CN109369994B - Low-zinc rubber composition - Google Patents
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Abstract
The invention discloses a low-zinc rubber composition, which is characterized by comprising at least one diene elastomer rubber composition, wherein the rubber composition contains 0.5-1 phr of zinc, phr refers to parts per hundred parts of rubber, and the rubber composition is based on at least: a filler system; a sulfur-based crosslinking system comprises a high-specific-surface-area nano zinc oxide taking zinc hydroxide particles as a carrier as a vulcanization activator and an auxiliary agent system. The vulcanization activator is characterized in that nano zinc oxide is uniformly loaded on the surface of zinc hydroxide particles in the decomposition process of precipitates, the chemical activity is high, the dispersibility is good, the good performance of a product can be ensured under the condition of reducing the use amount, and the residual amount of zinc in a rubber product is reduced. The method is applied to tire products, improves the environmental protection performance of the tire products and reduces the problem of zinc pollution caused by the tires.
Description
Technical Field
The invention belongs to the technical field of tire rubber material production, and particularly relates to a low-zinc rubber composition.
Background
Zinc compounds, particularly zinc oxide, are used in the production of almost all rubber articles. The amount is generally about 2% of the total amount of the compound, corresponding to about 3 to 5phr of zinc oxide. In the European Union, about 10 million tons of zinc oxide and a little other zinc compounds are used in the rubber industry every year, which accounts for about 40% of the total consumption of zinc oxide, while the consumption of zinc oxide in China is about 18-30 million tons every year. In sulfur vulcanization systems, zinc oxide is used primarily as an activator, and in addition, it may be added to peroxide vulcanization systems, or may be used as a crosslinking agent in rubbers containing halogen and carboxyl groups. It can also be used as a white dye for latex, occasionally also as a semi-reinforcing filler, and zinc oxide can also improve heat transfer properties, other zinc compounds used in sizing materials including zinc soap, zinc dithiocarbamate, zinc benzothiazol-2-mercaptide, zinc benzoimidyl-2-mercaptide.
Although zinc is very widely used. However, certain alloys of zinc can poison microorganisms and aquatic organisms when the zinc is released into the environment, into streams, rivers and oceans. Research shows that zinc in fish body in excess of certain concentration blocks the channels between layers to block respiratory movement, body growth and maturation, and the influence of zinc discharged to water ecosystem by human activities is gradually shown in the last 30 years. In 1993, the national institute of health and environmental protection in the Netherlands proposed a "unified Standard" for Zinc, suggesting that the concentration of Zn in water is 9. mu.g/L and the maximum allowable concentration is 25. mu.g/L. In 1995, zinc and zinc compounds were listed as the main substances in the list of rubber compounds compiled by the swedish environmental protection agency, and were suggested to be used instead or limited. In the same year, zinc and zinc oxide are listed again in the second category of hazardous substances in the risk assessment program of the european union. In4 months 2004, the european union committee mandates 2004/73/EC formally classified zinc oxide as an "environmentally hazardous" substance with a hazard classification of R50/53 "extremely harmful to aquatic life, which can have a long term adverse effect on aquatic ecosystem" and should "avoid discharge into the ecological environment". By the end of 2016 at 3 months, a law SB1260 was proposed by california in the united states that restricted the use of zinc or zinc oxide in tires, and that may prohibit the sale of tire products containing certain amounts of zinc, creating a high level of concern for zinc oxide and tire manufacturing companies. The act also considers rubber materials outdoors as a major source of zinc contamination in the environment. In overview, the proposal of the act is a warning in the current environment to the tire manufacturing industry to accelerate the upgrade of green products. Zinc pollution is a real existence, and as the requirement of the global rubber industry on environmental protection is continuously improved, the active search and development of zinc oxide substitute products are more and more emphasized, and the research on zinc reduction is trending.
