CN1386784A - Process for preparing SiO2-polymer composite material - Google Patents

Abstract

The invention provides a method for preparing a silicon dioxide-polymer composite material by using water glass as a raw material through a sol-gel method. The prior art has many disadvantages, such as complex preparation conditions, high cost, unsatisfactory performance of the obtained composite material, and the like. The method comprises the following steps: 1) adjusting the pH value of water glass to be acidic, adding an inorganic salt to a saturated aqueous phase, and then extracting the generated active silicic acid with an organic solvent; 2) adding the above active silicic acid solution and a suitable coupling agent into the monomer or polymer solution system, and mix evenly; 3) heat-treat the above solution at 60-380°C, and finally generate a composite material of silicon dioxide/polymer. Compared with the commonly used method of adding silica solid particles into the polymer system, this method has lower cost, more uniform dispersion of the silica inorganic phase in the polymer, easier control of the particle size, and convenient preparation of the inorganic phase. Nano-silica-polymer composite materials with a particle size below 100 nanometers. Compared with the polymer body, this composite material has better heat resistance, mechanical properties and lower thermal expansion coefficient, and can maintain the transparency of the polymer itself.

Description

Preparation method of silica-polymer composite material

technical field

The present invention relates to a novel method for preparing silica/polymer composite material.

Background technique

Organic-inorganic composite materials are a hot spot in material research at present and in the future. Compared with traditional composite materials, they have some very unique properties, so they are getting more and more attention. They have both the properties of organic polymer materials (such as flexibility, ductility, dielectricity, and processability, etc.) and the properties of inorganic materials (such as rigidity, high thermal stability, etc.). Especially organic-inorganic nanocomposite materials, due to the addition of nanoparticles, the composite materials often have some special properties and have a wider range of uses. Among them, silica-polymer composites are the most widely reported organic-inorganic composites.

At present, the method of preparing silica-polymer composite materials mainly adopts the method of mechanical blending. First, the silica is made into solid particles of a certain size. Polymers are mixed. This method has the advantages of simple method and low cost when the particle size is relatively large (micron scale) and the filling amount of silicon dioxide is small (generally <30%). However, since there are always two phases of organic and inorganic in the system, it is difficult to achieve a very uniform dispersion of silica in the polymer. Moreover, if the content of the inorganic phase is high, the viscosity of the system will increase sharply, resulting in difficulty in processing.

In addition, due to the very large surface area of nanoparticles, there is a great tendency to aggregate, and it is difficult to avoid the agglomeration of particles in the polymer by mechanical blending. At the same time, the manufacturing cost of nano-sized silica particles is also much higher than that of ordinary micron-sized silica particles. It has certain limitations for systems that require high dispersion uniformity.

Sol-gel technology is an important method developed in recent years to prepare organic-inorganic nanocomposites. It combines the hydrolysis and polycondensation reactions of metal alkoxy compounds with the polymerization reactions of polymers. By controlling the hydrolysis-polycondensation reactions To control the sol-gel process to obtain nanoscale inorganic phases. Because it can be carried out under milder conditions, and the inorganic particles in the prepared composite material are uniformly distributed and small in size, it has made great progress in the past 20 years.

Silica-polymer composites are prepared by the sol-gel method. At present, alkoxides or halides of silicon are mainly used, such as: tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), chlorosilane, etc. wait. However, due to the high cost of silicon alkoxides and halides, this method is still difficult to apply to large-scale industrial production. Moreover, the hydrolysis of silane oxide requires a certain amount of water to participate in the reaction and a small amount of acid as a catalyst. It is always difficult to achieve complete hydrolysis during the mixing process with the polymer, and some unhydrolyzed silane oxides always remain in the system. At the same time, the water in the system may also have an adverse effect on the performance of the final product.

The object of the present invention is to replace the hydrolysis products of siloxy compounds or halides with active silicic acid extracted from cheap industrial products water glass or sodium silicate to prepare silica-polymer composites to reduce costs, and The low water content in the system is beneficial to improve the performance of the final product, and the low viscosity of the system facilitates the preparation of composite materials with high inorganic phase content. The process is simpler and suitable for industrial production. Compared with the mechanical blending method, the particle size of the in-situ generated silica is small and easy to control, and the distribution is more uniform, which is more suitable for the preparation of nanocomposites.

