Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-11-05
2000-07-18
Nutter, Nathan M.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
525 55, 525100, 1621641, 1621643, 1621646, C08G 1808, C08G 1863, C08G 1870, D21H 1757
Patent
active
060908718
DESCRIPTION:
BRIEF SUMMARY
The invention relates to auxiliaries for paper finishing, i.e. sizing agents and wet and dry strength agents, which are based on polyisocyanates which contain ionic groups and/or polyether groups, preferably in the form of aqueous dispersions.
Polyamine-epichlorohydrin resins and polyamide-amine-epichlorohydrin resins have been employed for a long time for improving the dry and wet strength of paper. Cationic polycondensates with hydrophobic radicals, for example based on fatty acid-modified polyamines, are also suitable as sizing agents for paper. It is furthermore known that the strength of paper in the dry state can be increased by application of starch.
The use of starch on the surface also improves the printability of paper and generally increases surface strength.
Methods for chlorine-free wet strength treatment with water-dispersible polyisocyanates are known from the DE-OS (German Published Specifications) 42 11 480 and 42 26 110.
Binder systems for impregnation of paper which comprise polyisocyanates in blocked form are known from U.S. Pat. No. 3,531,429. The liberation of a split-off group is unsatisfactory to the user from the aspect of industrial hygiene.
U.S. Pat. No. 3,325,346 proposes reaction products of polyethyleneimines and polyisocyanates for improving wet strength and dry strength.
In DE 2 633 396, anionic aqueous PU dispersions are employed for improving the handle of paper. However, the multi-stage process is very expensive. The product contains no reactive NCO groups.
JP 80597 (800617) (Textilbericht reference No. 576/1981) discloses staining colours of acrylic copolymers and crosslinking agents based on, for example, polyisocyanates.
EP 250 598 describes pressure-sensitive recording materials for multiple use, in which use is made of copolymers having OH groups and polyisocyanates as adhesives.
JP 04119195 proposes combinations of alkyd resins and polyisocyanate crosslinking agents for the production of transparent paper. JP 04146296 also describes combinations of styrene-acrylate dispersions which serve the same purpose and impart to the paper an increased strength. Polyisocyanates are also employed as crosslinking agents there.
JP 05050778 and JP 05051896 propose blocked polyisocyanates (NaHSO.sub.3 adducts) for improving the dry and wet strength of paper. Problems here are the release of SO, into the ambient air and corrosion on machine components. Furthermore, the cellulose fibres may be damaged.
Combinations of isocyanate and starch or polyvinyl alcohol are known, for example, from JP 80/159993.
FR-A 2 360 714 proposes a two-component system comprising a polyfunctional isocyanate and a compound containing active hydrogen which is reactive towards isocyanates for coating paper. The finished paper contains 0.5 to 35% by weight of reacted polyurethane. However, the polyfunctional isocyanates have the disadvantage that organic auxiliary solvents must be added in order to achieve adequate dispersion in water.
Resin acid isocyanates which can be dispersed in water in the presence of nonionic and anionic emulsifiers are known from DE-OS (German Published Specification) 2 557 409.
The dispersions or emulsions of carbamoylsulphonates from isocyanates and alkali metal and ammonium bisulphites proposed in DE-OS (German Published Specification) 2 839 310 can be employed as sizing compositions.
U.S. Pat. No. 4,505,778 discloses beater and surface sizing compositions which comprise mixtures of aromatic polyisocyanates containing 1-10% by weight of an isocyanate prepolymer which is obtained, for example, by reaction of aromatic polyisocyanates with monofunctional polyethers.
Various polyurethane or polyurea dispersions which can be employed as sizing compositions furthermore are known. However, these usually anionic products (cf. DE-OS (German Published Specification) 2 457 972) contain no reactive groups in the form of isocyanate groups. Examples of such products are to be found in the following documents: FR-A 1 496 584, U.S. Pat. No. 3,989,659, DE-OS (German Published Specification) 2 537
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Jansen Bernhard
Konig Joachim
Kopp Jurgen
Probst Joachim
Reiners Jurgen
Bayer Aktiengesellschaft
Nutter Nathan M.
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