Alkyl Ketene Dimer CAS 144245-85-2 AKD
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Alkyl Ketene Dimer: The Complete Guide
Index of Alkyl Ketene Dimer Contents
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Basic Info of Alkyl Ketene Dimer
What is Alkyl Ketene Dimer?
The Chinese name of AKD is AlkylKetene Dimer. In 1956, AKD began to be industrialized and was only used in special paper that needs heavy sizing. In recent years, cultural paper has basically been changed to AKD neutral sizing. more application areas.
Alkyl ketene dimers (akds) are a class of organic compounds based on oxetan-2-one 4-membered ring system. They are also the central structural elements of propanolactone and diene ketones. The oxyheterocyclobutane ring of the alkyl vinyl ketone dimer related to the technology is connected, with a C 12 – C 16 alkyl group at position 3 and a C 13 – C 17 alkylene group at position 4.
Alkylated ketene dimers are mainly used in sizing of paper and paperboard and hydrophobicization of cellulose fibers. Such modified products are known for higher mechanical strength and less penetration of water, ink or printing ink.
AKD has slave β- The propanolactone ring extends to a hydrophobic alkyl group. A specific example comes from the dimerization of vinyl stearate. This vinyl ketone is produced by pyrolysis of stearyl chloride. AKD reacts with hydroxyl groups on cellulose through esterification. Esterification competes with the hydrolysis of AKD. Before the development of AKD, the hydrophobicity was given by adding rosin into the paper.
Related to AKD is alkenyl succinic anhydride (ASA). As for AKD, ASA reacts with the hydroxyl group of cellulose to form ester, which fixes the hydrophobic group on the surface. ASA is prepared by Olefination of unsaturated hydrocarbons with maleic anhydride.
Alkyl Ketene Dimer Uses
Since the early 19th century, the problem of acidic (aluminum sulfate mediated) quality sizing of paper with alkaline digested rosin resin has led to the search for alternative materials for sizing in neutral or alkaline environment in addition to using alkaline flocculants (such as chalk or calcium carbonate as alkali reserve). In addition to the significantly more reactive alkenyl succinic anhydride (which also hydrolyzes rapidly in the presence of water), alkylated vinyl ketone dimers have become the preferred surface and mass dimensions in the paper industry since the 1960s and 1950s.
AKD for industrial application comes from fatty acids with chain length between C14 (myristic acid) and C22 (behenic acid); Palmitoyl (C16) dienes and stearyl (C18) ones and mixtures thereof, as well as mixtures of fatty acids from animal and vegetable fat hydrolysis, are preferably used. Due to the chain length of the original fatty acids, AKD is a waxy solid with a melting point between 42 and about 70 ° C. The mixture of alkylated ketene dimer and water is a dispersion at a temperature below 40 ° C and a lotion at a temperature above 45 ° C. Liquid akds are not widely used, they are based on unsaturated fatty acids (such as oleic acid) or branched fatty acids (such as isostearic acid).
Aqueous alkyl diene dispersions usually contain 10-20 wt% AKD, And active protective colloids (especially polycations, such as copolymers of cationic starch, N-vinyl pyrrolidone and quaternized N-vinyl imidazole, acylated polyethyleneimine or cationic high molecular weight polyacrylamide with an average number of moles, with a mass of up to 7 million g / mol) and other stabilizers (usually anionic surfactants, such as condensation products of lignin sulfonate or sodium naphthalene sulfonate and formaldehyde). This stable AKD dispersion can maintain activity and stability for up to three months at room temperature, and can also tolerate the addition of different fillers for paper or paperboard (such as kaolin, chalk, talc, titanium dioxide, calcium sulfate, alumina, etc.) from 5 to 25%. The amount of alkyl ketene dimer used for sizing paper and paper products is preferably 0.15-0.8wt%, sometimes 0.05-0.2wt%, based on dry paper.
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Preparation of Alkyl Ketene Dimer
In 1945, the industrial synthesis patent of alkylated ketene dimer (still called ketene ketone at that time) was obtained from long-chain carboxylic acid chloride with triethylamine as tertiary amine in inert solvent (such as ether or benzene) under anhydrous conditions. The insoluble triethylamine hydrochloride was filtered and the solvent was evaporated to obtain long-chain alkyl dimer with a yield of more than 90%.
Trialkylamine hydrochloride or other amines, such as N, N, n ‘, n’ – tetramethyl-hexane-1,6-diamine, are more easily separated using other solvents (such as carboxylic acid esters or ketones).
A solvent free method is also described in which the resulting amine hydrochloride is filtered out or extracted with diluted aqueous acid.
A continuous method in which long-chain carboxyacyl chloride and tertiary amines (such as dimethylisopropylamine, dimethylcyclohexylamine or triethylamine) are separately supplied to a tubular reactor, kneader or preferably a twin-screw extruder or planetary roller extruder without solvent, and provide a lactone content of more than 90% in a short reaction time at 90 and 110 ° C. Treatment by phase separation or acid extraction.
- “AKD, Alkylketene Dimer”
- US 2627477, W.F. Downey, “Higher alkyl ketene dimer emulsion”, published 1953-02-03, assigned to Hercules Powder Co.
- Lindström, T.; Larsson, T. (2005), STFI-Packfors (ed.), A note on AKD-sizing: an investigation of real and apparent contradictions in literature regarding spreadin/diffusion of AKD on cellulose, Report no. 81 (PDF)