Polyimide, method for producing imide compound, and method for producing regenerated polyimide

Abstract

A polyimide according to one aspect of the present disclosure is configured from a non-crosslinked structure including a main chain. And the main chain contains a Si-O-C bond. The main chain may contain a C-O-Si-O-C bond. The main chain contains, for example, a group represented by-OSi (R1) (R2) O-. At least one oxygen atom contained in the group is bonded, for example, to a carbon atom adjacent to the group to form a Si-O-C bond.

Description

Technical Field

[0001] The present disclosure relates to a polyimide, a method for producing an imide compound, and a method for producing a regenerated polyimide. Background Art

[0002] Molded articles of thermosetting resins such as polyimide have excellent chemical resistance and therefore tend to be difficult to dissolve in all solvents. Unlike thermoplastics such as polystyrene, these molded articles also tend to be difficult to melt and reuse due to their excellent heat resistance. Therefore, these molded articles are difficult and unsuitable for recycling or resource recovery, and are disposed of by landfill or incineration. In this specification, molded articles include films.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-87148

[0006] Patent Document 2: Japanese Patent Application Publication No. 2022-12362

[0007] Patent Document 3: Japanese Patent Application Publication No. 2021-195319

[0008] Non-patent literature

[0009] Non-patent document 1: Lin Fan et al., "High Thermally Stable and Melt Processable Polyimide Resins Based on Phenylethynyl-Terminated Oligoimides ContainingSiloxane Structure" Materials, 2020, vol.13, p.3742. Summary of the invention

[0010] Problems to be solved by the invention

[0011] However, from the viewpoints of global environmental pollution problems, resource depletion, and the like, there is a demand for a technology for effectively recycling thermosetting resins, particularly polyimides.

[0012] An object of the present disclosure is to provide a novel polyimide suitable for recycling.

[0013] Means for solving problems

[0014] The polyimide in one embodiment of the present disclosure is composed of a non-crosslinked structure including a main chain including Si-OC bonds.

[0015] Effects of the Invention

[0016] The present disclosure provides a novel polyimide suitable for recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flowchart of a method for producing an imide compound according to one embodiment of the present disclosure.

[0018] Figure 2 This is a flowchart of a method for producing a regenerated polyimide according to one embodiment of the present disclosure.

[0019] Figure 3 is the polyamic acid in Measurement Example 1 1 H-NMR spectrum.

[0020] Figure 4 This is a graph showing the infrared absorption spectrum of the polyimide in Measurement Example 1.

[0021] Figure 5 is a decomposition product of the polyimide in Measurement Example 1. 1 H-NMR spectrum. DETAILED DESCRIPTION

[0022] (Insights that form the basis of this disclosure)

[0023] Polyimide, as an engineering plastic, has excellent heat resistance, mechanical properties, sliding properties, etc. Therefore, in recent years, the demand for polyimide has been rapidly increasing in electrical and electronic equipment applications, automobile parts applications, aerospace industry applications, office equipment applications, etc.

[0024] For example, polyimide film can be made by the following steps: coating the coating solution containing polyamic acid as the precursor of polyimide, after the obtained coating film is dried, the polyamic acid is imidized by utilizing the dehydration cyclization reaction caused by heating etc. The resin moldings such as polyimide film are extremely rigid, have good electrical properties, wear resistance etc., and at the same time have excellent chemical resistance and heat resistance. As an example, polyimide is insoluble in medicines such as organic solvents, and does not melt at high temperatures. However, the resin moldings such as polyimide film are different from many resins including engineering plastics commonly, and even if the moldings are made again after crushing, the bonding of the resin interface in the moldings is also insufficient, and satisfactory characteristics cannot be obtained.

[0025] Composite materials of polyimide and fiber materials such as glass fiber and carbon fiber are also known from the viewpoint of improving mechanical properties and insulation. However, since polyimide has high heat resistance and solvent resistance, the fiber materials are also pulverized and landfilled for waste treatment. As a result, a technology for separating and recovering polyimide and fiber materials from composite materials is also required.

[0026] In the past, chemical recycling has been studied, in which polyimide is converted into other compounds and the converted compounds are reused as raw materials. For example, attempts have been made to hydrolyze polyimide with an acid or alkali aqueous solution. However, in this method, since the decomposition products obtained are not uniform components, the properties of the products produced by recycling the decomposition products tend to be low. Therefore, there is still room for improvement in the material recycling process of polyimide.

[0027] In consideration of chemical recycling, a silicon-oxygen bond can be used as a bond that can be formed and cut. For example, in the case of a silyl protecting group known as a protecting group for alcohol, the silicon-oxygen bond is cut by reaction with a fluoride anion, thereby enabling deprotection.

[0028] Patent Document 1 discloses alkaline hydrolysis of polyimide using an alkaline aqueous solution. According to this method, polyimide can be decomposed into low molecular weight bodies. By decomposition, the polyimide film can be uniformly dissolved in a solvent. However, according to this method, since the decomposed product has a complex composition, it is difficult to reuse the decomposed product.

[0029] Polyimides containing silicon atoms are disclosed in Patent Document 2, Patent Document 3 and Non-Patent Document 1, respectively. However, the polyimides disclosed in these documents are not produced with the idea of ​​decomposition and recycling. In particular, the polyimide of Non-Patent Document 1 has a complex cross-linked structure. For example, the polyimide of Non-Patent Document 1 has a cross-linked structure derived from a carbon-carbon triple bond and a cross-linked structure containing silicon atoms. As a result, the decomposability is low. In addition, even if the polyimide of Non-Patent Document 1 is decomposed, it is difficult to reuse because the decomposed product obtained has a complex cross-linked structure. The polyimides of Patent Documents 2 and 3 also tend to have low solvent resistance and high thermal expansion coefficient.

