CN1189523C - Surface treatment method for improving hydrophobicity of Nano particles of calcium carbonate - Google Patents

Abstract

The present invention relates to a surface treatment method for improving the hydrophobicity of nano calcium carbonate particles. Acrylics copolymer emulsion obtained by emulsion polymerization is used as a surface modifying agent, and nano calcium carbonate slurry is processed by the acrylics copolymer emulsion under the condition of stirring to improve the hydrophobicity of the nano calcium carbonate particles. The surface treatment method has the advantages of simple process and low preparation cost and can be used for evenly and stably coating a thin layer on the surface of the nano particles. In addition, the particle diameter of the processed particles can be well controlled. Under the condition of increasing great quantities of the nano calcium carbonate particles, the toughness of PVC resin can be enhanced, and the aggregation of the calcium carbonate particles can not be caused. Meanwhile, the production cost of PVC can be greatly reduced.

Description

A surface treatment method for improving the hydrophobicity of nanometer calcium carbonate particles

Technical field:

The invention relates to a surface treatment method for improving the hydrophobicity of nanometer calcium carbonate particles.

Background technique:

As an important inorganic chemical product, calcium carbonate is widely used in various industries such as rubber, paint, paper, ink, printing, cable, food, medicine, cosmetics, toothpaste, feed, lubricants, etc. However, since the surface of calcium carbonate powder has many hydroxyl groups, the hydrophilic and oleophobic properties are obvious, it is easy to form agglomerates during production and storage, the dispersion is extremely poor, and it is difficult to apply directly, so it generally must be surface treated. With the rise of nano-materials, the production of nano-calcium carbonate has also been industrialized. Nano-scale calcium carbonate particles have smaller particle sizes and are more likely to agglomerate, which puts forward higher requirements for the surface treatment of nano-calcium carbonate.

Dispersing and filling inorganic nanoparticles in polymers such as PVC can not only reduce the cost of materials, but also significantly improve the mechanical properties of raw materials such as toughness. However, the surface of these particles is hydrophilic and oleophobic, and the binding performance with organic matter is poor, and the extremely small particle size of the nanoparticles brings about a large surface energy, which makes it very easy to self-agglomerate, and once the agglomeration occurs, it is generally used It is difficult to open it again by mechanical means, which greatly affects the dispersion of inorganic nanoparticles in the polymer matrix. Therefore, it is necessary to carry out surface treatment on the nano-calcium carbonate particles. At present, the surface modification of nano-calcium carbonate particles can be roughly divided into two methods: dry method and wet method.

The so-called dry surface treatment is to put the powder of nano-calcium carbonate into a high-speed kneader for stirring, and then add a dispersant or a surface modifier for surface treatment; the so-called wet method is to directly add a surface treatment agent or a dispersant to the calcium carbonate slurry Among them, this method can be divided into pre-carbonization and post-carbonization. However, the method before carbonization is not commonly used because it is easy to cause foam in the carbonization tower.

The surface modifiers used can be divided into the following categories:

1. Coupling agent Surface modifier, such as silane coupling agent, titanate coupling agent, aluminate coupling agent. Coupling agent is the most commonly used and traditional surface treatment agent for calcium carbonate powder. The principle is to combine various coupling agents with free protons on the surface of calcium carbonate powder (from bound water, crystallization water, chemically adsorbed water and physically adsorbed water, etc.) on the surface of calcium carbonate powder to form chemical bonds. The surface is covered with a layer of molecular film.

2. Inorganic surface modifiers, such as condensed phosphoric acid, metaphosphoric acid or pyrophosphoric acid.

3. Organic surface modifiers, such as phosphoric acid esters, fatty acids or fatty salts, stearic acid, etc.

4. Polymer surface modifiers, such as reactive cellulose; grafted polymers, usually polyacrylic acid (salt), etc.

Some of the above surface modifiers (such as silane coupling agents) are only suitable for dry processing. After the calcium carbonate particles processed by the above-mentioned modification method 1 are introduced into polymers such as PVC, since the coupling agent is generally a small molecule, it will overflow after a certain period of time, causing pollution to the environment and causing a decline in the quality of polymers such as PVC.