Contents of the invention

The purpose of the present invention is to study a low-cost, high-performance preparation method of silica-polymer composite material.

The purpose of the present invention is to study a kind of preparation method that is applicable to nano silicon dioxide-polymer composite material.

The object of the present invention is to develop a method for the preparation of a silica-polymer composite material with a simple method and a high silica content.

The preparation method of the present invention is prepared through three steps. The first step is to use acid to adjust the pH value of water glass or sodium silicate solution to acidity, add salt saturated aqueous phase, and extract the active silicic acid with organic solvent; the second step is to add the obtained active silicic acid solution to the single Polymerize in the body or prepolymer, or directly add the polymer solution, mix well; the third step is post-treatment, remove and recover the solvent in the system, and heat-treat the obtained mixed solution at 60-380°C, The silicic acid is dehydrated and polycondensed to become silica, but the polymer cannot be decomposed to obtain a silica-polymer composite material.

The solid content of the active silicic acid solution is determined by the thermogravimetric method, and the solid content is represented by the amount of silicon dioxide in the solution, and the content of silicon dioxide in the composite material is the solid content in the added active silicic acid solution.

The acid used in the above preparation process can be inorganic acid or organic acid, such as hydrochloric acid, sulfuric acid, phosphoric acid or acetic acid, etc., and the pH range is generally 1-5. The inorganic salts used are salts with good solubility such as NaCl, NaSO ₄ , Na ₂ CO ₃ , Na ₂ HPO ₄ or KCl. Used organic solvents such as tetrahydrofuran, dioxane, 2-propanol, tert-butanol and N-methyl-2-pyrrolidone and other solvents with good solubility or their mixtures.

The present invention is applicable to monomers, prepolymers or polymers that can be dissolved in organic solvents, generally polystyrene, polyacrylic acid, polymethacrylate, polyvinyl acetate, etc. or derivatives of monomers Homopolymers or copolymers of all can be used as raw materials for the polymers of the present invention. The solvent which dissolves the monomer, prepolymer or polymer must not separate phases when mixed with the solvent which dissolves the active silicic acid.

When the active silicic acid obtained in the first step reaction of the present invention is added to the monomer or prepolymer or polymer solution, a certain amount of coupling agent can be added and mixed evenly, so as to enhance the bonding force between silica and the polymer interface and make the silica The dispersion of silicon in the polymer is more uniform and the particle size is smaller. It is also possible to use a coupling agent containing a polymerizable group such as a double bond to first polymerize with the monomer or prepolymer, or use a coupling agent containing a group that can react with the polymer to react with the polymer first and then react with the active Silicic acid solution mixed. Coupling agents such as: γ-glycidyl ether trimethoxysilane, trimethoxysilyl propyl methacrylate and the like.

The general structural formula of the coupling agent used in the present invention is YRSiX ₃ , where X is a hydrolyzable group bound to a silicon atom, such as an alkoxy group, a chloro group, an acetoxy group, etc.; Y is an affinity group with a polymer molecule. Active functional groups with synergistic or reactive capabilities, such as amino, mercapto, vinyl, epoxy, methacryloxy, etc.; R is other aliphatic or aromatic groups.

While adding monomer or prepolymer or polymer solution to the active silicic acid solution, other inorganic particle sols are added and mixed evenly. Inorganic particle sol such as: titanium sol, aluminum sol, zirconium sol, etc.

Because the inorganic phases such as silicon dioxide in the method of the present invention are uniformly dispersed in the polymer, and the particle size is easy to control, it is possible to obtain a composite material with a high inorganic phase content in which the weight of silicon dioxide accounts for 0.1-99.5% of the total weight of the material, and obtain a unique properties of silica-polymer composites.

The particle size range of the silicon dioxide particles in the present invention can be controlled between 0.005-20 microns. The particle size of silica can be adjusted by the amount of silica or the amount of coupling agent. Generally, the amount of silica is small and the particle size is small, otherwise the particle size is large; the amount of coupling agent is large and the particle size is small, otherwise the particle size is large.

