KR100794729B1 - Process for preparing networked silica with good reinforcing property - Google Patents

Abstract

A method for preparing networked silica is provided to prepare the networked silica in a short time and improve the function of the networked silica in reinforcing an intension of rubber, by coupling silica particles with a coupling string material in a three-dimensional type to prepare the networked silica. A networked silica is prepared by dissolving a coupling string material in a methanol aqueous solution or an ethanol aqueous solution, and making the dissolved coupling material with silica particles at a temperature of 20-60°C. The methanol aqueous solution or the ethanol aqueous solution has 5-20 wt% of water. The silica particles react for 1-12 hours while the silica particles are suspended in the methanol aqueous solution or the ethanol aqueous solution.

Description

PROCESS FOR PREPARING NETWORKED SILICA WITH GOOD REINFORCING PROPERTY}

1 shows a structural model of nested silica.

2 shows a schematic diagram of a reactor for preparing nested silica in the liquid phase according to the method of the present invention.

3 shows the structure and H-NMR spectrum of 3-aminopropyltriethoxysilane.

4 is a schematic diagram of an apparatus for producing nested silica in a fluidized bed in accordance with the method of the present invention.

The present invention relates to a method for producing a nested silica excellent in blendability with rubber and excellent in tensile strength reinforcing effect of the blended rubber.

Rubber products vary depending on the application, but their use in the manufacture of tires, belts, conveyors, shoes, etc., must be high in elasticity and tensile strength to maintain their shape while absorbing external impacts. In particular, in rubber products that support large loads such as tires and must absorb irregular impacts while driving, elasticity and tensile strength are very important in determining the performance and stability of the product. Usually, carbon black or silica is added to rubber in order to reduce the addition amount of rubber and to improve the tensile strength of the compounded rubber. Carbon black, which has high affinity with rubber molecules, has been widely used as a physical property reinforcing agent of rubber products because it mixes well with rubber and has excellent property reinforcement. Recently, it has been increasing the amount of silica instead of carbon black by emphasizing the environmental friendliness of tires. Silica is widely used as a reinforcing agent because it can improve the fuel efficiency of tires and evenly improve the steering ability and braking power. However, unlike carbon black, silica is inorganic and hydrophilic, so it does not mix well with organic and hydrophobic rubber molecules. The surfaces of the silica particles are covered with silanol groups, which are easy to agglomerate with each other, and have low affinity with organics, making it difficult to disperse the silica particles in the rubber. For this reason, the silica particles are treated with an organic material so that they disperse well in the rubber. In order to convert the surface of the silica into hydrophobic, the reinforcing effect of the silica is maximized by treating it with an organic material that can be reacted with a silanol group. When a silane having an alkoxy functional group such as an ethoxy group or a methoxy group is reacted with silica, when the alkoxy group of the silane reacts with the silanol group of the silica, alcohol is produced and the silane is fixed to the silica surface. Although there are differences depending on the nature of the organic material bound to the silane, the surface of the silica is covered with the organic material and thus the hydrophobicity becomes stronger, so that the rubber molecules have good mixing properties.

Even if the surface is made hydrophobic by fixing the organic material on the surface by treating the silica with an aqueous surfactant solution, the dispersibility of the silica in rubber is greatly improved. When the silica particle surface is coated with an organic substance, the silica surface becomes hydrophobic and is dispersed in rubber well, but the repulsive force between silica particles is increased and blows badly, so it is not satisfactory for actual use. Dispersibility is certainly improved by surface treatment, but the affinity between silica particles and rubber molecules is not enhanced, and thus the modulus and tensile strength of the compounded rubber do not improve as expected. In view of this point, a coupling reagent for directly bonding silica particles with rubber molecules together with the surface treatment of silica has been developed [Patent Document 2]. In the middle of the silane to which the alkoxy group is attached, a substance containing a sulfide bond which can form a covalent bond with a rubber molecule is used as a binder. During vulcanization, sulfide bonds are activated by activators or accelerators added to the rubber to react with the double bonds of the rubber molecules, and the alkoxy groups of the silanes react with the silanol groups on the silica surface so that the rubber molecules and the silica particles are covalently bonded directly. Connected. Silanes containing sulfide bonds and alkoxy groups together, such as 3,3'-bis (triethoxysilylpropyl) tetrasulfide (TESPT), are typical binders. Although the performance varies slightly depending on the type of alkoxy group, the length of sulfide bonds, and the organic material bound in the center, the basic functions of bonding rubber molecules and silica particles are similar. Since the rubber and the silica particles are directly bonded during the vulcanization by using the silica and the binder together, the dispersibility and the reinforcing properties of the silica are greatly improved.

