Calcium carbonate modified formula has gained significant attention in various industries due to its enhanced properties. This modification process changes the surface traits of calcium carbonate. It helps calcium carbonate work better with various materials. The modified calcium carbonate shows better dispersion, more stability, and improved performance. This is useful in plastics, paints, and coatings. Researchers are always looking for new ways to improve the formula. They want to keep up with the changing needs of the market. Overall, the calcium carbonate modified formula represents a promising advancement in material science.
Ca2+ and CO32- particles from crushing heavy calcium carbonate react with water. This creates hydroxyl groups. As a result, heavy calcium carbonate becomes hydrophilic. However, organic polymers are lipophilic and hydrophobic. The different surface properties of heavy calcium carbonate and the organic polymer lead to poor compatibility. This results in uneven dispersion and weak bonding at the interface. Polymer-based composites often face interface defects during use. This can lower their performance. Therefore, the surface of heavy calcium carbonate must be organically modified.
Calcium carbonate modified formulas
Many types of surface modifiers exist. Their formulas, including variety, dosage, and use, are very specific. EPIC Powder has created 20 special formulas for modifying heavy calcium carbonate. The processes involve wet and dry methods. The types of modifiers include stearic acid (sodium), silane coupling agent, titanate coupling agent, aluminate coupling agent, surfactant, polymer organic matter, starch and composite modifiers, etc., for your reference only. The details are as follows:
- Formula 1: Stearic acid wet grinding modification
- Formula 2: Sodium stearate dry modification
- Formula 3: KH-550 wet modification
- Formula 4: Comparison of dry modification effects of titanate and aluminate coupling agent
- Formula 5: Comparing the effects of sodium stearate and aluminate coupling agent for wet modification.
- Formula 6: Comparison of wet modification effects of sodium stearate and coupling agent
- Formula 7: Comparison of dry modification effects of surfactants, silicone oil, etc.
- Formula 8: Coupling =Comparison of modification effects of surfactants and surfactants
- Formula 9: Comparison of dry modification effects of surfactants, stearic acid, coupling agents, and silicone oil
- Formula 10: Composite modification of stearic acid-titanate coupling agent (wet ball milling)
- Formula 11: Composite modification of stearic acid-titanate coupling agent (dry method)
- Formula 12: Composite modification of oleic acid and coupling agent
- Formula 13: Modification of water-based composite modifiers
- Formula 14: Dry modification of polymer emulsion
- Formula 15: Modification of dipalmitoyl tartaric acid diester
- Formula 16: Dry modification of eleostearic acid anhydride hydrolyzate
- Formula 17: Modification of sorbitan monostearate (Span60)
- Formula 18: Polyvinyl acetate polymerization modification
- Formula 19: Starch coating modification
- Formula 20: Integrated treatment of titanate coupling agent and air flow milling
Formulation 1: Stearic acid wet grinding modification
Modifier: stearic acid.
Modification method: Weigh 900g of calcium carbonate powder. The particle size should be about 45μm. Prepare a slurry with a solid mass fraction of 75%. Then, add stearic acid. The amount of stearic acid should be 1%-3% of the mass of the calcium carbonate powder. The initial viscosity of the slurry is 147mPa·s at 42°C, and the viscosity is 228mPa·s after standing for 20min. The volume of calcium carbonate slurry is about 600mL. Stir at a speed of 1000r/min for 90min in a stirring disperser. Stop stirring. Remove the slurry and put it in a drying oven set to 180°C. After drying, take out the modified block. Then, use a high-speed pulverizer to crush it for 3 minutes. This will give you modified calcium carbonate powder.
Test and characterization: particle size, surface activation, oil absorption value, whiteness.
Modification effect:
You can grind and modify heavy calcium carbonate at room temperature. This process reduces the particle size from 45μm to 2μm. As you add more stearic acid, the activation of heavy calcium carbonate goes up. At the same time, the oil absorption value goes down. As the stearic acid increases to 2% (mass fraction), heavy calcium carbonate activation goes over 98%. Also, the oil absorption value falls to 0.267g/g. Grinding and modifying heavy calcium carbonate together helps lower production costs. This makes the product more competitive.
Formula 2: Dry modification of sodium stearate
Modifier: sodium stearate.
Modification method: Start by drying the heavy calcium carbonate in an oven to remove moisture. Next, weigh a specific amount of the dry powder and add it to a three-necked flask. Place the flask in a water bath at a set temperature and stir. Then, add a measured amount of sodium stearate and stir for a designated time. Finally, cool the mixture to obtain the modified heavy calcium carbonate.
Test and characterization: FT-IR, XRD, SEM, Zeta potential.
Modification effect:
When the modification temperature is 70°C, the amount of sodium stearate is 1.5% of the mass of heavy calcium carbonate, the modification time is 50min, and the speed is 700r/min, the activation rate of sodium stearate modified heavy calcium carbonate is 85.6%, and the modification effect is good. The infrared spectrum of heavy calcium carbonate with sodium stearate showed peaks. There were -CH2- symmetric stretching peaks at 2850 cm-1 and antisymmetric stretching peaks at 2920 cm-1. The X-ray diffraction peak shifted to higher angles. Zeta potential increased from 14.1 mV to 30.2 mV, and the particle size decreased. This indicates that sodium stearate grafted onto heavy calcium carbonate’s surface. However, the modification did not alter the crystal form of calcium carbonate. The modified heavy calcium carbonate has good dispersibility.
