JPS5922084Y2 - disposable absorbent - Google Patents

Description

[Detailed description of the invention] The present invention relates to absorbent devices such as disposable diapers, sanitary napkins, disposable bed pads, and incontinence pads (bedwetting pads), which prevent the passage of liquids but allow the passage of gases. The present invention relates to an absorbent device with a backing sheet.

Absorbent devices such as diapers are well known and are used to absorb and retain fluids from the human body.

It is also well known to cover the outside of these absorbent devices with a flexible plastic sheet to prevent absorbed liquid from passing through the absorbent device and staining clothes, bedding, etc.

Although prior art waterproof plastic sheets do prevent liquid from passing through and help keep liquid in the absorbent, they also make the absorbent feel lukewarm and uncomfortable to the wearer and can cause rashes. It has disadvantages such as causing dryness and irritation, and furthermore, interfering with self-drying of the absorbent device, which may be caused by evaporation of the liquid retained in the absorbent device.

The breathable backing sheet 1 in the absorbent device according to the present invention is capable of trapping liquid in the absorbent material to prevent clothes from getting dirty, providing a cool wearing feeling, allowing self-drying of the absorbent material while being worn, etc. This is particularly advantageous when desired.

Although breathable backing sheets for absorbent articles are found in the prior art, these are generally intended to provide communication between the interior and exterior of the absorbent article, thus allowing circulation.

U.S. Pat. No. 2,570,011 seeks to provide a breathable backing for an absorbent device, and the diaper of this patent has an absorbent portion and a blocking portion, the blocking portion preventing urine from passing through the paper or cloth diaper. This is a chemically treated part that is folded towards the outside of the diaper.

U.S. Pat. No. 3,156,242 shows an absorbent article having an absorbent body covered by a non-absorbent flexible film, said film being breathable and thus allowing drying of the absorbent body held underneath. As the above-mentioned film, a microporous film having holes or cracks is used to provide breathability.

U.S. Pat. No. 2,119,610 shows a combination of a removable disposable absorbent pad and a pad holder, the pad holder being a sheet of perforated rubber or natural silk fabric, and the pad being a cellophane It has a perforated base made of an inexpensive non-hygroscopic material, such as, which is placed against the carrier.

U.S. Pat. No. 3,439,678 shows an infant panty suitable to be worn over a diaper, the panty being made from a laminated fabric having high water resistance, the fabric having at least two layers, each layer being , made from a fabric that can withstand standing water and be permeable to air and evaporation.

Other patents related to porous plastic sheets in the prior art include U.S. Pat. No. 2,027,810 and U.S. Pat.
No. 292,619, U.S. Pat. No. 3,426,754 and
US Pat. No. 3,446,208, etc.

One object of the present invention is to provide a disposable absorbent device with a substantially gas-permeable and liquid-impermeable backing sheet for the absorbent body.

Another object is to provide a disposable absorbent device with a backing sheet for the absorbent article that can remain substantially liquid-impermeable even when the absorbent pad is subjected to pressure.

Another object is to provide a disposable absorbent device with a backing sheet consisting of a two-layer combination of relatively high porosity.

Yet another object is to provide a disposable absorbent device with a liquid-impermeable, gas-permeable backing sheet for the absorbent body that is economical and easy to manufacture.

According to the present invention, the above-mentioned purpose is to provide a disposable absorbent device having an absorbent body and a backing sheet, in which the backing sheet (1) is a first layer and a second layer for forming an effective ventilation section of the backing sheet (1). (A) a liquid-impermeable, water-draining polymeric film; the second layer being located between the first layer and the absorbent body; The film has a property of exhibiting a permanent strain of 15% or less when stretched by 30%; , the height of said protrusion is at least 50μ, (C) a hole is made in said protrusion, and the average projected diameter of said hole is about 10-100μ; evenly distributed in the portion of the first layer having the same dimensions as the ventilation portion, the opening area of the portion of the first layer being about 0.01-1% of the area of the effective ventilation portion; The layer is composed of a fibrous sheet and a drainage material, the surfaces of the fibers constituting the sheets 1 to 1 are coated with the drainage material, and the coated sheet has a void ratio of at least 60% and has drainage properties. The fibrous sheet made into a water column has a water column of 12.
At least 3 m37m1n/m at a pressure difference of 7mm
'', so that the passage of liquid through the effective vent is substantially prevented, but the passage of vapor and gas can take place. .

