JP2524140B2 - Bag material for breathable bags - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention is a bag material for storing contents such as a heating element and having breathable micropores, which has high strength and breathability. The present invention relates to a bag material for a breathable bag, which is improved so that the temperature can be easily controlled.

(B) Conventional Technology A porous bag material is formed by laminating a porous resin sheet on a non-woven fabric, or laminating a resin sheet on a non-woven fabric, and then mechanically punching holes in the resin sheet.

A porous bag material is widely used as a heating bag that generates heat when contacted with air, a dehumidification bag that absorbs moisture in the air, an odor bag that contains a fragrance, etc., when formed into a bag material.

By the way, heating bags, dehumidifying bags, odor bags, etc. are generally
It is formed by accommodating contents such as a heating element, a dehumidifying agent, and a fragrance between a porous front sheet and a back sheet formed of a porous bag material and heat-sealing the peripheral portion thereof.

(C) Problems to be Solved by the Invention By the way, in the laminating method, a pressure-sensitive adhesive is applied to one or both sheets selected from a porous sheet or a synthetic resin porous sheet in a dot-like or linear manner, The part is joined.

However, the one obtained by partially joining the porous sheet and the porous sheet with an adhesive has a low adhesive strength of the adhesive and may cause delamination during its processing or use, However, there was a problem such as lack of reliability due to the lack of effective reinforcing effect.

Also, according to this method, the coating work and the drying work are troublesome, and the adhesive strength is not constant depending on the coating amount of the adhesive. Moreover, the flow of the adhesive causes the coating area to be inconsistent. There were problems such as variations in sex.

On the other hand, when the porous sheet and the porous sheet are partially joined with a hot-melt type adhesive, the part to which the adhesive is applied is heated and adhered using a heating body such as an embossing roll. However, when the porous sheets are laminated together using this heating element, it is not possible to visually judge whether they are strongly bonded to each other, and it is necessary to sample the sample and perform a peeling test etc. was there.

In this case, in particular, when a peeling test is performed by cutting a test piece from a sample (defective product) that has a part with insufficient adhesion, it cannot always be said that this insufficient adhesion can be sampled. There is a risk that a defective product will be judged as a good product.

When such a defective product is used for the above-mentioned purpose, the porous sheets are peeled from each other at a portion where adhesion is insufficient during use or handling depending on the purpose, and the bag material is broken at the peeled portion. , The contents (heating element, dehumidifier or fragrance) leaks, and this may cause skin irritation,
Occasionally, an accident such as adhesion to clothes and stains on the clothes may occur.

The present invention stores a content such as a heating element, a dehumidifying agent or a fragrance, generates heat by contact with air, absorbs and removes humidity in the air or sublimates the fragrance to form a comfortable environment. A bag material used for forming the bag material, wherein the bag material is formed of two or more porous sheets.
It is an object of the present invention to provide a bag material for a breathable bag, which allows the state of adhesion between two or more porous sheets to be easily confirmed with the naked eye and allows easy control of breathability. is there.

(D) Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have laminated two or more porous sheets having different colors and partially When heated and bonded to each other, there is a difference in shade of color between the joint and the other part, and this difference in shade of color is determined by the temperature and pressure at the time of bonding, that is, the joining conditions. The inventors have found that there is a correlation with the adhesive strength and the adhesive state between them, and that the air permeability can be easily controlled by changing the area of the above-mentioned joint portion, and the present invention has been completed.

That is, the present invention is a bag material containing contents such as a heating element and having air-permeable micropores, the bag material being a porous base material sheet, selected from a porous sheet or a hot-melt adhesive sheet. Formed by laminating one or both of the laminated sheets, which are joined together, and at least one sheet of the porous laminated sheet is colored in a different color from other sheets. It is characterized by being present.

 Hereinafter, the present invention will be described in detail.

The porous substrate sheet used in the present invention is for improving the strength of the bag material, and specific examples thereof include various non-woven fabrics, cloths, punching sheets made of synthetic resin, and the like.

In the present invention, one or both sheets selected from a porous sheet and a hot-melt adhesive sheet are laminated on the above-mentioned porous substrate sheet, and these are joined together.