Formula 3: KH-550 wet modification
Modifier: γ-chloropropyltriethoxysilane (KH-550), sodium stearate, titanate coupling agent.
Modification method:
- Graft modification by wet method.
- Weigh 200g of dried ultrafine heavy calcium carbonate.
- Disperse it in 300g of anhydrous ethanol.
- Heat and stir in a water bath at 80℃ for 10 minutes.
- Then, add 2.5% of the powder mass of the modification aid.
- Continue to react under the same conditions for 60 minutes.
- Finally, filter, wash, and dry while hot to get the modified ultrafine heavy calcium carbonate powder.
Testing and Characterization:
- Fourier transform infrared spectroscopy
- Thermogravimetric analysis
- Particle size analysis
- Silicone rubber rheological properties test
- Mechanical properties test
Modification effect:
Rheological data shows that the modified ultrafine heavy calcium carbonate disperses well in silicone rubber. It also has better compatibility with colloids than the unmodified version. Ultrafine heavy calcium carbonate lacks a nano-reinforcement effect in size. This weakens the interaction between the surface-treated ultrafine heavy calcium carbonate and silicone rubber. As a result, the performance of silicone rubber after vulcanization decreases compared to using unmodified ultrafine heavy calcium carbonate. KH-550 has special features like amino and alkoxy groups. Because of this, ultrafine heavy calcium carbonate treated with KH-550 spreads easily in silicone rubber. It also forms chemical bonds with the rubber. As a result, the RTV silicone rubber shows excellent mechanical properties.
Formula 4: Comparison of dry modification effects of titanate and aluminate coupling agents
Modifier: titanate coupling agent JN-114, aluminate coupling agent DL-411.
Modification method: weigh a certain amount of heavy calcium carbonate and add it into a high-speed mixer. After heating the material to the experimental temperature, add the surface modifier. After a certain reaction time, stop stirring to obtain surface-modified heavy calcium carbonate.
Test and characterization: activation index, contact angle, infrared spectrum, polypropylene composite material performance.
Modification effect:
(1) Titanate coupling agent JN-114 chemically adsorbs on the surface of heavy calcium carbonate.
The best conditions for dry modification of heavy calcium carbonate are:
- JN-114 dosage: 1.0%
- Modification temperature: 70℃
- Modification time: 30 minutes.
Under these conditions, the modified heavy calcium carbonate achieves a contact angle of 114.34°. The activation index also hits 99.21%.
(2) Aluminate coupling agent DL-411 chemically adsorbs on the surface of heavy calcium carbonate.
The best conditions for dry modifying heavy calcium carbonate are:
- DL-411 dosage: 1.0%
- Modification temperature: 90℃
- Modification time: 30 minutes
In these conditions, the contact angle of modified heavy calcium carbonate is 121.70°. The activation index also hits 100%.
(3) Surface modification of JN-114 and DL-411 can effectively improve the impact strength of PP composites. When the addition amount is 20%, the composite material has the highest impact strength. This strength is 38.87% and 41.97% greater than that of pure PP.
Formula 5: Comparison of wet modification effects of sodium stearate and aluminate coupling agent
Modifier: aluminate coupling agent DL-411 and sodium stearate.
Modification method:
(1) To make aluminate coupling agent DL-411 modified heavy calcium carbonate, follow these steps:
- Weigh 30g of heavy calcium carbonate and place it in a 250ml reaction bottle.
- Add some water and ethanol, then stir to create a suspension.
- Heat the mixture.
- Dissolve the aluminate coupling agent in a suitable amount of anhydrous ethanol and disperse it using an ultrasonic cleaner.
- Once the temperature reaches the desired level, add the aluminate-alcohol solution to the heavy calcium carbonate suspension.
- Stir for a while to allow the reaction to occur.
- After the reaction is done, wash the product several times with ethanol.
- Filter and separate it, then vacuum dry at 50°C for 24 hours to get the final product: aluminate coupling agent modified heavy calcium carbonate.
(2) Sodium stearate modified heavy calcium carbonate:
- Weigh 30g of heavy calcium carbonate into a 250ml reaction bottle.
- Add water and ethanol, then stir to make a smooth suspension.
- Heat the mixture until it reaches the desired temperature.
- Next, add sodium stearate solid particles to the suspension and stir for a while.
- Once the reaction is done, wash the product with water and ethanol.
- Filter and separate the mixture, then vacuum dry it at 50°C for 24 hours.
- This process yields sodium stearate modified heavy calcium carbonate.
Testing and Characterization:
- Oil absorption value
- Sedimentation volume
- Contact angle
- Performance test of calcium carbonate/polypropylene composites.
