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Superabsorbent

Principles & Properties VISION Consumer Products Conference

January 23-26, 2012

New Orleans, Louisiana

Patricia Brown (Technical Service)

[email protected]

980-218-1253

Hygiene Products

BASF Corporation

2 BASF Hygiene Products 2

Table of Contents

Introduction to Superabsorbents (SAP)

Definitions

Understanding SAP fluid absorption

SAP Properties

Testing explanations

Interrelationships of SAP product properties

SAP in Hygiene articles

Core design influence on SAP selection

SAP impact on testing

Product design and cost effects

3 BASF Hygiene Products

Introduction to Superabsorbents (SAP)


What is SAP?

SAP = Super Absorbent Polymer

Cross-linked sodium polyacrylate made of

partially neutralized acrylic acid

SAP is able to absorb large amounts of water

(up to 400 times its own weight)

SAP is able to absorb urine (up to 60 times its

own weight)

SAP is mostly prepared in a granular form, but

other forms are available like beads or fibers

Driving Forces for Absorption:

Osmotic Pressure

0.9 % Saline

(moderate Na content)

High Na

Content Reduced Na

Content

Swelling is limited by cross-links instead of gravity or concentration



Electrodynamic Repulsion

+

Negative charges repel

each other, so

the particle swells



Hydration Layer

OONa

Mobile water Bound water

(“layers)

Absorption Retention

OO - Na+ OO - Na+OO - Na+

OO - Na+

OO - Na+OO - Na+

OO - Na+

O O Na- +

O O Na- +

O O Na- + O O Na- + O O Na- +

O O Na- +O O Na- +

O O Na- +O O Na- +

OO - Na+ OO - Na+

Unbound water in solution

Water attracted to

acrylate Cross-link



Electrolyte Content of Aqueous Media

Capacity (Absorption + Retention) Relationships

Impact of salts

– As salt concentration increases, ability to swell decreases (reduced osmotic pressure)

– Metal ions with more than one charge have a more drastic effect because they act as cross-linker

Cross-linking with divalent ions

Increasing Salt Concentration

Ca

(g)

Flu

id / (

g)

SA

P

CaCl 2

NaCl


SAP Properties


SAP Properties

Standard tests: Capacity

FSC (Free Swell Capacity):

Absorption capacity of SAP without pressure. Solution partly removed by letting the tea bag drip off for 10min

CRC (Centrifuge Retention Capacity):

Absorption capacity of SAP without pressure. Solution between particles is removed by centrifugation of the tea bag

Teabag with

swollen SAP Tea bag with

dry SAP

Pure SAP is placed in a tea bag and submerged in 0.9% saline


SAP Properties

Standard tests: Gel Strength

AUL (Absorbency Under Load):

Typically uses a small cell and the loads applied vary

AAP (Absorbency Against Pressure):

An EDANA test with a larger cell with an applied pressure of 0.7 psi

Pure SAP is placed in a test cell and exposed to 0.9% saline while under a defined load

AAP

SAP


SAP Properties

Standard tests: Permeability

Permeability

Test parameters vary widely in the industry

Gel must contain capillaries and void spaces

Swollen particles must be able to retain their shape under load (High AUL / AAP required)

Pure SAP is swollen in a test solution and the rate of flow of 0.9% saline

through the swollen gel is measured while under a defined load

Preswollen

SAP

Weir

Load


SAP Properties

Interrelationships Among Key Properties

CRC

AUL

Permeability

Cross-linking

Property

(units)