The use of the binder not only disperses the silica well in the rubber, but also greatly improves the reinforcing effect of the silica, resulting in very good tensile properties. If the binder is added too much, the modulus may be too high and the elasticity may be lowered. However, since the blending ratio is properly adjusted, the tensile properties of the blended rubber and the dispersibility of the silica due to the addition of silica may be improved at the same time. In addition, the binder acts as a lubricant in the compounding step to lower the viscosity of the rubber to reduce the power required for the compounding, and to suppress the temperature rise during the compounding process has a large positive effect. Due to these advantages, most of the compounded rubbers using silica as a reinforcing agent are prepared by adding TESPT or a similar binder. Binders represented by TESPT are very effective additives that increase the dispersion of silica in rubber and improve the tensile properties of the rubber, but are also inconvenient to use. Most binders are liquid and react strongly with moisture, making them difficult to handle and difficult to store for a long time. It is mixed with carbon black for easy handling, and the storage period is strictly controlled in consideration of performance degradation. The fact that alcohol is inevitably generated when the binder combines with silica in the step of adding the binder to the rubber is inevitable when using the binder. If the alcohol generated when the rubber and silica particles bind the binder with the legs remains in the rubber, bubbles are produced when the temperature is elevated. Bubbles can be a starting point for rupture, so the alcohol produced during the blending process must be removed. However, alcohol has a high affinity with organics, so the removal of ethanol from very high molecular weight, viscous rubber requires a very complex and very harsh process. In addition, alcohol releases into the atmosphere, causing odors and turbidity, requiring further action to maintain a clean work environment. In addition, when adding a binder such as TESPT, there is a burden to control the process parameters such as temperature very precisely. This is because the mixing process of mixing rubber requires that the rubber and the additive mix well but the binder does not bind with the rubber. When the temperature increases during the blending, the sulfide bonds of the binder and the double bonds of the rubber react with each other, and thus the viscosity of the rubber becomes high and the blending process cannot be smoothly operated. Therefore, in the compounding process of the rubber in which the binder is added together with silica, the temperature is finely controlled so that the bonding reaction does not proceed.

In order to solve the problem of the use of a binder, a nested silica (networked silica), which is made of a bird nest by three-dimensionally bonding silica particles using organic materials as a binding string, has been developed [Patent Document 3]. The organic material combines the silica particles with each other to form a structure shown in FIG. 1. Since the organic material is bonded to the silica surface to improve hydrophobicity, the affinity with the rubber is improved, and the rubber enters the space between the silica particles to be mixed with each other, thereby greatly improving the dispersibility of the rubber in the silica. In addition, since the binding string and the rubber are entangled with each other to strengthen the tensile property of the rubber, the performance of the silica as a reinforcing agent is greatly improved.

Nest silica can be prepared in several ways. Reaction of silica bound with 3-aminopropyltriethoxysilane (APTES) and silica bound with 3-glycidoxypropyltrimethoxy silane (GPTMS) causes the amine and glycidoxy groups to be bound together with the silica particles. Non Patent Literature 1]. Since the APTES-bonded silica is bonded to the GPTMS-bonded silica, the silica particles are bonded to each other. By properly adjusting the number of functional groups bonded to the silica particles, the number of binding strings connecting the silica particles can be controlled. Nesting silica can also be made from a bond string material made of one type of silane connected to each other instead of another silane. When the APTES-bonded silica is reacted with dichlorohexane (DCH), the amino group bonded to the silica reacts with the chlorine group of the DCH to bind the silica particles to each other. Using long hydrocarbons, such as decane or dodecane instead of hexane, can also adjust the length of the bond string that connects the silica particles.

The nested silica produced through this process does not chemically react with rubber molecules or other additives during compounding with rubber. Therefore, no other substances, such as alcohol, are generated so that a process for removing them is not necessary, and the temperature of the compounding process does not need to be carefully controlled. Since the silica surface is covered with organic matter, the friction is small when blended with the rubber and the rubber penetrates through the bond string, so that the silica particles are well dispersed in the rubber. Silica and rubber molecules do not bond directly, so the modulus does not increase significantly compared to compounding rubber using a binder. However, the tensile strength is significantly higher due to the entanglement of the rubber molecules with the bond strings connecting the silica particles. The tensile strength is high and the elongation which shows the elasticity of rubber is excellent, and the toughness withstands a tear is very large. In addition, the compounded rubber with nested silica is very excellent as a rubber property reinforcing agent because of its high tensile strength and low hysteresis.

Nest silica is prepared by reacting silica and binding string materials in a liquid solvent such as toluene. APTES having an amino group capable of binding to glycidoxy group or chlorine group is added to silica in a solution of toluene, and the APTES is bonded to the silica surface by heating under reflux. In the same way GPTMS is bound to silica. When the silicas in which APTES and GPTMS are respectively bound are suspended in toluene and reacted with each other, these functional groups react with each other and the silica particles are bonded to each other. In this method, the nested silica can be prepared through three steps: reaction of APTES and silica, reaction of GPTMS and silica, and reaction between them. This requires a lot of equipment, such as a reactor, and the time required for the reaction increases the manufacturing cost. Compared to the method of adding a binder such as TESPT to the rubber together with silica, the method of adding only the nested silica is superior to the reinforcing function of the silica and is convenient to use, but the manufacturing cost of the nested silica is difficult and commercialization is difficult.

When APTES-bonded silica is reacted with DCH, silica particles are connected to each other using DCH as a bridge. Since the APTES-bonded silica is reacted with DCH, it is possible to prepare nested silica using only a two-step reaction. The reflux heating step can be reduced to reduce manufacturing costs.

When a silanol group on the surface of silica reacts with silica, an isocyanate group, which can react at room temperature, is reacted with silica, and the isocyanate group reacts with the silanol group to bond the silica particles to each other. When methylene diphenyl diisocyanate (MDI) is used as the binding string material, it is possible to form nested silica by bonding silica particles to each other in one step reaction at room temperature. However, nested silica made using isocyanate group as a binding string has lower reinforcing properties and thermal stability than nested silica made of silane.

