JP6309036B2 - Absorbent articles - Google Patents

Description

  The present invention relates to a biodegradable absorbent article such as a disposable diaper, a sanitary napkin, and an incontinence pad.

  In various industrial products such as fiber products and sheet products, products made of petroleum resins such as polyethylene and polystyrene may generate toxic gases or remain in the soil during disposal by incineration or landfill. In recent years, replacement of petroleum-based resins with biodegradable resins has been studied due to the large environmental load.

  Such substitution of petroleum-based resins with biodegradable resins has been studied in various absorbent articles such as disposable diapers, sanitary napkins, and incontinence pads. For example, Patent Document 1 discloses a sanitary article. The main constituent film, nonwoven fabric, adhesive tape and water-absorbing material are biodegradable, and the water-absorbing material is composed of galactomannan, boron ions and trivalent or higher polyvalent metal ions other than boron ions. Sexual hygiene products have been proposed. The sanitary article disclosed in Patent Document 1 has excellent water absorption performance and texture, and is further considered to have excellent biodegradability in soil and compost.

JP 2002-35037 A

  In the sanitary article disclosed in Patent Document 1, a hydrolyzable biodegradable resin such as a polylactic acid polymer is used as a resin for forming a nonwoven fabric (top sheet), a film (back sheet) and an adhesive tape. However, in general, such a hydrolyzable biodegradable resin has a lower moldability than the above-mentioned petroleum-based resin (synthetic resin), and is a resin that is easily reduced in molecular weight by hydrolysis. Each structural member such as a front sheet and a back sheet formed using such a resin and an absorbent article configured using each structural member are more durable than those using a conventional synthetic resin. Various physical properties required for absorbent articles such as strength and strength may be inferior.

Furthermore, since the absorbent article having biodegradability is not usually considered with respect to the timing at which each constituent member such as the top sheet and the back sheet is broken down by biodegradation (microbe decomposition), such an absorbent article is used. When the landfill process is performed after use, each constituent member collapses at different timings, and it is difficult to predict the timing at which the entire absorbent article collapses. In addition, depending on the disposal mode of the absorbent article, a component member (such as a front sheet or a back sheet) that has a late timing of disintegration inhibits the decomposition of an absorbent body made of pulp or the like that has a quick timing of disintegration, and the absorbent article There was also a possibility that the whole collapse might be prolonged.
Therefore, landfill processing of absorbent articles after use cannot be systematically performed, and there is a risk that the environment of the landfill processing site will be deteriorated, such as unexpected land subsidence occurring in the landfill processing site. .

  Therefore, the present invention can maintain the environment in the landfill processing place of the absorbent article after use while maintaining various physical properties equivalent to those of the absorbent article using the constituent members made of a conventional synthetic resin. An object is to provide an absorbent article having degradability.

The absorbent article which concerns on 1 aspect (aspect 1) of this invention is an absorbent article containing a some synthetic resin sheet, Comprising: Each of these synthetic resin sheets contains an oxidative decomposition agent, and is 80 degreeC. The disintegration time (D _h ) by the heat acceleration test of the above is 36 hours or more, and the plurality of synthetic resin sheets have a decomposition rate index (D _i ) of each synthetic resin sheet obtained based on the following formula (1). Difference (ΔD _i ) is an absorbent article satisfying the following formula (2).
D _i = B _r × S _a (1)
In Expression (1), _{B r,} the weight ratio of the oxidative decomposition agent to the synthetic resin component of the synthetic resin sheet (g / g) represents, _{S a} has a specific surface area of the synthetic resin sheet ^(cm 2 / g) Represents. ]
−36 / k ≦ ΔD _i ≦ 36 / k (2)
[In formula (2), k represents the slope in the approximate expression of the linear function obtained from the relationship between the decomposition rate index (D _i ) of each synthetic resin sheet and the decay time D _h by the thermal acceleration test at 80 ° C. . ]

In the absorbent article of this aspect 1, since the plurality of synthetic resin sheets constituting the absorbent article are sheets made of a synthetic resin containing an oxidative decomposition agent (that is, an oxidative decomposition type biodegradable resin), Unlike absorbent articles using sheets made of hydrolyzable biodegradable resins such as polylactic acid, modified starch, and aliphatic polyester, various physical properties equivalent to absorbent articles using conventional synthetic resin sheets (Durability, strength, etc.) can be maintained.
Furthermore, since the plurality of synthetic resin sheets have a disintegration time (D _h ) of 36 hours or more in a heat accelerated test at 80 ° C., the oxidative decomposition of each synthetic resin sheet (that is, lowering the molecular weight of the synthetic resin) proceeds. However, the quality (structure and function) of the absorbent article can be maintained for a necessary period of time (ie, at least about 6 months) after the absorbent article is manufactured, and further, absorption after use. Each synthetic resin sheet is easily decomposed by microorganisms when the property article is landfilled.
In addition, hydrolyzable biodegradable resins such as polylactic acid, modified starch, and aliphatic polyester are decomposed and decomposed through a low molecular weight step by hydrolysis and a biodegradation step by microorganisms. The oxidative degradation type biodegradable resin used in the present invention (that is, a synthetic resin containing an oxidative degradation agent) uses heat and light of the surrounding environment as an energy source (in a light-shielding environment such as in soil or in a package). In addition, heat is used as an energy source), and the decomposition proceeds and degrades through a low molecular weight step in which a synthetic resin (for example, polyolefin resin) is oxidatively decomposed by an oxidative decomposition agent and a biodegradation step by microorganisms.

And in the absorptive article of the above-mentioned aspect 1, in the plurality of synthetic resin sheets, the difference (ΔD _i ) in the decomposition rate index (D _i ) of each synthetic resin sheet obtained based on the above formula (1) is the above formula. Since (2) is satisfied, at least 6 months have passed since the absorbent article was manufactured (the manufacturing period of the absorbent article and the manufacturing period of each synthetic resin sheet are substantially the same period). The timing at which each synthetic resin sheet collapses due to decomposition can be controlled within about six months before and after (for example, the amount of the oxidative decomposition agent is satisfied so as to satisfy the above formula (1) and the above formula (2)) All the timings at which each synthetic resin sheet collapses can be controlled within about one year.
As a result, the absorbent article of the present aspect 1 can systematically carry out the landfill treatment of the absorbent article after use, thereby preventing problems such as unexpected ground subsidence in the landfill treatment area. Since it becomes easy, the environment in the landfill processing place can be preserved.

Moreover, in another aspect (aspect 2) of the present invention, in the absorbent article according to aspect 1, each of the plurality of synthetic resin sheets has the disintegration time (D _h ) of 432 hours or less.

Since the disintegration time (D _h ) of 432 hours in the thermal acceleration test at 80 ° C. corresponds to about 72 months (about 6 years) in an environment at 24 ° C., the absorbent article of the present aspect 2 is landfilled after use. However, it is difficult for the above-mentioned synthetic resin sheets to remain in the soil over a long period of time exceeding 6 years, and the environment of the landfill treatment area can be better preserved.

