CN1333004C - Method for preparing nano silicate fiber and rubber composite material - Google Patents

Abstract

The preparation method of nano silicate fiber and rubber composite material of the present invention is a method for preparing composite material by adopting a melt blending method with modified acicular silicate and rubber. In the preparation process of the modified natural acicular silicate, the surface modification treatment adopts dry treatment or on-site treatment. The dosage of the modifier is 0.5% to 20% of the mass of the natural acicular silicate, and the dosage of the release agent is 0.5% to 50% of the mass of the natural acicular silicate. The mass parts of the basic formula of the composite material are rubber 100, modified natural acicular silicate 10-120, active agent 3-10, accelerator 1-3, vulcanizing agent 0.5-12. The modified natural acicular silicate obtained by the invention has low cost and good dispersion in rubber, and the prepared nano silicate fiber and rubber composite material has more excellent mechanical properties.

Description

A kind of preparation method of nano silicate fiber and rubber composite material

technical field

The invention relates to a method for preparing nano silicate fiber and rubber composite material by using modified acicular silicate and rubber by means of a melt blending method.

Background technique

Rubber must be reinforced to have excellent performance. High-efficiency reinforcement of rubber materials must be nano-reinforced or micro-reinforced with a large shape factor ratio. Nano-carbon black, nano-silica, organic short fibers, etc. can effectively reinforce rubber, but the fly in the ointment is that carbon black depends on petroleum resources; silica is expensive, even if it is modified with a silane coupling agent, its The reinforcement performance is still inferior to that of carbon black; and the organic short fiber has a thick diameter and requires a large aspect ratio for reinforcement, so the processing fluidity of the composite material is very poor, the appearance of the product is not exquisite, and the price of the organic short fiber is also relatively high. high. Therefore, to obtain rubber composites with good mechanical properties and processing properties, nano-reinforcement is the most effective method.

Natural acicular silicate (FS) is a class of hydrous aluminum-magnesium silicate minerals, which includes sepiolite, attapulgite and palygorskite. Sepiolite and attapulgite are two independent minerals of the same group, their structures are roughly similar, and their single crystal structures are slightly different. Attapulgite (AT) is a subspecies of palygorskite, which has the same chemical composition and crystal structure as palygorskite, the difference is that palygorskite has good crystallinity, long single crystal fiber, low iron content and soft appearance .

When FS is dispersed in the polymer in nanometer size, the mechanical properties of the polymer can be improved. People such as Rong Junfeng disclosed polyethylene/sepiolite nanocomposite material in "a kind of nanoscale composite material of polyolefin and clay" (ZL98125042.4), and this material is made of 40-99.9 weight % polyethylene and 0.1-60% by weight of fibrous palygorskite clay (mainly selected from sepiolite or attapulgite), the composite material is prepared by in-situ polymerization. Wang Yizhong of Beijing University of Chemical Technology and others reported the synthesis of nylon 6/ Attapulgite nanocomposites, when the mass fraction of attapulgite is 5% and 10%, the tensile strength of the composite material increases from 68.6MPa to 87.2MPa, 77.7MPa, and the bending strength increases from 89.3MPa to 128MPa, 109MPa . However, AT seriously affects the polymerization reaction, and the in-situ polymerization method is complicated in process and high in cost, and has not yet been industrialized.

"Organic modification of attapulgite surface and its application in rubber" [Chemical Engineer, 1996, (2): 3-5] reported the use of self-made cationic surface modifiers with reactive groups to treat Attapulgite, the composite material of modified AT and natural rubber was prepared by melt blending method. The 300% modulus stress of the composite material was 5.6MPa, the tensile strength was 14.9MPa, and the tear strength was 13.5KN/m. However, in the rubber composite materials prepared above, the dispersion of modified attapulgite in rubber, the type of modifier and the treatment method have not been reported.

The use of natural clay minerals to prepare rubber nanocomposites is a research hotspot in recent years. Zhang Liqun of Beijing University of Chemical Technology and others disclosed a method of preparing layered silicate/rubber nanocomposites by using clay aqueous solution and rubber emulsion blending co-flocculation method in "Preparation Method of Clay/Rubber Nanocomposites" (ZL98101496.8). method. If this raw material is used, the traditional melt processing method can only obtain layered silicate/rubber micro-composites.

