阅读说明：本技术 一种倍半环状硅氧烷超临界二氧化碳增稠剂的制法与应用 (Preparation method and application of sesqui-cyclic siloxane supercritical carbon dioxide thickener ) 是由 陈勇 张潦源 张子麟 陈凯 杨峰 苏权生 王丽萍 张超 于 2019-10-25 设计创作，主要内容包括：本发明属于改善页岩油气资源采收率的油气开采技术领域,涉及一种倍半环状硅氧烷超临界二氧化碳增稠剂的制法与应用。本发明通过对倍半硅氧烷的改性,首先通过开环聚合反应制备了含有侧链活性基团的多元共聚硅氧烷初级产物,后将初级产物通过硅氢加成反应将含有侧链活性基团的多元共聚硅氧烷接枝到倍半硅氧烷的侧链,不仅可显著提高增稠剂在超临界二氧化碳中的溶解度,降低助溶剂的用量。而且能够在低含量下显著提高超临界二氧化碳的黏度、降低滤失系数和摩阻系数,改善携砂能力。(The invention belongs to the technical field of oil and gas exploitation for improving shale oil and gas resource recovery ratio, and relates to a preparation method and application of a sesquicyclic siloxane supercritical carbon dioxide thickener. According to the invention, through modification of silsesquioxane, firstly, a poly-copolymerized siloxane primary product containing side chain active groups is prepared through ring-opening polymerization reaction, and then the poly-copolymerized siloxane containing side chain active groups is grafted to the side chains of silsesquioxane through hydrosilylation reaction, so that the solubility of the thickener in supercritical carbon dioxide can be obviously improved, and the dosage of a cosolvent is reduced. But also can obviously improve the viscosity of the supercritical carbon dioxide, reduce the filtration loss coefficient and the friction coefficient and improve the sand carrying capacity under low content.)

1. A copolymerized branched silsesquioxane, characterized by the structural formula:

in the formula I, R is phenyl, methyl, hydrogen, vinyl or ethyl; r' has a structural formula shown in formula II:

in the formula II R₁The polymerization degree b is 3-18; r₂Is methyl, ethyl, phenyl, vinyl or active hydrogen, and the polymerization degree a is 12-71; r3 is methyl, phenyl, hydrogen or vinyl.

2. A method of preparing a copolymeric branched silsesquioxane as defined in claim 1 comprising the steps of:

step 1. preparation of side chain functionalized copoly (dimethylsiloxane): stirring a mixed system of cyclosiloxane, end-capping reagent, cyclohexane and acid catalyst, filling nitrogen and sealing, and reacting the mixed system at 85 ℃ for 10-24 hours; cooling the reactant to room temperature, and removing cyclohexane and micromolecular low-boiling-point substances to obtain the product;

step 2, preparation of copolymerized branched silsesquioxane: adding a catalyst into the prepared side chain functionalized polydimethylsiloxane, stirring, dropwise adding silsesquioxane, heating to 40-60 ℃, continuously stirring for 0.5-2.5h, and reacting for 1.5-11.5 h at 80-90 ℃; cooling the reactant to room temperature, adding active carbon, stirring for 1-2h, performing suction filtration, and performing rotary evaporation to obtain the catalyst.

3. The method according to claim 2, wherein the cyclic siloxane in step 1 is any two combinations of tetramethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, octamethylcyclotetrasiloxane, octavinylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldihydrocyclotetrasiloxane, hexamethylcyclotrisiloxane, octaphenylcyclotetrasiloxane, decaphenylcyclopentasiloxane, pentaphenylcyclopentasiloxane, tetraphenylcyclotetrasiloxane, or dodecamethylcyclohexasiloxane;

preferably, the siloxane is any two combination of tetramethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, octamethylcyclotetrasiloxane, octavinylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldihydrocyclotetrasiloxane, hexamethylcyclotrisiloxane or octaphenylcyclotetrasiloxane.

