EP1499680A1

EP1499680A1 - Anti-adhesive coatings for reactors

Info

Publication number: EP1499680A1
Application number: EP03718736A
Authority: EP
Inventors: Michael Mager; Christian MÄHNER; Gerhard Langstein
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 2002-04-18
Filing date: 2003-04-07
Publication date: 2005-01-26
Also published as: US20050196627A1; US20030198739A1; TW200403314A; JP2005522554A; CA2482835A1; AU2003222800A1; WO2003087229A1; DE10217202A1

Abstract

The invention relates to the use of specific compositions consisting of sol-gel materials as anti-adhesive coatings and to devices for producing and treating polymers, in particular rubbers. Said devices are characterised in that they have an anti-adhesive coating of this type consisting of a hydrophobic sol-gel material.

Description

Afati adhesive coatings for reactors

The present invention relates to the use of certain compositions from certain sol-gel materials as non-stick coatings and devices for the production and refinement of polymers, in particular rubbers, characterized in that they are made from a hydrophobic sol-gel coating by means of such a non-stick coating. Material.

It is very common in the manufacture and processing of polymers

Deposits of the educts used, the products to be isolated or auxiliary substances (additives). These deposits then lead, for example, to a significant reduction in the heat transfer of chemical reaction apparatus, and in many cases complete cleaning has to be carried out after just one batch. This is extremely cost-intensive, in particular because of the shutdown of the system, and cleaning is often associated with dangers and. there is waste (e.g. contaminated solvent) which

'must be disposed of appropriately. On the other hand, the deposits themselves can seriously impair the quality of the desired product. For example, they change color due to overheating on a heated reactor wall

Deposits can affect the entire product.

Because of the reasons mentioned above, deposits should therefore be prevented as far as possible during the manufacture and processing of polymers on the apparatus used. For example, in EP-A 0 847 404 there is a protective coating

("Putrefaction protection material") for the inner walls of polymerization reactors - which reduces the deposition of polymers. The protective coating is obtained by applying an alkaline solution of an alkylene sulfonic acid-substituted (hydroxy) Νaphtol. The protective coating obtained is yellow to brown and shows good effectiveness against polyvinyl chloride (hardly any deposits after

1000 reaction batches). In the manufacture of aci-nitrile-nitrile-butadiene-styrene (ABS) and polystyrene, however, the reactor had to be cleaned in the usual manner after 50 or 150 batches or batches. In addition to the limited number of batches that can be carried out without cleaning the reactor, the protective coating described in EP-B-0 847 404 has the particular disadvantage that it has to be renewed after each polymerization.

It is also known that materials based on fluorine-containing polymers, in particular based on polytetrafluoroethylene (Teflon®), can be used as anti-adhesive coatings. However, such polymers are complex in terms of their production and processing. They can be used without a suitable one

Pretreatment not on metallic substrates e.g. made of • steel (bad adhesion). Often, several additional, adhesion-promoting coatings are necessary for this. In addition, the polymers mentioned are often dissolved by aggressive solvents such as halogenated hydrocarbons (swelling) - and can therefore often not be used in rubber production and processing.

The object of the present invention was therefore to provide apparatus for the production and processing of polymers on which the deposition of polymers is significantly reduced or prevented by applying a suitable coating and the coating does not have to be renewed after each production or processing step.

In particular, the object of the present invention was to provide appropriately equipped apparatus for the production and processing of

Rubbers. Because of the extraordinarily high tendency of rubbers to deposit on the inner walls of corresponding apparatus, there was the greatest need for a technical solution.

It has now surprisingly been found that coating the above-mentioned apparatuses with a hydrophobic sol-gel material is very simple and effective the accumulation of polymers, especially rubbers, is prevented. In contrast to the prior art, the coatings do not have to be applied again after each processing step (for example the polymerization) and can be applied very easily. The coatings are colorless and adhere well to the materials commonly used in chemical equipment, such as steel or enamel, so that contamination of the manufactured or processed product can be excluded.