Taken together, FS can be composited with polymers at both the micro-filling and, hopefully, nano-reinforcement levels. For micron filling, even if organic modifier is used to modify FS, its performance improvement is very limited, mainly to increase the filling amount and reduce the cost. For nano-reinforcement, although the in-situ polymerization method is used to disperse FS in the polymer matrix as uniformly as possible in the form of nano-units, thereby preparing polymer-based nanocomposites and significantly improving the performance of the polymer, this method is complex and costly. .

The applicant provided a method for preparing a nanofiber reinforcement from natural acicular silicate in "A Preparation Method of Nanofiber Reinforcement" (publication number CN1511865A). The preparation method of the nanofiber reinforcing agent includes processes such as purification, dissociation, activation modification, coating isolation and drying, which is called wet treatment, and the obtained nanofiber reinforcing agent is modified FS. When the nanofiber reinforcing agent is mixed with polymer melt, solution and emulsion, it can form a nanoscale dispersed phase to prepare a polymer nanocomposite material. During the preparation of modified FS, impurities such as carbonate and quartz contained in the raw ore and layered silicate-montmorillonite are removed during the purification process. The dissociation process is to purify acicular silicate and disperse it in a polar medium. The weight concentration of acicular silicate is 5% to 30%, and the amount of polar medium is relatively large, which needs to be removed in the subsequent drying process. polar media. The activation modification process is to add a surface activation modifier and react at 50-80 DEG C for 0.5-6 hours. The amount of the surface activation modifier is 3%-50% of the weight of the purified acicular silicate. The coating isolation treatment is to add an organic surface isolation agent for coating isolation, and the dosage of the isolation agent is 5% to 80% of the weight of the purified acicular silicate. Finally, it is dried at 80-150° C. to obtain the nanofiber reinforcing agent. This wet treatment of the surface modification of acicular silicates requires the use of a large amount of polar media and needs to be removed at the end, and in the modification process, FS must be pulverized to obtain fine particles.

Contents of the invention

The invention provides a method for preparing composite material by using modified silicate and rubber by melt blending method. In the process of preparing modified natural acicular silicate, the amount of modifying agent, solvent and release agent used in this method is small, the preparation process is simplified, and the modified FS does not need to be pulverized and can be used directly. Therefore, the modified FS The cost is lower; the modified FS of the present invention can be successfully used in the melt blending method to prepare rubber composite materials, so as to realize nanometer dispersion of acicular silicate fibers in rubber. The melt blending method is mature and easy to operate, and the modified natural acicular silicate can significantly improve the performance of the composite material.

The invention discloses a method for preparing a nano silicate fiber and rubber composite material. The natural acicular silicate is purified and surface modified to obtain a modified natural acicular silicate. Acicular silicate is subjected to surface modification treatment, and then the modified natural acicular silicate and rubber, active agent, accelerator, vulcanizing agent, anti-aging agent and other additives are melt-blended and vulcanized to obtain nano-silicic acid Salt fiber and rubber composite material, characterized in that:

(1) In the preparation process of the modified natural acicular silicate, the surface modification treatment uses the following dry pretreatment or on-site treatment to prepare the modified natural acicular silicate;

①Dry treatment: Dilute the modifier with a solvent, stir and disperse the purified natural acicular silicate in a mixer, spray the modifier solution and stir to mix, then spray the release agent and continue to mix, and then After drying, the modified natural acicular silicate is obtained;

②On-site treatment: use rubber as a release agent and mix the purified natural acicular silicate in an internal mixer at 100-150°C, and add a modifier at the same time to obtain a modified natural acicular silicate; During the treatment process, the dosage of the modifier is 0.5% to 20% of the mass of the natural acicular silicate, and the dosage of the release agent is 0.5% to 50% of the mass of the natural acicular silicate;

(2) The parts by mass of the basic formula of the composite material are rubber 100, modified natural acicular silicate 10-120, active agent 3-10, accelerator 1-3, vulcanizing agent 0.5-12.

The natural acicular silicate used in the present invention is any one of attapulgite, palygorskite or sepiolite.

The solvent used in the surface modification dry treatment of the present invention is ethanol or acetone, and the ratio of the solvent to the modifying agent is 3ml:1g˜5ml:1g.

