[Technical Field]
7 CROSS-REFERENCE TO RELATED APPLICATION(S)
8 This application claims the benefit of Korean Patent Application No. 10-
9 2020-0168657 filed on December 4, 2020 with the Korean Intellectual Property
10 Office, the disclosures of which are herein incorporated by reference in their
11 entirety.
12
13 This invention relates to superabsorbent polymer that may exhibit
14 improved bacterial growth inhibition property without deterioration of the
15 properties of superabsorbent polymer, such as centrifuge retention capacity and
16 absorption under pressure, and the like, and a method for preparing the same.
17
18 [Background Art]
19 Super absorbent polymer (SAP) is synthetic polymer material that can
20 absorb moisture of 500 to 1000 times of self-weight, and is also named differently
21 as super absorbency material (SAM), absorbent gel material (AGM), etc.
22 according to developing companies. The superabsorbent polymer began to be
23 commercialized as sanitary items, and currently, it is being widely used as
24 hygienic goods such as a disposable diaper and so on, water-holding material for
2
soil, water stop material for civil engineering and 1 architecture, sheets for raising
2 seedling, freshness preservatives in the field of food circulation, fomentation
3 material, etc.
4 Such superabsorbent polymer is being most widely applied for hygiene
5 products or disposable absorbent products such as diapers for children or diapers
6 for adults. Among them, in case it is applied for adult diaper, secondary odor
7 caused by bacterial growth significantly causes displeasure to consumers. In
8 order to solve such a problem, previously, there have been attempts to
9 incorporate various bacterial growth inhibition ingredients or deodorization or
10 antibacterial functional ingredients in superabsorbent polymer.
11 However, when incorporating such antibacterial agent for inhibiting
12 bacterial growth, and the like in superabsorbent polymer, it was not easy to
13 selectively incorporate antibacterial ingredients that exhibit excellent bacterial
14 growth inhibition property and deodorization property, and yet, are harmless to
15 human body, satisfy economical efficiency, and do not deteriorate the basic
16 properties of superabsorbent polymer.
17 For example, these has been an attempt to incorporate antibacterial
18 ingredients containing antibacterial metal ions such as silver, copper, and the like,
19 such as copper oxide. Such antibacterial metal ion-containing ingredient destroys
20 the cell wall of microorganism such as bacteria, and thus, kills bacteria having
21 enzyme that could cause odor, thus providing deodorization property. However,
22 the metal ion-containing ingredient is classified as BIOCIDE that may kill even
23 microorganisms beneficial for the human body. As the result, in case the
24 superabsorbent polymer is applied for hygiene products such as diapers for
3
children or adults, the incorporation of the metal 1 ion-containing antibacterial
2 ingredients is excluded as much as possible.
3 Meanwhile, previously, when incorporating antibacterial agents for
4 inhibiting bacterial growth in superabsorbent polymer, a method of blending a
5 small amount of the antibacterial agent with superabsorbent polymer was mainly
6 applied. However, in case such a blending method is applied, it was difficult to
7 uniformly maintain bacterial growth inhibition property with the passage of time.
8 Moreover, such a blending method may cause non-uniform coating and
9 delamination of the antibacterial ingredients during mixing of the superabsorbent
10 polymer and antibacterial agent, or during the use of the superabsorbent polymer.
11 Thus, there was a need to install novel equipment for the blending of antibacterial
12 agent, and there was also a disadvantage such as generation of plenty of dust
13 during the use of superabsorbent polymer.
14 Thus, there is a continued demand for the development of technologies
15 relating to superabsorbent polymer in which metal ion-containing ingredients are
16 not incorporated, and which can uniformly maintain bacterial growth inhibition
17 property and deodorization property for a long time, and yet, inhibit dust
18 generation, without deteriorating the basic properties of superabsorbent polymer.
19
20 [Disclosure]
21 [Technical Problem]
22 It is an object of the invention to provide superabsorbent polymer that
23 can uniformly maintain excellent bacterial growth inhibition property and
24 deodorization property for a long time, and yet, maintain excellent basic
4
properties such as centrifuge retention capacity and 1 absorption under pressure,
2 and the like, and a method for preparing the same.
3 It is another object of the invention to provide hygiene products that
4 comprise the superabsorbent polymer, and thus, exhibit excellent bacterial
5 growth inhibition property and deodorization property for a long time, and yet,
6 maintain excellent basic absorption properties.
7
8 [Technical Solution]
9 There is provided herein superabsorbent polymer comprising base resin powder
10 comprising crosslinked polymer of water-soluble ethylenically unsaturated
11 monomers in which at least a part of the acid groups is neutralized; and a surface
12 crosslinked layer formed on the base resin powder by additional crosslinking of
13 the crosslinked polymer by a surface crosslinking agent, wherein the surface
14 crosslinked layer comprises diethyldithiocarbamic acid or a salt thereof.
15 There is also provided herein a method for preparing the
16 superabsorbent polymer, comprising steps of:
17 polymerizing a monomer composition comprising water-soluble
18 ethylenically unsaturated monomers in which at least a part of the acid groups is
19 neutralized, an internal crosslinking agent and a polymerization initiator, to
20 prepare hydrogel polymer (step 1);
21 drying, grinding and classifying the hydrogel polymer to prepare base
22 resin (step 2); and
23 conducting a surface crosslinking reaction of the base resin in the
24 presence of a surface crosslinking solution comprising a surface crosslinking
5
agent, to prepare superabsorbent polymer in which 1 a surface crosslinked layer is
2 formed (step 3),
3 wherein the method further comprises a step of mixing the
4 superabsorbent polymer having a surface crosslinked layer with additive
5 comprising diethyldithiocarbamic acid or a salt thereof (step 4), after the step 3,
6 or
7 in the step 3, the surface crosslinking solution further comprises
8 additive comprising diethyldithiocarbamic acid or a salt thereof.
9 There is also provided herein a hygiene product comprising
10 superabsorbent polymer prepared by the method.
11
12 [Advantageous Effects]
13 The superabsorbent polymer prepared by the method of the invention
14 comprises specific material, and thus, may exhibit excellent bacterial growth
15 inhibition property and deodorization property of selectively inhibiting the growth
16 of bacteria harmful to human body and inducing secondary odor.
17 And, in the superabsorbent polymer, additive comprising the specific
18 compound is applied during surface crosslinking or after surface crosslinking, and
19 thus, strongly bonded inside crosslinked polymer making up base resin powder
20 or inside the surface crosslinked layer, thereby uniformly exhibiting excellent
21 bacterial growth inhibition property and deodorization property for a long time,
22 and maintaining excellent centrifuge retention capacity and absorption under
23 pressure, and the like, without deterioration of the properties due to the addition
24 of the antibacterial agent.
6
Thus, the superabsorbent polymer can be 1 very preferably applied for
2 various hygiene products, such as adult diapers in which secondary odor poses
3 a particular problem.
4
5 [Mode for Invention]
6 The terms used herein are only to explain specific embodiments, and are
7 not intended to limit the invention. A singular expression includes a plural
8 expression thereof, unless it is expressly stated or obvious from the context that
9 such is not intended. As used herein, the terms “comprise”, “equipped” or “have”,
10 etc. are intended to designate the existence of practiced characteristic, number,
11 step, constructional element or combinations thereof, and they are not intended
12 to preclude the possibility of existence or addition of one or more other
13 characteristics, numbers, steps, constructional elements or combinations thereof.
14 Although various modifications can be made to the invention and the
15 invention may have various forms, specific examples will be illustrated and
16 explained in detail below. However, it should be understood that these are not
17 intended to limit the invention to specific disclosure, and that the invention
18 includes all the modifications, equivalents or replacements thereof without
19 departing from the spirit and technical scope of the invention.
