Extrusion molding material raw material for oil and gas exploitation, extrusion molding material and tool or component

Abstract

The invention relates to the field of polymer processing and forming, and discloses an extrusion forming material raw material for oil and gas exploitation, an extrusion forming material and a tool or component. The raw material contains polyglycolic acid of which the molecular weight is in multimodal distribution, and the polyglycolic acid contains a polyglycolic acid grafted copolymer and a polyglycolic acid homopolymer; the polyglycolic acid grafted copolymer at least contains a chain segment as shown in a formula (I): # imgabs0 #, in the formula (I), x, y1, y2, z and p independently represent polymerization degrees, x and p are independently positive integers, and y1, y2 and z are independently natural numbers; in the polyglycolic acid, the weight-average molecular weight of the polyglycolic acid grafted copolymer is greater than that of the polyglycolic acid homopolymer; the compression strength of the polyglycolic acid at the room temperature is 200 to 400 MPa.

Description

Technical Field

[0001] The invention relates to the technical field of polymer processing and molding, and in particular to an extrusion molding raw material and an extrusion molding and a tool or component for oil and gas extraction. Background Art

[0002] Polyglycolic acid (PGA), also known as polyglycolide or polyglycolic acid, is a fully biodegradable material that degrades completely within 1-3 months under natural conditions. PGA also exhibits excellent mechanical properties, strong barrier properties to O2 and CO2, and is non-toxic, harmless, and environmentally friendly. It has been certified as a safe biodegradable plastic material in the United States, the European Union, and Japan.

[0003] However, on the one hand, polyglycolide has poor toughness, with an elongation at break of only about 10% and a notched impact strength of less than 3kJ / m2; on the other hand, the molecular weight of polyglycolide obtained by traditional preparation methods is still not high enough, the melt flow rate at processing temperature is too large, and the melt strength is too low, which makes it difficult to meet the application requirements of rod extrusion and other applications that require a low melt flow rate. These shortcomings seriously limit the application of polyglycolide in corresponding fields.

[0004] Injection molding can be used to quickly and easily prepare polymer parts with complex three-dimensional structures, with high production efficiency and low unit cost. It is one of the most commonly used polymer processing methods. However, when the precision requirements of polymer parts are high, the dimensional accuracy is difficult to meet the standards due to the cooling shrinkage of the polymer itself, or it is necessary to equip it with expensive molds. In addition, when the size of the polymer parts is large (especially thick-walled and large-sized), due to factors such as uneven cooling and crystallization of the polymer, large internal stresses are easily accumulated, resulting in deformation and cracking of the parts, and the generation of holes inside. In order to solve the above problems, the polymer is first made into a dense and compact blank (including but not limited to solid round rods, hollow circular tubes, solid triangular rods, solid rectangular rods, solid pentagonal rods, solid hexagonal rods, flat plates, discs, etc.) larger than the target part, and then mechanical processing methods such as cutting, turning, and drilling are used to finally obtain the desired polymer parts, which becomes an advantageous processing strategy.

[0005] Furthermore, the aforementioned strategy of first forming a billet and then machining it is not suitable for all polymer types or application areas, as it places demands on the stiffness and thickness of both the polymer and the part. However, the stiffness and thickness of polyglycolic acid extrusion moldings and downhole tools used in oil and gas production precisely meet the requirements of the aforementioned processing strategy, and therefore offer promising application prospects. However, key issues still need to be addressed: (1) the polyglycolic acid raw material must have a high molecular weight and high melt strength to meet the requirements of extrusion molding; and (2) the problem of eliminating internal stress in thick-walled, large-sized polyglycolic acid billets and parts.

[0006] CN111647144 A discloses a method for adjusting the molecular chain structure of polyglycolic acid (PGA). This method modifies the physical properties of PGA by introducing functional groups with special properties (such as hydrophilic and hydrophobic groups -OH and -COOR) into the PGA molecule, or by branching or copolymerizing the PGA molecular chain. The document proposes the use of polyhydroxy compounds as initiators, but these only achieve branching or blocking effects. Furthermore, the polymerization conditions disclosed in the patent require low-temperature nitrogen protection, which is relatively harsh. The reaction time is at least 50 minutes. This long reaction time may cause thermal degradation of PGA, darkening the product color, and even producing an unpleasant odor, significantly reducing the quality of PGA products and limiting their application.

[0007] CN112513133 A discloses a novel PGA with high melt strength. By chain-extending polyglycolic acid with isocyanate during polymerization, the melt strength reaches 5-30 cN at 230°C. However, this method requires post-polymerization modification, which is a complex process. Furthermore, isocyanate modification is highly toxic, and the biodegradability of the resulting polyglycolic acid is reduced. Furthermore, the polymerization conditions disclosed in the patent require a low-temperature nitrogen atmosphere, which is quite demanding, requiring a reaction time of at least 160 minutes.

[0008] CN104640684 B discloses a polyglycolic acid with high melt viscosity and high-temperature tensile strength, which is achieved by adding 5 to 70% by mass of a filler. The invention also discloses a method of introducing a certain amount of comonomer into the glycolic acid molecule to increase its processing applicability. However, in order to improve mechanical strength and heat resistance, the fillers used in the present invention are mostly inorganic, metal or high-melting-point organic fibers or powders, most of which are difficult to degrade in oil and gas wells and may pose unpredictable risks. In addition, although the copolymerization modification of other monomers can improve the processing performance of polyglycolic acid to a certain extent, it also inevitably reduces the overall mechanical strength.

[0009] In summary, there is a continuing need in the art to address the challenges of polyglycolic acid (PGA) with low molecular weight and melt strength, resulting in its inability to achieve both high mechanical properties and processability. This need remains unmet by existing technologies. Therefore, the urgent challenge facing PGA materials is how to improve melt strength while maintaining good processability and reduce its melt flow rate at processing temperatures to better meet the demands of applications requiring a low melt flow rate, such as extrusion. This can also, to a certain extent, avoid the unpredictable risks associated with increasing mechanical strength through the addition of fillers. Summary of the Invention

[0010] The present invention aims to overcome the problems of prior art polyglycolic acid used in oil and gas extraction, such as low molecular weight and melt strength, which prevent it from achieving both high mechanical properties and good processability. The present invention provides an extrusion molding raw material, an extrusion molding, and a tool or component for oil and gas extraction. The extrusion molding exhibits excellent overall performance when used to prepare billets and when machined into downhole tools or components for oil and gas extraction.

[0011] The first aspect of the present invention provides a raw material for extrusion molding for oil and gas production, the raw material comprising polyglycolic acid having a multimodal molecular weight distribution,

[0012] Wherein, the polyglycolic acid contains a polyglycolic acid graft copolymer and a polyglycolic acid homopolymer; the polyglycolic acid graft copolymer contains at least a segment represented by formula (I):

[0013]

[0014] In formula (I), x, y1, y2, z and p each independently represent the degree of polymerization, wherein x and p each independently represent a positive integer, and y1, y2 and z each independently represent a natural number; in the polyglycolic acid, the weight average molecular weight of the polyglycolic acid graft copolymer is greater than the weight average molecular weight of the polyglycolic acid homopolymer; and the compressive strength of the polyglycolic acid at room temperature is 200-400 MPa.

