Silicone sealant with modified coarse whiting partially replacing nano calcium carbonate and preparation method

Abstract

The invention relates to a silicone sealant with nano calcium carbonate partially replaced by modified heavy calcium carbonate. The silicone sealant comprises the following components: 200 to 500 parts of hydroxyl-terminated polydimethylsiloxane, 300 to 800 parts of nano calcium carbonate, 10 to 250 parts of modified heavy calcium carbonate, 100 to 250 parts of heavy calcium carbonate, 1 to 10 parts of a catalyst, 50 to 200 parts of a plasticizer, 8 to 20 parts of a coupling agent and 25 to 60 parts of a cross-linking agent. In the preparation process, a certain part of modified heavy calcium carbonate is added and the same part of nano calcium carbonate is reduced to be applied to preparation of the sealant, so that the modified heavy calcium carbonate can partially replace the nano calcium carbonate to prepare the silicone sealant under the condition that the mechanical properties such as colloid strength and elongation at break are basically not reduced; the operation process is simple, and the production cost of a glue factory is reduced.

Description

Technical Field

[0001] The invention belongs to the field of organic silicon rubber, and particularly relates to a method for preparing silicone sealant by partially replacing nano calcium carbonate with modified heavy calcium. Background Art

[0002] Silicone sealant is a high-performance sealing material. Its preparation method is to mix the main raw material hydroxyl-terminated polydimethylsiloxane (PDMS-OH) and various auxiliary materials such as cross-linking agent, filler, plasticizer, coupling agent and catalyst evenly and dehydrate them under vacuum to obtain a paste. This sealant solidifies at room temperature by reacting with moisture in the air to eventually form elastic silicone rubber, which has the advantages of strong adhesion, high tensile strength, good weather resistance, moisture resistance and odor resistance, and is widely used in construction, automobiles, electronic appliances and other fields.

[0003] Nano calcium carbonate, as a filler component with an important reinforcing effect in silicone sealants, can significantly improve the adhesion, weather resistance and mechanical performance indicators of silicone sealants, such as elastic modulus and elongation at break, due to its small particle size, high specific surface area and surface energy. Modified heavy calcium carbonate is processed by a specific process on heavy calcium carbonate, and the particle morphology, dispersibility and surface activity are improved. Therefore, it can partially replace the nano calcium carbonate in silicone sealants and can also play a reinforcing role to a certain extent.

[0004] With the continuous development of technology, the formula and application methods of silicone structural sealants are also constantly updated. Under the premise of ensuring that the performance of silicone sealants remains basically unchanged, higher requirements are placed on reducing the cost of sealant production formulas. Summary of the invention

[0005] In order to solve the above-mentioned technical problem of reducing the cost of sealant production formula, the present invention provides a method for preparing silicone sealant by partially replacing nano calcium carbonate with modified heavy calcium.

[0006] The technical solution adopted by the present invention is: A method for preparing a silicone sealant by partially replacing nano calcium carbonate with modified heavy calcium, the silicone sealant contains the following components (by weight): 200-500 parts of hydroxyl-terminated polydimethylsiloxane, 300-800 parts of nano calcium carbonate, 10-250 parts of modified heavy calcium, 100-250 parts of heavy calcium, 1-10 parts of catalyst, 50-200 parts of plasticizer, 8-20 parts of coupling agent, and 25-60 parts of crosslinking agent. Preferably, the viscosity of the hydroxyl-terminated polydimethylsiloxane at 25°C is 20000-100000 mPa·s.

[0007] Preferably, the plasticizer is one of white oil, methylphenyl silicone oil, vinyl silicone oil and dimethyl silicone oil.

[0008] Preferably, the crosslinking agent is at least one of methyl triacetone oxime silane, phenyl triacetone oxime silane, methyl vinyl diacetone oxime silane and dimethyl diacetone oxime silane.

[0009] Preferably, the coupling agent is at least one of KH-550, KH-560, KH-570, and KH-792.

