CN118834372A - Degradable thermosetting composite material with bicontinuous microstructure and degradable underground plugging tool prepared from degradable thermosetting composite material - Google Patents

Abstract

The invention provides a degradable thermosetting composite material with a bicontinuous microstructure and a degradable underground plugging tool prepared from the same, wherein the degradable thermosetting composite material comprises the following raw materials in percentage by weight: the epoxy resin mixture comprises 0.1-99% of epoxy resin mixture, 0.1-99% of cycloaliphatic anhydride cross-linking agent and 0.01-10% of main catalyst, wherein the epoxy resin mixture comprises primary epoxy resin and secondary epoxy resin, the glass transition temperature of the primary epoxy resin is 120-200 ℃, the glass transition temperature of the secondary epoxy resin is 40-100 ℃, and the weight percentage of the primary epoxy resin in the epoxy resin mixture is 60-80%. The thermosetting composite material provided by the invention has the characteristics of high temperature resistance and degradability at low temperature, and also has excellent mechanical properties.

Description

A degradable thermosetting composite material with a dual continuous microstructure and a degradable downhole plugging tool prepared therefrom

Technical Field

The invention relates to the technical field of degradable polymer materials, and in particular to a degradable thermosetting composite material with a double continuous microstructure and a degradable downhole plugging tool prepared therefrom.

Background Art

During the development of oil and gas wells, it is necessary to establish a stable oil and gas migration channel. Therefore, a wide variety of downhole isolation tools are used in the wellbore, such as fracturing bridge plugs, packers, isolation valves, etc., to form an annular space between the oil and casing, separate the oil and gas into separate systems that do not interfere with each other, so as to achieve layered oil testing, oil production, water injection, layered acidification, layered fracturing, etc. After the fracturing is completed or the well is repaired, the downhole isolation tools need to be drilled and ground into debris and discharged to the ground. Usually, the isolation type temporary plugging tools are made of drillable metal materials such as cast iron, alloy, brass and aluminum. Drilling and grinding takes a long time and the construction cost is high. Therefore, it is necessary to develop a reliable and degradable downhole tool special material.

Compared with soluble metal bridge plugs, high molecular polymer soluble bridge plugs have obvious advantages. They are easy to dissolve, insensitive to mineralization, easy to backflow, pollution-free, and low cost. Currently, more than 90% of oil and gas wells use soluble metal bridge plugs for completion and production operations. There are relatively few bridge plug tools using polymer materials. However, as an environmentally friendly material, polymer materials can be used as one of the reserve technologies to replace soluble metal materials in the future. At the same time, due to the strong acid resistance of polymer materials, there is a large demand for them in the acid fracturing process. Polymer material soluble bridge plug products are the best choice for more than 90% of acid fracturing oil and gas wells.

Epoxy resins are one of the most widely used engineering resins and are well known for their use in high-strength fiber composites. Epoxy resins form glassy networks that exhibit good corrosion resistance, solvent resistance, good adhesion, reasonably high glass transition temperatures, and adequate electrical properties. The impact strength, fracture toughness, ductility, and most other physical properties of crosslinked epoxy resins can be controlled by the chemical makeup, epoxy resin ratio, crosslinker; by any added macrofillers, toughening agents, and other additives; and by the curing conditions used.

Although degradable polymers or polymer composites for making various downhole tools (including degradable plugs) are available on the market, they are mainly thermoplastic resins with a rated temperature below 80°C, which cannot meet the needs of developing ultra-deep shale wells where downhole temperatures can easily exceed 130°C. Thermosetting polymers with high rated temperatures are good candidates for meeting this market need. However, except for the cyanate ester composites developed by Baker Hughes, few of the degradable thermosetting polymer materials reported so far can withstand such harsh conditions. However, cyanate esters are extremely expensive and have fragile properties. To solve this problem, epoxy resin materials with high flexibility and cost-effectiveness are more attractive in material selection.

For bridge plug applications, it is not only required to have a high glass transition temperature suitable for high-temperature wells, but also to be able to degrade at relatively low temperatures. Any single epoxy resin material cannot meet this conflicting requirement, because high-temperature epoxy resins are almost impossible to degrade at low temperatures.

Summary of the invention

In order to solve the above technical problems, the purpose of the present invention is to provide a degradable thermosetting composite material and a degradable downhole plugging tool prepared therefrom. The degradable thermosetting composite material of the present invention has a bicontinuous microstructure, and the thermosetting resin generated by curing has a good balance of physical properties, including high glass transition temperature, high tensile strength, high tensile modulus, and can be degraded in water, salt and low temperature environments.

To achieve the above-mentioned purpose, the present invention provides a degradable thermosetting composite material, whose raw materials include: 0.1-99% of an epoxy resin mixture, 0.1-99% of a cycloaliphatic anhydride crosslinking agent and 0.01-10% of a main catalyst, wherein the epoxy resin mixture includes a primary epoxy resin (high glass transition temperature epoxy resin) and a secondary epoxy resin (low glass transition temperature epoxy resin), wherein the glass transition temperature of the primary epoxy resin is 120-200°C, the glass transition temperature of the secondary epoxy resin is 40-100°C, and the weight percentage of the primary epoxy resin in the epoxy resin mixture is 60-80%.

According to a specific embodiment of the present invention, preferably, the weight percentage of the primary epoxy resin in the epoxy resin mixture is 65-75%, more preferably 70%.

According to a specific embodiment of the present invention, preferably, the primary epoxy resin includes an aromatic epoxy resin; and the secondary epoxy resin includes a flexible aliphatic epoxy resin.

According to a specific embodiment of the present invention, preferably, the aromatic epoxy resin includes one or a combination of two or more of novolac epoxy resin, epoxy bisphenol A novolac resin, multifunctional epoxy resin, and bisphenol A epoxy resin.

According to a specific embodiment of the present invention, preferably, the cycloaliphatic anhydride crosslinking agent includes one or a combination of two or more of methyl nadic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, dodecyl succinic anhydride, phthalic anhydride, methyl hexahydrophthalic anhydride, tetrahydrophthalic anhydride and methyl tetrahydrophthalic anhydride.

According to a specific embodiment of the present invention, preferably, the main catalyst is a solid acid or a solid base.

According to a specific embodiment of the present invention, preferably, the main catalyst includes one or a combination of two or more of Ca(OH) ₂ , CaO, Mg(OH) ₂ , KOH, and NaOH.

According to a specific embodiment of the present invention, preferably, the solid acid comprises aminosulfonic acid.

According to a specific embodiment of the present invention, preferably, based on the total weight of the epoxy resin mixture, the cycloaliphatic anhydride crosslinking agent and the main catalyst, the weight percentage of the epoxy resin mixture is 5-95%, preferably 25-75%, more preferably 40-60%.

According to a specific embodiment of the present invention, preferably, based on the total weight of the epoxy resin mixture, the cycloaliphatic anhydride crosslinking agent and the primary catalyst, the weight percentage of the cycloaliphatic anhydride crosslinking agent is 5-95%, preferably 25-75%, more preferably 40-60%.

According to a specific embodiment of the present invention, preferably, based on the total weight of the epoxy resin mixture, the cycloaliphatic anhydride crosslinking agent and the main catalyst, the weight percentage of the main catalyst is 0.1-8%, preferably 0.5-6%, more preferably 1-4%.

According to a specific embodiment of the present invention, preferably, the raw materials of the degradable thermosetting composite material include: 25-75% of epoxy resin mixture, 25-75% of cycloaliphatic anhydride crosslinking agent and 1-8% of main catalyst.

According to a specific embodiment of the present invention, preferably, the raw materials of the degradable thermosetting composite material include: 40-60% of epoxy resin mixture, 40-60% of cycloaliphatic anhydride crosslinking agent and 1-9% of main catalyst.

According to a specific embodiment of the present invention, preferably, the cycloaliphatic anhydride crosslinking agent accounts for 30-50% of the total weight of the epoxy resin mixture and the cycloaliphatic anhydride crosslinking agent.

According to a specific embodiment of the present invention, preferably, the raw materials of the degradable thermosetting composite material further include: one or more of additional epoxy resin, additional crosslinking agent, curing agent, crosslinking or curing catalyst, additives, and fillers.

According to a specific embodiment of the present invention, preferably, the raw material of the degradable thermosetting composite material also includes fibers; the volume percentage of the fibers in the degradable thermosetting composite material is 20-60%, and the fibers include one or more of glass fibers, carbon fibers, and Kevlar fibers.