The present invention therefore relates to the use of certain compositions of certain sol-gel materials as non-stick coatings and apparatus for the production and processing of polymers, in particular rubbers, characterized in that they have a non-stick coating made of a hydrophobic sol-gel material ,

Hydrophobic sol-gel materials in the sense of the invention are essentially three-dimensionally crosslinked, organically modified amorphous glasses which are obtained by hydrolysis and condensation reactions of low molecular weight compounds, e.g. Silicon alkoxides can be obtained. After hydrolysis and condensation, the hydrophobic sol-gel materials according to the invention preferably have at least one structural element of the formula (I)

[R ¹ - (E) _i -] _j -Si [R (O _1/2 ) ₃ . _k ] ₄ - _j (I)

in which

i is 0 or 1, j 1, 2 or 3, and k is 0, 1 or 2, and

E is oxygen or sulfur, and R ^{1 is} an optionally substituted alkyl or aryl radical or a bridging one

Alkylene or arylene radical, and R is an optionally substituted alkyl or aryl radical,

on.

The sol-gel materials particularly preferably have a structural element of the formula

(II)

in which

j is 1, 2 or 3, and k is 0, 1 or 2, and

R ^{1 is} a bridging C ¹ -C 6 -alkylene radical, and R ^{2 is} an optionally substituted alkyl or aryl radical,

on.

The sol-gel materials very particularly preferably have a structural element of the formula (III)

[R ¹ ] _j -Si [R ² _k (O _1/2 ) ₃ - _k ] ₄ . _j (III)

in which

j is 1, k is 0, 1 or 2, and

R ^{1 is} a bridging d- to C -alkylene radical, and

R ^{2 is} a methyl or ethyl radical,

on. Polyfunctional organosilanes are preferably used for the production of sol-gel materials of the form n (I), (II) or (III), in which R ^{1 is} an alkylene radical. For the purposes of the invention, these are monomers, oligomers and / or polymers, characterized in that at least 2 silicon atoms with hydrolyzable and / or condensation-crosslinking groups each have at least one Si, C bond, preferably at least one alkylene group (-CH ₂ -) to one the unit linking silicon atoms are bound. Polyfunctional organosilanes with at least 3, better still with at least 4 silicon atoms with hydrolyzable and / or condensation-crosslinking groups are particularly preferred. As hydrolyzable groups which, after hydrolysis and condensation, finally give the radicals Si (Oι _{/ 2} ) in the formulas (I), (II) or (III) mentioned, alkoxy or aryloxy groups are particularly suitable, alkyloxy groups such as Methyloxy, ethyloxy, propyloxy or butyloxy called. Condensation crosslinking groups are in particular silanol groups (Si-OH). As a linking

Modules in the sense of the invention, both individual atoms and molecules may be mentioned. Molecular structural units can be, for example, linear or branched Q-C ₂ o-alkylene chains, Cs-Cio-cycloalkylene radicals or C ₆ -C ₂ -aromatic radicals, such as phenyl, naphthyl or biphenyl radicals. The radicals mentioned can be substituted one or more times and can in particular also contain heteroatoms, such as Si, N, P, O or S, within the chains or rings.

Coatings which are particularly resistant to chemicals are obtained if the linking structural unit of the polyfunctional organosilanes consists of linear, branched, cyclic or cage-shaped carbosilanes, carbosiloxanes or siloxanes.

Examples of such polyfunctional organosilanes are shown in the general formulas (fV), (V) and (VI).

[(R ³ O) ₃ - _a (R ⁴ ) _a Si (CH ₂ ) _e ] cX - [(CH ₂ ) _f Si (OR ⁵ ) ₃ . _b (R ⁶ ) b] d (IN)

in which R> 3, R, R and R independently of one another are C 1 -C ₈ -alkyl radicals or phenyl radicals, preferably methyl, ethyl or phenyl radicals,

a, b are independently 0, 1 or 2, preferably 0 or 1, and

c, d and e, f independently of one another are greater than or equal to 1, preferably greater than or equal to 2, and

X is a bridging structural unit for a linear, branched, cyclic or cage-shaped siloxane, carbosilane or carbosiloxane, preferably a cyclic or cage-shaped siloxane, carbosilane or carbosiloxane.

Cyclic carbosiloxanes of the general formula (V) are particularly preferably used,

in which

R ⁷ , R ⁸ and R ⁹ independently of one another are C 1 -C 4 -alkyl radicals, h is 0, 1 or 2, preferably 0 or 1, and g is an integer from 1 to 4, preferably 2, and i represents an integer from 3 to 10, preferably 4, 5 or 6.

