DE1494469B - Ni tr o ce Hu lose lacquer - Google Patents

Description

The invention relates to antistatic film-forming nitrocellulose lacquers and their application to plastic films.

Nitrocellulose lacquers are made up of non-volatile components that are in a volatile solvent are resolved.

It is already known to use plastic films such. B. polypropylene films, with a coating of nitrocellulose lacquer to form a heat-sealable composite film to provide. With the known lacquers, however, the composite film can be slightly electrostatic in use Obtain charges when they z. B. treated and processed with conventional packaging machines will. This property is disadvantageous because it makes handling of the film more difficult, as it then tends to adhere to other objects, stick together and attract dust. The acquired charge is also a possible source of sparks that could cause the solvent vapors to dissolve ignite when the coated film dries.

So far there are no known antistatic agents that can be added to cellulose lacquers, without the paint application suffering as a result. Surfactants, which so far in connection used with other materials and to which nitrocellulose emulsions have also been added generally not soluble in a nitrocellulose lacquer solution. If they are soluble, have them they have undesirable properties in the paint solution. For example, ionic surfactants have Agents including quaternary ammonium compounds and such surface active agents as Contain fatty acid residues that have more than 18 carbon atoms, a low solubility in nitrocellulose lacquer solutions. As a result, the nitrocellulose lacquer films so produced have a dull appearance, and the paint solutions do not spread well because they are greasy. Nonionic Surfactants have no antistatic effect on nitrocellulose paints.

The antistatic agents used in the nitrocellulose lacquers according to the invention are ionic Compounds which contain solubilizing groups in their molecular structure. Because of the solubility These, compounds in nitrocellulose lacquer solutions, it is possible to coat with such nitrocellulose lacquers produce that have an antistatic effect without affecting the clarity of the paint application suffers.

The invention thus relates to the use of ammonium or primary or secondary alkanolamine salts of alkyl sulfates or alkyl sulfonates with at least 8 carbon atoms in the alkyl radical as Antistatic agents in nitrocellulose paints.

The antistatic agent may conveniently be an ammonium or ethanolamine salt of an alkyl sulfate or alkylbenzenesulfonate in which the alkyl group contains at least 8 carbon atoms.

Suitable antistatic agents are ethanolamine laury Isulfate, ammonium lauryl sulfate, ammonium cetyl sulfate, ammonium stearyl sulfate, ethanolamine cetyl sulfate, Ethanolamine dodecylbenzenesulfate and ethanolamine stearyl sulfate. The paint suitably contains 5 to 20 parts of the antistatic agent per 100 parts of nitrocellulose.

The use of these antistatic agents in the nitrocellulose lacquers gives the coatings antistatic properties, and there is also an improvement in the "slip properties", d. This means that the films coated with the lacquer are more easily against each other or against other surfaces, such as

z. B. slide the metal parts of a processing machine, for example a packaging machine. The clarity of a lacquer is usually not impaired. However, if the long-chain alkyl group of the antistatic agent contains more than 15 carbon atoms, the paint coating may become invisible. The resulting cloudiness can be reduced by letting the paint solvent evaporate at an elevated temperature. The haze can also be reduced further by adding an amount of water to the paint that is one to three times the weight of the antistatic agent. One can expediently dissolve the antistatic agent in the water.
Nitrocellulose lacquers that contain a long-chain alkyl sulfate ammonium salt have, compared to nitrocellulose lacquers that contain the corresponding ethanolamine salt, an improved lubricity and also better so-called blocking properties, that is, several superimposed, z. B. film layers wound on top of one another have a lower tendency to stick to one another during prolonged contact, especially at elevated temperatures or under elevated pressure. On the other hand, the ethanolamine salts are superior to the corresponding ammonium salts in terms of antistatic effect. It may therefore be advantageous to use an antistatic agent consisting of a mixture of ethanolamine and ammonium salts in order to obtain paints that have good blocking and slip properties as well as good antistatic properties.

The slip properties of a lacquer improve as the length of the long-chain group increases of the antistatic agent, however, the solubility of the antistatic agent in the paint solution decreases accordingly Dimensions and is undesirably small when the alkyl chain contains more than 15 carbon atoms. It has been found that, however, the solubility of an antistatic agent with a very long Alkyl chain can be increased by having it with a relatively shorter alkyl chain containing antistatic agent is mixed up.

