Surface modification is an important means necessary to improve the application performance, applicability, market expansion and dosage of calcium carbonate. In the future, functionalization and specialization will become the main development trend of calcium carbonate, and the market demand for various surface modified calcium carbonate will be increasing.
1、Why is calcium carbonate surface modified?
（1）Improve calcium carbonate dispersibility
Ultrafine is an important way to improve the quality of calcium carbonate. However, the smaller the particle size of calcium carbonate, the higher the surface energy, the stronger the adsorption and the more serious the agglomeration.
By surface modification, the modifier can be adsorbed on the surface of calcium carbonate in a directional manner, so that the surface has charge characteristics. Due to the same charge exclusion, calcium carbonate is not easy to agglomerate, thus achieving good dispersion in the matrix.
（2）Improve the compatibility of calcium carbonate
By surface modification, the interface compatibility and compatibility between calcium carbonate and organism can be increased, so as to improve the product performance of calcium carbonate with rubber or plastic composite materials.
For example, calcium carbonate treated with titanate coupling agent has good compatibility with polymer molecules. At the same time, titanate coupling agent can form a molecular bridge between calcium carbonate molecules and polymer molecules, and enhance the interaction between organic polymer or resin and calcium carbonate, which can significantly improve the mechanical properties of thermoplastic composite materials, such as impact strength, tensile strength, bending strength and elongation.
（3）Reduce calcium carbonate oil absorption value
Surface modification is an important means to reduce the oil absorption value of powder. After the surface modification of calcium carbonate, state of aggregation particles decreases, dispersion, gap between particles decreases, at the same time modified molecular covering on the surface of calcium carbonate and reduce the gap in the granules, and the cover also change the surface properties of calcium carbonate, make its surface polarity is abate, decrease of friction between the particles, the better lubricity, so the accumulation of more closely, increase bulk density, oil absorption value decreases.
（4）Broaden the high-end application market of calcium carbonate
Calcium carbonate without surface modification has poor compatibility, easy agglomeration and poor application effect. Moreover, with the increase of dosage, these disadvantages become more obvious.
Through surface modification, calcium carbonate has good interface compatibility and lower oil absorption value, so it can be better used in high-end fields such as plastics, coatings, rubber, paper making, sealant, and permeable film, so as to improve product quality and further reduce the production cost of application enterprises.
（5）Give calcium carbonate more functional properties
Calcium carbonate without surface modification can only be used as a traditional filling material, and its application field and amount will be limited to some extent.
Calcium carbonate without surface modification can only be used as a traditional filling material, and its application field and amount will be limited to some extent.
The calcium carbonate coated with silicon dioxide can partially replace the silica and supplement the deficiency of silica in some properties.
Light calcium carbonate coated with metal can improve some special properties of rubber products.
The calcium carbonate composite coated with titanium dioxide can replace titanium dioxide to some extent.
Acid-resistant calcium carbonate can be prepared by phosphate, aluminate, silicate or barium salt treatment.
（6）Increase the added value of calcium carbonate products
At present, China’s general calcium carbonate overcapacity, product price competition is fierce. After surface modification of calcium carbonate, the use effect is significantly improved, the user experience is good, the product price naturally increases.
（7）Follow the development trend of calcium carbonate industry
The National Development and Reform Commission (NDRC) has listed the common grade calcium carbonate as a backward product in the Guidance Catalogue of Industrial Structure Adjustment (2019 Edition), which will be further eliminated in the future.
2、What fields can modified calcium carbonate be used in?
（1）PVC
Compared with ordinary calcium carbonate, modified calcium carbonate particles in the state of original particles uniformly distributed, reunion, and PVC resin has excellent compatibility and dispersity, plasticizing, not sticky roller, excellent processing performance, to improve processing efficiency, breaking strength and elongation at break and products improve, good physical and mechanical properties.