Modification effect:
The best conditions for modifying 1250 mesh heavy calcium carbonate with sodium stearate are:
- Temperature: 25℃
- Ratio: m(calcium carbonate):m(ethanol):m(water) = 3:1.5:3
- Sodium stearate to heavy calcium carbonate mass: 3.0%
- Stirring speed: 400 r/min
- Stirring time: 40 min
With these settings, the oil absorption value and sedimentation volume decrease by about 50%. The contact angle reaches 129.2°.
The best way to modify heavy calcium carbonate with the aluminate coupling agent DL-411 is as follows:
- Modification temperature: 25℃
- Mix ratio: m(calcium carbonate):m(ethanol):m(water) = 3:1.5:3
- Agent ratio: aluminate coupling agent/heavy calcium carbonate mass = 2.0%
- Triethylamine ratio: triethylamine/calcium carbonate mass = 0.5%
- Stirring speed: 300 r/min
- Stirring time: 2 min
When compared to unmodified calcium carbonate, the modified heavy calcium carbonate shows:
- Oil absorption value decrease: 47.0%
- Sedimentation volume decrease: 45.8%
- Contact angle: 136.3°
The optimal filling amount of sodium stearate modified heavy calcium carbonate in PP is 20%. Compared with the raw material PP, the elongation at break and the impact strength are increased by 12.5% and 15.7%. The best filling amount of aluminate modified heavy calcium carbonate in polypropylene is 30%. This increases the elongation at break by 15.0% and the impact strength by 16.0%.
Formula 6: Comparison of wet modification effects of sodium stearate and coupling agent
Modifier: sodium stearate, γ-chloropropyltriethoxysilane (KH-550), titanate coupling agent TC114.
Modification method: Weigh 200g of dried ultrafine heavy calcium carbonate. Place it in a round-bottom flask. Disperse with 300g of anhydrous ethanol. Heat and stir in a water bath at 80℃ for 10 minutes. Then, add 2.5% of the powder mass of the modification aid. Continue to react under the same conditions for 60 minutes. After that, filter, wash, and dry it while hot to get the modified ultrafine heavy calcium carbonate powder.
Test and Characterization:
- Fourier transform infrared spectroscopy
- Thermogravimetric analysis
- Particle size analysis
These methods assess the properties of RTV silicone rubber materials.
Modification effect:
Rheological data shows that modified ultrafine heavy calcium carbonate disperses well in silicone rubber. This is better than unmodified ultrafine heavy calcium carbonate. It also has improved compatibility with colloids. Ultrafine heavy calcium carbonate lacks a nano-reinforcement effect in size. This weakens the interaction between surface-treated ultrafine heavy calcium carbonate (TC114 and sodium stearate) and silicone rubber. As a result, the performance of silicone rubber after vulcanization decreases compared to using unmodified ultrafine heavy calcium carbonate. KH-550 has amino and alkoxy groups. Because of this, ultrafine heavy calcium carbonate treated with KH-550 disperses well in silicone rubber. It also forms chemical bonds with the rubber. As a result, the RTV silicone rubber shows excellent mechanical properties.
Formula 7: Comparison of dry modification effects of surfactants, silicone oil, etc.
Modifier: polyethylene glycol-200, diethylene glycol, triethanolamine and amino silicone oil-804.
Modification method: Use the dry modification method. Weigh 100g of heavy calcium carbonate powder and put it in a three-necked flask. Place this flask in a constant temperature water bath. Start the electric stirrer to mix. When the temperature reaches 95℃, add the surface modifier while stirring. Continue stirring and reacting at 95℃ for 30 minutes after adding. This will give you heavy calcium carbonate modified powder. Once the modified powder cools, take samples for testing and characterization.
Test and characterization: oil absorption value, infrared spectrum, thermogravimetric analysis.
Modification effect:
The order of the four surface modifiers that reduce the oil absorption of heavy calcium carbonate filler is as follows: aminosilicone oil-804 > polyethylene glycol-200 > triethanolamine > diethylene glycol. Also, the same modifier shows different oil absorption values based on its dosage. Usually, a larger dose of the modifier means a lower oil absorption value. All modifiers bond chemically with the hydroxyl group on heavy calcium carbonate powder. When aminosilicone oil-804 is used at 1.00%, the modified sample’s oil absorption value can reach 0.115 mL/g. Thermogravimetric analysis shows that the modified sample has the best thermal stability. Its thermal decomposition temperature is 325℃.
Formula 8: Comparison of the modification effects of coupling agent and surfactant
Modifiers include:
- Aluminate coupling agent (DL-411)
- Titanate coupling agent (NDZ-201)
- Silane coupling agent (KH-550)
- Stearic acid (SA)
- Sodium dodecyl sulfate (SDS)
- Glutamic acid (GLU)
- Hexadecyl phosphate (PO16)
- Octadecyl phosphate (PO18)
- Hexadecyl trimethyl ammonium bromide (CTAB) surfactants
Composite modifiers are the aluminate coupling agent (DL-411) and sodium dodecyl sulfate (SDS).
Modification method: dry modification and wet modification.
