Corrosion inhibiting composite material

The invention relates to a corrosion-inhibiting composite material which contains one or more corrosion inhibitors, a method for producing the composite material and the use thereof.

It is known that corrosion inhibitors, which tend to sublime in powder form under normal conditions and can reach metal surfaces to be protected via the gas phase, are used for the temporary corrosion protection of metal objects inside closed rooms, for example in packaging or display cases. These are so-called vapor phase inhibitors<i>(vapor phase inhibitors, VPI)</i> or volatile corrosion inhibitors <i>(volatile corrosion inhibitors, VCI)</i> used as a powder, packaged in bags made of a material which is permeable to the vaporous VPI's.

Variants of this type are, for example, from HH Uhlig "Corrosion and Corrosion Protection", Akademie-Verlag Berlin, 1970, p. 247 ff., Or IL Rozenfeld "Korrosioninhibitoren" (Russian), Izt-vo Chimija, Moskva 1977, p. 316 ff , known. They have the disadvantage that the VPI's are released undefined and a homogeneous distribution over the gas space cannot be guaranteed. Further disadvantages are the risk that the bags containing VPI are mechanically destroyed and lead to undesired contamination of the packaged goods, and the problems that result from the uneven distribution of the bags in large-sized storage rooms and large containers.

There have been various attempts to remedy these disadvantages. For example, US Pat. No. 3,836,077 proposes to use the VPI mixture in the form of pressed pellets and either to completely dispense with a gas-permeable container material or to dispense with a gas-permeable container material entirely or to use the pellets stored in foams provided with corresponding cutouts. In patents US 3,967,926; US 5 332 525 and US 5 393 457, on the other hand, propose to mix the VPI's with a chemically inert powder or a drying agent such as silica gel or zeolite and in mechanically more stable, air-permeable plastic films or capsules instead of the bags made of natural products (cotton , Lines, etc). Due to its structure-related porosity, the inert carrier material should contribute to the continuous sublimation of the VPI components distributed in between and at the same time counteract agglomeration of the finely dispersed VPI components to form larger mixed particles (e.g. formation of lumps with a crusted surface due to water absorption). However, the use of desiccants usually results in the opposite of the desired effect and leads to the preferred clumping after water absorption. In addition, the mechanically more stable container materials for the VPI's have a lower permeability than the natural products, so that their emission rate drops. This is why a larger number of VPI reservoirs are required to set the VPI concentration required for corrosion protection than when using containers made from natural products. With this disadvantage, temporary corrosion protection is made more difficult and more expensive, especially in large interior spaces.

In order to eliminate the complex step of evenly distributing VPI reservoirs in the interior of packaging in the context of automated packaging technologies, many attempts have been made to fix the VPI's directly on the packaging material in a suitable manner. Naturally, experiments with cardboard and packing paper dominated. In order to ensure that the applied VPI's emit directed into the interior of packaging, the VPI components are usually applied only to one side, while the other side, which is later arranged as the outer front, is provided with a protective lacquer which is water-repellent and also as a vapor barrier can act for the VPI on the back (see e.g. HH Uhlig, see above). Up to the present day, the dimensionally and quantity-stable fixation of the VPI on the surface of cardboard or wrapping paper has proven to be a problem. If the VPI is applied within an organic coating material, a large number of substances which act as a VPI cannot be used, since they undergo chemical reactions with the binder of the coating material, as a result of which they are firmly integrated into the resulting polymer matrix and no more are capable of sublimation. This disadvantage shows, for example VPI's, which were embedded in polymeric binders based on acrylate, alkyd, epoxy or phenolic resin.

As an alternative, the VPI's are dissolved in an organic solvent and soaked the packaging. Processes of this type with various active substances and solvents are described, for example, in JP 61-227188, JP 62-063686, JP 63-028888, JP 63-183182, JP 63-210285 and US 3 887 481. However, it has been found to be disadvantageous that the VPI's are present in the form of fine crystals after the evaporation of the solvent within the pores of the substrate in question, which adhere only slightly to the packaging material. There is therefore a risk of these active substances spreading and trickling out of or from the packaging material, so that it cannot be ensured that the cardboard and paper pretreated in this way have the required specific surface concentration of VPI for corrosion protection at the time of their use.