According to a specific embodiment of the present invention, preferably, the raw material of the degradable thermosetting composite material further includes a flexible epoxy resin.

According to a specific embodiment of the present invention, preferably, the flexible epoxy resin includes one or a combination of two or more of ethylene glycol-modified epoxy resin, polypropylene glycol-modified aliphatic epoxy resin, epoxidized polybutadiene, epoxidized caprolactone, caprolactone, silicone resin containing epoxy functionality, and epoxy vinyl ester resin.

According to a specific embodiment of the present invention, preferably, the flexible epoxy resin further comprises other linear polymers having terminal epoxy groups and/or polymers having pendant epoxy groups.

According to a specific embodiment of the present invention, preferably, the flexible epoxy resin further comprises a glycidyl resin. More preferably, the glycidyl resin comprises a polyglycidyl ether of a phenolic resin.

According to a specific embodiment of the present invention, preferably, the glass transition temperature of the degradable thermosetting composite material is ≥140°C, preferably ≥175°C.

According to a specific embodiment of the present invention, preferably, the elastic modulus of the degradable thermosetting composite material is ≥14500 psi, preferably ≥15000 psi.

According to a specific embodiment of the present invention, preferably, the tensile strength of the degradable thermosetting composite material is ≥10000 psi, preferably ≥12000 psi.

According to a specific embodiment of the present invention, preferably, the elongation at break of the degradable thermosetting composite material is ≥1%, preferably ≥2.5%.

According to a specific embodiment of the present invention, preferably, the method for preparing the degradable thermosetting composite material comprises the following steps:

The primary epoxy resin and the secondary epoxy resin are mixed evenly, and then a cycloaliphatic anhydride crosslinking agent and a main catalyst are added and mixed evenly, and then fibers or other raw materials are optionally added to obtain the degradable thermosetting composite material.

The present invention also provides a degradable downhole plugging tool prepared from the degradable thermosetting composite material.

According to a specific embodiment of the present invention, preferably, the degradable downhole plugging tool is a near-net-shape component.

According to a specific embodiment of the present invention, preferably, the preparation method of the degradable downhole plugging tool comprises the following steps: molding the degradable thermosetting composite material using a hot press, and post-processing the mold at 100-250°C to obtain the degradable downhole plugging tool.

The technical solution provided by the present invention has the following beneficial effects:

The present invention forms a bicontinuous microstructure by compounding a high glass transition temperature epoxy resin and a low glass transition temperature epoxy resin, and adds an alicyclic anhydride crosslinking agent and a main catalyst, so that the prepared thermosetting composite material can simultaneously have the characteristics of high temperature resistance (glass transition temperature ≥ 140°C) and degradability at low temperature, and also has excellent mechanical properties. The downhole plugging tool prepared from the thermosetting composite material can be used in ultra-deep well and high-temperature well hydraulic fracturing and acid fracturing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the microstructure of a degradable thermosetting composite material having a bicontinuous microstructure of the present invention (not to scale), wherein component A is an epoxy resin with a low degradation rate and a high glass transition temperature, and component B is an epoxy resin with a high degradation rate and a low glass transition temperature;

FIG2 is a flow chart of a method for preparing a degradable thermosetting composite material having a bicontinuous microstructure and a degradable downhole plugging tool according to the present invention;

FIG3 is a curing and hydrolysis process diagram of bisphenol A diglycidyl ether epoxy resin prepared using methyl nadic anhydride as a crosslinking agent;

FIG4 is a schematic diagram of the chemical degradation process of thermosetting polymers;

FIG5 is a dynamic mechanical analysis of a degradable epoxy resin (100% component A) with an extremely high temperature rating;

FIG6 is a dynamic mechanical analysis diagram of a degradable epoxy resin (50% component A + 50% component B) with a medium to high rated temperature;

FIG7 is a dynamic mechanical analysis diagram of a degradable thermosetting composite material prepared according to an embodiment of the present invention;

FIG8 shows the degradation of a thermosetting composite material prepared in another embodiment of the present invention after being immersed in a 3% KCl solution at 95° C. for 2 days;

FIG9 shows the degradation of a fiber-reinforced thermosetting composite material prepared in another embodiment of the present invention after being immersed in a 3% KCl solution at 95° C. for 2 days;

Figure 10 shows the tensile strength of recommended fibers at room temperature and elevated temperature.

DETAILED DESCRIPTION

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

In one aspect, the thermosetting composite material disclosed in the present invention comprises a curable component, which can form a thermosetting resin. For example, the curable component may include an aromatic epoxy resin mixture. For example, the crosslinking agent used in the curable component may include a cycloaliphatic anhydride. In one set of embodiments, the curable component disclosed in the present invention may include a mixture of the following substances: a) an aromatic epoxy resin; b) one or more aliphatic resins; c) a primary catalyst; d) a cycloaliphatic anhydride crosslinking agent. The aromatic epoxy resin may further include a novolac epoxy resin, an epoxy bisphenol A novolac resin, a multifunctional epoxy resin, a bisphenol A epoxy resin, or a synthesis of the above substances.

Once the above curing components are cured, such as thermal curing, the resulting thermosetting resin has a good balance of physical properties, including high glass transition temperature, high tensile strength, high tensile modulus, and degradation in water, salt and low temperature environments.

In addition to the above-mentioned curable components, the thermosetting composite material of the present invention also includes fibers and other reinforcing fillers.

The degradable thermosetting composite material may include the product of a mixture reaction of an epoxy resin mixture, a crosslinking agent, and a primary catalyst. The epoxy resin mixture may include at least one primary epoxy resin and a secondary epoxy resin. The primary epoxy resin has a glass transition temperature, which is higher than the glass transition temperature of the secondary epoxy resin. The primary epoxy resin may include an aromatic epoxy resin. The secondary epoxy resin may be composed of one or more flexible aliphatic resins. In some embodiments, the degradable thermosetting composite material may have a tensile modulus of at least about 145,000 psi. The aromatic epoxy resin may include a phenolic epoxy resin, an epoxy bisphenol A phenolic resin, a multifunctional epoxy resin, a bisphenol A epoxy resin, or a synthesis of the above substances.

The material used to prepare the bridge plug not only needs to have a high glass transition temperature suitable for high-temperature wells, but also needs to be degraded at a relatively low temperature. Any single epoxy resin material cannot meet this contradictory requirement, because epoxy resins with high glass transition temperatures are almost impossible to degrade at low temperatures. In order to solve this problem, the present invention mixes a high glass transition temperature epoxy resin (primary epoxy resin) with a lower glass transition temperature epoxy resin (secondary epoxy resin) to form a unique dual continuous microstructure, as shown in FIG1.

In Figure 1, the high glass transition temperature epoxy resin (component A of Figure 1) forms the main chain, providing high mechanical strength at high temperatures, while the low glass transition temperature epoxy resin (component B of Figure 1) accelerates the degradation rate, allowing the material to dissolve quickly in a lower temperature environment. After the low glass transition temperature epoxy resin component dissolves, the increased open channels and the resulting increased contact area can increase the degradation rate of the high glass transition temperature epoxy resin, thereby accelerating the degradation of the final bulk material. In addition to providing more channels for the degradation of higher glass transition temperature epoxy resins (i.e., significantly increasing the surface area), the inventors have also found that the degradation products of low glass transition temperature epoxy resins can also accelerate the degradation process of high glass transition temperature epoxy resins.

As shown in Figure 1, the present invention also uses solid base or solid acid as the main catalyst (dots in Figure 1) to accelerate the degradation rate. Fibers (such as glass, carbon fiber, Kevlar fiber, etc.) can be used to reinforce the structure to make what we call fiber-polymer composite materials.

The present invention provides a formulation for making a cost-effective, bicontinuous microstructured degradable thermosetting composite material that can be used as a temporary plugging tool at 110°C and degrade at a lower temperature below 100°C when the tool is no longer needed. This is a typical requirement for making downhole degradable plugs used for hydraulic fracturing in ultra-deep wells and high-temperature wells. So far, no polymer-based degradable plugs on the market can achieve this, mainly because of their low temperature rating (<80°C).

The thermosetting composite material disclosed in the present invention may have a glass transition temperature (Tg) of at least 150°C in some embodiments, as measured by differential scanning calorimetry (DSC) or dynamic thermomechanical analysis (DMTA; in accordance with ASTM D5045). In other embodiments, the thermosetting composite material disclosed in the present invention may have a glass transition temperature of at least 175°C; in other embodiments, it may have a glass transition temperature of at least 200°C; in other embodiments, it may have a glass transition temperature of at least 210°C; in other embodiments, it may have a glass transition temperature of at least 220°C; in other embodiments, it may have a glass transition temperature of at least 224°C; in other embodiments, it may have a glass transition temperature of at least 225°C; in other embodiments, it may have a glass transition temperature of at least 226°C.

