Modified calcium carbonate filler for silicone sealant, silicone sealant with high extrudability and low sag, and preparation method thereof

Abstract

This invention provides a modified calcium carbonate filler for silicone sealants, a silicone sealant with high extrudability and low sag, and a method for preparing the same. The modified calcium carbonate filler for silicone sealants comprises the following components in parts by weight: 100 parts calcium carbonate, 0.3-2.5 parts polyhydroxystearic acid, 2.5-4 parts stearic acid, and 0.3-2 parts aluminate coupling agent. By using a polyhydroxystearic acid compound combined with an aluminate coupling agent to partially replace stearic acid as a surface modifier for nano-calcium carbonate, the resulting silicone sealant exhibits excellent tensile strength and elongation at break while maintaining both high extrudability and low sag.

Description

Technical Field

[0001] This invention belongs to the field of silicone sealant technology, specifically relating to a modified calcium carbonate filler for silicone sealant, a silicone sealant with high extrudability and low sag, and its preparation method. Background Technology

[0002] Silicone sealant, as an important building sealing material, is widely used in interior decoration fields such as sealing building joints, glass installation, and waterproofing of kitchens and bathrooms due to its excellent weather resistance, elastic recovery rate, and displacement capacity. Silicone sealant not only needs good mechanical properties and durability but also excellent workability. In interior decoration construction, especially when applying sealant to vertical and ceiling joints, the sealant needs to have low sag (anti-flow properties) to prevent it from falling off the joint and ensure construction quality. To reduce construction intensity, the sealant also needs high extrudability to facilitate smooth extrusion from the caulking gun. Furthermore, to cope with the numerous adhesive sealing scenarios in interior decoration construction, the sealant also needs good tensile adhesion and elongation.

[0003] Currently available silicone sealants suffer from the following problems: high extrudability sealants typically have low viscosity and severe sagging, while high thixotropic sealants are often difficult to extrude, resulting in a poor application experience; high extrudability and high thixotropy are incompatible. Furthermore, because high thixotropic sealant formulations usually contain a large amount of calcium carbonate filler, they can easily lead to a decrease in the sealant's tensile strength and elongation, causing cracking and seal failure during interior application. Therefore, existing silicone sealants cannot simultaneously satisfy the requirements of high extrudability, low sagging, good tensile adhesion, and elongation.

[0004] Adding fillers can adjust the thixotropic properties of silicone sealants, and calcium carbonate is one of the most commonly used fillers in silicone sealants. Chinese patent document CN112694864B discloses silicone sealants, their preparation methods, and photovoltaic modules, including α,ω-dihydroxypolydimethylsiloxane, calcium carbonate filler, polycarboxylate superplasticizer, crosslinking agent, coupling agent, and catalyst. However, ordinary calcium carbonate has drawbacks such as poor dispersibility and weak compatibility with organic polymers; direct filling can lead to interfacial defects, affecting the mechanical properties and stability of the sealant. To improve the compatibility of calcium carbonate with silicone polymers, surface modification becomes a necessary step. However, current traditional modifiers have limited effectiveness in adjusting the rheological behavior of silicone sealants, making it difficult to simultaneously achieve high extrudability, low sag, and good tensile adhesion and elongation. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a modified calcium carbonate filler for silicone sealant, a silicone sealant with high extrudability and low sag, and a method for preparing the same. The invention uses a polyhydroxy stearic acid compound compounded with an aluminate coupling agent to partially replace stearic acid as a surface modifier for nano-calcium carbonate. The resulting silicone sealant has excellent tensile strength and elongation at break while maintaining high extrudability and low sag.

[0006] To address the aforementioned problems, a first aspect of the present invention provides a modified calcium carbonate filler for silicone sealants, the raw materials for which comprise the following components in parts by weight: 100 parts calcium carbonate, 0.3-2.5 parts polyhydroxystearic acid, 2.5-4 parts stearic acid, and 0.3-2 parts aluminate coupling agent.

[0007] Preferably, the raw materials for its preparation include the following components in parts by mass: 100 parts calcium carbonate, 0.5-2.1 parts polyhydroxystearic acid, 2-3.5 parts stearic acid, and 0.5-1.5 parts aluminate coupling agent.

[0008] Preferably, the polyhydroxystearic acid is 9,10-dihydroxystearic acid; The aluminate coupling agent is isopropyl distearate aluminate; The calcium carbonate particles have a diameter of 40~100nm.

