Superabsorbents preparation

Acrylates are primarily used to prepare emulsion and solution polymers. The emulsion polymerization process provides high yields of polymers in a form suitable for a variety of appHcations. Acrylate polymer emulsions were first used as coatings for leather in the eady 1930s and have found wide utiHty as coatings, finishes, and binders for leather, textiles, and paper. Acrylate emulsions are used in the preparation of both interior and exterior paints, door poHshes, and adhesives. Solution polymers of acrylates, frequentiy with minor concentrations of other monomers, are employed in the preparation of industrial coatings. Polymers of acryHc acid can be used as superabsorbents in disposable diapers, as well as in formulation of superior, reduced-phosphate-level detergents. 

J. Zhang, L. Wang, A. Wang, Preparation and properties of chitosan-g-poly(acrylic acid)/montmorillonite superabsorbent nanocomposite via In situ intercalative polymerization, Ind. Eng. Chem Res., vol. 46, pp. 2497-2505, 2007. 

Oligomeric agents were prepared by condensing trimethylolpropane with ethylene and/or propylene oxides and capping with acrylic acid. These materials were subsequently crosslinked using 2,2 -azobisamidinopropane dihydrochloride, which formed superabsorbent swellable hydrogel addition polymers and were useful as components in diapers or in feminine hygiene products. 

Preparation of a Superabsorbent Hydrogel Using Internal Crosslinkers... 

Additional superabsorbent hydrogel derivatives containing EO/PO ratios other than those of the current invention were prepared by the author [1] in a subsequent invention. 

Smith [2] prepared a series of superabsorbent polymers with high permeability consisting of the reaction product of NaOH, water, acrylic acid, methoxypo-lyethyleneglycol (750), monomethacrylate of trimethylolpropanetriacrylate, TMP-3EO, and hydroxymonoallyl ether-lOEO. These materials were useful in the transportation of liquids in the swollen state. 

Woven cloth, cotton wadding, cellulose fiber batt, papers, and foamed polyurethane have been used as traditional absorbent materials for water. These materials can absorb 1-20 g of water per gram material and the water absorbed is easily removed from the materials by applying low pressure. In recent years, superabsorbent polymers, which can absorb up to 1000 g of water per gram of polymer and up to about 100 g of dilute salt solution per gram of polymer and the water absorbed can hardly be removed from the polymers even by applying high pressure, have been prepared and commercially used in many applications. 

Up to the present, many types of superabsorbent polymers have been prepared and commercialized. Some... 

Many types of superabsorbents have been prepared from various materials, by various methods, and in different shapes. They are modified natural hydrophilic polymers such as starch, cellulose, alginic acids, etc. and synthetic hydrophilic polymers such as poly (acrylic acid) and poly(sodium acrylate). Most of them have anionic moieties such as poly(sodium acrylate) and poly(vinyl sulfonate). Now, many types of superabsorbents having not only anionic groups but also cationic groups such as ammonium groups, phospho-nium groups, or betaine have been prepared from both... 

Nonaka, T. Yamada, K. Watanabe, T. Kurihara, S. Preparation of superabsorbent polymer hydrogels from trialkyl-4-vinylbenzyl phosphonoium chloride-acrylamide-methylenebis-acrylamide copolymer and their properties. J. Appl. Polym. Sci. 2000, 78, 1883-1884. 

These amino acid anhydrides are usuaiiy made with phosgene. The use of dimethyi carbonate shouid be tested in the preparation of the monomers. Poiyaspartic acid can be made by heating aspartic acid without soivent to form a polysuccinimide which is then hydrolyzed (12.34).186 It can also be made directly from maleic anhydride and ammonia. It promises to be useful as a scale inhibitor in water, an antiredeposition agent in detergents, and such. Gamma-irradiation converts it to a biodegradable superabsorbent material that takes up 3400 g water per gram of dry polymer.187 (Most superabsorbent polymers are based on acrylamide, a neurotoxin.)... 

Clay and mineral fillers have been used for reducing production costs and improving the comprehensive water absorbing properties of superabsorbent materials For example, a poly(acrylic acid)/mica superabsorbent has been synthesized with water absorbency higher than 1100 g H20/g In a typical method of preparation, acrybc acid monomer is neutralized at ambient temperature with an amount of aqueous sodium hydroxide solution to achieve 65% neutralization (optimum) Dry ultrafine (<0.2 tm) mica powder (10 wt%) is added, followed by cross-linker N,N-methylene-bisacrylamide (0.10 wt%) and radical initiator, potassium persulfate The mixture is heated to 60-70°C in a water bath for 4 h. The product is washed, dried under vacuum at 50°C, and screened. 

From the research of Zhang [88], a novel flax yarn waste-g-poly(acrylic acid-co-acrylamide) [FYW/PAA] superabsorbent composite has been synthesized (Fig. 3.6). In order to develop an eco-friendly superabsorbent composite, flax yarn waste (FYW) was used as raw material. Acrylic acid (AA) and acrylamide (AM) were grafted onto the pretreated flax yarn waste (PFYW) by free-radical graft copolymerization in homogeneous aqueous solution. As a result, the prepared FYW/PAA attained the best water absorbency of 875 g/g in distilled water, 490 g/g in rainwater and 90 g/g in 0.9 wt% NaCl solution. 

In the work from Liu [105], an eco-friendly superabsorbent based on flax yarn waste for sanitary napkin applications has been successfully prepared. Till now, most of the waste cellulose materials from textile industry, such as cotton linter, cotton yarn waste and flax yarn waste, are still burned or land filled, causing both resource waste and environmental pollution [105, 106]. Reutlllzatlon of these waste materials could not only reduce the consumption of cotton or flax cellulose but also decrease the treatment of industrial waste. The major component [70%] of flax yarn waste is cellulose, which has been introduced as a basic skeleton of superabsorbent in previous studies [105, 106-109]. Fluff pulp, as a good absorbent material, is a kind of special pulp with villiform fibers. Nowadays, it is widely used as raw material for the production of sanitary napkin and paper diaper [105]. 

The objectives of this study were to investigate the preparation of an eco-friendly superabsorbent based on flax yarn waste under different synthesis conditions and to determine the properties of the resulting superabsorbent used for absorbent core layer of sanitary napkins. The results gained from this study strongly suggest that the prepared FYW/PAA superabsorbent has potential application in the field of eco-friendly sanitary napkins as a low-cost and eco-friendly synthetic material [105]. 

Wang,W., Wang, A. Preparation, characterization and properties of superabsorbent nanocomposites based on natural guar gum and modified rectorite. Carbohydr. Polym. 77, 4, 19, 891-897 (2009)... 

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