JP3720118B2 - Absorbent material with improved structural stability in dry and wet conditions and process for its preparation - Google Patents

Description

液体吸収速度およびぬれ感を吸収材料をおむつに使用して評価する。おむつを前記例に係る吸収性材料を含むラミネート製品より作る。おむつの性質を評価し、表２に提示する。

本発明のおむつ（試料No. １およびNo. ３）は、高い尿装入量、例えば、尿容量少なくとも１５０mlで試料No. ２より迅速な液体吸収速度を示す。液体吸収速度は、湿潤状態で吸収性ゲル状粒子の粒状物間のより迅速な流体輸送によって改善される。吸収性ゲル状粒子にポリエチレンが添加されている試料No. ３においては、ラミネート製品はより一層迅速な液体吸収速度を示す。試料No. ３における吸収性ゲル状粒子とポリエチレンイミンの結合力は、試料No. １のものより高い。表２にも示すように、本発明のぬれ感は、ポリ陽イオン重合体なしの吸収性材料の場合と同様で維持されている。
【０１００】
ここに記載の例および態様は、例示の目的のためのみのものであり且つそれに徴しての各種の修正または変更は、当業者に示唆されるものであり本願の精神および範囲および特許請求の範囲の範囲に包含されることが理解される。
【図面の簡単な説明】
【図１】本発明の吸収性材料を製造するための装置の概略図である。
【符号の説明】
１ 製造装置
１０ 粒子適用ユニット
１１ 担体層装置
１２ 吸収性ゲル状粒子供給ユニット
１７ グルー微小繊維供給ユニット
１８ ポリ陽イオン重合体噴霧ユニット
２１ 第一空気流
２２ 第二空気流
２３ 一体化空気流
２４ 第三空気流
２５ 担体層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an absorptive material that swells upon contact with liquids such as water and body fluids and absorbs such liquids. More particularly, the present invention relates to improved structural stability of absorbent materials in the dry and wet states. The absorbent material of the present invention is particularly suitable for absorbent articles such as diapers, adult incontinence pads, and sanitary napkins.
[0002]
[Background Art and Problems to be Solved by the Invention]
Water-insoluble water-swellable hydrogel-forming absorbent polymers can absorb large amounts of water, body fluids (eg, urine, blood, menstrual blood), industrial fluids, household fluids, etc. Can be held in. These absorbent properties of such polymeric materials are particularly useful when using polymeric materials in absorbent articles such as disposable diapers, adult incontinence pads and briefs, and sanitary products such as sanitary napkins. It is.
[0003]
The development of a superabsorbent member used in such an absorbent article is a particularly interesting subject in developing thin absorbent articles. For example, a thinner diaper is not too bulky to wear, fits better under clothing, and does not bother too much. In addition, the packaging of absorbent articles is also reduced in size, which is useful for reducing the storage and distribution costs of manufacturers and distributors when they wait.
[0004]
In order to provide thinner absorbent articles such as diapers, it is necessary to develop a relatively thin core that can absorb and retain large amounts of bodily fluids, especially urine. In this regard, the use of certain absorbent polymers (often referred to as “hydrogels”, “superabsorbents” or “hydrocolloid” materials) was particularly important. For example, the use of such absorbent polymers (hereinafter “water-insoluble absorbent hydrogel-forming polymers (WAHP)”) in absorbent articles is disclosed in US Pat. No. 3,699,103 issued Jun. 13, 1972. No. (Harper et al.) And US Pat. No. 3,670,731 (Harmon), issued Jun. 20, 1972.
[0005]
Furthermore, conventional absorbent articles generally consisted of a relatively small amount of WAHP absorbent gel-like particles (eg, about 50% by weight or less). For example, US Pat. No. 4,834,735 (Alemeni et al.) Issued on May 30, 1989 contains about 9 to about 50% WAHP in the fibrous matrix of the core contained in the absorbent article. Is disclosed. However, there are several problems in trying to provide a thin core with a concentration of absorbent gel-like particles greater than 50% by weight.
[0006]
Ordinary absorbent articles have the problem that the absorbent gel-like particles are not fixed correctly and move (shift) freely during the manufacturing process and / or during use (when worn). Movement of the absorbent gel-like particles during manufacture will result in handling loss of the absorbent material as well as a non-uniform distribution of particles within the core. In addition, the absorbent gel-like particles may move during or after swelling. The lack of the ability to lock the particles in the optimal position means that there is a lack of stability, that is, there is not enough urine absorption in one area but an excessive volume of urine flows out in the other area. Bring about a phenomenon.
[0007]
An important factor for solving the problem is to minimize and / or eliminate the transfer of absorbent gel-like particles consisting of WAHP from the first supply position to another position and handling losses during manufacture.
[0008]
Another important factor is that when wearing articles containing such absorbent gel-like particles, WAHP swelling (eg, in urine) particle movement and / or absorbability due to the movement and pressure of the article with the activity. Leak to the outside of the material. Particularly in an absorbent material containing a high concentration of WAHP, core shift and gel leakage frequently occur during use. Eliminating particle movement during use is also an important factor.
[0009]
Yet another important factor that must be considered is the liquid permeability of WAHP. The permeable or flow conductivity of the gel layer formed by swelling in the presence of body fluids allows these absorbent polymers to be used in the core at high concentrations, partially or over the entire area. Be extremely important in the case. It should be noted that the lack of liquid permeability or flow conductivity of the absorbent polymer can directly affect the ability of the gel layer to absorb and distribute bodily fluids.
[0010]
Yet another problem with WAHP used for thinner absorbent articles is the jelly-like or wrinkle feel when touching and handling the absorbent article after use. When WAHP is dispersed at high concentration in one or more regions, the swollen gel formed by absorbing body fluid becomes a gel layer. If the particles that have absorbed the liquid are movable, the gel layer will collapse when a force such as pushing or squeezing is applied when handling the absorbent article after use. This gives absorbent articles with a high concentration of WAHP a “wet / wrinkle-like” feel to the user or consumer when touched and handled from the outside.
[0011]
Therefore, the present invention seeks to solve the above problem by providing an absorbent material having improved structural stability in dry and wet conditions.