4. The method according to claim 2, wherein the end-capping agent in step 1 is any one of dodecamethylpentasiloxane, decamethyltetrasiloxane, octamethyldiphenyldisiloxane, tetramethyldisiloxane, heptamethyltrisiloxane, octamethyltrisiloxane, pentamethyldisiloxane, hexamethyldisiloxane, hexavinyldisiloxane, or hexaphenyldisiloxane;

preferably, the end-capping agent is any one of octamethyldiphenyldisiloxane, octamethyltrisiloxane, hexamethyldisiloxane, hexavinyldisiloxane or hexaphenyldisiloxane;

the catalyst in the step 1 is one of hydrochloric acid, sulfuric acid, hydrofluoric acid, perchloric acid, phosphoric acid, acetic acid or acid clay; preferably, the catalyst is one of hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid or acid clay; further preferably, the acid catalyst is selected from one of hydrochloric acid, sulfuric acid or acid clay.

5. The method according to claim 2, wherein the molar ratio of cyclic siloxane to the end-capping agent in step 1 is (7.2-34): 1, preferably (9.4-26): 1; the total concentration of the cyclic siloxane and the end-capping reagent in the cyclohexane is 37-86%, preferably 44-78%; the molar ratio of cyclic siloxane to catalyst is (61-302):1, preferably (84-256): 1.

6. The method according to claim 2, wherein the silsesquioxane in the step 2 is one of acrylic-based cage polysilsesquioxane, aminopropyl isobutyl silsesquioxane, octaphenyl octasilsesquioxane, trimethylsily cage polysilsesquioxane, octa (isobutyl silsesquioxane), octavinyl cage silsesquioxane or octahydro cage silsesquioxane;

preferably, the silsesquioxane is one of octaphenyl octasilsesquioxane, trimethylsilyl cage polysilsesquioxane, octavinyl cage silsesquioxane, or octahydro cage silsesquioxane;

the catalyst in the step 2 is one of chloroplatinic acid, ruthenium black or platinum palladium.

7. The method according to claim 2, wherein the molar ratio of the silsesquioxane to the side-chain functionalized copoly (dimethylsiloxane) in the step 2 is (0.5 to 10.7):1, the total concentration of the silsesquioxane and the side chain functionalized copolydimethylsiloxane in cyclohexane is 24-82%, and the molar ratio of the side chain functionalized copolydimethylsiloxane to the catalyst is (46-183): 1.

8. the process according to claim 2, wherein the catalyst is added dropwise while stirring at a rate of 300 to 500rpm at 0.4 drops/s in step 2^-15.4 drops s^-1。

9. The method according to claim 2, wherein the silsesquioxane is added at a rate of 0.2 drops s^-1-8 drops · s^-1。

10. Use of a copolymeric branched silsesquioxane as defined in claim 1 or prepared by a method as defined in any one of claims 2-9 as a thickener for improving the viscosity of supercritical carbon dioxide for oil field fracturing.

Technical Field

The invention belongs to the technical field of oil and gas exploitation for improving shale oil and gas resource recovery ratio, and relates to a preparation method and application of a sesquicyclic siloxane supercritical carbon dioxide thickener.

Background

With the continuous consumption of non-renewable energy and the rapid change of the world energy pattern, the field of oil and gas exploration and development at home and abroad begins to turn attention to the development and research of unconventional oil and gas resources. The hydraulic fracturing technology, as an efficient traditional oil and gas development technology, has many advantages when exploiting an oil field with common permeability, but is low in efficiency aiming at a low-permeability oil reservoir, particularly a low-permeability shale oil reservoir, and has many defects of large water demand, serious reservoir damage and the like. The supercritical carbon dioxide fracturing technology can obviously improve the defects, and the carbon dioxide is low in price, is directly obtained from the atmosphere and is directly used after being pressurized. After fracturing is completed, part of carbon dioxide can be sealed in an underground reservoir, and the rest carbon dioxide can be discharged from a production well along a fracture and then collected and pressurized for continuous use. The application and popularization of the carbon dioxide fracturing technology can not only obviously improve the greenhouse effect, but also reduce the damage of the stratum and the pollution of underground water resources, and a plurality of advantages show that the supercritical carbon dioxide fracturing technology has excellent development prospect. However, pure supercritical carbon dioxide itself has a low viscosity, generally less than 0.05mPa · s, and such a low viscosity cannot meet the requirement of fracturing operation, and when the viscosity of supercritical carbon dioxide is low, a gas channeling phenomenon is caused in the fracturing process of a reservoir, so that the carbon dioxide fracturing fluid is easy to float upwards, and the sweep coefficient is reduced. Secondly, fingering is liable to occur, resulting in a decrease in sweep efficiency, which leads to a decrease in fracture performance.

