JP2014087469A - Film for disposable body warmer, and disposable body warmer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for a disposable body warmer, which is advantageous for cost and which can be excellently printed on the outside surface of a bag when used as the bag, and a disposable body warmer using the film.SOLUTION: A disposable body warmer film 1 (1A and 1B) is formed of: a foam layer 2 composed mainly of a polyolefin-based resin and formed of communication bubbles 24; and a non-foam layer 3 composed mainly of a polyolefin-based resin and formed of a number of through holes 31. The film has a communication structure formed of the communication bubbles 24 and the through holes 31 from one face to the other face. Moreover, the disposable body warmer is formed to include a bag body formed of the film 1 (1A, 1B), and a heating element confined in the bag body.

Description

  The present invention relates to a film suitably used for forming an inner bag of a disposable body warmer and a disposable body warmer provided with an inner bag formed of the film.

  A disposable body warmer in which a heating element containing, for example, reduced iron powder is enclosed in a breathable bag (inner bag) is widely used. As a bag body, what was formed using the packaging material which the nonwoven fabric and the resin layer laminated | stacked is common. For example, in Patent Documents 1 and 2, such a packaging material includes a method of adhering a nonwoven fabric and a resin film for forming a resin layer with an adhesive, and a resin film for forming a nonwoven fabric and a resin layer. It is described that it is manufactured by a method in which a molten resin is extruded between the two and a nonwoven fabric and a resin film are laminated through the resin.

JP 11-56894 A JP 2002-209926 A

However, in order to manufacture such a conventional packaging material, it is necessary to use an adhesive or a molten resin for the purpose of laminating these in addition to the nonwoven fabric and the resin film as described above. Cost increases. Moreover, the process of manufacturing a nonwoven fabric, the process of manufacturing a resin film, and the process of bonding these are required, and there are many total manufacturing processes for obtaining a packaging material, and productivity is low. Furthermore, since the nonwoven fabric itself used for this purpose is also generally expensive, it is disadvantageous in terms of cost.
Also, in the method of extruding the molten resin between the nonwoven fabric and the resin film, the fibers constituting the nonwoven fabric may be melted by the heat of the molten resin, or the molten resin may block the voids of the nonwoven fabric. There is also a concern that the air permeability of the packaging material may be impaired.

  Moreover, when forming a bag body using a packaging material provided with a conventional nonwoven fabric, the nonwoven fabric side is usually the outer surface side of the bag body, and the resin layer side acting as a heat seal layer is the inner surface side of the bag body However, since the outer surface of the bag made of nonwoven fabric has irregularities and fluff, it is difficult to perform good printing on the outer surface. Therefore, the name of the product, usage method, precautions, etc. should be printed on the bag made of packaging material with non-woven fabric to call attention, or the design should be enhanced by clearly printing the pattern. I could not.

  The present invention has been made in view of the above circumstances, is advantageous in terms of cost, and uses a disposable warmer film capable of good printing on the outer surface of the bag body when the bag body is formed, and the warmer film. The issue is to provide disposable warmers.

The present invention has the following configuration.
[1] A foamed layer mainly composed of a polyolefin-based resin and formed with open cells, and a non-foamed layer mainly composed of a polyolefin-based resin and formed with a large number of through holes. A disposable body warmer film in which a communication structure from one surface to the other surface is formed by through holes.
[2] The film for disposable warmers according to [1], which is a coextruded film of the foamed layer and the non-foamed layer.
[3] The film for disposable warmers according to [1] or [2], wherein the air resistance according to the Gurley tester method is 5 to 2500 seconds / 100 ml.
[4] A disposable body warmer comprising a bag formed using the disposable body warming film according to any one of [1] to [3], and a heating element enclosed in the bag.

  The film for disposable warmers of the present invention is advantageous in terms of cost, can be printed on the outer surface of the bag body when it is made into a bag body, and can be suitably used for a disposable body warmer.

It is sectional drawing which shows the structure of the film for disposable warmers which is one example of embodiment of this invention. It is a scanning electron micrograph of the surface of a foaming layer. (A) About the disposable body warmer manufactured with the film for the disposable body warmer of FIG. 1, a graph schematically showing the temperature behavior of the outer surface at the time of actual use, and (b) a conventional body with a nonwoven fabric It is a graph which shows typically the temperature behavior of the outer surface at the time of the actual use about the disposable warmer provided with the bag manufactured with the film for warmers. It is sectional drawing which shows an example of the disposable body warmer provided with the bag body manufactured with the film for disposable body warmers of FIG. It is sectional drawing which shows another example of the disposable body warmer provided with the bag body manufactured with the film for disposable body warmers of FIG. It is sectional drawing which shows the structure of the film for disposable warmers which is another one Example of this invention. It is sectional drawing which shows an example of the disposable body warmer provided with the bag body manufactured with the film for disposable body warmers of FIG.

Embodiments of the present invention will be described below with reference to the drawings.
<Disposable warmer film>
FIG. 1 is a cross-sectional view showing a configuration of a disposable warmer film (hereinafter sometimes simply referred to as a warmer film) according to an embodiment of the present invention. It has a two-layer structure composed of the foam layer 3. FIG. 2 is a scanning electron micrograph of the surface of the foam layer of the warmer film.

