DE20320640U1 - Silicone rubber products - Google Patents

Abstract

Silicone rubber article, characterized in that it is obtainable by modifying the surface of a polymeric substrate containing one or more silicone oil residues, the process comprising the steps of:
(i) extracting at least a portion of the silicone oil residues;
(ii) Plasma treatment of the substrate.

Description

Object of protection

The The present invention relates to novel silicone rubber articles which by a method of treating a polymeric substrate, the Contains silicone oil residues are available.

It becomes explicit noted that in the claims the reference to a Procedure is required because the subject of the protection only by indication of the manufacturing process can be sufficiently defined. The in the present application described manufacturing method However, they only serve to describe the method with which the Silicone rubber article according to the invention can be produced, and become explicit from the protection request locked out.

background the invention

Liquid silicone rubber (Liquid silicone rubber, LSR) is usually by mixing made of 2 silicone components. A component contains one Catalyst, and the other component contains a cocatalyst or Crosslinkers. Both components are stable as such and include typically mainly vinyl-terminated polydimethylsiloxanes. The silicone oil components be a high pressure and high temperature in an extractor, for example the production of tubes, or in an injection molding machine exposed. Typical examples available Acceptable LSR classes are the Elastosilfamilie of Wacker and the silicone silopren family from GE Bayer. Many other types of Silicone rubbers are available, such as those which are crosslinked for example by peroxides, or Silicone rubbers with other than methyl groups attached to the silicon atoms are bound, for example ethyl or phenyl or trifluoromethyl. The term "silicone rubber" is used to indicate all types of silicone rubbers.

today Silicone rubbers are used in many applications. at For some of these uses, it is desirable to use the silicone rubber for example by modifying the surface, for example by painting or gluing the surface, or by incorporating, for example, pigments and others To change substances into the material.

By methods of the prior art, such as in US 5,338,574 described, it is highly complicated to provide a stable modification of the surface of silicone rubber, which then has improved adhesion for a paint. Incorporation of materials, such as pigments, to provide a homogeneous distribution of color is equally difficult, and moreover, the process of incorporating such materials is very difficult.

In many technical applications, such as as a cover for switches, for example in the automotive sector, telephone keypads, computer keyboards, Displays and the like, LSR articles become a surface treatment subjected. The surface may be subjected to plasma treatment at reduced pressure (i.e., below 1 bar), a plasma treatment at atmospheric pressure and / or a corona or flame treatment, to prevent the adhesion of LSR articles to improve or to another material, such as polyurethane strengthen. However, it has been found that the coating is a very short one Has durability.

Of the The object of the present invention is a new silicone rubber to provide its surface is modified, the obtained modification, for example Paint, a higher Lifespan than silicone rubbers of the prior art has.

epiphany the invention

These and other objects were achieved by providing the claims as defined in the claims Silicone rubbers dissolved, which is outlined below.

In the work of the present invention, it has surprisingly been found that the efficiency and quality of surface activation processes carried out to enable secondary processes such as coating or painting with non-silicone materials are related to the residues (residual silicone oil). The presence of a film or low molecular residues on the surface of an article means that the coating obtained by a subsequent process, instead of adhering to the surface of the main polymer, is adhered to the film residue, as desired. Consequently, the adhesion of the secondary coating, such as the paint or the electrical conductive polymers, weak, because the adhesion of the film residue to the rubber is the weakest link in the adhesion. The invention thereby provides a solution to the problem that articles of silicone rubber, and in particular LSR, residues of low molecular weight silicone oils, even if they have been completely treated, post-vulcanized or post-reacted. These residues may diffuse through the silicon substrate, for example, by injection molding or extrusion, and form a film on the surface of the substrate.

Objects of LSR and other silicone rubbers are mostly up to one degree from about 92-96% polymerized. Therefore, about 4-8% of silicone oil residues, also referred to herein as "residues", remain in the articles in the form of low molecular weight compounds of the class of polydimethylsiloxanes. Common examples of such compounds are: hexamethylcyclotrisiloxane, abbreviated D3, Octamethylcyclotetrasiloxane, abbreviated D4, and the like cyclic, linear or branched oligomers with silicone character and different molecular weight. For other types of silicone rubbers of course, the residues have different chemical compositions.

Some the low molecular weight compounds are chemically inert, others show chemical reactivity, for example due to some degree of vinyl functionalization.