  Furthermore, in another aspect (Aspect 3) of the present invention, in the absorbent article according to Aspect 1 or 2, each of the plurality of synthetic resin sheets contains 50 mass of polyolefin resin or polyolefin resin composition as a synthetic resin component. And at least one compound selected from the group consisting of a carboxylic acid metal salt, a hydroxycarboxylic acid, a transition metal compound, a rare earth compound and an aromatic ketone.

In the absorbent article according to aspect 3, each of the plurality of synthetic resin sheets contains 50% by mass or more of a polyolefin resin or a polyolefin resin composition as a synthetic resin component, and contains the specific compound as an oxidative decomposition agent. Therefore, each synthetic resin sheet can be decomposed more efficiently (specifically, even with a small amount of oxidative decomposition agent, it can be decomposed uniformly with few spots at a certain decomposition rate) The timing at which the synthetic resin sheet collapses due to decomposition can be controlled more accurately (that is, the timing at which each synthetic resin sheet collapses due to decomposition can be matched more accurately).
As a result, the absorbent article according to the present aspect 3 can reduce the environmental burden associated with biodegradation by microorganisms in the soil when the absorbent article after use is landfilled, and the landfill process can be performed more accurately. Since it becomes possible to implement it systematically (that is, it becomes easier to prevent problems such as unexpected land subsidence in landfills), the environment of the landfill can be more accurately preserved. it can.

Furthermore, in another aspect (Aspect 4) of the present invention, in the absorbent article according to Aspect 3, the oxidative decomposition agent comprises a mixture of a carboxylate and a rare earth compound, and each of the plurality of synthetic resin sheets includes The decomposition rate index (D _i ) is in the range of 0.5-5.

In the absorbent article of this aspect 4, since the oxidative decomposition agent is composed of the specific mixture, each synthetic resin sheet can be decomposed more efficiently (specifically, even with a smaller amount of oxidative decomposition agent above a certain level). The timing at which each synthetic resin sheet collapses due to decomposition is controlled more precisely (ie, the timing at which each synthetic resin sheet collapses due to decomposition) Can be matched accurately).
As a result, the absorbent article according to the present aspect 4 can further reduce the environmental load due to biodegradation by microorganisms in the soil when the absorbent article after use is landfilled, and the landfill process is more accurate. It becomes possible to implement it well in a planned manner (that is, it becomes easier to prevent problems such as unexpected land subsidence in landfill sites).
Further, the absorbent article of the present embodiment 4, the synthesis order degradation rate index of the resin sheet (D _i) is in the range of 0.5 to 5, the absorbent article is under 24 ° C. environment from being produced Each synthetic resin sheet can be disintegrated by decomposition after about 5 years and 6 months while maintaining the quality (structure, function, etc.) as an absorbent article for at least about 4 years.
Therefore, the absorbent article of this aspect 4 can maintain the environment in the landfill processing place of the absorbent article after use more accurately.

  Furthermore, another aspect (aspect 5) of the present invention is an absorbent article packaged with a light-shielding sheet, and the absorbent article is the absorbent article according to any one of aspects 1 to 4.

Since the absorbent article packaged in this aspect 5 is one in which the absorbent article in each of the above aspects is packaged by a light-shielding sheet, the light-shielding sheet can affect the oxidative decomposition of each synthetic resin sheet. The influence of light (particularly, ultraviolet rays) can be more reliably eliminated, and the timing at which each synthetic resin sheet collapses can be controlled more accurately.
As a result, the packaged absorbent article according to the present aspect 5 can perform the landfill process of the absorbent article after use more accurately and systematically (that is, an unexpected ground in the landfill processing place) Various problems such as subsidence can be further prevented), and the environment in the landfill site can be more accurately preserved.

Furthermore, in another aspect (aspect 6) of the present invention, in the packaged absorbent article according to aspect 5, the light-shielding sheet is composed of a synthetic resin sheet containing an oxidative decomposition agent, and is represented by the following formula (3): The difference (ΔD _is ) between the degradation rate index (D _is ) of the light-shielding sheet determined based on the degradation rate index (D _i ) of any synthetic resin sheet among the plurality of synthetic resin sheets _is It is the packaged absorbent article which satisfy | fills Formula (4).
D _is = B _rs × S _as (3)
[In formula (3), B _rs represents the mass ratio (g / g) of the oxidative decomposition agent to the synthetic resin component in the light-shielding sheet, and S _as is the specific surface area (cm ² / g) of the light-shielding sheet. Represents. ]
−36 / k ≦ ΔD _is ≦ 36 / k (4)
[In Formula (4), k is the same as k in Formula (2). ]

In the packaged absorbent article according to aspect 6, the above-described light-shielding sheet is a synthetic resin sheet containing an oxidative degradation agent, and the light-shielding sheet decomposition rate index is obtained based on the above formula (3). Since the difference (ΔD _is ) between (D _is ) and the decomposition rate index (D _i ) of any synthetic resin sheet among the plurality of synthetic resin sheets satisfies the above formula (4), The timing at which the light-shielding sheet collapses due to decomposition is also controlled to the same timing as each of the synthetic resin sheets (that is, the timing at which the light-shielding sheet collapses due to decomposition and the timing at which each synthetic resin sheet collapses due to decomposition are substantially the same. Can).
Therefore, even if the absorbent article packaged in this aspect 6 is landfilled together with the absorbent article after use with the above-described light-shielding sheet, the landfill process can be carried out systematically, which is not expected in the landfill treatment area. Since various problems such as land subsidence can be easily prevented, the environment in the landfill treatment area can be well preserved.

  ADVANTAGE OF THE INVENTION According to this invention, the environment in the landfill processing place of the absorbent article after use can be maintained, maintaining various physical properties equivalent to the absorbent article using the structural member which consists of conventional synthetic resins, An absorbent article having degradability can be provided.

FIG. 1 is a plan view of a biodegradable disposable diaper 1 (absorbent article) according to an embodiment of the present invention as viewed in the thickness direction from the top sheet side in a developed state. FIG. 2 is an end view of a cross section taken along the line II-II ′ of FIG. 1 in the disposable diaper 1 according to the embodiment of the present invention. FIG. 3 is a graph showing the relationship between the decomposition rate index (D _i ) of each synthetic resin sheet according to an example of the present invention and the disintegration time D _{h obtained} by the 80 ° C. thermal acceleration test.

  Hereinafter, preferred embodiments of the absorbent article of the present invention will be described in detail with reference to the drawings. In the present specification, unless otherwise specified, “the thickness of the target object (for example, an absorbent article, an absorbent body, etc.) placed on a horizontal surface in an unfolded state from the upper side in the vertical direction is described. “Looking in the direction” is simply called “plan view”.

