Organopolysiloxane-based adhesive for silicone materials

Abstract

The invention relates to an organopolysiloxane-based adhesive composition and to a method for producing a composite element in which the organopolysiloxane-based adhesive composition is used to adhesively bond silicone materials.

Description

[0001] Organopolysiloxane-based adhesive for silicone materials

[0002] The invention relates to an organopolysiloxane-based adhesive composition, as well as a method for producing a composite body in which the organopolysiloxane-based adhesive composition is used for bonding silicone materials.

[0003] Technological background

[0004] Silicone materials, such as silicone rubber, possess excellent properties: they are temperature-stable and elastic, biocompatible, and chemically very stable, i.e., unreactive. They are therefore used in numerous fields. Silicone rubber materials have a chemically extremely inert surface, comparable to Teflon (PTFE). However, this also means that silicone surfaces are difficult to bond. The prior art therefore describes various approaches to achieving sufficient adhesion, such as the use of adhesion promoters that are physiologically and environmentally problematic.

[0005] Liquid silicone rubber (LSR) can typically be produced by mixing two silicone components, A) and B). Component A) generally contains a vinyl-terminated polydimethylsiloxane and a catalyst, usually an organometallic platinum compound. Component B) then contains at least one crosslinker, such as polydimethylsiloxane with at least one, preferably two, SiH group(s). Both components A) and B) are stable as such.

[0006] For example, DE 602 15 872 T2 describes an adhesive for silicone rubber that can be easily bonded to silicone rubber materials. In addition to liquid silicone rubber, the adhesive also contains calcium carbonate powder.

[0007] WO 2020 / 110032 A1 discloses platinum-divinyltetramethyldisiloxane-vinylcyclohexanol complex catalysts for use in coating compositions. The catalyst ensures rapid curing while simultaneously inhibiting crosslinking at ambient temperatures, thereby improving the production pot life of the coatings. The coating composition comprises a crosslinkable silicone polymer with reactive functionalities; a silica-containing composition; a silicone crosslinking agent; and a catalyst, wherein the catalyst is inactive at ambient temperature and essentially consists of a platinum-divinyltetramethyldisiloxane-vinylcyclohexanol complex. The crosslinkable silicone polymer is, for example, a vinyl-terminated polydimethylsiloxane, and the silicone crosslinking agent is, for example, polymethylhydrosiloxane.The coating compositions described there are used for coating medical devices.

[0008] WO 2019 / 169609 A1 concerns self-adhesive, curable silicone rubber compositions that, after curing, achieve significant adhesion to substrates made of plastic / thermoplastic / resin material, in particular polycarbonate materials. The silicone rubber comprises one or more organopolysiloxanes with alkenyl groups; an organopolysiloxane with silicon-bonded hydrogen atoms, SiH-containing silicone polymers, a platinum group catalyst, fillers; and one or more rubber-modified epoxy resins.

[0009] US Patent 6,251,966 B1 describes an organopolysiloxane adhesive composition containing an organopolysiloxane rubber, a pressure-sensitive organopolysiloxane adhesive, a hydrogen-functional organopolysiloxane, and an unsaturated organopolysiloxane resin. The adhesives can be used in applications requiring a strong bond between materials with different surface properties, such as between a dental prosthesis and an elastomer pad.

[0010] However, the coating compositions based on liquid silicone rubbers (LSR) known from the prior art show only insufficient adhesive properties, especially between surfaces of silicone rubber materials.

[0011] Furthermore, there is a need for the recycling of old silicone material, which currently has to be disposed of as waste, since recycling silicones is only possible with high energy expenditure. Reusing waste silicones in the production of composite components can therefore also contribute to cost reduction in product development, as silicone is an expensive raw material.

[0012] Therefore, the object of the present invention is to provide a new adhesive composition based on liquid silicone rubber (LSR) that enables stable bonding of silicone surfaces and is thus suitable for the production of stable composite materials made of silicone materials. Furthermore, the object is to provide a method for the reuse (recycling) of waste silicones in the production of new silicone articles. Summary of the invention

[0013] The present invention relates in a first aspect to a two-component adhesive composition comprising a component A) containing oi) at least one vinyl group-terminated organopolysiloxane, ii) at least one platinum-based catalyst, and iii) at least one solvent selected from the group consisting of octamethyltrisiloxane, xylene, n-hexane, n-heptane, toluene, white spirit, or hexamethyldisiloxane, in a weight ratio range of 1:4.5 to 1:1, based on the total amount of (i) and (ii) to (iii); a component B) comprising o iv) at least one organopolysiloxane having at least one SiH group and iii) a solvent selected from the group consisting of octamethyltrisiloxane, xylene, n-hexane, n-heptane, toluene, white spirit or hexamethyldisiloxane, in a weight ratio range of 1 : 4.5 to 1 : 1 , based on the total amount of (iv) to (iii).