[0015] A second aspect of the present invention provides an extrusion molding for oil and gas production. The extrusion molding is obtained by mixing, melting, extruding, and cooling to shape the extrusion molding raw materials of the present invention.

[0016] A third aspect of the present invention provides a downhole tool or component for oil and gas production, wherein the tool or component is obtained by machining the extruded article of the present invention.

[0017] Through the above technical solution, the present invention uses polyglycolic acid comprising a higher molecular weight polyglycolic acid graft copolymer and a lower molecular weight polyglycolic acid homopolymer, wherein the higher molecular weight polyglycolic acid graft copolymer provides good melt strength and mechanical properties, and the lower molecular weight polyglycolic acid homopolymer provides good processability, which can achieve a balance between usage and processing performance, and exhibits good comprehensive performance when preparing billets from extruded products and machining them into downhole tools or components for oil and gas development. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 GPC curves of some preparation examples and comparative examples

[0019] Figure 2 The following are typical tensile stress-strain curves of injection molded parts from some preparation examples and comparison examples.

[0020] Figure 3 The melt strength test results of some preparation examples and comparison examples are shown.

[0021] Figure 4 The rod with a diameter of 50 mm was obtained by extrusion molding in Example 10.

[0022] Figure 5 The rod with a diameter of 125 mm was obtained by extrusion molding in Example 11.

[0023] Figure 6 The fracturing ball with a diameter of 45 mm obtained by machining in Example 12. DETAILED DESCRIPTION

[0024] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0025] In a first aspect, the present invention provides a raw material for an extrusion molding for oil and gas production, comprising polyglycolic acid having a multimodal molecular weight distribution, wherein the polyglycolic acid comprises a polyglycolic acid graft copolymer and a polyglycolic acid homopolymer; the polyglycolic acid graft copolymer comprises at least a segment represented by formula (I):

[0026]

[0027] In formula (I), x, y1, y2, z and p each independently represent the degree of polymerization, wherein x and p each independently are positive integers, and y1, y2 and z each independently are natural numbers; in the polyglycolic acid, the weight average molecular weight of the polyglycolic acid graft copolymer is greater than the weight average molecular weight of the polyglycolic acid homopolymer; and the compressive strength of the polyglycolic acid at room temperature is 200-400 MPa (e.g., 200 MPa, 271 MPa, 285 MPa, 300 MPa, 350 MPa, 400 MPa, etc.).

[0028] The compressive strength of the polyglycolic acid in the present invention is determined by testing the corresponding compressive strength of the polyglycolic acid by making the polyglycolic acid into a product.

[0029] The polyglycolic acid in the present invention exhibits a multimodal distribution and comprises a polyglycolic acid graft copolymer and a polyglycolic acid homopolymer. The weight-average molecular weight of the polyglycolic acid graft copolymer is greater than that of the polyglycolic acid homopolymer. The higher molecular weight polyglycolic acid graft copolymer provides excellent melt strength and mechanical properties, while the lower molecular weight polyglycolic acid homopolymer provides good processability, thereby achieving a balance between usability and processing performance. Furthermore, when extruded into billets and machined into downhole tools or components for oil and gas production, the material can be used in higher-pressure oilfield environments without damage, demonstrating excellent overall performance.

[0030] According to the present invention, in some preferred embodiments, in formula (I), the sum of x, y1, y2, and z is not less than 50, for example, 50, 100, 500, 1000, 2000, 3000, 4000, 5000, 6000, 7000, or a range consisting of any two of the above values, preferably 50-6000, more preferably 200-2500. The polyglycolic acid in the above embodiment has better use and processing properties, and exhibits good comprehensive performance when the extruded product is prepared into a billet and when it is mechanically processed into a downhole tool or component for oil and gas production.

[0031] According to the present invention, in some preferred embodiments, the proportion of z to the sum of x+y1+y2+z is 0%-50%.

[0032] According to the present invention, in some preferred embodiments, the ratio of y1 to the sum of x+y1+y2 is 0%-32%.

[0033] According to the present invention, in some particularly preferred embodiments, when the main chain of the polyglycolic acid graft copolymer is an ethylene-vinyl alcohol copolymer segment, the proportion of z in the sum of x+y1+y2+z is 1%-50%, preferably 20%-45%, and the proportion of y1 in the sum of x+y1+y2 is 0.1%-6%.

[0034] According to the present invention, in some particularly preferred embodiments, when the main chain of the polyglycolic acid graft copolymer is a polyvinyl alcohol segment, z is 0, and the proportion of y1 to the sum of x+y1+y2 is 1%-32%.

[0035] In the present invention, the sum of x+y1+y2+z is the degree of polymerization of polyvinyl alcohol or ethylene-vinyl alcohol copolymer, which can be calculated by the number average molecular weight of the raw material polyvinyl alcohol or ethylene-vinyl alcohol copolymer; and the proportion of z in the sum of x+y1+y2+z can be calculated by the integrated area of the corresponding characteristic peak of the nuclear magnetic hydrogen spectrum.

[0036] In the present invention, the ratio of x+y2 to the sum of x+y1+y2 (i.e., the ratio of 100% - y1 to the sum of x+y1+y2) is the alcoholysis degree of the ethylene-vinyl alcohol copolymer, which is a known parameter of the raw materials before leaving the factory and can also be detected by various detection methods in the field such as nuclear magnetic resonance and near infrared.

[0037] According to the present invention, as long as the purpose of the present invention can be achieved, the specific value of p in formula (I) is not particularly limited. In some preferred embodiments, in formula (I), p is not less than 50, for example, 50, 100, 200, 400, 500, 1000, 2000, or a range consisting of any two of the above values, preferably 70-2000. The polyglycolic acid under the aforementioned embodiment has better use and processing performance, and its use in preparing extrusion moldings to prepare blanks and mechanically processing them into downhole tools or components for oil and gas development has exerted good comprehensive performance.

[0038] According to the present invention, if the structure of the starting ethylene-vinyl alcohol copolymer macroinitiator is known, then p = (number average molecular weight of the high molecular weight part PGA - number average molecular weight of the macroinitiator) / (y*PGA repeating unit molecular weight). If the high molecular weight PGA of the graft copolymer structure described in the present invention is obtained directly, it can be fully hydrolyzed first, the initiator can be collected, its structure can be analyzed, and then tested in the above manner. According to the preparation examples of the present invention later, it is calculated that the p values in the obtained polymers are all greater than 50. According to the above technical solution, the GPC curve of the polyglycolic acid with a multimodal molecular weight distribution of the present invention has the characteristics of a multimodal molecular weight distribution, which contains two polyglycolic acid components with different chemical structures: the higher molecular weight is a polyglycolic acid graft copolymer, and the lower molecular weight is a polyglycolic acid homopolymer.