As described above, when manufacturing the nested silica, the step of heating the silica so that the silanol group and the binding string of the chemical bond is required, and the concentration of the reactant should be increased to increase the progress of the reaction. When preparing the nested silica by reflux heating method, a high boiling solvent that can be heated to a high temperature should be used so that the reaction can proceed rapidly. However, it is expensive to remove the high boiling solvent remaining in the nest silica after the reaction. When the nested silica is prepared by the reflux heating method, the reaction concept is clear and easy to grasp the progress of the reaction, but it takes much energy and time to proceed with the coupling reaction, which inevitably increases the manufacturing cost.

Patent Document 1: International Patent Application Publication WO 00/31180 (June 2, 2000)

Patent Document 2: U.S. Patent No. 3,873,489 (March 25, 1975)

Patent Document 3: International Patent Application Publication WO 2004/078835 (September 16, 2004)

[Non-Patent Document 1] Kwang Ha, Yun-Jo Lee, Han Ju Lee, and Kyung Byung Yoon, "Facile assembly of zeolite monolayers on glass, silica, alumina. And other zeolites using 3-halopropylsilyl reagents as covalent linkers", Adv. Mater., 12, 1114-1117 (2000).

The method of preparing the nested silica by bonding the binding string material dissolved in a high boiling point solvent to the surface of the silica by reflux heating method is complicated and expensive, making it difficult to take advantage of the nested silica. Therefore, the technical problem to be achieved in this invention in order to manufacture the nested silica cheaply is as follows.

(1) A technique for producing nested silica in which three-dimensional silica particles are connected by using a solvent that can be easily removed even at low temperatures due to low boiling point instead of a high boiling point solvent such as toluene.

(2) Technology that reduces the energy required for heating and cooling by reacting at room temperature, instead of reacting the bond string material and silica by heating to reflux by raising the temperature.

(3) Technology that uniformly combines silica particles with bound materials while reducing solvent usage and reducing solvent removal and recovery costs.

(4) The manufacturing technology of the nested silica which is excellent in reproducibility and easy to expand the production scale while reducing the cost and time according to the movement of the reactants by reducing the reaction step.

(5) Technology to properly control the surface state of the nested silica according to the use of the rubber product.

In order to achieve this technical problem, the inventors dissolve the binding string material in a solvent which can be easily volatilized and removed even at low temperature, and then reacts the silica particles with the binding string material at room temperature by adding an appropriate amount of water. After the hydroxyl group generated by the hydrolysis of the alkoxy group of the bond string material was adsorbed to the silanol group on the silica surface, the process was designed such that they react during the drying process. In the drying process, the generated water is removed and the silica particles combine with each other to form a three-dimensional network. In this method, nest silica can be produced without undergoing reflux heating, and the amount of energy used can be greatly reduced since the solvent is volatilized and removed at low temperature with a small amount of energy.

In addition, a technique for preparing nested silica has been developed by spraying and applying a solution prepared by adding a binding material and an appropriate amount of water to a solvent having a low boiling point to spray silica particles. In the drying process, the binding strip material is bonded to the silica surface while the solvent and water are removed together. In this process, the silica particles are bonded to each other to form a three-dimensional network. Since the alkoxy group of the binding string material is hydrolyzed and adsorbed onto the surface of the silica particles, the alkoxy group is heated and then heated, thereby manufacturing nested silica.

The manufacturing of the nested silica without the reflux heating process simplifies the process and greatly reduces the energy requirements, greatly reducing manufacturing costs. In particular, in the manufacturing method of spraying a solution of the binding string material on the silica particles in the fluid state, since all the binding string materials are bonded to the silica surface, it is possible to effectively form a three-dimensional network structure while using a little binding string material, thereby greatly increasing the manufacturing cost. Can be saved.

The present invention has been completed based on this finding.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

The present invention forms a three-dimensional networked structure by bonding silica particles to each other with an organic bond string, thereby improving the affinity between rubber and silica particles as the silica surface changes from hydrophilic to hydrophobic, and rubber molecules. As the rubber penetrates into the network structure between the silica particles, the rubber and silica particles are mixed well to improve dispersibility. In addition, the rubber molecules introduced into the network structure of the silica particles are entangled with each other, thereby greatly improving the tensile properties of the rubber due to the entanglement effect. Even if silica is added to the rubber, the silica particles are not dispersed well in the rubber unless a binder having an alkoxy group and a sulfide bond is added, so that the degree of improvement in tensile properties by silica is not so great. The use of a binder such as TESPT, which directly bonds rubber molecules with silica, improves the dispersion of silica particles and improves tensile properties, but also involves difficulties such as alcohol generation in the manufacturing process. Nested silica, which is a three-dimensional combination of silica particles with an organic binding string, is different from silica and binders, and silica particles disperse well above or equal to that of rubber compounded with TESPT binder without generating alcohol. As a result, the tensile strength of the compounded rubber is increased, and the reinforcing property is greatly improved. The nested silica prepared in the present invention is very effective as a reinforcing material of rubber because silica particles are bonded to each other by an organic binding string as shown in FIG. 1.

The present invention discloses a process for preparing nested silica through dispersion of silica particles, supply of binding string material, contact and reaction of binding string material and silica particles, formation of a three-dimensional network of silica particles, and solvent removal. The method of dispersing the silica particles and the method of reacting the binding string material with the dispersed silica varies from manufacturing process, but the basic components of the processes listed above are the same. The method of supplying the binding string material and the method of removing the solvent differ only depending on whether a solution of the binding string material is added to react with silica dispersed in the liquid phase or spray the binding string material on the silica in the fluid state.