Examples of cyclic carbosiloxanes are compounds of the formulas (Via) to (Vle), in which R ^{10 represents} methyl or ethyl:

(Via) cyclo- {OSi [(CH ₂ ) ₂ Si (OH) (CH ₃ ) ₂ ]} ₄ (VIb) cyclo- {OSi [(CH ₂ ) ₂ Si (OR ¹⁰ ) (CH ₃ ) ₂ ]} ₄ (VIc) cyclo- {OSi [(CH ₂ ) ₂ Si (OH) ₂ (CH ₃ )]} ₄ (VId) cyclo- {OSi [(CH ₂ ) ₂ Si (OR ¹⁰ ) ₂ (CH ₃ )] } ₄ (VIe) cyclo- {OSi [(CH ₂ ) ₂ Si (OR ¹⁰ ) ₃ ]} ₄ .

The oligomers of the cyclic carbosiloxanes mentioned in WO 98/52992 (page 2) can of course also be used as polyfunctional organosilanes in the process according to the invention. It is also possible to use mixtures of various cyclic monomeric or else oligomeric carbosiloxanes.

The sol-gel coating solution is prepared, for example, by mixing suitable low molecular weight compounds in a solvent, after which the hydrolysis and / or condensation reaction is initiated by adding water and, if appropriate, catalysts. The execution of such sol-gel processes is basically known to the person skilled in the art. For example, EP-A 0 743 313 describes the syntheses of polyfunctional organosilanes and organosiloxanes and processes for preparing corresponding sol-gel coating solutions, from which the sol-gel materials of the formula (III) can in turn be obtained.

EP-A 0 787 734 and WO-A 98/52992.

The apparatus according to the invention for the production and processing of rubbers is produced a) by application of suitable sol-gel coating solutions according to customary methods, b) evaporation of volatile constituents such as solvents and condensation products c) and curing, if appropriate at elevated temperatures, which ultimately leads to the

Coating of the hydrophobic sol-gel material is obtained.

The application can be carried out according to all common methods, such as dipping, spraying, flooding, spinning, knife coating or pouring, whereby the substrate can be coated on the entire surface or only on parts thereof. The use of

Sol-gel coating solutions have the particular advantage that, due to their usually very low viscosity and good adhesion, e.g. on steel, an internally coating of complicatedly shaped apparatuses for the production and processing of rubbers can be carried out. For example, existing reactors and / or pipelines by passing the sol-gel coating solution through them,

Evaporating the volatile components and curing, e.g. in a, if necessary warm, air or inert gas stream (e.g. nitrogen). For the application of appropriate coatings, see, for example, Organic Coatings: Science and Technology, John Wiley & Sons 1994, Chapter 22, pages 65-82.

Since pretreatment of the equipment, e.g. it is usually not necessary to apply a primer, the application can be carried out directly after the surface to be coated has been cleaned appropriately.

Typical materials from which the apparatus according to the invention can consist are metals or enamels, preferably iron-containing metallic materials, particularly preferably steels.

The apparatuses according to the invention, which are equipped with a hydrophobic sol-gel material, are particularly suitable for the production and enticing of chewing agents. such as butyl and bromine and chlorobutyl rubber, polybutadienes, acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, chloroprene rubber, ethylene-vinyl acetate rubber, butadiene rubber, styrene-butadiene rubber, ethylene-propylene.

They can be used in particular for the production and processing of polybutadienes, chloroprenes and ethylene-propylene rubbers and butyl rubber.

The following rubbers are mentioned in detail: see above.

The rubbers can be produced by all established ner processes, such as the processes described in more detail below. As a solvent, e.g. organic compounds (or their isomer mixtures), such as hexane, cyclohexane, benzene, methylene chloride, toluene or technical mixes such as DHΝ 50 (50-70% by weight n-hexane + 5-10% by weight cyclohexane + 25- 35 % By weight of methylcyclopentane, 0-5% by weight of 2-methylpentane, 0-10% by weight of 3-methylpentane) from Exxsol can be used. Due to the good thermal resistance and adhesion of the coatings to the inner walls of the equipment, the production and processing can be carried out at temperatures from -40 to 150 ° C, and

^'' Pressures from 0.1 to 6 bar.

The following ner processes for producing various rubbers are shown as examples:

chloroprene

Chloroprene is, as by F. Röthemeyer and F. Sommer, in "rubber technology"

Hanserverlag 2001, pp. 150-152, produced by adding chlorine to butadiene (Distillers-Nerfahren). The reaction produces a mixture of 1,2- and 1,4-dichlorobutene. After isomerization of 1,4-dichlorobutene to 1,2-dichlorobutene, 2-chloro-1,3-butadiene is obtained by elimination of HCl.