The modifying agent used in the dry treatment or on-site treatment of the present invention is a titanate coupling agent, an aluminate coupling agent or a silane coupling agent.

The release agent used in the dry process of the present invention is castor oil, sulfonated castor oil or sodium polyacrylate solution.

The rubber used in the present invention is natural rubber or synthetic rubber: styrene-butadiene rubber, butadiene rubber, EPDM rubber, nitrile rubber, carboxylated nitrile rubber, neoprene, butyl rubber, hydrogenated nitrile rubber, chlorine Alcohol rubber or Viton rubber.

The active agent used in the present invention is zinc oxide, stearic acid or stannous chloride.

The vulcanizing agent used in the present invention is sulfur, peroxide or resin vulcanizing agent.

The FS used in the present invention is purified. Since the raw ore contains a large amount of carbonate, quartz and other non-clay components, these substances cannot be finely dispersed in the conventional processing process, and the size is large, which affects the mechanical properties of the final material. . The purification process follows a known method ("a preparation method of a nanofiber reinforcing agent" (publication number CN1511865A) is one of the optional methods).

The present invention proposes a new method of dry treatment in the process of modifying FS, premixing FS in a high-speed mixer for 3 to 5 minutes to make it fluffy; the titanate coupling agent, alumina acid Ester coupling agent and silane coupling agent are well-known modifiers for FS modification. The modifier is diluted with ethanol or acetone solvent, and the ratio of solvent and modifier is preferably controlled at 3ml: 1g ~ 5ml: 1g , so that it is easy to add by spraying method, and mix with strong stirring for 7 to 10 minutes, so that the modifier and FS can be fully infiltrated and mixed evenly. Too little solvent is not conducive to the uniform mixing of modifier and FS; too much solvent will cause a large amount of solvent to volatilize in the agitator due to the heat generated during high-speed stirring, which may cause danger. The usage amount of the solvent of the present invention is much less than that of wet processing, and it is easy to remove when drying. The used release agent is castor oil, sulfonated castor oil and sodium polyacrylate solution, and the release agent is coated on the surface of the modifier to obtain the modified FS with fine particles. The dry treatment is carried out at normal temperature, the treatment time is short, and the amount of solvent is less; the obtained modified FS can be used without crushing. The wet treatment has high temperature and long time during the activation modification process, and the amount of modifier and release agent is large, and the amount of polar medium (solvent) is large. After the modified FS is dried, it needs to be pulverized to obtain fine particles. .

In the process of modifying FS, the present invention proposes another new treatment method, that is, on-site treatment, which is to use high mechanical shear force during the mixing process of rubber and FS at high temperature (100-150°C) to partially FS While being dissociated into smaller particles, a modifier is added to realize the surface modification of FS, so that FS is further dissociated into nanofibers, which are evenly dispersed in the rubber matrix to obtain agglomerated modified FS. At this time, the nanofibers have been isolated from each other by the rubber macromolecular chains, and are not easy to re-aggregate, and the rubber matrix itself acts as an isolating agent. On-site processing is simpler and does not require the use of solvents.

The surface tension of modified FS obtained by the above two treatment methods is reduced, the self-cohesion of single crystal fibers is weakened, the affinity with rubber is enhanced, the degree of dissociation and dispersion of FS is improved, and the interface between FS and rubber is enhanced.

Modified FS is obtained by adopting the modification method of the present invention, and mixed with rubber in an open mill or an internal mixer through a traditional melt blending processing method, and the single crystal contained in FS is dissociated and dispersed to obtain nano-silicon Silicate fiber and rubber compound, then add active agent, accelerator, vulcanizing agent and anti-aging agent in sequence, mix evenly, and vulcanize to obtain nano silicate fiber and rubber composite material. The active agent, accelerator, vulcanizing agent and anti-aging agent used and the consumption amount are conventionally known. In the composite material of the present invention, the amount of rubber is 100 parts, and the amount of modified FS is 10 to 120 parts. With the increase of the amount of modified FS, the mechanical properties of the composite material are improved, and too high an amount will cause the dissociation of modified FS The degree and dispersion are poor, but the mechanical properties of the composite material are reduced. The base rubber used in the method of the present invention is known natural rubber and synthetic rubber that can be processed by melt blending. Recently, the present invention adopts the modified FS processed by dry method or the modified FS processed on site and rubber to prepare nano-silicate fiber and rubber composite material by traditional melt blending method. The melt blending method does not involve the organic solvent of the rubber, does not require the existence of the rubber in the form of an aqueous emulsion, has a wider scope of application, and has a simple process. It is a method with mature technology and the easiest way to realize industrial production.

