NO761061L - - Google Patents

Abstract

Aid for the production of paper and cardboard.

Description

The invention relates to an aid, which alone or in a mixture with other water-soluble binders is used for the production of paper, cardboard, cardboard and cardboard with improved wet and dry resistance and/or with improved water resistance of the surface and which can be diluted without limit with water and is hardenable in the alkaline range and formed by condensation of an aminoplastic former, formaldehyde bg sulfamates in a molar ratio of 1 : 2.5 to 7 : 0.1 to 1.5 at temperatures between 80 and 120°C at a pH value between 7 and 11, condensation continues until a 50% resin content adjusted sample has a viscosity of at least 300 DIN seconds and a 2G% resin content adjusted sample has a viscosity of 300 DIN seconds maximum, measured at 20°C in 4 mm outlet cups as well as a method for the production of paper, cardboard, cardboard and felt with improved wet and dry resistance and/or with improved water resistance of the surface, where an aid according to the invention is added to the paper pulp in an amount of ra 0.5 to 5% by weight before sheeting or to the paper web or fiber web between sheeting and winding or on the finished paper or web in an amount up to 35%, referred to substrate. in the form of a 0.5 to 35% by weight solution, preferably 1 to 10%, possibly in a mixture with other water-soluble products.

It is already known that melarnine resins modified with sulphite can be used to improve paper strength properties (see e.g. DOS 2..301.035). It has also already been mentioned that these resins can be used to improve the wet and dry phase of paper, when they are applied from the surface of the paper

■ (e.g. with the help of the glue press). Such a procedure means

a significant advantage compared to the previous method, to make the melamine resin cationically active by adding considerable amounts of strong acids and allowing the mass to actively absorb the cellulose, as the saving of acid has a beneficial effect on durability

and firmness of the prepared paper and a waste water load are greatly reduced. However, it has been shown (compare e.g. Wochenblatt fur Papierfab. 17, 671/1973) that sulphite-modified•melamine resins can only be used according to this method when the paper contains a minimum content of aluminum sulphate, as the resins are only acid cured. This property, however, negates the aforementioned advantage of acid-free processing of the resins in practice, because aluminum sulphate clearly reacts with acid and gives the paper undesirable properties. The processing possibilities of the known sulfite-modified melamine resins in the glue press are further severely limited by the fact that the resins must have a relatively high degree of condensation to be effective. -However, this narrows down the applicable amount 'and thus also

the attainable firmness improvements, as the fast-running paper tap cannot absorb sufficient quantities of the viscous resin.

There is therefore a need for low-viscosity aids for paper, which can be applied through the surface and harden without the aid of acids or acidic salts.

It is also known (compare DOS 2.241.158.) that

one with melamine-formaldehyde resins in solutions containing surface adhesives, after drying not sufficiently water-resistant binders, such as e.g. starch, casein, polyvinyl alcohol, sodium carboxymethylcellulose, etc. can be made swell-resistant or waterproof. Previous designs of melamine-formaldehyde resins have for this application area a considerable disadvantage, that they are not sufficiently effective in the alkaline range. There is therefore a need for an aid to improve the water resistance of the agent for surface treatment of paper, which also in alkaline areas to approx. pH 11 still gives good values, for some important pulps for the surface treatment of paper run.alkaline. Hardenability in the alkaline range is therefore required for this area of application, while the viscosity of the curing agent itself does not play a decisive role, as the pulps for surface treatment of paper themselves have a relatively high viscosity. However, the known sulphite-modified melamine resins do not show the required hardening in alkaline areas to the desired extent.

