NO811763L - AIDS FOR PREPARATION OF PAPER AND PAPERBOARD. - Google Patents

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 paperboard with improved . wet and dry fastness and/or with improved water fastness of the surface and which is unlimitedly dilutable with water and is curable in the alkaline range and formed by condensation of an aminoplastic 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 set 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 4 mm outlet cups as well as a method for the production of paper, cardboard, cardboard and flour 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 pulp in one quantity'

from 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 the 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 melamine 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 strength of paper, when they are applied from the surface of the paper (e.g. using the glue press). Such a method 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 pulp to actively absorb the cellulose, as the saving of acid has a beneficial effect on the durability and firmness of the finished paper and a waste water load is 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. However, this property negates the aforementioned advantage of acid-free processing of the resins in practice, as aluminum sulphate reacts clearly more acidic and gives the paper undesirable properties. The processing possibilities of the known sulfite-modified melamine resins in the iimpressen are further severely limited by the fact that the resins must have a relatively high degree of condensation to be effective. However, this narrows the applicable quantity and thus also

the. attainable strength improvements, as the fast-running paper tap cannot absorb sufficient amounts of the viscous resin pitch.

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

The. is also known (compare DOS 2.2^1.158) that

with melamine-formaldehyde resins in solutions to surface-gluing-containing, after drying insufficiently water-resistant binders, such as, for example, starch, casein, polyvinyl alcohol, sodium carboxymethyl cellulose, etc., can be made swell-resistant or water resistant. 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 are run alkaline. Hardenability in the alkaline range is therefore required for this area of application, while the auxiliary agent's own viscosity does not play a decisive role, as the pulps for surface treatment of paper themselves have a relatively high viscosity. However, the known sulfite-modified melamine resins do not exhibit 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 resistance of paper, cardboard, cardboard and felt and/or to improve water resistance of the surface, as the agent is obtained by condensation of an aminoplastic 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, with condensation continuing until a sample set to 50% resin content has a viscosity measured in !J mm DIN outlet cups of at least 300 DIN seconds and a sample set to 20% resin content has a viscosity of a maximum of 300 DIN seconds, measured at 20 °C in 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. A mixture of 75 to 100% by weight melamine and 0 to 25% by weight urea, dicyandiami or guanamine is used as an aminoplast former 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 aminoplastic 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 way at temperatures between 80 and 100 PC. The degree of condensation of the aid according to the invention, characterized by the viscosity. For the production of the aid for the surface treatment of paper, such as e.g. adhesive masses, it is advantageous in many cases when it is condensed until a to 20% resin content adjusted 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.

The object of the invention is also 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 a condensation product according to the invention, which is freely miscible with water and hardenable in the alkaline range, is added to the paper pulp or 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%, possibly in mixing with other water-soluble products. A particularly advantageous 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 by 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 auxiliary agent according to the invention lies in the fact that the agent can be applied after leaf formation

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 pulp. This has the advantage of an extremely good use, as the agent is incorporated 100% into the paper and not like wood. pulp addition is lost up to 20% with the wire water. An introduction into 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 manufactured according to the invention or similar products, but surprisingly also a strong increase in the wet breaking load with increasing added quantity, - without the fact that with addition quantities of 8% a saturation value is already achieved (see the diagram in example 1), - Furthermore, there is an unusually strong increase in the dry breaking load and the dry pressure when using the aid according to the invention.

Special advantages are achieved through the combination

of the aid according to the invention with other water-soluble binders, such as e.g. 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 with one of these water-soluble binders to achieve a certain wet strength, without a decrease in the wet strength of the substrate occurring, even when the water-soluble binders used alone practically do not contribute to wet strength. Moreover, it allows with the aids

according to the invention obtainable dry strength 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 and 1008 g (8 mol) melamine and condensed at 90 °C and pH 10 for approx. 4 hours until a sample cooled to room temperature no longer floats. Now add 3600 ml of water and cool. A resin solution is obtained 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 40% sodium sulfamate solution and 252 g (2 mol) of melamine are condensed at pH 10 and 90°C for approx. 4 hours, until a sample cooled to room temperature no longer floats. Now add 900 ml of water and condense at 90°C again approx. 2 hours until a sample at 20°C

■mixed with the same amount of a 3% saline solution just gives a cloudiness. 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 caustic soda at pH 7 to 9 - You get a 20% resin solution with a viscosity of 50 DIN seconds.

d) Molar ratio 1:6: 0.1

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

mixed with 10 ml of 2 N caustic soda, 900 ml of water, 60 g (0.2 mol) of a 40% sodium sulfamate solution and 252 g (2 mol) of melamine and condensed at 90°C and pH 10 for approx. 2 hours until a sample cooled to room temperature no longer floats. Now add 1400 ml of water and, after cooling, adjust the pH. 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) 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. You get 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 a drying channel. Due to the residence time, the paper tap only achieves a dry content of approx. 95% when rolled up.