It will be explained in more detail below according to the attached drawings.
The thickness of the materials comprised is exaggerated for clarity.

FIG. 1 shows a diaper 21 as an example of a disposable absorbent device according to the present invention, and the diaper 21 is composed of multiple layers of various materials, as usual, and includes a top sheet 22, an absorbent body 23, and a back sheet. The back sheet is separated from the first layer 24 and the second layer 25.

The absorbent core 23 is stacked on the back sheet, and the front sheet 22 is stacked on the absorbent core 23.

The longitudinal dimension of the front sheet 22 is made longer than that of the absorbent body 23, so that the front sheets 1 to 22 are folded under the absorbent body 23 at both longitudinal ends of the absorbent body 23, as shown in FIG. It can be rare.

The combination of the absorbent body 23 and the top sheet 22 generally includes a back sheet (in the case of FIG. 1, the first layer 24), at both ends and/or near both longitudinal ends, and at these ends. Although they are adhered in parallel, it is of course possible to adhere the above combination to the backing sheet over the entire contact surface between them.

The top sheet 22 may be of any known type, but in this example the top sheet 22 is of the type shown in U.S. Pat. (hydrophobic, ie non-hygroscopic) non-woven rayon sheets held together by a thermoplastic binder.

The absorbent body 23 can be made from any known material with good hygroscopic properties; the above-cited patent No. 26151 describes some examples of such materials, such as multi-layered crepe paper, cotton, cellulose, etc. Fibers, felts, natural sponges, hygroscopic foam synthetic materials, etc. are shown.

As mentioned above, the backing sheet consists of a first layer 24 and a second layer 25, but in this example, the first layer 24 is a drainable polyethylene sheet with a large number of holes punched therein, and the second layer Layer 25 is a drainage porous creped tin.
d tissue) and each of these layers is liquid permeable by itself, but when both layers are superimposed they cooperate to form a liquid impermeable backsheet.

The first layer 24 is a flexible sheet of liquid-impermeable material that is perforated to make it permeable to liquids under pressure.

The properties of this first layer 24 are clear from the experimental data described below.

In this example, polyethylene is used as the material for the first layer, but the material is not limited to this.

In the preferred embodiment, first layer 24 is 1.8 mil (approximately 46
.mu.) thick polyethylene film, which is perforated as described below.

First layer 24 has a low void ratio.

That is, the void ratio of the first layer 24 with holes formed therein is the same as the opening area ratio in the layer when the projected diameter of the holes is used as the basis for calculation, but the opening area of the first layer 24 is It is about 0.01-1.0% of the surface area of the unperforated film.

The projected diameter of the holes is approximately 10-100μ. The second layer 25 in this example is a crepe tissue layer, that is, a fibrous sheet with a high void ratio, and is made drainable by paraffin impregnation (described in detail later), and the porosity of this second layer 25 is Even after paraffin impregnation, it is still large.

In the diaper of FIG. 1, the first layer 24 has larger dimensions than the absorbent body 23, thus providing longitudinal edges 26 and side edges 27.

Said side edges 27 are then folded over the top surface of the absorbent body 23, thus forming what may be referred to as "side flaps", which side flaps are attached to the top sheet 2.
2 may or may not be bonded.

The longitudinal edge 26 is folded over the top surface of the absorbent body 23 before the diaper 21 is placed on the infant.

By folding the above edge in this way, the absorbent body 2
3 will advantageously be placed in the "dish" formed by the first layer 24.

The side edges 27 and the longitudinal edges 26 can be perforated as shown in FIG. 1, or can be left unperforated if desired.

In Fig. 1, the first layer 24 is perforated substantially over the entire surface, but generally, only a portion with an area smaller than the entire area of the backing sheet of the absorbent material becomes an "effective ventilation section."It's just something you get.