It has now been shown that the existing requirements can be met in practice and the mentioned disadvantages of the known products can be avoided by using an aid to improve the wet and dry strength of paper, cardboard, cardboard and felt and/or to improve of water phase of the surface, the agent being obtained by condensation of an aminoplastic former, formaldehyde and sulfamates in, molar ratio 1 : 2.5 to 7 : .0.1 to 1.5 at temperatures between 80 and 120°C at a pH -value between 7 and 11, the condensation continuing until a sample adjusted to 50/5 resin content has a viscosity measured in a 4 mm DIN outlet cup of at least 300 DIN seconds and a sample adjusted to 20% resin content a viscosity of' a maximum of 300 DIN seconds, measured at 20°C in a 4 mm DIN outlet cup. This aminoplast resin according to the invention, which is used as an aid, is infinitely dilutable in water and hardenable in an alkaline range. As an aminoplastic former, a mixture of 75 to 100% by weight melamine and 0 to 25% by weight urea, dicyandiami or guanamine is used in the production of the aid according to the invention. Preferred auxiliaries according to the invention are obtained when melamine alone is used as the aminoplast former. Sodium sulfamate is preferably used as sulfamate in the condensation. Particularly advantageous products according to the invention are obtained when aminoplastic formers, formaldehyde and sulfamate are condensed in a molar ratio of 1:3>0 to 6:0.3 to 0.8. The condensation can be carried out in a technically particularly simple manner at temperatures between 80 and 100°C. Of particular importance for the chemical nature and the application technical properties is the degree of condensation of the aid according to the invention, characterized by its viscosity. Pre-production of the aid for surface treatment of paper, such as e.g. adhesive masses, it is in many cases advantageous when it is condensed until a to 20% resin content set aqueous solution of a sample at 20°C has a viscosity measured in 4 mm DIN outlet cup at least 12 DIN seconds.

The object of the invention is also a method

for the production of paper, cardboard, cardboard and nonwovens with improved wet and dry resistance and/or with improved water resistance of the surface, where a condensation product according to the invention, which is freely miscible with water and hardenable in an alkaline range, is added to the paper stock or .the paper tap or fiber web between sheet formation and winding or on the finished paper or web in an amount of up to 35% in the form of a 0.5 to 35% by weight solution, preferably 1 to 10%, optionally in a mixture with other water-soluble products. A special advantageous out-

embodiment consists in applying the condensation product according to the invention to the formed paper web in the glue press or in advance by e.g. spraying or with cardboard, before the different layers are caulked together, it being particularly preferred to apply the condensation product in the form of a 0.5 to 35% by weight solution, preferably 1 to 10%, possibly together with water-soluble products .

A particular advantage of the aid according to the invention lies in the fact that the agent can be applied after leaf formation over an application device, e.g. a glue press on the surface of the paper web and penetrates so well that there is an effect with regard to wet strength, at least when introduced into the mass. This has the advantage of an exceedingly good use, then. the agent is 100% incorporated into the paper and not, as with pulp addition, up to 20% is lost with the wire water. An introduction to

the mass after adjustment with acid to pH' 2-3 according to prior art is also possible for the new aid. The use of the aid according to the invention not only causes an increase in the wet breaking load of the paper produced according to the invention or similar products, but surprisingly also a strong increase in the wet breaking load with increasing added quantity, without a saturation value already being achieved with added quantities of 8%.

(see the diagram in example 1), Furthermore, an unusually strong increase in the dry breaking load and the dry pressure occurs when the aid according to the invention is used.

Special advantages are achieved through the combination

of the aid according to the invention with other water-soluble binders, such as starch or polyvinyl alcohol' in the pH range between 5 and 11, as up to 50% of the aid according to the invention can be used to achieve a certain wet strength with one of these water-soluble binders, without

■a decrease in the wet strength of the substrate occurs, also when the water-soluble binders are used alone, practically not

contributes to wet resistance. Furthermore, the dry strength achievable with the auxiliaries according to the invention can be improved by the addition of certain water-soluble binders, such as e.g. medium viscosity polyvinyl alcohol. Finally, the combination of the aid according to the invention with such water-soluble binders also achieves a clear improvement in dry strength and a reduction in water sensitivity of the surface and the thus treated substrate.

The % values mentioned in the following examples are percentages by weight.

