inner surface of the cold insulated cardboard box, and the inside of the container can be efficiently cooled.

In the present invention, in addition to the infrared emissivity normally considered in the cold insulation liner, the structure has also taken into consideration the moisture permeability of the cold insulation liner.
For example, when a cold-insulated cardboard box is stored in a high-temperature and high-humidity environment such as summer in Japan, high-temperature outside air containing water vapor passes through the cardboard and enters the internal space of the cold-insulated cardboard box. The entered outside air is cooled by the cold air existing in the internal space, but if the water vapor becomes water at that time, condensation heat is generated to raise the temperature of the internal space. In order to suppress the occurrence of such a phenomenon, it is preferable to suppress the water vapor transmission rate of the cardboard constituting the cold insulated cardboard box.

In the present embodiment, the moisture permeability of the cardboard 10 is reduced by the first liner 20 having the anchor layer 22 between the base paper 21 and the heat retaining layer 23. As a result, entry of water vapor into the internal space can be suppressed, and an increase in the temperature of the internal space due to condensation heat can be suitably suppressed.
From the viewpoint of suitably suppressing the temperature rise in the internal space due to condensation heat, the moisture permeability of the first liner 20 is set to 1000 g / m ² · day or less, and preferably 700 g / m ² · day or less.
When the anchor layer 22 contains a layered inorganic mineral, the moisture permeability can be further reduced by a labyrinth effect caused by the layered inorganic mineral.

  As described above, the cold insulation cardboard box according to the present embodiment is configured using the first liner 20 including the anchor layer 22 between the base paper 21 and the heat insulation layer 23, and the inner surface of the cold insulation cardboard box is the same as that of the first liner 20. Among them, the varnish layer 24 is provided on the side where the varnish layer 24 is provided, so that even in a high-temperature and high-humidity environment, low-temperature items stored in the internal space can be stored for a long time while suppressing temperature rise. it can.

  Further, since the heat retaining layer 23 of the first liner 20 can be provided by printing or the like instead of laminating films, it can be recycled as it is after the use of the cold insulated cardboard box, and the burden on the environment is small.

Furthermore, since at least a part of the heat insulating layer 23 is covered with the varnish layer 24, it is difficult for the contents, the fingers of the packing operator, or the like to directly contact the heat insulating layer 23. As a result, the wear resistance of the heat retaining layer 23 is enhanced, and exposed metal particles and the like are not easily dropped off.
Here, if the entire surface of the heat insulating layer 23 is covered with a varnish layer, the emissivity of the inner surface tends to increase. Therefore, if the coverage of the heat insulating layer 23 by the varnish layer 24 is in the range of 50% to 80%, radiation It is easy to achieve both a low rate reduction and improved wear resistance.

  With each configuration described above, the cold insulated cardboard box in this embodiment exhibits a good cold insulation performance with a much thinner configuration than expanded polystyrene, so the dimensions per unit volume can be reduced, and the transportation efficiency of the stored items Is significantly improved. Furthermore, since each layer formed on the first liner 20 can be formed by printing or coating, it can be manufactured at low cost and the environmental load can be reduced.

  The above-described cold insulation liner of the present embodiment will be further described using examples and comparative examples. However, the technical scope of the present invention is not limited by the specific contents of these examples.

Example 1
(Production of the first liner)
A C liner (trade name C160, manufactured by Koa Kogyo Co., Ltd.) was used as the base paper 21 of the first liner 20. An aqueous coating agent described in JP-A-2015-44944 was applied to one side of the base paper 21 to form an anchor layer 22 having a thickness of 2 μm. Thereafter, an ink containing urethane-vinyl chloride resin, aluminum paste and isocyanate curing agent (4 parts by mass with respect to the total of the resin and aluminum paste) is applied onto the anchor layer 22, and a heat-retaining layer having a thickness of 2 μm. 23 was formed. The ratio (content ratio) of aluminum in the dried coating film of the heat retaining layer 23 was 55% by weight (wt%). Further, an acrylic varnish was printed on the heat insulating layer 23 in a net pattern to form a 1 μm thick varnish layer 24 covering 70% of the heat insulating layer 23. Thus, the first liner 20 was produced.
(Preparation of the second liner)
The base paper 21 described above was prepared as the second liner 30.
(Production of cardboard)
A semi-chemical pulp core 40 (B flute, 120 g / m ² ) is sandwiched between the first liner 20 and the second liner 30 with the surface on which the heat retaining layer 23 and the varnish layer 24 are formed, and a corrugator is used. Corrugated cardboard 10 was produced.
(Production of cold cardboard box)
Using the above-described corrugated cardboard 10, a cold insulated cardboard box having a long side of 300 mm, a short side of 200 mm, and a height of 150 mm was manufactured with the first liner 20 as the inner surface side.

(Example 2)
A first liner of Example 2 was produced in the same procedure as in Example 1 except that a nitrified cotton resin was used instead of the urethane-vinyl acetate resin in the ink for forming the heat retaining layer 23. Thereafter, a corrugated cardboard and a cold insulated cardboard box were produced in the same procedure.

(Example 3)
A first liner of Example 3 was produced in the same procedure as Example 1 except that the isocyanate curing agent was not used. Thereafter, a corrugated cardboard and a cold insulated cardboard box were produced in the same procedure.

Example 4
A first liner of Example 4 was produced in the same procedure as in Example 1 except that the coverage of the heat insulating layer 23 by the varnish layer 24 was 50%. Thereafter, a corrugated cardboard and a cold insulated cardboard box were produced in the same procedure.

(Comparative Example 1)
A first liner of Comparative Example 1 was produced in the same procedure as Example 1 except that the anchor layer 22 was not provided. Thereafter, a corrugated cardboard and a cold insulated cardboard box were produced in the same procedure.

