Superabsorbent Polymer (SAP)"SANFRESH"

Superabsorbent Polymers Contribute to Solving Moisture Problems in Various Fields

What's Great about Sanyo Chemical's Superabsorbent Polymer "SANFRESH"

Superabsorbent polymer (SAP) is a polymeric material that absorbs several hundred to 1,000 times its own weight in water and does not release the absorbed water even if some pressure is applied. 


Development experience as a pioneer in Superabsorbent polymer commercialization

In 1978, we became the first company in the world to begin commercial production of superabsorbent polymers (SAP). Since then, SAP has been used in a wide range of fields, including disposable diapers, sanitary products such as napkins, agriculture and horticulture, pet-related products, and civil engineering and construction.

  Based on the technology we have accumulated over the years as a pioneer in the commercialization of SAP, we have developed products suitable for various applications to meet the needs of our customers. 


High water absorption and water retention

The "SANFRESH" series has high water absorption and water holding capacity through precise control of the cross-linked structure. 
 Even when absorbing alkaline solutions or liquids containing iron ions, the water-absorbing gel does not lose its shape and can retain water for a long period of time. 


Functionality added by our proprietary applied technology

Our proprietary superabsorbent resin application technology allows us to add a variety of functions. 

  • It has the property of absorbing moisture under high humidity and releasing moisture under low humidity, so-called moisture absorption and desorption. 
  • Small particle size "SANFRESH ST-500MPSA" and "SANFRESH ST-100MPS" have the property of thickening water and aqueous solutions. 
  • For applications requiring antimicrobial properties, we also offer " SANFRESH ST-900E". 


Low toxicity 

Our superabsorbent polymers have low residual acrylic acid monomer content and are highly safe.

Video of Water Absorption Experiment with Superabsorbent Polymer (SAP)

Mechanism of water absorption (concept)

  The "SANFRESH" products includes two types of acrylate polymer (acrylic acid polymer partial sodium salt cross-linked) and starch polymer (starch/acrylic acid graft polymer partial sodium salt), all of which have a three-dimensional cross-linked molecular structure. 

  When superabsorbent polymers come into contact with water, osmotic pressure generated by the difference in ion concentration between the inside and outside of the polymer allows water to enter between the molecular chains, and the repulsive force between negative ions expands the molecular chains to the area restricted by the three-dimensional cross-linking, causing water to be incorporated into each individual network. 

Main Applications of "SANFRESH"

SANFRESH " is a superabsorbent polymer (SAP) for non-sanitary materials that can help control moisture in various situations and contribute to SDGs Goal 6 "Provide the world with safe water and toilets" as a representative for portable toilet applications. 

  • Click here if you are looking for "SANWET" superabsorbent polymer for sanitary materials 

Consumer Goods 

Pet sheets and cat litter 

Pet sheets (indoor dog toilets) and cat litter are typical products. 

 Pet sheets consist of an absorbent layer made of pulp and superabsorbent polymer, a surface nonwoven fabric that directs urine to the absorbent layer, and a leak-proof film that prevents absorbed urine from seeping out to the backside. 

 Cat litter is usually in the form of pellets with superabsorbent polymers coated on the surface of a rounded nucleus of pulp, waste paper or sawdust. They are designed so that only the portion with urine clumps together, making disposal easy. In addition, the pellets are lighter in weight than conventional materials such as bentonite. SANFRESH ST-250*," which features high water absorption speed, is effective. 

Disposable body warmers 

Disposable body warmers use the heat generated when iron powder is oxidized by oxygen in the air to iron oxide. Saline solution is needed as a catalyst to accelerate this oxidation. 

 Superabsorbent polymers are used as agents to retain and release brine. A body warmer using superabsorbent polymers absorb and retain salt water well, while also releasing salt water slowly in the amount needed to accelerate oxidation. 

Our product, " SANFRESH ST-500D*," which has excellent long-term retention properties, is effective. 

Emergency toilet 

Superabsorbent polymers are used as urine solidifiers for portable toilets in times of natural disasters. A plastic bag is set in the toilet bowl, sprinkled with superabsorbent polymer, and the urine is gelatinized. It is required to gel fast so that excrement can be coagulated without spilling and to simplify disposal. 

  Similarly, portable toilets are also commercialized for convenient leisure and driving use. 

  Our product, " SANFRESH ST-250*," which gels quickly, is effective. 



Superabsorbent polymers are also used in cold insulators (polyethylene or other bags filled with gel-like material) used in the transportation of fresh produce such as vegetables, cakes, and frozen foods. 

 In such applications, it is necessary to change the hardness of the gel according to the item to be kept cold. " SANFRESH ST-500D*" is effective for hard gel types and " SANFRESH ST-250*" for soft gel types. 

Drip absorbing sheets

Water absorption function of superabsorbent polymers

Moisturizing sheets 

Moisture retention function of superabsorbent polymers

Medical and Cosmetics 

Medical Waste 

Superabsorbent polymers are used to absorb medical waste generated during surgical procedures in the medical field. Medical waste is collected in special containers and solidified with superabsorbent polymers to prevent the risk of secondary infection due to leakage of waste during storage, transportation, and treatment processes. 

Among our products, " SANFRESH ST-250*" is suitable for this application because of its rapid gelation and resistance to leakage. 