The fluorine-containing polymer is the most main and most effective thickening agent which can obviously improve the viscosity of the supercritical carbon dioxide fracturing fluid at present, can be completely dissolved in the supercritical carbon dioxide generally without adding a cosolvent, and has extremely excellent thickening performance. However, the high price and the pollution to water resources of the hypotonic reservoir are the mainstream thickeners that can be applied to increase the viscosity of supercritical carbon dioxide. In addition, the hydrocarbon polymer is another chemical agent capable of effectively improving the viscosity of the carbon dioxide, and although the carbon dioxide polymer is low in price and does not need to be additionally added with a cosolvent, the thickening performance of the carbon dioxide polymer is poor, and the significance of the carbon dioxide polymer thickening agent applied to supercritical carbon dioxide is not great. Fluorine-containing polymers and hydrocarbon polymers are disadvantageous for thickeners applied to supercritical carbon dioxide due to their disadvantages. In recent years, a plurality of experts and scholars aim at siloxane polymers, polydimethylsiloxane is used for improving the viscosity of supercritical carbon dioxide, and although the polydimethylsiloxane has certain thickening performance, the viscosity cannot meet the fracturing requirement of an oil field, the polydimethylsiloxane has the capability of improving the viscosity, and the performance of a reservoir layer cannot be polluted, so that the polydimethylsiloxane becomes the important point of research.

Disclosure of Invention

Aiming at the defects of polydimethylsiloxane in the prior art of thickening performance of supercritical carbon dioxide, the invention provides the copolymerization branched chain sesquicyclosiloxane, which has excellent thickening performance and can obviously improve the viscosity of the supercritical carbon dioxide for oil field fracturing; and has better solubility, and can reduce the use of cosolvent.

In order to achieve the purpose, the invention adopts the following technical scheme:

one of the objects of the present invention is to provide a copolymerized branched silsesquioxane, which has the following structural formula:

in the formula I, R is phenyl, methyl, hydrogen, vinyl or ethyl; r' has a structural formula shown in formula II:

in the formula II R₁The polymerization degree b is 3-18; r₂Is methyl, ethyl, phenyl, vinyl or active hydrogen, and the polymerization degree a is 12-71; r3 is methyl, phenyl, hydrogen or vinyl.

A second object of the present invention is to provide a process for the preparation of the above described copolymeric branched silsesquioxane, said process comprising the steps of:

step 1. preparation of side chain functionalized copoly (dimethylsiloxane): stirring a mixed system of cyclosiloxane, end-capping reagent, cyclohexane and acid catalyst, filling nitrogen and sealing, and reacting the mixed system at 85 ℃ for 10-24 hours; cooling the reactant to room temperature, and removing cyclohexane and micromolecular low-boiling-point substances to obtain the product;

step 2, preparation of copolymerized branched silsesquioxane: adding a catalyst into the prepared side chain functionalized polydimethylsiloxane, stirring, dropwise adding silsesquioxane, heating to 40-60 ℃, continuously stirring for 0.5-2.5h, and reacting for 1.5-11.5 h at 80-90 ℃; cooling the reactant to room temperature, adding active carbon, stirring for 1-2h, performing suction filtration, and performing rotary evaporation to obtain the catalyst.

According to the above-described method for producing a copolymerized branched silsesquioxane, preferably, the cyclic siloxane in step 1 is any two combinations of tetramethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, octamethylcyclotetrasiloxane, octavinylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldihydrocyclotetrasiloxane, hexamethylcyclotrisiloxane, octaphenylcyclotetrasiloxane, decaphenylcyclopentasiloxane, pentaphenylcyclopentasiloxane, tetraphenylcyclotetrasiloxane, or dodecamethylcyclohexasiloxane;

preferably, the siloxane is any two combination of tetramethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, octamethylcyclotetrasiloxane, octavinylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldihydrocyclotetrasiloxane, hexamethylcyclotrisiloxane or octaphenylcyclotetrasiloxane.