20
21 Hereinafter, superabsorbent polymer and a method for preparing the
22 same according to specific embodiments of the invention will be explained in
23 more detail.
24
7
The superabsorbent polymer according to one 1 embodiment comprises
2 base resin powder comprising crosslinked polymer of water-soluble ethylenically
3 unsaturated monomers in which at least a part of the acid groups is neutralized;
4 and a surface crosslinked layer formed on the base resin powder by additional
5 crosslinking of the crosslinked polymer by a surface crosslinking agent, wherein
6 the surface crosslinked layer comprises diethyldithiocarbamic acid or a salt
7 thereof.
8
9 The inventors have continuously studied on antibacterial ingredients
10 that may be preferably applied for superabsorbent polymer, instead of
11 antibacterial ingredients comprising antibacterial metal ions such as silver,
12 copper, and the like. As the result of such continuous studies, it was confirmed
13 that in case diethyldithiocarbamic acid or a salt thereof is incorporated in
14 superabsorbent polymer, excellent bacterial growth inhibition property and
15 deodorization property of inhibiting the growth of odor-inducing bacteria existing
16 in human skin may be invested to superabsorbent polymer, without deteriorating
17 basic properties of the superabsorbent polymer, such as centrifuge retention
18 capacity and absorption under pressure, and the like.
19 The diethyldithiocarbamic acid or a salt thereof is an ingredient
20 harmless to human body, of which safety is secured, and it does not correspond
21 to BIOCIDE material, and can solve the problem of the existing metal ion22
containing antibacterial agents. In addition, it is odorless and hydrophilic, and
23 thus, can be easily used in the preparation process of superabsorbent polymer.
24 Thus, the superabsorbent polymer of one embodiment can uniformly
8
exhibit excellent bacterial growth inhibition property and 1 deodorization property
2 for a long time, and can maintain excellent centrifuge retention capacity and
3 absorption under pressure, and the like, without deterioration of the properties
4 due to the addition of the antibacterial agent. As the result, the superabsorbent
5 polymer of one embodiment can be very preferably applied for various hygiene
6 products such as adult diapers in which secondary odor poses a particular
7 problem.
8
9 Preferably, the diethyldithiocarbamic acid or a salt thereof may be
10 sodium diethyldithiocarbamate.
11
12 Meanwhile, in the superabsorbent polymer of one embodiment, the
13 diethyldithiocarbamic acid or a salt thereof may be included in the content of 0.1
14 to 5 parts by weight, or 0.1 to 4 parts by weight, or 0.1 to 3 parts by weight, based
15 on 100 parts by weight of the base resin. If the content of the organic acid salt is
16 too low, it may be difficult to exhibit appropriate bacterial growth inhibition
17 property and deodorization property, and to the contrary, if the content is too high,
18 basic properties of superabsorbent polymer, such as centrifuge retention
19 capacity, and the like, may be deteriorated.
20
21 And, the surface crosslinked layer comprising additive comprising
22 diethyldithiocarbamic acid or a salt thereof may further comprise a chelating
23 agent or organic acid. The chelating agent may be, for example, one or more
24 selected from the group consisting of sodium salt of EDTA-2Na or EDTA-4Na,
9
cyclohexane diamine tetraacetic acid, diethylene 1 triamine pentaacetic acid,
2 ethyleneglycol-bis-(aminoethylether)-N,N,N'-triacetic acid, N-(2-hydroxyethyl)-
3 ethylene diamine-N,N,N'-triacetic acid, triethylene tetraamine hexaacetic acid,
4 and alkali metal a salt thereof. The chelating agent may serve as a bacterial
5 agent, and perform an antibacterial function of inhibiting the growth rate of various
6 bacteria, particularly, the growth of odor-inducing Proteus mirabilis.
7 The organic acid may be one or more selected from the group
8 consisting of citric acid, fumaric acid, maleic acid, and lactic acid. In case the
9 organic acid is used together with the chelating agent, synergistic effect may be
10 produced to exhibit deodorization/antibacterial properties.
11 The chelating agent or organic acid may be included in the content of
12 0.1 to 3 parts by weight, or 0.3 to 2 parts by weight, or 0.4 to 1 parts by weight,
13 based on 100 parts by weight of the base resin. By additionally using such a
14 chelating agent or organic acid, growth rate of odor-inducing bacteria may be
15 further inhibited to exhibit excellent antibacterial and deodorization properties.
16 However, if the content of the chelating agent or organic acid is too high,
17 absorption properties of superabsorbent polymer may be deteriorated.
18
19 Meanwhile, the above explained superabsorbent polymer of one
20 embodiment may have a common structure of superabsorbent polymer, except
21 comprising the additive component in the internal crosslinked structure of the
22 crosslinked polymer making up base resin powder, or in the crosslinked structure
23 of the surface crosslinked layer. For example, it may have a structure comprising
24 base resin powder comprising crosslinked polymer of water-soluble ethylenically
10
unsaturated monomers in which at least a part of the 1 acid groups is neutralized;
2 and a surface crosslinked layer formed on the base resin powder by additional
3 crosslinking of the crosslinked polymer by a surface crosslinking agent,
4
5 Wherein, as the water-soluble ethylenically unsaturated monomers,
6 commonly used monomers may be used without specific limitations. One or more
7 monomers selected from the group consisting of anionic monomers and a salt
8 thereof, non-ionic hydrophilic group-containing monomers, and amino group9
containing unsaturated monomers and quarternized products thereof may be
10 used.
11 Specifically, one or more selected from the group consisting of
12 (meth)acrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-
13 acryloylethane sulfonic acid, 2-methacryloylethane sulfonic acid, 2-
14 (meth)acryloylpropane sulfonic acid, or 2-(meth)acrylamide-2-methylpropane
15 sulfonic acid; non-ionic hydrophilic group-containing monomers selected from
16 (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate,
17 2-hydroxypropyl (meth)acrylate, methoxy polyethylene glycol (meth)acrylate or
18 polyethylene glycol (meth)acrylate; and amino group-containing unsaturated
19 monomers selected from (N,N)-dimethylaminoethyl (meth)acrylate or (N,N)-
20 dimethylaminopropyl (meth)acrylamide, and quarternized products thereof may
21 be used.
22 More preferably, acrylic acid or a salt thereof, for example, acrylic acid
23 or an alkali metal salt such as a sodium salt thereof may be used, and using such
24 monomers, superabsorbent polymer having more excellent properties can be
11
prepared. In case the alkali metal salt of acrylic acid 1 is used as monomer, acrylic
2 acid may be at least partially neutralized with a basic compound such as caustic
3 soda(NaOH) before use.
4 And, the base resin powder may be in the form of fine powder
5 comprising crosslinked polymer formed by crosslinking of such monomers by an
6 internal crosslinking agent.
7 As the internal crosslinking agent, crosslinking agents having one or
8 more functional groups capable of reacting with the water-soluble substituents of
9 the water-soluble ethylenically unsaturated monomers, and having one or more
10 ethylenically unsaturated groups; or crosslinking agents having 2 or more
11 functional groups capable of reacting with the water-soluble substituents of the
12 monomers and/or the water-soluble substituents formed by hydrolysis of the
13 monomers, may be used.
