CN119019977B - Low-temperature tear-resistant organic silicon sealant and preparation method thereof - Google Patents
Low-temperature tear-resistant organic silicon sealant and preparation method thereof Download PDFInfo
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J183/00—Adhesives based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Adhesives based on derivatives of such polymers
- C09J183/04—Polysiloxanes
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- C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
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Abstract
本发明涉及密封胶技术领域，具体涉及一种低温抗撕裂有机硅密封胶及其制备方法。本发明的低温抗撕裂有机硅密封胶包括以下重量份的原料组分：羟基封端聚二甲基硅氧烷100份，改性纳米碳酸钙60‑80份，二甲基硅油15‑20份，交联剂8‑12份，偶联剂3‑5份，催化剂1‑2份；所述改性纳米碳酸钙采用向饱和Ca(OH)2浆液中加入海藻糖和聚乙烯醇进行改性，由此制得的有机硅密封胶具有优异的低温抗撕裂性能。The present invention relates to the technical field of sealants, and in particular to a low-temperature tear-resistant organosilicon sealant and a preparation method thereof. The low-temperature tear-resistant organosilicon sealant of the present invention comprises the following raw material components in parts by weight: 100 parts of hydroxyl-terminated polydimethylsiloxane, 60-80 parts of modified nano-calcium carbonate, 15-20 parts of dimethyl silicone oil, 8-12 parts of a cross-linking agent, 3-5 parts of a coupling agent, and 1-2 parts of a catalyst; the modified nano-calcium carbonate is modified by adding trehalose and polyvinyl alcohol to a saturated Ca(OH) 2 slurry, and the organosilicon sealant prepared thereby has excellent low-temperature tear resistance.
Description
Technical Field
The invention relates to the technical field of sealants, in particular to a low-temperature tear-resistant organic silicon sealant and a preparation method thereof.
Background
The organic silicon sealant is a paste which is prepared by taking polydimethylsiloxane as a main raw material and adding a cross-linking agent, a filler, a plasticizer, a coupling agent and a catalyst to mix in a vacuum state, and is solidified into elastic silicon rubber by reacting with water in air at room temperature.
The low-temperature tear-resistant organic silicon sealant is one of the fastest-growing products in the organic silicon market, and is commonly used as a single-component room temperature vulcanized silicone Rubber (RTV) and has the main characteristics of excellent weather resistance and convenience in construction. Therefore, RTV is widely used in civil construction, electronic and electric appliances, vehicle transportation, aircraft and ships, machinery, chemical industry, light industry, and the like.
However, the traditional low-temperature anti-tearing organosilicon sealant is easy to harden and become brittle in a low-temperature environment, particularly below-50 ℃, the tearing strength is obviously lower, and the problems of tearing and degumming after use are caused.
Disclosure of Invention
In order to solve the problems, the invention provides a low-temperature tear-resistant organic silicon sealant and a preparation method thereof.
The invention provides a low-temperature tear-resistant organic silicon sealant which comprises, by weight, 100 parts of hydroxyl-terminated polydimethylsiloxane, 60-80 parts of modified nano calcium carbonate, 15-20 parts of polylactic acid, 10-15 parts of simethicone, 8-12 parts of a cross-linking agent, 3-5 parts of a coupling agent and 1-2 parts of a catalyst;
The preparation method of the modified nano calcium carbonate comprises the following steps of adding trehalose into saturated Ca (OH) 2 slurry, stirring uniformly, then introducing CO 2 gas and saturated Ca (OH) 2 slurry for mixing and carbonizing, heating to 80-85 ℃ when the pH value of the system is 9+/-0.2, adding polyvinyl alcohol, cooling while continuing to introduce CO 2 gas for mixing after uniform dispersion, stopping introducing CO 2 gas when the pH value of the system is 7.5+/-0.2, preparing modified CaCO 3 slurry, and carrying out filter pressing, drying and crushing on the modified CaCO 3 slurry to obtain the modified nano calcium carbonate.
