Starch graft copolymer, its preparation and use

Abstract

The application discloses a starch graft copolymer and a preparation method and application thereof. The starch graft copolymer raw material comprises the following components: starch, water, plasticizer, sodium bicarbonate, acrylamide, functional monomer, initiator and chain transfer agent. The preparation method comprises the following steps: (1) mixing acrylamide and the functional monomer, and introducing water and the initiator to react in the mixing process; (2) uniformly mixing the material obtained in the step (1), the starch, the sodium bicarbonate and the plasticizer; (3) uniformly mixing the material obtained in the step (2), the chain transfer agent and the initiator, and then introducing acrylamide, the functional monomer and water to react, and discharging the material after the reaction to further perform optional molding and drying treatment to obtain the starch graft copolymer. The obtained starch graft copolymer has good salt-resistant temperature-resistant filtration loss performance, and has the characteristics of environmental protection, lubrication, good water solubility, low cost and easy storage.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of starch-based high molecular polymers, and particularly relates to a temperature-resistant starch graft copolymer and a preparation method and application thereof. BACKGROUND

[0002] In recent years, deep wells, ultra-deep wells and high-temperature and high-salt reservoirs have put forward higher requirements for the performance of drilling fluids, and key additives with good salt resistance and temperature resistance are the technical core to protect the efficient development of deep complex reservoirs. The anti-sloughing solid wall material mainly based on sulfonated asphalt and the high-temperature resistant fluid loss additive material mainly based on functional synthetic polymers provide strong support for improving drilling efficiency and extending the safe construction period. However, with the continuous attention to the environmental performance of drilling and production additives on the upstream site, the existing key drilling fluid additives generally show the shortcoming of insufficient environmental friendly performance. Under this background, high-performance bio-based drilling and production additives using green and naturally degradable materials as raw materials have attracted more and more attention. Using natural high molecular materials such as starch, chitosan and lignin as main raw materials, the development of high-performance drilling and graft copolymer has become a research hotspot. At present, the temperature resistance of modified starch graft copolymer is continuously improved, and the starch graft copolymer with green degradable performance and salt resistance and temperature resistance has attracted attention.

[0003] Starch graft copolymer can be prepared by solution polymerization and reverse emulsion polymerization by using starch as raw material and copolymerizing with functional monomers. For example, patent CN 103113524 A discloses a preparation method of starch graft copolymer reverse emulsion for drilling fluid. The method uses an aqueous solution containing starch, 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, vinyl monomer, cationic monomer, polyoxyethylene sorbitan fatty acid ester, ethylenediaminetetraacetic acid disodium salt and potassium hydroxide as the water phase, and white oil containing emulsifier as the oil phase. After mixing and emulsifying, the initiator is added to polymerize the monomers, and the obtained starch graft copolymer reverse emulsion for drilling fluid has good fluid loss reduction, viscosity increase and flow pattern adjustment effect.

[0004] Patent CN 102286132 A discloses a method for preparing starch graft cationic hyperbranched amide polymer. First, a mixed phase containing starch, amide monomer, buffer, polar solvent is prepared, and then the mixed phase is gelatinized and a RAFT chain transfer agent is added to initiate solution polymerization. During the polymerization process, a branching agent is added, and before the reaction ends, a cationic monomer is added and the reaction continues for a period of time before discharging. The obtained starch graft cationic hyperbranched vinyl or acrylamide polymer is easy to control during the polymerization process, and the product has significant turbidity removal effect.

[0005] As described above, the preparation and application technology of high-performance starch graft copolymer is relatively mature, the related graft copolymer has good application performance, and plays the advantages of green degradable starch raw materials, and has good environmental friendly performance. However, due to the polymerization mode, in the prior art, the starch graft copolymer is mostly an emulsion product, and in the field application, the product addition amount is large, which easily affects the performance of the drilling fluid; if the dry method is adopted to prepare the powder product, the drying cost of the emulsion product with low solid content is high, which greatly increases the product preparation cost, thereby to a certain extent, the product popularization and application are restricted. It is of broad prospects to prepare the powder starch graft copolymer product with low water content and high solid content in an efficient and convenient manner. SUMMARY

[0006] In combination with the above analysis, in view of the deficiencies in the prior art, the core purpose of the present application is to provide a starch graft copolymer and a preparation method and application thereof. The starch graft copolymer has a temperature resistance of greater than or equal to 180 DEG C, a high temperature and high pressure filtration loss (HTHP) of not greater than 25 mL, a NaCl resistance of greater than or equal to 300000 mg / L, a CaCl2 resistance of greater than or equal to 50000 mg / L, good salt resistance and temperature resistance filtration loss performance, and the characteristics of environmental protection, lubrication, good water solubility, low cost and easy storage.

