JP5411629B2 - Porous packaging material and disposable body warmer - Google Patents

Description

  The present invention relates to a porous packaging material. In more detail, it uses an adhesive with excellent spray coating properties, and even when heat-sealing under high temperature and high pressure, the adhesive penetrates back (the adhesive penetrates during processing from the nonwoven fabric side). The present invention relates to a porous packaging material excellent in processability and productivity that can prevent the occurrence of adhesion to a roll. Furthermore, it is related with the disposable body warmer using this porous packaging material.

  Conventionally, a porous packaging material has been widely used as a member (bag body constituting member) constituting a bag body that encloses a heating element of a disposable body warmer, a dehumidifying agent, a deodorant, and the like. For example, from the viewpoint of air permeability, a porous packaging material manufactured by bonding a porous film and a nonwoven fabric with an adhesive layer formed by fiberizing by spraying an adhesive is known. Furthermore, from the viewpoint of adhesion between the porous film and the nonwoven fabric, storage stability, heat resistance, etc., an adhesive comprising a hot-melt polyamide copolymer as a component (hereinafter referred to as “polyamide adhesive”) Is known) (see, for example, Patent Document 1).

  In recent years, the production speed has been increased for the purpose of improving productivity such as warmers. Therefore, when heat-sealing the porous packaging material, a sealing process in a short time is required, and the processing conditions are becoming higher temperature and pressure. As the heat seal processing conditions are increased in temperature and pressure, the above-mentioned conventional polyamide-based adhesive has a problem that the adhesive adheres to the processing roll. In particular, as in Patent Document 1, for the purpose of improving the flowability of the adhesive and improving the spray coatability, in an adhesive comprising a polyamide copolymer having a reduced melt viscosity at 190 ° C. as a component, The melting point of the adhesive and the melt viscosity in the vicinity of the heat seal processing temperature also tend to be lowered, and the above problem is more remarkable.

Furthermore, in order to reduce costs, it has been required to reduce the basis weight of the nonwoven fabric (for example, about ²⁰ to 35 g / m ² , and further about 25 to 30 g / m ² ). Due to the low basis weight of the nonwoven fabric, heat is easily transferred to the nonwoven fabric during the sealing process, and the thickness of the nonwoven fabric is reduced and the adhesive is easily oozed out.

  That is, the present condition is that the porous packaging material which is compatible with the spray application property (productivity) of a polyamide-type adhesive and heat seal workability has not been obtained yet.

Japanese Patent Laid-Open No. 10-328224

  Accordingly, an object of the present invention is to provide a porous packaging material excellent in heat seal processability and productivity (adhesive spray applicability) and a disposable body warmer using the same.

  As a result of intensive studies to achieve the above object, the present inventor has made a porous adhesive formed by fiberizing a hot-melt type polyamide-based adhesive containing a polyamide-based copolymer having a specific melting point and melt viscosity. The present inventors have found that a porous packaging material excellent in productivity (spray coatability) and heat seal processability can be obtained by bonding a porous film and a nonwoven fabric through an agent layer.

  That is, the present invention relates to a porous packaging material in which a porous film and a nonwoven fabric are bonded via a porous adhesive layer formed by fiberizing a hot-melt type polyamide-based adhesive containing a polyamide-based copolymer. The melting point of the polyamide adhesive is 130 to 160 ° C., and the melt viscosity of the polyamide adhesive at 190 ° C. and a load of 2.16 kg is 100 Pa · s or less. Provide packaging materials.

  Furthermore, this invention provides the disposable body warmer containing the said porous packaging material.

  Since the porous packaging material of the present invention uses a hot-melt type polyamide adhesive containing a polyamide copolymer having a specific melt viscosity, it is produced with good spray coating properties when forming an adhesive layer. Excellent in properties. In addition, since the polyamide-based adhesive whose melting point is controlled within a specific range is used, even if heat sealing is performed under high temperature and high pressure, the adhesive can be prevented from passing through the nonwoven fabric and adhering to the processing roll. Excellent heat sealability. For this reason, for example, it is useful as a component of a warmer that is produced at high speed.

It is a schematic sectional drawing which shows an example of the porous packaging material of this invention. It is a schematic sectional drawing which shows an example of the disposable body warmer of this invention.

  The porous packaging material of the present invention is a porous material in which a porous film and a nonwoven fabric are bonded via a porous adhesive layer formed by fiberizing a hot-melt type polyamide-based adhesive containing a polyamide-based copolymer. Quality packaging material.

[Porous adhesive layer]
(Polyamide adhesive)
The porous adhesive layer in the present invention is formed of a polyamide-based adhesive from the viewpoints of adhesion between the porous film and the nonwoven fabric, storage stability, and heat resistance. The polyamide-based adhesive is a hot-melt adhesive that is melt-coated.

  The polyamide adhesive contains a polyamide copolymer as an essential component. The polyamide-based adhesive may be composed only of a polyamide-based copolymer, and may contain additives such as a softener and an anti-aging agent as necessary. Although content of the polyamide-type copolymer in a polyamide-type adhesive agent is not specifically limited, 80 to 100 weight% is preferable, More preferably, it is 90 to 100 weight%.

  The polyamide-based adhesive has a melt viscosity of 100 Pa · s or less and a melting point of 130 to 160 ° C. at 190 ° C. and a load of 2.16 kg, which will be described later.

  As the polyamide copolymer, for example, a polyamide copolymer obtained by polycondensation of amines, aliphatic dibasic acid and lactam is preferable. Examples of the amines include ethylenediamine, hexamethylenediamine, xylylenediamine, 4,4′-diaminodicyclohexylamine, p, p′-methylenediamine, and alkanolamine. Of these, 1,6-hexamethylenediamine is preferred. Examples of the aliphatic dibasic acid include saturated fatty acids such as adipic acid, sebacic acid and azelaic acid; and dimers of unsaturated fatty acids such as crotonic acid, myristoleic acid, palmitoleic acid, oleic acid and elaidic acid. A dimer acid etc. are illustrated. Among these, adipic acid, sebacic acid, or a combination of both (adipic acid and / or sebacic acid) is preferable. Examples of the lactam include ε-caprolactam, γ-butyrolactam, δ-valerolactam, lauryllactam, and the like. Of these, ε-caprolactam is preferable.

  More specifically, examples of the polyamide-based copolymer include polyamide-based copolymers represented by the following formulas.

  In the above formula, x represents a positive integer and y represents a positive integer. M represents an integer of 2 to 10, and n represents an integer of 2 to 10. In addition, different m may be contained in 1 molecule and different n may be contained in 1 molecule. The polyamide copolymer may be a block copolymer or a random copolymer.

