Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From aldehyde or derivative thereof as reactant
Patent
1991-11-06
1996-09-10
Acquah, Samuel A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From aldehyde or derivative thereof as reactant
528230, 528248, 528252, 528254, 528256, 528259, 528266, 528392, 528423, C08G 226, C08G 1402
Patent
active
055547184
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to cationic urea/formaldehyde resins which contain condensed polymers having vinylamine units, a process for their preparation and their use in papermaking as an agent for increasing the dry strength and wet strength of paper.
U.S. Pat. No. 3,275,605 discloses that urea and formaldehyde can be condensed in the presence of polyamines to give water-soluble resins. The reactants are first precondensed in the alkaline pH range, then condensed in the acidic pH range until gel formation begins, then subjected to post-condensation, for example with formaldehyde, and subsequently neutralized. The products are suitable as agents for increasing the wet strength of paper.
U.S. Pat. No. 3,752,781 discloses a process for the preparation of cationic resins, in which urea is first reacted with polyalkyleneimines, for example polyethyleneimine, with elimination of ammonia to give polyureas, the polyureas are then reacted with urea and the reaction product is methylolated. This gives a cationic resin in the form of an aqueous solution, which is neutralized by adding an acid. Products of this type have not been used to date in the paper industry because they are expensive and not very effective and furthermore lead to pronounced yellowing of the paper.
European Patent 0,123,1961discloses a process for the preparation of water-soluble cationic urea/formaldehyde resins, in which urea and formaldehyde are condensed in a molar ratio of from 1:1.5 to 1:3 in the presence of polyamines, the mixture first (a) being precondensed at a pH of from 8 to 14 and then acidified and (b) condensed at a pH of from 1 to 5 until gel formation begins, then (c) from 0.3 to 1.5 moles of formaldehyde being added per mole of urea used, (d) postcondensation being carried out and the resin solution subsequently being neutralized. From 5 to 50 g of polyethyleneimine which contains from 20 to 15,000 polymerized ethyleneimine units are used as polyamines, per mole of urea in the end product. The water-soluble cationic urea/formaldehyde resins thus obtained are used in papermaking as assistants for increasing the dry strength and wet strength of the paper. However, when the paper webs containing these resins as strengtheners are dried, undesirable elimination of formaldehyde is observed. Formaldehyde elimination during the drying of paper treated with the urea/formaldehyde resins disclosed in U.S. Pat. No. 3,275,605 as wet strength agents is, on the other hand, far greater than in the case of papers which contain condensates of European Patent 0,123,196 as strengtheners.
It is an object of the present invention to provide cationic urea/formaldehyde resins which increase the dry and wet strength of paper and impart to these papers the property of lower formaldehyde emission during drying compared with the conventional condensates based on urea and formaldehyde. The novel resins should furthermore ensure less dulling in papermaking.
We have found that this object is achieved, according to the invention, by cationic urea/formaldehyde resins which are obtainable by condensing urea and formaldehyde in a molar ratio of 1:1.5 to 1:3 in the presence of polymers which contain not less than 1 mol % of polymerized vinylamine units and have K values of from 5 to 300 (determined according to H. Fikentscher in 5% strength aqueous sodium chloride, solution at 25.degree. C. and at a polymer concentration of 1% by weight), in an amount of from 5 to 50 g, based on 1 mole of urea in the end product, where the mixture is first used,
The resulting solutions of cationic urea/formaldehyde resins are used in papermaking as assistants for increasing the dry and wet strength of paper.
Urea and formaldehyde are condensed in a molar ratio of from 1:1.5 to 1:3 in the presence of polymers containing polymerized vinylamine units.
Polymers containing vinylamine units are known, cf. for example U.S. Pat. Nos. 4,421,602, 4,623,699 and 4,255,548 and EP-A-0 216 387. Suitable polymers containing polymerized vinylamine units are advantageously prepared by hydroly
REFERENCES:
patent: 3275605 (1966-09-01), Eastes et al.
patent: 3752781 (1973-08-01), Muzyczko et al.
patent: 4663379 (1987-05-01), Fischer et al.
Fieser et al., (Fieser), "Carboxylic Acids," Organic Chemistry, p. 168, 2nd Ed., Reinhold Publishing Corp., NY 1950.
Royals, "Methods of Carbonyl Compounds," Advanced Organic Chemistry, p. 594, Prentice-Hall, Inc., NY 1954.
Flory Klaus
Kroener Michael
Sendhoff Norbert
Stange Andreas
Acquah Samuel A.
BASF - Aktiengesellschaft
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