EP0050223A1 - Process for preparing high wet-strength paper - Google Patents

Process for preparing high wet-strength paper Download PDF

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Publication number
EP0050223A1
EP0050223A1 EP81107478A EP81107478A EP0050223A1 EP 0050223 A1 EP0050223 A1 EP 0050223A1 EP 81107478 A EP81107478 A EP 81107478A EP 81107478 A EP81107478 A EP 81107478A EP 0050223 A1 EP0050223 A1 EP 0050223A1
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Prior art keywords
melamine
paper
mixing
formaldehyde resin
solution
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EP81107478A
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German (de)
French (fr)
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EP0050223B1 (en
Inventor
Sigberg Dr. Pfohl
Werner Weinle
Peter Dr. Zehner
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BASF SE
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BASF SE
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Priority to AT81107478T priority Critical patent/ATE4826T1/en
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/20—Macromolecular organic compounds
    • D21H17/33—Synthetic macromolecular compounds
    • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H17/47—Condensation polymers of aldehydes or ketones
    • D21H17/49—Condensation polymers of aldehydes or ketones with compounds containing hydrogen bound to nitrogen
    • D21H17/51—Triazines, e.g. melamine
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
    • D21H21/18—Reinforcing agents
    • D21H21/20—Wet strength agents

Definitions

  • colloidal aqueous solutions of melamine-formaldehyde resins which are prepared by dissolving an optionally modified methylolmelamine in aqueous acid and aging the solution formed, to increase the wet strength of paper to the paper stock.
  • the pH of the resin colloid solutions is in the range from 0.5 to 5, the solids content is max. 15% by weight. If the solids content is higher, the resin colloid solutions become unstable.
  • the object is achieved according to the invention by using a product as the melamine-formaldehyde resin colloid which is obtained by continuously mixing a 40 to 80% aqueous solution of an optionally modified melamine with water and acid in a mixing zone under turbulent flow, a temperature of 40 up to 110 ° C, a pH of 2 to 4 and a residence time from the mixing zone to the point of addition to the paper stock of 1 to 300 seconds, the solids content of the melamine-formaldehyde resin colloid solution being about 5 to 20% by weight. % is.
  • methylol melamines and the modified methylol melamines can be used to prepare the resin colloid solutions. Those methylol melamines in which the molar ratio of melamine to formaldehyde is 1: 2 to 1: 6 are preferably used.
  • the preparation of aqueous solutions of methylolmelamines and the corresponding modified methylolmelamines is known.
  • methylol melamines aqueous solution of melamine at temperatures between 70 and 95 0 e and adds formaldehyde, for example formalin or paraformaldehyde.
  • the pH of the reaction mixture is generally adjusted to between 7.5 and 11.
  • the methylolmelamines are stable in the alkaline pH range. They can be etherified very easily with alcohols in the acidic pH range. Methanol, ethanol and n- or iso-propanol or n- or iso-butanol are preferably used for the etherification. Etherification with methanol is particularly simple and therefore also preferred. It is possible to partially or completely etherify the methylolmelamines.
  • the resulting products can contain 1 to 6, preferably 2 to 5 ether groups.
  • the pH of the aqueous solution is adjusted to above 7 so that condensation is prevented.
  • the optionally etherified methylolmelamines are already produced in high concentration, for example as a 40 to 80% aqueous solution. They can also be obtained by concentrating dilute solutions.
  • the highly concentrated modified methylol melamine solutions can also be modified with alkali sulfites, alkali bisulfites or with amines.
  • the molar ratio of methylolmelamine to sulfite or bisulfite is preferably in a range from 1: 0.5 to 1: 5.
  • the main amines are ammonia, primary and secondary alkylamines, di- and polyamines and, for example, mono-, di- and triethanolamine.
  • the molar ratio of methylolmelamine to amine is preferably in a range from 1: 0.5 to 1: 5.
  • the concentrated aqueous solution of the optionally modified methylolmelamine is in a mixing zone by adding water and an acid - a reactant may have been premixed in the water - at a temperature of 40 to 110 ° C, preferably se 70 to 90 ° C, continuously mixed, so that a downstream also continuously flowed through-residence vessel, the polycondensation of the optionally modified methylolmelamine takes place within a very short time. At temperatures above 100 ° C, pressure equipment must be used.
  • a homogeneous solution - without concentration gradients - has to be prepared in a very short time, because due to the high reaction acceleration in the range of low acid concentrations this may be the case would polymerize modified methylol melamine to an insoluble resin within a few seconds.
  • the mixing of the reaction components with the water is preferably carried out in a jet mixer, which opens into a subsequent dwell period - designed as a reaction tube or container.
  • the water preferably the methylolmelamine solution, optionally modified with the water, is used by using it as a driving jet with turbulent flow at speeds of 5 to 50 m / s, preferably 10 to 20 m / s the jet of the jet mixer is given.
  • the energy density in the mixing zone is at least 20 kW / m 3 and is preferably above 50 kW / m 3 .
  • the resin solution if it is not already premixed with the water, as well as the acid required to start the condensation reaction, can be passed through the nozzle - which in this case is designed as a multi-component nozzle - as well as with separate inlet pipes next to the nozzle or be fed to the side of the mixing tube at the height of the nozzle.
  • the components leave the tube homogeneously mixed. Due to the short mixing time and the high energy density of 50 to 7000, preferably 50 to 2000 kW / m 3 entered with the mixing devices, it is possible to achieve the required reaction time until optimal ripening by setting suitable reaction conditions (pH from 3 to 4, temperature from 40 to 110 ° C) to 1 to 300 seconds, without getting disrupted by flocculation when condensation is too advanced or by loss of effectiveness if the dwell time is too short.
  • suitable reaction conditions pH from 3 to 4, temperature from 40 to 110 ° C
  • the ripening - polycondensation of the optionally modified methylolmelamine - takes place in the mixing zone and in the subsequent dwell period, preferably in a reaction tube which is integrated with the jet mixer and has a turbulent flow. After leaving the mixing process. direction, the homogeneously mixed solution - regardless of the mixing device used - passes through a tube or additional container in which the desired dwell time is achieved.
  • the required residence time is from a few seconds to several minutes, preferably from 15 seconds to 1 minute.
  • the acids used are preferably hydrochloric acid and phosphoric acid or carboxylic acids, such as formic acid, acetic acid and propionic acid.
  • a highly effective melamine-formaldehyde resin colloid solution with a solids content of about 5 to 20% by weight is obtained, which is metered in directly to the paper stock or added to the paper stock suspension after a further continuous or discontinuous dilution with water in a weight ratio of 1:10 to 1:20 becomes.
  • the colloid solutions prepared in this way are effective and are preferably used directly after leaving the mixing apparatus. They can also be stored for a few hours, but lose their effectiveness as a wet setting agent after a long time.
  • the parts given in the examples are parts by weight, the percentages relate to the weight of the substances.
  • the dry tear length was determined in accordance with DIN 53 112, sheet 1, and the wet tear length in accordance with DIN 53 112, sheet 2.
  • the alkali resistance of the paper was determined according to the procedure for the wet breaking length, but the standardized paper 'strip not in water but in 3% sodium hydroxide solution for 5 minutes at 80 ° C were stored.
  • the pH of the solution is then adjusted to about 4.0 using phosphoric acid and the temperature is kept at 40 ° C. for 30 minutes.
  • the solution is then concentrated under vacuum (about 10 mbar) at 60 ° C. to a solids content of 70% and then rapidly cooled to 20 ° C.
  • the 70% aqueous solution has a viscosity of approx. 500 mPas (Brookfield, 20 1 / min) and is infinitely miscible with water.
  • the components were mixed intensively and quickly into a homogeneous solution.
  • the energy density in the mixing room was 470 kW / m 3 .
  • a residence time in the form of a reaction tube was connected to the mixing tube.
  • the reaction tube had an inner diameter of 10 mm and a length of 30 m.
  • the residence time of the reaction mixture in the mixing zone and the downstream reaction tube to the point of addition to the paper stock was 30 seconds, the temperature was 75 ° C. and the pH of the mixture was 3.0.
  • the stirrer was then switched off and the mixture was aged at a temperature of 40 ° C. for 3 hours.
  • the pH of the mixture was 2.2.
  • the resin colloid was added to the paper stock in an amount of 150 g / min (corresponding to 5%) based on dry fiber material.
  • the pH of the stock suspension was adjusted to 4.5 with 2% aluminum sulfate and additionally with dilute sulfuric acid.
  • This stock suspension with a freeness of 35 0 SR was dewatered on the paper machine described in Example 1 at a speed of 66 m / min. Approx. 3 kg / min of paper made from bleached sulfite pulp with a basis weight of 60 g / cm 2 were made like this.
  • the properties of the paper are given in the table.
  • Comparative Example 1 was repeated with the exception that 300 g / min corresponding to 10%, based on the fiber material, of the 10% melamine-formaldehyde resin colloid solution were used for the paper stock.
  • the properties of the paper thus obtained are given in the table.