[0039] According to the present invention, in some preferred embodiments, the polyglycolic acid homopolymer is represented by formula (II):

[0040]

[0041] In formula (II), n1, ..., n i Each is independently the degree of polymerization; i is directly connected to R The number of,i≥1;,M1,······,M i Each is independently an imino group, a nitro group or an ether bond; R is hydrogen, an aliphatic group or an aromatic group; R is H, an alkane group or an aromatic hydrocarbon group.

[0042] According to the present invention, in some preferred embodiments, in formula (II), i is any integer between 1 and 20, for example, 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, or a range consisting of any two of the above values, preferably 2-6.

[0043] According to the present invention, in some preferred embodiments, in formula (II), R is an alkane group or an aromatic hydrocarbon group having a molecular weight of 14 to 1000 g / mol.

[0044] According to the present invention, it can be understood that when i>1, M1, M2, ..., M i Different or the same between n1, n2, ..., n i In some particularly preferred embodiments, when i in formula (II) is greater than 1, R is an alkane group or an aromatic hydrocarbon group having a molecular weight of 14 to 1000 g / mol.

[0045] According to the present invention, in some particularly preferred embodiments, in formula (II), when i is 1, R is H, an alkane group or an aromatic hydrocarbon group.

[0046] According to the present invention, n in the structural formula (II) i The range of n on each branch is wide and it is difficult to calculate the value of each. In a preferred embodiment, in formula (II), n1, ..., n i The sum is not less than 100.

[0047] According to the present invention, all n1, ..., n i The sum can be calculated by dividing the number average molecular weight of the lower molecular weight peak in the GPC result by the molecular weight of the PGA repeating unit. According to the preparation examples below of the present invention, it is calculated that all n1, ..., n i The sum is not less than 100.

[0048] According to the present invention, the average degree of polymerization (x, y1, y2, z, p and n) obtained by calculation needs to be rounded off during calculation.

[0049] According to the present invention, the content of each polymer segment in the polyglycolic acid with multimodal molecular weight distribution of the present invention can be selected in a wide range. In some preferred embodiments of the present invention, relative to 100 parts by mass of the polyglycolic acid segment (i.e. The total mass of The presence of In the structural formula (II), ), containing 0.001-10 parts by mass of Contains 0.001-10 parts by mass Wherein, the definitions of x, y1, y2, z and p are the same as those of x, y1, y2, z and p described in formula (I); the definitions of R, M, i are the same as those of R, M, i described in formula (II)

[0050] According to the present invention, in some particularly preferred embodiments, for 100 parts by mass of polyglycolic acid segments The raw material of the polyglycolic acid contains 0.01-1 parts by mass of Contains 0.01-1 parts by mass

[0051]

[0052] In the present invention, the mass content of each segment in the polyglycolic acid can be detected by methods known in the art, or can be calculated based on the amount of material added during the preparation process.

[0053] According to the present invention, in some preferred embodiments, the melt flow rate of the polyglycolic acid at 230°C / 2.16kg is not higher than 20.0g / 10min, for example, 0.1g / 10min, 0.5g / 10min, 1.0g / 10min, 2.0g / 10min, 3.0g / 10min, 4.0g / 10min, 5.0g / 10min, 6.0g / 10min, 7.0g / 10min, 8.0g / 10min, 9.0g / 10min, 10.0g / 10min, 15.0g / 10min, 20.0g / 10min, preferably 0.1-20.0g / 10min, preferably 0.1-10.0g / 10min.

[0054] In the present invention, the melt flow rate can be measured by methods known in the art, such as, but not limited to, the following methods: The test is conducted on a CEAST MF20 melt flow rate tester manufactured by Instron Corporation of the United States. The test temperature is 230°C, the load weight is 2.16 kg, and the preheating time is 4 minutes.

[0055] According to the present invention, as long as the purpose of the present invention can be achieved, the total weight average molecular weight of the polyglycolic acid is not particularly limited. In some preferred embodiments, the total weight average molecular weight of the polyglycolic acid is 200,000-1.5 million g / mol, for example, 250,000 g / mol, 300,000 g / mol, 350,000 g / mol, 400,000 g / mol, 450,000 g / mol, 500,000 g / mol, 800,000 g / mol, 1,000,000 g / mol, 1,500,000 g / mol, or a range consisting of any two of the above values, preferably 250,000-500,000 g / mol.

[0056] According to the present invention, as long as the purpose of the present invention can be achieved, the overall molecular weight distribution index of the polyglycolic acid is not particularly limited. In some preferred embodiments, the overall molecular weight distribution index of the polyglycolic acid is 1.5-20.0, for example, 1.5, 2.0, 3.0, 3.5, 5.0, 10.0, 20.0, or a range consisting of any two of the above values, preferably 2.0-3.5.

[0057] According to the present invention, as long as the purpose of the present invention can be achieved, the number of molecular weight distribution peaks of the polyglycolic acid is not particularly limited. In some embodiments, the number of molecular weight distribution peaks of the polyglycolic acid is at least 2, including but not limited to 2 and 3.

[0058] According to the present invention, in some particularly preferred embodiments, the peak molecular weight M p Greater than 500,000 (i.e., Log(M) of the peak value in the GPC curve) w ) greater than 5.7) and the peak molecular weight M p Less than 500,000 (i.e., Log(M) of the peak value in the GPC curve) w ) is less than 5.7) and the number of peaks is at least 1.

[0059] According to the present invention, in some preferred embodiments, in the polyglycolic acid, the weight-average molecular weight of the polyglycolic acid graft copolymer is 500,000-10 million g / mol, for example, 1 million g / mol, 1.5 million g / mol, 2 million g / mol, 3 million g / mol, 4 million g / mol, 5 million g / mol, 6 million g / mol, 8 million g / mol, 9 million g / mol, 10 million g / mol, or a range consisting of any two of the above values, preferably 1 million-6 million g / mol.

[0060] According to the present invention, in some preferred embodiments, in the polyglycolic acid, the weight-average molecular weight of the polyglycolic acid homopolymer is 50,000-350,000 g / mol, for example, it can be 100,000 g / mol, 120,000 g / mol, 140,000 g / mol, 160,000 g / mol, 180,000 g / mol, 200,000 g / mol, 300,000 g / mol, 350,000 g / mol, or a range consisting of any two of the above values, preferably 100,000-200,000 g / mol.

[0061] In the present invention, the number of molecular weight distribution peaks can be detected by gel permeation chromatography (GPC). The molecular weight distribution peak can be detected by finding the peak at the weight average molecular weight (M) in the GPC curve. w ) is greater than 10,000 g / mol (i.e. log(M w) is greater than 4.0) where the first-order derivative is zero and the second-order derivative is less than zero.

[0062] According to the present invention, in some preferred embodiments, in the polyglycolic acid, the molecular weight polydispersity index of the polyglycolic acid graft copolymer is 1.0-3.0, preferably 1.1-1.5.