[0010] Preferably, the dosage of the nano calcium carbonate powder is 300-500 parts, the oil absorption value is 22.0-27.0gdop / 100gCaCO3, and the specific surface area is 24-35m2 / g.

[0011] The preparation method of the modified heavy calcium carbonate is as follows: heavy calcium carbonate and water are added into a reaction kettle, stirred to obtain a slurry, stirred and heated, and when the slurry temperature rises to 65-80°C, a modifier is added, and the reaction is carried out for 50-70 minutes at a stirring speed of 800-1000 rad / min. After the reaction is completed, stirring is stopped, and the slurry is filtered, dried, and ground to obtain the modified heavy calcium carbonate.

[0012] In some preferred cases, the preparation method of the modified heavy calcium carbonate is to add water to 800 mesh heavy calcium carbonate to form a slurry with a mass fraction of 50-75%. When the slurry temperature rises to 65-80°C, 1.5%-4% of the modifier (based on the weight of dry basis heavy calcium carbonate powder) is added, and the reaction is stirred at 1000r / min for 50-70min. After the reaction is completed, the slurry is filtered, dried, and ground to obtain the modified heavy calcium carbonate.

[0013] The modifier is at least one of Peg-7 glyceryl cocoate, sodium octadecenoate and distearoyloxyisopropylaluminate, and the dosage ratio of the three modifiers is 0.1-1.0:1.0-1.3.6:1.0-3.7.

[0014] In some embodiments, the modified heavy calcium carbonate is 10-30% by mass of the nano calcium carbonate.

[0015] Another object of the present invention is a method for preparing silicone sealant by partially replacing nano calcium carbonate with modified heavy calcium carbonate, which is prepared by using the above formula, and the steps of the method are as follows: S1: Add the hydroxyl-terminated polydimethylsiloxane, nano calcium carbonate, heavy calcium carbonate and modified heavy calcium carbonate to a kneader, start stirring for 5 minutes, and after the materials are stirred and mixed evenly, heat and evacuate the materials, control the material heating temperature to 100-130° C., and the vacuum degree to -0.09-0.1 MPa. Dehydrate and stir the materials at a high temperature of 100° C. for 90-150 minutes. After the high-temperature dehydration is completed, stop heating, and when the material temperature drops below 40° C., add a plasticizer, stir in a vacuum for 20-40 minutes, and stop stirring to obtain a base rubber; S2: Add the above-mentioned base rubber, crosslinking agent, coupling agent and catalyst with a temperature below 50°C into a planetary mixer. Stir for 3-10 minutes at a stirring speed of 30-50 rad / min, and evacuate until the pressure in the cylinder is less than -0.08 MPa, then stir for 25-40 minutes at a stirring speed of 60-90 rad / min, stop stirring, and quickly discharge the material to obtain a sealant sample.

[0016] The beneficial effects of the present invention are: In the process of preparing silicone sealant, heavy calcium carbonate is activated and modified by using fatty acid and coupling agent modifiers, so that the lipophilicity and hydrophobicity of the modified heavy calcium carbonate and its compatibility with the organic matrix are improved, which is beneficial to improve its processing performance and mechanical properties in sealant applications. Therefore, a certain amount of modified heavy calcium carbonate is added to replace part of the nano calcium carbonate powder as a reinforcing filler, which improves the comprehensive performance and application value of silicone sealant to a certain extent. While ensuring that the mechanical properties such as colloid strength and elongation at break are basically maintained, the production formula cost of silicone sealant can also be reduced. This technical method is simple to operate, and the prepared silicone sealant can be used in the construction industry. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The described embodiments only belong to a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Example 1 According to the weight formula, 422 parts of polydimethylsiloxane with a viscosity of 20000 mPa·s, 682 parts of nano calcium carbonate powder, 34 parts of modified heavy calcium carbonate, and 192 parts of 800 mesh heavy calcium carbonate are added into a kneader, and stirring is started for 5 minutes. After the materials are stirred and mixed evenly, the materials are heated and evacuated, and the heating temperature of the materials is controlled to be 110° C., and the vacuum degree is less than -0.08MPa. The materials are dehydrated and stirred for 120 minutes at a temperature higher than 100° C. After the high-temperature dehydration is completed, the heating is stopped. When the material temperature drops below 40° C., 111 parts of white oil are added, and the materials are stirred at normal pressure for 30 minutes, and the stirring is stopped to obtain a base rubber; The amount of nano calcium carbonate powder is 682 parts, the oil absorption value is 25.3gdop / 100gCaCO3, and the specific surface area is 27.6m 2 / g.

