Compositions and methods for pretreating substrates for the subsequent fixing of vapor phase corrosion inhibitors

Abstract

Substance combinations are disclosed which include urea, at least one chitosan biopolymer having a degree of deacetylation of from 70% to 95%, and at least one dicarboxylic acid in aqueous solution. The substance combinations are useful as primers for the pretreating substrate surfaces, in particular flat or sheet-form, non-metallic substrates, which are provided as carrier materials for vapor phase corrosion inhibitors, to enable subsequent fixing to those substrate surfaces of vapor phase corrosion inhibitors from an aqueous or aqueous-alcoholic solution containing them. Certain embodiments of the substance combination include 0.1-2% by weight chitosan biopolymer, 10-25% by weight urea, and 0.5-2.5% by weight of a dicarboxylic acid, completely dissolved in deionized water. Yet a further, related aspect of the invention relates to a carrier material for vapor phase corrosion inhibitors, wherein the vapor phase corrosion inhibitors are fixed to a substrate surface pretreated with the substance combination.

Claims

1. A method for pretreating substrate surfaces, which are provided as carrier materials for vapor phase corrosion inhibitors, in order to facilitate or enable subsequent fixing to the substrate surfaces of vapor phase corrosion inhibitors from an aqueous or aqueous-alcoholic solution comprising the vapor phase corrosion inhibitors, which method comprises applying a substance combination which comprises urea, at least one chitosan biopolymer having a degree of deacetylation of from 70% to 95%, and at least one dicarboxylic acid in aqueous solution, as a primer onto said substrate surfaces.

2. The method according to claim 1, in which the at least one dicarboxylic acid is an aliphatic saturated dicarboxylic acid.

3. The method according to claim 2, wherein the at least one dicarboxylic acid is a member selected from the group consisting of butanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid, 2-aminobutanedioic acid, 2-aminopentanedioic acid and mixtures thereof.

4. The method according to claim 1, wherein the at least one chitosan biopolymer is present in the substance combination as component (1) in an amount of from 0.1 to 2% by weight, urea is present as component (2) in an amount of from 10 to 25% by weight and the at least one dicarboxylic acid is present as component (3) in an amount of from 0.5 to 2.5% by weight, completely dissolved in deionized water.

5. The method according to claim 1, wherein the substance combination further comprises cellulose-based, non-ionic thickeners as viscosity regulators.

6. The method according to claim 1, wherein the substrate surfaces are surfaces of non-metallic substrates.

7. The method according to claim 6, wherein the non-metallic substrates are flat or sheet-form non-metallic substrates.

8. The method according to claim 6, wherein the non-metallic substrates are members selected from the group consisting of paper, cardboard, flat or sheet-form plastic materials, biopolymers, textile woven fabrics and nonwovens.

9. The method according to claim 1, wherein substrates of the substrate surfaces are selected from the group consisting of polyethylene, polypropylene, polyurethane, polystyrene, acrylonitrile-butadiene-styrene (ABS), polylactide (PLA) and polyhydroxybutryate (PHB).

10. The method according to claim 1, wherein substrates of the substrate surfaces are carrier materials for corrosion protection of metallic materials within packaging, storage and transportation processes.

11. The method according to claim 1, wherein the vapor phase corrosion inhibitors comprise a combination of VpCI (vapor phase corrosion inhibitors) and VCI (volatile corrosion inhibitors).

12. The method according to claim 11, wherein the vapor phase corrosion inhibitors are members selected from the group consisting of aromatic and aliphatic amines and carboxylic acids, amino alcohols, organic and inorganic amine salts, amine and alkali nitrites, alkali salts of aromatic and aliphatic carboxylic acids, C.sub.3- to C.sub.5-aminoalkyldiols, primary aromatic amides, polysubstituted pyrimidines, benzotriazole and substituted benzotriazoles, benzimidazole, substituted benzimidazoles and aromatic mercaptothiazoles.

13. The method according to claim 1, which comprises applying the substance combination as a primer by use of a wet film having a weight per unit area of ≥1 g/m.sup.2.

14. The method according to claim 13, wherein the primer is applied by printing, knife application, brush coating or roller application with subsequent drying.

15. The method according to claim 14, wherein the drying is: (a) carried out in ambient air, (b) adapted to a water content of the wet film, and (c) in a temperature range from 60° C. to 75° C. in a drying channel or by use of infra-red radiators.

16. A method for providing a carrier material for vapor phase corrosion inhibitors, which comprises: pretreating a substrate with a substance combination which comprises urea, at least one chitosan biopolymer having a degree of deacetylation of from 70% to 95%, and at least one dicarboxylic acid in aqueous solution, so as to provide a pretreated substrate, and drying, and subsequently fixing to the pretreated substrate vapor phase corrosion inhibitors from an aqueous or aqueous-alcoholic solution comprising the vapor phase corrosion inhibitors.

17. The method according to claim 16, wherein the substrate is a non-metallic substrate.

Description

DESCRIPTION OF THE INVENTION

(1) The substance combination used according to the invention comprises urea, at least one chitosan biopolymer having a degree of deacetylation of from 70% to 95%, and at least one dicarboxylic acid in aqueous solution.

(2) The relative proportions of the different components can vary according to the specific field of application, and suitable compositions can easily be determined by a skilled person in this field by means of routine experiments.

(3) In a preferred embodiment of the substance combination used according to the invention, the chitosan is present as component (1) in an amount of from 0.1 to 2% by weight, urea is present as component (2) in an amount of from 10 to 25% by weight, and a dicarboxylic acid is present as component (3) in an amount of from 0.5 to 2.5% by weight, completely dissolved in water, preferably deionized water.