  As the polyamide copolymer in the present invention, in particular, the following structural unit derived from 1,6-hexamethylenediamine (sometimes referred to as “1,6-hexamethylenediamine unit (HMDA)”), ε -A structural unit derived from caprolactam (sometimes referred to as "caprolactam unit (CL)"), a structural unit derived from adipic acid (sometimes referred to as "adipic acid unit (AA)"), or derived from sebacic acid A polyamide-based copolymer having a structural unit (sometimes referred to as “sebacic acid unit (SA)”) as a structural unit is preferably exemplified. The composition ratio (molar ratio) of each structural unit in the polyamide-based copolymer is not particularly limited. For example, the composition ratio of a 1,6-hexamethylenediamine unit and a caprolactam unit [HMDA: CL] (molar ratio). ) Is preferably 1: 1/10 to 1:10, more preferably 1: 1/5 to 1: 5, and still more preferably 1: 1 to 1: 3. The composition ratio [AA: SA] (molar ratio) of the adipic acid unit to the sebacic acid unit is preferably 1: 1/10 to 1:10, more preferably 1: 1/5 to 1: 5, and even more preferably. Is 1: 1/3 to 1: 3. “Mole number of 1,6-hexamethylenediamine unit” and “total number of moles of adipic acid unit and sebacic acid unit” are substantially equal, and the composition ratio of the former and the latter [HMDA: (AA + SA)] (molar ratio) is The ratio is preferably 1: 1/10 to 1:10, more preferably 1: 1/5 to 1: 5, and still more preferably 1: 1/2 to 1: 2.

  Although the weight average molecular weight (Mw) of the said polyamide-type copolymer is not specifically limited, 5000-50000 are preferable, More preferably, it is 8000-20000. When the weight average molecular weight is less than 5,000, the melt viscosity is lowered and coating can be performed in a fibrous form, but the mechanical properties (tensile strength, durability) are lowered, so that the peeling force may not be obtained. On the other hand, if the weight average molecular weight exceeds 50,000, the melt viscosity is excessively increased and spray coating may not be possible. In addition, the weight average molecular weight in this invention is measured based on [GPC method (gel permeation chromatography method)].

  The polyamide copolymer can be used alone or in combination of two or more.

  The polyamide adhesive has a melt viscosity at 190 ° C. and a load of 2.16 kg (hereinafter sometimes referred to as “melt viscosity (190 ° C., 2.16 kg)”) of 100 Pa · s or less, more preferably 10 ~ 50 Pa · s. When the melt viscosity (190 ° C., 2.16 kg) exceeds 100 Pa · s, the viscosity is high and the spray applicability is lowered at a melt temperature near 190 ° C. For this reason, when the melting temperature is further increased, problems such as decomposition of the polyamide-based copolymer and thermal deformation of the nonwoven fabric and the porous film occur. On the other hand, if the pressure is less than 10 Pa · s and is too low, the polyamide-based adhesive may not be made into fibers well, which may affect the adhesion.

  The melt viscosity (190 ° C., 2.16 kg) is set according to ISO 1133 using “Melt Indexer MI-3 and MP-D” (manufactured by Gottfert) at a set temperature of 190 ° C. and a load of 2. It can be measured under the condition of 16 kg.

The polyamide-based adhesive has a melt viscosity at 130 ° C. (hereinafter sometimes referred to as “melt viscosity (130 ° C.)”) of preferably 1000 Pa · s or more, more preferably 10 ⁴ to 10 ⁹ Pa · s, Preferably, it is 10 ⁵ to 10 ⁸ Pa · s. When the melt viscosity (130 ° C.) is less than 1000 Pa · s, the adhesive layer may be melted or deformed when heat-sealing at a high temperature, and the adhesive may adhere to the work roll through the nonwoven fabric.

The polyamide-based adhesive has a melt viscosity at 100 ° C. (hereinafter sometimes referred to as “melt viscosity (100 ° C.)”) of preferably 1000000 Pa · s or more, more preferably 10 ⁶ to 10 ⁹ Pa · s, Preferably, it is 10 ⁶ to 10 ⁸ Pa · s. When the melt viscosity is less than 1000000 Pa · s, the adhesive layer may be melted or deformed when heat-sealing at a high temperature, and the adhesive may adhere to the work roll through the nonwoven fabric.

The melt viscosity (130 ° C.) and the melt viscosity (100 ° C.) are calculated as complex viscosities by forming a polyamide-based adhesive into a film and measuring solid viscoelasticity. The solid viscoelasticity measurement is performed at a measurement frequency (ω) = 1 Hz, and the complex viscosity (η ^* ) can be calculated from the following equation using the complex elastic modulus (E ^* ).
η ^* = G ^* / ω = E ^* / 3ω
G ^* : Complex elastic modulus in shear deformation ω: Measurement frequency

  Melting | fusing point of the said polyamide-type adhesive agent is 130-160 degreeC, More preferably, it is 135-155 degreeC. When the melting point is lower than 130 ° C., the adhesive easily adheres to the work roll during heat sealing, and heat seal processability is lowered. If the temperature exceeds 160 ° C., curtain spray application (coating) when the nonwoven fabric and the porous film are bonded together cannot be performed. In addition, melting | fusing point of a polyamide-type adhesive agent can be measured by differential scanning calorimetry (DSC), and is measured based on the below-mentioned method in detail.

(Porous adhesive layer)
The porous adhesive layer in the present invention is formed by fiberizing the polyamide-based adhesive by a spray method (spray coating). More specifically, the polyamide-based adhesive is formed by a method of spraying and applying fibers through hot air under heating and melting by a curtain spray method. Breathability can be maintained by applying by a spray method.

  The heating temperature (heating and melting temperature) in the curtain spray system is not particularly limited, but is preferably 180 ° C or higher, more preferably 190 to 220 ° C, and further preferably 195 to 210 ° C. When the heating temperature is less than 180 ° C., the viscosity of the polyamide-based adhesive is high, and pump clogging may occur or the coating state may deteriorate. On the other hand, if the temperature exceeds 220 ° C. and is too high, the curtain spray die may be distorted due to heat and cause a failure. Furthermore, the polyamide-based adhesive may deteriorate, and the bonding strength between the porous film and the nonwoven fabric may be weakened.

  The air flow rate (hot air flow rate) in the curtain spray method is not particularly limited, but is preferably 200 to 700 L / min, more preferably 300 to 600 L / min. Moreover, although air temperature (temperature of a hot air) is not specifically limited, 180-280 degreeC is preferable, More preferably, it is 200-260 degreeC.

