Organosilicon sealant with low water vapor transmittance and preparation method thereof

Abstract

The invention relates to an organosilicon sealant with low water vapor transmittance and a preparation method thereof. The organic silicon sealant with low water vapor transmittance is prepared from the following raw materials in parts by weight: 5 to 40 parts of alpha, omega-dihydroxy polydimethylsiloxane, 10 to 40 parts of silane modified polybutadiene, 0 to 50 parts of filler, 10 to 50 parts of intercalated mica, 0.5 to 5 parts of cross-linking agent, 0.3 to 4 parts of silane coupling agent and 0.2 to 2 parts of catalyst, the silane modified polybutadiene contains a polymer with a structure as shown in a formula (I). The silane modified polybutadiene and organic silicon hybrid system is adopted, then the mica powder with the intercalation structure is added into the system, and the water vapor transmittance of the organic silicon sealant can be remarkably reduced through the synergistic cooperation of the silane modified polybutadiene and the organic silicon hybrid system. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of sealants, and in particular relates to an organic silicon sealant with low water vapor transmission rate and a preparation method thereof. Background Art

[0002] Silicone sealants have good adhesion, excellent UV resistance, aging resistance, high and low temperature resistance, elasticity and environmental protection performance, and are widely used in many fields such as solar photovoltaics, LED lighting, electronic appliances, 5G communications, construction, transportation, aerospace, national defense and military industry. In the field of solar photovoltaics, silicone sealants are widely used for photovoltaic module frame sealing, junction box bonding and potting. With the continuous development of photovoltaic cell technology, new photovoltaic cells such as HJT, TOPCon, and perovskite with higher photoelectric conversion efficiency have made good progress in recent years. In the future, they are expected to gradually replace existing photovoltaic cell technology and become the mainstream photovoltaic cell technology in the future. However, new photovoltaic cell components such as HJT, TOPCon, and perovskite have put forward higher requirements on the water vapor permeability of sealants. Traditional silicone sealants can no longer meet the requirements. Therefore, it is necessary to develop silicone sealants with low water vapor permeability. Summary of the invention

[0003] Based on this, the object of the present invention is to provide a silicone sealant with low water vapor transmission rate.

[0004] The technical solutions for achieving the above-mentioned purpose include the following.

[0005] In a first aspect, the present invention provides a low water vapor transmission rate organic silicone sealant, which is prepared from raw materials including the following components in parts by weight:

[0006]

[0007]

[0008] The silane-modified polybutadiene contains a polymer having a structure shown in formula (I):

[0009]

[0010] Wherein, the ratio of a, b and c is 5-7:2-3:2-3, and R is methyl or ethyl.

[0011] The silane-modified polybutadiene can be obtained by reacting terminal hydroxyl polybutadiene with an isocyanate silane coupling agent; the structural formula of the terminal hydroxyl polybutadiene is:

[0012]

[0013] Among them, the ratio of a, b and c is 5-7:2-3:2-3.

[0014] The preparation method of the intercalated mica comprises the following steps: activating sericite at 750°C-900°C, and then treating it with nitric acid solution, saturated sodium chloride solution and hexadecyltrimethylammonium bromide solution in sequence to obtain the intercalated mica; wherein the temperature for treating with the nitric acid solution is 85°C-100°C, the temperature for treating with the saturated sodium chloride solution is 70°C-90°C, and the temperature for treating with the hexadecyltrimethylammonium bromide solution is 80°C-100°C.

[0015] In a second aspect, the present invention provides a method for preparing the low water vapor transmission rate organic silicone sealant, comprising the following steps:

[0016] The α,ω-dihydroxy polydimethylsiloxane, silane-modified polybutadiene, filler and intercalated mica are mixed and dehydrated for 60min to 120min at a temperature of 100°C to 120°C and a vacuum degree of -0.085MPa to -0.095MPa; after cooling to 40°C to 50°C, the crosslinking agent, coupling agent and catalyst are added, and the mixture is stirred for 20min to 60min at a vacuum degree of -0.085MPa to -0.095MPa to obtain the silicone sealant with low water vapor transmission rate.

[0017] The present invention has the following beneficial effects:

[0018] In order to solve the problem of excessively high water vapor permeability of existing silicone sealants, the present invention adopts a silane-modified polybutadiene and silicone hybrid system, and then adds intercalated mica powder to the system. The synergistic combination of the two can significantly reduce the water vapor permeability of the silicone sealant.

[0019] The silane-modified polybutadiene of the present invention is obtained by reacting terminal hydroxyl polybutadiene with an isocyanate silane coupling agent. The terminal hydroxyl polybutadiene is end-capped and modified by silane, so that the compatibility of polybutadiene with the silicone sealant system can be improved, so that the silane-modified polybutadiene can more effectively reduce the water vapor permeability of the silicone sealant than the unmodified polybutadiene. At the same time, the present invention further activates the sericite mica by high temperature, and then sequentially treats it with nitric acid, a saturated sodium chloride solution and hexadecyltrimethylammonium bromide to obtain mica powder with an intercalated structure. The mica powder with an intercalated structure can change the path of water vapor transmission, cooperate with the silane-modified polybutadiene, and further significantly reduce the water vapor permeability of the silicone sealant.