(4) “Deionized water”, as used herein, can in principle be prepared by any known method for desalination/demineralization, in particular ion exchange, membrane filtration or distillation, and is available commercially.

(5) In the preparation of such homogenized solutions, the urea component serves as an adjuvant in that it advantageously assists the dispersion of the customary chitosans having a degree of deacetylation of from 70% to 95% in the water initially introduced, in dependence on their differing mean molar mass, and thus facilitates the dissolution thereof by proteolytic reactions with the dicarboxylic acid in question.

(6) The water-soluble dicarboxylic acid is selected from the group of the aliphatic saturated dicarboxylic acids and preferably from the group which comprises butanedioic acid (succinic acid), pentanedioic acid (glutaric acid), hexanedioic acid (adipic acid), heptanedioic acid (pimelic acid), 2-aminobutanedioic acid (aspartic acid) or 2-aminopentanedioic acid (glutamic acid) and mixtures thereof.

(7) In a preferred embodiment, the substance combination used according to the invention further comprises viscosity regulators, in particular cellulose-based, non-ionic thickeners.

(8) Optionally, two or more components of the substance combination used according to the invention can also be present in the substance combination at least partially in a mutually associated form or in the form of conjugates.

(9) In terms of the method, the above object of the invention can be achieved in particular in that the substrate provided for the fixing of VpCI/VCI components is first coated with the substance combination used according to the invention, that is to say a urea-containing aqueous chitosan-dicarboxylic acid solution, as primer and subjected to thermal after-treatment, before being coated with an aqueous or aqueous-alcoholic solution containing the conventional VpCI/VCI active ingredients.

(10) By means of this method according to the invention there are obtained, in comparison to the analogous substrates without pretreatment according to the invention, higher specific concentrations of the VpCI/VCI components in question, or the fixing thereof is made possible for the first time, so that the substrates equipped according to the invention with these active ingredients, as efficient FGMs, can ensure particularly reliable temporary corrosion protection within packaging, storing and transportation processes of the common commodity metals.

(11) As is known, the biopolymer chitosan (poly-D-glucosamine) is prepared as a polyaminosaccharide from chitin (poly(N-acetyl-1,4-β-D-glucopyranosamine) by deacetylation. Since this operation usually remains incomplete, various products of chitosan are commercially available, depending on the mean molar mass and the degree of deacetylation (DA), present in the form of solid powders at room temperature and readily soluble in aqueous media of pH<6, see e.g.: V. Zargar, M. Asghari, A. Dashti, A Review on Chitin and Chitosan Polymers: Structure, Chemistry, Solubility, Derivatives, and Applications, Chem. Bio. Eng. 2 (2015) p. 204-226; B. Bellich, I. D'Agostino, S. Semeraro, A. Gamini, A Review: “The Good, the Bad and the Ugly” of Chitosans, MDPI-Journal Mar. Drugs 2016, 14(5), 99, 32 p. As is apparent from the cited review articles, a large number of applications for the various chitosan products have already opened up.

(12) In the field of packaging means, this relates mainly to the production and modification of papers with aqueous chitosan solutions for the purpose of making them into packaging means for foodstuffs.

(13) On account of the free amino groups formed by the deacetylation, chitosan is present in acidic solutions preferably in the form of a polycation with a high charge density. If the pH of such solutions is shifted into the alkaline range (pH≥6.5), for example by addition of sodium hydroxide solution, then the chitosan very quickly flocculates. This circumstance is used, for example, in order to provide an aramid paper with high abrasion resistance and a low water-absorbing capacity (see EP 0 953 081 B1, DE 6 9804586 T2). For this purpose, aramid fibers in the form of a pulp are dispersed in an acetic chitosan solution having a pH in the range 2.5≤pH≤4.5 and the chitosan is then precipitated onto the dispersed aramid fibers by shifting the pH into the range 6.5≤pH≤11. The coated fibers are then introduced in an amount of from 5 to 95% into the aqueous paper feed, in order subsequently to obtain the special paper of interest in the conventional manner (paper-making screen, water separation, drying). Primary and secondary celluloses can also be coated with chitosan in an analogous manner and used for the production of papers suitable preferably for foodstuffs packaging (see e.g.: Ji-Dong Xu, Ya-Shuai Niu, Pan-Pan Yue, Ya-Jie Hu, Jing Bian, Ming-Fei Li, Feng Peng, Run-Cang Sun, Composite Film Based on Pulping Industry Waste and Chitosan for Food Packaging, MDPI-Journal Materials 2018, 11, 2264, 11p.). Such papers, as well as the papers modified by the subsequent coating of conventional papers with a chitosan-containing aqueous solution, are distinguished not only by higher strengths but also by a very low water-absorbing capacity (low COBB index according to DIN EN 20535) and greatly reduced air and water vapor permeabilities (air permeation according to ISO 5636-3, water vapor transmission rate, WVTR according to DIN 53122-1) (see e.g.: S. Kopacic, A. Walzl, A. Zankel, E. Leitner, W. Bauer, Alginate and Chitosan as a Functional Barrier for Paper-Based Packaging Materials, MDPI-Journal Coatings 2018, 8, 235, 15 p.).

