Modified attapulgite
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- INNER MONGOLIA SAIDE TECHNOLOGY CO LTD
- Filing Date
- 2026-02-27
- Publication Date
- 2026-06-05
Abstract
Description
Technical Field
[0001] This invention relates to the field of inorganic functional materials and their modification technology, specifically to a modified attapulgite. Background Technology
[0002] Attapulgite, due to its unique chain-like layered structure and certain salt resistance, is often used as a slurry-forming material in drilling fluid systems. However, during ultra-deep well drilling, the drilling fluid is exposed to high temperature and high salt environment for a long time. The hydroxyl structure on the surface of attapulgite is prone to passivation, and particles are prone to agglomeration, resulting in a decrease in the rheological properties of the drilling fluid and an increase in filtration loss.
[0003] To improve the performance of attapulgite under harsh working conditions, existing technologies mostly use physical coating or simple ion exchange to modify it. However, the binding force between the modifier and attapulgite is weak in these modification methods, and it is easy to desorb or collapse in high-salt environments, making it difficult to maintain stable rheological properties under high temperature and high salt conditions for a long time.
[0004] Furthermore, some polymeric modifiers undergo severe chain shrinkage in high-salt environments due to the polyelectrolyte effect, leading to a loss of drilling fluid viscosity. Therefore, there is an urgent need for a structurally stable modification scheme for attapulgite that can maintain good rheological properties under high-salt and high-temperature environments. To this end, we propose a modified attapulgite. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a modified attapulgite soil that overcomes the deficiencies of existing technologies, has a reasonable design and compact structure, and solves the problems mentioned in the background art.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] A modified attapulgite soil, characterized in that it comprises:
[0008] attapulgite soil matrix;
[0009] And a zwitterionic polymer layer formed by in-situ grafting at the polymerizable active sites after introducing polymerizable active sites on the surface of the attapulgite matrix with a silane coupling agent using free radical-initiated polymerization.
[0010] The zwitterionic polymer is an internal salt type zwitterionic polymer, whose molecular chain contains both positively charged and negatively charged groups, and is fixed to the surface of the attapulgite matrix by covalent bonds.
[0011] Preferably, the polymerizable active sites are formed by the condensation of polymerizable silane coupling agents with silanol groups on the surface of attapulgite.
[0012] Preferably, the polymerizable group has a carbon-carbon double bond structure.
[0013] Preferably, the zwitterionic polymer is formed by polymerization of zwitterionic unsaturated monomers containing both positively charged and negatively charged groups.
[0014] Preferably, the zwitterionic polymer is grafted onto the surface of the attapulgite matrix via free radical-initiated polymerization.
[0015] Preferably, the zwitterionic polymer is fixed to the surface of the attapulgite matrix by covalent bonds and does not desorb under high salinity conditions.
[0016] Preferably, the zwitterionic polymer has an internal salt structure.
[0017] Preferably, the modified attapulgite is used in high-salt or high-temperature drilling fluid systems, wherein the high salt content is ≥10% by mass and / or the high temperature is ≥120°C.
[0018] This invention provides a modified attapulgite clay. It possesses the following beneficial effects:
[0019] 1. By introducing polymerizable active sites on the surface of attapulgite and covalently grafting zwitterionic polymers onto its surface, the modified components can maintain a stable structure under high salt and high temperature environments, effectively avoiding the problem of desorption or failure of modifiers in physical compound systems.
[0020] 2. By utilizing the environmental response characteristics of zwitterionic polymers under high salt or high temperature conditions, modified attapulgite retains good solvation ability and space support effect under harsh working conditions, thereby significantly improving the rheological retention performance of drilling fluid.
[0021] 3. By fixing functional polymers onto the surface of attapulgite through covalent grafting, the stability and durability of the modification effect are enhanced, and the adaptability of attapulgite in complex drilling fluid systems is improved. Detailed Implementation
[0023] Example 1: Preparation of attapulgite with polymerizable active sites introduced on its surface:
[0024] Attapulgite raw material is selected and dried at 80-120℃ for 2-6 hours to remove adsorbed water from its surface.
[0025] The dried attapulgite was dispersed in a polar solvent at a mass ratio of 1:(10-30) and dispersed under mechanical stirring for 30-90 min to fully expose its surface silanol groups.
[0026] Subsequently, under reaction conditions of 40–80°C, a silane coupling agent containing polymerizable groups is added to the dispersion system. The silane coupling agent is selected from at least one of vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane. The amount of silane coupling agent added is 0.5%–10% of the mass of the attapulgite.
[0027] Under the above conditions, the reaction proceeds for 1–6 hours, causing the silane groups in the silane coupling agent to undergo a condensation reaction with the silanol groups on the surface of the attapulgite.
[0028] When the silane coupling agent contains a carbon-carbon double bond structure, polymerizable active sites in the form of carbon-carbon double bonds are introduced into the surface of attapulgite.