[0020] At the same time, the organic silicon sealant prepared by the present invention not only has a very low water vapor permeability due to the coordinated cooperation of various components, but also has the advantages of good adhesion, aging resistance and the like, and excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 IR spectra of the hydroxy-terminated polybutadiene (A) and the silane-modified polybutadiene (B) in Example 1. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0023] The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0024] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in the present invention includes any and all combinations of one or more of the related listed items.

[0025] In addition, as used in the present invention, the term "or" is an inclusive "or" symbol and is equivalent to the term "and / or", unless the context clearly dictates otherwise. The term "based on" is not exclusive and allows for being based on other factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meanings of "a", "an", and "the" include plural referents. The meaning of "in..." includes "in..." and "on...".

[0026] Some of the embodiments involve a low water vapor transmission rate organic silicon sealant, which is prepared from raw materials including the following components in parts by weight:

[0027]

[0028]

[0029] The silane-modified polybutadiene contains a polymer having a structure shown in formula (I):

[0030]

[0031] Wherein, the ratio of a, b and c is 5-7:2-3:2-3, and R is methyl or ethyl.

[0032] In some preferred embodiments, the low water vapor transmission rate organic silicone sealant is prepared from raw materials including the following components in parts by weight:

[0033]

[0034] In some preferred embodiments, the low water vapor transmission rate organic silicone sealant is prepared from raw materials including the following components in parts by weight:

[0035]

[0036]

[0037] In some preferred embodiments, the silane-modified polybutadiene is obtained by reacting terminal hydroxyl polybutadiene with an isocyanate silane coupling agent; the structural formula of the terminal hydroxyl polybutadiene is:

[0038]

[0039] Among them, the ratio of a, b and c is 5-7:2-3:2-3, preferably 5.5-6.5:2-2.5:2-2.5, and more preferably 5.8-6:2-2.2:2-2.2.

[0040] In some preferred embodiments, the molecular weight of the hydroxy-terminated polybutadiene is 2500 mol / g-5000 mol / g, preferably 2500 mol / g-4500 mol / g, and more preferably 3300 mol / g-4400 mol / g.

[0041] In some preferred embodiments, the isocyanate silane coupling agent is an isocyanate propyl alkoxy silane, preferably at least one selected from isocyanate propyl trimethoxy silane, isocyanate propyl triethoxy silane and isocyanate propyl methyl dimethoxy silane; or a combination of two, such as a combination of isocyanate propyl trimethoxy silane and isocyanate propyl triethoxy silane, a combination of isocyanate propyl triethoxy silane and isocyanate propyl methyl dimethoxy silane, etc. More preferably, it is isocyanate propyl trimethoxy silane.

[0042] In some preferred embodiments, the molar ratio of the terminal hydroxyl polybutadiene to the isocyanate silane coupling agent is 1:1-2, such as 1:1, 1:1.2, 1:1.4, 1:1.5, 1:1.6, 1:1.8 or 1:2, and more preferably 1:2.

[0043] In some preferred embodiments, the method for preparing the silane-modified polybutadiene comprises the following steps: under the protection of an inert gas, reacting the terminal hydroxyl polybutadiene and the isocyanate silane coupling agent in the presence of a catalyst to obtain the silane-modified polybutadiene.

[0044] In some preferred embodiments, the catalyst is dibutyltin dilaurate.

[0045] In some preferred embodiments, the added amount of the catalyst is 0.05-1% of the total mass of the terminal hydroxyl polybutadiene and the isocyanate silane coupling agent; for example, 0.05%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9% or 1%, etc.

[0046] In some preferred embodiments, the reaction temperature is 60°C-70°C, such as 60°C, 62°C, 64°C, 66°C, 68°C or 70°C, etc.; the reaction time is 2h-6h, such as 2h, 3h, 4h, 5h or 6h, etc.

[0047] In some preferred embodiments, the preparation method of the intercalated mica comprises the following steps: activating sericite at 750°C-900°C, and then treating it with nitric acid solution, saturated sodium chloride solution and hexadecyltrimethylammonium bromide solution in sequence to obtain the intercalated mica; wherein the temperature for treating with nitric acid solution is 85°C-100°C, the temperature for treating with saturated sodium chloride solution is 70°C-90°C, and the temperature for treating with hexadecyltrimethylammonium bromide solution is 80°C-100°C.

[0048] In some preferred embodiments, the concentration of the nitric acid solution is 4 mol / L-6 mol / L.

[0049] In some preferred embodiments, the mass concentration of the hexadecyltrimethylammonium bromide solution is 20%-60%, preferably 30%-50%.

