EP0057813B1 - Aqueous dispersion and process for coating materials - Google Patents

Abstract

The present invention provides an aqueous dispersion for the production of corrosion- and weather-resistant coatings on work materials, especially on synthetic fibre fabrics, said aqueous dispersion comprising: 20 to 50% by weight polyvinylidene fluoride, 20 to 50% by weight water, 1.5 to 25% by weight of an acrylic co-polymer, 1.5 to 5% by weight of a pigment and/or a filling material, 0.05 to 0.75% by weight, referred to the polyvinylidene fluoride, of a light-protection agent and 4 to 20% by weight of a low boiling alcohol or of a mixture of a low boiling alcohol and of a high boiling solvent. The present invention also provides a process for the production of corrosion- and weather-resistant coatings on work materials, wherein the above dispersion is applied to a work material, followed by heating in.

Description

The invention relates to an aqueous dispersion for producing corrosion-resistant and weather-resistant coatings on materials such as fiber fabrics, in particular synthetic fiber fabrics, glass, glass fabrics, metal, ceramics and the like, which contains a polyvinylidene fluoride, an acrylic copolymer and a pigment, and a method for producing corrosion and weather resistant coatings using this dispersion.

It is already known to provide synthetic fiber fabrics such as polyester fabrics with thick polyvinyl chloride layers. The polyvinyl chloride used for this purpose is made soft with the aid of additives and generally contains a plasticizer content of 40 to 60% by weight. Despite the use of stabilizers and pigments, the polyvinyl chloride surface is subject to degradation and destruction under the influence of light when used outdoors, for example as a truck tarpaulin or as a material for air-filled halls. As a result of this degradation, the polyvinyl chloride becomes brittle, becomes rough and cracked, with the result that the surfaces coated with it become very dirty and attacked.

It is also known to use membrane building materials, e.g. glass fabric coated with polytetrafluoroethylene. These membrane building materials show excellent weather resistance outdoors, very good dirt-repellent properties and are practically non-flammable. Their disadvantage is the complex production method, which leads to a very expensive end product. Furthermore, only special glass filament fabrics can be used as fabrics, the yarns of which are made of fine threads and which are consequently also cost-intensive. These substrate fabrics also have a much lower elongation than polyester fabrics, for example. The tear resistance of coated glass fabrics is therefore lower than that of corresponding polyester fabrics.

Air drying aqueous polyvinylidene fluoride dispersions are known from DE-A 23 25 304 which contain vinylidene fluoride, an acrylate polymer and optionally pigments, flow control agents, solvents, surface-active agents, thickeners and the like. These dispersions result in hard and tough coatings. If they are applied to synthetic fiber fabrics in layer thicknesses, as are customary for coatings made of soft polyvinyl chloride, rigid products are obtained which are not suitable for truck tarpaulins, air-filled halls, conveyor belts and the like. In addition, the wetting agents to be used according to this prior art increase the susceptibility of the fiber fabrics to dirt.

DE-A 28 18 385 describes molded polyvinylidene fluoride bodies with a textile fabric which are obtained by pressing extruded polyvinylidene fluoride sheets at elevated temperature with a thermoplastic polyester fleece. The rigid composite panels obtained in this way serve as semi-finished products for container construction. Due to their rigidity, they are also unsuitable for the membrane construction materials application mentioned above.

The object of the present invention is now to provide an aqueous dispersion and a method with which it is possible to form corrosion-resistant and weather-resistant coatings on materials, in particular on synthetic fiber fabrics, so that membrane building materials are obtained which are used as truck tarpaulins for air-filled halls, Tents, cover mats, conveyor belts and the like are suitable, while at the same time minimizing environmental pollution by organic solvents.

This object is now achieved by the characterizing features of the aqueous dispersion according to claim 1.

The subclaims relate to particularly preferred embodiments of this object of the application and to a method for producing corrosion-resistant and weather-resistant coatings on materials, in particular synthetic fiber fabrics, using this aqueous dispersion according to the invention.

Surprisingly, the aqueous dispersion according to the invention results in homogeneous, firmly adhering and very flexible coatings, which are also smooth, glossy and waterproof, even in larger application amounts on synthetic fiber fabrics.

They envelop the synthetic fiber fabric very firmly and give the product obtained the special advantages and properties of polyvinylidene fluoride, namely an extraordinarily high chemical resistance, lightfastness, heat resistance, scratch resistance and low susceptibility to dirt.