[0019] The preparation method of the modified heavy calcium carbonate is as follows: 1000g of 800-mesh heavy calcium carbonate and 300g of water are added into a reactor to prepare a slurry with a mass fraction of 70%, stirring and heating are started, and when the slurry temperature rises to 75°C, 13g of sodium octadecenoate, 3.6g of Peg-7 glyceryl cocoate and 13.3g of distearyloxyisopropylaluminate and other modifiers are added in sequence, and the reaction is stirred for 60min under the conditions of a stirring speed of 1000rad / min and a reaction temperature of 75°C, and the stirring is stopped. The slurry is filtered, dried and ground to obtain the modified heavy calcium carbonate.

[0020] 940 parts of the base material prepared above were weighed and added into a planetary mixer, and then 21 parts of methyl triacetone oxime silane, 11 parts of methyl vinyl diacetone oxime silane, 10 parts of dimethyl diacetone oxime silane, 8 parts of KH-550 coupling agent, 6 parts of KH-560 coupling agent, and 4 parts of dibutyltin bis(acetylacetonate) were added, stirred at a stirring speed of 40 rad / min for 5 minutes and evacuated until the pressure in the cylinder was less than -0.08 MPa, and then stirred at a stirring speed of 80 rad / min for 30 minutes, stopped stirring, and quickly discharged to obtain a sealant sample.

[0021] Example 2 Based on Example 1, reduce the amount of nano calcium carbonate powder and add the same amount of modified heavy calcium carbonate. The nano calcium carbonate powder is used in 651 parts, the modified heavy calcium is added in 65 parts, and the amount of modified heavy calcium is 10% of the amount of nano calcium carbonate. Others are the same as in Example 1.

[0022] Example 3 Based on Example 1, reduce the amount of nano calcium carbonate powder and add the same amount of modified heavy calcium carbonate. The nano calcium carbonate powder is used in 623 parts, the modified heavy calcium is added in 93 parts, and the amount of modified heavy calcium is 15% of the amount of nano calcium carbonate. Others are the same as in Example 1.

[0023] Example 4 Based on Example 1, reduce the amount of nano calcium carbonate powder and add the same amount of modified heavy calcium carbonate. The nano calcium carbonate powder is used in an amount of 597 parts, and the modified heavy calcium is added in an amount of 119 parts. The amount of modified heavy calcium is 20% of the amount of nano calcium carbonate. Others are the same as in Example 1.

[0024] Example 5 Based on Example 1, reduce the amount of nano calcium carbonate powder and add the same amount of modified heavy calcium carbonate. The nano calcium carbonate powder is used in an amount of 551 parts, and the modified heavy calcium is added in an amount of 165 parts. The amount of modified heavy calcium is 30% of the amount of nano calcium carbonate. Others are the same as in Example 1.

[0025] Example 6 Based on Example 1, reduce the amount of nano calcium carbonate powder and add the same amount of modified heavy calcium carbonate. The nano calcium carbonate powder is used in an amount of 511 parts, and the modified heavy calcium is added in an amount of 205 parts. The amount of modified heavy calcium is 40% of the amount of nano calcium carbonate. Others are the same as in Example 1.

[0026] Example 7 Based on Example 1, reduce the amount of nano calcium carbonate powder and add the same amount of modified heavy calcium carbonate. The nano calcium carbonate powder is used in 477 parts, the modified heavy calcium is added in 239 parts, and the amount of modified heavy calcium is 50% of the amount of nano calcium carbonate. Others are the same as in Example 1.

