JPH0230308B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the field of metal substrate coatings. More particularly, one of the objects of the invention is a method of coating a metal substrate with plastic so as to provide a multilayer metal-plastic product.
The invention also relates to the products obtained by this method. Multilayer metal-plastic composite products or composites have been produced for decoration or anti-corrosion protection. The method used is to glue the plastic plate to a metal strip continuously fed from a coil, or to hot-roll the metal plate, which has been previously treated with an adhesive primer, in a calendar or rolling mill. Generally, the metal forming the metal plate is ferrous alloy, steel or galvanized steel, or aluminum or aluminum alloy. The plastic used is mainly polyvinyl chloride with a small amount of polyethylene. The invention relates to applying one or more plastic layers to a metal substrate so that the outer layer is always of the polyamide type. The aim of the invention is, on the one hand, to provide a process that is more economical than the known methods starting first with film production, and, on the other hand, to provide a process that is suitable for polyamides. In fact, said polyamides are particularly valuable because of their resistance to temperature, abrasion and chemicals, compared to the plastics used hitherto, e.g.
Better than PVC, completely protects the underlying metal substrate from corrosion. One of the objects of the invention is a method for applying and coating a metal plate with a primer layer and at least one plastic layer, the primer layer comprising an epoxy-phenolic resin, a mixture of an epoxy resin and a phenolic resin, and The primer composition according to the present invention is composed of a resin selected from a combination of resins and resin mixtures, and includes one or more compounds selected from the following compounds: -FP (abbreviation for Fusion Point) Thermoplastic linear polyester having a temperature of 100 to 150°, soluble in the solvent mixture used, its content being 10 to 25% by weight based on the total amount of primer, capable of dissociating at a temperature of -120°C, its content being Blocked aliphatic or aromatic isocyanate in an amount of 1 to 6% by weight based on the total amount of primer, the last plastic layer being in the organic liquid phase.
It is characterized in that it is a polyamide layer applied in the form of a suspension of polyamide powder with a particle size of less than 40 μm and that the whole is heated until the outer polyamide layer melts to obtain a continuous coating. Advantageous features of the invention derive from the combined selection of the primer for the plastic outer layer, which is applied in the form of a polyamide suspension. The present invention involves applying an organic adhesive primer having a heat-deformable structure to a substrate. In fact, it is essential to coat the metal substrate to be coated with the polyamide suspension with a primer beforehand. This is because, among other factors, the primer provides a bond between the metal and polyamide coating due to its very good adhesion to the metal and polyamide. The primer protects the metal provided by the polyamide coating by first preventing the penetration of gases such as oxygen, carbon dioxide, and steam between the metal and the polyamide, and then providing inherent protection to the polyamide. It works to strengthen the protective power of The causes of corrosion are diverse and depend on the use of the article made of the coated metal. As a cause of corrosion,
Examples include: - boiling water and detergent in the case of a clothes washer or dishwasher, - the various chemicals to be contained if metal plates are used to construct chemical storage tanks, - outdoor use of coated metal. If so, the weather conditions are. The application of a primer becomes even more essential if the metal plate to be coated is not pretreated. However, primers generally tend to exhibit yellowing. Due to the transparency of the polyamide coating, yellowing of the primer layer is visible from the outside, which is often a problem in terms of product quality. In the coating method according to the present invention, this yellowing phenomenon is completely suppressed by containing one or more compounds selected from thermoplastic linear polyester and blocked aliphatic or aromatic isocyanate in the primer. It is suppressed. Furthermore, the metal primer layer coated by the coating method according to the invention does not exhibit yellowing. Thermoplastic linear polyesters are those produced from diacids and aliphatic diols. Examples of products available on the market include the trade name Dynapol L441, which is based on aromatic and aliphatic dicarboxylic acids such as terephthalic acid or adipic acid and aliphatic diols, sold by Dynamit Nobel. ing. Blocked aliphatic or aromatic isocyanates are those produced from aliphatic or aromatic isocyanates by block copolymerization. Examples of products available on the market include phenol blocked diisocyanate hexamethylene.
