Coating compositions and uses thereof

Abstract

Provided are a leather coating composition, a silicone-based synthetic leather utilizing the same as a topcoat (5), a method for making the synthetic leather, and uses of the synthetic leather and leather coating composition. The leather coating composition includes a hydrosilylation-curable silicone elastomer composition containing component (i), one or more polydiorganosiloxane polymers having a viscosity of 1000 to 500,000 mPa.s at 25°C and an alkenyl and / or alkynyl content of at least 5% by weight of the polymer per molecule; component (ii), a reinforcing filler such as finely divided silica optionally treated with one or more known filler treating agents; component (iii), a silicone resin crosslinker having end groups containing silicone-bonded hydrogen; component (iv), a hydrosilylation catalyst; component (v), a cured silicone powder; and component (vi), an eco-diluent.

Description

Technical Field

[0001] The present disclosure relates to a silicone elastomer coating composition for synthetic leather, particularly silicone-based synthetic leather, a silicone elastomer coating formed as a reaction product of the curing of the composition, a top coat using the same, a method for producing synthetic leather, and the use of the synthetic leather product. The top coat is designed to provide synthetic leather having an improved abrasion resistance and scratch resistance top coat.

Summary of the Invention

Problems to be Solved by the Invention

[0002] A variety of synthetic alternatives mainly using polyurethane (PU) or polyvinyl chloride (PVC) - based materials have been developed to replace natural leather. They are used in a variety of applications, including furniture, decoration, handbags, luggage, clothing, footwear, and automotive interiors. However, for use as synthetic leather, in order to meet increasingly stringent safety regulations, for example, it is necessary to meet strict physical property requirements regarding flame retardancy, smoke density, suitable adhesive strength to prevent the coating layer from peeling off during use, heat resistance, stain resistance, solvent resistance, hydrolysis resistance, etc. In many cases, PU and / or PVC - based materials cannot meet the above - mentioned physical properties.

[0003] Silicone - based synthetic leather composite materials can exhibit better performance than conventional PU and PVC synthetic leathers from the perspective of physical properties, for example, due to better flexibility over a wide temperature range and the ability to provide excellent UV resistance and heat resistance. Furthermore, silicone - based synthetic leather materials are generally considered to be skin - friendly.

[0004] Considering that the production of synthetic leather is often based, at least in part, on the use of environmentally problematic solvents such as dimethylformamide (DMF) that remain after the production of synthetic leather products, another advantage of silicone-based synthetic leather composites over organic alternatives is that they can generally be prepared using more environmentally friendly manufacturing methods.

[0005] Silicone-based synthetic leather can be produced via several routes, but generally it is manufactured using a textile support layer and two or more layers of a hydrosilylation-curable liquid silicone rubber composition and release paper. For example, a first liquid silicone rubber (LSR) composition can be coated onto the release paper and then cured to form a first layer or skin layer. A second LSR composition, which usually has different physical properties from the first layer, is applied onto the cured first layer to form an adhesive layer, and then the textile support layer is placed onto the second LSR layer and subsequently cured. Thereafter, the second LSR composition is cured to form an adhesive layer positioned between the skin layer and the textile support layer. If necessary and when required, the release paper is then removed. One or more additional layers of the same or different LSR compositions, which are considered suitable for forming the silicone-based leather composite, may also be applied between the release paper and the textile layer. For example, a third layer may be provided as a protective topcoat on the skin layer.

[0006] The products obtained in this way are very well used as silicone-based synthetic leather (when the release paper is removed), but it has been confirmed that the skin layer and / or previous topcoat layer do not provide sufficient abrasion resistance (e.g., (≧) 75,000 or more Wyzenbeek abrasion resistance, or (≧) 100,000 or more test cycles), as well as suitable scratch resistance, i.e., no white lines or cracks after strong scratching with a nail, and no visually prominent discoloration (e.g., whitening) caused by stretching the synthetic leather. Therefore, there is still a need for improved topcoats that can address these problems.

[0007] Provided is one or more polydiorganosiloxane polymers having component (i), a viscosity of 1000 to 500,000 mPa·s at 25°C, and an alkenyl group and / or alkynyl group content of at least 5% by weight of the polymer per molecule, component (ii) a reinforcing filler such as finely divided silica optionally treated with one or more known filler treating agents, component (iii) a silicone resin crosslinking agent having a terminal (M) group containing silicone-bonded hydrogen, component (iv) a hydrosilylation catalyst, component (v) a cured silicone powder, component (vi) an eco diluent, and a hydrosilylation curable silicone elastomer composition containing the same, which is a leather coating composition.

[0008] The leather coating composition is particularly suitable as a top coat for synthetic leather, especially silicone-based synthetic leather.

[0009] Component (i) of the hydrosilylation curable silicone elastomer composition of the leather coating composition is one or more polydiorganosiloxane polymers having a viscosity of 1000 to 500,000 mPa·s at 25°C and an alkenyl group and / or alkynyl group content of at least 5% by weight of the polymer per molecule, For example, the polydiorganosiloxane polymer (i) has a plurality of groups of formula (I), R a SiO (4-a) / 2 (I) In the formula, each R is independently selected from an aliphatic hydrocarbyl, an aromatic hydrocarbyl, or an organo group (which is any organic substituent having one free valence on a carbon atom regardless of the type of functionality). Saturated aliphatic hydrocarbyls are exemplified by, but not limited to, alkyl groups such as methyl, ethyl, propyl, pentyl, octyl, undecyl, and octadecyl, and cycloalkyl groups such as cyclohexyl. Unsaturated aliphatic hydrocarbyls are exemplified by, but not limited to, alkenyl groups such as vinyl, allyl, butenyl, pentenyl, cyclohexenyl and hexenyl, and alkynyl groups. Aromatic hydrocarbon groups are exemplified by, but not limited to, phenyl, tolyl, xylyl, benzyl, styryl, and 2-phenylethyl. Organo groups are exemplified by, but not limited to, halogenated alkyl groups such as chloromethyl and 3-chloropropyl, nitrogen-containing groups such as amino groups, amide groups, imino groups, and imide groups, polyoxyalkylene groups, carbonyl groups, alkoxy groups, and oxygen-containing groups such as hydroxyl groups. Further organo groups may include sulfur-containing groups, phosphorus-containing groups, and / or boron-containing groups. The subscript "a" can be 0, 1, 2, or 3, but typically is mainly 2 or 3.

[0010] The siloxy group can be described by the shorthand (abbreviated) nomenclature, namely - "M", "D", "T", and "Q" when R is an organic group, typically a methyl group (further teachings on silicone nomenclature can be found in Walter Noll, Chemistry and Technology of Silicones, dated 1962, Chapter I, pages 1-9). The M group corresponds to the siloxy group when a = 3, i.e., R3SiO 1 / 2 and the D group corresponds to the siloxy group when a = 2, i.e., R2SiO 2 / 2 and the T group corresponds to the siloxy group when a = 1, i.e., R1SiO 3 / 2 and the Q group corresponds to the siloxy group when a = 0, i.e., SiO 4 / 2 corresponds to.

[0011] Examples of typical groups of the polydiorganosiloxane polymer (i) mainly include alkenyl, alkyl, and / or aryl groups. The groups may be in pendant positions (on D or T siloxy groups) or at terminal positions (on M siloxy groups). Thus, suitable alkenyl groups of the polydiorganosiloxane polymer (i) typically contain 2 to 10 carbon atoms, such as vinyl, isopropenyl, allyl, and 5-hexenyl, typically a vinyl group, and can be determined using quantitative infrared analysis according to ASTM E168. They are present on the polymer in an amount of at least 5% by weight of the polymer per molecule, or 5 to 15% by weight of the polymer per molecule, or 6 to 15% by weight of the polymer per molecule, or 7 to 15% by weight of the polymer per molecule as shown above.

[0012] Typically, the silicon-bonded organic groups bonded to the polydiorganosiloxane polymer (i) other than alkenyl and / or alkynyl groups are typically monovalent saturated hydrocarbon groups containing 1 to 10 carbon atoms, and monovalent aromatic hydrocarbon groups containing typically 6 to 12 carbon atoms, unsubstituted or substituted with groups that do not interfere with the curing of the composition of the present invention, such as halogen atoms. Preferred species of the silicon-bonded organic groups are, for example, alkyl groups such as methyl, ethyl, and propyl, and aryl groups such as phenyl.