That is, the porous sheet is laminated on the porous substrate sheet,
A product obtained by joining these, a hot-melt adhesive sheet laminated on a porous substrate sheet, and a product obtained by joining these, a porous substrate sheet and a porous sheet with a hot-melt adhesive sheet interposed It is formed by stacking and joining these.

With such a structure, the strength of the bag material for air-permeable bags is improved, and accidents such as breakage of the bag body formed by the bag material during use are prevented.

The above-mentioned porous sheet is not particularly limited as long as it is a porous sheet formed of a synthetic resin, and specifically, for example, a porous sheet directly formed by uniaxial stretching or biaxial stretching. The sheet may be a porous sheet obtained by stretching, and then the filler in the sheet is eluted with an acid, an alkali, water or the like to form a porous sheet.

A usual molding apparatus and a molding method may be used for forming the porous sheet, and an inflation molding machine, a T-die molding machine, or the like is suitably applied, and the sheet thus obtained is uniaxially or biaxially stretched. The porous sheet is formed by this, and this stretching method may be carried out in the usual manner using an ordinary stretching apparatus, and for example, roll stretching, simultaneous biaxial stretching, sequential biaxial stretching and the like are adopted.

Then, in this stretching treatment, the stretching ratio is 100 to 500% in the case of uniaxial stretching, and the stretching ratio is 10 to 300% in the case of biaxial stretching. Is preferable from the viewpoint of size, that is, air permeability. In particular, in the case of uniaxial stretching, if the stretching ratio is less than 100%, the stretched portion and the unstretched portion are mixed and the stretching becomes non-uniform, while if it exceeds 500%, it may break during stretching. Not preferable.

In the present specification, the stretch ratio is a value calculated by the following formula.

The above-mentioned porous sheet includes those formed of a thermoplastic resin, and examples of the thermoplastic resin include polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyamide resin, A sheet made of at least one resin selected from hot-melt resins, that is, a single-layer sheet made of these resins, two-layer or three-layer
Any porous sheet, that is, a composite sheet laminated in layers or more, may be used.

Among the above polyethylene resins, linear low-density polyethylene resin is most preferable because it is excellent in the production and processability of the porous sheet, the production cost is low, and the strength of the obtained porous sheet is high.

The linear low-density polyethylene resin is a copolymer of ethylene and α-olefin, and examples of the α-olefin include butene, hexene, octene and the like.

The above-mentioned porous sheet may include those mixed with a filler, if desired. Examples of such a filler include calcium carbonate, talc, clay, kaolin, silica, barium sulfate, kaolin sulfate, aluminum hydroxide and zinc oxide. ,
Examples thereof include calcium oxide, titanium oxide, alumina and mica.

The average particle diameter of this filler is 30 μm or less, preferably 0.1 to 10 μm.

If the particle size is too large, the through holes become large, and conversely, if it is too small, aggregation occurs and the dispersibility deteriorates, which is not preferable.

In addition, the porous sheet used in the present invention contains an olefin terpolymer in order to improve the kneading property and dispersibility of the filler, the molding / workability, or the functional strength of the film. A softening agent may be added.

The olefin terpolymer is not particularly limited as long as it is a rubber-like substance having a number average molecular weight of 5,000 to 200,000, and specific representative examples include ethylene and α.
A cyclic or acyclic copolymer having an olefin and the conjugated double bond (hereinafter referred to as EPDM) is used.

The EPDM is ethylene, propylene or butene-1.
And a terpolymer consisting of the polyene monomers listed below, wherein the polyene monomers include dicyclopentadiene, 1,5-cyclooctadiene, 1.1-cyclooctadiene, 1,6-cyclododecadiene, 1,7- Cyclododecadiene, 1,5,9-cyclododecatriene, 1,4-cycloheptadiene, 1,4-cyclohexadiene, 1,6-heptadiene, norbornadiene, methylenenorborene, 2-methylpentadiene-1,4 , 1,5-hexadiene, methyl-tetrahydroindene, 1,4-hexadiene and the like.

The copolymerization ratio of each monomer is preferably a terpolymer such that ethylene is 30 to 80 mol%, polyene is 0.1 to 20 mol% and the rest is α-olefin, and the Mooney viscosity ML _{1 + 4} (100 ° C) 1 to 60. The ones are good.