[0063] According to the present invention, in some preferred embodiments, in the polyglycolic acid, the molecular weight polydispersity index of the polyglycolic acid homopolymer is 1.0-3.0, preferably 1.4-2.9.

[0064] According to the present invention, as long as the purpose of the present invention can be achieved, the content of the polyglycolic acid graft copolymer and the polyglycolic acid homopolymer in the polyglycolic acid can be selected within a wide range. In some preferred embodiments, the content of the polyglycolic acid graft copolymer is 0.1% by mass to 80.0% by mass, preferably 1.0% by mass to 30.0% by mass, relative to the total mass of the polyglycolic acid; and the content of the polyglycolic acid homopolymer is 20% by mass to 99.9% by mass, preferably 70.0% by mass to 99.0% by mass.

[0065] In the present invention, parameters such as the total weight-average molecular weight of polyglycolic acid with a multimodal molecular weight distribution, the overall molecular weight distribution index of polyglycolic acid with a multimodal molecular weight distribution, the number of molecular weight distribution peaks of polyglycolic acid with a multimodal molecular weight distribution, the weight-average molecular weight of polyglycolic acid graft copolymers, the molecular weight polydispersity index of polyglycolic acid graft copolymers, the molecular weight polydispersity index of polyglycolic acid homopolymers, the mass fraction of polyglycolic acid graft copolymers, and the mass fraction of polyglycolic acid homopolymers can be measured by gel permeation chromatography (GPC). Specific detection methods can employ conventional detection parameters in the art. For example, but not limited to, the following method is employed: the test instrument is a PL-GPC50 gel permeation chromatograph from Angilent, USA, and the processing software is GPC offline. During the test, the mobile phase is hexafluoroisopropanol containing 5 mmol / L sodium trifluoroacetate, the flow rate is 1 mL / min, the column temperature is 40°C, the injection volume is 100 μL, the standard sample is PMMA, and the sample concentration is 1 mg / mL. The specific values of the above parameters are obtained according to analytical methods known in the art.

[0066] According to the present invention, the preparation method of the polyglycolic acid is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the preparation method of the polyglycolic acid comprises: polymerizing the polyglycolic acid segments The monomer, ethylene-vinyl alcohol copolymer and / or polyvinyl alcohol, and optionally a small molecule co-initiator are melt polymerized in the presence of a catalyst and optionally an antioxidant to obtain the polyglycolic acid with a multimodal molecular weight distribution.

[0067] According to the present invention, as long as the purpose of the present invention can be achieved, the monomer can be selected from a wide range. In some preferred embodiments, the monomer includes at least one of methyl glycolate, glycolic acid and glycolide, preferably glycolide.

[0068] According to the present invention, when the monomer is glycolide, the glycolide's moisture content, purity, and acid value all have a certain impact on the final product. In the present invention, the glycolide preferably has a moisture content of no more than 500 ppm, preferably no more than 300 ppm, a purity of no less than 99.0%, preferably no less than 99.8%, and an acid value of no more than 5.0 mmol / kg, preferably no more than 1.5 mmol / kg. Because water can also act as an initiator in the ring-opening polymerization of glycolide, the glycolide's moisture content must be monitored and controlled. Without the addition of any additional small molecule initiator, the low molecular weight portion of the polyglycolic acid having a multimodal molecular weight distribution in the present invention is a homopolymer derived from water as an initiator.

[0069] According to the present invention, the alcoholysis degree of the polyvinyl alcohol can be selected in a wide range. In some preferred embodiments, the alcoholysis degree of the polyvinyl alcohol is 68-99%.

[0070] According to the present invention, the degree of polymerization of the polyvinyl alcohol can be selected in a wide range. In some preferred embodiments, the degree of polymerization of the polyvinyl alcohol is 100-6000, for example, it can be 300, 500, 1000, 1500, 2000, 3000, 4000, 5000, 6000, or a range consisting of any two of the above values, preferably 300-2000.

[0071] According to the present invention, the ethylene-vinyl alcohol copolymer can be selected from a wide range. In some preferred embodiments, the content of the ethylene segment in the ethylene-vinyl alcohol copolymer is 25-50 mol%, for example, 25 mol%, 35 mol%, 45 mol%, 50 mol%, or any two values or any range.

[0072] According to the present invention, in some preferred embodiments, the degree of polymerization of the ethylene-vinyl alcohol copolymer is 50-6000, for example, it can be 300, 500, 1000, 1500, 2000, 3000, 4000, 5000, 6000, or a range consisting of any two of the above values, preferably 300-2000.

[0073] According to the present invention, the melt flow rate of the ethylene-vinyl alcohol copolymer can be selected within a wide range. In some preferred embodiments, the melt flow rate of the ethylene-vinyl alcohol copolymer at 190°C / 2.16kg is 0.1-50g / 10min.

[0074] According to the present invention, the small molecule co-initiator can be selected from a wide range. In a preferred embodiment of the present invention, the small molecule co-initiator is a hydroxyl- or amino-containing small molecule substance with a boiling point greater than 160°C, preferably with a molecular weight of no greater than 1000 g / mol, preferably 60-300 g / mol. Examples include, but are not limited to, ethylene glycol, butanediol, glycerol, serinol, leucinol, pentaerythritol, sorbitol, xylitol, amino acids, phenol, hydroquinone, resorcinol, benzyl alcohol, aniline, benzylamine, p-phenylenediamine, m-phenylenediamine, hexamethylenediamine, and dodecanediamine.

[0075] According to the present invention, the catalyst can be selected from a wide range. The catalyst is selected from salt compounds corresponding to at least one of transition metal elements, Group IIA metal elements, Group IIIA metal elements, Group IVA metal elements, and Group VA metal elements, and / or organic guanidine catalysts.

[0076] According to the present invention, in some preferred embodiments, the catalyst is a salt compound corresponding to at least one of Sn, Bi, Mg, Al, Ca, Fe, Mn, Ti and Zn, preferably a Sn salt (such as stannous octoate, anhydrous stannous chloride).

[0077] In the present invention, "optionally" means containing or not containing an example.

[0078] According to the present invention, in some embodiments, the antioxidant is selected from hindered phenol antioxidants and / or phosphite antioxidants, that is, it can be hindered phenols and phosphite antioxidants and any combination thereof, including but not limited to 2,6-di-tert-butyl-p-cresol, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 2,2'-methylenebis(6-tert-butyl-4-methylphenol), hexanediol bis[β-(3,5-dibutyl-4-hydroxyphenyl) propionate], tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester (such as BASF's antioxidant Irganox 1010), N,N'-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (such as antioxidant 1024), N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine (such as antioxidant 1098), β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid n-octadecyl ester (such as BASF's antioxidant Irganox 1076), at least one of 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, triphenyl phosphite, tris(4-nonphenyl) phosphite, diphenyl isooctyl phosphite, diphenyl isodecyl phosphite, diphenyl di(2-ethylhexyl) phosphite, phenyl diisodecyl phosphite, tris(2-ethylhexyl) phosphite, triisodecyl phosphite, tridodecyl phosphite, pentaerythritol diisodecyl diphosphite, tris[2,4-di-tert-butylphenyl] phosphite (such as antioxidant 168), bis(2,4-dicumylphenyl) pentaerythritol diphosphite (such as antioxidant 686) and bis(2,4-di-tert-butylphenyl) propionic acid] pentaerythritol diphosphite (such as antioxidant 626).

