Patent Description:
For a long time, a failure accident of a drilling tool, in particular a malignant fracture failure accident of a down-hole drilling tool, has always been threatening the drilling safety of the oil and gas well and the improvement of comprehensive benefits. Statistics over the years show that in the failure accidents of drilling tools, the failure of drilling tool joints and threads accounts for about <NUM>% of the failure accidents of drilling tools, and the economical loss cannot be underestimated.

Through a large number of failure analysis and research, it is found that most of the failures of drilling tools are due to the wear of the joints and threads of the drilling tools, which reduces the torsional strength of the connections and fails under the action of alternating bending stress. Due to the limited length of the joint of the drill pipe, the main tongs clamp the pipe body to buckle and unbuckle, the buckle torque is large, and the tooth scars of the main tongs will become larger. Among the various surface scars on the drill pipe, the tooth scars of the main tongs are the most common and serious, which can easily form stress concentration points and induce the failure of the joints and threads of the drilling tools. Therefore, it is a basic problem that cannot be ignored to reduce the tooth scars damage on the drill pipe body caused by the tongs.

Nitrile rubber is a copolymer obtained by emulsion polymerization of butadiene and acrylonitrile, and there is a strong polar cyano group on the molecular chain, and it is known for excellent oil resistance. Nitrile rubber as an oil-resistant rubber is widely used in the manufacture of oil-resistant products such as sealing articles, gaskets and the like. However, the nitrile rubber used as a protective tooth block in the drill tongs cannot meet the requirement of on-site working conditions, the high temperature environment will accelerate the aging process of the nitrile rubber, which will cause the rubber to be excessively cross-linked and reduce the hardness, tensile strength and other properties. Therefore, it is of great significance in the practice to prepare nitrile rubber with better mechanical behavior of temperature resistance and aging resistance.

Chinese Patent <CIT> discloses a graphene oxide modified antioxidant, a thermal oxygen aging resistance rubber containing the same and a preparation method thereof. The method utilizes organosilane and graphene oxide to perform dehydration condensation reaction, and the obtained product reacts with a sulfydryl antioxidant to modify nitrile rubber, and the heat resistance and aging resistance properties of the modified nitrile rubber are improved over the unmodified nitrile rubber. However, this method is not economical, and more products are generated during the reaction, the proportion of active ingredients cannot be explicitly defined, and the operation steps of this method are relatively complex, and has no applicability and universality.

Therefore, after the nitrile rubber in the related art is aged by thermal oxygen, the mechanical properties such as hardness and tensile strength will be reduced, and the compatibility problem will occur at the interface of the filler and the rubber.

<CIT> discloses a repairable nitrile rubber system. <CIT> discloses a high-strength and low-heat-generation composite material, comprising nature rubber, reduced oxide masterbatch, multi-walled carbon nanotube masterbatch, rubber auxiliary agents and carbon black, by means of a mechanical blending method.

In order to overcome the reduction of mechanical properties of the existing nitrile rubber such as hardness and tensile strength after thermal oxidation aging and the compatibility problem at the interface of the filler and the rubber, the present disclosure provides a reduced graphene oxide nitrile rubber and a method for preparing tooth-scar-free tooth block, which enables the nitrile rubber and the manufactured tooth-scar-free tooth block to have better mechanical properties such as hardness and tensile strength, and the interface between the filler and the rubber can be more compatible.

The present invention relates to a reduced graphene oxide nitrile rubber, comprising the following components in parts by weight: <NUM>-<NUM> parts of nitrile rubber, <NUM>-<NUM> parts of reduced graphene oxide nitrile rubber masterbatch, <NUM>-<NUM> parts of vulcanizing agent, <NUM>-<NUM> parts of vulcanization accelerator, <NUM>-<NUM> parts of vulcanization activator, <NUM>-<NUM> parts of plasticizer, <NUM>-<NUM> parts of antioxidant, <NUM>-<NUM> parts of filler, <NUM>-<NUM> part of curing agent and <NUM>-<NUM> parts of dichlorophenol.