In the liquid phase manufacturing process, silica is dispersed in a polar solvent so that the silica particles can be dispersed well. An appropriate amount of water is added to promote dispersion of the silica particles and for hydrolysis of the bond string material. In order to disperse the silica particles highly, a homogenizer is used for a certain time to disperse the agglomerated silica in particle units. A small amount of a base such as triethylamine or triethanolamine is added to treat the surface of the silica particles to control the suspended state. After the silica particles are sufficiently dispersed, a binding string solution diluted in a solvent is added to the silica suspension. The bond string material reacts with water in the solvent to produce an alcohol as the alkoxy group is hydrolyzed to the hydroxyl group. Since the hydroxyl group of the binding string has the same structure as the silanol group on the silica surface, the affinity for each other is strong, so that the binding string material is adsorbed on the surface of the silica particles. The reaction temperature of the silica particles and the bound string material is 15 to 80 캜, preferably 20 to 60 캜. Properly adjust the concentration of the silanol groups and the binding string material on the silica surface so that both ends of the binding string are adsorbed on different silicas. The alkoxy group of the binding string material is hydrolyzed and waits with stirring for an appropriate time so that the binding string material converted into hydroxyl groups is adsorbed on the surface of the silica particles. The silica is then separated by a centrifuge or a filter press to recover the solvent. The remaining solvent is removed and dried with hot air in the range of 100 to 140 ° C. to allow the hydroxyl and silanol groups to condense. When heated sufficiently, the water is removed to bond the bond string material to silica. When the silica particles bind to each other with their binding strings, they form a three-dimensionally nested silica.

2 shows a schematic diagram of a process for preparing nested silica in a liquid phase. That is, the silica and the solvent stored in the silica container 1 and the solvent container 2 are sent to the mixer 6 through the pump 3 and the valve 4, where the solvent is added to the silica while stirring with the stirrer 5. Added to disperse well to favor reaction with the bond string material. In order to increase the degree of dispersion, a small amount of a base such as triethyl amine or triethanolamine is added. In order to increase the degree of dispersion, it is transferred to the homogenizer 8 to disperse the silica in particle units using a high speed rotary stirrer. The sufficiently dispersed silica suspension is transferred to the hydrolysis reactor 10, and then stirred in the reactor 10, while a solution in which the binding string material is dissolved is added from the binding string container 9 to hydrolyze the binding string material to the surface of the silica. Adsorb. The rate of hydrolysis of the bond string material is highly dependent on the amount of water in the solvent. If more than 40% of water is contained, the hydrolysis reaction is so fast that the hydroxyl groups generated during the hydrolysis of the binding string material react with each other. Hydrolyzed bond string materials polymerize with each other without adsorbing onto the silica surface to form agglomerates. Since the hydrolyzed binding string material on the surface of silica is combined with each other to act as a binding string to create a three-dimensional network structure, the water content should be lower than this. On the other hand, if the water content is less than 2%, the hydrolysis reaction proceeds very slowly, resulting in a long time for adsorption on the silica surface after hydrolysis. The protons of the alkoxy group and the protons of the hydroxyl group are significantly different from each other in chemical shift, so the nuclear magnetic resonance method (NMR) confirms the progress of the hydrolysis reaction. As shown in FIG. 3, the protons of the ethoxy group of APTES show characteristic peaks at sites of 3.8 and 1.24 ppm of chemical shifts. The progress of the hydrolysis reaction can be determined from the extent to which the characteristic peak of ethoxy group decreases and the characteristic peak of ethanol increases.

When the binding string material is adsorbed onto the silica particles and the concentration of the binding string material in the suspension is sufficiently low, the silica to which the binding string material is adsorbed is transferred to a decomposing device 11 such as a centrifuge or a compression extractor to remove the solvent. Solvent recovery is important because solvent recovery is an important factor in manufacturing cost. Subsequently, it is transferred to the hot air dryer 13 and dried in a range of 100 to 140 ° C. so that the dehydration reaction proceeds between the hydroxyl group of the binding string material adsorbed on the silica and the silanol group on the silica surface, and the water is discharged through the outlet 12. To discharge. Since the binding string is bonded to silica only after the water is removed, the temperature of the heater 14 is raised to 140 ° C. to thoroughly remove moisture. In this process, the solvent remaining in the silica is removed together with water, and the silica particles are bonded to each other by a binding string material to form a three-dimensional network.

Because of using a homogenizer and dispersing the silica in a suitable solvent in the liquid phase, the dispersion state of the silica is good, and thus, the reaction state with the bonding string material is very even and rapidly progressed, resulting in a very uniform state of the prepared nested silica. Since the hydrolysis reaction is an acidic acid catalyzed reaction, the acid and base are added, so that the rate of the hydrolysis reaction can be controlled appropriately. However, adding too much acid may dehydrate and condense silanol groups on the silica surface, and it is reasonable to control the rate of the hydrolysis reaction by adding a small amount of base. The hydrolysis reaction and adsorption rate vary according to various factors such as the concentration of acid and base, the content of binding string and water, and the temperature of the hydrolysis reactor. Therefore, these factors should be properly adjusted to make the nested silica with the maximum function as a rubber additive. do.