[0009] A second aspect of the present invention provides a method for preparing the modified calcium carbonate filler for silicone sealant described above, comprising the following steps: Calcium carbonate, polyhydroxystearic acid, stearic acid, and aluminate coupling agent are mixed and stirred at 90-120°C for 1-3 hours to obtain the modified calcium carbonate filler for silicone sealant.

[0010] Preferably, it further includes: Before mixing calcium carbonate, polyhydroxystearic acid, stearic acid, and aluminate coupling agent, the calcium carbonate is dried at 120-140°C for 1-3 hours. After stirring, the mixed powder is washed with ethanol, then dried and sieved to obtain the modified calcium carbonate filler for silicone sealant.

[0011] A third aspect of this invention provides a highly extrudable, low-sagging silicone sealant, the raw materials of which comprise the following components in parts by weight: 70-120 parts of α,ω-dihydroxypolydimethylsiloxane, 5-15 parts of methyl silicone oil, 100 parts of modified calcium carbonate filler for the above-mentioned silicone sealant, 5-12 parts of crosslinking agent, 1-3 parts of silane coupling agent, and 0.02-0.2 parts of catalyst.

[0012] Preferably, the raw materials for its preparation include the following components in parts by mass: 80-100 parts of α,ω-dihydroxypolydimethylsiloxane, 7.5-15 parts of methyl silicone oil, 100 parts of modified calcium carbonate filler, 7-9 parts of crosslinking agent, 2-2.5 parts of silane coupling agent, and 0.05-0.15 parts of catalyst.

[0013] Preferably, the crosslinking agent is one or a combination of several of methyl tributanone oxime silane, vinyl tributanone oxime silane, phenyl tributanone oxime silane, and tetrabutanone oxime silane; The silane coupling agent is one or a combination of several of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane. The catalyst is one or a combination of several of dibutyltin dilaurate and dibutyltin diacetate.

[0014] Preferably, the viscosity of α,ω-dihydroxypolydimethylsiloxane is 30,000~80,000 mPa·s; and the viscosity of methyl silicone oil is 100 m~350 mPa·s.

[0015] A fourth aspect of the present invention provides a method for preparing the above-mentioned high extrudability and low sag silicone sealant, comprising the following steps: S1. Mix α,ω-dihydroxypolydimethylsiloxane, methyl silicone oil, and modified calcium carbonate filler according to the formula ratio, and stir for 30~40 min to obtain a premix; S2. Mix the crosslinking agent, silane coupling agent, catalyst and premix according to the formula, and stir for 30~50min to obtain the high extrudability and low sag silicone sealant.

[0016] Compared with the prior art, the present invention has the following advantages: The modified calcium carbonate filler for silicone sealants of this invention uses a polyhydroxy stearic acid compound combined with an aluminate coupling agent to partially replace stearic acid as a surface modifier for calcium carbonate. After modification, the carboxyl groups of the polyhydroxy stearic acid form chemical bonds with calcium ions on the surface of calcium carbonate. Thus, the multipolar groups of the polyhydroxy stearic acid allow reversible hydrogen bonds to form on the surface of the nano-calcium carbonate. Therefore, when this modified calcium carbonate is added to the silicone sealant as a filler, the sealant exhibits lower sag. Simultaneously, the aluminate coupling agent reacts well with the hydrophilic groups on the surface of the nano-calcium carbonate, reducing surface polarity while enhancing crosslinking with the polymer, thereby improving the tensile adhesion of the sealant. Furthermore, by appropriately increasing the amount of dimethyl silicone oil added, and synergistically modifying the powder, the silicone sealant of this invention achieves high extrudability while maintaining mechanical strength and adhesion performance. Therefore, the silicone sealant possesses high extrudability, low sag, and good tensile adhesion and elongation. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] A first aspect of this invention provides a modified calcium carbonate filler for silicone sealants, the raw materials for which comprise the following components in parts by weight: 100 parts calcium carbonate, 0.3-2.5 parts polyhydroxystearic acid, 2.5-4 parts stearic acid, and 0.3-2 parts aluminate coupling agent.

[0019] The modified calcium carbonate filler for silicone sealant in this invention uses a polyhydroxy stearic acid compound combined with an aluminate coupling agent to partially replace stearic acid as a surface modifier for calcium carbonate. After modification, the carboxyl groups of the polyhydroxy stearic acid form chemical bonds with calcium ions on the surface of calcium carbonate. Thus, the multipolar groups of the polyhydroxy stearic acid allow reversible hydrogen bonds to form on the surface of the nano-calcium carbonate. Therefore, when this modified calcium carbonate is added to the silicone sealant as a filler, the sealant exhibits lower sag. Simultaneously, the aluminate coupling agent reacts well with the hydrophilic groups on the surface of the nano-calcium carbonate, reducing surface polarity while enhancing crosslinking with the polymer, thereby improving the tensile adhesion of the sealant. Furthermore, by appropriately increasing the amount of dimethyl silicone oil added and synergistically modifying the powder, the silicone sealant of this invention achieves high extrudability while maintaining mechanical strength and adhesion performance. Therefore, the silicone sealant possesses high extrudability, low sag, and good tensile adhesion and elongation.

