Silicone rubber and preparation method thereof

Abstract

The invention provides silicone rubber and a preparation method thereof. The invention provides silicon rubber. The silicon rubber is prepared from the following raw materials: vinyl-terminated polydimethylsiloxane, vinyl MQ silicon resin, an adhesion promoter, titanium dioxide, polymethylhydrosiloxane and a reaction inhibitor. The preparation method of the silicone rubber comprises the following steps: in the presence of a catalyst, mixing a mixture of vinyl-terminated polydimethylsiloxane and vinyl MQ silicon resin, an adhesion promoter, titanium dioxide, polymethylhydrosiloxane and a reaction inhibitor to obtain the silicone rubber. The silicone rubber disclosed by the invention has high reflectivity, low thixotropy, high fluidity, high heat resistance and storage stability, and is relatively simple in production process and suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the field of silicone rubber preparation, and in particular to silicone rubber and a preparation method thereof. Background Art

[0002] In the field of electronic packaging, silicone rubber is widely used in key parts such as sealing, filling, heat insulation and heat dissipation of electronic equipment due to its advantages such as high temperature resistance, good electrical insulation, aging resistance and chemical stability, providing important support for the performance and reliability of electronic products. When used in high-reliability ceramic package LED white wall packaging, a higher proportion of titanium dioxide needs to be added to obtain a higher reflectivity, thereby increasing the brightness of the LED lamp and preventing light leakage from the side of the lamp bead. At the same time, this silicone rubber also needs to maintain a lower thixotropy to ensure that the silicone can fully fill the chip gap and achieve a better leveling effect, thereby achieving the required optical effect.

[0003] Although adding a higher proportion of titanium dioxide to silicone rubber can improve the reflectivity, it will also increase the viscosity and thixotropy of the composition. In addition, in order to improve the bonding strength between silicone rubber and substrates and chips, a certain proportion of adhesion promoter is often added during the preparation process, which will also introduce some groups that improve thixotropy, thereby increasing the viscosity and thixotropy of silicone rubber, which seriously affects the fluidity of silicone rubber, resulting in poor leveling problems during application.

[0004] Chinese patent document CN110494473B discloses a dispensable chemical composition having a large amount of filler material and a low thixotropic index level. The invention controls the thixotropy of the silicone mixture by selecting a composition with a specific molecular weight distribution and an appropriate combination of filler content.

[0005] Chinese patent document CN117384586A discloses a low-thixotropic dealcoholization type silicone sealant and a preparation method and application thereof. The low-thixotropic dealcoholization type silicone sealant of the invention has low thixotropy and good storage stability.

[0006] Addition-type organic silicone adhesives are easy to cure and do not produce small molecules. Adding a higher proportion of titanium dioxide can be used in LED packages with higher reflectivity requirements, but this also causes problems such as high viscosity and thixotropy and poor storage stability. In addition, in the existing technology, while controlling the thixotropy of silicone rubber, its high temperature resistance or reflectivity is often sacrificed, thus affecting the application effect of silicone rubber in high temperature environments.

[0007] Therefore, there is a need in the prior art for a silicone rubber with high reflectivity, low thixotropy, high fluidity and high temperature resistance, which has good storage stability and will be better applied in LED packaging. Summary of the invention

[0008] In order to solve the above problems in the prior art, the present invention provides a silicone rubber and a preparation method thereof.

[0009] In the first aspect, the present invention provides a silicone rubber, the raw materials of which include: vinyl-terminated polydimethylsiloxane, vinyl MQ silicone resin, adhesion promoter, titanium dioxide, polymethyl hydrogen siloxane, and reaction inhibitor. In the vinyl MQ silicone resin, M is a monofunctional siloxane chain segment R3SiO 1 / 2 , Q is a tetrafunctional siloxane chain SiO 4 / 2 .

[0010] As a specific embodiment of the present invention, the raw materials of silicone rubber include, by weight:

[0011] 100 parts vinyl terminated polydimethylsiloxane

[0012] 10-100 parts of vinyl MQ silicone resin

[0013] 0.1-5 parts of adhesion promoter

[0014] 40~200 parts of titanium dioxide

[0015] 1-15 parts polymethyl hydrogen siloxane

[0016] 0.001 to 0.5 parts of reaction inhibitor.