[0014] The adhesive composition according to the invention is characterized by improved adhesive properties, in particular adhesion to silicone surfaces.

[0015] A second aspect of the present invention is a method for producing a composite body comprising

[0016] (I) Mixing the components (A) and (B) of the invention

[0017] Adhesive composition for an adhesive mixture;

[0018] (II) Applying the adhesive mixture from step (I) to a surface of a

[0019] silicone substrate;

[0020] (III) Bringing the surface coated in step (II) into contact with a surface of a second silicone substrate, wherein the surface of the second silicone substrate is uncoated or coated with the adhesive mixture;

[0021] (IV) Removal of the solvent before or after step (III) and (V) Curing of the adhesive mixture.

[0022] In one embodiment, the composite body can be composed of at least two planar substrates made of silicone material.

[0023] Another aspect of the present invention is a method for producing a composite body, comprising

[0024] (I) Mixing the components (A) and (B) of the adhesive composition according to the invention to form an adhesive mixture;

[0025] (II) Removal of the solvent from the adhesive mixture,

[0026] (III) Provision of a silicone material;

[0027] (IV) Mixing the adhesive mixture from (II) with the silicone material from (III) to form a silicone composition and

[0028] (V) Curing of the silicone composition.

[0029] In a preferred embodiment, the adhesive mixture in step (I) comprises a recycled silicone material as a further component. Thus, an adhesive mixture consisting of components (A) and (B) plus a recycled component is obtained. For the purposes of this invention, a recycled silicone material is understood to be a previously used (old) vulcanized silicone material that is generated as waste. Preferably, the recycled silicone material contains one or more types of silicone. It is also preferably the case that the recycled silicone material is in the form of shredded particles.

[0030] It is therefore possible to produce silicone articles containing one or more silicone materials in a stable form. This ensures that the bonded joints do not give way even under stress. Furthermore, new silicone articles can be manufactured based on recycled silicone material.

[0031] Brief description of the characters

[0032] The invention is explained in more detail below with reference to an exemplary embodiment and accompanying drawings. The figure shows:

[0033] Fig. 1 shows a schematic representation of an embodiment of a silicone substrate to be bonded in top and side view.

[0034] Fig. 2 is a schematic representation of the size arrangements of the silicone substrate to be bonded from Fig. 1.

[0035] Fig. 3 shows a schematic representation of an embodiment of a test strip of the composite body according to the invention.

[0036] Detailed description of the invention

[0037] It is clear to a person skilled in the art that the present invention is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present invention.

[0038] Each aspect described in this way can be combined with any other aspect or several other aspects, unless explicitly stated otherwise.

[0039] In particular, any feature specified as preferred or advantageous may be combined with any other feature or features specified as preferred or advantageous.

[0040] Unless otherwise specified, the terms used in the context of the present invention shall be interpreted in accordance with the following definitions.

[0041] Unless otherwise stated, the terms “ein”, “eine” and “das” as used here include both singular and plural references.

[0042] The terms “comprehensive” and “encompasses”, as used here, are synonymous with “including”, “contains” or “contains”, and are inclusive or open and do not exclude additional, unlisted members, elements or process steps.

[0043] Unless otherwise specified, the specification of numerical endpoints includes all numbers and fractions subsumed in the respective ranges as well as the specified endpoints.

