Tertiary amino starches

Starch is the most widely used dry strength additive and is normally made in a cationic form by introducing a reactive monomeric or polymeric tertiary amine or quaternary ammonium derivative into the molecule. The most commonly used reagent for tertiary amino starch is 2-chloroethyldiethylammonium chloride, and for quaternary starch is 2,3-epoxypropyltrimethylammonium chloride (Figure 7.10). 

Cationic starch is a frequently-utilized retention aid, especially when paper strength improvement is a second objective.141,142 Low pH activates tertiary amino starch, but at pH 6 an amphoteric starch, and at pH above 7 a quartenary ammonium starch, will be needed. 

Cationic Starches. Commercial cationic starches are starch ethers that contain a tertiary amino or quaternary ammonium group, eg, the diethylaminoethyl ether of starch or the 2-hydroxy-3-(trimethylammonio)propyl ether of starch [9063-45-0], sold as its chloride salt [56780-58-6]. 

Figure 7.11 Protonation of tertiary amino cationic starches in aqueous solution.

Starches that contain tertiary amino groups can only be used in an acid papermaking system (pH <5.5), since they require protonation in order to become charged. Quartenary ammonium starches are inherently charged. They can be used at pH levels above 7, but their efficiency may be reduced at high pH due to screening by hydroxyl ions in the dispersion. 

The synthesis of tertiary amino cationic starch from diethylaminoethyl chloride and starch. 

An amphoteric starch composed of a tertiary amino cationic starch witii a phosphate ester. 

Cationic starches are obtained by reaction of starch with reagents containing amino, imino, ammonium, sulfonium groups. The two main types of commercial products are the tertiary amino and quaternary ammoniiun starch ethers (135). 

National Starch Products Inc. (1957) Improvements in or Relating to Ungelatinized Tertiary Amino Alkyl Ethers of Amylaceous Materials. GB Patent 765,880. 

Delval et al. (2003) showed that starch based materials containing tertiary amino groups have a low efficiency in dye uptake in the low pH... 

Dry strength additives are usually water soluble, hydrophilic natural or synthetic polymers, the commercially most important of which are starch, natural vegetable gums and polyacrylamides. These polymers are often made in cationic form by the introduction of tertiary or quaternary amino groups into the polymer, and are therefore polyelectrolytes. They are thus also able to function to some extent as drainage and retention aids. 

Various aminoalkyl and alkylaminoalkyl halides react with starch in alkaline media and are readily available by the reaction of epichlorohydrin with primary, secondary, and tertiary amines and even aqueous ammonia. Prior to the reaction with starch, the quaternary ammonium compounds were either decomposed to free amines, or they reacted as amminium compounds to give cationic aminium starches. Cationic starches were produced by the reaction of starch with arylalky-laminoalkyl epoxides. In the presence of formaldehyde, inorganic ammonium salts provided the source of amino groups.1316... 

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