At present, the indirect method zinc oxide is generally adopted in the rubber material formula of each part of the tire, metal zinc ingots or zinc slag obtained by smelting are taken as raw materials, the raw materials are converted into zinc steam at the high temperature of 1000 ℃, then blown air is used for oxidizing the zinc steam into zinc oxide, and zinc oxide particles are obtained by collecting the zinc oxide after cooling. The indirect method zinc oxide has simple production process, the particle diameter is about 0.1-10 microns, and the specific surface area is 3-7 m2(ii) in terms of/g. (the indirect method produces zinc oxide product as the attached figure 1)
Because the specific surface area of the indirect zinc oxide is small, only a small part of the indirect zinc oxide really plays a role of a vulcanization activator, the use amount is generally 3-5 phr, and the dosage of common zinc oxide in a special part such as a steel wire belt compound formula can be up to 8 phr. The rubber material with high zinc content is made into automobile tires through a series of production processes, and zinc enters the surrounding environment, soil and rivers along with the abrasion and the abandonment of the tires in the driving process of the automobile, so that adverse effects are caused on an ecological system. The nano zinc oxide has the special advantages of the nano particles, so the using amount can be reduced in use, but the nano particles are easy to agglomerate, and the exertion of the nano effect is limited. In order to solve the problem of dispersion of nano zinc oxide, it is attempted to add a dispersant or a lubricant in the production process of nano zinc oxide, or coat zinc oxide on nano clay or silica serving as a core or a carrier, but all lose part of the activity.
By the end of 2017, the automobile output and sales volume in China is ranked the first in the world for 9 years continuously, the automobile industry is a great driving force for the development of tires in China, and along with the adjustment of the product structure of the automobile industry in China, the development of new energy automobiles in particular can greatly drive the development of green tires, energy-saving and environment-friendly tires and other new structural tires in China. The development and application of the green tire have important strategic significance on improving the service performance of the tire, realizing energy conservation and emission reduction and protecting the environment. Therefore, how to research and develop the low-zinc low-rolling-resistance white carbon black filled rubber composition relates to the field of tire rubber material production, is applied to the low-zinc low-rolling-resistance green tire technology, and has important practical significance.
Disclosure of Invention
Aiming at the technical problem that the nano particles are easy to agglomerate to cause zinc pollution in the prior art, the invention aims to provide a low-zinc rubber composition, and the formula has the advantages of low zinc content and low rolling resistance.
The technical scheme adopted by the invention is as follows:
a low zinc rubber composition comprising at least one diene elastomer, a rubber composition containing zinc in an amount of 0.5 to 1phr, phr referring to parts per hundred parts of rubber, and the rubber composition being based on at least:
-a filler system;
-a sulfur-based crosslinking system comprising a high specific surface area nano zinc oxide supported on zinc hydroxide particles as a vulcanization activator;
also contains vulcanization accelerator, such as thiazoles, sulfenamides, thiurams, dithiocarbamates, benzoguanidines, etc.; vulcanizing agents, such as common sulfur powder, insoluble sulfur, and the like.
-an adjuvant system.
Furthermore, the mass fraction of the nano zinc oxide in the vulcanizing activator is 80 +/-5%, and the mass fraction of the zinc hydroxide is 20 +/-5%.
Further, the preparation method of the vulcanization activator comprises the following steps: by adopting the wet production principle, the zinc-containing solution is prepared by dissolving zinc in a soluble salt solution (the common soluble salt solution of zinc is ZnCl)2、ZnSO4、Zn(NO3)2Etc.) adding precipitant (ammonia water, urea or sodium hydroxide), decomposing at high temperature to obtain zinc hydroxide precipitate, heating, and mechanically stirring to dissolveThe zinc salt and the precipitator are mixed according to a certain molar ratio, and the precursor Zn (OH) is obtained by adjusting the hydrolysis reaction temperature, the hydrolysis reaction time, the pH value, the molar ratio of the raw materials and the type and the ratio of the surfactant2Precipitating; then washing, filtering and drying for a plurality of times by secondary distilled water to obtain Zn (OH)2And (3) powder. And then filtering, washing and drying the precipitate, then carrying out thermal decomposition, roasting at a high temperature, and adjusting roasting temperature and roasting time to obtain the nano zinc oxide taking zinc hydroxide as a carrier in certain parts by mass.
Further, the high temperature condition firing refers to 170 ℃ ± 30 ℃.
Furthermore, the nano zinc oxide has larger pore size distribution and the specific surface area of the nano zinc oxide is 20-80 m2/g。
Further, the filler system comprises one or more of carbon black, graphene, carbon nanotubes, or inorganic fillers.
Further, the inorganic filler is one or more of white carbon black, titanium dioxide, nano clay, calcium carbonate or magnesium carbonate.
