WO2001025318A1

WO2001025318A1 - Compositions for high-temperature resistant film coatings

Info

Publication number: WO2001025318A1
Application number: PCT/EP2000/009575
Authority: WO
Inventors: Ulrich Siemann; Christoph Roth; Dieter Thiele; Wilfried Weigt
Original assignee: Lofo High Tech Film Gmbh; Few Chemicals Gmbh
Priority date: 1999-10-01
Filing date: 2000-09-29
Publication date: 2001-04-12
Also published as: EP1232201A1; DE19947395A1; AU7910600A

Abstract

The invention relates to coating compositions, especially for cellulose triacetate films. The inventive coating compositions contain polycondensates of at least two hydrolyzable alkoxy compounds of the elements Si, Ti, Al and/or Zr. At least one of the hydrolyzable compounds contains at least one non-hydrolyzable group and the molar ratio of the hydrolyzable groups to the non-hydrolyzable groups ranges between 100:1 and 10:1. The metal oxide-based coatings obtained by the sol-gel method starting from these compositions impart a high thermal resistance to the cellulose triacetate films coated therewith, which are therefore especially useful as separating coats in the production of base materials for printed circuits and for other lamination processes that are performed at high temperatures.

Description

Compositions for high temperature resistant film coatings

The present invention relates to compositions based on modified inorganic polycondensation products and their use for coating films, in particular based on cellulose triacetate, to increase the temperature resistance, the films coated in this way and their use as release films in the production of thermosetting laminates.

Numerous coatings for films are known which are based on organically modified inorganic condensation products. As a rule, they are based on compounds of silicon, titanium, aluminum and zirconium. With the appropriate post-treatment (such as curing), the desired properties, e.g. B. transparency, scratch resistance and abrasion resistance, preserved or reinforced. Despite the abundance of the known coating compositions, there is interest in further improvements, in particular with regard to their non-stick properties in relation to chemically reactive systems such as epoxy resins, polyimides, phenolic resins and cyanic acid esters in the temperature range from 200 to 250 ° C. These properties are particularly important in the production of base materials for printed circuit boards and the production of printed circuit boards using multilayer technology.

To produce base materials for printed circuit boards, so-called prepregs are laminated to copper foil using pressure and temperature. The prepregs consist of reinforcing materials (usually glass fiber fabrics) impregnated with reactive resins (epoxides, imides, phenols, cyanic acid esters), the resins being partially crosslinked in order to maintain a certain consistency of the material. During the lamination process, the reactive resins are cured and form a firm bond with the reinforcing material and the copper foil.

The lamination process is usually done in stacks, with several sheets being laminated at the same time. This requires the use of release film between the individual pairs of laminates. The separating film has to withstand the applied pressures and temperatures to such an extent that the resulting plates have no problems after lamination can be separated from each other and no components of the film remain on the plates.

It is known that polyester films (PET, PEN) and in particular triacetate films are used as the release film. Triacetate films meet the requirements described in the range of 160 to 180 ° C with regard to their hydrophobicity and temperature stability. That is why they are mainly used for the production of prepregs themselves. For modern lamination processes and the unlimited use of the available reactive resins, higher temperatures up to over 200 ° C are required. Untreated triacetate films are no longer suitable for this. Embrittlement occurs because any plasticizer that is present escapes from the film and the polymer itself is denatured. On the one hand, the hydrophobicity of the material is lost, on the other hand, the cohesion of the film is destroyed and it partially sticks to the surfaces to be separated.

In order to remedy this deficiency, the film is surface-sealed in such a way that, despite the effect of temperature, the film properties are largely retained and the surface-sealing layer itself, with its hydrophobicity, takes on the required separating effect.

It is known that silicones (silicone oils, silicone resins) can be used as coating components for this purpose (EP-A-769 540). JP-A-11/020086 describes a PEN-based release film with a two-layer structure, which consists of a primer (acrylate ester copolymer latex and methyltrimethoxysilane) and a silicone layer. However, such foils are unsuitable for use as separating foils in the production of laths, since parts of these silicone compounds pass over to the copper foil when they come into contact under high temperatures and pressures because they are not firmly anchored in the layer structure. This can lead to serious problems in the subsequent steps of circuit board manufacture and functional failures in the later use of the circuit board. Heat-resistant release films for the production of PVC films with coating compositions from a network of amino and glycidyl-modified SiO ₂ sols are described in JP-A-02/214624. However, these networks are unsuitable for use in the production of printed circuit boards since even with equimolar use of the active groups (amino, glycidyl groups) a complete conversion does not take place in the layer. A reaction of the remaining active groups with the prepregs, which are mostly based on epoxy resins, is possible, ie at high temperatures there is a bond between the release film and the prepreg.

