JP6385701B2 - Resin composition for packaging material and laminate for packaging - Google Patents

Description

  The present invention relates to a resin composition for packaging material and a laminate for packaging.

An air-permeable laminate used for a packaging material such as food can be manufactured by pressing a roller having embossing on the laminate, for example.
On the other hand, a grassproof sheet having water permeability that does not collect rainwater on the sheet surface is also known (see, for example, Patent Documents 1 and 2).

JP 2003-333993 A JP 2003-333941 A

There is a demand for a resin composition capable of more easily producing a laminate having an appropriate air permeability (moisture permeability) for packaging materials such as foods and having excellent adhesion to a substrate.
In order to manufacture a stack having air permeability by pressing an embossed roller, a complicated manufacturing process is required.
On the other hand, the water-permeable sheets described in Patent Documents 1 and 2 are unsuitable as packaging materials for foods and the like.
The present invention has been made in view of the above, and can be manufactured by a simpler manufacturing method, and has an air permeability (moisture permeability) suitable as a packaging material for foods and the like excellent in adhesiveness to a base material. It aims at providing the resin composition for packaging materials which can obtain the laminated body which has this, and the laminated body for packaging, and makes it a subject to achieve this objective.

Specific means for achieving the above object are as follows.
<1> A resin composition for a packaging material comprising a polyolefin and a pyrolytic inorganic foaming agent, wherein the total gas generation amount is from 50 ml / kg to 1500 ml / kg.
<2> The resin composition for packaging materials according to <1>, wherein the total gas generation amount is 300 ml / kg or more and 700 ml / kg or less.
<3> The resin composition for a packaging material according to <1> or <2>, wherein the melt flow rate (JIS K7210-1999, 190 ° C., load 2160 g) of the polyolefin is 3 g / 10 min to 30 g / 10 min. object.
<4> The resin composition for packaging materials according to any one of <1> to <3>, wherein the polyolefin is low-density polyethylene.

<5> The resin composition for packaging materials according to any one of <1> to <4>, wherein the pyrolytic inorganic foaming agent is sodium hydrogen carbonate.
<6> Thermally decomposable inorganic foam provided on the base paper and at least one surface of the base paper using the resin composition for packaging materials according to any one of <1> to <5>. And a moisture-permeable film formed by foaming the agent after foaming.
It is formed by foaming a thermally decomposable inorganic foaming agent using a <7> base paper and the resin composition for packaging materials according to any one of <1> to <6> above. A laminate for packaging having a moisture-permeable film and a nonwoven fabric in this order.

<8> The moisture permeability of the packaging laminate is, 100g ^/ m 2 · day or more 4000g ^/ m 2 · day or less is the <6> or the packaging laminate according to <7>.
<9> The packaging laminate according to any one of <6> to <8>, wherein a mass per 1 m ^{2 of the} moisture-permeable film is 5 g or more and 50 g or less.
<10> The above <6> to <9>, wherein the adhesive strength between the base paper and the moisture-permeable film is 1 N or more under the conditions of a width of 15 mm, a peeling speed of 300 mm / min, and a peeling angle of 180 degrees. The laminated body for packaging as described in any one.

  According to the present invention, a resin composition for a packaging material that can be produced by a simpler production method and is excellent as a packaging material for food or the like having excellent adhesion to a substrate, and a laminate for packaging are provided. Provided.

It is principal part sectional drawing of the manufacturing apparatus which concerns on one embodiment for manufacturing the laminated body for packaging which concerns on this invention.

Hereinafter, the resin composition for packaging materials and the laminate for packaging according to the present invention will be described in detail.
<< Resin composition for packaging materials >>
The resin composition for a packaging material according to the present invention includes a polyolefin and a pyrolytic inorganic foaming agent, and has a total gas generation amount of 50 ml / kg or more and 1500 ml / kg or less.
The resin composition for a packaging material of the present invention can be applied to a base paper by a melt extrusion method to form, for example, a fixed polyolefin film on the surface of the base paper. Since air holes derived from a large number of bubbles generated from the foaming agent are formed, a packaging laminate having moisture permeability can be produced.

<Polyolefin>
Polyolefins include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, metallocene-catalyzed polyethylene, such as linear low-density polyethylene, ethylene / α-olefin copolymers based on ethylene, An ethylene / unsaturated carboxylic acid copolymer having ethylene as a main component, an ethylene / unsaturated carboxylic acid ester copolymer, and the like are included.