Example 1.

a) Molar ratio 1:3:0.6 1848 g (24 mol) formaldehyde, 39%, is mixed with 20 ml of 2-N caustic soda, 1440 g (4.8 mol) of a 40% sodium sulfamate solution .sning and 1008 g (8 mol) melamine and condensed at 90°C and pH 10 for approx. 4 hours until another beIcetempera trip, cooled sample no longer flows. Now add 3600 ml of water and cool down.- You get a resin solution with a viscosity of 14 seconds, (measured at 20oC in a 4 mm DIN cup) and a resin content of 27%.

b) Molar ratio 1:3: 0.3

462 g (6 mol) formaldehyde, 39%~ig, are mixed with

5 ml of 2 N caustic soda, 180 g (0.6 mol) of a H0% ± g sodium sulfamate solution. and: 252 g (2 mol) melamine is condensed at pH 10 and 90°C for approx. 4 hours, until a sample cooled to room temperature no longer flows. Now add 900 ml of water and condense at 90°C again'approx. 2 hours until a sample at 20°C is mixed with the same amount of a 3% saline solution. just gives an obscurity. It is cooled to room temperature and a further 300 ml of water is added. A resin solution with a viscosity of 35 DIN seconds and a content of 22% is obtained.

c) Molar ratio 1:6:0.2

924 g (12 mol) formaldehyde, 39%, is mixed with 7 ml of 2 N caustic soda, 120 g (0.4 mol) of a 40% sodium sulfamate solution and 252 g (2 mol) melamine and condensed at 90°C and pH 10 for approx. 2 hours until a sample no longer floats at room temperature. Now add 1500 ml of water, cool and adjust with 0.6 ml of 10 N sodium hydroxide solution at pH 7 to 9. A 20% resin solution with a viscosity of 50 DIN seconds is obtained.

d) Molar ratio 1 : 6 : 0.1

924 g (12 mol) formaldehyde solution, 39%,

mixed with 10 ml 2 M caustic soda, 900 ml water, 60 g (0.2 mol) of a 40% sodium sulfamate solution and 252 g (2 mol) melamine<p>g condensed at 90°C and pH 10 in about. 2 hours until a sample cooled to room temperature no longer floats. 1400 ml of water must be added and, after cooling, the pH is adjusted with 2 N caustic soda to 9. You get a 20% resin solution with a viscosity of 14 DIN seconds.

e) .Molar ratio 1 : 2.5 : '1.5

385 g (5 mol) formaldehyde, 39%, is mixed with

10 ml of 2 N caustic soda, 900 g (3 mol) of a 40% sodium sulfamate solution and 252 g (2 mol) of melamine and condensed at pH 11 approx. 4 hours under reflux, until a sample cooled to room temperature no longer floats. Now add 900 ml of water and cool. Mån gets a 20% resin solution with a viscosity of 20 DIN seconds. Example 2.

Aqueous solutions of the condensation product formed according to example la) with 2, -5; 5.0]7.5'and 10.0%

active substance is applied over a glue press on a wood-containing paper, with a basis weight of approx. 55 g/m20g is dried with hot air at 140°C

in drying channel. Due to the residence time, the paper tap only achieves a dry content of approx. 95% when rolled up.

The following measurements were carried out on the thus treated paper and, for comparison, on untreated paper:

1. On the dried paper, it stayed on for 24 hours after storage

20°C and . 65%'relative humidity measured by the breaking load'longitudinally and

■across and the breaking pressure. In table 1, the measured values are designated as breaking load

along I, across I and burst pressure..

2. The paper was stored for 24 hours at 20°C and € 5% relative humidity and then for 1 hour in water of 20°C and on the wet paper the breaking load was measured longitudinally and transversely. In table 1, measured values are designated as breaking load along II and across

II.

3- The paper was heated for 10 minutes at 120°C, then stored for one hour in water at 20°C and on the wet paper the breaking load was measured longitudinally and transversely. In table 1, the measured values are designated as breaking load along III and across III.

Table 1 shows in clear form the measured mechanical strength values of the paper depending on the amount applied.

If, instead of the aqueous solutions of the condensation product formed according to example la), the corresponding condensation products produced according to examples le).Id) and le) are used, comparable results are obtained.

Example 5-

A filter paper (S+S no, 557) was impregnated with a solution according to example 1b) in a concentration of 20 g of active substance per liters by immersion. Thereby, the solution was each time with caustic soda resp. formic acid set to

a specific pH value to determine the effect of the aid according to the invention at different pH values. After impregnation, the paper samples were lightly air-dried and then finished drying over a steam-heated drying cylinder at .. 120°C until a residual moisture of 2 - ~ j>% and then for examination climate-tized at 20°C and 65% relative humidity .

