Siloxane compositions and their uses

Abstract

A siloxane composition is disclosed comprising (a) at least one organopolysiloxane containing two alkenyl groups bonded to silicon atoms at both ends of the chain per molecule, (b) at least one organopolysiloxane containing at least three alkenyl groups bonded to silicon atoms per molecule, (c) at least one organopolysiloxane containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule, and (d) at least one hydrosilylation catalyst, wherein component (c) is present in an amount of 30 weight% or more based on the total weight of the composition, and component (e) at least one organopolysiloxane containing at least three hydrogen atoms bonded to silicon atoms per molecule is present in an amount of 0.01 weight% or less based on the total weight of the composition. The silicone gel cured from this has suitable low penetration, higher elongation at break, better gel adhesion, and excellent resistance to high temperature and negative pressure.

Description

Technology Field

[0001] The present disclosure relates to siloxane compositions and their uses. Background Technology

[0002] The silicone gel composition is typically an addition reaction curable organopolysiloxane composition comprising i) an organopolysiloxane having at least two silicon-bonded alkenyl groups, such as vinyl groups, as a base polymer, ii) an organohydrogenpolysiloxane having at least three silicon-bonded hydrogen atoms (i.e., Si-H groups) as a crosslinking agent, and iii) a platinum-based catalyst, and obtaining a cured product through an addition reaction of the Si-H groups to the alkenyl groups.

[0003] Cured products of conventional silicone gel compositions generally have high penetration values ​​(i.e., are very soft), which means that when these silicone gels are placed in negative pressure environments, for example at high altitudes, unwanted bubbles or delamination caused by low gel strength will inevitably occur. Increasing the hardness of the cured gel is used to mitigate this problem. However, cured gels with higher hardness generally cause reduced elongation and tackiness at break, which affects their application in display potting or optical bonding.

[0004] Silicone gel compositions using vinyl MQ silicone resin as a crosslinking agent have also been reported. EP1737504B discloses a silicone gel composition containing 100 parts by weight of vinyl-terminated polydimethylsiloxane with a viscosity of 400 mPa·s, 44 parts by weight of vinyl MQ silicone resin, 18 parts by weight of hydrogen-terminated polydimethylsiloxane with a viscosity of 15 mPa·s, and 0.01% of a platinum-based catalyst. However, this silicone gel still has a higher penetration value of 135, which is not suitable for use in negative pressure environments due to the occurrence of bubbles or delamination.

[0005] In consideration of existing problems, the present disclosure provides a siloxane composition and a silicone gel cured therefrom, wherein the cured silicone gel has a suitable low penetration and exhibits at least one of the following performance characteristics:

[0006] 1) Higher elongation at break compared to conventional gels with the same penetration value, and better resistance to deformation and tension;

[0007] 2) Better gel adhesion;

[0008] 3) Excellent resistance to high temperatures, with no bubbles or peeling occurring when the gel is subjected to 95°C for 200 hours;

[0009] 4) Excellent resistance to negative pressure, with no bubbles or peeling occurring when the gel is subjected to a negative pressure of -1 atm for 3 days.

[0010] There are two reasons why bubbles or delamination occur. One is that some invisible bubbles within the gel rapidly expand under high temperature or negative pressure, causing visible expanded bubbles, or if the gel's strength is not sufficiently high, it causes delamination or cracking. The other is that the substrate supporting the gel will bend under high temperature or negative pressure, and subsequently, if the gel's strength is low, the gel will detach and be pulled apart, causing delamination or cracking.

[0011] In this document, the term "silicone gel" refers to a cured product having a low crosslinking density, containing organopolysiloxane as a main component, and exhibiting a penetration value according to ASTM D1403 (1 / 4 cone) in the range of 20 to 200. This corresponds to a product in which the measured value (rubber hardness value) returns to 0 for rubber hardness measurement performed according to GB / T531-1999, and has a hardness sufficiently low to not exhibit an effective rubber hardness value.