The technical polymerization of chloroprene is carried out in an aqueous emulsion using a radical mechanism at temperatures between 10 and 45 ° C. Resin acids, NaOH and the Na salt of a condensation product of formaldehyde and naphthalenesulfonic acid are used as emulsifiers. The polymerization is started by potassium persulfate or by redox systems. Due to the high reactivity of chloroprene, gel formation occurs even at conversions of 30% by weight. The gel content can be reduced by adding regulators (thiols, xanthogen disulfide or sulfur). The polymerization is terminated by inhibitors such as Thiuram disulfide and tert. Catechol.

The excess monomer is removed by steam distillation in vacuo and recovered. The degassed latex is adjusted to a pH of approx. 6.0 with acid and coagulated on a freezer roller (-15 ° C). The rubber film is peeled off, washed and dried.

The rubbers are classified according to the controllers used as follows:

Homopolymers: mercaptan and xanthate modified types

Copolymers: sulfur modified types

butyl rubber

The monomers ϊsobutylene and isoprene are obtained as described by F. Röthemeyer and F. Sommer in "Kautschuktechnologie" Hanserverlag 2001, pp. 136-146, from the C4 and C5 cuts in naphtha production. Butyl rubber is produced by cationic copolymerization of isobutylene with small amounts of isoprene (0.5-2.5% by weight) in solution. The isoprene units are statistically distributed in the copolymer.

The growth reaction of the cationic polymerization proceeds very quickly. Therefore, the molar mass depends to an unusually high extent on the polymerization temperature. The poppy seed mass increases inversely with temperature. If isobutylene is polymerized at room temperature, oligomers are obtained because the chain transfer reaction is dominant. Long-chain polymer chains are only obtained at low temperatures (approx. -90 ° C). Weakly polar, e.g. chlorinated

Hydrocarbons (methylene chloride, chloroform). Lewis acids such as A1C1 ₃ or BF ₃ are used as catalysts, which are activated by small amounts of cocatalysts (water, acids). 1-Butene acts as a regulator, but also deactivates the catalyst.

The large-scale copolymerization of isobutylene and isoprene takes place in methylene chloride at temperatures of -100 ° C. The monomer concentration is 25% by weight, and A1C1 _{3 is} used as the catalyst. The cooled monomer mixture (isobutylene and 0.5-3% by weight of isoprene) and the catalyst dissolved in methylene chloride are fed to a continuous reactor. The polymerization is still very rapid at -100 ° C. Polybutylene is insoluble in methylene chloride and is obtained as a suspension (precipitation polymerization). The polymerization suspension is continuously drawn off and hot water is added. Solvents and monomer residues are removed by stripping and returned to the process after separation by distillation. A stabilizer and a mixture of stearic acid and zinc stearate (0.4-1% by weight) are added to the polymer suspension. Stearates are used to avoid agglomeration of the particles. In a second stage, the remaining hydrocarbons are removed in vacuo. Dewatering takes place using an extruder. The dry crumbs are then pressed into bales. EPDM

The monomers ethylene and propylene are obtained from natural gas or from crude gasoline by cracking, the termonomers are prepared by chemical synthesis as described by F. Röthemeyer and F. Sommer in "Kautschuktechnologie" Hanserverlag 2001, pp. 122-123.

The solution polymerization takes place in aliphatic hydrocarbons (pentane, hexane) at slightly elevated temperatures (30-60 ° C) continuously in stirred cascades. Due to the large differences in reactivity of the monomers, propene is used in

Excess used, ethene and the diene component are metered in continuously. The Ziegler-Natta catalyst is added as a dilute solution. Efficient cooling is required to dissipate the considerable heat of polymerization of 2500 kJ per kg of polymer. Since the copolymer is soluble in hexane, the reaction is carried out after a conversion of approx.