  The average fiber diameter of the porous adhesive layer is preferably 15 to 500 μm, more preferably 20 to 50 μm. When the average fiber diameter is less than 15 μm, the bonding strength between the nonwoven fabric and the porous film may be lowered. Moreover, it may be a hindrance to production due to splashing around when spraying. When the average fiber diameter exceeds 500 μm, the temperature of the adhesive is transmitted to the porous film, which may cause damage. The average fiber diameter can be controlled by the air flow rate (hot air flow rate) during spray coating, the height of the curtain spray die, the spray temperature (spray die temperature), and the like.

The application amount of the polyamide-based adhesive is preferably ² to 10 g / m ² , more preferably 3 to 5 g / m ² from the viewpoints of adhesion, curtain spray processability, and the like. When the coating amount is less than 2 g / m ² , unevenness in spray coating (coating) increases, and adhesiveness may decrease. When the coating amount exceeds 10 g / m ² , Even if spray coating is possible, air permeability cannot be obtained, and heat may accumulate and be transmitted to the porous film, which may have an adverse effect.

[Porous film]
The porous film in the porous packaging material of the present invention is not particularly limited as long as it is a film-like porous substrate composed of polyolefin resin, polyester resin, polystyrene resin, or the like. Among these, a porous film composed of a polyolefin resin can be suitably used from the viewpoints of price, flexibility, and heat sealability.

  The polyolefin-based resin is a monomer of at least an olefin component (such as ethylene, propylene, butene-1, pentene-1, hexene-1, 4-methyl-pentene-1, heptene-1, octene-1, etc. α-olefin). If it is resin made into a component, it will not restrict | limit in particular.

  Examples of the polyolefin resin include low density polyethylene, linear low density polyethylene (linear low density polyethylene), medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer. In addition to ethylene resins such as coalescence (for example, ethylene-propylene copolymer), propylene resins (polypropylene, propylene-α-olefin copolymer, etc.), polybutene resins (polybutene-1, etc.), poly- 4-methylpentene-1 etc. are mentioned. Examples of polyolefin resins include ethylene-unsaturated carboxylic acid copolymers such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers; ionomers; ethylene-methyl acrylate copolymers, ethylene- Ethylene- (meth) acrylic acid ester copolymers such as ethyl acrylate copolymer and ethylene-methyl methacrylate copolymer; ethylene-vinyl alcohol copolymer and the like can also be used. As the polyolefin-based resin, an ethylene-based resin is preferable, and among them, low-density polyethylene, linear low-density polyethylene, and ethylene-α-olefin copolymer are preferable.

The density of the low density polyethylene is preferably 0.90~0.93g / cm ^3, more preferably 0.91~0.92g / cm ^3. Further, the weight average molecular weight of the low density polyethylene is less than 300,000, and is not particularly limited, but is preferably 30,000 to 200,000, and more preferably 50,000 to 60,000. The MFR at 190 ° C. of the low density polyethylene is not particularly limited, but is preferably 1.0 to 5.0 (g / 10 minutes), more preferably 2.0 to 4.0 (g / 10 minutes). It is. In addition, the density in this invention shall mean the density obtained based on JISK7112.

  The linear low-density polyethylene is a straight chain having a short chain branch (the branch length is preferably 1 to 6 carbon atoms) obtained by polymerizing ethylene and an α-olefin monomer having 4 to 8 carbon atoms. It is a chain polyethylene. As the α-olefin monomer used in the linear low density polyethylene, 1-butene, 1-octene, 1-hexene and 4-methylpentene-1 are preferable. In the linear low-density polyethylene, the content (content ratio) of the ethylene monomer repeating units with respect to the repeating units of all the constituent monomers is preferably 90 mol% or more. As the linear low-density polyethylene, from the viewpoint of improving heat-sealability at a lower temperature, a so-called metallocene linear low-density polyethylene (metallocene LLDPE) prepared using a metallocene catalyst is particularly used. preferable.

The density of the linear low-density polyethylene is preferably 0.90~0.93g / cm ^3, more preferably 0.91~0.92g / cm ^3. The weight average molecular weight of the linear low density polyethylene is less than 300,000 and is not particularly limited, but is preferably 30,000 to 200,000, more preferably 50,000 to 100,000, and further preferably 50,000 to 60,000. The MFR at 190 ° C. of the linear low density polyethylene is not particularly limited, but is preferably 1.0 to 5.0 (g / 10 minutes), more preferably 2.0 to 4.0 (g / 10 minutes).

  The ethylene-α-olefin copolymer is a copolymer of ethylene and an α-olefin monomer. The α-olefin is not particularly limited as long as it is an α-olefin other than ethylene. For example, propylene, butene-1, pentene-1, hexene-1, 4-methyl-pentene-1, heptene-1, octene- Examples thereof include α-olefins having 4 to 8 carbon atoms such as 1. Among these, an ethylene-α-olefin copolymer elastomer using butene-1 is preferable. In the ethylene-α-olefin copolymer, the content of the ethylene monomer repeating units relative to the repeating units of all the constituent monomers is preferably 60 to 95 mol%, more preferably 80 to 90 mol%. The ethylene-α-olefin copolymer plays a role of further improving the heat sealability of the porous film.

The density of the ethylene-α-olefin copolymer is less than 0.90 g / cm ³ , preferably 0.86 to 0.89 g / cm ³ , more preferably 0.87 to 0.89 g / cm ³ . is there. The weight average molecular weight of the ethylene-α-olefin copolymer is less than 300,000, preferably 50,000 to 200,000, and more preferably 80,000 to 150,000. The MFR at 190 ° C. of the ethylene-α-olefin copolymer is not particularly limited, but is preferably 1.0 to 5.0 (g / 10 min), more preferably 2.0 to 4.0 (g / 10 minutes).

  From the viewpoint of particularly improving the adhesion between the porous film and the nonwoven fabric, the porous film in the present invention preferably contains polyethylene having a weight average molecular weight of 300,000 or more among the polyolefin resins. The porous film containing polyethylene having a weight average molecular weight of 300,000 or more has a delamination force between the porous film and the nonwoven fabric as compared with a porous film not containing polyethylene having a weight average molecular weight of 300,000 or more. There is a tendency to improve (for example, the delamination force increases 1.3 to 3.5 times).

  The polyethylene having a weight average molecular weight of 300,000 or more may be a polymer having ethylene as a main monomer component, may be a homopolymer of ethylene, or α having 3 to 8 carbon atoms and ethylene. -It may be a copolymer of olefin monomers. Among these, an ethylene-propylene copolymer is preferable. In the said polyethylene, 90-100 mol% is preferable for content of the repeating unit of the ethylene monomer with respect to the repeating unit of all the constituent monomers.

