Alcohol type organic silicon modified calcium carbonate powder and preparation method thereof

Abstract

The invention discloses an alcohol type organic silicon modified calcium carbonate powder and a preparation method thereof, and particularly relates to the technical field of fillers for silicone adhesives, the alcohol type organic silicon modified calcium carbonate powder comprises a calcium carbonate matrix and an organic silicon polymer coating layer grafted on the surface of the calcium carbonate matrix through chemical bonds, the organic silicon polymer coating layer is formed by a composite modifier comprising secondary amino silane and epoxy silane through an in-situ reaction. According to the method, secondary amino silane is grafted to the surface of calcium carbonate, then epoxy silane is introduced, and the secondary amino silane and the epoxy silane form a silane-silane interpenetrating network structure through a ring-opening reaction. The modified calcium carbonate powder prepared by the invention is excellent in dispersity in an alcohol type silicone adhesive and high in storage stability, the thixotropy and the sagging resistance of the sealant can be remarkably improved, and good mechanical strength and curing efficiency are still kept under high filling amount.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fillers for silicone sealant, more particularly, the present application relates to an alcohol type organosilicon modified calcium carbonate powder and a preparation method thereof. BACKGROUND

[0002] Calcium carbonate, as a widely available and low-cost inorganic filler, is widely used in silicone sealant to reduce production costs, adjust rheological properties and partially improve mechanical properties. Among them, alcohol-free silicone sealant has become one of the mainstream product types due to its mild odor and low corrosivity during the curing process.

[0003] However, the surface of unmodified calcium carbonate powder is rich in hydrophilic hydroxyl groups, which has poor compatibility with the hydrophobic silicone polymer body. Direct filling can easily lead to agglomeration, thereby causing problems such as sealant storage period sedimentation, caking and mechanical property degradation. To overcome this defect, the prior art usually uses a surface modifier to organically treat the calcium carbonate. The current mainstream modification methods include:

[0004] 1. Using a single silane coupling agent for modification, such as using gamma-aminopropyl triethoxysilane or gamma-(2,3-epoxypropoxy) propyl trimethoxysilane. Although this method can improve compatibility to some extent, the single modification layer has insufficient bonding strength with the surface of calcium carbonate, and can easily fail under long-term storage or high shear action. Moreover, a single amino silane can interfere with the condensation crosslinking reaction, and a single epoxy silane has a slow reaction rate, which can lead to incomplete modification.

[0005] 2. Using a fatty acid or its salt for surface coating. Although this method can provide good hydrophobicity, the chemical bonding force between the surface coating and the silicone sealant body is weak, mainly relying on physical adsorption, which has problems such as easy migration and poor thermal stability, and cannot guarantee long-term storage stability, and can affect the transparency and deep curing of the sealant.

[0006] 3. Using a simple mixture of multiple modifiers. Some technical solutions attempt to physically mix different types of modifiers and then treat the calcium carbonate. However, simple mixing cannot form a dense and stable coating structure on the surface of calcium carbonate, and different components can lead to uneven modification due to competitive adsorption, which cannot achieve synergistic effect.

[0007] In summary, the modified calcium carbonate prepared by the prior art is difficult to meet multiple requirements such as excellent dispersion stability, good construction rheological property and no negative impact on the crosslinking and curing process when applied to high-performance alcohol-free silicone sealant. Therefore, the present application provides an alcohol type organosilicon modified calcium carbonate powder and a preparation method thereof. SUMMARY

[0008] In order to overcome the above-mentioned defects of the prior art, the present application provides an alcohol-type organosilicon modified calcium carbonate powder and a preparation method thereof to solve the problems raised in the above background art.

[0009] To achieve the above object, the present application provides the following technical solution: an alcohol-type organosilicon modified calcium carbonate powder, comprising a calcium carbonate matrix and an organosilicon polymer coating layer grafted on the surface of the calcium carbonate matrix by chemical bonds, wherein the organosilicon polymer coating layer is formed by in-situ reaction of a composite modifier comprising a secondary amino silane and an epoxy silane.

[0010] Preferably, the secondary amino silane is N-phenyl-3-(trimethoxysilyl)-propylamine, and the epoxy silane is 3-glycidyloxypropyltrimethoxysilane.

[0011] Preferably, the amount of the secondary amino silane is 0.5-1.5 parts, and the amount of the epoxy silane is 0.8-2.0 parts, based on 100 parts of the mass of the calcium carbonate matrix, and the mass ratio of the secondary amino silane to the epoxy silane is 1:1.2-1.8.

[0012] Preferably, the calcium carbonate matrix is nano calcium carbonate, with an average particle size d50 of 50-100 nm and a specific surface area of 20-40 m 2 / g.