The fluidized-bed manufacturing process of the nested silica shown in FIG. 4 is also similar to the liquid phase manufacturing process shown in FIG. However, as shown in FIG. 4, the entire process can be performed in one apparatus, which is convenient. In Fig. 4, reference numeral 21 denotes a nitrogen cylinder, reference numeral 22 denotes a valve, reference numerals 23 and 24 denote engagement string containers 1 and 2, and reference numeral 25 denotes a nozzle. Silica is introduced into the reactor 34 through the hopper 35 'so as to be about one third of the reactor volume (the hopper 35' and the later cyclone 35 may be installed separately, but in a small apparatus, they are removable. It is convenient to install them interchangeably]. The stirrer 30 driven by the motor 26 is stirred at 500 to 1,500 rpm to fluidize the silica to float. In addition to stirring with a stirrer, nitrogen or air is flowed from the nitrogen cylinder 21 at a constant rate to stabilize the flow state of silica. After stirring for a certain time to disperse the silica in the form of particles, organic bases such as triethylamine and triethanolamine are dissolved in a low boiling solvent such as ethanol or dimethyl ether and sprayed to adjust the surface potential of the silica particles. After the solvent is mostly evaporated and removed in the fluidized state, a solution obtained by dissolving the binding string material stored in the binding string containers 1 and 2 in a polar solvent is sprayed to the reactor through the nozzle 25 and applied to the suspended silica particles. At this time, the heater 32 of the constant temperature circulation tank is operated to raise the temperature inside the reactor for reaction. The rate of the hydrolysis reaction is controlled by controlling the content of water and other substances in the solution of the bond string material. The silica particles are dispersed well so that the solution of the bond material can be evenly applied to the surface of the silica particles, and the solution is sprayed as slowly as possible to improve the uniformity. If the injection pressure is too high, silica particles cannot be collected in the cyclone 35, so the injection pressure is adjusted to within 2 to 15 bar. Since heat is generated by agitation and friction in the fluidization process, the cooling water is flowed into the constant temperature circulation tank cooler 33 installed around the reactor to control the temperature in the range of 30 to 40 ° C. If the reactor temperature is too high, the solvent evaporates too quickly and the tie strip solution is not evenly applied. After the binder string material solution is sprayed onto the fluidized silica particles, the bond string material applied to the silica is maintained in a fluidized state for a sufficient time to react with water to be hydrolyzed and adsorbed onto the silica surface. Increasing the content of water in the solution of the binding string material causes the hydrolysis and polymerization reaction to be too fast, so that the content of water is lowered to increase the stability of the binding, thereby allowing the hydrolysis reaction to proceed for a long time.

In this invention, the material used as a binding string material can be divided into three types. The first is a material prepared by reacting alkoxy silanes having different functional groups with each other. In other words, APTES and GPTMS mixed 1: 1. When the amino group of APTES and the glycidoxy group of GPTMS are combined, a trialkoxy silane is attached to both ends of the linear chain. Alternatively, APTES may be reacted with DCH to form a binding string material in which the amino group of APTES and the chlorine group of DCH are combined. A propyl group is attached at both ends of the hexane chain, and a triethoxy silane is bonded at the end. Secondly, it is made by reacting GPTMS with a high molecular weight polymer such as polyethylene imine (PEI). Triethoxy silane functional groups are suspended throughout the PEI chain. By adjusting the reaction composition ratio of PEI: GPTMS, the density of three-dimensional network can be changed in various ways. Third, the diisocyanate group is attached to both ends of the silane compound. Since the diisocyanate group can react directly with silanol groups on the silica surface even at room temperature, the organic bond string can be bonded to silica without undergoing a heating step, and thus can be used as a bond string material. Toluene diisocyanate (TDI), methylenediphenyl diisocyanate (MDI), MDI polymer (polymeric MDI: PMDI), hexanediisocyanate (HDI), 1,6,11-undecane triisocyanate (1,6,11- undecane triisocyanate: C ₁₂ DI), 3,3'-bis (triethoxysilylpropyl) tetrasulfide and the like are representative materials. The silane is hydrolyzed, fixed to the surface through an adsorbed state, and then bonded with silica in the heating step, but the diisocyanate-based adsorbent material reacts directly with the silanol groups on the surface to bond the silica particles to each other, thus preparing the preparation time of the nested silica. This shortens.

The treatment of silica particles with a bond string solution is difficult to fully control the hydrophobicity of the surface. The treatment of silica with a bond string solution with a hydroxyl-based material can enhance hydrophobicity. The treatment of nested silica with pentaerytritol, in which hydroxyl groups are attached to several organic chains, lowers the viscosity and increases hydrophobicity in the vulcanization process. Many hydroxyl-based glycerin, sorbitol, mannitol, glucose, polyethylene glycol and the like have the same effect. When reacted with the binding string solution, the binding string material and the binding string material competitively bind with the silanol groups on the surface, so it is more effective to fix the binding string material and then process it.

Nested silica prepared by the method proposed in the present invention has a three-dimensional network structure of silica particles, so that space is created in the middle of the particles, so that rubber molecules easily penetrate and the silica surface is covered with an organic material so that they have affinity with rubber molecules. high. At the same time, since the network structure of the rubber molecule and the nested silica is entangled with each other without using a binder, rubber properties as a reinforcement agent such as tensile strength are greatly improved. Nested silica is very suitable for the production of rubber products that must have excellent tensile properties, such as tire compounding rubbers, which must support large loads and minimize the impact deformation during driving.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, these examples are intended to illustrate this invention in detail and are not intended to limit it.

