Compositions containing silane-treated calcium carbonate

Abstract

Sealant, adhesive, and rubber compositions may include a polymer matrix and silane-treated calcium carbonate, providing compositions with improved mechanical properties.

Description

[0001] Cross-reference to related applications

[0002] The priority interests of U.S. Provisional Application No. 63 / 543,853, filed October 12, 2023, and U.S. Patent Application No. 63 / 596,936, filed November 7, 2023, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0003] This disclosure relates to compositions of silane-treated calcium carbonate, and more specifically to sealant, rubber and / or adhesive compositions containing silane-treated calcium carbonate as a filler. Background Technology

[0004] Calcium carbonate products have been used as fillers in sealants and rubber. A typical calcium carbonate used as a filler in such products is fatty acid-coated calcium carbonate. The nonpolar tails of the fatty acids provide the necessary interactions and dispersion of the filler within the polymer matrix. Summary of the Invention

[0005] The compositions disclosed herein comprise a polymer matrix and a filler containing silane-treated calcium carbonate. The compositions disclosed herein can be sealants, adhesives, or rubber compositions. Compared to compositions using fatty acid-treated PCC as a filler, the compositions disclosed herein exhibit significantly improved mechanical properties, such as tensile strength and / or modulus of elasticity. Attached Figure Description

[0006] Figure 1 This includes photographs showing puck-water tests of silane-treated PCCs according to this disclosure.

[0007] Figure 2 This is a graph showing comparative tensile strength tests of the composition according to this disclosure and a control composition containing stearic acid-treated PCC as a filler.

[0008] Figure 3 This is a graph showing the comparative tensile stress of the composition according to this disclosure and a control composition containing stearic acid-treated PCC as a filler under a 300% elongation test.

[0009] Figure 4 This is a graph showing a comparative viscosity test of the composition according to this disclosure and a control composition containing stearic acid-treated PCC as a filler. Detailed Implementation

[0010] The compositions according to this disclosure comprise a polymer matrix and a filler containing silane-treated calcium carbonate. The calcium carbonate may be precipitated calcium carbonate. The composition may be a sealant composition, a rubber composition, or an adhesive composition. Compared to compositions having the same polymer matrix and a filler containing fatty acid-treated calcium carbonate, the compositions of this disclosure exhibit surprising improvements in mechanical properties. Given the anticipated interaction between the silane-treated PCC and the polymer matrix, and the understanding of the interaction between the fatty acid-treated PCC and the polymer matrix, the magnitude of the improvement in mechanical properties is surprising and unexpected. For example, compared to sealant compositions having the same base composition but containing fatty acid-treated PCC as a filler, a 122% increase in sealant strength was observed in silicone-based polymer matrix sealants, and a 76% increase in sealant strength was observed in modified silicone-based polymer matrix sealants.

[0011] PCC itself exhibits poor coupling interactions with polymer rubbers, adhesives, and sealants. This is due to the polar inorganic nature of calcium carbonate and the largely nonpolar nature of the polymer matrix. While not wanting to be bound by theory, it is believed that by treating PCC with silanes, the silanes act as coupling agents between the filler and the polymer matrix, forming a durable bond between the two materials. Although it could be expected that incorporating a silane-coated substrate into the polymer matrix would improve dispersibility, hydrophobicity, polymer crosslinking, and provide some improvement in mechanical properties compared to filler-free compositions, the degree of improvement observed with the compositions of this disclosure is greater than expected. Furthermore, based on prior knowledge of the properties of fillers in polymer matrices, it was not expected that silane-treated calcium carbonate would exhibit such a significant improvement in mechanical properties compared to fatty acid-treated calcium carbonate.

[0012] The sealant compositions according to this disclosure may comprise a polymer matrix and a filler containing silane-treated calcium carbonate. The polymer matrix of the sealant composition may be any known polymer matrix used in sealant compositions. For example, the matrix may be oil-based or resin-based. The polymer matrix of the sealant compositions of this disclosure may include, but is not limited to, silicones, such as hydroxyl-terminated silicones and vinyl-terminated silicones, modified silicone polymers (i.e., polyether backbone polymers), butyl rubber, polyurethanes, polysulfides, epichlorohydrins, fluorocarbons, isoprene, chloroprene rubber, nitrile, polysulfides, epoxy resins, polyvinyl acetate (PVA), PVC plastisol, hydrocarbon rubber-based sealants, acrylic acid, chlorosulfonated polyethylene, synthetic rubber-based hot melt sealants, fluorosilicones and fluoropolymer sealants, styrene-butadiene copolymers, and chloroprene. For example, the sealant composition may comprise butyl rubber as the polymer matrix.