[0013] Preferably, the oil absorption value of the powder is less than 30 g / 100 g, and the dispersion of the powder in 107 silicone rubber has a sedimentation volume ratio of more than 95% after centrifugal sedimentation at 3500 r / min for 30 min.

[0014] The present application also provides a preparation method for preparing the above-mentioned alcohol-type organosilicon modified calcium carbonate powder, which specifically comprises the following steps:

[0015] S1, dispersing the calcium carbonate matrix in anhydrous ethanol to form a slurry with a solid content of 30-50%;

[0016] S2, adding the secondary amino silane to the slurry in the presence of a catalyst and reacting at 60-70°C for 1-2 h;

[0017] S3, maintaining the temperature and adding the epoxy silane to the mixture obtained in step S2, and continuing to react for 1.5-3 h;

[0018] S4, recovering the ethanol by vacuum distillation of the product obtained in step S3, and then drying and crushing to obtain the modified calcium carbonate powder.

[0019] Preferably, the catalyst in step S2 is an organotin catalyst, and the amount of the catalyst is 0.05-0.5% of the mass of the calcium carbonate matrix.

[0020] Preferably, the reactions in steps S2 and S3 are carried out under inert gas protection.

[0021] Preferably, the drying in step S4 is vacuum drying, the drying temperature is 100-120℃, and the drying time is 3-6h.

[0022] Preferably, in steps S2 and S3, the secondary amino silane and the epoxy silane are both added into the slurry uniformly by spraying after dilution.

[0023] Technical effects and advantages of the present application:

[0024] 1. The modified calcium carbonate prepared in the present application has excellent long-term dispersion stability in alcohol-type silicone systems, and does not settle or agglomerate during storage. The secondary amino silane and the epoxy silane form a silane-silane interpenetrating network coating layer through stepwise grafting, which can be firmly anchored to the calcium carbonate matrix through Si-O-Ca bonds and hydrogen bonds, and the organic silicone segment has excellent chemical similarity and compatibility with the silicone adhesive main body.

[0025] 2. The dealcoholized silicone sealant prepared based on the modified calcium carbonate in the present application has excellent thixotropy, significantly reduces the stringing phenomenon and does not drip. The uniformly dispersed and surface energy reduced filler particles can construct a stable three-dimensional network structure with the matrix resin, thereby finely controlling the rheological behavior of the system.

[0026] 3. The present application effectively shields the polar hydroxyl groups on the surface of calcium carbonate, greatly reduces the physical obstruction and chemical interference of the filler on the crosslinking reaction, and at the same time, its extreme dispersion in the matrix makes it become an efficient stress dispersion point, so that it can achieve high filler content while still ensuring excellent tensile strength and sufficient deep curing of the sealant. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The overall process flowchart of the present application is shown in the figure. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] Embodiment 1,

[0030] The present embodiment provides a kind of application in alcohol type silicone modified calcium carbonate powder, specifically includes the following raw materials:

[0031] Calcium carbonate matrix: 100 parts, average particle size d50 = 50 nm, specific surface area 40 m 2 / g of nanometer calcium carbonate;

[0032] Secondary amino silane: 0.5 parts, N-phenyl-3-(trimethoxysilyl)-propylamine;

[0033] Epoxy silane: 0.8 parts, 3-glycidoxypropyltrimethoxysilane;

[0034] Catalyst: 0.05 parts, dibutyltin dilaurate;

[0035] Solvent: sufficient anhydrous ethanol to form a slurry with a solid content of 30%;

[0036] Protective gas: high-purity nitrogen, 99.999%.

[0037] The present embodiment also provides a preparation method for preparing an alcohol-type silicone-modified calcium carbonate powder, specifically comprising the following steps:

[0038] S1. Disperse 100 parts of nanometer calcium carbonate in sufficient anhydrous ethanol to form a uniform slurry with a solid content of 30% in a 1000 mL reaction kettle;

[0039] S2. Continuously introduce nitrogen as a protective gas into the reaction kettle, add 0.05 parts of dibutyltin dilaurate catalyst, heat the system to 60°C and maintain, dilute 0.5 parts of secondary amino silane with 10 parts of anhydrous ethanol, and then uniformly spray it into the slurry within 30 minutes through a spraying device, and continue to react at 60°C for 1 hour after the spraying is completed;

[0040] S3. Maintain the system temperature at 60°C and the nitrogen atmosphere, dilute 0.8 parts of epoxy silane with 10 parts of anhydrous ethanol, and then uniformly spray it into the mixture obtained in step S2 within 30 minutes through a spraying device, and continue to react at this temperature for 1.5 hours after the spraying is completed;

[0041] S4. After the reaction is completed, connect the reaction system to a rotary evaporator for reduced pressure distillation to recover the ethanol solvent, transfer the obtained wet material to a vacuum drying oven, vacuum dry at 100°C for 6 hours, and finally, crush the dried block material through a small air flow crusher to obtain a modified calcium carbonate powder, marked as sample 1.

