DE19935326A1 - Use of self-organizing coatings based on fluorine-free polyfunctional organosilanes for the production of ultra-hydrophobic coatings - Google Patents

Abstract

The present invention relates to the use of mixtures based on fluorine-free polyfunctional organosilanes for the production of ultrahydrophobic, self-organizing coatings and to hybrid materials produced by their use.

Description

The present invention relates to the use based on fluorine-free polyfunction neller, self-organizing organosilanes, manufactured hybrid materials for Production of ultra-hydrophobic coatings.

DE-A 196 03 242, DE-A 196 03 241 and WO 94/06807 are numerous described polyfunctional organosilanes, from which a sol-gel process inorganic-organic hybrid materials can be produced. These materials can e.g. B. can be used for coating surfaces. These coatings stand out z. B. by excellent solvent resistance and good mechanical Ver wear resistance with simultaneous elasticity.

In many cases it is also necessary to render the substrates hydrophobic, so that for example, the material with a water-repellent surface in front of Witte influences is protected. A significant improvement in water repellency Properties of the substrates can be achieved by adding in addition to a suitable structure in the hydrophobic Introduces coating system. Through the combination of chemical hydropho bie and physical structuring can make contact angles of water droplets Chen / substrate greater than 160 ° can be reached. Furthermore, such are ultraphobic Observe surface roll angle of water droplets / substrate less than 10 °, which at the same time has a cleaning effect on dirt particles have, which adhere to the rolling water drops.

In the previously known ultrahydrophobic coating systems fluorine-containing compounds are used, which provides the necessary hydrophobicity of the coating system, but also bad Have solvent resistance or wear resistance.  

The object of the present invention was therefore to use mixtures Basis of monomeric polyfunctional organosilanes, which have a sufficiently high chemical Have hydrophobicity, so that the ultraphobic effect by suitable structuring can be achieved without the need to add a fluorine-containing Component must be mixed to produce ultrahydrophobic Be layers.

Surprisingly, it has now been found that the task with the invention Use of mixtures of monomeric polyfunctional organosilanes and Fillers with a suitable surface structure in a self-organizing System can be solved.

The present invention therefore relates to the use of mixtures comprising

• A) at least one linear, branched or cyclic monomeric organosilane, that over at least 2 silicon atoms with hydrolyzable and / or condensate has crosslinking groups, the silicon atoms each having at least 1 carbon atom via a linking unit are connected,
• B) alkoxides of the formula (I)
  Q (OR ") _z (I),
  in which
  QB, Al, Ga or In means
  z is 3 and
  R "is an optionally mono- or polysubstituted C ₁ -C ₆ alkyl or C ₆ -C ₁₂ aryl radical
  and / or in what
  Q means Si, Ge, Ti, Zr or Hf,
  z is 4 and
  R "has the meaning given above,
  and / or compounds of formula (II)
  (R ') _4-y Si (OR ") _y (II),
  wherein
  R 'is a C ₁ -C ₆ alkyl or C ₆ -C ₁₄ aryl radical which can be substituted one or more times,
  y is 1, 2 or 3 and
  R "has the same meaning as in formula (I)

for the production of ultra-hydrophobic coatings.

Alkoxides of the following formulas are particularly preferred:
Si (OCH ₃ ) ₄ (tetramethoxysilane),
Si (OC ₂ H ₅ ) ₄ (tetraethoxysilane),
CH ₃ -Si (OCH ₃ ) ₃ (methyltrimethoxysilane),
CH ₃ -Si (OC ₂ H ₅ ) ³ (methyltriethoxysilane),
C ₆ H ₅ -Si (OCH ₃ ) ₃ (phenyltrimethoxysilane),
C ₆ H ₅ -Si (OC ₂ H ₅ ) 3 (phenyltriethoxysilane).

The organosilanes of component (A) preferably contain at least 3, especially preferably at least 4 silicon atoms with hydrolyzable groups.

Linking structural units in the sense of the invention are both individual atoms and molecules. As molecular units are preferably linear or branched C ₁ - to C ₂₀ -alkylene chains, C ₅ - to C ₁₀ -cycloalkylene radicals, aromatic radicals, for. B. phenylene, naphthylene or biphenylene, or combinations of aromatic and aliphatic radicals. The aliphatic and aromatic radicals can also contain heteroatoms, such as Si, N, O or S.

Cyclic and cage-shaped siloxanes and branched carbosilanes may be mentioned in particular as linking units, preference being given to compounds of the formula (III) as monomeric organosilanes (A):

R ¹ _4-i Si [(CH ₂ ) _n Si (OR ² ) _a R ³ _3-a ] _i (III)

With
i = 2, 3, 4, preferably i = 4,
n = 1 to 10, preferably n = 2, 3, 4, particularly preferably n = 2 and
R ¹ = C ₁ -C ₆ alkyl, C ₆ aryl,
R ² = C ₁ -C ₆ alkyl, C ₆ aryl, preferably R ² = methyl,
a = 1 to 3,
R ³ = C ₁ -C ₆ alkyl, C ₆ aryl, preferably R ³ = methyl, ethyl, i-propyl, where a = 1 R ^{3 can} also be hydrogen.