On the thus treated paper and for comparison on untreated paper, the following measurements were carried out: 1. On the dried paper, after storage for 24 hours at 20°C and 65% relative humidity, the longitudinal and transverse breaking load and the breaking pressure were measured.

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

2. The paper was stored for 24 hours at 20°C and 65% relative humidity and then for 1 hour in water at 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 prepared according to examples le)', ld) and le) are used, then comparable results are obtained.

Example 3-

A filter paper (S+S no. 557) was impregnated with a solution according to example lb) 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 air-conditioned for examination 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 had to be run alkaline before application in the glue press or in ironing units, above all in combinations with other products for reasons of compatibility, viscosity or stability.

If, instead of the aqueous solutions of the condensation products formed according to example lb), the corresponding condensation products produced according to examples lc), ld) and le) are used, comparable results are obtained. Example 4.

On a wood-based paper with a basis weight of approx.

p

55 g/m, one of the following solutions was applied in the same way as in example 2: Solution: I:--Aqueous solutions of a medium-viscosity polyvinyl- alcohol type with 1.0; 2.0; 3.0; 4.0% active ingredient

(pH 5.7).

Solutions II: Aqueous solutions of the condensation product obtained according to example la) with 2.5;

5.0; 7.5; 10.0% active substance (pK -9.0-9.3). Solutions III: Aqueous solutions of medium-viscosity polyvinyl alcohol, which contain in 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). Solutions IV: Aqueous solutions of medium-viscosity polyvinyl alcohol, which were contained in solutions I and according to example la) formed condensation product; the concentration ratio between polyvinyl alcohol and condensation product each time being 1.0 : 1.0 dg 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 for 1 hour in water of

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 meanings:

NBL l_ kp_7 = longitudinal wet breaking load.

NBQ l_ kp_/-' = transverse wet breaking load.

-2

M L Sm _ J~applied amount of active substance referred to

the weight of treated paper.

= measurement point for solution I.

x = measuring point for resolution II.

= measurement point for resolution III.

o = measurement point for dissolution IV.

These measurements show the good responsiveness

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 (10)

1. Process for the production of paper, cardboard, cardboard and nonwovens with improved wet and dry resistance and/or with 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 sample adjusted to 20% resin content has a viscosity of a maximum of 300 DIN seconds measured at 20°C in a 4 mm DIN outlet cup, the papi.r pulp is added .i. an amount of 0.5-5% by weight of sheeting or is added: to the paper tap or fiber between sheeting and winding or on the finished paper or sheet in an amount up to 35%, referred to substrate, in form of a 0.5-35 wt-JJ-ig solution, preferably 1-1Q#-ig, optionally in a mixture with other water-soluble products. 2. Method according to claim 1, characterized in that it is added or applied: a condensation product, whose production as aminoplast uses a mixture of 75-100 wt.t-# melamine and 0-25 wt-% urea, dicyandiamide and guanamine . 3. Method according to claims 1 and 2, characterized in that a condensation product is added or applied, in the production of which melamine is used as an aminoplastic former. 4. Process according to claims 1-3, characterized in that a condensation product is added, in the preparation of which sodium sulfamate is used as sulfamate. 5- Method according to claims 1-4, 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. 6. Method according to claims 1-5, characterized in that a condensation product is supplied or applied, during the production of which it is condensed at temperatures between 80 and 100°C. 7. Method according to claims 1-6, characterized in that a condensation product is added or applied, during the preparation of which condensation is carried out until the 20% aqueous solution of a sample at 20 ft.C has a viscosity, measured in H mm DIN outlet cup in at least 12 DIN seconds. 8. Method according to claims 1-7, characterized in that the condensation product is added to the paper pulp in one quantity. of 1-3% by weight. 9. Method according to claims 1-8, characterized in that the condensation product is applied in the form of a 0.5-35% by weight solution, possibly in addition to other agents for surface treatment of paper, at pH values from 5-11 on the paper tap. 10. Method according to claim 9, characterized in that the solution of the condensation product, possibly together with other means for surface treatment of paper, is applied to the paper tap.