[0013] The molecular structure of the polydiorganosiloxane polymer (i) is typically linear, however, due to the presence of (the aforementioned) T groups in the molecule, some branching may exist.

[0014] In order to achieve useful levels of physical properties in the elastomer prepared by curing the composition as described above, the viscosity of the polydiorganosiloxane polymer (i) needs to be at least 1000 mPa·s at 25°C. The upper limit of the viscosity of the polydiorganosiloxane polymer (i) is limited to a viscosity of a maximum of 500,000 mPa·s at 25°C.

[0015] Generally, each polydiorganosiloxane containing alkenyl groups and / or alkynyl groups in an amount of at least 5% by weight of the polymer per molecule (determined using quantitative infrared analysis according to ASTM E168), of component (i), has a viscosity of 1000 mPa·s to 150,000 mPa·s at 25°C, or 2000 mPa·s to 125,000 mPa·s at 25°C, or 2000 mPa·s to 100,000 mPa·s at 25°C, or 5000 mPa·s to 80,000 mPa·s measured at 25°C, based on the cup / spindle method of ASTM D1084-16 using a spindle appropriate for the viscosity range, unless otherwise specified.

[0016] The polydiorganosiloxane polymer (i) can be selected from polydimethylsiloxane, alkylmethylpolysiloxane, alkylarylpolsiloxane, or copolymers thereof containing, for example, alkenyl and / or alkynyl groups, and can have any suitable end groups. For example, they can be trialkyl-terminated, alkenyldialkyl-terminated, or terminated with any other suitable combination of end groups, provided that each polymer contains at least 5% by weight of the polymer per molecule, which can be determined using quantitative infrared analysis according to ASTM E168.

[0017] Thus, the polydiorganosiloxane polymer (i) can be, by way of example, dimethylvinyl-terminated polydimethylsiloxane, dimethylvinyl-terminated dimethylmethylphenylsiloxane, trialkyl-terminated dimethylmethylvinylpolysiloxane, or dialkylvinyl-terminated dimethylmethylvinylpolysiloxane copolymer. However, considering the presence of a high level of alkenyl and / or alkynyl groups, or it can be a trialkyl-terminated dimethylmethylvinylpolysiloxane or a dialkylvinyl-terminated dimethylmethylvinylpolysiloxane copolymer.

[0018] For example, the polydiorganosiloxane polymer (i) containing an alkenyl group and / or an alkynyl group at both ends can be represented by the general formula (II): R´R”R”´SiO-(R”R”´SiO) m -SiOR´´´R”R´ (II) In formula (II), each R´ can typically be an alkenyl group or an alkynyl group containing 2 to 10 carbon atoms. Alkyl groups include, but are not limited to, vinyl, propenyl, butenyl, pentenyl, hexenyl, alkenylated cyclohexyl groups, heptenyl, octenyl, nonenyl, decenyl, or similar linear and branched alkenyl groups, as well as alkenylated aromatic ring structures. The alkynyl group can be selected from, but is not limited to, ethynyl, propynyl, butynyl, pentynyl, hexynyl, alkynylated cyclohexyl groups, heptynyl, octynyl, nonynyl, decynyl, or similar linear and branched alkenyl groups, as well as alkenylated aromatic ring structures.

[0019] R” does not contain ethylenic unsaturation, each R” may be the same or different, and is typically individually selected from a monovalent saturated hydrocarbon group containing 1 to 10 carbon atoms and a monovalent aromatic hydrocarbon group containing typically 6 to 12 carbon atoms. R” may be unsubstituted or substituted with one or more groups that do not interfere with the curing of the composition of the present invention, such as halogen atoms. R”´ is R´ or R”.

[0020] The organopolysiloxane polymer (i) is typically present in an amount of 3, or 10% to 30%, or 25% by weight of the composition. For example, the organopolysiloxane polymer (i) can be present in the range of 10 to 30%, or 10 to 25% by weight.

[0021] (ii) Reinforcing filler Component (ii) of the leather coating composition comprising a hydrosilylation-curable silicone elastomer composition is a reinforcing filler such as finely divided silica. In order to prevent a phenomenon called "creping" or "crepe hardening" during the processing of the curable composition, silica and other reinforcing fillers (ii) are often treated with one or more known filler treatment agents.

[0022] The finely divided form of silica is the preferred reinforcing filler (ii). Precipitated silica and / or fumed silica, or fumed silica, is particularly preferred because of its relatively large surface area of typically at least 50 m 2 / g (BET method according to ISO9277:2010). Fillers having a surface area of 50 to 450 m 2 / g (BET method according to ISO9277:2010), or 50 to 300 m 2 / g (BET method according to ISO9277:2010) are typically used. Both types of silica are commercially available.

[0023] The amount of the reinforcing filler (ii) in the composition of the present specification, for example, finely divided silica, is 5 to 40% by weight, or 5 to 30% by weight. In some cases, the amount of the reinforcing filler can be 7.5 to 30% by weight, or 10 to 30% by weight, or 15 to 30% by weight based on the weight of the composition.

[0024] When the reinforcing filler (ii) is inherently hydrophilic (for example, an untreated silica filler), it is typically treated with a treatment agent to make it hydrophobic. By surface treatment, these surface-modified reinforcing fillers (ii) can be wetted easily by the polydiorganosiloxane polymer (i), so they do not aggregate and can be homogeneously incorporated into the polydiorganosiloxane polymer (i). This results in improved room temperature mechanical properties of the composition and a cured material obtained by curing the composition.

[0025] The surface treatment can be carried out before introduction into the composition or in situ (i.e., by blending these components together at room temperature or above until the filler is fully treated, in the presence of at least some of the other components of the compositions herein. Typically, the untreated reinforcing filler (ii) is treated in situ with the treating agent in the presence of the polydiorganosiloxane polymer (i), and after mixing, a silicone rubber-based material is obtained, to which other components can be added.

[0026] Typically, the reinforcing filler (ii) can be surface treated with any low molecular weight organosilicon compound disclosed in the applicable art to prevent creping of the organosiloxane composition during processing. To make the filler hydrophobic and thus facilitate handling and obtain a homogeneous mixture with other components, for example, organosilanes, polydiorganosiloxanes, or organosilazanes such as hexaalkyldisilazane, short-chain siloxane diols, or fatty acids or fatty acid esters such as stearates. Specific examples include silanol-terminated trifluoropropylmethylsiloxane, silanol-terminated ViMe siloxane, tetramethyldi(trifluoropropyl)disilazane, tetramethyldivinyldisilazane, silanol-terminated MePh siloxane, liquid hydroxyl-terminated polydiorganosiloxanes containing on average 2 to 20 repeating units of diorganosiloxane per molecule, hexaorganodisiloxane, hexaorganodisilazane, but are not limited thereto. A small amount of water can be added together with the silica treating agent as a processing aid.

[0027] The filler can be introduced into the composition in the form of a masterbatch or a system, which contains the filler and an organopolysiloxane polymer. The organopolysiloxane polymer used in the masterbatch or system can be the component (i), or it can be an organopolysiloxane polymer having a viscosity in the same range as the component (i) but with an alkenyl and / or alkynyl content of <5 wt% of the polymer. If necessary, the fumed silica can be hydrophobized in situ by introducing a suitable hydrophobizing agent into the mixture during the preparation of the masterbatch.

[0028] The composition described herein is cured using a hydrosilylation curing package that includes an organohydrogenpolysiloxane (component (iii)) having three or more silicon-bonded hydrogen atoms per molecule and a hydrosilylation catalyst (component (iv)).

[0029] Component (iii) Organohydrogenpolysiloxane Component (iii) of the leather coating composition comprising a hydrosilylation-curable silicone elastomer composition is a silicone resin crosslinking agent having a terminal group containing silicone-bonded hydrogen that acts as a crosslinking agent for polymer (i) by an addition reaction between the silicon-bonded hydrogen atoms of component (iii) and the alkenyl and / or alkynyl groups of component (i) under the catalytic activity of component (iv) below. Component (iii) contains at least 5,000 parts per million (ppm) of silicon-bonded hydrogen (Si-H), or at least 7,000 ppm, or 7,000 - 12,000 ppm of silicon-bonded hydrogen, or 8,000 ppm - 11,000 ppm of silicon-bonded hydrogen. Therefore, the silicon-bonded hydrogen atoms of this component can react sufficiently with the alkenyl and / or alkynyl groups, typically alkenyl groups, especially vinyl groups of component (i) to form a network structure with them, thereby curing the composition. The amount of silicon-bonded hydrogen present is also determined using quantitative infrared analysis according to ASTM E168.