[0007] The first aspect of the present application provides a starch graft copolymer, and the raw materials of the starch graft copolymer include the following components in weight fraction: 100 parts of starch, 20-60 parts of water, 2-20 parts of plasticizer, 0.005-0.5 parts of flaky alkali, 50-250 parts of acrylamide, 20-80 parts of functional monomer, 0.6-6 parts of initiator and 0.1-1 part of chain transfer agent.

[0008] Further, according to the above starch graft copolymer method, as a preferred embodiment, the raw materials of the starch graft copolymer include the following components in weight fraction: 100 parts of starch, 30-50 parts of water, 5-15 parts of plasticizer, 0.01-0.3 parts of flaky alkali, 75-200 parts of acrylamide, 30-70 parts of functional monomer, 1-5 parts of initiator and 0.2-0.8 parts of chain transfer agent.

[0009] Further, according to the above starch graft copolymer, as a preferred embodiment, the starch is one or more of green bean starch, cassava starch, sweet potato starch, potato starch, cereal starch, lotus root starch, corn starch and / or potato starch.

[0010] Further according to the above starch graft copolymer, as a preferred embodiment, the plasticizer is one or more of polyhydric alcohol, amine, inorganic salt containing IA group metal, polyhydric alcohol, polyester. Among them, the polyhydric alcohol is C2-C6 polyhydric alcohol, which can be one or more of ethylene glycol, glycerol, sorbitol, mannitol, erythritol; the amine can be one or more of urea, thiourea, formamide; the inorganic salt containing IA group metal can be one or more of sodium chloride, sodium bromide, sodium sulfate, sodium sulfite, sodium carbonate, sodium bicarbonate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate, sodium silicate, potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, potassium hydrogen phosphate; the polyhydric alcohol can be at least one of polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, polyethylene glycol 2000, and the polyester can be one or more of glycerol mono-fatty acid ester, 1-ethyl-3-methyl imidazole acetate, polylactic acid, polybutylene succinate, polycaprolactone, polybutylene adipate terephthalate.

[0011] Further according to the above starch graft copolymer, as a preferred embodiment, the functional monomer is one or more of sulfonic acid monomer, phosphonic acid monomer. Specifically, it can be one or more of methacryloyloxyethyl-N,N-dimethyl propanesulfonate, N,N-dimethyl allylamine propanesulfonate, 4-vinylpyridine propanesulfonate, N-methylallyl propanesulfonate, N-methylallyl butanesulfonate, 2-methyl-2-acrylamidopropanesulfonic acid, 2-acryloyloxyisopentyl sulfonate sodium, sodium allylsulfonate, sodium styrene sulfonate, allyl phosphonic acid, (2-methylallyl) phosphonic acid diethyl ester, allyl phosphonic acid diethyl ester, allyl phosphonic acid dimethyl ester, vinyl phosphonic acid, 2-methyl vinyl phosphonic acid, 2-methyl-2-acrylamidopropanephosphonic acid.

[0012] Further according to the above starch graft copolymer, as a preferred embodiment, the initiator is any one or a mixture of two or more of potassium persulfate, sodium persulfate, ammonium persulfate.

[0013] Further according to the above starch graft copolymer, as a preferred embodiment, the chain transfer agent is one or a mixture of two or more of isopropyl alcohol, sodium bisulfite, mercaptoethanol, mercapto propanol, mercapto acetic acid, mercapto propanoic acid, sodium hypophosphite, sodium formate.

[0014] The second aspect of the present application provides a preparation method of a starch graft copolymer, which comprises the following steps:

[0015] (1) mixing acrylamide and functional monomer under contact conditions, and introducing water and initiator during the mixing process to react, and obtaining a first material after the reaction is completed;

[0016] (2) mixing the first material obtained in step (1), starch, sodium bicarbonate, plasticizer under mixing condition to obtain a second material;

[0017] (3) mixing the second material obtained in step (2), chain transfer agent, initiator, then introducing acrylamide, functional monomer, water to react, after reaction, the material is discharged and further processed by optional molding and drying to obtain the starch graft copolymer.

[0018] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the reaction in step (1) can be carried out in a kneading reactor, and the specific process is that acrylamide and functional monomer are first added into the kneading reactor, water is sprayed during kneading, and initiator is added at the same time, after sufficient mixing, the reaction temperature is adjusted to carry out explosive polymerization, and generally, heating can be stopped after explosive polymerization occurs. The kneading reactor can use the existing equipment in the art, which can be made of stainless steel and is provided with a vacuum pressure relief device in a sealed state.

[0019] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the functional monomer in step (1) and step (3) is one or more of sulfonic acid monomer and phosphonic acid monomer. The specific functional monomer can be one or more of methacryloyloxyethyl-N,N-dimethylpropane sulfonate, N,N-dimethylallylamine propanesulfonate, 4-vinylpyridine propanesulfonate, N-methylallyl propanesulfonate, N-methylallyl butanesulfonate, 2-methyl-2-acrylamidopropanesulfonic acid, 2-acryloyloxyisopentyl sulfonate sodium, allyl sulfonate sodium, styrene sulfonate sodium, allyl phosphonic acid, (2-methylallyl) phosphonic acid diethyl ester, allyl phosphonic acid diethyl ester, allyl phosphonic acid dimethyl ester, vinyl phosphonic acid, 2-methylvinyl phosphonic acid, and 2-methyl-2-acrylamidopropanephosphonic acid.