Glass transition temperature measurements are performed using differential scanning calorimetry, for example using a Q100 differential scanning calorimeter from T.A. Instruments, set at a scan rate of 10°C/min. Sample size is typically kept below 15 mg. A sealed flat-top pan with a perforated lid can be used to hold the sample in the differential scanning calorimeter cell. The final glass transition temperature of the differential scanning calorimeter is analyzed using semi-extrapolated tangent (glass transition temperature analysis).

Glass transition temperature measurements can be made using dynamic mechanical analysis, for example, at 1 Hz and 0.1% stress on three rectangular specimens according to ASTM D5045. The temperature range of these tests is chosen to be between 30 and 280°C. The sample dimensions are typically 17 mm long, 13 mm wide, and 4 mm thick. The sample is inserted between adjustable clamps, which are closed using a torque clamp. The sample is susceptible to torsional mode vibrations. The sample is susceptible to dynamic temperature ramps at a heating rate of 3°C/min. A slow heating rate of 3°C/min can be used to maintain thermal equilibrium while taking into account the thermal mass of the sample. Storage and loss moduli as well as loss tangent are recorded.

In some embodiments, the thermosetting composite material disclosed in the present invention has an elastic modulus of at least 14500 psi measured in accordance with the requirements of the American Society for Testing and Materials D638. In other embodiments, the thermosetting resin disclosed in the present invention may have an elastic modulus of at least 146000 Psi; in other embodiments, it may have an elastic modulus of at least 15000 Psi; in other embodiments, it may have an elastic modulus of at least 16000 Psi; in other embodiments, it may have an elastic modulus of at least 17000 Psi.

In some embodiments, the thermosetting composite material disclosed in the present invention has an elastic modulus of at least 10,000 psi when measured in accordance with the requirements of ASTM D638; in other embodiments, the thermosetting composite material disclosed in the present invention has a tensile strength of at least 12,000 psi; in other embodiments, it has a tensile strength of at least 13,000 psi; in other embodiments, it has a tensile strength of at least 14,000 psi; in other embodiments, it has a tensile strength of at least 15,000 psi.

In some embodiments, the thermosetting composite material disclosed in the present invention has at least 1% elongation at break, measured in accordance with the requirements of the American Society for Testing and Materials D638. In other embodiments, the thermosetting composite material disclosed in the present invention has at least 1.5% elongation at break; in other embodiments, at least 2.5% elongation; in other embodiments, at least 3% elongation.

Component A (primary epoxy resin, high glass transition temperature epoxy resin) shown in Figure 1 forms the bulk material backbone and is a continuous, dominant phase, providing high mechanical strength under high temperature conditions; while the low glass transition temperature epoxy resin accelerates the degradation rate, resulting in rapid dissolution at lower temperatures. Component B (secondary epoxy resin, low glass transition temperature epoxy resin) shown in Figure 1 rapidly dissolves, increasing the open channels, and then the increased contact area can accelerate the degradation rate of component A phase, thus leading to the final degradation of the bulk material. To achieve this, no dual continuous phase can do it. First, the volume ratio of component A should be at least higher than 50%. The higher the volume ratio, the better the effect of application in a high temperature environment, because component A provides mechanical strength at high temperatures. In addition, a solid base (such as Ca(OH) ₂ , CaO, Mg(OH) ₂ , KOH, etc.) or a solid acid (such as aminosulfonic acid) should be used as a degradation catalyst (main catalyst).

The thermosetting resin described above can be formed into a curing component by mixing an epoxy resin mixture, a primary catalyst, and an aliphatic anhydride crosslinking agent; in some embodiments, the curing component is exposed to a high temperature environment, such as a temperature greater than or equal to about 150°C, in other embodiments, a temperature greater than or equal to about 175°C; in other embodiments, a temperature greater than or equal to about 200°C. The curing component disclosed in the present invention, as described above, exhibits high reactivity; in some embodiments, the curing component can be cured by exposing the curing component to a temperature greater than the above-mentioned temperature for an exposure time of less than or equal to about 5 minutes; in other embodiments, the exposure time is less than or equal to 3 minutes; in other embodiments, the exposure time is less than or equal to about 2 minutes. In other embodiments, the exposure time is less than or equal to about 1 minute; in other embodiments, the exposure time is less than or equal to about 45 seconds.

More specifically, as shown in FIG. 2 , the process of forming a degradable thermosetting composite material may include the following steps: S1, mixing a low glass transition temperature epoxy resin with a high glass transition temperature epoxy resin; S2, adding a cross-linking agent and a solid catalyst (main catalyst) and mixing them evenly; S3, mixing with fibers to make raw materials, such as prefabricated integral molding materials, sheet molding materials, etc.; S4, molding into a near-net-shape part using a hot press; S5, post-heat treatment to improve mechanical properties, and if necessary, additional processing.

In order to maintain mechanical strength at high temperatures, the low glass transition temperature epoxy resin content needs to be less than 50% by weight. Above 50% by weight, the glass transition temperature of the final composite material is greatly reduced. The higher the high glass transition temperature epoxy resin content, the higher the glass transition temperature of the final component, but the degradation rate is relatively lower. In the second step, a crosslinking agent (acid anhydride) and a solid catalyst powder (main catalyst) are added and mixed evenly; the amount of the crosslinking agent and the solid catalyst (main catalyst) depends on the requirements of the degradation rate. Usually, a chemical equivalent ratio between epoxy resin and crosslinking agent is used, and 30% is also acceptable, or used to adjust the mechanical strength. The weight ratio between the organic resin (including the crosslinking agent) and the main catalyst is between about 5:1 and 2:1. Using standard industrial methods, fibers are introduced internally to make so-called prefabricated integral molding materials or sheet molding materials. The amount of added fibers is between about 20% and about 60%, which depends entirely on the mechanical strength requirements. Finally, these raw materials are cured under temperature and pressure (such as a hot pressing process) to form the degradable thermosetting composite material having a dual continuous microstructure. Post-heat treatment may be required to improve mechanical properties (e.g., reduce stress or increase crosslink density). If it cannot be directly molded into a web-like shape, additional processing may be required.

As described above, the curable component and the thermosetting resin can be formed from an epoxy resin mixture, and the mixture includes an aromatic epoxy resin mixture or a flexible epoxy resin mixture having at least a bisphenol A epoxy resin and a cycloaliphatic anhydride crosslinking agent. Other epoxy resins, added crosslinking agents, catalysts, toughening agents, flame retardants and other additives can also be used in the components disclosed in the present invention. Each of these components will be described in detail below.

Flexible epoxy resin

In the embodiments disclosed herein, useful flexible epoxy resins may include ethylene glycol modified epoxy resins, polypropylene glycol modified aliphatic epoxies; epoxidized polybutadiene; epoxidized caprolactone and caprolactone, silicone resins containing epoxy functionality; epoxy vinyl ester resins, etc. In some embodiments, the flexible epoxy resin may include bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate; bis(3,4-epoxycyclohexyl) adipate (ERL-4299 produced by The Dow Chemical Company, Midland, Michigan, USA). In other embodiments, the flexible epoxy resin may include zeta-caprolactone modified with (3'-4'-epoxycyclohexane) 3'-4'-epoxycyclohexylcarboxylic acid methyl ester (CELLOXIDE 2080 series produced by Daicel Chemical Industries, Ltd., Japan).

Other flexible epoxy resins may include polymeric epoxies, including linear polymers with terminal epoxy groups (e.g., diglycidyl ethers of polyoxyalkylene glycols), polymer backbone ethylene oxide units (e.g., polybutadiene polyepoxides), and polymers with pendant epoxy groups (e.g., glycidyl methacrylate polymers or copolymers).