Examples of the ethylene / α-olefin copolymer mainly composed of ethylene include ethylene and propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and 4-methyl-1-pentene. And a copolymer with an α-olefin having 3 to 30 carbon atoms.
Examples of the ethylene / unsaturated carboxylic acid copolymer mainly composed of ethylene include unsaturated carboxylic acids such as ethylene and acrylic acid, methacrylic acid, ethacrylic acid, fumaric acid, maleic acid, monoalkyl maleate, and maleic anhydride. Examples include copolymers with acids.
Further, ethylene / unsaturated carboxylic acid ester copolymers include ethylene and unsaturated carboxylic acid esters such as alkyl acrylate, alkyl methacrylate, ethacrylic acid alkyl ester, fumaric acid dialkyl ester and maleic acid dialkyl ester. A copolymer is mentioned. In addition, as said alkyl ester, ester, such as methyl, ethyl, n-butyl, i-butyl, 2-ethylhexyl, isooctyl, can be mentioned as a suitable example.

Furthermore, multi-component copolymers such as ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester terpolymer comprising ethylene and the above unsaturated carboxylic acid and unsaturated carboxylic acid ester,
Zinc or alkali metal ionomer of ethylene / unsaturated carboxylic acid copolymer or ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester terpolymer, ethylene / vinyl acetate copolymer and partially saponified product thereof Further, ethylene / vinyl propionate copolymers and partially saponified products thereof, and ethylene polymers such as polyvinyl alcohol are also included.
Furthermore, a resin composition in which two or more of these polymers are mixed can also be used.

  Among these, low-density polyethylene such as low-density polyethylene, linear low-density polyethylene, metallocene-catalyzed polymerized linear low-density polyethylene, ethylene / unsaturated carboxylic acid copolymer such as ethylene (meth) acrylic acid copolymer, etc. Preferred are ionomers such as coalesced, ethylene (meth) acrylic acid copolymer alkaline earth metals or alkali metal ionomers, especially low density polyethylene.

A polyolefin having a melt flow rate (hereinafter also referred to as “MFR”) of 3 g / 10 min or more and 30 g / 10 min or less is preferable in that it can be easily formed into a film by a melt extrusion method that is simple in production. The MFR is more preferably 6 g / 10 min or more and 15 g / 10 min or less.
MFR is a value measured by JIS K7210-1999, 190 degreeC, and load 2160g.

<Pyrolytic inorganic foaming agent>
The pyrolytic inorganic foaming agent is an inorganic compound that generates gas at a temperature near or above the melting temperature of polyolefin (hereinafter, the minimum temperature at which the pyrolytic inorganic foaming agent foams is also referred to as “foaming temperature”). Although not particularly limited, it is preferable to select an appropriate foaming agent in consideration of the melting temperature, melt viscosity, and other physical properties of the polymer.

Typical pyrolytic inorganic foaming agents that can be used in the present invention include, for example, sodium hydrogen carbonate (bicarbonate), hydrogen carbonates such as ammonium hydrogen carbonate, carbonates such as ammonium carbonate, and ammonium nitrite. Nitrites and the like.
Furthermore, so-called water foaming using water (water vapor) can be employed, and examples of the foaming agent used include water and inorganic substances containing crystal water.
Among these, sodium hydrogencarbonate is preferable as a resin composition for packaging materials that comes into contact with food. In addition, since it has both moderate moisture permeability and interlayer adhesive strength, there are desiccants, deodorizers, oxygen scavengers, etc. that are peeled off between the perforated film and the substrate and used for foods from the perforated film. A packaging material that does not leak from the inside can be obtained, and when packaging food, etc., the perforated film and the base material are peeled off, so that the food does not leak, and appropriate moisture permeability is obtained. This is preferable.

The pyrolysis inorganic foaming agent is prepared in advance as a masterbatch mixed in polyolefin, and the masterbatch and polyolefin are mixed so that the content of the pyrolysis inorganic foaming agent is in a desired range. You may prepare the resin composition for packaging materials which concerns on this invention.
The content of the pyrolytic inorganic foaming agent in the masterbatch is, for example, suitably in the range of 5% by mass to 50% by mass.

<Total gas generation>
The resin composition for packaging materials according to the present invention has a total gas generation amount of 50 ml / kg or more and 1500 ml / kg or less.
When the total gas generation amount is less than 50 ml / kg, the moisture permeability becomes insufficient, and when used for packaging foods in which water vapor, gas, etc. are generated, condensation occurs and the quality of the food is impaired. On the other hand, when the total gas generation amount exceeds 1500 ml / kg, only a laminate having insufficient adhesion to a base material such as a base paper can be obtained. For example, when packaging food or transporting the packaged food Inside, the base material and the moisture-permeable film are peeled off.