The following 'wet breaking loads' were measured on the samples:

The surprising result of the agent according to the invention is the small drop in the measured values with increasing pH value. This determination is particularly important, because a large part of the solutions before the application in the glue press<.>'or,

in ironing units■above all in combinations with other products for reasons of compatibility, viscosity or stability had to be run alkaline.

If used instead of the aqueous solutions

of the condensation products formed according to example lb) and the corresponding condensation products produced according to examples le), ld) and le) comparable results are obtained.

Example 4.

On a wood-based paper with a -surface weight' of approx.

55 g/m 2 -one of the following solutions was applied in the same way as in example 2:-

Solution: I:-Aqueous solutions of medium viscosity pclyvinyl alcohol type with 1.0; 2.0; 3.0; 4.0% active substance

(pH 5.7).

Resolutions. II: Aqueous solutions thereof according to example

la) obtained condensation product with- 2,5-;

5.0; 7.5; 10.0% active substance (pH 9.0-9.3). Solutions III: Aqueous solutions of medium-viscosity polyvinyl alcohol, which contain solutions I and the condensation product formed according to example la), the concentration ratio between polyvinyl alcohol and condensation product each time being 1.0 : 2.5 and the total concentration of the resolution amounted to 3.5; .7.0; 10.5 and 14.0% (pH 9.1-8.6). ,

Resolutions IV: . Aqueous solutions of medium viscosity polyvinyl alcohol, as contained in solutions I

and according to example la) condensation product formed, - the concentration ratio between polyvinyl alcohol and condensation product each time being 1.0:1.0 and the total concentration of the solutions 2.0; .4.0; 6.0 and 8.0% (pH 8.6-8.0).

The papers were then dried as indicated in Example 2.

The paper thus treated was stored for 24 hours

at 20°C and 65% relative humidity and then 1 hour in water off

20°C and on the wet paper measured the breaking load longitudinally and transversely.

Diagrams 1 and 2 show the measurement results obtained depending on the type of solution applied and the amount applied, as well as measurement values for untreated paper.

Abbreviations and symbols in diagrams 1 and 2 have the following meaning:

NBL _/ kp/ = longitudinal wet breaking load.

NBQ l_ kp/- = wet breaking load across..

-2

M /_ gm _7 = applied amount of active substance - referred to

the weight of treated paper.

<*>.- = measurement point for resolution I.

x = measurement point for resolution II-

= measuring point for solution III,

O' = measurement point for resolution IV.

From these measurements, the good reactivity is apparent

of the auxiliary agent according to the invention with polyvinyl alcohol. Exchanging up to 50% of the condensation product according to example la) with polyvinyl alcohol, which in itself contributes little to water resistance, does not lead to a decrease in the high water resistance of the paper, which is achieved by treatment with the condensation product according to example la) alone.

Claims (24)