Test and characterization include:
- Activation rate
- Oil absorption value
- Infrared analysis
- Particle size
- SEM
This focuses on the performance of the PBAT/modified calcium carbonate composite material.
Modification effect:
(1) When the content of the three coupling agents DL-411, NDZ-201 and KH-550 was 1.5% and the modification method was wet modification, the modified calcium carbonate had the best effect. The surface of calcium carbonate was lipophilic, the dispersibility was improved, and the average particle size was reduced.
(2) Among the six surfactants, when the content of SA, SDS and PO16 was 3%, the modification effect on calcium carbonate was the best, which successfully changed the surface of calcium carbonate from hydrophilic to hydrophobic, the average particle size was reduced, and the dispersibility was improved.
(3) Calcium carbonate was modified by coupling agent DL-411 and surfactant SDS.
The best modification effect on calcium carbonate happened with these conditions:
- Composite modifier ratio (DL:SDS) of 3:2
- Reaction time of 40 minutes
- Reaction temperature of 80 °C
- Composite modifier amount of 3%
Compared with a single modifier, the synergistic effect between DL-411 and SDS makes the composite modifier have a better modification effect on calcium carbonate.
Formula 9: Comparison of dry modification effects of surfactant, stearic acid, coupling agent and silicone oil
Modifier:
- New surfactant modifier JST-9001 (polyoxyethylene ether type composite modifier)
- JST-9002 (phosphate type composite modifier)
- JST-9003 (polyoxyethylene ether type composite modifier)
- JST-900
Modification method: Weigh 100g of heavy calcium carbonate powder. Place it in a 500mL three-necked flask. Set the constant temperature water bath to the desired temperature. Adjust the digital display electric stirrer to run at (1300±50) r/min. Then, add the modifier drop by drop onto the heavy calcium carbonate in the flask. Make sure to add it at a moderate speed, neither too fast nor too slow. After adding the modifier, seal the three-necked flask and start timing. After a certain period of time, turn off the instrument, wait for the sample to cool down, take it out and seal it in a sealed bag.
Test and characterization include:
- Oil absorption value
- Activation index
- Oil phase dispersion stability
- Water contact angle
- Infrared spectrum (FTIR)
- Thermogravimetric (TG) analysis.
Modification effect:
JST-9001 and JST-9003, along with stearic acid and aluminate F-2, work better than JST-9002 and JST-9004, hydroxy silicone oil, and amino silicone oil 585C. They offer a more effective modification for heavy calcium carbonate. The new modifiers JST-9001 and JST-9003 can achieve better modification effects than stearic acid and aluminate F-2 at a low modifier dosage (0.50%).
The oil absorption values of C525 heavy calcium carbonate samples modified by JST-9001 and JST-9003 are 0.11 mL/g and 0.10 mL/g, respectively. Their activation indexes are 98.77% and 99.19%. The turbidity change rates are 4.06% and 5.30%. The wetting contact angles are 154.2° and 151.4°.
For the 00 heavy calcium carbonate samples, the oil absorption values are 0.14 mL/g and 0.15 mL/g. Their activation indexes are 89.73% and 93.77%. The turbidity change rates are 16.04% and 9.59%. The wetting contact angles are 91.9° and 87.7°.
With the right dosage, the hydrophilic groups in JST-9001 and JST-9003 bonded with the —OH on heavy calcium carbonate’s surface. This created a layer of modifier molecules on the calcium carbonate particles. The surface properties of heavy calcium carbonate changed from hydrophilic to hydrophobic. Also, the oil absorption value dropped significantly.
Formula 10: Stearic acid-titanate coupling agent composite modification (wet ball milling)
Modifier: Stearic acid and titanate coupling agent are used as composite modifiers, and anhydrous ethanol is used as dispersant.
Modification method: Weigh 15.0g of heavy calcium powder and add it to a ball mill. Next, weigh a specific amount of stearic acid and titanate coupling agent based on the mass ratio. Add these to the ball mill as well. Then, pour in anhydrous ethanol until the powder is just covered. Finally, start the ball mill to modify the heavy calcium powder. The modified powder is placed in a drying oven and dried at 80°C, cooled to room temperature, and ground to obtain the modified product.
Test and characterization: activation degree, oil absorption value, sedimentation volume, particle size.
Modification effect:
After testing different factors and conducting an orthogonal experiment, we found the best process for modification. The optimal conditions are:
- Ball milling time: 1.5 hours
- Ball milling speed: 350 r/min
- Modifier dosage: 2.0%
- Modifier ratio: 1:3
Modified heavy calcium powder works better than unmodified powder. It has better activation, less oil absorption, lower sedimentation volume, and smaller particle size. Overall, the modification shows good results. With the optimized process, the modified heavy calcium powder shows an activation degree of 99.4%. Its oil absorption value is 14.27g per 100g of powder. The sedimentation volume measures 1.08mL/g, and the particle size D50 is 1.58μm.
Formula 11: Stearic acid-titanate coupling agent composite modification (dry method)
Modifier: stearic acid, titanate coupling agent.