[0017] As a specific embodiment of the present invention, at a shear rate of 20s -1 When the shear rate ratio is 1s -1 / 10s -1 When the thixotropic index of silicone rubber is 1.0-1.5, the reflectivity of silicone rubber is greater than or equal to 98% at a wavelength of 450nm.

[0018] As a specific embodiment of the present invention, the silanol content in the raw material of the silicone rubber is less than or equal to 0.07wt% based on the total weight of the raw material of the silicone rubber. The present invention finds that the thixotropy of the liquid silicone rubber is significantly correlated with the silanol content in the vinyl MQ silicone resin and the vinyl-terminated polydimethylsiloxane in its components. By strictly controlling the silanol content in the raw material of the silicone rubber, a silicone rubber with low thixotropy can be obtained, and on this basis, a large amount of titanium dioxide can be added to improve its reflectivity, and the prepared silicone rubber has low thixotropy and high reflectivity.

[0019] Preferably, the amount of the vinyl MQ silicone resin in the silicone rubber raw material is 20 to 80 parts by mass.

[0020] As a specific embodiment of the present invention, the content of silanol in the vinyl MQ silicone resin is less than or equal to 0.05 wt %.

[0021] As a specific embodiment of the present invention, the vinyl content in the vinyl MQ silicone resin is 0.5 to 2 mmol / g, and the ratio of M to Q in the vinyl MQ silicone resin is 0.7 to 1.2.

[0022] Preferably, the vinyl content in the vinyl MQ silicone resin is 0.7 to 1.7 mmol / g.

[0023] The present invention can make the prepared silicone rubber have suitable properties such as hardness and strength by adjusting the addition amount of the vinyl MQ resin in the silicone rubber and the vinyl content in the vinyl MQ silicone resin.

[0024] As a specific embodiment of the present invention, the content of silanol groups in the vinyl-terminated polydimethylsiloxane is less than or equal to 0.02 wt %.

[0025] As a specific embodiment of the present invention, at a shear rate of 20s -1 When the viscosity of the vinyl-terminated polydimethylsiloxane is 200 to 50000 mPa·s, preferably, at a shear rate of 20 s -1 When the viscosity of vinyl terminated polydimethylsiloxane is 500-20000mPa·s.

[0026] The present invention regulates the viscosity of the prepared silicone rubber by limiting the viscosity of the vinyl-terminated polydimethylsiloxane.

[0027] As a specific embodiment of the present invention, the silicon hydrogen content of the polymethyl hydrogen siloxane is 0.6 wt % to 1.6 wt %.

[0028] The present invention determines the addition amount of polymethylhydrogensiloxane and the silicon-hydrogen content of polymethylhydrogensiloxane according to the total vinyl content of vinyl MQ silicone resin and vinyl-terminated polydimethylsiloxane. The present invention controls the silicon-hydrogen to vinyl ratio to be between 1.5 and 2.5 to ensure that the prepared silicone rubber has a suitable hardness.

[0029] At a shear rate of 20 s -1 When the viscosity of polymethylhydrogensiloxane is 5 to 30 mPa·s.

[0030] Preferably, at a shear rate of 20 s -1 When the viscosity of polymethylhydrogensiloxane is 8 to 30 mPa·s.

[0031] As a specific embodiment of the present invention, the addition amount of the reaction inhibitor is preferably 0.01 to 0.05 parts by mass.

[0032] As a specific embodiment of the present invention, the reaction inhibitor is selected from at least one of phosphorus-containing compounds, nitrogen-containing compounds, vinyl silanes, acetylenic alcohol compounds, and maleate compounds.

[0033] Specifically, the phosphorus-containing compound is preferably triphenylphosphine.

[0034] The nitrogen-containing compound is preferably one or a combination of two or more of tributylamine, tetramethylethylenediamine and benzotriazole.

[0035] The vinyl silane is preferably 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane.

[0036] The acetylene alcohol compound is preferably one or a combination of two or more of 1-ethynylcyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, and 3-methylbutynol.

[0037] The maleate compound is preferably dimethyl maleate.

[0038] Preferably, the reaction inhibitor is an acetylenic alcohol compound.

[0039] More preferably, the reaction inhibitor is one or a combination of two or more of 1-ethynylcyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, and 3-methylbutynol.

[0040] The invention limits the addition amount and components of the reaction inhibitor, so that the prepared silicone rubber has good operation time and storage stability.