14 As specific examples of such internal crosslinking agent, C8 to 12
15 bisacrylamide, bismethaacrylamide, poly(meth)acrylate of C2 to 10 polyol or
16 poly(meth)allylether of C2 to 10 polyol, and the like may be mentioned, and more
17 specifically, one or more selected from the group consisting of N,N'-
18 methylenebis(meth)acrylate, ethyleneoxy(meth)acrylate,
19 polyethyleneoxy(meth)acrylate, propyleneoxy(meth)acrylate, glycerin
20 diacrylate, glycerin triacrylate, trimethylol triacrylate, triallylamine, triaryl
21 cyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol and
22 propylene glycol may be used.
23 And, the base resin powder may be in the form of fine powder having
24 a particle diameter of 150 to 850 ㎛.
12
Meanwhile, the superabsorbent polymer 1 comprises a surface
2 crosslinked layer that is formed on the base resin powder, by additional
3 crosslinking of the crosslinked polymer of such base resin powder by a surface
4 crosslinking agent.
5 As examples of such surface crosslinking agent, diol compounds,
6 alkylene carbonate compounds, or multivalent epoxy compounds, and the like
7 may be mentioned, and as more specific examples, 1,3-propanediol, propylene
8 glycol, 1,4-butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,3-hexanediol, 2-methyl-
9 1,3-propanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, 2-methyl-2,4-
10 pentanediol, tripropylene glycol, glycerol, ethylene carbonate, propylene
11 carbonate, glycerol carbonate, or alkylene glycol diglycidyl ether-based
12 compounds such as ethylene glycol diglycidyl ether, and the like, may be
13 mentioned, and besides, any multivalent compounds known to be usable as a
14 surface crosslinking agent of superabsorbent polymer may be used without
15 specific limitations.
16 In the above explained superabsorbent polymer of one embodiment,
17 the additive comprising diethyldithiocarbamic acid or a salt thereof may be
18 included, for example, in the surface crosslinking solution to form a surface
19 crosslinked layer, or superabsorbent polymer in which a surface crosslinked layer
20 is formed may be mixed with the additive, and thus, the antibacterial ingredient
21 may be included in the additional crosslinked structure of the surface crosslinked
22 layer or on the surface, while being strongly fixed or bonded. As the result, unlike
23 the previous blending, non-uniform coating, delamination and separation during
24 transportation of the antibacterial ingredient may not be generated, and the
13
antibacterial ingredient may be uniformly included to 1 stably exhibit excellent
2 bacterial growth inhibition property and deodorization property for a long time.
3 And, when using superabsorbent polymer, generation of dust derived from the
4 antibacterial ingredient may also be significantly reduced.
5
6 Such excellent bacterial growth inhibition property may be supported
7 by bacterial (Escherichia Coli; ATCC25922) inhibition rate represented by the
8 following Formula 1, as high as 90 % or more, or 93 % or more, or 95 to 100 %,
9 as evidenced in experimental examples described later.
10 [Formula 1]
11 Bacterial inhibition rate = [1- {CFU(12h) / CFUcontrol(12h)}]*100 (%)
12 in the Formula 1, CFU(12h) denotes the number of grown bacteria per
13 unit volume of artificial urine, when 50 ml of artificial urine containing nutrients is
14 inoculated with 2,500 CFU/ml of bacteria (Escherichia Coli, ATCC 25922), and 2
15 g of the superabsorbent polymer of claim 1 is added thereto, and then, incubated
16 at 35 ℃ for 12 hours; CFUcontrol(12h) denotes the number of grown bacteria
17 per unit volume of artificial urine, when 50 ml of artificial urine containing nutrient
18 is inoculated with 2,500 CFU/ml of bacteria (Escherichia Coli, ATCC 25922), and
19 incubated under the same conditions, using superabsorbent polymer prepared
20 without additive comprising diethyldithiocarbamic acid or a salt thereof, instead
21 of the above superabsorbent polymer.
22 The artificial urine containing nutrients may be prepared as follows.
23 1) Preparation of a stock solution
14
Into a 1 L flask, every compounds 1 (sodium chloride(0.15 M),
2 dipotassium hydrogen phosphate(0.02 M), sodium dihydrogen phosphate(0.01
3 M), ammonium chloride(0.05 M), disodium sulphate(0.02 M), lactic
4 acid(90%)(0.05 M), yeast extract(Becton Dikinson)) are introduced, and distilled
5 water is filled to 1000 ml to dissolve, and then, the solution is sterilized in an
6 autoclave. The prepared solution is stored at 4 ℃.
7 2) Preparation of urea/glucose solution
8 Into a 100 ml flask, every compounds (urea(6 M), D-glucose(0.01 M))
9 are introduced, and distilled water is filled to 100 ml to dissolve. From the solution,
10 bacteria are removed using a 0.22 micro filter. The prepared solution is stored at
11 4 ℃.
12 3) Preparation of cationic solution
13 Into a 100 ml flask, every compounds (magnesium
14 chloride(hexahydrate)(0.3 M), calcium chloride(dehydrate)(0.3 M)) are
15 introduced, and distilled water is filled to 20 ml to dissolve, and then, the solution
16 is sterilized in an autoclave. The prepared solution is stored at 4 ℃.
17 4) Artificial urine containing nutrients
18 94 ml of the stock solution, 5 ml of the urea/glucose solution, and 1 ml
19 of the cationic solution are mixed to prepare artificial urine containing nutrients.
20 After preparation, the solution is stored at 4 ℃, and used within 7 days from the
21 date of preparation.
22
15
Meanwhile, the above explained superabsorbent 1 polymer of one
2 embodiment may be obtained by progressing drying, grinding, classification and
3 surface crosslinking of the hydrogel polymer obtained by progressing thermal
4 polymerization or photopolymerization of a monomer composition comprising
5 water-soluble ethylenically unsaturated monomers and a polymerization initiator,
6 and if necessary, a fine reassembly process may be further conducted.
7 More specifically, a method for preparing the superabsorbent polymer
8 comprises steps of:
9 polymerizing a monomer composition comprising water-soluble
10 ethylenically unsaturated monomers in which at least a part of the acid groups is
11 neutralized, an internal crosslinking agent and a polymerization initiator, to
12 prepare hydrogel polymer (step 1);
13 drying, grinding and classifying the hydrogel polymer to prepare base
14 resin (step 2); and
15 conducting a surface crosslinking reaction of the base resin in the
16 presence of a surface crosslinking solution comprising a surface crosslinking
17 agent, to prepare superabsorbent polymer in which a surface crosslinked layer is
18 formed (step 3),
19 wherein the method further comprises a step of mixing the
20 superabsorbent polymer having a surface crosslinked layer with additives
21 comprising diethyldithiocarbamic acid or a salt thereof (step 4), after the step 3,
22 or
23 in the step 3, the surface crosslinking solution further comprises
24 additives comprising diethyldithiocarbamic acid or a salt thereof.
16
1
2 According to specific one example, the step 3 may be progressed
3 using a surface crosslinking solution comprising additive comprising
4 diethyldithiocarbamic acid or a salt thereof. Thereby, superabsorbent polymer of
5 one embodiment in which the additive is included in the additional crosslinked
6 structure of the surface crosslinked layer, may be obtained.
7 According to another example, in case the step 4 is progressed,
8 superabsorbent polymer of one embodiment in which the additive is included on
9 the surface of the surface crosslinked layer, may be obtained.
10 As such, by incorporating the additive component in the surface
11 crosslinking solution in the surface crosslinked layer forming step (step 3) to
12 progress the preparation process of superabsorbent polymer, or progressing a
13 step of mixing the additive with superabsorbent polymer in which a surface
14 crosslinked layer is formed (step 4), the antibacterial ingredients may be strongly
15 fixed inside/outside the surface crosslinked layer, and thus, may be prevented
16 from being delaminated or non-uniformly coated, and allow superabsorbent
17 polymer to maintain excellent and uniform bacterial growth inhibition property and
18 deodorization property for a long time.