[0042] Example 2,

[0043] The present embodiment provides an alcohol-type silicone-modified calcium carbonate powder, specifically comprising the following raw materials:

[0044] Calcium carbonate matrix: 100 parts, average particle size d50 = 80 nm, specific surface area 25 m 2Nano calcium carbonate with 100 m

[0045] Secondary amino silane: 1 part, same type as example 1

[0046] Epoxy silane: 1.5 parts, same type as example 1

[0047] Catalyst: 0.25 parts, dibutyl tin dilaurate

[0048] Solvent: sufficient anhydrous ethanol to form a slurry with a solid content of 40%

[0049] Protective gas: high purity nitrogen

[0050] The example also provides a preparation method for preparing the alcohol-type silicone-modified calcium carbonate powder, specifically comprising the following steps:

[0051] S1, preparing a slurry with a solid content of 40%;

[0052] S2, under nitrogen protection, adding 0.25 parts of catalyst, heating to 65°C, and adding 1 part of secondary amino silane diluted by ethanol by spraying within 40 min, and then reacting at 65°C for 1.5 h;

[0053] S3, keeping 65°C and nitrogen atmosphere, adding 1.5 parts of epoxy silane diluted by ethanol by spraying within 40 min, and then continuing to react for 2 h;

[0054] S4, after recovering ethanol by reduced pressure distillation, vacuum drying at 110°C for 4 h, and finally airflow crushing to obtain sample 2.

[0055] Example 3,

[0056] The example provides an alcohol-type silicone-modified calcium carbonate powder, specifically comprising the following raw materials:

[0057] Calcium carbonate matrix: 100 parts, average particle size d50 = 100 nm, specific surface area 20 m 2 Nano calcium carbonate with 100 m

[0058] Secondary amino silane: 1.5 parts, same type as example 1

[0059] Epoxy silane: 2 parts, same type as example 1

[0060] Catalyst: 0.5 parts, dibutyl tin dilaurate

[0061] Solvent: sufficient anhydrous ethanol to form a slurry with a solid content of 50%

[0062] Protective gas: high purity nitrogen

[0063] The embodiment also provides a preparation method for preparing the alcohol type silicone modified calcium carbonate powder, and specifically comprises the following steps:

[0064] S1, a slurry with a solid content of 50% is prepared;

[0065] S2, under nitrogen protection, 0.5 parts of a catalyst is added, and 1.5 parts of a secondary amino silane diluted by ethanol is added by spraying within 50 min at 70 DEG C, and then reacted for 2 h at 70 DEG C;

[0066] S3, 2 parts of an epoxy silane diluted by ethanol is added by spraying within 50 min at 70 DEG C under nitrogen atmosphere, and then reacted for 3 h continuously;

[0067] S4, after recovering ethanol by reduced pressure distillation, vacuum drying for 3 h at 120 DEG C, and finally airflow crushing, sample 3 is obtained.

[0068] Comparative Example 1, single component modification

[0069] In the embodiment, no epoxy silane is added, 2.5 parts of the total amount of secondary amino silane and epoxy silane is replaced by common amino silane (3-aminopropyl triethoxysilane, KH550), and other conditions are completely same with those in Example 2, and comparative sample 1 is obtained.

[0070] Comparative Example 2, changing feeding process

[0071] In the embodiment, all raw materials and proportions are same with those in Example 2, but in steps S2 and S3, the modifier is directly added into the slurry at one time without dilution and spraying, and other conditions are unchanged, and comparative sample 2 is obtained.

[0072] Comparative Example 3, changing feeding sequence

[0073] In the embodiment, all raw materials and proportions are same with those in Example 2, but in step S2, 1 part of secondary amino silane and 1.5 parts of epoxy silane are premixed, and then added into the slurry at one time by spraying and reacted for 3.5 h, and comparative sample 3 is obtained.

[0074] Comparative Example 4, commercially available product

[0075] The silicone modified calcium carbonate for silicone adhesive is purchased in the market, and is marked as comparative sample 4.