Further, the diene elastomer is one or more blends of polybutadiene (BR), synthetic polyisoprene (IR), Natural Rubber (NR), butadiene-Styrene (SBR) copolymer, isobutylene-isoprene (butyl IIR) copolymer and halogenated butyl rubber thereof.
Further, the content of all the main vulcanization accelerators and the secondary vulcanization accelerators of the crosslinking system is 0.5 to 5.0 phr.
Further, the auxiliary agent system comprises operation oil, including aromatic oil, environment-friendly aromatic oil, heavy naphthenic oil, paraffin oil and the like; antioxidants including quinoline-based, amine-based, triazine-based, naphthylamine-based antioxidants; in addition, the rubber composition may contain additives known in the rubber industry, such as plasticizers, peptizers, silane coupling agents, leveling agents, dispersants, tackifying resins, and scorch retarders.
The invention has the beneficial effects that:
in the sulfur-based crosslinking system, the mass fraction of zinc oxide is 80 +/-5%, and the mass fraction of zinc hydroxide is 20 +/-5%. The vulcanizing activator uniformly loads nano zinc oxide on the surface of zinc hydroxide particles in the decomposition process of precipitates. The nano zinc oxide is easy to agglomerate, the zinc hydroxide has a relatively loose accumulation state, and the nano zinc oxide is uniformly loaded on the relatively loose zinc hydroxide particles in the production process, so that the agglomeration degree among the nano zinc oxide can be effectively reduced. In the rubber mixing process, even if some agglomerated particles are not dispersed, when the mixing temperature reaches above 125 ℃, zinc hydroxide is heated to decompose, namely, the agglomerated structure is broken due to the decomposition of the zinc hydroxide, new small zinc oxide fragments are formed, and the zinc oxide fragments are further dispersed under the mechanical shearing action of an internal mixer. Thus, it can be visually assumed that zinc hydroxide is the structural disintegrant of the agglomerate. The nano zinc oxide using the zinc hydroxide as the carrier has high chemical activity and good dispersibility, can ensure good performance of products under the condition of reducing use, and can reduce the residual amount of zinc in rubber products.
The rubber composition with low zinc content and excellent comprehensive performance is designed and obtained, is applied to tire products, improves the environmental protection performance of the tire products, ensures and optimizes the performance of the tire, and simultaneously reduces the zinc content by 50-80%, thereby reducing the problem of zinc pollution caused by the tire.
Drawings
FIG. 1 is a diagram of a prior art zinc oxide product prepared by an indirect process;
FIG. 2 shows that the zinc oxide content is not less than 99.0% and the specific surface area is 45m, which meets the requirements of GB/T19589-2The conventional nano zinc oxide product per gram has obvious agglomeration;
FIG. 3 is a diagram of a high specific surface area nano zinc oxide product using zinc hydroxide as a carrier in the present application;
fig. 4 is a schematic diagram of the nano zinc oxide with high specific surface area and using zinc hydroxide as a carrier in the present application, which can be used in a reduced amount in rubber. In FIG. 4 ● represents zinc hydroxide, ● represents zinc oxide, and the black curve represents rubber macromolecules.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Zinc oxide has been used in rubber as a vulcanization activator for centuries, and can accelerate vulcanization and improve vulcanization degree. The zinc oxide has large affinity to electrons and large surface adsorption effect on an accelerant, and is an active agent with the strongest activity in metal oxides. Zinc oxide and stearic acid are classical combinations of rubber vulcanization activators, exemplified by thiazole accelerators (represented by the general formula XSH), which act by the following mechanism:
1) under the condition of vulcanization and in the presence of fatty acid, zinc oxide firstly reacts with XSH to generate promoter zinc salt
ZnO+2XSH→XS-Zn-SX
2) Reaction of zinc salt of promoter with sulfur 8 ring body to form zinc polysulfide salt
XS-Zn-SX+2Sm→XS-Sm-Zn-Sm-SX
3) Reaction of zinc polysulfide salt with rubber to form crosslinked precursor XSnR
XS-Sm-Zn-Sm-SX+RH→XS-Sm-R+ZnS+HSm-1X
4) Cross-linked precursor XSSmR then reacts with rubber molecules to complete crosslinking
XS-Sm-R+RH→R-Sm-1-R+XSH
As can be seen from the reaction formula (2), each Zn atom is bonded with 2 cyclic sulfur (S)m) And (4) acting. The atomic ratio of Zn to S was 1:16 as calculated by the reaction formula (2). If 3 parts of sulfur are used, the amount of zinc oxide should be 81.36 × 3/(32.06 × 16) to 0.48 parts. Chapmln, based on analysis of traditional vulcanization of natural rubber, found that the zinc oxide reacted as follows, 0.6 parts converted to zinc sulfide; 0.2 part is converted to stearic acid; less than or equal to 0.1 part of zinc-promoter complex. It can be seen that in the conventional formulation of 4 parts of zinc oxide, only 1 part is effectively used, so the space for reducing the amount of zinc oxide is large, but it should be considered that the cross-linking bonds in the rubber network are not all polysulfide bonds, but a small amount of monothio bonds and disulfide bonds, and other various factors affect. Researchers have been studying the problem of reducing the amount of zinc oxide used for many years and have sought different alternatives to zinc oxideThe product is usually added with a processing aid as a vulcanization activator, but the effect is not significant.