Hydrophobic and separating properties can also be achieved by adding fluorine-containing components. For example, EP-A-0 641 843 describes perfluorinated alkylsilanes as constituents of water- and oil-repellent layers. DE-T-69216581 describes coating compositions for water-repellent glass surfaces which have organically modified inorganic condensation products, the organic structural elements of which are methyl, ethyl or propyl groups, which may or may not be fluorinated. From DE-41 18 184 it is known to provide condensation products in hydrophobizing coating compositions which result from a combination of perfluorinated siloxanes and polymerizable siloxanes. An additional polymerization step (photopolymerization) is required to achieve the layer strength.

Fluorine-containing coating compositions can only be applied to triacetate film to a limited extent. Experience has shown that if the proportion of fluorine in the inorganic condensation product is greater than 3 mol%, based on the starting products of the condensation, coating on triacetate film is not possible due to wetting problems.

The object of the present invention is to provide an improved coating composition based on organically modified inorganic condensation products, which is particularly suitable for coating cellulose triacetate film and which, in addition to the necessary properties of already known coating systems, such as transparency, mechanical stability and abrasion resistance, also excellent non-stick properties compared to chemically reactive systems after an intensive Contact under pressure and at temperatures of 200 to 250 ° C enables. The object of the invention is also to provide an improved release film for lamination processes.

According to the invention, these objects are achieved by a coating composition and a film having the features according to patent claims 1 and 7, respectively.

Advantageous embodiments and uses of the invention result from the dependent claims.

The basic idea of the invention is to create a coating composition of at least two hydrolyzable alkoxy compounds of the elements silicon, titanium, aluminum and / or zirconium, wherein in at least one of the compounds, in addition to the (hydrolyzable) alkoxy groups, non-hydrolyzable groups such as, for example, alkyl groups, Phenyl groups and optionally fluoroalkyl groups are included. A metal oxide layer is formed from condensates of the alkoxy compounds, in particular on plastic films. Films based on cellulose triacetate are preferably coated. The coated foils are resistant to high temperatures and are particularly suitable for use as release foils for the production of lead plates or their base materials or prepregs.

According to the invention, the object is achieved in particular by coating compositions based on polycondensates of several, but at least two, hydrolyzable compounds of the elements Si, Ti, Al and / or Zr, wherein at least one of these hydrolyzable compounds in addition to the hydrolyzable groups and also non-hydrolyzable groups in the form of aliphatic or aromatic Contains hydrocarbon residues and the molar ratio of the total hydrolyzable to the non-hydrolyzable groups in the monomeric starting compounds is between 100: 1 and 10: 1.

The non-hydrolyzable groups are preferably alkyl groups, aryl groups and / or fluorinated alkyl groups. Preferred alkyl groups are C _1-6 alkyl groups and phenyl groups are preferred among the aryl groups. One, more or all of the hydrogen atoms in the fluorinated alkyl groups can be substituted by fluorine atoms. The hydrolyzable starting compounds preferably correspond to the following general formulas:

(R'-O .M (I), wherein

M represents silicon, titanium, aluminum or zirconium; n has the value 3 (for M = Al) or 4 (for M = Si, Ti, Zr) and the radicals R ^{1 are the} same or different and each represent C ^ alkyl;

(R ¹ -O) ₃ M ¹ -R ² (II), wherein

M ^{1 is} silicon, titanium or zirconium and preferably silicon,

R ^{1 has} the meaning given above, and R ² = Cr.rg-alkyl or phenyl and preferably C ^ alkyl, «-C ₈ H ₁₇ or

(R'-O ^ M'tR ³ ), (III), wherein

M ¹ and R ^{1 have} the meanings given above, and R ^{3 is} C, ^ - alkyl or phenyl

The starting compounds of the formula I are fully hydrolyzable monomers, while the compounds of the formulas II and III contain one or two non-hydrolyzable groups.

Examples of fully hydrolyzable monomers (I) are: tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium, tripropoxyaluminium, tributoxyaluminium, tetrapropoxyzirconium.

Examples of representatives with at least one nonhydrolyzable group (II, III) are: methyl trimethoxysilane, methyl triethoxysilane, ethyl trimethoxysilane, ethyl triethoxysilane, propyl tripropoxysilane, butyl trimethoxysilane, butyl triethoxysilane, propyl triethoxysilane pentyl, phenyl-triethoxysilane, octyl trimethoxysilane, octyl triethoxysilane, hexadecyl dodecyl triethoxysilane and trimethoxysilane (each a non-hydrolyzable group), as well as dimethyl dimethoxysilane, dimethyl -diethoxysilane, diethyl-diethoxysilane and diphenyl-dimethoxysilane (each two non-hydrolyzable groups).