Various directions and the like used in this specification are as follows unless otherwise specified.
In this specification, “width direction” refers to “a direction in which the length of a vertically long object (for example, an absorbent article) in a plan view is short (short direction)”, and “longitudinal direction” is “plane This refers to the direction in which the longitudinally long target object (for example, an absorbent article or the like) is long, and the “thickness direction” refers to the “perpendicular direction with respect to the target object placed on a horizontal plane”. The width direction, the longitudinal direction, and the thickness direction are in a relationship orthogonal to each other. Further, in the present specification, “in the width direction of the vertically long object, the side relatively proximal to the width direction central axis extending in the longitudinal direction” is referred to as “inward side in the width direction”, and “the vertically long object” In the width direction of the object, the “relatively distal side with respect to the central axis in the width direction” is referred to as “the outer side in the width direction”.
Further, in the present specification, unless otherwise specified, in the thickness direction of the absorbent article, “relatively proximal to the skin surface of the wearer when the absorbent article is worn” "Side", and "the distal side relative to the skin surface of the wearer when the absorbent article is worn" is referred to as "the non-skin facing surface side".

  FIG. 1 is a plan view of a disposable diaper 1 (absorbent article) having biodegradability according to an embodiment of the present invention as viewed in the thickness direction from the surface sheet side in an unfolded state, and FIG. It is an end elevation of the section which followed the II-II 'line of Drawing 1 in disposable diaper 1.

As shown in FIG.1 and FIG.2, the disposable diaper 1 which concerns on this embodiment has the longitudinal direction L, the width direction W, and the thickness direction T which are mutually orthogonally crossed, In the said thickness direction T, a wearer A liquid-permeable surface sheet 2 located on the skin-facing surface side, a liquid-impermeable back sheet 3 located on the non-skin-facing surface side of the wearer, and an absorber 4 located between these two sheets, A pair of side sheets 5 and 5 that are arranged on the skin facing surface side of the top sheet 2 and function as leak-proof walls when the disposable diaper 1 is worn are provided as main constituent members.
Furthermore, the disposable diaper 1 is disposed in the longitudinal direction of the left and right leg-around portions that are arranged in the vicinity of the outer edge in the width direction W of the pair of side sheets 5 and 5 and abut against the thigh of the wearer. A so-called tape-type disposable diaper comprising: an elastic member 6 made of rubber or the like that is expanded and contracted by L; and a connecting tape 7 made of a mechanical fastener or the like that connects the abdominal region and the back region of the disposable diaper 1 when worn. It is. In addition, in the disposable diaper 1 shown in FIG. 1, the area | region of the one end side of the longitudinal direction L located below FIG. 1 covers the wearer's abdomen, and the other end of the longitudinal direction L located above FIG. The region on the side is a dorsal region that covers the wearer's back (buttock).

  Hereinafter, various members constituting the disposable diaper 1 according to the present embodiment will be described in detail.

[Surface sheet]
In the present embodiment, the top sheet 2 is disposed on the skin-facing surface side of the absorbent body 4 in the disposable diaper 1 (above the absorbent body 4 in FIG. 2), and liquid excrement such as urine excreted from the wearer. Is a liquid-permeable synthetic resin sheet that quickly moves toward the absorber 4. This surface sheet 2 is an example of a synthetic resin sheet in the absorbent article of the present invention.
In addition, in this embodiment, although the surface sheet 2 has a rectangular planar view shape long in the direction along the longitudinal direction L of the disposable diaper 1, in the absorbent article of this invention, it is limited to such a shape. The surface sheet (synthetic resin sheet) may be of any shape and size in plan view.

  Examples of the liquid-permeable synthetic resin sheet forming the surface sheet 2 include any synthetic fiber sheet such as a nonwoven fabric, a woven fabric, and a knitted fabric, and a synthetic resin film or a synthetic resin sheet in which liquid-permeable holes are formed. Although a resin sheet can be used, among these, it is preferable to use a nonwoven fabric from the viewpoints of liquid permeability, flexibility, and touch. In addition, the kind in particular of a nonwoven fabric is not restrict | limited, Arbitrary nonwoven fabrics, such as an air through nonwoven fabric, a spun bond nonwoven fabric, a spunlace nonwoven fabric, and SMS, can be employ | adopted according to a desired function, a use, etc.

  In addition, the form of the fiber constituting the nonwoven fabric is not particularly limited, and in addition to a general form of fiber having a single structure with a substantially circular cross-sectional shape, for example, a core-sheath type composite fiber, a side-by-side type Various composite fibers such as composite fibers and sea-island type composite fibers; hollow fibers having a hollow internal structure; atypical cross-section fibers having a cross-sectional shape such as a flat shape, Y-type, and C-type; Various types of fibers such as split fibers that are split by a physical load such as water flow, heat, embossing, and the like can be used.

  The synthetic resin sheet forming the top sheet 2 is formed of a resin composition containing at least a synthetic resin and an oxidative decomposition agent. This resin composition may contain arbitrary additives and fillers in addition to the above-described synthetic resin component and oxidative degradation agent. A sheet made of a synthetic resin containing such an oxidative decomposition agent (that is, an oxidative decomposition type biodegradable resin) includes a sheet made of a hydrolyzable biodegradable resin such as polylactic acid, modified starch, and aliphatic polyester. In contrast, various physical properties (durability, strength, etc.) equivalent to those of a sheet made of a synthetic resin having no conventional biodegradability can be maintained.

The synthetic resin component contained in the synthetic resin sheet is not particularly limited as long as it can be used for absorbent articles. For example, polyethylene, polypropylene, polybutylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer Polyolefin resins such as polymers, ethylene-acrylic acid copolymers and ionomer resins; polystyrene resins such as polystyrene; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; and any synthetic resins such as polyamide resins such as nylon Can be used. In addition, these synthetic resins may be used alone or in combination of two or more resins. Among these synthetic resins, those containing 50% by mass or more of a polyolefin resin or a polyolefin resin composition from the viewpoints of strength, durability, oxidative decomposability after use of the absorbent article, biodegradability, and the like. Further, the polyolefin resin is particularly preferably polyethylene or polypropylene. In particular, when the synthetic resin sheet is made of a nonwoven fabric, it is preferable to use a core-sheath type composite fiber in which the core is made of polypropylene and the sheath is made of polyethylene.
In this specification, the polyolefin-based resin composition is a mixture of two or more types of polyolefin-based resins, or a mixture of a polyolefin-based resin and another resin and containing 50% by mass or more of the polyolefin-based resin. Say.

  The oxidative degradation agent contained in the synthetic resin sheet is not particularly limited as long as it is a substance capable of reducing the molecular weight of the synthetic resin to such an extent that it can be biodegraded by microorganisms in the soil by oxidizing and decomposing the above-mentioned synthetic resin. For example, US Pat. No. 3,840,512, US Pat. No. 5,308,906, US Pat. No. 5,565,503, US Pat. No. 5,854,304, WO 88/09354 Any oxidative degradation agent as disclosed in the above can be used.

