Celvol 823 Polyvinyl alcohol 25213-24-5 Celanese Polyvinyl alcohol (PVOH) ADHESIVE Celvol polyvinyl alcohol combines high tensile strength with ease of film formation. Additionally, Celvol resins show excellent adhesive and bonding characteristics. Partially hydrolyzed grades have better adhesion to hydrophobic surfaces. The degree of hydrolysis affects the water sensitivity of both the resin and film. Water resistance increases with increasing hydrolysis. The super hydrolyzed grades should be used when maximum water resistance and humidity resistance are desired. Celvol polyvinyl alcohol resins are generally unaffected by greases, petroleum hydrocarbons and animal or vegetable oils. Resistance to organic solvents increases with the degree of hydrolysis. Celvol polyvinyl alcohol film can be plasticized with glycerol or the lower molecular weight glycols. These materials generally act as humectants, holding water in the film. Polyvinyl alcohol resins react in a manner similar to other secondary polyhydric alcohols. Esterification reactions of polyvinyl alcohol can be carried out with a number of compounds. A commercially important reaction is the formation of tackified PVOH using boric acid or borax to form cyclicesters. This reaction is very sensitive to pH, and an insoluble gel is formed above 4.5-5.0. Other esterification reactions include those with chloroformate esters to yield polyvinyl carbonate, with urea to yield a polymeric carbamate ester, and with isocyanates to form substituted carbamate esters. Another commercially important reaction is acetalization with aldehydes. Polyvinyl butyral is produced by the reaction of polyvinyl alcohol with butyraldehyde and is used in the production of the inner adhesive film for safety glass. Reaction with dialdehydes such as glyoxal or gluteraldehyde can be used to crosslink polyvinyl alcohol. Other reactions include ethoxylation, propoxylation and cyanoethylation. All polyvinyl alcohol grades are crosslinkable through their secondary hydroxyl functionality. Even lower hydrolysis grades—which are so exceptional on paper surfaces for oil, grease and organic solvent resistance and Gurley porosity—can be made water resistant. Degrees of water resistance vary from grade to grade. The table below shows the effect of glyoxal, a commonly used and favored crosslinker for polyvinyl alcohol. When glyoxal was added to Celvol grades 540, 350 and 165 polyvinyl alcohol at 20% dry-on-dry, significant water resistance improvements resulted. Note that the wet tensile of Celvol 540 polyvinyl alcohol increased from no measurable wet strength uncrosslinked to 6.1 pli when crosslinked. Also, the wet tensile of crosslinked Celvol 350 polyvinyl alcohol was more than double that of uncrosslinked Celvol 350, and crosslinked Celvol 165 polyvinyl alcohol was 28% higher than uncrosslinked Celvol 165. A vast array of crosslinkers or insolubilizers are available. They include several classes: (1) aldehydes, of which glyoxal, a simple dialdehyde, is the most common, along with higher aldehydes, such as gluteraldehyde and hydroxyadipaldehyde; (2) thermosetting resins, such as urea-formaldehyde and melamineformaldehyde; and (3) salts of multivalent anions, such as zirconium ammonium carbonates. More recently, there has emerged a growing interest in zero-formaldehyde, or low-formaldehyde-type crosslinkers. Two such products are Polycup 172, a water soluble, polyamide-epichlorohydrin-type resin, and Bacote-20, a zirconium ammonium carbonate salt. The results in the table below indicate that the addition of Polycup 172 to Celvol 165 polyvinyl alcohol at 5% dry/dry parts was as effective as glyoxal added at 20%, both resulting in a 26% wet tensile improvement. The addition of 5% Bacote-20 resulted in an 11% wet tensile improvement. Celvol polyvinyl alcohol resins have been used for more than 40 years as modifiers for polyvinyl acetate emulsion adhesives because of their many outstanding characteristics. Polyvinyl alcohol adheres particularly well to cellulosic substrates such as paper and wood. Adding it to a polyvinyl acetate emulsion will increase the efficiency as well as the tensile strength of the resulting adhesive. Celvol 805, 823 and 840 polyvinyl alcohols are improved versions of our standard polymerization grades, Celvol 205, 523 and 540 polyvinyl alcohols, respectively. These products offer a number of advantages in emulsion polymerization applications including improved water solubility and lower foaming. Applications : polymerization. Improved partially hydrolyzed polyvinyl alcohol resin. Can be used as a modifier in polyvinyl acetate emulsion-based adhesives or as the major component in other adhesives. Provides high tensile strength, ease of film formation, very good adhesion to cellulosic substrates such as paper and wood and bonding characteristics. Shows resistance to greases, petroleum hydrocarbons and animal or vegetable oils, and to organic solvents. Can be crosslinked through its secondary hydroxyl functionality. Offers improved water solubility and lower foaming in emulsion polymerization applications. Applications : polymerization.