Modification method: Weigh a specific amount of dried heavy calcium carbonate and place it in a stirring tank. Next, put the tank in a water bath at the right temperature. Then, add a measured amount of stearic acid. Use a high-speed disperser to mix the calcium carbonate well. After that, add bis(dioctyloxypyrophosphate)ethylene titanate coupling agent. Finally, high-speed disperse the mixture to get modified heavy calcium carbonate. It was compounded with epoxy resin to prepare a modified heavy calcium carbonate/epoxy resin composite material.
Test and characterization include:
- Thermogravimetric analysis
- Near-infrared spectroscopy
- X-ray diffraction
- Electron microscopy
- Epoxy resin product performance
When stearic acid makes up 1.5% of heavy calcium carbonate’s mass, the modification time is 20 minutes. For titanate, at 2.0% of the mass, the modification time is just 10 minutes. In these conditions, the composite material has the best tensile properties at 10.2 MPa. It also shows the lowest oil absorption value. Heavy calcium carbonate’s crystal form stayed the same after being modified with stearic acid, titanate, and epoxy resin. The composite modifier also bonded well to its surface. The modified heavy calcium carbonate particles have good dispersion and strong bonding with epoxy resin.
Formula 12: Oleic acid and coupling agent composite modification
Modifiers:
- Aluminate coupling agent (DL-411)
- Alkyl-modified polysiloxane coupling agent (FD-1106)
- Stearic acid (SA)
- Oleic acid (OA)
Modification method:
(1) Wet modification: Weigh 10g of heavy calcium carbonate and place it in a 250mL beaker. Then, add 50g of water and 50g of ethanol. Stir well to create a suspension and heat it to 80°C. Next, dissolve the modifier in some ethanol. Use an ultrasonic cleaner to disperse it for 10 minutes. Once the temperature reaches the set level, add the modified solution to the beaker with heavy calcium carbonate. Stir for a while. Wash the mixture with water and ethanol after the reaction. Then, vacuum dry it at 60°C for 12 hours. This will give you modified calcium carbonate.
(2) Dry modification: First, add calcium carbonate powder to a high-speed mixer. Then, heat the powder to 80°C. Finally, spray the modifier to get modified calcium carbonate.
(3) Composite modification: Weigh 500g of heavy calcium carbonate powder and stir it in a high-speed mixer, and heat it up to 120℃. In the high-speed mixer, spray some mist surface modifier FD-1106 and OA. Then, mix and stir for a set time. This creates heavy calcium carbonate powder modified by the composite modifier.
Test and characterization: activation rate determination, oil absorption value test and particle size analysis.
Modification effect:
(1) When the addition amount of the four surface modifiers DL-411, SA, FD-1106 and OA is 1.5%, 1.0%, 1.5% and 1.0% of the mass of heavy calcium carbonate, respectively, the modification effect is the best. The modified calcium carbonate particles spread better and activate faster. Also, the oil absorption value goes down.
(2) The wet modification effect is relatively more obvious, but the dry modification process is simpler, easier to operate, and can save costs to a greater extent. Therefore, dry modification is more suitable for industrial production.
(3) The infrared test results of the four modified heavy calcium carbonates proved that the heavy calcium carbonate was successfully modified by the modifier. The particle size analysis showed that the average size of heavy calcium carbonate dropped a lot after using four modifiers. Among them, OA produced the largest average particle size at 23.6%, while the activation rate hit 98.8%.
(4) Alkyl-modified polysiloxane coupling agent (FD-1106) and OA were selected to carry out composite self-assembly modification of calcium carbonate. When the composite modifier ratio (FD-1106: OA) was 1:1, the best calcium carbonate modification occurred. We achieved this by adding 1% of the composite modifier. The reaction took 10 minutes at 110 °C. The modified calcium carbonate had an average particle size of 8.45 μm. Plus, the activation rate reached 99.6%. Filling 30% calcium carbonate in PBAT/PLA gives the best mechanical properties for the composite film. The tensile strengths are 19.37 MPa in the transverse direction and 29.67 MPa in the longitudinal direction. At this time, the composite film is a hydrophobic material with a hydrophobic angle of 95°.
Formula 13: Water-based composite modifier modification
Modifier: polyethylene glycol-300 (PEG-300), sodium dodecyl sulfate (SDS) and sodium stearate.
Modification method:
- Weigh 500g of heavy calcium carbonate.
- Weigh 10g of composite modifier.
- Measure 7mL of pure water.
- Heat these in a water bath at 80℃.
This creates an aqueous composite modifier solution for later use.
Put the heavy calcium carbonate powder in a high-speed mixer. Heat it to 100-110℃. Next, slowly add the modifier aqueous solution. Mix at high speed for 5 minutes. Then, stop stirring and open the mixer cover. Let the water evaporate for 10 minutes. Finally, mix at high speed for 20 more minutes. The material temperature stays between 100 and 110℃ during the process. This ensures we get activated heavy calcium carbonate powder.
Test and characterization: oil absorption value, sedimentation volume, surface morphology, and performance of PP/heavy calcium carbonate composite materials.