(Comparative Example 2)
A first liner of Comparative Example 1 was produced in the same procedure as Example 1 except that a 2 μm thick anchor layer was provided using polyvinyl alcohol (PVA). Thereafter, a corrugated cardboard and a cold insulated cardboard box were produced in the same procedure.

(Comparative Example 3)
A first liner of Comparative Example 3 was produced in the same procedure as in Example 1 except that the aluminum ratio in the dried coating film of the heat retaining layer 23 was 30 wt%. Thereafter, a corrugated cardboard and a cold insulated cardboard box were produced in the same procedure.

(Comparative Example 4)
A first liner of Comparative Example 4 was produced in the same procedure as in Example 1 except that the coverage of the heat insulating layer 23 by the varnish layer 24 was 30%. Thereafter, a corrugated cardboard and a cold insulated cardboard box were produced in the same procedure.

(Comparative Example 5)
A first liner of Comparative Example 5 was produced in the same procedure as in Example 1 except that the varnish layer 24 was formed by solid printing (coverage of the heat retaining layer 23 was 100%). Thereafter, a corrugated cardboard and a cold insulated cardboard box were produced in the same procedure.

The following items were evaluated for the corrugated cardboard or the cold insulated cardboard box in each example and comparative example.
(Evaluation of moisture permeability)
Using the first liner of each example, the moisture permeability was measured according to the moisture permeability test method of JIS Z0208 (cup method, condition B (40 ° C., 90% RH (relative humidity))).
(Evaluation of infrared emissivity)
The infrared emissivity on the surface of the first liner was measured using an emissivity measuring machine (TSS-5X, manufactured by Japan Sensor Co., Ltd.).
(Evaluation of heat insulating layer adhesion)
A tape material (18 mm width, manufactured by Nichiban Co., Ltd.) cut on the surface of the first liner was pasted by reciprocating a 2 kg roller. Thereafter, the tape material was quickly peeled off by pulling in the normal direction of the surface, and the presence or absence of adhesion of the heat insulating layer to the tape material was evaluated.
Evaluation was made in the following three stages.
X (bad): The heat insulating layer adheres to 80% or more of the tape material area.
Δ (fair): The heat insulating layer adheres to 50% or more and less than 80% of the tape material area.
○ (good): The heat insulating layer adheres to less than 50% of the tape material area.

(Evaluation of wear resistance of the first liner surface)
The surface condition after 500 reciprocations (30 reciprocations / min) were evaluated by bringing a friction piece attached with fine paper and a weight of 500 g into contact with the surface of the first liner. The reciprocating motion was performed by a Gakushin friction tester (RT-300, manufactured by Daiei Scientific Instruments).
Evaluation was made in the following three stages.
X (bad): The heat insulating layer adheres to 80% or more of the area of the friction element.
Δ (fair): The heat insulating layer adheres to 50% or more and less than 80% of the area of the friction element.
○ (good): The heat insulating layer adheres to less than 50% of the area of the friction element.
(Evaluation of cold insulation)
In each case, 1 kg of dry ice was put in the cold-insulated cardboard box, and the temperature of the internal space was continuously measured every minute in a sealed state. The time until the temperature of the internal space reached 20 ° C. was used as an index of cold insulation.

  The results are shown in Table 1.

In Examples 1 to 4, the moisture permeability was as good as 1000 g / m ² · day or less, and the cold insulation property was sufficient at around 450 minutes.
On the other hand, in Comparative Examples 1 and 2, it was considered that the cold insulation was not sufficient and the moisture permeability was high. Further, in Comparative Examples 1 and 2, the heat retaining layer did not have sufficient adhesion.
In Comparative Example 3 in which the content of the metal particles is too low, the cold insulation property was not sufficient.
In Comparative Example 4 in which the coverage of the varnish layer was too low, the heat resistance of the heat retaining layer was inferior. Moreover, in Comparative Example 5 in which the coverage of the varnish layer was too high, the infrared emissivity was high, and as a result, the cold insulation was not sufficient.
In addition, although it tried to make the ratio of aluminum in a dry coating film 70 wt% in a heat insulating layer, the film-shaped heat insulating layer was not able to be formed.

  Although one embodiment and examples of the present invention have been described above, the technical scope of the present invention is not limited to the contents of the above-described embodiments and the like, and various constituent elements can be used without departing from the spirit of the present invention. It is possible to make changes or delete them.

For example, in the above-described embodiment, the example in which the cold insulated cardboard box is formed by the cardboard provided with the first liner has been described, but instead, the box may be formed by only the first liner. Since the low moisture permeability described above is realized solely by the first liner including the anchor layer and the heat retaining layer, the same effect can be obtained even if the box is formed using only the first liner.
Further, when forming a cold insulated cardboard box with cardboard, a cardboard in which a core is sandwiched between two first liners may be used.

20 Cooling liner (first liner)
21 Base paper 22 Anchor layer 23 Thermal insulation layer 23a Resin component 23b Metal particle 24 Varnish layer

Claims (3)

With the base paper,
An anchor layer formed on the base paper and containing an acid group-containing polyurethane resin and a polyamine compound;
A heat insulating layer formed on the anchor layer and containing a resin component and metal particles;
A varnish layer disposed on the heat insulating layer in a net shape or a dot shape and covering a range of 50% to 80% of the heat insulating layer;
With
The content of the metal particles in the heat retaining layer is 45% or more and 65% or less,
The moisture permeability is 1000 g / m ² · day or less,
Cold insulation liner.   The cold insulation liner according to claim 1, wherein the anchor layer further contains a water-soluble polymer and an inorganic layered mineral.   The cold-retaining liner according to claim 1, wherein the resin component is a copolymer resin of urethane and vinyl chloride vinyl acetate.

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