[0027] Comparative Example 1 A method for preparing silicone sealant by partially replacing nano calcium carbonate with modified heavy calcium comprises the following steps: According to the weight formula, 422 parts of polydimethylsiloxane with a viscosity of 20000 mPa·s, 716 parts of nano calcium carbonate powder, and 192 parts of heavy calcium carbonate are added into a kneader, and stirring is started for 5 minutes. After the materials are stirred and mixed evenly, the materials are heated and evacuated, and the heating temperature of the materials is controlled to be 110° C., and the vacuum degree is less than -0.08MPa. The materials are dehydrated and stirred at a temperature higher than 100° C. for 120 minutes. After the high-temperature dehydration is completed, the heating is stopped. When the material temperature drops below 40° C., 111 parts of white oil are added, and the materials are stirred at normal pressure for 30 minutes, and the stirring is stopped to obtain a base rubber; The dosage of the nano calcium carbonate powder is 716 parts, the oil absorption value is 25.3gdop / 100gCaCO3, and the specific surface area is 27.6m2 / g.

[0028] 940 parts of the base material prepared above were weighed and added into a planetary mixer, and then 21 parts of methyl triacetone oxime silane, 11 parts of methyl vinyl diacetone oxime silane, 10 parts of dimethyl diacetone oxime silane, 8 parts of KH-550 coupling agent, 6 parts of KH-560 coupling agent, and 4 parts of dibutyltin bis(acetylacetonate) were added, stirred at a stirring speed of 40 rad / min for 5 minutes and evacuated until the pressure in the cylinder was less than -0.08 MPa, and then stirred at a stirring speed of 80 rad / min for 30 minutes, stopped stirring, and quickly discharged to obtain a sealant sample.

[0029] Comparative Example 2 Based on Example 5, the modifier was adjusted: the modifier did not contain Peg-7 glyceryl cocoate.

[0030] The dosage of nano calcium carbonate powder and modified heavy calcium carbonate in the silicone sealant of Examples 1-7 and Comparative Examples 1 and 2 is shown in Table 1.

[0031] Table 1 The dosage of nano calcium carbonate powder and modified heavy calcium carbonate in silicone sealant Example Nano calcium carbonate powder / portion Modified heavy calcium / part The proportion of modified heavy calcium to nano calcium carbonate powder Example 1 445 22 5% Example 2 425 42 10% Example 3 406 61 15% Example 4 389 78 20% Example 5 359 108 30% Example 6 334 133 40% Example 7 311 156 50% Comparative Example 1 467 0 0 Comparative Example 2 425 42 10% The test results of mechanical properties of the sealants of Examples 1-7 and the comparative example are shown in Table 2.

[0032] Table 2 Performance test results Example The proportion of modified heavy calcium to nano calcium carbonate powder <![CDATA[Glue specific gravity (g / cm 3 > Glue consistency (cm) Rubber extrusion (g / 20s) Tensile strength MPa Elongation at break % Example 1 5% 1.53 6.7 30.4 1.62 223 Example 2 10% 1.54 6.7 31.3 1.67 237 Example 3 15% 1.54 6.8 33.7 1.59 242 Example 4 20% 1.55 6.8 37.6 1.57 233 Example 5 30% 1.55 7.0 38.5 1.53 210 Example 6 40% 1.57 7.3 68.3 1.45 198 Example 7 50% 1.57 7.5 83.6 1.42 177 Comparative Example 1 0 1.53 6.7 29.6 1.51 215 Comparative Example 2 30% 1.53 6.8 31.5 1.46 184 As can be seen from Table 2, for the silicone sealant prepared by the formula and method of the present invention, when sodium octadecenoate, Peg-7 glyceryl cocoate and distearoyloxyisopropylaluminate are used to activate and modify the heavy calcium carbonate, when the proportion of the nano calcium carbonate used is 30%, that is, Example 2, the colloid properties are not much different from the comparative example test results, indicating that in the preparation process of silicone sealant, it is feasible for the rubber factory to reduce the production cost by partially replacing the nano calcium carbonate powder with modified heavy calcium carbonate.