(14) Although the coating of paper substrates with chitosan, in particular for the production of packaging means, was thus known in principle, it was very surprising that specifically the substance combination used according to the invention, which comprises urea, at least one chitosan biopolymer having a degree of deacetylation (DA) of from 70% to 95%, and at least one dicarboxylic acid in aqueous solution, is outstandingly suitable for providing a large number of different substrates, in particular also non-metallic substrate materials, with a primer coating which makes it possible subsequently to fix conventional combinations of vapor phase corrosion inhibitors, in particular from aqueous or aqueous-alcoholic solution, on such pretreated substrates in a relatively stable manner and thus to make them into particularly efficient VpCI/VCI-emitting packaging means.

(15) The solutions used according to the invention as primers usually have, at 20° C., a pH in the range 4.5≤pH≤6.0 and a dynamic viscosity η in the range 80≤η (mPa.Math.s)≤380. If required for adaptation to the surface properties of the substrate to be coated or the available application technology, the dynamic viscosity η can be correspondingly regulated by addition of a thickener, in particular of a cellulose-based, non-ionic thickener.

(16) The pretreatment of the surfaces of the substrates, in particular non-metallic substrates, conventional for packaging means which are provided as carrier materials for vapor phase corrosion inhibitors with a primer according to the invention can be carried out by any conventional coating process, such as printing, knife application, brush coating or roller application, and should leave behind a wet film, preferably having a weight per unit area of ≥1 g/m.sup.2. After subsequent drying, in particular drying in ambient air, adapted to the water content of the wet film in the temperature range from 60° C. to 75° C. in the drying channel or by means of infra-red radiators, the substrates so pretreated are ready for use, for the fixing thereon of individual or conventional combinations of vapor phase corrosion inhibitors from an aqueous or aqueous-alcoholic solution containing those active ingredients.

(17) By applying a primer according to the invention it is possible to fix vapor phase corrosion inhibitors not only to papers, cardboard and paperboard which can be wetted by aqueous solutions but also, for the first time, to flat or sheet-form plastics materials, such as polyethylene, polypropylene, polyurethane, polystyrene, ABS, biopolymers such as PLA and PHB as well as textile woven fabrics, nonwovens and other materials, in particular hydrophobic materials, in the form of a finely dispersed layer which adheres sufficiently well to the substrate in question and from which the VpCI/VCIs in question can then sublimate with low resistance. By means of the applied amount of VpCI/VCI coating composition it is additionally possible to adapt the VpCI/VCI depot to the requirements of build-up phases that are as short as possible, so that the substrates, in particular non-metallic substrates, treated in this manner according to the invention, as efficient functionally graded materials (FGMs), ensure particularly reliable temporary corrosion protection within packaging, storing and transportation processes of the common commodity metals.

(18) In more specific embodiments, the substrates, in particular non-metallic substrates, are selected from the group which comprises, in addition to paper and paperboard, also typically hydrophobic materials, such as polyethylene, polypropylene, polyurethane, polystyrene, ABS, biopolymers such as PLA and PHB, textile woven fabrics, nonwovens and similar materials, typically hydrophobic materials, in particular in sheet form or flat.

(19) In a typical embodiment, these substrates are carrier materials for the corrosion protection of metallic materials, in particular common commodity metals, within packaging, storage and transportation processes.

(20) The vapor phase corrosion inhibitors to be fixed are typically selected from the group of the conventional VpCI/VCI components and can be selected, for example, from the group which comprises aromatic and aliphatic amines and carboxylic acids, amino alcohols, organic and inorganic amine salts, amine and alkali nitrites, alkali salts of aromatic and aliphatic carboxylic acids, C.sub.3- to C.sub.5-aminoalkyldiols, primary aromatic amides, polysubstituted pyrimidines, benzotriazole and substituted benzotriazoles, benzimidazole and substituted benzimidazoles, as well as aromatic mercaptothiazoles.

(21) A further aspect of the present invention relates to a substance combination which comprises urea, at least one chitosan biopolymer having a degree of deacetylation of from 70% to 95%, and at least one dicarboxylic acid in aqueous solution, wherein the chitosan is present as component (1) in an amount of from 0.1 to 2% by weight, urea is present as component (2) in an amount of from 10 to 25% by weight, and a dicarboxylic acid is present as component (3) in an amount of from 0.5 to 2.5% by weight, completely dissolved in deionized water.

(22) The water-soluble dicarboxylic acid is selected from the group of the aliphatic saturated dicarboxylic acids and preferably from the group which comprises butanedioic acid (succinic acid), pentanedioic acid (glutaric acid), hexanedioic acid (adipic acid), heptanedioic acid (pimelic acid), 2-aminobutanedioic acid (aspartic acid) or 2-aminopentanedioic acid (glutamic acid) and mixtures thereof.

(23) In a preferred embodiment, the substance combination according to the invention further comprises viscosity regulators, in particular cellulose-based, non-ionic thickeners.

(24) Optionally, two or more components of the substance combination according to the invention can also be present in the substance combination at least partially in a mutually associated form or in the form of conjugates.

(25) Yet a further aspect of the present invention relates to a substrate surface which is coated with a substance combination used according to the invention as described above, in particular after drying thereof, as a primer.

(26) Typically, such substrate surfaces are non-metallic substrate surfaces, in particular in sheet form or flat.

(27) In more specific embodiments, the substrates are selected from the group which comprises, in addition to paper and paperboard, also typically hydrophobic materials, such as polyethylene, polypropylene, polyurethane, polystyrene, ABS, biopolymers such as PLA and PHB, textile woven fabrics, nonwovens and similar materials, typically hydrophobic materials, in particular in sheet form or flat.