Here, the total gas generation amount is the amount of gas (unit: ml) generated when the pyrolytic inorganic foaming agent per gram is held at 160 ° C. for 10 minutes, and the measured value is used for packaging materials. This is a value calculated by converting the amount of gas per kg of the resin composition.
The generated gas is collected according to its nature. For example, in the case of a gas that is insoluble in water, the gas is collected by replacement on the water, and in the case of a gas that is soluble in water, the gas is collected with a trap containing an appropriate solvent according to the type of gas, The volume of gas is calculated from the increase.

The total gas generation amount is more preferably from 300 ml / kg to 700 ml / kg, most preferably from 400 ml / kg to 600 ml / kg.
The content of the pyrolysis inorganic foaming agent contained in the resin composition for packaging material having the total gas generation amount as described above is a resin for packaging material prepared by changing the content of the pyrolysis inorganic foaming agent used. By preparing several types of compositions and measuring the total gas generation amount of each resin composition for packaging materials, by creating a calibration curve of the total gas generation amount with respect to the amount of pyrolytic inorganic foaming agent, It can be easily determined.
As a general guideline, for example, in the case of a resin composition for packaging material containing low density polyethylene and sodium hydrogen carbonate, 0.1 mass part or more of sodium hydrogen carbonate with respect to 100 mass parts of low density polyethylene It is selected from the range of 1 part by mass or less.

《Packaging for packaging》
The packaging laminate according to the present invention includes a base paper, a moisture-permeable film provided on at least one surface of the base paper, for example, fixed using the above-described resin composition for packaging material, Have
<Base paper>
The base paper is not particularly limited as long as it is general paper. The base paper preferably has a basis weight of 10 g / m ² or more and 200 g / m ² or less, and more preferably 20 g / m ² or more and 100 g / m ² or less.

<Moisture permeable film>
At least one surface of the base paper is provided with a moisture-permeable film (hereinafter, also simply referred to as “moisture-permeable film”) formed using the above-described resin composition for a packaging material.
Moisture-permeable film is the surface of the base paper, the packaging material for a resin composition by such laminated by melt extrusion laminator, after foaming the thermally decomposable inorganic blowing agent, can be formed by foam breaking.
In the present invention, after foaming the thermally decomposable inorganic foaming agent, the molten resin may be processed with an extrusion laminator at a temperature above the temperature at which the foaming agent decomposes.
The moisture-permeable film formed in this manner includes a large number of holes formed by the gas derived from the pyrolytic inorganic foaming agent in the film, and is thus excellent in moisture permeability.

As the pores contained in the moisture permeable film become larger, the moisture permeability becomes higher, but if it becomes too large, the function as an adhesive layer is impaired. Since the resin composition for packaging materials according to the present invention has a total gas generation amount of 50 ml / kg or more and 1500 ml / kg or less, the adhesive force between the base paper and the moisture-permeable film is sufficiently strong as a packaging laminate. In addition to being able to obtain a product, it has moisture permeability suitable for packaging of food that generates water vapor, gas, and the like.

The mass (g) per 1 m ^{2 of the} moisture-permeable film, that is, the basis weight (g / m ² ) is preferably 5 g / m ² or more and 50 g / m ² or less.
A basis weight of 5 g / m ² or more is advantageous in terms of adhesiveness. Moreover, it is advantageous in terms of moisture permeability because the basis weight is 50 g / m ² or less.

<Other configuration of laminated body for packaging>
The laminate for packaging according to the present invention preferably has a structure having a base paper, a moisture permeable film, and a nonwoven fabric in this order, particularly when used for food packaging. In the case of packaging food with the packaging laminate having this configuration, it is preferable that the nonwoven fabric be used so as to have a surface in contact with the food (hereinafter also referred to as “packaging surface”).

<Nonwoven fabric>
As the non-woven fabric, it is possible to use a non-woven fabric having a long fiber structure using a composite yarn using a polymer of two or more components such as a bimetal type (side-by-side type), a core-sheath type, a kidney type, and a matrix type. Since it has moderate fiber strength, it is preferable. From the viewpoint of non-adhesiveness (non-adhesiveness) when coming into contact with an article to be packaged, it is preferable that the surface to be the packaging surface is usually formed of a nonpolar thermoplastic resin, such as polyethylene, polypropylene, polybutene. It is preferable to use a polar material.