[0030] The molecular structure of component (iii) is resinous and contains a mixture of Q, T, D, and M groups. To obtain good miscibility with component (i), it has a viscosity of 10 - 5000 mPa·s at 25°C, or 10 - 1000 mPa·s at 25°C, or 10 - 500 mPa·s at 25°C, as measured using a Brookfield DV 3T rheometer.

[0031] Examples of component (iii) of the leather coating composition containing a hydrosilylation-curable silicone elastomer composition include, but are not limited to, the following. (CH3)2HSiO 1 / 2 M groups containing Si-H such as groups, (CH3)3SiO 1 / 2 groups and SiO 4 / 2 Silicone resins containing or consisting of trialkyl M groups such as groups, (CH3)2HSiO 1 / 2 groups and SiO 4 / 2 Silicone resins containing or consisting of M groups containing Si-H such as groups, (CH3)2HSiO 1 / 2 groups, (CH3)2SiO 2 / 2 groups, and SiO 4 / 2 Silicone resins containing or consisting of M groups containing Si-H such as groups, (CH3)2HSiO 1 / 2 groups, SiO 4 / 2 groups, and (C6H5)3SiO 1 / 2 M groups containing Si-H such as groups, as well as silicone resins containing or consisting of alternatives in which methyl is replaced by a phenyl group or other alkyl group or mixtures thereof. The silicone resin may also contain T groups and / or D groups, or T groups.

[0032] Optionally, other crosslinking agents may be further utilized. These may include the following. 1,1,3,3 - Tetramethyldisiloxane, 1,3,5,7 - Tetramethylcyclotetrasiloxane, Tris(hydrogendimethylsiloxy)methylsilane, Tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogen cyclopolysiloxane, Trimethylsiloxy-terminated block methylhydrogen polysiloxane, Trimethylsiloxy-terminated block dimethylsiloxane / methylhydrogensiloxane copolymer, Dimethylhydrogensiloxy-terminated block dimethylpolysiloxane, Dimethylhydrogensiloxy-terminated block dimethylsiloxane / methylhydrogensiloxane copolymer, Trimethylsiloxy-terminated block methylhydrogensiloxane / diphenylsiloxane copolymer, Trimethylsiloxy-terminated block methylhydrogensiloxane / diphenylsiloxane / -dimethylsiloxane copolymer, Trimethylsiloxy-terminated block methylhydrogensiloxane / methylphenylsiloxane / -dimethylsiloxane copolymer, Dimethylhydrogensiloxy-terminated block / dimethylsiloxane / -diphenylsiloxane copolymer, and / or Dimethylhydrogensiloxy-terminated block methylhydrogensiloxane / dimethylsiloxane / -methylphenylsiloxane copolymer. However, it is preferred that component (iii) is one or more of the above silicone resins.

[0033] Component (iii) is typically present in the total composition in an amount of 5 to 20% by weight, or 10 to 20% by weight of the composition, but the amount present is typically determined by the molar ratio of the silicon-bonded hydrogen atoms of component (iii) to the total number of all unsaturated groups, such as alkenyl and alkynyl groups, often vinyl groups. In the present composition, the molar ratio of the silicon-bonded hydrogen atoms of component (iii) to the total number of all unsaturated groups is preferably 0.5:1 to 20:1, or 0.5:1 to 10:1, or 0.5:1 to 5:1, or 1:1 to 5:1 with Si-H in excess.

[0034] iv) Hydrosilylation catalyst As described above, the leather coating composition is cured via a hydrosilylation (addition) reaction catalyzed by a hydrosilylation (addition curing) catalyst (iv) that is a metal selected from platinum metals, namely platinum, ruthenium, osmium, rhodium, iridium, and palladium, or a compound of such a metal. Due to the high activity levels of these catalysts in the hydrosilylation reaction, platinum and rhodium compounds are preferred.

[0035] Catalyst (iv) can be a platinum metal, a platinum metal deposited on a support such as silica gel or powdered carbon, or a compound or complex of a platinum group metal. Examples of hydrosilylation catalysts (iv) suitable for the hydrosilylation curable silicone elastomer composition of the leather coating composition include, but are not limited to, platinum black, platinum on various solid supports, chloroplatinic acid, an alcoholic solution of chloroplatinic acid, and complexes of chloroplatinic acid with ethylenically unsaturated compounds such as olefins and organosiloxanes containing ethylenically unsaturated silicon-bonded hydrocarbon groups.

[0036] Examples of suitable platinum-based catalysts (iv) include the following. (i) Complexes of chloroplatinic acid with organosiloxanes containing ethylenically unsaturated hydrocarbon groups, as described in US3,419,593, (ii) Chloroplatinic acid in either the hexahydrate form or the anhydrous form, (iii) Platinum-containing catalysts obtained by a method that includes reacting chloroplatinic acid with an aliphatically unsaturated organosilicon compound such as divinyltetramethyldisiloxane, (iv) Alkene-platinum-silyl complexes as described in US Patent No. 6,605,734, such as (COD)Pt(SiMeCl2)2 (where "COD" is 1,5-cyclooctadiene), and / or (v) Karstedt's catalyst, which is typically a platinum divinyltetramethyldisiloxane complex containing about 1 wt% platinum in a solvent such as toluene, can be used. These are described in US3,715,334 and US3,814,730.

[0037] The hydrosilylation catalyst (iv) is present in the total composition in a catalytic amount, i.e., an amount or quantity sufficient to promote the reaction or curing of the composition under the desired conditions. The level of the hydrosilylation catalyst (iv) can be varied to adjust the reaction rate and the curing rate. The catalytic amount of the hydrosilylation catalyst (iv) is generally from 0.01 ppm to 10,000 parts by weight, i.e., parts per million (ppm), or from 0.01 to 7500 ppm, or from 0.01 to 3,000 ppm, or from 100 to 6,000 ppm of platinum group metal, based on the combined weight of components (i) and (ii) and (v) when present. In a specific embodiment, the catalytic amount of the catalyst can be a metal in the range of 1000 to 6,000 ppm based on the weight of the composition. The range can specifically relate to only the metal content in the catalyst or to the entire catalyst (including its ligands), but typically these ranges relate simply to the metal content in the catalyst. The catalyst can be added as a single species or as a mixture of two or more different species. Typically, depending on the form / concentration in which the catalyst package is provided, the amount of catalyst present will be in the range of 0.01 to 3.0% by weight of the composition, or 0.1 to 3.0% by weight of the composition, or 0.1 to 2.0% of the composition, or 0.1 to 1.5% of the composition.

[0038] Component (v) is a cured silicone elastomer powder Any suitable cured silicone elastomer powder can be utilized. In one alternative, the cured silicone elastomer powder (v) has an average particle size of from 0.01 to 100 μm, or from 0.01 to 50 μm, or from 0.01 to 25 μm. They can contain chemically functional groups, such as epoxy groups, (meth)acryloxy groups, or can be coated, for example, with a silica-treated coating.

[0039] The cured silicone elastomer powder is made from a suitable curable silicone composition. These can include, for example, addition (hydrosilylation) reaction-cured silicone compositions, condensation reaction-cured silicone compositions, organic peroxide-cured silicone compositions, and ultraviolet-cured silicone compositions. Addition reaction-cured and condensation reaction-cured silicone compositions are preferred due to their ease of handling.