[0030] [Characteristics of polyimide]

[0031] Polyimide has a tendency to have high heat resistance, flame retardancy, and mechanical properties. And then, polyimide has high electrical insulation, so it can be used as an insulating material or substrate material of a circuit. The linear thermal expansion coefficient of polyimide is very low as an organic matter, and is a value close to that of a metal. Therefore, if polyimide is used as an insulating material of a circuit, it is difficult to produce the strain caused by the thermal expansion with the metal wiring, and wiring processing can be performed with high precision.

[0032] [Synthesis method of polyimide]

[0033] Polyimide can be generally synthesized by condensing diamine and anhydride in equimolar amounts. As an example, diamine and anhydride can be reacted in a highly polar organic solvent, and then the obtained polyamic acid is heated at a high temperature to synthesize polyimide. In this specification, the process of synthesizing polyimide by heat-treating polyamic acid is sometimes referred to as imidization.

[0034] [Polyimide molding method]

[0035] Polyimide generally has no thermoplasticity and is insoluble in various organic solvents. Therefore, it is molded by applying a solution containing a high concentration of polyamic acid as a precursor and performing imidization.

[0036] [Polyimide Decomposition Method]

[0037] Polyimide molded products are generally not thermoplastic and are mostly insoluble in various solvents. Therefore, unlike thermoplastic resins, these molded products are difficult to melt and reuse. Regarding molded products, hydrolysis reactions under high temperature and high pressure conditions, decomposition and recovery methods using alkaline aqueous solutions, etc. have been proposed. However, the decomposition under high temperature and high pressure conditions requires a lot of energy. When a strong base is used for decomposition, a neutralization process is required after treatment.

[0038] [Higher functionality of polyimide]

[0039] For polyimide, by adjusting the types of diamine and anhydride used as raw materials as needed, it is possible to appropriately design according to the purpose of thermal properties, mechanical properties, electrical insulation, optical properties and other properties. Therefore, sometimes two or more diamines are used in combination. For example, in order to achieve low thermal expansion, rigid and linear diamines and anhydrides can be selected. However, for polyimide composed only of rigid monomers, there is a tendency that the main chains lack entanglement with each other. Therefore, as needed, a method for synthesizing polyimide by mixing a portion of diamines that can impart bending properties. In order to reduce the dielectric constant and water absorption of polyimide, diamines or anhydrides with fluorine-containing groups such as trifluoromethyl can be selected. In addition, by selecting alicyclic anhydrides, polyimide with low dielectric constant and high transparency can be obtained. In order to give adhesion and flexibility to polyimide, diamines with polysiloxane structures can be selected. In this case, the longer the polysiloxane structure in the diamine, the more clear the phase separation structure of the polyimide. At this time, it is known that the properties of polyimide represented by the surface state have changed significantly. Through the significant change in properties, polyimide soluble in organic solvents can be obtained. This polyimide can be used for adhesives and other purposes.

[0040] As mentioned above, in the technical field of polyimide, many molecular structure designs that contribute to physical properties have been conducted. On the other hand, as far as the present inventors know, molecular structure designs for the purpose of giving polyimide decomposability and other recycling purposes have not been achieved so far. The present inventors have conducted careful studies and have completed a new polyimide that can be easily decomposed when it is not needed.

[0041] (Overview of one aspect of the present disclosure)

[0042] The polyimide according to the first aspect of the present disclosure is composed of a non-crosslinked structure including a main chain containing Si-OC bonds.

[0043] The polyimide of the first embodiment can be easily decomposed by, for example, a reaction with a fluorine-containing compound. This polyimide is suitable for recycling.

[0044] In the second aspect of the present disclosure, for example, in the polyimide according to the first aspect, the main chain may contain a CO-Si-OC bond.

[0045] When the polyimide of the second embodiment is decomposed by a fluorine-containing compound, the imide compound as the decomposition product has, for example, two hydroxyl groups and can be easily reused.

[0046] In the third embodiment of the present disclosure, for example, in the polyimide according to the first or second embodiment, the main chain may contain a group represented by -OSi(R1)(R2)O-, and at least one oxygen atom contained in the group may be bonded to a carbon atom adjacent to the group to form the Si-OC bond. In the above group, R1 and R2 may independently contain at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I.

[0047] In a fourth aspect of the present disclosure, for example, in the polyimide according to any one of the first to third aspects, the non-crosslinked structure may contain a first structural unit represented by the following formula (A1).

[0048] [Chemical formula number 1]

[0049]

[0050] In the formula (A1),

[0051] R1 and R2 independently contain at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I,

[0052] X and Y are independently a divalent group containing at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I,

[0053] Z is a tetravalent group containing at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I,

[0054] At least one selected from the group consisting of X and Y may include a carbon atom bonded to an adjacent oxygen atom to form the Si—OC bond.

[0055] In a fifth aspect of the present disclosure, for example, in the polyimide according to any one of the first to fourth aspects, the non-crosslinked structure may contain a second structural unit represented by the following formula (A2).

[0056] [Chemical formula number 2]

[0057]

[0058] In the formula (A2),

[0059] R1 to R 10 may contain, independently of one another, at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I,

[0060] Z may be a tetravalent group containing at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I.

[0061] When the polyimide of the third to fifth embodiments is decomposed by a fluorine-containing compound, the imide compound as the decomposition product has an alcohol structure such as a phenol structure at its terminal. This imide compound can be reused more easily.

[0062] In a sixth aspect of the present disclosure, for example, in the polyimide according to any one of the first to fifth aspects, the non-crosslinked structure may contain a third structural unit represented by the following formula (A3).

[0063] [Chemical formula number 3]

[0064]

[0065] In the formula (A3), R1 to R 12 At least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I may be contained independently of each other.