Other flexible epoxy resins may include glycidyl resins, epoxidized oils, etc. Glycidyl resins are usually the reaction product of epichlorohydrin and bisphenol compounds (such as bisphenol A, etc.); C4-C28 alkyl glycidyl ethers; C2-C28 alkyl glycidyl esters and alkenyl glycidyl esters; C1-C28 alkyl, monophenol and polyphenol glycidyl ethers; polyglycidyl ethers of polyvalent phenols, such as catechol, resorcinol, hydroquinone, 4,4'-dihydroxydiphenylmethane (or bisphenol F), 4,4'-dihydroxy-3,3'-dimethyldiphenylmethane, 4,4'-dihydroxydiphenylmethylmethane (or bisphenol A) , 4,4'-dihydroxydiphenylcyclohexane, 4,4'-dihydroxy-3,3'-dimethyldiphenylpropane, 4,4'-dihydroxydiphenyl sulfone and tris(4-hydroxyphenyl)methane; polyglycidyl ethers of chlorination and bromination products of the above dihydric phenols; polyglycidyl ethers of phenolic resins; diphenol polyglycidyl ethers obtained by esterifying a salt of an aromatic hydrocarboxylic acid with a dihalogenated alkane or a dihalogenated dialkyl ether, and then esterifying the diphenol ether; polyglycidyl ethers of polyphenols obtained by condensing phenol and a long-chain halogen alkane containing at least two halogen atoms. Other examples of epoxy resins used in the embodiments disclosed in the present invention include bis-4,4'-(1-methylethylidene)phenol diglycidyl ether and (chloromethyl)ethylene oxide bisphenol A diglycidyl ether.

Still other epoxy resin-containing materials are copolymers of glycidyl acrylates, such as glycidyl esters and glycidyl methacrylate with one or more copolymerizable vinyl compounds. Examples of such copolymer ratios are 1:1 styrene-glycidyl methacrylate, 1:1 methyl methacrylate-glycidyl ester, and 62.5:24:13.5 methyl methacrylate-ethyl acrylate-glycidyl methacrylate.

Other flexible epoxy resins may include, for example, cycloaliphatic epoxy resins or non-cycloaliphatic epoxy resins. Cycloaliphatic epoxy resins useful in various embodiments disclosed herein are described in U.S. Pat. Nos. 6,329,475, 6,329,473, 5,783,713, 5,703,195, 5,646,315, 5,585,446, 5,459,208, and 4,532,299, among others.

Since the main function of flexible epoxy resin is to provide a high dissolution or degradation rate, a high Tg value is not required. In order to increase the dissolution or degradation rate, there are two strategies: one is to use epoxy resins with linear polymer chains, and the other strategy is to select epoxy resins with ester groups on the polymer chain. For practical application in the plugging market, such epoxy resins should be cost-effective, safe/easy to process, and can be manufactured commercially on a large scale. The following selection scheme provides an embodiment that can meet these requirements:

1. Glycerol substituted polyglycidyl ether

2. Diglycidyl phthalate

3. Dimer acid diglycidyl ester

Phenolic resin and multifunctional epoxy resin

Epoxy novolac resins useful in some embodiments disclosed herein include formaldehyde-containing phenolic condensates obtained under acidic conditions such as phenol novolac resins, bisphenol A novolac resins, and cresol novolac resins.

Suitable polyfunctional (polyepoxide) compounds include resorcinol glycidyl ether (1,3-bisphenyl (2,3-epoxypropoxy)), triglycidyl p-aminophenol (4-(2,3-epoxypropoxy))-N,N-bis(2,3-epoxypropyl)aniline), m-aminophenol and/or p-aminophenol (3-(2,3-epoxypropoxy) N triglycidyl ether, N-bis(2,3-epoxypropyl)phthalic anhydride) and tetraglycidyl ether methylenedianiline (N,N,N′,N′-tetrakis(2,3-epoxypropyl) 4,4′-diaminodiphenylmethane), and mixtures of two or more polyepoxides. A more comprehensive list of useful epoxy resins is given in Handbook of Epoxy Resins by Lee, H. and Neville, K., republished by McGraw-Hill Book Company in 1982.

Other suitable epoxy resins include polyepoxides based on aromatic amines and epichlorohydrin, such as N,N′-diglycidylamine, N,N′-dimethyl-N,N′-diglycidyl-4,4′-diaminodiphenylmethane, N,N,N′,N′-tetraglycidylether-4,4′-diaminodiphenylmethane, N-diglycidyl-4-aminophenylglycidylether and N,N,N′,N′-tetraglycidyl-1,3-propadiene-4-p-aminobenzoate. Epoxy resins also include one or more glycidyl ether derivatives of the following: aromatic diamines, aromatic monoprimary amines, polyol phenolic compounds, polyhydric alcohols, polycarboxylic acids.

Other suitable epoxy resins are disclosed in U.S. Pat. No. 5,112,932, which is incorporated herein by reference. Such epoxy resins include epoxy-terminated polyoxazolidinone compounds, for example, including the reaction product of a polyepoxide and a polyisocyanate compound. Polyepoxides include 2,2-bis(4-hydroxypropyl)propane diglycidyl ether (commonly referred to as bisphenol A) and 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane diglycidyl ether (commonly referred to as tetrabromobisphenol A). Suitable polyisocyanates include 4,4′-methylenebis(phenyl isocyanate) (MDI) and its isomers, higher functional homologs of MDI (commonly designated as “polymeric MDI”), toluene diisocyanates (TDI), such as 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, meta-xylylene diisocyanate, hexamethylene isocyanate (HMDI), and isophorone diisocyanate.

Examples of epoxy novolac resins and epoxy bisphenol A novolac resins useful in the various embodiments disclosed herein include phenol formaldehyde novolac resins, such as those available under the trade designation D.E.N. 431, available under the trade designation D.E.N. 438 from The Dow Chemical Company, Midland, Michigan, USA, and available under the trade designation EPON SU-8 from Hanson Chemical Company, Inc.

Bisphenol A and Bisphenol F epoxy resin

Other epoxy resins that can be used in various embodiments disclosed herein include 4,4′-dihydroxybiphenyldimethylmethane (or bisphenol A), bis(4-hydroxyphenyl)methane (referred to as bisphenol F), bromobisphenol A (2,2-bis(4-(2,3-epoxypropoxy)3-bromo-phenyl)propane), bisphenol F (2,2-bis(p-2,3-epoxypropoxy)phenyl)methane, and other bisphenol A and bisphenol F based epoxy resins. Bisphenol-A based epoxy resins include, for example, bisphenol A diglycidyl ether, D.E.R. 332, D.E.R. 383, and D.E.R. 331 from The Dow Chemical Company, Midland, Michigan, USA. Bisphenol F based epoxy resins include, for example, bisphenol-F diglycidyl ether and D.E.R. 354 and D.E.R. 354LV, each available from The Dow Chemical Company, Midland, Michigan, USA.

Useful epoxy resins include, for example, polyhydroxy polyol polyglycidyl ethers such as ethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, glycerol and 2,2-bis(4-hydroxycyclohexyl)propane, polyol diglycidyl or polyglycidyl ethers such as 1,4-butanediol or polyalkylene glycols such as polypropylene glycol; polyol phenolic compounds including resorcinol, 2,2-bis(4′-hydroxy-3′,5′-dibromophenyl)propane, 1,2,6-hexanetriol, glycerol and 2,2-bis(4-hydroxycyclohexyl)propane; 1,2,2-(4′-hydroxy-phenyl)ethane, aliphatic and aromatic polyhydroxy acid polyglycidyl ethers, such as glycolic acid, succinic acid, glutaric acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid, dimerized linoleic acid; polyphenol polyglycidyl ethers, such as 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)isobutane and 1,5-dihydroxynaphthalene; epoxy resins partially modified with acrylates or urethanes, glycidylamine epoxy resins and phenolic resins.

Since the target operating temperature is from about 110 to about 175°C, the component A epoxy resin needs to have a glass transition temperature of at least about 120°C, preferably above about 180°C, given the reduced glass transition temperature when mixed with the low glass transition temperature component B. In addition to the high glass transition temperature, for bridge plug applications, this category of epoxy resins should be cost-effective, safe and easy to handle, and commercially available on a large scale. The following selections provide examples that meet these requirements:

2.1 Different brands of bisphenol A glycidyl ether (BADGE) epoxy resin include Resin series, DE series, series, series, Series and ERL Epoxy resin series

2.2 Phenolic resin polyglycidyl ether and cresol resin polyglycidyl ether

2.3 Aromatic glycidylamine

Anhydride crosslinking agent

The curable components disclosed herein include one or more cycloaliphatic anhydride crosslinking agents. Cycloaliphatic anhydride crosslinking agents include, for example, methyl nadic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, dodecyl succinic anhydride, phthalic anhydride, methyl hexahydrophthalic anhydride, tetrahydrophthalic anhydride, and methyl tetrahydrophthalic anhydride, etc. Anhydride curing agents also include copolymers of styrene and maleic anhydride and other anhydrides described in U.S. Pat. No. 6,613,839, which is incorporated herein by reference.