[0044] Component A) of the adhesive composition according to the invention comprises i) at least one vinyl-group-terminated organopolysiloxane, ii) at least one platinum catalyst, and iii) hexamethyldisiloxane as a solvent in a weight ratio of 1:1, based on the total amount of (i) and (ii). i) Vinyl-group-terminated polyorganosiloxane

[0045] Component A) contains at least one vinyl-terminated polyorganosiloxane. Preferred vinyl-terminated polyorganosiloxanes are vinyl-terminated polydialkylsiloxanes or vinyl-terminated polyalkylarylsiloxanes. Examples include polydimethylsiloxane, polydiphenylsilane-dimethylsiloxane copolymer, polyphenylmethylsiloxane, polyfluoropropylmethyl-dimethylsiloxane copolymer, and polydiethylsiloxane. The use of vinyl-terminated, crosslinkable polymethylsiloxane is preferred. ii) Platinum-based catalyst

[0046] Component ii) is a platinum-based catalyst for aiding the curing of the adhesive composition of the present invention. Examples of component ii) include fine platinum powder, platinum carbon black, chloroplatinic acid, platinum tetrachloride, alcoholic solutions of chloroplatinic acid, platinum olefin complexes, platinum alkenylsiloxane complexes, platinum carbonyl complexes, and fine powders obtained by dispersion of any of the above-mentioned platinum-based catalysts in methyl methacrylate resins, polycarbonate resins, polystyrene resins, silicone resins, and other thermoplastic organic resins. iii) The solvent is selected from the group consisting of octamethyltrisiloxane, xylene, n-hexane, n-heptane, toluene, white spirit, or hexamethyldisiloxane. Preferably, the solvent is selected from the group consisting of n-heptane, toluene, white spirit, or hexamethyldisiloxane; hexamethyldisiloxane is particularly preferred.

[0047] Component A) contains, in addition to components i) and ii), at least one solvent iii), preferably hexamethyldisiloxane as solvent iii). Component A contains solvent iii) in a weight ratio ranging from 1:4.5 to 1:1, preferably 1:2.5 to 1:1, and particularly preferably 1:1.5 to 1:1, based on the total amount of (i) and (ii) to (iii). The weight ratio of components i) and ii) to iii) can also be 1:4.5, preferably 1:2.5, particularly preferably 1:1.5, and most preferably 1:1. In a preferred embodiment, the weight ratio ranges from 1:2 to 1:0.25, preferably from 1:2 to 1:0.5, and particularly preferably from 1:1 to 1:0.25, based on the total amount of (i) and (ii) to (iii). The weight ratio of components i) and ii) to iii) can also be 1:2, 1:0.5, or 1:0.25.

[0048] Component B) of the adhesive composition according to the invention comprises iv) at least one organopolysiloxane with at least one SiH group and at least one solvent iii), preferably hexamethyldisiloxane as the solvent. Component B contains the solvent iii) in a weight ratio of 1:4.5 to 1:1, preferably 1:2.5 to 1:1, particularly preferably 1:1.5 to 1:1, based on the total amount of iv) to iii). The solvent can also be present in a weight ratio of 1:4.5, preferably 1:2.5, particularly preferably 1:1.5, most preferably 1:1, based on the total amount of iv) to iii). In a preferred embodiment, the weight ratio range is 1 : 2 to 1 : 0.25, preferably 1 : 2 to 1 : 0.5, particularly preferably 1 : 1 to 1 : 0.25, based on the total quantity of iv) to iii).The weight ratio of components iv) to iii) can also be 1 : 2, 1 : 0.5 or 1 : 0.25, based on the total quantity of iv) to iii).

[0049] Mixtures of the solvents mentioned above can also be used in components A) and B). Preferably, the solvent consists of hexamethyldisiloxane (100 wt.% hexamethyldisiloxane). iv) Organopolysiloxane with at least one SiH group

[0050] In one embodiment, the oganopolysiloxane with at least one -SiH group iv) can be a polydimethylsiloxane, with at least one, preferably at least two, -SiH groups, particularly preferably with two terminal -SiH groups. Component iv) serves as a crosslinking agent in the adhesive composition of the present invention. Suitable crosslinking agents are, for example, polymethylhydrosiloxane, polymethylhydro-co-polydimethylsiloxane, polyethylhydrosiloxane, polymethylhydrosiloxane-co-octylmethylsiloxane, and polymethylhydrosiloxane-co-methylphenylsiloxane.

[0051] In a further embodiment, a component C) can be added to the adhesive composition according to the invention. An example of a component C) is a silicon dioxide powder, which can improve the mechanical strength of the resulting cured adhesive. Further examples of component C) include pyrogenic silica, precipitated silica, baked silica, powdered quartz, and powders obtained by treating the surfaces of the aforementioned silicon dioxide powders with organosilicone compounds such as organoalkoxysilanes, organohalogenosilanes, and organosilasanes.