  In the nonwoven fabric, the portion other than the packaging surface may be made of a general-purpose thermoplastic resin that is usually used for synthetic fibers, such as polyolefins such as polyethylene, polypropylene, and polybutene, polyester (polyethylene terephthalate), styrene elastomer, polyamide, and the like. Is possible. Moreover, it is also possible to use the fiber which consists of a single polymer as a fiber which comprises a packaging surface.

Nonwoven fabrics having a weight per square meter of 3 g / m ² or more and 50 g / m ² or less are preferable because moderate heat retention and strength can be obtained, and those of 5 g / m ² or more and 30 g / m ² or less. Is more preferable.

<Moisture permeability of the laminate for packaging>
Moisture permeability of the packaging laminate according to the present invention is preferred since it is less 100g ^/ m 2 · day or more 4000g ^/ m 2 · day has an appropriate moisture permeability, also excellent in adhesion to the base material . The moisture permeability is more preferably 300 g / m ² · day to 1000 g / m ² · day.
Here, the moisture permeability is a value measured at a temperature of 40 ° C. and a relative humidity of 90% by the cup method defined in JIS Z 0208: 1976.
The moisture permeability can be adjusted by the selection and content of the pyrolytic inorganic foaming agent contained in the resin composition for packaging materials.

<Adhesive strength of laminate for packaging>
The adhesive strength between the base paper and the moisture-permeable film in the packaging laminate according to the present invention is preferably 1 N or more under the conditions of a width of 15 mm, a peeling speed of 300 mm / min, and a peeling angle of 180 degrees. In the present invention, by using an IM-20X-ST type tensile tester manufactured by Intesco Co., Ltd., the base paper of the packaging laminate and the moisture-permeable film cut into strips with a width of 15 mm are peeled at a peeling rate of 300 mm / min. It is a measured value when measured by peeling at an angle of 180 degrees.

<Manufacturing device for packaging laminate>
An example of the manufacturing apparatus for manufacturing the laminated body for packaging which concerns on this invention is shown in FIG.
FIG. 1 is a cross-sectional view of an essential part of a manufacturing apparatus (hereinafter also referred to as an “extrusion laminator”) for manufacturing a packaging laminate according to the present invention, and the size and the like are exaggerated and displayed. Yes.
In FIG. 1, an extrusion laminator 10 includes a cooling roll 1, a nip roll 2, and a T die 3. The T-die 3 is supplied with the resin composition 5 for a packaging material that has been melted by an extruder (not shown), spread in the manifold 51 in the width direction of the base paper, and extruded from the T-die 3 as a molten film 50. . The T die 3 is provided with a heater 52 so that the resin composition for packaging material in the manifold is maintained in a molten state. The molten film 50 pushed out from the T die 3 passes through the nip between the cooling roll 1 and the nip roll 2 while the molten film 50 is cooled together with the traveling base paper 4 fed out from a delivery roll (not shown). . Here, the molten film 50 extruded from the T-die 3 is foamed with the pyrolytic inorganic foaming agent, and continues to foam while flowing down the distance of the air gap 7, reaching the nip between the nip roll 2 and the cooling roll 1. . Between the nip between the nip roll 2 and the cooling roll 1, the molten film 50 containing a large number of bubbles formed by foaming the pyrolytic inorganic foaming agent and the base paper are cooled while being compressed, and the base paper 4 and the base paper Thus, a packaging laminate 6 composed of the moisture permeable film 60 fixed to one side of the No. 4 is obtained. In this way, the formation of the base paper 4 and the moisture permeable film 60 and the pressure bonding and fixing of the moisture permeable film 60 to the base paper 4 are completed at the same time, and the resulting packaging laminate is placed on a winder (not shown). It is wound up.

  When manufacturing the laminated body for packaging according to the present invention using the manufacturing apparatus shown in FIG. 1, the temperature of the resin composition 5 for a packaging material extruded from the T-die 3 is, for example, The conveyance speed of the base paper 4 is adjusted to a range of 200 ° C. to 330 ° C., for example, to a range of 50 m / min to 300 m / min, and the distance of the air gap 7 is adjusted to, for example, a range of 50 mm to 200 mm. It is preferable.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The melt flow rate (MFR) was measured by JIS K7210-1999, 190 degreeC, and load 2160g.