The organic silicon sealant is compounded by adopting the hydroxyl-terminated polydimethylsiloxane, the specific modified nano calcium carbonate, the polylactic acid and other additives strictly according to the set quantity, wherein the modified nano calcium carbonate is compounded and modified by trehalose and polyvinyl alcohol and has more side chain groups, the groups can enable the nano calcium carbonate to be uniformly dispersed in the hydroxyl-terminated polydimethylsiloxane to participate in crosslinking reaction and also form a bonding network structure with the polylactic acid, the formed network structure can still keep in good condition under the low-temperature environment due to the existence of the trehalose, the nano calcium carbonate and the polylactic acid can cooperatively reinforce the organic silicon sealant under the low-temperature environment, and the characteristics of small viscosity and good compatibility of the dimethyl silicone oil are utilized, so that the added set quantity of the dimethyl silicone oil can be well dispersed in gaps of the network structure to prevent the modified nano calcium carbonate and the polylactic acid from agglomerating, and the prepared organic silicon sealant has excellent low-temperature tear resistance;
The modified nano calcium carbonate is prepared by adding a set amount of trehalose into saturated Ca (OH) 2 slurry, wherein the molecular structure of the trehalose contains rich hydroxyl groups, and the polar groups and water molecules form hydrogen bonds, so that a large amount of water can be combined to initially promote nucleation;
In addition, the side chain groups in the trehalose molecular structure can also form hydrogen bonds with calcium carbonate, so that trehalose can be uniformly adsorbed on the surface of the calcium carbonate, the polar groups of the polyvinyl alcohol can promote the trehalose to be rapidly dispersed and attached to the surface of the calcium carbonate modified by the trehalose, and then the compatibility and the adhesiveness of the polyvinyl alcohol and the polymer are utilized to promote the calcium carbonate to be uniformly and stably dispersed in the sealant base material, so that the crosslinking effect of the sealant base material and the calcium carbonate is effectively improved. In addition, the trehalose is firstly added and then the modification step of the polyvinyl alcohol is added, so that on one hand, compared with polysaccharide such as chitosan and other molecular structures, the trehalose is smaller, the nucleation promotion efficiency is high, the nucleation can be continuously promoted while the adhesion of the surface of the calcium carbonate is realized, and on the other hand, the entanglement and crosslinking effect of the added molecular chain of the polyvinyl alcohol enable the surface of the calcium carbonate to realize better coating and modification and promote dispersion, so that the modified calcium carbonate with smaller particle size and better dispersibility can be obtained. Because the two modified raw material types of the nano calcium carbonate do not contain Na < + > and other metal ions, the obtained modified nano calcium carbonate does not contain Na < + > and other metal ions, and the content of Na < + > and other metal ions in the sealant can be effectively reduced so as to ensure the mechanical property of the sealant.
Preferably, the trehalose is added in an amount of 5-8% by weight of the saturated Ca (OH) 2 slurry.
Preferably, the polyvinyl alcohol is added in an amount of 3 to 6% by weight of the saturated Ca (OH) 2 slurry.
Preferably, the weight ratio of trehalose to polyvinyl alcohol is 3:2.
According to the technical scheme, if the consumption of the trehalose and the polyvinyl alcohol is too large, the obtained modified nano calcium carbonate has certain water absorption due to the increase of polar groups, and the waterproof property of the sealant is influenced to a certain extent, and if the consumption of the trehalose and the polyvinyl alcohol is too small, the obtained modified nano calcium carbonate is difficult to stably crosslink the hydroxyl-terminated polydimethylsiloxane and the polylactic acid, so that the consumption of the trehalose and the polyvinyl alcohol needs to be further controlled to ensure the excellent effect of the invention, and the consumption is further preferable.
Preferably, the weight ratio of the modified nano calcium carbonate to the polylactic acid to the dimethyl silicone oil is 72:18:12.
By adopting the technical scheme, the modified nano calcium carbonate, the polylactic acid and the dimethyl silicone oil are key components for realizing low-temperature tearing resistance of the sealant, and a large number of experiments prove that the change of the dosage of the modified nano calcium carbonate, the polylactic acid and the dimethyl silicone oil has great influence on the performance of the organic silicon sealant, and when the organic silicon sealant is configured according to the weight ratio of 72:18:12, the obtained organic silicon sealant has more excellent low-temperature tearing resistance, so that the organic silicon sealant is further preferable.
Preferably, the hydroxyl-terminated polydimethylsiloxane is prepared by mixing alpha, omega-dihydroxypolydimethylsiloxane with viscosity of 10000-50000 mPas at 25 ℃ and alpha, omega-dihydroxypolydimethylsiloxane with viscosity of 500000-1000000 mPas at 25 ℃ according to the weight ratio of 75-80:25-20.
Preferably, the hydroxyl-terminated polydimethylsiloxane is prepared by mixing alpha, omega-dihydroxypolydimethylsiloxane with the viscosity of 20000 mPas at 25 ℃ and alpha, omega-dihydroxypolydimethylsiloxane with the viscosity of 600000 mPas at 25 ℃ according to the weight ratio of 4:1.
By adopting the technical scheme, the hydroxyl-terminated polydimethylsiloxane is compounded by adopting a low-viscosity type and a high-viscosity type in a specific proportion, wherein the low-viscosity type can be uniformly and rapidly dispersed with the modified nano calcium carbonate and the polylactic acid to finish primary crosslinking, the high-viscosity type is used as a framework to be inserted into the low-viscosity type, and the fluidity of the low-viscosity type is utilized to finish further crosslinking, so that the obtained sealant has higher low-temperature tear resistance.