[0041] The amount of the adhesion promoter added is preferably 0.5 to 2 parts by weight. If the amount of the adhesion promoter added is too little, the adhesion between the silicone rubber and the substrate will be affected, and if the amount of the adhesion promoter added is too much, the tensile strength of the silicone rubber will be reduced.

[0042] As a specific embodiment of the present invention, the adhesion promoter is selected from one or more of silane coupling agents or semi-hydrolyzates of silane coupling agents. Silane coupling agents or semi-hydrolyzates of silane coupling agents are added to the raw materials of the silicone rubber of the present invention as adhesion promoters to improve the adhesion between the silicone rubber and the substrate. Therefore, the silicone rubber provided by the present invention has excellent adhesion in addition to high reflectivity, low thixotropy and high fluidity.

[0043] Specifically, the adhesion promoter in the present invention includes, but is not limited to: vinyl trimethoxy silane, vinyl triethoxy silane, 3-(2,3-epoxypropoxy) propyl trimethoxy silane, 3-(2,3-epoxypropoxy) propyl triethoxy silane, acryloxypropyl trimethoxy silane, acryloxypropyl triethoxy silane, methacryloxypropyl trimethoxy silane, methacryloxypropyl triethoxy silane, mercaptopropyl trimethoxy silane, mercaptopropyl triethoxy silane, isocyanate propyl trimethoxy silane, isocyanate propyl triethoxy silane, one or a combination of two or more thereof, or a combination of the hydrolysis products or semi-hydrolysis products of the above adhesion promoters.

[0044] Preferably, the adhesion promoter is one or a combination of two or more of vinyltrimethoxysilane, vinyltriethoxysilane, acryloxypropyltrimethoxysilane, acryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, and methacryloxypropyltriethoxysilane, or a combination of hydrolysis products or semi-hydrolysis products of the above adhesion promoters.

[0045] Calculated by weight, the addition amount of titanium dioxide is preferably 50 to 150 parts. If too little titanium dioxide is added, the reflectivity of the prepared silicone rubber will be low, which will affect the brightness of the packaged LED lamp. If too much titanium dioxide is added, the viscosity of the prepared silicone rubber will be high, which is not conducive to practical use.

[0046] The titanium dioxide in the present invention includes but is not limited to Chemours R980, R104, R960, Conos KRONOS2220, KRONOS2222, Ishihara R-930, R-980 and other titanium dioxides of similar specifications.

[0047] In a second aspect, the present invention provides a method for preparing the silicone rubber provided in the first aspect of the present invention, comprising the following steps: in the presence of a catalyst, mixing a mixture of vinyl-terminated polydimethylsiloxane and vinyl MQ silicone resin, an adhesion promoter, titanium dioxide, polymethyl hydrogen siloxane, and a reaction inhibitor to obtain silicone rubber.

[0048] As a specific embodiment of the present invention, the vinyl MQ silicone resin is a vinyl MQ silicone resin treated with silazane or chlorosilane.

[0049] As a specific embodiment of the present invention, the step of treating the vinyl MQ silicone resin with silazane or chlorosilane includes: mixing the vinyl MQ silicone resin with a solvent, adding silazane or chlorosilane, heating to reflux, drying and crushing to obtain the vinyl MQ silicone resin treated with silazane or chlorosilane.

[0050] As a specific embodiment of the present invention, the heating reflux temperature is 140-145° C., and the time is 1-2 hours.

[0051] Specifically, the heating reflux process uses xylene as a solvent.

[0052] As a specific embodiment of the present invention, the content of silazane or chlorosilane is 5% to 10% of the mass of the vinyl MQ silicone resin.

[0053] As a specific embodiment of the present invention, the catalyst contains any one of platinum, rhodium and palladium.

[0054] Preferably, the catalyst is selected from any one of a platinum complex, a rhodium complex and a palladium complex.

[0055] Preferably, the platinum complex is selected from any one of a platinum-olefin complex, a platinum-vinylsiloxane complex, a platinum-vinylsilane complex, a platinum-ketone complex, and a platinum-phosphine complex.

[0056] Preferably, the rhodium complex is selected from any one of a rhodium-phosphine complex and a rhodium-sulfur compound complex;

[0057] Preferably, the palladium complex is a palladium-phosphine complex.