(28) In yet a further, closely related aspect, the present invention relates also to a carrier material for vapor phase corrosion inhibitors, wherein the vapor phase corrosion inhibitors are fixed to a substrate surface, in particular of a substrate as described above, preferably of a non-metallic substrate, which has been pretreated with a substance combination used according to the invention.

(29) The substance combinations to be used according to the invention as primers advantageously consist solely of substances which can be processed easily and safely by methods known per se and are to be categorized in the amounts that are to be used as non-toxic and not damaging to the environment. They are thus suitable in particular for the production of anti-corrosive packaging means which are usable on a large scale inexpensively and without a significant risk potential.

(30) The subject-matter of the application is described in greater detail by the following examples. As is also apparent therefrom, the nature and amount of the individual components in an aqueous solution that is prepared according to the invention and is to be used as a primer are governed mainly by the type and surface condition of the substrate material to be coated and not by the VpCI/VCI components which are subsequently to be fixed to the chitosan-containing layer.

Example 1

(31) By metered addition of the individual components in the indicated order and intensive stirring at a maximum of 45° C., the following substance combination according to the invention was prepared as primer no. 1:

(32) TABLE-US-00001 75.5 wt. % deionized water 22.0 wt. % urea (technical-grade granules)  0.7 wt. % hexanedioic acid (adipic acid)  1.1 wt. % chitosan powder type 90/100 (DA = 90%, HEPPE Medical Chitosan, Halle/Sa)  0.5 wt. % hydroxyethylcellulose (Natrosol 250 GR/Aqualon/France)

(33) The resulting clear solution had the following characteristic values at 20° C.: pH=5.8; η=285 mPa.Math.s.

(34) Paper webs (kraft paper, unsized, grammage 70 g/m.sup.2) were coated with this primer no. 1, a wet film of (20±2) g/m.sup.2 being produced. After drying in an air flow channel, an increase in the weight per unit area of about 5 g/m.sup.2 was recorded, which corresponds to the dry matter remaining from the primer.

(35) The VpCI/VCI-containing solution no. 1 which was subsequently to be applied was prepared according to U.S. Pat. No. 7,824,482 B2 from the following substances:

(36) TABLE-US-00002 6.0 wt. % octanoic acid (caprylic acid) 2.0 wt. % 2,4-hexanedienoic acid 2.0 wt. % 1,6-hexanedioic acid (adipic acid) 1.2 wt. % methylparaben 2.0 wt. % nicotinic acid amide 1.0 wt. % 5,6-dimethylbenzimidazole 5.4 wt. % potassium hydroxide 0.4 wt. % Natrosol ® 250 GR 80.0 wt. % deionized water

(37) This solution with pH≈6.8 at 20° C. had a solids content of 12 wt. %.

(38) The paper webs pretreated with primer no. 1 according to the invention were then coated with this VpCI/VCI-containing solution no. 1, a wet film of (25±1) g/m.sup.2 being produced. After drying in an air flow channel, a further increase in the weight per unit area of about 4 g/m.sup.2 was recorded, attributable in this case to the mass fraction of the remaining VpCI/VCI components.

(39) As reference, paper webs of the same type (kraft paper, unsized, grammage 70 g/m.sup.2) without pretreatment according to the invention were coated directly with the same VpCI/VCI-containing solution no. 1, and a wet film of (25±1) g/m.sup.2 was likewise produced. The subsequent drying process in the air stream channel took several minutes longer, however, obviously because the water of the VpCI/VCI-containing coating solution no. 1 had penetrated the entire paper matrix and was more difficult to desorb without the supply of heat. In addition, the increase in the weight per unit area of these paper webs which could be recorded after drying was only about 2 g/m.sup.2 and demonstrates that, in comparison with the paper precoated according to the invention, a smaller mass fraction of the VpCI/VCI components to be fixed had remained. Testing of this paper by chemical analysis by means of HPLC of the methanolic extract revealed that the content of the carboxylic acids in question in particular was below expectations, obviously because some of the VpCI/VCI components, which are considered to be volatile in water vapor, had passed into the air stream channel together with the evaporating water during the drying process.

(40) In order to demonstrate that the VpCI/VCI components fixed to the paper pretreated according to the invention are also emitted in accordance with their relatively high specific surface concentrations, cut pieces from the VpCI/VCI paper were subjected to the conventional jar test in order to assess their VCI corrosion protection properties.

(41) The jar test was carried out using conventional jars (volume 1 liter) into each of which there had been introduced a bottom insert of PMMA, which ensures a distance of about 15 mm from the base of the jar. After the metered addition of 15 ml of deionized water beneath the bottom insert, the individual jars were lined with the VpCI/VCI paper to be tested. This was carried out in each case using a strip measuring 13×25 cm arranged as a liner and a circular cut piece of Ø9 cm for the lid, always with the coated side facing the insert with the test metal sheets to be protected against corrosion. The test metal sheets were placed on the bottom insert before the lid was fitted, for which purpose a strip of PMMA provided with 5 mm deep notches was used. In each case 4 carefully cleaned test metal sheets of different types measuring (90×50×d) mm were positioned therein, at an angle of about 15° to the horizontal and at a distance of 10 mm from one another. For each jar, the test metal sheets were 1 test metal sheet of each of DC 03 steel, cold-rolled, low-carbon, material no. 1.0347, d=0.5 mm, aluminum 99.5, d=0.625 mm (both from Q-Panel, Cleveland), Cu-ETP (MKM Mansfelder Kupfer and Messing GmbH), d=0.5 mm, and hot-dip galvanized steel DX56D+Z140MBO (fine-grain zinc coating 140 g/m.sup.2-70/70 g/m.sup.2-10 μm, ArcelorMittal), d≈0.8 mm.