Certain Silicone rubber articles, in particular LSR, used in medical Applications used are an after-reaction or vulcanization subjected, also as hardening is referred to reduce the amount of silicone oil residues. The LSR article be subjected to a heat treatment under an air or oxygen stream subjected. As a result, it was found that the proportion of residues for example from 2-8% to about 1.5-4% can be reduced. In this curing process, some of the chemically active species attached to the high molecular weight polymer chains (Silicon), others, chemically inert species, such as cyclic Siloxanes, can be expelled from the articles and evaporated. However, remove curing not all residues by far, even when the curing process carried out until no further weight loss occurs. One reason may be with no limitation on these or other hypotheses, that the temperature used in prior art processes too low to remove certain silicone species. Even though certain processes in the production and vulcanization of silicone rubber the prior art to a certain distance of the low molecular weight silicone oil guided on the silicone rubber there are still problems with the surface properties the silicone rubber article with respect to attachment and surface activation, especially in applications where a long life, high quality and chemical resistance required become.

In the process leading to the silicone rubber of the present invention at least a portion of the silicone oil residues extracted from the polymer substrate, and then the substrate becomes a surface treatment subjected. It was unexpectedly found that this procedure to greatly improved surface properties of the treated polymer article with respect to adhesion and surface activation for example the adhesion to another material leads.

• i) Extrahieren mindestens eines Teils der Siliconölrückstände; und
• ii) Oberflächenbehandlung des Substrats, beispielsweise durch eine Abscheidungsbehandlung.

A first aspect of the invention thus relates to a silicone rubber obtainable by modifying the surface of a polymer substrate containing one or more silicone oil residues. The method comprises the following stages:

• i) extracting at least a portion of the silicone oil residues; and
• ii) surface treatment of the substrate, for example by a deposition treatment.

Of the Expression "polymer substrate, containing silicone oil residues "includes all types of polymer silicone rubbers containing liquid residues which are substantially consist of low molecular weight compounds (compounds with molecular weights in the range of 70-3000 and higher, for example, D3, D4, D5, etc., and other cyclic or noncyclic Siloxanes). The polymer substrate may be prior to the modification of its surface for example, injection molded, extruded or pressed. In one embodiment For example, the polymer substrate is an LSR substrate. In this embodiment will be a very strong improvement in terms of the ability to adhere to the LSR substrate achieved.

As described above, silicone rubbers can be cured, which is typically done after injection or extrusion molding. In carrying out the process for producing the silicone rubber of the present invention, it has been found that the curing step can be omitted or its sharpness can be reduced. LSR articles containing adhesion promoters typically require some refinement to achieve the desired level of adhesion to polar plastics aim. In general, however, the reduction of the harsh curing conditions has the potential to improve the overall surface quality, especially with regard to the formation of small particles, such as silica, and other thermal or oxidative degradation products of silicone rubber.

The Substrate can be used for example Components in phones, computers and the like in general be used where polymer surface with excellent properties required are. The term "extract" includes any Kind of removal of the residues the polymer material. The extraction of the liquid in stage i) can be different Techniques, including Vacuum treatment and washing or washing or extraction, for example with fluids in the supercritical State, include. These treatments are detailed below described.

In an embodiment for producing the silicone rubber of the invention is at least a part, for example 50%, 70% or 90% of the silicone oil residues with a molecular weight up to about 3000, up to about 1000 or between 100 or 500 during the extraction stage i) extracted.

In an embodiment for producing the silicone rubber of the invention will be at least a part, for example 50%, 70%, or 90% of Silicone oil residues with a vapor pressure of 1 μbar or higher at 1 atmosphere and 100 ° C while the extraction stage i) extracted.

In an embodiment for producing the silicone rubber of the invention is the amount of during of stage i) removed silicone oil residues at least 0.1% by weight of the substrate, for example at least 0.5% by weight, at least 1.0% by weight of the substrate or at least 2.0% by weight of the Substrate. Treatment according to level i) can also to a distance from other fleeting ones Lead substances, which, if not removed, will have a detrimental effect the particulate Plasma and the CVD processes have or become reactor pollution to lead. Thus it is in one embodiment also desirable water in stage i).

The surface treatment in step ii) may comprise many known surface treatments, such as flame, corona and plasma treatment. Stage ii) can be immediate after stage i) within minutes or hours. In one embodiment stage ii) is carried out within 24 hours after stage i), wherein by the combination of stages i) and ii) a very good effect is achieved. In another embodiment, stage ii) may be weeks or even months after stage i), even then still a good surface activation is reached. In the process for producing the silicone rubber of the present invention become the new and surprising Effects of Excellent Surface Activation by Combination of the treatments according to stage i) and stage ii).

The Treatment according to the method of the invention generally has no significant adverse effect on the mechanical properties. In one embodiment, stage i) comprises a vacuum treatment of the substrate. The vacuum treatment is preferably performed in a vacuum reactor until a constant pressure of 10 mbar or less is reached, more preferably until a constant pressure of 10 microbar (μbar) or less is reached. The vacuum treatment can, for example, with other stages of extraction residue be combined.