Abstract

1. A process for the production of paper exhibiting high wet strenght by adding a melamine-formaldehyde resin colloid to the paper stock and dewatering the paper stock on the paper machine, wherein the melamine-formaldehyde resin colloid used is a product which has been obtained by continuously mixing a 40 to 80% strength aqueous solution of an optionally modified methylol melamine with water and acid in a mixing zone under conditions of turbulent flow at a temperature of from 40 to 110 degrees C and a pH of 2 to 4, the time which elapses between mixing of the components and addition of the mixture to the paper stock being from 1 to 300 seconds, the solids content of the melamine-formaldehyde resin colloid solution being from 5 to 20% by weight.

Description

Es ist seit langem bekannt, kolloidale wäßrige Lösungen von Melamin-Formaldehyd-Harzen, die durch Lösen eines gegebenenfalls modifizierten Methylolmelamins in wäßriger Säure und Altern der gebildeten Lösung hergestellt werden, zur Erhöhung der Naßfestigkeit von Papier dem Papierstoff zuzusetzen. Der pH-Wert der Harzkolloidlösungen liegt in dem Bereich von 0,5 bis 5, der Feststoffgehalt beträgt max. 15 Gew.-%. Bei höherem Feststoffgehalt werden die Harzkolloidlösungen instabil.It has long been known to add colloidal aqueous solutions of melamine-formaldehyde resins, which are prepared by dissolving an optionally modified methylolmelamine in aqueous acid and aging the solution formed, to increase the wet strength of paper to the paper stock. The pH of the resin colloid solutions is in the range from 0.5 to 5, the solids content is max. 15% by weight. If the solids content is higher, the resin colloid solutions become unstable.

Aus der DE-AS 10 90 078 ist es bekannt, die Wirksamkeit von Melamin-Formaldehyd-Harzkolloiden durch Zusatz von Formaldehyd und anschließendes Altern der erhaltenen Lösungen zu verbessern. Hierdurch wird eine Erhöhung der Naßfestigkeit des Papiers erzielt. Bei den bisher bekannten Verfahren zur Herstellung von Melamin-Formaldehyd-Harzkolloiden ist es unumgänglich, die Lösungen nach Zugabe einer Säure eine bestimmte Zeit, in der Regel 3 bis 12 Stunden, altern zu lassen, bevor die Lösungen als Naßfestigkeitsmittel bei der Papierherstellung eingesetzt werden können. Um die angesäuerten Melamin-Formaldehyd--Harzkolloide altern zu lassen, benötigt man in der Praxis Lagertanks. Bei der diskontinuierlichen Herstellung der Melamin-Formaldehyd-Harzkolloide ist man außerdem immer gezwungen, einen Kompromiß zwischen der Wirksamkeit der Harzkolloide und der Lagerstabilität der kolloidalen Lösungen einzugehen. Versucht man z.B., die Reifezeit durch Veränderung des pH-Wertes bzw. der Temperatur herabzusetzen, so fällt die Wirksamkeit der gereiften Lösung nach kurzer Zeit ab.From DE-AS 10 90 078 it is known to improve the effectiveness of melamine-formaldehyde resin colloids by adding formaldehyde and subsequent aging of the solutions obtained. This results in an increase in the wet strength of the paper. In the previously known processes for the production of melamine-formaldehyde resin colloids, it is essential to let the solutions age after adding an acid for a certain time, usually 3 to 12 hours, before the solutions can be used as wet strength agents in papermaking . In practice, storage tanks are required to age the acidified melamine formaldehyde resin colloids. In the discontinuous production of melamine-formaldehyde resin colloids, one is also always forced to compromise between the effectiveness of the resin colloids and the storage stability of the colloidal solutions. If, for example, you try to reduce the ripening time by changing the pH or the temperature, the effectiveness of the ripened solution drops after a short time.