It is therefore advantageous to use mixtures of antistatic agents with alkyl chains of different lengths and the antistatic agents need not necessarily be salts of the same amine. Antistatic agents such as B. ammonium stearyl sulfate or its mixture with ethanolamine stearyl sulfate, which contain very long alkyl groups and

• 55 are therefore sparingly soluble in paints at room temperature, but paints can be added to form a homogeneous medium by mixing the antistatic agent with an excess of water and the resulting mixture in the paint solution to form a water-in-oil Emulsion is dispersed. 3 to 30, preferably 10 to 20 parts of water are advantageously used per part of the antistatic agent.
Such an emulsion can be applied at room temperature or at just a slightly elevated temperature. To achieve clear layers, however, the volatile constituents from the emulsion must be removed at elevated temperatures, e.g. B. at 70

up to 110 ° C. The clarity of these paints is also improved if the paint is solvent a small amount of high-boiling solvent is added.

The nitrocellulose lacquers of the invention are heat sealable, although by being antistatic Means the weld strength is reduced. This reduction in weld strength one on one However, varnish applied to polypropylene film can be sufficiently compensated by using the spray discharge treatment the film to be welded is reinforced before the paint is applied.

The lacquers, which are particularly suitable as heat-sealable coatings for polypropylene films, contain Nitrocellulose and plasticizer preferably in a ratio of 10: 5 to 10:15, where at least 50 percent by weight of the plasticizer should consist of normally solid material (See British Patent 985 291). The varnish should also preferably be an isocyanate compound contain, which has several isocyanate groups in its molecule. Through such a connection the adhesion of the paint to a polypropylene film as well as its welding strength is strengthened. Man can also use other modifiers, such as. B. Resin, agents that improve lubricity ("slip agents"), and agents that prevent unwanted "baking" of several foils ("blocking agents"), add to the paint.

According to a further feature of the invention, a plastic film, such as. B. a polypropylene film, provided at least on one side with a coating of a nitrocellulose lacquer according to the invention.

The invention is illustrated below with reference to a few examples, all of which are quantitative are to be calculated according to weight, unless otherwise stated.

Examples 1 to 6

Paints with the compositions given in Table 1 are shown.

Table 1

Components

Examples
3 4

Nitrocellulose (when dry)

Dicyclohexyl phthalate

Triacetin

Ester resin

Iron resin modified with maleic acid

Isocyanate solution

Ethanolamine lauryl sulfate (27% solution in water) Ammonium lauryl sulfate (33% solution in water) Ethanolamine dodecylbenzenesulfate (33% solution in

Water)

Finely divided clay (slip agent)

0.13

10

■ 8.4
3.3
3.3

0.5

3.3

0.16

10
8.4
1.6

0.5
1.9

0.12

8.4
3.3

3.3
0.5
3.3

0.16

10
8.4
1.1

1
2.7

0.13

10
8.4
1.1

2.7

Weld Strength (g / cm) 47.2

35.4

35.4

The nitrocellulose had an average nitrogen content of 11.2 to 11.8% and was "moistened" with 30 parts of isopropanol per 70 parts of nitrocellulose. ^{After dissolving in 100 cm 3 of} a mixture consisting of 95 parts by volume of acetone and 5 parts by volume of water, 20 g (dry weight) of the nitrocellulose used in Example 1 had ^{a viscosity of 15 to 25 P at 20 °} C., and 40 g (dry weight) of that in the Nitrocellulose used in other examples had a viscosity of 3 to 5 P at 20 ° C. when dissolved in the same water-acetone mixture.

The isocyanate solution was a 75% solution of one obtained by reacting hexamethylene diisocyanate product produced with water which had a 19% content of unreacted isocyanate groups, in ethyl acetate.

In the presentation of the paints, all components except the isocyanate solution and the antistatic agent were used dispersed in a solvent mixture consisting of 60% butyl acetate and 40% toluene, wherein the amount of solvent used was chosen so that the final paint solution has an im Example 1 10% and in the other examples 25% content of non-volatile constituents had. The isocyanate solution was then added, followed by the antistatic agent. The paint solution was shortly after the addition of the isocyanate solution, i. H. while they still do most of their.

contained unreacted isocyanate groups, applied to a polypropylene film in order to form a 0.0013 mm thick layer thereon after drying. The polypropylene film was pretreated with a spray discharge in accordance with British patent specification 715 914 in such a way that its contact angle with water was less than 80 °. None of the coated films developed an apparent electrostatic charge after vigorous rubbing with a dry cloth. The weld strength values given in Table 1 were determined by the method according to British patent specification 985 291. According to this method, two pieces of film are welded together by V ₂ seconds at 130 ⁰ C under a pressure of 0.28 kg / cm ² advertising

■ 60 den, and the force is measured as the weld strength which is sufficient for this, the pieces of film over a width of 2.5 cm with a stripping speed to separate from 6 cm per minute.