[0050] In some preferred embodiments, the activation temperature is 800°C-850°C.

[0051] In some preferred embodiments, the activation time is 1 h-3 h, more preferably 1.5 h-2 h.

[0052] In some preferred embodiments, the temperature of the treatment with nitric acid solution is 90°C-95°C.

[0053] In some preferred embodiments, the treatment time with the nitric acid solution is 3h-6h, more preferably 4h-5h.

[0054] In some preferred embodiments, the temperature of treating with saturated sodium chloride solution is 75°C-85°C.

[0055] In some preferred embodiments, the treatment time with saturated sodium chloride solution is 3h-5h, more preferably 3h-4h.

[0056] In some preferred embodiments, the temperature of treating with hexadecyltrimethylammonium bromide is 85°C-95°C.

[0057] In some preferred embodiments, the treatment time with the cetyltrimethylammonium bromide solution is 20 h to 28 h, more preferably 20 h to 24 h.

[0058] In some preferred embodiments, the method for preparing the intercalated mica comprises the following steps:

[0059] (1) activating sericite at 800° C.-850° C. for 1.5-2 h, reacting with nitric acid solution at 90° C.-95° C. for 4 h-5 h, washing with water until neutral, and drying to obtain acid-activated mica;

[0060] (2) treating the acid-activated mica in a saturated sodium chloride solution at 75° C.-85° C. for 3 h-4 h, washing with water, and drying to obtain mica treated with acid and salt;

[0061] (3) reacting the mica treated with the acid and salt in a hexadecyltrimethylammonium bromide solution at 85° C.-95° C. for 20 h-24 h, washing with water, and drying to obtain the intercalated mica.

[0062] In some preferred embodiments, the water washing in step (2) is washing with water at 70° C.-85° C. to remove excess sodium chloride.

[0063] In some preferred embodiments, the water washing in step (3) is washing with water at 70° C.-80° C. to remove residual hexadecyltrimethylammonium bromide.

[0064] In some preferred embodiments, the drying temperature is 60°C-70°C.

[0065] In some preferred embodiments, the viscosity of the α,ω-dihydroxypolydimethylsiloxane at 25° C. is 100 mPa.s to 500,000 mPa.s, more preferably 10,000 mPa.s to 50,000 mPa.s.

[0066] In some preferred embodiments, the filler is selected from at least one of nano calcium carbonate, heavy calcium carbonate, silicon powder, nano fumed silica, alumina, aluminum hydroxide, talc, carbon black and mica powder.

[0067] In some preferred embodiments, the crosslinking agent is selected from at least one of methyltrimethoxysilane, methyltriethoxysilane, methyltriethoxysilane oligomers with a degree of polymerization of 2-4, dimethyldimethoxysilane, dimethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, diphenyldimethoxysilane, and diphenyldiethoxysilane.

[0068] In some preferred embodiments, the silane coupling agent is chloropropyltrimethoxysilane, chloropropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-glycidyloxypropyltriethoxysilane, cyclohexene oxide At least one of trimethoxysilane, epoxycyclohexyl triethoxysilane, mercaptopropyl trimethoxysilane, mercaptopropyl triethoxysilane, isocyanate propyl trimethoxysilane, isocyanate propyl triethoxysilane, methacryloxypropyl trimethoxysilane, methacryloxypropyl triethoxysilane, γ-ureidopropyl trimethoxysilane, γ-ureidopropyl triethoxysilane and diethylenetriaminepropyl trimethoxysilane.

[0069] In some preferred embodiments, the catalyst is selected from at least one of tetraisopropyl titanate, tetrabutyl titanate, diisopropoxybis(ethoxyacetoacetyl)titanium, di-n-butoxybis(ethoxyacetoacetyl)titanium and 1,3-dipropoxybis(ethoxyacetoacetyl)titanium.

[0070] Some embodiments of the present invention also involve a method for preparing the low water vapor transmission rate organic silicone sealant, comprising the following steps:

[0071] The α,ω-dihydroxy polydimethylsiloxane, silane-modified polybutadiene, filler and intercalated mica are mixed and dehydrated for 60min to 120min at a temperature of 100°C to 120°C and a vacuum of -0.085MPa to -0.095MPa; after cooling to 40°C to 50°C, the crosslinking agent, coupling agent and catalyst are added, and the mixture is stirred for 20min to 60min at a vacuum of -0.085MPa to -0.095MPa to obtain the silicone sealant with low water vapor transmission rate.

[0072] The present invention is further described in detail below with reference to specific embodiments.

[0073] In the following examples, unless otherwise specified, "parts" refer to parts by weight.

[0074] In the following examples, the general structural formula of hydroxy-terminated polybutadiene is:

[0075]

[0076] The reaction principle of silane-modified polybutadiene is as follows:

[0077]

[0078] That is, the silane-modified polybutadiene is obtained by reacting the hydroxyl group in the terminal hydroxyl polybutadiene with the isocyanate group in the isocyanate silane coupling agent, wherein R is the alkyl group in the isocyanate silane coupling agent, such as methyl or ethyl.