  The weight average molecular weight of the polyethylene having a weight average molecular weight of 300,000 or more is preferably 300,000 to 2,500,000, more preferably 400,000 to 2,000,000, and even more preferably 500,000 to 1,500,000. In the case of polyethylene having a weight average molecular weight of less than 300,000, the effect of improving the delamination force between the porous film and the nonwoven fabric may not be obtained. If the weight average molecular weight exceeds 2.5 million, extrusion failure and generation of defects (fish eyes) may be problematic.

Density polyethylene weight average molecular weight described above is 300,000 or more, from the viewpoint of stretchability, preferably 0.92~0.96g / cm ^3, more preferably at 0.93~0.955g / cm ³ .

  The content of polyethylene having a weight average molecular weight of 300,000 or more in the porous film is preferably 1% by weight or more, more preferably 1%, based on all polymer components (100% by weight) constituting the porous film. -40% by weight, more preferably 5-30% by weight. If the said content is less than 1 weight%, the effect which improves the delamination force of a porous film and a nonwoven fabric may not be acquired. Moreover, when the said content exceeds 40 weight%, generation | occurrence | production of a defective extrusion and a fault (fish eye) may become a problem.

  Although the porous film in this invention is not specifically limited, It is preferable to contain an inorganic filler. The inorganic filler plays a role of making the film porous by generating voids (pores) around the filler by stretching. Examples of the inorganic filler include, for example, talc, silica, stone powder, zeolite, alumina, aluminum powder, iron powder, and carbonate metal salts such as calcium carbonate, magnesium carbonate, magnesium carbonate-calcium, and barium carbonate; magnesium sulfate, Metal salts of sulfuric acid such as barium sulfate; metal oxides such as zinc oxide, titanium oxide and magnesium oxide; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, calcium hydroxide and barium hydroxide; oxidation Examples thereof include metal hydrates (hydrated metal compounds) such as magnesium-nickel oxide hydrate and magnesium oxide-zinc oxide hydrate. The shape of the inorganic filler is not particularly limited, and a flat plate shape, a granular shape, and the like can be used. From the viewpoint of forming a void (hole) by stretching, a granular shape (particle shape) is preferable. That is, as the inorganic filler, inorganic particles (inorganic fine particles) made of calcium carbonate are preferable.

  Although it does not specifically limit as a particle size (average particle diameter) of the said inorganic filler (inorganic fine particle), For example, it is preferable that it is 0.1-10.0 micrometers, More preferably, it is 0.5-5.0 micrometers. is there. If the particle size of the inorganic filler is less than 0.1 μm, the void formability may be deteriorated, and if it exceeds 10.0 μm, the film formation may be broken and the appearance may be deteriorated.

  Although content of the said inorganic filler (inorganic fine particle) is not specifically limited, For example, it is preferable that it is 50-150 weight part with respect to all the polymer components (100 weight part) which comprise a porous film, More Preferably it is 80-120 weight part. If the content of the inorganic filler is less than 50 parts by weight, the void formability may be reduced, and if it exceeds 150 parts by weight, the film formation may be broken and the appearance may be deteriorated.

  In the porous film of the present invention, various additives such as a colorant, an antioxidant, an antioxidant, an ultraviolet absorber, a flame retardant, and a stabilizer are blended within a range that does not impair the effects of the present invention. Also good.

  The porous film in the present invention can be produced by a melt film formation method (T-die method, inflation method). Of these, the T-die method is preferable. For example, the above polyolefin resin, inorganic filler, and, if necessary, various additives are mixed and dispersed by biaxial kneading extrusion, once pelletized, and then melt extruded by a single screw extruder. An unstretched film is produced, and the unstretched film is made porous by stretching uniaxially or biaxially. When a porous film is used as a laminated film, a coextrusion method can be preferably used.

  In the production of the porous film, the extrusion temperature is preferably 170 to 270 ° C, more preferably 180 to 260 ° C, still more preferably 230 to 250 ° C. Moreover, 5-25 m / min is preferable for the taking-up speed at the time of unstretched film preparation, and 5-40 degreeC is preferable for take-off roll temperature (cooling temperature), More preferably, it is 20-30 degreeC.

  As a method of stretching the unstretched film uniaxially or biaxially (sequentially biaxially, simultaneously biaxially), a known and commonly used stretching method such as a roll stretching method or a tenter stretching method can be used. The stretching temperature is preferably 50 to 100 ° C, more preferably 60 to 90 ° C. From the viewpoints of making it porous and stable film formation, the draw ratio (uniaxial direction) is preferably 2 to 5 times, more preferably 3 to 4 times. In the case of biaxial stretching, the area stretch ratio is preferably 2 to 10 times, more preferably 3 to 7 times.

  The thickness in particular of the said porous film is not restrict | limited, For example, 30-150 micrometers is preferable, More preferably, it is 50-120 micrometers.

  As described above, from the viewpoint of particularly improving the adhesion between the porous film and the nonwoven fabric, the porous film in the present invention is produced using at least the polyethylene having a weight average molecular weight of 300,000 or more as a raw material. It is preferable. For example, polyethylene having a weight average molecular weight of 300,000 or more, polyethylene having a weight average molecular weight of less than 300,000 (in particular, low density polyethylene, linear low density polyethylene, ethylene-α-olefin copolymer is preferable) and inorganic An unstretched film is produced using at least a filler, and the unstretched film is made porous by stretching uniaxially or biaxially to produce a porous film. In the above case, the content of polyethylene having a weight average molecular weight of 300,000 or more in the polymer raw material (100% by weight) used for the production of the porous film is preferably 1% by weight or more, more preferably 1 to 40% by weight. %, More preferably 5 to 30% by weight.

[Nonwoven fabric]
The nonwoven fabric in the porous packaging material of the present invention is not particularly limited. For example, a polyamide-based nonwoven fabric (nylon nonwoven fabric, etc.), a polyester-based nonwoven fabric (polyethylene terephthalate (PET) nonwoven fabric, polybutylene terephthalate (PBT) nonwoven fabric, etc.) ), Known non-woven fabrics such as polyolefin-based non-woven fabrics and rayon non-woven fabrics (non-woven fabrics made of natural fibers, non-woven fabrics made of synthetic fibers, etc.). Among these, a polyamide-based nonwoven fabric is preferable from the viewpoint of adhesion with a polyamide-based adhesive, and a nylon nonwoven fabric (nylon-based nonwoven fabric) is more preferable.