[0079] According to the present invention, in some embodiments, the amount of the antioxidant is 0 to 2 parts by mass, preferably 0.01 to 1 part by mass (phr), relative to 100 parts by mass of the monomer.

[0080] According to the present invention, as long as the purpose of the present invention can be achieved, the amount of ethylene-vinyl alcohol copolymer (and / or polyvinyl alcohol) used in the preparation of polyglycolic acid is not particularly limited. In some embodiments, the amount of ethylene-vinyl alcohol copolymer (and / or polyvinyl alcohol) used is 0.001 to 10 parts by mass, preferably 0.01 to 1 part, relative to 100 parts of monomers.

[0081] According to the present invention, as long as the purpose of the present invention can be achieved, the amount of the small molecule co-initiator used in the preparation of polyglycolic acid is not particularly limited. In some embodiments, the amount of the small molecule co-initiator used is 0.001-10 parts by mass, preferably 0.01-1 part, relative to 100 parts of monomer.

[0082] According to the present invention, as long as the purpose of the present invention can be achieved, the amount of the catalyst used in the preparation of polyglycolic acid is not particularly limited. In some embodiments, the amount of the catalyst used is 0.005 to 1 part by mass, preferably 0.01 to 0.2 parts by mass, relative to 100 parts of monomer.

[0083] According to the present invention, as long as the purpose of the present invention can be achieved, the conditions of melt polymerization are not particularly limited when preparing polyglycolic acid. In some embodiments, the conditions of the melt polymerization reaction include: a processing temperature of 180-250°C, preferably 210-240°C.

[0084] According to the present invention, in some embodiments, the conditions of the melt polymerization reaction include: a reaction time of 0.5 to 60 minutes, preferably 1 to 10 minutes.

[0085] According to the present invention, when preparing polyglycolic acid, the device for melt polymerization is not particularly limited, as long as it is carried out in a melt mixing device; preferably, the melt mixing device is a series combination of one or more of a kettle reactor, a tubular reactor, an internal mixer, a Farrel continuous mixer, a Banbury mixer, a single-screw extruder, a multi-screw extruder and a reciprocating single-screw extruder, preferably an internal mixer or a twin-screw extruder.

[0086] According to the present invention, the additional continuous twin-screw extruders connected in series can extend the residence time of the material in the twin screws (i.e., increase the reaction time) by increasing the aspect ratio, thereby lowering the reaction temperature or further improving the reaction conversion rate. More importantly, vacuum devolatilization can be added to the subsequent series-connected equipment to reduce the content of unreacted residual monomers, and a metal passivator can be added to reduce the effect of the catalyst on product stability.

[0087] According to the present invention, when a twin-screw extruder is used for melt polymerization, the aspect ratio of the twin-screw extruder can be selected, and the screw speed and feeding rate can be controlled as needed, for example, the aspect ratio is 25-80, preferably 40-70; and / or the screw speed is 5-300 rpm, preferably 40-150 rpm and / or the feeding rate is 0.5-5 kg / h, preferably 1-3 kg / h.

[0088] According to the present invention, in some embodiments, the melt polymerization process is carried out in an internal mixer; preferably, the internal mixer temperature is 180-250°C, preferably 200-230°C, the rotation speed is 5-150rpm, preferably 20-80rpm, and the reaction time is 1-20min, preferably 3-10min.

[0089] Internal mixer equipment suitable for use in the present invention includes internal mixers of various designs, such as the PolyLab HAAKE™ Rheomex OS 567-1000 internal mixer module manufactured by Thermo Fisher Scientific, USA. Continuous twin-screw extruder equipment suitable for use in the present invention includes twin-screw extruders of various designs, such as the HAAKE Eurolab 16 desktop parallel co-rotating twin-screw extruder manufactured by Thermo Fisher Scientific, USA, and the ZSK Mcc 18 or ZSK 40 co-rotating parallel twin-screw extruders manufactured by Coperion, Germany.

[0090] A second aspect of the present invention provides an extrusion molding for oil and gas production. The extrusion molding is obtained by mixing, melting, extruding, and cooling to shape the extrusion molding raw materials of the present invention.

[0091] In the present invention, the extrusion molding for oil and gas extraction prepared by using the extrusion molding raw material for oil and gas extraction of the present invention has excellent performance.

[0092] According to the present invention, the mixing, melting and extrusion can be carried out in an extruder. Generally, extruders are usually temperature-controlled in sections, and not every section is the same. As long as the purpose of the present invention can be achieved, in some embodiments, the mixing and melting temperature is 200-270°C. In the present invention, an extrusion die (the cross-section of the die can be selected as needed) can be installed at the front end of the extruder, and a cooling and shaping device is connected behind the die. The molten polyglycolic acid melt is fully mixed in the extruder, extruded through the die, and then fully cooled and shaped according to a set scheme in the cooling device. Preferably, in order to fully compact the prepared polyglycolic acid extrusion molding, a certain back pressure needs to be applied in the extrusion direction of the die to fully eliminate bubbles in the polyglycolic acid melt, so as to obtain a dense and compact polyglycolic acid extrusion molding.

[0093] According to the present invention, extruded articles of different shapes can be prepared as needed, including but not limited to at least one of a solid round rod, a hollow round tube, a solid triangular rod, a solid rectangular rod, a solid pentagonal rod, a solid hexagonal rod, a flat plate, and a disc.

[0094] A third aspect of the present invention provides a downhole tool or component for oil and gas production, wherein the tool or component is obtained by machining the extruded article of the present invention.

[0095] In the present invention, good comprehensiveness is exerted when the extruded product is used to prepare a blank and when it is mechanically processed into a downhole tool or component for oil and gas development.

[0096] According to the present invention, those skilled in the art can use the extruded article of the present invention to prepare corresponding downhole tools or components for oil and gas development as needed, including but not limited to at least one of downhole fracturing balls, gun bolts, bridge plugs, packers, and transfer devices for oil and gas development.

[0097] According to the present invention, those skilled in the art can use the extruded product of the present invention to obtain the downhole tools or components for oil and gas development with shapes and sizes that meet the requirements through mechanical processing as needed. The tools or components include but are not limited to at least one of downhole fracturing balls, gun bolts, bridge plugs, packers, and transfer devices for oil and gas development.

[0098] The present invention will be described in detail below through examples.

[0099] The raw materials used in the present invention are all commercially available.