A low zinc rubber composition comprising at least one diene elastomer, a rubber composition containing zinc in an amount of 0.5 to 1phr, phr referring to parts per hundred parts of rubber, and the rubber composition being based on at least:
-a filler system for improving the processability, mechanical properties, abrasion properties of the rubber matrix;
-a sulfur-based crosslinking system comprising a high specific surface area nano zinc oxide supported on zinc hydroxide particles as a vulcanization activator;
also contains vulcanization accelerator, such as thiazoles, sulfenamides, thiurams, dithiocarbamates, benzoguanidines, etc.; vulcanizing agents, such as common sulfur powder, insoluble sulfur, and the like. The rubber has the effect that a linear macromolecular chain forms a three-dimensional space network structure through chemical crosslinking, so that the physical property, the dynamic property, the abrasion performance and the like of the rubber are fundamentally changed, and the rubber has wider application.
An auxiliary agent system is mainly used for improving the processing performances of rubber such as mixing, calendering, extruding, forming and the like, for example, breaking a rubber macromolecular chain through chemical peptization and reducing the Mooney viscosity of rubber; the activity of the rubber macromolecular chain is improved by adding a physical lubricant, and the process performance is improved; the molding viscosity of the half part is improved by adding tackifying resin; the processing safety of the sizing material is improved by adding the scorch retarder.
The diene elastomer is one or more blends of polybutadiene (BR), synthetic polyisoprene (IR), Natural Rubber (NR), butadiene-Styrene (SBR) copolymers, isobutylene-isoprene (butyl IIR) copolymers and halogenated butyl rubbers thereof.
Furthermore, the mass fraction of the nano zinc oxide in the vulcanizing activator is 80 +/-5%, and the mass fraction of the zinc hydroxide is 20 +/-5%.
Further, the preparation method of the vulcanization activator comprises the following steps: adopts the wet production principle and adopts the solubility of zincAdding precipitant into salt as raw material, heating in thermostatic water bath, mechanically stirring, mixing soluble zinc salt with precipitant at a certain molar ratio, and regulating hydrolysis reaction temperature, hydrolysis reaction time, pH value, raw material molar ratio, and surfactant type and ratio to obtain precursor Zn (OH)2Precipitating; then washing, filtering and drying for a plurality of times by secondary distilled water to obtain Zn (OH)2And (3) powder. Roasting at high temperature, and regulating roasting temperature and roasting time to obtain the nano zinc oxide with zinc hydroxide as carrier in certain weight proportion.
Further, the soluble salt solution of zinc may be ZnCl2、ZnSO4、Zn(NO3)2, etc. adding a precipitant.
Further, the precipitant is ammonia, urea or sodium hydroxide.
Further, the high temperature condition firing refers to 170 ℃ ± 30 ℃.
Furthermore, the specific surface area of the nano zinc oxide taking the zinc hydroxide as the carrier is 20-80 m2/g。
Further, the filler system comprises one or more of carbon black, graphene, carbon nanotubes, or inorganic fillers.
Further, the inorganic filler is one or more of white carbon black, titanium dioxide, nano clay, calcium carbonate or magnesium carbonate.
Further, the diene elastomer is one or more blends of polybutadiene (BR), synthetic polyisoprene (IR), Natural Rubber (NR), butadiene-Styrene (SBR) copolymer, isobutylene-isoprene (butyl IIR) copolymer and halogenated butyl rubber thereof.