Above-mentioned modification method 2,3,4 introduces in the polymer with the calcium carbonate particles that surface modifiers such as inorganic matter, organic matter, polymer are processed, though can make some performances of polymer, as impact resistance performance improves to some extent, but The used surface treatment agent acid and salt will cause the thermal stability of the polymer to decrease at the same time, and the addition of nanoparticles is also low, generally only accounting for 5-6% of the polymer monomer, which has little contribution to the reduction of cost. The reason is that the above-mentioned surface modification method cannot make the coating of nanoparticles complete and stable, so the problem of agglomeration in the case of a large amount of inorganic nanoparticles added has not yet been solved. Therefore, the improvement of the final performance of the product and the reduction of the cost are greatly restricted.

As reported in "Polyvinyl Chloride" No. 2, 2001, "Preparation of Special Resin for PVC/Nano-Calcium Carbonate Composite Building Materials" by In-situ Polymerization, use stearic acid, aluminate, etc. to carry out surface treatment to Nano-Calcium Carbonate, and Vinyl chloride monomer is polymerized in situ. The impact resistance of its products is twice that of pure PVC resin. The addition of nano-calcium carbonate increases the relative molecular weight and distribution index of PVC resin. The relative number-average molecular mass Mn is 1.09 times that of pure PVC, the relative weight-average molecular mass Mw is 1.34 times that of pure PVC, the relative viscosity-average molecular mass Mv is 1.33 times that of pure PVC, and the relative molecular mass distribution Mw/Mn is that of pure PVC. 1.23 times. This shows that the addition of nano-calcium carbonate has a significant impact on the molecular weight of PVC, which will further affect the original various physical and chemical properties of PVC. But the addition amount of nano-calcium carbonate only accounts for 5.5% of vinyl chloride monomer at most. And cause thermal stability to drop.

Another example is "Polyvinyl Chloride" No. 4, 2001, mentioned in the article "In-situ Polymerization Technology of 10,000-ton Grade Vinyl Chloride in the Existence of Nano-Calcium Carbonate Microemulsion", a polymer-grade nano-calcium carbonate micro-emulsion system has been developed, which can Directly used in the in-situ polymerization of vinyl chloride. When the amount that can be added accounts for 3%-5% of vinyl chloride monomer, the impact strength of the product can be increased to 2-4 times that of pure PVC. In this method, the surface molecular modification of nano-calcium carbonate is firstly carried out to form a microemulsion dispersion of nano-calcium carbonate. After polymerizing with vinyl chloride, it is filled and polymerized with vinyl chloride in the PVC matrix, and then disintegrates into small particles below 10 nanometers. It may form a three-dimensional network frame node structure with the PVC matrix, thereby improving the toughness of the product.

Invention content:

The object of the present invention is to provide a kind of surface treatment method that improves the hydrophobicity of nanometer calcium carbonate particle. The acrylic copolymer emulsion obtained by emulsion polymerization is used as a surface modifier to treat the nano-calcium carbonate slurry under stirring conditions to improve the hydrophobicity of the nano-calcium carbonate particles. The process is simple, the preparation cost is low, the surface of the nanoparticles can be uniformly coated with a thin layer, the coating is stable, the effect is ideal, and the particle size of the processed particles can be well controlled. In the case of adding a large number (up to 20%) of nano-calcium carbonate, not only the toughness of the PVC resin is improved, but also the agglomeration of calcium carbonate particles will not be caused. At the same time, the production cost of PVC can be greatly reduced.

Summary of the invention: the present invention is a surface treatment method for improving the hydrophobicity of nanometer calcium carbonate particles, using the acrylic copolymer emulsion obtained by emulsion polymerization as a surface modifier to treat the nanometer calcium carbonate slurry under stirring conditions to achieve nanometer calcium carbonate Improvement of the hydrophobicity of calcium carbonate particles.