8-10 wt .-% canceled by adding water or carboxylic acids. In order to avoid side reactions (oxidation, gel formation), the catalyst residues must be washed out. Solvents and residual monomers are driven off by steam distillation. The polymer is then separated off, dried and pressed into bales. The molar mass is adjusted via the amount of catalyst and via a regulator. The suspension polymerization (precipitation polymerization) is carried out in liquid propene, the heat of vaporization of the propene being used for cooling. Catalyst, ethylene and / or termonomer are metered into the suspending agent (propene) continuously. The copolymer formed is not soluble in propylene and is obtained as a suspension. The suspension process enables significantly higher sales (up to 30% by weight) and the production of polymers with a higher poppy mass. The molar masses are regulated by adding hydrogen (hydride transfer). In the gas phase process (since 1996) ethylene, propylene and / or the termonomer are continuously fed to a fluidized bed reactor. The catalyst is placed directly in the fluid bed added. The gaseous monomers serve to fluidize the polymer particles as well as to remove the heat of polymerization.

polybutadiene

Butadiene can be polymerized anionically, coordinatively or radically as described by F. Röthemeyer and F. Sommer in "Kautschuktechnologie" Hanserverlag 2001, pp. 81-85 + 104-107. The anionic and coordinative polymerizations take place in solution, the radical polymerization takes place On an industrial scale, polybutadiene is produced with lithium alkylene or Ziegler-Natta catalysts, and the resulting polymers differ in their microstructure (ice, trans and vinyl content).

The polymerization with Li-alkylene is carried out in solution and follows an anionic mechanism. Aliphatic or cycloaliphatic hydrocarbons are used as solvents. The monomer concentrations are between 10 wt .-% _r 20, the reaction temperature is between 30-120 ° C. at

"Lower temperatures are linear, branched at higher temperatures

Products. The poppy mass depends only on the molar ratio of monomer to catalyst (no termination reaction). However, the polymerization can be carried out by adding

Stoppers (water, acids) can be broken off. The microstructure depends on the type of alkali metal and the polarity of the solvent.

The coordinative polymerization of butadiene with Ziegler-Natta catalysts takes place in solution. In order to avoid high viscosities, the mono _m * merante oil is limited to 10-15% by weight. The polymerization takes place in a series of stirred autoclaves under an inert atmosphere. Hydrogen is used as the molecular weight regulator. When the planned conversion is reached, the catalyst is deactivated and the monomer is protected by adding stabilizers. The Ziegler-Natta polybutadienes on the market are produced with the following catalyst systems: Titanium, cobalt, nickel, neodymium. The resulting polymers are characterized by a high cis content.

The radical polymerization of butadiene is carried out in an aqueous emulsion. Redox systems (hydroperoxide, sodium formaldehyde sulfonate and Fe (II) complexes) are used as catalysts, fatty acids and resin acids are used as emulsifiers.

Styrene butadiene rubber / SBR

The copolymerization of styrene and butadiene in solution takes place according to an anionic mechanism in solution. Due to the very different copolymerization parameters, the polymerization of butadiene takes place first and then styrene. This gives block copolymers with a defined transition region. By adding polar components (e.g. THF, tetramethylene diamine), the copolymerization parameters are changed so that the incorporation of styrene can take place statistically.

SBR can also be carried out radically initiated as an emulsion polymerization.

The degree of branching can be influenced by the reaction temperature. In the so-called cold polymerization process (T = 5 ° C) there is only a small proportion of branches. The hot polymerization process (T = 40-50 ° C) produces branched or pre-crosslinked polymer chains. In radical polymerization, the monomer units are statistically arranged in the resulting polymer. The emulsion polymerization has the advantage that it is easy to control thermally. Large-scale production takes place in continuous stirred tank cascades. Styrene, butadiene, regulator and emulsifier system are dispersed in water and pumped continuously through the reactors cooled to 5 ° C. Water-soluble peroxides, such as, for example, p-menthane hydroperoxide, are used as starters be activated in a redox system. The average residence time in the reactor is 8-10 hours. After conversion of 60-65% by weight has been reached, the process is terminated by adding a radical scavenger (for example dimethyldithiocarbamate). The latex formed after removal of the residual monomers (vacuum + water vapor) has a solids content of about 65% by weight.

Acrylic nitrile butadiene chew

Copolymers of butadiene and acrylonitrile are also known as nitrile rubber. They are of great importance for the manufacture of grease, oil and fuel resistant products.

Acrylonitrile butadiene rubber (NBR) is available with different acrylonitrile proportions as solid rubber and in the form of latex.

Today, acrylonitrile is mainly produced by reacting propylene with oxygen and ammonia.