Wherein, the plasticizer may be a mixture of stearic acid, dibutyl phthalate and tricresyl phosphate with a mass ratio of <NUM>-<NUM>:<NUM>-<NUM>:<NUM>-<NUM>; the antioxidant may be a mixture of antioxidant D and antioxidant <NUM> with a mass ratio of <NUM>:<NUM>; the filler can be a mixture of air-mixed carbon black, semi-reinforced furnace black and epoxy resin E44 with a mass ratio of <NUM>-<NUM>:<NUM>-<NUM>:<NUM>-<NUM>.

The present invention further relates to a reduced graphene oxide modified tooth-scar-free tooth block, which is made of the reduced graphene oxide nitrile rubber as described above, and the preparation process comprises the following steps:.

The reduced graphene oxide nitrile rubber and the method for preparing the tooth-scar-free tooth block provided by the present invention is simple in process and low in cost. By adding the reduced graphene oxide and the epoxy resin in the formula, the prepared reduced graphene oxide modified nitrile rubber tooth block has excellent mechanical properties, a wide range of applicable temperatures and strong using stability, and solves the problem of poor mechanical properties and interface compatibility between the filler and the rubber due to the high using temperature of the nitrile rubber in the related art.

<FIG> is a transmission electron microscope photograph of a reduced graphene oxide.

A first aspect of the present invention provides a reduced graphene oxide nitrile rubber, comprising the following components in parts by weight: <NUM>-<NUM> parts of nitrile rubber, <NUM>-<NUM> parts of reduced graphene oxide nitrile rubber masterbatch, <NUM>-<NUM> parts of vulcanizing agent, <NUM>-<NUM> parts of vulcanization accelerator, <NUM>-<NUM> parts of vulcanization activator, <NUM>-<NUM> parts of plasticizer, <NUM>-<NUM> parts of antioxidant, <NUM>-<NUM> parts of filler, <NUM>-<NUM> part of curing agent and <NUM>-<NUM> parts of dichlorophenol (DCP).

Wherein, the mass fraction of reduced graphene oxide in the reduced graphene oxide nitrile rubber masterbatch may be <NUM>-<NUM>%; the vulcanizing agent may be sulfur; the vulcanization accelerator may be accelerator DM (<NUM>,<NUM>'-dibenzothiazoledisulfde); the vulcanization activator may be zinc oxide; the plasticizer may be a mixture of stearic acid, dibutyl phthalate and tricresyl phosphate with a mass ratio of <NUM>-<NUM>:<NUM>-<NUM>:<NUM>-<NUM>, preferably <NUM>:<NUM>:<NUM>; the antioxidant may be a mixture of antioxidant D (N-Phenyl-<NUM>-naphthylamine) and antioxidant <NUM> (N-cyclohexyl-N'-phenyl-p-phenylenediamine) with a mass ratio of <NUM>:<NUM>; the filler may be a mixture of gas-mixture carbon black, semi-reinforcing furnace black, and epoxy resin E44 (E44 represents that the epoxy resin has an average epoxy value of <NUM>/<NUM>), the mass ratio thereof may be <NUM>-<NUM>:<NUM>-<NUM>:<NUM>-<NUM>, the preferred mass ratio is <NUM>:<NUM>:<NUM>; and the curing agent may be maleic anhydride.

The oxygen content, the carbon content, and the specific surface area of the reduced graphene oxide all affect the performance of the graphene. When the oxygen content is high and the carbon content is low, it means that the graphene does not have a high reduction degree, and the graphene can still maintain some characteristics of the graphene oxide, but the intrinsic characteristics of the graphene cannot be completely represented; and the size of the specific surface area affects the dispersion of the graphene in the rubber matrix and the interface compatibility between the graphene and the rubber matrix. The oxygen content in the reduced graphene oxide is <NUM>-<NUM>%, the carbon content is <NUM>-<NUM>%, and the specific surface area is <NUM>-800m2/g. The reduced graphene oxide used in the present invention with an oxygen content of <NUM>%, a carbon content of <NUM>%, and a specific surface area of <NUM> m2/g can not only ensure the performance of graphene's intrinsic properties, but also have better dispersibility and interface compatibility. A combination of these three parameters with respect to the reduced graphene oxide is not present in the related art.

The datas in the table above are the three parameters of different reduced graphene oxide tested and the moisture permeability of the modified epoxy coating, from which can be seen that the combination of the three parameters of the reduced graphene oxide used in the present invention is best. The larger the specific surface area is, the better the labyrinth effect formed in the rubber is. It can be seen from the moisture permeability that the larger the specific surface area is, the better the corrosion resistance of the modified product is, which can prolong the life span of the product.