Preferably, the method also comprises 10-15 parts of gas-phase white carbon black.
Preferably, the weight ratio of the gas-phase white carbon black to the modified nano calcium carbonate is 1:6.
By adopting the technical scheme, the organic silicon sealant provided by the invention can further increase the crosslinking effect of the sealant by adding the set amount of the fumed silica and the modified nano calcium carbonate to be matched with each other, so that the obtained sealant has more excellent low-temperature tear resistance, and in addition, the white carbon black has larger specific surface area and surface activity, can absorb ultraviolet rays to a certain extent, and further can improve the ultraviolet oxidation resistance of the sealant by being mutually matched with trehalose in the modified nano calcium carbonate.
In a second aspect, the invention provides a method for preparing a low-temperature tear-resistant organosilicon sealant, comprising the following steps:
Dividing a set amount of modified nano calcium carbonate into two parts, taking one part of modified nano calcium carbonate, firstly mixing the modified nano calcium carbonate with a set amount of hydroxyl-terminated polydimethylsiloxane and polylactic acid for 30min under the conditions of 160-170 ℃ and-0.06-0.09 MPa of vacuum degree, then taking the other part of modified nano calcium carbonate, adding, continuing to blend for 60-80min, and cooling to obtain a base material;
Mixing the base material with a preset amount of simethicone, a cross-linking agent, a coupling agent and a catalyst, and stirring and reacting for 60-120min under the condition that the vacuum degree is minus 0.08 to minus 0.09MPa to obtain the low-temperature tearing-resistant organic silicon sealant.
When the organic silicon sealant is prepared, the modified nano calcium carbonate is mixed with the hydroxy-terminated dimethyl siloxane twice, and compared with the one-time addition, the dispersing efficiency of the multi-time mixing is higher, the multi-time crosslinking of the hydroxy-terminated dimethyl siloxane is more facilitated, the crosslinking effect of the sealant is improved, and the low-temperature tear resistance of the sealant is further improved.
In a third aspect, the present invention provides another method for preparing a low temperature tear resistant silicone sealant, comprising the steps of:
Dividing a set amount of modified nano calcium carbonate into two parts, taking one part of modified nano calcium carbonate, firstly mixing the modified nano calcium carbonate with a set amount of hydroxyl-terminated polydimethylsiloxane and polylactic acid for 30min under the conditions of 160-170 ℃ and-0.06-0.09 MPa of vacuum degree, then taking the other part of modified nano calcium carbonate and gas-phase white carbon black, adding, continuously mixing for 60-80min, and cooling to obtain a base material;
Mixing the base material with a preset amount of simethicone, a cross-linking agent, a coupling agent and a catalyst, and stirring and reacting for 60-120min under the condition that the vacuum degree is minus 0.08 to minus 0.09MPa to obtain the low-temperature tearing-resistant organic silicon sealant.
According to the invention, the gas-phase white carbon black is added together when the modified nano calcium carbonate is added for the second time, the hydroxyl end-sealing polydimethylsiloxane is subjected to primary crosslinking, and trehalose in the modified nano calcium carbonate can promote the uniform dispersion of the gas-phase white carbon black to a certain extent, so that more excellent organosilicon sealant can be obtained.
In summary, the invention has the following beneficial effects:
1. the organic silicon sealant is compounded by adopting the hydroxyl-terminated polydimethylsiloxane, the specific modified nano calcium carbonate, the polylactic acid and other additives strictly according to the set quantity, wherein the modified nano calcium carbonate does not contain Na < + > and other metal ions, the modified nano calcium carbonate and the polylactic acid can cooperatively reinforce the organic silicon sealant in a low-temperature environment, and then the organic silicon sealant is lubricated by matching with the set quantity of simethicone, so that the low-temperature tear resistance of the organic silicon sealant can be effectively improved.
2. According to the invention, the dosage of trehalose and polyvinyl alcohol is strictly controlled, so that the modified nano calcium carbonate which has little influence on the waterproof property of the sealant and has excellent crosslinking effect is obtained.
3. The hydroxyl-terminated polydimethylsiloxane in the organic silicon sealant is compounded by adopting a low-viscosity type and a high-viscosity type with a specific proportion, so that the crosslinking effect of the hydroxyl-terminated polydimethylsiloxane, modified nano calcium carbonate and polylactic acid is further improved, and the obtained sealant has higher low-temperature tear resistance.