[0013] The adhesive composition according to this disclosure may comprise a polymer matrix and a filler containing silane-treated calcium carbonate. The polymer matrix of the adhesive composition may be any known polymer matrix used in adhesive compositions. The polymer matrix used in the adhesive composition according to this disclosure may include, but is not limited to, silicone, epoxy, polyurethane, and adhesives. Examples of adhesives may include bitumen adhesives or bitumen-based adhesives. The adhesive composition may be a curable adhesive or an adhesive applied to a backing, such as when forming a tape. For example, the adhesive composition may be used to form a foam tape, wherein the adhesive composition is applied to opposite sides of a substrate. The adhesive composition may be a flexible composition or a rigid composition.

[0014] The rubber composition according to this disclosure may comprise a polymer matrix and a filler containing silane-treated calcium carbonate. The polymer matrix of the rubber composition may be any known polymer matrix used in rubber compositions. For example, the rubber composition may be a tire rubber composition. For example, the polymer matrix of the rubber composition may be butyl rubber, natural rubber, styrene-butadiene rubber, butadiene rubber, vinyl / cis-polybutadiene rubber (A) comprising 1,4-cis-polybutadiene (a) and 1,2-polybutadiene crystalline fibers, and / or nitrile rubber. For example, the filler containing silane-treated calcium carbonate may be at least a partial substitute for silica commonly used in tire rubber compositions.

[0015] In any composition disclosed herein, the filler may be dispersed in a polymer matrix, for example, substantially uniformly dispersed in the polymer matrix.

[0016] In any composition disclosed herein, calcium carbonate may be precipitated calcium carbonate. Calcium carbonate may have an average particle size of about 10 nm to about 300 nm (e.g., about 100 nm to about 300 nm). Precipitated calcium carbonate may have an average particle size of about 10 nm. 2 / g to approximately 125m 2 / g average surface area.

[0017] In any composition disclosed herein, the silane used to treat calcium carbonate can be a trialkoxysilane, an organosilane, or an aminosilane. For example, the silane can be an oligomeric short-chain alkyl functional silane, such as Dynasylan. ® SIVO 408 (EVONIK). For example, in rubber compositions, the silane can be a bifunctional sulfur-containing organosilane, such as Si 69 (EVONIK).

[0018] For example, in the rubber compositions disclosed herein, the silane can be a sulfur-functionalized silane. For example, the silane can be bis(triethoxysilylpropyl)tetrasulfide, bis(triethoxysilylpropyl)disulfide, propyltriethoxysilane 3-thiocyanate, or mercaptosilane. For example, mercaptosilane can be Si 363. ® (EVONIK). Other commercially available silanes from EVONIK that can be used in the rubber compositions disclosed herein include, for example, Si 69. ® (bis(triethoxysilylpropyl)tetrasulfide); Si 75 ® (bis(triethoxysilylpropyl)disulfide); Si 266 ® (bis(triethoxysilylpropyl)disulfide), Si 264 ™ (Propylthiocyanate triethoxysilane). This type of silane can also be used in sealant compositions that use, for example, butyl rubber or synthetic rubber-based hot melts as a polymer matrix.

[0019] Calcium carbonate treated with sulfur-functionalized silanes can be used in various polymer matrices of the rubber compositions disclosed herein. For example, the polymer matrix may be or include butyl rubber, natural rubber, styrene-butadiene rubber, butadiene rubber, vinyl / cis-polybutadiene rubber (A) comprising 1,4-cis-polybutadiene (a) and 1,2-polybutadiene crystalline fibers, and / or nitrile rubber.

[0020] In any composition disclosed herein, calcium carbonate may be present in the composition in an amount of about 10% to about 50% based on the total weight of the polymer matrix.

[0021] Compared to compositions using fatty acid-treated calcium carbonate as a filler, the compositions of this disclosure advantageously exhibit significantly improved tensile strength. For example, the compositions of this disclosure may have at least 70% greater tensile strength than compositions using fatty acid-treated calcium carbonate. For instance, a comparison can be made with compositions using stearic acid-treated calcium carbonate.

[0022] Compared to compositions using fatty acid-treated calcium carbonate as a filler, the compositions of this disclosure advantageously have a significantly improved modulus of elasticity. For example, the compositions of this disclosure may have an elastic modulus at least 70% greater than that of compositions using fatty acid-treated calcium carbonate. For example, a comparison can be made with compositions using stearic acid-treated calcium carbonate.