The invention thus relates to an aqueous dispersion of the type defined at the outset, which is characterized by a content of

The aqueous dispersion preferably contains the polyvinylidene fluoride in an amount of 30 to 45% by weight. The polyvinylidene fluoride is preferably used with an average primary particle size of less than 0.5 μm, produced by the process according to DE-C 1 939 852. According to a further preferred embodiment of the invention, the aqueous dispersion contains 35 to 45% by weight of water.

The acrylic copolymer contained in the aqueous dispersion is preferably a water-soluble copolymer of acrylic acid and / or methacrylic acid and one or more monomers copolymerizable therewith, such as acrylamide, methacrylamide, acrylonitrile, methacrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, styrene, butadiene and / or vinyl acetate. The acrylic copolymer is preferably used in the form of the ammonium salt. The aqueous acrylic copolymer solutions, which can be obtained under the name “Glascol HA 4” ° from Allied Colloids, Ltd., Great Britain, are particularly preferably used. These are clear, white or pale yellow solutions of the ammonium salt of the acrylic copolymer, which have a viscosity of 3 to 7 Pa.s (30 to 70 poise) at 20 ° C, a solids content of 30 + or - 1%, a pH Value of 7.5 to 8.5, have a specific weight of 1.07 g / ml. These acrylic copolymer solutions form water-resistant, soft and flexible films. The acrylic copolymers used in the aqueous dispersion according to the invention result in an increase in the adhesive strength of the coating composition on the substrate and in an increase in the flexibility and softness of the grip of the entire composite material.

If corrosion and weather-resistant coatings are to be formed in particularly large quantities, the aqueous dispersion according to the invention preferably additionally contains 2.5 to 10% by weight, preferably 2.5 to 5% by weight, based on polyvinylidene fluoride, of a plasticizer, such as Polypropylene adipate, polybutylene adipate, polypropylene sebacate, polybutylene sebacate and / or an ethylene / vinyl acetate copolymer. The use of small amounts, preferably 0.01 to 1% by weight, of an adhesion promoter, such as a silane adhesion promoter, such as, for example, γ-methacryloxypropyltrimethoxysilane, is also recommended here.

In this case, it is advisable to add 1 to 30% by weight of an auxiliary solvent to the aqueous dispersion, which simultaneously serves as an auxiliary solvent for the light stabilizer, such as, for example, methyl ethyl ketone, ethyl acetate and / or xylene.

For easier wettability of the material to be coated, the aqueous dispersion according to the invention contains 4 to 20% by weight, preferably 5 to 15% by weight, of a low-boiling alcohol which has a boiling point of not more than 120 ° C. under normal pressure. Low molecular weight alcohols of this type which are preferred according to the invention are primary, secondary or tertiary aliphatic alcohols having 1 to 5 carbon atoms, such as methanol, ethanol, propyl alcohol, one of the butanols and in particular isopropyl alcohol. The consequence of this low molecular weight alcohol is that the claimed dispersion has good wetting of the substrate without introducing disruptive wetting agent residues into the finished coating. At the same time, this low-molecular alcohol makes it easier to disperse in the polyvinylidene fluoride. If the claimed dispersion dries too quickly, it is advisable to use the low-boiling alcohol in combination with a solvent that delays drying. Solvents with boiling points / ranges between 120 and 180 ° C such as e.g. Diethylene glycol dimethyl ether, xylene, butyl glycol or mixtures thereof. The amount of these higher-boiling solvents can replace up to 50% by weight of the low-boiling amount of alcohol.

According to a preferred embodiment of the invention, the aqueous dispersion contains 0.5 to 5% by weight of a thickener, for example a water-soluble ammonium polyacrylate. The “Latekoll AS” @ aqueous solution of ammonium polyacrylate available from BASF is particularly preferred.

As the light stabilizer, the aqueous dispersion according to the invention contains conventional UV light stabilizers, such as benzotriazole derivatives and / or light stabilizers containing sterically hindered amino groups. The mixture of light protection agents consisting of "Tinuvin P" ^@ and "Tinuvin 770" ⁰ is particularly preferred. This light stabilizer is preferably used as a solution in particular ethyl acetate.

Suitable pigments or fillers according to the invention are light-resistant and weather-resistant substrates, such as, for example, titanium dioxide of the rutile type, inorganic pigments or metal bronzes.

In order to make the coatings obtainable according to the invention flame-retardant, it is suitable to add antimony trioxide to the aqueous dispersion of the invention, the application rates expediently being between 3 and 7% by weight, based on the overall formulation. A particularly clear effect with regard to flame resistance is achieved by a synergistic combination of antimony trioxide and melamine cyanurate. Such particularly effective mixtures preferably consist of 1 to 5% by weight of antimony trioxide and 0 to 2% by weight of meiamin cyanurate, based on the overall formulation. Most preferred is a combination of about 2% by weight of antimony trioxide with about 1% by weight of melamine cyanurate.