(42) Two batches of this type were prepared as reference without positioning of a VpCI/VCI paper.

(43) These batches as well as the jars with the test metal sheets, the deionized water and the cut pieces of the VpCI/VCI paper were closed tightly, for which purpose a lid with a sealing ring and three tension clamps were used in each case. While a waiting time of 16 h at room temperature is generally allowed for the so-called build-up phase of the VCI components within the vessel, it was assumed for the VpCI/VCI paper prepared according to the invention which was to be tested that this build-up phase is already complete after a waiting time of 4 h. The individual jars were then exposed for 16 h in a heating cabinet according to DIN 50011-12 at 40° C. and then again for 8 h at room temperature. This cyclic loading (1 cycle=24 h) was interrupted for a short time after each 7 cycles and the jars were opened for about 2 minutes in order to replace any converted atmospheric oxygen and to inspect the surface state of the metal sheets. After a total of 35 cycles, the exposure was ended and each test specimen was visually assessed in detail outside the jars.

(44) Result of the test: The appearance of the test metal sheets of the 4 different metals which had been used together with the VpCI/VCI paper prepared according to the invention and coated was unchanged after 35 cycles in all 4 parallel batches.

(45) For the two batches which had been exposed as reference without a VpCI/VCI paper, the cyclic climatic stress was terminated after only 7 cycles because signs of corrosion were visible on all the test metal sheets, spots of rust and larger areas of rust at the edges in the case of the test metal sheets of DC 03, a yellowish-brown tarnish film on both sides in the case of Al 99.5, dark spots, in each case starting from the top, on the metal sheets of Cu-ETP, and initial spot-like signs of white rust in the edge regions in the case of the test metal sheets of galvanized steel.

(46) The results of the jar test demonstrate convincingly that, despite a reduced build-up phase, the paper pretreated according to the invention and then provided with a VpCI/VCI combination provides reliable VCI corrosion protection for the conventional common metals on long-term exposure even under extreme moist air conditions.

Example 2

(47) A corrugated cardboard produced largely from reclaimed material (type E flute, grammage 320 g/m.sup.2, Hans Kolb Wellpappe, Memmingen) was pretreated with primer no. 1 according to the invention from Example 1 by producing a wet layer of (30±3) g/m.sup.2 on one side of the sheet of corrugated cardboard by means of a doctor blade. After drying of the sheet of corrugated cardboard vertically in an air stream channel at room temperature, a dry layer of about 7.5 g/m.sup.2 was to be seen.

(48) The VpCI/VCI-containing solution no. 1 from Example 1 was then again applied by means of a doctor blade to the side of the corrugated cardboard which had been pretreated in that manner with primer no. 1 according to the invention, a wet film of (50±3) g/m.sup.2 being produced in this case for the purpose of multiple usage of the coated corrugated cardboard. After drying in an air stream channel, a further increase in the weight per unit area of about 8.5 g/m.sup.2 could be recorded, attributable in this case to the mass fraction of the remaining VpCI/VCI components.

(49) As reference, sheets of corrugated cardboard of the same type were coated directly with the same VpCI/VCI-containing solution no. 1 without pretreatment according to the invention, and a wet film of (50±3) g/m.sup.2 was likewise produced. The subsequent drying process in the air stream channel took longer, however, obviously because the water of this VpCI/VCI-containing coating solution no. 1 had penetrated deeper into the corrugated cardboard and could be brought into a touch-dry state only by supplying heat at 65° C. for 5 minutes. The increase in the weight per unit area of these paper webs which could be recorded after drying was significantly smaller compared with the corrugated cardboard pretreated according to the invention and was only about 3 g/m.sup.2. Testing of segments of this corrugated cardboard by chemical analysis by means of HPLC of the methanolic extract again revealed that in particular some of the carboxylic acids in question, which are considered to be volatile in water vapor, had again been lost during the drying process.

(50) In order to demonstrate the extent to which the VpCI/VCI components fixed to the corrugated cardboard from thicker wet films withstand relatively gentle mechanical stresses, circular segments of Ø9 cm were punched out of both coated sheets of corrugated cardboard, held over a Petri dish with the coated side downwards and tapped several times on the rear side with a laboratory spatula. The Petri dish was then rinsed with 5 ml of methanol and the eluate was analyzed by means of HPLC or GC/MS for the qualitative determination of any VpCI/VCI components which had run out.

(51) Result of the Test:

(52) In the case of the segments of the corrugated cardboard pretreated according to the invention and then provided with a VpCI/VCI combination, no running out or detachment of VpCI/VCI components occurred as a result of the described mechanical stress, because the methanol eluate in question did not show any attributable peculiarities even in GC/MS. In the case of the segments of the corrugated cardboard coated only with the VpCI/VCI-containing solution no. 1, slight dust-like specks could already be seen in the Petri dish after the tapping. In the methanol eluate in question, traces of octanoic acid, methylparaben and 5,6-dimethylbenzimidazole could be detected, which again demonstrates that the powdered solids remaining from aqueous solutions on paper or cardboard adhere only slightly, so that VpCI/VCI products produced in this manner are not suitable for reliable VCI corrosion protection. As the results of the described test show convincingly, the corresponding VpCI/VCI products prepared according to the invention and coated, on the other hand, have fixed the corresponding active ingredients, even in higher specific concentrations, at least sufficiently stably that they advantageously withstand relatively gentle mechanical stresses which do not have an abrasive action, without their ability to undergo sublimation, which is required for VCI corrosion protection, being impaired. The latter has already been demonstrated by the results of the jar test described in Example 1.