[0023] Silanes have very low reactivity with calcium carbonate. Methods for treating calcium carbonate with silanes, such as those described in U.S. Patent No. 9,328,244, can be performed. For example, the method may include: mixing calcium carbonate with sodium silicate under conditions sufficient to coat the calcium carbonate with sodium silicate, thereby providing a layer of active sites; and mixing the sodium silicate-coated calcium carbonate with silane under conditions sufficient to react the hydrolyzed silane with the active sites of the sodium silicate, thereby forming silane-treated calcium carbonate. The calcium carbonate may be, for example, precipitated calcium carbonate.

[0024] Siliceous silicates may be present in amounts from about 1% to about 25% by weight of calcium carbonate.

[0025] A hydrolyzed silane, based on calcium carbonate, in an amount of about 1% to about 15% by weight, can be added to a silicate-treated silane. The silane can be, for example, a trialkoxysilane, an organosilane, or an aminosilane, as described above. For example, the silane could be Dynasylan. ® SIVO 408 (Evonik).

[0026] This method may include hydrolyzing the silane just before adding the hydrolyzed silane to the sodium silicate-coated calcium carbonate. The hydrolysis of the silane can be carried out by adding the silane dropwise to a mixture of water and a dispersing agent. The dispersing agent may be, for example, methanol. The amount of water provided is such that the final molar ratio of water to silane is about 3:1. During the dropwise addition of the silane, the solution can be maintained at a pH of about 3.5 to about 4.5. After addition, the mixture can be mixed for a sufficient time to allow the silane to hydrolyze.

[0027] Example

[0028] Example 1: Silane treatment of PCC

[0029] Silane treatment of precipitated calcium carbonate was performed using the following procedure. DI water was added to a beaker to achieve a final water:silane molar ratio of 3:1, and the solution was stirred with a stir bar under ambient conditions. Methanol was then added to the DI water to achieve a final methanol:silane molar ratio of 3:1. The pH of the solution was maintained at pH 3.5 by adding 5% acetic acid catalyst solution, if necessary. Silane was then added dropwise to achieve the desired water:silane and methanol:silane ratios. Depending on the silane added, the solution was mixed at approximately 80°C to 85°C for 1 to 2 hours, 1 hour for trimethoxysilane, and 2 hours for triethoxysilane. It was observed that adding too much water inhibited hydrolysis, and the water:silane ratio showed low tolerance to excess water. Methanol acted as a solvent / dispersant and its molar ratio with silane had a relatively small effect on the hydrolysis process. Additional methanol may be added as needed, taking evaporation into account.

[0030] Sodium silicate was used as the silane PCC-silane coupling agent. An ultrafine PCC slurry was mixed with approximately 3.5 wt% of a siliceous sodium silicate solution based on PCC. A fully coated PCC of 3.5 wt% was observed, exhibiting a thickness of approximately 20 μm. 2 The average surface area of ​​ / g provides a monolayer of active sites.

[0031] Hydrolyzed silanes were added to the sodium silicate-coated PCC and covered with foil to retain moisture. The mixture was mixed for about 1 hour. The solids were filtered through a Buchner funnel under vacuum. The wet solids were spread out, scratched to maximize airflow and heat transfer, and dried in an oven at 110°C for 24 to 48 hours.

[0032] Compositions were prepared using PCCs treated with different silanes. The composition and reaction parameters of the silane treatments of the PCCs tested in the sealant compositions are shown in Table 1.

[0033] Table 1: Components of the Test

[0034]

[0035]

[0036]

[0037] The disc-to-water-drop test was used to test the silane-treated PCCs. Since the silane used is known to be hydrophobic, the degree of adhesion success was primarily determined by the formation / absorption of water droplets on the sample disc surface. The silane-treated PCCs were manually pressed into discs at 55 psi for 15 seconds. A larger contact angle of the water droplet on the disc indicated a higher degree of silane adhesion. Figure 1 These are images of some experiments conducted using the disc-droplet test.

[0038] Samples 19, 21, and 23 produced the most promising water droplet formation results among the tested samples. A minimum silane coating of 7.5 wt% (theoretical) was determined when sodium silicate coupling agent was added at 3.5 wt%. It was observed that reducing the proportion of sodium silicate while maintaining the silane amount was detrimental to this method. Hydrolysis was determined to be a necessary first step, as adding unhydrolyzed silane directly to aqueous PCC did not result in coating. A low pH of approximately 4.5 or 3.5 favored efficient hydrolysis. Dropwise addition of silane during hydrolysis was determined to be beneficial in mitigating the silane-silane reaction to form siloxanes and promoting the silane-water reaction.