Surface treatment method of the present invention is completed by following two steps:

A: Emulsion polymerization process: the present invention adopts the acrylate copolymer emulsion and its preparation method commonly used in the prior art and well known to those skilled in the art. What needs to be controlled is that the amount of emulsifier accounts for 1-1% of the total monomer amount. 2%, the weight ratio of the soft monomer to the hard monomer is 13:7-10:10, and the third component acid accounts for 0.5-3% of the total amount of the monomer.

B: surface treatment process: the acrylate copolymer emulsion obtained in step A is added dropwise to the nano-calcium carbonate particle slurry under stirring conditions, and the ratio of the solid content of the emulsion to the nano-calcium carbonate particle slurry is controlled to be 1:9-2 : 8, after the dropwise addition, continue to stir until the nano-calcium carbonate particles are all coated.

In the above-mentioned step A, the acrylate copolymer emulsion is a copolymer emulsion prepared by polymerization or copolymerization of acrylate monomers, and the solid content of the acrylate copolymer emulsion is 38-44%.

In the above step A, the initiator used is commonly used in the emulsion polymerization of acrylate copolymers, such as ammonium persulfate, ammonium persulfate-sodium bisulfite, etc., and the amount thereof accounts for 0.1-0.3% of the total monomer amount.

In the above step A, the third component acid used is a carboxylic acid containing a polymerizable double bond. Such as: methacrylic acid, acrylic acid or maleic acid.

In the above step A, the soft monomer used is ethyl acrylate or n-butyl acrylate or 2-ethylhexyl acrylate, and the hard monomer is methyl methacrylate. The used emulsifier is also commonly used in the prior art, such as sodium lauryl sulfate, alkylphenol polyoxyethylene ether and the like.

The present invention adopts acrylate copolymer emulsion as the surface modifier of nano-calcium carbonate particles, so that the surface of the particles is uniformly wrapped with a thin layer of polymer, and the coating effect is ideal. X-ray photoelectron spectroscopy (XPS) test shows that The thickness of the polymer coating layer on the surface of nano-calcium carbonate particles is about 10nm, which is consistent with the results shown by the electron microscope photos. In addition, the coating effect can also be seen from the comparison of Figure 1 and Figure 2. As the surface modifier of nano-calcium carbonate particles, acrylate copolymer emulsion itself is the plasticizer of PVC resin. Its introduction will not damage the resin like the aforementioned small molecule surfactants, acids and salt Some qualities, on the contrary, improve the mechanical properties of PVC.

The method of the invention can also well control the particle diameter of the treated particle, and effectively improve the hydrophobicity of the particle surface, so that it can have a good affinity with organic matter. It was found by transmission electron microscopy that there was no agglomeration of nano-calcium carbonate particles at the end of the surface treatment process.

In-situ suspension polymerization is performed on the nanometer calcium carbonate particles and the vinyl chloride monomer after the surface treatment by the method of the present invention. The addition of nano-calcium carbonate can reach 20%, which can greatly reduce the production cost of PVC. The polymerized product was observed by transmission electron microscope and scanning electron microscope, and it was found that almost all nano-calcium carbonate particles were uniformly present in the PVC polymer spheres, and there was no agglomeration, and the dispersion was very ideal, while the nano-calcium carbonate particles in the water phase Very few. The product pellets are processed into plastic splines, and the observation results of the sliced transmission electron microscope and scanning electron microscope remain unchanged. The impact strength test of the plastic splines shows that the impact resistance of the product increases with the increase in the number of nano-calcium carbonate. Increase accordingly. When the addition amount is 5%, the impact resistance of PVC composite material is about 2 times that of pure PVC, and when the addition amount is 20%, the impact resistance performance of PVC composite material is about 4.5 times that of pure PVC. The tensile strength reaches 53.7Kj/m ² .