[0100] Glycolide was purchased from Shenzhen Boli Biomaterial Co., Ltd. with a purity of ≥99.5%, a moisture content of ≤500 ppm, and an acid value of ≤3 mmol / kg.

[0101] Anhydrous stannous chloride, stannous octoate, 1,4-butanediol (BDO), and serinol were purchased from Sinopharm Chemical Reagent Co., Ltd. The purity of anhydrous stannous chloride, stannous octoate, and serinol was AR grade, and the purity of 1,4-butanediol was CP grade.

[0102] Antioxidant 1010 was purchased from BASF (China) Co., Ltd., and antioxidant 626 was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., with a purity of ≥95%.

[0103] Polyvinyl alcohol (PVA) was purchased from Chongqing Chuanwei Chemical Co., Ltd. of Sinopec Group with a brand name of 0588, a polymer weight of about 500, and a degree of alcoholysis of about 88%.

[0104] Ethylene-vinyl alcohol copolymer (EVOH) was purchased from Kuraray Co., Ltd. of Japan with a brand name of EVAL™ H171B. The ethylene content was 38 mol% and the melt flow rate at 190° C. / 2.16 kg was 1.7 g / 10 min.

[0105] Polyglycolide (PGA) was purchased from Cobion-Prak, the Netherlands, and is a GMP-grade glycolide homopolymer with an average intrinsic viscosity of 1.2 dl / g.

[0106] The present invention performs performance measurement according to the following method:

[0107] Melt flow rate measurement: Tests were conducted on a CEAST MF20 melt flow tester (Instron, USA). The test temperature was 230°C, the load was 2.16 kg, and the preheating time was 4 minutes.

[0108] Gel Permeation Chromatography (GPC): Testing was performed on a PL-GPC50 gel permeation chromatograph (Angilent, USA), using GPC offline software. The mobile phase consisted of hexafluoroisopropanol containing 5 mmol / L sodium trifluoroacetate, at a flow rate of 1 mL / min, a column temperature of 40°C, and an injection volume of 100 μL. The standard sample was PMMA, with a sample concentration of 1 mg / mL.

[0109] Injection Molding Processing and Tensile Testing: Samples were injection molded into 5A tensile bars (2 mm thick) on a HAAKE MiniJet microinjection molding machine according to GB / T 1040.2-2006. The barrel and mold temperatures were 240°C and 50°C, respectively. The injection pressure and duration were 400 bar and 5 seconds, respectively, and the holding pressure and duration were 100 bar and 10 seconds, respectively. Tensile testing was then performed on an Instron 3344 materials testing machine (USA) at a rate of 50 mm / min and a grip spacing of 50 mm.

[0110] Melt strength test: The test was conducted on a Rosand RH7 high-pressure capillary rheometer from Malvern Panalytical, China, with a Haul Off nozzle (diameter: 2.0 mm, length: 20 mm). The barrel push rod downward speed was 15 mm / min, the test temperature was 235°C, the initial draw-down speed was 3 mm / min, the final draw-down speed was 50 mm / min, and the acceleration time was 3 minutes.

[0111] Extruded Sample Compression Strength Test: PGA extruded samples were cut into 10mm x 10mm squares, with the thickness of the samples being as uniform as possible (the actual thickness was approximately 4.78mm). Compression strength tests were conducted on an Instron 3367 materials testing machine. The tests were conducted at room temperature and a compression rate of 5mm / min. The slope of the tangent to the compression curve at a compressive strain of 0.1mm / mm was taken as the compressive strength of the sample.

[0112] Preparation example of polyglycolic acid raw materials

[0113] Preparation Example 1

[0114] Glycolide (moisture content approximately 260 ppm), stannous octoate, polyvinyl alcohol (PVA), 1,4-butanediol (BDO), antioxidant 1010, and antioxidant 626 were uniformly mixed in a mass ratio of 100:0.1:0.005:0.045:0.3:0.6 and pelletized using a Labtech parallel, co-rotating twin-screw extruder (screw diameter: 20 mm, aspect ratio: 40). The extruder consisted of 11 sections, numbered 1-11, from the feed port to the die. Section 1 served only for feeding and was not heated. Sections 2-11 were set at 160°C, 200°C, 220°C, 220°C, 220°C, 220°C, 230°C, 235°C, and 240°C, respectively. The feed rate was 3 kg / h, the screw speed was 150 rpm, and the average residence time was approximately 3 min. Polyglycolic acid was finally produced.

[0115] Preparation Example 2

[0116] The method of Preparation Example 1 was followed, except that ethylene-vinyl alcohol copolymer (EVOH) was used instead of polyvinyl alcohol (PVA), and the ratio of glycolide (water content approximately 210 ppm), stannous octoate, EVOH, 1,4-butanediol (BDO), antioxidant 1010, and antioxidant 626 was set to 100:0.1:0.02:0.04:0.5:0.5. The temperature was changed to 160°C, 200°C, 220°C, 220°C, 220°C, 220°C, 220°C, 220°C, 220°C, and 220°C to finally produce polyglycolic acid.

[0117] Preparation Example 3

[0118] The method of Preparation Example 1 was followed, except that 1,4-butanediol (BDO) was not added and the amount of antioxidant was slightly adjusted, that is, the mass ratio of glycolide (water content of about 180 ppm) to antioxidant 626 was changed to 100:0.5, to finally prepare polyglycolic acid.

[0119] Preparation Example 4

[0120] The method of Preparation Example 2 was followed, except that the equipment was changed to a Eurolab parallel co-rotating twin-screw extruder (screw diameter: 16 mm, aspect ratio 40), the glycolide moisture content was about 240 ppm, and the amount of stannous octoate was changed to 0.03 parts by mass (phr) of anhydrous stannous chloride, the amount of ethylene-vinyl alcohol copolymer (EVOH) was changed to 1 part by mass (phr), and 1,4-butanediol was not added, the screw speed was changed to 100 rpm, the temperature was changed to: 120°C, 180°C, 230°C, 230°C, 230°C, 230°C, 230°C, 230°C, 230°C, 210°C, the feed rate was changed to 1 kg / h, the average residence time was about 6 min, and polyglycolic acid was finally prepared.

[0121] Preparation Example 5

[0122] The method of Preparation Example 4 was followed, except that the amount of ethylene-vinyl alcohol copolymer (EVOH) was changed to 3 parts by mass (phr), and polyglycolic acid was finally prepared.

[0123] Preparation Example 6

[0124] The method of Preparation Example 4 was followed, except that the amount of ethylene-vinyl alcohol copolymer (EVOH) was changed to 5 parts by mass (phr), the screw speed was changed to 50 rpm, and the average residence time was about 7 minutes, to finally prepare polyglycolic acid.

[0125] Preparation Example 7

[0126] The method of Preparation Example 4 was followed, except that antioxidant 1010 and antioxidant 626 were not added, and polyglycolic acid was finally prepared.

[0127] Preparation Example 8

[0128] Polyglycolic acid was finally prepared by following the method of Preparation Example 2, except that serinol was used instead of 1,4-butanediol and the water content of glycolide was about 220 ppm.