The dispersion of the modified FS in the rubber matrix can be observed through a transmission electron microscope. The modified FS obtained by the two modification treatments of the present invention is dissociated into nanofibers with a diameter less than 100nm in the rubber matrix, and the dispersion is uniform. Its dispersibility is much better than unmodified FS and wet modified FS. Instron electronic universal testing machine was used to test the mechanical properties of composite materials in accordance with national standards. The 300% modulus stress, tensile strength and tear strength of the nano silicate fiber and rubber composite material obtained in the invention are all higher than the nano silicate fiber and rubber composite material, showing good reinforcing effect. The modified FS obtained by the invention has better dispersibility in rubber, shorter vulcanization time of the compound, which is beneficial to energy saving, and the prepared nano silicate fiber/rubber composite material has better mechanical properties.

Description of drawings

Fig. 1 is a transmission electron microscope photo of FS dispersed in styrene-butadiene rubber in-situ treated in Example 2 of the present invention.

Fig. 2 is a transmission electron micrograph of dry-processed FS dispersed in styrene-butadiene rubber in Example 3 of the present invention.

Fig. 3 is a transmission electron micrograph of unmodified FS prepared in Comparative Example 1 dispersed in styrene-butadiene rubber.

Fig. 4 is a transmission electron micrograph of wet-modified FS dispersed in styrene-butadiene rubber in comparative example 2.

Detailed ways

Example 1 Dry treatment of FS: pre-mix 100gFS in a high-speed mixer for 5min to make it fluffy, then add a modifier: a mixed solution of 0.5g silane coupling agent Si69 and 2.5ml ethanol, stir for 10min, and make Mix the modifier and FS evenly, and then add the release agent: 10g of sulfonated castor oil, mix evenly, and dry at 82°C for 2 hours to obtain the modified FS with fine particles of 5-40μm.

On the double-roll mill, add 100g of natural rubber for mastication, then sequentially add activator: 7g of zinc oxide and 3g of stearic acid, accelerator: 0.5g each of DM and CZ, then add 50g of the above-mentioned modified FS, and finally add vulcanization Agent: sulfur 2g, mixed evenly to obtain rubber compound. The mixed rubber was vulcanized at 140°C to obtain a composite material of nano-silicate fiber and natural rubber, and its mechanical properties are shown in Table 1.

Example 2 On-site treatment of FS: add release agent: 400g styrene-butadiene rubber to a 1.0L internal mixer, masticate for 30 seconds, add 400gFS and modifier: 80g silane coupling agent KH570, and knead at 130°C for 5min A modified FS was obtained.

On the two-roll mill, add 100g of styrene-butadiene rubber for mastication, then add 40g of the above-mentioned modified FS, and then add vulcanizing agent: 0.8g of dicumyl peroxide, and mix evenly to obtain a rubber compound. Finally, it was vulcanized at 160°C to obtain a composite material of nano-silicate fiber and styrene-butadiene rubber. The mechanical properties are shown in Table 1, and the transmission electron microscope photos are shown in Figure 1. It can be seen from Figure 1 that the modified FS obtained by on-site treatment can be dissociated into fibers with a diameter of less than 100nm and dispersed uniformly in the styrene-butadiene rubber, and the dispersion of the modified FS is very good.

Example 3 Dry treatment of FS: The treatment process is the same as in Example 1, except that the modifier: the amount and type of the silane coupling agent are the same as in Example 2, and the release agent is 5g castor oil.

The preparation process of the composite material is the same as in Example 2, and its mechanical properties are shown in Table 1. The transmission electron microscope pictures are shown in Figure 1. It can be seen from Table 1 that the composite material has high hardness, 100% modulus stress, tensile strength, tear strength and high elongation, which are equivalent to the mechanical properties of the composite material obtained in Example 2. It can be seen from Figure 2 that the modified FS obtained by dry treatment can be dissociated into fibers with a diameter of less than 100 nm and uniformly dispersed in the styrene-butadiene rubber, and the dispersibility of the modified FS is very good.