  Further, the production method of the nonwoven fabric is not particularly limited, and may be, for example, a nonwoven fabric produced by a spunbond method (spunbond nonwoven fabric) or a nonwoven fabric produced by a spunlace method (spunlace nonwoven fabric). May be. Among these, a spunbonded nonwoven fabric is preferable from the viewpoint of adhesiveness. In addition, the nonwoven fabric may have any form of a single layer or a lamination.

In the nonwoven fabric, the fiber diameter, fiber length, basis weight, etc. are not particularly limited. The basis weight is preferably about ²⁰ to 100 g / m ² , more preferably about ²⁰ to 80 g / m ² . From the viewpoint of cost reduction, the basis weight is preferably ²⁰ to 35 g / m ² , more preferably 25 to 30 g / m ² . In particular, when a nonwoven fabric having a basis weight of 20 to 35 g / m ² is used, the effect of the present invention (preventing the adhesive from adhering to the roll through the nonwoven fabric) becomes significant. A nonwoven fabric may be comprised only from 1 type of fiber, and may be comprised combining multiple types of fiber.

[Porous packaging material]
The porous packaging material of the present invention includes the porous adhesive layer (the porous adhesive layer formed by fiberizing a hot-melt type polyamide-based adhesive containing a polyamide-based copolymer). It is a porous packaging material in which a film and the nonwoven fabric are bonded. FIG. 1 shows an example (schematic cross-sectional view) of the porous packaging material of the present invention. In the porous packaging material 1 of the present invention, a porous film 11 and a nonwoven fabric 13 are bonded together via a porous adhesive layer 12.

  In the porous packaging material, the porous film and the non-woven fabric are laminated by a method of bonding via a porous adhesive layer. In the present invention, as an adhesive for forming a porous adhesive layer, since a hot-melt type polyamide-based adhesive is used, it can be applied by being melted by heat without using a solvent, It has the advantage that an adhesive layer can be formed by directly applying to a nonwoven fabric. Furthermore, when a bag body is formed by heat-sealing the porous packaging material, the heat-sealing portion has an advantage that the nonwoven fabric and the porous film are more strongly bonded by heat-sealing.

  Specific examples of the method of laminating the porous film and the nonwoven fabric include a method in which a polyamide-based adhesive is applied onto the nonwoven fabric by spray coating, and then the porous film is bonded. By having the said structure, the effect that it is excellent in air permeability is exhibited.

  In the porous packaging material of the present invention, the peel force between the porous film and the nonwoven fabric (tensile speed 300 mm / min, T-type peel test) is 0.4 to 3.0 N / 25 mm (or the nonwoven fabric in the T-type peel test). Is preferable, and more preferably 0.5 to 2.0 N / 25 mm. (If the peel force exceeds 3.0 N / 25 mm, the nonwoven fabric often breaks during the T-type peel test.) If the peel force (also referred to as delamination force) is less than 0.4 N / 25 mm. In some cases, delamination between the porous film and the nonwoven fabric may occur during production, processing, and distribution.

[Bag body]
The porous packaging material of the present invention is not particularly limited as long as it is a packaging material, but is preferably used as a packaging material (bag body) having a bag-like structure. That is, the porous packaging material of the present invention can be used as at least a part of a member (bag member) constituting the bag. Moreover, since workability is good also at the time of high temperature and / or high pressure heat sealing, it is preferably used as a packaging material (heat sealing packaging material) to be subjected to heat sealing. That is, the porous packaging material of the present invention is particularly preferably used as a packaging material (packaging material for a heat sealing bag member) manufactured to a bag body by heat sealing. Furthermore, it is preferably used as a member constituting a bag body having air permeability from the viewpoints of air permeability and oxygen supply to the heating element. The porous packaging material of the present invention is not particularly limited, but is preferably used as a constituent member of a disposable body warmer, a dehumidifying agent, a deodorant, a fragrance, an oxygen scavenger, etc., and particularly preferably used as a constituent member of a disposable body warmer. It is done.

  The method for processing the porous packaging material into a bag is not particularly limited, and examples thereof include a method of forming a bag by bonding with an adhesive, a method of forming a bag by heat sealing, and the like. Among these, from the viewpoint of cost, workability, and the like, a method of forming a bag body by heat sealing is preferably used. As long as the porous packaging material of the present invention is used as at least a part of the bag body, the bag body can be configured by heat-sealing the porous packaging material of the present invention and other packaging materials. it can.

The method and apparatus for heat sealing when forming a bag body using the porous packaging material of the present invention is not particularly limited, but pressure bonding with a heat sealer is preferable. The heat seal temperature in that case is preferably 90 to 250 ° C, more preferably 130 to 200 ° C. The heat seal pressure is preferably 0.5 to 30 kg / cm ² , more preferably 2.0 to 10 kg / cm ² . Moreover, 0.02-1.0 second is preferable and, as for heat sealing time, More preferably, it is 0.05-0.5 second.

  The heat seal strength (measured by a T-type peel test under the condition of a tensile speed of 300 mm / min) of the heat seal portion of the bag formed using the porous packaging material of the present invention is, for example, that the bag is used as a disposable body warmer. In that case, 5.0 N / 25 mm or more is preferable, and more preferably 8.0 N / 25 mm or more. When the heat seal strength is less than 5.0 N / 25 mm, there may be a problem that the porous film and the nonwoven fabric layer are peeled off at the heat seal portion when used.

  In heat seal processing in the production of disposable body warmers, etc., since heat seal processing in a short time is required from the viewpoint of productivity improvement, strong heat seal conditions (heat seal temperature: high temperature, heat seal pressure: high pressure) are required. Desired. As described above, when the heat seal condition becomes high temperature and / or high pressure, the adhesive layer is deformed when processing a porous packaging material in which a nonwoven fabric and a porous film are bonded using a hot melt adhesive. And the problem (back-through) that an adhesive agent passes through a nonwoven fabric and adheres to a processing roll (heat seal roll etc.) becomes easy to occur. As a hot-melt type adhesive, it is effective to use an adhesive having a low melt viscosity (for example, a melt viscosity at 190 ° C.) in order to improve spray applicability. However, since such an adhesive generally tends to have a low melting point, the adhesive layer is more easily deformed at the time of high-temperature or high-pressure heat sealing, and the above-described problem of strikethrough occurs more significantly. On the other hand, when the heat seal conditions are weak (heat seal temperature: low temperature, heat seal pressure: low pressure), the heat seal strength tends to decrease, making it difficult to heat seal in a short time. This is a problem in terms of productivity.