[0012] In this document, the term "penetration" refers to the depth to which a standard cone falls into a gel sample under a constant load for a certain period of time. The greater the penetration, the softer the gel and the lower its mechanical strength. Since the mechanical strength of a silicone gel increases and penetration decreases with increasing crosslinking density, and the mechanical strength decreases and penetration increases with decreasing crosslinking density, the penetration value of a silicone gel can also be used to characterize its crosslinking density. The higher the penetration value, the lower the crosslinking density.

[0013] In this document, the term "silicone rubber" refers to a cured product that contains organopolysiloxane as a main component, indicates that the measured value (rubber hardness value) for rubber hardness measurement performed according to GB / T531-1999 is greater than 0, and indicates an effective rubber hardness value.

[0014] In this document, the term “tackiness” refers to the property of a material that is sticky upon contact but does not adhere to another material to any significant degree, which is essentially different from “adhesion.” “Adhesion” refers to the property of a material that adheres to another material, e.g., a substrate, through chemical action, and bond strength is generally used to evaluate adhesion. Furthermore, adhesion is irreversible, and once a material is peeled off, it cannot be reattached to another material. However, a tackiness material typically adheres to another material through physical action, and tackiness is reversible, and once a material is peeled off, it can be reattached to another material.

[0015] In this document, "viscosity" is measured according to the conventional methods of the industry unless otherwise specified.

[0016] A first aspect of the present disclosure is

[0017] (a) at least one organopolysiloxane containing two alkenyl groups bonded to silicon atoms at both ends of the chain per molecule,

[0018] (b) at least one type of organopolysiloxane containing at least three alkenyl groups bonded to silicon atoms per molecule,

[0019] (c) at least one organopolysiloxane containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule, and

[0020] (d) at least one type of hydrosilylation catalyst

[0021] As a siloxane composition comprising;

[0022] However, component (c) is used in an amount of 30% by weight or more, preferably 40% by weight or more, based on the total weight of the composition, and the composition provides a siloxane composition comprising at least one organopolysiloxane containing at least three hydrogen atoms bonded to a silicon atom per molecule of component (e) in an amount of 0.01% by weight or less based on the total weight of the composition.

[0023] Component (a)

[0024] Organopolysiloxane (a) is well known. Alkenyl groups are bonded to silicon atoms at both ends of the chain, and the groups bonded to the remaining silicon atoms are each independently selected from monovalent organic groups that are not aliphatic unsaturated.

[0025] Organopolysiloxane (a) is typically linear. Some exemplary polyorganosiloxanes (a) can be described by the following formula:

[0026] R 1 R 2 2SiO(R 2 2SiO) m SiR 2 2R 1

[0027] Here, R 1 is independently an alkenyl group having 2 to 6 carbon atoms in each case, e.g., vinyl, allyl, propene, butenyl, hexenyl, preferably vinyl, allyl, and propene, more preferably vinyl;

[0028] R 2 is independently a substituted or unsubstituted monovalent organic group in each case, in particular a monovalent hydrocarbon group having 1 to 20, preferably 1 to 10, carbon atoms, e.g., alkyl, e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, aryl or alkaryl, e.g., phenyl, tolyl, xylyl, mesithyl, ethylphenyl, benzyl, naphthyl, and a halogenated or organic-group-functionalized derivative of said group, e.g., 3,3,3-trifluoropropyl, o-, p- and m-chlorophenyl, aminopropyl, 3-isocyanatopropyl, cyanoethyl, preferably methyl and phenyl, more preferably methyl;

[0029] m is a positive number, and the organopolysiloxane (a) has a dynamic viscosity of 100 to 50,000 mPa·s at 25°C, for example 200 to 20,000 mPa·s, particularly 500 to 10,000 mPa·s.

[0030] Component (a) of the present disclosure may be a single alkenyl-terminated organopolysiloxane, or a mixture of different alkenyl-terminated organopolysiloxanes with different molecular structures (e.g., types and number of substituents) or viscosities. In the case of a mixture of organopolysiloxanes, m represents an average value, and the viscosity range satisfied by m is for the viscosity of the mixture.

