EP0116653A1 - Process for the production of a metal soap layer as an antifriction layer on a metallized registration support - Google Patents

Abstract

A sufficiently thick gliding layer is produced on the recording surface of a record carrier of the type comprising an aluminum layer applied over a lacquer layer coated on a support layer. The back surface of the support layer is also coated with a lacquer layer. A fatty acid or a mixture of fatty acids is admixed with one of the two lacquer layers and a metal-diketone or a metal-keto-ester is admixed with the other lacquer layer in approximately in a stoichiometric ratio to the fatty acid. Following the coating of the material with aluminum in a vacuum, the record carrier material is wound into a roll, and stored.

Description

The invention relates to a method for producing a sufficiently thick sliding layer on the surface of an aluminum layer of a recording medium lying over a carrier layer and a lacquer layer, the back of which is also coated with a lacquer layer, in which at least one of the two lacquer layers admixes a fatty acid or a mixture of fatty acids becomes.

Such a method and its further development are known per se from DE-A-3 007 331 and the DE-A-3 011 591, DE-A-3 040 485 and in particular DE-A 3 040 513 based thereon.

It is based on the basic idea that, by adding a fatty acid, an at least partial formation of a metal soap on the surface of a metallized recording medium is brought about. For this purpose, a fatty acid, for example oleic acid, has been introduced, for example during the vapor deposition or after vapor deposition of the aluminum onto the support material, and the vapor pressure of the fatty acid has been used to control the degree of conversion of the metal layer and thus the thickness of the metal soap layer produced.

The invention now takes a completely different route. It has been shown in extensive tests that it would be desirable not only to be able to influence the thickness of the sliding layer to be produced, but also to achieve a compact metal soap layer and which seemed particularly important to also influence the reaction time. In connection with this, it appeared desirable to become independent of the metal of the metal layer.

This object on which the invention is based is achieved in that, before the aluminum layer is applied, 0.5 to 2% by weight of an oligomeric fatty acid, based on the wet lacquer, is added to one of the two lacquer layers, and 0.1 to approx. 3% by weight of a metal diketone or a metal keto ester is admixed, the hydrogen form of which has a clear keto-enol tautomerism and that after the material has been coated with aluminum in a vacuum, the recording medium is wound up into a roll and is stored. The two components can be added in a stoichiometric ratio.

Further embodiments of the invention can be found in the subclaims.

The invention will now be explained in greater detail on the basis of exemplary embodiments in connection with corresponding technical considerations, with a drawing to clarify the invention.

The drawing shows a partial sectional view of a recording medium wound into a roll, in particular two superimposed sections of a recording medium, consisting of a substrate 1, e.g. made of paper, a front lacquer layer 2, a metal layer 3 and a rear lacquer layer 4.

These two tracks of the record carrier are so close together that there is an intimate contact between them the metal layer of the bottom sheet and the back coat layer of the top sheet.

If now the two lacquer layers according to the invention, for example, on the one hand with 0.1 to 1 wt.% Ca acetylacetonate or 0.5 to 2 wt.% Of a fatty acid consisting of about 80 to 90% dimer and 20 to 10% trimer or Tetramer are mixed, then diffusion of the two components in the opposite direction leads to mixing and thus to a reaction between the fatty acid and the metal complex.

A typical dimeric fatty acid has the following formulas

This fatty acid is converted into the desired metal soap with the aid of a metal diketone or a metal keto ester, the hydrogen form of which shows a clear keto-enol tautomerism.

In this connection, however, it must be pointed out that, when the oligomeric fatty acid is contained in the front lacquer layer, a certain reaction of the fatty acid with the aluminum already takes place during the evaporation with aluminum in a vacuum, even if to a small extent to form an aluminum soap , as already described in the aforementioned DE-A-3 007 331.

In contrast to this, in the method according to the invention the metal component is essentially not removed from the vapor-deposited metal layer, but rather from the metal complex admixed with the lacquer layer. The formation of the sliding layer is thus concentrated on the surface of the metal layer, which preferably consists of aluminum.