[0012]
[Means for Solving the Problems]
The present invention relates to an absorbent material with improved structural stability in dry and wet conditions. These absorbent materials include (a) absorbent gel-like particles comprising a water-insoluble absorbent hydrogel-forming polymer, (b) polycationic polymer, (c) glue microfibers, and (d) a carrier layer. The polycationic polymer binds to the absorbent gel-like particles and the glue microfibers act as an adhesive between the absorbent gel-like particles and the carrier layer. Since the glue microfibers are sticky, the absorbent gel-like particles containing WAHP are fixed at a desired position on the carrier layer, that is, do not move to another area in a dry state. In the wet state, when the absorbent material comes into contact with a liquid such as a body fluid, the polycation polymer binds to the absorbent gel-like particles containing WAHP, so that it is first fixed at a given position and does not move.
[0013]
The bond between the glue microfibers and the absorbent gel particles (they are bonded to the carrier layer) prevents the absorbent gel particles from moving during manufacture. The polycationic polymer bonded to the absorbent gel particles prevents the particles from moving after being swollen with liquid. Thus, the absorbent material of the present invention has an improved liquid absorption rate and low rewetness in use. It has been found that the absorbent material swells when in contact with a liquid, absorbs such liquid into the absorbent gel-like particles and maintains absorption even under pressure.
[0014]
In a preferred embodiment of the invention, the carrier layer is selected from the group consisting of woven and non-woven materials.
[0015]
These absorbent materials may further include cellulose fibers dispersed in the absorbent gel particles (the cellulose fibers are bonded to the absorbent gel particles by glue microfibers).
[0016]
Preferably, the absorbent material of the present invention comprises from about 50 to about 90 weight percent absorbent gel particles, from about 0.1 to about 10 weight percent polycationic polymer, from about 1 to about 10 thermoplastic polymeric microfibers. And about 5 to about 50% by weight of the carrier layer.
[0017]
Furthermore, this invention relates to the manufacturing method of an absorbent material, and the absorbent article containing an absorbent material.
[0018]
These and other features, aspects and advantages of the present invention will be described in further detail using the following description and the accompanying drawings.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The definition list of specific terms used here is shown below.
[0020]
In the present specification, “consisting of” means that other steps and other components that do not affect the result can be added. This term also encompasses the terms “consisting solely of” and “consisting essentially of”.
[0021]
“In the dry state” means the state of the absorbent material during manufacture.
[0022]
“In the wet state” refers to the absorption of large amounts of water, body fluids, industrial fluids, household fluids and other liquids when the absorbent material of the present invention is used and worn, for example, in diapers. By swollen absorbent material is meant.
[0023]
“Structural stability” means immobilizing (fixing) the absorbent material in the correct position where it was originally placed.
[0024]
“WAHP” means a water-insoluble absorbable hydrogel-forming polymer.
A. Absorbent material
The absorbent material of the present invention can quickly absorb a large amount of water, body fluid, industrial fluid, household fluid, and the like, and can retain the absorbed fluid under pressure. In particular, when the absorbent material has a high concentration of WAHP, the absorbent material of the present invention has improved structural stability in dry and wet conditions. Preferably, the absorbent material of the present invention comprises greater than about 50% by weight of WAHP. Furthermore, the absorbent material of the present invention does not move from the position where it was originally placed in the dry and wet state.
[0025]
If the absorbent gel-like particles cannot be fixed in the desired position in the dry state, the absorbent gel-like particles will migrate, e.g. agglomeration of the absorbent gel-like particles and lack of a uniform distribution of particles. There is a tendency to cause.
[0026]
If the absorbent gel-like particles cannot be fixed in the desired position in the wet state, the particles will move and there will be insufficiently absorbed particles in one part, but in the other part An excess ability of excess fluid to flow out may occur. Thereafter, the absorbent article will cause leakage of the absorbent gel-like particles during use (when worn). The migration of wet absorbent gel-like particles that also contain WAHP causes core migration and gel leakage when used or worn, especially in absorbent articles using absorbent materials containing high concentrations of WAHP.
[0027]
The absorbent material of the present invention achieves dry and wet structural stability even when having a concentration of WAHP greater than 50% by weight.
[0028]
The absorbent material of the present invention includes (a) an absorbent gel-like particle containing WAHP, (b) a polycation polymer, (c) glue microfibers, and (d) a carrier layer. Binds to the absorbent gel-like particles and the glue microfibers act as an adhesive between the absorbent gel-like particles and the carrier layer.
[0029]
The present invention, in its aspect, comprises an absorbent material comprising absorbent gel particles, a polycation polymer bonded to the absorbent gel particles, glue microfibers dispersed in the absorbent gel particles, and a carrier layer. Intended. In particular, the purpose is to fix the absorbent gel-like particles in the desired position of the carrier layer by the adhesiveness of the glue microfibers in the dry state, and the polycation weight when the absorbent material is in contact with the liquid in the wet state. It is to fix the absorbent gel-like particles by coalescence.
[0030]
The glue microfibers used here are melt blown in at least one step of manufacturing the absorbent material to form sticky fibers. Adhesive glue microfibers can fix absorbent gel-like particles at desired positions in the absorbent material during manufacture.
[0031]
In general, any polymer can be used as glue microfibers that are sufficiently tacky to be retained on the particles in contact therewith and thereby suitable as an adhesive polymer. Preferably, melt blown adhesive polymers that can be used to form the absorbent material include elastomers and non-elastomeric polymers. These polymers must be sufficiently tacky to form into a fiber system. Tackiness can be modified using adhesive resins (adhesive resins include rosin resins, mixed polyalkenes, polyterpenes, waxes), or carboxylic acid-containing polymers or oligomers are blended into adhesive resins Can be modified. The use of blends of adhesive polymers or blends of adhesive polymers with other polymers is also contemplated by the present invention.
[0032]
Useful elastomeric polymers include polyolefins and blends (eg, polypropylene, polybutylene, or ethylene acrylic acid copolymers), ethylene vinyl acetate copolymers, polyamides, polyesters, and reactive polyamides and polyesters.
[0033]
Pressure sensitive adhesives are also useful in forming the absorbent structure of the present invention. They are permanently sticky and do not change the physical state from an initial liquid to a solid after final bond formation. Illustrative elastomeric polymers are ethylene vinyl acetate copolymer, styrene / dientry block copolymer, poly (vinyl ether), polyacrylate, and silicone. The ABA type thermoplastic elastomer triblock copolymer has a large adhesion ability in the present invention and is advantageous in processing. The end blocks (A) in these polymers are plastic in nature and have a high glass transition (or melting) temperature, while the block (B) is rubbery. In particular, styrene-butadiene-styrene, styrene-isoprene-styrene, and styrene-ethylene-co-propylene-styrene copolymers are extremely useful in the present invention.