Example 4 Dry treatment of FS: The treatment process is the same as in Example 3, and the preparation of the composite material is the same as in Example 3, except that 10 g of modified FS is added. The mechanical properties of the composite material are shown in Table 1. Compared with Example 3, the amount of modified FS is reduced, the hardness, 100% modulus stress, tensile strength, and tear strength of the composite material are significantly reduced, and the elongation is significantly increased.

Example 5 Dry treatment of FS: The treatment process is the same as in Example 3, and the preparation of the composite material is the same as in Example 3, except that 60 g of modified FS is added. The mechanical properties of the composite material are shown in Table 1. Compared with Example 3, the amount of modified FS increased, the hardness, 100% modulus stress, tensile strength, and tear strength of the composite material increased significantly, and the elongation decreased significantly.

Example 6 Dry treatment of FS: pre-mix 100gFS in a high-speed mixer for 3 minutes to make it fluffy, then add modifier: a mixed solution of 10g silane coupling agent KH550 and 30ml ethanol, stir for 7min, and make the modified Mix the agent and the filler evenly, then add the release agent: 5g of sodium polyacrylate solution, mix evenly, and dry at 82°C for 2 hours to obtain the modified FS.

100g nitrile rubber (NBR) is masticated on a two-roller mill, then add active agent: tin protochloride 5g, vulcanizing agent: phenolic resin 12g, above-mentioned modified FS 120g, mix to obtain rubber compound. Finally, it is vulcanized at 170°C to obtain a composite material of nano silicate fiber and nitrile rubber. The mechanical properties of the composite materials are listed in Table 1.

Example 7 Put 400g of ethylene-propylene-diene rubber (EPDM) in a 1.0L internal mixer, masticate for 30 seconds, add active agents: zinc oxide 8g and stearic acid 4g, accelerators: CZ 3.0g, M 3.0 g and promote TT 3.0g, add the modified FS 300g of embodiment 1, finally add vulcanizing agent: sulfur 2.4g, mix to obtain rubber compound. Then vulcanized at 160°C to obtain a composite material of nano-silicate fiber and EPDM rubber, the mechanical properties of which are shown in Table 1.

Example 8 The on-site treatment of FS is the same as that of Example 2, the only difference is that the mixing temperature is 100°C to obtain a modified FS in the form of agglomerates.

The preparation of the composite material is the same as in Example 2, and its mechanical properties are shown in Table 1, which are equivalent to those of the composite material obtained in Example 2.

Example 9 The on-site treatment of FS is the same as that of Example 2, the only difference is that the mixing temperature is 150°C to obtain a modified FS in the form of agglomerates.

The preparation of the composite material is the same as in Example 2, and its mechanical properties are shown in Table 1, which are equivalent to those of the composite material obtained in Example 2.

The formula and process of comparative example 1 and embodiment 2 are identical, and difference is to adopt unmodified FS. The obtained composite material of silicate fiber and styrene-butadiene rubber is shown in Table 1 for its mechanical properties, and shown in FIG. 3 for transmission electron microscope photos. Compared with Example 2, the 100% modulus stress, tensile strength and tear strength of the composite material are lower, the elongation and permanent deformation are larger, and the vulcanization time is longer. It can be seen from Figure 3 that only a small part of unmodified FS can be dissociated into fibers with a diameter of less than 100 nm and dispersed in styrene-butadiene rubber. There are many FS aggregated particles with a size of 0.1-0.5 microns, and the dispersion of unmodified FS is very low. Difference.

Comparative example 2 The technical process of FS wet treatment is carried out according to the method of Chinese patent application (02159287.X), the preparation of modified FS adopts modifier KH570, and the consumption is the same as that of Example 2, and it needs to be pulverized in the modification process to obtain 5 ~ 40μm fine particles. The preparation process of the composite material is the same as in Example 2. The mechanical properties of the composite materials are shown in Table 1, and the transmission electron microscope photos are shown in Figure 4. Compared with Example 2, the 100% modulus stress, tensile strength and tear strength of the composite material are lower, the elongation and permanent deformation are higher, and the vulcanization time is longer. It can be seen from Figure 4 that most of the wet-modified FS can be dissociated into fibers with a diameter of less than 100 nm and dispersed in styrene-butadiene rubber. better.