[0020] Preferably, the raw materials for its preparation include the following components in parts by mass: 100 parts calcium carbonate, 0.5-2.1 parts polyhydroxystearic acid, 2-3.5 parts stearic acid, and 0.5-1.5 parts aluminate coupling agent.

[0021] By using the above-mentioned preferred mass fractions as filler, the silicone sealant can have higher extrudability, lower sag, and better tensile adhesion and elongation.

[0022] Preferably, the polyhydroxystearic acid is 9,10-dihydroxystearic acid.

[0023] Preferably, the aluminate coupling agent is isopropyl distearate aluminate.

[0024] The calcium carbonate has a particle size of 40~100nm. Specifically, the nano calcium carbonate is Wuhu Xinda New Materials XD-CA series calcium carbonate, and the particle size can be one or a mixture of several of the following: 40~80nm, 60~80nm, and 80~100nm.

[0025] A second aspect of this invention provides a method for preparing the modified calcium carbonate filler for silicone sealant described above, comprising the following steps: Calcium carbonate, polyhydroxystearic acid, stearic acid, and aluminate coupling agent are mixed and stirred at 90-120°C for 1-3 hours to obtain the modified calcium carbonate filler for silicone sealant.

[0026] Preferably, it further includes: Before mixing calcium carbonate, polyhydroxystearic acid, stearic acid, and aluminate coupling agent, the calcium carbonate is dried at 120-140°C for 1-3 hours. After stirring, the mixed powder is washed with ethanol, then dried and sieved to obtain the modified calcium carbonate filler for silicone sealant.

[0027] A third aspect of this invention provides a highly extrudable, low-sagging silicone sealant, the raw materials of which comprise the following components in parts by weight: 70-120 parts of α,ω-dihydroxypolydimethylsiloxane, 5-15 parts of methyl silicone oil, 100 parts of modified calcium carbonate filler for the above-mentioned silicone sealant, 5-12 parts of crosslinking agent, 1-3 parts of silane coupling agent, and 0.02-0.2 parts of catalyst.

[0028] The high extrudability and low sag silicone sealant of this invention, compared with traditional silicone sealants, exhibits excellent tensile strength and elongation at break while maintaining high extrudability and low sag. Compared with ordinary formulations using a single surface modifier to modify calcium carbonate, this formulation has good extrudability while maintaining high tensile bond strength and maximum elongation at break, under the premise of low vertical sag.

[0029] Preferably, the raw materials for its preparation include the following components in parts by mass: 80-100 parts of α,ω-dihydroxypolydimethylsiloxane, 7.5-15 parts of methyl silicone oil, 100 parts of modified calcium carbonate filler, 7-9 parts of crosslinking agent, 2-2.5 parts of silane coupling agent, and 0.05-0.15 parts of catalyst.

[0030] By using the above-mentioned preferred mass fraction range, the silicone sealant can have higher extrudability, lower sag, and better tensile adhesion and elongation.

[0031] Preferably, the crosslinking agent is one or a combination of several of methyltributanone oxime silane, vinyltributanone oxime silane, phenyltributanone oxime silane, and tetrabutanone oxime silane.

[0032] Preferably, the silane coupling agent is one or a combination of several of γ-aminopropyltriethoxysilane (KH-550), γ-glycidoxypropyltrimethoxysilane (KH-560), and γ-methacryloyloxypropyltrimethoxysilane (KH-570).

[0033] Preferably, the catalyst is one or a combination of several of dibutyltin dilaurate and dibutyltin diacetate.

[0034] Preferably, the viscosity of α,ω-dihydroxypolydimethylsiloxane is 30,000~80,000 mPa·s; more preferably, the viscosity of α,ω-dihydroxypolydimethylsiloxane is 50,000 mPa·s.

[0035] Preferably, the viscosity of the methyl silicone oil is 100 m~350 mPa·s; more preferably, the viscosity of the methyl silicone oil is 350 mPa·s.

