POLYACRYLIC ACID, SODIUM SALT

CAS: 9003-04-7 BOILER WATER ADDITIVE, WASHING OR SURFACE REMOVAL AGENT

POLYACRYLIC ACID, SODIUM SALT is a high‑molecular‑weight polymer salt of polyacrylic acid used primarily as an industrial surface‑treatment agent. In regulatory inventories it appears under multiple names and has specified uses in contact with food processing equipment and packaging materials under prescribed conditions.

What It Is

POLYACRYLIC ACID, SODIUM SALT is a polymeric salt derived from polyacrylic acid in which sodium ions neutralize the carboxylate groups along the polymer backbone. It belongs to a class of high‑molecular‑weight polymers known for their water‑absorbing and chelating properties. The CAS Registry Number 9003‑04‑7 uniquely identifies this substance in chemical inventories and regulatory lists. Multiple synonyms such as SODIUM POLYACRYLATE 2‑PROPENOIC ACID and POLY(ACRYLIC ACID), SODIUM SALT reflect slight nomenclature variations used across regulatory and scientific contexts. In material science and industrial chemistry, this polymer is appreciated for its ability to bind water, modify surface interactions, and disperse scale and precipitates during thermal and aqueous processing. In the context of food and food contact regulation, this material is not typically used as a direct ingredient added to food for consumption; rather, it appears in authorized regulatory sections of the U.S. Code of Federal Regulations where it is permitted for specific uses in food processing environments and equipment, such as scale control during sugar processing under strict concentration limits. These regulatory entries demonstrate that agencies recognize the controlled utility of this polymer in manufacturing rather than as a nutritive or functional food component. The polymer’s structure—composed of long chains of repeating acrylic acid units with sodium counterions—results in properties that differ markedly from small‑molecule food additives, and its regulatory treatment reflects these functional and exposure distinctions.

How It Is Made

The synthesis of POLYACRYLIC ACID, SODIUM SALT involves the polymerization of acrylic acid monomers, typically initiated by free‑radical mechanisms, to form a high‑molecular‑weight polyacrylic acid backbone. This polymerization step creates a long chain of repeating prop‑2‑enoic acid units. After polymerization, the acid groups can be neutralized with a sodium base such as sodium hydroxide, resulting in the sodium salt form. The degree of neutralization and the molecular weight distribution can be controlled through reaction conditions such as temperature, initiator concentration, and the ratio of monomer to base. The resulting polymer is a polyelectrolyte with sodium carboxylate functional groups along its chain, which imparts solubility in water and interaction capabilities with metal ions and mineral surfaces. In industrial settings, manufacturers may further process the polymer to meet purity standards required for regulatory compliance if used in food contact or processing environments. This can include steps to reduce residual monomer content, control molecular weight distribution, and ensure that by‑products are within acceptable limits. Analytical techniques such as gel permeation chromatography and titration of acid groups are commonly used to characterize the product. The production process does not involve the introduction of significant additional chemical functionalities beyond the backbone and salt form; rather, it focuses on obtaining the specified polymer characteristics necessary for its intended application.

Why It Is Used In Food

Although POLYACRYLIC ACID, SODIUM SALT is not a food ingredient in the traditional sense, it is authorized under U.S. food contact regulations for specific uses where its functional properties support food processing operations. For example, in the production of sugar from beet or cane juice, sodium polyacrylate can be used to control mineral scale formation during evaporation steps, helping prevent equipment fouling and supporting efficient processing. Regulatory provisions define the maximum concentrations and conditions under which this polymer can be used to ensure that any potential migration into food streams remains minimal and within safe limits. These uses align with the polymer’s ability to interact with ions and disperse mineral precipitates that could otherwise deposit on heat transfer surfaces. In other food contact scenarios, analogous polymers may be incorporated into packaging materials or processing aids where their functional properties—such as water absorption or surface modification—contribute to desirable manufacturing outcomes without becoming part of the food itself. The utility of this polymer class arises from its high water binding capacity and its capacity to interfere with mineral scaling, flocculate particles, and modify fluid behavior in aqueous systems. These properties make it valuable in industrial and food processing lines where controlling scale and deposits improves sanitary conditions, reduces maintenance, and enhances consistent product quality.

