Water-based adhesives solutions

Water-based adhesives are applied as aqueous solutions, dispersions or emulsions and are used mainly in paper and board applications, for example, side-seaming of cartons. Typical examples of adhesives applied in this way... 

Produced by a solution polymerization process, this material exhibited an ordered molecular structure with the styrene monomer located at the ends of the butadiene monomer chain. In addition, other monomers such as isoprene, ethylene, butylene, and others, could be added to the polymer chain, which further modified basic properties. These materials possess a continuous rubber phase for resilience and toughness, and a discontinuous plastic phase for solubility and thermoplasticity. A variety of different grades are also available for this type of SBR, with differences in molecular weight, differences in the types of monomers used, differences in structural configuration, and differences in the ratio of endblock to midblock. Both emulsion and solution polymerized grades of SBR are available as solvent-based and water-based adhesives and sealants. Block copolymers are extensively used for hot melt formulations and both water-based and solvent-based pressure sensitive adhesive applications. Today, SBR elastomers are the most popular elastomers used for the manufacture of adhesives and sealants. 

Elastomers used in water-based systems include various rubber latices, especially natural rubber and SBR, and occasionally, polychloroprene. The bulk of the market in water-based adhesives is now held by acrylic dispersions. Although these are designed for use without modification, it is normal to formulate, especially by addition of tackifiers. Commonly used tackifying resins include soft resins, or hard resins in solution, which may... 

In addition to the acidic monomer, contemporary SEAs typically contain a mixture of different co-monomers, polymerization initiators (mainly cam-phorquinone combined with a tertiary amine), inhibitors, fillers, and further additives. These adhesives also contain solvents which influence their viscosity, wetting, and flowing behavior. Water, ethanol, isopropanol, and acetone are the most commonly used solvents. It should be mentioned that water is an indispensable component of SEAs, in order to ionize the strongly acidic monomers. The monomers are the main component of SEAs. The adhesive monomers should present a good solubility in solutions of ethanol, acetone, or other nontoxic polar solvents or their mixtures with water, sufficient hydrolytic stability in water-based adhesives, as well as optimal wetting and film-forming properties. ... 

There are two general types of water-based adhesives solutions and latexes.Solutions are made from materials that are soluble only in water or in alkaline water. Examples of materials that are soluble only in water include animal glue, starch, dextrin, blood albumen, methyl cellulose, and polyvinyl alcohol. Examples of materials that are soluble in alkaline water include casein, rosin, shellac, copolymers of vinyl acetate or acrylates containing carboxyl groups, and carboxymethyl cellulose. 

Polymer dispersions (in non-solvent liquids, usually water) have much lower viscosities than solutions with the same polymer content. So great is the disparity in viscosities that a 50% solids dispersion may have a considerably lower viscosity than a 10% solution. Such dispersion or suspension adhesives, often called emulsion adhesives or even more loosely water-based adhesives , combine the advantages of a high solids content with low inflammability and toxicity hazard, but suffer from long drying times (see Emulsion and dispersion adhesives). Their use on non-porous substrates is restricted in a similar way to that of solution adhesives. 

For ease in do-it-yourself projects (adjustability, open time, easy application, etc.) and because most substrates to which the coverings are bonded are capable of absorbing moisture, it is preferable to use water-based adhesives in the form of solutions and emulsions. Solvent-containing adhesives are only used on nonporous substrates, for example, metals [86], [87]. 

Thermoplastic adhesives are generally available as solvent solutions, water-based emulsions, and hot melts. The first two systems are useful in bonding porous materials such as wood, plastic foam, and paper. Water-based systems are especially useful for bonding foams that could be affected adversely by solvents. When hardened, thermoplastic adhesives are very nonresistant to the solvent in which they are originally supplied. 

There are two general types of water-based adhesives solutions and latexes. Solutions are made from materials that are soluble only in water or in alkaline water. There are two sources for the... 