[0058] More preferably, the catalyst is a complex of platinum and vinylsiloxane.

[0059] Specifically, the catalyst is a Custer catalyst.

[0060] As a specific embodiment of the present invention, the amount of the catalyst is such that the content of the noble metal in the catalyst, such as metal platinum, is 0.1 to 100 ppm, preferably 0.5 to 50 ppm, of the total mass of the silicone rubber raw material. Too little catalyst addition will affect the curing of the silicone rubber, while too much catalyst addition will cause yellowing of the cured product, thereby reducing the reflectivity of the cured silicone rubber.

[0061] As a specific embodiment of the present invention, the mixture of vinyl-terminated polydimethylsiloxane and vinyl MQ silicone resin is prepared by mixing the vinyl-terminated polydimethylsiloxane and vinyl MQ silicone resin at 40 to 100° C. for 0.5 to 1 hour;

[0062] Preferably, the mixture of vinyl-terminated polydimethylsiloxane and vinyl MQ silicone resin, the adhesion promoter, titanium dioxide, polymethyl hydrogen siloxane, and the reaction inhibitor are mixed for 0.5 to 1 hour.

[0063] In a third aspect, the present invention provides an application of the silicone rubber provided in the first aspect of the present invention and the silicone rubber prepared by the preparation method provided in the second aspect of the present invention in automotive-grade high-reflection LED packaging.

[0064] Specifically, the silicone rubber in the present invention is centrifugally degassed using a vacuum planetary mixer and then coated on a substrate with a chip fixed thereon. After the silicone rubber is leveled, it is cured at 150°C for 3h, and then cut to obtain automotive-grade LED lamp beads that meet high reflectivity requirements.

[0065] Compared with the prior art, the present invention has the following beneficial effects.

[0066] The silicone rubber of the invention has high reflectivity, low thixotropy, high fluidity, high heat resistance and ultraviolet resistance.

[0067] The invention provides a method for preparing silicone rubber, so that the prepared silicone rubber has excellent heat resistance and ultraviolet resistance while ensuring high reflectivity, low thixotropy and high fluidity. DETAILED DESCRIPTION

[0068] The present invention will be further described below in conjunction with specific embodiments, but they do not constitute any limitation to the present invention.

[0069] The raw materials used in the embodiments of the present invention are all commercially available.

[0070] Vinyl MQ Silicone Treatment

[0071] MQ1: A vinyl MQ silicone resin having an M / Q (ratio of M to Q) of 0.8, a vinyl content of 1.0 mmol / g, a silanol content of 0.36 wt% and a molecular weight of 5600 was treated with silazane. The treatment method was as follows: 100 g of the vinyl MQ silicone resin was first dissolved in 100 mL of xylene in a three-necked flask to form a solution, and then 10% of the weight of the MQ silicone resin in hexamethyldisilazane was dropwise added to the solution. The solution was heated to 140° C. and kept at 140° C. for reflux for 1 hour to allow the residual silanols in the vinyl MQ silicone resin to fully react with the silazane. The solution was then directly dried into powder in a centrifugal spray dryer at an inlet temperature of 140° C., and the silanol content was measured to be 0.03 wt%.

[0072] MQ2, a vinyl MQ silicone resin with an M / Q (ratio of M to Q) of 1.0, a vinyl content of 1.5 mmol / g, a silanol content of 0.51 wt%, and a molecular weight of 3200, is treated with silazane. The treatment method is as follows: 100 g of the above-mentioned vinyl MQ silicone resin is first dissolved in 100 mL of xylene in a three-necked flask to form a solution, and then 10% of the weight of the above-mentioned MQ silicone resin, hexamethyldisilazane, is dropwise added to the solution, and the solution is heated to 140°C, maintained at 140°C and refluxed for 1 hour to allow the residual silanols in the vinyl MQ silicone resin to fully react with the silazane, and then directly dried into powder in a centrifugal spray dryer at an inlet temperature of 140°C, and the silanol content is measured to be 0.04 wt%.

[0073] MQ3, vinyl MQ silicone resin having an M / Q (ratio of M to Q) of 0.8, a vinyl content of 1.0 mmol / g, a silanol content of 0.36 wt %, and a molecular weight of 5600, namely, untreated MQ1.