"Effective ventilation part" is "a part where the first layer 24 and second layer 25 are combined to prevent the passage of liquid but allow the passage of gas", and in the example of FIG. Since the two layers are combined with each other on the entire surface, the entire back side of the diaper is an effective ventilation area.For example, the second layer covers the entire back side of the diaper,
50.8 mm (2 in) in the center of the first layer 24 (
If the pores are provided only in the circular part with a diameter of 50.8 mm, the effective ventilation area is limited to the circular part with a diameter of 50.8 mm, which is a small part of the first layer 24 that works together with the second layer. It just exists.

The diaper 21 can be attached to the infant by a variety of well-known fastening means, one of which is, of course, diaper pins, and other means, which are currently very popular on the market. Popular are pressure sensitive tape type fasteners, an example of which is shown in the above-mentioned US Pat. No. 26,151, although illustration of these fastening means has been omitted.

Now, as shown in the partially enlarged view of FIG. 2, protrusions are formed in the first layer 24 (made from a polyethylene sheet as described above), and holes (porous pores) are formed in the protrusions.

That is, protrusions 29 are made in the polyethylene sheet 28, and holes 30 are made in the protrusions 29.

As shown in FIG. 3, the sheet 28 is passed through a sandwich roll machine 36 consisting of two rolls to form holes and protrusions. The roll or receiver has a roll 31 and a perforated roll 32, which rolls are held on a frame and bearings (both not shown), and the pressure on the rolls and its control is provided by a suitable air cylinder and well known This is done by a pressure control valve such as.

A carded cloth (clothing) 33 is wound spirally around the perforated roll 32.

This card cloth 33 is made by cutting a four-ply cotton canvas glued with a rubber-based adhesive into strips of 3.2 mm (0.
, 125 inches) thick and 39 mm (1% 6 inches) wide, and straight needles are inserted into the belt perpendicular to the surface of the belt so as to form an even linear array.

The needle point protrudes 3.2 mm (0.125 in.) from the fabric surface, forming an upright pin 34 of circular cross section, so the total thickness of the carded fabric is 6.4 mm (0.250 in.).

Pin implantation density is 82 pins/cm2 (530 pins/1n2)
The pin has a diameter of 228 μ (0°009 in) and a weight of 182 to 203 kg/mm2 (260000-2
Made from hardened carbon steel with a tensile strength of 90,000 psi).

The diameter of the punching roll 32 wrapped with the card cloth 33 is exactly 76.2 mm (3 inches), and the length of the roll surface is 4 inches.
It is larger than 80 mm (19 inches) and is driven in the direction shown by the arrow in FIG.

The receiver is made of needle felt (needle felt) on the outer surface of the roll 31.
Tubular felt sleeve 3 made with ed felt)
The fibers in the sleeve 35 are a mixture of a small portion of polyester and a large portion of hypertonic canylon staples, with a thickness of 1.5 to 6.0 denier.
It has a length of 50.8 mm (1-2 in).

The thickness of the sleeve 35 in the radial direction is 6.4 mm (0,
250in), and the inner diameter is approximately 76.2mm (3i
n), and the weight is 967 g/m2 (87 g/m2) on the inner surface.
ft2) and the diameter of the roll 31 when the conosleaf 35 is attached is 89 mm (3.5 in).

In this receiver, the roll 31 is not driven.

The area occupied by the thin unit weight of the polyethylene film sheet 28 described above is approximately 32 m2/kg (220
00 in2/lb), and this sheet is passed through a sandwiching roll 36 pressurized to a roll length of approximately 16°1 kg/cm (911 b/in), and is rolled at approximately 66 m/min (22
(0 ft/m1n) (7) Effective drilling speed.

The height of the protrusions 29 made in the sheet 28 in the manner described above was approximately 50-150μ from the surface of the sheet 28, with a preferred height of approximately 150μ, which is similar to Therefore, the (unloaded) thickness of the first layer 24 is approximately four times the thickness of the unperforated sheet.

(L30 has a theoretical diameter of about 228μ, which is the same as the diameter of the card cloth pin.

The term "diameter" herein refers to the average length of the chord passing through the center of the hole.