Nitrile rubber is obtained by radical copolymerization of butadiene and acrylonitrile as by F. Röthemeyer and F. Sommer in "rubber technology"

Hanserverlag 2001, pp. 107-109, produced in an aqueous emulsion. Depending on the polymerization temperature, a distinction is made between warm and

Cold polymerization process, the latter being preferably used. As

Emulsifiers are used fatty acids (lauric palmitic, oleic acid), resin soaps (disproportionated abietic acid) or alkyl aryl sulfonic acids. The latter reduce the pollution of the vulcanization molds. As initiator either

Alkali persulfates or organic peroxides with reducing agents (redox systems) applied. Acrylonitrile can be copolymerized with butadiene in any ratio. The acrylonitrile content of the commercially available rubbers varies between 15 and 50% by weight. The poppy seed mass is adjusted by means of a regulator (alkyl mercaptans). To avoid chain branches, the polymerization is stopped at a conversion of 70-80% by adding stoppers (sodium hydrogen sulfide). The excess monomers are removed with steam in vacuo, recovered and used again. To improve storage stability and prevent

Cyclization reactions during the mixing process are added to the NBR latex slightly discolouring stabilizers (amines) or non-discoloring stabilizers (sterically hindered phenols).

Ausftihrungsbeispiele

The carbosiloxanes cyclo- {OSi [(CH ₂ ) ₂ SiOH (CH ₃ ) ₂ ]} ₄ and (oligomeric) cyclo- {OSi [(CH ₂ ) ₂ Si (OC ₂ H ₅ ) ₂ CH ₃ ]} ₄ were as described in US 5,880,305 and US 6,136,939. All other components were commercially available and were used without further cleaning.

Example 1: Production of sol-gel material 1 for coating equipment

a) To 8.3 g of cyclo- {OSi [(CH ₂ ) ₂ SiOH (CH ₃ ) ₂ ]} ₄ dissolved in 17.6 g of l-methoxy-2-propanol were added 10.7 g of tetraethyl orthosilicate and 1, 8 g of a 0.1 N aqueous solution of p-toluenesulfonic acid. After stirring for one hour, the mixture was finally diluted with 4.4 g of l-methoxy-2-propanol and 0.04 g of Tegoglide® 410 was added as a leveling additive. A low-viscosity, clear and colorless coating solution with a pot life of more than 5 hours was obtained.

b) The batch described under a) was treated with 139.6 g of cyclo-

{OSi [(CH ₂ ) ₂ SiOH (CH ₃ ) ₂ ]} ₄ , 295.5 g l-methoxy-2-propanol, 180.1 g tetraethyl ortho silicate, 30.4 g of a 0.1 N aqueous solution of p-toluenesulfonic acid, 74.0 g of l-methoxy-2-propanol and 0.7 g of Tegoglide® 410 were repeated, a corresponding coating solution being obtained.

Example 2: Production of sol-gel material 2 for coating equipment

180.1 g of tetraethyl orthosihkat and 30. Of 139.5 g of cyclo- {OSi [(CH ₂ ) ₂ SiOH (CH ₃ ) ₂ ]} ₄ dissolved in 295.5 g of l-methoxy-2-propanol were added to 139 , 4 g of a 1 N aqueous solution of p-toluenesulfonic acid. After stirring for one hour, the mixture was finally diluted with 74.0 g of l-methoxy-2-propanol; the addition of a leveling additive was omitted, however, in order not to influence the surface properties of the resulting film by the additive. As in example lb) a low-viscosity, clear and colorless coating solution with a pot life of more than 5 hours was obtained.

Example 3: Inner coating of a steel tube with the sol-gel material according to example lb)

200 g of a sol-gel coating solution prepared according to Example lb) were placed in a steel tube which was closed on one side and had a diameter of about 7 cm and a length of about 1.5 m. After the coating solution had been filled in, the still open side was also closed and the tube was rotated about its own axis for about 5 minutes. The closed ends were then opened, the coating solution was drained off and the steel tube was stored at ambient temperature for 15 hours. Finally, a stream of air at a temperature of approximately 80 ° C. was passed through for a further hour, as a result of which the sol-gel coating was further hardened. The visual inspection showed that the steel tube was evenly coated with an optically perfect coating (layer thickness approx. 5 μm).

Example 4: Coating of steel sheet with the sol-gel material la) and testing the tendency to stick to a rubber solution

Two commercially available steel sheets with a smooth surface were coated with the sol-gel solution from example la) by spinning (500 rpm, 20 sec). After briefly flashing off at room temperature (approx. 10 min), the coating was finally cured for one hour at 80 ° C., then for one hour at 130 ° C. An optically perfect film was obtained.