According to the preparation method of the copolymerized branched silsesquioxane, the end-capping agent in step 1 is preferably any one of dodecamethylpentasiloxane, decamethyltetrasiloxane, octamethyldiphenyldisiloxane, tetramethyldisiloxane, heptamethyltrisiloxane, octamethyltrisiloxane, pentamethyldisiloxane, hexamethyldisiloxane, hexavinyldisiloxane or hexaphenyldisiloxane;

preferably, the end-capping agent is any one of octamethyldiphenyldisiloxane, octamethyltrisiloxane, hexamethyldisiloxane, hexavinyldisiloxane or hexaphenyldisiloxane;

the catalyst in the step 1 is one of hydrochloric acid, sulfuric acid, hydrofluoric acid, perchloric acid, phosphoric acid, acetic acid or acid clay; preferably, the catalyst is one of hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid or acid clay; further preferably, the acid catalyst is selected from one of hydrochloric acid, sulfuric acid or acid clay.

According to the preparation method of the copolymerized branched silsesquioxane, the molar ratio of the cyclic siloxane to the end-capping agent in the step 1 is preferably (7.2-34): 1, preferably (9.4-26): 1; the total concentration of the cyclic siloxane and the end-capping reagent in the cyclohexane is 37-86%, preferably 44-78%; the molar ratio of cyclic siloxane to catalyst is (61-302):1, preferably (84-256): 1.

According to the preparation method of the copolymerized branched silsesquioxane, cyclohexane and small-molecule low-boiling-point substances are preferably removed for 0.4-6 h under the conditions of the vacuum degree of 0.09MPa and the temperature of 105 ℃ in the step 1 to obtain the side-chain functionalized copolymerized dimethylsiloxane.

According to the preparation method of the copolymerized branched silsesquioxane, in the step 2, the silsesquioxane is preferably one of acrylic-based cage polysilsesquioxane, aminopropyl isobutyl silsesquioxane, octaphenyl octasilsesquioxane, trimethylsilyl cage polysilsesquioxane, octa (isobutyl silsesquioxane), octavinyl cage silsesquioxane or octahydro cage silsesquioxane;

preferably, the silsesquioxane is one of octaphenyl octasilsesquioxane, trimethylsilyl cage polysilsesquioxane, octavinyl cage silsesquioxane, or octahydro cage silsesquioxane;

the catalyst in the step 2 is one of chloroplatinic acid, ruthenium black or platinum palladium.

According to the preparation method of the copolymerized branched silsesquioxane, preferably, the mol ratio of the silsesquioxane to the side chain functionalized copolymerized dimethyl siloxane in the step 2 is (0.5-10.7) to 1, the total concentration of the silsesquioxane and the side chain functionalized copolymerized dimethyl siloxane in cyclohexane is 24-82%, and the mol ratio of the side chain functionalized copolymerized dimethyl siloxane to the catalyst is (46-183): 1.

according to the preparation method of the copolymerized branched silsesquioxane, the catalyst is preferably added dropwise in step 2 while stirring, wherein the stirring speed is 300-500 rpm, and the dropping speed is 0.4 drops s^-15.4 drops s^-1。

According to the preparation method of the copolymerized branched silsesquioxane, the dropping speed of silsesquioxane is preferably 0.2 drops s^-1-8 drops · s^-1。

According to the preparation method of the copolymerization branched chain sesquicyclic siloxane, the product is preferably subjected to rotary evaporation for 0.4 h-3.2 h at the temperature of 55-85 ℃ and the pressure of 0.02-0.08 MPa for removing micromolecular low-boiling-point substances and cyclohexane.

The invention also provides application of the copolymerized branched silsesquioxane and the copolymerized branched silsesquioxane prepared by the method in any one of the above aspects as a thickening agent in improving the viscosity of supercritical carbon dioxide for oilfield fracturing.

Dimethylsilicone oil is difficult to dissolve in supercritical carbon dioxide because molecular chains of siloxane cannot interact with carbon dioxide molecules by intermolecular forces. In addition, due to poor solubility, a cosolvent is required to be added as a medium between the molecular chain of the simethicone and the carbon dioxide molecule to assist in improving the interaction between the two molecules, but the requirement of the cosolvent is large. And the dimethyl silicone oil has limited capability of thickening supercritical carbon dioxide, and cannot meet the viscosity requirement of the fracturing fluid. According to the invention, through modification of silsesquioxane, firstly, a poly-copolymerized siloxane primary product containing side chain active groups is prepared through ring-opening polymerization reaction, and then the poly-copolymerized siloxane containing side chain active groups is grafted to the side chains of silsesquioxane through hydrosilylation reaction, so that the solubility of the thickener in supercritical carbon dioxide can be obviously improved, and the dosage of a cosolvent is reduced. But also can obviously improve the viscosity of the supercritical carbon dioxide, reduce the filtration loss coefficient and the friction coefficient and improve the sand carrying capacity under low content.