Modification effect:
When the mass ratio of PEG-300, SDS, and sodium stearate is 6:2:2, the surface modification is most effective. The oil absorption value of heavy calcium carbonate powder drops from 32.7 mL/100g to 15.5 mL/100g. Also, the sedimentation volume decreases from 4.1 mL/g to 1.0 mL/g. The water-based composite heavy calcium carbonate has small particles. It offers higher dispersibility and better crystallization performance. The water-based composite modifier works better than stearic acid. When we add more heavy calcium carbonate powder, the mechanical properties of the PP/heavy calcium carbonate composite also change. They first improve, then decline. The best performance happens when the mass fraction is 30%. The flexural strength reaches 45.75MPa and the tensile strength reaches 32.58MPa.
Formula 14: Dry modification of polymer emulsion
Modifier: polymer emulsion.
Modification method: put calcium carbonate into an oven and dry it at 110℃ for 24h. Weigh a specific amount of dry heavy calcium carbonate powder after removing moisture. Then, add it to a three-necked flask. Put it into a water bath at 80℃ and stir it electrically at a speed of 500r/min. Add polymer emulsion to the three-necked flask and stir it electrically for 50min. Cool and discharge the material to obtain modified heavy calcium carbonate.
Test and characterization: activation rate, FT-IR, XRD, SEM, Zeta potential.
Modification effect: At 80℃, after 50 minutes, and at a speed of 500 r/min, the modified calcium carbonate achieves a 90.8% activation rate. This uses a 3% polymer emulsion based on the weight of Xianfeng heavy calcium carbonate. This shows a good modification effect. Calcium carbonate was characterized by FT-IR, XRD, SEM, and Zeta potential. The results show that we successfully grafted the polymer emulsion onto the calcium carbonate surface. The diffraction peak of modified calcium carbonate moves to a higher angle. However, the polymer emulsion does not alter the calcium carbonate crystal form. The Zeta potential of modified calcium carbonate rises from 14.1 mV to 29.8 mV. The particle size gets smaller, which improves dispersibility.
Formulation 15: Dipalmitoyl Tartaric Acid Diester Modification
Modifier: Dipalmitoyl tartaric acid diester.
Modification method:
(1) Synthesis of dipalmitoyl tartaric acid diester: Start with 10.3g of palmitic acid in a round-bottom flask. Then, slowly add 10mL of thionyl chloride while stirring. Heat the mixture to 80℃ for 3 hours, or until the solution is clear. Remove extra thionyl chloride using vacuum rotary evaporation. Then, add 5 mL of methyl tert-butyl ether. Continue rotary evaporation until you get brown-yellow palmitic acid chloride. Dissolve palmitic acid chloride in dichloromethane.
Then, transfer this mixture to a three-necked flask. Next, add 16.8 mL of triethylamine while keeping it in an ice-water bath. Weigh 3.0g tartaric acid, heat and dissolve it in acetone, and drip it into the three-necked flask. After completion, heat to room temperature and react overnight. Filter and vacuum evaporate the filtrate to get a paste-like solid. Then, recrystallize it twice with acetone. Finally, dry it to yield a white solid, which is dipalmitoyl tartaric acid diester, the target product.
(2) Modification of heavy calcium carbonate: Weigh some calcium carbonate powder. Add water and stir to make a slurry. Then, put it in a constant temperature water bath. Heat it while stirring at a speed of 450 r/min. Heat to the right temperature. Then, add the right mass fraction of the modifier. Stir and react at a steady temperature for a set time. Filter, dry, and grind to a particle size of <250μm to obtain a calcium carbonate modified product.
Test and characterization: oil absorption value, sedimentation volume, activation degree.
Modification effect:
To modify heavy calcium carbonate (10μm) with dipalmitoyl tartaric acid diester, use these optimal conditions: 2.0% modifier dosage, 55 minutes of modification time, and a temperature of 60℃.
Under these conditions, the modified calcium carbonate showed notable changes:
- Oil absorption value dropped from 0.2780 mL/g to 0.2039 mL/g.
- Sedimentation volume fell from 1.3 mL/g to 0.3 mL/g.
- Activation degree rose from 0% to 98.58%.
These results indicate significant modification effects.
Calcium carbonate with dipalmitoyl tartaric acid diester absorbs less oil and has a smaller sedimentation volume. This is different from calcium carbonate that uses stearic acid. However, its activation degree is better. This shows that the modification effect of dipalmitoyl tartaric acid diester with double hydrophobic chains and dicarboxylic acids is better than that of traditional single-chain stearic acid.
Formula 16: Dry modification of eleostearic acid anhydride hydrolyzate
Modifier: Eleostearic acid serves as the raw material. It reacts with maleic anhydride through a Diels-Alder reaction to create eleostearic anhydride. Then, this compound is hydrolyzed to produce tricarboxyl eleostearic anhydride hydrolyzate, a modifier with multiple action points.
Modification method:
(1) Synthesis of eleostearic anhydride hydrolyzate:
- Add 20.0g of eleostearic acid to a three-necked flask.
- Heat it to 65℃ while stirring constantly.
- Then, add 3.6g of maleic anhydride.