[0074] The test method for the mass content of silanol in the present invention is as follows:

[0075] Firstly, hydroxy silicone oil is subjected to silylation reaction with phenyldimethylsilyl chloride to obtain a crude sample of a standard sample, and then the crude sample is separated by column chromatography to obtain a pure standard sample, and then the standard sample is subjected to GPC-UV and nuclear magnetic resonance hydrogen spectrum analysis to calculate the phenyl content of the standard sample, and then a series of concentration standard samples are prepared and subjected to GPC-UV analysis, and a standard working curve of phenyl concentration is prepared by using the peak area, and finally the treated sample, including the treated vinyl MQ silicone resin or the treated terminal vinyl polymethylsiloxane, is dissolved in n-hexane, phenyldimethylsilyl chloride is added to react fully at room temperature, and then GPC-UV analysis is directly performed after filtering, and the silanol content is calculated through the standard curve.

[0076] Vi-PDMS1, vinyl terminated polydimethylsiloxane, has a dynamic viscosity of 1000 mPa·s and a silanol content of 0.02 wt%.

[0077] Vi-PDMS2, vinyl terminated polydimethylsiloxane, has a dynamic viscosity of 3000 mPa·s and a silanol content of 0.02 wt%.

[0078] Vi-PDMS3, vinyl terminated polydimethylsiloxane, has a dynamic viscosity of 5000 mPa·s and a silanol content of 0.02 wt%.

[0079] PMHS, polymethylhydrogensiloxane, silicon hydrogen content is 1.2wt%.

[0080] Titanium dioxide, rutile titanium dioxide prepared by the chloride process.

[0081] The catalyst used is a Custer catalyst with a platinum content of 0.5 wt%.

[0082] Example 1

[0083] 15 parts by weight of MQ1 and 100 parts by weight of Vi-PDMS3 were added to a beaker, heated to 100°C and mechanically stirred at 100 rpm for 1 hour, then 100 parts by weight of titanium dioxide, 4 parts by weight of PMHS, 2 parts by weight of adhesion promoter 3-(2,3-epoxypropoxy)propyltriethoxysilane, 0.1 parts by weight of reaction inhibitor 1-ethynylcyclohexanol, and 7 ppm (by platinum weight) of Custer catalyst based on the total weight of the silicone rubber raw materials were added, and after manual stirring for 10 minutes, the mixture was ground three times with a three-roll mill at a feed roller distance of 30 μm, a discharge roller distance of 10 μm, and a roller speed of 200 rpm, and then vacuum degassed to obtain silicone rubber. The prepared silicone rubber was heated at 150°C for 3 hours to obtain cured silicone rubber.

[0084] Example 2

[0085] 30 parts by weight of MQ1 and 100 parts by weight of Vi-PDMS1 were added to a beaker, heated to 100°C and mechanically stirred at 100 rpm for 1 hour, then 100 parts by weight of titanium dioxide, 7 parts by weight of PMHS, 2 parts by weight of adhesion promoter 3-(2,3-epoxypropoxy)propyltriethoxysilane, 0.1 parts by weight of reaction inhibitor 1-ethynylcyclohexanol, and 7 ppm (by platinum weight) of Custer catalyst based on the total weight of the silicone rubber raw materials were added, and after manual stirring for 10 minutes, the mixture was ground three times with a three-roll mill at a feed roller distance of 30 μm, a discharge roller distance of 10 μm, and a roller speed of 200 rpm, and then vacuum degassed to obtain silicone rubber. The prepared silicone rubber was heated at 150°C for 3 hours to cure to obtain cured silicone rubber.

[0086] Example 3

[0087] 50 parts by weight of MQ2 and 100 parts by weight of Vi-PDMS2 were added to a beaker, heated to 100°C and mechanically stirred at 100 rpm for 1 hour, then 100 parts by weight of titanium dioxide, 14 parts by weight of PMHS, 2 parts by weight of adhesion promoter 3-(2,3-epoxypropoxy)propyltriethoxysilane, 0.1 parts by weight of reaction inhibitor 1-ethynylcyclohexanol, and 7 ppm (by platinum weight) of Custer catalyst based on the total weight of the silicone rubber raw materials were added, and after manual stirring for 10 minutes, the mixture was ground three times with a three-roll mill at a feed roller distance of 30 μm, a discharge roller distance of 10 μm, and a roller speed of 200 rpm, and then vacuum degassed to obtain silicone rubber. The prepared silicone rubber was heated at 150°C for 3 hours to cure to obtain cured silicone rubber.