[0031] Generally, silicone compositions used as potting materials are required to have lower viscosity, and accordingly, the viscosity of alkenyl-terminated organopolysiloxanes is generally low. However, in order to obtain a silicone gel with reduced crosslinking density, higher elongation at break, better tackiness, and lower penetration, it is desirable to incorporate a small amount of alkenyl-terminated organopolysiloxane with high viscosity into component (a).

[0032] In one embodiment of the present invention, component (a) comprises (a1) an organopolysiloxane having two alkenyl groups bonded to silicon atoms at both ends of the chain per molecule, having a dynamic viscosity of 100 mPa·s or more and less than 5,000 mPa·s at 25°C, and (a2) an organopolysiloxane having two alkenyl groups bonded to silicon atoms at both ends of the chain per molecule, having a dynamic viscosity of 5,000 mPa·s or more and less than 50,000 mPa·s at 25°C. According to the above embodiment, component (a2) is suitably used in an amount of 2% to 20% by weight, for example, 5% to 15% by weight, based on the total weight of composition (a); and the ratio of the number of moles of alkenyl groups provided by component (a1) to the number of moles of alkenyl groups provided by component (a2) is preferably (10-50):1.

[0033] In the present disclosure, component (a) is suitably used in an amount of 20% to 70% by weight, for example, 35% to 55% by weight, based on the total weight of the composition.

[0034] Component (b)

[0035] The organopolysiloxane as component (b) acting as a crosslinking agent is different from the organopolysiloxane as component (a). The polyorganosiloxane (b) can be linear, branched, or resinous. Linear polyorganosiloxane (b) is typically R 2 3SiO 1 / 2 , R 1 R 2 SiO 2 / 2 , R 1 R 2 2SiO 1 / 2 and R 2 2SiO 2 / 2 It consists of units selected from, where R 1 and R 2 is as defined above. Branched or resinous polyorganosiloxane (b) is R 1 SiO 3 / 2 and R 2 SiO3 / 2 Trifunctional units such as and / or SiO 4 / 2 It additionally includes a succubic unit such as, where R 1 and R 2 is as defined above.

[0036] Some exemplary polyorganosiloxanes (b) are (b1) R 1 R 2 2SiO 1 / 2 and SiO 4 / 2 Organopolysiloxane essentially composed of units, (b2) R 2 3SiO 1 / 2 and R 1 R 2 SiO 2 / 2 Organopolysiloxane essentially composed of units, (b3) R 1 R 2 2SiO 1 / 2 , R 1 R 2 SiO 2 / 2 and R 2 2SiO 2 / 2 Organopolysiloxane essentially composed of units, and (b4) R 1 R 2 2SiO 1 / 2 , R 2 2SiO 2 / 2 and R 2 SiO 3 / 2 It comprises an organopolysiloxane essentially composed of units, where R 1 and R 2 is as defined above. In this invention, "essentially" means that the polyorganosiloxane (b) contains at least 80 mole%, e.g. at least 90 mole%, or even at least 95 mole% of the units listed above.

[0037] In the present disclosure, polyorganosiloxane (b1) is particularly preferred, and R 1 R 2 2SiO 1 / 2 Units versus SiO 4 / 2 The molar ratio of the units is suitably in the range of (0.4-1):1, for example (0.5-0.9):1.

[0038] Component (b) is suitably used in an amount of 1% to 10% by weight, for example, 2% to 8% by weight, based on the total weight of the composition.

[0039] Ingredients (c)

[0040] Component (c) is used as a chain extender. Preferably, component (c) has a dynamic viscosity of 30 mPa·s or more and less than 1,000 mPa·s at 25°C.

[0041] Organopolysiloxanes (c) are typically linear. Some exemplary polyorganosiloxanes (c) can be described by the following formula:

[0042] HR 2 2SiO(R 2 2SiO) n SiR 2 2H

[0043] Here, R 2 is as defined above;

[0044] n is positive, and the organopolysiloxane (c) has a dynamic viscosity of 30 mPa·s or more and less than 1,000 mPa·s at 25°C.