  In contrast, in the porous packaging material of the present invention, a specific polyamide adhesive having a relatively high melting point is used as the adhesive constituting the adhesive layer while keeping the melt viscosity at 190 ° C. low. Therefore, it has become possible to achieve both the spray applicability at the time of manufacturing the porous packaging material and the characteristic that the adhesive hardly adheres to the processing roll even under relatively strong heat seal conditions. Therefore, if the porous packaging material of the present invention is used, the heat sealing process conditions can be set strongly, heat sealing can be performed in a short time, which is advantageous from the viewpoint of productivity and cost.

  Examples of the contents to be enclosed in the bag include a heating element (a heating element for a disposable body warmer), a dehumidifying agent, a deodorant, a fragrance, and an oxygen scavenger. In the present invention, among the above, a heating element can be enclosed and used.

[Disposable body warmer]
The disposable body warmer of the present invention can be formed by using the porous packaging material of the present invention as at least a part of the constituent members (preferably a bag constituent member). Specifically, the porous packaging material of the present invention and the porous packaging material of the present invention are heat sealed to form a bag, or the packaging other than the porous packaging material of the present invention and the porous packaging material of the present invention. The disposable body warmer of the present invention can be formed by heat-sealing a material (sometimes referred to as “other packaging material”) to form a bag body and enclosing a heating element inside the bag body. FIG. 2 is a schematic cross-sectional view showing an example of a disposable body warmer using the porous packaging material of the present invention and other packaging materials. The disposable body warmer of the present invention shown in FIG. 2 heats the porous packaging material 1 of the present invention and the other packaging material 2 (consisting of the base material 21 and the pressure-sensitive adhesive layer 22) and the end portion (heat seal portion 4). A bag is formed by sealing, and the heating element 3 is enclosed inside. As described above, in the disposable body warmer for use in which an adhesive layer is provided on one surface and is attached to an adherend such as a body or clothing, the porous packaging material of the present invention is capable of supplying oxygen to the heating element. From this point of view, it is preferably used at least as a member (so-called surface material) opposite to the side in contact with the adherend.

  The other packaging materials are not particularly limited, and well-known and commonly used breathable and non-breathable packaging materials can be used. As other packaging materials, commercially available products can also be used suitably. “Nitotac” manufactured by Nitto Lifetech Co., Ltd. (Cairo adhesive which is a laminate of a polyolefin base material having heat sealability and a SIS adhesive layer) Sheet) and the like are available.

  The base material in the other packaging material is preferably composed of, for example, a heat seal layer, a fiber layer (for example, a nonwoven fabric layer), a film layer, or the like. More specifically, examples of the substrate include a laminate of a heat seal layer (including a heat sealable film layer) and a fiber layer, a laminate of a heat seal layer and a film layer having no heat sealability, and the like. It is done.

  The above-mentioned thing can be used as a nonwoven fabric used for the said nonwoven fabric layer.

  The heat seal layer is a layer having heat seal properties, and the resin exemplified in the porous film is preferably used. The heat seal layer may have either a single layer or a multiple layer form.

  As the film layer, a conventionally used film layer can be used. As the resin for forming the film layer, for example, a polyester resin, a polyolefin resin, or the like can be used. Among these, polyolefin resins can be suitably used from the viewpoints of price and flexibility. As the polyolefin-based resin, it is possible to use a resin similar to the resin exemplified in the porous film. The film layer may be a single layer film or a laminated film having two or more layers. Further, the film may be a non-oriented film or a film stretched and oriented in a uniaxial or biaxial direction, but is preferably a non-oriented film.

  The thickness in particular of the said base material is not restrict | limited, For example, about 10-500 micrometers, Preferably it is about 12-200 micrometers, More preferably, it is about 15-100 micrometers. The base material may be subjected to various treatments such as back treatment and antistatic treatment as necessary.

  The pressure-sensitive adhesive layer in the other packaging material plays a role of sticking the bag body to the adherend during use. The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. For example, a rubber-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive (acrylic urethane-based pressure-sensitive adhesive), an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, Known pressure-sensitive adhesives such as polyamide-based pressure-sensitive adhesives, epoxy-based pressure-sensitive adhesives, vinyl alkyl ether-based pressure-sensitive adhesives, and fluorine-based pressure-sensitive adhesives can be used. Moreover, the said adhesive can be used individually or in combination of 2 or more types. Among these, rubber-based and urethane (acrylic urethane) pressure-sensitive adhesives are particularly preferable.

  Examples of the rubber-based pressure-sensitive adhesive include rubber-based pressure-sensitive adhesives using natural rubber and various synthetic rubbers as a base polymer. Examples of rubber adhesives based on synthetic rubber include styrene / butadiene (SB) rubber, styrene / isoprene (SI) rubber, styrene / isoprene / styrene block copolymer (SIS) rubber, styrene / butadiene / Styrene block copolymer (SBS) rubber, Styrene / ethylene / butylene / styrene block copolymer (SEBS) rubber, Styrene / ethylene / propylene / styrene block copolymer (SEPS) rubber, Styrene / ethylene / isoprene / styrene block Copolymer (SIPS) rubber, styrene rubber (also called styrene elastomer) such as styrene / ethylene / propylene block copolymer (SEP) rubber, polyisoprene rubber, recycled rubber, butyl rubber, polyisobutylene, and their modifications Body And the like. Of these, styrene elastomer pressure-sensitive adhesives are preferable, and SIS and SBS are more preferable. These 1 type or 2 or more types of mixtures can be selected suitably, and can be used.

  As the urethane-based pressure-sensitive adhesive, known and commonly used urethane-based pressure-sensitive adhesives can be used, and are not particularly limited. For example, the urethane-based materials exemplified in Japanese Patent No. 3860880 and Japanese Patent Application Laid-Open No. 2006-288690. An adhesive or the like can be suitably used. Among these, an acrylic urethane pressure-sensitive adhesive composed of isocyanate / polyester polyol is preferable. Moreover, it is preferable that the said acrylic urethane type adhesive is a foaming type adhesive which has a bubble from a viewpoint of reducing the irritation | stimulation to the skin at the time of sticking directly on skin. Such a foaming type pressure-sensitive adhesive can be produced by, for example, a method of adding a known and usual foaming agent to the pressure-sensitive adhesive.

  In addition, the above-mentioned pressure-sensitive adhesive may be any pressure-sensitive adhesive, for example, a pressure-sensitive pressure-sensitive adhesive (thermosetting pressure-sensitive adhesive that cures by crosslinking or the like caused by heating). Agent) and a pressure-sensitive adhesive (active energy ray-curable pressure-sensitive adhesive) having active energy ray curability that is cured by crosslinking or the like caused by irradiation with active energy rays. Among these, an active energy ray-curable pressure-sensitive adhesive is preferable from the viewpoint of being solvent-free and not being excessively impregnated into a nonwoven fabric or a porous base material. For the thermosetting pressure-sensitive adhesive, a crosslinking agent, a polymerization initiator, or the like for exhibiting thermosetting properties is appropriately used. For the active energy ray-curable pressure-sensitive adhesive, a cross-linking agent or a photopolymerization initiator for exhibiting active energy ray curability is appropriately used.