19
20 Meanwhile, the kinds of the components that can be used in the
21 preparation method, namely, monomers, internal crosslinking agents and surface
22 crosslinking agents have been already explained in detail with regard to the
23 superabsorbent polymer of one embodiment, and thus, additional explanations
24 thereof will be omitted.
17
And, the kinds and amounts of the additive 1 components used in the
2 preparation method may correspond to the kinds and contents of the additive
3 components as already explained in detail.
4 Hereinafter, the preparation process of superabsorbent polymer will be
5 explained, while additional explanations of the content range of additives being
6 omitted.
7
8 According to specific one example, in the preparation step of hydrogel
9 polymer (step 1), a monomer composition comprising water-soluble ethylenically
10 unsaturated monomers, an internal crosslinking agent and a polymerization
11 initiator may be subjected to crosslinking polymerization to prepare hydrogel
12 polymer.
13 As the polymerization initiator included in the monomer aqueous
14 solution together with the above explained monomers and internal crosslinking
15 agent, any initiators commonly used for the preparation of superabsorbent
16 polymer may be used without specific limitations.
17 Specifically, as the polymerization initiator, thermal polymerization
18 initiators or photopolymeirzation initiator according to UV irradiation may be used
19 according to polymerization method. However, even in the case of
20 photopolymerization, since a certain amount of heat is generated by UV
21 irradiation, etc., and heat is generated to some degree according to the
22 progression of an exothermic polymerization reaction, a thermal polymerization
23 initiator may be additionally included. The photopolymerization initiator may be
24 used without limitations in terms of its constructions, as long as it is a compound
18
capable of forming 1 radicals by light such as UV.
2 As the photopolymerization initiator, one or more selected from the group
3 consisting of benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl
4 glyoxylate, benzyl dimethyl Ketal, acyl phosphine, and α-aminoketone may be
5 used. Meanwhile, as specific examples of acyl phosphine, diphenyl(2,4,6-
6 trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine
7 oxide, ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate, and the like may be
8 mentioned. More various photopolymerization initiators are described in Reinhold
9 Schwalm, "UV Coatings: Basics, Recent Developments and New
10 Application(Elsevier 2007)", page 115, and are not limited to the above described
11 examples.
12 The photopolymerization initiator may be included in the concentration of
13 0.0001 to 2.0 wt%, based on the monomer aqueous solution. If the concentration
14 of the photopolymerization initiator is too low, polymerization speed may become
15 slow, and if he concentration of the photopolymerization initiator is too high, the
16 molecular weight of superabsorbent polymer may be low and the properties may
17 become non-uniform.
18 And, as the thermal polymerization initiator, one or more selected from
19 the group consisting of a persulfate initiator, an azo initiator, hydrogen peroxide,
20 and ascorbic acid may be used. Specific examples of the persulfate initiator may
21 include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), ammonium
22 persulfate ((NH4)2S2O8), etc., and, specific examples of the azo initiator may
23 include 2,2-azobis(2-amidinopropane)dihydrochloride, 2,2-azobis-(N,N24
dimethylene)isobutyramidinedihydrochloride, 2-(carbamoylazo)isobutyronitril,
19
2,2-azobis[2-(2-imidazolin-2-yl)propane]d 1 ihydrochloride, 4,4-azobis-(4-
2 cyanovalericacid), etc. More various thermal initiators are described in "Principle
3 of Polymerization (Wiley, 1981)", Odian, page 203, and are not limited to the
4 above described examples.
5 The thermal polymerization initiator may be included in the
6 concentration of 0.001 to 2.0 wt%, based on the monomer aqueous solution. If
7 the concentration of the thermal polymerization initiator is too low, additional
8 thermal polymerization may hardly occur, and thus, the effect according to the
9 addition of the thermal polymerization initiator may be insignificant, and if the
10 concentration of the thermal polymerization initiator is too high, the molecular
11 weight of superabsorbent polymer may be low and the properties may become
12 non-uniform.
13 In case these photopolymerization initiator and thermal polymerization
14 initiator are used together, the thermal polymerization initiator may be lastly
15 added to the monomer aqueous solution immediately before initiating
16 polymerization. Wherein, the above explained aqueous solution of antibacterial
17 agent may be mixed together with the thermal polymerization initiator and added
18 to the monomer aqueous solution.
19 And, in the preparation method, the monomer aqueous solution may
20 further comprise additives such as a thickener, a plasticizer, a preservation
21 stabilizer or an antioxidant, and the like, as necessary.
22 Meanwhile, a method of thermal polymerization or
23 photopolymerization of such monomer aqueous solution to form hydrogel
24 polymer is not specifically limited in terms of its constructions, as long as it is a
20
commonly used 1 polymerization method.
2 Specifically, the polymerization method is largely classified into
3 thermal polymerization and photopolymerization according to energy source.
4 Commonly, thermal polymerization may be progressed in a reactor equipped with
5 a stirring axis such as a kneader, and photopolymerization may be progressed in
6 a reactor equipped with a movable conveyer belt, but the above explained
7 polymerization method is no more than one example, and the invention is not
8 limited thereto.
9 Wherein, the moisture content of hydrogel polymer obtained by such a
10 method may be commonly 40 to 80 wt%. Meanwhile, throughout the specification,
11 the “moisture content” is the content of moisture occupied based on the total
12 weight of hydrogel polymer, and it means a value obtained by subtracting the
13 weight of polymer of a dry state from the weight of hydrogel polymer. Specifically,
14 it is defined as a value calculated by measuring the weight loss according to
15 moisture evaporation in the polymer while raising the temperature of polymer
16 through infrared heating to dry. Wherein, the drying condition may be set up such
17 that the temperature is raised from room temperature to about 180℃ and then
18 maintained at 180℃, and the total drying time may be 20 minutes including a
19 temperature raising step of 5 minutes.
20
21 Next, the obtained hydrogel polymer is dried, ground and classified
22 (step 2).
23 When drying the hydrogel polymer, if necessary, in order to increase
21
the efficiency of the drying step, a step of coarse grinding 1 may be further
2 conducted before drying.
3 Wherein, grinders that can be used are not limited in terms of the
4 constructions, but specifically, one selected from the group consisting of a vertical
5 pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutter mill, a disc
6 mill, a shred crusher, a crusher, a chopper, a disc cutter may be used, but is not
7 limited thereto.
8 Wherein, the coarse grinding step may be conducted such that the
9 particle diameter of hydrogel polymer may become 2 to about 10 mm.
10 The hydrogel polymer coarsely ground as explained, or immediately after
11 polymerization without passing through the coarse grinding step, is dried.
12 The drying method of the drying step is not specifically limited as long
13 as it is commonly used for drying hydrogel polymer. Specifically, the drying step
14 may be conducted by hot wind supply, infrared ray irradiation, ultrahigh frequency
15 wave irradiation, or UV irradiation, and the like. The moisture content of polymer
16 after progressing such a drying step may be 0.1 to 10 wt%.
17 Next, dried polymer obtained through the drying step is ground.
18 The particle diameter of polymer obtained after the grinding step may
19 be 150 to 850㎛. As grinders used to grind to such a particle diameter,
20 specifically, pin mill, hammer mill, screw mill, roll mill, disc mill or jog mill, and the
21 like may be used, but the invention is not limited thereto.
22 And, After the grinding step, in order to manage the properties of
23 superabsorbent polymer powder finally productized, a separate process of
24 classifying polymer powder obtained after grinding according to particle diameter
22
may be passed through. Preferably, polymers having 1 a particle diameters of 150
2 to 850㎛ are classified.