Further, the content of all the main vulcanization accelerators and the secondary vulcanization accelerators of the crosslinking system is 0.5 to 5.0 phr.
The filler system comprises one or more of carbon black, graphene, carbon nanotubes, or inorganic fillers.
Non-limiting examples of such blacks, in particular of the type of HAF, ISAF, SAF, FEF, GPF, commonly used in tires, may mention the blacks N115, N134, N234, N330, N339, N347, N375, N550, N660.
The inorganic filler is one or more of white carbon black, titanium dioxide, nano clay, calcium carbonate or magnesium carbonate.
In the case of using white carbon black, it is preferable to use highly dispersed precipitated white carbon black, and as non-limiting examples of such highly dispersed precipitated white carbon black, mention may be made of Ultrasil 7000 by Evonic; silica 200MP, 1165MP, 1115MP of Soilve; Hi-Sil EZ150G silica from PPG, and the like.
It is well known to those skilled in the art that when white carbon is used, a coupling agent is required to establish the bond between the filler and the elastomer.
Common nano zinc oxide is easy to agglomerate, and the zinc oxide in the agglomeration center is difficult to play the role of a vulcanization activator. At present, the carrier zinc oxide appearing in China generally loads or coats zinc oxide on inert substances (such as nano clay, silicon dioxide and the like), and the activity of the inert core substance is low. The sulfurizing activator used in the present invention uses zinc hydroxide as carrier or core, and has the advantages that zinc hydroxide will decompose into zinc oxide at certain temperature to continue to exert sulfurizing activity and is carrier with certain activity. As shown in figure 4, the vulcanizing activator uniformly loads nano zinc oxide on the surface of zinc hydroxide particles in the decomposition process of the precipitate. The nano zinc oxide is easy to agglomerate, the zinc hydroxide has a relatively loose accumulation state, and the nano zinc oxide is uniformly loaded on the relatively loose zinc hydroxide particles in the production process, so that the agglomeration degree of the nano zinc oxide can be effectively reduced, and the dispersing capacity of the nano zinc oxide in rubber is improved. In the rubber mixing process, even if some agglomerated particles are not dispersed, when the mixing temperature reaches above 125 ℃, zinc hydroxide is heated to decompose, namely, the agglomerated structure is broken due to the decomposition of the zinc hydroxide, new small zinc oxide fragments are formed, and the zinc oxide fragments are further dispersed under the mechanical shearing action of an internal mixer. Thus, zinc hydroxide can be figuratively considered as a structural disintegrant of the agglomerate, whose principle resembles an effervescent tablet. The nano zinc oxide using zinc hydroxide as a carrier has high chemical activity and good dispersibility, can ensure good performance of products under the condition of reducing use, and can reduce the residual amount of zinc in rubber products.
The rubber composition may also comprise all or part of the usual additives normally desired in elastomeric compositions for the manufacture of tyres, such as plasticizers or extender oils (whether the latter are aromatic or non-aromatic), functional resins, protective agents such as antiozone waxes, chemical antiozonants, antioxidants, antifatigue agents, etc.
The rubber composition also comprises a vulcanization system, preferably based on sulfur, and based on primary vulcanization accelerators, in particular accelerators of the thiazole, sulfenamide type, such as 2-mercaptobenzothiazyl disulfide (abbreviated to "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide (abbreviated to "CBS"), N-dicyclohexyl-2-benzothiazyl sulfenamide (abbreviated to "DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide (abbreviated to "TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide (abbreviated to "TBSI"), and mixtures of these compounds.
The rubber compositions may be used in various rubber components of a tire, such as treads (including cap and base rubbers), sidewalls, apexes, chafers, innerliners, and the like.
Example 1
The indirect method zinc oxide meets the requirements of national standard GB/T3185-2016, the content of the zinc oxide is more than or equal to 99.7 percent, and as shown in figure 1, the indirect method zinc oxide is mostly rock candy-shaped irregular square.
Common nano zinc oxide A: meets the requirements of GB/T19589-2In terms of/g, there was a significant agglomeration as shown in FIG. 2.
Nano zinc oxide B: nano zinc oxide with zinc hydroxide as carrier and specific surface area of 45m2The mass fraction of zinc oxide is 80.2 percent and the mass fraction of zinc hydroxide is 19.5 percent, namely the nano zinc oxide is used in the invention, as shown in figure 3.