In an embodiment Stage i) comprises a heat treatment of the substrate, wherein the heat treatment preferably during at least 0.3 hours, for example during 1-2 hours or during 1-3 hours at a temperature above 100 ° C, for example about 130 ° C or higher, for example, between 150 and 200 ° C, wherein the heat treatment For example, under an air flow can be performed.

It was found to be a longer one continuous heat treatment before plasma treatment compared to Vacuum treatment is advantageous. It can be speculated that the vacuum treatment and in particular the mechanical compression the silicone article squeezes out silicone oils when pressed in the vacuum chamber, which remain on the surface for a certain time. In this way would one further surface treatment partly on a liquid Substrate and not on the polymer itself. To remove this "film" from oil, can be a vacuum treatment in stage i) preferably with another treatment, For example, a heat treatment or solvent treatment, combined become. When using a heat treatment for the extraction of silicone oil residues can, the surface treatment can in stage ii) in one embodiment within 24 hours after completion of the heat treatment extraction carried out become.

In an embodiment includes stage i) the extraction of residues through the use of solvents, selected from the group are those made from water containing a surfactant, such as Water with a surface tension of 70 dynes / cm or less, such as 50 dynes / cm or 20 dynes / cm; Microemulsions; and organic solvents, such as acetone and methyl ethyl ketone. The selected solvent or the selected ones solvent should preferably be selected be that they have good compatibility with the residues to make them look to extract the substrate. However, a skilled person will be able be the optimal solvent for the Extraction of a specific polymer substrate routinely or by routine examinations.

In one embodiment, a solvent containing CO ₂ or consisting of CO ₂ is used for the extraction.

In one embodiment for preparing the silicone rubber of the invention, step i) comprises the extraction of residues using one or more gases, preferably selected from the group consisting of CO ₂ and mixtures of CO ₂ with one or more gases selected from the group consisting of Selected from the group consisting of paraffins and oxygenates, more preferably selected from the group consisting of butane, pentane, methanol and acetone. The term "gas" refers to the state during extraction.

In one embodiment for making the silicone rubber of the invention, step i) comprises extracting residues using one or more supercritical solvents in their supercritical state during at least part of the extraction step, the supercritical solvent preferably containing one or more compounds selected from the group are C ₁ -C ₁₂ hydrocarbons, preferably C ₃ -C ₄ hydrocarbons, more preferably selected from the group consisting of propane, propene, isobutane, butane, butene, isobutene, methanol, acetone and CO ₂ , the supercritical solvent more preferably containing CO ₂ .

In one embodiment for making the silicone rubber of the present invention, the extraction using gas and extraction using a supercritical solvent is combined so that the solvent is very close to its supercritical state but still is a gas. The preferred solvent in this embodiment is CO ₂ , but any of the aforementioned gases / supercritical solvents may be used separately or in combination.

In an embodiment the extraction is done using gas extraction under Using a supercritical solvent and the extraction using a liquid so combined that the solvent while extraction from one of its three states, gaseous, liquid, supercritical, into another State converted.

The preferred solvent in this embodiment is CO ₂ , but any of the aforementioned gases / supercritical solvents may be used separately or in combination. In one embodiment, the solvent in the form of CO ₂ or a combination of at least 50% by weight CO ₂ and another solvent during the extraction step is partially in the form of a gas and partially in the form of a liquid.

The prior art discloses supercritical carbon dioxide extraction to remove residues from silicone rubbers used in medical articles, particularly implants (Val Krukonis et al., May 1988, "Supercritical fluids: their proliferation in the pharmaceutical industry ", European Pharmaceutical Contractor). The removal of lower quality silicone oil from silicone rubber molded articles is disclosed, for example, in US Pat EP 0,570,010 A1 and US 4,188,423 described.

nowadays is the supercritical Extraction a well-known process and is widely used, and the determination of the specific conditions necessary for the extraction are required on a specific polymer substrate are the Specialist known.

Table 1 lists some suitable and convenient solvents for supercritical extraction. Further information on supercritical extraction and methods of carrying it out can be found in "Solubility parameters of organic compounds", Handbook of Chemistry and Physics, 62nd edition, 1981-1982, CRC press, pages C699 ff, and "Critical temperatures and pressures". , Handbook of Chemistry and Physics, 62nd ed., 1981-1982, CRC press, pages F76 et seq., And in US 6,251,267 to be found by reference me be included here.

Table 1

The supercritical solvent or the supercritical solvent can preferably a hydrocarbon having a Hildebrand solubility of less than 9, preferably 7 or less (cf., for example, "Solubility Parameters: Theory and Application ", John Burke, The Oakland Museum of California. August 1984).

