AT527031B1 - primer - Google Patents

Abstract

Solvent-based printing pre-coat for application to an aluminum surface for subsequent application of a printed image with water-based inks using ink-jet technology. In order to achieve a good printed image, it is intended that it contains i) amino resin as iminotype, which contains methylol groups, etherified methylol groups and amino groups, ii) a mixture of a. a non-reactive polyester b. a reactive polyester containing hydroxyl groups, iii) a matting agent, iv) a surface additive, v) a catalyst which catalyzes the reaction of hydroxyl groups with methylol groups, etherified methylol groups and amino groups, or a mixture of such catalysts, vi) a mixture of solvents from the group of esters and ketones, viii) optionally a white pigment based on TiO2.

Description

Description

[0001] The disclosure described below relates to the problems that arise when water-soluble ink is applied to an aluminum surface using an inkjet printer. These problems relate in particular to the flow of the ink on the substrate and the resulting impossibility of obtaining a clean and neat print image. Such applications are increasingly in demand in the field of packaging, in particular for foodstuffs.

[0002] In the prior art, mostly from the time before the invention of inkjet printing, one finds the following:

[0003] From 1954, it is known from GB 800,479 that, when printing on aluminum, a primer containing, among other things, chromic acid, phosphoric acid, polyvinyl butyral, various alcohols and citric acid must first be applied: A special area of application for this primer is aluminum foils that have only been partially deoiled, so that a certain aggressiveness and a degreasing effect is required. This primer is completely unusable for the purposes stated above.

[0004] US 2,889,233 from 1957 describes that a vinyl resin is applied to the aluminum, and the print is applied to this vinyl resin coating using a vinyl resin-based ink, which at least partially dissolves the lower vinyl resin layer and creates a particularly close bond between the print and the substrate. The end product is then hardened in an oven. This process and the products used are not suitable for use, for example, for printing on aluminum foil for the food industry, especially for circuit boards, due to the effort involved and the nature of the products.

[0005] The proposal in US 3,123,516, which dates back to 1962, is to use a coating consisting essentially of vinyl chloride, acetate copolymer and a monolaurate as a primer for aluminium. The costs and nature of the application mean that its use in connection with foodstuffs does not seem advisable.

[0006] In 1963, DE 1 444 621 disclosed a reactive dye which has at least two chromogens without a water-soluble radical, at least two reactive radicals and at least one soluble or dispersible radical. Complexity, costs and the chemicals used make it impossible to use in the intended field of application.

[0007] From 1965, GB 999,061 discloses an emulsion which is essentially based on a vinyl chloride resin and which is applied directly to the aluminium and apparently combines priming properties and printing properties at the same time.

[0008] Dating back to 1972, US 3,904,790 discloses a special polyamide that can be used as a primer, particularly when using aluminum foil with food. Since the application takes place in the form of a solution, the absolutely necessary subsequent drying step is complex in terms of space, energy, time and therefore money and cannot be used without further ado. In addition, the resin obtained has a softening point of around 100°C and can therefore lead to problems when sealing.

[0009] In 1974, GB 1,503,384 was published in Great Britain in 1978, which deals with a coating on aluminum that is supposed to have a particularly high level of reflectivity and corrosion resistance. The solution is the use of mainly a terpolymer of vinyl chloride, vinyl acetate and maleic acid using alkyl methacrylate and some other components that are not suitable for the intended purposes in terms of price, processing and properties.

[0010] In 1984, BASF published DE 34 22 216, which specified a special coating agent, in detail a suitable binder, which consists of water-insoluble polycondensates, phenols and aldehydes or essentially contains them), whereby the polycondensates

tion can be specifically controlled. This agent is also not suitable for use in the intended field of application due to costs and the nature of the components.

[0011] In 1996, EP 0 795 418 A1 describes a base coat for the subsequent application of toner by means of a laser printing process or similar processes, in which 0.3 to 20% by weight of fine-grained components are added to a paint that is not considered critical. This can be silica, talc, silica, mica or organic particles. Nothing is said about the size of the particles. A number of compositions are mentioned, including those based on melamine or polyesters that can be crosslinked with urea resins or polystyrene acrylates, non-crosslinkable cellulose nitrates and more.