The formula is as follows:
performance:
besides the function of a vulcanization activator, the zinc oxide can play a positive role in the vulcanization and aging process of the rubber: in the vulcanization and aging process, the crosslinking bond, especially the polysulfide crosslinking bond is easy to break, the hydrogen sulfide generated by the breaking can enable rubber molecules to generate a cyclized structure, zinc oxide can act with the hydrogen sulfide, and the broken crosslinking bond is combined again to form a new crosslinking bond, so that the reduction of the crosslinking bond and the generation of the cyclized structure are avoided; during the vulcanization and aging process of the rubber compound, hydrogen sulfide can be generated particularly under high temperature conditions, polysulfide bonds can be decomposed, the number of crosslinking bonds is reduced, and zinc oxide can react with the hydrogen sulfide, so that the breakage of the polysulfide bonds is prevented; in addition, zinc oxide can react with polysulfide bond to remove sulfur atom in polysulfide bond, which becomes crosslinking bond with less sulfur atom, and the thermal stability of vulcanized rubber is improved. Therefore, whether the zinc oxide is well dispersed or not, whether the dosage is proper or not and whether the activity meets the requirement or not are very important for the performance of the rubber formula.
R97 is the time required for maximum torque MH to decrease by 3% on the vulcanization curve, and is characterized by the reversion resistance of the rubber compound, and the longer the R97 time is, the better the reversion resistance is characterized. It can be seen that comparative formulation 1-1 using indirect zinc oxide had R97 of 49min14sec, but the amount of zinc was high; the zinc consumption in the formula 1-2 is reduced by 67% by using the common nano zinc oxide A, but the R97 is shortened by 5min for 49sec, and the reversion resistance is reduced; while the embodiment 1 using the nano zinc oxide B not only reduces the zinc consumption by over 67 percent, but also can maintain the anti-reversion performance.
Aging resistance coefficient (tensile strength after aging) tensile elongation at break after aging/tensile strength before aging) tensile strength at break before aging 100%. The larger the aging resistance coefficient is, the better the aging resistance of the characterized rubber material is. It can be seen that the aging resistance of the comparative formula 1-2 using the common nano zinc oxide A is reduced by 14.7% compared with the comparative formula 1-1 using the indirect method zinc oxide; while the aging resistance of example 1 using nano zinc oxide B can be maintained.
In conclusion, the nano zinc oxide B used in the embodiment has better reversion resistance and aging resistance. The reason is that the common nano zinc oxide A is hard to disperse in the sizing material due to serious agglomeration. The nano zinc oxide takes zinc hydroxide as a carrier, and can be chemically decomposed when the mixing temperature reaches above 125 ℃, namely, the agglomerated structure is damaged due to the decomposition of the zinc hydroxide, so that new small zinc oxide fragments are formed, and are further dispersed under the mechanical shearing action of an internal mixer, and the function of a vulcanization activator is exerted.
Example 2
Nano zinc oxide B in example 2: nano zinc oxide with zinc hydroxide as carrier and specific surface area of 45m2The mass fraction of zinc oxide is 80.2 percent and the mass fraction of zinc hydroxide is 19.5 percent, namely the nano zinc oxide is used in the invention, as shown in figure 3.
The indirect method zinc oxide adopted in the comparative formula 2-1 meets the requirements of national standard GB/T3185-2016, the content of zinc oxide is more than or equal to 99.7%, and as shown in figure 1, most indirect method zinc oxide is rock candy-shaped irregular square.
The nano zinc oxide C adopted in the comparative formula 2-2 is: and (3) carrying out heat treatment on the nano zinc oxide B taking the zinc hydroxide as the carrier at 150 ℃ for 2h to completely decompose the zinc hydroxide into zinc oxide, thus obtaining the nano zinc oxide C.