[0066] In a seventh aspect of the present disclosure, for example, in the polyimide according to any one of the first to sixth aspects, the non-crosslinked structure may contain a fourth structural unit represented by the following formula (A4).

[0067] [Chemical formula number 4]

[0068]

[0069] In the formula (A4), R1 to R 10 and R 13 To R 18 At least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I may be contained independently of each other.

[0070] The polyimide of the sixth and seventh schemes has a tendency to have excellent solvent resistance and thermal properties. The coating liquid containing the polyamic acid as the precursor of the polyimide also has a tendency to be excellent in coating and film forming properties. The polyimide of the sixth and seventh schemes can be easily decomposed when not needed, for example, by reaction with a fluorine-containing compound. When the polyimide is decomposed, an imide compound having a phenol structure at the end and suitable for reuse can be obtained.

[0071] In an eighth aspect of the present disclosure, for example, in the polyimide according to any one of the third to seventh aspects, R1 and R2 may be independently a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms.

[0072] The polyimide of the eighth aspect can be easily synthesized. Furthermore, the polyimide can be easily decomposed by, for example, reacting with a fluorine-containing compound.

[0073] The polyimide according to the ninth aspect of the present disclosure may include a main chain including Si—OC bonds, wherein the ratio of the number of silicon atoms included in the main chain to the number of imide groups included in the main chain is 2% to 50%.

[0074] In the tenth aspect of the present disclosure, for example, the polyimide according to the first or ninth aspect may have a weight average molecular weight of 1,000 or more.

[0075] The polyimides of the ninth and tenth embodiments tend to have good solvent resistance and thermal properties.

[0076] In the polyimide of one embodiment of the present disclosure, the non-crosslinked structure may include a plurality of structural units. For example, the non-crosslinked structure may include the third structural unit represented by the formula (A3) and the fourth structural unit represented by the formula (A4).

[0077] The method for producing an imide compound according to the eleventh aspect of the present disclosure comprises:

[0078] contacting the polyimide according to any one of the first to tenth aspects with a fluorine-containing compound; and

[0079] The polyimide is reacted with the fluorine-containing compound to obtain an imide compound which is a decomposition product of the polyimide.

[0080] According to the eleventh aspect, the imide compound can be easily produced by decomposing the polyimide.

[0081] In a twelfth aspect of the present disclosure, for example, according to the production method of the eleventh aspect, the fluorine-containing compound may contain a fluoride salt.

[0082] According to the twelfth embodiment, the imide compound can be produced using a relatively easily available and inexpensive fluoride salt.

[0083] In the thirteenth aspect of the present disclosure, for example, according to the production method of the twelfth aspect, the fluoride salt may contain tetrabutylammonium fluoride.

[0084] According to the thirteenth aspect, for example, polyimide can be decomposed at room temperature to produce an imide compound.

[0085] A fourteenth aspect of the present disclosure provides a method for producing a regenerated polyimide, comprising: decomposing the polyimide according to any one of the first to tenth aspects to obtain a decomposition product of the polyimide; and

[0086] The decomposed product is used to synthesize a recycled polyimide.

[0087] According to the fourteenth aspect, the polyimide can be reused.

[0088] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The present disclosure is not limited to the following embodiments.

[0089] (Implementation Method)

[0090] The polyimide P of this embodiment has a Si-OC bond on the main chain. In other words, the polyimide P contains a structural unit A having a Si-OC bond on the main chain. From the perspective of ease of recycling, the polyimide P may also have a CO-Si-OC bond on the main chain. For example, if the polyimide P having a CO-Si-OC bond on the main chain is decomposed, an imide compound having two hydroxyl groups can be obtained. The imide compound can be easily reused.

[0091] The polyimide P is composed of a non-crosslinked structure. That is, the polyimide P does not have a crosslinked structure, and excludes those having a crosslinked structure. In detail, the polyimide P excludes those having multiple main chains and the multiple main chains are crosslinked with each other. In other words, with respect to the polyimide P of the present embodiment, the number of main chains is 1. In the polyimide P, the main chain extends in a straight line, for example. In addition, the polyimide P of the present embodiment is a main chain containing a Si-OC bond, and does not have multiple main chains. The above-mentioned polyimide P may also contain a structural unit having a crosslinked structure.

[0092] The polyimide P may also have a group g represented by -OSi(R1)(R2)O-. In other words, in the polyimide P, the structural unit A may also have a group g. At least one oxygen atom contained in the group g is bonded to a carbon atom adjacent to the group g to form a Si-OC bond, for example.

[0093] In the above-mentioned group g, R1 and R2 may be the same or different. R1 and R2 may independently contain at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. R1 and R2 may also independently contain at least one atom selected from the group consisting of H, C, O, F, Cl, Br and I. R1 and R2 may also independently contain hydrogen atoms, halogen atoms or hydrocarbon groups.

[0094] Examples of the halogen atom include F, Cl, Br, and I. In this specification, a halogen atom may be referred to as a halogen group.

[0095] The number of carbon atoms in the hydrocarbon group is not particularly limited, and may be, for example, 1 to 20, 1 to 10, or 1 to 6. The hydrocarbon group may be linear, branched, or cyclic.