Most commercially available anhydrides are easy to process and cost-effective. Examples include:

Among them, PA is polyamide, THPA is tetrahydrophthalic anhydride, HHPA is hexahydrophthalic anhydride, MTHPA is methyltetrahydrophthalic anhydride, MHHPA is methylhexahydrophthalic anhydride, MTHPA is methyltetrahydrophthalic anhydride, and NMA is methylacetamide.

Additional epoxy resin

Additional epoxy resins can be used to adjust the properties of the resulting thermosetting resin as desired. The additional epoxy resin component can be any type of epoxy resin, including any material containing one or more reactive oxirane groups, referred to herein as "epoxy groups" or "epoxy functionality". Additional epoxy resins useful in the embodiments disclosed herein include monofunctional epoxy resins, multifunctional or multifunctional epoxy resins, and combinations thereof. Monomeric and polymeric epoxy resins can be aliphatic, aromatic or heterocyclic epoxy resins. Epoxy resins can be compounds, but are typically mixtures or compounds based on molecules containing one or more epoxy groups. In some embodiments, epoxy resins also include reactive -OH groups that can react with anhydrides, organic acids, amino resins, phenolic resins or epoxy groups (when catalyzed) at higher temperatures to produce additional crosslinks.

Other suitable epoxy resins are disclosed, for example, in U.S. Pat. Nos. 7,163,973, 6,887,574, 6,632,893, 6,242,083, 7,037,958, 6,572,971, 6,153,719, and 5,405,688, Patent Cooperation Treaty International Publication No. WO 2006/052727, and U.S. Patent Application Publication Nos. 20060293172 and 20050171237, each of which is incorporated herein by reference.

Additional crosslinker/curing agent

In addition to the dicyandiamide described above, additional crosslinking agents or curing agents may also be provided to promote crosslinking of the epoxy resin component to form a polymer component. As with the epoxy resin, additional crosslinking agents or curing agents may also be used alone or as a mixture of two or more. The curing agent component (also called a crosslinking agent) includes any compound having an active group that reacts with the epoxy group of the epoxy resin. Curing agents include nitrogen-containing compounds, such as amines and their derivatives; oxygen-containing compounds, such as hydroxy acid-terminated polyethers, anhydrides, phenol novolac resins, bisphenol A novolac resins, DCPD-phenol condensation products, brominated phenol oligomers, amino-formaldehyde condensates, phenol, bisphenol A and cresol novolac resins, phenolic end epoxy resins; sulfur-containing compounds, such as polysulfides, polymercaptans, etc.; catalytic curing agents, such as tertiary amines, Lewis acids, Lewis bases, and two or more combinations of the above curing agents. In practice, for example, polyamines, dapsone and their isomers, aminobenzoic acid ester compounds, various acid anhydrides, phenol-phenolic resins and cresol-phenolic resins may be used, but the present disclosure does not limit the use of these compounds.

Other examples of crosslinking agents that may be used are described in US Pat. No. 6,613,839, and include copolymers of styrene and maleic anhydride having a molecular weight range of 1500 to 50,000 and an anhydride content exceeding 15%.

Other useful ingredients in the components disclosed in the present invention include curing catalysts. Examples of curing catalysts include imidazole derivatives, tertiary amines, ammonium salts, phosphonium salts, and organic metal salts. Other examples of such curing catalysts include free radical photoinitiators, such as azo compounds containing azobisisobutyl cyanide, and organic peroxides, such as tert-butyl perbenzoate, tert-butyl peroxyoctanoate, benzoyl peroxide, etc.; including butanone peroxide, peroxyacetoacetic acid, hydroxyisopropylbenzene peroxide, cyclohexanone hydroperoxide, diisopropylbenzene peroxide, and mixtures thereof. Methylethyl copper peroxide and benzoyl peroxide are preferably used in the present invention.

In some embodiments, the curing agent includes primary and secondary polyamines and adducts thereof, anhydrides and polyamides. For example, multifunctional amines include fatty amine compounds such as diethylenetriamine (D.E.H. 20 available from Dow Chemical Company, Midland, Michigan, USA), triethylenetetramine (D.E.H. 24 available from Dow Chemical Company, Midland, Michigan, USA), tetraethylenepentamine (D.E.H. 26 available from Dow Chemical Company, Midland, Michigan, USA) and adducts of the above amines with epoxy resins, diluents or other amine reactive compounds. Aromatic amines such as m-phenylenediamine and diaminodiphenyl sulfone, aliphatic polyamines such as aminoethylpiperazine and polyethylene polyamines, aromatic polyamines such as m-phenylenediamine, diaminodiphenyl sulfone, diethyltoluenediamine, etc. are also used.

In some embodiments, the phenolic novolac crosslinker includes a biphenyl or naphthyl moiety. The phenolic hydroxyl group is connected to the biphenyl or naphthyl moiety compound. This type of crosslinker is made, for example, according to the method described in EP915118A1. For example, a crosslinker containing a biphenyl group can be made by reacting phenol with bismethoxy-methylene biphenyl.

In other embodiments, the curing agent includes boron trifluoride monoethylamine and cyclohexanediamine. Curing agents also include imidazoles and their salts and adducts. These epoxy resin curing agents are generally solid at room temperature. Examples of suitable imidazole curing agents include 2-phenylimidazole; other suitable imidazole curing agents are disclosed in EP906927A1. Other curing agents include aromatic amines, aliphatic amines, anhydrides and phenols.

In some embodiments, the curing agent may be an amino compound having a molecular weight of up to 500 per amino group, such as an aromatic amine or a guanidine derivative, etc. Examples of amino curing agents include 4-chlorophenyl-N,N-dimethyl-urea and 3,4-dichlorophenyl-N,N-dimethyl-urea.

Other useful curing agent examples in the embodiments disclosed herein include: 3,3′- and 4,4′-diaminodiphenyl sulfone; diaminodiphenylmethane; bis(4-amino-3,5-dimethylphenyl)-1,4-diisopropylbenzene, such as Shell Chemical Company EPON 1062; bis(4-aminophenyl)-1,4-diisopropylbenzene, such as Shell Chemical Company EPON 1061.

Epoxy resin compound thiol curing agents are also used, for example, as described in U.S. Pat. No. 5,374,668. As thiols used in the present invention, polythiols or polythiols curing agents are also included. Exemplary thiols include aliphatic thiols such as methanedithiol, propylenedithiol, cyclohexanedithiol, 2-mercaptoethyl-2,3-dimercaptosuccinic acid, 2,3-dimercapto-1-propanol (2-mercaptoacetic acid ester), diethylene glycol bis(2-mercaptoacetic acid ester), 1,2-dimercaptopropyl methyl ether, bis(2-mercaptoethyl) ethyl ether, trimethylolpropane tris(mercaptoacetic acid), pentaerythritol tetra(mercaptopropionate), pentaerythritol tetra(mercaptoacetic acid), dithioglycolic acid Ethylene glycol esters, trimethylolpropane tris(β-thiopropionate), propoxylated alkyl triglycidyl ether trithiol derivatives, dipentaerythritol poly(β-thiopropionate); aliphatic thiol halogenated derivatives; aromatic thiols, such as dithiophenol, trithiophenol, tetrathiophenol, di(mercaptoalkyl)benzene, tri(mercaptoalkyl)benzene, tetra(mercaptoalkyl)benzene, dithiobiphenyl, toluene dithiol and naphthalene dithiol; aromatic thiol halogenated derivatives; heterocyclic thiols, such as amino-4,6 -dithiol-s-triazine, alkoxy-4,6-dithiol-s-triazine, aryloxy--4,6-dithiol-s-triazine and 1,3,5-tris(3-mercaptopropyl)isocyanurate; heterocyclic thiol halogenated derivatives; having at least two mercapto groups, in addition to the mercapto group, containing sulfur atoms, such as di(mercaptoalkyl)benzene, tri(mercaptoalkyl)benzene, tetra(mercaptoalkyl)benzene, di(mercaptoalkyl)alkanes, tri(mercaptoalkyl)alkanes, tetra(mercaptoalkyl)alkanes, di(mercaptoalkyl)alkanes (Mercaptoalkyl) disulfide, hydroxyalkylthiobis(mercaptopropionate), hydroxyalkylthiobis(mercaptoacetate), mercaptoethyl ether bis(mercaptopropionate), 1,4-dithiane-2,5-diol bis(mercaptoethyl ether), thiodiacetic acid bis(mercaptoalkyl ester), thiodipropionic acid bis(2-mercaptoalkyl ester), 4,4-thiobutyric acid bis(2-mercaptoalkyl ester), 3,4-thiophenedithiol, thiadiazole and 2,5-dimercapto-1,3,4-thiadiazole, etc.