These processes will now be considered in more detail in their most general form.

• Diese Reaktion wird noch durch die Tautomerie mit dem -stabilisierenden Resonanz-Effekt und durch die Wasserstoff-Brücken begünstigt. Die treibende Kraft der Reaktion zur Seifenbildung ist nämlich das Bestreben der Metallsalze der Diketone, ein Wasserstoffatom gegen das Metall auszutauschen, um die stabile Enolform zu erreichen.

The following is important:

• This reaction is further promoted by the tautomerism with the stabilizing resonance effect and by the hydrogen bridges. The driving force behind the soap-forming reaction is the tendency of the metal salts of the diketones to exchange a hydrogen atom for the metal in order to achieve the stable enol form.

• Acetylaceton steht mit seiner tautomeren Form in folgendem Gleichgewicht:
  

This should be explained using the example of Na acetylacetonate:

• With its tautomeric form, acetylacetone is in the following equilibrium:
  

When combined with sodium, both stabilizing effects are eliminated:

In fact, the alkali salts of acetylacetone are the least stable, with the stability increasing in this order:

Na, K, Ca, Ba, Mg, Al, Cu, Mn, Cr, ... Rh other heavy metals such as Co, Zn, Fe, Pb and Mo, V, Zr, Ti.

wobei die Pfeile eine kovalente Bindung darstellen.The divalent heavy metals form chelates, which are far more stable:

the arrows represent a covalent bond.

The metal salts of acetylacetone (2,4-pentanedione) are not the best in terms of an optimal reaction for soap formation. The choice of metal and _E is nolverbindung depending on the manufacturing process of the paper and is based on the following criteria:

desto stabiler der Metallkomplex.1. The higher the tautomerism constant

the more stable the metal complex.

ein K_T = 6 . 10^-2, woraus folgt, daß nur 7 % dieser Enolform bei Zimmertemperatur vorliegen.For example, the acetoacetic ester

a K _T = 6. 10 ^-2 , from which it follows that only 7% of this enol form is present at room temperature.

In contrast, the acetylacetone has a K _T = 3.6, which gives 82% of the enol and 12% of the β-diketone.

If you wanted to produce an Al soap on the Al paper, the Al acetoacetic ester would be a less stable complex than the Al acetylacetonate. The lower the stability of the metal complex, the faster the soap formation and the more the reaction equilibrium shifts to the right side of the reaction equation.

f Because of the lower stability of the Al-Acetoacetic ester, this compound should in principle deliver better results.

However, if you want to use acetylacetone for technical reasons, you should choose a metal that provides a less stable complex, ie, a Metal that is to the left of Al in the stability series mentioned above.

• wobei R_Fettsäure außer ölsäure, Steanrinsäure etc. auch die eingangs erwähnte dimere und trimere ungesättige Fettsäure sein kann und
• R₁ und R₂ eine aliphatische Kette, ein Benzolring, ein zyklischer Ring oder ein Ester-Rest sein kann.

2. The formation of the metal soap follows the following reaction:

• where R _{fatty acid in} addition to oleic acid, steanric acid etc. can also be the dimeric and trimeric unsaturated fatty acid mentioned at the outset and
• R ₁ and R _{2 can be} an aliphatic chain, a benzene ring, a cyclic ring or an ester radical.

This reaction equation is shown abbreviated as:

The thermodynamic equilibrium of this reaction depends on the size of the equilibrium constant K:

Even in the case of a very low value of K, the reaction equilibrium can be shifted further to the right by the component D, i.e. the free enol compound, disappearing from the reaction zone (separating surface between the Al front side and the back side of the paper) and thereby forcing further metal soap formation. This is achieved by high diffusion or high volatility of this component.

A higher yield of metal soap is therefore to be expected in the case of a metal complex with a symmetrical diketone such as 3,5-heptanedione (dipropionylmethane) and its boiling point of 47 C, than with an unsymmetrical such as 2,4-heptanedione, 83.6% Enol form, with its boiling point of 174 ° C:

The following table is intended to show some other suitable ends as a decision aid for the choice of the metal complex:

An advantageous embodiment of the invention results when Ca acetylacetonate (melting point 175 ° C.) and oligomeric fatty acids are used. Both are commercially available and are available in a purity of at least 99%.