4. According to the organic silicon sealant, the gas-phase white carbon black with a set amount is added, so that the organic silicon sealant can be synergistic with modified nano calcium carbonate, the crosslinking density of the sealant can be further increased, the low-temperature tear resistance performance can be improved, and the ultraviolet oxidation resistance performance of the sealant can be improved.
5. When the organic silicon sealant is prepared, the modified nano calcium carbonate is mixed with the hydroxy-terminated polydimethylsiloxane twice, so that the hydroxy-terminated polydimethylsiloxane is more conducive to realizing step-by-step crosslinking, the crosslinking effect of the sealant is improved, and the low-temperature tear resistance of the sealant is further improved.
Detailed Description
The following detailed description of the present invention will provide further details in order to make the above-mentioned objects, features and advantages of the present invention more comprehensible. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the invention, whereby the invention is not limited to the specific embodiments disclosed below.
Examples of preparation of starting materials and/or intermediates
The hydroxyl-terminated polydimethylsiloxane, the raw material for preparing the modified nano calcium carbonate, the dimethyl silicone oil, the cross-linking agent, the coupling agent, the catalyst and the gas-phase white carbon black are all commercial products.
Wherein, the hydroxyl end-capped polydimethylsiloxane is alpha, omega-dihydroxy polydimethylsiloxane, and more preferably is a mixture formed by compounding low-viscosity alpha, omega-dihydroxy polydimethylsiloxane (viscosity is 10000-50000 mPa.s at 25 ℃) and high-viscosity alpha, omega-dihydroxy polydimethylsiloxane (viscosity is 500000-1000000 mPa.s at 25 ℃) according to the weight ratio of 100 (20-30).
The polylactic acid adopts 800-mesh polylactic acid powder, the content of active ingredients is 99 percent, and the molecular weight is 10 ten thousand.
The dimethyl silicone oil can be 201 methyl silicone oil, and the viscosity of the dimethyl silicone oil is 100-500 mPa.s at 25 ℃. The dimethyl silicone oil can endow the low-temperature anti-tearing organic silicon sealant with better low-temperature flexibility, namely, the low-temperature anti-tearing organic silicon sealant is not easy to crack at low temperature.
The cross-linking agent can be selected from one or more of methyl tributyl ketoxime silane, phenyl tributyl ketoxime silane, vinyl tributyl ketoxime silane, methyl triacetonexime silane and vinyl triacetonexime silane, which is helpful for maintaining the flexibility and tear resistance of the low-temperature tear-resistant organic silicon sealant system at low temperature.
The coupling agent can be at least one of KH-550 and KH-560, which can further modify nano-calcium carbonate and the combination of polylactic acid and hydroxyl-terminated polydimethylsiloxane, so as to enhance the overall performance of the organosilicon sealant.
The catalyst can be at least one of dioctyltin dilaurate, stannous octoate and tin di Ding Yixian acetonate.
The fumed silica is specifically purchased from fumed hydrophobic silica with the model number of TH-8150, and has a better dispersing effect.
The trehalose is a product with CAS number of 99-20-7, and the content of effective substances is more than or equal to 98%.
The chitosan is prepared from products with CAS number of 9012-76-4, and the content of effective substances is more than or equal to 99%.
PVA 17-92 powder is used as polyvinyl alcohol, and the dissolution temperature is 75-80 ℃.
The present invention will be described in further detail with reference to examples and comparative examples.
Examples
Example 1
The preparation method of the low-temperature tear-resistant organic silicon sealant comprises the following steps:
(1) Preparation of modified nano calcium carbonate (1 kg of saturated Ca (OH) 2 slurry is taken as an example)
Weighing 1kg of saturated Ca (OH) 2 slurry, putting the slurry into an emulsifying and dispersing machine, adding 60g of trehalose into the saturated Ca (OH) 2 slurry, stirring uniformly, then introducing CO 2 gas and the saturated Ca (OH) 2 slurry for mixing and carbonizing, heating to 85 ℃ when the pH value of the system is 9 (fluctuation is allowed in the range of +/-0.2), adding 40g of polyvinyl alcohol for dispersing uniformly, continuously introducing CO 2 gas while cooling for mixing and emulsifying, and stopping introducing CO 2 gas when the temperature of the system is reduced to room temperature and the pH value is 7.5 (fluctuation is allowed in the range of +/-0.2) to prepare modified CaCO 3 slurry;
(2) Preparation of the base Material
Weighing 720g of modified nano calcium carbonate into two parts, wherein each part is 360g, taking one part of modified nano calcium carbonate, firstly mixing the one part of modified nano calcium carbonate with 1000g of hydroxyl-terminated polydimethylsiloxane (which is formed by mixing alpha, omega-dihydroxypolydimethylsiloxane with the viscosity of 20000 mPas at 25 ℃ and alpha, omega-dihydroxypolydimethylsiloxane with the viscosity of 600000 mPas at 25 ℃ according to the weight ratio of 4:1), and then taking another part of modified nano calcium carbonate, adding the other part of modified nano calcium carbonate, continuously mixing for 70min, and cooling to obtain a base material;
(3) Preparation of sealant
And (3) adding 120g of simethicone, 100g of methyltributylketon oxime silane, 40g of coupling agent (which is formed by mixing KH-550 and KH-560 according to the weight ratio of 1:1) and 15g of dioctyltin dilaurate into a planetary mixer for mixing, stirring and reacting for 100min under the condition of vacuum degree of-0.09 MPa, and stirring at the speed of 500rpm to obtain the low-temperature tear-resistant organosilicon sealant.