In order to limit this disadvantage at least in its extent, it is proposed in DE 9210805 to prepare only one layer of the corrugated cardboard structure as a carrier and depot for the sublimable corrosion inhibitors and to cover it on both sides with at least one further porous layer such that the VPI depot is located inside the Cardboard located. However, since the delivery of the VPIs into the interior of the packaging is thereby deteriorated, it is proposed in JP 4 083 943 to use a polyurethane foam instead of corrugated cardboard or paper, which has a substantially higher porosity and can therefore absorb much larger amounts of VPIs. However, there is also the disadvantage that the VPI's are present in the pores of the foam after the evaporation of the solvent is crystalline and not very adhesive, so that the VPI's can trickle out easily and uncontrollably when the packaging material is subjected to mechanical stress.

JP 58-063732 and US 4,275,835 therefore describe processes in which the VPI's are components of the foamed polymer. For this it is necessary that the crystalline VPI's are dispersed in one of the starting components. Despite a high level of technical and energy expenditure, this is only incompletely possible, since VPIs usually belong to other substance classes and the stability of the Dispergate is therefore low. To make matters worse, the modern VPI's themselves consist of several substances with different chemical properties. If these can be dispersed at all together with the components for foams, such dispersions usually have a very wide particle size range, low stability and problematic processability.

DD 295 668 describes a process for the production of polyurethane systems containing VPI, in which the VPI's are first dissolved in a polyfunctional alcohol with a molecular weight of 500 to 1000 g / mol and then introduced into the polyol before adding polyisocyanate, catalyst, stabilizer and blowing agent the polyurethane is produced. However, this process is only limited to VPIs which are soluble in such alcohols in the concentration required for corrosion protection and which then do not impair the process of foam formation as a component of the polyol component. It is therefore not suitable to meet the complex requirements that are placed on the temporary corrosion protection of ferrous and non-ferrous metals as well as multi-metal combinations, especially since it excludes practically all inorganic active substances from use.

In order to eliminate the disadvantages mentioned and to provide VPI-emitting packaging materials which can be used in modern packaging, storage and transport technologies, US Pat. No. 4,124,549, US Pat. No. 4,290,912, US Pat. No. 5,209,869, EP 0 639 657 and DE-OS 3 545 473 proposed to introduce the VPI's during the extrusion of films from polyolefins, so that a mechanically stable polymer packaging material is present, from which the VPI's are emitted. EP 0 662 527, DE-OS 4 040 586, DE-OS 3 518 625 and US 5 139 700 suggest refining to use such a VPI-containing film based on polyethylene or polypropylene only in the context of laminated multilayer materials. An outward-facing layer of Al foil or a densely cross-linked polymer layer should exist, which acts as a vapor barrier with respect to the active substances emitted from the VPI-containing layer and causes the VPI to be directed into the interior of the packaging. The production of inhibitor-containing polymer films by extrusion of a mixture which contains substances that tend to sublimation is naturally associated with a number of difficulties: (a) the high volatility of the VPI's at temperatures at which the extrusion process is carried out leads to significant losses of these substances as well as to the foaming of the film, to its closedness and thus to an uncontrolled reduction in its strength and protective properties, (b) it exists the possibility of thermal decomposition of the corrosion inhibitors and undesired thermochemical reactions with the polymer matrix. The decisive disadvantage of this is that it is hardly possible in this way to produce a packaging material with uniform surface properties in a reproducible manner.

From JP-A-0 3079780 a corrosion-resistant material is known which has a coating in which a metal oxide in the sol state is present in combination with an anti-corrosion agent. There are finished, commercially available SiO₂-Sole (Aerosile) used for the coatings, which are normally not gel-forming and therefore not film-forming. When coating any surface, they form powdery coatings. Therefore, an adhesive must be added to the coating composition. Due to the lack of gel formation, no admixed active ingredients are encapsulated in the aerosils. These are only adsorbed on the particle surface.

The object of the invention is to provide an improved material for the mechanically and chemically stable fixing of volatile corrosion inhibitors on solid surfaces and a corrosion-protective packaging material. In particular, the fixing material should be universal and technologically simple to use, regardless of the physicochemical properties of the active ingredients and the type of surface, and should eliminate the disadvantages of the methods described above. Another object of the invention is to provide a method for producing such a material.

These objects are achieved with a corrosion-inhibiting composite material, a packaging material and a method with the features of claims 1, 7 and 10, respectively. Advantageous embodiments of the invention result from the subclaims.