A trimer of is available under the trade name Desmodur L2248 (blocked aliphatic isocyanate) from Bayer. According to the invention, the primer comprises 1 to 20% by weight of an epoxy resin based on the total amount of the primer in combination with 1 to 20% by weight of a phenolic resin based on the total amount of the primer;
or 1 to 20% by weight of epoxyphenol resin based on the total amount of the primer, or a mixture of the above resins in the same amount as above. According to the invention, the anti-corrosion effect provided by the primer is achieved by the use of primer corrosion-inhibiting compounds such as zinc phosphate, zinc tetrahydroxychromate,
or by the addition of salts such as strontium chromate, alone or in mixtures. In a preferred embodiment, the primer according to the invention is selected from the group consisting of zinc phosphate, zinc tetrahydroxychromate, strontium chromate, used alone or in mixtures, with a total content of 0.5 to 15% by weight of the primer weight. Contains certain corrosion-inhibiting mineral salts. These primers can be prepared using conventional mixing equipment,
It is recommended to use a dispersing stirrer with a circumferentially toothed impeller, which can be easily carried out, for example, in a paint mixing device and is particularly suitable for preparing suspensions and pastes. This can be achieved by mixing solid additives (silica, mineral salts) or insoluble additives in a small amount of solvent beforehand and adding the resulting paste to the rest of the composition. These systematically described techniques are within the skill of the art and do not require further elaboration. According to the invention, the second stage of the coating process consists of coating the primer with a suspension of a fine thermoplastic powder based on polyamide dissolved in an organic solvent or a mixture of organic solvents. Once the metal substrate has been coated with the primer, it is generally more advantageous to dry it before applying the polyamide suspension. However, this step is not mandatory if the final heating step of the coating tends to provide adequate bonding of the primer to the substrate. A final heating step melts the polyamide particles and forms a smooth continuous layer on the substrate. This includes purely physical changes that occur in the polyamide layer due to temperature-increasing effects, for example in a heat treatment furnace. This feature is advantageous;
There is an important difference from prior art processes in which heat treatment attempts to produce chemical changes comparable to crosslinking within the final plastic layer. In contrast, according to the invention, the final or finishing layer is obtained by evaporating a liquid phase with polyamide particles suspended therein and melting the particles to form the final layer. According to an essential feature of the invention, the particle size of the polyamide powder exhibits a particle size distribution in a range of less than about 40μ, preferably from about 10 to 40μ, more particularly from about 10 to 30μ. The powders used for the suspension are polyamide powders, i.e. the hydrocarbon chains are, for example, caprolactam,
having 4 to 20 carbon atoms, such as enantlactam, dodecalactam, undecanolactam, dodecanolactam, 11-aminoundecanoic acid, 12-aminododecanoic acid. In addition, polyamides such as 6.6, 6.9, 6.10,
6.12, 9.6 - Condensation products of diamines and dicarboxylic acids such as polyamides, hexamethylene diamine and adipic acid, azelaic acid, sebacic acid, 1,
These are the condensation product of 12-dodecanedienoic acid and the condensation product of nonamethylenediamine and adipic acid. Of course, the powder can consist of copolyamides obtained by polymerization of the various above-listed monomers. The following powders are particularly suitable for carrying out the method: Polyamide 12 obtained by polycondensation of 6, 11-aminoundecanoic acid or polyamide 12 obtained by polycondensation of 6, 11-aminoundecanoic acid or dodecanolactam, or 2 to 3 of the above. Copolyamide obtained by copolymerization of simple substances. Valuable copolyamides are derived by polycondensation of ε-caprolactam, aminoundecanoic acid and/or lauryllactam. The higher the molecular weight of the polyamide component of the powder, the better the resistance to aging and mechanical properties. However, the melt viscosity is higher, making it disadvantageous to spread on the substrate during melting. According to the invention, the suspension may also contain auxiliaries which allow the melted polyamide to spread despite its high melt viscosity. Conversely, the lower the molecular weight, the worse the mechanical properties and resistance to aging and weather conditions, while the more fluid the coating is in the molten state. In general, the intrinsic viscosity of polyamide powder, which reflects the molecular weight (0.5 in 100 ml metacresol at 20°C)
g) has a value of about 0.75 to 1.40. The nature of the polyamide and the end use for the coated substrate are the determining factors in choosing the optimum value. The organic liquid phase containing suspended polyamide powder is