Hydrocarbons are generally preferred, such as C ₁ -C ₁₂ hydrocarbons, preferably C ₃ -C ₄ hydrocarbons, more preferably those selected from the group consisting of propane, propene, isobutane, butane, butene and isobutene.

It should be noted that silicone oil residues in the substrate material can wander, which means that big Amounts of silicone oils in the substrate material in the vicinity its surface are still present, so that these silicone oil residues migrate to the surface can and to an impairment surface activation and to peel off lead from applied material can.

at some embodiments for producing the silicone rubber of the invention it is preferred that the substrate after, overlapping in time or simultaneously with step i), the deposition of an intermediate primer become. The primer deposition involves the deposition of a material, wherein the precipitate precipitation a deposition material on both the surface of the Substrate and also in total may include the substrate. The Deposition material is preferably selected from the group consisting of consists of materials that are chemically and physically at least partially compatible with the materials used in the following surface coating or similar Procedures are used. Preferably, the deposition material becomes deposited simultaneously with or after the extraction of the residues from the substrate. The deposition material can serve the desired properties in the surface of the substrate, for example a better surface activation to enable and / or the adhesion properties to coating materials or paints applied in the subsequent stage strengthen.

In an embodiment For example, the step of depositing an intermediate primer is used a solvent, the dispersed or dissolved deposition material, as a dispersed or dissolved polymer. The dispersed or dissolved Material is preferably selected from the group consisting of PU (polyurethane Prepolymers) Acrylate, styrene, epoxy resins, glycols, polyethers or others Polymers, resins, pigments and mixtures thereof. The solvent can for example, as well surfactants Compounds such as siloxanes attached to polar chains, such as those characterized by the class of alkyl-terminated PDMS-ethylene and propylene oxide surfactants represents will be included. The siloxane chains can be, for example, siloxanes having a molecular weight in the range of 500 to 10,000.

The The above materials provide desired properties, for example for the Use in telephone keypads or computer keyboards ready.

The Solvent, containing a dispersed or dissolved deposition material, can in one embodiment on the surface be applied and gradually be evaporated, whereby the deposition of the deposition material on the surface, however, also in the pores or open structures of the substrate becomes. In one embodiment is it an extra Advantage if the mechanical surface structure by injection molding as rob surface which is a good basis for the adhesion of the deposition material on the surface of the substrate (the term "rough surface" means a surface which Bumps include, essentially as holes and elevations and crater-like ones holes with a depth or height of up to 0.1 mm and with a diameter of up to 1 mm, wherein the surface moreover May contain pores with a diameter of up to 0.1 mm).

In an embodiment becomes the stage of deposition of an intermediate primer at elevated gas pressure manufacturing and applying the dispersed or dissolved deposition material and by gradual Reducing the pressure to form a precipitate of the material on and performed inside the substrate, the precipitate preferably by gradual Evaporation of the solvent is achieved, resulting in a deposition of the deposition material leads.

In an embodiment becomes the stage of deposition of the intermediate primer in the presence of a supercritical solvent in his supercritical Condition performed. In one embodiment the pressure and the temperature so that the solvent near the transition between the supercritical State, the liquid and / or gaseous State is present, preferably so close that a change at 25 ° C or less, for example 10 ° C or less or 5 ° C or less to a change in the Condition of the solvent leads.

In one embodiment, the step of depositing the intermediate primer is carried out using a combination of gas, liquid and supercritical solvent as a carrier for the dispersed or dissolved deposition material. For example, the temperature and pressure conditions may be selected so that the solvent is very close to its supercritical state. The preferred solvent in this embodiment is CO ₂ , but any of the aforementioned gases / supercritical solvents may be used separately or in combination.

In one embodiment, the step of depositing the intermediate primer is carried out using a combination of gas, liquid and supercritical solvent as a carrier for the dispersed or dissolved deposition material. The temperature and pressure conditions may be selected so that the solvent converts from one of its three states, gaseous, liquid and supercritical, to another state during deposition. The preferred solvent in this embodiment is CO ₂ , but any of the aforementioned gases / supercritical solvents may be used separately or in combination. In one embodiment, the solvent in the form of CO ₂ or a combination of at least 50% by weight of CO ₂ and another solvent during the deposition step is partially in the form of a gas and partially in the form of a liquid.

To the Purposes of providing a uniform layer of the deposition material on the surface of the substrate, it is preferred that a gradual evaporation of the solvent a gradual or partial pressure reduction in the treatment reactor for separation of the polymer. A person skilled in the art will be able to do so with a few experiments optimal gradual Evaporation for a particular substrate and solvent or deposition material to find.