3 Through the above explained processes, base resin powder may be
4 prepared, and such base resin powder may be in the form of fine powder having
5 a particle diameter of 150 to 850 ㎛.
6
7 Meanwhile, according to one example of the invention, a step of
8 surface crosslinking base resin powder prepared through the grinding and/or
9 classification processes, may be further conducted (step 3).
10 Such a surface crosslinking step is a step of conducting additional
11 crosslinking using a surface crosslinking solution comprising a surface
12 crosslinking agent and a solvent, and forming a surface crosslinked layer so as
13 to increase the surface crosslinking density of the base resin powder, and in this
14 step, the unsaturated bonds of water-soluble ethylenically unsaturated
15 monomers remaining on the surface without being crosslinked are additionally
16 crosslinked, to form superabsorbent polymer with increased surface crosslinking
17 density. By heat treatment, surface crosslinking density, namely external
18 crosslinking density increases, while internal crosslinking density is not changed,
19 and thus, prepared superabsorbent polymer having a surface crosslinked layer
20 has a structure in which external crosslinking density is higher than internal
21 crosslinking density.
22 Such a surface crosslinking step may be progressed using a surface
23 crosslinking solution comprising the surface crosslinking agent, additive
24 comprising diethyldithiocarbamic acid or a salt thereof, and an aqueous solvent,
23
as explained above. The surface crosslinking solution 1 may optionally, further
2 comprise a chelating agent or organic acid.
3 The surface crosslinking agent may be used in the content of 0.001 to
4 2 parts by weight, based on 100 parts by weight of base resin powder. For
5 example, the surface crosslinking agent may be used in the content of 0.005 parts
6 by weight or more, 0.01 parts by weight or more, or 0.02 parts by weight or more,
7 and 1.5 parts by weight or less, 1 parts by weight or less, based on 100 parts by
8 weight of base resin powder. By controlling the content range of the surface
9 crosslinking agent within the above range, superabsorbent polymer exhibiting
10 excellent absorption properties and permeability may be prepared.
11 And, the method of mixing the surface crosslinking solution with base
12 resin powder is not limited in terms of its construction. For example, the surface
13 crosslinking solution and base resin powder may be put in a reactor and mixed,
14 or the surface crosslinking solution may be sprayed to base resin powder, or the
15 base resin powder and surface crosslinking solution may be continuously
16 supplied to a continuously operated mixed and mixed.
17 The surface crosslinking process may be conducted at a temperature
18 of 80 ℃ to 250 ℃. More specifically, the surface crosslinking process may be
19 conducted at a temperature of 100℃ to 220℃, or 120℃ to 200℃, for 20 minutes
20 to 2 hours, or 40 minutes to 80 minutes. When satisfying the above explained
21 surface crosslinking process conditions, the surface of base resin powder may
22 be sufficiently crosslinked, and thus, absorption under pressure or permeability
23 may be increased.
24
A temperature rise means for the surface 1 crosslinking reaction is not
2 specifically limited. A heating medium may be supplied, or a heat source may be
3 directly supplied to heat. Wherein, the kinds of the heating medium that can be
4 used may include temperature-increased fluid such as steam, hot air, hot oil, etc.,
5 but are not limited thereto, and may be appropriately selected considering the
6 means of the heating medium, temperature rise speed and a temperature to be
7 increased. Meanwhile, the heat source directly supplied may include electric
8 heating, gas heating, etc., but is not limited thereto.
9
10 Meanwhile, according to one example of the invention, a step of mixing
11 the superabsorbent polymer in which a surface crosslinked layer is formed with
12 additive comprising diethyldithiocarbamic acid or a salt thereof may be further
13 conducted (step 4). In case the step 4 is progressed, superabsorbent polymer of
14 one embodiment, in which the diethyldithiocarbamic acid or salt thereof is
15 included on the surface of the surface crosslinked layer, may be obtained
16
17 In the mixing step of the step 4, a chelating agent or organic acid may
18 be further included and mixed.
19
20 The step 4 is not specifically limited as long as it is a common mixing
21 method, and it may be dry mixing or wet mixing.
22
23 Meanwhile, the step 4 may be progressed for 0.1 to 2 hours, at a
24 temperature of 20 ℃ to 90 ℃. If the progression time of the step 4 is less than
25
0.1 hours, non-uniform dispersion of particles may be 1 generated, and if it is
2 greater than 2 hours, due to friction between particles, fine crushing on the
3 surface of SAP resin may be induced.
4
5 Consequently, without changing process conditions such as basic
6 crosslinking polymerization or surface crosslinking for the preparation of
7 superabsorbent polymer, superabsorbent polymer uniformly exhibiting excellent
8 bacterial growth inhibition property and deodorization property can be prepared.
9 And, since the antibacterial ingredient does not have an influence on the internal
10 crosslinking structure of the superabsorbent polymer, excellent centrifuge
11 retention capacity and absorption under pressure may be maintained without
12 deterioration of the properties due to the addition of the antibacterial ingredient.
13 In addition, since such fine antibacterial particles are uniformly coated on the
14 surface of superabsorbent polymer and relatively strongly fixed, generation of
15 plenty of dust due to the addition of the antibacterial agent may be overcome.
16
17 Through the processes illustratively explained above, by progressing
18 up to the surface crosslinking process, superabsorbent polymer may be prepared
19 and provided. Since such superabsorbent polymer comprises the above
20 explained specific antibacterial ingredient in the surface crosslinked layer while
21 being strongly fixed, it may exhibit excellent bacterial growth inhibition property
22 and deodorization property, and yet, maintain excellent basic absorption
23 properties.
24 Thus, such superabsorbent polymer may be preferably included and
26
used for various hygiene products, for example, 1 paper diapers for children,
2 diapers for adults or sanitary pads, and the like, and particularly, it may be very
3 preferably applied for adult diapers in which secondary odor caused by bacterial
4 growth poses a particular problem.
5 Such hygiene products may have common constructions of hygiene
6 products, except comprising the superabsorbent polymer of one embodiment in
7 absorber.
8
9 Hereinafter, preferable examples are presented for better
10 understanding of the invention. However, these examples are presented only as
11 the illustrations of the invention, and the invention is not limited thereby.
12
13
14 Example 1
15 Into a 3L glass container equipped with a stirrer, a thermometer, and
16 a cooler, 484 g of acrylic acid, 2100 ppmw of a polyethylene glycol
17 diacrylate(PEGDA 400, Mw=400) internal crosslinking agent, and 80 ppmw of a
18 diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide photoinitiator were introduced
19 and dissolved, and then, 643 g of 31.5 wt% sodium hydroxide solution was slowly
20 added to prepare an aqueous solution of water-soluble unsaturated monomers
21 (neutralization degree: 70 mol%; solid content: 45.8 wt%).
22 When the temperature of the water-soluble unsaturated monomer
23 aqueous solution increased to 40℃ due to neutralization heat, the solution was
27
put in a container including a sodium persulfate(SPS) 1 thermal polymerization
2 initiator, and then, irradiated by ultraviolet rays for 1 minute (irradiation dose: 10
3 mV/cm2) to conduct UV polymerization, and heated in an oven of 80 ℃ for 120
4 seconds to age, thus obtaining a hydrogel polymer sheet.