  Specifically, the film 1 for a warmer in the illustrated example has a polyolefin resin as a main component, a communication layer 24 is formed, a foam layer 2 having a labyrinth structure, a polyolefin resin as a main component, and a large number of through holes. It is a laminated body with the non-foamed layer 3 in which 31 is formed. Here, the communication bubbles 24 of the foam layer 2 are opened on both surfaces of the foam layer 2 and communicated from one surface to the other surface, and the through-hole 31 of the non-foam layer 3 extends in the thickness direction of the non-foam layer 3. Penetrates along. Therefore, the communication bubbles 24 of the foam layer 2 and the through holes 31 of the non-foam layer 3 communicate with each other, thereby forming a communication structure from one surface of the warmer film 1 to the other surface. Due to this communication structure, the warmer film 1 has air permeability and is suitably used as a packaging material for forming a disposable warmer bag (inner bag).

The disposable body warmer is generally put in an outer bag having an oxygen barrier property at the time of storage before use or the like, but in the present specification, when simply referred to as “bag body”, “bag body” It does not mean such an outer bag, but means an “inner bag” that contains, for example, reduced iron powder and further contains a heating element containing water, vermiculite, activated carbon, wood powder, salts, and the like.
Moreover, in this specification, a main component means the component contained exceeding 50 mass% among the whole.

  The total thickness of the warmer film 1 is not particularly limited, but is preferably 100 to 300 μm, more preferably 150 to 250 μm, and further preferably 180 to 230 μm. In such a range, the bag formed using the film 1 for a warmer has good feel such as flexibility and touch, has strength as a bag for a disposable warmer, and retains the warmth of the disposable warmer. Sustainability is also satisfied. In addition, as will be described in detail later, when forming a bag from the warmer film 1, the bag is usually made using the non-foamed layer 3 as a heat seal layer, but the heat sealability at that time is also good. It becomes.

  It is preferable that the air resistance according to the Gurley tester method is 5 to 2500 seconds / 100 ml in the film 1 for warmers. When the air resistance exceeds the above range, the disposable body warmer in which the heating element is sealed in the bag formed using the warmer film 1 has a slow oxidation reaction of the heating element, and therefore, it is difficult to reach a desired temperature. . On the other hand, if the air resistance is less than the above range, the oxidation reaction of the heating element may proceed excessively, and the temperature may rise excessively or the heat retention durability may deteriorate. When the air resistance is within the above range, the oxidation reaction is appropriately controlled, and it becomes easy to exhibit a temperature behavior suitable as a warmer.

Here, the air resistance measured by the Gurley tester method is the air resistance measured by the method described in JIS P8117 (2009), and is expressed as the time required for 100 ml of air to permeate.
Moreover, as long as the air resistance at an arbitrary measurement location is preferably in the range of 5 to 2500 seconds / 100 ml, the air resistance 1 is uniform over the entire surface of the film 1 for the warmer. It may be distributed in the surface direction.
The air resistance of the warmer film 1 can be controlled within the above range by adjusting the formation density of the through holes 31 formed in the non-foamed layer 3, the hole diameter of each through hole 31, and the like.

Next, the foam layer 2 will be specifically described.
The foam layer 2 is a layer mainly composed of a polyolefin-based resin and foamed with a foaming agent. In the foam layer 2, open cells 24 are formed. As shown in the figure, the communication bubbles 24 are formed by bubbles communicating with each other, and are open on both surfaces of the foam layer 2. In the figure, reference numeral 22 denotes an opening portion 22 in which the communication bubbles 24 are opened. In addition, not only the communication bubbles 24 but also the closed cells 26 may be formed in a part of the foam layer 2 as shown in the drawing.

  In this specification, the polyolefin-based resin is a homopolymer or copolymer of an olefin such as ethylene or propylene. Examples of such polymers include high density polyethylene, medium density polyethylene, high pressure method low density polyethylene, linear low density polyethylene, and the like; ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and the like. Copolymer of ethylene as a main component; polypropylene such as propylene homopolymer, propylene-ethylene copolymer (also referred to as propylene / ethylene-α-olefin block copolymer, so-called block PP, random PP); Can be mentioned. As the polyolefin resin forming the foamed layer 2, one or more of these polymers can be used.

  Among these polyolefin resins, they are excellent in flexibility, and open cells 24 are more easily formed by foaming than closed cells 26. Therefore, as the polyolefin resin forming the foamed layer 2, a high-pressure method low density polyethylene is used. A polyolefin resin having a main component is preferred.

As the high-pressure low-density polyethylene, known ones can be used, for example, a radical initiator such as oxygen in the air or a peroxide as a catalyst, for example, under conditions of 1000 to 4000 atmospheres, for example, 100 to 350 ° C. A polymer obtained by bulk polymerization of ethylene using a multistage gas compressor or the like can be preferably used. Moreover, as the high-pressure method low-density polyethylene, polyethylene (recycled polyethylene) that has already been subjected to a thermal history equal to or higher than the melting point may be used. Polyethylene having such a thermal history has a high melt tension because it has thermal crosslinking due to the thermal history. Therefore, when this is reused, the stability at the time of bubble formation is excellent.
The density of the high pressure method low density polyethylene is preferably 0.930 g / cm ³ or less, more preferably 0.927 g / cm ³ or less.

  Examples of the polyolefin resin forming the foam layer 2 include a mixture obtained by mixing high-density polyethylene for improving heat resistance with the above-described high-pressure method low-density polyethylene, and linear low-density polyethylene for improving moldability. It is also preferable to use a mixture in which polypropylene such as a propylene homopolymer or a propylene-ethylene copolymer (so-called block PP or random PP) is mixed in order to improve the moldability of the open cells 24.