[0088] Comparative Example 1

[0089] 15 parts by weight of MQ3 and 100 parts by weight of Vi-PDMS3 were added to a beaker, heated to 100°C and mechanically stirred at 100 rpm for 1 hour, then 100 parts by weight of titanium dioxide, 4 parts by weight of PMHS, 2 parts by weight of adhesion promoter 3-(2,3-epoxypropoxy)propyltriethoxysilane, 0.1 parts by weight of reaction inhibitor 1-ethynylcyclohexanol, and 7 ppm (by platinum weight) of Custer catalyst based on the total weight of the silicone rubber raw materials were added, and after manual stirring for 10 minutes, the mixture was ground three times with a three-roll mill at a feed roller distance of 30 μm, a discharge roller distance of 10 μm, and a roller speed of 200 rpm, and then vacuum degassed to obtain silicone rubber. The prepared silicone rubber was heated at 150°C for 3 hours to cure to obtain cured silicone rubber.

[0090] Comparative Example 2

[0091] 30 parts by weight of MQ3, 2 parts by weight of octyl trimethoxysilane and 100 parts by weight of Vi-PDMS1 were added to a beaker, heated to 100°C and mechanically stirred at 100 rpm for 1 hour, then 100 parts by weight of titanium dioxide, 7 parts by weight of PMHS, 2 parts by weight of adhesion promoter 3-(2,3-epoxypropoxy)propyl triethoxysilane, 0.1 parts by weight of reaction inhibitor 1-ethynyl cyclohexanol, and 7 ppm (by platinum weight) of Custer catalyst based on the total weight of the silicone rubber raw materials were added, and after manual stirring for 10 minutes, the mixture was ground three times with a three-roll mill at a feed roller distance of 30 μm, a discharge roller distance of 10 μm, and a roller speed of 200 rpm, and then vacuum degassed to obtain silicone rubber. The prepared silicone rubber was heated at 150°C for 3 hours to cure to obtain cured silicone rubber.

[0092] Comparative Example 3

[0093] 30 parts by weight of MQ3, 2 parts by weight of dodecyltrimethoxysilane and 100 parts by weight of Vi-PDMS1 were added to a beaker, heated to 100°C and mechanically stirred at 100 rpm for 1 hour, then 100 parts by weight of titanium dioxide, 7 parts by weight of PMHS, 2 parts by weight of adhesion promoter 3-(2,3-epoxypropoxy)propyltriethoxysilane, 0.1 parts by weight of reaction inhibitor 1-ethynylcyclohexanol, and 7 ppm (by platinum weight) of Custer catalyst based on the total weight of the silicone rubber raw materials were added, and after manual stirring for 10 minutes, the mixture was ground three times with a three-roll mill at a feed roller distance of 30 μm, a discharge roller distance of 10 μm, and a roller speed of 200 rpm, and then vacuum degassed to obtain silicone rubber. The prepared silicone rubber was heated at 150°C for 3 hours to obtain cured silicone rubber.

[0094] The performance tests of Examples 1 to 3 and Comparative Examples 1 to 3 were carried out according to the following test methods. The test results are shown in Table 1.

[0095] Test Method

[0096] (1) Viscosity and thixotropic index

[0097] After the prepared silicone rubber was stirred evenly and vacuum degassed, an MCR92 rheometer was used to measure its shear rate of 1s at 25°C. -1 , 10s -1 and 20s -1 The viscosity at 20s -1 The data at 1s is the viscosity of the sample. -1 / 10s -1 The data is the thixotropic index of the sample.

[0098] (2) Hardness

[0099] After vacuum degassing, the prepared silicone rubber was poured into a 20×15×10 mm PTFE mold and cured at 150°C for 3 hours to form a 10 mm thick sample. The hardness of the cured sample was measured using a Shore A rubber hardness tester according to the test method specified in the national standard GB / T 531.1-2008.

[0100] (3) Tensile strength and elongation at break

[0101] The prepared silicone rubber was stirred evenly and vacuum degassed, then poured into a 65×55×1 mm PTFE mold and cured at 150°C for 3 hours to form a 1 mm thick sample. According to the test method specified in the national standard GB / T 528-2009, the cured sample was cut into specimens of specified size, and the tensile strength and elongation at break of the specimens were measured using a universal material testing machine.