[0096] Examples of the hydrocarbon group include an aliphatic saturated hydrocarbon group, an alicyclic hydrocarbon group, an aliphatic unsaturated hydrocarbon group, and an aromatic hydrocarbon group. The aliphatic saturated hydrocarbon group may be an alkyl group. Examples of the aliphatic saturated hydrocarbon group include -CH3, -CH2CH3, -CH2CH2CH3, -CH(CH3)2, -CH(CH3)CH2CH3, -C(CH3)3, -CH2CH(CH3)2, -(CH2)3CH3, -(CH2)4CH3, -C(CH2CH3)(CH3)2, -CH2C(CH3)3, -(CH2)5CH3, -(CH2)6CH3, -(CH2)7CH3, -(CH2)8CH3, -(CH2)9CH3, -(CH2) 10 CH3, -(CH2) 11 CH3, -(CH2) 12 CH3, -(CH2)13 CH3, -(CH2) 14 CH3, -(CH2) 15 CH3, -(CH2) 16 CH3, -(CH2) 17 CH3, -(CH2) 18 CH3, -(CH2) 19 Examples of alicyclic hydrocarbon groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and adamantyl. Examples of aliphatic unsaturated hydrocarbon groups include -CH=CH2, -C≡CH, -C≡CCH3, -C(CH3)=CH2, -CH=CHCH3, and -CH2CH=CH2. Examples of aromatic hydrocarbon groups include phenyl, and the like.

[0097] R1 and R2 may be independently hydrogen atoms or hydrocarbon groups having a carbon number of 1 or more and 6 or less, or methyl groups or phenyl groups, or methyl groups. In the case where R1 and R2 are hydrogen atoms or hydrocarbon groups having a carbon number of 1 or more and 6 or less, since the steric hindrance of R1 and R2 is small, for example, the reaction of polyimide P with a fluorine-containing compound is not easily hindered. In other words, by reacting with a fluorine-containing compound, the Si-O bond in polyimide P can be easily cut, so polyimide P can be easily decomposed. In the case where R1 and R2 are hydrogen atoms or hydrocarbon groups having a carbon number of 1 or more and 6 or less, since the raw materials can be obtained relatively easily, there is also a tendency that polyimide P can be easily synthesized.

[0098] In the polyimide P, the structural unit A may be represented by the following formula (A1). In other words, the polyimide P may contain the structural unit A1 represented by the following formula (A1).

[0099] [Chemical formula number 5]

[0100]

[0101] In formula (A1), R1 and R2 independently contain at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. As examples of R1 and R2, those described above for group g can be cited.

[0102] X and Y are independently a divalent group containing at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. For example, at least one atom selected from the group consisting of X and Y contains a carbon atom bonded to an adjacent oxygen atom to form a Si-OC bond.

[0103] X and Y can be independently a divalent hydrocarbon group which may have a substituent. As the divalent hydrocarbon group, arylene, alkylene, etc. can be listed. X and Y can be phenylene which may have a substituent. In this case, by decomposing the polyimide P, an imide compound having a phenol structure at the end and suitable for recycling can be obtained. As the substituent of the divalent hydrocarbon group, those described above for R1 and R2 of the group g can be listed.

[0104] Z is a tetravalent group containing at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. Examples of Z include a group represented by the following formula (i) and a group represented by the following formula (ii).

[0105] [Chemical formula number 6]

[0106]

[0107] In formula (i), R 11 and R 12 Each of the above-mentioned atoms independently contains at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. 11 and R 12 Examples of R1 and R2 include those described above for group g. 11 and R 12 They may be hydrogen atoms respectively.

[0108] In formula (ii), R 13 To R 18 Each of the above-mentioned atoms independently contains at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. 13 To R 18 Examples of R1 and R2 include those described above for group g. 13 To R 18 They may be hydrogen atoms respectively.

[0109] In formula (ii), Q is a single bond or a divalent group containing at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. In Q, the divalent group, for example, contains at least one functional group selected from the group consisting of an ether group, an acyl group, an ester group and a sulfonyl group. The divalent group may also contain an acyl group. The divalent group may contain a divalent hydrocarbon group instead of the above functional group or may contain the above functional group and the divalent hydrocarbon group at the same time. The divalent hydrocarbon group may also have a substituent other than the above functional group. As the divalent hydrocarbon group, those described above for X and Y may be listed.

[0110] When Z is a group represented by formula (ii), the polyimide P tends to have flexibility.

[0111] Z may also be a group other than the group represented by formula (i) and the group represented by formula (ii). As an example, Z may also be a group containing an alicyclic hydrocarbon group. In this case, the polyimide P tends to have high transparency.

[0112] The structural unit A may be represented by the following formula (A2). In other words, the polyimide P may contain the structural unit A2 represented by the following formula (A2).

[0113] [Chemical formula number 7]

[0114]

[0115] In formula (A2), R1 to R 10 Each of R1 to R2 contains independently at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. 10 Examples of R1 to R2 include those described above for group g. 10 They may be hydrogen atoms respectively.

[0116] In formula (A2), Z is a tetravalent group containing at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. As examples of Z, those described above for formula (A1) can be cited.

[0117] The structural unit A may be represented by the following formula (A3) or the following formula (A4). In other words, the polyimide P may contain at least one selected from the group consisting of the structural unit A3 represented by the following formula (A3) and the structural unit A4 represented by the following formula (A4).

[0118] [Chemical formula number 8]

[0119]

[0120] In formula (A3), R1 to R 12 Each of R1 to R2 contains independently at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. 12 As examples, there can be cited those described above for R1 and R2 of group g.

[0121] In formula (A4), R1 to R 10 and R 13 To R 18Each of R1 to R2 contains independently at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. 10 and R 13 To R 18 As examples, there can be cited those described above for R1 and R2 of group g.

[0122] The content of the structural unit A in the polyimide P is, for example, 2 mol% or more, 5 mol% or more, 10 mol% or more, 30 mol% or more, 50 mol% or more, 80 mol% or more, or 90 mol% or more. The polyimide P may be substantially composed of only the structural unit A. However, depending on the circumstances, the content of the structural unit A in the polyimide P may be 80 mol% or less.

[0123] The polyimide P may further contain other structural units B other than the structural unit A. The structural unit B typically does not contain a Si-OC bond. The structural unit B is represented by the following formula (B1), for example.