Particularly good results have been achieved with such coating compositions in which 5 to 100 mol% of the non-hydrolyzable groups are optionally fluorinated octyl groups.

At least one of the hydrolyzable compounds is preferably a silicon compound.

Compositions in which 15 to 25 mol% of the hydrolyzable compounds relate to a trialkoxy-octylsilane or a mixture of several trialkoxy-octylsilanes are particularly preferred.

A further improvement in the properties of the coating compositions according to the invention can be achieved by adding hydrolyzable compounds having fluorinated alkyl groups in an amount of 0.1 to 3 mol% (based on the total amount of the hydrolyzable compounds).

By coating conventional films with the coating compositions according to the invention, high-temperature-resistant films with protective layers based on metal oxide are obtained.

CeUulosetriacetatfoUen are preferably coated, wherein the coating can be applied to only one or both sides of the film.

The coatings according to the invention are preferably produced by the processes known per se for producing metal oxides by the sol-gel method (see, for example, BCJ Blinker, GW Scherer “Sol-Gel Science”). The application of the brine to the Depending on the application, films are made using available application techniques (e.g. by brushing, spraying or rolling), either immediately after the film is shaped (e.g. by pouring a polymer solution) or in a separate process step. When drying takes place after the sol has been applied, gel formation and finally the formation of an organically modified metal oxide film take place.

The brine is preferably produced by dissolving the hydrolyzable starting compounds in alcohols or ketones and adding water and optionally a small amount of acid. Examples of alcohols and ketones are methanol, ethanol, isopropyl alcohol or acetone. These solvents allow high coating speeds and good drying at 70 to 90 ° C. By varying the sol concentration, the layer thickness can be controlled in a simple manner and easily adapted to the requirements.

As already mentioned, a particularly preferred use of the films coated according to the invention is the use as tremo films in the production of prepregs and lead plates or base materials for lead plates.

The invention has the following advantages in particular: The compositions according to the invention show very good wetting of cellulose triacetate and thus also allow the realization of large layer thicknesses which cannot be achieved using known fluorine-containing brine. The coated films are completely transparent and have very good sliding properties. Another advantage of the coating according to the invention is its barrier effect for volatile constituents in the raw film. This is shown by the fact that a raw film made of cellulose triacetate is brown and brittle after tempering at approx. 250 ° C. and no mechanical stress has grown, whereas a film coated according to the invention is only slightly colored and can be bent without restriction after tempering. Another advantage is the very good anchoring of the metal oxide sol layer on the base, so that there is no transfer to neighboring layers or substrates even at high temperatures and pressure. In addition to the use for coating release films for the production of conductive plates, the coating compositions according to the invention are also suitable for hydrophobicizing other substrates and can be used to achieve special non-stick properties.

The following examples illustrate the implementation of the invention, without any limitation.

Example 1 (Sol 1):

A sol was made from

27.7 g tetraethoxysilane 9.3 g octyl-triethoxysilane 15 ml water

2 ml 0.1 N hydrochloric acid 150 ml ethanol

The mixture of ethanol, water and hydrochloric acid was placed in a beaker with a stirrer and stirred. The weighed silanes were mixed well using a magnetic stirrer and the mixture was added to the solvent mixture initially introduced while stirring. The addition was controlled so that the temperature of the total mixture did not exceed 30 ° C. After the addition, this solution was stirred for a further 3 hours at medium stirring speed, the beaker being kept closed so that no evaporation could take place. After a further 3 days in a sealed beaker, the sol for the coating could be further diluted.

Example 2 (Sol 2):

It became a sol

26 g tetraethoxysilane 1, 23 g dimethyl-diethoxysilane 9.3 g of octyl-triethoxysilane 15 ml of water 2 ml of 0.1 N hydrochloric acid 150 ml of ethanol prepared as described in Example 1.

Example 3 (Sol 3):

It became a sol from 27.7 g of tetraethoxysilane

0.85 g 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl-triethoxysilane 9.3 g octyl-triethoxysilane 15 ml water 2 ml 0.1 N hydrochloric acid 150 ml of ethanol prepared as described in Example 1.

Example 4 (Sol 4):

It became a sol

30.1 g tetraethoxysilane

2.55 g 3,3,4,4,5, 5,6,6,7,7,8, 8, 8-tridecafluorooctyl-triethoxysilane 2.3 g octyl-triethoxysilane 15 ml water

2 ml 0.1 N hydrochloric acid 150 ml ethanol prepared as described in Example 1. Example 5 (Sol 5):

It became a sol

27.7 g tetraethoxysilane 9.3 g octyl-triethoxysilane

15 ml water

2 ml of trifluoroacetic acid (20%) 150 ml of ethanol prepared as described in Example 1.