[0012] From JP 2012/04,1373 it is known to apply an acrylic resin to the aluminium and to fire it on; the sandwich structure thus obtained can subsequently be strongly deformed (embossed), which is irrelevant for the intended purpose.

[0013] Since 2013, a process has been disclosed in US 2013/0150509 in which various TSSS and TISS coatings are applied to copper or aluminum in order to obtain very specific reflection spectra. This, too, does not represent a model for the intended use.

[0014] From EP 3 498 793, dating back to 2017, a primer is generally known for non-absorbent substrates, which comprises a chlorinated polyolefin resin and a ketone resin, for which various boundary conditions must be met. Cost and composition make this product unusable for the intended purpose.

[0015] With a priority of 2019, US 2022/0025196 was published in 2022, which discloses an aqueous primer composition specifically created for inkjet printing. In one example, the primer consists of a polyvalent metal salt contained in an aqueous solution and an amino-functionalized copolymer distributed as an emulsion in the aqueous solution. This composition is also unsuitable for the intended use due to cost reasons and the materials used.

[0016] There is therefore a need for a primer that makes it possible to print on aluminum surfaces using ink-jet processes and thereby achieve an optically perfect print image.

[0017] A solution to this problem is to use a solvent-based primer containing:

ij) Amino resin as imino type containing methylol groups, etherified methylol groups and amino groups

il) a mixture of a. a non-reactive polyester b. a hydroxyl-containing, reactive polyester

il) if necessary, a matting agent

iv) optionally a surface additive

(v) optionally a catalyst which catalyses the reaction of hydroxyl groups with methylol groups, etherified methylol groups and amino groups, or a mixture of such catalysts

vi) a mixture of solvents from the group of esters and ketones

vii) optionally a white pigment based on TiO2.

[0018] A paint formulation is thus proposed which is based on at least one mixture of polyesters with an amino resin in organic solvents, preferably a mixture of esters and ketones. The binders are a mixture of a low to medium and high molecular weight polyester. The preferred amino resin is an imino type. The amino resin acts as a crosslinker for the polyester binders. Both self-crosslinking and externally crosslinking reactions take place. The former take place at the free NH groups with the methyl

ol groups and etherified methylol groups of the neighboring amino resin molecules, whereby water or alcohol is split off. The external crosslinking takes place between the free hydroxy groups of the polyester mixture and the methylol groups and etherified methylol groups, also with water or alcohol split off. The imino resin type offers the possibility of formulating a low-formaldehyde varnish.

[0019] In addition, the following may be included: catalysts, surface additives, pigments, matting agents. According to the formulation according to the disclosure, the paint can be applied to an untreated aluminum surface using conventional industrial coating processes, with very good adhesion properties. In contrast to untreated aluminum surfaces and aluminum surfaces treated with other common technologies, the surface obtained in this way has a surface optimized for water-based ink applied using the inkjet process. The surface properties are largely determined by the combination of matting agent and surface additive.

[0020] For example, very good results are achieved with a pigment-free paint formulation based on 62.7% solvent, 25.5% polyester binder, 5% amino resin, 4% surface additive, 1.5% matting agent and 1.3% catalyst. In the case of a pigmented paint formulation, the composition changes as follows: 55.8% solvent, 22.9% polyester binder, 10% white pigment (here TiO2), 4.5% amino resin, 4% surface additive, 1.5% matting agent and 1.3% catalyst, all values 42%.

PAINT | COLORLESS FORMULATION

[0021] A solvent mixture of preferably ethyl acetate and methyl ethyl ketone is placed in a container at room temperature in a ratio of rounded 0.54 (22% EA and 40.7% MEK; gives 0.54). Then 12.5% of the high molecular weight polyester, for example Skybon ES 120 from IMCD Deutschland GmbH with a molecular weight of 28,000 g/mol, is added. Mixing the high molecular weight polyester into the solvent mixture has proven to be advantageous. The process is then continued in the following order with continuous stirring: Addition of 13% of the medium molecular weight polyester, for example Dynapol LH 826-05/A from Evonik Operations GmbH, with a molecular weight of 6,000 g/mol. Then 5% amino resin is added, for example Maprenal MF 988/80B from Prefere Melamines GmbH. The polyether macromer-modified polyacrylate as a surface additive, for example Byk 3560 from Byk-Chemie GmbH, is added at 4%. Then 1.5% of matting agent is added, for example Syloid 244 from Grace GmbH with a d50 value of 3.1um and an oil number of 300g/100g. Finally, 1.3% of the catalyst solution, for example Cycat 600 from Allnex Austria GmbH, is added. The information is given in percent by weight.

