DE1298406B - Process for the production of a paper coating slip based on protein - Google Patents

Description

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The invention relates to a method for washing out paper. Furthermore you can Production of a paper coating slip on casein - the masses lightly rolled to a smooth surface basis, especially for cast-coated and after, so that considerably lower calender roll remoistening temperature under pressure and elevated temperatures during the paper coating process dried glossy papers. 5 can be turned and thereby the original

One of the problems posed by a borrowed thickness, the gloss and the opaque casein coating process known paper with the trueness of the treated paper are retained, Zen production revealed, concerned the water solubility The protein, which is preferably from casein or

of the adhesive binder in the coating slip. The Er soy protein is made up of being expedient at or near Experience has shown that it is difficult to obtain a gloss io its isoelectric point in an aqueous Surface to be poured when the adhesive binder peptizes in medium containing 20 to 35% by weight of the Coating made water-soluble and in front of the proportion of protein and 4 to 10% by weight of salt Pouring has been dried. On the other hand, it must contain. The salt preferably consists of one Adhesive at any point during the alkali metal or ammonium salt of a vigorous Be made very water-soluble, if not a monobasic acid, and preferably must be a the finished product by water during the gel pH 4.5 to 7 in a 5% aqueous needs to be too easily attackable. Have a solution solution. Especially good for this purpose this problem was that the paper had suitable salts are ammonium and alkali metals Pour paint and if the paper in nitrates.

Entering the pouring gap, insoluble chemicals enter the 20 by heating the aqueous mixture of egg-rewetting solution white at the pouring gap and salt to over 60 ° C, d. H. to 80 to 95 ° C, to lead. Such a process has proven, in part, to be very rapid peptization. In the case of Successfully proven, one of its main drawbacks to casein seems to be protein in about 20 minutes however, that the liquid in the th dissolve. It also turned out Pouring gap tends to be a significant part of the 25 that adding a small amount to it Wash out the coating, using the washed-out water-soluble soap based on sebum (less than Part economically not withdrawn again 10% parts by weight based on casein) the peptisies become can. In order to also support an acceptable grading process. The soap is allowed, however The smoothing of the usual coating slip surfaces does not result in a display of the pH value above 7 by calendering without breaking the base material. Use a viscosity reducer to achieve the paper must be dried to remove the agent such as dicyandiamide the fibers in the base material are furthermore desirable.

To give firmness, which makes it the pressure of the salt peptized protein is generally considered

Can withstand calender roll. Generally clear liquid is present. By diluting it with sufficient to dry the paper in air to about 35% water, so that the salt con-4% moisture for this purpose falls, and the concentration falls substantially below 4%. When this is done, a calender deposition is smoothed out further by lowering the roller pressure from about 35,000 kg / m ² in general temperature to below 60 ° C. If that is enough, salt-peptized egg whites at an elevated temperature of the base material are sufficient for the coating slip surface without breaking. On the other hand, if 40 is held, it is prone to hydrolysis, thus earlier calendering is precipitated due to the excessive pressure required for coating shortly after peptization and materials to lower the temperature as well. In order to reduce the result that the thickness, the gloss and the light effects of the hydrolysis, the impermeability of the paper is reduced same time receives ... dejected to a coating according to the

The purpose of the invention is to provide this invention. The filler becomes preferable disadvantages to avoid. According to the invention, this is converted into an aqueous slurry which This is achieved by adding a protein-containing binding agent to the salt-peptized protein with constant stirring Medium, especially casein or soy protein, is added at 50. After that, the sharp temper caused neutral or acidic electrolytes, such as pre-temperature drop along with the dilution of the preferably sodium or ammonium nitrate, or salt-peptized protein through the water in the porridge near its isoelectric point, when heated, immediately a gelation of the egg white and / or a peptized above 60 ° C in a known manner, the precipitation and also a flocculation of the filler salt peptized Egg white with a standard aqueous 55-medium porridge. This will make the whole mix Bulking agent slurry to form a relatively stiff and difficult to stir. Will the stiffening Mixture mixed and then continued for so long, however, so the mixture gradually begins to stir until the mixture is so runny again to loosen up. After which the stirring is that it has been continued on a paper web by means of a stroke of a few minutes, the Device for the purpose of a subsequent drying mixture suddenly thin and completely liquid, voltage can be applied. Under the term It can be any conventional filler in the

"Salt-peptized protein" is understood to mean a protein, spreadable paste can be used. As useful Beidas by a salt at a pH value of 7 or games are named: clay, calcium carbonate, barite less peptized. white, talc and titanic acid.