Es ist daher Aufgabe der Erfindung, ein Verfahren zur Herstellung von Papier mit hoher Naßfestigkeit durch Zusatz von Melamin-Formaldehyd-Harzkolloiden zum Papierstoff und Entwässern des Papierstoffs auf der Papiermaschine aufzuzeigen, bei dem man nicht mehr gezwungen ist, die Melamin--Formaldehyd-Harzkolloide über einen längeren Zeitraum zu altern, so daß Lagertanks entfallen und bei dem man die Wirksamkeit der Harzkolloid-Lösungen leicht einstellen kann.It is therefore an object of the invention to provide a process for the production of paper with high wet strength by adding melamine-formaldehyde resin colloids to the paper stock and dewatering the paper stock on the paper machine, in which one is no longer forced to use the melamine-formaldehyde resin colloids to age over a longer period of time so that storage tanks are eliminated and the effectiveness of the resin colloid solutions can be easily adjusted.

Die Aufgabe wird erfindungsgemäß dadurch gelöst, daß man als Melamin-Formaldehyd-Harzkolloide ein Produkt einsetzt, das durch kontinuierliches Mischen einer 40 bis 80 %igen wäßrigen Lösung eines gegebenenfalls modifizierten Melamins mit Wasser und Säure in einer Mischungszone bei turbulenter Strömung, einer Temperatur von 40 bis 110°C, einem pH-Wert von 2 bis 4 und einer Verweilzeit von der Mischungszone bis zur Zugabestelle zum Papierstoff von 1 bis 300 Sekunden erhältlich ist, wobei der Feststoffgehalt der Melamin-Formaldehyd-Harzkolloid-Lösung etwa 5 bis 20 Gew.-% beträgt.The object is achieved according to the invention by using a product as the melamine-formaldehyde resin colloid which is obtained by continuously mixing a 40 to 80% aqueous solution of an optionally modified melamine with water and acid in a mixing zone under turbulent flow, a temperature of 40 up to 110 ° C, a pH of 2 to 4 and a residence time from the mixing zone to the point of addition to the paper stock of 1 to 300 seconds, the solids content of the melamine-formaldehyde resin colloid solution being about 5 to 20% by weight. % is.

Da nach dem erfindungsgemäßen Verfahren hochkonzentrierte, gegebenenfalls modifizierte Melamin-Lösungen, vorzugsweise 60 bis 70 %ige wäßrige Lösungen, verwendet werden, erzielt man gegenüber bekannten Verfahren eine entscheidende Verringerung von Transportkosten. -Zur Herstellung der Harzkolloidlösungen kommen alle bisher dafür verwendeten Methylolmelamine sowie die modifizierten Methylolmelamine in Betracht. Vorzugsweise verwendet man solche Methylolmelamine, bei denen das Molverhältnis von Melamin zu Formaldehyd 1:2 bis 1:6 beträgt. Die Herstellung wäßriger Lösungen von Methylolmelaminen und den entsprechenden modifizierten Methylolmelaminen ist bekannt. üblicherweise erhitzt man zur'Herstellung von Methylolmelaminen eine wäßrige Lösung von Melamin auf Temperaturen zwischen 70 und 950e und fügt Formaldehyd, z.B. Formalin oder Paraformaldehyd, zu. Der pH-Wert der Reaktionsmischung wird in der Regel auf Werte zwischen 7,5 und 11 eingestellt. Die Methylolmelamine sind bekanntlich im alkalischen pH-Bereich stabil. Sie können sehr leicht im sauren pH-Bereich mit Alkoholen verethert werden. Vorzugsweise verwendet man für die Veretherung Methanol, Ethanol und n- oder iso-Propanol oder n- oder iso-Butanol. Besonders einfach und daher auch bevorzugt ist die Veretherung mit Methanol. Es ist möglich, die Methylolmelamine teilweise oder vollständig zu verethern. Die dabei entstehenden Produkte können 1 bis 6, vorzugsweise 2 bis 5 Ethergruppierungen enthalten. Nach der Veretherung wird der pH-Wert der wäßrigen Lösung auf Werte oberhalb von 7 eingestellt, damit eine Kondensation unterbunden wird. Die gegebenenfalls veretherten Methylolmelamine werden bereits in hoher Konzentration hergestellt, z.B. als 40 bis 80 %ige wäßrige Lösung. Sie können auch durch Aufkonzentrieren verdünnter Lösungen erhalten werden. Die hochkonzentrierten modifizierten Methylolmelaminlösungen können auch mit Alkalisulfiten, Alkalibisulfiten bzw. mit Aminen modifiziert sein. Das Molverhältnis von Methylolmelamin zu Sulfit bzw. Bisulfit liegt bevorzugt in einem Bereich von 1:0,5 bis 1:5. Als Amine kommen hauptsächlich Ammoniak, primäre und sekundäre Alkylamine, Di- und Polyamine sowie z.B. Mono-, Di- und Triethanolamin in Frage. Das Molverhältnis von Methylolmelamin zu Amin liegt hier bevorzugt in einem Bereich von 1:0,5 bis 1:5.Since highly concentrated, optionally modified melamine solutions, preferably 60 to 70% aqueous solutions, are used in the process according to the invention, a decisive reduction in transport costs is achieved compared to known processes. -All previously used methylol melamines and the modified methylol melamines can be used to prepare the resin colloid solutions. Those methylol melamines in which the molar ratio of melamine to formaldehyde is 1: 2 to 1: 6 are preferably used. The preparation of aqueous solutions of methylolmelamines and the corresponding modified methylolmelamines is known. Usually, one is heated to produce methylol melamines aqueous solution of melamine at temperatures between 70 and 95 0 e and adds formaldehyde, for example formalin or paraformaldehyde. The pH of the reaction mixture is generally adjusted to between 7.5 and 11. As is known, the methylolmelamines are stable in the alkaline pH range. They can be etherified very easily with alcohols in the acidic pH range. Methanol, ethanol and n- or iso-propanol or n- or iso-butanol are preferably used for the etherification. Etherification with methanol is particularly simple and therefore also preferred. It is possible to partially or completely etherify the methylolmelamines. The resulting products can contain 1 to 6, preferably 2 to 5 ether groups. After etherification, the pH of the aqueous solution is adjusted to above 7 so that condensation is prevented. The optionally etherified methylolmelamines are already produced in high concentration, for example as a 40 to 80% aqueous solution. They can also be obtained by concentrating dilute solutions. The highly concentrated modified methylol melamine solutions can also be modified with alkali sulfites, alkali bisulfites or with amines. The molar ratio of methylolmelamine to sulfite or bisulfite is preferably in a range from 1: 0.5 to 1: 5. The main amines are ammonia, primary and secondary alkylamines, di- and polyamines and, for example, mono-, di- and triethanolamine. The molar ratio of methylolmelamine to amine here is preferably in a range from 1: 0.5 to 1: 5.