  The pressure-sensitive adhesive layer may be protected by a known or commonly used release film (separator) until use.

  The disposable warmer of the present invention is stored in an outer bag and sold as a warmer product. The base material (outer bag base material) constituting the outer bag is not particularly limited, and examples thereof include plastic base materials and fiber base materials (nonwoven fabric base materials and woven base materials made of various fibers). Metal base materials (such as metal foil base materials made of various metal components) can be used. As such a base material, a plastic base material can be suitably used. Examples of plastic base materials include polyolefin base materials (polypropylene base materials, polyethylene base materials, etc.), polyester base materials (polyethylene terephthalate base materials, etc.), styrene base materials (polystyrene base materials, Styrene copolymer base materials such as acrylonitrile-butadiene-styrene copolymer base materials), amide resin base materials, acrylic resin base materials and the like. The outer bag base material may be a single layer or a laminate. The thickness in particular of an outer bag is not restrict | limited, For example, 30-300 micrometers is preferable.

  The outer bag preferably has a layer (gas barrier layer) having a characteristic (gas barrier property) that prevents permeation of gas components such as oxygen gas and water vapor. Although it does not restrict | limit especially as a gas barrier layer, For example, an oxygen barrier resin layer (For example, it consists of a polyvinylidene chloride type resin, an ethylene vinyl alcohol copolymer, polyvinyl alcohol, a polyamide-type resin), a water vapor barrier resin layer (For example, a polyolefin resin, a polyvinylidene chloride resin), an oxygen barrier property or a water vapor barrier inorganic compound layer (for example, a metal simple substance such as aluminum, a metal oxide such as a metal oxide such as silicon oxide or aluminum oxide) Etc.). The gas barrier layer may be a single layer (may be the outer bag base material itself) or a laminate.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
Linear low density polyethylene (weight average molecular weight (Mw): 80,000) 100 parts by weight, ethylene / butene / diene terpolymer (EBT) (Mw: 140,000) 40 parts by weight as polymer components, average particle size 140 parts by weight of calcium carbonate (inorganic fine particles) having a diameter of 1.1 μm and 1 part by weight of an antioxidant were melt-kneaded at 180 ° C. to obtain a mixed material.
Using the above mixed material, melt extrusion is performed by a T-die method, and a polyethylene-based porous material having a thickness of 70 μm is stretched in the longitudinal (MD) direction at a stretching temperature of 100 ° C. and a stretching ratio of 4.0 times by a uniaxial roll stretching method. A quality film was obtained.
As the hot melt type polyamide adhesive, a polyamide copolymer having the following structural formula (Ms Chemie Japan Co., Ltd., melting point 152 ° C., melt viscosity (190 ° C./2.16 kg) 25 Pa · s) was used. . The polyamide-based copolymer is a polyamide-based copolymer having HMDA, AA, SA, and CL as structural units, and the composition ratio (HMDA: AA: SA: CL) is 2: 1: 1: 4 (molar ratio). ). Moreover, the weight average molecular weight (Mw) of the said polyamide-type copolymer is 11300 (measured by GPC method).

(In the above formula, a represents an integer.)

The polyamide-based adhesive pellets are put into an applicator tank, melted at 190 ° C., and placed on one side of a nylon-based non-woven fabric (trade name “ELTAS NO3030” manufactured by Asahi Kasei Fibers Co., Ltd., basis weight 30 g / m ² ). Then, a curtain spray method was applied to form a fibrous porous adhesive layer (average fiber diameter: 26 μm) having a basis weight of 5 g / m ² . Curtain spray application was performed at an air temperature of 230 ° C. and an air flow rate of 550 L / min.
Next, the polyethylene-based porous film was laminated on the adhesive layer to obtain a porous packaging material.
The production of the polyethylene-based porous film and the formation and lamination of the porous adhesive layer were performed inline on the same production line.

Example 2
The same procedure as in Example 1 was conducted except that the polyamide-based adhesive was changed to a polyamide-based copolymer (Ms Chemie Japan Co., Ltd., melting point 135 ° C., melt viscosity (190 ° C./2.16 kg) 32 Pa · s). Thus, a porous packaging material was produced. The average fiber diameter of the porous adhesive layer was 25 μm. In addition, the said polyamide-type copolymer is a polyamide-type copolymer which has HMDA, AA, SA, and CL as a structural unit. Moreover, the weight average molecular weight (Mw) of the said polyamide-type copolymer is 8000 (measured by GPC method).

Comparative Example 1
The polyamide-based adhesive is made of a thermoplastic copolymer polyamide resin (Daicel Evonik Co., Ltd. (formerly Daicel Degussa), trade name “VESTAMELT 722GETR”, melting point 105 ° C., melt viscosity (190 ° C./2.16 kg) 22 Pa · A porous packaging material was produced in the same manner as in Example 1 except for changing to s). The average fiber diameter of the porous adhesive layer was 24 μm.

Comparative Example 2
The polyamide-based adhesive was changed to a product name “Griltex D1556A” (melting point 135 ° C., melt viscosity (190 ° C./2.16 kg) 220 Pa · s) manufactured by Emschemy Japan Co., Ltd. However, at a curtain die temperature of 210 ° C., the adhesive could not be sufficiently melted and could not be applied in a fibrous form.

Example 3
100 parts by weight of linear low density polyethylene (Mw: 60,000), 20 parts by weight of ethylene-butene copolymer (Mw: 110,000) and 20 parts by weight of polyethylene (Mw: 400,000) are polymer components, and the average particle diameter 150 parts by weight of 1.1 μm calcium carbonate (inorganic fine particles) and 1 part by weight of an antioxidant were melt-kneaded at 180 ° C. to obtain a mixed material.
Using the above mixed material, melt extrusion is performed by a T-die method, and a polyethylene-based porous material having a thickness of 70 μm is stretched in the longitudinal (MD) direction at a stretching temperature of 100 ° C. and a stretching ratio of 4.0 times by a uniaxial roll stretching method. A quality film was obtained.
A porous packaging material was obtained in the same manner as in Example 1 except that the polyethylene-based porous film was used.

Example 4
A porous packaging material was obtained in the same manner as in Example 2 except that the same polyethylene-based porous film as in Example 3 was used.

Comparative Example 3
A porous packaging material was obtained in the same manner as in Comparative Example 1 except that the same polyethylene-based porous film as in Example 3 was used.