LACK II PIGMENTED FORMULATION

[0022] A solvent mixture of preferably ethyl acetate and methyl ethyl ketone is placed in a container at room temperature in a ratio of approximately 0.6 (21% EA and 34.8% MEK; gives 0.6). Then 11.5% of the high molecular weight polyester, for example Skybon ES 120 from IMCD Deutschland GmbH with a molecular weight of 28,000 g/mol, is added. Mixing the high molecular weight polyester into the solvent mixture has proven to be advantageous. Then the white pigment, for example Kronos 2066 from Kronos International, Inc., is added and ground to a grain size of less than 10 μm and greater than 5 μm. The temperature should not exceed 60°C. The process then continues in the following order with continuous stirring: Addition of 11.4% of the medium molecular weight polyester, for example Dynapol LH 826-05/A from Evonik Operations GmbH, with a molecular weight of 6000 g/mol. Then 4.5% of amino resin, Maprenal MF 988/80B from Prefere Melamines GmbH, is added. The polyether macromer-modified polyacrylate as a surface additive, for example Byk 3560 from Byk-Chemie GmbH, is added at 4%. Then 1.5% of matting agent is added, for example Syloid 244 from Grace GmbH with a d50 value of 3.1um and an oil number of

300g/100g. 1.3% of the catalyst solution, for example Cycat 600 from Allnex Austria GmbH, is added. The information is given in percent by weight.

[0023] The paints described can be applied to aluminum in an even layer using roller application, with the colorless paint having a grammage of 2.5g/m? + 0.7g/m* and the pigmented paint having a grammage of 2.5g/m* + 0.5g/m*®. The applied colorless or pigmented paint film is preferably processed at a baking temperature of 100°C and a belt speed of 180m/s.

[0024] Examples are given in the two tables, the percentages given are percentages by mass and are accurate to 42%. On the right-hand edge of the first column, the assignment to the above list is given, from I) to vi) or vil).

TABLE I: COLOURLESS FORMULATIONS

Raw material Form. 1 |Form. 2 |Form. 3 |Form. 4 |Form. 5 Amino resin i) |5.00 8.00 4.50 4.50 4.50 High molecular weight polyester ila) | 12.50 13.20 11.50 11.50 11.50 Low to medium molecular weight

polyester

Compound A ib) | 13.00 - 12.00 12.00 Compound B ib) |- 12.60 - - 12.60 Solvent

Ester vi) | 22.00 22.80 22.40 21.10 22.30 Ketone vi) | 42.70 42.10 41.40 39.10 41.30 Matting agent ill) | 1.50 - 6.50 6.50 2.50 Surface additive

Compound € iv) | 4.00 - - 4.00 4.00 Compound D iv) - 0.40 - Catalyst vV) | 1.30 1.30 1.30 1.30 1.30 Total 100.00 |-100.00 |-100.00 |-100.00 |-100.00 Compound A: Dynapol LH826-05/A

Compound B: Dynapol LH. 773

Compound C: Byk 3560

Compound D: Byk 3440

TABLE II: PIGMENTED FORMULATIONS

Raw material Form. 1 Form. 2 | Form.3 | Form 4 Form. 5 Amino resin i) [4.50 4.60 4.50 4.50 4.50 High molecular weight polyester ilia) | 11.50 11.10 11.00 11.00 11.00 Low to medium molecular weight

polyester

Compound A ib) | 11.40 - - 11.40 Compound B ib) |- 11.60 11.50 - 11.50 Solvent

Ester vi) 121.00 22.00 21.70 20.50 20.40 Ketone vi) 134.80 36.50 36.10 33.80 33.80 Matting agent il) |1.50 2.50 3.50 3.50 3.50 Surface additive