Example 6 (Sol 6):

26 g tetraethoxysilane 2.5 g dimethyl diethoxysilane 6.95 g octyl triethoxysilane

15 ml water 2 ml 0.1 N hydrochloric acid 150 ml isopropyl alcohol prepared as described in Example 1.

Example 7 (Sol 7):

It became a sol

24.2 g tetraethoxysilane 4.7 g tetrapropoxy titanium

9.3 g of octyl-triethoxysilane 15 ml of water 2 ml of 0.1 N hydrochloric acid 150 ml of isopropyl alcohol prepared as described in Example 1. Example 8 (Sol 8):

It became a sol

32.5 g triisobutoxy aluminum 9.3 g octyl triethoxysilane

15 ml water 6 ml hydrochloric acid (conc.) 150 ml isopropyl alcohol prepared as described in Example 1.

The “stock brines” obtained according to Examples 1 to 8 were diluted with methanol, ethanol, isopropyl alcohol or acetone to the concentration desired for the coating. The solids content of the coating composition formed by hydrolysis and condensation was 2.5% by weight in each case.

Example 9 (production of test samples):

In each case 100 ml of the stock brine described were diluted with 250 ml of ethanol. These coating compositions were applied with the aid of a roll coater on both sides in a coating machine on a 50 μm thick triacetate film and dried at 70 to 90 ° C. The dry layers obtained in this way had a thickness of approximately 0.5 μm, which corresponds to 20 ml / m ^{2 of} a coating solution with a solids content of 2.5%.

Patterns for wetting angle measurements and contacting experiments with the prepregs were cut from the materials obtained in this way. 10x10 cm sheets were cut for the contact angle measurement. The patterns for the contacting had an edge length of 6 cm. The contact partners (prepregs) were cut to an edge length of 4 cm. The measurements of the contact angle (foil against water) showed a value of> 90 ° for all samples. Contacting the prepregs proved to be a relevant evaluation method. For this purpose, the cut samples were stored and tempered between two glass plates in the following way.

6 sample foils were distributed on a 24x30 cm glass plate so that there was no overlap. A prepreg was placed in the middle of each sample film so that an edge of 1 cm remained visible from the film. A second film was placed on this stack parallel to the lower one. The two films in a stack are samples of a sample coating. A second glass plate of the same size was placed on this arrangement. This arrangement was placed in a preheated drying cabinet at 200 ° C and loaded with a weight of 1 kg. The tempering at 200 ° C was carried out over a period of 3 hours. After this time, the entire stack was removed from the drying cabinet and cooled to room temperature. The weight and the upper glass plate were then removed and the sample stacks checked for their separability.

Rating :

Untreated film: pattern glued all over

Examples 1-7: Foils can be easily separated from the prepreg

Example 8: Foils can be separated, small pieces of foil stick to the prepreg

These results show the excellent properties of release films coated according to the invention, which are therefore particularly well suited for the separation between stacked conductive plates during the lamination process.

Claims

claims

1. Coating composition containing polycondensates of at least two hydrolyzable alkoxy compounds of the elements Si, Ti, Al and / or Zr, characterized in that at least one of the hydrolyzable compounds contains at least one non-hydrolyzable group and the molar ratio of the hydrolyzable groups to the non-hydrolyzable groups between 100: 1 and 10: 1.

2. Coating composition according to claim 1, characterized in that the non-hydrolyzable groups are alkyl, aryl and / or fluorinated alkyl groups.

3. Coating composition according to claim 1 or 2, characterized in that 5 to 100% of the non-hydrolyzable groups are optionally fluorinated octyl groups.

4. Coating composition according to one of claims 1 to 3, characterized in that at least one of the hydrolyzable compounds is a silicon compound.

5. Coating composition according to one of claims 1 to 4, characterized in that 15 to 25 mol% of the hydrolyzable compounds consist of one or more trialkoxy-octylsilanes.

6. Coating composition according to one of claims 1 to 5, characterized in that 0.1 to 3 mol% of the hydrolyzable compounds used contain fluorinated alkyl groups.

7. High temperature resistant film, characterized by a coating based on a coating composition according to one of claims 1 to 6.

8. Film according to claim 7, characterized in that the coating is applied to one or both sides of a cellulose triacetate film.

9. Film according to claim 7 or 8, characterized in that the coating is formed by a sol-gel process from the coating composition.

10. Use of a film according to one of claims 7 to 9 as a release film in the manufacture of prepregs and Leiteφlatten.

11. Use of a coating composition according to one of claims 1 to 6 for coating films, preferably cellulose triacetate films.