The curing agent can also be a nucleophilic substance, such as amine, tertiary phosphine, quaternary ammonium salt of nucleophilic anion, quaternary phosphonium salt of nucleophilic anion, imidazole, tertiary arsenate of nucleophilic anion, tertiary sulfide salt of nucleophilic anion.

Aliphatic polyamines modified by addition with epoxy resins, acrylonitrile or (meth)acrylates can also be used as curing agents. In addition, different Mannich bases are also used. Aromatic amines in which the amino group is directly linked to the aromatic ring can also be used.

In the embodiments disclosed in the present invention, the nucleophilic anion quaternary ammonium salts which are very useful as curing agents include tetraethylammonium chloride, tetrapropylammonium acetate, hexyltrimethylammonium bromide, benzyltrimethylammonium cyanide, hexadecyltriethylammonium azide, N,N-dimethylpyridine cyanate, N-methylpyridine Hydrophenol, N-methyl-o-pyridinium chloride, methyl viologen dichloride, etc.

It has been reported that epoxy resins can be cured by different chemical components, including amines, acids, etc. In order to make epoxy resins degradable, anhydrides can be used as crosslinking agents to introduce ester bonds into the crosslinked polymer chains (Figure 3, middle). The esters are broken down by a hydrolysis process, as shown in the right part of Figure 3. This process is usually slow and requires extremely high temperatures to activate. In order to make the degradation process suitable for downhole applications, we add solid bases (such as Ca(OH) ₂ , CaO, Mg(OH) ₂ , KOH, etc.) as main catalysts or fillers to accelerate the hydrolysis process, as shown in Figure 4.

In some embodiments, at least one cationic photoinitiator may be used. Cationic photoinitiators include compounds that can be decomposed when exposed to electromagnetic radiation of a specific wavelength or a specific wavelength range to form cationic species, which can catalyze polymerization reactions between epoxy groups and hydroxyl groups, etc. Cationic species can also catalyze the reaction of epoxy groups with other epoxide reactive species contained in the curing component (such as other hydroxyl groups, amine groups, phenolic hydroxyl groups, thiol groups, anhydride groups, hydroxy acid groups, etc.). Examples of cationic photoinitiators include diaryliodonium Salt and triarylsulfonium gold For example, diaryliodonium salt-type photoinitiators are available from Seba-Gage Corporation under the trade name IRGACURE 250. A type photoinitiator is available from The Dow Chemical Company as triphenylthiohexafluorophosphate 6992. A cationic photoinitiator may be used in a catalytically effective amount, approximately 10% by weight of the curing composition.

Catalysts that promote reactions

In some embodiments, a catalyst may be used to promote the reaction between the epoxy resin component and the curing agent or crosslinking agent, including the dicyandiamide and phenolic crosslinking agents described above. The catalyst includes a Lewis acid (for example), and boron trifluoride is convenient as an amine salt derivative such as piperidine or methylethylamine. The catalyst may also be a basic, such as an imidazole or an amine. Other catalysts include other metal halide Lewis acids, including tin chloride, zinc chloride, etc., metal carboxylates, such as stannous octoate, etc., benzyl dimethylamine, dimethylaminomethylphenol and amines, such as triethylamine, imidazole derivatives, etc.

Tertiary amine catalysts are described, for example, in U.S. Pat. No. 5,385,990, which is incorporated herein by reference. Tertiary amines include methyldiethanolamine, triethanolamine, diethylaminopropylamine, benzyldimethylamine, m-xylenediamine (dimethylamine), N,N′-dimethylpiperazine, N-methylpyrrolidine, N-methylhydroxypiperidine, N,N,N′N′-tetramethyldiaminoethane, N,N,N′,N′,N′-pentamethyldiethylenetriamine, tributylamine, trimethylamine, decanediamine, triethylenediamine, N-methylmorpholine, N,N,N′N′-tetramethylpropylenediamine, N-methylpiperidine, N,N′-dimethyl-1,3-(4-piperidinylpropane), pyridine, and the like. Other tertiary amines include 1,8-diazobicyclo[5.4.0]-7-ene, 1,8-diazabicyclo[2.2.2]octane, 4-dimethylaminopyridine, 4-(N-pyridyl)pyridine, triethylamine, and 2,4,6-tris(dimethylaminomethyl)phenol.

Primary catalysts that aid in the degradation of composite materials

As discussed above, the solid base or solid acid includes but is not limited to Ca(OH) ₂ , CaO, Mg(OH) ₂ , KOH, NaOH, etc. Without the action of the primary catalyst, even the low glass transition temperature component B cannot be hydrolyzed.

Toughening agent

When epoxy resin is cured, toughening agent can be used to prevent the composite material disclosed by the present invention from becoming brittle. In certain embodiments, toughening agent can be rubber compound and ball-shaped copolymer. Toughening agent plays a role by forming a second phase in the polymer matrix. This second phase is rubbery, so it can inhibit crack growth and improve impact toughness.

The toughener used to improve the epoxy resin fracture toughness comprises FORTEGRA 100, group copolymer, carboxyl-terminated nitrile rubber, amphoteric group copolymer, linear polybutadiene-polyacrylonitrile copolymer, oligomeric polysiloxane and organopolysiloxane resin.Other tougheners can include carboxyl-terminated butadiene, based on polysulfide toughener, amino-terminated butadiene nitrile and polythioether.Toughener (for example) is described in No. 5262507, No. 7087304 and No. 7037958, U.S. Patent Application Publication No. 20050031870 and No. 20060205856, etc., of U.S. Patent. Amphiphilic toughening agents are disclosed, for example, in Patent Cooperation Treaty Patent Application Publications WO2006/052725, WO2006/052726, WO2006/052727, WO2006/052729, WO2006/052730, and WO2005/097893, U.S. Pat. No. 6,887,574, and U.S. Patent Application Publication No. 20040247881.

The amount of toughening agent used in the curable composition described in the present invention depends on many different factors, including the polymer equivalent weight, and the desired properties of the product made from the composition. In general, based on the total weight of the curable composition, in some embodiments, the amount of toughening agent is from 0.1 weight percent to 30 weight percent, in other embodiments, from 0.5 weight percent to 10 weight percent, and in other embodiments, from 1 weight percent to 5 weight percent.

Optional additives

The curable components and thermosetting resins disclosed in the present invention may optionally include conventional additives and fillers. Additives and fillers may include, for example, other flame retardants, boric acid, silicon dioxide, glass, talc, metal powder, titanium dioxide, wetting agents, pigments, colorants, mold release agents, coupling agents, ion scavengers, UV stabilizers, tougheners, tackifiers. Additives and fillers also include fumed silica, aggregates such as glass beads, polytetrafluoroethylene, polyol resins, polyester resins, phenolic resins, graphite, molybdenum disulfide, abrasive pigments, viscosity reducers, boron nitride, mica, nucleating agents and stabilizers, etc. Before adding the epoxy resin component, the filler and modifier are pretreated to remove moisture. In addition, before and after curing, these optional additives have an impact on the performance of the component, which needs to be taken into account when making the component and the desired reaction product. The curable components disclosed in the present invention may also optionally include other additives of the general conventional type, including, for example, stabilizers, other organic or non-organic additives, pigments, wetting agents, fluid modifiers, ultraviolet blockers, fluorescent additives. In some embodiments, these additives are present in an amount from 0 to 5 weight percent, and in other embodiments, less than 3 weight percent. Examples of suitable additives are also described in U.S. Patent No. 5,066,735 and Patent Cooperation Agreement U.S. 2005/017954.

Curable components

The thermosetting composite material of the present invention can be formed by synthesizing the following material compounds: a) aromatic epoxy resin, b) one or more flexible epoxy resins; c) primary catalyst; d) anhydride crosslinking agent. Aromatic epoxy resins include epoxy phenolic resins, epoxy bisphenol A phenolic resins, multifunctional epoxy resins, bisphenol A or bisphenol F based epoxy resins and (for example) polyether polyols. The above raw materials are also the raw materials of the curable component of the present invention, and the curable component can also be added with additional crosslinking agents, epoxy resins, catalysts, toughening agents and other additives.