5 The obtained hydrogel polymer sheet was passed through a chopper
6 having a hole size of 16 mm to prepare crumb. The crumb was dried in an oven
7 capable of transferring wind upward and downward. Hot air of 185 ℃ was made
8 to flow from the lower part to the upper part for 15 minutes, and flow from the
9 upper part to the lower part for 15 minutes, so as to uniformly dry, and the drying
10 was conducted such that the moisture content of dried product after drying
11 became 2 wt% or less. After drying, it was classified with a ASTM standard sieve
12 to obtain based resin powder having particle size of 150 to 850 ㎛.
13 Meanwhile, for surface crosslinking (additional crosslinking) of the
14 base resin powder, a surface crosslinking solution comprising 4.2 parts by weight
15 of water, 0.2 parts by weight of ethylene carbonate, 0.3 parts by weight of
16 aluminum sulfate, 0.2 parts by weight propylene glycol, and 0.1 parts by weight
17 of sodium diethyldithiocarbamate additive, based on 100 parts by weight of the
18 bas resin powder, was prepared. To 100 parts by weight of the base resin, the
19 surface crosslinking solution was sprayed using a 1000 rpm paddle type mixer.
20 And then, it was heated at the maximum temperature of 185 ℃ for 60 minutes
21 to progress surface crosslinking, thus preparing superabsorbent polymer of
22 Example 1.
28
1
2 Example 2
3 Superabsorbent polymer of Example 2 was prepared by the same
4 method as Example 1, except that the content of sodium diethyldithiocarbamate
5 was 0.3 parts by weight, based on 100 parts by weight of the base resin powder.
6
7 Example 3
8 Base resin powder was prepared by the same method as Example 1.
9 Meanwhile, for surface crosslinking (additional crosslinking) of the
10 base resin powder, a surface crosslinking solution comprising 4.2 parts by weight
11 of water, 0.2 parts by weight of ethylene carbonate, 0.3 parts by weight of
12 aluminum sulfate, and 0.2 parts by weight of propylene glycol, based on 100 parts
13 by weight of the base resin powder, was prepared. To 100 parts by weight of the
14 base resin, the surface crosslinking solution was sprayed using a 1000 rpm
15 paddle type mixer. And then, it was heated at the maximum temperature of 185
16 ℃ for 60 minutes to progress surface crosslinking.
17 After the surface crosslinking, a 1.5 wt% aqueous solution comprising
18 0.1 parts by weight of sodium diethyldithiocarbamate, based on 100 parts by
19 weight of the base resin powder, was mixed by hydration, and the mixture was
20 heated at the maximum temperature of 90 ℃ for 40 minutes to obtain
21 superabsorbent polymer of Example 3.
22
23 Example 4
29
Base resin powder was prepared by 1 the same method as Example 1.
2 Meanwhile, for surface crosslinking (additional crosslinking) of the
3 base resin powder, a surface crosslinking solution comprising 4.2 parts by weight
4 of water, 0.2 parts by weight of ethylene carbonate, 0.3 parts by weight of
5 aluminum sulfate, and 0.2 parts by weight of propylene glycol, based on 100 parts
6 by weight of the base resin powder, was prepared. To 100 parts by weight of the
7 base resin, the surface crosslinking solution was sprayed using a 1000 rpm
8 paddle type mixer. And then, it was heated at the maximum temperature of 185
9 ℃ for 60 minutes to progress surface crosslinking.
10 After the surface crosslinking, a 1.5 wt% aqueous solution comprising
11 0.3 parts by weight of sodium diethyldithiocarbamate, based on 100 parts by
12 weight of the base resin powder, was mixed by hydration, and the mixture was
13 heated at the maximum temperature of 90 ℃ for 40 minutes to obtain
14 superabsorbent polymer of Example 4.
15
16 Example 5
17 Base resin powder was prepared by the same method as Example 1.
18 Meanwhile, for surface crosslinking (additional crosslinking) of the
19 base resin powder, a surface crosslinking solution comprising 4.2 parts by weight
20 of water, 0.2 parts by weight of ethylene carbonate, 0.3 parts by weight of
21 aluminum sulfate, and 0.2 parts by weight of propylene glycol, based on 100 parts
22 by weight of the base resin powder, was prepared. To 100 parts by weight of the
23 base resin, the surface crosslinking solution was sprayed using a 1000 rpm
30
paddle type mixer. And then, it was heated at the maximum 1 temperature of 185
2 ℃ for 60 minutes to progress surface crosslinking.
3 After the surface crosslinking, 0.1 parts by weight of sodium
4 diethyldithiocarbamate, based on 100 parts by weight of the base resin powder,
5 was dry mixed at the maximum temperature of 50 ℃ for 10 minutes to obtain
6 superabsorbent polymer of Example 5.
7
8 Example 6
9 Base resin powder was prepared by the same method as Example 1.
10 Meanwhile, for surface crosslinking (additional crosslinking) of the
11 base resin powder, a surface crosslinking solution comprising 4.2 parts by weight
12 of water, 0.2 parts by weight of ethylene carbonate, 0.3 parts by weight of
13 aluminum sulfate, and 0.2 parts by weight of propylene glycol, based on 100 parts
14 by weight of the base resin powder, was prepared. To 100 parts by weight of the
15 base resin, the surface crosslinking solution was sprayed using a 1000 rpm
16 paddle type mixer. And then, it was heated at the maximum temperature of 185
17 ℃ for 60 minutes to progress surface crosslinking.
18 After the surface crosslinking, 0.3 parts by weight of sodium
19 diethyldithiocarbamate, based on 100 parts by weight of the base resin powder,
20 was dry mixed at the maximum temperature of 50 ℃ for 10 minutes to obtain
21 superabsorbent polymer of Example 6.
22
31
1 Comparative Example 1
2 Base resin powder was prepared by the same method as Example 1.
3 Meanwhile, for surface crosslinking (additional crosslinking) of the
4 base resin powder, a surface crosslinking solution comprising 4.2 parts by weight
5 of water, 0.2 parts by weight of ethylene carbonate, 0.3 parts by weight of
6 aluminum sulfate, and 0.2 parts by weight of propylene glycol, based on 100 parts
7 by weight of the base resin powder, was prepared. To 100 parts by weight of the
8 base resin, the surface crosslinking solution was sprayed using a 1000 rpm
9 paddle type mixer. And then, it was heated at the maximum temperature of 185
10 ℃ for 60 minutes to progress surface crosslinking.
11
12
14 For the superabsorbent polymer of Examples 1 to 6 and Comparative
15 Example 1, the properties were measured, and the results were shown in Table
16 1.
17
18 (1) Bacterial growth inhibition performance test
19 50 ml of artificial urine containing nutrients was inoculated with 2,500
20 CFU/ml of bacteria (Escherichia Coli,ATCC 25922), and 2 g of the
21 superabsorbent polymer of Comparative Example 1 was added thereto, and then,
22 it was incubated in an oven of 35 ℃ for 12 hours. After incubation for 12 hours,
23 150 ml of brine was added and shaken for 1 minute to wash, it was incubated in
32
solid medium (Nutrient agar plate, Difco) in a 35 ℃ incubator 1 for 24 hours, and
2 CFU(Colony Forming Unit; CFU/ml) was measured, thus obtaining the property
3 of control [CFUcontrol(12h)].
4 The ‘artificial urine containing nutrients’ was prepared as follows.
5
6 1) Preparation of a stock solution
7 Into a 1 L flask, every compounds (sodium chloride(0.15 M),
8 dipotassium hydrogen phosphate(0.02 M), sodium dihydrogen phosphate(0.01
9 M), ammonium chloride(0.05 M), disodium sulphate(0.02 M), lactic
10 acid(90%)(0.05 M), yeast extract(Becton Dikinson)) were introduced, and distilled
11 water was filled to 1000 ml to dissolve, and then, the solution was sterilized in an
12 autoclave. The prepared solution was stored at 4 ℃.