Example 3

(53) By metered addition of the individual components in the indicated order and intensive stirring at a maximum of 45° C., the following substance combination according to the invention was prepared as primer no. 2:

(54) TABLE-US-00003 79.5 wt. % deionized water 19.0 wt. % urea (technical-grade granules) 0.7 wt. % pentanedioic acid (glutaric acid) 1.0 wt. % chitosan powder type 90/100 (DA = 90%, HEPPE Medical Chitosan, Halle/Sa)

(55) The resulting clear solution had the following characteristic values at +20° C.: pH=5.5; η=85 mPa.Math.s.

(56) A 6 mm thick sheet material of expanded polystyrene (EPS, Saarpor Kunststoffe, Neunkirchen) was pretreated with this primer no. 2 by producing a wet film of (90±5) g/m.sup.2 on one side by means of a PUR foam roller. Drying of these sheets was carried out for 2 minutes at (65±5)° C. The coating was then dry to handle, the increase in the weight per unit area corresponding to dry matter of about 19 g/m.sup.2 remaining from primer no. 2. The resulting coating was cellophane-like, pure white in color and typically structured, so that it could also be visually well perceived.

(57) The aqueous-ethanolic VpCI/VCI-containing solution no. 2 which was subsequently to be applied was prepared from the following substances:

(58) TABLE-US-00004 65.0 wt. % deionized water 22.0 wt. % technical-grade ethanol 5.0 wt. % sodium benzoate 5.0 wt. % 1H-benzotriazole 0.5 wt. % methylparaben 1.5 wt. % sodium nitrite 1.0 wt. % sodium carbonate

(59) This solution with pH≈8.6 at 20° C. had a solids content of about 13 wt. %. The EPS sheets pretreated with primer no. 2 according to the invention were then coated with this VpCI/VCI-containing solution no. 2 by means of a PUR foam roller, a wet film of (25±1) g/m.sup.2 being produced. After drying in an air stream channel, a further increase in the weight per unit area of about 3 g/m.sup.2 could be recorded, attributable in this case to the mass fraction of the remaining VpCI/VCI components.

(60) The preparation of reference samples with EPS sheets which had not been pretreated according to the invention was not possible because the aqueous-ethanolic VpCI/VCI-containing solution no. 2 rolled off their surfaces without VCI active ingredients remaining thereon.

(61) In order to demonstrate that the VpCI/VCI components fixed to the EPS sheets pretreated according to the invention are also emitted in accordance with their specific surface concentrations, cut pieces of the VpCI/VCI EPS sheets measuring 90×50 mm were subjected to the jar test described in Example 1 in order to assess their VCI corrosion protection properties.

(62) Since the nitrite-containing preparation of the VpCI/VCI-containing solution no. 2 is to be used preferably for the corrosion protection of iron materials, the strip of PMMA positioned in the individual jars was in each case provided at the center with a test metal sheet of DC 03 steel and also a sheet of grey iron GGG25 of the same size but with a thickness of 2 mm, flanked on the outer sides in each case by a cut piece of the coated EPS material with the coated side oriented towards the test specimen to be protected. The 5 mm deep notches in the strips of PMMA had been adapted beforehand in terms of their width to the thickness of the GGG and EPS sheets.

(63) Two batches of this type were prepared as reference without positioning of the EPS sheets provided with the VpCI/VCI system.

(64) Otherwise, this jar test was again carried out in accordance with the description given in Example 1.

(65) Result of the Test:

(66) The appearance of the test specimens of DC03 steel and GGG25, which had been used together with segments of the EPS sheets prepared according to the invention and provided with VpCI/VCI, was unchanged after 35 cycles in all 4 parallel batches.

(67) For the two batches which had been exposed as reference without a VpCI/VCI system, the cyclic climatic stress had to be terminated after only 7 cycles because the test specimens of GGG25 especially were already covered with a thick layer of rust.

(68) The results of this jar test demonstrate convincingly that the EPS material pretreated according to the invention and then provided with a VpCI/VCI combination emits the fixed VpCI/VCI components to a sufficient extent, despite the reduced build-up phase, so that reliable VCI corrosion protection is obtained on long-term exposure even under the extreme moist air conditions.

(69) EPS sheets provided in the manner according to the invention with a different VpCI/VCI system can be used, for example, as inner sides or partitions functioning as VpCI/VCI emitters in VCI packaging containers such as small cartons or trays or lids for such containers.

Example 4

(70) By metered addition of the individual components in the indicated order and intensive stirring, the following substance combination according to the invention was prepared as primer no. 3:

(71) TABLE-US-00005 79.3 wt. % deionized water 19.0 wt. % urea (technical-grade granules) 0.7 wt. % pentanedioic acid (glutaric acid) 1.0 wt. % chitosan powder type 80/200 (DA = 80%, HEPPE Medical Chitosan, Halle/Sa.)

(72) The resulting clear solution had the following characteristic values at 20° C.: pH=5.8; dynamic viscosity η=185 mPa.Math.s.