The projected diameter of the hole, that is, the diameter of the hole 30 projected onto the plane of the sea I.28, is smaller than 228μ, because the hole 30 generally opens into the side wall of the boss 29 (
This is because the diameter of the hole contracts due to the elasticity of the sheet when the pin 34 of the card cloth is pulled out of the hole.

The perforated film (sheet) has the following properties (the measurement method is also listed below).

It is desirable that the permanent deformation of is 15% or less, and the air permeability (amount of air passing through) at a differential pressure of 10 cm in the water column is approximately 0.
It is desirable that it is 5 to 100 m3/SeC/cm2.

In this example, the second layer 25 is made of a creped, wet-strength, white tissue whose fiber surface has been treated with paraffin wax to make it drainable. can be kept extremely porous.

The tissue is made from bleached chemical pipes, 30% in the pipe is bleached sulfide pulp made from cottonwood layer, and 70% is made from cottonwood and pine) It is a kraft pulp made from Sakaishiro.

After the tissue is made, it is treated by applying a wet strength imparting resin of between 1% and 1% of the dry weight of the fibers, and then rolled in a conventional manner on a crepe paper making machine. created by

The crepe ratio [(Yankee speed roll winding speed)/Yankee speed] of this tissue was 14%.

” The double-layer tissue is then treated with dry wax.
waxing process), which has been widely used for a long time.

In this process, food-grade paraffin wax having a melting point of about 60°C (140°F) is deposited on the side of a fast-moving tissue band (strip speed about 28°, 5 m/m1n). A heated application roll partially immersed in a molten bath of paraffin wax and rotating relatively slowly (roll speed approximately 5% of band speed) is applied.

That is, molten wax is wiped off the surface of the applicator roll with a tissue, this wax adheres to the surface of the fibers, and eventually the waxed strip comes into contact with the surface of another heated roll. This ensures complete coverage of the wax and the strip is then rolled into a roll while the wax is above its melting point.

This dry waxing process is to coat the surface of the fibers within the tissue with wax, but the amount of wax applied is limited so that only the very small gaps between the fibers are cooled, thus allowing the air to pass through the tissue. The volume (air permeability) is limited so that only a relatively small reduction occurs.

The tissue thus made and used as the second layer 25 has the following properties before and after being made.

The waxed terrasque above has an appearance of 88% (
calculation) has a void ratio.

The calculation method used to calculate the void ratio will be described later.

The porosity ratio of the second layer 25 should be at least 60%, and the highly porosity layer used has a differential pressure of 12.7 mm of water column (
0.5in) at least 5 cm”/sec/c
It should have an air permeability of rn2 (10 ft3/min/ft2).

Other wax treatment methods can also be used to make such tissues drainable.

This method consists of preparing an approximately 5% (by volume) paraffin wax solution in chloroethane, passing a tissue through this solution to completely wet it, and then drying the tissue to evaporate the solvent. .

The second layer 25 may also be formed by treating the bottom surface of the high void ratio absorbent body with a drainage material such as those described above, whereby the bottom layer of the absorbent body is at least a few fibers deep. It is made drainable until the end.

A test of the present invention was constructed to determine the liquid impermeability and gas permeability (air permeability) of the backsheet as shown in the following example.

For all tests, the test pads are approximately the same size, i.e. approx.
It is 0cm square and made of multiple layers.

The first four layers of each test pad are identical, with the first layer corresponding to the top sheet 22 shown and having a basis weight of 23.9” g/m
2, the second layer has a basis weight of 19
．． Creped high wet strength bleached kraft tissue with 9g/m2, third layer is cellulose fluff (commonly known as Airfel 1~) made from bleached soft wood Kura 7I, basis weight 16.8g /m2,
The fourth layer is a gray 1 bleached kraft tissue with a basis weight of 19.9 g/m2; these second, third and fourth layers correspond to the absorbent body 23 shown.

Only the backing sheets in the test pads were varied as shown in the examples.

The test pad contains a "test fluid" that is likened to urine, i.e.
It was wetted with a 1% saline solution whose surface tension was lowered to 45 dine/cm by a surfactant.