As the softening agent, the number average molecular weight is 1000 to 3000.
There is no particular limitation as long as it is a softening agent of 0, and specific representative examples thereof include petroleum-based process oils, liquid paraffins, aliphatic oils, and low-molecular weight plasticizers as low-viscosity softening agents. As a highly viscous softening agent, polybutene,
Softeners such as low molecular weight polyisobutylene and liquid rubber are preferably used.

In the present invention, as described above, the linear low-density polyethylene resin may be blended with a filler and an olefin terpolymer or a softening agent, and the blending ratio of each is linear low-density polyethylene resin 100. 100 to 300 parts by weight of the filler, and 5 to 100 parts by weight of the olefin terpolymer or the softening agent are preferably contained in the parts by weight, and such a mixing ratio makes it possible to obtain excellent mechanical strength and air permeability. The porous sheet can be easily manufactured.

Further, a known mixer is used for mixing the linear low-density polyethylene resin, the filler and the olefin terpolymer or the softening agent, and a known mixer is used. In order to further improve moldability, mixing rolls, Banbury mixers,
It is desirable to use a mixer such as a twin-screw kneader or a Henschel mixer.

In addition, the above-mentioned porous sheet may be one obtained by adding an antioxidant, an ultraviolet stabilizer, an antistatic agent, a lubricant, a fluorescent agent and the like which are usually used.

The hot melt adhesive sheet is not particularly limited as long as it can be joined to the porous base material sheet or the porous sheet by heating.

Examples of the hot-melt adhesive sheet include ethylene-vinyl acetate copolymer resins, ethylene-acrylic acid ester copolymer resins such as ethylene-isobutyl acrylate copolymer resins, ethylene-based hot melt resins such as polyamide resins, polyamide-based hot melt resins and polyester resins. Hot melt resin, butyral hot melt resin, cellulose derivative hot melt resin, polymethylmethacrylate hot melt resin, polyvinyl ether hot melt resin, polyurethane hot melt resin, polycarbonate hot melt resin, vinyl acetate, vinyl chloride- An adhesive sheet formed of a hot melt resin such as a vinyl acetate copolymer can be used.

Further, the hot-melt resin may also be mixed with various antioxidants.

In the present invention, one or both sheets selected from the above-mentioned porous base material sheet and porous sheet or hot melt adhesive sheet are laminated, and this porous laminated sheet is bonded, but as a lamination method thereof, A lamination method, a two-layer extrusion method or the like is preferably used.

Then, when forming a porous laminated sheet by laminating these sheets and bonding them to each other, the air permeability of the porous laminated sheet, that is, the bag material formed of this porous laminated sheet is controlled. The area of the joint may be adjusted within the range of 1 to 100% of the area of the sheet depending on the application.

In this case, it is desirable that the area of the joint is generally 10 to 90%, particularly preferably 20 to 60%, and formed uniformly and preferably continuously over the entire surface.

If the area of the joint is less than 1%, the area may become too small and the strength of the sheet may become insufficient.
% Or more is preferable.

Also, if the area of the joint exceeds 90%, the fine pores formed by stretching may be crushed, or the pore size may become smaller,
The air permeability may decrease too much, and it is most desirable to obtain the desired air permeability by adjusting the area of the joint in the range of 20 to 60%.

In this way, the air permeability may be controlled by controlling the area of the joint.

In order to control the area of the bonding portion, it is possible to extremely easily control the area of the convex portion of the embossing roll, for example, by changing the area.

And, the feature of the present invention is that one or both of a sheet selected from a porous substrate sheet and a porous sheet or a hot-melt adhesive sheet as a bag material for containing contents such as a heating element, a dehumidifying agent or a fragrance. It is formed of a porous laminated sheet which is laminated and bonded to each other, and at least one of the porous laminated sheets is colored differently from other sheets.

That is, in the present invention, at least one sheet of the above-mentioned porous laminated sheets is colored in a different color from the other sheets, whereby the shade of the color of the partially joined portion and the non-joined portion is changed. Difference is determined by the temperature and pressure at the time of heating and bonding, and this point is closely related to whether or not the above-mentioned bonded portion is securely bonded, that is, the bonding strength.