[0124] [Chemical formula number 9]

[0125]

[0126] In formula (B1), G is a divalent group containing at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. In G, the divalent group, for example, contains at least one functional group selected from the group consisting of an ether group, an acyl group, an ester group, an amide group, a thioether group, a disulfide group and a sulfonyl group. The divalent group may contain an ether group. The divalent group, for example, contains the above functional group and a divalent hydrocarbon group at the same time. The divalent hydrocarbon group may also have a substituent other than the above functional group. As the divalent hydrocarbon group, those described above for X and Y can be cited. The divalent group may contain a phenylene group while containing an ether group.

[0127] L is a tetravalent group containing at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. As examples of L, those described above with respect to Z can be cited.

[0128] The structural unit B may be represented by the following formula (B2) or the following formula (B3). In other words, the polyimide P may contain at least one selected from the group consisting of the structural unit B2 represented by the following formula (B2) and the structural unit B3 represented by the following formula (B3).

[0129] [Chemical formula number 10]

[0130]

[0131] In formula (B2), R 19 To R 28 Each of the above-mentioned atoms independently contains at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. 19 To R 28 Examples of R1 and R2 include those described above for group g. 19 To R 28 Each may be a hydrogen atom.

[0132] In formula (B3), R 19 To R 26 and R 29 To R 34 Each of the above-mentioned atoms independently contains at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I. 19 To R 26 and R 29 To R 34 Examples of R1 and R2 include those described above for group g. 19 To R 26 and R 29 To R 34 Each may be a hydrogen atom.

[0133] The content of the structural unit B in the polyimide P is not particularly limited, and may be, for example, 98 mol% or less, 95 mol% or less, 90 mol% or less, 70 mol% or less, 50 mol% or less, 20 mol% or less, or 10 mol% or less. The polyimide P may not contain the structural unit B. However, depending on the circumstances, the content of the structural unit B in the polyimide P may be 20 mol% or more.

[0134] The polyimide P can be represented by the following formula (1).

[0135] [Chemical formula number 11]

[0136]

[0137] In formula (1), A represents structural unit A, and B represents structural unit B. n, m, and l are independently arbitrary integers. The polyimide P represented by formula (1) can be easily adjusted in physical properties based on the same molecular design as conventional polyimides.

[0138] In the polyimide P, the ratio p of the number of silicon atoms to the number of imide groups is, for example, 2% or more. More specifically, in the polyimide P having a main chain containing Si-OC bonds, the ratio p of the number of silicon atoms contained in the main chain to the number of imide groups contained in the main chain is 2% or more and 50% or less. The ratio p may also be 2% or more and 40% or less, 2% or more and 30% or less, or 2% or more and 10% or less. In other words, the ratio p may satisfy 2%≤p≤50%, 2%≤p≤40%, 2%≤p≤30% or 2%≤p≤10%. By adjusting the ratio p to the above range, the decrease in solvent resistance and thermal properties of the polyimide P can be suppressed. Furthermore, the coating solution containing the polyamic acid as a precursor of the polyimide P has good viscosity and also tends to have excellent coating properties and film-forming properties.

[0139] In addition, the main chain containing Si-OC bonds in the polyimide P is easily decomposed. Thus, an imide compound can be easily obtained as a decomposition product of the polyimide P. In addition, the obtained imide compound shows good solubility in an organic solvent and can be used for the production of a regenerated polyimide.

[0140] The weight average molecular weight of the polyimide P is, for example, 1000 or more, 2500 or more, 5000 or more, or 10000 or more. The upper limit of the weight average molecular weight of the polyimide P is not particularly limited, and is, for example, 1,000,000.

[0141] The polyimide P can be synthesized by reacting a diamine with tetracarboxylic dianhydride. In this specification, tetracarboxylic dianhydride may be simply referred to as anhydride. Specific examples of the diamine used to form the structural unit A include the following.

[0142] [Chemical formula number 12]

[0143]

[0144] Specific examples of other diamines for forming the polyimide P include the following.

[0145] [Chemical formula number 13]

[0146]

[0147]

[0148] Specific examples of the acid anhydride for forming the polyimide P include the following.

[0149] [Chemical formula number 14]

[0150]

[0151] The physical properties of polyimide P can be appropriately adjusted by the combination of diamine and anhydride used in the synthesis. As the physical properties of polyimide P, heat resistance, solvent resistance, transparency, dielectric constant, thermal expansion coefficient, etc. can be listed. As an example, in the case where diamine or anhydride contains an aromatic ring on the main chain and has a rigid structure, for polyimide P, the thermal expansion coefficient can be adjusted to a lower value while improving heat resistance and solvent resistance. In the case where diamine or anhydride contains an alicyclic hydrocarbon group, for polyimide P, the dielectric constant can be adjusted to a lower value while improving transparency. In the synthesis of polyimide P, diamine and anhydride can be used in combination of two or more.

[0152] Polyimide P can achieve the same degree of heat resistance and solvent resistance as conventional polyimides. Therefore, polyimide P can be used for the same purposes as before. As an example, polyimide P can be used as a resin contained in composite materials such as substrate materials or fiber reinforced plastics.

[0153] [Method for producing imide compound]

[0154] As described above, the polyimide P has Si-OC bonds in the main chain and is composed of a non-crosslinked structure. The polyimide P having such a structure can be easily decomposed, and thus an imide compound as a decomposition product of the polyimide P can be obtained.

[0155] The imide compound can be produced, for example, by the following method. Figure 1 This is a flow chart of a method for producing an imide compound. First, in step S11, a polyimide P is brought into contact with a fluorine-containing compound. The fluorine-containing compound may also contain a fluoride salt. The fluoride salt is soluble in water, an organic solvent, etc. The fluoride salt may also be an inexpensive ammonium fluoride salt that is relatively easy to obtain. Ammonium fluoride salts tend to have appropriate solubility in solvents. The fluoride salt may also contain tetrabutylammonium fluoride as an ammonium fluoride salt.