[0039] Example 2: Synthesis and Testing of Sealant Composition

[0040] Using Dynasylan ®PCC was treated with SIVO 408 (a triethoxysilane). PCC was coated with silane in a 30L reactor apparatus using the method described in Example 1. The sodium silicate-coated PCC slurry was sieved through a 325-mesh sieve before being added to the reactor. A 28L slurry containing a calculated solid content of 3209.2g was used as a base. According to Example 1, 3.5 wt% sodium silicate and 7.5 wt% SIVO 408 were added relative to the solids. For hydrolysis, water and methanol were mixed at a 3:1 molar ratio relative to SIVO 408, 24 drops of 5% acetic acid were added, and SIVO 408 was added dropwise. The hydrolysis reaction was carried out for 2 hours. The contents of the hydrolysis beaker were then poured into the reactor containing the sodium silicate-coated PCC slurry, and the attachment reaction was carried out at 80°C for 1 hour.

[0041] The silane-treated PCC was filtered overnight under vacuum in a large Buchner funnel, and then placed in an oven at 110°C for approximately 72 hours. It was then treated with Mikro Atomizer. ® Grind the dried silane-treated PCC.

[0042] The PCCs used to form the silane-treated PCCs are ultrafine PCCs (Minerals Technology Inc.). After silane treatment, the surface area of ​​the silane-treated PCCs is 14.2 μm. 2 / g. The primary particle size after silane treatment is 150nm.

[0043] The control sample used PCC packing material, specifically UltraPFlex. ® (Minerals Technology Inc.) This is a PCC surface-treated with stearic acid. The stearic acid-treated PCC has a primary particle size of 70 nm and a thickness of 18.6 μm. 2 / g surface area. This is a product commercially manufactured by Specialty Minerals, Inc.

[0044] Organosilicon and modified organosilicon (MS) polymer sealants were formulated using silane-treated PCC as filler to form compositions according to this disclosure. The control composition used for comparative testing employed the same sealant base formulation but contained UltraPFlex. ®(Stearic acid-treated PCC) is used as a filler. Silicone sealants (5057-132, Roger Bauer) are prepared according to the method described in Part 1 - RTV Silicone Sealants, and MS polymer sealants are prepared according to the method described in the Ross Dual Planetary Mixer SOP for Modifying Organic Polymers for Adhesives / Sealants. The base MS polymer sealant compositions are base MS polymer sealants made from commercially available MS polymers. The general composition of each is described in Tables 1 and 2 below. Silane-treated PCC or stearic acid-treated PCC is added as a filler to the sealant composition.

[0045] Table 2: Silicone Sealant Formulation (Premier Mill + Ross)

[0046]

[0047] Table 3: MS Polymer Formulation (Ross Mixer)

[0048]

[0049] The surface area, coating level, moisture content, viscosity, yield stress, thixotropy, extrudability, peel adhesion, hardness, Young's modulus, tensile stress, tensile strain, tensile strength at break and elongation at break of the compositions and control compositions according to this disclosure were tested respectively.

[0050] Uncured sealant was stretched to fill a 5" × 5" × 1 / 8" clamp and set to cure for seven days in a controlled environment at 73℉ and 50% relative humidity. On the seventh day, the cured sealant was cut into Type 4 dog bones and measured to be 4.5''L × 1''W (narrow segment 0.25''W). Mechanical properties were tested at 2 inches per minute according to ASTM Method D412 on an Instron Universal Tester Model #68TM-R44 / 55 / 5869. The mechanical strength results given below are the average of five specimens for each sample. Surface area testing was performed using a Horiba SA-9600 series. Rheological testing was performed on an Anton Paar MCR 102. Tensile testing was performed using an Instron 68TM-R.

[0051] Table 4 provides test data for the organosilicon polymer sealant according to this disclosure with silane-treated PCC, compared to a control composition with stearic acid-treated PCC.

[0052] Table 5 provides test data for the modified organosilicon polymer sealant according to this disclosure, which has PCC treated with silane, compared to a control composition having PCC treated with stearic acid.

[0053] Table 4: Comparison of Test Results for Silicone Sealants

[0054]

[0055] Table 5: Comparison of test results for MS polymer sealants

[0056]

[0057] Figures 2 to 4 This is a graphical illustration of the comparative tests, showing the ultimate tensile strength ("tensile stress at break"), tensile stress at 300% elongation, and stress at 0.1 s⁻¹. -1 10s -1 and 100s -1 Viscosity at that time.