[0052] In a process for producing the adhesive composition according to the invention, component A) is produced in one step by dispersing the i) vinyl-terminated polydimethylsiloxane and the ii) catalyst in at least one iii) solvent in the weight ratio mentioned above. In a further step, component B) is produced by dispersing the iv) polymethylhydrosiloxane crosslinker in at least one iii) solvent containing hexamethyldisiloxane in the weight ratio mentioned above. The two steps can be carried out in any order.

[0053] Preferably, the LSR silicone to be dissolved (or its components) is pre-swelled in the solvent for a suitable period of time before the solution is adjusted to the required strength. A suitable period ranges, for example, from a few minutes to one or two hours. The appropriate period depends on the properties of the LSR silicone and can be shortened, for example, by coarsely (or even finely) grinding the LSR silicone beforehand to increase its overall surface area and accelerate the swelling process. After the appropriate period has elapsed, the (viscous) LSR silicone-solvent mixture is preferably mixed, in particular whisked, to dilute the LSR silicone with the remaining solvent in the mixture, i.e., to essentially homogenize the mixture. Mixing is preferably carried out with a mechanical whisk.

[0054] Preferably, the components A) and B) of the adhesive composition according to the invention are present separately from each other, as a two-component product.

[0055] The molar ratio of silicon-bonded hydrogen atoms in component B) to vinyl groups in component A) is 0.01 to 20, i.e., 1 : 100 to 20 : 1, preferably 0.1 to 10, i.e., 1 : 10 to 10 : 1, and particularly preferably 0.1 to 5, i.e., 1 : 10 to 5 : 1.

[0056] The components i), ii) and iv) contained in the two-component adhesive composition according to the invention can, in a preferred embodiment, be commercially available LSR types, such as Elastosil® LR 5040 / 50 A / B (Wacker Chemie GmbH, DE), KEG 2000-20 A / B or KEG-2003H-60 A / B (ShinEtsu Silicones). These are offered, for example, as two components A) and B), wherein component A) contains components i) and ii) and component B) contains component iv).

[0057] A method for manufacturing a composite body is also provided, comprising

[0058] (I) Mixing the components (A) and (B) of the invention

[0059] Adhesive composition for an adhesive mixture;

[0060] (II) Applying the adhesive mixture from step (I) to a surface of a

[0061] silicone substrate;

[0062] (III) Contacting the surface coated in step (II) with a surface of a second silicone substrate, wherein the surface of the second silicone substrate is uncoated or coated with the adhesive mixture; (IV) Removal of the solvent before or after step (III) and

[0063] (V) Curing of the adhesive mixture.

[0064] The preparation of the adhesive mixture of the two components (A) and (B) in step (I) takes place shortly before the application of the adhesive mixture in step (II). Alternatively, step (I) can also take place during step (II).

[0065] In step (I) the components (A) and (B) are combined and mixed homogeneously.

[0066] The curable adhesive mixture can be easily produced in any conventional mixing plant suitable for mixing high-viscosity polymers (i.e., >1,000,000 mPa·s at 25°C), such as rubber. The mixing order is not critical if the mixture is to be used immediately.

[0067] The homogeneous mixing of components (A) and (B) of the adhesive composition according to the invention can be carried out using a suitable mixing device, such as a kneading mixer, a Z-knife mixer, a two-roll mill (open rolling mill), a three-roll mill, a Haake® Rheomix OS Lab mixer, a screw extruder or a twin-screw extruder or similar.

[0068] In step (II), the adhesive mixture is applied to the surface of a silicone substrate. The application of the adhesive mixture of the present invention can be carried out using conventional coating techniques and processes and conventional coating equipment. In a preferred embodiment, pretreatment of the surface of the silicone substrate is not necessary.

[0069] Suitable silicone substrates are, for example, high-temperature curing (HTV) silicones with Shore A 00-10 to Shore A 100, measured according to DIN ISO 48-4, preferably with Shore A 35 or Shore A 65.

[0070] Examples of coating equipment include simple dip coating tanks and inline convection ovens for curing the coating. Alternatively, the coating can also be applied by brushing, rolling, or spraying.

[0071] In step (III) the coated surface obtained from step (II) is then brought into contact with a surface of a second silicone substrate, wherein the surface of the second silicone substrate is either uncoated or coated with the adhesive mixture.