[0102] (4) Reflectivity

[0103] First, the silicone rubber was cured at 150°C for 3 hours to form a 1 mm thick sample, and then its reflectivity at a wavelength of 450 nm was tested using a spectrophotometer.

[0104] Table 1 Performance test results of the silicone rubber prepared in Examples 1 to 3 and Comparative Examples 1 to 3

[0105]

[0106] Compared with Example 1, the silicone rubber prepared in Comparative Example 1 of the present invention has a vinyl MQ silicone resin used in the preparation process of the silicone rubber in Comparative Example 1 that has not been treated with silazane or chlorosilane, and the content of silanol in the vinyl silicone resin is relatively high. Compared with Example 2, the silicone resin prepared in Comparative Example 2 has a vinyl MQ silicone resin used in the preparation process that has not been treated with silazane or chlorosilane, and the content of silanol in the vinyl silicone resin is relatively high, and octyltrimethoxysilane is additionally added to the raw materials. Compared with Example 2, the silicone resin prepared in Comparative Example 3 has a vinyl MQ silicone resin used in the preparation process that has not been treated with silazane or chlorosilane, and the content of silanol in the vinyl silicone resin is relatively high, and dodecyltrimethoxysilane is additionally added to the raw materials.

[0107] From the data in Table 1, it can be seen that the silicone rubber prepared by the vinyl MQ silicone resin treated with silazane in Examples 1 to 3 has a low viscosity and thixotropy before curing, while the surface of the untreated vinyl MQ silicone resin in Comparative Example 1 contains more silanol groups, so that the silicone rubber prepared under the action of hydrogen bonds has a high viscosity and thixotropy before curing and poor fluidity.

[0108] Since the proportion of titanium dioxide added to the silicone rubber prepared by the present invention is relatively high, the reflectivity of the prepared silicone rubber before aging is greater than 98%, and has excellent light reflection performance.

[0109] After aging at 200°C for 1000 hours, the reflectivity of the silicone rubber prepared in Examples 1 to 3 slightly decreased to 97%. Although the silicone rubber components added with octyltrimethoxysilane and dodecyltrimethoxysilane in Comparative Examples 2 and 3 also have relatively good low viscosity and low thixotropy, after aging at 200°C for 1000 hours, the silicone rubber prepared by this method showed obvious yellowing and the reflectivity also decreased significantly.

[0110] For 313nmUV aging, after 1000 hours, the reflectivity of the silicone rubber prepared in Examples 1 to 3 has almost no change, but in Comparative Examples 2 and 3, the reflectivity of the silicone rubber added with octyltrimethoxysilane and dodecyltrimethoxysilane components has dropped significantly, which shows that the anti-ultraviolet performance of alkyl silane is poor, while the silicone rubber prepared from vinyl MQ silicone resin treated with silazane has a strong tolerance to ultraviolet rays.

[0111] In addition, the samples prepared from the above silicone rubber for hardness measurement were aged for 1000 hours at 200°C. The Shore A hardness of the silicone rubber prepared in Examples 1 to 3 increased slightly by 3 to 5, with a small change in hardness. However, in Comparative Examples 2 and 3, the Shore A hardness of the silicone rubber to which octyltrimethoxysilane and dodecyltrimethoxysilane components were added increased by more than 20, with a large change, indicating that its high temperature resistance was poor.

[0112] The silicone rubber of the present invention has high reflectivity, low thixotropy, high fluidity, high heat resistance and UV aging resistance. The silicone rubber prepared by the methods in Comparative Examples 2 and 3 also has high reflectivity, low thixotropy and high fluidity. However, its tolerance to high temperature and ultraviolet rays is relatively poor.

[0113] Through the above implementation methods, the present invention effectively overcomes the problem that traditional silicone rubber is prone to performance degradation under high temperature and ultraviolet irradiation environments, improves the stability and durability of silicone rubber, and provides a new solution for the application of silicone rubber in high temperature and outdoor environments. Since the silicone rubber prepared by the present invention has high reflectivity, low thixotropy, high fluidity and excellent storage stability, the silicone rubber can be used in high-power LED packaging with high reflectivity requirements, and its excellent leveling and durability are suitable for industrial production.