  Among them, the oxidative decomposition agent preferably contains at least one compound selected from the group consisting of carboxylic acid metal salts, hydroxycarboxylic acids, transition metal compounds, rare earth compounds, and aromatic ketones. The oxidative degradation agent containing these specific compounds can decompose the above-described synthetic resin sheet more efficiently (specifically, even with a small amount of oxidative degradation agent, the degradation rate is more than a certain level and the spots are evenly distributed. In addition, there is an advantage that it is easy to control the timing at which the synthetic resin sheet collapses due to decomposition. Such advantages are more clearly exhibited when the synthetic resin sheet contains 50% by mass or more of a polyolefin resin or a polyolefin resin composition as a synthetic resin component. As a result, the specific synthetic resin sheet is used. Absorbent articles that have been used can reduce the environmental burden associated with biodegradation by microorganisms in the soil when the absorbent articles after use are landfilled, and the landfill process must be implemented more accurately and systematically. (That is, it becomes easier to prevent problems such as unexpected land subsidence in the landfill processing area), so that the environment of the landfill processing area can be more accurately preserved.

  Further, among the oxidative degradation agents containing the specific compound, the oxidative degradation agent comprising a mixture of a carboxylate and a rare earth compound exhibits the above-mentioned advantages more remarkably and further improves biodegradability after use. Since it can be promoted, it can be particularly preferably used. As a commercial item of such an oxidative decomposition agent, for example, “P-Life” (trade name) manufactured by P-Life Japan Inc. can be mentioned.

  Examples of the carboxylic acid metal salt that can be used as the oxidative decomposition agent include a metal salt of an aliphatic carboxylic acid having 10 to 20 carbon atoms, preferably a stearic acid metal salt. Examples of metal atoms that form metal salts with aliphatic carboxylic acids include cobalt, cerium, iron, aluminum, antimony, barium, bismuth, chromium, copper, gallium, lanthanum, lithium, magnesium, molybdenum, nickel, calcium, silver Sodium, tin, tungsten, vanadium, yttrium, zinc, zirconium and the like, preferably cobalt, cerium, iron and the like. The carboxylic acid metal salt may contain one kind of carboxylic acid metal salt alone or may contain two or more kinds of carboxylic acid metal salts in combination.

  Examples of the hydroxycarboxylic acid that can be used as the oxidative degradation agent include monohydroxytricarboxylic acids such as citric acid; polyhydroxydicarboxylic acids such as trihydroxyglutaric acid and saccharic acid; dihydroxydicarboxylic acids such as tartaric acid; tartronic acid and malic acid. Monohydroxydicarboxylic acids such as polyhydroxymonocarboxylic acids such as arabic acid; dihydroxymonocarboxylic acids such as glyoxylic acid and glyceric acid. The hydroxycarboxylic acid may contain one kind of hydroxycarboxylic acid alone or may contain two or more kinds of hydroxycarboxylic acids in combination.

  Examples of the transition metal compound that can be used as the oxidative decomposition agent include cobalt salts and magnesium salts, preferably cobalt salts or magnesium salts of aliphatic carboxylic acids having 12 to 20 carbon atoms, more preferably stearic acid. Examples include cobalt, cobalt oleate, magnesium stearate, magnesium oleate, and the like. The transition metal compound may contain one kind of transition metal compound alone or may contain two or more kinds of transition metal compounds in combination.

  Examples of the rare earth compound that can be used as an oxidative decomposition agent include rare earth elements such as cerium (Ce), yttrium (Y), and neodymium (Nd) belonging to Group 3 of the IUPAC periodic table, or oxides and hydroxides thereof. , Sulfate, nitrate, acetate, chloride, carboxylate, etc. More specifically, cerium oxide, ceric sulfate, ceric ammonium sulfate, ceric ammonium nitrate, cerium acetate, nitric acid Examples thereof include lanthanum, cerium chloride, cerium nitrate, cerium hydroxide, cerium octylate, lanthanum oxide, yttrium oxide, and scandium oxide. The rare earth compound may contain one kind of rare earth compound alone, or may contain two or more kinds of rare earth compounds in combination.

  Examples of the aromatic ketone that can be used as the oxidative decomposition agent include benzophenone, anthraquinone, anthrone, acetylbenzophenone, and 4-octylbenzophenone. The aromatic ketone may contain one kind of aromatic ketone alone or may contain two or more kinds of aromatic ketones in combination.

And in this embodiment, the synthetic resin sheet which forms the surface sheet 2 has the decay | disintegration time ( _Dh ) by a 80 degreeC thermal acceleration test for 36 hours or more. Here, the heat acceleration test at 80 ° C. means that the synthetic resin sheet is placed under a severer environment (temperature environment of 80 ° C.) than the actual ambient environment (temperature environment of 24 ° C.) in which oxidative decomposition proceeds. By accelerating the oxidative decomposition of the resin sheet, the time required for the synthetic resin sheet to decompose and fail to function as a synthetic resin sheet (that is, the synthetic resin sheet collapses due to decomposition) (that is, the disintegration time) (D _h )) is a test for predicting in a short time test, and the decay time (D _h ) by the 80 ° C. thermal acceleration test can be measured as follows. One day (24 hours) in the heat acceleration test at 80 ° C. corresponds to four months in a 24 ° C. environment.

<Measurement method of disintegration time ( _Dh ) by thermal acceleration test at 80 ° C.>
(1) A synthetic resin sheet to be measured (a synthetic fiber sheet such as a nonwoven fabric, a synthetic resin film, or a sheet) is cut into a predetermined size having a width of 25 mm and a length of 200 mm to obtain a measurement sample of the synthetic resin sheet.
(2) One end (upper end) in the longitudinal direction of the obtained measurement sample is fixed with an arbitrary jig to suspend the measurement sample, and further, the longitudinal direction of the measurement sample A measurement clip in a state where a load is applied is obtained by fixing a turn clip having a 10 g weight attached to the other end (lower end) in the direction.
(3) Further, the measurement sample in a state where this load is applied is put in an oven in which the internal temperature is set to 80 ° C., time measurement is started, and the strength of the measurement sample is 0.1 N / 25 mm. The time (h) until it becomes less than that and breaks is measured. The measured time (h) is defined as the decay time (D _h ) of the synthetic resin sheet.

As described above, the synthetic resin sheet forming the top sheet 2 has a disintegration time (D _h ) of not less than 36 hours in a heat accelerated test at 80 ° C. While the molecularization is progressing, the quality (structure, function, strength, etc.) of the surface sheet is maintained for a necessary period after production (ie, at least about 6 months in an environment of 24 ° C.). be able to.
The disintegration time of the synthetic resin sheet can be further delayed in consideration of the use guarantee period of the product and the environmental impact on the landfill site. At this time, it is easy to adjust the disintegration time of the synthetic resin sheet by appropriately adjusting the form (type, structure, size, etc.) of the sheet, the type of the synthetic resin, the type of the oxidative degradation agent, and the blending amount of the oxidative degradation agent. Can be done.