[0072] The removal of the solvent in step (IV) can be carried out by evaporation at room temperature or by applying heat in a temperature range of 30°C to 50°C.

[0073] In a preferred embodiment, step (IV) is performed before step (III). The solvent removal can, for example, be carried out in a heating oven.

[0074] Subsequently, in step (V), the adhesive joint can be vulcanized. During this step, the crosslinking reaction between components i) and iv) takes place. The fully crosslinked polymer is formed by a reaction between the functionalized crosslinkable polymer i) and the crosslinking agent iv), for example, a vinylsilylation reaction between i) vinyl-terminated polydimethylsiloxane and iv) polymethylhydrosiloxane, in the presence of a platinum complex catalyst iii). The vinyl-terminated linear polydimethylsiloxane polymers i) are fully crosslinked together by this reaction.

[0075] The crosslinking reaction during curing (V) can be completed in-line, for example, by passing the product through a drying oven. The curing time can be, for example, 20 seconds at 165°C, 120 seconds at 90°C, or 60 minutes at 70°C.

[0076] Preferred temperatures for curing the adhesive composition are in the range of 60°C to 200°C, more preferably from 90°C to 220°C and particularly preferably from 70°C to 165°C.

[0077] Other conventional curing techniques that can be used with the new adhesive compositions of the present invention include heat, ultraviolet light, plasma, microwave radiation, electromagnetic coupling, ionizing radiation, lasers and the like.

[0078] In one embodiment, prior to applying the adhesive mixture to the silicone substrate surface in step (I) of the inventive method, the surfaces of the silicone substrates can be pretreated in a conventional manner using conventional methods such as electropolishing, oxidation, ultrasonic cleaning, plasma, corona discharge treatment, chemical cleaning and the like.

[0079] The present invention also relates to a method for producing a composite body, comprising

[0080] (I) Mixing components (A) and (B) of the adhesive composition according to the invention to form an adhesive mixture; (II) Removing the solvent from the adhesive mixture,

[0081] (III) Provision of a silicone material;

[0082] (IV) Mixing the adhesive mixture from (II) with the silicone material from step (III) to form a silicone composition and

[0083] (V) Curing of the silicone composition from (IV).

[0084] In a preferred embodiment, step (I) comprises mixing components (A) and (B) of the adhesive composition according to the invention, as well as a recycled silicone material as a further component. This results in an adhesive mixture consisting of components A) and B) and a recycled component. For the purposes of this invention, a recycled silicone material is understood to be a previously used (old) vulcanized silicone material that is generated as waste.

[0085] The recycled silicone material can contain one or more silicone types selected from HTV (high-temperature curing) silicones, RTV (room-temperature curing) silicones, or LSR silicones. HTV silicones are preferred, such as addition-curing HTV silicones (with platinum catalyst) available in Shore A hardnesses of 5, 10, 20, 35, 65, and 70, for example, as DERMA-SIL and CSG HTV silicones. The HTV silicone CSG 35 / 1 with Shore A 35 from KauPo is particularly preferred.

[0086] The recycled silicone material can be in the form of shredded particles, which are added to the mixture of components (A) and (B) in step (I) and mixed with them in step (I). In a preferred embodiment, the recycled silicone material has a particle size of 0.2 mm to 1.5 mm, preferably 0.3 mm to 1.0 mm, particularly preferably 0.4 mm to 0.8 mm, and most preferably 0.4 mm to 0.6 mm.

[0087] In step (II), the solvent is removed from the adhesive mixture obtained in step (I). The solvent removal in step (II) can be carried out by evaporation at room temperature or by applying heat in a temperature range of 50°C to 110°C. In an alternative embodiment, the solvent removal can be carried out after step (IV).

[0088] In a preferred embodiment, the silicone material provided in step (III) comprises an RTV (room temperature curing) silicone, such as addition-curing silicones like ECOFLEX™ silicones with Shore hardnesses 5A, 00-50, 00-30, 00-20, and 00-10, or DRAGON SKIN™ with Shore A hardnesses of 10, 20, and 30 (KauPo). ECOFLEX™ 0030 or DRAGON SKIN™ 10 is particularly preferred. In step (IV), the adhesive mixture, preferably containing at least one recycled silicone material, is homogeneously mixed with the silicone material provided in step (III) to form a silicone composition.