[0114] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A silicone rubber, characterized in that: The raw materials of the silicone rubber include: vinyl-terminated polydimethylsiloxane, vinyl MQ silicone resin, adhesion promoter, titanium dioxide, polymethyl hydrogen siloxane and reaction inhibitor.

2. The silicone rubber according to claim 1, characterized in that The raw materials of the silicone rubber include, by weight: 100 parts vinyl terminated polydimethylsiloxane; 10-100 parts of vinyl MQ silicone resin; 0.1 to 5 parts of adhesion promoter; 40-200 parts of titanium dioxide; 1 to 15 parts of polymethyl hydrogen siloxane; 0.001 to 0.5 parts of reaction inhibitor.

3. The silicone rubber according to claim 1 or 2, characterized in that: At a shear rate of 20 s -1 When the viscosity of the silicone rubber is 3000-5500 mPa·s; when the shear rate is 1s -1 / 10s -1 When the thixotropic index of the silicone rubber is 1.0 to 1.5, the reflectivity of the silicone rubber is greater than or equal to 98% at a wavelength of 450 nm.

4. The silicone rubber according to claim 3, characterized in that: The content of silanol in the raw material of the silicone rubber is less than or equal to 0.07wt% based on the total weight of the raw material of the silicone rubber; and / or, the amount of the vinyl MQ silicone resin in the silicone rubber raw material is 20 to 80 parts by weight; and / or, the silanol content in the vinyl MQ silicone resin is less than or equal to 0.05wt%; And / or, the vinyl content in the vinyl MQ silicone resin is 0.5 to 2 mmol / g, and the ratio of M to Q in the vinyl MQ silicone resin is 0.7 to 1.

2.

5. The silicone rubber according to claim 4, characterized in that: The content of silanol in the vinyl-terminated polydimethylsiloxane is less than or equal to 0.02 wt %; and / or, at a shear rate of 20 s -1 When the viscosity of the vinyl-terminated polydimethylsiloxane is 200 to 50000 mPa·s; and / or, the polymethylhydrogensiloxane has a silicon hydrogen content of 0.6 wt% to 1.6 wt%; and / or, at a shear rate of 20 s -1 When the viscosity of the polymethyl hydrogen siloxane is 5 to 30 mPa·s.

6. The silicone rubber according to claim 4, characterized in that: The reaction inhibitor is added in an amount of 0.01 to 0.05 parts by mass; And / or, the reaction inhibitor is selected from at least one of phosphorus-containing compounds, nitrogen-containing compounds, vinyl silanes, acetylenic alcohol compounds, and maleate compounds; And / or, the amount of the adhesion promoter added is 0.5 to 2 parts by weight; the adhesion promoter is selected from one or more of a silane coupling agent or a semi-hydrolyzate of a silane coupling agent; And / or, the amount of titanium dioxide added is 50 to 150 parts by mass.

7. A method for preparing the silicone rubber according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: in the presence of a catalyst, mixing a mixture of vinyl-terminated polydimethylsiloxane and vinyl MQ silicone resin, an adhesion promoter, titanium dioxide, polymethyl hydrogen siloxane and a reaction inhibitor to obtain the silicone rubber.

8. The preparation method according to claim 7, characterized in that: The vinyl MQ silicone resin is a vinyl MQ silicone resin treated with silazane or chlorosilane; And / or, the catalyst contains any one of platinum, rhodium and palladium.

9. The preparation method according to claim 8, characterized in that: The step of treating the vinyl MQ silicone resin with silazane or chlorosilane comprises: mixing the vinyl MQ silicone resin with a solvent, adding silazane or chlorosilane, heating and refluxing, and drying to obtain the vinyl MQ silicone resin treated with silazane or chlorosilane; the heating and refluxing temperature is 140-145° C., and the time is 1-2 hours; the amount of silazane or chlorosilane used is 5%-10% of the mass of the vinyl MQ silicone resin; And / or, the catalyst is selected from any one of a platinum complex, a rhodium complex, and a palladium complex; And / or, the amount of the catalyst used is such that the content of the noble metal in the catalyst is 0.1 to 100 ppm of the total mass of the silicone rubber raw material.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The mixture of vinyl-terminated polydimethylsiloxane and vinyl MQ silicone resin is prepared by mixing the vinyl-terminated polydimethylsiloxane and vinyl MQ silicone resin at 40 to 100° C. for 0.5 to 1 hour.

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