[0040] The silicone elastomer powder is generally prepared by first dispersing the curable silicone composition in water or an aqueous surfactant solution, and then subjecting this dispersion to the action of a stirrer such as a homogenizer, a colloid mill, or a mixing device such as an ultrasonic vibrator to produce a homogeneous aqueous emulsion of the curable silicone composition. In order to obtain a very stable emulsion in which the curable silicone composition has a small average particle diameter, the aqueous curable silicone emulsion is preferably prepared using a surfactant. Then, by curing the curable silicone present in the aqueous emulsion, an aqueous dispersion of the cured silicone powder is produced. This curing can be affected by allowing the aqueous emulsion to stand at room temperature or by heating the aqueous emulsion. When heating the aqueous curable silicone emulsion, the preferred heating temperature should not exceed 100 °C, and a particularly preferred temperature range is from 40 °C to 95 °C. The techniques for heating the aqueous curable silicone emulsion are either by directly heating the aqueous emulsion or by adding the aqueous emulsion to hot water. Commercial examples that can be utilized as component (v) include, by way of example, Dowsil™ 23N, Dowsil™ 603T Additive, and Dowsil™ 9701 Cosmetic Powder from Dow Silicones Corporation.

[0041] The cured silicone rubber powder is present in the composition in an amount of 2.5 to 20% by weight, or 2.5 to 15% by weight of the composition, or 2.5 to 10% by weight of the composition when parts A and B of the composition are mixed together.

[0042] Component (vi) - eco solvent Component (vi) is an eco solvent. Any suitable eco solvent can be utilized. Examples include isopentadecane, isohexadecane, isoheptadecane, isooctadecane, isononadecane, and mixtures thereof, or trimethyl-terminated polydimethylsiloxane having a viscosity of (≧) 5 mPa·s or more at 25°C to (≦) 100 mPa·s or less at 25°C. It has been pointed out that using trimethyl-terminated polydimethylsiloxane having a viscosity of <5 mPa·s at 25°C appears to actually result in a leather material with white stretch marks. In one embodiment, the eco solvent comprises or consists of isohexadecane. The eco solvent is present in the composition as a means of diluting the composition and is present in the composition in an amount of 30 to 70% by weight of the composition.

[0043] Inhibitor Optionally, since a hydrosilylation curing system is utilized, a suitable inhibitor may be incorporated into the composition to delay or suppress the activity of the catalyst in order to obtain a longer working time or pot life of the hydrosilylation curable silicone elastomer composition used in or as the leather coating composition.

[0044] Platinum metal-based catalysts, and generally inhibitors of platinum metal-based catalysts, are well known in the art. Hydrosilylation or addition reaction inhibitors include hydrazine, triazole, phosphine, mercaptan, organic nitrogen compounds, acetylenic alcohols, silylated acetylenic alcohols such as methyl(tris(1,1-dimethyl-2-propynyloxy))silane, maleates, fumarates, ethylenic or aromatic unsaturated amides, ethylenic unsaturated isocyanates, olefin siloxanes, unsaturated hydrocarbon monoesters and diesters, conjugated en-ynes, hydroperoxides, nitriles, and diaziridines. The alkenyl-substituted siloxanes described in US 3,989,667 can be used, and among them, cyclic methylvinylsiloxane is preferred.

[0045] Another class of known inhibitors of platinum catalysts includes the acetylene compounds disclosed in US 3,445,420. Acetylenic alcohols such as 2-methyl-3-butyn-2-ol are a preferred class of inhibitors that will suppress the activity of platinum-containing catalysts at 25°C. Compositions containing these inhibitors typically need to be heated at a temperature of 70°C or higher in order to cure at a practical rate.

[0046] Examples of acetylenic alcohols and their derivatives include 1-ethynyl-1-cyclohexanol (ETCH), 2-methyl-3-butyn-2-ol, 3-butyn-1-ol, 3-butyn-2-ol, propargyl alcohol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclopentanol, 1-phenyl-2-propynol, 3-methyl-1-penten-4-yn-3-ol, and mixtures thereof.

[0047] In some cases, when present, a low inhibitor concentration of about 1 mole of inhibitor per mole of metal of catalyst (iv) will impart satisfactory storage stability and cure rate. In other cases, an inhibitor concentration of up to 500 moles of inhibitor per mole of metal of catalyst (iv) is required. The optimal concentration of a particular inhibitor in a given composition is readily determined by routine experimentation. When present in the composition, depending on the concentration and form in which the selected inhibitor is provided / commercially available, the inhibitor is typically present in an amount of 0.0125 to 10 wt% of the composition. The above mixtures may be used.

[0048] The aforementioned composition does not contain any thermally expandable microcapsules. Such thermally expandable microcapsules include a spherical shell composed of a thermoplastic resin material that holds a volatile substance, typically a liquid. The thermally expandable microcapsules are designed to expand when heated. The thermoplastic resin material may include polyethylene, polystyrene, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polymethyl methacrylate, polybutadiene, polychloroprene, and other vinyl polymers and copolymers thereof; nylon 6, nylon 66, and other polyamides; and polyethylene terephthalate, polyacetal, and blends thereof. The volatile substance is encapsulated within the spherical shell composed of the thermoplastic resin. For example, it may include butane, isobutene, propane, and other hydrocarbons; methanol, ethanol, and other alcohols; dichloroethane, trichloroethane, trichloroethylene, and other halogenated hydrocarbons; and diethyl ether, isopropyl ether, and other ethers. To avoid misunderstanding, the eco-diluent (vi) is not provided as a volatile substance, i.e., the liquid within the thermally expandable microcapsules.

[0049] Any additives The composition may contain one or more optional additives. One optional additive that may be utilized is a low-viscosity polydiorganosiloxane polymer having at least one, or at least two alkenyl and / or alkynyl groups per molecule and having a viscosity of 100 to 750 mPa·s as measured at 25 °C based on the cup / spindle method of ASTM D1084-16, using a spindle appropriate for the viscosity range, unless otherwise specified. The chemical structure of the low-viscosity polydiorganosiloxane polymer is similar to that of the polydiorganosiloxane polymer (i), except that it has a lower viscosity and a lower content of alkenyl and / or alkynyl groups per molecule than that in component (i), i.e., (determined using quantitative infrared analysis according to ASTM E168) a content of alkenyl and / or alkynyl groups of 0.75 wt% of the polymer per molecule. Examples include dimethylvinyl-terminated polydimethylsiloxanes such as dimethylvinyl-terminated dimethylmethylvinylpolysiloxane copolymers and dialkylalkenyl-terminated dialkylpolysiloxanes having a viscosity of 100 to 750 mPa·s at 25 °C, or 150 to 500 mPa·s at 25 °C, such as this copolymer. When the aforementioned low-viscosity polydiorganosiloxane polymer is present, it can be used to partially replace a part of component (i), but the cumulative total of the aforementioned component (i) + low-viscosity polydiorganosiloxane polymer can be up to 40 wt% of the composition, or up to 35 wt% of the composition. Thus, when component (i) and the low-viscosity polydiorganosiloxane polymer are present, the combined total amount is from 8, or 10 wt% to 40 wt%, or 35 wt%, or 30 wt%, or 25 wt% of the composition. For example, the cumulative weight of the organopolysiloxane polymer (i) and the low-viscosity polydiorganosiloxane polymer (when present) can range from 10 to 40 wt%, or 10 to 35 wt%.

[0050] Other additives When necessary and as needed, other commonly used additives may be present in the leather coating composition containing the hydrosilylation-curable silicone elastomer composition. Examples of these optional additives include non-reinforcing fillers, conductive fillers, non-conductive fillers, pot life extenders, flame retardants, pigments, colorants, chain extenders, heat stabilizers, compression set improvement additives, anti-squeal agents, anti-freezing agents, and / or biocides, as well as mixtures thereof.

[0051] Non-reinforcing filler Non-reinforcing fillers, when present, may include crushed quartz, diatomaceous earth, barium sulfate, iron oxide, titanium dioxide, and carbon black, wollastonite and graphite, graphene, talc, mica, clay, platelet-type fillers such as layered silicates, kaolin, montmorillonite, and mixtures thereof. Other non-reinforcing fillers that can be used alone or in addition to the above include bauxite, calcium sulfate (anhydrite), gypsum, calcium sulfate, magnesium carbonate, aluminum trihydroxide, magnesium hydroxide (brucite), graphite, copper carbonate, such as malachite, nickel carbonate, such as zarachite, barium carbonate, such as witherite, and / or strontium carbonate, such as strontianite.