Solvents selected from the group consisting of alcohols, esters, ketones and aromatic hydrocarbons, or mixtures thereof, are known to those skilled in the art in selecting suitable solvents for polyamides. Examples of suitable solvents include benzyl alcohol,
These include ethyl glycol acetate, dibutyl glycol acetate, N-methylpyrrolidone and mixtures sold under the tradenames Solbetuso 100 and 150. Suspensions based on polyamide powders can be prepared by adding various additives to form the suspension, such as expanded silica (e.g. a compound sold under the trade name Aerosil) or additives acting as surfactants, such as paints or Additives known to those skilled in the art for preparing lacquers can be included. The polyamide powder used according to the invention is
It can be obtained by all kinds of techniques known to those skilled in the art, such as grinding polyamide pellets precooled with liquid nitrogen or heating and dissolving such pellets in a solvent and cooling precipitation. The method of anionic polymerization of one or more monomers in a solvent which separates the polymer in powder form from the reaction medium in which it has become insoluble is a recommended method, and in particular are described in French patents nos. 1601194, 1601195 and 1602751. In fact, the particles forming the powder are small spheres which are particularly suitable for providing a satisfactory suspension and for providing a smooth coating on the metal plate after melting. Powders of this type are in their naturally occurring state and may thus give a colorless coating, or they may be colored, for which purpose it is possible to introduce pigments into the suspension by means of specially selected mixed resins. This is an additional advantage of the present invention. According to the invention, it is possible to coat various metal substrates, in particular sheets or plates of steel, galvanized steel, aluminum or aluminum alloys. In particular, metal plates of this type can be coated on one or both sides. This method is about 0.2 ~
Ideal for applying to 2mm thick metal strips. In this case, the thickness of the external finishing polyamide layer is approximately 20-50μ. Hereinafter, the method according to the present invention will be explained based on the drawings. In FIG. 1, there is a strip unwinding station on the left. This station includes a coil 1 and an accumulator 1a which handles the changes in length and tension caused by coil replacement. Surface treatment process 2 generally includes a plurality of stations as shown below. - Coarse pickling - Brushing - Careful pickling - Hot rinsing - Phosphate coating - Chromizing - Cold rinsing - Chrome rinsing The station consists of a separating tank feeding the strip. The strip then enters the priming station 3. As shown schematically in FIG. 1, the station 3 comprises two high grinding devices operated by the known so-called "reverse roll" technique. A modification of this primer application process is shown in FIG. This figure schematically shows the coating process using so-called rotogravure technology. In this case, the deposition solution is contained in a tank 10 and deposited into strips by two high-grinding devices 11, 12. Of course, to coat both sides of the strip, another coating station of the same type is provided. Generally, the final thickness as a primer is 6~
7 microns is sufficient. In FIG. 1, the reference numeral 4 generally refers to the station 3.
The furnace for drying and cross-linking the primer deposited in is shown. The temperature reached in the furnace 4 will of course depend on the nature of the primer. In fact, the temperature reached by the strip metal (referred to as peak metal temperature or PMT) is used as a measure of the true primer curing temperature. The plant shown in FIG. 1 for carrying out the method of the invention further includes an air cooling station 5 pulsed with primer coated strips. In station 6, a dispersed layer of polyamide fine powder according to the invention is applied to the strip already coated with a primer. As shown in the figure, the station 6 comprises two high grinding devices operating on the rotogravure principle (similar to FIG. 2). Using a dry gelling furnace 7, remove the solvent consisting of the organic phase,