[0156] In step S11, the polyimide P and the fluorine-containing compound may be brought into contact in a solvent. As the solvent, for example, a polar solvent such as water or tetrahydrofuran (THF) may be used.

[0157] Next, in step S12, the polyimide P is reacted with a fluorine-containing compound. The reaction of the polyimide P and the fluorine-containing compound can be carried out, for example, by placing the polyimide P in contact with the fluorine-containing compound. In step S12, the reaction can be promoted by adjusting the amount of the fluorine-containing compound used, the reaction temperature, the presence or absence of stirring, etc.

[0158] When the polyimide P is reacted with a fluorine-containing compound, the Si-O bond of the polyimide P is broken and the polyimide P is decomposed. Thus, an imide compound having an alcohol structure such as a phenol structure at the end is obtained as a decomposition product. As an example, when the polyimide P containing the above-mentioned structural unit A1 is decomposed, an imide compound represented by the following formula (2) can be obtained. In formula (2), X, Y and Z are the same as those described above for formula (A1).

[0159] [Chemical formula number 15]

[0160]

[0161] [Method for producing regenerated polyimide]

[0162] For the decomposition product of polyimide P, further molecular conversion can be performed. In particular, when the decomposition product is an imide compound having an alcohol structure at the end, molecular conversion can be easily performed. By performing molecular conversion, polyimide P can be reused. In other words, polyimide P can be upgraded. As an example, the decomposition product of polyimide P can also be used to synthesize regenerated polyimide P1. The composition of regenerated polyimide P1 may be different from that of polyimide P or the same as that of polyimide P.

[0163] The regenerated polyimide P1 can be produced, for example, by the following method. Figure 2 This is a flow chart of a method for producing a regenerated polyimide P1. First, in step S21, the polyimide P is decomposed. The decomposition of the polyimide P can be performed, for example, by the above-mentioned steps S11 and S12. By decomposing the polyimide P, a decomposition product of the polyimide P can be obtained. As described above, the decomposition product of the polyimide P is, for example, an imide compound having an alcohol structure at the end. In the case where a plurality of imide compounds are obtained by decomposing the polyimide P, a separation operation and a purification operation can also be performed as needed.

[0164] Then, in step S22, the regenerated polyimide P1 is synthesized using the decomposition product of the polyimide P. The synthesis conditions of the regenerated polyimide P1 can be appropriately set according to the composition of the decomposition product, the composition of the target regenerated polyimide P1, etc. In this way, according to the production method of this embodiment, the regenerated polyimide P1 can be produced from the polyimide P, and the polyimide P can be reused.

[0165] Example

[0166] Hereinafter, the present invention will be described in more detail by way of examples. In addition, the following examples are just examples, and the present disclosure is not limited to the following examples.

[0167] First, as synthetic raw materials for polyimide, anhydride and diamine were prepared. Specifically, as anhydride, the following compound A (manufactured by Tokyo Chemical Industry Co., Ltd.) and compound B (manufactured by Sigma-Aldrich Co., Ltd.) were prepared. As diamine, the following compound C and compound D (manufactured by Tokyo Chemical Industry Co., Ltd.) were prepared. In addition, as a solvent used in the reaction, dimethylacetamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade) was prepared.

[0168] [Chemical formula number 16]

[0169]

[0170]

[0171] [Synthesis of Compound C]

[0172] Compound C was synthesized according to the method described in Thermochimica Acta 2019, 671, 119-126. Compound C was prepared by 1 Identified by H-NMR.

[0173] <Example 1>

[0174] [Synthesis of polyamide]

[0175] By carrying out the following operation under a nitrogen atmosphere, a polyimide was synthesized. First, 1.090 g (5 mmol) of compound A was measured and 8.5 g of dimethylacetamide (super dehydrated) was added. The dimethylacetamide solution of the compound A obtained was stirred at a rotating speed of about 100 rpm, and a mixture of 1.090 g (4 mmol) of compound C and 0.200 g (1 mmol) of compound D was added. At this time, the mixture was added to the solution little by little with a time of about 2 minutes. The solution was stirred at room temperature for 30 minutes, thus obtaining a dimethylacetamide solution of polyamic acid.

[0176] Next, a dimethylacetamide solution of polyamic acid was applied on a glass plate having a size of 5 cm square and a thickness of 1 cm. Next, the solution was heated on a hot plate at 50° C. for 16 hours and dried to obtain a film made of polyamic acid.

[0177] The polyimide of Example 1 was obtained by heating a film composed of polyamic acid on a hot plate at 80°C for 1 hour, at 100°C for 1 hour, and at 130°C for 1 hour. The polyimide was identified by infrared absorption spectroscopy. It was confirmed that, when compared with the infrared absorption spectrum of polyamic acid, the infrared absorption spectrum of polyimide showed a peak at 1715 cm -1At the same time, the absorption from the imide group increased.

[0178] [Evaluation of decomposition]

[0179] 3 mL of a THF solution containing 1 mol / L tetrabutylammonium fluoride (TBAF) was added to 100 mg of the synthesized polyimide, and the mixture was allowed to stand at room temperature for 48 hours. The polyimide began to dissolve in the solution at the stage when the THF solution was added, and was completely dissolved after 48 hours. It is speculated that the polyimide of Example 1 was decomposed by reacting with tetrabutylammonium fluoride, thereby dissolving in the THF solution.

[0180] As a comparative experiment, 3 mL of THF was added to 100 mg of the synthesized polyimide. At this time, the polyimide did not dissolve in THF even after being left standing at room temperature for 48 hours, and no change was observed even after being left standing for 96 hours.