Moreover, the upper limit of the disintegration time of the synthetic resin sheet can be arbitrarily set in consideration of the use guarantee period of the product, the influence on the environment on the landfill, etc., but preferably disintegration by a heat acceleration test at 80 ° C. The time (D _h ) is 432 hours or less. The disintegration time (D _h ) of 432 hours in the thermal acceleration test at 80 ° C. corresponds to about 72 months (about 6 years) in an environment at 24 ° C. Therefore, even if a synthetic resin sheet having such a disintegration time is landfilled The synthetic resin sheet hardly remains in the soil for a long period of over 6 years, and the environment of the landfill treatment area can be better preserved.

And in this embodiment, the synthetic resin sheet which forms the surface sheet 2 is a decomposition rate index calculated | required based on following formula (1), when the mixture of the above-mentioned carboxylate and rare earth compound is used as an oxidative decomposition agent. (D _i ) is preferably in the range of 0.5 to 5.
D _i = B _r × S _a (1)
In Expression (1), _{B r,} the weight ratio of the oxidative decomposition agent to the synthetic resin component of the synthetic resin sheet (g / g) represents, _{S a} has a specific surface area of the synthetic resin sheet ^(cm 2 / g) Represents. ]

Here, the decomposition rate index D _i is an index of the decomposition rate in consideration of the quantitative element of the oxidative decomposition agent and the structural element of the synthetic resin sheet, and the oxidative decomposition agent with respect to the synthetic resin component in the synthetic resin sheet. It is an index expressed as the product of the mass ratio B _r (g / g) and the specific surface area S _a (cm ² / g) of the synthetic resin sheet.

The specific surface area S _a (cm ² / g) of the synthetic resin sheet used for the calculation of the decomposition rate index D _i represents the surface area per unit mass of the synthetic resin sheet. It can be determined as follows according to the form of the sheet.
(I) When the synthetic resin sheet is a film or sheet having a thickness of about 10 μm to 50 μm (excluding a fiber structure such as a nonwoven fabric (that is, a fiber sheet)), per unit area of the film or sheet The specific surface area S _a (cm ² / g) of the synthetic resin sheet can be obtained by multiplying the inverse of the mass (ie, basis weight) by ² . The specific surface area _S a of the case ^(cm 2 / g), the both sides of the area per unit mass of the film or sheet becomes the specific surface area ^{_{S a (cm 2 / g)}} .
(Ii) When the synthetic resin sheet is a synthetic fiber sheet (for example, non-woven fabric) made of synthetic fibers having a diameter of about 3 μm to 30 μm, using the resin specific gravity and fineness of the synthetic fibers, per unit mass of the synthetic fibers The specific surface area S _a (cm ² / g) of the synthetic resin sheet is obtained by determining the side area (the shape of the synthetic fiber is regarded as a cylinder and its side area (the area of the cylindrical surface (circumferential surface))). Can do.

As described above, in the present embodiment, the synthetic resin sheet forming the top sheet 2 has a decomposition rate index (D _i ) of 0.5 when the mixture of the carboxylate and rare earth compound described above is used as the oxidative decomposition agent. It is preferable to be within the range of ˜5. The oxidative degradation agent composed of a mixture of the above-mentioned carboxylate and rare earth compound can decompose the synthetic resin sheet particularly efficiently. Therefore, when the absorbent article after use is landfilled, it is produced by microorganisms in the soil. The environmental load accompanying decomposition can be reduced more effectively. When using an oxidative degradation agent comprising a mixture of such carboxylic acid salts and rare earth compound, degradation rate index of the synthetic resin sheet forming the surface sheet (D _i) is within the range of 0.5 to 5 The surface sheet is decomposed after about 5 years and 6 months while maintaining the quality (structure, function, etc.) as the surface sheet for at least about 4 years in an environment of 24 ° C after the surface sheet is manufactured. Therefore, the environment in the landfill processing place of the absorbent article after use can be more accurately preserved.

The degradation rate index (D _i ) of the synthetic resin sheet is adjusted as appropriate by adjusting the sheet form (type, structure, size, etc.), the type of synthetic resin, the type of oxidative degradation agent, the blending amount of the oxidative degradation agent, etc. This can be done easily.

  Further, the thickness, basis weight, density, etc. of the topsheet can be appropriately adjusted in consideration of the permeability, flexibility, touch, etc. of the liquid excreta within a range not impairing the effects of the present invention.

[Back sheet]
In this embodiment, the back surface sheet 3 is disposed on the non-skin facing surface side of the absorbent body 4 in the disposable diaper 1 (the lower side of the absorbent body 4 in FIG. 2), and liquid excretion such as urine excreted from the wearer. It is a liquid-impermeable synthetic resin sheet that prevents permeation of an object and prevents the liquid excrement from leaking into the clothes of the wearer. This back sheet 3 is also an example of the synthetic resin sheet in the absorbent article of the present invention.

  In this embodiment, the back sheet 3 is bonded to the top sheet 2 and the side sheets 5 and 5 with the absorber 4 being sandwiched between the back sheet 3 and the top sheet 2. For this bonding, for example, any bonding means such as bonding with a hot melt adhesive or bonding by various embossing treatments can be used. Moreover, in this embodiment, the back surface sheet 3 has the rectangular planar view shape long in the direction along the longitudinal direction L of the disposable diaper 1 like the above-mentioned surface sheet 2, but the absorptivity of the present invention. The article is not limited to such a shape, and a back sheet (synthetic resin sheet) having any shape and size in plan view can be adopted.

  Furthermore, although the back surface sheet 3 in this embodiment does not permeate | transmit liquids, such as a liquid excrement, it has fixed air permeability. When the back sheet has such air permeability, moisture released from the absorber to the non-skin facing surface side can be released through the back sheet, so that the inside of the absorbent article or the absorbency Moisture staying between the article and the skin surface of the wearer is reduced, and the wearer is less likely to feel stuffiness.

  As the liquid-impervious synthetic resin sheet forming the back sheet 3, for example, any synthetic resin sheet such as a synthetic fiber sheet such as a nonwoven fabric subjected to waterproofing treatment or a synthetic resin film can be used. The synthetic resin sheet that forms the back sheet 3 is also formed of a resin composition containing at least a synthetic resin and an oxidative decomposition agent, and is similar to the synthetic resin sheet that forms the top sheet 2 in terms of composition, structure, function, and the like. Therefore, specific description is omitted.

  Further, the thickness, basis weight, density, and the like of the back sheet can be appropriately adjusted in consideration of the liquid impermeability, air permeability, flexibility, etc. of the liquid excrement within the range not impairing the effects of the present invention. .

[Side sheet]
In this embodiment, a pair of side sheet | seats 5 and 5 are arrange | positioned at the skin opposing surface side (upper side of the surface sheet 2 in FIG. 2) of the surface sheet 2 in the disposable diaper 1, and the urine excreted from the wearer. It is a liquid-impermeable or water-repellent synthetic resin sheet that functions as a leak-proof wall so that liquid excrement such as the like does not leak from the width direction W of the disposable diaper 1. This pair of side sheets is also an example of the synthetic resin sheet in the absorbent article of the present invention.