The size of the inorganic phase in the silica-polymer composite material reaches the nanoscale, and its performance will be more satisfactory. In the present invention, by adjusting the amount of silica at 0.1-70%, or the coupling dose at 0.5-99%, or the heat treatment temperature at 60-380°C, the particle diameter of the silica particles in the composite material is 0.005 Between -0.5 microns, basically the range of nanoparticles.

The modulus of the water glass that the present invention selects is 2～6. Experiments have proved that the effect is good.

The modulus of the better water glass of the present invention is 3-5.

It is convenient and cheap to use inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid or organic acids such as acetic acid, benzenesulfonic acid and p-toluenesulfonic acid to adjust water glass or sodium silicate solution to acidity.

The organic solvent is tetrahydrofuran, dioxane, isopropanol, tert-butanol or N-methyl-2-pyrrolidone or mixed solvents.

Among the above-mentioned organic solvents, tetrahydrofuran and dioxane are most suitable.

Salts are inorganic salts, NaCl, Na ₂ SO ₄ , Na ₂ CO ₃ , Na ₂ HPO ₄ , KCl or their mixed salts are the most suitable. These salts come from a wide range of sources and have good solubility in water .

The monomer used in the present invention can be dissolved in tetrahydrofuran, dioxane, isopropanol, tert-butanol, N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide or their mixed solvents Among the best, such monomers as: styrene and its substitutes, acrylic acid and its substitutes, acrylate and its substitutes, methacrylic acid and its substitutes, methacrylate and its substitutes, vinyl acetate , caprolactone, hydroxyalkanoate, caprolactam, etc.;

The prepolymer in the present invention can be dissolved in tetrahydrofuran, dioxane, isopropanol, tert-butanol, N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide or their mixture The best among solvents, such prepolymers as: polyamic acid, epoxy resin and curing agent, polyether or polyester polyol and polyisocyanate, benzoxazine, etc.;

The polymer in the present invention can be dissolved in tetrahydrofuran, dioxane, isopropanol, tert-butanol or N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide or their mixed solvents Among the best, such polymers as: polystyrene and its substitutes, polyacrylic acid and its substitutes, polyacrylate and its substitutes, polymethacrylic acid and its substitutes, polymethacrylate and its substitutes Copolymers of two or more components of styrene, acrylic acid, methacrylic acid and their ester derivatives, maleic anhydride, etc., polyvinyl acetate, polyethylene-vinyl alcohol copolymer, poly Caprolactone, polyhydroxyalkanoate polymers and copolymers such as polylactide and polyglycolide and their copolymers, caprolactone and hydroxyalkanoate copolymers and polyamides, etc.

The present invention extracts active silicic acid from cheap industrial products water glass and sodium silicate to prepare silica-polymer composite materials. Compared with the method in which silica particles are directly added to the polymer system in the prior art, the inorganic phase is The dispersion in the composite material is more uniform, the phase size is smaller, and it is convenient to prepare nano-silica-polymer composite materials; compared with the existing sol-gel method using silane hydrolysis, the cost is much lower, and the water content in the system is less. Product performance is less affected. The invention can effectively control the particle size of the silicon dioxide, so the nanometer silicon dioxide-polymer composite material can be obtained conveniently. At the same time, like the usual sol-gel method, other inorganic sols can also be added to prepare multi-component inorganic/polymer composite materials. Due to the small viscosity of the system in the preparation process, the method of the present invention can prepare composite materials with high inorganic phase content, so that the materials have unique composite properties, such as good heat resistance, wear resistance, mechanical properties and low thermal expansion coefficient, and It can maintain the transparency of the polymer body. According to the amount of silica and other inorganic sols added and the choice of coupling agent, the refractive index of the composite material can be adjusted conveniently. It is suitable for manufacturing Optical materials with special properties such as index or surface coating of optical materials; and because the inorganic phase is well combined with polymers, it can be used as a structural material with special properties and applied in high temperature environments.

Detailed ways

Example 1

Slowly add 30ml of 3.2mol/l water glass solution dropwise to 30ml of 1mol/l H ₂ SO ₄ to adjust the pH value to about 3, add 10g of NaCl and 40ml of tetrahydrofuran to extract the active silicic acid in the water phase. The tetrahydrofuran layer was separated to obtain a tetrahydrofuran solution of active silicic acid. Its solid content (expressed as silicon dioxide weight concentration) measured by thermogravimetric method is 13%.