[0020] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the initiator in step (1) and step (3) can be any one or a mixture of two or more of potassium persulfate, sodium persulfate and ammonium persulfate.

[0021] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the amount of acrylamide, functional monomer, water and initiator in step (1) is 10-50 parts of acrylamide, 5-16 parts of functional monomer, 5-12 parts of water and 0.1-1 part of initiator; preferably, 15-40 parts of acrylamide, 6-14 parts of functional monomer, 6-10 parts of water and 0.2-0.8 part of initiator.

[0022] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the reaction temperature in step (1) is generally controlled at 45-55°C, and the reaction time can be generally controlled at 10-60 min.

[0023] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the starch in step (2) is one or more of mung bean starch, cassava starch, sweet potato starch, potato starch, cereal starch, lotus root starch, lotus stem starch, and corn starch, preferably corn starch and / or potato starch.

[0024] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the plasticizer in step (2) is one or more of polyhydric alcohol, amine, inorganic salt containing IA group metal, polyhydric alcohol, and polyester. The polyhydric alcohol is C2-C6 polyhydric alcohol, and can be one or more of ethylene glycol, glycerol, sorbitol, mannitol, and erythritol; the amine can be one or more of urea, thiourea, and formamide; the inorganic salt containing IA group metal can be one or more of sodium chloride, sodium bromide, sodium sulfate, sodium sulfite, sodium carbonate, sodium bicarbonate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate, sodium silicate, potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, and potassium hydrogen phosphate; the polyhydric alcohol can be at least one of polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, and polyethylene glycol 2000; and the polyester can be one or more of glycerol mono-fatty acid ester, 1-ethyl-3-methyl imidazole acetate, polylactic acid, polybutylene succinate, polycaprolactone, and polybutylene adipate terephthalate.

[0025] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the chain transfer agent in step (3) can be one or a mixture of two or more of isopropyl alcohol, sodium bisulfite, mercaptoethanol, mercapto-propanol, mercaptoacetic acid, mercapto-propionic acid, sodium hypophosphite, and sodium formate.

[0026] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the amounts of acrylamide, functional monomer, water, and initiator in step (3) are 40-200 parts of acrylamide, 15-64 parts of functional monomer, 15-48 parts of water, and 0.5-5 parts of initiator; preferably 50-160 parts of acrylamide, 24-56 parts of functional monomer, 24-40 parts of water, and 0.8-4.2 parts of initiator.

[0027] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the reaction temperature in step (3) is 40-50°C, and the reaction time is 20-60 min.

[0028] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the discharging temperature in step (3) is controlled to be 40-60 DEG C.

[0029] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the molding in step (3) can adopt any one of the existing molding processes in the art, and specifically can be any one of compression molding, extrusion molding and spray molding, and the method preferably adopts the extrusion molding process.

[0030] Further according to the preparation method of the starch graft copolymer, as a preferred embodiment, the drying temperature in step (3) is 80-120 DEG C, and the drying time is 0.5-2 h.

[0031] The third aspect of the present application further provides a water-based mud, which comprises the above-mentioned starch graft copolymer or the starch graft copolymer obtained by the above-mentioned preparation method, wherein the starch graft copolymer has good salt-resistant and temperature-resistant filtration loss reduction effect at a 0.5-3 wt% addition amount, has the characteristics of environmental protection, lubrication, low cost and easy storage, and is suitable for application in deep well high-salt brine formation and other complex well drilling and production.

[0032] The starch graft copolymer and the preparation method thereof provided by the present application have the following main technical effects compared with the prior art:

[0033] 1. The starch graft copolymer provided by the present application has good salt-resistant and temperature-resistant filtration loss reduction performance, wherein the temperature-resistant capacity is greater than or equal to 180 DEG C, the high temperature and high pressure filtration loss (HTHP) is not greater than 25 ml, the NaCl resistance is greater than or equal to 300000 mg / L, the CaCl2 resistance is greater than or equal to 50000 mg / L, and the starch graft copolymer has the characteristics of environmental protection, lubrication, good water solubility, low cost and easy storage.

