# US 8,568,883 B2 · Superabsorbent polymer particles with improved surface cross-linking and improved hydrophilicity and method of making them using vacuum UV radiation

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- Number: US 8,568,883 B2
- Document ID: US8568883B2
- Status: Granted
- Kind: B2
- Application number: 11/298,416
- Filed: 2005-12-08
- Published: 2006-06-15
- Granted: 2013-10-29
- Earliest claimed: 2004-12-10
- Assignees: Then Procter & Gamble Company
- Applicants: Andreas Flohr; Torsten Lindner
- Inventors: Andreas Flohr; Torsten Lindner
- Web page: https://patentgrep.com/patent/US8568883B2

## CPC

- C08J 3/28: Treatment by wave energy or particle radiation
- C08J 3/245: {Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking}
- C08J 2333/02: Homopolymers or copolymers of acids; Metal or ammonium salts thereof
- Y10T 428/2998: including synthetic resin or polymer
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The present invention relates to superabsorbent polymer particles with improved surface cross-linking and improved hydrophilicity and their use in absorbent articles. Superabsorbent polymer particles of the invention consist of cross-linked poly(meth)acrylic acid and salts thereof. The polymer chains comprised by the superabsorbent polymer particles are cross-linked to each other through direct covalent bonds and comprise alcoholic hydroxyl groups. Moreover, the invention relates to a method for surface cross-linking superabsorbent polymer particles using vacuum UV irradiation.

## Claims

### Claim 1

A method of surface cross-linking superabsorbent polymer particles which comprises the steps of
a) providing superabsorbent polymer particles comprising polymer chain segments, the polymer chain segments comprising poly(meth)acrylic acid and salts thereof, each superabsorbent polymer particle having a surface and a core, and
b) cross-linking the polymer chain segments by exposing said superabsorbent polymer particles to irradiation with vacuum UV radiation having a wavelength of from about 100 nm to about 200 nm.

### Claim 2 (depends on 1)

The method of claim 1, wherein surface cross-linking molecules having at least two C═C double bonds are added to said superabsorbent polymer particles prior to exposure to vacuum UV radiation.

### Claim 3 (depends on 1)

The method of claim 1, wherein said superabsorbent polymer particles provided for said method have a residual water content of less than about 5% by weight of said superabsorbent polymer particles.

### Claim 4 (depends on 1)

The method of claim 1, wherein said superabsorbent polymer particles are moisturized with water prior to exposure to vacuum UV radiation.

### Claim 5 (depends on 1)

The method of claim 1, wherein said vacuum UV radiation has a wavelength of from about 160 nm to about 200 nm with a radiation peak at a wavelength of about 172 nm.

### Claim 6 (depends on 1)

The method of claim 1, wherein said method is carried out at temperatures of less than about 100° C.

### Claim 7 (depends on 1)

The method of claim 1, wherein said superabsorbent polymer particles are exposed to vacuum UV radiation for from about 0.1 seconds to about 5 minutes.

### Claim 8 (depends on 1)

An absorbent article comprising superabsorbent polymer particles made according to a method of claim 1, wherein the superabsorbent polymer particles are at least partially surface cross-linked via direct covalent links between two carbon atoms in the backbone of the polymer chains.