Die konzentrierte wäßrige Lösung des gegebenenfalls modifizierten Methylolmelamins'wird in einer Mischungszone durch Hinzufügen von Wasser und einer Säure - wobei ein Reaktionspartner schon zuvor im Wasser vorgemischt sein kann - bei einer Temperatur von 40 bis 110°C, vorzugsweise 70 bis 90°C, kontinuierlich gemischt, so daß einem nachgeschalteten ebenfalls kontinuierlich durchflossenen Verweilzeit-Gefäß die Polykondensation des gegebenenfalls modifizierten Methylolmelamins innerhalb kürzester Zeit abläuft. Bei Temperaturen oberhalb 100°C muß in Druckapparaturen gearbeitet werden.The concentrated aqueous solution of the optionally modified methylolmelamine is in a mixing zone by adding water and an acid - a reactant may have been premixed in the water - at a temperature of 40 to 110 ° C, preferably se 70 to 90 ° C, continuously mixed, so that a downstream also continuously flowed through-residence vessel, the polycondensation of the optionally modified methylolmelamine takes place within a very short time. At temperatures above 100 ° C, pressure equipment must be used.

Zum kontinuierlichen Mischen der beiden Reaktionspartner - oder wenn einer schon mit Wasser vorgemischt ist, nur des einen Reaktionspartners, vorzugsweise die Säure - muß in kürzester Zeit eine homogene Lösung - ohne Konzentrationsgradienten - hergestellt werden, da wegen der hohen Reaktionsbeschleunigung im Bereich geringer Säurekonzentrationen das gegebenenfalls modifizierte Methylolmelamin innerhalb von wenigen Sekunden zu einem unlöslichen Harz polymerisieren würde.For the continuous mixing of the two reactants - or if one is already premixed with water, only one of the reactants, preferably the acid - a homogeneous solution - without concentration gradients - has to be prepared in a very short time, because due to the high reaction acceleration in the range of low acid concentrations this may be the case would polymerize modified methylol melamine to an insoluble resin within a few seconds.

Das Mischen geschieht deshalb in Mischgeräten mit geringem Mischvolumen. Die Mischungskomponenten durchlaufen die Mischungszone mit hoher turbulenter Strömung. Unter diesen Bedingungen wirken hohe Energiedichten auf die miteinander zu vermischenden Komponenten ein. Für das erfindungsgemäße Verfahren eignen sich z.B. folgende gebräuchliche Mischvorrichtungen:

  • a) Strahlmischer - Mischen mit schnellem Flüssigkeitstreibstrahl; wozu vorzugsweise das Wasser bzw. die wäßrige, gegebenenfalls modifizierte Methylolmelaminlösung verwendet wird,
  • b) In-line-Mischer (in Rohrleitung eingebauter Propeller--Mischer),
  • c) Statische Mischer und
  • d) Rotor - Stator - Mischer.
Mixing therefore takes place in mixing devices with a small mixing volume. The mixture components pass through the mixture zone with high turbulent flow. Under these conditions, high energy densities act on the components to be mixed. The following conventional mixing devices are suitable for the process according to the invention:
  • a) jet mixer - mixing with fast liquid jet; for which the water or the aqueous, optionally modified methylolmelamine solution is preferably used,
  • b) in-line mixer (propeller mixer installed in the pipeline),
  • c) static mixers and
  • d) rotor - stator mixer.

Vorzugsweise wird das Mischen der Reaktionskomponenten mit dem Wasser in einem Strahlmischer vorgenommen, der in einen nachgeschalteten Verweilzeitraum - als Reaktionsrohr oder -behälter ausgeführt - einmündet.The mixing of the reaction components with the water is preferably carried out in a jet mixer, which opens into a subsequent dwell period - designed as a reaction tube or container.

Zum Einbringen der erforderlichen Mischenergie in den Strahlmischer wird das Wasser, vorzugsweise die mit dem Wasser vorgemischte, gegebenenfalls modifizierte Methylolmelaminlösung verwendet, indem es als Treibstrahl mit turbulenter Strömung bei Geschwindigkeiten von 5 bis 50 m/s, vorzugsweise 10 bis 20 m/s, durch die Düse des Strahlmischers gegeben wird. Die Energiedichte in der Mischungszone beträgt mindestens 20 kW/m3 und liegt vorzugsweise oberhalb von 50 kW/m3.To introduce the required mixing energy into the jet mixer, the water, preferably the methylolmelamine solution, optionally modified with the water, is used by using it as a driving jet with turbulent flow at speeds of 5 to 50 m / s, preferably 10 to 20 m / s the jet of the jet mixer is given. The energy density in the mixing zone is at least 20 kW / m 3 and is preferably above 50 kW / m 3 .