Adi Example Calculation

Because POLYACRYLIC ACID, SODIUM SALT does not have an established numeric ADI from authoritative evaluations for direct ingestion, illustrative intake calculations based on body weight are not provided. Regulatory frameworks for indirect food contact substances emphasize adherence to prescribed use conditions and migration limits rather than applying a direct ADI. If exposure estimates were required for a specific scenario, risk assessors would model potential migration into food and compare that estimate with health‑based reference values from toxicological data for relevant components, but such numeric reference values are not established in this case.

Safety And Health Research

Regulatory safety assessments of POLYACRYLIC ACID, SODIUM SALT and related polymers are grounded in the principle that exposures through authorized indirect food contact uses are minimal when the substance is used as intended. For example, evaluations of cross‑linked polyacrylic acid sodium salt in absorbent pads for food packaging have concluded that, under conditions where the polymer does not directly contact food and its absorption capacity is not exceeded, no significant migration into food is expected. Such assessments consider aspects of polymer chemistry, potential for residual monomers, and migration behavior rather than attributing nutritional or pharmacological effects. Toxicological data for this class of polymers focus on their inertness due to high molecular weight and minimal systemic absorption if exposure occurs. Because they are not used as direct food ingredients, formal hazard studies such as chronic toxicity or reproductive toxicity are less central to regulatory decisions than in additives intended for ingestion. Instead, safety evaluations emphasize material characterization, residual monomer content, and potential for migration under specific use conditions. These evaluations are designed to ensure that any consumer exposure from authorized uses remains below levels of toxicological concern, consistent with established food contact material safety frameworks.

Regulatory Status Worldwide

In the United States, POLYACRYLIC ACID, SODIUM SALT is listed in the FDA’s Inventory of Food Contact Substances and appears in multiple sections of 21 CFR that authorize its use for specific indirect food contact applications under prescribed conditions. For example, 21 CFR 173.73 specifically recognizes sodium polyacrylate with CAS 9003‑04‑7 for scale control in sugar processing at defined maximum concentrations. These regulatory entries indicate that the polymer is permitted for use in food processing environments when used in compliance with the specified conditions, and they are intended to limit exposure and potential migration. Its presence in food contact regulations reflects an assessment that, under those conditions, it does not pose an unreasonable risk to health. In the European Union, the European Food Safety Authority has evaluated polyacrylic acid sodium salt in the context of food contact materials, particularly for uses such as absorbent pads in packaging. These evaluations focus on ensuring that migration into food is negligible when the polymer is not in direct contact with the food and is used as intended. Such safety assessments are part of broader frameworks governing materials intended to contact food, where functional barriers and intended use conditions are key determinants of authorization. At the international level, entities such as the Joint FAO/WHO Expert Committee on Food Additives provide general frameworks and compendia for food additive specifications, but specific numeric ADIs for this polymer are not established because its primary authorized roles are not direct food additives but technical processing and contact uses.

Taste And Functional Properties

Because POLYACRYLIC ACID, SODIUM SALT is a high‑molecular‑weight polymer and is not intended to be ingested as a food component, it does not have a taste profile that would contribute to flavor in food. In sensory contexts it is effectively inert because its large polymer chains do not interact with taste receptors. Its functional properties are rooted in its physicochemical behavior: in water, the polymer chain expands and interacts with ions and surfaces, making it effective at dispersing mineral precipitates and influencing the behavior of aqueous solutions. These functional traits are useful in regulatory‑permitted applications but do not translate into sensory contributions in food products. The polymer’s solubility and performance depend on factors such as pH, ionic strength, and temperature of the solution. In neutral to alkaline environments, the sodium carboxylate groups render the polymer highly soluble in water, while in acidic conditions, partial protonation may reduce solubility. These properties are important in industrial process control and equipment maintenance. Importantly, because it is not used for flavor or texture modification in food consumption, taste and mouthfeel are not relevant functional endpoints for this substance in regulated uses.