The relative proportions of epoxy resin and cycloaliphatic anhydride crosslinker depend in part on the properties desired of the curing component or thermosetting component produced, on the desired curing reaction of the component and on the desired storage stability of the component (desired shelf life).

In some embodiments, the epoxy resin mixture (a mixture of an aromatic epoxy resin and other epoxy resins as described above) may be present in the curing component, ranging from 0.1 to about 99 weight percent in the curing component, based on the total weight of the epoxy resin mixture, the primary catalyst, and the anhydride crosslinking agent. In other embodiments, the epoxy resin component ranges from about 5 to about 95 weight percent; in other embodiments, the weight ranges from about 5% to about 95%; in other embodiments, the weight ranges from about 15% to about 85%; in other embodiments, the weight ranges from about 25% to about 75%; in other embodiments, the weight ranges from about 35% to about 65%; in other embodiments, the ranges from about 40 to about 60 weight percent; wherein the above percentages are based on the total weight of the epoxy resin mixture, the primary catalyst, and the cycloaliphatic anhydride crosslinking agent.

In some embodiments, an anhydride crosslinking agent, such as a mixture of alicyclic crosslinking agents or cycloaliphatic anhydride crosslinking agents, may be present in the curable component in an amount ranging from 0.1 to 99 weight percent based on the total weight of the epoxy resin mixture, the primary catalyst, and the cycloaliphatic anhydride crosslinking agent. In other embodiments, the cycloaliphatic anhydride crosslinking agent ranges from 5 to 95 weight percent in the curable component; in other embodiments, ranging from 15 to 85 weight percent; in other embodiments, ranging from 25 to 75 weight percent; in other embodiments, ranging from 35 to 65 weight percent; in other embodiments, ranging from 40 to 60 weight percent; wherein the above percentages are based on the total weight of the epoxy resin mixture, the primary catalyst, and the cycloaliphatic anhydride crosslinking agent.

In some embodiments, the primary catalyst is present in the curable component in an amount ranging from 0.01 weight percent to 10 weight percent. In other embodiments, the primary catalyst is present in an amount ranging from 0.1 weight percent to 8 weight percent; in other embodiments, the primary catalyst is present in an amount ranging from 0.5 weight percent to 6 weight percent; the primary catalyst is present in an amount ranging from 1 weight percent to 4 weight percent; wherein the above percentages are based on the total weight of the epoxy resin mixture, the primary catalyst, and the cycloaliphatic anhydride crosslinking agent.

Additional epoxy resins may be used in some curable component embodiments in an amount ranging from 0.01 weight percent to 20 weight percent based on the total weight of the curable component. In other embodiments, the additional epoxy resin is present in an amount ranging from 0.1 weight percent to 8 weight percent; in other embodiments, the additional epoxy resin is present in an amount ranging from 0.5 weight percent to 6 weight percent; in other embodiments, the additional epoxy resin is present in an amount ranging from 1 weight percent to 4 weight percent;

Additional crosslinking resins may be used in some curable component embodiments in an amount ranging from 0.01 weight percent to 20 weight percent based on the total weight of the curable component. In other embodiments, the additional crosslinking agent is present in an amount ranging from 0.1 weight percent to 8 weight percent; in other embodiments, the additional crosslinking agent is present in an amount ranging from 0.5 weight percent to 6 weight percent; in other embodiments, the additional crosslinking agent is present in an amount ranging from 1 to 4 weight percent;

Based on the total volume of the curable component, in some embodiments, the curable component also includes from about 0.1 to about 50 volume percent of optional additives. In other embodiments, the curable component also includes from about 0.1 to about 5 volume percent of optional additives; in other embodiments, the curable component also includes from about 0.5 to about 2.5 volume percent of optional additives.

Composite materials and coated structures

In some embodiments, the composite material is formed by curing the curable components disclosed in the present invention. In other embodiments, the composite material can be formed by applying the curable components to a matrix or a reinforcing material. Such as by impregnating the matrix or reinforcing material, or by curing the curable components to form the composite material.

The curable component is present in the form of a powder, slurry or liquid. After the curable component is formed, it can be disposed on, in, between, before, during, or after curing the curable component, as described above.

For example, the composite material can be formed by coating a substrate with the curable composite material. Coating can be performed by various techniques including spraying, curtain coating, coating with a roll coater or gravure coater, brushing, dipping or immersion coating.

In various embodiments, the substrate can be a single layer or multiple layers. For example, the substrate can be two alloys, multiple layers of polymeric particles and metal-coated polymers, etc. For example, in other embodiments, one or more layers of curable components can be disposed on or within the substrate. Other multilayer composites formed by different substrate layers and different syntheses of curable components are also contemplated in the present invention.

In some embodiments, for example, heating of the curable component is localized so as to avoid overheating of a temperature sensitive substrate. In other embodiments, heating includes heating of the substrate and the curable component.

Curing of the curable components disclosed herein requires a temperature of at least about 30°C, up to about 250°C, for a period of several minutes to several hours, depending on the resin component, crosslinking agent, and primary catalyst (if used). In other embodiments, curing occurs at a temperature of at least about 100°C, for a period of several minutes to several hours. Post-treatments may also be used, such post-treatments are typically at a temperature of about 100°C to 250°C.

In some embodiments, curing can be performed in stages to prevent exotherm. For example, the staged curing includes curing at a certain temperature for a period of time, and then curing at a higher temperature for a period of time. The staged curing includes two or more curing stages, and in some embodiments, it can be started at a temperature below about 180°C. In other embodiments, it is started at a temperature below about 150°C.

In some embodiments, the curing temperature ranges from a lower temperature range of about 30°C, about 40°C, about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, about 110°C, about 120°C, about 130°C, about 140°C, about 150°C, about 160°C, about 170°C or about 180°C to an upper temperature range of about 250°C, about 240°C, about 230°C, about 220°C, about 210°C, about 200°C, about 190°C, about 180°C, about 170°C, about 160°C; wherein the range can be from any lower limit to any upper limit.

The curable components and composite materials described in the present invention are very useful, in addition to being used as downhole tools, they can also be used as adhesives, structural and electrical laminates, coatings, castings, downhole temporary plugging agents, aerospace industry structures, circuit boards, electrical industry circuit boards and other applications. The curable components disclosed in the present invention can also be used in electrical varnishes, potting glue, semiconductors, general molding powders, fiber winding pipes, storage tanks, pump cylinder liners, anti-corrosion coatings, and other aspects. In selected embodiments, the curable components described in the present invention are very useful in making resin coating films, which are similar to those described in U.S. Patent No. 6,432,541, which is incorporated by reference into the present invention.

Different processing techniques can be used to form the composite materials containing epoxy components disclosed in the present invention. For example, filament winding, solvent prepreg and pultrusion are typical processing techniques in which uncured epoxy resin can be used. In addition, bundled fibers can be coated with uncured epoxy resin components, laid by filament winding, and then cured to form a composite material.

Example

The cured degradable glass transition temperature is adjusted according to the ratio of component A epoxy resin to component B epoxy resin; the volume fraction of component A should be greater than 50%. As one example, FIG5 shows the upper limit of the glass transition temperature (Tg) in the production, which is about 200°C (100% component A), and FIG6 shows the lower limit of the glass transition temperature of the system, which is about 100°C (50% component A and 50% component B).

The present invention is described in detail below with reference to specific embodiments.

Example 1

The present embodiment provides a degradable thermosetting composite material, which is prepared from the following raw materials, measured by weight percentage: 33% of bisphenol A glycidyl ether (BADGE) epoxy resin (component A), 13% of dimer acid diglycidyl ester (component B), 46% of hexahydrophthalic anhydride (anhydride crosslinking agent), 7% of Mg(OH) ₂ (main catalyst) and 1% of 2-ethyl-4-methylimidazole (crosslinking catalyst).

The preparation method of the degradable thermosetting composite material is as follows: the raw materials are mixed and put into a mold, cross-linked for 10 minutes at a temperature of 150° C. and a pressure of 10 atm, and then heat-treated at 170° C. for 2 hours after vacuuming to obtain the degradable thermosetting composite material.

After testing, as shown in FIG. 7 , the glass transition temperature of the degradable thermosetting composite material can reach 140° C., and the degradable thermosetting composite material can be completely degraded in a 3% KCl solution at 95° C. within two weeks.

Example 2

The present embodiment provides a degradable thermosetting composite material, which includes a mixed resin and carbon fiber. The mixed resin is prepared from the following raw materials, in weight percentage: 33% of phenolic resin polyglycidyl ether epoxy resin (component A), 19% of dimer acid diglycidyl ester (component B), 38% of tetrahydrophthalic anhydride (anhydride crosslinking agent), 9% of NaOH (main catalyst) and 1% of 2-ethyl-4-methylimidazole (crosslinking catalyst).