The present invention relates to a corrosion-inhibiting composite material which consists of a composite which contains a metal oxide gel and one or more corrosion inhibitors, in which the corrosion inhibitor (s) is or are distributed as a solid solution in the metal oxide matrix.

Surprisingly, the object was achieved according to the invention in that known corrosion inhibitors are embedded in diffusion-inhibiting metal oxide gels (preferably in layer form), the inorganic matrix being able to be modified by organic polymers in such a way that synergistic effects with regard to immobilization and layer quality result. The porosity of the composites formed can be changed by the choice of the composition of the metal oxide gel and the production technology in such a way that the corrosion inhibitor is released into the gas phase over a long period of time.

The corrosion-inhibiting composite material is used for the production of corrosion-protective packaging materials, for coating metallic and metallized objects as well as for corrosion protection in closed rooms.

The invention further relates to a method for producing a corrosion-inhibiting material, or the use of a corrosion-inhibiting composite material for the production of corrosion-protective packaging materials, for coating metallic and metallized objects and for corrosion protection in closed rooms

Metal oxide gels such as SiO can be used as the matrix component₂, Al₂O₃, TiO₂, ZrO₂ or ZnO or mixtures thereof which are obtained by a sol-gel process, for example by hydrolysis of the corresponding metal alkoxides to the corresponding metal oxide sols and subsequent gel formation by neutralization, heating or concentration, cf. JCBrinker, GWScherer, "Sol-Gel Science", Academic Press, London 1990. The metal oxide brine is formed by acid or base-catalyzed hydrolysis of the corresponding metal alkoxides in water or any water-miscible organic solvent (usually ethanol): <maths id="math0001" num="(1)"><math display="block"><mrow><msub><mrow><mtext>Me (OR)</mtext></mrow><mrow><mtext>n</mtext></mrow></msub><msub><mrow><mtext> + n / 2 H</mtext></mrow><mrow><mtext>2</mtext></mrow></msub><msub><mrow><mtext>O -----&gt; (MeO</mtext></mrow><mrow><mtext>m</mtext></mrow></msub><msub><mrow><mtext>)</mtext></mrow><mrow><mtext>Sol</mtext></mrow></msub><mtext> + n R0H</mtext></mrow></math><img file="EP0861925B1_D0001.tif" /></maths>(Me = metal e.g. Si, Al, Ti, Zr, Zn, R = organic residue, e.g. alkyl, acyl)

The metal oxide brines are water-clear, stable solutions with a metal oxide content between 3 to 20%. The metal oxide particles are in nanocrystalline spherical form (approx. 2 to 5 nm). The solvent is freely selectable. The metal oxide brines show the following special features:<ul id="ul0001" list-style="none" compact="compact"><li>1. When the pH changes or the temperature rises, the brine gels to form water-clear gels which, when dried, produce porous powders <maths id="math0002" num="(2)"><math display="block"><mrow><msub><mrow><mtext>(MeO</mtext></mrow><mrow><mtext>m</mtext></mrow></msub><msub><mrow><mtext>)</mtext></mrow><mrow><mtext>Sol</mtext></mrow></msub><msub><mrow><mtext> -----&gt; (MeO</mtext></mrow><mrow><mtext>m</mtext></mrow></msub><msub><mrow><mtext>)</mtext></mrow><mrow><mtext>gel</mtext></mrow></msub></mrow></math><img file="EP0861925B1_D0002.tif" /></maths></li><li>2nd The brines gel when coating any films or moldings and form transparent films (or clear films).</li><li>3rd Different active ingredients can be dissolved in the brine and, after gelation, embedded effectively and homogeneously in the metal oxide structure. So-called metal oxide / active substance composites are formed (as powder or film). The active substance is distributed in the metal oxide matrix like a solid solution in a molecularly homogeneous or molecularly disperse manner.</li></ul>

The active ingredient content in the metal oxide is around 1 to 15% by weight, preferably around 1 to 5% by weight, based on the weight of the metal oxide in the sol (solids content) or in the gel.

For the modification of the layer properties, the hydrolysis process (1) of the metal alkoxides in the presence of admixed alkyl trialkoxysilanes R-Si (OR ')₃ are carried out, whereby modified metal oxide gels are formed which, based on 1 part by weight of metal oxide gel, contain 0 to 1 part by weight of R-SiO_n contain. R is an organic alkyl radical which can contain amino, hydroxyl or alkoxy groups, R 'is an alkyl radical, primarily with 1-4 carbon atoms and n is &lt;2. This form of modification allows the mechanical properties of the layer to be improved and the layer porosity to be varied.