- Once the maleic anhydride dissolves, raise the temperature to about 140℃.
- Let it react for 90 minutes to get a brown-yellow viscous eleostearic anhydride.
- Next, dissolve the eleostearic anhydride in some acetone to create a solution.
- Add a suitable amount of water to hydrolyze the anhydride.
- Let it sit at room temperature for 30 minutes to get the eleostearic anhydride hydrolyzate.
(2) Dry modification of heavy calcium carbonate:
- Start with 100g of heavy calcium carbonate powder.
- Place it in a high-speed disperser.
- Heat it to 50℃.
- Then, add a specific amount of acetone solution containing eleostearic acid anhydride hydrolyzate.
- Mix and stir for 15 minutes.
- After that, dry it until it reaches a constant mass.
- Finally
Test and characterization: activation degree, oil absorption value, contact angle, viscosity, and prepare calcium carbonate/PVC composite material to test performance.
Modification effect:
The best modification of calcium carbonate uses 1.5% eleostearic acid anhydride hydrolyzate. This results in an activation degree of 83.40%. It also reduces the oil absorption value to 28.29 mL/100g and lowers viscosity by 46.36%. The water contact angle measures 99°. Filling modified calcium carbonate into PVC boosts the composite’s notched impact strength. It rises from 8.455 kJ/m² to 10.216 kJ/m². The elongation at break also increases, going from 16.12% to 24.52%. Modified calcium carbonate has a toughening effect on PVC material.
Formulation 17: Span60 modification
Modifier: Sorbitan monostearate (Span60).
Modification method:
Weigh a specific amount of dried heavy calcium carbonate powder. Then, measure the same for ball milling beads. Next, place both into a clean, dry ball mill, following the ball-to-material ratio. Weigh the desired amount of modifier. Dissolve it in anhydrous ethanol. Then, pour the mixture into the ball mill. Start the ball mill to begin modification. After ball milling, remove the slurry. Then, place it in a drying oven at 80°C. Once dried, cool it to room temperature. Finally, grind it to get a modified heavy calcium powder sample.
Test and characterization: activation, sedimentation volume, oil absorption value, particle size.
Modification effect:
After modification, the surface activation of heavy calcium powder increases. Sedimentation volume, oil absorption value, and particle size decrease. The modifier Span60 has been successfully adsorbed onto the heavy calcium powder’s surface. This improves the powder’s surface properties. The amount of modifier has the biggest impact on the modification effect. Next comes the ball-to-material ratio. After that, ball milling time and ball milling speed also play important roles.
The best conditions for modification are:
- Ball milling speed: 300 r/min
- Ball milling time: 1.5 hours
- Ball-to-material ratio: 8:1
- Modifier dosage: 2.0%
Under these conditions, the activation degree of modified heavy calcium powder reaches 99.2%.
Formula 18: Polyvinyl acetate polymerization modification
Modifier: polyvinyl acetate.
Modification method:
(1) Direct modification of polyvinyl acetate. Heat the ground heavy calcium carbonate slurry to 90°C. Then, add the polymerized polyvinyl acetate while stirring quickly. Stir at 90°C for 1 hour to finish the modification.
(2) In-situ polymerization modification of polyvinyl acetate. Mix polyvinyl alcohol and sodium dodecylbenzene sulfonate into the ground heavy calcium carbonate slurry. Heat the slurry to 90°C. Then, turn on the emulsifier to fully dissolve the polyvinyl alcohol. Finally, let it cool down. Cool the mixture to 68–70°C. Then, add OP-10 and 30% of the total vinyl acetate. Stir for 20 minutes. Next, add 0.5% potassium persulfate based on the total vinyl acetate. Let it react for 30 minutes. Slowly add the remaining vinyl acetate and another 0.5% potassium persulfate. Maintain a temperature of 68–70°C while adding vinyl acetate. After adding all the vinyl acetate, raise the temperature to 90–95°C. Then, use a 10% sodium bicarbonate solution to adjust the pH to 6–7 until the reaction is finished and the modification is complete.
(3) Stearic acid modification. The ground heavy calcium carbonate slurry is heated to 90℃, and the heated and melted stearic acid is added under high-speed stirring. The temperature is maintained and stirred for 1h to complete the modification. Dehydration, drying, and crushing of heavy calcium carbonate: Use a centrifuge to dehydrate the modified heavy calcium carbonate slurry. This process creates a modified heavy calcium carbonate filter cake. The filter cake is placed in an oven and dried at 110℃ until the moisture content of the filter cake is less than 0.3%, which is considered to be completed. The dried filter cake is placed in a jet mill for crushing and sieving. The powder obtained after crushing and sieving is the heavy calcium carbonate powder used for PVC granulation.
Testing and characterization: thermogravimetric test, infrared spectrum test, PVC performance test.
Modification effect:
Calcium carbonate slurry needs a polymerization reaction. This helps polyvinyl acetate stick to the surface of calcium carbonate.