13 2) Preparation of urea/glucose solution
14 Into a 100 ml flask, every compounds (urea(6 M), D-glucose(0.01 M))
15 were introduced, and distilled water was filled to 100 ml to dissolve. From the
16 solution, bacteria were removed using a 0.22 micro filter. The prepared solution
17 was stored at 4 ℃.
18 3) Preparation of cationic solution
19 Into a 100 ml flask, every compounds (magnesium
20 chloride(hexahydrate)(0.3 M), calcium chloride(dehydrate)(0.3 M)) were
21 introduced, and distilled water was filled to 20 ml to dissolve, and then, the
22 solution was sterilized in an autoclave. The prepared solution was stored at 4 ℃.
33
4) Artificial 1 urine containing nutrient
2 94 ml of the stock solution, 5 ml of the urea/glucose solution, and 1 ml
3 of the cationic solution were mixed to prepare artificial urine containing nutrient.
4 After preparation, the solution was stored at 4 ℃, and used within 7 days from
5 the date of preparation.
6
7 2 g of each superabsorbent polymer of Examples or Comparative
8 Examples were added to 50 ml of the artificial urine containing nutrients, which
9 was inoculated with bacteria at 2,500 CFU/ml, and were shaken for 1 minute so
10 that they were uniformly mixed. It was incubated in a 35 ℃ oven for 12 hours.
11 After incubation for 24 hour, the artificial urine was sufficiently washed with 150
12 ml of brine, and incubated in solid medium (Nutrient agar plate, Difco) in a 35 ℃
13 incubator for 24 hours, and CFU(Colony Forming Unit; CFU/ml) was measured
14 [CFU(12h)].
15 Using the measurement results, bacterial (Escherichia Coli;
16 ATCC25922) growth rate represented by the following Formula 1 was calculated,
17 and based thereon, bacterial growth inhibition property of each Example and
18 Comparative Example was evaluated.
19 [Formula 1]
20 Bacterial growth inhibition rate = [1- {CFU(12h) /
21 CFUcontrol(12h)}]*100 (%)
22 in the Formula 1, CFU(12h) denotes the number of grown bacteria per
34
unit volume of artificial urine(CFU/ml), when 50 ml of 1 artificial urine containing
2 nutrients is inoculated with 2,500 CFU/ml of bacteria (Escherichia Coli, ATCC
3 25922), and 2 g of the superabsorbent polymer of Example or Comparative
4 Example is added thereto, and then, incubated at 35 ℃ for 12 hours; and
5 CFUcontrol(12h) denotes the number of grown bacteria per unit volume of
6 artificial urine(CFU/ml),when 50 ml of artificial urine containing nutrient is
7 inoculated with 2,500 CFU/ml of bacteria (Escherichia Coli, ATCC 25922), and
8 incubated under the same conditions, using superabsorbent polymer prepared
9 without additive comprising diethyldithiocarbamic acid or a salt thereof
10 (Comparative Example 1), instead of the above superabsorbent polymer, namely,
11 the number of grown bacteria per unit volume of artificial urine(CFU/ml) measured
12 for the control.
13
14 (2) Centrifugal Retention Capacity (CRC)
15 For the absorbent polymer, centrifuge retention capacity(CRC) according
16 to absorption rate under no load was measured according to EDANA(European
17 Disposables and Nonwovens Association) standard EDANA WSP 241.2. W0 (g,
18 about 0.2g) of the superabsorbent polymer were uniformly put in an envelope
19 made of non-woven fabric, and the envelope was sealed. And, the envelope was
20 soaked in a 0.9 wt% sodium chloride aqueous solution (saline solution) at room
21 temperature. After 30 minutes, the envelope was drained at 250G for 3 minutes
22 using a centrifuge, and then, the mass W2(g) of the envelope was measured.
23 And, after the same operation without using superabsorbent polymer, the mass
35
W1(g 1 ) at that time was measured.
2 Using the obtained weights, CRC (g/g) was calculated according to the
3 following Formula 2, thus confirming centrifuge retention capacity.
4 [Formula 2]
5 CRC(g/g) = {[W2(g) - W1(g)]/W0(g)} - 1
6 In the Formula 2,
7 W0(g) is the weight of absorbent polymer(g),
8 W1(g) is the weight of apparatus, measured after draining at 250G for
9 3 minutes using a centrifuge, without using absorbent polymer, and
10 W2(g) is the weight of apparatus including absorbent polymer, after
11 absorbent polymer is immersed in a 0.9 wt% saline solution at room temperature
12 for 30 minutes, and then, drained at 250G for 3 minutes using a centrifuge
13
14 (3) Absorption under Pressure (AUP)
15 Absorbency under pressure was measured according to
16 EDANA(European Disposables and Nonwovens Association) standard EDANA
17 WSP 242.2.
18 First, a 400 mesh wire netting made of stainless was installed on the
19 bottom of a plastic cylinder with an inner diameter of 60 mm. Under the conditions
20 of room temperature and humidity of 50%, W0(g, 0.90 g) of superabsorbent
21 polymer was uniformly scattered on the wire netting. Subsequently, a piston that
22 can uniformly give a load of 4.83 kPa(0.7 psi) was added on the superabsorbent
23 polymer. Wherein, as the piston, a piston having an outer diameter slightly
24 smaller than 60 mm was used such that there was no gap with the inner wall of
36
the cylinder, and the movement upward and downward w 1 as not hindered. At this
2 time, the weight W3(g) of the apparatus was measured.
3 Subsequently, on the inner side of a petri dish with a diameter of 150 mm,
4 a glass filter with a diameter of 90 mm and a thickness of 5 mm was positioned,
5 and a 0.90 wt% sodium chloride aqueous solution (saline solution) was poured
6 on the petri dish until the water level of the saline solution became the same level
7 to the upper side of the glass filter. And, one filter paper with a diameter of 90 mm
8 was put thereon. The above prepared measuring apparatus was mounted on the
9 filter paper, and the superabsorbent polymer in the apparatus was allowed to
10 absorb the solution under load for 1 hour. After 1 hour, the measuring apparatus
11 was lifted, and the weight W4(g) of the apparatus was measured.
12 Using the measured weights, AUP(g/g) was calculated according to the
13 following Formula 3, thus confirming absorbency under load.
14 [Formula 3]
15 AUP(g/g) = [W4(g) - W3(g)]/ W0(g)
16 In the Formula 3,
17 W0(g) is the weight(g) of absorbent polymer,
18 W3(g) is the sum of the weight of absorbent polymer and the weight of the
19 apparatus capable of applying load to the superabsorbent polymer, and
20 W4(g) is the sum of the weight of water-absorbed absorbent polymer after
21 supplying moisture to the absorbent polymer for 1 hour under load(0.7 psi) and
22 the weight of the apparatus capable of applying load to the superabsorbent
23 polymer.
24
37
(4) GPUP 1 (Gel Permeability Under Pressure)
2 Each superabsorbent polymer of Examples and Comparative
3 Examples was swollen in a saline solution (0.9 wt% sodium chloride aqueous
4 solution) for 1 hour, under pressure of 0.3 psi, and then, the saline solution was
5 poured to the superabsorbent polymer, and a flow rate for 5 minutes from the
6 time when the first drop fell was measured as GPUP. Specific measurement
7 method/conditions are as follows.