As can be seen from the data in the following table, the addition of nano-calcium carbonate processed by the method of the present invention has almost no impact on the molecular weight and molecular weight distribution of PVC, thereby ensuring that the PVC resin can basically maintain the original various physical and chemical properties.

Table 1: Comparison of molecular weight test results sample Add copies mn mw Mz Mv Mw/Mn Pure PVC 0 56442 110483 222667 102718 1.957460 Example 1 20 57864 119082 230090 110543 2.057961 Example 2 13 55213 115929 228780 107398 2.099683

In the table, Mv is the relative viscosity-average molecular mass, Mn is the relative number-average molecular mass, Mw is the relative weight-average molecular mass, Mz is the relative Z-average molecular mass, and Mw/Mn is the relative molecular mass distribution.

Description of drawings:

Figure 1 is a transmission electron micrograph of untreated nano-calcium carbonate particles.

Fig. 2 is the transmission electron micrograph of the nano-calcium carbonate particle processed by the method of the present invention.

Fig. 3 is the transmission electron micrograph (magnification is 2000) of the composite pellet after the nano-calcium carbonate particle and vinyl chloride surface-treated by the method of the present invention carry out in-situ suspension polymerization.

Fig. 4 is the transmission electron micrograph (magnification: 80,000) of composite pellets after in-situ suspension polymerization of nano-calcium carbonate particles and vinyl chloride surface-treated by the method of the present invention.

It can be seen from Figure 1 that the diameter of untreated nano-calcium carbonate particles is between 30nm and 50nm, the surface is relatively clean, the particle boundaries are relatively clear, and most of the particles are cubic. It can be seen from FIG. 2 that the diameter of the polymer-coated calcium carbonate particles is approximately between 50nm and 60nm. The diameter is large, and there seems to be a large number of tiny particles on the surface. The boundaries of the particles are fuzzy, and most of them are round. It shows that the coating effect is good.

It can be seen from Figure 3 and Figure 4 that a large number of nano-calcium carbonate particles are evenly filled in the primary PVC pellets, and the dispersion is good, and there are basically no nano-calcium carbonate particles in the water phase.

Detailed ways:

Example 1:

A. Emulsion polymerization:

The soft monomer is n-butyl acrylate, and the hard monomer is methyl methacrylate. Blend the soft monomer, hard monomer and methacrylic acid (the third component acid) in a weight ratio of 11:9:0.6 to form a monomer blend liquid. Emulsifier selects sodium dodecyl sulfate (SDS) and alkylphenol polyoxyethylene ether (OP-10), is respectively 0.25 gram and 0.55 gram, two kinds of emulsifiers are mixed in 15 grams of deionized water, heated to completely dissolved. Add the dissolved emulsifier solution into the reactor, then add 4.12 grams of the above-mentioned monomer blend solution, stir and heat up to 75 ° C, and add 0.06 grams of ammonium persulfate (analytical pure) dissolved in 23 grams of deionized water at one time . When the temperature rises back to 80°C, the monomers start to be triggered, and when the system obviously appears "blue", keep the reaction temperature at 80°C, then add 37.08 grams of the monomer blend solution dropwise, and at the same time add 20 0.06 gram of ammonium persulfate dissolved in gram of deionized water, and the rate of addition is controlled so that all the additions are added dropwise at a uniform speed in about 1 hour. Then continue to react for about 3.5 hours, then cool and discharge. The solid content of the finally prepared polymer emulsion: 42%.

B. Surface treatment:

Taking by weighing 405 grams of nano-calcium carbonate slurry (81 grams of nano-calcium carbonate dry weight) with a solid content of 20% is added to the reactor, and stirred at normal temperature until the system is uniform. Take by weighing 21.4 grams of the emulsion obtained in the A step (the solid content of the emulsion is 9 grams), slowly and evenly join in the nano-calcium carbonate slurry under stirring conditions, continue to stir, and it can be seen that the nano-calcium carbonate particles are wrapped in When the coverage is good, end the surface preparation process.