For example, one of two sheets formed of a thermoplastic resin and a hot melt resin, or two sheets formed of a thermoplastic resin and a resin composition including an inorganic filler and a hot melt resin. One sheet of
Color with dyes and pigments. When these two sheets are stretched, the uncolored sheet becomes white, while the colored sheet becomes a lighter color than the color before stretching, and the two sheets become porous sheets.

When the two porous sheets are partially heated by an embossing roll or the like to be securely joined, the white layer in the joined portion becomes translucent and approximates the color of the colored porous sheet. In this case, the shade of this color is determined by the number of copies of the pigment or dye, the thickness and stretching ratio of the sheet, the stretching temperature, the temperature and pressure of the embossing roll. Also, of the two or more porous sheets, two porous sheets or all the porous sheets are colored with dyes or pigments, and even if they are joined in the same manner as above, the color of the joint portion and the portion not Change occurs, which allows the adhered state to be confirmed.

That is, when there is no or little color change, the heating temperature, the heating time, the pressure are insufficient, and the adhesive strength is low. In this way, the adhesion state (adhesion strength) can be easily discriminated by the naked eye based on the shade of color.

In this case, in particular, when laminating and joining two or more porous sheets, those having different melting points are used as the porous sheets, and the low melting point sheet among these sheets is used. Although it is colored differently from that of the sheet, it is desirable because the change in the shade of the color at the time of joining becomes clearer and the state of adhesion between the sheets can be more reliably and easily observed with the naked eye. At this time, it is desirable that the difference in melting point between the high-melting-point porous sheet and the low-melting-point porous sheet be 50 ° C. or less, and if it exceeds 50 ° C., the low-melting-point sheet is deteriorated by heat or flows too much. This is not preferable because the fine pores of the sheet are crushed and blocked, resulting in poor air permeability.

The dye / pigment used in the present invention is not particularly limited as long as it can color the porous sheet, and achromatic or chromatic colors can be used.

(E) Action The present invention is a bag material having the above-mentioned configuration, containing contents such as a heating element, and having air-permeable micropores, wherein the bag material is a porous base material sheet and a porous sheet. It is composed of one or both sheets selected from hot-melt adhesive sheets, and at least one of these sheets is colored differently from other sheets.

When these porous sheets are laminated and joined together, a difference in color shade (change in color) occurs between this joined part and the part that does not, and these sheets are intercolored in the state of this color change. Since the bonded state can be easily and surely confirmed with the naked eye, the mechanical strength is always high, and the bag material for breathable bags having stable quality and excellent quality is obtained.

Further, in the present invention, since the air permeability of the bag material is adjusted by the area of the joint portion of the sheet, it is possible to control the air permeability of the bag material very easily and reliably. That is, the bag material having the property is easily obtained.

Further, in the present invention, the quality, grade, etc. of the bag material can be distinguished by the color of the colored porous sheet, so that quality control, inventory control, etc. can be performed very easily, and the aesthetic appearance can be improved. It has an action.

(F) Examples Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited thereto.

Structural Example of Breathable Bag Material In FIGS. 1 to 4, (1) is a bag material for a breathable bag that contains contents such as a heating element and has breathable micropores. The bag material (1) is composed of a porous portion (2) and a partially joined portion (3).

The breathable bag material (1) is a porous substrate sheet (4).
At least one of the porous sheet (5) and the hot-melt adhesive sheet (6) is laminated on the sheet. In this case, as shown in FIG. 1, the porous substrate sheet (4) made of polypropylene resin is used. Non-woven fabric and porous sheet (5)
A linear low-density polyethylene resin porous sheet that is
The hot-melt adhesive sheet (6) is formed of three porous sheets (4), (5) and (6) made of ethylene-vinyl acetate copolymer resin porous adhesive sheet. It is formed of a porous adhesive sheet obtained by laminating and joining these, and at least one of the three porous sheets (4), (5) and (6), The hot-melt adhesive sheet (6) is colored differently from other sheets.

The joint part (3) is 1-100 of the area of the porous sheet.
%, In this case, considering the strength and air permeability of the bag material (1), the area of this joint is generally 10 to 90%, especially 20 to 60%.
Is most desirable.