[Evaluation method]
Below, the measuring method used by this application and the evaluation method of an effect are illustrated. Moreover, the following methods evaluated the porous packaging material obtained by the said Example and the comparative example.

(1) Melting point (DSC) of polyamide adhesive
DSC measurement was performed in accordance with ISO11357 using DSC Q20 (manufactured by TA Instruments) as a measurement sample using a polyamide-based adhesive as a measurement sample. The temperature condition was such that the temperature was raised from room temperature to 250 ° C. at 20 K / min and lowered to room temperature at 5 K / min.
In addition, melting | fusing point of said polyamide-type adhesive represents melting | fusing point of the polyamide-type copolymer in an adhesive agent.

(2) Melt viscosity of polyamide adhesive (190 ° C / 2.16kg)
In accordance with ISO1133, measurement was performed under the conditions of a set temperature of 190 ° C. and a load of 2.16 kg using “Melt Indexer MI-3 and MP-D” (manufactured by Gottfert).

(3) Presence or absence of back-through of polyamide-based adhesive in heat seal processing The porous packaging materials obtained in the examples and comparative examples were cut into a size of width 50 mm × length 150 mm, and used as measurement samples.
Further, a mirror-finished stainless steel plate (width 50 mm × length 150 mm × thickness 5 mm) was used.
The measurement sample and the stainless steel plate are overlapped with each other so that the surface of the nonwoven fabric side of the porous packaging material is in contact with the stainless steel plate, and a heat seal device (manufactured by Tester Sangyo Co., Ltd., device name “HEAT SEAL TESTER”) is used. And pressurizing (heat sealing) at a pressure of 4.0 kgf / cm ² for 60 seconds. The heat sealing temperatures were 80, 90, 100, 110, 120, 130, 140, and 150 ° C., respectively.
Immediately after the pressurization (heat sealing), the measurement sample (porous packaging material) was peeled off from the stainless steel plate, and the back-through state of the measurement sample was confirmed. The entire area (width 40 mm × length 150 mm) in which the seal bar on the nonwoven fabric side surface of the measurement sample after heat sealing was hit was visually observed and judged according to the following criteria.
No see-through (O): No bleeding (back-through) of the adhesive on the surface of the nonwoven fabric side was observed.
Slightly penetrated (Δ): The proportion of the area of the portion where the adhesive oozes out from the surface of the nonwoven fabric side (exposed) was less than 10%.
Breakthrough is remarkable (x): The ratio of the area of the breakthrough was 10% or more.
In addition, as a porous packaging material for heat seal processing, ◯ is excellent, Δ is a usable level, and × is a non-usable level.

(4) Interlaminar peeling force (T-type peeling)
A strip-shaped measurement sample having a width of 25 mm and a length of 200 mm was prepared from the porous packaging material.
Using a tensile tester, a T-type peel test was performed in accordance with JIS K 6854, and the peel strength (N / 25 mm) between the porous film and the nonwoven fabric was measured to obtain an “interlaminar peel force”.
(Measurement condition)
Measuring device: Instron universal tensile testing machine Temperature and humidity: 23 ± 2 ° C, 50 ± 5% RH
Peeling angle: T type Number of tests: 5 times Pulling speed: 300 mm / min

(5) Average fiber diameter of porous adhesive layer The porous film and the nonwoven fabric were peeled off from the porous packaging materials obtained in the examples and comparative examples using industrial alcohol. An appropriate amount of industrial alcohol was applied to the nonwoven fabric surface at the end of the porous packaging material obtained in the examples and comparative examples, and the porous film and the nonwoven fabric were peeled off. It peeled even to the part which has no industrial alcohol.
Subsequently, the porous adhesive layer on the surface of the peeled porous film was observed with a digital microscope (KEYENCE VHX DIGITAL MICROSCOPE) at a magnification of 150 times. The length in the direction perpendicular to the fiber axis of the fibrous adhesive of the porous adhesive layer is taken as the fiber diameter, and the fiber diameter is measured at 10 random locations within the measurement field (measurement field size: 100 mm × 100 mm). The average value was defined as “average fiber diameter”.

  For the porous packaging materials obtained in Examples 1 and 2 and Comparative Example 1, the evaluation results of “(3) Presence / absence of back-through of polyamide-based adhesive in heat sealing process” are shown in Table 1.

  From the above results, it can be seen that the porous packaging material of the present invention (Examples 1 and 2) is excellent in heat-seal processability without any back-through of the polyamide-based adhesive up to the high-temperature heat-seal temperature region. It was. Moreover, as above-mentioned, it turned out that it is excellent also in productivity (spray application property). On the other hand, it was found that when a polyamide adhesive having a low melting point was used (Comparative Example 1), the back-through occurred at a heat sealing temperature lower than that in Examples, and the heat sealing processability was inferior. Furthermore, it was found that when a polyamide-based adhesive having a high melt viscosity (190 ° C./2.16 kg) was used (Comparative Example 2), the spray coatability was inferior.

  Table 2 shows the evaluation results of “(4) delamination force” for the porous packaging materials obtained in Examples and Comparative Examples.

  From the results of Table 2, when a porous film containing polyethylene having a weight average molecular weight of 300,000 or more is used as the porous film (Examples 3 and 4), the delamination force between the porous film and the nonwoven fabric is It turns out that it improves significantly.

DESCRIPTION OF SYMBOLS 1 Porous packaging material of this invention 11 Porous film 12 Porous adhesive layer 13 Nonwoven fabric 2 Other packaging materials 21 Base material 22 Adhesive layer 3 Heating element 4 Heat seal part

Claims (4)

A porous packaging material in which a porous film and a nonwoven fabric are bonded to each other through a porous adhesive layer formed by fiberizing a hot-melt type polyamide-based adhesive containing a polyamide-based copolymer, the polyamide systems the melting point of the adhesive is that 13 5 to 160 ° C., and the 190 ° C. of polyamide adhesives, porous wrapping material melt viscosity at a load 2.16kg is equal to or less than 100 Pa · s. The porous packaging material according to claim 1, wherein the polyamide-based copolymer has a weight average molecular weight of 5,000 to 50,000. The porous film is a low density polyethylene having a weight average molecular weight of less than 300,000, a linear low density polyethylene having a weight average molecular weight of less than 300,000, an ethylene-α-olefin copolymer having a weight average molecular weight of less than 300,000, The porous packaging material according to claim 1 or 2, which is a porous film composed of at least one polyolefin resin selected from the group consisting of polyethylene having a weight average molecular weight of 300,000 or more. The disposable body warmer containing the porous packaging material of any one of Claims 1-3.

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