[0034]
The non-elastomeric polymer may be non-elastomeric fibers that prepare resins or blends containing them. For example, such polymers include polyolefins, non-elastomeric polyamides, cellulose-derived polymers, vinyl chloride, and polyvinyl alcohol.
[0035]
In a preferred embodiment of the invention, the elastomeric styrene-isoprene-styrene block copolymer type is HL-1358 or Finely H-6752A supplied by Fuller Company. Non-elastomer glue microfibers include polyethyloxazolines such as XR-2676 (Fuller Company), polyvinylpyrrolidone such as H-1716 (Fuller Company) and ethylene vinyl acetate copolymers such as HT- 480 (Fuller Company). Glue microfibers containing polyethyloxazoline provide sufficient structural integrity in the dry state to absorbent articles containing the absorbent material of the present invention, while in the wet state polycationic polymers containing polyethyleneimine are active. To maintain the structural integrity of the absorbent article.
[0036]
The polycation polymer used here is a polymer having a large number of functional groups capable of binding to the surface of the absorbent gel particles. In a preferred embodiment, as the polycation polymer, a polymer containing an amino group or an imine group is used. Such polycationic polymers include polyamines, polyimines, and mixtures thereof. More preferably, the polyamine is a polymer having a primary amine group (eg, polyvinylamine, polyallylamine), a polymer having a secondary amine group (eg, polyethyleneamine), and a polymer having a tertiary amine group (eg, , Poly-N, N-dimethylalkylamine, poly-N-alkylamine). Preferably used polyimines include polyethyleneimine, modified polyethyleneimine crosslinked with epihalohydrin, polyamidoamine grafted with ethyleneimine, and mixtures thereof. Other suitable polycationic polymers include modified polyamidoamines, polyetheramines, polyvinylamines, polyalkylamines, polyamide polyamines and mixtures thereof grafted with ethyleneimine.
[0037]
In preferred embodiments, the polycationic polymer is a cationic polymer having an average molecular weight of at least about 200, more preferably at least 5,000, and most preferably about 10,000 or greater. The polycationic polymer useful in the present invention includes a polymer having a single maximum value (peak) in the molecular weight distribution and a polycationic polymer having one or more maximum values. The molecular weight distribution can be analyzed, for example, by gel permeation chromatography.
[0038]
Preferably, the amount of polycationic polymer used in the absorbent material is from about 0.1 to about 10% by weight of the absorbent material.
[0039]
In order to give a concentration of WAHP higher than 50% by weight of the absorbent material, the polycationic polymer used in the present invention has a concentration of about 80-99% by weight so that it can be tacky alone. A polycationic polymer with tacky properties can be melt-blown without glue microfibers and thus acts as an adhesive between the absorbent gel-like particles and the carrier layer. More preferably, a polycationic polymer fiber Has a molecular weight of at least about 70,000.
B. Water-insoluble absorbable hydrogel-forming polymer
1. Chemical composition
WAHPs useful in the present invention are commonly referred to as “hydrogel”, “hydrocolloid”, or “superabsorbent” polymers and polysaccharides such as carboxymethyl starch, carboxymethyl cellulose, hydroxypropyl cellulose; polyvinyl alcohol, polyvinyl Nonionic types such as ethers; cationic types, such as polyvinylpyridine, polyvinylmorpholinion, and N, N-dimethylaminoethyl or N, N-diethylaminopropyl acrylate and methacrylate, and their respective Quaternary salts can be mentioned. The WAHP useful in the present invention has a plurality of anionic functional groups such as sulfonic acid groups, more typically carboxy groups. Examples of polymers suitable for use herein include those produced from polymerizable unsaturated acid-containing monomers. Such monomers include olefinically unsaturated acids and anhydrides that contain at least one carbon-to-carbon olefinic double bond. More particularly, these monomers can be selected from olefinically unsaturated carboxylic acids and anhydrides, olefinically unsaturated sulfonic acids, and mixtures thereof.
[0040]
Some non-acid monomers may also be added, preferably in trace amounts, when preparing the WAHP of the present invention. Examples of such non-acid monomers include water-soluble or water-dispersible esters of acid-containing monomers and monomers that do not contain any carboxyl group or sulfonic acid group. Optional non-acid monomers include the following types of functional groups: carboxylic acid esters or sulfonic acid esters, hydroxyl groups, amide groups, amino groups, nitrile groups, quaternary ammonium bases, aryl groups (for example, Mention may be made of monomers containing phenyl groups, such as those derived from styrene monomers. These non-acid monomers are well-known substances such as US Pat. No. 4,076,663 (Masda et al.) Issued on Feb. 28, 1978 and Dec. 13, 1977. U.S. Pat. No. 4,062,817 (Westerman).
[0041]
Examples of olefinically unsaturated carboxylic acid and carboxylic anhydride monomers include acrylic acid itself, methacrylic acid, ethacrylic acid, α-chloroacrylic acid, α-cyanoacrylic acid, β-methylacrylic acid (crotonic acid), α -Phenylacrylic acid, β-acryloxypropionic acid, sorbic acid, α-chlorosorbic acid, angelic acid, cinnamic acid, p-chlorocinnamic acid, β-sterylacrylic acid, itaconic acid, citraconic acid, mesaconic acid, Acrylic acids represented by glutaconic acid, aconitic acid, maleic acid, fumaric acid, tricarboxyethylene and maleic anhydride.
[0042]
Olefinically unsaturated sulfonic acid monomers include aliphatic or aromatic vinyl sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, vinyl toluene sulfonic acid and styrene sulfonic acid; acrylic and methacrylic sulfonic acids such as Examples include sulfoethyl acrylate, sulfoethyl methacrylate, sulfopropyl acrylate, sulfopropyl methacrylate, 2-hydroxy-3-methacryloxypropyl sulfonic acid, and 2-acrylamido-2-methylpropane sulfonic acid.