B e i s ρ i e 1 e 7 to 14

The lacquers according to these examples were prepared in that the antistatic agents indicated in Table 2 were used with the following base coat solids

added and dispersed in a solvent according to Examples 2 to 6:

Parts

Nitrocellulose (in the dry state according to Examples 2 to 6) 10

Parts

Dicyclohexyl phthalate 8

Triacetin 3

Ester resin modified with maleic acid 3
Finely divided clay (slip agent) 0.12

Parts by weight Ammonium lauryl sulfate,
33% solution in
Water (dry) Table 2 Specific surface resistance
(Ohm) at 50 ° / ₀ iger more relative
humidity Ethanolamine lauryl sulfate,
27% solution in
Water (dry) at 34% relative
humidity 10 ⁸ example 1.00 0.25 Sliding ability 10 ⁹ 10 ⁹ 7th 0.75 0.50 bad 10 ⁹ 10 ⁹ 8th 0.50 0.75 bad 10 ⁹ 10 ⁹ 9 0.25 0.80 bad 10 ¹⁰ - 10 0.20 0.85 moderate 10 ^u - 11th 0.15 0.90 Well 10 ¹² - 12th 0.10 1.00 Well 10 ¹³ 10 ¹⁰ 13th - Well 10 ¹³ 14th Well

The paint solution was applied to a polypropylene film as in Examples 1 to 6, whereupon the Slidability and surface resistivity were measured.

From table 2 it can be seen that the lacquers which contain the ammonium salt are superior to the lacquers which contain a corresponding amount of an ethanolamine salt in terms of lubricity and inferior in terms of the specific surface resistance. The specific surface resistance is a measure of the consumability of the surface with regard to an electrostatic charge developed on it. A polypropylene film, which is coated with a nitrocellulose lacquer with a specific surface resistance of 10 ¹² ohms or less, has such antistatic properties that an electrostatic charge developed on the surface is quickly consumed, so that the film z. B. when rubbing with a dry cloth does not appear to acquire static electricity. The mixtures of ammonium and ethanolamine salts used in Examples 11 and 12 gave paints with ■ good sliding properties and a specific surface resistance of 10 ¹² or less even at the very low relative humidity of 34%.

50

Example 15

The paint according to this example contained a mixture of antistatic agents with various types Alkyl chains and had the following composition:

Parts

Nitrocellulose according to Example 1 10

Dicyclohexyl phthalate 6

Tricyclohexyl citrate 4

o / p-N-ethyltoluenesulfonamide 2

Ethanolamine Lauryl Sulphate

- 27% strength solution in water 1.1 ^e

Ammonium stearyl sulfate

- 25 ° / _o solution in water 1.2

Ammonium lauryl sulfate

■ - 33% strength solution in water 1.2 ^e

Isocyanate solution according to Examples 1

to 6 1

Finely divided clay (slip agent) 0.12

In the preparation of the paint, the above ingredients other than the three sulfates and the isocyanate solution were dispersed in a solvent consisting of 55 parts of ethyl acetate, 5 parts of butyl acetate and 40 parts of toluene. The three sulfates and the isocyanate solution were then added, and the resulting mixture was ^{heated to 40 °} C. on a water bath and stirred for 15 minutes in order to ensure complete dissolution of the sulfates, in particular the ammonium stearyl sulfate. Taking into account the “moistening” of the nitrocellulose by isopropanol and the water that accompanies the sulfates, the paint solution had a solids content of 10%.

This lacquer solution was kept at 30 ^° C., this temperature being sufficient to maintain the homogeneity of the lacquer solution, which was then applied to two different polypropylene film samples in order to have a thickness of 0.0013 mm ^{after evaporation of the volatile components at 90 ° C. for 15 seconds} Layer to yield on both samples. One of the film samples was pretreated with a spray discharge in such a way that the contact angle of a water drop located thereon was 72 °. The other film sample was treated more heavily, the corresponding contact angle being 62 °.