  Moreover, in this embodiment, although a pair of side part sheet | seats 5 and 5 have a vertically long planar view shape in the direction in alignment with the longitudinal direction L of the disposable diaper 1, as shown in FIG. The absorbent article is not limited to such a shape, and a side sheet (synthetic resin sheet) having any shape and size in plan view can be adopted.

  As the liquid-impermeable synthetic resin sheet forming the side sheet 5, for example, an arbitrary synthetic resin sheet such as a synthetic fiber sheet such as a nonwoven fabric subjected to a waterproof treatment or a water repellent treatment, or a synthetic resin film may be used. it can. The synthetic resin sheet that forms the side sheet 5 is also formed of a resin composition containing at least a synthetic resin and an oxidative decomposition agent, and the synthetic resin sheet that forms the surface sheet 2 described above in terms of composition, structure, action, etc. Since it is the same, detailed description is abbreviate | omitted.

Further, the thickness, basis weight, density, and the like of the side sheet can be appropriately adjusted in consideration of the liquid impermeability of the liquid excrement and the like within a range that does not impair the effects of the present invention.
In the present invention, since the side sheet is not an essential component of the absorbent article, the side sheet may not be provided depending on the type of the absorbent article.

[Absorber]
In the present embodiment, the absorbent body 4 is an absorbent member that is disposed between the top sheet 2 and the back sheet 3 in the disposable diaper 1 and absorbs and holds liquid excretion such as urine that has permeated through the top sheet 2. is there. In this embodiment, as shown in FIG. 1, the absorbent body 4 has an hourglass-shaped outer shape in plan view, and is disposed over a wide range in the longitudinal direction L of the disposable diaper 1. ing.

The absorbent body 4 is not particularly limited as long as it can absorb and retain liquid excreta. For example, an absorbent core made of an absorbent material including a water absorbent fiber and a super absorbent polymer, and an outer peripheral surface of the absorbent core And at least one liquid-permeable core wrap sheet covering the surface.
The water-absorbing fiber is not particularly limited as long as it can absorb and retain a liquid. For example, wood pulp obtained from softwood or hardwood as a raw material; non-wood pulp such as kenaf, bamboo, hemp, cotton; rayon Regenerated cellulose such as fibrillar rayon; semi-synthetic cellulose such as acetate and triacetate, etc., but considering the biodegradability when absorbent articles are reclaimed and the environmental impact of the landfill, It is preferable to use plant-derived cellulosic fibers such as wood pulp.
The core wrap sheet is not particularly limited as long as it has liquid permeability and can retain the shape of the absorber. For example, a liquid permeable sheet such as a tissue made of the above-described cellulose fiber is preferably used. be able to.
Further, the superabsorbent polymer is not particularly limited as long as it can absorb and retain a liquid. For example, starch, cellulose, and synthetic polymer superabsorbent polymers can be used. In consideration of the environmental impact on the ground, those having biodegradability are preferred. In addition, since a highly water-absorbing polymer is not an essential component in an absorption core, the absorption core may contain only the above-mentioned water absorption fiber.

In addition, the thickness, basis weight, density, etc. of the absorber can be adjusted as appropriate within the range not impairing the effects of the present invention, taking into account the absorbability and flexibility of liquid excrement such as urine.
In the present invention, if an absorbent layer (absorbing layer) is separately provided, the absorbent body having the above-described configuration is not an essential component of the absorbent article. The absorber having the above-described configuration may not be provided.

And in this embodiment, the above-mentioned surface sheet 2, back sheet 3, and side part sheet | seats 5 and 5 which comprise the disposable diaper 1 (these sheets are examples of the some synthetic resin sheet in this invention). As described above, each of them contains an oxidative decomposition agent and has a disintegration time (D _h ) of 36 hours or longer by a heat accelerated test at 80 ° C., and therefore, the disposable diaper 1 constituted by these sheets is made of polylactic acid or modified Unlike biodegradable disposable diapers using sheets made of hydrolyzable biodegradable resins such as starch and aliphatic polyester, they are equivalent to conventional disposable diapers (absorbent articles) using sheets made of synthetic resin. In addition to maintaining various physical properties (durability, strength, etc.), it is necessary after the disposable diaper 1 has been manufactured while the oxidative decomposition of each of the above-mentioned sheets proceeds. During (i.e., at least about 6 months) can maintain the quality (structure or function) as a disposable diaper, furthermore, when the landfill after use is made easier each sheet is decomposed by microorganisms.

Furthermore, in this embodiment, each of the above-described top sheet 2, back sheet 3, and side sheets 5 and 5 constituting the disposable diaper 1 is a decomposition rate index of each sheet (based on the above formula (1)) ( difference D _i) ([Delta] D _i) satisfies the following formula (2).
−36 / k ≦ ΔD _i ≦ 36 / k (2)
[In formula (2), k represents the slope in the approximate expression of the linear function obtained from the relationship between the decomposition rate index (D _i ) of each synthetic resin sheet and the decay time D _h by the thermal acceleration test at 80 ° C. . ]
As is clear from the definition of k in the above formula (2), the difference in disintegration time D _h (ΔD _h ) of each synthetic resin sheet by the thermal acceleration test at 80 ° C. and the decomposition rate index (D _i ) Difference (ΔD _i ) is ΔD _h = k · ΔD _i .

When the difference (ΔD _i ) in the decomposition rate index (D _i ) of the plurality of synthetic resin sheets constituting the absorbent article satisfies the above formula (2), the absorbent article is manufactured (the absorption The production time of the functional article and the production time of each of the above-mentioned synthetic resin sheets are almost the same period.) After at least 6 months have passed, the timing at which each synthetic resin sheet collapses due to decomposition is controlled within about half a year. can do. Therefore, for example, by adjusting the blending amount of the oxidative decomposition agent so as to satisfy the above formulas (1) and (2), all the timings at which the synthetic resin sheets collapse are controlled within about one year. be able to.
As a result, the absorbent article of the present invention can systematically carry out landfill treatment after use, and it is easy to prevent various problems such as unexpected ground subsidence in the landfill treatment area. The environment in the landfill site can be preserved.

Further, in the absorbent article of the present invention, each of the plurality of synthetic resin sheets constituting the absorbent article contains 50% by mass or more of a polyolefin resin or a polyolefin resin composition as a synthetic resin component, and an oxidative decomposition agent. It preferably contains at least one compound selected from the group consisting of carboxylic acid metal salts, hydroxycarboxylic acids, transition metal compounds, rare earth compounds and aromatic ketones.
When a plurality of synthetic resin sheets constituting the absorbent article are formed with such a specific composition, each synthetic resin sheet can be decomposed more efficiently, and the timing at which each synthetic resin sheet collapses due to decomposition Can be controlled more accurately (that is, the timing at which each sheet collapses due to decomposition can be matched more accurately), so that the environmental load associated with biodegradation by microorganisms in the soil can be reduced after landfilling of absorbent articles. In addition to being able to reduce more, it becomes possible to carry out landfill processing of absorbent articles more accurately and systematically (that is, it is easier to prevent problems such as unexpected land subsidence in landfill processing sites) It is possible to preserve the environment of the landfill processing area more accurately.