The powder fine particles are melted into a continuous layer. The strip leaving the furnace 7 passes through a cooling station 8 and is then wound up in a winding device 9 via an accumulator 9a. The temperature conditions of the furnace 7 depend on the nature of the polyamide used. A temperature curve recorded on a metal strip between the inlet and outlet of a furnace, lying between a horizontal axis (equally scaled with respect to distance or time) and two vertical lines corresponding to the inlet and outlet of the furnace The areas indicate the energy used to perform each step of solvent removal and polyamide powder melting. Experiments have shown that the PMT can be varied within the range of 230 DEG to 260 DEG C., depending on the intended use, required properties, and strength. These conditions are not limited to the above examples and can be changed within the scope of the present invention. Therefore, the method of the present invention can process coiled metal substrates using the continuous production line shown in FIG. In the following examples, various compositions used for the primer and finishing polyamide layers are shown. All examples are given in parts by weight unless otherwise specified, and the various ingredients are listed in the order of their operation and incorporated into the compositions. Composition Example 1 (Primer) Weight% Dynapol L441 (Dynamit Novel's thermoplastic linear polyester) 17 Ethylene glycol acetate 10.5 Solbetsuso 100 (Etsuso's solvent) 10.5 Aerosil 300 (Dogiyutsusa's finely dispersed silica) 0.3 Zinc phosphate 7.5 Dioxide Titanium 11 Phenolic resin PR897 (non-plastic phenol condensate from Hoechst) 6 Epicote 1001 (polycondensate of epichlorohydrin and diphenylpropane from Schiel)
1.5 10% phosphoric acid in butanol 1 Ethyl glycol acetate 34.7 100 This primer does not yellow at all and is flexible due to the presence of polyester. Composition example 2 (Primer) Weight % Phenoxy PK HH (polycondensate of epichlorohydrin and diphenylchloropropane manufactured by Union Carbide) 12 Zinc tetrahydroxychromate 10 Aerosil 300 0.5 Ethyl glycol 25 Toluene 29.5 Phenol resin PR897 2 Desmodyl L2248 ( Bayer's Blocked Aliphatic Isocyanate) 2 Ethyl Glycol Acetate 19 100 This primer also has the advantage of not yellowing. Comparative example 1 (Primer) Weight % ethyl glycol acetate 8 Phenolic resin PR897 12 Dimethylformamide 6.5 Titanium dioxide 38 Strontium chromate 3.8 Ethyl glycol acetate 3.1 Solbetsuso 100 (solvent from Etsuso) 3.1 Epicote 1007 (epichlorohydrin and diphenylol from Schiel) 4.3 Ethyl glycol acetate 4.3 10% phosphoric acid in butanol 2.5 Phenoxy resin PK HH (polycondensate of high molecular weight epichlorohydrin and diphenylolpropane manufactured by Union Carbide) 2.4 Ethyl glycol acetate 12 100 Comparison The primer of Example 1 has good resistance to hot water at 75°C, but exhibits yellowing. Yellowing of the primer layer is visible from the outside due to the transparency of the polyamide coating, which is undesirable in terms of product quality. On the other hand, the compositions disclosed in Composition Examples 1 and 2 have the advantage of not causing yellowing. Composition Example 3 (Polyamide) Polyamide dispersion 25% TiO ₂ -filled polyamide powder 40% Benzyl alcohol 60% 100% In this same composition, benzyl alcohol can be replaced with the following solvents. - Isofluorone - Ethyl glycol acetate - Dibutyl glycol acetate In expected applications, polyamide powder, 20%
Disperse at a concentration of ~50%. Composition Example 4 (Polyamide) Similar to the primers described above, a composition is shown in which the components are added in the order described below.

[Table] (2) Promotes adhesion to primer.
Supplier: Rehm and Haas Composition Example 5 (Polyamide)

[Table] Example 1 A continuous strip of 0.7 mm thick mild steel was pre-surfaced with a commercially available product called Bondarite 914 from Parker, for the dual purposes of anti-corrosion protection and adhesion promotion. After treatment, approximately 30m/mn
The primer is supplied to the primer deposition station 3 at a speed of . A primer layer of composition example 1 above having a thickness of 7 microns in the dry state is used and held in the oven 4 for about 30-60 seconds to reach a metal peak temperature (PMT) of 241°C. After passing this through a cooling station 5, it was passed through a polyamide adhering station for 30 minutes in a dry state.
Polyamide layer 11 according to composition example 3 with micron thickness
get. In furnace 7, the strip is PMT 230℃
After reaching , cool down. The resulting metal-plastic multilayer composite can be immersed in boiling water without the plastic coating peeling off.
It gave good results for the 1000 hour soak test. Example 2 A continuous aluminum strip with a thickness of 0.5 mm
A temporary surface treatment was performed in advance using a commercially available product called Coralgin 6204 from CFPI, and a primer layer according to Composition Example 2 having a thickness of 4 to 5 microns was supplied in a dry state to a primer application station 3. Heat PMT to 249℃ in furnace 4. Similarly, after the strip has been coated with the coating of composition example 5, it is brought to a PMT of 249 DEG C. in a second furnace 7. The remaining thickness of the polyamide coating after drying is 25 microns.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a method for successive coating of metal strips, and FIG. 2 is a schematic diagram illustrating a modification of the initial deposition step. DESCRIPTION OF SYMBOLS 1... Coil, 1a... Accumulator, 2... Surface treatment process, 3... Primer adhesion station, 4
... Furnace, 5... Air cooling station, 6... Polyamide deposition station, 7... Drying gelling oven, 8...
Cooling station, 9... Winding device, 9a... Accumulator, 10... Tank, 11... High grinding device.