[0045] Component (c) of the present disclosure may be a single hydrogen-terminated organopolysiloxane, or a mixture of different hydrogen-terminated organopolysiloxanes with different molecular structures (e.g., types and number of substituents) or viscosities. For a mixture of organopolysiloxanes, n represents an average value, and the viscosity range satisfied by n is for the viscosity of the mixture.

[0046] To obtain a silicone gel having better tackiness and lower penetration, component (c) of the present disclosure preferably comprises (c1) an organopolysiloxane containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule, having a dynamic viscosity of 30 mPa·s or more and 200 mPa·s or less at 25°C, and (c2) an organopolysiloxane containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule, having a dynamic viscosity of more than 200 mPa·s and 5,000 mPa·s or less at 25°C. According to the above embodiment, the ratio of the number of moles of Si-H groups provided by component (c1) to the number of moles of Si-H groups provided by component (c2) is preferably 2: (1-10), particularly 1: (1-5).

[0047] In the present disclosure, component (c) provides 0.6 to 1.0 moles of Si-H groups per mole of total silicon-bonded alkenyl groups in components (a) and (b).

[0048] Component (c) is suitably used in an amount of 30% to 70% by weight, for example, 40% to 60% by weight, based on the total weight of the composition.

[0049] Ingredient (d)

[0050] Component (d) may be various hydrosilylation catalysts used in the prior art to add-cure the silicon composition, preferably platinum-based catalysts, e.g., chloroplatinic acid, chloroplatinate, olefin complexes of platinum, and alkenylsiloxane complexes of platinum. The platinum-based catalyst may be used in an amount that takes into account the desired curing rate and cost-effectiveness, which is typically the minimum level required to ensure an effective hydrosilylation reaction. Generally, the weight of platinum metal in the siloxane composition is 0.1 to 500 ppm, e.g., 1 to 100 ppm.

[0051] Ingredient (e)

[0052] Polyorganosiloxanes (e) containing at least three hydrogen atoms bonded to silicon atoms per molecule may be linear, cyclic, branched, or resinous. Linear or cyclic polyorganosiloxanes (e) are typically R 2 3SiO 1 / 2 , HR 2 SiO 2 / 2 , HR 2 2SiO 1 / 2 and R 2 2SiO 2 / 2 It consists of units selected from, where R 2 is as defined above. Branched or resinous polyorganosiloxane (e) is a trifunctional unit, e.g., HSiO 3 / 2 and R 2 SiO 3 / 2 , and / or quaternary units, e.g., SiO 4 / 2 It additionally includes, where R 2 is as defined above.

[0053] The siloxane composition of the present disclosure is free of polyorganosiloxane (e). “Free of” means that polyorganosiloxane (e) is present in an amount of 0.01 weight% or less, even 0.001 weight% or less, based on the total weight of the composition.

[0054] Ingredients (f)

[0055] The siloxane composition may further include an inhibitor (f) to control the pot life and curing speed of the composition. The inhibitor may be various inhibitors used in the art, for example, alkinols such as 1-ethynyl-1-cyclohexanol, 2-methyl-3-butyn-2-ol; polymethylvinylcyclosiloxanes such as 1,3,5,7-tetravinyltetramethyltetracyclo-siloxane, alkyl maleate. The amount of the inhibitor may be selected according to its chemical structure and the desired curing speed. Generally, the weight of the inhibitor in the composition is 1 to 50,000 ppm, for example, 10 to 10,000 ppm.

[0056] Other optical components

[0057] The siloxane composition may additionally include a filler if necessary. Examples of fillers include, but are not limited to, non-thermal conductive fillers such as calcium carbonate, fuming silica, precipitated silica, silica powder, diatomite, zirconium silicate, organic montmorillonite, titanium dioxide, and thermal conductive fillers such as aluminum oxide, zinc oxide, magnesium oxide, aluminum hydroxide, aluminum nitride, boron nitride, silicon carbide, aluminum, copper, nickel, gold, silver, graphite, and graphene. As is known in the art, a siloxane composition used as an adhesive, sealant or protective agent, or as a potting material for electronic components may contain an appropriate amount of filler; on the other hand, a siloxane composition used as a potting material for displays or as an optical bonding material must not contain a filler due to light transmittance requirements.