[0036] A fourth aspect of this invention provides a method for preparing the above-mentioned high extrudability, low sag silicone sealant, comprising the following steps: S1. Mix α,ω-dihydroxypolydimethylsiloxane, methyl silicone oil, and modified calcium carbonate filler according to the formula ratio, and stir for 30~40 min to obtain a premix; S2. Mix the crosslinking agent, silane coupling agent, catalyst and premix according to the formula, and stir for 30~50min to obtain the high extrudability and low sag silicone sealant.

[0037] Example 1 The modified calcium carbonate filler for the silicone sealant in this embodiment is prepared from the following components in parts by weight: 100 parts of nano-calcium carbonate with a particle size of 60-80 nm, 0.5 parts of 9,10-dihydroxystearic acid, 3 parts of stearic acid, and 0.5 parts of isopropyl distearate aluminate.

[0038] The preparation method of modified calcium carbonate filler for silicone sealant in this embodiment is as follows: Nano-calcium carbonate powder is placed in an oven at 130℃ and dried for 2 hours; then, the dried calcium carbonate powder, 9,10-dihydroxystearic acid, stearic acid, and isopropyl distearate aluminate are placed in a three-necked flask, heated and stirred in a water bath at 1000 rpm for 2 hours at a modification temperature of 90℃. After washing with hot ethanol, the mixture is dried and sieved to obtain modified nano-calcium carbonate.

[0039] The high extrudability and low sag silicone sealant of this embodiment is prepared by means of the following components in parts by weight: 80 parts of α,ω-dihydroxypolydimethylsiloxane with a viscosity of 50000 mPa·s, 15 parts of methyl silicone oil with a viscosity of 350 mPa·s, 100 parts of modified calcium carbonate filler, 2.5 parts of methyl tributanone oxime silane, 2.5 parts of vinyl tributanone oxime silane, 2 parts of tetrabutylone oxime silane, 1 part of KH-550, 1 part of KH-560, 0.2 parts of KH570, and 0.05 parts of dibutyltin diacetate.

[0040] The preparation method of the high extrudability and low sag silicone sealant in this embodiment is as follows: 1. Take α,ω-dihydroxypolydimethylsiloxane, methyl silicone oil, and modified calcium carbonate according to the specified ratio and put them into a planetary mixer. Mix for 30 minutes to obtain a premix. 2. Add the crosslinking agent, silane coupling agent, catalyst and premix to a planetary mixer according to the formula, and mix for 40 min under a vacuum of -0.095 MPa to obtain the high extrudability and low sag silicone sealant.

[0041] Example 2 The modified calcium carbonate filler for the silicone sealant in this embodiment is prepared from the following components in parts by weight: 100 parts of nano-calcium carbonate with a particle size of 60-80 nm, 1 part of 9,10-dihydroxystearic acid, 2.5 parts of stearic acid, and 0.5 parts of isopropyl distearyloxyaluminate.

[0042] The preparation method of modified calcium carbonate filler for silicone sealant in this embodiment is as follows: Nano-calcium carbonate powder is placed in an oven at 130℃ and dried for 2 hours; then, the dried calcium carbonate powder, 9,10-dihydroxystearic acid, stearic acid, and isopropyl distearate aluminate are placed in a three-necked flask, heated and stirred in a water bath at 1200 rpm, with a modification temperature of 100℃ and a modification time of 1 hour. After washing with hot ethanol, the mixture is dried and sieved to obtain modified nano-calcium carbonate.

[0043] The high extrudability and low sag silicone sealant of this embodiment is prepared by means of the following components in parts by weight: 90 parts of α,ω-dihydroxypolydimethylsiloxane with a viscosity of 50000 mPa·s, 10 parts of methyl silicone oil with a viscosity of 350 mPa·s, 100 parts of modified calcium carbonate filler, 2.5 parts of methyl tributanone oxime silane, 2.5 parts of vinyl tributanone oxime silane, 2.5 parts of tetrabutylone oxime silane, 1.5 parts of KH-550, 0.5 parts of KH-560, and 0.1 parts of dibutyltin dilaurate.

[0044] The preparation method of the high extrudability and low sag silicone sealant in this embodiment is as follows: 1. Take α,ω-dihydroxypolydimethylsiloxane, methyl silicone oil, and modified calcium carbonate according to the specified ratio and put them into a planetary mixer. Mix for 30 minutes to obtain a premix. 2. Add the crosslinking agent, silane coupling agent, catalyst and premix to a planetary mixer according to the formula, and mix for 40 min under a vacuum of -0.095 MPa to obtain the high extrudability and low sag silicone sealant.