A further modification possibility of the metal oxide gel to improve the layer quality is that 1 part by weight of metal oxide gel is replaced by 0 to 1 part by weight of a dissolved or dispersed organic polymer such as cellulose derivatives, starch derivatives, polyalkylene glycols or their derivatives, homo- or copolymers based on acrylate and methacrylate , Polystyrene sulfone sulfonate or natural resins, or mixtures of the polymers mentioned, is modified. Examples of preferred polymers as a composite component are polystyrene sulfonic acid, hydroxypropyl, methyl and carboxymethyl cellulose or rosin. The polymer additive has two functions: (a) by changing the composite structure, possibly still supported by ionic groups as in the case of polystyrene sulfonate, the release of the corrosion inhibitor can be delayed, (b) by adding the polymer, in particular soluble cellulose derivatives, the viscosity of the brine and thus the layer thickness can be greatly increased under constant coating conditions. It is therefore possible to control the absolute amount of the corrosion inhibitor released within wide limits.

All substances whose presence inhibits corrosion can be used as corrosion-inhibiting substances, for example substituted phenols, hydroquinone and quinone derivatives, nitrites, organic acids, salts of organic acids, aliphatic or aromatic amines, amides, thiazoles, triazoles, imidazoles or mixtures thereof. Depending on the solubility, volatility and molecular weight, their proportion in the composite can be 1 to 50% by weight.

The process for producing a corrosion-inhibiting composite material is carried out in the following steps:<ul id="ul0002" list-style="none"><li>(a) Preparation of a metal oxide sol containing SiO₂, Al₂O₃, TiO₂, ZrO₂ or contains ZnO or mixtures of the metal oxides, or by R-SiO_n can be modified by hydrolysis of the corresponding metal alkoxides in an aqueous, organic or mixed solvent, optionally with the addition of dilute mineral acid, aqueous alkali, fluoride or tertiary amines as the hydrolysis catalyst. Ethanol, acetone or dioxane is preferably used as the organic solvent.</li><li>(b) Optional addition of dissolved or dispersed polymers to modify the layer properties, the proportion thereof with respect to the metal oxide sol being chosen so that the resulting modified metal oxide sol has a viscosity of at least 5 mPa / 20 ° C. The polymer content is typically in a range from 0.1 to 20% by weight, based on the metal oxide.</li><li>(c) dissolving the corrosion inhibitor in the optionally polymer-modified metal oxide sol. The inhibitor can also be mixed in before or during the hydrolytic formation of the metal oxide brine (1) if it is stable to the hydrolysis conditions (pH and solvent environment). When using inorganic inhibitors such as sodium nitrite, it is advisable to keep the proportion of organic solvents in the metal oxide sol low in order to avoid flocculation due to the limited solubility in organic solvents. This can be easily achieved, for example, by removing the organic solvent by distillation while simultaneously adding the volume-equivalent amount of water. In this way, sufficiently stable, purely aqueous modified metal oxide sols are obtained which result in homogeneous mixtures with the water-soluble inorganic corrosion inhibitors.</li><li>(d) gelling the inhibitor-containing metal oxide sol, in which the corrosion inhibitor (s) is or are distributed as a solid solution in the metal oxide matrix, by heating or neutralizing to produce bulk products, for example for the production of a powdery corrosion-inhibiting composite material, or by coating the metal oxide sol containing the active substance on a support, for example on paper, cardboard, polymeric foils or foams, textile fabric or on metallic or metallized objects to be protected directly. The coating can be carried out by conventional coating techniques such as dipping ("dip coating"), spraying ("spray coating"), spinning ("spin coating"), brushing or watering. For the coating of foams, it is beneficial to run the soaked foam through a roller mill before drying. The roller spacing makes it easy to regulate the desired loading of the corrosion-inhibiting composite material.</li><li>(f) The solvent can be removed by conventional drying methods such as air, vacuum or freeze drying. The dry layer thicknesses are typically in a range from 0.08 to 2 µm.</li></ul>

The corrosion-inhibiting composite materials obtained in this way are notable for their ease of manufacture, good long-term stability due to the known chemical inertness of the matrix component (in the simplest case, pure silicon dioxide), excellent layer-forming properties and effective immobilization with a high corrosion-inhibiting effect. Other advantages include suitability for practically all inorganic and organic substance classes, good adhesion to a wide variety of packaging materials and metallic objects, as well as the possibility of controlling the porosity of the composite material within wide limits using the recipe and manufacturing technology.