The aqueous dispersion according to the invention has the advantage that it can be produced not only using dried polyvinylidene fluoride but also using material that is moist with centrifuges. This relatively large amount of water-binding material (40% by weight of water) is mixed with the components already described (acrylic copolymer, pigments, fillers, etc.) to produce the claimed dispersion and gently ground on a ball mill, sand mill or the like. The light stabilizer and the plasticizer are each used pre-dissolved in suitable solvents. Only for the production of dispersions with a particularly high polyvinylidene fluoride content should part of the water or the entire residual moisture be removed from the centrifuge-moist material.

The claimed aqueous dispersion is used to produce corrosion-resistant and weather-resistant coatings on any materials, such as woven, non-woven or knitted fiber fabrics, in particular from synthetic materials suitable on glass, glass fabrics, metal, ceramics and the like. The claimed aqueous dispersion is particularly suitable for coating polyester fiber fabrics or polyamide fiber fabrics. These fiber fabrics preferably have basis weights of 80 to 350 g / m ² .

The invention further relates to a method for producing corrosion and weather-resistant coatings on materials, in particular synthetic fiber fabrics, which is characterized in that the aqueous dispersion described above is applied to the material and baked after a possible predrying. The aqueous dispersion is applied to the surface to be coated by customary application methods, such as brushing, rolling, dipping, spraying and the like, and is dried at from 100 to 140 ° C., preferably from 120 to 130 ° C.

The drying time is preferably 3 to 6 minutes. The applied coating is then baked at temperatures of 170 to 210 ° C, and in particular from 190 to 200 ° C for 1 to 3 minutes.

In the case of particularly smooth materials and to increase the adhesive strength, the material is pre-impregnated with a polyvinylidene fluoride latex. For this purpose, the polyvinylidene fluoride latices described in DE-C 19 39 852 are preferably used. The pre-impregnation produced in this way is dried and baked at the temperatures given above with regard to the coatings to be produced. The pre-impregnation of the material with the polyvinylidene fluoride latex can be repeated up to 3 times, with each application drying and baking, although this can also be done after the entire pre-impregnation has been completed. It is preferably dried at 100 to 140 ° C. for 3 to 6 minutes and baked at 170 to 190 ° C. for 1 to 3 minutes. Then the top coat is applied in the manner described above.

According to the invention, the material to be coated can also be pretreated with y-methacryloxypropyltrimethoxysilane as an adhesion promoter before the pre-impregnation is applied.

According to the invention, application amounts of 80 to 200 g / m ² are obtained per application of the dispersion, depending on its concentration and the type of material. With the help of the claimed aqueous dispersion, both sides of the material can be coated at the same time, for example in the dipping process. Additional surface smoothing, for example with the help of so-called smoothing rollers or structuring of the surface with the help of structure rollers, is also possible at temperatures of 180 to 220 ° C.

The aqueous dispersion according to the invention, which mainly consists of polyvinylidene fluoride, enables the permanent coating of synthetic fiber fabrics in particular, since it does not suffer any degradation reactions due to weather influences and thus maintains the decorative appearance of the coated surface unchanged.

The claimed aqueous dispersion also has the advantage that it is easy to apply even in thicker layers and, thanks to the low application temperatures, enables the use of high-strength polyester fiber fabrics. The tensile strength and the large number of these fabrics allow an exact adaptation to the intended use. The claimed dispersion and the process according to the invention provide weather-resistant, flexible, smooth, closed and dirt-repellent coatings of high quality. The fabrics coated in this way are particularly suitable for use in air-inflated halls, tent roofs, conveyor belts and special tarpaulins of all kinds.

The invention is further illustrated by the following examples.

example 1

A polyester fabric with a weight per unit area of 135 g / m ^{2 is used} as the material. Pre-impregnation is first effected by applying a polyvinylidene fluoride latex containing 0.1% y-methacryloxypropyltrimethoxysilane. It is pre-dried at 130 ° C. for 6 minutes and then baked at 210 ° C. for 2 minutes. Then the material is coated with an aqueous dispersion of the following composition:

Two coatings are applied, then dried at 130 to 135 ° C. for 5 to 6 minutes and baked at 200 to 210 ° C. for 2 to 3 minutes. A polymer coating with a basis weight of 180 to 210 g / m ² with a smooth, white and closed surface is obtained.