[0058] Additionally, the siloxane composition may include appropriate amounts of other additives, provided that such additives do not impair the effects of the present invention. Examples of such additives include, but are not limited to, solvents, diluents, surface treatment agents for fillers, and color pastes. Examples of solvents to be mentioned are decamethylcyclopentasiloxane, hexamethyldisiloxane, octamethyltrisiloxane, heptamethylhexyltrisiloxane, decamethyltetrasiloxane, dodecamethylpentasiloxane, tetradecamethylhexasiloxane, and isododecane. Examples of diluents to be measured are dimethyl silicone oil having a dynamic viscosity of 10 to 5,000 mPa·s at 25°C and MDT silicone oil having a dynamic viscosity of 15 to 300 mPa·s at 25°C. Preferably, the composition does not contain any of the above additives. "Not containing" means that the siloxane composition contains less than 0.1% by weight, or even less than 0.01% by weight, of the said additive based on the total weight of the composition.

[0059] In a preferred embodiment, the siloxane composition is

[0060] (a) 20 to 70 weight% of at least one organopolysiloxane containing two alkenyl groups bonded to silicon atoms at both ends of the chain per molecule,

[0061] (b) 1 to 10 weight% of at least one organopolysiloxane containing at least three alkenyl groups bonded to silicon atoms per molecule,

[0062] (c) 30 to 70 weight% of at least one organopolysiloxane containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule, and

[0063] (d) Includes at least one type of hydrosilylation catalyst.

[0064] Suitably, the siloxane composition of the present disclosure is stored as two or more separate packages in which components (b), (c) and (d) are not stored in the same package.

[0065] The siloxane composition of the present disclosure has a viscosity at room temperature (23±2)°C suitably from 200 to 10,000 mPa·s, e.g., from 500 to 5,000 mPa·s, and particularly from 500 to 2,000 mPa·s. In this invention, viscosity refers to the mixed viscosity of the composition before curing. If the composition is stored in two or more separate packages, viscosity also refers to the viscosity of each package.

[0066] A second aspect of the present disclosure provides a silicone gel cured from the siloxane composition of the first aspect of the present disclosure.

[0067] A composition described in the first embodiment of the present disclosure is obtained by crosslinking or curing, or by mixing separate packages as described above and then crosslinking or curing. Generally, crosslinking or curing is performed at a temperature of 15 to 180°C for 10 minutes to 72 hours. Lower curing temperatures and shorter curing times are preferred. It is preferable to cure at a temperature of 20 to 80°C for 15 to 120 minutes.

[0068] The silicone gel preferably has a penetration value of 20 to 50 as measured according to ASTM D1403 in a 1 / 4 cone.

[0069] A third aspect of the present disclosure provides the use of the siloxane composition of the first aspect as an adhesive, sealant, or protective agent for electronic components.

[0070] The cured siloxane composition of the present disclosure is in gel form and has excellent elongation, deformability, and followingness at break, and can be used as an adhesive, sealant, or protective agent for electronic components. Such electronic components include, but are not limited to, circuit boards, CPUs, and mobile phones.

[0071] A fourth aspect of the present disclosure provides a use of the siloxane composition of the first aspect as a potting material for electronic components or displays.

[0072] The siloxane composition of the present disclosure has low viscosity and good fluidity, which facilitates the porting of pressure sensors, metering sensors, insulated gate bipolar transistors, and displays, particularly large-format educational displays, outdoor displays, large-format touch screens and touch displays, such as automotive, navigation, or aviation displays. In this invention, large-format displays generally refer to displays having a size of 50 inches or more, even 86 inches or more.

[0073] The siloxane composition of the present disclosure is used to make the display anti-reflective by filling the gap between a large-format display and a glass panel to allow air within the gap to be expelled. Furthermore, the cured siloxane composition of the present disclosure is a gel with low penetration and excellent adhesion, light transmittance, and sound pressure resistance, which may be suitable for display potting at high altitudes.

[0074] A fifth aspect of the present disclosure provides the use of the siloxane composition of the first aspect as an optical bonding material for displays.