Examples 2 to 6
Examples 2-6 are based on the method of example 1, and the amounts of modified nano calcium carbonate, simethicone, cross-linking agent, coupling agent and catalyst in the silicone sealant component and the process parameters of the silicone sealant are adjusted, with specific adjustment conditions being shown in the following table.
Table 1-6 component amounts and Process parameter Table of Silicone sealants of examples
Examples 7 to 12
Examples 7-12 are based on the method of example 1, wherein the amount of the raw material of the modified nano calcium carbonate in the silicone sealant component is adjusted, and the specific adjustment is shown in the following table two.
Table II raw materials Meter (g) for modified nano calcium carbonate of examples 1, 7-12
Examples 13 to 17
Examples 13-17 are adjustments to the hydroxyl terminated polydimethyl siloxane in the silicone sealant component based on the method of example 1. Wherein,
The hydroxyl-terminated polydimethylsiloxane of example 13 was prepared by mixing α, ω -dihydroxypolydimethylsiloxane having a viscosity of 20000 mPas at 25℃and α, ω -dihydroxypolydimethylsiloxane having a viscosity of 600000 mPas at 25℃in a weight ratio of 3:1;
The hydroxyl-terminated polydimethylsiloxane of example 14 was prepared by mixing α, ω -dihydroxypolydimethylsiloxane having a viscosity of 20000 mPas at 25℃and α, ω -dihydroxypolydimethylsiloxane having a viscosity of 600000 mPas at 25℃in a weight ratio of 78:22;
The hydroxyl-terminated polydimethylsiloxane of example 15 was prepared by mixing an alpha, omega-dihydroxy polydimethylsiloxane having a viscosity of 30000 mPas at 25℃and an alpha, omega-dihydroxy polydimethylsiloxane having a viscosity of 700000 mPas at 25℃in a weight ratio of 4:1;
the hydroxyl-terminated polydimethylsiloxane of example 16 was prepared by mixing α, ω -dihydroxypolydimethylsiloxane having a viscosity of 40000 mPas at 25℃and α, ω -dihydroxypolydimethylsiloxane having a viscosity of 600000 mPas at 25℃in a weight ratio of 4:1;
The hydroxyl-terminated polydimethylsiloxane of example 17 was prepared by mixing an alpha, omega-dihydroxypolydimethylsiloxane having a viscosity of 10000 mPas at 25℃and an alpha, omega-dihydroxypolydimethylsiloxane having a viscosity of 1000000 mPas at 25℃in a weight ratio of 4:1.
Examples 18 to 20
Examples 18-20 are based on the method of example 1, the silicone sealant composition further comprising fumed silica. The preparation method of the embodiment comprises the following steps:
(1) Preparation of modified nano calcium carbonate the same preparation method as in example 1;
(2) Preparation of the base Material
Weighing 720g of modified nano calcium carbonate into two parts, wherein each part is 360g, taking one part of modified nano calcium carbonate, firstly mixing the one part of modified nano calcium carbonate with 1000g of hydroxyl-terminated polydimethylsiloxane (which is formed by mixing alpha, omega-dihydroxypolydimethylsiloxane with the viscosity of 20000 mPas at 25 ℃ and alpha, omega-dihydroxypolydimethylsiloxane with the viscosity of 600000 mPas at 25 ℃ according to the weight ratio of 4:1), and then blending 180g of polylactic acid for 30min under the conditions of the temperature of 165 ℃ and the vacuum degree of-0.08 MPa, then taking the other part of modified nano calcium carbonate, adding a set amount of gas-phase white carbon black, continuously blending for 70min, and cooling to obtain a base material;
Wherein, the addition amount of the fumed silica of the embodiment 18 is 100g (i.e. the weight ratio of the fumed silica to the modified nano calcium carbonate is 1:7.2), the addition amount of the fumed silica of the embodiment 19 is 120g (i.e. the weight ratio of the fumed silica to the modified nano calcium carbonate is 1:6), and the addition amount of the fumed silica of the embodiment 20 is 150g (i.e. the weight ratio of the fumed silica to the modified nano calcium carbonate is 1:4.8);
(3) And (3) preparing the sealant, wherein the preparation method is the same as that of the embodiment 1, and the low-temperature tearing-resistant organic silicon sealant is obtained.