Water retention function of superabsorbent polymers


Thickening function of superabsorbent polymers

Civil Engineering and Architecture

Water absorbent sandbags 

Superabsorbent polymers are used in "water-absorbent sandbags," which are widely used as disaster prevention equipment for flooding that occurs during typhoons and torrential rains. Ordinary sandbags are made by filling a bag with soil, but "water-absorbent sandbags" are completed by soaking a bag containing superabsorbent polymers in water. In addition to being quick to prepare, they are lightweight and take up little space for storage. 

 SANFRESH ST-500D*, which forms a hard gel, is effective for use when piled up. 

Moisture-regulating wallpaper

Moisture absorption and desorption function of superabsorbent polymers

Slope face plantings 

Water retention function of superabsorbent polymers

Agriculture and Horticulture

Soil water retention agent

Soil water retention agents are typical in the agricultural and horticultural fields. 

"Sanyo Seedling Sheet" is also used for seedling sheets and slow-release fertilizers and agrochemicals that are coated on the surface of fertilizers and agrochemicals to improve their slow release in soil. 

Soil modifiers

Water retention function of superabsorbent polymers

Seedling sheet 

Water retention function of superabsorbent polymers 

Note: The information contained herein does not constitute an endorsement of any patent or guarantee of its use.

Performance of Superabsorbent Polymer “SANFRESH" 

"SANFRESH " retains moisture well and contributes to labor and construction savings due to the aforementioned features.

Water absorption performance


Water absorption

It absorbs more than 80% of its saturated water absorption within 10 minutes. 


Relationship between pH and water absorption 

It shows stable water absorption in water with a pH of approximately 4 to 10. 


Relationship between electrolyte concentration and water absorption 
 (In the case of " SANFRESH ST-500D*") 

Non-electrolytes have no effect on water absorption, but electrolytes have a significant effect.


Relationship between Thermal History and Water Absorption 
 (In the case of " SANFRESH ST-500D*") 

Water absorption is hardly reduced even after standing at 150°C or below for about 5 hours.


Relationship between concentration of aqueous organic solvent solution and water absorption 
 (In the case of " SANFRESH ST-500D*") 

Water absorption of aqueous organic solvent solutions varies depending on their type and concentration. 


Relationship between temperature and water absorption of aqueous organic solvent solutions 
 (In the case of " SANFRESH ST-500D*") 

Water absorption of aqueous organic solvent solutions is largely unaffected by temperature.

Moisture absorption performance 


Moisture absorption speed 
 (In the case of " SANFRESH ST-500D*") 

As the relative humidity increases, the rate of moisture absorption increases. 


Equilibrium moisture absorption 
 (In the case of " SANFRESH ST-500D*") 

As the relative humidity increases, the equilibrium moisture absorption increases.


Moisture absorption and desorption (in the case of " SANFRESH ST-500D*")

Under high humidity, it absorbs moisture, and under low humidity, it releases moisture once absorbed. 

Viscosity (coagulation) properties

Viscosity of water dispersion liquid 
 (In the case of " SANFRESH ST-500MPSA")

Small particle size "SANFRESH ST-500MPSA" and "SANFRESH ST-100MPS" have the property of thickening water and aqueous solutions. Viscosity increases as the amount added increases. 

Main Lineup of Superabsorbent Polymer "SANFRESH" 

*1 Acrylic acid polymer partial sodium salt cross-linked 
 *2 Starch acrylic acid graft polymer partial sodium salt
 *3 In accordance with JIS K 7223
Note: The values shown on this page are representative values.
Features Appearance Water absorption*3
(deionized water)
Grain size
Acrylic acid salt*1
polymer typycal example
  • High water absorption
White powder 600 380
  • Forms a slightly hard water absobing gel
White powder 400 380
  • High water viscosity
  • Fine particle
White powder 600 30
  • Antimicrobial
White powder 500 380
typical example
  • High water absorption
White powder 800 380
  • High water viscosity
  • Fine particle
White powder 1,000 30

Precautions for use

Precautions against misuse 

  • If the powder adheres to each other due to moisture in the air or unintentional addition of water, it may cause blockage of the piping of the equipment or failure of moving parts due to increased load on the motor, etc. Therefore, avoid moisture absorption and unintentional addition of water to the resin before use. 
  • Water-absorbing gel tends to release water when left at high temperatures; use at temperatures below 50°C is recommended. 
  • Water-absorbing gel is sensitive to ultraviolet rays and tends to lose water if left in sunlight. When used outdoors or in other locations exposed to sunlight, it is recommended to use opaque or UV-absorbent containers or packaging materials. 

Other precautions 

  • Do not lick or eat this product. 
  • The gel that has absorbed water is slippery. Please be careful.
  • This product tends to absorb less water when left at high temperatures. Avoid high temperature and humidity, and store in a well ventilated place in a sealed container. 

Before handling this product, be sure to read the "Safety Data Sheet" (SDS) for this product and its sub-materials (chemicals). 
For SDSs not listed on our website, please contact our sales representative. 

Related Information

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Consequently anyone acting on information contained in this brochure does so entirely at his/her own risk.In particular, final determination of suitability of any material described in this brochure, including patent liability for intended applications, is the sole responsibility of the user. Such materials may present unknown health hazards and should be used with caution. Although certain hazards may be described in this brochure, Sanyo Chemical Industries, Ltd. cannot guarantee that these are the only hazards that exist