1. Auxiliary agent which alone or in a mixture with - other water-soluble binders serves for the production of paper, cardboard, cardboard - and felt with improved wet and dry resistance and/or with improved water resistance of the surface and which can be diluted without limit with water and is hardenable in the neutral and alkaline range, and formed by condensation of an aminoplast former, formaldehyde and_sulfamates in a molar ratio of 1 : 2.5 to 7 : 0.1 to 1.5 at temperatures between 80 and 120°C at a pH value between 7 and 11, the condensation continuing until a sample adjusted to 50% resin content has a viscosity of at least 300 DIN seconds and a sample adjusted to 20% resin content has a viscosity of 300 DIN seconds maximum, measured at 20°C in -i mm DIN outlet cup. 2. Aid according to claim 1, characterized in that a mixture of 75 to 100% by weight of melamine and 0 to 25% by weight of urea, dicyandiamine or guanamine is used as the aminoplast former during the condensation. . 3- Aid according to claims • 1 and 2, characterized '.ved. that melamine is used as the aminoplast former. 4. Excipient according to claims 1 to 3, k a'r-akterized' in that sodium sulfamate is used as sulfamate. 5- Aid according to claims 1 to 4, characterized in that it is condensed in a molar ratio of .1 : .3.0 to 6 : .3 to .8. 6. Aid according to claims 1 to 5, characterized in that it condenses at temperatures between 80 and 100°C-. 7- Aid according to claims 1 to 6, characterized in that it is condensed until the 20% aqueous solution of a sample at 20°C has a viscosity, measured in a 4 mm DIN outlet cup, of at least 12 DIN seconds. 8. Procedure for the production of an aid to. improvement of the wet and dry resistance of paper, cardboard, cardboard and cardboard and/or improved water resistance of the surface, characterized in that an aminoplastic former. fojrmaldehy_d and . sulfamate In a molar ratio of 1 : 2.5 to 7 : 0.1 to 1.5 is condensed at temperatures between 80 and 120°C at a pH value between 7 and 11, with the condensation continuing until a to 50% resin content set sample has a viscosity of at least 300 DIN seconds and a to 20% resin content set sample has a viscosity of a maximum of 300 DIN seconds, measured at 20°C in a 4 mm DIN outlet cup.' 9- Method according to claim 8, characterized in that a mixture of 75 to 100% by weight of melamine and 0 to 25% by weight of urea, dicyandiamide or guanamine is used as the aminoplast former during the condensation.- 10. Method according to claims 8 and 9, characterized in that the melamine is used as an aminoplast former. 11. Method according to claims 8 to 10, characterized in that sodium sulfamate is used as sulfamate. 12. Method according to claim 8 to. 11, characterized in that it is condensed in a molar ratio of 1:3.0 to 6:0.3 to 0.8. 13- Method according to claims 8 to 12, characterized in that - it is condensed at temperatures between 80 and 100°C. 14. Method according to claims 8 to 13, characterized in that it is condensed until the 20% aqueous solution of a sample at 20°C has a viscosity measured in a 4 mm DIN outlet cup, in at least 12 DIN seconds. 15- Process for the production of paper, cardboard, cardboard and fleece with improved wet and dry strength and/or with pre- improved water resistance' of the surface, characterized in that a condensation product formed by condensation of an aminoplastic former, formaldehyde and sulfamate in a molar ratio of 1: 2.5- to 7 : 0.1 to 1.5 at temperatures between 80 and 120°C at a pH value between 7 and 11, the condensation continuing until a sample adjusted to '50% resin content has a viscosity of at least 300 DIN seconds and a' to 20% resin content set sample has a viscosity of a maximum of 300 DIN- .seconds measured at 20°C in a 4 mm DIN outlet cup, is added to the paper pulp in an amount of 0.5 to 5% by weight of the sheeting or supplied to the paper tap or fiber web between sheeting and up <p> rolling or on the finished paper or -flour in an amount up to 35%, - referred to substrate, in form. of a 0.5 to 35% by weight solution, preferably 1 to 10%, possibly in admixture with other water-soluble products. 16. Method according to claim 15, characterized in that a condensation product is added or applied, the preparation of which as aminoplast uses a mixture of 75 to 100% by weight melamine and 0 to 25% by weight urea, dicyandiamide and guanamine-.. 17- Method according to claims 15 and 16, characterized in that a condensation product is added or applied, the production of which uses melamine as an amino plastic former. 18. Method according to claims 15 to 17, characterized in that a condensation product is added, if. preparation sodium sulfamate is used as sulfamate. 19- Method according to claim 15 to 18, characterized in that a condensation product is added or applied, during the preparation of which condensation is made in a molar ratio of 1:3.0 to 6:0.3 to 0.8. 20. Method according to claims 15 to 19/ characterized in that a condensation product is added or applied, during the production of which it is condensed at temperatures between 80 and 100°C. '21. Method according to claims 15 to 20, characterized in that a condensation product is added or applied, during the production of which it condenses, as long as the .20% aqueous solution of a sample at 20°C has a viscosity, measured in 4 mm DIN -outlet cup of at least 12 DIN seconds. 22. Method according to claims 15 to 21, characterized in that the condensation product is added to the paper pulp in an amount of 1 to 3% by weight. 23- Method according to claims 15 to 22, characterized in that the condensation product is applied in the form of a 0.5 to 35% by weight solution, optionally in addition to other agents for surface treatment of paper, at pH values from 5 to 11 on the paper web . 24. Method according to claim 23, characterized in that the solution of the condensation product, possibly together with other means for surface treatment of paper, is applied to the paper web.