Discipline 01 · Polymers

The polymer is chosen,
never defaulted.

Superabsorbent polymer — cross-linked sodium polyacrylate — is sold under one name and behaves in a hundred ways. We select it by model, by size and by its position in the core, qualify it from several producers, co-develop grades with producers in Asia, and mix grades when a single one cannot do the whole job.

4producing countries qualified: Korea, Japan, China, Germany

150–850 µmparticle window we specify

4properties traded off for every grade

What a superabsorbent is

A hard shell around a soft core

Each particle is a polymer network that swells as it drinks. The core is lightly cross-linked to hold a lot; the surface is cross-linked harder so the swollen gel stays firm when someone sits on it. That shell is the difference between a gel that keeps working under the body and one that collapses into a wet paste.

In pure water a good polymer holds hundreds of times its weight. In saline, far less — the ions screen the charges that make the network swell. That is why water figures are a laboratory ceiling, not a promise.

Four properties, no free lunch

No grade wins everything

Grades that hold the most often swell slowest and block first; the fastest grades usually hold less. Choosing a polymer means choosing a compromise — then placing it where that compromise is right.

Capacity

How much it holds

Free-swell and centrifuge retention (CRC, NWSP 241): what stays locked in once the gel is spun.

Under load

How much it holds when sat on

Absorption against pressure (AUL, NWSP 242). The body weighs on the core all night.

Speed

How fast it drinks

Uptake rate decides whether a surge is caught or runs to the leg cuff.

Permeability

Whether liquid can pass through the gel

A swollen bed must still let liquid through to the dry polymer behind it — or it blocks.

Mixing producers and grades

Swapping a polymer is a formulation change

We qualify superabsorbents from producers in Korea, Japan, China and Germany. Their kinetics differ: one grade wins on free-swell capacity and loses under pressure; another is fast but saturates early. A competitor that uses a single producer everywhere gets that producer’s compromise everywhere.

We work the other way round. The grade is chosen per product line and per size; where one grade cannot cover both the surge and the long hold, we combine them — a faster grade where the liquid lands, a higher-retention grade where it is stored.

Because kinetics differ, changing supplier is never a purchasing decision alone. Every change goes back on the line, is sampled and re-measured before it ships.

Our rule

Grade by position, not by price

Insult zone: speed and permeability first.
Storage zones: retention and behaviour under load.
Light products: fast, thin, no gel feel.
Night and heavy products: capacity under load, low rewet.
Every new grade: line trial, sampling, full test set.

Co-development

Polymers made for our industry

Most superabsorbent grades on the market were designed for baby diapers: small surges, light bodies, short wear. Adult incontinence asks for something else — larger and faster voids, the full weight of an adult sitting or lying on the core, and eight to twelve hours of wear.

So we do not only choose among existing grades. We work with superabsorbent producers in Asia to develop grades specific to adult incontinence — tuned for speed on large surges, retention under an adult’s load and permeability over a long night — and we validate every candidate on our own lines before it enters a recipe.

What we ask a producer for

An adult-incontinence specification

Uptake fast enough for adult void volumes.
Retention that holds under a seated adult’s pressure.
Permeability that stays open when the core is loaded.
A particle window with minimal fines.
Stable performance in saline, not only in water.

Granulometry

We specify the distribution, not the average

Two lots with the same average particle size can behave nothing alike. Fines — the dust below about 150 µm — swell first and seal the surface: gel blocking. They also migrate through the multi-cored wrap. Coarse particles above about 850 µm drink slowly and can be felt.

So the specification is a window and a shape, checked by sieve analysis (NWSP 220) — not a single number on a certificate.

Purity

What touches the skin is part of the specification

Consistency lot to lot

Certificates are read for moisture, extractable fraction and particle distribution — the parameters that move performance, not only the headline capacity.

Clean in use

Controlling fines keeps the polymer inside the core, not on the skin or in the air of the production hall.

Honest capacity

In saline, one gram of our polymer holds roughly four times what a gram of fluff holds. We count both — and publish the saline result.

Questions

Frequently asked

What is superabsorbent polymer (SAP) made of?

Superabsorbent polymer is cross-linked sodium polyacrylate: particles with a lightly cross-linked core that swells and a more cross-linked surface shell that keeps the gel firm under pressure.

What particle size should a superabsorbent have?

We specify a window of roughly 150 to 850 micrometres. Fines below about 150 µm cause gel blocking and dust; coarse particles above about 850 µm absorb slowly and can be felt.

What is gel blocking?

Gel blocking happens when swollen particles at the surface of the core form a barrier that stops liquid reaching dry polymer further in. The product then leaks or feels wet although capacity remains unused.

Are all superabsorbents the same?

No. Grades from different producers — we qualify polymers from Korea, Japan, China and Germany — differ in speed, absorption under load and permeability. Changing grade changes the product.

Does Nateen develop its own superabsorbent grades?

Yes. We work with superabsorbent producers in Asia to develop grades specific to adult incontinence — fast on large voids, retentive under an adult’s weight, permeable over a long night — and validate them on our own lines.

Nateen products