The material according to the invention is therefore particularly suitable for the production of corrosion-protective packaging materials, for coating metallic and metallized objects to be protected directly, and for corrosion protection in closed rooms by means of powdery, corrosion-inhibiting composite materials.

Embodiments

1. Production of the metal oxide brine

<i>(a) Aqueous alcoholic acidic SiO</i>

<b><i>2</i></b>

<i>-Sol A</i>

50 ml of tetraethoxysilane, 200 ml of ethanol and 100 ml of 0.01N hydrochloric acid are stirred for 20 hours at room temperature. A stable SiO is obtained₂-Sol (4.2% solids content in 70% ethanol, pH approx. 4)

<i>(b) Aqueous acidic SiO</i>

<b><i>2</i></b>

<i>-Sol B</i>

200 ml of Sol A are mixed with 140 ml of water. The mixture is heated in a distillation apparatus on the boiling water bath and 140 ml of ethanol are distilled off. After cooling, a clear SiO is obtained₂-Sol with 4.2% solids content in water (pH approx. 4).

<i>(c) Aqueous acidic SiO containing dioxane</i>

<b><i>2</i></b>

<i>-Sol C</i>

50 ml of tetraethoxysilane, 200 ml of dioxane and 100 ml of 0.01N hydrochloric acid are stirred for 20 hours at room temperature. A stable SiO is obtained₂-Sol (4.2% solids content in 70% dioxane, pH approx. 4)

<i>(d) Aqueous alcoholic alkaline SiO</i>

<b><i>2</i></b>

<i>-Sol D</i>

50 ml of tetraethoxysilane, 200 ml of ethanol and 100 ml of 0.25% ammonia solution are stirred for 20 hours at room temperature. A stable SiO is obtained₂-Sol (4.2% solids content in 70% ethanol, pH approx. 9)

<i>(e) Aqueous-alcoholic acid sol E from SiO</i>

<b><i>2</i></b>

<i>/ CH</i>

<b><i>3</i></b>

<i>SiO</i>

<b><i>1.5</i></b>

35 ml of tetraethoxysilane, 15 ml of trimethoxymethylsilane are stirred in 200 ml of ethanol and 100 ml of 0.01 N hydrochloric acid for 20 hours at room temperature. A stable modified SiO is obtained₂-Sol (4.2% solids content in 70% ethanol, pH approx. 4)

<i>(f) Alcoholic Sol F from SiO</i>

<b><i>2</i></b>

<i>-TiO</i>

<b><i>2</i></b>

1 g 1,1,1-tris (hydroxymethyl) propane in 10 ml ethanol, 10 ml tetraethoxysilane and 3 ml 3-glycidyloxypropyltrimethoxysilane and with 2.2 g titanium tetraisopropylate in 30 ml abs. Mixed ethanol. 3 ml of 0.01N hydrochloric acid in 10 ml of ethanol are slowly added dropwise with stirring at room temperature and the mixture is stirred for 10 hours. Approx. 12% solids content in pure ethanol, pH approx. 4.

<i>(g) Alcoholic polymer modified Sol G SiO</i>

<b><i>2</i></b>

<i>-TiO</i>

<b><i>2</i></b>

100 ml Sol F (viscosity 4.5 mPa, 20 ° C) are stirred with 0.2 g Klucel H / Aqualon GmbH (hydroxypropyl cellulose) for 20 hours and filtered through a glass frit. The resulting Sol G has a viscosity of 48 mPa, 20 ° C. When coating a steel plate by dipping, a typical drawing speed of 30 cm / min with sol results<b>F</b> a dry film thickness of 0.63 µm, with Sol G 2.82 µm.

<i>(h) Aqueous alcoholic sol H made of SiO</i>

<b><i>2</i></b>

<i>-ZnO</i>

80 ml of Sol F are stirred with 20 ml of 10% aqueous zinc acetate solution for 10 hours. Stable colorless sol, approx.11.5% solids.

2nd Manufacture of corrosion-inhibiting composite materials.

