can be crosslinked by heating to 150 C, but greater water resistance 

 can be obtained by the use of a dibasic acid, especially succinic 



acid 



37 



Dimethylol urea will crosslink compounds with hydroxyl, carboxyl, 

 amide and amino groups to form compounds with reduced water solubility. 

 For example, the reaction product of dimethylol urea and urea has been 

 used as a wood impregnant .-'° Reaction products with formaldehyde,-^" 

 urea,'^ and phthalic anhydride^-*- have been used to treat fabrics. Other 

 insoluble products have been made by the reaction of dimethylol urea 

 with polyamino compounds, ^^ formaldehyde in butanol,^^ butanol,^-* 

 furfuryl alcohol, ^^ furfuryl alcohol plus formaldehyde,^' alcohol 

 soluble butyric acid esters of cellulose, ^° allyl alcohol,^" cellulose, ^^ 

 partially hydrolvzed starch,^' potato flour,^^ ground corn cobs and 

 salicylic acid,-"-^ silicic acid,^^ and alkyl silicates.^-* 



EXPERIMENTAL 



The following reactions were conducted after a review of the 

 literature. They were chosen because they essentially met the three 

 constraints mentioned in the Introduction. 



Polyvinyl Alcohol 



Experiment 1 . Polyvinyl alcohol (4.5 g.) was slurried with cold 

 water (30 ml.) and heated, with stirring, until a solution was obtained. 

 A quantity of the solution was poured into 20 percent sodium sulfate 

 solution. A tough elastomeric solid precipitated. It was soluble in 

 boiling water, but had good resistance to cold water. 



Experiment 2 . Polyvinyl alcohol (45 g.) was slurried with 300 ml. 

 of cold water, then heated to about 88 for 60 minutes. Additional 

 water was added to lower the viscosity of the solution. After cooling, 

 thiourea (7.6 g.) in water (100 ml.) and formalin solution (20 g. , 36.6%) 

 were added and the solution was heated to 85 for Ih hours and allowed 

 to cool. A sample was poured into 20 percent sodium sulfate solution 

 and a tough elastomeric solid formed. It dissolved in boiling water, 

 had good resistance to cold water, but was not superior to precipitated 

 polyvinyl alcohol. 



Experiment 3 . Polyvinyl alcohol (11 g.) was slurried with and 

 then dissolved in water (89 ml.) at 88 C. After cooling, ethylenediamine 

 (0.2 g.) and a suspension of cyanurlc chloride (3.3 g.) in acetic acid 

 (10 ml.) were added. The mixture was stirred vigorously, and ten per- 

 cent sodium hydroxide solution was added to maintain an alkaline condi- 

 tion during the addition of the cyanuric chloride. A white suspension 

 formed, and a small quantity of this suspension was poured into a Petri 

 dish and dried under an infrared heat lamp. The film which formed was 

 not water resistant. 