Example 2

A polyester fabric with a weight per unit area of 275 g / m ^{2 is used} and the fabric is pre-impregnated in accordance with the procedure described in Example 1.

Then the material is coated three times with an aqueous dispersion of the following composition:

The mixture is dried at 120 to 125 ° C. for 6 minutes and baked at 190 to 200 ° C. for 3 minutes. A polymer coating with a basis weight of 250 to 270 g / m ^{2 is obtained} and a metallic shiny, flexible and waterproof membrane building material is obtained.

Example 3

A polyester fabric with a basis weight of 200 g / m ^{2 is} used as the material. The fabric is treated with aqueous 0.1% y-methacryloxypropyltrimethoxysilane (pH = 3.6, adjusted with acetic acid).

Then the polyester fabric is coated three times with an aqueous dispersion of the following composition:

It is dried at 130 to 135 ° C. for 5 minutes and then baked at 190 to 200 ° C. for 3 minutes. A polymer basis weight of 420 g / m ^{2 is} achieved in this way and a flexible membrane building material with a smooth, white and closed surface is obtained.

Example 4

A polyester fabric with a basis weight of 200 g / m ^{2 is} used as the material.

The polyester fabric is impregnated with a polyvinylidene fluoride latex which contains 0.1% γ-methacryloxypropyltrimethoxysilane. The material is applied by dipping and brushing, pre-drying at 130 ° C. for 6 minutes and baking at 210 ° C. for 3 minutes.

Then the material is coated with an aqueous dispersion of the composition given below:

The mixture is dried at 125 ° C. for 5 minutes and baked at 205 ° C. for 3 minutes. After coating three times, a polymer application amount of about 380 g / m ^{2 is obtained} and a very flexible, smooth membrane building material is obtained.

Example 5

The polyester fabric described in Example 4 is used and the pre-impregnation is effected in the manner described there. Then the pre-impregnated polyester fabric is coated three times with an aqueous dispersion of the composition given below:

Example 6

The polyester fabric described in Example 1 is used and the pre-impregnation is effected in the manner described there. Then the pre-impregnated polyester fabric is coated three times with an aqueous dispersion of the following composition:

Example 7

The polyester fabric described in Example 3 is used, but no pre-impregnation is carried out.

The polyester fabric is coated three times with an aqueous dispersion of the composition given below:

Example 8

Using the polyester fabric described in Example 2 with no pre-impregnation and coating this three times with an aqueous dispersion of the hereinbelow indicated composi- initially ^g:

A polymer application of 250 to 330 g / m ^{2 is achieved} and flexible, waterproof coatings are obtained.

Example 9

A polyester fabric with a basis weight of 200 g / m ^{2 is used} and this is coated three times with an aqueous dispersion of the following composition.

A polymer application of 410 to 430 g / m ^{2 is} achieved in this way.

Example 10

To demonstrate the flame retardancy of the coating, the same polyester fabric as in Example 9 is used and this is coated three times with the dispersion also mentioned in Example 9, in which 3.0% by weight of water by 2.0% by weight of antimony trioxide (Stibiox) and 1.0% by weight of melamine cyanurate were replaced.

The fabric coated in this way with a polymer application of 425 g / m ² proves to be significantly less flammable in comparison to the other coatings in the fire test according to DIN 4102.

Claims (34)

1. Aqueous dispersion for the production of corrosion- and weather-resistant coatings on work materials, especially on synthetic fibre fabrics, containing polyvinylidene fluoride, an acrylic co-polymer and a pigment, characterised by a content nf-

2. Dispersion according to claim 1, characterised in that it additionally contains 2.5 to 10 wt.%, referred to polyvinylidene fluoride, of a plasticiser.

3. Dispersion according to claims 1 or 2, characterised in that it additionally contains 0.01 to 1 wt. % of an adhesive agent.

4. Dispersion according to claims 1 to 3, characterised in that it additionally contains 1 to 30 wt. % of an adjuvant solvent for the light-protection agent and/or the plasticiser.

5. Dispersion according to claims 1 to 4, characterised in that it contains 30 to 45 wt.% of polyvinylidene fluoride.

6. Dispersion according to one of the preceding claims, characterised in that it contains the polyvinylidene fluoride with an average primary particle size of less than 0.5 J-tm.

7. Dispersion according to one of claims 1 to 6, characterised in that the acrylic co-polymer is a water-soluble co-polymer of acrylic acid and/or methacrylic acid and one or more monomers copolymerisable therewith.