[0079] Example 1

[0080] The low water vapor transmission rate organic silicon sealant provided in this embodiment is prepared from the following components in parts by weight:

[0081]

[0082] Among them, the viscosity of α,ω-dihydroxy polydimethylsiloxane at 25°C is 20000mPa.s;

[0083] The preparation method of silane-modified polybutadiene is as follows:

[0084] According to hydroxy-terminated polybutadiene (Evonik HT, molecular weight of 2900g / mol, ratio of a, b and c of 5.8:2.2:2) and molar ratio of isocyanatepropyltrimethoxysilane of 1:1.5, isocyanatepropyltrimethoxysilane is slowly added dropwise to terminal hydroxyl polybutadiene, and 0.05% of catalyst dibutyltin dilaurate based on the total mass of terminal hydroxyl polybutadiene and isocyanatepropyltrimethoxysilane is added, and the reaction is stirred at 60°C under nitrogen protection for about 5h (until the reaction is stopped after no isocyanate group is found in the system by back titration of di-n-butylamine), to obtain silane-modified polybutadiene.

[0085] like Figure 1 As shown: In the infrared spectrum of hydroxy-terminated polybutadiene, 3471cm -1 The characteristic peak of hydroxyl group is 1640cm -1 (-C=C), 990cm -1 and 910cm -1 (=CH stretch), 964cm -1 (=CH bend) is the characteristic peak in the chain; in the infrared spectrum of silane-modified polybutadiene terminated with silane, the hydroxyl absorption peak disappears and is replaced by a peak at 3320cm -1 (-NH), 1727cm -1A new characteristic peak appears at (-C=O), which is attributed to the characteristic peak of carbamate generated by the reaction of isocyanate and hydroxyl, indicating that the silane-modified polybutadiene with the above structural formula has been successfully prepared.

[0086] The preparation method of intercalated mica is as follows: sericite is placed in a muffle furnace, activated at 800°C for 1.5 hours, and then the activated mica is soaked in a nitric acid solution with a concentration of 5 mol / L, reacted at 90°C for 5 hours, then washed with distilled water until neutral, and dried at 60°C. The acid-activated mica is soaked in a saturated sodium chloride solution and treated at 80°C for 4 hours, then washed with distilled water at 70°C to remove excess sodium chloride, and dried at 70°C. The mica treated with acid and salt is then soaked in an aqueous solution of hexadecyltrimethylammonium bromide with a concentration of 50%wt, reacted at 90°C for 24 hours for intercalation treatment, then washed with distilled water at 80°C to remove residual hexadecyltrimethylammonium bromide, and dried at 70°C to obtain intercalated mica.

[0087] The preparation method of the low water vapor transmission rate organic silicon sealant provided in this embodiment is as follows:

[0088] The α,ω-dihydroxypolydimethylsiloxane, silane-modified polybutadiene, nano-calcium carbonate and intercalated mica are mixed and dehydrated for 120 minutes at a temperature of 110°C and a vacuum degree of -0.095MPa; after cooling to 45°C, methyltrimethoxysilane, γ-aminopropyltrimethoxysilane and diisopropoxybis(ethoxyacetoacetyl)titanium are added, and the mixture is mixed and stirred for 30 minutes at a vacuum degree of -0.09MPa to obtain the silicone sealant with low water vapor transmission rate.

[0089] Example 2

[0090] The low water vapor transmission rate organic silicon sealant provided in this embodiment is prepared from the following components in parts by weight:

[0091]

[0092] Among them, the viscosity of α,ω-dihydroxy polydimethylsiloxane at 25°C is 30000mPa.s;

[0093] The structural formula and preparation method of silane-modified polybutadiene are the same as those in Example 1.

[0094] The preparation method of intercalated mica is as follows: sericite is placed in a muffle furnace, activated at 850°C for 2h, and then the activated mica is immersed in a nitric acid solution with a concentration of 5mol / L, reacted at 95°C for 4h, then washed with distilled water until neutral, and dried at 65°C. The acid-activated mica is immersed in a saturated sodium chloride solution and treated at 80°C for 3.5h, then washed with distilled water at 80°C to remove excess sodium chloride, and dried at 70°C. The mica treated with acid and salt is then immersed in an aqueous solution of hexadecyltrimethylammonium bromide with a concentration of 30%wt, reacted at 90°C for 24h for intercalation treatment, then washed with distilled water at 80°C to remove residual hexadecyltrimethylammonium bromide, and dried at 65°C to obtain intercalated mica.