Each test pad was tested with an absorbent Ig (i.e.,
The test solution was wetted with the above test solution until approximately 5 g of solution was absorbed per total weight of the third and fourth layers (Ig) (this condition is hereinafter referred to as "5").
(He said, "I was twice as wet.")

The liquid impermeability of the backsheet was then measured by the "liquid passage" test (described below), and the gas permeability (air permeability) of the backsheet was determined by the "evaporation" test 1 (described below).

Liquid Passage Test Two layers of Whatman A4P paper are weighed to determine the dry weight of the filter paper, then a wet test pad is placed on the filter paper with its backing sheet touching the filter paper, and then the backing sheet and A pressure of 35.2 or 70.4 g/cm2 was applied to the pad by a pressure foot with a diameter of 5 cm (19.7 cm2 in area) placed at the center of the pad on the opposite pad surface, and after 15 minutes. The filter paper is weighed again to determine its wet weight, and by subtracting the dry weight of said filter paper from this weight, the amount of liquid absorbed by the filter paper is determined, i.e. the amount of liquid that has passed through the backing sheet. By dividing the amount by the pressurized area, that is, 19.7 cm2, the ratio of the amount of liquid that permeated through the back sheet under pressure is obtained as 270 m2, and this value is used as the numerical value (finger scale) that represents the liquid permeability of the back sheet. Ta.

Evaporation test The test pad is wetted approximately 5 times and covered with a non-porous polyethylene film, which is then placed on top of the top sheet and folded slightly to wrap around the edge of the pad, leaving the folded film behind. The edges are adhered to the backing sheet with commercially available polyester tape.

The portion of the backsheet left exposed (ie, not obscured by the film) is approximately 9 cm square.

The uncovered test pad is weighed to determine the initial weight of the pad, and the pad is then placed with the back seam 1 facing upwards.
Place the unobstructed area under outside air conditions (temperature approximately 22-24°C)
After being left in this condition for approximately 3 hours, the final pad weight is weighed again and this final weight is compared to the first one above. The weight loss due to evaporation is determined by subtracting it from the weight of It was converted to be expressed in units of /hr.

EXAMPLES I-IV Test pads were made by combining the first four layers described above with only one layer of perforated polyethylene sheet described above as a backing sheet.

At this time, the Botethylene sheet is placed next to the fourth layer at the protrusion 29.
was placed facing the inside of the pad.

The pads were then wetted approximately five times with the test liquid and then subjected to liquid passage and evaporation tests.

The test results are as shown in Table I below.

Examples ■~vnvn Test pads were made by combining the first four layers described above with a single layer of the paraffin waxed tissue described above as a backing sheet, with the waxed tissue being the fourth layer. was placed next.

The test pads were wetted approximately 5 times with the test liquid and then subjected to liquid passage and evaporation tests.

The results are shown in Table ■.

EXAMPLES IX-XII A test pad is made by combining the first four layers described above with a combination of one layer of paraffin waxed tissue as described above and one layer of perforated polyethylene film as described above as a backing sheet; In this case, the waxed tissue is placed next to the fourth layer and corresponds to the second layer 25 shown, and the perforated polyethylene film is placed next to the tissue and the outer layer shown (the first layer 25). ) corresponds to 24, and the boss was directed towards the tissue mentioned above.

The test pads were wetted approximately 5 times with the test liquid and then subjected to liquid passage and evaporation tests.

The results are shown in Table ■. EXAMPLE
After being wetted twice, it was subjected to an evaporation test.

The results are shown in Table I. Examples XVI-XV Test pads were made similar to those of Examples IX-XII, but replacing the wax treated tissue with a high void ratio silica treated tissue.

The silica-treated tissue is a silicone-coated fumed silicone that is similar to the previously described creped tissue.
It was made by applying a solids content of 5 g/rn2 (0.45 g/ft2) to Teizuyu by immersing it in a suspension of 0% (by volume) in chloroethane.

The test pads were wetted approximately six times with Test 1 test fluid and then subjected to fluid passage and evaporation tests.

The results are shown in Table ■.