Weighed 1.2 g of THF solution of active silicic acid and added to 100 g of polyamic acid in 10% DMAC solution, and vigorously stirred at room temperature for 3.5 hours to fully react. Then cast the reaction product on a glass plate and treat it at 60, 100, 200 and 300°C for 2 hours respectively to obtain a polyimide/silicon dioxide composite material. The particle size of the inorganic phase in the material is 30-100 nanometers between. The transparency of the material was the same as before the addition of silica. Through thermogravimetric analysis, it is measured that the content of the inorganic phase in the material is 1.1%. The thermal decomposition temperature of the material is 8°C higher than that without adding silica. Example 2

The tetrahydrofuran solution that takes by weighing 30 grams of active silicic acid in embodiment 1 joins in the 10% DMAC solution of 100 grams of polyamic acid, then adds 1.5 grams of gamma-glycidyl ether base trimethoxysilane, stirs vigorously at room temperature for 5 hours for full reaction. Then the reaction product was cast into film and treated at 60, 120, 200 and 300°C for 2 hours respectively. A polyimide/silicon dioxide nanocomposite material is obtained. Observed by a transmission electron microscope, the particle size of the inorganic phase in the material is less than 100 nanometers. Through thermogravimetric analysis, it is measured that the content of the inorganic phase in the material is 35%. The coefficient of thermal expansion of the material is reduced to half that before the addition of silica.

Example 3

Weigh 22 grams of the tetrahydrofuran solution of active silicic acid in Example 1 and add it to 50 grams of polystyrene in 10% tetrahydrofuran solution, stir at room temperature for 3 hours to make it fully react and mix uniformly. Then the obtained solution was added into 500 g of methanol for precipitation under stirring, the precipitate was filtered out, vacuum dried at 50°C and 100 Pa for 4 hours, and then treated at 60, 100, 140, and 180°C for 2 hours respectively to obtain silica- Polystyrene composite. Observing the cross-section of the material with a scanning electron microscope, it is found that the particle size of the inorganic phase is about 0.9-3 microns. The impact strength of the material is increased by 20% compared with that before adding silica particles, and the thermal decomposition temperature is increased by 20°C.

Example 4

Weigh 65 grams of the THF solution of active silicic acid in Example 1 and add it to 30 grams of polystyrene-maleic anhydride copolymer in 10% THF solution, and stir at room temperature for 6 hours to fully react. Then cast the reaction product into a film, dry it at room temperature, and then treat it at 60, 100, 140, and 180°C for 2 hours respectively. A composite material of silica-poly(styrene-maleic anhydride) copolymer was obtained. The content of the inorganic phase in the material was determined to be 80% by thermogravimetry. This material can be used in blends with polystyrene to improve the dispersion of silica in the polymer.

Example 5

The tetrahydrofuran solution that takes by weighing 10 grams of active silicic acid in embodiment 1 is added to the 100 milliliters of tetrahydrofuran that is dissolved with 13 grams of polymethyl methacrylate-trimethoxysilyl propyl methacrylate mol ratio 9:1 copolymers solution, stir well at room temperature. Then pour the reaction product into a mold, place it at room temperature to volatilize the solvent, and then treat it at 120° C. for 3 hours to obtain a nano-silicon dioxide reinforced polymethyl methacrylate material. The appearance of the material is colorless and transparent, and the section of the material is observed with a scanning electron microscope, and it can be seen that the particle size of the inorganic phase is less than 100 nanometers. The impact strength and compressive strength of the material are both increased by more than 50% compared with those without adding silica. Example 6

Weigh 10 grams of active silicic acid in tetrahydrofuran solution in Example 1 and add it to 50ml15% methyl methacrylate tetrahydrofuran solution, add 1.2g trimethoxysilyl propyl methacrylate and 0.8g Initiator AIBN, stir evenly.

Take 1g of butyl titanate (Ti(OBu) ₄ ), 0.1g of acetic acid, and 10ml of isopropanol, stir, mix evenly, and keep it sealed for 3 days to obtain a transparent light yellow titanium sol.