[0095] The preparation method of the low water vapor transmission rate organic silicon sealant provided in this embodiment is as follows:

[0096] The α,ω-dihydroxypolydimethylsiloxane, silane-modified polybutadiene, nano-calcium carbonate and intercalated mica are dehydrated and mixed for 120 minutes at a temperature of 120°C and a vacuum degree of -0.09 MPa; after cooling to 40°C, methyltriethoxysilane, γ-aminopropyltriethoxysilane and di-n-butoxybis(ethoxyacetoacetyl)titanium are added, and the mixture is mixed and stirred for 45 minutes at a vacuum degree of -0.09 MPa to obtain the silicone sealant with low water vapor transmission rate.

[0097] Example 3

[0098] The low water vapor transmission rate organic silicon sealant provided in this embodiment is prepared from the following components in parts by weight:

[0099]

[0100] Among them, the viscosity of α,ω-dihydroxy polydimethylsiloxane at 25°C is 20000mPa.s;

[0101] The preparation method of silane-modified polyolefin is as follows:

[0102] According to the molar ratio of hydroxy-terminated polybutadiene (Polybd CS-15 from ARCO, with a molecular weight of 2800 g / mol-3600 g / mol, and a ratio of a, b and c of 6:2:2) and isocyanate propyl triethoxysilane of 1:1.5, isocyanate propyl triethoxysilane is slowly added dropwise to the hydroxy-terminated polybutadiene, and 0.3% of the total mass of the hydroxy-terminated polybutadiene and isocyanate propyl triethoxysilane as a catalyst dibutyltin dilaurate is added, and the reaction is stirred at 60°C under nitrogen protection for about 5 hours (until the reaction is stopped after no isocyanate group is found in the system by back titration of di-n-butylamine), to obtain silane-modified polybutadiene.

[0103] The preparation of intercalated mica is the same as in Example 1.

[0104] The preparation method of the low water vapor transmission rate organic silicon sealant provided in this embodiment is as follows:

[0105] The α,ω-dihydroxypolydimethylsiloxane, silane-modified polybutadiene and intercalated mica are dehydrated and mixed for 120 minutes at a temperature of 110°C and a vacuum degree of -0.09MPa; after cooling to 45°C, methyltrimethoxysilane, γ-aminopropyltrimethoxysilane and diisopropoxybis(ethoxyacetoacetyl)titanium are added, and the mixture is mixed and stirred for 30 minutes at a vacuum degree of -0.085MPa to obtain the silicone sealant with low water vapor permeability.

[0106] Example 4

[0107] The low water vapor transmission rate organic silicon sealant provided in this embodiment is prepared from the following components in parts by weight:

[0108]

[0109] Among them, the viscosity of α,ω-dihydroxy polydimethylsiloxane at 25°C is 10000mPa.s;

[0110] The preparation method of silane-modified polyolefin is as follows:

[0111] According to the molar ratio of hydroxy-terminated polybutadiene (Polybd CN-15 from ARCO, with a molecular weight of 3300 g / mol-4400 g / mol, and a ratio of a, b and c of 6:2:2) and isocyanatepropyltrimethoxysilane of 1:2, isocyanatepropyltrimethoxysilane is slowly added dropwise to the hydroxy-terminated polybutadiene, and 0.07% of the catalyst dibutyltin dilaurate based on the total mass of the hydroxy-terminated polybutadiene and isocyanatepropyltrimethoxysilane is added, and the reaction is stirred at 60°C under nitrogen protection for about 5 hours (until the reaction is stopped after the absence of isocyanate groups in the system is measured by back titration of di-n-butylamine), to obtain silane-modified polybutadiene.

[0112] The preparation method of intercalated mica is as follows: sericite is placed in a muffle furnace, activated at 850°C for 2h, and then the activated mica is soaked in a nitric acid solution with a concentration of 5mol / L, reacted at 95°C for 4h, then washed with distilled water until neutral, and dried at 70°C. The acid-activated mica is soaked in a saturated sodium chloride solution and treated at 80°C for 4h, then washed with distilled water at 80°C to remove excess sodium chloride, and dried at 70°C. The mica treated with acid and salt is then soaked in an aqueous solution of hexadecyltrimethylammonium bromide with a concentration of 40%wt, reacted at 90°C for 24h for intercalation treatment, then washed with distilled water at 80°C to remove residual hexadecyltrimethylammonium bromide, and dried at 60°C to obtain intercalated mica.

[0113] The preparation method of the low water vapor transmission rate organic silicon sealant provided in this embodiment is as follows:

[0114] The α,ω-dihydroxypolydimethylsiloxane, silane-modified polybutadiene, nano-calcium carbonate and intercalated mica are dehydrated and mixed for 120 minutes at a temperature of 110° C. and a vacuum degree of -0.095 MPa; after cooling to 50° C., methyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane and tetraisopropyl titanate are added, and the mixture is mixed and stirred for 30 minutes at a vacuum degree of -0.085 MPa to obtain the low water vapor permeability silicone sealant.