（2）PP
By modifying the surface of light calcium carbonate with the coupling agent tetrahydrofuran homogeneous polyether (PTHF), the oil absorption value and contact Angle of calcium carbonate decreased to 22% and 68.6° respectively. The modified calcium carbonate is filled into polypropylene and dispersed well in polypropylene, which can alleviate the decreasing trend of tensile strength to a certain extent, making the elongation at break of the composite reach 28.47% and the impact strength reach 6.7kj /m2.
（3）HDPE
The mechanical and chemical modification of heavy calcium carbonate was carried out by using aluminate coupling agent. The surface of calcium carbonate particles was bonded by aluminate coupling agent to some extent, and the dispersibility of calcium carbonate particles was obviously improved after modification. With the increase of the content of modified calcium carbonate in HDPE, the abrasion loss and frictional work of the composite decreased, and the anti-friction performance increased. At the dosage of 8PHR, the mechanical properties of the composite were the best, and the tensile strength and impact strength were increased by 4.46% and 24.57%, respectively.
（4）LDPE
Using stearic acid (1.5%) and DL-411 aluminate (0.5%), the activation index of modified calcium carbonate was 99.71%, the oil absorption value was 46.19ml /100g, the final settling volume was 2.3ml /g, and the viscosity of 10g modified calcium carbonate and 100mL liquid paraffin mixture was 4.4pA ·s. When the content of modified calcium carbonate is 10%, the composite material has better mechanical properties.
（5）ABS
After surface modification, nano calcium carbonate improves the dispersibility in organic media, and the surface changes from hydrophilic to oleophilic. The application of nano calcium carbonate in ABS resin can improve the mechanical properties of ABS resin, such as impact strength, tensile strength, surface hardness, bending strength and thermal properties, such as thermal deformation temperature.
（6）PBAT
The surface of calcium carbonate was modified by double layer coupling agent coating method, the modified calcium carbonate filling amount could reach 50%, and the comprehensive mechanical properties of the composite products were good. In the composite material, the modified calcium carbonate particles were completely infiltrated and coated by PBAT resin matrix without dissolution, and the mutual fluidity between them was improved.
（7）EPDM
The in situ modification of calcium carbonate by using titanate coupling agent 105 with unsaturated functional group improved the dispersibility of modified calcium carbonate. In irradiated crosslinked EPDM, the modified calcium carbonate surface reacts with EPDM through oleic acid group, which makes calcium carbonate participate in the CROSS linked NETWORK of EPDM, improves the tensile strength, 100% constant elongation stress and Shor A hardness of the composite material, and makes calcium carbonate strengthen in irradiated crosslinked EPDM.
（8）PLA
The coupling agent is used to modify the surface of calcium carbonate, so that the specific surface area of calcium carbonate increases and the contact area between calcium carbonate and the matrix increases. When subjected to stress, more silver grain and plastic deformation zone will be generated, absorbing a large amount of energy, so as to achieve the purpose of toughening and strengthening.
（9）PVC coated fabric
Modification of heavy calcium carbonate can improve the compatibility of PVC paste resin with mixing system, in the case of equal to ordinary coarse whiting usage, can achieve lower viscosity, enhance and adhere to polyester fabric, can reduce the dosage of the glue, at the same time, can improve the feel of the coating material, in the case of a 40% increase in usage, the processing properties of materials, physical and mechanical properties, heat welding performance without adverse effect.
（10）PVC PVC fire pipe
Compared with the ordinary calcium carbonate, modified calcium carbonate particles in the state of primary particles uniformly distributed, not together, some of them exist in state of nanoparticles, so fill in polyvinyl chloride (PVC) fire tube, not only can improve the processing performance of system, and gives products with good physical and mechanical properties, to achieve the effect of toughening reinforcement.
（11）PVC Cable material and flame retardant masterbatch
The heavy calcium carbonate is modified by aluminate, titanate coupling agent and stearic acid, and the heavy calcium carbonate composite filler is used to prepare PVC cable material and flame retardant masterbatch with excellent performance. The use of composite modifier will become one of the development trends of surface modification of heavy calcium carbonate.