[0076] The performance tests are respectively conducted on sample 1-3 prepared in Examples 1-3 and comparative sample 1-4 provided by the comparative examples, and the test methods are as follows:

[0077] Oil absorption value: determined according to GB / T19281-2014;

[0078] Dispersion stability (sedimentation volume ratio): 10 g of modified calcium carbonate was mixed with 40 g of 107 silicone rubber, and dispersed for 5 min at 2000 rpm with a high-speed mixer to form a uniform paste, 5 g of the paste was taken and placed in a 10 mL centrifuge tube, and centrifuged at 3500 r / min for 30 min, the height of the supernatant after sedimentation and the total height were recorded, and the sedimentation volume ratio (sediment volume / total volume x 100%) was calculated;

[0079] Sealant tensile strength: 100 parts of 107 silicone rubber, 35 parts of the calcium carbonate sample to be tested, 2 parts of crosslinking agent tetraethyl orthosilicate and 0.5 parts of catalyst dibutyltin dilaurate were mixed uniformly, and standard dumbbell-shaped test pieces were prepared after vulcanization, and the tensile strength was determined according to GB / T 528-2009.

[0080] The final test table is as follows:

[0081]

[0082]

[0083] It is shown from the performance test results that:

[0084] The modified calcium carbonate powder prepared in examples 1-3 has an oil absorption value of less than 30 g / 100 g and a sedimentation volume ratio in 107 silicone rubber of greater than 95%, which fully proves that the composite modifier system composed of secondary amino silane and epoxy silane can significantly improve the dispersibility and compatibility of the powder in the alcohol-type silicone system, and this effect is much better than that of comparative examples 1 and 4, which highlights that the composite modifier system is the decisive factor for achieving excellent performance.

[0085] Among them, example 2 shows the best comprehensive performance, which is due to the synergistic effect of the specific ratio and the step-by-step grafting process, comparative example 2 has decreased performance due to not using spray feeding, which confirms the key influence of this feeding method on realizing uniform and sufficient modification, and more importantly, the performance of comparative example 3 is significantly inferior to that of example 2, which powerfully indicates that the specific order of grafting secondary amino silane first and then reacting with epoxy silane is the core of producing significant synergistic effect and bringing significant progress.

[0086] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An alcohol-type silicone-modified calcium carbonate powder for application, characterized by: The modified calcium carbonate powder comprises a calcium carbonate base and a silicone polymer coating layer grafted on the surface of the calcium carbonate base by chemical bonds, wherein the silicone polymer coating layer is formed by in-situ reaction of a composite modifier comprising a secondary amino silane and an epoxy silane.

2. The alcohol-type silicone-modified calcium carbonate powder for use according to claim 1, characterized in that: The secondary amino silane is N-phenyl-3-(trimethoxysilyl)-propylamine, and the epoxy silane is 3-glycidyloxypropyltrimethoxysilane.

3. The alcohol-type silicone-modified calcium carbonate powder for use according to claim 2, characterized in that: The amount of the secondary amino silane is 0.5-1.5 parts, and the amount of the epoxy silane is 0.8-2.0 parts, based on 100 parts of the mass of the calcium carbonate base, and the mass ratio of the secondary amino silane to the epoxy silane is 1:1.2-1.

8.

4. The alcohol-type silicone-modified calcium carbonate powder for use according to claim 3, characterized in that: The calcium carbonate base is nano calcium carbonate with an average particle size d50 of 50-100 nm and a specific surface area of 20-40 m 2 / g.

5. The alcohol-type silicone-modified calcium carbonate powder for use according to claim 4, characterized in that: The oil absorption value of the powder is less than 30 g / 100 g, and the sedimentation volume ratio of a dispersion of the powder in 107 silicone rubber after centrifugal sedimentation at 3500 r / min for 30 min is greater than 95%.

6. A production method for producing the alcohol-type silicone-modified calcium carbonate powder for use according to claim 5, characterized by: The method comprises the following steps: S1, dispersing the calcium carbonate base in anhydrous ethanol to form a slurry with a solid content of 30-50%; S2, adding the secondary amino silane to the slurry in the presence of a catalyst and reacting at 60-70℃ for 1-2 h; S3, maintaining the temperature, adding the epoxy silane to the mixture obtained in step S2 and continuing to react for 1.5-3 h; S4, recovering the ethanol by vacuum distillation of the product obtained in step S3, and then drying and crushing to obtain the modified calcium carbonate powder.

7. The method of claim 6, wherein: The catalyst in step S2 is an organic tin catalyst, and the amount of the catalyst is 0.05-0.5% of the mass of the calcium carbonate base.

8. The method of claim 7, wherein: The reactions in steps S2 and S3 are carried out under inert gas protection.

9. The method of claim 8, wherein: The drying in step S4 is vacuum drying, the drying temperature is 100-120℃, and the drying time is 3-6 h.

10. The method of claim 9, wherein: In steps S2 and S3, the secondary amino silane and the epoxy silane are both added uniformly into the slurry by spraying after dilution.

Images