The reduced graphene oxide in the present invention is not subjected to modification treatment, so that the original state of the graphene is maintained, various properties of the reduced graphene oxide are not changed, and the intrinsic properties of the graphene will not be reduced due to modification. Therefore, the mechanical properties of the modified rubber can also be improved by using a suitable dispersant to disperse the reduced graphene oxide uniformly in the rubber matrix. When the reduced graphene oxide is uniformly dispersed in the nitrile rubber system, the motion capability of the molecular chain in the nitrile rubber is largely limited by the sheet-like reduced graphene oxide having a large specific surface area, so that the nitrile rubber exhibits a relatively high using temperature range. Moreover, the intrinsic strength of the graphene reaches 130GPa, the fracture strain is about <NUM>%, and the elastic modulus can reach <NUM> TPa. The tensile strength of the graphene can be up to <NUM> N/m2, which is about <NUM> times that of the ordinary steel calculated by the two-dimensional strength limit theory. The experimental results show that the mechanical properties of the tooth blocks made of reduced graphene oxide nitrile rubber have been significantly improved. During high temperature vulcanization, the epoxy resin and the curing agent undergo in-situ polymerization in the rubber compound to form nanoscale particles or fibers, or to form a local interpenetrating network structure with the rubber molecules, and the comprehensive performance of the rubber compound is improved. The epoxy resin as an interface additive between the non-polar unsaturated rubber, the filler and the graphene oxide, forms a bridge function at the interface between the filler and the rubber, and the dispersion degree and the reinforcing effect of the filler are improved.

The preparation method of the reduced graphene oxide nitrile rubber masterbatch comprises the following steps: dispersing reduced graphene oxide in <NUM>,<NUM>-butanediol glycidyl ether dispersant, ultrasonically dispersing for <NUM>-<NUM> minutes to obtain a reduced graphene oxide dispersion, adding nitrile rubber latex and stirring for <NUM>-<NUM> to obtain a mixed solution, wherein the mass of the reduced graphene oxide accounts for <NUM>-<NUM>% of the mass of the mixed solution. The mixed solution above is added to a mixed liquid of a calcium chloride aqueous solution and ethanol with a volume ratio of <NUM>:<NUM>-<NUM> used as a coagulation solution for demulsification, wherein the volume ratio of the mixed solution to the coagulation solution is <NUM>-<NUM>:<NUM>-<NUM>, after suction filtration, washing and drying, a reduced graphene oxide nitrile rubber masterbatch is obtained. The solid content of the nitrile rubber latex may be <NUM>-<NUM>%.

A second aspect of the present invention relates to a tooth-scar-free tooth block made of reduced graphene oxide nitrile rubber, which is made of the reduced graphene oxide nitrile rubber as described above, and the preparation process comprises the following steps:.

The present invention will be further described in detail below with reference to specific examples.

A tooth-scar-free tooth block of reduced graphene oxide nitrile rubber, using reduced graphene oxide nitrile rubber as the raw material, comprising the following components in parts by weight:
<NUM> parts of nitrile rubber, <NUM> parts of reduced graphene oxide nitrile rubber masterbatch, <NUM> parts of vulcanizing agent, <NUM> parts of vulcanization accelerator, <NUM> parts of vulcanization activator, <NUM> parts of plasticizer, <NUM> parts of antioxidant, <NUM> parts of filler, <NUM> part of curing agent and <NUM> parts of dichlorophenol (DCP).

Wherein, the vulcanizing agent is sulfur; the vulcanization accelerator is accelerator DM; the vulcanization activator is zinc oxide; the plasticizer is stearic acid, dibutyl phthalate and tricresyl phosphate with a mass ratio of <NUM>:<NUM>:<NUM>; the antioxidant is a mixture of antioxidant D and antioxidant <NUM> with a mass ratio of <NUM>:<NUM>; the filler is gas-mixture carbon black, semi-reinforcing furnace black and epoxy resin E44 with a mass ratio of <NUM>:<NUM>:<NUM>; and the curing agent can be maleic anhydride.