A paper containing salt-peptized protein. The resulting coating slip has a Coating slips have a significantly reduced, astonishingly low viscosity, which is an off-water solubility and as a result, overdrawn binders for coating slips can become a problem not during the coating process from the turn with an air knife smoothing device

gives. In addition, there is the water retention of the liquid paint composition prior to painting very low, and the rate of water absorption of the finished, dried coating is high. The composition is also unusually pliable and can thus be reduced Pressing by calender rolls without a significant reduction in thickness, gloss and / or the opacity of the coated sheet can be smoothed. The composition is special useful for roller coating, since the precipitated salt-peptized coating, although it is water-insoluble, can be poured well, while at the same time it has a strong resistance to it opposed to washing out when it is passed through a rewetting bath at the pouring gap passes through during the casting process.

The coating composition can also contain other common ingredients, such as antifoam and release agents, as well as latex ao or other polymeric substances, usually contain are used in paper finishing processes.

The following exemplary embodiments are intended to explain the invention.

example 1

The following ingredients are mixed in the following proportions (parts by weight).

180 parts of water (at 82 ° C), 60 parts of casein,
12 parts of ammonium nitrate,
12 parts of dicyandiamide,
V22 part of soap (based on sebum).

35

The mixture has a pH of approximately 5.0. After stirring for about 20 minutes, during which the temperature gradually decreased to 60 ° C, the solution became quite clear and had slightly yellowish shades. In this condition the casein is likely to be essentially peptized.

This solution of peptized casein became at a temperature of about 60 ° C approximately 400 parts of clay and 400 parts of water at room temperature are added pulp, and the Mixture was stirred vigorously. The slurry became stiff and viscous, and became 2 or 3 minutes further stirring continued with great difficulty. But then the paste began to thin and became completely free and fluid.

In this condition the material was ready to be painted, and while it was believed that the When the casein was precipitated, the mixture was relatively free and without lumps. If on the other hand when these ingredients were painted on paper and examined microscopically, the appearance was essentially more granular in nature and not as smooth as a coating using alkaline dispersed casein. However, after the coating was calendered, the granular disappeared Appearance, and the coating was microscopically similar to conventional coating using alkaline dispersed casein.

B is ρ ie 1 2 _g

The same ingredients were used as in Example 1 with the exception that both Soap and dicyandiamide were omitted.

The casein was more difficult to peptize without these ingredients, but with continued vigor Stirring peptized the casein in about 30 minutes. The solution thus obtained was then with mixed with the same slurry as in Example 1 and stirred until it became free-flowing, and the one thus obtained Mass was used to paint the paper.

Example 3

The same procedure as in Example 1 was used except that the level of soap in of the casein-containing mixture was increased to approximately 1%. This mixture peptized a little faster and after combining with the clay it resulted in a coating which is especially suitable for a Hot calendering under light pressure worked well.

Example 4

In this example, the following ingredients were mixed in the following proportions by weight.

180 parts of water (at 82 ° C),
60 parts of casein,
12 parts of sodium nitrate.

The casein peptized in about 30 minutes on constant heat and vigorous stirring. One Coating slip was then prepared as in Example 1 and used to coat the paper.

The coating slip produced by the new process is suitable for every coating process. Particularly it is suitable for cast-coated and after remoistening under pressure and elevated temperature dried glossy papers, because they cannot be washed out if they are rewetted.

It is known to use various alkaline materials to dissolve casein. In an alkaline However, dissolved casein material does not gel like salt-peptized protein does. As a result, are these materials are not suitable for coating slips, especially not for those that require rewetting occurs and there is a risk of washing out.

Claims (2)

Patent claims: 1. Process for the production of a coating slip based on protein, especially for cast-coated ones and glossy papers that have been dried after remoistening under pressure and at increased temperature, characterized in that a protein-containing binder, in particular casein or Soy protein, with a neutral or acidic electrolyte, such as preferably sodium or Ammonium nitrate, at or near its isoelectric point with heating to over 60 ° C in Peptized in a manner known per se, the salt-peptized egg white with a conventional aqueous filler paste to form a relatively stiff mixture and then further agitating so long that it is on a paper web be applied by means of a coating device for the purpose of subsequent drying can. 2. The method according to claim 1, characterized in that the protein in an aqueous Medium with 20 to 35% parts by weight protein and 4 to 10% parts by weight salt S 6 is peptized and is precipitated by reducing the salt concentration 4. Method according to one of the preceding tration. Claims, characterized in that wäh-3. A method according to any one of the preceding rend of peptizing the protein a viscosity claims, characterized in that a micro-reducing agent is present.
ner amount of water-soluble soap based on sebum 5 5. The method according to claim 4, characterized in that the peptization of the protein voran indicates that the viscosity is the. Agent composed of dicyandiamide.