In one embodiment, the extraction process can be easily combined with a step of applying a primer and / or impregnating material whereby, at the end of the extraction process, a substrate which is soluble in CO ₂ at high pressure but less soluble at reduced pressure, is introduced into the high-pressure extraction vessel, whereby the pressure is reduced, so that the substance is precipitated into the silicon substrate. This process modification results in modified silicone surfaces that are easier to activate and, in addition, the color of the suspension may be changed depending on the choice of precipitated material, possibly circumventing one or more levels of coating and thus reducing the overall cost.

In the method of producing the silicone rubber of the present invention the substrate in step ii), for example using a or multiple flame, corona, or plasma, or CVD / PVD surface treatments can be treated, or the substrate can be made using chemicals in the liquid Condition treated, for example, as a silane treatment or other treatment involving primers in solution, such as epoxy resins are. After liquid Residues that a disturbing Film on the surface of the substrate, not just from the surface but also at least part of the substrate material in Susbstrat nearby the surface have been removed, the "true" surface of the Substrate treated and excellent surface activation provided.

In an embodiment for producing the silicone rubber of the invention includes the surface treatment in step ii) the deposition of one or more materials the surface the coating. The deposition can be done using, for example one or more plasma or CVD / PVD surface treatments, as disclosed in WO 00235895.

In an embodiment for producing the silicone rubber of the invention is the deposition of one or more materials in stage ii) as deposition of an intermediate Primers as described above and with those described above preferred embodiments achieved.

In a preferred embodiment the method of producing the silicone rubber of the present invention the substrate a coating method, advantageously after Stage i) and stage ii) subjected. The coating process is the appropriate application of one or more layers of paint electrically conductive polymer layers, coatings for biochemical purposes, such as Peptide dockers for analytical and sensory applications, and biochemical reagents in "biochip" fluid cell designs. The surface-modified according to the invention Substrate is within a wide range of technical applications used.

The Contains substrate preferably a material selected from the group made from silicone rubbers (RTV, HTV, compression-molded and injection-molded and extruded) with or without additives, such as adhesion promoters for 2K constructions (i.e., two-component articles, which consist of two types of plastic that are injection-molded in one machine ) and fillers, plasticized thermoplastics and thermoplastic Plastics consists of the oil and other liquid ones Components such as PVC, TPE, PU and vulcanized rubbers included.

• 0) Formen eines Substrats durch Spritzgießen, Extrudieren oder Pressen;
• i) Extrahieren mindestens eines Teils der Siliconölrückstände; und
• ii) Oberflächenbehandlung des Substrats.

The process for producing the silicone rubber of the invention also comprises a process for modifying the surface of a polymeric substrate containing one or more silicone oil residues, preferably as described above, the process comprising the steps of:

• 0) molding a substrate by injection molding, extruding or pressing;
• i) extracting at least a portion of the silicone oil residues; and
• ii) surface treatment of the substrate.

The Extraction of the silicone oil residue from the molded substrate and the surface treatment can in one combined procedures performed that is, the extraction step and the surface treatment step immediately after each other (or within a few minutes, such as 10 Min.) Or overlapping each other, for example, in the same reaction chamber.

Consequently can be the activation of the surface the substrate by the combination of the removal of liquid residues and a surface treatment described above can be achieved.

One embodiment of the method for producing the silicone rubber of the invention is that the extracted substrate is subjected to a vacuum in order to remove liquid residues, in particular water, preferably at a pressure of about 1 to 100 microbar before the surface treatment. The vacuum lowers the vapor pressure required to evaporate the liquid residue from the substrate, thus facilitating the removal of liquid residues by evaporation. Prolonged heat treatment at standard pressure, possibly in circulating air, is an alternative to vacuum treatment.

• i) Extrahieren mindestens eines Teils der Siliconölrückstände; und
• ii) Abscheidungsbehandlung auf das Substrat.

A second aspect of the present invention relates to a silicone rubber obtainable by a process for incorporating a material into a polymeric substrate containing one or more silicone oil residues, the process comprising the steps of:

• i) extracting at least a portion of the silicone oil residues; and
• ii) Deposition treatment on the substrate.

The Stages i) and ii) can as described above, especially when step ii) a deposition step, including precipitation of a deposition material into the substrate, or comprises. The deposition material can be the one described above. In one embodiment, the deposition material is a pigment or styrene. Styrene gives the substrate a white color, while pigments e.g. to a translucent color to lead can. The substrate may be, for example, simultaneously with or after the Extract the residues from the substrate subjected to a deposition step.

In an embodiment For example, the deposition step is carried out using a solvent which a dispersed or dissolved one Deposition material, as also described above, contains.

All in all may be any of the deposition steps described above for deposition an intermediary Primers described as deposition treatment ii) used become.