[0043]
Preferred WAHPs for use in the present invention contain a carboxy group. These polymers include hydrolyzed starch-acrylonitrile graft copolymer, partially neutralized hydrolyzed starch-acrylonitrile graft copolymer, starch-acrylic acid graft copolymer, partially neutralized starch-acrylic acid graft copolymer. Saponified vinyl acetate-acrylate copolymer, hydrolyzed acrylonitrile or acrylamide copolymer, slightly network crosslinked polymer of any of the above copolymers, partially neutralized polyacrylic acid, and partially neutralized A slightly network crosslinked polymer of polyacrylic acid. These polymers can be used either alone or in the form of a mixture of two or more different polymers. Examples of these polymeric materials are U.S. Pat. No. 4,076,663 (Masda et al.) Issued February 28, 1978, U.S. Pat. No. 4,093,776 issued June 6, 1978. Description (Aoki et al.), US Pat. No. 4,666,983 issued on May 19, 1987 (Tsubakimoto et al.) And US Pat. No. 4,734,478 issued on March 29, 1988. (Tsubakimoto et al.).
[0044]
More preferred polymeric materials used in preparing WAHP are slightly network cross-linked polymers of partially neutralized polyacrylic acid and their starch derivatives. More preferably, the WAHP comprises from about 50 to about 95%, more preferably about 75% neutralized slightly network crosslinked polyacrylic acid [eg, poly (sodium acrylate / acrylic acid)]. Network cross-linking renders the polymer substantially water insoluble and in part determines the absorption capacity and extractable polymer content characteristics of WAHP. The network cross-linking methods of these polymers and typical network cross-linking agents are described in greater detail in US Pat. No. 4,076,663 (Masda et al.), Issued February 28,1978.
[0045]
Surface cross-linked WAHP is used in a preferred embodiment of the present invention. They have a higher level of crosslinking near the surface than in the interior. As used herein, “surface” means, for example, the outer surface boundary of particles and fibers. In the case of porous WAHP (eg, porous particles), exposed internal boundaries can also be included. A high level of crosslinking at the surface means that the level of functional crosslinking of WAHP near the surface is generally higher than the level of functional crosslinking of internal WAHP.
[0046]
The gradation of cross-linking from the surface to the interior can be varied in both depth and profile. Thus, for example, the depth of surface cross-linking can be shallow with a relatively sharp transition to a low level of cross-linking. Alternatively, for example, the depth of surface cross-linking can be a significant fraction of the dimensions of WAHP with a wider transition.
[0047]
The degree of surface crosslinking and the gradient of surface crosslinking can vary within a given WAHP depending on size, shape, porosity and sensory considerations. In the case of granular WAHP, surface cross-linking can vary depending on particle size, porosity, and the like. It is not uncommon for the overall level of cross-linking to change (eg, between small and large particles) depending on the surface / volume ratio variation within the WAHP (eg, larger for smaller particles). ).
[0048]
Surface cross-linking is generally achieved after the final boundary of WAHP is essentially established (eg, by grinding, extruding, foaming, etc.). However, it is also possible to carry out the surface crosslinking simultaneously with the formation of the final boundary. Moreover, some additional changes in the boundaries can occur even after introducing surface cross-linking.
[0049]
Surface cross-linking can be achieved before or simultaneously with covalent bonding of the polycationic polymer to the surface of the absorbent gel-like particles.
[0050]
The WAHP preferably has a single polymer (ie, a homogeneous system), but mixtures of polymers can also be used in the present invention. For example, a mixture of a starch-acrylic acid graft copolymer and a slightly network crosslinked polymer of partially neutralized polyacrylic acid can be used in the present invention.
2. Physical form
The absorbent gel-like particles used in the present invention can have a size, shape and / or morphology that varies over a wide range. Absorbent gel-like particles may have a large ratio of maximum dimension to minimum dimension (eg, particulates, flakes, finely divided products, interparticle aggregates, cross-particle aggregates, etc.) and fibers, foams It can be in the form of
[0051]
In the case of WAHP particles useful in the present invention, the particle size is in the range of about 10 to about 1000 μm. WAHP can also consist of a mixture with a small amount of one or more additives such as powdered silica, surfactants, cellulose microfibers, and the like. The components in this mixture can be physically and / or chemically related in such a way that the WAHP component and the non-hydrogel-forming polymer additive cannot be easily physically separated. WAHP can be essentially non-porous or have substantial internal porosity.
[0052]
In the case of such particles, the particle size is defined as the dimension measured by sieve size analysis. Thus, for example, particles retained on a US standard test sieve (eg, No. 25 US series alternating sieve designation) having a sieve opening of 710 μm is considered to have a size greater than 710 μm; Particles that pass through a sieve having an aperture of 710 μm and are retained on a sieve having an aperture of 500 μm (eg, No. 35 US series alternating sieve designation) are considered to have a particle size of 500-710 μm; Particles that pass through a sieve having an opening of 500 μm are considered to have a size of less than 500 μm.
[0053]
C. Absorbent article containing absorbent material
The absorbent material according to the present invention can be used for many purposes in many fields of use. For example, absorbent materials can be stuffed containers, drug delivery devices, wound cleaning devices, burn treatment devices, ion exchange column materials, building materials, agricultural or horticultural materials such as seed sheets or water retention materials, and industrial applications such as sludge. Or it can be used for oil dehydrating agents, dew formation prevention materials, desiccants, and humidity control materials. Under these circumstances, the absorbent material of the present invention can have a variety of shapes and sizes. For example, the absorbent material can be used in the form of a sheet, film, cylinder, block, or other build material. The absorbent material can include cellulosic materials to enhance absorbency and / or can be applied to these applications and as described below.
[0054]
Due to the unique absorbency of the absorbent material of the present invention, the absorbent material of the present invention is particularly suitable for use as a core in absorbent articles, particularly disposable absorbent articles. As used herein, the term “absorbent article” refers to an article that absorbs and contains body fluids, and more particularly various types of excretions placed on or near the wearer's body and excreted from the body. An article that absorbs and contains fluid. Furthermore, “disposable” absorbent articles are intended to be discarded after a single use (ie, some or all of the absorbent article material may be recycled, reused, or composted). , The entire original absorbent article is not washed, otherwise restored, or reused as an absorbent article).
[0055]
In general, the absorbent article includes (a) a liquid permeable topsheet, (b) a liquid impervious backsheet, and (c) a core disposed between the topsheet and the backsheet, wherein the core is at least 1 Contains one absorbent material. As used herein, “core” refers to a part of an absorbent article that can respond to the fluid handling properties of the article, including primarily absorbing, distributing and storing bodily fluids. As such, the core preferably does not include the topsheet or backsheet of the absorbent article.