（12）PEEK
By modifying calcium carbonate whisker with sulfonated hyperbranched polyether ketone, the dispersion of calcium carbonate whisker in the matrix was improved, the interaction between two phases was enhanced, and the melt viscosity in the processing temperature range of the composite was reduced. At the same time, the young’s modulus, bending modulus and toughness of the composite obtained were improved.
（13）Plastic film
Calcium carbonate is widely used in thin films. After surface treatment, calcium carbonate is mostly combined with basic resin in the form of surface adsorption, physical winding, van der Waals force, etc., with more uniform dispersion and better film performance.
（14）Plastic food packaging
Nanometer calcium carbonate, as a plastics-filled superfine material, has special effects in changing product properties. Previous studies have shown that nanometer food packaging materials have such characteristics as barrier, antibacterial and preservation, and have been applied in food packaging such as beer, beverage, fruits, vegetables and dairy products. In order to obtain the filling state with good dispersion and small particle size, the nano action energy must be weakened or reduced. Currently, mechanical dispersion method is generally adopted, or dispersants are added, drying treatment and other methods.
（15）Breathable film
The breathable film is made by adding about 50% special calcium carbonate into PE or PP carrier, extruding the film and then stretching it to a certain ratio. It is widely used in the fields of pharmaceutical adhesive film, surgical suit, medical gloves, women’s sanitary napkin, baby diaper, disposable bed sheet, plastic wrap, composite film, cooked food packaging bag and so on. After surface modification, calcium carbonate has better than expected hydrophobic property, excellent dispersion property and thermal stability, so it can be used in production of permeable film.
（16）Room temperature vulcanization (RTV) one component silicone rubber sealant
The surface modification of superfine calcium carbonate with silane coupling agent shows that the modified calcium carbonate has a better strengthening effect on sealant, with the tensile strength of 0.57mpa and the maximum elongation of 159.60%.
（17）Polyurethane sealant
The modified calcium carbonate was copolymerized with methyl methacrylate (MMA) and silane coupling agent KH570. The modified calcium carbonate had a water contact Angle of 60° and a settlement value of 1.36 mL /g. It showed good dispersion in polyurethane and thixotropic property after mixing with polyurethane, and the mechanical properties of polyurethane were improved better than that of unmodified calcium carbonate.
（18）silicone adhesive
Nano calcium carbonate can be used instead of white carbon black in the certain degree to fill silicone rubber, silicone rubber is the main production of raw materials, nano calcium carbonate as a filling agent, strengthening agent, silicone rubber, can greatly reduce the cost of products, improve the processing performance of products, greatly improve the mechanical properties such as tensile strength, tear strength, through the nano calcium carbonate crystal shape, particle size and surface treatment of control, so that the products obtain excellent thixotropic property and sag resistance.
（19）Rubber goods
The surface modified active calcium carbonate has a reinforcing effect in rubber, and its reinforcing performance is comparable to that of silica. Commonly used as white, light color and color rubber products reinforcing agent, can be used to manufacture tire buffer layer rubber, inner tube, bicycle tire, belt covering rubber, rubber hose, rubber cloth products and rubber shoes, also suitable for natural rubber, SBS and rubber latex, in SBS reinforcing effect is obvious, coloring performance is also good.
（20）Natural rubber vulcanized rubber
Using resorcinol and six methyl tetramine to modification of calcium carbonate, calcium carbonate modified natural rubber vulcanizates than the mechanical properties of natural rubber vulcanizates modified calcium carbonate had obvious increase, compared with the unmodified calcium carbonate, tensile modulus of the natural rubber vulcanizates increased by 130%, a 101% increase in the tensile strength, tear strength increased by 70%.
（21）SBR
Compared with unmodified calcium carbonate, the properties of the vulcanized rubber increased by 60% in tensile strength, 70% in constant elongation stress and 30% in tear strength by using carboxylated polybutadiene (CPB) modified calcium carbonate as reinforcement for SBR.