[0089] In step (V), the resulting silicone composition is then cured. In one embodiment, further processing can take place before curing, for example by injection molding, compression molding, extrusion, transfer molding, press vulcanization or calendering.

[0090] The curing in step (V) can, for example, take place in a mold to form a shaped silicone article.

[0091] During the vulcanization of the waste silicone with the silicone composition in step (V), the crosslinking reaction between components i) and iv) takes place. The fully crosslinked polymer is formed by a reaction between the functionalized crosslinkable polymer i) and the crosslinking agent iv), for example, a vinylsilylation reaction between i) vinyl-terminated polydimethylsiloxane and iv) polymethylhydrosiloxane, in the presence of a platinum complex catalyst iii). The vinyl-terminated linear polydimethylsiloxane polymers i) are fully crosslinked together by this reaction.

[0092] The crosslinking reaction during curing (V) can be completed in-line, for example, by passing the product through a drying oven. The curing time can be, for example, 20 seconds at 165°C, 120 seconds at 90°C, or 60 minutes at 70°C.

[0093] Preferred temperatures for curing the adhesive composition are in the range of 60°C to 200°C, more preferably from 90°C to 220°C and particularly preferably from 70°C to 165°C.

[0094] Other conventional curing techniques that can be used with the new adhesive compositions of the present invention include heat, ultraviolet light, plasma, microwave radiation, electromagnetic coupling, ionizing radiation, lasers and the like.

[0095] The hardened composite body obtained in this way has, for example, a hardness (durometer) <75 Shore A.

[0096] The adhesive compositions according to the invention described above can achieve good adhesion to silicone materials. They also exhibit very good adhesive strength. Examples of composite components can be found in various industries, including the automotive, medical, consumer goods, and electronics sectors. In the automotive industry, these can include housings with silicone seals, connectors and terminals, components of various sensors, membranes, diaphragms, air conditioning ventilation components, and the like. Electronic applications include mobile phone covers, mobile phone accessories, precision electronic instruments, electrical switches and switch covers, watches and wristbands, wearable devices such as face masks, portable electronic devices, and the like.

[0097] A composite part can also be selected from parts of mobile phones, mobile telecommunications equipment, slot machines, watches, image receivers, DVD players, MD players, CD players and other precision electronic equipment, microwave ovens, refrigerators, electric rice cookers, cathode ray televisions, thin screen liquid crystal televisions and plasma televisions, various household appliances, copiers, printers, fax machines and other OA equipment, connector seals, spark plug caps, components of various sensors and other automotive parts.

[0098] Examples

[0099] Example 1

[0100] A series of tests was carried out in which the adhesive composition according to the invention was tested in comparison to commercially available silicone adhesives with regard to its adhesive properties.

[0101] Materials used:

[0102] Silicone adhesive:

[0103] Elastosil® E4, Wacker Chemie GmbH, DE

[0104] Elastosil® E43, Wacker, DE

[0105] Smooth-On Sil-Poxy (RTV Silicon)

[0106] Test strips:

[0107] Test strips made of HTV silicone Shore A 35, measuring 40 mm long, 25 mm wide, and 0.2 mm thick, as shown in Figures 1 and 2. The end to be bonded has been wedge-shaped for improved adhesion.

[0108] Three test strips per adhesive were glued together at the wedge-shaped ends and vulcanized according to the manufacturer's instructions (see Figure 1).

[0109] For the experiment, a test device was set up by firmly pressing the ends together. A tensile scale from the company Crans Scale was integrated as the measuring unit.

[0110] Table 1: Train results

[0111] Example 2: A series of tests was carried out in which the adhesive composition according to the invention was used in the production of a composite body based on recycled material. Recycled granules made of HTV (HÖR) from KauPo, CSG 35, in two grain sizes (0.6 mm to 1 mm and 0.4 mm to 0.6 mm) were used. The recycled material was bonded in Wacker Elastosil® 5040 / 50 and ShinEtsu KEG 2000-20. The recycled material was combined with LSR and hexamethyldisiloxane as

[0112] A solvent was mixed with the product. The solvent was then removed by evaporation. What remained was a paste / recycled material containing LSR. This mixture was incorporated in proportions into standard RTV silicone from KauPo (Dragon Skin™ 10; Exoflex™ 0030) and vulcanized. For comparison, measurements were also taken without the recycled material and with the recycled material but without LSR. Test strips were prepared as shown in Figure 3.