[0056]
In a more preferred embodiment, the core or absorbent member may further comprise fibers or fluff pulp (fibrous material or fibrous material), more particularly non-absorbent gelled fibers. Such a fiber material can be used as a core reinforcing member or an absorbent auxiliary member to improve the fluid handling of the core and serve as an auxiliary absorbent for the absorbent polymer. As used herein, the term “absorbent member” generally refers to a core component that provides one or more fluid handling properties, such as fluid absorption, fluid distribution, fluid transport, fluid storage, and the like. The absorbent member can constitute the entire core or only a portion of the core, i.e., the core can include one or more absorbent members.
[0057]
Any type of fibrous material that is suitable for use in conventional absorbent products can be used in the core or absorbent member of the present invention. Specific examples of such fiber materials include cellulose fibers, modified cellulose fibers, rayon, polypropylene, and polyester fibers such as polyethylene terephthalate (DACRON), hydrophilic nylon (HYDROFIL), and the like. . Examples of other fiber materials for use in the present invention in addition to some of the previously described are derived from hydrophobized hydrophobic fibers such as polyolefins such as polyethylene and polypropylene, polyacryl, polyamide, polystyrene, polyurethane, etc. Surfactant treated or silica treated thermoplastic fibers. In fact, hydrophobized hydrophobic fibers that themselves and themselves are not very absorbent and therefore do not provide a web with sufficient absorbent capacity to be useful in normal absorbent structures are good wicking Suitable for use in the core due to its nature. This is because, in the core of the present invention, the fiber wicking tendency is as important, if not more important than the absorbent capacity of the fiber material itself, due to the high fluid uptake rate and the lack of the core gel block. is there. Synthetic fibers are generally preferred for use herein as the fiber component of the core. More preferred are polyolefin fibers, especially polyethylene fibers.
[0058]
Other cellulosic fiber materials that are useful in certain cores or absorbent members of the present invention are chemically stiffened cellulosic fibers. Preferred chemically stiffened cellulosic fibers are stiffened twisted curled cellulosic fibers that can be produced by internally cross-linking cellulose fibers with a crosslinker. A suitable stiffened twisted curled cellulose fiber useful as the hydrophilic fiber material of the present invention is described in US Pat. No. 4,888,093 (Dean et al.), Issued on Dec. 19, 1989, December 1989. U.S. Pat. No. 4,889,595 issued on May 26 (Heron et al.), U.S. Pat. No. 4,889,596 issued on December 26, 1989 (Shogen et al.), 1989 12 U.S. Pat. No. 4,889,597 issued on May 26 (Bobon et al.) And U.S. Pat. No. 4,898,647 issued on Feb. 6, 1990 (Moore et al.) It is described in detail.
[0059]
A preferred embodiment of the disposable absorbent article is a diaper. As used herein, the term “diaper” refers to a garment (generally worn by infants and incontinent persons) worn around the wearer's lower torso. A preferred arrangement for a diaper having a core is generally described in US Pat. No. 3,860,003 (Buel), issued 14 January 1975. Alternatively, a preferred arrangement for the disposable diaper of the present invention is US Pat. No. 4,808,178 (Aziz et al.) Issued February 28, 1989, US Pat. No. 4,695 issued September 22, 1987. , 278 (Lawson), U.S. Pat. No. 4,816,025 (Foreman) issued March 28, 1989, and U.S. Pat. No. 5,151,092, issued September 29, 1992. It is also disclosed in the specification (Buel et al.).
[0060]
Another preferred embodiment of the disposable absorbent article is a sanitary product. Preferred sanitary products are U.S. Pat. No. 4,285,343 (Macneil) issued Aug. 25, 1981, U.S. Pat. No. 4,608,047 (Matchley) issued Aug. 26, 1986. ) And U.S. Pat. No. 4,687,478 issued on Aug. 18, 1987 (Van Chilburg).
[0061]
A preferred sanitary product is described in co-pending US patent application Ser. No. 984,071, “Absorbent article with elasticized side flaps,” assigned to the same person of Morita Yasco, filed Nov. 30, 1992. Can include wings, side flaps, and other structures and elements.
[0062]
However, the present invention is also applicable to other absorbent articles commercially known under other names, such as incontinence briefs, adult incontinence products, training pants, diaper inserts, decorative paper, paper towels and the like.
D. Production method of absorbent material
FIG. 1 illustrates a preferred apparatus useful in the method of the present invention. 1 generally includes a particle supply unit 10 and a laminating apparatus 11. The particle supply unit 10 includes an absorbent gel particle supply unit 12, a glue microfiber supply unit 16, and a polycation polymer spray unit 17. The absorbent gel-like particles are first charged, for example, into the K-tron screw feeder 12 for continuously supplying the absorbent gel-like particles to the vibration feeder 13 and then to the hopper 14. Absorbent gel-like particles pass through the eductor 15 from the outlet of the hopper 14 and are ejected from the nozzle 16 as a first air stream 21 by an air stream of about 50 psi. Preferably, the average diameter of the absorbent gelled particles is usually from about 10 μm to about 1,000 μm and is primarily discontinuous.
[0063]
The glue microfibers are about 0.2 to about 2.0 kgcm as the second air flow 22 through the glue gun 17 (J & M Company). ^-1 hr ^-1 Is ejected at a speed of The glue microfiber extrusion becomes a fine fiber when passing the second air stream. The temperature range is set to be sufficient to dissolve and spray the glue microfibers. The air gap is preferably kept at about 0.18 mm. The second air stream of glue microfibers preferably has a basis weight of about 10 g / m for the resulting absorbent material. ² And the operating range is preferably about 3.0 g / m. ² To about 50.0 g / m ² It is.
[0064]
The first air stream 21 merges with the second air stream 22 to form an integrated air stream 23. The integrated air stream 23 is jetted onto the carrier layer, preferably at about 70 m / min. The jetting speed of the integrated air stream 23 is adjusted to match the speed of the carrier unit and is preferably about 1.0 m / sec.
[0065]
The vacuum conveyor 19 is placed under the nozzle 16 and the glue gun 17. As the carrier layer 25 passes through the vacuum conveyor 19, the jetted integrated air stream 23 is tightly coupled to the carrier layer 25. The absorbent gel-like particles preferably cover at least half of the width of the carrier layer.