The brine specified in Tab. 1 are mixed with the dissolved corrosion inhibitors and thus (a) different carriers are coated or (b) the mixture is gelled by neutralization with 2% ammonia solution and heating to 60 ° C. The solid gel is dried in air to remove the organic solvent and then in a vacuum desiccator to remove the residual moisture.<tables id="tabl0001" num="0001"><table frame="all"><title>Table 1</title><tgroup cols="4" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><thead valign="top"><row rowsep="1"><entry namest="col1" nameend="col4" align="left"><b>Manufacture of corrosion-inhibiting composite materials</b></entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="center"><b>No.</b></entry><entry namest="col2" nameend="col2" align="center"><b>Sol (100 ml)</b></entry><entry namest="col3" nameend="col3" align="center"><b>Inhibitor</b></entry><entry namest="col4" nameend="col4" align="left"><b>Coating</b></entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">1</entry><entry namest="col2" nameend="col2" align="left">A</entry><entry namest="col3" nameend="col3" align="center">20 ml dicyclohexylammonium nitrite (5% in 90% EtOH)</entry><entry namest="col4" nameend="col4" align="left">Diving paper</entry></row><row><entry namest="col1" nameend="col1" align="left">2</entry><entry namest="col2" nameend="col2" align="left">D</entry><entry namest="col3" nameend="col3" align="center">"</entry><entry namest="col4" nameend="col4" align="left">Diving paper</entry></row><row><entry namest="col1" nameend="col1" align="left">3</entry><entry namest="col2" nameend="col2" align="left">B</entry><entry namest="col3" nameend="col3" align="center">50 ml NaN0₂ + subst. phenol¹⁾ (2% in 60% EtOH)</entry><entry namest="col4" nameend="col4" align="left">Diving paper</entry></row><row><entry namest="col1" nameend="col1" align="left">4</entry><entry namest="col2" nameend="col2" align="left">H</entry><entry namest="col3" nameend="col3" align="center">20 ml hydroquinone + subst. phenol²⁾ (2% in EtOH)</entry><entry namest="col4" nameend="col4" align="left">Diving paper</entry></row><row><entry namest="col1" nameend="col1" align="left">5</entry><entry namest="col2" nameend="col2" align="left">H</entry><entry namest="col3" nameend="col3" align="center">"</entry><entry namest="col4" nameend="col4" align="left">Dip coating, steel</entry></row><row><entry namest="col1" nameend="col1" align="left">6</entry><entry namest="col2" nameend="col2" align="left">C.</entry><entry namest="col3" nameend="col3" align="center">"</entry><entry namest="col4" nameend="col4" align="left">PUR foam, dipping, rolling</entry></row><row><entry namest="col1" nameend="col1" align="left">7</entry><entry namest="col2" nameend="col2" align="left">F</entry><entry namest="col3" nameend="col3" align="center">50 ml 8-oxyquinoline + subst. phenol¹⁾ (2% in EtOH)</entry><entry namest="col4" nameend="col4" align="left">Paint, paper</entry></row><row><entry namest="col1" nameend="col1" align="left">8</entry><entry namest="col2" nameend="col2" align="left">E</entry><entry namest="col3" nameend="col3" align="center">"</entry><entry namest="col4" nameend="col4" align="left">Paint, paper</entry></row><row><entry namest="col1" nameend="col1" align="left">9</entry><entry namest="col2" nameend="col2" align="left">E</entry><entry namest="col3" nameend="col3" align="center">"</entry><entry namest="col4" nameend="col4" align="left">Gell, dry mortars to powder</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">10</entry><entry namest="col2" nameend="col2" align="left">G</entry><entry namest="col3" nameend="col3" align="center">50 ml ascorbic acid + benzoquinone (2% in EtOH)</entry><entry namest="col4" nameend="col4" align="left">Paint, paper</entry></row></tbody></tgroup><tgroup cols="4" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><tbody valign="top"><row><entry namest="col1" nameend="col4" align="justify">1) 2.6 di-tert. butyl-4-methylphenol</entry></row><row><entry namest="col1" nameend="col4" align="justify">2) 2.6 di-octadecyl-4-methylphenol</entry></row></tbody></tgroup></table></tables>

3rd Testing the corrosion-inhibiting composite materials

<i>Sample No. 1 (see Table 1)</i>

The VPI-containing paper produced in accordance with the invention was compared to a commercially available corrosion protection paper (R1) serving as a reference system according to the usual method for "testing the corrosion-protecting effect of VPI packaging materials" (cf. "Packaging Review" 5/1988, 37 ff.) Tested. According to chemical analysis, (R1) contained the active ingredients dicyclohexylamine, Na nitrite, Na salt of caprylic acid, urea and benzotriazole, the two first-mentioned substances being present in approximately the same proportion as the dicyclohexylammonium nitrite in paper No. 1. Test specimens made of unalloyed steel St-38 u2 were used. These were pretreated according to the regulations and placed alone or together with the VPI packaging material to be tested in tightly sealed containers and set conditions therein which resulted in water condensation on the surface of the test specimens. As intended, the grinding surface of the test specimens was regularly inspected visually for the presence of corrosion.