The formula is as follows:
| formulation components | Comparative formulation 2-1 | Comparative formulation 2-2 | Example 2 |
| Oil-extended emulsion polymerized styrene-butadiene rubber | 110.0 | 110.0 | 110.0 |
| Natural rubber | 20.0 | 20.0 | 20.0 |
| High-dispersion white carbon black 200MP | 70.0 | 70.0 | 70.0 |
| N339 carbon black | 5.0 | 5.0 | 5.0 |
| Silane coupling agent Si75 | 6.4 | 6.4 | 6.4 |
| Stearic acid | 1.8 | 1.8 | 1.8 |
| Indirect zinc oxide | 3.0 | ||
| Nano zinc oxide B | 0.9 | ||
| Nano zinc oxide C | 0.9 | ||
| Environment-friendly aromatic oil | 6.0 | 6.0 | 6.0 |
| Anti-aging agent 4020 | 2.2 | 2.2 | 2.2 |
| Antiager RD | 1.8 | 1.8 | 1.8 |
| Protective wax | 1.5 | 1.5 | 1.5 |
| Accelerator DPG | 1.8 | 1.8 | 1.8 |
| Accelerator NS | 1.8 | 1.8 | 1.8 |
| Insoluble sulfur HD OT 20 | 2.0 | 2.0 | 2.0 |
Performance:
it can be seen that comparative formulation 2-1 using indirect zinc oxide had R97 of 47min24sec, but the amount of zinc was high; the zinc consumption in the comparative formula 2-2 using the nano zinc oxide C is reduced by 70%, but simultaneously R97 is shortened by 5min for 42sec, and the reversion resistance is reduced; and the embodiment 2 using the nano zinc oxide B not only reduces the zinc using amount by more than 70 percent, but also can maintain the anti-reversion performance.
The larger the aging resistance coefficient is, the better the aging resistance of the characterized rubber material is. It can be seen that the aging resistance of comparative formulation 2-2 using nano zinc oxide C is reduced by 9.5% compared to comparative formulation 2-1 using indirect zinc oxide; while the aging resistance of example 2 using nano zinc oxide B can be maintained.
After the nano zinc oxide B is subjected to heat treatment, the zinc hydroxide is decomposed into zinc oxide, the zinc hydroxide which can be heated to be chemically decomposed is structurally lost, and the dispersion is not facilitated, so that the reversion resistance and the aging resistance of the comparative formula 2-2 are reduced. The nano zinc oxide B used in the example 2 takes zinc hydroxide as a carrier, an agglomerated structure is damaged due to the high-temperature chemical decomposition of the zinc hydroxide, new small zinc oxide fragments are formed, and the zinc oxide fragments are further dispersed under the mechanical shearing action of an internal mixer, so that the activity of the zinc oxide fragments is fully exerted, and therefore, the formula in the example 2 shows better reversion resistance and aging resistance.
Examples 3 to 5
The indirect method zinc oxide adopted in the comparative formula 3 meets the requirements of national standard GB/T3185-2016, the content of the zinc oxide is more than or equal to 99.7 percent, and as shown in figure 1, most of the indirect method zinc oxide is rock candy-shaped irregular square.
Nano zinc oxide B in examples 3, 4, 5: nano zinc oxide with zinc hydroxide as carrier and specific surface area of 45m2The mass fraction of zinc oxide is 80.2 percent and the mass fraction of zinc hydroxide is 19.5 percent, namely the nano zinc oxide is used in the invention, as shown in figure 3.
The formula is as follows:
| formulation components | Comparative formulation 3 | Example 3 | Example 4 | Example 5 |
| Brominated butyl rubber | 80.0 | 80.0 | 90.0 | 70.0 |
| Natural rubber | 20.0 | 20.0 | 10.0 | 30.0 |
| N660 carbon Black | 64.0 | 58.0 | 55.0 | 45.0 |
| N550 carbon Black | 8.0 | 13.0 | 20.0 | |
| Homogenizing agent | 8.0 | 10.0 | 6.0 | 8.0 |
| Naphthenic oil | 4.0 | 7.0 | ||
| Paraffin oil | 8.0 | 6.0 | ||
| Stearic acid | 1.0 | 0.8 | 0.8 | 1.0 |
| Indirect zinc oxide | 3.0 | |||
| Nano zinc oxide B | 0.8 | 0.9 | 1.0 | |
| Accelerator DM | 1.5 | 1.4 | 1.3 | 1.6 |
| Accelerator NS | 0.8 | 0.9 | ||
| Accelerant CZ | 0.9 | 1.0 | ||
| Common sulfur | 0.5 | 0.5 | 0.6 | 0.7 |
Performance:
it can be seen that the zinc consumption can be reduced by about 70% to the maximum for the brominated butyl rubber based formulation system.