[0115] Example 5

[0116] The low water vapor transmission rate organic silicon sealant provided in this embodiment is prepared from the following components in parts by weight:

[0117]

[0118]

[0119] Among them, the viscosity of α,ω-dihydroxy polydimethylsiloxane at 25°C is 50000mPa.s;

[0120] The preparation method of silane-modified polybutadiene is as follows:

[0121] According to the molar ratio of hydroxy-terminated polybutadiene (Polybd R-15M from Sinclair Research Inc., with a molecular weight of 2700 g / mol-3300 g / mol and a ratio of a, b and c of 6:2:2) and isocyanatepropyltrimethoxysilane of 1:2, isocyanatepropyltrimethoxysilane is slowly added dropwise to the hydroxy-terminated polybutadiene, and 0.09% of the catalyst dibutyltin dilaurate based on the total mass of the hydroxy-terminated polybutadiene and isocyanatepropyltrimethoxysilane is added, and the reaction is stirred at 66°C under nitrogen protection for about 5 hours (until the reaction is stopped after no isocyanate group is found in the system by back titration of di-n-butylamine), to obtain silane-modified polybutadiene.

[0122] The preparation of intercalated mica is the same as in Example 1.

[0123] The preparation method of the low water vapor transmission rate organic silicon sealant provided in this embodiment is as follows:

[0124] The α,ω-dihydroxypolydimethylsiloxane, silane-modified polybutadiene, nano-calcium carbonate and intercalated mica are dehydrated and mixed for 120 minutes at a temperature of 100°C and a vacuum degree of -0.09MPa; after cooling to 45°C, methyltrimethoxysilane, γ-aminopropyltrimethoxysilane and diisopropoxybis(ethoxyacetoacetyl)titanium are added, and the mixture is mixed and stirred for 20 minutes at a vacuum degree of -0.09MPa to obtain the silicone sealant with low water vapor transmission rate.

[0125] Comparative Example 1

[0126] The difference between the organic silicone sealant provided in this comparative example and Example 1 is that the silane-modified polybutadiene in its preparation raw material is replaced by an equal amount of dimethyl silicone oil with a viscosity of 350 cps, and the other components and preparation method are the same as those in Example 1.

[0127] Comparative Example 2

[0128] The difference between the organosilicon sealant provided in this comparative example and Example 1 is that the intercalated mica is replaced by an equal amount of nano-calcium carbonate (i.e., the total amount of nano-calcium carbonate is 49 parts) in its preparation raw materials, and the other components and preparation method are the same as those in Example 1.

[0129] Comparative Example 3

[0130] The difference between the silicone sealant provided in this comparative example and Example 1 is that the silane-modified polybutadiene in its preparation raw materials is replaced by an equal amount of dimethyl silicone oil with a viscosity of 350 cps, and the intercalated mica is replaced by an equal amount of nano-calcium carbonate (i.e., the total amount of nano-calcium carbonate is 49 parts), and the other components and preparation method are the same as those in Example 1.

[0131] Comparative Example 4

[0132] The difference between the organic silicone sealant provided in this comparative example and Example 1 is that the silane-modified polybutadiene in its preparation raw material is replaced by an equal amount of terminal hydroxyl polybutadiene (Evonik HT, molecular weight is 2900g / mol, the ratio of a, b and c is 5.8:2.2:2), and the other components and preparation method are the same as those in Example 1.

[0133] Comparative Example 5

[0134] The difference between the organosilicon sealant provided in this comparative example and Example 1 is that the intercalated mica in its preparation raw material is replaced by an equal amount of sericite mica, and the other components and preparation method are the same as those in Example 1.

[0135] The following performance tests were performed on the low water vapor transmission rate silicone sealants prepared in Examples 1-5 and Comparative Examples 1-5:

[0136] Tensile strength: Tested according to GB / T 528 method.

[0137] Shear strength: Tested according to GB / T 7124 method.

[0138] Water vapor transmission rate: tested in accordance with GB / T 1037-2021 method.

[0139] The test results are shown in Table 1.

[0140] Table 1 Performance parameters of low water vapor transmission rate silicone sealant

[0141] project Tensile strength / MPa Shear strength / MPa <![CDATA[Water vapor transmission rate g / m 2 ·24h]]> Example 1 2.4 1.8 6.1 Example 2 2.5 1.9 4.7 Example 3 2.1 1.6 4.3 Example 4 2.6 2.0 3.6 Example 5 2.2 1.7 5.5 Comparative Example 1 1.9 1.6 39.3 Comparative Example 2 2.5 1.8 19.4 Comparative Example 3 2.0 1.7 52.6 Comparative Example 4 1.6 1.4 27.8 Comparative Example 5 2.1 1.7 12.5

[0142] It can be seen from the experimental results in Table 1 that the low water vapor permeability organic silicone sealants (Examples 1-5) prepared by using the silane-modified polybutadiene synthesized in the present invention all have relatively high tensile strength, shear strength and relatively low water vapor permeability.