[0033] The specific embodiments described herein are merely examples of the spirit of the present invention. Personnel skilled in the art may make various modifications or additions to the specific embodiments described, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A silicone sealant in which modified heavy calcium partially replaces nano calcium carbonate, characterized in that: Silicone sealant contains the following components: 200-500 parts of hydroxyl-terminated polydimethylsiloxane, 300-800 parts of nano calcium carbonate, 10-250 parts of modified heavy calcium carbonate, 100-250 parts of heavy calcium carbonate, 1-10 parts of catalyst, 50-200 parts of plasticizer, 8-20 parts of coupling agent, and 25-60 parts of cross-linking agent.

2. The silicone sealant according to claim 1 wherein the modified heavy calcium partially replaces the nano calcium carbonate, characterized in that: The viscosity of the hydroxyl-terminated polydimethylsiloxane is 20000-100000 mPa·s at room temperature.

3. The silicone sealant according to claim 1 wherein the modified heavy calcium partially replaces the nano calcium carbonate, characterized in that: The plasticizer is one of white oil, methylphenyl silicone oil, vinyl silicone oil and dimethyl silicone oil.

4. The silicone sealant in which the modified heavy calcium partially replaces the nano calcium carbonate according to claim 1 is characterized in that: The crosslinking agent is at least one of methyl triacetone oxime silane, phenyl triacetone oxime silane, methyl vinyl diacetone oxime silane and dimethyl diacetone oxime silane.

5. The silicone sealant according to claim 1 wherein the modified heavy calcium partially replaces the nano calcium carbonate, characterized in that: The coupling agent is at least one of KH-550, KH-560, KH-570, and KH-792.

6. The silicone sealant according to claim 1 wherein the modified heavy calcium partially replaces the nano calcium carbonate, characterized in that: The oil absorption value of nano calcium carbonate powder is 22.0-27.0gdop / 100gCaCO3, and the specific surface area is 24-35m2 / g.

7. The silicone sealant according to claim 1 wherein the modified heavy calcium partially replaces the nano calcium carbonate, characterized in that: The preparation method of the modified heavy calcium carbonate is as follows: heavy calcium carbonate and water are added into a reaction kettle, stirred to obtain a slurry, stirred and heated, and when the slurry temperature rises to 65-80°C, a modifier is added, and the reaction is carried out for 50-70 minutes at a stirring speed of 800-1000 rad / min. After the reaction is completed, stirring is stopped, and the slurry is filtered, dried, and ground to obtain the modified heavy calcium carbonate.

8. The method for preparing silicone sealant by partially replacing nano calcium carbonate with modified heavy calcium according to claim 7, characterized in that: The modifier comprises Peg-7 glyceryl cocoate, sodium octadecenoate and distearoyloxyisopropylaluminate, and the dosage ratio of the three ingredients is 0.1-1.0:1.0-1.3.6:1.0-3.7; the added amount of the modifier is 1.5%-4% of heavy calcium carbonate.

9. The method for preparing silicone sealant by partially replacing nano calcium carbonate with modified heavy calcium according to any one of claims 1 to 8, characterized in that: The method steps are as follows: S1: adding the hydroxyl-terminated polydimethylsiloxane, nano calcium carbonate, heavy calcium carbonate and modified heavy calcium carbonate materials into a kneader, starting to stir, and after the materials are stirred and mixed evenly, heating and vacuuming the materials, dehydrating and stirring at a high temperature of 100-130° C., stopping heating, and when the material temperature drops below 40° C., adding a plasticizer, and vacuum stirring to obtain a base rubber; S2: Add the above-mentioned base glue, cross-linking agent, coupling agent and catalyst into a mixer, and stir under vacuum to obtain a sealant sample.

10. The preparation method according to claim 9, characterized in that: The vacuum degree in step S1 and step S2 is -0.05 to -0.1 MPa.