EXAMPLES , placed against a perforated polyethylene film.

This nonwoven fabric exhibits a contact angle of 100° with water and 8
having a thickness of 0.33 mm under a pressure of g/cm2;
53 cm3/sec under a differential pressure of 12.7 mm of water column
/cm2, has a basis weight of 30 g/m2, and has a void ratio of 88.9%.

The test 1@ pad was wetted with the test 1@ solution to about 6 times the extent and then subjected to liquid passage and evaporation tests, and the results are shown in Table 3.

EXAMPLE In this method, the drilling creates a substantially cylindrical hole with a slightly protruding rim.

This film has a thickness of 46μ, i.e. 64,000
m2/kg), and the pore density is 50 pores/cm2.
and the diameter of the hole is 178μ.

The test pad was wetted with the test liquid to a depth of about 6 times, and then subjected to liquid passage and evaporation tests, and the results are shown in Table 3.

EXAMPLES XX-XXI The test pads were similar to those in Examples 1-IV, but the conically stamped and perforated film was used in Example XV.
II-XIX, the perforated polyethylene film was changed.

The test pad was wetted with the test liquid to a depth of about 6 times, and then subjected to liquid passage and evaporation tests, and the results are shown in Table 3.

As is clear from the results shown in Table 2, the perforated polyethylene film itself is not liquid-impermeable, and the wax-treated tissue itself is not liquid-impermeable either.
The combination of the film and the tissue is substantially liquid impermeable, yet the combination is gas permeable; It can work as a sheet.

In addition, the numerical values in Table 1 indicate that the high-drainage porosity layer other than the wax-treated tissue works effectively in the back seam I.
This shows that it provides a liquid-impermeable, gas-permeable backing.

It will be obvious to those of ordinary skill in the art that other highly porous materials, usually hydrophilic, can be used in combination with fatty acids and their salts, vegetable waxes, silicones, fluoroorganic resins, olefin resins, etc. Drainage properties can be improved by using various coating materials based on the coating material, and this can also be used as the highly porosity layer of the present invention.

Examples of porous hydrophilic materials with relatively high void ratios are natural and man-made open cell ohms and sponges, nonwoven and woven fabrics, various paper products, and the like.

Such materials (the water-draining materials described above) can also be made directly from open cell ohms or fiber assemblies made from naturally water-draining polymers such as the fluoroorganic and olefinic resins mentioned above. .

3-olefin film, especially polyethylene film,
Although preferred for the perforated sheets of the present invention because of their availability and low cost, many other materials may be used, such as polymers of vinyl chloride, polyvinyl chloride, propylene, butylene, etc.

These films can also be made of one or more layers of resin and provide the most effective combination of strength and waterproofing after drilling by providing a drainage coating with materials such as those listed for high porosity structures. You can also give matching.

Various other measurements were performed as follows.

Measurement of Height in Protrusion The height of the protrusion in the hole was measured optically using a microscope with a vernier lens lifting screw calibrated in μ.

First, the base of the protrusion (i.e., the top surface of the film) is focused and the vernier reading is recorded, then the vernier screw is turned to focus on the tip of the protrusion, the vernier is read again, and the The height of the protrusion was determined by the difference in the readings of the two verniers.

Emmendorf tear strength Tapi Metfod T 414
Measured by M-49.

Pole impact value is similar to ASTM-D1709, but instead of a dart, it has a diameter of 19 mm and a weight of 28.1.
A 6g steel ball is used and the diameter of the film fixing ring is 76
mm, and the impact force was adjusted by adjusting the falling height of the ball.

The height of the drop was taken as such that 50% of the drops created an open gap in the film (tearing the film).

Elastic strain meter type tensile testing machine (ASTM standard D-882-67
) was used, and the specimen was 25 mm wide and 50 mm long.
The speed of the crosshead of the testing machine was 500 mm/min for both tension and return, and the specimen was stretched to 30% or 50% elongation and then reached the 0 point (
(No load) and the permanent set was measured.

Projected Diameter of the Holes The perforated sheet was placed under a microscope with a graduated eyepiece and the diameter of the holes was measured.