Pour the above active silicic acid/monomer/coupling agent/initiator solution and titanium sol into a 100ml three-neck bottle, stir vigorously for 2 hours, after mixing evenly, connect the reflux condenser, and raise the temperature to 70°C under the protection of nitrogen , reacted for 5 hours to obtain a viscous solution. The solution is coated on the surface of the plastic optical lens by the spin coating method, and heat-treated at 60°C, 80°C and 120°C for 2 hours respectively to obtain a transparent wear-resistant coating, the hardness of which is 2 times higher than that of pure PMMA. The refractive index of the coating can be changed by adjusting the ratio of silicon/titanium two phases to adapt to different kinds of plastic lenses.

The embodiments illustrated and discussed in this specification are intended only to demonstrate to those skilled in the art the best modes known to the inventors to use the invention. Nothing in the specification should be considered as limiting the scope of the present invention. Modifications to the above embodiments may be made without departing from the scope of the invention, as will be apparent to those skilled in the art from the foregoing description. It is therefore to be understood that within the scope of the claims and their equivalents, the invention may be practiced otherwise than as specifically described above.

Claims (13)

1. a method for raw material preparation of silica-polymer composite material with water glass or sodium silicate, is characterized in that: 1) preparing an acidic aqueous solution of water glass or sodium silicate, adding an inorganic salt saturated aqueous phase, and then extracting the generated active silicic acid with an organic solvent; 2) Add monomers or prepolymers to the above active silicic acid solution for polymerization, or directly add the polymer solution, and mix well; 3) The above solution is heat-treated at 60-380° C. to remove the solvent, and finally generate a polymer/silicon dioxide composite material. 2. The method for preparing silica-polymer composite material according to claim 1, characterized in that monomer or prepolymer or polymer solution is added to the active silicic acid solution, while a coupling agent is added and mixed uniformly. 3. The method for preparing silica-polymer composite material according to claim 1, characterized in that the active silicic acid solution is added with monomer or prepolymer or polymer solution while adding inorganic particle sol, and mixed uniformly. 4. the method for preparing silica-polymer composite material according to claim 2 is characterized in that coupling agent carries out polymerization reaction with monomer earlier to generate polymkeric substance or prepolymer, then the polymkeric substance or prepolymer that generates The prepolymer solution and the reactive silicic acid solution are mixed. 5. The method for preparing silica-polymer composite material according to claim 2, characterized in that the general structural formula of the coupling agent selected is YRSiX ₃ , X is the hydrolyzable group combined on the silicon atom in the formula group, and Y is an active functional group that has affinity or reactivity with polymer molecules. 6. The method for preparing a silicon dioxide-polymer composite material according to claim 1, characterized in that the weight of silicon dioxide in the composite material accounts for 0.5-99.5% of the total weight of the material. 7. The method for preparing a silica-polymer composite material according to claim 1, characterized in that the particle size range of the silica particles in the composite material is 0.005-20 microns. 8. the method for preparing silicon dioxide-polymer composite material according to claim 1 is characterized in that when silicon dioxide amount is 0.1-70%, or when coupling dosage is 0.5-99%, two in composite material The particle size range of the silicon oxide particles is 0.005-0.5 micron. 9. the method for preparing silica-polymer composite material according to claim 1, is characterized in that the modulus of the water glass used in the preparation process is 2-6. 10. the method for preparing silica-polymer composite material according to claim 9, is characterized in that the modulus of water glass is 3-5. 11. The method for preparing silica-polymer composite material according to claim 1, characterized in that the acid used is hydrochloric acid, sulfuric acid, phosphoric acid inorganic acid or acetic acid, benzenesulfonic acid, p-toluenesulfonic acid organic acid. 12. The method for preparing silica-polymer composite material according to claim 1, characterized in that the organic solvent is THF, dioxane, Virahol, tert-butyl alcohol, N-methyl-2-pyrrolidone , dimethyl sulfoxide or dimethylacetamide or their mixed solvents. 13. The method for preparing silica-polymer composite material according to claim 1, characterized in that the selected inorganic salts are NaCl, Na ₂ SO ₄ , Na ₂ CO ₃ , Na ₂ HPO ₄ , KCl or They are mixed water-soluble salts.