A method for preparing a tooth-scar-free tooth block of reduced graphene oxide nitrile rubber, comprising the following steps:.

A modified nitrile rubber, comprising the following components in parts by weight:.

The preparation method comprises the following steps:.

A nitrile rubber, comprising the following raw material components in parts by weight:
<NUM> parts of nitrile rubber, <NUM> parts of graphene oxide modified antioxidant nitrile rubber masterbatch I, <NUM> part of sulfur, <NUM> part of stearic acid, <NUM> part of zinc oxide, <NUM> part of vulcanization activator Z311, <NUM> parts of carbon black, <NUM> part of tetramethylthiuram disulfide and <NUM> part of zinc dimethyldithiocarbamate.

The preparation method of the nitrile rubber described above comprises the following steps:.

A nitrile rubber, comprising the following raw material components in parts by weight:
<NUM> parts of nitrile rubber, <NUM> parts of graphene oxide modified antioxidant nitrile rubber masterbatch, <NUM> part of sulfur, <NUM> part of stearic acid, <NUM> part of zinc oxide, <NUM> part of vulcanization activator Z311, <NUM> parts of carbon black, <NUM> part of tetramethylthiuram disulfide and <NUM> part of zinc dimethyldithiocarbamate.

Referring to <FIG>, it is shown a transmission electron microscope image of the reduced graphene oxide used in Example <NUM>, in which the graphene sheets are lighter in color, looser, and fluffy.

The modified rubber tooth block prepared in Example <NUM> and the modified nitrile rubber prepared in Comparative Examples <NUM>-<NUM> were tested as follows:.

As can be seen from the table, compared with the modified nitrile rubber prepared in Comparative Examples <NUM>-<NUM>, the elongation at break of the reduced graphene oxide modified nitrile rubber prepared in Example <NUM> of the present invention is lower, and the Shore hardness is higher, indicating that the reduced graphene oxide modified nitrile rubber prepared in the embodiment of the present invention has good mechanical properties, small compression set, and good applicability to high temperature environments.

Claim 1:
A reduced graphene oxide nitrile rubber mixture, comprising the following components in parts by weight: <NUM>-<NUM> parts of nitrile rubber, <NUM>-<NUM> parts of reduced graphene oxide nitrile rubber masterbatch, <NUM>-<NUM> parts of vulcanizing agent, <NUM>-<NUM> parts of vulcanization accelerator, <NUM>-<NUM> parts of vulcanization activator, <NUM>-<NUM> parts of plasticizer, <NUM>-<NUM> parts of antioxidant, <NUM>-<NUM> parts of filler, <NUM>-<NUM> part of curing agent and <NUM>-<NUM> parts of dichlorophenol;
wherein a mass fraction of reduced graphene oxide in the reduced graphene oxide nitrile rubber masterbatch is <NUM>-<NUM>%; in the reduced graphene oxide, the oxygen content is <NUM>-<NUM>%, the carbon content is <NUM>-<NUM>%, and the specific surface area is <NUM>-<NUM> m2/g;
wherein the reduced graphene oxide nitrile rubber masterbatch is prepared by the following steps: dispersing reduced graphene oxide in <NUM>,<NUM>-butanediol glycidyl ether dispersant; ultrasonically dispersing for <NUM>-<NUM> minutes to obtain a reduced graphene oxide dispersion; adding nitrile rubber latex and stirring for <NUM>-<NUM> to obtain a mixed solution, wherein the mass of the reduced graphene oxide accounts for <NUM>-<NUM>% of the mass of the mixed solution; adding the mixed solution to a coagulation solution for demulsification, wherien the coagulation solution is a mixed liquid of a calcium chloride aqueous solution and ethanol with a volume ratio of <NUM>:<NUM>-<NUM>, wherein the volume ratio of the mixed solution to the coagulation solution is <NUM>-<NUM>:<NUM>-<NUM>; after suction filtration, washing and drying, obtaining the reduced graphene oxide nitrile rubber masterbatch;
wherein the filler is a mixture of gas-mixture carbon black, semi-reinforcing furnace black and epoxy resin with a mass ratio of <NUM>-<NUM> : <NUM>-<NUM> : <NUM>-<NUM>, wherein the epoxy resin has an average epoxy value of <NUM>/<NUM>.