[0034] 2. The preparation method of the starch graft copolymer provided by the present application is based on the explosive polymerization method, first, a small amount of acrylamide and a functional monomer are used as raw materials for pre-polymerization to form a synthetic pre-polymer with a certain chain length, then starch and a plasticizer are added for kneading, only a small amount of water is added to assist the plasticization in the process, so that the starch molecular chain is fully stretched in the non-solvent environment and is fully mixed with the pre-polymer, then monomers, initiators and chain transfer agents are added to initiate explosive polymerization at a relatively low initial temperature to form a high-temperature-resistant starch graft copolymer. In this process, the pre-polymer is blended with the starch, so that the molecular weight of the pre-polymer is similar to that of the natural high molecular starch, which avoids the self-polymerization of monomers to form a blend of high molecular polymers and thermoplastic starch due to the excessively high reactivity after the initiation of explosive polymerization; at the same time, the addition of the chain transfer agent effectively improves the transfer rate of free radicals to the starch molecular chain, which ensures the copolymerization.

[0035] 3、The preparation method of the starch graft copolymer provided by the application shortens the reaction time and improves the synthesis efficiency by using the semi-dry method to explode and polymerize, the heat released in the rapid polymerization process makes the water contained in the system evaporate rapidly, and the starch graft copolymer obtained after the polymerization ends can be directly extruded and granulated, and after rapid drying, the starch graft copolymer powder can be completely dehydrated and packaged, which greatly reduces the energy consumption in the preparation of the starch graft copolymer powder, reduces the overall cost of the process, and is also beneficial to the transportation and storage of the product.

[0036] 4、The preparation method of the starch graft copolymer provided by the application has simple and controllable preparation conditions, and the starch raw material is widely available, low in cost, green and degradable, which is beneficial to the production and popularization and application of the technical method. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The infrared spectrum of the starch graft copolymer prepared by the method of Example 1. DETAILED DESCRIPTION

[0038] The starch graft copolymer, the preparation method and the application thereof involved in the application will be further described below through specific examples, but do not constitute a limitation on the application.

[0039] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values should be interpreted as approximately between the stated values. Values between the endpoints of any range or the endpoints and single values stated within a range, and values within single values stated can be obtained by simply interpolating between the endpoints or single values. Any numerical range recited herein is intended to include all sub-ranges of the same numbers.

[0040] The material ratio in all the examples and comparative examples disclosed herein is the mass ratio of the materials.

[0041] In this paper, the molecular composition and structure of the sample are qualitatively analyzed by using the FTS-3000 Fourier infrared spectrometer of Bruker Company in Germany, the frequency collection range is selected to be 500-4000 cm -1 -1, and the scanning is repeated for 16 times. According to the intensity, position and shape of the absorption peak in the spectrum, the types of groups contained in the molecules of the sample are determined, and the structure of the sample is confirmed.

[0042] Example 1

[0043] Into a kneading reactor, 25 parts of acrylamide, 10 parts of N, N-dimethylallylamine propyl sulfonate, 0.6 parts of potassium persulfate were added at room temperature, 8 parts of water was sprayed during kneading, after fully mixed, the temperature was raised to 50°C, after the explosive polymerization occurred, the heating was stopped, the kneading was continued for 30 min, then the temperature was lowered to room temperature. Into the reactor, 100 parts of corn starch, 0.1 parts of sodium bicarbonate, 10 parts of polyethylene glycol 400 were added, and mixed at room temperature for 2 h. 0.5 parts of sodium bisulfite, 4 parts of potassium persulfate were added, after kneading, 33 parts of water, 150 parts of acrylamide, 30 parts of N, N-dimethylallylamine propyl sulfonate were added, the temperature was raised to 44°C, after the explosive polymerization occurred, the heating was stopped, the reaction was continued for 35 min, then the temperature in the reactor was adjusted to 55°C, and extruded into strips at the same temperature, to obtain a white starch graft copolymer A, which was dried at 115°C for 1 h, then sealed in a bag. The infrared spectrum of the sample is shown in Figure 1 Figure, the characteristic peak at 3420 cm -1 is the alcohol hydroxyl stretching vibration peak on the starch, due to the hydrogen bonding between the hydroxyl groups, the peak type shows a broad band; the characteristic peak at 2930 cm -1 is the anti-symmetrical stretching vibration peak of methylene (-CH2-), the -CH2- group on the molecular chain of the starch graft polymer belongs to the starch molecular structure, and also belongs to the -CH2- group produced by the free radical polymerization of the vinyl bond; the characteristic peaks at 1080 cm -1 and 1150 cm -1 belong to the C-O-H and C-O-C groups in the starch structure, respectively, indicating that the starch is the main structural unit in the graft copolymer; the characteristic peak at 1660 cm -1 is the amide carbonyl C=O vibration characteristic peak, the characteristic peak at 1200 cm -1 is the sulfonic acid group vibration characteristic peak on the molecular chain of the polymer, which belongs to the amide monomer and the functional monomer, respectively, indicating that the amide monomer, the functional monomer and the starch are successfully grafted.