Further, in the absorbent article according to the present invention, each of the plurality of synthetic resin sheets includes a mixture of a carboxylate and a rare earth compound as an oxidative decomposition agent contained in the synthetic resin sheet, and a decomposition rate index of each synthetic resin sheet. (D _i ) is preferably in the range of 0.5 to 5.
If the plurality of synthetic resin sheets constituting the absorbent article satisfy such specific requirements, each synthetic resin sheet can be decomposed more efficiently, and the above-mentioned synthetic resin sheets collapse due to decomposition. The timing at which the synthetic resin sheet is disintegrated due to decomposition can be more accurately controlled, and at least about 24 ° C. in an environment of 24 ° C. after the absorbent article is manufactured. For 4 years, while maintaining the quality (structure, function, etc.) as an absorbent article, each synthetic resin sheet can be disintegrated by decomposition after about 5 years and 6 months. Thereby, when the absorbent article after use is landfilled, it is possible to further reduce the environmental load accompanying biodegradation by microorganisms in the soil, and furthermore, landfill processing can be carried out more accurately and systematically. (That is, it becomes easier to prevent various problems such as unexpected land subsidence in the landfill site).

  The absorbent article to which the present invention is applied is not limited to the above-described embodiment, and can be applied to various absorbent articles such as pants-type disposable diapers, light incontinence pads, panty liners, sanitary napkins, and the like. In addition, various sheets of the synthetic resin sheet constituting the absorbent article are assumed depending on the type of the absorbent article to be applied. As such a sheet, for example, it is disposed between the top sheet and the absorber or between the absorber and the back sheet, and is liquid permeable to diffuse liquid excrement such as urine in the longitudinal direction or the width direction. Diffusion sheet; Liquid-impervious exterior sheet disposed on the non-skin facing side of the back sheet; Liquid-impermeable cover sheet disposed on the skin facing side of the top sheet in a pants-type disposable diaper, etc. Is mentioned. In the present invention, these sheets can also be an example of the synthetic resin sheet in the absorbent article of the present invention by forming with the same synthetic resin and mode as the top sheet in the above-described embodiment.

Furthermore, the present invention can be suitably applied to absorbent articles packaged by a packaging material (for example, package products in which a plurality of absorbent articles are packaged or individual packaged products in which absorbent articles are individually packaged). Can do. That is, the absorbent article of the present invention may be packaged by an arbitrary packaging material. In this case, the packaging material is preferably a light-shielding sheet.
When the absorbent article of the present invention is packaged by a light-shielding sheet, the light-shielding sheet has an influence of light (particularly, ultraviolet rays) that can affect the oxidative decomposition of a plurality of synthetic resin sheets constituting the absorbent article. Since it can exclude more reliably, the timing which each above-mentioned synthetic resin sheet collapses can be controlled still more accurately. Thereby, the absorbent article of the present invention packaged by the light-shielding sheet can perform the landfill treatment after use more accurately and systematically (that is, unexpected ground subsidence in the landfill treatment site) Therefore, the environment in the landfill site can be more accurately preserved.

The light-shielding sheet is not particularly limited as long as light (especially, ultraviolet rays) is not easily transmitted. For example, paper such as kraft paper or carton paper; synthetic resin film kneaded with titanium oxide or the like, aluminum vapor deposition Examples thereof include non-transparent films such as synthetic resin films and aluminum foils; transparent films such as laminated films and printed films subjected to ultraviolet ray cut treatment. Further, the light-shielding sheet is preferably a light-shielding synthetic resin sheet containing an oxidative decomposition agent, and more preferably a synthetic resin containing an oxidative decomposition agent, like the synthetic resin sheet forming the above-described surface sheet and the like. A decomposition rate index (D _is ) of the light-shielding sheet, which is made of the sheet and obtained on the basis of the following formula (3), and an arbitrary synthetic resin sheet among the plurality of synthetic resin sheets constituting the absorbent article of the present invention The difference (ΔD _is ) from the decomposition rate index (D _i ) satisfies the following formula (4).
D _is = B _rs × S _as (3)
[In formula (3), B _rs represents the mass ratio (g / g) of the oxidative decomposition agent to the synthetic resin component in the light-shielding sheet, and S _as is the specific surface area (cm ² / g) of the light-shielding sheet. Represents. ]
−36 / k ≦ ΔD _is ≦ 36 / k (4)
[In Formula (4), k is the same as k in Formula (2). ]

  When the light-shielding sheet for wrapping the absorbent article of the present invention is a synthetic resin sheet that satisfies such specific requirements, the timing at which the light-shielding sheet collapses due to decomposition also includes a plurality of synthetic resins constituting the absorbent article Since the timing can be controlled to the same timing as the sheet (that is, the timing at which the light-shielding sheet collapses due to decomposition and the timing at which each of the synthetic resin sheets collapses due to decomposition) can be used. Even when landfilled together with the absorbent article, landfill processing can be carried out systematically, and various problems such as unexpected ground subsidence in the landfill processing place can be easily prevented. Thereby, the environment in the landfill processing place can be well preserved.

  Hereinafter, the present invention will be described more specifically by way of examples and comparative examples. However, the present invention is not limited to these examples.

Example 1
As a synthetic resin sheet that can be used for absorbent articles, a polyethylene film having a thickness of 25 μm was produced as follows.
Commercially available oxidative degradation agent (trade name “P-Life”, manufactured by PLife Japan Inc., SMC2360) and three types of polyethylene resins (low density polyethylene (LDPE): 2.3 mass%, linear) Low density polyethylene (LLDPE): 83.90% by mass, high density polyethylene (HDPE): 10% by mass) and a pigment (titanium oxide) are kneaded in an extruder at a compounding ratio shown in Table 1, and then inflation is performed. A polyethylene film having a thickness of 25 μm was produced by this method.

Examples 2-4
The polyethylene films of Examples 2 to 4 were produced in the same manner as in Example 1 except that the blending ratio of the oxidative degradation agent and the three types of polyethylene resins was changed to the blending ratio shown in Table 1, respectively.

Examples 5-8
In the same manner as in Example 1, except that the blending ratio of the oxidative degradation agent and the three types of polyethylene resins was changed to the blending ratio shown in Table 1 and the thickness of the film was 37 μm, Example 5 Eight polyethylene films were produced.

Comparative Example 1
A polyethylene film of Comparative Example 1 was produced in the same manner as in Example 1 except that the oxidative degradation agent was not blended and the blending ratio of the three types of polyethylene resins was changed to the blending ratio shown in Table 1.

Comparative Example 2
Except that the oxidative degradation agent was not blended, the blending ratio of the three types of polyethylene resin was changed to the blending ratio shown in Table 1, and the thickness of the film was 37 μm, the same as in Example 1, The polyethylene film of Comparative Example 2 was produced.