As the high-density polyethylene, any of those produced by various production processes such as a bulk method, a solution method, a slurry method, a gas phase method using a Ziegler-Natta catalyst or a metallocene catalyst can be used.
The high-density polyethylene, density there is from 0.940 g / cm ³ to 0.970 g / cm ^3, the density of the high density polyethylene used in conjunction with high-pressure low-density polyethylene, 0.945 g / cm ³ or more Is preferably 0.955 g / cm ³ or more. When a high density polyethylene having a density of less than 0.945 g / cm ³ is used, the degree of blocking and the coefficient of friction of the foamed layer 2 may increase due to the slow crystallization rate.

  As described above, when the high-pressure method low-density polyethylene and the high-density polyethylene are used in combination as the polyolefin-based resin, the ratio of the high-density polyethylene is 5 to 30 in the total 100 mass% of the high-pressure method low-density polyethylene and the high-density polyethylene. It is preferable to be in the range of mass%.

The linear low-density polyethylene means one produced using a catalyst such as a Ziegler-Natta catalyst, a metallocene catalyst, or a single site catalyst. The production method is a bulk method, a solution method, a slurry method, a gas phase method, and the like, and is not particularly limited.
The density of the linear low density polyethylene is preferably less than 0.932 g / cm ³ , more preferably less than 0.930 g / cm ³ . The lower limit of the density is not particularly limited, but is generally 0.895 g / cm ³ or more. A density of 0.895 g / cm ³ or more can prevent blocking, transparent when less than 0.932 g / cm ^3, the impact resistance is improved.

  When the high-pressure low-density polyethylene and the linear low-density polyethylene are used in combination as the polyolefin resin, the total of 100% by mass of the high-pressure low-density polyethylene and the linear low-density polyethylene is The ratio is preferably in the range of 10 to 40% by mass.

  On the other hand, when the high-pressure method low-density polyethylene and polypropylene are used in combination as the polyolefin-based resin, the proportion of polypropylene is preferably less than 50% by mass in a total of 100% by mass of the high-pressure method low-density polyethylene and polypropylene. The mass% is more preferable. By setting it within the above range, it is possible to facilitate the formation of the communication bubbles 24 while utilizing the characteristics of the high-pressure low-density polyethylene.

The foam layer 2 may contain a resin other than the polyolefin resin as necessary, in addition to the polyolefin resin as a main component. Examples of such resins include elastomer resins such as ethylene-propylene rubber and styrene thermoplastic elastomer; adhesive resins such as modified polyolefins; polyester biodegradable resins such as polylactic acid.
In addition, the foamed layer 2 is a starch, a lubricant, a pigment, an antistatic agent, an antirust agent, an antibacterial agent, an oxygen scavenger, an extender, and an eye stain prevention, as long as the object of the present invention is not impaired. An additive such as an agent and an anti-seizure agent may be included as an optional component.
However, the proportion of the polyolefin resin in the foamed layer 2 is preferably 80% by mass or more, and more preferably 90% by mass or more.

The expansion ratio of the foam layer 2 is preferably 1.5 to 5.0 times, more preferably 2.0 to 4.0 times, and even more preferably 2.3 to 3.5 times. When the expansion ratio is in the above range, uniform open cells 24 are easily formed, and the warmer film 1 provided with the foamed layer 2 is excellent in touch and touch.
The expansion ratio is a value determined by the equation (resin density of the foam layer before foaming) / (film density of the foam layer after foaming).

  Although the thickness of the foamed layer 2 depends on the total thickness of the film 1 for warmers, it is preferably 80 to 240 μm, more preferably 120 to 250 μm, and still more preferably 150 to 180 μm. If the thickness of the foamed layer 2 is within the above range, the film 1 for a warmer equipped with the foamed layer 2 has a good feel such as flexibility and touch, and also has strength as a bag for a disposable warmer. It becomes.

There are no particular restrictions on the pore size and average pore size of the aperture 22 of the foamed layer 2, but the aperture 22 has a pore size of 100 to 3000 μm, preferably 200 to 2000 μm, and an average pore size of 200 to 500 μm, preferably 220. If it is -470 micrometers, More preferably, if it is 230-350 micrometers, the foaming layer 2 which has such an opening part 22 can be employ | adopted as a foaming layer 2 of the film 1 for warmers without a problem.
Further, if the pore diameter is less than 100 μm, communication bubbles inside the foam layer 2 tend to be difficult to be formed. On the other hand, when the pore diameter exceeds 3000 μm, the printability of the surface of the foam layer 2 tends to be lowered, or the surface appearance tends to be lowered.
In addition, a hole diameter means the diameter calculated by measuring the area of each opening part 22, and considering the opening part 22 as a perfect circle from the measured area. Moreover, an average hole diameter is an average value of all the hole diameters in the film for warmers of a measuring object.

In the foamed layer 2, the exposed surface on the side where the non-foamed layer 3 is not provided, that is, the aperture area ratio of the exposed surface 21 is not particularly limited, but is usually 30 to 80%, preferably 35 to 80%. More preferably, it is 45 to 70%. The foam layer 2 having such an open area ratio can be employed without any problem as the foam layer 2 of the warmer film 1.
In addition, an aperture area ratio is a ratio which the sum total of the area of the aperture part 22 per unit area occupies in the area of the exposed surface 21, and is a value calculated | required by following (1) Formula. Further, the area of each aperture 22 can be measured by image diffraction using SEM.