C. Polymerization and performance testing:

The surface-treated nano-calcium carbonate is added to a conventional polyvinyl chloride suspension polymerization reactor, and the added amount is 20% of the amount of the vinyl chloride monomer. The specific process is to first add a dispersant (polyvinyl alcohol, hydroxypropyl methylcellulose), an initiator (diethylhexyl peroxydicarbonate), water, and surface-treated nano-calcium carbonate slurry to the reactor. After stirring evenly at room temperature, add the monomer (vinyl chloride), raise the temperature to 57°C, and carry out the reaction. The impact strength of the reacted composite material is 11.2Kj/m ² after testing. The impact strength of pure PVC without adding nano-calcium carbonate is 2.49Kj/m ² , and the tensile strength reaches 53.7Kj/m ² .

Example 2:

A. Emulsion polymerization:

The soft monomer is 2-ethylhexyl acrylate, and the hard monomer is methyl methacrylate. Blend the soft monomer, hard monomer and methacrylic acid (the third component acid) at a weight ratio of 10:10:0.2 to form a monomer blend. Emulsifier selects sodium dodecyl sulfate (SDS) and alkylphenol polyoxyethylene ether (OP-10), is respectively 0.24 gram and 0.48 gram, two kinds of emulsifiers are mixed in 15 grams of deionized water, heated to completely dissolved. Add the dissolved emulsifier solution into the reactor, then add 4.242 grams of the above-mentioned monomer blend solution, stir and heat up to 75 ° C, and add 0.021 grams of ammonium persulfate (analytical pure) dissolved in 22 grams of deionized water at one time . When the temperature rises back to 80°C, the monomers start to be triggered, and when the system obviously appears "blue", keep the reaction temperature at 80°C, then add 37.178 grams of the monomer blend solution dropwise, and at the same time add 20 0.021 gram of ammonium persulfate dissolved in gram of deionized water, the rate of addition is controlled so that all the additions are added dropwise at a uniform speed in about 1 hour. Then continue to react for about 3.5 hours, then cool and discharge. The solid content of the finally prepared polymer emulsion: 44%.

B. Surface treatment:

The solid content of the nano-calcium carbonate slurry is 22%, and 500 grams (110 grams of nano-calcium carbonate dry weight) are weighed and added to the reactor, and stirred at normal temperature until the system is uniform. Take by weighing 27.73 grams of the emulsion of the A step gained (the solid content of the emulsion is 12.2 grams), slowly and evenly join in the nano-calcium carbonate slurry under the condition of stirring, continue to stir, it can be seen that the nano-calcium carbonate particles are wrapped in When the coverage is good, end the surface preparation process.

C. Polymerization and performance testing:

The surface-treated nano-calcium carbonate is added to a conventional polyvinyl chloride suspension polymerization reactor, and the added amount is 13% of the amount of the vinyl chloride monomer. The specific process is to first add a dispersant (polyvinyl alcohol, hydroxypropyl methylcellulose), an initiator (diethylhexyl peroxydicarbonate), water, and surface-treated nano-calcium carbonate slurry to the reactor. After stirring evenly at room temperature, add the monomer (vinyl chloride), raise the temperature to 57°C, and carry out the reaction. After the reaction, the composite material was tested, and the impact strength was 7.5Kj/m ² . The impact strength of pure PVC without adding nano-calcium carbonate is 2.49Kj/m ² , and the rest of the conditions are the same.