Die Harzlösung kann, wenn sie nicht bereits mit dem Wasser vorgemischt ist, ebenso wie die Säure, die zum Starten der Kondensationsreaktion benötigt wird, sowohl durch die Düse - die in diesem Fall als Mehrstoffdüse ausgebildet ist -, als auch mit gesonderten Einleitungsrohren neben der Düse oder seitlich am Mischrohr auf der Höhe der Düse zugeführt werden.The resin solution, if it is not already premixed with the water, as well as the acid required to start the condensation reaction, can be passed through the nozzle - which in this case is designed as a multi-component nozzle - as well as with separate inlet pipes next to the nozzle or be fed to the side of the mixing tube at the height of the nozzle.

Durch Impulsaustausch zwischen dem Treibstrahl und der ihn umgebenden Reaktionslösung kommt es zu einer schnellen und intensiven Durchmischung des als Rohr ausgebildeten Mischraumes. Die Durchmesserverhältnisse von d Rohr zu d Treibstrahl betragen 2 bis 20, vorzugsweise 3 bis 6; die Länge des Rohres verhält sich zum Durchmesser des Rohres lRohr/dRohr = 5 bis 20.Through the exchange of impulses between the driving jet and the reaction solution surrounding it, the mixing space designed as a tube is mixed quickly and intensively. The diameter ratios of d to d Tre tube bs i t rahl be 2 to 20, preferably 3 to 6; the length of the tube is related to the diameter of the tube l tube / d tube = 5 to 20.

Die Komponenten verlassen das Rohr homogen gemischt. Aufgrund der kurzen Mischzeit und der mit den Mischvorrichtungen eingetragenen hohen Energiedichte von 50 bis 7000, vorzugsweise 50 bis 2000 kW/m3, ist es möglich, die erforderliche Reaktionszeit bis zur optimalen Reifung durch Einstellen geeigneter Reaktionsbedingungen (pH von 3 bis 4, Temperatur von 40 bis 110°C) auf 1 bis 300 Sekunden zu verkürzen, ohne Störungen durch Flockenbildung bei zu weit fortgeschrittener Kondensation bzw. durch Wirksamkeitsverlust bei zu kurzer Verweilzeit zu erhalten.The components leave the tube homogeneously mixed. Due to the short mixing time and the high energy density of 50 to 7000, preferably 50 to 2000 kW / m 3 entered with the mixing devices, it is possible to achieve the required reaction time until optimal ripening by setting suitable reaction conditions (pH from 3 to 4, temperature from 40 to 110 ° C) to 1 to 300 seconds, without getting disrupted by flocculation when condensation is too advanced or by loss of effectiveness if the dwell time is too short.

Die Reifung - Polykondensation des gegebenenfalls modifizierten Methylolmelamins - geschieht in der Mischungszone sowie dem nachgeschalteten Verweilzeitraum, vorzugsweise in einem mit dem Strahlmischer integrierten und turbulent durchströmten Reaktionsrohr. Nach Verlassen der Mischvor-. richtung durchläuft die homogengemischte Lösung - unabhängig von der verwendeten Mischvorrichtüng - ein Rohr oder zusätzlich einen Behälter in dem die erwünschte Verweilzeit erreicht wird. Die erforderliche Verweilzeit beträgt je nach Reaktionsbedingungen (Temperatur, pH-Wert, Konzentration und Art des gegebenenfalls modifizierten Methylolmelamins) wenige Sekunden bis mehrere Minuten, vorzugsweise 15 Sekunden bis 1 Minute.The ripening - polycondensation of the optionally modified methylolmelamine - takes place in the mixing zone and in the subsequent dwell period, preferably in a reaction tube which is integrated with the jet mixer and has a turbulent flow. After leaving the mixing process. direction, the homogeneously mixed solution - regardless of the mixing device used - passes through a tube or additional container in which the desired dwell time is achieved. Depending on the reaction conditions (temperature, pH, concentration and type of methylolmelamine which may have been modified), the required residence time is from a few seconds to several minutes, preferably from 15 seconds to 1 minute.

Um die notwendige Temperatur während des Mischungsvorgangs einzustellen, kann man entweder alle zu mischenden Komponenten vorher auf diese Temperatur erhitzen bzw. man erhitzt nur das zum Verdünnen verwendete Wasser und zwar dann auf eine höhere Temperatur, so daß die Temperatur während des Mischens in dem angegebenen Bereich liegt. Dies kann beispielsweise dadurch geschehen, daß man Dampf in das Verdünnungswasser einleitet.In order to set the necessary temperature during the mixing process, you can either heat all the components to be mixed beforehand to this temperature or only heat the water used for dilution and then to a higher temperature, so that the temperature during the mixing is in the specified range lies. This can be done, for example, by introducing steam into the dilution water.

"Als Säuren verwendet man vorzugsweise Salzsäure und Phosphorsäure bzw. Carbonsäuren, wie Ameisensäure, Essigsäure und Propionsäure."The acids used are preferably hydrochloric acid and phosphoric acid or carboxylic acids, such as formic acid, acetic acid and propionic acid.

Man erhält eine hochwirksame Melamin-Formaldehyd-Harzkolloidlösung mit einem Feststoffgehalt von etwa 5 bis 20 Gew.-%, die direkt zum Papierstoff zudosiert bzw. nach einer weiteren kontinuierlichen oder diskontinuierlichen Verdünnung mit Wasser im Gewichtsverhältnis 1:10 bis 1:20 zur Papierstoffsuspension gegeben wird. Die so hergestellten Kolloidlösungen sind wirksam und werden vorzugsweise direkt nach Verlassen der Mischungsapparatur verwendet. Sie können auch einige Stunden gelagert werden, verlieren jedoch nach längerer Zeit an Wirksamkeit als Naßverfestigungsmittel.A highly effective melamine-formaldehyde resin colloid solution with a solids content of about 5 to 20% by weight is obtained, which is metered in directly to the paper stock or added to the paper stock suspension after a further continuous or discontinuous dilution with water in a weight ratio of 1:10 to 1:20 becomes. The colloid solutions prepared in this way are effective and are preferably used directly after leaving the mixing apparatus. They can also be stored for a few hours, but lose their effectiveness as a wet setting agent after a long time.