  Perforated area ratio (%) = (total area of apertures) ÷ (area of exposed surface) × 100 (1)

The porosity of the foam layer 2 is preferably 30 to 70% by volume, more preferably 35 to 65% by volume, and still more preferably 40 to 60% by volume. The bulk density of the foam layer 2 is preferably 0.20 to 0.60 g / cm ³ , more preferably 0.30 to 0.55 g / cm ³ , and still more preferably 0.30 to 0.45 g / cm ³ . cm ³ . The foamed layer 2 having such a porosity and bulk density can be employed without any problem as the foamed layer 2 of the warmer film 1.

  The porosity is a ratio of bubbles (hereinafter referred to as open cells) communicating with the outside of the foamed layer 2 through the aperture 22 in the foamed layer 2 and can be obtained by the following equation (2).

Porosity (volume%)
= (Total volume of open cells in the foam layer) / (apparent volume of the foam layer) × 100 (2)

  The hole diameter of the opening 22, the area ratio of the exposed surface 21, the porosity of the foamed layer, the bulk density, and the like are the types of polyolefin resin used for forming the foamed layer 2 and the method for producing the film 1 for a warmer described later. Can be adjusted by a combination of molding conditions and the like.

Next, the non-foamed layer 3 will be specifically described.
The non-foamed layer 3 is a non-foamed resin layer mainly composed of a polyolefin-based resin, and is provided in contact with one surface of the foamed layer 2. A large number of through holes 31 are formed in the non-foamed layer 3.

As the polyolefin-based resin for forming the non-foamed layer 3, one or more types can be used from among those exemplified above as the polyolefin-based resin used for forming the foamed layer 2, and among them, linear low density polyethylene Is preferably used. Since the linear low density polyethylene is excellent in heat sealability, when the non-foamed layer 3 is formed using the linear low-density polyethylene, the non-foamed layer 3 is used as a heat seal layer in the case of manufacturing a bag body using the film 1 for warmers. Works well. In addition, when linear low density polyethylene is used, as will be described in detail later, when the through hole 31 is drilled using an uneven roll (perforated roll) or the like, a through hole having a good shape that is difficult to tear and break is formed. Easy to form. Further, as in the case of the foamed layer 2, high-density polyethylene may be used in combination with the non-foamed layer 3 in order to improve heat resistance.
Further, as in the case of the foamed layer 2, the non-foamed layer 3 is a starch, a lubricant, a pigment, an antistatic agent, an antirust agent, an antibacterial agent, an oxygen scavenger, an increasing amount within the range not impairing the object of the present invention. An additive such as an agent, an anti-fogging agent, and a burn-in preventing agent may be included as an optional component.

  In addition, the non-foamed layer 3 may contain a resin other than the polyolefin resin as necessary, in addition to the polyolefin resin as a main component. Examples of such a resin include the same resins as those exemplified in the description of the foamed layer 2. However, the proportion of the polyolefin resin in the non-foamed layer 3 is preferably 80% by mass or more, and more preferably 90% by mass or more.

The thickness of the non-foamed layer 3 is preferably a thickness corresponding to 5 to 50% of the total thickness of the warmer film 1. When the thickness of the non-foamed layer 3 is less than 5% of the total thickness, the discharge of the raw resin of the non-foamed layer 3 is unstable in the film-forming process when the body film 1 is manufactured by coextrusion as will be described in detail later. Therefore, it tends to be difficult to form a good non-foamed layer 3. On the other hand, if the thickness of the non-foamed layer 3 exceeds 50% of the total thickness, the flexibility of the warmer film 1 provided with the non-foamed layer 3 is lowered, and the suitability as the warmer film 1 may be impaired. Further, it may be difficult to form the through hole 31.
Although the specific thickness of the non-foaming layer 3 is determined according to the total thickness of the film 1 for warmers, 20-60 micrometers is preferable, for example, 30-50 micrometers is more preferable, and 30-40 micrometers is further more preferable.

The formation density of the through holes 31 formed in the non-foamed layer 3 and the hole diameter of each hole are parameters for controlling the air resistance of the warmer film 1 as described above. Therefore, the through holes 31 are formed with a formation density and a hole diameter such that the air resistance of the warmer film is preferably in the range of 5 to 2500 seconds / 100 ml.
Although there is no restriction | limiting in particular in the formation method of the through-hole 31, after manufacturing the laminated | multilayer film of the foaming layer 2 and the non-foamed layer in which the through-hole is not formed by coextrusion etc. as mentioned later in detail, a roll Examples thereof include a method of mechanically forming the through-hole 31 using a punching means such as a concavo-convex roll having a concavo-convex surface.

<Method for producing disposable warmer film>
The film 1 for warmers in the illustrated example can be manufactured, for example, by the following method.
First, a component for a foam layer containing a polyolefin resin as a main component for forming the foam layer 2 and a component for a non-foam layer containing a polyolefin resin as a main component for forming the non-foam layer 3 are coextruded. In addition, the foam layer component is foamed. Thereby, the non-foamed layer in which the through-hole is not formed is formed on one surface of the foamed layer 2 while forming the foamed layer 2.
Next, by forming the through-hole 31 in the non-foamed layer in which no through-hole is formed, a co-extruded film having a two-layer structure of the foamed layer 2 and the non-foamed layer 3 is formed. The formed film 1 for warmers of the illustrated example can be manufactured.

  Here, when a chemical foaming method using a foaming agent is employed as the foaming method, a chemical foaming agent is added in advance to the foam layer component. On the other hand, when a physical foaming method using a gas (physical foaming agent) is adopted as the foaming method, the gas may be directly injected into the foam layer component when the foam layer component is extruded.