High

Low

High Low


SAP Properties

Absorption Speed

FAST

SLOW

Measurement

Vortex closure, gel lock up, GATS, FVAUL and others

Factors Influencing Speed

Surface area related primarily to particle size distribution

Freeswell capacity and gel strength

Large Surface Area

Small Surface Area

Dry SAP Penetration and swelling

Very High Gel Strength

H2O


SAP in Hygiene Articles

Baby

Diapers

Feminine

Care

Adult

Incontinence


Core Design Impact on SAP Performance Needs

Tier 2 Tier 1 Tier 3 New Constructions

Fluffless, composites,etc

Typical designs for diapers, briefs, and protective underwear

Characteristics

< 7 g SAP 7 – 14 g SAP > 10 g SAP > 10 g SAP

< 25% SAP 25 – 40% SAP 40 – 60% SAP 60 – 90% SAP

No ADL ADL or No ADL ADL ADL and adhesives

SAP swells easily SAP a bit crowded High SAP density Few to no fibers

Low retention but high

capacity

Pulp moves fluid ADL – speed and fluid

movement

ADL – speed and fluid

movement

SAP Properties Needed

Higher FSC / CRC Improved AAP High AAP & Permeability High Permeability


Testing of Hygiene Products

How much can the product hold?

Total Capacity and Retention (g)

Relates to

– Skin dryness (retention)

– Risk of leakage after extended use (absorption)

– SAP capacity and concentration (absorption + retention)

High relevance in tier 1 and tier 2 designs

Often a test requirement of retailers and third-party labs

Various methods

– Capacity:

– Dunk (5 min – 30 min) & Drip (2-5 min)

– Full or half article

– Retention:

– Centrifugation

– Vacuum compression



How dry is the product?

Rewet (g)

Relates to

– Skin health / dryness

– SAP CRC and sometimes AUL/AAP

– Many converters specify maximum rewet

Multiple methods

– Flat, curved

– Number and volume of insults

– Weight / pressure during insult and covered area

– Time interval between insults

– Material for rewet (filter paper size or grade, alternative materials)

– Pressure & time during rewet

– Number and position of paper stacks



How fast is the product?

Acquisition Time / Strikethrough (sec)

Relates to:

– Fluid management

– Leakage (early leakage and after extended use)

– SAP AUL/AAP and Permeability (increasing importance with increasing SAP percentage)

Highly depending on product design and methodology

– Valuable quality control tool to detect SAP damage, gel blocking and SAP distribution

– Typically 2nd and 3rd acquisition rates are most valuable due to higher stress on the product



How long can the product stay on?

Fluid Distribution

Maximum fluid distribution (core usage) is desirable

Relates to:

– Gel blocking

– Leakage after extended use

– AUL / AAP and Permeability

– Absorption Speed and ADL performance


Product Design and Cost Effects

22BASF Hygiene Products

Key Trends in the US/Canada Markets:

End Consumer Needs

Prevent leakage

Keep skin dry and healthy

Comfort and fit

Dry

Wet

Value

Improved portability

Odor control

Convenience

SAP has a potential positive

impact on all of these drivers!


Elastics

Leg cuffs

Training pants

Ultra thin diaper

Fluff-less diaper

Protective Underwear

Odor Control for

Heavy Inco Odor Control for

Light Inco

Mark

et

Pene

tration

Retail

Light Inco

Skin Care

Elastics

Baby Diaper

Adult Incontinence Products

Key Trends in the US/Canada Markets:

Market Penetration & Product Features

(first appearance of innovations)

Youth pants / night wear

Gender specific diapers

Time

Impact of History and Design Trends on

Hygiene Product Developers (US/Canada)

Baby Diapers

Mature market (penetration > 95%)

Margin erosion

Strong private label

Minimal returns on design changes due

to low leakage rates

Niche products to extend product life

cycle

Adult Incontinence

Rapid growth (demographics)

Large number of SKU’s

Large mass / product

Both – Product Cost Pressure

BASF Hygiene Products

Design Options to Improve Value


Consider two designs:

A B

Pulp Weight (g) 15 10

SAP Weight (g) 10 11.5

SAP Concentration (%) 40 53

Calculated Capacity (g) 605 645

Pulp = 1000 USD / ton

SAP = 2.50 USD / kg

A B

Cost / 1000 pads (USD) 40 37.5

High-performance SAP with

permeability can take some of the

function of pulp

Replacing pulp with the right SAP

can conserve or improve

performance and reduce cost

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