[0143] Comparative Example 1 replaces silane-modified polybutadiene with dimethyl silicone oil with a viscosity of 350cps on the basis of Example 1, and the strength of the obtained silicone sealant is significantly reduced, and the water vapor permeability is also significantly increased, indicating that the silane-modified polybutadiene prepared by the present invention has a significant effect on reducing the water vapor permeability of silicone sealant and can improve the strength of silicone sealant; Comparative Example 2 replaces intercalated mica with an equal amount of nano-calcium carbonate on the basis of Example 1, and the water vapor permeability of the obtained silicone sealant is significantly increased compared with Example 1; Comparative Example 3 further replaces intercalated mica with nano-calcium carbonate on the basis of Comparative Example 1, and becomes a common silicone sealant, and its water vapor permeability is further increased. These results show that the intercalated mica prepared by the present invention can cooperate with silane-modified polybutadiene to have a significant effect on reducing the water vapor permeability of silicone sealant.

[0144] Comparative Example 4 replaces the silane-modified polybutadiene with an equal amount of hydroxy-terminated polybutadiene on the basis of Example 1, and the mechanical properties of the obtained silicone sealant are significantly worse than those of Example 1, and the water vapor transmission rate is also significantly increased. This is because the silane-modified capped polybutadiene can improve the compatibility of the silicone sealant, and thus can more effectively reduce the water vapor transmission rate of the silicone sealant and improve the mechanical properties of the sealant compared to the unmodified polybutadiene.

[0145] Comparative Example 5 replaces the intercalated mica with an equal amount of sericite on the basis of Example 1, and the water vapor permeability of the obtained silicone sealant is significantly increased. This is because sericite has a large size, a low aspect ratio, and different surface polarities. Directly doping mica in silicone sealant will cause agglomeration, affecting the mechanical properties and water vapor barrier properties of the silicone sealant. The present invention obtains intercalated mica with a lamellar structure by thermal activation, acidification, sodiumization, and hexadecyltrimethylammonium bromide intercalation modification of natural sericite, which is beneficial to the combination of mica and silicone sealant, improves the compatibility of the organic-inorganic two phases, thereby making the water vapor permeation path longer, which is beneficial to further reduce the water vapor permeability of the silicone sealant.

[0146] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A low water vapor transmission rate silicone sealant, characterized in that: The composition is prepared from the following raw materials by weight: The silane-modified polybutadiene contains a polymer having a structure shown in formula (I): Wherein, the ratio of a, b and c is 5-7:2-3:2-3, and R is methyl or ethyl.

2. The low water vapor transmission rate organic silicone sealant according to claim 1, characterized in that: The composition is prepared from the following raw materials by weight: Preferably, the low water vapor transmission rate organic silicone sealant is prepared from raw materials including the following components in parts by weight:

3. The low water vapor transmission rate organic silicone sealant according to claim 1 or 2, characterized in that: The silane-modified polybutadiene is obtained by reacting terminal hydroxyl polybutadiene with an isocyanate silane coupling agent; the structural formula of the terminal hydroxyl polybutadiene is: Among them, the ratio of a, b and c is 5-7:2-3:2-3, preferably 5.5-6.5:2-2.5:2-2.5, and more preferably 5.8-6:2-2.2:2-2.

2.

4. The low water vapor transmission rate organic silicone sealant according to claim 3, characterized in that: The molecular weight of the hydroxy-terminated polybutadiene is 2500 mol / g-5000 mol / g, preferably 2500 mol / g-4500 mol / g, more preferably 3300 mol / g-4400 mol / g; and / or, The isocyanate silane coupling agent is isocyanate propyl alkoxy silane, preferably at least one selected from isocyanate propyl trimethoxy silane, isocyanate propyl triethoxy silane and isocyanate propyl methyl dimethoxy silane; and / or, The molar ratio of the terminal hydroxyl polybutadiene to the isocyanate silane coupling agent is 1:1-2, preferably 1:1.5-2, and more preferably 1:1.8-2.

5. The low water vapor transmission rate organic silicone sealant according to claim 3, characterized in that: The preparation method of the silane-modified polybutadiene comprises the following steps: Under the protection of an inert gas, reacting the terminal hydroxyl polybutadiene and the isocyanate silane coupling agent under the action of a catalyst to obtain the silane-modified polybutadiene; Preferably, the catalyst is dibutyltin dilaurate; Preferably, the added amount of the catalyst is 0.05-1% of the total mass of the terminal hydroxyl polybutadiene and the isocyanate silane coupling agent; Preferably, the reaction temperature is 60°C-70°C, and the reaction time is 2h-6h.