Out the text and examples show that the need to Residues on extracting a certain concentration varies from case to case. Likewise the substrates which are the method for producing the silicone rubber of the invention be subjected, in their chemical composition, geometry and application requirements vary. For certain applications, such as for medical Equipment, or as objects that have body fluids over one Period of more than one hour can be contacted high degree of extraction be beneficial. For industrial applications, as for switches and keyboards and the like, the removal of the residues with a boiling point between 60 and 300 ° C may be sufficient to achieve the desired improvement of adhesiveness in the subsequent deposition stage or coating stage achieve.

Therefore may be the best method for producing the silicone rubber of the present invention both according to the first as well as the second aspect vary from case to case.

For example, in mechanically stable parts, pressure variations during high pressure extraction using gases such as CO ₂ , for example, between 200 and 350 bar or 20 and 50 bar, may occur during transport of the gas through the polymer matrix and thus removal of the residues without damaging the matrix to be helpful. However, easily breakable parts can be advantageously extracted at low temperatures and moderate pressure, for example 10-50 ° C and 10-100 bar.

The efficient deposition of materials can be beneficial while exploiting the pressure dependence of solubility of the materials, i. be carried out using a pressure interval of 30-300 bar.

Economic constraints can lead to the extraction processes being advantageously carried out at pressures below 50 bar due to the high cost of high pressure reactors, but still exploiting the low surface tension of, for example, CO ₂ at these pressures below 50 bar.

The Invention will be described below with reference to some examples further illustrated.

Examples

example 1

This example relates to a process solution compared to standard surface activation (Plasma, flame, corona, etc.) has significant advantages. Various silicone articles (with and without adhesion promoter) were treated by methods a), b), or c): a) without special treatment, b) vacuum treatment at about 10 μbar for 8 hours, c) heat treatment at about 130 ° C during 2 hours.

After that were the quality and the durability of the surface coatings compared. (Surface tension over the Time, even in accelerated aging tests, absolute values, holding capacity etc.).

The standardized 30-50 Shore A silicone articles contained 2.3-2.9% by weight of oil, measured by acetone-soxlet extraction. The silicone products, the adhesion promoters contained 1.9-2.7% Silicone oil.

• – Das Fehlen einer Vorbehandlung führt zu mittleren bis guten Aktivierungsergebnissen, es wird jedoch Reaktorverschmutzung beobachtet, die höchstwahrscheinlich auf flüchtige Silicone zurückzuführen ist, die aus dem Siliconpolymer verdampft werden und schließlich auf den Plasmaelektroden zersetzt werden. Bestimmte "versteckte" Flächen auf den Siliconartikeln, insbesondere solche auf geometrisch komplexen Artikeln, zeigen niedrigere Aktivierungsniveaus, was möglicherweise auf das Verdampfen von Gas und darauf zurückzuführen ist, dass chemische Monomere (d.h. Plasmareaktanten) daran gehindert werden, die Polymerphase zu erreichen.
• – Die Vakuumvorbehandlung ist eine Verbesserung im Vergleich dazu, dass die Vorbehandlung ganz weggelassen wird. Es wird keine oder geringe Reaktorverschmutzung beobachtet, und die erhaltenen Plasmabeschichtungen sind über Wochen und Monate haltbar und stabil. Die Siliconölanteile über 2,6% für Standard-LSR und über 2,3% für LSR mit Haftvermittler tragen jedoch zu einer verringerten Stabilität (Lebensdauer) der Plasmaaktivierung bei. Dies ergibt sich daraus, dass nach einer Woche Siliconöle unter Verwendung von standardisierten Analyseverfahren, wie FTIR, auf den plasmaaktivierten Oberflächen nachgewiesen werden können. Für technische Zwecke, wenn Lebensdauern in der Größenordnung von mindestens 10 Tagen wünschenswert sind, können die Siliconartikel, die solche Konzentrationen von Siliconölen enthalten, deshalb unter Einsatz einer Vakuumvorbehandlung verarbeitet werden.
• – Es stellt sich heraus, dass die Hitzebehandlung für Siliconartikel, die mehr als 2,3% Siliconöle enthalten, gut geeignet ist. Die Haltbarkeit der auf solchen Artikeln hergestellten Beschichtungen ist normalerweise über 10 Tage. Außerdem ist die Diffusion von Siliconölen zu der Oberfläche für hitzebehandelte Artikel um einen Faktor von etwa 3–5 langsamer als für vakuumbehandelte Artikel.

The results can be summarized as follows.