Examples of the chemical foaming agent include azo compounds such as azodicarbonamide, barium azocarboxylate, and azobisisobutyronitrile; nitroso compounds such as N, N′-dinitrosopentamethylenetetramine, and hydrazine such as hydrazocarbonamide. Examples thereof include organic chemical blowing agents that generate nitrogen gas such as compounds; hydrazide compounds such as p-toluenesulfonyl hydrazide and p, p′-oxy-bis (benzenesulfonyl hydrazide);
Inorganic chemical foaming agents that generate carbon dioxide such as sodium hydrogen carbonate, ammonium carbonate, ammonium hydrogen carbonate; lower aliphatic carbonization such as propane, n-butane, i-butane, n-pentane, i-pentane, hexane Hydrogen compounds; cycloaliphatic hydrocarbon compounds such as cyclobutane and cyclopentane; aromatic hydrocarbon compounds such as benzene, toluene and xylene; lower aliphatic monohydric alcohol compounds such as methanol and ethanol; lower aliphatics such as acetone and methyl ethyl ketone Ketone compounds; low-boiling halogenated hydrocarbon compounds such as chloromethyl, chloroethyl, 1-chloro-1,1-difluoroethane, and the like.
Moreover, as a physical foaming agent, the foaming agent which consists of gas, such as argon gas, helium gas, Freon gas, carbon dioxide gas (carbon dioxide gas), and nitrogen gas, is mentioned.
A foaming agent may be used independently or may be used in combination of 2 or more type. Here, the gas includes not only a gas state but also a fluid in a subcritical state and a supercritical state.

Among these foaming agents, inorganic hydrogen carbonate, which is an inorganic chemical foaming agent, carbon dioxide gas which is a physical foaming agent, nitrogen gas, and the like are preferable because they are not toxic.
The blending amount of the foaming agent can be determined in consideration of the type of polyolefin resin, the foaming rate, and the like. When the foaming layer component containing the foaming agent is 100% by mass, the amount of the foaming agent is, for example, 0.01 to The range is preferably 2.0% by mass, and more preferably 0.03-1.5% by mass.

  In addition, as described above, a resin other than the polyolefin resin may be used in combination for the foam layer component and the non-foam layer component. In addition, the foam layer component and the non-foam layer component include starches, lubricants, pigments, antistatic agents, rust preventive agents, antibacterial agents, oxygen scavengers, extenders, as long as the object of the present invention is not impaired. You may mix | blend additives, such as an anti-glare agent and an anti-burning agent, as an arbitrary component.

Coextrusion methods include water cooling and air cooling depending on the cooling method, and T die molding and inflation molding using a circular die depending on the shape of the extrusion die. Among these, any method may be adopted, but the air-cooled inflation molding method is preferable from the viewpoint of film yield and secondary processing.
In inflation molding, for example, the foam layer component is coextruded under the conditions of 150 to 220 ° C. and the non-foam layer component is 160 to 200 ° C., and the blow ratio is 1.1 to 3.0, the take-off speed is 5.0 to It is preferable to mold at a condition of 20.0 m / min. By setting it as such conditions, in the foam layer component, the foaming agent foams to form bubbles, and each bubble breaks and communicates to form a communication bubble 24. And the layer which consists of a component for non-foaming layers is formed in the thickness according to blow ratio and taking-off speed on one side of the foaming layer 2 formed in this way.

  Examples of the method for forming the through hole 31 in the non-foamed layer 3 include a mechanical method such as a hot needle method using a hot needle, a method using laser processing, in addition to the method using the uneven roll described above. Among these, the mechanical method is preferable from the viewpoint of cost. Moreover, the process of forming the through-hole 31 may be performed in-line following a co-extrusion process, or may be performed off-line.

  The film 1 for warmers described above does not require a non-woven fabric, and includes the foamed layer 2 mainly composed of a polyolefin-based resin and the non-foamed layer 3 primarily composed of a polyolefin-based resin. The outer surface of the bag body manufactured using the above has a portion formed by either the foamed layer 2 or the non-foamed layer 3. The surface of the foamed layer 2 or non-foamed layer 3 has less surface irregularities and no wings compared to the nonwoven fabric. Therefore, it is excellent in printability. Therefore, the product name of the disposable body warmer can be printed on the outer surface of the bag made of the foamed layer 2 or the non-foamed layer 3 by gravure printing, or the design can be enhanced by printing a design.

In addition, such a warmer film 1 generally does not require an expensive non-woven fabric. Moreover, since it can manufacture by coextrusion, there are few manufacturing processes. Furthermore, it is not necessary to interpose an adhesive or other resin between the foam layer 2 and the non-foam layer 3. Therefore, the warmer film 1 can be manufactured at a very low cost, which is advantageous in terms of cost.
Further, such a warmer film 1 is not defibrated unlike a nonwoven fabric. Therefore, with the use of the disposable body warmer, the defibrated fibers do not adhere to the clothing, and there is no concern about foreign matter contamination or a decrease in cleanliness even in the production factory. In addition, since the foam layer 2 and the non-foam layer 3 are mainly composed of a polyolefin-based resin, the film 1 for a warmer can be directly recycled.