[0181] <Example 2>

[0182] The polyimide of Example 2 was synthesized in the same manner as in Example 1 except that 0.682 g (2.5 mmol) of Compound C and 0.500 g (2.5 mmol) of Compound D were used. The decomposability of the synthesized polyimide was evaluated in the same manner as in Example 1, and the same results as in Example 1 were obtained.

[0183] <Example 3>

[0184] The polyimide of Example 3 was synthesized in the same manner as in Example 1 except that 0.137 g (0.5 mmol) of Compound C and 0.900 g (4.5 mmol) of Compound D were used. The decomposability of the synthesized polyimide was evaluated in the same manner as in Example 1, and the same results as in Example 1 were obtained.

[0185] <Example 4>

[0186] The polyimide of Example 4 was synthesized in the same manner as in Example 1 except that 0.068 g (0.25 mmol) of Compound C and 0.950 g (4.75 mmol) of Compound D were used. The decomposability of the synthesized polyimide was evaluated in the same manner as in Example 1, and the same results as in Example 1 were obtained.

[0187] <Example 5>

[0188] The polyimide of Example 5 was synthesized in the same manner as in Example 3 except that 1.610 g (5 mmol) of Compound B was used instead of Compound A. Furthermore, the decomposability of the synthesized polyimide was evaluated in the same manner as in Example 1, and the same results as in Example 1 were obtained.

[0189] <Example 6>

[0190] Except using 1.365g (5mmol) compound C and not using compound D, the polyimide of embodiment 6 was synthesized by the same method as embodiment 1. However, in embodiment 6, the viscosity of the dimethylacetamide solution of polyamic acid is low, and the film consisting of polyamic acid can not be made. Therefore, in embodiment 6, a powder consisting of polyamic acid is made, and the powder is heat-treated to obtain a powder consisting of polyimide. And then, about the synthesized polyimide, the same method as embodiment 1 was used to evaluate decomposability, and the same result as embodiment 1 was obtained.

[0191] <Comparative Example 1>

[0192] Instead of using compound C, 1.001 g (5.0 mmol) of compound D was used, and the film composed of polyamic acid was heated at 80°C for 1 hour, at 100°C for 1 hour, at 130°C for 1 hour, and at 150°C for 1 hour. Except for this, the polyimide of Comparative Example 1 was synthesized by the same method as Example 1.

[0193] The synthesized polyimide was evaluated for decomposability using the same method as in Example 1. As a result, the polyimide did not dissolve in the THF solution containing tetrabutylammonium fluoride at a concentration of 1 mol / L, and no change was observed in appearance even when the solution was left standing at room temperature for 48 hours. Similarly, no change was observed in appearance even when the solution was left standing at room temperature for 120 hours. In the comparative experiment, no change was observed in appearance compared to the case where only THF was added to the polyimide.

[0194] <Comparative Example 2>

[0195] The polyimide of Comparative Example 2 was synthesized by the same method as Comparative Example 1 except that 1.610 g (5 mmol) of Compound B was used instead of Compound A.

[0196] The synthesized polyimide was evaluated for decomposability using the same method as in Example 1. As a result, the polyimide did not dissolve in the THF solution containing tetrabutylammonium fluoride at a concentration of 1 mol / L, and no change was observed in appearance even when the solution was left standing at room temperature for 48 hours. Similarly, no change was observed in appearance even when the solution was left standing at room temperature for 120 hours. In the comparative experiment, no change was observed in appearance compared to the case where only THF was added to the polyimide.

[0197] <Measurement of Weight Average Molecular Weight>

[0198] The molecular weight distribution of the polyamic acid synthesized in the examples and comparative examples was measured under the following conditions to determine the weight average molecular weight. The results are shown in Table 1.

[0199] ·Measurement conditions

[0200] Apparatus: Liquid chromatography apparatus (manufactured by Shimadzu Corporation, LC-Vp)

[0201] Chromatographic column: TSKgel Super AWM-HL Super AW2500 (manufactured by Tosoh Corporation)

[0202] Eluent: N, N-dimethylformamide + 30mmol / L lithium bromide + 10mmol / L phosphoric acid

[0203] Flow rate: 0.5mL / min

[0204] Injection volume: 40 μL

[0205] Column temperature: 40°C

[0206] Standard samples: monodisperse polyethylene oxide, polyethylene glycol

[0207] Detector: Differential Refractometer (RI)

[0208] Table 1

[0209] Number of silicon atoms / number of imide groups Decomposition Weight average molecular weight Types of Acid Anhydrides Example 1 40％ good 4100 Compound A Example 2 25％ good 4000 Compound A Example 3 5％ good 14000 Compound A Example 4 2.5％ good 12000 Compound A Example 5 5％ good 14000 Compound B Example 6 50％ good 1200 Compound A Comparative Example 1 0％ bad 61000 Compound A Comparative Example 2 0％ bad 18000 Compound B

[0210] In Table 1, the decomposability of the polyimide dissolved in the THF solution containing TBAF is recorded as "good", and the decomposability of the polyimide insoluble in the THF solution containing TBAF is recorded as "poor". As can be seen from Table 1, the polyimide of the example having Si-OC bonds on the main chain has better decomposability than the comparative example and is suitable for recycling. In particular, the polyimide of the example can be easily decomposed at room temperature by using a fluorinated compound.

[0211] In addition, as can be seen from Table 1, there is a tendency that the weight average molecular weight of the polyamic acid decreases as the proportion of the compound C used increases. This result is presumably caused by the fact that the silicon atom portion of the polyamic acid is easily hydrolyzed, and the number of cleavage sites in the main chain of the polyamic acid increases according to the molar fraction of the silicon atom, making it significantly easier to lower the molecular weight.

[0212] In Example 6, the polyamic acid has a relatively small weight average molecular weight of 1200, so the viscosity of the dimethylacetamide solution of the polyamic acid is low, and the coating and film forming properties are low. In contrast, in Examples 1 to 5, the polyamic acid has a weight average molecular weight suitable for coating and film forming.