[0075] The cured siloxane composition of the present disclosure is in the form of a gel and has excellent elongation, deformability, conformability, adhesion, and light transmittance at break, and can be used as an optical bonding material for displays, particularly large-format displays. In addition, the cured gel has low penetration and excellent resistance to negative pressure, which is suitable for optical bonding at high altitudes. Brief explanation of the drawing

[0076] Figure 1 shows the adhesion test curves of the silicone gels derived by Examples 1-2 and Comparative Examples 1-2. Specific details for implementing the invention

[0077] The present invention is further illustrated by the following examples, but does not limit the scope thereof. Any experimental method not having the conditions specified in the following examples is selected according to conventional methods and conditions or product specifications.

[0078] Determination of viscosity

[0079] The viscosity of components A and B was measured by a Brookfield viscometer using a No. 03 spindle at a speed of 10 rpm at room temperature (23±2)℃.

[0080] Determination of intrusion

[0081] This was performed according to ASTM D1403 using a 9.38 g quarter-scale cone at room temperature (23±2)°C. The sample to be tested was to have a diameter of at least 35 mm and a depth of at least 30 mm. Before testing, each siloxane composition was poured into a flat-bottom glass dish and cured at 65°C for 30 minutes. Subsequently, the glass dish containing the sample to be tested was placed on the platform of the penetration device, which had been adjusted to the appropriate position and fixed via a crane. Then, the rod connecting the cone was slowly lowered by a handwheel until the cone tip was observed in contact with the surface of the sample through a mirror. The standard cone was then dropped under its own weight for 10 seconds after zeroing, and the depth was recorded by a displacement indicator. The same sample was tested at least three times in parallel, with the distance between each test point and the edge of the glass dish being at least 10 mm. For each test, the standard cone was to be replaced with a clean one or wiped with a cotton pad or cloth soaked in alcohol. The average of each test was taken as the result.

[0082] Determination of Shore Hardness A

[0083] It was performed according to the standard GB / T531-1999.

[0084] adhesive crystals

[0085] The texture was measured using a P / 25 cone with a texture analyzer. Prior to the test, a flat-bottomed glass dish (with a diameter of 35 mm and a depth of 30 mm) was filled with a siloxane composition and treated at 65°C for 30 minutes. Subsequently, the glass dish filled with the sample to be tested was placed directly beneath the test cone, the texture analyzer was turned on, and the test cone was moved downward to the surface of the sample at a speed of 2 mm / s until it penetrated the sample to a depth of 2 mm. The test cone was then held for 5 seconds to ensure complete penetration of the sample, after which it was moved upward at a speed of 2 mm / s until the sample was separated from it. The force over time from the test cone's penetration into the sample to its withdrawal from the sample was recorded by the sensor. The adhesiveness of the sample can be evaluated based on the area enclosed under the time axis by the force-time curve and the time axis. The larger the area, the better the adhesiveness.

[0086] High temperature test

[0087] Each component A and B was mixed in a 1:1 ratio using a static mixer, and the resulting mixture was applied to the polarizer of an 80-inch display in the fishbone diagram mode, and then a glass panel was lightly placed over it. No bubbles should be generated during the entire process. Subsequently, the product was applied to 65°C for 30 minutes, left at room temperature for 3 days, and then placed in a 95°C oven for 200 hours. If no bubbles or delamination were observed after being placed at 95°C for 200 hours, or if no separation occurred between the gel and the polarizer or glass panel, the product was determined to have passed the high-temperature test.

[0088] Negative pressure test

[0089] Each component A and B was mixed in a 1:1 ratio using a static mixer, and the resulting mixture was applied to a polarizer of a 14-inch display in the mode of a fishbone diagram, and then a glass panel was lightly placed over it. No bubbles should be generated during the entire process. Subsequently, the product was applied to 65°C for 30 minutes, left at room temperature for 3 days, and then placed in an environment of -1 atm for 3 days. If no bubbles or delamination were observed or no separation occurred between the gel and the polarizer or glass panel after being placed at -1 atm for 3 days, the product was determined to have passed the negative pressure test.