[0044] Example 2

[0045] A kneading reactor was charged with 50 parts of acrylamide, 16 parts of methacryloyloxyethyl-N,N-dimethylpropane sulfonate, 1 part of ammonium persulfate at room temperature, 12 parts of water was sprayed during kneading, after fully mixed, heated to 55°C, after the explosive polymerization reaction, stop heating, continue to knead for 10 minutes, then cool to room temperature. 100 parts of green bean starch, 0.005 parts of sodium bicarbonate, 20 parts of ethylene glycol were added into the reactor, mixed at room temperature for 4 hours until mixed. 1 part of mercapto propanol, 5 parts of ammonium persulfate, after kneading evenly, 48 parts of water, 200 parts of acrylamide, 64 parts of N,N-dimethylallylamine propanesulfonate were added, heated to 50°C, after the explosive polymerization reaction, stop heating, continue to react for 20 minutes, then adjust the temperature in the reactor to 60°C, extruded into strips at the same temperature, white starch graft copolymer B was obtained, which was dried at 120°C for 0.5 hours, then sealed in a bag.

[0046] Example 3

[0047] A kneading reactor was charged with 10 parts of acrylamide, 5 parts of 2-acryloyloxyisopentyl sodium sulfonate, 0.1 parts of sodium persulfate at room temperature, 5 parts of water was sprayed during kneading, after fully mixed, heated to 45°C, after the explosive polymerization reaction, stop heating, continue to knead for 60 minutes, then cool to room temperature. 100 parts of wheat starch, 0.5 parts of sodium bicarbonate, 2 parts of urea were added into the reactor, mixed at room temperature for 0.5 hours until mixed. 0.1 parts of sodium hypophosphite, 0.5 parts of ammonium persulfate, after kneading evenly, 15 parts of water, 40 parts of acrylamide, 15 parts of 2-acryloyloxyisopentyl sodium sulfonate were added, heated to 40°C, after the explosive polymerization reaction, stop heating, continue to react for 60 minutes, then adjust the temperature in the reactor to constant 40°C, extruded into strips at the same temperature, light yellow starch graft copolymer C was obtained, which was dried at 80°C for 2 hours, then sealed in a bag.

[0048] Example 4

[0049] A kneading reactor was charged with 40 parts of acrylamide, 14 parts of diethyl allyl phosphonate, 0.8 parts of initiator (sodium persulfate: ammonium persulfate = 1:1) at room temperature, 10 parts of water was sprayed during kneading, after fully mixed, heated to 52°C, after the explosive polymerization reaction, stop heating, continue to knead for 50 minutes, then cool to room temperature. 100 parts of cassava starch, 0.01 parts of sodium bicarbonate, 15 parts of potassium chloride were added into the reactor, mixed at room temperature for 3.5 hours until mixed. 0.8 parts of mercapto acetic acid, 4.2 parts of initiator (sodium persulfate: ammonium persulfate = 1:1), after kneading evenly, 40 parts of water, 160 parts of acrylamide, 56 parts of diethyl allyl phosphonate were added, heated to 47°C, after the explosive polymerization reaction, stop heating, continue to react for 45 minutes, then adjust the temperature in the reactor to 56°C, extruded into strips at the same temperature, light yellow starch graft copolymer D was obtained, which was dried at 116°C for 1 hour, then sealed in a bag.

[0050] Example 5

[0051] A kneading reactor was charged with 15 parts of acrylamide, 6 parts of 2-methyl-2-acrylamidoglycine phosphonic acid, 0.2 parts of initiator (potassium persulfate: sodium persulfate = 4: 1) at room temperature, 6 parts of water was sprayed during kneading, after fully mixed, the temperature was raised to 47°C, after the explosive polymerization occurred, the heating was stopped, and the kneading was continued for 15 min, then the temperature was lowered to room temperature. 100 parts of potato starch, 0.3 parts of sodium bicarbonate, 5 parts of glycerol mono fatty acid ester were added into the reactor, and mixed at room temperature for 1.5 h until mixed. 0.2 parts of sodium formate, 0.8 parts of initiator (potassium persulfate: sodium persulfate = 4: 1) were added and mixed uniformly, then 24 parts of water, 50 parts of acrylamide, 24 parts of 2-methyl-2-acrylamidoglycine phosphonic acid were added, the temperature was raised to 42°C, after the explosive polymerization occurred, the heating was stopped, and the reaction was continued for 30 min, then the temperature in the reactor was adjusted to 44°C, and extruded into strips at the same temperature to obtain a light yellow starch graft copolymer E, which was dried at 90°C for 1.5 h, then sealed in a bag.

[0052] Comparative Example 1

[0053] A kneading reactor was charged with 25 parts of acrylamide, 10 parts of N, N-dimethylallylamine propyl sulfonate, 0.6 parts of potassium persulfate at room temperature, 8 parts of water was sprayed during kneading, after fully mixed, the temperature was raised to 50°C, after the explosive polymerization occurred, the heating was stopped, and the kneading was continued for 30 min, then the temperature was lowered to room temperature. 100 parts of corn starch, 0.1 parts of sodium bicarbonate, 10 parts of polyethylene glycol 400 were added into the reactor, and mixed at room temperature for 2 h until mixed. 4 parts of potassium persulfate was added and mixed uniformly, then 33 parts of water, 150 parts of acrylamide, 30 parts of N, N-dimethylallylamine propyl sulfonate were added, the temperature was raised to 44°C, after the explosive polymerization occurred, the heating was stopped, and the reaction was continued for 35 min, then the temperature in the reactor was adjusted to 55°C, and extruded into strips at the same temperature to obtain a white starch graft copolymer a, which was dried at 115°C for 1 h, then sealed in a bag.