[0213] <Measurement Example 1>

[0214] Next, the following measurements were performed to identify the molecular structure of the polyimide and the molecular structure of its decomposition product.

[0215] (NMR tube experiment)

[0216] [Synthesis of polyamic acid]

[0217] An NMR tube experiment using deuterated DMF solvent was performed at a ratio of about 1 / 1000 of that in Example 6. In this experiment, after adding compound C to deuterated DMF solvent of compound A, the reaction was observed at room temperature for about 10 minutes. 1 The generation of polyamic acid can be confirmed by H-NMR. Figure 3 is the polyamic acid in Measurement Example 1 1 H-NMR spectrum of polyamic acid 1 The H-NMR spectrum is as follows.

[0218] 1 H-NMR (600MHz, DMF-d7), δ (ppm): 10.42 (s, 2H), 8.41-8.00 (s, 2H), 7.75 (m, 4H), 7.03 (m, 4H), 0.41 (t, J = 5.4Hz, 6H).

[0219] (Infrared absorption spectrum of polyimide)

[0220] The polyimide synthesized in Example 6 was subjected to infrared spectroscopy to obtain an infrared absorption spectrum. Figure 4 This is a graph showing the infrared absorption spectrum of the polyimide in Measurement Example 1. Figure 4 It can be seen from the infrared absorption spectrum of polyimide that absorption derived from the imide group is confirmed.

[0221] (NMR tube experiment)

[0222] [Decomposition of polyimide]

[0223] The polyimide synthesized in Example 6 and deuterated DMSO solvent were added to the NMR tube for 1 H-NMR measurement. The result showed that polyimide was insoluble in the deuterated DMSO solvent, and no signal from polyimide was obtained. Then, a THF solution containing 1 mol / L tetrabutylammonium fluoride was added and immediately 1 H-NMR measurement. 1 H-NMR signal. Figure 5 This is a graph showing the decomposition products of the polyimide in Measurement Example 1. 1 H-NMR spectrum.

[0224] according to Figure 5 The decomposition product was determined to be a compound represented by the following formula (3). The compound was obtained by cutting the Si-O bond of the polyimide. - and + NBu4 forms a salt.

[0225] [Chemical formula number 16]

[0226]

[0227] It is believed that the Si-O bonds of the polyimides of Examples 1 to 5 were similarly cleaved by the reaction with the fluorine-containing compound to generate decomposition products. In the evaluation of the decomposability of Examples 1 to 6, it is believed that the polyimide was completely dissolved in the THF solution by generating decomposition products from the polyimide.

[0228] Industrial Applicability

[0229] The polyimide P disclosed in the present invention tends to have excellent solvent resistance and thermal properties. Furthermore, the polyimide P can be easily decomposed and removed when not needed. Therefore, the polyimide P can be used as a substrate material or a resin contained in a composite material such as a fiber-reinforced plastic.

Claims

1. A polyimide comprising a non-crosslinked structure having a main chain containing Si-OC bonds.

2. The polyimide according to claim 1, wherein The main chain contains CO-Si-OC bonds.

3. The polyimide according to claim 1 or 2, wherein The main chain contains a group represented by -OSi(R1)(R2)O-, At least one oxygen atom contained in the group is bonded to a carbon atom adjacent to the group to form the Si—OC bond, In the group, R1 and R2 independently contain at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I.

4. The polyimide according to any one of claims 1 to 3, wherein The non-crosslinked structure contains a first structural unit represented by the following formula (A1), [Chemical formula number 1] In the formula (A1), R1 and R2 independently contain at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I, X and Y are independently a divalent group containing at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I, Z is a tetravalent group containing at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I, At least one selected from the group consisting of X and Y is bonded to an adjacent oxygen atom to form the Si—OC bond.

5. The polyimide according to any one of claims 1 to 4, wherein The non-crosslinked structure contains a second structural unit represented by the following formula (A2), [Chemical formula number 2] In the formula (A2), R1 to R 10 independently contain at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I, Z is a tetravalent group containing at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I.

6. The polyimide according to any one of claims 1 to 5, wherein The non-crosslinked structure contains a third structural unit represented by the following formula (A3), [Chemical formula number 3] In the formula (A3), R1 to R 12 Each of the above-mentioned atoms independently contains at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I.

7. The polyimide according to any one of claims 1 to 6, wherein The non-crosslinked structure contains a fourth structural unit represented by the following formula (A4), [Chemical formula number 4] In the formula (A4), R1 to R 10 and R 13 To R 18 Each of the above-mentioned atoms independently contains at least one atom selected from the group consisting of H, C, N, O, S, F, Cl, Br and I.

8. The polyimide according to any one of claims 3 to 7, wherein R1 and R2 are independently a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms.

9. A polyimide having a main chain containing Si-OC bonds, The ratio of the number of silicon atoms contained in the main chain to the number of imide groups contained in the main chain is 2% or more and 50% or less. 10 . The polyimide according to claim 1 , which has a weight average molecular weight of 1,000 or more.

11. A method for producing an imide compound, comprising: contacting the polyimide according to any one of claims 1 to 10 with a fluorine-containing compound; and The polyimide is reacted with the fluorine-containing compound to obtain an imide compound which is a decomposition product of the polyimide.

12. The manufacturing method according to claim 11, wherein: The fluorine-containing compound contains a fluoride salt.

13. The manufacturing method according to claim 12, wherein: The fluoride salt contains tetrabutylammonium fluoride.

14. A method for producing a regenerated polyimide, comprising: decomposing the polyimide according to any one of claims 1 to 10 to obtain a decomposition product of the polyimide; and The decomposed product is used to synthesize a recycled polyimide.

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