Hydrophilic hydrogels with a high swelling capacity and method for producing and using them
First Claim
1. A hydrophilic, highly swellable hydrogel based on (co)polymerized monomers or based on graft (co)polymers and prepared bya) free-radically (co)polymerizing one or more hydrophilic monomers
- where R1 is hydrogen, methyl or ethyl, R2 is —
COOR4, hydroxysulfonyl, phosphonyl, a (C1-C4)-alkanol-esterified phosphonyl group or a group of the general formula (II) R3 is hydrogen, methyl, ethyl or carboxyl, R4 is hydrogen, amino-(C1-C4)-alkyl or hydroxy-(C1-C4)-alkyl, and R5 is hydroxysulfonyl, phosphonyl or carboxyl;
or
graft (co)polymerizing one or more hydrophilic monomers of the formula (I) onto a grafting base, the average degree of neutralization of the acid-functional monomers being from 0 to 40 mol %;
b) comminuting the acidic hydrogel;
c) neutralizing the acidic hydrogel to an ultimate degree of neutralization of 50-85 mol % by adding a neutralizing agent; and
d) drying, grinding and sieving the hydrogel particles characterized by a centrifuge retention of at least 29 g/g for a 0.9% aqueous NaCl solution, and a vertical absorption (1 g) swell height of at least 3.5 cm coupled with an extractables content (16 h value) of less than 5%;
or a centrifuge retention of at least 23 g/g for a 0.9% aqueous NaCl solution, and a vertical absorption (3 g) swell height of at least 5 cm an extractables content (16 h value) of less than 4%.
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Abstract
A hydrophilic, highly swellable hydrogel based on (co)polymerized monomers or based on graft (co)polymers and prepared by
a) free-radically (co)polymerizing one-or more hydrophilic monomers or graft (co)polymerizing one or more hydrophilic monomers onto a grafting base, the average degree of neutralization of the acid-functional monomers being from 0 to 40 mol %,
b) comminuting the acidic hydrogel,
c) neutralizing the acidic hydrogel to an ultimate degree of neutralization of 50-85 mol % by adding a neutralizing agent,
d) drying, grinding and sieving the hydrogel particles characterized by
a centrifuge retention and a vertical absorption swell height, each having a specified minimum.value, coupled with an extractables content having a specified maximum value or
a centrifuge retention and a vertical absorption swell height, each having a specified minimum value and
an extractables content having a specified maximum value.
61 Citations
23 Claims
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1. A hydrophilic, highly swellable hydrogel based on (co)polymerized monomers or based on graft (co)polymers and prepared by
a) free-radically (co)polymerizing one or more hydrophilic monomers - where
R1 is hydrogen, methyl or ethyl, R2 is —
COOR4, hydroxysulfonyl, phosphonyl, a (C1-C4)-alkanol-esterified phosphonyl group or a group of the general formula (II)R3 is hydrogen, methyl, ethyl or carboxyl, R4 is hydrogen, amino-(C1-C4)-alkyl or hydroxy-(C1-C4)-alkyl, and R5 is hydroxysulfonyl, phosphonyl or carboxyl;
or
graft (co)polymerizing one or more hydrophilic monomers of the formula (I) onto a grafting base, the average degree of neutralization of the acid-functional monomers being from 0 to 40 mol %;
b) comminuting the acidic hydrogel;
c) neutralizing the acidic hydrogel to an ultimate degree of neutralization of 50-85 mol % by adding a neutralizing agent; and
d) drying, grinding and sieving the hydrogel particles characterized by a centrifuge retention of at least 29 g/g for a 0.9% aqueous NaCl solution, and a vertical absorption (1 g) swell height of at least 3.5 cm coupled with an extractables content (16 h value) of less than 5%;
ora centrifuge retention of at least 23 g/g for a 0.9% aqueous NaCl solution, and a vertical absorption (3 g) swell height of at least 5 cm an extractables content (16 h value) of less than 4%. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
a) the mincer has a power output of from 1000 to 6000 Wh/m3. b) the hydrogel is passed through a zone having an energy dissipation intensity of from 400 to 800 W/l of mixing volume, c) the average hydrogel residence time in the mincer is from 5 to 30 seconds, d) the open area of the breaker plate is from 20 to 40% and the postneutralized hydrogel particles are subjected to the drying step without further shearing. -
6. The hydrogel of claim 1, wherein, as well as the neutralizing agent, one or more other reactive materials capable of reacting with free acrylic acid and/or with the carboxyl groups of the hydrogel and/or water-swellable hydrophilic polymer fines are added during the neutralization of the gel.
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7. The hydrogel of claim 1, wherein the postneutralization is carried out in two steps, the first neutralization step taking place in the mincer and the second neutralization step being effected by applying the neutralizing agent to the hydrogel particles without mechanical shearing stress.
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8. The hydrogel of claim 1, wherein the dried and ground hydrogel particles are covalently surface postcrosslinked.
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9. The hydrogel of claim 1, wherein the surface of the dried and ground hydrogel particles is modified by the formation of metal complexes.
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10. A method of absorbing water or aqueous fluid, comprising contacting the hydrogel according to claim 1 with water or aqueous fluid.
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11. A method of absorbing bodily fluid, comprising contacting the hydrogel according to claim 1 with bodily fluid.
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12. An absorbent, comprising the hydrogel according to claim 1.
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13. A method of absorbing water or aqueous fluid, comprising contacting the absorbent according to claim 12 with water or aqueous fluid.
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14. A method of absorbing bodily fluid, comprising contacting the absorbent according to claim 12 with bodily fluid.
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15. A diaper, comprising the hydrogel according to claim 1.
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16. A method of absorbing water or aqueous fluid, comprising contacting the diaper according to claim 15 with water or aqueous fluid.
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17. A method of absorbing bodily fluid, comprising contacting the diaper according to claim 15 with bodily fluid.
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18. A tampon, comprising the hydrogel according to claim 1.
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19. A method of absorbing water or aqueous fluid, comprising contacting the tampon according to claim 18 with water or aqueous fluid.
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20. A method of absorbing bodily fluid, comprising contacting the tampon according to claim 18 with bodily fluid.
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21. A sanitary napkin, comprising the hydrogel according to claim 1.
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22. A method of absorbing water or aqueous fluid, comprising contacting the sanitary napkin according to claim 21 with water or aqueous fluid.
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23. A method of absorbing bodily fluid, comprising contacting the sanitary napkin according to claim 21 with bodily fluid.
- where
Specification