Example 3:

A. Emulsion polymerization:

The soft monomer is selected from ethyl acrylate, and the hard monomer is selected from methyl methacrylate. Blend the soft monomer, hard monomer and acrylic acid (the third component acid) in a weight ratio of 10:10:0.1 to form a monomer blend liquid. Emulsifier selects sodium dodecyl sulfate (SDS) and alkylphenol polyoxyethylene ether (OP-10), is respectively 0.34 gram and 0.48 gram, two kinds of emulsifiers are mixed in 15 grams of deionized water, heated to Dissolve completely, add the emulsifier solution that has dissolved in the reactor, then add 4.12 grams of the above-mentioned monomer blends, stir and heat up to 75 ° C, and add 0.02 grams of ammonium persulfate dissolved in 23 grams of deionized water ( analytically pure). When the temperature rises to 80°C, the monomers start to be triggered, and when the system obviously appears "blue", keep the reaction temperature at 80°C, then add 37.08 grams of the monomer blend solution dropwise, and at the same time add 20 grams of 0.02 grams of ammonium persulfate dissolved in deionized water, and the rate of addition is controlled so that all the additions are added dropwise at a uniform speed in about 1 hour. Then continue to react for about 3.5 hours, then cool and discharge. The solid content of the finally prepared polymer emulsion: 38%.

B. Surface treatment:

Take by weighing 400 grams of nano-calcium carbonate slurry (100 grams of nano-calcium carbonate dry weight) with a solid content of 25%, add it to the reactor, and stir at normal temperature until the system is uniform. Take by weighing 29.2 grams of the emulsion obtained in the A step (the solid content of the emulsion is 11.1 grams), slowly and evenly join in the nano-calcium carbonate slurry under the condition of stirring, continue to stir, and it can be seen that the nano-calcium carbonate particles are wrapped in When the coverage is good, end the surface preparation process.

C. Polymerization and performance testing:

The surface-treated nano-calcium carbonate is added to a conventional polyvinyl chloride suspension polymerization reactor, and the added amount is 11% of the amount of the vinyl chloride monomer. The specific process is to first add a dispersant (polyvinyl alcohol, hydroxypropyl methylcellulose), an initiator (diethylhexyl peroxydicarbonate), water, and surface-treated nano-calcium carbonate slurry to the reactor. After stirring evenly at room temperature, add the monomer (vinyl chloride), raise the temperature to 57°C, and carry out the reaction. After the reaction, the composite material was tested, and the impact strength was 10.4Kj/m ² . The impact strength of pure PVC without adding nano-calcium carbonate is 2.49Kj/m ² .

Example 4:

A. Emulsion polymerization:

The soft monomer is 2-ethylhexyl acrylate, and the hard monomer is methyl methacrylate. Blend the soft monomer, hard monomer and methacrylic acid in a weight ratio of 11:9:0.4 to form a monomer blend liquid. Emulsifier selects sodium dodecyl sulfate (SDS) and alkylphenol polyoxyethylene ether (OP-10), is respectively 0.28 gram and 0.56 gram, two kinds of emulsifiers are mixed in 15 grams of deionized water, heated to Completely dissolve, add the dissolved emulsifier solution into the reactor, then add 4.284 grams of the above-mentioned monomer blend into the reactor, stir, and when the temperature rises to 75°C, add 20 grams of deionized water at one time to dissolve 0.042 grams of ammonium persulfate, when the temperature rises to 80°C, the monomers start to be triggered, and when the system obviously appears "blue", keep the reaction temperature at 80°C, add 38.556 grams of the monomer blend solution dropwise, and at the same time 0.042 g of ammonium persulfate dissolved in 22 g of deionized water was added dropwise to the reactor. Control the rate of addition so that all the additions are added dropwise at a uniform speed in about 1 hour. Cool the discharge. The solid content of the finally prepared polymer emulsion: 40%.

B. Surface treatment:

Weighing 500 grams of nano-calcium carbonate slurry with a solid content of 20.5% (102.5 grams of nano-calcium carbonate dry weight) was added to the reactor, and stirred at room temperature until the system was uniform. Take by weighing 64.05 grams of the emulsion of A step gained (the solid content of the emulsion is 25.62 grams), slowly and evenly join in the nano-calcium carbonate slurry under the condition of stirring, continue to stir, it can be seen that the nano-calcium carbonate particles are wrapped in When the coverage is good, end the surface preparation process.