[0045] Example 3 The modified calcium carbonate filler for the silicone sealant in this embodiment is prepared from the following components in parts by weight: 100 parts of nano-calcium carbonate with a particle size of 60-80 nm, 1 part of 9,10-dihydroxystearic acid, 2 parts of stearic acid, and 1.5 parts of isopropyl distearyloxyaluminate.

[0046] The preparation method of modified calcium carbonate filler for silicone sealant in this embodiment is as follows: Nano-calcium carbonate powder is placed in an oven at 130℃ and dried for 2 hours; then, the dried calcium carbonate powder, 9,10-dihydroxystearic acid, stearic acid, and isopropyl distearate aluminate are placed in a three-necked flask, heated and stirred in a water bath at 1500 rpm for 3 hours at a modification temperature of 120℃. After washing with hot ethanol, the mixture is dried and sieved to obtain modified nano-calcium carbonate.

[0047] The high extrudability and low sag silicone sealant of this embodiment is prepared by means of the following components in parts by weight: 95 parts of α,ω-dihydroxypolydimethylsiloxane with a viscosity of 50000 mPa·s, 10 parts of methyl silicone oil with a viscosity of 350 mPa·s, 100 parts of modified calcium carbonate filler, 3 parts of methyl tributanone oxime silane, 2 parts of vinyl tributanone oxime silane, 2.5 parts of tetrabutylone oxime silane, 1 part of KH-550, 0.5 parts of KH-560, 0.5 parts of KH-570, 0.05 parts of dibutyltin dilaurate, and 0.05 parts of dibutyltin diacetate.

[0048] The preparation method of the high extrudability and low sag silicone sealant in this embodiment is as follows: 1. Take α,ω-dihydroxypolydimethylsiloxane, methyl silicone oil, and modified calcium carbonate according to the specified ratio and put them into a planetary mixer. Mix for 30 minutes to obtain a premix. 2. Add the crosslinking agent, silane coupling agent, catalyst and premix to a planetary mixer according to the formula, and mix for 40 min under a vacuum of -0.095 MPa to obtain the high extrudability and low sag silicone sealant.

[0049] Example 4 The modified calcium carbonate filler for the silicone sealant in this embodiment is prepared from the following components in parts by weight: 100 parts of nano-calcium carbonate with a particle size of 60-80 nm, 0.5 parts of 9,10-dihydroxystearic acid, 3 parts of stearic acid, and 1 part of isopropyl distearate aluminate.

[0050] The preparation method of modified calcium carbonate filler for silicone sealant in this embodiment is as follows: Nano-calcium carbonate powder is placed in an oven at 130℃ and dried for 2 hours; then, the dried calcium carbonate powder, 9,10-dihydroxystearic acid, stearic acid, and isopropyl distearate aluminate are placed in a three-necked flask, heated and stirred in a water bath at 1200 rpm for 2.5 hours at a modification temperature of 100℃. After washing with hot ethanol, the mixture is dried and sieved to obtain modified nano-calcium carbonate.

[0051] The high extrudability and low sag silicone sealant of this embodiment is prepared by means of the following components in parts by weight: 100 parts of α,ω-dihydroxypolydimethylsiloxane with a viscosity of 50000 mPa·s, 12.5 parts of methyl silicone oil with a viscosity of 350 mPa·s, 100 parts of modified calcium carbonate filler, 3 parts of methyl tributanone oxime silane, 2.5 parts of vinyl tributanone oxime silane, 3 parts of tetrabutylone oxime silane, 1.5 parts of KH-550, 0.2 parts of KH-560, 0.5 parts of KH-570, 0.1 parts of dibutyltin dilaurate, and 0.05 parts of dibutyltin diacetate.

[0052] The preparation method of the high extrudability and low sag silicone sealant in this embodiment is as follows: 1. Take α,ω-dihydroxypolydimethylsiloxane, methyl silicone oil, and modified calcium carbonate according to the specified ratio and put them into a planetary mixer. Mix for 30 minutes to obtain a premix. 2. Add the crosslinking agent, silane coupling agent, catalyst and premix to a planetary mixer according to the formula, and mix for 40 min under a vacuum of -0.095 MPa to obtain the high extrudability and low sag silicone sealant.

[0053] Example 5 The modified calcium carbonate filler for the silicone sealant in this embodiment is prepared from the following components in parts by weight: 100 parts of nano-calcium carbonate with a particle size of 60-80 nm, 1.5 parts of 9,10-dihydroxystearic acid, 3.5 parts of stearic acid, and 1 part of isopropyl distearate aluminate.