Example 21
The preparation method of the low-temperature tear-resistant organic silicon sealant comprises the following steps:
(1) Preparation of modified nano calcium carbonate the same preparation method as in example 1;
(2) Preparation of the base Material
Weighing 720g of modified nano calcium carbonate and 1000g of hydroxyl-terminated polydimethylsiloxane (which is prepared by mixing alpha, omega-dihydroxypolydimethylsiloxane with the viscosity of 20000 mPas at 25 ℃ and alpha, omega-dihydroxypolydimethylsiloxane with the viscosity of 600000 mPas at 25 ℃ according to the weight ratio of 4:1), blending 180g of polylactic acid for 100min at the temperature of 165 ℃ and the vacuum degree of-0.08 MPa, and cooling to obtain a base material;
(3) And (3) preparing the sealant, wherein the preparation method is the same as that of the embodiment 1, and the low-temperature tearing-resistant organic silicon sealant is obtained.
Example 22
The preparation method of the low-temperature tear-resistant organic silicon sealant comprises the following steps:
(1) Preparation of modified nano calcium carbonate the same preparation method as in example 1;
(2) Preparation of the base Material
Weighing 720g of modified nano calcium carbonate, 180g of polylactic acid, 120g of gas-phase white carbon black and 1000g of hydroxyl-terminated polydimethylsiloxane (which is formed by mixing alpha, omega-dihydroxypolydimethylsiloxane with the viscosity of 20000 mPas at 25 ℃ and alpha, omega-dihydroxypolydimethylsiloxane with the viscosity of 600000 mPas at 25 ℃ according to the weight ratio of 4:1), blending for 100min at the temperature of 165 ℃ and the vacuum degree of-0.08 MPa, and cooling to obtain a base material;
(3) And (3) preparing the sealant, wherein the preparation method is the same as that of the embodiment 1, and the low-temperature tearing-resistant organic silicon sealant is obtained.
Comparative example
Comparative example 1
This comparative example was based on the procedure of example 1, substituting modified nano calcium carbonate with commercially available activated nano calcium carbonate with CAS number 471-34-1.
Comparative example 2
The comparative example replaces modified nano calcium carbonate with other existing modified nano calcium carbonate based on the method of example 1, and the specific modification steps comprise the following steps:
Uniformly mixing n-butyl titanate and a silane coupling agent KH-960 in a weight ratio of 1:1 to obtain a composite modifier, adding the composite modifier into active nano calcium carbonate with CAS number of 471-34-1 sold in the market for mixing, wherein the addition amount of the composite modifier is 2% of the total weight of the modified nano calcium carbonate, heating to 150 ℃ for reaction for 6 hours, and carrying out surface wrapping treatment to obtain the modified nano calcium carbonate.
Comparative example 3
In this comparative example, polylactic acid was not added in the method of example 1.
Comparative example 4
This comparative example uses chitosan in the same amount as trehalose in the preparation of modified nano calcium carbonate based on the method of example 1.
Performance test
The silicone sealants prepared in examples 1 to 22 and comparative examples 1 to 3 of the present invention were placed in an ultraviolet test box and irradiated with water for 300 hours under immersion, the power of an ultraviolet lamp tube was 300W, the lamp tube was 250mm from the test piece, the ultraviolet radiation intensity was 3000. Mu.W/cm 2, the water temperature was 40.+ -. 5 ℃ and the surface water was wiped off after the immersion irradiation was completed, and then the following performance test was conducted, and the test results were shown in Table III below. The 'immersion illumination' is used for increasing the test difficulty of a sample, and is based on further verifying whether the modified nano calcium carbonate provided by the invention can influence the performance of the sealant after being modified by trehalose.
(1) Tear strength test-test according to ASTM D624, type C test specimens are used.
(2) The low temperature flexibility test was carried out according to GB/T13477 part seven.
Table III Table of the results of the detection of the Silicone sealants of examples 1 to 22 and comparative examples 1 to 3
Referring to Table III, compared with comparative examples 1-4, the silicone sealants prepared in examples 1-22 of the present invention still had excellent tear strength and low temperature flexibility at-50℃and-70℃after immersion and UV irradiation, and still maintained higher tear strength and more excellent low temperature flexibility at-90℃and thus it was found that the silicone sealants of the present invention had excellent low temperature tear resistance, water resistance and UV aging resistance. In addition, the modified nano calcium carbonate disclosed by the invention adopts a trehalose modification mode, and has more excellent tearing strength and low-temperature flexibility under a low-temperature condition compared with other modified nano calcium carbonate (comprising the modified nano calcium carbonate prepared by replacing trehalose with chitosan in an equivalent manner).