Claims (1)

[Scope of Claims] 1. A method of depositing and coating a metal substrate with a primer layer and at least one plastic layer, wherein the primer layer comprises an epoxy-phenolic resin, a mixture of an epoxy resin and a phenolic resin, and a mixture of the resin and the resin. The primer is made of a resin selected from a combination of resin mixtures, and the primer has a melting point of 100 to 150°C, is soluble in the solvent mixture used, and its content is preferably 10 to 25% by weight based on the total amount of the primer. a plastic linear polyester; a blocked aliphatic or aromatic isocyanate which can be dissociated at a temperature of 120° C. and whose content is from 1 to 6% by weight based on the total amount of the primer;
The last plastic layer is in an organic liquid phase.
A metal substrate characterized in that it is a polyamide layer applied in the form of a suspension of polyamide powder with a particle size of less than 40μ, and the whole is heated until the outer polyamide layer melts to obtain a continuous coating. Method of covering with plastic. 2. The method according to claim 1, wherein the metal substrate is an iron alloy, steel, galvanized steel, aluminum or an aluminum alloy. 3. The method according to claim 1 or 2, wherein metal plates or strips having a thickness of about 0.2 mm to about 2 mm are continuously processed. 4. The method according to any one of claims 1 to 3, wherein the content of epoxy-phenolic resin or epoxy resin in combination with phenolic resin is 1 to 20% of the total amount of the primer for primer adhesion. . 5. The primer contains corrosion-inhibiting mineral salts selected from the group consisting of zinc phosphate, zinc tetrahydroxychromate, strontium chromate, used alone or in mixtures, the total content of which is from 0.5 to 15% of the weight of the primer. A certain patent claim, item 1~
The method according to any one of paragraph 4. 6. Process according to any one of claims 1 to 5, characterized in that the primer is dried and cross-linked, in particular by heating at a temperature of about 230 to about 26C. 7. Any one of claims 1 to 6, wherein the polyamide powder applied in suspension to the primer-coated substrate has a particle size of about 1 to 40 μm, in particular about 10 to 30 μm. Method described. 8. Process according to any one of claims 1 to 7, characterized in that the polyamide powder forming the suspension is based on a polyamide containing from 4 to 20 carbon atoms in the hydrocarbon chain. 9 Polyamide powder is polyamide 6, polyamide 11, polyamide 12 or copolyamide 6/11,
8. The method according to claim 1, wherein the main component is a polyamide belonging to the group consisting of 6/12, 6/11/12 and 11/12. 10. Claims 1 to 9, wherein the intrinsic viscosity of the polyamide powder, which reflects the molecular weight (measured with a solution of 0.5 g dissolved in 100 ml of metacresol at 20°C), is about 0.75 to 1.40. The method according to any one of the above. 11. Any one of claims 1 to 10, wherein the organic liquid phase containing the suspended polyamide powder comprises a solvent or solvent mixture selected from the group consisting of alcohols, esters, ketones and aromatic hydrocarbons. The method described in Section 1. 12 The polyamide powder can be introduced into suspension in its natural state or by compounding resin.
12. The method according to any one of claims 1 to 11, wherein at least one pigment is added. 13 Purely physical change (final heating to give a continuous polyamide outer layer by melting of the polyamide particles)
Claims 1 to 1 performed at a temperature of 230 to about 260°C
The method described in any one of Item 2. 14. The method according to any one of claims 1 to 13, wherein the primer has a thickness of about 6 to 7 microns. 15 The treatment is carried out on a metal strip with a thickness of about 0.2 to about 2 mm, and the thickness of the polyamide outer layer is about 20 to about 2 mm.
15. The method according to any one of claims 1 to 14, wherein the particle diameter is 50μ. 16. A method as claimed in any one of claims 1 to 15, in which the substrate is coated on one or both sides in the form of a metal plate or strip. 17. A composite metal-plastic product comprising one primer layer and at least one plastic layer applied to a metal substrate, the primer layer comprising an epoxy-phenolic resin, a mixture of an epoxy resin and a phenolic resin, and a combination of said resins and resin mixtures. a thermoplastic linear polyester having a melting point of 100 to 150° C. and soluble in the solvent mixture used, the content of which is preferably 10 to 25% by weight based on the total amount of the primer; a blocked aliphatic or aromatic isocyanate which can be dissociated at a temperature of 120° C. and whose content is 1 to 6% by weight based on the total amount of the primer;
one or more compounds selected from A composite metal-plastic product obtained by successive coatings by heating the whole until the outer polyamide layer melts. 18 The thickness of the metal strip is about 0.2 to about 5 mm,
18. The product of claim 17, wherein the primer and continuous polyamide outer layer have a thickness of about 20 to about 50 microns.