Furthermore, since such a film for warmers 1 includes the foamed layer 2 in which the communication bubbles 24 are formed, it is considered that the following effects are also exhibited.
That is, since the communication layer 24 formed by connecting a plurality of bubbles is formed in the foam layer 2, a bag body is manufactured using this warmer film 1, and a heating element is enclosed in the bag body. In the case of a disposable body warmer, it is considered that the heat of the heating element is temporarily stored in the communication bubbles 24 and then gradually transferred to the outer surface of the disposable body warmer or further to the outside by, for example, radiation or convection. It is done. Therefore, the outer surface temperature (outer surface temperature) of the disposable body warmer is set to a predetermined value without overheating to a high temperature that is equal to or higher than the predetermined temperature in the initial stage of the use of the disposable body warmer, as shown in the graph of FIG. Immediately stable at temperature. Moreover, it is thought that predetermined temperature continues for a long time by the effect of the said heat storage.
On the other hand, when a bag body is manufactured using a conventional packaging material provided with a non-woven fabric and a heating element is enclosed in the bag body to form a disposable body warmer, the heat of the heating element is stored. It is thought that it is transmitted to the outside of the disposable body warmer as it is. Therefore, as shown in the graph of FIG. 3B, the surface temperature outside the disposable body warmer is overheated at the initial stage of the use of the disposable body warmer. Moreover, it is considered that the sustainability of the predetermined temperature tends to be inferior as compared with the case where the warmer film 1 as shown in FIG. 1 is employed.

<Disposable Cairo>
Disposable body warmers are classified into “Haru type” that can be used by attaching to clothing etc., and “Non-type” as in the JIS standard. As the “haru type” disposable body warmer, generally, a part of the outer surface of the bag body is provided with an adhesive layer for causing the disposable body warmer to adhere to a user's clothing or the like. The film for warmers of the present invention can be used for bags of disposable warmers of any type of “Haru type” and “No hull type”.

FIG. 4 is a view showing a “non-type” disposable warmer having a bag 40 formed using the warmer film 1 of FIG. 1 and a heating element 50 enclosed in the bag 40. is there.
The bag body 40 in this example is formed by stacking two warmer films 1 and heat-sealing the periphery so that the non-foamed layer 3 acting as a heat seal layer is on the inner side and the foamed layer 2 is on the outer side. Thus, it is formed into a bag shape.
In such a disposable body warmer, the entire outer surface of the bag body 40 is made of the foam layer 2. Various printings can be applied to the outer surface. Moreover, since this foaming layer 2 forms the outer surface of the bag body 40, this disposable warmer exhibits a warm touch.

FIG. 5 shows a bag 60 formed using the warmer film 1 (1A, 1B) of FIG. 1, an adhesive layer 70 formed on a part (one side) of the outer surface of the bag 60, and a bag. It is a figure which shows the "haru type" disposable body warmer which has the heat generating body 50 enclosed in the body 60. FIG.
The bag body 60 in this example is formed by superposing two warmer films 1A and 1B so that the non-foamed layer 3 of one warmer film 1A and the foamed layer 2 of the other warmer film 1B are in contact with each other. Is formed into a bag shape by heat sealing. In this example, the non-foamed layer 3 of the one warmer film 1A functions as a heat seal layer. An adhesive layer 70 is formed on the entire outer surface of the non-foamed layer 3 of the other warmer film 1B among the two warmer films 1A and 1B constituting the bag body 60 of this example. Yes.
Since such a disposable body warmer bag body 60 has an outer surface made of the non-foamed layer 3 and an outer surface made of the foamed layer 2, the outer surface made of the non-foamed layer 3 has an adhesive surface. The layer 70 can be formed with good adhesion. On the other hand, the outer surface made of the foam layer 2 can exhibit a warm feel when touched by the user. Various printings can also be performed on the outer surface made of the foam layer 2.

  As described above, the heating element enclosed in the bag formed using the film for warmers preferably contains reduced iron powder and further contains water, vermiculite, activated carbon, wood powder, salts, etc. However, it is possible to use other metal powder in place of the reduced iron powder, and there is no particular limitation.

  Such a disposable body warmer has a bag body having a polyolefin resin as a main component and a foam layer in which communication bubbles are formed, and a non-foam layer having a polyolefin resin as a main component and a large number of through holes formed. It is formed using the film for warmers in which the communication structure from one surface to the other surface is formed by the communication bubbles of the foam layer and the through holes of the non-foam layer. Therefore, it is advantageous in terms of cost. In addition, since the warmer film used for forming the bag body is excellent in printability, it is possible to apply various prints to the outer surface of the bag body by gravure printing, etc. It can also be provided.

As mentioned above, although embodiment was illustrated and demonstrated about this invention, this invention is not limited to the above-mentioned embodiment.
The film for warmers of the present invention has a polyolefin resin as a main component, a foamed layer in which open cells are formed, and a polyolefin resin as a main component, and a non-foamed layer in which a large number of through-holes are formed, As long as a communication structure from one surface to the other surface is formed by the communication bubbles of the foam layer and the through-holes of the non-foam layer, the multilayer structure may be a two-layer structure or more, and is not limited to the two-layer structure.
For example, as shown in FIG. 6, a warmer film 10 having a three-layer structure in which non-foamed layers 3 (3 </ b> A and 3 </ b> B) are laminated on both sides of the foamed layer 2 can be given.
By using the warmer film 10 having such a three-layer structure, for example, as shown in FIG. 7, one non-foamed layer 3A in the warmer film 10 is arranged on the inside as a heat seal layer, and the other non-foamed layer 3B. Can be formed on the outside.
Since the entire outer surface of the bag body 80 is formed by the non-foamed layer 3B, the bag body 80 of such a disposable body warmer is more elaborate and clearer than the case where the outer surface is formed by the foamed layer 2. Printing can be applied to the entire outer surface. In addition, an adhesive layer can also be formed on the outer surface with good adhesion when making “Haru Cairo”. On the other hand, since heat sealing is performed by the non-foamed layers 3A, heat sealing properties are also excellent.