Casein is a natural polymer extracted from skim milk proteins. It represents a small but important percentage of all the natural polymers used for the manufacturing of water-based adhesives. The casein formulations are highly soluble in alkaline solutions and in water. Casein polymers (modified or not) are mainly used in the manufacture of adhesives and the packaging industry for breweries, wineries and refrigerated products. Casein is also a binder for paints and an additive for adhesives formulations. It can also be used as a plasticiser for concrete. Beyer Richard (2002) demonstrated die feasibility of preparing casein polymer to make edible films and for food products containing this polymer. 

It promotes adhesion of intaglio inks to the polypropylene surface. An acrylic based primer is a good choice because of its ability to effectively bond water-based inks. Dry powder form of acrylic primer is diluted with methyl ethyl ketone and xylene (each component is mixed in equal parts by weight). To create the opaque surface, 5wt% titanium dioxide pigment is added to the solution. 

Water-Based. In these adhesives, the polymers are in aqueous dispersions or solutions from which water evaporates to effect the transition in the case of dispersions, the particles coalesce to form a continuous film with solutions, the film is formed from polymer coming out of solution. 

In addition to the water-soluble and insoluble members of the condensed tannin family, both of which are soluble in polar organic solvents, there is a third related fraction, usually called a phenolic acid. This material can only be isolated by extraction with aqueous alkaline solutions or with sodium sulfite or bisulfite solution at elevated temperatures and pressures. Since the tannins and phlobaphenes are also soluble in aqueous base, they will be coextracted from bark along with the phenolic acids when bark is extracted with base. This is important to remember in the subsequent discussion on bark-based adhesives. 

The intermolecular attraction between like molecules in the liquid state, such as the water-water attraction based on hydrogen bonds, is called cohesion. The attractive interaction between a liquid and a solid phase, such as water and the walls of a glass capillary (a cylindrical tube with a small internal diameter), is called adhesion. When the water-wall adhesion is appreciable compared with the water-water cohesion, the walls are said to be wettable, and water then rises in such a vertical capillary. At the opposite extreme, when the intermolecular cohesive forces within the liquid are substantially greater than is the adhesion between the liquid and the wall material, the upper level of the liquid in such a capillary is lower than the surface of the solution. Capillary depression occurs for liquid mercury in glass capillaries. For water in glass capillaries or in xylem vessels, the... 

Adhesives are nonmetaUic substances used to join two surfaces by means of surface adherence (adhesion) and inherent strength (cohesion), DIN 16920. This definition of adhesives does not cover water glass adhesives, adhesive ceramics, or adhesive mortars. The substances used as adhesives are polymers that go through a liquid phase at least once (reactive adhesives) or more than once (hotmelts, thermally activated adhesives). The liquid phase can also be achieved by dissolution in suitable solvents (nonreactive adhesives). In dispersion adhesives, the polymer molecules are dispersed (finely distributed) in a liquid - usually water - whereby the polymer molecules themselves are not dissolved. Fig. 6. These adhesives are also known as water-based or aqueous adhesives. It must be remembered that solvents are contained in these adhesives in addition to the water. Genuine aqueous adhesives contain less than 5% solvents in the liquid phase. The dispersions crnitain, in contrast to the solute adhesive molecules, additional substances, disposal of which requires specific additional measures. Since the dispersions represent stable systems in water, the water-resistance of such adhesives is reduced. Their thermal and water resistance can be increased by additional crosslinking (usually with isocyanates). 

Soy flour dispersed in sodium bisulfite solution was blended with PF in a soyrPF ratio of up to 7 3. Particleboards made with the sprayable adhesive have acceptable strength attributes, and decreasing the mixture to as low as 20% soy flour produces boards with comparable strength and water-resistance as those made with only PF (Kuo et al., 2001 Kuo et al., 2003). PF is described as the primary cross-linking agent in the previously cited patents, and similar work was conducted by others. Wescott et al. (2005) reported that soy-based adhesives containing PF and 50—66%... 

Contact-Bond Adhesives. Another group of glues, referred to collectively as contact cements or contact-bond adhesives, bear some similarities to the pressure-sensitive adhesives in that they do not rapidly achieve full hardening. Until a few years ago, contact-bond formulations were mainly organic solvent solutions of elastomers, compounded with tackilying resins and antioxidants. However, with recent concerns over energy, environmental, and fire safety questions, interest has turned to water-based systems. 

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