[0066]
The third air stream 24 containing the pre-stirred polycationic polymer is placed after the jetting portion of the absorbent gel particle supply unit 18. The third air stream is sprayed onto the absorbent gel-like particles bonded to the carrier layer, so that the polycationic polymer is bonded to the absorbent gel-like particles. The line speed is preferably about 8 g / m ² To control.
[0067]
The folding board 20 is placed adjacent to and behind the polycationic polymer unit 18 and the absorbent material comprising absorbent gel-like particles, glue microfibers, polycationic polymer and carrier layer has a final width. Forming an edge-sealing laminate structure. The laminate of absorbent material is wound up at the end of the line.
[0068]
Moreover, this invention provides the manufacturing method of an absorptive material. The method includes (a) supplying absorbent gel-like particles containing WAHP onto the carrier layer, (b) supplying glue microfibers onto the carrier layer, and (c) absorbing the polycation polymer into the absorbent gel-like particles. And supplying the gel with the glue microfiber before the glue microfiber adheres to the carrier layer. Glue.
[0069]
In one embodiment, the method further includes the step of dispersing the cellulose fibers into the absorbent gel particles, wherein the glue microfibers act as an adhesive between the cellulose fibers and the absorbent gel particles.
[0070]
In a preferred embodiment, the absorbent gel-like particles are supplied onto the carrier layer via a first air stream.
[0071]
In a more preferred embodiment, the glue microfibers are supplied via a second air stream. The second air stream comprising glue microfibers preferably has a temperature of about 100 ° C to about 400 ° C.
[0072]
In a preferred embodiment, the polycationic polymer is supplied via a third air stream. The third air stream containing the polycationic polymer is preferably used as a solution having a concentration of about 0.1 to 10% by weight.
[0073]
The solution containing the polycation polymer is then fed onto the plurality of absorbent gel particles. In particular, at least two, preferably all, of the absorbent gel-like particles have a portion covered with a solution. In a preferred embodiment, at least about 70% of the surface area of the absorbent gelled particles is covered with a solution containing a polycationic polymer. The solution can be any of a variety of techniques and devices well known in the art that are suitable for applying the solution to the material, such as a method of coating the solution onto absorbent gel particles, a method of damping, a method of pouring, or dripping. Can be applied using spraying, spraying, atomizing, concentrating, or dipping methods. After applying the polycationic polymer, preferably about 90% or more of the surface area of the gelled particles is covered with the solution.
[0074]
In a preferred embodiment, the method comprises the step of heating the material obtained in step (c) at a temperature of about 50 ° C. to about 300 ° C. to covalently bond the polycationic polymer to the WAHP of absorbent gel particles. In addition.
[0075]
In a preferred embodiment, the polycation polymer is reacted with the absorbent gel-like particles such that the polycation polymer becomes covalently bonded to the absorbent gel-like particles in the surface area of the absorbent gel-like particles. More preferably, the covalent bond is made between the surface-located carboxy group of the absorbent gelling particle and the amino group of the polycationic polymer. Preferably, at least about 80 wt%, more preferably about 90 wt% or more of the polycationic polymer is covalently bonded to the absorbent gelled particles. When supplied with high thermal energy, absorbent articles containing absorbent material exhibit better fluid permeability. When fluid permeability is improved, for example, urine spread throughout the absorbent article comprising the absorbent material is increased, thus increasing the absorbent gel-like fluid absorption efficiency.
[0076]
Moreover, this invention relates to the manufacturing method of an absorptive material. The production method of the present invention includes (a) forming a first air stream containing absorbent gel-like particles containing WAHP, (b) forming a second air stream containing glue microfibers, and (c) a second air stream. Are combined with the first air stream to form an integrated air stream comprising a complete mixture of glue microfibers and absorbent gel-like particles, (d) supplying the integrated air stream over the carrier layer; e) forming a third air stream comprising a polycation polymer, and (f) providing a third air stream over the carrier layer so that the polycation polymer is bound to the absorbent gel particles. .
[0077]
More preferably, the method of making the absorbent material comprises (a) forming a first air stream comprising absorbent gel-like particles comprising WAHP, and (b) forming a second air stream comprising a polycationic polymer, (C) the second air stream merges with the first air stream to form an integrated air stream (the polycationic polymer binds to the absorbent gel-like particles), and (d) a second containing glue microfibers. Forming three air streams; (e) combining the integrated air stream with the third air stream to form a mixed air stream; and (f) absorbing gel-like particles bonded to the polycationic polymer are glue microscopic. A mixed air stream is fed over the carrier layer so that it adheres to the fibers and glue microfibers adhere to the carrier layer.
[0078]
In a more preferred embodiment, the second air stream is ejected at a temperature of at least about 400 ° C. and an air pressure of about 50 psi.
[0079]
In another aspect, the method applies (a) polycationic polymer fibers comprising a polycationic polymer having a concentration of about 80 to about 99% by weight onto absorbent gelled particles comprising WAHP; (B) supplying the absorbent gel-like particles onto the carrier layer, wherein the polycation polymer fiber acts as an adhesive between the absorbent gel-like particles and the carrier layer. Preferably, the polycationic polymer fiber has a molecular weight of at least about 70,000.
[0080]
In a preferred embodiment, the polycationic polymer fiber forms a first air stream containing the polycationic polymer and the absorbent gel particles form a second air stream to form the polycationic polymer fiber and An integrated air stream containing a complete mixture with the absorbent gel-like particles is formed.
[0081]
In a more preferred embodiment, the method forms (a) a first air stream containing polycationic polymer fibers and (b) a second air stream containing absorbent gelled particles comprising WAHP. (C) the second air stream merges with the first air stream to form an integrated air stream (the polycationic polymer fibers bind to the absorbent gel particles); (d) the absorbent gel An integrated air stream is provided on the carrier layer such that the particles are bonded to the polycationic polymer fibers on the carrier layer.
E. Test method
1. Synthetic urine
The specific synthetic urine used in the test methods described herein is referred to as “synthetic urine”. Synthetic urine is commonly known as Jayco SynUrine or Jaco Synthetic Urine and is available from the Jaco Pharmaceuticals Company of Camp Hill, PA. The synthetic urine formulation is KCl 2.0 g / l, Na ₂ SO _Four 2.0 g / l, (NH _Four ) H ₂ PO _Four 0.85 g / l, (NH _Four ) ₂ HPO _Four 0.15 g / l, CaCl ₂ 0.19 g / l and MgCl ₂ 0.23 g / l. All of the chemicals have reagent grade. The pH of synthetic urine is in the range of 6.0 to 6.4.