Now, 1 ml each of an approx. 10% by weight rubber solution (butyl rubber in n-hexane) was added to the coated side of the steel sheets and, after briefly flashing off at room temperature (approx. 10 min), the mixture was heat-treated at 70 ° C. for one hour (forced-air drying - cabinet). For comparison, an uncoated steel plate was treated in the same way with the rubber solution. After cooling to room temperature, the rubber could be easily and completely removed from the coated steel sheet, while it could only be detached from the uri-treated steel sheet by scraping with a fingernail.

Example 5: Coating of steel sheet with the sol-gel material la) and testing the resistance to dichloromethane

By testing the pencil hardness based on ASTM, the mechanical strength of the coatings produced according to Example 4 on the steel sheets was first examined. No damage was found with a pencil of hardness "2 H".

The steel plates were then (technically) immersed in dichloromethane for 24 hours; finally the pencil hardness was checked again. The optically unchanged coatings (no cracks, bubbles or detachment) again showed the pencil hardness "2 H", i.e. the coating was not damaged even by storage in this aggressive solvent.

Example 6: Coating of steel sheets with the sol-gel materials from Examples 1b) and 2) and testing the anti-stick effect during EPDM processing

a) Coating a steel sheet with a smooth surface: that according to the example

1 D) Sol-gel coating solution prepared was placed in a suitable immersion basin, then a steel sheet (approximately DIN A4 format) was immersed at constant speed and pulled out again. After briefly flashing off at room temperature (approx. 10 min), the coating was finally cured at 130 ° C. in a forced-air drying cabinet. The layer thickness of the optically perfect film was approximately between 6 and 8 μm, the adhesion was excellent (cross hatch test according to ISO 2409).

b) Coating a steel sheet with a rough surface: the coating described in 6a) with the sol-gel coating solution from Example 1b) was repeated, but in this case a steel sheet with a rough surface was used. The average roughness was approx. 50 μm.

c) in accordance with the method described in Example 6b), another rough steel sheet was coated, the sol-gel coating solution from Example 2) being used for this. After curing, an optically perfect coating with a layer thickness of approx. 8-10 μm was obtained.

d) Checking the effectiveness of EPDM processing:

The test panels produced according to Examples 6a), 6b) and 6c) were tested for their anti-stick effect in a plant for drying EPDM (dryer line). The test was carried out under extreme production conditions, i.e. at a temperature of approx. 120 ° C and a pH value of the wet EPDM dispersion of less than 1. As a comparison, a commercial coating system made of Teflon and an uncoated, smooth VA steel plate were tested under the same conditions. In a first screening, the sheets were mounted in the running product stream for approx. 24 hours directly at the critical entrance of the feed chamber. The dryer entrance is known to be the most problematic for adhesion

Job in the processing. Sensory testing of the sheet metal surfaces (adhesive properties of the rubber particles) gave adhesive notes in the range from 1-5 (very low adhesion, 1 to very strong adhesion, 5).

As can be seen in Table 1 below, the best commercial coating (Teflon) achieved adhesive 2 while the uncoated, smooth steel sheet showed very strong adhesion of rubber particles (rating 5).

With the coatings according to the invention made of sol-gel materials, very good adhesive marks (2) were achieved both on smooth and on rough surfaces. Surprisingly, despite the much simpler processing, the coatings according to the invention can achieve an anti-adhesive effect which is just as good as that of Teflon®.

Table 1

Claims

Patentansprtiche

1. Use of compositions containing at least one structural element of the formula (I)

[R ¹ - (E) _i -] _j -Si [R ² _k (O _1/2 ) ₃ - _k ] ₄ - _j (I)

where i is 0 or 1, j 1, 2 or 3, and k is 0, 1 or 2, and

E is oxygen or sulfur, as well

R ^{1 is} an optionally substituted alkyl or aryl radical or a bridging alkylene or arylene radical, and R ^{2 is} an optionally substituted alkyl or aryl radical,

as a non-stick coating in apparatus for the production and processing of polymers.

2. Device for the production or processing of polymers, characterized in that it is equipped with a non-stick coating according to claim 1.

3. Device for the production or processing of rubbers, characterized in that it is equipped with a non-stick coating according to claim 1.

4. Use of the device according to claim 2 for the production or processing of polymers.