[0090] The details of the raw materials used in the examples and comparative examples are as follows.

[0091] a1: Dimethylvinylsiloxy-terminated polydimethylsiloxane supplied by Wacker Chemicals, having a dynamic viscosity of about 1,000 mPa·s at 25°C and a vinyl content of 0.124 mmol / g.

[0092] a2: Dimethylvinylsiloxy-terminated polydimethylsiloxane supplied by Wacker Chemicals, having a dynamic viscosity of about 20,000 mPa·s at 25°C and a vinyl content of 0.042 mmol / g.

[0093] b1: Vinyl MQ resin supplied by Wacker Chemicals, having a molar ratio of M units to Q units of 0.7:1 and a vinyl content of 0.78 mmol / g.

[0094] b2: A trimethylsiloxy-terminated polydimethylsiloxane supplied by Wacker Chemicals, having a dynamic viscosity of 340 to 820 mPa·s at 25°C and a vinyl content of 2.8 mmol / g, having a plurality of vinyl groups bonded to silicon atoms of the side chain.

[0095] c1: Dimethylhydrosiloxy-terminated polydimethylsiloxane supplied by Wacker Chemicals, having a dynamic viscosity of about 65 mPa·s at 25°C and a hydrogen content of 0.53 mmol / g.

[0096] c2: Dimethylhydrosiloxy-terminated polydimethylsiloxane supplied by Wacker Chemicals, having a dynamic viscosity of about 1,000 mPa·s at 25°C and a hydrogen content of 0.12 mmol / g.

[0097] c3: Dimethylhydrosiloxy-terminated polydimethylsiloxane supplied by Wacker Chemicals, having a dynamic viscosity of about 15 mPa·s at 25°C and a hydrogen content of 1.8 mmol / g.

[0098] d: Platinum-based catalyst supplied by Wacker Chemicals, WACKER ® CATALYST EP.

[0099] e: Trimethylsiloxy-terminated polydimethylsiloxane supplied by Wacker Chemicals, having a dynamic viscosity of 150 mPa·s at 25°C and a hydrogen content of 1.8 mmol / g, having a number of hydrogen atoms bonded to silicon atoms in the side chain.

[0100] f: Inhibitor supplied by Wacker Chemicals, WACKER ® INHIBITOR PT 88.

[0101] g: Methyl MQ resin supplied by Wacker Chemicals, WACKER® MQ 803.

[0102] Examples 1-2 and Comparative Examples 1-3

[0103] According to the composition of Table 1, the components of each component A and component B were thoroughly mixed. Subsequently, components A and B were mixed separately, and the resulting mixture was cured at 65°C for 30 minutes to obtain a silicone gel.

[0104] Table 2 shows the penetration values ​​of the silicone gels obtained in each example and comparative example. Since silicone rubber was used instead of silicone gel in Comparative Example 3, Shore hardness A was measured.

[0105] Figure 1 shows the adhesion test curves of the silicone gels obtained by Examples 1-2 and Comparative Examples 1-2. It can be seen that the silicone gel obtained in Example 1 exhibits excellent adhesion and the silicone gel of Example 2 exhibits good adhesion, whereas Comparative Example 1-2 exhibits significantly worse adhesion than Example 1-2. The silicone rubber obtained in Example 3 had no adhesion, so the corresponding test was not performed.

[0106] Table 3 shows the test results of the silicone gels obtained in Examples 1-2 and Comparative Examples 1-2 under high temperature and negative pressure. Comparative Example 1 failed both tests because bubbles or delamination were observed after the test. Comparative Example 2 failed both tests because separation between the gel and the polarizer or glass panel was observed after the test.

[0107]

[0108] *: Not measured.

[0109]

[0110]

[0111] Effects of the invention

[0112] The present invention provides a siloxane composition and a silicone gel cured therefrom, which has a low penetration value and, compared to a conventional gel having the same penetration value, exhibits at least one of a higher elongation at break and better resistance to deformation and tension, better gel adhesion, better resistance to high temperature and better resistance to negative pressure.