[0054] The preparation method of modified calcium carbonate filler for silicone sealant in this embodiment is as follows: Nano-calcium carbonate powder is placed in an oven at 130℃ and dried for 2 hours; then, the dried calcium carbonate powder, 9,10-dihydroxystearic acid, stearic acid, and isopropyl distearate aluminate are placed in a three-necked flask, heated and stirred in a water bath at 1200 rpm, with a modification temperature of 110℃ and a modification time of 1.5 hours. After washing with hot ethanol, it is dried and sieved to obtain modified nano-calcium carbonate.

[0055] The high extrudability and low sag silicone sealant of this embodiment is prepared by means of the following components in parts by weight: 90 parts of α,ω-dihydroxypolydimethylsiloxane with a viscosity of 50000 mPa·s, 15 parts of methyl silicone oil with a viscosity of 350 mPa·s, 100 parts of modified calcium carbonate filler, 4 parts of methyl tributanone oxime silane, 2 parts of vinyl tributanone oxime silane, 3 parts of tetrabutylone oxime silane, 2 parts of KH-550, 0.5 parts of KH-560, and 0.15 parts of dibutyltin dilaurate.

[0056] The preparation method of the high extrudability and low sag silicone sealant in this embodiment is as follows: 1. Take α,ω-dihydroxypolydimethylsiloxane, methyl silicone oil, and modified calcium carbonate according to the specified ratio and put them into a planetary mixer. Mix for 30 minutes to obtain a premix. 2. Add the crosslinking agent, silane coupling agent, catalyst and premix to a planetary mixer according to the formula, and mix for 40 min under a vacuum of -0.095 MPa to obtain the high extrudability and low sag silicone sealant.

[0057] Example 6 The modified calcium carbonate filler for the silicone sealant in this embodiment is prepared from the following components in parts by weight: 100 parts of nano-calcium carbonate with a particle size of 60-80 nm, 2.1 parts of 9,10-dihydroxystearic acid, 3 parts of stearic acid, and 0.5 parts of isopropyl distearyloxyaluminate.

[0058] The preparation method of the modified calcium carbonate filler for the silicone sealant in this embodiment is the same as that in Example 1.

[0059] The high extrudability and low sag silicone sealant of this embodiment is prepared by means of the following components in parts by weight: 90 parts of α,ω-dihydroxypolydimethylsiloxane with a viscosity of 50000 mPa·s, 7.5 parts of methyl silicone oil with a viscosity of 350 mPa·s, 100 parts of modified calcium carbonate filler, 2.5 parts of methyl tributanone oxime silane, 2.5 parts of vinyl tributanone oxime silane, 2.5 parts of tetrabutylone oxime silane, 1 part of KH-550, 1 part of KH-560, 0.2 parts of KH-570, and 0.05 parts of dibutyltin dilaurate.

[0060] The preparation method of the high extrudability and low sag silicone sealant in this embodiment is the same as that in Example 1.

[0061] Example 7 The modified calcium carbonate filler for the silicone sealant in this embodiment is prepared from the following components in parts by weight: 100 parts of nano-calcium carbonate with a particle size of 60-80 nm, 0.3 parts of 9,10-dihydroxystearic acid, 4 parts of stearic acid, and 0.3 parts of isopropyl distearate aluminate.

[0062] The preparation method of the modified calcium carbonate filler for the silicone sealant in this embodiment is the same as that in Example 1.

[0063] The high extrudability and low sag silicone sealant of this embodiment is prepared by means of the following components in parts by weight: 70 parts of α,ω-dihydroxypolydimethylsiloxane with a viscosity of 50000 mPa·s, 15 parts of methyl silicone oil with a viscosity of 350 mPa·s, 100 parts of modified calcium carbonate filler, 2 parts of methyl tributanone oxime silane, 2 parts of vinyl tributanone oxime silane, 1 part of tetrabutylone oxime silane, 1.5 parts of KH-550, 1 part of KH-560, 0.5 parts of KH-570, 0.01 parts of dibutyltin dilaurate, and 0.01 parts of dibutyltin diacetate.

[0064] The preparation method of the high extrudability and low sag silicone sealant in this embodiment is the same as that in Example 1.

[0065] Example 8 The modified calcium carbonate filler for the silicone sealant in this embodiment is prepared from the following components in parts by weight: 100 parts of nano-calcium carbonate with a particle size of 60-80 nm, 2.5 parts of 9,10-dihydroxystearic acid, 2.5 parts of stearic acid, and 2 parts of isopropyl distearate aluminate.