Example 6
The vulcanization activator used in comparative formula 4 was activated zinc oxide with nanoclay as core or carrier and a specific surface area of 65m2The mass fraction of zinc oxide is 75.2 percent and the mass fraction of nano clay is 24.5 percent.
In example 6, the nano zinc oxide D takes zinc hydroxide as a carrier, and the specific surface area is 65m2The zinc oxide mass fraction is 75.0 percent, and the zinc hydroxide mass fraction is 24.6 percent.
The formula is as follows:
| formulation components | Comparative formulation 4 | Example 6 |
| Natural rubber | 40.0 | 40.0 |
| Cis-polybutadiene rubber | 60.0 | 60.0 |
| N330 carbon black | 35.0 | 35.0 |
| N660 carbon Black | 20.0 | 20.0 |
| Naphthenic oil | 4.0 | 4.0 |
| Stearic acid | 2.0 | 2.0 |
| Activated zinc oxide | 0.8 | |
| Nano zinc oxide D | 0.8 | |
| Accelerator NS | 0.8 | 0.8 |
| Common sulfur | 2.2 | 2.2 |
Performance:
compared with a comparative formula 4, the rubber material R97 in the example 6 is prolonged by 2min for 19sec, and the reversion resistance is improved; after aging, the tensile strength and the elongation at break are improved, the aging resistance coefficient is improved by about 15 percent, and the aging resistance of the rubber material is improved. This is because the nano zinc oxide using zinc hydroxide as a carrier or core used in example 6 was decomposed at a kneading temperature exceeding 125 ℃ during kneading to produce zinc oxide having a vulcanization activity. Whereas the activated zinc oxide used in comparative formulation 4 had an inert nanoclay as the carrier or core, the nanoclay being not sulfiding active.
The above description is not intended to be limiting, it being noted that: it will be apparent to those skilled in the art that various changes, modifications, additions and substitutions can be made without departing from the spirit and scope of the invention, and these improvements and modifications should also be considered to be within the scope of the invention.
Claims (7)
1. A low zinc rubber composition comprising at least one diene elastomer, a rubber composition containing zinc in an amount of 0.5 to 1phr, phr referring to parts per hundred parts of rubber, and the rubber composition being based on at least:
-a filler system;
-a sulfur-based crosslinking system comprising a high specific surface area nano zinc oxide supported on zinc hydroxide as a vulcanization activator;
-an adjuvant system;
the mass fraction of nano zinc oxide in the vulcanizing activator is 80 +/-5%, and the mass fraction of zinc hydroxide is 20 +/-5%; the preparation method of the vulcanization activator comprises the following steps: by adopting the wet production principle, a precipitator is added into a soluble salt solution of zinc, the solution is decomposed at high temperature to prepare zinc hydroxide precipitate, and then the precipitate is filtered, washed and dried and then is thermally decomposed to generate the nano zinc oxide taking the zinc hydroxide as a carrier.
2. The low-zinc rubber composition as claimed in claim 1, wherein the specific surface area of the nano-zinc oxide is 20-80 m2/g。
3. The low zinc rubber composition of claim 1, wherein the filler system comprises one or more of carbon black, graphene, carbon nanotubes, or inorganic fillers.
4. The low-zinc rubber composition according to claim 3, wherein the inorganic filler is one or more of white carbon, titanium dioxide, nanoclay, calcium carbonate or magnesium carbonate.
5. The low zinc rubber composition of claim 1, wherein the diene elastomer is one or more blends of polybutadiene (BR), synthetic polyisoprene (IR), Natural Rubber (NR), butadiene-Styrene (SBR) copolymer, isobutylene-isoprene (butyl rubber IIR) copolymer and halogenated butyl rubber thereof.
6. The low-zinc rubber composition according to claim 1, wherein the sulfur crosslinking system further comprises a vulcanization accelerator and a vulcanizing agent, and the vulcanization accelerator is one of thiazoles, sulfenamides, thiurams, dithiocarbamates and diphenylguanidines; the vulcanizing agent is sulfur powder or insoluble sulfur.
7. The low zinc rubber composition according to claim 1, wherein the auxiliary system comprises a process oil, the process oil being one of an aromatic oil, a naphthenic oil or a paraffinic oil; the anti-aging agent is one or more of quinoline, amine, triazine or naphthylamine; and further comprises a plasticizer, a peptizer, a silane coupling agent, a homogenizing agent, a dispersing agent, a tackifying resin or an anti-scorching agent.
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