Example 1

Nested silica bond string materials incorporating alkoxy silanes with amine groups or glycidoxy groups are prepared by the reflux heating method. 500 ml of toluene was added to a three-necked flask equipped with a thermometer and a cooler, and 110 g of APTES and 120 g of glycidoxypropyltrimethoxy silane (GPTMS) were added thereto. The temperature was raised to 110 ° C. while removing oxygen by flowing nitrogen, followed by heating under reflux with stirring for 12 hours. As the reaction proceeds, the color gradually turns to light brown, and thin layer chromatography (TLC) confirms the progress of the reaction. Fill a 50 ml beaker with 10 ml of ethyl acetate (EA) with TLC solvent. Immerse the reactants and products at a location on the TLC plate cut to 1 × 4 cm 2 and set aside in a beaker with EA solvent for a period of time. When the solvent rises to a certain height, take it out and dry it. When the specific label of the reaction disappeared and a new label appeared at a higher position, the reaction was all proceeded. After 12 hours, specific markers of APTES and GPTMS did not appear, indicating that they reacted quantitatively, and the progress of the reaction was verified from the H-NMR spectra of samples taken by reaction time.

In a three-necked flask, a thermometer and a cooler are installed and 110 g of APTES and 120 g of GPTMS are added without adding solvent. After flowing nitrogen to remove oxygen, the mixture is heated with stirring at 130 ° C. for 3 hours. Reaction progress is confirmed by color change and TLC method. NMR is used to investigate the production of products from chemical shifts of glycidoxy groups and acetone group protons. After 3 hours it was confirmed that they reacted quantitatively.

Add 110 g of APTES and 39 g of DCH to a three-necked flask equipped with a thermometer and cooler. 40 g of pyridine is added to remove oxygen by flowing nitrogen, followed by heating with stirring at 130 ° C. for 3 hours. As the reaction proceeds, the color changes to yellow. TLC method can be used to determine whether the reaction proceeds quantitatively.

In the same manner, GPTMS and diaminohexane (DAH) are reacted to synthesize the binding string material. When reacting chloropropyltriethoxysilane (CPTES) with DAH, pyridine is added to increase the rate of formation of the bond string material. In the same way, GPTMS and PEI can be reacted to synthesize the binding string material.

Example 2

After 1 kg of silica was suspended in 6 L of 95% ethanol, 500 mm of 5 mm and 10 mm alumina beads were placed in a porcelain ball mill having a diameter ㅧ height of 27 cm ㅧ 30 cm. The ball mill is stirred at 30-50 rpm for an hour and a half to disperse the silica. The silica suspension transferred to the reactor is stirred at a speed of 30-400 rpm. In 200 ml of 95% ethanol, the binding string solution prepared in Example 1 with APTES and GPTMS was dissolved at a concentration of 0.1 mmol / g, and the binding string solution was added at a rate of 10-15 ml / min. After stirring for 8 hours, it is filtered. The silica filtrate is placed in a drier and dried at 120 ° C. for 12 hours while flowing nitrogen gas at a rate of 100 cm 3 / min. The recovery rate of the nested silica was over 95%, the moisture content was less than 3%, and the organic bond amount calculated from the mass loss measured in the air stream by the thermogravimetric analyzer (TG) was 3%.

Example 3

600 L of 95% ethanol was put into a 1 m 3 homogenizer, and 100 kg of silica was suspended, followed by vigorous stirring for 1 hour to disperse the silica particles. The suspension was transferred to a 3 m 3 stirrer using a pump, and then 6 L of an ethanol solution of the binding string material having a concentration of 0.15 mmol / g was added thereto. 1.5 liter of triethylamine was added, adjusting reactor temperature between 25-35 degreeC, and it stirred at 50 rpm speed for 8 hours. The solvent was recovered by transferring to a centrifuge. The silica cake was put in a hot air dryer and dried at 110 ° C. for 8 hours to make nested silica. The recovery rate of silica was 80% and the moisture content of the prepared nested silica was 3%. The organic bond amount calculated from the mass reduction measured by TG was 3.5%.

Example 4

Into a 1 L flask, add 70 g of silica and 900 g of dichloroethane, stir for 30 minutes, transfer to an ultrasonic cleaner, and drop the suspension by ultrasonic for 20 minutes. 2.8 g of MDI is placed in a 50 ml glass jar and diluted with 20 ml of dichloroethane. A digital thermometer, a stirring rod, and a cooler are installed in a reactor for controlling temperature by connecting to a circulating thermostat and controlling the temperature to 60 ° C. The silica suspension is placed in a reactor and stirred for 5 minutes, followed by the MDI solution. Dichloroethane was further added to the reactor, and 70 g of silica was adjusted to 1,100 g of dichloroethane. After reacting for 5 hours, the silica is filtered off and dried sufficiently in an oven at 110 ° C. to make nested silica. The recovery of silica was more than 90%, the moisture content was 5%, and the amount of organic matter obtained from the mass reduction measured by TG was 4%.

In the same manner, nested silica was prepared by treating 70 g of silica with 4.2 g of PMDI. The recovery of silica was more than 90%, the moisture content was 4%, and the organic binding amount was 6% in TG results.

Example 5

In order to disperse the silica in the particle state, 200 g of silica was put in a fluidized bed reactor, and the propeller was stirred at 1,500-2,000 rpm for 1 hour. The binding string material made by combining GPTMS and APTES was diluted in 95% ethanol to a concentration of 0.2 mmol / g and filled in a binding string solution container. Nitrogen gas of 8 to 10 bar was added to the injection device to spray the binding string solution to the silica in the flow state. After apply | coating silica particle with the binding string solution, it was made to react for 4 hours, continuing to flow nitrogen gas. The silica was recovered from the reactor and dried for 4 hours in a 130 ° C dryer. The recovery of silica was more than 95%, the moisture content was 4%, and the content of organic matter analyzed by TG was 3.5%.