[0066] The preparation method of the modified calcium carbonate filler for the silicone sealant in this embodiment is the same as that in Example 1.

[0067] The high extrudability and low sag silicone sealant of this embodiment is prepared by means of the following components in parts by weight: 120 parts of α,ω-dihydroxypolydimethylsiloxane with a viscosity of 50000 mPa·s, 5 parts of methyl silicone oil with a viscosity of 350 mPa·s, 100 parts of modified calcium carbonate filler, 4 parts of methyl tributanone oxime silane, 4 parts of vinyl tributanone oxime silane, 4 parts of tetrabutylone oxime silane, 0.5 parts of KH-550, 0.5 parts of KH-560, 0.1 parts of dibutyltin dilaurate, and 0.1 parts of dibutyltin diacetate.

[0068] The preparation method of the high extrudability and low sag silicone sealant in this embodiment is the same as that in Example 1.

[0069] Comparative Example 1 The modified calcium carbonate filler used in this comparative example of silicone sealant is prepared from the following components in parts by weight: 100 parts of nano-calcium carbonate with a particle size of 60-80 nm, 1.5 parts of 9,10-dihydroxystearic acid, and 2.5 parts of stearic acid.

[0070] The preparation method of the modified calcium carbonate filler for the silicone sealant in this comparative example is the same as that in Example 2.

[0071] The difference between the modified calcium carbonate filler used in this comparative example of silicone sealant and Example 2 is that isopropyl distearate was not added.

[0072] The high extrudability and low sag silicone sealant of this comparative example uses the same raw materials and preparation method as in Example 2.

[0073] Comparative Example 2 The modified calcium carbonate filler used in this comparative example of silicone sealant is prepared from the following components in parts by weight: 100 parts of nano-calcium carbonate with a particle size of 60~80nm, 2 parts of stearic acid, and 2 parts of isopropyl distearate aluminate.

[0074] The preparation method of the modified calcium carbonate filler for the silicone sealant in this comparative example is the same as that in Example 3.

[0075] The difference between the modified calcium carbonate filler used in this comparative example of silicone sealant and Example 3 is that 9,10-dihydroxystearic acid was not added.

[0076] The high extrudability and low sag silicone sealant of this comparative example uses the same raw materials and preparation method as in Example 3.

[0077] Comparative Example 3 In this comparative example, the raw materials for preparing the modified calcium carbonate filler for silicone sealant and the high extrudability low sag silicone sealant are the same as in Example 4. The difference is that in the preparation of the modified calcium carbonate filler, the modification temperature is 80°C and the modification time is 4 hours.

[0078] Comparative Example 4 In this comparative example, the raw materials and preparation method for the modified calcium carbonate filler used in the silicone sealant are the same as in Example 5. The difference is that the raw materials for the high extrudability and low sag silicone sealant include the following components in parts by mass: 90 parts of α,ω-dihydroxypolydimethylsiloxane with a viscosity of 50000 mPa·s, 20 parts of methyl silicone oil with a viscosity of 350 mPa·s, 100 parts of modified calcium carbonate filler, 4 parts of methyl tributanone oxime silane, 2 parts of vinyl tributanone oxime silane, 3 parts of tetrabutylone oxime silane, 2 parts of KH-550, 0.5 parts of KH-560, and 0.15 parts of dibutyltin dilaurate.

[0079] That is, the mass fractions of the remaining components in the high extrudability and low sag silicone sealant are the same as in Example 5, except that the amount of methyl silicone oil is increased to 20 parts.

[0080] For the silicone sealants of the above embodiments and comparative examples, specimens were prepared according to standard GB / T 13477.8-2022. The specimens were cured for 28 days, and tensile adhesion tests were performed. Curing conditions were standard laboratory conditions: temperature (23±2)℃, relative humidity (50±5)%. Vertical and horizontal sag of the samples were tested according to standard GB / T 13477.6-2002, with the oven temperature set to 50±2℃. Extrudability tests were performed according to standard GB / T 13477.3-2017, using an extrusion orifice with a diameter of 4mm under an air pressure of 0.3MPa. Performance comparisons are shown in Table 1.

[0081] Table 1

[0082] As can be seen from the performance data in Table 1, in Comparative Example 1, the modified nano-calcium carbonate did not contain isopropyl distearate, resulting in low extrudability, poor tensile adhesion, and poor elongation of the silicone sealant. In Comparative Example 2, the modified nano-calcium carbonate did not contain 9,10-dihydroxystearic acid, resulting in low extrudability, poor tensile adhesion, and poor elongation of the silicone sealant, as well as high sag. In contrast, the silicone sealants in the embodiments of this application combine high extrudability and low sag while possessing superior tensile strength and elongation.