8. Dispersion according to claim 7, characterised in that the acrylic co-polymer contains, as co-polymerised monomer, acrylamide, methacrylamide, acrylonitrile, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, styrene, butadiene and/or vinyl acetate.

9. Dispersion according to one of claims 1 to 8, characterised in that it contains the acrylic co-polymer in the form of the ammonium salt.

10. Dispersion according to claims 2 to 9, characterised in that it contains 2.5 to 10 wt.%, referred to polyvinylidene fluoride, of a plasticiser.

11. Dispersion according to one of claims 2 to 10, characterised in that, as plasticiser, it contains polypropylene adipate, polybutylene adipate, polypropylene sebacate, polybutylene sebacate and/or an ethylene/vinyl acetate co-polymer.

12. Dispersion according to one of the preceding claims, characterised in that it contains 5 to 15 wt. % of the low boiling alcohol or of a mixture of low boiling alcohol and higher boiling solvent.

13. Dispersion according to claims 1 to 12, characterised in that, as low boiling alcohol, it contains a primary, secondary or tertiary aliphatic alcohol with 1 to 5 carbon atoms.

14. Dispersion according to claim 13, characterised in that, as low boiling alcohol, it contains isopropyl alcohol.

15. Dispersion according to claim 12, characterised in that the mixture composition of low boiling alcohol and higher boiling solvent contains up to 50 wt. % of higher boiling solvent.

16. Dispersion according to claim 12, characterised in that as higher boiling solvent there are used diethylene glycol dimethyl ether, xylene, butyl glycol or their mixtures.

17. Dispersion according to claims 3 to 16, characterised in that as adhesive agent it contains a silane adhesive.

18. Dispersion according to claim 17, characterised in that as adhesive agent it contains y-methacryloxypropyltrimethoxysilane.

19. Dispersion according to claims 4 to 17, characterised in that as adjuvant solvent it contains methyl ethyl ketone, ethyl acetate and/or xylene.

20. Dispersion according to one of the preceding claims, characterised in that it additionally contains 1 to 5 wt.% of a thickening agent.

21. Dispersion according to claim 20, characterised in that as thickening agent it contains water-soluble ammonium polyacrylate.

22. Dispersion according to one of the preceding claims, characterised in that as light-protection agent it contains a benzotriazole derivative and/or a UV light protection agent having sterically hindered amino groups.

23. Dispersion according to one of the preceding claims, characterised in that it additionally contains antimony trioxide.

24. Dispersion according to claim 23, characterised in that it additionally contains melamine cyanurate.

25. Dispersion according to claim 24, characterised in that it contains 1 to 5 wt.% of antimony trioxide and 0.5 to 2 wt.% of melamine cyanurate.

26. Process for the production of corrosion- and weather-resistant coatings on work materials, especially on synthetic fibre fabrics, by application and stoving of a dispersion, characterised in that one uses a dispersion according to claims 1 to 25, whereby the applied amount per application amounts to 80 to 200 g./m², and subsequently stoves at temperatures of 170 to 2101 C.

27. Process according to claim 26, characterised in that one pre-dries the applied dispersion at 100 to 140°C. and stoves at 170 to 210°C.

28. Process according to claim 27, characterised in that one pre-dries the applied dispersion for 3 to 6 minutes and then stoves for 1 to 3 minutes.

29. Process according to claims 26 to 28, characterised in that one applies the dispersion several times, in each case pre-dries the coatings at 100 to 140°C. for 3 to 6 minutes and subsequently stoves for 1 to 3 minutes at 170 to 210°C.

30. Process according to one of claims 26 to 29, characterised in that one pre-impregnates the synthetic fibre fabric with a polyvinylidene fluoride latex.

31. Process according to one of claims 26 to 30, characterised in that one pre-impregnates the synthetic fibre fabric with a polyvinylidene fluoride latex which contains 0.1% -y-methacryloxypropyltrimethoxysilane.

32. Process according to one of claims 30 to 31, characterised in that, after the pre-impregnation, one pre-dries the material at 100 to 140°C. and subsequently stoves at 170 to 210°C.

33. Process according to one of claims 30 to 32, characterised in that one pre-dries the pre-impregnation for 3 to 6 minutes and stoves for 1 to 3 minutes.

34. Process according to one of claims 30 to 33, characterised in that, in the case of several applications, in each case, one pre-dries the pre-impregnation for 3 to 6 minutes at 100 to 140°C. and subsequently stoves for 1 to 3 minutes at 170 to 210°C.