  You may use the film for warmers of this invention only for a part of bag body, such as only the single side | surface side of a bag body. Moreover, there is no restriction | limiting in particular in the form of the bag formed from the film for warmers of this invention, What kind of forms, such as what is called a back-pasted what is called a palm bag, the bag which sealed the periphery, may be sufficient.

Hereinafter, the present invention will be specifically described with reference to examples.
The polyolefin resin used in the examples is as follows.
(1) Polypropylene (PP): Q100F, MFR = 0.6 g / 10 min, density = 0.88 g / cm ³ , tensile breaking stress = 12 MPa, nominal strain at tensile breaking> 300%, flexural modulus = 105 MPa, melting point (DSC method) = 142 ° C., manufactured by Sun Allomer Co., Ltd. (2) High pressure method low density polyethylene (LDPE): LF128, MFR = 0.25 g / 10 min, density = 0.922 g / cm ³ , tensile breaking stress; Nominal strain at tensile break> 400%, flexural modulus = 260 MPa, melting point (DSC method) = 111 ° C., manufactured by Nippon Polyethylene Corporation (3) linear low density polyethylene (LLDPE): UF421, MFR = 0.9 g / 10 min, density = 0.925 g / cm ^3, a tensile yield stress = 12 MPa, the strain called tensile breaking> 400%, flexural modulus = 410 MPa Melting point (DSC method) = 124 ℃, Japan Polyethylene Co., Ltd.

Example 1
Inflation film molding machine equipped with a circular die (foaming layer component extruder: φ75 mm, L / D32, non-foaming layer component extruder: φ50 mm, L / D28, lip diameter: φ300 mm, lip clearance: 0.8 mm ) And 40 parts by mass of PPPE, 60 parts by mass of LDPE, 1.0 part by mass of sodium hydrogen carbonate as a foaming agent, and a component for non-foamed layer of LLDPE at a die temperature of 200 ° C. Extrusion and blown film formation were performed. The conditions for forming the inflation film were blow ratio: 2.3 and take-up speed 7.0 m / min. At this time, the foamed layer component was foamed to obtain a laminated film having a two-layer structure in which a foamed layer having a thickness of 165 μm and a non-foamed layer having a thickness of 35 μm (no through holes were formed) were laminated. Here, the foaming ratio of the foamed layer was 2.4 times.
Next, a large number of through-holes were uniformly formed on the entire surface of the non-foamed layer by a hot needle method to obtain a film for warmers in which a communication structure from one surface to the other surface was formed.
The air resistance of the film for warmers according to the Gurley tester method was uniform over the entire surface and was 30 seconds / 100 ml.

Next, two rectangular films having a length of 90 mm and a width of 55 mm are cut from the warmer film, and the two films are overlapped so that the non-foamed layers are in contact with each other, and a heating element (reduced iron powder) is placed between the two films. , Water, vermiculite, activated carbon, wood powder, salt-containing mixture.) After placing 20 g, the periphery was heat-sealed to obtain a disposable body warmer.
The obtained disposable body warmer was immediately placed on a desk in an environment at room temperature of 23 ° C., and the temperature at the center of the upper surface of the disposable body warmer was measured with a thermocouple.
As a result, when 15 minutes passed, it was confirmed that the measured temperature exceeded 40 ° C., then stabilized at 50 ° C., and the temperature of 40 ° C. or higher could be maintained for 8 hours or longer.

  Also, when barcodes are printed on both sides of the warmer film obtained as described above by gravure printing using oil-based ink, fine barcodes can be read with sufficient darkness on either side. I was able to print.

(Example 2)
Through holes were formed at a high formation density in a part of the non-foamed layer, and through holes were formed at a low formation density in the remaining part of the non-foamed layer. The air permeation resistance by the Gurley tester method of the part where the through holes are formed at a high formation density is 6 seconds / 100 ml, and the air permeation resistance by the Gurley test machine method of the part where the through holes are formed at a low formation density is 1800. Second / 100 ml.
Except for forming the through holes in this manner, a warmer film was obtained in the same manner as in Example 1, and a disposable warmer was obtained using the warmer film.
In the same manner as in Example 1, the obtained disposable body warmer was immediately placed on a desk in an environment at room temperature of 23 ° C., and the temperature at the center of the upper surface of the disposable body warmer was measured.
As a result, when 18 minutes passed, it was confirmed that the measured temperature exceeded 40 ° C., then stabilized at 45 ° C., and the temperature of 40 ° C. or higher could be maintained for 9 hours or longer.
As in Example 1, when barcodes were printed on both sides of the warmer film by gravure printing using oil-based ink, fine barcodes could be read with sufficient density on either side. I was able to print.

In addition, about the foaming layer of the film for warmers of Examples 1 and 2, the following items were measured. The results are shown in Table 1.
(1) Measurement of average pore diameter and open area ratio of exposed surface The exposed surface of the foam layer of the film for warmers was magnified (30 times) with SEM (S-4800, manufactured by Hitachi High-Technologies Corporation). This magnified image was printed, and the unprinted portion (margin portion) was removed to obtain an original image paper. With respect to the obtained original video paper, the area of the exposed surface that was magnified was calculated, and this area was defined as _S0 .
Subsequently, the mass (M ₀ ) of the original video paper was measured with an electronic balance (AEX200B, manufactured by Shimadzu Corporation). Each portion corresponding to the opening portion of the original video paper was cut out, and the cut paper was used as the opening portion video paper. The mass of all the opening video paper was measured with an electronic balance, the weight of the opening image each paper was M _1.
And the hole area ratio was computed by the following (3) formula.