Further examples are cyclic compounds of the general formula (IV)

With
m = 3 to 6, preferably m = 3 or 4,
o = 2 to 10, preferably n = 2,
R ⁶ = C ₁ -C ₆ alkyl or C ₆ -C ₁₄ aryl,
preferably R ⁶ = methyl, ethyl, particularly preferably R ⁶ = methyl,
R ⁵ = alkyl, aryl, preferably R ⁵ = methyl,
c = 1 to 3,
R ⁴ = alkyl, aryl, preferably R ⁴ = methyl, ethyl, isopropyl, for the case c = 1 R ^{4 can} also mean hydrogen.

Further examples are cyclic compounds of the general formula (V)

R ¹⁰ _4-i Si [OSiR ⁹ ₂ (CH ₂ ) _p Si (OR ⁷ ) _d R ⁸ _3-d ] _i (V),

With
1 = 2 to 4, preferably i = 4,
p = 1 to 10, preferably p = 2, 3, 4, particularly preferably p = 2,
R ⁹ = alkyl, aryl, preferably R ⁹ = methyl,
R ⁸ = alkyl, aryl, preferably R ⁸ = methyl,
d = 1, 2, 3,
R ⁷ = alkyl, aryl, preferably R ⁷ = methyl, ethyl, isopropyl, for the case d = 1 R ^{7 can} also be hydrogen.

According to the invention, alkyl is understood as C ₁ -C ₆ alkyl, preferably C ₁ -C ₄ alkyl, and aryl is C ₆ -C ₁₄ aryl, preferably C ₆ aryl.

In particular, as monomeric organosilanes, silanols (or their alkoxides) such as
Si [CCH ₂ ) ₂ Si (OH) (CH ₃ ) ₂ ] ₄ ,
cyclo- {OSiMe [(CH ₂ ) ₂ Si (OH) Me ₂ ]} ₄ ,
cyclo- {OSiMe [(CH ₂ ) ₂ Si (OEt) ₂ Me]} ₄ ,
cyclo- {OSiMe [(CH ₂ ) ₂ Si (OMe) Me ₂ ]} ₄ and / or
cyclo- {OSiMe [(CH ₂ ) ₂ Si (OEt) ₃ ]} ₄ ,
prefers.

For structuring the surface of the used by the invention Mixtures that can be produced, the mixtures optionally contain additional filler particles (C).

The filler particles used are in particular those whose surface structure has a suitable roughness in order to produce an ultraphobic effect in combination with the hydrophobic mixtures according to the invention by self-organization. Oxide, oxide hydrates, hydroxides and / or nitrides of the elements B, Al, Ga, In, Tl, Si, Ge, Sn, Ti, Zr, Hf, V, Nb, Ta, Fe, Co, Ni, are preferably used as filler particles. Ce, Zn, such as B. Al ₂ O ₃ , SiO ₂ , TiO ₂ , Ni (OH) ₂ used.

Furthermore, the mixtures used according to the invention optionally contain Solvent (D). Suitable solvents are, for. B. mono- and polyfunctional Alcohols such as B. methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, 1-methoxy-2-propanol and ethylene glycol, ketones such as e.g. B. acetone,  Methyl ethyl ketone and methyl isobutyl ketone and esters such as. B. n-butyl acetate turn. Mixtures of different solvents can also be used be used.

With an appropriate coordination of the solvents used (D) it is also possible, the mixtures according to the invention additionally organic, fluorine-free Add polymers. This can e.g. B. to improve the elasticity of the Mixtures produced coatings are used. But also the liability of one Coating, especially on plastics, as well as an intrinsic increase in Hydrophobia, can be improved by adding organic, fluorine-free polymers become.

Preferred organic polymers are those based on poly (meth) acrylates, Polyesters, polyamides, polyketones or polycarbamates called.

The mixtures used according to the invention can of course also soluble dyes or organic and inorganic pigments for coloring, as Corrosion protection or UV protection agents, as well as other paint aids such as e.g. B. flow aids are added.

Furthermore, the mixtures used according to the invention can also be catalysts included to accelerate the hydrolysis and condensation reactions. As Catalysts can include organic and inorganic acids or bases as well organometallic compounds or metal alkoxides are used.

The mixtures used according to the invention preferably have the following composition (mass fractions in solution):

• A) 1 to 80% by weight of at least one monomeric organosilane,
• B) 0 to 50% by weight alkoxides,

possibly

• A) 1 to 50 wt .-% filler particles and
• B) 0 to 80 wt .-% solvent

the sum of all the components present being 100% by weight.

The mixtures used according to the invention are preferably prepared in such a way that components (A), (B) and (D) are mixed in any order and component (C) is optionally added with stirring.

Another object of the invention are hybrid materials obtainable from Implementation of the mixtures used according to the invention in the presence of Water and optionally catalysts.