[0058] In silicone sealants and modified silicone sealant compositions, silane-treated PCC increases the ultimate tensile strength (break stress). For silicone sealants, filling with silane-treated products increases the strength by 122.3%. For MS polymer sealants, filling with silane-treated products increases the strength by 75.5%.

[0059] Increased stress was also observed at 100% and 300% elongation. The difference between the disclosed compositions and the control compositions was more significant at 300% elongation, where the stress of the silicone sealant increased by 56.4% and the stress of the modified silicone polymer sealant increased by 73.9%.

[0060] In both sealant types, Young's modulus increased with the addition of silane-treated PCC. The increase was 70.3% for silicone and 96.3% for modified silicone polymer sealant. It was observed that filling with silane-treated PCC increased the sealant's resistance to elastic deformation.

[0061] At low shear rates (0.1 s⁻¹) -1 At [specific conditions], compared to the control sample, the viscosity of the sealant according to this disclosure increased (15.6% for silicone and 28.7% for modified silicone polymer sealants). However, at higher shear rates, the viscosity of the sealant according to this disclosure decreased. At 10s [specific conditions], [the viscosity decreased]. -1 Under these conditions, the changes in silicone and modified silicone polymer sealants were -15.4% and -17.7%, respectively. (At 100s...) -1 The changes in silicone and modified silicone polymer sealants were -99.5% and -57.9%, respectively. Additionally, shear thinning of the sealant according to this disclosure was observed compared to the control composition.

[0062] The difference in shear stress between the control composition and the composition according to this disclosure was not significant. All samples experienced cohesive failure during the peel adhesion test. The Shore A hardness on day 1 and day 7 was comparable between the control composition and the composition according to this disclosure.

[0063] The foregoing description is provided for clarity only and should not be construed as an unnecessary limitation, as modifications within the scope of this disclosure will be readily apparent to those skilled in the art.

[0064] All patents, patent applications, government publications, government regulations, and references cited in this specification are incorporated herein by reference in their entirety. In case of conflict, this specification (including definitions) shall prevail.

[0065] Throughout this specification, unless otherwise stated, when a compound, composition, method, and / or process is described as including components, steps, or materials, it is contemplated that the compound, composition, method, and / or process may also include, substantially consist of, or consist of any combination of said components or materials. Unless otherwise specifically stated, component concentrations may be expressed as weight concentrations. In light of the foregoing disclosure, it will be understood by those skilled in the art that combinations of components are contemplated to include homogeneous and / or heterogeneous mixtures.

Claims

1. A sealant composition comprising: Polymer matrix; and A filler containing silane-treated calcium carbonate, wherein the sealant has improved mechanical properties.

2. The sealant composition according to claim 1, wherein the polymer matrix comprises silicone or a modified silicone polymer.

3. The sealant according to claim 1 or 2, wherein the silane is a trialkoxysilane, an organosilane, or an aminosilane.

4. The sealant composition according to any one of claims 1 to 3, wherein the calcium carbonate is precipitated calcium carbonate.

5. The sealant according to any one of claims 1 to 4, wherein the silane-treated calcium carbonate is present in an amount of about 10% to about 50% based on the total weight of the polymer matrix.

6. The sealant according to any one of claims 1 to 5, wherein the calcium carbonate has an average particle size of about 10 nm to about 300 nm.

7. The sealant according to any one of claims 1 to 6, wherein the calcium carbonate has a content of about 10 mg / L. 2 / g to approximately 125m 2 / g average surface area.

8. The sealant according to any one of claims 1 to 7, wherein the tensile strength of the composition is at least 70% greater than that of a composition comprising the polymer matrix and a filler containing calcium carbonate surface-treated with fatty acids.

9. The sealant according to any one of claims 1 to 8, wherein the elastic modulus of the composition is at least 70% greater than that of the composition comprising the polymer matrix and the filler containing calcium carbonate surface-treated with fatty acids.

10. The sealant according to claim 8 or 9, wherein the fatty acid is stearic acid.

11. An adhesive composition comprising: Adhesive matrix; and Filler containing calcium carbonate treated with silane.

12. The adhesive composition of claim 11, wherein the adhesive matrix comprises silicone, epoxy resin, polyurethane and an adhesive, wherein the adhesive is optionally a bitumen adhesive and a bitumen-based adhesive.