(73) The 6 mm thick sheet material of expanded polystyrene (EPS, Saarpor Kunststoffe KG, Neunkirchen) was again pretreated with this primer no. 3 by producing a wet film of (90±5) g/m.sup.2 on one side by means of a PUR foam roller. Drying of these sheets was carried out for 2 minutes at (65±5)° C. The coating was then dry to handle, the increase in the weight per unit area corresponding to dry matter of about 20 g/m.sup.2 remaining from primer no. 3. As in Example 3, the resulting coating was again cellophane-like, pure white in color and typically structured, so that it could also be visually well perceived.

(74) The VpCI/VCI-containing solution no. 3 which was subsequently to be applied was prepared according to EP 2 357 266 from the following substances:

(75) TABLE-US-00006 70 wt. % deionized water 19.5 wt. % technical-grade ethanol 4.7 wt. % sodium benzoate 2.6 wt. % 1H-benzotriazole 1.4 wt. % N-butylurea 1.3 wt. % 2-amino-4-methylpyrimidine 0.5 wt. % 2-amino-2-methyl-1,3-propanediol

(76) This solution with pH≈8.2 at 20° C. had a solids content of 10.5 wt. %. The EPS sheets pretreated with primer no. 3 according to the invention were then coated with this VpCI/VCI-containing solution no. 3 by means of a PUR foam roller, a wet film of (35±1) g/m.sup.2 being produced. After drying in an air stream channel, a further increase in the weight per unit area of about 3.7 g/m.sup.2 could be recorded, attributable in this case to the mass fraction of the remaining VpCI/VCI components.

(77) The preparation of reference samples with EPS sheets which had not been pretreated according to the invention was not possible because the aqueous-ethanolic VpCI/VCI-containing solution no. 3 rolled off their surfaces without VCI active ingredients remaining thereon.

(78) In order to demonstrate the extent to which the VpCI/VCI components fixed to the EPS sheets pretreated according to the invention from thicker wet films withstand relatively gentle mechanical stresses, cut pieces of these VpCI/VCI sheets measuring 90×50 mm were again held over a Petri dish with the coated side downwards and tapped several times on the rear side with a laboratory spatula. The Petri dish was then rinsed with 5 ml of methanol and the eluate was analyzed by means of HPLC or GC/MS for the qualitative determination of any VpCI/VCI components which had run out.

(79) Result of the Test:

(80) In the case of the cut pieces of the EPS sheets pretreated according to the invention and then provided with a VpCI/VCI combination, no detachment of VpCI/VCI components occurred as a result of the described mechanical stress, because the methanol eluate in question did not show any attributable peculiarities even in GC/MS.

(81) This result demonstrates convincingly that VpCI/VCI components from aqueous-alcoholic solutions are fixed on EPS sheets prepared according to the invention at least sufficiently stably, even in higher specific concentrations, that they advantageously withstand relatively gentle mechanical stresses which do not have an abrasive action, without their ability to undergo sublimation, which is necessary for VCI corrosion protection, being impaired. It thus appears wholly recommendable to provide efficient VpCI/VCI-emitting reusable packaging means in this manner, especially since this is not possible without the pretreatment according to the invention of the EPS surfaces.

Example 5

(82) By metered addition of the individual components in the indicated order and intensive stirring, the following substance combination according to the invention was prepared as primer no. 4:

(83) TABLE-US-00007 80.0 wt. % deionized water 18.0 wt. % urea (technical-grade granules) 0.9 wt. % butanedioic acid (succinic acid) 1.1 wt. % chitosan powder of batch 300.298 (DA = 90%, C. E. RÖPER, Hamburg)

(84) The resulting clear solution had the following characteristic values at 20° C.: pH=5.3; 72 =225 mPa.Math.s.

(85) A 12 mm thick PUR block foam MA 5080, white (METZELER Schaum, Memmingen) was coated with this medium viscosity primer no. 4 by means of rollers, a wet film of (75±5 g/m.sup.2) being produced. After the coated PUR block foam had been dried for about 2 minutes at from 60 to 70° C. in a recirculating air channel, an increase in the weight per unit area of about 15 g/m.sup.2 was recorded, which corresponds to the remaining dry matter from primer no. 4. The resulting coating was again cellophane-like, pure white in color and typically structured, so that it could be visually well perceived even on the white PUR block foam.

(86) The aqueous VpCI/VCI-containing solution no. 4 which was subsequently to be applied was prepared from the following substances:

(87) TABLE-US-00008 81.5 wt. % deionized water 8.5 wt. % sodium benzoate 7.0 wt. % 1H-benzotriazole 1.0 wt. % benzoic acid 2.0 wt. % sodium octanoate (sodium caprylate)

(88) This solution with pH≈5.5 at 20° C. has a solids content of 18.5 wt. %. The PUR block foam pretreated with primer no. 4 according to the invention was then coated with this VpCI/VCI-containing solution no. 4 by means of a PUR foam roller, a wet film of (30±3) g/m.sup.2 being produced.

(89) After drying in an air stream channel, a further increase in the weight per unit area of about 5.5 g/m.sup.2 could be recorded, attributable in this case to the mass fraction of the remaining VpCI/VCI components.

(90) The preparation of reference samples with PUR block foam MA 5080 which had not been pretreated according to the invention was not possible because the aqueous VpCI/VCI-containing solution no. 4 rolled off their surfaces without VCI active ingredients remaining thereon.

(91) In order to demonstrate the extent to which the VpCI/VCI components fixed to the PUR block foam pretreated according to the invention from thicker wet films withstand relatively gentle mechanical stresses, cut pieces of the VpCI/VCI block foam measuring 90×50 mm were tested analogously to the procedure described in Example 4.