2. Wet burst strength measurement
The standard burst strength test program measures load, deflection and energy at peak and failure loads at the end of the test. The purpose of this test is to evaluate the force (g) of the absorbent gel-like particle-containing laminate structure after being subjected to a constant load of synthetic urine. Absorbent gel particles having a size of 10 cm × 10 cm and a basis weight of 310 g / m ² Laminate samples with a weight of 3.6 ± 0.3 g are generally soaked in 70 ml of synthetic urine. Synthetic urine is completely absorbed by the absorbent gelled particle-containing laminate with a synthetic urine load of 20 times its original weight. The force (g) required to puncture a laminate sample charged with 20 times synthetic urine using a burst tester, Swing-Albert Instrument Company No. 177-1-B. Measure. The sample holder is a Plexiglas disk with a diameter of 4.5 inches (about 11.4 cm) and a thickness of 0.125 inches (about 3.175 mm) with a 0.75 inch (about 19.05 mm) diameter hole in the plexiglass. In the center of. The sample is punctured using a 0.25 inch diameter stainless ball head.
3. Absorption capacity (gel volume)
The absorption capacity of WAHP is defined as the retained absorption capacity after swelling with excess Jaycee synthetic urine. It is a measure of the maximum absorption capacity of the polymer under conditions of use where the pressure on the polymer is relatively low. Absorption capacity is measured by the centrifuge capability method described below using JC Synthetic Urine. Absorption capacity is calculated on a dry weight basis. The dry weight used in the absorption capacity calculation is measured by oven drying the WAHP at 105 ° C. for 3 hours. All of the chemicals have reagent grade. The pH of Jaycee synthetic urine is in the range of 6.0 to 6.4.
[0082]
Heat-sealable teabag paper is cut into 6 cm × 12 cm, folded in half in the length direction, and sealed with a T-bar sealer along the two sides to produce a 6 cm × 6 cm teabag square. Transfer 0.200 g (± 0.005 g) of WAHP to the tea bag and seal the top of the bag with its edges. Seal the top of an empty tea bag and use it as a blank. About 300 ml of Jako synthetic urine is poured into a 1,000 ml beaker, and tea bags and blanks containing WAHP are submerged in the beaker. After soaking for 30 minutes, blank and WAHP filled tea bags are removed from the solution by using tongs. A centrifuge (H-122 type, manufactured by Kokusan Enshinki Co., Ltd., Tokyo, Japan) with a direct reading tachometer and an electric timer is used for this measurement. Place sample tea bag and blank tea bag in centrifuge basket and centrifuge at 1100 rpm for 3 minutes. Calculate the absorption capacity as follows:
Absorption capacity (g / g) = (Ws−Wb−Wo) / Wo
[Ws is the weight of the sample tea bag after centrifugation, Wb is the weight of the blank tea bag after centrifugation, and Wo is the weight of WAHP (0.200 g)].
[0083]
The average of at least two measurements is reported.
4). Liquid absorption rate and wetting test
The liquid absorption rate and wetness of a laminate product comprising this absorbent material made according to the present invention is measured. A typical absorbent article has an airfilt as the absorbent layer and an absorbent gelled particle basis weight of at least 310 g / m. ² Includes laminate products that contain a core of Liquid absorption (velocity) and wetting measurements are performed in a flat configuration at an external pressure of 0.30 psi. After continuous loading of 200 ml of synthetic urine, several pieces of filter paper are placed on a wet pad and soaked under 0.40 psi for 30 minutes. The weight increase of the filter paper is totaled from the front part, the middle part and the back part, and is used as a measurement value of the wet feeling.
F. Example
The following examples illustrate the absorbent material of the present invention and are not intended to limit the scope of the claims.
[0084]
The composite according to the present invention is produced by the laminate product production line shown in FIG.
[0085]
All raw materials used in this example are generally available. H. Glue microfibers B. A styrene-isoprene-styrene block copolymer (HL-1358-XZP) manufactured by Fuller Company is used and heated and maintained at least at 350 ° C. during production. L76lf manufactured by Nippon Shokubai Co., Ltd. is used as the absorbent gel-like particles and has a particle size distribution of 300 μm to 600 μm. As the polycationic polymer, polyethyleneimine manufactured by Wako Chem Company is used, and its solid content is 30% and the molecular weight is 70,000 daltons. As the carrier layer, a tissue manufactured by Habix Company is used and has a tensile strength of 1.1 kg / inch in the machine direction.
[0086]
As the performance of the absorbent material of the present invention, wet burst strength (BBS) and gel volume (GV) were measured and shown in Table 1. Moreover, in the diaper containing the absorptive material of the present invention, the absorption speed and the wet feeling of the liquid were measured and shown in Table 2.
Example 1
The compressed air stream is maintained at an air pressure of 50 psi. L76lf is prepared in a Ktron screw feeder and fed continuously to the vibratory feeder and then to the hopper. Further, the first air flow is given from the hopper through the eductor and combined with the compressed air flow. L76lf first air flow injection speed about 1.0 ms to match line speed ^-1 Keep on.
[0087]
About 0.2 to about 2.0 kgcm of styrene-isoprene-styrene block copolymer (HL-1358-XZP) through a glue gun apparatus (J & M Company) ^-1 hr ^-1 Extrude at the speed of The glue gun air gap is kept at about 0.18 mm so that the glue block copolymer is a thin fiber.
[0088]
The extruded HL-1358-XZP is combined with the air flow to provide a second air flow. The second air stream is maintained at a temperature of about 400 ° C. and an air pressure of about 50 psi. The second air flow of HL-1358-XZP is about 3.0 g / m. ² To about 50.0 g / m ² Adjust so that
[0089]
Furthermore, the first air flow of L76lf and the second air flow of HL-1358-XZP are prepared as an integrated air flow.
[0090]
Meanwhile, the vacuum conveyor is placed under the glue gun and eductor.
[0091]
The tissue is run on a vacuum conveyor at about 70 m / min. The integrated air is injected into the vacuum suction section (point) on the conveyor, and L76lf, HL-1358-XZP is firmly bonded to the tissue. The tissue width is at least about 23 cm and the integral air flow coverage is at least about 9.50 cm.