[0129] Preparation Example 9

[0130] The method of Preparation Example 2 was followed, except that the ratio of glycolide (water content of about 200 ppm), stannous octoate, EVOH, 1,4-butanediol, antioxidant 1010 and antioxidant 626 was set to 100:0.1:0.015:0.035:0.3:0.6, and polyglycolic acid was finally prepared.

[0131] Comparative Preparation Example 1

[0132] The method of Preparation Example 1 was followed, except that no vinyl alcohol (PVA) was added, and the ratio of glycolide (water content of about 180 ppm), stannous octoate, 1,4-butanediol, antioxidant 1010 and antioxidant 626 was changed to 100:0.1:0.05:0.3:0.6, to finally prepare polyglycolic acid.

[0133] Comparative Preparation Example 2

[0134] Commercially available pure polyglycolide (PGA) was purchased from the GMP-grade glycolide homopolymer of Cobion-Prak, the Netherlands, with an average intrinsic viscosity of 1.2 dl / g.

[0135] Example (Extrusion molding, and preparation of downhole tools or components for oil and gas production)

[0136] Example 1

[0137] The polyglycolic acid prepared according to the method described in Preparation Example 2 was extruded in a single-screw extruder with a screw diameter of 45 mm and an aspect ratio of 30. The extruder was equipped with a circular die with a diameter of 55 mm and a length of 50 cm. The extruder temperature was 200-240°C, the screw speed was 10 rpm, the die temperature was set to 95°C, and a back pressure of approximately 0.6 MPa was provided by a clamping device to ensure the density of the extruded rod. The actual diameter of the extruded rod was approximately 50 mm, and the compressive strength of the extruded sample was tested according to the compressive strength test of the extruded sample described above, and the compressive strength was 271 MPa.

[0138] Example 2

[0139] The polyglycolic acid prepared according to the method described in Preparation Example 3 was extruded in a single-screw extruder with a screw diameter of 50 mm and an aspect ratio of 30. The extruder was equipped with a circular die with a diameter of 130 mm and a length of 60 cm and a cooling and temperature-control device with a length of 1 m. The extruder temperature was 220-250°C, the screw speed was 20 rpm, and the total residence time of the extruded rod at 90-200°C was about 21 hours through the synergistic effect of the die and the cooling and temperature-control device. A back pressure of about 1.0 MPa was provided by a pressing device to ensure the density of the extruded specimen. The actual diameter of the extruded rod was about 125 mm, and the compressive strength of the extruded sample was 285 MPa according to the compression strength test of the extruded sample described above.

[0140] Example 3

[0141] The PGA rod with a diameter of 50 mm prepared according to the method described in Example 1 was used as a blank and turned to produce a spherical part with a diameter of 45 mm. It can be used as a downhole fracturing ball for oil and gas development, and can exert a greater temporary plugging and pressurization effect. For other tools / components, it can be used in a higher pressure oilfield environment without being damaged.

[0142] Test Example 1

[0143] The molecular weight of some preparation examples and comparative examples was characterized by GPC. The analysis results are shown in Table 1. The GPC curves of some preparation examples and comparative examples are shown in Table 1. Figure 1 As shown. Figure 1 It can be seen that conventional commercially available PGA has a unimodal molecular weight distribution with a peak molecular weight Mp of less than 500,000 (i.e., the Log(Mw) of the peak in the figure is less than 5.7), while Preparation Examples 2 and 3 have a multimodal distribution, with not only a peak with a peak molecular weight Mp of less than 500,000 (i.e., polyglycolic acid graft copolymer), but also a peak with a peak molecular weight Mp greater than 500,000 (i.e., polyglycolic acid homopolymer).

[0144] Table 1

[0145]

[0146]

[0147] *Calculated from the integrated area ratio of the GPC curve. (The ordinate and abscissa of the GPC curve are related to the mass and molecular weight of the polymer, respectively. Therefore, integrating the curve yields the corresponding component mass. The ratio of the integrated area to the total integrated area is the corresponding mass ratio.)

[0148] Table 1 lists the analysis results of each peak calculated separately after peak separation, as well as the overall molecular weight and its distribution when all peaks are analyzed as a whole. The high molecular weight peak proportion refers to the percentage of the peak area with a weight-average molecular weight greater than 500,000 g / mol to the total peak area. As can be seen from Table 1, multiple peaks appeared in all preparation examples, and the weight-average molecular weight of the larger peaks was greater than 1,000,000 g / mol, and the overall molecular weight was also greater than 250,000 g / mol. The overall molecular weight distribution was also much wider than that of the comparative examples, as reflected in an overall molecular weight distribution index greater than 2, with the overall molecular weight distribution index of Preparation Example 4 reaching 11.36.

[0149] Furthermore, as shown in Table 1, the high molecular weight fraction, with a weight-average molecular weight greater than 500,000 g / mol, accounts for approximately 5-53% of the total, with a maximum proportion of approximately 52%. This indicates that the polyglycolic acid with a multimodal distribution of the present invention contains a high molecular weight polyglycolic acid graft copolymer, and that polyglycolic acid with a multimodal molecular weight distribution is obtained in situ from the polymerization reaction. Although the resulting product has a multimodal distribution and is not entirely ultrahigh molecular weight polyglycolic acid, its molecular weight is still significantly higher than that of polyglycolic acid obtained in the prior art. Using the polyglycolic acid with a multimodal distribution of the present invention as a raw material for extrusion moldings in oil and gas production, the extrusion moldings can be used in higher-pressure oilfield environments without damage.

[0150] Test Example 2

[0151] Melt flow rate tests were performed on some of the preparation examples and the preparation comparison examples to characterize their melt flow rates at the processing temperature. The test results are shown in Table 3.

[0152] Table 2

[0153]

[0154] As can be seen from Table 2, the melt flow rates of the preparation examples of the present invention are significantly lower than those of the preparation of Comparative Example 2. The melt flow rates of some preparation examples are even too small to be detected, that is, lower than the detection limit of the MFR instrument of 0.1 g / 10 min. It can be seen that the polymers of the present invention have a lower melt flow rate, which is more conducive to their application in extrusion molding.

[0155] Test Example 3

[0156] Mechanical properties were tested for some of the prepared examples and comparative examples. The samples were injection molded into 5A tensile bars (thickness: 2 mm) on a HAAKE MiniJet microinjection molding machine according to GB / T1040.2-2006. Tensile tests were then performed on an Instron 3344 material testing machine at a tensile rate of 50 mm / min and a clamp spacing of 50 mm. Typical stress-strain curves for the tensile tests are shown in Figure 2. Figure 2 , the specific analysis results are shown in Table 3. Figure 2 It can be seen that while maintaining relatively high strength and modulus, each preparation example has a significantly higher elongation at break than the preparation comparative example 2 (commercially available PGA), that is, the toughness is significantly improved.