The blank samples used without the use of VPI showed the first signs of corrosion in the edge area after only 26 h immersion; the test specimens exposed together with the R1 paper showed rust spots distributed relatively evenly over the surface after approx. 11 d. Paper no. 1 produced according to the invention still guaranteed its full anti-corrosion effect even after 21 d of exposure in accordance with the regulations, as can be seen from the flawless appearance of the corresponding test specimens.

<i>Sample No. 2 (see Table 1)</i>

The VPI-containing paper produced according to the invention was tested for its anti-corrosion properties, as was the PUR foam coated according to the invention (POLYFORM ET PF 193, Polyform Kunststofftechnik GmbH Rinteln), by cutting segments cut from it together with sheets made of Al 99 or galvanized steel (Zn coating 8 µm) were stored in closed glass vessels over saturated disodium hydrogen phosphate solution. The latter provides a rel. Air humidity (RH) = 95% on. The segments of the VPI packaging material had the same geometric surface as the test sheets used and were arranged at a distance of about 2 cm from each other. The test panels were coated with 0.01 M saline immediately before exposure in the test chamber. In reference to the packaging materials according to the invention, a VPI paper (R2) commercially available for this purpose was examined in the same way, which contained the active ingredients di- and triethanolamine, the Na salts of caprylic and benzoic acid and benzotriazole.

While the Al sheets used as blank samples already showed the first whitish, punctiform efflorescence after approx. 40 h, the system (R2) ensured its protective function for around 9 d. The tests with the VPI packaging materials of paper and PUR foam according to the invention were stopped after 32 days with the test sheets having a completely perfect appearance.

In the case of the galvanized sheets used as blank samples, the first whitish deposits in the edge areas were recognizable after approx. 30 h. The use of (R2) delayed this effect to about 12 d. The experiments with the VPI packaging materials according to the invention have already been followed for about 40 days and show no changes whatsoever.

<i>Sample No. 3 (see Table 1)</i>

Sheets of dimensions (76 x 152 x 5) mm made of cast iron GGl 25, which had been freed of visible impurities by sanding with paper with grain size 280, were in a closed damp room with (RH) = 93% and 40 ° C without or with a simultaneous installation of a bowl containing VPI-dispensing powder. In addition to the composite no. 3rd A commercially available granulate (R3) was examined, which after chemical analysis contained the active ingredients dicyclohexylammonium molybdate, sodium nitrite and benzotriazole.

The VPI-containing solids were finely divided in a large bowl at 1 g / 100 cm³ Wet room volume applied. In the pure damp air, the first spotty signs of rust were already visible on the cast iron plates after about 7 hours. The corrosion protection was maintained in the chamber loaded with the commercially available VPI granules for about 62 hours. The samples which, together with the VPI-emitting powder produced according to the invention, were exposed to the wet room climate, did not show any rust formation even after the tests were stopped after 20 days. According to the invention, both the novel combination of corrosion inhibitors used and the constitution of the composite containing the VPI, which ensures continuous discharge into the gas phase, are responsible for this.

<i>Sample No. 4 (see Table 1)</i>

The paper available according to the manufacturing process No. 4 according to the invention was examined for its suitability for preserving the gloss behavior of anodized Al plates. The CLOSScomp / OPTRONIK Berlin measuring system was used to assess the gloss. This takes the measured values ​​maximum value P / dB (peak height), maximum rise A / (dB / degree), half width HW / degree from the reflection curve from the respective reflection curve of the substrate and calculates the visual gloss level Gt in%.

A loss of gloss caused by the first signs of corrosion is represented by lower values ​​for P, A and Gt as well as an increase in HW.