The invention has the following excellent effects:

1. the preparation materials used in the invention are easy to obtain, the price is low, the body can not be damaged in the preparation process, and the safety is excellent. The preparation condition is mild.

2. The thickener of the invention has simple preparation process, simple and convenient steps, can be completed in a common chemical laboratory, and has mild preparation conditions.

3. The preparation process of the invention has higher reaction yield, the substances which do not participate in the preparation process are easy to remove, the purification steps are simple and convenient, and the separated substances can not pollute the environment.

4. The copolymer branched silsesquioxane polymer prepared by the invention has stable property and can be stored for a long time under the condition of air isolation at normal temperature.

5. The copolymer branched sesquicyclic siloxane polymer prepared by the invention has excellent performance of supercritical carbon dioxide, and compared with pure supercritical carbon dioxide, the viscosity of the thickened supercritical carbon dioxide is obviously improved.

6. The thickening agent prepared by the invention belongs to a nonpolar chemical agent, can quickly flow out of a production well along with crude oil after fracturing is finished, and secondly, a few siloxane thickening agents which cannot flow out cannot be adsorbed to the surface of a rock containing nonionic property and flow back to a reservoir along with other fluids.

In conclusion, the copolymerization branched chain sesqui-cyclic siloxane prepared by the method has the advantages of simple and convenient equipment for production, no need of any special instrument and low cost, and can realize industrialized mass production. Furthermore, the stable physicochemical properties facilitate the preservation of the thickener. The excellent performance of thickening the supercritical carbon dioxide can generate good fracturing effect and sand carrying performance on the oil and gas development of a low-permeability reservoir, particularly a shale reservoir.

Drawings

FIG. 1 is an IR spectrum of a copoly branched silsesquioxane of example 1 of the present invention.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of the stated features, steps, operations, and/or combinations thereof, unless the context clearly indicates otherwise.

In order to make the technical solutions of the present invention more clearly understood by those skilled in the art, the technical solutions of the present invention will be described in detail below with reference to specific embodiments.

The instruments, reagents, materials and the like used in the following examples are conventional instruments, reagents, materials and the like in the prior art and are commercially available in a normal manner unless otherwise specified. Unless otherwise specified, the experimental methods, detection methods, and the like described in the following examples are conventional experimental methods, detection methods, and the like in the prior art.

EXAMPLE 1 preparation of copolymerized branched silsesquioxane

A method for preparing a copolymerized branched silsesquioxane polymer comprising the steps of:

1) preparation of side-chain functionalized copoly (dimethylsiloxanes)

14.83g of octamethylcyclotetrasiloxane, 60g of tetramethylcyclotetrasiloxane, 3.3g of hexamethyldisiloxane, 160mL of cyclohexane and 0.2g of sulfuric acid are added into a 500mL three-neck flask, the three-neck flask containing the three substances is placed on a magnetic stirrer, stirred at the temperature of 25 ℃ and the rotating speed of 550rpm for 20min, then nitrogen gas at the temperature of 25 ℃ is introduced for 40min, then the opening of the three-neck flask is sealed, and the three-neck flask is transferred into an oil bath pot to react for 15h at the temperature of 85 ℃. Then taking out and reducing the temperature to 25 ℃, and removing cyclohexane and micromolecular low-boiling-point substances for 1.5h under the conditions of the vacuum degree of 0.09MPa and the temperature of 105 ℃ to obtain the side chain functionalized copoly (dimethylsiloxane).

(2) Preparation of copoly branched silsesquioxanes

A solution of 40g of the side-chain-functionalized copolydimethylsiloxane prepared in 175mL of cyclohexane was poured into a three-necked flask, 0.04g of chloroplatinic acid was dropped at 25 ℃ and then stirred at 350rpm for 45min, and 0.4 drops/s was added^-1The dropping speed of (1) 44.3g of octavinyl cage-type silsesquioxane was added to a three-necked flask, and after the completion of the addition, the temperature was raised to 50 ℃ and the stirring was continued for 1 hour. And then raising the temperature to 85 ℃ for reaction for 8h, cooling the reaction product to room temperature, pouring a small amount of active carbon into a cyclohexane solution containing the product, stirring for 1.5h, performing suction filtration under reduced pressure to remove the active carbon and the chloroplatinic acid catalyst, and performing rotary evaporation on the product at 0.07MPa and 75 ℃ for 1.5h to remove small-molecular low-boiling-point substances and cyclohexane to obtain colorless, clear and slightly sticky transparent liquid.