[0113] The test strips are 57 mm long and have a thickness of 2.5 mm.

[0114] The test strips were subjected to a tensile test. A tensile testing device (Sauter manual test stand) with a measuring unit of Sauter FC 1 K was used. The tensile tests were measured in units of N. Each test was repeated three times.

[0115] The results are summarized in Table 2:

[0116] Table 2:

[0117] Example 3:

[0118] Various solvents were used in different LSR to solvent ratios and their adhesive properties were investigated. The following silicones, comprising components A and B as separate parts, were used: Wacker-Elastosil® 5040 / 50; ShinEtsu KEG 2000-20; ShinEtsu KEG 2003H-60

[0119] Solvents: Herxamethydisiloxane, n-heptane, toluene, and white spirit. The amount of solvent refers to the amount added to components A and B of the silicones, respectively. Test strips made of vulcanized HTV (HCR) from KauPo-CSG 35 were bonded.

[0120] Tables 3a to 3d show that all mixing ratios resulted in very good adhesion. "Good adhesion" means that the silicone tore, but the bonded joint remained intact. Table 3a:

[0121] Table 3b:

[0122] Table 3c:

[0123] Table 3d:

Claims

Patent claims 1. Two-component adhesive composition comprising one component A) containing i) at least one vinyl group-terminated organopolysiloxane, ii) at least one platinum-based catalyst, and iii) at least one solvent selected from the group consisting of octamethyltrisiloxane, xylene, n-hexane, n-heptane, toluene, white spirit, or hexamethyldisiloxane, in a weight ratio ranging from 1:4.5 to 1:0.25, based on the total amount of (i) and (ii) to (iii); a component B) comprising iv) at least one organopolysiloxane having at least one SiH group and iii) at least one solvent selected from the group consisting of octamethyltrisiloxane, xylene, n-hexane, n-heptane, toluene, white spirit or hexamethyldisiloxane, in a weight ratio range of 1 : 4.5 to 1 : 0.25, based on the total amount of (iv) to (iii).

2. The two-component adhesive composition according to claim 1, wherein the solvent in component A) is present in a weight ratio range of 1 : 2 to 1 : 0.25, based on the total amount of (i) and (ii) to (iii).

3. The two-component adhesive composition according to claim 1, wherein the solvent in component B) is present in a weight ratio range of 1 : 1 to 1 : 0.25, based on the total amount of (iv) to (iii).

4. The two-component adhesive composition according to one or more of claims 1 to 3, wherein the solvent is hexamethyldisiloxane.

5. A method for producing a composite body, comprising (I) Mixing the components (A) and (B) of the adhesive composition according to claim 1 to form an adhesive mixture; (II) Applying the adhesive mixture from step (I) to a surface of a silicone substrate; (III) Bringing the surface coated in step (II) into contact with a surface of a second silicone substrate, wherein the surface of the second silicone substrate is uncoated or coated with the adhesive mixture; (IV) Removal of the solvent before or after step (III) as well as (V) Curing of the adhesive mixture.

6. The method according to claim 5, wherein step (IV) is performed before step (III).

7. The method according to claim 5 or 6, wherein the silicone substrate from step (II) and the second silicone substrate from step (III) are planar substrates.

8. A method for producing a composite body, comprising (I) Mixing the components (A) and (B) of the adhesive composition according to claim 1 to form an adhesive mixture; (II) Removal of the solvent from the adhesive mixture, (III) Provision of a silicone material; (IV) Mixing the adhesive mixture with the silicone material from step (III) to form a silicone composition and (V) Curing of the silicone composition.

9. The method according to claim 8, wherein the adhesive mixture in step (I) comprises a recycled silicone material as a further component.

10. The method according to claim 9, wherein the recycled silicone material is in the form of shredded particles.

11. The method according to claim 10, wherein the recycled silicone material has a grain size of 0.2 mm to 1.5 mm.

12. The method according to one or more of claims 9 to 11, wherein the recycled silicone material contains one or more types of silicone.

13. The method according to claim 12, wherein the silicone types are selected from high-temperature curing, HTV silicones, room-temperature curing, RTV silicones or liquid silicone rubber, LSR silicones.

14. A composite body obtainable by the method according to one or more of claims 5 to 7.

15. A composite body obtainable by the method according to one or more of claims 8 to 13.

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