Examples of catalysts are e.g. B. called: organic and inorganic Acids and bases, such as formic acid, p-toluenesulfonic acid, hydrochloric acid or sodium and potassium hydroxide, organometallic catalysts, such as. B. Dibutyltin laurate and catalytically active alkoxides, such as. B. Ti and Al alkoxides.

The amount of water is preferably at least so much that all hydrolyze baren groups of the mixture can react. This is particularly preferred molar ratio of hydrolyzable groups to water between 1: 1 and 1: 3.

Another object of the invention are coatings, obtainable by Auf bring (application) of the mixtures or hybrid used according to the invention materials on a substrate surface and their hardening by evaporation of the volatile components.  

This can, for example, at temperatures from -30 ° C to + 250 ° C, preferably at Normal pressure. If necessary, the coating obtained can be given to the at the specified temperatures.

The mixtures used according to the invention are particularly suitable for the manufacture provision of hybrid materials or coatings, which are characterized by ultra hydrophobic properties, excellent resistance to solvents and chemicals, thermal resistance and mechanical wear resistance. Forth It should also be emphasized that through the self-organization of the mixtures or hybrid materials during the coating and curing process required combination of chemical hydrophobicity and physical Structuring of the surface occurs, which leads to the achievement of the ultraphobic effect leads.

Because of the property profile mentioned above, they are suitable according to the invention mixtures used mainly for coating substrates that before a Wetting with liquids, preferably water, should be permanently protected should.

Examples are the material protection of wood, mineral substrates such as Concrete roof tiles or bricks but also called metallic surfaces who is permanently protected against weathering, dirt deposits and corrosion that can.  

Examples Preliminary remarks

Cyclo- {SiO (CH ₃ ) [(CH ₂ ) ₂ Si (OH) (CH ₃ ) 2]} ₄ (hereinafter: D4-silanol) was prepared as described in DE-A-196 03 241. Aerosils from Degussa were used as filler particles. In the following embodiment, the AEROSIL® R 812 was used (hereinafter: R 812).

The coatings were applied using a film puller with a Gap width of 120 µm on glass plates. After evaporation the volatile stock parts at room temperature, the coatings were dried in a circulating air cabinet cured.

The contact angles were measured with water drops with a volume of 10 µl, which are put to the test with a syringe. The static water edge angle was on a flat, horizontally aligned surface based on the silhouette certainly. The advancement and retraction angles are increased by increasing (advancement angle) or smaller (retraction angle) of the drop volumes with the help of the Syringe detected. To do this, the silhouette of the drop with a video camera filmed and the contact angle based on the single image immediately before (Vorwinwin kel), or immediately after (retraction angle) the change in the contact area of the drop with the sample surface. The Nei Specification of the sample surface to the horizontal, at which a drop of water with a volume of 10 µl begins to move on the sample surface.

Example: Production of fluorine-free, ultraphobic coatings

4.1 g of R 812 are dissolved in 28.5 g of 1-methoxy-2-propanol, 5.0 g of D4-silanol and 6.5 g Dispersed tetraethoxysilane. For this, the water specified in Table 1 quantities including catalyst (addition takes place as pure acid quantity) and  the mixture was stirred for one hour at room temperature (23 ° C). After that the the resulting coating solution is applied to glass (120 μm wet film thickness) and coated cured substrate at 130 ° C for one hour in a circulating air oven. The mitit The water edge, advancement, retraction and roll-off angles are shown in Table 2 leads.

Table 1: Manufacturing

Table 2: Test results

Claims (4)

1. Using mixtures containing

• A) at least one linear, branched or cyclic monomeric organosilane which has at least 2 silicon atoms with hydrolyzable and / or condensation-crosslinking groups, the silicon atoms in each case being connected to one another via at least 1 carbon atom via a linking unit,
• B) alkoxides of the formula (I)
  Q (OR ") _z (I),
  in which
  QB, Al, Ga or In means
  z is 3 and
  R "is an optionally mono- or polysubstituted C ₁ -C ₆ alkyl or C ₆ -C ₁₂ aryl radical,
  and / or in what
  Q means Si, Ge, Ti, Zr or Hf and
  z is 4 and
  R "has the meaning given above,
  and / or compounds of formula (II)
  (R ') _4-y Si (OR ") _y (II),
  wherein
  R 'is a C ₁ -C ₆ alkyl or C ₆ -C ₁₄ aryl radical which can be mono- or polysubstituted,
  y is 1, 2 or 3 and
  R "has the same meaning as in formula (I),

for the production of ultra-hydrophobic coatings. 2. Use according to claim 1 containing

• A) 1 to 80% by weight of at least one monomeric organosilane,
• B) 0 to 50 wt .-% alkoxides

possibly

• A) 1 to 50 wt .-% filler particles and
• B) 0 to 80 wt .-% solvent

the sum of all the components present being 100% by weight. 3. Hybrid materials according to claim 1, characterized in that the after Claim 1 used mixtures in the presence of water and given if necessary, catalysts are implemented. 4. Coatings made by applying the mixtures used Mixtures used according to claim 1 to 2 on substrate surfaces.