[0052] When present, the non-reinforcing filler may alternatively or additionally be selected from silicates from the group consisting of aluminum oxide, cordierite group, garnet group, aluminosilicates, cyclic silicates, chain silicates, and layered silicates. The cordierite group includes, but is not limited to, silicate minerals such as forsterite and Mg2SiO4. The garnet group includes pyrope, Mg3Al2Si3O 12 , grossular, and Ca2Al2Si3O 12including, but not limited to, ground silicate minerals such as. Aluminosilicates include, but are not limited to, ground silicate minerals such as sillimanite, Al2SiO5, mullite, 3Al2O3.2SiO2, kyanite, and Al2SiO5. The cyclic silicate group includes, but is not limited to, silicate minerals such as cordierite, and Al3(Mg,Fe)2[Si4AlO 18 , etc., including, but not limited to, silicate minerals. The chain silicate group includes, but is not limited to, ground silicate minerals such as wollastonite, and Ca[SiO3].

[0053] Suitable layered silicates that can be used, such as silicate minerals, include, but are not limited to, mica, K2AI 14 [Si6Al2O 20 (OH)4, pyrophyllite, Al4[Si8O 20 (OH)4, talc, Mg6[Si8O 20 (OH)4, serpentine (such as asbestos), kaolinite, Al4[Si4O 10 (OH)8, and vermiculite, but are not limited to these. When present, the non-reinforcing filler is present in the composition at a maximum of 1 - 50 wt% in total cumulative amount.

[0054] In one embodiment, the non-reinforcing filler can include microbeads or microspheres such as glass to improve the insulation of the material. The microbeads or microspheres can be glass, such as borosilicate glass microbeads and / or microspheres.

[0055] When deemed necessary, the non-reinforcing fillers can also be treated as described above with respect to the reinforcing fillers (ii) to make them hydrophobic, thereby facilitating handling and obtaining a homogeneous mixture with other components. As in the case of the reinforcing fillers (ii), surface treatment of the non-reinforcing fillers makes the polydiorganosiloxane polymer (i) and, when present, the resin (v) more wettable, resulting in improved properties of the composition such as better processability (e.g., lower viscosity, better release ability, and / or lower adhesion to processing equipment such as a two-roll mill), heat resistance, and mechanical properties.

[0056] Examples of conductive fillers include metal particles, metal oxide particles, metal-coated metal particles (such as silver-plated nickel), metal-coated non-metallic core particles (such as silver-coated talc, mica, quartz), and combinations thereof. The metal particles can be in the form of powders, flakes or filaments, and mixtures or derivatives thereof.

[0057] Examples of non-conductive fillers include quartz powder, diatomaceous earth, talc, clay, mica, calcium carbonate, magnesium carbonate, hollow glass, glass fiber, hollow resin and plating powder, and mixtures or derivatives thereof.

[0058] A pot life extender such as triazole may be used, but is not considered necessary within the scope of the present invention. Accordingly, the liquid curable silicone rubber composition may not contain a pot life extender.

[0059] Examples of flame retardants include aluminum trihydrate, magnesium hydroxide, calcium carbonate, zinc borate, wollastonite, mica and chlorinated paraffin, hexabromocyclododecane, triphenyl phosphate, dimethyl methylphosphonate, tris(2,3-dibromopropyl) phosphate (brominated tris), and mixtures or derivatives thereof.

[0060] Examples of pigments include carbon black, iron oxide, titanium dioxide, chromium oxide, bismuth vanadium oxide, and mixtures or derivatives thereof.

[0061] Examples of colorants include mordant dyes, reactive dyes, acid dyes, chrome dyes, disperse dyes, cationic dyes, and mixtures thereof.

[0062] Examples of chain extenders include disiloxane or low molecular weight polyorganosiloxanes containing two silicon-bonded hydrogen atoms at the terminal positions. The chain extender typically reacts with the alkenyl and / or alkynyl groups of the polydiorganosiloxane polymer (i), thereby linking together two or more molecules of the polydiorganosiloxane polymer (i) and increasing its effective molecular weight and the distance between potential crosslinking sites.

[0063] Disiloxane is typically represented by the general formula (HR a 2Si)2O. When the chain extender is a polyorganosiloxane, it has terminal groups of the general formula HR a 2SiO 1 / 2 and non-terminal groups of the formula R b 2SiO. In these formulas, R a and R b each represent an unsubstituted or substituted monovalent hydrocarbon group containing no ethylenic unsaturation, including alkyl groups containing 1 to 10 carbon atoms, substituted alkyl groups containing 1 to 10 carbon atoms such as chloromethyl and 3,3,3-trifluoropropyl, cycloalkyl groups containing 3 to 10 carbon atoms, aryls containing 6 to 10 carbon atoms, alkaryl groups containing 7 to 10 carbon atoms such as tolyl and xylyl, and aralkyl groups containing 7 to 10 carbon atoms such as benzyl, but are not limited thereto.

[0064] Further examples of chain extenders include tetramethyldihydrogendisiloxane or dimethylhydrogen-terminated polydimethylsiloxane.

[0065] When present, for more than one reason, for example when any additives can be used as non-reinforcing fillers and flame retardants, they can function in both roles. When present or in the case where they are present, the aforementioned additional constituents are present in an amount of 0.1 to 30% by weight, or 0.1 to 20% by weight, cumulatively, based on the weight of the composition.

[0066] To prevent premature hardening during storage, the composition will be stored in two parts, part A and part B, prior to use. Typically, part A contains a portion of the polydiorganosiloxane polymer (i), and the reinforcing filler (ii), and the hydrosilylation catalyst (iv), and part B will contain the remaining polydiorganosiloxane polymer (i), and the reinforcing filler (ii), and, when present, the inhibitor, together with the organohydrogenpolysiloxane (iii) which is a constituent. The two-part composition can be designed to be mixed together in any suitable ratio depending on the amounts of the polydiorganosiloxane polymer (i) and the reinforcing filler (ii) in part B, and thus can be mixed at a weight ratio of part A: part B of 15:1 to 1:2, but preferably at a weight ratio of part A: part B of 2:1 to 1:2, or 1.5:1 to 1:1.5, or 1:1.

[0067] Any additives can be introduced into either the silicone elastomer composition of part A or part B, as required, provided that they do not cause any adverse effects to any of the other components of each part.

[0068] The individual parts of the hydrosilylation-curable silicone elastomer composition used in the leather coating composition can be prepared in any suitable manner. For this purpose, any mixing techniques and devices described in the prior art can be used. The specific device used will be determined depending on the viscosities of the components and the final curable coating composition. Suitable mixers include, but are not limited to, paddle type mixers such as planetary mixers and kneader type mixers. Cooling of the components during mixing may be desirable to avoid premature curing of the composition.

[0069] As discussed previously, the component (ii) reinforcing filler can be introduced into the composition in the form of a fumed silica masterbatch for introducing fumed silica into both part A or part B of the composition, and can contain 25 to 40% by weight of fumed silica, as well as 55 to 75% by weight of a polydiorganosiloxane containing at least two alkenyl and / or alkynyl groups per molecule. The polydiorganosiloxane can be the same as component (i) above and / or in the same viscosity range as component (i), but is a polydiorganosiloxane having an alkenyl and / or alkynyl content of <5% by weight of the polymer. In one embodiment, in the fumed silica masterbatch, the polydiorganosiloxane containing at least two alkenyl and / or alkynyl groups per molecule has a viscosity of 50,000 to 80,000 mPa·s at 25°C, and a vinyl content of 0.05 to 0.2% by weight of the polymer, or a vinyl content of 0.05 to 0.15% by weight of the polymer, determined using quantitative infrared analysis according to ASTM E168, and is dimethylvinyl-terminated polydimethylsiloxane. Such a masterbatch can contain only fumed silica and the polymer, but can also optionally contain small amounts of other components such as hexamethyldisiloxane, divinyltetramethyldisiloxane, dimethylhydroxy-terminated methylvinylsiloxane polymer having a viscosity of 10 to 100 mPa·s and a vinyl content of 5 to 20% by weight, or 7.5 to 15% by weight of the polymer (determined using quantitative infrared analysis according to ASTM E168), and / or water.