By comparing the detection results of the examples 1-6, it can be obtained that when the modified nano calcium carbonate, the polylactic acid and the simethicone are configured according to the weight ratio of 72:18:12, the obtained organosilicon sealant has more excellent low-temperature tear resistance, and is further preferable. In addition, when the organosilicon sealant is prepared, the organosilicon sealant with more excellent performance can be obtained when the blending temperature of the hydroxyl-terminated polydimethylsiloxane, the modified nano calcium carbonate and the polylactic acid is 160-170 ℃, and the polylactic acid particles at the temperature are in a softened state, so that the polylactic acid particles can better participate in the crosslinking reaction of the modified nano calcium carbonate and the hydroxyl-terminated polydimethylsiloxane, and a more compact network structure can be obtained.
By comparing the detection results of the embodiment 1 with the detection results of the embodiment 7-12, it can be obtained that in the organic silicon sealant of the invention, when preparing the modified nano calcium carbonate, the addition amount of trehalose and polyvinyl alcohol can influence the effect of the modified nano calcium carbonate on the organic silicon sealant. Wherein, when the addition amount of trehalose is 5-8% of the weight of saturated Ca (OH) 2 slurry and the addition amount of polyvinyl alcohol is 3-6% of the weight of saturated Ca (OH) 2 slurry, the obtained modified nano calcium carbonate has more excellent tearing strength and low-temperature flexibility at-50 ℃ and-70 ℃ corresponding to the prepared organosilicon sealant, and in addition, when the weight ratio of trehalose to polyvinyl alcohol is 3:2, the organosilicon sealant can still maintain excellent tearing strength and low-temperature flexibility at-90 ℃, so that the organosilicon sealant is further preferable.
As can be seen from the results of the test conducted in examples 1 and 13 to 17, in the silicone sealant of the present invention, the hydroxyl-terminated polydimethylsiloxane has excellent tear strength and low temperature flexibility at-50 ℃, -70 ℃ and-90 ℃ when mixed with alpha, omega-dihydroxy polydimethylsiloxane having a viscosity of 10000 to 50000 mPas at 25 ℃ and alpha, omega-dihydroxy polydimethylsiloxane having a viscosity of 500000 to 1000000 mPas at 25 ℃ in a weight ratio of 75 to 80:25 to 20.
Comparing the test results of examples 1 and 13-17, it can be seen that the specific type of the hydroxy-terminated polydimethylsiloxane in the present invention also affects the performance of the silicone sealant, and when the low-viscosity hydroxy-terminated polydimethylsiloxane (abbreviated as low-viscosity type) and the high-viscosity hydroxy-terminated polydimethylsiloxane (abbreviated as high-viscosity type) are used in combination, the higher the amount of the low-viscosity type, the higher the tear strength of the silicone sealant obtained at a relatively high temperature, and the better the retention effect of the tear strength at a low temperature, and in addition, the higher the selected viscosities of the low-viscosity type and the high-viscosity type, the poorer the retention effect of the tear strength of the silicone sealant obtained at a low temperature. The present invention is further preferably a hydroxyl-terminated polydimethylsiloxane prepared by mixing an α, ω -dihydroxypolydimethylsiloxane having a viscosity of 20000 mPas at 25℃and an α, ω -dihydroxypolydimethylsiloxane having a viscosity of 600000 mPas at 25℃in a weight ratio of 4:1.
By combining the detection results of the embodiment 1 and the embodiment 18-20, the organic silicon sealant of the invention is additionally added with a set amount of gas-phase white carbon black, which can be matched with modified nano calcium carbonate, so that the crosslinking density of the sealant is further improved, and the obtained sealant has more excellent low-temperature tear resistance. Among them, when the weight ratio of fumed silica to modified nano calcium carbonate is 1:6 (example 19), the effect of the obtained silicone sealant is significantly better than the other (examples 18 and 20), so that it is further preferable.
Comparing the detection results of the embodiment 1 and the embodiment 21, the invention can obtain that when the organic silicon sealant is prepared, the modified nano calcium carbonate is mixed with the hydroxy-end-seal dimethyl siloxane twice, and compared with the one-time addition, the invention has higher dispersion efficiency of the multi-time mixing, is more beneficial to realizing step cross-linking of the hydroxy-end-seal dimethyl siloxane, improves the cross-linking effect of the sealant, and further improves the low-temperature tear resistance of the sealant after soaking and illumination.