R is vinyl; r₁Is methyl, and the degree of polymerization b is 10; r₂Is hydrogen, the degree of polymerization a is 53; r₃Is methyl.

The polymer product was characterized as shown in FIG. 1. 2972cm in the infrared spectrum of the copolymerized branched sesquicyclic siloxane shown in figure 1^-1Is the hydrocarbon absorption peak of the methyl group, thisOutside, 1417cm^-1Another absorption peak also considered to be methyl; the symmetric deformation absorption peak of the methyl group is considered to be 1265cm^-1At 2883cm^-1An absorption peak attributed to methylene; 1021cm^-1To 1102cm^-1The doublet of (2) is a typical absorption peak of a silicon-oxygen bond, and the absorption peak of a silicon-carbon bond is ascribed to 798cm^-1，715cm^-1Is considered to be a symmetric stretching vibration of silicon-carbon bonds.

EXAMPLE 2 preparation of copoly branched silsesquioxane

This example is different from example 1 in that the amounts of octamethylcyclotetrasiloxane and tetramethylcyclotetrasiloxane used in step 1 were 29.6g and 48g, respectively, and the other steps were the same as in example 1.

The obtained product has a structure shown in formula I, wherein R₁Is methyl, and the degree of polymerization b is 18; r₂Is hydrogen, the degree of polymerization a is 44; r₃Is methyl and R is vinyl.

EXAMPLE 3 preparation of copoly branched silsesquioxane

This example differs from example 1 in that the cyclic siloxanes used in step 1 are tetraphenylcyclotetrasiloxane and octamethylcyclotetrasiloxane, and the other steps are the same as in example 1.

EXAMPLE 4 preparation of copoly branched silsesquioxane

This example is different from example 1 in that the amount of sulfuric acid used in step 1 was 0.11g, and the other steps were the same as example 1.

The species and degree of polymerization of each group of the obtained product were the same as those of example 1.

EXAMPLE 5 preparation of copolymerized branched silsesquioxane

This example is different from example 1 in that acetic acid is used as the catalyst in step 1, and the other steps are the same as example 1.

EXAMPLE 6 preparation of copoly branched silsesquioxane

This example differs from example 1 in that the molar ratio of cyclosiloxane to hexamethyldisiloxane in step 1 was changed to 20:1, and the other steps were the same as in example 1.

EXAMPLE 7 preparation of copoly branched silsesquioxane

This example differs from example 1 in that the end-capping agent used was octamethyltrisiloxane and the other steps were the same as in example 1.

EXAMPLE 8 preparation of copoly branched silsesquioxane

This example differs from example 1 in that the catalyst in step 2 was changed to a platinum palladium catalyst and the side-chain functionalized copoly (dimethylsiloxane) to catalyst molar ratio was 172: 1, the other steps are the same as in example 1

Examples product performance evaluation:

solutions of 1.3 wt% polymer concentration were prepared from 2 volumes of copolymerized branched silsesquioxane prepared in examples 1-8 in toluene, respectively, using a capillary viscosity measuring device at 12MPa, 35 deg.C and 240s^～1The viscosity of each polymer, toluene and supercritical carbon dioxide mixed high pressure liquid was tested at shear rates and the viscosity values are shown in table 1. In addition, the following control groups were set up in this experiment:

control group 1: linear polydimethylsiloxanes manufactured by dow corning corporation, usa;

control group 2: the silicone polymer obtained was prepared according to the method of example 1 of patent application CN 108003349A.

TABLE 1 evaluation results of shear resistance

Sample numbering	Viscosity, mPas
		Example 1	10.2
Example 2	9.3
		Example 3	5.5
Example 4	6.7
		Example 5	4.3
Example 6	6.4
		Example 7	10.0
Example 8	9.8
		Comparative example 1	1.2
Comparative example 2	3.9

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.