6. The low water vapor transmission rate organic silicone sealant according to claim 1 or 2, characterized in that: The preparation method of the intercalated mica comprises the following steps: activating sericite at 750°C-900°C, and then treating it with nitric acid solution, saturated sodium chloride solution and hexadecyltrimethylammonium bromide solution in sequence to obtain the intercalated mica; wherein the temperature for treating with the nitric acid solution is 85°C-100°C, the temperature for treating with the saturated sodium chloride solution is 70°C-90°C, and the temperature for treating with the hexadecyltrimethylammonium bromide solution is 80°C-100°C.

7. The low water vapor transmission rate organic silicon sealant according to claim 6, characterized in that: The concentration of the nitric acid solution is 4 mol / L-6 mol / L; and / or, The mass concentration of the hexadecyltrimethylammonium bromide solution is 20%-60%, preferably 30%-50%; The activation temperature is 800°C-850°C; and / or, The activation time is 1h-3h, preferably 1.5h-2h; and / or, The temperature of the nitric acid solution treatment is 90°C-95°C; and / or, The treatment time with nitric acid solution is 3h-6h, preferably 4h-5h; and / or, The temperature of the treatment with saturated sodium chloride solution is 75°C-85°C; and / or, The treatment time with saturated sodium chloride solution is 3h-5h, preferably 3h-4h; and / or, The temperature of the treatment with the cetyltrimethylammonium bromide solution is 85°C-95°C; and / or, The treatment time with the hexadecyltrimethylammonium bromide solution is 20 h to 28 h, preferably 20 h to 24 h.

8. The low water vapor transmission rate organic silicon sealant according to claim 6, characterized in that: The preparation method of the intercalated mica comprises the following steps: (1) activating sericite at 800° C.-850° C. for 1.5-2 h, reacting with nitric acid solution at 90° C.-95° C. for 4 h-5 h, washing with water until neutral, and drying to obtain acid-activated mica; (2) treating the acid-activated mica in a saturated sodium chloride solution at 75° C.-85° C. for 3 h-4 h, washing with water, and drying to obtain mica treated with acid and salt; (3) reacting the mica treated with the acid and salt in a hexadecyltrimethylammonium bromide solution at 85° C.-95° C. for 20 h-24 h, washing with water, and drying to obtain the intercalated mica; Preferably, the water washing in step (2) is washing with water at 70° C. to 85° C. to remove excess sodium chloride; Preferably, the water washing in step (3) is washing with water at 70° C. to 80° C. to remove residual hexadecyltrimethylammonium bromide; Preferably, the drying temperature is 60°C-70°C.

9. The low water vapor transmission rate organic silicone sealant according to claim 1 or 2, characterized in that: The viscosity of the α,ω-dihydroxy polydimethylsiloxane at 25° C. is 100 mPa.s to 500,000 mPa.s, preferably 10,000 mPa.s to 50,000 mPa.s; and / or, The filler is at least one selected from nano calcium carbonate, heavy calcium carbonate, silicon powder, nano fumed silica, aluminum oxide, aluminum hydroxide, talc, carbon black and mica powder; and / or, The crosslinking agent is selected from at least one of methyltrimethoxysilane, methyltriethoxysilane, methyltriethoxysilane oligomer with a polymerization degree of 2-4, dimethyldimethoxysilane, dimethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, diphenyldimethoxysilane and diphenyldiethoxysilane; and / or, The silane coupling agent is chloropropyl trimethoxysilane, chloropropyl triethoxysilane, γ-aminopropyl trimethoxysilane, γ-aminopropyl triethoxysilane, N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl triethoxysilane, γ-glycidyl ether oxypropyl trimethoxysilane, γ-glycidyl ether oxypropyl triethoxysilane, epoxy cyclohexyl trimethoxysilane, At least one of epoxycyclohexyl triethoxysilane, mercaptopropyl trimethoxysilane, mercaptopropyl triethoxysilane, isocyanate propyl trimethoxysilane, isocyanate propyl triethoxysilane, methacryloxypropyl trimethoxysilane, methacryloxypropyl triethoxysilane, γ-ureidopropyl trimethoxysilane, γ-ureidopropyl triethoxysilane and diethylenetriamine propyl trimethoxysilane; and / or, The catalyst is selected from at least one of tetraisopropyl titanate, tetrabutyl titanate, diisopropoxybis(ethoxyacetoacetyl)titanium, di-n-butoxybis(ethoxyacetoacetyl)titanium and 1,3-dipropoxybis(ethoxyacetoacetyl)titanium.

10. A method for preparing the low water vapor transmission rate organic silicone sealant according to any one of claims 1 to 9, characterized in that: The steps include: The α,ω-dihydroxy polydimethylsiloxane, silane-modified polybutadiene, filler and intercalated mica are mixed and dehydrated for 60min to 120min at a temperature of 100°C to 120°C and a vacuum degree of -0.085MPa to -0.095MPa; after cooling to 40°C to 50°C, the crosslinking agent, coupling agent and catalyst are added, and the mixture is stirred for 20min to 60min at a vacuum degree of -0.085MPa to -0.095MPa to obtain the silicone sealant with low water vapor transmission rate.

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