Comparative example 3 cites the performance data of FS/NR composite material in the document "organic modification of attapulgite surface and its application in rubber" [Chemical Engineer, 1996, (2): 3-5], and the examples 1, the 300% modulus stress, tensile strength and tear strength of the composite material are lower, the permanent deformation is larger, and the vulcanization time is slightly longer.

The performance comparison of the embodiment of the present invention and comparative example of table 1

performance hardness 100% modulus stress Tensile Strength Elongation at break   Tear Strength permanent deformation Vulcanization time unit Shao A MPa MPa % KN/M % min Example 1 60 16.8 ^* 23.0 427 57.6 12 5 Example 2 78 9.1 16.8 261 26.9 8 12 Example 3 79 10.1 17.5 289 27.5 4 10 Example 4 58 2.6 8.6 385 15.9 8 8 Example 5 85 13.3 19.8 176 35.6 3 12 Example 6 90 32.5 33.8 101 44.2 2 10 Example 7 87 15.1 18.6 175 38.9 4 11 Example 8 75 8.1 15.6 253 25.3 8 11 Example 9 79 8.6 16.1 236 26.1 6 12 Comparative example 1 71 3.1 5.6 354 17.1 25 25 Comparative example 2 70 6.7 14.3 256 23.2 16 18 Comparative example 3 54 5.6 ^* 14.9 530 13.5 29 7

^* 300% modulus stress

Claims (8)

1. A preparation method of nano silicate fiber and rubber composite material, the natural acicular silicate is purified and surface modified to obtain modified natural acicular silicate, and the natural acicular silicate is treated with a modifier and a release agent. Acicular silicate is subjected to surface modification treatment, and then the modified natural acicular silicate and rubber are melt-blended and vulcanized to obtain nano-silicate fiber and rubber with active agent, accelerator, vulcanizing agent and anti-aging agent. Composite material, characterized in that: (1) In the preparation process of the modified natural acicular silicate, the surface modification treatment prepares the modified natural acicular silicate with the following dry treatment or on-site treatment; ①Dry treatment: Dilute the modifier with a solvent, stir and disperse the purified natural acicular silicate in a mixer, spray the modifier solution and stir to mix, then spray the release agent and continue to mix, and then After drying, the modified natural acicular silicate is obtained; the release agent is castor oil, sulfonated castor oil or sodium polyacrylate solution; ②On-site treatment: use rubber as a release agent and mix the purified natural acicular silicate in an internal mixer at 100-150°C, and add a modifier at the same time to obtain a modified natural acicular silicate; During the treatment process, the amount of modifier used is 0.5% to 20% of the mass of natural acicular silicate, and the amount of release agent is 0.5% to 50% of the mass of natural acicular silicate; (2) The parts by mass of the basic formula of the composite material are rubber 100, modified natural acicular silicate 10-120, active agent 3-10, accelerator 1-3, vulcanizing agent 0.5-12. 2. The method according to claim 1, characterized in that the natural acicular silicate is any one of attapulgite, palygorskite or sepiolite. 3. The method according to claim 1, characterized in that the solvent used in the surface modification dry treatment is ethanol or acetone, and the ratio of the solvent to the modifying agent is 3ml:1g-5ml:1g. 4. The method according to claim 1, characterized in that the modifier used for dry treatment or on-site treatment is titanate coupling agent, aluminate coupling agent or silane coupling agent. 5. The method according to claim 1, wherein the rubber is natural rubber or synthetic rubber: styrene-butadiene rubber, butadiene rubber, EPDM rubber, nitrile rubber, carboxylated nitrile rubber, neoprene, Butyl rubber, hydrogenated nitrile rubber, epichlorohydrin rubber or Viton rubber. 6. The method according to claim 1, characterized in that the active agent is zinc oxide, stearic acid or stannous chloride. 7. The method according to claim 1, characterized in that the accelerator is thiurams, thiazoles or guanidines. 8. The method according to claim 1, characterized in that the vulcanizing agent is sulfur, peroxide or resin vulcanizing agent.

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