Hole area ratio (%) = (ΣM ₁ ) ÷ M ₀ × 100 (3)
(ΣM ₁ represents the sum total of the mass M ₁ of the aperture portion image paper cut from the original image paper.)

In addition, the area of each opening portion (S ₁₎ was calculated by the following equation (4).

S ₁ = M ₁ ÷ M ₀ × S ₀ (4)

For the average pore diameter of the exposed surface, the pore diameter (R ₁ ) of each aperture was calculated by the following formula (5), and based on the calculated R ₁ , the average pore diameter (R _μ ) was calculated by the following formula (6).

R ₁ = 2 × √ (S ₁ / π) (5)
R _μ = (ΣR ₁ ) ÷ n (6)
(S ₁ is the area of the aperture calculated by the above equation (4), ΣR ₁ indicates the sum of the hole diameters R ₁ of the apertures on the exposed surface, and n is the aperture of the exposed surface. Indicates the sum of numbers.)

(2) Measurement of porosity The body film for each example was cut into 10 cm × 10 cm to form test pieces, and the mass (W ₀ ) of the test pieces was measured with an electronic balance. The thickness of this test piece was measured with a thickness measuring instrument (G-6C, manufactured by Ozaki Manufacturing Co., Ltd.), and the volume (V ₀ ) of the test piece was calculated. In addition, the thickness of the non-foamed layer was calculated from the molding conditions (discharge amount, film forming width, take-off speed) and the density of the non-foamed layer component, and the volume (V _s ) of the non-foamed layer was calculated. In addition, the thickness of the non-foamed layer was calculated by the following formula (7).

Non-foamed layer thickness (cm) = Discharged amount of non-foamed layer component (g / min) ÷ {Non-foamed layer film forming width (cm) × Taking speed (cm / min) × Non-foamed layer component density ( g / cm ³ )} (7)

A vacuum constant-temperature dryer (DP23, DP23, 25 ° C.) immersed in an alcohol solution (ethanol / isopropyl alcohol mixture, density: 0.792 g / cm ³ , AP-7 (manufactured by Nippon Alcohol Sales Co., Ltd.)) The pressure was reduced to −0.09 MPa in Yamato Kagaku Co., Ltd., and the bubbles of the test piece were impregnated with an alcohol solution.
The inside of the vacuum constant temperature dryer was decompressed to -0.09 MPa in 20 seconds, held for 1 second, and then returned to normal pressure in 10 seconds. Subsequently, the test piece was taken out from the alcohol solution, and the taken out test piece was passed between two metal rolls (mass: 60 g / piece) having a width of 30 cm to remove the alcohol solution adhering to the surface of the test piece. Thus, a liquid-impregnated test piece in which bubbles were impregnated with an alcohol liquid was obtained. The exposed surface of this liquid-impregnated test piece was in a state where the hole portion was also impregnated with the alcohol liquid.
The mass (W _a ) of the obtained liquid-impregnated test piece was measured with an electronic balance, and the porosity (ε) was calculated by the following equation (8).

ε (%) = {(W _a −W ₀ ) ÷ 0.792} ÷ (V ₀ −V _s ) × 100 (8)

(3) Measurement of bulk density The film for body warmers of each example was cut into 10 cm × 10 cm to obtain test pieces, and the volume (V ₀ ) and non-existence of the test pieces were determined in the same manner as in “(2) Measurement of porosity” described above. The volume (V _s ) of the foam layer was calculated. And the volume ( _Vf ) of the foaming layer was computed by subtracting the volume of a non-foaming layer from the volume of a test piece. The mass of the test piece (W ₀₎ as well as measured by an electron balance was calculated for the non-foamed layer weight (W _s) by the following equation (9). Furthermore, the mass (W _f ) of the foamed layer was calculated from the following formula (10) from the mass (W ₀ ) of the test piece and the mass (W _s ) of the non-foamed layer determined by the formula (9).

W _s = V _s × density of component for non-foamed layer (9)
W _f = W ₀ −W _s (10)

From the calculated volume (V _f ) of the foamed layer and the mass (W _f ) of the foamed layer, the bulk density (ρ) of the foamed layer was calculated by the following formula (11).

ρ = W _f ÷ V _f (11)

1, 1A, 1B, 10 Film for warmer 2 Foam layer 3, 3A, 3B Non-foam layer 24 Open cell 31 Through hole

Claims (4)

It has a polyolefin resin as a main component, a foamed layer in which open cells are formed, and a polyolefin resin as a main component, a non-foamed layer in which a large number of through holes are formed,
A disposable warmer film in which a communication structure from one surface to the other surface is formed by the communication bubbles and the through holes.   The film for disposable body warmers according to claim 1, which is a coextruded film of the foamed layer and the non-foamed layer.   The film for disposable body warmers according to claim 1 or 2, wherein the air permeation resistance according to the Gurley tester method is 5 to 2500 seconds / 100 ml. The disposable body warmer which has the bag body formed using the film for disposable body warmers as described in any one of Claims 1-3, and the heat generating body enclosed with this bag body.