[0083] Compared with Example 4, the difference in Comparative Example 3 is that the modification temperature was lowered to 80°C in the preparation of the modified calcium carbonate filler. Since the melting point of the modifier is 90°C, the overall activation degree is too low at 80°C, and the modification effect is not obvious.

[0084] Compared with Example 5, Comparative Example 4 differs in that the amount of methyl silicone oil used was increased, exceeding the optimal range for the amount of methyl silicone oil used, which affected the adhesion and led to a decrease in overall performance.

[0085] Examples 1-6 are preferred embodiments, which have higher extrudability, lower sag, and superior tensile strength and elongation.

[0086] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A modified calcium carbonate filler for silicone sealant, characterized in that, Its preparation raw materials include the following components in parts by mass: 100 parts calcium carbonate, 0.3-2.5 parts polyhydroxystearic acid, 2.5-4 parts stearic acid, and 0.3-2 parts aluminate coupling agent.

2. The modified calcium carbonate filler for silicone sealant according to claim 1, characterized in that, Its preparation raw materials include the following components in parts by mass: 100 parts calcium carbonate, 0.5-2.1 parts polyhydroxystearic acid, 2-3.5 parts stearic acid, and 0.5-1.5 parts aluminate coupling agent.

3. The modified calcium carbonate filler for silicone sealant according to claim 1, characterized in that: The polyhydroxystearic acid is 9,10-dihydroxystearic acid; The aluminate coupling agent is isopropyl distearate aluminate; The calcium carbonate particles have a diameter of 40~100nm.

4. A method for preparing a modified calcium carbonate filler for silicone sealant as described in any one of claims 1-3, characterized in that, Includes the following steps: Calcium carbonate, polyhydroxystearic acid, stearic acid, and aluminate coupling agent are mixed and stirred at 90-120°C for 1-3 hours to obtain the modified calcium carbonate filler for silicone sealant.

5. The preparation method according to claim 4, characterized in that, Also includes: Before mixing calcium carbonate, polyhydroxystearic acid, stearic acid, and aluminate coupling agent, the calcium carbonate is dried at 120-140°C for 1-3 hours. After stirring, the mixed powder is washed with ethanol, then dried and sieved to obtain the modified calcium carbonate filler for silicone sealant.

6. A silicone sealant with high extrudability and low sag, characterized in that, Its preparation raw materials include the following components in parts by mass: 70-120 parts of α,ω-dihydroxypolydimethylsiloxane, 5-15 parts of methyl silicone oil, 100 parts of modified calcium carbonate filler for silicone sealant as described in any one of claims 1-3, 5-12 parts of crosslinking agent, 1-3 parts of silane coupling agent, and 0.02-0.2 parts of catalyst.

7. The high extrudability, low sag silicone sealant according to claim 6, characterized in that, Its preparation raw materials include the following components in parts by mass: 80-100 parts of α,ω-dihydroxypolydimethylsiloxane, 7.5-15 parts of methyl silicone oil, 100 parts of modified calcium carbonate filler, 7-9 parts of crosslinking agent, 2-2.5 parts of silane coupling agent, and 0.05-0.15 parts of catalyst.

8. The high extrudability, low sag silicone sealant according to claim 6, characterized in that: The crosslinking agent is one or a combination of several of methyl tributanone oxime silane, vinyl tributanone oxime silane, phenyl tributanone oxime silane, and tetrabutylone oxime silane; The silane coupling agent is one or a combination of several of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane. The catalyst is one or a combination of several of dibutyltin dilaurate and dibutyltin diacetate.

9. The high extrudability, low sag silicone sealant according to claim 6, characterized in that: The viscosity of α,ω-dihydroxy polydimethylsiloxane is 30,000~80,000 mPa·s; the viscosity of methyl silicone oil is 100 m~350 mPa·s.

10. A method for preparing a high extrudability, low sag silicone sealant as described in any one of claims 6-9, characterized in that, Includes the following steps: S1. Mix α,ω-dihydroxypolydimethylsiloxane, methyl silicone oil, and modified calcium carbonate filler according to the formula ratio, and stir for 30~40 min to obtain a premix; S2. Mix the crosslinking agent, silane coupling agent, catalyst and premix according to the formula, and stir for 30~50min to obtain the high extrudability and low sag silicone sealant.

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