Al plates with the output data P = 46.2 dB, A = 14.9 dB degrees, HW = 7.6 and Gt = 77.7% were unpacked or wrapped with a layer of VPI-emitting paper in a condensation water climate (KFW) Exposed to DIN 50017. A commercially available VPI paper, which according to chemical analysis contained the active substances monoethanolamine, benzoic acid, Na benzoate, urea and glycerol (R4), served as the reference system.

In the Al plates used as blank samples, only Gt = 28.9% was determined after an exposure of 3 d. After this time, the plates packed with (R4) still had a gloss value of Gt = 74.5%, the plates packed with the paper produced according to the invention Gt = 77.0%. After 16 d exposure, this value had not changed within the scope of the measurement error, while only Gt = 33% was measured on the samples packed in (R4). This documents the superiority of paper No. 4 treated according to the invention for the purposes of corrosion protection.

<i>Sample No. 5 (see Table 1)</i>

Sheets of anodized aluminum coated according to the invention were also characterized with regard to their gloss behavior using the measuring system CLOSScomp mentioned in Example No. 4. Compared to uncoated Al plates, the visual gloss level before the start of the experiment was on average Gt = 82% even about 5% higher. The dry layer thicknesses of approx. 5% produced as a reference system (R5) with a commercially available alkyd resin clearcoat in a centrifugal process 20 In comparison, µm only gave values ​​of Gt at 68% in the initial state. The coated and the uncoated panels were cyclically loaded with moist air in a climatic cabinet in accordance with IEC 68-2-30. A 24 h cycle consists of the following stages: 6 h 25 ° C and (RH) = 98%, 3 h heating phase from 25 to 55 ° C at (RH) = 95%, 9 h 55 ° C at (RH) 93% and 6 h cooling phase from 55 to 25 ° C at (RH) = 98%. After each cycle, the surface condition of the sample plates is visually assessed.

After 4 cycles, the untreated aluminum sheets already started to stain, which led to locally differing Gt values ​​of 36%. With (R5) sheets, a reduction in the Gt values ​​was found after 8 cycles, initially due to the swelling of the organic coating associated with water absorption. The Gt values ​​of the Al plates coated according to the invention were unchanged after 30 cycles within the scope of the measurement error.

<i>Sample No. 6 (see Table 1)</i>

Polished plates made of Cu and brass Ms63 were layered between sheets of PUR foam coated according to the invention with the same area and welded into foils made of pure polyethylene (100 μm). The samples packaged in this way were exposed to the wet climate stress described in No. 5 in accordance with IEC 68-2-30. At the same time, test specimens of the specified materials were packed together with a commercially available film material as a reference system (R6) and deposited in the climate cabinet. According to chemical analysis, (R6) contained the active ingredients ammonium molybdate, triethanolamine and benzotriazole.

The blank samples showed a slight darkening of their surface after 7 cycles. In the test specimens packaged in (R6), similar staining occurred on the Cu after 12 cycles and on the Ms after 16 cycles. The plates deposited with the VPI-emitting packaging material produced according to the invention still looked completely unchanged after the tests were stopped after 31 cycles.

<i>Sample No. 7 (see Table 1)</i>

The corrosion protection function of VPI paper No. 7 produced according to the invention was tested in the same way as described for No. 1. A similar inhibitory effect resulted. That seems particularly remarkable. While it is in the no. 1 applied VPI is the dicyclohexylammonium nitrite, which has been known and used for many years and was fixed in the manner described only as a stable functioning reservoir, the use of 8-oxyquinoline as VPI was only possible by the fixation according to the invention on solid surfaces. This example proves that with the production of corrosion-inhibiting composite materials according to the invention, in addition to already proven active ingredients, substances which could not be applied with the previous processing methods can also be introduced as new CPIs. This has also been successfully tested with a number of other active ingredients not mentioned here as examples.

<i>Sample No. 8 (see Table 1)</i>

Copper fins, which are electrolessly (chemically) provided with a thin layer of nickel, must remain bondable for the semiconductor industry, even after prolonged storage in dry air at room temperature. This is generally not the case due to the aging of the primary oxide film present on the nickel surface in conjunction with the residues of chemical nickel plating still present there. With the no. 1 mentioned reference system (R1) did not delay this aging process. The chemically nickel-plated lamellae could no longer be bonded on average in this VPI paper after 5 d of storage. On the other hand, the lamellae were transferred immediately after the end of the nickel plating to a desiccator, the bottom part of which was made with powder no. 8th was filled, the aging of the Ni primary oxide film remained inhibited and the lamellae could still be bonded after storage for 24 d.