Die in den Beispielen angegebenen Teile sind Gewichtsteile, die Angaben in Prozent beziehen sich auf das Gewicht der Stoffe. Die Trockenreißlänge wurde gemäß DIN 53 112, Blatt 1, und die Naßreißlänge gemäß DIN 53 112, Blatt 2, bestimmt. Die Laugenfestigkeit des Papiers wurde entsprechend der Arbeitsweise für die Naßreißlänge ermittelt, wobei jedoch die genormten Papier- 'streifen nicht in Wasser, sondern in 3 %iger Natronlauge 5 Minuten bei 80°C gelagert wurden.The parts given in the examples are parts by weight, the percentages relate to the weight of the substances. The dry tear length was determined in accordance with DIN 53 112, sheet 1, and the wet tear length in accordance with DIN 53 112, sheet 2. The alkali resistance of the paper was determined according to the procedure for the wet breaking length, but the standardized paper 'strip not in water but in 3% sodium hydroxide solution for 5 minutes at 80 ° C were stored.

Herstellung einer veretherten Methylolmelaminlösung in Wasser:

  • 127 Teile (ca. 1 Mol) Melamin wurden mit 365 Teilen einer 37 %igen wäßrigen Lösung von Formaldehyd (ca. 4,5 Mol CH2O) gemischt. Die Mischung wird mit Natronlauge auf pH 8,5 eingestellt und auf 70°C erhitzt, bis das gesamte Melamin völlig in Lösung gegangen ist. Man läßt weitere 5 Minuten bei 70°C nachreagieren und gibt anschließend 1
Preparation of an etherified methylolmelamine solution in water:
  • 127 parts (approx. 1 mol) of melamine were mixed with 365 parts of a 37% aqueous solution of formaldehyde (approx. 4.5 mol of CH 2 O). The mixture is adjusted to pH 8.5 with sodium hydroxide solution and heated to 70 ° C. until all of the melamine has completely dissolved. The mixture is left to react for a further 5 minutes at 70 ° C. and then 1

r640 Teile (ca. 20 mol) an Methanol zu. Mit Phosphorsäure wird nun der pH-Wert der Lösung auf ca. 4,0 eingestellt und 30 Minuten lang die Temperatur bei 40°C gehalten. Nach Erhöhung des pH-Wertes auf ca. 7 mit Natronlauge wird anschließend die Lösung unter Vakuum (ca. 10 mbar) bei 60°C auf einen Feststoffgehalt von 70 % aufkonzentriert und dann schnell auf 20°C abgekühlt. Die 70 %ige wäßrige Lösung weist eine Viskosität von ca. 500 mPas (Brookfield, 201/min) auf und ist unendlich mit Wasser mischbar. r 640 parts (approx. 20 mol) of methanol. The pH of the solution is then adjusted to about 4.0 using phosphoric acid and the temperature is kept at 40 ° C. for 30 minutes. After increasing the pH to about 7 with sodium hydroxide solution, the solution is then concentrated under vacuum (about 10 mbar) at 60 ° C. to a solids content of 70% and then rapidly cooled to 20 ° C. The 70% aqueous solution has a viscosity of approx. 500 mPas (Brookfield, 20 1 / min) and is infinitely miscible with water.

Beispiel 1example 1

226 kg/h Wasser von 80°C und 38,3 kg/h 70 %ige wäßrige Lösung des oben beschriebenen veretherten Methylolmelamins und 3,8 kg/h konzentrierte Salzsäure (37 %ig) wurden mit einem Strahlmischer bestehend aus einer Zweistoffdüse mit einem Durchmesser der inneren Bohrung von 2 mm und einem Ringspalt mit einer Spaltbreite von 1 mm, die in ein Mischrohr mündete mit 100 mm Länge und 20 mm Durchmesser und einer Prallplatte im Abstand von 85 mm von der Düsenmündung kontinuierlich in der Weise gemischt, daß das Wasser als Treibstrahl durch die innere Bohrung mit einer Strahlgeschwindigkeit von 20 m/s (turbulente Strömung) gegeben wurde. Durch den Ringspalt wurde die veretherte Methylolmelaminlösung und die konzentrierte Salzsäure durch einen seitlich am Mischrohr auf der Höhe der Düsenmündung angebrachten Stutzen zudosiert.226 kg / h of water at 80 ° C and 38.3 kg / h of 70% aqueous solution of the etherified methylolmelamine described above and 3.8 kg / h of concentrated hydrochloric acid (37%) were with a jet mixer consisting of a two-fluid nozzle with a Diameter of the inner bore of 2 mm and an annular gap with a gap width of 1 mm, which opened into a mixing tube with a length of 100 mm and a diameter of 20 mm and a baffle plate at a distance of 85 mm from the nozzle mouth, continuously mixed in such a way that the water was given as a driving jet through the inner bore at a jet speed of 20 m / s (turbulent flow). The etherified methylolmelamine solution and the concentrated hydrochloric acid were metered in through the annular gap through a nozzle attached to the side of the mixing tube at the level of the nozzle mouth.

In dem als Rohr ausgeführten Mischraum wurden die Komponenten intensiv und schnell zu einer homogenen Lösung gemischt. Die Energiedichte im Mischraum betrug 470 kW/m3. Zur Vervollständigung der Polykondensation (Reifung) war ein Verweilzeitraum in Form eines Reaktionsrohres am Mischrohr angeschlossen. Das Reaktionsrohr hatte einen Innendurchmesser von 10 mm und eine Länge von 30 m. Die Verweilzeit der Reaktionsmischung in der Mischungszone und dem nachgeschalteten Reaktionsrohr bis zur Zugabestelle zum Papierstoff betrug 30 Sekunden, die Temperatur 75°C und der pH-Wert der Mischung 3,0.In the mixing room designed as a tube, the components were mixed intensively and quickly into a homogeneous solution. The energy density in the mixing room was 470 kW / m 3 . To complete the polycondensation (ripening), a residence time in the form of a reaction tube was connected to the mixing tube. The reaction tube had an inner diameter of 10 mm and a length of 30 m. The residence time of the reaction mixture in the mixing zone and the downstream reaction tube to the point of addition to the paper stock was 30 seconds, the temperature was 75 ° C. and the pH of the mixture was 3.0.