(92) Result of the Test:

(93) In the case of the cut pieces of the PUR block foam pretreated according to the invention and then provided with a VpCI/VCI combination, no detachment or running out of VpCI/VCI components occurred as a result of the described mechanical stress, because the methanol eluate in question from the Petri dish did not show any attributable peculiarities even in GC/MS.

(94) This result demonstrates convincingly that VpCI/VCI components from aqueous solutions are fixed on PUR block foam prepared according to the invention at least sufficiently stably, even in higher specific concentrations, that they advantageously withstand relatively gentle mechanical stresses which do not have an abrasive action, without their ability to undergo sublimation, which is necessary for VCI corrosion protection, being impaired. It again appears recommendable to provide efficient VpCI/VCI donors in this manner, for example, as intermediate layers in plastics trays used for temporary corrosion protection, especially since this is not possible without the pretreatment according to the invention of a PUR block foam.

Example 6

(95) By metered addition of the individual components in the indicated order and intensive stirring, the following substance combination according to the invention was prepared as primer no. 5:

(96) TABLE-US-00009 80.0 wt. % deionized water 18.0 wt. % urea (technical-grade granules) 0.9 wt. % pentanedioic acid (glutaric acid) 1.1 wt. % chitosan powder of batch 300.298 (DA = 90%, C. E. RÖPER, Hamburg)

(97) The resulting clear solution had the following characteristic values at 20° C.: pH=5.4; dynamic viscosity η=220 mPa.Math.s.

(98) Sheets of expanded polypropylene (EPP, BS Systems, Zusmarshausen) were coated with this medium viscosity primer no. 5, a wet film of (20±2) g/m.sup.2 being produced. After drying in an air stream channel, an increase in the weight per unit area of about 5 g/m.sup.2 was recorded, which corresponds to the dry matter remaining from the primer. The resulting coating was again cellophane-like, pure white in color and typically structured, so that it could also be visually well perceived.

(99) The aqueous VpCI/VCI-containing solution no. 5 which was subsequently to be applied was prepared from the following substances:

(100) TABLE-US-00010 80.0 wt. % deionized water 10.0 wt. % sodium benzoate 6.0 wt. % 1H-benzotriazole 6.0 wt. % cyclohexylammonium benzoate

(101) This solution with pH≈6.7 at 20° C. has a solids content of 22 wt. %. The EPP sheets pretreated with primer no. 5 according to the invention were then coated with this VpCI/VCI-containing solution no. 5 by means of a PUR foam roller, a wet film of (15±2) g/m.sup.2 being produced.

(102) After drying in an air stream channel, a further increase in the weight per unit area of about 4.0 g/m.sup.2 could be recorded, attributable in this case to the mass fraction of the remaining VpCI/VCI components.

(103) The preparation of reference samples with the EPP sheets which had not been pretreated according to the invention was not possible, as expected, because the aqueous VpCI/VCI-containing solution no. 5 rolled off their surfaces without VCI active ingredients remaining thereon.

(104) In order to demonstrate that the VpCI/VCI components fixed to the EPP plates pretreated according to the invention are also emitted in accordance with their specific surface concentrations, cut pieces of the VpCI/VCI EPP sheets measuring 90×50×2 mm were subjected to the jar test described in Example 1 in order to assess their VCI corrosion protection properties.

(105) Since the preparation of the VpCI/VCI-containing solution no. 5 is to be used preferably for the corrosion protection of Al materials and galvanized steels, the strip of PMMA positioned in the individual jars was in each case provided at the center with a test metal sheet of aluminum 99.5, d=0.625 mm (both Q-Panel Cleveland) and also a test metal sheet of hot-dip galvanized steel DX56D+Z140MBO (fine-grain zinc coating 140 g/m.sup.2-70/70 g/m.sup.2-10 μm, ArcelorMittal), d≈0.8 mm, flanked on the outer sides in each case by a cut piece of the EPP material coated according to the invention with the coated side oriented towards the test specimen to be protected. The 5 mm deep notches in the strips of PMMA had been adapted beforehand in terms of their width to the thickness of the EPP sheets at those points.

(106) Two batches of this type were prepared as reference without positioning of the EPP plates provided with the VpCI/VCI system. Otherwise, this jar test was again carried out in accordance with the description given in Example 1.

(107) Result of the Test:

(108) The appearance of the test specimens of Al 99.5 and the hot-dip galvanized steel, which had been used together with segments of the EPP plates prepared according to the invention and provided with VpCI/VCI, was unchanged after 35 cycles in all 4 parallel batches.

(109) For the two batches which had been exposed as reference without a VpCI/VCI system, the cyclic climatic stress had to be terminated after only 7 cycles because the test specimens of hot-dip galvanized zinc especially were already covered with a thick layer of red and white rust.

(110) The results of this jar test demonstrate convincingly that the EPP material pretreated according to the invention and then provided with a VpCI/VCI combination emits the fixed VpCI/VCI components to a sufficient extent, despite the reduced build-up phase, so that reliable VCI corrosion protection is obtained on long-term exposure even under the extreme moist air conditions.

(111) Analogous results were obtained when extruded PP solid sheets with a very slight relief (Eicoplast Kunststoffverarbeitung, Rodinghausen) were treated and tested.

(112) Polyolefin sheets provided in this manner according to the invention with a different VpCI/VCI system can advantageously likewise be used as inner sides or partitions, functioning as VpCI/VCI emitters, of plastics trays which are to be used for temporary corrosion protection.