C. Polymerization and performance testing:

The surface-treated nano-calcium carbonate is added to a conventional polyvinyl chloride suspension polymerization reaction kettle, and the added amount is 8% of the amount of the vinyl chloride monomer. The specific process is to first add a dispersant (polyvinyl alcohol, hydroxypropyl methylcellulose), an initiator (diethylhexyl peroxydicarbonate), water, and surface-treated nano-calcium carbonate slurry to the reactor. After stirring evenly at room temperature, add the monomer (vinyl chloride), raise the temperature to 57°C, and carry out the reaction. After the reaction, the composite material was tested, and the impact strength was 5.5Kj/m ² . The impact strength of pure PVC without adding nano calcium carbonate is 2.49Kj/m ² .

Example 5:

A. Emulsion polymerization:

The soft monomer is 2-ethylhexyl acrylate, and the hard monomer is methyl methacrylate. The soft monomer, the hard monomer, and the acrylic acid are blended in a ratio of 13:7:0.1 parts by weight to form a monomer blend liquid. Emulsifier selects sodium dodecyl sulfate (SDS) and alkylphenol polyoxyethylene ether (OP-10), is respectively 0.25 gram and 0.55 gram, then two kinds of emulsifiers are mixed in the deionized water of 15 grams, heating When it is completely dissolved, add the dissolved emulsifier solution into the reactor, then add 4.02 grams of the above-mentioned monomer blend into the reactor, stir, and when the temperature rises to 75°C, add 20 grams of deionized water at one time Dissolved 0.04 grams of ammonium persulfate, when the temperature rises to 80°C, the monomer starts to be triggered, and when the system obviously appears "blue", keep the reaction temperature at 80°C, add 36.18 grams of the monomer blend solution dropwise, and at the same time 0.04 g of ammonium persulfate dissolved in 24 g of deionized water was added dropwise to the reactor. Control the rate of addition so that all the additions are added dropwise at a uniform speed in about 1 hour. Cool the discharge. The solid content of the finally prepared polymer emulsion: 42%.

B. Surface treatment:

Weighing 458 grams of nano-calcium carbonate slurry with a solid content of 23% (105.34 grams of nano-calcium carbonate dry weight) was added to the reactor, and stirred at normal temperature until the system was uniform. Take by weighing 41.8 grams of the emulsion of A step gained (the solid content of the emulsion is 17.56 grams), slowly and evenly join in the nano-calcium carbonate slurry under the condition of stirring, continue to stir, it can be seen that the nano-calcium carbonate particle wrapping When the coverage is good, end the surface preparation process.

C. Polymerization and performance testing:

The surface-treated nano-calcium carbonate is added to a conventional polyvinyl chloride suspension polymerization reactor, and the added amount is 5% of the amount of the vinyl chloride monomer. The specific process is to first add a dispersant (polyvinyl alcohol, hydroxypropyl methylcellulose), an initiator (diethylhexyl peroxydicarbonate), water, and surface-treated nano-calcium carbonate slurry to the reactor. After stirring evenly at room temperature, add the monomer (vinyl chloride), raise the temperature to 57°C, and carry out the reaction. The impact strength of the reacted composite material is 5.1Kj/m ² after testing. The impact strength of pure PVC without adding nano-calcium carbonate is 2.49Kj/m ² , and the rest of the conditions are the same.