Calcium carbonate modified with polyvinyl acetate helps PVC products stay closer to the original heavy calcium carbonate color. This is better than calcium carbonate modified with stearic acid. The polyvinyl acetate reduces friction between calcium carbonate and PVC resin. It also lowers melt viscosity and prevents PVC resin from breaking down during plasticization.
Calcium carbonate modified with polyvinyl acetate has better mechanical properties in PVC materials. This is true when compared to modification with stearic acid. This is mainly because polyvinyl acetate helps calcium carbonate mix well with PVC resin and adds elastomers.
Calcium carbonate modified with polyvinyl acetate (in-situ polymerization) looks better in colored PVC injection-molded parts than calcium carbonate modified with stearic acid. This is due to the fact that polyvinyl acetate helps solve the compatibility issue between heavy calcium carbonate and PVC resin.
Formula 19: Starch coating modification
Modifier: Starch is the main modifier, and sodium stearate and sodium hexametaphosphate are auxiliary agents.
Modification method:
Natural polymer starch is used as the modifier. First, mix the starch and heavy calcium carbonate evenly. Then, prepare them into a suspension with the right proportion and concentration. Then, stir and heat the mixture to 95°C. After a while, add a certain amount of sodium stearate solution. The mixture’s starch goes through a composite reaction for a specific time. This process helps achieve a desired level of hydrophobicity. After a period of reaction, the temperature is lowered to improve the utilization rate of starch. Next, add some sodium hexametaphosphate solution. This will crosslink and precipitate the starch in water. It helps us use starch more effectively. It also boosts the shear resistance of the complex on the surface of heavy calcium carbonate.
Testing and characterization include:
- Whiteness
- Opacity
- Zeta potential
- Particle size and distribution
- Optical properties
- Strength properties of filled paper.
Modification effect:
The best conditions for modified heavy calcium carbonate are:
- 1.5% sodium hexametaphosphate
- 20% blend concentration
- 60℃ for the precipitation reaction
- 200rpm stirring speed.
Modification lowers the whiteness and opacity of heavy calcium carbonate. The Zeta potential shifts from positive to negative. Modified heavy calcium carbonate has particles that are about six times larger than those of unmodified heavy calcium carbonate. Its consistency is roughly 1/11 that of the unmodified type. Also, the particle size distribution range is narrower.
With the same ash content, modified heavy calcium carbonate filler paper has much stronger performance. Its Z-direction fiber bonding strength is much higher than that of unmodified heavy calcium carbonate filler paper. The modified heavy calcium carbonate filler paper is less white and less opaque than the unmodified version. However, the difference isn’t significant. As the filling amount increases, unmodified heavy calcium carbonate holds more initially. Then, modified heavy calcium carbonate takes the lead. Overall, their retention rates are similar. As cationic polyacrylamide (CPAM) increases, the modified heavy calcium carbonate retains more than the unmodified type at first. Then, the retention rate for unmodified heavy calcium carbonate becomes higher again. However, the overall retention rates for both types are quite similar. Starch modification of heavy calcium carbonate can improve the sizing effect of alkyl ketene dimer (AKD) in filled paper.
Formula 20: Titanate coupling agent and air flow milling integrated processing
Modifier: titanate coupling agent; it makes up 50% of the modifier solution. The solvent used is anhydrous ethanol.
Modification method:
The integrated treatment method of airflow crushing and surface modification is adopted. First, add 1.5 kg of heavy calcium particles to the airflow crushing chamber. Next, use the atomizing nozzle and a peristaltic pump to spray the modifier solution into the modification chamber. The supersonic crushing nozzle is turned on. High-pressure air crushes the heavy calcium particles in the chamber. This process helps modify the surface and achieve airflow crushing. Weigh the ultrafine heavy calcium powder every 5 minutes. Then, add the same amount of heavy calcium powder to the crushing chamber. This keeps the mass of heavy calcium powder constant in the chamber. The integrated crushing and modification experiment ends after 30 minutes.
Test and characterization:
The crushing discharge rate is used to evaluate the airflow crushing effect of heavy calcium particles. A faster crushing discharge rate uses less crushing energy for heavy calcium particles, even at the same wheel speed. This also leads to a better crushing effect. We examine the particle size distribution of the powder. This helps us check if the modification process changes the size of the heavy calcium powder. When the particle size of the heavy calcium powder does not change much, the faster the discharge rate, the better the crushing effect. Ultrafine heavy calcium and liquid paraffin show how surface modification affects viscosity. Lower viscosity means ultrafine heavy calcium powder mixes better with the organic matrix. It also makes it easier to disperse evenly. This results in a better surface modification effect.
Modification effect:
Changing the surface during air flow pulverization can boost the discharge rate of ultrafine heavy calcium powder. When the air flow temperature hits 60°C, the modifier solution has a 50% coupling agent mass fraction and flows at 1.5 mL/min. As a result, the discharge rate of heavy calcium particles climbs from 21.0 g/min to 56.7 g/min. This is a 170% increase. Air flow pulverization changes the surface of heavy calcium powder. This makes it mix well with the organic matrix. This process doesn’t greatly alter the particle size of the ultrafine heavy calcium powder. The size mainly relies on the rotation speed of the grading wheel.