By comparing the detection results of the embodiment 19 and the embodiment 22, the invention can obtain more excellent organic silicon sealant by adding the gas-phase white carbon black together with the modified nano calcium carbonate added for the second time on the basis of adding the gas-phase white carbon black, wherein the hydroxyl end-sealing polydimethylsiloxane is subjected to primary crosslinking, and trehalose in the modified nano calcium carbonate can promote the uniform dispersion of the gas-phase white carbon black to a certain extent.
The present embodiment is only for explanation of the present invention and is not to be construed as limiting the present invention, and modifications to the present embodiment, which may not creatively contribute to the present invention as required by those skilled in the art after reading the present specification, are all protected by patent laws within the scope of claims of the present invention.
Claims (7)
1. The low-temperature tear-resistant organic silicon sealant is characterized by comprising the following raw materials, by weight, 100 parts of hydroxyl-terminated polydimethylsiloxane, 60-80 parts of modified nano calcium carbonate, 15-20 parts of polylactic acid, 10-15 parts of simethicone, 8-12 parts of a cross-linking agent, 3-5 parts of a coupling agent and 1-2 parts of a catalyst;
Adding trehalose into saturated Ca (OH) 2 slurry, stirring uniformly, then introducing CO 2 gas and saturated Ca (OH) 2 slurry for mixing and carbonizing, heating to 80-85 ℃ when the pH value of the system is 9+/-0.2, adding polyvinyl alcohol, cooling while continuing to introduce CO 2 gas for mixing after uniform dispersion, and stopping introducing CO 2 gas when the pH value of the system is 7.5+/-0.2 to obtain modified CaCO 3 slurry, and performing filter pressing, drying and crushing on the modified CaCO 3 slurry to obtain the modified nano calcium carbonate;
The addition amount of the trehalose is 5-8% of the weight of the saturated Ca (OH) 2 slurry, and the addition amount of the polyvinyl alcohol is 3-6% of the weight of the saturated Ca (OH) 2 slurry;
the hydroxyl-terminated polydimethylsiloxane is prepared by mixing alpha, omega-dihydroxyl polydimethylsiloxane with viscosity of 10000-50000 mPas at 25 ℃ and alpha, omega-dihydroxyl polydimethylsiloxane with viscosity of 500000-1000000 mPas at 25 ℃ according to the weight ratio of 75-80:25-20.
2. The low temperature tear resistant silicone sealant according to claim 1, wherein the weight ratio of trehalose to polyvinyl alcohol is 3:2.
3. The low-temperature tear-resistant organosilicon sealant according to claim 1, wherein the weight ratio of the modified nano calcium carbonate to the polylactic acid to the simethicone is 72:18:12.
4. The low temperature tear resistant silicone sealant of claim 1 further comprising 10-15 parts fumed silica.
5. The low temperature tear resistant silicone sealant of claim 4 wherein the weight ratio of fumed silica to modified nano calcium carbonate is 1:6.
6. A method for preparing the low-temperature tear-resistant organosilicon sealant according to any one of claims 1 to 3, which comprises the following steps:
Dividing a set amount of modified nano calcium carbonate into two parts, taking one part of modified nano calcium carbonate, firstly mixing the modified nano calcium carbonate with a set amount of hydroxyl-terminated polydimethylsiloxane and polylactic acid for 30min under the conditions of 160-170 ℃ and-0.06-0.09 MPa of vacuum degree, then taking the other part of modified nano calcium carbonate, adding, continuing to blend for 60-80min, and cooling to obtain a base material;
Mixing the base material with a preset amount of simethicone, a cross-linking agent, a coupling agent and a catalyst, and stirring and reacting for 60-120min under the condition that the vacuum degree is minus 0.08 to minus 0.09MPa to obtain the low-temperature tearing-resistant organic silicon sealant.
7. The method for preparing the low-temperature tear-resistant organosilicon sealant according to claim 6, comprising the following steps:
Dividing a set amount of modified nano calcium carbonate into two parts, taking one part of modified nano calcium carbonate, firstly mixing the modified nano calcium carbonate with a set amount of hydroxyl-terminated polydimethylsiloxane and polylactic acid for 30min under the conditions of 160-170 ℃ and-0.06-0.09 MPa of vacuum degree, then taking the other part of modified nano calcium carbonate and gas-phase white carbon black, adding, continuously mixing for 60-80min, and cooling to obtain a base material;
Mixing the base material with a preset amount of simethicone, a cross-linking agent, a coupling agent and a catalyst, and stirring and reacting for 60-120min under the condition that the vacuum degree is minus 0.08 to minus 0.09MPa to obtain the low-temperature tearing-resistant organic silicon sealant.
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