[0054] Comparative Example 2

[0055] A kneading reactor was charged with 25 parts of acrylamide, 10 parts of N, N-dimethylallylamine propyl sulfonate, 0.6 parts of potassium persulfate at room temperature, 8 parts of water was sprayed during kneading, after fully mixed, the temperature was raised to 50°C, after the explosive polymerization occurred, the heating was stopped, and the kneading was continued for 30 min, then the temperature was lowered to room temperature. 100 parts of corn starch, 0.1 parts of sodium bicarbonate were added into the reactor, and mixed at room temperature for 2 h until mixed. 0.5 parts of sodium bisulfite, 4 parts of potassium persulfate were added and mixed uniformly, then 33 parts of water, 150 parts of acrylamide, 30 parts of N, N-dimethylallylamine propyl sulfonate were added, the temperature was raised to 44°C, after the explosive polymerization occurred, the heating was stopped, and the reaction was continued for 35 min, then the temperature in the reactor was adjusted to 55°C, and extruded into strips at the same temperature to obtain a white starch graft copolymer b, which was dried at 115°C for 1 h, then sealed in a bag.

[0056] Comparative Example 3

[0057] Into a kneading reactor, 100 parts of corn starch, 0.1 part of flake soda, 10 parts of polyethylene glycol 400 were added, and kneaded at room temperature for 2 h until mixed. 0.5 parts of sodium bisulfite, 4.6 parts of potassium persulfate were added, and after kneading, 41 parts of water, 175 parts of acrylamide, 40 parts of N, N-dimethylallylamine propyl sulfonate were added, the temperature was raised to 44°C, and after the polymerization explosion occurred, the heating was stopped, and the reaction was continued for 35 min, and then the temperature in the reactor was adjusted to 55°C, and extruded into a strip at the same temperature, to obtain a white starch graft copolymer c, which was dried at 115°C for 1 h, and then sealed in a bag.

[0058] Performance test

[0059] 1. Medium-pressure fluid loss test (API)

[0060] The performance of the starch graft copolymers obtained in Examples 1-5 and Comparative Examples 1-3 was evaluated using a medium-temperature and medium-pressure fluid loss instrument. Experimental instruments: medium-temperature and medium-pressure fluid loss instrument, stirrer, settling tank, roller-type heating furnace. Experimental materials: prepared drilling fluid, samples obtained in Examples 1-5, and samples obtained in Comparative Examples 1-3.

[0061] Experimental steps:

[0062] Into a high-speed stirring cup, 400 mL of distilled water was added, 120 g of sodium chloride was added, and after dissolving under stirring, 40 g of bentonite for drilling fluid test slurry preparation and 1.5 g (accurate to 0.01 g) of anhydrous sodium bicarbonate were slowly added in sequence under stirring at a speed of (11000±300) r / min, and high-speed stirring was performed for 20 min, and the sodium chloride brine-based slurry was obtained by sealing and curing at room temperature for 24 h, and a total of 2 portions of the slurry were prepared.

[0063] 400 mL of each of the two portions of the above slurry was taken, 12.0 g of the sample (3 wt%) was added to one portion, high-speed stirring was performed at a speed of (11000±300) r / min for 20 min, and then the slurry was poured into an aging tank and placed in a high-temperature roller furnace to roll at 180°C for 16 h, and then taken out, cooled to room temperature, high-speed stirred for 5 min, and the medium-pressure fluid loss was determined according to the provisions in GB / T 16783.1. The fluid loss reduction rate was calculated according to formula (1).

[0064]

[0065] In the formula:

[0066] f — fluid loss reduction rate;

[0067] FL0 — fluid loss of the slurry, mL;

[0068] FL — fluid loss of the sample-added slurry, mL.

[0069] The above steps are used to test the calcium resistance of the sample. The "add 120 g of sodium chloride" is adjusted to "add 20 g of calcium chloride", and the rest of the steps remain unchanged.

[0070] Experimental results:

[0071] The reduction rate of the filtration loss of the drilling fluid after 30 minutes of the evaluation experiment is evaluated. The results of the sodium salt resistance temperature experiment are shown in Table 1, and the results of the calcium salt resistance temperature experiment are shown in Table 2.