[Examples and Comparative Examples]
Extrusion laminator 10 (extruder: manufactured by Sumitomo Heavy Industries Modern Co., Ltd., T die: 900 mm width, processing temperature: 320 ° C., cooling roll 600 mmφ, nip roll 250 mmφ, base paper transport speed: 220 m / min) shown in FIG. The air gap was adjusted to 110 mm and set.
Low density polyethylene (LDPE, MFR: 7 g / 10 min) as a polyolefin, and a resin composition for a packaging material having a composition shown in Table 1 below using a foaming agent containing sodium hydrogen carbonate as a pyrolytic inorganic foaming agent 1 was prepared.
Similarly, azodicarbonamide, which is an organic foaming agent, is used in place of the pyrolytic inorganic foaming agent, and the others have the compositions shown in Table 1 below in the same manner as in the case of the resin composition 1 for packaging materials. A resin composition 2 for a packaging material was prepared. Furthermore, the resin composition 3 for packaging materials which has a composition of the following Table 1 which has the composition similar to the resin composition 1 for packaging materials except the point which does not contain a foaming agent was prepared.
The unit of numerical values in Table 1 relating to the composition is parts by mass.
The total gas generation amount of the prepared resin composition for packaging materials was measured by the method described above, and the results are shown in Table 1.
Using the prepared resin composition for packaging material, a 14 g / m ² moisture-permeable film is fixed and formed on one side of a base paper (basis weight 50 g / m ² ) by the above-described extrusion laminator. A laminate was produced. Table 1 also describes “processability” regarding whether or not the moisture-permeable film can be fixed and formed on the surface of the base paper when the packaging laminate is manufactured.
The moisture permeability and adhesive strength of each manufactured laminate for packaging were measured by the method described above and are shown in Table 1. The results are shown in Table 1. In addition, since the hole of the moisture-permeable film was too large and the function as an contact bonding layer was impaired, the resin composition 3 for packaging materials was not able to be measured.

As shown in Table 1, the resin composition for packaging material according to the present invention is formed on the surface of the base paper having high moisture permeability just by forming the resin composition for packaging material on the base paper by a melt extrusion method. It can be seen that it is fixed with high adhesive strength. Furthermore, it can be seen that the polyolefin film is formed with ventilation holes derived from a large number of bubbles generated from the foaming agent, so that a packaging laminate having excellent moisture permeability can be obtained. On the other hand, in Comparative Example 1 using azodicarbonamide, the moisture permeability is very large and the pores of the perforated film are large, so the function as the adhesive layer is impaired. In addition, azodicarbonamide is often used in combination with foaming aids, and depending on the type of foaming aid, it may be toxic, the odor of the generated gas will be severe, or the residual decomposition may cause deterioration or discoloration of the resin. Or cause it. In Japan, use as a food additive is prohibited, and it is not preferable to use it for packaging materials that come into direct or indirect contact with food.
Therefore, according to this invention, the laminated body suitable for packaging materials, such as foodstuffs which can be manufactured with a simpler manufacturing method, is obtained.

10 Extrusion Laminator 1 Cooling Roll 2 Nip Roll 3 T Die 4 Base Paper 50 Molten Film

Claims (9)

A moisture-permeable film having a vent hole obtained from a resin composition for a packaging material, comprising a polyolefin and a pyrolytic inorganic foaming agent, wherein the total gas generation amount is from 50 ml / kg to 1500 ml / kg;
The base paper,
The containing, moisture permeability 100g ^/ m 2 · day or more 4000g ^/ m 2 · day or less is packaging laminate.   The packaging laminate according to claim 1, wherein the total gas generation amount of the packaging material resin composition is 300 ml / kg or more and 700 ml / kg or less.   The laminate for packaging according to claim 1 or 2, wherein the polyolefin has a melt flow rate (JIS K7210-1999, 190 ° C, load 2160 g) of 3 g / 10 min to 30 g / 10 min.   The said polyolefin is a low density polyethylene, The laminated body for packaging as described in any one of Claims 1-3.   The laminate for packaging according to any one of claims 1 to 4, wherein the pyrolytic inorganic foaming agent is sodium hydrogen carbonate.   The moisture-permeable film is a moisture-permeable film formed by foaming and then foaming the thermally decomposable inorganic foaming agent of the packaging material resin composition. The laminate for packaging described.   The laminated body for packaging according to any one of claims 1 to 6, comprising the base paper, the moisture-permeable film, and a nonwoven fabric in this order. The mass per 1 m < ² > of the said moisture-permeable film is 5 g or more and 50 g or less, The laminated body for packaging as described in any one of Claims 1-7.   9. The adhesive strength between the base paper and the moisture permeable film is 1 N or more under the conditions of a width of 15 mm, a peeling speed of 300 mm / min, and a peeling angle of 180 degrees. 9. Laminate for packaging.