Sodium Hyaluronate Crosspolymer-4 is a chemical compound, a form of hyaluronic acid used in various cosmetic and personal care products. This polymer is created by crosslinking hyaluronic acid with 1,4-butanediol diglycidyl ether, enhancing its moisturizing and anti-aging properties and providing long-lasting hydration and improved skin elasticity.

Chemical Composition and Structure

Sodium Hyaluronate Crosspolymer-4 is the sodium salt of hyaluronic acid crosslinked with 1,4-butanediol diglycidyl ether. This crosslinking process forms a three-dimensional network that significantly enhances the molecule's ability to retain water, offering sustained hydration. The chemical structure consists of hyaluronic acid molecules interconnected by 1,4-butanediol diglycidyl ether, creating a robust and flexible polymer network.

Physical Properties

Sodium Hyaluronate Crosspolymer-4 typically appears as a white or off-white powder. It is highly soluble in water, forming a gel-like substance when hydrated. This gel provides a smooth, non-greasy texture, making it suitable for various cosmetic formulations. The crosslinked structure offers improved stability and controlled release of moisture over time.

Chemical Industrial Synthesis Process

• Preparation of reagents. The main raw materials include hyaluronic acid (HA), sodium chloride (NaCl), and 1,4-butanediol diglycidyl ether as the crosslinking agent.
• Solubilization. Hyaluronic acid is solubilized in an aqueous sodium chloride solution to obtain a sodium hyaluronate solution.
• Addition of crosslinking agent. 1,4-Butanediol diglycidyl ether is added to the sodium hyaluronate solution under continuous stirring.
• Crosslinking reaction. The mixture is maintained at a controlled temperature (approximately 20-25°C) to allow the crosslinking reaction between hyaluronic acid and 1,4-butanediol diglycidyl ether. This reaction forms the sodium hyaluronate crosspolymer-4.
• Neutralization. The reaction mixture is neutralized with a sodium hydroxide (NaOH) solution to ensure the pH is neutral.
• Dialysis. The crosspolymer solution is dialyzed against distilled water to remove residual salts and unreacted crosslinking agents.
• Concentration. The dialyzed solution is concentrated by vacuum evaporation to obtain a more concentrated sodium hyaluronate crosspolymer-4 solution.
• Drying. The concentrated solution is dried by lyophilization to obtain a dry product.
• Grinding. The dried product is ground to obtain a fine and uniform powder.
• Classification. The dried powder is classified to ensure a uniform particle size. This step may involve sieving or the use of air classifiers.
• Stabilization. The sodium hyaluronate crosspolymer-4 is stabilized to ensure its stability during transportation and storage, preventing aggregation and degradation.
• Quality control. The sodium hyaluronate crosspolymer-4 undergoes rigorous quality testing to ensure it meets standards for purity, safety, and functionality. These tests include chemical analysis, spectroscopy, and physical tests to determine particle size and rheological properties.

What it is used for and where

Cosmetics - INCI Functions

Skin conditioning agent - Emollient. Emollients have the characteristic of enhancing the skin barrier through a source of exogenous lipids that adhere to the skin, improving barrier properties by filling gaps in intercorneocyte clusters to improve hydration while protecting against inflammation. In practice, they have the ability to create a barrier that prevents transepidermal water loss.  Emollients are described as degreasing or refreshing additives that improve the lipid content of the upper layers of the skin by preventing degreasing and drying of the skin. The problem with emollients is that many have a strong lipophilic character and are identified as occlusive ingredients; they are oily and fatty materials that remain on the skin surface and reduce transepidermal water loss. In cosmetics, emollients and moisturisers are often considered synonymous with humectants and occlusives.

Humectant. Hygroscopic compound used to minimise water loss in the skin and to prevent it from drying out by facilitating faster and greater absorption of water into the stratum corneum of the epidermis.  The epidermis is the most superficial of the three layers that make up human skin (epidermis, dermis and hypodermis) and is the layer that maintains hydration in all three layers. In turn, the epidermis is composed of five layers: horny, the most superficial, granular, spinous, shiny, and basal. Humectants have the ability to retain the water they attract from the air in the stratum corneum and have the function of moisturising the skin. They are best used before emollients, which are oil-based.

Skin conditioning agent. It is the mainstay of topical skin treatment as it has the function of restoring, increasing or improving skin tolerance to external factors, including melanocyte tolerance. The most important function of the conditioning agent is to prevent skin dehydration, but the subject is rather complex and involves emollients and humectants that can be added in the formulation.

CAS    781214-94-6

Applications

Moisturizers and Creams: Sodium Hyaluronate Crosspolymer-4 is widely used in moisturizers and creams for its ability to provide long-lasting hydration. It forms a protective barrier on the skin, reducing transepidermal water loss and keeping the skin hydrated.

Anti-Aging Products: Due to its excellent water retention properties, this ingredient is commonly found in anti-aging products. It helps to plump the skin, reducing the appearance of fine lines and wrinkles, and improving overall skin elasticity.

Serums and Essences: In serums and essences, Sodium Hyaluronate Crosspolymer-4 acts as a powerful hydrating agent, enhancing the delivery and effectiveness of active ingredients.

Sun Care: It is also used in sun care products to provide hydration and soothing effects, helping to protect the skin from the drying effects of sun exposure.

Eye Creams and Gels: The ingredient is ideal for use in eye creams and gels due to its gentle yet effective moisturizing properties, helping to reduce puffiness and dark circles.

Safety

Sodium Hyaluronate Crosspolymer-4 is generally considered safe for use in cosmetic and personal care products. It is non-irritating and suitable for all skin types, including sensitive skin. The ingredient is biodegradable and poses minimal risk to the environment when disposed of properly. As with all cosmetic ingredients, it is important to use it within the recommended guidelines to ensure safety and efficacy.