[0157] Table 3

[0158]

[0159] As can be seen from Table 3, the polyglycolic acid with multimodal molecular weight distribution obtained in the present invention has significantly improved toughness compared with traditional polyglycolic acid. Figure 2 The injection-molded bars of Comparative Example 2 (PGA homopolymer) exhibit typical brittle fracture, with an elongation at break and a fracture energy of only 6.9% and 1.1 J, respectively. In contrast, the injection-molded bars of Example 9 of the present invention exhibit ductile fracture, high elongation at break, and a long yield plateau (approximately 22% to 80%) on the tensile stress-strain curve. This exceptionally tough, yielding tensile property of polyglycolic acid is a completely unexpected discovery in polyglycolic acid. Using the polyglycolic acid with a multimodal distribution of the present invention as a raw material for extrusion moldings in oil and gas production, the extrusions can be used in higher-pressure oilfield environments without damage.

[0160] Test Example 4

[0161] Melt stretching tests were performed on some of the preparation examples and the comparative examples at 235°C to characterize their melt strength. The test results are shown in Tables 4 and Figure 3 .Depend on Figure 3 It can be seen that the melt strength of Preparation Example 1 at 230° C. is significantly higher than that of Preparation Comparative Example 2 (commercially available PGA), reaching about 20 cN, while the melt strength of Preparation Comparative Example 2 is less than 1 cN.

[0162] Table 4

[0163] Melt strength (cN) Preparation Example 1 20 Preparation Example 9 9 Comparative Example 1 3 Comparative Example 2 0.3

[0164] As shown in Table 4, the polyglycolide obtained in the present invention (Preparation Examples 1 and 9) exhibited significantly improved melt strength compared to the polyglycolide homopolymer (Comparative Examples 1 and 2). The melt strength increased from 0.3 cN (Comparative Example 2) to 20 cN (Preparation Example 9), a more than 60-fold increase, fully demonstrating the unique and unexpectedly high melt strength of the polyglycolic acid with a multimodal molecular weight distribution of the present invention. The other preparations were not significantly inferior to Preparation Example 9. Extrusions produced using the polyglycolic acid with a multimodal molecular weight distribution of the present invention as raw material for oil and gas production can be used in higher-pressure oilfield environments without damage.

[0165] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A raw material for extrusion molding for oil and gas production, characterized in that: The raw material contains polyglycolic acid with a multimodal molecular weight distribution. Wherein, the polyglycolic acid contains a polyglycolic acid graft copolymer and a polyglycolic acid homopolymer; the polyglycolic acid graft copolymer contains at least a segment represented by formula (I): In formula (I), x, y1, y2, z and p each independently represent the degree of polymerization, wherein x and p each independently represent a positive integer, and y1, y2 and z each independently represent a natural number; In the polyglycolic acid, the weight average molecular weight of the polyglycolic acid graft copolymer is greater than the weight average molecular weight of the polyglycolic acid homopolymer; The compressive strength of the polyglycolic acid at room temperature is 200-400 MPa.

2. The raw material according to claim 1, wherein In formula (I), the sum of x, y1, y2 and z is not less than 50, preferably 50-6000, more preferably 200-2500; and / or z accounts for 0%-50% of the sum of x+y1+y2+z; and / or y1 accounts for 0%-32% of the sum of x+y1+y2; and / or p is not less than 10, preferably p is not less than 50, preferably 70-2000.

3. The raw material according to claim 1 or 2, wherein The polyglycolic acid homopolymer is shown in formula (II): In formula (II), n1, ..., n i Each is independently the degree of polymerization; i is directly connected to R The number of, i≥1; M1, ······, M i Each is independently an imino group, a nitro group or an ether bond; R is hydrogen, an aliphatic group or an aromatic group, and R is H, an alkane group or an aromatic hydrocarbon group; Preferably, in formula (II), i is any integer between 1 and 20, preferably 2 to 6; and / or n1,……,n i The sum is not less than 100; and / or R is an alkane group or an aromatic hydrocarbon group having a molecular weight of 14-1000 g / mol.

4. The raw material according to claim 3, wherein Relative to 100 parts by mass of polyglycolic acid segment The raw material of the polyglycolic acid contains 0.001-10 parts by mass of Contains 0.001-10 parts by mass wherein, the definitions of x, y1, y2, z and p are the same as those of x, y1, y2, z and p in any one of claims 1 to 3; the definitions of R, M, i are the same as those of R, M, i in claim 3; preferably, Relative to 100 parts by mass of polyglycolic acid segment The raw material of the polyglycolic acid contains 0.01-1 parts by mass of Contains 0.01-1 parts by mass 5. The raw material according to any one of claims 1 to 4, wherein The polyglycolic acid has a melt flow rate at 230°C / 2.16kg of not more than 20.0g / 10min, preferably 0.1-20.0g / 10min, preferably 0.1-10.0g / 10min; and / or The total weight average molecular weight of the polyglycolic acid is 200,000-1.5 million g / mol, preferably 250,000-500,000 g / mol; and / or, The overall molecular weight distribution index of the polyglycolic acid is 1.5-20.0, preferably 2.0-3.5; and / or, The polyglycolic acid has at least two molecular weight distribution peaks.

6. The raw material according to any one of claims 1 to 5, wherein In the polyglycolic acid, the weight average molecular weight of the polyglycolic acid graft copolymer is 500,000-10,000,000 g / mol, preferably 1,000,000-6,000,000 g / mol; and / or the weight average molecular weight of the polyglycolic acid homopolymer is 50,000-350,000 g / mol, preferably 100,000-200,000 g / mol; and / or In the polyglycolic acid, the molecular weight polydispersity index of the polyglycolic acid graft copolymer is 1.0-3.0, preferably 1.1-1.5; and / or the molecular weight polydispersity index of the polyglycolic acid homopolymer is 1.0-3.0, preferably 1.4-2.

9.

7. The raw material according to any one of claims 1 to 6, wherein The content of the polyglycolic acid graft copolymer is 0.1% to 80.0% by mass, preferably 1.0% to 30.0% by mass, relative to the total mass of the polyglycolic acid; the content of the polyglycolic acid homopolymer is 20% to 99.9% by mass, preferably 70.0% to 99.0% by mass.

8. An extruded article for oil and gas production, characterized in that: The extrusion molding is obtained by mixing, melting, extruding, cooling and shaping the extrusion molding raw materials according to any one of claims 1 to 7.

9. The extrudate according to claim 8, wherein The temperature of the mixing and melting is 200-270°C; and / or The shape of the extruded product includes at least one of a solid round rod, a hollow round tube, a solid triangular rod, a solid rectangular rod, a solid pentagonal rod, a solid hexagonal rod, a flat plate and a disc.

10. A downhole tool or component for oil and gas production, characterized in that: The tool or component is obtained by mechanical processing of the extruded product described in claim 8 or 9; Preferably, the tool or component comprises at least one of a fracturing ball, a gun bolt, a bridge plug, a packer and a transfer device; and / or The machining method includes at least one of cutting, turning and drilling.

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