（22）Semi-steel radial tyre airtight layer
Adding 40 parts of modified calcium carbonate into the air-tight layer of semi-steel radial tire can improve the air-tightness of the rubber, and has little influence on the flexure resistance and processing performance of the rubber. According to the factory test results of the tire, the air tightness of the 40 parts of modified calcium carbonate airtight layer is 30% higher than that of the ordinary airtight layer. Meanwhile, the cost is reduced by 3.65 yuan /kg, and the high speed and durability of the tire are not affected.
（23）Paper packing
Starch coated modified calcium carbonate is used as papermaking filler. Modified calcium carbonate has strong shear resistance and high retention rate, so that the strength of the paper is higher, and the decline of the strength of the paper is significantly slowed down.
（24）Reengineering tobacco
Sodium hexametaphosphate and citric acid (with a compound ratio of 1:L) were used to modify calcium carbonate. The ash content of modified calcium carbonate added into the remanufactured tobacco leaves was 8.25% higher than that of commercial calcium carbonate. The results of conventional flue gas indexes and sensory evaluation were all better than that of commercial calcium carbonate.
（25）Powder coating
Modified calcium carbonate plays a skeleton role in powder coatings, which can increase the film thickness, improve the wear resistance and durability of coatings. Generally modified calcium carbonate is more expensive than other inorganic fillers, so it can reduce the cost of powder coating, and improve the powder rate and spraying area.
（26）latex paint
The preparation of PVC content is 43% modified nanometer calcium carbonate using latex paint, add modification of nanometer calcium carbonate coating coating surface smoothness good, dense, and contamination resistance, wash resistance, aging resistance performance are improved, such as modified with stearic acid and sodium sulfonate of nanometer calcium carbonate for greater influence on the tensile strength, and the stearic acid and ester titanate modified nanometer calcium carbonate on the contamination resistance and washing resistance effect is remarkable.
（27）electrophoretic paint
Calcium carbonate is modified by hydrated fluorosilicic acid. The modified surface of calcium carbonate is covered with a mixture of amorphous silicon and calcium fluoride to form a dense film, which greatly enhances the acid resistance of calcium carbonate and can be used in weak acid anodic electrophoretic paint.
（28）PVC car chassis anti-stone primer
The calcium carbonate with particle size of 40~80nm modified by fatty acid or fatty acid salt has good thixotropy, which is used in PVC automobile chassis anti-stone-hit primer and has good thixotropy and yield value.
（29）Printing ink
Modified calcium carbonate ink body bone and viscosity is better, has good printing performance, drying fast, and no side effects. Because the particles are small, used in ink products to show excellent dispersion, transparency, excellent gloss and covering power, as well as excellent ink absorption and dryness, so the printing is fine, dot integrity. Especially in the ink widely used resin binder, modified calcium carbonate with its excellent stability, has almost replaced the other fillers.
（30）Toothpaste
Guangdong La Fang Personal Care Products Co., LTD modified the surface of toothpaste with the abrasive agent calcium carbonate by coating micron grade spherical calcium carbonate particles with silicon dioxide, and added the modified calcium carbonate into the toothpaste under the condition of the same wear value, and the compatibility with fluoride was significantly improved.
（31）Commodity
Adding active nanometer calcium carbonate in cosmetics can make the products delicate and smooth. As an additive, it can eliminate the brightness of base powder, protect the skin’s adhesion, and have the function of oil absorption and anti-sweat. It is used for smooth powder, it does not irritate the skin, the color is even, it has certain hiding power.
（32）The stone artificial hills
The surface modified calcium carbonate has low oil absorption value and is an important raw material of artificial stone.
（33）Composite conductive powder
The acid resistance of calcium carbonate in acidic environment can be improved by coating modification. Then the composite conductive powder is prepared by combining calcium carbonate with polyaniline, which can not only give calcium carbonate good electrical conductivity, but also improve the defects of single polyaniline which is difficult to be processed and formed, and has a broad application prospect.
（34）lubricating oil
Adding modifier in the digestion process to produce active nano calcium carbonate can reduce the negative effect of surfactant on lubricating oil, improve the dispersion stability of nano calcium carbonate in lubricating oil, and thus improve its anti-wear and anti-friction properties.