[0092]
Polyethyleneimine is dissolved in distilled water at a concentration of about 10 to about 20% by weight. Third Air Flow Spray Air Pressure Spray System (B1 / 8 VAU-SS + SUV 67-SS from Spraying System Company 0.5-1.2 kg / cm ² ) Is placed after the integrated air stream containing HL-1358-XZP and L76lf has been injected. According to the line speed, the spraying speed of the third air flow is 8g / m ² To control. Polyethyleneimine constitutes about 2.0% by weight of the laminate product.
[0093]
Place the folding board next to the third air stream spray of polyethyleneimine solution. The tissue formed with tissue, L76lf, HL-1358-XZP and polyethyleneimine is folded to form an edge sealed laminate structure with a final width of about 10 cm. Wrap the laminate product at the end of the line. Absorbent gel particles about 310 g / m ² The thickness of the forming laminate is about 1.3 mm.
[0094]
The properties of the laminate product containing this absorbent material produced according to this example are evaluated. The wet burst strength and absorption capacity are 61 g and 33 g / g. The results surprisingly show high wet burst strength (BBS) and high absorption capacity (GV) with the absorbent material according to the invention.
Example 2
The basic composition of the sample is the same as in Example 1 except that a third airflow spray of polyethyleneimine additive is not used.
[0095]
The properties of the laminate product containing this absorbent material prepared according to this example are evaluated. The wet burst strength and absorption capacity are 25 g and 35 g / g.
Example 3
In this example, the basic composition of the sample is the same as in Example 1 except for the following.
[0096]
(1) “URIC absorbent gel-like particles” that use “URIC absorbent gel-like particles” in the first air stream are absorbent modified heavy weights such as polycationic polymer bonded to the absorbent gel-like particles. Absorptive gel-like particles having improved absorptivity by coalescence.
[0097]
(2) There is no third air flow spray.
[0098]
The properties of the laminate product containing this absorbent material prepared according to this example are evaluated. The wet burst strength and absorption capacity are 45 g and 31 g / g. The results surprisingly show high wet burst strength (BBS) and high absorption capacity (GV) with the absorbent material according to the invention.
Example 4
The basic composition of the sample is the same as in Example 1 except that a second air stream of thermoplastic polymer microfibers is not used and a third air stream spray of polyethyleneimine additive is used.
[0099]
The properties of the laminate product containing this absorbent material prepared according to this example are evaluated. The wet burst strength and absorption capacity are 0 g and 38 g / g.

The liquid absorption rate and wet feeling are evaluated using an absorbent material on the diaper. A diaper is made from a laminated product containing the absorbent material according to the above example. The properties of diapers are evaluated and presented in Table 2.

The diapers of the present invention (Sample No. 1 and No. 3) show a faster liquid absorption rate than Sample No. 2 at high urine load, eg, urine volume of at least 150 ml. The liquid absorption rate is improved by faster fluid transport between the absorbent gel-like particles in the wet state. In sample No. 3, in which polyethylene is added to the absorbent gel-like particles, the laminate product shows a much faster liquid absorption rate. The binding force between the absorbent gel particles and polyethyleneimine in sample No. 3 is higher than that of sample No. 1. As shown in Table 2, the wet feeling of the present invention is maintained in the same manner as in the case of the absorbent material without the polycation polymer.
[0100]
The examples and embodiments described herein are for illustrative purposes only, and various modifications or alterations associated therewith are suggested to those skilled in the art and are within the spirit and scope of the present application and the claims. It is understood that it is included in the range.
[Brief description of the drawings]
FIG. 1 is a schematic view of an apparatus for producing the absorbent material of the present invention.
[Explanation of symbols]
1 Manufacturing equipment
10 Particle application unit
11 Carrier layer device
12 Absorbent gel-like particle supply unit
17 Glue microfiber supply unit
18 Polycation polymer spray unit
21 First air flow
22 Second air flow
23 Integrated air flow
24 Third air flow
25 Carrier layer

Claims (8)

(A) absorbent gel-like particles comprising a water-insoluble absorbent hydrogel-forming polymer,
(B) a polycationic polymer,
(C) glue microfibers, and (d) an absorbent material comprising a carrier layer, wherein the polycationic polymer is bonded to the absorbent gel particles, and the glue microfibers are absorbed. An absorbent material characterized in that it acts as an adhesive between the gel-like particles and the carrier layer,
Further comprising cellulose fibers dispersed in the absorbent gel particles, the cellulose fibers are bonded to the absorbent gel particles by glue microfibers,
The glue microfibers are selected from the group consisting of elastomeric microfibers and non-elastomeric microfibers;
An absorbent material, wherein the non-elastomeric microfibers are selected from the group consisting of water-soluble microfibers and water-insoluble microfibers.   The absorbent material according to claim 1, wherein the water-soluble microfibers are selected from the group consisting of polyethyloxazoline, polyvinylpyrrolidone, ethylene vinyl acetate copolymer glue and mixtures thereof. (A) absorbent gel-like particles comprising a water-insoluble absorbent hydrogel-forming polymer,
(B) a polycationic polymer fiber comprising a polycationic polymer, and (c) an absorbent material comprising a carrier layer, comprising a polycationic polymer having a concentration of about 80-99% by weight. The polycation polymer fiber is bonded to the absorbent gel-like particles, and the polycation polymer fiber acts as an adhesive between the absorbent gel-like particles and the carrier layer. Absorbent material.   4. The absorbent material of claim 3, wherein the polycationic polymer fiber has a molecular weight of at least about 70,000. (A) a liquid permeable top sheet,
An absorbent article comprising (b) a liquid-impermeable back sheet, and (c) an absorbent core disposed between the top sheet and the back sheet, wherein the absorbent core is defined in claim 3. An absorbent article comprising: an absorbent material. (A) applying polycationic polymer fibers comprising a polycationic polymer having a concentration of about 80 to about 99% by weight onto absorbent gel-like particles comprising a water-insoluble absorbent hydrogel-forming polymer;
(B) providing the absorbent gel-like particles on a carrier layer, wherein the polycation polymer fiber acts as an adhesive between the absorbent gel-like particles and the carrier layer. , Manufacturing method of absorbent material.   The method of making an absorbent material according to claim 6, wherein the polycationic polymer fiber has a molecular weight of at least about 70,000.   The method for producing an absorbent material according to claim 6, wherein the polycation polymer fiber and the absorbent gel-like particles are provided by a first air flow and a second air flow, respectively.

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