[0072] Table 1 Evaluation of sodium salt filtration loss

[0073] Item FL0 FL f Example 1 75.0 6.9 90.80％ Example 2 72.3 10.2 85.89％ Example 3 68.4 8.7 87.28％ Example 4 72.5 8.5 88.28％ Example 5 74.8 7.6 89.83％ Comparative Example 1 79.2 38.5 51.39％ Comparative Example 2 76.5 36.2 52.68％ Comparative Example 3 77.8 44.1 43.32％

[0074] Table 2 Evaluation of calcium salt filtration loss

[0075] Item FL0 FL f Example 1 86.3 11.8 86.33％ Example 2 84.2 12.2 85.51％ Example 3 75.6 14.5 80.82％ Example 4 82.9 13.8 83.35％ Example 5 79.2 14.6 81.57％ Comparative Example 1 83.5 42.4 49.22％ Comparative Example 2 74.6 48.5 34.99％ Comparative Example 3 80.1 55.7 30.46％

[0076] 2. High temperature and high pressure filtration loss test (HTHP)

[0077] Two high-speed stirring cups are taken, 400 mL of distilled water and 0.96 g (accurately weighed to 0.01 g) of anhydrous sodium carbonate are added respectively, after dissolution, 16.0 g (accurately weighed to 0.01 g) of bentonite for drilling fluid test slurry is slowly added under high-speed stirring, after high-speed stirring for 20 min, the base slurry is cured at 25℃±1℃ for 24 h in a sealed state. Take one cup of the cured base slurry, high-speed stir for 5 min, and measure the high temperature and high pressure filtration loss of the base slurry under the conditions of 180℃ and a pressure difference of 3.45 MPa according to the test procedure specified in GB / T 16783.1.

[0078] Another cup of base slurry is taken, 12.0 g (3 wt%) of the sample is slowly added under high-speed stirring, after high-speed stirring for 20 min, the sample slurry is cured at 25℃±1℃ for 24 h in a sealed state. The high temperature and high pressure filtration loss of the sample slurry is measured under the conditions of 180℃ and a pressure difference of 3.45 MPa according to the test procedure specified in GB / T 16783.1. The results are shown in Table 3, FL1 and FL2 are the high temperature and high pressure filtration losses of the base slurry and the sample slurry respectively.

[0079] Table 3 Evaluation of high temperature and high pressure filtration loss

[0080]

[0081]

[0082] As shown in Table 1, Table 2 and Table 3, the salt and halogen resistance of the starch graft copolymers prepared in Examples 1-5 is good, the reduction rate of the medium pressure filtration loss in sodium salt and calcium salt resistance is higher than 80%, the salt and temperature resistance of the samples prepared in Comparative Examples 1-3 is weak, the reduction rate of the medium pressure filtration loss is lower than 50%; the high temperature and high pressure filtration loss of the starch graft copolymers prepared in Examples 1-5 is less than 20 mL, the minimum is only 13.5 mL, in comparison, the high temperature and high pressure filtration loss of the samples prepared in Comparative Examples 1-3 is higher than 35 mL, the high temperature and high pressure filtration loss capacity is relatively weak.

Claims

1. A starch graft copolymer, raw materials of the starch graft copolymer comprising, in parts by weight: 100 parts of starch, 20-60 parts of water, 2-20 parts of plasticizer, 0.005-0.5 parts of sodium bicarbonate, 50-250 parts of acrylamide, 20-80 parts of functional monomer, 0.6-6 parts of initiator, 0.1-1 parts of chain transfer agent; wherein, The functional monomer is one or more of a sulfonic acid monomer and a phosphonic acid monomer; the plasticizer is one or more of a polyhydric alcohol, an amine, an inorganic salt containing an IA group metal, a polymeric alcohol, and a polyester; and the method for preparing the starch graft copolymer comprises the following steps: (1) mixing acrylamide and the functional monomer under a contact condition, and introducing water and an initiator during the mixing process to perform a reaction, and obtaining a first material after the reaction is completed; the reaction process is as follows: firstly, acrylamide and the functional monomer are added into a kneading reactor, water is sprayed during kneading, and the initiator is added, and after being fully mixed, the reaction temperature is adjusted to perform a polymerization reaction; (2) mixing the first material obtained in step (1), starch, sodium hydroxide, and the plasticizer under a mixing condition to obtain a second material; (3) mixing the second material obtained in step (2), a chain transfer agent, and an initiator, and then introducing acrylamide, the functional monomer, and water to perform a reaction, and after the reaction, the material is further subjected to optional molding and drying treatment to obtain the starch graft copolymer.

2. Starch graft copolymer according to claim 1, characterized in that: The starch graft copolymer raw material comprises the following components in parts by weight: 100 parts of starch, 30-50 parts of water, 5-15 parts of the plasticizer, 0.01-0.3 parts of sodium hydroxide, 75-200 parts of acrylamide, 30-70 parts of the functional monomer, 1-5 parts of the initiator, and 0.2-0.8 parts of the chain transfer agent.