By the way, in order to form the joint portion (3) uniformly over the entire surface of the porous sheet, the joint portion (3) may be continuously formed in a regular hexagonal shape as shown in FIG. Instead of this, as shown in FIG. 3, it may be formed in a swirling toe pattern shape, and in place of these, as shown in FIG. 4, it may be formed in a substantially lattice shape.

Production Example of Porous Sheet Production Example of Thermoplastic Porous Sheet As shown in Tables 1 and 2, linear low-density polyethylene resin (MI 2.0, density 0.9
3), EPDM as olefin terpolymer (trade name, EPT
9720, Mooney viscosity 20, Mitsui Petrochemical Co., Ltd.), polybutene (number average molecular weight 1260) as a softening agent, calcium carbonate (average particle size 2 μm, fatty acid treatment) as a filler, and stearic acid as a lubricant. The composition obtained by mixing the components in the mixing ratios shown in Table 2 and thoroughly stirring and mixing the mixture was thoroughly kneaded with a twin-screw kneader (TEM-50, manufactured by Toshiba Machine Co., Ltd.). Granulate by the method.

On the other hand, ethylene-vinyl acetate copolymer resin (vinyl acetate content 25% by weight, MI 2, density
0.95) 100 parts by weight and calcium carbonate (average particle size 2 μm,
(Fatty acid treatment) 200 parts by weight, and further 0.5 parts by weight of a known pigment are sufficiently mixed by stirring, and the mixture is mixed with a twin-screw kneader (TEM-50,
The composition obtained by sufficiently kneading by Toshiba Machine Co., Ltd. (manufactured) is granulated by a conventional method.

Each of the above linear low-density polyethylene resin composition and hot-melt resin composition is coextruded by a two-layer extruder to obtain a linear low-density polyethylene resin sheet and a laminate of hot-melt resin sheet. Then, this was subjected to uniaxial stretching (Examples 1 to 14 shown in Table 3) by a roll stretching machine or biaxial stretching (Examples 15 to 22 shown in Table 4) by a sequential biaxial stretching method. Porous sheets having the stretching ratios shown in Tables 3 and 4 were obtained.

In this case, the stretching conditions include a stretching temperature of 40 ° C and a stretching speed.
The rate of 6 m / min and the stretching rate were adjusted to the values shown in Tables 3 and 4 by changing the speed ratio of the rolls.

The obtained porous sheet had no stretching unevenness and was a porous sheet.

Examples 1 to 22, in each of the porous sheets obtained, on the hot melt adhesive sheet side, a porous sheet made of polypropylene nonwoven fabric having a thickness of 1 mm was laminated, and this was heated at a temperature of 80 to
It is introduced between an embossing roll of 100 ° C and a silicone rubber roll, heated, and pressurized under the condition of a pressure of 10 kg / cm ² ,
The bag materials for the air-permeable bag of the present invention shown in Tables and Table 6 were obtained.

The characteristics of each example product thus obtained are shown in Tables 5 and 6.

Comparative Example 1 A sheet formed of the above linear low-density polyethylene resin composition was stretched (stretching ratio 400%) to obtain a porous sheet having a thickness of 100 μm, and the porous sheet thus obtained had 10% of the total area thereof. % Was applied to an acrylic pressure-sensitive adhesive, and a polypropylene nonwoven fabric similar to that used in the above example was adhered to the pressure-sensitive adhesive forming surface side to obtain a sample.

Comparative Example 2 A sheet formed of the above linear low-density polyethylene resin composition was stretched (stretching ratio: 400%) to obtain a porous sheet having a thickness of 100 μm, and the porous sheet thus obtained had a total area of 10 %, A hot melt resin similar to that of the above-mentioned example product is applied, and a polypropylene non-woven fabric similar to that of the above-mentioned example is laminated on the coated surface side, and this is heated and pressed in the same manner as in the above-mentioned example to bond. The sample was used as a sample.

The characteristics of each comparative product thus obtained are shown in Tables 5 and 6.

Note 1) The tearing force shown in Tables 5 and 6 is JIS K 67.
Measured based on 72.

Note 2) The moisture permeability shown in Tables 5 and 6 was measured by the moisture permeable cup method in JIS Z 0208.

Note 3) The air permeability shown in Tables 5 and 6 is JIS-P-8.
It was measured based on 117.