Man erhielt auf diese Weise eine 10 %ige Harzkolloidlösung, die entsprechend einer Dosiermenge von 5 % Harzkolloidlösung, bezogen auf trockenes Fasermaterial, direkt zum Papierstoff einer Langsiebversuchspapiermaschine mit einer Arbeitsbreite von 75 cm gegeben wurde. Die Arbeitsgeschwindigkeit der Papiermaschine betrug 66 m/min. Das Papier bestand aus gebleichtem Sulfit-Zellstoff und hatte ein Flächengewicht von 60 g/m2. Der pH-Wert der Stoffsuspension wurde durch Zusatz von 2 % Aluminiumsulfat und durch Zugabe verdünnter Schwefelsäure auf einen Wert von 4,5 eingestellt. Der Mahlgrad betrug 35°SR. Der Papiermaschine wurden 3 kg/min des Sulfitzellstoffs zugeführt. Die Eigenschaften des erhaltenen Papiers sind in Tabelle 1 zusammengestellt.In this way, a 10% resin colloid solution was obtained, which was added according to a dosage of 5% resin colloid solution, based on dry fiber material, directly to the paper stock of a four-wire test paper machine with a working width of 75 cm. The working speed of the paper machine was 66 m / min. The paper consisted of bleached sulfite pulp and had a basis weight of 60 g / m 2 . The pH of the stock suspension was adjusted to 4.5 by adding 2% aluminum sulfate and by adding dilute sulfuric acid. The freeness was 35 ° SR. The paper machine was fed 3 kg / min of the sulfite pulp. The properties of the paper obtained are summarized in Table 1.

Beispiel 2Example 2

148,3 kg/h Wasser von 80°C wurden mit 28,8 kg/h 70 %iger wäßriger Lösung des oben beschriebenen veretherten Methylolmelamins auf der Saugseite einer Kreiselpumpe kontinuierlich zugegeben, in der Pumpe gemischt und in einen Strahlmischer durch eine I-Stoff-Düse mit 2 mm-Bohrung mit einer Strahlgeschwindigkeit von 15 m/s (turbulente Strömung) entsprechend einer Energiedichte von 200 kW/m3 gedüst. 2,8 kg/h konzentrierte Salzsäure wurden in den wie im Beispiel 1 angegebenen Mischraum zudosiert. Das Reaktionsrohr hatte dieselben Abmessungen wie im Beispiel 1. Die Verweilzeit der Reaktionsmischung bis zur Zugabestelle zum Papierstoff betrug 50 Sekunden, die Temperatur 75°C und der pH-Wert der Mischung 3,0.148.3 kg / h of water at 80 ° C. were continuously added to the suction side of a centrifugal pump with 28.8 kg / h of 70% strength aqueous solution of the etherified methylolmelamine described above, mixed in the pump and into a jet mixer by an I substance - Nozzle with 2 mm bore with a jet speed of 15 m / s (turbulent flow) corresponding to an energy density of 200 kW / m 3 . 2.8 kg / h of concentrated hydrochloric acid were metered into the mixing room as specified in Example 1. The reaction tube had the same dimensions as in Example 1. The residence time of the reaction mixture up to the point of addition to the paper stock was 50 seconds, the temperature was 75 ° C. and the pH of the mixture was 3.0.

Von dieser 10 %igen Harzkolloidlösung wurden der Papiermaschine bei gleichem Stoffeinsatz wie in Beispiel 1 angegeben, 10 %, bezogen auf trockenes Fasermaterial,' zudosiert. Die Eigenschaften des so erhaltenen Papiers sind in der Tabelle 1 zusammengestellt.Of this 10% resin colloid solution of the paper machine with the same material used were as described in Example 1, 10%, based on dry fiber material, 'added. The properties of the paper thus obtained are summarized in Table 1.

Vergleichsbeispiel 1Comparative Example 1

In einem 250 1 fassenden beheizbaren Behälter der mit einem Rührer ausgerüstet war, wurden 84,5 kg Wasser auf eine Temperatur von 40°C erwärmt. Man hielt die Temperatur konstant und gab 1,4 kg konzentrierte Salzsäure (37 %ig) zu und nachdem eine verdünnte Säurelösung entstanden war, 14,3 kg der oben beschriebenen 70 %igen wäßrigen Lösung des veretherten Methylolmelamins. Um die Reaktionspartner zu durchmischen wurde die Lösung mit einer Energiedichte von 0,4 kW/m3 gerührt. Das Durchmischen war nach etwa 5 Minuten beendet.84.5 kg of water were heated to a temperature of 40 ° C. in a 250 liter heatable container equipped with a stirrer. The temperature was kept constant and 1.4 kg of concentrated hydrochloric acid (37%) were added and, after a dilute acid solution had formed, 14.3 kg of the above-described 70% aqueous solution of the etherified methylolmelamine. In order to mix the reactants, the solution was stirred with an energy density of 0.4 kW / m 3 . Mixing was complete after about 5 minutes.

Danach wurde der Rührer abgestellt und die Mischung 3 Stunden bei einer Temperatur von 40°C gealtert. Der pH-Wert der Mischung betrug 2,2.The stirrer was then switched off and the mixture was aged at a temperature of 40 ° C. for 3 hours. The pH of the mixture was 2.2.