• The absence of pretreatment results in moderate to good activation results, but reactor fouling is most likely due to volatile silicones that are vaporized from the silicone polymer and eventually decomposed on the plasma electrodes. Certain "hidden" areas on the silicone articles, particularly those on geometrically complex articles, exhibit lower levels of activation, possibly due to vaporization of gas and due to chemical monomers (ie, plasma reactants) being prevented from reaching the polymer phase.
• - The vacuum pretreatment is an improvement compared to the fact that the pretreatment is completely omitted. No or little reactor fouling is observed, and the resulting plasma coatings are stable and durable for weeks and months. However, silicone oil levels above 2.6% for standard LSR and above 2.3% for LSR with coupling agents contribute to reduced stability (lifetime) of plasma activation. This is because after one week, silicone oils can be detected on the plasma-activated surfaces using standard analytical techniques, such as FTIR. For technical purposes, if lifetimes on the order of at least 10 days are desirable, the silicone articles containing such concentrations of silicone oils can therefore be processed using a vacuum pretreatment.
• It has been found that the heat treatment is well suited for silicone articles containing more than 2.3% of silicone oils. The durability of the coatings produced on such articles is usually over 10 days. In addition, the diffusion of silicone oils to the surface for heat-treated articles is slower by a factor of about 3-5 than for vacuum-treated articles.

It It should be noted that heated and evacuated items a Plasma treatment or other surface treatment preferably within 24 hours, such as 4 hours after heating or evacuation, should be subjected or, alternatively, with exclusion of moisture should be stored. The reversible water absorption in silicone otherwise progresses within 4-24 hours.

Example 2

Injection molded articles made of various two-component LSR grades (Wacker Elastosil grades, GE Bayer Silopren) were subjected to extraction with supercritical CO ₂ . To speed up the process, pressures of up to 350 bar and temperatures of up to 80 ° C were selected, while in principle pressures of up to 35 bar down and a temperature of about room temperature could have been selected. Both autoclaves and flow reactors were used. Due to the high solubility of silicones in supercritical CO ₂ extraction proceeds rapidly. The content of extractable silicones, which was determined in control experiments by Soxleth acetone reflux extraction at 2.5-4 wt .-%, was reduced to <0.2 to 0.7 wt .-%. The remaining liquid silicones typically have a high boiling point, ie> 400 ° C.

The The resulting substrates were subjected to vacuum plasma and flame treatment treated. The quality parameters for the surface treatment are u.a. Surface tension, Longevity of the surface coating, stability the coating in accelerated aging experiments, stability of the coating across from solvents staying power the coating in adhesion measurements. More more indirect, however relevant tests are the stability of another coating, like a paint.

It should be noted that certain plasma coating on LSR (such as those based on NKT patents WO 96/18756, WO 98/00457, WO 00/44207 and WO 02/35895) are already high in view of the above parameters Quality. CO ₂ -extracted silicone articles exceed standard LSR. The lifetime of the plasma coatings and coatings produced by flame treatments has been measured even at 80 ° C so far with over 3 months, while esp In particular, the flame treatment of standard silicone only has a lifespan of hours or at best even days at room temperature. The holding power and the surface tension are not changed with respect to standard oil-containing LSR, but this has not been expected because each of these parameters is determined by the chemical nature of the coating. The stability of the accelerated aging parameters was improved as described above.

Example 3

LSR containing primer is becoming more important because of the practical advantages such as the ability to spray-mold it onto thermoplastics such as polyamide. However, this strain has traditionally been very difficult to plasma plaque, due to the increased tendency for bleeding. (It can be speculated that the primer itself is also the reason for the higher tendency to bleed out of these species due to its partially polar or hydrophilic nature, which allows it to adhere to polar plastics.) Articles based on such LSR varieties, were subjected to CO ₂ extraction with others and without other thermoplastics (polyamide was used in the described experiments) as described in the first example. The results are completely consistent with the results described above. In addition, only negligible delamination, ie, reduction in adhesion between silicone and polyamide in two-component articles has been observed. In the selected cases where the silicone peeled away from the polyamide, it was apparent that the injection molding had not been performed properly. Therefore, CO ₂ extraction can have the additional advantage that it can be used to select or screen the quality of the injection molding or extrusion process, which may be relevant to articles for medical use.

Example 4

items with sophisticated geometries were using the above extracted parameters and process conditions. As an an example a telephone keypad was selected and analyzed for residues. It was found that the extraction process, if it is over more as 10 minutes at 200 bar and 60 ° C carried out will, independent from the substrate thickness and geometry to a uniform extraction leads. This is natural a requirement for the success of the subsequent surface treatment.

2-K Articles, like silicone / polyamide constructions, show less uniform extraction profiles. Larger surfaces of restrict rigid plastics the extraction efficiency obviously. A reduction in the oil content by at least 30% and typically 50% was found, wherein the remaining oil had high molecular weight and therefore for the subsequent coating processes less dangerous was.