• 1. Metallsalze der ß-Diketone sind quellbar bis löslich in organischen Lösungsmitteln und darin genügend stabil.
• 2. Im Gegensatz zu vielen metallorganischen Verbindungen sind die Metallsalze der Keto-Enole nicht selbstentzündlich und schwer entflammbar.
• 3. Die Reaktionszeit bzw. Bildungsdauer der Metallseifen läßt sich steuern durch geeignete Wahl des Enols und evtl. des Metalls, wodurch technische Erfordernisse optimal erfüllt werden können. Allerdings kann nur ein solches Metall verwendet werden, das eine gute Seife ergibt: Ca, Ba, Al, Na, etc.
• 4. Die Reaktionszone läßt sich im wesentlichen auf die Oberfläche der Trennfläche zwischen dem aufgedampften Al und der Rückseitenlackierung beschränken.
• 5. Es können ziemlich dicke und kompakte Seifenschichten erzeugt werden, so daß der Gleiteffekt auf der Al-Oberfläche wesentlich verstärkt wird, nicht zuletzt deshalb, weil es möglich ist, die oligomeren Seifen nachzupolymerisieren. Dies läßt sich durch die Zugabe einer Manganseife in Form von Palmitat oder Stearat zum Rückseitenlack in einer Menge von 0,1 bis 0,5 % der Naßlackmischung erreichen. Die Mn-Seife wirkt hier als Vernetzungs- oder Polymerisations-Katalysator. GE 983 002

This procedure has the following advantages:

• 1. Metal salts of the ß-diketones are swellable to soluble in organic solvents and are sufficiently stable therein.
• 2. In contrast to many organometallic compounds, the metal salts of the keto enols are not self-igniting and flame-retardant.
• 3. The reaction time or duration of formation of the metal soaps can be controlled by a suitable choice of the enol and possibly the metal, as a result of which technical requirements can be optimally met. However, only a metal can be used that gives a good soap: Ca, Ba, Al, Na, etc.
• 4. The reaction zone can essentially be limited to the surface of the separating surface between the vapor-deposited Al and the rear coating.
• 5. Quite thick and compact soap layers can be produced, so that the sliding effect on the Al surface is significantly increased, not least because it is possible to post-polymerize the oligomeric soaps. This can be achieved by adding a manganese soap in the form of palmitate or stearate to the back coat in an amount of 0.1 to 0.5% of the wet paint mixture. The Mn soap acts here as a crosslinking or polymerization catalyst. GE 983 002

Claims (5)

1. A method for producing a sufficiently thick sliding layer on the surface of an aluminum layer of a recording medium lying over a carrier layer and a lacquer layer, the back of which is also coated with a lacquer layer in which at least one of the two lacquer layers is admixed with a fatty acid or a mixture of fatty acids, characterized in that 0.1 to about 3% by weight, based on the wet paint _{j, of} a metal diketone or a metal keto ester is admixed approximately in a stoichiometric ratio to the fatty acid or the mixture of fatty acids, wherein the hydrogen form of the metal complex has a clear keto-enol tautomerism and that after the material has been coated with aluminum in a vacuum, the recording medium is wound up into a roll and stored. 2. The method according to claim 1, characterized in that an oligomeric fatty acid is used as the fatty acid, which consists of 80 to 90% of dimer, the rest of trimer and tetramer. 3. The method according to claim 1, characterized in that the oligomeric fatty acid is added to the front coating and the metal diketone to the back coating. 4. Process according to claims 1 to 3, characterized in that the dimer and the trimer of linoleic acid or octadecadienoic acid are used as the oligomeric fatty acid and the calcium acetylacetonate is used as the metal complex. 5. The method according to any one of claims 1 to 4, characterized in that the wet coating mixture 0.1 to 0.5% did a manganese soap in the form of _P or almi- stearate is admixed.

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