For each of the obtained polyethylene films of Examples 1 to 8 and Comparative Examples 1 and 2, the specific surface area and decomposition rate index (D _i ) were calculated according to the calculation method described above, and the above-described heat acceleration test at <80 ° C. The disintegration time (D _h ) of each polyethylene film was measured according to the method of measuring disintegration time (D _h ) by These calculation results and measurement results are shown in Table 1 below.
In addition, each polyethylene film of Comparative Examples 1 and 2 did not collapse in the 80 ° C. heat acceleration test.

Example 9
Moreover, the nonwoven fabric which consists of polyolefin resin fibers was manufactured as follows as a synthetic resin sheet which can be used for an absorbent article.
First, a polypropylene resin blended with a commercially available oxidative degradation agent (trade name “P-Life”, manufactured by PLife Japan Inc., SMC2360) and a polyethylene resin blended with the oxidative degradation agent were respectively melted. While discharging from the spinning nozzle, a composite synthetic fiber (fineness: 2.2 dtex, length: 51 mm) having a core-sheath structure in which the core part is polypropylene resin and the sheath part is polyethylene resin was obtained. The blending ratio of the oxidative degradation agent to the polypropylene resin and the blending ratio of the oxidative degradation agent to the polyethylene resin were the same.
After laminating the obtained composite synthetic fiber with a basis weight of 25 g / m ² , the air-through nonwoven fabric of Example 9 was manufactured by bonding the laminate with hot air.

Examples 10-12
The air-through nonwoven fabrics of Examples 10 to 12 were produced in the same manner as in Example 9, except that the blending ratio of the oxidative decomposition agent was changed to the blending ratio shown in Table 2, respectively.

Comparative Example 3
An air-through nonwoven fabric of Comparative Example 3 was produced in the same manner as in Example 9, except that the oxidative decomposition agent was not blended.

For each of the air-through nonwoven fabrics of Examples 9 to 12 and Comparative Example 3 obtained, the specific surface area and the decomposition rate index (D _i ) were calculated, and the disintegration time (D _h ) by the above-described heat acceleration test at <80 ° C. In accordance with the measurement method, the disintegration time (D _h ) of each air-through nonwoven fabric was measured. These calculation results and measurement results are shown in Table 2 below.
In addition, the side area used for calculation of the specific surface area was obtained by calculating the volume from the average specific gravity of the fiber, and regarding the fiber as a cylinder having a height of 10,000 m, and calculating the side area of the cylinder.
Further, the air-through nonwoven fabric of Comparative Example 3 did not collapse in the 80 ° C. heat acceleration test.

FIG. 3 shows a degradation rate index (D _i ) of each polyethylene film (synthetic resin sheet) of Examples 1 to 8 and an air-through nonwoven fabric (synthetic resin sheet) of Examples 9 to 12 and a disintegration time by a heat accelerated test at 80 ° C. is a graph showing the relationship between D _h. As shown in the graph of FIG. 3, the decomposition rate index (D _i ) of the synthetic resin sheet obtained in each of the above examples and the disintegration time D _h by the heat acceleration test at 80 ° C. are proportional to each other. The approximate expression of the linear function was D _h = −24.2 × D _i +405.6 (that is, k = −24.2).
Therefore, by adjusting the difference (ΔD _i ) in the decomposition rate index (D _i ) of the plurality of synthetic resin sheets constituting the absorbent article so as to satisfy the above formula (2), each synthetic resin sheet is decomposed by It was confirmed that the collapse timing can be controlled within about half a year.

  In addition, the absorbent article of the present invention is not limited to the above-described embodiments, and can be appropriately combined and changed without departing from the object and spirit of the present invention.

1 disposable diaper (absorbent article)
2 Top sheet (an example of synthetic resin sheet)
3 Back sheet (an example of synthetic resin sheet)
4 Absorber 5 Side sheet (an example of a synthetic resin sheet)
6 Stretchable member 7 Connecting tape

Claims (5)

An absorbent article comprising a plurality of synthetic resin sheets,
Each of the plurality of synthetic resin sheets includes a polyolefin resin or a polyolefin resin composition as a synthetic resin component in an amount of 50% by mass or more , and an oxidative decomposition agent composed of a mixture of a carboxylate and a rare earth compound , and 80 ℃ heat accelerated test by disintegration time _{(D h)} is Ru der least 36 hours, a film or sheet having a thickness of 10 m to 50 m (excluding fiber sheet.) or from synthetic fibers having a diameter of 3μm~30μm Formed by a synthetic fiber sheet,
Further, the plurality of synthetic resin sheet, for all combinations of any combination of two synthetic resin sheets in the plurality of synthetic resin sheet, the following equation (1) Based on the two of the synthetic resin sheet obtained The difference (ΔD _i ) in the decomposition rate index (D _i ) satisfies the following formula (2).
The absorbent article.
D _i = B _r × S _a (1)
In Expression (1), _{B r,} the weight ratio of the oxidative decomposition agent to the synthetic resin component of the synthetic resin sheet (g / g) represents, _{S a} has a specific surface area of the synthetic resin sheet ^(cm 2 / g) Represents. ]
−36 / k ≦ ΔD _i ≦ 36 / k (2)
[In formula (2), k represents the slope in the approximate expression of the linear function obtained from the relationship between the decomposition rate index (D _i ) of each synthetic resin sheet and the decay time D _h by the thermal acceleration test at 80 ° C. . ] 2. The absorbent article according to claim 1, wherein each of the plurality of synthetic resin sheets has the decay time (D _h ) of 432 hours or less. Each of the previous SL plurality of synthetic resin sheet, the degradation rate index (D _i) is in the range of 0.5 to 5, the absorbent article according to claim 1 or 2. An absorbent article packaged with a light-shielding sheet,
The packaged absorbent article, wherein the absorbent article is the absorbent article according to any one of claims 1 to 3 . The light-shielding sheet is synthesized with the polyolefin resin or polyolefin-based resin composition comprising more than 50 wt% as a resin component, a synthetic resin sheet containing oxidative degradation agent comprising a mixture of carboxylic acid salts and rare earth compounds, 10 [mu] m It consists of the said synthetic resin sheet | seat formed with the film or sheet | seat (however, except a fiber sheet) which has a thickness of -50 micrometers (however, except a fiber sheet) or the synthetic fiber sheet | seat which consists of a synthetic fiber which has a diameter of 3 micrometers-30 micrometers, ) Based on the degradation rate index (D _is ) of the light-shielding sheet and the degradation rate index (D _i ) of any synthetic resin sheet among the plurality of synthetic resin sheets (ΔD _is ) The packaged absorbent article according to claim 4 , which satisfies the following formula (4).
D _is = B _rs × S _as (3)
[In formula (3), B _rs represents the mass ratio (g / g) of the oxidative decomposition agent to the synthetic resin component in the light-shielding sheet, and S _as is the specific surface area (cm ² / g) of the light-shielding sheet. Represents. ]
−36 / k ≦ ΔD _is ≦ 36 / k (4)
[In Formula (4), k is the same as k in Formula (2). ]

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