Example 6

According to the method described in Example 5, nested silica was prepared using MDI as a binding string. 500 g of silica was put into a gas phase reactor, and a propeller was turned to fluidize. After flowing for an hour, a binding string solution diluted with 25 g of MDI in 250 ml of 99.5% ethyl acetate was sprayed onto the silica in the flowing state. After applying MDI to the silica particles, the silica was further flowed for 1 hour while flowing nitrogen. The nest silica was prepared by drying in an oven at 110 ° C. for 4 hours. The yield was more than 95%, the moisture content was 4%, the organic content analyzed by TG was 5%.

Nest silica was prepared using a binding string solution diluted in ethanol in the same manner. 21 g of PMDI was added to 300 g of silica. The yield was more than 95%, the moisture content was 4%, the organic content calculated from the TG analysis result was 6%.

In addition, nest silica was prepared using Aekyung Chemical's IP-75, a triisocyanate in three-dimensional form, and L-75 from Korea Fine Chemicals. 32 g of IP-75 was diluted in 200 ml of 99.5% ethyl acetate and sprayed onto 300 g of fluidized silica. The yield of the nested silica was 95% or more, the water content was 4-5%, and the organic matter content measured by TG was 8% or more.

Example 7

70 g of the nested silica prepared in Example 3 was suspended in 99.5% ethanol and placed in a 1 L round bottom flask. A solution of 3 g of pentaerythritol in 50 ml of 99.5% ethanol was added to a silica suspension. Hang the flask containing the silica suspension on a rotary evaporator to rotate at room temperature while removing the solvent in vacuo. Dry in an oven at 110-140 ° C. The yield was more than 95%, the moisture content was reduced by 0.5% to 3.5%, and the organic content calculated from the TG analysis resulted in 8.8%.

Example 8

70 g of the nested silica prepared in Example 3 was suspended in 99.5% ethanol and placed in a 1 L round bottom flask. A solution of 3 g of glycerin in 50 ml of 99.5% ethanol was added to a silica suspension. Hang the flask containing the silica suspension on a rotary evaporator to remove the solvent in vacuo while rotating at room temperature. Dry in an oven at 110-140 ° C. The yield was more than 95%, the moisture content was 3.5%, the organic content calculated from the TG analysis was more than 7.5%.

Example 9

Synthetic rubber containing nested silica was prepared and tensile rubber was compared with compounded rubber using silica and TESPT. As the basic rubber, a solution-polymerized styrene-butadiene rubber (S-SBR) swelled with oil was used, and 40 phr of the nested silica prepared according to Examples 2 to 8 was added. Comparative compound rubber was prepared by adding 3.2 phr of TESPT binder to 40 phr of highly disperse silica used in the manufacture of high-grade tires. Table 1 summarizes the composition of the compounded rubber.

Table 1. Composition of Rubber Compound for Tensile Properties Evaluation

¹⁾ S-SBR swelled with oil (containing Kumho 37.5 phr oil).

²⁾ Nest silica prepared in Example 2-8

³⁾ 7000 (Degussa Co.).

⁴⁾ Bis- (triethoxysilylpropyl) tetrasulfane (Degussa Co.).

⁵⁾ Hanil Co.

⁶⁾ Pyunghwa Co.

⁷⁾ Miwon Co.

⁸⁾ N -cyclohexyl-2-benzothiazole sulfenamide (DC Chemical Co., Ltd.).

⁹⁾ N, N -diphenylguanidine (Kumho Monsanto. Co.).

Rubber was blended in two stages, primary and secondary. In the primary formulation, the initial speed was adjusted to 135 ° C. at the rotor speed of 30 rpm. The S-SBR rubber was added and then a 40 second USSR, silica. After blending silica for 220 seconds, zinc oxide and stearic acid were added, followed by mixing for 140 seconds. After taking out and cooling, secondary blending was started. The rotor speed was the same at 30 rpm but the initial temperature was set low at 90 ° C. After 30 seconds of blending, sulfur and a vulcanization accelerator were added and further blended for 120 seconds. A plate-shaped compound rubber was made by repeating 3/4 cutting and end-wise while rotating for 5 minutes at a speed of 8 rpm on a two-roll mill having a mill spacing of 3 mm.

Table 2. Tensile Properties of Compounded Rubber with 40 phr Nest Silica

¹⁾ Manufacture in Example 2

²⁾ Preparation in Example 3

³⁾ Manufacture in Example 4

⁴⁾ Preparation in Example 5

⁵⁾ Preparation in Example 7

⁶⁾ Preparation in Example 8

⁷⁾ Comparative compound rubber of Table 1

⁸⁾ Standard Deviation

The oscillatory Disk rheometer was used to draw a vulcanization curve at 160 ° C to determine t ₉₀ hours. Unvulcanized rubber was placed in a compression press set to 160 ° C. and vulcanized for t ₉₀ ㅧ 1.5 hours to produce a tensile test specimen. After mounting a dumbbell-shaped specimen in the universal tensile tester, a strain-strain curve was drawn while pulling at a speed of 100 mm / min to determine modulus, tensile strength, and elongation.