Embodiment 6:

A. Emulsion polymerization:

The soft monomer is selected from ethyl acrylate, and the hard monomer is selected from methyl methacrylate. Blend the soft monomer, hard monomer and methacrylic acid (the third component acid) in a weight ratio of 13:7:0.5 to form a monomer blend. Emulsifier selects sodium dodecyl sulfate (SDS) and alkylphenol polyoxyethylene ether (OP-10), is respectively 0.3 gram and 0.5 gram, two kinds of emulsifiers are mixed in 15 grams of deionized water, heated to completely dissolved. Add the dissolved emulsifier solution into the reactor, then add 4.12 grams of the above-mentioned monomer blend, stir and raise the temperature to 75°C to keep the temperature constant, and add 0.05 grams of persulfuric acid dissolved in 23 grams of deionized water at one time Ammonium (analytical pure). When the temperature rises to 80°C, the monomers start to be triggered, and when the system obviously appears "blue", keep the reaction temperature at 80°C, then add 37.08 grams of the monomer blend solution dropwise, and at the same time add 20 grams of 0.05 grams of ammonium persulfate dissolved in deionized water, and the rate of addition is controlled so that all the additions are added dropwise at a uniform speed in about 1 hour. Then continue to react for about 3.5 hours, then cool and discharge. The solid content of the finally prepared polymer emulsion: 41%.

B. Surface treatment:

The solid content of the nano-calcium carbonate slurry is 20%. Weigh 400 grams and add it to a 1000ml glass beaker, i.e. the dry weight of the nano-calcium carbonate is 80 grams. Stir at a low speed at room temperature until the system is uniform with an electric stirrer. Weigh 24.39 grams of the emulsion obtained in the A step, that is, the solid content of the emulsion is 10 grams, slowly and evenly add it to the stirring nano-calcium carbonate slurry, stir, and electron microscope observation can be seen that the nano-calcium carbonate particles with good coating conditions , the surface treatment process is considered complete.

C. Polymerization and performance testing:

The surface-treated nano-calcium carbonate is added to a conventional polyvinyl chloride suspension polymerization reactor, and the added amount is 17% of the amount of the vinyl chloride monomer. The specific process is to first add a dispersant (polyvinyl alcohol, hydroxypropyl methylcellulose), an initiator (diethylhexyl peroxydicarbonate), water, and surface-treated nano-calcium carbonate slurry to the reactor. After stirring evenly at room temperature, add the monomer (vinyl chloride), raise the temperature to 57°C, and carry out the reaction. After the reaction, the composite material was tested, and the impact strength was 9.97Kj/m ² . The impact strength of pure PVC without adding nano-calcium carbonate is 2.49Kj/m ² , and the tensile strength reaches 51.8Kj/m ² .

Claims (3)

1. surface treatment method that improves hydrophobicity of Nano particles of calcium carbonate, the acrylic acid esters co-polymer emulsion that adopts letex polymerization to obtain is handled the nano-calcium carbonate slurries under stirring condition as surface-modifying agent and is realized; Its feature and concrete steps are:

A: emulsion polymerization process: the consumption of emulsifying agent accounts for the 1-2% of the total consumption of monomer, and soft monomer and hard monomer ratio of weight and number are 13: 7-10: 10, the three component acid account for the 0.5-3% of the total consumption of monomer;

Said emulsifying agent is sodium lauryl sulphate, alkylphenol polyoxyethylene or their miscellany in the steps A; Said soft monomer is ethyl propenoate or n-butyl acrylate or 2-EHA; Hard monomer is a methyl methacrylate; Initiator is the miscellany of ammonium persulphate or ammonium persulphate and sodium bisulfite; The acid of the 3rd component is methacrylic acid, vinylformic acid or maleic acid;

B: surface treatment process: the acrylic acid esters co-polymer emulsion that steps A is obtained is added drop-wise in the Nano particles of calcium carbonate slurries under stirring condition, the ratio of control emulsion and Nano particles of calcium carbonate slurry solid content is 1: 9-2: 8, and dropwise and continue to be stirred to Nano particles of calcium carbonate and all coated.

2. according to the surface treatment method of claim 1, it is characterized in that: the copolymer emulsion of acrylic acid esters co-polymer emulsion for being made by acrylic ester monomer polymerization or copolymerization, solid content is 38-44%.

3. according to the surface treatment method of claim 1, it is characterized in that: the consumption of initiator accounts for the 0.1-0.3% of the total consumption of monomer.

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