[0029] When the silane coupling agent contains a thiol structure, it introduces active thiol sites that can participate in free radical grafting reactions onto the surface of attapulgite.
[0030] This provides a reaction initiation site for the subsequent free radical graft polymerization of zwitterionic monomers.
[0031] After the reaction is complete, the product is filtered, washed and dried at 60–100°C to obtain modified attapulgite with polymerizable active sites introduced on its surface.
[0032] Example 2: Surface grafting process of zwitterionic polymers:
[0033] The modified attapulgite obtained in Example 1 was redispersed in the reaction medium at a mass ratio of attapulgite to reaction medium of 1:(5-20).
[0034] Under nitrogen protection, the reaction system is heated to 50–90°C, and a free radical initiator is added. The amount of initiator added is 0.1%–3% of the mass of the attapulgite.
[0035] Subsequently, a zwitterionic unsaturated monomer is added. This monomer is selected from at least one of sulfonate-betaine type, carboxylate-betaine type, or phosphate-betaine type unsaturated monomers, preferably [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonate-propyl)ammonium hydroxide (SBMA) or [2-(acryloyloxy)ethyl]dimethyl-(3-carboxypropyl)ammonium hydroxide (CBMA). After the monomer is added, it initiates a polymerization reaction using the polymerizable active sites introduced on the surface of the attapulgite clay as starting sites. The polymerization reaction time is 2–10 h.
[0036] After the reaction is complete, the product is washed to remove unreacted monomers and dried at 60–100°C to obtain modified attapulgite with zwitterionic polymers covalently grafted onto its surface.
[0037] Example 3: Experimental verification and mechanism explanation of the environmental response behavior of zwitterionic polymers under high salt and high temperature conditions:
[0038] The results of dispersion stability observation and rheological property testing under high salt and high temperature conditions show that...
[0039] The modified attapulgite with its surface covalently grafted with zwitterionic polymers maintains good dispersion and structural stability even in high-salt and high-temperature environments. Analysis of the experimental results suggests that the zwitterionic polymer molecular chains contain both positively and negatively charged groups. In low-salt environments, the interaction between positive and negative charges within the molecular chain causes the polymer chain to relatively contract. In high-salt or high-temperature environments, external ion shielding weakens the charge interactions within the molecular chain, allowing the zwitterionic polymer molecular chains to maintain a good solvation state and effective steric hindrance, thereby inhibiting the aggregation of attapulgite particles. Since the zwitterionic polymer is covalently fixed to the attapulgite surface, the aforementioned state changes do not lead to polymer desorption, thus ensuring the modified attapulgite maintains good dispersion stability under high-salt and high-temperature conditions.
[0040] Example 4: Application in drilling fluid systems
[0041] The modified attapulgite obtained in Example 2 was added to the drilling fluid system at a rate of 1% to 6% (mass fraction).
[0042] Under high-salt conditions (salt mass fraction 5%–20%) and high-temperature aging conditions (120–180℃, 16–72 h), modified attapulgite can still maintain relatively stable rheological properties and structural integrity compared with unmodified attapulgite.
[0043] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.
[0044] The above description is only used to illustrate the technical solutions of the present invention, and is not intended to limit them. Although the present invention has been described in detail with reference to the foregoing, those skilled in the art should understand that modifications can still be made to the foregoing technical solutions, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A modified attapulgite soil, characterized in that, include: attapulgite soil matrix; And a zwitterionic polymer layer formed by in-situ grafting at the polymerizable active sites after introducing polymerizable active sites on the surface of the attapulgite matrix with a silane coupling agent using free radical-initiated polymerization. The zwitterionic polymer is an internal salt type zwitterionic polymer, whose molecular chain contains both positively charged and negatively charged groups, and is fixed to the surface of the attapulgite matrix by covalent bonds.
2. The modified attapulgite soil as described in claim 1, characterized in that, Polymerizable active sites are formed by the condensation of polymerizable silane coupling agents with silanol groups on the surface of attapulgite.
3. The modified attapulgite soil as described in claim 2, characterized in that, The polymerizable group has a carbon-carbon double bond structure.
4. The modified attapulgite soil as described in claim 1, characterized in that, Zwitterionic polymers are formed by the polymerization of zwitterionic unsaturated monomers that contain both positively charged and negatively charged groups.
5. The modified attapulgite soil as described in claim 1, characterized in that, Amphoteric polymers are grafted onto the surface of attapulgite matrix via free radical-initiated polymerization.
6. The modified attapulgite soil as described in claim 1, characterized in that, The zwitterionic polymer is fixed to the surface of the attapulgite matrix by covalent bonds and does not desorb under high salt conditions.
7. The modified attapulgite soil as claimed in claim 1, characterized in that, The zwitterionic polymer has an internal salt structure.
8. The modified attapulgite soil according to any one of claims 1 to 7, characterized in that, Modified attapulgite is used in high-salt or high-temperature drilling fluid systems, wherein high salt content is defined as a salt mass fraction ≥10%, and / or high temperature is defined as ≥120°C.