[0070] Thus, when part A and part B are mixed together in a 1:1 weight ratio, the part A composition according to the present disclosure can include: One or more polydiorganosiloxane polymers having alkenyl and / or alkynyl groups, typically vinyl group content, of at least 5 wt% of polymer per molecule and which can be determined using quantitative infrared analysis according to ASTM E168 (present on the polymer in an amount of at least 5 wt% of polymer per molecule, or 5 - 15 wt% of polymer per molecule, or 6 - 15 wt% of polymer per molecule, or 7 - 15 wt% of polymer per molecule as shown previously), having a viscosity of from 1000 to 500,000 mPa·s at 25°C, or from 1000 mPa·s to 150,000 mPa·s at 25°C, or from 2000 mPa to 125,000 mPa·s, or from 2000 mPa·s to 100,000 mPa·s at 25°C, or from 5000 mPa·s to 80,000 mPa·s at 25°C; Component (i) is present in an amount of 3 wt% of Part A composition, or 10 wt% of Part A composition, or from 20 wt% to 60 wt% of Part A composition, or 50 wt% of Part A composition, for example, the composition can contain Component (i) in an amount of from 20 - 60 wt% of Part A composition, or from 20 - 50 wt% of Part A composition. Component (ii) is fumed silica, which may be introduced directly into the composition or in the form of a masterbatch. When in the form of a masterbatch, the masterbatch comprises 25 to 40% by weight of fumed silica, as well as 55 to 75% by weight of component (i), and / or a viscosity between 50,000 and 80,000 mPa at 25 °C, and a vinyl content of 0.05 to 0.2% by weight of the polymer, or a dimethylvinyl terminated polydimethylsiloxane having a vinyl content of 0.05 to 0.15% by weight of the polymer; or may contain 55 to 75% by weight of dimethylvinyl terminated polydimethylsiloxane as described above. The masterbatch composition may also contain a treating agent for treating the filler in situ in order to first make the filler hydrophobic and thus facilitate mixing with the polymer. When introduced as a fumed silica masterbatch, the masterbatch may be present in an amount of 5 to 30% by weight of the part A composition, or 5 to 20% by weight of the part A composition, or 6 to 15% by weight of the part A composition. The hydrosilylation catalyst composition of component (iv), which provides the amount of catalyst present, is in the range of 0.01 to 3.0% by weight of the composition, or 0.1 to 3.0% by weight of the composition, or 0.1 to 2.0% of the composition, or 0.1 to 1.5% of the composition, based on the combined weight of components (i) and (ii) and (v) when present, and will contain from 0.01 ppm to 10,000 parts per million (ppm); or from 0.01 to 7,500 ppm, 0.01 to 3,000 ppm, or 100 to 6,000 ppm of a platinum group metal. Component (v) a cured silicone powder in an amount of 5 to 30% by weight of the composition, or 5 to 20% by weight of the part A composition, and Component (vi) an eco diluent in an amount of 25 to 75% by weight of the part A composition.

[0071] When part A is as described above in a 1:1 weight ratio with part B, part B may comprise: Component (ii) 25 to 40% by weight of fumed silica, and 55 to 75% by weight of component (i), and / or a viscosity between 50,000 and 80,000 mPa at 25°C, and a vinyl content of 0.05 to 0.2% by weight of the polymer, or a dimethylvinyl-terminated polydimethylsiloxane having a vinyl content of 0.05 to 0.15% by weight of the polymer; or a fumed silica masterbatch containing 55 to 75% by weight of dimethylvinyl-terminated polydimethylsiloxane as described above. When introduced as a fumed silica masterbatch into part B, the masterbatch may be present in an amount of 20% by weight of the part B composition, or 25% by weight of the part B composition, or 30% to 60% by weight of the part B composition, or 50% by weight of the part B composition, or 45% by weight of the part B composition, for example, in the range of 20 to 60% by weight of the part B composition, or 20 to 50% by weight of the part B composition, or 20 to 45% by weight of the part B composition, or 30 to 50% by weight of the part B composition, or 25 to 45% by weight of the part B composition. Component (iii) is present in the total composition in an amount of 10 to 30% by weight, or 10 to 20% by weight of the Part B composition, or 12 to 20% by weight of the Part B composition, but the amount present is typically determined by the molar ratio of the silicon-bonded hydrogen atoms of Component (iii) to the total number of all unsaturated groups, and contains at least 5,000 parts per million (ppm) of silicon-bonded hydrogen (Si-H), or at least 7,000 ppm, or 7,000 to 12,000 ppm of silicon-bonded hydrogen, or 8,000 ppm to 11,000 ppm of silicon-bonded hydrogen. A silicone resin crosslinking agent having a terminal group containing silicone-bonded hydrogen (the viscosity of Component (iii) is 15 to 50 mPa·s at 25°C, or 15 to 40 mPa·s at 25°C, or 20 to 35 mPa·s at 25°C), and Component (vi) an eco-diluent in an amount of 25 to 75% by weight of the Part B composition. When present in the composition, the cure inhibitor will typically be added to Part B to keep the cure inhibitor away from the catalyst. If present, the inhibitor is present in an amount of 0.005 to 15% by weight of the Part B composition, or in an amount of 0.0125 to 10% by weight of the Part B composition.

[0072] The order of mixing the components in the hydrosilylation-curable silicone elastomer composition of the leather coating composition is not important. Prepare suitable Parts A and B, and then mix Part A and Part B together at a ratio of 1:1 shortly before use. It will be understood that for all compositions, the total weight % is 100% by weight.

[0073] The curing of the hydrosilylation-curable silicone elastomer composition of the leather coating composition can be carried out at a temperature suitable for hydrosilylation curing. For example, a curing temperature of about 80°C to 180°C, or 80°C to 150°C, or 80°C to 130°C.

[0074] The described coating composition, once cured, provides excellent abrasion resistance and scratch protection, and thus is used as a top coat for synthetic leather materials, especially synthetic silicone leather materials. The leather coating composition can also be applied to various other types of leather, such as conventional leather, nubuck, or suede. The aforementioned leather coating composition can be applied to the finished leather or during the final wetting stage in the finishing of the leather, but it is preferably used as a top coat for synthetic leather, especially silicone-based synthetic leather. Leather having a top coat in the form of a reaction product from the curing of the above leather coating composition has significantly increased abrasion resistance. This increase in abrasion resistance is achieved without compromising the compatibility and flexibility of the final coating, and other additives often used to increase abrasion resistance can damage the feel of the coated leather, increase the resistance to bending, and cause cracks in the structure of the coating.

Brief Description of the Drawings

[0075]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0076] A detailed description of a method for producing a silicone-based synthetic leather using the foregoing composition in conjunction with the foregoing figures.

[0077] A silicone-based synthetic leather containing a coating that is a reaction product from the curing of the foregoing leather coating composition (5) may include several layers (3, 4) of cured liquid silicone rubber, each having a different function, as well as a fabric support layer (2). Except for the top coat made from the described leather coating composition, the synthetic silicone leather includes at least a fabric support layer (2), an adhesive layer (3) made from a first liquid silicone rubber material, and a second layer or skin layer (4) made from a second liquid silicone rubber material. The adhesive layer (3) is provided between the fabric support layer (2) and the second (skin) layer (4) as an effective adhesive. In use, the adhesive layer or the first layer (3) is adhered to the fabric support layer (2) and adhered or laminated to the skin layer (4). The foregoing leather coating composition functions as a protective top coat (5), which is a third layer on and bonded to the skin layer (4), i.e., the second layer (4) is located between the adhesive layer (3) and the top coat layer (5).

[0078] The fabric support layer (2) can be made from any suitable fabric material, such as a woven fabric, a knitted fabric, or a non-woven fabric made from synthetic resin fibers, natural fibers, and / or microfibers. These can include polyester fibers, viscose rayon fibers, polyamide fibers, nylon, acrylic fibers, polyolefin fibers; cellulose fibers such as cotton; and elastic fabric materials such as spandex, but are not limited thereto and can be used as a mixture of any two or more of the above. The fabric support layer is designed to improve the mechanical strength of the silicone leather.

[0079] The coating composition described above is designed as a protective synthetic leather topcoat. It can be applied to any silicone-based synthetic leather. Any suitable liquid silicone rubber composition may be utilized as the adhesive layer or the first layer (3). This needs to be capable of adhering to the fabric support layer (2) and typically has a low durometer Shore A hardness, for example, 20 - 40, and a soft touch when touched upon curing. A commercial example of a suitable hydrosilylation-curable liquid silicone rubber composition designed to function as the adhesive layer (3) is Dowsil™ LCF 8400 Binder from Dow Silicones Corporation. Dowsil™ LCF 8400 Binder is provided to customers in a two-part form as a standard for hydrosilylation-curable compositions to avoid early curing, and thus, the two parts of Dowsil™ LCF 8400 Binder are mixed together immediately before use.