The weld strength of the films was determined using the method according to the British patent specification 985 291 with the difference that the films at 12O ⁰ C for 1 second were welded.

The films had the following properties:

Plate 3

Contact angle
the polypropylene film

Weld strength
g'cm

72 °
62 °

27.56
43.31

More specific
Surface resistance (ohms)
at 40%

more relative
humidity

10 ^u
10 ¹¹

Sliding ability

Well
Well

From this table it can be seen that a stronger spray discharge pretreatment increases the welding strength is increased. The antistatic properties of both films were satisfactory.

Examples 16-18

The paints according to these examples had the following compositions:

Plate 4

Components
¹ f 16 Examples
17th 18th Nitrocellulose according to Example 1
(atro)
Dicyclohexyl phthalate
Tricyclohexyl citrate
o / pN-ethyltoluenesulfonamide ..
Ammonium lauryl sulfate
- 33% solution in water
Ammonium cetyl sulfate
- 25% solution in water
Isocyanate solution
according to example 1
Finely divided clay 10
6th
4th
2
3
1
0.12 10
6th
4th
2
1.5
2
1
0.12 10
6th
4th
2
4th
1
0.12 "Slip" (coefficient of friction) 0.31 0.25 0.24

The paints according to Examples 16 and 17 were as shown in Example 15, and the paint according to Example 18 was shown in a similar manner, except that the lacquer solution had to be used to dissolve the ammonium cetyl sulfate be heated to 50 ° C. After application to polypropylene films at 30 ° C gave the paints according to Examples 16 and 17 clear layers. In the case of the paint according to Example 18, however, the paint had to can be applied to the polypropylene film with a device that also applies the paint when it is applied a temperature of 50 ° C and the solvent immediately after application to complete Evaporation brought about without the freshly applied layer being able to cool down beforehand. The coatings off each paint exhibited satisfactory antistatic properties. The lubricity for with the Polypropylene films coated with varnishes according to Examples 16 to 18 is given in Table 4 as the coefficient the kinetic friction indicated and was determined by the fact that a wrapped with the film 2.5 cm cube was placed on a flat piece of foil, whereupon one can see the inclination of the latter found at which the cube was currently performing an intermittent slide.

The paint according to Example 17 is to be preferred to those according to Examples 16 and 18, because it can be applied at 30 ^° C. and also has good lubricity. If the antistatic agent is omitted, these paints have a "slip value" of 0.41.

Example 19

A varnish of the following composition:

Parts
Nitrocellulose according to Examples 2 to 14

(atro) 10

Isocyanate solution according to Examples 1

to 6 1

Tricyclohexyl Citrate 12

Ethanolamine stearyl sulfate

- 21% solution in water (atro) 0.75
. Ammonium stearyl sulfate

- 27% solution in water (atro) 0.75
Finely divided clay (slip agent) 0.12

was represented by first dissolving the nitrocellulose, isocyanate solution, tricyclohexyl citrate and 3 parts of the high-boiling solvent, methylcyclohexyl acetate, in a solvent of the composition according to Example 15, after which the lubricant was added to form a starting varnish. To the antistatic agents were added 30 parts of water and 3 parts of ethyl acetate (to facilitate dissolution of the antistatic agent), and the resulting mixture was stirred at 35 ° C. to give a solution. This solution was then poured into the cold output varnish with rapid stirring to give a stable emulsion having a 72% strength ⁿ solids content resulted. This emulsion was applied to a polypropylene film at room temperature and the volatile components were allowed to evaporate at 80 ° C. The layer obtained in this way had good lubricity and was antistatic, the surface resistivity being 10 "ohms at 40% relative humidity...;

Claims (2)

Patent claims: 1. Use of ammonium or primary or secondary alkanolamine salts of alkyl sulfates or alkyl sulfonates with at least 8 carbon atoms in the alkyl radical as antistatic agents in nitrocellulose lacquers. V V 2. Use of ammonium or primary or secondary alkanolamine salts of alkyl sulfates or alkyl sulfonates with at least 8 carbon atoms in the alkyl radical as antistatic agents according to claim 1 in nitrocellulose lacquers for the production of coatings on plastic films, especially those made of polypropylene. 009 529/261