Example 5

LSR in the form of sheets or films are suitable precursors for membranes as well as the gas separation as well the liquid / liquid separation and similar Separation tasks. The extraction results coincide with those which have been described above. In addition, substrates were used with an artificial one low degree of vulcanization (i.e., <95%) to increase the permeability of the membranes increase. It has been observed that the tendency to delaminate or destroy the Articles subjected to extraction with reduction the degree of vulcanization increases, the webs or foils being thinner than 1 mm, but are typically without any visible damage extractable.

Example 6

LSR-IPN: According to the standard extraction method described above, a dye (rhodamine) was dissolved in CO ₂ and added to the reactor. In the pressure reduction, the dye was precipitated in the extracted LSR articles, resulting in a dye uniformly dispersed in LSR. The resulting color was translucent. Similarly, low molecular weight fractions of polyethylene, polypropylene, the respective glycols, prepolymers of diisocyanates and other thermoplastics were impregnated into the LSR structure using the same procedure. The resulting substrates can be described as interlocking networks (IPNs) of the thermoplastics in silicone, and exhibit surface properties between the two pure components. IPNs are easier to plasma-coat than pure silicone, due to the increased lifetime of the plasma coating will be shown. Similarly, many dyes can be incorporated into silicone rubber using the described technology. As a separate development, silicone-based surfactants, ie, those containing a siloxane chain, a number of polymerized ethylene or propylene oxide units, and finally an alkyl group (terminal), have been impregnated into both silicone and solvent using supercritical carbon dioxide. The products are not IPNs, but show very interesting properties in terms of increased hydrophilicity and facilitated surface activation.

Claims (16)

Silicone rubber article, characterized in that it is obtainable by modifying the surface of a polymeric substrate containing one or more silicone oil residues, the process comprising the steps of: (i) extracting at least a portion of the silicone oil residues; (ii) Plasma treatment of the substrate. Silicone rubber article according to claim 1, characterized characterized in that at least a portion of the silicone oil residues with a molecular weight of up to about 3,000 during the extraction step (i) is extracted. Silicon rubber article according to claim 2, characterized characterized in that at least a portion of the silicone oil residues with a molecular weight of up to about 1000 during the extraction step (i) is extracted. Silicon rubber article according to one of the preceding Claims, characterized in that the amount of silicone oil residues, the while of step (i), at least 0.1% by weight of the substrate is. Silicone rubber article according to one of the preceding Claims, characterized in that the amount of silicone oil residues, the while of step (i), at least 0.5% by weight of the substrate is. Silicone rubber article according to one of the preceding Claims, characterized in that the amount of silicone oil residues, the while of step (i), at least 1.0% by weight of the substrate is. Silicone rubber article according to one of the preceding Claims, wherein step (i) comprises a heat treatment of the substrate. Silicone rubber article according to one of the preceding Claims, characterized in that the step (i) the extraction of residues under Use of one or more solvents includes. Silicone rubber article according to any one of the preceding claims, characterized in that step (i) comprises the extraction of residues using one or more gases, preferably selected from the group consisting of CO ₂ and mixtures of CO ₂ with one or more gases which are selected from the group consisting of paraffins and oxygenates, more preferably selected from the group consisting of butane, pentane, methanol and acetone, wherein the term "gas" refers to the state during the extraction. Silicone rubber article according to any one of the preceding claims, characterized in that step (i) comprises the extraction of residues using one or more supercritical solvents in their supercritical state during at least part of the extraction step, the supercritical solvent preferably comprising one or more compounds are selected from the group consisting of C ₁ -C ₁₂ -hydrocarbons, preferably C ₃ -C ₄ -hydrocarbons, more preferably selected from the group consisting of propane, propene, isobutane, butane, butene, isobutene, methanol, Acetone and CO ₂ , wherein the supercritical solvent more preferably contains CO ₂ . Silicone rubber article according to one of the preceding Claims, characterized in that the surface treatment in step (ii) the deposition of materials on the surface of the substrate comprises. Silicone rubber article according to any one of the preceding claims, characterized in that, in an additional treatment according to step (ii), the substrate is subjected to a coating process which on the application of one or more layers of paint. Silicone rubber article according to one of the preceding Claims, characterized in that the substrate before the step (i) by injection molding, Extruding or pressing is formed. Silicone rubber article according to one of the preceding Claims, characterized in that it is obtainable by a method the following stages include: - Molds of a silicone material forming a switch cover; - extract at least one Part of the silicone oil residues; - To treat the surface with plasma; and - coating the treated surface with a paint. Silicone rubber article according to one of the preceding Claims, characterized in that the article is a silicone rubber switch cover is. Silicone rubber article according to one of the preceding Claims, characterized in that the treated surface with coated with a varnish, whereby the adhesion of the varnish to the surface is higher as the adhesion would be, if the extraction of silicone oil residue is not Have been carried out would.