Um die Melaminformaldehyd-Harzkolloidlösung als Naßfestigkeitsmittel zu prüfen, wurde das Harzkolloid in einer Menge von 150 g/min (entsprechend 5 %) bezogen auf trockenes Fasermaterial dem Papierstoff zugesetzt. Der pH-Wert der Stoffsuspension wurde mit 2 % Aluminiumsulfat und zusätzlich mit verdünnter Schwefelsäure auf einen Wert von 4,5 eingestellt. Diese Stoffsupension mit einem Mahlgrad von 350SR wurde auf der in Beispiel 1 beschriebenen Papiermaschine bei einer Geschwindigkeit von 66 m/min entwässert. Ca. 3 kg/min eines Papiers aus gebleichtem Sulfitzellstoff mit einem Flächengewicht von 60 g/cm2 wurden so hergestellt. Die Eigenschaften des Papiers sind in der Tabelle angegeben.In order to test the melamine-formaldehyde resin colloid solution as a wet strength agent, the resin colloid was added to the paper stock in an amount of 150 g / min (corresponding to 5%) based on dry fiber material. The pH of the stock suspension was adjusted to 4.5 with 2% aluminum sulfate and additionally with dilute sulfuric acid. This stock suspension with a freeness of 35 0 SR was dewatered on the paper machine described in Example 1 at a speed of 66 m / min. Approx. 3 kg / min of paper made from bleached sulfite pulp with a basis weight of 60 g / cm 2 were made like this. The properties of the paper are given in the table.

Vergleichsbeispiel 2Comparative Example 2

Das Vergleichsbeispiel 1 wurde mit der Ausnahme wiederholt, daß zum Papierstoff 300 g/min entsprechend 10 %, bezogen auf das Fasermaterial, der 10 %igen Melamin-Formaldehyd-Harzkolloidlösung verwendet wurden. Die Eigenschaften des so erhaltenen Papiers sind in der Tabelle angegeben.

Figure imgb0001
Comparative Example 1 was repeated with the exception that 300 g / min corresponding to 10%, based on the fiber material, of the 10% melamine-formaldehyde resin colloid solution were used for the paper stock. The properties of the paper thus obtained are given in the table.
Figure imgb0001

Claims (3)

1. Verfahren zur Herstellung von Papier mit hoher Naßfestigkeit durch Zusatz von Melamin-Formaldehyd-Harzkolloiden zum Papierstoff und Entwässern des Papierstoffs auf der Papiermaschine, dadurch gekennzeichnet, daß man als Melamin-Formaldehyd-Harzkolloid ein Produkt einsetzt, das durch kontinuierliches Mischen einer 40 bis 80 %igen wäßrigen Lösung eines gegebenenfalls modifizierten Melamins mit Wasser und Säure in einer Mischungszone bei turbulenter Strömung, einer Temperatur von 40 bis 110°C, einem pH-Wert von 2 bis 4 und einer Verweilzeit von der Mischungszone bis zur Zugabestelle zum Papierstoff von 1 bis 300 Sekunden erhältlich ist, wobei der Feststoffgehalt der Melamin-Formaldehyd-Harzkolloid-Lösung etwa 5 bis 20 Gew.-% beträgt.1. A process for the production of paper with high wet strength by adding melamine-formaldehyde resin colloids to the paper stock and dewatering the paper stock on the paper machine, characterized in that a product is used as the melamine-formaldehyde resin colloid which is obtained by continuously mixing a 40 to 80% aqueous solution of an optionally modified melamine with water and acid in a mixing zone with turbulent flow, a temperature of 40 to 110 ° C, a pH of 2 to 4 and a residence time from the mixing zone to the point of addition to the pulp of 1 is available up to 300 seconds, the solids content of the melamine-formaldehyde resin colloid solution being about 5 to 20% by weight. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Verweilzeit der Stoffe von der Mischungszone bis zur Zugabestelle zum Papierstoff 15 bis 60 Sekunden beträgt.2. The method according to claim 1, characterized in that the residence time of the substances from the mixing zone to the addition point to the paper stock is 15 to 60 seconds. 3. Verfahren nach den Ansprüchen 1 und 2, dadurch gekennzeichnet, daß die Energiedichte in der Mischungszone mindestens 20 kW/m3 beträgt.3. Process according to claims 1 and 2, characterized in that the energy density in the mixing zone is at least 20 kW / m 3 .
EP81107478A 1980-10-22 1981-09-21 Process for preparing high wet-strength paper Expired EP0050223B1 (en)

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Cited By (3)

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US5286347A (en) * 1992-05-05 1994-02-15 Calgon Corporation Melamine formaldehyde polymer for pitch control method
GB2293612A (en) * 1994-09-30 1996-04-03 Ricoh Kk Reusable recording paper
WO2020229215A1 (en) 2019-05-10 2020-11-19 Hauni Maschinenbau Gmbh Production of drinking straws from paper

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DE9214170U1 (en) * 1992-10-17 1993-03-11 Gustav Demmler Gmbh & Co., 1000 Berlin, De

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DE921300C (en) * 1948-10-10 1954-12-13 Cassella Farbwerke Mainkur Ag Process for refining fiber material
DE1090078B (en) * 1956-10-08 1960-09-29 American Cyanamid Co Process for making paper with improved wet strength
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DE2309334A1 (en) * 1973-02-24 1974-08-29 Cassella Farbwerke Mainkur Ag METHOD FOR THE PRODUCTION OF MELAMINE RESIN FILMS
FR2446889A1 (en) * 1979-01-17 1980-08-14 Protex Manuf Prod Chimiq Paper pulp pigmentation - by in situ formation or organic pigments from an aminoplast foam

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US2233965A (en) * 1937-05-14 1941-03-04 Bennett Inc Method of delivering and diluting aqueous dispersions of wax, rosin, and the like
DE921300C (en) * 1948-10-10 1954-12-13 Cassella Farbwerke Mainkur Ag Process for refining fiber material
DE1090078B (en) * 1956-10-08 1960-09-29 American Cyanamid Co Process for making paper with improved wet strength
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DE2309334A1 (en) * 1973-02-24 1974-08-29 Cassella Farbwerke Mainkur Ag METHOD FOR THE PRODUCTION OF MELAMINE RESIN FILMS
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US5286347A (en) * 1992-05-05 1994-02-15 Calgon Corporation Melamine formaldehyde polymer for pitch control method
GB2293612A (en) * 1994-09-30 1996-04-03 Ricoh Kk Reusable recording paper
GB2293612B (en) * 1994-09-30 1997-04-16 Ricoh Kk Recording material, method of producing the same and method of recycling recording material
WO2020229215A1 (en) 2019-05-10 2020-11-19 Hauni Maschinenbau Gmbh Production of drinking straws from paper

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