Tensile test results are summarized in Table 2. The tensile properties of the compounded rubber with 40 phr of nested silica were almost the same as that of the compounded rubber with TESPT binder with silica. The modulus of the nested silica-added rubber is slightly lower than that of the rubber compounded with the binder, but the tensile strength is generally similar. In comparison, the elongation is much higher. In the compounded rubber containing the nested silica, the reinforcing properties are enhanced by the effect of the rubber molecules penetrating into the silica network and the twisting effect of the rubber molecules in direct contact with the silica particles. Therefore, the modulus is low if the rubber molecule and silica are not directly bonded. Tensile strength, on the other hand, may be higher or lower than the compounding rubber added with the binder, depending on the type and amount of bond. However, unlike the binder, the elongation is considerably high because it does not bind in the nested silica-added rubber. The addition of nested silica made of various bond string materials in various ways significantly improved the tensile properties of the compounded rubber. Nested silica with proper physical properties such as tensile strength, modulus and elongation determined according to the use of rubber products can be selected and used.

Example 10

Silica may be used in amounts of up to 70-80 phr depending on the purpose of the rubber product. The higher the amount of silica added, the higher the viscosity of the rubber and the higher the inorganic content, making it difficult to blend. In order to examine the performance of the nested silica under a large amount of silica, 70 phr additive rubber was prepared to evaluate tensile properties. Only the amount of nest silica added was increased to 70 phr, and the other compositions were prepared in the same manner as in Example 9. In the comparative compound rubber, the silica addition amount increased to 70 phr, so the binder addition amount increased to 5.6 phr. The compound was added in the same manner as in Example 9, but the silica was added in two steps. Other compounding processes and vulcanization and tensile test methods were the same as in Example 9.

Table 3 summarizes the tensile properties of the compounded rubber with 70 phr of nested silica. As the amount of nested silica was increased, the modulus and tensile strength were increased and the elongation was lower than that of 40 phr rubber. The addition of nested silica made of bonding strings made of APTES and DCH resulted in an excellent reinforcing effect because both tensile strength and elongation were significantly higher than those of TESPT compounded rubber. In the compounded rubber containing TESPT as a binder, it is very suitable as a reinforcing agent for compounded rubber, which has high tensile strength and elongation. However, unlike TESPT binders, ethanol is not generated, making the manufacturing process much simpler.

Table 3. Tensile Properties of Compounded Rubber with 70 phr Nest Silica

¹⁾ Manufacture in Example 6

²⁾ prepared by the method of Example 3 from the binding string material made by combining APTES and DCH

³⁾ Comparative compound rubber for comparison

According to the method of the present invention, it was possible to inexpensively prepare the nested silica in which the silica particles were three-dimensionally bonded with the organic binding string in a short time, and the tensile properties of the nested silica prepared by this method were very excellent. It was. The surface of the silica particles was covered with an organic substance, and a space was formed between the particles, and rubber molecules easily penetrated into the inner space of the nested silica, so that the silica particles in the rubber were also excellent in dispersion. The organic binding string and rubber molecules were twisted together and the reinforcing effect of the silica particles was maximized. Thus, the compounded rubber with nested silica showed similar or better tensile properties than the compounded rubber with binder. When nested silica is blended into rubber, it is possible to eliminate the contamination of working environment due to alcohol production and the additional process for removing alcohol, while maintaining the dispersibility of silica and the tensile properties of the compounded rubber, compared to the rubber compounded with silica and silane-based binder. Can be improved. Nested silica is suitable as a reinforcing agent for rubber products in which elasticity, support ability and durability of compound rubber such as tires, shoes and hoses are important.

Claims (10)

A method for producing nested silica, characterized by dissolving the binding string material in methanol or ethanol aqueous solution and reacting with silica particles at 20 to 60 ° C. The method of claim 1, wherein the aqueous methanol or ethanol solution is an aqueous solution containing 5 to 20 wt% of water. The method for producing nested silica according to claim 1, wherein the silica particles are suspended in methanol or ethanol and reacted for 1 to 12 hours. The method for producing a nested silica according to claim 1, wherein the bonding silica solution is sprayed and applied to the silica in a fluid state, and then reacted for 1 to 6 hours. A mixture of glycidoxypropyltrimethoxy silane and 3-aminopropyltriethoxysilane, glycidoxypropyltrimethoxy silane and diaminohexane as claimed in claim 1. , Mixtures of 3-aminopropyltriethoxysilane and dichlorohexane, mixtures of polyethylene imine and glycidoxypropyltrimethoxy silane, toluene diisocyanate, methylenediphenyl diisocyanate, hexanediisocyananate and 3,3 '-Bis (triethoxysilylpropyl) tetrasulfide. The method for producing nested silica according to any one of claims 1 to 4, wherein the bonding string material is supported on the silica particles to bond the silica particles to each other. The process for producing nested silica according to any one of claims 1 to 4, wherein the bond string material is used in an amount of 0.5 to 10 wt% based on the silica particles. The method according to any one of claims 1 to 4, wherein one or more selected from the group consisting of diethylamine, triethylamine, triethanolamine and dimethylguanidine is added at 0.1 to 2 wt% based on silica. The manufacturing method of the nested silica characterized by the above-mentioned. The method according to any one of claims 1 to 4, wherein one or more selected from the group consisting of pentaerythritol, glycerin, sorbitol, mannitol, glucose and polyethylene glycol is added to the nest silica to enhance the hydrophobicity of the silica particles. Method for producing a nested silica, characterized in that added in an amount of 0.1 to 3 wt%. delete

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