Acceptable Daily Intake Explained

An acceptable daily intake (ADI) is a concept used by regulatory bodies to describe the amount of a substance that can be consumed daily over a lifetime without appreciable health risk, typically expressed in milligrams per kilogram of body weight. ADIs are most relevant for direct food additives where ingestion is expected. For POLYACRYLIC ACID, SODIUM SALT, because its authorized roles are indirect and involve technical processing or food contact uses that minimize consumer exposure, specific numeric ADIs have not been established by international expert committees in the same way as they are for direct food additives. Instead, regulatory evaluations focus on ensuring that migration into food is negligible under intended conditions of use. When regulatory agencies assess indirect food contact substances, they consider conservative exposure estimates and the potential for systemic exposure. If exposure is expected to be minimal or negligible due to functional barriers and use conditions, numeric ADIs may not be assigned. In such cases, compliance with use conditions and migration limits serves as the primary protective measure for consumer safety.

Comparison With Similar Additives

POLYACRYLIC ACID, SODIUM SALT can be contrasted with other polymers used in food contact contexts where functional requirements and regulatory treatment differ. For example, carboxymethyl cellulose is a polymeric additive used directly in food for thickening and stabilizing, with established regulatory provisions for direct food use. In contrast, sodium polyacrylate’s authorized roles are technical and indirect. Another comparison is with cross‑linked polyacrylic acid used in absorbent pads for packaging; regulatory evaluations of those applications focus on migration potential rather than direct consumption. Direct food additives such as pectin or xanthan gum serve sensory and structural roles in foods, are ingested, and therefore have established acceptable intake levels based on toxicological data. POLYACRYLIC ACID, SODIUM SALT differs because its high molecular weight and functional context minimize ingestion. This fundamental distinction between polymers intended for contact versus those formulated as ingredients informs both their regulatory pathways and the nature of safety assessments.

Common Food Applications Narrative

In food processing industries, POLYACRYLIC ACID, SODIUM SALT is encountered not as a direct food additive but as a processing aid or food contact substance under defined regulatory conditions in certain jurisdictions. One well‑established example is its authorized use in the sugar industry, where it helps control mineral scale during the evaporation of beet or cane juice. In sugar production facilities, scaling—the precipitation of calcium, magnesium, and other mineral salts on heat exchange surfaces—can compromise efficiency and increase maintenance needs. When used within the permitted concentration limits specified by regulatory authorities, the polymer’s ability to interact with mineral ions can reduce deposit formation, aiding consistent sugar crystallization and plant operations. Beyond sugar processing, similar high‑molecular‑weight polymers are used in other food contact applications in manufacturing lines where their water binding or surface conditioning properties help maintain equipment cleanliness and processing efficiency. These could include water treatment systems in food plants where scale control helps preserve heat transfer efficiency and surface sanitation. In packaging contexts, cross‑linked variants of polyacrylic acid sodium salt are used in absorbent pads within meat and produce packaging materials to manage exudate; regulatory assessments specific to those uses focus on ensuring that the polymer does not migrate into food when used as intended, and that it remains embedded within the packaging structure. Because these applications are technical in nature and do not involve the polymer becoming a food ingredient, they are classified separately from direct food additives and are governed by food contact material regulations.

Safety & Regulations

FDA

  • Approved: True
  • Regulation: 21 CFR 173.73

EFSA

  • Notes: EFSA evaluations focus on food contact materials and do not assign a numeric ADI.

JECFA

  • Notes: No JECFA evaluation with numeric ADI explicitly found for direct food use.

Sources

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