[0080] As previously shown, the first layer or adhesive layer (3) is sandwiched between and designed to adhere to the fabric support (2) and the second layer or skin coating layer (4).

[0081] The aforementioned second composition or skin coating composition (4) is typically designed as a protective synthetic leather that is bonded to the adhesive layer (3). It can be used alone or together with a suitable top coat (5) such as those described herein. Any suitable liquid silicone rubber composition can be utilized to form the second layer or skin layer (4), which typically, upon curing, has a durometer shore A hardness higher than that of the first layer or adhesive layer (3), e.g., (≧) 50 or higher, or (≧) 60 or higher. Commercial examples of suitable liquid silicone rubber compositions that can be cured to function as the second layer or skin layer (4) are both Dowsil™ LCF 8300 Skin and Dowsil™ LCF 8500 Skin from Dow Silicones Corporation, which are both provided to the user in two parts that are mixed together immediately before use to avoid premature curing during storage prior to use, considering that they are both hydrosilylation-curable liquid silicone rubber compositions. Dowsil™ LCF 8300 Skin and Dowsil™ LCF 8500 Skin have a high shore A durometer value of approximately 65, provide abrasion resistance, and have a relatively low viscosity compared to Dowsil™ LCF 8500 Skin. The latter has a much higher viscosity as it is a fumed silica-reinforced version of the former with high mechanical strength. In many cases, a mixture of Dowsil™ LCF 8300 Skin and Dowsil™ LCF 8500 Skin is used as the second layer or skin layer (4) to benefit from the advantages of both compositions.

[0082] The aforementioned leather coating composition can be applied as a top coat onto a pre-formed silicone-based synthetic leather material, e.g., (2, 3, 4), as shown in Figure 2, by any suitable coating method, such as spraying, rolling, brushing, spin coating, dip coating, solvent casting, slot die coating, spray coating, knife coating, or gravure coating.

[0083] In such a situation, the pre-formed silicone-based synthetic leather material has typically been prepared as follows (i) applying a liquid silicone rubber skin-type composition (4) onto a release paper (1), (ii) curing the skin layer composition of (i) on the release paper (1) to form a cured skin layer (4), (iii) applying a silicone adhesive composition onto the cured skin layer (4), (iv) disposing a fabric support layer (2) onto the adhesive layer (3) before or during the curing of the adhesive layer (3) such that the adhesive layer (3) is sandwiched between the skin layer (4) and the fabric support layer (2), (v) curing the adhesive layer (3), and (vi) removing the release paper (1) if necessary. Shown in FIGS. 1 and 2 are a silicone-based synthetic leather material with a release layer present (FIG. 1) and a silicone-based synthetic leather material without a release layer (FIG. 2). In the case of FIG. 2, the silicone-based synthetic leather material is prepared, and thus, it is ready for applying the aforementioned top coat onto the skin layer (4) by any suitable application means (e.g., spraying, rolling, brushing, spin coating, dip coating, solvent casting, slot die coating, spray coating, knife coating, or gravure coating).

[0084] Next, the aforementioned leather coating composition is applied onto the surface of the skin layer (4) from which the release paper (1) has been removed and cured to form a protective top coat on the silicone-based synthetic leather material. The leather coating composition is applied at a wet film thickness of 10 - 100 μm, or 10 - 60 μm, corresponding to a dry film thickness of, for example, about 2 - 50 μm, or 2 - 30 μm, or 5 - 25 μm.

[0085] Following the application of the leather coating composition, curing is carried out by heating the coated material at a temperature of about 80°C to 180°C, or 80°C to 150°C, or 80°C to 130°C for about 1 to 20 minutes to cure the leather coating composition on the skin layer. If the curing temperature is low, curing takes a relatively long time, and if the curing temperature is too high, the fabric base may be deteriorated due to heat. Thus, a curing temperature of 80 - 150°C, or 80°C to 130°C is preferred.

[0086] In an alternative embodiment, the silicone-based synthetic leather may be prepared in a continuous process using the aforementioned leather coating composition in a continuous process with a top coat. In this case, the subsequent process may be as follows: (i) Applying the aforementioned leather coating composition onto the release paper (1); (ii) Curing the aforementioned leather coating composition on the release paper (1) to form a cured top coat (5); (iii) Applying a silicone skin layer onto the cured top coat (5); (iv) Curing the silicone skin layer to form a cured skin layer (4) such that the cured top coat layer (f) is sandwiched between the release paper (1) and the cured skin layer (4); (v) Applying a silicone adhesive composition onto the cured skin layer (4); (vi) Placing or laminating the fabric support layer (2) onto the uncured or curing adhesive layer (3), preferably, the fabric support layer is effectively laminated to the adhesive layer; (vii) Curing the adhesive layer (3) such that the cured adhesive layer (3) is sandwiched between the skin layer (4) and the fabric support layer (2); and (viii) Removing the release paper (1) if necessary.

[0087] The different layers of such a process are shown in FIGS. 3 and 4, FIG. 3 shows the existing release layer (1), and FIG. 4 shows the final silicone-based synthetic leather material with the release paper removed.

[0088] Any suitable release paper can be used, such as the Supermat release paper ARX175DM from Japan Asahi company. Each curing step can be carried out in a suitable oven, for example, by curing and drying in a hot air oven, or in a conveyor oven in the case of a continuous process.

[0089] The aforementioned top coat layer (5) is typically applied onto the release paper (1) with a wet film thickness of 10 - 100 μm, or 10 - 60 μm, corresponding to a dry coating thickness of about 2 - 50 μm, or 2 - 30 μm, or 5 - 25 μm. It can be cured at any suitable temperature, for example, for a period of 30 seconds - 5 minutes, or 30 seconds - 2.5 minutes at about 80°C - 180°C, or 80°C - 150°C, or 80°C - 130°C.

[0090] The skin coat layer (4) is typically 0.05 - 1 mm thick, or 0.05 - 0.8 mm thick, or 0.1 - 0.4 mm thick after curing. It can be cured at any suitable temperature, for example, for a period of 30 seconds - 5 minutes, or 30 seconds - 2.5 minutes at about 100°C - 150°C, or 110°C - 135°C, or 110°C - 125°C.

[0091] The adhesive coat layer (3) is typically 0.05 - 1 mm thick, or 0.1 - 0.75 mm thick after curing. It can be cured at any suitable temperature, for example, for a period of 1.5 minutes - 5 minutes, or 1.5 minutes - 4 minutes at 125 - 180°C, or 130 - 170°C, or 135 - 160°C.

[0092] The above process shows the preparation of silicone-based synthetic leather materials. The viewer should understand that additional layers may need to be introduced into the material if desired.

[0093] Synthetic leather, especially silicone-based synthetic leather, can be designed to have various properties considering the content of different layers. For example, it can have excellent flame retardancy, smoke density, heat resistance, stain resistance, solvent resistance, hydrolysis resistance, etc. required for the end use of the leather. The assumed end uses include, but are not limited to, furniture, decoration, handbags, luggage, clothing, footwear, automotive interiors, medical beds / sheets, etc.

Examples

[0094] In the following examples, coating compositions and several comparisons were tested to demonstrate the advantages of the coatings described herein with respect to providing sufficient abrasion resistance (e.g., Wyzenbeek abrasion resistance of (≧) 75,000 or more, or (≧) 100,000 or more tests), as well as suitable scratch resistance, i.e., no white lines or cracks after strong scratching with a nail and no whitening caused by stretching. All viscosities were measured at 25 °C based on the cup / spindle method of ASTM D1084-16 Method Β using a spindle appropriate for the viscosity range, unless otherwise specified. The alkyl and / or alkynyl content and the Si-H content were determined using quantitative infrared analysis according to ASTM E168.