8 First, on the bottom of a plastic cylinder having an inner diameter of 60
9 mm, a 400 mesh wire netting made of stainless was installed. And, a piston
10 having an outer diameter slightly smaller than 60 mm and capable of further
11 applying 2.1 kPa(0.3 psi) load was installed thereon so that there was no gap with
12 the inner wall of the cylinder and the up and down movement was not hindered,
13 and the height(t0) was measured. In the cylinder, superabsorbent polymer(about
14 1.8 ±0.05g) was uniformly applied and the piston was raised, and then, inside a
15 petri dish having a diameter of 200 mm, a glass filter having a diameter of 90mm
16 and a thickness of 5mm was laid, and a saline solution consisting of 0.9 wt%
17 sodium chloride was put to the level 5mm higher than the upper side of the glass
18 filter, and the superabsorbent polymer was absorbed/swollen under load for 1
19 hour. Thereafter, a saline solution consisting of 0.9 wt% sodium chloride was
20 poured, and the weight of the saline solution passing through for 5 minutes from
21 the time when the first drop passed through the swollen superabsorbent polymer
22 gel(Fg), was measured. After the saline solution was passed through for 5
23 minutes, the height of the measuring device(t1) was measured. From the
24 measurement results, GPUP was calculated according to the following Formulas
38
1 4 and 5:
2 [Formula 4]
3 Ｋ(10-7 m3s/g)=(Fg*t/ρ*A*P)
4 Fg = weight of saline solution passing through gel per unit time(g/s)
5 t(cm) = thickness of superabsorbent polymer gel (t1-t0)/10
6 ρ= density of saline solution (~1 g/cm3)
7 A = area of cylinder, 28.27 cm2
8 P = hydrostatic pressure, 4920 dyn/cm2
9 [Formula 5]
10 GPUP(10-13 m2)=(Ｋ*η*10/10000)*1000000
11 η = viscosity of saline solution (~ 0.0009 [Pa.s])
12
13 [Table 1]
Content of sodium
diethyldithiocarbamate
(parts by weight)
Additive
introduction step
Bacterial
inhibition rate
(%)
CRC
(g/g)
AUP
(g/g)
GPUP
(10-13m2)
Example1 0.1 Surface
crosslinking
solution
99 29.8 23.2 28
Example2 0.3 Surface
crosslinking
solution
99 29.5 23 30
Example3 0.1 Wet mixing after
surface
crosslinking
99 30 23 27
Example4 0.3 Wet mixing after
surface
crosslinking
98 29.5 22.5 30
Example5 0.1 Dry mixing after
surface
crosslinking
96 30 22.4 24
Example6 0.3 Dry mixing after
surface
crosslinking
95 29 22.7 29
Comparativ
e Example1
0 - 0 29.5 23 27
14
39
The content of sodium diethyldithiocarbamate 1 of Table 1 was based
2 on 100 parts by weight of base resin.
3 Referring to Table 1, it was confirmed that the superabsorbent
4 polymers of Examples maintain excellent basic absorption properties such as
5 centrifuge retention capacity, absorption under pressure, and the like, which are
6 equivalent to those of Comparative Example 1, and yet, exhibit excellent bacterial
7 growth inhibition property. Thus, it is expected to have excellent deodorization
8 property.
9

[CLAIMS]
2 [Claim 1]
3 Superabsorbent polymer comprising
4 base resin powder comprising crosslinked polymer of water-soluble
5 ethylenically unsaturated monomers in which at least a part of the acid groups is
6 neutralized; and
7 a surface crosslinked layer formed on the base resin powder by
8 additional crosslinking of the crosslinked polymer by a surface crosslinking agent,
9 wherein the surface crosslinked layer comprises diethyldithiocarbamic
10 acid or a salt thereof.
11
12 [Claim 2]
13 The superabsorbent polymer according to claim 1, wherein the
14 diethyldithiocarbamic acid or a salt thereof is sodium diethyldithiocarbamate.
15
16 [Claim 3]
17 The superabsorbent polymer according to claim 1, wherein the
18 diethyldithiocarbamic acid or a salt thereof is included in the content of 0.1 to 5
19 parts by weight, based on 100 parts by weight of the base resin.
20
21 [Claim 4]
22 The superabsorbent polymer according to claim 1, wherein the surface
23 crosslinked layer further comprises a chelating agent or organic acid.
24
41
1 [Claim 5]
2 The superabsorbent polymer according to claim 1, wherein the surface
3 crosslinked layer comprises a diol compound, an alkylene carbonate compound
4 or a multivalent polyepoxy compound.
5
6 [Claim 6]
7 The superabsorbent polymer according to claim 1, wherein the
8 superabsorbent polymer has bacterial (Escherichia Coli; ATCC25922) inhibition
9 rate represented by the following Formula 1, of 90% or more:
10 [Formula 1]
11 Bacterial inhibition rate = [1- {CFU(12h) / CFUcontrol(12h)}]*100 (%)
12 in the Formula 1, CFU(12h) denotes the number of grown bacteria per
13 unit volume of artificial urine, when 50 ml of artificial urine containing nutrients is
14 inoculated with 2,500 CFU/ml of bacteria (Escherichia Coli, ATCC 25922), and 2
15 g of the superabsorbent polymer of claim 1 is added thereto, and then, incubated
16 at 35 ℃ for 12 hours; CFUcontrol(12h) denotes the number of grown bacteria
17 per unit volume of artificial urine, when 50 ml of artificial urine containing nutrient
18 is inoculated with 2,500 CFU/ml of bacteria (Escherichia Coli, ATCC 25922), and
19 incubated under the same conditions, using superabsorbent polymer prepared
20 without additive comprising diethyldithiocarbamic acid or a salt thereof, instead
21 of the above superabsorbent polymer.
22
23 [Claim 7]
42
A method for preparing the superabsorbent 1 polymer of claim 1,
2 comprising steps of:
3 polymerizing a monomer composition comprising water-soluble
4 ethylenically unsaturated monomers in which at least a part of the acid groups is
5 neutralized, an internal crosslinking agent and a polymerization initiator, to
6 prepare hydrogel polymer (step 1);
7 drying, grinding and classifying the hydrogel polymer to prepare base
8 resin (step 2); and
9 conducting a surface crosslinking reaction of the base resin in the
10 presence of a surface crosslinking solution comprising a surface crosslinking
11 agent, to prepare superabsorbent polymer in which a surface crosslinked layer is
12 formed (step 3),
13 wherein the method further comprises a step of mixing the
14 superabsorbent polymer in which a surface crosslinked layer is formed with
15 additive comprising diethyldithiocarbamic acid or a salt thereof (step 4), after the
16 step 3, or
17 in the step 3, the surface crosslinking solution further comprises
18 additive comprising diethyldithiocarbamic acid or a salt thereof.
19
20 [Claim 8]
21 The method for preparing superabsorbent polymer according to claim
22 7, wherein the diethyldithiocarbamic acid or a salt thereof is sodium
23 diethyldithiocarbamate.
24
43
1 [Claim 9]
2 The method for preparing superabsorbent polymer according to claim
3 7, wherein the diethyldithiocarbamic acid or a salt thereof is used in the content
4 of 0.1 to 5 parts by weight, based on 100 parts by weight of the base resin.
5
6 [Claim 10]
7 The method for preparing superabsorbent polymer according to claim
8 7, wherein in the step 4, a chelating agent or organic acid is further incorporated
9 and mixed, or
10 in the step 3, the surface crosslinking solution further comprises a
11 chelating agent or organic acid.
12
13 [Claim 11]
14 The method for preparing superabsorbent polymer according to claim
15 7, wherein the mixing of the step 4 is dry mixing or wet mixing.
16
17 [Claim 12]
18 A hygiene product comprising the superabsorbent polymer of claim 1.
19