The preparation method of the degradable thermosetting composite material is as follows: the above raw materials are mixed to obtain a mixed resin, the mixed resin and carbon fiber (length 2 inches) are stirred in air at room temperature for 1 hour at a weight ratio of 2:1, and then placed in a mold, and cross-linked for 30 minutes under the conditions of a temperature of 160° C. and a pressure of 10 atm to obtain the degradable thermosetting composite material.

Example 3

The present embodiment provides a degradable thermosetting composite material, which includes a mixed resin and glass fiber. The mixed resin is prepared from the following raw materials, in terms of weight percentage: 33% of bisphenol A glycidyl ether (BADGE) epoxy resin (component A), 13% of dimer acid diglycidyl ester (component B), 44% of phthalic anhydride (anhydride crosslinking agent), 9% of Ca(OH) ₂ (main catalyst) and 1% of 2-ethyl-4-methylimidazole (crosslinking catalyst).

The preparation method of the degradable thermosetting composite material is as follows: the above raw materials are mixed to obtain a mixed resin, the mixed resin and glass fiber (length 0.5 inches) are stirred in air at room temperature for 1 hour at a weight ratio of 2:3, and then placed in a mold, and cross-linked for 30 minutes under the conditions of a temperature of 160° C. and a pressure of 10 atm to obtain the degradable thermosetting composite material.

Example 4

This embodiment provides a degradable thermosetting composite material, which is prepared from the following raw materials by weight percentage: 28% of phenolic resin polyglycidyl ether epoxy resin (component A), 18% of dimer acid diglycidyl ester (component B), 46% of phthalic anhydride (anhydride crosslinking agent), 7% of Ca(OH) ₂ (main catalyst) and 1% of 2-ethyl-4-methylimidazole (crosslinking catalyst). The preparation method of the degradable thermosetting composite material is the same as that of Example 1.

As shown in FIG8 , the degradable thermosetting composite material prepared in this embodiment can be degraded after being immersed in a 95° C., 3% KCl solution for 2 days; the glass transition temperature of the composite material is higher than 110° C. After the composite material is mixed with fibers to make a fiber-reinforced composite material, as shown in FIG9 , the fiber-reinforced composite material can also be degraded after being immersed in a 95° C., 3% KCl solution for 2 days, leaving short fibers.

Solid base main catalyst is very important for the hydrolysis of components A and B. Without the main catalyst, even component B cannot be degraded at low or high temperatures, not to mention component A with a high glass transition temperature. Experiments show that both solid acid and solid base can catalyze the hydrolysis process, but solid base is better because its material can be degraded in the form of a surface etching process, and during the degradation process, the mechanical properties of the entire material will not be destroyed.

The mechanical strength of the final composite material prepared by the present invention depends on different parameters, including fiber selection, length, filling, fiber/matrix bonding, molding process, etc. As shown in Figure 10, the tensile strength of typical recommended fibers is between about 10 ksi and about 30 ksi, and their mechanical strength will not be destroyed as long as it is below the glass transition temperature.

Claims (22)

1. A degradable thermosetting composite material, wherein the raw materials include, by weight percentage: 0.1-99% of an epoxy resin mixture, 0.1-99% of a cycloaliphatic anhydride crosslinking agent, and 0.01-10% of a main catalyst, wherein the epoxy resin mixture includes a primary epoxy resin and a secondary epoxy resin, wherein the glass transition temperature of the primary epoxy resin is 120-200° C., the glass transition temperature of the secondary epoxy resin is 40-100° C., and the weight percentage of the primary epoxy resin in the epoxy resin mixture is 60-80%. 2. The degradable thermosetting composite material according to claim 1, wherein the weight percentage of the primary epoxy resin in the epoxy resin mixture is 65-75%, more preferably 70%. 3. The degradable thermosetting composite material according to claim 1, wherein the primary epoxy resin comprises an aromatic epoxy resin; and the secondary epoxy resin comprises a flexible aliphatic epoxy resin. 4. The degradable thermosetting composite material according to claim 3, wherein the aromatic epoxy resin comprises one or a combination of two or more of novolac epoxy resin, epoxy bisphenol A novolac resin, multifunctional epoxy resin, and bisphenol A epoxy resin. 5. The degradable thermosetting composite material according to claim 3, wherein the cycloaliphatic anhydride crosslinking agent comprises one or a combination of two or more of methyl nadic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, dodecyl succinic anhydride, phthalic anhydride, methyl hexahydrophthalic anhydride, tetrahydrophthalic anhydride and methyl tetrahydrophthalic anhydride. 6. The degradable thermosetting composite material according to claim 1, wherein the main catalyst is a solid acid or a solid base; Preferably, the main catalyst comprises one or a combination of two or more of Ca(OH) ₂ , CaO, Mg(OH) ₂ , KOH, and NaOH; Preferably, the solid acid comprises aminosulfonic acid. 7. The degradable thermosetting composite material according to claim 1, wherein the weight percentage of the epoxy resin mixture is 5-95%, preferably 25-75%, and more preferably 40-60%, based on the total weight of the epoxy resin mixture, the cycloaliphatic anhydride crosslinking agent and the main catalyst. 8. The degradable thermosetting composite material according to claim 1, wherein the weight percentage of the cycloaliphatic anhydride crosslinking agent is 5-95%, preferably 25-75%, and more preferably 40-60%, based on the total weight of the epoxy resin mixture, the cycloaliphatic anhydride crosslinking agent and the main catalyst. 9. The degradable thermosetting composite material according to claim 1, wherein the weight percentage of the main catalyst is 0.1-8%, preferably 0.5-6%, and more preferably 1-4%, based on the total weight of the epoxy resin mixture, the cycloaliphatic anhydride crosslinking agent and the main catalyst. 10. The degradable thermosetting composite material according to claim 1, wherein the raw materials of the degradable thermosetting composite material include: 40-60% of epoxy resin mixture, 40-60% of cycloaliphatic anhydride crosslinking agent and 1-9% of main catalyst. 11. The degradable thermosetting composite material according to claim 1, wherein the cycloaliphatic anhydride crosslinking agent accounts for 30-50% of the total weight of the epoxy resin mixture and the cycloaliphatic anhydride crosslinking agent. 12. The degradable thermosetting composite material according to claim 1, wherein the raw materials further comprise: one or more of an additional epoxy resin, an additional cross-linking agent, a curing agent, a cross-linking or curing catalyst, an additive, and a filler. 13. The degradable thermosetting composite material according to claim 1, wherein the raw material further comprises fibers; the volume percentage of the fibers in the degradable thermosetting composite material is 20-60%, and the fibers comprise one or more of glass fibers, carbon fibers, and Kevlar fibers. 14. The degradable thermosetting composite material according to claim 1, wherein the raw material further comprises a flexible epoxy resin. 15 . The degradable thermosetting composite material according to claim 1 , wherein the glass transition temperature of the degradable thermosetting composite material is ≥140° C., preferably ≥175° C. 16 . The degradable thermosetting composite material according to claim 1 , wherein the elastic modulus of the degradable thermosetting composite material is ≥14,500 psi, preferably ≥15,000 psi. 17 . The degradable thermosetting composite material according to claim 1 , wherein the tensile strength of the degradable thermosetting composite material is ≥10,000 psi, preferably ≥12,000 psi. 18. The degradable thermosetting composite material according to claim 1, wherein the elongation at break of the degradable thermosetting composite material is ≥1%, preferably ≥2.5%. 19. The degradable thermosetting composite material according to claim 1, wherein the preparation method of the degradable thermosetting composite material comprises the following steps: The primary epoxy resin and the secondary epoxy resin are mixed evenly, and then a cycloaliphatic anhydride crosslinking agent and a main catalyst are added and mixed evenly, and then fibers or other raw materials are optionally added to obtain the degradable thermosetting composite material. 20. A degradable downhole plugging tool made from the degradable thermosetting composite material according to any one of claims 1 to 19. 21. The degradable downhole plugging tool according to claim 20, wherein the degradable downhole plugging tool is a near-net-shape component. 22. The degradable downhole plugging tool according to claim 20, wherein the preparation method of the degradable downhole plugging tool comprises the following steps: molding the degradable thermosetting composite material using a hot press, and post-processing the mold at 100-250°C to obtain the degradable downhole plugging tool.