13. The adhesive composition according to claim 11 or 12, wherein the calcium carbonate is precipitated calcium carbonate.

14. The adhesive composition according to any one of claims 11 to 13, wherein the silane is a trialkoxysilane, an organosilane, or an aminosilane.

15. The adhesive composition according to any one of claims 11 to 14, wherein the silane-treated calcium carbonate is present in an amount of about 10% to about 50% based on the total weight of the polymer matrix.

16. The adhesive composition according to any one of claims 11 to 15, wherein the calcium carbonate has an average particle size of about 10 nm to about 300 nm.

17. The adhesive composition according to any one of claims 11 to 16, wherein the calcium carbonate has a content of about 10 mg / m³. 2 / g to approximately 125m 2 / g average surface area.

18. The adhesive composition according to any one of claims 11 to 17, wherein the tensile strength of the composition is at least 70% greater than that of a composition comprising the polymer matrix and a filler containing calcium carbonate surface-treated with fatty acids.

19. The adhesive composition according to any one of claims 11 to 18, wherein the elastic modulus of the composition is at least 70% greater than that of the composition comprising the polymer matrix and the filler containing calcium carbonate surface-treated with fatty acids.

20. The adhesive composition according to claim 18 or 19, wherein the fatty acid is stearic acid.

21. A rubber composition comprising: Rubber polymer matrix; and Filler containing calcium carbonate treated with silane.

22. The rubber composition according to claim 21, wherein the rubber polymer matrix is ​​tire rubber, butyl rubber, natural rubber, styrene-butadiene rubber, butadiene rubber, vinyl / cis-polybutadiene rubber (A) comprising 1,4-cis-polybutadiene (a) and 1,2-polybutadiene crystalline fibers, and / or nitrile rubber.

23. The rubber composition according to claim 21 or 22, wherein the calcium carbonate is precipitated calcium carbonate.

24. The rubber composition according to any one of claims 21 to 23, wherein the silane is a trialkoxysilane, an organosilane, or an aminosilane.

25. The rubber composition according to claim 24, wherein the silane is a sulfur-functionalized silane.

26. The rubber composition according to claim 25, wherein the sulfur-functionalized silane is bis(triethoxysilylpropyl)tetrasulfide, bis(triethoxysilylpropyl)disulfide, propyltriethoxysilane 3-thiocyanate, or mercaptosilane.

27. The rubber composition according to any one of claims 21 to 26, wherein the silane-treated calcium carbonate is present in an amount of about 10% to about 50% based on the total weight of the polymer matrix.

28. The rubber composition according to any one of claims 21 to 27, wherein the calcium carbonate has an average particle size of about 10 nm to about 300 nm.

29. The rubber composition according to any one of claims 21 to 28, wherein the calcium carbonate has a content of about 10 mg / m³. 2 / g to approximately 125m 2 / g average surface area.

30. The rubber composition according to any one of claims 21 to 29, wherein the tensile strength of the composition is at least 70% greater than that of a composition comprising the polymer matrix and a filler containing calcium carbonate surface-treated with fatty acids.

31. The rubber composition according to any one of claims 21 to 30, wherein the elastic modulus of the composition is at least 70% greater than that of the composition comprising the polymer matrix and the filler containing calcium carbonate surface-treated with fatty acids.

32. The rubber composition according to claim 30 or 32, wherein the fatty acid is stearic acid.

33. A method for producing silane-treated calcium carbonate, comprising: Under conditions sufficient to coat sodium silicate with calcium carbonate, the calcium carbonate is mixed with the sodium silicate to provide a layer of active sites. as well as Under conditions sufficient to cause the hydrolyzed silane to react with the active sites of the sodium silicate, the sodium silicate-coated calcium carbonate is mixed with the silane to form the silane-treated calcium carbonate.

34. The method of claim 33, wherein the calcium carbonate is precipitated calcium carbonate.

35. The method according to claim 33 or 34, wherein the sodium silicate is present in an amount of about 1% to about 25% by weight based on calcium carbonate.

36. The method according to any one of claims 33 to 35, wherein the hydrolyzed silane is present in an amount of about 1% to about 15% by weight based on the calcium carbonate.

37. The method according to any one of claims 33 to 36, wherein the silane is a trialkoxysilane, an organosilane, or an aminosilane.

38. The method according to any one of claims 33 to 37, further comprising forming the hydrolyzed silane by adding the silane dropwise to a mixture of water and methanol at a pH of about 3.5 to 4.5, wherein the mixture comprises water in a 3:1 ratio of silane.

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