Compound € iv) |4.00 - - 4.00 4.00 Compound D iv) |- 0.40 0.40 - Catalyst v) |1.30 1.30 1.30 1.30 1.30 Pigment vil) | 10.00 10.00 10.00 10.00 10.00 Total 100.00 100.00 |-100.00 |-100.00 |->100.00 Compound A: Dynapol LH 826-05/A

Compound B: Dynapol LH. 773

Compound C: Byk 3560

Compound D: Byk 3440

[0025] The high molecular weight polyester should expediently have a hydroxyl number of 0-6 mg KOH/g, preferably 3 mg KOH/g. The average molecular weight of the high molecular weight polyester should be between 15,000 and 35,000 g/mol, preferably between 20,000 and 30,000 g/mol and particularly preferably between 25,000 and 28,000 g/mol. The glass transition temperature Tg should be between 60-80°C and preferably between 65-70°C.

[0026] The low to medium molecular weight polyester should expediently have a hydroxyl number of 15-40 mg KOH/g, preferably 20-35 mg KOH/g. The average molecular weight of the low to medium molecular weight polyester should be between 3000-9000 g/mol and particularly preferably between 4000 and 6000 g/mol. The glass transition temperature Tg should be between 20-40°C and preferably 30°C.

[0027] The amino resin should preferably have a reactivity of 4 per molecular unit and preferably have methylol groups etherified with butanol.

[0028] The matting agent should have a suitable average grain size d50 of 3-12 µm, preferably 3-6 µm and particularly preferably 3.1 µm. The oil number should suitably be between 10-400 g/100g, preferably 200-300 g/100g and particularly preferably 300 g/100g.

[0029] Regarding the surface additive and catalyst, it can be said that it is easy for the person skilled in the art, with knowledge of the disclosure, to make the appropriate selection from the range on offer.

[0030] All percentages given in the disclosure, tables and claims are by mass unless otherwise indicated and are accurate to 42%. For such ranges as: 12.3% 42% this does not mean 10.3-14.3% but 12.054-12.546%.

[0031] If required, further additives can be added to the composition; for the person skilled in the art of printing technology and priming, with knowledge of the invention and the respective requirements, it is readily possible to make the appropriate selection from the prior art for such additives.

EFFECT:

[0032] The present disclosure offers the solution of modifying an aluminum surface so that it can be printed with water-based inks using the ink-jet process. The print quality corresponds to the usual market requirements and even exceeds the print quality of the normally used gravure printing process. In addition, the level of requirements for the technical properties can be easily achieved with the present disclosure.

Claims (2)

patent claims 1. Solvent-based printing pre-varnish for application to an aluminium surface for subsequent application of a print image with water-based inks using ink-jet technology, characterized in that it i) Amino resin as imino type containing methylol groups, etherified methylol groups and amino groups, il) a mixture of a. a non-reactive polyester b. a hydroxyl-containing reactive polyester ill) a matting agent iv) if necessary, a surface additive V) a catalyst which catalyzes the reaction of hydroxyl groups with methylol groups, etherified methylol groups and amino groups, or a mixture of such catalysts vi) a mixture of solvents from the group of esters and ketones vil) optionally a white pigment based on TiO2, contains. 2. Printing pre-lacquer according to claim 1, characterized in that it contains, based on the total mass, i) to the extent of 4-6%, il) in total to the extent of 22.5-28%, ill) to the extent of 1-7%, iv) to the extent of 0-4.5%, V) to the extent of 1-1.5%, Vi) in total to the extent of 55-66% and vil) to the extent of 0-14%. 3. Printing pre-lacquer according to claim 1 or 2, characterized in that the mass ratio in the mixture ii) of the non-reactive polyester to the hydroxyl group-containing, reactive polyester is from 0.8 to 1.2. 4. Printing pre-lacquer according to one of claims 1 to 3, characterized in that the mass ratio in the mixture vi) of the ester to the ketone is from 0.5 to 0.85. No drawings for this 717