Note 4) The interlayer adhesive strength shown in Tables 5 and 6 is JIS-
It was measured based on Z-0237.

From the results shown in Table 5 (Examples 1 to 4), increasing the area of the partial joint decreases the moisture permeability and air permeability,
It can be seen that the water vapor transmission rate can be controlled and the tearing power improves.

Further, from the characteristic results of Examples 8 to 10 shown in Table 5, the tear strength is improved by decreasing the stretching ratio of the sheet, but the moisture permeability becomes low, and the characteristics as a breathable bag material are impaired. It is caught.

Furthermore, the heating temperature, heating time, and pressure are insufficient,
When there is no change in the color of the joint portion and the porous portion (non-joint portion), the mounting strength is weak and the quality varies, but in each example, as is clear from Tables 5 and 6, It is recognized that the difference between the two is large and the excellent interlayer adhesive force is retained.

That is, it is recognized that the adhesion state can be easily and surely determined by observing the color change with the naked eye.

In particular, from the results shown in Comparative Example 1, it can be seen that those bonded with an adhesive material have a small interlayer adhesive force and peeling occurs or the tearing force varies.

Further, in Comparative Example 2, there is a portion where the porous sheets are not joined to each other, and even in this case, it is recognized that the tearing force varies.

The breathable bag bag material (1) of the present invention is obtained by laminating a porous sheet (5) on a porous substrate sheet (4) as shown in FIG. It may be formed of a porous laminated sheet formed by joining, or as shown in FIG. 6, a hot melt adhesive sheet (6) is laminated on a porous base material sheet (4) and then joined. It may be formed of a porous laminated sheet.

(G) Effect of the Invention The bag material for a breathable bag of the present invention has the above-mentioned configuration, and the breathability and moisture permeability can be easily controlled by adjusting the area of the joint portion in the bag material. As a result, there is an effect that a bag material having air permeability and moisture permeability depending on the application can be obtained.

Further, by visually observing the change in color between the joint portion and the non-joint portion in the bag material for a breathable bag of the present invention, the joint state of the porous sheets can be confirmed very easily and surely. Therefore, it is possible to obtain a product of which quality is always stable and to have an effect such as excellent breathability and moisture permeability.

Furthermore, the bag material for a breathable bag of the present invention is obtained by laminating at least one of a porous sheet and a hot-melt adhesive sheet on a porous substrate sheet, and firmly joining the porous sheets to each other. As a result, since the porous sheets are reinforced with each other, the mechanical strength such as the tearing force and the yield stress is remarkably improved.

In addition, this breathable bag material distinguishes quality and grade such as sheet thickness and breathability by the color difference of dyeing / pigmenting it, which facilitates selection of applications. In addition, quality control and inventory control can be performed very easily, and it has the effect of improving the aesthetic appearance of the sheet.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIGS. 2 to 4 are plan views showing the pattern and form of the joint portion of the present invention, and FIGS. 5 and 6 are other drawings. It is sectional drawing which shows the Example of. (1) ... Bag material for breathable bag, (2) ... Porous part, (3) ...
Joining part, (4) ... Porous substrate sheet, (5) ... Porous sheet, (6) ... Hot melt adhesive sheet.

Claims (6)

(57) [Claims] 1. A bag material for accommodating contents such as a heating element and having air-permeable micropores, wherein the bag material is selected from a porous base material sheet, a porous sheet or a hot-melt adhesive sheet. One or both of the sheets are laminated and formed by joining the sheets, and at least one of the sheets is colored in a different color from the other sheets. A bag material for a breathable bag, which is characterized in that 2. The bag material for a breathable bag according to claim 1, wherein the porous base material sheet is a nonwoven fabric, a cloth or a punching sheet made of a synthetic resin. 3. The porous sheet is formed of a resin selected from polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyamide resin and hot melt resin. The bag material for a breathable bag according to item 1 or 2. 4. The bag material for a breathable bag according to claim 3, wherein the polyethylene resin is a linear low density polyethylene resin. 5. A bag material for a breathable bag according to any one of claims 1 to 4, wherein the porous laminated sheet is formed by partial joints over the entire surface of the sheet. . 6. The bag material for a breathable bag according to claim 5, wherein the area of the partially joined portion is 10 to 90% of the area of the porous sheet.