[0095] The components used in the leather coating compositions used in the following examples are defined in Table 1 below

Table 1

[0096] Table 2 provides details of the starting materials used in the silica masterbatch of the following composition. Fumed silica was mixed with a vinyl-terminated PDMS polymer in the presence of small molecules that act as a hydrophobizing agent for the silica, resulting in in-situ treatment of the silica while the silica and polymer were being mixed. As shown previously, the polymer used can be component (i), or, if desired, a mixture of component (i) and another polymer, in which case component (i) is not present in the masterbatch.

Table 2

[0097] Several LSR compositions were prepared as examples and comparative examples of two - part compositions. The part A compositions are shown in Table 3a and the part B compositions are shown in Table 3b. Shortly before use, the part A compositions and their respective part B compositions were mixed together at a 1:1 weight ratio to produce the final compositions under test.

Table 3

Table 4

[0098] The weight % levels of fumed silica, high - vinyl polymer, and resinous cross - linker after evaporation of the eco - solvent when the part A and part B compositions are mixed together in the final compositions which are their respective compositions are shown in Table 3c below.

Table 5

[0099] The silicone-based synthetic leather with a topcoat using the compositions of Tables 3a and 3b was prepared in a continuous mode in the manner shown in FIGS. 3 and 4 of this specification. In this case, the topcoat compositions shown in Tables 3a and 3b were mixed and applied onto a continuous release paper (Supermat Release Paper ARX175DM from Japan Asahi Company) with a dry film thickness of 10-15 μm. After application onto the release paper, the topcoat (5) was cured at a temperature of 120° C. for 1.0-1.5 minutes. Then, a skin layer was applied on top of the topcoat (5). The skin layer (4) is a mixture of Dowsil™ LCF 8300 Skin and Dowsil™ LCF 8500 Skin, the mixture was applied to a thickness of 0.12-0.25 mm and then cured at 120° C. for 1.5 minutes. Then, an adhesive layer (3) in the form of Dowsil™ LCF 8400 Binder was applied onto the skin layer (4) at a thickness of 0.12-0.25 mm, and before this hardened, a lamination bonding process was applied to the microfiber-based fabric layer (2), and then this combination was cured at a temperature of 150° C. for a period of 3 minutes. After removing the release paper (1) if necessary, the final silicone-based synthetic leather sample was post-cured at a temperature of 80° C. for 16-20 hours or at 150° C. for 2-3 hours additionally.

[0100] Physical Tests The ability of the silicone leather to withstand abrasion is measured according to ASTM D4157-13 using the performance of the prepared samples tested using the Wyzenbeek abrasion test. The abrasion resistance ability of the silicone leather is measured according to Ford BN 108-13 using the abrasion resistance test (in this technique, the observer visually inspects each scratch line using a controlled light source and evaluates it according to an evaluation scale of 1-5 (1 = no scratch line at all, 5 = severe scratch line)). The whitening discoloration of the stretch marks was observed by stretching the sample of the analyzed synthetic silicone leather using the thumb. The results are shown in Table 4 below.

Table 6

[0101] Examples 1, 2, and 3 passed both the Wyzenbeek abrasion test and the stretch / whitening test, and thus showed optimal performance. Comparative Examples 1 and 2 were found to be unacceptable in the Wyzenbeek abrasion test despite passing the stretch / whitening test, and thus were not suitable. Comparative Examples 3 and 4 also passed the Wyzenbeek abrasion test but failed the stretch / whitening test and were not considered suitable for use for different reasons. Figure 5 shows a leather product coated with the cured product of the composition of Comparative Example 3 (using a trimethyl-terminated polydimethylsiloxane having a viscosity of 1 mPa·s at 25°C), where whitening was observed during stretching, but no discoloration was visually observed as shown in Figure 6 when using the composition of Example 1 of this specification using isohexadecane as an eco-solvent in the leather coating composition.

Claims

A leather coating composition comprising a hydrosilylation-curable silicone elastomer composition, Component (i), having a viscosity of 1000 to 500,000 mPa·s at 25°C, and one or more polydiorganosiloxane polymers having an alkenyl group and / or alkynyl group content of at least 5% by weight of the polymer per molecule, Component (ii) A reinforcing filler which is precipitated silica or fumed silica optionally treated with one or more known filler treatment agents, Component (iii) A silicone resin crosslinking agent having a terminal group containing silicone-bonded hydrogen, Component (iv) A hydrosilylation catalyst, Component (v) A cured silicone powder, Component (vi) An eco-diluent comprising or consisting of isopentadecane, isohexadecane, isoheptadecane, isooctadecane, isononadecane, and mixtures thereof, a leather coating composition.

2. Component (iii) of the hydrosilylation-curable silicone elastomer composition is as follows: M groups containing Si-H, (CH ３ ) ３ SiO １／２ groups, and silicone resins containing or consisting of SiO ４／２ groups An M group containing Si—H and SiO ４／２ A silicone resin containing or consisting of an M group containing Si—H, (CH ３ ) ２ SiO ２／２ group, and a silicone resin containing or consisting of SiO ４／２ group An M group containing Si—H, SiO ４／２ groups, and (C ６ H ５ ) ３ SiO １／２ A silicone resin containing or consisting of groups, and alternatives in which methyl is replaced by a phenyl group or other alkyl group or mixtures thereof, one or more of each of the above, each of which may contain one or more T groups, the leather coating composition according to claim 1.

3. The leather coating composition according to claim 1 or 2, wherein the cured silicone elastomer powder (v) has an average particle size of 0.01 to 100 μm.

4. The leather coating composition according to any one of claims 1 to 3, wherein the eco-diluent (vi) comprises or consists of isohexadecane.

5. The composition may contain one or more additives selected from at least one, or at least two alkenyl and / or alkynyl groups per molecule, and one or more low-viscosity polydiorganosiloxane polymers having a viscosity of 100 to 750 mPa·s at 25°C, a platinum catalyst inhibitor, a non-reinforcing filler, a conductive filler, a non-conductive filler, a pot life extender, a flame retardant, a pigment, a colorant, a chain extender, a heat stabilizer, a compression set improving additive, a squeak inhibitor, an antifreeze, and / or a biocide. The leather coating composition according to any one of claims 1 to 4.

6. The leather coating composition according to any one of claims 1 to 5, which is a top coat composition for silicone-based synthetic leather.

7. A silicone-based synthetic leather comprising a top coat which is a reaction product of the composition according to any one of claims 1 to 6 obtained upon curing.

8. The silicone-based synthetic leather according to claim 7, comprising a fabric support layer selected from one or more of polyester fibers, viscose rayon fibers, polyamide fibers, nylon, acrylic fibers, polyolefin fibers, cellulose fibers, and elastic fabric materials.

9. The silicone-based synthetic leather according to claim 7 or 8, wherein the top coat has a Wyzenbeek abrasion resistance of 75,000 or more according to ASTM D4157-13.

10. Including the following: A method of applying the leather coating composition according to any one of claims 1 to 5 to a silicone-based synthetic leather by one or more of spraying, rolling, brushing, spin coating, dip coating, solvent casting, slot die coating, spray coating, knife coating, or gravure coating.

11. The following steps (i) Applying the aforementioned coating composition onto a release paper; (ii) Curing the aforementioned coating composition on the release paper to form a cured top coat; (iii) Applying a silicone skin layer onto the cured top coat; (iv) Curing the silicone skin layer to form a cured skin layer, wherein the cured skin layer is formed such that the cured top coat layer is sandwiched between the release paper and the cured skin layer; (v) Applying a silicone adhesive composition onto the cured skin layer to form an adhesive layer; (vi) Disposing a fabric support layer onto the adhesive layer, wherein the adhesive layer is sandwiched between the skin layer and the fabric support layer; (vii) Curing the adhesive layer, and (viii) Removing the release paper if necessary. A method of applying the leather coating composition according to any one of claims 1 to 4 to a silicone-based synthetic leather by the above steps.

12. Use of the silicone-based synthetic leather according to claim 7, 8 or 9 for or in furniture, decoration, handbags, luggage, clothing, footwear, automotive interiors, medical beds / sheets, etc.

13. Use of the leather coating composition according to any one of claims 1 to 5 as a top coat for synthetic leather to improve abrasion resistance and scratch resistance upon curing.

14. The use according to claim 13, wherein the top coat has a Wyzenbeek abrasion resistance of 75,000 or more in accordance with ASTM D4157-13.

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