Air permeability of the perforated film with holes 36 mm in diameter (100 m2 in area)
A sample holder is used, which has an airtight chamber attached below it, an air source is connected to the chamber, the air pressure is controlled by an air controller, and a flow rate is established between the chamber and the controller. A correction water column gauge was also installed in the chamber to measure the pressure difference between the chamber and the atmosphere.

A specimen approximately 38 mm wide was cut from the perforated sheet and mounted above the hole in a specimen holder with the protrusion facing away from the chamber, and air Air is sent from the source, and the water column meter reading, that is, the pressure difference ΔP (pressure drop) on both sides of the specimen, is controlled so that it is the predetermined value, the air flow rate is measured by the flow meter, and the air amount/time/ It was converted into a unit called the exposed area of the specimen.

Tissue air permeability per ASTM, D-737-69, cfm/ft2
ato, 5inH20△P (differential pressure water column Q, 5in
The amount of permeation (ft3) per area (ft2) was measured.

Tissue void ratio (calculation example) Weight of unwaxed tissue 12.4 lb/3000 ft2 Weight of waxed tissue 15,41b 73000 ft2 Thickness... under pressure of 80 g/in2 0.005i
n Teishno volume per 3000ft2 (80g/i above)
(under n2) Area x Thickness Volume of fibers in tissue Volume of wax Total solid volume Volume of fibers + volume of wax Void ratio of perforated polyethylene film (calculation example) Weight of polyethylene film , the area and the density calculated from the engineered thickness are very close to the density determined by classical drainage methods, and therefore, for the purposes of the present invention, it is a substantially void-free solid. You can think that.

If this film is perforated with a card cloth having 530 needles/in2 (diameter of each needle is 0.0091n2) and each hole can have a perfect shape, then the perforation will reduce the void ratio of the holes. Increased in proportion to area (total total).

The area (total) of two voids after drilling ÷ Surface area Due to its elasticity, the film contracts after drilling, and the diameter of the holes is therefore reduced, so the void ratio is smaller than the value calculated above, and The apertured polyethylene film described in , also has a low void ratio.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway perspective view of a diaper as an embodiment of the disposable absorbent device according to the present invention in an unfolded state, and Fig. 2 is a partially cutaway view of the back seam I. FIG. 3 is a perspective view of a portion of an apparatus for drilling holes in a waterproof sheath I. FIG. 21...disposable diaper, 22...front sheet, 23...absorbent material, 24.25...
・First and second layers to back sea 1, 26.27...
...Longitudinal edge and side edge of the first layer to the back seam 1,
28...Polyethylene seams 1 to 1 forming the first layer. 29...Protrusions in the above sheet, 30.
... Hole, 36 ... Sandwich roll machine, 31.
32...The receiver is a roll and a punching roll, 33
... Card cloth, 34 ... Card cloth needle, 35 ... Fell l-sleeve.

Claims (1)

[Claims for Utility Model Registration] In a disposable absorbent device having an absorbent body and a breathable, liquid-impermeable backing sheet 1, the backing sheet has a first part for forming an effective ventilation section of the backing sheet. Distinguished from the combination of the first layer and the second layer, the second layer is placed between the first layer and the absorbent body, and the first layer has (A) liquid impermeability and drainage properties; (B) The film has a number of protrusions protruding in the direction of the absorbent body. provided, and the height of the protrusion is at least 5
(C) pores are formed in the protrusions, the pores have an average projected diameter of about lO to 100μ, and the pores are formed in a portion of the first layer of the same size as the effective ventilation area the opening area of the portion of the first layer is about 0.01 to 1% of the area of the effective ventilation portion, and the second layer is made of a fibrous sheet and a drainage material; The surfaces of the fibers constituting the sheets 1 to 1 are coated with the drainage material, the coated sheets I have a void ratio of at least 60%, and the drainable fibrous sheet has a water column of 12
．． At least 3m37m1n/m at a pressure difference of 7mm
2. A disposable absorbent device constructed so as to have an air permeability of 2, so that the passage of liquid through the effective vent is substantially prevented, but the passage of vapor and gas can take place.