Claims

Claim 1 A siloxane composition comprising (a) at least one organopolysiloxane containing two alkenyl groups bonded to silicon atoms at both ends of the chain per molecule, (b) at least one organopolysiloxane containing at least three alkenyl groups bonded to silicon atoms per molecule, (c) at least one organopolysiloxane containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule, and (d) at least one hydrosilylation catalyst, wherein component (c) is used in an amount of 30 wt% or more based on the total weight of the composition, and the composition comprises component (e) in an amount of 0.01 wt% or less based on the total weight of the composition, and component (e) comprises at least one organopolysiloxane containing at least three hydrogen atoms bonded to silicon atoms per molecule; and component (c) has a dynamic viscosity of 30 mPa·s or more and less than 1,000 mPa·s at 25°C, and component (c) a siloxane composition comprising (c1) an organopolysiloxane having a dynamic viscosity of 30 mPa·s or more and 200 mPa·s or less at 25°C, containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule, and (c2) an organopolysiloxane having a dynamic viscosity of more than 200 mPa·s and 5,000 mPa·s or less at 25°C, containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule. Claim 2 A siloxane composition according to claim 1, wherein component (c) is used in an amount of 40% by weight or more based on the total weight of the composition. Claim 3 A siloxane composition according to claim 1, wherein the ratio of the number of moles of Si-H groups provided by component (c1) to the number of moles of Si-H groups provided by component (c2) is 2:(1-10). Claim 4 A siloxane composition according to claim 1, wherein component (c) provides 0.6 to 1.0 moles of Si-H groups per mole of total silicon-bonded alkenyl groups of components (a) and (b). Claim 5 In paragraph 1, component (b) is (b1) R 1 R 2 2SiO 1 / 2 and SiO 4 / 2 Organopolysiloxane essentially composed of units, (b2) R 2 3SiO 1 / 2 and R 1 R 2 SiO 2 / 2 Organopolysiloxane essentially composed of units, (b3) R 1 R 2 2SiO 1 / 2 , R 1 R 2 SiO 2 / 2 and R 2 2SiO 2 / 2 Organopolysiloxane essentially composed of units, and (b4) R 1 R 2 2SiO 1 / 2 , R 2 2SiO 2 / 2 and R 2 SiO 3 / 2 Selected from the group consisting of organopolysiloxanes essentially composed of units; where, R 1 is an alkenyl group having 2 to 6 carbon atoms independently in each case, and R 2 A siloxane composition having 1 to 20 carbon atoms independently in each case, which is a monovalent hydrocarbon without aliphatic unsaturation. Claim 6 A siloxane composition according to claim 1, wherein component (a) comprises (a1) an organopolysiloxane having two alkenyl groups bonded to silicon atoms at both ends of the chain per molecule, having a dynamic viscosity of 100 mPa·s or more and less than 5,000 mPa·s at 25°C, and (a2) an organopolysiloxane having two alkenyl groups bonded to silicon atoms at both ends of the chain per molecule, having a dynamic viscosity of 5,000 mPa·s or more and less than 50,000 mPa·s at 25°C. Claim 7 A siloxane composition according to claim 1, wherein the composition comprises (a) 20-55 wt% of at least one organopolysiloxane containing two alkenyl groups bonded to silicon atoms at both ends of the chain per molecule, (b) 1-10 wt% of at least one organopolysiloxane containing at least three alkenyl groups bonded to silicon atoms per molecule, (c) 30-70 wt% of at least one organopolysiloxane containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule, and (d) at least one hydrosilylation catalyst. Claim 8 A silicone gel cured from a siloxane composition of any one of claims 1 to 7. Claim 9 In claim 8, a silicone gel characterized by a penetration value of 20 to 50 measured according to ASTM D1403 in a 1 / 4 cone. Claim 10 A siloxane composition used as a potting material in any one of claims 1 to 7. Claim 11 In item 10, a siloxane composition used as a potting material for displays. Claim 12 A siloxane composition used as an optical binding material in any one of claims 1 to 7. Claim 13 In Clause 12, a siloxane composition used as an optical bonding material for displays. Claim 14 delete Claim 15 delete

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