3. The starch graft copolymer according to claim 1, characterized in that: The starch is one or more of green bean starch, cassava starch, sweet potato starch, potato starch, wheat starch, water chestnut starch, lotus root starch, and corn starch.

4. The starch graft copolymer according to claim 1, characterized in that: The starch is corn starch and / or potato starch.

5. The starch graft copolymer according to claim 1, characterized in that: The polyhydric alcohol is a C2-C6 polyhydric alcohol; the amine is one or more of urea, thiourea, and formamide; the inorganic salt containing an IA group metal is one or more of sodium chloride, sodium bromide, sodium sulfate, sodium sulfite, sodium carbonate, sodium bicarbonate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate, sodium silicate, potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, and potassium hydrogen phosphate; the polymeric alcohol is at least one selected from polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, and polyethylene glycol 2000; and the polyester is one or more of glycerol mono-fatty acid ester, 1-ethyl-3-methyl imidazole acetate, polylactic acid, polybutylene succinate, polycaprolactone, and polybutylene adipate terephthalate.

6. Starch graft copolymer according to claim 1 or 5, characterized in that: The polyhydric alcohol is one or more of ethylene glycol, glycerol, sorbitol, mannitol, and erythritol.

7. The starch graft copolymer according to claim 1, characterized in that: The functional monomer is one or more of methacryloyloxyethyl-N,N-dimethylpropane sulfonate, N,N-dimethylallylamine propane sulfonate, 4-vinylpyridine propane sulfonate, N-methylallyl propane sulfonate, N-methylallyl butane sulfonate, 2-methyl-2-acrylamidopropane sulfonic acid, 2-acryloyloxyisopentyl sulfonate sodium, allyl sulfonate sodium, styrene sulfonate sodium, allyl phosphonic acid, (2-methylallyl) phosphonic acid diethyl ester, allyl phosphonic acid diethyl ester, allyl phosphonic acid dimethyl ester, vinyl phosphonic acid, 2-methylvinyl phosphonic acid, and 2-methyl-2-acrylamidopropane phosphonic acid.

8. The starch graft copolymer according to claim 1, characterized in that: The initiator is any one or a mixture of two or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

9. The starch graft copolymer according to claim 1, characterized in that: The chain transfer agent is one or a mixture of two or more of isopropyl alcohol, sodium bisulfite, mercaptoethanol, mercapto propanol, mercapto acetic acid, mercapto propionic acid, sodium hypophosphite, sodium formate.

10. A method for preparing the starch graft copolymer of any one of claims 1-9, the method comprising the steps of: (1) mixing acrylamide and functional monomer under contact conditions and introducing water and initiator during the mixing to react, and obtaining a first material after the reaction; the reaction process is that acrylamide and functional monomer are first added to a kneading reactor, water is sprayed during kneading, and initiator is added, and after being fully mixed, the reaction temperature is adjusted to perform explosive polymerization; (2) mixing the first material obtained in step (1), starch, sodium bicarbonate, and plasticizer under mixing conditions to obtain a second material; (3) mixing the second material obtained in step (2), chain transfer agent, and initiator, and then introducing acrylamide, functional monomer, and water to react, and further performing optional molding and drying treatment after discharging to obtain the starch graft copolymer.

11. The process for the preparation of starch graft copolymer as claimed in claim 10, wherein: The amount of acrylamide, functional monomer, water, and initiator in step (1) is 10-50 parts of acrylamide, 5-16 parts of functional monomer, 5-12 parts of water, and 0.1-1 part of initiator.

12. The process for preparing a starch graft copolymer according to claim 10, characterized in that: The amount of acrylamide, functional monomer, water, and initiator in step (1) is 15-40 parts of acrylamide, 6-14 parts of functional monomer, 6-10 parts of water, and 0.2-0.8 part of initiator.

13. The process for preparing a starch graft copolymer according to claim 10, characterized in that: The amount of acrylamide, functional monomer, water, and initiator in step (3) is 40-200 parts of acrylamide, 15-64 parts of functional monomer, 15-48 parts of water, and 0.5-5 parts of initiator.

14. The process for preparing a starch graft copolymer according to claim 10, characterized by: The amount of acrylamide, functional monomer, water, and initiator in step (3) is 50-160 parts of acrylamide, 24-56 parts of functional monomer, 24-40 parts of water, and 0.8-4.2 parts of initiator.

15. The process for preparing a starch graft copolymer according to claim 10, characterized by: The reaction temperature in step (3) is 40-50°C, and the reaction time is 20-60 min.

16. The process for preparing a starch graft copolymer according to claim 10, characterized by: The discharge temperature is controlled to be 40-60°C in step (3).

17. The process for preparing a starch graft copolymer according to claim 10, characterized by: The drying temperature in step (3) is 80-120°C, and the drying time is 0.5-2 h.

18. A water-based mud comprising the starch graft copolymer of any one of claims 1-9 or obtained by the preparation method of any one of claims 10-17.

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